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:
2919 A thread ID as shown in the first field of the @samp{info threads}
2920 display, with or without an inferior qualifier. E.g., @samp{2.1} or
2924 A range of thread numbers, again with or without an inferior
2925 qualifier, as in @var{inf}.@var{thr1}-@var{thr2} or
2926 @var{thr1}-@var{thr2}. E.g., @samp{1.2-4} or @samp{2-4}.
2929 All threads of an inferior, specified with a star wildcard, with or
2930 without an inferior qualifier, as in @var{inf}.@code{*} (e.g.,
2931 @samp{1.*}) or @code{*}. The former refers to all threads of the
2932 given inferior, and the latter form without an inferior qualifier
2933 refers to all threads of the current inferior.
2937 For example, if the current inferior is 1, and inferior 7 has one
2938 thread with ID 7.1, the thread list @samp{1 2-3 4.5 6.7-9 7.*}
2939 includes threads 1 to 3 of inferior 1, thread 5 of inferior 4, threads
2940 7 to 9 of inferior 6 and all threads of inferior 7. That is, in
2941 expanded qualified form, the same as @samp{1.1 1.2 1.3 4.5 6.7 6.8 6.9
2945 @anchor{global thread numbers}
2946 @cindex global thread number
2947 @cindex global thread identifier (GDB)
2948 In addition to a @emph{per-inferior} number, each thread is also
2949 assigned a unique @emph{global} number, also known as @dfn{global
2950 thread ID}, a single integer. Unlike the thread number component of
2951 the thread ID, no two threads have the same global ID, even when
2952 you're debugging multiple inferiors.
2954 From @value{GDBN}'s perspective, a process always has at least one
2955 thread. In other words, @value{GDBN} assigns a thread number to the
2956 program's ``main thread'' even if the program is not multi-threaded.
2958 @vindex $_thread@r{, convenience variable}
2959 @vindex $_gthread@r{, convenience variable}
2960 The debugger convenience variables @samp{$_thread} and
2961 @samp{$_gthread} contain, respectively, the per-inferior thread number
2962 and the global thread number of the current thread. You may find this
2963 useful in writing breakpoint conditional expressions, command scripts,
2964 and so forth. @xref{Convenience Vars,, Convenience Variables}, for
2965 general information on convenience variables.
2967 If @value{GDBN} detects the program is multi-threaded, it augments the
2968 usual message about stopping at a breakpoint with the ID and name of
2969 the thread that hit the breakpoint.
2972 Thread 2 "client" hit Breakpoint 1, send_message () at client.c:68
2975 Likewise when the program receives a signal:
2978 Thread 1 "main" received signal SIGINT, Interrupt.
2982 @kindex info threads
2983 @item info threads @r{[}@var{thread-id-list}@r{]}
2985 Display information about one or more threads. With no arguments
2986 displays information about all threads. You can specify the list of
2987 threads that you want to display using the thread ID list syntax
2988 (@pxref{thread ID lists}).
2990 @value{GDBN} displays for each thread (in this order):
2994 the per-inferior thread number assigned by @value{GDBN}
2997 the global thread number assigned by @value{GDBN}, if the @samp{-gid}
2998 option was specified
3001 the target system's thread identifier (@var{systag})
3004 the thread's name, if one is known. A thread can either be named by
3005 the user (see @code{thread name}, below), or, in some cases, by the
3009 the current stack frame summary for that thread
3013 An asterisk @samp{*} to the left of the @value{GDBN} thread number
3014 indicates the current thread.
3018 @c end table here to get a little more width for example
3021 (@value{GDBP}) info threads
3023 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3024 2 process 35 thread 23 0x34e5 in sigpause ()
3025 3 process 35 thread 27 0x34e5 in sigpause ()
3029 If you're debugging multiple inferiors, @value{GDBN} displays thread
3030 IDs using the qualified @var{inferior-num}.@var{thread-num} format.
3031 Otherwise, only @var{thread-num} is shown.
3033 If you specify the @samp{-gid} option, @value{GDBN} displays a column
3034 indicating each thread's global thread ID:
3037 (@value{GDBP}) info threads
3038 Id GId Target Id Frame
3039 1.1 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3040 1.2 3 process 35 thread 23 0x34e5 in sigpause ()
3041 1.3 4 process 35 thread 27 0x34e5 in sigpause ()
3042 * 2.1 2 process 65 thread 1 main (argc=1, argv=0x7ffffff8)
3045 On Solaris, you can display more information about user threads with a
3046 Solaris-specific command:
3049 @item maint info sol-threads
3050 @kindex maint info sol-threads
3051 @cindex thread info (Solaris)
3052 Display info on Solaris user threads.
3056 @kindex thread @var{thread-id}
3057 @item thread @var{thread-id}
3058 Make thread ID @var{thread-id} the current thread. The command
3059 argument @var{thread-id} is the @value{GDBN} thread ID, as shown in
3060 the first field of the @samp{info threads} display, with or without an
3061 inferior qualifier (e.g., @samp{2.1} or @samp{1}).
3063 @value{GDBN} responds by displaying the system identifier of the
3064 thread you selected, and its current stack frame summary:
3067 (@value{GDBP}) thread 2
3068 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
3069 #0 some_function (ignore=0x0) at example.c:8
3070 8 printf ("hello\n");
3074 As with the @samp{[New @dots{}]} message, the form of the text after
3075 @samp{Switching to} depends on your system's conventions for identifying
3078 @kindex thread apply
3079 @cindex apply command to several threads
3080 @item thread apply [@var{thread-id-list} | all [-ascending]] @var{command}
3081 The @code{thread apply} command allows you to apply the named
3082 @var{command} to one or more threads. Specify the threads that you
3083 want affected using the thread ID list syntax (@pxref{thread ID
3084 lists}), or specify @code{all} to apply to all threads. To apply a
3085 command to all threads in descending order, type @kbd{thread apply all
3086 @var{command}}. To apply a command to all threads in ascending order,
3087 type @kbd{thread apply all -ascending @var{command}}.
3091 @cindex name a thread
3092 @item thread name [@var{name}]
3093 This command assigns a name to the current thread. If no argument is
3094 given, any existing user-specified name is removed. The thread name
3095 appears in the @samp{info threads} display.
3097 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3098 determine the name of the thread as given by the OS. On these
3099 systems, a name specified with @samp{thread name} will override the
3100 system-give name, and removing the user-specified name will cause
3101 @value{GDBN} to once again display the system-specified name.
3104 @cindex search for a thread
3105 @item thread find [@var{regexp}]
3106 Search for and display thread ids whose name or @var{systag}
3107 matches the supplied regular expression.
3109 As well as being the complement to the @samp{thread name} command,
3110 this command also allows you to identify a thread by its target
3111 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3115 (@value{GDBN}) thread find 26688
3116 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3117 (@value{GDBN}) info thread 4
3119 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3122 @kindex set print thread-events
3123 @cindex print messages on thread start and exit
3124 @item set print thread-events
3125 @itemx set print thread-events on
3126 @itemx set print thread-events off
3127 The @code{set print thread-events} command allows you to enable or
3128 disable printing of messages when @value{GDBN} notices that new threads have
3129 started or that threads have exited. By default, these messages will
3130 be printed if detection of these events is supported by the target.
3131 Note that these messages cannot be disabled on all targets.
3133 @kindex show print thread-events
3134 @item show print thread-events
3135 Show whether messages will be printed when @value{GDBN} detects that threads
3136 have started and exited.
3139 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3140 more information about how @value{GDBN} behaves when you stop and start
3141 programs with multiple threads.
3143 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3144 watchpoints in programs with multiple threads.
3146 @anchor{set libthread-db-search-path}
3148 @kindex set libthread-db-search-path
3149 @cindex search path for @code{libthread_db}
3150 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3151 If this variable is set, @var{path} is a colon-separated list of
3152 directories @value{GDBN} will use to search for @code{libthread_db}.
3153 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3154 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3155 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3158 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3159 @code{libthread_db} library to obtain information about threads in the
3160 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3161 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3162 specific thread debugging library loading is enabled
3163 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3165 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3166 refers to the default system directories that are
3167 normally searched for loading shared libraries. The @samp{$sdir} entry
3168 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3169 (@pxref{libthread_db.so.1 file}).
3171 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3172 refers to the directory from which @code{libpthread}
3173 was loaded in the inferior process.
3175 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3176 @value{GDBN} attempts to initialize it with the current inferior process.
3177 If this initialization fails (which could happen because of a version
3178 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3179 will unload @code{libthread_db}, and continue with the next directory.
3180 If none of @code{libthread_db} libraries initialize successfully,
3181 @value{GDBN} will issue a warning and thread debugging will be disabled.
3183 Setting @code{libthread-db-search-path} is currently implemented
3184 only on some platforms.
3186 @kindex show libthread-db-search-path
3187 @item show libthread-db-search-path
3188 Display current libthread_db search path.
3190 @kindex set debug libthread-db
3191 @kindex show debug libthread-db
3192 @cindex debugging @code{libthread_db}
3193 @item set debug libthread-db
3194 @itemx show debug libthread-db
3195 Turns on or off display of @code{libthread_db}-related events.
3196 Use @code{1} to enable, @code{0} to disable.
3200 @section Debugging Forks
3202 @cindex fork, debugging programs which call
3203 @cindex multiple processes
3204 @cindex processes, multiple
3205 On most systems, @value{GDBN} has no special support for debugging
3206 programs which create additional processes using the @code{fork}
3207 function. When a program forks, @value{GDBN} will continue to debug the
3208 parent process and the child process will run unimpeded. If you have
3209 set a breakpoint in any code which the child then executes, the child
3210 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3211 will cause it to terminate.
3213 However, if you want to debug the child process there is a workaround
3214 which isn't too painful. Put a call to @code{sleep} in the code which
3215 the child process executes after the fork. It may be useful to sleep
3216 only if a certain environment variable is set, or a certain file exists,
3217 so that the delay need not occur when you don't want to run @value{GDBN}
3218 on the child. While the child is sleeping, use the @code{ps} program to
3219 get its process ID. Then tell @value{GDBN} (a new invocation of
3220 @value{GDBN} if you are also debugging the parent process) to attach to
3221 the child process (@pxref{Attach}). From that point on you can debug
3222 the child process just like any other process which you attached to.
3224 On some systems, @value{GDBN} provides support for debugging programs
3225 that create additional processes using the @code{fork} or @code{vfork}
3226 functions. On @sc{gnu}/Linux platforms, this feature is supported
3227 with kernel version 2.5.46 and later.
3229 The fork debugging commands are supported in native mode and when
3230 connected to @code{gdbserver} in either @code{target remote} mode or
3231 @code{target extended-remote} mode.
3233 By default, when a program forks, @value{GDBN} will continue to debug
3234 the parent process and the child process will run unimpeded.
3236 If you want to follow the child process instead of the parent process,
3237 use the command @w{@code{set follow-fork-mode}}.
3240 @kindex set follow-fork-mode
3241 @item set follow-fork-mode @var{mode}
3242 Set the debugger response to a program call of @code{fork} or
3243 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3244 process. The @var{mode} argument can be:
3248 The original process is debugged after a fork. The child process runs
3249 unimpeded. This is the default.
3252 The new process is debugged after a fork. The parent process runs
3257 @kindex show follow-fork-mode
3258 @item show follow-fork-mode
3259 Display the current debugger response to a @code{fork} or @code{vfork} call.
3262 @cindex debugging multiple processes
3263 On Linux, if you want to debug both the parent and child processes, use the
3264 command @w{@code{set detach-on-fork}}.
3267 @kindex set detach-on-fork
3268 @item set detach-on-fork @var{mode}
3269 Tells gdb whether to detach one of the processes after a fork, or
3270 retain debugger control over them both.
3274 The child process (or parent process, depending on the value of
3275 @code{follow-fork-mode}) will be detached and allowed to run
3276 independently. This is the default.
3279 Both processes will be held under the control of @value{GDBN}.
3280 One process (child or parent, depending on the value of
3281 @code{follow-fork-mode}) is debugged as usual, while the other
3286 @kindex show detach-on-fork
3287 @item show detach-on-fork
3288 Show whether detach-on-fork mode is on/off.
3291 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3292 will retain control of all forked processes (including nested forks).
3293 You can list the forked processes under the control of @value{GDBN} by
3294 using the @w{@code{info inferiors}} command, and switch from one fork
3295 to another by using the @code{inferior} command (@pxref{Inferiors and
3296 Programs, ,Debugging Multiple Inferiors and Programs}).
3298 To quit debugging one of the forked processes, you can either detach
3299 from it by using the @w{@code{detach inferiors}} command (allowing it
3300 to run independently), or kill it using the @w{@code{kill inferiors}}
3301 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3304 If you ask to debug a child process and a @code{vfork} is followed by an
3305 @code{exec}, @value{GDBN} executes the new target up to the first
3306 breakpoint in the new target. If you have a breakpoint set on
3307 @code{main} in your original program, the breakpoint will also be set on
3308 the child process's @code{main}.
3310 On some systems, when a child process is spawned by @code{vfork}, you
3311 cannot debug the child or parent until an @code{exec} call completes.
3313 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3314 call executes, the new target restarts. To restart the parent
3315 process, use the @code{file} command with the parent executable name
3316 as its argument. By default, after an @code{exec} call executes,
3317 @value{GDBN} discards the symbols of the previous executable image.
3318 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3322 @kindex set follow-exec-mode
3323 @item set follow-exec-mode @var{mode}
3325 Set debugger response to a program call of @code{exec}. An
3326 @code{exec} call replaces the program image of a process.
3328 @code{follow-exec-mode} can be:
3332 @value{GDBN} creates a new inferior and rebinds the process to this
3333 new inferior. The program the process was running before the
3334 @code{exec} call can be restarted afterwards by restarting the
3340 (@value{GDBP}) info inferiors
3342 Id Description Executable
3345 process 12020 is executing new program: prog2
3346 Program exited normally.
3347 (@value{GDBP}) info inferiors
3348 Id Description Executable
3354 @value{GDBN} keeps the process bound to the same inferior. The new
3355 executable image replaces the previous executable loaded in the
3356 inferior. Restarting the inferior after the @code{exec} call, with
3357 e.g., the @code{run} command, restarts the executable the process was
3358 running after the @code{exec} call. This is the default mode.
3363 (@value{GDBP}) info inferiors
3364 Id Description Executable
3367 process 12020 is executing new program: prog2
3368 Program exited normally.
3369 (@value{GDBP}) info inferiors
3370 Id Description Executable
3377 @code{follow-exec-mode} is supported in native mode and
3378 @code{target extended-remote} mode.
3380 You can use the @code{catch} command to make @value{GDBN} stop whenever
3381 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3382 Catchpoints, ,Setting Catchpoints}.
3384 @node Checkpoint/Restart
3385 @section Setting a @emph{Bookmark} to Return to Later
3390 @cindex snapshot of a process
3391 @cindex rewind program state
3393 On certain operating systems@footnote{Currently, only
3394 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3395 program's state, called a @dfn{checkpoint}, and come back to it
3398 Returning to a checkpoint effectively undoes everything that has
3399 happened in the program since the @code{checkpoint} was saved. This
3400 includes changes in memory, registers, and even (within some limits)
3401 system state. Effectively, it is like going back in time to the
3402 moment when the checkpoint was saved.
3404 Thus, if you're stepping thru a program and you think you're
3405 getting close to the point where things go wrong, you can save
3406 a checkpoint. Then, if you accidentally go too far and miss
3407 the critical statement, instead of having to restart your program
3408 from the beginning, you can just go back to the checkpoint and
3409 start again from there.
3411 This can be especially useful if it takes a lot of time or
3412 steps to reach the point where you think the bug occurs.
3414 To use the @code{checkpoint}/@code{restart} method of debugging:
3419 Save a snapshot of the debugged program's current execution state.
3420 The @code{checkpoint} command takes no arguments, but each checkpoint
3421 is assigned a small integer id, similar to a breakpoint id.
3423 @kindex info checkpoints
3424 @item info checkpoints
3425 List the checkpoints that have been saved in the current debugging
3426 session. For each checkpoint, the following information will be
3433 @item Source line, or label
3436 @kindex restart @var{checkpoint-id}
3437 @item restart @var{checkpoint-id}
3438 Restore the program state that was saved as checkpoint number
3439 @var{checkpoint-id}. All program variables, registers, stack frames
3440 etc.@: will be returned to the values that they had when the checkpoint
3441 was saved. In essence, gdb will ``wind back the clock'' to the point
3442 in time when the checkpoint was saved.
3444 Note that breakpoints, @value{GDBN} variables, command history etc.
3445 are not affected by restoring a checkpoint. In general, a checkpoint
3446 only restores things that reside in the program being debugged, not in
3449 @kindex delete checkpoint @var{checkpoint-id}
3450 @item delete checkpoint @var{checkpoint-id}
3451 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3455 Returning to a previously saved checkpoint will restore the user state
3456 of the program being debugged, plus a significant subset of the system
3457 (OS) state, including file pointers. It won't ``un-write'' data from
3458 a file, but it will rewind the file pointer to the previous location,
3459 so that the previously written data can be overwritten. For files
3460 opened in read mode, the pointer will also be restored so that the
3461 previously read data can be read again.
3463 Of course, characters that have been sent to a printer (or other
3464 external device) cannot be ``snatched back'', and characters received
3465 from eg.@: a serial device can be removed from internal program buffers,
3466 but they cannot be ``pushed back'' into the serial pipeline, ready to
3467 be received again. Similarly, the actual contents of files that have
3468 been changed cannot be restored (at this time).
3470 However, within those constraints, you actually can ``rewind'' your
3471 program to a previously saved point in time, and begin debugging it
3472 again --- and you can change the course of events so as to debug a
3473 different execution path this time.
3475 @cindex checkpoints and process id
3476 Finally, there is one bit of internal program state that will be
3477 different when you return to a checkpoint --- the program's process
3478 id. Each checkpoint will have a unique process id (or @var{pid}),
3479 and each will be different from the program's original @var{pid}.
3480 If your program has saved a local copy of its process id, this could
3481 potentially pose a problem.
3483 @subsection A Non-obvious Benefit of Using Checkpoints
3485 On some systems such as @sc{gnu}/Linux, address space randomization
3486 is performed on new processes for security reasons. This makes it
3487 difficult or impossible to set a breakpoint, or watchpoint, on an
3488 absolute address if you have to restart the program, since the
3489 absolute location of a symbol will change from one execution to the
3492 A checkpoint, however, is an @emph{identical} copy of a process.
3493 Therefore if you create a checkpoint at (eg.@:) the start of main,
3494 and simply return to that checkpoint instead of restarting the
3495 process, you can avoid the effects of address randomization and
3496 your symbols will all stay in the same place.
3499 @chapter Stopping and Continuing
3501 The principal purposes of using a debugger are so that you can stop your
3502 program before it terminates; or so that, if your program runs into
3503 trouble, you can investigate and find out why.
3505 Inside @value{GDBN}, your program may stop for any of several reasons,
3506 such as a signal, a breakpoint, or reaching a new line after a
3507 @value{GDBN} command such as @code{step}. You may then examine and
3508 change variables, set new breakpoints or remove old ones, and then
3509 continue execution. Usually, the messages shown by @value{GDBN} provide
3510 ample explanation of the status of your program---but you can also
3511 explicitly request this information at any time.
3514 @kindex info program
3516 Display information about the status of your program: whether it is
3517 running or not, what process it is, and why it stopped.
3521 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3522 * Continuing and Stepping:: Resuming execution
3523 * Skipping Over Functions and Files::
3524 Skipping over functions and files
3526 * Thread Stops:: Stopping and starting multi-thread programs
3530 @section Breakpoints, Watchpoints, and Catchpoints
3533 A @dfn{breakpoint} makes your program stop whenever a certain point in
3534 the program is reached. For each breakpoint, you can add conditions to
3535 control in finer detail whether your program stops. You can set
3536 breakpoints with the @code{break} command and its variants (@pxref{Set
3537 Breaks, ,Setting Breakpoints}), to specify the place where your program
3538 should stop by line number, function name or exact address in the
3541 On some systems, you can set breakpoints in shared libraries before
3542 the executable is run.
3545 @cindex data breakpoints
3546 @cindex memory tracing
3547 @cindex breakpoint on memory address
3548 @cindex breakpoint on variable modification
3549 A @dfn{watchpoint} is a special breakpoint that stops your program
3550 when the value of an expression changes. The expression may be a value
3551 of a variable, or it could involve values of one or more variables
3552 combined by operators, such as @samp{a + b}. This is sometimes called
3553 @dfn{data breakpoints}. You must use a different command to set
3554 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3555 from that, you can manage a watchpoint like any other breakpoint: you
3556 enable, disable, and delete both breakpoints and watchpoints using the
3559 You can arrange to have values from your program displayed automatically
3560 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3564 @cindex breakpoint on events
3565 A @dfn{catchpoint} is another special breakpoint that stops your program
3566 when a certain kind of event occurs, such as the throwing of a C@t{++}
3567 exception or the loading of a library. As with watchpoints, you use a
3568 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3569 Catchpoints}), but aside from that, you can manage a catchpoint like any
3570 other breakpoint. (To stop when your program receives a signal, use the
3571 @code{handle} command; see @ref{Signals, ,Signals}.)
3573 @cindex breakpoint numbers
3574 @cindex numbers for breakpoints
3575 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3576 catchpoint when you create it; these numbers are successive integers
3577 starting with one. In many of the commands for controlling various
3578 features of breakpoints you use the breakpoint number to say which
3579 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3580 @dfn{disabled}; if disabled, it has no effect on your program until you
3583 @cindex breakpoint ranges
3584 @cindex ranges of breakpoints
3585 Some @value{GDBN} commands accept a range of breakpoints on which to
3586 operate. A breakpoint range is either a single breakpoint number, like
3587 @samp{5}, or two such numbers, in increasing order, separated by a
3588 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3589 all breakpoints in that range are operated on.
3592 * Set Breaks:: Setting breakpoints
3593 * Set Watchpoints:: Setting watchpoints
3594 * Set Catchpoints:: Setting catchpoints
3595 * Delete Breaks:: Deleting breakpoints
3596 * Disabling:: Disabling breakpoints
3597 * Conditions:: Break conditions
3598 * Break Commands:: Breakpoint command lists
3599 * Dynamic Printf:: Dynamic printf
3600 * Save Breakpoints:: How to save breakpoints in a file
3601 * Static Probe Points:: Listing static probe points
3602 * Error in Breakpoints:: ``Cannot insert breakpoints''
3603 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3607 @subsection Setting Breakpoints
3609 @c FIXME LMB what does GDB do if no code on line of breakpt?
3610 @c consider in particular declaration with/without initialization.
3612 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3615 @kindex b @r{(@code{break})}
3616 @vindex $bpnum@r{, convenience variable}
3617 @cindex latest breakpoint
3618 Breakpoints are set with the @code{break} command (abbreviated
3619 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3620 number of the breakpoint you've set most recently; see @ref{Convenience
3621 Vars,, Convenience Variables}, for a discussion of what you can do with
3622 convenience variables.
3625 @item break @var{location}
3626 Set a breakpoint at the given @var{location}, which can specify a
3627 function name, a line number, or an address of an instruction.
3628 (@xref{Specify Location}, for a list of all the possible ways to
3629 specify a @var{location}.) The breakpoint will stop your program just
3630 before it executes any of the code in the specified @var{location}.
3632 When using source languages that permit overloading of symbols, such as
3633 C@t{++}, a function name may refer to more than one possible place to break.
3634 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3637 It is also possible to insert a breakpoint that will stop the program
3638 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3639 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3642 When called without any arguments, @code{break} sets a breakpoint at
3643 the next instruction to be executed in the selected stack frame
3644 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3645 innermost, this makes your program stop as soon as control
3646 returns to that frame. This is similar to the effect of a
3647 @code{finish} command in the frame inside the selected frame---except
3648 that @code{finish} does not leave an active breakpoint. If you use
3649 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3650 the next time it reaches the current location; this may be useful
3653 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3654 least one instruction has been executed. If it did not do this, you
3655 would be unable to proceed past a breakpoint without first disabling the
3656 breakpoint. This rule applies whether or not the breakpoint already
3657 existed when your program stopped.
3659 @item break @dots{} if @var{cond}
3660 Set a breakpoint with condition @var{cond}; evaluate the expression
3661 @var{cond} each time the breakpoint is reached, and stop only if the
3662 value is nonzero---that is, if @var{cond} evaluates as true.
3663 @samp{@dots{}} stands for one of the possible arguments described
3664 above (or no argument) specifying where to break. @xref{Conditions,
3665 ,Break Conditions}, for more information on breakpoint conditions.
3668 @item tbreak @var{args}
3669 Set a breakpoint enabled only for one stop. The @var{args} are the
3670 same as for the @code{break} command, and the breakpoint is set in the same
3671 way, but the breakpoint is automatically deleted after the first time your
3672 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3675 @cindex hardware breakpoints
3676 @item hbreak @var{args}
3677 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
3678 @code{break} command and the breakpoint is set in the same way, but the
3679 breakpoint requires hardware support and some target hardware may not
3680 have this support. The main purpose of this is EPROM/ROM code
3681 debugging, so you can set a breakpoint at an instruction without
3682 changing the instruction. This can be used with the new trap-generation
3683 provided by SPARClite DSU and most x86-based targets. These targets
3684 will generate traps when a program accesses some data or instruction
3685 address that is assigned to the debug registers. However the hardware
3686 breakpoint registers can take a limited number of breakpoints. For
3687 example, on the DSU, only two data breakpoints can be set at a time, and
3688 @value{GDBN} will reject this command if more than two are used. Delete
3689 or disable unused hardware breakpoints before setting new ones
3690 (@pxref{Disabling, ,Disabling Breakpoints}).
3691 @xref{Conditions, ,Break Conditions}.
3692 For remote targets, you can restrict the number of hardware
3693 breakpoints @value{GDBN} will use, see @ref{set remote
3694 hardware-breakpoint-limit}.
3697 @item thbreak @var{args}
3698 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
3699 are the same as for the @code{hbreak} command and the breakpoint is set in
3700 the same way. However, like the @code{tbreak} command,
3701 the breakpoint is automatically deleted after the
3702 first time your program stops there. Also, like the @code{hbreak}
3703 command, the breakpoint requires hardware support and some target hardware
3704 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3705 See also @ref{Conditions, ,Break Conditions}.
3708 @cindex regular expression
3709 @cindex breakpoints at functions matching a regexp
3710 @cindex set breakpoints in many functions
3711 @item rbreak @var{regex}
3712 Set breakpoints on all functions matching the regular expression
3713 @var{regex}. This command sets an unconditional breakpoint on all
3714 matches, printing a list of all breakpoints it set. Once these
3715 breakpoints are set, they are treated just like the breakpoints set with
3716 the @code{break} command. You can delete them, disable them, or make
3717 them conditional the same way as any other breakpoint.
3719 The syntax of the regular expression is the standard one used with tools
3720 like @file{grep}. Note that this is different from the syntax used by
3721 shells, so for instance @code{foo*} matches all functions that include
3722 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3723 @code{.*} leading and trailing the regular expression you supply, so to
3724 match only functions that begin with @code{foo}, use @code{^foo}.
3726 @cindex non-member C@t{++} functions, set breakpoint in
3727 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3728 breakpoints on overloaded functions that are not members of any special
3731 @cindex set breakpoints on all functions
3732 The @code{rbreak} command can be used to set breakpoints in
3733 @strong{all} the functions in a program, like this:
3736 (@value{GDBP}) rbreak .
3739 @item rbreak @var{file}:@var{regex}
3740 If @code{rbreak} is called with a filename qualification, it limits
3741 the search for functions matching the given regular expression to the
3742 specified @var{file}. This can be used, for example, to set breakpoints on
3743 every function in a given file:
3746 (@value{GDBP}) rbreak file.c:.
3749 The colon separating the filename qualifier from the regex may
3750 optionally be surrounded by spaces.
3752 @kindex info breakpoints
3753 @cindex @code{$_} and @code{info breakpoints}
3754 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3755 @itemx info break @r{[}@var{n}@dots{}@r{]}
3756 Print a table of all breakpoints, watchpoints, and catchpoints set and
3757 not deleted. Optional argument @var{n} means print information only
3758 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3759 For each breakpoint, following columns are printed:
3762 @item Breakpoint Numbers
3764 Breakpoint, watchpoint, or catchpoint.
3766 Whether the breakpoint is marked to be disabled or deleted when hit.
3767 @item Enabled or Disabled
3768 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3769 that are not enabled.
3771 Where the breakpoint is in your program, as a memory address. For a
3772 pending breakpoint whose address is not yet known, this field will
3773 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3774 library that has the symbol or line referred by breakpoint is loaded.
3775 See below for details. A breakpoint with several locations will
3776 have @samp{<MULTIPLE>} in this field---see below for details.
3778 Where the breakpoint is in the source for your program, as a file and
3779 line number. For a pending breakpoint, the original string passed to
3780 the breakpoint command will be listed as it cannot be resolved until
3781 the appropriate shared library is loaded in the future.
3785 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3786 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3787 @value{GDBN} on the host's side. If it is ``target'', then the condition
3788 is evaluated by the target. The @code{info break} command shows
3789 the condition on the line following the affected breakpoint, together with
3790 its condition evaluation mode in between parentheses.
3792 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3793 allowed to have a condition specified for it. The condition is not parsed for
3794 validity until a shared library is loaded that allows the pending
3795 breakpoint to resolve to a valid location.
3798 @code{info break} with a breakpoint
3799 number @var{n} as argument lists only that breakpoint. The
3800 convenience variable @code{$_} and the default examining-address for
3801 the @code{x} command are set to the address of the last breakpoint
3802 listed (@pxref{Memory, ,Examining Memory}).
3805 @code{info break} displays a count of the number of times the breakpoint
3806 has been hit. This is especially useful in conjunction with the
3807 @code{ignore} command. You can ignore a large number of breakpoint
3808 hits, look at the breakpoint info to see how many times the breakpoint
3809 was hit, and then run again, ignoring one less than that number. This
3810 will get you quickly to the last hit of that breakpoint.
3813 For a breakpoints with an enable count (xref) greater than 1,
3814 @code{info break} also displays that count.
3818 @value{GDBN} allows you to set any number of breakpoints at the same place in
3819 your program. There is nothing silly or meaningless about this. When
3820 the breakpoints are conditional, this is even useful
3821 (@pxref{Conditions, ,Break Conditions}).
3823 @cindex multiple locations, breakpoints
3824 @cindex breakpoints, multiple locations
3825 It is possible that a breakpoint corresponds to several locations
3826 in your program. Examples of this situation are:
3830 Multiple functions in the program may have the same name.
3833 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3834 instances of the function body, used in different cases.
3837 For a C@t{++} template function, a given line in the function can
3838 correspond to any number of instantiations.
3841 For an inlined function, a given source line can correspond to
3842 several places where that function is inlined.
3845 In all those cases, @value{GDBN} will insert a breakpoint at all
3846 the relevant locations.
3848 A breakpoint with multiple locations is displayed in the breakpoint
3849 table using several rows---one header row, followed by one row for
3850 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3851 address column. The rows for individual locations contain the actual
3852 addresses for locations, and show the functions to which those
3853 locations belong. The number column for a location is of the form
3854 @var{breakpoint-number}.@var{location-number}.
3859 Num Type Disp Enb Address What
3860 1 breakpoint keep y <MULTIPLE>
3862 breakpoint already hit 1 time
3863 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3864 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3867 Each location can be individually enabled or disabled by passing
3868 @var{breakpoint-number}.@var{location-number} as argument to the
3869 @code{enable} and @code{disable} commands. Note that you cannot
3870 delete the individual locations from the list, you can only delete the
3871 entire list of locations that belong to their parent breakpoint (with
3872 the @kbd{delete @var{num}} command, where @var{num} is the number of
3873 the parent breakpoint, 1 in the above example). Disabling or enabling
3874 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3875 that belong to that breakpoint.
3877 @cindex pending breakpoints
3878 It's quite common to have a breakpoint inside a shared library.
3879 Shared libraries can be loaded and unloaded explicitly,
3880 and possibly repeatedly, as the program is executed. To support
3881 this use case, @value{GDBN} updates breakpoint locations whenever
3882 any shared library is loaded or unloaded. Typically, you would
3883 set a breakpoint in a shared library at the beginning of your
3884 debugging session, when the library is not loaded, and when the
3885 symbols from the library are not available. When you try to set
3886 breakpoint, @value{GDBN} will ask you if you want to set
3887 a so called @dfn{pending breakpoint}---breakpoint whose address
3888 is not yet resolved.
3890 After the program is run, whenever a new shared library is loaded,
3891 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3892 shared library contains the symbol or line referred to by some
3893 pending breakpoint, that breakpoint is resolved and becomes an
3894 ordinary breakpoint. When a library is unloaded, all breakpoints
3895 that refer to its symbols or source lines become pending again.
3897 This logic works for breakpoints with multiple locations, too. For
3898 example, if you have a breakpoint in a C@t{++} template function, and
3899 a newly loaded shared library has an instantiation of that template,
3900 a new location is added to the list of locations for the breakpoint.
3902 Except for having unresolved address, pending breakpoints do not
3903 differ from regular breakpoints. You can set conditions or commands,
3904 enable and disable them and perform other breakpoint operations.
3906 @value{GDBN} provides some additional commands for controlling what
3907 happens when the @samp{break} command cannot resolve breakpoint
3908 address specification to an address:
3910 @kindex set breakpoint pending
3911 @kindex show breakpoint pending
3913 @item set breakpoint pending auto
3914 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3915 location, it queries you whether a pending breakpoint should be created.
3917 @item set breakpoint pending on
3918 This indicates that an unrecognized breakpoint location should automatically
3919 result in a pending breakpoint being created.
3921 @item set breakpoint pending off
3922 This indicates that pending breakpoints are not to be created. Any
3923 unrecognized breakpoint location results in an error. This setting does
3924 not affect any pending breakpoints previously created.
3926 @item show breakpoint pending
3927 Show the current behavior setting for creating pending breakpoints.
3930 The settings above only affect the @code{break} command and its
3931 variants. Once breakpoint is set, it will be automatically updated
3932 as shared libraries are loaded and unloaded.
3934 @cindex automatic hardware breakpoints
3935 For some targets, @value{GDBN} can automatically decide if hardware or
3936 software breakpoints should be used, depending on whether the
3937 breakpoint address is read-only or read-write. This applies to
3938 breakpoints set with the @code{break} command as well as to internal
3939 breakpoints set by commands like @code{next} and @code{finish}. For
3940 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3943 You can control this automatic behaviour with the following commands::
3945 @kindex set breakpoint auto-hw
3946 @kindex show breakpoint auto-hw
3948 @item set breakpoint auto-hw on
3949 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3950 will try to use the target memory map to decide if software or hardware
3951 breakpoint must be used.
3953 @item set breakpoint auto-hw off
3954 This indicates @value{GDBN} should not automatically select breakpoint
3955 type. If the target provides a memory map, @value{GDBN} will warn when
3956 trying to set software breakpoint at a read-only address.
3959 @value{GDBN} normally implements breakpoints by replacing the program code
3960 at the breakpoint address with a special instruction, which, when
3961 executed, given control to the debugger. By default, the program
3962 code is so modified only when the program is resumed. As soon as
3963 the program stops, @value{GDBN} restores the original instructions. This
3964 behaviour guards against leaving breakpoints inserted in the
3965 target should gdb abrubptly disconnect. However, with slow remote
3966 targets, inserting and removing breakpoint can reduce the performance.
3967 This behavior can be controlled with the following commands::
3969 @kindex set breakpoint always-inserted
3970 @kindex show breakpoint always-inserted
3972 @item set breakpoint always-inserted off
3973 All breakpoints, including newly added by the user, are inserted in
3974 the target only when the target is resumed. All breakpoints are
3975 removed from the target when it stops. This is the default mode.
3977 @item set breakpoint always-inserted on
3978 Causes all breakpoints to be inserted in the target at all times. If
3979 the user adds a new breakpoint, or changes an existing breakpoint, the
3980 breakpoints in the target are updated immediately. A breakpoint is
3981 removed from the target only when breakpoint itself is deleted.
3984 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3985 when a breakpoint breaks. If the condition is true, then the process being
3986 debugged stops, otherwise the process is resumed.
3988 If the target supports evaluating conditions on its end, @value{GDBN} may
3989 download the breakpoint, together with its conditions, to it.
3991 This feature can be controlled via the following commands:
3993 @kindex set breakpoint condition-evaluation
3994 @kindex show breakpoint condition-evaluation
3996 @item set breakpoint condition-evaluation host
3997 This option commands @value{GDBN} to evaluate the breakpoint
3998 conditions on the host's side. Unconditional breakpoints are sent to
3999 the target which in turn receives the triggers and reports them back to GDB
4000 for condition evaluation. This is the standard evaluation mode.
4002 @item set breakpoint condition-evaluation target
4003 This option commands @value{GDBN} to download breakpoint conditions
4004 to the target at the moment of their insertion. The target
4005 is responsible for evaluating the conditional expression and reporting
4006 breakpoint stop events back to @value{GDBN} whenever the condition
4007 is true. Due to limitations of target-side evaluation, some conditions
4008 cannot be evaluated there, e.g., conditions that depend on local data
4009 that is only known to the host. Examples include
4010 conditional expressions involving convenience variables, complex types
4011 that cannot be handled by the agent expression parser and expressions
4012 that are too long to be sent over to the target, specially when the
4013 target is a remote system. In these cases, the conditions will be
4014 evaluated by @value{GDBN}.
4016 @item set breakpoint condition-evaluation auto
4017 This is the default mode. If the target supports evaluating breakpoint
4018 conditions on its end, @value{GDBN} will download breakpoint conditions to
4019 the target (limitations mentioned previously apply). If the target does
4020 not support breakpoint condition evaluation, then @value{GDBN} will fallback
4021 to evaluating all these conditions on the host's side.
4025 @cindex negative breakpoint numbers
4026 @cindex internal @value{GDBN} breakpoints
4027 @value{GDBN} itself sometimes sets breakpoints in your program for
4028 special purposes, such as proper handling of @code{longjmp} (in C
4029 programs). These internal breakpoints are assigned negative numbers,
4030 starting with @code{-1}; @samp{info breakpoints} does not display them.
4031 You can see these breakpoints with the @value{GDBN} maintenance command
4032 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
4035 @node Set Watchpoints
4036 @subsection Setting Watchpoints
4038 @cindex setting watchpoints
4039 You can use a watchpoint to stop execution whenever the value of an
4040 expression changes, without having to predict a particular place where
4041 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
4042 The expression may be as simple as the value of a single variable, or
4043 as complex as many variables combined by operators. Examples include:
4047 A reference to the value of a single variable.
4050 An address cast to an appropriate data type. For example,
4051 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
4052 address (assuming an @code{int} occupies 4 bytes).
4055 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
4056 expression can use any operators valid in the program's native
4057 language (@pxref{Languages}).
4060 You can set a watchpoint on an expression even if the expression can
4061 not be evaluated yet. For instance, you can set a watchpoint on
4062 @samp{*global_ptr} before @samp{global_ptr} is initialized.
4063 @value{GDBN} will stop when your program sets @samp{global_ptr} and
4064 the expression produces a valid value. If the expression becomes
4065 valid in some other way than changing a variable (e.g.@: if the memory
4066 pointed to by @samp{*global_ptr} becomes readable as the result of a
4067 @code{malloc} call), @value{GDBN} may not stop until the next time
4068 the expression changes.
4070 @cindex software watchpoints
4071 @cindex hardware watchpoints
4072 Depending on your system, watchpoints may be implemented in software or
4073 hardware. @value{GDBN} does software watchpointing by single-stepping your
4074 program and testing the variable's value each time, which is hundreds of
4075 times slower than normal execution. (But this may still be worth it, to
4076 catch errors where you have no clue what part of your program is the
4079 On some systems, such as most PowerPC or x86-based targets,
4080 @value{GDBN} includes support for hardware watchpoints, which do not
4081 slow down the running of your program.
4085 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4086 Set a watchpoint for an expression. @value{GDBN} will break when the
4087 expression @var{expr} is written into by the program and its value
4088 changes. The simplest (and the most popular) use of this command is
4089 to watch the value of a single variable:
4092 (@value{GDBP}) watch foo
4095 If the command includes a @code{@r{[}thread @var{thread-id}@r{]}}
4096 argument, @value{GDBN} breaks only when the thread identified by
4097 @var{thread-id} changes the value of @var{expr}. If any other threads
4098 change the value of @var{expr}, @value{GDBN} will not break. Note
4099 that watchpoints restricted to a single thread in this way only work
4100 with Hardware Watchpoints.
4102 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4103 (see below). The @code{-location} argument tells @value{GDBN} to
4104 instead watch the memory referred to by @var{expr}. In this case,
4105 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4106 and watch the memory at that address. The type of the result is used
4107 to determine the size of the watched memory. If the expression's
4108 result does not have an address, then @value{GDBN} will print an
4111 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4112 of masked watchpoints, if the current architecture supports this
4113 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4114 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4115 to an address to watch. The mask specifies that some bits of an address
4116 (the bits which are reset in the mask) should be ignored when matching
4117 the address accessed by the inferior against the watchpoint address.
4118 Thus, a masked watchpoint watches many addresses simultaneously---those
4119 addresses whose unmasked bits are identical to the unmasked bits in the
4120 watchpoint address. The @code{mask} argument implies @code{-location}.
4124 (@value{GDBP}) watch foo mask 0xffff00ff
4125 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4129 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4130 Set a watchpoint that will break when the value of @var{expr} is read
4134 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4135 Set a watchpoint that will break when @var{expr} is either read from
4136 or written into by the program.
4138 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
4139 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
4140 This command prints a list of watchpoints, using the same format as
4141 @code{info break} (@pxref{Set Breaks}).
4144 If you watch for a change in a numerically entered address you need to
4145 dereference it, as the address itself is just a constant number which will
4146 never change. @value{GDBN} refuses to create a watchpoint that watches
4147 a never-changing value:
4150 (@value{GDBP}) watch 0x600850
4151 Cannot watch constant value 0x600850.
4152 (@value{GDBP}) watch *(int *) 0x600850
4153 Watchpoint 1: *(int *) 6293584
4156 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4157 watchpoints execute very quickly, and the debugger reports a change in
4158 value at the exact instruction where the change occurs. If @value{GDBN}
4159 cannot set a hardware watchpoint, it sets a software watchpoint, which
4160 executes more slowly and reports the change in value at the next
4161 @emph{statement}, not the instruction, after the change occurs.
4163 @cindex use only software watchpoints
4164 You can force @value{GDBN} to use only software watchpoints with the
4165 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4166 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4167 the underlying system supports them. (Note that hardware-assisted
4168 watchpoints that were set @emph{before} setting
4169 @code{can-use-hw-watchpoints} to zero will still use the hardware
4170 mechanism of watching expression values.)
4173 @item set can-use-hw-watchpoints
4174 @kindex set can-use-hw-watchpoints
4175 Set whether or not to use hardware watchpoints.
4177 @item show can-use-hw-watchpoints
4178 @kindex show can-use-hw-watchpoints
4179 Show the current mode of using hardware watchpoints.
4182 For remote targets, you can restrict the number of hardware
4183 watchpoints @value{GDBN} will use, see @ref{set remote
4184 hardware-breakpoint-limit}.
4186 When you issue the @code{watch} command, @value{GDBN} reports
4189 Hardware watchpoint @var{num}: @var{expr}
4193 if it was able to set a hardware watchpoint.
4195 Currently, the @code{awatch} and @code{rwatch} commands can only set
4196 hardware watchpoints, because accesses to data that don't change the
4197 value of the watched expression cannot be detected without examining
4198 every instruction as it is being executed, and @value{GDBN} does not do
4199 that currently. If @value{GDBN} finds that it is unable to set a
4200 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4201 will print a message like this:
4204 Expression cannot be implemented with read/access watchpoint.
4207 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4208 data type of the watched expression is wider than what a hardware
4209 watchpoint on the target machine can handle. For example, some systems
4210 can only watch regions that are up to 4 bytes wide; on such systems you
4211 cannot set hardware watchpoints for an expression that yields a
4212 double-precision floating-point number (which is typically 8 bytes
4213 wide). As a work-around, it might be possible to break the large region
4214 into a series of smaller ones and watch them with separate watchpoints.
4216 If you set too many hardware watchpoints, @value{GDBN} might be unable
4217 to insert all of them when you resume the execution of your program.
4218 Since the precise number of active watchpoints is unknown until such
4219 time as the program is about to be resumed, @value{GDBN} might not be
4220 able to warn you about this when you set the watchpoints, and the
4221 warning will be printed only when the program is resumed:
4224 Hardware watchpoint @var{num}: Could not insert watchpoint
4228 If this happens, delete or disable some of the watchpoints.
4230 Watching complex expressions that reference many variables can also
4231 exhaust the resources available for hardware-assisted watchpoints.
4232 That's because @value{GDBN} needs to watch every variable in the
4233 expression with separately allocated resources.
4235 If you call a function interactively using @code{print} or @code{call},
4236 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4237 kind of breakpoint or the call completes.
4239 @value{GDBN} automatically deletes watchpoints that watch local
4240 (automatic) variables, or expressions that involve such variables, when
4241 they go out of scope, that is, when the execution leaves the block in
4242 which these variables were defined. In particular, when the program
4243 being debugged terminates, @emph{all} local variables go out of scope,
4244 and so only watchpoints that watch global variables remain set. If you
4245 rerun the program, you will need to set all such watchpoints again. One
4246 way of doing that would be to set a code breakpoint at the entry to the
4247 @code{main} function and when it breaks, set all the watchpoints.
4249 @cindex watchpoints and threads
4250 @cindex threads and watchpoints
4251 In multi-threaded programs, watchpoints will detect changes to the
4252 watched expression from every thread.
4255 @emph{Warning:} In multi-threaded programs, software watchpoints
4256 have only limited usefulness. If @value{GDBN} creates a software
4257 watchpoint, it can only watch the value of an expression @emph{in a
4258 single thread}. If you are confident that the expression can only
4259 change due to the current thread's activity (and if you are also
4260 confident that no other thread can become current), then you can use
4261 software watchpoints as usual. However, @value{GDBN} may not notice
4262 when a non-current thread's activity changes the expression. (Hardware
4263 watchpoints, in contrast, watch an expression in all threads.)
4266 @xref{set remote hardware-watchpoint-limit}.
4268 @node Set Catchpoints
4269 @subsection Setting Catchpoints
4270 @cindex catchpoints, setting
4271 @cindex exception handlers
4272 @cindex event handling
4274 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4275 kinds of program events, such as C@t{++} exceptions or the loading of a
4276 shared library. Use the @code{catch} command to set a catchpoint.
4280 @item catch @var{event}
4281 Stop when @var{event} occurs. The @var{event} can be any of the following:
4284 @item throw @r{[}@var{regexp}@r{]}
4285 @itemx rethrow @r{[}@var{regexp}@r{]}
4286 @itemx catch @r{[}@var{regexp}@r{]}
4288 @kindex catch rethrow
4290 @cindex stop on C@t{++} exceptions
4291 The throwing, re-throwing, or catching of a C@t{++} exception.
4293 If @var{regexp} is given, then only exceptions whose type matches the
4294 regular expression will be caught.
4296 @vindex $_exception@r{, convenience variable}
4297 The convenience variable @code{$_exception} is available at an
4298 exception-related catchpoint, on some systems. This holds the
4299 exception being thrown.
4301 There are currently some limitations to C@t{++} exception handling in
4306 The support for these commands is system-dependent. Currently, only
4307 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4311 The regular expression feature and the @code{$_exception} convenience
4312 variable rely on the presence of some SDT probes in @code{libstdc++}.
4313 If these probes are not present, then these features cannot be used.
4314 These probes were first available in the GCC 4.8 release, but whether
4315 or not they are available in your GCC also depends on how it was
4319 The @code{$_exception} convenience variable is only valid at the
4320 instruction at which an exception-related catchpoint is set.
4323 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4324 location in the system library which implements runtime exception
4325 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4326 (@pxref{Selection}) to get to your code.
4329 If you call a function interactively, @value{GDBN} normally returns
4330 control to you when the function has finished executing. If the call
4331 raises an exception, however, the call may bypass the mechanism that
4332 returns control to you and cause your program either to abort or to
4333 simply continue running until it hits a breakpoint, catches a signal
4334 that @value{GDBN} is listening for, or exits. This is the case even if
4335 you set a catchpoint for the exception; catchpoints on exceptions are
4336 disabled within interactive calls. @xref{Calling}, for information on
4337 controlling this with @code{set unwind-on-terminating-exception}.
4340 You cannot raise an exception interactively.
4343 You cannot install an exception handler interactively.
4347 @kindex catch exception
4348 @cindex Ada exception catching
4349 @cindex catch Ada exceptions
4350 An Ada exception being raised. If an exception name is specified
4351 at the end of the command (eg @code{catch exception Program_Error}),
4352 the debugger will stop only when this specific exception is raised.
4353 Otherwise, the debugger stops execution when any Ada exception is raised.
4355 When inserting an exception catchpoint on a user-defined exception whose
4356 name is identical to one of the exceptions defined by the language, the
4357 fully qualified name must be used as the exception name. Otherwise,
4358 @value{GDBN} will assume that it should stop on the pre-defined exception
4359 rather than the user-defined one. For instance, assuming an exception
4360 called @code{Constraint_Error} is defined in package @code{Pck}, then
4361 the command to use to catch such exceptions is @kbd{catch exception
4362 Pck.Constraint_Error}.
4364 @item exception unhandled
4365 @kindex catch exception unhandled
4366 An exception that was raised but is not handled by the program.
4369 @kindex catch assert
4370 A failed Ada assertion.
4374 @cindex break on fork/exec
4375 A call to @code{exec}.
4378 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4379 @kindex catch syscall
4380 @cindex break on a system call.
4381 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4382 syscall is a mechanism for application programs to request a service
4383 from the operating system (OS) or one of the OS system services.
4384 @value{GDBN} can catch some or all of the syscalls issued by the
4385 debuggee, and show the related information for each syscall. If no
4386 argument is specified, calls to and returns from all system calls
4389 @var{name} can be any system call name that is valid for the
4390 underlying OS. Just what syscalls are valid depends on the OS. On
4391 GNU and Unix systems, you can find the full list of valid syscall
4392 names on @file{/usr/include/asm/unistd.h}.
4394 @c For MS-Windows, the syscall names and the corresponding numbers
4395 @c can be found, e.g., on this URL:
4396 @c http://www.metasploit.com/users/opcode/syscalls.html
4397 @c but we don't support Windows syscalls yet.
4399 Normally, @value{GDBN} knows in advance which syscalls are valid for
4400 each OS, so you can use the @value{GDBN} command-line completion
4401 facilities (@pxref{Completion,, command completion}) to list the
4404 You may also specify the system call numerically. A syscall's
4405 number is the value passed to the OS's syscall dispatcher to
4406 identify the requested service. When you specify the syscall by its
4407 name, @value{GDBN} uses its database of syscalls to convert the name
4408 into the corresponding numeric code, but using the number directly
4409 may be useful if @value{GDBN}'s database does not have the complete
4410 list of syscalls on your system (e.g., because @value{GDBN} lags
4411 behind the OS upgrades).
4413 The example below illustrates how this command works if you don't provide
4417 (@value{GDBP}) catch syscall
4418 Catchpoint 1 (syscall)
4420 Starting program: /tmp/catch-syscall
4422 Catchpoint 1 (call to syscall 'close'), \
4423 0xffffe424 in __kernel_vsyscall ()
4427 Catchpoint 1 (returned from syscall 'close'), \
4428 0xffffe424 in __kernel_vsyscall ()
4432 Here is an example of catching a system call by name:
4435 (@value{GDBP}) catch syscall chroot
4436 Catchpoint 1 (syscall 'chroot' [61])
4438 Starting program: /tmp/catch-syscall
4440 Catchpoint 1 (call to syscall 'chroot'), \
4441 0xffffe424 in __kernel_vsyscall ()
4445 Catchpoint 1 (returned from syscall 'chroot'), \
4446 0xffffe424 in __kernel_vsyscall ()
4450 An example of specifying a system call numerically. In the case
4451 below, the syscall number has a corresponding entry in the XML
4452 file, so @value{GDBN} finds its name and prints it:
4455 (@value{GDBP}) catch syscall 252
4456 Catchpoint 1 (syscall(s) 'exit_group')
4458 Starting program: /tmp/catch-syscall
4460 Catchpoint 1 (call to syscall 'exit_group'), \
4461 0xffffe424 in __kernel_vsyscall ()
4465 Program exited normally.
4469 However, there can be situations when there is no corresponding name
4470 in XML file for that syscall number. In this case, @value{GDBN} prints
4471 a warning message saying that it was not able to find the syscall name,
4472 but the catchpoint will be set anyway. See the example below:
4475 (@value{GDBP}) catch syscall 764
4476 warning: The number '764' does not represent a known syscall.
4477 Catchpoint 2 (syscall 764)
4481 If you configure @value{GDBN} using the @samp{--without-expat} option,
4482 it will not be able to display syscall names. Also, if your
4483 architecture does not have an XML file describing its system calls,
4484 you will not be able to see the syscall names. It is important to
4485 notice that these two features are used for accessing the syscall
4486 name database. In either case, you will see a warning like this:
4489 (@value{GDBP}) catch syscall
4490 warning: Could not open "syscalls/i386-linux.xml"
4491 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4492 GDB will not be able to display syscall names.
4493 Catchpoint 1 (syscall)
4497 Of course, the file name will change depending on your architecture and system.
4499 Still using the example above, you can also try to catch a syscall by its
4500 number. In this case, you would see something like:
4503 (@value{GDBP}) catch syscall 252
4504 Catchpoint 1 (syscall(s) 252)
4507 Again, in this case @value{GDBN} would not be able to display syscall's names.
4511 A call to @code{fork}.
4515 A call to @code{vfork}.
4517 @item load @r{[}regexp@r{]}
4518 @itemx unload @r{[}regexp@r{]}
4520 @kindex catch unload
4521 The loading or unloading of a shared library. If @var{regexp} is
4522 given, then the catchpoint will stop only if the regular expression
4523 matches one of the affected libraries.
4525 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4526 @kindex catch signal
4527 The delivery of a signal.
4529 With no arguments, this catchpoint will catch any signal that is not
4530 used internally by @value{GDBN}, specifically, all signals except
4531 @samp{SIGTRAP} and @samp{SIGINT}.
4533 With the argument @samp{all}, all signals, including those used by
4534 @value{GDBN}, will be caught. This argument cannot be used with other
4537 Otherwise, the arguments are a list of signal names as given to
4538 @code{handle} (@pxref{Signals}). Only signals specified in this list
4541 One reason that @code{catch signal} can be more useful than
4542 @code{handle} is that you can attach commands and conditions to the
4545 When a signal is caught by a catchpoint, the signal's @code{stop} and
4546 @code{print} settings, as specified by @code{handle}, are ignored.
4547 However, whether the signal is still delivered to the inferior depends
4548 on the @code{pass} setting; this can be changed in the catchpoint's
4553 @item tcatch @var{event}
4555 Set a catchpoint that is enabled only for one stop. The catchpoint is
4556 automatically deleted after the first time the event is caught.
4560 Use the @code{info break} command to list the current catchpoints.
4564 @subsection Deleting Breakpoints
4566 @cindex clearing breakpoints, watchpoints, catchpoints
4567 @cindex deleting breakpoints, watchpoints, catchpoints
4568 It is often necessary to eliminate a breakpoint, watchpoint, or
4569 catchpoint once it has done its job and you no longer want your program
4570 to stop there. This is called @dfn{deleting} the breakpoint. A
4571 breakpoint that has been deleted no longer exists; it is forgotten.
4573 With the @code{clear} command you can delete breakpoints according to
4574 where they are in your program. With the @code{delete} command you can
4575 delete individual breakpoints, watchpoints, or catchpoints by specifying
4576 their breakpoint numbers.
4578 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4579 automatically ignores breakpoints on the first instruction to be executed
4580 when you continue execution without changing the execution address.
4585 Delete any breakpoints at the next instruction to be executed in the
4586 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4587 the innermost frame is selected, this is a good way to delete a
4588 breakpoint where your program just stopped.
4590 @item clear @var{location}
4591 Delete any breakpoints set at the specified @var{location}.
4592 @xref{Specify Location}, for the various forms of @var{location}; the
4593 most useful ones are listed below:
4596 @item clear @var{function}
4597 @itemx clear @var{filename}:@var{function}
4598 Delete any breakpoints set at entry to the named @var{function}.
4600 @item clear @var{linenum}
4601 @itemx clear @var{filename}:@var{linenum}
4602 Delete any breakpoints set at or within the code of the specified
4603 @var{linenum} of the specified @var{filename}.
4606 @cindex delete breakpoints
4608 @kindex d @r{(@code{delete})}
4609 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4610 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4611 ranges specified as arguments. If no argument is specified, delete all
4612 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4613 confirm off}). You can abbreviate this command as @code{d}.
4617 @subsection Disabling Breakpoints
4619 @cindex enable/disable a breakpoint
4620 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4621 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4622 it had been deleted, but remembers the information on the breakpoint so
4623 that you can @dfn{enable} it again later.
4625 You disable and enable breakpoints, watchpoints, and catchpoints with
4626 the @code{enable} and @code{disable} commands, optionally specifying
4627 one or more breakpoint numbers as arguments. Use @code{info break} to
4628 print a list of all breakpoints, watchpoints, and catchpoints if you
4629 do not know which numbers to use.
4631 Disabling and enabling a breakpoint that has multiple locations
4632 affects all of its locations.
4634 A breakpoint, watchpoint, or catchpoint can have any of several
4635 different states of enablement:
4639 Enabled. The breakpoint stops your program. A breakpoint set
4640 with the @code{break} command starts out in this state.
4642 Disabled. The breakpoint has no effect on your program.
4644 Enabled once. The breakpoint stops your program, but then becomes
4647 Enabled for a count. The breakpoint stops your program for the next
4648 N times, then becomes disabled.
4650 Enabled for deletion. The breakpoint stops your program, but
4651 immediately after it does so it is deleted permanently. A breakpoint
4652 set with the @code{tbreak} command starts out in this state.
4655 You can use the following commands to enable or disable breakpoints,
4656 watchpoints, and catchpoints:
4660 @kindex dis @r{(@code{disable})}
4661 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4662 Disable the specified breakpoints---or all breakpoints, if none are
4663 listed. A disabled breakpoint has no effect but is not forgotten. All
4664 options such as ignore-counts, conditions and commands are remembered in
4665 case the breakpoint is enabled again later. You may abbreviate
4666 @code{disable} as @code{dis}.
4669 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4670 Enable the specified breakpoints (or all defined breakpoints). They
4671 become effective once again in stopping your program.
4673 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4674 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4675 of these breakpoints immediately after stopping your program.
4677 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4678 Enable the specified breakpoints temporarily. @value{GDBN} records
4679 @var{count} with each of the specified breakpoints, and decrements a
4680 breakpoint's count when it is hit. When any count reaches 0,
4681 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4682 count (@pxref{Conditions, ,Break Conditions}), that will be
4683 decremented to 0 before @var{count} is affected.
4685 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4686 Enable the specified breakpoints to work once, then die. @value{GDBN}
4687 deletes any of these breakpoints as soon as your program stops there.
4688 Breakpoints set by the @code{tbreak} command start out in this state.
4691 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4692 @c confusing: tbreak is also initially enabled.
4693 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4694 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4695 subsequently, they become disabled or enabled only when you use one of
4696 the commands above. (The command @code{until} can set and delete a
4697 breakpoint of its own, but it does not change the state of your other
4698 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4702 @subsection Break Conditions
4703 @cindex conditional breakpoints
4704 @cindex breakpoint conditions
4706 @c FIXME what is scope of break condition expr? Context where wanted?
4707 @c in particular for a watchpoint?
4708 The simplest sort of breakpoint breaks every time your program reaches a
4709 specified place. You can also specify a @dfn{condition} for a
4710 breakpoint. A condition is just a Boolean expression in your
4711 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4712 a condition evaluates the expression each time your program reaches it,
4713 and your program stops only if the condition is @emph{true}.
4715 This is the converse of using assertions for program validation; in that
4716 situation, you want to stop when the assertion is violated---that is,
4717 when the condition is false. In C, if you want to test an assertion expressed
4718 by the condition @var{assert}, you should set the condition
4719 @samp{! @var{assert}} on the appropriate breakpoint.
4721 Conditions are also accepted for watchpoints; you may not need them,
4722 since a watchpoint is inspecting the value of an expression anyhow---but
4723 it might be simpler, say, to just set a watchpoint on a variable name,
4724 and specify a condition that tests whether the new value is an interesting
4727 Break conditions can have side effects, and may even call functions in
4728 your program. This can be useful, for example, to activate functions
4729 that log program progress, or to use your own print functions to
4730 format special data structures. The effects are completely predictable
4731 unless there is another enabled breakpoint at the same address. (In
4732 that case, @value{GDBN} might see the other breakpoint first and stop your
4733 program without checking the condition of this one.) Note that
4734 breakpoint commands are usually more convenient and flexible than break
4736 purpose of performing side effects when a breakpoint is reached
4737 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4739 Breakpoint conditions can also be evaluated on the target's side if
4740 the target supports it. Instead of evaluating the conditions locally,
4741 @value{GDBN} encodes the expression into an agent expression
4742 (@pxref{Agent Expressions}) suitable for execution on the target,
4743 independently of @value{GDBN}. Global variables become raw memory
4744 locations, locals become stack accesses, and so forth.
4746 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4747 when its condition evaluates to true. This mechanism may provide faster
4748 response times depending on the performance characteristics of the target
4749 since it does not need to keep @value{GDBN} informed about
4750 every breakpoint trigger, even those with false conditions.
4752 Break conditions can be specified when a breakpoint is set, by using
4753 @samp{if} in the arguments to the @code{break} command. @xref{Set
4754 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4755 with the @code{condition} command.
4757 You can also use the @code{if} keyword with the @code{watch} command.
4758 The @code{catch} command does not recognize the @code{if} keyword;
4759 @code{condition} is the only way to impose a further condition on a
4764 @item condition @var{bnum} @var{expression}
4765 Specify @var{expression} as the break condition for breakpoint,
4766 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4767 breakpoint @var{bnum} stops your program only if the value of
4768 @var{expression} is true (nonzero, in C). When you use
4769 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4770 syntactic correctness, and to determine whether symbols in it have
4771 referents in the context of your breakpoint. If @var{expression} uses
4772 symbols not referenced in the context of the breakpoint, @value{GDBN}
4773 prints an error message:
4776 No symbol "foo" in current context.
4781 not actually evaluate @var{expression} at the time the @code{condition}
4782 command (or a command that sets a breakpoint with a condition, like
4783 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4785 @item condition @var{bnum}
4786 Remove the condition from breakpoint number @var{bnum}. It becomes
4787 an ordinary unconditional breakpoint.
4790 @cindex ignore count (of breakpoint)
4791 A special case of a breakpoint condition is to stop only when the
4792 breakpoint has been reached a certain number of times. This is so
4793 useful that there is a special way to do it, using the @dfn{ignore
4794 count} of the breakpoint. Every breakpoint has an ignore count, which
4795 is an integer. Most of the time, the ignore count is zero, and
4796 therefore has no effect. But if your program reaches a breakpoint whose
4797 ignore count is positive, then instead of stopping, it just decrements
4798 the ignore count by one and continues. As a result, if the ignore count
4799 value is @var{n}, the breakpoint does not stop the next @var{n} times
4800 your program reaches it.
4804 @item ignore @var{bnum} @var{count}
4805 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4806 The next @var{count} times the breakpoint is reached, your program's
4807 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4810 To make the breakpoint stop the next time it is reached, specify
4813 When you use @code{continue} to resume execution of your program from a
4814 breakpoint, you can specify an ignore count directly as an argument to
4815 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4816 Stepping,,Continuing and Stepping}.
4818 If a breakpoint has a positive ignore count and a condition, the
4819 condition is not checked. Once the ignore count reaches zero,
4820 @value{GDBN} resumes checking the condition.
4822 You could achieve the effect of the ignore count with a condition such
4823 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4824 is decremented each time. @xref{Convenience Vars, ,Convenience
4828 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4831 @node Break Commands
4832 @subsection Breakpoint Command Lists
4834 @cindex breakpoint commands
4835 You can give any breakpoint (or watchpoint or catchpoint) a series of
4836 commands to execute when your program stops due to that breakpoint. For
4837 example, you might want to print the values of certain expressions, or
4838 enable other breakpoints.
4842 @kindex end@r{ (breakpoint commands)}
4843 @item commands @r{[}@var{range}@dots{}@r{]}
4844 @itemx @dots{} @var{command-list} @dots{}
4846 Specify a list of commands for the given breakpoints. The commands
4847 themselves appear on the following lines. Type a line containing just
4848 @code{end} to terminate the commands.
4850 To remove all commands from a breakpoint, type @code{commands} and
4851 follow it immediately with @code{end}; that is, give no commands.
4853 With no argument, @code{commands} refers to the last breakpoint,
4854 watchpoint, or catchpoint set (not to the breakpoint most recently
4855 encountered). If the most recent breakpoints were set with a single
4856 command, then the @code{commands} will apply to all the breakpoints
4857 set by that command. This applies to breakpoints set by
4858 @code{rbreak}, and also applies when a single @code{break} command
4859 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4863 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4864 disabled within a @var{command-list}.
4866 You can use breakpoint commands to start your program up again. Simply
4867 use the @code{continue} command, or @code{step}, or any other command
4868 that resumes execution.
4870 Any other commands in the command list, after a command that resumes
4871 execution, are ignored. This is because any time you resume execution
4872 (even with a simple @code{next} or @code{step}), you may encounter
4873 another breakpoint---which could have its own command list, leading to
4874 ambiguities about which list to execute.
4877 If the first command you specify in a command list is @code{silent}, the
4878 usual message about stopping at a breakpoint is not printed. This may
4879 be desirable for breakpoints that are to print a specific message and
4880 then continue. If none of the remaining commands print anything, you
4881 see no sign that the breakpoint was reached. @code{silent} is
4882 meaningful only at the beginning of a breakpoint command list.
4884 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4885 print precisely controlled output, and are often useful in silent
4886 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4888 For example, here is how you could use breakpoint commands to print the
4889 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4895 printf "x is %d\n",x
4900 One application for breakpoint commands is to compensate for one bug so
4901 you can test for another. Put a breakpoint just after the erroneous line
4902 of code, give it a condition to detect the case in which something
4903 erroneous has been done, and give it commands to assign correct values
4904 to any variables that need them. End with the @code{continue} command
4905 so that your program does not stop, and start with the @code{silent}
4906 command so that no output is produced. Here is an example:
4917 @node Dynamic Printf
4918 @subsection Dynamic Printf
4920 @cindex dynamic printf
4922 The dynamic printf command @code{dprintf} combines a breakpoint with
4923 formatted printing of your program's data to give you the effect of
4924 inserting @code{printf} calls into your program on-the-fly, without
4925 having to recompile it.
4927 In its most basic form, the output goes to the GDB console. However,
4928 you can set the variable @code{dprintf-style} for alternate handling.
4929 For instance, you can ask to format the output by calling your
4930 program's @code{printf} function. This has the advantage that the
4931 characters go to the program's output device, so they can recorded in
4932 redirects to files and so forth.
4934 If you are doing remote debugging with a stub or agent, you can also
4935 ask to have the printf handled by the remote agent. In addition to
4936 ensuring that the output goes to the remote program's device along
4937 with any other output the program might produce, you can also ask that
4938 the dprintf remain active even after disconnecting from the remote
4939 target. Using the stub/agent is also more efficient, as it can do
4940 everything without needing to communicate with @value{GDBN}.
4944 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4945 Whenever execution reaches @var{location}, print the values of one or
4946 more @var{expressions} under the control of the string @var{template}.
4947 To print several values, separate them with commas.
4949 @item set dprintf-style @var{style}
4950 Set the dprintf output to be handled in one of several different
4951 styles enumerated below. A change of style affects all existing
4952 dynamic printfs immediately. (If you need individual control over the
4953 print commands, simply define normal breakpoints with
4954 explicitly-supplied command lists.)
4957 @kindex dprintf-style gdb
4958 Handle the output using the @value{GDBN} @code{printf} command.
4961 @kindex dprintf-style call
4962 Handle the output by calling a function in your program (normally
4966 @kindex dprintf-style agent
4967 Have the remote debugging agent (such as @code{gdbserver}) handle
4968 the output itself. This style is only available for agents that
4969 support running commands on the target.
4971 @item set dprintf-function @var{function}
4972 Set the function to call if the dprintf style is @code{call}. By
4973 default its value is @code{printf}. You may set it to any expression.
4974 that @value{GDBN} can evaluate to a function, as per the @code{call}
4977 @item set dprintf-channel @var{channel}
4978 Set a ``channel'' for dprintf. If set to a non-empty value,
4979 @value{GDBN} will evaluate it as an expression and pass the result as
4980 a first argument to the @code{dprintf-function}, in the manner of
4981 @code{fprintf} and similar functions. Otherwise, the dprintf format
4982 string will be the first argument, in the manner of @code{printf}.
4984 As an example, if you wanted @code{dprintf} output to go to a logfile
4985 that is a standard I/O stream assigned to the variable @code{mylog},
4986 you could do the following:
4989 (gdb) set dprintf-style call
4990 (gdb) set dprintf-function fprintf
4991 (gdb) set dprintf-channel mylog
4992 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4993 Dprintf 1 at 0x123456: file main.c, line 25.
4995 1 dprintf keep y 0x00123456 in main at main.c:25
4996 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
5001 Note that the @code{info break} displays the dynamic printf commands
5002 as normal breakpoint commands; you can thus easily see the effect of
5003 the variable settings.
5005 @item set disconnected-dprintf on
5006 @itemx set disconnected-dprintf off
5007 @kindex set disconnected-dprintf
5008 Choose whether @code{dprintf} commands should continue to run if
5009 @value{GDBN} has disconnected from the target. This only applies
5010 if the @code{dprintf-style} is @code{agent}.
5012 @item show disconnected-dprintf off
5013 @kindex show disconnected-dprintf
5014 Show the current choice for disconnected @code{dprintf}.
5018 @value{GDBN} does not check the validity of function and channel,
5019 relying on you to supply values that are meaningful for the contexts
5020 in which they are being used. For instance, the function and channel
5021 may be the values of local variables, but if that is the case, then
5022 all enabled dynamic prints must be at locations within the scope of
5023 those locals. If evaluation fails, @value{GDBN} will report an error.
5025 @node Save Breakpoints
5026 @subsection How to save breakpoints to a file
5028 To save breakpoint definitions to a file use the @w{@code{save
5029 breakpoints}} command.
5032 @kindex save breakpoints
5033 @cindex save breakpoints to a file for future sessions
5034 @item save breakpoints [@var{filename}]
5035 This command saves all current breakpoint definitions together with
5036 their commands and ignore counts, into a file @file{@var{filename}}
5037 suitable for use in a later debugging session. This includes all
5038 types of breakpoints (breakpoints, watchpoints, catchpoints,
5039 tracepoints). To read the saved breakpoint definitions, use the
5040 @code{source} command (@pxref{Command Files}). Note that watchpoints
5041 with expressions involving local variables may fail to be recreated
5042 because it may not be possible to access the context where the
5043 watchpoint is valid anymore. Because the saved breakpoint definitions
5044 are simply a sequence of @value{GDBN} commands that recreate the
5045 breakpoints, you can edit the file in your favorite editing program,
5046 and remove the breakpoint definitions you're not interested in, or
5047 that can no longer be recreated.
5050 @node Static Probe Points
5051 @subsection Static Probe Points
5053 @cindex static probe point, SystemTap
5054 @cindex static probe point, DTrace
5055 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
5056 for Statically Defined Tracing, and the probes are designed to have a tiny
5057 runtime code and data footprint, and no dynamic relocations.
5059 Currently, the following types of probes are supported on
5060 ELF-compatible systems:
5064 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
5065 @acronym{SDT} probes@footnote{See
5066 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
5067 for more information on how to add @code{SystemTap} @acronym{SDT}
5068 probes in your applications.}. @code{SystemTap} probes are usable
5069 from assembly, C and C@t{++} languages@footnote{See
5070 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
5071 for a good reference on how the @acronym{SDT} probes are implemented.}.
5073 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
5074 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
5078 @cindex semaphores on static probe points
5079 Some @code{SystemTap} probes have an associated semaphore variable;
5080 for instance, this happens automatically if you defined your probe
5081 using a DTrace-style @file{.d} file. If your probe has a semaphore,
5082 @value{GDBN} will automatically enable it when you specify a
5083 breakpoint using the @samp{-probe-stap} notation. But, if you put a
5084 breakpoint at a probe's location by some other method (e.g.,
5085 @code{break file:line}), then @value{GDBN} will not automatically set
5086 the semaphore. @code{DTrace} probes do not support semaphores.
5088 You can examine the available static static probes using @code{info
5089 probes}, with optional arguments:
5093 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5094 If given, @var{type} is either @code{stap} for listing
5095 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5096 probes. If omitted all probes are listed regardless of their types.
5098 If given, @var{provider} is a regular expression used to match against provider
5099 names when selecting which probes to list. If omitted, probes by all
5100 probes from all providers are listed.
5102 If given, @var{name} is a regular expression to match against probe names
5103 when selecting which probes to list. If omitted, probe names are not
5104 considered when deciding whether to display them.
5106 If given, @var{objfile} is a regular expression used to select which
5107 object files (executable or shared libraries) to examine. If not
5108 given, all object files are considered.
5110 @item info probes all
5111 List the available static probes, from all types.
5114 @cindex enabling and disabling probes
5115 Some probe points can be enabled and/or disabled. The effect of
5116 enabling or disabling a probe depends on the type of probe being
5117 handled. Some @code{DTrace} probes can be enabled or
5118 disabled, but @code{SystemTap} probes cannot be disabled.
5120 You can enable (or disable) one or more probes using the following
5121 commands, with optional arguments:
5124 @kindex enable probes
5125 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5126 If given, @var{provider} is a regular expression used to match against
5127 provider names when selecting which probes to enable. If omitted,
5128 all probes from all providers are enabled.
5130 If given, @var{name} is a regular expression to match against probe
5131 names when selecting which probes to enable. If omitted, probe names
5132 are not considered when deciding whether to enable them.
5134 If given, @var{objfile} is a regular expression used to select which
5135 object files (executable or shared libraries) to examine. If not
5136 given, all object files are considered.
5138 @kindex disable probes
5139 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5140 See the @code{enable probes} command above for a description of the
5141 optional arguments accepted by this command.
5144 @vindex $_probe_arg@r{, convenience variable}
5145 A probe may specify up to twelve arguments. These are available at the
5146 point at which the probe is defined---that is, when the current PC is
5147 at the probe's location. The arguments are available using the
5148 convenience variables (@pxref{Convenience Vars})
5149 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5150 probes each probe argument is an integer of the appropriate size;
5151 types are not preserved. In @code{DTrace} probes types are preserved
5152 provided that they are recognized as such by @value{GDBN}; otherwise
5153 the value of the probe argument will be a long integer. The
5154 convenience variable @code{$_probe_argc} holds the number of arguments
5155 at the current probe point.
5157 These variables are always available, but attempts to access them at
5158 any location other than a probe point will cause @value{GDBN} to give
5162 @c @ifclear BARETARGET
5163 @node Error in Breakpoints
5164 @subsection ``Cannot insert breakpoints''
5166 If you request too many active hardware-assisted breakpoints and
5167 watchpoints, you will see this error message:
5169 @c FIXME: the precise wording of this message may change; the relevant
5170 @c source change is not committed yet (Sep 3, 1999).
5172 Stopped; cannot insert breakpoints.
5173 You may have requested too many hardware breakpoints and watchpoints.
5177 This message is printed when you attempt to resume the program, since
5178 only then @value{GDBN} knows exactly how many hardware breakpoints and
5179 watchpoints it needs to insert.
5181 When this message is printed, you need to disable or remove some of the
5182 hardware-assisted breakpoints and watchpoints, and then continue.
5184 @node Breakpoint-related Warnings
5185 @subsection ``Breakpoint address adjusted...''
5186 @cindex breakpoint address adjusted
5188 Some processor architectures place constraints on the addresses at
5189 which breakpoints may be placed. For architectures thus constrained,
5190 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5191 with the constraints dictated by the architecture.
5193 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5194 a VLIW architecture in which a number of RISC-like instructions may be
5195 bundled together for parallel execution. The FR-V architecture
5196 constrains the location of a breakpoint instruction within such a
5197 bundle to the instruction with the lowest address. @value{GDBN}
5198 honors this constraint by adjusting a breakpoint's address to the
5199 first in the bundle.
5201 It is not uncommon for optimized code to have bundles which contain
5202 instructions from different source statements, thus it may happen that
5203 a breakpoint's address will be adjusted from one source statement to
5204 another. Since this adjustment may significantly alter @value{GDBN}'s
5205 breakpoint related behavior from what the user expects, a warning is
5206 printed when the breakpoint is first set and also when the breakpoint
5209 A warning like the one below is printed when setting a breakpoint
5210 that's been subject to address adjustment:
5213 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5216 Such warnings are printed both for user settable and @value{GDBN}'s
5217 internal breakpoints. If you see one of these warnings, you should
5218 verify that a breakpoint set at the adjusted address will have the
5219 desired affect. If not, the breakpoint in question may be removed and
5220 other breakpoints may be set which will have the desired behavior.
5221 E.g., it may be sufficient to place the breakpoint at a later
5222 instruction. A conditional breakpoint may also be useful in some
5223 cases to prevent the breakpoint from triggering too often.
5225 @value{GDBN} will also issue a warning when stopping at one of these
5226 adjusted breakpoints:
5229 warning: Breakpoint 1 address previously adjusted from 0x00010414
5233 When this warning is encountered, it may be too late to take remedial
5234 action except in cases where the breakpoint is hit earlier or more
5235 frequently than expected.
5237 @node Continuing and Stepping
5238 @section Continuing and Stepping
5242 @cindex resuming execution
5243 @dfn{Continuing} means resuming program execution until your program
5244 completes normally. In contrast, @dfn{stepping} means executing just
5245 one more ``step'' of your program, where ``step'' may mean either one
5246 line of source code, or one machine instruction (depending on what
5247 particular command you use). Either when continuing or when stepping,
5248 your program may stop even sooner, due to a breakpoint or a signal. (If
5249 it stops due to a signal, you may want to use @code{handle}, or use
5250 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5251 or you may step into the signal's handler (@pxref{stepping and signal
5256 @kindex c @r{(@code{continue})}
5257 @kindex fg @r{(resume foreground execution)}
5258 @item continue @r{[}@var{ignore-count}@r{]}
5259 @itemx c @r{[}@var{ignore-count}@r{]}
5260 @itemx fg @r{[}@var{ignore-count}@r{]}
5261 Resume program execution, at the address where your program last stopped;
5262 any breakpoints set at that address are bypassed. The optional argument
5263 @var{ignore-count} allows you to specify a further number of times to
5264 ignore a breakpoint at this location; its effect is like that of
5265 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5267 The argument @var{ignore-count} is meaningful only when your program
5268 stopped due to a breakpoint. At other times, the argument to
5269 @code{continue} is ignored.
5271 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5272 debugged program is deemed to be the foreground program) are provided
5273 purely for convenience, and have exactly the same behavior as
5277 To resume execution at a different place, you can use @code{return}
5278 (@pxref{Returning, ,Returning from a Function}) to go back to the
5279 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5280 Different Address}) to go to an arbitrary location in your program.
5282 A typical technique for using stepping is to set a breakpoint
5283 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5284 beginning of the function or the section of your program where a problem
5285 is believed to lie, run your program until it stops at that breakpoint,
5286 and then step through the suspect area, examining the variables that are
5287 interesting, until you see the problem happen.
5291 @kindex s @r{(@code{step})}
5293 Continue running your program until control reaches a different source
5294 line, then stop it and return control to @value{GDBN}. This command is
5295 abbreviated @code{s}.
5298 @c "without debugging information" is imprecise; actually "without line
5299 @c numbers in the debugging information". (gcc -g1 has debugging info but
5300 @c not line numbers). But it seems complex to try to make that
5301 @c distinction here.
5302 @emph{Warning:} If you use the @code{step} command while control is
5303 within a function that was compiled without debugging information,
5304 execution proceeds until control reaches a function that does have
5305 debugging information. Likewise, it will not step into a function which
5306 is compiled without debugging information. To step through functions
5307 without debugging information, use the @code{stepi} command, described
5311 The @code{step} command only stops at the first instruction of a source
5312 line. This prevents the multiple stops that could otherwise occur in
5313 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5314 to stop if a function that has debugging information is called within
5315 the line. In other words, @code{step} @emph{steps inside} any functions
5316 called within the line.
5318 Also, the @code{step} command only enters a function if there is line
5319 number information for the function. Otherwise it acts like the
5320 @code{next} command. This avoids problems when using @code{cc -gl}
5321 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5322 was any debugging information about the routine.
5324 @item step @var{count}
5325 Continue running as in @code{step}, but do so @var{count} times. If a
5326 breakpoint is reached, or a signal not related to stepping occurs before
5327 @var{count} steps, stepping stops right away.
5330 @kindex n @r{(@code{next})}
5331 @item next @r{[}@var{count}@r{]}
5332 Continue to the next source line in the current (innermost) stack frame.
5333 This is similar to @code{step}, but function calls that appear within
5334 the line of code are executed without stopping. Execution stops when
5335 control reaches a different line of code at the original stack level
5336 that was executing when you gave the @code{next} command. This command
5337 is abbreviated @code{n}.
5339 An argument @var{count} is a repeat count, as for @code{step}.
5342 @c FIX ME!! Do we delete this, or is there a way it fits in with
5343 @c the following paragraph? --- Vctoria
5345 @c @code{next} within a function that lacks debugging information acts like
5346 @c @code{step}, but any function calls appearing within the code of the
5347 @c function are executed without stopping.
5349 The @code{next} command only stops at the first instruction of a
5350 source line. This prevents multiple stops that could otherwise occur in
5351 @code{switch} statements, @code{for} loops, etc.
5353 @kindex set step-mode
5355 @cindex functions without line info, and stepping
5356 @cindex stepping into functions with no line info
5357 @itemx set step-mode on
5358 The @code{set step-mode on} command causes the @code{step} command to
5359 stop at the first instruction of a function which contains no debug line
5360 information rather than stepping over it.
5362 This is useful in cases where you may be interested in inspecting the
5363 machine instructions of a function which has no symbolic info and do not
5364 want @value{GDBN} to automatically skip over this function.
5366 @item set step-mode off
5367 Causes the @code{step} command to step over any functions which contains no
5368 debug information. This is the default.
5370 @item show step-mode
5371 Show whether @value{GDBN} will stop in or step over functions without
5372 source line debug information.
5375 @kindex fin @r{(@code{finish})}
5377 Continue running until just after function in the selected stack frame
5378 returns. Print the returned value (if any). This command can be
5379 abbreviated as @code{fin}.
5381 Contrast this with the @code{return} command (@pxref{Returning,
5382 ,Returning from a Function}).
5385 @kindex u @r{(@code{until})}
5386 @cindex run until specified location
5389 Continue running until a source line past the current line, in the
5390 current stack frame, is reached. This command is used to avoid single
5391 stepping through a loop more than once. It is like the @code{next}
5392 command, except that when @code{until} encounters a jump, it
5393 automatically continues execution until the program counter is greater
5394 than the address of the jump.
5396 This means that when you reach the end of a loop after single stepping
5397 though it, @code{until} makes your program continue execution until it
5398 exits the loop. In contrast, a @code{next} command at the end of a loop
5399 simply steps back to the beginning of the loop, which forces you to step
5400 through the next iteration.
5402 @code{until} always stops your program if it attempts to exit the current
5405 @code{until} may produce somewhat counterintuitive results if the order
5406 of machine code does not match the order of the source lines. For
5407 example, in the following excerpt from a debugging session, the @code{f}
5408 (@code{frame}) command shows that execution is stopped at line
5409 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5413 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5415 (@value{GDBP}) until
5416 195 for ( ; argc > 0; NEXTARG) @{
5419 This happened because, for execution efficiency, the compiler had
5420 generated code for the loop closure test at the end, rather than the
5421 start, of the loop---even though the test in a C @code{for}-loop is
5422 written before the body of the loop. The @code{until} command appeared
5423 to step back to the beginning of the loop when it advanced to this
5424 expression; however, it has not really gone to an earlier
5425 statement---not in terms of the actual machine code.
5427 @code{until} with no argument works by means of single
5428 instruction stepping, and hence is slower than @code{until} with an
5431 @item until @var{location}
5432 @itemx u @var{location}
5433 Continue running your program until either the specified @var{location} is
5434 reached, or the current stack frame returns. The location is any of
5435 the forms described in @ref{Specify Location}.
5436 This form of the command uses temporary breakpoints, and
5437 hence is quicker than @code{until} without an argument. The specified
5438 location is actually reached only if it is in the current frame. This
5439 implies that @code{until} can be used to skip over recursive function
5440 invocations. For instance in the code below, if the current location is
5441 line @code{96}, issuing @code{until 99} will execute the program up to
5442 line @code{99} in the same invocation of factorial, i.e., after the inner
5443 invocations have returned.
5446 94 int factorial (int value)
5448 96 if (value > 1) @{
5449 97 value *= factorial (value - 1);
5456 @kindex advance @var{location}
5457 @item advance @var{location}
5458 Continue running the program up to the given @var{location}. An argument is
5459 required, which should be of one of the forms described in
5460 @ref{Specify Location}.
5461 Execution will also stop upon exit from the current stack
5462 frame. This command is similar to @code{until}, but @code{advance} will
5463 not skip over recursive function calls, and the target location doesn't
5464 have to be in the same frame as the current one.
5468 @kindex si @r{(@code{stepi})}
5470 @itemx stepi @var{arg}
5472 Execute one machine instruction, then stop and return to the debugger.
5474 It is often useful to do @samp{display/i $pc} when stepping by machine
5475 instructions. This makes @value{GDBN} automatically display the next
5476 instruction to be executed, each time your program stops. @xref{Auto
5477 Display,, Automatic Display}.
5479 An argument is a repeat count, as in @code{step}.
5483 @kindex ni @r{(@code{nexti})}
5485 @itemx nexti @var{arg}
5487 Execute one machine instruction, but if it is a function call,
5488 proceed until the function returns.
5490 An argument is a repeat count, as in @code{next}.
5494 @anchor{range stepping}
5495 @cindex range stepping
5496 @cindex target-assisted range stepping
5497 By default, and if available, @value{GDBN} makes use of
5498 target-assisted @dfn{range stepping}. In other words, whenever you
5499 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5500 tells the target to step the corresponding range of instruction
5501 addresses instead of issuing multiple single-steps. This speeds up
5502 line stepping, particularly for remote targets. Ideally, there should
5503 be no reason you would want to turn range stepping off. However, it's
5504 possible that a bug in the debug info, a bug in the remote stub (for
5505 remote targets), or even a bug in @value{GDBN} could make line
5506 stepping behave incorrectly when target-assisted range stepping is
5507 enabled. You can use the following command to turn off range stepping
5511 @kindex set range-stepping
5512 @kindex show range-stepping
5513 @item set range-stepping
5514 @itemx show range-stepping
5515 Control whether range stepping is enabled.
5517 If @code{on}, and the target supports it, @value{GDBN} tells the
5518 target to step a range of addresses itself, instead of issuing
5519 multiple single-steps. If @code{off}, @value{GDBN} always issues
5520 single-steps, even if range stepping is supported by the target. The
5521 default is @code{on}.
5525 @node Skipping Over Functions and Files
5526 @section Skipping Over Functions and Files
5527 @cindex skipping over functions and files
5529 The program you are debugging may contain some functions which are
5530 uninteresting to debug. The @code{skip} command lets you tell @value{GDBN} to
5531 skip a function, all functions in a file or a particular function in
5532 a particular file when stepping.
5534 For example, consider the following C function:
5545 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5546 are not interested in stepping through @code{boring}. If you run @code{step}
5547 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5548 step over both @code{foo} and @code{boring}!
5550 One solution is to @code{step} into @code{boring} and use the @code{finish}
5551 command to immediately exit it. But this can become tedious if @code{boring}
5552 is called from many places.
5554 A more flexible solution is to execute @kbd{skip boring}. This instructs
5555 @value{GDBN} never to step into @code{boring}. Now when you execute
5556 @code{step} at line 103, you'll step over @code{boring} and directly into
5559 Functions may be skipped by providing either a function name, linespec
5560 (@pxref{Specify Location}), regular expression that matches the function's
5561 name, file name or a @code{glob}-style pattern that matches the file name.
5563 On Posix systems the form of the regular expression is
5564 ``Extended Regular Expressions''. See for example @samp{man 7 regex}
5565 on @sc{gnu}/Linux systems. On non-Posix systems the form of the regular
5566 expression is whatever is provided by the @code{regcomp} function of
5567 the underlying system.
5568 See for example @samp{man 7 glob} on @sc{gnu}/Linux systems for a
5569 description of @code{glob}-style patterns.
5573 @item skip @r{[}@var{options}@r{]}
5574 The basic form of the @code{skip} command takes zero or more options
5575 that specify what to skip.
5576 The @var{options} argument is any useful combination of the following:
5579 @item -file @var{file}
5580 @itemx -fi @var{file}
5581 Functions in @var{file} will be skipped over when stepping.
5583 @item -gfile @var{file-glob-pattern}
5584 @itemx -gfi @var{file-glob-pattern}
5585 @cindex skipping over files via glob-style patterns
5586 Functions in files matching @var{file-glob-pattern} will be skipped
5590 (gdb) skip -gfi utils/*.c
5593 @item -function @var{linespec}
5594 @itemx -fu @var{linespec}
5595 Functions named by @var{linespec} or the function containing the line
5596 named by @var{linespec} will be skipped over when stepping.
5597 @xref{Specify Location}.
5599 @item -rfunction @var{regexp}
5600 @itemx -rfu @var{regexp}
5601 @cindex skipping over functions via regular expressions
5602 Functions whose name matches @var{regexp} will be skipped over when stepping.
5604 This form is useful for complex function names.
5605 For example, there is generally no need to step into C@t{++} @code{std::string}
5606 constructors or destructors. Plus with C@t{++} templates it can be hard to
5607 write out the full name of the function, and often it doesn't matter what
5608 the template arguments are. Specifying the function to be skipped as a
5609 regular expression makes this easier.
5612 (gdb) skip -rfu ^std::(allocator|basic_string)<.*>::~?\1 *\(
5615 If you want to skip every templated C@t{++} constructor and destructor
5616 in the @code{std} namespace you can do:
5619 (gdb) skip -rfu ^std::([a-zA-z0-9_]+)<.*>::~?\1 *\(
5623 If no options are specified, the function you're currently debugging
5626 @kindex skip function
5627 @item skip function @r{[}@var{linespec}@r{]}
5628 After running this command, the function named by @var{linespec} or the
5629 function containing the line named by @var{linespec} will be skipped over when
5630 stepping. @xref{Specify Location}.
5632 If you do not specify @var{linespec}, the function you're currently debugging
5635 (If you have a function called @code{file} that you want to skip, use
5636 @kbd{skip function file}.)
5639 @item skip file @r{[}@var{filename}@r{]}
5640 After running this command, any function whose source lives in @var{filename}
5641 will be skipped over when stepping.
5644 (gdb) skip file boring.c
5645 File boring.c will be skipped when stepping.
5648 If you do not specify @var{filename}, functions whose source lives in the file
5649 you're currently debugging will be skipped.
5652 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5653 These are the commands for managing your list of skips:
5657 @item info skip @r{[}@var{range}@r{]}
5658 Print details about the specified skip(s). If @var{range} is not specified,
5659 print a table with details about all functions and files marked for skipping.
5660 @code{info skip} prints the following information about each skip:
5664 A number identifying this skip.
5665 @item Enabled or Disabled
5666 Enabled skips are marked with @samp{y}.
5667 Disabled skips are marked with @samp{n}.
5669 If the file name is a @samp{glob} pattern this is @samp{y}.
5670 Otherwise it is @samp{n}.
5672 The name or @samp{glob} pattern of the file to be skipped.
5673 If no file is specified this is @samp{<none>}.
5675 If the function name is a @samp{regular expression} this is @samp{y}.
5676 Otherwise it is @samp{n}.
5678 The name or regular expression of the function to skip.
5679 If no function is specified this is @samp{<none>}.
5683 @item skip delete @r{[}@var{range}@r{]}
5684 Delete the specified skip(s). If @var{range} is not specified, delete all
5688 @item skip enable @r{[}@var{range}@r{]}
5689 Enable the specified skip(s). If @var{range} is not specified, enable all
5692 @kindex skip disable
5693 @item skip disable @r{[}@var{range}@r{]}
5694 Disable the specified skip(s). If @var{range} is not specified, disable all
5703 A signal is an asynchronous event that can happen in a program. The
5704 operating system defines the possible kinds of signals, and gives each
5705 kind a name and a number. For example, in Unix @code{SIGINT} is the
5706 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5707 @code{SIGSEGV} is the signal a program gets from referencing a place in
5708 memory far away from all the areas in use; @code{SIGALRM} occurs when
5709 the alarm clock timer goes off (which happens only if your program has
5710 requested an alarm).
5712 @cindex fatal signals
5713 Some signals, including @code{SIGALRM}, are a normal part of the
5714 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5715 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5716 program has not specified in advance some other way to handle the signal.
5717 @code{SIGINT} does not indicate an error in your program, but it is normally
5718 fatal so it can carry out the purpose of the interrupt: to kill the program.
5720 @value{GDBN} has the ability to detect any occurrence of a signal in your
5721 program. You can tell @value{GDBN} in advance what to do for each kind of
5724 @cindex handling signals
5725 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5726 @code{SIGALRM} be silently passed to your program
5727 (so as not to interfere with their role in the program's functioning)
5728 but to stop your program immediately whenever an error signal happens.
5729 You can change these settings with the @code{handle} command.
5732 @kindex info signals
5736 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5737 handle each one. You can use this to see the signal numbers of all
5738 the defined types of signals.
5740 @item info signals @var{sig}
5741 Similar, but print information only about the specified signal number.
5743 @code{info handle} is an alias for @code{info signals}.
5745 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5746 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5747 for details about this command.
5750 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5751 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5752 can be the number of a signal or its name (with or without the
5753 @samp{SIG} at the beginning); a list of signal numbers of the form
5754 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5755 known signals. Optional arguments @var{keywords}, described below,
5756 say what change to make.
5760 The keywords allowed by the @code{handle} command can be abbreviated.
5761 Their full names are:
5765 @value{GDBN} should not stop your program when this signal happens. It may
5766 still print a message telling you that the signal has come in.
5769 @value{GDBN} should stop your program when this signal happens. This implies
5770 the @code{print} keyword as well.
5773 @value{GDBN} should print a message when this signal happens.
5776 @value{GDBN} should not mention the occurrence of the signal at all. This
5777 implies the @code{nostop} keyword as well.
5781 @value{GDBN} should allow your program to see this signal; your program
5782 can handle the signal, or else it may terminate if the signal is fatal
5783 and not handled. @code{pass} and @code{noignore} are synonyms.
5787 @value{GDBN} should not allow your program to see this signal.
5788 @code{nopass} and @code{ignore} are synonyms.
5792 When a signal stops your program, the signal is not visible to the
5794 continue. Your program sees the signal then, if @code{pass} is in
5795 effect for the signal in question @emph{at that time}. In other words,
5796 after @value{GDBN} reports a signal, you can use the @code{handle}
5797 command with @code{pass} or @code{nopass} to control whether your
5798 program sees that signal when you continue.
5800 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5801 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5802 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5805 You can also use the @code{signal} command to prevent your program from
5806 seeing a signal, or cause it to see a signal it normally would not see,
5807 or to give it any signal at any time. For example, if your program stopped
5808 due to some sort of memory reference error, you might store correct
5809 values into the erroneous variables and continue, hoping to see more
5810 execution; but your program would probably terminate immediately as
5811 a result of the fatal signal once it saw the signal. To prevent this,
5812 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5815 @cindex stepping and signal handlers
5816 @anchor{stepping and signal handlers}
5818 @value{GDBN} optimizes for stepping the mainline code. If a signal
5819 that has @code{handle nostop} and @code{handle pass} set arrives while
5820 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
5821 in progress, @value{GDBN} lets the signal handler run and then resumes
5822 stepping the mainline code once the signal handler returns. In other
5823 words, @value{GDBN} steps over the signal handler. This prevents
5824 signals that you've specified as not interesting (with @code{handle
5825 nostop}) from changing the focus of debugging unexpectedly. Note that
5826 the signal handler itself may still hit a breakpoint, stop for another
5827 signal that has @code{handle stop} in effect, or for any other event
5828 that normally results in stopping the stepping command sooner. Also
5829 note that @value{GDBN} still informs you that the program received a
5830 signal if @code{handle print} is set.
5832 @anchor{stepping into signal handlers}
5834 If you set @code{handle pass} for a signal, and your program sets up a
5835 handler for it, then issuing a stepping command, such as @code{step}
5836 or @code{stepi}, when your program is stopped due to the signal will
5837 step @emph{into} the signal handler (if the target supports that).
5839 Likewise, if you use the @code{queue-signal} command to queue a signal
5840 to be delivered to the current thread when execution of the thread
5841 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
5842 stepping command will step into the signal handler.
5844 Here's an example, using @code{stepi} to step to the first instruction
5845 of @code{SIGUSR1}'s handler:
5848 (@value{GDBP}) handle SIGUSR1
5849 Signal Stop Print Pass to program Description
5850 SIGUSR1 Yes Yes Yes User defined signal 1
5854 Program received signal SIGUSR1, User defined signal 1.
5855 main () sigusr1.c:28
5858 sigusr1_handler () at sigusr1.c:9
5862 The same, but using @code{queue-signal} instead of waiting for the
5863 program to receive the signal first:
5868 (@value{GDBP}) queue-signal SIGUSR1
5870 sigusr1_handler () at sigusr1.c:9
5875 @cindex extra signal information
5876 @anchor{extra signal information}
5878 On some targets, @value{GDBN} can inspect extra signal information
5879 associated with the intercepted signal, before it is actually
5880 delivered to the program being debugged. This information is exported
5881 by the convenience variable @code{$_siginfo}, and consists of data
5882 that is passed by the kernel to the signal handler at the time of the
5883 receipt of a signal. The data type of the information itself is
5884 target dependent. You can see the data type using the @code{ptype
5885 $_siginfo} command. On Unix systems, it typically corresponds to the
5886 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5889 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5890 referenced address that raised a segmentation fault.
5894 (@value{GDBP}) continue
5895 Program received signal SIGSEGV, Segmentation fault.
5896 0x0000000000400766 in main ()
5898 (@value{GDBP}) ptype $_siginfo
5905 struct @{...@} _kill;
5906 struct @{...@} _timer;
5908 struct @{...@} _sigchld;
5909 struct @{...@} _sigfault;
5910 struct @{...@} _sigpoll;
5913 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5917 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5918 $1 = (void *) 0x7ffff7ff7000
5922 Depending on target support, @code{$_siginfo} may also be writable.
5924 @cindex Intel MPX boundary violations
5925 @cindex boundary violations, Intel MPX
5926 On some targets, a @code{SIGSEGV} can be caused by a boundary
5927 violation, i.e., accessing an address outside of the allowed range.
5928 In those cases @value{GDBN} may displays additional information,
5929 depending on how @value{GDBN} has been told to handle the signal.
5930 With @code{handle stop SIGSEGV}, @value{GDBN} displays the violation
5931 kind: "Upper" or "Lower", the memory address accessed and the
5932 bounds, while with @code{handle nostop SIGSEGV} no additional
5933 information is displayed.
5935 The usual output of a segfault is:
5937 Program received signal SIGSEGV, Segmentation fault
5938 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
5939 68 value = *(p + len);
5942 While a bound violation is presented as:
5944 Program received signal SIGSEGV, Segmentation fault
5945 Upper bound violation while accessing address 0x7fffffffc3b3
5946 Bounds: [lower = 0x7fffffffc390, upper = 0x7fffffffc3a3]
5947 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
5948 68 value = *(p + len);
5952 @section Stopping and Starting Multi-thread Programs
5954 @cindex stopped threads
5955 @cindex threads, stopped
5957 @cindex continuing threads
5958 @cindex threads, continuing
5960 @value{GDBN} supports debugging programs with multiple threads
5961 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5962 are two modes of controlling execution of your program within the
5963 debugger. In the default mode, referred to as @dfn{all-stop mode},
5964 when any thread in your program stops (for example, at a breakpoint
5965 or while being stepped), all other threads in the program are also stopped by
5966 @value{GDBN}. On some targets, @value{GDBN} also supports
5967 @dfn{non-stop mode}, in which other threads can continue to run freely while
5968 you examine the stopped thread in the debugger.
5971 * All-Stop Mode:: All threads stop when GDB takes control
5972 * Non-Stop Mode:: Other threads continue to execute
5973 * Background Execution:: Running your program asynchronously
5974 * Thread-Specific Breakpoints:: Controlling breakpoints
5975 * Interrupted System Calls:: GDB may interfere with system calls
5976 * Observer Mode:: GDB does not alter program behavior
5980 @subsection All-Stop Mode
5982 @cindex all-stop mode
5984 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5985 @emph{all} threads of execution stop, not just the current thread. This
5986 allows you to examine the overall state of the program, including
5987 switching between threads, without worrying that things may change
5990 Conversely, whenever you restart the program, @emph{all} threads start
5991 executing. @emph{This is true even when single-stepping} with commands
5992 like @code{step} or @code{next}.
5994 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5995 Since thread scheduling is up to your debugging target's operating
5996 system (not controlled by @value{GDBN}), other threads may
5997 execute more than one statement while the current thread completes a
5998 single step. Moreover, in general other threads stop in the middle of a
5999 statement, rather than at a clean statement boundary, when the program
6002 You might even find your program stopped in another thread after
6003 continuing or even single-stepping. This happens whenever some other
6004 thread runs into a breakpoint, a signal, or an exception before the
6005 first thread completes whatever you requested.
6007 @cindex automatic thread selection
6008 @cindex switching threads automatically
6009 @cindex threads, automatic switching
6010 Whenever @value{GDBN} stops your program, due to a breakpoint or a
6011 signal, it automatically selects the thread where that breakpoint or
6012 signal happened. @value{GDBN} alerts you to the context switch with a
6013 message such as @samp{[Switching to Thread @var{n}]} to identify the
6016 On some OSes, you can modify @value{GDBN}'s default behavior by
6017 locking the OS scheduler to allow only a single thread to run.
6020 @item set scheduler-locking @var{mode}
6021 @cindex scheduler locking mode
6022 @cindex lock scheduler
6023 Set the scheduler locking mode. It applies to normal execution,
6024 record mode, and replay mode. If it is @code{off}, then there is no
6025 locking and any thread may run at any time. If @code{on}, then only
6026 the current thread may run when the inferior is resumed. The
6027 @code{step} mode optimizes for single-stepping; it prevents other
6028 threads from preempting the current thread while you are stepping, so
6029 that the focus of debugging does not change unexpectedly. Other
6030 threads never get a chance to run when you step, and they are
6031 completely free to run when you use commands like @samp{continue},
6032 @samp{until}, or @samp{finish}. However, unless another thread hits a
6033 breakpoint during its timeslice, @value{GDBN} does not change the
6034 current thread away from the thread that you are debugging. The
6035 @code{replay} mode behaves like @code{off} in record mode and like
6036 @code{on} in replay mode.
6038 @item show scheduler-locking
6039 Display the current scheduler locking mode.
6042 @cindex resume threads of multiple processes simultaneously
6043 By default, when you issue one of the execution commands such as
6044 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
6045 threads of the current inferior to run. For example, if @value{GDBN}
6046 is attached to two inferiors, each with two threads, the
6047 @code{continue} command resumes only the two threads of the current
6048 inferior. This is useful, for example, when you debug a program that
6049 forks and you want to hold the parent stopped (so that, for instance,
6050 it doesn't run to exit), while you debug the child. In other
6051 situations, you may not be interested in inspecting the current state
6052 of any of the processes @value{GDBN} is attached to, and you may want
6053 to resume them all until some breakpoint is hit. In the latter case,
6054 you can instruct @value{GDBN} to allow all threads of all the
6055 inferiors to run with the @w{@code{set schedule-multiple}} command.
6058 @kindex set schedule-multiple
6059 @item set schedule-multiple
6060 Set the mode for allowing threads of multiple processes to be resumed
6061 when an execution command is issued. When @code{on}, all threads of
6062 all processes are allowed to run. When @code{off}, only the threads
6063 of the current process are resumed. The default is @code{off}. The
6064 @code{scheduler-locking} mode takes precedence when set to @code{on},
6065 or while you are stepping and set to @code{step}.
6067 @item show schedule-multiple
6068 Display the current mode for resuming the execution of threads of
6073 @subsection Non-Stop Mode
6075 @cindex non-stop mode
6077 @c This section is really only a place-holder, and needs to be expanded
6078 @c with more details.
6080 For some multi-threaded targets, @value{GDBN} supports an optional
6081 mode of operation in which you can examine stopped program threads in
6082 the debugger while other threads continue to execute freely. This
6083 minimizes intrusion when debugging live systems, such as programs
6084 where some threads have real-time constraints or must continue to
6085 respond to external events. This is referred to as @dfn{non-stop} mode.
6087 In non-stop mode, when a thread stops to report a debugging event,
6088 @emph{only} that thread is stopped; @value{GDBN} does not stop other
6089 threads as well, in contrast to the all-stop mode behavior. Additionally,
6090 execution commands such as @code{continue} and @code{step} apply by default
6091 only to the current thread in non-stop mode, rather than all threads as
6092 in all-stop mode. This allows you to control threads explicitly in
6093 ways that are not possible in all-stop mode --- for example, stepping
6094 one thread while allowing others to run freely, stepping
6095 one thread while holding all others stopped, or stepping several threads
6096 independently and simultaneously.
6098 To enter non-stop mode, use this sequence of commands before you run
6099 or attach to your program:
6102 # If using the CLI, pagination breaks non-stop.
6105 # Finally, turn it on!
6109 You can use these commands to manipulate the non-stop mode setting:
6112 @kindex set non-stop
6113 @item set non-stop on
6114 Enable selection of non-stop mode.
6115 @item set non-stop off
6116 Disable selection of non-stop mode.
6117 @kindex show non-stop
6119 Show the current non-stop enablement setting.
6122 Note these commands only reflect whether non-stop mode is enabled,
6123 not whether the currently-executing program is being run in non-stop mode.
6124 In particular, the @code{set non-stop} preference is only consulted when
6125 @value{GDBN} starts or connects to the target program, and it is generally
6126 not possible to switch modes once debugging has started. Furthermore,
6127 since not all targets support non-stop mode, even when you have enabled
6128 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
6131 In non-stop mode, all execution commands apply only to the current thread
6132 by default. That is, @code{continue} only continues one thread.
6133 To continue all threads, issue @code{continue -a} or @code{c -a}.
6135 You can use @value{GDBN}'s background execution commands
6136 (@pxref{Background Execution}) to run some threads in the background
6137 while you continue to examine or step others from @value{GDBN}.
6138 The MI execution commands (@pxref{GDB/MI Program Execution}) are
6139 always executed asynchronously in non-stop mode.
6141 Suspending execution is done with the @code{interrupt} command when
6142 running in the background, or @kbd{Ctrl-c} during foreground execution.
6143 In all-stop mode, this stops the whole process;
6144 but in non-stop mode the interrupt applies only to the current thread.
6145 To stop the whole program, use @code{interrupt -a}.
6147 Other execution commands do not currently support the @code{-a} option.
6149 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
6150 that thread current, as it does in all-stop mode. This is because the
6151 thread stop notifications are asynchronous with respect to @value{GDBN}'s
6152 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
6153 changed to a different thread just as you entered a command to operate on the
6154 previously current thread.
6156 @node Background Execution
6157 @subsection Background Execution
6159 @cindex foreground execution
6160 @cindex background execution
6161 @cindex asynchronous execution
6162 @cindex execution, foreground, background and asynchronous
6164 @value{GDBN}'s execution commands have two variants: the normal
6165 foreground (synchronous) behavior, and a background
6166 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
6167 the program to report that some thread has stopped before prompting for
6168 another command. In background execution, @value{GDBN} immediately gives
6169 a command prompt so that you can issue other commands while your program runs.
6171 If the target doesn't support async mode, @value{GDBN} issues an error
6172 message if you attempt to use the background execution commands.
6174 To specify background execution, add a @code{&} to the command. For example,
6175 the background form of the @code{continue} command is @code{continue&}, or
6176 just @code{c&}. The execution commands that accept background execution
6182 @xref{Starting, , Starting your Program}.
6186 @xref{Attach, , Debugging an Already-running Process}.
6190 @xref{Continuing and Stepping, step}.
6194 @xref{Continuing and Stepping, stepi}.
6198 @xref{Continuing and Stepping, next}.
6202 @xref{Continuing and Stepping, nexti}.
6206 @xref{Continuing and Stepping, continue}.
6210 @xref{Continuing and Stepping, finish}.
6214 @xref{Continuing and Stepping, until}.
6218 Background execution is especially useful in conjunction with non-stop
6219 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6220 However, you can also use these commands in the normal all-stop mode with
6221 the restriction that you cannot issue another execution command until the
6222 previous one finishes. Examples of commands that are valid in all-stop
6223 mode while the program is running include @code{help} and @code{info break}.
6225 You can interrupt your program while it is running in the background by
6226 using the @code{interrupt} command.
6233 Suspend execution of the running program. In all-stop mode,
6234 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6235 only the current thread. To stop the whole program in non-stop mode,
6236 use @code{interrupt -a}.
6239 @node Thread-Specific Breakpoints
6240 @subsection Thread-Specific Breakpoints
6242 When your program has multiple threads (@pxref{Threads,, Debugging
6243 Programs with Multiple Threads}), you can choose whether to set
6244 breakpoints on all threads, or on a particular thread.
6247 @cindex breakpoints and threads
6248 @cindex thread breakpoints
6249 @kindex break @dots{} thread @var{thread-id}
6250 @item break @var{location} thread @var{thread-id}
6251 @itemx break @var{location} thread @var{thread-id} if @dots{}
6252 @var{location} specifies source lines; there are several ways of
6253 writing them (@pxref{Specify Location}), but the effect is always to
6254 specify some source line.
6256 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
6257 to specify that you only want @value{GDBN} to stop the program when a
6258 particular thread reaches this breakpoint. The @var{thread-id} specifier
6259 is one of the thread identifiers assigned by @value{GDBN}, shown
6260 in the first column of the @samp{info threads} display.
6262 If you do not specify @samp{thread @var{thread-id}} when you set a
6263 breakpoint, the breakpoint applies to @emph{all} threads of your
6266 You can use the @code{thread} qualifier on conditional breakpoints as
6267 well; in this case, place @samp{thread @var{thread-id}} before or
6268 after the breakpoint condition, like this:
6271 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6276 Thread-specific breakpoints are automatically deleted when
6277 @value{GDBN} detects the corresponding thread is no longer in the
6278 thread list. For example:
6282 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6285 There are several ways for a thread to disappear, such as a regular
6286 thread exit, but also when you detach from the process with the
6287 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6288 Process}), or if @value{GDBN} loses the remote connection
6289 (@pxref{Remote Debugging}), etc. Note that with some targets,
6290 @value{GDBN} is only able to detect a thread has exited when the user
6291 explictly asks for the thread list with the @code{info threads}
6294 @node Interrupted System Calls
6295 @subsection Interrupted System Calls
6297 @cindex thread breakpoints and system calls
6298 @cindex system calls and thread breakpoints
6299 @cindex premature return from system calls
6300 There is an unfortunate side effect when using @value{GDBN} to debug
6301 multi-threaded programs. If one thread stops for a
6302 breakpoint, or for some other reason, and another thread is blocked in a
6303 system call, then the system call may return prematurely. This is a
6304 consequence of the interaction between multiple threads and the signals
6305 that @value{GDBN} uses to implement breakpoints and other events that
6308 To handle this problem, your program should check the return value of
6309 each system call and react appropriately. This is good programming
6312 For example, do not write code like this:
6318 The call to @code{sleep} will return early if a different thread stops
6319 at a breakpoint or for some other reason.
6321 Instead, write this:
6326 unslept = sleep (unslept);
6329 A system call is allowed to return early, so the system is still
6330 conforming to its specification. But @value{GDBN} does cause your
6331 multi-threaded program to behave differently than it would without
6334 Also, @value{GDBN} uses internal breakpoints in the thread library to
6335 monitor certain events such as thread creation and thread destruction.
6336 When such an event happens, a system call in another thread may return
6337 prematurely, even though your program does not appear to stop.
6340 @subsection Observer Mode
6342 If you want to build on non-stop mode and observe program behavior
6343 without any chance of disruption by @value{GDBN}, you can set
6344 variables to disable all of the debugger's attempts to modify state,
6345 whether by writing memory, inserting breakpoints, etc. These operate
6346 at a low level, intercepting operations from all commands.
6348 When all of these are set to @code{off}, then @value{GDBN} is said to
6349 be @dfn{observer mode}. As a convenience, the variable
6350 @code{observer} can be set to disable these, plus enable non-stop
6353 Note that @value{GDBN} will not prevent you from making nonsensical
6354 combinations of these settings. For instance, if you have enabled
6355 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6356 then breakpoints that work by writing trap instructions into the code
6357 stream will still not be able to be placed.
6362 @item set observer on
6363 @itemx set observer off
6364 When set to @code{on}, this disables all the permission variables
6365 below (except for @code{insert-fast-tracepoints}), plus enables
6366 non-stop debugging. Setting this to @code{off} switches back to
6367 normal debugging, though remaining in non-stop mode.
6370 Show whether observer mode is on or off.
6372 @kindex may-write-registers
6373 @item set may-write-registers on
6374 @itemx set may-write-registers off
6375 This controls whether @value{GDBN} will attempt to alter the values of
6376 registers, such as with assignment expressions in @code{print}, or the
6377 @code{jump} command. It defaults to @code{on}.
6379 @item show may-write-registers
6380 Show the current permission to write registers.
6382 @kindex may-write-memory
6383 @item set may-write-memory on
6384 @itemx set may-write-memory off
6385 This controls whether @value{GDBN} will attempt to alter the contents
6386 of memory, such as with assignment expressions in @code{print}. It
6387 defaults to @code{on}.
6389 @item show may-write-memory
6390 Show the current permission to write memory.
6392 @kindex may-insert-breakpoints
6393 @item set may-insert-breakpoints on
6394 @itemx set may-insert-breakpoints off
6395 This controls whether @value{GDBN} will attempt to insert breakpoints.
6396 This affects all breakpoints, including internal breakpoints defined
6397 by @value{GDBN}. It defaults to @code{on}.
6399 @item show may-insert-breakpoints
6400 Show the current permission to insert breakpoints.
6402 @kindex may-insert-tracepoints
6403 @item set may-insert-tracepoints on
6404 @itemx set may-insert-tracepoints off
6405 This controls whether @value{GDBN} will attempt to insert (regular)
6406 tracepoints at the beginning of a tracing experiment. It affects only
6407 non-fast tracepoints, fast tracepoints being under the control of
6408 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6410 @item show may-insert-tracepoints
6411 Show the current permission to insert tracepoints.
6413 @kindex may-insert-fast-tracepoints
6414 @item set may-insert-fast-tracepoints on
6415 @itemx set may-insert-fast-tracepoints off
6416 This controls whether @value{GDBN} will attempt to insert fast
6417 tracepoints at the beginning of a tracing experiment. It affects only
6418 fast tracepoints, regular (non-fast) tracepoints being under the
6419 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6421 @item show may-insert-fast-tracepoints
6422 Show the current permission to insert fast tracepoints.
6424 @kindex may-interrupt
6425 @item set may-interrupt on
6426 @itemx set may-interrupt off
6427 This controls whether @value{GDBN} will attempt to interrupt or stop
6428 program execution. When this variable is @code{off}, the
6429 @code{interrupt} command will have no effect, nor will
6430 @kbd{Ctrl-c}. It defaults to @code{on}.
6432 @item show may-interrupt
6433 Show the current permission to interrupt or stop the program.
6437 @node Reverse Execution
6438 @chapter Running programs backward
6439 @cindex reverse execution
6440 @cindex running programs backward
6442 When you are debugging a program, it is not unusual to realize that
6443 you have gone too far, and some event of interest has already happened.
6444 If the target environment supports it, @value{GDBN} can allow you to
6445 ``rewind'' the program by running it backward.
6447 A target environment that supports reverse execution should be able
6448 to ``undo'' the changes in machine state that have taken place as the
6449 program was executing normally. Variables, registers etc.@: should
6450 revert to their previous values. Obviously this requires a great
6451 deal of sophistication on the part of the target environment; not
6452 all target environments can support reverse execution.
6454 When a program is executed in reverse, the instructions that
6455 have most recently been executed are ``un-executed'', in reverse
6456 order. The program counter runs backward, following the previous
6457 thread of execution in reverse. As each instruction is ``un-executed'',
6458 the values of memory and/or registers that were changed by that
6459 instruction are reverted to their previous states. After executing
6460 a piece of source code in reverse, all side effects of that code
6461 should be ``undone'', and all variables should be returned to their
6462 prior values@footnote{
6463 Note that some side effects are easier to undo than others. For instance,
6464 memory and registers are relatively easy, but device I/O is hard. Some
6465 targets may be able undo things like device I/O, and some may not.
6467 The contract between @value{GDBN} and the reverse executing target
6468 requires only that the target do something reasonable when
6469 @value{GDBN} tells it to execute backwards, and then report the
6470 results back to @value{GDBN}. Whatever the target reports back to
6471 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6472 assumes that the memory and registers that the target reports are in a
6473 consistant state, but @value{GDBN} accepts whatever it is given.
6476 If you are debugging in a target environment that supports
6477 reverse execution, @value{GDBN} provides the following commands.
6480 @kindex reverse-continue
6481 @kindex rc @r{(@code{reverse-continue})}
6482 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6483 @itemx rc @r{[}@var{ignore-count}@r{]}
6484 Beginning at the point where your program last stopped, start executing
6485 in reverse. Reverse execution will stop for breakpoints and synchronous
6486 exceptions (signals), just like normal execution. Behavior of
6487 asynchronous signals depends on the target environment.
6489 @kindex reverse-step
6490 @kindex rs @r{(@code{step})}
6491 @item reverse-step @r{[}@var{count}@r{]}
6492 Run the program backward until control reaches the start of a
6493 different source line; then stop it, and return control to @value{GDBN}.
6495 Like the @code{step} command, @code{reverse-step} will only stop
6496 at the beginning of a source line. It ``un-executes'' the previously
6497 executed source line. If the previous source line included calls to
6498 debuggable functions, @code{reverse-step} will step (backward) into
6499 the called function, stopping at the beginning of the @emph{last}
6500 statement in the called function (typically a return statement).
6502 Also, as with the @code{step} command, if non-debuggable functions are
6503 called, @code{reverse-step} will run thru them backward without stopping.
6505 @kindex reverse-stepi
6506 @kindex rsi @r{(@code{reverse-stepi})}
6507 @item reverse-stepi @r{[}@var{count}@r{]}
6508 Reverse-execute one machine instruction. Note that the instruction
6509 to be reverse-executed is @emph{not} the one pointed to by the program
6510 counter, but the instruction executed prior to that one. For instance,
6511 if the last instruction was a jump, @code{reverse-stepi} will take you
6512 back from the destination of the jump to the jump instruction itself.
6514 @kindex reverse-next
6515 @kindex rn @r{(@code{reverse-next})}
6516 @item reverse-next @r{[}@var{count}@r{]}
6517 Run backward to the beginning of the previous line executed in
6518 the current (innermost) stack frame. If the line contains function
6519 calls, they will be ``un-executed'' without stopping. Starting from
6520 the first line of a function, @code{reverse-next} will take you back
6521 to the caller of that function, @emph{before} the function was called,
6522 just as the normal @code{next} command would take you from the last
6523 line of a function back to its return to its caller
6524 @footnote{Unless the code is too heavily optimized.}.
6526 @kindex reverse-nexti
6527 @kindex rni @r{(@code{reverse-nexti})}
6528 @item reverse-nexti @r{[}@var{count}@r{]}
6529 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6530 in reverse, except that called functions are ``un-executed'' atomically.
6531 That is, if the previously executed instruction was a return from
6532 another function, @code{reverse-nexti} will continue to execute
6533 in reverse until the call to that function (from the current stack
6536 @kindex reverse-finish
6537 @item reverse-finish
6538 Just as the @code{finish} command takes you to the point where the
6539 current function returns, @code{reverse-finish} takes you to the point
6540 where it was called. Instead of ending up at the end of the current
6541 function invocation, you end up at the beginning.
6543 @kindex set exec-direction
6544 @item set exec-direction
6545 Set the direction of target execution.
6546 @item set exec-direction reverse
6547 @cindex execute forward or backward in time
6548 @value{GDBN} will perform all execution commands in reverse, until the
6549 exec-direction mode is changed to ``forward''. Affected commands include
6550 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6551 command cannot be used in reverse mode.
6552 @item set exec-direction forward
6553 @value{GDBN} will perform all execution commands in the normal fashion.
6554 This is the default.
6558 @node Process Record and Replay
6559 @chapter Recording Inferior's Execution and Replaying It
6560 @cindex process record and replay
6561 @cindex recording inferior's execution and replaying it
6563 On some platforms, @value{GDBN} provides a special @dfn{process record
6564 and replay} target that can record a log of the process execution, and
6565 replay it later with both forward and reverse execution commands.
6568 When this target is in use, if the execution log includes the record
6569 for the next instruction, @value{GDBN} will debug in @dfn{replay
6570 mode}. In the replay mode, the inferior does not really execute code
6571 instructions. Instead, all the events that normally happen during
6572 code execution are taken from the execution log. While code is not
6573 really executed in replay mode, the values of registers (including the
6574 program counter register) and the memory of the inferior are still
6575 changed as they normally would. Their contents are taken from the
6579 If the record for the next instruction is not in the execution log,
6580 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6581 inferior executes normally, and @value{GDBN} records the execution log
6584 The process record and replay target supports reverse execution
6585 (@pxref{Reverse Execution}), even if the platform on which the
6586 inferior runs does not. However, the reverse execution is limited in
6587 this case by the range of the instructions recorded in the execution
6588 log. In other words, reverse execution on platforms that don't
6589 support it directly can only be done in the replay mode.
6591 When debugging in the reverse direction, @value{GDBN} will work in
6592 replay mode as long as the execution log includes the record for the
6593 previous instruction; otherwise, it will work in record mode, if the
6594 platform supports reverse execution, or stop if not.
6596 For architecture environments that support process record and replay,
6597 @value{GDBN} provides the following commands:
6600 @kindex target record
6601 @kindex target record-full
6602 @kindex target record-btrace
6605 @kindex record btrace
6606 @kindex record btrace bts
6607 @kindex record btrace pt
6613 @kindex rec btrace bts
6614 @kindex rec btrace pt
6617 @item record @var{method}
6618 This command starts the process record and replay target. The
6619 recording method can be specified as parameter. Without a parameter
6620 the command uses the @code{full} recording method. The following
6621 recording methods are available:
6625 Full record/replay recording using @value{GDBN}'s software record and
6626 replay implementation. This method allows replaying and reverse
6629 @item btrace @var{format}
6630 Hardware-supported instruction recording. This method does not record
6631 data. Further, the data is collected in a ring buffer so old data will
6632 be overwritten when the buffer is full. It allows limited reverse
6633 execution. Variables and registers are not available during reverse
6636 The recording format can be specified as parameter. Without a parameter
6637 the command chooses the recording format. The following recording
6638 formats are available:
6642 @cindex branch trace store
6643 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
6644 this format, the processor stores a from/to record for each executed
6645 branch in the btrace ring buffer.
6648 @cindex Intel Processor Trace
6649 Use the @dfn{Intel Processor Trace} recording format. In this
6650 format, the processor stores the execution trace in a compressed form
6651 that is afterwards decoded by @value{GDBN}.
6653 The trace can be recorded with very low overhead. The compressed
6654 trace format also allows small trace buffers to already contain a big
6655 number of instructions compared to @acronym{BTS}.
6657 Decoding the recorded execution trace, on the other hand, is more
6658 expensive than decoding @acronym{BTS} trace. This is mostly due to the
6659 increased number of instructions to process. You should increase the
6660 buffer-size with care.
6663 Not all recording formats may be available on all processors.
6666 The process record and replay target can only debug a process that is
6667 already running. Therefore, you need first to start the process with
6668 the @kbd{run} or @kbd{start} commands, and then start the recording
6669 with the @kbd{record @var{method}} command.
6671 @cindex displaced stepping, and process record and replay
6672 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6673 will be automatically disabled when process record and replay target
6674 is started. That's because the process record and replay target
6675 doesn't support displaced stepping.
6677 @cindex non-stop mode, and process record and replay
6678 @cindex asynchronous execution, and process record and replay
6679 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6680 the asynchronous execution mode (@pxref{Background Execution}), not
6681 all recording methods are available. The @code{full} recording method
6682 does not support these two modes.
6687 Stop the process record and replay target. When process record and
6688 replay target stops, the entire execution log will be deleted and the
6689 inferior will either be terminated, or will remain in its final state.
6691 When you stop the process record and replay target in record mode (at
6692 the end of the execution log), the inferior will be stopped at the
6693 next instruction that would have been recorded. In other words, if
6694 you record for a while and then stop recording, the inferior process
6695 will be left in the same state as if the recording never happened.
6697 On the other hand, if the process record and replay target is stopped
6698 while in replay mode (that is, not at the end of the execution log,
6699 but at some earlier point), the inferior process will become ``live''
6700 at that earlier state, and it will then be possible to continue the
6701 usual ``live'' debugging of the process from that state.
6703 When the inferior process exits, or @value{GDBN} detaches from it,
6704 process record and replay target will automatically stop itself.
6708 Go to a specific location in the execution log. There are several
6709 ways to specify the location to go to:
6712 @item record goto begin
6713 @itemx record goto start
6714 Go to the beginning of the execution log.
6716 @item record goto end
6717 Go to the end of the execution log.
6719 @item record goto @var{n}
6720 Go to instruction number @var{n} in the execution log.
6724 @item record save @var{filename}
6725 Save the execution log to a file @file{@var{filename}}.
6726 Default filename is @file{gdb_record.@var{process_id}}, where
6727 @var{process_id} is the process ID of the inferior.
6729 This command may not be available for all recording methods.
6731 @kindex record restore
6732 @item record restore @var{filename}
6733 Restore the execution log from a file @file{@var{filename}}.
6734 File must have been created with @code{record save}.
6736 @kindex set record full
6737 @item set record full insn-number-max @var{limit}
6738 @itemx set record full insn-number-max unlimited
6739 Set the limit of instructions to be recorded for the @code{full}
6740 recording method. Default value is 200000.
6742 If @var{limit} is a positive number, then @value{GDBN} will start
6743 deleting instructions from the log once the number of the record
6744 instructions becomes greater than @var{limit}. For every new recorded
6745 instruction, @value{GDBN} will delete the earliest recorded
6746 instruction to keep the number of recorded instructions at the limit.
6747 (Since deleting recorded instructions loses information, @value{GDBN}
6748 lets you control what happens when the limit is reached, by means of
6749 the @code{stop-at-limit} option, described below.)
6751 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6752 delete recorded instructions from the execution log. The number of
6753 recorded instructions is limited only by the available memory.
6755 @kindex show record full
6756 @item show record full insn-number-max
6757 Show the limit of instructions to be recorded with the @code{full}
6760 @item set record full stop-at-limit
6761 Control the behavior of the @code{full} recording method when the
6762 number of recorded instructions reaches the limit. If ON (the
6763 default), @value{GDBN} will stop when the limit is reached for the
6764 first time and ask you whether you want to stop the inferior or
6765 continue running it and recording the execution log. If you decide
6766 to continue recording, each new recorded instruction will cause the
6767 oldest one to be deleted.
6769 If this option is OFF, @value{GDBN} will automatically delete the
6770 oldest record to make room for each new one, without asking.
6772 @item show record full stop-at-limit
6773 Show the current setting of @code{stop-at-limit}.
6775 @item set record full memory-query
6776 Control the behavior when @value{GDBN} is unable to record memory
6777 changes caused by an instruction for the @code{full} recording method.
6778 If ON, @value{GDBN} will query whether to stop the inferior in that
6781 If this option is OFF (the default), @value{GDBN} will automatically
6782 ignore the effect of such instructions on memory. Later, when
6783 @value{GDBN} replays this execution log, it will mark the log of this
6784 instruction as not accessible, and it will not affect the replay
6787 @item show record full memory-query
6788 Show the current setting of @code{memory-query}.
6790 @kindex set record btrace
6791 The @code{btrace} record target does not trace data. As a
6792 convenience, when replaying, @value{GDBN} reads read-only memory off
6793 the live program directly, assuming that the addresses of the
6794 read-only areas don't change. This for example makes it possible to
6795 disassemble code while replaying, but not to print variables.
6796 In some cases, being able to inspect variables might be useful.
6797 You can use the following command for that:
6799 @item set record btrace replay-memory-access
6800 Control the behavior of the @code{btrace} recording method when
6801 accessing memory during replay. If @code{read-only} (the default),
6802 @value{GDBN} will only allow accesses to read-only memory.
6803 If @code{read-write}, @value{GDBN} will allow accesses to read-only
6804 and to read-write memory. Beware that the accessed memory corresponds
6805 to the live target and not necessarily to the current replay
6808 @kindex show record btrace
6809 @item show record btrace replay-memory-access
6810 Show the current setting of @code{replay-memory-access}.
6812 @kindex set record btrace bts
6813 @item set record btrace bts buffer-size @var{size}
6814 @itemx set record btrace bts buffer-size unlimited
6815 Set the requested ring buffer size for branch tracing in @acronym{BTS}
6816 format. Default is 64KB.
6818 If @var{size} is a positive number, then @value{GDBN} will try to
6819 allocate a buffer of at least @var{size} bytes for each new thread
6820 that uses the btrace recording method and the @acronym{BTS} format.
6821 The actually obtained buffer size may differ from the requested
6822 @var{size}. Use the @code{info record} command to see the actual
6823 buffer size for each thread that uses the btrace recording method and
6824 the @acronym{BTS} format.
6826 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6827 allocate a buffer of 4MB.
6829 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6830 also need longer to process the branch trace data before it can be used.
6832 @item show record btrace bts buffer-size @var{size}
6833 Show the current setting of the requested ring buffer size for branch
6834 tracing in @acronym{BTS} format.
6836 @kindex set record btrace pt
6837 @item set record btrace pt buffer-size @var{size}
6838 @itemx set record btrace pt buffer-size unlimited
6839 Set the requested ring buffer size for branch tracing in Intel
6840 Processor Trace format. Default is 16KB.
6842 If @var{size} is a positive number, then @value{GDBN} will try to
6843 allocate a buffer of at least @var{size} bytes for each new thread
6844 that uses the btrace recording method and the Intel Processor Trace
6845 format. The actually obtained buffer size may differ from the
6846 requested @var{size}. Use the @code{info record} command to see the
6847 actual buffer size for each thread.
6849 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6850 allocate a buffer of 4MB.
6852 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6853 also need longer to process the branch trace data before it can be used.
6855 @item show record btrace pt buffer-size @var{size}
6856 Show the current setting of the requested ring buffer size for branch
6857 tracing in Intel Processor Trace format.
6861 Show various statistics about the recording depending on the recording
6866 For the @code{full} recording method, it shows the state of process
6867 record and its in-memory execution log buffer, including:
6871 Whether in record mode or replay mode.
6873 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6875 Highest recorded instruction number.
6877 Current instruction about to be replayed (if in replay mode).
6879 Number of instructions contained in the execution log.
6881 Maximum number of instructions that may be contained in the execution log.
6885 For the @code{btrace} recording method, it shows:
6891 Number of instructions that have been recorded.
6893 Number of blocks of sequential control-flow formed by the recorded
6896 Whether in record mode or replay mode.
6899 For the @code{bts} recording format, it also shows:
6902 Size of the perf ring buffer.
6905 For the @code{pt} recording format, it also shows:
6908 Size of the perf ring buffer.
6912 @kindex record delete
6915 When record target runs in replay mode (``in the past''), delete the
6916 subsequent execution log and begin to record a new execution log starting
6917 from the current address. This means you will abandon the previously
6918 recorded ``future'' and begin recording a new ``future''.
6920 @kindex record instruction-history
6921 @kindex rec instruction-history
6922 @item record instruction-history
6923 Disassembles instructions from the recorded execution log. By
6924 default, ten instructions are disassembled. This can be changed using
6925 the @code{set record instruction-history-size} command. Instructions
6926 are printed in execution order.
6928 It can also print mixed source+disassembly if you specify the the
6929 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
6930 as well as in symbolic form by specifying the @code{/r} modifier.
6932 The current position marker is printed for the instruction at the
6933 current program counter value. This instruction can appear multiple
6934 times in the trace and the current position marker will be printed
6935 every time. To omit the current position marker, specify the
6938 To better align the printed instructions when the trace contains
6939 instructions from more than one function, the function name may be
6940 omitted by specifying the @code{/f} modifier.
6942 Speculatively executed instructions are prefixed with @samp{?}. This
6943 feature is not available for all recording formats.
6945 There are several ways to specify what part of the execution log to
6949 @item record instruction-history @var{insn}
6950 Disassembles ten instructions starting from instruction number
6953 @item record instruction-history @var{insn}, +/-@var{n}
6954 Disassembles @var{n} instructions around instruction number
6955 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6956 @var{n} instructions after instruction number @var{insn}. If
6957 @var{n} is preceded with @code{-}, disassembles @var{n}
6958 instructions before instruction number @var{insn}.
6960 @item record instruction-history
6961 Disassembles ten more instructions after the last disassembly.
6963 @item record instruction-history -
6964 Disassembles ten more instructions before the last disassembly.
6966 @item record instruction-history @var{begin}, @var{end}
6967 Disassembles instructions beginning with instruction number
6968 @var{begin} until instruction number @var{end}. The instruction
6969 number @var{end} is included.
6972 This command may not be available for all recording methods.
6975 @item set record instruction-history-size @var{size}
6976 @itemx set record instruction-history-size unlimited
6977 Define how many instructions to disassemble in the @code{record
6978 instruction-history} command. The default value is 10.
6979 A @var{size} of @code{unlimited} means unlimited instructions.
6982 @item show record instruction-history-size
6983 Show how many instructions to disassemble in the @code{record
6984 instruction-history} command.
6986 @kindex record function-call-history
6987 @kindex rec function-call-history
6988 @item record function-call-history
6989 Prints the execution history at function granularity. It prints one
6990 line for each sequence of instructions that belong to the same
6991 function giving the name of that function, the source lines
6992 for this instruction sequence (if the @code{/l} modifier is
6993 specified), and the instructions numbers that form the sequence (if
6994 the @code{/i} modifier is specified). The function names are indented
6995 to reflect the call stack depth if the @code{/c} modifier is
6996 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
7000 (@value{GDBP}) @b{list 1, 10}
7011 (@value{GDBP}) @b{record function-call-history /ilc}
7012 1 bar inst 1,4 at foo.c:6,8
7013 2 foo inst 5,10 at foo.c:2,3
7014 3 bar inst 11,13 at foo.c:9,10
7017 By default, ten lines are printed. This can be changed using the
7018 @code{set record function-call-history-size} command. Functions are
7019 printed in execution order. There are several ways to specify what
7023 @item record function-call-history @var{func}
7024 Prints ten functions starting from function number @var{func}.
7026 @item record function-call-history @var{func}, +/-@var{n}
7027 Prints @var{n} functions around function number @var{func}. If
7028 @var{n} is preceded with @code{+}, prints @var{n} functions after
7029 function number @var{func}. If @var{n} is preceded with @code{-},
7030 prints @var{n} functions before function number @var{func}.
7032 @item record function-call-history
7033 Prints ten more functions after the last ten-line print.
7035 @item record function-call-history -
7036 Prints ten more functions before the last ten-line print.
7038 @item record function-call-history @var{begin}, @var{end}
7039 Prints functions beginning with function number @var{begin} until
7040 function number @var{end}. The function number @var{end} is included.
7043 This command may not be available for all recording methods.
7045 @item set record function-call-history-size @var{size}
7046 @itemx set record function-call-history-size unlimited
7047 Define how many lines to print in the
7048 @code{record function-call-history} command. The default value is 10.
7049 A size of @code{unlimited} means unlimited lines.
7051 @item show record function-call-history-size
7052 Show how many lines to print in the
7053 @code{record function-call-history} command.
7058 @chapter Examining the Stack
7060 When your program has stopped, the first thing you need to know is where it
7061 stopped and how it got there.
7064 Each time your program performs a function call, information about the call
7066 That information includes the location of the call in your program,
7067 the arguments of the call,
7068 and the local variables of the function being called.
7069 The information is saved in a block of data called a @dfn{stack frame}.
7070 The stack frames are allocated in a region of memory called the @dfn{call
7073 When your program stops, the @value{GDBN} commands for examining the
7074 stack allow you to see all of this information.
7076 @cindex selected frame
7077 One of the stack frames is @dfn{selected} by @value{GDBN} and many
7078 @value{GDBN} commands refer implicitly to the selected frame. In
7079 particular, whenever you ask @value{GDBN} for the value of a variable in
7080 your program, the value is found in the selected frame. There are
7081 special @value{GDBN} commands to select whichever frame you are
7082 interested in. @xref{Selection, ,Selecting a Frame}.
7084 When your program stops, @value{GDBN} automatically selects the
7085 currently executing frame and describes it briefly, similar to the
7086 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
7089 * Frames:: Stack frames
7090 * Backtrace:: Backtraces
7091 * Selection:: Selecting a frame
7092 * Frame Info:: Information on a frame
7093 * Frame Filter Management:: Managing frame filters
7098 @section Stack Frames
7100 @cindex frame, definition
7102 The call stack is divided up into contiguous pieces called @dfn{stack
7103 frames}, or @dfn{frames} for short; each frame is the data associated
7104 with one call to one function. The frame contains the arguments given
7105 to the function, the function's local variables, and the address at
7106 which the function is executing.
7108 @cindex initial frame
7109 @cindex outermost frame
7110 @cindex innermost frame
7111 When your program is started, the stack has only one frame, that of the
7112 function @code{main}. This is called the @dfn{initial} frame or the
7113 @dfn{outermost} frame. Each time a function is called, a new frame is
7114 made. Each time a function returns, the frame for that function invocation
7115 is eliminated. If a function is recursive, there can be many frames for
7116 the same function. The frame for the function in which execution is
7117 actually occurring is called the @dfn{innermost} frame. This is the most
7118 recently created of all the stack frames that still exist.
7120 @cindex frame pointer
7121 Inside your program, stack frames are identified by their addresses. A
7122 stack frame consists of many bytes, each of which has its own address; each
7123 kind of computer has a convention for choosing one byte whose
7124 address serves as the address of the frame. Usually this address is kept
7125 in a register called the @dfn{frame pointer register}
7126 (@pxref{Registers, $fp}) while execution is going on in that frame.
7128 @cindex frame number
7129 @value{GDBN} assigns numbers to all existing stack frames, starting with
7130 zero for the innermost frame, one for the frame that called it,
7131 and so on upward. These numbers do not really exist in your program;
7132 they are assigned by @value{GDBN} to give you a way of designating stack
7133 frames in @value{GDBN} commands.
7135 @c The -fomit-frame-pointer below perennially causes hbox overflow
7136 @c underflow problems.
7137 @cindex frameless execution
7138 Some compilers provide a way to compile functions so that they operate
7139 without stack frames. (For example, the @value{NGCC} option
7141 @samp{-fomit-frame-pointer}
7143 generates functions without a frame.)
7144 This is occasionally done with heavily used library functions to save
7145 the frame setup time. @value{GDBN} has limited facilities for dealing
7146 with these function invocations. If the innermost function invocation
7147 has no stack frame, @value{GDBN} nevertheless regards it as though
7148 it had a separate frame, which is numbered zero as usual, allowing
7149 correct tracing of the function call chain. However, @value{GDBN} has
7150 no provision for frameless functions elsewhere in the stack.
7156 @cindex call stack traces
7157 A backtrace is a summary of how your program got where it is. It shows one
7158 line per frame, for many frames, starting with the currently executing
7159 frame (frame zero), followed by its caller (frame one), and on up the
7162 @anchor{backtrace-command}
7165 @kindex bt @r{(@code{backtrace})}
7168 Print a backtrace of the entire stack: one line per frame for all
7169 frames in the stack.
7171 You can stop the backtrace at any time by typing the system interrupt
7172 character, normally @kbd{Ctrl-c}.
7174 @item backtrace @var{n}
7176 Similar, but print only the innermost @var{n} frames.
7178 @item backtrace -@var{n}
7180 Similar, but print only the outermost @var{n} frames.
7182 @item backtrace full
7184 @itemx bt full @var{n}
7185 @itemx bt full -@var{n}
7186 Print the values of the local variables also. As described above,
7187 @var{n} specifies the number of frames to print.
7189 @item backtrace no-filters
7190 @itemx bt no-filters
7191 @itemx bt no-filters @var{n}
7192 @itemx bt no-filters -@var{n}
7193 @itemx bt no-filters full
7194 @itemx bt no-filters full @var{n}
7195 @itemx bt no-filters full -@var{n}
7196 Do not run Python frame filters on this backtrace. @xref{Frame
7197 Filter API}, for more information. Additionally use @ref{disable
7198 frame-filter all} to turn off all frame filters. This is only
7199 relevant when @value{GDBN} has been configured with @code{Python}
7205 The names @code{where} and @code{info stack} (abbreviated @code{info s})
7206 are additional aliases for @code{backtrace}.
7208 @cindex multiple threads, backtrace
7209 In a multi-threaded program, @value{GDBN} by default shows the
7210 backtrace only for the current thread. To display the backtrace for
7211 several or all of the threads, use the command @code{thread apply}
7212 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
7213 apply all backtrace}, @value{GDBN} will display the backtrace for all
7214 the threads; this is handy when you debug a core dump of a
7215 multi-threaded program.
7217 Each line in the backtrace shows the frame number and the function name.
7218 The program counter value is also shown---unless you use @code{set
7219 print address off}. The backtrace also shows the source file name and
7220 line number, as well as the arguments to the function. The program
7221 counter value is omitted if it is at the beginning of the code for that
7224 Here is an example of a backtrace. It was made with the command
7225 @samp{bt 3}, so it shows the innermost three frames.
7229 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7231 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
7232 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
7234 (More stack frames follow...)
7239 The display for frame zero does not begin with a program counter
7240 value, indicating that your program has stopped at the beginning of the
7241 code for line @code{993} of @code{builtin.c}.
7244 The value of parameter @code{data} in frame 1 has been replaced by
7245 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7246 only if it is a scalar (integer, pointer, enumeration, etc). See command
7247 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7248 on how to configure the way function parameter values are printed.
7250 @cindex optimized out, in backtrace
7251 @cindex function call arguments, optimized out
7252 If your program was compiled with optimizations, some compilers will
7253 optimize away arguments passed to functions if those arguments are
7254 never used after the call. Such optimizations generate code that
7255 passes arguments through registers, but doesn't store those arguments
7256 in the stack frame. @value{GDBN} has no way of displaying such
7257 arguments in stack frames other than the innermost one. Here's what
7258 such a backtrace might look like:
7262 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7264 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
7265 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
7267 (More stack frames follow...)
7272 The values of arguments that were not saved in their stack frames are
7273 shown as @samp{<optimized out>}.
7275 If you need to display the values of such optimized-out arguments,
7276 either deduce that from other variables whose values depend on the one
7277 you are interested in, or recompile without optimizations.
7279 @cindex backtrace beyond @code{main} function
7280 @cindex program entry point
7281 @cindex startup code, and backtrace
7282 Most programs have a standard user entry point---a place where system
7283 libraries and startup code transition into user code. For C this is
7284 @code{main}@footnote{
7285 Note that embedded programs (the so-called ``free-standing''
7286 environment) are not required to have a @code{main} function as the
7287 entry point. They could even have multiple entry points.}.
7288 When @value{GDBN} finds the entry function in a backtrace
7289 it will terminate the backtrace, to avoid tracing into highly
7290 system-specific (and generally uninteresting) code.
7292 If you need to examine the startup code, or limit the number of levels
7293 in a backtrace, you can change this behavior:
7296 @item set backtrace past-main
7297 @itemx set backtrace past-main on
7298 @kindex set backtrace
7299 Backtraces will continue past the user entry point.
7301 @item set backtrace past-main off
7302 Backtraces will stop when they encounter the user entry point. This is the
7305 @item show backtrace past-main
7306 @kindex show backtrace
7307 Display the current user entry point backtrace policy.
7309 @item set backtrace past-entry
7310 @itemx set backtrace past-entry on
7311 Backtraces will continue past the internal entry point of an application.
7312 This entry point is encoded by the linker when the application is built,
7313 and is likely before the user entry point @code{main} (or equivalent) is called.
7315 @item set backtrace past-entry off
7316 Backtraces will stop when they encounter the internal entry point of an
7317 application. This is the default.
7319 @item show backtrace past-entry
7320 Display the current internal entry point backtrace policy.
7322 @item set backtrace limit @var{n}
7323 @itemx set backtrace limit 0
7324 @itemx set backtrace limit unlimited
7325 @cindex backtrace limit
7326 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7327 or zero means unlimited levels.
7329 @item show backtrace limit
7330 Display the current limit on backtrace levels.
7333 You can control how file names are displayed.
7336 @item set filename-display
7337 @itemx set filename-display relative
7338 @cindex filename-display
7339 Display file names relative to the compilation directory. This is the default.
7341 @item set filename-display basename
7342 Display only basename of a filename.
7344 @item set filename-display absolute
7345 Display an absolute filename.
7347 @item show filename-display
7348 Show the current way to display filenames.
7352 @section Selecting a Frame
7354 Most commands for examining the stack and other data in your program work on
7355 whichever stack frame is selected at the moment. Here are the commands for
7356 selecting a stack frame; all of them finish by printing a brief description
7357 of the stack frame just selected.
7360 @kindex frame@r{, selecting}
7361 @kindex f @r{(@code{frame})}
7364 Select frame number @var{n}. Recall that frame zero is the innermost
7365 (currently executing) frame, frame one is the frame that called the
7366 innermost one, and so on. The highest-numbered frame is the one for
7369 @item frame @var{stack-addr} [ @var{pc-addr} ]
7370 @itemx f @var{stack-addr} [ @var{pc-addr} ]
7371 Select the frame at address @var{stack-addr}. This is useful mainly if the
7372 chaining of stack frames has been damaged by a bug, making it
7373 impossible for @value{GDBN} to assign numbers properly to all frames. In
7374 addition, this can be useful when your program has multiple stacks and
7375 switches between them. The optional @var{pc-addr} can also be given to
7376 specify the value of PC for the stack frame.
7380 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7381 numbers @var{n}, this advances toward the outermost frame, to higher
7382 frame numbers, to frames that have existed longer.
7385 @kindex do @r{(@code{down})}
7387 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7388 positive numbers @var{n}, this advances toward the innermost frame, to
7389 lower frame numbers, to frames that were created more recently.
7390 You may abbreviate @code{down} as @code{do}.
7393 All of these commands end by printing two lines of output describing the
7394 frame. The first line shows the frame number, the function name, the
7395 arguments, and the source file and line number of execution in that
7396 frame. The second line shows the text of that source line.
7404 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7406 10 read_input_file (argv[i]);
7410 After such a printout, the @code{list} command with no arguments
7411 prints ten lines centered on the point of execution in the frame.
7412 You can also edit the program at the point of execution with your favorite
7413 editing program by typing @code{edit}.
7414 @xref{List, ,Printing Source Lines},
7418 @kindex select-frame
7420 The @code{select-frame} command is a variant of @code{frame} that does
7421 not display the new frame after selecting it. This command is
7422 intended primarily for use in @value{GDBN} command scripts, where the
7423 output might be unnecessary and distracting.
7425 @kindex down-silently
7427 @item up-silently @var{n}
7428 @itemx down-silently @var{n}
7429 These two commands are variants of @code{up} and @code{down},
7430 respectively; they differ in that they do their work silently, without
7431 causing display of the new frame. They are intended primarily for use
7432 in @value{GDBN} command scripts, where the output might be unnecessary and
7437 @section Information About a Frame
7439 There are several other commands to print information about the selected
7445 When used without any argument, this command does not change which
7446 frame is selected, but prints a brief description of the currently
7447 selected stack frame. It can be abbreviated @code{f}. With an
7448 argument, this command is used to select a stack frame.
7449 @xref{Selection, ,Selecting a Frame}.
7452 @kindex info f @r{(@code{info frame})}
7455 This command prints a verbose description of the selected stack frame,
7460 the address of the frame
7462 the address of the next frame down (called by this frame)
7464 the address of the next frame up (caller of this frame)
7466 the language in which the source code corresponding to this frame is written
7468 the address of the frame's arguments
7470 the address of the frame's local variables
7472 the program counter saved in it (the address of execution in the caller frame)
7474 which registers were saved in the frame
7477 @noindent The verbose description is useful when
7478 something has gone wrong that has made the stack format fail to fit
7479 the usual conventions.
7481 @item info frame @var{addr}
7482 @itemx info f @var{addr}
7483 Print a verbose description of the frame at address @var{addr}, without
7484 selecting that frame. The selected frame remains unchanged by this
7485 command. This requires the same kind of address (more than one for some
7486 architectures) that you specify in the @code{frame} command.
7487 @xref{Selection, ,Selecting a Frame}.
7491 Print the arguments of the selected frame, each on a separate line.
7495 Print the local variables of the selected frame, each on a separate
7496 line. These are all variables (declared either static or automatic)
7497 accessible at the point of execution of the selected frame.
7501 @node Frame Filter Management
7502 @section Management of Frame Filters.
7503 @cindex managing frame filters
7505 Frame filters are Python based utilities to manage and decorate the
7506 output of frames. @xref{Frame Filter API}, for further information.
7508 Managing frame filters is performed by several commands available
7509 within @value{GDBN}, detailed here.
7512 @kindex info frame-filter
7513 @item info frame-filter
7514 Print a list of installed frame filters from all dictionaries, showing
7515 their name, priority and enabled status.
7517 @kindex disable frame-filter
7518 @anchor{disable frame-filter all}
7519 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
7520 Disable a frame filter in the dictionary matching
7521 @var{filter-dictionary} and @var{filter-name}. The
7522 @var{filter-dictionary} may be @code{all}, @code{global},
7523 @code{progspace}, or the name of the object file where the frame filter
7524 dictionary resides. When @code{all} is specified, all frame filters
7525 across all dictionaries are disabled. The @var{filter-name} is the name
7526 of the frame filter and is used when @code{all} is not the option for
7527 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
7528 may be enabled again later.
7530 @kindex enable frame-filter
7531 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
7532 Enable a frame filter in the dictionary matching
7533 @var{filter-dictionary} and @var{filter-name}. The
7534 @var{filter-dictionary} may be @code{all}, @code{global},
7535 @code{progspace} or the name of the object file where the frame filter
7536 dictionary resides. When @code{all} is specified, all frame filters across
7537 all dictionaries are enabled. The @var{filter-name} is the name of the frame
7538 filter and is used when @code{all} is not the option for
7539 @var{filter-dictionary}.
7544 (gdb) info frame-filter
7546 global frame-filters:
7547 Priority Enabled Name
7548 1000 No PrimaryFunctionFilter
7551 progspace /build/test frame-filters:
7552 Priority Enabled Name
7553 100 Yes ProgspaceFilter
7555 objfile /build/test frame-filters:
7556 Priority Enabled Name
7557 999 Yes BuildProgra Filter
7559 (gdb) disable frame-filter /build/test BuildProgramFilter
7560 (gdb) info frame-filter
7562 global frame-filters:
7563 Priority Enabled Name
7564 1000 No PrimaryFunctionFilter
7567 progspace /build/test frame-filters:
7568 Priority Enabled Name
7569 100 Yes ProgspaceFilter
7571 objfile /build/test frame-filters:
7572 Priority Enabled Name
7573 999 No BuildProgramFilter
7575 (gdb) enable frame-filter global PrimaryFunctionFilter
7576 (gdb) info frame-filter
7578 global frame-filters:
7579 Priority Enabled Name
7580 1000 Yes PrimaryFunctionFilter
7583 progspace /build/test frame-filters:
7584 Priority Enabled Name
7585 100 Yes ProgspaceFilter
7587 objfile /build/test frame-filters:
7588 Priority Enabled Name
7589 999 No BuildProgramFilter
7592 @kindex set frame-filter priority
7593 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
7594 Set the @var{priority} of a frame filter in the dictionary matching
7595 @var{filter-dictionary}, and the frame filter name matching
7596 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7597 @code{progspace} or the name of the object file where the frame filter
7598 dictionary resides. The @var{priority} is an integer.
7600 @kindex show frame-filter priority
7601 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
7602 Show the @var{priority} of a frame filter in the dictionary matching
7603 @var{filter-dictionary}, and the frame filter name matching
7604 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7605 @code{progspace} or the name of the object file where the frame filter
7611 (gdb) info frame-filter
7613 global frame-filters:
7614 Priority Enabled Name
7615 1000 Yes PrimaryFunctionFilter
7618 progspace /build/test frame-filters:
7619 Priority Enabled Name
7620 100 Yes ProgspaceFilter
7622 objfile /build/test frame-filters:
7623 Priority Enabled Name
7624 999 No BuildProgramFilter
7626 (gdb) set frame-filter priority global Reverse 50
7627 (gdb) info frame-filter
7629 global frame-filters:
7630 Priority Enabled Name
7631 1000 Yes PrimaryFunctionFilter
7634 progspace /build/test frame-filters:
7635 Priority Enabled Name
7636 100 Yes ProgspaceFilter
7638 objfile /build/test frame-filters:
7639 Priority Enabled Name
7640 999 No BuildProgramFilter
7645 @chapter Examining Source Files
7647 @value{GDBN} can print parts of your program's source, since the debugging
7648 information recorded in the program tells @value{GDBN} what source files were
7649 used to build it. When your program stops, @value{GDBN} spontaneously prints
7650 the line where it stopped. Likewise, when you select a stack frame
7651 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7652 execution in that frame has stopped. You can print other portions of
7653 source files by explicit command.
7655 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7656 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7657 @value{GDBN} under @sc{gnu} Emacs}.
7660 * List:: Printing source lines
7661 * Specify Location:: How to specify code locations
7662 * Edit:: Editing source files
7663 * Search:: Searching source files
7664 * Source Path:: Specifying source directories
7665 * Machine Code:: Source and machine code
7669 @section Printing Source Lines
7672 @kindex l @r{(@code{list})}
7673 To print lines from a source file, use the @code{list} command
7674 (abbreviated @code{l}). By default, ten lines are printed.
7675 There are several ways to specify what part of the file you want to
7676 print; see @ref{Specify Location}, for the full list.
7678 Here are the forms of the @code{list} command most commonly used:
7681 @item list @var{linenum}
7682 Print lines centered around line number @var{linenum} in the
7683 current source file.
7685 @item list @var{function}
7686 Print lines centered around the beginning of function
7690 Print more lines. If the last lines printed were printed with a
7691 @code{list} command, this prints lines following the last lines
7692 printed; however, if the last line printed was a solitary line printed
7693 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7694 Stack}), this prints lines centered around that line.
7697 Print lines just before the lines last printed.
7700 @cindex @code{list}, how many lines to display
7701 By default, @value{GDBN} prints ten source lines with any of these forms of
7702 the @code{list} command. You can change this using @code{set listsize}:
7705 @kindex set listsize
7706 @item set listsize @var{count}
7707 @itemx set listsize unlimited
7708 Make the @code{list} command display @var{count} source lines (unless
7709 the @code{list} argument explicitly specifies some other number).
7710 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7712 @kindex show listsize
7714 Display the number of lines that @code{list} prints.
7717 Repeating a @code{list} command with @key{RET} discards the argument,
7718 so it is equivalent to typing just @code{list}. This is more useful
7719 than listing the same lines again. An exception is made for an
7720 argument of @samp{-}; that argument is preserved in repetition so that
7721 each repetition moves up in the source file.
7723 In general, the @code{list} command expects you to supply zero, one or two
7724 @dfn{locations}. Locations specify source lines; there are several ways
7725 of writing them (@pxref{Specify Location}), but the effect is always
7726 to specify some source line.
7728 Here is a complete description of the possible arguments for @code{list}:
7731 @item list @var{location}
7732 Print lines centered around the line specified by @var{location}.
7734 @item list @var{first},@var{last}
7735 Print lines from @var{first} to @var{last}. Both arguments are
7736 locations. When a @code{list} command has two locations, and the
7737 source file of the second location is omitted, this refers to
7738 the same source file as the first location.
7740 @item list ,@var{last}
7741 Print lines ending with @var{last}.
7743 @item list @var{first},
7744 Print lines starting with @var{first}.
7747 Print lines just after the lines last printed.
7750 Print lines just before the lines last printed.
7753 As described in the preceding table.
7756 @node Specify Location
7757 @section Specifying a Location
7758 @cindex specifying location
7760 @cindex source location
7763 * Linespec Locations:: Linespec locations
7764 * Explicit Locations:: Explicit locations
7765 * Address Locations:: Address locations
7768 Several @value{GDBN} commands accept arguments that specify a location
7769 of your program's code. Since @value{GDBN} is a source-level
7770 debugger, a location usually specifies some line in the source code.
7771 Locations may be specified using three different formats:
7772 linespec locations, explicit locations, or address locations.
7774 @node Linespec Locations
7775 @subsection Linespec Locations
7776 @cindex linespec locations
7778 A @dfn{linespec} is a colon-separated list of source location parameters such
7779 as file name, function name, etc. Here are all the different ways of
7780 specifying a linespec:
7784 Specifies the line number @var{linenum} of the current source file.
7787 @itemx +@var{offset}
7788 Specifies the line @var{offset} lines before or after the @dfn{current
7789 line}. For the @code{list} command, the current line is the last one
7790 printed; for the breakpoint commands, this is the line at which
7791 execution stopped in the currently selected @dfn{stack frame}
7792 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7793 used as the second of the two linespecs in a @code{list} command,
7794 this specifies the line @var{offset} lines up or down from the first
7797 @item @var{filename}:@var{linenum}
7798 Specifies the line @var{linenum} in the source file @var{filename}.
7799 If @var{filename} is a relative file name, then it will match any
7800 source file name with the same trailing components. For example, if
7801 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7802 name of @file{/build/trunk/gcc/expr.c}, but not
7803 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7805 @item @var{function}
7806 Specifies the line that begins the body of the function @var{function}.
7807 For example, in C, this is the line with the open brace.
7809 @item @var{function}:@var{label}
7810 Specifies the line where @var{label} appears in @var{function}.
7812 @item @var{filename}:@var{function}
7813 Specifies the line that begins the body of the function @var{function}
7814 in the file @var{filename}. You only need the file name with a
7815 function name to avoid ambiguity when there are identically named
7816 functions in different source files.
7819 Specifies the line at which the label named @var{label} appears
7820 in the function corresponding to the currently selected stack frame.
7821 If there is no current selected stack frame (for instance, if the inferior
7822 is not running), then @value{GDBN} will not search for a label.
7824 @cindex breakpoint at static probe point
7825 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7826 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7827 applications to embed static probes. @xref{Static Probe Points}, for more
7828 information on finding and using static probes. This form of linespec
7829 specifies the location of such a static probe.
7831 If @var{objfile} is given, only probes coming from that shared library
7832 or executable matching @var{objfile} as a regular expression are considered.
7833 If @var{provider} is given, then only probes from that provider are considered.
7834 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7835 each one of those probes.
7838 @node Explicit Locations
7839 @subsection Explicit Locations
7840 @cindex explicit locations
7842 @dfn{Explicit locations} allow the user to directly specify the source
7843 location's parameters using option-value pairs.
7845 Explicit locations are useful when several functions, labels, or
7846 file names have the same name (base name for files) in the program's
7847 sources. In these cases, explicit locations point to the source
7848 line you meant more accurately and unambiguously. Also, using
7849 explicit locations might be faster in large programs.
7851 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
7852 defined in the file named @file{foo} or the label @code{bar} in a function
7853 named @code{foo}. @value{GDBN} must search either the file system or
7854 the symbol table to know.
7856 The list of valid explicit location options is summarized in the
7860 @item -source @var{filename}
7861 The value specifies the source file name. To differentiate between
7862 files with the same base name, prepend as many directories as is necessary
7863 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
7864 @value{GDBN} will use the first file it finds with the given base
7865 name. This option requires the use of either @code{-function} or @code{-line}.
7867 @item -function @var{function}
7868 The value specifies the name of a function. Operations
7869 on function locations unmodified by other options (such as @code{-label}
7870 or @code{-line}) refer to the line that begins the body of the function.
7871 In C, for example, this is the line with the open brace.
7873 @item -label @var{label}
7874 The value specifies the name of a label. When the function
7875 name is not specified, the label is searched in the function of the currently
7876 selected stack frame.
7878 @item -line @var{number}
7879 The value specifies a line offset for the location. The offset may either
7880 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
7881 the command. When specified without any other options, the line offset is
7882 relative to the current line.
7885 Explicit location options may be abbreviated by omitting any non-unique
7886 trailing characters from the option name, e.g., @code{break -s main.c -li 3}.
7888 @node Address Locations
7889 @subsection Address Locations
7890 @cindex address locations
7892 @dfn{Address locations} indicate a specific program address. They have
7893 the generalized form *@var{address}.
7895 For line-oriented commands, such as @code{list} and @code{edit}, this
7896 specifies a source line that contains @var{address}. For @code{break} and
7897 other breakpoint-oriented commands, this can be used to set breakpoints in
7898 parts of your program which do not have debugging information or
7901 Here @var{address} may be any expression valid in the current working
7902 language (@pxref{Languages, working language}) that specifies a code
7903 address. In addition, as a convenience, @value{GDBN} extends the
7904 semantics of expressions used in locations to cover several situations
7905 that frequently occur during debugging. Here are the various forms
7909 @item @var{expression}
7910 Any expression valid in the current working language.
7912 @item @var{funcaddr}
7913 An address of a function or procedure derived from its name. In C,
7914 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
7915 simply the function's name @var{function} (and actually a special case
7916 of a valid expression). In Pascal and Modula-2, this is
7917 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7918 (although the Pascal form also works).
7920 This form specifies the address of the function's first instruction,
7921 before the stack frame and arguments have been set up.
7923 @item '@var{filename}':@var{funcaddr}
7924 Like @var{funcaddr} above, but also specifies the name of the source
7925 file explicitly. This is useful if the name of the function does not
7926 specify the function unambiguously, e.g., if there are several
7927 functions with identical names in different source files.
7931 @section Editing Source Files
7932 @cindex editing source files
7935 @kindex e @r{(@code{edit})}
7936 To edit the lines in a source file, use the @code{edit} command.
7937 The editing program of your choice
7938 is invoked with the current line set to
7939 the active line in the program.
7940 Alternatively, there are several ways to specify what part of the file you
7941 want to print if you want to see other parts of the program:
7944 @item edit @var{location}
7945 Edit the source file specified by @code{location}. Editing starts at
7946 that @var{location}, e.g., at the specified source line of the
7947 specified file. @xref{Specify Location}, for all the possible forms
7948 of the @var{location} argument; here are the forms of the @code{edit}
7949 command most commonly used:
7952 @item edit @var{number}
7953 Edit the current source file with @var{number} as the active line number.
7955 @item edit @var{function}
7956 Edit the file containing @var{function} at the beginning of its definition.
7961 @subsection Choosing your Editor
7962 You can customize @value{GDBN} to use any editor you want
7964 The only restriction is that your editor (say @code{ex}), recognizes the
7965 following command-line syntax:
7967 ex +@var{number} file
7969 The optional numeric value +@var{number} specifies the number of the line in
7970 the file where to start editing.}.
7971 By default, it is @file{@value{EDITOR}}, but you can change this
7972 by setting the environment variable @code{EDITOR} before using
7973 @value{GDBN}. For example, to configure @value{GDBN} to use the
7974 @code{vi} editor, you could use these commands with the @code{sh} shell:
7980 or in the @code{csh} shell,
7982 setenv EDITOR /usr/bin/vi
7987 @section Searching Source Files
7988 @cindex searching source files
7990 There are two commands for searching through the current source file for a
7995 @kindex forward-search
7996 @kindex fo @r{(@code{forward-search})}
7997 @item forward-search @var{regexp}
7998 @itemx search @var{regexp}
7999 The command @samp{forward-search @var{regexp}} checks each line,
8000 starting with the one following the last line listed, for a match for
8001 @var{regexp}. It lists the line that is found. You can use the
8002 synonym @samp{search @var{regexp}} or abbreviate the command name as
8005 @kindex reverse-search
8006 @item reverse-search @var{regexp}
8007 The command @samp{reverse-search @var{regexp}} checks each line, starting
8008 with the one before the last line listed and going backward, for a match
8009 for @var{regexp}. It lists the line that is found. You can abbreviate
8010 this command as @code{rev}.
8014 @section Specifying Source Directories
8017 @cindex directories for source files
8018 Executable programs sometimes do not record the directories of the source
8019 files from which they were compiled, just the names. Even when they do,
8020 the directories could be moved between the compilation and your debugging
8021 session. @value{GDBN} has a list of directories to search for source files;
8022 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
8023 it tries all the directories in the list, in the order they are present
8024 in the list, until it finds a file with the desired name.
8026 For example, suppose an executable references the file
8027 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
8028 @file{/mnt/cross}. The file is first looked up literally; if this
8029 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
8030 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
8031 message is printed. @value{GDBN} does not look up the parts of the
8032 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
8033 Likewise, the subdirectories of the source path are not searched: if
8034 the source path is @file{/mnt/cross}, and the binary refers to
8035 @file{foo.c}, @value{GDBN} would not find it under
8036 @file{/mnt/cross/usr/src/foo-1.0/lib}.
8038 Plain file names, relative file names with leading directories, file
8039 names containing dots, etc.@: are all treated as described above; for
8040 instance, if the source path is @file{/mnt/cross}, and the source file
8041 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
8042 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
8043 that---@file{/mnt/cross/foo.c}.
8045 Note that the executable search path is @emph{not} used to locate the
8048 Whenever you reset or rearrange the source path, @value{GDBN} clears out
8049 any information it has cached about where source files are found and where
8050 each line is in the file.
8054 When you start @value{GDBN}, its source path includes only @samp{cdir}
8055 and @samp{cwd}, in that order.
8056 To add other directories, use the @code{directory} command.
8058 The search path is used to find both program source files and @value{GDBN}
8059 script files (read using the @samp{-command} option and @samp{source} command).
8061 In addition to the source path, @value{GDBN} provides a set of commands
8062 that manage a list of source path substitution rules. A @dfn{substitution
8063 rule} specifies how to rewrite source directories stored in the program's
8064 debug information in case the sources were moved to a different
8065 directory between compilation and debugging. A rule is made of
8066 two strings, the first specifying what needs to be rewritten in
8067 the path, and the second specifying how it should be rewritten.
8068 In @ref{set substitute-path}, we name these two parts @var{from} and
8069 @var{to} respectively. @value{GDBN} does a simple string replacement
8070 of @var{from} with @var{to} at the start of the directory part of the
8071 source file name, and uses that result instead of the original file
8072 name to look up the sources.
8074 Using the previous example, suppose the @file{foo-1.0} tree has been
8075 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
8076 @value{GDBN} to replace @file{/usr/src} in all source path names with
8077 @file{/mnt/cross}. The first lookup will then be
8078 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
8079 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
8080 substitution rule, use the @code{set substitute-path} command
8081 (@pxref{set substitute-path}).
8083 To avoid unexpected substitution results, a rule is applied only if the
8084 @var{from} part of the directory name ends at a directory separator.
8085 For instance, a rule substituting @file{/usr/source} into
8086 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
8087 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
8088 is applied only at the beginning of the directory name, this rule will
8089 not be applied to @file{/root/usr/source/baz.c} either.
8091 In many cases, you can achieve the same result using the @code{directory}
8092 command. However, @code{set substitute-path} can be more efficient in
8093 the case where the sources are organized in a complex tree with multiple
8094 subdirectories. With the @code{directory} command, you need to add each
8095 subdirectory of your project. If you moved the entire tree while
8096 preserving its internal organization, then @code{set substitute-path}
8097 allows you to direct the debugger to all the sources with one single
8100 @code{set substitute-path} is also more than just a shortcut command.
8101 The source path is only used if the file at the original location no
8102 longer exists. On the other hand, @code{set substitute-path} modifies
8103 the debugger behavior to look at the rewritten location instead. So, if
8104 for any reason a source file that is not relevant to your executable is
8105 located at the original location, a substitution rule is the only
8106 method available to point @value{GDBN} at the new location.
8108 @cindex @samp{--with-relocated-sources}
8109 @cindex default source path substitution
8110 You can configure a default source path substitution rule by
8111 configuring @value{GDBN} with the
8112 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
8113 should be the name of a directory under @value{GDBN}'s configured
8114 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
8115 directory names in debug information under @var{dir} will be adjusted
8116 automatically if the installed @value{GDBN} is moved to a new
8117 location. This is useful if @value{GDBN}, libraries or executables
8118 with debug information and corresponding source code are being moved
8122 @item directory @var{dirname} @dots{}
8123 @item dir @var{dirname} @dots{}
8124 Add directory @var{dirname} to the front of the source path. Several
8125 directory names may be given to this command, separated by @samp{:}
8126 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
8127 part of absolute file names) or
8128 whitespace. You may specify a directory that is already in the source
8129 path; this moves it forward, so @value{GDBN} searches it sooner.
8133 @vindex $cdir@r{, convenience variable}
8134 @vindex $cwd@r{, convenience variable}
8135 @cindex compilation directory
8136 @cindex current directory
8137 @cindex working directory
8138 @cindex directory, current
8139 @cindex directory, compilation
8140 You can use the string @samp{$cdir} to refer to the compilation
8141 directory (if one is recorded), and @samp{$cwd} to refer to the current
8142 working directory. @samp{$cwd} is not the same as @samp{.}---the former
8143 tracks the current working directory as it changes during your @value{GDBN}
8144 session, while the latter is immediately expanded to the current
8145 directory at the time you add an entry to the source path.
8148 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
8150 @c RET-repeat for @code{directory} is explicitly disabled, but since
8151 @c repeating it would be a no-op we do not say that. (thanks to RMS)
8153 @item set directories @var{path-list}
8154 @kindex set directories
8155 Set the source path to @var{path-list}.
8156 @samp{$cdir:$cwd} are added if missing.
8158 @item show directories
8159 @kindex show directories
8160 Print the source path: show which directories it contains.
8162 @anchor{set substitute-path}
8163 @item set substitute-path @var{from} @var{to}
8164 @kindex set substitute-path
8165 Define a source path substitution rule, and add it at the end of the
8166 current list of existing substitution rules. If a rule with the same
8167 @var{from} was already defined, then the old rule is also deleted.
8169 For example, if the file @file{/foo/bar/baz.c} was moved to
8170 @file{/mnt/cross/baz.c}, then the command
8173 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
8177 will tell @value{GDBN} to replace @samp{/foo/bar} with
8178 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
8179 @file{baz.c} even though it was moved.
8181 In the case when more than one substitution rule have been defined,
8182 the rules are evaluated one by one in the order where they have been
8183 defined. The first one matching, if any, is selected to perform
8186 For instance, if we had entered the following commands:
8189 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
8190 (@value{GDBP}) set substitute-path /usr/src /mnt/src
8194 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
8195 @file{/mnt/include/defs.h} by using the first rule. However, it would
8196 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
8197 @file{/mnt/src/lib/foo.c}.
8200 @item unset substitute-path [path]
8201 @kindex unset substitute-path
8202 If a path is specified, search the current list of substitution rules
8203 for a rule that would rewrite that path. Delete that rule if found.
8204 A warning is emitted by the debugger if no rule could be found.
8206 If no path is specified, then all substitution rules are deleted.
8208 @item show substitute-path [path]
8209 @kindex show substitute-path
8210 If a path is specified, then print the source path substitution rule
8211 which would rewrite that path, if any.
8213 If no path is specified, then print all existing source path substitution
8218 If your source path is cluttered with directories that are no longer of
8219 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
8220 versions of source. You can correct the situation as follows:
8224 Use @code{directory} with no argument to reset the source path to its default value.
8227 Use @code{directory} with suitable arguments to reinstall the
8228 directories you want in the source path. You can add all the
8229 directories in one command.
8233 @section Source and Machine Code
8234 @cindex source line and its code address
8236 You can use the command @code{info line} to map source lines to program
8237 addresses (and vice versa), and the command @code{disassemble} to display
8238 a range of addresses as machine instructions. You can use the command
8239 @code{set disassemble-next-line} to set whether to disassemble next
8240 source line when execution stops. When run under @sc{gnu} Emacs
8241 mode, the @code{info line} command causes the arrow to point to the
8242 line specified. Also, @code{info line} prints addresses in symbolic form as
8247 @item info line @var{location}
8248 Print the starting and ending addresses of the compiled code for
8249 source line @var{location}. You can specify source lines in any of
8250 the ways documented in @ref{Specify Location}.
8253 For example, we can use @code{info line} to discover the location of
8254 the object code for the first line of function
8255 @code{m4_changequote}:
8257 @c FIXME: I think this example should also show the addresses in
8258 @c symbolic form, as they usually would be displayed.
8260 (@value{GDBP}) info line m4_changequote
8261 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
8265 @cindex code address and its source line
8266 We can also inquire (using @code{*@var{addr}} as the form for
8267 @var{location}) what source line covers a particular address:
8269 (@value{GDBP}) info line *0x63ff
8270 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
8273 @cindex @code{$_} and @code{info line}
8274 @cindex @code{x} command, default address
8275 @kindex x@r{(examine), and} info line
8276 After @code{info line}, the default address for the @code{x} command
8277 is changed to the starting address of the line, so that @samp{x/i} is
8278 sufficient to begin examining the machine code (@pxref{Memory,
8279 ,Examining Memory}). Also, this address is saved as the value of the
8280 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
8285 @cindex assembly instructions
8286 @cindex instructions, assembly
8287 @cindex machine instructions
8288 @cindex listing machine instructions
8290 @itemx disassemble /m
8291 @itemx disassemble /s
8292 @itemx disassemble /r
8293 This specialized command dumps a range of memory as machine
8294 instructions. It can also print mixed source+disassembly by specifying
8295 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
8296 as well as in symbolic form by specifying the @code{/r} modifier.
8297 The default memory range is the function surrounding the
8298 program counter of the selected frame. A single argument to this
8299 command is a program counter value; @value{GDBN} dumps the function
8300 surrounding this value. When two arguments are given, they should
8301 be separated by a comma, possibly surrounded by whitespace. The
8302 arguments specify a range of addresses to dump, in one of two forms:
8305 @item @var{start},@var{end}
8306 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
8307 @item @var{start},+@var{length}
8308 the addresses from @var{start} (inclusive) to
8309 @code{@var{start}+@var{length}} (exclusive).
8313 When 2 arguments are specified, the name of the function is also
8314 printed (since there could be several functions in the given range).
8316 The argument(s) can be any expression yielding a numeric value, such as
8317 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
8319 If the range of memory being disassembled contains current program counter,
8320 the instruction at that location is shown with a @code{=>} marker.
8323 The following example shows the disassembly of a range of addresses of
8324 HP PA-RISC 2.0 code:
8327 (@value{GDBP}) disas 0x32c4, 0x32e4
8328 Dump of assembler code from 0x32c4 to 0x32e4:
8329 0x32c4 <main+204>: addil 0,dp
8330 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
8331 0x32cc <main+212>: ldil 0x3000,r31
8332 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
8333 0x32d4 <main+220>: ldo 0(r31),rp
8334 0x32d8 <main+224>: addil -0x800,dp
8335 0x32dc <main+228>: ldo 0x588(r1),r26
8336 0x32e0 <main+232>: ldil 0x3000,r31
8337 End of assembler dump.
8340 Here is an example showing mixed source+assembly for Intel x86
8341 with @code{/m} or @code{/s}, when the program is stopped just after
8342 function prologue in a non-optimized function with no inline code.
8345 (@value{GDBP}) disas /m main
8346 Dump of assembler code for function main:
8348 0x08048330 <+0>: push %ebp
8349 0x08048331 <+1>: mov %esp,%ebp
8350 0x08048333 <+3>: sub $0x8,%esp
8351 0x08048336 <+6>: and $0xfffffff0,%esp
8352 0x08048339 <+9>: sub $0x10,%esp
8354 6 printf ("Hello.\n");
8355 => 0x0804833c <+12>: movl $0x8048440,(%esp)
8356 0x08048343 <+19>: call 0x8048284 <puts@@plt>
8360 0x08048348 <+24>: mov $0x0,%eax
8361 0x0804834d <+29>: leave
8362 0x0804834e <+30>: ret
8364 End of assembler dump.
8367 The @code{/m} option is deprecated as its output is not useful when
8368 there is either inlined code or re-ordered code.
8369 The @code{/s} option is the preferred choice.
8370 Here is an example for AMD x86-64 showing the difference between
8371 @code{/m} output and @code{/s} output.
8372 This example has one inline function defined in a header file,
8373 and the code is compiled with @samp{-O2} optimization.
8374 Note how the @code{/m} output is missing the disassembly of
8375 several instructions that are present in the @code{/s} output.
8405 (@value{GDBP}) disas /m main
8406 Dump of assembler code for function main:
8410 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8411 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8415 0x000000000040041d <+29>: xor %eax,%eax
8416 0x000000000040041f <+31>: retq
8417 0x0000000000400420 <+32>: add %eax,%eax
8418 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8420 End of assembler dump.
8421 (@value{GDBP}) disas /s main
8422 Dump of assembler code for function main:
8426 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8430 0x0000000000400406 <+6>: test %eax,%eax
8431 0x0000000000400408 <+8>: js 0x400420 <main+32>
8436 0x000000000040040a <+10>: lea 0xa(%rax),%edx
8437 0x000000000040040d <+13>: test %eax,%eax
8438 0x000000000040040f <+15>: mov $0x1,%eax
8439 0x0000000000400414 <+20>: cmovne %edx,%eax
8443 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8447 0x000000000040041d <+29>: xor %eax,%eax
8448 0x000000000040041f <+31>: retq
8452 0x0000000000400420 <+32>: add %eax,%eax
8453 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8454 End of assembler dump.
8457 Here is another example showing raw instructions in hex for AMD x86-64,
8460 (gdb) disas /r 0x400281,+10
8461 Dump of assembler code from 0x400281 to 0x40028b:
8462 0x0000000000400281: 38 36 cmp %dh,(%rsi)
8463 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
8464 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
8465 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
8466 End of assembler dump.
8469 Addresses cannot be specified as a location (@pxref{Specify Location}).
8470 So, for example, if you want to disassemble function @code{bar}
8471 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
8472 and not @samp{disassemble foo.c:bar}.
8474 Some architectures have more than one commonly-used set of instruction
8475 mnemonics or other syntax.
8477 For programs that were dynamically linked and use shared libraries,
8478 instructions that call functions or branch to locations in the shared
8479 libraries might show a seemingly bogus location---it's actually a
8480 location of the relocation table. On some architectures, @value{GDBN}
8481 might be able to resolve these to actual function names.
8484 @kindex set disassembly-flavor
8485 @cindex Intel disassembly flavor
8486 @cindex AT&T disassembly flavor
8487 @item set disassembly-flavor @var{instruction-set}
8488 Select the instruction set to use when disassembling the
8489 program via the @code{disassemble} or @code{x/i} commands.
8491 Currently this command is only defined for the Intel x86 family. You
8492 can set @var{instruction-set} to either @code{intel} or @code{att}.
8493 The default is @code{att}, the AT&T flavor used by default by Unix
8494 assemblers for x86-based targets.
8496 @kindex show disassembly-flavor
8497 @item show disassembly-flavor
8498 Show the current setting of the disassembly flavor.
8502 @kindex set disassemble-next-line
8503 @kindex show disassemble-next-line
8504 @item set disassemble-next-line
8505 @itemx show disassemble-next-line
8506 Control whether or not @value{GDBN} will disassemble the next source
8507 line or instruction when execution stops. If ON, @value{GDBN} will
8508 display disassembly of the next source line when execution of the
8509 program being debugged stops. This is @emph{in addition} to
8510 displaying the source line itself, which @value{GDBN} always does if
8511 possible. If the next source line cannot be displayed for some reason
8512 (e.g., if @value{GDBN} cannot find the source file, or there's no line
8513 info in the debug info), @value{GDBN} will display disassembly of the
8514 next @emph{instruction} instead of showing the next source line. If
8515 AUTO, @value{GDBN} will display disassembly of next instruction only
8516 if the source line cannot be displayed. This setting causes
8517 @value{GDBN} to display some feedback when you step through a function
8518 with no line info or whose source file is unavailable. The default is
8519 OFF, which means never display the disassembly of the next line or
8525 @chapter Examining Data
8527 @cindex printing data
8528 @cindex examining data
8531 The usual way to examine data in your program is with the @code{print}
8532 command (abbreviated @code{p}), or its synonym @code{inspect}. It
8533 evaluates and prints the value of an expression of the language your
8534 program is written in (@pxref{Languages, ,Using @value{GDBN} with
8535 Different Languages}). It may also print the expression using a
8536 Python-based pretty-printer (@pxref{Pretty Printing}).
8539 @item print @var{expr}
8540 @itemx print /@var{f} @var{expr}
8541 @var{expr} is an expression (in the source language). By default the
8542 value of @var{expr} is printed in a format appropriate to its data type;
8543 you can choose a different format by specifying @samp{/@var{f}}, where
8544 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
8548 @itemx print /@var{f}
8549 @cindex reprint the last value
8550 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
8551 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
8552 conveniently inspect the same value in an alternative format.
8555 A more low-level way of examining data is with the @code{x} command.
8556 It examines data in memory at a specified address and prints it in a
8557 specified format. @xref{Memory, ,Examining Memory}.
8559 If you are interested in information about types, or about how the
8560 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
8561 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
8564 @cindex exploring hierarchical data structures
8566 Another way of examining values of expressions and type information is
8567 through the Python extension command @code{explore} (available only if
8568 the @value{GDBN} build is configured with @code{--with-python}). It
8569 offers an interactive way to start at the highest level (or, the most
8570 abstract level) of the data type of an expression (or, the data type
8571 itself) and explore all the way down to leaf scalar values/fields
8572 embedded in the higher level data types.
8575 @item explore @var{arg}
8576 @var{arg} is either an expression (in the source language), or a type
8577 visible in the current context of the program being debugged.
8580 The working of the @code{explore} command can be illustrated with an
8581 example. If a data type @code{struct ComplexStruct} is defined in your
8591 struct ComplexStruct
8593 struct SimpleStruct *ss_p;
8599 followed by variable declarations as
8602 struct SimpleStruct ss = @{ 10, 1.11 @};
8603 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
8607 then, the value of the variable @code{cs} can be explored using the
8608 @code{explore} command as follows.
8612 The value of `cs' is a struct/class of type `struct ComplexStruct' with
8613 the following fields:
8615 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
8616 arr = <Enter 1 to explore this field of type `int [10]'>
8618 Enter the field number of choice:
8622 Since the fields of @code{cs} are not scalar values, you are being
8623 prompted to chose the field you want to explore. Let's say you choose
8624 the field @code{ss_p} by entering @code{0}. Then, since this field is a
8625 pointer, you will be asked if it is pointing to a single value. From
8626 the declaration of @code{cs} above, it is indeed pointing to a single
8627 value, hence you enter @code{y}. If you enter @code{n}, then you will
8628 be asked if it were pointing to an array of values, in which case this
8629 field will be explored as if it were an array.
8632 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
8633 Continue exploring it as a pointer to a single value [y/n]: y
8634 The value of `*(cs.ss_p)' is a struct/class of type `struct
8635 SimpleStruct' with the following fields:
8637 i = 10 .. (Value of type `int')
8638 d = 1.1100000000000001 .. (Value of type `double')
8640 Press enter to return to parent value:
8644 If the field @code{arr} of @code{cs} was chosen for exploration by
8645 entering @code{1} earlier, then since it is as array, you will be
8646 prompted to enter the index of the element in the array that you want
8650 `cs.arr' is an array of `int'.
8651 Enter the index of the element you want to explore in `cs.arr': 5
8653 `(cs.arr)[5]' is a scalar value of type `int'.
8657 Press enter to return to parent value:
8660 In general, at any stage of exploration, you can go deeper towards the
8661 leaf values by responding to the prompts appropriately, or hit the
8662 return key to return to the enclosing data structure (the @i{higher}
8663 level data structure).
8665 Similar to exploring values, you can use the @code{explore} command to
8666 explore types. Instead of specifying a value (which is typically a
8667 variable name or an expression valid in the current context of the
8668 program being debugged), you specify a type name. If you consider the
8669 same example as above, your can explore the type
8670 @code{struct ComplexStruct} by passing the argument
8671 @code{struct ComplexStruct} to the @code{explore} command.
8674 (gdb) explore struct ComplexStruct
8678 By responding to the prompts appropriately in the subsequent interactive
8679 session, you can explore the type @code{struct ComplexStruct} in a
8680 manner similar to how the value @code{cs} was explored in the above
8683 The @code{explore} command also has two sub-commands,
8684 @code{explore value} and @code{explore type}. The former sub-command is
8685 a way to explicitly specify that value exploration of the argument is
8686 being invoked, while the latter is a way to explicitly specify that type
8687 exploration of the argument is being invoked.
8690 @item explore value @var{expr}
8691 @cindex explore value
8692 This sub-command of @code{explore} explores the value of the
8693 expression @var{expr} (if @var{expr} is an expression valid in the
8694 current context of the program being debugged). The behavior of this
8695 command is identical to that of the behavior of the @code{explore}
8696 command being passed the argument @var{expr}.
8698 @item explore type @var{arg}
8699 @cindex explore type
8700 This sub-command of @code{explore} explores the type of @var{arg} (if
8701 @var{arg} is a type visible in the current context of program being
8702 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8703 is an expression valid in the current context of the program being
8704 debugged). If @var{arg} is a type, then the behavior of this command is
8705 identical to that of the @code{explore} command being passed the
8706 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8707 this command will be identical to that of the @code{explore} command
8708 being passed the type of @var{arg} as the argument.
8712 * Expressions:: Expressions
8713 * Ambiguous Expressions:: Ambiguous Expressions
8714 * Variables:: Program variables
8715 * Arrays:: Artificial arrays
8716 * Output Formats:: Output formats
8717 * Memory:: Examining memory
8718 * Auto Display:: Automatic display
8719 * Print Settings:: Print settings
8720 * Pretty Printing:: Python pretty printing
8721 * Value History:: Value history
8722 * Convenience Vars:: Convenience variables
8723 * Convenience Funs:: Convenience functions
8724 * Registers:: Registers
8725 * Floating Point Hardware:: Floating point hardware
8726 * Vector Unit:: Vector Unit
8727 * OS Information:: Auxiliary data provided by operating system
8728 * Memory Region Attributes:: Memory region attributes
8729 * Dump/Restore Files:: Copy between memory and a file
8730 * Core File Generation:: Cause a program dump its core
8731 * Character Sets:: Debugging programs that use a different
8732 character set than GDB does
8733 * Caching Target Data:: Data caching for targets
8734 * Searching Memory:: Searching memory for a sequence of bytes
8735 * Value Sizes:: Managing memory allocated for values
8739 @section Expressions
8742 @code{print} and many other @value{GDBN} commands accept an expression and
8743 compute its value. Any kind of constant, variable or operator defined
8744 by the programming language you are using is valid in an expression in
8745 @value{GDBN}. This includes conditional expressions, function calls,
8746 casts, and string constants. It also includes preprocessor macros, if
8747 you compiled your program to include this information; see
8750 @cindex arrays in expressions
8751 @value{GDBN} supports array constants in expressions input by
8752 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8753 you can use the command @code{print @{1, 2, 3@}} to create an array
8754 of three integers. If you pass an array to a function or assign it
8755 to a program variable, @value{GDBN} copies the array to memory that
8756 is @code{malloc}ed in the target program.
8758 Because C is so widespread, most of the expressions shown in examples in
8759 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8760 Languages}, for information on how to use expressions in other
8763 In this section, we discuss operators that you can use in @value{GDBN}
8764 expressions regardless of your programming language.
8766 @cindex casts, in expressions
8767 Casts are supported in all languages, not just in C, because it is so
8768 useful to cast a number into a pointer in order to examine a structure
8769 at that address in memory.
8770 @c FIXME: casts supported---Mod2 true?
8772 @value{GDBN} supports these operators, in addition to those common
8773 to programming languages:
8777 @samp{@@} is a binary operator for treating parts of memory as arrays.
8778 @xref{Arrays, ,Artificial Arrays}, for more information.
8781 @samp{::} allows you to specify a variable in terms of the file or
8782 function where it is defined. @xref{Variables, ,Program Variables}.
8784 @cindex @{@var{type}@}
8785 @cindex type casting memory
8786 @cindex memory, viewing as typed object
8787 @cindex casts, to view memory
8788 @item @{@var{type}@} @var{addr}
8789 Refers to an object of type @var{type} stored at address @var{addr} in
8790 memory. The address @var{addr} may be any expression whose value is
8791 an integer or pointer (but parentheses are required around binary
8792 operators, just as in a cast). This construct is allowed regardless
8793 of what kind of data is normally supposed to reside at @var{addr}.
8796 @node Ambiguous Expressions
8797 @section Ambiguous Expressions
8798 @cindex ambiguous expressions
8800 Expressions can sometimes contain some ambiguous elements. For instance,
8801 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8802 a single function name to be defined several times, for application in
8803 different contexts. This is called @dfn{overloading}. Another example
8804 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8805 templates and is typically instantiated several times, resulting in
8806 the same function name being defined in different contexts.
8808 In some cases and depending on the language, it is possible to adjust
8809 the expression to remove the ambiguity. For instance in C@t{++}, you
8810 can specify the signature of the function you want to break on, as in
8811 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8812 qualified name of your function often makes the expression unambiguous
8815 When an ambiguity that needs to be resolved is detected, the debugger
8816 has the capability to display a menu of numbered choices for each
8817 possibility, and then waits for the selection with the prompt @samp{>}.
8818 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
8819 aborts the current command. If the command in which the expression was
8820 used allows more than one choice to be selected, the next option in the
8821 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
8824 For example, the following session excerpt shows an attempt to set a
8825 breakpoint at the overloaded symbol @code{String::after}.
8826 We choose three particular definitions of that function name:
8828 @c FIXME! This is likely to change to show arg type lists, at least
8831 (@value{GDBP}) b String::after
8834 [2] file:String.cc; line number:867
8835 [3] file:String.cc; line number:860
8836 [4] file:String.cc; line number:875
8837 [5] file:String.cc; line number:853
8838 [6] file:String.cc; line number:846
8839 [7] file:String.cc; line number:735
8841 Breakpoint 1 at 0xb26c: file String.cc, line 867.
8842 Breakpoint 2 at 0xb344: file String.cc, line 875.
8843 Breakpoint 3 at 0xafcc: file String.cc, line 846.
8844 Multiple breakpoints were set.
8845 Use the "delete" command to delete unwanted
8852 @kindex set multiple-symbols
8853 @item set multiple-symbols @var{mode}
8854 @cindex multiple-symbols menu
8856 This option allows you to adjust the debugger behavior when an expression
8859 By default, @var{mode} is set to @code{all}. If the command with which
8860 the expression is used allows more than one choice, then @value{GDBN}
8861 automatically selects all possible choices. For instance, inserting
8862 a breakpoint on a function using an ambiguous name results in a breakpoint
8863 inserted on each possible match. However, if a unique choice must be made,
8864 then @value{GDBN} uses the menu to help you disambiguate the expression.
8865 For instance, printing the address of an overloaded function will result
8866 in the use of the menu.
8868 When @var{mode} is set to @code{ask}, the debugger always uses the menu
8869 when an ambiguity is detected.
8871 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
8872 an error due to the ambiguity and the command is aborted.
8874 @kindex show multiple-symbols
8875 @item show multiple-symbols
8876 Show the current value of the @code{multiple-symbols} setting.
8880 @section Program Variables
8882 The most common kind of expression to use is the name of a variable
8885 Variables in expressions are understood in the selected stack frame
8886 (@pxref{Selection, ,Selecting a Frame}); they must be either:
8890 global (or file-static)
8897 visible according to the scope rules of the
8898 programming language from the point of execution in that frame
8901 @noindent This means that in the function
8916 you can examine and use the variable @code{a} whenever your program is
8917 executing within the function @code{foo}, but you can only use or
8918 examine the variable @code{b} while your program is executing inside
8919 the block where @code{b} is declared.
8921 @cindex variable name conflict
8922 There is an exception: you can refer to a variable or function whose
8923 scope is a single source file even if the current execution point is not
8924 in this file. But it is possible to have more than one such variable or
8925 function with the same name (in different source files). If that
8926 happens, referring to that name has unpredictable effects. If you wish,
8927 you can specify a static variable in a particular function or file by
8928 using the colon-colon (@code{::}) notation:
8930 @cindex colon-colon, context for variables/functions
8932 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
8933 @cindex @code{::}, context for variables/functions
8936 @var{file}::@var{variable}
8937 @var{function}::@var{variable}
8941 Here @var{file} or @var{function} is the name of the context for the
8942 static @var{variable}. In the case of file names, you can use quotes to
8943 make sure @value{GDBN} parses the file name as a single word---for example,
8944 to print a global value of @code{x} defined in @file{f2.c}:
8947 (@value{GDBP}) p 'f2.c'::x
8950 The @code{::} notation is normally used for referring to
8951 static variables, since you typically disambiguate uses of local variables
8952 in functions by selecting the appropriate frame and using the
8953 simple name of the variable. However, you may also use this notation
8954 to refer to local variables in frames enclosing the selected frame:
8963 process (a); /* Stop here */
8974 For example, if there is a breakpoint at the commented line,
8975 here is what you might see
8976 when the program stops after executing the call @code{bar(0)}:
8981 (@value{GDBP}) p bar::a
8984 #2 0x080483d0 in foo (a=5) at foobar.c:12
8987 (@value{GDBP}) p bar::a
8991 @cindex C@t{++} scope resolution
8992 These uses of @samp{::} are very rarely in conflict with the very
8993 similar use of the same notation in C@t{++}. When they are in
8994 conflict, the C@t{++} meaning takes precedence; however, this can be
8995 overridden by quoting the file or function name with single quotes.
8997 For example, suppose the program is stopped in a method of a class
8998 that has a field named @code{includefile}, and there is also an
8999 include file named @file{includefile} that defines a variable,
9003 (@value{GDBP}) p includefile
9005 (@value{GDBP}) p includefile::some_global
9006 A syntax error in expression, near `'.
9007 (@value{GDBP}) p 'includefile'::some_global
9011 @cindex wrong values
9012 @cindex variable values, wrong
9013 @cindex function entry/exit, wrong values of variables
9014 @cindex optimized code, wrong values of variables
9016 @emph{Warning:} Occasionally, a local variable may appear to have the
9017 wrong value at certain points in a function---just after entry to a new
9018 scope, and just before exit.
9020 You may see this problem when you are stepping by machine instructions.
9021 This is because, on most machines, it takes more than one instruction to
9022 set up a stack frame (including local variable definitions); if you are
9023 stepping by machine instructions, variables may appear to have the wrong
9024 values until the stack frame is completely built. On exit, it usually
9025 also takes more than one machine instruction to destroy a stack frame;
9026 after you begin stepping through that group of instructions, local
9027 variable definitions may be gone.
9029 This may also happen when the compiler does significant optimizations.
9030 To be sure of always seeing accurate values, turn off all optimization
9033 @cindex ``No symbol "foo" in current context''
9034 Another possible effect of compiler optimizations is to optimize
9035 unused variables out of existence, or assign variables to registers (as
9036 opposed to memory addresses). Depending on the support for such cases
9037 offered by the debug info format used by the compiler, @value{GDBN}
9038 might not be able to display values for such local variables. If that
9039 happens, @value{GDBN} will print a message like this:
9042 No symbol "foo" in current context.
9045 To solve such problems, either recompile without optimizations, or use a
9046 different debug info format, if the compiler supports several such
9047 formats. @xref{Compilation}, for more information on choosing compiler
9048 options. @xref{C, ,C and C@t{++}}, for more information about debug
9049 info formats that are best suited to C@t{++} programs.
9051 If you ask to print an object whose contents are unknown to
9052 @value{GDBN}, e.g., because its data type is not completely specified
9053 by the debug information, @value{GDBN} will say @samp{<incomplete
9054 type>}. @xref{Symbols, incomplete type}, for more about this.
9056 If you append @kbd{@@entry} string to a function parameter name you get its
9057 value at the time the function got called. If the value is not available an
9058 error message is printed. Entry values are available only with some compilers.
9059 Entry values are normally also printed at the function parameter list according
9060 to @ref{set print entry-values}.
9063 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
9069 (gdb) print i@@entry
9073 Strings are identified as arrays of @code{char} values without specified
9074 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
9075 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
9076 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
9077 defines literal string type @code{"char"} as @code{char} without a sign.
9082 signed char var1[] = "A";
9085 You get during debugging
9090 $2 = @{65 'A', 0 '\0'@}
9094 @section Artificial Arrays
9096 @cindex artificial array
9098 @kindex @@@r{, referencing memory as an array}
9099 It is often useful to print out several successive objects of the
9100 same type in memory; a section of an array, or an array of
9101 dynamically determined size for which only a pointer exists in the
9104 You can do this by referring to a contiguous span of memory as an
9105 @dfn{artificial array}, using the binary operator @samp{@@}. The left
9106 operand of @samp{@@} should be the first element of the desired array
9107 and be an individual object. The right operand should be the desired length
9108 of the array. The result is an array value whose elements are all of
9109 the type of the left argument. The first element is actually the left
9110 argument; the second element comes from bytes of memory immediately
9111 following those that hold the first element, and so on. Here is an
9112 example. If a program says
9115 int *array = (int *) malloc (len * sizeof (int));
9119 you can print the contents of @code{array} with
9125 The left operand of @samp{@@} must reside in memory. Array values made
9126 with @samp{@@} in this way behave just like other arrays in terms of
9127 subscripting, and are coerced to pointers when used in expressions.
9128 Artificial arrays most often appear in expressions via the value history
9129 (@pxref{Value History, ,Value History}), after printing one out.
9131 Another way to create an artificial array is to use a cast.
9132 This re-interprets a value as if it were an array.
9133 The value need not be in memory:
9135 (@value{GDBP}) p/x (short[2])0x12345678
9136 $1 = @{0x1234, 0x5678@}
9139 As a convenience, if you leave the array length out (as in
9140 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
9141 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
9143 (@value{GDBP}) p/x (short[])0x12345678
9144 $2 = @{0x1234, 0x5678@}
9147 Sometimes the artificial array mechanism is not quite enough; in
9148 moderately complex data structures, the elements of interest may not
9149 actually be adjacent---for example, if you are interested in the values
9150 of pointers in an array. One useful work-around in this situation is
9151 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
9152 Variables}) as a counter in an expression that prints the first
9153 interesting value, and then repeat that expression via @key{RET}. For
9154 instance, suppose you have an array @code{dtab} of pointers to
9155 structures, and you are interested in the values of a field @code{fv}
9156 in each structure. Here is an example of what you might type:
9166 @node Output Formats
9167 @section Output Formats
9169 @cindex formatted output
9170 @cindex output formats
9171 By default, @value{GDBN} prints a value according to its data type. Sometimes
9172 this is not what you want. For example, you might want to print a number
9173 in hex, or a pointer in decimal. Or you might want to view data in memory
9174 at a certain address as a character string or as an instruction. To do
9175 these things, specify an @dfn{output format} when you print a value.
9177 The simplest use of output formats is to say how to print a value
9178 already computed. This is done by starting the arguments of the
9179 @code{print} command with a slash and a format letter. The format
9180 letters supported are:
9184 Regard the bits of the value as an integer, and print the integer in
9188 Print as integer in signed decimal.
9191 Print as integer in unsigned decimal.
9194 Print as integer in octal.
9197 Print as integer in binary. The letter @samp{t} stands for ``two''.
9198 @footnote{@samp{b} cannot be used because these format letters are also
9199 used with the @code{x} command, where @samp{b} stands for ``byte'';
9200 see @ref{Memory,,Examining Memory}.}
9203 @cindex unknown address, locating
9204 @cindex locate address
9205 Print as an address, both absolute in hexadecimal and as an offset from
9206 the nearest preceding symbol. You can use this format used to discover
9207 where (in what function) an unknown address is located:
9210 (@value{GDBP}) p/a 0x54320
9211 $3 = 0x54320 <_initialize_vx+396>
9215 The command @code{info symbol 0x54320} yields similar results.
9216 @xref{Symbols, info symbol}.
9219 Regard as an integer and print it as a character constant. This
9220 prints both the numerical value and its character representation. The
9221 character representation is replaced with the octal escape @samp{\nnn}
9222 for characters outside the 7-bit @sc{ascii} range.
9224 Without this format, @value{GDBN} displays @code{char},
9225 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
9226 constants. Single-byte members of vectors are displayed as integer
9230 Regard the bits of the value as a floating point number and print
9231 using typical floating point syntax.
9234 @cindex printing strings
9235 @cindex printing byte arrays
9236 Regard as a string, if possible. With this format, pointers to single-byte
9237 data are displayed as null-terminated strings and arrays of single-byte data
9238 are displayed as fixed-length strings. Other values are displayed in their
9241 Without this format, @value{GDBN} displays pointers to and arrays of
9242 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
9243 strings. Single-byte members of a vector are displayed as an integer
9247 Like @samp{x} formatting, the value is treated as an integer and
9248 printed as hexadecimal, but leading zeros are printed to pad the value
9249 to the size of the integer type.
9252 @cindex raw printing
9253 Print using the @samp{raw} formatting. By default, @value{GDBN} will
9254 use a Python-based pretty-printer, if one is available (@pxref{Pretty
9255 Printing}). This typically results in a higher-level display of the
9256 value's contents. The @samp{r} format bypasses any Python
9257 pretty-printer which might exist.
9260 For example, to print the program counter in hex (@pxref{Registers}), type
9267 Note that no space is required before the slash; this is because command
9268 names in @value{GDBN} cannot contain a slash.
9270 To reprint the last value in the value history with a different format,
9271 you can use the @code{print} command with just a format and no
9272 expression. For example, @samp{p/x} reprints the last value in hex.
9275 @section Examining Memory
9277 You can use the command @code{x} (for ``examine'') to examine memory in
9278 any of several formats, independently of your program's data types.
9280 @cindex examining memory
9282 @kindex x @r{(examine memory)}
9283 @item x/@var{nfu} @var{addr}
9286 Use the @code{x} command to examine memory.
9289 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
9290 much memory to display and how to format it; @var{addr} is an
9291 expression giving the address where you want to start displaying memory.
9292 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
9293 Several commands set convenient defaults for @var{addr}.
9296 @item @var{n}, the repeat count
9297 The repeat count is a decimal integer; the default is 1. It specifies
9298 how much memory (counting by units @var{u}) to display.
9299 @c This really is **decimal**; unaffected by 'set radix' as of GDB
9302 @item @var{f}, the display format
9303 The display format is one of the formats used by @code{print}
9304 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
9305 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
9306 The default is @samp{x} (hexadecimal) initially. The default changes
9307 each time you use either @code{x} or @code{print}.
9309 @item @var{u}, the unit size
9310 The unit size is any of
9316 Halfwords (two bytes).
9318 Words (four bytes). This is the initial default.
9320 Giant words (eight bytes).
9323 Each time you specify a unit size with @code{x}, that size becomes the
9324 default unit the next time you use @code{x}. For the @samp{i} format,
9325 the unit size is ignored and is normally not written. For the @samp{s} format,
9326 the unit size defaults to @samp{b}, unless it is explicitly given.
9327 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
9328 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
9329 Note that the results depend on the programming language of the
9330 current compilation unit. If the language is C, the @samp{s}
9331 modifier will use the UTF-16 encoding while @samp{w} will use
9332 UTF-32. The encoding is set by the programming language and cannot
9335 @item @var{addr}, starting display address
9336 @var{addr} is the address where you want @value{GDBN} to begin displaying
9337 memory. The expression need not have a pointer value (though it may);
9338 it is always interpreted as an integer address of a byte of memory.
9339 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
9340 @var{addr} is usually just after the last address examined---but several
9341 other commands also set the default address: @code{info breakpoints} (to
9342 the address of the last breakpoint listed), @code{info line} (to the
9343 starting address of a line), and @code{print} (if you use it to display
9344 a value from memory).
9347 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
9348 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
9349 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
9350 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
9351 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
9353 Since the letters indicating unit sizes are all distinct from the
9354 letters specifying output formats, you do not have to remember whether
9355 unit size or format comes first; either order works. The output
9356 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
9357 (However, the count @var{n} must come first; @samp{wx4} does not work.)
9359 Even though the unit size @var{u} is ignored for the formats @samp{s}
9360 and @samp{i}, you might still want to use a count @var{n}; for example,
9361 @samp{3i} specifies that you want to see three machine instructions,
9362 including any operands. For convenience, especially when used with
9363 the @code{display} command, the @samp{i} format also prints branch delay
9364 slot instructions, if any, beyond the count specified, which immediately
9365 follow the last instruction that is within the count. The command
9366 @code{disassemble} gives an alternative way of inspecting machine
9367 instructions; see @ref{Machine Code,,Source and Machine Code}.
9369 All the defaults for the arguments to @code{x} are designed to make it
9370 easy to continue scanning memory with minimal specifications each time
9371 you use @code{x}. For example, after you have inspected three machine
9372 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
9373 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
9374 the repeat count @var{n} is used again; the other arguments default as
9375 for successive uses of @code{x}.
9377 When examining machine instructions, the instruction at current program
9378 counter is shown with a @code{=>} marker. For example:
9381 (@value{GDBP}) x/5i $pc-6
9382 0x804837f <main+11>: mov %esp,%ebp
9383 0x8048381 <main+13>: push %ecx
9384 0x8048382 <main+14>: sub $0x4,%esp
9385 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
9386 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
9389 @cindex @code{$_}, @code{$__}, and value history
9390 The addresses and contents printed by the @code{x} command are not saved
9391 in the value history because there is often too much of them and they
9392 would get in the way. Instead, @value{GDBN} makes these values available for
9393 subsequent use in expressions as values of the convenience variables
9394 @code{$_} and @code{$__}. After an @code{x} command, the last address
9395 examined is available for use in expressions in the convenience variable
9396 @code{$_}. The contents of that address, as examined, are available in
9397 the convenience variable @code{$__}.
9399 If the @code{x} command has a repeat count, the address and contents saved
9400 are from the last memory unit printed; this is not the same as the last
9401 address printed if several units were printed on the last line of output.
9403 @anchor{addressable memory unit}
9404 @cindex addressable memory unit
9405 Most targets have an addressable memory unit size of 8 bits. This means
9406 that to each memory address are associated 8 bits of data. Some
9407 targets, however, have other addressable memory unit sizes.
9408 Within @value{GDBN} and this document, the term
9409 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
9410 when explicitly referring to a chunk of data of that size. The word
9411 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
9412 the addressable memory unit size of the target. For most systems,
9413 addressable memory unit is a synonym of byte.
9415 @cindex remote memory comparison
9416 @cindex target memory comparison
9417 @cindex verify remote memory image
9418 @cindex verify target memory image
9419 When you are debugging a program running on a remote target machine
9420 (@pxref{Remote Debugging}), you may wish to verify the program's image
9421 in the remote machine's memory against the executable file you
9422 downloaded to the target. Or, on any target, you may want to check
9423 whether the program has corrupted its own read-only sections. The
9424 @code{compare-sections} command is provided for such situations.
9427 @kindex compare-sections
9428 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
9429 Compare the data of a loadable section @var{section-name} in the
9430 executable file of the program being debugged with the same section in
9431 the target machine's memory, and report any mismatches. With no
9432 arguments, compares all loadable sections. With an argument of
9433 @code{-r}, compares all loadable read-only sections.
9435 Note: for remote targets, this command can be accelerated if the
9436 target supports computing the CRC checksum of a block of memory
9437 (@pxref{qCRC packet}).
9441 @section Automatic Display
9442 @cindex automatic display
9443 @cindex display of expressions
9445 If you find that you want to print the value of an expression frequently
9446 (to see how it changes), you might want to add it to the @dfn{automatic
9447 display list} so that @value{GDBN} prints its value each time your program stops.
9448 Each expression added to the list is given a number to identify it;
9449 to remove an expression from the list, you specify that number.
9450 The automatic display looks like this:
9454 3: bar[5] = (struct hack *) 0x3804
9458 This display shows item numbers, expressions and their current values. As with
9459 displays you request manually using @code{x} or @code{print}, you can
9460 specify the output format you prefer; in fact, @code{display} decides
9461 whether to use @code{print} or @code{x} depending your format
9462 specification---it uses @code{x} if you specify either the @samp{i}
9463 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
9467 @item display @var{expr}
9468 Add the expression @var{expr} to the list of expressions to display
9469 each time your program stops. @xref{Expressions, ,Expressions}.
9471 @code{display} does not repeat if you press @key{RET} again after using it.
9473 @item display/@var{fmt} @var{expr}
9474 For @var{fmt} specifying only a display format and not a size or
9475 count, add the expression @var{expr} to the auto-display list but
9476 arrange to display it each time in the specified format @var{fmt}.
9477 @xref{Output Formats,,Output Formats}.
9479 @item display/@var{fmt} @var{addr}
9480 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
9481 number of units, add the expression @var{addr} as a memory address to
9482 be examined each time your program stops. Examining means in effect
9483 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
9486 For example, @samp{display/i $pc} can be helpful, to see the machine
9487 instruction about to be executed each time execution stops (@samp{$pc}
9488 is a common name for the program counter; @pxref{Registers, ,Registers}).
9491 @kindex delete display
9493 @item undisplay @var{dnums}@dots{}
9494 @itemx delete display @var{dnums}@dots{}
9495 Remove items from the list of expressions to display. Specify the
9496 numbers of the displays that you want affected with the command
9497 argument @var{dnums}. It can be a single display number, one of the
9498 numbers shown in the first field of the @samp{info display} display;
9499 or it could be a range of display numbers, as in @code{2-4}.
9501 @code{undisplay} does not repeat if you press @key{RET} after using it.
9502 (Otherwise you would just get the error @samp{No display number @dots{}}.)
9504 @kindex disable display
9505 @item disable display @var{dnums}@dots{}
9506 Disable the display of item numbers @var{dnums}. A disabled display
9507 item is not printed automatically, but is not forgotten. It may be
9508 enabled again later. Specify the numbers of the displays that you
9509 want affected with the command argument @var{dnums}. It can be a
9510 single display number, one of the numbers shown in the first field of
9511 the @samp{info display} display; or it could be a range of display
9512 numbers, as in @code{2-4}.
9514 @kindex enable display
9515 @item enable display @var{dnums}@dots{}
9516 Enable display of item numbers @var{dnums}. It becomes effective once
9517 again in auto display of its expression, until you specify otherwise.
9518 Specify the numbers of the displays that you want affected with the
9519 command argument @var{dnums}. It can be a single display number, one
9520 of the numbers shown in the first field of the @samp{info display}
9521 display; or it could be a range of display numbers, as in @code{2-4}.
9524 Display the current values of the expressions on the list, just as is
9525 done when your program stops.
9527 @kindex info display
9529 Print the list of expressions previously set up to display
9530 automatically, each one with its item number, but without showing the
9531 values. This includes disabled expressions, which are marked as such.
9532 It also includes expressions which would not be displayed right now
9533 because they refer to automatic variables not currently available.
9536 @cindex display disabled out of scope
9537 If a display expression refers to local variables, then it does not make
9538 sense outside the lexical context for which it was set up. Such an
9539 expression is disabled when execution enters a context where one of its
9540 variables is not defined. For example, if you give the command
9541 @code{display last_char} while inside a function with an argument
9542 @code{last_char}, @value{GDBN} displays this argument while your program
9543 continues to stop inside that function. When it stops elsewhere---where
9544 there is no variable @code{last_char}---the display is disabled
9545 automatically. The next time your program stops where @code{last_char}
9546 is meaningful, you can enable the display expression once again.
9548 @node Print Settings
9549 @section Print Settings
9551 @cindex format options
9552 @cindex print settings
9553 @value{GDBN} provides the following ways to control how arrays, structures,
9554 and symbols are printed.
9557 These settings are useful for debugging programs in any language:
9561 @item set print address
9562 @itemx set print address on
9563 @cindex print/don't print memory addresses
9564 @value{GDBN} prints memory addresses showing the location of stack
9565 traces, structure values, pointer values, breakpoints, and so forth,
9566 even when it also displays the contents of those addresses. The default
9567 is @code{on}. For example, this is what a stack frame display looks like with
9568 @code{set print address on}:
9573 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
9575 530 if (lquote != def_lquote)
9579 @item set print address off
9580 Do not print addresses when displaying their contents. For example,
9581 this is the same stack frame displayed with @code{set print address off}:
9585 (@value{GDBP}) set print addr off
9587 #0 set_quotes (lq="<<", rq=">>") at input.c:530
9588 530 if (lquote != def_lquote)
9592 You can use @samp{set print address off} to eliminate all machine
9593 dependent displays from the @value{GDBN} interface. For example, with
9594 @code{print address off}, you should get the same text for backtraces on
9595 all machines---whether or not they involve pointer arguments.
9598 @item show print address
9599 Show whether or not addresses are to be printed.
9602 When @value{GDBN} prints a symbolic address, it normally prints the
9603 closest earlier symbol plus an offset. If that symbol does not uniquely
9604 identify the address (for example, it is a name whose scope is a single
9605 source file), you may need to clarify. One way to do this is with
9606 @code{info line}, for example @samp{info line *0x4537}. Alternately,
9607 you can set @value{GDBN} to print the source file and line number when
9608 it prints a symbolic address:
9611 @item set print symbol-filename on
9612 @cindex source file and line of a symbol
9613 @cindex symbol, source file and line
9614 Tell @value{GDBN} to print the source file name and line number of a
9615 symbol in the symbolic form of an address.
9617 @item set print symbol-filename off
9618 Do not print source file name and line number of a symbol. This is the
9621 @item show print symbol-filename
9622 Show whether or not @value{GDBN} will print the source file name and
9623 line number of a symbol in the symbolic form of an address.
9626 Another situation where it is helpful to show symbol filenames and line
9627 numbers is when disassembling code; @value{GDBN} shows you the line
9628 number and source file that corresponds to each instruction.
9630 Also, you may wish to see the symbolic form only if the address being
9631 printed is reasonably close to the closest earlier symbol:
9634 @item set print max-symbolic-offset @var{max-offset}
9635 @itemx set print max-symbolic-offset unlimited
9636 @cindex maximum value for offset of closest symbol
9637 Tell @value{GDBN} to only display the symbolic form of an address if the
9638 offset between the closest earlier symbol and the address is less than
9639 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
9640 to always print the symbolic form of an address if any symbol precedes
9641 it. Zero is equivalent to @code{unlimited}.
9643 @item show print max-symbolic-offset
9644 Ask how large the maximum offset is that @value{GDBN} prints in a
9648 @cindex wild pointer, interpreting
9649 @cindex pointer, finding referent
9650 If you have a pointer and you are not sure where it points, try
9651 @samp{set print symbol-filename on}. Then you can determine the name
9652 and source file location of the variable where it points, using
9653 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
9654 For example, here @value{GDBN} shows that a variable @code{ptt} points
9655 at another variable @code{t}, defined in @file{hi2.c}:
9658 (@value{GDBP}) set print symbol-filename on
9659 (@value{GDBP}) p/a ptt
9660 $4 = 0xe008 <t in hi2.c>
9664 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
9665 does not show the symbol name and filename of the referent, even with
9666 the appropriate @code{set print} options turned on.
9669 You can also enable @samp{/a}-like formatting all the time using
9670 @samp{set print symbol on}:
9673 @item set print symbol on
9674 Tell @value{GDBN} to print the symbol corresponding to an address, if
9677 @item set print symbol off
9678 Tell @value{GDBN} not to print the symbol corresponding to an
9679 address. In this mode, @value{GDBN} will still print the symbol
9680 corresponding to pointers to functions. This is the default.
9682 @item show print symbol
9683 Show whether @value{GDBN} will display the symbol corresponding to an
9687 Other settings control how different kinds of objects are printed:
9690 @item set print array
9691 @itemx set print array on
9692 @cindex pretty print arrays
9693 Pretty print arrays. This format is more convenient to read,
9694 but uses more space. The default is off.
9696 @item set print array off
9697 Return to compressed format for arrays.
9699 @item show print array
9700 Show whether compressed or pretty format is selected for displaying
9703 @cindex print array indexes
9704 @item set print array-indexes
9705 @itemx set print array-indexes on
9706 Print the index of each element when displaying arrays. May be more
9707 convenient to locate a given element in the array or quickly find the
9708 index of a given element in that printed array. The default is off.
9710 @item set print array-indexes off
9711 Stop printing element indexes when displaying arrays.
9713 @item show print array-indexes
9714 Show whether the index of each element is printed when displaying
9717 @item set print elements @var{number-of-elements}
9718 @itemx set print elements unlimited
9719 @cindex number of array elements to print
9720 @cindex limit on number of printed array elements
9721 Set a limit on how many elements of an array @value{GDBN} will print.
9722 If @value{GDBN} is printing a large array, it stops printing after it has
9723 printed the number of elements set by the @code{set print elements} command.
9724 This limit also applies to the display of strings.
9725 When @value{GDBN} starts, this limit is set to 200.
9726 Setting @var{number-of-elements} to @code{unlimited} or zero means
9727 that the number of elements to print is unlimited.
9729 @item show print elements
9730 Display the number of elements of a large array that @value{GDBN} will print.
9731 If the number is 0, then the printing is unlimited.
9733 @item set print frame-arguments @var{value}
9734 @kindex set print frame-arguments
9735 @cindex printing frame argument values
9736 @cindex print all frame argument values
9737 @cindex print frame argument values for scalars only
9738 @cindex do not print frame argument values
9739 This command allows to control how the values of arguments are printed
9740 when the debugger prints a frame (@pxref{Frames}). The possible
9745 The values of all arguments are printed.
9748 Print the value of an argument only if it is a scalar. The value of more
9749 complex arguments such as arrays, structures, unions, etc, is replaced
9750 by @code{@dots{}}. This is the default. Here is an example where
9751 only scalar arguments are shown:
9754 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9759 None of the argument values are printed. Instead, the value of each argument
9760 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9763 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9768 By default, only scalar arguments are printed. This command can be used
9769 to configure the debugger to print the value of all arguments, regardless
9770 of their type. However, it is often advantageous to not print the value
9771 of more complex parameters. For instance, it reduces the amount of
9772 information printed in each frame, making the backtrace more readable.
9773 Also, it improves performance when displaying Ada frames, because
9774 the computation of large arguments can sometimes be CPU-intensive,
9775 especially in large applications. Setting @code{print frame-arguments}
9776 to @code{scalars} (the default) or @code{none} avoids this computation,
9777 thus speeding up the display of each Ada frame.
9779 @item show print frame-arguments
9780 Show how the value of arguments should be displayed when printing a frame.
9782 @item set print raw frame-arguments on
9783 Print frame arguments in raw, non pretty-printed, form.
9785 @item set print raw frame-arguments off
9786 Print frame arguments in pretty-printed form, if there is a pretty-printer
9787 for the value (@pxref{Pretty Printing}),
9788 otherwise print the value in raw form.
9789 This is the default.
9791 @item show print raw frame-arguments
9792 Show whether to print frame arguments in raw form.
9794 @anchor{set print entry-values}
9795 @item set print entry-values @var{value}
9796 @kindex set print entry-values
9797 Set printing of frame argument values at function entry. In some cases
9798 @value{GDBN} can determine the value of function argument which was passed by
9799 the function caller, even if the value was modified inside the called function
9800 and therefore is different. With optimized code, the current value could be
9801 unavailable, but the entry value may still be known.
9803 The default value is @code{default} (see below for its description). Older
9804 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
9805 this feature will behave in the @code{default} setting the same way as with the
9808 This functionality is currently supported only by DWARF 2 debugging format and
9809 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9810 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9813 The @var{value} parameter can be one of the following:
9817 Print only actual parameter values, never print values from function entry
9821 #0 different (val=6)
9822 #0 lost (val=<optimized out>)
9824 #0 invalid (val=<optimized out>)
9828 Print only parameter values from function entry point. The actual parameter
9829 values are never printed.
9831 #0 equal (val@@entry=5)
9832 #0 different (val@@entry=5)
9833 #0 lost (val@@entry=5)
9834 #0 born (val@@entry=<optimized out>)
9835 #0 invalid (val@@entry=<optimized out>)
9839 Print only parameter values from function entry point. If value from function
9840 entry point is not known while the actual value is known, print the actual
9841 value for such parameter.
9843 #0 equal (val@@entry=5)
9844 #0 different (val@@entry=5)
9845 #0 lost (val@@entry=5)
9847 #0 invalid (val@@entry=<optimized out>)
9851 Print actual parameter values. If actual parameter value is not known while
9852 value from function entry point is known, print the entry point value for such
9856 #0 different (val=6)
9857 #0 lost (val@@entry=5)
9859 #0 invalid (val=<optimized out>)
9863 Always print both the actual parameter value and its value from function entry
9864 point, even if values of one or both are not available due to compiler
9867 #0 equal (val=5, val@@entry=5)
9868 #0 different (val=6, val@@entry=5)
9869 #0 lost (val=<optimized out>, val@@entry=5)
9870 #0 born (val=10, val@@entry=<optimized out>)
9871 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
9875 Print the actual parameter value if it is known and also its value from
9876 function entry point if it is known. If neither is known, print for the actual
9877 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
9878 values are known and identical, print the shortened
9879 @code{param=param@@entry=VALUE} notation.
9881 #0 equal (val=val@@entry=5)
9882 #0 different (val=6, val@@entry=5)
9883 #0 lost (val@@entry=5)
9885 #0 invalid (val=<optimized out>)
9889 Always print the actual parameter value. Print also its value from function
9890 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
9891 if both values are known and identical, print the shortened
9892 @code{param=param@@entry=VALUE} notation.
9894 #0 equal (val=val@@entry=5)
9895 #0 different (val=6, val@@entry=5)
9896 #0 lost (val=<optimized out>, val@@entry=5)
9898 #0 invalid (val=<optimized out>)
9902 For analysis messages on possible failures of frame argument values at function
9903 entry resolution see @ref{set debug entry-values}.
9905 @item show print entry-values
9906 Show the method being used for printing of frame argument values at function
9909 @item set print repeats @var{number-of-repeats}
9910 @itemx set print repeats unlimited
9911 @cindex repeated array elements
9912 Set the threshold for suppressing display of repeated array
9913 elements. When the number of consecutive identical elements of an
9914 array exceeds the threshold, @value{GDBN} prints the string
9915 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
9916 identical repetitions, instead of displaying the identical elements
9917 themselves. Setting the threshold to @code{unlimited} or zero will
9918 cause all elements to be individually printed. The default threshold
9921 @item show print repeats
9922 Display the current threshold for printing repeated identical
9925 @item set print null-stop
9926 @cindex @sc{null} elements in arrays
9927 Cause @value{GDBN} to stop printing the characters of an array when the first
9928 @sc{null} is encountered. This is useful when large arrays actually
9929 contain only short strings.
9932 @item show print null-stop
9933 Show whether @value{GDBN} stops printing an array on the first
9934 @sc{null} character.
9936 @item set print pretty on
9937 @cindex print structures in indented form
9938 @cindex indentation in structure display
9939 Cause @value{GDBN} to print structures in an indented format with one member
9940 per line, like this:
9955 @item set print pretty off
9956 Cause @value{GDBN} to print structures in a compact format, like this:
9960 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
9961 meat = 0x54 "Pork"@}
9966 This is the default format.
9968 @item show print pretty
9969 Show which format @value{GDBN} is using to print structures.
9971 @item set print sevenbit-strings on
9972 @cindex eight-bit characters in strings
9973 @cindex octal escapes in strings
9974 Print using only seven-bit characters; if this option is set,
9975 @value{GDBN} displays any eight-bit characters (in strings or
9976 character values) using the notation @code{\}@var{nnn}. This setting is
9977 best if you are working in English (@sc{ascii}) and you use the
9978 high-order bit of characters as a marker or ``meta'' bit.
9980 @item set print sevenbit-strings off
9981 Print full eight-bit characters. This allows the use of more
9982 international character sets, and is the default.
9984 @item show print sevenbit-strings
9985 Show whether or not @value{GDBN} is printing only seven-bit characters.
9987 @item set print union on
9988 @cindex unions in structures, printing
9989 Tell @value{GDBN} to print unions which are contained in structures
9990 and other unions. This is the default setting.
9992 @item set print union off
9993 Tell @value{GDBN} not to print unions which are contained in
9994 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
9997 @item show print union
9998 Ask @value{GDBN} whether or not it will print unions which are contained in
9999 structures and other unions.
10001 For example, given the declarations
10004 typedef enum @{Tree, Bug@} Species;
10005 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
10006 typedef enum @{Caterpillar, Cocoon, Butterfly@}
10017 struct thing foo = @{Tree, @{Acorn@}@};
10021 with @code{set print union on} in effect @samp{p foo} would print
10024 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
10028 and with @code{set print union off} in effect it would print
10031 $1 = @{it = Tree, form = @{...@}@}
10035 @code{set print union} affects programs written in C-like languages
10041 These settings are of interest when debugging C@t{++} programs:
10044 @cindex demangling C@t{++} names
10045 @item set print demangle
10046 @itemx set print demangle on
10047 Print C@t{++} names in their source form rather than in the encoded
10048 (``mangled'') form passed to the assembler and linker for type-safe
10049 linkage. The default is on.
10051 @item show print demangle
10052 Show whether C@t{++} names are printed in mangled or demangled form.
10054 @item set print asm-demangle
10055 @itemx set print asm-demangle on
10056 Print C@t{++} names in their source form rather than their mangled form, even
10057 in assembler code printouts such as instruction disassemblies.
10058 The default is off.
10060 @item show print asm-demangle
10061 Show whether C@t{++} names in assembly listings are printed in mangled
10064 @cindex C@t{++} symbol decoding style
10065 @cindex symbol decoding style, C@t{++}
10066 @kindex set demangle-style
10067 @item set demangle-style @var{style}
10068 Choose among several encoding schemes used by different compilers to
10069 represent C@t{++} names. The choices for @var{style} are currently:
10073 Allow @value{GDBN} to choose a decoding style by inspecting your program.
10074 This is the default.
10077 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
10080 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
10083 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
10086 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
10087 @strong{Warning:} this setting alone is not sufficient to allow
10088 debugging @code{cfront}-generated executables. @value{GDBN} would
10089 require further enhancement to permit that.
10092 If you omit @var{style}, you will see a list of possible formats.
10094 @item show demangle-style
10095 Display the encoding style currently in use for decoding C@t{++} symbols.
10097 @item set print object
10098 @itemx set print object on
10099 @cindex derived type of an object, printing
10100 @cindex display derived types
10101 When displaying a pointer to an object, identify the @emph{actual}
10102 (derived) type of the object rather than the @emph{declared} type, using
10103 the virtual function table. Note that the virtual function table is
10104 required---this feature can only work for objects that have run-time
10105 type identification; a single virtual method in the object's declared
10106 type is sufficient. Note that this setting is also taken into account when
10107 working with variable objects via MI (@pxref{GDB/MI}).
10109 @item set print object off
10110 Display only the declared type of objects, without reference to the
10111 virtual function table. This is the default setting.
10113 @item show print object
10114 Show whether actual, or declared, object types are displayed.
10116 @item set print static-members
10117 @itemx set print static-members on
10118 @cindex static members of C@t{++} objects
10119 Print static members when displaying a C@t{++} object. The default is on.
10121 @item set print static-members off
10122 Do not print static members when displaying a C@t{++} object.
10124 @item show print static-members
10125 Show whether C@t{++} static members are printed or not.
10127 @item set print pascal_static-members
10128 @itemx set print pascal_static-members on
10129 @cindex static members of Pascal objects
10130 @cindex Pascal objects, static members display
10131 Print static members when displaying a Pascal object. The default is on.
10133 @item set print pascal_static-members off
10134 Do not print static members when displaying a Pascal object.
10136 @item show print pascal_static-members
10137 Show whether Pascal static members are printed or not.
10139 @c These don't work with HP ANSI C++ yet.
10140 @item set print vtbl
10141 @itemx set print vtbl on
10142 @cindex pretty print C@t{++} virtual function tables
10143 @cindex virtual functions (C@t{++}) display
10144 @cindex VTBL display
10145 Pretty print C@t{++} virtual function tables. The default is off.
10146 (The @code{vtbl} commands do not work on programs compiled with the HP
10147 ANSI C@t{++} compiler (@code{aCC}).)
10149 @item set print vtbl off
10150 Do not pretty print C@t{++} virtual function tables.
10152 @item show print vtbl
10153 Show whether C@t{++} virtual function tables are pretty printed, or not.
10156 @node Pretty Printing
10157 @section Pretty Printing
10159 @value{GDBN} provides a mechanism to allow pretty-printing of values using
10160 Python code. It greatly simplifies the display of complex objects. This
10161 mechanism works for both MI and the CLI.
10164 * Pretty-Printer Introduction:: Introduction to pretty-printers
10165 * Pretty-Printer Example:: An example pretty-printer
10166 * Pretty-Printer Commands:: Pretty-printer commands
10169 @node Pretty-Printer Introduction
10170 @subsection Pretty-Printer Introduction
10172 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
10173 registered for the value. If there is then @value{GDBN} invokes the
10174 pretty-printer to print the value. Otherwise the value is printed normally.
10176 Pretty-printers are normally named. This makes them easy to manage.
10177 The @samp{info pretty-printer} command will list all the installed
10178 pretty-printers with their names.
10179 If a pretty-printer can handle multiple data types, then its
10180 @dfn{subprinters} are the printers for the individual data types.
10181 Each such subprinter has its own name.
10182 The format of the name is @var{printer-name};@var{subprinter-name}.
10184 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
10185 Typically they are automatically loaded and registered when the corresponding
10186 debug information is loaded, thus making them available without having to
10187 do anything special.
10189 There are three places where a pretty-printer can be registered.
10193 Pretty-printers registered globally are available when debugging
10197 Pretty-printers registered with a program space are available only
10198 when debugging that program.
10199 @xref{Progspaces In Python}, for more details on program spaces in Python.
10202 Pretty-printers registered with an objfile are loaded and unloaded
10203 with the corresponding objfile (e.g., shared library).
10204 @xref{Objfiles In Python}, for more details on objfiles in Python.
10207 @xref{Selecting Pretty-Printers}, for further information on how
10208 pretty-printers are selected,
10210 @xref{Writing a Pretty-Printer}, for implementing pretty printers
10213 @node Pretty-Printer Example
10214 @subsection Pretty-Printer Example
10216 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
10219 (@value{GDBP}) print s
10221 static npos = 4294967295,
10223 <std::allocator<char>> = @{
10224 <__gnu_cxx::new_allocator<char>> = @{
10225 <No data fields>@}, <No data fields>
10227 members of std::basic_string<char, std::char_traits<char>,
10228 std::allocator<char> >::_Alloc_hider:
10229 _M_p = 0x804a014 "abcd"
10234 With a pretty-printer for @code{std::string} only the contents are printed:
10237 (@value{GDBP}) print s
10241 @node Pretty-Printer Commands
10242 @subsection Pretty-Printer Commands
10243 @cindex pretty-printer commands
10246 @kindex info pretty-printer
10247 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10248 Print the list of installed pretty-printers.
10249 This includes disabled pretty-printers, which are marked as such.
10251 @var{object-regexp} is a regular expression matching the objects
10252 whose pretty-printers to list.
10253 Objects can be @code{global}, the program space's file
10254 (@pxref{Progspaces In Python}),
10255 and the object files within that program space (@pxref{Objfiles In Python}).
10256 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
10257 looks up a printer from these three objects.
10259 @var{name-regexp} is a regular expression matching the name of the printers
10262 @kindex disable pretty-printer
10263 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10264 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10265 A disabled pretty-printer is not forgotten, it may be enabled again later.
10267 @kindex enable pretty-printer
10268 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10269 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10274 Suppose we have three pretty-printers installed: one from library1.so
10275 named @code{foo} that prints objects of type @code{foo}, and
10276 another from library2.so named @code{bar} that prints two types of objects,
10277 @code{bar1} and @code{bar2}.
10280 (gdb) info pretty-printer
10287 (gdb) info pretty-printer library2
10292 (gdb) disable pretty-printer library1
10294 2 of 3 printers enabled
10295 (gdb) info pretty-printer
10302 (gdb) disable pretty-printer library2 bar:bar1
10304 1 of 3 printers enabled
10305 (gdb) info pretty-printer library2
10312 (gdb) disable pretty-printer library2 bar
10314 0 of 3 printers enabled
10315 (gdb) info pretty-printer library2
10324 Note that for @code{bar} the entire printer can be disabled,
10325 as can each individual subprinter.
10327 @node Value History
10328 @section Value History
10330 @cindex value history
10331 @cindex history of values printed by @value{GDBN}
10332 Values printed by the @code{print} command are saved in the @value{GDBN}
10333 @dfn{value history}. This allows you to refer to them in other expressions.
10334 Values are kept until the symbol table is re-read or discarded
10335 (for example with the @code{file} or @code{symbol-file} commands).
10336 When the symbol table changes, the value history is discarded,
10337 since the values may contain pointers back to the types defined in the
10342 @cindex history number
10343 The values printed are given @dfn{history numbers} by which you can
10344 refer to them. These are successive integers starting with one.
10345 @code{print} shows you the history number assigned to a value by
10346 printing @samp{$@var{num} = } before the value; here @var{num} is the
10349 To refer to any previous value, use @samp{$} followed by the value's
10350 history number. The way @code{print} labels its output is designed to
10351 remind you of this. Just @code{$} refers to the most recent value in
10352 the history, and @code{$$} refers to the value before that.
10353 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
10354 is the value just prior to @code{$$}, @code{$$1} is equivalent to
10355 @code{$$}, and @code{$$0} is equivalent to @code{$}.
10357 For example, suppose you have just printed a pointer to a structure and
10358 want to see the contents of the structure. It suffices to type
10364 If you have a chain of structures where the component @code{next} points
10365 to the next one, you can print the contents of the next one with this:
10372 You can print successive links in the chain by repeating this
10373 command---which you can do by just typing @key{RET}.
10375 Note that the history records values, not expressions. If the value of
10376 @code{x} is 4 and you type these commands:
10384 then the value recorded in the value history by the @code{print} command
10385 remains 4 even though the value of @code{x} has changed.
10388 @kindex show values
10390 Print the last ten values in the value history, with their item numbers.
10391 This is like @samp{p@ $$9} repeated ten times, except that @code{show
10392 values} does not change the history.
10394 @item show values @var{n}
10395 Print ten history values centered on history item number @var{n}.
10397 @item show values +
10398 Print ten history values just after the values last printed. If no more
10399 values are available, @code{show values +} produces no display.
10402 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
10403 same effect as @samp{show values +}.
10405 @node Convenience Vars
10406 @section Convenience Variables
10408 @cindex convenience variables
10409 @cindex user-defined variables
10410 @value{GDBN} provides @dfn{convenience variables} that you can use within
10411 @value{GDBN} to hold on to a value and refer to it later. These variables
10412 exist entirely within @value{GDBN}; they are not part of your program, and
10413 setting a convenience variable has no direct effect on further execution
10414 of your program. That is why you can use them freely.
10416 Convenience variables are prefixed with @samp{$}. Any name preceded by
10417 @samp{$} can be used for a convenience variable, unless it is one of
10418 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
10419 (Value history references, in contrast, are @emph{numbers} preceded
10420 by @samp{$}. @xref{Value History, ,Value History}.)
10422 You can save a value in a convenience variable with an assignment
10423 expression, just as you would set a variable in your program.
10427 set $foo = *object_ptr
10431 would save in @code{$foo} the value contained in the object pointed to by
10434 Using a convenience variable for the first time creates it, but its
10435 value is @code{void} until you assign a new value. You can alter the
10436 value with another assignment at any time.
10438 Convenience variables have no fixed types. You can assign a convenience
10439 variable any type of value, including structures and arrays, even if
10440 that variable already has a value of a different type. The convenience
10441 variable, when used as an expression, has the type of its current value.
10444 @kindex show convenience
10445 @cindex show all user variables and functions
10446 @item show convenience
10447 Print a list of convenience variables used so far, and their values,
10448 as well as a list of the convenience functions.
10449 Abbreviated @code{show conv}.
10451 @kindex init-if-undefined
10452 @cindex convenience variables, initializing
10453 @item init-if-undefined $@var{variable} = @var{expression}
10454 Set a convenience variable if it has not already been set. This is useful
10455 for user-defined commands that keep some state. It is similar, in concept,
10456 to using local static variables with initializers in C (except that
10457 convenience variables are global). It can also be used to allow users to
10458 override default values used in a command script.
10460 If the variable is already defined then the expression is not evaluated so
10461 any side-effects do not occur.
10464 One of the ways to use a convenience variable is as a counter to be
10465 incremented or a pointer to be advanced. For example, to print
10466 a field from successive elements of an array of structures:
10470 print bar[$i++]->contents
10474 Repeat that command by typing @key{RET}.
10476 Some convenience variables are created automatically by @value{GDBN} and given
10477 values likely to be useful.
10480 @vindex $_@r{, convenience variable}
10482 The variable @code{$_} is automatically set by the @code{x} command to
10483 the last address examined (@pxref{Memory, ,Examining Memory}). Other
10484 commands which provide a default address for @code{x} to examine also
10485 set @code{$_} to that address; these commands include @code{info line}
10486 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
10487 except when set by the @code{x} command, in which case it is a pointer
10488 to the type of @code{$__}.
10490 @vindex $__@r{, convenience variable}
10492 The variable @code{$__} is automatically set by the @code{x} command
10493 to the value found in the last address examined. Its type is chosen
10494 to match the format in which the data was printed.
10497 @vindex $_exitcode@r{, convenience variable}
10498 When the program being debugged terminates normally, @value{GDBN}
10499 automatically sets this variable to the exit code of the program, and
10500 resets @code{$_exitsignal} to @code{void}.
10503 @vindex $_exitsignal@r{, convenience variable}
10504 When the program being debugged dies due to an uncaught signal,
10505 @value{GDBN} automatically sets this variable to that signal's number,
10506 and resets @code{$_exitcode} to @code{void}.
10508 To distinguish between whether the program being debugged has exited
10509 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
10510 @code{$_exitsignal} is not @code{void}), the convenience function
10511 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
10512 Functions}). For example, considering the following source code:
10515 #include <signal.h>
10518 main (int argc, char *argv[])
10525 A valid way of telling whether the program being debugged has exited
10526 or signalled would be:
10529 (@value{GDBP}) define has_exited_or_signalled
10530 Type commands for definition of ``has_exited_or_signalled''.
10531 End with a line saying just ``end''.
10532 >if $_isvoid ($_exitsignal)
10533 >echo The program has exited\n
10535 >echo The program has signalled\n
10541 Program terminated with signal SIGALRM, Alarm clock.
10542 The program no longer exists.
10543 (@value{GDBP}) has_exited_or_signalled
10544 The program has signalled
10547 As can be seen, @value{GDBN} correctly informs that the program being
10548 debugged has signalled, since it calls @code{raise} and raises a
10549 @code{SIGALRM} signal. If the program being debugged had not called
10550 @code{raise}, then @value{GDBN} would report a normal exit:
10553 (@value{GDBP}) has_exited_or_signalled
10554 The program has exited
10558 The variable @code{$_exception} is set to the exception object being
10559 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
10562 @itemx $_probe_arg0@dots{}$_probe_arg11
10563 Arguments to a static probe. @xref{Static Probe Points}.
10566 @vindex $_sdata@r{, inspect, convenience variable}
10567 The variable @code{$_sdata} contains extra collected static tracepoint
10568 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
10569 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
10570 if extra static tracepoint data has not been collected.
10573 @vindex $_siginfo@r{, convenience variable}
10574 The variable @code{$_siginfo} contains extra signal information
10575 (@pxref{extra signal information}). Note that @code{$_siginfo}
10576 could be empty, if the application has not yet received any signals.
10577 For example, it will be empty before you execute the @code{run} command.
10580 @vindex $_tlb@r{, convenience variable}
10581 The variable @code{$_tlb} is automatically set when debugging
10582 applications running on MS-Windows in native mode or connected to
10583 gdbserver that supports the @code{qGetTIBAddr} request.
10584 @xref{General Query Packets}.
10585 This variable contains the address of the thread information block.
10588 The number of the current inferior. @xref{Inferiors and
10589 Programs, ,Debugging Multiple Inferiors and Programs}.
10592 The thread number of the current thread. @xref{thread numbers}.
10595 The global number of the current thread. @xref{global thread numbers}.
10599 @node Convenience Funs
10600 @section Convenience Functions
10602 @cindex convenience functions
10603 @value{GDBN} also supplies some @dfn{convenience functions}. These
10604 have a syntax similar to convenience variables. A convenience
10605 function can be used in an expression just like an ordinary function;
10606 however, a convenience function is implemented internally to
10609 These functions do not require @value{GDBN} to be configured with
10610 @code{Python} support, which means that they are always available.
10614 @item $_isvoid (@var{expr})
10615 @findex $_isvoid@r{, convenience function}
10616 Return one if the expression @var{expr} is @code{void}. Otherwise it
10619 A @code{void} expression is an expression where the type of the result
10620 is @code{void}. For example, you can examine a convenience variable
10621 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
10625 (@value{GDBP}) print $_exitcode
10627 (@value{GDBP}) print $_isvoid ($_exitcode)
10630 Starting program: ./a.out
10631 [Inferior 1 (process 29572) exited normally]
10632 (@value{GDBP}) print $_exitcode
10634 (@value{GDBP}) print $_isvoid ($_exitcode)
10638 In the example above, we used @code{$_isvoid} to check whether
10639 @code{$_exitcode} is @code{void} before and after the execution of the
10640 program being debugged. Before the execution there is no exit code to
10641 be examined, therefore @code{$_exitcode} is @code{void}. After the
10642 execution the program being debugged returned zero, therefore
10643 @code{$_exitcode} is zero, which means that it is not @code{void}
10646 The @code{void} expression can also be a call of a function from the
10647 program being debugged. For example, given the following function:
10656 The result of calling it inside @value{GDBN} is @code{void}:
10659 (@value{GDBP}) print foo ()
10661 (@value{GDBP}) print $_isvoid (foo ())
10663 (@value{GDBP}) set $v = foo ()
10664 (@value{GDBP}) print $v
10666 (@value{GDBP}) print $_isvoid ($v)
10672 These functions require @value{GDBN} to be configured with
10673 @code{Python} support.
10677 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10678 @findex $_memeq@r{, convenience function}
10679 Returns one if the @var{length} bytes at the addresses given by
10680 @var{buf1} and @var{buf2} are equal.
10681 Otherwise it returns zero.
10683 @item $_regex(@var{str}, @var{regex})
10684 @findex $_regex@r{, convenience function}
10685 Returns one if the string @var{str} matches the regular expression
10686 @var{regex}. Otherwise it returns zero.
10687 The syntax of the regular expression is that specified by @code{Python}'s
10688 regular expression support.
10690 @item $_streq(@var{str1}, @var{str2})
10691 @findex $_streq@r{, convenience function}
10692 Returns one if the strings @var{str1} and @var{str2} are equal.
10693 Otherwise it returns zero.
10695 @item $_strlen(@var{str})
10696 @findex $_strlen@r{, convenience function}
10697 Returns the length of string @var{str}.
10699 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10700 @findex $_caller_is@r{, convenience function}
10701 Returns one if the calling function's name is equal to @var{name}.
10702 Otherwise it returns zero.
10704 If the optional argument @var{number_of_frames} is provided,
10705 it is the number of frames up in the stack to look.
10713 at testsuite/gdb.python/py-caller-is.c:21
10714 #1 0x00000000004005a0 in middle_func ()
10715 at testsuite/gdb.python/py-caller-is.c:27
10716 #2 0x00000000004005ab in top_func ()
10717 at testsuite/gdb.python/py-caller-is.c:33
10718 #3 0x00000000004005b6 in main ()
10719 at testsuite/gdb.python/py-caller-is.c:39
10720 (gdb) print $_caller_is ("middle_func")
10722 (gdb) print $_caller_is ("top_func", 2)
10726 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10727 @findex $_caller_matches@r{, convenience function}
10728 Returns one if the calling function's name matches the regular expression
10729 @var{regexp}. Otherwise it returns zero.
10731 If the optional argument @var{number_of_frames} is provided,
10732 it is the number of frames up in the stack to look.
10735 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10736 @findex $_any_caller_is@r{, convenience function}
10737 Returns one if any calling function's name is equal to @var{name}.
10738 Otherwise it returns zero.
10740 If the optional argument @var{number_of_frames} is provided,
10741 it is the number of frames up in the stack to look.
10744 This function differs from @code{$_caller_is} in that this function
10745 checks all stack frames from the immediate caller to the frame specified
10746 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
10747 frame specified by @var{number_of_frames}.
10749 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10750 @findex $_any_caller_matches@r{, convenience function}
10751 Returns one if any calling function's name matches the regular expression
10752 @var{regexp}. Otherwise it returns zero.
10754 If the optional argument @var{number_of_frames} is provided,
10755 it is the number of frames up in the stack to look.
10758 This function differs from @code{$_caller_matches} in that this function
10759 checks all stack frames from the immediate caller to the frame specified
10760 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
10761 frame specified by @var{number_of_frames}.
10765 @value{GDBN} provides the ability to list and get help on
10766 convenience functions.
10769 @item help function
10770 @kindex help function
10771 @cindex show all convenience functions
10772 Print a list of all convenience functions.
10779 You can refer to machine register contents, in expressions, as variables
10780 with names starting with @samp{$}. The names of registers are different
10781 for each machine; use @code{info registers} to see the names used on
10785 @kindex info registers
10786 @item info registers
10787 Print the names and values of all registers except floating-point
10788 and vector registers (in the selected stack frame).
10790 @kindex info all-registers
10791 @cindex floating point registers
10792 @item info all-registers
10793 Print the names and values of all registers, including floating-point
10794 and vector registers (in the selected stack frame).
10796 @item info registers @var{regname} @dots{}
10797 Print the @dfn{relativized} value of each specified register @var{regname}.
10798 As discussed in detail below, register values are normally relative to
10799 the selected stack frame. The @var{regname} may be any register name valid on
10800 the machine you are using, with or without the initial @samp{$}.
10803 @anchor{standard registers}
10804 @cindex stack pointer register
10805 @cindex program counter register
10806 @cindex process status register
10807 @cindex frame pointer register
10808 @cindex standard registers
10809 @value{GDBN} has four ``standard'' register names that are available (in
10810 expressions) on most machines---whenever they do not conflict with an
10811 architecture's canonical mnemonics for registers. The register names
10812 @code{$pc} and @code{$sp} are used for the program counter register and
10813 the stack pointer. @code{$fp} is used for a register that contains a
10814 pointer to the current stack frame, and @code{$ps} is used for a
10815 register that contains the processor status. For example,
10816 you could print the program counter in hex with
10823 or print the instruction to be executed next with
10830 or add four to the stack pointer@footnote{This is a way of removing
10831 one word from the stack, on machines where stacks grow downward in
10832 memory (most machines, nowadays). This assumes that the innermost
10833 stack frame is selected; setting @code{$sp} is not allowed when other
10834 stack frames are selected. To pop entire frames off the stack,
10835 regardless of machine architecture, use @code{return};
10836 see @ref{Returning, ,Returning from a Function}.} with
10842 Whenever possible, these four standard register names are available on
10843 your machine even though the machine has different canonical mnemonics,
10844 so long as there is no conflict. The @code{info registers} command
10845 shows the canonical names. For example, on the SPARC, @code{info
10846 registers} displays the processor status register as @code{$psr} but you
10847 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
10848 is an alias for the @sc{eflags} register.
10850 @value{GDBN} always considers the contents of an ordinary register as an
10851 integer when the register is examined in this way. Some machines have
10852 special registers which can hold nothing but floating point; these
10853 registers are considered to have floating point values. There is no way
10854 to refer to the contents of an ordinary register as floating point value
10855 (although you can @emph{print} it as a floating point value with
10856 @samp{print/f $@var{regname}}).
10858 Some registers have distinct ``raw'' and ``virtual'' data formats. This
10859 means that the data format in which the register contents are saved by
10860 the operating system is not the same one that your program normally
10861 sees. For example, the registers of the 68881 floating point
10862 coprocessor are always saved in ``extended'' (raw) format, but all C
10863 programs expect to work with ``double'' (virtual) format. In such
10864 cases, @value{GDBN} normally works with the virtual format only (the format
10865 that makes sense for your program), but the @code{info registers} command
10866 prints the data in both formats.
10868 @cindex SSE registers (x86)
10869 @cindex MMX registers (x86)
10870 Some machines have special registers whose contents can be interpreted
10871 in several different ways. For example, modern x86-based machines
10872 have SSE and MMX registers that can hold several values packed
10873 together in several different formats. @value{GDBN} refers to such
10874 registers in @code{struct} notation:
10877 (@value{GDBP}) print $xmm1
10879 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
10880 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
10881 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
10882 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
10883 v4_int32 = @{0, 20657912, 11, 13@},
10884 v2_int64 = @{88725056443645952, 55834574859@},
10885 uint128 = 0x0000000d0000000b013b36f800000000
10890 To set values of such registers, you need to tell @value{GDBN} which
10891 view of the register you wish to change, as if you were assigning
10892 value to a @code{struct} member:
10895 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
10898 Normally, register values are relative to the selected stack frame
10899 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
10900 value that the register would contain if all stack frames farther in
10901 were exited and their saved registers restored. In order to see the
10902 true contents of hardware registers, you must select the innermost
10903 frame (with @samp{frame 0}).
10905 @cindex caller-saved registers
10906 @cindex call-clobbered registers
10907 @cindex volatile registers
10908 @cindex <not saved> values
10909 Usually ABIs reserve some registers as not needed to be saved by the
10910 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
10911 registers). It may therefore not be possible for @value{GDBN} to know
10912 the value a register had before the call (in other words, in the outer
10913 frame), if the register value has since been changed by the callee.
10914 @value{GDBN} tries to deduce where the inner frame saved
10915 (``callee-saved'') registers, from the debug info, unwind info, or the
10916 machine code generated by your compiler. If some register is not
10917 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
10918 its own knowledge of the ABI, or because the debug/unwind info
10919 explicitly says the register's value is undefined), @value{GDBN}
10920 displays @w{@samp{<not saved>}} as the register's value. With targets
10921 that @value{GDBN} has no knowledge of the register saving convention,
10922 if a register was not saved by the callee, then its value and location
10923 in the outer frame are assumed to be the same of the inner frame.
10924 This is usually harmless, because if the register is call-clobbered,
10925 the caller either does not care what is in the register after the
10926 call, or has code to restore the value that it does care about. Note,
10927 however, that if you change such a register in the outer frame, you
10928 may also be affecting the inner frame. Also, the more ``outer'' the
10929 frame is you're looking at, the more likely a call-clobbered
10930 register's value is to be wrong, in the sense that it doesn't actually
10931 represent the value the register had just before the call.
10933 @node Floating Point Hardware
10934 @section Floating Point Hardware
10935 @cindex floating point
10937 Depending on the configuration, @value{GDBN} may be able to give
10938 you more information about the status of the floating point hardware.
10943 Display hardware-dependent information about the floating
10944 point unit. The exact contents and layout vary depending on the
10945 floating point chip. Currently, @samp{info float} is supported on
10946 the ARM and x86 machines.
10950 @section Vector Unit
10951 @cindex vector unit
10953 Depending on the configuration, @value{GDBN} may be able to give you
10954 more information about the status of the vector unit.
10957 @kindex info vector
10959 Display information about the vector unit. The exact contents and
10960 layout vary depending on the hardware.
10963 @node OS Information
10964 @section Operating System Auxiliary Information
10965 @cindex OS information
10967 @value{GDBN} provides interfaces to useful OS facilities that can help
10968 you debug your program.
10970 @cindex auxiliary vector
10971 @cindex vector, auxiliary
10972 Some operating systems supply an @dfn{auxiliary vector} to programs at
10973 startup. This is akin to the arguments and environment that you
10974 specify for a program, but contains a system-dependent variety of
10975 binary values that tell system libraries important details about the
10976 hardware, operating system, and process. Each value's purpose is
10977 identified by an integer tag; the meanings are well-known but system-specific.
10978 Depending on the configuration and operating system facilities,
10979 @value{GDBN} may be able to show you this information. For remote
10980 targets, this functionality may further depend on the remote stub's
10981 support of the @samp{qXfer:auxv:read} packet, see
10982 @ref{qXfer auxiliary vector read}.
10987 Display the auxiliary vector of the inferior, which can be either a
10988 live process or a core dump file. @value{GDBN} prints each tag value
10989 numerically, and also shows names and text descriptions for recognized
10990 tags. Some values in the vector are numbers, some bit masks, and some
10991 pointers to strings or other data. @value{GDBN} displays each value in the
10992 most appropriate form for a recognized tag, and in hexadecimal for
10993 an unrecognized tag.
10996 On some targets, @value{GDBN} can access operating system-specific
10997 information and show it to you. The types of information available
10998 will differ depending on the type of operating system running on the
10999 target. The mechanism used to fetch the data is described in
11000 @ref{Operating System Information}. For remote targets, this
11001 functionality depends on the remote stub's support of the
11002 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
11006 @item info os @var{infotype}
11008 Display OS information of the requested type.
11010 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
11012 @anchor{linux info os infotypes}
11014 @kindex info os cpus
11016 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
11017 the available fields from /proc/cpuinfo. For each supported architecture
11018 different fields are available. Two common entries are processor which gives
11019 CPU number and bogomips; a system constant that is calculated during
11020 kernel initialization.
11022 @kindex info os files
11024 Display the list of open file descriptors on the target. For each
11025 file descriptor, @value{GDBN} prints the identifier of the process
11026 owning the descriptor, the command of the owning process, the value
11027 of the descriptor, and the target of the descriptor.
11029 @kindex info os modules
11031 Display the list of all loaded kernel modules on the target. For each
11032 module, @value{GDBN} prints the module name, the size of the module in
11033 bytes, the number of times the module is used, the dependencies of the
11034 module, the status of the module, and the address of the loaded module
11037 @kindex info os msg
11039 Display the list of all System V message queues on the target. For each
11040 message queue, @value{GDBN} prints the message queue key, the message
11041 queue identifier, the access permissions, the current number of bytes
11042 on the queue, the current number of messages on the queue, the processes
11043 that last sent and received a message on the queue, the user and group
11044 of the owner and creator of the message queue, the times at which a
11045 message was last sent and received on the queue, and the time at which
11046 the message queue was last changed.
11048 @kindex info os processes
11050 Display the list of processes on the target. For each process,
11051 @value{GDBN} prints the process identifier, the name of the user, the
11052 command corresponding to the process, and the list of processor cores
11053 that the process is currently running on. (To understand what these
11054 properties mean, for this and the following info types, please consult
11055 the general @sc{gnu}/Linux documentation.)
11057 @kindex info os procgroups
11059 Display the list of process groups on the target. For each process,
11060 @value{GDBN} prints the identifier of the process group that it belongs
11061 to, the command corresponding to the process group leader, the process
11062 identifier, and the command line of the process. The list is sorted
11063 first by the process group identifier, then by the process identifier,
11064 so that processes belonging to the same process group are grouped together
11065 and the process group leader is listed first.
11067 @kindex info os semaphores
11069 Display the list of all System V semaphore sets on the target. For each
11070 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
11071 set identifier, the access permissions, the number of semaphores in the
11072 set, the user and group of the owner and creator of the semaphore set,
11073 and the times at which the semaphore set was operated upon and changed.
11075 @kindex info os shm
11077 Display the list of all System V shared-memory regions on the target.
11078 For each shared-memory region, @value{GDBN} prints the region key,
11079 the shared-memory identifier, the access permissions, the size of the
11080 region, the process that created the region, the process that last
11081 attached to or detached from the region, the current number of live
11082 attaches to the region, and the times at which the region was last
11083 attached to, detach from, and changed.
11085 @kindex info os sockets
11087 Display the list of Internet-domain sockets on the target. For each
11088 socket, @value{GDBN} prints the address and port of the local and
11089 remote endpoints, the current state of the connection, the creator of
11090 the socket, the IP address family of the socket, and the type of the
11093 @kindex info os threads
11095 Display the list of threads running on the target. For each thread,
11096 @value{GDBN} prints the identifier of the process that the thread
11097 belongs to, the command of the process, the thread identifier, and the
11098 processor core that it is currently running on. The main thread of a
11099 process is not listed.
11103 If @var{infotype} is omitted, then list the possible values for
11104 @var{infotype} and the kind of OS information available for each
11105 @var{infotype}. If the target does not return a list of possible
11106 types, this command will report an error.
11109 @node Memory Region Attributes
11110 @section Memory Region Attributes
11111 @cindex memory region attributes
11113 @dfn{Memory region attributes} allow you to describe special handling
11114 required by regions of your target's memory. @value{GDBN} uses
11115 attributes to determine whether to allow certain types of memory
11116 accesses; whether to use specific width accesses; and whether to cache
11117 target memory. By default the description of memory regions is
11118 fetched from the target (if the current target supports this), but the
11119 user can override the fetched regions.
11121 Defined memory regions can be individually enabled and disabled. When a
11122 memory region is disabled, @value{GDBN} uses the default attributes when
11123 accessing memory in that region. Similarly, if no memory regions have
11124 been defined, @value{GDBN} uses the default attributes when accessing
11127 When a memory region is defined, it is given a number to identify it;
11128 to enable, disable, or remove a memory region, you specify that number.
11132 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
11133 Define a memory region bounded by @var{lower} and @var{upper} with
11134 attributes @var{attributes}@dots{}, and add it to the list of regions
11135 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
11136 case: it is treated as the target's maximum memory address.
11137 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
11140 Discard any user changes to the memory regions and use target-supplied
11141 regions, if available, or no regions if the target does not support.
11144 @item delete mem @var{nums}@dots{}
11145 Remove memory regions @var{nums}@dots{} from the list of regions
11146 monitored by @value{GDBN}.
11148 @kindex disable mem
11149 @item disable mem @var{nums}@dots{}
11150 Disable monitoring of memory regions @var{nums}@dots{}.
11151 A disabled memory region is not forgotten.
11152 It may be enabled again later.
11155 @item enable mem @var{nums}@dots{}
11156 Enable monitoring of memory regions @var{nums}@dots{}.
11160 Print a table of all defined memory regions, with the following columns
11164 @item Memory Region Number
11165 @item Enabled or Disabled.
11166 Enabled memory regions are marked with @samp{y}.
11167 Disabled memory regions are marked with @samp{n}.
11170 The address defining the inclusive lower bound of the memory region.
11173 The address defining the exclusive upper bound of the memory region.
11176 The list of attributes set for this memory region.
11181 @subsection Attributes
11183 @subsubsection Memory Access Mode
11184 The access mode attributes set whether @value{GDBN} may make read or
11185 write accesses to a memory region.
11187 While these attributes prevent @value{GDBN} from performing invalid
11188 memory accesses, they do nothing to prevent the target system, I/O DMA,
11189 etc.@: from accessing memory.
11193 Memory is read only.
11195 Memory is write only.
11197 Memory is read/write. This is the default.
11200 @subsubsection Memory Access Size
11201 The access size attribute tells @value{GDBN} to use specific sized
11202 accesses in the memory region. Often memory mapped device registers
11203 require specific sized accesses. If no access size attribute is
11204 specified, @value{GDBN} may use accesses of any size.
11208 Use 8 bit memory accesses.
11210 Use 16 bit memory accesses.
11212 Use 32 bit memory accesses.
11214 Use 64 bit memory accesses.
11217 @c @subsubsection Hardware/Software Breakpoints
11218 @c The hardware/software breakpoint attributes set whether @value{GDBN}
11219 @c will use hardware or software breakpoints for the internal breakpoints
11220 @c used by the step, next, finish, until, etc. commands.
11224 @c Always use hardware breakpoints
11225 @c @item swbreak (default)
11228 @subsubsection Data Cache
11229 The data cache attributes set whether @value{GDBN} will cache target
11230 memory. While this generally improves performance by reducing debug
11231 protocol overhead, it can lead to incorrect results because @value{GDBN}
11232 does not know about volatile variables or memory mapped device
11237 Enable @value{GDBN} to cache target memory.
11239 Disable @value{GDBN} from caching target memory. This is the default.
11242 @subsection Memory Access Checking
11243 @value{GDBN} can be instructed to refuse accesses to memory that is
11244 not explicitly described. This can be useful if accessing such
11245 regions has undesired effects for a specific target, or to provide
11246 better error checking. The following commands control this behaviour.
11249 @kindex set mem inaccessible-by-default
11250 @item set mem inaccessible-by-default [on|off]
11251 If @code{on} is specified, make @value{GDBN} treat memory not
11252 explicitly described by the memory ranges as non-existent and refuse accesses
11253 to such memory. The checks are only performed if there's at least one
11254 memory range defined. If @code{off} is specified, make @value{GDBN}
11255 treat the memory not explicitly described by the memory ranges as RAM.
11256 The default value is @code{on}.
11257 @kindex show mem inaccessible-by-default
11258 @item show mem inaccessible-by-default
11259 Show the current handling of accesses to unknown memory.
11263 @c @subsubsection Memory Write Verification
11264 @c The memory write verification attributes set whether @value{GDBN}
11265 @c will re-reads data after each write to verify the write was successful.
11269 @c @item noverify (default)
11272 @node Dump/Restore Files
11273 @section Copy Between Memory and a File
11274 @cindex dump/restore files
11275 @cindex append data to a file
11276 @cindex dump data to a file
11277 @cindex restore data from a file
11279 You can use the commands @code{dump}, @code{append}, and
11280 @code{restore} to copy data between target memory and a file. The
11281 @code{dump} and @code{append} commands write data to a file, and the
11282 @code{restore} command reads data from a file back into the inferior's
11283 memory. Files may be in binary, Motorola S-record, Intel hex,
11284 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
11285 append to binary files, and cannot read from Verilog Hex files.
11290 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11291 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
11292 Dump the contents of memory from @var{start_addr} to @var{end_addr},
11293 or the value of @var{expr}, to @var{filename} in the given format.
11295 The @var{format} parameter may be any one of:
11302 Motorola S-record format.
11304 Tektronix Hex format.
11306 Verilog Hex format.
11309 @value{GDBN} uses the same definitions of these formats as the
11310 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
11311 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
11315 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11316 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
11317 Append the contents of memory from @var{start_addr} to @var{end_addr},
11318 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
11319 (@value{GDBN} can only append data to files in raw binary form.)
11322 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
11323 Restore the contents of file @var{filename} into memory. The
11324 @code{restore} command can automatically recognize any known @sc{bfd}
11325 file format, except for raw binary. To restore a raw binary file you
11326 must specify the optional keyword @code{binary} after the filename.
11328 If @var{bias} is non-zero, its value will be added to the addresses
11329 contained in the file. Binary files always start at address zero, so
11330 they will be restored at address @var{bias}. Other bfd files have
11331 a built-in location; they will be restored at offset @var{bias}
11332 from that location.
11334 If @var{start} and/or @var{end} are non-zero, then only data between
11335 file offset @var{start} and file offset @var{end} will be restored.
11336 These offsets are relative to the addresses in the file, before
11337 the @var{bias} argument is applied.
11341 @node Core File Generation
11342 @section How to Produce a Core File from Your Program
11343 @cindex dump core from inferior
11345 A @dfn{core file} or @dfn{core dump} is a file that records the memory
11346 image of a running process and its process status (register values
11347 etc.). Its primary use is post-mortem debugging of a program that
11348 crashed while it ran outside a debugger. A program that crashes
11349 automatically produces a core file, unless this feature is disabled by
11350 the user. @xref{Files}, for information on invoking @value{GDBN} in
11351 the post-mortem debugging mode.
11353 Occasionally, you may wish to produce a core file of the program you
11354 are debugging in order to preserve a snapshot of its state.
11355 @value{GDBN} has a special command for that.
11359 @kindex generate-core-file
11360 @item generate-core-file [@var{file}]
11361 @itemx gcore [@var{file}]
11362 Produce a core dump of the inferior process. The optional argument
11363 @var{file} specifies the file name where to put the core dump. If not
11364 specified, the file name defaults to @file{core.@var{pid}}, where
11365 @var{pid} is the inferior process ID.
11367 Note that this command is implemented only for some systems (as of
11368 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
11370 On @sc{gnu}/Linux, this command can take into account the value of the
11371 file @file{/proc/@var{pid}/coredump_filter} when generating the core
11372 dump (@pxref{set use-coredump-filter}).
11374 @kindex set use-coredump-filter
11375 @anchor{set use-coredump-filter}
11376 @item set use-coredump-filter on
11377 @itemx set use-coredump-filter off
11378 Enable or disable the use of the file
11379 @file{/proc/@var{pid}/coredump_filter} when generating core dump
11380 files. This file is used by the Linux kernel to decide what types of
11381 memory mappings will be dumped or ignored when generating a core dump
11382 file. @var{pid} is the process ID of a currently running process.
11384 To make use of this feature, you have to write in the
11385 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
11386 which is a bit mask representing the memory mapping types. If a bit
11387 is set in the bit mask, then the memory mappings of the corresponding
11388 types will be dumped; otherwise, they will be ignored. This
11389 configuration is inherited by child processes. For more information
11390 about the bits that can be set in the
11391 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
11392 manpage of @code{core(5)}.
11394 By default, this option is @code{on}. If this option is turned
11395 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
11396 and instead uses the same default value as the Linux kernel in order
11397 to decide which pages will be dumped in the core dump file. This
11398 value is currently @code{0x33}, which means that bits @code{0}
11399 (anonymous private mappings), @code{1} (anonymous shared mappings),
11400 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
11401 This will cause these memory mappings to be dumped automatically.
11404 @node Character Sets
11405 @section Character Sets
11406 @cindex character sets
11408 @cindex translating between character sets
11409 @cindex host character set
11410 @cindex target character set
11412 If the program you are debugging uses a different character set to
11413 represent characters and strings than the one @value{GDBN} uses itself,
11414 @value{GDBN} can automatically translate between the character sets for
11415 you. The character set @value{GDBN} uses we call the @dfn{host
11416 character set}; the one the inferior program uses we call the
11417 @dfn{target character set}.
11419 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
11420 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
11421 remote protocol (@pxref{Remote Debugging}) to debug a program
11422 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
11423 then the host character set is Latin-1, and the target character set is
11424 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
11425 target-charset EBCDIC-US}, then @value{GDBN} translates between
11426 @sc{ebcdic} and Latin 1 as you print character or string values, or use
11427 character and string literals in expressions.
11429 @value{GDBN} has no way to automatically recognize which character set
11430 the inferior program uses; you must tell it, using the @code{set
11431 target-charset} command, described below.
11433 Here are the commands for controlling @value{GDBN}'s character set
11437 @item set target-charset @var{charset}
11438 @kindex set target-charset
11439 Set the current target character set to @var{charset}. To display the
11440 list of supported target character sets, type
11441 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
11443 @item set host-charset @var{charset}
11444 @kindex set host-charset
11445 Set the current host character set to @var{charset}.
11447 By default, @value{GDBN} uses a host character set appropriate to the
11448 system it is running on; you can override that default using the
11449 @code{set host-charset} command. On some systems, @value{GDBN} cannot
11450 automatically determine the appropriate host character set. In this
11451 case, @value{GDBN} uses @samp{UTF-8}.
11453 @value{GDBN} can only use certain character sets as its host character
11454 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
11455 @value{GDBN} will list the host character sets it supports.
11457 @item set charset @var{charset}
11458 @kindex set charset
11459 Set the current host and target character sets to @var{charset}. As
11460 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
11461 @value{GDBN} will list the names of the character sets that can be used
11462 for both host and target.
11465 @kindex show charset
11466 Show the names of the current host and target character sets.
11468 @item show host-charset
11469 @kindex show host-charset
11470 Show the name of the current host character set.
11472 @item show target-charset
11473 @kindex show target-charset
11474 Show the name of the current target character set.
11476 @item set target-wide-charset @var{charset}
11477 @kindex set target-wide-charset
11478 Set the current target's wide character set to @var{charset}. This is
11479 the character set used by the target's @code{wchar_t} type. To
11480 display the list of supported wide character sets, type
11481 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
11483 @item show target-wide-charset
11484 @kindex show target-wide-charset
11485 Show the name of the current target's wide character set.
11488 Here is an example of @value{GDBN}'s character set support in action.
11489 Assume that the following source code has been placed in the file
11490 @file{charset-test.c}:
11496 = @{72, 101, 108, 108, 111, 44, 32, 119,
11497 111, 114, 108, 100, 33, 10, 0@};
11498 char ibm1047_hello[]
11499 = @{200, 133, 147, 147, 150, 107, 64, 166,
11500 150, 153, 147, 132, 90, 37, 0@};
11504 printf ("Hello, world!\n");
11508 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
11509 containing the string @samp{Hello, world!} followed by a newline,
11510 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
11512 We compile the program, and invoke the debugger on it:
11515 $ gcc -g charset-test.c -o charset-test
11516 $ gdb -nw charset-test
11517 GNU gdb 2001-12-19-cvs
11518 Copyright 2001 Free Software Foundation, Inc.
11523 We can use the @code{show charset} command to see what character sets
11524 @value{GDBN} is currently using to interpret and display characters and
11528 (@value{GDBP}) show charset
11529 The current host and target character set is `ISO-8859-1'.
11533 For the sake of printing this manual, let's use @sc{ascii} as our
11534 initial character set:
11536 (@value{GDBP}) set charset ASCII
11537 (@value{GDBP}) show charset
11538 The current host and target character set is `ASCII'.
11542 Let's assume that @sc{ascii} is indeed the correct character set for our
11543 host system --- in other words, let's assume that if @value{GDBN} prints
11544 characters using the @sc{ascii} character set, our terminal will display
11545 them properly. Since our current target character set is also
11546 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
11549 (@value{GDBP}) print ascii_hello
11550 $1 = 0x401698 "Hello, world!\n"
11551 (@value{GDBP}) print ascii_hello[0]
11556 @value{GDBN} uses the target character set for character and string
11557 literals you use in expressions:
11560 (@value{GDBP}) print '+'
11565 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
11568 @value{GDBN} relies on the user to tell it which character set the
11569 target program uses. If we print @code{ibm1047_hello} while our target
11570 character set is still @sc{ascii}, we get jibberish:
11573 (@value{GDBP}) print ibm1047_hello
11574 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
11575 (@value{GDBP}) print ibm1047_hello[0]
11580 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
11581 @value{GDBN} tells us the character sets it supports:
11584 (@value{GDBP}) set target-charset
11585 ASCII EBCDIC-US IBM1047 ISO-8859-1
11586 (@value{GDBP}) set target-charset
11589 We can select @sc{ibm1047} as our target character set, and examine the
11590 program's strings again. Now the @sc{ascii} string is wrong, but
11591 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
11592 target character set, @sc{ibm1047}, to the host character set,
11593 @sc{ascii}, and they display correctly:
11596 (@value{GDBP}) set target-charset IBM1047
11597 (@value{GDBP}) show charset
11598 The current host character set is `ASCII'.
11599 The current target character set is `IBM1047'.
11600 (@value{GDBP}) print ascii_hello
11601 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
11602 (@value{GDBP}) print ascii_hello[0]
11604 (@value{GDBP}) print ibm1047_hello
11605 $8 = 0x4016a8 "Hello, world!\n"
11606 (@value{GDBP}) print ibm1047_hello[0]
11611 As above, @value{GDBN} uses the target character set for character and
11612 string literals you use in expressions:
11615 (@value{GDBP}) print '+'
11620 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
11623 @node Caching Target Data
11624 @section Caching Data of Targets
11625 @cindex caching data of targets
11627 @value{GDBN} caches data exchanged between the debugger and a target.
11628 Each cache is associated with the address space of the inferior.
11629 @xref{Inferiors and Programs}, about inferior and address space.
11630 Such caching generally improves performance in remote debugging
11631 (@pxref{Remote Debugging}), because it reduces the overhead of the
11632 remote protocol by bundling memory reads and writes into large chunks.
11633 Unfortunately, simply caching everything would lead to incorrect results,
11634 since @value{GDBN} does not necessarily know anything about volatile
11635 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
11636 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
11638 Therefore, by default, @value{GDBN} only caches data
11639 known to be on the stack@footnote{In non-stop mode, it is moderately
11640 rare for a running thread to modify the stack of a stopped thread
11641 in a way that would interfere with a backtrace, and caching of
11642 stack reads provides a significant speed up of remote backtraces.} or
11643 in the code segment.
11644 Other regions of memory can be explicitly marked as
11645 cacheable; @pxref{Memory Region Attributes}.
11648 @kindex set remotecache
11649 @item set remotecache on
11650 @itemx set remotecache off
11651 This option no longer does anything; it exists for compatibility
11654 @kindex show remotecache
11655 @item show remotecache
11656 Show the current state of the obsolete remotecache flag.
11658 @kindex set stack-cache
11659 @item set stack-cache on
11660 @itemx set stack-cache off
11661 Enable or disable caching of stack accesses. When @code{on}, use
11662 caching. By default, this option is @code{on}.
11664 @kindex show stack-cache
11665 @item show stack-cache
11666 Show the current state of data caching for memory accesses.
11668 @kindex set code-cache
11669 @item set code-cache on
11670 @itemx set code-cache off
11671 Enable or disable caching of code segment accesses. When @code{on},
11672 use caching. By default, this option is @code{on}. This improves
11673 performance of disassembly in remote debugging.
11675 @kindex show code-cache
11676 @item show code-cache
11677 Show the current state of target memory cache for code segment
11680 @kindex info dcache
11681 @item info dcache @r{[}line@r{]}
11682 Print the information about the performance of data cache of the
11683 current inferior's address space. The information displayed
11684 includes the dcache width and depth, and for each cache line, its
11685 number, address, and how many times it was referenced. This
11686 command is useful for debugging the data cache operation.
11688 If a line number is specified, the contents of that line will be
11691 @item set dcache size @var{size}
11692 @cindex dcache size
11693 @kindex set dcache size
11694 Set maximum number of entries in dcache (dcache depth above).
11696 @item set dcache line-size @var{line-size}
11697 @cindex dcache line-size
11698 @kindex set dcache line-size
11699 Set number of bytes each dcache entry caches (dcache width above).
11700 Must be a power of 2.
11702 @item show dcache size
11703 @kindex show dcache size
11704 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
11706 @item show dcache line-size
11707 @kindex show dcache line-size
11708 Show default size of dcache lines.
11712 @node Searching Memory
11713 @section Search Memory
11714 @cindex searching memory
11716 Memory can be searched for a particular sequence of bytes with the
11717 @code{find} command.
11721 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11722 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11723 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
11724 etc. The search begins at address @var{start_addr} and continues for either
11725 @var{len} bytes or through to @var{end_addr} inclusive.
11728 @var{s} and @var{n} are optional parameters.
11729 They may be specified in either order, apart or together.
11732 @item @var{s}, search query size
11733 The size of each search query value.
11739 halfwords (two bytes)
11743 giant words (eight bytes)
11746 All values are interpreted in the current language.
11747 This means, for example, that if the current source language is C/C@t{++}
11748 then searching for the string ``hello'' includes the trailing '\0'.
11750 If the value size is not specified, it is taken from the
11751 value's type in the current language.
11752 This is useful when one wants to specify the search
11753 pattern as a mixture of types.
11754 Note that this means, for example, that in the case of C-like languages
11755 a search for an untyped 0x42 will search for @samp{(int) 0x42}
11756 which is typically four bytes.
11758 @item @var{n}, maximum number of finds
11759 The maximum number of matches to print. The default is to print all finds.
11762 You can use strings as search values. Quote them with double-quotes
11764 The string value is copied into the search pattern byte by byte,
11765 regardless of the endianness of the target and the size specification.
11767 The address of each match found is printed as well as a count of the
11768 number of matches found.
11770 The address of the last value found is stored in convenience variable
11772 A count of the number of matches is stored in @samp{$numfound}.
11774 For example, if stopped at the @code{printf} in this function:
11780 static char hello[] = "hello-hello";
11781 static struct @{ char c; short s; int i; @}
11782 __attribute__ ((packed)) mixed
11783 = @{ 'c', 0x1234, 0x87654321 @};
11784 printf ("%s\n", hello);
11789 you get during debugging:
11792 (gdb) find &hello[0], +sizeof(hello), "hello"
11793 0x804956d <hello.1620+6>
11795 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
11796 0x8049567 <hello.1620>
11797 0x804956d <hello.1620+6>
11799 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
11800 0x8049567 <hello.1620>
11802 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
11803 0x8049560 <mixed.1625>
11805 (gdb) print $numfound
11808 $2 = (void *) 0x8049560
11812 @section Value Sizes
11814 Whenever @value{GDBN} prints a value memory will be allocated within
11815 @value{GDBN} to hold the contents of the value. It is possible in
11816 some languages with dynamic typing systems, that an invalid program
11817 may indicate a value that is incorrectly large, this in turn may cause
11818 @value{GDBN} to try and allocate an overly large ammount of memory.
11821 @kindex set max-value-size
11822 @item set max-value-size @var{bytes}
11823 @itemx set max-value-size unlimited
11824 Set the maximum size of memory that @value{GDBN} will allocate for the
11825 contents of a value to @var{bytes}, trying to display a value that
11826 requires more memory than that will result in an error.
11828 Setting this variable does not effect values that have already been
11829 allocated within @value{GDBN}, only future allocations.
11831 There's a minimum size that @code{max-value-size} can be set to in
11832 order that @value{GDBN} can still operate correctly, this minimum is
11833 currently 16 bytes.
11835 The limit applies to the results of some subexpressions as well as to
11836 complete expressions. For example, an expression denoting a simple
11837 integer component, such as @code{x.y.z}, may fail if the size of
11838 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
11839 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
11840 @var{A} is an array variable with non-constant size, will generally
11841 succeed regardless of the bounds on @var{A}, as long as the component
11842 size is less than @var{bytes}.
11844 The default value of @code{max-value-size} is currently 64k.
11846 @kindex show max-value-size
11847 @item show max-value-size
11848 Show the maximum size of memory, in bytes, that @value{GDBN} will
11849 allocate for the contents of a value.
11852 @node Optimized Code
11853 @chapter Debugging Optimized Code
11854 @cindex optimized code, debugging
11855 @cindex debugging optimized code
11857 Almost all compilers support optimization. With optimization
11858 disabled, the compiler generates assembly code that corresponds
11859 directly to your source code, in a simplistic way. As the compiler
11860 applies more powerful optimizations, the generated assembly code
11861 diverges from your original source code. With help from debugging
11862 information generated by the compiler, @value{GDBN} can map from
11863 the running program back to constructs from your original source.
11865 @value{GDBN} is more accurate with optimization disabled. If you
11866 can recompile without optimization, it is easier to follow the
11867 progress of your program during debugging. But, there are many cases
11868 where you may need to debug an optimized version.
11870 When you debug a program compiled with @samp{-g -O}, remember that the
11871 optimizer has rearranged your code; the debugger shows you what is
11872 really there. Do not be too surprised when the execution path does not
11873 exactly match your source file! An extreme example: if you define a
11874 variable, but never use it, @value{GDBN} never sees that
11875 variable---because the compiler optimizes it out of existence.
11877 Some things do not work as well with @samp{-g -O} as with just
11878 @samp{-g}, particularly on machines with instruction scheduling. If in
11879 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
11880 please report it to us as a bug (including a test case!).
11881 @xref{Variables}, for more information about debugging optimized code.
11884 * Inline Functions:: How @value{GDBN} presents inlining
11885 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
11888 @node Inline Functions
11889 @section Inline Functions
11890 @cindex inline functions, debugging
11892 @dfn{Inlining} is an optimization that inserts a copy of the function
11893 body directly at each call site, instead of jumping to a shared
11894 routine. @value{GDBN} displays inlined functions just like
11895 non-inlined functions. They appear in backtraces. You can view their
11896 arguments and local variables, step into them with @code{step}, skip
11897 them with @code{next}, and escape from them with @code{finish}.
11898 You can check whether a function was inlined by using the
11899 @code{info frame} command.
11901 For @value{GDBN} to support inlined functions, the compiler must
11902 record information about inlining in the debug information ---
11903 @value{NGCC} using the @sc{dwarf 2} format does this, and several
11904 other compilers do also. @value{GDBN} only supports inlined functions
11905 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
11906 do not emit two required attributes (@samp{DW_AT_call_file} and
11907 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
11908 function calls with earlier versions of @value{NGCC}. It instead
11909 displays the arguments and local variables of inlined functions as
11910 local variables in the caller.
11912 The body of an inlined function is directly included at its call site;
11913 unlike a non-inlined function, there are no instructions devoted to
11914 the call. @value{GDBN} still pretends that the call site and the
11915 start of the inlined function are different instructions. Stepping to
11916 the call site shows the call site, and then stepping again shows
11917 the first line of the inlined function, even though no additional
11918 instructions are executed.
11920 This makes source-level debugging much clearer; you can see both the
11921 context of the call and then the effect of the call. Only stepping by
11922 a single instruction using @code{stepi} or @code{nexti} does not do
11923 this; single instruction steps always show the inlined body.
11925 There are some ways that @value{GDBN} does not pretend that inlined
11926 function calls are the same as normal calls:
11930 Setting breakpoints at the call site of an inlined function may not
11931 work, because the call site does not contain any code. @value{GDBN}
11932 may incorrectly move the breakpoint to the next line of the enclosing
11933 function, after the call. This limitation will be removed in a future
11934 version of @value{GDBN}; until then, set a breakpoint on an earlier line
11935 or inside the inlined function instead.
11938 @value{GDBN} cannot locate the return value of inlined calls after
11939 using the @code{finish} command. This is a limitation of compiler-generated
11940 debugging information; after @code{finish}, you can step to the next line
11941 and print a variable where your program stored the return value.
11945 @node Tail Call Frames
11946 @section Tail Call Frames
11947 @cindex tail call frames, debugging
11949 Function @code{B} can call function @code{C} in its very last statement. In
11950 unoptimized compilation the call of @code{C} is immediately followed by return
11951 instruction at the end of @code{B} code. Optimizing compiler may replace the
11952 call and return in function @code{B} into one jump to function @code{C}
11953 instead. Such use of a jump instruction is called @dfn{tail call}.
11955 During execution of function @code{C}, there will be no indication in the
11956 function call stack frames that it was tail-called from @code{B}. If function
11957 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
11958 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
11959 some cases @value{GDBN} can determine that @code{C} was tail-called from
11960 @code{B}, and it will then create fictitious call frame for that, with the
11961 return address set up as if @code{B} called @code{C} normally.
11963 This functionality is currently supported only by DWARF 2 debugging format and
11964 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
11965 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11968 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
11969 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
11973 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
11975 Stack level 1, frame at 0x7fffffffda30:
11976 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
11977 tail call frame, caller of frame at 0x7fffffffda30
11978 source language c++.
11979 Arglist at unknown address.
11980 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
11983 The detection of all the possible code path executions can find them ambiguous.
11984 There is no execution history stored (possible @ref{Reverse Execution} is never
11985 used for this purpose) and the last known caller could have reached the known
11986 callee by multiple different jump sequences. In such case @value{GDBN} still
11987 tries to show at least all the unambiguous top tail callers and all the
11988 unambiguous bottom tail calees, if any.
11991 @anchor{set debug entry-values}
11992 @item set debug entry-values
11993 @kindex set debug entry-values
11994 When set to on, enables printing of analysis messages for both frame argument
11995 values at function entry and tail calls. It will show all the possible valid
11996 tail calls code paths it has considered. It will also print the intersection
11997 of them with the final unambiguous (possibly partial or even empty) code path
12000 @item show debug entry-values
12001 @kindex show debug entry-values
12002 Show the current state of analysis messages printing for both frame argument
12003 values at function entry and tail calls.
12006 The analysis messages for tail calls can for example show why the virtual tail
12007 call frame for function @code{c} has not been recognized (due to the indirect
12008 reference by variable @code{x}):
12011 static void __attribute__((noinline, noclone)) c (void);
12012 void (*x) (void) = c;
12013 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12014 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
12015 int main (void) @{ x (); return 0; @}
12017 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
12018 DW_TAG_GNU_call_site 0x40039a in main
12020 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12023 #1 0x000000000040039a in main () at t.c:5
12026 Another possibility is an ambiguous virtual tail call frames resolution:
12030 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
12031 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
12032 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
12033 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
12034 static void __attribute__((noinline, noclone)) b (void)
12035 @{ if (i) c (); else e (); @}
12036 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
12037 int main (void) @{ a (); return 0; @}
12039 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
12040 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
12041 tailcall: reduced: 0x4004d2(a) |
12044 #1 0x00000000004004d2 in a () at t.c:8
12045 #2 0x0000000000400395 in main () at t.c:9
12048 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
12049 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
12051 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
12052 @ifset HAVE_MAKEINFO_CLICK
12053 @set ARROW @click{}
12054 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
12055 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
12057 @ifclear HAVE_MAKEINFO_CLICK
12059 @set CALLSEQ1B @value{CALLSEQ1A}
12060 @set CALLSEQ2B @value{CALLSEQ2A}
12063 Frames #0 and #2 are real, #1 is a virtual tail call frame.
12064 The code can have possible execution paths @value{CALLSEQ1B} or
12065 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
12067 @code{initial:} state shows some random possible calling sequence @value{GDBN}
12068 has found. It then finds another possible calling sequcen - that one is
12069 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
12070 printed as the @code{reduced:} calling sequence. That one could have many
12071 futher @code{compare:} and @code{reduced:} statements as long as there remain
12072 any non-ambiguous sequence entries.
12074 For the frame of function @code{b} in both cases there are different possible
12075 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
12076 also ambigous. The only non-ambiguous frame is the one for function @code{a},
12077 therefore this one is displayed to the user while the ambiguous frames are
12080 There can be also reasons why printing of frame argument values at function
12085 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
12086 static void __attribute__((noinline, noclone)) a (int i);
12087 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
12088 static void __attribute__((noinline, noclone)) a (int i)
12089 @{ if (i) b (i - 1); else c (0); @}
12090 int main (void) @{ a (5); return 0; @}
12093 #0 c (i=i@@entry=0) at t.c:2
12094 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
12095 function "a" at 0x400420 can call itself via tail calls
12096 i=<optimized out>) at t.c:6
12097 #2 0x000000000040036e in main () at t.c:7
12100 @value{GDBN} cannot find out from the inferior state if and how many times did
12101 function @code{a} call itself (via function @code{b}) as these calls would be
12102 tail calls. Such tail calls would modify thue @code{i} variable, therefore
12103 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
12104 prints @code{<optimized out>} instead.
12107 @chapter C Preprocessor Macros
12109 Some languages, such as C and C@t{++}, provide a way to define and invoke
12110 ``preprocessor macros'' which expand into strings of tokens.
12111 @value{GDBN} can evaluate expressions containing macro invocations, show
12112 the result of macro expansion, and show a macro's definition, including
12113 where it was defined.
12115 You may need to compile your program specially to provide @value{GDBN}
12116 with information about preprocessor macros. Most compilers do not
12117 include macros in their debugging information, even when you compile
12118 with the @option{-g} flag. @xref{Compilation}.
12120 A program may define a macro at one point, remove that definition later,
12121 and then provide a different definition after that. Thus, at different
12122 points in the program, a macro may have different definitions, or have
12123 no definition at all. If there is a current stack frame, @value{GDBN}
12124 uses the macros in scope at that frame's source code line. Otherwise,
12125 @value{GDBN} uses the macros in scope at the current listing location;
12128 Whenever @value{GDBN} evaluates an expression, it always expands any
12129 macro invocations present in the expression. @value{GDBN} also provides
12130 the following commands for working with macros explicitly.
12134 @kindex macro expand
12135 @cindex macro expansion, showing the results of preprocessor
12136 @cindex preprocessor macro expansion, showing the results of
12137 @cindex expanding preprocessor macros
12138 @item macro expand @var{expression}
12139 @itemx macro exp @var{expression}
12140 Show the results of expanding all preprocessor macro invocations in
12141 @var{expression}. Since @value{GDBN} simply expands macros, but does
12142 not parse the result, @var{expression} need not be a valid expression;
12143 it can be any string of tokens.
12146 @item macro expand-once @var{expression}
12147 @itemx macro exp1 @var{expression}
12148 @cindex expand macro once
12149 @i{(This command is not yet implemented.)} Show the results of
12150 expanding those preprocessor macro invocations that appear explicitly in
12151 @var{expression}. Macro invocations appearing in that expansion are
12152 left unchanged. This command allows you to see the effect of a
12153 particular macro more clearly, without being confused by further
12154 expansions. Since @value{GDBN} simply expands macros, but does not
12155 parse the result, @var{expression} need not be a valid expression; it
12156 can be any string of tokens.
12159 @cindex macro definition, showing
12160 @cindex definition of a macro, showing
12161 @cindex macros, from debug info
12162 @item info macro [-a|-all] [--] @var{macro}
12163 Show the current definition or all definitions of the named @var{macro},
12164 and describe the source location or compiler command-line where that
12165 definition was established. The optional double dash is to signify the end of
12166 argument processing and the beginning of @var{macro} for non C-like macros where
12167 the macro may begin with a hyphen.
12169 @kindex info macros
12170 @item info macros @var{location}
12171 Show all macro definitions that are in effect at the location specified
12172 by @var{location}, and describe the source location or compiler
12173 command-line where those definitions were established.
12175 @kindex macro define
12176 @cindex user-defined macros
12177 @cindex defining macros interactively
12178 @cindex macros, user-defined
12179 @item macro define @var{macro} @var{replacement-list}
12180 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
12181 Introduce a definition for a preprocessor macro named @var{macro},
12182 invocations of which are replaced by the tokens given in
12183 @var{replacement-list}. The first form of this command defines an
12184 ``object-like'' macro, which takes no arguments; the second form
12185 defines a ``function-like'' macro, which takes the arguments given in
12188 A definition introduced by this command is in scope in every
12189 expression evaluated in @value{GDBN}, until it is removed with the
12190 @code{macro undef} command, described below. The definition overrides
12191 all definitions for @var{macro} present in the program being debugged,
12192 as well as any previous user-supplied definition.
12194 @kindex macro undef
12195 @item macro undef @var{macro}
12196 Remove any user-supplied definition for the macro named @var{macro}.
12197 This command only affects definitions provided with the @code{macro
12198 define} command, described above; it cannot remove definitions present
12199 in the program being debugged.
12203 List all the macros defined using the @code{macro define} command.
12206 @cindex macros, example of debugging with
12207 Here is a transcript showing the above commands in action. First, we
12208 show our source files:
12213 #include "sample.h"
12216 #define ADD(x) (M + x)
12221 printf ("Hello, world!\n");
12223 printf ("We're so creative.\n");
12225 printf ("Goodbye, world!\n");
12232 Now, we compile the program using the @sc{gnu} C compiler,
12233 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
12234 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
12235 and @option{-gdwarf-4}; we recommend always choosing the most recent
12236 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
12237 includes information about preprocessor macros in the debugging
12241 $ gcc -gdwarf-2 -g3 sample.c -o sample
12245 Now, we start @value{GDBN} on our sample program:
12249 GNU gdb 2002-05-06-cvs
12250 Copyright 2002 Free Software Foundation, Inc.
12251 GDB is free software, @dots{}
12255 We can expand macros and examine their definitions, even when the
12256 program is not running. @value{GDBN} uses the current listing position
12257 to decide which macro definitions are in scope:
12260 (@value{GDBP}) list main
12263 5 #define ADD(x) (M + x)
12268 10 printf ("Hello, world!\n");
12270 12 printf ("We're so creative.\n");
12271 (@value{GDBP}) info macro ADD
12272 Defined at /home/jimb/gdb/macros/play/sample.c:5
12273 #define ADD(x) (M + x)
12274 (@value{GDBP}) info macro Q
12275 Defined at /home/jimb/gdb/macros/play/sample.h:1
12276 included at /home/jimb/gdb/macros/play/sample.c:2
12278 (@value{GDBP}) macro expand ADD(1)
12279 expands to: (42 + 1)
12280 (@value{GDBP}) macro expand-once ADD(1)
12281 expands to: once (M + 1)
12285 In the example above, note that @code{macro expand-once} expands only
12286 the macro invocation explicit in the original text --- the invocation of
12287 @code{ADD} --- but does not expand the invocation of the macro @code{M},
12288 which was introduced by @code{ADD}.
12290 Once the program is running, @value{GDBN} uses the macro definitions in
12291 force at the source line of the current stack frame:
12294 (@value{GDBP}) break main
12295 Breakpoint 1 at 0x8048370: file sample.c, line 10.
12297 Starting program: /home/jimb/gdb/macros/play/sample
12299 Breakpoint 1, main () at sample.c:10
12300 10 printf ("Hello, world!\n");
12304 At line 10, the definition of the macro @code{N} at line 9 is in force:
12307 (@value{GDBP}) info macro N
12308 Defined at /home/jimb/gdb/macros/play/sample.c:9
12310 (@value{GDBP}) macro expand N Q M
12311 expands to: 28 < 42
12312 (@value{GDBP}) print N Q M
12317 As we step over directives that remove @code{N}'s definition, and then
12318 give it a new definition, @value{GDBN} finds the definition (or lack
12319 thereof) in force at each point:
12322 (@value{GDBP}) next
12324 12 printf ("We're so creative.\n");
12325 (@value{GDBP}) info macro N
12326 The symbol `N' has no definition as a C/C++ preprocessor macro
12327 at /home/jimb/gdb/macros/play/sample.c:12
12328 (@value{GDBP}) next
12330 14 printf ("Goodbye, world!\n");
12331 (@value{GDBP}) info macro N
12332 Defined at /home/jimb/gdb/macros/play/sample.c:13
12334 (@value{GDBP}) macro expand N Q M
12335 expands to: 1729 < 42
12336 (@value{GDBP}) print N Q M
12341 In addition to source files, macros can be defined on the compilation command
12342 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
12343 such a way, @value{GDBN} displays the location of their definition as line zero
12344 of the source file submitted to the compiler.
12347 (@value{GDBP}) info macro __STDC__
12348 Defined at /home/jimb/gdb/macros/play/sample.c:0
12355 @chapter Tracepoints
12356 @c This chapter is based on the documentation written by Michael
12357 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
12359 @cindex tracepoints
12360 In some applications, it is not feasible for the debugger to interrupt
12361 the program's execution long enough for the developer to learn
12362 anything helpful about its behavior. If the program's correctness
12363 depends on its real-time behavior, delays introduced by a debugger
12364 might cause the program to change its behavior drastically, or perhaps
12365 fail, even when the code itself is correct. It is useful to be able
12366 to observe the program's behavior without interrupting it.
12368 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
12369 specify locations in the program, called @dfn{tracepoints}, and
12370 arbitrary expressions to evaluate when those tracepoints are reached.
12371 Later, using the @code{tfind} command, you can examine the values
12372 those expressions had when the program hit the tracepoints. The
12373 expressions may also denote objects in memory---structures or arrays,
12374 for example---whose values @value{GDBN} should record; while visiting
12375 a particular tracepoint, you may inspect those objects as if they were
12376 in memory at that moment. However, because @value{GDBN} records these
12377 values without interacting with you, it can do so quickly and
12378 unobtrusively, hopefully not disturbing the program's behavior.
12380 The tracepoint facility is currently available only for remote
12381 targets. @xref{Targets}. In addition, your remote target must know
12382 how to collect trace data. This functionality is implemented in the
12383 remote stub; however, none of the stubs distributed with @value{GDBN}
12384 support tracepoints as of this writing. The format of the remote
12385 packets used to implement tracepoints are described in @ref{Tracepoint
12388 It is also possible to get trace data from a file, in a manner reminiscent
12389 of corefiles; you specify the filename, and use @code{tfind} to search
12390 through the file. @xref{Trace Files}, for more details.
12392 This chapter describes the tracepoint commands and features.
12395 * Set Tracepoints::
12396 * Analyze Collected Data::
12397 * Tracepoint Variables::
12401 @node Set Tracepoints
12402 @section Commands to Set Tracepoints
12404 Before running such a @dfn{trace experiment}, an arbitrary number of
12405 tracepoints can be set. A tracepoint is actually a special type of
12406 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
12407 standard breakpoint commands. For instance, as with breakpoints,
12408 tracepoint numbers are successive integers starting from one, and many
12409 of the commands associated with tracepoints take the tracepoint number
12410 as their argument, to identify which tracepoint to work on.
12412 For each tracepoint, you can specify, in advance, some arbitrary set
12413 of data that you want the target to collect in the trace buffer when
12414 it hits that tracepoint. The collected data can include registers,
12415 local variables, or global data. Later, you can use @value{GDBN}
12416 commands to examine the values these data had at the time the
12417 tracepoint was hit.
12419 Tracepoints do not support every breakpoint feature. Ignore counts on
12420 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
12421 commands when they are hit. Tracepoints may not be thread-specific
12424 @cindex fast tracepoints
12425 Some targets may support @dfn{fast tracepoints}, which are inserted in
12426 a different way (such as with a jump instead of a trap), that is
12427 faster but possibly restricted in where they may be installed.
12429 @cindex static tracepoints
12430 @cindex markers, static tracepoints
12431 @cindex probing markers, static tracepoints
12432 Regular and fast tracepoints are dynamic tracing facilities, meaning
12433 that they can be used to insert tracepoints at (almost) any location
12434 in the target. Some targets may also support controlling @dfn{static
12435 tracepoints} from @value{GDBN}. With static tracing, a set of
12436 instrumentation points, also known as @dfn{markers}, are embedded in
12437 the target program, and can be activated or deactivated by name or
12438 address. These are usually placed at locations which facilitate
12439 investigating what the target is actually doing. @value{GDBN}'s
12440 support for static tracing includes being able to list instrumentation
12441 points, and attach them with @value{GDBN} defined high level
12442 tracepoints that expose the whole range of convenience of
12443 @value{GDBN}'s tracepoints support. Namely, support for collecting
12444 registers values and values of global or local (to the instrumentation
12445 point) variables; tracepoint conditions and trace state variables.
12446 The act of installing a @value{GDBN} static tracepoint on an
12447 instrumentation point, or marker, is referred to as @dfn{probing} a
12448 static tracepoint marker.
12450 @code{gdbserver} supports tracepoints on some target systems.
12451 @xref{Server,,Tracepoints support in @code{gdbserver}}.
12453 This section describes commands to set tracepoints and associated
12454 conditions and actions.
12457 * Create and Delete Tracepoints::
12458 * Enable and Disable Tracepoints::
12459 * Tracepoint Passcounts::
12460 * Tracepoint Conditions::
12461 * Trace State Variables::
12462 * Tracepoint Actions::
12463 * Listing Tracepoints::
12464 * Listing Static Tracepoint Markers::
12465 * Starting and Stopping Trace Experiments::
12466 * Tracepoint Restrictions::
12469 @node Create and Delete Tracepoints
12470 @subsection Create and Delete Tracepoints
12473 @cindex set tracepoint
12475 @item trace @var{location}
12476 The @code{trace} command is very similar to the @code{break} command.
12477 Its argument @var{location} can be any valid location.
12478 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
12479 which is a point in the target program where the debugger will briefly stop,
12480 collect some data, and then allow the program to continue. Setting a tracepoint
12481 or changing its actions takes effect immediately if the remote stub
12482 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
12484 If remote stub doesn't support the @samp{InstallInTrace} feature, all
12485 these changes don't take effect until the next @code{tstart}
12486 command, and once a trace experiment is running, further changes will
12487 not have any effect until the next trace experiment starts. In addition,
12488 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
12489 address is not yet resolved. (This is similar to pending breakpoints.)
12490 Pending tracepoints are not downloaded to the target and not installed
12491 until they are resolved. The resolution of pending tracepoints requires
12492 @value{GDBN} support---when debugging with the remote target, and
12493 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
12494 tracing}), pending tracepoints can not be resolved (and downloaded to
12495 the remote stub) while @value{GDBN} is disconnected.
12497 Here are some examples of using the @code{trace} command:
12500 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
12502 (@value{GDBP}) @b{trace +2} // 2 lines forward
12504 (@value{GDBP}) @b{trace my_function} // first source line of function
12506 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
12508 (@value{GDBP}) @b{trace *0x2117c4} // an address
12512 You can abbreviate @code{trace} as @code{tr}.
12514 @item trace @var{location} if @var{cond}
12515 Set a tracepoint with condition @var{cond}; evaluate the expression
12516 @var{cond} each time the tracepoint is reached, and collect data only
12517 if the value is nonzero---that is, if @var{cond} evaluates as true.
12518 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
12519 information on tracepoint conditions.
12521 @item ftrace @var{location} [ if @var{cond} ]
12522 @cindex set fast tracepoint
12523 @cindex fast tracepoints, setting
12525 The @code{ftrace} command sets a fast tracepoint. For targets that
12526 support them, fast tracepoints will use a more efficient but possibly
12527 less general technique to trigger data collection, such as a jump
12528 instruction instead of a trap, or some sort of hardware support. It
12529 may not be possible to create a fast tracepoint at the desired
12530 location, in which case the command will exit with an explanatory
12533 @value{GDBN} handles arguments to @code{ftrace} exactly as for
12536 On 32-bit x86-architecture systems, fast tracepoints normally need to
12537 be placed at an instruction that is 5 bytes or longer, but can be
12538 placed at 4-byte instructions if the low 64K of memory of the target
12539 program is available to install trampolines. Some Unix-type systems,
12540 such as @sc{gnu}/Linux, exclude low addresses from the program's
12541 address space; but for instance with the Linux kernel it is possible
12542 to let @value{GDBN} use this area by doing a @command{sysctl} command
12543 to set the @code{mmap_min_addr} kernel parameter, as in
12546 sudo sysctl -w vm.mmap_min_addr=32768
12550 which sets the low address to 32K, which leaves plenty of room for
12551 trampolines. The minimum address should be set to a page boundary.
12553 @item strace @var{location} [ if @var{cond} ]
12554 @cindex set static tracepoint
12555 @cindex static tracepoints, setting
12556 @cindex probe static tracepoint marker
12558 The @code{strace} command sets a static tracepoint. For targets that
12559 support it, setting a static tracepoint probes a static
12560 instrumentation point, or marker, found at @var{location}. It may not
12561 be possible to set a static tracepoint at the desired location, in
12562 which case the command will exit with an explanatory message.
12564 @value{GDBN} handles arguments to @code{strace} exactly as for
12565 @code{trace}, with the addition that the user can also specify
12566 @code{-m @var{marker}} as @var{location}. This probes the marker
12567 identified by the @var{marker} string identifier. This identifier
12568 depends on the static tracepoint backend library your program is
12569 using. You can find all the marker identifiers in the @samp{ID} field
12570 of the @code{info static-tracepoint-markers} command output.
12571 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
12572 Markers}. For example, in the following small program using the UST
12578 trace_mark(ust, bar33, "str %s", "FOOBAZ");
12583 the marker id is composed of joining the first two arguments to the
12584 @code{trace_mark} call with a slash, which translates to:
12587 (@value{GDBP}) info static-tracepoint-markers
12588 Cnt Enb ID Address What
12589 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
12595 so you may probe the marker above with:
12598 (@value{GDBP}) strace -m ust/bar33
12601 Static tracepoints accept an extra collect action --- @code{collect
12602 $_sdata}. This collects arbitrary user data passed in the probe point
12603 call to the tracing library. In the UST example above, you'll see
12604 that the third argument to @code{trace_mark} is a printf-like format
12605 string. The user data is then the result of running that formating
12606 string against the following arguments. Note that @code{info
12607 static-tracepoint-markers} command output lists that format string in
12608 the @samp{Data:} field.
12610 You can inspect this data when analyzing the trace buffer, by printing
12611 the $_sdata variable like any other variable available to
12612 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
12615 @cindex last tracepoint number
12616 @cindex recent tracepoint number
12617 @cindex tracepoint number
12618 The convenience variable @code{$tpnum} records the tracepoint number
12619 of the most recently set tracepoint.
12621 @kindex delete tracepoint
12622 @cindex tracepoint deletion
12623 @item delete tracepoint @r{[}@var{num}@r{]}
12624 Permanently delete one or more tracepoints. With no argument, the
12625 default is to delete all tracepoints. Note that the regular
12626 @code{delete} command can remove tracepoints also.
12631 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
12633 (@value{GDBP}) @b{delete trace} // remove all tracepoints
12637 You can abbreviate this command as @code{del tr}.
12640 @node Enable and Disable Tracepoints
12641 @subsection Enable and Disable Tracepoints
12643 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
12646 @kindex disable tracepoint
12647 @item disable tracepoint @r{[}@var{num}@r{]}
12648 Disable tracepoint @var{num}, or all tracepoints if no argument
12649 @var{num} is given. A disabled tracepoint will have no effect during
12650 a trace experiment, but it is not forgotten. You can re-enable
12651 a disabled tracepoint using the @code{enable tracepoint} command.
12652 If the command is issued during a trace experiment and the debug target
12653 has support for disabling tracepoints during a trace experiment, then the
12654 change will be effective immediately. Otherwise, it will be applied to the
12655 next trace experiment.
12657 @kindex enable tracepoint
12658 @item enable tracepoint @r{[}@var{num}@r{]}
12659 Enable tracepoint @var{num}, or all tracepoints. If this command is
12660 issued during a trace experiment and the debug target supports enabling
12661 tracepoints during a trace experiment, then the enabled tracepoints will
12662 become effective immediately. Otherwise, they will become effective the
12663 next time a trace experiment is run.
12666 @node Tracepoint Passcounts
12667 @subsection Tracepoint Passcounts
12671 @cindex tracepoint pass count
12672 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
12673 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
12674 automatically stop a trace experiment. If a tracepoint's passcount is
12675 @var{n}, then the trace experiment will be automatically stopped on
12676 the @var{n}'th time that tracepoint is hit. If the tracepoint number
12677 @var{num} is not specified, the @code{passcount} command sets the
12678 passcount of the most recently defined tracepoint. If no passcount is
12679 given, the trace experiment will run until stopped explicitly by the
12685 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
12686 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
12688 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
12689 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
12690 (@value{GDBP}) @b{trace foo}
12691 (@value{GDBP}) @b{pass 3}
12692 (@value{GDBP}) @b{trace bar}
12693 (@value{GDBP}) @b{pass 2}
12694 (@value{GDBP}) @b{trace baz}
12695 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
12696 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
12697 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
12698 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
12702 @node Tracepoint Conditions
12703 @subsection Tracepoint Conditions
12704 @cindex conditional tracepoints
12705 @cindex tracepoint conditions
12707 The simplest sort of tracepoint collects data every time your program
12708 reaches a specified place. You can also specify a @dfn{condition} for
12709 a tracepoint. A condition is just a Boolean expression in your
12710 programming language (@pxref{Expressions, ,Expressions}). A
12711 tracepoint with a condition evaluates the expression each time your
12712 program reaches it, and data collection happens only if the condition
12715 Tracepoint conditions can be specified when a tracepoint is set, by
12716 using @samp{if} in the arguments to the @code{trace} command.
12717 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
12718 also be set or changed at any time with the @code{condition} command,
12719 just as with breakpoints.
12721 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
12722 the conditional expression itself. Instead, @value{GDBN} encodes the
12723 expression into an agent expression (@pxref{Agent Expressions})
12724 suitable for execution on the target, independently of @value{GDBN}.
12725 Global variables become raw memory locations, locals become stack
12726 accesses, and so forth.
12728 For instance, suppose you have a function that is usually called
12729 frequently, but should not be called after an error has occurred. You
12730 could use the following tracepoint command to collect data about calls
12731 of that function that happen while the error code is propagating
12732 through the program; an unconditional tracepoint could end up
12733 collecting thousands of useless trace frames that you would have to
12737 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
12740 @node Trace State Variables
12741 @subsection Trace State Variables
12742 @cindex trace state variables
12744 A @dfn{trace state variable} is a special type of variable that is
12745 created and managed by target-side code. The syntax is the same as
12746 that for GDB's convenience variables (a string prefixed with ``$''),
12747 but they are stored on the target. They must be created explicitly,
12748 using a @code{tvariable} command. They are always 64-bit signed
12751 Trace state variables are remembered by @value{GDBN}, and downloaded
12752 to the target along with tracepoint information when the trace
12753 experiment starts. There are no intrinsic limits on the number of
12754 trace state variables, beyond memory limitations of the target.
12756 @cindex convenience variables, and trace state variables
12757 Although trace state variables are managed by the target, you can use
12758 them in print commands and expressions as if they were convenience
12759 variables; @value{GDBN} will get the current value from the target
12760 while the trace experiment is running. Trace state variables share
12761 the same namespace as other ``$'' variables, which means that you
12762 cannot have trace state variables with names like @code{$23} or
12763 @code{$pc}, nor can you have a trace state variable and a convenience
12764 variable with the same name.
12768 @item tvariable $@var{name} [ = @var{expression} ]
12770 The @code{tvariable} command creates a new trace state variable named
12771 @code{$@var{name}}, and optionally gives it an initial value of
12772 @var{expression}. The @var{expression} is evaluated when this command is
12773 entered; the result will be converted to an integer if possible,
12774 otherwise @value{GDBN} will report an error. A subsequent
12775 @code{tvariable} command specifying the same name does not create a
12776 variable, but instead assigns the supplied initial value to the
12777 existing variable of that name, overwriting any previous initial
12778 value. The default initial value is 0.
12780 @item info tvariables
12781 @kindex info tvariables
12782 List all the trace state variables along with their initial values.
12783 Their current values may also be displayed, if the trace experiment is
12786 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
12787 @kindex delete tvariable
12788 Delete the given trace state variables, or all of them if no arguments
12793 @node Tracepoint Actions
12794 @subsection Tracepoint Action Lists
12798 @cindex tracepoint actions
12799 @item actions @r{[}@var{num}@r{]}
12800 This command will prompt for a list of actions to be taken when the
12801 tracepoint is hit. If the tracepoint number @var{num} is not
12802 specified, this command sets the actions for the one that was most
12803 recently defined (so that you can define a tracepoint and then say
12804 @code{actions} without bothering about its number). You specify the
12805 actions themselves on the following lines, one action at a time, and
12806 terminate the actions list with a line containing just @code{end}. So
12807 far, the only defined actions are @code{collect}, @code{teval}, and
12808 @code{while-stepping}.
12810 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
12811 Commands, ,Breakpoint Command Lists}), except that only the defined
12812 actions are allowed; any other @value{GDBN} command is rejected.
12814 @cindex remove actions from a tracepoint
12815 To remove all actions from a tracepoint, type @samp{actions @var{num}}
12816 and follow it immediately with @samp{end}.
12819 (@value{GDBP}) @b{collect @var{data}} // collect some data
12821 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
12823 (@value{GDBP}) @b{end} // signals the end of actions.
12826 In the following example, the action list begins with @code{collect}
12827 commands indicating the things to be collected when the tracepoint is
12828 hit. Then, in order to single-step and collect additional data
12829 following the tracepoint, a @code{while-stepping} command is used,
12830 followed by the list of things to be collected after each step in a
12831 sequence of single steps. The @code{while-stepping} command is
12832 terminated by its own separate @code{end} command. Lastly, the action
12833 list is terminated by an @code{end} command.
12836 (@value{GDBP}) @b{trace foo}
12837 (@value{GDBP}) @b{actions}
12838 Enter actions for tracepoint 1, one per line:
12841 > while-stepping 12
12842 > collect $pc, arr[i]
12847 @kindex collect @r{(tracepoints)}
12848 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
12849 Collect values of the given expressions when the tracepoint is hit.
12850 This command accepts a comma-separated list of any valid expressions.
12851 In addition to global, static, or local variables, the following
12852 special arguments are supported:
12856 Collect all registers.
12859 Collect all function arguments.
12862 Collect all local variables.
12865 Collect the return address. This is helpful if you want to see more
12869 Collects the number of arguments from the static probe at which the
12870 tracepoint is located.
12871 @xref{Static Probe Points}.
12873 @item $_probe_arg@var{n}
12874 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
12875 from the static probe at which the tracepoint is located.
12876 @xref{Static Probe Points}.
12879 @vindex $_sdata@r{, collect}
12880 Collect static tracepoint marker specific data. Only available for
12881 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
12882 Lists}. On the UST static tracepoints library backend, an
12883 instrumentation point resembles a @code{printf} function call. The
12884 tracing library is able to collect user specified data formatted to a
12885 character string using the format provided by the programmer that
12886 instrumented the program. Other backends have similar mechanisms.
12887 Here's an example of a UST marker call:
12890 const char master_name[] = "$your_name";
12891 trace_mark(channel1, marker1, "hello %s", master_name)
12894 In this case, collecting @code{$_sdata} collects the string
12895 @samp{hello $yourname}. When analyzing the trace buffer, you can
12896 inspect @samp{$_sdata} like any other variable available to
12900 You can give several consecutive @code{collect} commands, each one
12901 with a single argument, or one @code{collect} command with several
12902 arguments separated by commas; the effect is the same.
12904 The optional @var{mods} changes the usual handling of the arguments.
12905 @code{s} requests that pointers to chars be handled as strings, in
12906 particular collecting the contents of the memory being pointed at, up
12907 to the first zero. The upper bound is by default the value of the
12908 @code{print elements} variable; if @code{s} is followed by a decimal
12909 number, that is the upper bound instead. So for instance
12910 @samp{collect/s25 mystr} collects as many as 25 characters at
12913 The command @code{info scope} (@pxref{Symbols, info scope}) is
12914 particularly useful for figuring out what data to collect.
12916 @kindex teval @r{(tracepoints)}
12917 @item teval @var{expr1}, @var{expr2}, @dots{}
12918 Evaluate the given expressions when the tracepoint is hit. This
12919 command accepts a comma-separated list of expressions. The results
12920 are discarded, so this is mainly useful for assigning values to trace
12921 state variables (@pxref{Trace State Variables}) without adding those
12922 values to the trace buffer, as would be the case if the @code{collect}
12925 @kindex while-stepping @r{(tracepoints)}
12926 @item while-stepping @var{n}
12927 Perform @var{n} single-step instruction traces after the tracepoint,
12928 collecting new data after each step. The @code{while-stepping}
12929 command is followed by the list of what to collect while stepping
12930 (followed by its own @code{end} command):
12933 > while-stepping 12
12934 > collect $regs, myglobal
12940 Note that @code{$pc} is not automatically collected by
12941 @code{while-stepping}; you need to explicitly collect that register if
12942 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
12945 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
12946 @kindex set default-collect
12947 @cindex default collection action
12948 This variable is a list of expressions to collect at each tracepoint
12949 hit. It is effectively an additional @code{collect} action prepended
12950 to every tracepoint action list. The expressions are parsed
12951 individually for each tracepoint, so for instance a variable named
12952 @code{xyz} may be interpreted as a global for one tracepoint, and a
12953 local for another, as appropriate to the tracepoint's location.
12955 @item show default-collect
12956 @kindex show default-collect
12957 Show the list of expressions that are collected by default at each
12962 @node Listing Tracepoints
12963 @subsection Listing Tracepoints
12966 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
12967 @kindex info tp @r{[}@var{n}@dots{}@r{]}
12968 @cindex information about tracepoints
12969 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
12970 Display information about the tracepoint @var{num}. If you don't
12971 specify a tracepoint number, displays information about all the
12972 tracepoints defined so far. The format is similar to that used for
12973 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
12974 command, simply restricting itself to tracepoints.
12976 A tracepoint's listing may include additional information specific to
12981 its passcount as given by the @code{passcount @var{n}} command
12984 the state about installed on target of each location
12988 (@value{GDBP}) @b{info trace}
12989 Num Type Disp Enb Address What
12990 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
12992 collect globfoo, $regs
12997 2 tracepoint keep y <MULTIPLE>
12999 2.1 y 0x0804859c in func4 at change-loc.h:35
13000 installed on target
13001 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
13002 installed on target
13003 2.3 y <PENDING> set_tracepoint
13004 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
13005 not installed on target
13010 This command can be abbreviated @code{info tp}.
13013 @node Listing Static Tracepoint Markers
13014 @subsection Listing Static Tracepoint Markers
13017 @kindex info static-tracepoint-markers
13018 @cindex information about static tracepoint markers
13019 @item info static-tracepoint-markers
13020 Display information about all static tracepoint markers defined in the
13023 For each marker, the following columns are printed:
13027 An incrementing counter, output to help readability. This is not a
13030 The marker ID, as reported by the target.
13031 @item Enabled or Disabled
13032 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
13033 that are not enabled.
13035 Where the marker is in your program, as a memory address.
13037 Where the marker is in the source for your program, as a file and line
13038 number. If the debug information included in the program does not
13039 allow @value{GDBN} to locate the source of the marker, this column
13040 will be left blank.
13044 In addition, the following information may be printed for each marker:
13048 User data passed to the tracing library by the marker call. In the
13049 UST backend, this is the format string passed as argument to the
13051 @item Static tracepoints probing the marker
13052 The list of static tracepoints attached to the marker.
13056 (@value{GDBP}) info static-tracepoint-markers
13057 Cnt ID Enb Address What
13058 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
13059 Data: number1 %d number2 %d
13060 Probed by static tracepoints: #2
13061 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
13067 @node Starting and Stopping Trace Experiments
13068 @subsection Starting and Stopping Trace Experiments
13071 @kindex tstart [ @var{notes} ]
13072 @cindex start a new trace experiment
13073 @cindex collected data discarded
13075 This command starts the trace experiment, and begins collecting data.
13076 It has the side effect of discarding all the data collected in the
13077 trace buffer during the previous trace experiment. If any arguments
13078 are supplied, they are taken as a note and stored with the trace
13079 experiment's state. The notes may be arbitrary text, and are
13080 especially useful with disconnected tracing in a multi-user context;
13081 the notes can explain what the trace is doing, supply user contact
13082 information, and so forth.
13084 @kindex tstop [ @var{notes} ]
13085 @cindex stop a running trace experiment
13087 This command stops the trace experiment. If any arguments are
13088 supplied, they are recorded with the experiment as a note. This is
13089 useful if you are stopping a trace started by someone else, for
13090 instance if the trace is interfering with the system's behavior and
13091 needs to be stopped quickly.
13093 @strong{Note}: a trace experiment and data collection may stop
13094 automatically if any tracepoint's passcount is reached
13095 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
13098 @cindex status of trace data collection
13099 @cindex trace experiment, status of
13101 This command displays the status of the current trace data
13105 Here is an example of the commands we described so far:
13108 (@value{GDBP}) @b{trace gdb_c_test}
13109 (@value{GDBP}) @b{actions}
13110 Enter actions for tracepoint #1, one per line.
13111 > collect $regs,$locals,$args
13112 > while-stepping 11
13116 (@value{GDBP}) @b{tstart}
13117 [time passes @dots{}]
13118 (@value{GDBP}) @b{tstop}
13121 @anchor{disconnected tracing}
13122 @cindex disconnected tracing
13123 You can choose to continue running the trace experiment even if
13124 @value{GDBN} disconnects from the target, voluntarily or
13125 involuntarily. For commands such as @code{detach}, the debugger will
13126 ask what you want to do with the trace. But for unexpected
13127 terminations (@value{GDBN} crash, network outage), it would be
13128 unfortunate to lose hard-won trace data, so the variable
13129 @code{disconnected-tracing} lets you decide whether the trace should
13130 continue running without @value{GDBN}.
13133 @item set disconnected-tracing on
13134 @itemx set disconnected-tracing off
13135 @kindex set disconnected-tracing
13136 Choose whether a tracing run should continue to run if @value{GDBN}
13137 has disconnected from the target. Note that @code{detach} or
13138 @code{quit} will ask you directly what to do about a running trace no
13139 matter what this variable's setting, so the variable is mainly useful
13140 for handling unexpected situations, such as loss of the network.
13142 @item show disconnected-tracing
13143 @kindex show disconnected-tracing
13144 Show the current choice for disconnected tracing.
13148 When you reconnect to the target, the trace experiment may or may not
13149 still be running; it might have filled the trace buffer in the
13150 meantime, or stopped for one of the other reasons. If it is running,
13151 it will continue after reconnection.
13153 Upon reconnection, the target will upload information about the
13154 tracepoints in effect. @value{GDBN} will then compare that
13155 information to the set of tracepoints currently defined, and attempt
13156 to match them up, allowing for the possibility that the numbers may
13157 have changed due to creation and deletion in the meantime. If one of
13158 the target's tracepoints does not match any in @value{GDBN}, the
13159 debugger will create a new tracepoint, so that you have a number with
13160 which to specify that tracepoint. This matching-up process is
13161 necessarily heuristic, and it may result in useless tracepoints being
13162 created; you may simply delete them if they are of no use.
13164 @cindex circular trace buffer
13165 If your target agent supports a @dfn{circular trace buffer}, then you
13166 can run a trace experiment indefinitely without filling the trace
13167 buffer; when space runs out, the agent deletes already-collected trace
13168 frames, oldest first, until there is enough room to continue
13169 collecting. This is especially useful if your tracepoints are being
13170 hit too often, and your trace gets terminated prematurely because the
13171 buffer is full. To ask for a circular trace buffer, simply set
13172 @samp{circular-trace-buffer} to on. You can set this at any time,
13173 including during tracing; if the agent can do it, it will change
13174 buffer handling on the fly, otherwise it will not take effect until
13178 @item set circular-trace-buffer on
13179 @itemx set circular-trace-buffer off
13180 @kindex set circular-trace-buffer
13181 Choose whether a tracing run should use a linear or circular buffer
13182 for trace data. A linear buffer will not lose any trace data, but may
13183 fill up prematurely, while a circular buffer will discard old trace
13184 data, but it will have always room for the latest tracepoint hits.
13186 @item show circular-trace-buffer
13187 @kindex show circular-trace-buffer
13188 Show the current choice for the trace buffer. Note that this may not
13189 match the agent's current buffer handling, nor is it guaranteed to
13190 match the setting that might have been in effect during a past run,
13191 for instance if you are looking at frames from a trace file.
13196 @item set trace-buffer-size @var{n}
13197 @itemx set trace-buffer-size unlimited
13198 @kindex set trace-buffer-size
13199 Request that the target use a trace buffer of @var{n} bytes. Not all
13200 targets will honor the request; they may have a compiled-in size for
13201 the trace buffer, or some other limitation. Set to a value of
13202 @code{unlimited} or @code{-1} to let the target use whatever size it
13203 likes. This is also the default.
13205 @item show trace-buffer-size
13206 @kindex show trace-buffer-size
13207 Show the current requested size for the trace buffer. Note that this
13208 will only match the actual size if the target supports size-setting,
13209 and was able to handle the requested size. For instance, if the
13210 target can only change buffer size between runs, this variable will
13211 not reflect the change until the next run starts. Use @code{tstatus}
13212 to get a report of the actual buffer size.
13216 @item set trace-user @var{text}
13217 @kindex set trace-user
13219 @item show trace-user
13220 @kindex show trace-user
13222 @item set trace-notes @var{text}
13223 @kindex set trace-notes
13224 Set the trace run's notes.
13226 @item show trace-notes
13227 @kindex show trace-notes
13228 Show the trace run's notes.
13230 @item set trace-stop-notes @var{text}
13231 @kindex set trace-stop-notes
13232 Set the trace run's stop notes. The handling of the note is as for
13233 @code{tstop} arguments; the set command is convenient way to fix a
13234 stop note that is mistaken or incomplete.
13236 @item show trace-stop-notes
13237 @kindex show trace-stop-notes
13238 Show the trace run's stop notes.
13242 @node Tracepoint Restrictions
13243 @subsection Tracepoint Restrictions
13245 @cindex tracepoint restrictions
13246 There are a number of restrictions on the use of tracepoints. As
13247 described above, tracepoint data gathering occurs on the target
13248 without interaction from @value{GDBN}. Thus the full capabilities of
13249 the debugger are not available during data gathering, and then at data
13250 examination time, you will be limited by only having what was
13251 collected. The following items describe some common problems, but it
13252 is not exhaustive, and you may run into additional difficulties not
13258 Tracepoint expressions are intended to gather objects (lvalues). Thus
13259 the full flexibility of GDB's expression evaluator is not available.
13260 You cannot call functions, cast objects to aggregate types, access
13261 convenience variables or modify values (except by assignment to trace
13262 state variables). Some language features may implicitly call
13263 functions (for instance Objective-C fields with accessors), and therefore
13264 cannot be collected either.
13267 Collection of local variables, either individually or in bulk with
13268 @code{$locals} or @code{$args}, during @code{while-stepping} may
13269 behave erratically. The stepping action may enter a new scope (for
13270 instance by stepping into a function), or the location of the variable
13271 may change (for instance it is loaded into a register). The
13272 tracepoint data recorded uses the location information for the
13273 variables that is correct for the tracepoint location. When the
13274 tracepoint is created, it is not possible, in general, to determine
13275 where the steps of a @code{while-stepping} sequence will advance the
13276 program---particularly if a conditional branch is stepped.
13279 Collection of an incompletely-initialized or partially-destroyed object
13280 may result in something that @value{GDBN} cannot display, or displays
13281 in a misleading way.
13284 When @value{GDBN} displays a pointer to character it automatically
13285 dereferences the pointer to also display characters of the string
13286 being pointed to. However, collecting the pointer during tracing does
13287 not automatically collect the string. You need to explicitly
13288 dereference the pointer and provide size information if you want to
13289 collect not only the pointer, but the memory pointed to. For example,
13290 @code{*ptr@@50} can be used to collect the 50 element array pointed to
13294 It is not possible to collect a complete stack backtrace at a
13295 tracepoint. Instead, you may collect the registers and a few hundred
13296 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
13297 (adjust to use the name of the actual stack pointer register on your
13298 target architecture, and the amount of stack you wish to capture).
13299 Then the @code{backtrace} command will show a partial backtrace when
13300 using a trace frame. The number of stack frames that can be examined
13301 depends on the sizes of the frames in the collected stack. Note that
13302 if you ask for a block so large that it goes past the bottom of the
13303 stack, the target agent may report an error trying to read from an
13307 If you do not collect registers at a tracepoint, @value{GDBN} can
13308 infer that the value of @code{$pc} must be the same as the address of
13309 the tracepoint and use that when you are looking at a trace frame
13310 for that tracepoint. However, this cannot work if the tracepoint has
13311 multiple locations (for instance if it was set in a function that was
13312 inlined), or if it has a @code{while-stepping} loop. In those cases
13313 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
13318 @node Analyze Collected Data
13319 @section Using the Collected Data
13321 After the tracepoint experiment ends, you use @value{GDBN} commands
13322 for examining the trace data. The basic idea is that each tracepoint
13323 collects a trace @dfn{snapshot} every time it is hit and another
13324 snapshot every time it single-steps. All these snapshots are
13325 consecutively numbered from zero and go into a buffer, and you can
13326 examine them later. The way you examine them is to @dfn{focus} on a
13327 specific trace snapshot. When the remote stub is focused on a trace
13328 snapshot, it will respond to all @value{GDBN} requests for memory and
13329 registers by reading from the buffer which belongs to that snapshot,
13330 rather than from @emph{real} memory or registers of the program being
13331 debugged. This means that @strong{all} @value{GDBN} commands
13332 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
13333 behave as if we were currently debugging the program state as it was
13334 when the tracepoint occurred. Any requests for data that are not in
13335 the buffer will fail.
13338 * tfind:: How to select a trace snapshot
13339 * tdump:: How to display all data for a snapshot
13340 * save tracepoints:: How to save tracepoints for a future run
13344 @subsection @code{tfind @var{n}}
13347 @cindex select trace snapshot
13348 @cindex find trace snapshot
13349 The basic command for selecting a trace snapshot from the buffer is
13350 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
13351 counting from zero. If no argument @var{n} is given, the next
13352 snapshot is selected.
13354 Here are the various forms of using the @code{tfind} command.
13358 Find the first snapshot in the buffer. This is a synonym for
13359 @code{tfind 0} (since 0 is the number of the first snapshot).
13362 Stop debugging trace snapshots, resume @emph{live} debugging.
13365 Same as @samp{tfind none}.
13368 No argument means find the next trace snapshot.
13371 Find the previous trace snapshot before the current one. This permits
13372 retracing earlier steps.
13374 @item tfind tracepoint @var{num}
13375 Find the next snapshot associated with tracepoint @var{num}. Search
13376 proceeds forward from the last examined trace snapshot. If no
13377 argument @var{num} is given, it means find the next snapshot collected
13378 for the same tracepoint as the current snapshot.
13380 @item tfind pc @var{addr}
13381 Find the next snapshot associated with the value @var{addr} of the
13382 program counter. Search proceeds forward from the last examined trace
13383 snapshot. If no argument @var{addr} is given, it means find the next
13384 snapshot with the same value of PC as the current snapshot.
13386 @item tfind outside @var{addr1}, @var{addr2}
13387 Find the next snapshot whose PC is outside the given range of
13388 addresses (exclusive).
13390 @item tfind range @var{addr1}, @var{addr2}
13391 Find the next snapshot whose PC is between @var{addr1} and
13392 @var{addr2} (inclusive).
13394 @item tfind line @r{[}@var{file}:@r{]}@var{n}
13395 Find the next snapshot associated with the source line @var{n}. If
13396 the optional argument @var{file} is given, refer to line @var{n} in
13397 that source file. Search proceeds forward from the last examined
13398 trace snapshot. If no argument @var{n} is given, it means find the
13399 next line other than the one currently being examined; thus saying
13400 @code{tfind line} repeatedly can appear to have the same effect as
13401 stepping from line to line in a @emph{live} debugging session.
13404 The default arguments for the @code{tfind} commands are specifically
13405 designed to make it easy to scan through the trace buffer. For
13406 instance, @code{tfind} with no argument selects the next trace
13407 snapshot, and @code{tfind -} with no argument selects the previous
13408 trace snapshot. So, by giving one @code{tfind} command, and then
13409 simply hitting @key{RET} repeatedly you can examine all the trace
13410 snapshots in order. Or, by saying @code{tfind -} and then hitting
13411 @key{RET} repeatedly you can examine the snapshots in reverse order.
13412 The @code{tfind line} command with no argument selects the snapshot
13413 for the next source line executed. The @code{tfind pc} command with
13414 no argument selects the next snapshot with the same program counter
13415 (PC) as the current frame. The @code{tfind tracepoint} command with
13416 no argument selects the next trace snapshot collected by the same
13417 tracepoint as the current one.
13419 In addition to letting you scan through the trace buffer manually,
13420 these commands make it easy to construct @value{GDBN} scripts that
13421 scan through the trace buffer and print out whatever collected data
13422 you are interested in. Thus, if we want to examine the PC, FP, and SP
13423 registers from each trace frame in the buffer, we can say this:
13426 (@value{GDBP}) @b{tfind start}
13427 (@value{GDBP}) @b{while ($trace_frame != -1)}
13428 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
13429 $trace_frame, $pc, $sp, $fp
13433 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
13434 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
13435 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
13436 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
13437 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
13438 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
13439 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
13440 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
13441 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
13442 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
13443 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
13446 Or, if we want to examine the variable @code{X} at each source line in
13450 (@value{GDBP}) @b{tfind start}
13451 (@value{GDBP}) @b{while ($trace_frame != -1)}
13452 > printf "Frame %d, X == %d\n", $trace_frame, X
13462 @subsection @code{tdump}
13464 @cindex dump all data collected at tracepoint
13465 @cindex tracepoint data, display
13467 This command takes no arguments. It prints all the data collected at
13468 the current trace snapshot.
13471 (@value{GDBP}) @b{trace 444}
13472 (@value{GDBP}) @b{actions}
13473 Enter actions for tracepoint #2, one per line:
13474 > collect $regs, $locals, $args, gdb_long_test
13477 (@value{GDBP}) @b{tstart}
13479 (@value{GDBP}) @b{tfind line 444}
13480 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
13482 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
13484 (@value{GDBP}) @b{tdump}
13485 Data collected at tracepoint 2, trace frame 1:
13486 d0 0xc4aa0085 -995491707
13490 d4 0x71aea3d 119204413
13493 d7 0x380035 3670069
13494 a0 0x19e24a 1696330
13495 a1 0x3000668 50333288
13497 a3 0x322000 3284992
13498 a4 0x3000698 50333336
13499 a5 0x1ad3cc 1758156
13500 fp 0x30bf3c 0x30bf3c
13501 sp 0x30bf34 0x30bf34
13503 pc 0x20b2c8 0x20b2c8
13507 p = 0x20e5b4 "gdb-test"
13514 gdb_long_test = 17 '\021'
13519 @code{tdump} works by scanning the tracepoint's current collection
13520 actions and printing the value of each expression listed. So
13521 @code{tdump} can fail, if after a run, you change the tracepoint's
13522 actions to mention variables that were not collected during the run.
13524 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
13525 uses the collected value of @code{$pc} to distinguish between trace
13526 frames that were collected at the tracepoint hit, and frames that were
13527 collected while stepping. This allows it to correctly choose whether
13528 to display the basic list of collections, or the collections from the
13529 body of the while-stepping loop. However, if @code{$pc} was not collected,
13530 then @code{tdump} will always attempt to dump using the basic collection
13531 list, and may fail if a while-stepping frame does not include all the
13532 same data that is collected at the tracepoint hit.
13533 @c This is getting pretty arcane, example would be good.
13535 @node save tracepoints
13536 @subsection @code{save tracepoints @var{filename}}
13537 @kindex save tracepoints
13538 @kindex save-tracepoints
13539 @cindex save tracepoints for future sessions
13541 This command saves all current tracepoint definitions together with
13542 their actions and passcounts, into a file @file{@var{filename}}
13543 suitable for use in a later debugging session. To read the saved
13544 tracepoint definitions, use the @code{source} command (@pxref{Command
13545 Files}). The @w{@code{save-tracepoints}} command is a deprecated
13546 alias for @w{@code{save tracepoints}}
13548 @node Tracepoint Variables
13549 @section Convenience Variables for Tracepoints
13550 @cindex tracepoint variables
13551 @cindex convenience variables for tracepoints
13554 @vindex $trace_frame
13555 @item (int) $trace_frame
13556 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
13557 snapshot is selected.
13559 @vindex $tracepoint
13560 @item (int) $tracepoint
13561 The tracepoint for the current trace snapshot.
13563 @vindex $trace_line
13564 @item (int) $trace_line
13565 The line number for the current trace snapshot.
13567 @vindex $trace_file
13568 @item (char []) $trace_file
13569 The source file for the current trace snapshot.
13571 @vindex $trace_func
13572 @item (char []) $trace_func
13573 The name of the function containing @code{$tracepoint}.
13576 Note: @code{$trace_file} is not suitable for use in @code{printf},
13577 use @code{output} instead.
13579 Here's a simple example of using these convenience variables for
13580 stepping through all the trace snapshots and printing some of their
13581 data. Note that these are not the same as trace state variables,
13582 which are managed by the target.
13585 (@value{GDBP}) @b{tfind start}
13587 (@value{GDBP}) @b{while $trace_frame != -1}
13588 > output $trace_file
13589 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
13595 @section Using Trace Files
13596 @cindex trace files
13598 In some situations, the target running a trace experiment may no
13599 longer be available; perhaps it crashed, or the hardware was needed
13600 for a different activity. To handle these cases, you can arrange to
13601 dump the trace data into a file, and later use that file as a source
13602 of trace data, via the @code{target tfile} command.
13607 @item tsave [ -r ] @var{filename}
13608 @itemx tsave [-ctf] @var{dirname}
13609 Save the trace data to @var{filename}. By default, this command
13610 assumes that @var{filename} refers to the host filesystem, so if
13611 necessary @value{GDBN} will copy raw trace data up from the target and
13612 then save it. If the target supports it, you can also supply the
13613 optional argument @code{-r} (``remote'') to direct the target to save
13614 the data directly into @var{filename} in its own filesystem, which may be
13615 more efficient if the trace buffer is very large. (Note, however, that
13616 @code{target tfile} can only read from files accessible to the host.)
13617 By default, this command will save trace frame in tfile format.
13618 You can supply the optional argument @code{-ctf} to save date in CTF
13619 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
13620 that can be shared by multiple debugging and tracing tools. Please go to
13621 @indicateurl{http://www.efficios.com/ctf} to get more information.
13623 @kindex target tfile
13627 @item target tfile @var{filename}
13628 @itemx target ctf @var{dirname}
13629 Use the file named @var{filename} or directory named @var{dirname} as
13630 a source of trace data. Commands that examine data work as they do with
13631 a live target, but it is not possible to run any new trace experiments.
13632 @code{tstatus} will report the state of the trace run at the moment
13633 the data was saved, as well as the current trace frame you are examining.
13634 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
13638 (@value{GDBP}) target ctf ctf.ctf
13639 (@value{GDBP}) tfind
13640 Found trace frame 0, tracepoint 2
13641 39 ++a; /* set tracepoint 1 here */
13642 (@value{GDBP}) tdump
13643 Data collected at tracepoint 2, trace frame 0:
13647 c = @{"123", "456", "789", "123", "456", "789"@}
13648 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
13656 @chapter Debugging Programs That Use Overlays
13659 If your program is too large to fit completely in your target system's
13660 memory, you can sometimes use @dfn{overlays} to work around this
13661 problem. @value{GDBN} provides some support for debugging programs that
13665 * How Overlays Work:: A general explanation of overlays.
13666 * Overlay Commands:: Managing overlays in @value{GDBN}.
13667 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
13668 mapped by asking the inferior.
13669 * Overlay Sample Program:: A sample program using overlays.
13672 @node How Overlays Work
13673 @section How Overlays Work
13674 @cindex mapped overlays
13675 @cindex unmapped overlays
13676 @cindex load address, overlay's
13677 @cindex mapped address
13678 @cindex overlay area
13680 Suppose you have a computer whose instruction address space is only 64
13681 kilobytes long, but which has much more memory which can be accessed by
13682 other means: special instructions, segment registers, or memory
13683 management hardware, for example. Suppose further that you want to
13684 adapt a program which is larger than 64 kilobytes to run on this system.
13686 One solution is to identify modules of your program which are relatively
13687 independent, and need not call each other directly; call these modules
13688 @dfn{overlays}. Separate the overlays from the main program, and place
13689 their machine code in the larger memory. Place your main program in
13690 instruction memory, but leave at least enough space there to hold the
13691 largest overlay as well.
13693 Now, to call a function located in an overlay, you must first copy that
13694 overlay's machine code from the large memory into the space set aside
13695 for it in the instruction memory, and then jump to its entry point
13698 @c NB: In the below the mapped area's size is greater or equal to the
13699 @c size of all overlays. This is intentional to remind the developer
13700 @c that overlays don't necessarily need to be the same size.
13704 Data Instruction Larger
13705 Address Space Address Space Address Space
13706 +-----------+ +-----------+ +-----------+
13708 +-----------+ +-----------+ +-----------+<-- overlay 1
13709 | program | | main | .----| overlay 1 | load address
13710 | variables | | program | | +-----------+
13711 | and heap | | | | | |
13712 +-----------+ | | | +-----------+<-- overlay 2
13713 | | +-----------+ | | | load address
13714 +-----------+ | | | .-| overlay 2 |
13716 mapped --->+-----------+ | | +-----------+
13717 address | | | | | |
13718 | overlay | <-' | | |
13719 | area | <---' +-----------+<-- overlay 3
13720 | | <---. | | load address
13721 +-----------+ `--| overlay 3 |
13728 @anchor{A code overlay}A code overlay
13732 The diagram (@pxref{A code overlay}) shows a system with separate data
13733 and instruction address spaces. To map an overlay, the program copies
13734 its code from the larger address space to the instruction address space.
13735 Since the overlays shown here all use the same mapped address, only one
13736 may be mapped at a time. For a system with a single address space for
13737 data and instructions, the diagram would be similar, except that the
13738 program variables and heap would share an address space with the main
13739 program and the overlay area.
13741 An overlay loaded into instruction memory and ready for use is called a
13742 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
13743 instruction memory. An overlay not present (or only partially present)
13744 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
13745 is its address in the larger memory. The mapped address is also called
13746 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
13747 called the @dfn{load memory address}, or @dfn{LMA}.
13749 Unfortunately, overlays are not a completely transparent way to adapt a
13750 program to limited instruction memory. They introduce a new set of
13751 global constraints you must keep in mind as you design your program:
13756 Before calling or returning to a function in an overlay, your program
13757 must make sure that overlay is actually mapped. Otherwise, the call or
13758 return will transfer control to the right address, but in the wrong
13759 overlay, and your program will probably crash.
13762 If the process of mapping an overlay is expensive on your system, you
13763 will need to choose your overlays carefully to minimize their effect on
13764 your program's performance.
13767 The executable file you load onto your system must contain each
13768 overlay's instructions, appearing at the overlay's load address, not its
13769 mapped address. However, each overlay's instructions must be relocated
13770 and its symbols defined as if the overlay were at its mapped address.
13771 You can use GNU linker scripts to specify different load and relocation
13772 addresses for pieces of your program; see @ref{Overlay Description,,,
13773 ld.info, Using ld: the GNU linker}.
13776 The procedure for loading executable files onto your system must be able
13777 to load their contents into the larger address space as well as the
13778 instruction and data spaces.
13782 The overlay system described above is rather simple, and could be
13783 improved in many ways:
13788 If your system has suitable bank switch registers or memory management
13789 hardware, you could use those facilities to make an overlay's load area
13790 contents simply appear at their mapped address in instruction space.
13791 This would probably be faster than copying the overlay to its mapped
13792 area in the usual way.
13795 If your overlays are small enough, you could set aside more than one
13796 overlay area, and have more than one overlay mapped at a time.
13799 You can use overlays to manage data, as well as instructions. In
13800 general, data overlays are even less transparent to your design than
13801 code overlays: whereas code overlays only require care when you call or
13802 return to functions, data overlays require care every time you access
13803 the data. Also, if you change the contents of a data overlay, you
13804 must copy its contents back out to its load address before you can copy a
13805 different data overlay into the same mapped area.
13810 @node Overlay Commands
13811 @section Overlay Commands
13813 To use @value{GDBN}'s overlay support, each overlay in your program must
13814 correspond to a separate section of the executable file. The section's
13815 virtual memory address and load memory address must be the overlay's
13816 mapped and load addresses. Identifying overlays with sections allows
13817 @value{GDBN} to determine the appropriate address of a function or
13818 variable, depending on whether the overlay is mapped or not.
13820 @value{GDBN}'s overlay commands all start with the word @code{overlay};
13821 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
13826 Disable @value{GDBN}'s overlay support. When overlay support is
13827 disabled, @value{GDBN} assumes that all functions and variables are
13828 always present at their mapped addresses. By default, @value{GDBN}'s
13829 overlay support is disabled.
13831 @item overlay manual
13832 @cindex manual overlay debugging
13833 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
13834 relies on you to tell it which overlays are mapped, and which are not,
13835 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
13836 commands described below.
13838 @item overlay map-overlay @var{overlay}
13839 @itemx overlay map @var{overlay}
13840 @cindex map an overlay
13841 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
13842 be the name of the object file section containing the overlay. When an
13843 overlay is mapped, @value{GDBN} assumes it can find the overlay's
13844 functions and variables at their mapped addresses. @value{GDBN} assumes
13845 that any other overlays whose mapped ranges overlap that of
13846 @var{overlay} are now unmapped.
13848 @item overlay unmap-overlay @var{overlay}
13849 @itemx overlay unmap @var{overlay}
13850 @cindex unmap an overlay
13851 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
13852 must be the name of the object file section containing the overlay.
13853 When an overlay is unmapped, @value{GDBN} assumes it can find the
13854 overlay's functions and variables at their load addresses.
13857 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
13858 consults a data structure the overlay manager maintains in the inferior
13859 to see which overlays are mapped. For details, see @ref{Automatic
13860 Overlay Debugging}.
13862 @item overlay load-target
13863 @itemx overlay load
13864 @cindex reloading the overlay table
13865 Re-read the overlay table from the inferior. Normally, @value{GDBN}
13866 re-reads the table @value{GDBN} automatically each time the inferior
13867 stops, so this command should only be necessary if you have changed the
13868 overlay mapping yourself using @value{GDBN}. This command is only
13869 useful when using automatic overlay debugging.
13871 @item overlay list-overlays
13872 @itemx overlay list
13873 @cindex listing mapped overlays
13874 Display a list of the overlays currently mapped, along with their mapped
13875 addresses, load addresses, and sizes.
13879 Normally, when @value{GDBN} prints a code address, it includes the name
13880 of the function the address falls in:
13883 (@value{GDBP}) print main
13884 $3 = @{int ()@} 0x11a0 <main>
13887 When overlay debugging is enabled, @value{GDBN} recognizes code in
13888 unmapped overlays, and prints the names of unmapped functions with
13889 asterisks around them. For example, if @code{foo} is a function in an
13890 unmapped overlay, @value{GDBN} prints it this way:
13893 (@value{GDBP}) overlay list
13894 No sections are mapped.
13895 (@value{GDBP}) print foo
13896 $5 = @{int (int)@} 0x100000 <*foo*>
13899 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
13903 (@value{GDBP}) overlay list
13904 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
13905 mapped at 0x1016 - 0x104a
13906 (@value{GDBP}) print foo
13907 $6 = @{int (int)@} 0x1016 <foo>
13910 When overlay debugging is enabled, @value{GDBN} can find the correct
13911 address for functions and variables in an overlay, whether or not the
13912 overlay is mapped. This allows most @value{GDBN} commands, like
13913 @code{break} and @code{disassemble}, to work normally, even on unmapped
13914 code. However, @value{GDBN}'s breakpoint support has some limitations:
13918 @cindex breakpoints in overlays
13919 @cindex overlays, setting breakpoints in
13920 You can set breakpoints in functions in unmapped overlays, as long as
13921 @value{GDBN} can write to the overlay at its load address.
13923 @value{GDBN} can not set hardware or simulator-based breakpoints in
13924 unmapped overlays. However, if you set a breakpoint at the end of your
13925 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
13926 you are using manual overlay management), @value{GDBN} will re-set its
13927 breakpoints properly.
13931 @node Automatic Overlay Debugging
13932 @section Automatic Overlay Debugging
13933 @cindex automatic overlay debugging
13935 @value{GDBN} can automatically track which overlays are mapped and which
13936 are not, given some simple co-operation from the overlay manager in the
13937 inferior. If you enable automatic overlay debugging with the
13938 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
13939 looks in the inferior's memory for certain variables describing the
13940 current state of the overlays.
13942 Here are the variables your overlay manager must define to support
13943 @value{GDBN}'s automatic overlay debugging:
13947 @item @code{_ovly_table}:
13948 This variable must be an array of the following structures:
13953 /* The overlay's mapped address. */
13956 /* The size of the overlay, in bytes. */
13957 unsigned long size;
13959 /* The overlay's load address. */
13962 /* Non-zero if the overlay is currently mapped;
13964 unsigned long mapped;
13968 @item @code{_novlys}:
13969 This variable must be a four-byte signed integer, holding the total
13970 number of elements in @code{_ovly_table}.
13974 To decide whether a particular overlay is mapped or not, @value{GDBN}
13975 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
13976 @code{lma} members equal the VMA and LMA of the overlay's section in the
13977 executable file. When @value{GDBN} finds a matching entry, it consults
13978 the entry's @code{mapped} member to determine whether the overlay is
13981 In addition, your overlay manager may define a function called
13982 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
13983 will silently set a breakpoint there. If the overlay manager then
13984 calls this function whenever it has changed the overlay table, this
13985 will enable @value{GDBN} to accurately keep track of which overlays
13986 are in program memory, and update any breakpoints that may be set
13987 in overlays. This will allow breakpoints to work even if the
13988 overlays are kept in ROM or other non-writable memory while they
13989 are not being executed.
13991 @node Overlay Sample Program
13992 @section Overlay Sample Program
13993 @cindex overlay example program
13995 When linking a program which uses overlays, you must place the overlays
13996 at their load addresses, while relocating them to run at their mapped
13997 addresses. To do this, you must write a linker script (@pxref{Overlay
13998 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
13999 since linker scripts are specific to a particular host system, target
14000 architecture, and target memory layout, this manual cannot provide
14001 portable sample code demonstrating @value{GDBN}'s overlay support.
14003 However, the @value{GDBN} source distribution does contain an overlaid
14004 program, with linker scripts for a few systems, as part of its test
14005 suite. The program consists of the following files from
14006 @file{gdb/testsuite/gdb.base}:
14010 The main program file.
14012 A simple overlay manager, used by @file{overlays.c}.
14017 Overlay modules, loaded and used by @file{overlays.c}.
14020 Linker scripts for linking the test program on the @code{d10v-elf}
14021 and @code{m32r-elf} targets.
14024 You can build the test program using the @code{d10v-elf} GCC
14025 cross-compiler like this:
14028 $ d10v-elf-gcc -g -c overlays.c
14029 $ d10v-elf-gcc -g -c ovlymgr.c
14030 $ d10v-elf-gcc -g -c foo.c
14031 $ d10v-elf-gcc -g -c bar.c
14032 $ d10v-elf-gcc -g -c baz.c
14033 $ d10v-elf-gcc -g -c grbx.c
14034 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
14035 baz.o grbx.o -Wl,-Td10v.ld -o overlays
14038 The build process is identical for any other architecture, except that
14039 you must substitute the appropriate compiler and linker script for the
14040 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
14044 @chapter Using @value{GDBN} with Different Languages
14047 Although programming languages generally have common aspects, they are
14048 rarely expressed in the same manner. For instance, in ANSI C,
14049 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
14050 Modula-2, it is accomplished by @code{p^}. Values can also be
14051 represented (and displayed) differently. Hex numbers in C appear as
14052 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
14054 @cindex working language
14055 Language-specific information is built into @value{GDBN} for some languages,
14056 allowing you to express operations like the above in your program's
14057 native language, and allowing @value{GDBN} to output values in a manner
14058 consistent with the syntax of your program's native language. The
14059 language you use to build expressions is called the @dfn{working
14063 * Setting:: Switching between source languages
14064 * Show:: Displaying the language
14065 * Checks:: Type and range checks
14066 * Supported Languages:: Supported languages
14067 * Unsupported Languages:: Unsupported languages
14071 @section Switching Between Source Languages
14073 There are two ways to control the working language---either have @value{GDBN}
14074 set it automatically, or select it manually yourself. You can use the
14075 @code{set language} command for either purpose. On startup, @value{GDBN}
14076 defaults to setting the language automatically. The working language is
14077 used to determine how expressions you type are interpreted, how values
14080 In addition to the working language, every source file that
14081 @value{GDBN} knows about has its own working language. For some object
14082 file formats, the compiler might indicate which language a particular
14083 source file is in. However, most of the time @value{GDBN} infers the
14084 language from the name of the file. The language of a source file
14085 controls whether C@t{++} names are demangled---this way @code{backtrace} can
14086 show each frame appropriately for its own language. There is no way to
14087 set the language of a source file from within @value{GDBN}, but you can
14088 set the language associated with a filename extension. @xref{Show, ,
14089 Displaying the Language}.
14091 This is most commonly a problem when you use a program, such
14092 as @code{cfront} or @code{f2c}, that generates C but is written in
14093 another language. In that case, make the
14094 program use @code{#line} directives in its C output; that way
14095 @value{GDBN} will know the correct language of the source code of the original
14096 program, and will display that source code, not the generated C code.
14099 * Filenames:: Filename extensions and languages.
14100 * Manually:: Setting the working language manually
14101 * Automatically:: Having @value{GDBN} infer the source language
14105 @subsection List of Filename Extensions and Languages
14107 If a source file name ends in one of the following extensions, then
14108 @value{GDBN} infers that its language is the one indicated.
14126 C@t{++} source file
14132 Objective-C source file
14136 Fortran source file
14139 Modula-2 source file
14143 Assembler source file. This actually behaves almost like C, but
14144 @value{GDBN} does not skip over function prologues when stepping.
14147 In addition, you may set the language associated with a filename
14148 extension. @xref{Show, , Displaying the Language}.
14151 @subsection Setting the Working Language
14153 If you allow @value{GDBN} to set the language automatically,
14154 expressions are interpreted the same way in your debugging session and
14157 @kindex set language
14158 If you wish, you may set the language manually. To do this, issue the
14159 command @samp{set language @var{lang}}, where @var{lang} is the name of
14160 a language, such as
14161 @code{c} or @code{modula-2}.
14162 For a list of the supported languages, type @samp{set language}.
14164 Setting the language manually prevents @value{GDBN} from updating the working
14165 language automatically. This can lead to confusion if you try
14166 to debug a program when the working language is not the same as the
14167 source language, when an expression is acceptable to both
14168 languages---but means different things. For instance, if the current
14169 source file were written in C, and @value{GDBN} was parsing Modula-2, a
14177 might not have the effect you intended. In C, this means to add
14178 @code{b} and @code{c} and place the result in @code{a}. The result
14179 printed would be the value of @code{a}. In Modula-2, this means to compare
14180 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
14182 @node Automatically
14183 @subsection Having @value{GDBN} Infer the Source Language
14185 To have @value{GDBN} set the working language automatically, use
14186 @samp{set language local} or @samp{set language auto}. @value{GDBN}
14187 then infers the working language. That is, when your program stops in a
14188 frame (usually by encountering a breakpoint), @value{GDBN} sets the
14189 working language to the language recorded for the function in that
14190 frame. If the language for a frame is unknown (that is, if the function
14191 or block corresponding to the frame was defined in a source file that
14192 does not have a recognized extension), the current working language is
14193 not changed, and @value{GDBN} issues a warning.
14195 This may not seem necessary for most programs, which are written
14196 entirely in one source language. However, program modules and libraries
14197 written in one source language can be used by a main program written in
14198 a different source language. Using @samp{set language auto} in this
14199 case frees you from having to set the working language manually.
14202 @section Displaying the Language
14204 The following commands help you find out which language is the
14205 working language, and also what language source files were written in.
14208 @item show language
14209 @anchor{show language}
14210 @kindex show language
14211 Display the current working language. This is the
14212 language you can use with commands such as @code{print} to
14213 build and compute expressions that may involve variables in your program.
14216 @kindex info frame@r{, show the source language}
14217 Display the source language for this frame. This language becomes the
14218 working language if you use an identifier from this frame.
14219 @xref{Frame Info, ,Information about a Frame}, to identify the other
14220 information listed here.
14223 @kindex info source@r{, show the source language}
14224 Display the source language of this source file.
14225 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
14226 information listed here.
14229 In unusual circumstances, you may have source files with extensions
14230 not in the standard list. You can then set the extension associated
14231 with a language explicitly:
14234 @item set extension-language @var{ext} @var{language}
14235 @kindex set extension-language
14236 Tell @value{GDBN} that source files with extension @var{ext} are to be
14237 assumed as written in the source language @var{language}.
14239 @item info extensions
14240 @kindex info extensions
14241 List all the filename extensions and the associated languages.
14245 @section Type and Range Checking
14247 Some languages are designed to guard you against making seemingly common
14248 errors through a series of compile- and run-time checks. These include
14249 checking the type of arguments to functions and operators and making
14250 sure mathematical overflows are caught at run time. Checks such as
14251 these help to ensure a program's correctness once it has been compiled
14252 by eliminating type mismatches and providing active checks for range
14253 errors when your program is running.
14255 By default @value{GDBN} checks for these errors according to the
14256 rules of the current source language. Although @value{GDBN} does not check
14257 the statements in your program, it can check expressions entered directly
14258 into @value{GDBN} for evaluation via the @code{print} command, for example.
14261 * Type Checking:: An overview of type checking
14262 * Range Checking:: An overview of range checking
14265 @cindex type checking
14266 @cindex checks, type
14267 @node Type Checking
14268 @subsection An Overview of Type Checking
14270 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
14271 arguments to operators and functions have to be of the correct type,
14272 otherwise an error occurs. These checks prevent type mismatch
14273 errors from ever causing any run-time problems. For example,
14276 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
14278 (@value{GDBP}) print obj.my_method (0)
14281 (@value{GDBP}) print obj.my_method (0x1234)
14282 Cannot resolve method klass::my_method to any overloaded instance
14285 The second example fails because in C@t{++} the integer constant
14286 @samp{0x1234} is not type-compatible with the pointer parameter type.
14288 For the expressions you use in @value{GDBN} commands, you can tell
14289 @value{GDBN} to not enforce strict type checking or
14290 to treat any mismatches as errors and abandon the expression;
14291 When type checking is disabled, @value{GDBN} successfully evaluates
14292 expressions like the second example above.
14294 Even if type checking is off, there may be other reasons
14295 related to type that prevent @value{GDBN} from evaluating an expression.
14296 For instance, @value{GDBN} does not know how to add an @code{int} and
14297 a @code{struct foo}. These particular type errors have nothing to do
14298 with the language in use and usually arise from expressions which make
14299 little sense to evaluate anyway.
14301 @value{GDBN} provides some additional commands for controlling type checking:
14303 @kindex set check type
14304 @kindex show check type
14306 @item set check type on
14307 @itemx set check type off
14308 Set strict type checking on or off. If any type mismatches occur in
14309 evaluating an expression while type checking is on, @value{GDBN} prints a
14310 message and aborts evaluation of the expression.
14312 @item show check type
14313 Show the current setting of type checking and whether @value{GDBN}
14314 is enforcing strict type checking rules.
14317 @cindex range checking
14318 @cindex checks, range
14319 @node Range Checking
14320 @subsection An Overview of Range Checking
14322 In some languages (such as Modula-2), it is an error to exceed the
14323 bounds of a type; this is enforced with run-time checks. Such range
14324 checking is meant to ensure program correctness by making sure
14325 computations do not overflow, or indices on an array element access do
14326 not exceed the bounds of the array.
14328 For expressions you use in @value{GDBN} commands, you can tell
14329 @value{GDBN} to treat range errors in one of three ways: ignore them,
14330 always treat them as errors and abandon the expression, or issue
14331 warnings but evaluate the expression anyway.
14333 A range error can result from numerical overflow, from exceeding an
14334 array index bound, or when you type a constant that is not a member
14335 of any type. Some languages, however, do not treat overflows as an
14336 error. In many implementations of C, mathematical overflow causes the
14337 result to ``wrap around'' to lower values---for example, if @var{m} is
14338 the largest integer value, and @var{s} is the smallest, then
14341 @var{m} + 1 @result{} @var{s}
14344 This, too, is specific to individual languages, and in some cases
14345 specific to individual compilers or machines. @xref{Supported Languages, ,
14346 Supported Languages}, for further details on specific languages.
14348 @value{GDBN} provides some additional commands for controlling the range checker:
14350 @kindex set check range
14351 @kindex show check range
14353 @item set check range auto
14354 Set range checking on or off based on the current working language.
14355 @xref{Supported Languages, ,Supported Languages}, for the default settings for
14358 @item set check range on
14359 @itemx set check range off
14360 Set range checking on or off, overriding the default setting for the
14361 current working language. A warning is issued if the setting does not
14362 match the language default. If a range error occurs and range checking is on,
14363 then a message is printed and evaluation of the expression is aborted.
14365 @item set check range warn
14366 Output messages when the @value{GDBN} range checker detects a range error,
14367 but attempt to evaluate the expression anyway. Evaluating the
14368 expression may still be impossible for other reasons, such as accessing
14369 memory that the process does not own (a typical example from many Unix
14373 Show the current setting of the range checker, and whether or not it is
14374 being set automatically by @value{GDBN}.
14377 @node Supported Languages
14378 @section Supported Languages
14380 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
14381 OpenCL C, Pascal, assembly, Modula-2, and Ada.
14382 @c This is false ...
14383 Some @value{GDBN} features may be used in expressions regardless of the
14384 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
14385 and the @samp{@{type@}addr} construct (@pxref{Expressions,
14386 ,Expressions}) can be used with the constructs of any supported
14389 The following sections detail to what degree each source language is
14390 supported by @value{GDBN}. These sections are not meant to be language
14391 tutorials or references, but serve only as a reference guide to what the
14392 @value{GDBN} expression parser accepts, and what input and output
14393 formats should look like for different languages. There are many good
14394 books written on each of these languages; please look to these for a
14395 language reference or tutorial.
14398 * C:: C and C@t{++}
14401 * Objective-C:: Objective-C
14402 * OpenCL C:: OpenCL C
14403 * Fortran:: Fortran
14405 * Modula-2:: Modula-2
14410 @subsection C and C@t{++}
14412 @cindex C and C@t{++}
14413 @cindex expressions in C or C@t{++}
14415 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
14416 to both languages. Whenever this is the case, we discuss those languages
14420 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
14421 @cindex @sc{gnu} C@t{++}
14422 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
14423 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
14424 effectively, you must compile your C@t{++} programs with a supported
14425 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
14426 compiler (@code{aCC}).
14429 * C Operators:: C and C@t{++} operators
14430 * C Constants:: C and C@t{++} constants
14431 * C Plus Plus Expressions:: C@t{++} expressions
14432 * C Defaults:: Default settings for C and C@t{++}
14433 * C Checks:: C and C@t{++} type and range checks
14434 * Debugging C:: @value{GDBN} and C
14435 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
14436 * Decimal Floating Point:: Numbers in Decimal Floating Point format
14440 @subsubsection C and C@t{++} Operators
14442 @cindex C and C@t{++} operators
14444 Operators must be defined on values of specific types. For instance,
14445 @code{+} is defined on numbers, but not on structures. Operators are
14446 often defined on groups of types.
14448 For the purposes of C and C@t{++}, the following definitions hold:
14453 @emph{Integral types} include @code{int} with any of its storage-class
14454 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
14457 @emph{Floating-point types} include @code{float}, @code{double}, and
14458 @code{long double} (if supported by the target platform).
14461 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
14464 @emph{Scalar types} include all of the above.
14469 The following operators are supported. They are listed here
14470 in order of increasing precedence:
14474 The comma or sequencing operator. Expressions in a comma-separated list
14475 are evaluated from left to right, with the result of the entire
14476 expression being the last expression evaluated.
14479 Assignment. The value of an assignment expression is the value
14480 assigned. Defined on scalar types.
14483 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
14484 and translated to @w{@code{@var{a} = @var{a op b}}}.
14485 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
14486 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
14487 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
14490 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
14491 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
14492 should be of an integral type.
14495 Logical @sc{or}. Defined on integral types.
14498 Logical @sc{and}. Defined on integral types.
14501 Bitwise @sc{or}. Defined on integral types.
14504 Bitwise exclusive-@sc{or}. Defined on integral types.
14507 Bitwise @sc{and}. Defined on integral types.
14510 Equality and inequality. Defined on scalar types. The value of these
14511 expressions is 0 for false and non-zero for true.
14513 @item <@r{, }>@r{, }<=@r{, }>=
14514 Less than, greater than, less than or equal, greater than or equal.
14515 Defined on scalar types. The value of these expressions is 0 for false
14516 and non-zero for true.
14519 left shift, and right shift. Defined on integral types.
14522 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14525 Addition and subtraction. Defined on integral types, floating-point types and
14528 @item *@r{, }/@r{, }%
14529 Multiplication, division, and modulus. Multiplication and division are
14530 defined on integral and floating-point types. Modulus is defined on
14534 Increment and decrement. When appearing before a variable, the
14535 operation is performed before the variable is used in an expression;
14536 when appearing after it, the variable's value is used before the
14537 operation takes place.
14540 Pointer dereferencing. Defined on pointer types. Same precedence as
14544 Address operator. Defined on variables. Same precedence as @code{++}.
14546 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
14547 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
14548 to examine the address
14549 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
14553 Negative. Defined on integral and floating-point types. Same
14554 precedence as @code{++}.
14557 Logical negation. Defined on integral types. Same precedence as
14561 Bitwise complement operator. Defined on integral types. Same precedence as
14566 Structure member, and pointer-to-structure member. For convenience,
14567 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
14568 pointer based on the stored type information.
14569 Defined on @code{struct} and @code{union} data.
14572 Dereferences of pointers to members.
14575 Array indexing. @code{@var{a}[@var{i}]} is defined as
14576 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
14579 Function parameter list. Same precedence as @code{->}.
14582 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
14583 and @code{class} types.
14586 Doubled colons also represent the @value{GDBN} scope operator
14587 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
14591 If an operator is redefined in the user code, @value{GDBN} usually
14592 attempts to invoke the redefined version instead of using the operator's
14593 predefined meaning.
14596 @subsubsection C and C@t{++} Constants
14598 @cindex C and C@t{++} constants
14600 @value{GDBN} allows you to express the constants of C and C@t{++} in the
14605 Integer constants are a sequence of digits. Octal constants are
14606 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
14607 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
14608 @samp{l}, specifying that the constant should be treated as a
14612 Floating point constants are a sequence of digits, followed by a decimal
14613 point, followed by a sequence of digits, and optionally followed by an
14614 exponent. An exponent is of the form:
14615 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
14616 sequence of digits. The @samp{+} is optional for positive exponents.
14617 A floating-point constant may also end with a letter @samp{f} or
14618 @samp{F}, specifying that the constant should be treated as being of
14619 the @code{float} (as opposed to the default @code{double}) type; or with
14620 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
14624 Enumerated constants consist of enumerated identifiers, or their
14625 integral equivalents.
14628 Character constants are a single character surrounded by single quotes
14629 (@code{'}), or a number---the ordinal value of the corresponding character
14630 (usually its @sc{ascii} value). Within quotes, the single character may
14631 be represented by a letter or by @dfn{escape sequences}, which are of
14632 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
14633 of the character's ordinal value; or of the form @samp{\@var{x}}, where
14634 @samp{@var{x}} is a predefined special character---for example,
14635 @samp{\n} for newline.
14637 Wide character constants can be written by prefixing a character
14638 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
14639 form of @samp{x}. The target wide character set is used when
14640 computing the value of this constant (@pxref{Character Sets}).
14643 String constants are a sequence of character constants surrounded by
14644 double quotes (@code{"}). Any valid character constant (as described
14645 above) may appear. Double quotes within the string must be preceded by
14646 a backslash, so for instance @samp{"a\"b'c"} is a string of five
14649 Wide string constants can be written by prefixing a string constant
14650 with @samp{L}, as in C. The target wide character set is used when
14651 computing the value of this constant (@pxref{Character Sets}).
14654 Pointer constants are an integral value. You can also write pointers
14655 to constants using the C operator @samp{&}.
14658 Array constants are comma-separated lists surrounded by braces @samp{@{}
14659 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
14660 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
14661 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
14664 @node C Plus Plus Expressions
14665 @subsubsection C@t{++} Expressions
14667 @cindex expressions in C@t{++}
14668 @value{GDBN} expression handling can interpret most C@t{++} expressions.
14670 @cindex debugging C@t{++} programs
14671 @cindex C@t{++} compilers
14672 @cindex debug formats and C@t{++}
14673 @cindex @value{NGCC} and C@t{++}
14675 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
14676 the proper compiler and the proper debug format. Currently,
14677 @value{GDBN} works best when debugging C@t{++} code that is compiled
14678 with the most recent version of @value{NGCC} possible. The DWARF
14679 debugging format is preferred; @value{NGCC} defaults to this on most
14680 popular platforms. Other compilers and/or debug formats are likely to
14681 work badly or not at all when using @value{GDBN} to debug C@t{++}
14682 code. @xref{Compilation}.
14687 @cindex member functions
14689 Member function calls are allowed; you can use expressions like
14692 count = aml->GetOriginal(x, y)
14695 @vindex this@r{, inside C@t{++} member functions}
14696 @cindex namespace in C@t{++}
14698 While a member function is active (in the selected stack frame), your
14699 expressions have the same namespace available as the member function;
14700 that is, @value{GDBN} allows implicit references to the class instance
14701 pointer @code{this} following the same rules as C@t{++}. @code{using}
14702 declarations in the current scope are also respected by @value{GDBN}.
14704 @cindex call overloaded functions
14705 @cindex overloaded functions, calling
14706 @cindex type conversions in C@t{++}
14708 You can call overloaded functions; @value{GDBN} resolves the function
14709 call to the right definition, with some restrictions. @value{GDBN} does not
14710 perform overload resolution involving user-defined type conversions,
14711 calls to constructors, or instantiations of templates that do not exist
14712 in the program. It also cannot handle ellipsis argument lists or
14715 It does perform integral conversions and promotions, floating-point
14716 promotions, arithmetic conversions, pointer conversions, conversions of
14717 class objects to base classes, and standard conversions such as those of
14718 functions or arrays to pointers; it requires an exact match on the
14719 number of function arguments.
14721 Overload resolution is always performed, unless you have specified
14722 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
14723 ,@value{GDBN} Features for C@t{++}}.
14725 You must specify @code{set overload-resolution off} in order to use an
14726 explicit function signature to call an overloaded function, as in
14728 p 'foo(char,int)'('x', 13)
14731 The @value{GDBN} command-completion facility can simplify this;
14732 see @ref{Completion, ,Command Completion}.
14734 @cindex reference declarations
14736 @value{GDBN} understands variables declared as C@t{++} references; you can use
14737 them in expressions just as you do in C@t{++} source---they are automatically
14740 In the parameter list shown when @value{GDBN} displays a frame, the values of
14741 reference variables are not displayed (unlike other variables); this
14742 avoids clutter, since references are often used for large structures.
14743 The @emph{address} of a reference variable is always shown, unless
14744 you have specified @samp{set print address off}.
14747 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
14748 expressions can use it just as expressions in your program do. Since
14749 one scope may be defined in another, you can use @code{::} repeatedly if
14750 necessary, for example in an expression like
14751 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
14752 resolving name scope by reference to source files, in both C and C@t{++}
14753 debugging (@pxref{Variables, ,Program Variables}).
14756 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
14761 @subsubsection C and C@t{++} Defaults
14763 @cindex C and C@t{++} defaults
14765 If you allow @value{GDBN} to set range checking automatically, it
14766 defaults to @code{off} whenever the working language changes to
14767 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
14768 selects the working language.
14770 If you allow @value{GDBN} to set the language automatically, it
14771 recognizes source files whose names end with @file{.c}, @file{.C}, or
14772 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
14773 these files, it sets the working language to C or C@t{++}.
14774 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
14775 for further details.
14778 @subsubsection C and C@t{++} Type and Range Checks
14780 @cindex C and C@t{++} checks
14782 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
14783 checking is used. However, if you turn type checking off, @value{GDBN}
14784 will allow certain non-standard conversions, such as promoting integer
14785 constants to pointers.
14787 Range checking, if turned on, is done on mathematical operations. Array
14788 indices are not checked, since they are often used to index a pointer
14789 that is not itself an array.
14792 @subsubsection @value{GDBN} and C
14794 The @code{set print union} and @code{show print union} commands apply to
14795 the @code{union} type. When set to @samp{on}, any @code{union} that is
14796 inside a @code{struct} or @code{class} is also printed. Otherwise, it
14797 appears as @samp{@{...@}}.
14799 The @code{@@} operator aids in the debugging of dynamic arrays, formed
14800 with pointers and a memory allocation function. @xref{Expressions,
14803 @node Debugging C Plus Plus
14804 @subsubsection @value{GDBN} Features for C@t{++}
14806 @cindex commands for C@t{++}
14808 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
14809 designed specifically for use with C@t{++}. Here is a summary:
14812 @cindex break in overloaded functions
14813 @item @r{breakpoint menus}
14814 When you want a breakpoint in a function whose name is overloaded,
14815 @value{GDBN} has the capability to display a menu of possible breakpoint
14816 locations to help you specify which function definition you want.
14817 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
14819 @cindex overloading in C@t{++}
14820 @item rbreak @var{regex}
14821 Setting breakpoints using regular expressions is helpful for setting
14822 breakpoints on overloaded functions that are not members of any special
14824 @xref{Set Breaks, ,Setting Breakpoints}.
14826 @cindex C@t{++} exception handling
14828 @itemx catch rethrow
14830 Debug C@t{++} exception handling using these commands. @xref{Set
14831 Catchpoints, , Setting Catchpoints}.
14833 @cindex inheritance
14834 @item ptype @var{typename}
14835 Print inheritance relationships as well as other information for type
14837 @xref{Symbols, ,Examining the Symbol Table}.
14839 @item info vtbl @var{expression}.
14840 The @code{info vtbl} command can be used to display the virtual
14841 method tables of the object computed by @var{expression}. This shows
14842 one entry per virtual table; there may be multiple virtual tables when
14843 multiple inheritance is in use.
14845 @cindex C@t{++} demangling
14846 @item demangle @var{name}
14847 Demangle @var{name}.
14848 @xref{Symbols}, for a more complete description of the @code{demangle} command.
14850 @cindex C@t{++} symbol display
14851 @item set print demangle
14852 @itemx show print demangle
14853 @itemx set print asm-demangle
14854 @itemx show print asm-demangle
14855 Control whether C@t{++} symbols display in their source form, both when
14856 displaying code as C@t{++} source and when displaying disassemblies.
14857 @xref{Print Settings, ,Print Settings}.
14859 @item set print object
14860 @itemx show print object
14861 Choose whether to print derived (actual) or declared types of objects.
14862 @xref{Print Settings, ,Print Settings}.
14864 @item set print vtbl
14865 @itemx show print vtbl
14866 Control the format for printing virtual function tables.
14867 @xref{Print Settings, ,Print Settings}.
14868 (The @code{vtbl} commands do not work on programs compiled with the HP
14869 ANSI C@t{++} compiler (@code{aCC}).)
14871 @kindex set overload-resolution
14872 @cindex overloaded functions, overload resolution
14873 @item set overload-resolution on
14874 Enable overload resolution for C@t{++} expression evaluation. The default
14875 is on. For overloaded functions, @value{GDBN} evaluates the arguments
14876 and searches for a function whose signature matches the argument types,
14877 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
14878 Expressions, ,C@t{++} Expressions}, for details).
14879 If it cannot find a match, it emits a message.
14881 @item set overload-resolution off
14882 Disable overload resolution for C@t{++} expression evaluation. For
14883 overloaded functions that are not class member functions, @value{GDBN}
14884 chooses the first function of the specified name that it finds in the
14885 symbol table, whether or not its arguments are of the correct type. For
14886 overloaded functions that are class member functions, @value{GDBN}
14887 searches for a function whose signature @emph{exactly} matches the
14890 @kindex show overload-resolution
14891 @item show overload-resolution
14892 Show the current setting of overload resolution.
14894 @item @r{Overloaded symbol names}
14895 You can specify a particular definition of an overloaded symbol, using
14896 the same notation that is used to declare such symbols in C@t{++}: type
14897 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
14898 also use the @value{GDBN} command-line word completion facilities to list the
14899 available choices, or to finish the type list for you.
14900 @xref{Completion,, Command Completion}, for details on how to do this.
14903 @node Decimal Floating Point
14904 @subsubsection Decimal Floating Point format
14905 @cindex decimal floating point format
14907 @value{GDBN} can examine, set and perform computations with numbers in
14908 decimal floating point format, which in the C language correspond to the
14909 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
14910 specified by the extension to support decimal floating-point arithmetic.
14912 There are two encodings in use, depending on the architecture: BID (Binary
14913 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
14914 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
14917 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
14918 to manipulate decimal floating point numbers, it is not possible to convert
14919 (using a cast, for example) integers wider than 32-bit to decimal float.
14921 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
14922 point computations, error checking in decimal float operations ignores
14923 underflow, overflow and divide by zero exceptions.
14925 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
14926 to inspect @code{_Decimal128} values stored in floating point registers.
14927 See @ref{PowerPC,,PowerPC} for more details.
14933 @value{GDBN} can be used to debug programs written in D and compiled with
14934 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
14935 specific feature --- dynamic arrays.
14940 @cindex Go (programming language)
14941 @value{GDBN} can be used to debug programs written in Go and compiled with
14942 @file{gccgo} or @file{6g} compilers.
14944 Here is a summary of the Go-specific features and restrictions:
14947 @cindex current Go package
14948 @item The current Go package
14949 The name of the current package does not need to be specified when
14950 specifying global variables and functions.
14952 For example, given the program:
14956 var myglob = "Shall we?"
14962 When stopped inside @code{main} either of these work:
14966 (gdb) p main.myglob
14969 @cindex builtin Go types
14970 @item Builtin Go types
14971 The @code{string} type is recognized by @value{GDBN} and is printed
14974 @cindex builtin Go functions
14975 @item Builtin Go functions
14976 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
14977 function and handles it internally.
14979 @cindex restrictions on Go expressions
14980 @item Restrictions on Go expressions
14981 All Go operators are supported except @code{&^}.
14982 The Go @code{_} ``blank identifier'' is not supported.
14983 Automatic dereferencing of pointers is not supported.
14987 @subsection Objective-C
14989 @cindex Objective-C
14990 This section provides information about some commands and command
14991 options that are useful for debugging Objective-C code. See also
14992 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
14993 few more commands specific to Objective-C support.
14996 * Method Names in Commands::
14997 * The Print Command with Objective-C::
15000 @node Method Names in Commands
15001 @subsubsection Method Names in Commands
15003 The following commands have been extended to accept Objective-C method
15004 names as line specifications:
15006 @kindex clear@r{, and Objective-C}
15007 @kindex break@r{, and Objective-C}
15008 @kindex info line@r{, and Objective-C}
15009 @kindex jump@r{, and Objective-C}
15010 @kindex list@r{, and Objective-C}
15014 @item @code{info line}
15019 A fully qualified Objective-C method name is specified as
15022 -[@var{Class} @var{methodName}]
15025 where the minus sign is used to indicate an instance method and a
15026 plus sign (not shown) is used to indicate a class method. The class
15027 name @var{Class} and method name @var{methodName} are enclosed in
15028 brackets, similar to the way messages are specified in Objective-C
15029 source code. For example, to set a breakpoint at the @code{create}
15030 instance method of class @code{Fruit} in the program currently being
15034 break -[Fruit create]
15037 To list ten program lines around the @code{initialize} class method,
15041 list +[NSText initialize]
15044 In the current version of @value{GDBN}, the plus or minus sign is
15045 required. In future versions of @value{GDBN}, the plus or minus
15046 sign will be optional, but you can use it to narrow the search. It
15047 is also possible to specify just a method name:
15053 You must specify the complete method name, including any colons. If
15054 your program's source files contain more than one @code{create} method,
15055 you'll be presented with a numbered list of classes that implement that
15056 method. Indicate your choice by number, or type @samp{0} to exit if
15059 As another example, to clear a breakpoint established at the
15060 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
15063 clear -[NSWindow makeKeyAndOrderFront:]
15066 @node The Print Command with Objective-C
15067 @subsubsection The Print Command With Objective-C
15068 @cindex Objective-C, print objects
15069 @kindex print-object
15070 @kindex po @r{(@code{print-object})}
15072 The print command has also been extended to accept methods. For example:
15075 print -[@var{object} hash]
15078 @cindex print an Objective-C object description
15079 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
15081 will tell @value{GDBN} to send the @code{hash} message to @var{object}
15082 and print the result. Also, an additional command has been added,
15083 @code{print-object} or @code{po} for short, which is meant to print
15084 the description of an object. However, this command may only work
15085 with certain Objective-C libraries that have a particular hook
15086 function, @code{_NSPrintForDebugger}, defined.
15089 @subsection OpenCL C
15092 This section provides information about @value{GDBN}s OpenCL C support.
15095 * OpenCL C Datatypes::
15096 * OpenCL C Expressions::
15097 * OpenCL C Operators::
15100 @node OpenCL C Datatypes
15101 @subsubsection OpenCL C Datatypes
15103 @cindex OpenCL C Datatypes
15104 @value{GDBN} supports the builtin scalar and vector datatypes specified
15105 by OpenCL 1.1. In addition the half- and double-precision floating point
15106 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
15107 extensions are also known to @value{GDBN}.
15109 @node OpenCL C Expressions
15110 @subsubsection OpenCL C Expressions
15112 @cindex OpenCL C Expressions
15113 @value{GDBN} supports accesses to vector components including the access as
15114 lvalue where possible. Since OpenCL C is based on C99 most C expressions
15115 supported by @value{GDBN} can be used as well.
15117 @node OpenCL C Operators
15118 @subsubsection OpenCL C Operators
15120 @cindex OpenCL C Operators
15121 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
15125 @subsection Fortran
15126 @cindex Fortran-specific support in @value{GDBN}
15128 @value{GDBN} can be used to debug programs written in Fortran, but it
15129 currently supports only the features of Fortran 77 language.
15131 @cindex trailing underscore, in Fortran symbols
15132 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
15133 among them) append an underscore to the names of variables and
15134 functions. When you debug programs compiled by those compilers, you
15135 will need to refer to variables and functions with a trailing
15139 * Fortran Operators:: Fortran operators and expressions
15140 * Fortran Defaults:: Default settings for Fortran
15141 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
15144 @node Fortran Operators
15145 @subsubsection Fortran Operators and Expressions
15147 @cindex Fortran operators and expressions
15149 Operators must be defined on values of specific types. For instance,
15150 @code{+} is defined on numbers, but not on characters or other non-
15151 arithmetic types. Operators are often defined on groups of types.
15155 The exponentiation operator. It raises the first operand to the power
15159 The range operator. Normally used in the form of array(low:high) to
15160 represent a section of array.
15163 The access component operator. Normally used to access elements in derived
15164 types. Also suitable for unions. As unions aren't part of regular Fortran,
15165 this can only happen when accessing a register that uses a gdbarch-defined
15169 @node Fortran Defaults
15170 @subsubsection Fortran Defaults
15172 @cindex Fortran Defaults
15174 Fortran symbols are usually case-insensitive, so @value{GDBN} by
15175 default uses case-insensitive matches for Fortran symbols. You can
15176 change that with the @samp{set case-insensitive} command, see
15177 @ref{Symbols}, for the details.
15179 @node Special Fortran Commands
15180 @subsubsection Special Fortran Commands
15182 @cindex Special Fortran commands
15184 @value{GDBN} has some commands to support Fortran-specific features,
15185 such as displaying common blocks.
15188 @cindex @code{COMMON} blocks, Fortran
15189 @kindex info common
15190 @item info common @r{[}@var{common-name}@r{]}
15191 This command prints the values contained in the Fortran @code{COMMON}
15192 block whose name is @var{common-name}. With no argument, the names of
15193 all @code{COMMON} blocks visible at the current program location are
15200 @cindex Pascal support in @value{GDBN}, limitations
15201 Debugging Pascal programs which use sets, subranges, file variables, or
15202 nested functions does not currently work. @value{GDBN} does not support
15203 entering expressions, printing values, or similar features using Pascal
15206 The Pascal-specific command @code{set print pascal_static-members}
15207 controls whether static members of Pascal objects are displayed.
15208 @xref{Print Settings, pascal_static-members}.
15211 @subsection Modula-2
15213 @cindex Modula-2, @value{GDBN} support
15215 The extensions made to @value{GDBN} to support Modula-2 only support
15216 output from the @sc{gnu} Modula-2 compiler (which is currently being
15217 developed). Other Modula-2 compilers are not currently supported, and
15218 attempting to debug executables produced by them is most likely
15219 to give an error as @value{GDBN} reads in the executable's symbol
15222 @cindex expressions in Modula-2
15224 * M2 Operators:: Built-in operators
15225 * Built-In Func/Proc:: Built-in functions and procedures
15226 * M2 Constants:: Modula-2 constants
15227 * M2 Types:: Modula-2 types
15228 * M2 Defaults:: Default settings for Modula-2
15229 * Deviations:: Deviations from standard Modula-2
15230 * M2 Checks:: Modula-2 type and range checks
15231 * M2 Scope:: The scope operators @code{::} and @code{.}
15232 * GDB/M2:: @value{GDBN} and Modula-2
15236 @subsubsection Operators
15237 @cindex Modula-2 operators
15239 Operators must be defined on values of specific types. For instance,
15240 @code{+} is defined on numbers, but not on structures. Operators are
15241 often defined on groups of types. For the purposes of Modula-2, the
15242 following definitions hold:
15247 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
15251 @emph{Character types} consist of @code{CHAR} and its subranges.
15254 @emph{Floating-point types} consist of @code{REAL}.
15257 @emph{Pointer types} consist of anything declared as @code{POINTER TO
15261 @emph{Scalar types} consist of all of the above.
15264 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
15267 @emph{Boolean types} consist of @code{BOOLEAN}.
15271 The following operators are supported, and appear in order of
15272 increasing precedence:
15276 Function argument or array index separator.
15279 Assignment. The value of @var{var} @code{:=} @var{value} is
15283 Less than, greater than on integral, floating-point, or enumerated
15287 Less than or equal to, greater than or equal to
15288 on integral, floating-point and enumerated types, or set inclusion on
15289 set types. Same precedence as @code{<}.
15291 @item =@r{, }<>@r{, }#
15292 Equality and two ways of expressing inequality, valid on scalar types.
15293 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
15294 available for inequality, since @code{#} conflicts with the script
15298 Set membership. Defined on set types and the types of their members.
15299 Same precedence as @code{<}.
15302 Boolean disjunction. Defined on boolean types.
15305 Boolean conjunction. Defined on boolean types.
15308 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
15311 Addition and subtraction on integral and floating-point types, or union
15312 and difference on set types.
15315 Multiplication on integral and floating-point types, or set intersection
15319 Division on floating-point types, or symmetric set difference on set
15320 types. Same precedence as @code{*}.
15323 Integer division and remainder. Defined on integral types. Same
15324 precedence as @code{*}.
15327 Negative. Defined on @code{INTEGER} and @code{REAL} data.
15330 Pointer dereferencing. Defined on pointer types.
15333 Boolean negation. Defined on boolean types. Same precedence as
15337 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
15338 precedence as @code{^}.
15341 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
15344 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
15348 @value{GDBN} and Modula-2 scope operators.
15352 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
15353 treats the use of the operator @code{IN}, or the use of operators
15354 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
15355 @code{<=}, and @code{>=} on sets as an error.
15359 @node Built-In Func/Proc
15360 @subsubsection Built-in Functions and Procedures
15361 @cindex Modula-2 built-ins
15363 Modula-2 also makes available several built-in procedures and functions.
15364 In describing these, the following metavariables are used:
15369 represents an @code{ARRAY} variable.
15372 represents a @code{CHAR} constant or variable.
15375 represents a variable or constant of integral type.
15378 represents an identifier that belongs to a set. Generally used in the
15379 same function with the metavariable @var{s}. The type of @var{s} should
15380 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
15383 represents a variable or constant of integral or floating-point type.
15386 represents a variable or constant of floating-point type.
15392 represents a variable.
15395 represents a variable or constant of one of many types. See the
15396 explanation of the function for details.
15399 All Modula-2 built-in procedures also return a result, described below.
15403 Returns the absolute value of @var{n}.
15406 If @var{c} is a lower case letter, it returns its upper case
15407 equivalent, otherwise it returns its argument.
15410 Returns the character whose ordinal value is @var{i}.
15413 Decrements the value in the variable @var{v} by one. Returns the new value.
15415 @item DEC(@var{v},@var{i})
15416 Decrements the value in the variable @var{v} by @var{i}. Returns the
15419 @item EXCL(@var{m},@var{s})
15420 Removes the element @var{m} from the set @var{s}. Returns the new
15423 @item FLOAT(@var{i})
15424 Returns the floating point equivalent of the integer @var{i}.
15426 @item HIGH(@var{a})
15427 Returns the index of the last member of @var{a}.
15430 Increments the value in the variable @var{v} by one. Returns the new value.
15432 @item INC(@var{v},@var{i})
15433 Increments the value in the variable @var{v} by @var{i}. Returns the
15436 @item INCL(@var{m},@var{s})
15437 Adds the element @var{m} to the set @var{s} if it is not already
15438 there. Returns the new set.
15441 Returns the maximum value of the type @var{t}.
15444 Returns the minimum value of the type @var{t}.
15447 Returns boolean TRUE if @var{i} is an odd number.
15450 Returns the ordinal value of its argument. For example, the ordinal
15451 value of a character is its @sc{ascii} value (on machines supporting
15452 the @sc{ascii} character set). The argument @var{x} must be of an
15453 ordered type, which include integral, character and enumerated types.
15455 @item SIZE(@var{x})
15456 Returns the size of its argument. The argument @var{x} can be a
15457 variable or a type.
15459 @item TRUNC(@var{r})
15460 Returns the integral part of @var{r}.
15462 @item TSIZE(@var{x})
15463 Returns the size of its argument. The argument @var{x} can be a
15464 variable or a type.
15466 @item VAL(@var{t},@var{i})
15467 Returns the member of the type @var{t} whose ordinal value is @var{i}.
15471 @emph{Warning:} Sets and their operations are not yet supported, so
15472 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
15476 @cindex Modula-2 constants
15478 @subsubsection Constants
15480 @value{GDBN} allows you to express the constants of Modula-2 in the following
15486 Integer constants are simply a sequence of digits. When used in an
15487 expression, a constant is interpreted to be type-compatible with the
15488 rest of the expression. Hexadecimal integers are specified by a
15489 trailing @samp{H}, and octal integers by a trailing @samp{B}.
15492 Floating point constants appear as a sequence of digits, followed by a
15493 decimal point and another sequence of digits. An optional exponent can
15494 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
15495 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
15496 digits of the floating point constant must be valid decimal (base 10)
15500 Character constants consist of a single character enclosed by a pair of
15501 like quotes, either single (@code{'}) or double (@code{"}). They may
15502 also be expressed by their ordinal value (their @sc{ascii} value, usually)
15503 followed by a @samp{C}.
15506 String constants consist of a sequence of characters enclosed by a
15507 pair of like quotes, either single (@code{'}) or double (@code{"}).
15508 Escape sequences in the style of C are also allowed. @xref{C
15509 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
15513 Enumerated constants consist of an enumerated identifier.
15516 Boolean constants consist of the identifiers @code{TRUE} and
15520 Pointer constants consist of integral values only.
15523 Set constants are not yet supported.
15527 @subsubsection Modula-2 Types
15528 @cindex Modula-2 types
15530 Currently @value{GDBN} can print the following data types in Modula-2
15531 syntax: array types, record types, set types, pointer types, procedure
15532 types, enumerated types, subrange types and base types. You can also
15533 print the contents of variables declared using these type.
15534 This section gives a number of simple source code examples together with
15535 sample @value{GDBN} sessions.
15537 The first example contains the following section of code:
15546 and you can request @value{GDBN} to interrogate the type and value of
15547 @code{r} and @code{s}.
15550 (@value{GDBP}) print s
15552 (@value{GDBP}) ptype s
15554 (@value{GDBP}) print r
15556 (@value{GDBP}) ptype r
15561 Likewise if your source code declares @code{s} as:
15565 s: SET ['A'..'Z'] ;
15569 then you may query the type of @code{s} by:
15572 (@value{GDBP}) ptype s
15573 type = SET ['A'..'Z']
15577 Note that at present you cannot interactively manipulate set
15578 expressions using the debugger.
15580 The following example shows how you might declare an array in Modula-2
15581 and how you can interact with @value{GDBN} to print its type and contents:
15585 s: ARRAY [-10..10] OF CHAR ;
15589 (@value{GDBP}) ptype s
15590 ARRAY [-10..10] OF CHAR
15593 Note that the array handling is not yet complete and although the type
15594 is printed correctly, expression handling still assumes that all
15595 arrays have a lower bound of zero and not @code{-10} as in the example
15598 Here are some more type related Modula-2 examples:
15602 colour = (blue, red, yellow, green) ;
15603 t = [blue..yellow] ;
15611 The @value{GDBN} interaction shows how you can query the data type
15612 and value of a variable.
15615 (@value{GDBP}) print s
15617 (@value{GDBP}) ptype t
15618 type = [blue..yellow]
15622 In this example a Modula-2 array is declared and its contents
15623 displayed. Observe that the contents are written in the same way as
15624 their @code{C} counterparts.
15628 s: ARRAY [1..5] OF CARDINAL ;
15634 (@value{GDBP}) print s
15635 $1 = @{1, 0, 0, 0, 0@}
15636 (@value{GDBP}) ptype s
15637 type = ARRAY [1..5] OF CARDINAL
15640 The Modula-2 language interface to @value{GDBN} also understands
15641 pointer types as shown in this example:
15645 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
15652 and you can request that @value{GDBN} describes the type of @code{s}.
15655 (@value{GDBP}) ptype s
15656 type = POINTER TO ARRAY [1..5] OF CARDINAL
15659 @value{GDBN} handles compound types as we can see in this example.
15660 Here we combine array types, record types, pointer types and subrange
15671 myarray = ARRAY myrange OF CARDINAL ;
15672 myrange = [-2..2] ;
15674 s: POINTER TO ARRAY myrange OF foo ;
15678 and you can ask @value{GDBN} to describe the type of @code{s} as shown
15682 (@value{GDBP}) ptype s
15683 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
15686 f3 : ARRAY [-2..2] OF CARDINAL;
15691 @subsubsection Modula-2 Defaults
15692 @cindex Modula-2 defaults
15694 If type and range checking are set automatically by @value{GDBN}, they
15695 both default to @code{on} whenever the working language changes to
15696 Modula-2. This happens regardless of whether you or @value{GDBN}
15697 selected the working language.
15699 If you allow @value{GDBN} to set the language automatically, then entering
15700 code compiled from a file whose name ends with @file{.mod} sets the
15701 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
15702 Infer the Source Language}, for further details.
15705 @subsubsection Deviations from Standard Modula-2
15706 @cindex Modula-2, deviations from
15708 A few changes have been made to make Modula-2 programs easier to debug.
15709 This is done primarily via loosening its type strictness:
15713 Unlike in standard Modula-2, pointer constants can be formed by
15714 integers. This allows you to modify pointer variables during
15715 debugging. (In standard Modula-2, the actual address contained in a
15716 pointer variable is hidden from you; it can only be modified
15717 through direct assignment to another pointer variable or expression that
15718 returned a pointer.)
15721 C escape sequences can be used in strings and characters to represent
15722 non-printable characters. @value{GDBN} prints out strings with these
15723 escape sequences embedded. Single non-printable characters are
15724 printed using the @samp{CHR(@var{nnn})} format.
15727 The assignment operator (@code{:=}) returns the value of its right-hand
15731 All built-in procedures both modify @emph{and} return their argument.
15735 @subsubsection Modula-2 Type and Range Checks
15736 @cindex Modula-2 checks
15739 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
15742 @c FIXME remove warning when type/range checks added
15744 @value{GDBN} considers two Modula-2 variables type equivalent if:
15748 They are of types that have been declared equivalent via a @code{TYPE
15749 @var{t1} = @var{t2}} statement
15752 They have been declared on the same line. (Note: This is true of the
15753 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
15756 As long as type checking is enabled, any attempt to combine variables
15757 whose types are not equivalent is an error.
15759 Range checking is done on all mathematical operations, assignment, array
15760 index bounds, and all built-in functions and procedures.
15763 @subsubsection The Scope Operators @code{::} and @code{.}
15765 @cindex @code{.}, Modula-2 scope operator
15766 @cindex colon, doubled as scope operator
15768 @vindex colon-colon@r{, in Modula-2}
15769 @c Info cannot handle :: but TeX can.
15772 @vindex ::@r{, in Modula-2}
15775 There are a few subtle differences between the Modula-2 scope operator
15776 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
15781 @var{module} . @var{id}
15782 @var{scope} :: @var{id}
15786 where @var{scope} is the name of a module or a procedure,
15787 @var{module} the name of a module, and @var{id} is any declared
15788 identifier within your program, except another module.
15790 Using the @code{::} operator makes @value{GDBN} search the scope
15791 specified by @var{scope} for the identifier @var{id}. If it is not
15792 found in the specified scope, then @value{GDBN} searches all scopes
15793 enclosing the one specified by @var{scope}.
15795 Using the @code{.} operator makes @value{GDBN} search the current scope for
15796 the identifier specified by @var{id} that was imported from the
15797 definition module specified by @var{module}. With this operator, it is
15798 an error if the identifier @var{id} was not imported from definition
15799 module @var{module}, or if @var{id} is not an identifier in
15803 @subsubsection @value{GDBN} and Modula-2
15805 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
15806 Five subcommands of @code{set print} and @code{show print} apply
15807 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
15808 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
15809 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
15810 analogue in Modula-2.
15812 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
15813 with any language, is not useful with Modula-2. Its
15814 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
15815 created in Modula-2 as they can in C or C@t{++}. However, because an
15816 address can be specified by an integral constant, the construct
15817 @samp{@{@var{type}@}@var{adrexp}} is still useful.
15819 @cindex @code{#} in Modula-2
15820 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
15821 interpreted as the beginning of a comment. Use @code{<>} instead.
15827 The extensions made to @value{GDBN} for Ada only support
15828 output from the @sc{gnu} Ada (GNAT) compiler.
15829 Other Ada compilers are not currently supported, and
15830 attempting to debug executables produced by them is most likely
15834 @cindex expressions in Ada
15836 * Ada Mode Intro:: General remarks on the Ada syntax
15837 and semantics supported by Ada mode
15839 * Omissions from Ada:: Restrictions on the Ada expression syntax.
15840 * Additions to Ada:: Extensions of the Ada expression syntax.
15841 * Overloading support for Ada:: Support for expressions involving overloaded
15843 * Stopping Before Main Program:: Debugging the program during elaboration.
15844 * Ada Exceptions:: Ada Exceptions
15845 * Ada Tasks:: Listing and setting breakpoints in tasks.
15846 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
15847 * Ravenscar Profile:: Tasking Support when using the Ravenscar
15849 * Ada Glitches:: Known peculiarities of Ada mode.
15852 @node Ada Mode Intro
15853 @subsubsection Introduction
15854 @cindex Ada mode, general
15856 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
15857 syntax, with some extensions.
15858 The philosophy behind the design of this subset is
15862 That @value{GDBN} should provide basic literals and access to operations for
15863 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
15864 leaving more sophisticated computations to subprograms written into the
15865 program (which therefore may be called from @value{GDBN}).
15868 That type safety and strict adherence to Ada language restrictions
15869 are not particularly important to the @value{GDBN} user.
15872 That brevity is important to the @value{GDBN} user.
15875 Thus, for brevity, the debugger acts as if all names declared in
15876 user-written packages are directly visible, even if they are not visible
15877 according to Ada rules, thus making it unnecessary to fully qualify most
15878 names with their packages, regardless of context. Where this causes
15879 ambiguity, @value{GDBN} asks the user's intent.
15881 The debugger will start in Ada mode if it detects an Ada main program.
15882 As for other languages, it will enter Ada mode when stopped in a program that
15883 was translated from an Ada source file.
15885 While in Ada mode, you may use `@t{--}' for comments. This is useful
15886 mostly for documenting command files. The standard @value{GDBN} comment
15887 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
15888 middle (to allow based literals).
15890 @node Omissions from Ada
15891 @subsubsection Omissions from Ada
15892 @cindex Ada, omissions from
15894 Here are the notable omissions from the subset:
15898 Only a subset of the attributes are supported:
15902 @t{'First}, @t{'Last}, and @t{'Length}
15903 on array objects (not on types and subtypes).
15906 @t{'Min} and @t{'Max}.
15909 @t{'Pos} and @t{'Val}.
15915 @t{'Range} on array objects (not subtypes), but only as the right
15916 operand of the membership (@code{in}) operator.
15919 @t{'Access}, @t{'Unchecked_Access}, and
15920 @t{'Unrestricted_Access} (a GNAT extension).
15928 @code{Characters.Latin_1} are not available and
15929 concatenation is not implemented. Thus, escape characters in strings are
15930 not currently available.
15933 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
15934 equality of representations. They will generally work correctly
15935 for strings and arrays whose elements have integer or enumeration types.
15936 They may not work correctly for arrays whose element
15937 types have user-defined equality, for arrays of real values
15938 (in particular, IEEE-conformant floating point, because of negative
15939 zeroes and NaNs), and for arrays whose elements contain unused bits with
15940 indeterminate values.
15943 The other component-by-component array operations (@code{and}, @code{or},
15944 @code{xor}, @code{not}, and relational tests other than equality)
15945 are not implemented.
15948 @cindex array aggregates (Ada)
15949 @cindex record aggregates (Ada)
15950 @cindex aggregates (Ada)
15951 There is limited support for array and record aggregates. They are
15952 permitted only on the right sides of assignments, as in these examples:
15955 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
15956 (@value{GDBP}) set An_Array := (1, others => 0)
15957 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
15958 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
15959 (@value{GDBP}) set A_Record := (1, "Peter", True);
15960 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
15964 discriminant's value by assigning an aggregate has an
15965 undefined effect if that discriminant is used within the record.
15966 However, you can first modify discriminants by directly assigning to
15967 them (which normally would not be allowed in Ada), and then performing an
15968 aggregate assignment. For example, given a variable @code{A_Rec}
15969 declared to have a type such as:
15972 type Rec (Len : Small_Integer := 0) is record
15974 Vals : IntArray (1 .. Len);
15978 you can assign a value with a different size of @code{Vals} with two
15982 (@value{GDBP}) set A_Rec.Len := 4
15983 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
15986 As this example also illustrates, @value{GDBN} is very loose about the usual
15987 rules concerning aggregates. You may leave out some of the
15988 components of an array or record aggregate (such as the @code{Len}
15989 component in the assignment to @code{A_Rec} above); they will retain their
15990 original values upon assignment. You may freely use dynamic values as
15991 indices in component associations. You may even use overlapping or
15992 redundant component associations, although which component values are
15993 assigned in such cases is not defined.
15996 Calls to dispatching subprograms are not implemented.
15999 The overloading algorithm is much more limited (i.e., less selective)
16000 than that of real Ada. It makes only limited use of the context in
16001 which a subexpression appears to resolve its meaning, and it is much
16002 looser in its rules for allowing type matches. As a result, some
16003 function calls will be ambiguous, and the user will be asked to choose
16004 the proper resolution.
16007 The @code{new} operator is not implemented.
16010 Entry calls are not implemented.
16013 Aside from printing, arithmetic operations on the native VAX floating-point
16014 formats are not supported.
16017 It is not possible to slice a packed array.
16020 The names @code{True} and @code{False}, when not part of a qualified name,
16021 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
16023 Should your program
16024 redefine these names in a package or procedure (at best a dubious practice),
16025 you will have to use fully qualified names to access their new definitions.
16028 @node Additions to Ada
16029 @subsubsection Additions to Ada
16030 @cindex Ada, deviations from
16032 As it does for other languages, @value{GDBN} makes certain generic
16033 extensions to Ada (@pxref{Expressions}):
16037 If the expression @var{E} is a variable residing in memory (typically
16038 a local variable or array element) and @var{N} is a positive integer,
16039 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
16040 @var{N}-1 adjacent variables following it in memory as an array. In
16041 Ada, this operator is generally not necessary, since its prime use is
16042 in displaying parts of an array, and slicing will usually do this in
16043 Ada. However, there are occasional uses when debugging programs in
16044 which certain debugging information has been optimized away.
16047 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
16048 appears in function or file @var{B}.'' When @var{B} is a file name,
16049 you must typically surround it in single quotes.
16052 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
16053 @var{type} that appears at address @var{addr}.''
16056 A name starting with @samp{$} is a convenience variable
16057 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
16060 In addition, @value{GDBN} provides a few other shortcuts and outright
16061 additions specific to Ada:
16065 The assignment statement is allowed as an expression, returning
16066 its right-hand operand as its value. Thus, you may enter
16069 (@value{GDBP}) set x := y + 3
16070 (@value{GDBP}) print A(tmp := y + 1)
16074 The semicolon is allowed as an ``operator,'' returning as its value
16075 the value of its right-hand operand.
16076 This allows, for example,
16077 complex conditional breaks:
16080 (@value{GDBP}) break f
16081 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
16085 Rather than use catenation and symbolic character names to introduce special
16086 characters into strings, one may instead use a special bracket notation,
16087 which is also used to print strings. A sequence of characters of the form
16088 @samp{["@var{XX}"]} within a string or character literal denotes the
16089 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
16090 sequence of characters @samp{["""]} also denotes a single quotation mark
16091 in strings. For example,
16093 "One line.["0a"]Next line.["0a"]"
16096 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
16100 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
16101 @t{'Max} is optional (and is ignored in any case). For example, it is valid
16105 (@value{GDBP}) print 'max(x, y)
16109 When printing arrays, @value{GDBN} uses positional notation when the
16110 array has a lower bound of 1, and uses a modified named notation otherwise.
16111 For example, a one-dimensional array of three integers with a lower bound
16112 of 3 might print as
16119 That is, in contrast to valid Ada, only the first component has a @code{=>}
16123 You may abbreviate attributes in expressions with any unique,
16124 multi-character subsequence of
16125 their names (an exact match gets preference).
16126 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
16127 in place of @t{a'length}.
16130 @cindex quoting Ada internal identifiers
16131 Since Ada is case-insensitive, the debugger normally maps identifiers you type
16132 to lower case. The GNAT compiler uses upper-case characters for
16133 some of its internal identifiers, which are normally of no interest to users.
16134 For the rare occasions when you actually have to look at them,
16135 enclose them in angle brackets to avoid the lower-case mapping.
16138 (@value{GDBP}) print <JMPBUF_SAVE>[0]
16142 Printing an object of class-wide type or dereferencing an
16143 access-to-class-wide value will display all the components of the object's
16144 specific type (as indicated by its run-time tag). Likewise, component
16145 selection on such a value will operate on the specific type of the
16150 @node Overloading support for Ada
16151 @subsubsection Overloading support for Ada
16152 @cindex overloading, Ada
16154 The debugger supports limited overloading. Given a subprogram call in which
16155 the function symbol has multiple definitions, it will use the number of
16156 actual parameters and some information about their types to attempt to narrow
16157 the set of definitions. It also makes very limited use of context, preferring
16158 procedures to functions in the context of the @code{call} command, and
16159 functions to procedures elsewhere.
16161 If, after narrowing, the set of matching definitions still contains more than
16162 one definition, @value{GDBN} will display a menu to query which one it should
16166 (@value{GDBP}) print f(1)
16167 Multiple matches for f
16169 [1] foo.f (integer) return boolean at foo.adb:23
16170 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
16174 In this case, just select one menu entry either to cancel expression evaluation
16175 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
16176 instance (type the corresponding number and press @key{RET}).
16178 Here are a couple of commands to customize @value{GDBN}'s behavior in this
16183 @kindex set ada print-signatures
16184 @item set ada print-signatures
16185 Control whether parameter types and return types are displayed in overloads
16186 selection menus. It is @code{on} by default.
16187 @xref{Overloading support for Ada}.
16189 @kindex show ada print-signatures
16190 @item show ada print-signatures
16191 Show the current setting for displaying parameter types and return types in
16192 overloads selection menu.
16193 @xref{Overloading support for Ada}.
16197 @node Stopping Before Main Program
16198 @subsubsection Stopping at the Very Beginning
16200 @cindex breakpointing Ada elaboration code
16201 It is sometimes necessary to debug the program during elaboration, and
16202 before reaching the main procedure.
16203 As defined in the Ada Reference
16204 Manual, the elaboration code is invoked from a procedure called
16205 @code{adainit}. To run your program up to the beginning of
16206 elaboration, simply use the following two commands:
16207 @code{tbreak adainit} and @code{run}.
16209 @node Ada Exceptions
16210 @subsubsection Ada Exceptions
16212 A command is provided to list all Ada exceptions:
16215 @kindex info exceptions
16216 @item info exceptions
16217 @itemx info exceptions @var{regexp}
16218 The @code{info exceptions} command allows you to list all Ada exceptions
16219 defined within the program being debugged, as well as their addresses.
16220 With a regular expression, @var{regexp}, as argument, only those exceptions
16221 whose names match @var{regexp} are listed.
16224 Below is a small example, showing how the command can be used, first
16225 without argument, and next with a regular expression passed as an
16229 (@value{GDBP}) info exceptions
16230 All defined Ada exceptions:
16231 constraint_error: 0x613da0
16232 program_error: 0x613d20
16233 storage_error: 0x613ce0
16234 tasking_error: 0x613ca0
16235 const.aint_global_e: 0x613b00
16236 (@value{GDBP}) info exceptions const.aint
16237 All Ada exceptions matching regular expression "const.aint":
16238 constraint_error: 0x613da0
16239 const.aint_global_e: 0x613b00
16242 It is also possible to ask @value{GDBN} to stop your program's execution
16243 when an exception is raised. For more details, see @ref{Set Catchpoints}.
16246 @subsubsection Extensions for Ada Tasks
16247 @cindex Ada, tasking
16249 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
16250 @value{GDBN} provides the following task-related commands:
16255 This command shows a list of current Ada tasks, as in the following example:
16262 (@value{GDBP}) info tasks
16263 ID TID P-ID Pri State Name
16264 1 8088000 0 15 Child Activation Wait main_task
16265 2 80a4000 1 15 Accept Statement b
16266 3 809a800 1 15 Child Activation Wait a
16267 * 4 80ae800 3 15 Runnable c
16272 In this listing, the asterisk before the last task indicates it to be the
16273 task currently being inspected.
16277 Represents @value{GDBN}'s internal task number.
16283 The parent's task ID (@value{GDBN}'s internal task number).
16286 The base priority of the task.
16289 Current state of the task.
16293 The task has been created but has not been activated. It cannot be
16297 The task is not blocked for any reason known to Ada. (It may be waiting
16298 for a mutex, though.) It is conceptually "executing" in normal mode.
16301 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
16302 that were waiting on terminate alternatives have been awakened and have
16303 terminated themselves.
16305 @item Child Activation Wait
16306 The task is waiting for created tasks to complete activation.
16308 @item Accept Statement
16309 The task is waiting on an accept or selective wait statement.
16311 @item Waiting on entry call
16312 The task is waiting on an entry call.
16314 @item Async Select Wait
16315 The task is waiting to start the abortable part of an asynchronous
16319 The task is waiting on a select statement with only a delay
16322 @item Child Termination Wait
16323 The task is sleeping having completed a master within itself, and is
16324 waiting for the tasks dependent on that master to become terminated or
16325 waiting on a terminate Phase.
16327 @item Wait Child in Term Alt
16328 The task is sleeping waiting for tasks on terminate alternatives to
16329 finish terminating.
16331 @item Accepting RV with @var{taskno}
16332 The task is accepting a rendez-vous with the task @var{taskno}.
16336 Name of the task in the program.
16340 @kindex info task @var{taskno}
16341 @item info task @var{taskno}
16342 This command shows detailled informations on the specified task, as in
16343 the following example:
16348 (@value{GDBP}) info tasks
16349 ID TID P-ID Pri State Name
16350 1 8077880 0 15 Child Activation Wait main_task
16351 * 2 807c468 1 15 Runnable task_1
16352 (@value{GDBP}) info task 2
16353 Ada Task: 0x807c468
16356 Parent: 1 (main_task)
16362 @kindex task@r{ (Ada)}
16363 @cindex current Ada task ID
16364 This command prints the ID of the current task.
16370 (@value{GDBP}) info tasks
16371 ID TID P-ID Pri State Name
16372 1 8077870 0 15 Child Activation Wait main_task
16373 * 2 807c458 1 15 Runnable t
16374 (@value{GDBP}) task
16375 [Current task is 2]
16378 @item task @var{taskno}
16379 @cindex Ada task switching
16380 This command is like the @code{thread @var{thread-id}}
16381 command (@pxref{Threads}). It switches the context of debugging
16382 from the current task to the given task.
16388 (@value{GDBP}) info tasks
16389 ID TID P-ID Pri State Name
16390 1 8077870 0 15 Child Activation Wait main_task
16391 * 2 807c458 1 15 Runnable t
16392 (@value{GDBP}) task 1
16393 [Switching to task 1]
16394 #0 0x8067726 in pthread_cond_wait ()
16396 #0 0x8067726 in pthread_cond_wait ()
16397 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
16398 #2 0x805cb63 in system.task_primitives.operations.sleep ()
16399 #3 0x806153e in system.tasking.stages.activate_tasks ()
16400 #4 0x804aacc in un () at un.adb:5
16403 @item break @var{location} task @var{taskno}
16404 @itemx break @var{location} task @var{taskno} if @dots{}
16405 @cindex breakpoints and tasks, in Ada
16406 @cindex task breakpoints, in Ada
16407 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
16408 These commands are like the @code{break @dots{} thread @dots{}}
16409 command (@pxref{Thread Stops}). The
16410 @var{location} argument specifies source lines, as described
16411 in @ref{Specify Location}.
16413 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
16414 to specify that you only want @value{GDBN} to stop the program when a
16415 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
16416 numeric task identifiers assigned by @value{GDBN}, shown in the first
16417 column of the @samp{info tasks} display.
16419 If you do not specify @samp{task @var{taskno}} when you set a
16420 breakpoint, the breakpoint applies to @emph{all} tasks of your
16423 You can use the @code{task} qualifier on conditional breakpoints as
16424 well; in this case, place @samp{task @var{taskno}} before the
16425 breakpoint condition (before the @code{if}).
16433 (@value{GDBP}) info tasks
16434 ID TID P-ID Pri State Name
16435 1 140022020 0 15 Child Activation Wait main_task
16436 2 140045060 1 15 Accept/Select Wait t2
16437 3 140044840 1 15 Runnable t1
16438 * 4 140056040 1 15 Runnable t3
16439 (@value{GDBP}) b 15 task 2
16440 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
16441 (@value{GDBP}) cont
16446 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
16448 (@value{GDBP}) info tasks
16449 ID TID P-ID Pri State Name
16450 1 140022020 0 15 Child Activation Wait main_task
16451 * 2 140045060 1 15 Runnable t2
16452 3 140044840 1 15 Runnable t1
16453 4 140056040 1 15 Delay Sleep t3
16457 @node Ada Tasks and Core Files
16458 @subsubsection Tasking Support when Debugging Core Files
16459 @cindex Ada tasking and core file debugging
16461 When inspecting a core file, as opposed to debugging a live program,
16462 tasking support may be limited or even unavailable, depending on
16463 the platform being used.
16464 For instance, on x86-linux, the list of tasks is available, but task
16465 switching is not supported.
16467 On certain platforms, the debugger needs to perform some
16468 memory writes in order to provide Ada tasking support. When inspecting
16469 a core file, this means that the core file must be opened with read-write
16470 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
16471 Under these circumstances, you should make a backup copy of the core
16472 file before inspecting it with @value{GDBN}.
16474 @node Ravenscar Profile
16475 @subsubsection Tasking Support when using the Ravenscar Profile
16476 @cindex Ravenscar Profile
16478 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
16479 specifically designed for systems with safety-critical real-time
16483 @kindex set ravenscar task-switching on
16484 @cindex task switching with program using Ravenscar Profile
16485 @item set ravenscar task-switching on
16486 Allows task switching when debugging a program that uses the Ravenscar
16487 Profile. This is the default.
16489 @kindex set ravenscar task-switching off
16490 @item set ravenscar task-switching off
16491 Turn off task switching when debugging a program that uses the Ravenscar
16492 Profile. This is mostly intended to disable the code that adds support
16493 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
16494 the Ravenscar runtime is preventing @value{GDBN} from working properly.
16495 To be effective, this command should be run before the program is started.
16497 @kindex show ravenscar task-switching
16498 @item show ravenscar task-switching
16499 Show whether it is possible to switch from task to task in a program
16500 using the Ravenscar Profile.
16505 @subsubsection Known Peculiarities of Ada Mode
16506 @cindex Ada, problems
16508 Besides the omissions listed previously (@pxref{Omissions from Ada}),
16509 we know of several problems with and limitations of Ada mode in
16511 some of which will be fixed with planned future releases of the debugger
16512 and the GNU Ada compiler.
16516 Static constants that the compiler chooses not to materialize as objects in
16517 storage are invisible to the debugger.
16520 Named parameter associations in function argument lists are ignored (the
16521 argument lists are treated as positional).
16524 Many useful library packages are currently invisible to the debugger.
16527 Fixed-point arithmetic, conversions, input, and output is carried out using
16528 floating-point arithmetic, and may give results that only approximate those on
16532 The GNAT compiler never generates the prefix @code{Standard} for any of
16533 the standard symbols defined by the Ada language. @value{GDBN} knows about
16534 this: it will strip the prefix from names when you use it, and will never
16535 look for a name you have so qualified among local symbols, nor match against
16536 symbols in other packages or subprograms. If you have
16537 defined entities anywhere in your program other than parameters and
16538 local variables whose simple names match names in @code{Standard},
16539 GNAT's lack of qualification here can cause confusion. When this happens,
16540 you can usually resolve the confusion
16541 by qualifying the problematic names with package
16542 @code{Standard} explicitly.
16545 Older versions of the compiler sometimes generate erroneous debugging
16546 information, resulting in the debugger incorrectly printing the value
16547 of affected entities. In some cases, the debugger is able to work
16548 around an issue automatically. In other cases, the debugger is able
16549 to work around the issue, but the work-around has to be specifically
16552 @kindex set ada trust-PAD-over-XVS
16553 @kindex show ada trust-PAD-over-XVS
16556 @item set ada trust-PAD-over-XVS on
16557 Configure GDB to strictly follow the GNAT encoding when computing the
16558 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
16559 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
16560 a complete description of the encoding used by the GNAT compiler).
16561 This is the default.
16563 @item set ada trust-PAD-over-XVS off
16564 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
16565 sometimes prints the wrong value for certain entities, changing @code{ada
16566 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
16567 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
16568 @code{off}, but this incurs a slight performance penalty, so it is
16569 recommended to leave this setting to @code{on} unless necessary.
16573 @cindex GNAT descriptive types
16574 @cindex GNAT encoding
16575 Internally, the debugger also relies on the compiler following a number
16576 of conventions known as the @samp{GNAT Encoding}, all documented in
16577 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
16578 how the debugging information should be generated for certain types.
16579 In particular, this convention makes use of @dfn{descriptive types},
16580 which are artificial types generated purely to help the debugger.
16582 These encodings were defined at a time when the debugging information
16583 format used was not powerful enough to describe some of the more complex
16584 types available in Ada. Since DWARF allows us to express nearly all
16585 Ada features, the long-term goal is to slowly replace these descriptive
16586 types by their pure DWARF equivalent. To facilitate that transition,
16587 a new maintenance option is available to force the debugger to ignore
16588 those descriptive types. It allows the user to quickly evaluate how
16589 well @value{GDBN} works without them.
16593 @kindex maint ada set ignore-descriptive-types
16594 @item maintenance ada set ignore-descriptive-types [on|off]
16595 Control whether the debugger should ignore descriptive types.
16596 The default is not to ignore descriptives types (@code{off}).
16598 @kindex maint ada show ignore-descriptive-types
16599 @item maintenance ada show ignore-descriptive-types
16600 Show if descriptive types are ignored by @value{GDBN}.
16604 @node Unsupported Languages
16605 @section Unsupported Languages
16607 @cindex unsupported languages
16608 @cindex minimal language
16609 In addition to the other fully-supported programming languages,
16610 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
16611 It does not represent a real programming language, but provides a set
16612 of capabilities close to what the C or assembly languages provide.
16613 This should allow most simple operations to be performed while debugging
16614 an application that uses a language currently not supported by @value{GDBN}.
16616 If the language is set to @code{auto}, @value{GDBN} will automatically
16617 select this language if the current frame corresponds to an unsupported
16621 @chapter Examining the Symbol Table
16623 The commands described in this chapter allow you to inquire about the
16624 symbols (names of variables, functions and types) defined in your
16625 program. This information is inherent in the text of your program and
16626 does not change as your program executes. @value{GDBN} finds it in your
16627 program's symbol table, in the file indicated when you started @value{GDBN}
16628 (@pxref{File Options, ,Choosing Files}), or by one of the
16629 file-management commands (@pxref{Files, ,Commands to Specify Files}).
16631 @cindex symbol names
16632 @cindex names of symbols
16633 @cindex quoting names
16634 Occasionally, you may need to refer to symbols that contain unusual
16635 characters, which @value{GDBN} ordinarily treats as word delimiters. The
16636 most frequent case is in referring to static variables in other
16637 source files (@pxref{Variables,,Program Variables}). File names
16638 are recorded in object files as debugging symbols, but @value{GDBN} would
16639 ordinarily parse a typical file name, like @file{foo.c}, as the three words
16640 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
16641 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
16648 looks up the value of @code{x} in the scope of the file @file{foo.c}.
16651 @cindex case-insensitive symbol names
16652 @cindex case sensitivity in symbol names
16653 @kindex set case-sensitive
16654 @item set case-sensitive on
16655 @itemx set case-sensitive off
16656 @itemx set case-sensitive auto
16657 Normally, when @value{GDBN} looks up symbols, it matches their names
16658 with case sensitivity determined by the current source language.
16659 Occasionally, you may wish to control that. The command @code{set
16660 case-sensitive} lets you do that by specifying @code{on} for
16661 case-sensitive matches or @code{off} for case-insensitive ones. If
16662 you specify @code{auto}, case sensitivity is reset to the default
16663 suitable for the source language. The default is case-sensitive
16664 matches for all languages except for Fortran, for which the default is
16665 case-insensitive matches.
16667 @kindex show case-sensitive
16668 @item show case-sensitive
16669 This command shows the current setting of case sensitivity for symbols
16672 @kindex set print type methods
16673 @item set print type methods
16674 @itemx set print type methods on
16675 @itemx set print type methods off
16676 Normally, when @value{GDBN} prints a class, it displays any methods
16677 declared in that class. You can control this behavior either by
16678 passing the appropriate flag to @code{ptype}, or using @command{set
16679 print type methods}. Specifying @code{on} will cause @value{GDBN} to
16680 display the methods; this is the default. Specifying @code{off} will
16681 cause @value{GDBN} to omit the methods.
16683 @kindex show print type methods
16684 @item show print type methods
16685 This command shows the current setting of method display when printing
16688 @kindex set print type typedefs
16689 @item set print type typedefs
16690 @itemx set print type typedefs on
16691 @itemx set print type typedefs off
16693 Normally, when @value{GDBN} prints a class, it displays any typedefs
16694 defined in that class. You can control this behavior either by
16695 passing the appropriate flag to @code{ptype}, or using @command{set
16696 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
16697 display the typedef definitions; this is the default. Specifying
16698 @code{off} will cause @value{GDBN} to omit the typedef definitions.
16699 Note that this controls whether the typedef definition itself is
16700 printed, not whether typedef names are substituted when printing other
16703 @kindex show print type typedefs
16704 @item show print type typedefs
16705 This command shows the current setting of typedef display when
16708 @kindex info address
16709 @cindex address of a symbol
16710 @item info address @var{symbol}
16711 Describe where the data for @var{symbol} is stored. For a register
16712 variable, this says which register it is kept in. For a non-register
16713 local variable, this prints the stack-frame offset at which the variable
16716 Note the contrast with @samp{print &@var{symbol}}, which does not work
16717 at all for a register variable, and for a stack local variable prints
16718 the exact address of the current instantiation of the variable.
16720 @kindex info symbol
16721 @cindex symbol from address
16722 @cindex closest symbol and offset for an address
16723 @item info symbol @var{addr}
16724 Print the name of a symbol which is stored at the address @var{addr}.
16725 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
16726 nearest symbol and an offset from it:
16729 (@value{GDBP}) info symbol 0x54320
16730 _initialize_vx + 396 in section .text
16734 This is the opposite of the @code{info address} command. You can use
16735 it to find out the name of a variable or a function given its address.
16737 For dynamically linked executables, the name of executable or shared
16738 library containing the symbol is also printed:
16741 (@value{GDBP}) info symbol 0x400225
16742 _start + 5 in section .text of /tmp/a.out
16743 (@value{GDBP}) info symbol 0x2aaaac2811cf
16744 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
16749 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
16750 Demangle @var{name}.
16751 If @var{language} is provided it is the name of the language to demangle
16752 @var{name} in. Otherwise @var{name} is demangled in the current language.
16754 The @samp{--} option specifies the end of options,
16755 and is useful when @var{name} begins with a dash.
16757 The parameter @code{demangle-style} specifies how to interpret the kind
16758 of mangling used. @xref{Print Settings}.
16761 @item whatis[/@var{flags}] [@var{arg}]
16762 Print the data type of @var{arg}, which can be either an expression
16763 or a name of a data type. With no argument, print the data type of
16764 @code{$}, the last value in the value history.
16766 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
16767 is not actually evaluated, and any side-effecting operations (such as
16768 assignments or function calls) inside it do not take place.
16770 If @var{arg} is a variable or an expression, @code{whatis} prints its
16771 literal type as it is used in the source code. If the type was
16772 defined using a @code{typedef}, @code{whatis} will @emph{not} print
16773 the data type underlying the @code{typedef}. If the type of the
16774 variable or the expression is a compound data type, such as
16775 @code{struct} or @code{class}, @code{whatis} never prints their
16776 fields or methods. It just prints the @code{struct}/@code{class}
16777 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
16778 such a compound data type, use @code{ptype}.
16780 If @var{arg} is a type name that was defined using @code{typedef},
16781 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
16782 Unrolling means that @code{whatis} will show the underlying type used
16783 in the @code{typedef} declaration of @var{arg}. However, if that
16784 underlying type is also a @code{typedef}, @code{whatis} will not
16787 For C code, the type names may also have the form @samp{class
16788 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
16789 @var{union-tag}} or @samp{enum @var{enum-tag}}.
16791 @var{flags} can be used to modify how the type is displayed.
16792 Available flags are:
16796 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
16797 parameters and typedefs defined in a class when printing the class'
16798 members. The @code{/r} flag disables this.
16801 Do not print methods defined in the class.
16804 Print methods defined in the class. This is the default, but the flag
16805 exists in case you change the default with @command{set print type methods}.
16808 Do not print typedefs defined in the class. Note that this controls
16809 whether the typedef definition itself is printed, not whether typedef
16810 names are substituted when printing other types.
16813 Print typedefs defined in the class. This is the default, but the flag
16814 exists in case you change the default with @command{set print type typedefs}.
16818 @item ptype[/@var{flags}] [@var{arg}]
16819 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
16820 detailed description of the type, instead of just the name of the type.
16821 @xref{Expressions, ,Expressions}.
16823 Contrary to @code{whatis}, @code{ptype} always unrolls any
16824 @code{typedef}s in its argument declaration, whether the argument is
16825 a variable, expression, or a data type. This means that @code{ptype}
16826 of a variable or an expression will not print literally its type as
16827 present in the source code---use @code{whatis} for that. @code{typedef}s at
16828 the pointer or reference targets are also unrolled. Only @code{typedef}s of
16829 fields, methods and inner @code{class typedef}s of @code{struct}s,
16830 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
16832 For example, for this variable declaration:
16835 typedef double real_t;
16836 struct complex @{ real_t real; double imag; @};
16837 typedef struct complex complex_t;
16839 real_t *real_pointer_var;
16843 the two commands give this output:
16847 (@value{GDBP}) whatis var
16849 (@value{GDBP}) ptype var
16850 type = struct complex @{
16854 (@value{GDBP}) whatis complex_t
16855 type = struct complex
16856 (@value{GDBP}) whatis struct complex
16857 type = struct complex
16858 (@value{GDBP}) ptype struct complex
16859 type = struct complex @{
16863 (@value{GDBP}) whatis real_pointer_var
16865 (@value{GDBP}) ptype real_pointer_var
16871 As with @code{whatis}, using @code{ptype} without an argument refers to
16872 the type of @code{$}, the last value in the value history.
16874 @cindex incomplete type
16875 Sometimes, programs use opaque data types or incomplete specifications
16876 of complex data structure. If the debug information included in the
16877 program does not allow @value{GDBN} to display a full declaration of
16878 the data type, it will say @samp{<incomplete type>}. For example,
16879 given these declarations:
16883 struct foo *fooptr;
16887 but no definition for @code{struct foo} itself, @value{GDBN} will say:
16890 (@value{GDBP}) ptype foo
16891 $1 = <incomplete type>
16895 ``Incomplete type'' is C terminology for data types that are not
16896 completely specified.
16899 @item info types @var{regexp}
16901 Print a brief description of all types whose names match the regular
16902 expression @var{regexp} (or all types in your program, if you supply
16903 no argument). Each complete typename is matched as though it were a
16904 complete line; thus, @samp{i type value} gives information on all
16905 types in your program whose names include the string @code{value}, but
16906 @samp{i type ^value$} gives information only on types whose complete
16907 name is @code{value}.
16909 This command differs from @code{ptype} in two ways: first, like
16910 @code{whatis}, it does not print a detailed description; second, it
16911 lists all source files where a type is defined.
16913 @kindex info type-printers
16914 @item info type-printers
16915 Versions of @value{GDBN} that ship with Python scripting enabled may
16916 have ``type printers'' available. When using @command{ptype} or
16917 @command{whatis}, these printers are consulted when the name of a type
16918 is needed. @xref{Type Printing API}, for more information on writing
16921 @code{info type-printers} displays all the available type printers.
16923 @kindex enable type-printer
16924 @kindex disable type-printer
16925 @item enable type-printer @var{name}@dots{}
16926 @item disable type-printer @var{name}@dots{}
16927 These commands can be used to enable or disable type printers.
16930 @cindex local variables
16931 @item info scope @var{location}
16932 List all the variables local to a particular scope. This command
16933 accepts a @var{location} argument---a function name, a source line, or
16934 an address preceded by a @samp{*}, and prints all the variables local
16935 to the scope defined by that location. (@xref{Specify Location}, for
16936 details about supported forms of @var{location}.) For example:
16939 (@value{GDBP}) @b{info scope command_line_handler}
16940 Scope for command_line_handler:
16941 Symbol rl is an argument at stack/frame offset 8, length 4.
16942 Symbol linebuffer is in static storage at address 0x150a18, length 4.
16943 Symbol linelength is in static storage at address 0x150a1c, length 4.
16944 Symbol p is a local variable in register $esi, length 4.
16945 Symbol p1 is a local variable in register $ebx, length 4.
16946 Symbol nline is a local variable in register $edx, length 4.
16947 Symbol repeat is a local variable at frame offset -8, length 4.
16951 This command is especially useful for determining what data to collect
16952 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
16955 @kindex info source
16957 Show information about the current source file---that is, the source file for
16958 the function containing the current point of execution:
16961 the name of the source file, and the directory containing it,
16963 the directory it was compiled in,
16965 its length, in lines,
16967 which programming language it is written in,
16969 if the debug information provides it, the program that compiled the file
16970 (which may include, e.g., the compiler version and command line arguments),
16972 whether the executable includes debugging information for that file, and
16973 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
16975 whether the debugging information includes information about
16976 preprocessor macros.
16980 @kindex info sources
16982 Print the names of all source files in your program for which there is
16983 debugging information, organized into two lists: files whose symbols
16984 have already been read, and files whose symbols will be read when needed.
16986 @kindex info functions
16987 @item info functions
16988 Print the names and data types of all defined functions.
16990 @item info functions @var{regexp}
16991 Print the names and data types of all defined functions
16992 whose names contain a match for regular expression @var{regexp}.
16993 Thus, @samp{info fun step} finds all functions whose names
16994 include @code{step}; @samp{info fun ^step} finds those whose names
16995 start with @code{step}. If a function name contains characters
16996 that conflict with the regular expression language (e.g.@:
16997 @samp{operator*()}), they may be quoted with a backslash.
16999 @kindex info variables
17000 @item info variables
17001 Print the names and data types of all variables that are defined
17002 outside of functions (i.e.@: excluding local variables).
17004 @item info variables @var{regexp}
17005 Print the names and data types of all variables (except for local
17006 variables) whose names contain a match for regular expression
17009 @kindex info classes
17010 @cindex Objective-C, classes and selectors
17012 @itemx info classes @var{regexp}
17013 Display all Objective-C classes in your program, or
17014 (with the @var{regexp} argument) all those matching a particular regular
17017 @kindex info selectors
17018 @item info selectors
17019 @itemx info selectors @var{regexp}
17020 Display all Objective-C selectors in your program, or
17021 (with the @var{regexp} argument) all those matching a particular regular
17025 This was never implemented.
17026 @kindex info methods
17028 @itemx info methods @var{regexp}
17029 The @code{info methods} command permits the user to examine all defined
17030 methods within C@t{++} program, or (with the @var{regexp} argument) a
17031 specific set of methods found in the various C@t{++} classes. Many
17032 C@t{++} classes provide a large number of methods. Thus, the output
17033 from the @code{ptype} command can be overwhelming and hard to use. The
17034 @code{info-methods} command filters the methods, printing only those
17035 which match the regular-expression @var{regexp}.
17038 @cindex opaque data types
17039 @kindex set opaque-type-resolution
17040 @item set opaque-type-resolution on
17041 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
17042 declared as a pointer to a @code{struct}, @code{class}, or
17043 @code{union}---for example, @code{struct MyType *}---that is used in one
17044 source file although the full declaration of @code{struct MyType} is in
17045 another source file. The default is on.
17047 A change in the setting of this subcommand will not take effect until
17048 the next time symbols for a file are loaded.
17050 @item set opaque-type-resolution off
17051 Tell @value{GDBN} not to resolve opaque types. In this case, the type
17052 is printed as follows:
17054 @{<no data fields>@}
17057 @kindex show opaque-type-resolution
17058 @item show opaque-type-resolution
17059 Show whether opaque types are resolved or not.
17061 @kindex set print symbol-loading
17062 @cindex print messages when symbols are loaded
17063 @item set print symbol-loading
17064 @itemx set print symbol-loading full
17065 @itemx set print symbol-loading brief
17066 @itemx set print symbol-loading off
17067 The @code{set print symbol-loading} command allows you to control the
17068 printing of messages when @value{GDBN} loads symbol information.
17069 By default a message is printed for the executable and one for each
17070 shared library, and normally this is what you want. However, when
17071 debugging apps with large numbers of shared libraries these messages
17073 When set to @code{brief} a message is printed for each executable,
17074 and when @value{GDBN} loads a collection of shared libraries at once
17075 it will only print one message regardless of the number of shared
17076 libraries. When set to @code{off} no messages are printed.
17078 @kindex show print symbol-loading
17079 @item show print symbol-loading
17080 Show whether messages will be printed when a @value{GDBN} command
17081 entered from the keyboard causes symbol information to be loaded.
17083 @kindex maint print symbols
17084 @cindex symbol dump
17085 @kindex maint print psymbols
17086 @cindex partial symbol dump
17087 @kindex maint print msymbols
17088 @cindex minimal symbol dump
17089 @item maint print symbols @var{filename}
17090 @itemx maint print psymbols @var{filename}
17091 @itemx maint print msymbols @var{filename}
17092 Write a dump of debugging symbol data into the file @var{filename}.
17093 These commands are used to debug the @value{GDBN} symbol-reading code. Only
17094 symbols with debugging data are included. If you use @samp{maint print
17095 symbols}, @value{GDBN} includes all the symbols for which it has already
17096 collected full details: that is, @var{filename} reflects symbols for
17097 only those files whose symbols @value{GDBN} has read. You can use the
17098 command @code{info sources} to find out which files these are. If you
17099 use @samp{maint print psymbols} instead, the dump shows information about
17100 symbols that @value{GDBN} only knows partially---that is, symbols defined in
17101 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
17102 @samp{maint print msymbols} dumps just the minimal symbol information
17103 required for each object file from which @value{GDBN} has read some symbols.
17104 @xref{Files, ,Commands to Specify Files}, for a discussion of how
17105 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
17107 @kindex maint info symtabs
17108 @kindex maint info psymtabs
17109 @cindex listing @value{GDBN}'s internal symbol tables
17110 @cindex symbol tables, listing @value{GDBN}'s internal
17111 @cindex full symbol tables, listing @value{GDBN}'s internal
17112 @cindex partial symbol tables, listing @value{GDBN}'s internal
17113 @item maint info symtabs @r{[} @var{regexp} @r{]}
17114 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
17116 List the @code{struct symtab} or @code{struct partial_symtab}
17117 structures whose names match @var{regexp}. If @var{regexp} is not
17118 given, list them all. The output includes expressions which you can
17119 copy into a @value{GDBN} debugging this one to examine a particular
17120 structure in more detail. For example:
17123 (@value{GDBP}) maint info psymtabs dwarf2read
17124 @{ objfile /home/gnu/build/gdb/gdb
17125 ((struct objfile *) 0x82e69d0)
17126 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
17127 ((struct partial_symtab *) 0x8474b10)
17130 text addresses 0x814d3c8 -- 0x8158074
17131 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
17132 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
17133 dependencies (none)
17136 (@value{GDBP}) maint info symtabs
17140 We see that there is one partial symbol table whose filename contains
17141 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
17142 and we see that @value{GDBN} has not read in any symtabs yet at all.
17143 If we set a breakpoint on a function, that will cause @value{GDBN} to
17144 read the symtab for the compilation unit containing that function:
17147 (@value{GDBP}) break dwarf2_psymtab_to_symtab
17148 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
17150 (@value{GDBP}) maint info symtabs
17151 @{ objfile /home/gnu/build/gdb/gdb
17152 ((struct objfile *) 0x82e69d0)
17153 @{ symtab /home/gnu/src/gdb/dwarf2read.c
17154 ((struct symtab *) 0x86c1f38)
17157 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
17158 linetable ((struct linetable *) 0x8370fa0)
17159 debugformat DWARF 2
17165 @kindex maint set symbol-cache-size
17166 @cindex symbol cache size
17167 @item maint set symbol-cache-size @var{size}
17168 Set the size of the symbol cache to @var{size}.
17169 The default size is intended to be good enough for debugging
17170 most applications. This option exists to allow for experimenting
17171 with different sizes.
17173 @kindex maint show symbol-cache-size
17174 @item maint show symbol-cache-size
17175 Show the size of the symbol cache.
17177 @kindex maint print symbol-cache
17178 @cindex symbol cache, printing its contents
17179 @item maint print symbol-cache
17180 Print the contents of the symbol cache.
17181 This is useful when debugging symbol cache issues.
17183 @kindex maint print symbol-cache-statistics
17184 @cindex symbol cache, printing usage statistics
17185 @item maint print symbol-cache-statistics
17186 Print symbol cache usage statistics.
17187 This helps determine how well the cache is being utilized.
17189 @kindex maint flush-symbol-cache
17190 @cindex symbol cache, flushing
17191 @item maint flush-symbol-cache
17192 Flush the contents of the symbol cache, all entries are removed.
17193 This command is useful when debugging the symbol cache.
17194 It is also useful when collecting performance data.
17199 @chapter Altering Execution
17201 Once you think you have found an error in your program, you might want to
17202 find out for certain whether correcting the apparent error would lead to
17203 correct results in the rest of the run. You can find the answer by
17204 experiment, using the @value{GDBN} features for altering execution of the
17207 For example, you can store new values into variables or memory
17208 locations, give your program a signal, restart it at a different
17209 address, or even return prematurely from a function.
17212 * Assignment:: Assignment to variables
17213 * Jumping:: Continuing at a different address
17214 * Signaling:: Giving your program a signal
17215 * Returning:: Returning from a function
17216 * Calling:: Calling your program's functions
17217 * Patching:: Patching your program
17218 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
17222 @section Assignment to Variables
17225 @cindex setting variables
17226 To alter the value of a variable, evaluate an assignment expression.
17227 @xref{Expressions, ,Expressions}. For example,
17234 stores the value 4 into the variable @code{x}, and then prints the
17235 value of the assignment expression (which is 4).
17236 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
17237 information on operators in supported languages.
17239 @kindex set variable
17240 @cindex variables, setting
17241 If you are not interested in seeing the value of the assignment, use the
17242 @code{set} command instead of the @code{print} command. @code{set} is
17243 really the same as @code{print} except that the expression's value is
17244 not printed and is not put in the value history (@pxref{Value History,
17245 ,Value History}). The expression is evaluated only for its effects.
17247 If the beginning of the argument string of the @code{set} command
17248 appears identical to a @code{set} subcommand, use the @code{set
17249 variable} command instead of just @code{set}. This command is identical
17250 to @code{set} except for its lack of subcommands. For example, if your
17251 program has a variable @code{width}, you get an error if you try to set
17252 a new value with just @samp{set width=13}, because @value{GDBN} has the
17253 command @code{set width}:
17256 (@value{GDBP}) whatis width
17258 (@value{GDBP}) p width
17260 (@value{GDBP}) set width=47
17261 Invalid syntax in expression.
17265 The invalid expression, of course, is @samp{=47}. In
17266 order to actually set the program's variable @code{width}, use
17269 (@value{GDBP}) set var width=47
17272 Because the @code{set} command has many subcommands that can conflict
17273 with the names of program variables, it is a good idea to use the
17274 @code{set variable} command instead of just @code{set}. For example, if
17275 your program has a variable @code{g}, you run into problems if you try
17276 to set a new value with just @samp{set g=4}, because @value{GDBN} has
17277 the command @code{set gnutarget}, abbreviated @code{set g}:
17281 (@value{GDBP}) whatis g
17285 (@value{GDBP}) set g=4
17289 The program being debugged has been started already.
17290 Start it from the beginning? (y or n) y
17291 Starting program: /home/smith/cc_progs/a.out
17292 "/home/smith/cc_progs/a.out": can't open to read symbols:
17293 Invalid bfd target.
17294 (@value{GDBP}) show g
17295 The current BFD target is "=4".
17300 The program variable @code{g} did not change, and you silently set the
17301 @code{gnutarget} to an invalid value. In order to set the variable
17305 (@value{GDBP}) set var g=4
17308 @value{GDBN} allows more implicit conversions in assignments than C; you can
17309 freely store an integer value into a pointer variable or vice versa,
17310 and you can convert any structure to any other structure that is the
17311 same length or shorter.
17312 @comment FIXME: how do structs align/pad in these conversions?
17313 @comment /doc@cygnus.com 18dec1990
17315 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
17316 construct to generate a value of specified type at a specified address
17317 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
17318 to memory location @code{0x83040} as an integer (which implies a certain size
17319 and representation in memory), and
17322 set @{int@}0x83040 = 4
17326 stores the value 4 into that memory location.
17329 @section Continuing at a Different Address
17331 Ordinarily, when you continue your program, you do so at the place where
17332 it stopped, with the @code{continue} command. You can instead continue at
17333 an address of your own choosing, with the following commands:
17337 @kindex j @r{(@code{jump})}
17338 @item jump @var{location}
17339 @itemx j @var{location}
17340 Resume execution at @var{location}. Execution stops again immediately
17341 if there is a breakpoint there. @xref{Specify Location}, for a description
17342 of the different forms of @var{location}. It is common
17343 practice to use the @code{tbreak} command in conjunction with
17344 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
17346 The @code{jump} command does not change the current stack frame, or
17347 the stack pointer, or the contents of any memory location or any
17348 register other than the program counter. If @var{location} is in
17349 a different function from the one currently executing, the results may
17350 be bizarre if the two functions expect different patterns of arguments or
17351 of local variables. For this reason, the @code{jump} command requests
17352 confirmation if the specified line is not in the function currently
17353 executing. However, even bizarre results are predictable if you are
17354 well acquainted with the machine-language code of your program.
17357 On many systems, you can get much the same effect as the @code{jump}
17358 command by storing a new value into the register @code{$pc}. The
17359 difference is that this does not start your program running; it only
17360 changes the address of where it @emph{will} run when you continue. For
17368 makes the next @code{continue} command or stepping command execute at
17369 address @code{0x485}, rather than at the address where your program stopped.
17370 @xref{Continuing and Stepping, ,Continuing and Stepping}.
17372 The most common occasion to use the @code{jump} command is to back
17373 up---perhaps with more breakpoints set---over a portion of a program
17374 that has already executed, in order to examine its execution in more
17379 @section Giving your Program a Signal
17380 @cindex deliver a signal to a program
17384 @item signal @var{signal}
17385 Resume execution where your program is stopped, but immediately give it the
17386 signal @var{signal}. The @var{signal} can be the name or the number of a
17387 signal. For example, on many systems @code{signal 2} and @code{signal
17388 SIGINT} are both ways of sending an interrupt signal.
17390 Alternatively, if @var{signal} is zero, continue execution without
17391 giving a signal. This is useful when your program stopped on account of
17392 a signal and would ordinarily see the signal when resumed with the
17393 @code{continue} command; @samp{signal 0} causes it to resume without a
17396 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
17397 delivered to the currently selected thread, not the thread that last
17398 reported a stop. This includes the situation where a thread was
17399 stopped due to a signal. So if you want to continue execution
17400 suppressing the signal that stopped a thread, you should select that
17401 same thread before issuing the @samp{signal 0} command. If you issue
17402 the @samp{signal 0} command with another thread as the selected one,
17403 @value{GDBN} detects that and asks for confirmation.
17405 Invoking the @code{signal} command is not the same as invoking the
17406 @code{kill} utility from the shell. Sending a signal with @code{kill}
17407 causes @value{GDBN} to decide what to do with the signal depending on
17408 the signal handling tables (@pxref{Signals}). The @code{signal} command
17409 passes the signal directly to your program.
17411 @code{signal} does not repeat when you press @key{RET} a second time
17412 after executing the command.
17414 @kindex queue-signal
17415 @item queue-signal @var{signal}
17416 Queue @var{signal} to be delivered immediately to the current thread
17417 when execution of the thread resumes. The @var{signal} can be the name or
17418 the number of a signal. For example, on many systems @code{signal 2} and
17419 @code{signal SIGINT} are both ways of sending an interrupt signal.
17420 The handling of the signal must be set to pass the signal to the program,
17421 otherwise @value{GDBN} will report an error.
17422 You can control the handling of signals from @value{GDBN} with the
17423 @code{handle} command (@pxref{Signals}).
17425 Alternatively, if @var{signal} is zero, any currently queued signal
17426 for the current thread is discarded and when execution resumes no signal
17427 will be delivered. This is useful when your program stopped on account
17428 of a signal and would ordinarily see the signal when resumed with the
17429 @code{continue} command.
17431 This command differs from the @code{signal} command in that the signal
17432 is just queued, execution is not resumed. And @code{queue-signal} cannot
17433 be used to pass a signal whose handling state has been set to @code{nopass}
17438 @xref{stepping into signal handlers}, for information on how stepping
17439 commands behave when the thread has a signal queued.
17442 @section Returning from a Function
17445 @cindex returning from a function
17448 @itemx return @var{expression}
17449 You can cancel execution of a function call with the @code{return}
17450 command. If you give an
17451 @var{expression} argument, its value is used as the function's return
17455 When you use @code{return}, @value{GDBN} discards the selected stack frame
17456 (and all frames within it). You can think of this as making the
17457 discarded frame return prematurely. If you wish to specify a value to
17458 be returned, give that value as the argument to @code{return}.
17460 This pops the selected stack frame (@pxref{Selection, ,Selecting a
17461 Frame}), and any other frames inside of it, leaving its caller as the
17462 innermost remaining frame. That frame becomes selected. The
17463 specified value is stored in the registers used for returning values
17466 The @code{return} command does not resume execution; it leaves the
17467 program stopped in the state that would exist if the function had just
17468 returned. In contrast, the @code{finish} command (@pxref{Continuing
17469 and Stepping, ,Continuing and Stepping}) resumes execution until the
17470 selected stack frame returns naturally.
17472 @value{GDBN} needs to know how the @var{expression} argument should be set for
17473 the inferior. The concrete registers assignment depends on the OS ABI and the
17474 type being returned by the selected stack frame. For example it is common for
17475 OS ABI to return floating point values in FPU registers while integer values in
17476 CPU registers. Still some ABIs return even floating point values in CPU
17477 registers. Larger integer widths (such as @code{long long int}) also have
17478 specific placement rules. @value{GDBN} already knows the OS ABI from its
17479 current target so it needs to find out also the type being returned to make the
17480 assignment into the right register(s).
17482 Normally, the selected stack frame has debug info. @value{GDBN} will always
17483 use the debug info instead of the implicit type of @var{expression} when the
17484 debug info is available. For example, if you type @kbd{return -1}, and the
17485 function in the current stack frame is declared to return a @code{long long
17486 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
17487 into a @code{long long int}:
17490 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
17492 (@value{GDBP}) return -1
17493 Make func return now? (y or n) y
17494 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
17495 43 printf ("result=%lld\n", func ());
17499 However, if the selected stack frame does not have a debug info, e.g., if the
17500 function was compiled without debug info, @value{GDBN} has to find out the type
17501 to return from user. Specifying a different type by mistake may set the value
17502 in different inferior registers than the caller code expects. For example,
17503 typing @kbd{return -1} with its implicit type @code{int} would set only a part
17504 of a @code{long long int} result for a debug info less function (on 32-bit
17505 architectures). Therefore the user is required to specify the return type by
17506 an appropriate cast explicitly:
17509 Breakpoint 2, 0x0040050b in func ()
17510 (@value{GDBP}) return -1
17511 Return value type not available for selected stack frame.
17512 Please use an explicit cast of the value to return.
17513 (@value{GDBP}) return (long long int) -1
17514 Make selected stack frame return now? (y or n) y
17515 #0 0x00400526 in main ()
17520 @section Calling Program Functions
17523 @cindex calling functions
17524 @cindex inferior functions, calling
17525 @item print @var{expr}
17526 Evaluate the expression @var{expr} and display the resulting value.
17527 The expression may include calls to functions in the program being
17531 @item call @var{expr}
17532 Evaluate the expression @var{expr} without displaying @code{void}
17535 You can use this variant of the @code{print} command if you want to
17536 execute a function from your program that does not return anything
17537 (a.k.a.@: @dfn{a void function}), but without cluttering the output
17538 with @code{void} returned values that @value{GDBN} will otherwise
17539 print. If the result is not void, it is printed and saved in the
17543 It is possible for the function you call via the @code{print} or
17544 @code{call} command to generate a signal (e.g., if there's a bug in
17545 the function, or if you passed it incorrect arguments). What happens
17546 in that case is controlled by the @code{set unwindonsignal} command.
17548 Similarly, with a C@t{++} program it is possible for the function you
17549 call via the @code{print} or @code{call} command to generate an
17550 exception that is not handled due to the constraints of the dummy
17551 frame. In this case, any exception that is raised in the frame, but has
17552 an out-of-frame exception handler will not be found. GDB builds a
17553 dummy-frame for the inferior function call, and the unwinder cannot
17554 seek for exception handlers outside of this dummy-frame. What happens
17555 in that case is controlled by the
17556 @code{set unwind-on-terminating-exception} command.
17559 @item set unwindonsignal
17560 @kindex set unwindonsignal
17561 @cindex unwind stack in called functions
17562 @cindex call dummy stack unwinding
17563 Set unwinding of the stack if a signal is received while in a function
17564 that @value{GDBN} called in the program being debugged. If set to on,
17565 @value{GDBN} unwinds the stack it created for the call and restores
17566 the context to what it was before the call. If set to off (the
17567 default), @value{GDBN} stops in the frame where the signal was
17570 @item show unwindonsignal
17571 @kindex show unwindonsignal
17572 Show the current setting of stack unwinding in the functions called by
17575 @item set unwind-on-terminating-exception
17576 @kindex set unwind-on-terminating-exception
17577 @cindex unwind stack in called functions with unhandled exceptions
17578 @cindex call dummy stack unwinding on unhandled exception.
17579 Set unwinding of the stack if a C@t{++} exception is raised, but left
17580 unhandled while in a function that @value{GDBN} called in the program being
17581 debugged. If set to on (the default), @value{GDBN} unwinds the stack
17582 it created for the call and restores the context to what it was before
17583 the call. If set to off, @value{GDBN} the exception is delivered to
17584 the default C@t{++} exception handler and the inferior terminated.
17586 @item show unwind-on-terminating-exception
17587 @kindex show unwind-on-terminating-exception
17588 Show the current setting of stack unwinding in the functions called by
17593 @cindex weak alias functions
17594 Sometimes, a function you wish to call is actually a @dfn{weak alias}
17595 for another function. In such case, @value{GDBN} might not pick up
17596 the type information, including the types of the function arguments,
17597 which causes @value{GDBN} to call the inferior function incorrectly.
17598 As a result, the called function will function erroneously and may
17599 even crash. A solution to that is to use the name of the aliased
17603 @section Patching Programs
17605 @cindex patching binaries
17606 @cindex writing into executables
17607 @cindex writing into corefiles
17609 By default, @value{GDBN} opens the file containing your program's
17610 executable code (or the corefile) read-only. This prevents accidental
17611 alterations to machine code; but it also prevents you from intentionally
17612 patching your program's binary.
17614 If you'd like to be able to patch the binary, you can specify that
17615 explicitly with the @code{set write} command. For example, you might
17616 want to turn on internal debugging flags, or even to make emergency
17622 @itemx set write off
17623 If you specify @samp{set write on}, @value{GDBN} opens executable and
17624 core files for both reading and writing; if you specify @kbd{set write
17625 off} (the default), @value{GDBN} opens them read-only.
17627 If you have already loaded a file, you must load it again (using the
17628 @code{exec-file} or @code{core-file} command) after changing @code{set
17629 write}, for your new setting to take effect.
17633 Display whether executable files and core files are opened for writing
17634 as well as reading.
17637 @node Compiling and Injecting Code
17638 @section Compiling and injecting code in @value{GDBN}
17639 @cindex injecting code
17640 @cindex writing into executables
17641 @cindex compiling code
17643 @value{GDBN} supports on-demand compilation and code injection into
17644 programs running under @value{GDBN}. GCC 5.0 or higher built with
17645 @file{libcc1.so} must be installed for this functionality to be enabled.
17646 This functionality is implemented with the following commands.
17649 @kindex compile code
17650 @item compile code @var{source-code}
17651 @itemx compile code -raw @var{--} @var{source-code}
17652 Compile @var{source-code} with the compiler language found as the current
17653 language in @value{GDBN} (@pxref{Languages}). If compilation and
17654 injection is not supported with the current language specified in
17655 @value{GDBN}, or the compiler does not support this feature, an error
17656 message will be printed. If @var{source-code} compiles and links
17657 successfully, @value{GDBN} will load the object-code emitted,
17658 and execute it within the context of the currently selected inferior.
17659 It is important to note that the compiled code is executed immediately.
17660 After execution, the compiled code is removed from @value{GDBN} and any
17661 new types or variables you have defined will be deleted.
17663 The command allows you to specify @var{source-code} in two ways.
17664 The simplest method is to provide a single line of code to the command.
17668 compile code printf ("hello world\n");
17671 If you specify options on the command line as well as source code, they
17672 may conflict. The @samp{--} delimiter can be used to separate options
17673 from actual source code. E.g.:
17676 compile code -r -- printf ("hello world\n");
17679 Alternatively you can enter source code as multiple lines of text. To
17680 enter this mode, invoke the @samp{compile code} command without any text
17681 following the command. This will start the multiple-line editor and
17682 allow you to type as many lines of source code as required. When you
17683 have completed typing, enter @samp{end} on its own line to exit the
17688 >printf ("hello\n");
17689 >printf ("world\n");
17693 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
17694 provided @var{source-code} in a callable scope. In this case, you must
17695 specify the entry point of the code by defining a function named
17696 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
17697 inferior. Using @samp{-raw} option may be needed for example when
17698 @var{source-code} requires @samp{#include} lines which may conflict with
17699 inferior symbols otherwise.
17701 @kindex compile file
17702 @item compile file @var{filename}
17703 @itemx compile file -raw @var{filename}
17704 Like @code{compile code}, but take the source code from @var{filename}.
17707 compile file /home/user/example.c
17712 @item compile print @var{expr}
17713 @itemx compile print /@var{f} @var{expr}
17714 Compile and execute @var{expr} with the compiler language found as the
17715 current language in @value{GDBN} (@pxref{Languages}). By default the
17716 value of @var{expr} is printed in a format appropriate to its data type;
17717 you can choose a different format by specifying @samp{/@var{f}}, where
17718 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
17721 @item compile print
17722 @itemx compile print /@var{f}
17723 @cindex reprint the last value
17724 Alternatively you can enter the expression (source code producing it) as
17725 multiple lines of text. To enter this mode, invoke the @samp{compile print}
17726 command without any text following the command. This will start the
17727 multiple-line editor.
17731 The process of compiling and injecting the code can be inspected using:
17734 @anchor{set debug compile}
17735 @item set debug compile
17736 @cindex compile command debugging info
17737 Turns on or off display of @value{GDBN} process of compiling and
17738 injecting the code. The default is off.
17740 @item show debug compile
17741 Displays the current state of displaying @value{GDBN} process of
17742 compiling and injecting the code.
17745 @subsection Compilation options for the @code{compile} command
17747 @value{GDBN} needs to specify the right compilation options for the code
17748 to be injected, in part to make its ABI compatible with the inferior
17749 and in part to make the injected code compatible with @value{GDBN}'s
17753 The options used, in increasing precedence:
17756 @item target architecture and OS options (@code{gdbarch})
17757 These options depend on target processor type and target operating
17758 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
17759 (@code{-m64}) compilation option.
17761 @item compilation options recorded in the target
17762 @value{NGCC} (since version 4.7) stores the options used for compilation
17763 into @code{DW_AT_producer} part of DWARF debugging information according
17764 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
17765 explicitly specify @code{-g} during inferior compilation otherwise
17766 @value{NGCC} produces no DWARF. This feature is only relevant for
17767 platforms where @code{-g} produces DWARF by default, otherwise one may
17768 try to enforce DWARF by using @code{-gdwarf-4}.
17770 @item compilation options set by @code{set compile-args}
17774 You can override compilation options using the following command:
17777 @item set compile-args
17778 @cindex compile command options override
17779 Set compilation options used for compiling and injecting code with the
17780 @code{compile} commands. These options override any conflicting ones
17781 from the target architecture and/or options stored during inferior
17784 @item show compile-args
17785 Displays the current state of compilation options override.
17786 This does not show all the options actually used during compilation,
17787 use @ref{set debug compile} for that.
17790 @subsection Caveats when using the @code{compile} command
17792 There are a few caveats to keep in mind when using the @code{compile}
17793 command. As the caveats are different per language, the table below
17794 highlights specific issues on a per language basis.
17797 @item C code examples and caveats
17798 When the language in @value{GDBN} is set to @samp{C}, the compiler will
17799 attempt to compile the source code with a @samp{C} compiler. The source
17800 code provided to the @code{compile} command will have much the same
17801 access to variables and types as it normally would if it were part of
17802 the program currently being debugged in @value{GDBN}.
17804 Below is a sample program that forms the basis of the examples that
17805 follow. This program has been compiled and loaded into @value{GDBN},
17806 much like any other normal debugging session.
17809 void function1 (void)
17812 printf ("function 1\n");
17815 void function2 (void)
17830 For the purposes of the examples in this section, the program above has
17831 been compiled, loaded into @value{GDBN}, stopped at the function
17832 @code{main}, and @value{GDBN} is awaiting input from the user.
17834 To access variables and types for any program in @value{GDBN}, the
17835 program must be compiled and packaged with debug information. The
17836 @code{compile} command is not an exception to this rule. Without debug
17837 information, you can still use the @code{compile} command, but you will
17838 be very limited in what variables and types you can access.
17840 So with that in mind, the example above has been compiled with debug
17841 information enabled. The @code{compile} command will have access to
17842 all variables and types (except those that may have been optimized
17843 out). Currently, as @value{GDBN} has stopped the program in the
17844 @code{main} function, the @code{compile} command would have access to
17845 the variable @code{k}. You could invoke the @code{compile} command
17846 and type some source code to set the value of @code{k}. You can also
17847 read it, or do anything with that variable you would normally do in
17848 @code{C}. Be aware that changes to inferior variables in the
17849 @code{compile} command are persistent. In the following example:
17852 compile code k = 3;
17856 the variable @code{k} is now 3. It will retain that value until
17857 something else in the example program changes it, or another
17858 @code{compile} command changes it.
17860 Normal scope and access rules apply to source code compiled and
17861 injected by the @code{compile} command. In the example, the variables
17862 @code{j} and @code{k} are not accessible yet, because the program is
17863 currently stopped in the @code{main} function, where these variables
17864 are not in scope. Therefore, the following command
17867 compile code j = 3;
17871 will result in a compilation error message.
17873 Once the program is continued, execution will bring these variables in
17874 scope, and they will become accessible; then the code you specify via
17875 the @code{compile} command will be able to access them.
17877 You can create variables and types with the @code{compile} command as
17878 part of your source code. Variables and types that are created as part
17879 of the @code{compile} command are not visible to the rest of the program for
17880 the duration of its run. This example is valid:
17883 compile code int ff = 5; printf ("ff is %d\n", ff);
17886 However, if you were to type the following into @value{GDBN} after that
17887 command has completed:
17890 compile code printf ("ff is %d\n'', ff);
17894 a compiler error would be raised as the variable @code{ff} no longer
17895 exists. Object code generated and injected by the @code{compile}
17896 command is removed when its execution ends. Caution is advised
17897 when assigning to program variables values of variables created by the
17898 code submitted to the @code{compile} command. This example is valid:
17901 compile code int ff = 5; k = ff;
17904 The value of the variable @code{ff} is assigned to @code{k}. The variable
17905 @code{k} does not require the existence of @code{ff} to maintain the value
17906 it has been assigned. However, pointers require particular care in
17907 assignment. If the source code compiled with the @code{compile} command
17908 changed the address of a pointer in the example program, perhaps to a
17909 variable created in the @code{compile} command, that pointer would point
17910 to an invalid location when the command exits. The following example
17911 would likely cause issues with your debugged program:
17914 compile code int ff = 5; p = &ff;
17917 In this example, @code{p} would point to @code{ff} when the
17918 @code{compile} command is executing the source code provided to it.
17919 However, as variables in the (example) program persist with their
17920 assigned values, the variable @code{p} would point to an invalid
17921 location when the command exists. A general rule should be followed
17922 in that you should either assign @code{NULL} to any assigned pointers,
17923 or restore a valid location to the pointer before the command exits.
17925 Similar caution must be exercised with any structs, unions, and typedefs
17926 defined in @code{compile} command. Types defined in the @code{compile}
17927 command will no longer be available in the next @code{compile} command.
17928 Therefore, if you cast a variable to a type defined in the
17929 @code{compile} command, care must be taken to ensure that any future
17930 need to resolve the type can be achieved.
17933 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
17934 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
17935 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
17936 Compilation failed.
17937 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
17941 Variables that have been optimized away by the compiler are not
17942 accessible to the code submitted to the @code{compile} command.
17943 Access to those variables will generate a compiler error which @value{GDBN}
17944 will print to the console.
17947 @subsection Compiler search for the @code{compile} command
17949 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged which
17950 may not be obvious for remote targets of different architecture than where
17951 @value{GDBN} is running. Environment variable @code{PATH} (@code{PATH} from
17952 shell that executed @value{GDBN}, not the one set by @value{GDBN}
17953 command @code{set environment}). @xref{Environment}. @code{PATH} on
17954 @value{GDBN} host is searched for @value{NGCC} binary matching the
17955 target architecture and operating system.
17957 Specifically @code{PATH} is searched for binaries matching regular expression
17958 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
17959 debugged. @var{arch} is processor name --- multiarch is supported, so for
17960 example both @code{i386} and @code{x86_64} targets look for pattern
17961 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
17962 for pattern @code{s390x?}. @var{os} is currently supported only for
17963 pattern @code{linux(-gnu)?}.
17966 @chapter @value{GDBN} Files
17968 @value{GDBN} needs to know the file name of the program to be debugged,
17969 both in order to read its symbol table and in order to start your
17970 program. To debug a core dump of a previous run, you must also tell
17971 @value{GDBN} the name of the core dump file.
17974 * Files:: Commands to specify files
17975 * File Caching:: Information about @value{GDBN}'s file caching
17976 * Separate Debug Files:: Debugging information in separate files
17977 * MiniDebugInfo:: Debugging information in a special section
17978 * Index Files:: Index files speed up GDB
17979 * Symbol Errors:: Errors reading symbol files
17980 * Data Files:: GDB data files
17984 @section Commands to Specify Files
17986 @cindex symbol table
17987 @cindex core dump file
17989 You may want to specify executable and core dump file names. The usual
17990 way to do this is at start-up time, using the arguments to
17991 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
17992 Out of @value{GDBN}}).
17994 Occasionally it is necessary to change to a different file during a
17995 @value{GDBN} session. Or you may run @value{GDBN} and forget to
17996 specify a file you want to use. Or you are debugging a remote target
17997 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
17998 Program}). In these situations the @value{GDBN} commands to specify
17999 new files are useful.
18002 @cindex executable file
18004 @item file @var{filename}
18005 Use @var{filename} as the program to be debugged. It is read for its
18006 symbols and for the contents of pure memory. It is also the program
18007 executed when you use the @code{run} command. If you do not specify a
18008 directory and the file is not found in the @value{GDBN} working directory,
18009 @value{GDBN} uses the environment variable @code{PATH} as a list of
18010 directories to search, just as the shell does when looking for a program
18011 to run. You can change the value of this variable, for both @value{GDBN}
18012 and your program, using the @code{path} command.
18014 @cindex unlinked object files
18015 @cindex patching object files
18016 You can load unlinked object @file{.o} files into @value{GDBN} using
18017 the @code{file} command. You will not be able to ``run'' an object
18018 file, but you can disassemble functions and inspect variables. Also,
18019 if the underlying BFD functionality supports it, you could use
18020 @kbd{gdb -write} to patch object files using this technique. Note
18021 that @value{GDBN} can neither interpret nor modify relocations in this
18022 case, so branches and some initialized variables will appear to go to
18023 the wrong place. But this feature is still handy from time to time.
18026 @code{file} with no argument makes @value{GDBN} discard any information it
18027 has on both executable file and the symbol table.
18030 @item exec-file @r{[} @var{filename} @r{]}
18031 Specify that the program to be run (but not the symbol table) is found
18032 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
18033 if necessary to locate your program. Omitting @var{filename} means to
18034 discard information on the executable file.
18036 @kindex symbol-file
18037 @item symbol-file @r{[} @var{filename} @r{]}
18038 Read symbol table information from file @var{filename}. @code{PATH} is
18039 searched when necessary. Use the @code{file} command to get both symbol
18040 table and program to run from the same file.
18042 @code{symbol-file} with no argument clears out @value{GDBN} information on your
18043 program's symbol table.
18045 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
18046 some breakpoints and auto-display expressions. This is because they may
18047 contain pointers to the internal data recording symbols and data types,
18048 which are part of the old symbol table data being discarded inside
18051 @code{symbol-file} does not repeat if you press @key{RET} again after
18054 When @value{GDBN} is configured for a particular environment, it
18055 understands debugging information in whatever format is the standard
18056 generated for that environment; you may use either a @sc{gnu} compiler, or
18057 other compilers that adhere to the local conventions.
18058 Best results are usually obtained from @sc{gnu} compilers; for example,
18059 using @code{@value{NGCC}} you can generate debugging information for
18062 For most kinds of object files, with the exception of old SVR3 systems
18063 using COFF, the @code{symbol-file} command does not normally read the
18064 symbol table in full right away. Instead, it scans the symbol table
18065 quickly to find which source files and which symbols are present. The
18066 details are read later, one source file at a time, as they are needed.
18068 The purpose of this two-stage reading strategy is to make @value{GDBN}
18069 start up faster. For the most part, it is invisible except for
18070 occasional pauses while the symbol table details for a particular source
18071 file are being read. (The @code{set verbose} command can turn these
18072 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
18073 Warnings and Messages}.)
18075 We have not implemented the two-stage strategy for COFF yet. When the
18076 symbol table is stored in COFF format, @code{symbol-file} reads the
18077 symbol table data in full right away. Note that ``stabs-in-COFF''
18078 still does the two-stage strategy, since the debug info is actually
18082 @cindex reading symbols immediately
18083 @cindex symbols, reading immediately
18084 @item symbol-file @r{[} -readnow @r{]} @var{filename}
18085 @itemx file @r{[} -readnow @r{]} @var{filename}
18086 You can override the @value{GDBN} two-stage strategy for reading symbol
18087 tables by using the @samp{-readnow} option with any of the commands that
18088 load symbol table information, if you want to be sure @value{GDBN} has the
18089 entire symbol table available.
18091 @c FIXME: for now no mention of directories, since this seems to be in
18092 @c flux. 13mar1992 status is that in theory GDB would look either in
18093 @c current dir or in same dir as myprog; but issues like competing
18094 @c GDB's, or clutter in system dirs, mean that in practice right now
18095 @c only current dir is used. FFish says maybe a special GDB hierarchy
18096 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
18100 @item core-file @r{[}@var{filename}@r{]}
18102 Specify the whereabouts of a core dump file to be used as the ``contents
18103 of memory''. Traditionally, core files contain only some parts of the
18104 address space of the process that generated them; @value{GDBN} can access the
18105 executable file itself for other parts.
18107 @code{core-file} with no argument specifies that no core file is
18110 Note that the core file is ignored when your program is actually running
18111 under @value{GDBN}. So, if you have been running your program and you
18112 wish to debug a core file instead, you must kill the subprocess in which
18113 the program is running. To do this, use the @code{kill} command
18114 (@pxref{Kill Process, ,Killing the Child Process}).
18116 @kindex add-symbol-file
18117 @cindex dynamic linking
18118 @item add-symbol-file @var{filename} @var{address}
18119 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
18120 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
18121 The @code{add-symbol-file} command reads additional symbol table
18122 information from the file @var{filename}. You would use this command
18123 when @var{filename} has been dynamically loaded (by some other means)
18124 into the program that is running. The @var{address} should give the memory
18125 address at which the file has been loaded; @value{GDBN} cannot figure
18126 this out for itself. You can additionally specify an arbitrary number
18127 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
18128 section name and base address for that section. You can specify any
18129 @var{address} as an expression.
18131 The symbol table of the file @var{filename} is added to the symbol table
18132 originally read with the @code{symbol-file} command. You can use the
18133 @code{add-symbol-file} command any number of times; the new symbol data
18134 thus read is kept in addition to the old.
18136 Changes can be reverted using the command @code{remove-symbol-file}.
18138 @cindex relocatable object files, reading symbols from
18139 @cindex object files, relocatable, reading symbols from
18140 @cindex reading symbols from relocatable object files
18141 @cindex symbols, reading from relocatable object files
18142 @cindex @file{.o} files, reading symbols from
18143 Although @var{filename} is typically a shared library file, an
18144 executable file, or some other object file which has been fully
18145 relocated for loading into a process, you can also load symbolic
18146 information from relocatable @file{.o} files, as long as:
18150 the file's symbolic information refers only to linker symbols defined in
18151 that file, not to symbols defined by other object files,
18153 every section the file's symbolic information refers to has actually
18154 been loaded into the inferior, as it appears in the file, and
18156 you can determine the address at which every section was loaded, and
18157 provide these to the @code{add-symbol-file} command.
18161 Some embedded operating systems, like Sun Chorus and VxWorks, can load
18162 relocatable files into an already running program; such systems
18163 typically make the requirements above easy to meet. However, it's
18164 important to recognize that many native systems use complex link
18165 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
18166 assembly, for example) that make the requirements difficult to meet. In
18167 general, one cannot assume that using @code{add-symbol-file} to read a
18168 relocatable object file's symbolic information will have the same effect
18169 as linking the relocatable object file into the program in the normal
18172 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
18174 @kindex remove-symbol-file
18175 @item remove-symbol-file @var{filename}
18176 @item remove-symbol-file -a @var{address}
18177 Remove a symbol file added via the @code{add-symbol-file} command. The
18178 file to remove can be identified by its @var{filename} or by an @var{address}
18179 that lies within the boundaries of this symbol file in memory. Example:
18182 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
18183 add symbol table from file "/home/user/gdb/mylib.so" at
18184 .text_addr = 0x7ffff7ff9480
18186 Reading symbols from /home/user/gdb/mylib.so...done.
18187 (gdb) remove-symbol-file -a 0x7ffff7ff9480
18188 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
18193 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
18195 @kindex add-symbol-file-from-memory
18196 @cindex @code{syscall DSO}
18197 @cindex load symbols from memory
18198 @item add-symbol-file-from-memory @var{address}
18199 Load symbols from the given @var{address} in a dynamically loaded
18200 object file whose image is mapped directly into the inferior's memory.
18201 For example, the Linux kernel maps a @code{syscall DSO} into each
18202 process's address space; this DSO provides kernel-specific code for
18203 some system calls. The argument can be any expression whose
18204 evaluation yields the address of the file's shared object file header.
18205 For this command to work, you must have used @code{symbol-file} or
18206 @code{exec-file} commands in advance.
18209 @item section @var{section} @var{addr}
18210 The @code{section} command changes the base address of the named
18211 @var{section} of the exec file to @var{addr}. This can be used if the
18212 exec file does not contain section addresses, (such as in the
18213 @code{a.out} format), or when the addresses specified in the file
18214 itself are wrong. Each section must be changed separately. The
18215 @code{info files} command, described below, lists all the sections and
18219 @kindex info target
18222 @code{info files} and @code{info target} are synonymous; both print the
18223 current target (@pxref{Targets, ,Specifying a Debugging Target}),
18224 including the names of the executable and core dump files currently in
18225 use by @value{GDBN}, and the files from which symbols were loaded. The
18226 command @code{help target} lists all possible targets rather than
18229 @kindex maint info sections
18230 @item maint info sections
18231 Another command that can give you extra information about program sections
18232 is @code{maint info sections}. In addition to the section information
18233 displayed by @code{info files}, this command displays the flags and file
18234 offset of each section in the executable and core dump files. In addition,
18235 @code{maint info sections} provides the following command options (which
18236 may be arbitrarily combined):
18240 Display sections for all loaded object files, including shared libraries.
18241 @item @var{sections}
18242 Display info only for named @var{sections}.
18243 @item @var{section-flags}
18244 Display info only for sections for which @var{section-flags} are true.
18245 The section flags that @value{GDBN} currently knows about are:
18248 Section will have space allocated in the process when loaded.
18249 Set for all sections except those containing debug information.
18251 Section will be loaded from the file into the child process memory.
18252 Set for pre-initialized code and data, clear for @code{.bss} sections.
18254 Section needs to be relocated before loading.
18256 Section cannot be modified by the child process.
18258 Section contains executable code only.
18260 Section contains data only (no executable code).
18262 Section will reside in ROM.
18264 Section contains data for constructor/destructor lists.
18266 Section is not empty.
18268 An instruction to the linker to not output the section.
18269 @item COFF_SHARED_LIBRARY
18270 A notification to the linker that the section contains
18271 COFF shared library information.
18273 Section contains common symbols.
18276 @kindex set trust-readonly-sections
18277 @cindex read-only sections
18278 @item set trust-readonly-sections on
18279 Tell @value{GDBN} that readonly sections in your object file
18280 really are read-only (i.e.@: that their contents will not change).
18281 In that case, @value{GDBN} can fetch values from these sections
18282 out of the object file, rather than from the target program.
18283 For some targets (notably embedded ones), this can be a significant
18284 enhancement to debugging performance.
18286 The default is off.
18288 @item set trust-readonly-sections off
18289 Tell @value{GDBN} not to trust readonly sections. This means that
18290 the contents of the section might change while the program is running,
18291 and must therefore be fetched from the target when needed.
18293 @item show trust-readonly-sections
18294 Show the current setting of trusting readonly sections.
18297 All file-specifying commands allow both absolute and relative file names
18298 as arguments. @value{GDBN} always converts the file name to an absolute file
18299 name and remembers it that way.
18301 @cindex shared libraries
18302 @anchor{Shared Libraries}
18303 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
18304 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
18305 DSBT (TIC6X) shared libraries.
18307 On MS-Windows @value{GDBN} must be linked with the Expat library to support
18308 shared libraries. @xref{Expat}.
18310 @value{GDBN} automatically loads symbol definitions from shared libraries
18311 when you use the @code{run} command, or when you examine a core file.
18312 (Before you issue the @code{run} command, @value{GDBN} does not understand
18313 references to a function in a shared library, however---unless you are
18314 debugging a core file).
18316 @c FIXME: some @value{GDBN} release may permit some refs to undef
18317 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
18318 @c FIXME...lib; check this from time to time when updating manual
18320 There are times, however, when you may wish to not automatically load
18321 symbol definitions from shared libraries, such as when they are
18322 particularly large or there are many of them.
18324 To control the automatic loading of shared library symbols, use the
18328 @kindex set auto-solib-add
18329 @item set auto-solib-add @var{mode}
18330 If @var{mode} is @code{on}, symbols from all shared object libraries
18331 will be loaded automatically when the inferior begins execution, you
18332 attach to an independently started inferior, or when the dynamic linker
18333 informs @value{GDBN} that a new library has been loaded. If @var{mode}
18334 is @code{off}, symbols must be loaded manually, using the
18335 @code{sharedlibrary} command. The default value is @code{on}.
18337 @cindex memory used for symbol tables
18338 If your program uses lots of shared libraries with debug info that
18339 takes large amounts of memory, you can decrease the @value{GDBN}
18340 memory footprint by preventing it from automatically loading the
18341 symbols from shared libraries. To that end, type @kbd{set
18342 auto-solib-add off} before running the inferior, then load each
18343 library whose debug symbols you do need with @kbd{sharedlibrary
18344 @var{regexp}}, where @var{regexp} is a regular expression that matches
18345 the libraries whose symbols you want to be loaded.
18347 @kindex show auto-solib-add
18348 @item show auto-solib-add
18349 Display the current autoloading mode.
18352 @cindex load shared library
18353 To explicitly load shared library symbols, use the @code{sharedlibrary}
18357 @kindex info sharedlibrary
18359 @item info share @var{regex}
18360 @itemx info sharedlibrary @var{regex}
18361 Print the names of the shared libraries which are currently loaded
18362 that match @var{regex}. If @var{regex} is omitted then print
18363 all shared libraries that are loaded.
18366 @item info dll @var{regex}
18367 This is an alias of @code{info sharedlibrary}.
18369 @kindex sharedlibrary
18371 @item sharedlibrary @var{regex}
18372 @itemx share @var{regex}
18373 Load shared object library symbols for files matching a
18374 Unix regular expression.
18375 As with files loaded automatically, it only loads shared libraries
18376 required by your program for a core file or after typing @code{run}. If
18377 @var{regex} is omitted all shared libraries required by your program are
18380 @item nosharedlibrary
18381 @kindex nosharedlibrary
18382 @cindex unload symbols from shared libraries
18383 Unload all shared object library symbols. This discards all symbols
18384 that have been loaded from all shared libraries. Symbols from shared
18385 libraries that were loaded by explicit user requests are not
18389 Sometimes you may wish that @value{GDBN} stops and gives you control
18390 when any of shared library events happen. The best way to do this is
18391 to use @code{catch load} and @code{catch unload} (@pxref{Set
18394 @value{GDBN} also supports the the @code{set stop-on-solib-events}
18395 command for this. This command exists for historical reasons. It is
18396 less useful than setting a catchpoint, because it does not allow for
18397 conditions or commands as a catchpoint does.
18400 @item set stop-on-solib-events
18401 @kindex set stop-on-solib-events
18402 This command controls whether @value{GDBN} should give you control
18403 when the dynamic linker notifies it about some shared library event.
18404 The most common event of interest is loading or unloading of a new
18407 @item show stop-on-solib-events
18408 @kindex show stop-on-solib-events
18409 Show whether @value{GDBN} stops and gives you control when shared
18410 library events happen.
18413 Shared libraries are also supported in many cross or remote debugging
18414 configurations. @value{GDBN} needs to have access to the target's libraries;
18415 this can be accomplished either by providing copies of the libraries
18416 on the host system, or by asking @value{GDBN} to automatically retrieve the
18417 libraries from the target. If copies of the target libraries are
18418 provided, they need to be the same as the target libraries, although the
18419 copies on the target can be stripped as long as the copies on the host are
18422 @cindex where to look for shared libraries
18423 For remote debugging, you need to tell @value{GDBN} where the target
18424 libraries are, so that it can load the correct copies---otherwise, it
18425 may try to load the host's libraries. @value{GDBN} has two variables
18426 to specify the search directories for target libraries.
18429 @cindex prefix for executable and shared library file names
18430 @cindex system root, alternate
18431 @kindex set solib-absolute-prefix
18432 @kindex set sysroot
18433 @item set sysroot @var{path}
18434 Use @var{path} as the system root for the program being debugged. Any
18435 absolute shared library paths will be prefixed with @var{path}; many
18436 runtime loaders store the absolute paths to the shared library in the
18437 target program's memory. When starting processes remotely, and when
18438 attaching to already-running processes (local or remote), their
18439 executable filenames will be prefixed with @var{path} if reported to
18440 @value{GDBN} as absolute by the operating system. If you use
18441 @code{set sysroot} to find executables and shared libraries, they need
18442 to be laid out in the same way that they are on the target, with
18443 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
18446 If @var{path} starts with the sequence @file{target:} and the target
18447 system is remote then @value{GDBN} will retrieve the target binaries
18448 from the remote system. This is only supported when using a remote
18449 target that supports the @code{remote get} command (@pxref{File
18450 Transfer,,Sending files to a remote system}). The part of @var{path}
18451 following the initial @file{target:} (if present) is used as system
18452 root prefix on the remote file system. If @var{path} starts with the
18453 sequence @file{remote:} this is converted to the sequence
18454 @file{target:} by @code{set sysroot}@footnote{Historically the
18455 functionality to retrieve binaries from the remote system was
18456 provided by prefixing @var{path} with @file{remote:}}. If you want
18457 to specify a local system root using a directory that happens to be
18458 named @file{target:} or @file{remote:}, you need to use some
18459 equivalent variant of the name like @file{./target:}.
18461 For targets with an MS-DOS based filesystem, such as MS-Windows and
18462 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
18463 absolute file name with @var{path}. But first, on Unix hosts,
18464 @value{GDBN} converts all backslash directory separators into forward
18465 slashes, because the backslash is not a directory separator on Unix:
18468 c:\foo\bar.dll @result{} c:/foo/bar.dll
18471 Then, @value{GDBN} attempts prefixing the target file name with
18472 @var{path}, and looks for the resulting file name in the host file
18476 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
18479 If that does not find the binary, @value{GDBN} tries removing
18480 the @samp{:} character from the drive spec, both for convenience, and,
18481 for the case of the host file system not supporting file names with
18485 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
18488 This makes it possible to have a system root that mirrors a target
18489 with more than one drive. E.g., you may want to setup your local
18490 copies of the target system shared libraries like so (note @samp{c} vs
18494 @file{/path/to/sysroot/c/sys/bin/foo.dll}
18495 @file{/path/to/sysroot/c/sys/bin/bar.dll}
18496 @file{/path/to/sysroot/z/sys/bin/bar.dll}
18500 and point the system root at @file{/path/to/sysroot}, so that
18501 @value{GDBN} can find the correct copies of both
18502 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
18504 If that still does not find the binary, @value{GDBN} tries
18505 removing the whole drive spec from the target file name:
18508 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
18511 This last lookup makes it possible to not care about the drive name,
18512 if you don't want or need to.
18514 The @code{set solib-absolute-prefix} command is an alias for @code{set
18517 @cindex default system root
18518 @cindex @samp{--with-sysroot}
18519 You can set the default system root by using the configure-time
18520 @samp{--with-sysroot} option. If the system root is inside
18521 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
18522 @samp{--exec-prefix}), then the default system root will be updated
18523 automatically if the installed @value{GDBN} is moved to a new
18526 @kindex show sysroot
18528 Display the current executable and shared library prefix.
18530 @kindex set solib-search-path
18531 @item set solib-search-path @var{path}
18532 If this variable is set, @var{path} is a colon-separated list of
18533 directories to search for shared libraries. @samp{solib-search-path}
18534 is used after @samp{sysroot} fails to locate the library, or if the
18535 path to the library is relative instead of absolute. If you want to
18536 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
18537 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
18538 finding your host's libraries. @samp{sysroot} is preferred; setting
18539 it to a nonexistent directory may interfere with automatic loading
18540 of shared library symbols.
18542 @kindex show solib-search-path
18543 @item show solib-search-path
18544 Display the current shared library search path.
18546 @cindex DOS file-name semantics of file names.
18547 @kindex set target-file-system-kind (unix|dos-based|auto)
18548 @kindex show target-file-system-kind
18549 @item set target-file-system-kind @var{kind}
18550 Set assumed file system kind for target reported file names.
18552 Shared library file names as reported by the target system may not
18553 make sense as is on the system @value{GDBN} is running on. For
18554 example, when remote debugging a target that has MS-DOS based file
18555 system semantics, from a Unix host, the target may be reporting to
18556 @value{GDBN} a list of loaded shared libraries with file names such as
18557 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
18558 drive letters, so the @samp{c:\} prefix is not normally understood as
18559 indicating an absolute file name, and neither is the backslash
18560 normally considered a directory separator character. In that case,
18561 the native file system would interpret this whole absolute file name
18562 as a relative file name with no directory components. This would make
18563 it impossible to point @value{GDBN} at a copy of the remote target's
18564 shared libraries on the host using @code{set sysroot}, and impractical
18565 with @code{set solib-search-path}. Setting
18566 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
18567 to interpret such file names similarly to how the target would, and to
18568 map them to file names valid on @value{GDBN}'s native file system
18569 semantics. The value of @var{kind} can be @code{"auto"}, in addition
18570 to one of the supported file system kinds. In that case, @value{GDBN}
18571 tries to determine the appropriate file system variant based on the
18572 current target's operating system (@pxref{ABI, ,Configuring the
18573 Current ABI}). The supported file system settings are:
18577 Instruct @value{GDBN} to assume the target file system is of Unix
18578 kind. Only file names starting the forward slash (@samp{/}) character
18579 are considered absolute, and the directory separator character is also
18583 Instruct @value{GDBN} to assume the target file system is DOS based.
18584 File names starting with either a forward slash, or a drive letter
18585 followed by a colon (e.g., @samp{c:}), are considered absolute, and
18586 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
18587 considered directory separators.
18590 Instruct @value{GDBN} to use the file system kind associated with the
18591 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
18592 This is the default.
18596 @cindex file name canonicalization
18597 @cindex base name differences
18598 When processing file names provided by the user, @value{GDBN}
18599 frequently needs to compare them to the file names recorded in the
18600 program's debug info. Normally, @value{GDBN} compares just the
18601 @dfn{base names} of the files as strings, which is reasonably fast
18602 even for very large programs. (The base name of a file is the last
18603 portion of its name, after stripping all the leading directories.)
18604 This shortcut in comparison is based upon the assumption that files
18605 cannot have more than one base name. This is usually true, but
18606 references to files that use symlinks or similar filesystem
18607 facilities violate that assumption. If your program records files
18608 using such facilities, or if you provide file names to @value{GDBN}
18609 using symlinks etc., you can set @code{basenames-may-differ} to
18610 @code{true} to instruct @value{GDBN} to completely canonicalize each
18611 pair of file names it needs to compare. This will make file-name
18612 comparisons accurate, but at a price of a significant slowdown.
18615 @item set basenames-may-differ
18616 @kindex set basenames-may-differ
18617 Set whether a source file may have multiple base names.
18619 @item show basenames-may-differ
18620 @kindex show basenames-may-differ
18621 Show whether a source file may have multiple base names.
18625 @section File Caching
18626 @cindex caching of opened files
18627 @cindex caching of bfd objects
18629 To speed up file loading, and reduce memory usage, @value{GDBN} will
18630 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
18631 BFD, bfd, The Binary File Descriptor Library}. The following commands
18632 allow visibility and control of the caching behavior.
18635 @kindex maint info bfds
18636 @item maint info bfds
18637 This prints information about each @code{bfd} object that is known to
18640 @kindex maint set bfd-sharing
18641 @kindex maint show bfd-sharing
18642 @kindex bfd caching
18643 @item maint set bfd-sharing
18644 @item maint show bfd-sharing
18645 Control whether @code{bfd} objects can be shared. When sharing is
18646 enabled @value{GDBN} reuses already open @code{bfd} objects rather
18647 than reopening the same file. Turning sharing off does not cause
18648 already shared @code{bfd} objects to be unshared, but all future files
18649 that are opened will create a new @code{bfd} object. Similarly,
18650 re-enabling sharing does not cause multiple existing @code{bfd}
18651 objects to be collapsed into a single shared @code{bfd} object.
18653 @kindex set debug bfd-cache @var{level}
18654 @kindex bfd caching
18655 @item set debug bfd-cache @var{level}
18656 Turns on debugging of the bfd cache, setting the level to @var{level}.
18658 @kindex show debug bfd-cache
18659 @kindex bfd caching
18660 @item show debug bfd-cache
18661 Show the current debugging level of the bfd cache.
18664 @node Separate Debug Files
18665 @section Debugging Information in Separate Files
18666 @cindex separate debugging information files
18667 @cindex debugging information in separate files
18668 @cindex @file{.debug} subdirectories
18669 @cindex debugging information directory, global
18670 @cindex global debugging information directories
18671 @cindex build ID, and separate debugging files
18672 @cindex @file{.build-id} directory
18674 @value{GDBN} allows you to put a program's debugging information in a
18675 file separate from the executable itself, in a way that allows
18676 @value{GDBN} to find and load the debugging information automatically.
18677 Since debugging information can be very large---sometimes larger
18678 than the executable code itself---some systems distribute debugging
18679 information for their executables in separate files, which users can
18680 install only when they need to debug a problem.
18682 @value{GDBN} supports two ways of specifying the separate debug info
18687 The executable contains a @dfn{debug link} that specifies the name of
18688 the separate debug info file. The separate debug file's name is
18689 usually @file{@var{executable}.debug}, where @var{executable} is the
18690 name of the corresponding executable file without leading directories
18691 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
18692 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
18693 checksum for the debug file, which @value{GDBN} uses to validate that
18694 the executable and the debug file came from the same build.
18697 The executable contains a @dfn{build ID}, a unique bit string that is
18698 also present in the corresponding debug info file. (This is supported
18699 only on some operating systems, when using the ELF or PE file formats
18700 for binary files and the @sc{gnu} Binutils.) For more details about
18701 this feature, see the description of the @option{--build-id}
18702 command-line option in @ref{Options, , Command Line Options, ld.info,
18703 The GNU Linker}. The debug info file's name is not specified
18704 explicitly by the build ID, but can be computed from the build ID, see
18708 Depending on the way the debug info file is specified, @value{GDBN}
18709 uses two different methods of looking for the debug file:
18713 For the ``debug link'' method, @value{GDBN} looks up the named file in
18714 the directory of the executable file, then in a subdirectory of that
18715 directory named @file{.debug}, and finally under each one of the global debug
18716 directories, in a subdirectory whose name is identical to the leading
18717 directories of the executable's absolute file name.
18720 For the ``build ID'' method, @value{GDBN} looks in the
18721 @file{.build-id} subdirectory of each one of the global debug directories for
18722 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
18723 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
18724 are the rest of the bit string. (Real build ID strings are 32 or more
18725 hex characters, not 10.)
18728 So, for example, suppose you ask @value{GDBN} to debug
18729 @file{/usr/bin/ls}, which has a debug link that specifies the
18730 file @file{ls.debug}, and a build ID whose value in hex is
18731 @code{abcdef1234}. If the list of the global debug directories includes
18732 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
18733 debug information files, in the indicated order:
18737 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
18739 @file{/usr/bin/ls.debug}
18741 @file{/usr/bin/.debug/ls.debug}
18743 @file{/usr/lib/debug/usr/bin/ls.debug}.
18746 @anchor{debug-file-directory}
18747 Global debugging info directories default to what is set by @value{GDBN}
18748 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
18749 you can also set the global debugging info directories, and view the list
18750 @value{GDBN} is currently using.
18754 @kindex set debug-file-directory
18755 @item set debug-file-directory @var{directories}
18756 Set the directories which @value{GDBN} searches for separate debugging
18757 information files to @var{directory}. Multiple path components can be set
18758 concatenating them by a path separator.
18760 @kindex show debug-file-directory
18761 @item show debug-file-directory
18762 Show the directories @value{GDBN} searches for separate debugging
18767 @cindex @code{.gnu_debuglink} sections
18768 @cindex debug link sections
18769 A debug link is a special section of the executable file named
18770 @code{.gnu_debuglink}. The section must contain:
18774 A filename, with any leading directory components removed, followed by
18777 zero to three bytes of padding, as needed to reach the next four-byte
18778 boundary within the section, and
18780 a four-byte CRC checksum, stored in the same endianness used for the
18781 executable file itself. The checksum is computed on the debugging
18782 information file's full contents by the function given below, passing
18783 zero as the @var{crc} argument.
18786 Any executable file format can carry a debug link, as long as it can
18787 contain a section named @code{.gnu_debuglink} with the contents
18790 @cindex @code{.note.gnu.build-id} sections
18791 @cindex build ID sections
18792 The build ID is a special section in the executable file (and in other
18793 ELF binary files that @value{GDBN} may consider). This section is
18794 often named @code{.note.gnu.build-id}, but that name is not mandatory.
18795 It contains unique identification for the built files---the ID remains
18796 the same across multiple builds of the same build tree. The default
18797 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
18798 content for the build ID string. The same section with an identical
18799 value is present in the original built binary with symbols, in its
18800 stripped variant, and in the separate debugging information file.
18802 The debugging information file itself should be an ordinary
18803 executable, containing a full set of linker symbols, sections, and
18804 debugging information. The sections of the debugging information file
18805 should have the same names, addresses, and sizes as the original file,
18806 but they need not contain any data---much like a @code{.bss} section
18807 in an ordinary executable.
18809 The @sc{gnu} binary utilities (Binutils) package includes the
18810 @samp{objcopy} utility that can produce
18811 the separated executable / debugging information file pairs using the
18812 following commands:
18815 @kbd{objcopy --only-keep-debug foo foo.debug}
18820 These commands remove the debugging
18821 information from the executable file @file{foo} and place it in the file
18822 @file{foo.debug}. You can use the first, second or both methods to link the
18827 The debug link method needs the following additional command to also leave
18828 behind a debug link in @file{foo}:
18831 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
18834 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
18835 a version of the @code{strip} command such that the command @kbd{strip foo -f
18836 foo.debug} has the same functionality as the two @code{objcopy} commands and
18837 the @code{ln -s} command above, together.
18840 Build ID gets embedded into the main executable using @code{ld --build-id} or
18841 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
18842 compatibility fixes for debug files separation are present in @sc{gnu} binary
18843 utilities (Binutils) package since version 2.18.
18848 @cindex CRC algorithm definition
18849 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
18850 IEEE 802.3 using the polynomial:
18852 @c TexInfo requires naked braces for multi-digit exponents for Tex
18853 @c output, but this causes HTML output to barf. HTML has to be set using
18854 @c raw commands. So we end up having to specify this equation in 2
18859 <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>
18860 + <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
18866 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
18867 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
18871 The function is computed byte at a time, taking the least
18872 significant bit of each byte first. The initial pattern
18873 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
18874 the final result is inverted to ensure trailing zeros also affect the
18877 @emph{Note:} This is the same CRC polynomial as used in handling the
18878 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
18879 However in the case of the Remote Serial Protocol, the CRC is computed
18880 @emph{most} significant bit first, and the result is not inverted, so
18881 trailing zeros have no effect on the CRC value.
18883 To complete the description, we show below the code of the function
18884 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
18885 initially supplied @code{crc} argument means that an initial call to
18886 this function passing in zero will start computing the CRC using
18889 @kindex gnu_debuglink_crc32
18892 gnu_debuglink_crc32 (unsigned long crc,
18893 unsigned char *buf, size_t len)
18895 static const unsigned long crc32_table[256] =
18897 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
18898 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
18899 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
18900 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
18901 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
18902 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
18903 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
18904 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
18905 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
18906 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
18907 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
18908 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
18909 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
18910 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
18911 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
18912 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
18913 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
18914 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
18915 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
18916 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
18917 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
18918 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
18919 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
18920 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
18921 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
18922 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
18923 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
18924 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
18925 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
18926 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
18927 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
18928 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
18929 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
18930 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
18931 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
18932 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
18933 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
18934 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
18935 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
18936 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
18937 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
18938 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
18939 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
18940 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
18941 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
18942 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
18943 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
18944 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
18945 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
18946 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
18947 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
18950 unsigned char *end;
18952 crc = ~crc & 0xffffffff;
18953 for (end = buf + len; buf < end; ++buf)
18954 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
18955 return ~crc & 0xffffffff;
18960 This computation does not apply to the ``build ID'' method.
18962 @node MiniDebugInfo
18963 @section Debugging information in a special section
18964 @cindex separate debug sections
18965 @cindex @samp{.gnu_debugdata} section
18967 Some systems ship pre-built executables and libraries that have a
18968 special @samp{.gnu_debugdata} section. This feature is called
18969 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
18970 is used to supply extra symbols for backtraces.
18972 The intent of this section is to provide extra minimal debugging
18973 information for use in simple backtraces. It is not intended to be a
18974 replacement for full separate debugging information (@pxref{Separate
18975 Debug Files}). The example below shows the intended use; however,
18976 @value{GDBN} does not currently put restrictions on what sort of
18977 debugging information might be included in the section.
18979 @value{GDBN} has support for this extension. If the section exists,
18980 then it is used provided that no other source of debugging information
18981 can be found, and that @value{GDBN} was configured with LZMA support.
18983 This section can be easily created using @command{objcopy} and other
18984 standard utilities:
18987 # Extract the dynamic symbols from the main binary, there is no need
18988 # to also have these in the normal symbol table.
18989 nm -D @var{binary} --format=posix --defined-only \
18990 | awk '@{ print $1 @}' | sort > dynsyms
18992 # Extract all the text (i.e. function) symbols from the debuginfo.
18993 # (Note that we actually also accept "D" symbols, for the benefit
18994 # of platforms like PowerPC64 that use function descriptors.)
18995 nm @var{binary} --format=posix --defined-only \
18996 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
18999 # Keep all the function symbols not already in the dynamic symbol
19001 comm -13 dynsyms funcsyms > keep_symbols
19003 # Separate full debug info into debug binary.
19004 objcopy --only-keep-debug @var{binary} debug
19006 # Copy the full debuginfo, keeping only a minimal set of symbols and
19007 # removing some unnecessary sections.
19008 objcopy -S --remove-section .gdb_index --remove-section .comment \
19009 --keep-symbols=keep_symbols debug mini_debuginfo
19011 # Drop the full debug info from the original binary.
19012 strip --strip-all -R .comment @var{binary}
19014 # Inject the compressed data into the .gnu_debugdata section of the
19017 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
19021 @section Index Files Speed Up @value{GDBN}
19022 @cindex index files
19023 @cindex @samp{.gdb_index} section
19025 When @value{GDBN} finds a symbol file, it scans the symbols in the
19026 file in order to construct an internal symbol table. This lets most
19027 @value{GDBN} operations work quickly---at the cost of a delay early
19028 on. For large programs, this delay can be quite lengthy, so
19029 @value{GDBN} provides a way to build an index, which speeds up
19032 The index is stored as a section in the symbol file. @value{GDBN} can
19033 write the index to a file, then you can put it into the symbol file
19034 using @command{objcopy}.
19036 To create an index file, use the @code{save gdb-index} command:
19039 @item save gdb-index @var{directory}
19040 @kindex save gdb-index
19041 Create an index file for each symbol file currently known by
19042 @value{GDBN}. Each file is named after its corresponding symbol file,
19043 with @samp{.gdb-index} appended, and is written into the given
19047 Once you have created an index file you can merge it into your symbol
19048 file, here named @file{symfile}, using @command{objcopy}:
19051 $ objcopy --add-section .gdb_index=symfile.gdb-index \
19052 --set-section-flags .gdb_index=readonly symfile symfile
19055 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
19056 sections that have been deprecated. Usually they are deprecated because
19057 they are missing a new feature or have performance issues.
19058 To tell @value{GDBN} to use a deprecated index section anyway
19059 specify @code{set use-deprecated-index-sections on}.
19060 The default is @code{off}.
19061 This can speed up startup, but may result in some functionality being lost.
19062 @xref{Index Section Format}.
19064 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
19065 must be done before gdb reads the file. The following will not work:
19068 $ gdb -ex "set use-deprecated-index-sections on" <program>
19071 Instead you must do, for example,
19074 $ gdb -iex "set use-deprecated-index-sections on" <program>
19077 There are currently some limitation on indices. They only work when
19078 for DWARF debugging information, not stabs. And, they do not
19079 currently work for programs using Ada.
19081 @node Symbol Errors
19082 @section Errors Reading Symbol Files
19084 While reading a symbol file, @value{GDBN} occasionally encounters problems,
19085 such as symbol types it does not recognize, or known bugs in compiler
19086 output. By default, @value{GDBN} does not notify you of such problems, since
19087 they are relatively common and primarily of interest to people
19088 debugging compilers. If you are interested in seeing information
19089 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
19090 only one message about each such type of problem, no matter how many
19091 times the problem occurs; or you can ask @value{GDBN} to print more messages,
19092 to see how many times the problems occur, with the @code{set
19093 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
19096 The messages currently printed, and their meanings, include:
19099 @item inner block not inside outer block in @var{symbol}
19101 The symbol information shows where symbol scopes begin and end
19102 (such as at the start of a function or a block of statements). This
19103 error indicates that an inner scope block is not fully contained
19104 in its outer scope blocks.
19106 @value{GDBN} circumvents the problem by treating the inner block as if it had
19107 the same scope as the outer block. In the error message, @var{symbol}
19108 may be shown as ``@code{(don't know)}'' if the outer block is not a
19111 @item block at @var{address} out of order
19113 The symbol information for symbol scope blocks should occur in
19114 order of increasing addresses. This error indicates that it does not
19117 @value{GDBN} does not circumvent this problem, and has trouble
19118 locating symbols in the source file whose symbols it is reading. (You
19119 can often determine what source file is affected by specifying
19120 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
19123 @item bad block start address patched
19125 The symbol information for a symbol scope block has a start address
19126 smaller than the address of the preceding source line. This is known
19127 to occur in the SunOS 4.1.1 (and earlier) C compiler.
19129 @value{GDBN} circumvents the problem by treating the symbol scope block as
19130 starting on the previous source line.
19132 @item bad string table offset in symbol @var{n}
19135 Symbol number @var{n} contains a pointer into the string table which is
19136 larger than the size of the string table.
19138 @value{GDBN} circumvents the problem by considering the symbol to have the
19139 name @code{foo}, which may cause other problems if many symbols end up
19142 @item unknown symbol type @code{0x@var{nn}}
19144 The symbol information contains new data types that @value{GDBN} does
19145 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
19146 uncomprehended information, in hexadecimal.
19148 @value{GDBN} circumvents the error by ignoring this symbol information.
19149 This usually allows you to debug your program, though certain symbols
19150 are not accessible. If you encounter such a problem and feel like
19151 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
19152 on @code{complain}, then go up to the function @code{read_dbx_symtab}
19153 and examine @code{*bufp} to see the symbol.
19155 @item stub type has NULL name
19157 @value{GDBN} could not find the full definition for a struct or class.
19159 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
19160 The symbol information for a C@t{++} member function is missing some
19161 information that recent versions of the compiler should have output for
19164 @item info mismatch between compiler and debugger
19166 @value{GDBN} could not parse a type specification output by the compiler.
19171 @section GDB Data Files
19173 @cindex prefix for data files
19174 @value{GDBN} will sometimes read an auxiliary data file. These files
19175 are kept in a directory known as the @dfn{data directory}.
19177 You can set the data directory's name, and view the name @value{GDBN}
19178 is currently using.
19181 @kindex set data-directory
19182 @item set data-directory @var{directory}
19183 Set the directory which @value{GDBN} searches for auxiliary data files
19184 to @var{directory}.
19186 @kindex show data-directory
19187 @item show data-directory
19188 Show the directory @value{GDBN} searches for auxiliary data files.
19191 @cindex default data directory
19192 @cindex @samp{--with-gdb-datadir}
19193 You can set the default data directory by using the configure-time
19194 @samp{--with-gdb-datadir} option. If the data directory is inside
19195 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
19196 @samp{--exec-prefix}), then the default data directory will be updated
19197 automatically if the installed @value{GDBN} is moved to a new
19200 The data directory may also be specified with the
19201 @code{--data-directory} command line option.
19202 @xref{Mode Options}.
19205 @chapter Specifying a Debugging Target
19207 @cindex debugging target
19208 A @dfn{target} is the execution environment occupied by your program.
19210 Often, @value{GDBN} runs in the same host environment as your program;
19211 in that case, the debugging target is specified as a side effect when
19212 you use the @code{file} or @code{core} commands. When you need more
19213 flexibility---for example, running @value{GDBN} on a physically separate
19214 host, or controlling a standalone system over a serial port or a
19215 realtime system over a TCP/IP connection---you can use the @code{target}
19216 command to specify one of the target types configured for @value{GDBN}
19217 (@pxref{Target Commands, ,Commands for Managing Targets}).
19219 @cindex target architecture
19220 It is possible to build @value{GDBN} for several different @dfn{target
19221 architectures}. When @value{GDBN} is built like that, you can choose
19222 one of the available architectures with the @kbd{set architecture}
19226 @kindex set architecture
19227 @kindex show architecture
19228 @item set architecture @var{arch}
19229 This command sets the current target architecture to @var{arch}. The
19230 value of @var{arch} can be @code{"auto"}, in addition to one of the
19231 supported architectures.
19233 @item show architecture
19234 Show the current target architecture.
19236 @item set processor
19238 @kindex set processor
19239 @kindex show processor
19240 These are alias commands for, respectively, @code{set architecture}
19241 and @code{show architecture}.
19245 * Active Targets:: Active targets
19246 * Target Commands:: Commands for managing targets
19247 * Byte Order:: Choosing target byte order
19250 @node Active Targets
19251 @section Active Targets
19253 @cindex stacking targets
19254 @cindex active targets
19255 @cindex multiple targets
19257 There are multiple classes of targets such as: processes, executable files or
19258 recording sessions. Core files belong to the process class, making core file
19259 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
19260 on multiple active targets, one in each class. This allows you to (for
19261 example) start a process and inspect its activity, while still having access to
19262 the executable file after the process finishes. Or if you start process
19263 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
19264 presented a virtual layer of the recording target, while the process target
19265 remains stopped at the chronologically last point of the process execution.
19267 Use the @code{core-file} and @code{exec-file} commands to select a new core
19268 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
19269 specify as a target a process that is already running, use the @code{attach}
19270 command (@pxref{Attach, ,Debugging an Already-running Process}).
19272 @node Target Commands
19273 @section Commands for Managing Targets
19276 @item target @var{type} @var{parameters}
19277 Connects the @value{GDBN} host environment to a target machine or
19278 process. A target is typically a protocol for talking to debugging
19279 facilities. You use the argument @var{type} to specify the type or
19280 protocol of the target machine.
19282 Further @var{parameters} are interpreted by the target protocol, but
19283 typically include things like device names or host names to connect
19284 with, process numbers, and baud rates.
19286 The @code{target} command does not repeat if you press @key{RET} again
19287 after executing the command.
19289 @kindex help target
19291 Displays the names of all targets available. To display targets
19292 currently selected, use either @code{info target} or @code{info files}
19293 (@pxref{Files, ,Commands to Specify Files}).
19295 @item help target @var{name}
19296 Describe a particular target, including any parameters necessary to
19299 @kindex set gnutarget
19300 @item set gnutarget @var{args}
19301 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
19302 knows whether it is reading an @dfn{executable},
19303 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
19304 with the @code{set gnutarget} command. Unlike most @code{target} commands,
19305 with @code{gnutarget} the @code{target} refers to a program, not a machine.
19308 @emph{Warning:} To specify a file format with @code{set gnutarget},
19309 you must know the actual BFD name.
19313 @xref{Files, , Commands to Specify Files}.
19315 @kindex show gnutarget
19316 @item show gnutarget
19317 Use the @code{show gnutarget} command to display what file format
19318 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
19319 @value{GDBN} will determine the file format for each file automatically,
19320 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
19323 @cindex common targets
19324 Here are some common targets (available, or not, depending on the GDB
19329 @item target exec @var{program}
19330 @cindex executable file target
19331 An executable file. @samp{target exec @var{program}} is the same as
19332 @samp{exec-file @var{program}}.
19334 @item target core @var{filename}
19335 @cindex core dump file target
19336 A core dump file. @samp{target core @var{filename}} is the same as
19337 @samp{core-file @var{filename}}.
19339 @item target remote @var{medium}
19340 @cindex remote target
19341 A remote system connected to @value{GDBN} via a serial line or network
19342 connection. This command tells @value{GDBN} to use its own remote
19343 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
19345 For example, if you have a board connected to @file{/dev/ttya} on the
19346 machine running @value{GDBN}, you could say:
19349 target remote /dev/ttya
19352 @code{target remote} supports the @code{load} command. This is only
19353 useful if you have some other way of getting the stub to the target
19354 system, and you can put it somewhere in memory where it won't get
19355 clobbered by the download.
19357 @item target sim @r{[}@var{simargs}@r{]} @dots{}
19358 @cindex built-in simulator target
19359 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
19367 works; however, you cannot assume that a specific memory map, device
19368 drivers, or even basic I/O is available, although some simulators do
19369 provide these. For info about any processor-specific simulator details,
19370 see the appropriate section in @ref{Embedded Processors, ,Embedded
19373 @item target native
19374 @cindex native target
19375 Setup for local/native process debugging. Useful to make the
19376 @code{run} command spawn native processes (likewise @code{attach},
19377 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
19378 (@pxref{set auto-connect-native-target}).
19382 Different targets are available on different configurations of @value{GDBN};
19383 your configuration may have more or fewer targets.
19385 Many remote targets require you to download the executable's code once
19386 you've successfully established a connection. You may wish to control
19387 various aspects of this process.
19392 @kindex set hash@r{, for remote monitors}
19393 @cindex hash mark while downloading
19394 This command controls whether a hash mark @samp{#} is displayed while
19395 downloading a file to the remote monitor. If on, a hash mark is
19396 displayed after each S-record is successfully downloaded to the
19400 @kindex show hash@r{, for remote monitors}
19401 Show the current status of displaying the hash mark.
19403 @item set debug monitor
19404 @kindex set debug monitor
19405 @cindex display remote monitor communications
19406 Enable or disable display of communications messages between
19407 @value{GDBN} and the remote monitor.
19409 @item show debug monitor
19410 @kindex show debug monitor
19411 Show the current status of displaying communications between
19412 @value{GDBN} and the remote monitor.
19417 @kindex load @var{filename}
19418 @item load @var{filename}
19420 Depending on what remote debugging facilities are configured into
19421 @value{GDBN}, the @code{load} command may be available. Where it exists, it
19422 is meant to make @var{filename} (an executable) available for debugging
19423 on the remote system---by downloading, or dynamic linking, for example.
19424 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
19425 the @code{add-symbol-file} command.
19427 If your @value{GDBN} does not have a @code{load} command, attempting to
19428 execute it gets the error message ``@code{You can't do that when your
19429 target is @dots{}}''
19431 The file is loaded at whatever address is specified in the executable.
19432 For some object file formats, you can specify the load address when you
19433 link the program; for other formats, like a.out, the object file format
19434 specifies a fixed address.
19435 @c FIXME! This would be a good place for an xref to the GNU linker doc.
19437 Depending on the remote side capabilities, @value{GDBN} may be able to
19438 load programs into flash memory.
19440 @code{load} does not repeat if you press @key{RET} again after using it.
19444 @section Choosing Target Byte Order
19446 @cindex choosing target byte order
19447 @cindex target byte order
19449 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
19450 offer the ability to run either big-endian or little-endian byte
19451 orders. Usually the executable or symbol will include a bit to
19452 designate the endian-ness, and you will not need to worry about
19453 which to use. However, you may still find it useful to adjust
19454 @value{GDBN}'s idea of processor endian-ness manually.
19458 @item set endian big
19459 Instruct @value{GDBN} to assume the target is big-endian.
19461 @item set endian little
19462 Instruct @value{GDBN} to assume the target is little-endian.
19464 @item set endian auto
19465 Instruct @value{GDBN} to use the byte order associated with the
19469 Display @value{GDBN}'s current idea of the target byte order.
19473 Note that these commands merely adjust interpretation of symbolic
19474 data on the host, and that they have absolutely no effect on the
19478 @node Remote Debugging
19479 @chapter Debugging Remote Programs
19480 @cindex remote debugging
19482 If you are trying to debug a program running on a machine that cannot run
19483 @value{GDBN} in the usual way, it is often useful to use remote debugging.
19484 For example, you might use remote debugging on an operating system kernel,
19485 or on a small system which does not have a general purpose operating system
19486 powerful enough to run a full-featured debugger.
19488 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
19489 to make this work with particular debugging targets. In addition,
19490 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
19491 but not specific to any particular target system) which you can use if you
19492 write the remote stubs---the code that runs on the remote system to
19493 communicate with @value{GDBN}.
19495 Other remote targets may be available in your
19496 configuration of @value{GDBN}; use @code{help target} to list them.
19499 * Connecting:: Connecting to a remote target
19500 * File Transfer:: Sending files to a remote system
19501 * Server:: Using the gdbserver program
19502 * Remote Configuration:: Remote configuration
19503 * Remote Stub:: Implementing a remote stub
19507 @section Connecting to a Remote Target
19508 @cindex remote debugging, connecting
19509 @cindex @code{gdbserver}, connecting
19510 @cindex remote debugging, types of connections
19511 @cindex @code{gdbserver}, types of connections
19512 @cindex @code{gdbserver}, @code{target remote} mode
19513 @cindex @code{gdbserver}, @code{target extended-remote} mode
19515 This section describes how to connect to a remote target, including the
19516 types of connections and their differences, how to set up executable and
19517 symbol files on the host and target, and the commands used for
19518 connecting to and disconnecting from the remote target.
19520 @subsection Types of Remote Connections
19522 @value{GDBN} supports two types of remote connections, @code{target remote}
19523 mode and @code{target extended-remote} mode. Note that many remote targets
19524 support only @code{target remote} mode. There are several major
19525 differences between the two types of connections, enumerated here:
19529 @cindex remote debugging, detach and program exit
19530 @item Result of detach or program exit
19531 @strong{With target remote mode:} When the debugged program exits or you
19532 detach from it, @value{GDBN} disconnects from the target. When using
19533 @code{gdbserver}, @code{gdbserver} will exit.
19535 @strong{With target extended-remote mode:} When the debugged program exits or
19536 you detach from it, @value{GDBN} remains connected to the target, even
19537 though no program is running. You can rerun the program, attach to a
19538 running program, or use @code{monitor} commands specific to the target.
19540 When using @code{gdbserver} in this case, it does not exit unless it was
19541 invoked using the @option{--once} option. If the @option{--once} option
19542 was not used, you can ask @code{gdbserver} to exit using the
19543 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
19545 @item Specifying the program to debug
19546 For both connection types you use the @code{file} command to specify the
19547 program on the host system. If you are using @code{gdbserver} there are
19548 some differences in how to specify the location of the program on the
19551 @strong{With target remote mode:} You must either specify the program to debug
19552 on the @code{gdbserver} command line or use the @option{--attach} option
19553 (@pxref{Attaching to a program,,Attaching to a Running Program}).
19555 @cindex @option{--multi}, @code{gdbserver} option
19556 @strong{With target extended-remote mode:} You may specify the program to debug
19557 on the @code{gdbserver} command line, or you can load the program or attach
19558 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
19560 @anchor{--multi Option in Types of Remote Connnections}
19561 You can start @code{gdbserver} without supplying an initial command to run
19562 or process ID to attach. To do this, use the @option{--multi} command line
19563 option. Then you can connect using @code{target extended-remote} and start
19564 the program you want to debug (see below for details on using the
19565 @code{run} command in this scenario). Note that the conditions under which
19566 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
19567 (@code{target remote} or @code{target extended-remote}). The
19568 @option{--multi} option to @code{gdbserver} has no influence on that.
19570 @item The @code{run} command
19571 @strong{With target remote mode:} The @code{run} command is not
19572 supported. Once a connection has been established, you can use all
19573 the usual @value{GDBN} commands to examine and change data. The
19574 remote program is already running, so you can use commands like
19575 @kbd{step} and @kbd{continue}.
19577 @strong{With target extended-remote mode:} The @code{run} command is
19578 supported. The @code{run} command uses the value set by
19579 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
19580 the program to run. Command line arguments are supported, except for
19581 wildcard expansion and I/O redirection (@pxref{Arguments}).
19583 If you specify the program to debug on the command line, then the
19584 @code{run} command is not required to start execution, and you can
19585 resume using commands like @kbd{step} and @kbd{continue} as with
19586 @code{target remote} mode.
19588 @anchor{Attaching in Types of Remote Connections}
19590 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
19591 not supported. To attach to a running program using @code{gdbserver}, you
19592 must use the @option{--attach} option (@pxref{Running gdbserver}).
19594 @strong{With target extended-remote mode:} To attach to a running program,
19595 you may use the @code{attach} command after the connection has been
19596 established. If you are using @code{gdbserver}, you may also invoke
19597 @code{gdbserver} using the @option{--attach} option
19598 (@pxref{Running gdbserver}).
19602 @anchor{Host and target files}
19603 @subsection Host and Target Files
19604 @cindex remote debugging, symbol files
19605 @cindex symbol files, remote debugging
19607 @value{GDBN}, running on the host, needs access to symbol and debugging
19608 information for your program running on the target. This requires
19609 access to an unstripped copy of your program, and possibly any associated
19610 symbol files. Note that this section applies equally to both @code{target
19611 remote} mode and @code{target extended-remote} mode.
19613 Some remote targets (@pxref{qXfer executable filename read}, and
19614 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
19615 the same connection used to communicate with @value{GDBN}. With such a
19616 target, if the remote program is unstripped, the only command you need is
19617 @code{target remote} (or @code{target extended-remote}).
19619 If the remote program is stripped, or the target does not support remote
19620 program file access, start up @value{GDBN} using the name of the local
19621 unstripped copy of your program as the first argument, or use the
19622 @code{file} command. Use @code{set sysroot} to specify the location (on
19623 the host) of target libraries (unless your @value{GDBN} was compiled with
19624 the correct sysroot using @code{--with-sysroot}). Alternatively, you
19625 may use @code{set solib-search-path} to specify how @value{GDBN} locates
19628 The symbol file and target libraries must exactly match the executable
19629 and libraries on the target, with one exception: the files on the host
19630 system should not be stripped, even if the files on the target system
19631 are. Mismatched or missing files will lead to confusing results
19632 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
19633 files may also prevent @code{gdbserver} from debugging multi-threaded
19636 @subsection Remote Connection Commands
19637 @cindex remote connection commands
19638 @value{GDBN} can communicate with the target over a serial line, or
19639 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
19640 each case, @value{GDBN} uses the same protocol for debugging your
19641 program; only the medium carrying the debugging packets varies. The
19642 @code{target remote} and @code{target extended-remote} commands
19643 establish a connection to the target. Both commands accept the same
19644 arguments, which indicate the medium to use:
19648 @item target remote @var{serial-device}
19649 @itemx target extended-remote @var{serial-device}
19650 @cindex serial line, @code{target remote}
19651 Use @var{serial-device} to communicate with the target. For example,
19652 to use a serial line connected to the device named @file{/dev/ttyb}:
19655 target remote /dev/ttyb
19658 If you're using a serial line, you may want to give @value{GDBN} the
19659 @samp{--baud} option, or use the @code{set serial baud} command
19660 (@pxref{Remote Configuration, set serial baud}) before the
19661 @code{target} command.
19663 @item target remote @code{@var{host}:@var{port}}
19664 @itemx target remote @code{tcp:@var{host}:@var{port}}
19665 @itemx target extended-remote @code{@var{host}:@var{port}}
19666 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
19667 @cindex @acronym{TCP} port, @code{target remote}
19668 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
19669 The @var{host} may be either a host name or a numeric @acronym{IP}
19670 address; @var{port} must be a decimal number. The @var{host} could be
19671 the target machine itself, if it is directly connected to the net, or
19672 it might be a terminal server which in turn has a serial line to the
19675 For example, to connect to port 2828 on a terminal server named
19679 target remote manyfarms:2828
19682 If your remote target is actually running on the same machine as your
19683 debugger session (e.g.@: a simulator for your target running on the
19684 same host), you can omit the hostname. For example, to connect to
19685 port 1234 on your local machine:
19688 target remote :1234
19692 Note that the colon is still required here.
19694 @item target remote @code{udp:@var{host}:@var{port}}
19695 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
19696 @cindex @acronym{UDP} port, @code{target remote}
19697 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
19698 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
19701 target remote udp:manyfarms:2828
19704 When using a @acronym{UDP} connection for remote debugging, you should
19705 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
19706 can silently drop packets on busy or unreliable networks, which will
19707 cause havoc with your debugging session.
19709 @item target remote | @var{command}
19710 @itemx target extended-remote | @var{command}
19711 @cindex pipe, @code{target remote} to
19712 Run @var{command} in the background and communicate with it using a
19713 pipe. The @var{command} is a shell command, to be parsed and expanded
19714 by the system's command shell, @code{/bin/sh}; it should expect remote
19715 protocol packets on its standard input, and send replies on its
19716 standard output. You could use this to run a stand-alone simulator
19717 that speaks the remote debugging protocol, to make net connections
19718 using programs like @code{ssh}, or for other similar tricks.
19720 If @var{command} closes its standard output (perhaps by exiting),
19721 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
19722 program has already exited, this will have no effect.)
19726 @cindex interrupting remote programs
19727 @cindex remote programs, interrupting
19728 Whenever @value{GDBN} is waiting for the remote program, if you type the
19729 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
19730 program. This may or may not succeed, depending in part on the hardware
19731 and the serial drivers the remote system uses. If you type the
19732 interrupt character once again, @value{GDBN} displays this prompt:
19735 Interrupted while waiting for the program.
19736 Give up (and stop debugging it)? (y or n)
19739 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
19740 the remote debugging session. (If you decide you want to try again later,
19741 you can use @kbd{target remote} again to connect once more.) If you type
19742 @kbd{n}, @value{GDBN} goes back to waiting.
19744 In @code{target extended-remote} mode, typing @kbd{n} will leave
19745 @value{GDBN} connected to the target.
19748 @kindex detach (remote)
19750 When you have finished debugging the remote program, you can use the
19751 @code{detach} command to release it from @value{GDBN} control.
19752 Detaching from the target normally resumes its execution, but the results
19753 will depend on your particular remote stub. After the @code{detach}
19754 command in @code{target remote} mode, @value{GDBN} is free to connect to
19755 another target. In @code{target extended-remote} mode, @value{GDBN} is
19756 still connected to the target.
19760 The @code{disconnect} command closes the connection to the target, and
19761 the target is generally not resumed. It will wait for @value{GDBN}
19762 (this instance or another one) to connect and continue debugging. After
19763 the @code{disconnect} command, @value{GDBN} is again free to connect to
19766 @cindex send command to remote monitor
19767 @cindex extend @value{GDBN} for remote targets
19768 @cindex add new commands for external monitor
19770 @item monitor @var{cmd}
19771 This command allows you to send arbitrary commands directly to the
19772 remote monitor. Since @value{GDBN} doesn't care about the commands it
19773 sends like this, this command is the way to extend @value{GDBN}---you
19774 can add new commands that only the external monitor will understand
19778 @node File Transfer
19779 @section Sending files to a remote system
19780 @cindex remote target, file transfer
19781 @cindex file transfer
19782 @cindex sending files to remote systems
19784 Some remote targets offer the ability to transfer files over the same
19785 connection used to communicate with @value{GDBN}. This is convenient
19786 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
19787 running @code{gdbserver} over a network interface. For other targets,
19788 e.g.@: embedded devices with only a single serial port, this may be
19789 the only way to upload or download files.
19791 Not all remote targets support these commands.
19795 @item remote put @var{hostfile} @var{targetfile}
19796 Copy file @var{hostfile} from the host system (the machine running
19797 @value{GDBN}) to @var{targetfile} on the target system.
19800 @item remote get @var{targetfile} @var{hostfile}
19801 Copy file @var{targetfile} from the target system to @var{hostfile}
19802 on the host system.
19804 @kindex remote delete
19805 @item remote delete @var{targetfile}
19806 Delete @var{targetfile} from the target system.
19811 @section Using the @code{gdbserver} Program
19814 @cindex remote connection without stubs
19815 @code{gdbserver} is a control program for Unix-like systems, which
19816 allows you to connect your program with a remote @value{GDBN} via
19817 @code{target remote} or @code{target extended-remote}---but without
19818 linking in the usual debugging stub.
19820 @code{gdbserver} is not a complete replacement for the debugging stubs,
19821 because it requires essentially the same operating-system facilities
19822 that @value{GDBN} itself does. In fact, a system that can run
19823 @code{gdbserver} to connect to a remote @value{GDBN} could also run
19824 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
19825 because it is a much smaller program than @value{GDBN} itself. It is
19826 also easier to port than all of @value{GDBN}, so you may be able to get
19827 started more quickly on a new system by using @code{gdbserver}.
19828 Finally, if you develop code for real-time systems, you may find that
19829 the tradeoffs involved in real-time operation make it more convenient to
19830 do as much development work as possible on another system, for example
19831 by cross-compiling. You can use @code{gdbserver} to make a similar
19832 choice for debugging.
19834 @value{GDBN} and @code{gdbserver} communicate via either a serial line
19835 or a TCP connection, using the standard @value{GDBN} remote serial
19839 @emph{Warning:} @code{gdbserver} does not have any built-in security.
19840 Do not run @code{gdbserver} connected to any public network; a
19841 @value{GDBN} connection to @code{gdbserver} provides access to the
19842 target system with the same privileges as the user running
19846 @anchor{Running gdbserver}
19847 @subsection Running @code{gdbserver}
19848 @cindex arguments, to @code{gdbserver}
19849 @cindex @code{gdbserver}, command-line arguments
19851 Run @code{gdbserver} on the target system. You need a copy of the
19852 program you want to debug, including any libraries it requires.
19853 @code{gdbserver} does not need your program's symbol table, so you can
19854 strip the program if necessary to save space. @value{GDBN} on the host
19855 system does all the symbol handling.
19857 To use the server, you must tell it how to communicate with @value{GDBN};
19858 the name of your program; and the arguments for your program. The usual
19862 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
19865 @var{comm} is either a device name (to use a serial line), or a TCP
19866 hostname and portnumber, or @code{-} or @code{stdio} to use
19867 stdin/stdout of @code{gdbserver}.
19868 For example, to debug Emacs with the argument
19869 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
19873 target> gdbserver /dev/com1 emacs foo.txt
19876 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
19879 To use a TCP connection instead of a serial line:
19882 target> gdbserver host:2345 emacs foo.txt
19885 The only difference from the previous example is the first argument,
19886 specifying that you are communicating with the host @value{GDBN} via
19887 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
19888 expect a TCP connection from machine @samp{host} to local TCP port 2345.
19889 (Currently, the @samp{host} part is ignored.) You can choose any number
19890 you want for the port number as long as it does not conflict with any
19891 TCP ports already in use on the target system (for example, @code{23} is
19892 reserved for @code{telnet}).@footnote{If you choose a port number that
19893 conflicts with another service, @code{gdbserver} prints an error message
19894 and exits.} You must use the same port number with the host @value{GDBN}
19895 @code{target remote} command.
19897 The @code{stdio} connection is useful when starting @code{gdbserver}
19901 (gdb) target remote | ssh -T hostname gdbserver - hello
19904 The @samp{-T} option to ssh is provided because we don't need a remote pty,
19905 and we don't want escape-character handling. Ssh does this by default when
19906 a command is provided, the flag is provided to make it explicit.
19907 You could elide it if you want to.
19909 Programs started with stdio-connected gdbserver have @file{/dev/null} for
19910 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
19911 display through a pipe connected to gdbserver.
19912 Both @code{stdout} and @code{stderr} use the same pipe.
19914 @anchor{Attaching to a program}
19915 @subsubsection Attaching to a Running Program
19916 @cindex attach to a program, @code{gdbserver}
19917 @cindex @option{--attach}, @code{gdbserver} option
19919 On some targets, @code{gdbserver} can also attach to running programs.
19920 This is accomplished via the @code{--attach} argument. The syntax is:
19923 target> gdbserver --attach @var{comm} @var{pid}
19926 @var{pid} is the process ID of a currently running process. It isn't
19927 necessary to point @code{gdbserver} at a binary for the running process.
19929 In @code{target extended-remote} mode, you can also attach using the
19930 @value{GDBN} attach command
19931 (@pxref{Attaching in Types of Remote Connections}).
19934 You can debug processes by name instead of process ID if your target has the
19935 @code{pidof} utility:
19938 target> gdbserver --attach @var{comm} `pidof @var{program}`
19941 In case more than one copy of @var{program} is running, or @var{program}
19942 has multiple threads, most versions of @code{pidof} support the
19943 @code{-s} option to only return the first process ID.
19945 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
19947 This section applies only when @code{gdbserver} is run to listen on a TCP
19950 @code{gdbserver} normally terminates after all of its debugged processes have
19951 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
19952 extended-remote}, @code{gdbserver} stays running even with no processes left.
19953 @value{GDBN} normally terminates the spawned debugged process on its exit,
19954 which normally also terminates @code{gdbserver} in the @kbd{target remote}
19955 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
19956 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
19957 stays running even in the @kbd{target remote} mode.
19959 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
19960 Such reconnecting is useful for features like @ref{disconnected tracing}. For
19961 completeness, at most one @value{GDBN} can be connected at a time.
19963 @cindex @option{--once}, @code{gdbserver} option
19964 By default, @code{gdbserver} keeps the listening TCP port open, so that
19965 subsequent connections are possible. However, if you start @code{gdbserver}
19966 with the @option{--once} option, it will stop listening for any further
19967 connection attempts after connecting to the first @value{GDBN} session. This
19968 means no further connections to @code{gdbserver} will be possible after the
19969 first one. It also means @code{gdbserver} will terminate after the first
19970 connection with remote @value{GDBN} has closed, even for unexpectedly closed
19971 connections and even in the @kbd{target extended-remote} mode. The
19972 @option{--once} option allows reusing the same port number for connecting to
19973 multiple instances of @code{gdbserver} running on the same host, since each
19974 instance closes its port after the first connection.
19976 @anchor{Other Command-Line Arguments for gdbserver}
19977 @subsubsection Other Command-Line Arguments for @code{gdbserver}
19979 You can use the @option{--multi} option to start @code{gdbserver} without
19980 specifying a program to debug or a process to attach to. Then you can
19981 attach in @code{target extended-remote} mode and run or attach to a
19982 program. For more information,
19983 @pxref{--multi Option in Types of Remote Connnections}.
19985 @cindex @option{--debug}, @code{gdbserver} option
19986 The @option{--debug} option tells @code{gdbserver} to display extra
19987 status information about the debugging process.
19988 @cindex @option{--remote-debug}, @code{gdbserver} option
19989 The @option{--remote-debug} option tells @code{gdbserver} to display
19990 remote protocol debug output. These options are intended for
19991 @code{gdbserver} development and for bug reports to the developers.
19993 @cindex @option{--debug-format}, @code{gdbserver} option
19994 The @option{--debug-format=option1[,option2,...]} option tells
19995 @code{gdbserver} to include additional information in each output.
19996 Possible options are:
20000 Turn off all extra information in debugging output.
20002 Turn on all extra information in debugging output.
20004 Include a timestamp in each line of debugging output.
20007 Options are processed in order. Thus, for example, if @option{none}
20008 appears last then no additional information is added to debugging output.
20010 @cindex @option{--wrapper}, @code{gdbserver} option
20011 The @option{--wrapper} option specifies a wrapper to launch programs
20012 for debugging. The option should be followed by the name of the
20013 wrapper, then any command-line arguments to pass to the wrapper, then
20014 @kbd{--} indicating the end of the wrapper arguments.
20016 @code{gdbserver} runs the specified wrapper program with a combined
20017 command line including the wrapper arguments, then the name of the
20018 program to debug, then any arguments to the program. The wrapper
20019 runs until it executes your program, and then @value{GDBN} gains control.
20021 You can use any program that eventually calls @code{execve} with
20022 its arguments as a wrapper. Several standard Unix utilities do
20023 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
20024 with @code{exec "$@@"} will also work.
20026 For example, you can use @code{env} to pass an environment variable to
20027 the debugged program, without setting the variable in @code{gdbserver}'s
20031 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
20034 @subsection Connecting to @code{gdbserver}
20036 The basic procedure for connecting to the remote target is:
20040 Run @value{GDBN} on the host system.
20043 Make sure you have the necessary symbol files
20044 (@pxref{Host and target files}).
20045 Load symbols for your application using the @code{file} command before you
20046 connect. Use @code{set sysroot} to locate target libraries (unless your
20047 @value{GDBN} was compiled with the correct sysroot using
20048 @code{--with-sysroot}).
20051 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
20052 For TCP connections, you must start up @code{gdbserver} prior to using
20053 the @code{target} command. Otherwise you may get an error whose
20054 text depends on the host system, but which usually looks something like
20055 @samp{Connection refused}. Don't use the @code{load}
20056 command in @value{GDBN} when using @code{target remote} mode, since the
20057 program is already on the target.
20061 @anchor{Monitor Commands for gdbserver}
20062 @subsection Monitor Commands for @code{gdbserver}
20063 @cindex monitor commands, for @code{gdbserver}
20065 During a @value{GDBN} session using @code{gdbserver}, you can use the
20066 @code{monitor} command to send special requests to @code{gdbserver}.
20067 Here are the available commands.
20071 List the available monitor commands.
20073 @item monitor set debug 0
20074 @itemx monitor set debug 1
20075 Disable or enable general debugging messages.
20077 @item monitor set remote-debug 0
20078 @itemx monitor set remote-debug 1
20079 Disable or enable specific debugging messages associated with the remote
20080 protocol (@pxref{Remote Protocol}).
20082 @item monitor set debug-format option1@r{[},option2,...@r{]}
20083 Specify additional text to add to debugging messages.
20084 Possible options are:
20088 Turn off all extra information in debugging output.
20090 Turn on all extra information in debugging output.
20092 Include a timestamp in each line of debugging output.
20095 Options are processed in order. Thus, for example, if @option{none}
20096 appears last then no additional information is added to debugging output.
20098 @item monitor set libthread-db-search-path [PATH]
20099 @cindex gdbserver, search path for @code{libthread_db}
20100 When this command is issued, @var{path} is a colon-separated list of
20101 directories to search for @code{libthread_db} (@pxref{Threads,,set
20102 libthread-db-search-path}). If you omit @var{path},
20103 @samp{libthread-db-search-path} will be reset to its default value.
20105 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
20106 not supported in @code{gdbserver}.
20109 Tell gdbserver to exit immediately. This command should be followed by
20110 @code{disconnect} to close the debugging session. @code{gdbserver} will
20111 detach from any attached processes and kill any processes it created.
20112 Use @code{monitor exit} to terminate @code{gdbserver} at the end
20113 of a multi-process mode debug session.
20117 @subsection Tracepoints support in @code{gdbserver}
20118 @cindex tracepoints support in @code{gdbserver}
20120 On some targets, @code{gdbserver} supports tracepoints, fast
20121 tracepoints and static tracepoints.
20123 For fast or static tracepoints to work, a special library called the
20124 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
20125 This library is built and distributed as an integral part of
20126 @code{gdbserver}. In addition, support for static tracepoints
20127 requires building the in-process agent library with static tracepoints
20128 support. At present, the UST (LTTng Userspace Tracer,
20129 @url{http://lttng.org/ust}) tracing engine is supported. This support
20130 is automatically available if UST development headers are found in the
20131 standard include path when @code{gdbserver} is built, or if
20132 @code{gdbserver} was explicitly configured using @option{--with-ust}
20133 to point at such headers. You can explicitly disable the support
20134 using @option{--with-ust=no}.
20136 There are several ways to load the in-process agent in your program:
20139 @item Specifying it as dependency at link time
20141 You can link your program dynamically with the in-process agent
20142 library. On most systems, this is accomplished by adding
20143 @code{-linproctrace} to the link command.
20145 @item Using the system's preloading mechanisms
20147 You can force loading the in-process agent at startup time by using
20148 your system's support for preloading shared libraries. Many Unixes
20149 support the concept of preloading user defined libraries. In most
20150 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
20151 in the environment. See also the description of @code{gdbserver}'s
20152 @option{--wrapper} command line option.
20154 @item Using @value{GDBN} to force loading the agent at run time
20156 On some systems, you can force the inferior to load a shared library,
20157 by calling a dynamic loader function in the inferior that takes care
20158 of dynamically looking up and loading a shared library. On most Unix
20159 systems, the function is @code{dlopen}. You'll use the @code{call}
20160 command for that. For example:
20163 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
20166 Note that on most Unix systems, for the @code{dlopen} function to be
20167 available, the program needs to be linked with @code{-ldl}.
20170 On systems that have a userspace dynamic loader, like most Unix
20171 systems, when you connect to @code{gdbserver} using @code{target
20172 remote}, you'll find that the program is stopped at the dynamic
20173 loader's entry point, and no shared library has been loaded in the
20174 program's address space yet, including the in-process agent. In that
20175 case, before being able to use any of the fast or static tracepoints
20176 features, you need to let the loader run and load the shared
20177 libraries. The simplest way to do that is to run the program to the
20178 main procedure. E.g., if debugging a C or C@t{++} program, start
20179 @code{gdbserver} like so:
20182 $ gdbserver :9999 myprogram
20185 Start GDB and connect to @code{gdbserver} like so, and run to main:
20189 (@value{GDBP}) target remote myhost:9999
20190 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
20191 (@value{GDBP}) b main
20192 (@value{GDBP}) continue
20195 The in-process tracing agent library should now be loaded into the
20196 process; you can confirm it with the @code{info sharedlibrary}
20197 command, which will list @file{libinproctrace.so} as loaded in the
20198 process. You are now ready to install fast tracepoints, list static
20199 tracepoint markers, probe static tracepoints markers, and start
20202 @node Remote Configuration
20203 @section Remote Configuration
20206 @kindex show remote
20207 This section documents the configuration options available when
20208 debugging remote programs. For the options related to the File I/O
20209 extensions of the remote protocol, see @ref{system,
20210 system-call-allowed}.
20213 @item set remoteaddresssize @var{bits}
20214 @cindex address size for remote targets
20215 @cindex bits in remote address
20216 Set the maximum size of address in a memory packet to the specified
20217 number of bits. @value{GDBN} will mask off the address bits above
20218 that number, when it passes addresses to the remote target. The
20219 default value is the number of bits in the target's address.
20221 @item show remoteaddresssize
20222 Show the current value of remote address size in bits.
20224 @item set serial baud @var{n}
20225 @cindex baud rate for remote targets
20226 Set the baud rate for the remote serial I/O to @var{n} baud. The
20227 value is used to set the speed of the serial port used for debugging
20230 @item show serial baud
20231 Show the current speed of the remote connection.
20233 @item set serial parity @var{parity}
20234 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
20235 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
20237 @item show serial parity
20238 Show the current parity of the serial port.
20240 @item set remotebreak
20241 @cindex interrupt remote programs
20242 @cindex BREAK signal instead of Ctrl-C
20243 @anchor{set remotebreak}
20244 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
20245 when you type @kbd{Ctrl-c} to interrupt the program running
20246 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
20247 character instead. The default is off, since most remote systems
20248 expect to see @samp{Ctrl-C} as the interrupt signal.
20250 @item show remotebreak
20251 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
20252 interrupt the remote program.
20254 @item set remoteflow on
20255 @itemx set remoteflow off
20256 @kindex set remoteflow
20257 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
20258 on the serial port used to communicate to the remote target.
20260 @item show remoteflow
20261 @kindex show remoteflow
20262 Show the current setting of hardware flow control.
20264 @item set remotelogbase @var{base}
20265 Set the base (a.k.a.@: radix) of logging serial protocol
20266 communications to @var{base}. Supported values of @var{base} are:
20267 @code{ascii}, @code{octal}, and @code{hex}. The default is
20270 @item show remotelogbase
20271 Show the current setting of the radix for logging remote serial
20274 @item set remotelogfile @var{file}
20275 @cindex record serial communications on file
20276 Record remote serial communications on the named @var{file}. The
20277 default is not to record at all.
20279 @item show remotelogfile.
20280 Show the current setting of the file name on which to record the
20281 serial communications.
20283 @item set remotetimeout @var{num}
20284 @cindex timeout for serial communications
20285 @cindex remote timeout
20286 Set the timeout limit to wait for the remote target to respond to
20287 @var{num} seconds. The default is 2 seconds.
20289 @item show remotetimeout
20290 Show the current number of seconds to wait for the remote target
20293 @cindex limit hardware breakpoints and watchpoints
20294 @cindex remote target, limit break- and watchpoints
20295 @anchor{set remote hardware-watchpoint-limit}
20296 @anchor{set remote hardware-breakpoint-limit}
20297 @item set remote hardware-watchpoint-limit @var{limit}
20298 @itemx set remote hardware-breakpoint-limit @var{limit}
20299 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
20300 watchpoints. A limit of -1, the default, is treated as unlimited.
20302 @cindex limit hardware watchpoints length
20303 @cindex remote target, limit watchpoints length
20304 @anchor{set remote hardware-watchpoint-length-limit}
20305 @item set remote hardware-watchpoint-length-limit @var{limit}
20306 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
20307 a remote hardware watchpoint. A limit of -1, the default, is treated
20310 @item show remote hardware-watchpoint-length-limit
20311 Show the current limit (in bytes) of the maximum length of
20312 a remote hardware watchpoint.
20314 @item set remote exec-file @var{filename}
20315 @itemx show remote exec-file
20316 @anchor{set remote exec-file}
20317 @cindex executable file, for remote target
20318 Select the file used for @code{run} with @code{target
20319 extended-remote}. This should be set to a filename valid on the
20320 target system. If it is not set, the target will use a default
20321 filename (e.g.@: the last program run).
20323 @item set remote interrupt-sequence
20324 @cindex interrupt remote programs
20325 @cindex select Ctrl-C, BREAK or BREAK-g
20326 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
20327 @samp{BREAK-g} as the
20328 sequence to the remote target in order to interrupt the execution.
20329 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
20330 is high level of serial line for some certain time.
20331 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
20332 It is @code{BREAK} signal followed by character @code{g}.
20334 @item show interrupt-sequence
20335 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
20336 is sent by @value{GDBN} to interrupt the remote program.
20337 @code{BREAK-g} is BREAK signal followed by @code{g} and
20338 also known as Magic SysRq g.
20340 @item set remote interrupt-on-connect
20341 @cindex send interrupt-sequence on start
20342 Specify whether interrupt-sequence is sent to remote target when
20343 @value{GDBN} connects to it. This is mostly needed when you debug
20344 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
20345 which is known as Magic SysRq g in order to connect @value{GDBN}.
20347 @item show interrupt-on-connect
20348 Show whether interrupt-sequence is sent
20349 to remote target when @value{GDBN} connects to it.
20353 @item set tcp auto-retry on
20354 @cindex auto-retry, for remote TCP target
20355 Enable auto-retry for remote TCP connections. This is useful if the remote
20356 debugging agent is launched in parallel with @value{GDBN}; there is a race
20357 condition because the agent may not become ready to accept the connection
20358 before @value{GDBN} attempts to connect. When auto-retry is
20359 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
20360 to establish the connection using the timeout specified by
20361 @code{set tcp connect-timeout}.
20363 @item set tcp auto-retry off
20364 Do not auto-retry failed TCP connections.
20366 @item show tcp auto-retry
20367 Show the current auto-retry setting.
20369 @item set tcp connect-timeout @var{seconds}
20370 @itemx set tcp connect-timeout unlimited
20371 @cindex connection timeout, for remote TCP target
20372 @cindex timeout, for remote target connection
20373 Set the timeout for establishing a TCP connection to the remote target to
20374 @var{seconds}. The timeout affects both polling to retry failed connections
20375 (enabled by @code{set tcp auto-retry on}) and waiting for connections
20376 that are merely slow to complete, and represents an approximate cumulative
20377 value. If @var{seconds} is @code{unlimited}, there is no timeout and
20378 @value{GDBN} will keep attempting to establish a connection forever,
20379 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
20381 @item show tcp connect-timeout
20382 Show the current connection timeout setting.
20385 @cindex remote packets, enabling and disabling
20386 The @value{GDBN} remote protocol autodetects the packets supported by
20387 your debugging stub. If you need to override the autodetection, you
20388 can use these commands to enable or disable individual packets. Each
20389 packet can be set to @samp{on} (the remote target supports this
20390 packet), @samp{off} (the remote target does not support this packet),
20391 or @samp{auto} (detect remote target support for this packet). They
20392 all default to @samp{auto}. For more information about each packet,
20393 see @ref{Remote Protocol}.
20395 During normal use, you should not have to use any of these commands.
20396 If you do, that may be a bug in your remote debugging stub, or a bug
20397 in @value{GDBN}. You may want to report the problem to the
20398 @value{GDBN} developers.
20400 For each packet @var{name}, the command to enable or disable the
20401 packet is @code{set remote @var{name}-packet}. The available settings
20404 @multitable @columnfractions 0.28 0.32 0.25
20407 @tab Related Features
20409 @item @code{fetch-register}
20411 @tab @code{info registers}
20413 @item @code{set-register}
20417 @item @code{binary-download}
20419 @tab @code{load}, @code{set}
20421 @item @code{read-aux-vector}
20422 @tab @code{qXfer:auxv:read}
20423 @tab @code{info auxv}
20425 @item @code{symbol-lookup}
20426 @tab @code{qSymbol}
20427 @tab Detecting multiple threads
20429 @item @code{attach}
20430 @tab @code{vAttach}
20433 @item @code{verbose-resume}
20435 @tab Stepping or resuming multiple threads
20441 @item @code{software-breakpoint}
20445 @item @code{hardware-breakpoint}
20449 @item @code{write-watchpoint}
20453 @item @code{read-watchpoint}
20457 @item @code{access-watchpoint}
20461 @item @code{pid-to-exec-file}
20462 @tab @code{qXfer:exec-file:read}
20463 @tab @code{attach}, @code{run}
20465 @item @code{target-features}
20466 @tab @code{qXfer:features:read}
20467 @tab @code{set architecture}
20469 @item @code{library-info}
20470 @tab @code{qXfer:libraries:read}
20471 @tab @code{info sharedlibrary}
20473 @item @code{memory-map}
20474 @tab @code{qXfer:memory-map:read}
20475 @tab @code{info mem}
20477 @item @code{read-sdata-object}
20478 @tab @code{qXfer:sdata:read}
20479 @tab @code{print $_sdata}
20481 @item @code{read-spu-object}
20482 @tab @code{qXfer:spu:read}
20483 @tab @code{info spu}
20485 @item @code{write-spu-object}
20486 @tab @code{qXfer:spu:write}
20487 @tab @code{info spu}
20489 @item @code{read-siginfo-object}
20490 @tab @code{qXfer:siginfo:read}
20491 @tab @code{print $_siginfo}
20493 @item @code{write-siginfo-object}
20494 @tab @code{qXfer:siginfo:write}
20495 @tab @code{set $_siginfo}
20497 @item @code{threads}
20498 @tab @code{qXfer:threads:read}
20499 @tab @code{info threads}
20501 @item @code{get-thread-local-@*storage-address}
20502 @tab @code{qGetTLSAddr}
20503 @tab Displaying @code{__thread} variables
20505 @item @code{get-thread-information-block-address}
20506 @tab @code{qGetTIBAddr}
20507 @tab Display MS-Windows Thread Information Block.
20509 @item @code{search-memory}
20510 @tab @code{qSearch:memory}
20513 @item @code{supported-packets}
20514 @tab @code{qSupported}
20515 @tab Remote communications parameters
20517 @item @code{catch-syscalls}
20518 @tab @code{QCatchSyscalls}
20519 @tab @code{catch syscall}
20521 @item @code{pass-signals}
20522 @tab @code{QPassSignals}
20523 @tab @code{handle @var{signal}}
20525 @item @code{program-signals}
20526 @tab @code{QProgramSignals}
20527 @tab @code{handle @var{signal}}
20529 @item @code{hostio-close-packet}
20530 @tab @code{vFile:close}
20531 @tab @code{remote get}, @code{remote put}
20533 @item @code{hostio-open-packet}
20534 @tab @code{vFile:open}
20535 @tab @code{remote get}, @code{remote put}
20537 @item @code{hostio-pread-packet}
20538 @tab @code{vFile:pread}
20539 @tab @code{remote get}, @code{remote put}
20541 @item @code{hostio-pwrite-packet}
20542 @tab @code{vFile:pwrite}
20543 @tab @code{remote get}, @code{remote put}
20545 @item @code{hostio-unlink-packet}
20546 @tab @code{vFile:unlink}
20547 @tab @code{remote delete}
20549 @item @code{hostio-readlink-packet}
20550 @tab @code{vFile:readlink}
20553 @item @code{hostio-fstat-packet}
20554 @tab @code{vFile:fstat}
20557 @item @code{hostio-setfs-packet}
20558 @tab @code{vFile:setfs}
20561 @item @code{noack-packet}
20562 @tab @code{QStartNoAckMode}
20563 @tab Packet acknowledgment
20565 @item @code{osdata}
20566 @tab @code{qXfer:osdata:read}
20567 @tab @code{info os}
20569 @item @code{query-attached}
20570 @tab @code{qAttached}
20571 @tab Querying remote process attach state.
20573 @item @code{trace-buffer-size}
20574 @tab @code{QTBuffer:size}
20575 @tab @code{set trace-buffer-size}
20577 @item @code{trace-status}
20578 @tab @code{qTStatus}
20579 @tab @code{tstatus}
20581 @item @code{traceframe-info}
20582 @tab @code{qXfer:traceframe-info:read}
20583 @tab Traceframe info
20585 @item @code{install-in-trace}
20586 @tab @code{InstallInTrace}
20587 @tab Install tracepoint in tracing
20589 @item @code{disable-randomization}
20590 @tab @code{QDisableRandomization}
20591 @tab @code{set disable-randomization}
20593 @item @code{conditional-breakpoints-packet}
20594 @tab @code{Z0 and Z1}
20595 @tab @code{Support for target-side breakpoint condition evaluation}
20597 @item @code{multiprocess-extensions}
20598 @tab @code{multiprocess extensions}
20599 @tab Debug multiple processes and remote process PID awareness
20601 @item @code{swbreak-feature}
20602 @tab @code{swbreak stop reason}
20605 @item @code{hwbreak-feature}
20606 @tab @code{hwbreak stop reason}
20609 @item @code{fork-event-feature}
20610 @tab @code{fork stop reason}
20613 @item @code{vfork-event-feature}
20614 @tab @code{vfork stop reason}
20617 @item @code{exec-event-feature}
20618 @tab @code{exec stop reason}
20621 @item @code{thread-events}
20622 @tab @code{QThreadEvents}
20623 @tab Tracking thread lifetime.
20625 @item @code{no-resumed-stop-reply}
20626 @tab @code{no resumed thread left stop reply}
20627 @tab Tracking thread lifetime.
20632 @section Implementing a Remote Stub
20634 @cindex debugging stub, example
20635 @cindex remote stub, example
20636 @cindex stub example, remote debugging
20637 The stub files provided with @value{GDBN} implement the target side of the
20638 communication protocol, and the @value{GDBN} side is implemented in the
20639 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
20640 these subroutines to communicate, and ignore the details. (If you're
20641 implementing your own stub file, you can still ignore the details: start
20642 with one of the existing stub files. @file{sparc-stub.c} is the best
20643 organized, and therefore the easiest to read.)
20645 @cindex remote serial debugging, overview
20646 To debug a program running on another machine (the debugging
20647 @dfn{target} machine), you must first arrange for all the usual
20648 prerequisites for the program to run by itself. For example, for a C
20653 A startup routine to set up the C runtime environment; these usually
20654 have a name like @file{crt0}. The startup routine may be supplied by
20655 your hardware supplier, or you may have to write your own.
20658 A C subroutine library to support your program's
20659 subroutine calls, notably managing input and output.
20662 A way of getting your program to the other machine---for example, a
20663 download program. These are often supplied by the hardware
20664 manufacturer, but you may have to write your own from hardware
20668 The next step is to arrange for your program to use a serial port to
20669 communicate with the machine where @value{GDBN} is running (the @dfn{host}
20670 machine). In general terms, the scheme looks like this:
20674 @value{GDBN} already understands how to use this protocol; when everything
20675 else is set up, you can simply use the @samp{target remote} command
20676 (@pxref{Targets,,Specifying a Debugging Target}).
20678 @item On the target,
20679 you must link with your program a few special-purpose subroutines that
20680 implement the @value{GDBN} remote serial protocol. The file containing these
20681 subroutines is called a @dfn{debugging stub}.
20683 On certain remote targets, you can use an auxiliary program
20684 @code{gdbserver} instead of linking a stub into your program.
20685 @xref{Server,,Using the @code{gdbserver} Program}, for details.
20688 The debugging stub is specific to the architecture of the remote
20689 machine; for example, use @file{sparc-stub.c} to debug programs on
20692 @cindex remote serial stub list
20693 These working remote stubs are distributed with @value{GDBN}:
20698 @cindex @file{i386-stub.c}
20701 For Intel 386 and compatible architectures.
20704 @cindex @file{m68k-stub.c}
20705 @cindex Motorola 680x0
20707 For Motorola 680x0 architectures.
20710 @cindex @file{sh-stub.c}
20713 For Renesas SH architectures.
20716 @cindex @file{sparc-stub.c}
20718 For @sc{sparc} architectures.
20720 @item sparcl-stub.c
20721 @cindex @file{sparcl-stub.c}
20724 For Fujitsu @sc{sparclite} architectures.
20728 The @file{README} file in the @value{GDBN} distribution may list other
20729 recently added stubs.
20732 * Stub Contents:: What the stub can do for you
20733 * Bootstrapping:: What you must do for the stub
20734 * Debug Session:: Putting it all together
20737 @node Stub Contents
20738 @subsection What the Stub Can Do for You
20740 @cindex remote serial stub
20741 The debugging stub for your architecture supplies these three
20745 @item set_debug_traps
20746 @findex set_debug_traps
20747 @cindex remote serial stub, initialization
20748 This routine arranges for @code{handle_exception} to run when your
20749 program stops. You must call this subroutine explicitly in your
20750 program's startup code.
20752 @item handle_exception
20753 @findex handle_exception
20754 @cindex remote serial stub, main routine
20755 This is the central workhorse, but your program never calls it
20756 explicitly---the setup code arranges for @code{handle_exception} to
20757 run when a trap is triggered.
20759 @code{handle_exception} takes control when your program stops during
20760 execution (for example, on a breakpoint), and mediates communications
20761 with @value{GDBN} on the host machine. This is where the communications
20762 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
20763 representative on the target machine. It begins by sending summary
20764 information on the state of your program, then continues to execute,
20765 retrieving and transmitting any information @value{GDBN} needs, until you
20766 execute a @value{GDBN} command that makes your program resume; at that point,
20767 @code{handle_exception} returns control to your own code on the target
20771 @cindex @code{breakpoint} subroutine, remote
20772 Use this auxiliary subroutine to make your program contain a
20773 breakpoint. Depending on the particular situation, this may be the only
20774 way for @value{GDBN} to get control. For instance, if your target
20775 machine has some sort of interrupt button, you won't need to call this;
20776 pressing the interrupt button transfers control to
20777 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
20778 simply receiving characters on the serial port may also trigger a trap;
20779 again, in that situation, you don't need to call @code{breakpoint} from
20780 your own program---simply running @samp{target remote} from the host
20781 @value{GDBN} session gets control.
20783 Call @code{breakpoint} if none of these is true, or if you simply want
20784 to make certain your program stops at a predetermined point for the
20785 start of your debugging session.
20788 @node Bootstrapping
20789 @subsection What You Must Do for the Stub
20791 @cindex remote stub, support routines
20792 The debugging stubs that come with @value{GDBN} are set up for a particular
20793 chip architecture, but they have no information about the rest of your
20794 debugging target machine.
20796 First of all you need to tell the stub how to communicate with the
20800 @item int getDebugChar()
20801 @findex getDebugChar
20802 Write this subroutine to read a single character from the serial port.
20803 It may be identical to @code{getchar} for your target system; a
20804 different name is used to allow you to distinguish the two if you wish.
20806 @item void putDebugChar(int)
20807 @findex putDebugChar
20808 Write this subroutine to write a single character to the serial port.
20809 It may be identical to @code{putchar} for your target system; a
20810 different name is used to allow you to distinguish the two if you wish.
20813 @cindex control C, and remote debugging
20814 @cindex interrupting remote targets
20815 If you want @value{GDBN} to be able to stop your program while it is
20816 running, you need to use an interrupt-driven serial driver, and arrange
20817 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
20818 character). That is the character which @value{GDBN} uses to tell the
20819 remote system to stop.
20821 Getting the debugging target to return the proper status to @value{GDBN}
20822 probably requires changes to the standard stub; one quick and dirty way
20823 is to just execute a breakpoint instruction (the ``dirty'' part is that
20824 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
20826 Other routines you need to supply are:
20829 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
20830 @findex exceptionHandler
20831 Write this function to install @var{exception_address} in the exception
20832 handling tables. You need to do this because the stub does not have any
20833 way of knowing what the exception handling tables on your target system
20834 are like (for example, the processor's table might be in @sc{rom},
20835 containing entries which point to a table in @sc{ram}).
20836 The @var{exception_number} specifies the exception which should be changed;
20837 its meaning is architecture-dependent (for example, different numbers
20838 might represent divide by zero, misaligned access, etc). When this
20839 exception occurs, control should be transferred directly to
20840 @var{exception_address}, and the processor state (stack, registers,
20841 and so on) should be just as it is when a processor exception occurs. So if
20842 you want to use a jump instruction to reach @var{exception_address}, it
20843 should be a simple jump, not a jump to subroutine.
20845 For the 386, @var{exception_address} should be installed as an interrupt
20846 gate so that interrupts are masked while the handler runs. The gate
20847 should be at privilege level 0 (the most privileged level). The
20848 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
20849 help from @code{exceptionHandler}.
20851 @item void flush_i_cache()
20852 @findex flush_i_cache
20853 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
20854 instruction cache, if any, on your target machine. If there is no
20855 instruction cache, this subroutine may be a no-op.
20857 On target machines that have instruction caches, @value{GDBN} requires this
20858 function to make certain that the state of your program is stable.
20862 You must also make sure this library routine is available:
20865 @item void *memset(void *, int, int)
20867 This is the standard library function @code{memset} that sets an area of
20868 memory to a known value. If you have one of the free versions of
20869 @code{libc.a}, @code{memset} can be found there; otherwise, you must
20870 either obtain it from your hardware manufacturer, or write your own.
20873 If you do not use the GNU C compiler, you may need other standard
20874 library subroutines as well; this varies from one stub to another,
20875 but in general the stubs are likely to use any of the common library
20876 subroutines which @code{@value{NGCC}} generates as inline code.
20879 @node Debug Session
20880 @subsection Putting it All Together
20882 @cindex remote serial debugging summary
20883 In summary, when your program is ready to debug, you must follow these
20888 Make sure you have defined the supporting low-level routines
20889 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
20891 @code{getDebugChar}, @code{putDebugChar},
20892 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
20896 Insert these lines in your program's startup code, before the main
20897 procedure is called:
20904 On some machines, when a breakpoint trap is raised, the hardware
20905 automatically makes the PC point to the instruction after the
20906 breakpoint. If your machine doesn't do that, you may need to adjust
20907 @code{handle_exception} to arrange for it to return to the instruction
20908 after the breakpoint on this first invocation, so that your program
20909 doesn't keep hitting the initial breakpoint instead of making
20913 For the 680x0 stub only, you need to provide a variable called
20914 @code{exceptionHook}. Normally you just use:
20917 void (*exceptionHook)() = 0;
20921 but if before calling @code{set_debug_traps}, you set it to point to a
20922 function in your program, that function is called when
20923 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
20924 error). The function indicated by @code{exceptionHook} is called with
20925 one parameter: an @code{int} which is the exception number.
20928 Compile and link together: your program, the @value{GDBN} debugging stub for
20929 your target architecture, and the supporting subroutines.
20932 Make sure you have a serial connection between your target machine and
20933 the @value{GDBN} host, and identify the serial port on the host.
20936 @c The "remote" target now provides a `load' command, so we should
20937 @c document that. FIXME.
20938 Download your program to your target machine (or get it there by
20939 whatever means the manufacturer provides), and start it.
20942 Start @value{GDBN} on the host, and connect to the target
20943 (@pxref{Connecting,,Connecting to a Remote Target}).
20947 @node Configurations
20948 @chapter Configuration-Specific Information
20950 While nearly all @value{GDBN} commands are available for all native and
20951 cross versions of the debugger, there are some exceptions. This chapter
20952 describes things that are only available in certain configurations.
20954 There are three major categories of configurations: native
20955 configurations, where the host and target are the same, embedded
20956 operating system configurations, which are usually the same for several
20957 different processor architectures, and bare embedded processors, which
20958 are quite different from each other.
20963 * Embedded Processors::
20970 This section describes details specific to particular native
20974 * BSD libkvm Interface:: Debugging BSD kernel memory images
20975 * SVR4 Process Information:: SVR4 process information
20976 * DJGPP Native:: Features specific to the DJGPP port
20977 * Cygwin Native:: Features specific to the Cygwin port
20978 * Hurd Native:: Features specific to @sc{gnu} Hurd
20979 * Darwin:: Features specific to Darwin
20982 @node BSD libkvm Interface
20983 @subsection BSD libkvm Interface
20986 @cindex kernel memory image
20987 @cindex kernel crash dump
20989 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
20990 interface that provides a uniform interface for accessing kernel virtual
20991 memory images, including live systems and crash dumps. @value{GDBN}
20992 uses this interface to allow you to debug live kernels and kernel crash
20993 dumps on many native BSD configurations. This is implemented as a
20994 special @code{kvm} debugging target. For debugging a live system, load
20995 the currently running kernel into @value{GDBN} and connect to the
20999 (@value{GDBP}) @b{target kvm}
21002 For debugging crash dumps, provide the file name of the crash dump as an
21006 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
21009 Once connected to the @code{kvm} target, the following commands are
21015 Set current context from the @dfn{Process Control Block} (PCB) address.
21018 Set current context from proc address. This command isn't available on
21019 modern FreeBSD systems.
21022 @node SVR4 Process Information
21023 @subsection SVR4 Process Information
21025 @cindex examine process image
21026 @cindex process info via @file{/proc}
21028 Many versions of SVR4 and compatible systems provide a facility called
21029 @samp{/proc} that can be used to examine the image of a running
21030 process using file-system subroutines.
21032 If @value{GDBN} is configured for an operating system with this
21033 facility, the command @code{info proc} is available to report
21034 information about the process running your program, or about any
21035 process running on your system. This includes, as of this writing,
21036 @sc{gnu}/Linux and Solaris, for example.
21038 This command may also work on core files that were created on a system
21039 that has the @samp{/proc} facility.
21045 @itemx info proc @var{process-id}
21046 Summarize available information about any running process. If a
21047 process ID is specified by @var{process-id}, display information about
21048 that process; otherwise display information about the program being
21049 debugged. The summary includes the debugged process ID, the command
21050 line used to invoke it, its current working directory, and its
21051 executable file's absolute file name.
21053 On some systems, @var{process-id} can be of the form
21054 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
21055 within a process. If the optional @var{pid} part is missing, it means
21056 a thread from the process being debugged (the leading @samp{/} still
21057 needs to be present, or else @value{GDBN} will interpret the number as
21058 a process ID rather than a thread ID).
21060 @item info proc cmdline
21061 @cindex info proc cmdline
21062 Show the original command line of the process. This command is
21063 specific to @sc{gnu}/Linux.
21065 @item info proc cwd
21066 @cindex info proc cwd
21067 Show the current working directory of the process. This command is
21068 specific to @sc{gnu}/Linux.
21070 @item info proc exe
21071 @cindex info proc exe
21072 Show the name of executable of the process. This command is specific
21075 @item info proc mappings
21076 @cindex memory address space mappings
21077 Report the memory address space ranges accessible in the program, with
21078 information on whether the process has read, write, or execute access
21079 rights to each range. On @sc{gnu}/Linux systems, each memory range
21080 includes the object file which is mapped to that range, instead of the
21081 memory access rights to that range.
21083 @item info proc stat
21084 @itemx info proc status
21085 @cindex process detailed status information
21086 These subcommands are specific to @sc{gnu}/Linux systems. They show
21087 the process-related information, including the user ID and group ID;
21088 how many threads are there in the process; its virtual memory usage;
21089 the signals that are pending, blocked, and ignored; its TTY; its
21090 consumption of system and user time; its stack size; its @samp{nice}
21091 value; etc. For more information, see the @samp{proc} man page
21092 (type @kbd{man 5 proc} from your shell prompt).
21094 @item info proc all
21095 Show all the information about the process described under all of the
21096 above @code{info proc} subcommands.
21099 @comment These sub-options of 'info proc' were not included when
21100 @comment procfs.c was re-written. Keep their descriptions around
21101 @comment against the day when someone finds the time to put them back in.
21102 @kindex info proc times
21103 @item info proc times
21104 Starting time, user CPU time, and system CPU time for your program and
21107 @kindex info proc id
21109 Report on the process IDs related to your program: its own process ID,
21110 the ID of its parent, the process group ID, and the session ID.
21113 @item set procfs-trace
21114 @kindex set procfs-trace
21115 @cindex @code{procfs} API calls
21116 This command enables and disables tracing of @code{procfs} API calls.
21118 @item show procfs-trace
21119 @kindex show procfs-trace
21120 Show the current state of @code{procfs} API call tracing.
21122 @item set procfs-file @var{file}
21123 @kindex set procfs-file
21124 Tell @value{GDBN} to write @code{procfs} API trace to the named
21125 @var{file}. @value{GDBN} appends the trace info to the previous
21126 contents of the file. The default is to display the trace on the
21129 @item show procfs-file
21130 @kindex show procfs-file
21131 Show the file to which @code{procfs} API trace is written.
21133 @item proc-trace-entry
21134 @itemx proc-trace-exit
21135 @itemx proc-untrace-entry
21136 @itemx proc-untrace-exit
21137 @kindex proc-trace-entry
21138 @kindex proc-trace-exit
21139 @kindex proc-untrace-entry
21140 @kindex proc-untrace-exit
21141 These commands enable and disable tracing of entries into and exits
21142 from the @code{syscall} interface.
21145 @kindex info pidlist
21146 @cindex process list, QNX Neutrino
21147 For QNX Neutrino only, this command displays the list of all the
21148 processes and all the threads within each process.
21151 @kindex info meminfo
21152 @cindex mapinfo list, QNX Neutrino
21153 For QNX Neutrino only, this command displays the list of all mapinfos.
21157 @subsection Features for Debugging @sc{djgpp} Programs
21158 @cindex @sc{djgpp} debugging
21159 @cindex native @sc{djgpp} debugging
21160 @cindex MS-DOS-specific commands
21163 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
21164 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
21165 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
21166 top of real-mode DOS systems and their emulations.
21168 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
21169 defines a few commands specific to the @sc{djgpp} port. This
21170 subsection describes those commands.
21175 This is a prefix of @sc{djgpp}-specific commands which print
21176 information about the target system and important OS structures.
21179 @cindex MS-DOS system info
21180 @cindex free memory information (MS-DOS)
21181 @item info dos sysinfo
21182 This command displays assorted information about the underlying
21183 platform: the CPU type and features, the OS version and flavor, the
21184 DPMI version, and the available conventional and DPMI memory.
21189 @cindex segment descriptor tables
21190 @cindex descriptor tables display
21192 @itemx info dos ldt
21193 @itemx info dos idt
21194 These 3 commands display entries from, respectively, Global, Local,
21195 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
21196 tables are data structures which store a descriptor for each segment
21197 that is currently in use. The segment's selector is an index into a
21198 descriptor table; the table entry for that index holds the
21199 descriptor's base address and limit, and its attributes and access
21202 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
21203 segment (used for both data and the stack), and a DOS segment (which
21204 allows access to DOS/BIOS data structures and absolute addresses in
21205 conventional memory). However, the DPMI host will usually define
21206 additional segments in order to support the DPMI environment.
21208 @cindex garbled pointers
21209 These commands allow to display entries from the descriptor tables.
21210 Without an argument, all entries from the specified table are
21211 displayed. An argument, which should be an integer expression, means
21212 display a single entry whose index is given by the argument. For
21213 example, here's a convenient way to display information about the
21214 debugged program's data segment:
21217 @exdent @code{(@value{GDBP}) info dos ldt $ds}
21218 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
21222 This comes in handy when you want to see whether a pointer is outside
21223 the data segment's limit (i.e.@: @dfn{garbled}).
21225 @cindex page tables display (MS-DOS)
21227 @itemx info dos pte
21228 These two commands display entries from, respectively, the Page
21229 Directory and the Page Tables. Page Directories and Page Tables are
21230 data structures which control how virtual memory addresses are mapped
21231 into physical addresses. A Page Table includes an entry for every
21232 page of memory that is mapped into the program's address space; there
21233 may be several Page Tables, each one holding up to 4096 entries. A
21234 Page Directory has up to 4096 entries, one each for every Page Table
21235 that is currently in use.
21237 Without an argument, @kbd{info dos pde} displays the entire Page
21238 Directory, and @kbd{info dos pte} displays all the entries in all of
21239 the Page Tables. An argument, an integer expression, given to the
21240 @kbd{info dos pde} command means display only that entry from the Page
21241 Directory table. An argument given to the @kbd{info dos pte} command
21242 means display entries from a single Page Table, the one pointed to by
21243 the specified entry in the Page Directory.
21245 @cindex direct memory access (DMA) on MS-DOS
21246 These commands are useful when your program uses @dfn{DMA} (Direct
21247 Memory Access), which needs physical addresses to program the DMA
21250 These commands are supported only with some DPMI servers.
21252 @cindex physical address from linear address
21253 @item info dos address-pte @var{addr}
21254 This command displays the Page Table entry for a specified linear
21255 address. The argument @var{addr} is a linear address which should
21256 already have the appropriate segment's base address added to it,
21257 because this command accepts addresses which may belong to @emph{any}
21258 segment. For example, here's how to display the Page Table entry for
21259 the page where a variable @code{i} is stored:
21262 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
21263 @exdent @code{Page Table entry for address 0x11a00d30:}
21264 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
21268 This says that @code{i} is stored at offset @code{0xd30} from the page
21269 whose physical base address is @code{0x02698000}, and shows all the
21270 attributes of that page.
21272 Note that you must cast the addresses of variables to a @code{char *},
21273 since otherwise the value of @code{__djgpp_base_address}, the base
21274 address of all variables and functions in a @sc{djgpp} program, will
21275 be added using the rules of C pointer arithmetics: if @code{i} is
21276 declared an @code{int}, @value{GDBN} will add 4 times the value of
21277 @code{__djgpp_base_address} to the address of @code{i}.
21279 Here's another example, it displays the Page Table entry for the
21283 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
21284 @exdent @code{Page Table entry for address 0x29110:}
21285 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
21289 (The @code{+ 3} offset is because the transfer buffer's address is the
21290 3rd member of the @code{_go32_info_block} structure.) The output
21291 clearly shows that this DPMI server maps the addresses in conventional
21292 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
21293 linear (@code{0x29110}) addresses are identical.
21295 This command is supported only with some DPMI servers.
21298 @cindex DOS serial data link, remote debugging
21299 In addition to native debugging, the DJGPP port supports remote
21300 debugging via a serial data link. The following commands are specific
21301 to remote serial debugging in the DJGPP port of @value{GDBN}.
21304 @kindex set com1base
21305 @kindex set com1irq
21306 @kindex set com2base
21307 @kindex set com2irq
21308 @kindex set com3base
21309 @kindex set com3irq
21310 @kindex set com4base
21311 @kindex set com4irq
21312 @item set com1base @var{addr}
21313 This command sets the base I/O port address of the @file{COM1} serial
21316 @item set com1irq @var{irq}
21317 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
21318 for the @file{COM1} serial port.
21320 There are similar commands @samp{set com2base}, @samp{set com3irq},
21321 etc.@: for setting the port address and the @code{IRQ} lines for the
21324 @kindex show com1base
21325 @kindex show com1irq
21326 @kindex show com2base
21327 @kindex show com2irq
21328 @kindex show com3base
21329 @kindex show com3irq
21330 @kindex show com4base
21331 @kindex show com4irq
21332 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
21333 display the current settings of the base address and the @code{IRQ}
21334 lines used by the COM ports.
21337 @kindex info serial
21338 @cindex DOS serial port status
21339 This command prints the status of the 4 DOS serial ports. For each
21340 port, it prints whether it's active or not, its I/O base address and
21341 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
21342 counts of various errors encountered so far.
21346 @node Cygwin Native
21347 @subsection Features for Debugging MS Windows PE Executables
21348 @cindex MS Windows debugging
21349 @cindex native Cygwin debugging
21350 @cindex Cygwin-specific commands
21352 @value{GDBN} supports native debugging of MS Windows programs, including
21353 DLLs with and without symbolic debugging information.
21355 @cindex Ctrl-BREAK, MS-Windows
21356 @cindex interrupt debuggee on MS-Windows
21357 MS-Windows programs that call @code{SetConsoleMode} to switch off the
21358 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
21359 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
21360 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
21361 sequence, which can be used to interrupt the debuggee even if it
21364 There are various additional Cygwin-specific commands, described in
21365 this section. Working with DLLs that have no debugging symbols is
21366 described in @ref{Non-debug DLL Symbols}.
21371 This is a prefix of MS Windows-specific commands which print
21372 information about the target system and important OS structures.
21374 @item info w32 selector
21375 This command displays information returned by
21376 the Win32 API @code{GetThreadSelectorEntry} function.
21377 It takes an optional argument that is evaluated to
21378 a long value to give the information about this given selector.
21379 Without argument, this command displays information
21380 about the six segment registers.
21382 @item info w32 thread-information-block
21383 This command displays thread specific information stored in the
21384 Thread Information Block (readable on the X86 CPU family using @code{$fs}
21385 selector for 32-bit programs and @code{$gs} for 64-bit programs).
21387 @kindex set cygwin-exceptions
21388 @cindex debugging the Cygwin DLL
21389 @cindex Cygwin DLL, debugging
21390 @item set cygwin-exceptions @var{mode}
21391 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
21392 happen inside the Cygwin DLL. If @var{mode} is @code{off},
21393 @value{GDBN} will delay recognition of exceptions, and may ignore some
21394 exceptions which seem to be caused by internal Cygwin DLL
21395 ``bookkeeping''. This option is meant primarily for debugging the
21396 Cygwin DLL itself; the default value is @code{off} to avoid annoying
21397 @value{GDBN} users with false @code{SIGSEGV} signals.
21399 @kindex show cygwin-exceptions
21400 @item show cygwin-exceptions
21401 Displays whether @value{GDBN} will break on exceptions that happen
21402 inside the Cygwin DLL itself.
21404 @kindex set new-console
21405 @item set new-console @var{mode}
21406 If @var{mode} is @code{on} the debuggee will
21407 be started in a new console on next start.
21408 If @var{mode} is @code{off}, the debuggee will
21409 be started in the same console as the debugger.
21411 @kindex show new-console
21412 @item show new-console
21413 Displays whether a new console is used
21414 when the debuggee is started.
21416 @kindex set new-group
21417 @item set new-group @var{mode}
21418 This boolean value controls whether the debuggee should
21419 start a new group or stay in the same group as the debugger.
21420 This affects the way the Windows OS handles
21423 @kindex show new-group
21424 @item show new-group
21425 Displays current value of new-group boolean.
21427 @kindex set debugevents
21428 @item set debugevents
21429 This boolean value adds debug output concerning kernel events related
21430 to the debuggee seen by the debugger. This includes events that
21431 signal thread and process creation and exit, DLL loading and
21432 unloading, console interrupts, and debugging messages produced by the
21433 Windows @code{OutputDebugString} API call.
21435 @kindex set debugexec
21436 @item set debugexec
21437 This boolean value adds debug output concerning execute events
21438 (such as resume thread) seen by the debugger.
21440 @kindex set debugexceptions
21441 @item set debugexceptions
21442 This boolean value adds debug output concerning exceptions in the
21443 debuggee seen by the debugger.
21445 @kindex set debugmemory
21446 @item set debugmemory
21447 This boolean value adds debug output concerning debuggee memory reads
21448 and writes by the debugger.
21452 This boolean values specifies whether the debuggee is called
21453 via a shell or directly (default value is on).
21457 Displays if the debuggee will be started with a shell.
21462 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
21465 @node Non-debug DLL Symbols
21466 @subsubsection Support for DLLs without Debugging Symbols
21467 @cindex DLLs with no debugging symbols
21468 @cindex Minimal symbols and DLLs
21470 Very often on windows, some of the DLLs that your program relies on do
21471 not include symbolic debugging information (for example,
21472 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
21473 symbols in a DLL, it relies on the minimal amount of symbolic
21474 information contained in the DLL's export table. This section
21475 describes working with such symbols, known internally to @value{GDBN} as
21476 ``minimal symbols''.
21478 Note that before the debugged program has started execution, no DLLs
21479 will have been loaded. The easiest way around this problem is simply to
21480 start the program --- either by setting a breakpoint or letting the
21481 program run once to completion.
21483 @subsubsection DLL Name Prefixes
21485 In keeping with the naming conventions used by the Microsoft debugging
21486 tools, DLL export symbols are made available with a prefix based on the
21487 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
21488 also entered into the symbol table, so @code{CreateFileA} is often
21489 sufficient. In some cases there will be name clashes within a program
21490 (particularly if the executable itself includes full debugging symbols)
21491 necessitating the use of the fully qualified name when referring to the
21492 contents of the DLL. Use single-quotes around the name to avoid the
21493 exclamation mark (``!'') being interpreted as a language operator.
21495 Note that the internal name of the DLL may be all upper-case, even
21496 though the file name of the DLL is lower-case, or vice-versa. Since
21497 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
21498 some confusion. If in doubt, try the @code{info functions} and
21499 @code{info variables} commands or even @code{maint print msymbols}
21500 (@pxref{Symbols}). Here's an example:
21503 (@value{GDBP}) info function CreateFileA
21504 All functions matching regular expression "CreateFileA":
21506 Non-debugging symbols:
21507 0x77e885f4 CreateFileA
21508 0x77e885f4 KERNEL32!CreateFileA
21512 (@value{GDBP}) info function !
21513 All functions matching regular expression "!":
21515 Non-debugging symbols:
21516 0x6100114c cygwin1!__assert
21517 0x61004034 cygwin1!_dll_crt0@@0
21518 0x61004240 cygwin1!dll_crt0(per_process *)
21522 @subsubsection Working with Minimal Symbols
21524 Symbols extracted from a DLL's export table do not contain very much
21525 type information. All that @value{GDBN} can do is guess whether a symbol
21526 refers to a function or variable depending on the linker section that
21527 contains the symbol. Also note that the actual contents of the memory
21528 contained in a DLL are not available unless the program is running. This
21529 means that you cannot examine the contents of a variable or disassemble
21530 a function within a DLL without a running program.
21532 Variables are generally treated as pointers and dereferenced
21533 automatically. For this reason, it is often necessary to prefix a
21534 variable name with the address-of operator (``&'') and provide explicit
21535 type information in the command. Here's an example of the type of
21539 (@value{GDBP}) print 'cygwin1!__argv'
21544 (@value{GDBP}) x 'cygwin1!__argv'
21545 0x10021610: "\230y\""
21548 And two possible solutions:
21551 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
21552 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
21556 (@value{GDBP}) x/2x &'cygwin1!__argv'
21557 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
21558 (@value{GDBP}) x/x 0x10021608
21559 0x10021608: 0x0022fd98
21560 (@value{GDBP}) x/s 0x0022fd98
21561 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
21564 Setting a break point within a DLL is possible even before the program
21565 starts execution. However, under these circumstances, @value{GDBN} can't
21566 examine the initial instructions of the function in order to skip the
21567 function's frame set-up code. You can work around this by using ``*&''
21568 to set the breakpoint at a raw memory address:
21571 (@value{GDBP}) break *&'python22!PyOS_Readline'
21572 Breakpoint 1 at 0x1e04eff0
21575 The author of these extensions is not entirely convinced that setting a
21576 break point within a shared DLL like @file{kernel32.dll} is completely
21580 @subsection Commands Specific to @sc{gnu} Hurd Systems
21581 @cindex @sc{gnu} Hurd debugging
21583 This subsection describes @value{GDBN} commands specific to the
21584 @sc{gnu} Hurd native debugging.
21589 @kindex set signals@r{, Hurd command}
21590 @kindex set sigs@r{, Hurd command}
21591 This command toggles the state of inferior signal interception by
21592 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
21593 affected by this command. @code{sigs} is a shorthand alias for
21598 @kindex show signals@r{, Hurd command}
21599 @kindex show sigs@r{, Hurd command}
21600 Show the current state of intercepting inferior's signals.
21602 @item set signal-thread
21603 @itemx set sigthread
21604 @kindex set signal-thread
21605 @kindex set sigthread
21606 This command tells @value{GDBN} which thread is the @code{libc} signal
21607 thread. That thread is run when a signal is delivered to a running
21608 process. @code{set sigthread} is the shorthand alias of @code{set
21611 @item show signal-thread
21612 @itemx show sigthread
21613 @kindex show signal-thread
21614 @kindex show sigthread
21615 These two commands show which thread will run when the inferior is
21616 delivered a signal.
21619 @kindex set stopped@r{, Hurd command}
21620 This commands tells @value{GDBN} that the inferior process is stopped,
21621 as with the @code{SIGSTOP} signal. The stopped process can be
21622 continued by delivering a signal to it.
21625 @kindex show stopped@r{, Hurd command}
21626 This command shows whether @value{GDBN} thinks the debuggee is
21629 @item set exceptions
21630 @kindex set exceptions@r{, Hurd command}
21631 Use this command to turn off trapping of exceptions in the inferior.
21632 When exception trapping is off, neither breakpoints nor
21633 single-stepping will work. To restore the default, set exception
21636 @item show exceptions
21637 @kindex show exceptions@r{, Hurd command}
21638 Show the current state of trapping exceptions in the inferior.
21640 @item set task pause
21641 @kindex set task@r{, Hurd commands}
21642 @cindex task attributes (@sc{gnu} Hurd)
21643 @cindex pause current task (@sc{gnu} Hurd)
21644 This command toggles task suspension when @value{GDBN} has control.
21645 Setting it to on takes effect immediately, and the task is suspended
21646 whenever @value{GDBN} gets control. Setting it to off will take
21647 effect the next time the inferior is continued. If this option is set
21648 to off, you can use @code{set thread default pause on} or @code{set
21649 thread pause on} (see below) to pause individual threads.
21651 @item show task pause
21652 @kindex show task@r{, Hurd commands}
21653 Show the current state of task suspension.
21655 @item set task detach-suspend-count
21656 @cindex task suspend count
21657 @cindex detach from task, @sc{gnu} Hurd
21658 This command sets the suspend count the task will be left with when
21659 @value{GDBN} detaches from it.
21661 @item show task detach-suspend-count
21662 Show the suspend count the task will be left with when detaching.
21664 @item set task exception-port
21665 @itemx set task excp
21666 @cindex task exception port, @sc{gnu} Hurd
21667 This command sets the task exception port to which @value{GDBN} will
21668 forward exceptions. The argument should be the value of the @dfn{send
21669 rights} of the task. @code{set task excp} is a shorthand alias.
21671 @item set noninvasive
21672 @cindex noninvasive task options
21673 This command switches @value{GDBN} to a mode that is the least
21674 invasive as far as interfering with the inferior is concerned. This
21675 is the same as using @code{set task pause}, @code{set exceptions}, and
21676 @code{set signals} to values opposite to the defaults.
21678 @item info send-rights
21679 @itemx info receive-rights
21680 @itemx info port-rights
21681 @itemx info port-sets
21682 @itemx info dead-names
21685 @cindex send rights, @sc{gnu} Hurd
21686 @cindex receive rights, @sc{gnu} Hurd
21687 @cindex port rights, @sc{gnu} Hurd
21688 @cindex port sets, @sc{gnu} Hurd
21689 @cindex dead names, @sc{gnu} Hurd
21690 These commands display information about, respectively, send rights,
21691 receive rights, port rights, port sets, and dead names of a task.
21692 There are also shorthand aliases: @code{info ports} for @code{info
21693 port-rights} and @code{info psets} for @code{info port-sets}.
21695 @item set thread pause
21696 @kindex set thread@r{, Hurd command}
21697 @cindex thread properties, @sc{gnu} Hurd
21698 @cindex pause current thread (@sc{gnu} Hurd)
21699 This command toggles current thread suspension when @value{GDBN} has
21700 control. Setting it to on takes effect immediately, and the current
21701 thread is suspended whenever @value{GDBN} gets control. Setting it to
21702 off will take effect the next time the inferior is continued.
21703 Normally, this command has no effect, since when @value{GDBN} has
21704 control, the whole task is suspended. However, if you used @code{set
21705 task pause off} (see above), this command comes in handy to suspend
21706 only the current thread.
21708 @item show thread pause
21709 @kindex show thread@r{, Hurd command}
21710 This command shows the state of current thread suspension.
21712 @item set thread run
21713 This command sets whether the current thread is allowed to run.
21715 @item show thread run
21716 Show whether the current thread is allowed to run.
21718 @item set thread detach-suspend-count
21719 @cindex thread suspend count, @sc{gnu} Hurd
21720 @cindex detach from thread, @sc{gnu} Hurd
21721 This command sets the suspend count @value{GDBN} will leave on a
21722 thread when detaching. This number is relative to the suspend count
21723 found by @value{GDBN} when it notices the thread; use @code{set thread
21724 takeover-suspend-count} to force it to an absolute value.
21726 @item show thread detach-suspend-count
21727 Show the suspend count @value{GDBN} will leave on the thread when
21730 @item set thread exception-port
21731 @itemx set thread excp
21732 Set the thread exception port to which to forward exceptions. This
21733 overrides the port set by @code{set task exception-port} (see above).
21734 @code{set thread excp} is the shorthand alias.
21736 @item set thread takeover-suspend-count
21737 Normally, @value{GDBN}'s thread suspend counts are relative to the
21738 value @value{GDBN} finds when it notices each thread. This command
21739 changes the suspend counts to be absolute instead.
21741 @item set thread default
21742 @itemx show thread default
21743 @cindex thread default settings, @sc{gnu} Hurd
21744 Each of the above @code{set thread} commands has a @code{set thread
21745 default} counterpart (e.g., @code{set thread default pause}, @code{set
21746 thread default exception-port}, etc.). The @code{thread default}
21747 variety of commands sets the default thread properties for all
21748 threads; you can then change the properties of individual threads with
21749 the non-default commands.
21756 @value{GDBN} provides the following commands specific to the Darwin target:
21759 @item set debug darwin @var{num}
21760 @kindex set debug darwin
21761 When set to a non zero value, enables debugging messages specific to
21762 the Darwin support. Higher values produce more verbose output.
21764 @item show debug darwin
21765 @kindex show debug darwin
21766 Show the current state of Darwin messages.
21768 @item set debug mach-o @var{num}
21769 @kindex set debug mach-o
21770 When set to a non zero value, enables debugging messages while
21771 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
21772 file format used on Darwin for object and executable files.) Higher
21773 values produce more verbose output. This is a command to diagnose
21774 problems internal to @value{GDBN} and should not be needed in normal
21777 @item show debug mach-o
21778 @kindex show debug mach-o
21779 Show the current state of Mach-O file messages.
21781 @item set mach-exceptions on
21782 @itemx set mach-exceptions off
21783 @kindex set mach-exceptions
21784 On Darwin, faults are first reported as a Mach exception and are then
21785 mapped to a Posix signal. Use this command to turn on trapping of
21786 Mach exceptions in the inferior. This might be sometimes useful to
21787 better understand the cause of a fault. The default is off.
21789 @item show mach-exceptions
21790 @kindex show mach-exceptions
21791 Show the current state of exceptions trapping.
21796 @section Embedded Operating Systems
21798 This section describes configurations involving the debugging of
21799 embedded operating systems that are available for several different
21802 @value{GDBN} includes the ability to debug programs running on
21803 various real-time operating systems.
21805 @node Embedded Processors
21806 @section Embedded Processors
21808 This section goes into details specific to particular embedded
21811 @cindex send command to simulator
21812 Whenever a specific embedded processor has a simulator, @value{GDBN}
21813 allows to send an arbitrary command to the simulator.
21816 @item sim @var{command}
21817 @kindex sim@r{, a command}
21818 Send an arbitrary @var{command} string to the simulator. Consult the
21819 documentation for the specific simulator in use for information about
21820 acceptable commands.
21826 * M32R/SDI:: Renesas M32R/SDI
21827 * M68K:: Motorola M68K
21828 * MicroBlaze:: Xilinx MicroBlaze
21829 * MIPS Embedded:: MIPS Embedded
21830 * PowerPC Embedded:: PowerPC Embedded
21833 * Super-H:: Renesas Super-H
21839 @value{GDBN} provides the following ARM-specific commands:
21842 @item set arm disassembler
21844 This commands selects from a list of disassembly styles. The
21845 @code{"std"} style is the standard style.
21847 @item show arm disassembler
21849 Show the current disassembly style.
21851 @item set arm apcs32
21852 @cindex ARM 32-bit mode
21853 This command toggles ARM operation mode between 32-bit and 26-bit.
21855 @item show arm apcs32
21856 Display the current usage of the ARM 32-bit mode.
21858 @item set arm fpu @var{fputype}
21859 This command sets the ARM floating-point unit (FPU) type. The
21860 argument @var{fputype} can be one of these:
21864 Determine the FPU type by querying the OS ABI.
21866 Software FPU, with mixed-endian doubles on little-endian ARM
21869 GCC-compiled FPA co-processor.
21871 Software FPU with pure-endian doubles.
21877 Show the current type of the FPU.
21880 This command forces @value{GDBN} to use the specified ABI.
21883 Show the currently used ABI.
21885 @item set arm fallback-mode (arm|thumb|auto)
21886 @value{GDBN} uses the symbol table, when available, to determine
21887 whether instructions are ARM or Thumb. This command controls
21888 @value{GDBN}'s default behavior when the symbol table is not
21889 available. The default is @samp{auto}, which causes @value{GDBN} to
21890 use the current execution mode (from the @code{T} bit in the @code{CPSR}
21893 @item show arm fallback-mode
21894 Show the current fallback instruction mode.
21896 @item set arm force-mode (arm|thumb|auto)
21897 This command overrides use of the symbol table to determine whether
21898 instructions are ARM or Thumb. The default is @samp{auto}, which
21899 causes @value{GDBN} to use the symbol table and then the setting
21900 of @samp{set arm fallback-mode}.
21902 @item show arm force-mode
21903 Show the current forced instruction mode.
21905 @item set debug arm
21906 Toggle whether to display ARM-specific debugging messages from the ARM
21907 target support subsystem.
21909 @item show debug arm
21910 Show whether ARM-specific debugging messages are enabled.
21914 @item target sim @r{[}@var{simargs}@r{]} @dots{}
21915 The @value{GDBN} ARM simulator accepts the following optional arguments.
21918 @item --swi-support=@var{type}
21919 Tell the simulator which SWI interfaces to support. The argument
21920 @var{type} may be a comma separated list of the following values.
21921 The default value is @code{all}.
21934 @subsection Renesas M32R/SDI
21936 The following commands are available for M32R/SDI:
21941 @cindex reset SDI connection, M32R
21942 This command resets the SDI connection.
21946 This command shows the SDI connection status.
21949 @kindex debug_chaos
21950 @cindex M32R/Chaos debugging
21951 Instructs the remote that M32R/Chaos debugging is to be used.
21953 @item use_debug_dma
21954 @kindex use_debug_dma
21955 Instructs the remote to use the DEBUG_DMA method of accessing memory.
21958 @kindex use_mon_code
21959 Instructs the remote to use the MON_CODE method of accessing memory.
21962 @kindex use_ib_break
21963 Instructs the remote to set breakpoints by IB break.
21965 @item use_dbt_break
21966 @kindex use_dbt_break
21967 Instructs the remote to set breakpoints by DBT.
21973 The Motorola m68k configuration includes ColdFire support.
21976 @subsection MicroBlaze
21977 @cindex Xilinx MicroBlaze
21978 @cindex XMD, Xilinx Microprocessor Debugger
21980 The MicroBlaze is a soft-core processor supported on various Xilinx
21981 FPGAs, such as Spartan or Virtex series. Boards with these processors
21982 usually have JTAG ports which connect to a host system running the Xilinx
21983 Embedded Development Kit (EDK) or Software Development Kit (SDK).
21984 This host system is used to download the configuration bitstream to
21985 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
21986 communicates with the target board using the JTAG interface and
21987 presents a @code{gdbserver} interface to the board. By default
21988 @code{xmd} uses port @code{1234}. (While it is possible to change
21989 this default port, it requires the use of undocumented @code{xmd}
21990 commands. Contact Xilinx support if you need to do this.)
21992 Use these GDB commands to connect to the MicroBlaze target processor.
21995 @item target remote :1234
21996 Use this command to connect to the target if you are running @value{GDBN}
21997 on the same system as @code{xmd}.
21999 @item target remote @var{xmd-host}:1234
22000 Use this command to connect to the target if it is connected to @code{xmd}
22001 running on a different system named @var{xmd-host}.
22004 Use this command to download a program to the MicroBlaze target.
22006 @item set debug microblaze @var{n}
22007 Enable MicroBlaze-specific debugging messages if non-zero.
22009 @item show debug microblaze @var{n}
22010 Show MicroBlaze-specific debugging level.
22013 @node MIPS Embedded
22014 @subsection @acronym{MIPS} Embedded
22016 @cindex @acronym{MIPS} boards
22017 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
22018 @acronym{MIPS} board attached to a serial line. This is available when
22019 you configure @value{GDBN} with @samp{--target=mips-elf}.
22022 Use these @value{GDBN} commands to specify the connection to your target board:
22025 @item target mips @var{port}
22026 @kindex target mips @var{port}
22027 To run a program on the board, start up @code{@value{GDBP}} with the
22028 name of your program as the argument. To connect to the board, use the
22029 command @samp{target mips @var{port}}, where @var{port} is the name of
22030 the serial port connected to the board. If the program has not already
22031 been downloaded to the board, you may use the @code{load} command to
22032 download it. You can then use all the usual @value{GDBN} commands.
22034 For example, this sequence connects to the target board through a serial
22035 port, and loads and runs a program called @var{prog} through the
22039 host$ @value{GDBP} @var{prog}
22040 @value{GDBN} is free software and @dots{}
22041 (@value{GDBP}) target mips /dev/ttyb
22042 (@value{GDBP}) load @var{prog}
22046 @item target mips @var{hostname}:@var{portnumber}
22047 On some @value{GDBN} host configurations, you can specify a TCP
22048 connection (for instance, to a serial line managed by a terminal
22049 concentrator) instead of a serial port, using the syntax
22050 @samp{@var{hostname}:@var{portnumber}}.
22052 @item target pmon @var{port}
22053 @kindex target pmon @var{port}
22056 @item target ddb @var{port}
22057 @kindex target ddb @var{port}
22058 NEC's DDB variant of PMON for Vr4300.
22060 @item target lsi @var{port}
22061 @kindex target lsi @var{port}
22062 LSI variant of PMON.
22068 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
22071 @item set mipsfpu double
22072 @itemx set mipsfpu single
22073 @itemx set mipsfpu none
22074 @itemx set mipsfpu auto
22075 @itemx show mipsfpu
22076 @kindex set mipsfpu
22077 @kindex show mipsfpu
22078 @cindex @acronym{MIPS} remote floating point
22079 @cindex floating point, @acronym{MIPS} remote
22080 If your target board does not support the @acronym{MIPS} floating point
22081 coprocessor, you should use the command @samp{set mipsfpu none} (if you
22082 need this, you may wish to put the command in your @value{GDBN} init
22083 file). This tells @value{GDBN} how to find the return value of
22084 functions which return floating point values. It also allows
22085 @value{GDBN} to avoid saving the floating point registers when calling
22086 functions on the board. If you are using a floating point coprocessor
22087 with only single precision floating point support, as on the @sc{r4650}
22088 processor, use the command @samp{set mipsfpu single}. The default
22089 double precision floating point coprocessor may be selected using
22090 @samp{set mipsfpu double}.
22092 In previous versions the only choices were double precision or no
22093 floating point, so @samp{set mipsfpu on} will select double precision
22094 and @samp{set mipsfpu off} will select no floating point.
22096 As usual, you can inquire about the @code{mipsfpu} variable with
22097 @samp{show mipsfpu}.
22099 @item set timeout @var{seconds}
22100 @itemx set retransmit-timeout @var{seconds}
22101 @itemx show timeout
22102 @itemx show retransmit-timeout
22103 @cindex @code{timeout}, @acronym{MIPS} protocol
22104 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
22105 @kindex set timeout
22106 @kindex show timeout
22107 @kindex set retransmit-timeout
22108 @kindex show retransmit-timeout
22109 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
22110 remote protocol, with the @code{set timeout @var{seconds}} command. The
22111 default is 5 seconds. Similarly, you can control the timeout used while
22112 waiting for an acknowledgment of a packet with the @code{set
22113 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
22114 You can inspect both values with @code{show timeout} and @code{show
22115 retransmit-timeout}. (These commands are @emph{only} available when
22116 @value{GDBN} is configured for @samp{--target=mips-elf}.)
22118 The timeout set by @code{set timeout} does not apply when @value{GDBN}
22119 is waiting for your program to stop. In that case, @value{GDBN} waits
22120 forever because it has no way of knowing how long the program is going
22121 to run before stopping.
22123 @item set syn-garbage-limit @var{num}
22124 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
22125 @cindex synchronize with remote @acronym{MIPS} target
22126 Limit the maximum number of characters @value{GDBN} should ignore when
22127 it tries to synchronize with the remote target. The default is 10
22128 characters. Setting the limit to -1 means there's no limit.
22130 @item show syn-garbage-limit
22131 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
22132 Show the current limit on the number of characters to ignore when
22133 trying to synchronize with the remote system.
22135 @item set monitor-prompt @var{prompt}
22136 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
22137 @cindex remote monitor prompt
22138 Tell @value{GDBN} to expect the specified @var{prompt} string from the
22139 remote monitor. The default depends on the target:
22149 @item show monitor-prompt
22150 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
22151 Show the current strings @value{GDBN} expects as the prompt from the
22154 @item set monitor-warnings
22155 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
22156 Enable or disable monitor warnings about hardware breakpoints. This
22157 has effect only for the @code{lsi} target. When on, @value{GDBN} will
22158 display warning messages whose codes are returned by the @code{lsi}
22159 PMON monitor for breakpoint commands.
22161 @item show monitor-warnings
22162 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
22163 Show the current setting of printing monitor warnings.
22165 @item pmon @var{command}
22166 @kindex pmon@r{, @acronym{MIPS} remote}
22167 @cindex send PMON command
22168 This command allows sending an arbitrary @var{command} string to the
22169 monitor. The monitor must be in debug mode for this to work.
22172 @node PowerPC Embedded
22173 @subsection PowerPC Embedded
22175 @cindex DVC register
22176 @value{GDBN} supports using the DVC (Data Value Compare) register to
22177 implement in hardware simple hardware watchpoint conditions of the form:
22180 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
22181 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
22184 The DVC register will be automatically used when @value{GDBN} detects
22185 such pattern in a condition expression, and the created watchpoint uses one
22186 debug register (either the @code{exact-watchpoints} option is on and the
22187 variable is scalar, or the variable has a length of one byte). This feature
22188 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
22191 When running on PowerPC embedded processors, @value{GDBN} automatically uses
22192 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
22193 in which case watchpoints using only one debug register are created when
22194 watching variables of scalar types.
22196 You can create an artificial array to watch an arbitrary memory
22197 region using one of the following commands (@pxref{Expressions}):
22200 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
22201 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
22204 PowerPC embedded processors support masked watchpoints. See the discussion
22205 about the @code{mask} argument in @ref{Set Watchpoints}.
22207 @cindex ranged breakpoint
22208 PowerPC embedded processors support hardware accelerated
22209 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
22210 the inferior whenever it executes an instruction at any address within
22211 the range it specifies. To set a ranged breakpoint in @value{GDBN},
22212 use the @code{break-range} command.
22214 @value{GDBN} provides the following PowerPC-specific commands:
22217 @kindex break-range
22218 @item break-range @var{start-location}, @var{end-location}
22219 Set a breakpoint for an address range given by
22220 @var{start-location} and @var{end-location}, which can specify a function name,
22221 a line number, an offset of lines from the current line or from the start
22222 location, or an address of an instruction (see @ref{Specify Location},
22223 for a list of all the possible ways to specify a @var{location}.)
22224 The breakpoint will stop execution of the inferior whenever it
22225 executes an instruction at any address within the specified range,
22226 (including @var{start-location} and @var{end-location}.)
22228 @kindex set powerpc
22229 @item set powerpc soft-float
22230 @itemx show powerpc soft-float
22231 Force @value{GDBN} to use (or not use) a software floating point calling
22232 convention. By default, @value{GDBN} selects the calling convention based
22233 on the selected architecture and the provided executable file.
22235 @item set powerpc vector-abi
22236 @itemx show powerpc vector-abi
22237 Force @value{GDBN} to use the specified calling convention for vector
22238 arguments and return values. The valid options are @samp{auto};
22239 @samp{generic}, to avoid vector registers even if they are present;
22240 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
22241 registers. By default, @value{GDBN} selects the calling convention
22242 based on the selected architecture and the provided executable file.
22244 @item set powerpc exact-watchpoints
22245 @itemx show powerpc exact-watchpoints
22246 Allow @value{GDBN} to use only one debug register when watching a variable
22247 of scalar type, thus assuming that the variable is accessed through the
22248 address of its first byte.
22253 @subsection Atmel AVR
22256 When configured for debugging the Atmel AVR, @value{GDBN} supports the
22257 following AVR-specific commands:
22260 @item info io_registers
22261 @kindex info io_registers@r{, AVR}
22262 @cindex I/O registers (Atmel AVR)
22263 This command displays information about the AVR I/O registers. For
22264 each register, @value{GDBN} prints its number and value.
22271 When configured for debugging CRIS, @value{GDBN} provides the
22272 following CRIS-specific commands:
22275 @item set cris-version @var{ver}
22276 @cindex CRIS version
22277 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
22278 The CRIS version affects register names and sizes. This command is useful in
22279 case autodetection of the CRIS version fails.
22281 @item show cris-version
22282 Show the current CRIS version.
22284 @item set cris-dwarf2-cfi
22285 @cindex DWARF-2 CFI and CRIS
22286 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
22287 Change to @samp{off} when using @code{gcc-cris} whose version is below
22290 @item show cris-dwarf2-cfi
22291 Show the current state of using DWARF-2 CFI.
22293 @item set cris-mode @var{mode}
22295 Set the current CRIS mode to @var{mode}. It should only be changed when
22296 debugging in guru mode, in which case it should be set to
22297 @samp{guru} (the default is @samp{normal}).
22299 @item show cris-mode
22300 Show the current CRIS mode.
22304 @subsection Renesas Super-H
22307 For the Renesas Super-H processor, @value{GDBN} provides these
22311 @item set sh calling-convention @var{convention}
22312 @kindex set sh calling-convention
22313 Set the calling-convention used when calling functions from @value{GDBN}.
22314 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
22315 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
22316 convention. If the DWARF-2 information of the called function specifies
22317 that the function follows the Renesas calling convention, the function
22318 is called using the Renesas calling convention. If the calling convention
22319 is set to @samp{renesas}, the Renesas calling convention is always used,
22320 regardless of the DWARF-2 information. This can be used to override the
22321 default of @samp{gcc} if debug information is missing, or the compiler
22322 does not emit the DWARF-2 calling convention entry for a function.
22324 @item show sh calling-convention
22325 @kindex show sh calling-convention
22326 Show the current calling convention setting.
22331 @node Architectures
22332 @section Architectures
22334 This section describes characteristics of architectures that affect
22335 all uses of @value{GDBN} with the architecture, both native and cross.
22342 * HPPA:: HP PA architecture
22343 * SPU:: Cell Broadband Engine SPU architecture
22349 @subsection AArch64
22350 @cindex AArch64 support
22352 When @value{GDBN} is debugging the AArch64 architecture, it provides the
22353 following special commands:
22356 @item set debug aarch64
22357 @kindex set debug aarch64
22358 This command determines whether AArch64 architecture-specific debugging
22359 messages are to be displayed.
22361 @item show debug aarch64
22362 Show whether AArch64 debugging messages are displayed.
22367 @subsection x86 Architecture-specific Issues
22370 @item set struct-convention @var{mode}
22371 @kindex set struct-convention
22372 @cindex struct return convention
22373 @cindex struct/union returned in registers
22374 Set the convention used by the inferior to return @code{struct}s and
22375 @code{union}s from functions to @var{mode}. Possible values of
22376 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
22377 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
22378 are returned on the stack, while @code{"reg"} means that a
22379 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
22380 be returned in a register.
22382 @item show struct-convention
22383 @kindex show struct-convention
22384 Show the current setting of the convention to return @code{struct}s
22389 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
22390 @cindex Intel Memory Protection Extensions (MPX).
22392 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
22393 @footnote{The register named with capital letters represent the architecture
22394 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
22395 which are the lower bound and upper bound. Bounds are effective addresses or
22396 memory locations. The upper bounds are architecturally represented in 1's
22397 complement form. A bound having lower bound = 0, and upper bound = 0
22398 (1's complement of all bits set) will allow access to the entire address space.
22400 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
22401 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
22402 display the upper bound performing the complement of one operation on the
22403 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
22404 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
22405 can also be noted that the upper bounds are inclusive.
22407 As an example, assume that the register BND0 holds bounds for a pointer having
22408 access allowed for the range between 0x32 and 0x71. The values present on
22409 bnd0raw and bnd registers are presented as follows:
22412 bnd0raw = @{0x32, 0xffffffff8e@}
22413 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
22416 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
22417 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
22418 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
22419 Python, the display includes the memory size, in bits, accessible to
22422 Bounds can also be stored in bounds tables, which are stored in
22423 application memory. These tables store bounds for pointers by specifying
22424 the bounds pointer's value along with its bounds. Evaluating and changing
22425 bounds located in bound tables is therefore interesting while investigating
22426 bugs on MPX context. @value{GDBN} provides commands for this purpose:
22429 @item show mpx bound @var{pointer}
22430 @kindex show mpx bound
22431 Display bounds of the given @var{pointer}.
22433 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
22434 @kindex set mpx bound
22435 Set the bounds of a pointer in the bound table.
22436 This command takes three parameters: @var{pointer} is the pointers
22437 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
22438 for lower and upper bounds respectively.
22444 See the following section.
22447 @subsection @acronym{MIPS}
22449 @cindex stack on Alpha
22450 @cindex stack on @acronym{MIPS}
22451 @cindex Alpha stack
22452 @cindex @acronym{MIPS} stack
22453 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
22454 sometimes requires @value{GDBN} to search backward in the object code to
22455 find the beginning of a function.
22457 @cindex response time, @acronym{MIPS} debugging
22458 To improve response time (especially for embedded applications, where
22459 @value{GDBN} may be restricted to a slow serial line for this search)
22460 you may want to limit the size of this search, using one of these
22464 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
22465 @item set heuristic-fence-post @var{limit}
22466 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
22467 search for the beginning of a function. A value of @var{0} (the
22468 default) means there is no limit. However, except for @var{0}, the
22469 larger the limit the more bytes @code{heuristic-fence-post} must search
22470 and therefore the longer it takes to run. You should only need to use
22471 this command when debugging a stripped executable.
22473 @item show heuristic-fence-post
22474 Display the current limit.
22478 These commands are available @emph{only} when @value{GDBN} is configured
22479 for debugging programs on Alpha or @acronym{MIPS} processors.
22481 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
22485 @item set mips abi @var{arg}
22486 @kindex set mips abi
22487 @cindex set ABI for @acronym{MIPS}
22488 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
22489 values of @var{arg} are:
22493 The default ABI associated with the current binary (this is the
22503 @item show mips abi
22504 @kindex show mips abi
22505 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
22507 @item set mips compression @var{arg}
22508 @kindex set mips compression
22509 @cindex code compression, @acronym{MIPS}
22510 Tell @value{GDBN} which @acronym{MIPS} compressed
22511 @acronym{ISA, Instruction Set Architecture} encoding is used by the
22512 inferior. @value{GDBN} uses this for code disassembly and other
22513 internal interpretation purposes. This setting is only referred to
22514 when no executable has been associated with the debugging session or
22515 the executable does not provide information about the encoding it uses.
22516 Otherwise this setting is automatically updated from information
22517 provided by the executable.
22519 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
22520 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
22521 executables containing @acronym{MIPS16} code frequently are not
22522 identified as such.
22524 This setting is ``sticky''; that is, it retains its value across
22525 debugging sessions until reset either explicitly with this command or
22526 implicitly from an executable.
22528 The compiler and/or assembler typically add symbol table annotations to
22529 identify functions compiled for the @acronym{MIPS16} or
22530 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
22531 are present, @value{GDBN} uses them in preference to the global
22532 compressed @acronym{ISA} encoding setting.
22534 @item show mips compression
22535 @kindex show mips compression
22536 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
22537 @value{GDBN} to debug the inferior.
22540 @itemx show mipsfpu
22541 @xref{MIPS Embedded, set mipsfpu}.
22543 @item set mips mask-address @var{arg}
22544 @kindex set mips mask-address
22545 @cindex @acronym{MIPS} addresses, masking
22546 This command determines whether the most-significant 32 bits of 64-bit
22547 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
22548 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
22549 setting, which lets @value{GDBN} determine the correct value.
22551 @item show mips mask-address
22552 @kindex show mips mask-address
22553 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
22556 @item set remote-mips64-transfers-32bit-regs
22557 @kindex set remote-mips64-transfers-32bit-regs
22558 This command controls compatibility with 64-bit @acronym{MIPS} targets that
22559 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
22560 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
22561 and 64 bits for other registers, set this option to @samp{on}.
22563 @item show remote-mips64-transfers-32bit-regs
22564 @kindex show remote-mips64-transfers-32bit-regs
22565 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
22567 @item set debug mips
22568 @kindex set debug mips
22569 This command turns on and off debugging messages for the @acronym{MIPS}-specific
22570 target code in @value{GDBN}.
22572 @item show debug mips
22573 @kindex show debug mips
22574 Show the current setting of @acronym{MIPS} debugging messages.
22580 @cindex HPPA support
22582 When @value{GDBN} is debugging the HP PA architecture, it provides the
22583 following special commands:
22586 @item set debug hppa
22587 @kindex set debug hppa
22588 This command determines whether HPPA architecture-specific debugging
22589 messages are to be displayed.
22591 @item show debug hppa
22592 Show whether HPPA debugging messages are displayed.
22594 @item maint print unwind @var{address}
22595 @kindex maint print unwind@r{, HPPA}
22596 This command displays the contents of the unwind table entry at the
22597 given @var{address}.
22603 @subsection Cell Broadband Engine SPU architecture
22604 @cindex Cell Broadband Engine
22607 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
22608 it provides the following special commands:
22611 @item info spu event
22613 Display SPU event facility status. Shows current event mask
22614 and pending event status.
22616 @item info spu signal
22617 Display SPU signal notification facility status. Shows pending
22618 signal-control word and signal notification mode of both signal
22619 notification channels.
22621 @item info spu mailbox
22622 Display SPU mailbox facility status. Shows all pending entries,
22623 in order of processing, in each of the SPU Write Outbound,
22624 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
22627 Display MFC DMA status. Shows all pending commands in the MFC
22628 DMA queue. For each entry, opcode, tag, class IDs, effective
22629 and local store addresses and transfer size are shown.
22631 @item info spu proxydma
22632 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
22633 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
22634 and local store addresses and transfer size are shown.
22638 When @value{GDBN} is debugging a combined PowerPC/SPU application
22639 on the Cell Broadband Engine, it provides in addition the following
22643 @item set spu stop-on-load @var{arg}
22645 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
22646 will give control to the user when a new SPE thread enters its @code{main}
22647 function. The default is @code{off}.
22649 @item show spu stop-on-load
22651 Show whether to stop for new SPE threads.
22653 @item set spu auto-flush-cache @var{arg}
22654 Set whether to automatically flush the software-managed cache. When set to
22655 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
22656 cache to be flushed whenever SPE execution stops. This provides a consistent
22657 view of PowerPC memory that is accessed via the cache. If an application
22658 does not use the software-managed cache, this option has no effect.
22660 @item show spu auto-flush-cache
22661 Show whether to automatically flush the software-managed cache.
22666 @subsection PowerPC
22667 @cindex PowerPC architecture
22669 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
22670 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
22671 numbers stored in the floating point registers. These values must be stored
22672 in two consecutive registers, always starting at an even register like
22673 @code{f0} or @code{f2}.
22675 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
22676 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
22677 @code{f2} and @code{f3} for @code{$dl1} and so on.
22679 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
22680 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
22683 @subsection Nios II
22684 @cindex Nios II architecture
22686 When @value{GDBN} is debugging the Nios II architecture,
22687 it provides the following special commands:
22691 @item set debug nios2
22692 @kindex set debug nios2
22693 This command turns on and off debugging messages for the Nios II
22694 target code in @value{GDBN}.
22696 @item show debug nios2
22697 @kindex show debug nios2
22698 Show the current setting of Nios II debugging messages.
22701 @node Controlling GDB
22702 @chapter Controlling @value{GDBN}
22704 You can alter the way @value{GDBN} interacts with you by using the
22705 @code{set} command. For commands controlling how @value{GDBN} displays
22706 data, see @ref{Print Settings, ,Print Settings}. Other settings are
22711 * Editing:: Command editing
22712 * Command History:: Command history
22713 * Screen Size:: Screen size
22714 * Numbers:: Numbers
22715 * ABI:: Configuring the current ABI
22716 * Auto-loading:: Automatically loading associated files
22717 * Messages/Warnings:: Optional warnings and messages
22718 * Debugging Output:: Optional messages about internal happenings
22719 * Other Misc Settings:: Other Miscellaneous Settings
22727 @value{GDBN} indicates its readiness to read a command by printing a string
22728 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
22729 can change the prompt string with the @code{set prompt} command. For
22730 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
22731 the prompt in one of the @value{GDBN} sessions so that you can always tell
22732 which one you are talking to.
22734 @emph{Note:} @code{set prompt} does not add a space for you after the
22735 prompt you set. This allows you to set a prompt which ends in a space
22736 or a prompt that does not.
22740 @item set prompt @var{newprompt}
22741 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
22743 @kindex show prompt
22745 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
22748 Versions of @value{GDBN} that ship with Python scripting enabled have
22749 prompt extensions. The commands for interacting with these extensions
22753 @kindex set extended-prompt
22754 @item set extended-prompt @var{prompt}
22755 Set an extended prompt that allows for substitutions.
22756 @xref{gdb.prompt}, for a list of escape sequences that can be used for
22757 substitution. Any escape sequences specified as part of the prompt
22758 string are replaced with the corresponding strings each time the prompt
22764 set extended-prompt Current working directory: \w (gdb)
22767 Note that when an extended-prompt is set, it takes control of the
22768 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
22770 @kindex show extended-prompt
22771 @item show extended-prompt
22772 Prints the extended prompt. Any escape sequences specified as part of
22773 the prompt string with @code{set extended-prompt}, are replaced with the
22774 corresponding strings each time the prompt is displayed.
22778 @section Command Editing
22780 @cindex command line editing
22782 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
22783 @sc{gnu} library provides consistent behavior for programs which provide a
22784 command line interface to the user. Advantages are @sc{gnu} Emacs-style
22785 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
22786 substitution, and a storage and recall of command history across
22787 debugging sessions.
22789 You may control the behavior of command line editing in @value{GDBN} with the
22790 command @code{set}.
22793 @kindex set editing
22796 @itemx set editing on
22797 Enable command line editing (enabled by default).
22799 @item set editing off
22800 Disable command line editing.
22802 @kindex show editing
22804 Show whether command line editing is enabled.
22807 @ifset SYSTEM_READLINE
22808 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
22810 @ifclear SYSTEM_READLINE
22811 @xref{Command Line Editing},
22813 for more details about the Readline
22814 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
22815 encouraged to read that chapter.
22817 @node Command History
22818 @section Command History
22819 @cindex command history
22821 @value{GDBN} can keep track of the commands you type during your
22822 debugging sessions, so that you can be certain of precisely what
22823 happened. Use these commands to manage the @value{GDBN} command
22826 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
22827 package, to provide the history facility.
22828 @ifset SYSTEM_READLINE
22829 @xref{Using History Interactively, , , history, GNU History Library},
22831 @ifclear SYSTEM_READLINE
22832 @xref{Using History Interactively},
22834 for the detailed description of the History library.
22836 To issue a command to @value{GDBN} without affecting certain aspects of
22837 the state which is seen by users, prefix it with @samp{server }
22838 (@pxref{Server Prefix}). This
22839 means that this command will not affect the command history, nor will it
22840 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
22841 pressed on a line by itself.
22843 @cindex @code{server}, command prefix
22844 The server prefix does not affect the recording of values into the value
22845 history; to print a value without recording it into the value history,
22846 use the @code{output} command instead of the @code{print} command.
22848 Here is the description of @value{GDBN} commands related to command
22852 @cindex history substitution
22853 @cindex history file
22854 @kindex set history filename
22855 @cindex @env{GDBHISTFILE}, environment variable
22856 @item set history filename @var{fname}
22857 Set the name of the @value{GDBN} command history file to @var{fname}.
22858 This is the file where @value{GDBN} reads an initial command history
22859 list, and where it writes the command history from this session when it
22860 exits. You can access this list through history expansion or through
22861 the history command editing characters listed below. This file defaults
22862 to the value of the environment variable @code{GDBHISTFILE}, or to
22863 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
22866 @cindex save command history
22867 @kindex set history save
22868 @item set history save
22869 @itemx set history save on
22870 Record command history in a file, whose name may be specified with the
22871 @code{set history filename} command. By default, this option is disabled.
22873 @item set history save off
22874 Stop recording command history in a file.
22876 @cindex history size
22877 @kindex set history size
22878 @cindex @env{GDBHISTSIZE}, environment variable
22879 @item set history size @var{size}
22880 @itemx set history size unlimited
22881 Set the number of commands which @value{GDBN} keeps in its history list.
22882 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
22883 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
22884 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
22885 either a negative number or the empty string, then the number of commands
22886 @value{GDBN} keeps in the history list is unlimited.
22888 @cindex remove duplicate history
22889 @kindex set history remove-duplicates
22890 @item set history remove-duplicates @var{count}
22891 @itemx set history remove-duplicates unlimited
22892 Control the removal of duplicate history entries in the command history list.
22893 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
22894 history entries and remove the first entry that is a duplicate of the current
22895 entry being added to the command history list. If @var{count} is
22896 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
22897 removal of duplicate history entries is disabled.
22899 Only history entries added during the current session are considered for
22900 removal. This option is set to 0 by default.
22904 History expansion assigns special meaning to the character @kbd{!}.
22905 @ifset SYSTEM_READLINE
22906 @xref{Event Designators, , , history, GNU History Library},
22908 @ifclear SYSTEM_READLINE
22909 @xref{Event Designators},
22913 @cindex history expansion, turn on/off
22914 Since @kbd{!} is also the logical not operator in C, history expansion
22915 is off by default. If you decide to enable history expansion with the
22916 @code{set history expansion on} command, you may sometimes need to
22917 follow @kbd{!} (when it is used as logical not, in an expression) with
22918 a space or a tab to prevent it from being expanded. The readline
22919 history facilities do not attempt substitution on the strings
22920 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
22922 The commands to control history expansion are:
22925 @item set history expansion on
22926 @itemx set history expansion
22927 @kindex set history expansion
22928 Enable history expansion. History expansion is off by default.
22930 @item set history expansion off
22931 Disable history expansion.
22934 @kindex show history
22936 @itemx show history filename
22937 @itemx show history save
22938 @itemx show history size
22939 @itemx show history expansion
22940 These commands display the state of the @value{GDBN} history parameters.
22941 @code{show history} by itself displays all four states.
22946 @kindex show commands
22947 @cindex show last commands
22948 @cindex display command history
22949 @item show commands
22950 Display the last ten commands in the command history.
22952 @item show commands @var{n}
22953 Print ten commands centered on command number @var{n}.
22955 @item show commands +
22956 Print ten commands just after the commands last printed.
22960 @section Screen Size
22961 @cindex size of screen
22962 @cindex screen size
22965 @cindex pauses in output
22967 Certain commands to @value{GDBN} may produce large amounts of
22968 information output to the screen. To help you read all of it,
22969 @value{GDBN} pauses and asks you for input at the end of each page of
22970 output. Type @key{RET} when you want to continue the output, or @kbd{q}
22971 to discard the remaining output. Also, the screen width setting
22972 determines when to wrap lines of output. Depending on what is being
22973 printed, @value{GDBN} tries to break the line at a readable place,
22974 rather than simply letting it overflow onto the following line.
22976 Normally @value{GDBN} knows the size of the screen from the terminal
22977 driver software. For example, on Unix @value{GDBN} uses the termcap data base
22978 together with the value of the @code{TERM} environment variable and the
22979 @code{stty rows} and @code{stty cols} settings. If this is not correct,
22980 you can override it with the @code{set height} and @code{set
22987 @kindex show height
22988 @item set height @var{lpp}
22989 @itemx set height unlimited
22991 @itemx set width @var{cpl}
22992 @itemx set width unlimited
22994 These @code{set} commands specify a screen height of @var{lpp} lines and
22995 a screen width of @var{cpl} characters. The associated @code{show}
22996 commands display the current settings.
22998 If you specify a height of either @code{unlimited} or zero lines,
22999 @value{GDBN} does not pause during output no matter how long the
23000 output is. This is useful if output is to a file or to an editor
23003 Likewise, you can specify @samp{set width unlimited} or @samp{set
23004 width 0} to prevent @value{GDBN} from wrapping its output.
23006 @item set pagination on
23007 @itemx set pagination off
23008 @kindex set pagination
23009 Turn the output pagination on or off; the default is on. Turning
23010 pagination off is the alternative to @code{set height unlimited}. Note that
23011 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
23012 Options, -batch}) also automatically disables pagination.
23014 @item show pagination
23015 @kindex show pagination
23016 Show the current pagination mode.
23021 @cindex number representation
23022 @cindex entering numbers
23024 You can always enter numbers in octal, decimal, or hexadecimal in
23025 @value{GDBN} by the usual conventions: octal numbers begin with
23026 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
23027 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
23028 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
23029 10; likewise, the default display for numbers---when no particular
23030 format is specified---is base 10. You can change the default base for
23031 both input and output with the commands described below.
23034 @kindex set input-radix
23035 @item set input-radix @var{base}
23036 Set the default base for numeric input. Supported choices
23037 for @var{base} are decimal 8, 10, or 16. The base must itself be
23038 specified either unambiguously or using the current input radix; for
23042 set input-radix 012
23043 set input-radix 10.
23044 set input-radix 0xa
23048 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
23049 leaves the input radix unchanged, no matter what it was, since
23050 @samp{10}, being without any leading or trailing signs of its base, is
23051 interpreted in the current radix. Thus, if the current radix is 16,
23052 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
23055 @kindex set output-radix
23056 @item set output-radix @var{base}
23057 Set the default base for numeric display. Supported choices
23058 for @var{base} are decimal 8, 10, or 16. The base must itself be
23059 specified either unambiguously or using the current input radix.
23061 @kindex show input-radix
23062 @item show input-radix
23063 Display the current default base for numeric input.
23065 @kindex show output-radix
23066 @item show output-radix
23067 Display the current default base for numeric display.
23069 @item set radix @r{[}@var{base}@r{]}
23073 These commands set and show the default base for both input and output
23074 of numbers. @code{set radix} sets the radix of input and output to
23075 the same base; without an argument, it resets the radix back to its
23076 default value of 10.
23081 @section Configuring the Current ABI
23083 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
23084 application automatically. However, sometimes you need to override its
23085 conclusions. Use these commands to manage @value{GDBN}'s view of the
23091 @cindex Newlib OS ABI and its influence on the longjmp handling
23093 One @value{GDBN} configuration can debug binaries for multiple operating
23094 system targets, either via remote debugging or native emulation.
23095 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
23096 but you can override its conclusion using the @code{set osabi} command.
23097 One example where this is useful is in debugging of binaries which use
23098 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
23099 not have the same identifying marks that the standard C library for your
23102 When @value{GDBN} is debugging the AArch64 architecture, it provides a
23103 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
23104 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
23105 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
23109 Show the OS ABI currently in use.
23112 With no argument, show the list of registered available OS ABI's.
23114 @item set osabi @var{abi}
23115 Set the current OS ABI to @var{abi}.
23118 @cindex float promotion
23120 Generally, the way that an argument of type @code{float} is passed to a
23121 function depends on whether the function is prototyped. For a prototyped
23122 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
23123 according to the architecture's convention for @code{float}. For unprototyped
23124 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
23125 @code{double} and then passed.
23127 Unfortunately, some forms of debug information do not reliably indicate whether
23128 a function is prototyped. If @value{GDBN} calls a function that is not marked
23129 as prototyped, it consults @kbd{set coerce-float-to-double}.
23132 @kindex set coerce-float-to-double
23133 @item set coerce-float-to-double
23134 @itemx set coerce-float-to-double on
23135 Arguments of type @code{float} will be promoted to @code{double} when passed
23136 to an unprototyped function. This is the default setting.
23138 @item set coerce-float-to-double off
23139 Arguments of type @code{float} will be passed directly to unprototyped
23142 @kindex show coerce-float-to-double
23143 @item show coerce-float-to-double
23144 Show the current setting of promoting @code{float} to @code{double}.
23148 @kindex show cp-abi
23149 @value{GDBN} needs to know the ABI used for your program's C@t{++}
23150 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
23151 used to build your application. @value{GDBN} only fully supports
23152 programs with a single C@t{++} ABI; if your program contains code using
23153 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
23154 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
23155 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
23156 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
23157 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
23158 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
23163 Show the C@t{++} ABI currently in use.
23166 With no argument, show the list of supported C@t{++} ABI's.
23168 @item set cp-abi @var{abi}
23169 @itemx set cp-abi auto
23170 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
23174 @section Automatically loading associated files
23175 @cindex auto-loading
23177 @value{GDBN} sometimes reads files with commands and settings automatically,
23178 without being explicitly told so by the user. We call this feature
23179 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
23180 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
23181 results or introduce security risks (e.g., if the file comes from untrusted
23185 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
23186 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
23188 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
23189 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
23192 There are various kinds of files @value{GDBN} can automatically load.
23193 In addition to these files, @value{GDBN} supports auto-loading code written
23194 in various extension languages. @xref{Auto-loading extensions}.
23196 Note that loading of these associated files (including the local @file{.gdbinit}
23197 file) requires accordingly configured @code{auto-load safe-path}
23198 (@pxref{Auto-loading safe path}).
23200 For these reasons, @value{GDBN} includes commands and options to let you
23201 control when to auto-load files and which files should be auto-loaded.
23204 @anchor{set auto-load off}
23205 @kindex set auto-load off
23206 @item set auto-load off
23207 Globally disable loading of all auto-loaded files.
23208 You may want to use this command with the @samp{-iex} option
23209 (@pxref{Option -init-eval-command}) such as:
23211 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
23214 Be aware that system init file (@pxref{System-wide configuration})
23215 and init files from your home directory (@pxref{Home Directory Init File})
23216 still get read (as they come from generally trusted directories).
23217 To prevent @value{GDBN} from auto-loading even those init files, use the
23218 @option{-nx} option (@pxref{Mode Options}), in addition to
23219 @code{set auto-load no}.
23221 @anchor{show auto-load}
23222 @kindex show auto-load
23223 @item show auto-load
23224 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
23228 (gdb) show auto-load
23229 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
23230 libthread-db: Auto-loading of inferior specific libthread_db is on.
23231 local-gdbinit: Auto-loading of .gdbinit script from current directory
23233 python-scripts: Auto-loading of Python scripts is on.
23234 safe-path: List of directories from which it is safe to auto-load files
23235 is $debugdir:$datadir/auto-load.
23236 scripts-directory: List of directories from which to load auto-loaded scripts
23237 is $debugdir:$datadir/auto-load.
23240 @anchor{info auto-load}
23241 @kindex info auto-load
23242 @item info auto-load
23243 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
23247 (gdb) info auto-load
23250 Yes /home/user/gdb/gdb-gdb.gdb
23251 libthread-db: No auto-loaded libthread-db.
23252 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
23256 Yes /home/user/gdb/gdb-gdb.py
23260 These are @value{GDBN} control commands for the auto-loading:
23262 @multitable @columnfractions .5 .5
23263 @item @xref{set auto-load off}.
23264 @tab Disable auto-loading globally.
23265 @item @xref{show auto-load}.
23266 @tab Show setting of all kinds of files.
23267 @item @xref{info auto-load}.
23268 @tab Show state of all kinds of files.
23269 @item @xref{set auto-load gdb-scripts}.
23270 @tab Control for @value{GDBN} command scripts.
23271 @item @xref{show auto-load gdb-scripts}.
23272 @tab Show setting of @value{GDBN} command scripts.
23273 @item @xref{info auto-load gdb-scripts}.
23274 @tab Show state of @value{GDBN} command scripts.
23275 @item @xref{set auto-load python-scripts}.
23276 @tab Control for @value{GDBN} Python scripts.
23277 @item @xref{show auto-load python-scripts}.
23278 @tab Show setting of @value{GDBN} Python scripts.
23279 @item @xref{info auto-load python-scripts}.
23280 @tab Show state of @value{GDBN} Python scripts.
23281 @item @xref{set auto-load guile-scripts}.
23282 @tab Control for @value{GDBN} Guile scripts.
23283 @item @xref{show auto-load guile-scripts}.
23284 @tab Show setting of @value{GDBN} Guile scripts.
23285 @item @xref{info auto-load guile-scripts}.
23286 @tab Show state of @value{GDBN} Guile scripts.
23287 @item @xref{set auto-load scripts-directory}.
23288 @tab Control for @value{GDBN} auto-loaded scripts location.
23289 @item @xref{show auto-load scripts-directory}.
23290 @tab Show @value{GDBN} auto-loaded scripts location.
23291 @item @xref{add-auto-load-scripts-directory}.
23292 @tab Add directory for auto-loaded scripts location list.
23293 @item @xref{set auto-load local-gdbinit}.
23294 @tab Control for init file in the current directory.
23295 @item @xref{show auto-load local-gdbinit}.
23296 @tab Show setting of init file in the current directory.
23297 @item @xref{info auto-load local-gdbinit}.
23298 @tab Show state of init file in the current directory.
23299 @item @xref{set auto-load libthread-db}.
23300 @tab Control for thread debugging library.
23301 @item @xref{show auto-load libthread-db}.
23302 @tab Show setting of thread debugging library.
23303 @item @xref{info auto-load libthread-db}.
23304 @tab Show state of thread debugging library.
23305 @item @xref{set auto-load safe-path}.
23306 @tab Control directories trusted for automatic loading.
23307 @item @xref{show auto-load safe-path}.
23308 @tab Show directories trusted for automatic loading.
23309 @item @xref{add-auto-load-safe-path}.
23310 @tab Add directory trusted for automatic loading.
23313 @node Init File in the Current Directory
23314 @subsection Automatically loading init file in the current directory
23315 @cindex auto-loading init file in the current directory
23317 By default, @value{GDBN} reads and executes the canned sequences of commands
23318 from init file (if any) in the current working directory,
23319 see @ref{Init File in the Current Directory during Startup}.
23321 Note that loading of this local @file{.gdbinit} file also requires accordingly
23322 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23325 @anchor{set auto-load local-gdbinit}
23326 @kindex set auto-load local-gdbinit
23327 @item set auto-load local-gdbinit [on|off]
23328 Enable or disable the auto-loading of canned sequences of commands
23329 (@pxref{Sequences}) found in init file in the current directory.
23331 @anchor{show auto-load local-gdbinit}
23332 @kindex show auto-load local-gdbinit
23333 @item show auto-load local-gdbinit
23334 Show whether auto-loading of canned sequences of commands from init file in the
23335 current directory is enabled or disabled.
23337 @anchor{info auto-load local-gdbinit}
23338 @kindex info auto-load local-gdbinit
23339 @item info auto-load local-gdbinit
23340 Print whether canned sequences of commands from init file in the
23341 current directory have been auto-loaded.
23344 @node libthread_db.so.1 file
23345 @subsection Automatically loading thread debugging library
23346 @cindex auto-loading libthread_db.so.1
23348 This feature is currently present only on @sc{gnu}/Linux native hosts.
23350 @value{GDBN} reads in some cases thread debugging library from places specific
23351 to the inferior (@pxref{set libthread-db-search-path}).
23353 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
23354 without checking this @samp{set auto-load libthread-db} switch as system
23355 libraries have to be trusted in general. In all other cases of
23356 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
23357 auto-load libthread-db} is enabled before trying to open such thread debugging
23360 Note that loading of this debugging library also requires accordingly configured
23361 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23364 @anchor{set auto-load libthread-db}
23365 @kindex set auto-load libthread-db
23366 @item set auto-load libthread-db [on|off]
23367 Enable or disable the auto-loading of inferior specific thread debugging library.
23369 @anchor{show auto-load libthread-db}
23370 @kindex show auto-load libthread-db
23371 @item show auto-load libthread-db
23372 Show whether auto-loading of inferior specific thread debugging library is
23373 enabled or disabled.
23375 @anchor{info auto-load libthread-db}
23376 @kindex info auto-load libthread-db
23377 @item info auto-load libthread-db
23378 Print the list of all loaded inferior specific thread debugging libraries and
23379 for each such library print list of inferior @var{pid}s using it.
23382 @node Auto-loading safe path
23383 @subsection Security restriction for auto-loading
23384 @cindex auto-loading safe-path
23386 As the files of inferior can come from untrusted source (such as submitted by
23387 an application user) @value{GDBN} does not always load any files automatically.
23388 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
23389 directories trusted for loading files not explicitly requested by user.
23390 Each directory can also be a shell wildcard pattern.
23392 If the path is not set properly you will see a warning and the file will not
23397 Reading symbols from /home/user/gdb/gdb...done.
23398 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
23399 declined by your `auto-load safe-path' set
23400 to "$debugdir:$datadir/auto-load".
23401 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
23402 declined by your `auto-load safe-path' set
23403 to "$debugdir:$datadir/auto-load".
23407 To instruct @value{GDBN} to go ahead and use the init files anyway,
23408 invoke @value{GDBN} like this:
23411 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
23414 The list of trusted directories is controlled by the following commands:
23417 @anchor{set auto-load safe-path}
23418 @kindex set auto-load safe-path
23419 @item set auto-load safe-path @r{[}@var{directories}@r{]}
23420 Set the list of directories (and their subdirectories) trusted for automatic
23421 loading and execution of scripts. You can also enter a specific trusted file.
23422 Each directory can also be a shell wildcard pattern; wildcards do not match
23423 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
23424 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
23425 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
23426 its default value as specified during @value{GDBN} compilation.
23428 The list of directories uses path separator (@samp{:} on GNU and Unix
23429 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
23430 to the @env{PATH} environment variable.
23432 @anchor{show auto-load safe-path}
23433 @kindex show auto-load safe-path
23434 @item show auto-load safe-path
23435 Show the list of directories trusted for automatic loading and execution of
23438 @anchor{add-auto-load-safe-path}
23439 @kindex add-auto-load-safe-path
23440 @item add-auto-load-safe-path
23441 Add an entry (or list of entries) to the list of directories trusted for
23442 automatic loading and execution of scripts. Multiple entries may be delimited
23443 by the host platform path separator in use.
23446 This variable defaults to what @code{--with-auto-load-dir} has been configured
23447 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
23448 substitution applies the same as for @ref{set auto-load scripts-directory}.
23449 The default @code{set auto-load safe-path} value can be also overriden by
23450 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
23452 Setting this variable to @file{/} disables this security protection,
23453 corresponding @value{GDBN} configuration option is
23454 @option{--without-auto-load-safe-path}.
23455 This variable is supposed to be set to the system directories writable by the
23456 system superuser only. Users can add their source directories in init files in
23457 their home directories (@pxref{Home Directory Init File}). See also deprecated
23458 init file in the current directory
23459 (@pxref{Init File in the Current Directory during Startup}).
23461 To force @value{GDBN} to load the files it declined to load in the previous
23462 example, you could use one of the following ways:
23465 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
23466 Specify this trusted directory (or a file) as additional component of the list.
23467 You have to specify also any existing directories displayed by
23468 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
23470 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
23471 Specify this directory as in the previous case but just for a single
23472 @value{GDBN} session.
23474 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
23475 Disable auto-loading safety for a single @value{GDBN} session.
23476 This assumes all the files you debug during this @value{GDBN} session will come
23477 from trusted sources.
23479 @item @kbd{./configure --without-auto-load-safe-path}
23480 During compilation of @value{GDBN} you may disable any auto-loading safety.
23481 This assumes all the files you will ever debug with this @value{GDBN} come from
23485 On the other hand you can also explicitly forbid automatic files loading which
23486 also suppresses any such warning messages:
23489 @item @kbd{gdb -iex "set auto-load no" @dots{}}
23490 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
23492 @item @file{~/.gdbinit}: @samp{set auto-load no}
23493 Disable auto-loading globally for the user
23494 (@pxref{Home Directory Init File}). While it is improbable, you could also
23495 use system init file instead (@pxref{System-wide configuration}).
23498 This setting applies to the file names as entered by user. If no entry matches
23499 @value{GDBN} tries as a last resort to also resolve all the file names into
23500 their canonical form (typically resolving symbolic links) and compare the
23501 entries again. @value{GDBN} already canonicalizes most of the filenames on its
23502 own before starting the comparison so a canonical form of directories is
23503 recommended to be entered.
23505 @node Auto-loading verbose mode
23506 @subsection Displaying files tried for auto-load
23507 @cindex auto-loading verbose mode
23509 For better visibility of all the file locations where you can place scripts to
23510 be auto-loaded with inferior --- or to protect yourself against accidental
23511 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
23512 all the files attempted to be loaded. Both existing and non-existing files may
23515 For example the list of directories from which it is safe to auto-load files
23516 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
23517 may not be too obvious while setting it up.
23520 (gdb) set debug auto-load on
23521 (gdb) file ~/src/t/true
23522 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
23523 for objfile "/tmp/true".
23524 auto-load: Updating directories of "/usr:/opt".
23525 auto-load: Using directory "/usr".
23526 auto-load: Using directory "/opt".
23527 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
23528 by your `auto-load safe-path' set to "/usr:/opt".
23532 @anchor{set debug auto-load}
23533 @kindex set debug auto-load
23534 @item set debug auto-load [on|off]
23535 Set whether to print the filenames attempted to be auto-loaded.
23537 @anchor{show debug auto-load}
23538 @kindex show debug auto-load
23539 @item show debug auto-load
23540 Show whether printing of the filenames attempted to be auto-loaded is turned
23544 @node Messages/Warnings
23545 @section Optional Warnings and Messages
23547 @cindex verbose operation
23548 @cindex optional warnings
23549 By default, @value{GDBN} is silent about its inner workings. If you are
23550 running on a slow machine, you may want to use the @code{set verbose}
23551 command. This makes @value{GDBN} tell you when it does a lengthy
23552 internal operation, so you will not think it has crashed.
23554 Currently, the messages controlled by @code{set verbose} are those
23555 which announce that the symbol table for a source file is being read;
23556 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
23559 @kindex set verbose
23560 @item set verbose on
23561 Enables @value{GDBN} output of certain informational messages.
23563 @item set verbose off
23564 Disables @value{GDBN} output of certain informational messages.
23566 @kindex show verbose
23568 Displays whether @code{set verbose} is on or off.
23571 By default, if @value{GDBN} encounters bugs in the symbol table of an
23572 object file, it is silent; but if you are debugging a compiler, you may
23573 find this information useful (@pxref{Symbol Errors, ,Errors Reading
23578 @kindex set complaints
23579 @item set complaints @var{limit}
23580 Permits @value{GDBN} to output @var{limit} complaints about each type of
23581 unusual symbols before becoming silent about the problem. Set
23582 @var{limit} to zero to suppress all complaints; set it to a large number
23583 to prevent complaints from being suppressed.
23585 @kindex show complaints
23586 @item show complaints
23587 Displays how many symbol complaints @value{GDBN} is permitted to produce.
23591 @anchor{confirmation requests}
23592 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
23593 lot of stupid questions to confirm certain commands. For example, if
23594 you try to run a program which is already running:
23598 The program being debugged has been started already.
23599 Start it from the beginning? (y or n)
23602 If you are willing to unflinchingly face the consequences of your own
23603 commands, you can disable this ``feature'':
23607 @kindex set confirm
23609 @cindex confirmation
23610 @cindex stupid questions
23611 @item set confirm off
23612 Disables confirmation requests. Note that running @value{GDBN} with
23613 the @option{--batch} option (@pxref{Mode Options, -batch}) also
23614 automatically disables confirmation requests.
23616 @item set confirm on
23617 Enables confirmation requests (the default).
23619 @kindex show confirm
23621 Displays state of confirmation requests.
23625 @cindex command tracing
23626 If you need to debug user-defined commands or sourced files you may find it
23627 useful to enable @dfn{command tracing}. In this mode each command will be
23628 printed as it is executed, prefixed with one or more @samp{+} symbols, the
23629 quantity denoting the call depth of each command.
23632 @kindex set trace-commands
23633 @cindex command scripts, debugging
23634 @item set trace-commands on
23635 Enable command tracing.
23636 @item set trace-commands off
23637 Disable command tracing.
23638 @item show trace-commands
23639 Display the current state of command tracing.
23642 @node Debugging Output
23643 @section Optional Messages about Internal Happenings
23644 @cindex optional debugging messages
23646 @value{GDBN} has commands that enable optional debugging messages from
23647 various @value{GDBN} subsystems; normally these commands are of
23648 interest to @value{GDBN} maintainers, or when reporting a bug. This
23649 section documents those commands.
23652 @kindex set exec-done-display
23653 @item set exec-done-display
23654 Turns on or off the notification of asynchronous commands'
23655 completion. When on, @value{GDBN} will print a message when an
23656 asynchronous command finishes its execution. The default is off.
23657 @kindex show exec-done-display
23658 @item show exec-done-display
23659 Displays the current setting of asynchronous command completion
23662 @cindex ARM AArch64
23663 @item set debug aarch64
23664 Turns on or off display of debugging messages related to ARM AArch64.
23665 The default is off.
23667 @item show debug aarch64
23668 Displays the current state of displaying debugging messages related to
23670 @cindex gdbarch debugging info
23671 @cindex architecture debugging info
23672 @item set debug arch
23673 Turns on or off display of gdbarch debugging info. The default is off
23674 @item show debug arch
23675 Displays the current state of displaying gdbarch debugging info.
23676 @item set debug aix-solib
23677 @cindex AIX shared library debugging
23678 Control display of debugging messages from the AIX shared library
23679 support module. The default is off.
23680 @item show debug aix-thread
23681 Show the current state of displaying AIX shared library debugging messages.
23682 @item set debug aix-thread
23683 @cindex AIX threads
23684 Display debugging messages about inner workings of the AIX thread
23686 @item show debug aix-thread
23687 Show the current state of AIX thread debugging info display.
23688 @item set debug check-physname
23690 Check the results of the ``physname'' computation. When reading DWARF
23691 debugging information for C@t{++}, @value{GDBN} attempts to compute
23692 each entity's name. @value{GDBN} can do this computation in two
23693 different ways, depending on exactly what information is present.
23694 When enabled, this setting causes @value{GDBN} to compute the names
23695 both ways and display any discrepancies.
23696 @item show debug check-physname
23697 Show the current state of ``physname'' checking.
23698 @item set debug coff-pe-read
23699 @cindex COFF/PE exported symbols
23700 Control display of debugging messages related to reading of COFF/PE
23701 exported symbols. The default is off.
23702 @item show debug coff-pe-read
23703 Displays the current state of displaying debugging messages related to
23704 reading of COFF/PE exported symbols.
23705 @item set debug dwarf-die
23707 Dump DWARF DIEs after they are read in.
23708 The value is the number of nesting levels to print.
23709 A value of zero turns off the display.
23710 @item show debug dwarf-die
23711 Show the current state of DWARF DIE debugging.
23712 @item set debug dwarf-line
23713 @cindex DWARF Line Tables
23714 Turns on or off display of debugging messages related to reading
23715 DWARF line tables. The default is 0 (off).
23716 A value of 1 provides basic information.
23717 A value greater than 1 provides more verbose information.
23718 @item show debug dwarf-line
23719 Show the current state of DWARF line table debugging.
23720 @item set debug dwarf-read
23721 @cindex DWARF Reading
23722 Turns on or off display of debugging messages related to reading
23723 DWARF debug info. The default is 0 (off).
23724 A value of 1 provides basic information.
23725 A value greater than 1 provides more verbose information.
23726 @item show debug dwarf-read
23727 Show the current state of DWARF reader debugging.
23728 @item set debug displaced
23729 @cindex displaced stepping debugging info
23730 Turns on or off display of @value{GDBN} debugging info for the
23731 displaced stepping support. The default is off.
23732 @item show debug displaced
23733 Displays the current state of displaying @value{GDBN} debugging info
23734 related to displaced stepping.
23735 @item set debug event
23736 @cindex event debugging info
23737 Turns on or off display of @value{GDBN} event debugging info. The
23739 @item show debug event
23740 Displays the current state of displaying @value{GDBN} event debugging
23742 @item set debug expression
23743 @cindex expression debugging info
23744 Turns on or off display of debugging info about @value{GDBN}
23745 expression parsing. The default is off.
23746 @item show debug expression
23747 Displays the current state of displaying debugging info about
23748 @value{GDBN} expression parsing.
23749 @item set debug fbsd-lwp
23750 @cindex FreeBSD LWP debug messages
23751 Turns on or off debugging messages from the FreeBSD LWP debug support.
23752 @item show debug fbsd-lwp
23753 Show the current state of FreeBSD LWP debugging messages.
23754 @item set debug frame
23755 @cindex frame debugging info
23756 Turns on or off display of @value{GDBN} frame debugging info. The
23758 @item show debug frame
23759 Displays the current state of displaying @value{GDBN} frame debugging
23761 @item set debug gnu-nat
23762 @cindex @sc{gnu}/Hurd debug messages
23763 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
23764 @item show debug gnu-nat
23765 Show the current state of @sc{gnu}/Hurd debugging messages.
23766 @item set debug infrun
23767 @cindex inferior debugging info
23768 Turns on or off display of @value{GDBN} debugging info for running the inferior.
23769 The default is off. @file{infrun.c} contains GDB's runtime state machine used
23770 for implementing operations such as single-stepping the inferior.
23771 @item show debug infrun
23772 Displays the current state of @value{GDBN} inferior debugging.
23773 @item set debug jit
23774 @cindex just-in-time compilation, debugging messages
23775 Turn on or off debugging messages from JIT debug support.
23776 @item show debug jit
23777 Displays the current state of @value{GDBN} JIT debugging.
23778 @item set debug lin-lwp
23779 @cindex @sc{gnu}/Linux LWP debug messages
23780 @cindex Linux lightweight processes
23781 Turn on or off debugging messages from the Linux LWP debug support.
23782 @item show debug lin-lwp
23783 Show the current state of Linux LWP debugging messages.
23784 @item set debug linux-namespaces
23785 @cindex @sc{gnu}/Linux namespaces debug messages
23786 Turn on or off debugging messages from the Linux namespaces debug support.
23787 @item show debug linux-namespaces
23788 Show the current state of Linux namespaces debugging messages.
23789 @item set debug mach-o
23790 @cindex Mach-O symbols processing
23791 Control display of debugging messages related to Mach-O symbols
23792 processing. The default is off.
23793 @item show debug mach-o
23794 Displays the current state of displaying debugging messages related to
23795 reading of COFF/PE exported symbols.
23796 @item set debug notification
23797 @cindex remote async notification debugging info
23798 Turn on or off debugging messages about remote async notification.
23799 The default is off.
23800 @item show debug notification
23801 Displays the current state of remote async notification debugging messages.
23802 @item set debug observer
23803 @cindex observer debugging info
23804 Turns on or off display of @value{GDBN} observer debugging. This
23805 includes info such as the notification of observable events.
23806 @item show debug observer
23807 Displays the current state of observer debugging.
23808 @item set debug overload
23809 @cindex C@t{++} overload debugging info
23810 Turns on or off display of @value{GDBN} C@t{++} overload debugging
23811 info. This includes info such as ranking of functions, etc. The default
23813 @item show debug overload
23814 Displays the current state of displaying @value{GDBN} C@t{++} overload
23816 @cindex expression parser, debugging info
23817 @cindex debug expression parser
23818 @item set debug parser
23819 Turns on or off the display of expression parser debugging output.
23820 Internally, this sets the @code{yydebug} variable in the expression
23821 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
23822 details. The default is off.
23823 @item show debug parser
23824 Show the current state of expression parser debugging.
23825 @cindex packets, reporting on stdout
23826 @cindex serial connections, debugging
23827 @cindex debug remote protocol
23828 @cindex remote protocol debugging
23829 @cindex display remote packets
23830 @item set debug remote
23831 Turns on or off display of reports on all packets sent back and forth across
23832 the serial line to the remote machine. The info is printed on the
23833 @value{GDBN} standard output stream. The default is off.
23834 @item show debug remote
23835 Displays the state of display of remote packets.
23836 @item set debug serial
23837 Turns on or off display of @value{GDBN} serial debugging info. The
23839 @item show debug serial
23840 Displays the current state of displaying @value{GDBN} serial debugging
23842 @item set debug solib-frv
23843 @cindex FR-V shared-library debugging
23844 Turn on or off debugging messages for FR-V shared-library code.
23845 @item show debug solib-frv
23846 Display the current state of FR-V shared-library code debugging
23848 @item set debug symbol-lookup
23849 @cindex symbol lookup
23850 Turns on or off display of debugging messages related to symbol lookup.
23851 The default is 0 (off).
23852 A value of 1 provides basic information.
23853 A value greater than 1 provides more verbose information.
23854 @item show debug symbol-lookup
23855 Show the current state of symbol lookup debugging messages.
23856 @item set debug symfile
23857 @cindex symbol file functions
23858 Turns on or off display of debugging messages related to symbol file functions.
23859 The default is off. @xref{Files}.
23860 @item show debug symfile
23861 Show the current state of symbol file debugging messages.
23862 @item set debug symtab-create
23863 @cindex symbol table creation
23864 Turns on or off display of debugging messages related to symbol table creation.
23865 The default is 0 (off).
23866 A value of 1 provides basic information.
23867 A value greater than 1 provides more verbose information.
23868 @item show debug symtab-create
23869 Show the current state of symbol table creation debugging.
23870 @item set debug target
23871 @cindex target debugging info
23872 Turns on or off display of @value{GDBN} target debugging info. This info
23873 includes what is going on at the target level of GDB, as it happens. The
23874 default is 0. Set it to 1 to track events, and to 2 to also track the
23875 value of large memory transfers.
23876 @item show debug target
23877 Displays the current state of displaying @value{GDBN} target debugging
23879 @item set debug timestamp
23880 @cindex timestampping debugging info
23881 Turns on or off display of timestamps with @value{GDBN} debugging info.
23882 When enabled, seconds and microseconds are displayed before each debugging
23884 @item show debug timestamp
23885 Displays the current state of displaying timestamps with @value{GDBN}
23887 @item set debug varobj
23888 @cindex variable object debugging info
23889 Turns on or off display of @value{GDBN} variable object debugging
23890 info. The default is off.
23891 @item show debug varobj
23892 Displays the current state of displaying @value{GDBN} variable object
23894 @item set debug xml
23895 @cindex XML parser debugging
23896 Turn on or off debugging messages for built-in XML parsers.
23897 @item show debug xml
23898 Displays the current state of XML debugging messages.
23901 @node Other Misc Settings
23902 @section Other Miscellaneous Settings
23903 @cindex miscellaneous settings
23906 @kindex set interactive-mode
23907 @item set interactive-mode
23908 If @code{on}, forces @value{GDBN} to assume that GDB was started
23909 in a terminal. In practice, this means that @value{GDBN} should wait
23910 for the user to answer queries generated by commands entered at
23911 the command prompt. If @code{off}, forces @value{GDBN} to operate
23912 in the opposite mode, and it uses the default answers to all queries.
23913 If @code{auto} (the default), @value{GDBN} tries to determine whether
23914 its standard input is a terminal, and works in interactive-mode if it
23915 is, non-interactively otherwise.
23917 In the vast majority of cases, the debugger should be able to guess
23918 correctly which mode should be used. But this setting can be useful
23919 in certain specific cases, such as running a MinGW @value{GDBN}
23920 inside a cygwin window.
23922 @kindex show interactive-mode
23923 @item show interactive-mode
23924 Displays whether the debugger is operating in interactive mode or not.
23927 @node Extending GDB
23928 @chapter Extending @value{GDBN}
23929 @cindex extending GDB
23931 @value{GDBN} provides several mechanisms for extension.
23932 @value{GDBN} also provides the ability to automatically load
23933 extensions when it reads a file for debugging. This allows the
23934 user to automatically customize @value{GDBN} for the program
23938 * Sequences:: Canned Sequences of @value{GDBN} Commands
23939 * Python:: Extending @value{GDBN} using Python
23940 * Guile:: Extending @value{GDBN} using Guile
23941 * Auto-loading extensions:: Automatically loading extensions
23942 * Multiple Extension Languages:: Working with multiple extension languages
23943 * Aliases:: Creating new spellings of existing commands
23946 To facilitate the use of extension languages, @value{GDBN} is capable
23947 of evaluating the contents of a file. When doing so, @value{GDBN}
23948 can recognize which extension language is being used by looking at
23949 the filename extension. Files with an unrecognized filename extension
23950 are always treated as a @value{GDBN} Command Files.
23951 @xref{Command Files,, Command files}.
23953 You can control how @value{GDBN} evaluates these files with the following
23957 @kindex set script-extension
23958 @kindex show script-extension
23959 @item set script-extension off
23960 All scripts are always evaluated as @value{GDBN} Command Files.
23962 @item set script-extension soft
23963 The debugger determines the scripting language based on filename
23964 extension. If this scripting language is supported, @value{GDBN}
23965 evaluates the script using that language. Otherwise, it evaluates
23966 the file as a @value{GDBN} Command File.
23968 @item set script-extension strict
23969 The debugger determines the scripting language based on filename
23970 extension, and evaluates the script using that language. If the
23971 language is not supported, then the evaluation fails.
23973 @item show script-extension
23974 Display the current value of the @code{script-extension} option.
23979 @section Canned Sequences of Commands
23981 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
23982 Command Lists}), @value{GDBN} provides two ways to store sequences of
23983 commands for execution as a unit: user-defined commands and command
23987 * Define:: How to define your own commands
23988 * Hooks:: Hooks for user-defined commands
23989 * Command Files:: How to write scripts of commands to be stored in a file
23990 * Output:: Commands for controlled output
23991 * Auto-loading sequences:: Controlling auto-loaded command files
23995 @subsection User-defined Commands
23997 @cindex user-defined command
23998 @cindex arguments, to user-defined commands
23999 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
24000 which you assign a new name as a command. This is done with the
24001 @code{define} command. User commands may accept up to 10 arguments
24002 separated by whitespace. Arguments are accessed within the user command
24003 via @code{$arg0@dots{}$arg9}. A trivial example:
24007 print $arg0 + $arg1 + $arg2
24012 To execute the command use:
24019 This defines the command @code{adder}, which prints the sum of
24020 its three arguments. Note the arguments are text substitutions, so they may
24021 reference variables, use complex expressions, or even perform inferior
24024 @cindex argument count in user-defined commands
24025 @cindex how many arguments (user-defined commands)
24026 In addition, @code{$argc} may be used to find out how many arguments have
24027 been passed. This expands to a number in the range 0@dots{}10.
24032 print $arg0 + $arg1
24035 print $arg0 + $arg1 + $arg2
24043 @item define @var{commandname}
24044 Define a command named @var{commandname}. If there is already a command
24045 by that name, you are asked to confirm that you want to redefine it.
24046 The argument @var{commandname} may be a bare command name consisting of letters,
24047 numbers, dashes, and underscores. It may also start with any predefined
24048 prefix command. For example, @samp{define target my-target} creates
24049 a user-defined @samp{target my-target} command.
24051 The definition of the command is made up of other @value{GDBN} command lines,
24052 which are given following the @code{define} command. The end of these
24053 commands is marked by a line containing @code{end}.
24056 @kindex end@r{ (user-defined commands)}
24057 @item document @var{commandname}
24058 Document the user-defined command @var{commandname}, so that it can be
24059 accessed by @code{help}. The command @var{commandname} must already be
24060 defined. This command reads lines of documentation just as @code{define}
24061 reads the lines of the command definition, ending with @code{end}.
24062 After the @code{document} command is finished, @code{help} on command
24063 @var{commandname} displays the documentation you have written.
24065 You may use the @code{document} command again to change the
24066 documentation of a command. Redefining the command with @code{define}
24067 does not change the documentation.
24069 @kindex dont-repeat
24070 @cindex don't repeat command
24072 Used inside a user-defined command, this tells @value{GDBN} that this
24073 command should not be repeated when the user hits @key{RET}
24074 (@pxref{Command Syntax, repeat last command}).
24076 @kindex help user-defined
24077 @item help user-defined
24078 List all user-defined commands and all python commands defined in class
24079 COMAND_USER. The first line of the documentation or docstring is
24084 @itemx show user @var{commandname}
24085 Display the @value{GDBN} commands used to define @var{commandname} (but
24086 not its documentation). If no @var{commandname} is given, display the
24087 definitions for all user-defined commands.
24088 This does not work for user-defined python commands.
24090 @cindex infinite recursion in user-defined commands
24091 @kindex show max-user-call-depth
24092 @kindex set max-user-call-depth
24093 @item show max-user-call-depth
24094 @itemx set max-user-call-depth
24095 The value of @code{max-user-call-depth} controls how many recursion
24096 levels are allowed in user-defined commands before @value{GDBN} suspects an
24097 infinite recursion and aborts the command.
24098 This does not apply to user-defined python commands.
24101 In addition to the above commands, user-defined commands frequently
24102 use control flow commands, described in @ref{Command Files}.
24104 When user-defined commands are executed, the
24105 commands of the definition are not printed. An error in any command
24106 stops execution of the user-defined command.
24108 If used interactively, commands that would ask for confirmation proceed
24109 without asking when used inside a user-defined command. Many @value{GDBN}
24110 commands that normally print messages to say what they are doing omit the
24111 messages when used in a user-defined command.
24114 @subsection User-defined Command Hooks
24115 @cindex command hooks
24116 @cindex hooks, for commands
24117 @cindex hooks, pre-command
24120 You may define @dfn{hooks}, which are a special kind of user-defined
24121 command. Whenever you run the command @samp{foo}, if the user-defined
24122 command @samp{hook-foo} exists, it is executed (with no arguments)
24123 before that command.
24125 @cindex hooks, post-command
24127 A hook may also be defined which is run after the command you executed.
24128 Whenever you run the command @samp{foo}, if the user-defined command
24129 @samp{hookpost-foo} exists, it is executed (with no arguments) after
24130 that command. Post-execution hooks may exist simultaneously with
24131 pre-execution hooks, for the same command.
24133 It is valid for a hook to call the command which it hooks. If this
24134 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
24136 @c It would be nice if hookpost could be passed a parameter indicating
24137 @c if the command it hooks executed properly or not. FIXME!
24139 @kindex stop@r{, a pseudo-command}
24140 In addition, a pseudo-command, @samp{stop} exists. Defining
24141 (@samp{hook-stop}) makes the associated commands execute every time
24142 execution stops in your program: before breakpoint commands are run,
24143 displays are printed, or the stack frame is printed.
24145 For example, to ignore @code{SIGALRM} signals while
24146 single-stepping, but treat them normally during normal execution,
24151 handle SIGALRM nopass
24155 handle SIGALRM pass
24158 define hook-continue
24159 handle SIGALRM pass
24163 As a further example, to hook at the beginning and end of the @code{echo}
24164 command, and to add extra text to the beginning and end of the message,
24172 define hookpost-echo
24176 (@value{GDBP}) echo Hello World
24177 <<<---Hello World--->>>
24182 You can define a hook for any single-word command in @value{GDBN}, but
24183 not for command aliases; you should define a hook for the basic command
24184 name, e.g.@: @code{backtrace} rather than @code{bt}.
24185 @c FIXME! So how does Joe User discover whether a command is an alias
24187 You can hook a multi-word command by adding @code{hook-} or
24188 @code{hookpost-} to the last word of the command, e.g.@:
24189 @samp{define target hook-remote} to add a hook to @samp{target remote}.
24191 If an error occurs during the execution of your hook, execution of
24192 @value{GDBN} commands stops and @value{GDBN} issues a prompt
24193 (before the command that you actually typed had a chance to run).
24195 If you try to define a hook which does not match any known command, you
24196 get a warning from the @code{define} command.
24198 @node Command Files
24199 @subsection Command Files
24201 @cindex command files
24202 @cindex scripting commands
24203 A command file for @value{GDBN} is a text file made of lines that are
24204 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
24205 also be included. An empty line in a command file does nothing; it
24206 does not mean to repeat the last command, as it would from the
24209 You can request the execution of a command file with the @code{source}
24210 command. Note that the @code{source} command is also used to evaluate
24211 scripts that are not Command Files. The exact behavior can be configured
24212 using the @code{script-extension} setting.
24213 @xref{Extending GDB,, Extending GDB}.
24217 @cindex execute commands from a file
24218 @item source [-s] [-v] @var{filename}
24219 Execute the command file @var{filename}.
24222 The lines in a command file are generally executed sequentially,
24223 unless the order of execution is changed by one of the
24224 @emph{flow-control commands} described below. The commands are not
24225 printed as they are executed. An error in any command terminates
24226 execution of the command file and control is returned to the console.
24228 @value{GDBN} first searches for @var{filename} in the current directory.
24229 If the file is not found there, and @var{filename} does not specify a
24230 directory, then @value{GDBN} also looks for the file on the source search path
24231 (specified with the @samp{directory} command);
24232 except that @file{$cdir} is not searched because the compilation directory
24233 is not relevant to scripts.
24235 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
24236 on the search path even if @var{filename} specifies a directory.
24237 The search is done by appending @var{filename} to each element of the
24238 search path. So, for example, if @var{filename} is @file{mylib/myscript}
24239 and the search path contains @file{/home/user} then @value{GDBN} will
24240 look for the script @file{/home/user/mylib/myscript}.
24241 The search is also done if @var{filename} is an absolute path.
24242 For example, if @var{filename} is @file{/tmp/myscript} and
24243 the search path contains @file{/home/user} then @value{GDBN} will
24244 look for the script @file{/home/user/tmp/myscript}.
24245 For DOS-like systems, if @var{filename} contains a drive specification,
24246 it is stripped before concatenation. For example, if @var{filename} is
24247 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
24248 will look for the script @file{c:/tmp/myscript}.
24250 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
24251 each command as it is executed. The option must be given before
24252 @var{filename}, and is interpreted as part of the filename anywhere else.
24254 Commands that would ask for confirmation if used interactively proceed
24255 without asking when used in a command file. Many @value{GDBN} commands that
24256 normally print messages to say what they are doing omit the messages
24257 when called from command files.
24259 @value{GDBN} also accepts command input from standard input. In this
24260 mode, normal output goes to standard output and error output goes to
24261 standard error. Errors in a command file supplied on standard input do
24262 not terminate execution of the command file---execution continues with
24266 gdb < cmds > log 2>&1
24269 (The syntax above will vary depending on the shell used.) This example
24270 will execute commands from the file @file{cmds}. All output and errors
24271 would be directed to @file{log}.
24273 Since commands stored on command files tend to be more general than
24274 commands typed interactively, they frequently need to deal with
24275 complicated situations, such as different or unexpected values of
24276 variables and symbols, changes in how the program being debugged is
24277 built, etc. @value{GDBN} provides a set of flow-control commands to
24278 deal with these complexities. Using these commands, you can write
24279 complex scripts that loop over data structures, execute commands
24280 conditionally, etc.
24287 This command allows to include in your script conditionally executed
24288 commands. The @code{if} command takes a single argument, which is an
24289 expression to evaluate. It is followed by a series of commands that
24290 are executed only if the expression is true (its value is nonzero).
24291 There can then optionally be an @code{else} line, followed by a series
24292 of commands that are only executed if the expression was false. The
24293 end of the list is marked by a line containing @code{end}.
24297 This command allows to write loops. Its syntax is similar to
24298 @code{if}: the command takes a single argument, which is an expression
24299 to evaluate, and must be followed by the commands to execute, one per
24300 line, terminated by an @code{end}. These commands are called the
24301 @dfn{body} of the loop. The commands in the body of @code{while} are
24302 executed repeatedly as long as the expression evaluates to true.
24306 This command exits the @code{while} loop in whose body it is included.
24307 Execution of the script continues after that @code{while}s @code{end}
24310 @kindex loop_continue
24311 @item loop_continue
24312 This command skips the execution of the rest of the body of commands
24313 in the @code{while} loop in whose body it is included. Execution
24314 branches to the beginning of the @code{while} loop, where it evaluates
24315 the controlling expression.
24317 @kindex end@r{ (if/else/while commands)}
24319 Terminate the block of commands that are the body of @code{if},
24320 @code{else}, or @code{while} flow-control commands.
24325 @subsection Commands for Controlled Output
24327 During the execution of a command file or a user-defined command, normal
24328 @value{GDBN} output is suppressed; the only output that appears is what is
24329 explicitly printed by the commands in the definition. This section
24330 describes three commands useful for generating exactly the output you
24335 @item echo @var{text}
24336 @c I do not consider backslash-space a standard C escape sequence
24337 @c because it is not in ANSI.
24338 Print @var{text}. Nonprinting characters can be included in
24339 @var{text} using C escape sequences, such as @samp{\n} to print a
24340 newline. @strong{No newline is printed unless you specify one.}
24341 In addition to the standard C escape sequences, a backslash followed
24342 by a space stands for a space. This is useful for displaying a
24343 string with spaces at the beginning or the end, since leading and
24344 trailing spaces are otherwise trimmed from all arguments.
24345 To print @samp{@w{ }and foo =@w{ }}, use the command
24346 @samp{echo \@w{ }and foo = \@w{ }}.
24348 A backslash at the end of @var{text} can be used, as in C, to continue
24349 the command onto subsequent lines. For example,
24352 echo This is some text\n\
24353 which is continued\n\
24354 onto several lines.\n
24357 produces the same output as
24360 echo This is some text\n
24361 echo which is continued\n
24362 echo onto several lines.\n
24366 @item output @var{expression}
24367 Print the value of @var{expression} and nothing but that value: no
24368 newlines, no @samp{$@var{nn} = }. The value is not entered in the
24369 value history either. @xref{Expressions, ,Expressions}, for more information
24372 @item output/@var{fmt} @var{expression}
24373 Print the value of @var{expression} in format @var{fmt}. You can use
24374 the same formats as for @code{print}. @xref{Output Formats,,Output
24375 Formats}, for more information.
24378 @item printf @var{template}, @var{expressions}@dots{}
24379 Print the values of one or more @var{expressions} under the control of
24380 the string @var{template}. To print several values, make
24381 @var{expressions} be a comma-separated list of individual expressions,
24382 which may be either numbers or pointers. Their values are printed as
24383 specified by @var{template}, exactly as a C program would do by
24384 executing the code below:
24387 printf (@var{template}, @var{expressions}@dots{});
24390 As in @code{C} @code{printf}, ordinary characters in @var{template}
24391 are printed verbatim, while @dfn{conversion specification} introduced
24392 by the @samp{%} character cause subsequent @var{expressions} to be
24393 evaluated, their values converted and formatted according to type and
24394 style information encoded in the conversion specifications, and then
24397 For example, you can print two values in hex like this:
24400 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
24403 @code{printf} supports all the standard @code{C} conversion
24404 specifications, including the flags and modifiers between the @samp{%}
24405 character and the conversion letter, with the following exceptions:
24409 The argument-ordering modifiers, such as @samp{2$}, are not supported.
24412 The modifier @samp{*} is not supported for specifying precision or
24416 The @samp{'} flag (for separation of digits into groups according to
24417 @code{LC_NUMERIC'}) is not supported.
24420 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
24424 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
24427 The conversion letters @samp{a} and @samp{A} are not supported.
24431 Note that the @samp{ll} type modifier is supported only if the
24432 underlying @code{C} implementation used to build @value{GDBN} supports
24433 the @code{long long int} type, and the @samp{L} type modifier is
24434 supported only if @code{long double} type is available.
24436 As in @code{C}, @code{printf} supports simple backslash-escape
24437 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
24438 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
24439 single character. Octal and hexadecimal escape sequences are not
24442 Additionally, @code{printf} supports conversion specifications for DFP
24443 (@dfn{Decimal Floating Point}) types using the following length modifiers
24444 together with a floating point specifier.
24449 @samp{H} for printing @code{Decimal32} types.
24452 @samp{D} for printing @code{Decimal64} types.
24455 @samp{DD} for printing @code{Decimal128} types.
24458 If the underlying @code{C} implementation used to build @value{GDBN} has
24459 support for the three length modifiers for DFP types, other modifiers
24460 such as width and precision will also be available for @value{GDBN} to use.
24462 In case there is no such @code{C} support, no additional modifiers will be
24463 available and the value will be printed in the standard way.
24465 Here's an example of printing DFP types using the above conversion letters:
24467 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
24471 @item eval @var{template}, @var{expressions}@dots{}
24472 Convert the values of one or more @var{expressions} under the control of
24473 the string @var{template} to a command line, and call it.
24477 @node Auto-loading sequences
24478 @subsection Controlling auto-loading native @value{GDBN} scripts
24479 @cindex native script auto-loading
24481 When a new object file is read (for example, due to the @code{file}
24482 command, or because the inferior has loaded a shared library),
24483 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
24484 @xref{Auto-loading extensions}.
24486 Auto-loading can be enabled or disabled,
24487 and the list of auto-loaded scripts can be printed.
24490 @anchor{set auto-load gdb-scripts}
24491 @kindex set auto-load gdb-scripts
24492 @item set auto-load gdb-scripts [on|off]
24493 Enable or disable the auto-loading of canned sequences of commands scripts.
24495 @anchor{show auto-load gdb-scripts}
24496 @kindex show auto-load gdb-scripts
24497 @item show auto-load gdb-scripts
24498 Show whether auto-loading of canned sequences of commands scripts is enabled or
24501 @anchor{info auto-load gdb-scripts}
24502 @kindex info auto-load gdb-scripts
24503 @cindex print list of auto-loaded canned sequences of commands scripts
24504 @item info auto-load gdb-scripts [@var{regexp}]
24505 Print the list of all canned sequences of commands scripts that @value{GDBN}
24509 If @var{regexp} is supplied only canned sequences of commands scripts with
24510 matching names are printed.
24512 @c Python docs live in a separate file.
24513 @include python.texi
24515 @c Guile docs live in a separate file.
24516 @include guile.texi
24518 @node Auto-loading extensions
24519 @section Auto-loading extensions
24520 @cindex auto-loading extensions
24522 @value{GDBN} provides two mechanisms for automatically loading extensions
24523 when a new object file is read (for example, due to the @code{file}
24524 command, or because the inferior has loaded a shared library):
24525 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
24526 section of modern file formats like ELF.
24529 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
24530 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
24531 * Which flavor to choose?::
24534 The auto-loading feature is useful for supplying application-specific
24535 debugging commands and features.
24537 Auto-loading can be enabled or disabled,
24538 and the list of auto-loaded scripts can be printed.
24539 See the @samp{auto-loading} section of each extension language
24540 for more information.
24541 For @value{GDBN} command files see @ref{Auto-loading sequences}.
24542 For Python files see @ref{Python Auto-loading}.
24544 Note that loading of this script file also requires accordingly configured
24545 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24547 @node objfile-gdbdotext file
24548 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
24549 @cindex @file{@var{objfile}-gdb.gdb}
24550 @cindex @file{@var{objfile}-gdb.py}
24551 @cindex @file{@var{objfile}-gdb.scm}
24553 When a new object file is read, @value{GDBN} looks for a file named
24554 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
24555 where @var{objfile} is the object file's name and
24556 where @var{ext} is the file extension for the extension language:
24559 @item @file{@var{objfile}-gdb.gdb}
24560 GDB's own command language
24561 @item @file{@var{objfile}-gdb.py}
24563 @item @file{@var{objfile}-gdb.scm}
24567 @var{script-name} is formed by ensuring that the file name of @var{objfile}
24568 is absolute, following all symlinks, and resolving @code{.} and @code{..}
24569 components, and appending the @file{-gdb.@var{ext}} suffix.
24570 If this file exists and is readable, @value{GDBN} will evaluate it as a
24571 script in the specified extension language.
24573 If this file does not exist, then @value{GDBN} will look for
24574 @var{script-name} file in all of the directories as specified below.
24576 Note that loading of these files requires an accordingly configured
24577 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24579 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
24580 scripts normally according to its @file{.exe} filename. But if no scripts are
24581 found @value{GDBN} also tries script filenames matching the object file without
24582 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
24583 is attempted on any platform. This makes the script filenames compatible
24584 between Unix and MS-Windows hosts.
24587 @anchor{set auto-load scripts-directory}
24588 @kindex set auto-load scripts-directory
24589 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
24590 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
24591 may be delimited by the host platform path separator in use
24592 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
24594 Each entry here needs to be covered also by the security setting
24595 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
24597 @anchor{with-auto-load-dir}
24598 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
24599 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
24600 configuration option @option{--with-auto-load-dir}.
24602 Any reference to @file{$debugdir} will get replaced by
24603 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
24604 reference to @file{$datadir} will get replaced by @var{data-directory} which is
24605 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
24606 @file{$datadir} must be placed as a directory component --- either alone or
24607 delimited by @file{/} or @file{\} directory separators, depending on the host
24610 The list of directories uses path separator (@samp{:} on GNU and Unix
24611 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
24612 to the @env{PATH} environment variable.
24614 @anchor{show auto-load scripts-directory}
24615 @kindex show auto-load scripts-directory
24616 @item show auto-load scripts-directory
24617 Show @value{GDBN} auto-loaded scripts location.
24619 @anchor{add-auto-load-scripts-directory}
24620 @kindex add-auto-load-scripts-directory
24621 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
24622 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
24623 Multiple entries may be delimited by the host platform path separator in use.
24626 @value{GDBN} does not track which files it has already auto-loaded this way.
24627 @value{GDBN} will load the associated script every time the corresponding
24628 @var{objfile} is opened.
24629 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
24630 is evaluated more than once.
24632 @node dotdebug_gdb_scripts section
24633 @subsection The @code{.debug_gdb_scripts} section
24634 @cindex @code{.debug_gdb_scripts} section
24636 For systems using file formats like ELF and COFF,
24637 when @value{GDBN} loads a new object file
24638 it will look for a special section named @code{.debug_gdb_scripts}.
24639 If this section exists, its contents is a list of null-terminated entries
24640 specifying scripts to load. Each entry begins with a non-null prefix byte that
24641 specifies the kind of entry, typically the extension language and whether the
24642 script is in a file or inlined in @code{.debug_gdb_scripts}.
24644 The following entries are supported:
24647 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
24648 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
24649 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
24650 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
24653 @subsubsection Script File Entries
24655 If the entry specifies a file, @value{GDBN} will look for the file first
24656 in the current directory and then along the source search path
24657 (@pxref{Source Path, ,Specifying Source Directories}),
24658 except that @file{$cdir} is not searched, since the compilation
24659 directory is not relevant to scripts.
24661 File entries can be placed in section @code{.debug_gdb_scripts} with,
24662 for example, this GCC macro for Python scripts.
24665 /* Note: The "MS" section flags are to remove duplicates. */
24666 #define DEFINE_GDB_PY_SCRIPT(script_name) \
24668 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
24669 .byte 1 /* Python */\n\
24670 .asciz \"" script_name "\"\n\
24676 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
24677 Then one can reference the macro in a header or source file like this:
24680 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
24683 The script name may include directories if desired.
24685 Note that loading of this script file also requires accordingly configured
24686 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24688 If the macro invocation is put in a header, any application or library
24689 using this header will get a reference to the specified script,
24690 and with the use of @code{"MS"} attributes on the section, the linker
24691 will remove duplicates.
24693 @subsubsection Script Text Entries
24695 Script text entries allow to put the executable script in the entry
24696 itself instead of loading it from a file.
24697 The first line of the entry, everything after the prefix byte and up to
24698 the first newline (@code{0xa}) character, is the script name, and must not
24699 contain any kind of space character, e.g., spaces or tabs.
24700 The rest of the entry, up to the trailing null byte, is the script to
24701 execute in the specified language. The name needs to be unique among
24702 all script names, as @value{GDBN} executes each script only once based
24705 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
24709 #include "symcat.h"
24710 #include "gdb/section-scripts.h"
24712 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
24713 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
24714 ".ascii \"gdb.inlined-script\\n\"\n"
24715 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
24716 ".ascii \" def __init__ (self):\\n\"\n"
24717 ".ascii \" super (test_cmd, self).__init__ ("
24718 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
24719 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
24720 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
24721 ".ascii \"test_cmd ()\\n\"\n"
24727 Loading of inlined scripts requires a properly configured
24728 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24729 The path to specify in @code{auto-load safe-path} is the path of the file
24730 containing the @code{.debug_gdb_scripts} section.
24732 @node Which flavor to choose?
24733 @subsection Which flavor to choose?
24735 Given the multiple ways of auto-loading extensions, it might not always
24736 be clear which one to choose. This section provides some guidance.
24739 Benefits of the @file{-gdb.@var{ext}} way:
24743 Can be used with file formats that don't support multiple sections.
24746 Ease of finding scripts for public libraries.
24748 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
24749 in the source search path.
24750 For publicly installed libraries, e.g., @file{libstdc++}, there typically
24751 isn't a source directory in which to find the script.
24754 Doesn't require source code additions.
24758 Benefits of the @code{.debug_gdb_scripts} way:
24762 Works with static linking.
24764 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
24765 trigger their loading. When an application is statically linked the only
24766 objfile available is the executable, and it is cumbersome to attach all the
24767 scripts from all the input libraries to the executable's
24768 @file{-gdb.@var{ext}} script.
24771 Works with classes that are entirely inlined.
24773 Some classes can be entirely inlined, and thus there may not be an associated
24774 shared library to attach a @file{-gdb.@var{ext}} script to.
24777 Scripts needn't be copied out of the source tree.
24779 In some circumstances, apps can be built out of large collections of internal
24780 libraries, and the build infrastructure necessary to install the
24781 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
24782 cumbersome. It may be easier to specify the scripts in the
24783 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
24784 top of the source tree to the source search path.
24787 @node Multiple Extension Languages
24788 @section Multiple Extension Languages
24790 The Guile and Python extension languages do not share any state,
24791 and generally do not interfere with each other.
24792 There are some things to be aware of, however.
24794 @subsection Python comes first
24796 Python was @value{GDBN}'s first extension language, and to avoid breaking
24797 existing behaviour Python comes first. This is generally solved by the
24798 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
24799 extension languages, and when it makes a call to an extension language,
24800 (say to pretty-print a value), it tries each in turn until an extension
24801 language indicates it has performed the request (e.g., has returned the
24802 pretty-printed form of a value).
24803 This extends to errors while performing such requests: If an error happens
24804 while, for example, trying to pretty-print an object then the error is
24805 reported and any following extension languages are not tried.
24808 @section Creating new spellings of existing commands
24809 @cindex aliases for commands
24811 It is often useful to define alternate spellings of existing commands.
24812 For example, if a new @value{GDBN} command defined in Python has
24813 a long name to type, it is handy to have an abbreviated version of it
24814 that involves less typing.
24816 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
24817 of the @samp{step} command even though it is otherwise an ambiguous
24818 abbreviation of other commands like @samp{set} and @samp{show}.
24820 Aliases are also used to provide shortened or more common versions
24821 of multi-word commands. For example, @value{GDBN} provides the
24822 @samp{tty} alias of the @samp{set inferior-tty} command.
24824 You can define a new alias with the @samp{alias} command.
24829 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
24833 @var{ALIAS} specifies the name of the new alias.
24834 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
24837 @var{COMMAND} specifies the name of an existing command
24838 that is being aliased.
24840 The @samp{-a} option specifies that the new alias is an abbreviation
24841 of the command. Abbreviations are not shown in command
24842 lists displayed by the @samp{help} command.
24844 The @samp{--} option specifies the end of options,
24845 and is useful when @var{ALIAS} begins with a dash.
24847 Here is a simple example showing how to make an abbreviation
24848 of a command so that there is less to type.
24849 Suppose you were tired of typing @samp{disas}, the current
24850 shortest unambiguous abbreviation of the @samp{disassemble} command
24851 and you wanted an even shorter version named @samp{di}.
24852 The following will accomplish this.
24855 (gdb) alias -a di = disas
24858 Note that aliases are different from user-defined commands.
24859 With a user-defined command, you also need to write documentation
24860 for it with the @samp{document} command.
24861 An alias automatically picks up the documentation of the existing command.
24863 Here is an example where we make @samp{elms} an abbreviation of
24864 @samp{elements} in the @samp{set print elements} command.
24865 This is to show that you can make an abbreviation of any part
24869 (gdb) alias -a set print elms = set print elements
24870 (gdb) alias -a show print elms = show print elements
24871 (gdb) set p elms 20
24873 Limit on string chars or array elements to print is 200.
24876 Note that if you are defining an alias of a @samp{set} command,
24877 and you want to have an alias for the corresponding @samp{show}
24878 command, then you need to define the latter separately.
24880 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
24881 @var{ALIAS}, just as they are normally.
24884 (gdb) alias -a set pr elms = set p ele
24887 Finally, here is an example showing the creation of a one word
24888 alias for a more complex command.
24889 This creates alias @samp{spe} of the command @samp{set print elements}.
24892 (gdb) alias spe = set print elements
24897 @chapter Command Interpreters
24898 @cindex command interpreters
24900 @value{GDBN} supports multiple command interpreters, and some command
24901 infrastructure to allow users or user interface writers to switch
24902 between interpreters or run commands in other interpreters.
24904 @value{GDBN} currently supports two command interpreters, the console
24905 interpreter (sometimes called the command-line interpreter or @sc{cli})
24906 and the machine interface interpreter (or @sc{gdb/mi}). This manual
24907 describes both of these interfaces in great detail.
24909 By default, @value{GDBN} will start with the console interpreter.
24910 However, the user may choose to start @value{GDBN} with another
24911 interpreter by specifying the @option{-i} or @option{--interpreter}
24912 startup options. Defined interpreters include:
24916 @cindex console interpreter
24917 The traditional console or command-line interpreter. This is the most often
24918 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
24919 @value{GDBN} will use this interpreter.
24922 @cindex mi interpreter
24923 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
24924 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
24925 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
24929 @cindex mi2 interpreter
24930 The current @sc{gdb/mi} interface.
24933 @cindex mi1 interpreter
24934 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
24938 @cindex invoke another interpreter
24939 The interpreter being used by @value{GDBN} may not be dynamically
24940 switched at runtime. Although possible, this could lead to a very
24941 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
24942 enters the command "interpreter-set console" in a console view,
24943 @value{GDBN} would switch to using the console interpreter, rendering
24944 the IDE inoperable!
24946 @kindex interpreter-exec
24947 Although you may only choose a single interpreter at startup, you may execute
24948 commands in any interpreter from the current interpreter using the appropriate
24949 command. If you are running the console interpreter, simply use the
24950 @code{interpreter-exec} command:
24953 interpreter-exec mi "-data-list-register-names"
24956 @sc{gdb/mi} has a similar command, although it is only available in versions of
24957 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
24960 @chapter @value{GDBN} Text User Interface
24962 @cindex Text User Interface
24965 * TUI Overview:: TUI overview
24966 * TUI Keys:: TUI key bindings
24967 * TUI Single Key Mode:: TUI single key mode
24968 * TUI Commands:: TUI-specific commands
24969 * TUI Configuration:: TUI configuration variables
24972 The @value{GDBN} Text User Interface (TUI) is a terminal
24973 interface which uses the @code{curses} library to show the source
24974 file, the assembly output, the program registers and @value{GDBN}
24975 commands in separate text windows. The TUI mode is supported only
24976 on platforms where a suitable version of the @code{curses} library
24979 The TUI mode is enabled by default when you invoke @value{GDBN} as
24980 @samp{@value{GDBP} -tui}.
24981 You can also switch in and out of TUI mode while @value{GDBN} runs by
24982 using various TUI commands and key bindings, such as @command{tui
24983 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
24984 @ref{TUI Keys, ,TUI Key Bindings}.
24987 @section TUI Overview
24989 In TUI mode, @value{GDBN} can display several text windows:
24993 This window is the @value{GDBN} command window with the @value{GDBN}
24994 prompt and the @value{GDBN} output. The @value{GDBN} input is still
24995 managed using readline.
24998 The source window shows the source file of the program. The current
24999 line and active breakpoints are displayed in this window.
25002 The assembly window shows the disassembly output of the program.
25005 This window shows the processor registers. Registers are highlighted
25006 when their values change.
25009 The source and assembly windows show the current program position
25010 by highlighting the current line and marking it with a @samp{>} marker.
25011 Breakpoints are indicated with two markers. The first marker
25012 indicates the breakpoint type:
25016 Breakpoint which was hit at least once.
25019 Breakpoint which was never hit.
25022 Hardware breakpoint which was hit at least once.
25025 Hardware breakpoint which was never hit.
25028 The second marker indicates whether the breakpoint is enabled or not:
25032 Breakpoint is enabled.
25035 Breakpoint is disabled.
25038 The source, assembly and register windows are updated when the current
25039 thread changes, when the frame changes, or when the program counter
25042 These windows are not all visible at the same time. The command
25043 window is always visible. The others can be arranged in several
25054 source and assembly,
25057 source and registers, or
25060 assembly and registers.
25063 A status line above the command window shows the following information:
25067 Indicates the current @value{GDBN} target.
25068 (@pxref{Targets, ,Specifying a Debugging Target}).
25071 Gives the current process or thread number.
25072 When no process is being debugged, this field is set to @code{No process}.
25075 Gives the current function name for the selected frame.
25076 The name is demangled if demangling is turned on (@pxref{Print Settings}).
25077 When there is no symbol corresponding to the current program counter,
25078 the string @code{??} is displayed.
25081 Indicates the current line number for the selected frame.
25082 When the current line number is not known, the string @code{??} is displayed.
25085 Indicates the current program counter address.
25089 @section TUI Key Bindings
25090 @cindex TUI key bindings
25092 The TUI installs several key bindings in the readline keymaps
25093 @ifset SYSTEM_READLINE
25094 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
25096 @ifclear SYSTEM_READLINE
25097 (@pxref{Command Line Editing}).
25099 The following key bindings are installed for both TUI mode and the
25100 @value{GDBN} standard mode.
25109 Enter or leave the TUI mode. When leaving the TUI mode,
25110 the curses window management stops and @value{GDBN} operates using
25111 its standard mode, writing on the terminal directly. When reentering
25112 the TUI mode, control is given back to the curses windows.
25113 The screen is then refreshed.
25117 Use a TUI layout with only one window. The layout will
25118 either be @samp{source} or @samp{assembly}. When the TUI mode
25119 is not active, it will switch to the TUI mode.
25121 Think of this key binding as the Emacs @kbd{C-x 1} binding.
25125 Use a TUI layout with at least two windows. When the current
25126 layout already has two windows, the next layout with two windows is used.
25127 When a new layout is chosen, one window will always be common to the
25128 previous layout and the new one.
25130 Think of it as the Emacs @kbd{C-x 2} binding.
25134 Change the active window. The TUI associates several key bindings
25135 (like scrolling and arrow keys) with the active window. This command
25136 gives the focus to the next TUI window.
25138 Think of it as the Emacs @kbd{C-x o} binding.
25142 Switch in and out of the TUI SingleKey mode that binds single
25143 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
25146 The following key bindings only work in the TUI mode:
25151 Scroll the active window one page up.
25155 Scroll the active window one page down.
25159 Scroll the active window one line up.
25163 Scroll the active window one line down.
25167 Scroll the active window one column left.
25171 Scroll the active window one column right.
25175 Refresh the screen.
25178 Because the arrow keys scroll the active window in the TUI mode, they
25179 are not available for their normal use by readline unless the command
25180 window has the focus. When another window is active, you must use
25181 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
25182 and @kbd{C-f} to control the command window.
25184 @node TUI Single Key Mode
25185 @section TUI Single Key Mode
25186 @cindex TUI single key mode
25188 The TUI also provides a @dfn{SingleKey} mode, which binds several
25189 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
25190 switch into this mode, where the following key bindings are used:
25193 @kindex c @r{(SingleKey TUI key)}
25197 @kindex d @r{(SingleKey TUI key)}
25201 @kindex f @r{(SingleKey TUI key)}
25205 @kindex n @r{(SingleKey TUI key)}
25209 @kindex q @r{(SingleKey TUI key)}
25211 exit the SingleKey mode.
25213 @kindex r @r{(SingleKey TUI key)}
25217 @kindex s @r{(SingleKey TUI key)}
25221 @kindex u @r{(SingleKey TUI key)}
25225 @kindex v @r{(SingleKey TUI key)}
25229 @kindex w @r{(SingleKey TUI key)}
25234 Other keys temporarily switch to the @value{GDBN} command prompt.
25235 The key that was pressed is inserted in the editing buffer so that
25236 it is possible to type most @value{GDBN} commands without interaction
25237 with the TUI SingleKey mode. Once the command is entered the TUI
25238 SingleKey mode is restored. The only way to permanently leave
25239 this mode is by typing @kbd{q} or @kbd{C-x s}.
25243 @section TUI-specific Commands
25244 @cindex TUI commands
25246 The TUI has specific commands to control the text windows.
25247 These commands are always available, even when @value{GDBN} is not in
25248 the TUI mode. When @value{GDBN} is in the standard mode, most
25249 of these commands will automatically switch to the TUI mode.
25251 Note that if @value{GDBN}'s @code{stdout} is not connected to a
25252 terminal, or @value{GDBN} has been started with the machine interface
25253 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
25254 these commands will fail with an error, because it would not be
25255 possible or desirable to enable curses window management.
25260 Activate TUI mode. The last active TUI window layout will be used if
25261 TUI mode has prevsiouly been used in the current debugging session,
25262 otherwise a default layout is used.
25265 @kindex tui disable
25266 Disable TUI mode, returning to the console interpreter.
25270 List and give the size of all displayed windows.
25272 @item layout @var{name}
25274 Changes which TUI windows are displayed. In each layout the command
25275 window is always displayed, the @var{name} parameter controls which
25276 additional windows are displayed, and can be any of the following:
25280 Display the next layout.
25283 Display the previous layout.
25286 Display the source and command windows.
25289 Display the assembly and command windows.
25292 Display the source, assembly, and command windows.
25295 When in @code{src} layout display the register, source, and command
25296 windows. When in @code{asm} or @code{split} layout display the
25297 register, assembler, and command windows.
25300 @item focus @var{name}
25302 Changes which TUI window is currently active for scrolling. The
25303 @var{name} parameter can be any of the following:
25307 Make the next window active for scrolling.
25310 Make the previous window active for scrolling.
25313 Make the source window active for scrolling.
25316 Make the assembly window active for scrolling.
25319 Make the register window active for scrolling.
25322 Make the command window active for scrolling.
25327 Refresh the screen. This is similar to typing @kbd{C-L}.
25329 @item tui reg @var{group}
25331 Changes the register group displayed in the tui register window to
25332 @var{group}. If the register window is not currently displayed this
25333 command will cause the register window to be displayed. The list of
25334 register groups, as well as their order is target specific. The
25335 following groups are available on most targets:
25338 Repeatedly selecting this group will cause the display to cycle
25339 through all of the available register groups.
25342 Repeatedly selecting this group will cause the display to cycle
25343 through all of the available register groups in the reverse order to
25347 Display the general registers.
25349 Display the floating point registers.
25351 Display the system registers.
25353 Display the vector registers.
25355 Display all registers.
25360 Update the source window and the current execution point.
25362 @item winheight @var{name} +@var{count}
25363 @itemx winheight @var{name} -@var{count}
25365 Change the height of the window @var{name} by @var{count}
25366 lines. Positive counts increase the height, while negative counts
25367 decrease it. The @var{name} parameter can be one of @code{src} (the
25368 source window), @code{cmd} (the command window), @code{asm} (the
25369 disassembly window), or @code{regs} (the register display window).
25371 @item tabset @var{nchars}
25373 Set the width of tab stops to be @var{nchars} characters. This
25374 setting affects the display of TAB characters in the source and
25378 @node TUI Configuration
25379 @section TUI Configuration Variables
25380 @cindex TUI configuration variables
25382 Several configuration variables control the appearance of TUI windows.
25385 @item set tui border-kind @var{kind}
25386 @kindex set tui border-kind
25387 Select the border appearance for the source, assembly and register windows.
25388 The possible values are the following:
25391 Use a space character to draw the border.
25394 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
25397 Use the Alternate Character Set to draw the border. The border is
25398 drawn using character line graphics if the terminal supports them.
25401 @item set tui border-mode @var{mode}
25402 @kindex set tui border-mode
25403 @itemx set tui active-border-mode @var{mode}
25404 @kindex set tui active-border-mode
25405 Select the display attributes for the borders of the inactive windows
25406 or the active window. The @var{mode} can be one of the following:
25409 Use normal attributes to display the border.
25415 Use reverse video mode.
25418 Use half bright mode.
25420 @item half-standout
25421 Use half bright and standout mode.
25424 Use extra bright or bold mode.
25426 @item bold-standout
25427 Use extra bright or bold and standout mode.
25432 @chapter Using @value{GDBN} under @sc{gnu} Emacs
25435 @cindex @sc{gnu} Emacs
25436 A special interface allows you to use @sc{gnu} Emacs to view (and
25437 edit) the source files for the program you are debugging with
25440 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
25441 executable file you want to debug as an argument. This command starts
25442 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
25443 created Emacs buffer.
25444 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
25446 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
25451 All ``terminal'' input and output goes through an Emacs buffer, called
25454 This applies both to @value{GDBN} commands and their output, and to the input
25455 and output done by the program you are debugging.
25457 This is useful because it means that you can copy the text of previous
25458 commands and input them again; you can even use parts of the output
25461 All the facilities of Emacs' Shell mode are available for interacting
25462 with your program. In particular, you can send signals the usual
25463 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
25467 @value{GDBN} displays source code through Emacs.
25469 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
25470 source file for that frame and puts an arrow (@samp{=>}) at the
25471 left margin of the current line. Emacs uses a separate buffer for
25472 source display, and splits the screen to show both your @value{GDBN} session
25475 Explicit @value{GDBN} @code{list} or search commands still produce output as
25476 usual, but you probably have no reason to use them from Emacs.
25479 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
25480 a graphical mode, enabled by default, which provides further buffers
25481 that can control the execution and describe the state of your program.
25482 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
25484 If you specify an absolute file name when prompted for the @kbd{M-x
25485 gdb} argument, then Emacs sets your current working directory to where
25486 your program resides. If you only specify the file name, then Emacs
25487 sets your current working directory to the directory associated
25488 with the previous buffer. In this case, @value{GDBN} may find your
25489 program by searching your environment's @code{PATH} variable, but on
25490 some operating systems it might not find the source. So, although the
25491 @value{GDBN} input and output session proceeds normally, the auxiliary
25492 buffer does not display the current source and line of execution.
25494 The initial working directory of @value{GDBN} is printed on the top
25495 line of the GUD buffer and this serves as a default for the commands
25496 that specify files for @value{GDBN} to operate on. @xref{Files,
25497 ,Commands to Specify Files}.
25499 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
25500 need to call @value{GDBN} by a different name (for example, if you
25501 keep several configurations around, with different names) you can
25502 customize the Emacs variable @code{gud-gdb-command-name} to run the
25505 In the GUD buffer, you can use these special Emacs commands in
25506 addition to the standard Shell mode commands:
25510 Describe the features of Emacs' GUD Mode.
25513 Execute to another source line, like the @value{GDBN} @code{step} command; also
25514 update the display window to show the current file and location.
25517 Execute to next source line in this function, skipping all function
25518 calls, like the @value{GDBN} @code{next} command. Then update the display window
25519 to show the current file and location.
25522 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
25523 display window accordingly.
25526 Execute until exit from the selected stack frame, like the @value{GDBN}
25527 @code{finish} command.
25530 Continue execution of your program, like the @value{GDBN} @code{continue}
25534 Go up the number of frames indicated by the numeric argument
25535 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
25536 like the @value{GDBN} @code{up} command.
25539 Go down the number of frames indicated by the numeric argument, like the
25540 @value{GDBN} @code{down} command.
25543 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
25544 tells @value{GDBN} to set a breakpoint on the source line point is on.
25546 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
25547 separate frame which shows a backtrace when the GUD buffer is current.
25548 Move point to any frame in the stack and type @key{RET} to make it
25549 become the current frame and display the associated source in the
25550 source buffer. Alternatively, click @kbd{Mouse-2} to make the
25551 selected frame become the current one. In graphical mode, the
25552 speedbar displays watch expressions.
25554 If you accidentally delete the source-display buffer, an easy way to get
25555 it back is to type the command @code{f} in the @value{GDBN} buffer, to
25556 request a frame display; when you run under Emacs, this recreates
25557 the source buffer if necessary to show you the context of the current
25560 The source files displayed in Emacs are in ordinary Emacs buffers
25561 which are visiting the source files in the usual way. You can edit
25562 the files with these buffers if you wish; but keep in mind that @value{GDBN}
25563 communicates with Emacs in terms of line numbers. If you add or
25564 delete lines from the text, the line numbers that @value{GDBN} knows cease
25565 to correspond properly with the code.
25567 A more detailed description of Emacs' interaction with @value{GDBN} is
25568 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
25572 @chapter The @sc{gdb/mi} Interface
25574 @unnumberedsec Function and Purpose
25576 @cindex @sc{gdb/mi}, its purpose
25577 @sc{gdb/mi} is a line based machine oriented text interface to
25578 @value{GDBN} and is activated by specifying using the
25579 @option{--interpreter} command line option (@pxref{Mode Options}). It
25580 is specifically intended to support the development of systems which
25581 use the debugger as just one small component of a larger system.
25583 This chapter is a specification of the @sc{gdb/mi} interface. It is written
25584 in the form of a reference manual.
25586 Note that @sc{gdb/mi} is still under construction, so some of the
25587 features described below are incomplete and subject to change
25588 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
25590 @unnumberedsec Notation and Terminology
25592 @cindex notational conventions, for @sc{gdb/mi}
25593 This chapter uses the following notation:
25597 @code{|} separates two alternatives.
25600 @code{[ @var{something} ]} indicates that @var{something} is optional:
25601 it may or may not be given.
25604 @code{( @var{group} )*} means that @var{group} inside the parentheses
25605 may repeat zero or more times.
25608 @code{( @var{group} )+} means that @var{group} inside the parentheses
25609 may repeat one or more times.
25612 @code{"@var{string}"} means a literal @var{string}.
25616 @heading Dependencies
25620 * GDB/MI General Design::
25621 * GDB/MI Command Syntax::
25622 * GDB/MI Compatibility with CLI::
25623 * GDB/MI Development and Front Ends::
25624 * GDB/MI Output Records::
25625 * GDB/MI Simple Examples::
25626 * GDB/MI Command Description Format::
25627 * GDB/MI Breakpoint Commands::
25628 * GDB/MI Catchpoint Commands::
25629 * GDB/MI Program Context::
25630 * GDB/MI Thread Commands::
25631 * GDB/MI Ada Tasking Commands::
25632 * GDB/MI Program Execution::
25633 * GDB/MI Stack Manipulation::
25634 * GDB/MI Variable Objects::
25635 * GDB/MI Data Manipulation::
25636 * GDB/MI Tracepoint Commands::
25637 * GDB/MI Symbol Query::
25638 * GDB/MI File Commands::
25640 * GDB/MI Kod Commands::
25641 * GDB/MI Memory Overlay Commands::
25642 * GDB/MI Signal Handling Commands::
25644 * GDB/MI Target Manipulation::
25645 * GDB/MI File Transfer Commands::
25646 * GDB/MI Ada Exceptions Commands::
25647 * GDB/MI Support Commands::
25648 * GDB/MI Miscellaneous Commands::
25651 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25652 @node GDB/MI General Design
25653 @section @sc{gdb/mi} General Design
25654 @cindex GDB/MI General Design
25656 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
25657 parts---commands sent to @value{GDBN}, responses to those commands
25658 and notifications. Each command results in exactly one response,
25659 indicating either successful completion of the command, or an error.
25660 For the commands that do not resume the target, the response contains the
25661 requested information. For the commands that resume the target, the
25662 response only indicates whether the target was successfully resumed.
25663 Notifications is the mechanism for reporting changes in the state of the
25664 target, or in @value{GDBN} state, that cannot conveniently be associated with
25665 a command and reported as part of that command response.
25667 The important examples of notifications are:
25671 Exec notifications. These are used to report changes in
25672 target state---when a target is resumed, or stopped. It would not
25673 be feasible to include this information in response of resuming
25674 commands, because one resume commands can result in multiple events in
25675 different threads. Also, quite some time may pass before any event
25676 happens in the target, while a frontend needs to know whether the resuming
25677 command itself was successfully executed.
25680 Console output, and status notifications. Console output
25681 notifications are used to report output of CLI commands, as well as
25682 diagnostics for other commands. Status notifications are used to
25683 report the progress of a long-running operation. Naturally, including
25684 this information in command response would mean no output is produced
25685 until the command is finished, which is undesirable.
25688 General notifications. Commands may have various side effects on
25689 the @value{GDBN} or target state beyond their official purpose. For example,
25690 a command may change the selected thread. Although such changes can
25691 be included in command response, using notification allows for more
25692 orthogonal frontend design.
25696 There's no guarantee that whenever an MI command reports an error,
25697 @value{GDBN} or the target are in any specific state, and especially,
25698 the state is not reverted to the state before the MI command was
25699 processed. Therefore, whenever an MI command results in an error,
25700 we recommend that the frontend refreshes all the information shown in
25701 the user interface.
25705 * Context management::
25706 * Asynchronous and non-stop modes::
25710 @node Context management
25711 @subsection Context management
25713 @subsubsection Threads and Frames
25715 In most cases when @value{GDBN} accesses the target, this access is
25716 done in context of a specific thread and frame (@pxref{Frames}).
25717 Often, even when accessing global data, the target requires that a thread
25718 be specified. The CLI interface maintains the selected thread and frame,
25719 and supplies them to target on each command. This is convenient,
25720 because a command line user would not want to specify that information
25721 explicitly on each command, and because user interacts with
25722 @value{GDBN} via a single terminal, so no confusion is possible as
25723 to what thread and frame are the current ones.
25725 In the case of MI, the concept of selected thread and frame is less
25726 useful. First, a frontend can easily remember this information
25727 itself. Second, a graphical frontend can have more than one window,
25728 each one used for debugging a different thread, and the frontend might
25729 want to access additional threads for internal purposes. This
25730 increases the risk that by relying on implicitly selected thread, the
25731 frontend may be operating on a wrong one. Therefore, each MI command
25732 should explicitly specify which thread and frame to operate on. To
25733 make it possible, each MI command accepts the @samp{--thread} and
25734 @samp{--frame} options, the value to each is @value{GDBN} global
25735 identifier for thread and frame to operate on.
25737 Usually, each top-level window in a frontend allows the user to select
25738 a thread and a frame, and remembers the user selection for further
25739 operations. However, in some cases @value{GDBN} may suggest that the
25740 current thread be changed. For example, when stopping on a breakpoint
25741 it is reasonable to switch to the thread where breakpoint is hit. For
25742 another example, if the user issues the CLI @samp{thread} command via
25743 the frontend, it is desirable to change the frontend's selected thread to the
25744 one specified by user. @value{GDBN} communicates the suggestion to
25745 change current thread using the @samp{=thread-selected} notification.
25746 No such notification is available for the selected frame at the moment.
25748 Note that historically, MI shares the selected thread with CLI, so
25749 frontends used the @code{-thread-select} to execute commands in the
25750 right context. However, getting this to work right is cumbersome. The
25751 simplest way is for frontend to emit @code{-thread-select} command
25752 before every command. This doubles the number of commands that need
25753 to be sent. The alternative approach is to suppress @code{-thread-select}
25754 if the selected thread in @value{GDBN} is supposed to be identical to the
25755 thread the frontend wants to operate on. However, getting this
25756 optimization right can be tricky. In particular, if the frontend
25757 sends several commands to @value{GDBN}, and one of the commands changes the
25758 selected thread, then the behaviour of subsequent commands will
25759 change. So, a frontend should either wait for response from such
25760 problematic commands, or explicitly add @code{-thread-select} for
25761 all subsequent commands. No frontend is known to do this exactly
25762 right, so it is suggested to just always pass the @samp{--thread} and
25763 @samp{--frame} options.
25765 @subsubsection Language
25767 The execution of several commands depends on which language is selected.
25768 By default, the current language (@pxref{show language}) is used.
25769 But for commands known to be language-sensitive, it is recommended
25770 to use the @samp{--language} option. This option takes one argument,
25771 which is the name of the language to use while executing the command.
25775 -data-evaluate-expression --language c "sizeof (void*)"
25780 The valid language names are the same names accepted by the
25781 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
25782 @samp{local} or @samp{unknown}.
25784 @node Asynchronous and non-stop modes
25785 @subsection Asynchronous command execution and non-stop mode
25787 On some targets, @value{GDBN} is capable of processing MI commands
25788 even while the target is running. This is called @dfn{asynchronous
25789 command execution} (@pxref{Background Execution}). The frontend may
25790 specify a preferrence for asynchronous execution using the
25791 @code{-gdb-set mi-async 1} command, which should be emitted before
25792 either running the executable or attaching to the target. After the
25793 frontend has started the executable or attached to the target, it can
25794 find if asynchronous execution is enabled using the
25795 @code{-list-target-features} command.
25798 @item -gdb-set mi-async on
25799 @item -gdb-set mi-async off
25800 Set whether MI is in asynchronous mode.
25802 When @code{off}, which is the default, MI execution commands (e.g.,
25803 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
25804 for the program to stop before processing further commands.
25806 When @code{on}, MI execution commands are background execution
25807 commands (e.g., @code{-exec-continue} becomes the equivalent of the
25808 @code{c&} CLI command), and so @value{GDBN} is capable of processing
25809 MI commands even while the target is running.
25811 @item -gdb-show mi-async
25812 Show whether MI asynchronous mode is enabled.
25815 Note: In @value{GDBN} version 7.7 and earlier, this option was called
25816 @code{target-async} instead of @code{mi-async}, and it had the effect
25817 of both putting MI in asynchronous mode and making CLI background
25818 commands possible. CLI background commands are now always possible
25819 ``out of the box'' if the target supports them. The old spelling is
25820 kept as a deprecated alias for backwards compatibility.
25822 Even if @value{GDBN} can accept a command while target is running,
25823 many commands that access the target do not work when the target is
25824 running. Therefore, asynchronous command execution is most useful
25825 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
25826 it is possible to examine the state of one thread, while other threads
25829 When a given thread is running, MI commands that try to access the
25830 target in the context of that thread may not work, or may work only on
25831 some targets. In particular, commands that try to operate on thread's
25832 stack will not work, on any target. Commands that read memory, or
25833 modify breakpoints, may work or not work, depending on the target. Note
25834 that even commands that operate on global state, such as @code{print},
25835 @code{set}, and breakpoint commands, still access the target in the
25836 context of a specific thread, so frontend should try to find a
25837 stopped thread and perform the operation on that thread (using the
25838 @samp{--thread} option).
25840 Which commands will work in the context of a running thread is
25841 highly target dependent. However, the two commands
25842 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
25843 to find the state of a thread, will always work.
25845 @node Thread groups
25846 @subsection Thread groups
25847 @value{GDBN} may be used to debug several processes at the same time.
25848 On some platfroms, @value{GDBN} may support debugging of several
25849 hardware systems, each one having several cores with several different
25850 processes running on each core. This section describes the MI
25851 mechanism to support such debugging scenarios.
25853 The key observation is that regardless of the structure of the
25854 target, MI can have a global list of threads, because most commands that
25855 accept the @samp{--thread} option do not need to know what process that
25856 thread belongs to. Therefore, it is not necessary to introduce
25857 neither additional @samp{--process} option, nor an notion of the
25858 current process in the MI interface. The only strictly new feature
25859 that is required is the ability to find how the threads are grouped
25862 To allow the user to discover such grouping, and to support arbitrary
25863 hierarchy of machines/cores/processes, MI introduces the concept of a
25864 @dfn{thread group}. Thread group is a collection of threads and other
25865 thread groups. A thread group always has a string identifier, a type,
25866 and may have additional attributes specific to the type. A new
25867 command, @code{-list-thread-groups}, returns the list of top-level
25868 thread groups, which correspond to processes that @value{GDBN} is
25869 debugging at the moment. By passing an identifier of a thread group
25870 to the @code{-list-thread-groups} command, it is possible to obtain
25871 the members of specific thread group.
25873 To allow the user to easily discover processes, and other objects, he
25874 wishes to debug, a concept of @dfn{available thread group} is
25875 introduced. Available thread group is an thread group that
25876 @value{GDBN} is not debugging, but that can be attached to, using the
25877 @code{-target-attach} command. The list of available top-level thread
25878 groups can be obtained using @samp{-list-thread-groups --available}.
25879 In general, the content of a thread group may be only retrieved only
25880 after attaching to that thread group.
25882 Thread groups are related to inferiors (@pxref{Inferiors and
25883 Programs}). Each inferior corresponds to a thread group of a special
25884 type @samp{process}, and some additional operations are permitted on
25885 such thread groups.
25887 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25888 @node GDB/MI Command Syntax
25889 @section @sc{gdb/mi} Command Syntax
25892 * GDB/MI Input Syntax::
25893 * GDB/MI Output Syntax::
25896 @node GDB/MI Input Syntax
25897 @subsection @sc{gdb/mi} Input Syntax
25899 @cindex input syntax for @sc{gdb/mi}
25900 @cindex @sc{gdb/mi}, input syntax
25902 @item @var{command} @expansion{}
25903 @code{@var{cli-command} | @var{mi-command}}
25905 @item @var{cli-command} @expansion{}
25906 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
25907 @var{cli-command} is any existing @value{GDBN} CLI command.
25909 @item @var{mi-command} @expansion{}
25910 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
25911 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
25913 @item @var{token} @expansion{}
25914 "any sequence of digits"
25916 @item @var{option} @expansion{}
25917 @code{"-" @var{parameter} [ " " @var{parameter} ]}
25919 @item @var{parameter} @expansion{}
25920 @code{@var{non-blank-sequence} | @var{c-string}}
25922 @item @var{operation} @expansion{}
25923 @emph{any of the operations described in this chapter}
25925 @item @var{non-blank-sequence} @expansion{}
25926 @emph{anything, provided it doesn't contain special characters such as
25927 "-", @var{nl}, """ and of course " "}
25929 @item @var{c-string} @expansion{}
25930 @code{""" @var{seven-bit-iso-c-string-content} """}
25932 @item @var{nl} @expansion{}
25941 The CLI commands are still handled by the @sc{mi} interpreter; their
25942 output is described below.
25945 The @code{@var{token}}, when present, is passed back when the command
25949 Some @sc{mi} commands accept optional arguments as part of the parameter
25950 list. Each option is identified by a leading @samp{-} (dash) and may be
25951 followed by an optional argument parameter. Options occur first in the
25952 parameter list and can be delimited from normal parameters using
25953 @samp{--} (this is useful when some parameters begin with a dash).
25960 We want easy access to the existing CLI syntax (for debugging).
25963 We want it to be easy to spot a @sc{mi} operation.
25966 @node GDB/MI Output Syntax
25967 @subsection @sc{gdb/mi} Output Syntax
25969 @cindex output syntax of @sc{gdb/mi}
25970 @cindex @sc{gdb/mi}, output syntax
25971 The output from @sc{gdb/mi} consists of zero or more out-of-band records
25972 followed, optionally, by a single result record. This result record
25973 is for the most recent command. The sequence of output records is
25974 terminated by @samp{(gdb)}.
25976 If an input command was prefixed with a @code{@var{token}} then the
25977 corresponding output for that command will also be prefixed by that same
25981 @item @var{output} @expansion{}
25982 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
25984 @item @var{result-record} @expansion{}
25985 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
25987 @item @var{out-of-band-record} @expansion{}
25988 @code{@var{async-record} | @var{stream-record}}
25990 @item @var{async-record} @expansion{}
25991 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
25993 @item @var{exec-async-output} @expansion{}
25994 @code{[ @var{token} ] "*" @var{async-output nl}}
25996 @item @var{status-async-output} @expansion{}
25997 @code{[ @var{token} ] "+" @var{async-output nl}}
25999 @item @var{notify-async-output} @expansion{}
26000 @code{[ @var{token} ] "=" @var{async-output nl}}
26002 @item @var{async-output} @expansion{}
26003 @code{@var{async-class} ( "," @var{result} )*}
26005 @item @var{result-class} @expansion{}
26006 @code{"done" | "running" | "connected" | "error" | "exit"}
26008 @item @var{async-class} @expansion{}
26009 @code{"stopped" | @var{others}} (where @var{others} will be added
26010 depending on the needs---this is still in development).
26012 @item @var{result} @expansion{}
26013 @code{ @var{variable} "=" @var{value}}
26015 @item @var{variable} @expansion{}
26016 @code{ @var{string} }
26018 @item @var{value} @expansion{}
26019 @code{ @var{const} | @var{tuple} | @var{list} }
26021 @item @var{const} @expansion{}
26022 @code{@var{c-string}}
26024 @item @var{tuple} @expansion{}
26025 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
26027 @item @var{list} @expansion{}
26028 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
26029 @var{result} ( "," @var{result} )* "]" }
26031 @item @var{stream-record} @expansion{}
26032 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
26034 @item @var{console-stream-output} @expansion{}
26035 @code{"~" @var{c-string nl}}
26037 @item @var{target-stream-output} @expansion{}
26038 @code{"@@" @var{c-string nl}}
26040 @item @var{log-stream-output} @expansion{}
26041 @code{"&" @var{c-string nl}}
26043 @item @var{nl} @expansion{}
26046 @item @var{token} @expansion{}
26047 @emph{any sequence of digits}.
26055 All output sequences end in a single line containing a period.
26058 The @code{@var{token}} is from the corresponding request. Note that
26059 for all async output, while the token is allowed by the grammar and
26060 may be output by future versions of @value{GDBN} for select async
26061 output messages, it is generally omitted. Frontends should treat
26062 all async output as reporting general changes in the state of the
26063 target and there should be no need to associate async output to any
26067 @cindex status output in @sc{gdb/mi}
26068 @var{status-async-output} contains on-going status information about the
26069 progress of a slow operation. It can be discarded. All status output is
26070 prefixed by @samp{+}.
26073 @cindex async output in @sc{gdb/mi}
26074 @var{exec-async-output} contains asynchronous state change on the target
26075 (stopped, started, disappeared). All async output is prefixed by
26079 @cindex notify output in @sc{gdb/mi}
26080 @var{notify-async-output} contains supplementary information that the
26081 client should handle (e.g., a new breakpoint information). All notify
26082 output is prefixed by @samp{=}.
26085 @cindex console output in @sc{gdb/mi}
26086 @var{console-stream-output} is output that should be displayed as is in the
26087 console. It is the textual response to a CLI command. All the console
26088 output is prefixed by @samp{~}.
26091 @cindex target output in @sc{gdb/mi}
26092 @var{target-stream-output} is the output produced by the target program.
26093 All the target output is prefixed by @samp{@@}.
26096 @cindex log output in @sc{gdb/mi}
26097 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
26098 instance messages that should be displayed as part of an error log. All
26099 the log output is prefixed by @samp{&}.
26102 @cindex list output in @sc{gdb/mi}
26103 New @sc{gdb/mi} commands should only output @var{lists} containing
26109 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
26110 details about the various output records.
26112 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26113 @node GDB/MI Compatibility with CLI
26114 @section @sc{gdb/mi} Compatibility with CLI
26116 @cindex compatibility, @sc{gdb/mi} and CLI
26117 @cindex @sc{gdb/mi}, compatibility with CLI
26119 For the developers convenience CLI commands can be entered directly,
26120 but there may be some unexpected behaviour. For example, commands
26121 that query the user will behave as if the user replied yes, breakpoint
26122 command lists are not executed and some CLI commands, such as
26123 @code{if}, @code{when} and @code{define}, prompt for further input with
26124 @samp{>}, which is not valid MI output.
26126 This feature may be removed at some stage in the future and it is
26127 recommended that front ends use the @code{-interpreter-exec} command
26128 (@pxref{-interpreter-exec}).
26130 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26131 @node GDB/MI Development and Front Ends
26132 @section @sc{gdb/mi} Development and Front Ends
26133 @cindex @sc{gdb/mi} development
26135 The application which takes the MI output and presents the state of the
26136 program being debugged to the user is called a @dfn{front end}.
26138 Although @sc{gdb/mi} is still incomplete, it is currently being used
26139 by a variety of front ends to @value{GDBN}. This makes it difficult
26140 to introduce new functionality without breaking existing usage. This
26141 section tries to minimize the problems by describing how the protocol
26144 Some changes in MI need not break a carefully designed front end, and
26145 for these the MI version will remain unchanged. The following is a
26146 list of changes that may occur within one level, so front ends should
26147 parse MI output in a way that can handle them:
26151 New MI commands may be added.
26154 New fields may be added to the output of any MI command.
26157 The range of values for fields with specified values, e.g.,
26158 @code{in_scope} (@pxref{-var-update}) may be extended.
26160 @c The format of field's content e.g type prefix, may change so parse it
26161 @c at your own risk. Yes, in general?
26163 @c The order of fields may change? Shouldn't really matter but it might
26164 @c resolve inconsistencies.
26167 If the changes are likely to break front ends, the MI version level
26168 will be increased by one. This will allow the front end to parse the
26169 output according to the MI version. Apart from mi0, new versions of
26170 @value{GDBN} will not support old versions of MI and it will be the
26171 responsibility of the front end to work with the new one.
26173 @c Starting with mi3, add a new command -mi-version that prints the MI
26176 The best way to avoid unexpected changes in MI that might break your front
26177 end is to make your project known to @value{GDBN} developers and
26178 follow development on @email{gdb@@sourceware.org} and
26179 @email{gdb-patches@@sourceware.org}.
26180 @cindex mailing lists
26182 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26183 @node GDB/MI Output Records
26184 @section @sc{gdb/mi} Output Records
26187 * GDB/MI Result Records::
26188 * GDB/MI Stream Records::
26189 * GDB/MI Async Records::
26190 * GDB/MI Breakpoint Information::
26191 * GDB/MI Frame Information::
26192 * GDB/MI Thread Information::
26193 * GDB/MI Ada Exception Information::
26196 @node GDB/MI Result Records
26197 @subsection @sc{gdb/mi} Result Records
26199 @cindex result records in @sc{gdb/mi}
26200 @cindex @sc{gdb/mi}, result records
26201 In addition to a number of out-of-band notifications, the response to a
26202 @sc{gdb/mi} command includes one of the following result indications:
26206 @item "^done" [ "," @var{results} ]
26207 The synchronous operation was successful, @code{@var{results}} are the return
26212 This result record is equivalent to @samp{^done}. Historically, it
26213 was output instead of @samp{^done} if the command has resumed the
26214 target. This behaviour is maintained for backward compatibility, but
26215 all frontends should treat @samp{^done} and @samp{^running}
26216 identically and rely on the @samp{*running} output record to determine
26217 which threads are resumed.
26221 @value{GDBN} has connected to a remote target.
26223 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
26225 The operation failed. The @code{msg=@var{c-string}} variable contains
26226 the corresponding error message.
26228 If present, the @code{code=@var{c-string}} variable provides an error
26229 code on which consumers can rely on to detect the corresponding
26230 error condition. At present, only one error code is defined:
26233 @item "undefined-command"
26234 Indicates that the command causing the error does not exist.
26239 @value{GDBN} has terminated.
26243 @node GDB/MI Stream Records
26244 @subsection @sc{gdb/mi} Stream Records
26246 @cindex @sc{gdb/mi}, stream records
26247 @cindex stream records in @sc{gdb/mi}
26248 @value{GDBN} internally maintains a number of output streams: the console, the
26249 target, and the log. The output intended for each of these streams is
26250 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
26252 Each stream record begins with a unique @dfn{prefix character} which
26253 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
26254 Syntax}). In addition to the prefix, each stream record contains a
26255 @code{@var{string-output}}. This is either raw text (with an implicit new
26256 line) or a quoted C string (which does not contain an implicit newline).
26259 @item "~" @var{string-output}
26260 The console output stream contains text that should be displayed in the
26261 CLI console window. It contains the textual responses to CLI commands.
26263 @item "@@" @var{string-output}
26264 The target output stream contains any textual output from the running
26265 target. This is only present when GDB's event loop is truly
26266 asynchronous, which is currently only the case for remote targets.
26268 @item "&" @var{string-output}
26269 The log stream contains debugging messages being produced by @value{GDBN}'s
26273 @node GDB/MI Async Records
26274 @subsection @sc{gdb/mi} Async Records
26276 @cindex async records in @sc{gdb/mi}
26277 @cindex @sc{gdb/mi}, async records
26278 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
26279 additional changes that have occurred. Those changes can either be a
26280 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
26281 target activity (e.g., target stopped).
26283 The following is the list of possible async records:
26287 @item *running,thread-id="@var{thread}"
26288 The target is now running. The @var{thread} field can be the global
26289 thread ID of the the thread that is now running, and it can be
26290 @samp{all} if all threads are running. The frontend should assume
26291 that no interaction with a running thread is possible after this
26292 notification is produced. The frontend should not assume that this
26293 notification is output only once for any command. @value{GDBN} may
26294 emit this notification several times, either for different threads,
26295 because it cannot resume all threads together, or even for a single
26296 thread, if the thread must be stepped though some code before letting
26299 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
26300 The target has stopped. The @var{reason} field can have one of the
26304 @item breakpoint-hit
26305 A breakpoint was reached.
26306 @item watchpoint-trigger
26307 A watchpoint was triggered.
26308 @item read-watchpoint-trigger
26309 A read watchpoint was triggered.
26310 @item access-watchpoint-trigger
26311 An access watchpoint was triggered.
26312 @item function-finished
26313 An -exec-finish or similar CLI command was accomplished.
26314 @item location-reached
26315 An -exec-until or similar CLI command was accomplished.
26316 @item watchpoint-scope
26317 A watchpoint has gone out of scope.
26318 @item end-stepping-range
26319 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
26320 similar CLI command was accomplished.
26321 @item exited-signalled
26322 The inferior exited because of a signal.
26324 The inferior exited.
26325 @item exited-normally
26326 The inferior exited normally.
26327 @item signal-received
26328 A signal was received by the inferior.
26330 The inferior has stopped due to a library being loaded or unloaded.
26331 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
26332 set or when a @code{catch load} or @code{catch unload} catchpoint is
26333 in use (@pxref{Set Catchpoints}).
26335 The inferior has forked. This is reported when @code{catch fork}
26336 (@pxref{Set Catchpoints}) has been used.
26338 The inferior has vforked. This is reported in when @code{catch vfork}
26339 (@pxref{Set Catchpoints}) has been used.
26340 @item syscall-entry
26341 The inferior entered a system call. This is reported when @code{catch
26342 syscall} (@pxref{Set Catchpoints}) has been used.
26343 @item syscall-return
26344 The inferior returned from a system call. This is reported when
26345 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
26347 The inferior called @code{exec}. This is reported when @code{catch exec}
26348 (@pxref{Set Catchpoints}) has been used.
26351 The @var{id} field identifies the global thread ID of the thread
26352 that directly caused the stop -- for example by hitting a breakpoint.
26353 Depending on whether all-stop
26354 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
26355 stop all threads, or only the thread that directly triggered the stop.
26356 If all threads are stopped, the @var{stopped} field will have the
26357 value of @code{"all"}. Otherwise, the value of the @var{stopped}
26358 field will be a list of thread identifiers. Presently, this list will
26359 always include a single thread, but frontend should be prepared to see
26360 several threads in the list. The @var{core} field reports the
26361 processor core on which the stop event has happened. This field may be absent
26362 if such information is not available.
26364 @item =thread-group-added,id="@var{id}"
26365 @itemx =thread-group-removed,id="@var{id}"
26366 A thread group was either added or removed. The @var{id} field
26367 contains the @value{GDBN} identifier of the thread group. When a thread
26368 group is added, it generally might not be associated with a running
26369 process. When a thread group is removed, its id becomes invalid and
26370 cannot be used in any way.
26372 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
26373 A thread group became associated with a running program,
26374 either because the program was just started or the thread group
26375 was attached to a program. The @var{id} field contains the
26376 @value{GDBN} identifier of the thread group. The @var{pid} field
26377 contains process identifier, specific to the operating system.
26379 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
26380 A thread group is no longer associated with a running program,
26381 either because the program has exited, or because it was detached
26382 from. The @var{id} field contains the @value{GDBN} identifier of the
26383 thread group. The @var{code} field is the exit code of the inferior; it exists
26384 only when the inferior exited with some code.
26386 @item =thread-created,id="@var{id}",group-id="@var{gid}"
26387 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
26388 A thread either was created, or has exited. The @var{id} field
26389 contains the global @value{GDBN} identifier of the thread. The @var{gid}
26390 field identifies the thread group this thread belongs to.
26392 @item =thread-selected,id="@var{id}"
26393 Informs that the selected thread was changed as result of the last
26394 command. This notification is not emitted as result of @code{-thread-select}
26395 command but is emitted whenever an MI command that is not documented
26396 to change the selected thread actually changes it. In particular,
26397 invoking, directly or indirectly (via user-defined command), the CLI
26398 @code{thread} command, will generate this notification.
26400 We suggest that in response to this notification, front ends
26401 highlight the selected thread and cause subsequent commands to apply to
26404 @item =library-loaded,...
26405 Reports that a new library file was loaded by the program. This
26406 notification has 4 fields---@var{id}, @var{target-name},
26407 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
26408 opaque identifier of the library. For remote debugging case,
26409 @var{target-name} and @var{host-name} fields give the name of the
26410 library file on the target, and on the host respectively. For native
26411 debugging, both those fields have the same value. The
26412 @var{symbols-loaded} field is emitted only for backward compatibility
26413 and should not be relied on to convey any useful information. The
26414 @var{thread-group} field, if present, specifies the id of the thread
26415 group in whose context the library was loaded. If the field is
26416 absent, it means the library was loaded in the context of all present
26419 @item =library-unloaded,...
26420 Reports that a library was unloaded by the program. This notification
26421 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
26422 the same meaning as for the @code{=library-loaded} notification.
26423 The @var{thread-group} field, if present, specifies the id of the
26424 thread group in whose context the library was unloaded. If the field is
26425 absent, it means the library was unloaded in the context of all present
26428 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
26429 @itemx =traceframe-changed,end
26430 Reports that the trace frame was changed and its new number is
26431 @var{tfnum}. The number of the tracepoint associated with this trace
26432 frame is @var{tpnum}.
26434 @item =tsv-created,name=@var{name},initial=@var{initial}
26435 Reports that the new trace state variable @var{name} is created with
26436 initial value @var{initial}.
26438 @item =tsv-deleted,name=@var{name}
26439 @itemx =tsv-deleted
26440 Reports that the trace state variable @var{name} is deleted or all
26441 trace state variables are deleted.
26443 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
26444 Reports that the trace state variable @var{name} is modified with
26445 the initial value @var{initial}. The current value @var{current} of
26446 trace state variable is optional and is reported if the current
26447 value of trace state variable is known.
26449 @item =breakpoint-created,bkpt=@{...@}
26450 @itemx =breakpoint-modified,bkpt=@{...@}
26451 @itemx =breakpoint-deleted,id=@var{number}
26452 Reports that a breakpoint was created, modified, or deleted,
26453 respectively. Only user-visible breakpoints are reported to the MI
26456 The @var{bkpt} argument is of the same form as returned by the various
26457 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
26458 @var{number} is the ordinal number of the breakpoint.
26460 Note that if a breakpoint is emitted in the result record of a
26461 command, then it will not also be emitted in an async record.
26463 @item =record-started,thread-group="@var{id}"
26464 @itemx =record-stopped,thread-group="@var{id}"
26465 Execution log recording was either started or stopped on an
26466 inferior. The @var{id} is the @value{GDBN} identifier of the thread
26467 group corresponding to the affected inferior.
26469 @item =cmd-param-changed,param=@var{param},value=@var{value}
26470 Reports that a parameter of the command @code{set @var{param}} is
26471 changed to @var{value}. In the multi-word @code{set} command,
26472 the @var{param} is the whole parameter list to @code{set} command.
26473 For example, In command @code{set check type on}, @var{param}
26474 is @code{check type} and @var{value} is @code{on}.
26476 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
26477 Reports that bytes from @var{addr} to @var{data} + @var{len} were
26478 written in an inferior. The @var{id} is the identifier of the
26479 thread group corresponding to the affected inferior. The optional
26480 @code{type="code"} part is reported if the memory written to holds
26484 @node GDB/MI Breakpoint Information
26485 @subsection @sc{gdb/mi} Breakpoint Information
26487 When @value{GDBN} reports information about a breakpoint, a
26488 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
26493 The breakpoint number. For a breakpoint that represents one location
26494 of a multi-location breakpoint, this will be a dotted pair, like
26498 The type of the breakpoint. For ordinary breakpoints this will be
26499 @samp{breakpoint}, but many values are possible.
26502 If the type of the breakpoint is @samp{catchpoint}, then this
26503 indicates the exact type of catchpoint.
26506 This is the breakpoint disposition---either @samp{del}, meaning that
26507 the breakpoint will be deleted at the next stop, or @samp{keep},
26508 meaning that the breakpoint will not be deleted.
26511 This indicates whether the breakpoint is enabled, in which case the
26512 value is @samp{y}, or disabled, in which case the value is @samp{n}.
26513 Note that this is not the same as the field @code{enable}.
26516 The address of the breakpoint. This may be a hexidecimal number,
26517 giving the address; or the string @samp{<PENDING>}, for a pending
26518 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
26519 multiple locations. This field will not be present if no address can
26520 be determined. For example, a watchpoint does not have an address.
26523 If known, the function in which the breakpoint appears.
26524 If not known, this field is not present.
26527 The name of the source file which contains this function, if known.
26528 If not known, this field is not present.
26531 The full file name of the source file which contains this function, if
26532 known. If not known, this field is not present.
26535 The line number at which this breakpoint appears, if known.
26536 If not known, this field is not present.
26539 If the source file is not known, this field may be provided. If
26540 provided, this holds the address of the breakpoint, possibly followed
26544 If this breakpoint is pending, this field is present and holds the
26545 text used to set the breakpoint, as entered by the user.
26548 Where this breakpoint's condition is evaluated, either @samp{host} or
26552 If this is a thread-specific breakpoint, then this identifies the
26553 thread in which the breakpoint can trigger.
26556 If this breakpoint is restricted to a particular Ada task, then this
26557 field will hold the task identifier.
26560 If the breakpoint is conditional, this is the condition expression.
26563 The ignore count of the breakpoint.
26566 The enable count of the breakpoint.
26568 @item traceframe-usage
26571 @item static-tracepoint-marker-string-id
26572 For a static tracepoint, the name of the static tracepoint marker.
26575 For a masked watchpoint, this is the mask.
26578 A tracepoint's pass count.
26580 @item original-location
26581 The location of the breakpoint as originally specified by the user.
26582 This field is optional.
26585 The number of times the breakpoint has been hit.
26588 This field is only given for tracepoints. This is either @samp{y},
26589 meaning that the tracepoint is installed, or @samp{n}, meaning that it
26593 Some extra data, the exact contents of which are type-dependent.
26597 For example, here is what the output of @code{-break-insert}
26598 (@pxref{GDB/MI Breakpoint Commands}) might be:
26601 -> -break-insert main
26602 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26603 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26604 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26609 @node GDB/MI Frame Information
26610 @subsection @sc{gdb/mi} Frame Information
26612 Response from many MI commands includes an information about stack
26613 frame. This information is a tuple that may have the following
26618 The level of the stack frame. The innermost frame has the level of
26619 zero. This field is always present.
26622 The name of the function corresponding to the frame. This field may
26623 be absent if @value{GDBN} is unable to determine the function name.
26626 The code address for the frame. This field is always present.
26629 The name of the source files that correspond to the frame's code
26630 address. This field may be absent.
26633 The source line corresponding to the frames' code address. This field
26637 The name of the binary file (either executable or shared library) the
26638 corresponds to the frame's code address. This field may be absent.
26642 @node GDB/MI Thread Information
26643 @subsection @sc{gdb/mi} Thread Information
26645 Whenever @value{GDBN} has to report an information about a thread, it
26646 uses a tuple with the following fields:
26650 The global numeric id assigned to the thread by @value{GDBN}. This field is
26654 Target-specific string identifying the thread. This field is always present.
26657 Additional information about the thread provided by the target.
26658 It is supposed to be human-readable and not interpreted by the
26659 frontend. This field is optional.
26662 Either @samp{stopped} or @samp{running}, depending on whether the
26663 thread is presently running. This field is always present.
26666 The value of this field is an integer number of the processor core the
26667 thread was last seen on. This field is optional.
26670 @node GDB/MI Ada Exception Information
26671 @subsection @sc{gdb/mi} Ada Exception Information
26673 Whenever a @code{*stopped} record is emitted because the program
26674 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
26675 @value{GDBN} provides the name of the exception that was raised via
26676 the @code{exception-name} field.
26678 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26679 @node GDB/MI Simple Examples
26680 @section Simple Examples of @sc{gdb/mi} Interaction
26681 @cindex @sc{gdb/mi}, simple examples
26683 This subsection presents several simple examples of interaction using
26684 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
26685 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
26686 the output received from @sc{gdb/mi}.
26688 Note the line breaks shown in the examples are here only for
26689 readability, they don't appear in the real output.
26691 @subheading Setting a Breakpoint
26693 Setting a breakpoint generates synchronous output which contains detailed
26694 information of the breakpoint.
26697 -> -break-insert main
26698 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26699 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26700 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26705 @subheading Program Execution
26707 Program execution generates asynchronous records and MI gives the
26708 reason that execution stopped.
26714 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
26715 frame=@{addr="0x08048564",func="main",
26716 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
26717 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
26722 <- *stopped,reason="exited-normally"
26726 @subheading Quitting @value{GDBN}
26728 Quitting @value{GDBN} just prints the result class @samp{^exit}.
26736 Please note that @samp{^exit} is printed immediately, but it might
26737 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
26738 performs necessary cleanups, including killing programs being debugged
26739 or disconnecting from debug hardware, so the frontend should wait till
26740 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
26741 fails to exit in reasonable time.
26743 @subheading A Bad Command
26745 Here's what happens if you pass a non-existent command:
26749 <- ^error,msg="Undefined MI command: rubbish"
26754 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26755 @node GDB/MI Command Description Format
26756 @section @sc{gdb/mi} Command Description Format
26758 The remaining sections describe blocks of commands. Each block of
26759 commands is laid out in a fashion similar to this section.
26761 @subheading Motivation
26763 The motivation for this collection of commands.
26765 @subheading Introduction
26767 A brief introduction to this collection of commands as a whole.
26769 @subheading Commands
26771 For each command in the block, the following is described:
26773 @subsubheading Synopsis
26776 -command @var{args}@dots{}
26779 @subsubheading Result
26781 @subsubheading @value{GDBN} Command
26783 The corresponding @value{GDBN} CLI command(s), if any.
26785 @subsubheading Example
26787 Example(s) formatted for readability. Some of the described commands have
26788 not been implemented yet and these are labeled N.A.@: (not available).
26791 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26792 @node GDB/MI Breakpoint Commands
26793 @section @sc{gdb/mi} Breakpoint Commands
26795 @cindex breakpoint commands for @sc{gdb/mi}
26796 @cindex @sc{gdb/mi}, breakpoint commands
26797 This section documents @sc{gdb/mi} commands for manipulating
26800 @subheading The @code{-break-after} Command
26801 @findex -break-after
26803 @subsubheading Synopsis
26806 -break-after @var{number} @var{count}
26809 The breakpoint number @var{number} is not in effect until it has been
26810 hit @var{count} times. To see how this is reflected in the output of
26811 the @samp{-break-list} command, see the description of the
26812 @samp{-break-list} command below.
26814 @subsubheading @value{GDBN} Command
26816 The corresponding @value{GDBN} command is @samp{ignore}.
26818 @subsubheading Example
26823 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26824 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26825 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26833 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26834 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26835 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26836 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26837 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26838 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26839 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26840 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26841 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26842 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
26847 @subheading The @code{-break-catch} Command
26848 @findex -break-catch
26851 @subheading The @code{-break-commands} Command
26852 @findex -break-commands
26854 @subsubheading Synopsis
26857 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
26860 Specifies the CLI commands that should be executed when breakpoint
26861 @var{number} is hit. The parameters @var{command1} to @var{commandN}
26862 are the commands. If no command is specified, any previously-set
26863 commands are cleared. @xref{Break Commands}. Typical use of this
26864 functionality is tracing a program, that is, printing of values of
26865 some variables whenever breakpoint is hit and then continuing.
26867 @subsubheading @value{GDBN} Command
26869 The corresponding @value{GDBN} command is @samp{commands}.
26871 @subsubheading Example
26876 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26877 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26878 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26881 -break-commands 1 "print v" "continue"
26886 @subheading The @code{-break-condition} Command
26887 @findex -break-condition
26889 @subsubheading Synopsis
26892 -break-condition @var{number} @var{expr}
26895 Breakpoint @var{number} will stop the program only if the condition in
26896 @var{expr} is true. The condition becomes part of the
26897 @samp{-break-list} output (see the description of the @samp{-break-list}
26900 @subsubheading @value{GDBN} Command
26902 The corresponding @value{GDBN} command is @samp{condition}.
26904 @subsubheading Example
26908 -break-condition 1 1
26912 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26913 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26914 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26915 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26916 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26917 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26918 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26919 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26920 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26921 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
26925 @subheading The @code{-break-delete} Command
26926 @findex -break-delete
26928 @subsubheading Synopsis
26931 -break-delete ( @var{breakpoint} )+
26934 Delete the breakpoint(s) whose number(s) are specified in the argument
26935 list. This is obviously reflected in the breakpoint list.
26937 @subsubheading @value{GDBN} Command
26939 The corresponding @value{GDBN} command is @samp{delete}.
26941 @subsubheading Example
26949 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26950 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26951 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26952 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26953 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26954 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26955 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26960 @subheading The @code{-break-disable} Command
26961 @findex -break-disable
26963 @subsubheading Synopsis
26966 -break-disable ( @var{breakpoint} )+
26969 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
26970 break list is now set to @samp{n} for the named @var{breakpoint}(s).
26972 @subsubheading @value{GDBN} Command
26974 The corresponding @value{GDBN} command is @samp{disable}.
26976 @subsubheading Example
26984 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26985 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26986 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26987 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26988 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26989 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26990 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26991 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
26992 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26993 line="5",thread-groups=["i1"],times="0"@}]@}
26997 @subheading The @code{-break-enable} Command
26998 @findex -break-enable
27000 @subsubheading Synopsis
27003 -break-enable ( @var{breakpoint} )+
27006 Enable (previously disabled) @var{breakpoint}(s).
27008 @subsubheading @value{GDBN} Command
27010 The corresponding @value{GDBN} command is @samp{enable}.
27012 @subsubheading Example
27020 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27021 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27022 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27023 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27024 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27025 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27026 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27027 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27028 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27029 line="5",thread-groups=["i1"],times="0"@}]@}
27033 @subheading The @code{-break-info} Command
27034 @findex -break-info
27036 @subsubheading Synopsis
27039 -break-info @var{breakpoint}
27043 Get information about a single breakpoint.
27045 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
27046 Information}, for details on the format of each breakpoint in the
27049 @subsubheading @value{GDBN} Command
27051 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
27053 @subsubheading Example
27056 @subheading The @code{-break-insert} Command
27057 @findex -break-insert
27058 @anchor{-break-insert}
27060 @subsubheading Synopsis
27063 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
27064 [ -c @var{condition} ] [ -i @var{ignore-count} ]
27065 [ -p @var{thread-id} ] [ @var{location} ]
27069 If specified, @var{location}, can be one of:
27072 @item linespec location
27073 A linespec location. @xref{Linespec Locations}.
27075 @item explicit location
27076 An explicit location. @sc{gdb/mi} explicit locations are
27077 analogous to the CLI's explicit locations using the option names
27078 listed below. @xref{Explicit Locations}.
27081 @item --source @var{filename}
27082 The source file name of the location. This option requires the use
27083 of either @samp{--function} or @samp{--line}.
27085 @item --function @var{function}
27086 The name of a function or method.
27088 @item --label @var{label}
27089 The name of a label.
27091 @item --line @var{lineoffset}
27092 An absolute or relative line offset from the start of the location.
27095 @item address location
27096 An address location, *@var{address}. @xref{Address Locations}.
27100 The possible optional parameters of this command are:
27104 Insert a temporary breakpoint.
27106 Insert a hardware breakpoint.
27108 If @var{location} cannot be parsed (for example if it
27109 refers to unknown files or functions), create a pending
27110 breakpoint. Without this flag, @value{GDBN} will report
27111 an error, and won't create a breakpoint, if @var{location}
27114 Create a disabled breakpoint.
27116 Create a tracepoint. @xref{Tracepoints}. When this parameter
27117 is used together with @samp{-h}, a fast tracepoint is created.
27118 @item -c @var{condition}
27119 Make the breakpoint conditional on @var{condition}.
27120 @item -i @var{ignore-count}
27121 Initialize the @var{ignore-count}.
27122 @item -p @var{thread-id}
27123 Restrict the breakpoint to the thread with the specified global
27127 @subsubheading Result
27129 @xref{GDB/MI Breakpoint Information}, for details on the format of the
27130 resulting breakpoint.
27132 Note: this format is open to change.
27133 @c An out-of-band breakpoint instead of part of the result?
27135 @subsubheading @value{GDBN} Command
27137 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
27138 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
27140 @subsubheading Example
27145 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
27146 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
27149 -break-insert -t foo
27150 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
27151 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
27155 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27156 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27157 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27158 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27159 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27160 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27161 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27162 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27163 addr="0x0001072c", func="main",file="recursive2.c",
27164 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
27166 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
27167 addr="0x00010774",func="foo",file="recursive2.c",
27168 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
27171 @c -break-insert -r foo.*
27172 @c ~int foo(int, int);
27173 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
27174 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
27179 @subheading The @code{-dprintf-insert} Command
27180 @findex -dprintf-insert
27182 @subsubheading Synopsis
27185 -dprintf-insert [ -t ] [ -f ] [ -d ]
27186 [ -c @var{condition} ] [ -i @var{ignore-count} ]
27187 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
27192 If supplied, @var{location} may be specified the same way as for
27193 the @code{-break-insert} command. @xref{-break-insert}.
27195 The possible optional parameters of this command are:
27199 Insert a temporary breakpoint.
27201 If @var{location} cannot be parsed (for example, if it
27202 refers to unknown files or functions), create a pending
27203 breakpoint. Without this flag, @value{GDBN} will report
27204 an error, and won't create a breakpoint, if @var{location}
27207 Create a disabled breakpoint.
27208 @item -c @var{condition}
27209 Make the breakpoint conditional on @var{condition}.
27210 @item -i @var{ignore-count}
27211 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
27212 to @var{ignore-count}.
27213 @item -p @var{thread-id}
27214 Restrict the breakpoint to the thread with the specified global
27218 @subsubheading Result
27220 @xref{GDB/MI Breakpoint Information}, for details on the format of the
27221 resulting breakpoint.
27223 @c An out-of-band breakpoint instead of part of the result?
27225 @subsubheading @value{GDBN} Command
27227 The corresponding @value{GDBN} command is @samp{dprintf}.
27229 @subsubheading Example
27233 4-dprintf-insert foo "At foo entry\n"
27234 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
27235 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
27236 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
27237 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
27238 original-location="foo"@}
27240 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
27241 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
27242 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
27243 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
27244 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
27245 original-location="mi-dprintf.c:26"@}
27249 @subheading The @code{-break-list} Command
27250 @findex -break-list
27252 @subsubheading Synopsis
27258 Displays the list of inserted breakpoints, showing the following fields:
27262 number of the breakpoint
27264 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
27266 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
27269 is the breakpoint enabled or no: @samp{y} or @samp{n}
27271 memory location at which the breakpoint is set
27273 logical location of the breakpoint, expressed by function name, file
27275 @item Thread-groups
27276 list of thread groups to which this breakpoint applies
27278 number of times the breakpoint has been hit
27281 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
27282 @code{body} field is an empty list.
27284 @subsubheading @value{GDBN} Command
27286 The corresponding @value{GDBN} command is @samp{info break}.
27288 @subsubheading Example
27293 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27294 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27295 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27296 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27297 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27298 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27299 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27300 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27301 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
27303 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27304 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
27305 line="13",thread-groups=["i1"],times="0"@}]@}
27309 Here's an example of the result when there are no breakpoints:
27314 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27315 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27316 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27317 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27318 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27319 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27320 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27325 @subheading The @code{-break-passcount} Command
27326 @findex -break-passcount
27328 @subsubheading Synopsis
27331 -break-passcount @var{tracepoint-number} @var{passcount}
27334 Set the passcount for tracepoint @var{tracepoint-number} to
27335 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
27336 is not a tracepoint, error is emitted. This corresponds to CLI
27337 command @samp{passcount}.
27339 @subheading The @code{-break-watch} Command
27340 @findex -break-watch
27342 @subsubheading Synopsis
27345 -break-watch [ -a | -r ]
27348 Create a watchpoint. With the @samp{-a} option it will create an
27349 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
27350 read from or on a write to the memory location. With the @samp{-r}
27351 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
27352 trigger only when the memory location is accessed for reading. Without
27353 either of the options, the watchpoint created is a regular watchpoint,
27354 i.e., it will trigger when the memory location is accessed for writing.
27355 @xref{Set Watchpoints, , Setting Watchpoints}.
27357 Note that @samp{-break-list} will report a single list of watchpoints and
27358 breakpoints inserted.
27360 @subsubheading @value{GDBN} Command
27362 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
27365 @subsubheading Example
27367 Setting a watchpoint on a variable in the @code{main} function:
27372 ^done,wpt=@{number="2",exp="x"@}
27377 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
27378 value=@{old="-268439212",new="55"@},
27379 frame=@{func="main",args=[],file="recursive2.c",
27380 fullname="/home/foo/bar/recursive2.c",line="5"@}
27384 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
27385 the program execution twice: first for the variable changing value, then
27386 for the watchpoint going out of scope.
27391 ^done,wpt=@{number="5",exp="C"@}
27396 *stopped,reason="watchpoint-trigger",
27397 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
27398 frame=@{func="callee4",args=[],
27399 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27400 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27405 *stopped,reason="watchpoint-scope",wpnum="5",
27406 frame=@{func="callee3",args=[@{name="strarg",
27407 value="0x11940 \"A string argument.\""@}],
27408 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27409 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27413 Listing breakpoints and watchpoints, at different points in the program
27414 execution. Note that once the watchpoint goes out of scope, it is
27420 ^done,wpt=@{number="2",exp="C"@}
27423 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27424 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27425 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27426 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27427 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27428 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27429 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27430 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27431 addr="0x00010734",func="callee4",
27432 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27433 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
27435 bkpt=@{number="2",type="watchpoint",disp="keep",
27436 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
27441 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
27442 value=@{old="-276895068",new="3"@},
27443 frame=@{func="callee4",args=[],
27444 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27445 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27448 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27449 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27450 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27451 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27452 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27453 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27454 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27455 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27456 addr="0x00010734",func="callee4",
27457 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27458 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
27460 bkpt=@{number="2",type="watchpoint",disp="keep",
27461 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
27465 ^done,reason="watchpoint-scope",wpnum="2",
27466 frame=@{func="callee3",args=[@{name="strarg",
27467 value="0x11940 \"A string argument.\""@}],
27468 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27469 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27472 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27473 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27474 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27475 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27476 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27477 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27478 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27479 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27480 addr="0x00010734",func="callee4",
27481 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27482 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
27483 thread-groups=["i1"],times="1"@}]@}
27488 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27489 @node GDB/MI Catchpoint Commands
27490 @section @sc{gdb/mi} Catchpoint Commands
27492 This section documents @sc{gdb/mi} commands for manipulating
27496 * Shared Library GDB/MI Catchpoint Commands::
27497 * Ada Exception GDB/MI Catchpoint Commands::
27500 @node Shared Library GDB/MI Catchpoint Commands
27501 @subsection Shared Library @sc{gdb/mi} Catchpoints
27503 @subheading The @code{-catch-load} Command
27504 @findex -catch-load
27506 @subsubheading Synopsis
27509 -catch-load [ -t ] [ -d ] @var{regexp}
27512 Add a catchpoint for library load events. If the @samp{-t} option is used,
27513 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27514 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
27515 in a disabled state. The @samp{regexp} argument is a regular
27516 expression used to match the name of the loaded library.
27519 @subsubheading @value{GDBN} Command
27521 The corresponding @value{GDBN} command is @samp{catch load}.
27523 @subsubheading Example
27526 -catch-load -t foo.so
27527 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
27528 what="load of library matching foo.so",catch-type="load",times="0"@}
27533 @subheading The @code{-catch-unload} Command
27534 @findex -catch-unload
27536 @subsubheading Synopsis
27539 -catch-unload [ -t ] [ -d ] @var{regexp}
27542 Add a catchpoint for library unload events. If the @samp{-t} option is
27543 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27544 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
27545 created in a disabled state. The @samp{regexp} argument is a regular
27546 expression used to match the name of the unloaded library.
27548 @subsubheading @value{GDBN} Command
27550 The corresponding @value{GDBN} command is @samp{catch unload}.
27552 @subsubheading Example
27555 -catch-unload -d bar.so
27556 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
27557 what="load of library matching bar.so",catch-type="unload",times="0"@}
27561 @node Ada Exception GDB/MI Catchpoint Commands
27562 @subsection Ada Exception @sc{gdb/mi} Catchpoints
27564 The following @sc{gdb/mi} commands can be used to create catchpoints
27565 that stop the execution when Ada exceptions are being raised.
27567 @subheading The @code{-catch-assert} Command
27568 @findex -catch-assert
27570 @subsubheading Synopsis
27573 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
27576 Add a catchpoint for failed Ada assertions.
27578 The possible optional parameters for this command are:
27581 @item -c @var{condition}
27582 Make the catchpoint conditional on @var{condition}.
27584 Create a disabled catchpoint.
27586 Create a temporary catchpoint.
27589 @subsubheading @value{GDBN} Command
27591 The corresponding @value{GDBN} command is @samp{catch assert}.
27593 @subsubheading Example
27597 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
27598 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
27599 thread-groups=["i1"],times="0",
27600 original-location="__gnat_debug_raise_assert_failure"@}
27604 @subheading The @code{-catch-exception} Command
27605 @findex -catch-exception
27607 @subsubheading Synopsis
27610 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
27614 Add a catchpoint stopping when Ada exceptions are raised.
27615 By default, the command stops the program when any Ada exception
27616 gets raised. But it is also possible, by using some of the
27617 optional parameters described below, to create more selective
27620 The possible optional parameters for this command are:
27623 @item -c @var{condition}
27624 Make the catchpoint conditional on @var{condition}.
27626 Create a disabled catchpoint.
27627 @item -e @var{exception-name}
27628 Only stop when @var{exception-name} is raised. This option cannot
27629 be used combined with @samp{-u}.
27631 Create a temporary catchpoint.
27633 Stop only when an unhandled exception gets raised. This option
27634 cannot be used combined with @samp{-e}.
27637 @subsubheading @value{GDBN} Command
27639 The corresponding @value{GDBN} commands are @samp{catch exception}
27640 and @samp{catch exception unhandled}.
27642 @subsubheading Example
27645 -catch-exception -e Program_Error
27646 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
27647 enabled="y",addr="0x0000000000404874",
27648 what="`Program_Error' Ada exception", thread-groups=["i1"],
27649 times="0",original-location="__gnat_debug_raise_exception"@}
27653 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27654 @node GDB/MI Program Context
27655 @section @sc{gdb/mi} Program Context
27657 @subheading The @code{-exec-arguments} Command
27658 @findex -exec-arguments
27661 @subsubheading Synopsis
27664 -exec-arguments @var{args}
27667 Set the inferior program arguments, to be used in the next
27670 @subsubheading @value{GDBN} Command
27672 The corresponding @value{GDBN} command is @samp{set args}.
27674 @subsubheading Example
27678 -exec-arguments -v word
27685 @subheading The @code{-exec-show-arguments} Command
27686 @findex -exec-show-arguments
27688 @subsubheading Synopsis
27691 -exec-show-arguments
27694 Print the arguments of the program.
27696 @subsubheading @value{GDBN} Command
27698 The corresponding @value{GDBN} command is @samp{show args}.
27700 @subsubheading Example
27705 @subheading The @code{-environment-cd} Command
27706 @findex -environment-cd
27708 @subsubheading Synopsis
27711 -environment-cd @var{pathdir}
27714 Set @value{GDBN}'s working directory.
27716 @subsubheading @value{GDBN} Command
27718 The corresponding @value{GDBN} command is @samp{cd}.
27720 @subsubheading Example
27724 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27730 @subheading The @code{-environment-directory} Command
27731 @findex -environment-directory
27733 @subsubheading Synopsis
27736 -environment-directory [ -r ] [ @var{pathdir} ]+
27739 Add directories @var{pathdir} to beginning of search path for source files.
27740 If the @samp{-r} option is used, the search path is reset to the default
27741 search path. If directories @var{pathdir} are supplied in addition to the
27742 @samp{-r} option, the search path is first reset and then addition
27744 Multiple directories may be specified, separated by blanks. Specifying
27745 multiple directories in a single command
27746 results in the directories added to the beginning of the
27747 search path in the same order they were presented in the command.
27748 If blanks are needed as
27749 part of a directory name, double-quotes should be used around
27750 the name. In the command output, the path will show up separated
27751 by the system directory-separator character. The directory-separator
27752 character must not be used
27753 in any directory name.
27754 If no directories are specified, the current search path is displayed.
27756 @subsubheading @value{GDBN} Command
27758 The corresponding @value{GDBN} command is @samp{dir}.
27760 @subsubheading Example
27764 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27765 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27767 -environment-directory ""
27768 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27770 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
27771 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
27773 -environment-directory -r
27774 ^done,source-path="$cdir:$cwd"
27779 @subheading The @code{-environment-path} Command
27780 @findex -environment-path
27782 @subsubheading Synopsis
27785 -environment-path [ -r ] [ @var{pathdir} ]+
27788 Add directories @var{pathdir} to beginning of search path for object files.
27789 If the @samp{-r} option is used, the search path is reset to the original
27790 search path that existed at gdb start-up. If directories @var{pathdir} are
27791 supplied in addition to the
27792 @samp{-r} option, the search path is first reset and then addition
27794 Multiple directories may be specified, separated by blanks. Specifying
27795 multiple directories in a single command
27796 results in the directories added to the beginning of the
27797 search path in the same order they were presented in the command.
27798 If blanks are needed as
27799 part of a directory name, double-quotes should be used around
27800 the name. In the command output, the path will show up separated
27801 by the system directory-separator character. The directory-separator
27802 character must not be used
27803 in any directory name.
27804 If no directories are specified, the current path is displayed.
27807 @subsubheading @value{GDBN} Command
27809 The corresponding @value{GDBN} command is @samp{path}.
27811 @subsubheading Example
27816 ^done,path="/usr/bin"
27818 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
27819 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
27821 -environment-path -r /usr/local/bin
27822 ^done,path="/usr/local/bin:/usr/bin"
27827 @subheading The @code{-environment-pwd} Command
27828 @findex -environment-pwd
27830 @subsubheading Synopsis
27836 Show the current working directory.
27838 @subsubheading @value{GDBN} Command
27840 The corresponding @value{GDBN} command is @samp{pwd}.
27842 @subsubheading Example
27847 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
27851 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27852 @node GDB/MI Thread Commands
27853 @section @sc{gdb/mi} Thread Commands
27856 @subheading The @code{-thread-info} Command
27857 @findex -thread-info
27859 @subsubheading Synopsis
27862 -thread-info [ @var{thread-id} ]
27865 Reports information about either a specific thread, if the
27866 @var{thread-id} parameter is present, or about all threads.
27867 @var{thread-id} is the thread's global thread ID. When printing
27868 information about all threads, also reports the global ID of the
27871 @subsubheading @value{GDBN} Command
27873 The @samp{info thread} command prints the same information
27876 @subsubheading Result
27878 The result is a list of threads. The following attributes are
27879 defined for a given thread:
27883 This field exists only for the current thread. It has the value @samp{*}.
27886 The global identifier that @value{GDBN} uses to refer to the thread.
27889 The identifier that the target uses to refer to the thread.
27892 Extra information about the thread, in a target-specific format. This
27896 The name of the thread. If the user specified a name using the
27897 @code{thread name} command, then this name is given. Otherwise, if
27898 @value{GDBN} can extract the thread name from the target, then that
27899 name is given. If @value{GDBN} cannot find the thread name, then this
27903 The stack frame currently executing in the thread.
27906 The thread's state. The @samp{state} field may have the following
27911 The thread is stopped. Frame information is available for stopped
27915 The thread is running. There's no frame information for running
27921 If @value{GDBN} can find the CPU core on which this thread is running,
27922 then this field is the core identifier. This field is optional.
27926 @subsubheading Example
27931 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
27932 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
27933 args=[]@},state="running"@},
27934 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
27935 frame=@{level="0",addr="0x0804891f",func="foo",
27936 args=[@{name="i",value="10"@}],
27937 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
27938 state="running"@}],
27939 current-thread-id="1"
27943 @subheading The @code{-thread-list-ids} Command
27944 @findex -thread-list-ids
27946 @subsubheading Synopsis
27952 Produces a list of the currently known global @value{GDBN} thread ids.
27953 At the end of the list it also prints the total number of such
27956 This command is retained for historical reasons, the
27957 @code{-thread-info} command should be used instead.
27959 @subsubheading @value{GDBN} Command
27961 Part of @samp{info threads} supplies the same information.
27963 @subsubheading Example
27968 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27969 current-thread-id="1",number-of-threads="3"
27974 @subheading The @code{-thread-select} Command
27975 @findex -thread-select
27977 @subsubheading Synopsis
27980 -thread-select @var{thread-id}
27983 Make thread with global thread number @var{thread-id} the current
27984 thread. It prints the number of the new current thread, and the
27985 topmost frame for that thread.
27987 This command is deprecated in favor of explicitly using the
27988 @samp{--thread} option to each command.
27990 @subsubheading @value{GDBN} Command
27992 The corresponding @value{GDBN} command is @samp{thread}.
27994 @subsubheading Example
28001 *stopped,reason="end-stepping-range",thread-id="2",line="187",
28002 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
28006 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
28007 number-of-threads="3"
28010 ^done,new-thread-id="3",
28011 frame=@{level="0",func="vprintf",
28012 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
28013 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
28017 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28018 @node GDB/MI Ada Tasking Commands
28019 @section @sc{gdb/mi} Ada Tasking Commands
28021 @subheading The @code{-ada-task-info} Command
28022 @findex -ada-task-info
28024 @subsubheading Synopsis
28027 -ada-task-info [ @var{task-id} ]
28030 Reports information about either a specific Ada task, if the
28031 @var{task-id} parameter is present, or about all Ada tasks.
28033 @subsubheading @value{GDBN} Command
28035 The @samp{info tasks} command prints the same information
28036 about all Ada tasks (@pxref{Ada Tasks}).
28038 @subsubheading Result
28040 The result is a table of Ada tasks. The following columns are
28041 defined for each Ada task:
28045 This field exists only for the current thread. It has the value @samp{*}.
28048 The identifier that @value{GDBN} uses to refer to the Ada task.
28051 The identifier that the target uses to refer to the Ada task.
28054 The global thread identifier of the thread corresponding to the Ada
28057 This field should always exist, as Ada tasks are always implemented
28058 on top of a thread. But if @value{GDBN} cannot find this corresponding
28059 thread for any reason, the field is omitted.
28062 This field exists only when the task was created by another task.
28063 In this case, it provides the ID of the parent task.
28066 The base priority of the task.
28069 The current state of the task. For a detailed description of the
28070 possible states, see @ref{Ada Tasks}.
28073 The name of the task.
28077 @subsubheading Example
28081 ^done,tasks=@{nr_rows="3",nr_cols="8",
28082 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
28083 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
28084 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
28085 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
28086 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
28087 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
28088 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
28089 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
28090 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
28091 state="Child Termination Wait",name="main_task"@}]@}
28095 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28096 @node GDB/MI Program Execution
28097 @section @sc{gdb/mi} Program Execution
28099 These are the asynchronous commands which generate the out-of-band
28100 record @samp{*stopped}. Currently @value{GDBN} only really executes
28101 asynchronously with remote targets and this interaction is mimicked in
28104 @subheading The @code{-exec-continue} Command
28105 @findex -exec-continue
28107 @subsubheading Synopsis
28110 -exec-continue [--reverse] [--all|--thread-group N]
28113 Resumes the execution of the inferior program, which will continue
28114 to execute until it reaches a debugger stop event. If the
28115 @samp{--reverse} option is specified, execution resumes in reverse until
28116 it reaches a stop event. Stop events may include
28119 breakpoints or watchpoints
28121 signals or exceptions
28123 the end of the process (or its beginning under @samp{--reverse})
28125 the end or beginning of a replay log if one is being used.
28127 In all-stop mode (@pxref{All-Stop
28128 Mode}), may resume only one thread, or all threads, depending on the
28129 value of the @samp{scheduler-locking} variable. If @samp{--all} is
28130 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
28131 ignored in all-stop mode. If the @samp{--thread-group} options is
28132 specified, then all threads in that thread group are resumed.
28134 @subsubheading @value{GDBN} Command
28136 The corresponding @value{GDBN} corresponding is @samp{continue}.
28138 @subsubheading Example
28145 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
28146 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
28152 @subheading The @code{-exec-finish} Command
28153 @findex -exec-finish
28155 @subsubheading Synopsis
28158 -exec-finish [--reverse]
28161 Resumes the execution of the inferior program until the current
28162 function is exited. Displays the results returned by the function.
28163 If the @samp{--reverse} option is specified, resumes the reverse
28164 execution of the inferior program until the point where current
28165 function was called.
28167 @subsubheading @value{GDBN} Command
28169 The corresponding @value{GDBN} command is @samp{finish}.
28171 @subsubheading Example
28173 Function returning @code{void}.
28180 *stopped,reason="function-finished",frame=@{func="main",args=[],
28181 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
28185 Function returning other than @code{void}. The name of the internal
28186 @value{GDBN} variable storing the result is printed, together with the
28193 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
28194 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
28195 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28196 gdb-result-var="$1",return-value="0"
28201 @subheading The @code{-exec-interrupt} Command
28202 @findex -exec-interrupt
28204 @subsubheading Synopsis
28207 -exec-interrupt [--all|--thread-group N]
28210 Interrupts the background execution of the target. Note how the token
28211 associated with the stop message is the one for the execution command
28212 that has been interrupted. The token for the interrupt itself only
28213 appears in the @samp{^done} output. If the user is trying to
28214 interrupt a non-running program, an error message will be printed.
28216 Note that when asynchronous execution is enabled, this command is
28217 asynchronous just like other execution commands. That is, first the
28218 @samp{^done} response will be printed, and the target stop will be
28219 reported after that using the @samp{*stopped} notification.
28221 In non-stop mode, only the context thread is interrupted by default.
28222 All threads (in all inferiors) will be interrupted if the
28223 @samp{--all} option is specified. If the @samp{--thread-group}
28224 option is specified, all threads in that group will be interrupted.
28226 @subsubheading @value{GDBN} Command
28228 The corresponding @value{GDBN} command is @samp{interrupt}.
28230 @subsubheading Example
28241 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
28242 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
28243 fullname="/home/foo/bar/try.c",line="13"@}
28248 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
28252 @subheading The @code{-exec-jump} Command
28255 @subsubheading Synopsis
28258 -exec-jump @var{location}
28261 Resumes execution of the inferior program at the location specified by
28262 parameter. @xref{Specify Location}, for a description of the
28263 different forms of @var{location}.
28265 @subsubheading @value{GDBN} Command
28267 The corresponding @value{GDBN} command is @samp{jump}.
28269 @subsubheading Example
28272 -exec-jump foo.c:10
28273 *running,thread-id="all"
28278 @subheading The @code{-exec-next} Command
28281 @subsubheading Synopsis
28284 -exec-next [--reverse]
28287 Resumes execution of the inferior program, stopping when the beginning
28288 of the next source line is reached.
28290 If the @samp{--reverse} option is specified, resumes reverse execution
28291 of the inferior program, stopping at the beginning of the previous
28292 source line. If you issue this command on the first line of a
28293 function, it will take you back to the caller of that function, to the
28294 source line where the function was called.
28297 @subsubheading @value{GDBN} Command
28299 The corresponding @value{GDBN} command is @samp{next}.
28301 @subsubheading Example
28307 *stopped,reason="end-stepping-range",line="8",file="hello.c"
28312 @subheading The @code{-exec-next-instruction} Command
28313 @findex -exec-next-instruction
28315 @subsubheading Synopsis
28318 -exec-next-instruction [--reverse]
28321 Executes one machine instruction. If the instruction is a function
28322 call, continues until the function returns. If the program stops at an
28323 instruction in the middle of a source line, the address will be
28326 If the @samp{--reverse} option is specified, resumes reverse execution
28327 of the inferior program, stopping at the previous instruction. If the
28328 previously executed instruction was a return from another function,
28329 it will continue to execute in reverse until the call to that function
28330 (from the current stack frame) is reached.
28332 @subsubheading @value{GDBN} Command
28334 The corresponding @value{GDBN} command is @samp{nexti}.
28336 @subsubheading Example
28340 -exec-next-instruction
28344 *stopped,reason="end-stepping-range",
28345 addr="0x000100d4",line="5",file="hello.c"
28350 @subheading The @code{-exec-return} Command
28351 @findex -exec-return
28353 @subsubheading Synopsis
28359 Makes current function return immediately. Doesn't execute the inferior.
28360 Displays the new current frame.
28362 @subsubheading @value{GDBN} Command
28364 The corresponding @value{GDBN} command is @samp{return}.
28366 @subsubheading Example
28370 200-break-insert callee4
28371 200^done,bkpt=@{number="1",addr="0x00010734",
28372 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28377 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28378 frame=@{func="callee4",args=[],
28379 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28380 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28386 111^done,frame=@{level="0",func="callee3",
28387 args=[@{name="strarg",
28388 value="0x11940 \"A string argument.\""@}],
28389 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28390 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28395 @subheading The @code{-exec-run} Command
28398 @subsubheading Synopsis
28401 -exec-run [ --all | --thread-group N ] [ --start ]
28404 Starts execution of the inferior from the beginning. The inferior
28405 executes until either a breakpoint is encountered or the program
28406 exits. In the latter case the output will include an exit code, if
28407 the program has exited exceptionally.
28409 When neither the @samp{--all} nor the @samp{--thread-group} option
28410 is specified, the current inferior is started. If the
28411 @samp{--thread-group} option is specified, it should refer to a thread
28412 group of type @samp{process}, and that thread group will be started.
28413 If the @samp{--all} option is specified, then all inferiors will be started.
28415 Using the @samp{--start} option instructs the debugger to stop
28416 the execution at the start of the inferior's main subprogram,
28417 following the same behavior as the @code{start} command
28418 (@pxref{Starting}).
28420 @subsubheading @value{GDBN} Command
28422 The corresponding @value{GDBN} command is @samp{run}.
28424 @subsubheading Examples
28429 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
28434 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28435 frame=@{func="main",args=[],file="recursive2.c",
28436 fullname="/home/foo/bar/recursive2.c",line="4"@}
28441 Program exited normally:
28449 *stopped,reason="exited-normally"
28454 Program exited exceptionally:
28462 *stopped,reason="exited",exit-code="01"
28466 Another way the program can terminate is if it receives a signal such as
28467 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
28471 *stopped,reason="exited-signalled",signal-name="SIGINT",
28472 signal-meaning="Interrupt"
28476 @c @subheading -exec-signal
28479 @subheading The @code{-exec-step} Command
28482 @subsubheading Synopsis
28485 -exec-step [--reverse]
28488 Resumes execution of the inferior program, stopping when the beginning
28489 of the next source line is reached, if the next source line is not a
28490 function call. If it is, stop at the first instruction of the called
28491 function. If the @samp{--reverse} option is specified, resumes reverse
28492 execution of the inferior program, stopping at the beginning of the
28493 previously executed source line.
28495 @subsubheading @value{GDBN} Command
28497 The corresponding @value{GDBN} command is @samp{step}.
28499 @subsubheading Example
28501 Stepping into a function:
28507 *stopped,reason="end-stepping-range",
28508 frame=@{func="foo",args=[@{name="a",value="10"@},
28509 @{name="b",value="0"@}],file="recursive2.c",
28510 fullname="/home/foo/bar/recursive2.c",line="11"@}
28520 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
28525 @subheading The @code{-exec-step-instruction} Command
28526 @findex -exec-step-instruction
28528 @subsubheading Synopsis
28531 -exec-step-instruction [--reverse]
28534 Resumes the inferior which executes one machine instruction. If the
28535 @samp{--reverse} option is specified, resumes reverse execution of the
28536 inferior program, stopping at the previously executed instruction.
28537 The output, once @value{GDBN} has stopped, will vary depending on
28538 whether we have stopped in the middle of a source line or not. In the
28539 former case, the address at which the program stopped will be printed
28542 @subsubheading @value{GDBN} Command
28544 The corresponding @value{GDBN} command is @samp{stepi}.
28546 @subsubheading Example
28550 -exec-step-instruction
28554 *stopped,reason="end-stepping-range",
28555 frame=@{func="foo",args=[],file="try.c",
28556 fullname="/home/foo/bar/try.c",line="10"@}
28558 -exec-step-instruction
28562 *stopped,reason="end-stepping-range",
28563 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
28564 fullname="/home/foo/bar/try.c",line="10"@}
28569 @subheading The @code{-exec-until} Command
28570 @findex -exec-until
28572 @subsubheading Synopsis
28575 -exec-until [ @var{location} ]
28578 Executes the inferior until the @var{location} specified in the
28579 argument is reached. If there is no argument, the inferior executes
28580 until a source line greater than the current one is reached. The
28581 reason for stopping in this case will be @samp{location-reached}.
28583 @subsubheading @value{GDBN} Command
28585 The corresponding @value{GDBN} command is @samp{until}.
28587 @subsubheading Example
28591 -exec-until recursive2.c:6
28595 *stopped,reason="location-reached",frame=@{func="main",args=[],
28596 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
28601 @subheading -file-clear
28602 Is this going away????
28605 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28606 @node GDB/MI Stack Manipulation
28607 @section @sc{gdb/mi} Stack Manipulation Commands
28609 @subheading The @code{-enable-frame-filters} Command
28610 @findex -enable-frame-filters
28613 -enable-frame-filters
28616 @value{GDBN} allows Python-based frame filters to affect the output of
28617 the MI commands relating to stack traces. As there is no way to
28618 implement this in a fully backward-compatible way, a front end must
28619 request that this functionality be enabled.
28621 Once enabled, this feature cannot be disabled.
28623 Note that if Python support has not been compiled into @value{GDBN},
28624 this command will still succeed (and do nothing).
28626 @subheading The @code{-stack-info-frame} Command
28627 @findex -stack-info-frame
28629 @subsubheading Synopsis
28635 Get info on the selected frame.
28637 @subsubheading @value{GDBN} Command
28639 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
28640 (without arguments).
28642 @subsubheading Example
28647 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
28648 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28649 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
28653 @subheading The @code{-stack-info-depth} Command
28654 @findex -stack-info-depth
28656 @subsubheading Synopsis
28659 -stack-info-depth [ @var{max-depth} ]
28662 Return the depth of the stack. If the integer argument @var{max-depth}
28663 is specified, do not count beyond @var{max-depth} frames.
28665 @subsubheading @value{GDBN} Command
28667 There's no equivalent @value{GDBN} command.
28669 @subsubheading Example
28671 For a stack with frame levels 0 through 11:
28678 -stack-info-depth 4
28681 -stack-info-depth 12
28684 -stack-info-depth 11
28687 -stack-info-depth 13
28692 @anchor{-stack-list-arguments}
28693 @subheading The @code{-stack-list-arguments} Command
28694 @findex -stack-list-arguments
28696 @subsubheading Synopsis
28699 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28700 [ @var{low-frame} @var{high-frame} ]
28703 Display a list of the arguments for the frames between @var{low-frame}
28704 and @var{high-frame} (inclusive). If @var{low-frame} and
28705 @var{high-frame} are not provided, list the arguments for the whole
28706 call stack. If the two arguments are equal, show the single frame
28707 at the corresponding level. It is an error if @var{low-frame} is
28708 larger than the actual number of frames. On the other hand,
28709 @var{high-frame} may be larger than the actual number of frames, in
28710 which case only existing frames will be returned.
28712 If @var{print-values} is 0 or @code{--no-values}, print only the names of
28713 the variables; if it is 1 or @code{--all-values}, print also their
28714 values; and if it is 2 or @code{--simple-values}, print the name,
28715 type and value for simple data types, and the name and type for arrays,
28716 structures and unions. If the option @code{--no-frame-filters} is
28717 supplied, then Python frame filters will not be executed.
28719 If the @code{--skip-unavailable} option is specified, arguments that
28720 are not available are not listed. Partially available arguments
28721 are still displayed, however.
28723 Use of this command to obtain arguments in a single frame is
28724 deprecated in favor of the @samp{-stack-list-variables} command.
28726 @subsubheading @value{GDBN} Command
28728 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
28729 @samp{gdb_get_args} command which partially overlaps with the
28730 functionality of @samp{-stack-list-arguments}.
28732 @subsubheading Example
28739 frame=@{level="0",addr="0x00010734",func="callee4",
28740 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28741 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
28742 frame=@{level="1",addr="0x0001076c",func="callee3",
28743 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28744 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
28745 frame=@{level="2",addr="0x0001078c",func="callee2",
28746 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28747 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
28748 frame=@{level="3",addr="0x000107b4",func="callee1",
28749 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28750 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
28751 frame=@{level="4",addr="0x000107e0",func="main",
28752 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28753 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
28755 -stack-list-arguments 0
28758 frame=@{level="0",args=[]@},
28759 frame=@{level="1",args=[name="strarg"]@},
28760 frame=@{level="2",args=[name="intarg",name="strarg"]@},
28761 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
28762 frame=@{level="4",args=[]@}]
28764 -stack-list-arguments 1
28767 frame=@{level="0",args=[]@},
28769 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28770 frame=@{level="2",args=[
28771 @{name="intarg",value="2"@},
28772 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28773 @{frame=@{level="3",args=[
28774 @{name="intarg",value="2"@},
28775 @{name="strarg",value="0x11940 \"A string argument.\""@},
28776 @{name="fltarg",value="3.5"@}]@},
28777 frame=@{level="4",args=[]@}]
28779 -stack-list-arguments 0 2 2
28780 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
28782 -stack-list-arguments 1 2 2
28783 ^done,stack-args=[frame=@{level="2",
28784 args=[@{name="intarg",value="2"@},
28785 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
28789 @c @subheading -stack-list-exception-handlers
28792 @anchor{-stack-list-frames}
28793 @subheading The @code{-stack-list-frames} Command
28794 @findex -stack-list-frames
28796 @subsubheading Synopsis
28799 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
28802 List the frames currently on the stack. For each frame it displays the
28807 The frame number, 0 being the topmost frame, i.e., the innermost function.
28809 The @code{$pc} value for that frame.
28813 File name of the source file where the function lives.
28814 @item @var{fullname}
28815 The full file name of the source file where the function lives.
28817 Line number corresponding to the @code{$pc}.
28819 The shared library where this function is defined. This is only given
28820 if the frame's function is not known.
28823 If invoked without arguments, this command prints a backtrace for the
28824 whole stack. If given two integer arguments, it shows the frames whose
28825 levels are between the two arguments (inclusive). If the two arguments
28826 are equal, it shows the single frame at the corresponding level. It is
28827 an error if @var{low-frame} is larger than the actual number of
28828 frames. On the other hand, @var{high-frame} may be larger than the
28829 actual number of frames, in which case only existing frames will be
28830 returned. If the option @code{--no-frame-filters} is supplied, then
28831 Python frame filters will not be executed.
28833 @subsubheading @value{GDBN} Command
28835 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
28837 @subsubheading Example
28839 Full stack backtrace:
28845 [frame=@{level="0",addr="0x0001076c",func="foo",
28846 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
28847 frame=@{level="1",addr="0x000107a4",func="foo",
28848 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28849 frame=@{level="2",addr="0x000107a4",func="foo",
28850 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28851 frame=@{level="3",addr="0x000107a4",func="foo",
28852 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28853 frame=@{level="4",addr="0x000107a4",func="foo",
28854 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28855 frame=@{level="5",addr="0x000107a4",func="foo",
28856 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28857 frame=@{level="6",addr="0x000107a4",func="foo",
28858 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28859 frame=@{level="7",addr="0x000107a4",func="foo",
28860 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28861 frame=@{level="8",addr="0x000107a4",func="foo",
28862 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28863 frame=@{level="9",addr="0x000107a4",func="foo",
28864 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28865 frame=@{level="10",addr="0x000107a4",func="foo",
28866 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28867 frame=@{level="11",addr="0x00010738",func="main",
28868 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
28872 Show frames between @var{low_frame} and @var{high_frame}:
28876 -stack-list-frames 3 5
28878 [frame=@{level="3",addr="0x000107a4",func="foo",
28879 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28880 frame=@{level="4",addr="0x000107a4",func="foo",
28881 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28882 frame=@{level="5",addr="0x000107a4",func="foo",
28883 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28887 Show a single frame:
28891 -stack-list-frames 3 3
28893 [frame=@{level="3",addr="0x000107a4",func="foo",
28894 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28899 @subheading The @code{-stack-list-locals} Command
28900 @findex -stack-list-locals
28901 @anchor{-stack-list-locals}
28903 @subsubheading Synopsis
28906 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28909 Display the local variable names for the selected frame. If
28910 @var{print-values} is 0 or @code{--no-values}, print only the names of
28911 the variables; if it is 1 or @code{--all-values}, print also their
28912 values; and if it is 2 or @code{--simple-values}, print the name,
28913 type and value for simple data types, and the name and type for arrays,
28914 structures and unions. In this last case, a frontend can immediately
28915 display the value of simple data types and create variable objects for
28916 other data types when the user wishes to explore their values in
28917 more detail. If the option @code{--no-frame-filters} is supplied, then
28918 Python frame filters will not be executed.
28920 If the @code{--skip-unavailable} option is specified, local variables
28921 that are not available are not listed. Partially available local
28922 variables are still displayed, however.
28924 This command is deprecated in favor of the
28925 @samp{-stack-list-variables} command.
28927 @subsubheading @value{GDBN} Command
28929 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
28931 @subsubheading Example
28935 -stack-list-locals 0
28936 ^done,locals=[name="A",name="B",name="C"]
28938 -stack-list-locals --all-values
28939 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
28940 @{name="C",value="@{1, 2, 3@}"@}]
28941 -stack-list-locals --simple-values
28942 ^done,locals=[@{name="A",type="int",value="1"@},
28943 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
28947 @anchor{-stack-list-variables}
28948 @subheading The @code{-stack-list-variables} Command
28949 @findex -stack-list-variables
28951 @subsubheading Synopsis
28954 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28957 Display the names of local variables and function arguments for the selected frame. If
28958 @var{print-values} is 0 or @code{--no-values}, print only the names of
28959 the variables; if it is 1 or @code{--all-values}, print also their
28960 values; and if it is 2 or @code{--simple-values}, print the name,
28961 type and value for simple data types, and the name and type for arrays,
28962 structures and unions. If the option @code{--no-frame-filters} is
28963 supplied, then Python frame filters will not be executed.
28965 If the @code{--skip-unavailable} option is specified, local variables
28966 and arguments that are not available are not listed. Partially
28967 available arguments and local variables are still displayed, however.
28969 @subsubheading Example
28973 -stack-list-variables --thread 1 --frame 0 --all-values
28974 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
28979 @subheading The @code{-stack-select-frame} Command
28980 @findex -stack-select-frame
28982 @subsubheading Synopsis
28985 -stack-select-frame @var{framenum}
28988 Change the selected frame. Select a different frame @var{framenum} on
28991 This command in deprecated in favor of passing the @samp{--frame}
28992 option to every command.
28994 @subsubheading @value{GDBN} Command
28996 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
28997 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
28999 @subsubheading Example
29003 -stack-select-frame 2
29008 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29009 @node GDB/MI Variable Objects
29010 @section @sc{gdb/mi} Variable Objects
29014 @subheading Motivation for Variable Objects in @sc{gdb/mi}
29016 For the implementation of a variable debugger window (locals, watched
29017 expressions, etc.), we are proposing the adaptation of the existing code
29018 used by @code{Insight}.
29020 The two main reasons for that are:
29024 It has been proven in practice (it is already on its second generation).
29027 It will shorten development time (needless to say how important it is
29031 The original interface was designed to be used by Tcl code, so it was
29032 slightly changed so it could be used through @sc{gdb/mi}. This section
29033 describes the @sc{gdb/mi} operations that will be available and gives some
29034 hints about their use.
29036 @emph{Note}: In addition to the set of operations described here, we
29037 expect the @sc{gui} implementation of a variable window to require, at
29038 least, the following operations:
29041 @item @code{-gdb-show} @code{output-radix}
29042 @item @code{-stack-list-arguments}
29043 @item @code{-stack-list-locals}
29044 @item @code{-stack-select-frame}
29049 @subheading Introduction to Variable Objects
29051 @cindex variable objects in @sc{gdb/mi}
29053 Variable objects are "object-oriented" MI interface for examining and
29054 changing values of expressions. Unlike some other MI interfaces that
29055 work with expressions, variable objects are specifically designed for
29056 simple and efficient presentation in the frontend. A variable object
29057 is identified by string name. When a variable object is created, the
29058 frontend specifies the expression for that variable object. The
29059 expression can be a simple variable, or it can be an arbitrary complex
29060 expression, and can even involve CPU registers. After creating a
29061 variable object, the frontend can invoke other variable object
29062 operations---for example to obtain or change the value of a variable
29063 object, or to change display format.
29065 Variable objects have hierarchical tree structure. Any variable object
29066 that corresponds to a composite type, such as structure in C, has
29067 a number of child variable objects, for example corresponding to each
29068 element of a structure. A child variable object can itself have
29069 children, recursively. Recursion ends when we reach
29070 leaf variable objects, which always have built-in types. Child variable
29071 objects are created only by explicit request, so if a frontend
29072 is not interested in the children of a particular variable object, no
29073 child will be created.
29075 For a leaf variable object it is possible to obtain its value as a
29076 string, or set the value from a string. String value can be also
29077 obtained for a non-leaf variable object, but it's generally a string
29078 that only indicates the type of the object, and does not list its
29079 contents. Assignment to a non-leaf variable object is not allowed.
29081 A frontend does not need to read the values of all variable objects each time
29082 the program stops. Instead, MI provides an update command that lists all
29083 variable objects whose values has changed since the last update
29084 operation. This considerably reduces the amount of data that must
29085 be transferred to the frontend. As noted above, children variable
29086 objects are created on demand, and only leaf variable objects have a
29087 real value. As result, gdb will read target memory only for leaf
29088 variables that frontend has created.
29090 The automatic update is not always desirable. For example, a frontend
29091 might want to keep a value of some expression for future reference,
29092 and never update it. For another example, fetching memory is
29093 relatively slow for embedded targets, so a frontend might want
29094 to disable automatic update for the variables that are either not
29095 visible on the screen, or ``closed''. This is possible using so
29096 called ``frozen variable objects''. Such variable objects are never
29097 implicitly updated.
29099 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
29100 fixed variable object, the expression is parsed when the variable
29101 object is created, including associating identifiers to specific
29102 variables. The meaning of expression never changes. For a floating
29103 variable object the values of variables whose names appear in the
29104 expressions are re-evaluated every time in the context of the current
29105 frame. Consider this example:
29110 struct work_state state;
29117 If a fixed variable object for the @code{state} variable is created in
29118 this function, and we enter the recursive call, the variable
29119 object will report the value of @code{state} in the top-level
29120 @code{do_work} invocation. On the other hand, a floating variable
29121 object will report the value of @code{state} in the current frame.
29123 If an expression specified when creating a fixed variable object
29124 refers to a local variable, the variable object becomes bound to the
29125 thread and frame in which the variable object is created. When such
29126 variable object is updated, @value{GDBN} makes sure that the
29127 thread/frame combination the variable object is bound to still exists,
29128 and re-evaluates the variable object in context of that thread/frame.
29130 The following is the complete set of @sc{gdb/mi} operations defined to
29131 access this functionality:
29133 @multitable @columnfractions .4 .6
29134 @item @strong{Operation}
29135 @tab @strong{Description}
29137 @item @code{-enable-pretty-printing}
29138 @tab enable Python-based pretty-printing
29139 @item @code{-var-create}
29140 @tab create a variable object
29141 @item @code{-var-delete}
29142 @tab delete the variable object and/or its children
29143 @item @code{-var-set-format}
29144 @tab set the display format of this variable
29145 @item @code{-var-show-format}
29146 @tab show the display format of this variable
29147 @item @code{-var-info-num-children}
29148 @tab tells how many children this object has
29149 @item @code{-var-list-children}
29150 @tab return a list of the object's children
29151 @item @code{-var-info-type}
29152 @tab show the type of this variable object
29153 @item @code{-var-info-expression}
29154 @tab print parent-relative expression that this variable object represents
29155 @item @code{-var-info-path-expression}
29156 @tab print full expression that this variable object represents
29157 @item @code{-var-show-attributes}
29158 @tab is this variable editable? does it exist here?
29159 @item @code{-var-evaluate-expression}
29160 @tab get the value of this variable
29161 @item @code{-var-assign}
29162 @tab set the value of this variable
29163 @item @code{-var-update}
29164 @tab update the variable and its children
29165 @item @code{-var-set-frozen}
29166 @tab set frozeness attribute
29167 @item @code{-var-set-update-range}
29168 @tab set range of children to display on update
29171 In the next subsection we describe each operation in detail and suggest
29172 how it can be used.
29174 @subheading Description And Use of Operations on Variable Objects
29176 @subheading The @code{-enable-pretty-printing} Command
29177 @findex -enable-pretty-printing
29180 -enable-pretty-printing
29183 @value{GDBN} allows Python-based visualizers to affect the output of the
29184 MI variable object commands. However, because there was no way to
29185 implement this in a fully backward-compatible way, a front end must
29186 request that this functionality be enabled.
29188 Once enabled, this feature cannot be disabled.
29190 Note that if Python support has not been compiled into @value{GDBN},
29191 this command will still succeed (and do nothing).
29193 This feature is currently (as of @value{GDBN} 7.0) experimental, and
29194 may work differently in future versions of @value{GDBN}.
29196 @subheading The @code{-var-create} Command
29197 @findex -var-create
29199 @subsubheading Synopsis
29202 -var-create @{@var{name} | "-"@}
29203 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
29206 This operation creates a variable object, which allows the monitoring of
29207 a variable, the result of an expression, a memory cell or a CPU
29210 The @var{name} parameter is the string by which the object can be
29211 referenced. It must be unique. If @samp{-} is specified, the varobj
29212 system will generate a string ``varNNNNNN'' automatically. It will be
29213 unique provided that one does not specify @var{name} of that format.
29214 The command fails if a duplicate name is found.
29216 The frame under which the expression should be evaluated can be
29217 specified by @var{frame-addr}. A @samp{*} indicates that the current
29218 frame should be used. A @samp{@@} indicates that a floating variable
29219 object must be created.
29221 @var{expression} is any expression valid on the current language set (must not
29222 begin with a @samp{*}), or one of the following:
29226 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
29229 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
29232 @samp{$@var{regname}} --- a CPU register name
29235 @cindex dynamic varobj
29236 A varobj's contents may be provided by a Python-based pretty-printer. In this
29237 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
29238 have slightly different semantics in some cases. If the
29239 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
29240 will never create a dynamic varobj. This ensures backward
29241 compatibility for existing clients.
29243 @subsubheading Result
29245 This operation returns attributes of the newly-created varobj. These
29250 The name of the varobj.
29253 The number of children of the varobj. This number is not necessarily
29254 reliable for a dynamic varobj. Instead, you must examine the
29255 @samp{has_more} attribute.
29258 The varobj's scalar value. For a varobj whose type is some sort of
29259 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
29260 will not be interesting.
29263 The varobj's type. This is a string representation of the type, as
29264 would be printed by the @value{GDBN} CLI. If @samp{print object}
29265 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29266 @emph{actual} (derived) type of the object is shown rather than the
29267 @emph{declared} one.
29270 If a variable object is bound to a specific thread, then this is the
29271 thread's global identifier.
29274 For a dynamic varobj, this indicates whether there appear to be any
29275 children available. For a non-dynamic varobj, this will be 0.
29278 This attribute will be present and have the value @samp{1} if the
29279 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29280 then this attribute will not be present.
29283 A dynamic varobj can supply a display hint to the front end. The
29284 value comes directly from the Python pretty-printer object's
29285 @code{display_hint} method. @xref{Pretty Printing API}.
29288 Typical output will look like this:
29291 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
29292 has_more="@var{has_more}"
29296 @subheading The @code{-var-delete} Command
29297 @findex -var-delete
29299 @subsubheading Synopsis
29302 -var-delete [ -c ] @var{name}
29305 Deletes a previously created variable object and all of its children.
29306 With the @samp{-c} option, just deletes the children.
29308 Returns an error if the object @var{name} is not found.
29311 @subheading The @code{-var-set-format} Command
29312 @findex -var-set-format
29314 @subsubheading Synopsis
29317 -var-set-format @var{name} @var{format-spec}
29320 Sets the output format for the value of the object @var{name} to be
29323 @anchor{-var-set-format}
29324 The syntax for the @var{format-spec} is as follows:
29327 @var{format-spec} @expansion{}
29328 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
29331 The natural format is the default format choosen automatically
29332 based on the variable type (like decimal for an @code{int}, hex
29333 for pointers, etc.).
29335 The zero-hexadecimal format has a representation similar to hexadecimal
29336 but with padding zeroes to the left of the value. For example, a 32-bit
29337 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
29338 zero-hexadecimal format.
29340 For a variable with children, the format is set only on the
29341 variable itself, and the children are not affected.
29343 @subheading The @code{-var-show-format} Command
29344 @findex -var-show-format
29346 @subsubheading Synopsis
29349 -var-show-format @var{name}
29352 Returns the format used to display the value of the object @var{name}.
29355 @var{format} @expansion{}
29360 @subheading The @code{-var-info-num-children} Command
29361 @findex -var-info-num-children
29363 @subsubheading Synopsis
29366 -var-info-num-children @var{name}
29369 Returns the number of children of a variable object @var{name}:
29375 Note that this number is not completely reliable for a dynamic varobj.
29376 It will return the current number of children, but more children may
29380 @subheading The @code{-var-list-children} Command
29381 @findex -var-list-children
29383 @subsubheading Synopsis
29386 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
29388 @anchor{-var-list-children}
29390 Return a list of the children of the specified variable object and
29391 create variable objects for them, if they do not already exist. With
29392 a single argument or if @var{print-values} has a value of 0 or
29393 @code{--no-values}, print only the names of the variables; if
29394 @var{print-values} is 1 or @code{--all-values}, also print their
29395 values; and if it is 2 or @code{--simple-values} print the name and
29396 value for simple data types and just the name for arrays, structures
29399 @var{from} and @var{to}, if specified, indicate the range of children
29400 to report. If @var{from} or @var{to} is less than zero, the range is
29401 reset and all children will be reported. Otherwise, children starting
29402 at @var{from} (zero-based) and up to and excluding @var{to} will be
29405 If a child range is requested, it will only affect the current call to
29406 @code{-var-list-children}, but not future calls to @code{-var-update}.
29407 For this, you must instead use @code{-var-set-update-range}. The
29408 intent of this approach is to enable a front end to implement any
29409 update approach it likes; for example, scrolling a view may cause the
29410 front end to request more children with @code{-var-list-children}, and
29411 then the front end could call @code{-var-set-update-range} with a
29412 different range to ensure that future updates are restricted to just
29415 For each child the following results are returned:
29420 Name of the variable object created for this child.
29423 The expression to be shown to the user by the front end to designate this child.
29424 For example this may be the name of a structure member.
29426 For a dynamic varobj, this value cannot be used to form an
29427 expression. There is no way to do this at all with a dynamic varobj.
29429 For C/C@t{++} structures there are several pseudo children returned to
29430 designate access qualifiers. For these pseudo children @var{exp} is
29431 @samp{public}, @samp{private}, or @samp{protected}. In this case the
29432 type and value are not present.
29434 A dynamic varobj will not report the access qualifying
29435 pseudo-children, regardless of the language. This information is not
29436 available at all with a dynamic varobj.
29439 Number of children this child has. For a dynamic varobj, this will be
29443 The type of the child. If @samp{print object}
29444 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29445 @emph{actual} (derived) type of the object is shown rather than the
29446 @emph{declared} one.
29449 If values were requested, this is the value.
29452 If this variable object is associated with a thread, this is the
29453 thread's global thread id. Otherwise this result is not present.
29456 If the variable object is frozen, this variable will be present with a value of 1.
29459 A dynamic varobj can supply a display hint to the front end. The
29460 value comes directly from the Python pretty-printer object's
29461 @code{display_hint} method. @xref{Pretty Printing API}.
29464 This attribute will be present and have the value @samp{1} if the
29465 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29466 then this attribute will not be present.
29470 The result may have its own attributes:
29474 A dynamic varobj can supply a display hint to the front end. The
29475 value comes directly from the Python pretty-printer object's
29476 @code{display_hint} method. @xref{Pretty Printing API}.
29479 This is an integer attribute which is nonzero if there are children
29480 remaining after the end of the selected range.
29483 @subsubheading Example
29487 -var-list-children n
29488 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29489 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
29491 -var-list-children --all-values n
29492 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29493 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
29497 @subheading The @code{-var-info-type} Command
29498 @findex -var-info-type
29500 @subsubheading Synopsis
29503 -var-info-type @var{name}
29506 Returns the type of the specified variable @var{name}. The type is
29507 returned as a string in the same format as it is output by the
29511 type=@var{typename}
29515 @subheading The @code{-var-info-expression} Command
29516 @findex -var-info-expression
29518 @subsubheading Synopsis
29521 -var-info-expression @var{name}
29524 Returns a string that is suitable for presenting this
29525 variable object in user interface. The string is generally
29526 not valid expression in the current language, and cannot be evaluated.
29528 For example, if @code{a} is an array, and variable object
29529 @code{A} was created for @code{a}, then we'll get this output:
29532 (gdb) -var-info-expression A.1
29533 ^done,lang="C",exp="1"
29537 Here, the value of @code{lang} is the language name, which can be
29538 found in @ref{Supported Languages}.
29540 Note that the output of the @code{-var-list-children} command also
29541 includes those expressions, so the @code{-var-info-expression} command
29544 @subheading The @code{-var-info-path-expression} Command
29545 @findex -var-info-path-expression
29547 @subsubheading Synopsis
29550 -var-info-path-expression @var{name}
29553 Returns an expression that can be evaluated in the current
29554 context and will yield the same value that a variable object has.
29555 Compare this with the @code{-var-info-expression} command, which
29556 result can be used only for UI presentation. Typical use of
29557 the @code{-var-info-path-expression} command is creating a
29558 watchpoint from a variable object.
29560 This command is currently not valid for children of a dynamic varobj,
29561 and will give an error when invoked on one.
29563 For example, suppose @code{C} is a C@t{++} class, derived from class
29564 @code{Base}, and that the @code{Base} class has a member called
29565 @code{m_size}. Assume a variable @code{c} is has the type of
29566 @code{C} and a variable object @code{C} was created for variable
29567 @code{c}. Then, we'll get this output:
29569 (gdb) -var-info-path-expression C.Base.public.m_size
29570 ^done,path_expr=((Base)c).m_size)
29573 @subheading The @code{-var-show-attributes} Command
29574 @findex -var-show-attributes
29576 @subsubheading Synopsis
29579 -var-show-attributes @var{name}
29582 List attributes of the specified variable object @var{name}:
29585 status=@var{attr} [ ( ,@var{attr} )* ]
29589 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
29591 @subheading The @code{-var-evaluate-expression} Command
29592 @findex -var-evaluate-expression
29594 @subsubheading Synopsis
29597 -var-evaluate-expression [-f @var{format-spec}] @var{name}
29600 Evaluates the expression that is represented by the specified variable
29601 object and returns its value as a string. The format of the string
29602 can be specified with the @samp{-f} option. The possible values of
29603 this option are the same as for @code{-var-set-format}
29604 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
29605 the current display format will be used. The current display format
29606 can be changed using the @code{-var-set-format} command.
29612 Note that one must invoke @code{-var-list-children} for a variable
29613 before the value of a child variable can be evaluated.
29615 @subheading The @code{-var-assign} Command
29616 @findex -var-assign
29618 @subsubheading Synopsis
29621 -var-assign @var{name} @var{expression}
29624 Assigns the value of @var{expression} to the variable object specified
29625 by @var{name}. The object must be @samp{editable}. If the variable's
29626 value is altered by the assign, the variable will show up in any
29627 subsequent @code{-var-update} list.
29629 @subsubheading Example
29637 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
29641 @subheading The @code{-var-update} Command
29642 @findex -var-update
29644 @subsubheading Synopsis
29647 -var-update [@var{print-values}] @{@var{name} | "*"@}
29650 Reevaluate the expressions corresponding to the variable object
29651 @var{name} and all its direct and indirect children, and return the
29652 list of variable objects whose values have changed; @var{name} must
29653 be a root variable object. Here, ``changed'' means that the result of
29654 @code{-var-evaluate-expression} before and after the
29655 @code{-var-update} is different. If @samp{*} is used as the variable
29656 object names, all existing variable objects are updated, except
29657 for frozen ones (@pxref{-var-set-frozen}). The option
29658 @var{print-values} determines whether both names and values, or just
29659 names are printed. The possible values of this option are the same
29660 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
29661 recommended to use the @samp{--all-values} option, to reduce the
29662 number of MI commands needed on each program stop.
29664 With the @samp{*} parameter, if a variable object is bound to a
29665 currently running thread, it will not be updated, without any
29668 If @code{-var-set-update-range} was previously used on a varobj, then
29669 only the selected range of children will be reported.
29671 @code{-var-update} reports all the changed varobjs in a tuple named
29674 Each item in the change list is itself a tuple holding:
29678 The name of the varobj.
29681 If values were requested for this update, then this field will be
29682 present and will hold the value of the varobj.
29685 @anchor{-var-update}
29686 This field is a string which may take one of three values:
29690 The variable object's current value is valid.
29693 The variable object does not currently hold a valid value but it may
29694 hold one in the future if its associated expression comes back into
29698 The variable object no longer holds a valid value.
29699 This can occur when the executable file being debugged has changed,
29700 either through recompilation or by using the @value{GDBN} @code{file}
29701 command. The front end should normally choose to delete these variable
29705 In the future new values may be added to this list so the front should
29706 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
29709 This is only present if the varobj is still valid. If the type
29710 changed, then this will be the string @samp{true}; otherwise it will
29713 When a varobj's type changes, its children are also likely to have
29714 become incorrect. Therefore, the varobj's children are automatically
29715 deleted when this attribute is @samp{true}. Also, the varobj's update
29716 range, when set using the @code{-var-set-update-range} command, is
29720 If the varobj's type changed, then this field will be present and will
29723 @item new_num_children
29724 For a dynamic varobj, if the number of children changed, or if the
29725 type changed, this will be the new number of children.
29727 The @samp{numchild} field in other varobj responses is generally not
29728 valid for a dynamic varobj -- it will show the number of children that
29729 @value{GDBN} knows about, but because dynamic varobjs lazily
29730 instantiate their children, this will not reflect the number of
29731 children which may be available.
29733 The @samp{new_num_children} attribute only reports changes to the
29734 number of children known by @value{GDBN}. This is the only way to
29735 detect whether an update has removed children (which necessarily can
29736 only happen at the end of the update range).
29739 The display hint, if any.
29742 This is an integer value, which will be 1 if there are more children
29743 available outside the varobj's update range.
29746 This attribute will be present and have the value @samp{1} if the
29747 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29748 then this attribute will not be present.
29751 If new children were added to a dynamic varobj within the selected
29752 update range (as set by @code{-var-set-update-range}), then they will
29753 be listed in this attribute.
29756 @subsubheading Example
29763 -var-update --all-values var1
29764 ^done,changelist=[@{name="var1",value="3",in_scope="true",
29765 type_changed="false"@}]
29769 @subheading The @code{-var-set-frozen} Command
29770 @findex -var-set-frozen
29771 @anchor{-var-set-frozen}
29773 @subsubheading Synopsis
29776 -var-set-frozen @var{name} @var{flag}
29779 Set the frozenness flag on the variable object @var{name}. The
29780 @var{flag} parameter should be either @samp{1} to make the variable
29781 frozen or @samp{0} to make it unfrozen. If a variable object is
29782 frozen, then neither itself, nor any of its children, are
29783 implicitly updated by @code{-var-update} of
29784 a parent variable or by @code{-var-update *}. Only
29785 @code{-var-update} of the variable itself will update its value and
29786 values of its children. After a variable object is unfrozen, it is
29787 implicitly updated by all subsequent @code{-var-update} operations.
29788 Unfreezing a variable does not update it, only subsequent
29789 @code{-var-update} does.
29791 @subsubheading Example
29795 -var-set-frozen V 1
29800 @subheading The @code{-var-set-update-range} command
29801 @findex -var-set-update-range
29802 @anchor{-var-set-update-range}
29804 @subsubheading Synopsis
29807 -var-set-update-range @var{name} @var{from} @var{to}
29810 Set the range of children to be returned by future invocations of
29811 @code{-var-update}.
29813 @var{from} and @var{to} indicate the range of children to report. If
29814 @var{from} or @var{to} is less than zero, the range is reset and all
29815 children will be reported. Otherwise, children starting at @var{from}
29816 (zero-based) and up to and excluding @var{to} will be reported.
29818 @subsubheading Example
29822 -var-set-update-range V 1 2
29826 @subheading The @code{-var-set-visualizer} command
29827 @findex -var-set-visualizer
29828 @anchor{-var-set-visualizer}
29830 @subsubheading Synopsis
29833 -var-set-visualizer @var{name} @var{visualizer}
29836 Set a visualizer for the variable object @var{name}.
29838 @var{visualizer} is the visualizer to use. The special value
29839 @samp{None} means to disable any visualizer in use.
29841 If not @samp{None}, @var{visualizer} must be a Python expression.
29842 This expression must evaluate to a callable object which accepts a
29843 single argument. @value{GDBN} will call this object with the value of
29844 the varobj @var{name} as an argument (this is done so that the same
29845 Python pretty-printing code can be used for both the CLI and MI).
29846 When called, this object must return an object which conforms to the
29847 pretty-printing interface (@pxref{Pretty Printing API}).
29849 The pre-defined function @code{gdb.default_visualizer} may be used to
29850 select a visualizer by following the built-in process
29851 (@pxref{Selecting Pretty-Printers}). This is done automatically when
29852 a varobj is created, and so ordinarily is not needed.
29854 This feature is only available if Python support is enabled. The MI
29855 command @code{-list-features} (@pxref{GDB/MI Support Commands})
29856 can be used to check this.
29858 @subsubheading Example
29860 Resetting the visualizer:
29864 -var-set-visualizer V None
29868 Reselecting the default (type-based) visualizer:
29872 -var-set-visualizer V gdb.default_visualizer
29876 Suppose @code{SomeClass} is a visualizer class. A lambda expression
29877 can be used to instantiate this class for a varobj:
29881 -var-set-visualizer V "lambda val: SomeClass()"
29885 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29886 @node GDB/MI Data Manipulation
29887 @section @sc{gdb/mi} Data Manipulation
29889 @cindex data manipulation, in @sc{gdb/mi}
29890 @cindex @sc{gdb/mi}, data manipulation
29891 This section describes the @sc{gdb/mi} commands that manipulate data:
29892 examine memory and registers, evaluate expressions, etc.
29894 For details about what an addressable memory unit is,
29895 @pxref{addressable memory unit}.
29897 @c REMOVED FROM THE INTERFACE.
29898 @c @subheading -data-assign
29899 @c Change the value of a program variable. Plenty of side effects.
29900 @c @subsubheading GDB Command
29902 @c @subsubheading Example
29905 @subheading The @code{-data-disassemble} Command
29906 @findex -data-disassemble
29908 @subsubheading Synopsis
29912 [ -s @var{start-addr} -e @var{end-addr} ]
29913 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
29921 @item @var{start-addr}
29922 is the beginning address (or @code{$pc})
29923 @item @var{end-addr}
29925 @item @var{filename}
29926 is the name of the file to disassemble
29927 @item @var{linenum}
29928 is the line number to disassemble around
29930 is the number of disassembly lines to be produced. If it is -1,
29931 the whole function will be disassembled, in case no @var{end-addr} is
29932 specified. If @var{end-addr} is specified as a non-zero value, and
29933 @var{lines} is lower than the number of disassembly lines between
29934 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
29935 displayed; if @var{lines} is higher than the number of lines between
29936 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
29941 @item 0 disassembly only
29942 @item 1 mixed source and disassembly (deprecated)
29943 @item 2 disassembly with raw opcodes
29944 @item 3 mixed source and disassembly with raw opcodes (deprecated)
29945 @item 4 mixed source and disassembly
29946 @item 5 mixed source and disassembly with raw opcodes
29949 Modes 1 and 3 are deprecated. The output is ``source centric''
29950 which hasn't proved useful in practice.
29951 @xref{Machine Code}, for a discussion of the difference between
29952 @code{/m} and @code{/s} output of the @code{disassemble} command.
29955 @subsubheading Result
29957 The result of the @code{-data-disassemble} command will be a list named
29958 @samp{asm_insns}, the contents of this list depend on the @var{mode}
29959 used with the @code{-data-disassemble} command.
29961 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
29966 The address at which this instruction was disassembled.
29969 The name of the function this instruction is within.
29972 The decimal offset in bytes from the start of @samp{func-name}.
29975 The text disassembly for this @samp{address}.
29978 This field is only present for modes 2, 3 and 5. This contains the raw opcode
29979 bytes for the @samp{inst} field.
29983 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
29984 @samp{src_and_asm_line}, each of which has the following fields:
29988 The line number within @samp{file}.
29991 The file name from the compilation unit. This might be an absolute
29992 file name or a relative file name depending on the compile command
29996 Absolute file name of @samp{file}. It is converted to a canonical form
29997 using the source file search path
29998 (@pxref{Source Path, ,Specifying Source Directories})
29999 and after resolving all the symbolic links.
30001 If the source file is not found this field will contain the path as
30002 present in the debug information.
30004 @item line_asm_insn
30005 This is a list of tuples containing the disassembly for @samp{line} in
30006 @samp{file}. The fields of each tuple are the same as for
30007 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
30008 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
30013 Note that whatever included in the @samp{inst} field, is not
30014 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
30017 @subsubheading @value{GDBN} Command
30019 The corresponding @value{GDBN} command is @samp{disassemble}.
30021 @subsubheading Example
30023 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
30027 -data-disassemble -s $pc -e "$pc + 20" -- 0
30030 @{address="0x000107c0",func-name="main",offset="4",
30031 inst="mov 2, %o0"@},
30032 @{address="0x000107c4",func-name="main",offset="8",
30033 inst="sethi %hi(0x11800), %o2"@},
30034 @{address="0x000107c8",func-name="main",offset="12",
30035 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
30036 @{address="0x000107cc",func-name="main",offset="16",
30037 inst="sethi %hi(0x11800), %o2"@},
30038 @{address="0x000107d0",func-name="main",offset="20",
30039 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
30043 Disassemble the whole @code{main} function. Line 32 is part of
30047 -data-disassemble -f basics.c -l 32 -- 0
30049 @{address="0x000107bc",func-name="main",offset="0",
30050 inst="save %sp, -112, %sp"@},
30051 @{address="0x000107c0",func-name="main",offset="4",
30052 inst="mov 2, %o0"@},
30053 @{address="0x000107c4",func-name="main",offset="8",
30054 inst="sethi %hi(0x11800), %o2"@},
30056 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
30057 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
30061 Disassemble 3 instructions from the start of @code{main}:
30065 -data-disassemble -f basics.c -l 32 -n 3 -- 0
30067 @{address="0x000107bc",func-name="main",offset="0",
30068 inst="save %sp, -112, %sp"@},
30069 @{address="0x000107c0",func-name="main",offset="4",
30070 inst="mov 2, %o0"@},
30071 @{address="0x000107c4",func-name="main",offset="8",
30072 inst="sethi %hi(0x11800), %o2"@}]
30076 Disassemble 3 instructions from the start of @code{main} in mixed mode:
30080 -data-disassemble -f basics.c -l 32 -n 3 -- 1
30082 src_and_asm_line=@{line="31",
30083 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
30084 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
30085 line_asm_insn=[@{address="0x000107bc",
30086 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
30087 src_and_asm_line=@{line="32",
30088 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
30089 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
30090 line_asm_insn=[@{address="0x000107c0",
30091 func-name="main",offset="4",inst="mov 2, %o0"@},
30092 @{address="0x000107c4",func-name="main",offset="8",
30093 inst="sethi %hi(0x11800), %o2"@}]@}]
30098 @subheading The @code{-data-evaluate-expression} Command
30099 @findex -data-evaluate-expression
30101 @subsubheading Synopsis
30104 -data-evaluate-expression @var{expr}
30107 Evaluate @var{expr} as an expression. The expression could contain an
30108 inferior function call. The function call will execute synchronously.
30109 If the expression contains spaces, it must be enclosed in double quotes.
30111 @subsubheading @value{GDBN} Command
30113 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
30114 @samp{call}. In @code{gdbtk} only, there's a corresponding
30115 @samp{gdb_eval} command.
30117 @subsubheading Example
30119 In the following example, the numbers that precede the commands are the
30120 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
30121 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
30125 211-data-evaluate-expression A
30128 311-data-evaluate-expression &A
30129 311^done,value="0xefffeb7c"
30131 411-data-evaluate-expression A+3
30134 511-data-evaluate-expression "A + 3"
30140 @subheading The @code{-data-list-changed-registers} Command
30141 @findex -data-list-changed-registers
30143 @subsubheading Synopsis
30146 -data-list-changed-registers
30149 Display a list of the registers that have changed.
30151 @subsubheading @value{GDBN} Command
30153 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
30154 has the corresponding command @samp{gdb_changed_register_list}.
30156 @subsubheading Example
30158 On a PPC MBX board:
30166 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
30167 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
30170 -data-list-changed-registers
30171 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
30172 "10","11","13","14","15","16","17","18","19","20","21","22","23",
30173 "24","25","26","27","28","30","31","64","65","66","67","69"]
30178 @subheading The @code{-data-list-register-names} Command
30179 @findex -data-list-register-names
30181 @subsubheading Synopsis
30184 -data-list-register-names [ ( @var{regno} )+ ]
30187 Show a list of register names for the current target. If no arguments
30188 are given, it shows a list of the names of all the registers. If
30189 integer numbers are given as arguments, it will print a list of the
30190 names of the registers corresponding to the arguments. To ensure
30191 consistency between a register name and its number, the output list may
30192 include empty register names.
30194 @subsubheading @value{GDBN} Command
30196 @value{GDBN} does not have a command which corresponds to
30197 @samp{-data-list-register-names}. In @code{gdbtk} there is a
30198 corresponding command @samp{gdb_regnames}.
30200 @subsubheading Example
30202 For the PPC MBX board:
30205 -data-list-register-names
30206 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
30207 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
30208 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
30209 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
30210 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
30211 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
30212 "", "pc","ps","cr","lr","ctr","xer"]
30214 -data-list-register-names 1 2 3
30215 ^done,register-names=["r1","r2","r3"]
30219 @subheading The @code{-data-list-register-values} Command
30220 @findex -data-list-register-values
30222 @subsubheading Synopsis
30225 -data-list-register-values
30226 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
30229 Display the registers' contents. The format according to which the
30230 registers' contents are to be returned is given by @var{fmt}, followed
30231 by an optional list of numbers specifying the registers to display. A
30232 missing list of numbers indicates that the contents of all the
30233 registers must be returned. The @code{--skip-unavailable} option
30234 indicates that only the available registers are to be returned.
30236 Allowed formats for @var{fmt} are:
30253 @subsubheading @value{GDBN} Command
30255 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
30256 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
30258 @subsubheading Example
30260 For a PPC MBX board (note: line breaks are for readability only, they
30261 don't appear in the actual output):
30265 -data-list-register-values r 64 65
30266 ^done,register-values=[@{number="64",value="0xfe00a300"@},
30267 @{number="65",value="0x00029002"@}]
30269 -data-list-register-values x
30270 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
30271 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
30272 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
30273 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
30274 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
30275 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
30276 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
30277 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
30278 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
30279 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
30280 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
30281 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
30282 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
30283 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
30284 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
30285 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
30286 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
30287 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
30288 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
30289 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
30290 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
30291 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
30292 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
30293 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
30294 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
30295 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
30296 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
30297 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
30298 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
30299 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
30300 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
30301 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
30302 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
30303 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
30304 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
30305 @{number="69",value="0x20002b03"@}]
30310 @subheading The @code{-data-read-memory} Command
30311 @findex -data-read-memory
30313 This command is deprecated, use @code{-data-read-memory-bytes} instead.
30315 @subsubheading Synopsis
30318 -data-read-memory [ -o @var{byte-offset} ]
30319 @var{address} @var{word-format} @var{word-size}
30320 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
30327 @item @var{address}
30328 An expression specifying the address of the first memory word to be
30329 read. Complex expressions containing embedded white space should be
30330 quoted using the C convention.
30332 @item @var{word-format}
30333 The format to be used to print the memory words. The notation is the
30334 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
30337 @item @var{word-size}
30338 The size of each memory word in bytes.
30340 @item @var{nr-rows}
30341 The number of rows in the output table.
30343 @item @var{nr-cols}
30344 The number of columns in the output table.
30347 If present, indicates that each row should include an @sc{ascii} dump. The
30348 value of @var{aschar} is used as a padding character when a byte is not a
30349 member of the printable @sc{ascii} character set (printable @sc{ascii}
30350 characters are those whose code is between 32 and 126, inclusively).
30352 @item @var{byte-offset}
30353 An offset to add to the @var{address} before fetching memory.
30356 This command displays memory contents as a table of @var{nr-rows} by
30357 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
30358 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
30359 (returned as @samp{total-bytes}). Should less than the requested number
30360 of bytes be returned by the target, the missing words are identified
30361 using @samp{N/A}. The number of bytes read from the target is returned
30362 in @samp{nr-bytes} and the starting address used to read memory in
30365 The address of the next/previous row or page is available in
30366 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
30369 @subsubheading @value{GDBN} Command
30371 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
30372 @samp{gdb_get_mem} memory read command.
30374 @subsubheading Example
30376 Read six bytes of memory starting at @code{bytes+6} but then offset by
30377 @code{-6} bytes. Format as three rows of two columns. One byte per
30378 word. Display each word in hex.
30382 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
30383 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
30384 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
30385 prev-page="0x0000138a",memory=[
30386 @{addr="0x00001390",data=["0x00","0x01"]@},
30387 @{addr="0x00001392",data=["0x02","0x03"]@},
30388 @{addr="0x00001394",data=["0x04","0x05"]@}]
30392 Read two bytes of memory starting at address @code{shorts + 64} and
30393 display as a single word formatted in decimal.
30397 5-data-read-memory shorts+64 d 2 1 1
30398 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
30399 next-row="0x00001512",prev-row="0x0000150e",
30400 next-page="0x00001512",prev-page="0x0000150e",memory=[
30401 @{addr="0x00001510",data=["128"]@}]
30405 Read thirty two bytes of memory starting at @code{bytes+16} and format
30406 as eight rows of four columns. Include a string encoding with @samp{x}
30407 used as the non-printable character.
30411 4-data-read-memory bytes+16 x 1 8 4 x
30412 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
30413 next-row="0x000013c0",prev-row="0x0000139c",
30414 next-page="0x000013c0",prev-page="0x00001380",memory=[
30415 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
30416 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
30417 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
30418 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
30419 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
30420 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
30421 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
30422 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
30426 @subheading The @code{-data-read-memory-bytes} Command
30427 @findex -data-read-memory-bytes
30429 @subsubheading Synopsis
30432 -data-read-memory-bytes [ -o @var{offset} ]
30433 @var{address} @var{count}
30440 @item @var{address}
30441 An expression specifying the address of the first addressable memory unit
30442 to be read. Complex expressions containing embedded white space should be
30443 quoted using the C convention.
30446 The number of addressable memory units to read. This should be an integer
30450 The offset relative to @var{address} at which to start reading. This
30451 should be an integer literal. This option is provided so that a frontend
30452 is not required to first evaluate address and then perform address
30453 arithmetics itself.
30457 This command attempts to read all accessible memory regions in the
30458 specified range. First, all regions marked as unreadable in the memory
30459 map (if one is defined) will be skipped. @xref{Memory Region
30460 Attributes}. Second, @value{GDBN} will attempt to read the remaining
30461 regions. For each one, if reading full region results in an errors,
30462 @value{GDBN} will try to read a subset of the region.
30464 In general, every single memory unit in the region may be readable or not,
30465 and the only way to read every readable unit is to try a read at
30466 every address, which is not practical. Therefore, @value{GDBN} will
30467 attempt to read all accessible memory units at either beginning or the end
30468 of the region, using a binary division scheme. This heuristic works
30469 well for reading accross a memory map boundary. Note that if a region
30470 has a readable range that is neither at the beginning or the end,
30471 @value{GDBN} will not read it.
30473 The result record (@pxref{GDB/MI Result Records}) that is output of
30474 the command includes a field named @samp{memory} whose content is a
30475 list of tuples. Each tuple represent a successfully read memory block
30476 and has the following fields:
30480 The start address of the memory block, as hexadecimal literal.
30483 The end address of the memory block, as hexadecimal literal.
30486 The offset of the memory block, as hexadecimal literal, relative to
30487 the start address passed to @code{-data-read-memory-bytes}.
30490 The contents of the memory block, in hex.
30496 @subsubheading @value{GDBN} Command
30498 The corresponding @value{GDBN} command is @samp{x}.
30500 @subsubheading Example
30504 -data-read-memory-bytes &a 10
30505 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
30507 contents="01000000020000000300"@}]
30512 @subheading The @code{-data-write-memory-bytes} Command
30513 @findex -data-write-memory-bytes
30515 @subsubheading Synopsis
30518 -data-write-memory-bytes @var{address} @var{contents}
30519 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
30526 @item @var{address}
30527 An expression specifying the address of the first addressable memory unit
30528 to be written. Complex expressions containing embedded white space should
30529 be quoted using the C convention.
30531 @item @var{contents}
30532 The hex-encoded data to write. It is an error if @var{contents} does
30533 not represent an integral number of addressable memory units.
30536 Optional argument indicating the number of addressable memory units to be
30537 written. If @var{count} is greater than @var{contents}' length,
30538 @value{GDBN} will repeatedly write @var{contents} until it fills
30539 @var{count} memory units.
30543 @subsubheading @value{GDBN} Command
30545 There's no corresponding @value{GDBN} command.
30547 @subsubheading Example
30551 -data-write-memory-bytes &a "aabbccdd"
30558 -data-write-memory-bytes &a "aabbccdd" 16e
30563 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30564 @node GDB/MI Tracepoint Commands
30565 @section @sc{gdb/mi} Tracepoint Commands
30567 The commands defined in this section implement MI support for
30568 tracepoints. For detailed introduction, see @ref{Tracepoints}.
30570 @subheading The @code{-trace-find} Command
30571 @findex -trace-find
30573 @subsubheading Synopsis
30576 -trace-find @var{mode} [@var{parameters}@dots{}]
30579 Find a trace frame using criteria defined by @var{mode} and
30580 @var{parameters}. The following table lists permissible
30581 modes and their parameters. For details of operation, see @ref{tfind}.
30586 No parameters are required. Stops examining trace frames.
30589 An integer is required as parameter. Selects tracepoint frame with
30592 @item tracepoint-number
30593 An integer is required as parameter. Finds next
30594 trace frame that corresponds to tracepoint with the specified number.
30597 An address is required as parameter. Finds
30598 next trace frame that corresponds to any tracepoint at the specified
30601 @item pc-inside-range
30602 Two addresses are required as parameters. Finds next trace
30603 frame that corresponds to a tracepoint at an address inside the
30604 specified range. Both bounds are considered to be inside the range.
30606 @item pc-outside-range
30607 Two addresses are required as parameters. Finds
30608 next trace frame that corresponds to a tracepoint at an address outside
30609 the specified range. Both bounds are considered to be inside the range.
30612 Line specification is required as parameter. @xref{Specify Location}.
30613 Finds next trace frame that corresponds to a tracepoint at
30614 the specified location.
30618 If @samp{none} was passed as @var{mode}, the response does not
30619 have fields. Otherwise, the response may have the following fields:
30623 This field has either @samp{0} or @samp{1} as the value, depending
30624 on whether a matching tracepoint was found.
30627 The index of the found traceframe. This field is present iff
30628 the @samp{found} field has value of @samp{1}.
30631 The index of the found tracepoint. This field is present iff
30632 the @samp{found} field has value of @samp{1}.
30635 The information about the frame corresponding to the found trace
30636 frame. This field is present only if a trace frame was found.
30637 @xref{GDB/MI Frame Information}, for description of this field.
30641 @subsubheading @value{GDBN} Command
30643 The corresponding @value{GDBN} command is @samp{tfind}.
30645 @subheading -trace-define-variable
30646 @findex -trace-define-variable
30648 @subsubheading Synopsis
30651 -trace-define-variable @var{name} [ @var{value} ]
30654 Create trace variable @var{name} if it does not exist. If
30655 @var{value} is specified, sets the initial value of the specified
30656 trace variable to that value. Note that the @var{name} should start
30657 with the @samp{$} character.
30659 @subsubheading @value{GDBN} Command
30661 The corresponding @value{GDBN} command is @samp{tvariable}.
30663 @subheading The @code{-trace-frame-collected} Command
30664 @findex -trace-frame-collected
30666 @subsubheading Synopsis
30669 -trace-frame-collected
30670 [--var-print-values @var{var_pval}]
30671 [--comp-print-values @var{comp_pval}]
30672 [--registers-format @var{regformat}]
30673 [--memory-contents]
30676 This command returns the set of collected objects, register names,
30677 trace state variable names, memory ranges and computed expressions
30678 that have been collected at a particular trace frame. The optional
30679 parameters to the command affect the output format in different ways.
30680 See the output description table below for more details.
30682 The reported names can be used in the normal manner to create
30683 varobjs and inspect the objects themselves. The items returned by
30684 this command are categorized so that it is clear which is a variable,
30685 which is a register, which is a trace state variable, which is a
30686 memory range and which is a computed expression.
30688 For instance, if the actions were
30690 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
30691 collect *(int*)0xaf02bef0@@40
30695 the object collected in its entirety would be @code{myVar}. The
30696 object @code{myArray} would be partially collected, because only the
30697 element at index @code{myIndex} would be collected. The remaining
30698 objects would be computed expressions.
30700 An example output would be:
30704 -trace-frame-collected
30706 explicit-variables=[@{name="myVar",value="1"@}],
30707 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
30708 @{name="myObj.field",value="0"@},
30709 @{name="myPtr->field",value="1"@},
30710 @{name="myCount + 2",value="3"@},
30711 @{name="$tvar1 + 1",value="43970027"@}],
30712 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
30713 @{number="1",value="0x0"@},
30714 @{number="2",value="0x4"@},
30716 @{number="125",value="0x0"@}],
30717 tvars=[@{name="$tvar1",current="43970026"@}],
30718 memory=[@{address="0x0000000000602264",length="4"@},
30719 @{address="0x0000000000615bc0",length="4"@}]
30726 @item explicit-variables
30727 The set of objects that have been collected in their entirety (as
30728 opposed to collecting just a few elements of an array or a few struct
30729 members). For each object, its name and value are printed.
30730 The @code{--var-print-values} option affects how or whether the value
30731 field is output. If @var{var_pval} is 0, then print only the names;
30732 if it is 1, print also their values; and if it is 2, print the name,
30733 type and value for simple data types, and the name and type for
30734 arrays, structures and unions.
30736 @item computed-expressions
30737 The set of computed expressions that have been collected at the
30738 current trace frame. The @code{--comp-print-values} option affects
30739 this set like the @code{--var-print-values} option affects the
30740 @code{explicit-variables} set. See above.
30743 The registers that have been collected at the current trace frame.
30744 For each register collected, the name and current value are returned.
30745 The value is formatted according to the @code{--registers-format}
30746 option. See the @command{-data-list-register-values} command for a
30747 list of the allowed formats. The default is @samp{x}.
30750 The trace state variables that have been collected at the current
30751 trace frame. For each trace state variable collected, the name and
30752 current value are returned.
30755 The set of memory ranges that have been collected at the current trace
30756 frame. Its content is a list of tuples. Each tuple represents a
30757 collected memory range and has the following fields:
30761 The start address of the memory range, as hexadecimal literal.
30764 The length of the memory range, as decimal literal.
30767 The contents of the memory block, in hex. This field is only present
30768 if the @code{--memory-contents} option is specified.
30774 @subsubheading @value{GDBN} Command
30776 There is no corresponding @value{GDBN} command.
30778 @subsubheading Example
30780 @subheading -trace-list-variables
30781 @findex -trace-list-variables
30783 @subsubheading Synopsis
30786 -trace-list-variables
30789 Return a table of all defined trace variables. Each element of the
30790 table has the following fields:
30794 The name of the trace variable. This field is always present.
30797 The initial value. This is a 64-bit signed integer. This
30798 field is always present.
30801 The value the trace variable has at the moment. This is a 64-bit
30802 signed integer. This field is absent iff current value is
30803 not defined, for example if the trace was never run, or is
30808 @subsubheading @value{GDBN} Command
30810 The corresponding @value{GDBN} command is @samp{tvariables}.
30812 @subsubheading Example
30816 -trace-list-variables
30817 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
30818 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
30819 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
30820 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
30821 body=[variable=@{name="$trace_timestamp",initial="0"@}
30822 variable=@{name="$foo",initial="10",current="15"@}]@}
30826 @subheading -trace-save
30827 @findex -trace-save
30829 @subsubheading Synopsis
30832 -trace-save [-r ] @var{filename}
30835 Saves the collected trace data to @var{filename}. Without the
30836 @samp{-r} option, the data is downloaded from the target and saved
30837 in a local file. With the @samp{-r} option the target is asked
30838 to perform the save.
30840 @subsubheading @value{GDBN} Command
30842 The corresponding @value{GDBN} command is @samp{tsave}.
30845 @subheading -trace-start
30846 @findex -trace-start
30848 @subsubheading Synopsis
30854 Starts a tracing experiments. The result of this command does not
30857 @subsubheading @value{GDBN} Command
30859 The corresponding @value{GDBN} command is @samp{tstart}.
30861 @subheading -trace-status
30862 @findex -trace-status
30864 @subsubheading Synopsis
30870 Obtains the status of a tracing experiment. The result may include
30871 the following fields:
30876 May have a value of either @samp{0}, when no tracing operations are
30877 supported, @samp{1}, when all tracing operations are supported, or
30878 @samp{file} when examining trace file. In the latter case, examining
30879 of trace frame is possible but new tracing experiement cannot be
30880 started. This field is always present.
30883 May have a value of either @samp{0} or @samp{1} depending on whether
30884 tracing experiement is in progress on target. This field is present
30885 if @samp{supported} field is not @samp{0}.
30888 Report the reason why the tracing was stopped last time. This field
30889 may be absent iff tracing was never stopped on target yet. The
30890 value of @samp{request} means the tracing was stopped as result of
30891 the @code{-trace-stop} command. The value of @samp{overflow} means
30892 the tracing buffer is full. The value of @samp{disconnection} means
30893 tracing was automatically stopped when @value{GDBN} has disconnected.
30894 The value of @samp{passcount} means tracing was stopped when a
30895 tracepoint was passed a maximal number of times for that tracepoint.
30896 This field is present if @samp{supported} field is not @samp{0}.
30898 @item stopping-tracepoint
30899 The number of tracepoint whose passcount as exceeded. This field is
30900 present iff the @samp{stop-reason} field has the value of
30904 @itemx frames-created
30905 The @samp{frames} field is a count of the total number of trace frames
30906 in the trace buffer, while @samp{frames-created} is the total created
30907 during the run, including ones that were discarded, such as when a
30908 circular trace buffer filled up. Both fields are optional.
30912 These fields tell the current size of the tracing buffer and the
30913 remaining space. These fields are optional.
30916 The value of the circular trace buffer flag. @code{1} means that the
30917 trace buffer is circular and old trace frames will be discarded if
30918 necessary to make room, @code{0} means that the trace buffer is linear
30922 The value of the disconnected tracing flag. @code{1} means that
30923 tracing will continue after @value{GDBN} disconnects, @code{0} means
30924 that the trace run will stop.
30927 The filename of the trace file being examined. This field is
30928 optional, and only present when examining a trace file.
30932 @subsubheading @value{GDBN} Command
30934 The corresponding @value{GDBN} command is @samp{tstatus}.
30936 @subheading -trace-stop
30937 @findex -trace-stop
30939 @subsubheading Synopsis
30945 Stops a tracing experiment. The result of this command has the same
30946 fields as @code{-trace-status}, except that the @samp{supported} and
30947 @samp{running} fields are not output.
30949 @subsubheading @value{GDBN} Command
30951 The corresponding @value{GDBN} command is @samp{tstop}.
30954 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30955 @node GDB/MI Symbol Query
30956 @section @sc{gdb/mi} Symbol Query Commands
30960 @subheading The @code{-symbol-info-address} Command
30961 @findex -symbol-info-address
30963 @subsubheading Synopsis
30966 -symbol-info-address @var{symbol}
30969 Describe where @var{symbol} is stored.
30971 @subsubheading @value{GDBN} Command
30973 The corresponding @value{GDBN} command is @samp{info address}.
30975 @subsubheading Example
30979 @subheading The @code{-symbol-info-file} Command
30980 @findex -symbol-info-file
30982 @subsubheading Synopsis
30988 Show the file for the symbol.
30990 @subsubheading @value{GDBN} Command
30992 There's no equivalent @value{GDBN} command. @code{gdbtk} has
30993 @samp{gdb_find_file}.
30995 @subsubheading Example
30999 @subheading The @code{-symbol-info-function} Command
31000 @findex -symbol-info-function
31002 @subsubheading Synopsis
31005 -symbol-info-function
31008 Show which function the symbol lives in.
31010 @subsubheading @value{GDBN} Command
31012 @samp{gdb_get_function} in @code{gdbtk}.
31014 @subsubheading Example
31018 @subheading The @code{-symbol-info-line} Command
31019 @findex -symbol-info-line
31021 @subsubheading Synopsis
31027 Show the core addresses of the code for a source line.
31029 @subsubheading @value{GDBN} Command
31031 The corresponding @value{GDBN} command is @samp{info line}.
31032 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
31034 @subsubheading Example
31038 @subheading The @code{-symbol-info-symbol} Command
31039 @findex -symbol-info-symbol
31041 @subsubheading Synopsis
31044 -symbol-info-symbol @var{addr}
31047 Describe what symbol is at location @var{addr}.
31049 @subsubheading @value{GDBN} Command
31051 The corresponding @value{GDBN} command is @samp{info symbol}.
31053 @subsubheading Example
31057 @subheading The @code{-symbol-list-functions} Command
31058 @findex -symbol-list-functions
31060 @subsubheading Synopsis
31063 -symbol-list-functions
31066 List the functions in the executable.
31068 @subsubheading @value{GDBN} Command
31070 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
31071 @samp{gdb_search} in @code{gdbtk}.
31073 @subsubheading Example
31078 @subheading The @code{-symbol-list-lines} Command
31079 @findex -symbol-list-lines
31081 @subsubheading Synopsis
31084 -symbol-list-lines @var{filename}
31087 Print the list of lines that contain code and their associated program
31088 addresses for the given source filename. The entries are sorted in
31089 ascending PC order.
31091 @subsubheading @value{GDBN} Command
31093 There is no corresponding @value{GDBN} command.
31095 @subsubheading Example
31098 -symbol-list-lines basics.c
31099 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
31105 @subheading The @code{-symbol-list-types} Command
31106 @findex -symbol-list-types
31108 @subsubheading Synopsis
31114 List all the type names.
31116 @subsubheading @value{GDBN} Command
31118 The corresponding commands are @samp{info types} in @value{GDBN},
31119 @samp{gdb_search} in @code{gdbtk}.
31121 @subsubheading Example
31125 @subheading The @code{-symbol-list-variables} Command
31126 @findex -symbol-list-variables
31128 @subsubheading Synopsis
31131 -symbol-list-variables
31134 List all the global and static variable names.
31136 @subsubheading @value{GDBN} Command
31138 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
31140 @subsubheading Example
31144 @subheading The @code{-symbol-locate} Command
31145 @findex -symbol-locate
31147 @subsubheading Synopsis
31153 @subsubheading @value{GDBN} Command
31155 @samp{gdb_loc} in @code{gdbtk}.
31157 @subsubheading Example
31161 @subheading The @code{-symbol-type} Command
31162 @findex -symbol-type
31164 @subsubheading Synopsis
31167 -symbol-type @var{variable}
31170 Show type of @var{variable}.
31172 @subsubheading @value{GDBN} Command
31174 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
31175 @samp{gdb_obj_variable}.
31177 @subsubheading Example
31182 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31183 @node GDB/MI File Commands
31184 @section @sc{gdb/mi} File Commands
31186 This section describes the GDB/MI commands to specify executable file names
31187 and to read in and obtain symbol table information.
31189 @subheading The @code{-file-exec-and-symbols} Command
31190 @findex -file-exec-and-symbols
31192 @subsubheading Synopsis
31195 -file-exec-and-symbols @var{file}
31198 Specify the executable file to be debugged. This file is the one from
31199 which the symbol table is also read. If no file is specified, the
31200 command clears the executable and symbol information. If breakpoints
31201 are set when using this command with no arguments, @value{GDBN} will produce
31202 error messages. Otherwise, no output is produced, except a completion
31205 @subsubheading @value{GDBN} Command
31207 The corresponding @value{GDBN} command is @samp{file}.
31209 @subsubheading Example
31213 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31219 @subheading The @code{-file-exec-file} Command
31220 @findex -file-exec-file
31222 @subsubheading Synopsis
31225 -file-exec-file @var{file}
31228 Specify the executable file to be debugged. Unlike
31229 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
31230 from this file. If used without argument, @value{GDBN} clears the information
31231 about the executable file. No output is produced, except a completion
31234 @subsubheading @value{GDBN} Command
31236 The corresponding @value{GDBN} command is @samp{exec-file}.
31238 @subsubheading Example
31242 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31249 @subheading The @code{-file-list-exec-sections} Command
31250 @findex -file-list-exec-sections
31252 @subsubheading Synopsis
31255 -file-list-exec-sections
31258 List the sections of the current executable file.
31260 @subsubheading @value{GDBN} Command
31262 The @value{GDBN} command @samp{info file} shows, among the rest, the same
31263 information as this command. @code{gdbtk} has a corresponding command
31264 @samp{gdb_load_info}.
31266 @subsubheading Example
31271 @subheading The @code{-file-list-exec-source-file} Command
31272 @findex -file-list-exec-source-file
31274 @subsubheading Synopsis
31277 -file-list-exec-source-file
31280 List the line number, the current source file, and the absolute path
31281 to the current source file for the current executable. The macro
31282 information field has a value of @samp{1} or @samp{0} depending on
31283 whether or not the file includes preprocessor macro information.
31285 @subsubheading @value{GDBN} Command
31287 The @value{GDBN} equivalent is @samp{info source}
31289 @subsubheading Example
31293 123-file-list-exec-source-file
31294 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
31299 @subheading The @code{-file-list-exec-source-files} Command
31300 @findex -file-list-exec-source-files
31302 @subsubheading Synopsis
31305 -file-list-exec-source-files
31308 List the source files for the current executable.
31310 It will always output both the filename and fullname (absolute file
31311 name) of a source file.
31313 @subsubheading @value{GDBN} Command
31315 The @value{GDBN} equivalent is @samp{info sources}.
31316 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
31318 @subsubheading Example
31321 -file-list-exec-source-files
31323 @{file=foo.c,fullname=/home/foo.c@},
31324 @{file=/home/bar.c,fullname=/home/bar.c@},
31325 @{file=gdb_could_not_find_fullpath.c@}]
31330 @subheading The @code{-file-list-shared-libraries} Command
31331 @findex -file-list-shared-libraries
31333 @subsubheading Synopsis
31336 -file-list-shared-libraries
31339 List the shared libraries in the program.
31341 @subsubheading @value{GDBN} Command
31343 The corresponding @value{GDBN} command is @samp{info shared}.
31345 @subsubheading Example
31349 @subheading The @code{-file-list-symbol-files} Command
31350 @findex -file-list-symbol-files
31352 @subsubheading Synopsis
31355 -file-list-symbol-files
31360 @subsubheading @value{GDBN} Command
31362 The corresponding @value{GDBN} command is @samp{info file} (part of it).
31364 @subsubheading Example
31369 @subheading The @code{-file-symbol-file} Command
31370 @findex -file-symbol-file
31372 @subsubheading Synopsis
31375 -file-symbol-file @var{file}
31378 Read symbol table info from the specified @var{file} argument. When
31379 used without arguments, clears @value{GDBN}'s symbol table info. No output is
31380 produced, except for a completion notification.
31382 @subsubheading @value{GDBN} Command
31384 The corresponding @value{GDBN} command is @samp{symbol-file}.
31386 @subsubheading Example
31390 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31396 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31397 @node GDB/MI Memory Overlay Commands
31398 @section @sc{gdb/mi} Memory Overlay Commands
31400 The memory overlay commands are not implemented.
31402 @c @subheading -overlay-auto
31404 @c @subheading -overlay-list-mapping-state
31406 @c @subheading -overlay-list-overlays
31408 @c @subheading -overlay-map
31410 @c @subheading -overlay-off
31412 @c @subheading -overlay-on
31414 @c @subheading -overlay-unmap
31416 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31417 @node GDB/MI Signal Handling Commands
31418 @section @sc{gdb/mi} Signal Handling Commands
31420 Signal handling commands are not implemented.
31422 @c @subheading -signal-handle
31424 @c @subheading -signal-list-handle-actions
31426 @c @subheading -signal-list-signal-types
31430 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31431 @node GDB/MI Target Manipulation
31432 @section @sc{gdb/mi} Target Manipulation Commands
31435 @subheading The @code{-target-attach} Command
31436 @findex -target-attach
31438 @subsubheading Synopsis
31441 -target-attach @var{pid} | @var{gid} | @var{file}
31444 Attach to a process @var{pid} or a file @var{file} outside of
31445 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
31446 group, the id previously returned by
31447 @samp{-list-thread-groups --available} must be used.
31449 @subsubheading @value{GDBN} Command
31451 The corresponding @value{GDBN} command is @samp{attach}.
31453 @subsubheading Example
31457 =thread-created,id="1"
31458 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
31464 @subheading The @code{-target-compare-sections} Command
31465 @findex -target-compare-sections
31467 @subsubheading Synopsis
31470 -target-compare-sections [ @var{section} ]
31473 Compare data of section @var{section} on target to the exec file.
31474 Without the argument, all sections are compared.
31476 @subsubheading @value{GDBN} Command
31478 The @value{GDBN} equivalent is @samp{compare-sections}.
31480 @subsubheading Example
31485 @subheading The @code{-target-detach} Command
31486 @findex -target-detach
31488 @subsubheading Synopsis
31491 -target-detach [ @var{pid} | @var{gid} ]
31494 Detach from the remote target which normally resumes its execution.
31495 If either @var{pid} or @var{gid} is specified, detaches from either
31496 the specified process, or specified thread group. There's no output.
31498 @subsubheading @value{GDBN} Command
31500 The corresponding @value{GDBN} command is @samp{detach}.
31502 @subsubheading Example
31512 @subheading The @code{-target-disconnect} Command
31513 @findex -target-disconnect
31515 @subsubheading Synopsis
31521 Disconnect from the remote target. There's no output and the target is
31522 generally not resumed.
31524 @subsubheading @value{GDBN} Command
31526 The corresponding @value{GDBN} command is @samp{disconnect}.
31528 @subsubheading Example
31538 @subheading The @code{-target-download} Command
31539 @findex -target-download
31541 @subsubheading Synopsis
31547 Loads the executable onto the remote target.
31548 It prints out an update message every half second, which includes the fields:
31552 The name of the section.
31554 The size of what has been sent so far for that section.
31556 The size of the section.
31558 The total size of what was sent so far (the current and the previous sections).
31560 The size of the overall executable to download.
31564 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
31565 @sc{gdb/mi} Output Syntax}).
31567 In addition, it prints the name and size of the sections, as they are
31568 downloaded. These messages include the following fields:
31572 The name of the section.
31574 The size of the section.
31576 The size of the overall executable to download.
31580 At the end, a summary is printed.
31582 @subsubheading @value{GDBN} Command
31584 The corresponding @value{GDBN} command is @samp{load}.
31586 @subsubheading Example
31588 Note: each status message appears on a single line. Here the messages
31589 have been broken down so that they can fit onto a page.
31594 +download,@{section=".text",section-size="6668",total-size="9880"@}
31595 +download,@{section=".text",section-sent="512",section-size="6668",
31596 total-sent="512",total-size="9880"@}
31597 +download,@{section=".text",section-sent="1024",section-size="6668",
31598 total-sent="1024",total-size="9880"@}
31599 +download,@{section=".text",section-sent="1536",section-size="6668",
31600 total-sent="1536",total-size="9880"@}
31601 +download,@{section=".text",section-sent="2048",section-size="6668",
31602 total-sent="2048",total-size="9880"@}
31603 +download,@{section=".text",section-sent="2560",section-size="6668",
31604 total-sent="2560",total-size="9880"@}
31605 +download,@{section=".text",section-sent="3072",section-size="6668",
31606 total-sent="3072",total-size="9880"@}
31607 +download,@{section=".text",section-sent="3584",section-size="6668",
31608 total-sent="3584",total-size="9880"@}
31609 +download,@{section=".text",section-sent="4096",section-size="6668",
31610 total-sent="4096",total-size="9880"@}
31611 +download,@{section=".text",section-sent="4608",section-size="6668",
31612 total-sent="4608",total-size="9880"@}
31613 +download,@{section=".text",section-sent="5120",section-size="6668",
31614 total-sent="5120",total-size="9880"@}
31615 +download,@{section=".text",section-sent="5632",section-size="6668",
31616 total-sent="5632",total-size="9880"@}
31617 +download,@{section=".text",section-sent="6144",section-size="6668",
31618 total-sent="6144",total-size="9880"@}
31619 +download,@{section=".text",section-sent="6656",section-size="6668",
31620 total-sent="6656",total-size="9880"@}
31621 +download,@{section=".init",section-size="28",total-size="9880"@}
31622 +download,@{section=".fini",section-size="28",total-size="9880"@}
31623 +download,@{section=".data",section-size="3156",total-size="9880"@}
31624 +download,@{section=".data",section-sent="512",section-size="3156",
31625 total-sent="7236",total-size="9880"@}
31626 +download,@{section=".data",section-sent="1024",section-size="3156",
31627 total-sent="7748",total-size="9880"@}
31628 +download,@{section=".data",section-sent="1536",section-size="3156",
31629 total-sent="8260",total-size="9880"@}
31630 +download,@{section=".data",section-sent="2048",section-size="3156",
31631 total-sent="8772",total-size="9880"@}
31632 +download,@{section=".data",section-sent="2560",section-size="3156",
31633 total-sent="9284",total-size="9880"@}
31634 +download,@{section=".data",section-sent="3072",section-size="3156",
31635 total-sent="9796",total-size="9880"@}
31636 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
31643 @subheading The @code{-target-exec-status} Command
31644 @findex -target-exec-status
31646 @subsubheading Synopsis
31649 -target-exec-status
31652 Provide information on the state of the target (whether it is running or
31653 not, for instance).
31655 @subsubheading @value{GDBN} Command
31657 There's no equivalent @value{GDBN} command.
31659 @subsubheading Example
31663 @subheading The @code{-target-list-available-targets} Command
31664 @findex -target-list-available-targets
31666 @subsubheading Synopsis
31669 -target-list-available-targets
31672 List the possible targets to connect to.
31674 @subsubheading @value{GDBN} Command
31676 The corresponding @value{GDBN} command is @samp{help target}.
31678 @subsubheading Example
31682 @subheading The @code{-target-list-current-targets} Command
31683 @findex -target-list-current-targets
31685 @subsubheading Synopsis
31688 -target-list-current-targets
31691 Describe the current target.
31693 @subsubheading @value{GDBN} Command
31695 The corresponding information is printed by @samp{info file} (among
31698 @subsubheading Example
31702 @subheading The @code{-target-list-parameters} Command
31703 @findex -target-list-parameters
31705 @subsubheading Synopsis
31708 -target-list-parameters
31714 @subsubheading @value{GDBN} Command
31718 @subsubheading Example
31722 @subheading The @code{-target-select} Command
31723 @findex -target-select
31725 @subsubheading Synopsis
31728 -target-select @var{type} @var{parameters @dots{}}
31731 Connect @value{GDBN} to the remote target. This command takes two args:
31735 The type of target, for instance @samp{remote}, etc.
31736 @item @var{parameters}
31737 Device names, host names and the like. @xref{Target Commands, ,
31738 Commands for Managing Targets}, for more details.
31741 The output is a connection notification, followed by the address at
31742 which the target program is, in the following form:
31745 ^connected,addr="@var{address}",func="@var{function name}",
31746 args=[@var{arg list}]
31749 @subsubheading @value{GDBN} Command
31751 The corresponding @value{GDBN} command is @samp{target}.
31753 @subsubheading Example
31757 -target-select remote /dev/ttya
31758 ^connected,addr="0xfe00a300",func="??",args=[]
31762 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31763 @node GDB/MI File Transfer Commands
31764 @section @sc{gdb/mi} File Transfer Commands
31767 @subheading The @code{-target-file-put} Command
31768 @findex -target-file-put
31770 @subsubheading Synopsis
31773 -target-file-put @var{hostfile} @var{targetfile}
31776 Copy file @var{hostfile} from the host system (the machine running
31777 @value{GDBN}) to @var{targetfile} on the target system.
31779 @subsubheading @value{GDBN} Command
31781 The corresponding @value{GDBN} command is @samp{remote put}.
31783 @subsubheading Example
31787 -target-file-put localfile remotefile
31793 @subheading The @code{-target-file-get} Command
31794 @findex -target-file-get
31796 @subsubheading Synopsis
31799 -target-file-get @var{targetfile} @var{hostfile}
31802 Copy file @var{targetfile} from the target system to @var{hostfile}
31803 on the host system.
31805 @subsubheading @value{GDBN} Command
31807 The corresponding @value{GDBN} command is @samp{remote get}.
31809 @subsubheading Example
31813 -target-file-get remotefile localfile
31819 @subheading The @code{-target-file-delete} Command
31820 @findex -target-file-delete
31822 @subsubheading Synopsis
31825 -target-file-delete @var{targetfile}
31828 Delete @var{targetfile} from the target system.
31830 @subsubheading @value{GDBN} Command
31832 The corresponding @value{GDBN} command is @samp{remote delete}.
31834 @subsubheading Example
31838 -target-file-delete remotefile
31844 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31845 @node GDB/MI Ada Exceptions Commands
31846 @section Ada Exceptions @sc{gdb/mi} Commands
31848 @subheading The @code{-info-ada-exceptions} Command
31849 @findex -info-ada-exceptions
31851 @subsubheading Synopsis
31854 -info-ada-exceptions [ @var{regexp}]
31857 List all Ada exceptions defined within the program being debugged.
31858 With a regular expression @var{regexp}, only those exceptions whose
31859 names match @var{regexp} are listed.
31861 @subsubheading @value{GDBN} Command
31863 The corresponding @value{GDBN} command is @samp{info exceptions}.
31865 @subsubheading Result
31867 The result is a table of Ada exceptions. The following columns are
31868 defined for each exception:
31872 The name of the exception.
31875 The address of the exception.
31879 @subsubheading Example
31882 -info-ada-exceptions aint
31883 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
31884 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
31885 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
31886 body=[@{name="constraint_error",address="0x0000000000613da0"@},
31887 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
31890 @subheading Catching Ada Exceptions
31892 The commands describing how to ask @value{GDBN} to stop when a program
31893 raises an exception are described at @ref{Ada Exception GDB/MI
31894 Catchpoint Commands}.
31897 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31898 @node GDB/MI Support Commands
31899 @section @sc{gdb/mi} Support Commands
31901 Since new commands and features get regularly added to @sc{gdb/mi},
31902 some commands are available to help front-ends query the debugger
31903 about support for these capabilities. Similarly, it is also possible
31904 to query @value{GDBN} about target support of certain features.
31906 @subheading The @code{-info-gdb-mi-command} Command
31907 @cindex @code{-info-gdb-mi-command}
31908 @findex -info-gdb-mi-command
31910 @subsubheading Synopsis
31913 -info-gdb-mi-command @var{cmd_name}
31916 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
31918 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
31919 is technically not part of the command name (@pxref{GDB/MI Input
31920 Syntax}), and thus should be omitted in @var{cmd_name}. However,
31921 for ease of use, this command also accepts the form with the leading
31924 @subsubheading @value{GDBN} Command
31926 There is no corresponding @value{GDBN} command.
31928 @subsubheading Result
31930 The result is a tuple. There is currently only one field:
31934 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
31935 @code{"false"} otherwise.
31939 @subsubheading Example
31941 Here is an example where the @sc{gdb/mi} command does not exist:
31944 -info-gdb-mi-command unsupported-command
31945 ^done,command=@{exists="false"@}
31949 And here is an example where the @sc{gdb/mi} command is known
31953 -info-gdb-mi-command symbol-list-lines
31954 ^done,command=@{exists="true"@}
31957 @subheading The @code{-list-features} Command
31958 @findex -list-features
31959 @cindex supported @sc{gdb/mi} features, list
31961 Returns a list of particular features of the MI protocol that
31962 this version of gdb implements. A feature can be a command,
31963 or a new field in an output of some command, or even an
31964 important bugfix. While a frontend can sometimes detect presence
31965 of a feature at runtime, it is easier to perform detection at debugger
31968 The command returns a list of strings, with each string naming an
31969 available feature. Each returned string is just a name, it does not
31970 have any internal structure. The list of possible feature names
31976 (gdb) -list-features
31977 ^done,result=["feature1","feature2"]
31980 The current list of features is:
31983 @item frozen-varobjs
31984 Indicates support for the @code{-var-set-frozen} command, as well
31985 as possible presense of the @code{frozen} field in the output
31986 of @code{-varobj-create}.
31987 @item pending-breakpoints
31988 Indicates support for the @option{-f} option to the @code{-break-insert}
31991 Indicates Python scripting support, Python-based
31992 pretty-printing commands, and possible presence of the
31993 @samp{display_hint} field in the output of @code{-var-list-children}
31995 Indicates support for the @code{-thread-info} command.
31996 @item data-read-memory-bytes
31997 Indicates support for the @code{-data-read-memory-bytes} and the
31998 @code{-data-write-memory-bytes} commands.
31999 @item breakpoint-notifications
32000 Indicates that changes to breakpoints and breakpoints created via the
32001 CLI will be announced via async records.
32002 @item ada-task-info
32003 Indicates support for the @code{-ada-task-info} command.
32004 @item language-option
32005 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
32006 option (@pxref{Context management}).
32007 @item info-gdb-mi-command
32008 Indicates support for the @code{-info-gdb-mi-command} command.
32009 @item undefined-command-error-code
32010 Indicates support for the "undefined-command" error code in error result
32011 records, produced when trying to execute an undefined @sc{gdb/mi} command
32012 (@pxref{GDB/MI Result Records}).
32013 @item exec-run-start-option
32014 Indicates that the @code{-exec-run} command supports the @option{--start}
32015 option (@pxref{GDB/MI Program Execution}).
32018 @subheading The @code{-list-target-features} Command
32019 @findex -list-target-features
32021 Returns a list of particular features that are supported by the
32022 target. Those features affect the permitted MI commands, but
32023 unlike the features reported by the @code{-list-features} command, the
32024 features depend on which target GDB is using at the moment. Whenever
32025 a target can change, due to commands such as @code{-target-select},
32026 @code{-target-attach} or @code{-exec-run}, the list of target features
32027 may change, and the frontend should obtain it again.
32031 (gdb) -list-target-features
32032 ^done,result=["async"]
32035 The current list of features is:
32039 Indicates that the target is capable of asynchronous command
32040 execution, which means that @value{GDBN} will accept further commands
32041 while the target is running.
32044 Indicates that the target is capable of reverse execution.
32045 @xref{Reverse Execution}, for more information.
32049 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32050 @node GDB/MI Miscellaneous Commands
32051 @section Miscellaneous @sc{gdb/mi} Commands
32053 @c @subheading -gdb-complete
32055 @subheading The @code{-gdb-exit} Command
32058 @subsubheading Synopsis
32064 Exit @value{GDBN} immediately.
32066 @subsubheading @value{GDBN} Command
32068 Approximately corresponds to @samp{quit}.
32070 @subsubheading Example
32080 @subheading The @code{-exec-abort} Command
32081 @findex -exec-abort
32083 @subsubheading Synopsis
32089 Kill the inferior running program.
32091 @subsubheading @value{GDBN} Command
32093 The corresponding @value{GDBN} command is @samp{kill}.
32095 @subsubheading Example
32100 @subheading The @code{-gdb-set} Command
32103 @subsubheading Synopsis
32109 Set an internal @value{GDBN} variable.
32110 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
32112 @subsubheading @value{GDBN} Command
32114 The corresponding @value{GDBN} command is @samp{set}.
32116 @subsubheading Example
32126 @subheading The @code{-gdb-show} Command
32129 @subsubheading Synopsis
32135 Show the current value of a @value{GDBN} variable.
32137 @subsubheading @value{GDBN} Command
32139 The corresponding @value{GDBN} command is @samp{show}.
32141 @subsubheading Example
32150 @c @subheading -gdb-source
32153 @subheading The @code{-gdb-version} Command
32154 @findex -gdb-version
32156 @subsubheading Synopsis
32162 Show version information for @value{GDBN}. Used mostly in testing.
32164 @subsubheading @value{GDBN} Command
32166 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
32167 default shows this information when you start an interactive session.
32169 @subsubheading Example
32171 @c This example modifies the actual output from GDB to avoid overfull
32177 ~Copyright 2000 Free Software Foundation, Inc.
32178 ~GDB is free software, covered by the GNU General Public License, and
32179 ~you are welcome to change it and/or distribute copies of it under
32180 ~ certain conditions.
32181 ~Type "show copying" to see the conditions.
32182 ~There is absolutely no warranty for GDB. Type "show warranty" for
32184 ~This GDB was configured as
32185 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
32190 @subheading The @code{-list-thread-groups} Command
32191 @findex -list-thread-groups
32193 @subheading Synopsis
32196 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
32199 Lists thread groups (@pxref{Thread groups}). When a single thread
32200 group is passed as the argument, lists the children of that group.
32201 When several thread group are passed, lists information about those
32202 thread groups. Without any parameters, lists information about all
32203 top-level thread groups.
32205 Normally, thread groups that are being debugged are reported.
32206 With the @samp{--available} option, @value{GDBN} reports thread groups
32207 available on the target.
32209 The output of this command may have either a @samp{threads} result or
32210 a @samp{groups} result. The @samp{thread} result has a list of tuples
32211 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
32212 Information}). The @samp{groups} result has a list of tuples as value,
32213 each tuple describing a thread group. If top-level groups are
32214 requested (that is, no parameter is passed), or when several groups
32215 are passed, the output always has a @samp{groups} result. The format
32216 of the @samp{group} result is described below.
32218 To reduce the number of roundtrips it's possible to list thread groups
32219 together with their children, by passing the @samp{--recurse} option
32220 and the recursion depth. Presently, only recursion depth of 1 is
32221 permitted. If this option is present, then every reported thread group
32222 will also include its children, either as @samp{group} or
32223 @samp{threads} field.
32225 In general, any combination of option and parameters is permitted, with
32226 the following caveats:
32230 When a single thread group is passed, the output will typically
32231 be the @samp{threads} result. Because threads may not contain
32232 anything, the @samp{recurse} option will be ignored.
32235 When the @samp{--available} option is passed, limited information may
32236 be available. In particular, the list of threads of a process might
32237 be inaccessible. Further, specifying specific thread groups might
32238 not give any performance advantage over listing all thread groups.
32239 The frontend should assume that @samp{-list-thread-groups --available}
32240 is always an expensive operation and cache the results.
32244 The @samp{groups} result is a list of tuples, where each tuple may
32245 have the following fields:
32249 Identifier of the thread group. This field is always present.
32250 The identifier is an opaque string; frontends should not try to
32251 convert it to an integer, even though it might look like one.
32254 The type of the thread group. At present, only @samp{process} is a
32258 The target-specific process identifier. This field is only present
32259 for thread groups of type @samp{process} and only if the process exists.
32262 The exit code of this group's last exited thread, formatted in octal.
32263 This field is only present for thread groups of type @samp{process} and
32264 only if the process is not running.
32267 The number of children this thread group has. This field may be
32268 absent for an available thread group.
32271 This field has a list of tuples as value, each tuple describing a
32272 thread. It may be present if the @samp{--recurse} option is
32273 specified, and it's actually possible to obtain the threads.
32276 This field is a list of integers, each identifying a core that one
32277 thread of the group is running on. This field may be absent if
32278 such information is not available.
32281 The name of the executable file that corresponds to this thread group.
32282 The field is only present for thread groups of type @samp{process},
32283 and only if there is a corresponding executable file.
32287 @subheading Example
32291 -list-thread-groups
32292 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
32293 -list-thread-groups 17
32294 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
32295 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
32296 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
32297 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
32298 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
32299 -list-thread-groups --available
32300 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
32301 -list-thread-groups --available --recurse 1
32302 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32303 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32304 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
32305 -list-thread-groups --available --recurse 1 17 18
32306 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32307 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32308 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
32311 @subheading The @code{-info-os} Command
32314 @subsubheading Synopsis
32317 -info-os [ @var{type} ]
32320 If no argument is supplied, the command returns a table of available
32321 operating-system-specific information types. If one of these types is
32322 supplied as an argument @var{type}, then the command returns a table
32323 of data of that type.
32325 The types of information available depend on the target operating
32328 @subsubheading @value{GDBN} Command
32330 The corresponding @value{GDBN} command is @samp{info os}.
32332 @subsubheading Example
32334 When run on a @sc{gnu}/Linux system, the output will look something
32340 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
32341 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
32342 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
32343 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
32344 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
32346 item=@{col0="files",col1="Listing of all file descriptors",
32347 col2="File descriptors"@},
32348 item=@{col0="modules",col1="Listing of all loaded kernel modules",
32349 col2="Kernel modules"@},
32350 item=@{col0="msg",col1="Listing of all message queues",
32351 col2="Message queues"@},
32352 item=@{col0="processes",col1="Listing of all processes",
32353 col2="Processes"@},
32354 item=@{col0="procgroups",col1="Listing of all process groups",
32355 col2="Process groups"@},
32356 item=@{col0="semaphores",col1="Listing of all semaphores",
32357 col2="Semaphores"@},
32358 item=@{col0="shm",col1="Listing of all shared-memory regions",
32359 col2="Shared-memory regions"@},
32360 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
32362 item=@{col0="threads",col1="Listing of all threads",
32366 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
32367 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
32368 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
32369 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
32370 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
32371 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
32372 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
32373 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
32375 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
32376 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
32380 (Note that the MI output here includes a @code{"Title"} column that
32381 does not appear in command-line @code{info os}; this column is useful
32382 for MI clients that want to enumerate the types of data, such as in a
32383 popup menu, but is needless clutter on the command line, and
32384 @code{info os} omits it.)
32386 @subheading The @code{-add-inferior} Command
32387 @findex -add-inferior
32389 @subheading Synopsis
32395 Creates a new inferior (@pxref{Inferiors and Programs}). The created
32396 inferior is not associated with any executable. Such association may
32397 be established with the @samp{-file-exec-and-symbols} command
32398 (@pxref{GDB/MI File Commands}). The command response has a single
32399 field, @samp{inferior}, whose value is the identifier of the
32400 thread group corresponding to the new inferior.
32402 @subheading Example
32407 ^done,inferior="i3"
32410 @subheading The @code{-interpreter-exec} Command
32411 @findex -interpreter-exec
32413 @subheading Synopsis
32416 -interpreter-exec @var{interpreter} @var{command}
32418 @anchor{-interpreter-exec}
32420 Execute the specified @var{command} in the given @var{interpreter}.
32422 @subheading @value{GDBN} Command
32424 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
32426 @subheading Example
32430 -interpreter-exec console "break main"
32431 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
32432 &"During symbol reading, bad structure-type format.\n"
32433 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
32438 @subheading The @code{-inferior-tty-set} Command
32439 @findex -inferior-tty-set
32441 @subheading Synopsis
32444 -inferior-tty-set /dev/pts/1
32447 Set terminal for future runs of the program being debugged.
32449 @subheading @value{GDBN} Command
32451 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
32453 @subheading Example
32457 -inferior-tty-set /dev/pts/1
32462 @subheading The @code{-inferior-tty-show} Command
32463 @findex -inferior-tty-show
32465 @subheading Synopsis
32471 Show terminal for future runs of program being debugged.
32473 @subheading @value{GDBN} Command
32475 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
32477 @subheading Example
32481 -inferior-tty-set /dev/pts/1
32485 ^done,inferior_tty_terminal="/dev/pts/1"
32489 @subheading The @code{-enable-timings} Command
32490 @findex -enable-timings
32492 @subheading Synopsis
32495 -enable-timings [yes | no]
32498 Toggle the printing of the wallclock, user and system times for an MI
32499 command as a field in its output. This command is to help frontend
32500 developers optimize the performance of their code. No argument is
32501 equivalent to @samp{yes}.
32503 @subheading @value{GDBN} Command
32507 @subheading Example
32515 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
32516 addr="0x080484ed",func="main",file="myprog.c",
32517 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
32519 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
32527 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
32528 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
32529 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
32530 fullname="/home/nickrob/myprog.c",line="73"@}
32535 @chapter @value{GDBN} Annotations
32537 This chapter describes annotations in @value{GDBN}. Annotations were
32538 designed to interface @value{GDBN} to graphical user interfaces or other
32539 similar programs which want to interact with @value{GDBN} at a
32540 relatively high level.
32542 The annotation mechanism has largely been superseded by @sc{gdb/mi}
32546 This is Edition @value{EDITION}, @value{DATE}.
32550 * Annotations Overview:: What annotations are; the general syntax.
32551 * Server Prefix:: Issuing a command without affecting user state.
32552 * Prompting:: Annotations marking @value{GDBN}'s need for input.
32553 * Errors:: Annotations for error messages.
32554 * Invalidation:: Some annotations describe things now invalid.
32555 * Annotations for Running::
32556 Whether the program is running, how it stopped, etc.
32557 * Source Annotations:: Annotations describing source code.
32560 @node Annotations Overview
32561 @section What is an Annotation?
32562 @cindex annotations
32564 Annotations start with a newline character, two @samp{control-z}
32565 characters, and the name of the annotation. If there is no additional
32566 information associated with this annotation, the name of the annotation
32567 is followed immediately by a newline. If there is additional
32568 information, the name of the annotation is followed by a space, the
32569 additional information, and a newline. The additional information
32570 cannot contain newline characters.
32572 Any output not beginning with a newline and two @samp{control-z}
32573 characters denotes literal output from @value{GDBN}. Currently there is
32574 no need for @value{GDBN} to output a newline followed by two
32575 @samp{control-z} characters, but if there was such a need, the
32576 annotations could be extended with an @samp{escape} annotation which
32577 means those three characters as output.
32579 The annotation @var{level}, which is specified using the
32580 @option{--annotate} command line option (@pxref{Mode Options}), controls
32581 how much information @value{GDBN} prints together with its prompt,
32582 values of expressions, source lines, and other types of output. Level 0
32583 is for no annotations, level 1 is for use when @value{GDBN} is run as a
32584 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
32585 for programs that control @value{GDBN}, and level 2 annotations have
32586 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
32587 Interface, annotate, GDB's Obsolete Annotations}).
32590 @kindex set annotate
32591 @item set annotate @var{level}
32592 The @value{GDBN} command @code{set annotate} sets the level of
32593 annotations to the specified @var{level}.
32595 @item show annotate
32596 @kindex show annotate
32597 Show the current annotation level.
32600 This chapter describes level 3 annotations.
32602 A simple example of starting up @value{GDBN} with annotations is:
32605 $ @kbd{gdb --annotate=3}
32607 Copyright 2003 Free Software Foundation, Inc.
32608 GDB is free software, covered by the GNU General Public License,
32609 and you are welcome to change it and/or distribute copies of it
32610 under certain conditions.
32611 Type "show copying" to see the conditions.
32612 There is absolutely no warranty for GDB. Type "show warranty"
32614 This GDB was configured as "i386-pc-linux-gnu"
32625 Here @samp{quit} is input to @value{GDBN}; the rest is output from
32626 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
32627 denotes a @samp{control-z} character) are annotations; the rest is
32628 output from @value{GDBN}.
32630 @node Server Prefix
32631 @section The Server Prefix
32632 @cindex server prefix
32634 If you prefix a command with @samp{server } then it will not affect
32635 the command history, nor will it affect @value{GDBN}'s notion of which
32636 command to repeat if @key{RET} is pressed on a line by itself. This
32637 means that commands can be run behind a user's back by a front-end in
32638 a transparent manner.
32640 The @code{server } prefix does not affect the recording of values into
32641 the value history; to print a value without recording it into the
32642 value history, use the @code{output} command instead of the
32643 @code{print} command.
32645 Using this prefix also disables confirmation requests
32646 (@pxref{confirmation requests}).
32649 @section Annotation for @value{GDBN} Input
32651 @cindex annotations for prompts
32652 When @value{GDBN} prompts for input, it annotates this fact so it is possible
32653 to know when to send output, when the output from a given command is
32656 Different kinds of input each have a different @dfn{input type}. Each
32657 input type has three annotations: a @code{pre-} annotation, which
32658 denotes the beginning of any prompt which is being output, a plain
32659 annotation, which denotes the end of the prompt, and then a @code{post-}
32660 annotation which denotes the end of any echo which may (or may not) be
32661 associated with the input. For example, the @code{prompt} input type
32662 features the following annotations:
32670 The input types are
32673 @findex pre-prompt annotation
32674 @findex prompt annotation
32675 @findex post-prompt annotation
32677 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
32679 @findex pre-commands annotation
32680 @findex commands annotation
32681 @findex post-commands annotation
32683 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
32684 command. The annotations are repeated for each command which is input.
32686 @findex pre-overload-choice annotation
32687 @findex overload-choice annotation
32688 @findex post-overload-choice annotation
32689 @item overload-choice
32690 When @value{GDBN} wants the user to select between various overloaded functions.
32692 @findex pre-query annotation
32693 @findex query annotation
32694 @findex post-query annotation
32696 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
32698 @findex pre-prompt-for-continue annotation
32699 @findex prompt-for-continue annotation
32700 @findex post-prompt-for-continue annotation
32701 @item prompt-for-continue
32702 When @value{GDBN} is asking the user to press return to continue. Note: Don't
32703 expect this to work well; instead use @code{set height 0} to disable
32704 prompting. This is because the counting of lines is buggy in the
32705 presence of annotations.
32710 @cindex annotations for errors, warnings and interrupts
32712 @findex quit annotation
32717 This annotation occurs right before @value{GDBN} responds to an interrupt.
32719 @findex error annotation
32724 This annotation occurs right before @value{GDBN} responds to an error.
32726 Quit and error annotations indicate that any annotations which @value{GDBN} was
32727 in the middle of may end abruptly. For example, if a
32728 @code{value-history-begin} annotation is followed by a @code{error}, one
32729 cannot expect to receive the matching @code{value-history-end}. One
32730 cannot expect not to receive it either, however; an error annotation
32731 does not necessarily mean that @value{GDBN} is immediately returning all the way
32734 @findex error-begin annotation
32735 A quit or error annotation may be preceded by
32741 Any output between that and the quit or error annotation is the error
32744 Warning messages are not yet annotated.
32745 @c If we want to change that, need to fix warning(), type_error(),
32746 @c range_error(), and possibly other places.
32749 @section Invalidation Notices
32751 @cindex annotations for invalidation messages
32752 The following annotations say that certain pieces of state may have
32756 @findex frames-invalid annotation
32757 @item ^Z^Zframes-invalid
32759 The frames (for example, output from the @code{backtrace} command) may
32762 @findex breakpoints-invalid annotation
32763 @item ^Z^Zbreakpoints-invalid
32765 The breakpoints may have changed. For example, the user just added or
32766 deleted a breakpoint.
32769 @node Annotations for Running
32770 @section Running the Program
32771 @cindex annotations for running programs
32773 @findex starting annotation
32774 @findex stopping annotation
32775 When the program starts executing due to a @value{GDBN} command such as
32776 @code{step} or @code{continue},
32782 is output. When the program stops,
32788 is output. Before the @code{stopped} annotation, a variety of
32789 annotations describe how the program stopped.
32792 @findex exited annotation
32793 @item ^Z^Zexited @var{exit-status}
32794 The program exited, and @var{exit-status} is the exit status (zero for
32795 successful exit, otherwise nonzero).
32797 @findex signalled annotation
32798 @findex signal-name annotation
32799 @findex signal-name-end annotation
32800 @findex signal-string annotation
32801 @findex signal-string-end annotation
32802 @item ^Z^Zsignalled
32803 The program exited with a signal. After the @code{^Z^Zsignalled}, the
32804 annotation continues:
32810 ^Z^Zsignal-name-end
32814 ^Z^Zsignal-string-end
32819 where @var{name} is the name of the signal, such as @code{SIGILL} or
32820 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
32821 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
32822 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
32823 user's benefit and have no particular format.
32825 @findex signal annotation
32827 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
32828 just saying that the program received the signal, not that it was
32829 terminated with it.
32831 @findex breakpoint annotation
32832 @item ^Z^Zbreakpoint @var{number}
32833 The program hit breakpoint number @var{number}.
32835 @findex watchpoint annotation
32836 @item ^Z^Zwatchpoint @var{number}
32837 The program hit watchpoint number @var{number}.
32840 @node Source Annotations
32841 @section Displaying Source
32842 @cindex annotations for source display
32844 @findex source annotation
32845 The following annotation is used instead of displaying source code:
32848 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
32851 where @var{filename} is an absolute file name indicating which source
32852 file, @var{line} is the line number within that file (where 1 is the
32853 first line in the file), @var{character} is the character position
32854 within the file (where 0 is the first character in the file) (for most
32855 debug formats this will necessarily point to the beginning of a line),
32856 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
32857 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
32858 @var{addr} is the address in the target program associated with the
32859 source which is being displayed. The @var{addr} is in the form @samp{0x}
32860 followed by one or more lowercase hex digits (note that this does not
32861 depend on the language).
32863 @node JIT Interface
32864 @chapter JIT Compilation Interface
32865 @cindex just-in-time compilation
32866 @cindex JIT compilation interface
32868 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
32869 interface. A JIT compiler is a program or library that generates native
32870 executable code at runtime and executes it, usually in order to achieve good
32871 performance while maintaining platform independence.
32873 Programs that use JIT compilation are normally difficult to debug because
32874 portions of their code are generated at runtime, instead of being loaded from
32875 object files, which is where @value{GDBN} normally finds the program's symbols
32876 and debug information. In order to debug programs that use JIT compilation,
32877 @value{GDBN} has an interface that allows the program to register in-memory
32878 symbol files with @value{GDBN} at runtime.
32880 If you are using @value{GDBN} to debug a program that uses this interface, then
32881 it should work transparently so long as you have not stripped the binary. If
32882 you are developing a JIT compiler, then the interface is documented in the rest
32883 of this chapter. At this time, the only known client of this interface is the
32886 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
32887 JIT compiler communicates with @value{GDBN} by writing data into a global
32888 variable and calling a fuction at a well-known symbol. When @value{GDBN}
32889 attaches, it reads a linked list of symbol files from the global variable to
32890 find existing code, and puts a breakpoint in the function so that it can find
32891 out about additional code.
32894 * Declarations:: Relevant C struct declarations
32895 * Registering Code:: Steps to register code
32896 * Unregistering Code:: Steps to unregister code
32897 * Custom Debug Info:: Emit debug information in a custom format
32901 @section JIT Declarations
32903 These are the relevant struct declarations that a C program should include to
32904 implement the interface:
32914 struct jit_code_entry
32916 struct jit_code_entry *next_entry;
32917 struct jit_code_entry *prev_entry;
32918 const char *symfile_addr;
32919 uint64_t symfile_size;
32922 struct jit_descriptor
32925 /* This type should be jit_actions_t, but we use uint32_t
32926 to be explicit about the bitwidth. */
32927 uint32_t action_flag;
32928 struct jit_code_entry *relevant_entry;
32929 struct jit_code_entry *first_entry;
32932 /* GDB puts a breakpoint in this function. */
32933 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
32935 /* Make sure to specify the version statically, because the
32936 debugger may check the version before we can set it. */
32937 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
32940 If the JIT is multi-threaded, then it is important that the JIT synchronize any
32941 modifications to this global data properly, which can easily be done by putting
32942 a global mutex around modifications to these structures.
32944 @node Registering Code
32945 @section Registering Code
32947 To register code with @value{GDBN}, the JIT should follow this protocol:
32951 Generate an object file in memory with symbols and other desired debug
32952 information. The file must include the virtual addresses of the sections.
32955 Create a code entry for the file, which gives the start and size of the symbol
32959 Add it to the linked list in the JIT descriptor.
32962 Point the relevant_entry field of the descriptor at the entry.
32965 Set @code{action_flag} to @code{JIT_REGISTER} and call
32966 @code{__jit_debug_register_code}.
32969 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
32970 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
32971 new code. However, the linked list must still be maintained in order to allow
32972 @value{GDBN} to attach to a running process and still find the symbol files.
32974 @node Unregistering Code
32975 @section Unregistering Code
32977 If code is freed, then the JIT should use the following protocol:
32981 Remove the code entry corresponding to the code from the linked list.
32984 Point the @code{relevant_entry} field of the descriptor at the code entry.
32987 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
32988 @code{__jit_debug_register_code}.
32991 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
32992 and the JIT will leak the memory used for the associated symbol files.
32994 @node Custom Debug Info
32995 @section Custom Debug Info
32996 @cindex custom JIT debug info
32997 @cindex JIT debug info reader
32999 Generating debug information in platform-native file formats (like ELF
33000 or COFF) may be an overkill for JIT compilers; especially if all the
33001 debug info is used for is displaying a meaningful backtrace. The
33002 issue can be resolved by having the JIT writers decide on a debug info
33003 format and also provide a reader that parses the debug info generated
33004 by the JIT compiler. This section gives a brief overview on writing
33005 such a parser. More specific details can be found in the source file
33006 @file{gdb/jit-reader.in}, which is also installed as a header at
33007 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
33009 The reader is implemented as a shared object (so this functionality is
33010 not available on platforms which don't allow loading shared objects at
33011 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
33012 @code{jit-reader-unload} are provided, to be used to load and unload
33013 the readers from a preconfigured directory. Once loaded, the shared
33014 object is used the parse the debug information emitted by the JIT
33018 * Using JIT Debug Info Readers:: How to use supplied readers correctly
33019 * Writing JIT Debug Info Readers:: Creating a debug-info reader
33022 @node Using JIT Debug Info Readers
33023 @subsection Using JIT Debug Info Readers
33024 @kindex jit-reader-load
33025 @kindex jit-reader-unload
33027 Readers can be loaded and unloaded using the @code{jit-reader-load}
33028 and @code{jit-reader-unload} commands.
33031 @item jit-reader-load @var{reader}
33032 Load the JIT reader named @var{reader}, which is a shared
33033 object specified as either an absolute or a relative file name. In
33034 the latter case, @value{GDBN} will try to load the reader from a
33035 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
33036 system (here @var{libdir} is the system library directory, often
33037 @file{/usr/local/lib}).
33039 Only one reader can be active at a time; trying to load a second
33040 reader when one is already loaded will result in @value{GDBN}
33041 reporting an error. A new JIT reader can be loaded by first unloading
33042 the current one using @code{jit-reader-unload} and then invoking
33043 @code{jit-reader-load}.
33045 @item jit-reader-unload
33046 Unload the currently loaded JIT reader.
33050 @node Writing JIT Debug Info Readers
33051 @subsection Writing JIT Debug Info Readers
33052 @cindex writing JIT debug info readers
33054 As mentioned, a reader is essentially a shared object conforming to a
33055 certain ABI. This ABI is described in @file{jit-reader.h}.
33057 @file{jit-reader.h} defines the structures, macros and functions
33058 required to write a reader. It is installed (along with
33059 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
33060 the system include directory.
33062 Readers need to be released under a GPL compatible license. A reader
33063 can be declared as released under such a license by placing the macro
33064 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
33066 The entry point for readers is the symbol @code{gdb_init_reader},
33067 which is expected to be a function with the prototype
33069 @findex gdb_init_reader
33071 extern struct gdb_reader_funcs *gdb_init_reader (void);
33074 @cindex @code{struct gdb_reader_funcs}
33076 @code{struct gdb_reader_funcs} contains a set of pointers to callback
33077 functions. These functions are executed to read the debug info
33078 generated by the JIT compiler (@code{read}), to unwind stack frames
33079 (@code{unwind}) and to create canonical frame IDs
33080 (@code{get_Frame_id}). It also has a callback that is called when the
33081 reader is being unloaded (@code{destroy}). The struct looks like this
33084 struct gdb_reader_funcs
33086 /* Must be set to GDB_READER_INTERFACE_VERSION. */
33087 int reader_version;
33089 /* For use by the reader. */
33092 gdb_read_debug_info *read;
33093 gdb_unwind_frame *unwind;
33094 gdb_get_frame_id *get_frame_id;
33095 gdb_destroy_reader *destroy;
33099 @cindex @code{struct gdb_symbol_callbacks}
33100 @cindex @code{struct gdb_unwind_callbacks}
33102 The callbacks are provided with another set of callbacks by
33103 @value{GDBN} to do their job. For @code{read}, these callbacks are
33104 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
33105 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
33106 @code{struct gdb_symbol_callbacks} has callbacks to create new object
33107 files and new symbol tables inside those object files. @code{struct
33108 gdb_unwind_callbacks} has callbacks to read registers off the current
33109 frame and to write out the values of the registers in the previous
33110 frame. Both have a callback (@code{target_read}) to read bytes off the
33111 target's address space.
33113 @node In-Process Agent
33114 @chapter In-Process Agent
33115 @cindex debugging agent
33116 The traditional debugging model is conceptually low-speed, but works fine,
33117 because most bugs can be reproduced in debugging-mode execution. However,
33118 as multi-core or many-core processors are becoming mainstream, and
33119 multi-threaded programs become more and more popular, there should be more
33120 and more bugs that only manifest themselves at normal-mode execution, for
33121 example, thread races, because debugger's interference with the program's
33122 timing may conceal the bugs. On the other hand, in some applications,
33123 it is not feasible for the debugger to interrupt the program's execution
33124 long enough for the developer to learn anything helpful about its behavior.
33125 If the program's correctness depends on its real-time behavior, delays
33126 introduced by a debugger might cause the program to fail, even when the
33127 code itself is correct. It is useful to be able to observe the program's
33128 behavior without interrupting it.
33130 Therefore, traditional debugging model is too intrusive to reproduce
33131 some bugs. In order to reduce the interference with the program, we can
33132 reduce the number of operations performed by debugger. The
33133 @dfn{In-Process Agent}, a shared library, is running within the same
33134 process with inferior, and is able to perform some debugging operations
33135 itself. As a result, debugger is only involved when necessary, and
33136 performance of debugging can be improved accordingly. Note that
33137 interference with program can be reduced but can't be removed completely,
33138 because the in-process agent will still stop or slow down the program.
33140 The in-process agent can interpret and execute Agent Expressions
33141 (@pxref{Agent Expressions}) during performing debugging operations. The
33142 agent expressions can be used for different purposes, such as collecting
33143 data in tracepoints, and condition evaluation in breakpoints.
33145 @anchor{Control Agent}
33146 You can control whether the in-process agent is used as an aid for
33147 debugging with the following commands:
33150 @kindex set agent on
33152 Causes the in-process agent to perform some operations on behalf of the
33153 debugger. Just which operations requested by the user will be done
33154 by the in-process agent depends on the its capabilities. For example,
33155 if you request to evaluate breakpoint conditions in the in-process agent,
33156 and the in-process agent has such capability as well, then breakpoint
33157 conditions will be evaluated in the in-process agent.
33159 @kindex set agent off
33160 @item set agent off
33161 Disables execution of debugging operations by the in-process agent. All
33162 of the operations will be performed by @value{GDBN}.
33166 Display the current setting of execution of debugging operations by
33167 the in-process agent.
33171 * In-Process Agent Protocol::
33174 @node In-Process Agent Protocol
33175 @section In-Process Agent Protocol
33176 @cindex in-process agent protocol
33178 The in-process agent is able to communicate with both @value{GDBN} and
33179 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
33180 used for communications between @value{GDBN} or GDBserver and the IPA.
33181 In general, @value{GDBN} or GDBserver sends commands
33182 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
33183 in-process agent replies back with the return result of the command, or
33184 some other information. The data sent to in-process agent is composed
33185 of primitive data types, such as 4-byte or 8-byte type, and composite
33186 types, which are called objects (@pxref{IPA Protocol Objects}).
33189 * IPA Protocol Objects::
33190 * IPA Protocol Commands::
33193 @node IPA Protocol Objects
33194 @subsection IPA Protocol Objects
33195 @cindex ipa protocol objects
33197 The commands sent to and results received from agent may contain some
33198 complex data types called @dfn{objects}.
33200 The in-process agent is running on the same machine with @value{GDBN}
33201 or GDBserver, so it doesn't have to handle as much differences between
33202 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
33203 However, there are still some differences of two ends in two processes:
33207 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
33208 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
33210 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
33211 GDBserver is compiled with one, and in-process agent is compiled with
33215 Here are the IPA Protocol Objects:
33219 agent expression object. It represents an agent expression
33220 (@pxref{Agent Expressions}).
33221 @anchor{agent expression object}
33223 tracepoint action object. It represents a tracepoint action
33224 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
33225 memory, static trace data and to evaluate expression.
33226 @anchor{tracepoint action object}
33228 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
33229 @anchor{tracepoint object}
33233 The following table describes important attributes of each IPA protocol
33236 @multitable @columnfractions .30 .20 .50
33237 @headitem Name @tab Size @tab Description
33238 @item @emph{agent expression object} @tab @tab
33239 @item length @tab 4 @tab length of bytes code
33240 @item byte code @tab @var{length} @tab contents of byte code
33241 @item @emph{tracepoint action for collecting memory} @tab @tab
33242 @item 'M' @tab 1 @tab type of tracepoint action
33243 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
33244 address of the lowest byte to collect, otherwise @var{addr} is the offset
33245 of @var{basereg} for memory collecting.
33246 @item len @tab 8 @tab length of memory for collecting
33247 @item basereg @tab 4 @tab the register number containing the starting
33248 memory address for collecting.
33249 @item @emph{tracepoint action for collecting registers} @tab @tab
33250 @item 'R' @tab 1 @tab type of tracepoint action
33251 @item @emph{tracepoint action for collecting static trace data} @tab @tab
33252 @item 'L' @tab 1 @tab type of tracepoint action
33253 @item @emph{tracepoint action for expression evaluation} @tab @tab
33254 @item 'X' @tab 1 @tab type of tracepoint action
33255 @item agent expression @tab length of @tab @ref{agent expression object}
33256 @item @emph{tracepoint object} @tab @tab
33257 @item number @tab 4 @tab number of tracepoint
33258 @item address @tab 8 @tab address of tracepoint inserted on
33259 @item type @tab 4 @tab type of tracepoint
33260 @item enabled @tab 1 @tab enable or disable of tracepoint
33261 @item step_count @tab 8 @tab step
33262 @item pass_count @tab 8 @tab pass
33263 @item numactions @tab 4 @tab number of tracepoint actions
33264 @item hit count @tab 8 @tab hit count
33265 @item trace frame usage @tab 8 @tab trace frame usage
33266 @item compiled_cond @tab 8 @tab compiled condition
33267 @item orig_size @tab 8 @tab orig size
33268 @item condition @tab 4 if condition is NULL otherwise length of
33269 @ref{agent expression object}
33270 @tab zero if condition is NULL, otherwise is
33271 @ref{agent expression object}
33272 @item actions @tab variable
33273 @tab numactions number of @ref{tracepoint action object}
33276 @node IPA Protocol Commands
33277 @subsection IPA Protocol Commands
33278 @cindex ipa protocol commands
33280 The spaces in each command are delimiters to ease reading this commands
33281 specification. They don't exist in real commands.
33285 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
33286 Installs a new fast tracepoint described by @var{tracepoint_object}
33287 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
33288 head of @dfn{jumppad}, which is used to jump to data collection routine
33293 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
33294 @var{target_address} is address of tracepoint in the inferior.
33295 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
33296 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
33297 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
33298 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
33305 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
33306 is about to kill inferiors.
33314 @item probe_marker_at:@var{address}
33315 Asks in-process agent to probe the marker at @var{address}.
33322 @item unprobe_marker_at:@var{address}
33323 Asks in-process agent to unprobe the marker at @var{address}.
33327 @chapter Reporting Bugs in @value{GDBN}
33328 @cindex bugs in @value{GDBN}
33329 @cindex reporting bugs in @value{GDBN}
33331 Your bug reports play an essential role in making @value{GDBN} reliable.
33333 Reporting a bug may help you by bringing a solution to your problem, or it
33334 may not. But in any case the principal function of a bug report is to help
33335 the entire community by making the next version of @value{GDBN} work better. Bug
33336 reports are your contribution to the maintenance of @value{GDBN}.
33338 In order for a bug report to serve its purpose, you must include the
33339 information that enables us to fix the bug.
33342 * Bug Criteria:: Have you found a bug?
33343 * Bug Reporting:: How to report bugs
33347 @section Have You Found a Bug?
33348 @cindex bug criteria
33350 If you are not sure whether you have found a bug, here are some guidelines:
33353 @cindex fatal signal
33354 @cindex debugger crash
33355 @cindex crash of debugger
33357 If the debugger gets a fatal signal, for any input whatever, that is a
33358 @value{GDBN} bug. Reliable debuggers never crash.
33360 @cindex error on valid input
33362 If @value{GDBN} produces an error message for valid input, that is a
33363 bug. (Note that if you're cross debugging, the problem may also be
33364 somewhere in the connection to the target.)
33366 @cindex invalid input
33368 If @value{GDBN} does not produce an error message for invalid input,
33369 that is a bug. However, you should note that your idea of
33370 ``invalid input'' might be our idea of ``an extension'' or ``support
33371 for traditional practice''.
33374 If you are an experienced user of debugging tools, your suggestions
33375 for improvement of @value{GDBN} are welcome in any case.
33378 @node Bug Reporting
33379 @section How to Report Bugs
33380 @cindex bug reports
33381 @cindex @value{GDBN} bugs, reporting
33383 A number of companies and individuals offer support for @sc{gnu} products.
33384 If you obtained @value{GDBN} from a support organization, we recommend you
33385 contact that organization first.
33387 You can find contact information for many support companies and
33388 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
33390 @c should add a web page ref...
33393 @ifset BUGURL_DEFAULT
33394 In any event, we also recommend that you submit bug reports for
33395 @value{GDBN}. The preferred method is to submit them directly using
33396 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
33397 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
33400 @strong{Do not send bug reports to @samp{info-gdb}, or to
33401 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
33402 not want to receive bug reports. Those that do have arranged to receive
33405 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
33406 serves as a repeater. The mailing list and the newsgroup carry exactly
33407 the same messages. Often people think of posting bug reports to the
33408 newsgroup instead of mailing them. This appears to work, but it has one
33409 problem which can be crucial: a newsgroup posting often lacks a mail
33410 path back to the sender. Thus, if we need to ask for more information,
33411 we may be unable to reach you. For this reason, it is better to send
33412 bug reports to the mailing list.
33414 @ifclear BUGURL_DEFAULT
33415 In any event, we also recommend that you submit bug reports for
33416 @value{GDBN} to @value{BUGURL}.
33420 The fundamental principle of reporting bugs usefully is this:
33421 @strong{report all the facts}. If you are not sure whether to state a
33422 fact or leave it out, state it!
33424 Often people omit facts because they think they know what causes the
33425 problem and assume that some details do not matter. Thus, you might
33426 assume that the name of the variable you use in an example does not matter.
33427 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
33428 stray memory reference which happens to fetch from the location where that
33429 name is stored in memory; perhaps, if the name were different, the contents
33430 of that location would fool the debugger into doing the right thing despite
33431 the bug. Play it safe and give a specific, complete example. That is the
33432 easiest thing for you to do, and the most helpful.
33434 Keep in mind that the purpose of a bug report is to enable us to fix the
33435 bug. It may be that the bug has been reported previously, but neither
33436 you nor we can know that unless your bug report is complete and
33439 Sometimes people give a few sketchy facts and ask, ``Does this ring a
33440 bell?'' Those bug reports are useless, and we urge everyone to
33441 @emph{refuse to respond to them} except to chide the sender to report
33444 To enable us to fix the bug, you should include all these things:
33448 The version of @value{GDBN}. @value{GDBN} announces it if you start
33449 with no arguments; you can also print it at any time using @code{show
33452 Without this, we will not know whether there is any point in looking for
33453 the bug in the current version of @value{GDBN}.
33456 The type of machine you are using, and the operating system name and
33460 The details of the @value{GDBN} build-time configuration.
33461 @value{GDBN} shows these details if you invoke it with the
33462 @option{--configuration} command-line option, or if you type
33463 @code{show configuration} at @value{GDBN}'s prompt.
33466 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
33467 ``@value{GCC}--2.8.1''.
33470 What compiler (and its version) was used to compile the program you are
33471 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
33472 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
33473 to get this information; for other compilers, see the documentation for
33477 The command arguments you gave the compiler to compile your example and
33478 observe the bug. For example, did you use @samp{-O}? To guarantee
33479 you will not omit something important, list them all. A copy of the
33480 Makefile (or the output from make) is sufficient.
33482 If we were to try to guess the arguments, we would probably guess wrong
33483 and then we might not encounter the bug.
33486 A complete input script, and all necessary source files, that will
33490 A description of what behavior you observe that you believe is
33491 incorrect. For example, ``It gets a fatal signal.''
33493 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
33494 will certainly notice it. But if the bug is incorrect output, we might
33495 not notice unless it is glaringly wrong. You might as well not give us
33496 a chance to make a mistake.
33498 Even if the problem you experience is a fatal signal, you should still
33499 say so explicitly. Suppose something strange is going on, such as, your
33500 copy of @value{GDBN} is out of synch, or you have encountered a bug in
33501 the C library on your system. (This has happened!) Your copy might
33502 crash and ours would not. If you told us to expect a crash, then when
33503 ours fails to crash, we would know that the bug was not happening for
33504 us. If you had not told us to expect a crash, then we would not be able
33505 to draw any conclusion from our observations.
33508 @cindex recording a session script
33509 To collect all this information, you can use a session recording program
33510 such as @command{script}, which is available on many Unix systems.
33511 Just run your @value{GDBN} session inside @command{script} and then
33512 include the @file{typescript} file with your bug report.
33514 Another way to record a @value{GDBN} session is to run @value{GDBN}
33515 inside Emacs and then save the entire buffer to a file.
33518 If you wish to suggest changes to the @value{GDBN} source, send us context
33519 diffs. If you even discuss something in the @value{GDBN} source, refer to
33520 it by context, not by line number.
33522 The line numbers in our development sources will not match those in your
33523 sources. Your line numbers would convey no useful information to us.
33527 Here are some things that are not necessary:
33531 A description of the envelope of the bug.
33533 Often people who encounter a bug spend a lot of time investigating
33534 which changes to the input file will make the bug go away and which
33535 changes will not affect it.
33537 This is often time consuming and not very useful, because the way we
33538 will find the bug is by running a single example under the debugger
33539 with breakpoints, not by pure deduction from a series of examples.
33540 We recommend that you save your time for something else.
33542 Of course, if you can find a simpler example to report @emph{instead}
33543 of the original one, that is a convenience for us. Errors in the
33544 output will be easier to spot, running under the debugger will take
33545 less time, and so on.
33547 However, simplification is not vital; if you do not want to do this,
33548 report the bug anyway and send us the entire test case you used.
33551 A patch for the bug.
33553 A patch for the bug does help us if it is a good one. But do not omit
33554 the necessary information, such as the test case, on the assumption that
33555 a patch is all we need. We might see problems with your patch and decide
33556 to fix the problem another way, or we might not understand it at all.
33558 Sometimes with a program as complicated as @value{GDBN} it is very hard to
33559 construct an example that will make the program follow a certain path
33560 through the code. If you do not send us the example, we will not be able
33561 to construct one, so we will not be able to verify that the bug is fixed.
33563 And if we cannot understand what bug you are trying to fix, or why your
33564 patch should be an improvement, we will not install it. A test case will
33565 help us to understand.
33568 A guess about what the bug is or what it depends on.
33570 Such guesses are usually wrong. Even we cannot guess right about such
33571 things without first using the debugger to find the facts.
33574 @c The readline documentation is distributed with the readline code
33575 @c and consists of the two following files:
33578 @c Use -I with makeinfo to point to the appropriate directory,
33579 @c environment var TEXINPUTS with TeX.
33580 @ifclear SYSTEM_READLINE
33581 @include rluser.texi
33582 @include hsuser.texi
33586 @appendix In Memoriam
33588 The @value{GDBN} project mourns the loss of the following long-time
33593 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
33594 to Free Software in general. Outside of @value{GDBN}, he was known in
33595 the Amiga world for his series of Fish Disks, and the GeekGadget project.
33597 @item Michael Snyder
33598 Michael was one of the Global Maintainers of the @value{GDBN} project,
33599 with contributions recorded as early as 1996, until 2011. In addition
33600 to his day to day participation, he was a large driving force behind
33601 adding Reverse Debugging to @value{GDBN}.
33604 Beyond their technical contributions to the project, they were also
33605 enjoyable members of the Free Software Community. We will miss them.
33607 @node Formatting Documentation
33608 @appendix Formatting Documentation
33610 @cindex @value{GDBN} reference card
33611 @cindex reference card
33612 The @value{GDBN} 4 release includes an already-formatted reference card, ready
33613 for printing with PostScript or Ghostscript, in the @file{gdb}
33614 subdirectory of the main source directory@footnote{In
33615 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
33616 release.}. If you can use PostScript or Ghostscript with your printer,
33617 you can print the reference card immediately with @file{refcard.ps}.
33619 The release also includes the source for the reference card. You
33620 can format it, using @TeX{}, by typing:
33626 The @value{GDBN} reference card is designed to print in @dfn{landscape}
33627 mode on US ``letter'' size paper;
33628 that is, on a sheet 11 inches wide by 8.5 inches
33629 high. You will need to specify this form of printing as an option to
33630 your @sc{dvi} output program.
33632 @cindex documentation
33634 All the documentation for @value{GDBN} comes as part of the machine-readable
33635 distribution. The documentation is written in Texinfo format, which is
33636 a documentation system that uses a single source file to produce both
33637 on-line information and a printed manual. You can use one of the Info
33638 formatting commands to create the on-line version of the documentation
33639 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
33641 @value{GDBN} includes an already formatted copy of the on-line Info
33642 version of this manual in the @file{gdb} subdirectory. The main Info
33643 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
33644 subordinate files matching @samp{gdb.info*} in the same directory. If
33645 necessary, you can print out these files, or read them with any editor;
33646 but they are easier to read using the @code{info} subsystem in @sc{gnu}
33647 Emacs or the standalone @code{info} program, available as part of the
33648 @sc{gnu} Texinfo distribution.
33650 If you want to format these Info files yourself, you need one of the
33651 Info formatting programs, such as @code{texinfo-format-buffer} or
33654 If you have @code{makeinfo} installed, and are in the top level
33655 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
33656 version @value{GDBVN}), you can make the Info file by typing:
33663 If you want to typeset and print copies of this manual, you need @TeX{},
33664 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
33665 Texinfo definitions file.
33667 @TeX{} is a typesetting program; it does not print files directly, but
33668 produces output files called @sc{dvi} files. To print a typeset
33669 document, you need a program to print @sc{dvi} files. If your system
33670 has @TeX{} installed, chances are it has such a program. The precise
33671 command to use depends on your system; @kbd{lpr -d} is common; another
33672 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
33673 require a file name without any extension or a @samp{.dvi} extension.
33675 @TeX{} also requires a macro definitions file called
33676 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
33677 written in Texinfo format. On its own, @TeX{} cannot either read or
33678 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
33679 and is located in the @file{gdb-@var{version-number}/texinfo}
33682 If you have @TeX{} and a @sc{dvi} printer program installed, you can
33683 typeset and print this manual. First switch to the @file{gdb}
33684 subdirectory of the main source directory (for example, to
33685 @file{gdb-@value{GDBVN}/gdb}) and type:
33691 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
33693 @node Installing GDB
33694 @appendix Installing @value{GDBN}
33695 @cindex installation
33698 * Requirements:: Requirements for building @value{GDBN}
33699 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
33700 * Separate Objdir:: Compiling @value{GDBN} in another directory
33701 * Config Names:: Specifying names for hosts and targets
33702 * Configure Options:: Summary of options for configure
33703 * System-wide configuration:: Having a system-wide init file
33707 @section Requirements for Building @value{GDBN}
33708 @cindex building @value{GDBN}, requirements for
33710 Building @value{GDBN} requires various tools and packages to be available.
33711 Other packages will be used only if they are found.
33713 @heading Tools/Packages Necessary for Building @value{GDBN}
33715 @item ISO C90 compiler
33716 @value{GDBN} is written in ISO C90. It should be buildable with any
33717 working C90 compiler, e.g.@: GCC.
33721 @heading Tools/Packages Optional for Building @value{GDBN}
33725 @value{GDBN} can use the Expat XML parsing library. This library may be
33726 included with your operating system distribution; if it is not, you
33727 can get the latest version from @url{http://expat.sourceforge.net}.
33728 The @file{configure} script will search for this library in several
33729 standard locations; if it is installed in an unusual path, you can
33730 use the @option{--with-libexpat-prefix} option to specify its location.
33736 Remote protocol memory maps (@pxref{Memory Map Format})
33738 Target descriptions (@pxref{Target Descriptions})
33740 Remote shared library lists (@xref{Library List Format},
33741 or alternatively @pxref{Library List Format for SVR4 Targets})
33743 MS-Windows shared libraries (@pxref{Shared Libraries})
33745 Traceframe info (@pxref{Traceframe Info Format})
33747 Branch trace (@pxref{Branch Trace Format},
33748 @pxref{Branch Trace Configuration Format})
33752 @cindex compressed debug sections
33753 @value{GDBN} will use the @samp{zlib} library, if available, to read
33754 compressed debug sections. Some linkers, such as GNU gold, are capable
33755 of producing binaries with compressed debug sections. If @value{GDBN}
33756 is compiled with @samp{zlib}, it will be able to read the debug
33757 information in such binaries.
33759 The @samp{zlib} library is likely included with your operating system
33760 distribution; if it is not, you can get the latest version from
33761 @url{http://zlib.net}.
33764 @value{GDBN}'s features related to character sets (@pxref{Character
33765 Sets}) require a functioning @code{iconv} implementation. If you are
33766 on a GNU system, then this is provided by the GNU C Library. Some
33767 other systems also provide a working @code{iconv}.
33769 If @value{GDBN} is using the @code{iconv} program which is installed
33770 in a non-standard place, you will need to tell @value{GDBN} where to find it.
33771 This is done with @option{--with-iconv-bin} which specifies the
33772 directory that contains the @code{iconv} program.
33774 On systems without @code{iconv}, you can install GNU Libiconv. If you
33775 have previously installed Libiconv, you can use the
33776 @option{--with-libiconv-prefix} option to configure.
33778 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
33779 arrange to build Libiconv if a directory named @file{libiconv} appears
33780 in the top-most source directory. If Libiconv is built this way, and
33781 if the operating system does not provide a suitable @code{iconv}
33782 implementation, then the just-built library will automatically be used
33783 by @value{GDBN}. One easy way to set this up is to download GNU
33784 Libiconv, unpack it, and then rename the directory holding the
33785 Libiconv source code to @samp{libiconv}.
33788 @node Running Configure
33789 @section Invoking the @value{GDBN} @file{configure} Script
33790 @cindex configuring @value{GDBN}
33791 @value{GDBN} comes with a @file{configure} script that automates the process
33792 of preparing @value{GDBN} for installation; you can then use @code{make} to
33793 build the @code{gdb} program.
33795 @c irrelevant in info file; it's as current as the code it lives with.
33796 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
33797 look at the @file{README} file in the sources; we may have improved the
33798 installation procedures since publishing this manual.}
33801 The @value{GDBN} distribution includes all the source code you need for
33802 @value{GDBN} in a single directory, whose name is usually composed by
33803 appending the version number to @samp{gdb}.
33805 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
33806 @file{gdb-@value{GDBVN}} directory. That directory contains:
33809 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
33810 script for configuring @value{GDBN} and all its supporting libraries
33812 @item gdb-@value{GDBVN}/gdb
33813 the source specific to @value{GDBN} itself
33815 @item gdb-@value{GDBVN}/bfd
33816 source for the Binary File Descriptor library
33818 @item gdb-@value{GDBVN}/include
33819 @sc{gnu} include files
33821 @item gdb-@value{GDBVN}/libiberty
33822 source for the @samp{-liberty} free software library
33824 @item gdb-@value{GDBVN}/opcodes
33825 source for the library of opcode tables and disassemblers
33827 @item gdb-@value{GDBVN}/readline
33828 source for the @sc{gnu} command-line interface
33830 @item gdb-@value{GDBVN}/glob
33831 source for the @sc{gnu} filename pattern-matching subroutine
33833 @item gdb-@value{GDBVN}/mmalloc
33834 source for the @sc{gnu} memory-mapped malloc package
33837 The simplest way to configure and build @value{GDBN} is to run @file{configure}
33838 from the @file{gdb-@var{version-number}} source directory, which in
33839 this example is the @file{gdb-@value{GDBVN}} directory.
33841 First switch to the @file{gdb-@var{version-number}} source directory
33842 if you are not already in it; then run @file{configure}. Pass the
33843 identifier for the platform on which @value{GDBN} will run as an
33849 cd gdb-@value{GDBVN}
33850 ./configure @var{host}
33855 where @var{host} is an identifier such as @samp{sun4} or
33856 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
33857 (You can often leave off @var{host}; @file{configure} tries to guess the
33858 correct value by examining your system.)
33860 Running @samp{configure @var{host}} and then running @code{make} builds the
33861 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
33862 libraries, then @code{gdb} itself. The configured source files, and the
33863 binaries, are left in the corresponding source directories.
33866 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
33867 system does not recognize this automatically when you run a different
33868 shell, you may need to run @code{sh} on it explicitly:
33871 sh configure @var{host}
33874 If you run @file{configure} from a directory that contains source
33875 directories for multiple libraries or programs, such as the
33876 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
33878 creates configuration files for every directory level underneath (unless
33879 you tell it not to, with the @samp{--norecursion} option).
33881 You should run the @file{configure} script from the top directory in the
33882 source tree, the @file{gdb-@var{version-number}} directory. If you run
33883 @file{configure} from one of the subdirectories, you will configure only
33884 that subdirectory. That is usually not what you want. In particular,
33885 if you run the first @file{configure} from the @file{gdb} subdirectory
33886 of the @file{gdb-@var{version-number}} directory, you will omit the
33887 configuration of @file{bfd}, @file{readline}, and other sibling
33888 directories of the @file{gdb} subdirectory. This leads to build errors
33889 about missing include files such as @file{bfd/bfd.h}.
33891 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
33892 However, you should make sure that the shell on your path (named by
33893 the @samp{SHELL} environment variable) is publicly readable. Remember
33894 that @value{GDBN} uses the shell to start your program---some systems refuse to
33895 let @value{GDBN} debug child processes whose programs are not readable.
33897 @node Separate Objdir
33898 @section Compiling @value{GDBN} in Another Directory
33900 If you want to run @value{GDBN} versions for several host or target machines,
33901 you need a different @code{gdb} compiled for each combination of
33902 host and target. @file{configure} is designed to make this easy by
33903 allowing you to generate each configuration in a separate subdirectory,
33904 rather than in the source directory. If your @code{make} program
33905 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
33906 @code{make} in each of these directories builds the @code{gdb}
33907 program specified there.
33909 To build @code{gdb} in a separate directory, run @file{configure}
33910 with the @samp{--srcdir} option to specify where to find the source.
33911 (You also need to specify a path to find @file{configure}
33912 itself from your working directory. If the path to @file{configure}
33913 would be the same as the argument to @samp{--srcdir}, you can leave out
33914 the @samp{--srcdir} option; it is assumed.)
33916 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
33917 separate directory for a Sun 4 like this:
33921 cd gdb-@value{GDBVN}
33924 ../gdb-@value{GDBVN}/configure sun4
33929 When @file{configure} builds a configuration using a remote source
33930 directory, it creates a tree for the binaries with the same structure
33931 (and using the same names) as the tree under the source directory. In
33932 the example, you'd find the Sun 4 library @file{libiberty.a} in the
33933 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
33934 @file{gdb-sun4/gdb}.
33936 Make sure that your path to the @file{configure} script has just one
33937 instance of @file{gdb} in it. If your path to @file{configure} looks
33938 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
33939 one subdirectory of @value{GDBN}, not the whole package. This leads to
33940 build errors about missing include files such as @file{bfd/bfd.h}.
33942 One popular reason to build several @value{GDBN} configurations in separate
33943 directories is to configure @value{GDBN} for cross-compiling (where
33944 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
33945 programs that run on another machine---the @dfn{target}).
33946 You specify a cross-debugging target by
33947 giving the @samp{--target=@var{target}} option to @file{configure}.
33949 When you run @code{make} to build a program or library, you must run
33950 it in a configured directory---whatever directory you were in when you
33951 called @file{configure} (or one of its subdirectories).
33953 The @code{Makefile} that @file{configure} generates in each source
33954 directory also runs recursively. If you type @code{make} in a source
33955 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
33956 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
33957 will build all the required libraries, and then build GDB.
33959 When you have multiple hosts or targets configured in separate
33960 directories, you can run @code{make} on them in parallel (for example,
33961 if they are NFS-mounted on each of the hosts); they will not interfere
33965 @section Specifying Names for Hosts and Targets
33967 The specifications used for hosts and targets in the @file{configure}
33968 script are based on a three-part naming scheme, but some short predefined
33969 aliases are also supported. The full naming scheme encodes three pieces
33970 of information in the following pattern:
33973 @var{architecture}-@var{vendor}-@var{os}
33976 For example, you can use the alias @code{sun4} as a @var{host} argument,
33977 or as the value for @var{target} in a @code{--target=@var{target}}
33978 option. The equivalent full name is @samp{sparc-sun-sunos4}.
33980 The @file{configure} script accompanying @value{GDBN} does not provide
33981 any query facility to list all supported host and target names or
33982 aliases. @file{configure} calls the Bourne shell script
33983 @code{config.sub} to map abbreviations to full names; you can read the
33984 script, if you wish, or you can use it to test your guesses on
33985 abbreviations---for example:
33988 % sh config.sub i386-linux
33990 % sh config.sub alpha-linux
33991 alpha-unknown-linux-gnu
33992 % sh config.sub hp9k700
33994 % sh config.sub sun4
33995 sparc-sun-sunos4.1.1
33996 % sh config.sub sun3
33997 m68k-sun-sunos4.1.1
33998 % sh config.sub i986v
33999 Invalid configuration `i986v': machine `i986v' not recognized
34003 @code{config.sub} is also distributed in the @value{GDBN} source
34004 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
34006 @node Configure Options
34007 @section @file{configure} Options
34009 Here is a summary of the @file{configure} options and arguments that
34010 are most often useful for building @value{GDBN}. @file{configure} also has
34011 several other options not listed here. @inforef{What Configure
34012 Does,,configure.info}, for a full explanation of @file{configure}.
34015 configure @r{[}--help@r{]}
34016 @r{[}--prefix=@var{dir}@r{]}
34017 @r{[}--exec-prefix=@var{dir}@r{]}
34018 @r{[}--srcdir=@var{dirname}@r{]}
34019 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
34020 @r{[}--target=@var{target}@r{]}
34025 You may introduce options with a single @samp{-} rather than
34026 @samp{--} if you prefer; but you may abbreviate option names if you use
34031 Display a quick summary of how to invoke @file{configure}.
34033 @item --prefix=@var{dir}
34034 Configure the source to install programs and files under directory
34037 @item --exec-prefix=@var{dir}
34038 Configure the source to install programs under directory
34041 @c avoid splitting the warning from the explanation:
34043 @item --srcdir=@var{dirname}
34044 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
34045 @code{make} that implements the @code{VPATH} feature.}@*
34046 Use this option to make configurations in directories separate from the
34047 @value{GDBN} source directories. Among other things, you can use this to
34048 build (or maintain) several configurations simultaneously, in separate
34049 directories. @file{configure} writes configuration-specific files in
34050 the current directory, but arranges for them to use the source in the
34051 directory @var{dirname}. @file{configure} creates directories under
34052 the working directory in parallel to the source directories below
34055 @item --norecursion
34056 Configure only the directory level where @file{configure} is executed; do not
34057 propagate configuration to subdirectories.
34059 @item --target=@var{target}
34060 Configure @value{GDBN} for cross-debugging programs running on the specified
34061 @var{target}. Without this option, @value{GDBN} is configured to debug
34062 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
34064 There is no convenient way to generate a list of all available targets.
34066 @item @var{host} @dots{}
34067 Configure @value{GDBN} to run on the specified @var{host}.
34069 There is no convenient way to generate a list of all available hosts.
34072 There are many other options available as well, but they are generally
34073 needed for special purposes only.
34075 @node System-wide configuration
34076 @section System-wide configuration and settings
34077 @cindex system-wide init file
34079 @value{GDBN} can be configured to have a system-wide init file;
34080 this file will be read and executed at startup (@pxref{Startup, , What
34081 @value{GDBN} does during startup}).
34083 Here is the corresponding configure option:
34086 @item --with-system-gdbinit=@var{file}
34087 Specify that the default location of the system-wide init file is
34091 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
34092 it may be subject to relocation. Two possible cases:
34096 If the default location of this init file contains @file{$prefix},
34097 it will be subject to relocation. Suppose that the configure options
34098 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
34099 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
34100 init file is looked for as @file{$install/etc/gdbinit} instead of
34101 @file{$prefix/etc/gdbinit}.
34104 By contrast, if the default location does not contain the prefix,
34105 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
34106 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
34107 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
34108 wherever @value{GDBN} is installed.
34111 If the configured location of the system-wide init file (as given by the
34112 @option{--with-system-gdbinit} option at configure time) is in the
34113 data-directory (as specified by @option{--with-gdb-datadir} at configure
34114 time) or in one of its subdirectories, then @value{GDBN} will look for the
34115 system-wide init file in the directory specified by the
34116 @option{--data-directory} command-line option.
34117 Note that the system-wide init file is only read once, during @value{GDBN}
34118 initialization. If the data-directory is changed after @value{GDBN} has
34119 started with the @code{set data-directory} command, the file will not be
34123 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
34126 @node System-wide Configuration Scripts
34127 @subsection Installed System-wide Configuration Scripts
34128 @cindex system-wide configuration scripts
34130 The @file{system-gdbinit} directory, located inside the data-directory
34131 (as specified by @option{--with-gdb-datadir} at configure time) contains
34132 a number of scripts which can be used as system-wide init files. To
34133 automatically source those scripts at startup, @value{GDBN} should be
34134 configured with @option{--with-system-gdbinit}. Otherwise, any user
34135 should be able to source them by hand as needed.
34137 The following scripts are currently available:
34140 @item @file{elinos.py}
34142 @cindex ELinOS system-wide configuration script
34143 This script is useful when debugging a program on an ELinOS target.
34144 It takes advantage of the environment variables defined in a standard
34145 ELinOS environment in order to determine the location of the system
34146 shared libraries, and then sets the @samp{solib-absolute-prefix}
34147 and @samp{solib-search-path} variables appropriately.
34149 @item @file{wrs-linux.py}
34150 @pindex wrs-linux.py
34151 @cindex Wind River Linux system-wide configuration script
34152 This script is useful when debugging a program on a target running
34153 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
34154 the host-side sysroot used by the target system.
34158 @node Maintenance Commands
34159 @appendix Maintenance Commands
34160 @cindex maintenance commands
34161 @cindex internal commands
34163 In addition to commands intended for @value{GDBN} users, @value{GDBN}
34164 includes a number of commands intended for @value{GDBN} developers,
34165 that are not documented elsewhere in this manual. These commands are
34166 provided here for reference. (For commands that turn on debugging
34167 messages, see @ref{Debugging Output}.)
34170 @kindex maint agent
34171 @kindex maint agent-eval
34172 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
34173 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
34174 Translate the given @var{expression} into remote agent bytecodes.
34175 This command is useful for debugging the Agent Expression mechanism
34176 (@pxref{Agent Expressions}). The @samp{agent} version produces an
34177 expression useful for data collection, such as by tracepoints, while
34178 @samp{maint agent-eval} produces an expression that evaluates directly
34179 to a result. For instance, a collection expression for @code{globa +
34180 globb} will include bytecodes to record four bytes of memory at each
34181 of the addresses of @code{globa} and @code{globb}, while discarding
34182 the result of the addition, while an evaluation expression will do the
34183 addition and return the sum.
34184 If @code{-at} is given, generate remote agent bytecode for @var{location}.
34185 If not, generate remote agent bytecode for current frame PC address.
34187 @kindex maint agent-printf
34188 @item maint agent-printf @var{format},@var{expr},...
34189 Translate the given format string and list of argument expressions
34190 into remote agent bytecodes and display them as a disassembled list.
34191 This command is useful for debugging the agent version of dynamic
34192 printf (@pxref{Dynamic Printf}).
34194 @kindex maint info breakpoints
34195 @item @anchor{maint info breakpoints}maint info breakpoints
34196 Using the same format as @samp{info breakpoints}, display both the
34197 breakpoints you've set explicitly, and those @value{GDBN} is using for
34198 internal purposes. Internal breakpoints are shown with negative
34199 breakpoint numbers. The type column identifies what kind of breakpoint
34204 Normal, explicitly set breakpoint.
34207 Normal, explicitly set watchpoint.
34210 Internal breakpoint, used to handle correctly stepping through
34211 @code{longjmp} calls.
34213 @item longjmp resume
34214 Internal breakpoint at the target of a @code{longjmp}.
34217 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
34220 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
34223 Shared library events.
34227 @kindex maint info btrace
34228 @item maint info btrace
34229 Pint information about raw branch tracing data.
34231 @kindex maint btrace packet-history
34232 @item maint btrace packet-history
34233 Print the raw branch trace packets that are used to compute the
34234 execution history for the @samp{record btrace} command. Both the
34235 information and the format in which it is printed depend on the btrace
34240 For the BTS recording format, print a list of blocks of sequential
34241 code. For each block, the following information is printed:
34245 Newer blocks have higher numbers. The oldest block has number zero.
34246 @item Lowest @samp{PC}
34247 @item Highest @samp{PC}
34251 For the Intel Processor Trace recording format, print a list of
34252 Intel Processor Trace packets. For each packet, the following
34253 information is printed:
34256 @item Packet number
34257 Newer packets have higher numbers. The oldest packet has number zero.
34259 The packet's offset in the trace stream.
34260 @item Packet opcode and payload
34264 @kindex maint btrace clear-packet-history
34265 @item maint btrace clear-packet-history
34266 Discards the cached packet history printed by the @samp{maint btrace
34267 packet-history} command. The history will be computed again when
34270 @kindex maint btrace clear
34271 @item maint btrace clear
34272 Discard the branch trace data. The data will be fetched anew and the
34273 branch trace will be recomputed when needed.
34275 This implicitly truncates the branch trace to a single branch trace
34276 buffer. When updating branch trace incrementally, the branch trace
34277 available to @value{GDBN} may be bigger than a single branch trace
34280 @kindex maint set btrace pt skip-pad
34281 @item maint set btrace pt skip-pad
34282 @kindex maint show btrace pt skip-pad
34283 @item maint show btrace pt skip-pad
34284 Control whether @value{GDBN} will skip PAD packets when computing the
34287 @kindex set displaced-stepping
34288 @kindex show displaced-stepping
34289 @cindex displaced stepping support
34290 @cindex out-of-line single-stepping
34291 @item set displaced-stepping
34292 @itemx show displaced-stepping
34293 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
34294 if the target supports it. Displaced stepping is a way to single-step
34295 over breakpoints without removing them from the inferior, by executing
34296 an out-of-line copy of the instruction that was originally at the
34297 breakpoint location. It is also known as out-of-line single-stepping.
34300 @item set displaced-stepping on
34301 If the target architecture supports it, @value{GDBN} will use
34302 displaced stepping to step over breakpoints.
34304 @item set displaced-stepping off
34305 @value{GDBN} will not use displaced stepping to step over breakpoints,
34306 even if such is supported by the target architecture.
34308 @cindex non-stop mode, and @samp{set displaced-stepping}
34309 @item set displaced-stepping auto
34310 This is the default mode. @value{GDBN} will use displaced stepping
34311 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
34312 architecture supports displaced stepping.
34315 @kindex maint check-psymtabs
34316 @item maint check-psymtabs
34317 Check the consistency of currently expanded psymtabs versus symtabs.
34318 Use this to check, for example, whether a symbol is in one but not the other.
34320 @kindex maint check-symtabs
34321 @item maint check-symtabs
34322 Check the consistency of currently expanded symtabs.
34324 @kindex maint expand-symtabs
34325 @item maint expand-symtabs [@var{regexp}]
34326 Expand symbol tables.
34327 If @var{regexp} is specified, only expand symbol tables for file
34328 names matching @var{regexp}.
34330 @kindex maint set catch-demangler-crashes
34331 @kindex maint show catch-demangler-crashes
34332 @cindex demangler crashes
34333 @item maint set catch-demangler-crashes [on|off]
34334 @itemx maint show catch-demangler-crashes
34335 Control whether @value{GDBN} should attempt to catch crashes in the
34336 symbol name demangler. The default is to attempt to catch crashes.
34337 If enabled, the first time a crash is caught, a core file is created,
34338 the offending symbol is displayed and the user is presented with the
34339 option to terminate the current session.
34341 @kindex maint cplus first_component
34342 @item maint cplus first_component @var{name}
34343 Print the first C@t{++} class/namespace component of @var{name}.
34345 @kindex maint cplus namespace
34346 @item maint cplus namespace
34347 Print the list of possible C@t{++} namespaces.
34349 @kindex maint deprecate
34350 @kindex maint undeprecate
34351 @cindex deprecated commands
34352 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
34353 @itemx maint undeprecate @var{command}
34354 Deprecate or undeprecate the named @var{command}. Deprecated commands
34355 cause @value{GDBN} to issue a warning when you use them. The optional
34356 argument @var{replacement} says which newer command should be used in
34357 favor of the deprecated one; if it is given, @value{GDBN} will mention
34358 the replacement as part of the warning.
34360 @kindex maint dump-me
34361 @item maint dump-me
34362 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
34363 Cause a fatal signal in the debugger and force it to dump its core.
34364 This is supported only on systems which support aborting a program
34365 with the @code{SIGQUIT} signal.
34367 @kindex maint internal-error
34368 @kindex maint internal-warning
34369 @kindex maint demangler-warning
34370 @cindex demangler crashes
34371 @item maint internal-error @r{[}@var{message-text}@r{]}
34372 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
34373 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
34375 Cause @value{GDBN} to call the internal function @code{internal_error},
34376 @code{internal_warning} or @code{demangler_warning} and hence behave
34377 as though an internal problem has been detected. In addition to
34378 reporting the internal problem, these functions give the user the
34379 opportunity to either quit @value{GDBN} or (for @code{internal_error}
34380 and @code{internal_warning}) create a core file of the current
34381 @value{GDBN} session.
34383 These commands take an optional parameter @var{message-text} that is
34384 used as the text of the error or warning message.
34386 Here's an example of using @code{internal-error}:
34389 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
34390 @dots{}/maint.c:121: internal-error: testing, 1, 2
34391 A problem internal to GDB has been detected. Further
34392 debugging may prove unreliable.
34393 Quit this debugging session? (y or n) @kbd{n}
34394 Create a core file? (y or n) @kbd{n}
34398 @cindex @value{GDBN} internal error
34399 @cindex internal errors, control of @value{GDBN} behavior
34400 @cindex demangler crashes
34402 @kindex maint set internal-error
34403 @kindex maint show internal-error
34404 @kindex maint set internal-warning
34405 @kindex maint show internal-warning
34406 @kindex maint set demangler-warning
34407 @kindex maint show demangler-warning
34408 @item maint set internal-error @var{action} [ask|yes|no]
34409 @itemx maint show internal-error @var{action}
34410 @itemx maint set internal-warning @var{action} [ask|yes|no]
34411 @itemx maint show internal-warning @var{action}
34412 @itemx maint set demangler-warning @var{action} [ask|yes|no]
34413 @itemx maint show demangler-warning @var{action}
34414 When @value{GDBN} reports an internal problem (error or warning) it
34415 gives the user the opportunity to both quit @value{GDBN} and create a
34416 core file of the current @value{GDBN} session. These commands let you
34417 override the default behaviour for each particular @var{action},
34418 described in the table below.
34422 You can specify that @value{GDBN} should always (yes) or never (no)
34423 quit. The default is to ask the user what to do.
34426 You can specify that @value{GDBN} should always (yes) or never (no)
34427 create a core file. The default is to ask the user what to do. Note
34428 that there is no @code{corefile} option for @code{demangler-warning}:
34429 demangler warnings always create a core file and this cannot be
34433 @kindex maint packet
34434 @item maint packet @var{text}
34435 If @value{GDBN} is talking to an inferior via the serial protocol,
34436 then this command sends the string @var{text} to the inferior, and
34437 displays the response packet. @value{GDBN} supplies the initial
34438 @samp{$} character, the terminating @samp{#} character, and the
34441 @kindex maint print architecture
34442 @item maint print architecture @r{[}@var{file}@r{]}
34443 Print the entire architecture configuration. The optional argument
34444 @var{file} names the file where the output goes.
34446 @kindex maint print c-tdesc
34447 @item maint print c-tdesc
34448 Print the current target description (@pxref{Target Descriptions}) as
34449 a C source file. The created source file can be used in @value{GDBN}
34450 when an XML parser is not available to parse the description.
34452 @kindex maint print dummy-frames
34453 @item maint print dummy-frames
34454 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
34457 (@value{GDBP}) @kbd{b add}
34459 (@value{GDBP}) @kbd{print add(2,3)}
34460 Breakpoint 2, add (a=2, b=3) at @dots{}
34462 The program being debugged stopped while in a function called from GDB.
34464 (@value{GDBP}) @kbd{maint print dummy-frames}
34465 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
34469 Takes an optional file parameter.
34471 @kindex maint print registers
34472 @kindex maint print raw-registers
34473 @kindex maint print cooked-registers
34474 @kindex maint print register-groups
34475 @kindex maint print remote-registers
34476 @item maint print registers @r{[}@var{file}@r{]}
34477 @itemx maint print raw-registers @r{[}@var{file}@r{]}
34478 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
34479 @itemx maint print register-groups @r{[}@var{file}@r{]}
34480 @itemx maint print remote-registers @r{[}@var{file}@r{]}
34481 Print @value{GDBN}'s internal register data structures.
34483 The command @code{maint print raw-registers} includes the contents of
34484 the raw register cache; the command @code{maint print
34485 cooked-registers} includes the (cooked) value of all registers,
34486 including registers which aren't available on the target nor visible
34487 to user; the command @code{maint print register-groups} includes the
34488 groups that each register is a member of; and the command @code{maint
34489 print remote-registers} includes the remote target's register numbers
34490 and offsets in the `G' packets.
34492 These commands take an optional parameter, a file name to which to
34493 write the information.
34495 @kindex maint print reggroups
34496 @item maint print reggroups @r{[}@var{file}@r{]}
34497 Print @value{GDBN}'s internal register group data structures. The
34498 optional argument @var{file} tells to what file to write the
34501 The register groups info looks like this:
34504 (@value{GDBP}) @kbd{maint print reggroups}
34517 This command forces @value{GDBN} to flush its internal register cache.
34519 @kindex maint print objfiles
34520 @cindex info for known object files
34521 @item maint print objfiles @r{[}@var{regexp}@r{]}
34522 Print a dump of all known object files.
34523 If @var{regexp} is specified, only print object files whose names
34524 match @var{regexp}. For each object file, this command prints its name,
34525 address in memory, and all of its psymtabs and symtabs.
34527 @kindex maint print user-registers
34528 @cindex user registers
34529 @item maint print user-registers
34530 List all currently available @dfn{user registers}. User registers
34531 typically provide alternate names for actual hardware registers. They
34532 include the four ``standard'' registers @code{$fp}, @code{$pc},
34533 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
34534 registers can be used in expressions in the same way as the canonical
34535 register names, but only the latter are listed by the @code{info
34536 registers} and @code{maint print registers} commands.
34538 @kindex maint print section-scripts
34539 @cindex info for known .debug_gdb_scripts-loaded scripts
34540 @item maint print section-scripts [@var{regexp}]
34541 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
34542 If @var{regexp} is specified, only print scripts loaded by object files
34543 matching @var{regexp}.
34544 For each script, this command prints its name as specified in the objfile,
34545 and the full path if known.
34546 @xref{dotdebug_gdb_scripts section}.
34548 @kindex maint print statistics
34549 @cindex bcache statistics
34550 @item maint print statistics
34551 This command prints, for each object file in the program, various data
34552 about that object file followed by the byte cache (@dfn{bcache})
34553 statistics for the object file. The objfile data includes the number
34554 of minimal, partial, full, and stabs symbols, the number of types
34555 defined by the objfile, the number of as yet unexpanded psym tables,
34556 the number of line tables and string tables, and the amount of memory
34557 used by the various tables. The bcache statistics include the counts,
34558 sizes, and counts of duplicates of all and unique objects, max,
34559 average, and median entry size, total memory used and its overhead and
34560 savings, and various measures of the hash table size and chain
34563 @kindex maint print target-stack
34564 @cindex target stack description
34565 @item maint print target-stack
34566 A @dfn{target} is an interface between the debugger and a particular
34567 kind of file or process. Targets can be stacked in @dfn{strata},
34568 so that more than one target can potentially respond to a request.
34569 In particular, memory accesses will walk down the stack of targets
34570 until they find a target that is interested in handling that particular
34573 This command prints a short description of each layer that was pushed on
34574 the @dfn{target stack}, starting from the top layer down to the bottom one.
34576 @kindex maint print type
34577 @cindex type chain of a data type
34578 @item maint print type @var{expr}
34579 Print the type chain for a type specified by @var{expr}. The argument
34580 can be either a type name or a symbol. If it is a symbol, the type of
34581 that symbol is described. The type chain produced by this command is
34582 a recursive definition of the data type as stored in @value{GDBN}'s
34583 data structures, including its flags and contained types.
34585 @kindex maint set dwarf always-disassemble
34586 @kindex maint show dwarf always-disassemble
34587 @item maint set dwarf always-disassemble
34588 @item maint show dwarf always-disassemble
34589 Control the behavior of @code{info address} when using DWARF debugging
34592 The default is @code{off}, which means that @value{GDBN} should try to
34593 describe a variable's location in an easily readable format. When
34594 @code{on}, @value{GDBN} will instead display the DWARF location
34595 expression in an assembly-like format. Note that some locations are
34596 too complex for @value{GDBN} to describe simply; in this case you will
34597 always see the disassembly form.
34599 Here is an example of the resulting disassembly:
34602 (gdb) info addr argc
34603 Symbol "argc" is a complex DWARF expression:
34607 For more information on these expressions, see
34608 @uref{http://www.dwarfstd.org/, the DWARF standard}.
34610 @kindex maint set dwarf max-cache-age
34611 @kindex maint show dwarf max-cache-age
34612 @item maint set dwarf max-cache-age
34613 @itemx maint show dwarf max-cache-age
34614 Control the DWARF compilation unit cache.
34616 @cindex DWARF compilation units cache
34617 In object files with inter-compilation-unit references, such as those
34618 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
34619 reader needs to frequently refer to previously read compilation units.
34620 This setting controls how long a compilation unit will remain in the
34621 cache if it is not referenced. A higher limit means that cached
34622 compilation units will be stored in memory longer, and more total
34623 memory will be used. Setting it to zero disables caching, which will
34624 slow down @value{GDBN} startup, but reduce memory consumption.
34626 @kindex maint set profile
34627 @kindex maint show profile
34628 @cindex profiling GDB
34629 @item maint set profile
34630 @itemx maint show profile
34631 Control profiling of @value{GDBN}.
34633 Profiling will be disabled until you use the @samp{maint set profile}
34634 command to enable it. When you enable profiling, the system will begin
34635 collecting timing and execution count data; when you disable profiling or
34636 exit @value{GDBN}, the results will be written to a log file. Remember that
34637 if you use profiling, @value{GDBN} will overwrite the profiling log file
34638 (often called @file{gmon.out}). If you have a record of important profiling
34639 data in a @file{gmon.out} file, be sure to move it to a safe location.
34641 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
34642 compiled with the @samp{-pg} compiler option.
34644 @kindex maint set show-debug-regs
34645 @kindex maint show show-debug-regs
34646 @cindex hardware debug registers
34647 @item maint set show-debug-regs
34648 @itemx maint show show-debug-regs
34649 Control whether to show variables that mirror the hardware debug
34650 registers. Use @code{on} to enable, @code{off} to disable. If
34651 enabled, the debug registers values are shown when @value{GDBN} inserts or
34652 removes a hardware breakpoint or watchpoint, and when the inferior
34653 triggers a hardware-assisted breakpoint or watchpoint.
34655 @kindex maint set show-all-tib
34656 @kindex maint show show-all-tib
34657 @item maint set show-all-tib
34658 @itemx maint show show-all-tib
34659 Control whether to show all non zero areas within a 1k block starting
34660 at thread local base, when using the @samp{info w32 thread-information-block}
34663 @kindex maint set target-async
34664 @kindex maint show target-async
34665 @item maint set target-async
34666 @itemx maint show target-async
34667 This controls whether @value{GDBN} targets operate in synchronous or
34668 asynchronous mode (@pxref{Background Execution}). Normally the
34669 default is asynchronous, if it is available; but this can be changed
34670 to more easily debug problems occurring only in synchronous mode.
34672 @kindex maint set target-non-stop @var{mode} [on|off|auto]
34673 @kindex maint show target-non-stop
34674 @item maint set target-non-stop
34675 @itemx maint show target-non-stop
34677 This controls whether @value{GDBN} targets always operate in non-stop
34678 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
34679 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
34680 if supported by the target.
34683 @item maint set target-non-stop auto
34684 This is the default mode. @value{GDBN} controls the target in
34685 non-stop mode if the target supports it.
34687 @item maint set target-non-stop on
34688 @value{GDBN} controls the target in non-stop mode even if the target
34689 does not indicate support.
34691 @item maint set target-non-stop off
34692 @value{GDBN} does not control the target in non-stop mode even if the
34693 target supports it.
34696 @kindex maint set per-command
34697 @kindex maint show per-command
34698 @item maint set per-command
34699 @itemx maint show per-command
34700 @cindex resources used by commands
34702 @value{GDBN} can display the resources used by each command.
34703 This is useful in debugging performance problems.
34706 @item maint set per-command space [on|off]
34707 @itemx maint show per-command space
34708 Enable or disable the printing of the memory used by GDB for each command.
34709 If enabled, @value{GDBN} will display how much memory each command
34710 took, following the command's own output.
34711 This can also be requested by invoking @value{GDBN} with the
34712 @option{--statistics} command-line switch (@pxref{Mode Options}).
34714 @item maint set per-command time [on|off]
34715 @itemx maint show per-command time
34716 Enable or disable the printing of the execution time of @value{GDBN}
34718 If enabled, @value{GDBN} will display how much time it
34719 took to execute each command, following the command's own output.
34720 Both CPU time and wallclock time are printed.
34721 Printing both is useful when trying to determine whether the cost is
34722 CPU or, e.g., disk/network latency.
34723 Note that the CPU time printed is for @value{GDBN} only, it does not include
34724 the execution time of the inferior because there's no mechanism currently
34725 to compute how much time was spent by @value{GDBN} and how much time was
34726 spent by the program been debugged.
34727 This can also be requested by invoking @value{GDBN} with the
34728 @option{--statistics} command-line switch (@pxref{Mode Options}).
34730 @item maint set per-command symtab [on|off]
34731 @itemx maint show per-command symtab
34732 Enable or disable the printing of basic symbol table statistics
34734 If enabled, @value{GDBN} will display the following information:
34738 number of symbol tables
34740 number of primary symbol tables
34742 number of blocks in the blockvector
34746 @kindex maint space
34747 @cindex memory used by commands
34748 @item maint space @var{value}
34749 An alias for @code{maint set per-command space}.
34750 A non-zero value enables it, zero disables it.
34753 @cindex time of command execution
34754 @item maint time @var{value}
34755 An alias for @code{maint set per-command time}.
34756 A non-zero value enables it, zero disables it.
34758 @kindex maint translate-address
34759 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
34760 Find the symbol stored at the location specified by the address
34761 @var{addr} and an optional section name @var{section}. If found,
34762 @value{GDBN} prints the name of the closest symbol and an offset from
34763 the symbol's location to the specified address. This is similar to
34764 the @code{info address} command (@pxref{Symbols}), except that this
34765 command also allows to find symbols in other sections.
34767 If section was not specified, the section in which the symbol was found
34768 is also printed. For dynamically linked executables, the name of
34769 executable or shared library containing the symbol is printed as well.
34773 The following command is useful for non-interactive invocations of
34774 @value{GDBN}, such as in the test suite.
34777 @item set watchdog @var{nsec}
34778 @kindex set watchdog
34779 @cindex watchdog timer
34780 @cindex timeout for commands
34781 Set the maximum number of seconds @value{GDBN} will wait for the
34782 target operation to finish. If this time expires, @value{GDBN}
34783 reports and error and the command is aborted.
34785 @item show watchdog
34786 Show the current setting of the target wait timeout.
34789 @node Remote Protocol
34790 @appendix @value{GDBN} Remote Serial Protocol
34795 * Stop Reply Packets::
34796 * General Query Packets::
34797 * Architecture-Specific Protocol Details::
34798 * Tracepoint Packets::
34799 * Host I/O Packets::
34801 * Notification Packets::
34802 * Remote Non-Stop::
34803 * Packet Acknowledgment::
34805 * File-I/O Remote Protocol Extension::
34806 * Library List Format::
34807 * Library List Format for SVR4 Targets::
34808 * Memory Map Format::
34809 * Thread List Format::
34810 * Traceframe Info Format::
34811 * Branch Trace Format::
34812 * Branch Trace Configuration Format::
34818 There may be occasions when you need to know something about the
34819 protocol---for example, if there is only one serial port to your target
34820 machine, you might want your program to do something special if it
34821 recognizes a packet meant for @value{GDBN}.
34823 In the examples below, @samp{->} and @samp{<-} are used to indicate
34824 transmitted and received data, respectively.
34826 @cindex protocol, @value{GDBN} remote serial
34827 @cindex serial protocol, @value{GDBN} remote
34828 @cindex remote serial protocol
34829 All @value{GDBN} commands and responses (other than acknowledgments
34830 and notifications, see @ref{Notification Packets}) are sent as a
34831 @var{packet}. A @var{packet} is introduced with the character
34832 @samp{$}, the actual @var{packet-data}, and the terminating character
34833 @samp{#} followed by a two-digit @var{checksum}:
34836 @code{$}@var{packet-data}@code{#}@var{checksum}
34840 @cindex checksum, for @value{GDBN} remote
34842 The two-digit @var{checksum} is computed as the modulo 256 sum of all
34843 characters between the leading @samp{$} and the trailing @samp{#} (an
34844 eight bit unsigned checksum).
34846 Implementors should note that prior to @value{GDBN} 5.0 the protocol
34847 specification also included an optional two-digit @var{sequence-id}:
34850 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
34853 @cindex sequence-id, for @value{GDBN} remote
34855 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
34856 has never output @var{sequence-id}s. Stubs that handle packets added
34857 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
34859 When either the host or the target machine receives a packet, the first
34860 response expected is an acknowledgment: either @samp{+} (to indicate
34861 the package was received correctly) or @samp{-} (to request
34865 -> @code{$}@var{packet-data}@code{#}@var{checksum}
34870 The @samp{+}/@samp{-} acknowledgments can be disabled
34871 once a connection is established.
34872 @xref{Packet Acknowledgment}, for details.
34874 The host (@value{GDBN}) sends @var{command}s, and the target (the
34875 debugging stub incorporated in your program) sends a @var{response}. In
34876 the case of step and continue @var{command}s, the response is only sent
34877 when the operation has completed, and the target has again stopped all
34878 threads in all attached processes. This is the default all-stop mode
34879 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
34880 execution mode; see @ref{Remote Non-Stop}, for details.
34882 @var{packet-data} consists of a sequence of characters with the
34883 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
34886 @cindex remote protocol, field separator
34887 Fields within the packet should be separated using @samp{,} @samp{;} or
34888 @samp{:}. Except where otherwise noted all numbers are represented in
34889 @sc{hex} with leading zeros suppressed.
34891 Implementors should note that prior to @value{GDBN} 5.0, the character
34892 @samp{:} could not appear as the third character in a packet (as it
34893 would potentially conflict with the @var{sequence-id}).
34895 @cindex remote protocol, binary data
34896 @anchor{Binary Data}
34897 Binary data in most packets is encoded either as two hexadecimal
34898 digits per byte of binary data. This allowed the traditional remote
34899 protocol to work over connections which were only seven-bit clean.
34900 Some packets designed more recently assume an eight-bit clean
34901 connection, and use a more efficient encoding to send and receive
34904 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
34905 as an escape character. Any escaped byte is transmitted as the escape
34906 character followed by the original character XORed with @code{0x20}.
34907 For example, the byte @code{0x7d} would be transmitted as the two
34908 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
34909 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
34910 @samp{@}}) must always be escaped. Responses sent by the stub
34911 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
34912 is not interpreted as the start of a run-length encoded sequence
34915 Response @var{data} can be run-length encoded to save space.
34916 Run-length encoding replaces runs of identical characters with one
34917 instance of the repeated character, followed by a @samp{*} and a
34918 repeat count. The repeat count is itself sent encoded, to avoid
34919 binary characters in @var{data}: a value of @var{n} is sent as
34920 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
34921 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
34922 code 32) for a repeat count of 3. (This is because run-length
34923 encoding starts to win for counts 3 or more.) Thus, for example,
34924 @samp{0* } is a run-length encoding of ``0000'': the space character
34925 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
34928 The printable characters @samp{#} and @samp{$} or with a numeric value
34929 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
34930 seven repeats (@samp{$}) can be expanded using a repeat count of only
34931 five (@samp{"}). For example, @samp{00000000} can be encoded as
34934 The error response returned for some packets includes a two character
34935 error number. That number is not well defined.
34937 @cindex empty response, for unsupported packets
34938 For any @var{command} not supported by the stub, an empty response
34939 (@samp{$#00}) should be returned. That way it is possible to extend the
34940 protocol. A newer @value{GDBN} can tell if a packet is supported based
34943 At a minimum, a stub is required to support the @samp{g} and @samp{G}
34944 commands for register access, and the @samp{m} and @samp{M} commands
34945 for memory access. Stubs that only control single-threaded targets
34946 can implement run control with the @samp{c} (continue), and @samp{s}
34947 (step) commands. Stubs that support multi-threading targets should
34948 support the @samp{vCont} command. All other commands are optional.
34953 The following table provides a complete list of all currently defined
34954 @var{command}s and their corresponding response @var{data}.
34955 @xref{File-I/O Remote Protocol Extension}, for details about the File
34956 I/O extension of the remote protocol.
34958 Each packet's description has a template showing the packet's overall
34959 syntax, followed by an explanation of the packet's meaning. We
34960 include spaces in some of the templates for clarity; these are not
34961 part of the packet's syntax. No @value{GDBN} packet uses spaces to
34962 separate its components. For example, a template like @samp{foo
34963 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
34964 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
34965 @var{baz}. @value{GDBN} does not transmit a space character between the
34966 @samp{foo} and the @var{bar}, or between the @var{bar} and the
34969 @cindex @var{thread-id}, in remote protocol
34970 @anchor{thread-id syntax}
34971 Several packets and replies include a @var{thread-id} field to identify
34972 a thread. Normally these are positive numbers with a target-specific
34973 interpretation, formatted as big-endian hex strings. A @var{thread-id}
34974 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
34977 In addition, the remote protocol supports a multiprocess feature in
34978 which the @var{thread-id} syntax is extended to optionally include both
34979 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
34980 The @var{pid} (process) and @var{tid} (thread) components each have the
34981 format described above: a positive number with target-specific
34982 interpretation formatted as a big-endian hex string, literal @samp{-1}
34983 to indicate all processes or threads (respectively), or @samp{0} to
34984 indicate an arbitrary process or thread. Specifying just a process, as
34985 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
34986 error to specify all processes but a specific thread, such as
34987 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
34988 for those packets and replies explicitly documented to include a process
34989 ID, rather than a @var{thread-id}.
34991 The multiprocess @var{thread-id} syntax extensions are only used if both
34992 @value{GDBN} and the stub report support for the @samp{multiprocess}
34993 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
34996 Note that all packet forms beginning with an upper- or lower-case
34997 letter, other than those described here, are reserved for future use.
34999 Here are the packet descriptions.
35004 @cindex @samp{!} packet
35005 @anchor{extended mode}
35006 Enable extended mode. In extended mode, the remote server is made
35007 persistent. The @samp{R} packet is used to restart the program being
35013 The remote target both supports and has enabled extended mode.
35017 @cindex @samp{?} packet
35019 Indicate the reason the target halted. The reply is the same as for
35020 step and continue. This packet has a special interpretation when the
35021 target is in non-stop mode; see @ref{Remote Non-Stop}.
35024 @xref{Stop Reply Packets}, for the reply specifications.
35026 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
35027 @cindex @samp{A} packet
35028 Initialized @code{argv[]} array passed into program. @var{arglen}
35029 specifies the number of bytes in the hex encoded byte stream
35030 @var{arg}. See @code{gdbserver} for more details.
35035 The arguments were set.
35041 @cindex @samp{b} packet
35042 (Don't use this packet; its behavior is not well-defined.)
35043 Change the serial line speed to @var{baud}.
35045 JTC: @emph{When does the transport layer state change? When it's
35046 received, or after the ACK is transmitted. In either case, there are
35047 problems if the command or the acknowledgment packet is dropped.}
35049 Stan: @emph{If people really wanted to add something like this, and get
35050 it working for the first time, they ought to modify ser-unix.c to send
35051 some kind of out-of-band message to a specially-setup stub and have the
35052 switch happen "in between" packets, so that from remote protocol's point
35053 of view, nothing actually happened.}
35055 @item B @var{addr},@var{mode}
35056 @cindex @samp{B} packet
35057 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
35058 breakpoint at @var{addr}.
35060 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
35061 (@pxref{insert breakpoint or watchpoint packet}).
35063 @cindex @samp{bc} packet
35066 Backward continue. Execute the target system in reverse. No parameter.
35067 @xref{Reverse Execution}, for more information.
35070 @xref{Stop Reply Packets}, for the reply specifications.
35072 @cindex @samp{bs} packet
35075 Backward single step. Execute one instruction in reverse. No parameter.
35076 @xref{Reverse Execution}, for more information.
35079 @xref{Stop Reply Packets}, for the reply specifications.
35081 @item c @r{[}@var{addr}@r{]}
35082 @cindex @samp{c} packet
35083 Continue at @var{addr}, which is the address to resume. If @var{addr}
35084 is omitted, resume at current address.
35086 This packet is deprecated for multi-threading support. @xref{vCont
35090 @xref{Stop Reply Packets}, for the reply specifications.
35092 @item C @var{sig}@r{[};@var{addr}@r{]}
35093 @cindex @samp{C} packet
35094 Continue with signal @var{sig} (hex signal number). If
35095 @samp{;@var{addr}} is omitted, resume at same address.
35097 This packet is deprecated for multi-threading support. @xref{vCont
35101 @xref{Stop Reply Packets}, for the reply specifications.
35104 @cindex @samp{d} packet
35107 Don't use this packet; instead, define a general set packet
35108 (@pxref{General Query Packets}).
35112 @cindex @samp{D} packet
35113 The first form of the packet is used to detach @value{GDBN} from the
35114 remote system. It is sent to the remote target
35115 before @value{GDBN} disconnects via the @code{detach} command.
35117 The second form, including a process ID, is used when multiprocess
35118 protocol extensions are enabled (@pxref{multiprocess extensions}), to
35119 detach only a specific process. The @var{pid} is specified as a
35120 big-endian hex string.
35130 @item F @var{RC},@var{EE},@var{CF};@var{XX}
35131 @cindex @samp{F} packet
35132 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
35133 This is part of the File-I/O protocol extension. @xref{File-I/O
35134 Remote Protocol Extension}, for the specification.
35137 @anchor{read registers packet}
35138 @cindex @samp{g} packet
35139 Read general registers.
35143 @item @var{XX@dots{}}
35144 Each byte of register data is described by two hex digits. The bytes
35145 with the register are transmitted in target byte order. The size of
35146 each register and their position within the @samp{g} packet are
35147 determined by the @value{GDBN} internal gdbarch functions
35148 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
35149 specification of several standard @samp{g} packets is specified below.
35151 When reading registers from a trace frame (@pxref{Analyze Collected
35152 Data,,Using the Collected Data}), the stub may also return a string of
35153 literal @samp{x}'s in place of the register data digits, to indicate
35154 that the corresponding register has not been collected, thus its value
35155 is unavailable. For example, for an architecture with 4 registers of
35156 4 bytes each, the following reply indicates to @value{GDBN} that
35157 registers 0 and 2 have not been collected, while registers 1 and 3
35158 have been collected, and both have zero value:
35162 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
35169 @item G @var{XX@dots{}}
35170 @cindex @samp{G} packet
35171 Write general registers. @xref{read registers packet}, for a
35172 description of the @var{XX@dots{}} data.
35182 @item H @var{op} @var{thread-id}
35183 @cindex @samp{H} packet
35184 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
35185 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
35186 should be @samp{c} for step and continue operations (note that this
35187 is deprecated, supporting the @samp{vCont} command is a better
35188 option), and @samp{g} for other operations. The thread designator
35189 @var{thread-id} has the format and interpretation described in
35190 @ref{thread-id syntax}.
35201 @c 'H': How restrictive (or permissive) is the thread model. If a
35202 @c thread is selected and stopped, are other threads allowed
35203 @c to continue to execute? As I mentioned above, I think the
35204 @c semantics of each command when a thread is selected must be
35205 @c described. For example:
35207 @c 'g': If the stub supports threads and a specific thread is
35208 @c selected, returns the register block from that thread;
35209 @c otherwise returns current registers.
35211 @c 'G' If the stub supports threads and a specific thread is
35212 @c selected, sets the registers of the register block of
35213 @c that thread; otherwise sets current registers.
35215 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
35216 @anchor{cycle step packet}
35217 @cindex @samp{i} packet
35218 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
35219 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
35220 step starting at that address.
35223 @cindex @samp{I} packet
35224 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
35228 @cindex @samp{k} packet
35231 The exact effect of this packet is not specified.
35233 For a bare-metal target, it may power cycle or reset the target
35234 system. For that reason, the @samp{k} packet has no reply.
35236 For a single-process target, it may kill that process if possible.
35238 A multiple-process target may choose to kill just one process, or all
35239 that are under @value{GDBN}'s control. For more precise control, use
35240 the vKill packet (@pxref{vKill packet}).
35242 If the target system immediately closes the connection in response to
35243 @samp{k}, @value{GDBN} does not consider the lack of packet
35244 acknowledgment to be an error, and assumes the kill was successful.
35246 If connected using @kbd{target extended-remote}, and the target does
35247 not close the connection in response to a kill request, @value{GDBN}
35248 probes the target state as if a new connection was opened
35249 (@pxref{? packet}).
35251 @item m @var{addr},@var{length}
35252 @cindex @samp{m} packet
35253 Read @var{length} addressable memory units starting at address @var{addr}
35254 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
35255 any particular boundary.
35257 The stub need not use any particular size or alignment when gathering
35258 data from memory for the response; even if @var{addr} is word-aligned
35259 and @var{length} is a multiple of the word size, the stub is free to
35260 use byte accesses, or not. For this reason, this packet may not be
35261 suitable for accessing memory-mapped I/O devices.
35262 @cindex alignment of remote memory accesses
35263 @cindex size of remote memory accesses
35264 @cindex memory, alignment and size of remote accesses
35268 @item @var{XX@dots{}}
35269 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
35270 The reply may contain fewer addressable memory units than requested if the
35271 server was able to read only part of the region of memory.
35276 @item M @var{addr},@var{length}:@var{XX@dots{}}
35277 @cindex @samp{M} packet
35278 Write @var{length} addressable memory units starting at address @var{addr}
35279 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
35280 byte is transmitted as a two-digit hexadecimal number.
35287 for an error (this includes the case where only part of the data was
35292 @cindex @samp{p} packet
35293 Read the value of register @var{n}; @var{n} is in hex.
35294 @xref{read registers packet}, for a description of how the returned
35295 register value is encoded.
35299 @item @var{XX@dots{}}
35300 the register's value
35304 Indicating an unrecognized @var{query}.
35307 @item P @var{n@dots{}}=@var{r@dots{}}
35308 @anchor{write register packet}
35309 @cindex @samp{P} packet
35310 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
35311 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
35312 digits for each byte in the register (target byte order).
35322 @item q @var{name} @var{params}@dots{}
35323 @itemx Q @var{name} @var{params}@dots{}
35324 @cindex @samp{q} packet
35325 @cindex @samp{Q} packet
35326 General query (@samp{q}) and set (@samp{Q}). These packets are
35327 described fully in @ref{General Query Packets}.
35330 @cindex @samp{r} packet
35331 Reset the entire system.
35333 Don't use this packet; use the @samp{R} packet instead.
35336 @cindex @samp{R} packet
35337 Restart the program being debugged. The @var{XX}, while needed, is ignored.
35338 This packet is only available in extended mode (@pxref{extended mode}).
35340 The @samp{R} packet has no reply.
35342 @item s @r{[}@var{addr}@r{]}
35343 @cindex @samp{s} packet
35344 Single step, resuming at @var{addr}. If
35345 @var{addr} is omitted, resume at same address.
35347 This packet is deprecated for multi-threading support. @xref{vCont
35351 @xref{Stop Reply Packets}, for the reply specifications.
35353 @item S @var{sig}@r{[};@var{addr}@r{]}
35354 @anchor{step with signal packet}
35355 @cindex @samp{S} packet
35356 Step with signal. This is analogous to the @samp{C} packet, but
35357 requests a single-step, rather than a normal resumption of execution.
35359 This packet is deprecated for multi-threading support. @xref{vCont
35363 @xref{Stop Reply Packets}, for the reply specifications.
35365 @item t @var{addr}:@var{PP},@var{MM}
35366 @cindex @samp{t} packet
35367 Search backwards starting at address @var{addr} for a match with pattern
35368 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
35369 There must be at least 3 digits in @var{addr}.
35371 @item T @var{thread-id}
35372 @cindex @samp{T} packet
35373 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
35378 thread is still alive
35384 Packets starting with @samp{v} are identified by a multi-letter name,
35385 up to the first @samp{;} or @samp{?} (or the end of the packet).
35387 @item vAttach;@var{pid}
35388 @cindex @samp{vAttach} packet
35389 Attach to a new process with the specified process ID @var{pid}.
35390 The process ID is a
35391 hexadecimal integer identifying the process. In all-stop mode, all
35392 threads in the attached process are stopped; in non-stop mode, it may be
35393 attached without being stopped if that is supported by the target.
35395 @c In non-stop mode, on a successful vAttach, the stub should set the
35396 @c current thread to a thread of the newly-attached process. After
35397 @c attaching, GDB queries for the attached process's thread ID with qC.
35398 @c Also note that, from a user perspective, whether or not the
35399 @c target is stopped on attach in non-stop mode depends on whether you
35400 @c use the foreground or background version of the attach command, not
35401 @c on what vAttach does; GDB does the right thing with respect to either
35402 @c stopping or restarting threads.
35404 This packet is only available in extended mode (@pxref{extended mode}).
35410 @item @r{Any stop packet}
35411 for success in all-stop mode (@pxref{Stop Reply Packets})
35413 for success in non-stop mode (@pxref{Remote Non-Stop})
35416 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
35417 @cindex @samp{vCont} packet
35418 @anchor{vCont packet}
35419 Resume the inferior, specifying different actions for each thread.
35420 If an action is specified with no @var{thread-id}, then it is applied to any
35421 threads that don't have a specific action specified; if no default action is
35422 specified then other threads should remain stopped in all-stop mode and
35423 in their current state in non-stop mode.
35424 Specifying multiple
35425 default actions is an error; specifying no actions is also an error.
35426 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
35428 Currently supported actions are:
35434 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
35438 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
35441 @item r @var{start},@var{end}
35442 Step once, and then keep stepping as long as the thread stops at
35443 addresses between @var{start} (inclusive) and @var{end} (exclusive).
35444 The remote stub reports a stop reply when either the thread goes out
35445 of the range or is stopped due to an unrelated reason, such as hitting
35446 a breakpoint. @xref{range stepping}.
35448 If the range is empty (@var{start} == @var{end}), then the action
35449 becomes equivalent to the @samp{s} action. In other words,
35450 single-step once, and report the stop (even if the stepped instruction
35451 jumps to @var{start}).
35453 (A stop reply may be sent at any point even if the PC is still within
35454 the stepping range; for example, it is valid to implement this packet
35455 in a degenerate way as a single instruction step operation.)
35459 The optional argument @var{addr} normally associated with the
35460 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
35461 not supported in @samp{vCont}.
35463 The @samp{t} action is only relevant in non-stop mode
35464 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
35465 A stop reply should be generated for any affected thread not already stopped.
35466 When a thread is stopped by means of a @samp{t} action,
35467 the corresponding stop reply should indicate that the thread has stopped with
35468 signal @samp{0}, regardless of whether the target uses some other signal
35469 as an implementation detail.
35471 The stub must support @samp{vCont} if it reports support for
35472 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
35473 this case @samp{vCont} actions can be specified to apply to all threads
35474 in a process by using the @samp{p@var{pid}.-1} form of the
35478 @xref{Stop Reply Packets}, for the reply specifications.
35481 @cindex @samp{vCont?} packet
35482 Request a list of actions supported by the @samp{vCont} packet.
35486 @item vCont@r{[};@var{action}@dots{}@r{]}
35487 The @samp{vCont} packet is supported. Each @var{action} is a supported
35488 command in the @samp{vCont} packet.
35490 The @samp{vCont} packet is not supported.
35493 @anchor{vCtrlC packet}
35495 @cindex @samp{vCtrlC} packet
35496 Interrupt remote target as if a control-C was pressed on the remote
35497 terminal. This is the equivalent to reacting to the @code{^C}
35498 (@samp{\003}, the control-C character) character in all-stop mode
35499 while the target is running, except this works in non-stop mode.
35500 @xref{interrupting remote targets}, for more info on the all-stop
35511 @item vFile:@var{operation}:@var{parameter}@dots{}
35512 @cindex @samp{vFile} packet
35513 Perform a file operation on the target system. For details,
35514 see @ref{Host I/O Packets}.
35516 @item vFlashErase:@var{addr},@var{length}
35517 @cindex @samp{vFlashErase} packet
35518 Direct the stub to erase @var{length} bytes of flash starting at
35519 @var{addr}. The region may enclose any number of flash blocks, but
35520 its start and end must fall on block boundaries, as indicated by the
35521 flash block size appearing in the memory map (@pxref{Memory Map
35522 Format}). @value{GDBN} groups flash memory programming operations
35523 together, and sends a @samp{vFlashDone} request after each group; the
35524 stub is allowed to delay erase operation until the @samp{vFlashDone}
35525 packet is received.
35535 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
35536 @cindex @samp{vFlashWrite} packet
35537 Direct the stub to write data to flash address @var{addr}. The data
35538 is passed in binary form using the same encoding as for the @samp{X}
35539 packet (@pxref{Binary Data}). The memory ranges specified by
35540 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
35541 not overlap, and must appear in order of increasing addresses
35542 (although @samp{vFlashErase} packets for higher addresses may already
35543 have been received; the ordering is guaranteed only between
35544 @samp{vFlashWrite} packets). If a packet writes to an address that was
35545 neither erased by a preceding @samp{vFlashErase} packet nor by some other
35546 target-specific method, the results are unpredictable.
35554 for vFlashWrite addressing non-flash memory
35560 @cindex @samp{vFlashDone} packet
35561 Indicate to the stub that flash programming operation is finished.
35562 The stub is permitted to delay or batch the effects of a group of
35563 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
35564 @samp{vFlashDone} packet is received. The contents of the affected
35565 regions of flash memory are unpredictable until the @samp{vFlashDone}
35566 request is completed.
35568 @item vKill;@var{pid}
35569 @cindex @samp{vKill} packet
35570 @anchor{vKill packet}
35571 Kill the process with the specified process ID @var{pid}, which is a
35572 hexadecimal integer identifying the process. This packet is used in
35573 preference to @samp{k} when multiprocess protocol extensions are
35574 supported; see @ref{multiprocess extensions}.
35584 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
35585 @cindex @samp{vRun} packet
35586 Run the program @var{filename}, passing it each @var{argument} on its
35587 command line. The file and arguments are hex-encoded strings. If
35588 @var{filename} is an empty string, the stub may use a default program
35589 (e.g.@: the last program run). The program is created in the stopped
35592 @c FIXME: What about non-stop mode?
35594 This packet is only available in extended mode (@pxref{extended mode}).
35600 @item @r{Any stop packet}
35601 for success (@pxref{Stop Reply Packets})
35605 @cindex @samp{vStopped} packet
35606 @xref{Notification Packets}.
35608 @item X @var{addr},@var{length}:@var{XX@dots{}}
35610 @cindex @samp{X} packet
35611 Write data to memory, where the data is transmitted in binary.
35612 Memory is specified by its address @var{addr} and number of addressable memory
35613 units @var{length} (@pxref{addressable memory unit});
35614 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
35624 @item z @var{type},@var{addr},@var{kind}
35625 @itemx Z @var{type},@var{addr},@var{kind}
35626 @anchor{insert breakpoint or watchpoint packet}
35627 @cindex @samp{z} packet
35628 @cindex @samp{Z} packets
35629 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
35630 watchpoint starting at address @var{address} of kind @var{kind}.
35632 Each breakpoint and watchpoint packet @var{type} is documented
35635 @emph{Implementation notes: A remote target shall return an empty string
35636 for an unrecognized breakpoint or watchpoint packet @var{type}. A
35637 remote target shall support either both or neither of a given
35638 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
35639 avoid potential problems with duplicate packets, the operations should
35640 be implemented in an idempotent way.}
35642 @item z0,@var{addr},@var{kind}
35643 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
35644 @cindex @samp{z0} packet
35645 @cindex @samp{Z0} packet
35646 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
35647 @var{addr} of type @var{kind}.
35649 A memory breakpoint is implemented by replacing the instruction at
35650 @var{addr} with a software breakpoint or trap instruction. The
35651 @var{kind} is target-specific and typically indicates the size of
35652 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
35653 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
35654 architectures have additional meanings for @var{kind};
35655 @var{cond_list} is an optional list of conditional expressions in bytecode
35656 form that should be evaluated on the target's side. These are the
35657 conditions that should be taken into consideration when deciding if
35658 the breakpoint trigger should be reported back to @var{GDBN}.
35660 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
35661 for how to best report a memory breakpoint event to @value{GDBN}.
35663 The @var{cond_list} parameter is comprised of a series of expressions,
35664 concatenated without separators. Each expression has the following form:
35668 @item X @var{len},@var{expr}
35669 @var{len} is the length of the bytecode expression and @var{expr} is the
35670 actual conditional expression in bytecode form.
35674 The optional @var{cmd_list} parameter introduces commands that may be
35675 run on the target, rather than being reported back to @value{GDBN}.
35676 The parameter starts with a numeric flag @var{persist}; if the flag is
35677 nonzero, then the breakpoint may remain active and the commands
35678 continue to be run even when @value{GDBN} disconnects from the target.
35679 Following this flag is a series of expressions concatenated with no
35680 separators. Each expression has the following form:
35684 @item X @var{len},@var{expr}
35685 @var{len} is the length of the bytecode expression and @var{expr} is the
35686 actual conditional expression in bytecode form.
35690 see @ref{Architecture-Specific Protocol Details}.
35692 @emph{Implementation note: It is possible for a target to copy or move
35693 code that contains memory breakpoints (e.g., when implementing
35694 overlays). The behavior of this packet, in the presence of such a
35695 target, is not defined.}
35707 @item z1,@var{addr},@var{kind}
35708 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
35709 @cindex @samp{z1} packet
35710 @cindex @samp{Z1} packet
35711 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
35712 address @var{addr}.
35714 A hardware breakpoint is implemented using a mechanism that is not
35715 dependant on being able to modify the target's memory. The @var{kind}
35716 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
35718 @emph{Implementation note: A hardware breakpoint is not affected by code
35731 @item z2,@var{addr},@var{kind}
35732 @itemx Z2,@var{addr},@var{kind}
35733 @cindex @samp{z2} packet
35734 @cindex @samp{Z2} packet
35735 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
35736 The number of bytes to watch is specified by @var{kind}.
35748 @item z3,@var{addr},@var{kind}
35749 @itemx Z3,@var{addr},@var{kind}
35750 @cindex @samp{z3} packet
35751 @cindex @samp{Z3} packet
35752 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
35753 The number of bytes to watch is specified by @var{kind}.
35765 @item z4,@var{addr},@var{kind}
35766 @itemx Z4,@var{addr},@var{kind}
35767 @cindex @samp{z4} packet
35768 @cindex @samp{Z4} packet
35769 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
35770 The number of bytes to watch is specified by @var{kind}.
35784 @node Stop Reply Packets
35785 @section Stop Reply Packets
35786 @cindex stop reply packets
35788 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
35789 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
35790 receive any of the below as a reply. Except for @samp{?}
35791 and @samp{vStopped}, that reply is only returned
35792 when the target halts. In the below the exact meaning of @dfn{signal
35793 number} is defined by the header @file{include/gdb/signals.h} in the
35794 @value{GDBN} source code.
35796 As in the description of request packets, we include spaces in the
35797 reply templates for clarity; these are not part of the reply packet's
35798 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
35804 The program received signal number @var{AA} (a two-digit hexadecimal
35805 number). This is equivalent to a @samp{T} response with no
35806 @var{n}:@var{r} pairs.
35808 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
35809 @cindex @samp{T} packet reply
35810 The program received signal number @var{AA} (a two-digit hexadecimal
35811 number). This is equivalent to an @samp{S} response, except that the
35812 @samp{@var{n}:@var{r}} pairs can carry values of important registers
35813 and other information directly in the stop reply packet, reducing
35814 round-trip latency. Single-step and breakpoint traps are reported
35815 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
35819 If @var{n} is a hexadecimal number, it is a register number, and the
35820 corresponding @var{r} gives that register's value. The data @var{r} is a
35821 series of bytes in target byte order, with each byte given by a
35822 two-digit hex number.
35825 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
35826 the stopped thread, as specified in @ref{thread-id syntax}.
35829 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
35830 the core on which the stop event was detected.
35833 If @var{n} is a recognized @dfn{stop reason}, it describes a more
35834 specific event that stopped the target. The currently defined stop
35835 reasons are listed below. The @var{aa} should be @samp{05}, the trap
35836 signal. At most one stop reason should be present.
35839 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
35840 and go on to the next; this allows us to extend the protocol in the
35844 The currently defined stop reasons are:
35850 The packet indicates a watchpoint hit, and @var{r} is the data address, in
35853 @item syscall_entry
35854 @itemx syscall_return
35855 The packet indicates a syscall entry or return, and @var{r} is the
35856 syscall number, in hex.
35858 @cindex shared library events, remote reply
35860 The packet indicates that the loaded libraries have changed.
35861 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
35862 list of loaded libraries. The @var{r} part is ignored.
35864 @cindex replay log events, remote reply
35866 The packet indicates that the target cannot continue replaying
35867 logged execution events, because it has reached the end (or the
35868 beginning when executing backward) of the log. The value of @var{r}
35869 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
35870 for more information.
35873 @anchor{swbreak stop reason}
35874 The packet indicates a memory breakpoint instruction was executed,
35875 irrespective of whether it was @value{GDBN} that planted the
35876 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
35877 part must be left empty.
35879 On some architectures, such as x86, at the architecture level, when a
35880 breakpoint instruction executes the program counter points at the
35881 breakpoint address plus an offset. On such targets, the stub is
35882 responsible for adjusting the PC to point back at the breakpoint
35885 This packet should not be sent by default; older @value{GDBN} versions
35886 did not support it. @value{GDBN} requests it, by supplying an
35887 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35888 remote stub must also supply the appropriate @samp{qSupported} feature
35889 indicating support.
35891 This packet is required for correct non-stop mode operation.
35894 The packet indicates the target stopped for a hardware breakpoint.
35895 The @var{r} part must be left empty.
35897 The same remarks about @samp{qSupported} and non-stop mode above
35900 @cindex fork events, remote reply
35902 The packet indicates that @code{fork} was called, and @var{r}
35903 is the thread ID of the new child process. Refer to
35904 @ref{thread-id syntax} for the format of the @var{thread-id}
35905 field. This packet is only applicable to targets that support
35908 This packet should not be sent by default; older @value{GDBN} versions
35909 did not support it. @value{GDBN} requests it, by supplying an
35910 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35911 remote stub must also supply the appropriate @samp{qSupported} feature
35912 indicating support.
35914 @cindex vfork events, remote reply
35916 The packet indicates that @code{vfork} was called, and @var{r}
35917 is the thread ID of the new child process. Refer to
35918 @ref{thread-id syntax} for the format of the @var{thread-id}
35919 field. This packet is only applicable to targets that support
35922 This packet should not be sent by default; older @value{GDBN} versions
35923 did not support it. @value{GDBN} requests it, by supplying an
35924 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35925 remote stub must also supply the appropriate @samp{qSupported} feature
35926 indicating support.
35928 @cindex vforkdone events, remote reply
35930 The packet indicates that a child process created by a vfork
35931 has either called @code{exec} or terminated, so that the
35932 address spaces of the parent and child process are no longer
35933 shared. The @var{r} part is ignored. This packet is only
35934 applicable to targets that support vforkdone events.
35936 This packet should not be sent by default; older @value{GDBN} versions
35937 did not support it. @value{GDBN} requests it, by supplying an
35938 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35939 remote stub must also supply the appropriate @samp{qSupported} feature
35940 indicating support.
35942 @cindex exec events, remote reply
35944 The packet indicates that @code{execve} was called, and @var{r}
35945 is the absolute pathname of the file that was executed, in hex.
35946 This packet is only applicable to targets that support exec events.
35948 This packet should not be sent by default; older @value{GDBN} versions
35949 did not support it. @value{GDBN} requests it, by supplying an
35950 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35951 remote stub must also supply the appropriate @samp{qSupported} feature
35952 indicating support.
35954 @cindex thread create event, remote reply
35955 @anchor{thread create event}
35957 The packet indicates that the thread was just created. The new thread
35958 is stopped until @value{GDBN} sets it running with a resumption packet
35959 (@pxref{vCont packet}). This packet should not be sent by default;
35960 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
35961 also the @samp{w} (@ref{thread exit event}) remote reply below.
35966 @itemx W @var{AA} ; process:@var{pid}
35967 The process exited, and @var{AA} is the exit status. This is only
35968 applicable to certain targets.
35970 The second form of the response, including the process ID of the exited
35971 process, can be used only when @value{GDBN} has reported support for
35972 multiprocess protocol extensions; see @ref{multiprocess extensions}.
35973 The @var{pid} is formatted as a big-endian hex string.
35976 @itemx X @var{AA} ; process:@var{pid}
35977 The process terminated with signal @var{AA}.
35979 The second form of the response, including the process ID of the
35980 terminated process, can be used only when @value{GDBN} has reported
35981 support for multiprocess protocol extensions; see @ref{multiprocess
35982 extensions}. The @var{pid} is formatted as a big-endian hex string.
35984 @anchor{thread exit event}
35985 @cindex thread exit event, remote reply
35986 @item w @var{AA} ; @var{tid}
35988 The thread exited, and @var{AA} is the exit status. This response
35989 should not be sent by default; @value{GDBN} requests it with the
35990 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
35993 There are no resumed threads left in the target. In other words, even
35994 though the process is alive, the last resumed thread has exited. For
35995 example, say the target process has two threads: thread 1 and thread
35996 2. The client leaves thread 1 stopped, and resumes thread 2, which
35997 subsequently exits. At this point, even though the process is still
35998 alive, and thus no @samp{W} stop reply is sent, no thread is actually
35999 executing either. The @samp{N} stop reply thus informs the client
36000 that it can stop waiting for stop replies. This packet should not be
36001 sent by default; older @value{GDBN} versions did not support it.
36002 @value{GDBN} requests it, by supplying an appropriate
36003 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
36004 also supply the appropriate @samp{qSupported} feature indicating
36007 @item O @var{XX}@dots{}
36008 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
36009 written as the program's console output. This can happen at any time
36010 while the program is running and the debugger should continue to wait
36011 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
36013 @item F @var{call-id},@var{parameter}@dots{}
36014 @var{call-id} is the identifier which says which host system call should
36015 be called. This is just the name of the function. Translation into the
36016 correct system call is only applicable as it's defined in @value{GDBN}.
36017 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
36020 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
36021 this very system call.
36023 The target replies with this packet when it expects @value{GDBN} to
36024 call a host system call on behalf of the target. @value{GDBN} replies
36025 with an appropriate @samp{F} packet and keeps up waiting for the next
36026 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
36027 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
36028 Protocol Extension}, for more details.
36032 @node General Query Packets
36033 @section General Query Packets
36034 @cindex remote query requests
36036 Packets starting with @samp{q} are @dfn{general query packets};
36037 packets starting with @samp{Q} are @dfn{general set packets}. General
36038 query and set packets are a semi-unified form for retrieving and
36039 sending information to and from the stub.
36041 The initial letter of a query or set packet is followed by a name
36042 indicating what sort of thing the packet applies to. For example,
36043 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
36044 definitions with the stub. These packet names follow some
36049 The name must not contain commas, colons or semicolons.
36051 Most @value{GDBN} query and set packets have a leading upper case
36054 The names of custom vendor packets should use a company prefix, in
36055 lower case, followed by a period. For example, packets designed at
36056 the Acme Corporation might begin with @samp{qacme.foo} (for querying
36057 foos) or @samp{Qacme.bar} (for setting bars).
36060 The name of a query or set packet should be separated from any
36061 parameters by a @samp{:}; the parameters themselves should be
36062 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
36063 full packet name, and check for a separator or the end of the packet,
36064 in case two packet names share a common prefix. New packets should not begin
36065 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
36066 packets predate these conventions, and have arguments without any terminator
36067 for the packet name; we suspect they are in widespread use in places that
36068 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
36069 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
36072 Like the descriptions of the other packets, each description here
36073 has a template showing the packet's overall syntax, followed by an
36074 explanation of the packet's meaning. We include spaces in some of the
36075 templates for clarity; these are not part of the packet's syntax. No
36076 @value{GDBN} packet uses spaces to separate its components.
36078 Here are the currently defined query and set packets:
36084 Turn on or off the agent as a helper to perform some debugging operations
36085 delegated from @value{GDBN} (@pxref{Control Agent}).
36087 @item QAllow:@var{op}:@var{val}@dots{}
36088 @cindex @samp{QAllow} packet
36089 Specify which operations @value{GDBN} expects to request of the
36090 target, as a semicolon-separated list of operation name and value
36091 pairs. Possible values for @var{op} include @samp{WriteReg},
36092 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
36093 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
36094 indicating that @value{GDBN} will not request the operation, or 1,
36095 indicating that it may. (The target can then use this to set up its
36096 own internals optimally, for instance if the debugger never expects to
36097 insert breakpoints, it may not need to install its own trap handler.)
36100 @cindex current thread, remote request
36101 @cindex @samp{qC} packet
36102 Return the current thread ID.
36106 @item QC @var{thread-id}
36107 Where @var{thread-id} is a thread ID as documented in
36108 @ref{thread-id syntax}.
36109 @item @r{(anything else)}
36110 Any other reply implies the old thread ID.
36113 @item qCRC:@var{addr},@var{length}
36114 @cindex CRC of memory block, remote request
36115 @cindex @samp{qCRC} packet
36116 @anchor{qCRC packet}
36117 Compute the CRC checksum of a block of memory using CRC-32 defined in
36118 IEEE 802.3. The CRC is computed byte at a time, taking the most
36119 significant bit of each byte first. The initial pattern code
36120 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
36122 @emph{Note:} This is the same CRC used in validating separate debug
36123 files (@pxref{Separate Debug Files, , Debugging Information in Separate
36124 Files}). However the algorithm is slightly different. When validating
36125 separate debug files, the CRC is computed taking the @emph{least}
36126 significant bit of each byte first, and the final result is inverted to
36127 detect trailing zeros.
36132 An error (such as memory fault)
36133 @item C @var{crc32}
36134 The specified memory region's checksum is @var{crc32}.
36137 @item QDisableRandomization:@var{value}
36138 @cindex disable address space randomization, remote request
36139 @cindex @samp{QDisableRandomization} packet
36140 Some target operating systems will randomize the virtual address space
36141 of the inferior process as a security feature, but provide a feature
36142 to disable such randomization, e.g.@: to allow for a more deterministic
36143 debugging experience. On such systems, this packet with a @var{value}
36144 of 1 directs the target to disable address space randomization for
36145 processes subsequently started via @samp{vRun} packets, while a packet
36146 with a @var{value} of 0 tells the target to enable address space
36149 This packet is only available in extended mode (@pxref{extended mode}).
36154 The request succeeded.
36157 An error occurred. The error number @var{nn} is given as hex digits.
36160 An empty reply indicates that @samp{QDisableRandomization} is not supported
36164 This packet is not probed by default; the remote stub must request it,
36165 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36166 This should only be done on targets that actually support disabling
36167 address space randomization.
36170 @itemx qsThreadInfo
36171 @cindex list active threads, remote request
36172 @cindex @samp{qfThreadInfo} packet
36173 @cindex @samp{qsThreadInfo} packet
36174 Obtain a list of all active thread IDs from the target (OS). Since there
36175 may be too many active threads to fit into one reply packet, this query
36176 works iteratively: it may require more than one query/reply sequence to
36177 obtain the entire list of threads. The first query of the sequence will
36178 be the @samp{qfThreadInfo} query; subsequent queries in the
36179 sequence will be the @samp{qsThreadInfo} query.
36181 NOTE: This packet replaces the @samp{qL} query (see below).
36185 @item m @var{thread-id}
36187 @item m @var{thread-id},@var{thread-id}@dots{}
36188 a comma-separated list of thread IDs
36190 (lower case letter @samp{L}) denotes end of list.
36193 In response to each query, the target will reply with a list of one or
36194 more thread IDs, separated by commas.
36195 @value{GDBN} will respond to each reply with a request for more thread
36196 ids (using the @samp{qs} form of the query), until the target responds
36197 with @samp{l} (lower-case ell, for @dfn{last}).
36198 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
36201 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
36202 initial connection with the remote target, and the very first thread ID
36203 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
36204 message. Therefore, the stub should ensure that the first thread ID in
36205 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
36207 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
36208 @cindex get thread-local storage address, remote request
36209 @cindex @samp{qGetTLSAddr} packet
36210 Fetch the address associated with thread local storage specified
36211 by @var{thread-id}, @var{offset}, and @var{lm}.
36213 @var{thread-id} is the thread ID associated with the
36214 thread for which to fetch the TLS address. @xref{thread-id syntax}.
36216 @var{offset} is the (big endian, hex encoded) offset associated with the
36217 thread local variable. (This offset is obtained from the debug
36218 information associated with the variable.)
36220 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
36221 load module associated with the thread local storage. For example,
36222 a @sc{gnu}/Linux system will pass the link map address of the shared
36223 object associated with the thread local storage under consideration.
36224 Other operating environments may choose to represent the load module
36225 differently, so the precise meaning of this parameter will vary.
36229 @item @var{XX}@dots{}
36230 Hex encoded (big endian) bytes representing the address of the thread
36231 local storage requested.
36234 An error occurred. The error number @var{nn} is given as hex digits.
36237 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
36240 @item qGetTIBAddr:@var{thread-id}
36241 @cindex get thread information block address
36242 @cindex @samp{qGetTIBAddr} packet
36243 Fetch address of the Windows OS specific Thread Information Block.
36245 @var{thread-id} is the thread ID associated with the thread.
36249 @item @var{XX}@dots{}
36250 Hex encoded (big endian) bytes representing the linear address of the
36251 thread information block.
36254 An error occured. This means that either the thread was not found, or the
36255 address could not be retrieved.
36258 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
36261 @item qL @var{startflag} @var{threadcount} @var{nextthread}
36262 Obtain thread information from RTOS. Where: @var{startflag} (one hex
36263 digit) is one to indicate the first query and zero to indicate a
36264 subsequent query; @var{threadcount} (two hex digits) is the maximum
36265 number of threads the response packet can contain; and @var{nextthread}
36266 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
36267 returned in the response as @var{argthread}.
36269 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
36273 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
36274 Where: @var{count} (two hex digits) is the number of threads being
36275 returned; @var{done} (one hex digit) is zero to indicate more threads
36276 and one indicates no further threads; @var{argthreadid} (eight hex
36277 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
36278 is a sequence of thread IDs, @var{threadid} (eight hex
36279 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
36283 @cindex section offsets, remote request
36284 @cindex @samp{qOffsets} packet
36285 Get section offsets that the target used when relocating the downloaded
36290 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
36291 Relocate the @code{Text} section by @var{xxx} from its original address.
36292 Relocate the @code{Data} section by @var{yyy} from its original address.
36293 If the object file format provides segment information (e.g.@: @sc{elf}
36294 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
36295 segments by the supplied offsets.
36297 @emph{Note: while a @code{Bss} offset may be included in the response,
36298 @value{GDBN} ignores this and instead applies the @code{Data} offset
36299 to the @code{Bss} section.}
36301 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
36302 Relocate the first segment of the object file, which conventionally
36303 contains program code, to a starting address of @var{xxx}. If
36304 @samp{DataSeg} is specified, relocate the second segment, which
36305 conventionally contains modifiable data, to a starting address of
36306 @var{yyy}. @value{GDBN} will report an error if the object file
36307 does not contain segment information, or does not contain at least
36308 as many segments as mentioned in the reply. Extra segments are
36309 kept at fixed offsets relative to the last relocated segment.
36312 @item qP @var{mode} @var{thread-id}
36313 @cindex thread information, remote request
36314 @cindex @samp{qP} packet
36315 Returns information on @var{thread-id}. Where: @var{mode} is a hex
36316 encoded 32 bit mode; @var{thread-id} is a thread ID
36317 (@pxref{thread-id syntax}).
36319 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
36322 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
36326 @cindex non-stop mode, remote request
36327 @cindex @samp{QNonStop} packet
36329 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
36330 @xref{Remote Non-Stop}, for more information.
36335 The request succeeded.
36338 An error occurred. The error number @var{nn} is given as hex digits.
36341 An empty reply indicates that @samp{QNonStop} is not supported by
36345 This packet is not probed by default; the remote stub must request it,
36346 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36347 Use of this packet is controlled by the @code{set non-stop} command;
36348 @pxref{Non-Stop Mode}.
36350 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
36351 @itemx QCatchSyscalls:0
36352 @cindex catch syscalls from inferior, remote request
36353 @cindex @samp{QCatchSyscalls} packet
36354 @anchor{QCatchSyscalls}
36355 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
36356 catching syscalls from the inferior process.
36358 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
36359 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
36360 is listed, every system call should be reported.
36362 Note that if a syscall not in the list is reported, @value{GDBN} will
36363 still filter the event according to its own list from all corresponding
36364 @code{catch syscall} commands. However, it is more efficient to only
36365 report the requested syscalls.
36367 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
36368 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
36370 If the inferior process execs, the state of @samp{QCatchSyscalls} is
36371 kept for the new process too. On targets where exec may affect syscall
36372 numbers, for example with exec between 32 and 64-bit processes, the
36373 client should send a new packet with the new syscall list.
36378 The request succeeded.
36381 An error occurred. @var{nn} are hex digits.
36384 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
36388 Use of this packet is controlled by the @code{set remote catch-syscalls}
36389 command (@pxref{Remote Configuration, set remote catch-syscalls}).
36390 This packet is not probed by default; the remote stub must request it,
36391 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36393 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
36394 @cindex pass signals to inferior, remote request
36395 @cindex @samp{QPassSignals} packet
36396 @anchor{QPassSignals}
36397 Each listed @var{signal} should be passed directly to the inferior process.
36398 Signals are numbered identically to continue packets and stop replies
36399 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
36400 strictly greater than the previous item. These signals do not need to stop
36401 the inferior, or be reported to @value{GDBN}. All other signals should be
36402 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
36403 combine; any earlier @samp{QPassSignals} list is completely replaced by the
36404 new list. This packet improves performance when using @samp{handle
36405 @var{signal} nostop noprint pass}.
36410 The request succeeded.
36413 An error occurred. The error number @var{nn} is given as hex digits.
36416 An empty reply indicates that @samp{QPassSignals} is not supported by
36420 Use of this packet is controlled by the @code{set remote pass-signals}
36421 command (@pxref{Remote Configuration, set remote pass-signals}).
36422 This packet is not probed by default; the remote stub must request it,
36423 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36425 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
36426 @cindex signals the inferior may see, remote request
36427 @cindex @samp{QProgramSignals} packet
36428 @anchor{QProgramSignals}
36429 Each listed @var{signal} may be delivered to the inferior process.
36430 Others should be silently discarded.
36432 In some cases, the remote stub may need to decide whether to deliver a
36433 signal to the program or not without @value{GDBN} involvement. One
36434 example of that is while detaching --- the program's threads may have
36435 stopped for signals that haven't yet had a chance of being reported to
36436 @value{GDBN}, and so the remote stub can use the signal list specified
36437 by this packet to know whether to deliver or ignore those pending
36440 This does not influence whether to deliver a signal as requested by a
36441 resumption packet (@pxref{vCont packet}).
36443 Signals are numbered identically to continue packets and stop replies
36444 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
36445 strictly greater than the previous item. Multiple
36446 @samp{QProgramSignals} packets do not combine; any earlier
36447 @samp{QProgramSignals} list is completely replaced by the new list.
36452 The request succeeded.
36455 An error occurred. The error number @var{nn} is given as hex digits.
36458 An empty reply indicates that @samp{QProgramSignals} is not supported
36462 Use of this packet is controlled by the @code{set remote program-signals}
36463 command (@pxref{Remote Configuration, set remote program-signals}).
36464 This packet is not probed by default; the remote stub must request it,
36465 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36467 @anchor{QThreadEvents}
36468 @item QThreadEvents:1
36469 @itemx QThreadEvents:0
36470 @cindex thread create/exit events, remote request
36471 @cindex @samp{QThreadEvents} packet
36473 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
36474 reporting of thread create and exit events. @xref{thread create
36475 event}, for the reply specifications. For example, this is used in
36476 non-stop mode when @value{GDBN} stops a set of threads and
36477 synchronously waits for the their corresponding stop replies. Without
36478 exit events, if one of the threads exits, @value{GDBN} would hang
36479 forever not knowing that it should no longer expect a stop for that
36480 same thread. @value{GDBN} does not enable this feature unless the
36481 stub reports that it supports it by including @samp{QThreadEvents+} in
36482 its @samp{qSupported} reply.
36487 The request succeeded.
36490 An error occurred. The error number @var{nn} is given as hex digits.
36493 An empty reply indicates that @samp{QThreadEvents} is not supported by
36497 Use of this packet is controlled by the @code{set remote thread-events}
36498 command (@pxref{Remote Configuration, set remote thread-events}).
36500 @item qRcmd,@var{command}
36501 @cindex execute remote command, remote request
36502 @cindex @samp{qRcmd} packet
36503 @var{command} (hex encoded) is passed to the local interpreter for
36504 execution. Invalid commands should be reported using the output
36505 string. Before the final result packet, the target may also respond
36506 with a number of intermediate @samp{O@var{output}} console output
36507 packets. @emph{Implementors should note that providing access to a
36508 stubs's interpreter may have security implications}.
36513 A command response with no output.
36515 A command response with the hex encoded output string @var{OUTPUT}.
36517 Indicate a badly formed request.
36519 An empty reply indicates that @samp{qRcmd} is not recognized.
36522 (Note that the @code{qRcmd} packet's name is separated from the
36523 command by a @samp{,}, not a @samp{:}, contrary to the naming
36524 conventions above. Please don't use this packet as a model for new
36527 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
36528 @cindex searching memory, in remote debugging
36530 @cindex @samp{qSearch:memory} packet
36532 @cindex @samp{qSearch memory} packet
36533 @anchor{qSearch memory}
36534 Search @var{length} bytes at @var{address} for @var{search-pattern}.
36535 Both @var{address} and @var{length} are encoded in hex;
36536 @var{search-pattern} is a sequence of bytes, also hex encoded.
36541 The pattern was not found.
36543 The pattern was found at @var{address}.
36545 A badly formed request or an error was encountered while searching memory.
36547 An empty reply indicates that @samp{qSearch:memory} is not recognized.
36550 @item QStartNoAckMode
36551 @cindex @samp{QStartNoAckMode} packet
36552 @anchor{QStartNoAckMode}
36553 Request that the remote stub disable the normal @samp{+}/@samp{-}
36554 protocol acknowledgments (@pxref{Packet Acknowledgment}).
36559 The stub has switched to no-acknowledgment mode.
36560 @value{GDBN} acknowledges this reponse,
36561 but neither the stub nor @value{GDBN} shall send or expect further
36562 @samp{+}/@samp{-} acknowledgments in the current connection.
36564 An empty reply indicates that the stub does not support no-acknowledgment mode.
36567 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
36568 @cindex supported packets, remote query
36569 @cindex features of the remote protocol
36570 @cindex @samp{qSupported} packet
36571 @anchor{qSupported}
36572 Tell the remote stub about features supported by @value{GDBN}, and
36573 query the stub for features it supports. This packet allows
36574 @value{GDBN} and the remote stub to take advantage of each others'
36575 features. @samp{qSupported} also consolidates multiple feature probes
36576 at startup, to improve @value{GDBN} performance---a single larger
36577 packet performs better than multiple smaller probe packets on
36578 high-latency links. Some features may enable behavior which must not
36579 be on by default, e.g.@: because it would confuse older clients or
36580 stubs. Other features may describe packets which could be
36581 automatically probed for, but are not. These features must be
36582 reported before @value{GDBN} will use them. This ``default
36583 unsupported'' behavior is not appropriate for all packets, but it
36584 helps to keep the initial connection time under control with new
36585 versions of @value{GDBN} which support increasing numbers of packets.
36589 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
36590 The stub supports or does not support each returned @var{stubfeature},
36591 depending on the form of each @var{stubfeature} (see below for the
36594 An empty reply indicates that @samp{qSupported} is not recognized,
36595 or that no features needed to be reported to @value{GDBN}.
36598 The allowed forms for each feature (either a @var{gdbfeature} in the
36599 @samp{qSupported} packet, or a @var{stubfeature} in the response)
36603 @item @var{name}=@var{value}
36604 The remote protocol feature @var{name} is supported, and associated
36605 with the specified @var{value}. The format of @var{value} depends
36606 on the feature, but it must not include a semicolon.
36608 The remote protocol feature @var{name} is supported, and does not
36609 need an associated value.
36611 The remote protocol feature @var{name} is not supported.
36613 The remote protocol feature @var{name} may be supported, and
36614 @value{GDBN} should auto-detect support in some other way when it is
36615 needed. This form will not be used for @var{gdbfeature} notifications,
36616 but may be used for @var{stubfeature} responses.
36619 Whenever the stub receives a @samp{qSupported} request, the
36620 supplied set of @value{GDBN} features should override any previous
36621 request. This allows @value{GDBN} to put the stub in a known
36622 state, even if the stub had previously been communicating with
36623 a different version of @value{GDBN}.
36625 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
36630 This feature indicates whether @value{GDBN} supports multiprocess
36631 extensions to the remote protocol. @value{GDBN} does not use such
36632 extensions unless the stub also reports that it supports them by
36633 including @samp{multiprocess+} in its @samp{qSupported} reply.
36634 @xref{multiprocess extensions}, for details.
36637 This feature indicates that @value{GDBN} supports the XML target
36638 description. If the stub sees @samp{xmlRegisters=} with target
36639 specific strings separated by a comma, it will report register
36643 This feature indicates whether @value{GDBN} supports the
36644 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
36645 instruction reply packet}).
36648 This feature indicates whether @value{GDBN} supports the swbreak stop
36649 reason in stop replies. @xref{swbreak stop reason}, for details.
36652 This feature indicates whether @value{GDBN} supports the hwbreak stop
36653 reason in stop replies. @xref{swbreak stop reason}, for details.
36656 This feature indicates whether @value{GDBN} supports fork event
36657 extensions to the remote protocol. @value{GDBN} does not use such
36658 extensions unless the stub also reports that it supports them by
36659 including @samp{fork-events+} in its @samp{qSupported} reply.
36662 This feature indicates whether @value{GDBN} supports vfork event
36663 extensions to the remote protocol. @value{GDBN} does not use such
36664 extensions unless the stub also reports that it supports them by
36665 including @samp{vfork-events+} in its @samp{qSupported} reply.
36668 This feature indicates whether @value{GDBN} supports exec event
36669 extensions to the remote protocol. @value{GDBN} does not use such
36670 extensions unless the stub also reports that it supports them by
36671 including @samp{exec-events+} in its @samp{qSupported} reply.
36673 @item vContSupported
36674 This feature indicates whether @value{GDBN} wants to know the
36675 supported actions in the reply to @samp{vCont?} packet.
36678 Stubs should ignore any unknown values for
36679 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
36680 packet supports receiving packets of unlimited length (earlier
36681 versions of @value{GDBN} may reject overly long responses). Additional values
36682 for @var{gdbfeature} may be defined in the future to let the stub take
36683 advantage of new features in @value{GDBN}, e.g.@: incompatible
36684 improvements in the remote protocol---the @samp{multiprocess} feature is
36685 an example of such a feature. The stub's reply should be independent
36686 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
36687 describes all the features it supports, and then the stub replies with
36688 all the features it supports.
36690 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
36691 responses, as long as each response uses one of the standard forms.
36693 Some features are flags. A stub which supports a flag feature
36694 should respond with a @samp{+} form response. Other features
36695 require values, and the stub should respond with an @samp{=}
36698 Each feature has a default value, which @value{GDBN} will use if
36699 @samp{qSupported} is not available or if the feature is not mentioned
36700 in the @samp{qSupported} response. The default values are fixed; a
36701 stub is free to omit any feature responses that match the defaults.
36703 Not all features can be probed, but for those which can, the probing
36704 mechanism is useful: in some cases, a stub's internal
36705 architecture may not allow the protocol layer to know some information
36706 about the underlying target in advance. This is especially common in
36707 stubs which may be configured for multiple targets.
36709 These are the currently defined stub features and their properties:
36711 @multitable @columnfractions 0.35 0.2 0.12 0.2
36712 @c NOTE: The first row should be @headitem, but we do not yet require
36713 @c a new enough version of Texinfo (4.7) to use @headitem.
36715 @tab Value Required
36719 @item @samp{PacketSize}
36724 @item @samp{qXfer:auxv:read}
36729 @item @samp{qXfer:btrace:read}
36734 @item @samp{qXfer:btrace-conf:read}
36739 @item @samp{qXfer:exec-file:read}
36744 @item @samp{qXfer:features:read}
36749 @item @samp{qXfer:libraries:read}
36754 @item @samp{qXfer:libraries-svr4:read}
36759 @item @samp{augmented-libraries-svr4-read}
36764 @item @samp{qXfer:memory-map:read}
36769 @item @samp{qXfer:sdata:read}
36774 @item @samp{qXfer:spu:read}
36779 @item @samp{qXfer:spu:write}
36784 @item @samp{qXfer:siginfo:read}
36789 @item @samp{qXfer:siginfo:write}
36794 @item @samp{qXfer:threads:read}
36799 @item @samp{qXfer:traceframe-info:read}
36804 @item @samp{qXfer:uib:read}
36809 @item @samp{qXfer:fdpic:read}
36814 @item @samp{Qbtrace:off}
36819 @item @samp{Qbtrace:bts}
36824 @item @samp{Qbtrace:pt}
36829 @item @samp{Qbtrace-conf:bts:size}
36834 @item @samp{Qbtrace-conf:pt:size}
36839 @item @samp{QNonStop}
36844 @item @samp{QCatchSyscalls}
36849 @item @samp{QPassSignals}
36854 @item @samp{QStartNoAckMode}
36859 @item @samp{multiprocess}
36864 @item @samp{ConditionalBreakpoints}
36869 @item @samp{ConditionalTracepoints}
36874 @item @samp{ReverseContinue}
36879 @item @samp{ReverseStep}
36884 @item @samp{TracepointSource}
36889 @item @samp{QAgent}
36894 @item @samp{QAllow}
36899 @item @samp{QDisableRandomization}
36904 @item @samp{EnableDisableTracepoints}
36909 @item @samp{QTBuffer:size}
36914 @item @samp{tracenz}
36919 @item @samp{BreakpointCommands}
36924 @item @samp{swbreak}
36929 @item @samp{hwbreak}
36934 @item @samp{fork-events}
36939 @item @samp{vfork-events}
36944 @item @samp{exec-events}
36949 @item @samp{QThreadEvents}
36954 @item @samp{no-resumed}
36961 These are the currently defined stub features, in more detail:
36964 @cindex packet size, remote protocol
36965 @item PacketSize=@var{bytes}
36966 The remote stub can accept packets up to at least @var{bytes} in
36967 length. @value{GDBN} will send packets up to this size for bulk
36968 transfers, and will never send larger packets. This is a limit on the
36969 data characters in the packet, including the frame and checksum.
36970 There is no trailing NUL byte in a remote protocol packet; if the stub
36971 stores packets in a NUL-terminated format, it should allow an extra
36972 byte in its buffer for the NUL. If this stub feature is not supported,
36973 @value{GDBN} guesses based on the size of the @samp{g} packet response.
36975 @item qXfer:auxv:read
36976 The remote stub understands the @samp{qXfer:auxv:read} packet
36977 (@pxref{qXfer auxiliary vector read}).
36979 @item qXfer:btrace:read
36980 The remote stub understands the @samp{qXfer:btrace:read}
36981 packet (@pxref{qXfer btrace read}).
36983 @item qXfer:btrace-conf:read
36984 The remote stub understands the @samp{qXfer:btrace-conf:read}
36985 packet (@pxref{qXfer btrace-conf read}).
36987 @item qXfer:exec-file:read
36988 The remote stub understands the @samp{qXfer:exec-file:read} packet
36989 (@pxref{qXfer executable filename read}).
36991 @item qXfer:features:read
36992 The remote stub understands the @samp{qXfer:features:read} packet
36993 (@pxref{qXfer target description read}).
36995 @item qXfer:libraries:read
36996 The remote stub understands the @samp{qXfer:libraries:read} packet
36997 (@pxref{qXfer library list read}).
36999 @item qXfer:libraries-svr4:read
37000 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
37001 (@pxref{qXfer svr4 library list read}).
37003 @item augmented-libraries-svr4-read
37004 The remote stub understands the augmented form of the
37005 @samp{qXfer:libraries-svr4:read} packet
37006 (@pxref{qXfer svr4 library list read}).
37008 @item qXfer:memory-map:read
37009 The remote stub understands the @samp{qXfer:memory-map:read} packet
37010 (@pxref{qXfer memory map read}).
37012 @item qXfer:sdata:read
37013 The remote stub understands the @samp{qXfer:sdata:read} packet
37014 (@pxref{qXfer sdata read}).
37016 @item qXfer:spu:read
37017 The remote stub understands the @samp{qXfer:spu:read} packet
37018 (@pxref{qXfer spu read}).
37020 @item qXfer:spu:write
37021 The remote stub understands the @samp{qXfer:spu:write} packet
37022 (@pxref{qXfer spu write}).
37024 @item qXfer:siginfo:read
37025 The remote stub understands the @samp{qXfer:siginfo:read} packet
37026 (@pxref{qXfer siginfo read}).
37028 @item qXfer:siginfo:write
37029 The remote stub understands the @samp{qXfer:siginfo:write} packet
37030 (@pxref{qXfer siginfo write}).
37032 @item qXfer:threads:read
37033 The remote stub understands the @samp{qXfer:threads:read} packet
37034 (@pxref{qXfer threads read}).
37036 @item qXfer:traceframe-info:read
37037 The remote stub understands the @samp{qXfer:traceframe-info:read}
37038 packet (@pxref{qXfer traceframe info read}).
37040 @item qXfer:uib:read
37041 The remote stub understands the @samp{qXfer:uib:read}
37042 packet (@pxref{qXfer unwind info block}).
37044 @item qXfer:fdpic:read
37045 The remote stub understands the @samp{qXfer:fdpic:read}
37046 packet (@pxref{qXfer fdpic loadmap read}).
37049 The remote stub understands the @samp{QNonStop} packet
37050 (@pxref{QNonStop}).
37052 @item QCatchSyscalls
37053 The remote stub understands the @samp{QCatchSyscalls} packet
37054 (@pxref{QCatchSyscalls}).
37057 The remote stub understands the @samp{QPassSignals} packet
37058 (@pxref{QPassSignals}).
37060 @item QStartNoAckMode
37061 The remote stub understands the @samp{QStartNoAckMode} packet and
37062 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
37065 @anchor{multiprocess extensions}
37066 @cindex multiprocess extensions, in remote protocol
37067 The remote stub understands the multiprocess extensions to the remote
37068 protocol syntax. The multiprocess extensions affect the syntax of
37069 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
37070 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
37071 replies. Note that reporting this feature indicates support for the
37072 syntactic extensions only, not that the stub necessarily supports
37073 debugging of more than one process at a time. The stub must not use
37074 multiprocess extensions in packet replies unless @value{GDBN} has also
37075 indicated it supports them in its @samp{qSupported} request.
37077 @item qXfer:osdata:read
37078 The remote stub understands the @samp{qXfer:osdata:read} packet
37079 ((@pxref{qXfer osdata read}).
37081 @item ConditionalBreakpoints
37082 The target accepts and implements evaluation of conditional expressions
37083 defined for breakpoints. The target will only report breakpoint triggers
37084 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
37086 @item ConditionalTracepoints
37087 The remote stub accepts and implements conditional expressions defined
37088 for tracepoints (@pxref{Tracepoint Conditions}).
37090 @item ReverseContinue
37091 The remote stub accepts and implements the reverse continue packet
37095 The remote stub accepts and implements the reverse step packet
37098 @item TracepointSource
37099 The remote stub understands the @samp{QTDPsrc} packet that supplies
37100 the source form of tracepoint definitions.
37103 The remote stub understands the @samp{QAgent} packet.
37106 The remote stub understands the @samp{QAllow} packet.
37108 @item QDisableRandomization
37109 The remote stub understands the @samp{QDisableRandomization} packet.
37111 @item StaticTracepoint
37112 @cindex static tracepoints, in remote protocol
37113 The remote stub supports static tracepoints.
37115 @item InstallInTrace
37116 @anchor{install tracepoint in tracing}
37117 The remote stub supports installing tracepoint in tracing.
37119 @item EnableDisableTracepoints
37120 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
37121 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
37122 to be enabled and disabled while a trace experiment is running.
37124 @item QTBuffer:size
37125 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
37126 packet that allows to change the size of the trace buffer.
37129 @cindex string tracing, in remote protocol
37130 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
37131 See @ref{Bytecode Descriptions} for details about the bytecode.
37133 @item BreakpointCommands
37134 @cindex breakpoint commands, in remote protocol
37135 The remote stub supports running a breakpoint's command list itself,
37136 rather than reporting the hit to @value{GDBN}.
37139 The remote stub understands the @samp{Qbtrace:off} packet.
37142 The remote stub understands the @samp{Qbtrace:bts} packet.
37145 The remote stub understands the @samp{Qbtrace:pt} packet.
37147 @item Qbtrace-conf:bts:size
37148 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
37150 @item Qbtrace-conf:pt:size
37151 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
37154 The remote stub reports the @samp{swbreak} stop reason for memory
37158 The remote stub reports the @samp{hwbreak} stop reason for hardware
37162 The remote stub reports the @samp{fork} stop reason for fork events.
37165 The remote stub reports the @samp{vfork} stop reason for vfork events
37166 and vforkdone events.
37169 The remote stub reports the @samp{exec} stop reason for exec events.
37171 @item vContSupported
37172 The remote stub reports the supported actions in the reply to
37173 @samp{vCont?} packet.
37175 @item QThreadEvents
37176 The remote stub understands the @samp{QThreadEvents} packet.
37179 The remote stub reports the @samp{N} stop reply.
37184 @cindex symbol lookup, remote request
37185 @cindex @samp{qSymbol} packet
37186 Notify the target that @value{GDBN} is prepared to serve symbol lookup
37187 requests. Accept requests from the target for the values of symbols.
37192 The target does not need to look up any (more) symbols.
37193 @item qSymbol:@var{sym_name}
37194 The target requests the value of symbol @var{sym_name} (hex encoded).
37195 @value{GDBN} may provide the value by using the
37196 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
37200 @item qSymbol:@var{sym_value}:@var{sym_name}
37201 Set the value of @var{sym_name} to @var{sym_value}.
37203 @var{sym_name} (hex encoded) is the name of a symbol whose value the
37204 target has previously requested.
37206 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
37207 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
37213 The target does not need to look up any (more) symbols.
37214 @item qSymbol:@var{sym_name}
37215 The target requests the value of a new symbol @var{sym_name} (hex
37216 encoded). @value{GDBN} will continue to supply the values of symbols
37217 (if available), until the target ceases to request them.
37222 @itemx QTDisconnected
37229 @itemx qTMinFTPILen
37231 @xref{Tracepoint Packets}.
37233 @item qThreadExtraInfo,@var{thread-id}
37234 @cindex thread attributes info, remote request
37235 @cindex @samp{qThreadExtraInfo} packet
37236 Obtain from the target OS a printable string description of thread
37237 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
37238 for the forms of @var{thread-id}. This
37239 string may contain anything that the target OS thinks is interesting
37240 for @value{GDBN} to tell the user about the thread. The string is
37241 displayed in @value{GDBN}'s @code{info threads} display. Some
37242 examples of possible thread extra info strings are @samp{Runnable}, or
37243 @samp{Blocked on Mutex}.
37247 @item @var{XX}@dots{}
37248 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
37249 comprising the printable string containing the extra information about
37250 the thread's attributes.
37253 (Note that the @code{qThreadExtraInfo} packet's name is separated from
37254 the command by a @samp{,}, not a @samp{:}, contrary to the naming
37255 conventions above. Please don't use this packet as a model for new
37274 @xref{Tracepoint Packets}.
37276 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
37277 @cindex read special object, remote request
37278 @cindex @samp{qXfer} packet
37279 @anchor{qXfer read}
37280 Read uninterpreted bytes from the target's special data area
37281 identified by the keyword @var{object}. Request @var{length} bytes
37282 starting at @var{offset} bytes into the data. The content and
37283 encoding of @var{annex} is specific to @var{object}; it can supply
37284 additional details about what data to access.
37286 Here are the specific requests of this form defined so far. All
37287 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
37288 formats, listed below.
37291 @item qXfer:auxv:read::@var{offset},@var{length}
37292 @anchor{qXfer auxiliary vector read}
37293 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
37294 auxiliary vector}. Note @var{annex} must be empty.
37296 This packet is not probed by default; the remote stub must request it,
37297 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37299 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
37300 @anchor{qXfer btrace read}
37302 Return a description of the current branch trace.
37303 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
37304 packet may have one of the following values:
37308 Returns all available branch trace.
37311 Returns all available branch trace if the branch trace changed since
37312 the last read request.
37315 Returns the new branch trace since the last read request. Adds a new
37316 block to the end of the trace that begins at zero and ends at the source
37317 location of the first branch in the trace buffer. This extra block is
37318 used to stitch traces together.
37320 If the trace buffer overflowed, returns an error indicating the overflow.
37323 This packet is not probed by default; the remote stub must request it
37324 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37326 @item qXfer:btrace-conf:read::@var{offset},@var{length}
37327 @anchor{qXfer btrace-conf read}
37329 Return a description of the current branch trace configuration.
37330 @xref{Branch Trace Configuration Format}.
37332 This packet is not probed by default; the remote stub must request it
37333 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37335 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
37336 @anchor{qXfer executable filename read}
37337 Return the full absolute name of the file that was executed to create
37338 a process running on the remote system. The annex specifies the
37339 numeric process ID of the process to query, encoded as a hexadecimal
37340 number. If the annex part is empty the remote stub should return the
37341 filename corresponding to the currently executing process.
37343 This packet is not probed by default; the remote stub must request it,
37344 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37346 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
37347 @anchor{qXfer target description read}
37348 Access the @dfn{target description}. @xref{Target Descriptions}. The
37349 annex specifies which XML document to access. The main description is
37350 always loaded from the @samp{target.xml} annex.
37352 This packet is not probed by default; the remote stub must request it,
37353 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37355 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
37356 @anchor{qXfer library list read}
37357 Access the target's list of loaded libraries. @xref{Library List Format}.
37358 The annex part of the generic @samp{qXfer} packet must be empty
37359 (@pxref{qXfer read}).
37361 Targets which maintain a list of libraries in the program's memory do
37362 not need to implement this packet; it is designed for platforms where
37363 the operating system manages the list of loaded libraries.
37365 This packet is not probed by default; the remote stub must request it,
37366 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37368 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
37369 @anchor{qXfer svr4 library list read}
37370 Access the target's list of loaded libraries when the target is an SVR4
37371 platform. @xref{Library List Format for SVR4 Targets}. The annex part
37372 of the generic @samp{qXfer} packet must be empty unless the remote
37373 stub indicated it supports the augmented form of this packet
37374 by supplying an appropriate @samp{qSupported} response
37375 (@pxref{qXfer read}, @ref{qSupported}).
37377 This packet is optional for better performance on SVR4 targets.
37378 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
37380 This packet is not probed by default; the remote stub must request it,
37381 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37383 If the remote stub indicates it supports the augmented form of this
37384 packet then the annex part of the generic @samp{qXfer} packet may
37385 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
37386 arguments. The currently supported arguments are:
37389 @item start=@var{address}
37390 A hexadecimal number specifying the address of the @samp{struct
37391 link_map} to start reading the library list from. If unset or zero
37392 then the first @samp{struct link_map} in the library list will be
37393 chosen as the starting point.
37395 @item prev=@var{address}
37396 A hexadecimal number specifying the address of the @samp{struct
37397 link_map} immediately preceding the @samp{struct link_map}
37398 specified by the @samp{start} argument. If unset or zero then
37399 the remote stub will expect that no @samp{struct link_map}
37400 exists prior to the starting point.
37404 Arguments that are not understood by the remote stub will be silently
37407 @item qXfer:memory-map:read::@var{offset},@var{length}
37408 @anchor{qXfer memory map read}
37409 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
37410 annex part of the generic @samp{qXfer} packet must be empty
37411 (@pxref{qXfer read}).
37413 This packet is not probed by default; the remote stub must request it,
37414 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37416 @item qXfer:sdata:read::@var{offset},@var{length}
37417 @anchor{qXfer sdata read}
37419 Read contents of the extra collected static tracepoint marker
37420 information. The annex part of the generic @samp{qXfer} packet must
37421 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
37424 This packet is not probed by default; the remote stub must request it,
37425 by supplying an appropriate @samp{qSupported} response
37426 (@pxref{qSupported}).
37428 @item qXfer:siginfo:read::@var{offset},@var{length}
37429 @anchor{qXfer siginfo read}
37430 Read contents of the extra signal information on the target
37431 system. The annex part of the generic @samp{qXfer} packet must be
37432 empty (@pxref{qXfer read}).
37434 This packet is not probed by default; the remote stub must request it,
37435 by supplying an appropriate @samp{qSupported} response
37436 (@pxref{qSupported}).
37438 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
37439 @anchor{qXfer spu read}
37440 Read contents of an @code{spufs} file on the target system. The
37441 annex specifies which file to read; it must be of the form
37442 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37443 in the target process, and @var{name} identifes the @code{spufs} file
37444 in that context to be accessed.
37446 This packet is not probed by default; the remote stub must request it,
37447 by supplying an appropriate @samp{qSupported} response
37448 (@pxref{qSupported}).
37450 @item qXfer:threads:read::@var{offset},@var{length}
37451 @anchor{qXfer threads read}
37452 Access the list of threads on target. @xref{Thread List Format}. The
37453 annex part of the generic @samp{qXfer} packet must be empty
37454 (@pxref{qXfer read}).
37456 This packet is not probed by default; the remote stub must request it,
37457 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37459 @item qXfer:traceframe-info:read::@var{offset},@var{length}
37460 @anchor{qXfer traceframe info read}
37462 Return a description of the current traceframe's contents.
37463 @xref{Traceframe Info Format}. The annex part of the generic
37464 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
37466 This packet is not probed by default; the remote stub must request it,
37467 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37469 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
37470 @anchor{qXfer unwind info block}
37472 Return the unwind information block for @var{pc}. This packet is used
37473 on OpenVMS/ia64 to ask the kernel unwind information.
37475 This packet is not probed by default.
37477 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
37478 @anchor{qXfer fdpic loadmap read}
37479 Read contents of @code{loadmap}s on the target system. The
37480 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
37481 executable @code{loadmap} or interpreter @code{loadmap} to read.
37483 This packet is not probed by default; the remote stub must request it,
37484 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37486 @item qXfer:osdata:read::@var{offset},@var{length}
37487 @anchor{qXfer osdata read}
37488 Access the target's @dfn{operating system information}.
37489 @xref{Operating System Information}.
37496 Data @var{data} (@pxref{Binary Data}) has been read from the
37497 target. There may be more data at a higher address (although
37498 it is permitted to return @samp{m} even for the last valid
37499 block of data, as long as at least one byte of data was read).
37500 It is possible for @var{data} to have fewer bytes than the @var{length} in the
37504 Data @var{data} (@pxref{Binary Data}) has been read from the target.
37505 There is no more data to be read. It is possible for @var{data} to
37506 have fewer bytes than the @var{length} in the request.
37509 The @var{offset} in the request is at the end of the data.
37510 There is no more data to be read.
37513 The request was malformed, or @var{annex} was invalid.
37516 The offset was invalid, or there was an error encountered reading the data.
37517 The @var{nn} part is a hex-encoded @code{errno} value.
37520 An empty reply indicates the @var{object} string was not recognized by
37521 the stub, or that the object does not support reading.
37524 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
37525 @cindex write data into object, remote request
37526 @anchor{qXfer write}
37527 Write uninterpreted bytes into the target's special data area
37528 identified by the keyword @var{object}, starting at @var{offset} bytes
37529 into the data. The binary-encoded data (@pxref{Binary Data}) to be
37530 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
37531 is specific to @var{object}; it can supply additional details about what data
37534 Here are the specific requests of this form defined so far. All
37535 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
37536 formats, listed below.
37539 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
37540 @anchor{qXfer siginfo write}
37541 Write @var{data} to the extra signal information on the target system.
37542 The annex part of the generic @samp{qXfer} packet must be
37543 empty (@pxref{qXfer write}).
37545 This packet is not probed by default; the remote stub must request it,
37546 by supplying an appropriate @samp{qSupported} response
37547 (@pxref{qSupported}).
37549 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
37550 @anchor{qXfer spu write}
37551 Write @var{data} to an @code{spufs} file on the target system. The
37552 annex specifies which file to write; it must be of the form
37553 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37554 in the target process, and @var{name} identifes the @code{spufs} file
37555 in that context to be accessed.
37557 This packet is not probed by default; the remote stub must request it,
37558 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37564 @var{nn} (hex encoded) is the number of bytes written.
37565 This may be fewer bytes than supplied in the request.
37568 The request was malformed, or @var{annex} was invalid.
37571 The offset was invalid, or there was an error encountered writing the data.
37572 The @var{nn} part is a hex-encoded @code{errno} value.
37575 An empty reply indicates the @var{object} string was not
37576 recognized by the stub, or that the object does not support writing.
37579 @item qXfer:@var{object}:@var{operation}:@dots{}
37580 Requests of this form may be added in the future. When a stub does
37581 not recognize the @var{object} keyword, or its support for
37582 @var{object} does not recognize the @var{operation} keyword, the stub
37583 must respond with an empty packet.
37585 @item qAttached:@var{pid}
37586 @cindex query attached, remote request
37587 @cindex @samp{qAttached} packet
37588 Return an indication of whether the remote server attached to an
37589 existing process or created a new process. When the multiprocess
37590 protocol extensions are supported (@pxref{multiprocess extensions}),
37591 @var{pid} is an integer in hexadecimal format identifying the target
37592 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
37593 the query packet will be simplified as @samp{qAttached}.
37595 This query is used, for example, to know whether the remote process
37596 should be detached or killed when a @value{GDBN} session is ended with
37597 the @code{quit} command.
37602 The remote server attached to an existing process.
37604 The remote server created a new process.
37606 A badly formed request or an error was encountered.
37610 Enable branch tracing for the current thread using Branch Trace Store.
37615 Branch tracing has been enabled.
37617 A badly formed request or an error was encountered.
37621 Enable branch tracing for the current thread using Intel Processor Trace.
37626 Branch tracing has been enabled.
37628 A badly formed request or an error was encountered.
37632 Disable branch tracing for the current thread.
37637 Branch tracing has been disabled.
37639 A badly formed request or an error was encountered.
37642 @item Qbtrace-conf:bts:size=@var{value}
37643 Set the requested ring buffer size for new threads that use the
37644 btrace recording method in bts format.
37649 The ring buffer size has been set.
37651 A badly formed request or an error was encountered.
37654 @item Qbtrace-conf:pt:size=@var{value}
37655 Set the requested ring buffer size for new threads that use the
37656 btrace recording method in pt format.
37661 The ring buffer size has been set.
37663 A badly formed request or an error was encountered.
37668 @node Architecture-Specific Protocol Details
37669 @section Architecture-Specific Protocol Details
37671 This section describes how the remote protocol is applied to specific
37672 target architectures. Also see @ref{Standard Target Features}, for
37673 details of XML target descriptions for each architecture.
37676 * ARM-Specific Protocol Details::
37677 * MIPS-Specific Protocol Details::
37680 @node ARM-Specific Protocol Details
37681 @subsection @acronym{ARM}-specific Protocol Details
37684 * ARM Breakpoint Kinds::
37687 @node ARM Breakpoint Kinds
37688 @subsubsection @acronym{ARM} Breakpoint Kinds
37689 @cindex breakpoint kinds, @acronym{ARM}
37691 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37696 16-bit Thumb mode breakpoint.
37699 32-bit Thumb mode (Thumb-2) breakpoint.
37702 32-bit @acronym{ARM} mode breakpoint.
37706 @node MIPS-Specific Protocol Details
37707 @subsection @acronym{MIPS}-specific Protocol Details
37710 * MIPS Register packet Format::
37711 * MIPS Breakpoint Kinds::
37714 @node MIPS Register packet Format
37715 @subsubsection @acronym{MIPS} Register Packet Format
37716 @cindex register packet format, @acronym{MIPS}
37718 The following @code{g}/@code{G} packets have previously been defined.
37719 In the below, some thirty-two bit registers are transferred as
37720 sixty-four bits. Those registers should be zero/sign extended (which?)
37721 to fill the space allocated. Register bytes are transferred in target
37722 byte order. The two nibbles within a register byte are transferred
37723 most-significant -- least-significant.
37728 All registers are transferred as thirty-two bit quantities in the order:
37729 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
37730 registers; fsr; fir; fp.
37733 All registers are transferred as sixty-four bit quantities (including
37734 thirty-two bit registers such as @code{sr}). The ordering is the same
37739 @node MIPS Breakpoint Kinds
37740 @subsubsection @acronym{MIPS} Breakpoint Kinds
37741 @cindex breakpoint kinds, @acronym{MIPS}
37743 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37748 16-bit @acronym{MIPS16} mode breakpoint.
37751 16-bit @acronym{microMIPS} mode breakpoint.
37754 32-bit standard @acronym{MIPS} mode breakpoint.
37757 32-bit @acronym{microMIPS} mode breakpoint.
37761 @node Tracepoint Packets
37762 @section Tracepoint Packets
37763 @cindex tracepoint packets
37764 @cindex packets, tracepoint
37766 Here we describe the packets @value{GDBN} uses to implement
37767 tracepoints (@pxref{Tracepoints}).
37771 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
37772 @cindex @samp{QTDP} packet
37773 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
37774 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
37775 the tracepoint is disabled. The @var{step} gives the tracepoint's step
37776 count, and @var{pass} gives its pass count. If an @samp{F} is present,
37777 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
37778 the number of bytes that the target should copy elsewhere to make room
37779 for the tracepoint. If an @samp{X} is present, it introduces a
37780 tracepoint condition, which consists of a hexadecimal length, followed
37781 by a comma and hex-encoded bytes, in a manner similar to action
37782 encodings as described below. If the trailing @samp{-} is present,
37783 further @samp{QTDP} packets will follow to specify this tracepoint's
37789 The packet was understood and carried out.
37791 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
37793 The packet was not recognized.
37796 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
37797 Define actions to be taken when a tracepoint is hit. The @var{n} and
37798 @var{addr} must be the same as in the initial @samp{QTDP} packet for
37799 this tracepoint. This packet may only be sent immediately after
37800 another @samp{QTDP} packet that ended with a @samp{-}. If the
37801 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
37802 specifying more actions for this tracepoint.
37804 In the series of action packets for a given tracepoint, at most one
37805 can have an @samp{S} before its first @var{action}. If such a packet
37806 is sent, it and the following packets define ``while-stepping''
37807 actions. Any prior packets define ordinary actions --- that is, those
37808 taken when the tracepoint is first hit. If no action packet has an
37809 @samp{S}, then all the packets in the series specify ordinary
37810 tracepoint actions.
37812 The @samp{@var{action}@dots{}} portion of the packet is a series of
37813 actions, concatenated without separators. Each action has one of the
37819 Collect the registers whose bits are set in @var{mask},
37820 a hexadecimal number whose @var{i}'th bit is set if register number
37821 @var{i} should be collected. (The least significant bit is numbered
37822 zero.) Note that @var{mask} may be any number of digits long; it may
37823 not fit in a 32-bit word.
37825 @item M @var{basereg},@var{offset},@var{len}
37826 Collect @var{len} bytes of memory starting at the address in register
37827 number @var{basereg}, plus @var{offset}. If @var{basereg} is
37828 @samp{-1}, then the range has a fixed address: @var{offset} is the
37829 address of the lowest byte to collect. The @var{basereg},
37830 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
37831 values (the @samp{-1} value for @var{basereg} is a special case).
37833 @item X @var{len},@var{expr}
37834 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
37835 it directs. The agent expression @var{expr} is as described in
37836 @ref{Agent Expressions}. Each byte of the expression is encoded as a
37837 two-digit hex number in the packet; @var{len} is the number of bytes
37838 in the expression (and thus one-half the number of hex digits in the
37843 Any number of actions may be packed together in a single @samp{QTDP}
37844 packet, as long as the packet does not exceed the maximum packet
37845 length (400 bytes, for many stubs). There may be only one @samp{R}
37846 action per tracepoint, and it must precede any @samp{M} or @samp{X}
37847 actions. Any registers referred to by @samp{M} and @samp{X} actions
37848 must be collected by a preceding @samp{R} action. (The
37849 ``while-stepping'' actions are treated as if they were attached to a
37850 separate tracepoint, as far as these restrictions are concerned.)
37855 The packet was understood and carried out.
37857 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
37859 The packet was not recognized.
37862 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
37863 @cindex @samp{QTDPsrc} packet
37864 Specify a source string of tracepoint @var{n} at address @var{addr}.
37865 This is useful to get accurate reproduction of the tracepoints
37866 originally downloaded at the beginning of the trace run. The @var{type}
37867 is the name of the tracepoint part, such as @samp{cond} for the
37868 tracepoint's conditional expression (see below for a list of types), while
37869 @var{bytes} is the string, encoded in hexadecimal.
37871 @var{start} is the offset of the @var{bytes} within the overall source
37872 string, while @var{slen} is the total length of the source string.
37873 This is intended for handling source strings that are longer than will
37874 fit in a single packet.
37875 @c Add detailed example when this info is moved into a dedicated
37876 @c tracepoint descriptions section.
37878 The available string types are @samp{at} for the location,
37879 @samp{cond} for the conditional, and @samp{cmd} for an action command.
37880 @value{GDBN} sends a separate packet for each command in the action
37881 list, in the same order in which the commands are stored in the list.
37883 The target does not need to do anything with source strings except
37884 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
37887 Although this packet is optional, and @value{GDBN} will only send it
37888 if the target replies with @samp{TracepointSource} @xref{General
37889 Query Packets}, it makes both disconnected tracing and trace files
37890 much easier to use. Otherwise the user must be careful that the
37891 tracepoints in effect while looking at trace frames are identical to
37892 the ones in effect during the trace run; even a small discrepancy
37893 could cause @samp{tdump} not to work, or a particular trace frame not
37896 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
37897 @cindex define trace state variable, remote request
37898 @cindex @samp{QTDV} packet
37899 Create a new trace state variable, number @var{n}, with an initial
37900 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
37901 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
37902 the option of not using this packet for initial values of zero; the
37903 target should simply create the trace state variables as they are
37904 mentioned in expressions. The value @var{builtin} should be 1 (one)
37905 if the trace state variable is builtin and 0 (zero) if it is not builtin.
37906 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
37907 @samp{qTsV} packet had it set. The contents of @var{name} is the
37908 hex-encoded name (without the leading @samp{$}) of the trace state
37911 @item QTFrame:@var{n}
37912 @cindex @samp{QTFrame} packet
37913 Select the @var{n}'th tracepoint frame from the buffer, and use the
37914 register and memory contents recorded there to answer subsequent
37915 request packets from @value{GDBN}.
37917 A successful reply from the stub indicates that the stub has found the
37918 requested frame. The response is a series of parts, concatenated
37919 without separators, describing the frame we selected. Each part has
37920 one of the following forms:
37924 The selected frame is number @var{n} in the trace frame buffer;
37925 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
37926 was no frame matching the criteria in the request packet.
37929 The selected trace frame records a hit of tracepoint number @var{t};
37930 @var{t} is a hexadecimal number.
37934 @item QTFrame:pc:@var{addr}
37935 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37936 currently selected frame whose PC is @var{addr};
37937 @var{addr} is a hexadecimal number.
37939 @item QTFrame:tdp:@var{t}
37940 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37941 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
37942 is a hexadecimal number.
37944 @item QTFrame:range:@var{start}:@var{end}
37945 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37946 currently selected frame whose PC is between @var{start} (inclusive)
37947 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
37950 @item QTFrame:outside:@var{start}:@var{end}
37951 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
37952 frame @emph{outside} the given range of addresses (exclusive).
37955 @cindex @samp{qTMinFTPILen} packet
37956 This packet requests the minimum length of instruction at which a fast
37957 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
37958 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
37959 it depends on the target system being able to create trampolines in
37960 the first 64K of memory, which might or might not be possible for that
37961 system. So the reply to this packet will be 4 if it is able to
37968 The minimum instruction length is currently unknown.
37970 The minimum instruction length is @var{length}, where @var{length}
37971 is a hexadecimal number greater or equal to 1. A reply
37972 of 1 means that a fast tracepoint may be placed on any instruction
37973 regardless of size.
37975 An error has occurred.
37977 An empty reply indicates that the request is not supported by the stub.
37981 @cindex @samp{QTStart} packet
37982 Begin the tracepoint experiment. Begin collecting data from
37983 tracepoint hits in the trace frame buffer. This packet supports the
37984 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
37985 instruction reply packet}).
37988 @cindex @samp{QTStop} packet
37989 End the tracepoint experiment. Stop collecting trace frames.
37991 @item QTEnable:@var{n}:@var{addr}
37993 @cindex @samp{QTEnable} packet
37994 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
37995 experiment. If the tracepoint was previously disabled, then collection
37996 of data from it will resume.
37998 @item QTDisable:@var{n}:@var{addr}
38000 @cindex @samp{QTDisable} packet
38001 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
38002 experiment. No more data will be collected from the tracepoint unless
38003 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
38006 @cindex @samp{QTinit} packet
38007 Clear the table of tracepoints, and empty the trace frame buffer.
38009 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
38010 @cindex @samp{QTro} packet
38011 Establish the given ranges of memory as ``transparent''. The stub
38012 will answer requests for these ranges from memory's current contents,
38013 if they were not collected as part of the tracepoint hit.
38015 @value{GDBN} uses this to mark read-only regions of memory, like those
38016 containing program code. Since these areas never change, they should
38017 still have the same contents they did when the tracepoint was hit, so
38018 there's no reason for the stub to refuse to provide their contents.
38020 @item QTDisconnected:@var{value}
38021 @cindex @samp{QTDisconnected} packet
38022 Set the choice to what to do with the tracing run when @value{GDBN}
38023 disconnects from the target. A @var{value} of 1 directs the target to
38024 continue the tracing run, while 0 tells the target to stop tracing if
38025 @value{GDBN} is no longer in the picture.
38028 @cindex @samp{qTStatus} packet
38029 Ask the stub if there is a trace experiment running right now.
38031 The reply has the form:
38035 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
38036 @var{running} is a single digit @code{1} if the trace is presently
38037 running, or @code{0} if not. It is followed by semicolon-separated
38038 optional fields that an agent may use to report additional status.
38042 If the trace is not running, the agent may report any of several
38043 explanations as one of the optional fields:
38048 No trace has been run yet.
38050 @item tstop[:@var{text}]:0
38051 The trace was stopped by a user-originated stop command. The optional
38052 @var{text} field is a user-supplied string supplied as part of the
38053 stop command (for instance, an explanation of why the trace was
38054 stopped manually). It is hex-encoded.
38057 The trace stopped because the trace buffer filled up.
38059 @item tdisconnected:0
38060 The trace stopped because @value{GDBN} disconnected from the target.
38062 @item tpasscount:@var{tpnum}
38063 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
38065 @item terror:@var{text}:@var{tpnum}
38066 The trace stopped because tracepoint @var{tpnum} had an error. The
38067 string @var{text} is available to describe the nature of the error
38068 (for instance, a divide by zero in the condition expression); it
38072 The trace stopped for some other reason.
38076 Additional optional fields supply statistical and other information.
38077 Although not required, they are extremely useful for users monitoring
38078 the progress of a trace run. If a trace has stopped, and these
38079 numbers are reported, they must reflect the state of the just-stopped
38084 @item tframes:@var{n}
38085 The number of trace frames in the buffer.
38087 @item tcreated:@var{n}
38088 The total number of trace frames created during the run. This may
38089 be larger than the trace frame count, if the buffer is circular.
38091 @item tsize:@var{n}
38092 The total size of the trace buffer, in bytes.
38094 @item tfree:@var{n}
38095 The number of bytes still unused in the buffer.
38097 @item circular:@var{n}
38098 The value of the circular trace buffer flag. @code{1} means that the
38099 trace buffer is circular and old trace frames will be discarded if
38100 necessary to make room, @code{0} means that the trace buffer is linear
38103 @item disconn:@var{n}
38104 The value of the disconnected tracing flag. @code{1} means that
38105 tracing will continue after @value{GDBN} disconnects, @code{0} means
38106 that the trace run will stop.
38110 @item qTP:@var{tp}:@var{addr}
38111 @cindex tracepoint status, remote request
38112 @cindex @samp{qTP} packet
38113 Ask the stub for the current state of tracepoint number @var{tp} at
38114 address @var{addr}.
38118 @item V@var{hits}:@var{usage}
38119 The tracepoint has been hit @var{hits} times so far during the trace
38120 run, and accounts for @var{usage} in the trace buffer. Note that
38121 @code{while-stepping} steps are not counted as separate hits, but the
38122 steps' space consumption is added into the usage number.
38126 @item qTV:@var{var}
38127 @cindex trace state variable value, remote request
38128 @cindex @samp{qTV} packet
38129 Ask the stub for the value of the trace state variable number @var{var}.
38134 The value of the variable is @var{value}. This will be the current
38135 value of the variable if the user is examining a running target, or a
38136 saved value if the variable was collected in the trace frame that the
38137 user is looking at. Note that multiple requests may result in
38138 different reply values, such as when requesting values while the
38139 program is running.
38142 The value of the variable is unknown. This would occur, for example,
38143 if the user is examining a trace frame in which the requested variable
38148 @cindex @samp{qTfP} packet
38150 @cindex @samp{qTsP} packet
38151 These packets request data about tracepoints that are being used by
38152 the target. @value{GDBN} sends @code{qTfP} to get the first piece
38153 of data, and multiple @code{qTsP} to get additional pieces. Replies
38154 to these packets generally take the form of the @code{QTDP} packets
38155 that define tracepoints. (FIXME add detailed syntax)
38158 @cindex @samp{qTfV} packet
38160 @cindex @samp{qTsV} packet
38161 These packets request data about trace state variables that are on the
38162 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
38163 and multiple @code{qTsV} to get additional variables. Replies to
38164 these packets follow the syntax of the @code{QTDV} packets that define
38165 trace state variables.
38171 @cindex @samp{qTfSTM} packet
38172 @cindex @samp{qTsSTM} packet
38173 These packets request data about static tracepoint markers that exist
38174 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
38175 first piece of data, and multiple @code{qTsSTM} to get additional
38176 pieces. Replies to these packets take the following form:
38180 @item m @var{address}:@var{id}:@var{extra}
38182 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
38183 a comma-separated list of markers
38185 (lower case letter @samp{L}) denotes end of list.
38187 An error occurred. The error number @var{nn} is given as hex digits.
38189 An empty reply indicates that the request is not supported by the
38193 The @var{address} is encoded in hex;
38194 @var{id} and @var{extra} are strings encoded in hex.
38196 In response to each query, the target will reply with a list of one or
38197 more markers, separated by commas. @value{GDBN} will respond to each
38198 reply with a request for more markers (using the @samp{qs} form of the
38199 query), until the target responds with @samp{l} (lower-case ell, for
38202 @item qTSTMat:@var{address}
38204 @cindex @samp{qTSTMat} packet
38205 This packets requests data about static tracepoint markers in the
38206 target program at @var{address}. Replies to this packet follow the
38207 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
38208 tracepoint markers.
38210 @item QTSave:@var{filename}
38211 @cindex @samp{QTSave} packet
38212 This packet directs the target to save trace data to the file name
38213 @var{filename} in the target's filesystem. The @var{filename} is encoded
38214 as a hex string; the interpretation of the file name (relative vs
38215 absolute, wild cards, etc) is up to the target.
38217 @item qTBuffer:@var{offset},@var{len}
38218 @cindex @samp{qTBuffer} packet
38219 Return up to @var{len} bytes of the current contents of trace buffer,
38220 starting at @var{offset}. The trace buffer is treated as if it were
38221 a contiguous collection of traceframes, as per the trace file format.
38222 The reply consists as many hex-encoded bytes as the target can deliver
38223 in a packet; it is not an error to return fewer than were asked for.
38224 A reply consisting of just @code{l} indicates that no bytes are
38227 @item QTBuffer:circular:@var{value}
38228 This packet directs the target to use a circular trace buffer if
38229 @var{value} is 1, or a linear buffer if the value is 0.
38231 @item QTBuffer:size:@var{size}
38232 @anchor{QTBuffer-size}
38233 @cindex @samp{QTBuffer size} packet
38234 This packet directs the target to make the trace buffer be of size
38235 @var{size} if possible. A value of @code{-1} tells the target to
38236 use whatever size it prefers.
38238 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
38239 @cindex @samp{QTNotes} packet
38240 This packet adds optional textual notes to the trace run. Allowable
38241 types include @code{user}, @code{notes}, and @code{tstop}, the
38242 @var{text} fields are arbitrary strings, hex-encoded.
38246 @subsection Relocate instruction reply packet
38247 When installing fast tracepoints in memory, the target may need to
38248 relocate the instruction currently at the tracepoint address to a
38249 different address in memory. For most instructions, a simple copy is
38250 enough, but, for example, call instructions that implicitly push the
38251 return address on the stack, and relative branches or other
38252 PC-relative instructions require offset adjustment, so that the effect
38253 of executing the instruction at a different address is the same as if
38254 it had executed in the original location.
38256 In response to several of the tracepoint packets, the target may also
38257 respond with a number of intermediate @samp{qRelocInsn} request
38258 packets before the final result packet, to have @value{GDBN} handle
38259 this relocation operation. If a packet supports this mechanism, its
38260 documentation will explicitly say so. See for example the above
38261 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
38262 format of the request is:
38265 @item qRelocInsn:@var{from};@var{to}
38267 This requests @value{GDBN} to copy instruction at address @var{from}
38268 to address @var{to}, possibly adjusted so that executing the
38269 instruction at @var{to} has the same effect as executing it at
38270 @var{from}. @value{GDBN} writes the adjusted instruction to target
38271 memory starting at @var{to}.
38276 @item qRelocInsn:@var{adjusted_size}
38277 Informs the stub the relocation is complete. The @var{adjusted_size} is
38278 the length in bytes of resulting relocated instruction sequence.
38280 A badly formed request was detected, or an error was encountered while
38281 relocating the instruction.
38284 @node Host I/O Packets
38285 @section Host I/O Packets
38286 @cindex Host I/O, remote protocol
38287 @cindex file transfer, remote protocol
38289 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
38290 operations on the far side of a remote link. For example, Host I/O is
38291 used to upload and download files to a remote target with its own
38292 filesystem. Host I/O uses the same constant values and data structure
38293 layout as the target-initiated File-I/O protocol. However, the
38294 Host I/O packets are structured differently. The target-initiated
38295 protocol relies on target memory to store parameters and buffers.
38296 Host I/O requests are initiated by @value{GDBN}, and the
38297 target's memory is not involved. @xref{File-I/O Remote Protocol
38298 Extension}, for more details on the target-initiated protocol.
38300 The Host I/O request packets all encode a single operation along with
38301 its arguments. They have this format:
38305 @item vFile:@var{operation}: @var{parameter}@dots{}
38306 @var{operation} is the name of the particular request; the target
38307 should compare the entire packet name up to the second colon when checking
38308 for a supported operation. The format of @var{parameter} depends on
38309 the operation. Numbers are always passed in hexadecimal. Negative
38310 numbers have an explicit minus sign (i.e.@: two's complement is not
38311 used). Strings (e.g.@: filenames) are encoded as a series of
38312 hexadecimal bytes. The last argument to a system call may be a
38313 buffer of escaped binary data (@pxref{Binary Data}).
38317 The valid responses to Host I/O packets are:
38321 @item F @var{result} [, @var{errno}] [; @var{attachment}]
38322 @var{result} is the integer value returned by this operation, usually
38323 non-negative for success and -1 for errors. If an error has occured,
38324 @var{errno} will be included in the result specifying a
38325 value defined by the File-I/O protocol (@pxref{Errno Values}). For
38326 operations which return data, @var{attachment} supplies the data as a
38327 binary buffer. Binary buffers in response packets are escaped in the
38328 normal way (@pxref{Binary Data}). See the individual packet
38329 documentation for the interpretation of @var{result} and
38333 An empty response indicates that this operation is not recognized.
38337 These are the supported Host I/O operations:
38340 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
38341 Open a file at @var{filename} and return a file descriptor for it, or
38342 return -1 if an error occurs. The @var{filename} is a string,
38343 @var{flags} is an integer indicating a mask of open flags
38344 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
38345 of mode bits to use if the file is created (@pxref{mode_t Values}).
38346 @xref{open}, for details of the open flags and mode values.
38348 @item vFile:close: @var{fd}
38349 Close the open file corresponding to @var{fd} and return 0, or
38350 -1 if an error occurs.
38352 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
38353 Read data from the open file corresponding to @var{fd}. Up to
38354 @var{count} bytes will be read from the file, starting at @var{offset}
38355 relative to the start of the file. The target may read fewer bytes;
38356 common reasons include packet size limits and an end-of-file
38357 condition. The number of bytes read is returned. Zero should only be
38358 returned for a successful read at the end of the file, or if
38359 @var{count} was zero.
38361 The data read should be returned as a binary attachment on success.
38362 If zero bytes were read, the response should include an empty binary
38363 attachment (i.e.@: a trailing semicolon). The return value is the
38364 number of target bytes read; the binary attachment may be longer if
38365 some characters were escaped.
38367 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
38368 Write @var{data} (a binary buffer) to the open file corresponding
38369 to @var{fd}. Start the write at @var{offset} from the start of the
38370 file. Unlike many @code{write} system calls, there is no
38371 separate @var{count} argument; the length of @var{data} in the
38372 packet is used. @samp{vFile:write} returns the number of bytes written,
38373 which may be shorter than the length of @var{data}, or -1 if an
38376 @item vFile:fstat: @var{fd}
38377 Get information about the open file corresponding to @var{fd}.
38378 On success the information is returned as a binary attachment
38379 and the return value is the size of this attachment in bytes.
38380 If an error occurs the return value is -1. The format of the
38381 returned binary attachment is as described in @ref{struct stat}.
38383 @item vFile:unlink: @var{filename}
38384 Delete the file at @var{filename} on the target. Return 0,
38385 or -1 if an error occurs. The @var{filename} is a string.
38387 @item vFile:readlink: @var{filename}
38388 Read value of symbolic link @var{filename} on the target. Return
38389 the number of bytes read, or -1 if an error occurs.
38391 The data read should be returned as a binary attachment on success.
38392 If zero bytes were read, the response should include an empty binary
38393 attachment (i.e.@: a trailing semicolon). The return value is the
38394 number of target bytes read; the binary attachment may be longer if
38395 some characters were escaped.
38397 @item vFile:setfs: @var{pid}
38398 Select the filesystem on which @code{vFile} operations with
38399 @var{filename} arguments will operate. This is required for
38400 @value{GDBN} to be able to access files on remote targets where
38401 the remote stub does not share a common filesystem with the
38404 If @var{pid} is nonzero, select the filesystem as seen by process
38405 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
38406 the remote stub. Return 0 on success, or -1 if an error occurs.
38407 If @code{vFile:setfs:} indicates success, the selected filesystem
38408 remains selected until the next successful @code{vFile:setfs:}
38414 @section Interrupts
38415 @cindex interrupts (remote protocol)
38416 @anchor{interrupting remote targets}
38418 In all-stop mode, when a program on the remote target is running,
38419 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
38420 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
38421 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
38423 The precise meaning of @code{BREAK} is defined by the transport
38424 mechanism and may, in fact, be undefined. @value{GDBN} does not
38425 currently define a @code{BREAK} mechanism for any of the network
38426 interfaces except for TCP, in which case @value{GDBN} sends the
38427 @code{telnet} BREAK sequence.
38429 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
38430 transport mechanisms. It is represented by sending the single byte
38431 @code{0x03} without any of the usual packet overhead described in
38432 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
38433 transmitted as part of a packet, it is considered to be packet data
38434 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
38435 (@pxref{X packet}), used for binary downloads, may include an unescaped
38436 @code{0x03} as part of its packet.
38438 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
38439 When Linux kernel receives this sequence from serial port,
38440 it stops execution and connects to gdb.
38442 In non-stop mode, because packet resumptions are asynchronous
38443 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
38444 command to the remote stub, even when the target is running. For that
38445 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
38446 packet}) with the usual packet framing instead of the single byte
38449 Stubs are not required to recognize these interrupt mechanisms and the
38450 precise meaning associated with receipt of the interrupt is
38451 implementation defined. If the target supports debugging of multiple
38452 threads and/or processes, it should attempt to interrupt all
38453 currently-executing threads and processes.
38454 If the stub is successful at interrupting the
38455 running program, it should send one of the stop
38456 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
38457 of successfully stopping the program in all-stop mode, and a stop reply
38458 for each stopped thread in non-stop mode.
38459 Interrupts received while the
38460 program is stopped are queued and the program will be interrupted when
38461 it is resumed next time.
38463 @node Notification Packets
38464 @section Notification Packets
38465 @cindex notification packets
38466 @cindex packets, notification
38468 The @value{GDBN} remote serial protocol includes @dfn{notifications},
38469 packets that require no acknowledgment. Both the GDB and the stub
38470 may send notifications (although the only notifications defined at
38471 present are sent by the stub). Notifications carry information
38472 without incurring the round-trip latency of an acknowledgment, and so
38473 are useful for low-impact communications where occasional packet loss
38476 A notification packet has the form @samp{% @var{data} #
38477 @var{checksum}}, where @var{data} is the content of the notification,
38478 and @var{checksum} is a checksum of @var{data}, computed and formatted
38479 as for ordinary @value{GDBN} packets. A notification's @var{data}
38480 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
38481 receiving a notification, the recipient sends no @samp{+} or @samp{-}
38482 to acknowledge the notification's receipt or to report its corruption.
38484 Every notification's @var{data} begins with a name, which contains no
38485 colon characters, followed by a colon character.
38487 Recipients should silently ignore corrupted notifications and
38488 notifications they do not understand. Recipients should restart
38489 timeout periods on receipt of a well-formed notification, whether or
38490 not they understand it.
38492 Senders should only send the notifications described here when this
38493 protocol description specifies that they are permitted. In the
38494 future, we may extend the protocol to permit existing notifications in
38495 new contexts; this rule helps older senders avoid confusing newer
38498 (Older versions of @value{GDBN} ignore bytes received until they see
38499 the @samp{$} byte that begins an ordinary packet, so new stubs may
38500 transmit notifications without fear of confusing older clients. There
38501 are no notifications defined for @value{GDBN} to send at the moment, but we
38502 assume that most older stubs would ignore them, as well.)
38504 Each notification is comprised of three parts:
38506 @item @var{name}:@var{event}
38507 The notification packet is sent by the side that initiates the
38508 exchange (currently, only the stub does that), with @var{event}
38509 carrying the specific information about the notification, and
38510 @var{name} specifying the name of the notification.
38512 The acknowledge sent by the other side, usually @value{GDBN}, to
38513 acknowledge the exchange and request the event.
38516 The purpose of an asynchronous notification mechanism is to report to
38517 @value{GDBN} that something interesting happened in the remote stub.
38519 The remote stub may send notification @var{name}:@var{event}
38520 at any time, but @value{GDBN} acknowledges the notification when
38521 appropriate. The notification event is pending before @value{GDBN}
38522 acknowledges. Only one notification at a time may be pending; if
38523 additional events occur before @value{GDBN} has acknowledged the
38524 previous notification, they must be queued by the stub for later
38525 synchronous transmission in response to @var{ack} packets from
38526 @value{GDBN}. Because the notification mechanism is unreliable,
38527 the stub is permitted to resend a notification if it believes
38528 @value{GDBN} may not have received it.
38530 Specifically, notifications may appear when @value{GDBN} is not
38531 otherwise reading input from the stub, or when @value{GDBN} is
38532 expecting to read a normal synchronous response or a
38533 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
38534 Notification packets are distinct from any other communication from
38535 the stub so there is no ambiguity.
38537 After receiving a notification, @value{GDBN} shall acknowledge it by
38538 sending a @var{ack} packet as a regular, synchronous request to the
38539 stub. Such acknowledgment is not required to happen immediately, as
38540 @value{GDBN} is permitted to send other, unrelated packets to the
38541 stub first, which the stub should process normally.
38543 Upon receiving a @var{ack} packet, if the stub has other queued
38544 events to report to @value{GDBN}, it shall respond by sending a
38545 normal @var{event}. @value{GDBN} shall then send another @var{ack}
38546 packet to solicit further responses; again, it is permitted to send
38547 other, unrelated packets as well which the stub should process
38550 If the stub receives a @var{ack} packet and there are no additional
38551 @var{event} to report, the stub shall return an @samp{OK} response.
38552 At this point, @value{GDBN} has finished processing a notification
38553 and the stub has completed sending any queued events. @value{GDBN}
38554 won't accept any new notifications until the final @samp{OK} is
38555 received . If further notification events occur, the stub shall send
38556 a new notification, @value{GDBN} shall accept the notification, and
38557 the process shall be repeated.
38559 The process of asynchronous notification can be illustrated by the
38562 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
38565 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
38567 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
38572 The following notifications are defined:
38573 @multitable @columnfractions 0.12 0.12 0.38 0.38
38582 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
38583 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
38584 for information on how these notifications are acknowledged by
38586 @tab Report an asynchronous stop event in non-stop mode.
38590 @node Remote Non-Stop
38591 @section Remote Protocol Support for Non-Stop Mode
38593 @value{GDBN}'s remote protocol supports non-stop debugging of
38594 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
38595 supports non-stop mode, it should report that to @value{GDBN} by including
38596 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
38598 @value{GDBN} typically sends a @samp{QNonStop} packet only when
38599 establishing a new connection with the stub. Entering non-stop mode
38600 does not alter the state of any currently-running threads, but targets
38601 must stop all threads in any already-attached processes when entering
38602 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
38603 probe the target state after a mode change.
38605 In non-stop mode, when an attached process encounters an event that
38606 would otherwise be reported with a stop reply, it uses the
38607 asynchronous notification mechanism (@pxref{Notification Packets}) to
38608 inform @value{GDBN}. In contrast to all-stop mode, where all threads
38609 in all processes are stopped when a stop reply is sent, in non-stop
38610 mode only the thread reporting the stop event is stopped. That is,
38611 when reporting a @samp{S} or @samp{T} response to indicate completion
38612 of a step operation, hitting a breakpoint, or a fault, only the
38613 affected thread is stopped; any other still-running threads continue
38614 to run. When reporting a @samp{W} or @samp{X} response, all running
38615 threads belonging to other attached processes continue to run.
38617 In non-stop mode, the target shall respond to the @samp{?} packet as
38618 follows. First, any incomplete stop reply notification/@samp{vStopped}
38619 sequence in progress is abandoned. The target must begin a new
38620 sequence reporting stop events for all stopped threads, whether or not
38621 it has previously reported those events to @value{GDBN}. The first
38622 stop reply is sent as a synchronous reply to the @samp{?} packet, and
38623 subsequent stop replies are sent as responses to @samp{vStopped} packets
38624 using the mechanism described above. The target must not send
38625 asynchronous stop reply notifications until the sequence is complete.
38626 If all threads are running when the target receives the @samp{?} packet,
38627 or if the target is not attached to any process, it shall respond
38630 If the stub supports non-stop mode, it should also support the
38631 @samp{swbreak} stop reason if software breakpoints are supported, and
38632 the @samp{hwbreak} stop reason if hardware breakpoints are supported
38633 (@pxref{swbreak stop reason}). This is because given the asynchronous
38634 nature of non-stop mode, between the time a thread hits a breakpoint
38635 and the time the event is finally processed by @value{GDBN}, the
38636 breakpoint may have already been removed from the target. Due to
38637 this, @value{GDBN} needs to be able to tell whether a trap stop was
38638 caused by a delayed breakpoint event, which should be ignored, as
38639 opposed to a random trap signal, which should be reported to the user.
38640 Note the @samp{swbreak} feature implies that the target is responsible
38641 for adjusting the PC when a software breakpoint triggers, if
38642 necessary, such as on the x86 architecture.
38644 @node Packet Acknowledgment
38645 @section Packet Acknowledgment
38647 @cindex acknowledgment, for @value{GDBN} remote
38648 @cindex packet acknowledgment, for @value{GDBN} remote
38649 By default, when either the host or the target machine receives a packet,
38650 the first response expected is an acknowledgment: either @samp{+} (to indicate
38651 the package was received correctly) or @samp{-} (to request retransmission).
38652 This mechanism allows the @value{GDBN} remote protocol to operate over
38653 unreliable transport mechanisms, such as a serial line.
38655 In cases where the transport mechanism is itself reliable (such as a pipe or
38656 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
38657 It may be desirable to disable them in that case to reduce communication
38658 overhead, or for other reasons. This can be accomplished by means of the
38659 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
38661 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
38662 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
38663 and response format still includes the normal checksum, as described in
38664 @ref{Overview}, but the checksum may be ignored by the receiver.
38666 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
38667 no-acknowledgment mode, it should report that to @value{GDBN}
38668 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
38669 @pxref{qSupported}.
38670 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
38671 disabled via the @code{set remote noack-packet off} command
38672 (@pxref{Remote Configuration}),
38673 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
38674 Only then may the stub actually turn off packet acknowledgments.
38675 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
38676 response, which can be safely ignored by the stub.
38678 Note that @code{set remote noack-packet} command only affects negotiation
38679 between @value{GDBN} and the stub when subsequent connections are made;
38680 it does not affect the protocol acknowledgment state for any current
38682 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
38683 new connection is established,
38684 there is also no protocol request to re-enable the acknowledgments
38685 for the current connection, once disabled.
38690 Example sequence of a target being re-started. Notice how the restart
38691 does not get any direct output:
38696 @emph{target restarts}
38699 <- @code{T001:1234123412341234}
38703 Example sequence of a target being stepped by a single instruction:
38706 -> @code{G1445@dots{}}
38711 <- @code{T001:1234123412341234}
38715 <- @code{1455@dots{}}
38719 @node File-I/O Remote Protocol Extension
38720 @section File-I/O Remote Protocol Extension
38721 @cindex File-I/O remote protocol extension
38724 * File-I/O Overview::
38725 * Protocol Basics::
38726 * The F Request Packet::
38727 * The F Reply Packet::
38728 * The Ctrl-C Message::
38730 * List of Supported Calls::
38731 * Protocol-specific Representation of Datatypes::
38733 * File-I/O Examples::
38736 @node File-I/O Overview
38737 @subsection File-I/O Overview
38738 @cindex file-i/o overview
38740 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
38741 target to use the host's file system and console I/O to perform various
38742 system calls. System calls on the target system are translated into a
38743 remote protocol packet to the host system, which then performs the needed
38744 actions and returns a response packet to the target system.
38745 This simulates file system operations even on targets that lack file systems.
38747 The protocol is defined to be independent of both the host and target systems.
38748 It uses its own internal representation of datatypes and values. Both
38749 @value{GDBN} and the target's @value{GDBN} stub are responsible for
38750 translating the system-dependent value representations into the internal
38751 protocol representations when data is transmitted.
38753 The communication is synchronous. A system call is possible only when
38754 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
38755 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
38756 the target is stopped to allow deterministic access to the target's
38757 memory. Therefore File-I/O is not interruptible by target signals. On
38758 the other hand, it is possible to interrupt File-I/O by a user interrupt
38759 (@samp{Ctrl-C}) within @value{GDBN}.
38761 The target's request to perform a host system call does not finish
38762 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
38763 after finishing the system call, the target returns to continuing the
38764 previous activity (continue, step). No additional continue or step
38765 request from @value{GDBN} is required.
38768 (@value{GDBP}) continue
38769 <- target requests 'system call X'
38770 target is stopped, @value{GDBN} executes system call
38771 -> @value{GDBN} returns result
38772 ... target continues, @value{GDBN} returns to wait for the target
38773 <- target hits breakpoint and sends a Txx packet
38776 The protocol only supports I/O on the console and to regular files on
38777 the host file system. Character or block special devices, pipes,
38778 named pipes, sockets or any other communication method on the host
38779 system are not supported by this protocol.
38781 File I/O is not supported in non-stop mode.
38783 @node Protocol Basics
38784 @subsection Protocol Basics
38785 @cindex protocol basics, file-i/o
38787 The File-I/O protocol uses the @code{F} packet as the request as well
38788 as reply packet. Since a File-I/O system call can only occur when
38789 @value{GDBN} is waiting for a response from the continuing or stepping target,
38790 the File-I/O request is a reply that @value{GDBN} has to expect as a result
38791 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
38792 This @code{F} packet contains all information needed to allow @value{GDBN}
38793 to call the appropriate host system call:
38797 A unique identifier for the requested system call.
38800 All parameters to the system call. Pointers are given as addresses
38801 in the target memory address space. Pointers to strings are given as
38802 pointer/length pair. Numerical values are given as they are.
38803 Numerical control flags are given in a protocol-specific representation.
38807 At this point, @value{GDBN} has to perform the following actions.
38811 If the parameters include pointer values to data needed as input to a
38812 system call, @value{GDBN} requests this data from the target with a
38813 standard @code{m} packet request. This additional communication has to be
38814 expected by the target implementation and is handled as any other @code{m}
38818 @value{GDBN} translates all value from protocol representation to host
38819 representation as needed. Datatypes are coerced into the host types.
38822 @value{GDBN} calls the system call.
38825 It then coerces datatypes back to protocol representation.
38828 If the system call is expected to return data in buffer space specified
38829 by pointer parameters to the call, the data is transmitted to the
38830 target using a @code{M} or @code{X} packet. This packet has to be expected
38831 by the target implementation and is handled as any other @code{M} or @code{X}
38836 Eventually @value{GDBN} replies with another @code{F} packet which contains all
38837 necessary information for the target to continue. This at least contains
38844 @code{errno}, if has been changed by the system call.
38851 After having done the needed type and value coercion, the target continues
38852 the latest continue or step action.
38854 @node The F Request Packet
38855 @subsection The @code{F} Request Packet
38856 @cindex file-i/o request packet
38857 @cindex @code{F} request packet
38859 The @code{F} request packet has the following format:
38862 @item F@var{call-id},@var{parameter@dots{}}
38864 @var{call-id} is the identifier to indicate the host system call to be called.
38865 This is just the name of the function.
38867 @var{parameter@dots{}} are the parameters to the system call.
38868 Parameters are hexadecimal integer values, either the actual values in case
38869 of scalar datatypes, pointers to target buffer space in case of compound
38870 datatypes and unspecified memory areas, or pointer/length pairs in case
38871 of string parameters. These are appended to the @var{call-id} as a
38872 comma-delimited list. All values are transmitted in ASCII
38873 string representation, pointer/length pairs separated by a slash.
38879 @node The F Reply Packet
38880 @subsection The @code{F} Reply Packet
38881 @cindex file-i/o reply packet
38882 @cindex @code{F} reply packet
38884 The @code{F} reply packet has the following format:
38888 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
38890 @var{retcode} is the return code of the system call as hexadecimal value.
38892 @var{errno} is the @code{errno} set by the call, in protocol-specific
38894 This parameter can be omitted if the call was successful.
38896 @var{Ctrl-C flag} is only sent if the user requested a break. In this
38897 case, @var{errno} must be sent as well, even if the call was successful.
38898 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
38905 or, if the call was interrupted before the host call has been performed:
38912 assuming 4 is the protocol-specific representation of @code{EINTR}.
38917 @node The Ctrl-C Message
38918 @subsection The @samp{Ctrl-C} Message
38919 @cindex ctrl-c message, in file-i/o protocol
38921 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
38922 reply packet (@pxref{The F Reply Packet}),
38923 the target should behave as if it had
38924 gotten a break message. The meaning for the target is ``system call
38925 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
38926 (as with a break message) and return to @value{GDBN} with a @code{T02}
38929 It's important for the target to know in which
38930 state the system call was interrupted. There are two possible cases:
38934 The system call hasn't been performed on the host yet.
38937 The system call on the host has been finished.
38941 These two states can be distinguished by the target by the value of the
38942 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
38943 call hasn't been performed. This is equivalent to the @code{EINTR} handling
38944 on POSIX systems. In any other case, the target may presume that the
38945 system call has been finished --- successfully or not --- and should behave
38946 as if the break message arrived right after the system call.
38948 @value{GDBN} must behave reliably. If the system call has not been called
38949 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
38950 @code{errno} in the packet. If the system call on the host has been finished
38951 before the user requests a break, the full action must be finished by
38952 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
38953 The @code{F} packet may only be sent when either nothing has happened
38954 or the full action has been completed.
38957 @subsection Console I/O
38958 @cindex console i/o as part of file-i/o
38960 By default and if not explicitly closed by the target system, the file
38961 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
38962 on the @value{GDBN} console is handled as any other file output operation
38963 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
38964 by @value{GDBN} so that after the target read request from file descriptor
38965 0 all following typing is buffered until either one of the following
38970 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
38972 system call is treated as finished.
38975 The user presses @key{RET}. This is treated as end of input with a trailing
38979 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
38980 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
38984 If the user has typed more characters than fit in the buffer given to
38985 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
38986 either another @code{read(0, @dots{})} is requested by the target, or debugging
38987 is stopped at the user's request.
38990 @node List of Supported Calls
38991 @subsection List of Supported Calls
38992 @cindex list of supported file-i/o calls
39009 @unnumberedsubsubsec open
39010 @cindex open, file-i/o system call
39015 int open(const char *pathname, int flags);
39016 int open(const char *pathname, int flags, mode_t mode);
39020 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
39023 @var{flags} is the bitwise @code{OR} of the following values:
39027 If the file does not exist it will be created. The host
39028 rules apply as far as file ownership and time stamps
39032 When used with @code{O_CREAT}, if the file already exists it is
39033 an error and open() fails.
39036 If the file already exists and the open mode allows
39037 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
39038 truncated to zero length.
39041 The file is opened in append mode.
39044 The file is opened for reading only.
39047 The file is opened for writing only.
39050 The file is opened for reading and writing.
39054 Other bits are silently ignored.
39058 @var{mode} is the bitwise @code{OR} of the following values:
39062 User has read permission.
39065 User has write permission.
39068 Group has read permission.
39071 Group has write permission.
39074 Others have read permission.
39077 Others have write permission.
39081 Other bits are silently ignored.
39084 @item Return value:
39085 @code{open} returns the new file descriptor or -1 if an error
39092 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
39095 @var{pathname} refers to a directory.
39098 The requested access is not allowed.
39101 @var{pathname} was too long.
39104 A directory component in @var{pathname} does not exist.
39107 @var{pathname} refers to a device, pipe, named pipe or socket.
39110 @var{pathname} refers to a file on a read-only filesystem and
39111 write access was requested.
39114 @var{pathname} is an invalid pointer value.
39117 No space on device to create the file.
39120 The process already has the maximum number of files open.
39123 The limit on the total number of files open on the system
39127 The call was interrupted by the user.
39133 @unnumberedsubsubsec close
39134 @cindex close, file-i/o system call
39143 @samp{Fclose,@var{fd}}
39145 @item Return value:
39146 @code{close} returns zero on success, or -1 if an error occurred.
39152 @var{fd} isn't a valid open file descriptor.
39155 The call was interrupted by the user.
39161 @unnumberedsubsubsec read
39162 @cindex read, file-i/o system call
39167 int read(int fd, void *buf, unsigned int count);
39171 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
39173 @item Return value:
39174 On success, the number of bytes read is returned.
39175 Zero indicates end of file. If count is zero, read
39176 returns zero as well. On error, -1 is returned.
39182 @var{fd} is not a valid file descriptor or is not open for
39186 @var{bufptr} is an invalid pointer value.
39189 The call was interrupted by the user.
39195 @unnumberedsubsubsec write
39196 @cindex write, file-i/o system call
39201 int write(int fd, const void *buf, unsigned int count);
39205 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
39207 @item Return value:
39208 On success, the number of bytes written are returned.
39209 Zero indicates nothing was written. On error, -1
39216 @var{fd} is not a valid file descriptor or is not open for
39220 @var{bufptr} is an invalid pointer value.
39223 An attempt was made to write a file that exceeds the
39224 host-specific maximum file size allowed.
39227 No space on device to write the data.
39230 The call was interrupted by the user.
39236 @unnumberedsubsubsec lseek
39237 @cindex lseek, file-i/o system call
39242 long lseek (int fd, long offset, int flag);
39246 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
39248 @var{flag} is one of:
39252 The offset is set to @var{offset} bytes.
39255 The offset is set to its current location plus @var{offset}
39259 The offset is set to the size of the file plus @var{offset}
39263 @item Return value:
39264 On success, the resulting unsigned offset in bytes from
39265 the beginning of the file is returned. Otherwise, a
39266 value of -1 is returned.
39272 @var{fd} is not a valid open file descriptor.
39275 @var{fd} is associated with the @value{GDBN} console.
39278 @var{flag} is not a proper value.
39281 The call was interrupted by the user.
39287 @unnumberedsubsubsec rename
39288 @cindex rename, file-i/o system call
39293 int rename(const char *oldpath, const char *newpath);
39297 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
39299 @item Return value:
39300 On success, zero is returned. On error, -1 is returned.
39306 @var{newpath} is an existing directory, but @var{oldpath} is not a
39310 @var{newpath} is a non-empty directory.
39313 @var{oldpath} or @var{newpath} is a directory that is in use by some
39317 An attempt was made to make a directory a subdirectory
39321 A component used as a directory in @var{oldpath} or new
39322 path is not a directory. Or @var{oldpath} is a directory
39323 and @var{newpath} exists but is not a directory.
39326 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
39329 No access to the file or the path of the file.
39333 @var{oldpath} or @var{newpath} was too long.
39336 A directory component in @var{oldpath} or @var{newpath} does not exist.
39339 The file is on a read-only filesystem.
39342 The device containing the file has no room for the new
39346 The call was interrupted by the user.
39352 @unnumberedsubsubsec unlink
39353 @cindex unlink, file-i/o system call
39358 int unlink(const char *pathname);
39362 @samp{Funlink,@var{pathnameptr}/@var{len}}
39364 @item Return value:
39365 On success, zero is returned. On error, -1 is returned.
39371 No access to the file or the path of the file.
39374 The system does not allow unlinking of directories.
39377 The file @var{pathname} cannot be unlinked because it's
39378 being used by another process.
39381 @var{pathnameptr} is an invalid pointer value.
39384 @var{pathname} was too long.
39387 A directory component in @var{pathname} does not exist.
39390 A component of the path is not a directory.
39393 The file is on a read-only filesystem.
39396 The call was interrupted by the user.
39402 @unnumberedsubsubsec stat/fstat
39403 @cindex fstat, file-i/o system call
39404 @cindex stat, file-i/o system call
39409 int stat(const char *pathname, struct stat *buf);
39410 int fstat(int fd, struct stat *buf);
39414 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
39415 @samp{Ffstat,@var{fd},@var{bufptr}}
39417 @item Return value:
39418 On success, zero is returned. On error, -1 is returned.
39424 @var{fd} is not a valid open file.
39427 A directory component in @var{pathname} does not exist or the
39428 path is an empty string.
39431 A component of the path is not a directory.
39434 @var{pathnameptr} is an invalid pointer value.
39437 No access to the file or the path of the file.
39440 @var{pathname} was too long.
39443 The call was interrupted by the user.
39449 @unnumberedsubsubsec gettimeofday
39450 @cindex gettimeofday, file-i/o system call
39455 int gettimeofday(struct timeval *tv, void *tz);
39459 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
39461 @item Return value:
39462 On success, 0 is returned, -1 otherwise.
39468 @var{tz} is a non-NULL pointer.
39471 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
39477 @unnumberedsubsubsec isatty
39478 @cindex isatty, file-i/o system call
39483 int isatty(int fd);
39487 @samp{Fisatty,@var{fd}}
39489 @item Return value:
39490 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
39496 The call was interrupted by the user.
39501 Note that the @code{isatty} call is treated as a special case: it returns
39502 1 to the target if the file descriptor is attached
39503 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
39504 would require implementing @code{ioctl} and would be more complex than
39509 @unnumberedsubsubsec system
39510 @cindex system, file-i/o system call
39515 int system(const char *command);
39519 @samp{Fsystem,@var{commandptr}/@var{len}}
39521 @item Return value:
39522 If @var{len} is zero, the return value indicates whether a shell is
39523 available. A zero return value indicates a shell is not available.
39524 For non-zero @var{len}, the value returned is -1 on error and the
39525 return status of the command otherwise. Only the exit status of the
39526 command is returned, which is extracted from the host's @code{system}
39527 return value by calling @code{WEXITSTATUS(retval)}. In case
39528 @file{/bin/sh} could not be executed, 127 is returned.
39534 The call was interrupted by the user.
39539 @value{GDBN} takes over the full task of calling the necessary host calls
39540 to perform the @code{system} call. The return value of @code{system} on
39541 the host is simplified before it's returned
39542 to the target. Any termination signal information from the child process
39543 is discarded, and the return value consists
39544 entirely of the exit status of the called command.
39546 Due to security concerns, the @code{system} call is by default refused
39547 by @value{GDBN}. The user has to allow this call explicitly with the
39548 @code{set remote system-call-allowed 1} command.
39551 @item set remote system-call-allowed
39552 @kindex set remote system-call-allowed
39553 Control whether to allow the @code{system} calls in the File I/O
39554 protocol for the remote target. The default is zero (disabled).
39556 @item show remote system-call-allowed
39557 @kindex show remote system-call-allowed
39558 Show whether the @code{system} calls are allowed in the File I/O
39562 @node Protocol-specific Representation of Datatypes
39563 @subsection Protocol-specific Representation of Datatypes
39564 @cindex protocol-specific representation of datatypes, in file-i/o protocol
39567 * Integral Datatypes::
39569 * Memory Transfer::
39574 @node Integral Datatypes
39575 @unnumberedsubsubsec Integral Datatypes
39576 @cindex integral datatypes, in file-i/o protocol
39578 The integral datatypes used in the system calls are @code{int},
39579 @code{unsigned int}, @code{long}, @code{unsigned long},
39580 @code{mode_t}, and @code{time_t}.
39582 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
39583 implemented as 32 bit values in this protocol.
39585 @code{long} and @code{unsigned long} are implemented as 64 bit types.
39587 @xref{Limits}, for corresponding MIN and MAX values (similar to those
39588 in @file{limits.h}) to allow range checking on host and target.
39590 @code{time_t} datatypes are defined as seconds since the Epoch.
39592 All integral datatypes transferred as part of a memory read or write of a
39593 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
39596 @node Pointer Values
39597 @unnumberedsubsubsec Pointer Values
39598 @cindex pointer values, in file-i/o protocol
39600 Pointers to target data are transmitted as they are. An exception
39601 is made for pointers to buffers for which the length isn't
39602 transmitted as part of the function call, namely strings. Strings
39603 are transmitted as a pointer/length pair, both as hex values, e.g.@:
39610 which is a pointer to data of length 18 bytes at position 0x1aaf.
39611 The length is defined as the full string length in bytes, including
39612 the trailing null byte. For example, the string @code{"hello world"}
39613 at address 0x123456 is transmitted as
39619 @node Memory Transfer
39620 @unnumberedsubsubsec Memory Transfer
39621 @cindex memory transfer, in file-i/o protocol
39623 Structured data which is transferred using a memory read or write (for
39624 example, a @code{struct stat}) is expected to be in a protocol-specific format
39625 with all scalar multibyte datatypes being big endian. Translation to
39626 this representation needs to be done both by the target before the @code{F}
39627 packet is sent, and by @value{GDBN} before
39628 it transfers memory to the target. Transferred pointers to structured
39629 data should point to the already-coerced data at any time.
39633 @unnumberedsubsubsec struct stat
39634 @cindex struct stat, in file-i/o protocol
39636 The buffer of type @code{struct stat} used by the target and @value{GDBN}
39637 is defined as follows:
39641 unsigned int st_dev; /* device */
39642 unsigned int st_ino; /* inode */
39643 mode_t st_mode; /* protection */
39644 unsigned int st_nlink; /* number of hard links */
39645 unsigned int st_uid; /* user ID of owner */
39646 unsigned int st_gid; /* group ID of owner */
39647 unsigned int st_rdev; /* device type (if inode device) */
39648 unsigned long st_size; /* total size, in bytes */
39649 unsigned long st_blksize; /* blocksize for filesystem I/O */
39650 unsigned long st_blocks; /* number of blocks allocated */
39651 time_t st_atime; /* time of last access */
39652 time_t st_mtime; /* time of last modification */
39653 time_t st_ctime; /* time of last change */
39657 The integral datatypes conform to the definitions given in the
39658 appropriate section (see @ref{Integral Datatypes}, for details) so this
39659 structure is of size 64 bytes.
39661 The values of several fields have a restricted meaning and/or
39667 A value of 0 represents a file, 1 the console.
39670 No valid meaning for the target. Transmitted unchanged.
39673 Valid mode bits are described in @ref{Constants}. Any other
39674 bits have currently no meaning for the target.
39679 No valid meaning for the target. Transmitted unchanged.
39684 These values have a host and file system dependent
39685 accuracy. Especially on Windows hosts, the file system may not
39686 support exact timing values.
39689 The target gets a @code{struct stat} of the above representation and is
39690 responsible for coercing it to the target representation before
39693 Note that due to size differences between the host, target, and protocol
39694 representations of @code{struct stat} members, these members could eventually
39695 get truncated on the target.
39697 @node struct timeval
39698 @unnumberedsubsubsec struct timeval
39699 @cindex struct timeval, in file-i/o protocol
39701 The buffer of type @code{struct timeval} used by the File-I/O protocol
39702 is defined as follows:
39706 time_t tv_sec; /* second */
39707 long tv_usec; /* microsecond */
39711 The integral datatypes conform to the definitions given in the
39712 appropriate section (see @ref{Integral Datatypes}, for details) so this
39713 structure is of size 8 bytes.
39716 @subsection Constants
39717 @cindex constants, in file-i/o protocol
39719 The following values are used for the constants inside of the
39720 protocol. @value{GDBN} and target are responsible for translating these
39721 values before and after the call as needed.
39732 @unnumberedsubsubsec Open Flags
39733 @cindex open flags, in file-i/o protocol
39735 All values are given in hexadecimal representation.
39747 @node mode_t Values
39748 @unnumberedsubsubsec mode_t Values
39749 @cindex mode_t values, in file-i/o protocol
39751 All values are given in octal representation.
39768 @unnumberedsubsubsec Errno Values
39769 @cindex errno values, in file-i/o protocol
39771 All values are given in decimal representation.
39796 @code{EUNKNOWN} is used as a fallback error value if a host system returns
39797 any error value not in the list of supported error numbers.
39800 @unnumberedsubsubsec Lseek Flags
39801 @cindex lseek flags, in file-i/o protocol
39810 @unnumberedsubsubsec Limits
39811 @cindex limits, in file-i/o protocol
39813 All values are given in decimal representation.
39816 INT_MIN -2147483648
39818 UINT_MAX 4294967295
39819 LONG_MIN -9223372036854775808
39820 LONG_MAX 9223372036854775807
39821 ULONG_MAX 18446744073709551615
39824 @node File-I/O Examples
39825 @subsection File-I/O Examples
39826 @cindex file-i/o examples
39828 Example sequence of a write call, file descriptor 3, buffer is at target
39829 address 0x1234, 6 bytes should be written:
39832 <- @code{Fwrite,3,1234,6}
39833 @emph{request memory read from target}
39836 @emph{return "6 bytes written"}
39840 Example sequence of a read call, file descriptor 3, buffer is at target
39841 address 0x1234, 6 bytes should be read:
39844 <- @code{Fread,3,1234,6}
39845 @emph{request memory write to target}
39846 -> @code{X1234,6:XXXXXX}
39847 @emph{return "6 bytes read"}
39851 Example sequence of a read call, call fails on the host due to invalid
39852 file descriptor (@code{EBADF}):
39855 <- @code{Fread,3,1234,6}
39859 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
39863 <- @code{Fread,3,1234,6}
39868 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
39872 <- @code{Fread,3,1234,6}
39873 -> @code{X1234,6:XXXXXX}
39877 @node Library List Format
39878 @section Library List Format
39879 @cindex library list format, remote protocol
39881 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
39882 same process as your application to manage libraries. In this case,
39883 @value{GDBN} can use the loader's symbol table and normal memory
39884 operations to maintain a list of shared libraries. On other
39885 platforms, the operating system manages loaded libraries.
39886 @value{GDBN} can not retrieve the list of currently loaded libraries
39887 through memory operations, so it uses the @samp{qXfer:libraries:read}
39888 packet (@pxref{qXfer library list read}) instead. The remote stub
39889 queries the target's operating system and reports which libraries
39892 The @samp{qXfer:libraries:read} packet returns an XML document which
39893 lists loaded libraries and their offsets. Each library has an
39894 associated name and one or more segment or section base addresses,
39895 which report where the library was loaded in memory.
39897 For the common case of libraries that are fully linked binaries, the
39898 library should have a list of segments. If the target supports
39899 dynamic linking of a relocatable object file, its library XML element
39900 should instead include a list of allocated sections. The segment or
39901 section bases are start addresses, not relocation offsets; they do not
39902 depend on the library's link-time base addresses.
39904 @value{GDBN} must be linked with the Expat library to support XML
39905 library lists. @xref{Expat}.
39907 A simple memory map, with one loaded library relocated by a single
39908 offset, looks like this:
39912 <library name="/lib/libc.so.6">
39913 <segment address="0x10000000"/>
39918 Another simple memory map, with one loaded library with three
39919 allocated sections (.text, .data, .bss), looks like this:
39923 <library name="sharedlib.o">
39924 <section address="0x10000000"/>
39925 <section address="0x20000000"/>
39926 <section address="0x30000000"/>
39931 The format of a library list is described by this DTD:
39934 <!-- library-list: Root element with versioning -->
39935 <!ELEMENT library-list (library)*>
39936 <!ATTLIST library-list version CDATA #FIXED "1.0">
39937 <!ELEMENT library (segment*, section*)>
39938 <!ATTLIST library name CDATA #REQUIRED>
39939 <!ELEMENT segment EMPTY>
39940 <!ATTLIST segment address CDATA #REQUIRED>
39941 <!ELEMENT section EMPTY>
39942 <!ATTLIST section address CDATA #REQUIRED>
39945 In addition, segments and section descriptors cannot be mixed within a
39946 single library element, and you must supply at least one segment or
39947 section for each library.
39949 @node Library List Format for SVR4 Targets
39950 @section Library List Format for SVR4 Targets
39951 @cindex library list format, remote protocol
39953 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
39954 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
39955 shared libraries. Still a special library list provided by this packet is
39956 more efficient for the @value{GDBN} remote protocol.
39958 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
39959 loaded libraries and their SVR4 linker parameters. For each library on SVR4
39960 target, the following parameters are reported:
39964 @code{name}, the absolute file name from the @code{l_name} field of
39965 @code{struct link_map}.
39967 @code{lm} with address of @code{struct link_map} used for TLS
39968 (Thread Local Storage) access.
39970 @code{l_addr}, the displacement as read from the field @code{l_addr} of
39971 @code{struct link_map}. For prelinked libraries this is not an absolute
39972 memory address. It is a displacement of absolute memory address against
39973 address the file was prelinked to during the library load.
39975 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
39978 Additionally the single @code{main-lm} attribute specifies address of
39979 @code{struct link_map} used for the main executable. This parameter is used
39980 for TLS access and its presence is optional.
39982 @value{GDBN} must be linked with the Expat library to support XML
39983 SVR4 library lists. @xref{Expat}.
39985 A simple memory map, with two loaded libraries (which do not use prelink),
39989 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
39990 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
39992 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
39994 </library-list-svr>
39997 The format of an SVR4 library list is described by this DTD:
40000 <!-- library-list-svr4: Root element with versioning -->
40001 <!ELEMENT library-list-svr4 (library)*>
40002 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
40003 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
40004 <!ELEMENT library EMPTY>
40005 <!ATTLIST library name CDATA #REQUIRED>
40006 <!ATTLIST library lm CDATA #REQUIRED>
40007 <!ATTLIST library l_addr CDATA #REQUIRED>
40008 <!ATTLIST library l_ld CDATA #REQUIRED>
40011 @node Memory Map Format
40012 @section Memory Map Format
40013 @cindex memory map format
40015 To be able to write into flash memory, @value{GDBN} needs to obtain a
40016 memory map from the target. This section describes the format of the
40019 The memory map is obtained using the @samp{qXfer:memory-map:read}
40020 (@pxref{qXfer memory map read}) packet and is an XML document that
40021 lists memory regions.
40023 @value{GDBN} must be linked with the Expat library to support XML
40024 memory maps. @xref{Expat}.
40026 The top-level structure of the document is shown below:
40029 <?xml version="1.0"?>
40030 <!DOCTYPE memory-map
40031 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40032 "http://sourceware.org/gdb/gdb-memory-map.dtd">
40038 Each region can be either:
40043 A region of RAM starting at @var{addr} and extending for @var{length}
40047 <memory type="ram" start="@var{addr}" length="@var{length}"/>
40052 A region of read-only memory:
40055 <memory type="rom" start="@var{addr}" length="@var{length}"/>
40060 A region of flash memory, with erasure blocks @var{blocksize}
40064 <memory type="flash" start="@var{addr}" length="@var{length}">
40065 <property name="blocksize">@var{blocksize}</property>
40071 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
40072 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
40073 packets to write to addresses in such ranges.
40075 The formal DTD for memory map format is given below:
40078 <!-- ................................................... -->
40079 <!-- Memory Map XML DTD ................................ -->
40080 <!-- File: memory-map.dtd .............................. -->
40081 <!-- .................................... .............. -->
40082 <!-- memory-map.dtd -->
40083 <!-- memory-map: Root element with versioning -->
40084 <!ELEMENT memory-map (memory | property)>
40085 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
40086 <!ELEMENT memory (property)>
40087 <!-- memory: Specifies a memory region,
40088 and its type, or device. -->
40089 <!ATTLIST memory type CDATA #REQUIRED
40090 start CDATA #REQUIRED
40091 length CDATA #REQUIRED
40092 device CDATA #IMPLIED>
40093 <!-- property: Generic attribute tag -->
40094 <!ELEMENT property (#PCDATA | property)*>
40095 <!ATTLIST property name CDATA #REQUIRED>
40098 @node Thread List Format
40099 @section Thread List Format
40100 @cindex thread list format
40102 To efficiently update the list of threads and their attributes,
40103 @value{GDBN} issues the @samp{qXfer:threads:read} packet
40104 (@pxref{qXfer threads read}) and obtains the XML document with
40105 the following structure:
40108 <?xml version="1.0"?>
40110 <thread id="id" core="0" name="name">
40111 ... description ...
40116 Each @samp{thread} element must have the @samp{id} attribute that
40117 identifies the thread (@pxref{thread-id syntax}). The
40118 @samp{core} attribute, if present, specifies which processor core
40119 the thread was last executing on. The @samp{name} attribute, if
40120 present, specifies the human-readable name of the thread. The content
40121 of the of @samp{thread} element is interpreted as human-readable
40122 auxiliary information.
40124 @node Traceframe Info Format
40125 @section Traceframe Info Format
40126 @cindex traceframe info format
40128 To be able to know which objects in the inferior can be examined when
40129 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
40130 memory ranges, registers and trace state variables that have been
40131 collected in a traceframe.
40133 This list is obtained using the @samp{qXfer:traceframe-info:read}
40134 (@pxref{qXfer traceframe info read}) packet and is an XML document.
40136 @value{GDBN} must be linked with the Expat library to support XML
40137 traceframe info discovery. @xref{Expat}.
40139 The top-level structure of the document is shown below:
40142 <?xml version="1.0"?>
40143 <!DOCTYPE traceframe-info
40144 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40145 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
40151 Each traceframe block can be either:
40156 A region of collected memory starting at @var{addr} and extending for
40157 @var{length} bytes from there:
40160 <memory start="@var{addr}" length="@var{length}"/>
40164 A block indicating trace state variable numbered @var{number} has been
40168 <tvar id="@var{number}"/>
40173 The formal DTD for the traceframe info format is given below:
40176 <!ELEMENT traceframe-info (memory | tvar)* >
40177 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
40179 <!ELEMENT memory EMPTY>
40180 <!ATTLIST memory start CDATA #REQUIRED
40181 length CDATA #REQUIRED>
40183 <!ATTLIST tvar id CDATA #REQUIRED>
40186 @node Branch Trace Format
40187 @section Branch Trace Format
40188 @cindex branch trace format
40190 In order to display the branch trace of an inferior thread,
40191 @value{GDBN} needs to obtain the list of branches. This list is
40192 represented as list of sequential code blocks that are connected via
40193 branches. The code in each block has been executed sequentially.
40195 This list is obtained using the @samp{qXfer:btrace:read}
40196 (@pxref{qXfer btrace read}) packet and is an XML document.
40198 @value{GDBN} must be linked with the Expat library to support XML
40199 traceframe info discovery. @xref{Expat}.
40201 The top-level structure of the document is shown below:
40204 <?xml version="1.0"?>
40206 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
40207 "http://sourceware.org/gdb/gdb-btrace.dtd">
40216 A block of sequentially executed instructions starting at @var{begin}
40217 and ending at @var{end}:
40220 <block begin="@var{begin}" end="@var{end}"/>
40225 The formal DTD for the branch trace format is given below:
40228 <!ELEMENT btrace (block* | pt) >
40229 <!ATTLIST btrace version CDATA #FIXED "1.0">
40231 <!ELEMENT block EMPTY>
40232 <!ATTLIST block begin CDATA #REQUIRED
40233 end CDATA #REQUIRED>
40235 <!ELEMENT pt (pt-config?, raw?)>
40237 <!ELEMENT pt-config (cpu?)>
40239 <!ELEMENT cpu EMPTY>
40240 <!ATTLIST cpu vendor CDATA #REQUIRED
40241 family CDATA #REQUIRED
40242 model CDATA #REQUIRED
40243 stepping CDATA #REQUIRED>
40245 <!ELEMENT raw (#PCDATA)>
40248 @node Branch Trace Configuration Format
40249 @section Branch Trace Configuration Format
40250 @cindex branch trace configuration format
40252 For each inferior thread, @value{GDBN} can obtain the branch trace
40253 configuration using the @samp{qXfer:btrace-conf:read}
40254 (@pxref{qXfer btrace-conf read}) packet.
40256 The configuration describes the branch trace format and configuration
40257 settings for that format. The following information is described:
40261 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
40264 The size of the @acronym{BTS} ring buffer in bytes.
40267 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
40271 The size of the @acronym{Intel PT} ring buffer in bytes.
40275 @value{GDBN} must be linked with the Expat library to support XML
40276 branch trace configuration discovery. @xref{Expat}.
40278 The formal DTD for the branch trace configuration format is given below:
40281 <!ELEMENT btrace-conf (bts?, pt?)>
40282 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
40284 <!ELEMENT bts EMPTY>
40285 <!ATTLIST bts size CDATA #IMPLIED>
40287 <!ELEMENT pt EMPTY>
40288 <!ATTLIST pt size CDATA #IMPLIED>
40291 @include agentexpr.texi
40293 @node Target Descriptions
40294 @appendix Target Descriptions
40295 @cindex target descriptions
40297 One of the challenges of using @value{GDBN} to debug embedded systems
40298 is that there are so many minor variants of each processor
40299 architecture in use. It is common practice for vendors to start with
40300 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
40301 and then make changes to adapt it to a particular market niche. Some
40302 architectures have hundreds of variants, available from dozens of
40303 vendors. This leads to a number of problems:
40307 With so many different customized processors, it is difficult for
40308 the @value{GDBN} maintainers to keep up with the changes.
40310 Since individual variants may have short lifetimes or limited
40311 audiences, it may not be worthwhile to carry information about every
40312 variant in the @value{GDBN} source tree.
40314 When @value{GDBN} does support the architecture of the embedded system
40315 at hand, the task of finding the correct architecture name to give the
40316 @command{set architecture} command can be error-prone.
40319 To address these problems, the @value{GDBN} remote protocol allows a
40320 target system to not only identify itself to @value{GDBN}, but to
40321 actually describe its own features. This lets @value{GDBN} support
40322 processor variants it has never seen before --- to the extent that the
40323 descriptions are accurate, and that @value{GDBN} understands them.
40325 @value{GDBN} must be linked with the Expat library to support XML
40326 target descriptions. @xref{Expat}.
40329 * Retrieving Descriptions:: How descriptions are fetched from a target.
40330 * Target Description Format:: The contents of a target description.
40331 * Predefined Target Types:: Standard types available for target
40333 * Standard Target Features:: Features @value{GDBN} knows about.
40336 @node Retrieving Descriptions
40337 @section Retrieving Descriptions
40339 Target descriptions can be read from the target automatically, or
40340 specified by the user manually. The default behavior is to read the
40341 description from the target. @value{GDBN} retrieves it via the remote
40342 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
40343 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
40344 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
40345 XML document, of the form described in @ref{Target Description
40348 Alternatively, you can specify a file to read for the target description.
40349 If a file is set, the target will not be queried. The commands to
40350 specify a file are:
40353 @cindex set tdesc filename
40354 @item set tdesc filename @var{path}
40355 Read the target description from @var{path}.
40357 @cindex unset tdesc filename
40358 @item unset tdesc filename
40359 Do not read the XML target description from a file. @value{GDBN}
40360 will use the description supplied by the current target.
40362 @cindex show tdesc filename
40363 @item show tdesc filename
40364 Show the filename to read for a target description, if any.
40368 @node Target Description Format
40369 @section Target Description Format
40370 @cindex target descriptions, XML format
40372 A target description annex is an @uref{http://www.w3.org/XML/, XML}
40373 document which complies with the Document Type Definition provided in
40374 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
40375 means you can use generally available tools like @command{xmllint} to
40376 check that your feature descriptions are well-formed and valid.
40377 However, to help people unfamiliar with XML write descriptions for
40378 their targets, we also describe the grammar here.
40380 Target descriptions can identify the architecture of the remote target
40381 and (for some architectures) provide information about custom register
40382 sets. They can also identify the OS ABI of the remote target.
40383 @value{GDBN} can use this information to autoconfigure for your
40384 target, or to warn you if you connect to an unsupported target.
40386 Here is a simple target description:
40389 <target version="1.0">
40390 <architecture>i386:x86-64</architecture>
40395 This minimal description only says that the target uses
40396 the x86-64 architecture.
40398 A target description has the following overall form, with [ ] marking
40399 optional elements and @dots{} marking repeatable elements. The elements
40400 are explained further below.
40403 <?xml version="1.0"?>
40404 <!DOCTYPE target SYSTEM "gdb-target.dtd">
40405 <target version="1.0">
40406 @r{[}@var{architecture}@r{]}
40407 @r{[}@var{osabi}@r{]}
40408 @r{[}@var{compatible}@r{]}
40409 @r{[}@var{feature}@dots{}@r{]}
40414 The description is generally insensitive to whitespace and line
40415 breaks, under the usual common-sense rules. The XML version
40416 declaration and document type declaration can generally be omitted
40417 (@value{GDBN} does not require them), but specifying them may be
40418 useful for XML validation tools. The @samp{version} attribute for
40419 @samp{<target>} may also be omitted, but we recommend
40420 including it; if future versions of @value{GDBN} use an incompatible
40421 revision of @file{gdb-target.dtd}, they will detect and report
40422 the version mismatch.
40424 @subsection Inclusion
40425 @cindex target descriptions, inclusion
40428 @cindex <xi:include>
40431 It can sometimes be valuable to split a target description up into
40432 several different annexes, either for organizational purposes, or to
40433 share files between different possible target descriptions. You can
40434 divide a description into multiple files by replacing any element of
40435 the target description with an inclusion directive of the form:
40438 <xi:include href="@var{document}"/>
40442 When @value{GDBN} encounters an element of this form, it will retrieve
40443 the named XML @var{document}, and replace the inclusion directive with
40444 the contents of that document. If the current description was read
40445 using @samp{qXfer}, then so will be the included document;
40446 @var{document} will be interpreted as the name of an annex. If the
40447 current description was read from a file, @value{GDBN} will look for
40448 @var{document} as a file in the same directory where it found the
40449 original description.
40451 @subsection Architecture
40452 @cindex <architecture>
40454 An @samp{<architecture>} element has this form:
40457 <architecture>@var{arch}</architecture>
40460 @var{arch} is one of the architectures from the set accepted by
40461 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40464 @cindex @code{<osabi>}
40466 This optional field was introduced in @value{GDBN} version 7.0.
40467 Previous versions of @value{GDBN} ignore it.
40469 An @samp{<osabi>} element has this form:
40472 <osabi>@var{abi-name}</osabi>
40475 @var{abi-name} is an OS ABI name from the same selection accepted by
40476 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
40478 @subsection Compatible Architecture
40479 @cindex @code{<compatible>}
40481 This optional field was introduced in @value{GDBN} version 7.0.
40482 Previous versions of @value{GDBN} ignore it.
40484 A @samp{<compatible>} element has this form:
40487 <compatible>@var{arch}</compatible>
40490 @var{arch} is one of the architectures from the set accepted by
40491 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40493 A @samp{<compatible>} element is used to specify that the target
40494 is able to run binaries in some other than the main target architecture
40495 given by the @samp{<architecture>} element. For example, on the
40496 Cell Broadband Engine, the main architecture is @code{powerpc:common}
40497 or @code{powerpc:common64}, but the system is able to run binaries
40498 in the @code{spu} architecture as well. The way to describe this
40499 capability with @samp{<compatible>} is as follows:
40502 <architecture>powerpc:common</architecture>
40503 <compatible>spu</compatible>
40506 @subsection Features
40509 Each @samp{<feature>} describes some logical portion of the target
40510 system. Features are currently used to describe available CPU
40511 registers and the types of their contents. A @samp{<feature>} element
40515 <feature name="@var{name}">
40516 @r{[}@var{type}@dots{}@r{]}
40522 Each feature's name should be unique within the description. The name
40523 of a feature does not matter unless @value{GDBN} has some special
40524 knowledge of the contents of that feature; if it does, the feature
40525 should have its standard name. @xref{Standard Target Features}.
40529 Any register's value is a collection of bits which @value{GDBN} must
40530 interpret. The default interpretation is a two's complement integer,
40531 but other types can be requested by name in the register description.
40532 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
40533 Target Types}), and the description can define additional composite types.
40535 Each type element must have an @samp{id} attribute, which gives
40536 a unique (within the containing @samp{<feature>}) name to the type.
40537 Types must be defined before they are used.
40540 Some targets offer vector registers, which can be treated as arrays
40541 of scalar elements. These types are written as @samp{<vector>} elements,
40542 specifying the array element type, @var{type}, and the number of elements,
40546 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
40550 If a register's value is usefully viewed in multiple ways, define it
40551 with a union type containing the useful representations. The
40552 @samp{<union>} element contains one or more @samp{<field>} elements,
40553 each of which has a @var{name} and a @var{type}:
40556 <union id="@var{id}">
40557 <field name="@var{name}" type="@var{type}"/>
40563 If a register's value is composed from several separate values, define
40564 it with a structure type. There are two forms of the @samp{<struct>}
40565 element; a @samp{<struct>} element must either contain only bitfields
40566 or contain no bitfields. If the structure contains only bitfields,
40567 its total size in bytes must be specified, each bitfield must have an
40568 explicit start and end, and bitfields are automatically assigned an
40569 integer type. The field's @var{start} should be less than or
40570 equal to its @var{end}, and zero represents the least significant bit.
40573 <struct id="@var{id}" size="@var{size}">
40574 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40579 If the structure contains no bitfields, then each field has an
40580 explicit type, and no implicit padding is added.
40583 <struct id="@var{id}">
40584 <field name="@var{name}" type="@var{type}"/>
40590 If a register's value is a series of single-bit flags, define it with
40591 a flags type. The @samp{<flags>} element has an explicit @var{size}
40592 and contains one or more @samp{<field>} elements. Each field has a
40593 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
40597 <flags id="@var{id}" size="@var{size}">
40598 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40603 @subsection Registers
40606 Each register is represented as an element with this form:
40609 <reg name="@var{name}"
40610 bitsize="@var{size}"
40611 @r{[}regnum="@var{num}"@r{]}
40612 @r{[}save-restore="@var{save-restore}"@r{]}
40613 @r{[}type="@var{type}"@r{]}
40614 @r{[}group="@var{group}"@r{]}/>
40618 The components are as follows:
40623 The register's name; it must be unique within the target description.
40626 The register's size, in bits.
40629 The register's number. If omitted, a register's number is one greater
40630 than that of the previous register (either in the current feature or in
40631 a preceding feature); the first register in the target description
40632 defaults to zero. This register number is used to read or write
40633 the register; e.g.@: it is used in the remote @code{p} and @code{P}
40634 packets, and registers appear in the @code{g} and @code{G} packets
40635 in order of increasing register number.
40638 Whether the register should be preserved across inferior function
40639 calls; this must be either @code{yes} or @code{no}. The default is
40640 @code{yes}, which is appropriate for most registers except for
40641 some system control registers; this is not related to the target's
40645 The type of the register. It may be a predefined type, a type
40646 defined in the current feature, or one of the special types @code{int}
40647 and @code{float}. @code{int} is an integer type of the correct size
40648 for @var{bitsize}, and @code{float} is a floating point type (in the
40649 architecture's normal floating point format) of the correct size for
40650 @var{bitsize}. The default is @code{int}.
40653 The register group to which this register belongs. It must
40654 be either @code{general}, @code{float}, or @code{vector}. If no
40655 @var{group} is specified, @value{GDBN} will not display the register
40656 in @code{info registers}.
40660 @node Predefined Target Types
40661 @section Predefined Target Types
40662 @cindex target descriptions, predefined types
40664 Type definitions in the self-description can build up composite types
40665 from basic building blocks, but can not define fundamental types. Instead,
40666 standard identifiers are provided by @value{GDBN} for the fundamental
40667 types. The currently supported types are:
40676 Signed integer types holding the specified number of bits.
40683 Unsigned integer types holding the specified number of bits.
40687 Pointers to unspecified code and data. The program counter and
40688 any dedicated return address register may be marked as code
40689 pointers; printing a code pointer converts it into a symbolic
40690 address. The stack pointer and any dedicated address registers
40691 may be marked as data pointers.
40694 Single precision IEEE floating point.
40697 Double precision IEEE floating point.
40700 The 12-byte extended precision format used by ARM FPA registers.
40703 The 10-byte extended precision format used by x87 registers.
40706 32bit @sc{eflags} register used by x86.
40709 32bit @sc{mxcsr} register used by x86.
40713 @node Standard Target Features
40714 @section Standard Target Features
40715 @cindex target descriptions, standard features
40717 A target description must contain either no registers or all the
40718 target's registers. If the description contains no registers, then
40719 @value{GDBN} will assume a default register layout, selected based on
40720 the architecture. If the description contains any registers, the
40721 default layout will not be used; the standard registers must be
40722 described in the target description, in such a way that @value{GDBN}
40723 can recognize them.
40725 This is accomplished by giving specific names to feature elements
40726 which contain standard registers. @value{GDBN} will look for features
40727 with those names and verify that they contain the expected registers;
40728 if any known feature is missing required registers, or if any required
40729 feature is missing, @value{GDBN} will reject the target
40730 description. You can add additional registers to any of the
40731 standard features --- @value{GDBN} will display them just as if
40732 they were added to an unrecognized feature.
40734 This section lists the known features and their expected contents.
40735 Sample XML documents for these features are included in the
40736 @value{GDBN} source tree, in the directory @file{gdb/features}.
40738 Names recognized by @value{GDBN} should include the name of the
40739 company or organization which selected the name, and the overall
40740 architecture to which the feature applies; so e.g.@: the feature
40741 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
40743 The names of registers are not case sensitive for the purpose
40744 of recognizing standard features, but @value{GDBN} will only display
40745 registers using the capitalization used in the description.
40748 * AArch64 Features::
40751 * MicroBlaze Features::
40754 * Nios II Features::
40755 * PowerPC Features::
40756 * S/390 and System z Features::
40761 @node AArch64 Features
40762 @subsection AArch64 Features
40763 @cindex target descriptions, AArch64 features
40765 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
40766 targets. It should contain registers @samp{x0} through @samp{x30},
40767 @samp{sp}, @samp{pc}, and @samp{cpsr}.
40769 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
40770 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
40774 @subsection ARM Features
40775 @cindex target descriptions, ARM features
40777 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
40779 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
40780 @samp{lr}, @samp{pc}, and @samp{cpsr}.
40782 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
40783 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
40784 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
40787 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
40788 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
40790 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
40791 it should contain at least registers @samp{wR0} through @samp{wR15} and
40792 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
40793 @samp{wCSSF}, and @samp{wCASF} registers are optional.
40795 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
40796 should contain at least registers @samp{d0} through @samp{d15}. If
40797 they are present, @samp{d16} through @samp{d31} should also be included.
40798 @value{GDBN} will synthesize the single-precision registers from
40799 halves of the double-precision registers.
40801 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
40802 need to contain registers; it instructs @value{GDBN} to display the
40803 VFP double-precision registers as vectors and to synthesize the
40804 quad-precision registers from pairs of double-precision registers.
40805 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
40806 be present and include 32 double-precision registers.
40808 @node i386 Features
40809 @subsection i386 Features
40810 @cindex target descriptions, i386 features
40812 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
40813 targets. It should describe the following registers:
40817 @samp{eax} through @samp{edi} plus @samp{eip} for i386
40819 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
40821 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
40822 @samp{fs}, @samp{gs}
40824 @samp{st0} through @samp{st7}
40826 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
40827 @samp{foseg}, @samp{fooff} and @samp{fop}
40830 The register sets may be different, depending on the target.
40832 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
40833 describe registers:
40837 @samp{xmm0} through @samp{xmm7} for i386
40839 @samp{xmm0} through @samp{xmm15} for amd64
40844 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
40845 @samp{org.gnu.gdb.i386.sse} feature. It should
40846 describe the upper 128 bits of @sc{ymm} registers:
40850 @samp{ymm0h} through @samp{ymm7h} for i386
40852 @samp{ymm0h} through @samp{ymm15h} for amd64
40855 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
40856 Memory Protection Extension (MPX). It should describe the following registers:
40860 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
40862 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
40865 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
40866 describe a single register, @samp{orig_eax}.
40868 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
40869 @samp{org.gnu.gdb.i386.avx} feature. It should
40870 describe additional @sc{xmm} registers:
40874 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
40877 It should describe the upper 128 bits of additional @sc{ymm} registers:
40881 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
40885 describe the upper 256 bits of @sc{zmm} registers:
40889 @samp{zmm0h} through @samp{zmm7h} for i386.
40891 @samp{zmm0h} through @samp{zmm15h} for amd64.
40895 describe the additional @sc{zmm} registers:
40899 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
40902 @node MicroBlaze Features
40903 @subsection MicroBlaze Features
40904 @cindex target descriptions, MicroBlaze features
40906 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
40907 targets. It should contain registers @samp{r0} through @samp{r31},
40908 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
40909 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
40910 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
40912 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
40913 If present, it should contain registers @samp{rshr} and @samp{rslr}
40915 @node MIPS Features
40916 @subsection @acronym{MIPS} Features
40917 @cindex target descriptions, @acronym{MIPS} features
40919 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
40920 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
40921 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
40924 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
40925 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
40926 registers. They may be 32-bit or 64-bit depending on the target.
40928 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
40929 it may be optional in a future version of @value{GDBN}. It should
40930 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
40931 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
40933 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
40934 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
40935 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
40936 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
40938 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
40939 contain a single register, @samp{restart}, which is used by the
40940 Linux kernel to control restartable syscalls.
40942 @node M68K Features
40943 @subsection M68K Features
40944 @cindex target descriptions, M68K features
40947 @item @samp{org.gnu.gdb.m68k.core}
40948 @itemx @samp{org.gnu.gdb.coldfire.core}
40949 @itemx @samp{org.gnu.gdb.fido.core}
40950 One of those features must be always present.
40951 The feature that is present determines which flavor of m68k is
40952 used. The feature that is present should contain registers
40953 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
40954 @samp{sp}, @samp{ps} and @samp{pc}.
40956 @item @samp{org.gnu.gdb.coldfire.fp}
40957 This feature is optional. If present, it should contain registers
40958 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
40962 @node Nios II Features
40963 @subsection Nios II Features
40964 @cindex target descriptions, Nios II features
40966 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
40967 targets. It should contain the 32 core registers (@samp{zero},
40968 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
40969 @samp{pc}, and the 16 control registers (@samp{status} through
40972 @node PowerPC Features
40973 @subsection PowerPC Features
40974 @cindex target descriptions, PowerPC features
40976 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
40977 targets. It should contain registers @samp{r0} through @samp{r31},
40978 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
40979 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
40981 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
40982 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
40984 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
40985 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
40988 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
40989 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
40990 will combine these registers with the floating point registers
40991 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
40992 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
40993 through @samp{vs63}, the set of vector registers for POWER7.
40995 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
40996 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
40997 @samp{spefscr}. SPE targets should provide 32-bit registers in
40998 @samp{org.gnu.gdb.power.core} and provide the upper halves in
40999 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
41000 these to present registers @samp{ev0} through @samp{ev31} to the
41003 @node S/390 and System z Features
41004 @subsection S/390 and System z Features
41005 @cindex target descriptions, S/390 features
41006 @cindex target descriptions, System z features
41008 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
41009 System z targets. It should contain the PSW and the 16 general
41010 registers. In particular, System z targets should provide the 64-bit
41011 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
41012 S/390 targets should provide the 32-bit versions of these registers.
41013 A System z target that runs in 31-bit addressing mode should provide
41014 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
41015 register's upper halves @samp{r0h} through @samp{r15h}, and their
41016 lower halves @samp{r0l} through @samp{r15l}.
41018 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
41019 contain the 64-bit registers @samp{f0} through @samp{f15}, and
41022 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
41023 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
41025 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
41026 contain the register @samp{orig_r2}, which is 64-bit wide on System z
41027 targets and 32-bit otherwise. In addition, the feature may contain
41028 the @samp{last_break} register, whose width depends on the addressing
41029 mode, as well as the @samp{system_call} register, which is always
41032 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
41033 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
41034 @samp{atia}, and @samp{tr0} through @samp{tr15}.
41036 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
41037 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
41038 combined by @value{GDBN} with the floating point registers @samp{f0}
41039 through @samp{f15} to present the 128-bit wide vector registers
41040 @samp{v0} through @samp{v15}. In addition, this feature should
41041 contain the 128-bit wide vector registers @samp{v16} through
41044 @node TIC6x Features
41045 @subsection TMS320C6x Features
41046 @cindex target descriptions, TIC6x features
41047 @cindex target descriptions, TMS320C6x features
41048 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
41049 targets. It should contain registers @samp{A0} through @samp{A15},
41050 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
41052 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
41053 contain registers @samp{A16} through @samp{A31} and @samp{B16}
41054 through @samp{B31}.
41056 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
41057 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
41059 @node Operating System Information
41060 @appendix Operating System Information
41061 @cindex operating system information
41067 Users of @value{GDBN} often wish to obtain information about the state of
41068 the operating system running on the target---for example the list of
41069 processes, or the list of open files. This section describes the
41070 mechanism that makes it possible. This mechanism is similar to the
41071 target features mechanism (@pxref{Target Descriptions}), but focuses
41072 on a different aspect of target.
41074 Operating system information is retrived from the target via the
41075 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
41076 read}). The object name in the request should be @samp{osdata}, and
41077 the @var{annex} identifies the data to be fetched.
41080 @appendixsection Process list
41081 @cindex operating system information, process list
41083 When requesting the process list, the @var{annex} field in the
41084 @samp{qXfer} request should be @samp{processes}. The returned data is
41085 an XML document. The formal syntax of this document is defined in
41086 @file{gdb/features/osdata.dtd}.
41088 An example document is:
41091 <?xml version="1.0"?>
41092 <!DOCTYPE target SYSTEM "osdata.dtd">
41093 <osdata type="processes">
41095 <column name="pid">1</column>
41096 <column name="user">root</column>
41097 <column name="command">/sbin/init</column>
41098 <column name="cores">1,2,3</column>
41103 Each item should include a column whose name is @samp{pid}. The value
41104 of that column should identify the process on the target. The
41105 @samp{user} and @samp{command} columns are optional, and will be
41106 displayed by @value{GDBN}. The @samp{cores} column, if present,
41107 should contain a comma-separated list of cores that this process
41108 is running on. Target may provide additional columns,
41109 which @value{GDBN} currently ignores.
41111 @node Trace File Format
41112 @appendix Trace File Format
41113 @cindex trace file format
41115 The trace file comes in three parts: a header, a textual description
41116 section, and a trace frame section with binary data.
41118 The header has the form @code{\x7fTRACE0\n}. The first byte is
41119 @code{0x7f} so as to indicate that the file contains binary data,
41120 while the @code{0} is a version number that may have different values
41123 The description section consists of multiple lines of @sc{ascii} text
41124 separated by newline characters (@code{0xa}). The lines may include a
41125 variety of optional descriptive or context-setting information, such
41126 as tracepoint definitions or register set size. @value{GDBN} will
41127 ignore any line that it does not recognize. An empty line marks the end
41132 Specifies the size of a register block in bytes. This is equal to the
41133 size of a @code{g} packet payload in the remote protocol. @var{size}
41134 is an ascii decimal number. There should be only one such line in
41135 a single trace file.
41137 @item status @var{status}
41138 Trace status. @var{status} has the same format as a @code{qTStatus}
41139 remote packet reply. There should be only one such line in a single trace
41142 @item tp @var{payload}
41143 Tracepoint definition. The @var{payload} has the same format as
41144 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
41145 may take multiple lines of definition, corresponding to the multiple
41148 @item tsv @var{payload}
41149 Trace state variable definition. The @var{payload} has the same format as
41150 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
41151 may take multiple lines of definition, corresponding to the multiple
41154 @item tdesc @var{payload}
41155 Target description in XML format. The @var{payload} is a single line of
41156 the XML file. All such lines should be concatenated together to get
41157 the original XML file. This file is in the same format as @code{qXfer}
41158 @code{features} payload, and corresponds to the main @code{target.xml}
41159 file. Includes are not allowed.
41163 The trace frame section consists of a number of consecutive frames.
41164 Each frame begins with a two-byte tracepoint number, followed by a
41165 four-byte size giving the amount of data in the frame. The data in
41166 the frame consists of a number of blocks, each introduced by a
41167 character indicating its type (at least register, memory, and trace
41168 state variable). The data in this section is raw binary, not a
41169 hexadecimal or other encoding; its endianness matches the target's
41172 @c FIXME bi-arch may require endianness/arch info in description section
41175 @item R @var{bytes}
41176 Register block. The number and ordering of bytes matches that of a
41177 @code{g} packet in the remote protocol. Note that these are the
41178 actual bytes, in target order, not a hexadecimal encoding.
41180 @item M @var{address} @var{length} @var{bytes}...
41181 Memory block. This is a contiguous block of memory, at the 8-byte
41182 address @var{address}, with a 2-byte length @var{length}, followed by
41183 @var{length} bytes.
41185 @item V @var{number} @var{value}
41186 Trace state variable block. This records the 8-byte signed value
41187 @var{value} of trace state variable numbered @var{number}.
41191 Future enhancements of the trace file format may include additional types
41194 @node Index Section Format
41195 @appendix @code{.gdb_index} section format
41196 @cindex .gdb_index section format
41197 @cindex index section format
41199 This section documents the index section that is created by @code{save
41200 gdb-index} (@pxref{Index Files}). The index section is
41201 DWARF-specific; some knowledge of DWARF is assumed in this
41204 The mapped index file format is designed to be directly
41205 @code{mmap}able on any architecture. In most cases, a datum is
41206 represented using a little-endian 32-bit integer value, called an
41207 @code{offset_type}. Big endian machines must byte-swap the values
41208 before using them. Exceptions to this rule are noted. The data is
41209 laid out such that alignment is always respected.
41211 A mapped index consists of several areas, laid out in order.
41215 The file header. This is a sequence of values, of @code{offset_type}
41216 unless otherwise noted:
41220 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
41221 Version 4 uses a different hashing function from versions 5 and 6.
41222 Version 6 includes symbols for inlined functions, whereas versions 4
41223 and 5 do not. Version 7 adds attributes to the CU indices in the
41224 symbol table. Version 8 specifies that symbols from DWARF type units
41225 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
41226 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
41228 @value{GDBN} will only read version 4, 5, or 6 indices
41229 by specifying @code{set use-deprecated-index-sections on}.
41230 GDB has a workaround for potentially broken version 7 indices so it is
41231 currently not flagged as deprecated.
41234 The offset, from the start of the file, of the CU list.
41237 The offset, from the start of the file, of the types CU list. Note
41238 that this area can be empty, in which case this offset will be equal
41239 to the next offset.
41242 The offset, from the start of the file, of the address area.
41245 The offset, from the start of the file, of the symbol table.
41248 The offset, from the start of the file, of the constant pool.
41252 The CU list. This is a sequence of pairs of 64-bit little-endian
41253 values, sorted by the CU offset. The first element in each pair is
41254 the offset of a CU in the @code{.debug_info} section. The second
41255 element in each pair is the length of that CU. References to a CU
41256 elsewhere in the map are done using a CU index, which is just the
41257 0-based index into this table. Note that if there are type CUs, then
41258 conceptually CUs and type CUs form a single list for the purposes of
41262 The types CU list. This is a sequence of triplets of 64-bit
41263 little-endian values. In a triplet, the first value is the CU offset,
41264 the second value is the type offset in the CU, and the third value is
41265 the type signature. The types CU list is not sorted.
41268 The address area. The address area consists of a sequence of address
41269 entries. Each address entry has three elements:
41273 The low address. This is a 64-bit little-endian value.
41276 The high address. This is a 64-bit little-endian value. Like
41277 @code{DW_AT_high_pc}, the value is one byte beyond the end.
41280 The CU index. This is an @code{offset_type} value.
41284 The symbol table. This is an open-addressed hash table. The size of
41285 the hash table is always a power of 2.
41287 Each slot in the hash table consists of a pair of @code{offset_type}
41288 values. The first value is the offset of the symbol's name in the
41289 constant pool. The second value is the offset of the CU vector in the
41292 If both values are 0, then this slot in the hash table is empty. This
41293 is ok because while 0 is a valid constant pool index, it cannot be a
41294 valid index for both a string and a CU vector.
41296 The hash value for a table entry is computed by applying an
41297 iterative hash function to the symbol's name. Starting with an
41298 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
41299 the string is incorporated into the hash using the formula depending on the
41304 The formula is @code{r = r * 67 + c - 113}.
41306 @item Versions 5 to 7
41307 The formula is @code{r = r * 67 + tolower (c) - 113}.
41310 The terminating @samp{\0} is not incorporated into the hash.
41312 The step size used in the hash table is computed via
41313 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
41314 value, and @samp{size} is the size of the hash table. The step size
41315 is used to find the next candidate slot when handling a hash
41318 The names of C@t{++} symbols in the hash table are canonicalized. We
41319 don't currently have a simple description of the canonicalization
41320 algorithm; if you intend to create new index sections, you must read
41324 The constant pool. This is simply a bunch of bytes. It is organized
41325 so that alignment is correct: CU vectors are stored first, followed by
41328 A CU vector in the constant pool is a sequence of @code{offset_type}
41329 values. The first value is the number of CU indices in the vector.
41330 Each subsequent value is the index and symbol attributes of a CU in
41331 the CU list. This element in the hash table is used to indicate which
41332 CUs define the symbol and how the symbol is used.
41333 See below for the format of each CU index+attributes entry.
41335 A string in the constant pool is zero-terminated.
41338 Attributes were added to CU index values in @code{.gdb_index} version 7.
41339 If a symbol has multiple uses within a CU then there is one
41340 CU index+attributes value for each use.
41342 The format of each CU index+attributes entry is as follows
41348 This is the index of the CU in the CU list.
41350 These bits are reserved for future purposes and must be zero.
41352 The kind of the symbol in the CU.
41356 This value is reserved and should not be used.
41357 By reserving zero the full @code{offset_type} value is backwards compatible
41358 with previous versions of the index.
41360 The symbol is a type.
41362 The symbol is a variable or an enum value.
41364 The symbol is a function.
41366 Any other kind of symbol.
41368 These values are reserved.
41372 This bit is zero if the value is global and one if it is static.
41374 The determination of whether a symbol is global or static is complicated.
41375 The authorative reference is the file @file{dwarf2read.c} in
41376 @value{GDBN} sources.
41380 This pseudo-code describes the computation of a symbol's kind and
41381 global/static attributes in the index.
41384 is_external = get_attribute (die, DW_AT_external);
41385 language = get_attribute (cu_die, DW_AT_language);
41388 case DW_TAG_typedef:
41389 case DW_TAG_base_type:
41390 case DW_TAG_subrange_type:
41394 case DW_TAG_enumerator:
41396 is_static = (language != CPLUS && language != JAVA);
41398 case DW_TAG_subprogram:
41400 is_static = ! (is_external || language == ADA);
41402 case DW_TAG_constant:
41404 is_static = ! is_external;
41406 case DW_TAG_variable:
41408 is_static = ! is_external;
41410 case DW_TAG_namespace:
41414 case DW_TAG_class_type:
41415 case DW_TAG_interface_type:
41416 case DW_TAG_structure_type:
41417 case DW_TAG_union_type:
41418 case DW_TAG_enumeration_type:
41420 is_static = (language != CPLUS && language != JAVA);
41428 @appendix Manual pages
41432 * gdb man:: The GNU Debugger man page
41433 * gdbserver man:: Remote Server for the GNU Debugger man page
41434 * gcore man:: Generate a core file of a running program
41435 * gdbinit man:: gdbinit scripts
41441 @c man title gdb The GNU Debugger
41443 @c man begin SYNOPSIS gdb
41444 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
41445 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
41446 [@option{-b}@w{ }@var{bps}]
41447 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
41448 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
41449 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
41450 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
41451 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
41454 @c man begin DESCRIPTION gdb
41455 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
41456 going on ``inside'' another program while it executes -- or what another
41457 program was doing at the moment it crashed.
41459 @value{GDBN} can do four main kinds of things (plus other things in support of
41460 these) to help you catch bugs in the act:
41464 Start your program, specifying anything that might affect its behavior.
41467 Make your program stop on specified conditions.
41470 Examine what has happened, when your program has stopped.
41473 Change things in your program, so you can experiment with correcting the
41474 effects of one bug and go on to learn about another.
41477 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
41480 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
41481 commands from the terminal until you tell it to exit with the @value{GDBN}
41482 command @code{quit}. You can get online help from @value{GDBN} itself
41483 by using the command @code{help}.
41485 You can run @code{gdb} with no arguments or options; but the most
41486 usual way to start @value{GDBN} is with one argument or two, specifying an
41487 executable program as the argument:
41493 You can also start with both an executable program and a core file specified:
41499 You can, instead, specify a process ID as a second argument, if you want
41500 to debug a running process:
41508 would attach @value{GDBN} to process @code{1234} (unless you also have a file
41509 named @file{1234}; @value{GDBN} does check for a core file first).
41510 With option @option{-p} you can omit the @var{program} filename.
41512 Here are some of the most frequently needed @value{GDBN} commands:
41514 @c pod2man highlights the right hand side of the @item lines.
41516 @item break [@var{file}:]@var{functiop}
41517 Set a breakpoint at @var{function} (in @var{file}).
41519 @item run [@var{arglist}]
41520 Start your program (with @var{arglist}, if specified).
41523 Backtrace: display the program stack.
41525 @item print @var{expr}
41526 Display the value of an expression.
41529 Continue running your program (after stopping, e.g. at a breakpoint).
41532 Execute next program line (after stopping); step @emph{over} any
41533 function calls in the line.
41535 @item edit [@var{file}:]@var{function}
41536 look at the program line where it is presently stopped.
41538 @item list [@var{file}:]@var{function}
41539 type the text of the program in the vicinity of where it is presently stopped.
41542 Execute next program line (after stopping); step @emph{into} any
41543 function calls in the line.
41545 @item help [@var{name}]
41546 Show information about @value{GDBN} command @var{name}, or general information
41547 about using @value{GDBN}.
41550 Exit from @value{GDBN}.
41554 For full details on @value{GDBN},
41555 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41556 by Richard M. Stallman and Roland H. Pesch. The same text is available online
41557 as the @code{gdb} entry in the @code{info} program.
41561 @c man begin OPTIONS gdb
41562 Any arguments other than options specify an executable
41563 file and core file (or process ID); that is, the first argument
41564 encountered with no
41565 associated option flag is equivalent to a @option{-se} option, and the second,
41566 if any, is equivalent to a @option{-c} option if it's the name of a file.
41568 both long and short forms; both are shown here. The long forms are also
41569 recognized if you truncate them, so long as enough of the option is
41570 present to be unambiguous. (If you prefer, you can flag option
41571 arguments with @option{+} rather than @option{-}, though we illustrate the
41572 more usual convention.)
41574 All the options and command line arguments you give are processed
41575 in sequential order. The order makes a difference when the @option{-x}
41581 List all options, with brief explanations.
41583 @item -symbols=@var{file}
41584 @itemx -s @var{file}
41585 Read symbol table from file @var{file}.
41588 Enable writing into executable and core files.
41590 @item -exec=@var{file}
41591 @itemx -e @var{file}
41592 Use file @var{file} as the executable file to execute when
41593 appropriate, and for examining pure data in conjunction with a core
41596 @item -se=@var{file}
41597 Read symbol table from file @var{file} and use it as the executable
41600 @item -core=@var{file}
41601 @itemx -c @var{file}
41602 Use file @var{file} as a core dump to examine.
41604 @item -command=@var{file}
41605 @itemx -x @var{file}
41606 Execute @value{GDBN} commands from file @var{file}.
41608 @item -ex @var{command}
41609 Execute given @value{GDBN} @var{command}.
41611 @item -directory=@var{directory}
41612 @itemx -d @var{directory}
41613 Add @var{directory} to the path to search for source files.
41616 Do not execute commands from @file{~/.gdbinit}.
41620 Do not execute commands from any @file{.gdbinit} initialization files.
41624 ``Quiet''. Do not print the introductory and copyright messages. These
41625 messages are also suppressed in batch mode.
41628 Run in batch mode. Exit with status @code{0} after processing all the command
41629 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
41630 Exit with nonzero status if an error occurs in executing the @value{GDBN}
41631 commands in the command files.
41633 Batch mode may be useful for running @value{GDBN} as a filter, for example to
41634 download and run a program on another computer; in order to make this
41635 more useful, the message
41638 Program exited normally.
41642 (which is ordinarily issued whenever a program running under @value{GDBN} control
41643 terminates) is not issued when running in batch mode.
41645 @item -cd=@var{directory}
41646 Run @value{GDBN} using @var{directory} as its working directory,
41647 instead of the current directory.
41651 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
41652 @value{GDBN} to output the full file name and line number in a standard,
41653 recognizable fashion each time a stack frame is displayed (which
41654 includes each time the program stops). This recognizable format looks
41655 like two @samp{\032} characters, followed by the file name, line number
41656 and character position separated by colons, and a newline. The
41657 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
41658 characters as a signal to display the source code for the frame.
41661 Set the line speed (baud rate or bits per second) of any serial
41662 interface used by @value{GDBN} for remote debugging.
41664 @item -tty=@var{device}
41665 Run using @var{device} for your program's standard input and output.
41669 @c man begin SEEALSO gdb
41671 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41672 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41673 documentation are properly installed at your site, the command
41680 should give you access to the complete manual.
41682 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41683 Richard M. Stallman and Roland H. Pesch, July 1991.
41687 @node gdbserver man
41688 @heading gdbserver man
41690 @c man title gdbserver Remote Server for the GNU Debugger
41692 @c man begin SYNOPSIS gdbserver
41693 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
41695 gdbserver --attach @var{comm} @var{pid}
41697 gdbserver --multi @var{comm}
41701 @c man begin DESCRIPTION gdbserver
41702 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
41703 than the one which is running the program being debugged.
41706 @subheading Usage (server (target) side)
41709 Usage (server (target) side):
41712 First, you need to have a copy of the program you want to debug put onto
41713 the target system. The program can be stripped to save space if needed, as
41714 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
41715 the @value{GDBN} running on the host system.
41717 To use the server, you log on to the target system, and run the @command{gdbserver}
41718 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
41719 your program, and (c) its arguments. The general syntax is:
41722 target> gdbserver @var{comm} @var{program} [@var{args} ...]
41725 For example, using a serial port, you might say:
41729 @c @file would wrap it as F</dev/com1>.
41730 target> gdbserver /dev/com1 emacs foo.txt
41733 target> gdbserver @file{/dev/com1} emacs foo.txt
41737 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
41738 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
41739 waits patiently for the host @value{GDBN} to communicate with it.
41741 To use a TCP connection, you could say:
41744 target> gdbserver host:2345 emacs foo.txt
41747 This says pretty much the same thing as the last example, except that we are
41748 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
41749 that we are expecting to see a TCP connection from @code{host} to local TCP port
41750 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
41751 want for the port number as long as it does not conflict with any existing TCP
41752 ports on the target system. This same port number must be used in the host
41753 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
41754 you chose a port number that conflicts with another service, @command{gdbserver} will
41755 print an error message and exit.
41757 @command{gdbserver} can also attach to running programs.
41758 This is accomplished via the @option{--attach} argument. The syntax is:
41761 target> gdbserver --attach @var{comm} @var{pid}
41764 @var{pid} is the process ID of a currently running process. It isn't
41765 necessary to point @command{gdbserver} at a binary for the running process.
41767 To start @code{gdbserver} without supplying an initial command to run
41768 or process ID to attach, use the @option{--multi} command line option.
41769 In such case you should connect using @kbd{target extended-remote} to start
41770 the program you want to debug.
41773 target> gdbserver --multi @var{comm}
41777 @subheading Usage (host side)
41783 You need an unstripped copy of the target program on your host system, since
41784 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
41785 would, with the target program as the first argument. (You may need to use the
41786 @option{--baud} option if the serial line is running at anything except 9600 baud.)
41787 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
41788 new command you need to know about is @code{target remote}
41789 (or @code{target extended-remote}). Its argument is either
41790 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
41791 descriptor. For example:
41795 @c @file would wrap it as F</dev/ttyb>.
41796 (gdb) target remote /dev/ttyb
41799 (gdb) target remote @file{/dev/ttyb}
41804 communicates with the server via serial line @file{/dev/ttyb}, and:
41807 (gdb) target remote the-target:2345
41811 communicates via a TCP connection to port 2345 on host `the-target', where
41812 you previously started up @command{gdbserver} with the same port number. Note that for
41813 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
41814 command, otherwise you may get an error that looks something like
41815 `Connection refused'.
41817 @command{gdbserver} can also debug multiple inferiors at once,
41820 the @value{GDBN} manual in node @code{Inferiors and Programs}
41821 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
41824 @ref{Inferiors and Programs}.
41826 In such case use the @code{extended-remote} @value{GDBN} command variant:
41829 (gdb) target extended-remote the-target:2345
41832 The @command{gdbserver} option @option{--multi} may or may not be used in such
41836 @c man begin OPTIONS gdbserver
41837 There are three different modes for invoking @command{gdbserver}:
41842 Debug a specific program specified by its program name:
41845 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
41848 The @var{comm} parameter specifies how should the server communicate
41849 with @value{GDBN}; it is either a device name (to use a serial line),
41850 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
41851 stdin/stdout of @code{gdbserver}. Specify the name of the program to
41852 debug in @var{prog}. Any remaining arguments will be passed to the
41853 program verbatim. When the program exits, @value{GDBN} will close the
41854 connection, and @code{gdbserver} will exit.
41857 Debug a specific program by specifying the process ID of a running
41861 gdbserver --attach @var{comm} @var{pid}
41864 The @var{comm} parameter is as described above. Supply the process ID
41865 of a running program in @var{pid}; @value{GDBN} will do everything
41866 else. Like with the previous mode, when the process @var{pid} exits,
41867 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
41870 Multi-process mode -- debug more than one program/process:
41873 gdbserver --multi @var{comm}
41876 In this mode, @value{GDBN} can instruct @command{gdbserver} which
41877 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
41878 close the connection when a process being debugged exits, so you can
41879 debug several processes in the same session.
41882 In each of the modes you may specify these options:
41887 List all options, with brief explanations.
41890 This option causes @command{gdbserver} to print its version number and exit.
41893 @command{gdbserver} will attach to a running program. The syntax is:
41896 target> gdbserver --attach @var{comm} @var{pid}
41899 @var{pid} is the process ID of a currently running process. It isn't
41900 necessary to point @command{gdbserver} at a binary for the running process.
41903 To start @code{gdbserver} without supplying an initial command to run
41904 or process ID to attach, use this command line option.
41905 Then you can connect using @kbd{target extended-remote} and start
41906 the program you want to debug. The syntax is:
41909 target> gdbserver --multi @var{comm}
41913 Instruct @code{gdbserver} to display extra status information about the debugging
41915 This option is intended for @code{gdbserver} development and for bug reports to
41918 @item --remote-debug
41919 Instruct @code{gdbserver} to display remote protocol debug output.
41920 This option is intended for @code{gdbserver} development and for bug reports to
41923 @item --debug-format=option1@r{[},option2,...@r{]}
41924 Instruct @code{gdbserver} to include extra information in each line
41925 of debugging output.
41926 @xref{Other Command-Line Arguments for gdbserver}.
41929 Specify a wrapper to launch programs
41930 for debugging. The option should be followed by the name of the
41931 wrapper, then any command-line arguments to pass to the wrapper, then
41932 @kbd{--} indicating the end of the wrapper arguments.
41935 By default, @command{gdbserver} keeps the listening TCP port open, so that
41936 additional connections are possible. However, if you start @code{gdbserver}
41937 with the @option{--once} option, it will stop listening for any further
41938 connection attempts after connecting to the first @value{GDBN} session.
41940 @c --disable-packet is not documented for users.
41942 @c --disable-randomization and --no-disable-randomization are superseded by
41943 @c QDisableRandomization.
41948 @c man begin SEEALSO gdbserver
41950 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41951 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41952 documentation are properly installed at your site, the command
41958 should give you access to the complete manual.
41960 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41961 Richard M. Stallman and Roland H. Pesch, July 1991.
41968 @c man title gcore Generate a core file of a running program
41971 @c man begin SYNOPSIS gcore
41972 gcore [-o @var{filename}] @var{pid}
41976 @c man begin DESCRIPTION gcore
41977 Generate a core dump of a running program with process ID @var{pid}.
41978 Produced file is equivalent to a kernel produced core file as if the process
41979 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
41980 limit). Unlike after a crash, after @command{gcore} the program remains
41981 running without any change.
41984 @c man begin OPTIONS gcore
41986 @item -o @var{filename}
41987 The optional argument
41988 @var{filename} specifies the file name where to put the core dump.
41989 If not specified, the file name defaults to @file{core.@var{pid}},
41990 where @var{pid} is the running program process ID.
41994 @c man begin SEEALSO gcore
41996 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41997 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41998 documentation are properly installed at your site, the command
42005 should give you access to the complete manual.
42007 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42008 Richard M. Stallman and Roland H. Pesch, July 1991.
42015 @c man title gdbinit GDB initialization scripts
42018 @c man begin SYNOPSIS gdbinit
42019 @ifset SYSTEM_GDBINIT
42020 @value{SYSTEM_GDBINIT}
42029 @c man begin DESCRIPTION gdbinit
42030 These files contain @value{GDBN} commands to automatically execute during
42031 @value{GDBN} startup. The lines of contents are canned sequences of commands,
42034 the @value{GDBN} manual in node @code{Sequences}
42035 -- shell command @code{info -f gdb -n Sequences}.
42041 Please read more in
42043 the @value{GDBN} manual in node @code{Startup}
42044 -- shell command @code{info -f gdb -n Startup}.
42051 @ifset SYSTEM_GDBINIT
42052 @item @value{SYSTEM_GDBINIT}
42054 @ifclear SYSTEM_GDBINIT
42055 @item (not enabled with @code{--with-system-gdbinit} during compilation)
42057 System-wide initialization file. It is executed unless user specified
42058 @value{GDBN} option @code{-nx} or @code{-n}.
42061 the @value{GDBN} manual in node @code{System-wide configuration}
42062 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
42065 @ref{System-wide configuration}.
42069 User initialization file. It is executed unless user specified
42070 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
42073 Initialization file for current directory. It may need to be enabled with
42074 @value{GDBN} security command @code{set auto-load local-gdbinit}.
42077 the @value{GDBN} manual in node @code{Init File in the Current Directory}
42078 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
42081 @ref{Init File in the Current Directory}.
42086 @c man begin SEEALSO gdbinit
42088 gdb(1), @code{info -f gdb -n Startup}
42090 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42091 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42092 documentation are properly installed at your site, the command
42098 should give you access to the complete manual.
42100 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42101 Richard M. Stallman and Roland H. Pesch, July 1991.
42107 @node GNU Free Documentation License
42108 @appendix GNU Free Documentation License
42111 @node Concept Index
42112 @unnumbered Concept Index
42116 @node Command and Variable Index
42117 @unnumbered Command, Variable, and Function Index
42122 % I think something like @@colophon should be in texinfo. In the
42124 \long\def\colophon{\hbox to0pt{}\vfill
42125 \centerline{The body of this manual is set in}
42126 \centerline{\fontname\tenrm,}
42127 \centerline{with headings in {\bf\fontname\tenbf}}
42128 \centerline{and examples in {\tt\fontname\tentt}.}
42129 \centerline{{\it\fontname\tenit\/},}
42130 \centerline{{\bf\fontname\tenbf}, and}
42131 \centerline{{\sl\fontname\tensl\/}}
42132 \centerline{are used for emphasis.}\vfill}
42134 % Blame: doc@@cygnus.com, 1991.