1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2015 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{} 1988-2015 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) 1988-2015 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.
2662 You can get multiple executables into a debugging session via the
2663 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2664 systems @value{GDBN} can add inferiors to the debug session
2665 automatically by following calls to @code{fork} and @code{exec}. To
2666 remove inferiors from the debugging session use the
2667 @w{@code{remove-inferiors}} command.
2670 @kindex add-inferior
2671 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2672 Adds @var{n} inferiors to be run using @var{executable} as the
2673 executable; @var{n} defaults to 1. If no executable is specified,
2674 the inferiors begins empty, with no program. You can still assign or
2675 change the program assigned to the inferior at any time by using the
2676 @code{file} command with the executable name as its argument.
2678 @kindex clone-inferior
2679 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2680 Adds @var{n} inferiors ready to execute the same program as inferior
2681 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
2682 number of the current inferior. This is a convenient command when you
2683 want to run another instance of the inferior you are debugging.
2686 (@value{GDBP}) info inferiors
2687 Num Description Executable
2688 * 1 process 29964 helloworld
2689 (@value{GDBP}) clone-inferior
2692 (@value{GDBP}) info inferiors
2693 Num Description Executable
2695 * 1 process 29964 helloworld
2698 You can now simply switch focus to inferior 2 and run it.
2700 @kindex remove-inferiors
2701 @item remove-inferiors @var{infno}@dots{}
2702 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2703 possible to remove an inferior that is running with this command. For
2704 those, use the @code{kill} or @code{detach} command first.
2708 To quit debugging one of the running inferiors that is not the current
2709 inferior, you can either detach from it by using the @w{@code{detach
2710 inferior}} command (allowing it to run independently), or kill it
2711 using the @w{@code{kill inferiors}} command:
2714 @kindex detach inferiors @var{infno}@dots{}
2715 @item detach inferior @var{infno}@dots{}
2716 Detach from the inferior or inferiors identified by @value{GDBN}
2717 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2718 still stays on the list of inferiors shown by @code{info inferiors},
2719 but its Description will show @samp{<null>}.
2721 @kindex kill inferiors @var{infno}@dots{}
2722 @item kill inferiors @var{infno}@dots{}
2723 Kill the inferior or inferiors identified by @value{GDBN} inferior
2724 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2725 stays on the list of inferiors shown by @code{info inferiors}, but its
2726 Description will show @samp{<null>}.
2729 After the successful completion of a command such as @code{detach},
2730 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2731 a normal process exit, the inferior is still valid and listed with
2732 @code{info inferiors}, ready to be restarted.
2735 To be notified when inferiors are started or exit under @value{GDBN}'s
2736 control use @w{@code{set print inferior-events}}:
2739 @kindex set print inferior-events
2740 @cindex print messages on inferior start and exit
2741 @item set print inferior-events
2742 @itemx set print inferior-events on
2743 @itemx set print inferior-events off
2744 The @code{set print inferior-events} command allows you to enable or
2745 disable printing of messages when @value{GDBN} notices that new
2746 inferiors have started or that inferiors have exited or have been
2747 detached. By default, these messages will not be printed.
2749 @kindex show print inferior-events
2750 @item show print inferior-events
2751 Show whether messages will be printed when @value{GDBN} detects that
2752 inferiors have started, exited or have been detached.
2755 Many commands will work the same with multiple programs as with a
2756 single program: e.g., @code{print myglobal} will simply display the
2757 value of @code{myglobal} in the current inferior.
2760 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2761 get more info about the relationship of inferiors, programs, address
2762 spaces in a debug session. You can do that with the @w{@code{maint
2763 info program-spaces}} command.
2766 @kindex maint info program-spaces
2767 @item maint info program-spaces
2768 Print a list of all program spaces currently being managed by
2771 @value{GDBN} displays for each program space (in this order):
2775 the program space number assigned by @value{GDBN}
2778 the name of the executable loaded into the program space, with e.g.,
2779 the @code{file} command.
2784 An asterisk @samp{*} preceding the @value{GDBN} program space number
2785 indicates the current program space.
2787 In addition, below each program space line, @value{GDBN} prints extra
2788 information that isn't suitable to display in tabular form. For
2789 example, the list of inferiors bound to the program space.
2792 (@value{GDBP}) maint info program-spaces
2795 Bound inferiors: ID 1 (process 21561)
2799 Here we can see that no inferior is running the program @code{hello},
2800 while @code{process 21561} is running the program @code{goodbye}. On
2801 some targets, it is possible that multiple inferiors are bound to the
2802 same program space. The most common example is that of debugging both
2803 the parent and child processes of a @code{vfork} call. For example,
2806 (@value{GDBP}) maint info program-spaces
2809 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2812 Here, both inferior 2 and inferior 1 are running in the same program
2813 space as a result of inferior 1 having executed a @code{vfork} call.
2817 @section Debugging Programs with Multiple Threads
2819 @cindex threads of execution
2820 @cindex multiple threads
2821 @cindex switching threads
2822 In some operating systems, such as HP-UX and Solaris, a single program
2823 may have more than one @dfn{thread} of execution. The precise semantics
2824 of threads differ from one operating system to another, but in general
2825 the threads of a single program are akin to multiple processes---except
2826 that they share one address space (that is, they can all examine and
2827 modify the same variables). On the other hand, each thread has its own
2828 registers and execution stack, and perhaps private memory.
2830 @value{GDBN} provides these facilities for debugging multi-thread
2834 @item automatic notification of new threads
2835 @item @samp{thread @var{threadno}}, a command to switch among threads
2836 @item @samp{info threads}, a command to inquire about existing threads
2837 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2838 a command to apply a command to a list of threads
2839 @item thread-specific breakpoints
2840 @item @samp{set print thread-events}, which controls printing of
2841 messages on thread start and exit.
2842 @item @samp{set libthread-db-search-path @var{path}}, which lets
2843 the user specify which @code{libthread_db} to use if the default choice
2844 isn't compatible with the program.
2848 @emph{Warning:} These facilities are not yet available on every
2849 @value{GDBN} configuration where the operating system supports threads.
2850 If your @value{GDBN} does not support threads, these commands have no
2851 effect. For example, a system without thread support shows no output
2852 from @samp{info threads}, and always rejects the @code{thread} command,
2856 (@value{GDBP}) info threads
2857 (@value{GDBP}) thread 1
2858 Thread ID 1 not known. Use the "info threads" command to
2859 see the IDs of currently known threads.
2861 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2862 @c doesn't support threads"?
2865 @cindex focus of debugging
2866 @cindex current thread
2867 The @value{GDBN} thread debugging facility allows you to observe all
2868 threads while your program runs---but whenever @value{GDBN} takes
2869 control, one thread in particular is always the focus of debugging.
2870 This thread is called the @dfn{current thread}. Debugging commands show
2871 program information from the perspective of the current thread.
2873 @cindex @code{New} @var{systag} message
2874 @cindex thread identifier (system)
2875 @c FIXME-implementors!! It would be more helpful if the [New...] message
2876 @c included GDB's numeric thread handle, so you could just go to that
2877 @c thread without first checking `info threads'.
2878 Whenever @value{GDBN} detects a new thread in your program, it displays
2879 the target system's identification for the thread with a message in the
2880 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
2881 whose form varies depending on the particular system. For example, on
2882 @sc{gnu}/Linux, you might see
2885 [New Thread 0x41e02940 (LWP 25582)]
2889 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2890 the @var{systag} is simply something like @samp{process 368}, with no
2893 @c FIXME!! (1) Does the [New...] message appear even for the very first
2894 @c thread of a program, or does it only appear for the
2895 @c second---i.e.@: when it becomes obvious we have a multithread
2897 @c (2) *Is* there necessarily a first thread always? Or do some
2898 @c multithread systems permit starting a program with multiple
2899 @c threads ab initio?
2901 @cindex thread number
2902 @cindex thread identifier (GDB)
2903 For debugging purposes, @value{GDBN} associates its own thread
2904 number---always a single integer---with each thread in your program.
2907 @kindex info threads
2908 @item info threads @r{[}@var{id}@dots{}@r{]}
2909 Display a summary of all threads currently in your program. Optional
2910 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2911 means to print information only about the specified thread or threads.
2912 @value{GDBN} displays for each thread (in this order):
2916 the thread number assigned by @value{GDBN}
2919 the target system's thread identifier (@var{systag})
2922 the thread's name, if one is known. A thread can either be named by
2923 the user (see @code{thread name}, below), or, in some cases, by the
2927 the current stack frame summary for that thread
2931 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2932 indicates the current thread.
2936 @c end table here to get a little more width for example
2939 (@value{GDBP}) info threads
2941 3 process 35 thread 27 0x34e5 in sigpause ()
2942 2 process 35 thread 23 0x34e5 in sigpause ()
2943 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2947 On Solaris, you can display more information about user threads with a
2948 Solaris-specific command:
2951 @item maint info sol-threads
2952 @kindex maint info sol-threads
2953 @cindex thread info (Solaris)
2954 Display info on Solaris user threads.
2958 @kindex thread @var{threadno}
2959 @item thread @var{threadno}
2960 Make thread number @var{threadno} the current thread. The command
2961 argument @var{threadno} is the internal @value{GDBN} thread number, as
2962 shown in the first field of the @samp{info threads} display.
2963 @value{GDBN} responds by displaying the system identifier of the thread
2964 you selected, and its current stack frame summary:
2967 (@value{GDBP}) thread 2
2968 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2969 #0 some_function (ignore=0x0) at example.c:8
2970 8 printf ("hello\n");
2974 As with the @samp{[New @dots{}]} message, the form of the text after
2975 @samp{Switching to} depends on your system's conventions for identifying
2978 @vindex $_thread@r{, convenience variable}
2979 The debugger convenience variable @samp{$_thread} contains the number
2980 of the current thread. You may find this useful in writing breakpoint
2981 conditional expressions, command scripts, and so forth. See
2982 @xref{Convenience Vars,, Convenience Variables}, for general
2983 information on convenience variables.
2985 @kindex thread apply
2986 @cindex apply command to several threads
2987 @item thread apply [@var{threadno} | all [-ascending]] @var{command}
2988 The @code{thread apply} command allows you to apply the named
2989 @var{command} to one or more threads. Specify the numbers of the
2990 threads that you want affected with the command argument
2991 @var{threadno}. It can be a single thread number, one of the numbers
2992 shown in the first field of the @samp{info threads} display; or it
2993 could be a range of thread numbers, as in @code{2-4}. To apply
2994 a command to all threads in descending order, type @kbd{thread apply all
2995 @var{command}}. To apply a command to all threads in ascending order,
2996 type @kbd{thread apply all -ascending @var{command}}.
3000 @cindex name a thread
3001 @item thread name [@var{name}]
3002 This command assigns a name to the current thread. If no argument is
3003 given, any existing user-specified name is removed. The thread name
3004 appears in the @samp{info threads} display.
3006 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3007 determine the name of the thread as given by the OS. On these
3008 systems, a name specified with @samp{thread name} will override the
3009 system-give name, and removing the user-specified name will cause
3010 @value{GDBN} to once again display the system-specified name.
3013 @cindex search for a thread
3014 @item thread find [@var{regexp}]
3015 Search for and display thread ids whose name or @var{systag}
3016 matches the supplied regular expression.
3018 As well as being the complement to the @samp{thread name} command,
3019 this command also allows you to identify a thread by its target
3020 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3024 (@value{GDBN}) thread find 26688
3025 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3026 (@value{GDBN}) info thread 4
3028 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3031 @kindex set print thread-events
3032 @cindex print messages on thread start and exit
3033 @item set print thread-events
3034 @itemx set print thread-events on
3035 @itemx set print thread-events off
3036 The @code{set print thread-events} command allows you to enable or
3037 disable printing of messages when @value{GDBN} notices that new threads have
3038 started or that threads have exited. By default, these messages will
3039 be printed if detection of these events is supported by the target.
3040 Note that these messages cannot be disabled on all targets.
3042 @kindex show print thread-events
3043 @item show print thread-events
3044 Show whether messages will be printed when @value{GDBN} detects that threads
3045 have started and exited.
3048 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3049 more information about how @value{GDBN} behaves when you stop and start
3050 programs with multiple threads.
3052 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3053 watchpoints in programs with multiple threads.
3055 @anchor{set libthread-db-search-path}
3057 @kindex set libthread-db-search-path
3058 @cindex search path for @code{libthread_db}
3059 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3060 If this variable is set, @var{path} is a colon-separated list of
3061 directories @value{GDBN} will use to search for @code{libthread_db}.
3062 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3063 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3064 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3067 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3068 @code{libthread_db} library to obtain information about threads in the
3069 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3070 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3071 specific thread debugging library loading is enabled
3072 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3074 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3075 refers to the default system directories that are
3076 normally searched for loading shared libraries. The @samp{$sdir} entry
3077 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3078 (@pxref{libthread_db.so.1 file}).
3080 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3081 refers to the directory from which @code{libpthread}
3082 was loaded in the inferior process.
3084 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3085 @value{GDBN} attempts to initialize it with the current inferior process.
3086 If this initialization fails (which could happen because of a version
3087 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3088 will unload @code{libthread_db}, and continue with the next directory.
3089 If none of @code{libthread_db} libraries initialize successfully,
3090 @value{GDBN} will issue a warning and thread debugging will be disabled.
3092 Setting @code{libthread-db-search-path} is currently implemented
3093 only on some platforms.
3095 @kindex show libthread-db-search-path
3096 @item show libthread-db-search-path
3097 Display current libthread_db search path.
3099 @kindex set debug libthread-db
3100 @kindex show debug libthread-db
3101 @cindex debugging @code{libthread_db}
3102 @item set debug libthread-db
3103 @itemx show debug libthread-db
3104 Turns on or off display of @code{libthread_db}-related events.
3105 Use @code{1} to enable, @code{0} to disable.
3109 @section Debugging Forks
3111 @cindex fork, debugging programs which call
3112 @cindex multiple processes
3113 @cindex processes, multiple
3114 On most systems, @value{GDBN} has no special support for debugging
3115 programs which create additional processes using the @code{fork}
3116 function. When a program forks, @value{GDBN} will continue to debug the
3117 parent process and the child process will run unimpeded. If you have
3118 set a breakpoint in any code which the child then executes, the child
3119 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3120 will cause it to terminate.
3122 However, if you want to debug the child process there is a workaround
3123 which isn't too painful. Put a call to @code{sleep} in the code which
3124 the child process executes after the fork. It may be useful to sleep
3125 only if a certain environment variable is set, or a certain file exists,
3126 so that the delay need not occur when you don't want to run @value{GDBN}
3127 on the child. While the child is sleeping, use the @code{ps} program to
3128 get its process ID. Then tell @value{GDBN} (a new invocation of
3129 @value{GDBN} if you are also debugging the parent process) to attach to
3130 the child process (@pxref{Attach}). From that point on you can debug
3131 the child process just like any other process which you attached to.
3133 On some systems, @value{GDBN} provides support for debugging programs that
3134 create additional processes using the @code{fork} or @code{vfork} functions.
3135 Currently, the only platforms with this feature are HP-UX (11.x and later
3136 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
3138 The fork debugging commands are supported in both native mode and when
3139 connected to @code{gdbserver} using @kbd{target extended-remote}.
3141 By default, when a program forks, @value{GDBN} will continue to debug
3142 the parent process and the child process will run unimpeded.
3144 If you want to follow the child process instead of the parent process,
3145 use the command @w{@code{set follow-fork-mode}}.
3148 @kindex set follow-fork-mode
3149 @item set follow-fork-mode @var{mode}
3150 Set the debugger response to a program call of @code{fork} or
3151 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3152 process. The @var{mode} argument can be:
3156 The original process is debugged after a fork. The child process runs
3157 unimpeded. This is the default.
3160 The new process is debugged after a fork. The parent process runs
3165 @kindex show follow-fork-mode
3166 @item show follow-fork-mode
3167 Display the current debugger response to a @code{fork} or @code{vfork} call.
3170 @cindex debugging multiple processes
3171 On Linux, if you want to debug both the parent and child processes, use the
3172 command @w{@code{set detach-on-fork}}.
3175 @kindex set detach-on-fork
3176 @item set detach-on-fork @var{mode}
3177 Tells gdb whether to detach one of the processes after a fork, or
3178 retain debugger control over them both.
3182 The child process (or parent process, depending on the value of
3183 @code{follow-fork-mode}) will be detached and allowed to run
3184 independently. This is the default.
3187 Both processes will be held under the control of @value{GDBN}.
3188 One process (child or parent, depending on the value of
3189 @code{follow-fork-mode}) is debugged as usual, while the other
3194 @kindex show detach-on-fork
3195 @item show detach-on-fork
3196 Show whether detach-on-fork mode is on/off.
3199 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3200 will retain control of all forked processes (including nested forks).
3201 You can list the forked processes under the control of @value{GDBN} by
3202 using the @w{@code{info inferiors}} command, and switch from one fork
3203 to another by using the @code{inferior} command (@pxref{Inferiors and
3204 Programs, ,Debugging Multiple Inferiors and Programs}).
3206 To quit debugging one of the forked processes, you can either detach
3207 from it by using the @w{@code{detach inferiors}} command (allowing it
3208 to run independently), or kill it using the @w{@code{kill inferiors}}
3209 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3212 If you ask to debug a child process and a @code{vfork} is followed by an
3213 @code{exec}, @value{GDBN} executes the new target up to the first
3214 breakpoint in the new target. If you have a breakpoint set on
3215 @code{main} in your original program, the breakpoint will also be set on
3216 the child process's @code{main}.
3218 On some systems, when a child process is spawned by @code{vfork}, you
3219 cannot debug the child or parent until an @code{exec} call completes.
3221 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3222 call executes, the new target restarts. To restart the parent
3223 process, use the @code{file} command with the parent executable name
3224 as its argument. By default, after an @code{exec} call executes,
3225 @value{GDBN} discards the symbols of the previous executable image.
3226 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3230 @kindex set follow-exec-mode
3231 @item set follow-exec-mode @var{mode}
3233 Set debugger response to a program call of @code{exec}. An
3234 @code{exec} call replaces the program image of a process.
3236 @code{follow-exec-mode} can be:
3240 @value{GDBN} creates a new inferior and rebinds the process to this
3241 new inferior. The program the process was running before the
3242 @code{exec} call can be restarted afterwards by restarting the
3248 (@value{GDBP}) info inferiors
3250 Id Description Executable
3253 process 12020 is executing new program: prog2
3254 Program exited normally.
3255 (@value{GDBP}) info inferiors
3256 Id Description Executable
3262 @value{GDBN} keeps the process bound to the same inferior. The new
3263 executable image replaces the previous executable loaded in the
3264 inferior. Restarting the inferior after the @code{exec} call, with
3265 e.g., the @code{run} command, restarts the executable the process was
3266 running after the @code{exec} call. This is the default mode.
3271 (@value{GDBP}) info inferiors
3272 Id Description Executable
3275 process 12020 is executing new program: prog2
3276 Program exited normally.
3277 (@value{GDBP}) info inferiors
3278 Id Description Executable
3285 You can use the @code{catch} command to make @value{GDBN} stop whenever
3286 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3287 Catchpoints, ,Setting Catchpoints}.
3289 @node Checkpoint/Restart
3290 @section Setting a @emph{Bookmark} to Return to Later
3295 @cindex snapshot of a process
3296 @cindex rewind program state
3298 On certain operating systems@footnote{Currently, only
3299 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3300 program's state, called a @dfn{checkpoint}, and come back to it
3303 Returning to a checkpoint effectively undoes everything that has
3304 happened in the program since the @code{checkpoint} was saved. This
3305 includes changes in memory, registers, and even (within some limits)
3306 system state. Effectively, it is like going back in time to the
3307 moment when the checkpoint was saved.
3309 Thus, if you're stepping thru a program and you think you're
3310 getting close to the point where things go wrong, you can save
3311 a checkpoint. Then, if you accidentally go too far and miss
3312 the critical statement, instead of having to restart your program
3313 from the beginning, you can just go back to the checkpoint and
3314 start again from there.
3316 This can be especially useful if it takes a lot of time or
3317 steps to reach the point where you think the bug occurs.
3319 To use the @code{checkpoint}/@code{restart} method of debugging:
3324 Save a snapshot of the debugged program's current execution state.
3325 The @code{checkpoint} command takes no arguments, but each checkpoint
3326 is assigned a small integer id, similar to a breakpoint id.
3328 @kindex info checkpoints
3329 @item info checkpoints
3330 List the checkpoints that have been saved in the current debugging
3331 session. For each checkpoint, the following information will be
3338 @item Source line, or label
3341 @kindex restart @var{checkpoint-id}
3342 @item restart @var{checkpoint-id}
3343 Restore the program state that was saved as checkpoint number
3344 @var{checkpoint-id}. All program variables, registers, stack frames
3345 etc.@: will be returned to the values that they had when the checkpoint
3346 was saved. In essence, gdb will ``wind back the clock'' to the point
3347 in time when the checkpoint was saved.
3349 Note that breakpoints, @value{GDBN} variables, command history etc.
3350 are not affected by restoring a checkpoint. In general, a checkpoint
3351 only restores things that reside in the program being debugged, not in
3354 @kindex delete checkpoint @var{checkpoint-id}
3355 @item delete checkpoint @var{checkpoint-id}
3356 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3360 Returning to a previously saved checkpoint will restore the user state
3361 of the program being debugged, plus a significant subset of the system
3362 (OS) state, including file pointers. It won't ``un-write'' data from
3363 a file, but it will rewind the file pointer to the previous location,
3364 so that the previously written data can be overwritten. For files
3365 opened in read mode, the pointer will also be restored so that the
3366 previously read data can be read again.
3368 Of course, characters that have been sent to a printer (or other
3369 external device) cannot be ``snatched back'', and characters received
3370 from eg.@: a serial device can be removed from internal program buffers,
3371 but they cannot be ``pushed back'' into the serial pipeline, ready to
3372 be received again. Similarly, the actual contents of files that have
3373 been changed cannot be restored (at this time).
3375 However, within those constraints, you actually can ``rewind'' your
3376 program to a previously saved point in time, and begin debugging it
3377 again --- and you can change the course of events so as to debug a
3378 different execution path this time.
3380 @cindex checkpoints and process id
3381 Finally, there is one bit of internal program state that will be
3382 different when you return to a checkpoint --- the program's process
3383 id. Each checkpoint will have a unique process id (or @var{pid}),
3384 and each will be different from the program's original @var{pid}.
3385 If your program has saved a local copy of its process id, this could
3386 potentially pose a problem.
3388 @subsection A Non-obvious Benefit of Using Checkpoints
3390 On some systems such as @sc{gnu}/Linux, address space randomization
3391 is performed on new processes for security reasons. This makes it
3392 difficult or impossible to set a breakpoint, or watchpoint, on an
3393 absolute address if you have to restart the program, since the
3394 absolute location of a symbol will change from one execution to the
3397 A checkpoint, however, is an @emph{identical} copy of a process.
3398 Therefore if you create a checkpoint at (eg.@:) the start of main,
3399 and simply return to that checkpoint instead of restarting the
3400 process, you can avoid the effects of address randomization and
3401 your symbols will all stay in the same place.
3404 @chapter Stopping and Continuing
3406 The principal purposes of using a debugger are so that you can stop your
3407 program before it terminates; or so that, if your program runs into
3408 trouble, you can investigate and find out why.
3410 Inside @value{GDBN}, your program may stop for any of several reasons,
3411 such as a signal, a breakpoint, or reaching a new line after a
3412 @value{GDBN} command such as @code{step}. You may then examine and
3413 change variables, set new breakpoints or remove old ones, and then
3414 continue execution. Usually, the messages shown by @value{GDBN} provide
3415 ample explanation of the status of your program---but you can also
3416 explicitly request this information at any time.
3419 @kindex info program
3421 Display information about the status of your program: whether it is
3422 running or not, what process it is, and why it stopped.
3426 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3427 * Continuing and Stepping:: Resuming execution
3428 * Skipping Over Functions and Files::
3429 Skipping over functions and files
3431 * Thread Stops:: Stopping and starting multi-thread programs
3435 @section Breakpoints, Watchpoints, and Catchpoints
3438 A @dfn{breakpoint} makes your program stop whenever a certain point in
3439 the program is reached. For each breakpoint, you can add conditions to
3440 control in finer detail whether your program stops. You can set
3441 breakpoints with the @code{break} command and its variants (@pxref{Set
3442 Breaks, ,Setting Breakpoints}), to specify the place where your program
3443 should stop by line number, function name or exact address in the
3446 On some systems, you can set breakpoints in shared libraries before
3447 the executable is run. There is a minor limitation on HP-UX systems:
3448 you must wait until the executable is run in order to set breakpoints
3449 in shared library routines that are not called directly by the program
3450 (for example, routines that are arguments in a @code{pthread_create}
3454 @cindex data breakpoints
3455 @cindex memory tracing
3456 @cindex breakpoint on memory address
3457 @cindex breakpoint on variable modification
3458 A @dfn{watchpoint} is a special breakpoint that stops your program
3459 when the value of an expression changes. The expression may be a value
3460 of a variable, or it could involve values of one or more variables
3461 combined by operators, such as @samp{a + b}. This is sometimes called
3462 @dfn{data breakpoints}. You must use a different command to set
3463 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3464 from that, you can manage a watchpoint like any other breakpoint: you
3465 enable, disable, and delete both breakpoints and watchpoints using the
3468 You can arrange to have values from your program displayed automatically
3469 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3473 @cindex breakpoint on events
3474 A @dfn{catchpoint} is another special breakpoint that stops your program
3475 when a certain kind of event occurs, such as the throwing of a C@t{++}
3476 exception or the loading of a library. As with watchpoints, you use a
3477 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3478 Catchpoints}), but aside from that, you can manage a catchpoint like any
3479 other breakpoint. (To stop when your program receives a signal, use the
3480 @code{handle} command; see @ref{Signals, ,Signals}.)
3482 @cindex breakpoint numbers
3483 @cindex numbers for breakpoints
3484 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3485 catchpoint when you create it; these numbers are successive integers
3486 starting with one. In many of the commands for controlling various
3487 features of breakpoints you use the breakpoint number to say which
3488 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3489 @dfn{disabled}; if disabled, it has no effect on your program until you
3492 @cindex breakpoint ranges
3493 @cindex ranges of breakpoints
3494 Some @value{GDBN} commands accept a range of breakpoints on which to
3495 operate. A breakpoint range is either a single breakpoint number, like
3496 @samp{5}, or two such numbers, in increasing order, separated by a
3497 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3498 all breakpoints in that range are operated on.
3501 * Set Breaks:: Setting breakpoints
3502 * Set Watchpoints:: Setting watchpoints
3503 * Set Catchpoints:: Setting catchpoints
3504 * Delete Breaks:: Deleting breakpoints
3505 * Disabling:: Disabling breakpoints
3506 * Conditions:: Break conditions
3507 * Break Commands:: Breakpoint command lists
3508 * Dynamic Printf:: Dynamic printf
3509 * Save Breakpoints:: How to save breakpoints in a file
3510 * Static Probe Points:: Listing static probe points
3511 * Error in Breakpoints:: ``Cannot insert breakpoints''
3512 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3516 @subsection Setting Breakpoints
3518 @c FIXME LMB what does GDB do if no code on line of breakpt?
3519 @c consider in particular declaration with/without initialization.
3521 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3524 @kindex b @r{(@code{break})}
3525 @vindex $bpnum@r{, convenience variable}
3526 @cindex latest breakpoint
3527 Breakpoints are set with the @code{break} command (abbreviated
3528 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3529 number of the breakpoint you've set most recently; see @ref{Convenience
3530 Vars,, Convenience Variables}, for a discussion of what you can do with
3531 convenience variables.
3534 @item break @var{location}
3535 Set a breakpoint at the given @var{location}, which can specify a
3536 function name, a line number, or an address of an instruction.
3537 (@xref{Specify Location}, for a list of all the possible ways to
3538 specify a @var{location}.) The breakpoint will stop your program just
3539 before it executes any of the code in the specified @var{location}.
3541 When using source languages that permit overloading of symbols, such as
3542 C@t{++}, a function name may refer to more than one possible place to break.
3543 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3546 It is also possible to insert a breakpoint that will stop the program
3547 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3548 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3551 When called without any arguments, @code{break} sets a breakpoint at
3552 the next instruction to be executed in the selected stack frame
3553 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3554 innermost, this makes your program stop as soon as control
3555 returns to that frame. This is similar to the effect of a
3556 @code{finish} command in the frame inside the selected frame---except
3557 that @code{finish} does not leave an active breakpoint. If you use
3558 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3559 the next time it reaches the current location; this may be useful
3562 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3563 least one instruction has been executed. If it did not do this, you
3564 would be unable to proceed past a breakpoint without first disabling the
3565 breakpoint. This rule applies whether or not the breakpoint already
3566 existed when your program stopped.
3568 @item break @dots{} if @var{cond}
3569 Set a breakpoint with condition @var{cond}; evaluate the expression
3570 @var{cond} each time the breakpoint is reached, and stop only if the
3571 value is nonzero---that is, if @var{cond} evaluates as true.
3572 @samp{@dots{}} stands for one of the possible arguments described
3573 above (or no argument) specifying where to break. @xref{Conditions,
3574 ,Break Conditions}, for more information on breakpoint conditions.
3577 @item tbreak @var{args}
3578 Set a breakpoint enabled only for one stop. The @var{args} are the
3579 same as for the @code{break} command, and the breakpoint is set in the same
3580 way, but the breakpoint is automatically deleted after the first time your
3581 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3584 @cindex hardware breakpoints
3585 @item hbreak @var{args}
3586 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
3587 @code{break} command and the breakpoint is set in the same way, but the
3588 breakpoint requires hardware support and some target hardware may not
3589 have this support. The main purpose of this is EPROM/ROM code
3590 debugging, so you can set a breakpoint at an instruction without
3591 changing the instruction. This can be used with the new trap-generation
3592 provided by SPARClite DSU and most x86-based targets. These targets
3593 will generate traps when a program accesses some data or instruction
3594 address that is assigned to the debug registers. However the hardware
3595 breakpoint registers can take a limited number of breakpoints. For
3596 example, on the DSU, only two data breakpoints can be set at a time, and
3597 @value{GDBN} will reject this command if more than two are used. Delete
3598 or disable unused hardware breakpoints before setting new ones
3599 (@pxref{Disabling, ,Disabling Breakpoints}).
3600 @xref{Conditions, ,Break Conditions}.
3601 For remote targets, you can restrict the number of hardware
3602 breakpoints @value{GDBN} will use, see @ref{set remote
3603 hardware-breakpoint-limit}.
3606 @item thbreak @var{args}
3607 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
3608 are the same as for the @code{hbreak} command and the breakpoint is set in
3609 the same way. However, like the @code{tbreak} command,
3610 the breakpoint is automatically deleted after the
3611 first time your program stops there. Also, like the @code{hbreak}
3612 command, the breakpoint requires hardware support and some target hardware
3613 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3614 See also @ref{Conditions, ,Break Conditions}.
3617 @cindex regular expression
3618 @cindex breakpoints at functions matching a regexp
3619 @cindex set breakpoints in many functions
3620 @item rbreak @var{regex}
3621 Set breakpoints on all functions matching the regular expression
3622 @var{regex}. This command sets an unconditional breakpoint on all
3623 matches, printing a list of all breakpoints it set. Once these
3624 breakpoints are set, they are treated just like the breakpoints set with
3625 the @code{break} command. You can delete them, disable them, or make
3626 them conditional the same way as any other breakpoint.
3628 The syntax of the regular expression is the standard one used with tools
3629 like @file{grep}. Note that this is different from the syntax used by
3630 shells, so for instance @code{foo*} matches all functions that include
3631 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3632 @code{.*} leading and trailing the regular expression you supply, so to
3633 match only functions that begin with @code{foo}, use @code{^foo}.
3635 @cindex non-member C@t{++} functions, set breakpoint in
3636 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3637 breakpoints on overloaded functions that are not members of any special
3640 @cindex set breakpoints on all functions
3641 The @code{rbreak} command can be used to set breakpoints in
3642 @strong{all} the functions in a program, like this:
3645 (@value{GDBP}) rbreak .
3648 @item rbreak @var{file}:@var{regex}
3649 If @code{rbreak} is called with a filename qualification, it limits
3650 the search for functions matching the given regular expression to the
3651 specified @var{file}. This can be used, for example, to set breakpoints on
3652 every function in a given file:
3655 (@value{GDBP}) rbreak file.c:.
3658 The colon separating the filename qualifier from the regex may
3659 optionally be surrounded by spaces.
3661 @kindex info breakpoints
3662 @cindex @code{$_} and @code{info breakpoints}
3663 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3664 @itemx info break @r{[}@var{n}@dots{}@r{]}
3665 Print a table of all breakpoints, watchpoints, and catchpoints set and
3666 not deleted. Optional argument @var{n} means print information only
3667 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3668 For each breakpoint, following columns are printed:
3671 @item Breakpoint Numbers
3673 Breakpoint, watchpoint, or catchpoint.
3675 Whether the breakpoint is marked to be disabled or deleted when hit.
3676 @item Enabled or Disabled
3677 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3678 that are not enabled.
3680 Where the breakpoint is in your program, as a memory address. For a
3681 pending breakpoint whose address is not yet known, this field will
3682 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3683 library that has the symbol or line referred by breakpoint is loaded.
3684 See below for details. A breakpoint with several locations will
3685 have @samp{<MULTIPLE>} in this field---see below for details.
3687 Where the breakpoint is in the source for your program, as a file and
3688 line number. For a pending breakpoint, the original string passed to
3689 the breakpoint command will be listed as it cannot be resolved until
3690 the appropriate shared library is loaded in the future.
3694 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3695 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3696 @value{GDBN} on the host's side. If it is ``target'', then the condition
3697 is evaluated by the target. The @code{info break} command shows
3698 the condition on the line following the affected breakpoint, together with
3699 its condition evaluation mode in between parentheses.
3701 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3702 allowed to have a condition specified for it. The condition is not parsed for
3703 validity until a shared library is loaded that allows the pending
3704 breakpoint to resolve to a valid location.
3707 @code{info break} with a breakpoint
3708 number @var{n} as argument lists only that breakpoint. The
3709 convenience variable @code{$_} and the default examining-address for
3710 the @code{x} command are set to the address of the last breakpoint
3711 listed (@pxref{Memory, ,Examining Memory}).
3714 @code{info break} displays a count of the number of times the breakpoint
3715 has been hit. This is especially useful in conjunction with the
3716 @code{ignore} command. You can ignore a large number of breakpoint
3717 hits, look at the breakpoint info to see how many times the breakpoint
3718 was hit, and then run again, ignoring one less than that number. This
3719 will get you quickly to the last hit of that breakpoint.
3722 For a breakpoints with an enable count (xref) greater than 1,
3723 @code{info break} also displays that count.
3727 @value{GDBN} allows you to set any number of breakpoints at the same place in
3728 your program. There is nothing silly or meaningless about this. When
3729 the breakpoints are conditional, this is even useful
3730 (@pxref{Conditions, ,Break Conditions}).
3732 @cindex multiple locations, breakpoints
3733 @cindex breakpoints, multiple locations
3734 It is possible that a breakpoint corresponds to several locations
3735 in your program. Examples of this situation are:
3739 Multiple functions in the program may have the same name.
3742 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3743 instances of the function body, used in different cases.
3746 For a C@t{++} template function, a given line in the function can
3747 correspond to any number of instantiations.
3750 For an inlined function, a given source line can correspond to
3751 several places where that function is inlined.
3754 In all those cases, @value{GDBN} will insert a breakpoint at all
3755 the relevant locations.
3757 A breakpoint with multiple locations is displayed in the breakpoint
3758 table using several rows---one header row, followed by one row for
3759 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3760 address column. The rows for individual locations contain the actual
3761 addresses for locations, and show the functions to which those
3762 locations belong. The number column for a location is of the form
3763 @var{breakpoint-number}.@var{location-number}.
3768 Num Type Disp Enb Address What
3769 1 breakpoint keep y <MULTIPLE>
3771 breakpoint already hit 1 time
3772 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3773 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3776 Each location can be individually enabled or disabled by passing
3777 @var{breakpoint-number}.@var{location-number} as argument to the
3778 @code{enable} and @code{disable} commands. Note that you cannot
3779 delete the individual locations from the list, you can only delete the
3780 entire list of locations that belong to their parent breakpoint (with
3781 the @kbd{delete @var{num}} command, where @var{num} is the number of
3782 the parent breakpoint, 1 in the above example). Disabling or enabling
3783 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3784 that belong to that breakpoint.
3786 @cindex pending breakpoints
3787 It's quite common to have a breakpoint inside a shared library.
3788 Shared libraries can be loaded and unloaded explicitly,
3789 and possibly repeatedly, as the program is executed. To support
3790 this use case, @value{GDBN} updates breakpoint locations whenever
3791 any shared library is loaded or unloaded. Typically, you would
3792 set a breakpoint in a shared library at the beginning of your
3793 debugging session, when the library is not loaded, and when the
3794 symbols from the library are not available. When you try to set
3795 breakpoint, @value{GDBN} will ask you if you want to set
3796 a so called @dfn{pending breakpoint}---breakpoint whose address
3797 is not yet resolved.
3799 After the program is run, whenever a new shared library is loaded,
3800 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3801 shared library contains the symbol or line referred to by some
3802 pending breakpoint, that breakpoint is resolved and becomes an
3803 ordinary breakpoint. When a library is unloaded, all breakpoints
3804 that refer to its symbols or source lines become pending again.
3806 This logic works for breakpoints with multiple locations, too. For
3807 example, if you have a breakpoint in a C@t{++} template function, and
3808 a newly loaded shared library has an instantiation of that template,
3809 a new location is added to the list of locations for the breakpoint.
3811 Except for having unresolved address, pending breakpoints do not
3812 differ from regular breakpoints. You can set conditions or commands,
3813 enable and disable them and perform other breakpoint operations.
3815 @value{GDBN} provides some additional commands for controlling what
3816 happens when the @samp{break} command cannot resolve breakpoint
3817 address specification to an address:
3819 @kindex set breakpoint pending
3820 @kindex show breakpoint pending
3822 @item set breakpoint pending auto
3823 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3824 location, it queries you whether a pending breakpoint should be created.
3826 @item set breakpoint pending on
3827 This indicates that an unrecognized breakpoint location should automatically
3828 result in a pending breakpoint being created.
3830 @item set breakpoint pending off
3831 This indicates that pending breakpoints are not to be created. Any
3832 unrecognized breakpoint location results in an error. This setting does
3833 not affect any pending breakpoints previously created.
3835 @item show breakpoint pending
3836 Show the current behavior setting for creating pending breakpoints.
3839 The settings above only affect the @code{break} command and its
3840 variants. Once breakpoint is set, it will be automatically updated
3841 as shared libraries are loaded and unloaded.
3843 @cindex automatic hardware breakpoints
3844 For some targets, @value{GDBN} can automatically decide if hardware or
3845 software breakpoints should be used, depending on whether the
3846 breakpoint address is read-only or read-write. This applies to
3847 breakpoints set with the @code{break} command as well as to internal
3848 breakpoints set by commands like @code{next} and @code{finish}. For
3849 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3852 You can control this automatic behaviour with the following commands::
3854 @kindex set breakpoint auto-hw
3855 @kindex show breakpoint auto-hw
3857 @item set breakpoint auto-hw on
3858 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3859 will try to use the target memory map to decide if software or hardware
3860 breakpoint must be used.
3862 @item set breakpoint auto-hw off
3863 This indicates @value{GDBN} should not automatically select breakpoint
3864 type. If the target provides a memory map, @value{GDBN} will warn when
3865 trying to set software breakpoint at a read-only address.
3868 @value{GDBN} normally implements breakpoints by replacing the program code
3869 at the breakpoint address with a special instruction, which, when
3870 executed, given control to the debugger. By default, the program
3871 code is so modified only when the program is resumed. As soon as
3872 the program stops, @value{GDBN} restores the original instructions. This
3873 behaviour guards against leaving breakpoints inserted in the
3874 target should gdb abrubptly disconnect. However, with slow remote
3875 targets, inserting and removing breakpoint can reduce the performance.
3876 This behavior can be controlled with the following commands::
3878 @kindex set breakpoint always-inserted
3879 @kindex show breakpoint always-inserted
3881 @item set breakpoint always-inserted off
3882 All breakpoints, including newly added by the user, are inserted in
3883 the target only when the target is resumed. All breakpoints are
3884 removed from the target when it stops. This is the default mode.
3886 @item set breakpoint always-inserted on
3887 Causes all breakpoints to be inserted in the target at all times. If
3888 the user adds a new breakpoint, or changes an existing breakpoint, the
3889 breakpoints in the target are updated immediately. A breakpoint is
3890 removed from the target only when breakpoint itself is deleted.
3893 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3894 when a breakpoint breaks. If the condition is true, then the process being
3895 debugged stops, otherwise the process is resumed.
3897 If the target supports evaluating conditions on its end, @value{GDBN} may
3898 download the breakpoint, together with its conditions, to it.
3900 This feature can be controlled via the following commands:
3902 @kindex set breakpoint condition-evaluation
3903 @kindex show breakpoint condition-evaluation
3905 @item set breakpoint condition-evaluation host
3906 This option commands @value{GDBN} to evaluate the breakpoint
3907 conditions on the host's side. Unconditional breakpoints are sent to
3908 the target which in turn receives the triggers and reports them back to GDB
3909 for condition evaluation. This is the standard evaluation mode.
3911 @item set breakpoint condition-evaluation target
3912 This option commands @value{GDBN} to download breakpoint conditions
3913 to the target at the moment of their insertion. The target
3914 is responsible for evaluating the conditional expression and reporting
3915 breakpoint stop events back to @value{GDBN} whenever the condition
3916 is true. Due to limitations of target-side evaluation, some conditions
3917 cannot be evaluated there, e.g., conditions that depend on local data
3918 that is only known to the host. Examples include
3919 conditional expressions involving convenience variables, complex types
3920 that cannot be handled by the agent expression parser and expressions
3921 that are too long to be sent over to the target, specially when the
3922 target is a remote system. In these cases, the conditions will be
3923 evaluated by @value{GDBN}.
3925 @item set breakpoint condition-evaluation auto
3926 This is the default mode. If the target supports evaluating breakpoint
3927 conditions on its end, @value{GDBN} will download breakpoint conditions to
3928 the target (limitations mentioned previously apply). If the target does
3929 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3930 to evaluating all these conditions on the host's side.
3934 @cindex negative breakpoint numbers
3935 @cindex internal @value{GDBN} breakpoints
3936 @value{GDBN} itself sometimes sets breakpoints in your program for
3937 special purposes, such as proper handling of @code{longjmp} (in C
3938 programs). These internal breakpoints are assigned negative numbers,
3939 starting with @code{-1}; @samp{info breakpoints} does not display them.
3940 You can see these breakpoints with the @value{GDBN} maintenance command
3941 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3944 @node Set Watchpoints
3945 @subsection Setting Watchpoints
3947 @cindex setting watchpoints
3948 You can use a watchpoint to stop execution whenever the value of an
3949 expression changes, without having to predict a particular place where
3950 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3951 The expression may be as simple as the value of a single variable, or
3952 as complex as many variables combined by operators. Examples include:
3956 A reference to the value of a single variable.
3959 An address cast to an appropriate data type. For example,
3960 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3961 address (assuming an @code{int} occupies 4 bytes).
3964 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3965 expression can use any operators valid in the program's native
3966 language (@pxref{Languages}).
3969 You can set a watchpoint on an expression even if the expression can
3970 not be evaluated yet. For instance, you can set a watchpoint on
3971 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3972 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3973 the expression produces a valid value. If the expression becomes
3974 valid in some other way than changing a variable (e.g.@: if the memory
3975 pointed to by @samp{*global_ptr} becomes readable as the result of a
3976 @code{malloc} call), @value{GDBN} may not stop until the next time
3977 the expression changes.
3979 @cindex software watchpoints
3980 @cindex hardware watchpoints
3981 Depending on your system, watchpoints may be implemented in software or
3982 hardware. @value{GDBN} does software watchpointing by single-stepping your
3983 program and testing the variable's value each time, which is hundreds of
3984 times slower than normal execution. (But this may still be worth it, to
3985 catch errors where you have no clue what part of your program is the
3988 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3989 x86-based targets, @value{GDBN} includes support for hardware
3990 watchpoints, which do not slow down the running of your program.
3994 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3995 Set a watchpoint for an expression. @value{GDBN} will break when the
3996 expression @var{expr} is written into by the program and its value
3997 changes. The simplest (and the most popular) use of this command is
3998 to watch the value of a single variable:
4001 (@value{GDBP}) watch foo
4004 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
4005 argument, @value{GDBN} breaks only when the thread identified by
4006 @var{threadnum} changes the value of @var{expr}. If any other threads
4007 change the value of @var{expr}, @value{GDBN} will not break. Note
4008 that watchpoints restricted to a single thread in this way only work
4009 with Hardware Watchpoints.
4011 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4012 (see below). The @code{-location} argument tells @value{GDBN} to
4013 instead watch the memory referred to by @var{expr}. In this case,
4014 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4015 and watch the memory at that address. The type of the result is used
4016 to determine the size of the watched memory. If the expression's
4017 result does not have an address, then @value{GDBN} will print an
4020 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4021 of masked watchpoints, if the current architecture supports this
4022 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4023 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4024 to an address to watch. The mask specifies that some bits of an address
4025 (the bits which are reset in the mask) should be ignored when matching
4026 the address accessed by the inferior against the watchpoint address.
4027 Thus, a masked watchpoint watches many addresses simultaneously---those
4028 addresses whose unmasked bits are identical to the unmasked bits in the
4029 watchpoint address. The @code{mask} argument implies @code{-location}.
4033 (@value{GDBP}) watch foo mask 0xffff00ff
4034 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4038 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
4039 Set a watchpoint that will break when the value of @var{expr} is read
4043 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
4044 Set a watchpoint that will break when @var{expr} is either read from
4045 or written into by the program.
4047 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
4048 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
4049 This command prints a list of watchpoints, using the same format as
4050 @code{info break} (@pxref{Set Breaks}).
4053 If you watch for a change in a numerically entered address you need to
4054 dereference it, as the address itself is just a constant number which will
4055 never change. @value{GDBN} refuses to create a watchpoint that watches
4056 a never-changing value:
4059 (@value{GDBP}) watch 0x600850
4060 Cannot watch constant value 0x600850.
4061 (@value{GDBP}) watch *(int *) 0x600850
4062 Watchpoint 1: *(int *) 6293584
4065 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4066 watchpoints execute very quickly, and the debugger reports a change in
4067 value at the exact instruction where the change occurs. If @value{GDBN}
4068 cannot set a hardware watchpoint, it sets a software watchpoint, which
4069 executes more slowly and reports the change in value at the next
4070 @emph{statement}, not the instruction, after the change occurs.
4072 @cindex use only software watchpoints
4073 You can force @value{GDBN} to use only software watchpoints with the
4074 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4075 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4076 the underlying system supports them. (Note that hardware-assisted
4077 watchpoints that were set @emph{before} setting
4078 @code{can-use-hw-watchpoints} to zero will still use the hardware
4079 mechanism of watching expression values.)
4082 @item set can-use-hw-watchpoints
4083 @kindex set can-use-hw-watchpoints
4084 Set whether or not to use hardware watchpoints.
4086 @item show can-use-hw-watchpoints
4087 @kindex show can-use-hw-watchpoints
4088 Show the current mode of using hardware watchpoints.
4091 For remote targets, you can restrict the number of hardware
4092 watchpoints @value{GDBN} will use, see @ref{set remote
4093 hardware-breakpoint-limit}.
4095 When you issue the @code{watch} command, @value{GDBN} reports
4098 Hardware watchpoint @var{num}: @var{expr}
4102 if it was able to set a hardware watchpoint.
4104 Currently, the @code{awatch} and @code{rwatch} commands can only set
4105 hardware watchpoints, because accesses to data that don't change the
4106 value of the watched expression cannot be detected without examining
4107 every instruction as it is being executed, and @value{GDBN} does not do
4108 that currently. If @value{GDBN} finds that it is unable to set a
4109 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4110 will print a message like this:
4113 Expression cannot be implemented with read/access watchpoint.
4116 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4117 data type of the watched expression is wider than what a hardware
4118 watchpoint on the target machine can handle. For example, some systems
4119 can only watch regions that are up to 4 bytes wide; on such systems you
4120 cannot set hardware watchpoints for an expression that yields a
4121 double-precision floating-point number (which is typically 8 bytes
4122 wide). As a work-around, it might be possible to break the large region
4123 into a series of smaller ones and watch them with separate watchpoints.
4125 If you set too many hardware watchpoints, @value{GDBN} might be unable
4126 to insert all of them when you resume the execution of your program.
4127 Since the precise number of active watchpoints is unknown until such
4128 time as the program is about to be resumed, @value{GDBN} might not be
4129 able to warn you about this when you set the watchpoints, and the
4130 warning will be printed only when the program is resumed:
4133 Hardware watchpoint @var{num}: Could not insert watchpoint
4137 If this happens, delete or disable some of the watchpoints.
4139 Watching complex expressions that reference many variables can also
4140 exhaust the resources available for hardware-assisted watchpoints.
4141 That's because @value{GDBN} needs to watch every variable in the
4142 expression with separately allocated resources.
4144 If you call a function interactively using @code{print} or @code{call},
4145 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4146 kind of breakpoint or the call completes.
4148 @value{GDBN} automatically deletes watchpoints that watch local
4149 (automatic) variables, or expressions that involve such variables, when
4150 they go out of scope, that is, when the execution leaves the block in
4151 which these variables were defined. In particular, when the program
4152 being debugged terminates, @emph{all} local variables go out of scope,
4153 and so only watchpoints that watch global variables remain set. If you
4154 rerun the program, you will need to set all such watchpoints again. One
4155 way of doing that would be to set a code breakpoint at the entry to the
4156 @code{main} function and when it breaks, set all the watchpoints.
4158 @cindex watchpoints and threads
4159 @cindex threads and watchpoints
4160 In multi-threaded programs, watchpoints will detect changes to the
4161 watched expression from every thread.
4164 @emph{Warning:} In multi-threaded programs, software watchpoints
4165 have only limited usefulness. If @value{GDBN} creates a software
4166 watchpoint, it can only watch the value of an expression @emph{in a
4167 single thread}. If you are confident that the expression can only
4168 change due to the current thread's activity (and if you are also
4169 confident that no other thread can become current), then you can use
4170 software watchpoints as usual. However, @value{GDBN} may not notice
4171 when a non-current thread's activity changes the expression. (Hardware
4172 watchpoints, in contrast, watch an expression in all threads.)
4175 @xref{set remote hardware-watchpoint-limit}.
4177 @node Set Catchpoints
4178 @subsection Setting Catchpoints
4179 @cindex catchpoints, setting
4180 @cindex exception handlers
4181 @cindex event handling
4183 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4184 kinds of program events, such as C@t{++} exceptions or the loading of a
4185 shared library. Use the @code{catch} command to set a catchpoint.
4189 @item catch @var{event}
4190 Stop when @var{event} occurs. The @var{event} can be any of the following:
4193 @item throw @r{[}@var{regexp}@r{]}
4194 @itemx rethrow @r{[}@var{regexp}@r{]}
4195 @itemx catch @r{[}@var{regexp}@r{]}
4197 @kindex catch rethrow
4199 @cindex stop on C@t{++} exceptions
4200 The throwing, re-throwing, or catching of a C@t{++} exception.
4202 If @var{regexp} is given, then only exceptions whose type matches the
4203 regular expression will be caught.
4205 @vindex $_exception@r{, convenience variable}
4206 The convenience variable @code{$_exception} is available at an
4207 exception-related catchpoint, on some systems. This holds the
4208 exception being thrown.
4210 There are currently some limitations to C@t{++} exception handling in
4215 The support for these commands is system-dependent. Currently, only
4216 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4220 The regular expression feature and the @code{$_exception} convenience
4221 variable rely on the presence of some SDT probes in @code{libstdc++}.
4222 If these probes are not present, then these features cannot be used.
4223 These probes were first available in the GCC 4.8 release, but whether
4224 or not they are available in your GCC also depends on how it was
4228 The @code{$_exception} convenience variable is only valid at the
4229 instruction at which an exception-related catchpoint is set.
4232 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4233 location in the system library which implements runtime exception
4234 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4235 (@pxref{Selection}) to get to your code.
4238 If you call a function interactively, @value{GDBN} normally returns
4239 control to you when the function has finished executing. If the call
4240 raises an exception, however, the call may bypass the mechanism that
4241 returns control to you and cause your program either to abort or to
4242 simply continue running until it hits a breakpoint, catches a signal
4243 that @value{GDBN} is listening for, or exits. This is the case even if
4244 you set a catchpoint for the exception; catchpoints on exceptions are
4245 disabled within interactive calls. @xref{Calling}, for information on
4246 controlling this with @code{set unwind-on-terminating-exception}.
4249 You cannot raise an exception interactively.
4252 You cannot install an exception handler interactively.
4256 @kindex catch exception
4257 @cindex Ada exception catching
4258 @cindex catch Ada exceptions
4259 An Ada exception being raised. If an exception name is specified
4260 at the end of the command (eg @code{catch exception Program_Error}),
4261 the debugger will stop only when this specific exception is raised.
4262 Otherwise, the debugger stops execution when any Ada exception is raised.
4264 When inserting an exception catchpoint on a user-defined exception whose
4265 name is identical to one of the exceptions defined by the language, the
4266 fully qualified name must be used as the exception name. Otherwise,
4267 @value{GDBN} will assume that it should stop on the pre-defined exception
4268 rather than the user-defined one. For instance, assuming an exception
4269 called @code{Constraint_Error} is defined in package @code{Pck}, then
4270 the command to use to catch such exceptions is @kbd{catch exception
4271 Pck.Constraint_Error}.
4273 @item exception unhandled
4274 @kindex catch exception unhandled
4275 An exception that was raised but is not handled by the program.
4278 @kindex catch assert
4279 A failed Ada assertion.
4283 @cindex break on fork/exec
4284 A call to @code{exec}. This is currently only available for HP-UX
4288 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4289 @kindex catch syscall
4290 @cindex break on a system call.
4291 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4292 syscall is a mechanism for application programs to request a service
4293 from the operating system (OS) or one of the OS system services.
4294 @value{GDBN} can catch some or all of the syscalls issued by the
4295 debuggee, and show the related information for each syscall. If no
4296 argument is specified, calls to and returns from all system calls
4299 @var{name} can be any system call name that is valid for the
4300 underlying OS. Just what syscalls are valid depends on the OS. On
4301 GNU and Unix systems, you can find the full list of valid syscall
4302 names on @file{/usr/include/asm/unistd.h}.
4304 @c For MS-Windows, the syscall names and the corresponding numbers
4305 @c can be found, e.g., on this URL:
4306 @c http://www.metasploit.com/users/opcode/syscalls.html
4307 @c but we don't support Windows syscalls yet.
4309 Normally, @value{GDBN} knows in advance which syscalls are valid for
4310 each OS, so you can use the @value{GDBN} command-line completion
4311 facilities (@pxref{Completion,, command completion}) to list the
4314 You may also specify the system call numerically. A syscall's
4315 number is the value passed to the OS's syscall dispatcher to
4316 identify the requested service. When you specify the syscall by its
4317 name, @value{GDBN} uses its database of syscalls to convert the name
4318 into the corresponding numeric code, but using the number directly
4319 may be useful if @value{GDBN}'s database does not have the complete
4320 list of syscalls on your system (e.g., because @value{GDBN} lags
4321 behind the OS upgrades).
4323 The example below illustrates how this command works if you don't provide
4327 (@value{GDBP}) catch syscall
4328 Catchpoint 1 (syscall)
4330 Starting program: /tmp/catch-syscall
4332 Catchpoint 1 (call to syscall 'close'), \
4333 0xffffe424 in __kernel_vsyscall ()
4337 Catchpoint 1 (returned from syscall 'close'), \
4338 0xffffe424 in __kernel_vsyscall ()
4342 Here is an example of catching a system call by name:
4345 (@value{GDBP}) catch syscall chroot
4346 Catchpoint 1 (syscall 'chroot' [61])
4348 Starting program: /tmp/catch-syscall
4350 Catchpoint 1 (call to syscall 'chroot'), \
4351 0xffffe424 in __kernel_vsyscall ()
4355 Catchpoint 1 (returned from syscall 'chroot'), \
4356 0xffffe424 in __kernel_vsyscall ()
4360 An example of specifying a system call numerically. In the case
4361 below, the syscall number has a corresponding entry in the XML
4362 file, so @value{GDBN} finds its name and prints it:
4365 (@value{GDBP}) catch syscall 252
4366 Catchpoint 1 (syscall(s) 'exit_group')
4368 Starting program: /tmp/catch-syscall
4370 Catchpoint 1 (call to syscall 'exit_group'), \
4371 0xffffe424 in __kernel_vsyscall ()
4375 Program exited normally.
4379 However, there can be situations when there is no corresponding name
4380 in XML file for that syscall number. In this case, @value{GDBN} prints
4381 a warning message saying that it was not able to find the syscall name,
4382 but the catchpoint will be set anyway. See the example below:
4385 (@value{GDBP}) catch syscall 764
4386 warning: The number '764' does not represent a known syscall.
4387 Catchpoint 2 (syscall 764)
4391 If you configure @value{GDBN} using the @samp{--without-expat} option,
4392 it will not be able to display syscall names. Also, if your
4393 architecture does not have an XML file describing its system calls,
4394 you will not be able to see the syscall names. It is important to
4395 notice that these two features are used for accessing the syscall
4396 name database. In either case, you will see a warning like this:
4399 (@value{GDBP}) catch syscall
4400 warning: Could not open "syscalls/i386-linux.xml"
4401 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4402 GDB will not be able to display syscall names.
4403 Catchpoint 1 (syscall)
4407 Of course, the file name will change depending on your architecture and system.
4409 Still using the example above, you can also try to catch a syscall by its
4410 number. In this case, you would see something like:
4413 (@value{GDBP}) catch syscall 252
4414 Catchpoint 1 (syscall(s) 252)
4417 Again, in this case @value{GDBN} would not be able to display syscall's names.
4421 A call to @code{fork}. This is currently only available for HP-UX
4426 A call to @code{vfork}. This is currently only available for HP-UX
4429 @item load @r{[}regexp@r{]}
4430 @itemx unload @r{[}regexp@r{]}
4432 @kindex catch unload
4433 The loading or unloading of a shared library. If @var{regexp} is
4434 given, then the catchpoint will stop only if the regular expression
4435 matches one of the affected libraries.
4437 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4438 @kindex catch signal
4439 The delivery of a signal.
4441 With no arguments, this catchpoint will catch any signal that is not
4442 used internally by @value{GDBN}, specifically, all signals except
4443 @samp{SIGTRAP} and @samp{SIGINT}.
4445 With the argument @samp{all}, all signals, including those used by
4446 @value{GDBN}, will be caught. This argument cannot be used with other
4449 Otherwise, the arguments are a list of signal names as given to
4450 @code{handle} (@pxref{Signals}). Only signals specified in this list
4453 One reason that @code{catch signal} can be more useful than
4454 @code{handle} is that you can attach commands and conditions to the
4457 When a signal is caught by a catchpoint, the signal's @code{stop} and
4458 @code{print} settings, as specified by @code{handle}, are ignored.
4459 However, whether the signal is still delivered to the inferior depends
4460 on the @code{pass} setting; this can be changed in the catchpoint's
4465 @item tcatch @var{event}
4467 Set a catchpoint that is enabled only for one stop. The catchpoint is
4468 automatically deleted after the first time the event is caught.
4472 Use the @code{info break} command to list the current catchpoints.
4476 @subsection Deleting Breakpoints
4478 @cindex clearing breakpoints, watchpoints, catchpoints
4479 @cindex deleting breakpoints, watchpoints, catchpoints
4480 It is often necessary to eliminate a breakpoint, watchpoint, or
4481 catchpoint once it has done its job and you no longer want your program
4482 to stop there. This is called @dfn{deleting} the breakpoint. A
4483 breakpoint that has been deleted no longer exists; it is forgotten.
4485 With the @code{clear} command you can delete breakpoints according to
4486 where they are in your program. With the @code{delete} command you can
4487 delete individual breakpoints, watchpoints, or catchpoints by specifying
4488 their breakpoint numbers.
4490 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4491 automatically ignores breakpoints on the first instruction to be executed
4492 when you continue execution without changing the execution address.
4497 Delete any breakpoints at the next instruction to be executed in the
4498 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4499 the innermost frame is selected, this is a good way to delete a
4500 breakpoint where your program just stopped.
4502 @item clear @var{location}
4503 Delete any breakpoints set at the specified @var{location}.
4504 @xref{Specify Location}, for the various forms of @var{location}; the
4505 most useful ones are listed below:
4508 @item clear @var{function}
4509 @itemx clear @var{filename}:@var{function}
4510 Delete any breakpoints set at entry to the named @var{function}.
4512 @item clear @var{linenum}
4513 @itemx clear @var{filename}:@var{linenum}
4514 Delete any breakpoints set at or within the code of the specified
4515 @var{linenum} of the specified @var{filename}.
4518 @cindex delete breakpoints
4520 @kindex d @r{(@code{delete})}
4521 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4522 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4523 ranges specified as arguments. If no argument is specified, delete all
4524 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4525 confirm off}). You can abbreviate this command as @code{d}.
4529 @subsection Disabling Breakpoints
4531 @cindex enable/disable a breakpoint
4532 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4533 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4534 it had been deleted, but remembers the information on the breakpoint so
4535 that you can @dfn{enable} it again later.
4537 You disable and enable breakpoints, watchpoints, and catchpoints with
4538 the @code{enable} and @code{disable} commands, optionally specifying
4539 one or more breakpoint numbers as arguments. Use @code{info break} to
4540 print a list of all breakpoints, watchpoints, and catchpoints if you
4541 do not know which numbers to use.
4543 Disabling and enabling a breakpoint that has multiple locations
4544 affects all of its locations.
4546 A breakpoint, watchpoint, or catchpoint can have any of several
4547 different states of enablement:
4551 Enabled. The breakpoint stops your program. A breakpoint set
4552 with the @code{break} command starts out in this state.
4554 Disabled. The breakpoint has no effect on your program.
4556 Enabled once. The breakpoint stops your program, but then becomes
4559 Enabled for a count. The breakpoint stops your program for the next
4560 N times, then becomes disabled.
4562 Enabled for deletion. The breakpoint stops your program, but
4563 immediately after it does so it is deleted permanently. A breakpoint
4564 set with the @code{tbreak} command starts out in this state.
4567 You can use the following commands to enable or disable breakpoints,
4568 watchpoints, and catchpoints:
4572 @kindex dis @r{(@code{disable})}
4573 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4574 Disable the specified breakpoints---or all breakpoints, if none are
4575 listed. A disabled breakpoint has no effect but is not forgotten. All
4576 options such as ignore-counts, conditions and commands are remembered in
4577 case the breakpoint is enabled again later. You may abbreviate
4578 @code{disable} as @code{dis}.
4581 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4582 Enable the specified breakpoints (or all defined breakpoints). They
4583 become effective once again in stopping your program.
4585 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4586 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4587 of these breakpoints immediately after stopping your program.
4589 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4590 Enable the specified breakpoints temporarily. @value{GDBN} records
4591 @var{count} with each of the specified breakpoints, and decrements a
4592 breakpoint's count when it is hit. When any count reaches 0,
4593 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4594 count (@pxref{Conditions, ,Break Conditions}), that will be
4595 decremented to 0 before @var{count} is affected.
4597 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4598 Enable the specified breakpoints to work once, then die. @value{GDBN}
4599 deletes any of these breakpoints as soon as your program stops there.
4600 Breakpoints set by the @code{tbreak} command start out in this state.
4603 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4604 @c confusing: tbreak is also initially enabled.
4605 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4606 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4607 subsequently, they become disabled or enabled only when you use one of
4608 the commands above. (The command @code{until} can set and delete a
4609 breakpoint of its own, but it does not change the state of your other
4610 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4614 @subsection Break Conditions
4615 @cindex conditional breakpoints
4616 @cindex breakpoint conditions
4618 @c FIXME what is scope of break condition expr? Context where wanted?
4619 @c in particular for a watchpoint?
4620 The simplest sort of breakpoint breaks every time your program reaches a
4621 specified place. You can also specify a @dfn{condition} for a
4622 breakpoint. A condition is just a Boolean expression in your
4623 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4624 a condition evaluates the expression each time your program reaches it,
4625 and your program stops only if the condition is @emph{true}.
4627 This is the converse of using assertions for program validation; in that
4628 situation, you want to stop when the assertion is violated---that is,
4629 when the condition is false. In C, if you want to test an assertion expressed
4630 by the condition @var{assert}, you should set the condition
4631 @samp{! @var{assert}} on the appropriate breakpoint.
4633 Conditions are also accepted for watchpoints; you may not need them,
4634 since a watchpoint is inspecting the value of an expression anyhow---but
4635 it might be simpler, say, to just set a watchpoint on a variable name,
4636 and specify a condition that tests whether the new value is an interesting
4639 Break conditions can have side effects, and may even call functions in
4640 your program. This can be useful, for example, to activate functions
4641 that log program progress, or to use your own print functions to
4642 format special data structures. The effects are completely predictable
4643 unless there is another enabled breakpoint at the same address. (In
4644 that case, @value{GDBN} might see the other breakpoint first and stop your
4645 program without checking the condition of this one.) Note that
4646 breakpoint commands are usually more convenient and flexible than break
4648 purpose of performing side effects when a breakpoint is reached
4649 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4651 Breakpoint conditions can also be evaluated on the target's side if
4652 the target supports it. Instead of evaluating the conditions locally,
4653 @value{GDBN} encodes the expression into an agent expression
4654 (@pxref{Agent Expressions}) suitable for execution on the target,
4655 independently of @value{GDBN}. Global variables become raw memory
4656 locations, locals become stack accesses, and so forth.
4658 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4659 when its condition evaluates to true. This mechanism may provide faster
4660 response times depending on the performance characteristics of the target
4661 since it does not need to keep @value{GDBN} informed about
4662 every breakpoint trigger, even those with false conditions.
4664 Break conditions can be specified when a breakpoint is set, by using
4665 @samp{if} in the arguments to the @code{break} command. @xref{Set
4666 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4667 with the @code{condition} command.
4669 You can also use the @code{if} keyword with the @code{watch} command.
4670 The @code{catch} command does not recognize the @code{if} keyword;
4671 @code{condition} is the only way to impose a further condition on a
4676 @item condition @var{bnum} @var{expression}
4677 Specify @var{expression} as the break condition for breakpoint,
4678 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4679 breakpoint @var{bnum} stops your program only if the value of
4680 @var{expression} is true (nonzero, in C). When you use
4681 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4682 syntactic correctness, and to determine whether symbols in it have
4683 referents in the context of your breakpoint. If @var{expression} uses
4684 symbols not referenced in the context of the breakpoint, @value{GDBN}
4685 prints an error message:
4688 No symbol "foo" in current context.
4693 not actually evaluate @var{expression} at the time the @code{condition}
4694 command (or a command that sets a breakpoint with a condition, like
4695 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4697 @item condition @var{bnum}
4698 Remove the condition from breakpoint number @var{bnum}. It becomes
4699 an ordinary unconditional breakpoint.
4702 @cindex ignore count (of breakpoint)
4703 A special case of a breakpoint condition is to stop only when the
4704 breakpoint has been reached a certain number of times. This is so
4705 useful that there is a special way to do it, using the @dfn{ignore
4706 count} of the breakpoint. Every breakpoint has an ignore count, which
4707 is an integer. Most of the time, the ignore count is zero, and
4708 therefore has no effect. But if your program reaches a breakpoint whose
4709 ignore count is positive, then instead of stopping, it just decrements
4710 the ignore count by one and continues. As a result, if the ignore count
4711 value is @var{n}, the breakpoint does not stop the next @var{n} times
4712 your program reaches it.
4716 @item ignore @var{bnum} @var{count}
4717 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4718 The next @var{count} times the breakpoint is reached, your program's
4719 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4722 To make the breakpoint stop the next time it is reached, specify
4725 When you use @code{continue} to resume execution of your program from a
4726 breakpoint, you can specify an ignore count directly as an argument to
4727 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4728 Stepping,,Continuing and Stepping}.
4730 If a breakpoint has a positive ignore count and a condition, the
4731 condition is not checked. Once the ignore count reaches zero,
4732 @value{GDBN} resumes checking the condition.
4734 You could achieve the effect of the ignore count with a condition such
4735 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4736 is decremented each time. @xref{Convenience Vars, ,Convenience
4740 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4743 @node Break Commands
4744 @subsection Breakpoint Command Lists
4746 @cindex breakpoint commands
4747 You can give any breakpoint (or watchpoint or catchpoint) a series of
4748 commands to execute when your program stops due to that breakpoint. For
4749 example, you might want to print the values of certain expressions, or
4750 enable other breakpoints.
4754 @kindex end@r{ (breakpoint commands)}
4755 @item commands @r{[}@var{range}@dots{}@r{]}
4756 @itemx @dots{} @var{command-list} @dots{}
4758 Specify a list of commands for the given breakpoints. The commands
4759 themselves appear on the following lines. Type a line containing just
4760 @code{end} to terminate the commands.
4762 To remove all commands from a breakpoint, type @code{commands} and
4763 follow it immediately with @code{end}; that is, give no commands.
4765 With no argument, @code{commands} refers to the last breakpoint,
4766 watchpoint, or catchpoint set (not to the breakpoint most recently
4767 encountered). If the most recent breakpoints were set with a single
4768 command, then the @code{commands} will apply to all the breakpoints
4769 set by that command. This applies to breakpoints set by
4770 @code{rbreak}, and also applies when a single @code{break} command
4771 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4775 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4776 disabled within a @var{command-list}.
4778 You can use breakpoint commands to start your program up again. Simply
4779 use the @code{continue} command, or @code{step}, or any other command
4780 that resumes execution.
4782 Any other commands in the command list, after a command that resumes
4783 execution, are ignored. This is because any time you resume execution
4784 (even with a simple @code{next} or @code{step}), you may encounter
4785 another breakpoint---which could have its own command list, leading to
4786 ambiguities about which list to execute.
4789 If the first command you specify in a command list is @code{silent}, the
4790 usual message about stopping at a breakpoint is not printed. This may
4791 be desirable for breakpoints that are to print a specific message and
4792 then continue. If none of the remaining commands print anything, you
4793 see no sign that the breakpoint was reached. @code{silent} is
4794 meaningful only at the beginning of a breakpoint command list.
4796 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4797 print precisely controlled output, and are often useful in silent
4798 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4800 For example, here is how you could use breakpoint commands to print the
4801 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4807 printf "x is %d\n",x
4812 One application for breakpoint commands is to compensate for one bug so
4813 you can test for another. Put a breakpoint just after the erroneous line
4814 of code, give it a condition to detect the case in which something
4815 erroneous has been done, and give it commands to assign correct values
4816 to any variables that need them. End with the @code{continue} command
4817 so that your program does not stop, and start with the @code{silent}
4818 command so that no output is produced. Here is an example:
4829 @node Dynamic Printf
4830 @subsection Dynamic Printf
4832 @cindex dynamic printf
4834 The dynamic printf command @code{dprintf} combines a breakpoint with
4835 formatted printing of your program's data to give you the effect of
4836 inserting @code{printf} calls into your program on-the-fly, without
4837 having to recompile it.
4839 In its most basic form, the output goes to the GDB console. However,
4840 you can set the variable @code{dprintf-style} for alternate handling.
4841 For instance, you can ask to format the output by calling your
4842 program's @code{printf} function. This has the advantage that the
4843 characters go to the program's output device, so they can recorded in
4844 redirects to files and so forth.
4846 If you are doing remote debugging with a stub or agent, you can also
4847 ask to have the printf handled by the remote agent. In addition to
4848 ensuring that the output goes to the remote program's device along
4849 with any other output the program might produce, you can also ask that
4850 the dprintf remain active even after disconnecting from the remote
4851 target. Using the stub/agent is also more efficient, as it can do
4852 everything without needing to communicate with @value{GDBN}.
4856 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4857 Whenever execution reaches @var{location}, print the values of one or
4858 more @var{expressions} under the control of the string @var{template}.
4859 To print several values, separate them with commas.
4861 @item set dprintf-style @var{style}
4862 Set the dprintf output to be handled in one of several different
4863 styles enumerated below. A change of style affects all existing
4864 dynamic printfs immediately. (If you need individual control over the
4865 print commands, simply define normal breakpoints with
4866 explicitly-supplied command lists.)
4869 @kindex dprintf-style gdb
4870 Handle the output using the @value{GDBN} @code{printf} command.
4873 @kindex dprintf-style call
4874 Handle the output by calling a function in your program (normally
4878 @kindex dprintf-style agent
4879 Have the remote debugging agent (such as @code{gdbserver}) handle
4880 the output itself. This style is only available for agents that
4881 support running commands on the target.
4883 @item set dprintf-function @var{function}
4884 Set the function to call if the dprintf style is @code{call}. By
4885 default its value is @code{printf}. You may set it to any expression.
4886 that @value{GDBN} can evaluate to a function, as per the @code{call}
4889 @item set dprintf-channel @var{channel}
4890 Set a ``channel'' for dprintf. If set to a non-empty value,
4891 @value{GDBN} will evaluate it as an expression and pass the result as
4892 a first argument to the @code{dprintf-function}, in the manner of
4893 @code{fprintf} and similar functions. Otherwise, the dprintf format
4894 string will be the first argument, in the manner of @code{printf}.
4896 As an example, if you wanted @code{dprintf} output to go to a logfile
4897 that is a standard I/O stream assigned to the variable @code{mylog},
4898 you could do the following:
4901 (gdb) set dprintf-style call
4902 (gdb) set dprintf-function fprintf
4903 (gdb) set dprintf-channel mylog
4904 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4905 Dprintf 1 at 0x123456: file main.c, line 25.
4907 1 dprintf keep y 0x00123456 in main at main.c:25
4908 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
4913 Note that the @code{info break} displays the dynamic printf commands
4914 as normal breakpoint commands; you can thus easily see the effect of
4915 the variable settings.
4917 @item set disconnected-dprintf on
4918 @itemx set disconnected-dprintf off
4919 @kindex set disconnected-dprintf
4920 Choose whether @code{dprintf} commands should continue to run if
4921 @value{GDBN} has disconnected from the target. This only applies
4922 if the @code{dprintf-style} is @code{agent}.
4924 @item show disconnected-dprintf off
4925 @kindex show disconnected-dprintf
4926 Show the current choice for disconnected @code{dprintf}.
4930 @value{GDBN} does not check the validity of function and channel,
4931 relying on you to supply values that are meaningful for the contexts
4932 in which they are being used. For instance, the function and channel
4933 may be the values of local variables, but if that is the case, then
4934 all enabled dynamic prints must be at locations within the scope of
4935 those locals. If evaluation fails, @value{GDBN} will report an error.
4937 @node Save Breakpoints
4938 @subsection How to save breakpoints to a file
4940 To save breakpoint definitions to a file use the @w{@code{save
4941 breakpoints}} command.
4944 @kindex save breakpoints
4945 @cindex save breakpoints to a file for future sessions
4946 @item save breakpoints [@var{filename}]
4947 This command saves all current breakpoint definitions together with
4948 their commands and ignore counts, into a file @file{@var{filename}}
4949 suitable for use in a later debugging session. This includes all
4950 types of breakpoints (breakpoints, watchpoints, catchpoints,
4951 tracepoints). To read the saved breakpoint definitions, use the
4952 @code{source} command (@pxref{Command Files}). Note that watchpoints
4953 with expressions involving local variables may fail to be recreated
4954 because it may not be possible to access the context where the
4955 watchpoint is valid anymore. Because the saved breakpoint definitions
4956 are simply a sequence of @value{GDBN} commands that recreate the
4957 breakpoints, you can edit the file in your favorite editing program,
4958 and remove the breakpoint definitions you're not interested in, or
4959 that can no longer be recreated.
4962 @node Static Probe Points
4963 @subsection Static Probe Points
4965 @cindex static probe point, SystemTap
4966 @cindex static probe point, DTrace
4967 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
4968 for Statically Defined Tracing, and the probes are designed to have a tiny
4969 runtime code and data footprint, and no dynamic relocations.
4971 Currently, the following types of probes are supported on
4972 ELF-compatible systems:
4976 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
4977 @acronym{SDT} probes@footnote{See
4978 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
4979 for more information on how to add @code{SystemTap} @acronym{SDT}
4980 probes in your applications.}. @code{SystemTap} probes are usable
4981 from assembly, C and C@t{++} languages@footnote{See
4982 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
4983 for a good reference on how the @acronym{SDT} probes are implemented.}.
4985 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
4986 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
4990 @cindex semaphores on static probe points
4991 Some @code{SystemTap} probes have an associated semaphore variable;
4992 for instance, this happens automatically if you defined your probe
4993 using a DTrace-style @file{.d} file. If your probe has a semaphore,
4994 @value{GDBN} will automatically enable it when you specify a
4995 breakpoint using the @samp{-probe-stap} notation. But, if you put a
4996 breakpoint at a probe's location by some other method (e.g.,
4997 @code{break file:line}), then @value{GDBN} will not automatically set
4998 the semaphore. @code{DTrace} probes do not support semaphores.
5000 You can examine the available static static probes using @code{info
5001 probes}, with optional arguments:
5005 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5006 If given, @var{type} is either @code{stap} for listing
5007 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5008 probes. If omitted all probes are listed regardless of their types.
5010 If given, @var{provider} is a regular expression used to match against provider
5011 names when selecting which probes to list. If omitted, probes by all
5012 probes from all providers are listed.
5014 If given, @var{name} is a regular expression to match against probe names
5015 when selecting which probes to list. If omitted, probe names are not
5016 considered when deciding whether to display them.
5018 If given, @var{objfile} is a regular expression used to select which
5019 object files (executable or shared libraries) to examine. If not
5020 given, all object files are considered.
5022 @item info probes all
5023 List the available static probes, from all types.
5026 @cindex enabling and disabling probes
5027 Some probe points can be enabled and/or disabled. The effect of
5028 enabling or disabling a probe depends on the type of probe being
5029 handled. Some @code{DTrace} probes can be enabled or
5030 disabled, but @code{SystemTap} probes cannot be disabled.
5032 You can enable (or disable) one or more probes using the following
5033 commands, with optional arguments:
5036 @kindex enable probes
5037 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5038 If given, @var{provider} is a regular expression used to match against
5039 provider names when selecting which probes to enable. If omitted,
5040 all probes from all providers are enabled.
5042 If given, @var{name} is a regular expression to match against probe
5043 names when selecting which probes to enable. If omitted, probe names
5044 are not considered when deciding whether to enable them.
5046 If given, @var{objfile} is a regular expression used to select which
5047 object files (executable or shared libraries) to examine. If not
5048 given, all object files are considered.
5050 @kindex disable probes
5051 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5052 See the @code{enable probes} command above for a description of the
5053 optional arguments accepted by this command.
5056 @vindex $_probe_arg@r{, convenience variable}
5057 A probe may specify up to twelve arguments. These are available at the
5058 point at which the probe is defined---that is, when the current PC is
5059 at the probe's location. The arguments are available using the
5060 convenience variables (@pxref{Convenience Vars})
5061 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5062 probes each probe argument is an integer of the appropriate size;
5063 types are not preserved. In @code{DTrace} probes types are preserved
5064 provided that they are recognized as such by @value{GDBN}; otherwise
5065 the value of the probe argument will be a long integer. The
5066 convenience variable @code{$_probe_argc} holds the number of arguments
5067 at the current probe point.
5069 These variables are always available, but attempts to access them at
5070 any location other than a probe point will cause @value{GDBN} to give
5074 @c @ifclear BARETARGET
5075 @node Error in Breakpoints
5076 @subsection ``Cannot insert breakpoints''
5078 If you request too many active hardware-assisted breakpoints and
5079 watchpoints, you will see this error message:
5081 @c FIXME: the precise wording of this message may change; the relevant
5082 @c source change is not committed yet (Sep 3, 1999).
5084 Stopped; cannot insert breakpoints.
5085 You may have requested too many hardware breakpoints and watchpoints.
5089 This message is printed when you attempt to resume the program, since
5090 only then @value{GDBN} knows exactly how many hardware breakpoints and
5091 watchpoints it needs to insert.
5093 When this message is printed, you need to disable or remove some of the
5094 hardware-assisted breakpoints and watchpoints, and then continue.
5096 @node Breakpoint-related Warnings
5097 @subsection ``Breakpoint address adjusted...''
5098 @cindex breakpoint address adjusted
5100 Some processor architectures place constraints on the addresses at
5101 which breakpoints may be placed. For architectures thus constrained,
5102 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5103 with the constraints dictated by the architecture.
5105 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5106 a VLIW architecture in which a number of RISC-like instructions may be
5107 bundled together for parallel execution. The FR-V architecture
5108 constrains the location of a breakpoint instruction within such a
5109 bundle to the instruction with the lowest address. @value{GDBN}
5110 honors this constraint by adjusting a breakpoint's address to the
5111 first in the bundle.
5113 It is not uncommon for optimized code to have bundles which contain
5114 instructions from different source statements, thus it may happen that
5115 a breakpoint's address will be adjusted from one source statement to
5116 another. Since this adjustment may significantly alter @value{GDBN}'s
5117 breakpoint related behavior from what the user expects, a warning is
5118 printed when the breakpoint is first set and also when the breakpoint
5121 A warning like the one below is printed when setting a breakpoint
5122 that's been subject to address adjustment:
5125 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5128 Such warnings are printed both for user settable and @value{GDBN}'s
5129 internal breakpoints. If you see one of these warnings, you should
5130 verify that a breakpoint set at the adjusted address will have the
5131 desired affect. If not, the breakpoint in question may be removed and
5132 other breakpoints may be set which will have the desired behavior.
5133 E.g., it may be sufficient to place the breakpoint at a later
5134 instruction. A conditional breakpoint may also be useful in some
5135 cases to prevent the breakpoint from triggering too often.
5137 @value{GDBN} will also issue a warning when stopping at one of these
5138 adjusted breakpoints:
5141 warning: Breakpoint 1 address previously adjusted from 0x00010414
5145 When this warning is encountered, it may be too late to take remedial
5146 action except in cases where the breakpoint is hit earlier or more
5147 frequently than expected.
5149 @node Continuing and Stepping
5150 @section Continuing and Stepping
5154 @cindex resuming execution
5155 @dfn{Continuing} means resuming program execution until your program
5156 completes normally. In contrast, @dfn{stepping} means executing just
5157 one more ``step'' of your program, where ``step'' may mean either one
5158 line of source code, or one machine instruction (depending on what
5159 particular command you use). Either when continuing or when stepping,
5160 your program may stop even sooner, due to a breakpoint or a signal. (If
5161 it stops due to a signal, you may want to use @code{handle}, or use
5162 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5163 or you may step into the signal's handler (@pxref{stepping and signal
5168 @kindex c @r{(@code{continue})}
5169 @kindex fg @r{(resume foreground execution)}
5170 @item continue @r{[}@var{ignore-count}@r{]}
5171 @itemx c @r{[}@var{ignore-count}@r{]}
5172 @itemx fg @r{[}@var{ignore-count}@r{]}
5173 Resume program execution, at the address where your program last stopped;
5174 any breakpoints set at that address are bypassed. The optional argument
5175 @var{ignore-count} allows you to specify a further number of times to
5176 ignore a breakpoint at this location; its effect is like that of
5177 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5179 The argument @var{ignore-count} is meaningful only when your program
5180 stopped due to a breakpoint. At other times, the argument to
5181 @code{continue} is ignored.
5183 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5184 debugged program is deemed to be the foreground program) are provided
5185 purely for convenience, and have exactly the same behavior as
5189 To resume execution at a different place, you can use @code{return}
5190 (@pxref{Returning, ,Returning from a Function}) to go back to the
5191 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5192 Different Address}) to go to an arbitrary location in your program.
5194 A typical technique for using stepping is to set a breakpoint
5195 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5196 beginning of the function or the section of your program where a problem
5197 is believed to lie, run your program until it stops at that breakpoint,
5198 and then step through the suspect area, examining the variables that are
5199 interesting, until you see the problem happen.
5203 @kindex s @r{(@code{step})}
5205 Continue running your program until control reaches a different source
5206 line, then stop it and return control to @value{GDBN}. This command is
5207 abbreviated @code{s}.
5210 @c "without debugging information" is imprecise; actually "without line
5211 @c numbers in the debugging information". (gcc -g1 has debugging info but
5212 @c not line numbers). But it seems complex to try to make that
5213 @c distinction here.
5214 @emph{Warning:} If you use the @code{step} command while control is
5215 within a function that was compiled without debugging information,
5216 execution proceeds until control reaches a function that does have
5217 debugging information. Likewise, it will not step into a function which
5218 is compiled without debugging information. To step through functions
5219 without debugging information, use the @code{stepi} command, described
5223 The @code{step} command only stops at the first instruction of a source
5224 line. This prevents the multiple stops that could otherwise occur in
5225 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5226 to stop if a function that has debugging information is called within
5227 the line. In other words, @code{step} @emph{steps inside} any functions
5228 called within the line.
5230 Also, the @code{step} command only enters a function if there is line
5231 number information for the function. Otherwise it acts like the
5232 @code{next} command. This avoids problems when using @code{cc -gl}
5233 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5234 was any debugging information about the routine.
5236 @item step @var{count}
5237 Continue running as in @code{step}, but do so @var{count} times. If a
5238 breakpoint is reached, or a signal not related to stepping occurs before
5239 @var{count} steps, stepping stops right away.
5242 @kindex n @r{(@code{next})}
5243 @item next @r{[}@var{count}@r{]}
5244 Continue to the next source line in the current (innermost) stack frame.
5245 This is similar to @code{step}, but function calls that appear within
5246 the line of code are executed without stopping. Execution stops when
5247 control reaches a different line of code at the original stack level
5248 that was executing when you gave the @code{next} command. This command
5249 is abbreviated @code{n}.
5251 An argument @var{count} is a repeat count, as for @code{step}.
5254 @c FIX ME!! Do we delete this, or is there a way it fits in with
5255 @c the following paragraph? --- Vctoria
5257 @c @code{next} within a function that lacks debugging information acts like
5258 @c @code{step}, but any function calls appearing within the code of the
5259 @c function are executed without stopping.
5261 The @code{next} command only stops at the first instruction of a
5262 source line. This prevents multiple stops that could otherwise occur in
5263 @code{switch} statements, @code{for} loops, etc.
5265 @kindex set step-mode
5267 @cindex functions without line info, and stepping
5268 @cindex stepping into functions with no line info
5269 @itemx set step-mode on
5270 The @code{set step-mode on} command causes the @code{step} command to
5271 stop at the first instruction of a function which contains no debug line
5272 information rather than stepping over it.
5274 This is useful in cases where you may be interested in inspecting the
5275 machine instructions of a function which has no symbolic info and do not
5276 want @value{GDBN} to automatically skip over this function.
5278 @item set step-mode off
5279 Causes the @code{step} command to step over any functions which contains no
5280 debug information. This is the default.
5282 @item show step-mode
5283 Show whether @value{GDBN} will stop in or step over functions without
5284 source line debug information.
5287 @kindex fin @r{(@code{finish})}
5289 Continue running until just after function in the selected stack frame
5290 returns. Print the returned value (if any). This command can be
5291 abbreviated as @code{fin}.
5293 Contrast this with the @code{return} command (@pxref{Returning,
5294 ,Returning from a Function}).
5297 @kindex u @r{(@code{until})}
5298 @cindex run until specified location
5301 Continue running until a source line past the current line, in the
5302 current stack frame, is reached. This command is used to avoid single
5303 stepping through a loop more than once. It is like the @code{next}
5304 command, except that when @code{until} encounters a jump, it
5305 automatically continues execution until the program counter is greater
5306 than the address of the jump.
5308 This means that when you reach the end of a loop after single stepping
5309 though it, @code{until} makes your program continue execution until it
5310 exits the loop. In contrast, a @code{next} command at the end of a loop
5311 simply steps back to the beginning of the loop, which forces you to step
5312 through the next iteration.
5314 @code{until} always stops your program if it attempts to exit the current
5317 @code{until} may produce somewhat counterintuitive results if the order
5318 of machine code does not match the order of the source lines. For
5319 example, in the following excerpt from a debugging session, the @code{f}
5320 (@code{frame}) command shows that execution is stopped at line
5321 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5325 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5327 (@value{GDBP}) until
5328 195 for ( ; argc > 0; NEXTARG) @{
5331 This happened because, for execution efficiency, the compiler had
5332 generated code for the loop closure test at the end, rather than the
5333 start, of the loop---even though the test in a C @code{for}-loop is
5334 written before the body of the loop. The @code{until} command appeared
5335 to step back to the beginning of the loop when it advanced to this
5336 expression; however, it has not really gone to an earlier
5337 statement---not in terms of the actual machine code.
5339 @code{until} with no argument works by means of single
5340 instruction stepping, and hence is slower than @code{until} with an
5343 @item until @var{location}
5344 @itemx u @var{location}
5345 Continue running your program until either the specified @var{location} is
5346 reached, or the current stack frame returns. The location is any of
5347 the forms described in @ref{Specify Location}.
5348 This form of the command uses temporary breakpoints, and
5349 hence is quicker than @code{until} without an argument. The specified
5350 location is actually reached only if it is in the current frame. This
5351 implies that @code{until} can be used to skip over recursive function
5352 invocations. For instance in the code below, if the current location is
5353 line @code{96}, issuing @code{until 99} will execute the program up to
5354 line @code{99} in the same invocation of factorial, i.e., after the inner
5355 invocations have returned.
5358 94 int factorial (int value)
5360 96 if (value > 1) @{
5361 97 value *= factorial (value - 1);
5368 @kindex advance @var{location}
5369 @item advance @var{location}
5370 Continue running the program up to the given @var{location}. An argument is
5371 required, which should be of one of the forms described in
5372 @ref{Specify Location}.
5373 Execution will also stop upon exit from the current stack
5374 frame. This command is similar to @code{until}, but @code{advance} will
5375 not skip over recursive function calls, and the target location doesn't
5376 have to be in the same frame as the current one.
5380 @kindex si @r{(@code{stepi})}
5382 @itemx stepi @var{arg}
5384 Execute one machine instruction, then stop and return to the debugger.
5386 It is often useful to do @samp{display/i $pc} when stepping by machine
5387 instructions. This makes @value{GDBN} automatically display the next
5388 instruction to be executed, each time your program stops. @xref{Auto
5389 Display,, Automatic Display}.
5391 An argument is a repeat count, as in @code{step}.
5395 @kindex ni @r{(@code{nexti})}
5397 @itemx nexti @var{arg}
5399 Execute one machine instruction, but if it is a function call,
5400 proceed until the function returns.
5402 An argument is a repeat count, as in @code{next}.
5406 @anchor{range stepping}
5407 @cindex range stepping
5408 @cindex target-assisted range stepping
5409 By default, and if available, @value{GDBN} makes use of
5410 target-assisted @dfn{range stepping}. In other words, whenever you
5411 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5412 tells the target to step the corresponding range of instruction
5413 addresses instead of issuing multiple single-steps. This speeds up
5414 line stepping, particularly for remote targets. Ideally, there should
5415 be no reason you would want to turn range stepping off. However, it's
5416 possible that a bug in the debug info, a bug in the remote stub (for
5417 remote targets), or even a bug in @value{GDBN} could make line
5418 stepping behave incorrectly when target-assisted range stepping is
5419 enabled. You can use the following command to turn off range stepping
5423 @kindex set range-stepping
5424 @kindex show range-stepping
5425 @item set range-stepping
5426 @itemx show range-stepping
5427 Control whether range stepping is enabled.
5429 If @code{on}, and the target supports it, @value{GDBN} tells the
5430 target to step a range of addresses itself, instead of issuing
5431 multiple single-steps. If @code{off}, @value{GDBN} always issues
5432 single-steps, even if range stepping is supported by the target. The
5433 default is @code{on}.
5437 @node Skipping Over Functions and Files
5438 @section Skipping Over Functions and Files
5439 @cindex skipping over functions and files
5441 The program you are debugging may contain some functions which are
5442 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
5443 skip a function or all functions in a file when stepping.
5445 For example, consider the following C function:
5456 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5457 are not interested in stepping through @code{boring}. If you run @code{step}
5458 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5459 step over both @code{foo} and @code{boring}!
5461 One solution is to @code{step} into @code{boring} and use the @code{finish}
5462 command to immediately exit it. But this can become tedious if @code{boring}
5463 is called from many places.
5465 A more flexible solution is to execute @kbd{skip boring}. This instructs
5466 @value{GDBN} never to step into @code{boring}. Now when you execute
5467 @code{step} at line 103, you'll step over @code{boring} and directly into
5470 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5471 example, @code{skip file boring.c}.
5474 @kindex skip function
5475 @item skip @r{[}@var{linespec}@r{]}
5476 @itemx skip function @r{[}@var{linespec}@r{]}
5477 After running this command, the function named by @var{linespec} or the
5478 function containing the line named by @var{linespec} will be skipped over when
5479 stepping. @xref{Specify Location}.
5481 If you do not specify @var{linespec}, the function you're currently debugging
5484 (If you have a function called @code{file} that you want to skip, use
5485 @kbd{skip function file}.)
5488 @item skip file @r{[}@var{filename}@r{]}
5489 After running this command, any function whose source lives in @var{filename}
5490 will be skipped over when stepping.
5492 If you do not specify @var{filename}, functions whose source lives in the file
5493 you're currently debugging will be skipped.
5496 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5497 These are the commands for managing your list of skips:
5501 @item info skip @r{[}@var{range}@r{]}
5502 Print details about the specified skip(s). If @var{range} is not specified,
5503 print a table with details about all functions and files marked for skipping.
5504 @code{info skip} prints the following information about each skip:
5508 A number identifying this skip.
5510 The type of this skip, either @samp{function} or @samp{file}.
5511 @item Enabled or Disabled
5512 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5514 For function skips, this column indicates the address in memory of the function
5515 being skipped. If you've set a function skip on a function which has not yet
5516 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5517 which has the function is loaded, @code{info skip} will show the function's
5520 For file skips, this field contains the filename being skipped. For functions
5521 skips, this field contains the function name and its line number in the file
5522 where it is defined.
5526 @item skip delete @r{[}@var{range}@r{]}
5527 Delete the specified skip(s). If @var{range} is not specified, delete all
5531 @item skip enable @r{[}@var{range}@r{]}
5532 Enable the specified skip(s). If @var{range} is not specified, enable all
5535 @kindex skip disable
5536 @item skip disable @r{[}@var{range}@r{]}
5537 Disable the specified skip(s). If @var{range} is not specified, disable all
5546 A signal is an asynchronous event that can happen in a program. The
5547 operating system defines the possible kinds of signals, and gives each
5548 kind a name and a number. For example, in Unix @code{SIGINT} is the
5549 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5550 @code{SIGSEGV} is the signal a program gets from referencing a place in
5551 memory far away from all the areas in use; @code{SIGALRM} occurs when
5552 the alarm clock timer goes off (which happens only if your program has
5553 requested an alarm).
5555 @cindex fatal signals
5556 Some signals, including @code{SIGALRM}, are a normal part of the
5557 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5558 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5559 program has not specified in advance some other way to handle the signal.
5560 @code{SIGINT} does not indicate an error in your program, but it is normally
5561 fatal so it can carry out the purpose of the interrupt: to kill the program.
5563 @value{GDBN} has the ability to detect any occurrence of a signal in your
5564 program. You can tell @value{GDBN} in advance what to do for each kind of
5567 @cindex handling signals
5568 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5569 @code{SIGALRM} be silently passed to your program
5570 (so as not to interfere with their role in the program's functioning)
5571 but to stop your program immediately whenever an error signal happens.
5572 You can change these settings with the @code{handle} command.
5575 @kindex info signals
5579 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5580 handle each one. You can use this to see the signal numbers of all
5581 the defined types of signals.
5583 @item info signals @var{sig}
5584 Similar, but print information only about the specified signal number.
5586 @code{info handle} is an alias for @code{info signals}.
5588 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5589 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5590 for details about this command.
5593 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5594 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5595 can be the number of a signal or its name (with or without the
5596 @samp{SIG} at the beginning); a list of signal numbers of the form
5597 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5598 known signals. Optional arguments @var{keywords}, described below,
5599 say what change to make.
5603 The keywords allowed by the @code{handle} command can be abbreviated.
5604 Their full names are:
5608 @value{GDBN} should not stop your program when this signal happens. It may
5609 still print a message telling you that the signal has come in.
5612 @value{GDBN} should stop your program when this signal happens. This implies
5613 the @code{print} keyword as well.
5616 @value{GDBN} should print a message when this signal happens.
5619 @value{GDBN} should not mention the occurrence of the signal at all. This
5620 implies the @code{nostop} keyword as well.
5624 @value{GDBN} should allow your program to see this signal; your program
5625 can handle the signal, or else it may terminate if the signal is fatal
5626 and not handled. @code{pass} and @code{noignore} are synonyms.
5630 @value{GDBN} should not allow your program to see this signal.
5631 @code{nopass} and @code{ignore} are synonyms.
5635 When a signal stops your program, the signal is not visible to the
5637 continue. Your program sees the signal then, if @code{pass} is in
5638 effect for the signal in question @emph{at that time}. In other words,
5639 after @value{GDBN} reports a signal, you can use the @code{handle}
5640 command with @code{pass} or @code{nopass} to control whether your
5641 program sees that signal when you continue.
5643 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5644 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5645 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5648 You can also use the @code{signal} command to prevent your program from
5649 seeing a signal, or cause it to see a signal it normally would not see,
5650 or to give it any signal at any time. For example, if your program stopped
5651 due to some sort of memory reference error, you might store correct
5652 values into the erroneous variables and continue, hoping to see more
5653 execution; but your program would probably terminate immediately as
5654 a result of the fatal signal once it saw the signal. To prevent this,
5655 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5658 @cindex stepping and signal handlers
5659 @anchor{stepping and signal handlers}
5661 @value{GDBN} optimizes for stepping the mainline code. If a signal
5662 that has @code{handle nostop} and @code{handle pass} set arrives while
5663 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
5664 in progress, @value{GDBN} lets the signal handler run and then resumes
5665 stepping the mainline code once the signal handler returns. In other
5666 words, @value{GDBN} steps over the signal handler. This prevents
5667 signals that you've specified as not interesting (with @code{handle
5668 nostop}) from changing the focus of debugging unexpectedly. Note that
5669 the signal handler itself may still hit a breakpoint, stop for another
5670 signal that has @code{handle stop} in effect, or for any other event
5671 that normally results in stopping the stepping command sooner. Also
5672 note that @value{GDBN} still informs you that the program received a
5673 signal if @code{handle print} is set.
5675 @anchor{stepping into signal handlers}
5677 If you set @code{handle pass} for a signal, and your program sets up a
5678 handler for it, then issuing a stepping command, such as @code{step}
5679 or @code{stepi}, when your program is stopped due to the signal will
5680 step @emph{into} the signal handler (if the target supports that).
5682 Likewise, if you use the @code{queue-signal} command to queue a signal
5683 to be delivered to the current thread when execution of the thread
5684 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
5685 stepping command will step into the signal handler.
5687 Here's an example, using @code{stepi} to step to the first instruction
5688 of @code{SIGUSR1}'s handler:
5691 (@value{GDBP}) handle SIGUSR1
5692 Signal Stop Print Pass to program Description
5693 SIGUSR1 Yes Yes Yes User defined signal 1
5697 Program received signal SIGUSR1, User defined signal 1.
5698 main () sigusr1.c:28
5701 sigusr1_handler () at sigusr1.c:9
5705 The same, but using @code{queue-signal} instead of waiting for the
5706 program to receive the signal first:
5711 (@value{GDBP}) queue-signal SIGUSR1
5713 sigusr1_handler () at sigusr1.c:9
5718 @cindex extra signal information
5719 @anchor{extra signal information}
5721 On some targets, @value{GDBN} can inspect extra signal information
5722 associated with the intercepted signal, before it is actually
5723 delivered to the program being debugged. This information is exported
5724 by the convenience variable @code{$_siginfo}, and consists of data
5725 that is passed by the kernel to the signal handler at the time of the
5726 receipt of a signal. The data type of the information itself is
5727 target dependent. You can see the data type using the @code{ptype
5728 $_siginfo} command. On Unix systems, it typically corresponds to the
5729 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5732 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5733 referenced address that raised a segmentation fault.
5737 (@value{GDBP}) continue
5738 Program received signal SIGSEGV, Segmentation fault.
5739 0x0000000000400766 in main ()
5741 (@value{GDBP}) ptype $_siginfo
5748 struct @{...@} _kill;
5749 struct @{...@} _timer;
5751 struct @{...@} _sigchld;
5752 struct @{...@} _sigfault;
5753 struct @{...@} _sigpoll;
5756 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5760 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5761 $1 = (void *) 0x7ffff7ff7000
5765 Depending on target support, @code{$_siginfo} may also be writable.
5768 @section Stopping and Starting Multi-thread Programs
5770 @cindex stopped threads
5771 @cindex threads, stopped
5773 @cindex continuing threads
5774 @cindex threads, continuing
5776 @value{GDBN} supports debugging programs with multiple threads
5777 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5778 are two modes of controlling execution of your program within the
5779 debugger. In the default mode, referred to as @dfn{all-stop mode},
5780 when any thread in your program stops (for example, at a breakpoint
5781 or while being stepped), all other threads in the program are also stopped by
5782 @value{GDBN}. On some targets, @value{GDBN} also supports
5783 @dfn{non-stop mode}, in which other threads can continue to run freely while
5784 you examine the stopped thread in the debugger.
5787 * All-Stop Mode:: All threads stop when GDB takes control
5788 * Non-Stop Mode:: Other threads continue to execute
5789 * Background Execution:: Running your program asynchronously
5790 * Thread-Specific Breakpoints:: Controlling breakpoints
5791 * Interrupted System Calls:: GDB may interfere with system calls
5792 * Observer Mode:: GDB does not alter program behavior
5796 @subsection All-Stop Mode
5798 @cindex all-stop mode
5800 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5801 @emph{all} threads of execution stop, not just the current thread. This
5802 allows you to examine the overall state of the program, including
5803 switching between threads, without worrying that things may change
5806 Conversely, whenever you restart the program, @emph{all} threads start
5807 executing. @emph{This is true even when single-stepping} with commands
5808 like @code{step} or @code{next}.
5810 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5811 Since thread scheduling is up to your debugging target's operating
5812 system (not controlled by @value{GDBN}), other threads may
5813 execute more than one statement while the current thread completes a
5814 single step. Moreover, in general other threads stop in the middle of a
5815 statement, rather than at a clean statement boundary, when the program
5818 You might even find your program stopped in another thread after
5819 continuing or even single-stepping. This happens whenever some other
5820 thread runs into a breakpoint, a signal, or an exception before the
5821 first thread completes whatever you requested.
5823 @cindex automatic thread selection
5824 @cindex switching threads automatically
5825 @cindex threads, automatic switching
5826 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5827 signal, it automatically selects the thread where that breakpoint or
5828 signal happened. @value{GDBN} alerts you to the context switch with a
5829 message such as @samp{[Switching to Thread @var{n}]} to identify the
5832 On some OSes, you can modify @value{GDBN}'s default behavior by
5833 locking the OS scheduler to allow only a single thread to run.
5836 @item set scheduler-locking @var{mode}
5837 @cindex scheduler locking mode
5838 @cindex lock scheduler
5839 Set the scheduler locking mode. It applies to normal execution,
5840 record mode, and replay mode. If it is @code{off}, then there is no
5841 locking and any thread may run at any time. If @code{on}, then only
5842 the current thread may run when the inferior is resumed. The
5843 @code{step} mode optimizes for single-stepping; it prevents other
5844 threads from preempting the current thread while you are stepping, so
5845 that the focus of debugging does not change unexpectedly. Other
5846 threads never get a chance to run when you step, and they are
5847 completely free to run when you use commands like @samp{continue},
5848 @samp{until}, or @samp{finish}. However, unless another thread hits a
5849 breakpoint during its timeslice, @value{GDBN} does not change the
5850 current thread away from the thread that you are debugging. The
5851 @code{replay} mode behaves like @code{off} in record mode and like
5852 @code{on} in replay mode.
5854 @item show scheduler-locking
5855 Display the current scheduler locking mode.
5858 @cindex resume threads of multiple processes simultaneously
5859 By default, when you issue one of the execution commands such as
5860 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5861 threads of the current inferior to run. For example, if @value{GDBN}
5862 is attached to two inferiors, each with two threads, the
5863 @code{continue} command resumes only the two threads of the current
5864 inferior. This is useful, for example, when you debug a program that
5865 forks and you want to hold the parent stopped (so that, for instance,
5866 it doesn't run to exit), while you debug the child. In other
5867 situations, you may not be interested in inspecting the current state
5868 of any of the processes @value{GDBN} is attached to, and you may want
5869 to resume them all until some breakpoint is hit. In the latter case,
5870 you can instruct @value{GDBN} to allow all threads of all the
5871 inferiors to run with the @w{@code{set schedule-multiple}} command.
5874 @kindex set schedule-multiple
5875 @item set schedule-multiple
5876 Set the mode for allowing threads of multiple processes to be resumed
5877 when an execution command is issued. When @code{on}, all threads of
5878 all processes are allowed to run. When @code{off}, only the threads
5879 of the current process are resumed. The default is @code{off}. The
5880 @code{scheduler-locking} mode takes precedence when set to @code{on},
5881 or while you are stepping and set to @code{step}.
5883 @item show schedule-multiple
5884 Display the current mode for resuming the execution of threads of
5889 @subsection Non-Stop Mode
5891 @cindex non-stop mode
5893 @c This section is really only a place-holder, and needs to be expanded
5894 @c with more details.
5896 For some multi-threaded targets, @value{GDBN} supports an optional
5897 mode of operation in which you can examine stopped program threads in
5898 the debugger while other threads continue to execute freely. This
5899 minimizes intrusion when debugging live systems, such as programs
5900 where some threads have real-time constraints or must continue to
5901 respond to external events. This is referred to as @dfn{non-stop} mode.
5903 In non-stop mode, when a thread stops to report a debugging event,
5904 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5905 threads as well, in contrast to the all-stop mode behavior. Additionally,
5906 execution commands such as @code{continue} and @code{step} apply by default
5907 only to the current thread in non-stop mode, rather than all threads as
5908 in all-stop mode. This allows you to control threads explicitly in
5909 ways that are not possible in all-stop mode --- for example, stepping
5910 one thread while allowing others to run freely, stepping
5911 one thread while holding all others stopped, or stepping several threads
5912 independently and simultaneously.
5914 To enter non-stop mode, use this sequence of commands before you run
5915 or attach to your program:
5918 # If using the CLI, pagination breaks non-stop.
5921 # Finally, turn it on!
5925 You can use these commands to manipulate the non-stop mode setting:
5928 @kindex set non-stop
5929 @item set non-stop on
5930 Enable selection of non-stop mode.
5931 @item set non-stop off
5932 Disable selection of non-stop mode.
5933 @kindex show non-stop
5935 Show the current non-stop enablement setting.
5938 Note these commands only reflect whether non-stop mode is enabled,
5939 not whether the currently-executing program is being run in non-stop mode.
5940 In particular, the @code{set non-stop} preference is only consulted when
5941 @value{GDBN} starts or connects to the target program, and it is generally
5942 not possible to switch modes once debugging has started. Furthermore,
5943 since not all targets support non-stop mode, even when you have enabled
5944 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5947 In non-stop mode, all execution commands apply only to the current thread
5948 by default. That is, @code{continue} only continues one thread.
5949 To continue all threads, issue @code{continue -a} or @code{c -a}.
5951 You can use @value{GDBN}'s background execution commands
5952 (@pxref{Background Execution}) to run some threads in the background
5953 while you continue to examine or step others from @value{GDBN}.
5954 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5955 always executed asynchronously in non-stop mode.
5957 Suspending execution is done with the @code{interrupt} command when
5958 running in the background, or @kbd{Ctrl-c} during foreground execution.
5959 In all-stop mode, this stops the whole process;
5960 but in non-stop mode the interrupt applies only to the current thread.
5961 To stop the whole program, use @code{interrupt -a}.
5963 Other execution commands do not currently support the @code{-a} option.
5965 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5966 that thread current, as it does in all-stop mode. This is because the
5967 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5968 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5969 changed to a different thread just as you entered a command to operate on the
5970 previously current thread.
5972 @node Background Execution
5973 @subsection Background Execution
5975 @cindex foreground execution
5976 @cindex background execution
5977 @cindex asynchronous execution
5978 @cindex execution, foreground, background and asynchronous
5980 @value{GDBN}'s execution commands have two variants: the normal
5981 foreground (synchronous) behavior, and a background
5982 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5983 the program to report that some thread has stopped before prompting for
5984 another command. In background execution, @value{GDBN} immediately gives
5985 a command prompt so that you can issue other commands while your program runs.
5987 If the target doesn't support async mode, @value{GDBN} issues an error
5988 message if you attempt to use the background execution commands.
5990 To specify background execution, add a @code{&} to the command. For example,
5991 the background form of the @code{continue} command is @code{continue&}, or
5992 just @code{c&}. The execution commands that accept background execution
5998 @xref{Starting, , Starting your Program}.
6002 @xref{Attach, , Debugging an Already-running Process}.
6006 @xref{Continuing and Stepping, step}.
6010 @xref{Continuing and Stepping, stepi}.
6014 @xref{Continuing and Stepping, next}.
6018 @xref{Continuing and Stepping, nexti}.
6022 @xref{Continuing and Stepping, continue}.
6026 @xref{Continuing and Stepping, finish}.
6030 @xref{Continuing and Stepping, until}.
6034 Background execution is especially useful in conjunction with non-stop
6035 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6036 However, you can also use these commands in the normal all-stop mode with
6037 the restriction that you cannot issue another execution command until the
6038 previous one finishes. Examples of commands that are valid in all-stop
6039 mode while the program is running include @code{help} and @code{info break}.
6041 You can interrupt your program while it is running in the background by
6042 using the @code{interrupt} command.
6049 Suspend execution of the running program. In all-stop mode,
6050 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6051 only the current thread. To stop the whole program in non-stop mode,
6052 use @code{interrupt -a}.
6055 @node Thread-Specific Breakpoints
6056 @subsection Thread-Specific Breakpoints
6058 When your program has multiple threads (@pxref{Threads,, Debugging
6059 Programs with Multiple Threads}), you can choose whether to set
6060 breakpoints on all threads, or on a particular thread.
6063 @cindex breakpoints and threads
6064 @cindex thread breakpoints
6065 @kindex break @dots{} thread @var{threadno}
6066 @item break @var{location} thread @var{threadno}
6067 @itemx break @var{location} thread @var{threadno} if @dots{}
6068 @var{location} specifies source lines; there are several ways of
6069 writing them (@pxref{Specify Location}), but the effect is always to
6070 specify some source line.
6072 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
6073 to specify that you only want @value{GDBN} to stop the program when a
6074 particular thread reaches this breakpoint. The @var{threadno} specifier
6075 is one of the numeric thread identifiers assigned by @value{GDBN}, shown
6076 in the first column of the @samp{info threads} display.
6078 If you do not specify @samp{thread @var{threadno}} when you set a
6079 breakpoint, the breakpoint applies to @emph{all} threads of your
6082 You can use the @code{thread} qualifier on conditional breakpoints as
6083 well; in this case, place @samp{thread @var{threadno}} before or
6084 after the breakpoint condition, like this:
6087 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6092 Thread-specific breakpoints are automatically deleted when
6093 @value{GDBN} detects the corresponding thread is no longer in the
6094 thread list. For example:
6098 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6101 There are several ways for a thread to disappear, such as a regular
6102 thread exit, but also when you detach from the process with the
6103 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6104 Process}), or if @value{GDBN} loses the remote connection
6105 (@pxref{Remote Debugging}), etc. Note that with some targets,
6106 @value{GDBN} is only able to detect a thread has exited when the user
6107 explictly asks for the thread list with the @code{info threads}
6110 @node Interrupted System Calls
6111 @subsection Interrupted System Calls
6113 @cindex thread breakpoints and system calls
6114 @cindex system calls and thread breakpoints
6115 @cindex premature return from system calls
6116 There is an unfortunate side effect when using @value{GDBN} to debug
6117 multi-threaded programs. If one thread stops for a
6118 breakpoint, or for some other reason, and another thread is blocked in a
6119 system call, then the system call may return prematurely. This is a
6120 consequence of the interaction between multiple threads and the signals
6121 that @value{GDBN} uses to implement breakpoints and other events that
6124 To handle this problem, your program should check the return value of
6125 each system call and react appropriately. This is good programming
6128 For example, do not write code like this:
6134 The call to @code{sleep} will return early if a different thread stops
6135 at a breakpoint or for some other reason.
6137 Instead, write this:
6142 unslept = sleep (unslept);
6145 A system call is allowed to return early, so the system is still
6146 conforming to its specification. But @value{GDBN} does cause your
6147 multi-threaded program to behave differently than it would without
6150 Also, @value{GDBN} uses internal breakpoints in the thread library to
6151 monitor certain events such as thread creation and thread destruction.
6152 When such an event happens, a system call in another thread may return
6153 prematurely, even though your program does not appear to stop.
6156 @subsection Observer Mode
6158 If you want to build on non-stop mode and observe program behavior
6159 without any chance of disruption by @value{GDBN}, you can set
6160 variables to disable all of the debugger's attempts to modify state,
6161 whether by writing memory, inserting breakpoints, etc. These operate
6162 at a low level, intercepting operations from all commands.
6164 When all of these are set to @code{off}, then @value{GDBN} is said to
6165 be @dfn{observer mode}. As a convenience, the variable
6166 @code{observer} can be set to disable these, plus enable non-stop
6169 Note that @value{GDBN} will not prevent you from making nonsensical
6170 combinations of these settings. For instance, if you have enabled
6171 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6172 then breakpoints that work by writing trap instructions into the code
6173 stream will still not be able to be placed.
6178 @item set observer on
6179 @itemx set observer off
6180 When set to @code{on}, this disables all the permission variables
6181 below (except for @code{insert-fast-tracepoints}), plus enables
6182 non-stop debugging. Setting this to @code{off} switches back to
6183 normal debugging, though remaining in non-stop mode.
6186 Show whether observer mode is on or off.
6188 @kindex may-write-registers
6189 @item set may-write-registers on
6190 @itemx set may-write-registers off
6191 This controls whether @value{GDBN} will attempt to alter the values of
6192 registers, such as with assignment expressions in @code{print}, or the
6193 @code{jump} command. It defaults to @code{on}.
6195 @item show may-write-registers
6196 Show the current permission to write registers.
6198 @kindex may-write-memory
6199 @item set may-write-memory on
6200 @itemx set may-write-memory off
6201 This controls whether @value{GDBN} will attempt to alter the contents
6202 of memory, such as with assignment expressions in @code{print}. It
6203 defaults to @code{on}.
6205 @item show may-write-memory
6206 Show the current permission to write memory.
6208 @kindex may-insert-breakpoints
6209 @item set may-insert-breakpoints on
6210 @itemx set may-insert-breakpoints off
6211 This controls whether @value{GDBN} will attempt to insert breakpoints.
6212 This affects all breakpoints, including internal breakpoints defined
6213 by @value{GDBN}. It defaults to @code{on}.
6215 @item show may-insert-breakpoints
6216 Show the current permission to insert breakpoints.
6218 @kindex may-insert-tracepoints
6219 @item set may-insert-tracepoints on
6220 @itemx set may-insert-tracepoints off
6221 This controls whether @value{GDBN} will attempt to insert (regular)
6222 tracepoints at the beginning of a tracing experiment. It affects only
6223 non-fast tracepoints, fast tracepoints being under the control of
6224 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6226 @item show may-insert-tracepoints
6227 Show the current permission to insert tracepoints.
6229 @kindex may-insert-fast-tracepoints
6230 @item set may-insert-fast-tracepoints on
6231 @itemx set may-insert-fast-tracepoints off
6232 This controls whether @value{GDBN} will attempt to insert fast
6233 tracepoints at the beginning of a tracing experiment. It affects only
6234 fast tracepoints, regular (non-fast) tracepoints being under the
6235 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6237 @item show may-insert-fast-tracepoints
6238 Show the current permission to insert fast tracepoints.
6240 @kindex may-interrupt
6241 @item set may-interrupt on
6242 @itemx set may-interrupt off
6243 This controls whether @value{GDBN} will attempt to interrupt or stop
6244 program execution. When this variable is @code{off}, the
6245 @code{interrupt} command will have no effect, nor will
6246 @kbd{Ctrl-c}. It defaults to @code{on}.
6248 @item show may-interrupt
6249 Show the current permission to interrupt or stop the program.
6253 @node Reverse Execution
6254 @chapter Running programs backward
6255 @cindex reverse execution
6256 @cindex running programs backward
6258 When you are debugging a program, it is not unusual to realize that
6259 you have gone too far, and some event of interest has already happened.
6260 If the target environment supports it, @value{GDBN} can allow you to
6261 ``rewind'' the program by running it backward.
6263 A target environment that supports reverse execution should be able
6264 to ``undo'' the changes in machine state that have taken place as the
6265 program was executing normally. Variables, registers etc.@: should
6266 revert to their previous values. Obviously this requires a great
6267 deal of sophistication on the part of the target environment; not
6268 all target environments can support reverse execution.
6270 When a program is executed in reverse, the instructions that
6271 have most recently been executed are ``un-executed'', in reverse
6272 order. The program counter runs backward, following the previous
6273 thread of execution in reverse. As each instruction is ``un-executed'',
6274 the values of memory and/or registers that were changed by that
6275 instruction are reverted to their previous states. After executing
6276 a piece of source code in reverse, all side effects of that code
6277 should be ``undone'', and all variables should be returned to their
6278 prior values@footnote{
6279 Note that some side effects are easier to undo than others. For instance,
6280 memory and registers are relatively easy, but device I/O is hard. Some
6281 targets may be able undo things like device I/O, and some may not.
6283 The contract between @value{GDBN} and the reverse executing target
6284 requires only that the target do something reasonable when
6285 @value{GDBN} tells it to execute backwards, and then report the
6286 results back to @value{GDBN}. Whatever the target reports back to
6287 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6288 assumes that the memory and registers that the target reports are in a
6289 consistant state, but @value{GDBN} accepts whatever it is given.
6292 If you are debugging in a target environment that supports
6293 reverse execution, @value{GDBN} provides the following commands.
6296 @kindex reverse-continue
6297 @kindex rc @r{(@code{reverse-continue})}
6298 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6299 @itemx rc @r{[}@var{ignore-count}@r{]}
6300 Beginning at the point where your program last stopped, start executing
6301 in reverse. Reverse execution will stop for breakpoints and synchronous
6302 exceptions (signals), just like normal execution. Behavior of
6303 asynchronous signals depends on the target environment.
6305 @kindex reverse-step
6306 @kindex rs @r{(@code{step})}
6307 @item reverse-step @r{[}@var{count}@r{]}
6308 Run the program backward until control reaches the start of a
6309 different source line; then stop it, and return control to @value{GDBN}.
6311 Like the @code{step} command, @code{reverse-step} will only stop
6312 at the beginning of a source line. It ``un-executes'' the previously
6313 executed source line. If the previous source line included calls to
6314 debuggable functions, @code{reverse-step} will step (backward) into
6315 the called function, stopping at the beginning of the @emph{last}
6316 statement in the called function (typically a return statement).
6318 Also, as with the @code{step} command, if non-debuggable functions are
6319 called, @code{reverse-step} will run thru them backward without stopping.
6321 @kindex reverse-stepi
6322 @kindex rsi @r{(@code{reverse-stepi})}
6323 @item reverse-stepi @r{[}@var{count}@r{]}
6324 Reverse-execute one machine instruction. Note that the instruction
6325 to be reverse-executed is @emph{not} the one pointed to by the program
6326 counter, but the instruction executed prior to that one. For instance,
6327 if the last instruction was a jump, @code{reverse-stepi} will take you
6328 back from the destination of the jump to the jump instruction itself.
6330 @kindex reverse-next
6331 @kindex rn @r{(@code{reverse-next})}
6332 @item reverse-next @r{[}@var{count}@r{]}
6333 Run backward to the beginning of the previous line executed in
6334 the current (innermost) stack frame. If the line contains function
6335 calls, they will be ``un-executed'' without stopping. Starting from
6336 the first line of a function, @code{reverse-next} will take you back
6337 to the caller of that function, @emph{before} the function was called,
6338 just as the normal @code{next} command would take you from the last
6339 line of a function back to its return to its caller
6340 @footnote{Unless the code is too heavily optimized.}.
6342 @kindex reverse-nexti
6343 @kindex rni @r{(@code{reverse-nexti})}
6344 @item reverse-nexti @r{[}@var{count}@r{]}
6345 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6346 in reverse, except that called functions are ``un-executed'' atomically.
6347 That is, if the previously executed instruction was a return from
6348 another function, @code{reverse-nexti} will continue to execute
6349 in reverse until the call to that function (from the current stack
6352 @kindex reverse-finish
6353 @item reverse-finish
6354 Just as the @code{finish} command takes you to the point where the
6355 current function returns, @code{reverse-finish} takes you to the point
6356 where it was called. Instead of ending up at the end of the current
6357 function invocation, you end up at the beginning.
6359 @kindex set exec-direction
6360 @item set exec-direction
6361 Set the direction of target execution.
6362 @item set exec-direction reverse
6363 @cindex execute forward or backward in time
6364 @value{GDBN} will perform all execution commands in reverse, until the
6365 exec-direction mode is changed to ``forward''. Affected commands include
6366 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6367 command cannot be used in reverse mode.
6368 @item set exec-direction forward
6369 @value{GDBN} will perform all execution commands in the normal fashion.
6370 This is the default.
6374 @node Process Record and Replay
6375 @chapter Recording Inferior's Execution and Replaying It
6376 @cindex process record and replay
6377 @cindex recording inferior's execution and replaying it
6379 On some platforms, @value{GDBN} provides a special @dfn{process record
6380 and replay} target that can record a log of the process execution, and
6381 replay it later with both forward and reverse execution commands.
6384 When this target is in use, if the execution log includes the record
6385 for the next instruction, @value{GDBN} will debug in @dfn{replay
6386 mode}. In the replay mode, the inferior does not really execute code
6387 instructions. Instead, all the events that normally happen during
6388 code execution are taken from the execution log. While code is not
6389 really executed in replay mode, the values of registers (including the
6390 program counter register) and the memory of the inferior are still
6391 changed as they normally would. Their contents are taken from the
6395 If the record for the next instruction is not in the execution log,
6396 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6397 inferior executes normally, and @value{GDBN} records the execution log
6400 The process record and replay target supports reverse execution
6401 (@pxref{Reverse Execution}), even if the platform on which the
6402 inferior runs does not. However, the reverse execution is limited in
6403 this case by the range of the instructions recorded in the execution
6404 log. In other words, reverse execution on platforms that don't
6405 support it directly can only be done in the replay mode.
6407 When debugging in the reverse direction, @value{GDBN} will work in
6408 replay mode as long as the execution log includes the record for the
6409 previous instruction; otherwise, it will work in record mode, if the
6410 platform supports reverse execution, or stop if not.
6412 For architecture environments that support process record and replay,
6413 @value{GDBN} provides the following commands:
6416 @kindex target record
6417 @kindex target record-full
6418 @kindex target record-btrace
6421 @kindex record btrace
6422 @kindex record btrace bts
6423 @kindex record btrace pt
6429 @kindex rec btrace bts
6430 @kindex rec btrace pt
6433 @item record @var{method}
6434 This command starts the process record and replay target. The
6435 recording method can be specified as parameter. Without a parameter
6436 the command uses the @code{full} recording method. The following
6437 recording methods are available:
6441 Full record/replay recording using @value{GDBN}'s software record and
6442 replay implementation. This method allows replaying and reverse
6445 @item btrace @var{format}
6446 Hardware-supported instruction recording. This method does not record
6447 data. Further, the data is collected in a ring buffer so old data will
6448 be overwritten when the buffer is full. It allows limited reverse
6449 execution. Variables and registers are not available during reverse
6452 The recording format can be specified as parameter. Without a parameter
6453 the command chooses the recording format. The following recording
6454 formats are available:
6458 @cindex branch trace store
6459 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
6460 this format, the processor stores a from/to record for each executed
6461 branch in the btrace ring buffer.
6464 @cindex Intel(R) Processor Trace
6465 Use the @dfn{Intel(R) Processor Trace} recording format. In this
6466 format, the processor stores the execution trace in a compressed form
6467 that is afterwards decoded by @value{GDBN}.
6469 The trace can be recorded with very low overhead. The compressed
6470 trace format also allows small trace buffers to already contain a big
6471 number of instructions compared to @acronym{BTS}.
6473 Decoding the recorded execution trace, on the other hand, is more
6474 expensive than decoding @acronym{BTS} trace. This is mostly due to the
6475 increased number of instructions to process. You should increase the
6476 buffer-size with care.
6479 Not all recording formats may be available on all processors.
6482 The process record and replay target can only debug a process that is
6483 already running. Therefore, you need first to start the process with
6484 the @kbd{run} or @kbd{start} commands, and then start the recording
6485 with the @kbd{record @var{method}} command.
6487 @cindex displaced stepping, and process record and replay
6488 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6489 will be automatically disabled when process record and replay target
6490 is started. That's because the process record and replay target
6491 doesn't support displaced stepping.
6493 @cindex non-stop mode, and process record and replay
6494 @cindex asynchronous execution, and process record and replay
6495 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6496 the asynchronous execution mode (@pxref{Background Execution}), not
6497 all recording methods are available. The @code{full} recording method
6498 does not support these two modes.
6503 Stop the process record and replay target. When process record and
6504 replay target stops, the entire execution log will be deleted and the
6505 inferior will either be terminated, or will remain in its final state.
6507 When you stop the process record and replay target in record mode (at
6508 the end of the execution log), the inferior will be stopped at the
6509 next instruction that would have been recorded. In other words, if
6510 you record for a while and then stop recording, the inferior process
6511 will be left in the same state as if the recording never happened.
6513 On the other hand, if the process record and replay target is stopped
6514 while in replay mode (that is, not at the end of the execution log,
6515 but at some earlier point), the inferior process will become ``live''
6516 at that earlier state, and it will then be possible to continue the
6517 usual ``live'' debugging of the process from that state.
6519 When the inferior process exits, or @value{GDBN} detaches from it,
6520 process record and replay target will automatically stop itself.
6524 Go to a specific location in the execution log. There are several
6525 ways to specify the location to go to:
6528 @item record goto begin
6529 @itemx record goto start
6530 Go to the beginning of the execution log.
6532 @item record goto end
6533 Go to the end of the execution log.
6535 @item record goto @var{n}
6536 Go to instruction number @var{n} in the execution log.
6540 @item record save @var{filename}
6541 Save the execution log to a file @file{@var{filename}}.
6542 Default filename is @file{gdb_record.@var{process_id}}, where
6543 @var{process_id} is the process ID of the inferior.
6545 This command may not be available for all recording methods.
6547 @kindex record restore
6548 @item record restore @var{filename}
6549 Restore the execution log from a file @file{@var{filename}}.
6550 File must have been created with @code{record save}.
6552 @kindex set record full
6553 @item set record full insn-number-max @var{limit}
6554 @itemx set record full insn-number-max unlimited
6555 Set the limit of instructions to be recorded for the @code{full}
6556 recording method. Default value is 200000.
6558 If @var{limit} is a positive number, then @value{GDBN} will start
6559 deleting instructions from the log once the number of the record
6560 instructions becomes greater than @var{limit}. For every new recorded
6561 instruction, @value{GDBN} will delete the earliest recorded
6562 instruction to keep the number of recorded instructions at the limit.
6563 (Since deleting recorded instructions loses information, @value{GDBN}
6564 lets you control what happens when the limit is reached, by means of
6565 the @code{stop-at-limit} option, described below.)
6567 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6568 delete recorded instructions from the execution log. The number of
6569 recorded instructions is limited only by the available memory.
6571 @kindex show record full
6572 @item show record full insn-number-max
6573 Show the limit of instructions to be recorded with the @code{full}
6576 @item set record full stop-at-limit
6577 Control the behavior of the @code{full} recording method when the
6578 number of recorded instructions reaches the limit. If ON (the
6579 default), @value{GDBN} will stop when the limit is reached for the
6580 first time and ask you whether you want to stop the inferior or
6581 continue running it and recording the execution log. If you decide
6582 to continue recording, each new recorded instruction will cause the
6583 oldest one to be deleted.
6585 If this option is OFF, @value{GDBN} will automatically delete the
6586 oldest record to make room for each new one, without asking.
6588 @item show record full stop-at-limit
6589 Show the current setting of @code{stop-at-limit}.
6591 @item set record full memory-query
6592 Control the behavior when @value{GDBN} is unable to record memory
6593 changes caused by an instruction for the @code{full} recording method.
6594 If ON, @value{GDBN} will query whether to stop the inferior in that
6597 If this option is OFF (the default), @value{GDBN} will automatically
6598 ignore the effect of such instructions on memory. Later, when
6599 @value{GDBN} replays this execution log, it will mark the log of this
6600 instruction as not accessible, and it will not affect the replay
6603 @item show record full memory-query
6604 Show the current setting of @code{memory-query}.
6606 @kindex set record btrace
6607 The @code{btrace} record target does not trace data. As a
6608 convenience, when replaying, @value{GDBN} reads read-only memory off
6609 the live program directly, assuming that the addresses of the
6610 read-only areas don't change. This for example makes it possible to
6611 disassemble code while replaying, but not to print variables.
6612 In some cases, being able to inspect variables might be useful.
6613 You can use the following command for that:
6615 @item set record btrace replay-memory-access
6616 Control the behavior of the @code{btrace} recording method when
6617 accessing memory during replay. If @code{read-only} (the default),
6618 @value{GDBN} will only allow accesses to read-only memory.
6619 If @code{read-write}, @value{GDBN} will allow accesses to read-only
6620 and to read-write memory. Beware that the accessed memory corresponds
6621 to the live target and not necessarily to the current replay
6624 @kindex show record btrace
6625 @item show record btrace replay-memory-access
6626 Show the current setting of @code{replay-memory-access}.
6628 @kindex set record btrace bts
6629 @item set record btrace bts buffer-size @var{size}
6630 @itemx set record btrace bts buffer-size unlimited
6631 Set the requested ring buffer size for branch tracing in @acronym{BTS}
6632 format. Default is 64KB.
6634 If @var{size} is a positive number, then @value{GDBN} will try to
6635 allocate a buffer of at least @var{size} bytes for each new thread
6636 that uses the btrace recording method and the @acronym{BTS} format.
6637 The actually obtained buffer size may differ from the requested
6638 @var{size}. Use the @code{info record} command to see the actual
6639 buffer size for each thread that uses the btrace recording method and
6640 the @acronym{BTS} format.
6642 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6643 allocate a buffer of 4MB.
6645 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6646 also need longer to process the branch trace data before it can be used.
6648 @item show record btrace bts buffer-size @var{size}
6649 Show the current setting of the requested ring buffer size for branch
6650 tracing in @acronym{BTS} format.
6652 @kindex set record btrace pt
6653 @item set record btrace pt buffer-size @var{size}
6654 @itemx set record btrace pt buffer-size unlimited
6655 Set the requested ring buffer size for branch tracing in Intel(R)
6656 Processor Trace format. Default is 16KB.
6658 If @var{size} is a positive number, then @value{GDBN} will try to
6659 allocate a buffer of at least @var{size} bytes for each new thread
6660 that uses the btrace recording method and the Intel(R) Processor Trace
6661 format. The actually obtained buffer size may differ from the
6662 requested @var{size}. Use the @code{info record} command to see the
6663 actual buffer size for each thread.
6665 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6666 allocate a buffer of 4MB.
6668 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6669 also need longer to process the branch trace data before it can be used.
6671 @item show record btrace pt buffer-size @var{size}
6672 Show the current setting of the requested ring buffer size for branch
6673 tracing in Intel(R) Processor Trace format.
6677 Show various statistics about the recording depending on the recording
6682 For the @code{full} recording method, it shows the state of process
6683 record and its in-memory execution log buffer, including:
6687 Whether in record mode or replay mode.
6689 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6691 Highest recorded instruction number.
6693 Current instruction about to be replayed (if in replay mode).
6695 Number of instructions contained in the execution log.
6697 Maximum number of instructions that may be contained in the execution log.
6701 For the @code{btrace} recording method, it shows:
6707 Number of instructions that have been recorded.
6709 Number of blocks of sequential control-flow formed by the recorded
6712 Whether in record mode or replay mode.
6715 For the @code{bts} recording format, it also shows:
6718 Size of the perf ring buffer.
6721 For the @code{pt} recording format, it also shows:
6724 Size of the perf ring buffer.
6728 @kindex record delete
6731 When record target runs in replay mode (``in the past''), delete the
6732 subsequent execution log and begin to record a new execution log starting
6733 from the current address. This means you will abandon the previously
6734 recorded ``future'' and begin recording a new ``future''.
6736 @kindex record instruction-history
6737 @kindex rec instruction-history
6738 @item record instruction-history
6739 Disassembles instructions from the recorded execution log. By
6740 default, ten instructions are disassembled. This can be changed using
6741 the @code{set record instruction-history-size} command. Instructions
6742 are printed in execution order.
6744 Speculatively executed instructions are prefixed with @samp{?}. This
6745 feature is not available for all recording formats.
6747 There are several ways to specify what part of the execution log to
6751 @item record instruction-history @var{insn}
6752 Disassembles ten instructions starting from instruction number
6755 @item record instruction-history @var{insn}, +/-@var{n}
6756 Disassembles @var{n} instructions around instruction number
6757 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6758 @var{n} instructions after instruction number @var{insn}. If
6759 @var{n} is preceded with @code{-}, disassembles @var{n}
6760 instructions before instruction number @var{insn}.
6762 @item record instruction-history
6763 Disassembles ten more instructions after the last disassembly.
6765 @item record instruction-history -
6766 Disassembles ten more instructions before the last disassembly.
6768 @item record instruction-history @var{begin} @var{end}
6769 Disassembles instructions beginning with instruction number
6770 @var{begin} until instruction number @var{end}. The instruction
6771 number @var{end} is included.
6774 This command may not be available for all recording methods.
6777 @item set record instruction-history-size @var{size}
6778 @itemx set record instruction-history-size unlimited
6779 Define how many instructions to disassemble in the @code{record
6780 instruction-history} command. The default value is 10.
6781 A @var{size} of @code{unlimited} means unlimited instructions.
6784 @item show record instruction-history-size
6785 Show how many instructions to disassemble in the @code{record
6786 instruction-history} command.
6788 @kindex record function-call-history
6789 @kindex rec function-call-history
6790 @item record function-call-history
6791 Prints the execution history at function granularity. It prints one
6792 line for each sequence of instructions that belong to the same
6793 function giving the name of that function, the source lines
6794 for this instruction sequence (if the @code{/l} modifier is
6795 specified), and the instructions numbers that form the sequence (if
6796 the @code{/i} modifier is specified). The function names are indented
6797 to reflect the call stack depth if the @code{/c} modifier is
6798 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
6802 (@value{GDBP}) @b{list 1, 10}
6813 (@value{GDBP}) @b{record function-call-history /ilc}
6814 1 bar inst 1,4 at foo.c:6,8
6815 2 foo inst 5,10 at foo.c:2,3
6816 3 bar inst 11,13 at foo.c:9,10
6819 By default, ten lines are printed. This can be changed using the
6820 @code{set record function-call-history-size} command. Functions are
6821 printed in execution order. There are several ways to specify what
6825 @item record function-call-history @var{func}
6826 Prints ten functions starting from function number @var{func}.
6828 @item record function-call-history @var{func}, +/-@var{n}
6829 Prints @var{n} functions around function number @var{func}. If
6830 @var{n} is preceded with @code{+}, prints @var{n} functions after
6831 function number @var{func}. If @var{n} is preceded with @code{-},
6832 prints @var{n} functions before function number @var{func}.
6834 @item record function-call-history
6835 Prints ten more functions after the last ten-line print.
6837 @item record function-call-history -
6838 Prints ten more functions before the last ten-line print.
6840 @item record function-call-history @var{begin} @var{end}
6841 Prints functions beginning with function number @var{begin} until
6842 function number @var{end}. The function number @var{end} is included.
6845 This command may not be available for all recording methods.
6847 @item set record function-call-history-size @var{size}
6848 @itemx set record function-call-history-size unlimited
6849 Define how many lines to print in the
6850 @code{record function-call-history} command. The default value is 10.
6851 A size of @code{unlimited} means unlimited lines.
6853 @item show record function-call-history-size
6854 Show how many lines to print in the
6855 @code{record function-call-history} command.
6860 @chapter Examining the Stack
6862 When your program has stopped, the first thing you need to know is where it
6863 stopped and how it got there.
6866 Each time your program performs a function call, information about the call
6868 That information includes the location of the call in your program,
6869 the arguments of the call,
6870 and the local variables of the function being called.
6871 The information is saved in a block of data called a @dfn{stack frame}.
6872 The stack frames are allocated in a region of memory called the @dfn{call
6875 When your program stops, the @value{GDBN} commands for examining the
6876 stack allow you to see all of this information.
6878 @cindex selected frame
6879 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6880 @value{GDBN} commands refer implicitly to the selected frame. In
6881 particular, whenever you ask @value{GDBN} for the value of a variable in
6882 your program, the value is found in the selected frame. There are
6883 special @value{GDBN} commands to select whichever frame you are
6884 interested in. @xref{Selection, ,Selecting a Frame}.
6886 When your program stops, @value{GDBN} automatically selects the
6887 currently executing frame and describes it briefly, similar to the
6888 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6891 * Frames:: Stack frames
6892 * Backtrace:: Backtraces
6893 * Frame Filter Management:: Managing frame filters
6894 * Selection:: Selecting a frame
6895 * Frame Info:: Information on a frame
6900 @section Stack Frames
6902 @cindex frame, definition
6904 The call stack is divided up into contiguous pieces called @dfn{stack
6905 frames}, or @dfn{frames} for short; each frame is the data associated
6906 with one call to one function. The frame contains the arguments given
6907 to the function, the function's local variables, and the address at
6908 which the function is executing.
6910 @cindex initial frame
6911 @cindex outermost frame
6912 @cindex innermost frame
6913 When your program is started, the stack has only one frame, that of the
6914 function @code{main}. This is called the @dfn{initial} frame or the
6915 @dfn{outermost} frame. Each time a function is called, a new frame is
6916 made. Each time a function returns, the frame for that function invocation
6917 is eliminated. If a function is recursive, there can be many frames for
6918 the same function. The frame for the function in which execution is
6919 actually occurring is called the @dfn{innermost} frame. This is the most
6920 recently created of all the stack frames that still exist.
6922 @cindex frame pointer
6923 Inside your program, stack frames are identified by their addresses. A
6924 stack frame consists of many bytes, each of which has its own address; each
6925 kind of computer has a convention for choosing one byte whose
6926 address serves as the address of the frame. Usually this address is kept
6927 in a register called the @dfn{frame pointer register}
6928 (@pxref{Registers, $fp}) while execution is going on in that frame.
6930 @cindex frame number
6931 @value{GDBN} assigns numbers to all existing stack frames, starting with
6932 zero for the innermost frame, one for the frame that called it,
6933 and so on upward. These numbers do not really exist in your program;
6934 they are assigned by @value{GDBN} to give you a way of designating stack
6935 frames in @value{GDBN} commands.
6937 @c The -fomit-frame-pointer below perennially causes hbox overflow
6938 @c underflow problems.
6939 @cindex frameless execution
6940 Some compilers provide a way to compile functions so that they operate
6941 without stack frames. (For example, the @value{NGCC} option
6943 @samp{-fomit-frame-pointer}
6945 generates functions without a frame.)
6946 This is occasionally done with heavily used library functions to save
6947 the frame setup time. @value{GDBN} has limited facilities for dealing
6948 with these function invocations. If the innermost function invocation
6949 has no stack frame, @value{GDBN} nevertheless regards it as though
6950 it had a separate frame, which is numbered zero as usual, allowing
6951 correct tracing of the function call chain. However, @value{GDBN} has
6952 no provision for frameless functions elsewhere in the stack.
6955 @kindex frame@r{, command}
6956 @cindex current stack frame
6957 @item frame @r{[}@var{framespec}@r{]}
6958 The @code{frame} command allows you to move from one stack frame to another,
6959 and to print the stack frame you select. The @var{framespec} may be either the
6960 address of the frame or the stack frame number. Without an argument,
6961 @code{frame} prints the current stack frame.
6963 @kindex select-frame
6964 @cindex selecting frame silently
6966 The @code{select-frame} command allows you to move from one stack frame
6967 to another without printing the frame. This is the silent version of
6975 @cindex call stack traces
6976 A backtrace is a summary of how your program got where it is. It shows one
6977 line per frame, for many frames, starting with the currently executing
6978 frame (frame zero), followed by its caller (frame one), and on up the
6981 @anchor{backtrace-command}
6984 @kindex bt @r{(@code{backtrace})}
6987 Print a backtrace of the entire stack: one line per frame for all
6988 frames in the stack.
6990 You can stop the backtrace at any time by typing the system interrupt
6991 character, normally @kbd{Ctrl-c}.
6993 @item backtrace @var{n}
6995 Similar, but print only the innermost @var{n} frames.
6997 @item backtrace -@var{n}
6999 Similar, but print only the outermost @var{n} frames.
7001 @item backtrace full
7003 @itemx bt full @var{n}
7004 @itemx bt full -@var{n}
7005 Print the values of the local variables also. As described above,
7006 @var{n} specifies the number of frames to print.
7008 @item backtrace no-filters
7009 @itemx bt no-filters
7010 @itemx bt no-filters @var{n}
7011 @itemx bt no-filters -@var{n}
7012 @itemx bt no-filters full
7013 @itemx bt no-filters full @var{n}
7014 @itemx bt no-filters full -@var{n}
7015 Do not run Python frame filters on this backtrace. @xref{Frame
7016 Filter API}, for more information. Additionally use @ref{disable
7017 frame-filter all} to turn off all frame filters. This is only
7018 relevant when @value{GDBN} has been configured with @code{Python}
7024 The names @code{where} and @code{info stack} (abbreviated @code{info s})
7025 are additional aliases for @code{backtrace}.
7027 @cindex multiple threads, backtrace
7028 In a multi-threaded program, @value{GDBN} by default shows the
7029 backtrace only for the current thread. To display the backtrace for
7030 several or all of the threads, use the command @code{thread apply}
7031 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
7032 apply all backtrace}, @value{GDBN} will display the backtrace for all
7033 the threads; this is handy when you debug a core dump of a
7034 multi-threaded program.
7036 Each line in the backtrace shows the frame number and the function name.
7037 The program counter value is also shown---unless you use @code{set
7038 print address off}. The backtrace also shows the source file name and
7039 line number, as well as the arguments to the function. The program
7040 counter value is omitted if it is at the beginning of the code for that
7043 Here is an example of a backtrace. It was made with the command
7044 @samp{bt 3}, so it shows the innermost three frames.
7048 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7050 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
7051 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
7053 (More stack frames follow...)
7058 The display for frame zero does not begin with a program counter
7059 value, indicating that your program has stopped at the beginning of the
7060 code for line @code{993} of @code{builtin.c}.
7063 The value of parameter @code{data} in frame 1 has been replaced by
7064 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7065 only if it is a scalar (integer, pointer, enumeration, etc). See command
7066 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7067 on how to configure the way function parameter values are printed.
7069 @cindex optimized out, in backtrace
7070 @cindex function call arguments, optimized out
7071 If your program was compiled with optimizations, some compilers will
7072 optimize away arguments passed to functions if those arguments are
7073 never used after the call. Such optimizations generate code that
7074 passes arguments through registers, but doesn't store those arguments
7075 in the stack frame. @value{GDBN} has no way of displaying such
7076 arguments in stack frames other than the innermost one. Here's what
7077 such a backtrace might look like:
7081 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7083 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
7084 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
7086 (More stack frames follow...)
7091 The values of arguments that were not saved in their stack frames are
7092 shown as @samp{<optimized out>}.
7094 If you need to display the values of such optimized-out arguments,
7095 either deduce that from other variables whose values depend on the one
7096 you are interested in, or recompile without optimizations.
7098 @cindex backtrace beyond @code{main} function
7099 @cindex program entry point
7100 @cindex startup code, and backtrace
7101 Most programs have a standard user entry point---a place where system
7102 libraries and startup code transition into user code. For C this is
7103 @code{main}@footnote{
7104 Note that embedded programs (the so-called ``free-standing''
7105 environment) are not required to have a @code{main} function as the
7106 entry point. They could even have multiple entry points.}.
7107 When @value{GDBN} finds the entry function in a backtrace
7108 it will terminate the backtrace, to avoid tracing into highly
7109 system-specific (and generally uninteresting) code.
7111 If you need to examine the startup code, or limit the number of levels
7112 in a backtrace, you can change this behavior:
7115 @item set backtrace past-main
7116 @itemx set backtrace past-main on
7117 @kindex set backtrace
7118 Backtraces will continue past the user entry point.
7120 @item set backtrace past-main off
7121 Backtraces will stop when they encounter the user entry point. This is the
7124 @item show backtrace past-main
7125 @kindex show backtrace
7126 Display the current user entry point backtrace policy.
7128 @item set backtrace past-entry
7129 @itemx set backtrace past-entry on
7130 Backtraces will continue past the internal entry point of an application.
7131 This entry point is encoded by the linker when the application is built,
7132 and is likely before the user entry point @code{main} (or equivalent) is called.
7134 @item set backtrace past-entry off
7135 Backtraces will stop when they encounter the internal entry point of an
7136 application. This is the default.
7138 @item show backtrace past-entry
7139 Display the current internal entry point backtrace policy.
7141 @item set backtrace limit @var{n}
7142 @itemx set backtrace limit 0
7143 @itemx set backtrace limit unlimited
7144 @cindex backtrace limit
7145 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7146 or zero means unlimited levels.
7148 @item show backtrace limit
7149 Display the current limit on backtrace levels.
7152 You can control how file names are displayed.
7155 @item set filename-display
7156 @itemx set filename-display relative
7157 @cindex filename-display
7158 Display file names relative to the compilation directory. This is the default.
7160 @item set filename-display basename
7161 Display only basename of a filename.
7163 @item set filename-display absolute
7164 Display an absolute filename.
7166 @item show filename-display
7167 Show the current way to display filenames.
7170 @node Frame Filter Management
7171 @section Management of Frame Filters.
7172 @cindex managing frame filters
7174 Frame filters are Python based utilities to manage and decorate the
7175 output of frames. @xref{Frame Filter API}, for further information.
7177 Managing frame filters is performed by several commands available
7178 within @value{GDBN}, detailed here.
7181 @kindex info frame-filter
7182 @item info frame-filter
7183 Print a list of installed frame filters from all dictionaries, showing
7184 their name, priority and enabled status.
7186 @kindex disable frame-filter
7187 @anchor{disable frame-filter all}
7188 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
7189 Disable a frame filter in the dictionary matching
7190 @var{filter-dictionary} and @var{filter-name}. The
7191 @var{filter-dictionary} may be @code{all}, @code{global},
7192 @code{progspace}, or the name of the object file where the frame filter
7193 dictionary resides. When @code{all} is specified, all frame filters
7194 across all dictionaries are disabled. The @var{filter-name} is the name
7195 of the frame filter and is used when @code{all} is not the option for
7196 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
7197 may be enabled again later.
7199 @kindex enable frame-filter
7200 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
7201 Enable a frame filter in the dictionary matching
7202 @var{filter-dictionary} and @var{filter-name}. The
7203 @var{filter-dictionary} may be @code{all}, @code{global},
7204 @code{progspace} or the name of the object file where the frame filter
7205 dictionary resides. When @code{all} is specified, all frame filters across
7206 all dictionaries are enabled. The @var{filter-name} is the name of the frame
7207 filter and is used when @code{all} is not the option for
7208 @var{filter-dictionary}.
7213 (gdb) info frame-filter
7215 global frame-filters:
7216 Priority Enabled Name
7217 1000 No PrimaryFunctionFilter
7220 progspace /build/test frame-filters:
7221 Priority Enabled Name
7222 100 Yes ProgspaceFilter
7224 objfile /build/test frame-filters:
7225 Priority Enabled Name
7226 999 Yes BuildProgra Filter
7228 (gdb) disable frame-filter /build/test BuildProgramFilter
7229 (gdb) info frame-filter
7231 global frame-filters:
7232 Priority Enabled Name
7233 1000 No PrimaryFunctionFilter
7236 progspace /build/test frame-filters:
7237 Priority Enabled Name
7238 100 Yes ProgspaceFilter
7240 objfile /build/test frame-filters:
7241 Priority Enabled Name
7242 999 No BuildProgramFilter
7244 (gdb) enable frame-filter global PrimaryFunctionFilter
7245 (gdb) info frame-filter
7247 global frame-filters:
7248 Priority Enabled Name
7249 1000 Yes PrimaryFunctionFilter
7252 progspace /build/test frame-filters:
7253 Priority Enabled Name
7254 100 Yes ProgspaceFilter
7256 objfile /build/test frame-filters:
7257 Priority Enabled Name
7258 999 No BuildProgramFilter
7261 @kindex set frame-filter priority
7262 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
7263 Set the @var{priority} of a frame filter in the dictionary matching
7264 @var{filter-dictionary}, and the frame filter name matching
7265 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7266 @code{progspace} or the name of the object file where the frame filter
7267 dictionary resides. The @var{priority} is an integer.
7269 @kindex show frame-filter priority
7270 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
7271 Show the @var{priority} of a frame filter in the dictionary matching
7272 @var{filter-dictionary}, and the frame filter name matching
7273 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7274 @code{progspace} or the name of the object file where the frame filter
7280 (gdb) info frame-filter
7282 global frame-filters:
7283 Priority Enabled Name
7284 1000 Yes PrimaryFunctionFilter
7287 progspace /build/test frame-filters:
7288 Priority Enabled Name
7289 100 Yes ProgspaceFilter
7291 objfile /build/test frame-filters:
7292 Priority Enabled Name
7293 999 No BuildProgramFilter
7295 (gdb) set frame-filter priority global Reverse 50
7296 (gdb) info frame-filter
7298 global frame-filters:
7299 Priority Enabled Name
7300 1000 Yes PrimaryFunctionFilter
7303 progspace /build/test frame-filters:
7304 Priority Enabled Name
7305 100 Yes ProgspaceFilter
7307 objfile /build/test frame-filters:
7308 Priority Enabled Name
7309 999 No BuildProgramFilter
7314 @section Selecting a Frame
7316 Most commands for examining the stack and other data in your program work on
7317 whichever stack frame is selected at the moment. Here are the commands for
7318 selecting a stack frame; all of them finish by printing a brief description
7319 of the stack frame just selected.
7322 @kindex frame@r{, selecting}
7323 @kindex f @r{(@code{frame})}
7326 Select frame number @var{n}. Recall that frame zero is the innermost
7327 (currently executing) frame, frame one is the frame that called the
7328 innermost one, and so on. The highest-numbered frame is the one for
7331 @item frame @var{stack-addr} [ @var{pc-addr} ]
7332 @itemx f @var{stack-addr} [ @var{pc-addr} ]
7333 Select the frame at address @var{stack-addr}. This is useful mainly if the
7334 chaining of stack frames has been damaged by a bug, making it
7335 impossible for @value{GDBN} to assign numbers properly to all frames. In
7336 addition, this can be useful when your program has multiple stacks and
7337 switches between them. The optional @var{pc-addr} can also be given to
7338 specify the value of PC for the stack frame.
7342 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7343 numbers @var{n}, this advances toward the outermost frame, to higher
7344 frame numbers, to frames that have existed longer.
7347 @kindex do @r{(@code{down})}
7349 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7350 positive numbers @var{n}, this advances toward the innermost frame, to
7351 lower frame numbers, to frames that were created more recently.
7352 You may abbreviate @code{down} as @code{do}.
7355 All of these commands end by printing two lines of output describing the
7356 frame. The first line shows the frame number, the function name, the
7357 arguments, and the source file and line number of execution in that
7358 frame. The second line shows the text of that source line.
7366 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7368 10 read_input_file (argv[i]);
7372 After such a printout, the @code{list} command with no arguments
7373 prints ten lines centered on the point of execution in the frame.
7374 You can also edit the program at the point of execution with your favorite
7375 editing program by typing @code{edit}.
7376 @xref{List, ,Printing Source Lines},
7380 @kindex down-silently
7382 @item up-silently @var{n}
7383 @itemx down-silently @var{n}
7384 These two commands are variants of @code{up} and @code{down},
7385 respectively; they differ in that they do their work silently, without
7386 causing display of the new frame. They are intended primarily for use
7387 in @value{GDBN} command scripts, where the output might be unnecessary and
7392 @section Information About a Frame
7394 There are several other commands to print information about the selected
7400 When used without any argument, this command does not change which
7401 frame is selected, but prints a brief description of the currently
7402 selected stack frame. It can be abbreviated @code{f}. With an
7403 argument, this command is used to select a stack frame.
7404 @xref{Selection, ,Selecting a Frame}.
7407 @kindex info f @r{(@code{info frame})}
7410 This command prints a verbose description of the selected stack frame,
7415 the address of the frame
7417 the address of the next frame down (called by this frame)
7419 the address of the next frame up (caller of this frame)
7421 the language in which the source code corresponding to this frame is written
7423 the address of the frame's arguments
7425 the address of the frame's local variables
7427 the program counter saved in it (the address of execution in the caller frame)
7429 which registers were saved in the frame
7432 @noindent The verbose description is useful when
7433 something has gone wrong that has made the stack format fail to fit
7434 the usual conventions.
7436 @item info frame @var{addr}
7437 @itemx info f @var{addr}
7438 Print a verbose description of the frame at address @var{addr}, without
7439 selecting that frame. The selected frame remains unchanged by this
7440 command. This requires the same kind of address (more than one for some
7441 architectures) that you specify in the @code{frame} command.
7442 @xref{Selection, ,Selecting a Frame}.
7446 Print the arguments of the selected frame, each on a separate line.
7450 Print the local variables of the selected frame, each on a separate
7451 line. These are all variables (declared either static or automatic)
7452 accessible at the point of execution of the selected frame.
7458 @chapter Examining Source Files
7460 @value{GDBN} can print parts of your program's source, since the debugging
7461 information recorded in the program tells @value{GDBN} what source files were
7462 used to build it. When your program stops, @value{GDBN} spontaneously prints
7463 the line where it stopped. Likewise, when you select a stack frame
7464 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7465 execution in that frame has stopped. You can print other portions of
7466 source files by explicit command.
7468 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7469 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7470 @value{GDBN} under @sc{gnu} Emacs}.
7473 * List:: Printing source lines
7474 * Specify Location:: How to specify code locations
7475 * Edit:: Editing source files
7476 * Search:: Searching source files
7477 * Source Path:: Specifying source directories
7478 * Machine Code:: Source and machine code
7482 @section Printing Source Lines
7485 @kindex l @r{(@code{list})}
7486 To print lines from a source file, use the @code{list} command
7487 (abbreviated @code{l}). By default, ten lines are printed.
7488 There are several ways to specify what part of the file you want to
7489 print; see @ref{Specify Location}, for the full list.
7491 Here are the forms of the @code{list} command most commonly used:
7494 @item list @var{linenum}
7495 Print lines centered around line number @var{linenum} in the
7496 current source file.
7498 @item list @var{function}
7499 Print lines centered around the beginning of function
7503 Print more lines. If the last lines printed were printed with a
7504 @code{list} command, this prints lines following the last lines
7505 printed; however, if the last line printed was a solitary line printed
7506 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7507 Stack}), this prints lines centered around that line.
7510 Print lines just before the lines last printed.
7513 @cindex @code{list}, how many lines to display
7514 By default, @value{GDBN} prints ten source lines with any of these forms of
7515 the @code{list} command. You can change this using @code{set listsize}:
7518 @kindex set listsize
7519 @item set listsize @var{count}
7520 @itemx set listsize unlimited
7521 Make the @code{list} command display @var{count} source lines (unless
7522 the @code{list} argument explicitly specifies some other number).
7523 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7525 @kindex show listsize
7527 Display the number of lines that @code{list} prints.
7530 Repeating a @code{list} command with @key{RET} discards the argument,
7531 so it is equivalent to typing just @code{list}. This is more useful
7532 than listing the same lines again. An exception is made for an
7533 argument of @samp{-}; that argument is preserved in repetition so that
7534 each repetition moves up in the source file.
7536 In general, the @code{list} command expects you to supply zero, one or two
7537 @dfn{locations}. Locations specify source lines; there are several ways
7538 of writing them (@pxref{Specify Location}), but the effect is always
7539 to specify some source line.
7541 Here is a complete description of the possible arguments for @code{list}:
7544 @item list @var{location}
7545 Print lines centered around the line specified by @var{location}.
7547 @item list @var{first},@var{last}
7548 Print lines from @var{first} to @var{last}. Both arguments are
7549 locations. When a @code{list} command has two locations, and the
7550 source file of the second location is omitted, this refers to
7551 the same source file as the first location.
7553 @item list ,@var{last}
7554 Print lines ending with @var{last}.
7556 @item list @var{first},
7557 Print lines starting with @var{first}.
7560 Print lines just after the lines last printed.
7563 Print lines just before the lines last printed.
7566 As described in the preceding table.
7569 @node Specify Location
7570 @section Specifying a Location
7571 @cindex specifying location
7573 @cindex source location
7576 * Linespec Locations:: Linespec locations
7577 * Explicit Locations:: Explicit locations
7578 * Address Locations:: Address locations
7581 Several @value{GDBN} commands accept arguments that specify a location
7582 of your program's code. Since @value{GDBN} is a source-level
7583 debugger, a location usually specifies some line in the source code.
7584 Locations may be specified using three different formats:
7585 linespec locations, explicit locations, or address locations.
7587 @node Linespec Locations
7588 @subsection Linespec Locations
7589 @cindex linespec locations
7591 A @dfn{linespec} is a colon-separated list of source location parameters such
7592 as file name, function name, etc. Here are all the different ways of
7593 specifying a linespec:
7597 Specifies the line number @var{linenum} of the current source file.
7600 @itemx +@var{offset}
7601 Specifies the line @var{offset} lines before or after the @dfn{current
7602 line}. For the @code{list} command, the current line is the last one
7603 printed; for the breakpoint commands, this is the line at which
7604 execution stopped in the currently selected @dfn{stack frame}
7605 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7606 used as the second of the two linespecs in a @code{list} command,
7607 this specifies the line @var{offset} lines up or down from the first
7610 @item @var{filename}:@var{linenum}
7611 Specifies the line @var{linenum} in the source file @var{filename}.
7612 If @var{filename} is a relative file name, then it will match any
7613 source file name with the same trailing components. For example, if
7614 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7615 name of @file{/build/trunk/gcc/expr.c}, but not
7616 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7618 @item @var{function}
7619 Specifies the line that begins the body of the function @var{function}.
7620 For example, in C, this is the line with the open brace.
7622 @item @var{function}:@var{label}
7623 Specifies the line where @var{label} appears in @var{function}.
7625 @item @var{filename}:@var{function}
7626 Specifies the line that begins the body of the function @var{function}
7627 in the file @var{filename}. You only need the file name with a
7628 function name to avoid ambiguity when there are identically named
7629 functions in different source files.
7632 Specifies the line at which the label named @var{label} appears
7633 in the function corresponding to the currently selected stack frame.
7634 If there is no current selected stack frame (for instance, if the inferior
7635 is not running), then @value{GDBN} will not search for a label.
7637 @cindex breakpoint at static probe point
7638 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7639 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7640 applications to embed static probes. @xref{Static Probe Points}, for more
7641 information on finding and using static probes. This form of linespec
7642 specifies the location of such a static probe.
7644 If @var{objfile} is given, only probes coming from that shared library
7645 or executable matching @var{objfile} as a regular expression are considered.
7646 If @var{provider} is given, then only probes from that provider are considered.
7647 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7648 each one of those probes.
7651 @node Explicit Locations
7652 @subsection Explicit Locations
7653 @cindex explicit locations
7655 @dfn{Explicit locations} allow the user to directly specify the source
7656 location's parameters using option-value pairs.
7658 Explicit locations are useful when several functions, labels, or
7659 file names have the same name (base name for files) in the program's
7660 sources. In these cases, explicit locations point to the source
7661 line you meant more accurately and unambiguously. Also, using
7662 explicit locations might be faster in large programs.
7664 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
7665 defined in the file named @file{foo} or the label @code{bar} in a function
7666 named @code{foo}. @value{GDBN} must search either the file system or
7667 the symbol table to know.
7669 The list of valid explicit location options is summarized in the
7673 @item -source @var{filename}
7674 The value specifies the source file name. To differentiate between
7675 files with the same base name, prepend as many directories as is necessary
7676 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
7677 @value{GDBN} will use the first file it finds with the given base
7678 name. This option requires the use of either @code{-function} or @code{-line}.
7680 @item -function @var{function}
7681 The value specifies the name of a function. Operations
7682 on function locations unmodified by other options (such as @code{-label}
7683 or @code{-line}) refer to the line that begins the body of the function.
7684 In C, for example, this is the line with the open brace.
7686 @item -label @var{label}
7687 The value specifies the name of a label. When the function
7688 name is not specified, the label is searched in the function of the currently
7689 selected stack frame.
7691 @item -line @var{number}
7692 The value specifies a line offset for the location. The offset may either
7693 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
7694 the command. When specified without any other options, the line offset is
7695 relative to the current line.
7698 Explicit location options may be abbreviated by omitting any non-unique
7699 trailing characters from the option name, e.g., @code{break -s main.c -li 3}.
7701 @node Address Locations
7702 @subsection Address Locations
7703 @cindex address locations
7705 @dfn{Address locations} indicate a specific program address. They have
7706 the generalized form *@var{address}.
7708 For line-oriented commands, such as @code{list} and @code{edit}, this
7709 specifies a source line that contains @var{address}. For @code{break} and
7710 other breakpoint-oriented commands, this can be used to set breakpoints in
7711 parts of your program which do not have debugging information or
7714 Here @var{address} may be any expression valid in the current working
7715 language (@pxref{Languages, working language}) that specifies a code
7716 address. In addition, as a convenience, @value{GDBN} extends the
7717 semantics of expressions used in locations to cover several situations
7718 that frequently occur during debugging. Here are the various forms
7722 @item @var{expression}
7723 Any expression valid in the current working language.
7725 @item @var{funcaddr}
7726 An address of a function or procedure derived from its name. In C,
7727 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
7728 simply the function's name @var{function} (and actually a special case
7729 of a valid expression). In Pascal and Modula-2, this is
7730 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7731 (although the Pascal form also works).
7733 This form specifies the address of the function's first instruction,
7734 before the stack frame and arguments have been set up.
7736 @item '@var{filename}':@var{funcaddr}
7737 Like @var{funcaddr} above, but also specifies the name of the source
7738 file explicitly. This is useful if the name of the function does not
7739 specify the function unambiguously, e.g., if there are several
7740 functions with identical names in different source files.
7744 @section Editing Source Files
7745 @cindex editing source files
7748 @kindex e @r{(@code{edit})}
7749 To edit the lines in a source file, use the @code{edit} command.
7750 The editing program of your choice
7751 is invoked with the current line set to
7752 the active line in the program.
7753 Alternatively, there are several ways to specify what part of the file you
7754 want to print if you want to see other parts of the program:
7757 @item edit @var{location}
7758 Edit the source file specified by @code{location}. Editing starts at
7759 that @var{location}, e.g., at the specified source line of the
7760 specified file. @xref{Specify Location}, for all the possible forms
7761 of the @var{location} argument; here are the forms of the @code{edit}
7762 command most commonly used:
7765 @item edit @var{number}
7766 Edit the current source file with @var{number} as the active line number.
7768 @item edit @var{function}
7769 Edit the file containing @var{function} at the beginning of its definition.
7774 @subsection Choosing your Editor
7775 You can customize @value{GDBN} to use any editor you want
7777 The only restriction is that your editor (say @code{ex}), recognizes the
7778 following command-line syntax:
7780 ex +@var{number} file
7782 The optional numeric value +@var{number} specifies the number of the line in
7783 the file where to start editing.}.
7784 By default, it is @file{@value{EDITOR}}, but you can change this
7785 by setting the environment variable @code{EDITOR} before using
7786 @value{GDBN}. For example, to configure @value{GDBN} to use the
7787 @code{vi} editor, you could use these commands with the @code{sh} shell:
7793 or in the @code{csh} shell,
7795 setenv EDITOR /usr/bin/vi
7800 @section Searching Source Files
7801 @cindex searching source files
7803 There are two commands for searching through the current source file for a
7808 @kindex forward-search
7809 @kindex fo @r{(@code{forward-search})}
7810 @item forward-search @var{regexp}
7811 @itemx search @var{regexp}
7812 The command @samp{forward-search @var{regexp}} checks each line,
7813 starting with the one following the last line listed, for a match for
7814 @var{regexp}. It lists the line that is found. You can use the
7815 synonym @samp{search @var{regexp}} or abbreviate the command name as
7818 @kindex reverse-search
7819 @item reverse-search @var{regexp}
7820 The command @samp{reverse-search @var{regexp}} checks each line, starting
7821 with the one before the last line listed and going backward, for a match
7822 for @var{regexp}. It lists the line that is found. You can abbreviate
7823 this command as @code{rev}.
7827 @section Specifying Source Directories
7830 @cindex directories for source files
7831 Executable programs sometimes do not record the directories of the source
7832 files from which they were compiled, just the names. Even when they do,
7833 the directories could be moved between the compilation and your debugging
7834 session. @value{GDBN} has a list of directories to search for source files;
7835 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
7836 it tries all the directories in the list, in the order they are present
7837 in the list, until it finds a file with the desired name.
7839 For example, suppose an executable references the file
7840 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
7841 @file{/mnt/cross}. The file is first looked up literally; if this
7842 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
7843 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
7844 message is printed. @value{GDBN} does not look up the parts of the
7845 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
7846 Likewise, the subdirectories of the source path are not searched: if
7847 the source path is @file{/mnt/cross}, and the binary refers to
7848 @file{foo.c}, @value{GDBN} would not find it under
7849 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7851 Plain file names, relative file names with leading directories, file
7852 names containing dots, etc.@: are all treated as described above; for
7853 instance, if the source path is @file{/mnt/cross}, and the source file
7854 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7855 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7856 that---@file{/mnt/cross/foo.c}.
7858 Note that the executable search path is @emph{not} used to locate the
7861 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7862 any information it has cached about where source files are found and where
7863 each line is in the file.
7867 When you start @value{GDBN}, its source path includes only @samp{cdir}
7868 and @samp{cwd}, in that order.
7869 To add other directories, use the @code{directory} command.
7871 The search path is used to find both program source files and @value{GDBN}
7872 script files (read using the @samp{-command} option and @samp{source} command).
7874 In addition to the source path, @value{GDBN} provides a set of commands
7875 that manage a list of source path substitution rules. A @dfn{substitution
7876 rule} specifies how to rewrite source directories stored in the program's
7877 debug information in case the sources were moved to a different
7878 directory between compilation and debugging. A rule is made of
7879 two strings, the first specifying what needs to be rewritten in
7880 the path, and the second specifying how it should be rewritten.
7881 In @ref{set substitute-path}, we name these two parts @var{from} and
7882 @var{to} respectively. @value{GDBN} does a simple string replacement
7883 of @var{from} with @var{to} at the start of the directory part of the
7884 source file name, and uses that result instead of the original file
7885 name to look up the sources.
7887 Using the previous example, suppose the @file{foo-1.0} tree has been
7888 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7889 @value{GDBN} to replace @file{/usr/src} in all source path names with
7890 @file{/mnt/cross}. The first lookup will then be
7891 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7892 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7893 substitution rule, use the @code{set substitute-path} command
7894 (@pxref{set substitute-path}).
7896 To avoid unexpected substitution results, a rule is applied only if the
7897 @var{from} part of the directory name ends at a directory separator.
7898 For instance, a rule substituting @file{/usr/source} into
7899 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7900 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7901 is applied only at the beginning of the directory name, this rule will
7902 not be applied to @file{/root/usr/source/baz.c} either.
7904 In many cases, you can achieve the same result using the @code{directory}
7905 command. However, @code{set substitute-path} can be more efficient in
7906 the case where the sources are organized in a complex tree with multiple
7907 subdirectories. With the @code{directory} command, you need to add each
7908 subdirectory of your project. If you moved the entire tree while
7909 preserving its internal organization, then @code{set substitute-path}
7910 allows you to direct the debugger to all the sources with one single
7913 @code{set substitute-path} is also more than just a shortcut command.
7914 The source path is only used if the file at the original location no
7915 longer exists. On the other hand, @code{set substitute-path} modifies
7916 the debugger behavior to look at the rewritten location instead. So, if
7917 for any reason a source file that is not relevant to your executable is
7918 located at the original location, a substitution rule is the only
7919 method available to point @value{GDBN} at the new location.
7921 @cindex @samp{--with-relocated-sources}
7922 @cindex default source path substitution
7923 You can configure a default source path substitution rule by
7924 configuring @value{GDBN} with the
7925 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7926 should be the name of a directory under @value{GDBN}'s configured
7927 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7928 directory names in debug information under @var{dir} will be adjusted
7929 automatically if the installed @value{GDBN} is moved to a new
7930 location. This is useful if @value{GDBN}, libraries or executables
7931 with debug information and corresponding source code are being moved
7935 @item directory @var{dirname} @dots{}
7936 @item dir @var{dirname} @dots{}
7937 Add directory @var{dirname} to the front of the source path. Several
7938 directory names may be given to this command, separated by @samp{:}
7939 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7940 part of absolute file names) or
7941 whitespace. You may specify a directory that is already in the source
7942 path; this moves it forward, so @value{GDBN} searches it sooner.
7946 @vindex $cdir@r{, convenience variable}
7947 @vindex $cwd@r{, convenience variable}
7948 @cindex compilation directory
7949 @cindex current directory
7950 @cindex working directory
7951 @cindex directory, current
7952 @cindex directory, compilation
7953 You can use the string @samp{$cdir} to refer to the compilation
7954 directory (if one is recorded), and @samp{$cwd} to refer to the current
7955 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7956 tracks the current working directory as it changes during your @value{GDBN}
7957 session, while the latter is immediately expanded to the current
7958 directory at the time you add an entry to the source path.
7961 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7963 @c RET-repeat for @code{directory} is explicitly disabled, but since
7964 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7966 @item set directories @var{path-list}
7967 @kindex set directories
7968 Set the source path to @var{path-list}.
7969 @samp{$cdir:$cwd} are added if missing.
7971 @item show directories
7972 @kindex show directories
7973 Print the source path: show which directories it contains.
7975 @anchor{set substitute-path}
7976 @item set substitute-path @var{from} @var{to}
7977 @kindex set substitute-path
7978 Define a source path substitution rule, and add it at the end of the
7979 current list of existing substitution rules. If a rule with the same
7980 @var{from} was already defined, then the old rule is also deleted.
7982 For example, if the file @file{/foo/bar/baz.c} was moved to
7983 @file{/mnt/cross/baz.c}, then the command
7986 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
7990 will tell @value{GDBN} to replace @samp{/usr/src} with
7991 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7992 @file{baz.c} even though it was moved.
7994 In the case when more than one substitution rule have been defined,
7995 the rules are evaluated one by one in the order where they have been
7996 defined. The first one matching, if any, is selected to perform
7999 For instance, if we had entered the following commands:
8002 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
8003 (@value{GDBP}) set substitute-path /usr/src /mnt/src
8007 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
8008 @file{/mnt/include/defs.h} by using the first rule. However, it would
8009 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
8010 @file{/mnt/src/lib/foo.c}.
8013 @item unset substitute-path [path]
8014 @kindex unset substitute-path
8015 If a path is specified, search the current list of substitution rules
8016 for a rule that would rewrite that path. Delete that rule if found.
8017 A warning is emitted by the debugger if no rule could be found.
8019 If no path is specified, then all substitution rules are deleted.
8021 @item show substitute-path [path]
8022 @kindex show substitute-path
8023 If a path is specified, then print the source path substitution rule
8024 which would rewrite that path, if any.
8026 If no path is specified, then print all existing source path substitution
8031 If your source path is cluttered with directories that are no longer of
8032 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
8033 versions of source. You can correct the situation as follows:
8037 Use @code{directory} with no argument to reset the source path to its default value.
8040 Use @code{directory} with suitable arguments to reinstall the
8041 directories you want in the source path. You can add all the
8042 directories in one command.
8046 @section Source and Machine Code
8047 @cindex source line and its code address
8049 You can use the command @code{info line} to map source lines to program
8050 addresses (and vice versa), and the command @code{disassemble} to display
8051 a range of addresses as machine instructions. You can use the command
8052 @code{set disassemble-next-line} to set whether to disassemble next
8053 source line when execution stops. When run under @sc{gnu} Emacs
8054 mode, the @code{info line} command causes the arrow to point to the
8055 line specified. Also, @code{info line} prints addresses in symbolic form as
8060 @item info line @var{location}
8061 Print the starting and ending addresses of the compiled code for
8062 source line @var{location}. You can specify source lines in any of
8063 the ways documented in @ref{Specify Location}.
8066 For example, we can use @code{info line} to discover the location of
8067 the object code for the first line of function
8068 @code{m4_changequote}:
8070 @c FIXME: I think this example should also show the addresses in
8071 @c symbolic form, as they usually would be displayed.
8073 (@value{GDBP}) info line m4_changequote
8074 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
8078 @cindex code address and its source line
8079 We can also inquire (using @code{*@var{addr}} as the form for
8080 @var{location}) what source line covers a particular address:
8082 (@value{GDBP}) info line *0x63ff
8083 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
8086 @cindex @code{$_} and @code{info line}
8087 @cindex @code{x} command, default address
8088 @kindex x@r{(examine), and} info line
8089 After @code{info line}, the default address for the @code{x} command
8090 is changed to the starting address of the line, so that @samp{x/i} is
8091 sufficient to begin examining the machine code (@pxref{Memory,
8092 ,Examining Memory}). Also, this address is saved as the value of the
8093 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
8098 @cindex assembly instructions
8099 @cindex instructions, assembly
8100 @cindex machine instructions
8101 @cindex listing machine instructions
8103 @itemx disassemble /m
8104 @itemx disassemble /s
8105 @itemx disassemble /r
8106 This specialized command dumps a range of memory as machine
8107 instructions. It can also print mixed source+disassembly by specifying
8108 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
8109 as well as in symbolic form by specifying the @code{/r} modifier.
8110 The default memory range is the function surrounding the
8111 program counter of the selected frame. A single argument to this
8112 command is a program counter value; @value{GDBN} dumps the function
8113 surrounding this value. When two arguments are given, they should
8114 be separated by a comma, possibly surrounded by whitespace. The
8115 arguments specify a range of addresses to dump, in one of two forms:
8118 @item @var{start},@var{end}
8119 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
8120 @item @var{start},+@var{length}
8121 the addresses from @var{start} (inclusive) to
8122 @code{@var{start}+@var{length}} (exclusive).
8126 When 2 arguments are specified, the name of the function is also
8127 printed (since there could be several functions in the given range).
8129 The argument(s) can be any expression yielding a numeric value, such as
8130 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
8132 If the range of memory being disassembled contains current program counter,
8133 the instruction at that location is shown with a @code{=>} marker.
8136 The following example shows the disassembly of a range of addresses of
8137 HP PA-RISC 2.0 code:
8140 (@value{GDBP}) disas 0x32c4, 0x32e4
8141 Dump of assembler code from 0x32c4 to 0x32e4:
8142 0x32c4 <main+204>: addil 0,dp
8143 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
8144 0x32cc <main+212>: ldil 0x3000,r31
8145 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
8146 0x32d4 <main+220>: ldo 0(r31),rp
8147 0x32d8 <main+224>: addil -0x800,dp
8148 0x32dc <main+228>: ldo 0x588(r1),r26
8149 0x32e0 <main+232>: ldil 0x3000,r31
8150 End of assembler dump.
8153 Here is an example showing mixed source+assembly for Intel x86
8154 with @code{/m} or @code{/s}, when the program is stopped just after
8155 function prologue in a non-optimized function with no inline code.
8158 (@value{GDBP}) disas /m main
8159 Dump of assembler code for function main:
8161 0x08048330 <+0>: push %ebp
8162 0x08048331 <+1>: mov %esp,%ebp
8163 0x08048333 <+3>: sub $0x8,%esp
8164 0x08048336 <+6>: and $0xfffffff0,%esp
8165 0x08048339 <+9>: sub $0x10,%esp
8167 6 printf ("Hello.\n");
8168 => 0x0804833c <+12>: movl $0x8048440,(%esp)
8169 0x08048343 <+19>: call 0x8048284 <puts@@plt>
8173 0x08048348 <+24>: mov $0x0,%eax
8174 0x0804834d <+29>: leave
8175 0x0804834e <+30>: ret
8177 End of assembler dump.
8180 The @code{/m} option is deprecated as its output is not useful when
8181 there is either inlined code or re-ordered code.
8182 The @code{/s} option is the preferred choice.
8183 Here is an example for AMD x86-64 showing the difference between
8184 @code{/m} output and @code{/s} output.
8185 This example has one inline function defined in a header file,
8186 and the code is compiled with @samp{-O2} optimization.
8187 Note how the @code{/m} output is missing the disassembly of
8188 several instructions that are present in the @code{/s} output.
8218 (@value{GDBP}) disas /m main
8219 Dump of assembler code for function main:
8223 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8224 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8228 0x000000000040041d <+29>: xor %eax,%eax
8229 0x000000000040041f <+31>: retq
8230 0x0000000000400420 <+32>: add %eax,%eax
8231 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8233 End of assembler dump.
8234 (@value{GDBP}) disas /s main
8235 Dump of assembler code for function main:
8239 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8243 0x0000000000400406 <+6>: test %eax,%eax
8244 0x0000000000400408 <+8>: js 0x400420 <main+32>
8249 0x000000000040040a <+10>: lea 0xa(%rax),%edx
8250 0x000000000040040d <+13>: test %eax,%eax
8251 0x000000000040040f <+15>: mov $0x1,%eax
8252 0x0000000000400414 <+20>: cmovne %edx,%eax
8256 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8260 0x000000000040041d <+29>: xor %eax,%eax
8261 0x000000000040041f <+31>: retq
8265 0x0000000000400420 <+32>: add %eax,%eax
8266 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8267 End of assembler dump.
8270 Here is another example showing raw instructions in hex for AMD x86-64,
8273 (gdb) disas /r 0x400281,+10
8274 Dump of assembler code from 0x400281 to 0x40028b:
8275 0x0000000000400281: 38 36 cmp %dh,(%rsi)
8276 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
8277 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
8278 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
8279 End of assembler dump.
8282 Addresses cannot be specified as a location (@pxref{Specify Location}).
8283 So, for example, if you want to disassemble function @code{bar}
8284 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
8285 and not @samp{disassemble foo.c:bar}.
8287 Some architectures have more than one commonly-used set of instruction
8288 mnemonics or other syntax.
8290 For programs that were dynamically linked and use shared libraries,
8291 instructions that call functions or branch to locations in the shared
8292 libraries might show a seemingly bogus location---it's actually a
8293 location of the relocation table. On some architectures, @value{GDBN}
8294 might be able to resolve these to actual function names.
8297 @kindex set disassembly-flavor
8298 @cindex Intel disassembly flavor
8299 @cindex AT&T disassembly flavor
8300 @item set disassembly-flavor @var{instruction-set}
8301 Select the instruction set to use when disassembling the
8302 program via the @code{disassemble} or @code{x/i} commands.
8304 Currently this command is only defined for the Intel x86 family. You
8305 can set @var{instruction-set} to either @code{intel} or @code{att}.
8306 The default is @code{att}, the AT&T flavor used by default by Unix
8307 assemblers for x86-based targets.
8309 @kindex show disassembly-flavor
8310 @item show disassembly-flavor
8311 Show the current setting of the disassembly flavor.
8315 @kindex set disassemble-next-line
8316 @kindex show disassemble-next-line
8317 @item set disassemble-next-line
8318 @itemx show disassemble-next-line
8319 Control whether or not @value{GDBN} will disassemble the next source
8320 line or instruction when execution stops. If ON, @value{GDBN} will
8321 display disassembly of the next source line when execution of the
8322 program being debugged stops. This is @emph{in addition} to
8323 displaying the source line itself, which @value{GDBN} always does if
8324 possible. If the next source line cannot be displayed for some reason
8325 (e.g., if @value{GDBN} cannot find the source file, or there's no line
8326 info in the debug info), @value{GDBN} will display disassembly of the
8327 next @emph{instruction} instead of showing the next source line. If
8328 AUTO, @value{GDBN} will display disassembly of next instruction only
8329 if the source line cannot be displayed. This setting causes
8330 @value{GDBN} to display some feedback when you step through a function
8331 with no line info or whose source file is unavailable. The default is
8332 OFF, which means never display the disassembly of the next line or
8338 @chapter Examining Data
8340 @cindex printing data
8341 @cindex examining data
8344 The usual way to examine data in your program is with the @code{print}
8345 command (abbreviated @code{p}), or its synonym @code{inspect}. It
8346 evaluates and prints the value of an expression of the language your
8347 program is written in (@pxref{Languages, ,Using @value{GDBN} with
8348 Different Languages}). It may also print the expression using a
8349 Python-based pretty-printer (@pxref{Pretty Printing}).
8352 @item print @var{expr}
8353 @itemx print /@var{f} @var{expr}
8354 @var{expr} is an expression (in the source language). By default the
8355 value of @var{expr} is printed in a format appropriate to its data type;
8356 you can choose a different format by specifying @samp{/@var{f}}, where
8357 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
8361 @itemx print /@var{f}
8362 @cindex reprint the last value
8363 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
8364 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
8365 conveniently inspect the same value in an alternative format.
8368 A more low-level way of examining data is with the @code{x} command.
8369 It examines data in memory at a specified address and prints it in a
8370 specified format. @xref{Memory, ,Examining Memory}.
8372 If you are interested in information about types, or about how the
8373 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
8374 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
8377 @cindex exploring hierarchical data structures
8379 Another way of examining values of expressions and type information is
8380 through the Python extension command @code{explore} (available only if
8381 the @value{GDBN} build is configured with @code{--with-python}). It
8382 offers an interactive way to start at the highest level (or, the most
8383 abstract level) of the data type of an expression (or, the data type
8384 itself) and explore all the way down to leaf scalar values/fields
8385 embedded in the higher level data types.
8388 @item explore @var{arg}
8389 @var{arg} is either an expression (in the source language), or a type
8390 visible in the current context of the program being debugged.
8393 The working of the @code{explore} command can be illustrated with an
8394 example. If a data type @code{struct ComplexStruct} is defined in your
8404 struct ComplexStruct
8406 struct SimpleStruct *ss_p;
8412 followed by variable declarations as
8415 struct SimpleStruct ss = @{ 10, 1.11 @};
8416 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
8420 then, the value of the variable @code{cs} can be explored using the
8421 @code{explore} command as follows.
8425 The value of `cs' is a struct/class of type `struct ComplexStruct' with
8426 the following fields:
8428 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
8429 arr = <Enter 1 to explore this field of type `int [10]'>
8431 Enter the field number of choice:
8435 Since the fields of @code{cs} are not scalar values, you are being
8436 prompted to chose the field you want to explore. Let's say you choose
8437 the field @code{ss_p} by entering @code{0}. Then, since this field is a
8438 pointer, you will be asked if it is pointing to a single value. From
8439 the declaration of @code{cs} above, it is indeed pointing to a single
8440 value, hence you enter @code{y}. If you enter @code{n}, then you will
8441 be asked if it were pointing to an array of values, in which case this
8442 field will be explored as if it were an array.
8445 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
8446 Continue exploring it as a pointer to a single value [y/n]: y
8447 The value of `*(cs.ss_p)' is a struct/class of type `struct
8448 SimpleStruct' with the following fields:
8450 i = 10 .. (Value of type `int')
8451 d = 1.1100000000000001 .. (Value of type `double')
8453 Press enter to return to parent value:
8457 If the field @code{arr} of @code{cs} was chosen for exploration by
8458 entering @code{1} earlier, then since it is as array, you will be
8459 prompted to enter the index of the element in the array that you want
8463 `cs.arr' is an array of `int'.
8464 Enter the index of the element you want to explore in `cs.arr': 5
8466 `(cs.arr)[5]' is a scalar value of type `int'.
8470 Press enter to return to parent value:
8473 In general, at any stage of exploration, you can go deeper towards the
8474 leaf values by responding to the prompts appropriately, or hit the
8475 return key to return to the enclosing data structure (the @i{higher}
8476 level data structure).
8478 Similar to exploring values, you can use the @code{explore} command to
8479 explore types. Instead of specifying a value (which is typically a
8480 variable name or an expression valid in the current context of the
8481 program being debugged), you specify a type name. If you consider the
8482 same example as above, your can explore the type
8483 @code{struct ComplexStruct} by passing the argument
8484 @code{struct ComplexStruct} to the @code{explore} command.
8487 (gdb) explore struct ComplexStruct
8491 By responding to the prompts appropriately in the subsequent interactive
8492 session, you can explore the type @code{struct ComplexStruct} in a
8493 manner similar to how the value @code{cs} was explored in the above
8496 The @code{explore} command also has two sub-commands,
8497 @code{explore value} and @code{explore type}. The former sub-command is
8498 a way to explicitly specify that value exploration of the argument is
8499 being invoked, while the latter is a way to explicitly specify that type
8500 exploration of the argument is being invoked.
8503 @item explore value @var{expr}
8504 @cindex explore value
8505 This sub-command of @code{explore} explores the value of the
8506 expression @var{expr} (if @var{expr} is an expression valid in the
8507 current context of the program being debugged). The behavior of this
8508 command is identical to that of the behavior of the @code{explore}
8509 command being passed the argument @var{expr}.
8511 @item explore type @var{arg}
8512 @cindex explore type
8513 This sub-command of @code{explore} explores the type of @var{arg} (if
8514 @var{arg} is a type visible in the current context of program being
8515 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8516 is an expression valid in the current context of the program being
8517 debugged). If @var{arg} is a type, then the behavior of this command is
8518 identical to that of the @code{explore} command being passed the
8519 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8520 this command will be identical to that of the @code{explore} command
8521 being passed the type of @var{arg} as the argument.
8525 * Expressions:: Expressions
8526 * Ambiguous Expressions:: Ambiguous Expressions
8527 * Variables:: Program variables
8528 * Arrays:: Artificial arrays
8529 * Output Formats:: Output formats
8530 * Memory:: Examining memory
8531 * Auto Display:: Automatic display
8532 * Print Settings:: Print settings
8533 * Pretty Printing:: Python pretty printing
8534 * Value History:: Value history
8535 * Convenience Vars:: Convenience variables
8536 * Convenience Funs:: Convenience functions
8537 * Registers:: Registers
8538 * Floating Point Hardware:: Floating point hardware
8539 * Vector Unit:: Vector Unit
8540 * OS Information:: Auxiliary data provided by operating system
8541 * Memory Region Attributes:: Memory region attributes
8542 * Dump/Restore Files:: Copy between memory and a file
8543 * Core File Generation:: Cause a program dump its core
8544 * Character Sets:: Debugging programs that use a different
8545 character set than GDB does
8546 * Caching Target Data:: Data caching for targets
8547 * Searching Memory:: Searching memory for a sequence of bytes
8551 @section Expressions
8554 @code{print} and many other @value{GDBN} commands accept an expression and
8555 compute its value. Any kind of constant, variable or operator defined
8556 by the programming language you are using is valid in an expression in
8557 @value{GDBN}. This includes conditional expressions, function calls,
8558 casts, and string constants. It also includes preprocessor macros, if
8559 you compiled your program to include this information; see
8562 @cindex arrays in expressions
8563 @value{GDBN} supports array constants in expressions input by
8564 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8565 you can use the command @code{print @{1, 2, 3@}} to create an array
8566 of three integers. If you pass an array to a function or assign it
8567 to a program variable, @value{GDBN} copies the array to memory that
8568 is @code{malloc}ed in the target program.
8570 Because C is so widespread, most of the expressions shown in examples in
8571 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8572 Languages}, for information on how to use expressions in other
8575 In this section, we discuss operators that you can use in @value{GDBN}
8576 expressions regardless of your programming language.
8578 @cindex casts, in expressions
8579 Casts are supported in all languages, not just in C, because it is so
8580 useful to cast a number into a pointer in order to examine a structure
8581 at that address in memory.
8582 @c FIXME: casts supported---Mod2 true?
8584 @value{GDBN} supports these operators, in addition to those common
8585 to programming languages:
8589 @samp{@@} is a binary operator for treating parts of memory as arrays.
8590 @xref{Arrays, ,Artificial Arrays}, for more information.
8593 @samp{::} allows you to specify a variable in terms of the file or
8594 function where it is defined. @xref{Variables, ,Program Variables}.
8596 @cindex @{@var{type}@}
8597 @cindex type casting memory
8598 @cindex memory, viewing as typed object
8599 @cindex casts, to view memory
8600 @item @{@var{type}@} @var{addr}
8601 Refers to an object of type @var{type} stored at address @var{addr} in
8602 memory. The address @var{addr} may be any expression whose value is
8603 an integer or pointer (but parentheses are required around binary
8604 operators, just as in a cast). This construct is allowed regardless
8605 of what kind of data is normally supposed to reside at @var{addr}.
8608 @node Ambiguous Expressions
8609 @section Ambiguous Expressions
8610 @cindex ambiguous expressions
8612 Expressions can sometimes contain some ambiguous elements. For instance,
8613 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8614 a single function name to be defined several times, for application in
8615 different contexts. This is called @dfn{overloading}. Another example
8616 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8617 templates and is typically instantiated several times, resulting in
8618 the same function name being defined in different contexts.
8620 In some cases and depending on the language, it is possible to adjust
8621 the expression to remove the ambiguity. For instance in C@t{++}, you
8622 can specify the signature of the function you want to break on, as in
8623 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8624 qualified name of your function often makes the expression unambiguous
8627 When an ambiguity that needs to be resolved is detected, the debugger
8628 has the capability to display a menu of numbered choices for each
8629 possibility, and then waits for the selection with the prompt @samp{>}.
8630 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
8631 aborts the current command. If the command in which the expression was
8632 used allows more than one choice to be selected, the next option in the
8633 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
8636 For example, the following session excerpt shows an attempt to set a
8637 breakpoint at the overloaded symbol @code{String::after}.
8638 We choose three particular definitions of that function name:
8640 @c FIXME! This is likely to change to show arg type lists, at least
8643 (@value{GDBP}) b String::after
8646 [2] file:String.cc; line number:867
8647 [3] file:String.cc; line number:860
8648 [4] file:String.cc; line number:875
8649 [5] file:String.cc; line number:853
8650 [6] file:String.cc; line number:846
8651 [7] file:String.cc; line number:735
8653 Breakpoint 1 at 0xb26c: file String.cc, line 867.
8654 Breakpoint 2 at 0xb344: file String.cc, line 875.
8655 Breakpoint 3 at 0xafcc: file String.cc, line 846.
8656 Multiple breakpoints were set.
8657 Use the "delete" command to delete unwanted
8664 @kindex set multiple-symbols
8665 @item set multiple-symbols @var{mode}
8666 @cindex multiple-symbols menu
8668 This option allows you to adjust the debugger behavior when an expression
8671 By default, @var{mode} is set to @code{all}. If the command with which
8672 the expression is used allows more than one choice, then @value{GDBN}
8673 automatically selects all possible choices. For instance, inserting
8674 a breakpoint on a function using an ambiguous name results in a breakpoint
8675 inserted on each possible match. However, if a unique choice must be made,
8676 then @value{GDBN} uses the menu to help you disambiguate the expression.
8677 For instance, printing the address of an overloaded function will result
8678 in the use of the menu.
8680 When @var{mode} is set to @code{ask}, the debugger always uses the menu
8681 when an ambiguity is detected.
8683 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
8684 an error due to the ambiguity and the command is aborted.
8686 @kindex show multiple-symbols
8687 @item show multiple-symbols
8688 Show the current value of the @code{multiple-symbols} setting.
8692 @section Program Variables
8694 The most common kind of expression to use is the name of a variable
8697 Variables in expressions are understood in the selected stack frame
8698 (@pxref{Selection, ,Selecting a Frame}); they must be either:
8702 global (or file-static)
8709 visible according to the scope rules of the
8710 programming language from the point of execution in that frame
8713 @noindent This means that in the function
8728 you can examine and use the variable @code{a} whenever your program is
8729 executing within the function @code{foo}, but you can only use or
8730 examine the variable @code{b} while your program is executing inside
8731 the block where @code{b} is declared.
8733 @cindex variable name conflict
8734 There is an exception: you can refer to a variable or function whose
8735 scope is a single source file even if the current execution point is not
8736 in this file. But it is possible to have more than one such variable or
8737 function with the same name (in different source files). If that
8738 happens, referring to that name has unpredictable effects. If you wish,
8739 you can specify a static variable in a particular function or file by
8740 using the colon-colon (@code{::}) notation:
8742 @cindex colon-colon, context for variables/functions
8744 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
8745 @cindex @code{::}, context for variables/functions
8748 @var{file}::@var{variable}
8749 @var{function}::@var{variable}
8753 Here @var{file} or @var{function} is the name of the context for the
8754 static @var{variable}. In the case of file names, you can use quotes to
8755 make sure @value{GDBN} parses the file name as a single word---for example,
8756 to print a global value of @code{x} defined in @file{f2.c}:
8759 (@value{GDBP}) p 'f2.c'::x
8762 The @code{::} notation is normally used for referring to
8763 static variables, since you typically disambiguate uses of local variables
8764 in functions by selecting the appropriate frame and using the
8765 simple name of the variable. However, you may also use this notation
8766 to refer to local variables in frames enclosing the selected frame:
8775 process (a); /* Stop here */
8786 For example, if there is a breakpoint at the commented line,
8787 here is what you might see
8788 when the program stops after executing the call @code{bar(0)}:
8793 (@value{GDBP}) p bar::a
8796 #2 0x080483d0 in foo (a=5) at foobar.c:12
8799 (@value{GDBP}) p bar::a
8803 @cindex C@t{++} scope resolution
8804 These uses of @samp{::} are very rarely in conflict with the very
8805 similar use of the same notation in C@t{++}. When they are in
8806 conflict, the C@t{++} meaning takes precedence; however, this can be
8807 overridden by quoting the file or function name with single quotes.
8809 For example, suppose the program is stopped in a method of a class
8810 that has a field named @code{includefile}, and there is also an
8811 include file named @file{includefile} that defines a variable,
8815 (@value{GDBP}) p includefile
8817 (@value{GDBP}) p includefile::some_global
8818 A syntax error in expression, near `'.
8819 (@value{GDBP}) p 'includefile'::some_global
8823 @cindex wrong values
8824 @cindex variable values, wrong
8825 @cindex function entry/exit, wrong values of variables
8826 @cindex optimized code, wrong values of variables
8828 @emph{Warning:} Occasionally, a local variable may appear to have the
8829 wrong value at certain points in a function---just after entry to a new
8830 scope, and just before exit.
8832 You may see this problem when you are stepping by machine instructions.
8833 This is because, on most machines, it takes more than one instruction to
8834 set up a stack frame (including local variable definitions); if you are
8835 stepping by machine instructions, variables may appear to have the wrong
8836 values until the stack frame is completely built. On exit, it usually
8837 also takes more than one machine instruction to destroy a stack frame;
8838 after you begin stepping through that group of instructions, local
8839 variable definitions may be gone.
8841 This may also happen when the compiler does significant optimizations.
8842 To be sure of always seeing accurate values, turn off all optimization
8845 @cindex ``No symbol "foo" in current context''
8846 Another possible effect of compiler optimizations is to optimize
8847 unused variables out of existence, or assign variables to registers (as
8848 opposed to memory addresses). Depending on the support for such cases
8849 offered by the debug info format used by the compiler, @value{GDBN}
8850 might not be able to display values for such local variables. If that
8851 happens, @value{GDBN} will print a message like this:
8854 No symbol "foo" in current context.
8857 To solve such problems, either recompile without optimizations, or use a
8858 different debug info format, if the compiler supports several such
8859 formats. @xref{Compilation}, for more information on choosing compiler
8860 options. @xref{C, ,C and C@t{++}}, for more information about debug
8861 info formats that are best suited to C@t{++} programs.
8863 If you ask to print an object whose contents are unknown to
8864 @value{GDBN}, e.g., because its data type is not completely specified
8865 by the debug information, @value{GDBN} will say @samp{<incomplete
8866 type>}. @xref{Symbols, incomplete type}, for more about this.
8868 If you append @kbd{@@entry} string to a function parameter name you get its
8869 value at the time the function got called. If the value is not available an
8870 error message is printed. Entry values are available only with some compilers.
8871 Entry values are normally also printed at the function parameter list according
8872 to @ref{set print entry-values}.
8875 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
8881 (gdb) print i@@entry
8885 Strings are identified as arrays of @code{char} values without specified
8886 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
8887 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
8888 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
8889 defines literal string type @code{"char"} as @code{char} without a sign.
8894 signed char var1[] = "A";
8897 You get during debugging
8902 $2 = @{65 'A', 0 '\0'@}
8906 @section Artificial Arrays
8908 @cindex artificial array
8910 @kindex @@@r{, referencing memory as an array}
8911 It is often useful to print out several successive objects of the
8912 same type in memory; a section of an array, or an array of
8913 dynamically determined size for which only a pointer exists in the
8916 You can do this by referring to a contiguous span of memory as an
8917 @dfn{artificial array}, using the binary operator @samp{@@}. The left
8918 operand of @samp{@@} should be the first element of the desired array
8919 and be an individual object. The right operand should be the desired length
8920 of the array. The result is an array value whose elements are all of
8921 the type of the left argument. The first element is actually the left
8922 argument; the second element comes from bytes of memory immediately
8923 following those that hold the first element, and so on. Here is an
8924 example. If a program says
8927 int *array = (int *) malloc (len * sizeof (int));
8931 you can print the contents of @code{array} with
8937 The left operand of @samp{@@} must reside in memory. Array values made
8938 with @samp{@@} in this way behave just like other arrays in terms of
8939 subscripting, and are coerced to pointers when used in expressions.
8940 Artificial arrays most often appear in expressions via the value history
8941 (@pxref{Value History, ,Value History}), after printing one out.
8943 Another way to create an artificial array is to use a cast.
8944 This re-interprets a value as if it were an array.
8945 The value need not be in memory:
8947 (@value{GDBP}) p/x (short[2])0x12345678
8948 $1 = @{0x1234, 0x5678@}
8951 As a convenience, if you leave the array length out (as in
8952 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
8953 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
8955 (@value{GDBP}) p/x (short[])0x12345678
8956 $2 = @{0x1234, 0x5678@}
8959 Sometimes the artificial array mechanism is not quite enough; in
8960 moderately complex data structures, the elements of interest may not
8961 actually be adjacent---for example, if you are interested in the values
8962 of pointers in an array. One useful work-around in this situation is
8963 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8964 Variables}) as a counter in an expression that prints the first
8965 interesting value, and then repeat that expression via @key{RET}. For
8966 instance, suppose you have an array @code{dtab} of pointers to
8967 structures, and you are interested in the values of a field @code{fv}
8968 in each structure. Here is an example of what you might type:
8978 @node Output Formats
8979 @section Output Formats
8981 @cindex formatted output
8982 @cindex output formats
8983 By default, @value{GDBN} prints a value according to its data type. Sometimes
8984 this is not what you want. For example, you might want to print a number
8985 in hex, or a pointer in decimal. Or you might want to view data in memory
8986 at a certain address as a character string or as an instruction. To do
8987 these things, specify an @dfn{output format} when you print a value.
8989 The simplest use of output formats is to say how to print a value
8990 already computed. This is done by starting the arguments of the
8991 @code{print} command with a slash and a format letter. The format
8992 letters supported are:
8996 Regard the bits of the value as an integer, and print the integer in
9000 Print as integer in signed decimal.
9003 Print as integer in unsigned decimal.
9006 Print as integer in octal.
9009 Print as integer in binary. The letter @samp{t} stands for ``two''.
9010 @footnote{@samp{b} cannot be used because these format letters are also
9011 used with the @code{x} command, where @samp{b} stands for ``byte'';
9012 see @ref{Memory,,Examining Memory}.}
9015 @cindex unknown address, locating
9016 @cindex locate address
9017 Print as an address, both absolute in hexadecimal and as an offset from
9018 the nearest preceding symbol. You can use this format used to discover
9019 where (in what function) an unknown address is located:
9022 (@value{GDBP}) p/a 0x54320
9023 $3 = 0x54320 <_initialize_vx+396>
9027 The command @code{info symbol 0x54320} yields similar results.
9028 @xref{Symbols, info symbol}.
9031 Regard as an integer and print it as a character constant. This
9032 prints both the numerical value and its character representation. The
9033 character representation is replaced with the octal escape @samp{\nnn}
9034 for characters outside the 7-bit @sc{ascii} range.
9036 Without this format, @value{GDBN} displays @code{char},
9037 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
9038 constants. Single-byte members of vectors are displayed as integer
9042 Regard the bits of the value as a floating point number and print
9043 using typical floating point syntax.
9046 @cindex printing strings
9047 @cindex printing byte arrays
9048 Regard as a string, if possible. With this format, pointers to single-byte
9049 data are displayed as null-terminated strings and arrays of single-byte data
9050 are displayed as fixed-length strings. Other values are displayed in their
9053 Without this format, @value{GDBN} displays pointers to and arrays of
9054 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
9055 strings. Single-byte members of a vector are displayed as an integer
9059 Like @samp{x} formatting, the value is treated as an integer and
9060 printed as hexadecimal, but leading zeros are printed to pad the value
9061 to the size of the integer type.
9064 @cindex raw printing
9065 Print using the @samp{raw} formatting. By default, @value{GDBN} will
9066 use a Python-based pretty-printer, if one is available (@pxref{Pretty
9067 Printing}). This typically results in a higher-level display of the
9068 value's contents. The @samp{r} format bypasses any Python
9069 pretty-printer which might exist.
9072 For example, to print the program counter in hex (@pxref{Registers}), type
9079 Note that no space is required before the slash; this is because command
9080 names in @value{GDBN} cannot contain a slash.
9082 To reprint the last value in the value history with a different format,
9083 you can use the @code{print} command with just a format and no
9084 expression. For example, @samp{p/x} reprints the last value in hex.
9087 @section Examining Memory
9089 You can use the command @code{x} (for ``examine'') to examine memory in
9090 any of several formats, independently of your program's data types.
9092 @cindex examining memory
9094 @kindex x @r{(examine memory)}
9095 @item x/@var{nfu} @var{addr}
9098 Use the @code{x} command to examine memory.
9101 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
9102 much memory to display and how to format it; @var{addr} is an
9103 expression giving the address where you want to start displaying memory.
9104 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
9105 Several commands set convenient defaults for @var{addr}.
9108 @item @var{n}, the repeat count
9109 The repeat count is a decimal integer; the default is 1. It specifies
9110 how much memory (counting by units @var{u}) to display.
9111 @c This really is **decimal**; unaffected by 'set radix' as of GDB
9114 @item @var{f}, the display format
9115 The display format is one of the formats used by @code{print}
9116 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
9117 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
9118 The default is @samp{x} (hexadecimal) initially. The default changes
9119 each time you use either @code{x} or @code{print}.
9121 @item @var{u}, the unit size
9122 The unit size is any of
9128 Halfwords (two bytes).
9130 Words (four bytes). This is the initial default.
9132 Giant words (eight bytes).
9135 Each time you specify a unit size with @code{x}, that size becomes the
9136 default unit the next time you use @code{x}. For the @samp{i} format,
9137 the unit size is ignored and is normally not written. For the @samp{s} format,
9138 the unit size defaults to @samp{b}, unless it is explicitly given.
9139 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
9140 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
9141 Note that the results depend on the programming language of the
9142 current compilation unit. If the language is C, the @samp{s}
9143 modifier will use the UTF-16 encoding while @samp{w} will use
9144 UTF-32. The encoding is set by the programming language and cannot
9147 @item @var{addr}, starting display address
9148 @var{addr} is the address where you want @value{GDBN} to begin displaying
9149 memory. The expression need not have a pointer value (though it may);
9150 it is always interpreted as an integer address of a byte of memory.
9151 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
9152 @var{addr} is usually just after the last address examined---but several
9153 other commands also set the default address: @code{info breakpoints} (to
9154 the address of the last breakpoint listed), @code{info line} (to the
9155 starting address of a line), and @code{print} (if you use it to display
9156 a value from memory).
9159 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
9160 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
9161 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
9162 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
9163 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
9165 Since the letters indicating unit sizes are all distinct from the
9166 letters specifying output formats, you do not have to remember whether
9167 unit size or format comes first; either order works. The output
9168 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
9169 (However, the count @var{n} must come first; @samp{wx4} does not work.)
9171 Even though the unit size @var{u} is ignored for the formats @samp{s}
9172 and @samp{i}, you might still want to use a count @var{n}; for example,
9173 @samp{3i} specifies that you want to see three machine instructions,
9174 including any operands. For convenience, especially when used with
9175 the @code{display} command, the @samp{i} format also prints branch delay
9176 slot instructions, if any, beyond the count specified, which immediately
9177 follow the last instruction that is within the count. The command
9178 @code{disassemble} gives an alternative way of inspecting machine
9179 instructions; see @ref{Machine Code,,Source and Machine Code}.
9181 All the defaults for the arguments to @code{x} are designed to make it
9182 easy to continue scanning memory with minimal specifications each time
9183 you use @code{x}. For example, after you have inspected three machine
9184 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
9185 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
9186 the repeat count @var{n} is used again; the other arguments default as
9187 for successive uses of @code{x}.
9189 When examining machine instructions, the instruction at current program
9190 counter is shown with a @code{=>} marker. For example:
9193 (@value{GDBP}) x/5i $pc-6
9194 0x804837f <main+11>: mov %esp,%ebp
9195 0x8048381 <main+13>: push %ecx
9196 0x8048382 <main+14>: sub $0x4,%esp
9197 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
9198 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
9201 @cindex @code{$_}, @code{$__}, and value history
9202 The addresses and contents printed by the @code{x} command are not saved
9203 in the value history because there is often too much of them and they
9204 would get in the way. Instead, @value{GDBN} makes these values available for
9205 subsequent use in expressions as values of the convenience variables
9206 @code{$_} and @code{$__}. After an @code{x} command, the last address
9207 examined is available for use in expressions in the convenience variable
9208 @code{$_}. The contents of that address, as examined, are available in
9209 the convenience variable @code{$__}.
9211 If the @code{x} command has a repeat count, the address and contents saved
9212 are from the last memory unit printed; this is not the same as the last
9213 address printed if several units were printed on the last line of output.
9215 @anchor{addressable memory unit}
9216 @cindex addressable memory unit
9217 Most targets have an addressable memory unit size of 8 bits. This means
9218 that to each memory address are associated 8 bits of data. Some
9219 targets, however, have other addressable memory unit sizes.
9220 Within @value{GDBN} and this document, the term
9221 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
9222 when explicitly referring to a chunk of data of that size. The word
9223 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
9224 the addressable memory unit size of the target. For most systems,
9225 addressable memory unit is a synonym of byte.
9227 @cindex remote memory comparison
9228 @cindex target memory comparison
9229 @cindex verify remote memory image
9230 @cindex verify target memory image
9231 When you are debugging a program running on a remote target machine
9232 (@pxref{Remote Debugging}), you may wish to verify the program's image
9233 in the remote machine's memory against the executable file you
9234 downloaded to the target. Or, on any target, you may want to check
9235 whether the program has corrupted its own read-only sections. The
9236 @code{compare-sections} command is provided for such situations.
9239 @kindex compare-sections
9240 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
9241 Compare the data of a loadable section @var{section-name} in the
9242 executable file of the program being debugged with the same section in
9243 the target machine's memory, and report any mismatches. With no
9244 arguments, compares all loadable sections. With an argument of
9245 @code{-r}, compares all loadable read-only sections.
9247 Note: for remote targets, this command can be accelerated if the
9248 target supports computing the CRC checksum of a block of memory
9249 (@pxref{qCRC packet}).
9253 @section Automatic Display
9254 @cindex automatic display
9255 @cindex display of expressions
9257 If you find that you want to print the value of an expression frequently
9258 (to see how it changes), you might want to add it to the @dfn{automatic
9259 display list} so that @value{GDBN} prints its value each time your program stops.
9260 Each expression added to the list is given a number to identify it;
9261 to remove an expression from the list, you specify that number.
9262 The automatic display looks like this:
9266 3: bar[5] = (struct hack *) 0x3804
9270 This display shows item numbers, expressions and their current values. As with
9271 displays you request manually using @code{x} or @code{print}, you can
9272 specify the output format you prefer; in fact, @code{display} decides
9273 whether to use @code{print} or @code{x} depending your format
9274 specification---it uses @code{x} if you specify either the @samp{i}
9275 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
9279 @item display @var{expr}
9280 Add the expression @var{expr} to the list of expressions to display
9281 each time your program stops. @xref{Expressions, ,Expressions}.
9283 @code{display} does not repeat if you press @key{RET} again after using it.
9285 @item display/@var{fmt} @var{expr}
9286 For @var{fmt} specifying only a display format and not a size or
9287 count, add the expression @var{expr} to the auto-display list but
9288 arrange to display it each time in the specified format @var{fmt}.
9289 @xref{Output Formats,,Output Formats}.
9291 @item display/@var{fmt} @var{addr}
9292 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
9293 number of units, add the expression @var{addr} as a memory address to
9294 be examined each time your program stops. Examining means in effect
9295 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
9298 For example, @samp{display/i $pc} can be helpful, to see the machine
9299 instruction about to be executed each time execution stops (@samp{$pc}
9300 is a common name for the program counter; @pxref{Registers, ,Registers}).
9303 @kindex delete display
9305 @item undisplay @var{dnums}@dots{}
9306 @itemx delete display @var{dnums}@dots{}
9307 Remove items from the list of expressions to display. Specify the
9308 numbers of the displays that you want affected with the command
9309 argument @var{dnums}. It can be a single display number, one of the
9310 numbers shown in the first field of the @samp{info display} display;
9311 or it could be a range of display numbers, as in @code{2-4}.
9313 @code{undisplay} does not repeat if you press @key{RET} after using it.
9314 (Otherwise you would just get the error @samp{No display number @dots{}}.)
9316 @kindex disable display
9317 @item disable display @var{dnums}@dots{}
9318 Disable the display of item numbers @var{dnums}. A disabled display
9319 item is not printed automatically, but is not forgotten. It may be
9320 enabled again later. Specify the numbers of the displays that you
9321 want affected with the command argument @var{dnums}. It can be a
9322 single display number, one of the numbers shown in the first field of
9323 the @samp{info display} display; or it could be a range of display
9324 numbers, as in @code{2-4}.
9326 @kindex enable display
9327 @item enable display @var{dnums}@dots{}
9328 Enable display of item numbers @var{dnums}. It becomes effective once
9329 again in auto display of its expression, until you specify otherwise.
9330 Specify the numbers of the displays that you want affected with the
9331 command argument @var{dnums}. It can be a single display number, one
9332 of the numbers shown in the first field of the @samp{info display}
9333 display; or it could be a range of display numbers, as in @code{2-4}.
9336 Display the current values of the expressions on the list, just as is
9337 done when your program stops.
9339 @kindex info display
9341 Print the list of expressions previously set up to display
9342 automatically, each one with its item number, but without showing the
9343 values. This includes disabled expressions, which are marked as such.
9344 It also includes expressions which would not be displayed right now
9345 because they refer to automatic variables not currently available.
9348 @cindex display disabled out of scope
9349 If a display expression refers to local variables, then it does not make
9350 sense outside the lexical context for which it was set up. Such an
9351 expression is disabled when execution enters a context where one of its
9352 variables is not defined. For example, if you give the command
9353 @code{display last_char} while inside a function with an argument
9354 @code{last_char}, @value{GDBN} displays this argument while your program
9355 continues to stop inside that function. When it stops elsewhere---where
9356 there is no variable @code{last_char}---the display is disabled
9357 automatically. The next time your program stops where @code{last_char}
9358 is meaningful, you can enable the display expression once again.
9360 @node Print Settings
9361 @section Print Settings
9363 @cindex format options
9364 @cindex print settings
9365 @value{GDBN} provides the following ways to control how arrays, structures,
9366 and symbols are printed.
9369 These settings are useful for debugging programs in any language:
9373 @item set print address
9374 @itemx set print address on
9375 @cindex print/don't print memory addresses
9376 @value{GDBN} prints memory addresses showing the location of stack
9377 traces, structure values, pointer values, breakpoints, and so forth,
9378 even when it also displays the contents of those addresses. The default
9379 is @code{on}. For example, this is what a stack frame display looks like with
9380 @code{set print address on}:
9385 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
9387 530 if (lquote != def_lquote)
9391 @item set print address off
9392 Do not print addresses when displaying their contents. For example,
9393 this is the same stack frame displayed with @code{set print address off}:
9397 (@value{GDBP}) set print addr off
9399 #0 set_quotes (lq="<<", rq=">>") at input.c:530
9400 530 if (lquote != def_lquote)
9404 You can use @samp{set print address off} to eliminate all machine
9405 dependent displays from the @value{GDBN} interface. For example, with
9406 @code{print address off}, you should get the same text for backtraces on
9407 all machines---whether or not they involve pointer arguments.
9410 @item show print address
9411 Show whether or not addresses are to be printed.
9414 When @value{GDBN} prints a symbolic address, it normally prints the
9415 closest earlier symbol plus an offset. If that symbol does not uniquely
9416 identify the address (for example, it is a name whose scope is a single
9417 source file), you may need to clarify. One way to do this is with
9418 @code{info line}, for example @samp{info line *0x4537}. Alternately,
9419 you can set @value{GDBN} to print the source file and line number when
9420 it prints a symbolic address:
9423 @item set print symbol-filename on
9424 @cindex source file and line of a symbol
9425 @cindex symbol, source file and line
9426 Tell @value{GDBN} to print the source file name and line number of a
9427 symbol in the symbolic form of an address.
9429 @item set print symbol-filename off
9430 Do not print source file name and line number of a symbol. This is the
9433 @item show print symbol-filename
9434 Show whether or not @value{GDBN} will print the source file name and
9435 line number of a symbol in the symbolic form of an address.
9438 Another situation where it is helpful to show symbol filenames and line
9439 numbers is when disassembling code; @value{GDBN} shows you the line
9440 number and source file that corresponds to each instruction.
9442 Also, you may wish to see the symbolic form only if the address being
9443 printed is reasonably close to the closest earlier symbol:
9446 @item set print max-symbolic-offset @var{max-offset}
9447 @itemx set print max-symbolic-offset unlimited
9448 @cindex maximum value for offset of closest symbol
9449 Tell @value{GDBN} to only display the symbolic form of an address if the
9450 offset between the closest earlier symbol and the address is less than
9451 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
9452 to always print the symbolic form of an address if any symbol precedes
9453 it. Zero is equivalent to @code{unlimited}.
9455 @item show print max-symbolic-offset
9456 Ask how large the maximum offset is that @value{GDBN} prints in a
9460 @cindex wild pointer, interpreting
9461 @cindex pointer, finding referent
9462 If you have a pointer and you are not sure where it points, try
9463 @samp{set print symbol-filename on}. Then you can determine the name
9464 and source file location of the variable where it points, using
9465 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
9466 For example, here @value{GDBN} shows that a variable @code{ptt} points
9467 at another variable @code{t}, defined in @file{hi2.c}:
9470 (@value{GDBP}) set print symbol-filename on
9471 (@value{GDBP}) p/a ptt
9472 $4 = 0xe008 <t in hi2.c>
9476 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
9477 does not show the symbol name and filename of the referent, even with
9478 the appropriate @code{set print} options turned on.
9481 You can also enable @samp{/a}-like formatting all the time using
9482 @samp{set print symbol on}:
9485 @item set print symbol on
9486 Tell @value{GDBN} to print the symbol corresponding to an address, if
9489 @item set print symbol off
9490 Tell @value{GDBN} not to print the symbol corresponding to an
9491 address. In this mode, @value{GDBN} will still print the symbol
9492 corresponding to pointers to functions. This is the default.
9494 @item show print symbol
9495 Show whether @value{GDBN} will display the symbol corresponding to an
9499 Other settings control how different kinds of objects are printed:
9502 @item set print array
9503 @itemx set print array on
9504 @cindex pretty print arrays
9505 Pretty print arrays. This format is more convenient to read,
9506 but uses more space. The default is off.
9508 @item set print array off
9509 Return to compressed format for arrays.
9511 @item show print array
9512 Show whether compressed or pretty format is selected for displaying
9515 @cindex print array indexes
9516 @item set print array-indexes
9517 @itemx set print array-indexes on
9518 Print the index of each element when displaying arrays. May be more
9519 convenient to locate a given element in the array or quickly find the
9520 index of a given element in that printed array. The default is off.
9522 @item set print array-indexes off
9523 Stop printing element indexes when displaying arrays.
9525 @item show print array-indexes
9526 Show whether the index of each element is printed when displaying
9529 @item set print elements @var{number-of-elements}
9530 @itemx set print elements unlimited
9531 @cindex number of array elements to print
9532 @cindex limit on number of printed array elements
9533 Set a limit on how many elements of an array @value{GDBN} will print.
9534 If @value{GDBN} is printing a large array, it stops printing after it has
9535 printed the number of elements set by the @code{set print elements} command.
9536 This limit also applies to the display of strings.
9537 When @value{GDBN} starts, this limit is set to 200.
9538 Setting @var{number-of-elements} to @code{unlimited} or zero means
9539 that the number of elements to print is unlimited.
9541 @item show print elements
9542 Display the number of elements of a large array that @value{GDBN} will print.
9543 If the number is 0, then the printing is unlimited.
9545 @item set print frame-arguments @var{value}
9546 @kindex set print frame-arguments
9547 @cindex printing frame argument values
9548 @cindex print all frame argument values
9549 @cindex print frame argument values for scalars only
9550 @cindex do not print frame argument values
9551 This command allows to control how the values of arguments are printed
9552 when the debugger prints a frame (@pxref{Frames}). The possible
9557 The values of all arguments are printed.
9560 Print the value of an argument only if it is a scalar. The value of more
9561 complex arguments such as arrays, structures, unions, etc, is replaced
9562 by @code{@dots{}}. This is the default. Here is an example where
9563 only scalar arguments are shown:
9566 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9571 None of the argument values are printed. Instead, the value of each argument
9572 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9575 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9580 By default, only scalar arguments are printed. This command can be used
9581 to configure the debugger to print the value of all arguments, regardless
9582 of their type. However, it is often advantageous to not print the value
9583 of more complex parameters. For instance, it reduces the amount of
9584 information printed in each frame, making the backtrace more readable.
9585 Also, it improves performance when displaying Ada frames, because
9586 the computation of large arguments can sometimes be CPU-intensive,
9587 especially in large applications. Setting @code{print frame-arguments}
9588 to @code{scalars} (the default) or @code{none} avoids this computation,
9589 thus speeding up the display of each Ada frame.
9591 @item show print frame-arguments
9592 Show how the value of arguments should be displayed when printing a frame.
9594 @item set print raw frame-arguments on
9595 Print frame arguments in raw, non pretty-printed, form.
9597 @item set print raw frame-arguments off
9598 Print frame arguments in pretty-printed form, if there is a pretty-printer
9599 for the value (@pxref{Pretty Printing}),
9600 otherwise print the value in raw form.
9601 This is the default.
9603 @item show print raw frame-arguments
9604 Show whether to print frame arguments in raw form.
9606 @anchor{set print entry-values}
9607 @item set print entry-values @var{value}
9608 @kindex set print entry-values
9609 Set printing of frame argument values at function entry. In some cases
9610 @value{GDBN} can determine the value of function argument which was passed by
9611 the function caller, even if the value was modified inside the called function
9612 and therefore is different. With optimized code, the current value could be
9613 unavailable, but the entry value may still be known.
9615 The default value is @code{default} (see below for its description). Older
9616 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
9617 this feature will behave in the @code{default} setting the same way as with the
9620 This functionality is currently supported only by DWARF 2 debugging format and
9621 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9622 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9625 The @var{value} parameter can be one of the following:
9629 Print only actual parameter values, never print values from function entry
9633 #0 different (val=6)
9634 #0 lost (val=<optimized out>)
9636 #0 invalid (val=<optimized out>)
9640 Print only parameter values from function entry point. The actual parameter
9641 values are never printed.
9643 #0 equal (val@@entry=5)
9644 #0 different (val@@entry=5)
9645 #0 lost (val@@entry=5)
9646 #0 born (val@@entry=<optimized out>)
9647 #0 invalid (val@@entry=<optimized out>)
9651 Print only parameter values from function entry point. If value from function
9652 entry point is not known while the actual value is known, print the actual
9653 value for such parameter.
9655 #0 equal (val@@entry=5)
9656 #0 different (val@@entry=5)
9657 #0 lost (val@@entry=5)
9659 #0 invalid (val@@entry=<optimized out>)
9663 Print actual parameter values. If actual parameter value is not known while
9664 value from function entry point is known, print the entry point value for such
9668 #0 different (val=6)
9669 #0 lost (val@@entry=5)
9671 #0 invalid (val=<optimized out>)
9675 Always print both the actual parameter value and its value from function entry
9676 point, even if values of one or both are not available due to compiler
9679 #0 equal (val=5, val@@entry=5)
9680 #0 different (val=6, val@@entry=5)
9681 #0 lost (val=<optimized out>, val@@entry=5)
9682 #0 born (val=10, val@@entry=<optimized out>)
9683 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
9687 Print the actual parameter value if it is known and also its value from
9688 function entry point if it is known. If neither is known, print for the actual
9689 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
9690 values are known and identical, print the shortened
9691 @code{param=param@@entry=VALUE} notation.
9693 #0 equal (val=val@@entry=5)
9694 #0 different (val=6, val@@entry=5)
9695 #0 lost (val@@entry=5)
9697 #0 invalid (val=<optimized out>)
9701 Always print the actual parameter value. Print also its value from function
9702 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
9703 if both values are known and identical, print the shortened
9704 @code{param=param@@entry=VALUE} notation.
9706 #0 equal (val=val@@entry=5)
9707 #0 different (val=6, val@@entry=5)
9708 #0 lost (val=<optimized out>, val@@entry=5)
9710 #0 invalid (val=<optimized out>)
9714 For analysis messages on possible failures of frame argument values at function
9715 entry resolution see @ref{set debug entry-values}.
9717 @item show print entry-values
9718 Show the method being used for printing of frame argument values at function
9721 @item set print repeats @var{number-of-repeats}
9722 @itemx set print repeats unlimited
9723 @cindex repeated array elements
9724 Set the threshold for suppressing display of repeated array
9725 elements. When the number of consecutive identical elements of an
9726 array exceeds the threshold, @value{GDBN} prints the string
9727 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
9728 identical repetitions, instead of displaying the identical elements
9729 themselves. Setting the threshold to @code{unlimited} or zero will
9730 cause all elements to be individually printed. The default threshold
9733 @item show print repeats
9734 Display the current threshold for printing repeated identical
9737 @item set print null-stop
9738 @cindex @sc{null} elements in arrays
9739 Cause @value{GDBN} to stop printing the characters of an array when the first
9740 @sc{null} is encountered. This is useful when large arrays actually
9741 contain only short strings.
9744 @item show print null-stop
9745 Show whether @value{GDBN} stops printing an array on the first
9746 @sc{null} character.
9748 @item set print pretty on
9749 @cindex print structures in indented form
9750 @cindex indentation in structure display
9751 Cause @value{GDBN} to print structures in an indented format with one member
9752 per line, like this:
9767 @item set print pretty off
9768 Cause @value{GDBN} to print structures in a compact format, like this:
9772 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
9773 meat = 0x54 "Pork"@}
9778 This is the default format.
9780 @item show print pretty
9781 Show which format @value{GDBN} is using to print structures.
9783 @item set print sevenbit-strings on
9784 @cindex eight-bit characters in strings
9785 @cindex octal escapes in strings
9786 Print using only seven-bit characters; if this option is set,
9787 @value{GDBN} displays any eight-bit characters (in strings or
9788 character values) using the notation @code{\}@var{nnn}. This setting is
9789 best if you are working in English (@sc{ascii}) and you use the
9790 high-order bit of characters as a marker or ``meta'' bit.
9792 @item set print sevenbit-strings off
9793 Print full eight-bit characters. This allows the use of more
9794 international character sets, and is the default.
9796 @item show print sevenbit-strings
9797 Show whether or not @value{GDBN} is printing only seven-bit characters.
9799 @item set print union on
9800 @cindex unions in structures, printing
9801 Tell @value{GDBN} to print unions which are contained in structures
9802 and other unions. This is the default setting.
9804 @item set print union off
9805 Tell @value{GDBN} not to print unions which are contained in
9806 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
9809 @item show print union
9810 Ask @value{GDBN} whether or not it will print unions which are contained in
9811 structures and other unions.
9813 For example, given the declarations
9816 typedef enum @{Tree, Bug@} Species;
9817 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
9818 typedef enum @{Caterpillar, Cocoon, Butterfly@}
9829 struct thing foo = @{Tree, @{Acorn@}@};
9833 with @code{set print union on} in effect @samp{p foo} would print
9836 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
9840 and with @code{set print union off} in effect it would print
9843 $1 = @{it = Tree, form = @{...@}@}
9847 @code{set print union} affects programs written in C-like languages
9853 These settings are of interest when debugging C@t{++} programs:
9856 @cindex demangling C@t{++} names
9857 @item set print demangle
9858 @itemx set print demangle on
9859 Print C@t{++} names in their source form rather than in the encoded
9860 (``mangled'') form passed to the assembler and linker for type-safe
9861 linkage. The default is on.
9863 @item show print demangle
9864 Show whether C@t{++} names are printed in mangled or demangled form.
9866 @item set print asm-demangle
9867 @itemx set print asm-demangle on
9868 Print C@t{++} names in their source form rather than their mangled form, even
9869 in assembler code printouts such as instruction disassemblies.
9872 @item show print asm-demangle
9873 Show whether C@t{++} names in assembly listings are printed in mangled
9876 @cindex C@t{++} symbol decoding style
9877 @cindex symbol decoding style, C@t{++}
9878 @kindex set demangle-style
9879 @item set demangle-style @var{style}
9880 Choose among several encoding schemes used by different compilers to
9881 represent C@t{++} names. The choices for @var{style} are currently:
9885 Allow @value{GDBN} to choose a decoding style by inspecting your program.
9886 This is the default.
9889 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
9892 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
9895 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
9898 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
9899 @strong{Warning:} this setting alone is not sufficient to allow
9900 debugging @code{cfront}-generated executables. @value{GDBN} would
9901 require further enhancement to permit that.
9904 If you omit @var{style}, you will see a list of possible formats.
9906 @item show demangle-style
9907 Display the encoding style currently in use for decoding C@t{++} symbols.
9909 @item set print object
9910 @itemx set print object on
9911 @cindex derived type of an object, printing
9912 @cindex display derived types
9913 When displaying a pointer to an object, identify the @emph{actual}
9914 (derived) type of the object rather than the @emph{declared} type, using
9915 the virtual function table. Note that the virtual function table is
9916 required---this feature can only work for objects that have run-time
9917 type identification; a single virtual method in the object's declared
9918 type is sufficient. Note that this setting is also taken into account when
9919 working with variable objects via MI (@pxref{GDB/MI}).
9921 @item set print object off
9922 Display only the declared type of objects, without reference to the
9923 virtual function table. This is the default setting.
9925 @item show print object
9926 Show whether actual, or declared, object types are displayed.
9928 @item set print static-members
9929 @itemx set print static-members on
9930 @cindex static members of C@t{++} objects
9931 Print static members when displaying a C@t{++} object. The default is on.
9933 @item set print static-members off
9934 Do not print static members when displaying a C@t{++} object.
9936 @item show print static-members
9937 Show whether C@t{++} static members are printed or not.
9939 @item set print pascal_static-members
9940 @itemx set print pascal_static-members on
9941 @cindex static members of Pascal objects
9942 @cindex Pascal objects, static members display
9943 Print static members when displaying a Pascal object. The default is on.
9945 @item set print pascal_static-members off
9946 Do not print static members when displaying a Pascal object.
9948 @item show print pascal_static-members
9949 Show whether Pascal static members are printed or not.
9951 @c These don't work with HP ANSI C++ yet.
9952 @item set print vtbl
9953 @itemx set print vtbl on
9954 @cindex pretty print C@t{++} virtual function tables
9955 @cindex virtual functions (C@t{++}) display
9956 @cindex VTBL display
9957 Pretty print C@t{++} virtual function tables. The default is off.
9958 (The @code{vtbl} commands do not work on programs compiled with the HP
9959 ANSI C@t{++} compiler (@code{aCC}).)
9961 @item set print vtbl off
9962 Do not pretty print C@t{++} virtual function tables.
9964 @item show print vtbl
9965 Show whether C@t{++} virtual function tables are pretty printed, or not.
9968 @node Pretty Printing
9969 @section Pretty Printing
9971 @value{GDBN} provides a mechanism to allow pretty-printing of values using
9972 Python code. It greatly simplifies the display of complex objects. This
9973 mechanism works for both MI and the CLI.
9976 * Pretty-Printer Introduction:: Introduction to pretty-printers
9977 * Pretty-Printer Example:: An example pretty-printer
9978 * Pretty-Printer Commands:: Pretty-printer commands
9981 @node Pretty-Printer Introduction
9982 @subsection Pretty-Printer Introduction
9984 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
9985 registered for the value. If there is then @value{GDBN} invokes the
9986 pretty-printer to print the value. Otherwise the value is printed normally.
9988 Pretty-printers are normally named. This makes them easy to manage.
9989 The @samp{info pretty-printer} command will list all the installed
9990 pretty-printers with their names.
9991 If a pretty-printer can handle multiple data types, then its
9992 @dfn{subprinters} are the printers for the individual data types.
9993 Each such subprinter has its own name.
9994 The format of the name is @var{printer-name};@var{subprinter-name}.
9996 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
9997 Typically they are automatically loaded and registered when the corresponding
9998 debug information is loaded, thus making them available without having to
9999 do anything special.
10001 There are three places where a pretty-printer can be registered.
10005 Pretty-printers registered globally are available when debugging
10009 Pretty-printers registered with a program space are available only
10010 when debugging that program.
10011 @xref{Progspaces In Python}, for more details on program spaces in Python.
10014 Pretty-printers registered with an objfile are loaded and unloaded
10015 with the corresponding objfile (e.g., shared library).
10016 @xref{Objfiles In Python}, for more details on objfiles in Python.
10019 @xref{Selecting Pretty-Printers}, for further information on how
10020 pretty-printers are selected,
10022 @xref{Writing a Pretty-Printer}, for implementing pretty printers
10025 @node Pretty-Printer Example
10026 @subsection Pretty-Printer Example
10028 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
10031 (@value{GDBP}) print s
10033 static npos = 4294967295,
10035 <std::allocator<char>> = @{
10036 <__gnu_cxx::new_allocator<char>> = @{
10037 <No data fields>@}, <No data fields>
10039 members of std::basic_string<char, std::char_traits<char>,
10040 std::allocator<char> >::_Alloc_hider:
10041 _M_p = 0x804a014 "abcd"
10046 With a pretty-printer for @code{std::string} only the contents are printed:
10049 (@value{GDBP}) print s
10053 @node Pretty-Printer Commands
10054 @subsection Pretty-Printer Commands
10055 @cindex pretty-printer commands
10058 @kindex info pretty-printer
10059 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10060 Print the list of installed pretty-printers.
10061 This includes disabled pretty-printers, which are marked as such.
10063 @var{object-regexp} is a regular expression matching the objects
10064 whose pretty-printers to list.
10065 Objects can be @code{global}, the program space's file
10066 (@pxref{Progspaces In Python}),
10067 and the object files within that program space (@pxref{Objfiles In Python}).
10068 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
10069 looks up a printer from these three objects.
10071 @var{name-regexp} is a regular expression matching the name of the printers
10074 @kindex disable pretty-printer
10075 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10076 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10077 A disabled pretty-printer is not forgotten, it may be enabled again later.
10079 @kindex enable pretty-printer
10080 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10081 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10086 Suppose we have three pretty-printers installed: one from library1.so
10087 named @code{foo} that prints objects of type @code{foo}, and
10088 another from library2.so named @code{bar} that prints two types of objects,
10089 @code{bar1} and @code{bar2}.
10092 (gdb) info pretty-printer
10099 (gdb) info pretty-printer library2
10104 (gdb) disable pretty-printer library1
10106 2 of 3 printers enabled
10107 (gdb) info pretty-printer
10114 (gdb) disable pretty-printer library2 bar:bar1
10116 1 of 3 printers enabled
10117 (gdb) info pretty-printer library2
10124 (gdb) disable pretty-printer library2 bar
10126 0 of 3 printers enabled
10127 (gdb) info pretty-printer library2
10136 Note that for @code{bar} the entire printer can be disabled,
10137 as can each individual subprinter.
10139 @node Value History
10140 @section Value History
10142 @cindex value history
10143 @cindex history of values printed by @value{GDBN}
10144 Values printed by the @code{print} command are saved in the @value{GDBN}
10145 @dfn{value history}. This allows you to refer to them in other expressions.
10146 Values are kept until the symbol table is re-read or discarded
10147 (for example with the @code{file} or @code{symbol-file} commands).
10148 When the symbol table changes, the value history is discarded,
10149 since the values may contain pointers back to the types defined in the
10154 @cindex history number
10155 The values printed are given @dfn{history numbers} by which you can
10156 refer to them. These are successive integers starting with one.
10157 @code{print} shows you the history number assigned to a value by
10158 printing @samp{$@var{num} = } before the value; here @var{num} is the
10161 To refer to any previous value, use @samp{$} followed by the value's
10162 history number. The way @code{print} labels its output is designed to
10163 remind you of this. Just @code{$} refers to the most recent value in
10164 the history, and @code{$$} refers to the value before that.
10165 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
10166 is the value just prior to @code{$$}, @code{$$1} is equivalent to
10167 @code{$$}, and @code{$$0} is equivalent to @code{$}.
10169 For example, suppose you have just printed a pointer to a structure and
10170 want to see the contents of the structure. It suffices to type
10176 If you have a chain of structures where the component @code{next} points
10177 to the next one, you can print the contents of the next one with this:
10184 You can print successive links in the chain by repeating this
10185 command---which you can do by just typing @key{RET}.
10187 Note that the history records values, not expressions. If the value of
10188 @code{x} is 4 and you type these commands:
10196 then the value recorded in the value history by the @code{print} command
10197 remains 4 even though the value of @code{x} has changed.
10200 @kindex show values
10202 Print the last ten values in the value history, with their item numbers.
10203 This is like @samp{p@ $$9} repeated ten times, except that @code{show
10204 values} does not change the history.
10206 @item show values @var{n}
10207 Print ten history values centered on history item number @var{n}.
10209 @item show values +
10210 Print ten history values just after the values last printed. If no more
10211 values are available, @code{show values +} produces no display.
10214 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
10215 same effect as @samp{show values +}.
10217 @node Convenience Vars
10218 @section Convenience Variables
10220 @cindex convenience variables
10221 @cindex user-defined variables
10222 @value{GDBN} provides @dfn{convenience variables} that you can use within
10223 @value{GDBN} to hold on to a value and refer to it later. These variables
10224 exist entirely within @value{GDBN}; they are not part of your program, and
10225 setting a convenience variable has no direct effect on further execution
10226 of your program. That is why you can use them freely.
10228 Convenience variables are prefixed with @samp{$}. Any name preceded by
10229 @samp{$} can be used for a convenience variable, unless it is one of
10230 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
10231 (Value history references, in contrast, are @emph{numbers} preceded
10232 by @samp{$}. @xref{Value History, ,Value History}.)
10234 You can save a value in a convenience variable with an assignment
10235 expression, just as you would set a variable in your program.
10239 set $foo = *object_ptr
10243 would save in @code{$foo} the value contained in the object pointed to by
10246 Using a convenience variable for the first time creates it, but its
10247 value is @code{void} until you assign a new value. You can alter the
10248 value with another assignment at any time.
10250 Convenience variables have no fixed types. You can assign a convenience
10251 variable any type of value, including structures and arrays, even if
10252 that variable already has a value of a different type. The convenience
10253 variable, when used as an expression, has the type of its current value.
10256 @kindex show convenience
10257 @cindex show all user variables and functions
10258 @item show convenience
10259 Print a list of convenience variables used so far, and their values,
10260 as well as a list of the convenience functions.
10261 Abbreviated @code{show conv}.
10263 @kindex init-if-undefined
10264 @cindex convenience variables, initializing
10265 @item init-if-undefined $@var{variable} = @var{expression}
10266 Set a convenience variable if it has not already been set. This is useful
10267 for user-defined commands that keep some state. It is similar, in concept,
10268 to using local static variables with initializers in C (except that
10269 convenience variables are global). It can also be used to allow users to
10270 override default values used in a command script.
10272 If the variable is already defined then the expression is not evaluated so
10273 any side-effects do not occur.
10276 One of the ways to use a convenience variable is as a counter to be
10277 incremented or a pointer to be advanced. For example, to print
10278 a field from successive elements of an array of structures:
10282 print bar[$i++]->contents
10286 Repeat that command by typing @key{RET}.
10288 Some convenience variables are created automatically by @value{GDBN} and given
10289 values likely to be useful.
10292 @vindex $_@r{, convenience variable}
10294 The variable @code{$_} is automatically set by the @code{x} command to
10295 the last address examined (@pxref{Memory, ,Examining Memory}). Other
10296 commands which provide a default address for @code{x} to examine also
10297 set @code{$_} to that address; these commands include @code{info line}
10298 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
10299 except when set by the @code{x} command, in which case it is a pointer
10300 to the type of @code{$__}.
10302 @vindex $__@r{, convenience variable}
10304 The variable @code{$__} is automatically set by the @code{x} command
10305 to the value found in the last address examined. Its type is chosen
10306 to match the format in which the data was printed.
10309 @vindex $_exitcode@r{, convenience variable}
10310 When the program being debugged terminates normally, @value{GDBN}
10311 automatically sets this variable to the exit code of the program, and
10312 resets @code{$_exitsignal} to @code{void}.
10315 @vindex $_exitsignal@r{, convenience variable}
10316 When the program being debugged dies due to an uncaught signal,
10317 @value{GDBN} automatically sets this variable to that signal's number,
10318 and resets @code{$_exitcode} to @code{void}.
10320 To distinguish between whether the program being debugged has exited
10321 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
10322 @code{$_exitsignal} is not @code{void}), the convenience function
10323 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
10324 Functions}). For example, considering the following source code:
10327 #include <signal.h>
10330 main (int argc, char *argv[])
10337 A valid way of telling whether the program being debugged has exited
10338 or signalled would be:
10341 (@value{GDBP}) define has_exited_or_signalled
10342 Type commands for definition of ``has_exited_or_signalled''.
10343 End with a line saying just ``end''.
10344 >if $_isvoid ($_exitsignal)
10345 >echo The program has exited\n
10347 >echo The program has signalled\n
10353 Program terminated with signal SIGALRM, Alarm clock.
10354 The program no longer exists.
10355 (@value{GDBP}) has_exited_or_signalled
10356 The program has signalled
10359 As can be seen, @value{GDBN} correctly informs that the program being
10360 debugged has signalled, since it calls @code{raise} and raises a
10361 @code{SIGALRM} signal. If the program being debugged had not called
10362 @code{raise}, then @value{GDBN} would report a normal exit:
10365 (@value{GDBP}) has_exited_or_signalled
10366 The program has exited
10370 The variable @code{$_exception} is set to the exception object being
10371 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
10374 @itemx $_probe_arg0@dots{}$_probe_arg11
10375 Arguments to a static probe. @xref{Static Probe Points}.
10378 @vindex $_sdata@r{, inspect, convenience variable}
10379 The variable @code{$_sdata} contains extra collected static tracepoint
10380 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
10381 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
10382 if extra static tracepoint data has not been collected.
10385 @vindex $_siginfo@r{, convenience variable}
10386 The variable @code{$_siginfo} contains extra signal information
10387 (@pxref{extra signal information}). Note that @code{$_siginfo}
10388 could be empty, if the application has not yet received any signals.
10389 For example, it will be empty before you execute the @code{run} command.
10392 @vindex $_tlb@r{, convenience variable}
10393 The variable @code{$_tlb} is automatically set when debugging
10394 applications running on MS-Windows in native mode or connected to
10395 gdbserver that supports the @code{qGetTIBAddr} request.
10396 @xref{General Query Packets}.
10397 This variable contains the address of the thread information block.
10401 On HP-UX systems, if you refer to a function or variable name that
10402 begins with a dollar sign, @value{GDBN} searches for a user or system
10403 name first, before it searches for a convenience variable.
10405 @node Convenience Funs
10406 @section Convenience Functions
10408 @cindex convenience functions
10409 @value{GDBN} also supplies some @dfn{convenience functions}. These
10410 have a syntax similar to convenience variables. A convenience
10411 function can be used in an expression just like an ordinary function;
10412 however, a convenience function is implemented internally to
10415 These functions do not require @value{GDBN} to be configured with
10416 @code{Python} support, which means that they are always available.
10420 @item $_isvoid (@var{expr})
10421 @findex $_isvoid@r{, convenience function}
10422 Return one if the expression @var{expr} is @code{void}. Otherwise it
10425 A @code{void} expression is an expression where the type of the result
10426 is @code{void}. For example, you can examine a convenience variable
10427 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
10431 (@value{GDBP}) print $_exitcode
10433 (@value{GDBP}) print $_isvoid ($_exitcode)
10436 Starting program: ./a.out
10437 [Inferior 1 (process 29572) exited normally]
10438 (@value{GDBP}) print $_exitcode
10440 (@value{GDBP}) print $_isvoid ($_exitcode)
10444 In the example above, we used @code{$_isvoid} to check whether
10445 @code{$_exitcode} is @code{void} before and after the execution of the
10446 program being debugged. Before the execution there is no exit code to
10447 be examined, therefore @code{$_exitcode} is @code{void}. After the
10448 execution the program being debugged returned zero, therefore
10449 @code{$_exitcode} is zero, which means that it is not @code{void}
10452 The @code{void} expression can also be a call of a function from the
10453 program being debugged. For example, given the following function:
10462 The result of calling it inside @value{GDBN} is @code{void}:
10465 (@value{GDBP}) print foo ()
10467 (@value{GDBP}) print $_isvoid (foo ())
10469 (@value{GDBP}) set $v = foo ()
10470 (@value{GDBP}) print $v
10472 (@value{GDBP}) print $_isvoid ($v)
10478 These functions require @value{GDBN} to be configured with
10479 @code{Python} support.
10483 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10484 @findex $_memeq@r{, convenience function}
10485 Returns one if the @var{length} bytes at the addresses given by
10486 @var{buf1} and @var{buf2} are equal.
10487 Otherwise it returns zero.
10489 @item $_regex(@var{str}, @var{regex})
10490 @findex $_regex@r{, convenience function}
10491 Returns one if the string @var{str} matches the regular expression
10492 @var{regex}. Otherwise it returns zero.
10493 The syntax of the regular expression is that specified by @code{Python}'s
10494 regular expression support.
10496 @item $_streq(@var{str1}, @var{str2})
10497 @findex $_streq@r{, convenience function}
10498 Returns one if the strings @var{str1} and @var{str2} are equal.
10499 Otherwise it returns zero.
10501 @item $_strlen(@var{str})
10502 @findex $_strlen@r{, convenience function}
10503 Returns the length of string @var{str}.
10505 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10506 @findex $_caller_is@r{, convenience function}
10507 Returns one if the calling function's name is equal to @var{name}.
10508 Otherwise it returns zero.
10510 If the optional argument @var{number_of_frames} is provided,
10511 it is the number of frames up in the stack to look.
10519 at testsuite/gdb.python/py-caller-is.c:21
10520 #1 0x00000000004005a0 in middle_func ()
10521 at testsuite/gdb.python/py-caller-is.c:27
10522 #2 0x00000000004005ab in top_func ()
10523 at testsuite/gdb.python/py-caller-is.c:33
10524 #3 0x00000000004005b6 in main ()
10525 at testsuite/gdb.python/py-caller-is.c:39
10526 (gdb) print $_caller_is ("middle_func")
10528 (gdb) print $_caller_is ("top_func", 2)
10532 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10533 @findex $_caller_matches@r{, convenience function}
10534 Returns one if the calling function's name matches the regular expression
10535 @var{regexp}. Otherwise it returns zero.
10537 If the optional argument @var{number_of_frames} is provided,
10538 it is the number of frames up in the stack to look.
10541 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10542 @findex $_any_caller_is@r{, convenience function}
10543 Returns one if any calling function's name is equal to @var{name}.
10544 Otherwise it returns zero.
10546 If the optional argument @var{number_of_frames} is provided,
10547 it is the number of frames up in the stack to look.
10550 This function differs from @code{$_caller_is} in that this function
10551 checks all stack frames from the immediate caller to the frame specified
10552 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
10553 frame specified by @var{number_of_frames}.
10555 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10556 @findex $_any_caller_matches@r{, convenience function}
10557 Returns one if any calling function's name matches the regular expression
10558 @var{regexp}. Otherwise it returns zero.
10560 If the optional argument @var{number_of_frames} is provided,
10561 it is the number of frames up in the stack to look.
10564 This function differs from @code{$_caller_matches} in that this function
10565 checks all stack frames from the immediate caller to the frame specified
10566 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
10567 frame specified by @var{number_of_frames}.
10571 @value{GDBN} provides the ability to list and get help on
10572 convenience functions.
10575 @item help function
10576 @kindex help function
10577 @cindex show all convenience functions
10578 Print a list of all convenience functions.
10585 You can refer to machine register contents, in expressions, as variables
10586 with names starting with @samp{$}. The names of registers are different
10587 for each machine; use @code{info registers} to see the names used on
10591 @kindex info registers
10592 @item info registers
10593 Print the names and values of all registers except floating-point
10594 and vector registers (in the selected stack frame).
10596 @kindex info all-registers
10597 @cindex floating point registers
10598 @item info all-registers
10599 Print the names and values of all registers, including floating-point
10600 and vector registers (in the selected stack frame).
10602 @item info registers @var{regname} @dots{}
10603 Print the @dfn{relativized} value of each specified register @var{regname}.
10604 As discussed in detail below, register values are normally relative to
10605 the selected stack frame. The @var{regname} may be any register name valid on
10606 the machine you are using, with or without the initial @samp{$}.
10609 @anchor{standard registers}
10610 @cindex stack pointer register
10611 @cindex program counter register
10612 @cindex process status register
10613 @cindex frame pointer register
10614 @cindex standard registers
10615 @value{GDBN} has four ``standard'' register names that are available (in
10616 expressions) on most machines---whenever they do not conflict with an
10617 architecture's canonical mnemonics for registers. The register names
10618 @code{$pc} and @code{$sp} are used for the program counter register and
10619 the stack pointer. @code{$fp} is used for a register that contains a
10620 pointer to the current stack frame, and @code{$ps} is used for a
10621 register that contains the processor status. For example,
10622 you could print the program counter in hex with
10629 or print the instruction to be executed next with
10636 or add four to the stack pointer@footnote{This is a way of removing
10637 one word from the stack, on machines where stacks grow downward in
10638 memory (most machines, nowadays). This assumes that the innermost
10639 stack frame is selected; setting @code{$sp} is not allowed when other
10640 stack frames are selected. To pop entire frames off the stack,
10641 regardless of machine architecture, use @code{return};
10642 see @ref{Returning, ,Returning from a Function}.} with
10648 Whenever possible, these four standard register names are available on
10649 your machine even though the machine has different canonical mnemonics,
10650 so long as there is no conflict. The @code{info registers} command
10651 shows the canonical names. For example, on the SPARC, @code{info
10652 registers} displays the processor status register as @code{$psr} but you
10653 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
10654 is an alias for the @sc{eflags} register.
10656 @value{GDBN} always considers the contents of an ordinary register as an
10657 integer when the register is examined in this way. Some machines have
10658 special registers which can hold nothing but floating point; these
10659 registers are considered to have floating point values. There is no way
10660 to refer to the contents of an ordinary register as floating point value
10661 (although you can @emph{print} it as a floating point value with
10662 @samp{print/f $@var{regname}}).
10664 Some registers have distinct ``raw'' and ``virtual'' data formats. This
10665 means that the data format in which the register contents are saved by
10666 the operating system is not the same one that your program normally
10667 sees. For example, the registers of the 68881 floating point
10668 coprocessor are always saved in ``extended'' (raw) format, but all C
10669 programs expect to work with ``double'' (virtual) format. In such
10670 cases, @value{GDBN} normally works with the virtual format only (the format
10671 that makes sense for your program), but the @code{info registers} command
10672 prints the data in both formats.
10674 @cindex SSE registers (x86)
10675 @cindex MMX registers (x86)
10676 Some machines have special registers whose contents can be interpreted
10677 in several different ways. For example, modern x86-based machines
10678 have SSE and MMX registers that can hold several values packed
10679 together in several different formats. @value{GDBN} refers to such
10680 registers in @code{struct} notation:
10683 (@value{GDBP}) print $xmm1
10685 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
10686 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
10687 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
10688 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
10689 v4_int32 = @{0, 20657912, 11, 13@},
10690 v2_int64 = @{88725056443645952, 55834574859@},
10691 uint128 = 0x0000000d0000000b013b36f800000000
10696 To set values of such registers, you need to tell @value{GDBN} which
10697 view of the register you wish to change, as if you were assigning
10698 value to a @code{struct} member:
10701 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
10704 Normally, register values are relative to the selected stack frame
10705 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
10706 value that the register would contain if all stack frames farther in
10707 were exited and their saved registers restored. In order to see the
10708 true contents of hardware registers, you must select the innermost
10709 frame (with @samp{frame 0}).
10711 @cindex caller-saved registers
10712 @cindex call-clobbered registers
10713 @cindex volatile registers
10714 @cindex <not saved> values
10715 Usually ABIs reserve some registers as not needed to be saved by the
10716 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
10717 registers). It may therefore not be possible for @value{GDBN} to know
10718 the value a register had before the call (in other words, in the outer
10719 frame), if the register value has since been changed by the callee.
10720 @value{GDBN} tries to deduce where the inner frame saved
10721 (``callee-saved'') registers, from the debug info, unwind info, or the
10722 machine code generated by your compiler. If some register is not
10723 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
10724 its own knowledge of the ABI, or because the debug/unwind info
10725 explicitly says the register's value is undefined), @value{GDBN}
10726 displays @w{@samp{<not saved>}} as the register's value. With targets
10727 that @value{GDBN} has no knowledge of the register saving convention,
10728 if a register was not saved by the callee, then its value and location
10729 in the outer frame are assumed to be the same of the inner frame.
10730 This is usually harmless, because if the register is call-clobbered,
10731 the caller either does not care what is in the register after the
10732 call, or has code to restore the value that it does care about. Note,
10733 however, that if you change such a register in the outer frame, you
10734 may also be affecting the inner frame. Also, the more ``outer'' the
10735 frame is you're looking at, the more likely a call-clobbered
10736 register's value is to be wrong, in the sense that it doesn't actually
10737 represent the value the register had just before the call.
10739 @node Floating Point Hardware
10740 @section Floating Point Hardware
10741 @cindex floating point
10743 Depending on the configuration, @value{GDBN} may be able to give
10744 you more information about the status of the floating point hardware.
10749 Display hardware-dependent information about the floating
10750 point unit. The exact contents and layout vary depending on the
10751 floating point chip. Currently, @samp{info float} is supported on
10752 the ARM and x86 machines.
10756 @section Vector Unit
10757 @cindex vector unit
10759 Depending on the configuration, @value{GDBN} may be able to give you
10760 more information about the status of the vector unit.
10763 @kindex info vector
10765 Display information about the vector unit. The exact contents and
10766 layout vary depending on the hardware.
10769 @node OS Information
10770 @section Operating System Auxiliary Information
10771 @cindex OS information
10773 @value{GDBN} provides interfaces to useful OS facilities that can help
10774 you debug your program.
10776 @cindex auxiliary vector
10777 @cindex vector, auxiliary
10778 Some operating systems supply an @dfn{auxiliary vector} to programs at
10779 startup. This is akin to the arguments and environment that you
10780 specify for a program, but contains a system-dependent variety of
10781 binary values that tell system libraries important details about the
10782 hardware, operating system, and process. Each value's purpose is
10783 identified by an integer tag; the meanings are well-known but system-specific.
10784 Depending on the configuration and operating system facilities,
10785 @value{GDBN} may be able to show you this information. For remote
10786 targets, this functionality may further depend on the remote stub's
10787 support of the @samp{qXfer:auxv:read} packet, see
10788 @ref{qXfer auxiliary vector read}.
10793 Display the auxiliary vector of the inferior, which can be either a
10794 live process or a core dump file. @value{GDBN} prints each tag value
10795 numerically, and also shows names and text descriptions for recognized
10796 tags. Some values in the vector are numbers, some bit masks, and some
10797 pointers to strings or other data. @value{GDBN} displays each value in the
10798 most appropriate form for a recognized tag, and in hexadecimal for
10799 an unrecognized tag.
10802 On some targets, @value{GDBN} can access operating system-specific
10803 information and show it to you. The types of information available
10804 will differ depending on the type of operating system running on the
10805 target. The mechanism used to fetch the data is described in
10806 @ref{Operating System Information}. For remote targets, this
10807 functionality depends on the remote stub's support of the
10808 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
10812 @item info os @var{infotype}
10814 Display OS information of the requested type.
10816 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
10818 @anchor{linux info os infotypes}
10820 @kindex info os cpus
10822 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
10823 the available fields from /proc/cpuinfo. For each supported architecture
10824 different fields are available. Two common entries are processor which gives
10825 CPU number and bogomips; a system constant that is calculated during
10826 kernel initialization.
10828 @kindex info os files
10830 Display the list of open file descriptors on the target. For each
10831 file descriptor, @value{GDBN} prints the identifier of the process
10832 owning the descriptor, the command of the owning process, the value
10833 of the descriptor, and the target of the descriptor.
10835 @kindex info os modules
10837 Display the list of all loaded kernel modules on the target. For each
10838 module, @value{GDBN} prints the module name, the size of the module in
10839 bytes, the number of times the module is used, the dependencies of the
10840 module, the status of the module, and the address of the loaded module
10843 @kindex info os msg
10845 Display the list of all System V message queues on the target. For each
10846 message queue, @value{GDBN} prints the message queue key, the message
10847 queue identifier, the access permissions, the current number of bytes
10848 on the queue, the current number of messages on the queue, the processes
10849 that last sent and received a message on the queue, the user and group
10850 of the owner and creator of the message queue, the times at which a
10851 message was last sent and received on the queue, and the time at which
10852 the message queue was last changed.
10854 @kindex info os processes
10856 Display the list of processes on the target. For each process,
10857 @value{GDBN} prints the process identifier, the name of the user, the
10858 command corresponding to the process, and the list of processor cores
10859 that the process is currently running on. (To understand what these
10860 properties mean, for this and the following info types, please consult
10861 the general @sc{gnu}/Linux documentation.)
10863 @kindex info os procgroups
10865 Display the list of process groups on the target. For each process,
10866 @value{GDBN} prints the identifier of the process group that it belongs
10867 to, the command corresponding to the process group leader, the process
10868 identifier, and the command line of the process. The list is sorted
10869 first by the process group identifier, then by the process identifier,
10870 so that processes belonging to the same process group are grouped together
10871 and the process group leader is listed first.
10873 @kindex info os semaphores
10875 Display the list of all System V semaphore sets on the target. For each
10876 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
10877 set identifier, the access permissions, the number of semaphores in the
10878 set, the user and group of the owner and creator of the semaphore set,
10879 and the times at which the semaphore set was operated upon and changed.
10881 @kindex info os shm
10883 Display the list of all System V shared-memory regions on the target.
10884 For each shared-memory region, @value{GDBN} prints the region key,
10885 the shared-memory identifier, the access permissions, the size of the
10886 region, the process that created the region, the process that last
10887 attached to or detached from the region, the current number of live
10888 attaches to the region, and the times at which the region was last
10889 attached to, detach from, and changed.
10891 @kindex info os sockets
10893 Display the list of Internet-domain sockets on the target. For each
10894 socket, @value{GDBN} prints the address and port of the local and
10895 remote endpoints, the current state of the connection, the creator of
10896 the socket, the IP address family of the socket, and the type of the
10899 @kindex info os threads
10901 Display the list of threads running on the target. For each thread,
10902 @value{GDBN} prints the identifier of the process that the thread
10903 belongs to, the command of the process, the thread identifier, and the
10904 processor core that it is currently running on. The main thread of a
10905 process is not listed.
10909 If @var{infotype} is omitted, then list the possible values for
10910 @var{infotype} and the kind of OS information available for each
10911 @var{infotype}. If the target does not return a list of possible
10912 types, this command will report an error.
10915 @node Memory Region Attributes
10916 @section Memory Region Attributes
10917 @cindex memory region attributes
10919 @dfn{Memory region attributes} allow you to describe special handling
10920 required by regions of your target's memory. @value{GDBN} uses
10921 attributes to determine whether to allow certain types of memory
10922 accesses; whether to use specific width accesses; and whether to cache
10923 target memory. By default the description of memory regions is
10924 fetched from the target (if the current target supports this), but the
10925 user can override the fetched regions.
10927 Defined memory regions can be individually enabled and disabled. When a
10928 memory region is disabled, @value{GDBN} uses the default attributes when
10929 accessing memory in that region. Similarly, if no memory regions have
10930 been defined, @value{GDBN} uses the default attributes when accessing
10933 When a memory region is defined, it is given a number to identify it;
10934 to enable, disable, or remove a memory region, you specify that number.
10938 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
10939 Define a memory region bounded by @var{lower} and @var{upper} with
10940 attributes @var{attributes}@dots{}, and add it to the list of regions
10941 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
10942 case: it is treated as the target's maximum memory address.
10943 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
10946 Discard any user changes to the memory regions and use target-supplied
10947 regions, if available, or no regions if the target does not support.
10950 @item delete mem @var{nums}@dots{}
10951 Remove memory regions @var{nums}@dots{} from the list of regions
10952 monitored by @value{GDBN}.
10954 @kindex disable mem
10955 @item disable mem @var{nums}@dots{}
10956 Disable monitoring of memory regions @var{nums}@dots{}.
10957 A disabled memory region is not forgotten.
10958 It may be enabled again later.
10961 @item enable mem @var{nums}@dots{}
10962 Enable monitoring of memory regions @var{nums}@dots{}.
10966 Print a table of all defined memory regions, with the following columns
10970 @item Memory Region Number
10971 @item Enabled or Disabled.
10972 Enabled memory regions are marked with @samp{y}.
10973 Disabled memory regions are marked with @samp{n}.
10976 The address defining the inclusive lower bound of the memory region.
10979 The address defining the exclusive upper bound of the memory region.
10982 The list of attributes set for this memory region.
10987 @subsection Attributes
10989 @subsubsection Memory Access Mode
10990 The access mode attributes set whether @value{GDBN} may make read or
10991 write accesses to a memory region.
10993 While these attributes prevent @value{GDBN} from performing invalid
10994 memory accesses, they do nothing to prevent the target system, I/O DMA,
10995 etc.@: from accessing memory.
10999 Memory is read only.
11001 Memory is write only.
11003 Memory is read/write. This is the default.
11006 @subsubsection Memory Access Size
11007 The access size attribute tells @value{GDBN} to use specific sized
11008 accesses in the memory region. Often memory mapped device registers
11009 require specific sized accesses. If no access size attribute is
11010 specified, @value{GDBN} may use accesses of any size.
11014 Use 8 bit memory accesses.
11016 Use 16 bit memory accesses.
11018 Use 32 bit memory accesses.
11020 Use 64 bit memory accesses.
11023 @c @subsubsection Hardware/Software Breakpoints
11024 @c The hardware/software breakpoint attributes set whether @value{GDBN}
11025 @c will use hardware or software breakpoints for the internal breakpoints
11026 @c used by the step, next, finish, until, etc. commands.
11030 @c Always use hardware breakpoints
11031 @c @item swbreak (default)
11034 @subsubsection Data Cache
11035 The data cache attributes set whether @value{GDBN} will cache target
11036 memory. While this generally improves performance by reducing debug
11037 protocol overhead, it can lead to incorrect results because @value{GDBN}
11038 does not know about volatile variables or memory mapped device
11043 Enable @value{GDBN} to cache target memory.
11045 Disable @value{GDBN} from caching target memory. This is the default.
11048 @subsection Memory Access Checking
11049 @value{GDBN} can be instructed to refuse accesses to memory that is
11050 not explicitly described. This can be useful if accessing such
11051 regions has undesired effects for a specific target, or to provide
11052 better error checking. The following commands control this behaviour.
11055 @kindex set mem inaccessible-by-default
11056 @item set mem inaccessible-by-default [on|off]
11057 If @code{on} is specified, make @value{GDBN} treat memory not
11058 explicitly described by the memory ranges as non-existent and refuse accesses
11059 to such memory. The checks are only performed if there's at least one
11060 memory range defined. If @code{off} is specified, make @value{GDBN}
11061 treat the memory not explicitly described by the memory ranges as RAM.
11062 The default value is @code{on}.
11063 @kindex show mem inaccessible-by-default
11064 @item show mem inaccessible-by-default
11065 Show the current handling of accesses to unknown memory.
11069 @c @subsubsection Memory Write Verification
11070 @c The memory write verification attributes set whether @value{GDBN}
11071 @c will re-reads data after each write to verify the write was successful.
11075 @c @item noverify (default)
11078 @node Dump/Restore Files
11079 @section Copy Between Memory and a File
11080 @cindex dump/restore files
11081 @cindex append data to a file
11082 @cindex dump data to a file
11083 @cindex restore data from a file
11085 You can use the commands @code{dump}, @code{append}, and
11086 @code{restore} to copy data between target memory and a file. The
11087 @code{dump} and @code{append} commands write data to a file, and the
11088 @code{restore} command reads data from a file back into the inferior's
11089 memory. Files may be in binary, Motorola S-record, Intel hex,
11090 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
11091 append to binary files, and cannot read from Verilog Hex files.
11096 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11097 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
11098 Dump the contents of memory from @var{start_addr} to @var{end_addr},
11099 or the value of @var{expr}, to @var{filename} in the given format.
11101 The @var{format} parameter may be any one of:
11108 Motorola S-record format.
11110 Tektronix Hex format.
11112 Verilog Hex format.
11115 @value{GDBN} uses the same definitions of these formats as the
11116 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
11117 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
11121 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11122 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
11123 Append the contents of memory from @var{start_addr} to @var{end_addr},
11124 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
11125 (@value{GDBN} can only append data to files in raw binary form.)
11128 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
11129 Restore the contents of file @var{filename} into memory. The
11130 @code{restore} command can automatically recognize any known @sc{bfd}
11131 file format, except for raw binary. To restore a raw binary file you
11132 must specify the optional keyword @code{binary} after the filename.
11134 If @var{bias} is non-zero, its value will be added to the addresses
11135 contained in the file. Binary files always start at address zero, so
11136 they will be restored at address @var{bias}. Other bfd files have
11137 a built-in location; they will be restored at offset @var{bias}
11138 from that location.
11140 If @var{start} and/or @var{end} are non-zero, then only data between
11141 file offset @var{start} and file offset @var{end} will be restored.
11142 These offsets are relative to the addresses in the file, before
11143 the @var{bias} argument is applied.
11147 @node Core File Generation
11148 @section How to Produce a Core File from Your Program
11149 @cindex dump core from inferior
11151 A @dfn{core file} or @dfn{core dump} is a file that records the memory
11152 image of a running process and its process status (register values
11153 etc.). Its primary use is post-mortem debugging of a program that
11154 crashed while it ran outside a debugger. A program that crashes
11155 automatically produces a core file, unless this feature is disabled by
11156 the user. @xref{Files}, for information on invoking @value{GDBN} in
11157 the post-mortem debugging mode.
11159 Occasionally, you may wish to produce a core file of the program you
11160 are debugging in order to preserve a snapshot of its state.
11161 @value{GDBN} has a special command for that.
11165 @kindex generate-core-file
11166 @item generate-core-file [@var{file}]
11167 @itemx gcore [@var{file}]
11168 Produce a core dump of the inferior process. The optional argument
11169 @var{file} specifies the file name where to put the core dump. If not
11170 specified, the file name defaults to @file{core.@var{pid}}, where
11171 @var{pid} is the inferior process ID.
11173 Note that this command is implemented only for some systems (as of
11174 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
11176 On @sc{gnu}/Linux, this command can take into account the value of the
11177 file @file{/proc/@var{pid}/coredump_filter} when generating the core
11178 dump (@pxref{set use-coredump-filter}).
11180 @kindex set use-coredump-filter
11181 @anchor{set use-coredump-filter}
11182 @item set use-coredump-filter on
11183 @itemx set use-coredump-filter off
11184 Enable or disable the use of the file
11185 @file{/proc/@var{pid}/coredump_filter} when generating core dump
11186 files. This file is used by the Linux kernel to decide what types of
11187 memory mappings will be dumped or ignored when generating a core dump
11188 file. @var{pid} is the process ID of a currently running process.
11190 To make use of this feature, you have to write in the
11191 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
11192 which is a bit mask representing the memory mapping types. If a bit
11193 is set in the bit mask, then the memory mappings of the corresponding
11194 types will be dumped; otherwise, they will be ignored. This
11195 configuration is inherited by child processes. For more information
11196 about the bits that can be set in the
11197 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
11198 manpage of @code{core(5)}.
11200 By default, this option is @code{on}. If this option is turned
11201 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
11202 and instead uses the same default value as the Linux kernel in order
11203 to decide which pages will be dumped in the core dump file. This
11204 value is currently @code{0x33}, which means that bits @code{0}
11205 (anonymous private mappings), @code{1} (anonymous shared mappings),
11206 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
11207 This will cause these memory mappings to be dumped automatically.
11210 @node Character Sets
11211 @section Character Sets
11212 @cindex character sets
11214 @cindex translating between character sets
11215 @cindex host character set
11216 @cindex target character set
11218 If the program you are debugging uses a different character set to
11219 represent characters and strings than the one @value{GDBN} uses itself,
11220 @value{GDBN} can automatically translate between the character sets for
11221 you. The character set @value{GDBN} uses we call the @dfn{host
11222 character set}; the one the inferior program uses we call the
11223 @dfn{target character set}.
11225 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
11226 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
11227 remote protocol (@pxref{Remote Debugging}) to debug a program
11228 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
11229 then the host character set is Latin-1, and the target character set is
11230 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
11231 target-charset EBCDIC-US}, then @value{GDBN} translates between
11232 @sc{ebcdic} and Latin 1 as you print character or string values, or use
11233 character and string literals in expressions.
11235 @value{GDBN} has no way to automatically recognize which character set
11236 the inferior program uses; you must tell it, using the @code{set
11237 target-charset} command, described below.
11239 Here are the commands for controlling @value{GDBN}'s character set
11243 @item set target-charset @var{charset}
11244 @kindex set target-charset
11245 Set the current target character set to @var{charset}. To display the
11246 list of supported target character sets, type
11247 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
11249 @item set host-charset @var{charset}
11250 @kindex set host-charset
11251 Set the current host character set to @var{charset}.
11253 By default, @value{GDBN} uses a host character set appropriate to the
11254 system it is running on; you can override that default using the
11255 @code{set host-charset} command. On some systems, @value{GDBN} cannot
11256 automatically determine the appropriate host character set. In this
11257 case, @value{GDBN} uses @samp{UTF-8}.
11259 @value{GDBN} can only use certain character sets as its host character
11260 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
11261 @value{GDBN} will list the host character sets it supports.
11263 @item set charset @var{charset}
11264 @kindex set charset
11265 Set the current host and target character sets to @var{charset}. As
11266 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
11267 @value{GDBN} will list the names of the character sets that can be used
11268 for both host and target.
11271 @kindex show charset
11272 Show the names of the current host and target character sets.
11274 @item show host-charset
11275 @kindex show host-charset
11276 Show the name of the current host character set.
11278 @item show target-charset
11279 @kindex show target-charset
11280 Show the name of the current target character set.
11282 @item set target-wide-charset @var{charset}
11283 @kindex set target-wide-charset
11284 Set the current target's wide character set to @var{charset}. This is
11285 the character set used by the target's @code{wchar_t} type. To
11286 display the list of supported wide character sets, type
11287 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
11289 @item show target-wide-charset
11290 @kindex show target-wide-charset
11291 Show the name of the current target's wide character set.
11294 Here is an example of @value{GDBN}'s character set support in action.
11295 Assume that the following source code has been placed in the file
11296 @file{charset-test.c}:
11302 = @{72, 101, 108, 108, 111, 44, 32, 119,
11303 111, 114, 108, 100, 33, 10, 0@};
11304 char ibm1047_hello[]
11305 = @{200, 133, 147, 147, 150, 107, 64, 166,
11306 150, 153, 147, 132, 90, 37, 0@};
11310 printf ("Hello, world!\n");
11314 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
11315 containing the string @samp{Hello, world!} followed by a newline,
11316 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
11318 We compile the program, and invoke the debugger on it:
11321 $ gcc -g charset-test.c -o charset-test
11322 $ gdb -nw charset-test
11323 GNU gdb 2001-12-19-cvs
11324 Copyright 2001 Free Software Foundation, Inc.
11329 We can use the @code{show charset} command to see what character sets
11330 @value{GDBN} is currently using to interpret and display characters and
11334 (@value{GDBP}) show charset
11335 The current host and target character set is `ISO-8859-1'.
11339 For the sake of printing this manual, let's use @sc{ascii} as our
11340 initial character set:
11342 (@value{GDBP}) set charset ASCII
11343 (@value{GDBP}) show charset
11344 The current host and target character set is `ASCII'.
11348 Let's assume that @sc{ascii} is indeed the correct character set for our
11349 host system --- in other words, let's assume that if @value{GDBN} prints
11350 characters using the @sc{ascii} character set, our terminal will display
11351 them properly. Since our current target character set is also
11352 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
11355 (@value{GDBP}) print ascii_hello
11356 $1 = 0x401698 "Hello, world!\n"
11357 (@value{GDBP}) print ascii_hello[0]
11362 @value{GDBN} uses the target character set for character and string
11363 literals you use in expressions:
11366 (@value{GDBP}) print '+'
11371 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
11374 @value{GDBN} relies on the user to tell it which character set the
11375 target program uses. If we print @code{ibm1047_hello} while our target
11376 character set is still @sc{ascii}, we get jibberish:
11379 (@value{GDBP}) print ibm1047_hello
11380 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
11381 (@value{GDBP}) print ibm1047_hello[0]
11386 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
11387 @value{GDBN} tells us the character sets it supports:
11390 (@value{GDBP}) set target-charset
11391 ASCII EBCDIC-US IBM1047 ISO-8859-1
11392 (@value{GDBP}) set target-charset
11395 We can select @sc{ibm1047} as our target character set, and examine the
11396 program's strings again. Now the @sc{ascii} string is wrong, but
11397 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
11398 target character set, @sc{ibm1047}, to the host character set,
11399 @sc{ascii}, and they display correctly:
11402 (@value{GDBP}) set target-charset IBM1047
11403 (@value{GDBP}) show charset
11404 The current host character set is `ASCII'.
11405 The current target character set is `IBM1047'.
11406 (@value{GDBP}) print ascii_hello
11407 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
11408 (@value{GDBP}) print ascii_hello[0]
11410 (@value{GDBP}) print ibm1047_hello
11411 $8 = 0x4016a8 "Hello, world!\n"
11412 (@value{GDBP}) print ibm1047_hello[0]
11417 As above, @value{GDBN} uses the target character set for character and
11418 string literals you use in expressions:
11421 (@value{GDBP}) print '+'
11426 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
11429 @node Caching Target Data
11430 @section Caching Data of Targets
11431 @cindex caching data of targets
11433 @value{GDBN} caches data exchanged between the debugger and a target.
11434 Each cache is associated with the address space of the inferior.
11435 @xref{Inferiors and Programs}, about inferior and address space.
11436 Such caching generally improves performance in remote debugging
11437 (@pxref{Remote Debugging}), because it reduces the overhead of the
11438 remote protocol by bundling memory reads and writes into large chunks.
11439 Unfortunately, simply caching everything would lead to incorrect results,
11440 since @value{GDBN} does not necessarily know anything about volatile
11441 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
11442 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
11444 Therefore, by default, @value{GDBN} only caches data
11445 known to be on the stack@footnote{In non-stop mode, it is moderately
11446 rare for a running thread to modify the stack of a stopped thread
11447 in a way that would interfere with a backtrace, and caching of
11448 stack reads provides a significant speed up of remote backtraces.} or
11449 in the code segment.
11450 Other regions of memory can be explicitly marked as
11451 cacheable; @pxref{Memory Region Attributes}.
11454 @kindex set remotecache
11455 @item set remotecache on
11456 @itemx set remotecache off
11457 This option no longer does anything; it exists for compatibility
11460 @kindex show remotecache
11461 @item show remotecache
11462 Show the current state of the obsolete remotecache flag.
11464 @kindex set stack-cache
11465 @item set stack-cache on
11466 @itemx set stack-cache off
11467 Enable or disable caching of stack accesses. When @code{on}, use
11468 caching. By default, this option is @code{on}.
11470 @kindex show stack-cache
11471 @item show stack-cache
11472 Show the current state of data caching for memory accesses.
11474 @kindex set code-cache
11475 @item set code-cache on
11476 @itemx set code-cache off
11477 Enable or disable caching of code segment accesses. When @code{on},
11478 use caching. By default, this option is @code{on}. This improves
11479 performance of disassembly in remote debugging.
11481 @kindex show code-cache
11482 @item show code-cache
11483 Show the current state of target memory cache for code segment
11486 @kindex info dcache
11487 @item info dcache @r{[}line@r{]}
11488 Print the information about the performance of data cache of the
11489 current inferior's address space. The information displayed
11490 includes the dcache width and depth, and for each cache line, its
11491 number, address, and how many times it was referenced. This
11492 command is useful for debugging the data cache operation.
11494 If a line number is specified, the contents of that line will be
11497 @item set dcache size @var{size}
11498 @cindex dcache size
11499 @kindex set dcache size
11500 Set maximum number of entries in dcache (dcache depth above).
11502 @item set dcache line-size @var{line-size}
11503 @cindex dcache line-size
11504 @kindex set dcache line-size
11505 Set number of bytes each dcache entry caches (dcache width above).
11506 Must be a power of 2.
11508 @item show dcache size
11509 @kindex show dcache size
11510 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
11512 @item show dcache line-size
11513 @kindex show dcache line-size
11514 Show default size of dcache lines.
11518 @node Searching Memory
11519 @section Search Memory
11520 @cindex searching memory
11522 Memory can be searched for a particular sequence of bytes with the
11523 @code{find} command.
11527 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11528 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11529 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
11530 etc. The search begins at address @var{start_addr} and continues for either
11531 @var{len} bytes or through to @var{end_addr} inclusive.
11534 @var{s} and @var{n} are optional parameters.
11535 They may be specified in either order, apart or together.
11538 @item @var{s}, search query size
11539 The size of each search query value.
11545 halfwords (two bytes)
11549 giant words (eight bytes)
11552 All values are interpreted in the current language.
11553 This means, for example, that if the current source language is C/C@t{++}
11554 then searching for the string ``hello'' includes the trailing '\0'.
11556 If the value size is not specified, it is taken from the
11557 value's type in the current language.
11558 This is useful when one wants to specify the search
11559 pattern as a mixture of types.
11560 Note that this means, for example, that in the case of C-like languages
11561 a search for an untyped 0x42 will search for @samp{(int) 0x42}
11562 which is typically four bytes.
11564 @item @var{n}, maximum number of finds
11565 The maximum number of matches to print. The default is to print all finds.
11568 You can use strings as search values. Quote them with double-quotes
11570 The string value is copied into the search pattern byte by byte,
11571 regardless of the endianness of the target and the size specification.
11573 The address of each match found is printed as well as a count of the
11574 number of matches found.
11576 The address of the last value found is stored in convenience variable
11578 A count of the number of matches is stored in @samp{$numfound}.
11580 For example, if stopped at the @code{printf} in this function:
11586 static char hello[] = "hello-hello";
11587 static struct @{ char c; short s; int i; @}
11588 __attribute__ ((packed)) mixed
11589 = @{ 'c', 0x1234, 0x87654321 @};
11590 printf ("%s\n", hello);
11595 you get during debugging:
11598 (gdb) find &hello[0], +sizeof(hello), "hello"
11599 0x804956d <hello.1620+6>
11601 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
11602 0x8049567 <hello.1620>
11603 0x804956d <hello.1620+6>
11605 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
11606 0x8049567 <hello.1620>
11608 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
11609 0x8049560 <mixed.1625>
11611 (gdb) print $numfound
11614 $2 = (void *) 0x8049560
11617 @node Optimized Code
11618 @chapter Debugging Optimized Code
11619 @cindex optimized code, debugging
11620 @cindex debugging optimized code
11622 Almost all compilers support optimization. With optimization
11623 disabled, the compiler generates assembly code that corresponds
11624 directly to your source code, in a simplistic way. As the compiler
11625 applies more powerful optimizations, the generated assembly code
11626 diverges from your original source code. With help from debugging
11627 information generated by the compiler, @value{GDBN} can map from
11628 the running program back to constructs from your original source.
11630 @value{GDBN} is more accurate with optimization disabled. If you
11631 can recompile without optimization, it is easier to follow the
11632 progress of your program during debugging. But, there are many cases
11633 where you may need to debug an optimized version.
11635 When you debug a program compiled with @samp{-g -O}, remember that the
11636 optimizer has rearranged your code; the debugger shows you what is
11637 really there. Do not be too surprised when the execution path does not
11638 exactly match your source file! An extreme example: if you define a
11639 variable, but never use it, @value{GDBN} never sees that
11640 variable---because the compiler optimizes it out of existence.
11642 Some things do not work as well with @samp{-g -O} as with just
11643 @samp{-g}, particularly on machines with instruction scheduling. If in
11644 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
11645 please report it to us as a bug (including a test case!).
11646 @xref{Variables}, for more information about debugging optimized code.
11649 * Inline Functions:: How @value{GDBN} presents inlining
11650 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
11653 @node Inline Functions
11654 @section Inline Functions
11655 @cindex inline functions, debugging
11657 @dfn{Inlining} is an optimization that inserts a copy of the function
11658 body directly at each call site, instead of jumping to a shared
11659 routine. @value{GDBN} displays inlined functions just like
11660 non-inlined functions. They appear in backtraces. You can view their
11661 arguments and local variables, step into them with @code{step}, skip
11662 them with @code{next}, and escape from them with @code{finish}.
11663 You can check whether a function was inlined by using the
11664 @code{info frame} command.
11666 For @value{GDBN} to support inlined functions, the compiler must
11667 record information about inlining in the debug information ---
11668 @value{NGCC} using the @sc{dwarf 2} format does this, and several
11669 other compilers do also. @value{GDBN} only supports inlined functions
11670 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
11671 do not emit two required attributes (@samp{DW_AT_call_file} and
11672 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
11673 function calls with earlier versions of @value{NGCC}. It instead
11674 displays the arguments and local variables of inlined functions as
11675 local variables in the caller.
11677 The body of an inlined function is directly included at its call site;
11678 unlike a non-inlined function, there are no instructions devoted to
11679 the call. @value{GDBN} still pretends that the call site and the
11680 start of the inlined function are different instructions. Stepping to
11681 the call site shows the call site, and then stepping again shows
11682 the first line of the inlined function, even though no additional
11683 instructions are executed.
11685 This makes source-level debugging much clearer; you can see both the
11686 context of the call and then the effect of the call. Only stepping by
11687 a single instruction using @code{stepi} or @code{nexti} does not do
11688 this; single instruction steps always show the inlined body.
11690 There are some ways that @value{GDBN} does not pretend that inlined
11691 function calls are the same as normal calls:
11695 Setting breakpoints at the call site of an inlined function may not
11696 work, because the call site does not contain any code. @value{GDBN}
11697 may incorrectly move the breakpoint to the next line of the enclosing
11698 function, after the call. This limitation will be removed in a future
11699 version of @value{GDBN}; until then, set a breakpoint on an earlier line
11700 or inside the inlined function instead.
11703 @value{GDBN} cannot locate the return value of inlined calls after
11704 using the @code{finish} command. This is a limitation of compiler-generated
11705 debugging information; after @code{finish}, you can step to the next line
11706 and print a variable where your program stored the return value.
11710 @node Tail Call Frames
11711 @section Tail Call Frames
11712 @cindex tail call frames, debugging
11714 Function @code{B} can call function @code{C} in its very last statement. In
11715 unoptimized compilation the call of @code{C} is immediately followed by return
11716 instruction at the end of @code{B} code. Optimizing compiler may replace the
11717 call and return in function @code{B} into one jump to function @code{C}
11718 instead. Such use of a jump instruction is called @dfn{tail call}.
11720 During execution of function @code{C}, there will be no indication in the
11721 function call stack frames that it was tail-called from @code{B}. If function
11722 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
11723 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
11724 some cases @value{GDBN} can determine that @code{C} was tail-called from
11725 @code{B}, and it will then create fictitious call frame for that, with the
11726 return address set up as if @code{B} called @code{C} normally.
11728 This functionality is currently supported only by DWARF 2 debugging format and
11729 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
11730 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11733 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
11734 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
11738 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
11740 Stack level 1, frame at 0x7fffffffda30:
11741 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
11742 tail call frame, caller of frame at 0x7fffffffda30
11743 source language c++.
11744 Arglist at unknown address.
11745 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
11748 The detection of all the possible code path executions can find them ambiguous.
11749 There is no execution history stored (possible @ref{Reverse Execution} is never
11750 used for this purpose) and the last known caller could have reached the known
11751 callee by multiple different jump sequences. In such case @value{GDBN} still
11752 tries to show at least all the unambiguous top tail callers and all the
11753 unambiguous bottom tail calees, if any.
11756 @anchor{set debug entry-values}
11757 @item set debug entry-values
11758 @kindex set debug entry-values
11759 When set to on, enables printing of analysis messages for both frame argument
11760 values at function entry and tail calls. It will show all the possible valid
11761 tail calls code paths it has considered. It will also print the intersection
11762 of them with the final unambiguous (possibly partial or even empty) code path
11765 @item show debug entry-values
11766 @kindex show debug entry-values
11767 Show the current state of analysis messages printing for both frame argument
11768 values at function entry and tail calls.
11771 The analysis messages for tail calls can for example show why the virtual tail
11772 call frame for function @code{c} has not been recognized (due to the indirect
11773 reference by variable @code{x}):
11776 static void __attribute__((noinline, noclone)) c (void);
11777 void (*x) (void) = c;
11778 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11779 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
11780 int main (void) @{ x (); return 0; @}
11782 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
11783 DW_TAG_GNU_call_site 0x40039a in main
11785 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11788 #1 0x000000000040039a in main () at t.c:5
11791 Another possibility is an ambiguous virtual tail call frames resolution:
11795 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
11796 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
11797 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
11798 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
11799 static void __attribute__((noinline, noclone)) b (void)
11800 @{ if (i) c (); else e (); @}
11801 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
11802 int main (void) @{ a (); return 0; @}
11804 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
11805 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
11806 tailcall: reduced: 0x4004d2(a) |
11809 #1 0x00000000004004d2 in a () at t.c:8
11810 #2 0x0000000000400395 in main () at t.c:9
11813 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
11814 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
11816 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
11817 @ifset HAVE_MAKEINFO_CLICK
11818 @set ARROW @click{}
11819 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
11820 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
11822 @ifclear HAVE_MAKEINFO_CLICK
11824 @set CALLSEQ1B @value{CALLSEQ1A}
11825 @set CALLSEQ2B @value{CALLSEQ2A}
11828 Frames #0 and #2 are real, #1 is a virtual tail call frame.
11829 The code can have possible execution paths @value{CALLSEQ1B} or
11830 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
11832 @code{initial:} state shows some random possible calling sequence @value{GDBN}
11833 has found. It then finds another possible calling sequcen - that one is
11834 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
11835 printed as the @code{reduced:} calling sequence. That one could have many
11836 futher @code{compare:} and @code{reduced:} statements as long as there remain
11837 any non-ambiguous sequence entries.
11839 For the frame of function @code{b} in both cases there are different possible
11840 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
11841 also ambigous. The only non-ambiguous frame is the one for function @code{a},
11842 therefore this one is displayed to the user while the ambiguous frames are
11845 There can be also reasons why printing of frame argument values at function
11850 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
11851 static void __attribute__((noinline, noclone)) a (int i);
11852 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
11853 static void __attribute__((noinline, noclone)) a (int i)
11854 @{ if (i) b (i - 1); else c (0); @}
11855 int main (void) @{ a (5); return 0; @}
11858 #0 c (i=i@@entry=0) at t.c:2
11859 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
11860 function "a" at 0x400420 can call itself via tail calls
11861 i=<optimized out>) at t.c:6
11862 #2 0x000000000040036e in main () at t.c:7
11865 @value{GDBN} cannot find out from the inferior state if and how many times did
11866 function @code{a} call itself (via function @code{b}) as these calls would be
11867 tail calls. Such tail calls would modify thue @code{i} variable, therefore
11868 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
11869 prints @code{<optimized out>} instead.
11872 @chapter C Preprocessor Macros
11874 Some languages, such as C and C@t{++}, provide a way to define and invoke
11875 ``preprocessor macros'' which expand into strings of tokens.
11876 @value{GDBN} can evaluate expressions containing macro invocations, show
11877 the result of macro expansion, and show a macro's definition, including
11878 where it was defined.
11880 You may need to compile your program specially to provide @value{GDBN}
11881 with information about preprocessor macros. Most compilers do not
11882 include macros in their debugging information, even when you compile
11883 with the @option{-g} flag. @xref{Compilation}.
11885 A program may define a macro at one point, remove that definition later,
11886 and then provide a different definition after that. Thus, at different
11887 points in the program, a macro may have different definitions, or have
11888 no definition at all. If there is a current stack frame, @value{GDBN}
11889 uses the macros in scope at that frame's source code line. Otherwise,
11890 @value{GDBN} uses the macros in scope at the current listing location;
11893 Whenever @value{GDBN} evaluates an expression, it always expands any
11894 macro invocations present in the expression. @value{GDBN} also provides
11895 the following commands for working with macros explicitly.
11899 @kindex macro expand
11900 @cindex macro expansion, showing the results of preprocessor
11901 @cindex preprocessor macro expansion, showing the results of
11902 @cindex expanding preprocessor macros
11903 @item macro expand @var{expression}
11904 @itemx macro exp @var{expression}
11905 Show the results of expanding all preprocessor macro invocations in
11906 @var{expression}. Since @value{GDBN} simply expands macros, but does
11907 not parse the result, @var{expression} need not be a valid expression;
11908 it can be any string of tokens.
11911 @item macro expand-once @var{expression}
11912 @itemx macro exp1 @var{expression}
11913 @cindex expand macro once
11914 @i{(This command is not yet implemented.)} Show the results of
11915 expanding those preprocessor macro invocations that appear explicitly in
11916 @var{expression}. Macro invocations appearing in that expansion are
11917 left unchanged. This command allows you to see the effect of a
11918 particular macro more clearly, without being confused by further
11919 expansions. Since @value{GDBN} simply expands macros, but does not
11920 parse the result, @var{expression} need not be a valid expression; it
11921 can be any string of tokens.
11924 @cindex macro definition, showing
11925 @cindex definition of a macro, showing
11926 @cindex macros, from debug info
11927 @item info macro [-a|-all] [--] @var{macro}
11928 Show the current definition or all definitions of the named @var{macro},
11929 and describe the source location or compiler command-line where that
11930 definition was established. The optional double dash is to signify the end of
11931 argument processing and the beginning of @var{macro} for non C-like macros where
11932 the macro may begin with a hyphen.
11934 @kindex info macros
11935 @item info macros @var{location}
11936 Show all macro definitions that are in effect at the location specified
11937 by @var{location}, and describe the source location or compiler
11938 command-line where those definitions were established.
11940 @kindex macro define
11941 @cindex user-defined macros
11942 @cindex defining macros interactively
11943 @cindex macros, user-defined
11944 @item macro define @var{macro} @var{replacement-list}
11945 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
11946 Introduce a definition for a preprocessor macro named @var{macro},
11947 invocations of which are replaced by the tokens given in
11948 @var{replacement-list}. The first form of this command defines an
11949 ``object-like'' macro, which takes no arguments; the second form
11950 defines a ``function-like'' macro, which takes the arguments given in
11953 A definition introduced by this command is in scope in every
11954 expression evaluated in @value{GDBN}, until it is removed with the
11955 @code{macro undef} command, described below. The definition overrides
11956 all definitions for @var{macro} present in the program being debugged,
11957 as well as any previous user-supplied definition.
11959 @kindex macro undef
11960 @item macro undef @var{macro}
11961 Remove any user-supplied definition for the macro named @var{macro}.
11962 This command only affects definitions provided with the @code{macro
11963 define} command, described above; it cannot remove definitions present
11964 in the program being debugged.
11968 List all the macros defined using the @code{macro define} command.
11971 @cindex macros, example of debugging with
11972 Here is a transcript showing the above commands in action. First, we
11973 show our source files:
11978 #include "sample.h"
11981 #define ADD(x) (M + x)
11986 printf ("Hello, world!\n");
11988 printf ("We're so creative.\n");
11990 printf ("Goodbye, world!\n");
11997 Now, we compile the program using the @sc{gnu} C compiler,
11998 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
11999 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
12000 and @option{-gdwarf-4}; we recommend always choosing the most recent
12001 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
12002 includes information about preprocessor macros in the debugging
12006 $ gcc -gdwarf-2 -g3 sample.c -o sample
12010 Now, we start @value{GDBN} on our sample program:
12014 GNU gdb 2002-05-06-cvs
12015 Copyright 2002 Free Software Foundation, Inc.
12016 GDB is free software, @dots{}
12020 We can expand macros and examine their definitions, even when the
12021 program is not running. @value{GDBN} uses the current listing position
12022 to decide which macro definitions are in scope:
12025 (@value{GDBP}) list main
12028 5 #define ADD(x) (M + x)
12033 10 printf ("Hello, world!\n");
12035 12 printf ("We're so creative.\n");
12036 (@value{GDBP}) info macro ADD
12037 Defined at /home/jimb/gdb/macros/play/sample.c:5
12038 #define ADD(x) (M + x)
12039 (@value{GDBP}) info macro Q
12040 Defined at /home/jimb/gdb/macros/play/sample.h:1
12041 included at /home/jimb/gdb/macros/play/sample.c:2
12043 (@value{GDBP}) macro expand ADD(1)
12044 expands to: (42 + 1)
12045 (@value{GDBP}) macro expand-once ADD(1)
12046 expands to: once (M + 1)
12050 In the example above, note that @code{macro expand-once} expands only
12051 the macro invocation explicit in the original text --- the invocation of
12052 @code{ADD} --- but does not expand the invocation of the macro @code{M},
12053 which was introduced by @code{ADD}.
12055 Once the program is running, @value{GDBN} uses the macro definitions in
12056 force at the source line of the current stack frame:
12059 (@value{GDBP}) break main
12060 Breakpoint 1 at 0x8048370: file sample.c, line 10.
12062 Starting program: /home/jimb/gdb/macros/play/sample
12064 Breakpoint 1, main () at sample.c:10
12065 10 printf ("Hello, world!\n");
12069 At line 10, the definition of the macro @code{N} at line 9 is in force:
12072 (@value{GDBP}) info macro N
12073 Defined at /home/jimb/gdb/macros/play/sample.c:9
12075 (@value{GDBP}) macro expand N Q M
12076 expands to: 28 < 42
12077 (@value{GDBP}) print N Q M
12082 As we step over directives that remove @code{N}'s definition, and then
12083 give it a new definition, @value{GDBN} finds the definition (or lack
12084 thereof) in force at each point:
12087 (@value{GDBP}) next
12089 12 printf ("We're so creative.\n");
12090 (@value{GDBP}) info macro N
12091 The symbol `N' has no definition as a C/C++ preprocessor macro
12092 at /home/jimb/gdb/macros/play/sample.c:12
12093 (@value{GDBP}) next
12095 14 printf ("Goodbye, world!\n");
12096 (@value{GDBP}) info macro N
12097 Defined at /home/jimb/gdb/macros/play/sample.c:13
12099 (@value{GDBP}) macro expand N Q M
12100 expands to: 1729 < 42
12101 (@value{GDBP}) print N Q M
12106 In addition to source files, macros can be defined on the compilation command
12107 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
12108 such a way, @value{GDBN} displays the location of their definition as line zero
12109 of the source file submitted to the compiler.
12112 (@value{GDBP}) info macro __STDC__
12113 Defined at /home/jimb/gdb/macros/play/sample.c:0
12120 @chapter Tracepoints
12121 @c This chapter is based on the documentation written by Michael
12122 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
12124 @cindex tracepoints
12125 In some applications, it is not feasible for the debugger to interrupt
12126 the program's execution long enough for the developer to learn
12127 anything helpful about its behavior. If the program's correctness
12128 depends on its real-time behavior, delays introduced by a debugger
12129 might cause the program to change its behavior drastically, or perhaps
12130 fail, even when the code itself is correct. It is useful to be able
12131 to observe the program's behavior without interrupting it.
12133 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
12134 specify locations in the program, called @dfn{tracepoints}, and
12135 arbitrary expressions to evaluate when those tracepoints are reached.
12136 Later, using the @code{tfind} command, you can examine the values
12137 those expressions had when the program hit the tracepoints. The
12138 expressions may also denote objects in memory---structures or arrays,
12139 for example---whose values @value{GDBN} should record; while visiting
12140 a particular tracepoint, you may inspect those objects as if they were
12141 in memory at that moment. However, because @value{GDBN} records these
12142 values without interacting with you, it can do so quickly and
12143 unobtrusively, hopefully not disturbing the program's behavior.
12145 The tracepoint facility is currently available only for remote
12146 targets. @xref{Targets}. In addition, your remote target must know
12147 how to collect trace data. This functionality is implemented in the
12148 remote stub; however, none of the stubs distributed with @value{GDBN}
12149 support tracepoints as of this writing. The format of the remote
12150 packets used to implement tracepoints are described in @ref{Tracepoint
12153 It is also possible to get trace data from a file, in a manner reminiscent
12154 of corefiles; you specify the filename, and use @code{tfind} to search
12155 through the file. @xref{Trace Files}, for more details.
12157 This chapter describes the tracepoint commands and features.
12160 * Set Tracepoints::
12161 * Analyze Collected Data::
12162 * Tracepoint Variables::
12166 @node Set Tracepoints
12167 @section Commands to Set Tracepoints
12169 Before running such a @dfn{trace experiment}, an arbitrary number of
12170 tracepoints can be set. A tracepoint is actually a special type of
12171 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
12172 standard breakpoint commands. For instance, as with breakpoints,
12173 tracepoint numbers are successive integers starting from one, and many
12174 of the commands associated with tracepoints take the tracepoint number
12175 as their argument, to identify which tracepoint to work on.
12177 For each tracepoint, you can specify, in advance, some arbitrary set
12178 of data that you want the target to collect in the trace buffer when
12179 it hits that tracepoint. The collected data can include registers,
12180 local variables, or global data. Later, you can use @value{GDBN}
12181 commands to examine the values these data had at the time the
12182 tracepoint was hit.
12184 Tracepoints do not support every breakpoint feature. Ignore counts on
12185 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
12186 commands when they are hit. Tracepoints may not be thread-specific
12189 @cindex fast tracepoints
12190 Some targets may support @dfn{fast tracepoints}, which are inserted in
12191 a different way (such as with a jump instead of a trap), that is
12192 faster but possibly restricted in where they may be installed.
12194 @cindex static tracepoints
12195 @cindex markers, static tracepoints
12196 @cindex probing markers, static tracepoints
12197 Regular and fast tracepoints are dynamic tracing facilities, meaning
12198 that they can be used to insert tracepoints at (almost) any location
12199 in the target. Some targets may also support controlling @dfn{static
12200 tracepoints} from @value{GDBN}. With static tracing, a set of
12201 instrumentation points, also known as @dfn{markers}, are embedded in
12202 the target program, and can be activated or deactivated by name or
12203 address. These are usually placed at locations which facilitate
12204 investigating what the target is actually doing. @value{GDBN}'s
12205 support for static tracing includes being able to list instrumentation
12206 points, and attach them with @value{GDBN} defined high level
12207 tracepoints that expose the whole range of convenience of
12208 @value{GDBN}'s tracepoints support. Namely, support for collecting
12209 registers values and values of global or local (to the instrumentation
12210 point) variables; tracepoint conditions and trace state variables.
12211 The act of installing a @value{GDBN} static tracepoint on an
12212 instrumentation point, or marker, is referred to as @dfn{probing} a
12213 static tracepoint marker.
12215 @code{gdbserver} supports tracepoints on some target systems.
12216 @xref{Server,,Tracepoints support in @code{gdbserver}}.
12218 This section describes commands to set tracepoints and associated
12219 conditions and actions.
12222 * Create and Delete Tracepoints::
12223 * Enable and Disable Tracepoints::
12224 * Tracepoint Passcounts::
12225 * Tracepoint Conditions::
12226 * Trace State Variables::
12227 * Tracepoint Actions::
12228 * Listing Tracepoints::
12229 * Listing Static Tracepoint Markers::
12230 * Starting and Stopping Trace Experiments::
12231 * Tracepoint Restrictions::
12234 @node Create and Delete Tracepoints
12235 @subsection Create and Delete Tracepoints
12238 @cindex set tracepoint
12240 @item trace @var{location}
12241 The @code{trace} command is very similar to the @code{break} command.
12242 Its argument @var{location} can be any valid location.
12243 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
12244 which is a point in the target program where the debugger will briefly stop,
12245 collect some data, and then allow the program to continue. Setting a tracepoint
12246 or changing its actions takes effect immediately if the remote stub
12247 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
12249 If remote stub doesn't support the @samp{InstallInTrace} feature, all
12250 these changes don't take effect until the next @code{tstart}
12251 command, and once a trace experiment is running, further changes will
12252 not have any effect until the next trace experiment starts. In addition,
12253 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
12254 address is not yet resolved. (This is similar to pending breakpoints.)
12255 Pending tracepoints are not downloaded to the target and not installed
12256 until they are resolved. The resolution of pending tracepoints requires
12257 @value{GDBN} support---when debugging with the remote target, and
12258 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
12259 tracing}), pending tracepoints can not be resolved (and downloaded to
12260 the remote stub) while @value{GDBN} is disconnected.
12262 Here are some examples of using the @code{trace} command:
12265 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
12267 (@value{GDBP}) @b{trace +2} // 2 lines forward
12269 (@value{GDBP}) @b{trace my_function} // first source line of function
12271 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
12273 (@value{GDBP}) @b{trace *0x2117c4} // an address
12277 You can abbreviate @code{trace} as @code{tr}.
12279 @item trace @var{location} if @var{cond}
12280 Set a tracepoint with condition @var{cond}; evaluate the expression
12281 @var{cond} each time the tracepoint is reached, and collect data only
12282 if the value is nonzero---that is, if @var{cond} evaluates as true.
12283 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
12284 information on tracepoint conditions.
12286 @item ftrace @var{location} [ if @var{cond} ]
12287 @cindex set fast tracepoint
12288 @cindex fast tracepoints, setting
12290 The @code{ftrace} command sets a fast tracepoint. For targets that
12291 support them, fast tracepoints will use a more efficient but possibly
12292 less general technique to trigger data collection, such as a jump
12293 instruction instead of a trap, or some sort of hardware support. It
12294 may not be possible to create a fast tracepoint at the desired
12295 location, in which case the command will exit with an explanatory
12298 @value{GDBN} handles arguments to @code{ftrace} exactly as for
12301 On 32-bit x86-architecture systems, fast tracepoints normally need to
12302 be placed at an instruction that is 5 bytes or longer, but can be
12303 placed at 4-byte instructions if the low 64K of memory of the target
12304 program is available to install trampolines. Some Unix-type systems,
12305 such as @sc{gnu}/Linux, exclude low addresses from the program's
12306 address space; but for instance with the Linux kernel it is possible
12307 to let @value{GDBN} use this area by doing a @command{sysctl} command
12308 to set the @code{mmap_min_addr} kernel parameter, as in
12311 sudo sysctl -w vm.mmap_min_addr=32768
12315 which sets the low address to 32K, which leaves plenty of room for
12316 trampolines. The minimum address should be set to a page boundary.
12318 @item strace @var{location} [ if @var{cond} ]
12319 @cindex set static tracepoint
12320 @cindex static tracepoints, setting
12321 @cindex probe static tracepoint marker
12323 The @code{strace} command sets a static tracepoint. For targets that
12324 support it, setting a static tracepoint probes a static
12325 instrumentation point, or marker, found at @var{location}. It may not
12326 be possible to set a static tracepoint at the desired location, in
12327 which case the command will exit with an explanatory message.
12329 @value{GDBN} handles arguments to @code{strace} exactly as for
12330 @code{trace}, with the addition that the user can also specify
12331 @code{-m @var{marker}} as @var{location}. This probes the marker
12332 identified by the @var{marker} string identifier. This identifier
12333 depends on the static tracepoint backend library your program is
12334 using. You can find all the marker identifiers in the @samp{ID} field
12335 of the @code{info static-tracepoint-markers} command output.
12336 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
12337 Markers}. For example, in the following small program using the UST
12343 trace_mark(ust, bar33, "str %s", "FOOBAZ");
12348 the marker id is composed of joining the first two arguments to the
12349 @code{trace_mark} call with a slash, which translates to:
12352 (@value{GDBP}) info static-tracepoint-markers
12353 Cnt Enb ID Address What
12354 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
12360 so you may probe the marker above with:
12363 (@value{GDBP}) strace -m ust/bar33
12366 Static tracepoints accept an extra collect action --- @code{collect
12367 $_sdata}. This collects arbitrary user data passed in the probe point
12368 call to the tracing library. In the UST example above, you'll see
12369 that the third argument to @code{trace_mark} is a printf-like format
12370 string. The user data is then the result of running that formating
12371 string against the following arguments. Note that @code{info
12372 static-tracepoint-markers} command output lists that format string in
12373 the @samp{Data:} field.
12375 You can inspect this data when analyzing the trace buffer, by printing
12376 the $_sdata variable like any other variable available to
12377 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
12380 @cindex last tracepoint number
12381 @cindex recent tracepoint number
12382 @cindex tracepoint number
12383 The convenience variable @code{$tpnum} records the tracepoint number
12384 of the most recently set tracepoint.
12386 @kindex delete tracepoint
12387 @cindex tracepoint deletion
12388 @item delete tracepoint @r{[}@var{num}@r{]}
12389 Permanently delete one or more tracepoints. With no argument, the
12390 default is to delete all tracepoints. Note that the regular
12391 @code{delete} command can remove tracepoints also.
12396 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
12398 (@value{GDBP}) @b{delete trace} // remove all tracepoints
12402 You can abbreviate this command as @code{del tr}.
12405 @node Enable and Disable Tracepoints
12406 @subsection Enable and Disable Tracepoints
12408 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
12411 @kindex disable tracepoint
12412 @item disable tracepoint @r{[}@var{num}@r{]}
12413 Disable tracepoint @var{num}, or all tracepoints if no argument
12414 @var{num} is given. A disabled tracepoint will have no effect during
12415 a trace experiment, but it is not forgotten. You can re-enable
12416 a disabled tracepoint using the @code{enable tracepoint} command.
12417 If the command is issued during a trace experiment and the debug target
12418 has support for disabling tracepoints during a trace experiment, then the
12419 change will be effective immediately. Otherwise, it will be applied to the
12420 next trace experiment.
12422 @kindex enable tracepoint
12423 @item enable tracepoint @r{[}@var{num}@r{]}
12424 Enable tracepoint @var{num}, or all tracepoints. If this command is
12425 issued during a trace experiment and the debug target supports enabling
12426 tracepoints during a trace experiment, then the enabled tracepoints will
12427 become effective immediately. Otherwise, they will become effective the
12428 next time a trace experiment is run.
12431 @node Tracepoint Passcounts
12432 @subsection Tracepoint Passcounts
12436 @cindex tracepoint pass count
12437 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
12438 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
12439 automatically stop a trace experiment. If a tracepoint's passcount is
12440 @var{n}, then the trace experiment will be automatically stopped on
12441 the @var{n}'th time that tracepoint is hit. If the tracepoint number
12442 @var{num} is not specified, the @code{passcount} command sets the
12443 passcount of the most recently defined tracepoint. If no passcount is
12444 given, the trace experiment will run until stopped explicitly by the
12450 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
12451 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
12453 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
12454 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
12455 (@value{GDBP}) @b{trace foo}
12456 (@value{GDBP}) @b{pass 3}
12457 (@value{GDBP}) @b{trace bar}
12458 (@value{GDBP}) @b{pass 2}
12459 (@value{GDBP}) @b{trace baz}
12460 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
12461 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
12462 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
12463 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
12467 @node Tracepoint Conditions
12468 @subsection Tracepoint Conditions
12469 @cindex conditional tracepoints
12470 @cindex tracepoint conditions
12472 The simplest sort of tracepoint collects data every time your program
12473 reaches a specified place. You can also specify a @dfn{condition} for
12474 a tracepoint. A condition is just a Boolean expression in your
12475 programming language (@pxref{Expressions, ,Expressions}). A
12476 tracepoint with a condition evaluates the expression each time your
12477 program reaches it, and data collection happens only if the condition
12480 Tracepoint conditions can be specified when a tracepoint is set, by
12481 using @samp{if} in the arguments to the @code{trace} command.
12482 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
12483 also be set or changed at any time with the @code{condition} command,
12484 just as with breakpoints.
12486 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
12487 the conditional expression itself. Instead, @value{GDBN} encodes the
12488 expression into an agent expression (@pxref{Agent Expressions})
12489 suitable for execution on the target, independently of @value{GDBN}.
12490 Global variables become raw memory locations, locals become stack
12491 accesses, and so forth.
12493 For instance, suppose you have a function that is usually called
12494 frequently, but should not be called after an error has occurred. You
12495 could use the following tracepoint command to collect data about calls
12496 of that function that happen while the error code is propagating
12497 through the program; an unconditional tracepoint could end up
12498 collecting thousands of useless trace frames that you would have to
12502 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
12505 @node Trace State Variables
12506 @subsection Trace State Variables
12507 @cindex trace state variables
12509 A @dfn{trace state variable} is a special type of variable that is
12510 created and managed by target-side code. The syntax is the same as
12511 that for GDB's convenience variables (a string prefixed with ``$''),
12512 but they are stored on the target. They must be created explicitly,
12513 using a @code{tvariable} command. They are always 64-bit signed
12516 Trace state variables are remembered by @value{GDBN}, and downloaded
12517 to the target along with tracepoint information when the trace
12518 experiment starts. There are no intrinsic limits on the number of
12519 trace state variables, beyond memory limitations of the target.
12521 @cindex convenience variables, and trace state variables
12522 Although trace state variables are managed by the target, you can use
12523 them in print commands and expressions as if they were convenience
12524 variables; @value{GDBN} will get the current value from the target
12525 while the trace experiment is running. Trace state variables share
12526 the same namespace as other ``$'' variables, which means that you
12527 cannot have trace state variables with names like @code{$23} or
12528 @code{$pc}, nor can you have a trace state variable and a convenience
12529 variable with the same name.
12533 @item tvariable $@var{name} [ = @var{expression} ]
12535 The @code{tvariable} command creates a new trace state variable named
12536 @code{$@var{name}}, and optionally gives it an initial value of
12537 @var{expression}. The @var{expression} is evaluated when this command is
12538 entered; the result will be converted to an integer if possible,
12539 otherwise @value{GDBN} will report an error. A subsequent
12540 @code{tvariable} command specifying the same name does not create a
12541 variable, but instead assigns the supplied initial value to the
12542 existing variable of that name, overwriting any previous initial
12543 value. The default initial value is 0.
12545 @item info tvariables
12546 @kindex info tvariables
12547 List all the trace state variables along with their initial values.
12548 Their current values may also be displayed, if the trace experiment is
12551 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
12552 @kindex delete tvariable
12553 Delete the given trace state variables, or all of them if no arguments
12558 @node Tracepoint Actions
12559 @subsection Tracepoint Action Lists
12563 @cindex tracepoint actions
12564 @item actions @r{[}@var{num}@r{]}
12565 This command will prompt for a list of actions to be taken when the
12566 tracepoint is hit. If the tracepoint number @var{num} is not
12567 specified, this command sets the actions for the one that was most
12568 recently defined (so that you can define a tracepoint and then say
12569 @code{actions} without bothering about its number). You specify the
12570 actions themselves on the following lines, one action at a time, and
12571 terminate the actions list with a line containing just @code{end}. So
12572 far, the only defined actions are @code{collect}, @code{teval}, and
12573 @code{while-stepping}.
12575 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
12576 Commands, ,Breakpoint Command Lists}), except that only the defined
12577 actions are allowed; any other @value{GDBN} command is rejected.
12579 @cindex remove actions from a tracepoint
12580 To remove all actions from a tracepoint, type @samp{actions @var{num}}
12581 and follow it immediately with @samp{end}.
12584 (@value{GDBP}) @b{collect @var{data}} // collect some data
12586 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
12588 (@value{GDBP}) @b{end} // signals the end of actions.
12591 In the following example, the action list begins with @code{collect}
12592 commands indicating the things to be collected when the tracepoint is
12593 hit. Then, in order to single-step and collect additional data
12594 following the tracepoint, a @code{while-stepping} command is used,
12595 followed by the list of things to be collected after each step in a
12596 sequence of single steps. The @code{while-stepping} command is
12597 terminated by its own separate @code{end} command. Lastly, the action
12598 list is terminated by an @code{end} command.
12601 (@value{GDBP}) @b{trace foo}
12602 (@value{GDBP}) @b{actions}
12603 Enter actions for tracepoint 1, one per line:
12606 > while-stepping 12
12607 > collect $pc, arr[i]
12612 @kindex collect @r{(tracepoints)}
12613 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
12614 Collect values of the given expressions when the tracepoint is hit.
12615 This command accepts a comma-separated list of any valid expressions.
12616 In addition to global, static, or local variables, the following
12617 special arguments are supported:
12621 Collect all registers.
12624 Collect all function arguments.
12627 Collect all local variables.
12630 Collect the return address. This is helpful if you want to see more
12634 Collects the number of arguments from the static probe at which the
12635 tracepoint is located.
12636 @xref{Static Probe Points}.
12638 @item $_probe_arg@var{n}
12639 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
12640 from the static probe at which the tracepoint is located.
12641 @xref{Static Probe Points}.
12644 @vindex $_sdata@r{, collect}
12645 Collect static tracepoint marker specific data. Only available for
12646 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
12647 Lists}. On the UST static tracepoints library backend, an
12648 instrumentation point resembles a @code{printf} function call. The
12649 tracing library is able to collect user specified data formatted to a
12650 character string using the format provided by the programmer that
12651 instrumented the program. Other backends have similar mechanisms.
12652 Here's an example of a UST marker call:
12655 const char master_name[] = "$your_name";
12656 trace_mark(channel1, marker1, "hello %s", master_name)
12659 In this case, collecting @code{$_sdata} collects the string
12660 @samp{hello $yourname}. When analyzing the trace buffer, you can
12661 inspect @samp{$_sdata} like any other variable available to
12665 You can give several consecutive @code{collect} commands, each one
12666 with a single argument, or one @code{collect} command with several
12667 arguments separated by commas; the effect is the same.
12669 The optional @var{mods} changes the usual handling of the arguments.
12670 @code{s} requests that pointers to chars be handled as strings, in
12671 particular collecting the contents of the memory being pointed at, up
12672 to the first zero. The upper bound is by default the value of the
12673 @code{print elements} variable; if @code{s} is followed by a decimal
12674 number, that is the upper bound instead. So for instance
12675 @samp{collect/s25 mystr} collects as many as 25 characters at
12678 The command @code{info scope} (@pxref{Symbols, info scope}) is
12679 particularly useful for figuring out what data to collect.
12681 @kindex teval @r{(tracepoints)}
12682 @item teval @var{expr1}, @var{expr2}, @dots{}
12683 Evaluate the given expressions when the tracepoint is hit. This
12684 command accepts a comma-separated list of expressions. The results
12685 are discarded, so this is mainly useful for assigning values to trace
12686 state variables (@pxref{Trace State Variables}) without adding those
12687 values to the trace buffer, as would be the case if the @code{collect}
12690 @kindex while-stepping @r{(tracepoints)}
12691 @item while-stepping @var{n}
12692 Perform @var{n} single-step instruction traces after the tracepoint,
12693 collecting new data after each step. The @code{while-stepping}
12694 command is followed by the list of what to collect while stepping
12695 (followed by its own @code{end} command):
12698 > while-stepping 12
12699 > collect $regs, myglobal
12705 Note that @code{$pc} is not automatically collected by
12706 @code{while-stepping}; you need to explicitly collect that register if
12707 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
12710 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
12711 @kindex set default-collect
12712 @cindex default collection action
12713 This variable is a list of expressions to collect at each tracepoint
12714 hit. It is effectively an additional @code{collect} action prepended
12715 to every tracepoint action list. The expressions are parsed
12716 individually for each tracepoint, so for instance a variable named
12717 @code{xyz} may be interpreted as a global for one tracepoint, and a
12718 local for another, as appropriate to the tracepoint's location.
12720 @item show default-collect
12721 @kindex show default-collect
12722 Show the list of expressions that are collected by default at each
12727 @node Listing Tracepoints
12728 @subsection Listing Tracepoints
12731 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
12732 @kindex info tp @r{[}@var{n}@dots{}@r{]}
12733 @cindex information about tracepoints
12734 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
12735 Display information about the tracepoint @var{num}. If you don't
12736 specify a tracepoint number, displays information about all the
12737 tracepoints defined so far. The format is similar to that used for
12738 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
12739 command, simply restricting itself to tracepoints.
12741 A tracepoint's listing may include additional information specific to
12746 its passcount as given by the @code{passcount @var{n}} command
12749 the state about installed on target of each location
12753 (@value{GDBP}) @b{info trace}
12754 Num Type Disp Enb Address What
12755 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
12757 collect globfoo, $regs
12762 2 tracepoint keep y <MULTIPLE>
12764 2.1 y 0x0804859c in func4 at change-loc.h:35
12765 installed on target
12766 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
12767 installed on target
12768 2.3 y <PENDING> set_tracepoint
12769 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
12770 not installed on target
12775 This command can be abbreviated @code{info tp}.
12778 @node Listing Static Tracepoint Markers
12779 @subsection Listing Static Tracepoint Markers
12782 @kindex info static-tracepoint-markers
12783 @cindex information about static tracepoint markers
12784 @item info static-tracepoint-markers
12785 Display information about all static tracepoint markers defined in the
12788 For each marker, the following columns are printed:
12792 An incrementing counter, output to help readability. This is not a
12795 The marker ID, as reported by the target.
12796 @item Enabled or Disabled
12797 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
12798 that are not enabled.
12800 Where the marker is in your program, as a memory address.
12802 Where the marker is in the source for your program, as a file and line
12803 number. If the debug information included in the program does not
12804 allow @value{GDBN} to locate the source of the marker, this column
12805 will be left blank.
12809 In addition, the following information may be printed for each marker:
12813 User data passed to the tracing library by the marker call. In the
12814 UST backend, this is the format string passed as argument to the
12816 @item Static tracepoints probing the marker
12817 The list of static tracepoints attached to the marker.
12821 (@value{GDBP}) info static-tracepoint-markers
12822 Cnt ID Enb Address What
12823 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
12824 Data: number1 %d number2 %d
12825 Probed by static tracepoints: #2
12826 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
12832 @node Starting and Stopping Trace Experiments
12833 @subsection Starting and Stopping Trace Experiments
12836 @kindex tstart [ @var{notes} ]
12837 @cindex start a new trace experiment
12838 @cindex collected data discarded
12840 This command starts the trace experiment, and begins collecting data.
12841 It has the side effect of discarding all the data collected in the
12842 trace buffer during the previous trace experiment. If any arguments
12843 are supplied, they are taken as a note and stored with the trace
12844 experiment's state. The notes may be arbitrary text, and are
12845 especially useful with disconnected tracing in a multi-user context;
12846 the notes can explain what the trace is doing, supply user contact
12847 information, and so forth.
12849 @kindex tstop [ @var{notes} ]
12850 @cindex stop a running trace experiment
12852 This command stops the trace experiment. If any arguments are
12853 supplied, they are recorded with the experiment as a note. This is
12854 useful if you are stopping a trace started by someone else, for
12855 instance if the trace is interfering with the system's behavior and
12856 needs to be stopped quickly.
12858 @strong{Note}: a trace experiment and data collection may stop
12859 automatically if any tracepoint's passcount is reached
12860 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
12863 @cindex status of trace data collection
12864 @cindex trace experiment, status of
12866 This command displays the status of the current trace data
12870 Here is an example of the commands we described so far:
12873 (@value{GDBP}) @b{trace gdb_c_test}
12874 (@value{GDBP}) @b{actions}
12875 Enter actions for tracepoint #1, one per line.
12876 > collect $regs,$locals,$args
12877 > while-stepping 11
12881 (@value{GDBP}) @b{tstart}
12882 [time passes @dots{}]
12883 (@value{GDBP}) @b{tstop}
12886 @anchor{disconnected tracing}
12887 @cindex disconnected tracing
12888 You can choose to continue running the trace experiment even if
12889 @value{GDBN} disconnects from the target, voluntarily or
12890 involuntarily. For commands such as @code{detach}, the debugger will
12891 ask what you want to do with the trace. But for unexpected
12892 terminations (@value{GDBN} crash, network outage), it would be
12893 unfortunate to lose hard-won trace data, so the variable
12894 @code{disconnected-tracing} lets you decide whether the trace should
12895 continue running without @value{GDBN}.
12898 @item set disconnected-tracing on
12899 @itemx set disconnected-tracing off
12900 @kindex set disconnected-tracing
12901 Choose whether a tracing run should continue to run if @value{GDBN}
12902 has disconnected from the target. Note that @code{detach} or
12903 @code{quit} will ask you directly what to do about a running trace no
12904 matter what this variable's setting, so the variable is mainly useful
12905 for handling unexpected situations, such as loss of the network.
12907 @item show disconnected-tracing
12908 @kindex show disconnected-tracing
12909 Show the current choice for disconnected tracing.
12913 When you reconnect to the target, the trace experiment may or may not
12914 still be running; it might have filled the trace buffer in the
12915 meantime, or stopped for one of the other reasons. If it is running,
12916 it will continue after reconnection.
12918 Upon reconnection, the target will upload information about the
12919 tracepoints in effect. @value{GDBN} will then compare that
12920 information to the set of tracepoints currently defined, and attempt
12921 to match them up, allowing for the possibility that the numbers may
12922 have changed due to creation and deletion in the meantime. If one of
12923 the target's tracepoints does not match any in @value{GDBN}, the
12924 debugger will create a new tracepoint, so that you have a number with
12925 which to specify that tracepoint. This matching-up process is
12926 necessarily heuristic, and it may result in useless tracepoints being
12927 created; you may simply delete them if they are of no use.
12929 @cindex circular trace buffer
12930 If your target agent supports a @dfn{circular trace buffer}, then you
12931 can run a trace experiment indefinitely without filling the trace
12932 buffer; when space runs out, the agent deletes already-collected trace
12933 frames, oldest first, until there is enough room to continue
12934 collecting. This is especially useful if your tracepoints are being
12935 hit too often, and your trace gets terminated prematurely because the
12936 buffer is full. To ask for a circular trace buffer, simply set
12937 @samp{circular-trace-buffer} to on. You can set this at any time,
12938 including during tracing; if the agent can do it, it will change
12939 buffer handling on the fly, otherwise it will not take effect until
12943 @item set circular-trace-buffer on
12944 @itemx set circular-trace-buffer off
12945 @kindex set circular-trace-buffer
12946 Choose whether a tracing run should use a linear or circular buffer
12947 for trace data. A linear buffer will not lose any trace data, but may
12948 fill up prematurely, while a circular buffer will discard old trace
12949 data, but it will have always room for the latest tracepoint hits.
12951 @item show circular-trace-buffer
12952 @kindex show circular-trace-buffer
12953 Show the current choice for the trace buffer. Note that this may not
12954 match the agent's current buffer handling, nor is it guaranteed to
12955 match the setting that might have been in effect during a past run,
12956 for instance if you are looking at frames from a trace file.
12961 @item set trace-buffer-size @var{n}
12962 @itemx set trace-buffer-size unlimited
12963 @kindex set trace-buffer-size
12964 Request that the target use a trace buffer of @var{n} bytes. Not all
12965 targets will honor the request; they may have a compiled-in size for
12966 the trace buffer, or some other limitation. Set to a value of
12967 @code{unlimited} or @code{-1} to let the target use whatever size it
12968 likes. This is also the default.
12970 @item show trace-buffer-size
12971 @kindex show trace-buffer-size
12972 Show the current requested size for the trace buffer. Note that this
12973 will only match the actual size if the target supports size-setting,
12974 and was able to handle the requested size. For instance, if the
12975 target can only change buffer size between runs, this variable will
12976 not reflect the change until the next run starts. Use @code{tstatus}
12977 to get a report of the actual buffer size.
12981 @item set trace-user @var{text}
12982 @kindex set trace-user
12984 @item show trace-user
12985 @kindex show trace-user
12987 @item set trace-notes @var{text}
12988 @kindex set trace-notes
12989 Set the trace run's notes.
12991 @item show trace-notes
12992 @kindex show trace-notes
12993 Show the trace run's notes.
12995 @item set trace-stop-notes @var{text}
12996 @kindex set trace-stop-notes
12997 Set the trace run's stop notes. The handling of the note is as for
12998 @code{tstop} arguments; the set command is convenient way to fix a
12999 stop note that is mistaken or incomplete.
13001 @item show trace-stop-notes
13002 @kindex show trace-stop-notes
13003 Show the trace run's stop notes.
13007 @node Tracepoint Restrictions
13008 @subsection Tracepoint Restrictions
13010 @cindex tracepoint restrictions
13011 There are a number of restrictions on the use of tracepoints. As
13012 described above, tracepoint data gathering occurs on the target
13013 without interaction from @value{GDBN}. Thus the full capabilities of
13014 the debugger are not available during data gathering, and then at data
13015 examination time, you will be limited by only having what was
13016 collected. The following items describe some common problems, but it
13017 is not exhaustive, and you may run into additional difficulties not
13023 Tracepoint expressions are intended to gather objects (lvalues). Thus
13024 the full flexibility of GDB's expression evaluator is not available.
13025 You cannot call functions, cast objects to aggregate types, access
13026 convenience variables or modify values (except by assignment to trace
13027 state variables). Some language features may implicitly call
13028 functions (for instance Objective-C fields with accessors), and therefore
13029 cannot be collected either.
13032 Collection of local variables, either individually or in bulk with
13033 @code{$locals} or @code{$args}, during @code{while-stepping} may
13034 behave erratically. The stepping action may enter a new scope (for
13035 instance by stepping into a function), or the location of the variable
13036 may change (for instance it is loaded into a register). The
13037 tracepoint data recorded uses the location information for the
13038 variables that is correct for the tracepoint location. When the
13039 tracepoint is created, it is not possible, in general, to determine
13040 where the steps of a @code{while-stepping} sequence will advance the
13041 program---particularly if a conditional branch is stepped.
13044 Collection of an incompletely-initialized or partially-destroyed object
13045 may result in something that @value{GDBN} cannot display, or displays
13046 in a misleading way.
13049 When @value{GDBN} displays a pointer to character it automatically
13050 dereferences the pointer to also display characters of the string
13051 being pointed to. However, collecting the pointer during tracing does
13052 not automatically collect the string. You need to explicitly
13053 dereference the pointer and provide size information if you want to
13054 collect not only the pointer, but the memory pointed to. For example,
13055 @code{*ptr@@50} can be used to collect the 50 element array pointed to
13059 It is not possible to collect a complete stack backtrace at a
13060 tracepoint. Instead, you may collect the registers and a few hundred
13061 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
13062 (adjust to use the name of the actual stack pointer register on your
13063 target architecture, and the amount of stack you wish to capture).
13064 Then the @code{backtrace} command will show a partial backtrace when
13065 using a trace frame. The number of stack frames that can be examined
13066 depends on the sizes of the frames in the collected stack. Note that
13067 if you ask for a block so large that it goes past the bottom of the
13068 stack, the target agent may report an error trying to read from an
13072 If you do not collect registers at a tracepoint, @value{GDBN} can
13073 infer that the value of @code{$pc} must be the same as the address of
13074 the tracepoint and use that when you are looking at a trace frame
13075 for that tracepoint. However, this cannot work if the tracepoint has
13076 multiple locations (for instance if it was set in a function that was
13077 inlined), or if it has a @code{while-stepping} loop. In those cases
13078 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
13083 @node Analyze Collected Data
13084 @section Using the Collected Data
13086 After the tracepoint experiment ends, you use @value{GDBN} commands
13087 for examining the trace data. The basic idea is that each tracepoint
13088 collects a trace @dfn{snapshot} every time it is hit and another
13089 snapshot every time it single-steps. All these snapshots are
13090 consecutively numbered from zero and go into a buffer, and you can
13091 examine them later. The way you examine them is to @dfn{focus} on a
13092 specific trace snapshot. When the remote stub is focused on a trace
13093 snapshot, it will respond to all @value{GDBN} requests for memory and
13094 registers by reading from the buffer which belongs to that snapshot,
13095 rather than from @emph{real} memory or registers of the program being
13096 debugged. This means that @strong{all} @value{GDBN} commands
13097 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
13098 behave as if we were currently debugging the program state as it was
13099 when the tracepoint occurred. Any requests for data that are not in
13100 the buffer will fail.
13103 * tfind:: How to select a trace snapshot
13104 * tdump:: How to display all data for a snapshot
13105 * save tracepoints:: How to save tracepoints for a future run
13109 @subsection @code{tfind @var{n}}
13112 @cindex select trace snapshot
13113 @cindex find trace snapshot
13114 The basic command for selecting a trace snapshot from the buffer is
13115 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
13116 counting from zero. If no argument @var{n} is given, the next
13117 snapshot is selected.
13119 Here are the various forms of using the @code{tfind} command.
13123 Find the first snapshot in the buffer. This is a synonym for
13124 @code{tfind 0} (since 0 is the number of the first snapshot).
13127 Stop debugging trace snapshots, resume @emph{live} debugging.
13130 Same as @samp{tfind none}.
13133 No argument means find the next trace snapshot.
13136 Find the previous trace snapshot before the current one. This permits
13137 retracing earlier steps.
13139 @item tfind tracepoint @var{num}
13140 Find the next snapshot associated with tracepoint @var{num}. Search
13141 proceeds forward from the last examined trace snapshot. If no
13142 argument @var{num} is given, it means find the next snapshot collected
13143 for the same tracepoint as the current snapshot.
13145 @item tfind pc @var{addr}
13146 Find the next snapshot associated with the value @var{addr} of the
13147 program counter. Search proceeds forward from the last examined trace
13148 snapshot. If no argument @var{addr} is given, it means find the next
13149 snapshot with the same value of PC as the current snapshot.
13151 @item tfind outside @var{addr1}, @var{addr2}
13152 Find the next snapshot whose PC is outside the given range of
13153 addresses (exclusive).
13155 @item tfind range @var{addr1}, @var{addr2}
13156 Find the next snapshot whose PC is between @var{addr1} and
13157 @var{addr2} (inclusive).
13159 @item tfind line @r{[}@var{file}:@r{]}@var{n}
13160 Find the next snapshot associated with the source line @var{n}. If
13161 the optional argument @var{file} is given, refer to line @var{n} in
13162 that source file. Search proceeds forward from the last examined
13163 trace snapshot. If no argument @var{n} is given, it means find the
13164 next line other than the one currently being examined; thus saying
13165 @code{tfind line} repeatedly can appear to have the same effect as
13166 stepping from line to line in a @emph{live} debugging session.
13169 The default arguments for the @code{tfind} commands are specifically
13170 designed to make it easy to scan through the trace buffer. For
13171 instance, @code{tfind} with no argument selects the next trace
13172 snapshot, and @code{tfind -} with no argument selects the previous
13173 trace snapshot. So, by giving one @code{tfind} command, and then
13174 simply hitting @key{RET} repeatedly you can examine all the trace
13175 snapshots in order. Or, by saying @code{tfind -} and then hitting
13176 @key{RET} repeatedly you can examine the snapshots in reverse order.
13177 The @code{tfind line} command with no argument selects the snapshot
13178 for the next source line executed. The @code{tfind pc} command with
13179 no argument selects the next snapshot with the same program counter
13180 (PC) as the current frame. The @code{tfind tracepoint} command with
13181 no argument selects the next trace snapshot collected by the same
13182 tracepoint as the current one.
13184 In addition to letting you scan through the trace buffer manually,
13185 these commands make it easy to construct @value{GDBN} scripts that
13186 scan through the trace buffer and print out whatever collected data
13187 you are interested in. Thus, if we want to examine the PC, FP, and SP
13188 registers from each trace frame in the buffer, we can say this:
13191 (@value{GDBP}) @b{tfind start}
13192 (@value{GDBP}) @b{while ($trace_frame != -1)}
13193 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
13194 $trace_frame, $pc, $sp, $fp
13198 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
13199 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
13200 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
13201 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
13202 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
13203 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
13204 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
13205 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
13206 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
13207 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
13208 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
13211 Or, if we want to examine the variable @code{X} at each source line in
13215 (@value{GDBP}) @b{tfind start}
13216 (@value{GDBP}) @b{while ($trace_frame != -1)}
13217 > printf "Frame %d, X == %d\n", $trace_frame, X
13227 @subsection @code{tdump}
13229 @cindex dump all data collected at tracepoint
13230 @cindex tracepoint data, display
13232 This command takes no arguments. It prints all the data collected at
13233 the current trace snapshot.
13236 (@value{GDBP}) @b{trace 444}
13237 (@value{GDBP}) @b{actions}
13238 Enter actions for tracepoint #2, one per line:
13239 > collect $regs, $locals, $args, gdb_long_test
13242 (@value{GDBP}) @b{tstart}
13244 (@value{GDBP}) @b{tfind line 444}
13245 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
13247 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
13249 (@value{GDBP}) @b{tdump}
13250 Data collected at tracepoint 2, trace frame 1:
13251 d0 0xc4aa0085 -995491707
13255 d4 0x71aea3d 119204413
13258 d7 0x380035 3670069
13259 a0 0x19e24a 1696330
13260 a1 0x3000668 50333288
13262 a3 0x322000 3284992
13263 a4 0x3000698 50333336
13264 a5 0x1ad3cc 1758156
13265 fp 0x30bf3c 0x30bf3c
13266 sp 0x30bf34 0x30bf34
13268 pc 0x20b2c8 0x20b2c8
13272 p = 0x20e5b4 "gdb-test"
13279 gdb_long_test = 17 '\021'
13284 @code{tdump} works by scanning the tracepoint's current collection
13285 actions and printing the value of each expression listed. So
13286 @code{tdump} can fail, if after a run, you change the tracepoint's
13287 actions to mention variables that were not collected during the run.
13289 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
13290 uses the collected value of @code{$pc} to distinguish between trace
13291 frames that were collected at the tracepoint hit, and frames that were
13292 collected while stepping. This allows it to correctly choose whether
13293 to display the basic list of collections, or the collections from the
13294 body of the while-stepping loop. However, if @code{$pc} was not collected,
13295 then @code{tdump} will always attempt to dump using the basic collection
13296 list, and may fail if a while-stepping frame does not include all the
13297 same data that is collected at the tracepoint hit.
13298 @c This is getting pretty arcane, example would be good.
13300 @node save tracepoints
13301 @subsection @code{save tracepoints @var{filename}}
13302 @kindex save tracepoints
13303 @kindex save-tracepoints
13304 @cindex save tracepoints for future sessions
13306 This command saves all current tracepoint definitions together with
13307 their actions and passcounts, into a file @file{@var{filename}}
13308 suitable for use in a later debugging session. To read the saved
13309 tracepoint definitions, use the @code{source} command (@pxref{Command
13310 Files}). The @w{@code{save-tracepoints}} command is a deprecated
13311 alias for @w{@code{save tracepoints}}
13313 @node Tracepoint Variables
13314 @section Convenience Variables for Tracepoints
13315 @cindex tracepoint variables
13316 @cindex convenience variables for tracepoints
13319 @vindex $trace_frame
13320 @item (int) $trace_frame
13321 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
13322 snapshot is selected.
13324 @vindex $tracepoint
13325 @item (int) $tracepoint
13326 The tracepoint for the current trace snapshot.
13328 @vindex $trace_line
13329 @item (int) $trace_line
13330 The line number for the current trace snapshot.
13332 @vindex $trace_file
13333 @item (char []) $trace_file
13334 The source file for the current trace snapshot.
13336 @vindex $trace_func
13337 @item (char []) $trace_func
13338 The name of the function containing @code{$tracepoint}.
13341 Note: @code{$trace_file} is not suitable for use in @code{printf},
13342 use @code{output} instead.
13344 Here's a simple example of using these convenience variables for
13345 stepping through all the trace snapshots and printing some of their
13346 data. Note that these are not the same as trace state variables,
13347 which are managed by the target.
13350 (@value{GDBP}) @b{tfind start}
13352 (@value{GDBP}) @b{while $trace_frame != -1}
13353 > output $trace_file
13354 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
13360 @section Using Trace Files
13361 @cindex trace files
13363 In some situations, the target running a trace experiment may no
13364 longer be available; perhaps it crashed, or the hardware was needed
13365 for a different activity. To handle these cases, you can arrange to
13366 dump the trace data into a file, and later use that file as a source
13367 of trace data, via the @code{target tfile} command.
13372 @item tsave [ -r ] @var{filename}
13373 @itemx tsave [-ctf] @var{dirname}
13374 Save the trace data to @var{filename}. By default, this command
13375 assumes that @var{filename} refers to the host filesystem, so if
13376 necessary @value{GDBN} will copy raw trace data up from the target and
13377 then save it. If the target supports it, you can also supply the
13378 optional argument @code{-r} (``remote'') to direct the target to save
13379 the data directly into @var{filename} in its own filesystem, which may be
13380 more efficient if the trace buffer is very large. (Note, however, that
13381 @code{target tfile} can only read from files accessible to the host.)
13382 By default, this command will save trace frame in tfile format.
13383 You can supply the optional argument @code{-ctf} to save date in CTF
13384 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
13385 that can be shared by multiple debugging and tracing tools. Please go to
13386 @indicateurl{http://www.efficios.com/ctf} to get more information.
13388 @kindex target tfile
13392 @item target tfile @var{filename}
13393 @itemx target ctf @var{dirname}
13394 Use the file named @var{filename} or directory named @var{dirname} as
13395 a source of trace data. Commands that examine data work as they do with
13396 a live target, but it is not possible to run any new trace experiments.
13397 @code{tstatus} will report the state of the trace run at the moment
13398 the data was saved, as well as the current trace frame you are examining.
13399 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
13403 (@value{GDBP}) target ctf ctf.ctf
13404 (@value{GDBP}) tfind
13405 Found trace frame 0, tracepoint 2
13406 39 ++a; /* set tracepoint 1 here */
13407 (@value{GDBP}) tdump
13408 Data collected at tracepoint 2, trace frame 0:
13412 c = @{"123", "456", "789", "123", "456", "789"@}
13413 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
13421 @chapter Debugging Programs That Use Overlays
13424 If your program is too large to fit completely in your target system's
13425 memory, you can sometimes use @dfn{overlays} to work around this
13426 problem. @value{GDBN} provides some support for debugging programs that
13430 * How Overlays Work:: A general explanation of overlays.
13431 * Overlay Commands:: Managing overlays in @value{GDBN}.
13432 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
13433 mapped by asking the inferior.
13434 * Overlay Sample Program:: A sample program using overlays.
13437 @node How Overlays Work
13438 @section How Overlays Work
13439 @cindex mapped overlays
13440 @cindex unmapped overlays
13441 @cindex load address, overlay's
13442 @cindex mapped address
13443 @cindex overlay area
13445 Suppose you have a computer whose instruction address space is only 64
13446 kilobytes long, but which has much more memory which can be accessed by
13447 other means: special instructions, segment registers, or memory
13448 management hardware, for example. Suppose further that you want to
13449 adapt a program which is larger than 64 kilobytes to run on this system.
13451 One solution is to identify modules of your program which are relatively
13452 independent, and need not call each other directly; call these modules
13453 @dfn{overlays}. Separate the overlays from the main program, and place
13454 their machine code in the larger memory. Place your main program in
13455 instruction memory, but leave at least enough space there to hold the
13456 largest overlay as well.
13458 Now, to call a function located in an overlay, you must first copy that
13459 overlay's machine code from the large memory into the space set aside
13460 for it in the instruction memory, and then jump to its entry point
13463 @c NB: In the below the mapped area's size is greater or equal to the
13464 @c size of all overlays. This is intentional to remind the developer
13465 @c that overlays don't necessarily need to be the same size.
13469 Data Instruction Larger
13470 Address Space Address Space Address Space
13471 +-----------+ +-----------+ +-----------+
13473 +-----------+ +-----------+ +-----------+<-- overlay 1
13474 | program | | main | .----| overlay 1 | load address
13475 | variables | | program | | +-----------+
13476 | and heap | | | | | |
13477 +-----------+ | | | +-----------+<-- overlay 2
13478 | | +-----------+ | | | load address
13479 +-----------+ | | | .-| overlay 2 |
13481 mapped --->+-----------+ | | +-----------+
13482 address | | | | | |
13483 | overlay | <-' | | |
13484 | area | <---' +-----------+<-- overlay 3
13485 | | <---. | | load address
13486 +-----------+ `--| overlay 3 |
13493 @anchor{A code overlay}A code overlay
13497 The diagram (@pxref{A code overlay}) shows a system with separate data
13498 and instruction address spaces. To map an overlay, the program copies
13499 its code from the larger address space to the instruction address space.
13500 Since the overlays shown here all use the same mapped address, only one
13501 may be mapped at a time. For a system with a single address space for
13502 data and instructions, the diagram would be similar, except that the
13503 program variables and heap would share an address space with the main
13504 program and the overlay area.
13506 An overlay loaded into instruction memory and ready for use is called a
13507 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
13508 instruction memory. An overlay not present (or only partially present)
13509 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
13510 is its address in the larger memory. The mapped address is also called
13511 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
13512 called the @dfn{load memory address}, or @dfn{LMA}.
13514 Unfortunately, overlays are not a completely transparent way to adapt a
13515 program to limited instruction memory. They introduce a new set of
13516 global constraints you must keep in mind as you design your program:
13521 Before calling or returning to a function in an overlay, your program
13522 must make sure that overlay is actually mapped. Otherwise, the call or
13523 return will transfer control to the right address, but in the wrong
13524 overlay, and your program will probably crash.
13527 If the process of mapping an overlay is expensive on your system, you
13528 will need to choose your overlays carefully to minimize their effect on
13529 your program's performance.
13532 The executable file you load onto your system must contain each
13533 overlay's instructions, appearing at the overlay's load address, not its
13534 mapped address. However, each overlay's instructions must be relocated
13535 and its symbols defined as if the overlay were at its mapped address.
13536 You can use GNU linker scripts to specify different load and relocation
13537 addresses for pieces of your program; see @ref{Overlay Description,,,
13538 ld.info, Using ld: the GNU linker}.
13541 The procedure for loading executable files onto your system must be able
13542 to load their contents into the larger address space as well as the
13543 instruction and data spaces.
13547 The overlay system described above is rather simple, and could be
13548 improved in many ways:
13553 If your system has suitable bank switch registers or memory management
13554 hardware, you could use those facilities to make an overlay's load area
13555 contents simply appear at their mapped address in instruction space.
13556 This would probably be faster than copying the overlay to its mapped
13557 area in the usual way.
13560 If your overlays are small enough, you could set aside more than one
13561 overlay area, and have more than one overlay mapped at a time.
13564 You can use overlays to manage data, as well as instructions. In
13565 general, data overlays are even less transparent to your design than
13566 code overlays: whereas code overlays only require care when you call or
13567 return to functions, data overlays require care every time you access
13568 the data. Also, if you change the contents of a data overlay, you
13569 must copy its contents back out to its load address before you can copy a
13570 different data overlay into the same mapped area.
13575 @node Overlay Commands
13576 @section Overlay Commands
13578 To use @value{GDBN}'s overlay support, each overlay in your program must
13579 correspond to a separate section of the executable file. The section's
13580 virtual memory address and load memory address must be the overlay's
13581 mapped and load addresses. Identifying overlays with sections allows
13582 @value{GDBN} to determine the appropriate address of a function or
13583 variable, depending on whether the overlay is mapped or not.
13585 @value{GDBN}'s overlay commands all start with the word @code{overlay};
13586 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
13591 Disable @value{GDBN}'s overlay support. When overlay support is
13592 disabled, @value{GDBN} assumes that all functions and variables are
13593 always present at their mapped addresses. By default, @value{GDBN}'s
13594 overlay support is disabled.
13596 @item overlay manual
13597 @cindex manual overlay debugging
13598 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
13599 relies on you to tell it which overlays are mapped, and which are not,
13600 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
13601 commands described below.
13603 @item overlay map-overlay @var{overlay}
13604 @itemx overlay map @var{overlay}
13605 @cindex map an overlay
13606 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
13607 be the name of the object file section containing the overlay. When an
13608 overlay is mapped, @value{GDBN} assumes it can find the overlay's
13609 functions and variables at their mapped addresses. @value{GDBN} assumes
13610 that any other overlays whose mapped ranges overlap that of
13611 @var{overlay} are now unmapped.
13613 @item overlay unmap-overlay @var{overlay}
13614 @itemx overlay unmap @var{overlay}
13615 @cindex unmap an overlay
13616 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
13617 must be the name of the object file section containing the overlay.
13618 When an overlay is unmapped, @value{GDBN} assumes it can find the
13619 overlay's functions and variables at their load addresses.
13622 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
13623 consults a data structure the overlay manager maintains in the inferior
13624 to see which overlays are mapped. For details, see @ref{Automatic
13625 Overlay Debugging}.
13627 @item overlay load-target
13628 @itemx overlay load
13629 @cindex reloading the overlay table
13630 Re-read the overlay table from the inferior. Normally, @value{GDBN}
13631 re-reads the table @value{GDBN} automatically each time the inferior
13632 stops, so this command should only be necessary if you have changed the
13633 overlay mapping yourself using @value{GDBN}. This command is only
13634 useful when using automatic overlay debugging.
13636 @item overlay list-overlays
13637 @itemx overlay list
13638 @cindex listing mapped overlays
13639 Display a list of the overlays currently mapped, along with their mapped
13640 addresses, load addresses, and sizes.
13644 Normally, when @value{GDBN} prints a code address, it includes the name
13645 of the function the address falls in:
13648 (@value{GDBP}) print main
13649 $3 = @{int ()@} 0x11a0 <main>
13652 When overlay debugging is enabled, @value{GDBN} recognizes code in
13653 unmapped overlays, and prints the names of unmapped functions with
13654 asterisks around them. For example, if @code{foo} is a function in an
13655 unmapped overlay, @value{GDBN} prints it this way:
13658 (@value{GDBP}) overlay list
13659 No sections are mapped.
13660 (@value{GDBP}) print foo
13661 $5 = @{int (int)@} 0x100000 <*foo*>
13664 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
13668 (@value{GDBP}) overlay list
13669 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
13670 mapped at 0x1016 - 0x104a
13671 (@value{GDBP}) print foo
13672 $6 = @{int (int)@} 0x1016 <foo>
13675 When overlay debugging is enabled, @value{GDBN} can find the correct
13676 address for functions and variables in an overlay, whether or not the
13677 overlay is mapped. This allows most @value{GDBN} commands, like
13678 @code{break} and @code{disassemble}, to work normally, even on unmapped
13679 code. However, @value{GDBN}'s breakpoint support has some limitations:
13683 @cindex breakpoints in overlays
13684 @cindex overlays, setting breakpoints in
13685 You can set breakpoints in functions in unmapped overlays, as long as
13686 @value{GDBN} can write to the overlay at its load address.
13688 @value{GDBN} can not set hardware or simulator-based breakpoints in
13689 unmapped overlays. However, if you set a breakpoint at the end of your
13690 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
13691 you are using manual overlay management), @value{GDBN} will re-set its
13692 breakpoints properly.
13696 @node Automatic Overlay Debugging
13697 @section Automatic Overlay Debugging
13698 @cindex automatic overlay debugging
13700 @value{GDBN} can automatically track which overlays are mapped and which
13701 are not, given some simple co-operation from the overlay manager in the
13702 inferior. If you enable automatic overlay debugging with the
13703 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
13704 looks in the inferior's memory for certain variables describing the
13705 current state of the overlays.
13707 Here are the variables your overlay manager must define to support
13708 @value{GDBN}'s automatic overlay debugging:
13712 @item @code{_ovly_table}:
13713 This variable must be an array of the following structures:
13718 /* The overlay's mapped address. */
13721 /* The size of the overlay, in bytes. */
13722 unsigned long size;
13724 /* The overlay's load address. */
13727 /* Non-zero if the overlay is currently mapped;
13729 unsigned long mapped;
13733 @item @code{_novlys}:
13734 This variable must be a four-byte signed integer, holding the total
13735 number of elements in @code{_ovly_table}.
13739 To decide whether a particular overlay is mapped or not, @value{GDBN}
13740 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
13741 @code{lma} members equal the VMA and LMA of the overlay's section in the
13742 executable file. When @value{GDBN} finds a matching entry, it consults
13743 the entry's @code{mapped} member to determine whether the overlay is
13746 In addition, your overlay manager may define a function called
13747 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
13748 will silently set a breakpoint there. If the overlay manager then
13749 calls this function whenever it has changed the overlay table, this
13750 will enable @value{GDBN} to accurately keep track of which overlays
13751 are in program memory, and update any breakpoints that may be set
13752 in overlays. This will allow breakpoints to work even if the
13753 overlays are kept in ROM or other non-writable memory while they
13754 are not being executed.
13756 @node Overlay Sample Program
13757 @section Overlay Sample Program
13758 @cindex overlay example program
13760 When linking a program which uses overlays, you must place the overlays
13761 at their load addresses, while relocating them to run at their mapped
13762 addresses. To do this, you must write a linker script (@pxref{Overlay
13763 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
13764 since linker scripts are specific to a particular host system, target
13765 architecture, and target memory layout, this manual cannot provide
13766 portable sample code demonstrating @value{GDBN}'s overlay support.
13768 However, the @value{GDBN} source distribution does contain an overlaid
13769 program, with linker scripts for a few systems, as part of its test
13770 suite. The program consists of the following files from
13771 @file{gdb/testsuite/gdb.base}:
13775 The main program file.
13777 A simple overlay manager, used by @file{overlays.c}.
13782 Overlay modules, loaded and used by @file{overlays.c}.
13785 Linker scripts for linking the test program on the @code{d10v-elf}
13786 and @code{m32r-elf} targets.
13789 You can build the test program using the @code{d10v-elf} GCC
13790 cross-compiler like this:
13793 $ d10v-elf-gcc -g -c overlays.c
13794 $ d10v-elf-gcc -g -c ovlymgr.c
13795 $ d10v-elf-gcc -g -c foo.c
13796 $ d10v-elf-gcc -g -c bar.c
13797 $ d10v-elf-gcc -g -c baz.c
13798 $ d10v-elf-gcc -g -c grbx.c
13799 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
13800 baz.o grbx.o -Wl,-Td10v.ld -o overlays
13803 The build process is identical for any other architecture, except that
13804 you must substitute the appropriate compiler and linker script for the
13805 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
13809 @chapter Using @value{GDBN} with Different Languages
13812 Although programming languages generally have common aspects, they are
13813 rarely expressed in the same manner. For instance, in ANSI C,
13814 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
13815 Modula-2, it is accomplished by @code{p^}. Values can also be
13816 represented (and displayed) differently. Hex numbers in C appear as
13817 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
13819 @cindex working language
13820 Language-specific information is built into @value{GDBN} for some languages,
13821 allowing you to express operations like the above in your program's
13822 native language, and allowing @value{GDBN} to output values in a manner
13823 consistent with the syntax of your program's native language. The
13824 language you use to build expressions is called the @dfn{working
13828 * Setting:: Switching between source languages
13829 * Show:: Displaying the language
13830 * Checks:: Type and range checks
13831 * Supported Languages:: Supported languages
13832 * Unsupported Languages:: Unsupported languages
13836 @section Switching Between Source Languages
13838 There are two ways to control the working language---either have @value{GDBN}
13839 set it automatically, or select it manually yourself. You can use the
13840 @code{set language} command for either purpose. On startup, @value{GDBN}
13841 defaults to setting the language automatically. The working language is
13842 used to determine how expressions you type are interpreted, how values
13845 In addition to the working language, every source file that
13846 @value{GDBN} knows about has its own working language. For some object
13847 file formats, the compiler might indicate which language a particular
13848 source file is in. However, most of the time @value{GDBN} infers the
13849 language from the name of the file. The language of a source file
13850 controls whether C@t{++} names are demangled---this way @code{backtrace} can
13851 show each frame appropriately for its own language. There is no way to
13852 set the language of a source file from within @value{GDBN}, but you can
13853 set the language associated with a filename extension. @xref{Show, ,
13854 Displaying the Language}.
13856 This is most commonly a problem when you use a program, such
13857 as @code{cfront} or @code{f2c}, that generates C but is written in
13858 another language. In that case, make the
13859 program use @code{#line} directives in its C output; that way
13860 @value{GDBN} will know the correct language of the source code of the original
13861 program, and will display that source code, not the generated C code.
13864 * Filenames:: Filename extensions and languages.
13865 * Manually:: Setting the working language manually
13866 * Automatically:: Having @value{GDBN} infer the source language
13870 @subsection List of Filename Extensions and Languages
13872 If a source file name ends in one of the following extensions, then
13873 @value{GDBN} infers that its language is the one indicated.
13891 C@t{++} source file
13897 Objective-C source file
13901 Fortran source file
13904 Modula-2 source file
13908 Assembler source file. This actually behaves almost like C, but
13909 @value{GDBN} does not skip over function prologues when stepping.
13912 In addition, you may set the language associated with a filename
13913 extension. @xref{Show, , Displaying the Language}.
13916 @subsection Setting the Working Language
13918 If you allow @value{GDBN} to set the language automatically,
13919 expressions are interpreted the same way in your debugging session and
13922 @kindex set language
13923 If you wish, you may set the language manually. To do this, issue the
13924 command @samp{set language @var{lang}}, where @var{lang} is the name of
13925 a language, such as
13926 @code{c} or @code{modula-2}.
13927 For a list of the supported languages, type @samp{set language}.
13929 Setting the language manually prevents @value{GDBN} from updating the working
13930 language automatically. This can lead to confusion if you try
13931 to debug a program when the working language is not the same as the
13932 source language, when an expression is acceptable to both
13933 languages---but means different things. For instance, if the current
13934 source file were written in C, and @value{GDBN} was parsing Modula-2, a
13942 might not have the effect you intended. In C, this means to add
13943 @code{b} and @code{c} and place the result in @code{a}. The result
13944 printed would be the value of @code{a}. In Modula-2, this means to compare
13945 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
13947 @node Automatically
13948 @subsection Having @value{GDBN} Infer the Source Language
13950 To have @value{GDBN} set the working language automatically, use
13951 @samp{set language local} or @samp{set language auto}. @value{GDBN}
13952 then infers the working language. That is, when your program stops in a
13953 frame (usually by encountering a breakpoint), @value{GDBN} sets the
13954 working language to the language recorded for the function in that
13955 frame. If the language for a frame is unknown (that is, if the function
13956 or block corresponding to the frame was defined in a source file that
13957 does not have a recognized extension), the current working language is
13958 not changed, and @value{GDBN} issues a warning.
13960 This may not seem necessary for most programs, which are written
13961 entirely in one source language. However, program modules and libraries
13962 written in one source language can be used by a main program written in
13963 a different source language. Using @samp{set language auto} in this
13964 case frees you from having to set the working language manually.
13967 @section Displaying the Language
13969 The following commands help you find out which language is the
13970 working language, and also what language source files were written in.
13973 @item show language
13974 @anchor{show language}
13975 @kindex show language
13976 Display the current working language. This is the
13977 language you can use with commands such as @code{print} to
13978 build and compute expressions that may involve variables in your program.
13981 @kindex info frame@r{, show the source language}
13982 Display the source language for this frame. This language becomes the
13983 working language if you use an identifier from this frame.
13984 @xref{Frame Info, ,Information about a Frame}, to identify the other
13985 information listed here.
13988 @kindex info source@r{, show the source language}
13989 Display the source language of this source file.
13990 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
13991 information listed here.
13994 In unusual circumstances, you may have source files with extensions
13995 not in the standard list. You can then set the extension associated
13996 with a language explicitly:
13999 @item set extension-language @var{ext} @var{language}
14000 @kindex set extension-language
14001 Tell @value{GDBN} that source files with extension @var{ext} are to be
14002 assumed as written in the source language @var{language}.
14004 @item info extensions
14005 @kindex info extensions
14006 List all the filename extensions and the associated languages.
14010 @section Type and Range Checking
14012 Some languages are designed to guard you against making seemingly common
14013 errors through a series of compile- and run-time checks. These include
14014 checking the type of arguments to functions and operators and making
14015 sure mathematical overflows are caught at run time. Checks such as
14016 these help to ensure a program's correctness once it has been compiled
14017 by eliminating type mismatches and providing active checks for range
14018 errors when your program is running.
14020 By default @value{GDBN} checks for these errors according to the
14021 rules of the current source language. Although @value{GDBN} does not check
14022 the statements in your program, it can check expressions entered directly
14023 into @value{GDBN} for evaluation via the @code{print} command, for example.
14026 * Type Checking:: An overview of type checking
14027 * Range Checking:: An overview of range checking
14030 @cindex type checking
14031 @cindex checks, type
14032 @node Type Checking
14033 @subsection An Overview of Type Checking
14035 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
14036 arguments to operators and functions have to be of the correct type,
14037 otherwise an error occurs. These checks prevent type mismatch
14038 errors from ever causing any run-time problems. For example,
14041 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
14043 (@value{GDBP}) print obj.my_method (0)
14046 (@value{GDBP}) print obj.my_method (0x1234)
14047 Cannot resolve method klass::my_method to any overloaded instance
14050 The second example fails because in C@t{++} the integer constant
14051 @samp{0x1234} is not type-compatible with the pointer parameter type.
14053 For the expressions you use in @value{GDBN} commands, you can tell
14054 @value{GDBN} to not enforce strict type checking or
14055 to treat any mismatches as errors and abandon the expression;
14056 When type checking is disabled, @value{GDBN} successfully evaluates
14057 expressions like the second example above.
14059 Even if type checking is off, there may be other reasons
14060 related to type that prevent @value{GDBN} from evaluating an expression.
14061 For instance, @value{GDBN} does not know how to add an @code{int} and
14062 a @code{struct foo}. These particular type errors have nothing to do
14063 with the language in use and usually arise from expressions which make
14064 little sense to evaluate anyway.
14066 @value{GDBN} provides some additional commands for controlling type checking:
14068 @kindex set check type
14069 @kindex show check type
14071 @item set check type on
14072 @itemx set check type off
14073 Set strict type checking on or off. If any type mismatches occur in
14074 evaluating an expression while type checking is on, @value{GDBN} prints a
14075 message and aborts evaluation of the expression.
14077 @item show check type
14078 Show the current setting of type checking and whether @value{GDBN}
14079 is enforcing strict type checking rules.
14082 @cindex range checking
14083 @cindex checks, range
14084 @node Range Checking
14085 @subsection An Overview of Range Checking
14087 In some languages (such as Modula-2), it is an error to exceed the
14088 bounds of a type; this is enforced with run-time checks. Such range
14089 checking is meant to ensure program correctness by making sure
14090 computations do not overflow, or indices on an array element access do
14091 not exceed the bounds of the array.
14093 For expressions you use in @value{GDBN} commands, you can tell
14094 @value{GDBN} to treat range errors in one of three ways: ignore them,
14095 always treat them as errors and abandon the expression, or issue
14096 warnings but evaluate the expression anyway.
14098 A range error can result from numerical overflow, from exceeding an
14099 array index bound, or when you type a constant that is not a member
14100 of any type. Some languages, however, do not treat overflows as an
14101 error. In many implementations of C, mathematical overflow causes the
14102 result to ``wrap around'' to lower values---for example, if @var{m} is
14103 the largest integer value, and @var{s} is the smallest, then
14106 @var{m} + 1 @result{} @var{s}
14109 This, too, is specific to individual languages, and in some cases
14110 specific to individual compilers or machines. @xref{Supported Languages, ,
14111 Supported Languages}, for further details on specific languages.
14113 @value{GDBN} provides some additional commands for controlling the range checker:
14115 @kindex set check range
14116 @kindex show check range
14118 @item set check range auto
14119 Set range checking on or off based on the current working language.
14120 @xref{Supported Languages, ,Supported Languages}, for the default settings for
14123 @item set check range on
14124 @itemx set check range off
14125 Set range checking on or off, overriding the default setting for the
14126 current working language. A warning is issued if the setting does not
14127 match the language default. If a range error occurs and range checking is on,
14128 then a message is printed and evaluation of the expression is aborted.
14130 @item set check range warn
14131 Output messages when the @value{GDBN} range checker detects a range error,
14132 but attempt to evaluate the expression anyway. Evaluating the
14133 expression may still be impossible for other reasons, such as accessing
14134 memory that the process does not own (a typical example from many Unix
14138 Show the current setting of the range checker, and whether or not it is
14139 being set automatically by @value{GDBN}.
14142 @node Supported Languages
14143 @section Supported Languages
14145 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
14146 OpenCL C, Pascal, assembly, Modula-2, and Ada.
14147 @c This is false ...
14148 Some @value{GDBN} features may be used in expressions regardless of the
14149 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
14150 and the @samp{@{type@}addr} construct (@pxref{Expressions,
14151 ,Expressions}) can be used with the constructs of any supported
14154 The following sections detail to what degree each source language is
14155 supported by @value{GDBN}. These sections are not meant to be language
14156 tutorials or references, but serve only as a reference guide to what the
14157 @value{GDBN} expression parser accepts, and what input and output
14158 formats should look like for different languages. There are many good
14159 books written on each of these languages; please look to these for a
14160 language reference or tutorial.
14163 * C:: C and C@t{++}
14166 * Objective-C:: Objective-C
14167 * OpenCL C:: OpenCL C
14168 * Fortran:: Fortran
14170 * Modula-2:: Modula-2
14175 @subsection C and C@t{++}
14177 @cindex C and C@t{++}
14178 @cindex expressions in C or C@t{++}
14180 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
14181 to both languages. Whenever this is the case, we discuss those languages
14185 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
14186 @cindex @sc{gnu} C@t{++}
14187 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
14188 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
14189 effectively, you must compile your C@t{++} programs with a supported
14190 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
14191 compiler (@code{aCC}).
14194 * C Operators:: C and C@t{++} operators
14195 * C Constants:: C and C@t{++} constants
14196 * C Plus Plus Expressions:: C@t{++} expressions
14197 * C Defaults:: Default settings for C and C@t{++}
14198 * C Checks:: C and C@t{++} type and range checks
14199 * Debugging C:: @value{GDBN} and C
14200 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
14201 * Decimal Floating Point:: Numbers in Decimal Floating Point format
14205 @subsubsection C and C@t{++} Operators
14207 @cindex C and C@t{++} operators
14209 Operators must be defined on values of specific types. For instance,
14210 @code{+} is defined on numbers, but not on structures. Operators are
14211 often defined on groups of types.
14213 For the purposes of C and C@t{++}, the following definitions hold:
14218 @emph{Integral types} include @code{int} with any of its storage-class
14219 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
14222 @emph{Floating-point types} include @code{float}, @code{double}, and
14223 @code{long double} (if supported by the target platform).
14226 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
14229 @emph{Scalar types} include all of the above.
14234 The following operators are supported. They are listed here
14235 in order of increasing precedence:
14239 The comma or sequencing operator. Expressions in a comma-separated list
14240 are evaluated from left to right, with the result of the entire
14241 expression being the last expression evaluated.
14244 Assignment. The value of an assignment expression is the value
14245 assigned. Defined on scalar types.
14248 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
14249 and translated to @w{@code{@var{a} = @var{a op b}}}.
14250 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
14251 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
14252 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
14255 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
14256 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
14257 should be of an integral type.
14260 Logical @sc{or}. Defined on integral types.
14263 Logical @sc{and}. Defined on integral types.
14266 Bitwise @sc{or}. Defined on integral types.
14269 Bitwise exclusive-@sc{or}. Defined on integral types.
14272 Bitwise @sc{and}. Defined on integral types.
14275 Equality and inequality. Defined on scalar types. The value of these
14276 expressions is 0 for false and non-zero for true.
14278 @item <@r{, }>@r{, }<=@r{, }>=
14279 Less than, greater than, less than or equal, greater than or equal.
14280 Defined on scalar types. The value of these expressions is 0 for false
14281 and non-zero for true.
14284 left shift, and right shift. Defined on integral types.
14287 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14290 Addition and subtraction. Defined on integral types, floating-point types and
14293 @item *@r{, }/@r{, }%
14294 Multiplication, division, and modulus. Multiplication and division are
14295 defined on integral and floating-point types. Modulus is defined on
14299 Increment and decrement. When appearing before a variable, the
14300 operation is performed before the variable is used in an expression;
14301 when appearing after it, the variable's value is used before the
14302 operation takes place.
14305 Pointer dereferencing. Defined on pointer types. Same precedence as
14309 Address operator. Defined on variables. Same precedence as @code{++}.
14311 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
14312 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
14313 to examine the address
14314 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
14318 Negative. Defined on integral and floating-point types. Same
14319 precedence as @code{++}.
14322 Logical negation. Defined on integral types. Same precedence as
14326 Bitwise complement operator. Defined on integral types. Same precedence as
14331 Structure member, and pointer-to-structure member. For convenience,
14332 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
14333 pointer based on the stored type information.
14334 Defined on @code{struct} and @code{union} data.
14337 Dereferences of pointers to members.
14340 Array indexing. @code{@var{a}[@var{i}]} is defined as
14341 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
14344 Function parameter list. Same precedence as @code{->}.
14347 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
14348 and @code{class} types.
14351 Doubled colons also represent the @value{GDBN} scope operator
14352 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
14356 If an operator is redefined in the user code, @value{GDBN} usually
14357 attempts to invoke the redefined version instead of using the operator's
14358 predefined meaning.
14361 @subsubsection C and C@t{++} Constants
14363 @cindex C and C@t{++} constants
14365 @value{GDBN} allows you to express the constants of C and C@t{++} in the
14370 Integer constants are a sequence of digits. Octal constants are
14371 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
14372 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
14373 @samp{l}, specifying that the constant should be treated as a
14377 Floating point constants are a sequence of digits, followed by a decimal
14378 point, followed by a sequence of digits, and optionally followed by an
14379 exponent. An exponent is of the form:
14380 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
14381 sequence of digits. The @samp{+} is optional for positive exponents.
14382 A floating-point constant may also end with a letter @samp{f} or
14383 @samp{F}, specifying that the constant should be treated as being of
14384 the @code{float} (as opposed to the default @code{double}) type; or with
14385 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
14389 Enumerated constants consist of enumerated identifiers, or their
14390 integral equivalents.
14393 Character constants are a single character surrounded by single quotes
14394 (@code{'}), or a number---the ordinal value of the corresponding character
14395 (usually its @sc{ascii} value). Within quotes, the single character may
14396 be represented by a letter or by @dfn{escape sequences}, which are of
14397 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
14398 of the character's ordinal value; or of the form @samp{\@var{x}}, where
14399 @samp{@var{x}} is a predefined special character---for example,
14400 @samp{\n} for newline.
14402 Wide character constants can be written by prefixing a character
14403 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
14404 form of @samp{x}. The target wide character set is used when
14405 computing the value of this constant (@pxref{Character Sets}).
14408 String constants are a sequence of character constants surrounded by
14409 double quotes (@code{"}). Any valid character constant (as described
14410 above) may appear. Double quotes within the string must be preceded by
14411 a backslash, so for instance @samp{"a\"b'c"} is a string of five
14414 Wide string constants can be written by prefixing a string constant
14415 with @samp{L}, as in C. The target wide character set is used when
14416 computing the value of this constant (@pxref{Character Sets}).
14419 Pointer constants are an integral value. You can also write pointers
14420 to constants using the C operator @samp{&}.
14423 Array constants are comma-separated lists surrounded by braces @samp{@{}
14424 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
14425 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
14426 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
14429 @node C Plus Plus Expressions
14430 @subsubsection C@t{++} Expressions
14432 @cindex expressions in C@t{++}
14433 @value{GDBN} expression handling can interpret most C@t{++} expressions.
14435 @cindex debugging C@t{++} programs
14436 @cindex C@t{++} compilers
14437 @cindex debug formats and C@t{++}
14438 @cindex @value{NGCC} and C@t{++}
14440 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
14441 the proper compiler and the proper debug format. Currently,
14442 @value{GDBN} works best when debugging C@t{++} code that is compiled
14443 with the most recent version of @value{NGCC} possible. The DWARF
14444 debugging format is preferred; @value{NGCC} defaults to this on most
14445 popular platforms. Other compilers and/or debug formats are likely to
14446 work badly or not at all when using @value{GDBN} to debug C@t{++}
14447 code. @xref{Compilation}.
14452 @cindex member functions
14454 Member function calls are allowed; you can use expressions like
14457 count = aml->GetOriginal(x, y)
14460 @vindex this@r{, inside C@t{++} member functions}
14461 @cindex namespace in C@t{++}
14463 While a member function is active (in the selected stack frame), your
14464 expressions have the same namespace available as the member function;
14465 that is, @value{GDBN} allows implicit references to the class instance
14466 pointer @code{this} following the same rules as C@t{++}. @code{using}
14467 declarations in the current scope are also respected by @value{GDBN}.
14469 @cindex call overloaded functions
14470 @cindex overloaded functions, calling
14471 @cindex type conversions in C@t{++}
14473 You can call overloaded functions; @value{GDBN} resolves the function
14474 call to the right definition, with some restrictions. @value{GDBN} does not
14475 perform overload resolution involving user-defined type conversions,
14476 calls to constructors, or instantiations of templates that do not exist
14477 in the program. It also cannot handle ellipsis argument lists or
14480 It does perform integral conversions and promotions, floating-point
14481 promotions, arithmetic conversions, pointer conversions, conversions of
14482 class objects to base classes, and standard conversions such as those of
14483 functions or arrays to pointers; it requires an exact match on the
14484 number of function arguments.
14486 Overload resolution is always performed, unless you have specified
14487 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
14488 ,@value{GDBN} Features for C@t{++}}.
14490 You must specify @code{set overload-resolution off} in order to use an
14491 explicit function signature to call an overloaded function, as in
14493 p 'foo(char,int)'('x', 13)
14496 The @value{GDBN} command-completion facility can simplify this;
14497 see @ref{Completion, ,Command Completion}.
14499 @cindex reference declarations
14501 @value{GDBN} understands variables declared as C@t{++} references; you can use
14502 them in expressions just as you do in C@t{++} source---they are automatically
14505 In the parameter list shown when @value{GDBN} displays a frame, the values of
14506 reference variables are not displayed (unlike other variables); this
14507 avoids clutter, since references are often used for large structures.
14508 The @emph{address} of a reference variable is always shown, unless
14509 you have specified @samp{set print address off}.
14512 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
14513 expressions can use it just as expressions in your program do. Since
14514 one scope may be defined in another, you can use @code{::} repeatedly if
14515 necessary, for example in an expression like
14516 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
14517 resolving name scope by reference to source files, in both C and C@t{++}
14518 debugging (@pxref{Variables, ,Program Variables}).
14521 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
14526 @subsubsection C and C@t{++} Defaults
14528 @cindex C and C@t{++} defaults
14530 If you allow @value{GDBN} to set range checking automatically, it
14531 defaults to @code{off} whenever the working language changes to
14532 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
14533 selects the working language.
14535 If you allow @value{GDBN} to set the language automatically, it
14536 recognizes source files whose names end with @file{.c}, @file{.C}, or
14537 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
14538 these files, it sets the working language to C or C@t{++}.
14539 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
14540 for further details.
14543 @subsubsection C and C@t{++} Type and Range Checks
14545 @cindex C and C@t{++} checks
14547 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
14548 checking is used. However, if you turn type checking off, @value{GDBN}
14549 will allow certain non-standard conversions, such as promoting integer
14550 constants to pointers.
14552 Range checking, if turned on, is done on mathematical operations. Array
14553 indices are not checked, since they are often used to index a pointer
14554 that is not itself an array.
14557 @subsubsection @value{GDBN} and C
14559 The @code{set print union} and @code{show print union} commands apply to
14560 the @code{union} type. When set to @samp{on}, any @code{union} that is
14561 inside a @code{struct} or @code{class} is also printed. Otherwise, it
14562 appears as @samp{@{...@}}.
14564 The @code{@@} operator aids in the debugging of dynamic arrays, formed
14565 with pointers and a memory allocation function. @xref{Expressions,
14568 @node Debugging C Plus Plus
14569 @subsubsection @value{GDBN} Features for C@t{++}
14571 @cindex commands for C@t{++}
14573 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
14574 designed specifically for use with C@t{++}. Here is a summary:
14577 @cindex break in overloaded functions
14578 @item @r{breakpoint menus}
14579 When you want a breakpoint in a function whose name is overloaded,
14580 @value{GDBN} has the capability to display a menu of possible breakpoint
14581 locations to help you specify which function definition you want.
14582 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
14584 @cindex overloading in C@t{++}
14585 @item rbreak @var{regex}
14586 Setting breakpoints using regular expressions is helpful for setting
14587 breakpoints on overloaded functions that are not members of any special
14589 @xref{Set Breaks, ,Setting Breakpoints}.
14591 @cindex C@t{++} exception handling
14593 @itemx catch rethrow
14595 Debug C@t{++} exception handling using these commands. @xref{Set
14596 Catchpoints, , Setting Catchpoints}.
14598 @cindex inheritance
14599 @item ptype @var{typename}
14600 Print inheritance relationships as well as other information for type
14602 @xref{Symbols, ,Examining the Symbol Table}.
14604 @item info vtbl @var{expression}.
14605 The @code{info vtbl} command can be used to display the virtual
14606 method tables of the object computed by @var{expression}. This shows
14607 one entry per virtual table; there may be multiple virtual tables when
14608 multiple inheritance is in use.
14610 @cindex C@t{++} demangling
14611 @item demangle @var{name}
14612 Demangle @var{name}.
14613 @xref{Symbols}, for a more complete description of the @code{demangle} command.
14615 @cindex C@t{++} symbol display
14616 @item set print demangle
14617 @itemx show print demangle
14618 @itemx set print asm-demangle
14619 @itemx show print asm-demangle
14620 Control whether C@t{++} symbols display in their source form, both when
14621 displaying code as C@t{++} source and when displaying disassemblies.
14622 @xref{Print Settings, ,Print Settings}.
14624 @item set print object
14625 @itemx show print object
14626 Choose whether to print derived (actual) or declared types of objects.
14627 @xref{Print Settings, ,Print Settings}.
14629 @item set print vtbl
14630 @itemx show print vtbl
14631 Control the format for printing virtual function tables.
14632 @xref{Print Settings, ,Print Settings}.
14633 (The @code{vtbl} commands do not work on programs compiled with the HP
14634 ANSI C@t{++} compiler (@code{aCC}).)
14636 @kindex set overload-resolution
14637 @cindex overloaded functions, overload resolution
14638 @item set overload-resolution on
14639 Enable overload resolution for C@t{++} expression evaluation. The default
14640 is on. For overloaded functions, @value{GDBN} evaluates the arguments
14641 and searches for a function whose signature matches the argument types,
14642 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
14643 Expressions, ,C@t{++} Expressions}, for details).
14644 If it cannot find a match, it emits a message.
14646 @item set overload-resolution off
14647 Disable overload resolution for C@t{++} expression evaluation. For
14648 overloaded functions that are not class member functions, @value{GDBN}
14649 chooses the first function of the specified name that it finds in the
14650 symbol table, whether or not its arguments are of the correct type. For
14651 overloaded functions that are class member functions, @value{GDBN}
14652 searches for a function whose signature @emph{exactly} matches the
14655 @kindex show overload-resolution
14656 @item show overload-resolution
14657 Show the current setting of overload resolution.
14659 @item @r{Overloaded symbol names}
14660 You can specify a particular definition of an overloaded symbol, using
14661 the same notation that is used to declare such symbols in C@t{++}: type
14662 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
14663 also use the @value{GDBN} command-line word completion facilities to list the
14664 available choices, or to finish the type list for you.
14665 @xref{Completion,, Command Completion}, for details on how to do this.
14668 @node Decimal Floating Point
14669 @subsubsection Decimal Floating Point format
14670 @cindex decimal floating point format
14672 @value{GDBN} can examine, set and perform computations with numbers in
14673 decimal floating point format, which in the C language correspond to the
14674 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
14675 specified by the extension to support decimal floating-point arithmetic.
14677 There are two encodings in use, depending on the architecture: BID (Binary
14678 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
14679 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
14682 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
14683 to manipulate decimal floating point numbers, it is not possible to convert
14684 (using a cast, for example) integers wider than 32-bit to decimal float.
14686 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
14687 point computations, error checking in decimal float operations ignores
14688 underflow, overflow and divide by zero exceptions.
14690 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
14691 to inspect @code{_Decimal128} values stored in floating point registers.
14692 See @ref{PowerPC,,PowerPC} for more details.
14698 @value{GDBN} can be used to debug programs written in D and compiled with
14699 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
14700 specific feature --- dynamic arrays.
14705 @cindex Go (programming language)
14706 @value{GDBN} can be used to debug programs written in Go and compiled with
14707 @file{gccgo} or @file{6g} compilers.
14709 Here is a summary of the Go-specific features and restrictions:
14712 @cindex current Go package
14713 @item The current Go package
14714 The name of the current package does not need to be specified when
14715 specifying global variables and functions.
14717 For example, given the program:
14721 var myglob = "Shall we?"
14727 When stopped inside @code{main} either of these work:
14731 (gdb) p main.myglob
14734 @cindex builtin Go types
14735 @item Builtin Go types
14736 The @code{string} type is recognized by @value{GDBN} and is printed
14739 @cindex builtin Go functions
14740 @item Builtin Go functions
14741 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
14742 function and handles it internally.
14744 @cindex restrictions on Go expressions
14745 @item Restrictions on Go expressions
14746 All Go operators are supported except @code{&^}.
14747 The Go @code{_} ``blank identifier'' is not supported.
14748 Automatic dereferencing of pointers is not supported.
14752 @subsection Objective-C
14754 @cindex Objective-C
14755 This section provides information about some commands and command
14756 options that are useful for debugging Objective-C code. See also
14757 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
14758 few more commands specific to Objective-C support.
14761 * Method Names in Commands::
14762 * The Print Command with Objective-C::
14765 @node Method Names in Commands
14766 @subsubsection Method Names in Commands
14768 The following commands have been extended to accept Objective-C method
14769 names as line specifications:
14771 @kindex clear@r{, and Objective-C}
14772 @kindex break@r{, and Objective-C}
14773 @kindex info line@r{, and Objective-C}
14774 @kindex jump@r{, and Objective-C}
14775 @kindex list@r{, and Objective-C}
14779 @item @code{info line}
14784 A fully qualified Objective-C method name is specified as
14787 -[@var{Class} @var{methodName}]
14790 where the minus sign is used to indicate an instance method and a
14791 plus sign (not shown) is used to indicate a class method. The class
14792 name @var{Class} and method name @var{methodName} are enclosed in
14793 brackets, similar to the way messages are specified in Objective-C
14794 source code. For example, to set a breakpoint at the @code{create}
14795 instance method of class @code{Fruit} in the program currently being
14799 break -[Fruit create]
14802 To list ten program lines around the @code{initialize} class method,
14806 list +[NSText initialize]
14809 In the current version of @value{GDBN}, the plus or minus sign is
14810 required. In future versions of @value{GDBN}, the plus or minus
14811 sign will be optional, but you can use it to narrow the search. It
14812 is also possible to specify just a method name:
14818 You must specify the complete method name, including any colons. If
14819 your program's source files contain more than one @code{create} method,
14820 you'll be presented with a numbered list of classes that implement that
14821 method. Indicate your choice by number, or type @samp{0} to exit if
14824 As another example, to clear a breakpoint established at the
14825 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
14828 clear -[NSWindow makeKeyAndOrderFront:]
14831 @node The Print Command with Objective-C
14832 @subsubsection The Print Command With Objective-C
14833 @cindex Objective-C, print objects
14834 @kindex print-object
14835 @kindex po @r{(@code{print-object})}
14837 The print command has also been extended to accept methods. For example:
14840 print -[@var{object} hash]
14843 @cindex print an Objective-C object description
14844 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
14846 will tell @value{GDBN} to send the @code{hash} message to @var{object}
14847 and print the result. Also, an additional command has been added,
14848 @code{print-object} or @code{po} for short, which is meant to print
14849 the description of an object. However, this command may only work
14850 with certain Objective-C libraries that have a particular hook
14851 function, @code{_NSPrintForDebugger}, defined.
14854 @subsection OpenCL C
14857 This section provides information about @value{GDBN}s OpenCL C support.
14860 * OpenCL C Datatypes::
14861 * OpenCL C Expressions::
14862 * OpenCL C Operators::
14865 @node OpenCL C Datatypes
14866 @subsubsection OpenCL C Datatypes
14868 @cindex OpenCL C Datatypes
14869 @value{GDBN} supports the builtin scalar and vector datatypes specified
14870 by OpenCL 1.1. In addition the half- and double-precision floating point
14871 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
14872 extensions are also known to @value{GDBN}.
14874 @node OpenCL C Expressions
14875 @subsubsection OpenCL C Expressions
14877 @cindex OpenCL C Expressions
14878 @value{GDBN} supports accesses to vector components including the access as
14879 lvalue where possible. Since OpenCL C is based on C99 most C expressions
14880 supported by @value{GDBN} can be used as well.
14882 @node OpenCL C Operators
14883 @subsubsection OpenCL C Operators
14885 @cindex OpenCL C Operators
14886 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
14890 @subsection Fortran
14891 @cindex Fortran-specific support in @value{GDBN}
14893 @value{GDBN} can be used to debug programs written in Fortran, but it
14894 currently supports only the features of Fortran 77 language.
14896 @cindex trailing underscore, in Fortran symbols
14897 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
14898 among them) append an underscore to the names of variables and
14899 functions. When you debug programs compiled by those compilers, you
14900 will need to refer to variables and functions with a trailing
14904 * Fortran Operators:: Fortran operators and expressions
14905 * Fortran Defaults:: Default settings for Fortran
14906 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
14909 @node Fortran Operators
14910 @subsubsection Fortran Operators and Expressions
14912 @cindex Fortran operators and expressions
14914 Operators must be defined on values of specific types. For instance,
14915 @code{+} is defined on numbers, but not on characters or other non-
14916 arithmetic types. Operators are often defined on groups of types.
14920 The exponentiation operator. It raises the first operand to the power
14924 The range operator. Normally used in the form of array(low:high) to
14925 represent a section of array.
14928 The access component operator. Normally used to access elements in derived
14929 types. Also suitable for unions. As unions aren't part of regular Fortran,
14930 this can only happen when accessing a register that uses a gdbarch-defined
14934 @node Fortran Defaults
14935 @subsubsection Fortran Defaults
14937 @cindex Fortran Defaults
14939 Fortran symbols are usually case-insensitive, so @value{GDBN} by
14940 default uses case-insensitive matches for Fortran symbols. You can
14941 change that with the @samp{set case-insensitive} command, see
14942 @ref{Symbols}, for the details.
14944 @node Special Fortran Commands
14945 @subsubsection Special Fortran Commands
14947 @cindex Special Fortran commands
14949 @value{GDBN} has some commands to support Fortran-specific features,
14950 such as displaying common blocks.
14953 @cindex @code{COMMON} blocks, Fortran
14954 @kindex info common
14955 @item info common @r{[}@var{common-name}@r{]}
14956 This command prints the values contained in the Fortran @code{COMMON}
14957 block whose name is @var{common-name}. With no argument, the names of
14958 all @code{COMMON} blocks visible at the current program location are
14965 @cindex Pascal support in @value{GDBN}, limitations
14966 Debugging Pascal programs which use sets, subranges, file variables, or
14967 nested functions does not currently work. @value{GDBN} does not support
14968 entering expressions, printing values, or similar features using Pascal
14971 The Pascal-specific command @code{set print pascal_static-members}
14972 controls whether static members of Pascal objects are displayed.
14973 @xref{Print Settings, pascal_static-members}.
14976 @subsection Modula-2
14978 @cindex Modula-2, @value{GDBN} support
14980 The extensions made to @value{GDBN} to support Modula-2 only support
14981 output from the @sc{gnu} Modula-2 compiler (which is currently being
14982 developed). Other Modula-2 compilers are not currently supported, and
14983 attempting to debug executables produced by them is most likely
14984 to give an error as @value{GDBN} reads in the executable's symbol
14987 @cindex expressions in Modula-2
14989 * M2 Operators:: Built-in operators
14990 * Built-In Func/Proc:: Built-in functions and procedures
14991 * M2 Constants:: Modula-2 constants
14992 * M2 Types:: Modula-2 types
14993 * M2 Defaults:: Default settings for Modula-2
14994 * Deviations:: Deviations from standard Modula-2
14995 * M2 Checks:: Modula-2 type and range checks
14996 * M2 Scope:: The scope operators @code{::} and @code{.}
14997 * GDB/M2:: @value{GDBN} and Modula-2
15001 @subsubsection Operators
15002 @cindex Modula-2 operators
15004 Operators must be defined on values of specific types. For instance,
15005 @code{+} is defined on numbers, but not on structures. Operators are
15006 often defined on groups of types. For the purposes of Modula-2, the
15007 following definitions hold:
15012 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
15016 @emph{Character types} consist of @code{CHAR} and its subranges.
15019 @emph{Floating-point types} consist of @code{REAL}.
15022 @emph{Pointer types} consist of anything declared as @code{POINTER TO
15026 @emph{Scalar types} consist of all of the above.
15029 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
15032 @emph{Boolean types} consist of @code{BOOLEAN}.
15036 The following operators are supported, and appear in order of
15037 increasing precedence:
15041 Function argument or array index separator.
15044 Assignment. The value of @var{var} @code{:=} @var{value} is
15048 Less than, greater than on integral, floating-point, or enumerated
15052 Less than or equal to, greater than or equal to
15053 on integral, floating-point and enumerated types, or set inclusion on
15054 set types. Same precedence as @code{<}.
15056 @item =@r{, }<>@r{, }#
15057 Equality and two ways of expressing inequality, valid on scalar types.
15058 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
15059 available for inequality, since @code{#} conflicts with the script
15063 Set membership. Defined on set types and the types of their members.
15064 Same precedence as @code{<}.
15067 Boolean disjunction. Defined on boolean types.
15070 Boolean conjunction. Defined on boolean types.
15073 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
15076 Addition and subtraction on integral and floating-point types, or union
15077 and difference on set types.
15080 Multiplication on integral and floating-point types, or set intersection
15084 Division on floating-point types, or symmetric set difference on set
15085 types. Same precedence as @code{*}.
15088 Integer division and remainder. Defined on integral types. Same
15089 precedence as @code{*}.
15092 Negative. Defined on @code{INTEGER} and @code{REAL} data.
15095 Pointer dereferencing. Defined on pointer types.
15098 Boolean negation. Defined on boolean types. Same precedence as
15102 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
15103 precedence as @code{^}.
15106 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
15109 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
15113 @value{GDBN} and Modula-2 scope operators.
15117 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
15118 treats the use of the operator @code{IN}, or the use of operators
15119 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
15120 @code{<=}, and @code{>=} on sets as an error.
15124 @node Built-In Func/Proc
15125 @subsubsection Built-in Functions and Procedures
15126 @cindex Modula-2 built-ins
15128 Modula-2 also makes available several built-in procedures and functions.
15129 In describing these, the following metavariables are used:
15134 represents an @code{ARRAY} variable.
15137 represents a @code{CHAR} constant or variable.
15140 represents a variable or constant of integral type.
15143 represents an identifier that belongs to a set. Generally used in the
15144 same function with the metavariable @var{s}. The type of @var{s} should
15145 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
15148 represents a variable or constant of integral or floating-point type.
15151 represents a variable or constant of floating-point type.
15157 represents a variable.
15160 represents a variable or constant of one of many types. See the
15161 explanation of the function for details.
15164 All Modula-2 built-in procedures also return a result, described below.
15168 Returns the absolute value of @var{n}.
15171 If @var{c} is a lower case letter, it returns its upper case
15172 equivalent, otherwise it returns its argument.
15175 Returns the character whose ordinal value is @var{i}.
15178 Decrements the value in the variable @var{v} by one. Returns the new value.
15180 @item DEC(@var{v},@var{i})
15181 Decrements the value in the variable @var{v} by @var{i}. Returns the
15184 @item EXCL(@var{m},@var{s})
15185 Removes the element @var{m} from the set @var{s}. Returns the new
15188 @item FLOAT(@var{i})
15189 Returns the floating point equivalent of the integer @var{i}.
15191 @item HIGH(@var{a})
15192 Returns the index of the last member of @var{a}.
15195 Increments the value in the variable @var{v} by one. Returns the new value.
15197 @item INC(@var{v},@var{i})
15198 Increments the value in the variable @var{v} by @var{i}. Returns the
15201 @item INCL(@var{m},@var{s})
15202 Adds the element @var{m} to the set @var{s} if it is not already
15203 there. Returns the new set.
15206 Returns the maximum value of the type @var{t}.
15209 Returns the minimum value of the type @var{t}.
15212 Returns boolean TRUE if @var{i} is an odd number.
15215 Returns the ordinal value of its argument. For example, the ordinal
15216 value of a character is its @sc{ascii} value (on machines supporting
15217 the @sc{ascii} character set). The argument @var{x} must be of an
15218 ordered type, which include integral, character and enumerated types.
15220 @item SIZE(@var{x})
15221 Returns the size of its argument. The argument @var{x} can be a
15222 variable or a type.
15224 @item TRUNC(@var{r})
15225 Returns the integral part of @var{r}.
15227 @item TSIZE(@var{x})
15228 Returns the size of its argument. The argument @var{x} can be a
15229 variable or a type.
15231 @item VAL(@var{t},@var{i})
15232 Returns the member of the type @var{t} whose ordinal value is @var{i}.
15236 @emph{Warning:} Sets and their operations are not yet supported, so
15237 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
15241 @cindex Modula-2 constants
15243 @subsubsection Constants
15245 @value{GDBN} allows you to express the constants of Modula-2 in the following
15251 Integer constants are simply a sequence of digits. When used in an
15252 expression, a constant is interpreted to be type-compatible with the
15253 rest of the expression. Hexadecimal integers are specified by a
15254 trailing @samp{H}, and octal integers by a trailing @samp{B}.
15257 Floating point constants appear as a sequence of digits, followed by a
15258 decimal point and another sequence of digits. An optional exponent can
15259 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
15260 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
15261 digits of the floating point constant must be valid decimal (base 10)
15265 Character constants consist of a single character enclosed by a pair of
15266 like quotes, either single (@code{'}) or double (@code{"}). They may
15267 also be expressed by their ordinal value (their @sc{ascii} value, usually)
15268 followed by a @samp{C}.
15271 String constants consist of a sequence of characters enclosed by a
15272 pair of like quotes, either single (@code{'}) or double (@code{"}).
15273 Escape sequences in the style of C are also allowed. @xref{C
15274 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
15278 Enumerated constants consist of an enumerated identifier.
15281 Boolean constants consist of the identifiers @code{TRUE} and
15285 Pointer constants consist of integral values only.
15288 Set constants are not yet supported.
15292 @subsubsection Modula-2 Types
15293 @cindex Modula-2 types
15295 Currently @value{GDBN} can print the following data types in Modula-2
15296 syntax: array types, record types, set types, pointer types, procedure
15297 types, enumerated types, subrange types and base types. You can also
15298 print the contents of variables declared using these type.
15299 This section gives a number of simple source code examples together with
15300 sample @value{GDBN} sessions.
15302 The first example contains the following section of code:
15311 and you can request @value{GDBN} to interrogate the type and value of
15312 @code{r} and @code{s}.
15315 (@value{GDBP}) print s
15317 (@value{GDBP}) ptype s
15319 (@value{GDBP}) print r
15321 (@value{GDBP}) ptype r
15326 Likewise if your source code declares @code{s} as:
15330 s: SET ['A'..'Z'] ;
15334 then you may query the type of @code{s} by:
15337 (@value{GDBP}) ptype s
15338 type = SET ['A'..'Z']
15342 Note that at present you cannot interactively manipulate set
15343 expressions using the debugger.
15345 The following example shows how you might declare an array in Modula-2
15346 and how you can interact with @value{GDBN} to print its type and contents:
15350 s: ARRAY [-10..10] OF CHAR ;
15354 (@value{GDBP}) ptype s
15355 ARRAY [-10..10] OF CHAR
15358 Note that the array handling is not yet complete and although the type
15359 is printed correctly, expression handling still assumes that all
15360 arrays have a lower bound of zero and not @code{-10} as in the example
15363 Here are some more type related Modula-2 examples:
15367 colour = (blue, red, yellow, green) ;
15368 t = [blue..yellow] ;
15376 The @value{GDBN} interaction shows how you can query the data type
15377 and value of a variable.
15380 (@value{GDBP}) print s
15382 (@value{GDBP}) ptype t
15383 type = [blue..yellow]
15387 In this example a Modula-2 array is declared and its contents
15388 displayed. Observe that the contents are written in the same way as
15389 their @code{C} counterparts.
15393 s: ARRAY [1..5] OF CARDINAL ;
15399 (@value{GDBP}) print s
15400 $1 = @{1, 0, 0, 0, 0@}
15401 (@value{GDBP}) ptype s
15402 type = ARRAY [1..5] OF CARDINAL
15405 The Modula-2 language interface to @value{GDBN} also understands
15406 pointer types as shown in this example:
15410 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
15417 and you can request that @value{GDBN} describes the type of @code{s}.
15420 (@value{GDBP}) ptype s
15421 type = POINTER TO ARRAY [1..5] OF CARDINAL
15424 @value{GDBN} handles compound types as we can see in this example.
15425 Here we combine array types, record types, pointer types and subrange
15436 myarray = ARRAY myrange OF CARDINAL ;
15437 myrange = [-2..2] ;
15439 s: POINTER TO ARRAY myrange OF foo ;
15443 and you can ask @value{GDBN} to describe the type of @code{s} as shown
15447 (@value{GDBP}) ptype s
15448 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
15451 f3 : ARRAY [-2..2] OF CARDINAL;
15456 @subsubsection Modula-2 Defaults
15457 @cindex Modula-2 defaults
15459 If type and range checking are set automatically by @value{GDBN}, they
15460 both default to @code{on} whenever the working language changes to
15461 Modula-2. This happens regardless of whether you or @value{GDBN}
15462 selected the working language.
15464 If you allow @value{GDBN} to set the language automatically, then entering
15465 code compiled from a file whose name ends with @file{.mod} sets the
15466 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
15467 Infer the Source Language}, for further details.
15470 @subsubsection Deviations from Standard Modula-2
15471 @cindex Modula-2, deviations from
15473 A few changes have been made to make Modula-2 programs easier to debug.
15474 This is done primarily via loosening its type strictness:
15478 Unlike in standard Modula-2, pointer constants can be formed by
15479 integers. This allows you to modify pointer variables during
15480 debugging. (In standard Modula-2, the actual address contained in a
15481 pointer variable is hidden from you; it can only be modified
15482 through direct assignment to another pointer variable or expression that
15483 returned a pointer.)
15486 C escape sequences can be used in strings and characters to represent
15487 non-printable characters. @value{GDBN} prints out strings with these
15488 escape sequences embedded. Single non-printable characters are
15489 printed using the @samp{CHR(@var{nnn})} format.
15492 The assignment operator (@code{:=}) returns the value of its right-hand
15496 All built-in procedures both modify @emph{and} return their argument.
15500 @subsubsection Modula-2 Type and Range Checks
15501 @cindex Modula-2 checks
15504 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
15507 @c FIXME remove warning when type/range checks added
15509 @value{GDBN} considers two Modula-2 variables type equivalent if:
15513 They are of types that have been declared equivalent via a @code{TYPE
15514 @var{t1} = @var{t2}} statement
15517 They have been declared on the same line. (Note: This is true of the
15518 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
15521 As long as type checking is enabled, any attempt to combine variables
15522 whose types are not equivalent is an error.
15524 Range checking is done on all mathematical operations, assignment, array
15525 index bounds, and all built-in functions and procedures.
15528 @subsubsection The Scope Operators @code{::} and @code{.}
15530 @cindex @code{.}, Modula-2 scope operator
15531 @cindex colon, doubled as scope operator
15533 @vindex colon-colon@r{, in Modula-2}
15534 @c Info cannot handle :: but TeX can.
15537 @vindex ::@r{, in Modula-2}
15540 There are a few subtle differences between the Modula-2 scope operator
15541 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
15546 @var{module} . @var{id}
15547 @var{scope} :: @var{id}
15551 where @var{scope} is the name of a module or a procedure,
15552 @var{module} the name of a module, and @var{id} is any declared
15553 identifier within your program, except another module.
15555 Using the @code{::} operator makes @value{GDBN} search the scope
15556 specified by @var{scope} for the identifier @var{id}. If it is not
15557 found in the specified scope, then @value{GDBN} searches all scopes
15558 enclosing the one specified by @var{scope}.
15560 Using the @code{.} operator makes @value{GDBN} search the current scope for
15561 the identifier specified by @var{id} that was imported from the
15562 definition module specified by @var{module}. With this operator, it is
15563 an error if the identifier @var{id} was not imported from definition
15564 module @var{module}, or if @var{id} is not an identifier in
15568 @subsubsection @value{GDBN} and Modula-2
15570 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
15571 Five subcommands of @code{set print} and @code{show print} apply
15572 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
15573 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
15574 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
15575 analogue in Modula-2.
15577 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
15578 with any language, is not useful with Modula-2. Its
15579 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
15580 created in Modula-2 as they can in C or C@t{++}. However, because an
15581 address can be specified by an integral constant, the construct
15582 @samp{@{@var{type}@}@var{adrexp}} is still useful.
15584 @cindex @code{#} in Modula-2
15585 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
15586 interpreted as the beginning of a comment. Use @code{<>} instead.
15592 The extensions made to @value{GDBN} for Ada only support
15593 output from the @sc{gnu} Ada (GNAT) compiler.
15594 Other Ada compilers are not currently supported, and
15595 attempting to debug executables produced by them is most likely
15599 @cindex expressions in Ada
15601 * Ada Mode Intro:: General remarks on the Ada syntax
15602 and semantics supported by Ada mode
15604 * Omissions from Ada:: Restrictions on the Ada expression syntax.
15605 * Additions to Ada:: Extensions of the Ada expression syntax.
15606 * Stopping Before Main Program:: Debugging the program during elaboration.
15607 * Ada Exceptions:: Ada Exceptions
15608 * Ada Tasks:: Listing and setting breakpoints in tasks.
15609 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
15610 * Ravenscar Profile:: Tasking Support when using the Ravenscar
15612 * Ada Glitches:: Known peculiarities of Ada mode.
15615 @node Ada Mode Intro
15616 @subsubsection Introduction
15617 @cindex Ada mode, general
15619 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
15620 syntax, with some extensions.
15621 The philosophy behind the design of this subset is
15625 That @value{GDBN} should provide basic literals and access to operations for
15626 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
15627 leaving more sophisticated computations to subprograms written into the
15628 program (which therefore may be called from @value{GDBN}).
15631 That type safety and strict adherence to Ada language restrictions
15632 are not particularly important to the @value{GDBN} user.
15635 That brevity is important to the @value{GDBN} user.
15638 Thus, for brevity, the debugger acts as if all names declared in
15639 user-written packages are directly visible, even if they are not visible
15640 according to Ada rules, thus making it unnecessary to fully qualify most
15641 names with their packages, regardless of context. Where this causes
15642 ambiguity, @value{GDBN} asks the user's intent.
15644 The debugger will start in Ada mode if it detects an Ada main program.
15645 As for other languages, it will enter Ada mode when stopped in a program that
15646 was translated from an Ada source file.
15648 While in Ada mode, you may use `@t{--}' for comments. This is useful
15649 mostly for documenting command files. The standard @value{GDBN} comment
15650 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
15651 middle (to allow based literals).
15653 The debugger supports limited overloading. Given a subprogram call in which
15654 the function symbol has multiple definitions, it will use the number of
15655 actual parameters and some information about their types to attempt to narrow
15656 the set of definitions. It also makes very limited use of context, preferring
15657 procedures to functions in the context of the @code{call} command, and
15658 functions to procedures elsewhere.
15660 @node Omissions from Ada
15661 @subsubsection Omissions from Ada
15662 @cindex Ada, omissions from
15664 Here are the notable omissions from the subset:
15668 Only a subset of the attributes are supported:
15672 @t{'First}, @t{'Last}, and @t{'Length}
15673 on array objects (not on types and subtypes).
15676 @t{'Min} and @t{'Max}.
15679 @t{'Pos} and @t{'Val}.
15685 @t{'Range} on array objects (not subtypes), but only as the right
15686 operand of the membership (@code{in}) operator.
15689 @t{'Access}, @t{'Unchecked_Access}, and
15690 @t{'Unrestricted_Access} (a GNAT extension).
15698 @code{Characters.Latin_1} are not available and
15699 concatenation is not implemented. Thus, escape characters in strings are
15700 not currently available.
15703 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
15704 equality of representations. They will generally work correctly
15705 for strings and arrays whose elements have integer or enumeration types.
15706 They may not work correctly for arrays whose element
15707 types have user-defined equality, for arrays of real values
15708 (in particular, IEEE-conformant floating point, because of negative
15709 zeroes and NaNs), and for arrays whose elements contain unused bits with
15710 indeterminate values.
15713 The other component-by-component array operations (@code{and}, @code{or},
15714 @code{xor}, @code{not}, and relational tests other than equality)
15715 are not implemented.
15718 @cindex array aggregates (Ada)
15719 @cindex record aggregates (Ada)
15720 @cindex aggregates (Ada)
15721 There is limited support for array and record aggregates. They are
15722 permitted only on the right sides of assignments, as in these examples:
15725 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
15726 (@value{GDBP}) set An_Array := (1, others => 0)
15727 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
15728 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
15729 (@value{GDBP}) set A_Record := (1, "Peter", True);
15730 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
15734 discriminant's value by assigning an aggregate has an
15735 undefined effect if that discriminant is used within the record.
15736 However, you can first modify discriminants by directly assigning to
15737 them (which normally would not be allowed in Ada), and then performing an
15738 aggregate assignment. For example, given a variable @code{A_Rec}
15739 declared to have a type such as:
15742 type Rec (Len : Small_Integer := 0) is record
15744 Vals : IntArray (1 .. Len);
15748 you can assign a value with a different size of @code{Vals} with two
15752 (@value{GDBP}) set A_Rec.Len := 4
15753 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
15756 As this example also illustrates, @value{GDBN} is very loose about the usual
15757 rules concerning aggregates. You may leave out some of the
15758 components of an array or record aggregate (such as the @code{Len}
15759 component in the assignment to @code{A_Rec} above); they will retain their
15760 original values upon assignment. You may freely use dynamic values as
15761 indices in component associations. You may even use overlapping or
15762 redundant component associations, although which component values are
15763 assigned in such cases is not defined.
15766 Calls to dispatching subprograms are not implemented.
15769 The overloading algorithm is much more limited (i.e., less selective)
15770 than that of real Ada. It makes only limited use of the context in
15771 which a subexpression appears to resolve its meaning, and it is much
15772 looser in its rules for allowing type matches. As a result, some
15773 function calls will be ambiguous, and the user will be asked to choose
15774 the proper resolution.
15777 The @code{new} operator is not implemented.
15780 Entry calls are not implemented.
15783 Aside from printing, arithmetic operations on the native VAX floating-point
15784 formats are not supported.
15787 It is not possible to slice a packed array.
15790 The names @code{True} and @code{False}, when not part of a qualified name,
15791 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
15793 Should your program
15794 redefine these names in a package or procedure (at best a dubious practice),
15795 you will have to use fully qualified names to access their new definitions.
15798 @node Additions to Ada
15799 @subsubsection Additions to Ada
15800 @cindex Ada, deviations from
15802 As it does for other languages, @value{GDBN} makes certain generic
15803 extensions to Ada (@pxref{Expressions}):
15807 If the expression @var{E} is a variable residing in memory (typically
15808 a local variable or array element) and @var{N} is a positive integer,
15809 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
15810 @var{N}-1 adjacent variables following it in memory as an array. In
15811 Ada, this operator is generally not necessary, since its prime use is
15812 in displaying parts of an array, and slicing will usually do this in
15813 Ada. However, there are occasional uses when debugging programs in
15814 which certain debugging information has been optimized away.
15817 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
15818 appears in function or file @var{B}.'' When @var{B} is a file name,
15819 you must typically surround it in single quotes.
15822 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
15823 @var{type} that appears at address @var{addr}.''
15826 A name starting with @samp{$} is a convenience variable
15827 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
15830 In addition, @value{GDBN} provides a few other shortcuts and outright
15831 additions specific to Ada:
15835 The assignment statement is allowed as an expression, returning
15836 its right-hand operand as its value. Thus, you may enter
15839 (@value{GDBP}) set x := y + 3
15840 (@value{GDBP}) print A(tmp := y + 1)
15844 The semicolon is allowed as an ``operator,'' returning as its value
15845 the value of its right-hand operand.
15846 This allows, for example,
15847 complex conditional breaks:
15850 (@value{GDBP}) break f
15851 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
15855 Rather than use catenation and symbolic character names to introduce special
15856 characters into strings, one may instead use a special bracket notation,
15857 which is also used to print strings. A sequence of characters of the form
15858 @samp{["@var{XX}"]} within a string or character literal denotes the
15859 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
15860 sequence of characters @samp{["""]} also denotes a single quotation mark
15861 in strings. For example,
15863 "One line.["0a"]Next line.["0a"]"
15866 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
15870 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
15871 @t{'Max} is optional (and is ignored in any case). For example, it is valid
15875 (@value{GDBP}) print 'max(x, y)
15879 When printing arrays, @value{GDBN} uses positional notation when the
15880 array has a lower bound of 1, and uses a modified named notation otherwise.
15881 For example, a one-dimensional array of three integers with a lower bound
15882 of 3 might print as
15889 That is, in contrast to valid Ada, only the first component has a @code{=>}
15893 You may abbreviate attributes in expressions with any unique,
15894 multi-character subsequence of
15895 their names (an exact match gets preference).
15896 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
15897 in place of @t{a'length}.
15900 @cindex quoting Ada internal identifiers
15901 Since Ada is case-insensitive, the debugger normally maps identifiers you type
15902 to lower case. The GNAT compiler uses upper-case characters for
15903 some of its internal identifiers, which are normally of no interest to users.
15904 For the rare occasions when you actually have to look at them,
15905 enclose them in angle brackets to avoid the lower-case mapping.
15908 (@value{GDBP}) print <JMPBUF_SAVE>[0]
15912 Printing an object of class-wide type or dereferencing an
15913 access-to-class-wide value will display all the components of the object's
15914 specific type (as indicated by its run-time tag). Likewise, component
15915 selection on such a value will operate on the specific type of the
15920 @node Stopping Before Main Program
15921 @subsubsection Stopping at the Very Beginning
15923 @cindex breakpointing Ada elaboration code
15924 It is sometimes necessary to debug the program during elaboration, and
15925 before reaching the main procedure.
15926 As defined in the Ada Reference
15927 Manual, the elaboration code is invoked from a procedure called
15928 @code{adainit}. To run your program up to the beginning of
15929 elaboration, simply use the following two commands:
15930 @code{tbreak adainit} and @code{run}.
15932 @node Ada Exceptions
15933 @subsubsection Ada Exceptions
15935 A command is provided to list all Ada exceptions:
15938 @kindex info exceptions
15939 @item info exceptions
15940 @itemx info exceptions @var{regexp}
15941 The @code{info exceptions} command allows you to list all Ada exceptions
15942 defined within the program being debugged, as well as their addresses.
15943 With a regular expression, @var{regexp}, as argument, only those exceptions
15944 whose names match @var{regexp} are listed.
15947 Below is a small example, showing how the command can be used, first
15948 without argument, and next with a regular expression passed as an
15952 (@value{GDBP}) info exceptions
15953 All defined Ada exceptions:
15954 constraint_error: 0x613da0
15955 program_error: 0x613d20
15956 storage_error: 0x613ce0
15957 tasking_error: 0x613ca0
15958 const.aint_global_e: 0x613b00
15959 (@value{GDBP}) info exceptions const.aint
15960 All Ada exceptions matching regular expression "const.aint":
15961 constraint_error: 0x613da0
15962 const.aint_global_e: 0x613b00
15965 It is also possible to ask @value{GDBN} to stop your program's execution
15966 when an exception is raised. For more details, see @ref{Set Catchpoints}.
15969 @subsubsection Extensions for Ada Tasks
15970 @cindex Ada, tasking
15972 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
15973 @value{GDBN} provides the following task-related commands:
15978 This command shows a list of current Ada tasks, as in the following example:
15985 (@value{GDBP}) info tasks
15986 ID TID P-ID Pri State Name
15987 1 8088000 0 15 Child Activation Wait main_task
15988 2 80a4000 1 15 Accept Statement b
15989 3 809a800 1 15 Child Activation Wait a
15990 * 4 80ae800 3 15 Runnable c
15995 In this listing, the asterisk before the last task indicates it to be the
15996 task currently being inspected.
16000 Represents @value{GDBN}'s internal task number.
16006 The parent's task ID (@value{GDBN}'s internal task number).
16009 The base priority of the task.
16012 Current state of the task.
16016 The task has been created but has not been activated. It cannot be
16020 The task is not blocked for any reason known to Ada. (It may be waiting
16021 for a mutex, though.) It is conceptually "executing" in normal mode.
16024 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
16025 that were waiting on terminate alternatives have been awakened and have
16026 terminated themselves.
16028 @item Child Activation Wait
16029 The task is waiting for created tasks to complete activation.
16031 @item Accept Statement
16032 The task is waiting on an accept or selective wait statement.
16034 @item Waiting on entry call
16035 The task is waiting on an entry call.
16037 @item Async Select Wait
16038 The task is waiting to start the abortable part of an asynchronous
16042 The task is waiting on a select statement with only a delay
16045 @item Child Termination Wait
16046 The task is sleeping having completed a master within itself, and is
16047 waiting for the tasks dependent on that master to become terminated or
16048 waiting on a terminate Phase.
16050 @item Wait Child in Term Alt
16051 The task is sleeping waiting for tasks on terminate alternatives to
16052 finish terminating.
16054 @item Accepting RV with @var{taskno}
16055 The task is accepting a rendez-vous with the task @var{taskno}.
16059 Name of the task in the program.
16063 @kindex info task @var{taskno}
16064 @item info task @var{taskno}
16065 This command shows detailled informations on the specified task, as in
16066 the following example:
16071 (@value{GDBP}) info tasks
16072 ID TID P-ID Pri State Name
16073 1 8077880 0 15 Child Activation Wait main_task
16074 * 2 807c468 1 15 Runnable task_1
16075 (@value{GDBP}) info task 2
16076 Ada Task: 0x807c468
16079 Parent: 1 (main_task)
16085 @kindex task@r{ (Ada)}
16086 @cindex current Ada task ID
16087 This command prints the ID of the current task.
16093 (@value{GDBP}) info tasks
16094 ID TID P-ID Pri State Name
16095 1 8077870 0 15 Child Activation Wait main_task
16096 * 2 807c458 1 15 Runnable t
16097 (@value{GDBP}) task
16098 [Current task is 2]
16101 @item task @var{taskno}
16102 @cindex Ada task switching
16103 This command is like the @code{thread @var{threadno}}
16104 command (@pxref{Threads}). It switches the context of debugging
16105 from the current task to the given task.
16111 (@value{GDBP}) info tasks
16112 ID TID P-ID Pri State Name
16113 1 8077870 0 15 Child Activation Wait main_task
16114 * 2 807c458 1 15 Runnable t
16115 (@value{GDBP}) task 1
16116 [Switching to task 1]
16117 #0 0x8067726 in pthread_cond_wait ()
16119 #0 0x8067726 in pthread_cond_wait ()
16120 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
16121 #2 0x805cb63 in system.task_primitives.operations.sleep ()
16122 #3 0x806153e in system.tasking.stages.activate_tasks ()
16123 #4 0x804aacc in un () at un.adb:5
16126 @item break @var{location} task @var{taskno}
16127 @itemx break @var{location} task @var{taskno} if @dots{}
16128 @cindex breakpoints and tasks, in Ada
16129 @cindex task breakpoints, in Ada
16130 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
16131 These commands are like the @code{break @dots{} thread @dots{}}
16132 command (@pxref{Thread Stops}). The
16133 @var{location} argument specifies source lines, as described
16134 in @ref{Specify Location}.
16136 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
16137 to specify that you only want @value{GDBN} to stop the program when a
16138 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
16139 numeric task identifiers assigned by @value{GDBN}, shown in the first
16140 column of the @samp{info tasks} display.
16142 If you do not specify @samp{task @var{taskno}} when you set a
16143 breakpoint, the breakpoint applies to @emph{all} tasks of your
16146 You can use the @code{task} qualifier on conditional breakpoints as
16147 well; in this case, place @samp{task @var{taskno}} before the
16148 breakpoint condition (before the @code{if}).
16156 (@value{GDBP}) info tasks
16157 ID TID P-ID Pri State Name
16158 1 140022020 0 15 Child Activation Wait main_task
16159 2 140045060 1 15 Accept/Select Wait t2
16160 3 140044840 1 15 Runnable t1
16161 * 4 140056040 1 15 Runnable t3
16162 (@value{GDBP}) b 15 task 2
16163 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
16164 (@value{GDBP}) cont
16169 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
16171 (@value{GDBP}) info tasks
16172 ID TID P-ID Pri State Name
16173 1 140022020 0 15 Child Activation Wait main_task
16174 * 2 140045060 1 15 Runnable t2
16175 3 140044840 1 15 Runnable t1
16176 4 140056040 1 15 Delay Sleep t3
16180 @node Ada Tasks and Core Files
16181 @subsubsection Tasking Support when Debugging Core Files
16182 @cindex Ada tasking and core file debugging
16184 When inspecting a core file, as opposed to debugging a live program,
16185 tasking support may be limited or even unavailable, depending on
16186 the platform being used.
16187 For instance, on x86-linux, the list of tasks is available, but task
16188 switching is not supported.
16190 On certain platforms, the debugger needs to perform some
16191 memory writes in order to provide Ada tasking support. When inspecting
16192 a core file, this means that the core file must be opened with read-write
16193 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
16194 Under these circumstances, you should make a backup copy of the core
16195 file before inspecting it with @value{GDBN}.
16197 @node Ravenscar Profile
16198 @subsubsection Tasking Support when using the Ravenscar Profile
16199 @cindex Ravenscar Profile
16201 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
16202 specifically designed for systems with safety-critical real-time
16206 @kindex set ravenscar task-switching on
16207 @cindex task switching with program using Ravenscar Profile
16208 @item set ravenscar task-switching on
16209 Allows task switching when debugging a program that uses the Ravenscar
16210 Profile. This is the default.
16212 @kindex set ravenscar task-switching off
16213 @item set ravenscar task-switching off
16214 Turn off task switching when debugging a program that uses the Ravenscar
16215 Profile. This is mostly intended to disable the code that adds support
16216 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
16217 the Ravenscar runtime is preventing @value{GDBN} from working properly.
16218 To be effective, this command should be run before the program is started.
16220 @kindex show ravenscar task-switching
16221 @item show ravenscar task-switching
16222 Show whether it is possible to switch from task to task in a program
16223 using the Ravenscar Profile.
16228 @subsubsection Known Peculiarities of Ada Mode
16229 @cindex Ada, problems
16231 Besides the omissions listed previously (@pxref{Omissions from Ada}),
16232 we know of several problems with and limitations of Ada mode in
16234 some of which will be fixed with planned future releases of the debugger
16235 and the GNU Ada compiler.
16239 Static constants that the compiler chooses not to materialize as objects in
16240 storage are invisible to the debugger.
16243 Named parameter associations in function argument lists are ignored (the
16244 argument lists are treated as positional).
16247 Many useful library packages are currently invisible to the debugger.
16250 Fixed-point arithmetic, conversions, input, and output is carried out using
16251 floating-point arithmetic, and may give results that only approximate those on
16255 The GNAT compiler never generates the prefix @code{Standard} for any of
16256 the standard symbols defined by the Ada language. @value{GDBN} knows about
16257 this: it will strip the prefix from names when you use it, and will never
16258 look for a name you have so qualified among local symbols, nor match against
16259 symbols in other packages or subprograms. If you have
16260 defined entities anywhere in your program other than parameters and
16261 local variables whose simple names match names in @code{Standard},
16262 GNAT's lack of qualification here can cause confusion. When this happens,
16263 you can usually resolve the confusion
16264 by qualifying the problematic names with package
16265 @code{Standard} explicitly.
16268 Older versions of the compiler sometimes generate erroneous debugging
16269 information, resulting in the debugger incorrectly printing the value
16270 of affected entities. In some cases, the debugger is able to work
16271 around an issue automatically. In other cases, the debugger is able
16272 to work around the issue, but the work-around has to be specifically
16275 @kindex set ada trust-PAD-over-XVS
16276 @kindex show ada trust-PAD-over-XVS
16279 @item set ada trust-PAD-over-XVS on
16280 Configure GDB to strictly follow the GNAT encoding when computing the
16281 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
16282 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
16283 a complete description of the encoding used by the GNAT compiler).
16284 This is the default.
16286 @item set ada trust-PAD-over-XVS off
16287 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
16288 sometimes prints the wrong value for certain entities, changing @code{ada
16289 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
16290 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
16291 @code{off}, but this incurs a slight performance penalty, so it is
16292 recommended to leave this setting to @code{on} unless necessary.
16296 @cindex GNAT descriptive types
16297 @cindex GNAT encoding
16298 Internally, the debugger also relies on the compiler following a number
16299 of conventions known as the @samp{GNAT Encoding}, all documented in
16300 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
16301 how the debugging information should be generated for certain types.
16302 In particular, this convention makes use of @dfn{descriptive types},
16303 which are artificial types generated purely to help the debugger.
16305 These encodings were defined at a time when the debugging information
16306 format used was not powerful enough to describe some of the more complex
16307 types available in Ada. Since DWARF allows us to express nearly all
16308 Ada features, the long-term goal is to slowly replace these descriptive
16309 types by their pure DWARF equivalent. To facilitate that transition,
16310 a new maintenance option is available to force the debugger to ignore
16311 those descriptive types. It allows the user to quickly evaluate how
16312 well @value{GDBN} works without them.
16316 @kindex maint ada set ignore-descriptive-types
16317 @item maintenance ada set ignore-descriptive-types [on|off]
16318 Control whether the debugger should ignore descriptive types.
16319 The default is not to ignore descriptives types (@code{off}).
16321 @kindex maint ada show ignore-descriptive-types
16322 @item maintenance ada show ignore-descriptive-types
16323 Show if descriptive types are ignored by @value{GDBN}.
16327 @node Unsupported Languages
16328 @section Unsupported Languages
16330 @cindex unsupported languages
16331 @cindex minimal language
16332 In addition to the other fully-supported programming languages,
16333 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
16334 It does not represent a real programming language, but provides a set
16335 of capabilities close to what the C or assembly languages provide.
16336 This should allow most simple operations to be performed while debugging
16337 an application that uses a language currently not supported by @value{GDBN}.
16339 If the language is set to @code{auto}, @value{GDBN} will automatically
16340 select this language if the current frame corresponds to an unsupported
16344 @chapter Examining the Symbol Table
16346 The commands described in this chapter allow you to inquire about the
16347 symbols (names of variables, functions and types) defined in your
16348 program. This information is inherent in the text of your program and
16349 does not change as your program executes. @value{GDBN} finds it in your
16350 program's symbol table, in the file indicated when you started @value{GDBN}
16351 (@pxref{File Options, ,Choosing Files}), or by one of the
16352 file-management commands (@pxref{Files, ,Commands to Specify Files}).
16354 @cindex symbol names
16355 @cindex names of symbols
16356 @cindex quoting names
16357 Occasionally, you may need to refer to symbols that contain unusual
16358 characters, which @value{GDBN} ordinarily treats as word delimiters. The
16359 most frequent case is in referring to static variables in other
16360 source files (@pxref{Variables,,Program Variables}). File names
16361 are recorded in object files as debugging symbols, but @value{GDBN} would
16362 ordinarily parse a typical file name, like @file{foo.c}, as the three words
16363 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
16364 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
16371 looks up the value of @code{x} in the scope of the file @file{foo.c}.
16374 @cindex case-insensitive symbol names
16375 @cindex case sensitivity in symbol names
16376 @kindex set case-sensitive
16377 @item set case-sensitive on
16378 @itemx set case-sensitive off
16379 @itemx set case-sensitive auto
16380 Normally, when @value{GDBN} looks up symbols, it matches their names
16381 with case sensitivity determined by the current source language.
16382 Occasionally, you may wish to control that. The command @code{set
16383 case-sensitive} lets you do that by specifying @code{on} for
16384 case-sensitive matches or @code{off} for case-insensitive ones. If
16385 you specify @code{auto}, case sensitivity is reset to the default
16386 suitable for the source language. The default is case-sensitive
16387 matches for all languages except for Fortran, for which the default is
16388 case-insensitive matches.
16390 @kindex show case-sensitive
16391 @item show case-sensitive
16392 This command shows the current setting of case sensitivity for symbols
16395 @kindex set print type methods
16396 @item set print type methods
16397 @itemx set print type methods on
16398 @itemx set print type methods off
16399 Normally, when @value{GDBN} prints a class, it displays any methods
16400 declared in that class. You can control this behavior either by
16401 passing the appropriate flag to @code{ptype}, or using @command{set
16402 print type methods}. Specifying @code{on} will cause @value{GDBN} to
16403 display the methods; this is the default. Specifying @code{off} will
16404 cause @value{GDBN} to omit the methods.
16406 @kindex show print type methods
16407 @item show print type methods
16408 This command shows the current setting of method display when printing
16411 @kindex set print type typedefs
16412 @item set print type typedefs
16413 @itemx set print type typedefs on
16414 @itemx set print type typedefs off
16416 Normally, when @value{GDBN} prints a class, it displays any typedefs
16417 defined in that class. You can control this behavior either by
16418 passing the appropriate flag to @code{ptype}, or using @command{set
16419 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
16420 display the typedef definitions; this is the default. Specifying
16421 @code{off} will cause @value{GDBN} to omit the typedef definitions.
16422 Note that this controls whether the typedef definition itself is
16423 printed, not whether typedef names are substituted when printing other
16426 @kindex show print type typedefs
16427 @item show print type typedefs
16428 This command shows the current setting of typedef display when
16431 @kindex info address
16432 @cindex address of a symbol
16433 @item info address @var{symbol}
16434 Describe where the data for @var{symbol} is stored. For a register
16435 variable, this says which register it is kept in. For a non-register
16436 local variable, this prints the stack-frame offset at which the variable
16439 Note the contrast with @samp{print &@var{symbol}}, which does not work
16440 at all for a register variable, and for a stack local variable prints
16441 the exact address of the current instantiation of the variable.
16443 @kindex info symbol
16444 @cindex symbol from address
16445 @cindex closest symbol and offset for an address
16446 @item info symbol @var{addr}
16447 Print the name of a symbol which is stored at the address @var{addr}.
16448 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
16449 nearest symbol and an offset from it:
16452 (@value{GDBP}) info symbol 0x54320
16453 _initialize_vx + 396 in section .text
16457 This is the opposite of the @code{info address} command. You can use
16458 it to find out the name of a variable or a function given its address.
16460 For dynamically linked executables, the name of executable or shared
16461 library containing the symbol is also printed:
16464 (@value{GDBP}) info symbol 0x400225
16465 _start + 5 in section .text of /tmp/a.out
16466 (@value{GDBP}) info symbol 0x2aaaac2811cf
16467 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
16472 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
16473 Demangle @var{name}.
16474 If @var{language} is provided it is the name of the language to demangle
16475 @var{name} in. Otherwise @var{name} is demangled in the current language.
16477 The @samp{--} option specifies the end of options,
16478 and is useful when @var{name} begins with a dash.
16480 The parameter @code{demangle-style} specifies how to interpret the kind
16481 of mangling used. @xref{Print Settings}.
16484 @item whatis[/@var{flags}] [@var{arg}]
16485 Print the data type of @var{arg}, which can be either an expression
16486 or a name of a data type. With no argument, print the data type of
16487 @code{$}, the last value in the value history.
16489 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
16490 is not actually evaluated, and any side-effecting operations (such as
16491 assignments or function calls) inside it do not take place.
16493 If @var{arg} is a variable or an expression, @code{whatis} prints its
16494 literal type as it is used in the source code. If the type was
16495 defined using a @code{typedef}, @code{whatis} will @emph{not} print
16496 the data type underlying the @code{typedef}. If the type of the
16497 variable or the expression is a compound data type, such as
16498 @code{struct} or @code{class}, @code{whatis} never prints their
16499 fields or methods. It just prints the @code{struct}/@code{class}
16500 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
16501 such a compound data type, use @code{ptype}.
16503 If @var{arg} is a type name that was defined using @code{typedef},
16504 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
16505 Unrolling means that @code{whatis} will show the underlying type used
16506 in the @code{typedef} declaration of @var{arg}. However, if that
16507 underlying type is also a @code{typedef}, @code{whatis} will not
16510 For C code, the type names may also have the form @samp{class
16511 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
16512 @var{union-tag}} or @samp{enum @var{enum-tag}}.
16514 @var{flags} can be used to modify how the type is displayed.
16515 Available flags are:
16519 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
16520 parameters and typedefs defined in a class when printing the class'
16521 members. The @code{/r} flag disables this.
16524 Do not print methods defined in the class.
16527 Print methods defined in the class. This is the default, but the flag
16528 exists in case you change the default with @command{set print type methods}.
16531 Do not print typedefs defined in the class. Note that this controls
16532 whether the typedef definition itself is printed, not whether typedef
16533 names are substituted when printing other types.
16536 Print typedefs defined in the class. This is the default, but the flag
16537 exists in case you change the default with @command{set print type typedefs}.
16541 @item ptype[/@var{flags}] [@var{arg}]
16542 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
16543 detailed description of the type, instead of just the name of the type.
16544 @xref{Expressions, ,Expressions}.
16546 Contrary to @code{whatis}, @code{ptype} always unrolls any
16547 @code{typedef}s in its argument declaration, whether the argument is
16548 a variable, expression, or a data type. This means that @code{ptype}
16549 of a variable or an expression will not print literally its type as
16550 present in the source code---use @code{whatis} for that. @code{typedef}s at
16551 the pointer or reference targets are also unrolled. Only @code{typedef}s of
16552 fields, methods and inner @code{class typedef}s of @code{struct}s,
16553 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
16555 For example, for this variable declaration:
16558 typedef double real_t;
16559 struct complex @{ real_t real; double imag; @};
16560 typedef struct complex complex_t;
16562 real_t *real_pointer_var;
16566 the two commands give this output:
16570 (@value{GDBP}) whatis var
16572 (@value{GDBP}) ptype var
16573 type = struct complex @{
16577 (@value{GDBP}) whatis complex_t
16578 type = struct complex
16579 (@value{GDBP}) whatis struct complex
16580 type = struct complex
16581 (@value{GDBP}) ptype struct complex
16582 type = struct complex @{
16586 (@value{GDBP}) whatis real_pointer_var
16588 (@value{GDBP}) ptype real_pointer_var
16594 As with @code{whatis}, using @code{ptype} without an argument refers to
16595 the type of @code{$}, the last value in the value history.
16597 @cindex incomplete type
16598 Sometimes, programs use opaque data types or incomplete specifications
16599 of complex data structure. If the debug information included in the
16600 program does not allow @value{GDBN} to display a full declaration of
16601 the data type, it will say @samp{<incomplete type>}. For example,
16602 given these declarations:
16606 struct foo *fooptr;
16610 but no definition for @code{struct foo} itself, @value{GDBN} will say:
16613 (@value{GDBP}) ptype foo
16614 $1 = <incomplete type>
16618 ``Incomplete type'' is C terminology for data types that are not
16619 completely specified.
16622 @item info types @var{regexp}
16624 Print a brief description of all types whose names match the regular
16625 expression @var{regexp} (or all types in your program, if you supply
16626 no argument). Each complete typename is matched as though it were a
16627 complete line; thus, @samp{i type value} gives information on all
16628 types in your program whose names include the string @code{value}, but
16629 @samp{i type ^value$} gives information only on types whose complete
16630 name is @code{value}.
16632 This command differs from @code{ptype} in two ways: first, like
16633 @code{whatis}, it does not print a detailed description; second, it
16634 lists all source files where a type is defined.
16636 @kindex info type-printers
16637 @item info type-printers
16638 Versions of @value{GDBN} that ship with Python scripting enabled may
16639 have ``type printers'' available. When using @command{ptype} or
16640 @command{whatis}, these printers are consulted when the name of a type
16641 is needed. @xref{Type Printing API}, for more information on writing
16644 @code{info type-printers} displays all the available type printers.
16646 @kindex enable type-printer
16647 @kindex disable type-printer
16648 @item enable type-printer @var{name}@dots{}
16649 @item disable type-printer @var{name}@dots{}
16650 These commands can be used to enable or disable type printers.
16653 @cindex local variables
16654 @item info scope @var{location}
16655 List all the variables local to a particular scope. This command
16656 accepts a @var{location} argument---a function name, a source line, or
16657 an address preceded by a @samp{*}, and prints all the variables local
16658 to the scope defined by that location. (@xref{Specify Location}, for
16659 details about supported forms of @var{location}.) For example:
16662 (@value{GDBP}) @b{info scope command_line_handler}
16663 Scope for command_line_handler:
16664 Symbol rl is an argument at stack/frame offset 8, length 4.
16665 Symbol linebuffer is in static storage at address 0x150a18, length 4.
16666 Symbol linelength is in static storage at address 0x150a1c, length 4.
16667 Symbol p is a local variable in register $esi, length 4.
16668 Symbol p1 is a local variable in register $ebx, length 4.
16669 Symbol nline is a local variable in register $edx, length 4.
16670 Symbol repeat is a local variable at frame offset -8, length 4.
16674 This command is especially useful for determining what data to collect
16675 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
16678 @kindex info source
16680 Show information about the current source file---that is, the source file for
16681 the function containing the current point of execution:
16684 the name of the source file, and the directory containing it,
16686 the directory it was compiled in,
16688 its length, in lines,
16690 which programming language it is written in,
16692 if the debug information provides it, the program that compiled the file
16693 (which may include, e.g., the compiler version and command line arguments),
16695 whether the executable includes debugging information for that file, and
16696 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
16698 whether the debugging information includes information about
16699 preprocessor macros.
16703 @kindex info sources
16705 Print the names of all source files in your program for which there is
16706 debugging information, organized into two lists: files whose symbols
16707 have already been read, and files whose symbols will be read when needed.
16709 @kindex info functions
16710 @item info functions
16711 Print the names and data types of all defined functions.
16713 @item info functions @var{regexp}
16714 Print the names and data types of all defined functions
16715 whose names contain a match for regular expression @var{regexp}.
16716 Thus, @samp{info fun step} finds all functions whose names
16717 include @code{step}; @samp{info fun ^step} finds those whose names
16718 start with @code{step}. If a function name contains characters
16719 that conflict with the regular expression language (e.g.@:
16720 @samp{operator*()}), they may be quoted with a backslash.
16722 @kindex info variables
16723 @item info variables
16724 Print the names and data types of all variables that are defined
16725 outside of functions (i.e.@: excluding local variables).
16727 @item info variables @var{regexp}
16728 Print the names and data types of all variables (except for local
16729 variables) whose names contain a match for regular expression
16732 @kindex info classes
16733 @cindex Objective-C, classes and selectors
16735 @itemx info classes @var{regexp}
16736 Display all Objective-C classes in your program, or
16737 (with the @var{regexp} argument) all those matching a particular regular
16740 @kindex info selectors
16741 @item info selectors
16742 @itemx info selectors @var{regexp}
16743 Display all Objective-C selectors in your program, or
16744 (with the @var{regexp} argument) all those matching a particular regular
16748 This was never implemented.
16749 @kindex info methods
16751 @itemx info methods @var{regexp}
16752 The @code{info methods} command permits the user to examine all defined
16753 methods within C@t{++} program, or (with the @var{regexp} argument) a
16754 specific set of methods found in the various C@t{++} classes. Many
16755 C@t{++} classes provide a large number of methods. Thus, the output
16756 from the @code{ptype} command can be overwhelming and hard to use. The
16757 @code{info-methods} command filters the methods, printing only those
16758 which match the regular-expression @var{regexp}.
16761 @cindex opaque data types
16762 @kindex set opaque-type-resolution
16763 @item set opaque-type-resolution on
16764 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
16765 declared as a pointer to a @code{struct}, @code{class}, or
16766 @code{union}---for example, @code{struct MyType *}---that is used in one
16767 source file although the full declaration of @code{struct MyType} is in
16768 another source file. The default is on.
16770 A change in the setting of this subcommand will not take effect until
16771 the next time symbols for a file are loaded.
16773 @item set opaque-type-resolution off
16774 Tell @value{GDBN} not to resolve opaque types. In this case, the type
16775 is printed as follows:
16777 @{<no data fields>@}
16780 @kindex show opaque-type-resolution
16781 @item show opaque-type-resolution
16782 Show whether opaque types are resolved or not.
16784 @kindex set print symbol-loading
16785 @cindex print messages when symbols are loaded
16786 @item set print symbol-loading
16787 @itemx set print symbol-loading full
16788 @itemx set print symbol-loading brief
16789 @itemx set print symbol-loading off
16790 The @code{set print symbol-loading} command allows you to control the
16791 printing of messages when @value{GDBN} loads symbol information.
16792 By default a message is printed for the executable and one for each
16793 shared library, and normally this is what you want. However, when
16794 debugging apps with large numbers of shared libraries these messages
16796 When set to @code{brief} a message is printed for each executable,
16797 and when @value{GDBN} loads a collection of shared libraries at once
16798 it will only print one message regardless of the number of shared
16799 libraries. When set to @code{off} no messages are printed.
16801 @kindex show print symbol-loading
16802 @item show print symbol-loading
16803 Show whether messages will be printed when a @value{GDBN} command
16804 entered from the keyboard causes symbol information to be loaded.
16806 @kindex maint print symbols
16807 @cindex symbol dump
16808 @kindex maint print psymbols
16809 @cindex partial symbol dump
16810 @kindex maint print msymbols
16811 @cindex minimal symbol dump
16812 @item maint print symbols @var{filename}
16813 @itemx maint print psymbols @var{filename}
16814 @itemx maint print msymbols @var{filename}
16815 Write a dump of debugging symbol data into the file @var{filename}.
16816 These commands are used to debug the @value{GDBN} symbol-reading code. Only
16817 symbols with debugging data are included. If you use @samp{maint print
16818 symbols}, @value{GDBN} includes all the symbols for which it has already
16819 collected full details: that is, @var{filename} reflects symbols for
16820 only those files whose symbols @value{GDBN} has read. You can use the
16821 command @code{info sources} to find out which files these are. If you
16822 use @samp{maint print psymbols} instead, the dump shows information about
16823 symbols that @value{GDBN} only knows partially---that is, symbols defined in
16824 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
16825 @samp{maint print msymbols} dumps just the minimal symbol information
16826 required for each object file from which @value{GDBN} has read some symbols.
16827 @xref{Files, ,Commands to Specify Files}, for a discussion of how
16828 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
16830 @kindex maint info symtabs
16831 @kindex maint info psymtabs
16832 @cindex listing @value{GDBN}'s internal symbol tables
16833 @cindex symbol tables, listing @value{GDBN}'s internal
16834 @cindex full symbol tables, listing @value{GDBN}'s internal
16835 @cindex partial symbol tables, listing @value{GDBN}'s internal
16836 @item maint info symtabs @r{[} @var{regexp} @r{]}
16837 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
16839 List the @code{struct symtab} or @code{struct partial_symtab}
16840 structures whose names match @var{regexp}. If @var{regexp} is not
16841 given, list them all. The output includes expressions which you can
16842 copy into a @value{GDBN} debugging this one to examine a particular
16843 structure in more detail. For example:
16846 (@value{GDBP}) maint info psymtabs dwarf2read
16847 @{ objfile /home/gnu/build/gdb/gdb
16848 ((struct objfile *) 0x82e69d0)
16849 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
16850 ((struct partial_symtab *) 0x8474b10)
16853 text addresses 0x814d3c8 -- 0x8158074
16854 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
16855 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
16856 dependencies (none)
16859 (@value{GDBP}) maint info symtabs
16863 We see that there is one partial symbol table whose filename contains
16864 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
16865 and we see that @value{GDBN} has not read in any symtabs yet at all.
16866 If we set a breakpoint on a function, that will cause @value{GDBN} to
16867 read the symtab for the compilation unit containing that function:
16870 (@value{GDBP}) break dwarf2_psymtab_to_symtab
16871 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
16873 (@value{GDBP}) maint info symtabs
16874 @{ objfile /home/gnu/build/gdb/gdb
16875 ((struct objfile *) 0x82e69d0)
16876 @{ symtab /home/gnu/src/gdb/dwarf2read.c
16877 ((struct symtab *) 0x86c1f38)
16880 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
16881 linetable ((struct linetable *) 0x8370fa0)
16882 debugformat DWARF 2
16888 @kindex maint set symbol-cache-size
16889 @cindex symbol cache size
16890 @item maint set symbol-cache-size @var{size}
16891 Set the size of the symbol cache to @var{size}.
16892 The default size is intended to be good enough for debugging
16893 most applications. This option exists to allow for experimenting
16894 with different sizes.
16896 @kindex maint show symbol-cache-size
16897 @item maint show symbol-cache-size
16898 Show the size of the symbol cache.
16900 @kindex maint print symbol-cache
16901 @cindex symbol cache, printing its contents
16902 @item maint print symbol-cache
16903 Print the contents of the symbol cache.
16904 This is useful when debugging symbol cache issues.
16906 @kindex maint print symbol-cache-statistics
16907 @cindex symbol cache, printing usage statistics
16908 @item maint print symbol-cache-statistics
16909 Print symbol cache usage statistics.
16910 This helps determine how well the cache is being utilized.
16912 @kindex maint flush-symbol-cache
16913 @cindex symbol cache, flushing
16914 @item maint flush-symbol-cache
16915 Flush the contents of the symbol cache, all entries are removed.
16916 This command is useful when debugging the symbol cache.
16917 It is also useful when collecting performance data.
16922 @chapter Altering Execution
16924 Once you think you have found an error in your program, you might want to
16925 find out for certain whether correcting the apparent error would lead to
16926 correct results in the rest of the run. You can find the answer by
16927 experiment, using the @value{GDBN} features for altering execution of the
16930 For example, you can store new values into variables or memory
16931 locations, give your program a signal, restart it at a different
16932 address, or even return prematurely from a function.
16935 * Assignment:: Assignment to variables
16936 * Jumping:: Continuing at a different address
16937 * Signaling:: Giving your program a signal
16938 * Returning:: Returning from a function
16939 * Calling:: Calling your program's functions
16940 * Patching:: Patching your program
16941 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
16945 @section Assignment to Variables
16948 @cindex setting variables
16949 To alter the value of a variable, evaluate an assignment expression.
16950 @xref{Expressions, ,Expressions}. For example,
16957 stores the value 4 into the variable @code{x}, and then prints the
16958 value of the assignment expression (which is 4).
16959 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
16960 information on operators in supported languages.
16962 @kindex set variable
16963 @cindex variables, setting
16964 If you are not interested in seeing the value of the assignment, use the
16965 @code{set} command instead of the @code{print} command. @code{set} is
16966 really the same as @code{print} except that the expression's value is
16967 not printed and is not put in the value history (@pxref{Value History,
16968 ,Value History}). The expression is evaluated only for its effects.
16970 If the beginning of the argument string of the @code{set} command
16971 appears identical to a @code{set} subcommand, use the @code{set
16972 variable} command instead of just @code{set}. This command is identical
16973 to @code{set} except for its lack of subcommands. For example, if your
16974 program has a variable @code{width}, you get an error if you try to set
16975 a new value with just @samp{set width=13}, because @value{GDBN} has the
16976 command @code{set width}:
16979 (@value{GDBP}) whatis width
16981 (@value{GDBP}) p width
16983 (@value{GDBP}) set width=47
16984 Invalid syntax in expression.
16988 The invalid expression, of course, is @samp{=47}. In
16989 order to actually set the program's variable @code{width}, use
16992 (@value{GDBP}) set var width=47
16995 Because the @code{set} command has many subcommands that can conflict
16996 with the names of program variables, it is a good idea to use the
16997 @code{set variable} command instead of just @code{set}. For example, if
16998 your program has a variable @code{g}, you run into problems if you try
16999 to set a new value with just @samp{set g=4}, because @value{GDBN} has
17000 the command @code{set gnutarget}, abbreviated @code{set g}:
17004 (@value{GDBP}) whatis g
17008 (@value{GDBP}) set g=4
17012 The program being debugged has been started already.
17013 Start it from the beginning? (y or n) y
17014 Starting program: /home/smith/cc_progs/a.out
17015 "/home/smith/cc_progs/a.out": can't open to read symbols:
17016 Invalid bfd target.
17017 (@value{GDBP}) show g
17018 The current BFD target is "=4".
17023 The program variable @code{g} did not change, and you silently set the
17024 @code{gnutarget} to an invalid value. In order to set the variable
17028 (@value{GDBP}) set var g=4
17031 @value{GDBN} allows more implicit conversions in assignments than C; you can
17032 freely store an integer value into a pointer variable or vice versa,
17033 and you can convert any structure to any other structure that is the
17034 same length or shorter.
17035 @comment FIXME: how do structs align/pad in these conversions?
17036 @comment /doc@cygnus.com 18dec1990
17038 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
17039 construct to generate a value of specified type at a specified address
17040 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
17041 to memory location @code{0x83040} as an integer (which implies a certain size
17042 and representation in memory), and
17045 set @{int@}0x83040 = 4
17049 stores the value 4 into that memory location.
17052 @section Continuing at a Different Address
17054 Ordinarily, when you continue your program, you do so at the place where
17055 it stopped, with the @code{continue} command. You can instead continue at
17056 an address of your own choosing, with the following commands:
17060 @kindex j @r{(@code{jump})}
17061 @item jump @var{location}
17062 @itemx j @var{location}
17063 Resume execution at @var{location}. Execution stops again immediately
17064 if there is a breakpoint there. @xref{Specify Location}, for a description
17065 of the different forms of @var{location}. It is common
17066 practice to use the @code{tbreak} command in conjunction with
17067 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
17069 The @code{jump} command does not change the current stack frame, or
17070 the stack pointer, or the contents of any memory location or any
17071 register other than the program counter. If @var{location} is in
17072 a different function from the one currently executing, the results may
17073 be bizarre if the two functions expect different patterns of arguments or
17074 of local variables. For this reason, the @code{jump} command requests
17075 confirmation if the specified line is not in the function currently
17076 executing. However, even bizarre results are predictable if you are
17077 well acquainted with the machine-language code of your program.
17080 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
17081 On many systems, you can get much the same effect as the @code{jump}
17082 command by storing a new value into the register @code{$pc}. The
17083 difference is that this does not start your program running; it only
17084 changes the address of where it @emph{will} run when you continue. For
17092 makes the next @code{continue} command or stepping command execute at
17093 address @code{0x485}, rather than at the address where your program stopped.
17094 @xref{Continuing and Stepping, ,Continuing and Stepping}.
17096 The most common occasion to use the @code{jump} command is to back
17097 up---perhaps with more breakpoints set---over a portion of a program
17098 that has already executed, in order to examine its execution in more
17103 @section Giving your Program a Signal
17104 @cindex deliver a signal to a program
17108 @item signal @var{signal}
17109 Resume execution where your program is stopped, but immediately give it the
17110 signal @var{signal}. The @var{signal} can be the name or the number of a
17111 signal. For example, on many systems @code{signal 2} and @code{signal
17112 SIGINT} are both ways of sending an interrupt signal.
17114 Alternatively, if @var{signal} is zero, continue execution without
17115 giving a signal. This is useful when your program stopped on account of
17116 a signal and would ordinarily see the signal when resumed with the
17117 @code{continue} command; @samp{signal 0} causes it to resume without a
17120 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
17121 delivered to the currently selected thread, not the thread that last
17122 reported a stop. This includes the situation where a thread was
17123 stopped due to a signal. So if you want to continue execution
17124 suppressing the signal that stopped a thread, you should select that
17125 same thread before issuing the @samp{signal 0} command. If you issue
17126 the @samp{signal 0} command with another thread as the selected one,
17127 @value{GDBN} detects that and asks for confirmation.
17129 Invoking the @code{signal} command is not the same as invoking the
17130 @code{kill} utility from the shell. Sending a signal with @code{kill}
17131 causes @value{GDBN} to decide what to do with the signal depending on
17132 the signal handling tables (@pxref{Signals}). The @code{signal} command
17133 passes the signal directly to your program.
17135 @code{signal} does not repeat when you press @key{RET} a second time
17136 after executing the command.
17138 @kindex queue-signal
17139 @item queue-signal @var{signal}
17140 Queue @var{signal} to be delivered immediately to the current thread
17141 when execution of the thread resumes. The @var{signal} can be the name or
17142 the number of a signal. For example, on many systems @code{signal 2} and
17143 @code{signal SIGINT} are both ways of sending an interrupt signal.
17144 The handling of the signal must be set to pass the signal to the program,
17145 otherwise @value{GDBN} will report an error.
17146 You can control the handling of signals from @value{GDBN} with the
17147 @code{handle} command (@pxref{Signals}).
17149 Alternatively, if @var{signal} is zero, any currently queued signal
17150 for the current thread is discarded and when execution resumes no signal
17151 will be delivered. This is useful when your program stopped on account
17152 of a signal and would ordinarily see the signal when resumed with the
17153 @code{continue} command.
17155 This command differs from the @code{signal} command in that the signal
17156 is just queued, execution is not resumed. And @code{queue-signal} cannot
17157 be used to pass a signal whose handling state has been set to @code{nopass}
17162 @xref{stepping into signal handlers}, for information on how stepping
17163 commands behave when the thread has a signal queued.
17166 @section Returning from a Function
17169 @cindex returning from a function
17172 @itemx return @var{expression}
17173 You can cancel execution of a function call with the @code{return}
17174 command. If you give an
17175 @var{expression} argument, its value is used as the function's return
17179 When you use @code{return}, @value{GDBN} discards the selected stack frame
17180 (and all frames within it). You can think of this as making the
17181 discarded frame return prematurely. If you wish to specify a value to
17182 be returned, give that value as the argument to @code{return}.
17184 This pops the selected stack frame (@pxref{Selection, ,Selecting a
17185 Frame}), and any other frames inside of it, leaving its caller as the
17186 innermost remaining frame. That frame becomes selected. The
17187 specified value is stored in the registers used for returning values
17190 The @code{return} command does not resume execution; it leaves the
17191 program stopped in the state that would exist if the function had just
17192 returned. In contrast, the @code{finish} command (@pxref{Continuing
17193 and Stepping, ,Continuing and Stepping}) resumes execution until the
17194 selected stack frame returns naturally.
17196 @value{GDBN} needs to know how the @var{expression} argument should be set for
17197 the inferior. The concrete registers assignment depends on the OS ABI and the
17198 type being returned by the selected stack frame. For example it is common for
17199 OS ABI to return floating point values in FPU registers while integer values in
17200 CPU registers. Still some ABIs return even floating point values in CPU
17201 registers. Larger integer widths (such as @code{long long int}) also have
17202 specific placement rules. @value{GDBN} already knows the OS ABI from its
17203 current target so it needs to find out also the type being returned to make the
17204 assignment into the right register(s).
17206 Normally, the selected stack frame has debug info. @value{GDBN} will always
17207 use the debug info instead of the implicit type of @var{expression} when the
17208 debug info is available. For example, if you type @kbd{return -1}, and the
17209 function in the current stack frame is declared to return a @code{long long
17210 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
17211 into a @code{long long int}:
17214 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
17216 (@value{GDBP}) return -1
17217 Make func return now? (y or n) y
17218 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
17219 43 printf ("result=%lld\n", func ());
17223 However, if the selected stack frame does not have a debug info, e.g., if the
17224 function was compiled without debug info, @value{GDBN} has to find out the type
17225 to return from user. Specifying a different type by mistake may set the value
17226 in different inferior registers than the caller code expects. For example,
17227 typing @kbd{return -1} with its implicit type @code{int} would set only a part
17228 of a @code{long long int} result for a debug info less function (on 32-bit
17229 architectures). Therefore the user is required to specify the return type by
17230 an appropriate cast explicitly:
17233 Breakpoint 2, 0x0040050b in func ()
17234 (@value{GDBP}) return -1
17235 Return value type not available for selected stack frame.
17236 Please use an explicit cast of the value to return.
17237 (@value{GDBP}) return (long long int) -1
17238 Make selected stack frame return now? (y or n) y
17239 #0 0x00400526 in main ()
17244 @section Calling Program Functions
17247 @cindex calling functions
17248 @cindex inferior functions, calling
17249 @item print @var{expr}
17250 Evaluate the expression @var{expr} and display the resulting value.
17251 The expression may include calls to functions in the program being
17255 @item call @var{expr}
17256 Evaluate the expression @var{expr} without displaying @code{void}
17259 You can use this variant of the @code{print} command if you want to
17260 execute a function from your program that does not return anything
17261 (a.k.a.@: @dfn{a void function}), but without cluttering the output
17262 with @code{void} returned values that @value{GDBN} will otherwise
17263 print. If the result is not void, it is printed and saved in the
17267 It is possible for the function you call via the @code{print} or
17268 @code{call} command to generate a signal (e.g., if there's a bug in
17269 the function, or if you passed it incorrect arguments). What happens
17270 in that case is controlled by the @code{set unwindonsignal} command.
17272 Similarly, with a C@t{++} program it is possible for the function you
17273 call via the @code{print} or @code{call} command to generate an
17274 exception that is not handled due to the constraints of the dummy
17275 frame. In this case, any exception that is raised in the frame, but has
17276 an out-of-frame exception handler will not be found. GDB builds a
17277 dummy-frame for the inferior function call, and the unwinder cannot
17278 seek for exception handlers outside of this dummy-frame. What happens
17279 in that case is controlled by the
17280 @code{set unwind-on-terminating-exception} command.
17283 @item set unwindonsignal
17284 @kindex set unwindonsignal
17285 @cindex unwind stack in called functions
17286 @cindex call dummy stack unwinding
17287 Set unwinding of the stack if a signal is received while in a function
17288 that @value{GDBN} called in the program being debugged. If set to on,
17289 @value{GDBN} unwinds the stack it created for the call and restores
17290 the context to what it was before the call. If set to off (the
17291 default), @value{GDBN} stops in the frame where the signal was
17294 @item show unwindonsignal
17295 @kindex show unwindonsignal
17296 Show the current setting of stack unwinding in the functions called by
17299 @item set unwind-on-terminating-exception
17300 @kindex set unwind-on-terminating-exception
17301 @cindex unwind stack in called functions with unhandled exceptions
17302 @cindex call dummy stack unwinding on unhandled exception.
17303 Set unwinding of the stack if a C@t{++} exception is raised, but left
17304 unhandled while in a function that @value{GDBN} called in the program being
17305 debugged. If set to on (the default), @value{GDBN} unwinds the stack
17306 it created for the call and restores the context to what it was before
17307 the call. If set to off, @value{GDBN} the exception is delivered to
17308 the default C@t{++} exception handler and the inferior terminated.
17310 @item show unwind-on-terminating-exception
17311 @kindex show unwind-on-terminating-exception
17312 Show the current setting of stack unwinding in the functions called by
17317 @cindex weak alias functions
17318 Sometimes, a function you wish to call is actually a @dfn{weak alias}
17319 for another function. In such case, @value{GDBN} might not pick up
17320 the type information, including the types of the function arguments,
17321 which causes @value{GDBN} to call the inferior function incorrectly.
17322 As a result, the called function will function erroneously and may
17323 even crash. A solution to that is to use the name of the aliased
17327 @section Patching Programs
17329 @cindex patching binaries
17330 @cindex writing into executables
17331 @cindex writing into corefiles
17333 By default, @value{GDBN} opens the file containing your program's
17334 executable code (or the corefile) read-only. This prevents accidental
17335 alterations to machine code; but it also prevents you from intentionally
17336 patching your program's binary.
17338 If you'd like to be able to patch the binary, you can specify that
17339 explicitly with the @code{set write} command. For example, you might
17340 want to turn on internal debugging flags, or even to make emergency
17346 @itemx set write off
17347 If you specify @samp{set write on}, @value{GDBN} opens executable and
17348 core files for both reading and writing; if you specify @kbd{set write
17349 off} (the default), @value{GDBN} opens them read-only.
17351 If you have already loaded a file, you must load it again (using the
17352 @code{exec-file} or @code{core-file} command) after changing @code{set
17353 write}, for your new setting to take effect.
17357 Display whether executable files and core files are opened for writing
17358 as well as reading.
17361 @node Compiling and Injecting Code
17362 @section Compiling and injecting code in @value{GDBN}
17363 @cindex injecting code
17364 @cindex writing into executables
17365 @cindex compiling code
17367 @value{GDBN} supports on-demand compilation and code injection into
17368 programs running under @value{GDBN}. GCC 5.0 or higher built with
17369 @file{libcc1.so} must be installed for this functionality to be enabled.
17370 This functionality is implemented with the following commands.
17373 @kindex compile code
17374 @item compile code @var{source-code}
17375 @itemx compile code -raw @var{--} @var{source-code}
17376 Compile @var{source-code} with the compiler language found as the current
17377 language in @value{GDBN} (@pxref{Languages}). If compilation and
17378 injection is not supported with the current language specified in
17379 @value{GDBN}, or the compiler does not support this feature, an error
17380 message will be printed. If @var{source-code} compiles and links
17381 successfully, @value{GDBN} will load the object-code emitted,
17382 and execute it within the context of the currently selected inferior.
17383 It is important to note that the compiled code is executed immediately.
17384 After execution, the compiled code is removed from @value{GDBN} and any
17385 new types or variables you have defined will be deleted.
17387 The command allows you to specify @var{source-code} in two ways.
17388 The simplest method is to provide a single line of code to the command.
17392 compile code printf ("hello world\n");
17395 If you specify options on the command line as well as source code, they
17396 may conflict. The @samp{--} delimiter can be used to separate options
17397 from actual source code. E.g.:
17400 compile code -r -- printf ("hello world\n");
17403 Alternatively you can enter source code as multiple lines of text. To
17404 enter this mode, invoke the @samp{compile code} command without any text
17405 following the command. This will start the multiple-line editor and
17406 allow you to type as many lines of source code as required. When you
17407 have completed typing, enter @samp{end} on its own line to exit the
17412 >printf ("hello\n");
17413 >printf ("world\n");
17417 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
17418 provided @var{source-code} in a callable scope. In this case, you must
17419 specify the entry point of the code by defining a function named
17420 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
17421 inferior. Using @samp{-raw} option may be needed for example when
17422 @var{source-code} requires @samp{#include} lines which may conflict with
17423 inferior symbols otherwise.
17425 @kindex compile file
17426 @item compile file @var{filename}
17427 @itemx compile file -raw @var{filename}
17428 Like @code{compile code}, but take the source code from @var{filename}.
17431 compile file /home/user/example.c
17436 @item compile print @var{expr}
17437 @itemx compile print /@var{f} @var{expr}
17438 Compile and execute @var{expr} with the compiler language found as the
17439 current language in @value{GDBN} (@pxref{Languages}). By default the
17440 value of @var{expr} is printed in a format appropriate to its data type;
17441 you can choose a different format by specifying @samp{/@var{f}}, where
17442 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
17445 @item compile print
17446 @itemx compile print /@var{f}
17447 @cindex reprint the last value
17448 Alternatively you can enter the expression (source code producing it) as
17449 multiple lines of text. To enter this mode, invoke the @samp{compile print}
17450 command without any text following the command. This will start the
17451 multiple-line editor.
17455 The process of compiling and injecting the code can be inspected using:
17458 @anchor{set debug compile}
17459 @item set debug compile
17460 @cindex compile command debugging info
17461 Turns on or off display of @value{GDBN} process of compiling and
17462 injecting the code. The default is off.
17464 @item show debug compile
17465 Displays the current state of displaying @value{GDBN} process of
17466 compiling and injecting the code.
17469 @subsection Compilation options for the @code{compile} command
17471 @value{GDBN} needs to specify the right compilation options for the code
17472 to be injected, in part to make its ABI compatible with the inferior
17473 and in part to make the injected code compatible with @value{GDBN}'s
17477 The options used, in increasing precedence:
17480 @item target architecture and OS options (@code{gdbarch})
17481 These options depend on target processor type and target operating
17482 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
17483 (@code{-m64}) compilation option.
17485 @item compilation options recorded in the target
17486 @value{NGCC} (since version 4.7) stores the options used for compilation
17487 into @code{DW_AT_producer} part of DWARF debugging information according
17488 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
17489 explicitly specify @code{-g} during inferior compilation otherwise
17490 @value{NGCC} produces no DWARF. This feature is only relevant for
17491 platforms where @code{-g} produces DWARF by default, otherwise one may
17492 try to enforce DWARF by using @code{-gdwarf-4}.
17494 @item compilation options set by @code{set compile-args}
17498 You can override compilation options using the following command:
17501 @item set compile-args
17502 @cindex compile command options override
17503 Set compilation options used for compiling and injecting code with the
17504 @code{compile} commands. These options override any conflicting ones
17505 from the target architecture and/or options stored during inferior
17508 @item show compile-args
17509 Displays the current state of compilation options override.
17510 This does not show all the options actually used during compilation,
17511 use @ref{set debug compile} for that.
17514 @subsection Caveats when using the @code{compile} command
17516 There are a few caveats to keep in mind when using the @code{compile}
17517 command. As the caveats are different per language, the table below
17518 highlights specific issues on a per language basis.
17521 @item C code examples and caveats
17522 When the language in @value{GDBN} is set to @samp{C}, the compiler will
17523 attempt to compile the source code with a @samp{C} compiler. The source
17524 code provided to the @code{compile} command will have much the same
17525 access to variables and types as it normally would if it were part of
17526 the program currently being debugged in @value{GDBN}.
17528 Below is a sample program that forms the basis of the examples that
17529 follow. This program has been compiled and loaded into @value{GDBN},
17530 much like any other normal debugging session.
17533 void function1 (void)
17536 printf ("function 1\n");
17539 void function2 (void)
17554 For the purposes of the examples in this section, the program above has
17555 been compiled, loaded into @value{GDBN}, stopped at the function
17556 @code{main}, and @value{GDBN} is awaiting input from the user.
17558 To access variables and types for any program in @value{GDBN}, the
17559 program must be compiled and packaged with debug information. The
17560 @code{compile} command is not an exception to this rule. Without debug
17561 information, you can still use the @code{compile} command, but you will
17562 be very limited in what variables and types you can access.
17564 So with that in mind, the example above has been compiled with debug
17565 information enabled. The @code{compile} command will have access to
17566 all variables and types (except those that may have been optimized
17567 out). Currently, as @value{GDBN} has stopped the program in the
17568 @code{main} function, the @code{compile} command would have access to
17569 the variable @code{k}. You could invoke the @code{compile} command
17570 and type some source code to set the value of @code{k}. You can also
17571 read it, or do anything with that variable you would normally do in
17572 @code{C}. Be aware that changes to inferior variables in the
17573 @code{compile} command are persistent. In the following example:
17576 compile code k = 3;
17580 the variable @code{k} is now 3. It will retain that value until
17581 something else in the example program changes it, or another
17582 @code{compile} command changes it.
17584 Normal scope and access rules apply to source code compiled and
17585 injected by the @code{compile} command. In the example, the variables
17586 @code{j} and @code{k} are not accessible yet, because the program is
17587 currently stopped in the @code{main} function, where these variables
17588 are not in scope. Therefore, the following command
17591 compile code j = 3;
17595 will result in a compilation error message.
17597 Once the program is continued, execution will bring these variables in
17598 scope, and they will become accessible; then the code you specify via
17599 the @code{compile} command will be able to access them.
17601 You can create variables and types with the @code{compile} command as
17602 part of your source code. Variables and types that are created as part
17603 of the @code{compile} command are not visible to the rest of the program for
17604 the duration of its run. This example is valid:
17607 compile code int ff = 5; printf ("ff is %d\n", ff);
17610 However, if you were to type the following into @value{GDBN} after that
17611 command has completed:
17614 compile code printf ("ff is %d\n'', ff);
17618 a compiler error would be raised as the variable @code{ff} no longer
17619 exists. Object code generated and injected by the @code{compile}
17620 command is removed when its execution ends. Caution is advised
17621 when assigning to program variables values of variables created by the
17622 code submitted to the @code{compile} command. This example is valid:
17625 compile code int ff = 5; k = ff;
17628 The value of the variable @code{ff} is assigned to @code{k}. The variable
17629 @code{k} does not require the existence of @code{ff} to maintain the value
17630 it has been assigned. However, pointers require particular care in
17631 assignment. If the source code compiled with the @code{compile} command
17632 changed the address of a pointer in the example program, perhaps to a
17633 variable created in the @code{compile} command, that pointer would point
17634 to an invalid location when the command exits. The following example
17635 would likely cause issues with your debugged program:
17638 compile code int ff = 5; p = &ff;
17641 In this example, @code{p} would point to @code{ff} when the
17642 @code{compile} command is executing the source code provided to it.
17643 However, as variables in the (example) program persist with their
17644 assigned values, the variable @code{p} would point to an invalid
17645 location when the command exists. A general rule should be followed
17646 in that you should either assign @code{NULL} to any assigned pointers,
17647 or restore a valid location to the pointer before the command exits.
17649 Similar caution must be exercised with any structs, unions, and typedefs
17650 defined in @code{compile} command. Types defined in the @code{compile}
17651 command will no longer be available in the next @code{compile} command.
17652 Therefore, if you cast a variable to a type defined in the
17653 @code{compile} command, care must be taken to ensure that any future
17654 need to resolve the type can be achieved.
17657 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
17658 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
17659 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
17660 Compilation failed.
17661 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
17665 Variables that have been optimized away by the compiler are not
17666 accessible to the code submitted to the @code{compile} command.
17667 Access to those variables will generate a compiler error which @value{GDBN}
17668 will print to the console.
17671 @subsection Compiler search for the @code{compile} command
17673 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged which
17674 may not be obvious for remote targets of different architecture than where
17675 @value{GDBN} is running. Environment variable @code{PATH} (@code{PATH} from
17676 shell that executed @value{GDBN}, not the one set by @value{GDBN}
17677 command @code{set environment}). @xref{Environment}. @code{PATH} on
17678 @value{GDBN} host is searched for @value{NGCC} binary matching the
17679 target architecture and operating system.
17681 Specifically @code{PATH} is searched for binaries matching regular expression
17682 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
17683 debugged. @var{arch} is processor name --- multiarch is supported, so for
17684 example both @code{i386} and @code{x86_64} targets look for pattern
17685 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
17686 for pattern @code{s390x?}. @var{os} is currently supported only for
17687 pattern @code{linux(-gnu)?}.
17690 @chapter @value{GDBN} Files
17692 @value{GDBN} needs to know the file name of the program to be debugged,
17693 both in order to read its symbol table and in order to start your
17694 program. To debug a core dump of a previous run, you must also tell
17695 @value{GDBN} the name of the core dump file.
17698 * Files:: Commands to specify files
17699 * File Caching:: Information about @value{GDBN}'s file caching
17700 * Separate Debug Files:: Debugging information in separate files
17701 * MiniDebugInfo:: Debugging information in a special section
17702 * Index Files:: Index files speed up GDB
17703 * Symbol Errors:: Errors reading symbol files
17704 * Data Files:: GDB data files
17708 @section Commands to Specify Files
17710 @cindex symbol table
17711 @cindex core dump file
17713 You may want to specify executable and core dump file names. The usual
17714 way to do this is at start-up time, using the arguments to
17715 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
17716 Out of @value{GDBN}}).
17718 Occasionally it is necessary to change to a different file during a
17719 @value{GDBN} session. Or you may run @value{GDBN} and forget to
17720 specify a file you want to use. Or you are debugging a remote target
17721 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
17722 Program}). In these situations the @value{GDBN} commands to specify
17723 new files are useful.
17726 @cindex executable file
17728 @item file @var{filename}
17729 Use @var{filename} as the program to be debugged. It is read for its
17730 symbols and for the contents of pure memory. It is also the program
17731 executed when you use the @code{run} command. If you do not specify a
17732 directory and the file is not found in the @value{GDBN} working directory,
17733 @value{GDBN} uses the environment variable @code{PATH} as a list of
17734 directories to search, just as the shell does when looking for a program
17735 to run. You can change the value of this variable, for both @value{GDBN}
17736 and your program, using the @code{path} command.
17738 @cindex unlinked object files
17739 @cindex patching object files
17740 You can load unlinked object @file{.o} files into @value{GDBN} using
17741 the @code{file} command. You will not be able to ``run'' an object
17742 file, but you can disassemble functions and inspect variables. Also,
17743 if the underlying BFD functionality supports it, you could use
17744 @kbd{gdb -write} to patch object files using this technique. Note
17745 that @value{GDBN} can neither interpret nor modify relocations in this
17746 case, so branches and some initialized variables will appear to go to
17747 the wrong place. But this feature is still handy from time to time.
17750 @code{file} with no argument makes @value{GDBN} discard any information it
17751 has on both executable file and the symbol table.
17754 @item exec-file @r{[} @var{filename} @r{]}
17755 Specify that the program to be run (but not the symbol table) is found
17756 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
17757 if necessary to locate your program. Omitting @var{filename} means to
17758 discard information on the executable file.
17760 @kindex symbol-file
17761 @item symbol-file @r{[} @var{filename} @r{]}
17762 Read symbol table information from file @var{filename}. @code{PATH} is
17763 searched when necessary. Use the @code{file} command to get both symbol
17764 table and program to run from the same file.
17766 @code{symbol-file} with no argument clears out @value{GDBN} information on your
17767 program's symbol table.
17769 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
17770 some breakpoints and auto-display expressions. This is because they may
17771 contain pointers to the internal data recording symbols and data types,
17772 which are part of the old symbol table data being discarded inside
17775 @code{symbol-file} does not repeat if you press @key{RET} again after
17778 When @value{GDBN} is configured for a particular environment, it
17779 understands debugging information in whatever format is the standard
17780 generated for that environment; you may use either a @sc{gnu} compiler, or
17781 other compilers that adhere to the local conventions.
17782 Best results are usually obtained from @sc{gnu} compilers; for example,
17783 using @code{@value{NGCC}} you can generate debugging information for
17786 For most kinds of object files, with the exception of old SVR3 systems
17787 using COFF, the @code{symbol-file} command does not normally read the
17788 symbol table in full right away. Instead, it scans the symbol table
17789 quickly to find which source files and which symbols are present. The
17790 details are read later, one source file at a time, as they are needed.
17792 The purpose of this two-stage reading strategy is to make @value{GDBN}
17793 start up faster. For the most part, it is invisible except for
17794 occasional pauses while the symbol table details for a particular source
17795 file are being read. (The @code{set verbose} command can turn these
17796 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
17797 Warnings and Messages}.)
17799 We have not implemented the two-stage strategy for COFF yet. When the
17800 symbol table is stored in COFF format, @code{symbol-file} reads the
17801 symbol table data in full right away. Note that ``stabs-in-COFF''
17802 still does the two-stage strategy, since the debug info is actually
17806 @cindex reading symbols immediately
17807 @cindex symbols, reading immediately
17808 @item symbol-file @r{[} -readnow @r{]} @var{filename}
17809 @itemx file @r{[} -readnow @r{]} @var{filename}
17810 You can override the @value{GDBN} two-stage strategy for reading symbol
17811 tables by using the @samp{-readnow} option with any of the commands that
17812 load symbol table information, if you want to be sure @value{GDBN} has the
17813 entire symbol table available.
17815 @c FIXME: for now no mention of directories, since this seems to be in
17816 @c flux. 13mar1992 status is that in theory GDB would look either in
17817 @c current dir or in same dir as myprog; but issues like competing
17818 @c GDB's, or clutter in system dirs, mean that in practice right now
17819 @c only current dir is used. FFish says maybe a special GDB hierarchy
17820 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
17824 @item core-file @r{[}@var{filename}@r{]}
17826 Specify the whereabouts of a core dump file to be used as the ``contents
17827 of memory''. Traditionally, core files contain only some parts of the
17828 address space of the process that generated them; @value{GDBN} can access the
17829 executable file itself for other parts.
17831 @code{core-file} with no argument specifies that no core file is
17834 Note that the core file is ignored when your program is actually running
17835 under @value{GDBN}. So, if you have been running your program and you
17836 wish to debug a core file instead, you must kill the subprocess in which
17837 the program is running. To do this, use the @code{kill} command
17838 (@pxref{Kill Process, ,Killing the Child Process}).
17840 @kindex add-symbol-file
17841 @cindex dynamic linking
17842 @item add-symbol-file @var{filename} @var{address}
17843 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
17844 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
17845 The @code{add-symbol-file} command reads additional symbol table
17846 information from the file @var{filename}. You would use this command
17847 when @var{filename} has been dynamically loaded (by some other means)
17848 into the program that is running. The @var{address} should give the memory
17849 address at which the file has been loaded; @value{GDBN} cannot figure
17850 this out for itself. You can additionally specify an arbitrary number
17851 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
17852 section name and base address for that section. You can specify any
17853 @var{address} as an expression.
17855 The symbol table of the file @var{filename} is added to the symbol table
17856 originally read with the @code{symbol-file} command. You can use the
17857 @code{add-symbol-file} command any number of times; the new symbol data
17858 thus read is kept in addition to the old.
17860 Changes can be reverted using the command @code{remove-symbol-file}.
17862 @cindex relocatable object files, reading symbols from
17863 @cindex object files, relocatable, reading symbols from
17864 @cindex reading symbols from relocatable object files
17865 @cindex symbols, reading from relocatable object files
17866 @cindex @file{.o} files, reading symbols from
17867 Although @var{filename} is typically a shared library file, an
17868 executable file, or some other object file which has been fully
17869 relocated for loading into a process, you can also load symbolic
17870 information from relocatable @file{.o} files, as long as:
17874 the file's symbolic information refers only to linker symbols defined in
17875 that file, not to symbols defined by other object files,
17877 every section the file's symbolic information refers to has actually
17878 been loaded into the inferior, as it appears in the file, and
17880 you can determine the address at which every section was loaded, and
17881 provide these to the @code{add-symbol-file} command.
17885 Some embedded operating systems, like Sun Chorus and VxWorks, can load
17886 relocatable files into an already running program; such systems
17887 typically make the requirements above easy to meet. However, it's
17888 important to recognize that many native systems use complex link
17889 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
17890 assembly, for example) that make the requirements difficult to meet. In
17891 general, one cannot assume that using @code{add-symbol-file} to read a
17892 relocatable object file's symbolic information will have the same effect
17893 as linking the relocatable object file into the program in the normal
17896 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
17898 @kindex remove-symbol-file
17899 @item remove-symbol-file @var{filename}
17900 @item remove-symbol-file -a @var{address}
17901 Remove a symbol file added via the @code{add-symbol-file} command. The
17902 file to remove can be identified by its @var{filename} or by an @var{address}
17903 that lies within the boundaries of this symbol file in memory. Example:
17906 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
17907 add symbol table from file "/home/user/gdb/mylib.so" at
17908 .text_addr = 0x7ffff7ff9480
17910 Reading symbols from /home/user/gdb/mylib.so...done.
17911 (gdb) remove-symbol-file -a 0x7ffff7ff9480
17912 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
17917 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
17919 @kindex add-symbol-file-from-memory
17920 @cindex @code{syscall DSO}
17921 @cindex load symbols from memory
17922 @item add-symbol-file-from-memory @var{address}
17923 Load symbols from the given @var{address} in a dynamically loaded
17924 object file whose image is mapped directly into the inferior's memory.
17925 For example, the Linux kernel maps a @code{syscall DSO} into each
17926 process's address space; this DSO provides kernel-specific code for
17927 some system calls. The argument can be any expression whose
17928 evaluation yields the address of the file's shared object file header.
17929 For this command to work, you must have used @code{symbol-file} or
17930 @code{exec-file} commands in advance.
17933 @item section @var{section} @var{addr}
17934 The @code{section} command changes the base address of the named
17935 @var{section} of the exec file to @var{addr}. This can be used if the
17936 exec file does not contain section addresses, (such as in the
17937 @code{a.out} format), or when the addresses specified in the file
17938 itself are wrong. Each section must be changed separately. The
17939 @code{info files} command, described below, lists all the sections and
17943 @kindex info target
17946 @code{info files} and @code{info target} are synonymous; both print the
17947 current target (@pxref{Targets, ,Specifying a Debugging Target}),
17948 including the names of the executable and core dump files currently in
17949 use by @value{GDBN}, and the files from which symbols were loaded. The
17950 command @code{help target} lists all possible targets rather than
17953 @kindex maint info sections
17954 @item maint info sections
17955 Another command that can give you extra information about program sections
17956 is @code{maint info sections}. In addition to the section information
17957 displayed by @code{info files}, this command displays the flags and file
17958 offset of each section in the executable and core dump files. In addition,
17959 @code{maint info sections} provides the following command options (which
17960 may be arbitrarily combined):
17964 Display sections for all loaded object files, including shared libraries.
17965 @item @var{sections}
17966 Display info only for named @var{sections}.
17967 @item @var{section-flags}
17968 Display info only for sections for which @var{section-flags} are true.
17969 The section flags that @value{GDBN} currently knows about are:
17972 Section will have space allocated in the process when loaded.
17973 Set for all sections except those containing debug information.
17975 Section will be loaded from the file into the child process memory.
17976 Set for pre-initialized code and data, clear for @code{.bss} sections.
17978 Section needs to be relocated before loading.
17980 Section cannot be modified by the child process.
17982 Section contains executable code only.
17984 Section contains data only (no executable code).
17986 Section will reside in ROM.
17988 Section contains data for constructor/destructor lists.
17990 Section is not empty.
17992 An instruction to the linker to not output the section.
17993 @item COFF_SHARED_LIBRARY
17994 A notification to the linker that the section contains
17995 COFF shared library information.
17997 Section contains common symbols.
18000 @kindex set trust-readonly-sections
18001 @cindex read-only sections
18002 @item set trust-readonly-sections on
18003 Tell @value{GDBN} that readonly sections in your object file
18004 really are read-only (i.e.@: that their contents will not change).
18005 In that case, @value{GDBN} can fetch values from these sections
18006 out of the object file, rather than from the target program.
18007 For some targets (notably embedded ones), this can be a significant
18008 enhancement to debugging performance.
18010 The default is off.
18012 @item set trust-readonly-sections off
18013 Tell @value{GDBN} not to trust readonly sections. This means that
18014 the contents of the section might change while the program is running,
18015 and must therefore be fetched from the target when needed.
18017 @item show trust-readonly-sections
18018 Show the current setting of trusting readonly sections.
18021 All file-specifying commands allow both absolute and relative file names
18022 as arguments. @value{GDBN} always converts the file name to an absolute file
18023 name and remembers it that way.
18025 @cindex shared libraries
18026 @anchor{Shared Libraries}
18027 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
18028 and IBM RS/6000 AIX shared libraries.
18030 On MS-Windows @value{GDBN} must be linked with the Expat library to support
18031 shared libraries. @xref{Expat}.
18033 @value{GDBN} automatically loads symbol definitions from shared libraries
18034 when you use the @code{run} command, or when you examine a core file.
18035 (Before you issue the @code{run} command, @value{GDBN} does not understand
18036 references to a function in a shared library, however---unless you are
18037 debugging a core file).
18039 On HP-UX, if the program loads a library explicitly, @value{GDBN}
18040 automatically loads the symbols at the time of the @code{shl_load} call.
18042 @c FIXME: some @value{GDBN} release may permit some refs to undef
18043 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
18044 @c FIXME...lib; check this from time to time when updating manual
18046 There are times, however, when you may wish to not automatically load
18047 symbol definitions from shared libraries, such as when they are
18048 particularly large or there are many of them.
18050 To control the automatic loading of shared library symbols, use the
18054 @kindex set auto-solib-add
18055 @item set auto-solib-add @var{mode}
18056 If @var{mode} is @code{on}, symbols from all shared object libraries
18057 will be loaded automatically when the inferior begins execution, you
18058 attach to an independently started inferior, or when the dynamic linker
18059 informs @value{GDBN} that a new library has been loaded. If @var{mode}
18060 is @code{off}, symbols must be loaded manually, using the
18061 @code{sharedlibrary} command. The default value is @code{on}.
18063 @cindex memory used for symbol tables
18064 If your program uses lots of shared libraries with debug info that
18065 takes large amounts of memory, you can decrease the @value{GDBN}
18066 memory footprint by preventing it from automatically loading the
18067 symbols from shared libraries. To that end, type @kbd{set
18068 auto-solib-add off} before running the inferior, then load each
18069 library whose debug symbols you do need with @kbd{sharedlibrary
18070 @var{regexp}}, where @var{regexp} is a regular expression that matches
18071 the libraries whose symbols you want to be loaded.
18073 @kindex show auto-solib-add
18074 @item show auto-solib-add
18075 Display the current autoloading mode.
18078 @cindex load shared library
18079 To explicitly load shared library symbols, use the @code{sharedlibrary}
18083 @kindex info sharedlibrary
18085 @item info share @var{regex}
18086 @itemx info sharedlibrary @var{regex}
18087 Print the names of the shared libraries which are currently loaded
18088 that match @var{regex}. If @var{regex} is omitted then print
18089 all shared libraries that are loaded.
18092 @item info dll @var{regex}
18093 This is an alias of @code{info sharedlibrary}.
18095 @kindex sharedlibrary
18097 @item sharedlibrary @var{regex}
18098 @itemx share @var{regex}
18099 Load shared object library symbols for files matching a
18100 Unix regular expression.
18101 As with files loaded automatically, it only loads shared libraries
18102 required by your program for a core file or after typing @code{run}. If
18103 @var{regex} is omitted all shared libraries required by your program are
18106 @item nosharedlibrary
18107 @kindex nosharedlibrary
18108 @cindex unload symbols from shared libraries
18109 Unload all shared object library symbols. This discards all symbols
18110 that have been loaded from all shared libraries. Symbols from shared
18111 libraries that were loaded by explicit user requests are not
18115 Sometimes you may wish that @value{GDBN} stops and gives you control
18116 when any of shared library events happen. The best way to do this is
18117 to use @code{catch load} and @code{catch unload} (@pxref{Set
18120 @value{GDBN} also supports the the @code{set stop-on-solib-events}
18121 command for this. This command exists for historical reasons. It is
18122 less useful than setting a catchpoint, because it does not allow for
18123 conditions or commands as a catchpoint does.
18126 @item set stop-on-solib-events
18127 @kindex set stop-on-solib-events
18128 This command controls whether @value{GDBN} should give you control
18129 when the dynamic linker notifies it about some shared library event.
18130 The most common event of interest is loading or unloading of a new
18133 @item show stop-on-solib-events
18134 @kindex show stop-on-solib-events
18135 Show whether @value{GDBN} stops and gives you control when shared
18136 library events happen.
18139 Shared libraries are also supported in many cross or remote debugging
18140 configurations. @value{GDBN} needs to have access to the target's libraries;
18141 this can be accomplished either by providing copies of the libraries
18142 on the host system, or by asking @value{GDBN} to automatically retrieve the
18143 libraries from the target. If copies of the target libraries are
18144 provided, they need to be the same as the target libraries, although the
18145 copies on the target can be stripped as long as the copies on the host are
18148 @cindex where to look for shared libraries
18149 For remote debugging, you need to tell @value{GDBN} where the target
18150 libraries are, so that it can load the correct copies---otherwise, it
18151 may try to load the host's libraries. @value{GDBN} has two variables
18152 to specify the search directories for target libraries.
18155 @cindex prefix for executable and shared library file names
18156 @cindex system root, alternate
18157 @kindex set solib-absolute-prefix
18158 @kindex set sysroot
18159 @item set sysroot @var{path}
18160 Use @var{path} as the system root for the program being debugged. Any
18161 absolute shared library paths will be prefixed with @var{path}; many
18162 runtime loaders store the absolute paths to the shared library in the
18163 target program's memory. When starting processes remotely, and when
18164 attaching to already-running processes (local or remote), their
18165 executable filenames will be prefixed with @var{path} if reported to
18166 @value{GDBN} as absolute by the operating system. If you use
18167 @code{set sysroot} to find executables and shared libraries, they need
18168 to be laid out in the same way that they are on the target, with
18169 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
18172 If @var{path} starts with the sequence @file{target:} and the target
18173 system is remote then @value{GDBN} will retrieve the target binaries
18174 from the remote system. This is only supported when using a remote
18175 target that supports the @code{remote get} command (@pxref{File
18176 Transfer,,Sending files to a remote system}). The part of @var{path}
18177 following the initial @file{target:} (if present) is used as system
18178 root prefix on the remote file system. If @var{path} starts with the
18179 sequence @file{remote:} this is converted to the sequence
18180 @file{target:} by @code{set sysroot}@footnote{Historically the
18181 functionality to retrieve binaries from the remote system was
18182 provided by prefixing @var{path} with @file{remote:}}. If you want
18183 to specify a local system root using a directory that happens to be
18184 named @file{target:} or @file{remote:}, you need to use some
18185 equivalent variant of the name like @file{./target:}.
18187 For targets with an MS-DOS based filesystem, such as MS-Windows and
18188 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
18189 absolute file name with @var{path}. But first, on Unix hosts,
18190 @value{GDBN} converts all backslash directory separators into forward
18191 slashes, because the backslash is not a directory separator on Unix:
18194 c:\foo\bar.dll @result{} c:/foo/bar.dll
18197 Then, @value{GDBN} attempts prefixing the target file name with
18198 @var{path}, and looks for the resulting file name in the host file
18202 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
18205 If that does not find the binary, @value{GDBN} tries removing
18206 the @samp{:} character from the drive spec, both for convenience, and,
18207 for the case of the host file system not supporting file names with
18211 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
18214 This makes it possible to have a system root that mirrors a target
18215 with more than one drive. E.g., you may want to setup your local
18216 copies of the target system shared libraries like so (note @samp{c} vs
18220 @file{/path/to/sysroot/c/sys/bin/foo.dll}
18221 @file{/path/to/sysroot/c/sys/bin/bar.dll}
18222 @file{/path/to/sysroot/z/sys/bin/bar.dll}
18226 and point the system root at @file{/path/to/sysroot}, so that
18227 @value{GDBN} can find the correct copies of both
18228 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
18230 If that still does not find the binary, @value{GDBN} tries
18231 removing the whole drive spec from the target file name:
18234 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
18237 This last lookup makes it possible to not care about the drive name,
18238 if you don't want or need to.
18240 The @code{set solib-absolute-prefix} command is an alias for @code{set
18243 @cindex default system root
18244 @cindex @samp{--with-sysroot}
18245 You can set the default system root by using the configure-time
18246 @samp{--with-sysroot} option. If the system root is inside
18247 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
18248 @samp{--exec-prefix}), then the default system root will be updated
18249 automatically if the installed @value{GDBN} is moved to a new
18252 @kindex show sysroot
18254 Display the current executable and shared library prefix.
18256 @kindex set solib-search-path
18257 @item set solib-search-path @var{path}
18258 If this variable is set, @var{path} is a colon-separated list of
18259 directories to search for shared libraries. @samp{solib-search-path}
18260 is used after @samp{sysroot} fails to locate the library, or if the
18261 path to the library is relative instead of absolute. If you want to
18262 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
18263 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
18264 finding your host's libraries. @samp{sysroot} is preferred; setting
18265 it to a nonexistent directory may interfere with automatic loading
18266 of shared library symbols.
18268 @kindex show solib-search-path
18269 @item show solib-search-path
18270 Display the current shared library search path.
18272 @cindex DOS file-name semantics of file names.
18273 @kindex set target-file-system-kind (unix|dos-based|auto)
18274 @kindex show target-file-system-kind
18275 @item set target-file-system-kind @var{kind}
18276 Set assumed file system kind for target reported file names.
18278 Shared library file names as reported by the target system may not
18279 make sense as is on the system @value{GDBN} is running on. For
18280 example, when remote debugging a target that has MS-DOS based file
18281 system semantics, from a Unix host, the target may be reporting to
18282 @value{GDBN} a list of loaded shared libraries with file names such as
18283 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
18284 drive letters, so the @samp{c:\} prefix is not normally understood as
18285 indicating an absolute file name, and neither is the backslash
18286 normally considered a directory separator character. In that case,
18287 the native file system would interpret this whole absolute file name
18288 as a relative file name with no directory components. This would make
18289 it impossible to point @value{GDBN} at a copy of the remote target's
18290 shared libraries on the host using @code{set sysroot}, and impractical
18291 with @code{set solib-search-path}. Setting
18292 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
18293 to interpret such file names similarly to how the target would, and to
18294 map them to file names valid on @value{GDBN}'s native file system
18295 semantics. The value of @var{kind} can be @code{"auto"}, in addition
18296 to one of the supported file system kinds. In that case, @value{GDBN}
18297 tries to determine the appropriate file system variant based on the
18298 current target's operating system (@pxref{ABI, ,Configuring the
18299 Current ABI}). The supported file system settings are:
18303 Instruct @value{GDBN} to assume the target file system is of Unix
18304 kind. Only file names starting the forward slash (@samp{/}) character
18305 are considered absolute, and the directory separator character is also
18309 Instruct @value{GDBN} to assume the target file system is DOS based.
18310 File names starting with either a forward slash, or a drive letter
18311 followed by a colon (e.g., @samp{c:}), are considered absolute, and
18312 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
18313 considered directory separators.
18316 Instruct @value{GDBN} to use the file system kind associated with the
18317 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
18318 This is the default.
18322 @cindex file name canonicalization
18323 @cindex base name differences
18324 When processing file names provided by the user, @value{GDBN}
18325 frequently needs to compare them to the file names recorded in the
18326 program's debug info. Normally, @value{GDBN} compares just the
18327 @dfn{base names} of the files as strings, which is reasonably fast
18328 even for very large programs. (The base name of a file is the last
18329 portion of its name, after stripping all the leading directories.)
18330 This shortcut in comparison is based upon the assumption that files
18331 cannot have more than one base name. This is usually true, but
18332 references to files that use symlinks or similar filesystem
18333 facilities violate that assumption. If your program records files
18334 using such facilities, or if you provide file names to @value{GDBN}
18335 using symlinks etc., you can set @code{basenames-may-differ} to
18336 @code{true} to instruct @value{GDBN} to completely canonicalize each
18337 pair of file names it needs to compare. This will make file-name
18338 comparisons accurate, but at a price of a significant slowdown.
18341 @item set basenames-may-differ
18342 @kindex set basenames-may-differ
18343 Set whether a source file may have multiple base names.
18345 @item show basenames-may-differ
18346 @kindex show basenames-may-differ
18347 Show whether a source file may have multiple base names.
18351 @section File Caching
18352 @cindex caching of opened files
18353 @cindex caching of bfd objects
18355 To speed up file loading, and reduce memory usage, @value{GDBN} will
18356 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
18357 BFD, bfd, The Binary File Descriptor Library}. The following commands
18358 allow visibility and control of the caching behavior.
18361 @kindex maint info bfds
18362 @item maint info bfds
18363 This prints information about each @code{bfd} object that is known to
18366 @kindex maint set bfd-sharing
18367 @kindex maint show bfd-sharing
18368 @kindex bfd caching
18369 @item maint set bfd-sharing
18370 @item maint show bfd-sharing
18371 Control whether @code{bfd} objects can be shared. When sharing is
18372 enabled @value{GDBN} reuses already open @code{bfd} objects rather
18373 than reopening the same file. Turning sharing off does not cause
18374 already shared @code{bfd} objects to be unshared, but all future files
18375 that are opened will create a new @code{bfd} object. Similarly,
18376 re-enabling sharing does not cause multiple existing @code{bfd}
18377 objects to be collapsed into a single shared @code{bfd} object.
18379 @kindex set debug bfd-cache @var{level}
18380 @kindex bfd caching
18381 @item set debug bfd-cache @var{level}
18382 Turns on debugging of the bfd cache, setting the level to @var{level}.
18384 @kindex show debug bfd-cache
18385 @kindex bfd caching
18386 @item show debug bfd-cache
18387 Show the current debugging level of the bfd cache.
18390 @node Separate Debug Files
18391 @section Debugging Information in Separate Files
18392 @cindex separate debugging information files
18393 @cindex debugging information in separate files
18394 @cindex @file{.debug} subdirectories
18395 @cindex debugging information directory, global
18396 @cindex global debugging information directories
18397 @cindex build ID, and separate debugging files
18398 @cindex @file{.build-id} directory
18400 @value{GDBN} allows you to put a program's debugging information in a
18401 file separate from the executable itself, in a way that allows
18402 @value{GDBN} to find and load the debugging information automatically.
18403 Since debugging information can be very large---sometimes larger
18404 than the executable code itself---some systems distribute debugging
18405 information for their executables in separate files, which users can
18406 install only when they need to debug a problem.
18408 @value{GDBN} supports two ways of specifying the separate debug info
18413 The executable contains a @dfn{debug link} that specifies the name of
18414 the separate debug info file. The separate debug file's name is
18415 usually @file{@var{executable}.debug}, where @var{executable} is the
18416 name of the corresponding executable file without leading directories
18417 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
18418 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
18419 checksum for the debug file, which @value{GDBN} uses to validate that
18420 the executable and the debug file came from the same build.
18423 The executable contains a @dfn{build ID}, a unique bit string that is
18424 also present in the corresponding debug info file. (This is supported
18425 only on some operating systems, when using the ELF or PE file formats
18426 for binary files and the @sc{gnu} Binutils.) For more details about
18427 this feature, see the description of the @option{--build-id}
18428 command-line option in @ref{Options, , Command Line Options, ld.info,
18429 The GNU Linker}. The debug info file's name is not specified
18430 explicitly by the build ID, but can be computed from the build ID, see
18434 Depending on the way the debug info file is specified, @value{GDBN}
18435 uses two different methods of looking for the debug file:
18439 For the ``debug link'' method, @value{GDBN} looks up the named file in
18440 the directory of the executable file, then in a subdirectory of that
18441 directory named @file{.debug}, and finally under each one of the global debug
18442 directories, in a subdirectory whose name is identical to the leading
18443 directories of the executable's absolute file name.
18446 For the ``build ID'' method, @value{GDBN} looks in the
18447 @file{.build-id} subdirectory of each one of the global debug directories for
18448 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
18449 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
18450 are the rest of the bit string. (Real build ID strings are 32 or more
18451 hex characters, not 10.)
18454 So, for example, suppose you ask @value{GDBN} to debug
18455 @file{/usr/bin/ls}, which has a debug link that specifies the
18456 file @file{ls.debug}, and a build ID whose value in hex is
18457 @code{abcdef1234}. If the list of the global debug directories includes
18458 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
18459 debug information files, in the indicated order:
18463 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
18465 @file{/usr/bin/ls.debug}
18467 @file{/usr/bin/.debug/ls.debug}
18469 @file{/usr/lib/debug/usr/bin/ls.debug}.
18472 @anchor{debug-file-directory}
18473 Global debugging info directories default to what is set by @value{GDBN}
18474 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
18475 you can also set the global debugging info directories, and view the list
18476 @value{GDBN} is currently using.
18480 @kindex set debug-file-directory
18481 @item set debug-file-directory @var{directories}
18482 Set the directories which @value{GDBN} searches for separate debugging
18483 information files to @var{directory}. Multiple path components can be set
18484 concatenating them by a path separator.
18486 @kindex show debug-file-directory
18487 @item show debug-file-directory
18488 Show the directories @value{GDBN} searches for separate debugging
18493 @cindex @code{.gnu_debuglink} sections
18494 @cindex debug link sections
18495 A debug link is a special section of the executable file named
18496 @code{.gnu_debuglink}. The section must contain:
18500 A filename, with any leading directory components removed, followed by
18503 zero to three bytes of padding, as needed to reach the next four-byte
18504 boundary within the section, and
18506 a four-byte CRC checksum, stored in the same endianness used for the
18507 executable file itself. The checksum is computed on the debugging
18508 information file's full contents by the function given below, passing
18509 zero as the @var{crc} argument.
18512 Any executable file format can carry a debug link, as long as it can
18513 contain a section named @code{.gnu_debuglink} with the contents
18516 @cindex @code{.note.gnu.build-id} sections
18517 @cindex build ID sections
18518 The build ID is a special section in the executable file (and in other
18519 ELF binary files that @value{GDBN} may consider). This section is
18520 often named @code{.note.gnu.build-id}, but that name is not mandatory.
18521 It contains unique identification for the built files---the ID remains
18522 the same across multiple builds of the same build tree. The default
18523 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
18524 content for the build ID string. The same section with an identical
18525 value is present in the original built binary with symbols, in its
18526 stripped variant, and in the separate debugging information file.
18528 The debugging information file itself should be an ordinary
18529 executable, containing a full set of linker symbols, sections, and
18530 debugging information. The sections of the debugging information file
18531 should have the same names, addresses, and sizes as the original file,
18532 but they need not contain any data---much like a @code{.bss} section
18533 in an ordinary executable.
18535 The @sc{gnu} binary utilities (Binutils) package includes the
18536 @samp{objcopy} utility that can produce
18537 the separated executable / debugging information file pairs using the
18538 following commands:
18541 @kbd{objcopy --only-keep-debug foo foo.debug}
18546 These commands remove the debugging
18547 information from the executable file @file{foo} and place it in the file
18548 @file{foo.debug}. You can use the first, second or both methods to link the
18553 The debug link method needs the following additional command to also leave
18554 behind a debug link in @file{foo}:
18557 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
18560 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
18561 a version of the @code{strip} command such that the command @kbd{strip foo -f
18562 foo.debug} has the same functionality as the two @code{objcopy} commands and
18563 the @code{ln -s} command above, together.
18566 Build ID gets embedded into the main executable using @code{ld --build-id} or
18567 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
18568 compatibility fixes for debug files separation are present in @sc{gnu} binary
18569 utilities (Binutils) package since version 2.18.
18574 @cindex CRC algorithm definition
18575 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
18576 IEEE 802.3 using the polynomial:
18578 @c TexInfo requires naked braces for multi-digit exponents for Tex
18579 @c output, but this causes HTML output to barf. HTML has to be set using
18580 @c raw commands. So we end up having to specify this equation in 2
18585 <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>
18586 + <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
18592 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
18593 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
18597 The function is computed byte at a time, taking the least
18598 significant bit of each byte first. The initial pattern
18599 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
18600 the final result is inverted to ensure trailing zeros also affect the
18603 @emph{Note:} This is the same CRC polynomial as used in handling the
18604 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
18605 However in the case of the Remote Serial Protocol, the CRC is computed
18606 @emph{most} significant bit first, and the result is not inverted, so
18607 trailing zeros have no effect on the CRC value.
18609 To complete the description, we show below the code of the function
18610 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
18611 initially supplied @code{crc} argument means that an initial call to
18612 this function passing in zero will start computing the CRC using
18615 @kindex gnu_debuglink_crc32
18618 gnu_debuglink_crc32 (unsigned long crc,
18619 unsigned char *buf, size_t len)
18621 static const unsigned long crc32_table[256] =
18623 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
18624 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
18625 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
18626 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
18627 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
18628 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
18629 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
18630 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
18631 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
18632 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
18633 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
18634 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
18635 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
18636 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
18637 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
18638 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
18639 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
18640 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
18641 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
18642 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
18643 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
18644 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
18645 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
18646 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
18647 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
18648 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
18649 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
18650 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
18651 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
18652 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
18653 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
18654 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
18655 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
18656 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
18657 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
18658 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
18659 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
18660 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
18661 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
18662 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
18663 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
18664 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
18665 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
18666 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
18667 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
18668 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
18669 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
18670 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
18671 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
18672 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
18673 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
18676 unsigned char *end;
18678 crc = ~crc & 0xffffffff;
18679 for (end = buf + len; buf < end; ++buf)
18680 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
18681 return ~crc & 0xffffffff;
18686 This computation does not apply to the ``build ID'' method.
18688 @node MiniDebugInfo
18689 @section Debugging information in a special section
18690 @cindex separate debug sections
18691 @cindex @samp{.gnu_debugdata} section
18693 Some systems ship pre-built executables and libraries that have a
18694 special @samp{.gnu_debugdata} section. This feature is called
18695 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
18696 is used to supply extra symbols for backtraces.
18698 The intent of this section is to provide extra minimal debugging
18699 information for use in simple backtraces. It is not intended to be a
18700 replacement for full separate debugging information (@pxref{Separate
18701 Debug Files}). The example below shows the intended use; however,
18702 @value{GDBN} does not currently put restrictions on what sort of
18703 debugging information might be included in the section.
18705 @value{GDBN} has support for this extension. If the section exists,
18706 then it is used provided that no other source of debugging information
18707 can be found, and that @value{GDBN} was configured with LZMA support.
18709 This section can be easily created using @command{objcopy} and other
18710 standard utilities:
18713 # Extract the dynamic symbols from the main binary, there is no need
18714 # to also have these in the normal symbol table.
18715 nm -D @var{binary} --format=posix --defined-only \
18716 | awk '@{ print $1 @}' | sort > dynsyms
18718 # Extract all the text (i.e. function) symbols from the debuginfo.
18719 # (Note that we actually also accept "D" symbols, for the benefit
18720 # of platforms like PowerPC64 that use function descriptors.)
18721 nm @var{binary} --format=posix --defined-only \
18722 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
18725 # Keep all the function symbols not already in the dynamic symbol
18727 comm -13 dynsyms funcsyms > keep_symbols
18729 # Separate full debug info into debug binary.
18730 objcopy --only-keep-debug @var{binary} debug
18732 # Copy the full debuginfo, keeping only a minimal set of symbols and
18733 # removing some unnecessary sections.
18734 objcopy -S --remove-section .gdb_index --remove-section .comment \
18735 --keep-symbols=keep_symbols debug mini_debuginfo
18737 # Drop the full debug info from the original binary.
18738 strip --strip-all -R .comment @var{binary}
18740 # Inject the compressed data into the .gnu_debugdata section of the
18743 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
18747 @section Index Files Speed Up @value{GDBN}
18748 @cindex index files
18749 @cindex @samp{.gdb_index} section
18751 When @value{GDBN} finds a symbol file, it scans the symbols in the
18752 file in order to construct an internal symbol table. This lets most
18753 @value{GDBN} operations work quickly---at the cost of a delay early
18754 on. For large programs, this delay can be quite lengthy, so
18755 @value{GDBN} provides a way to build an index, which speeds up
18758 The index is stored as a section in the symbol file. @value{GDBN} can
18759 write the index to a file, then you can put it into the symbol file
18760 using @command{objcopy}.
18762 To create an index file, use the @code{save gdb-index} command:
18765 @item save gdb-index @var{directory}
18766 @kindex save gdb-index
18767 Create an index file for each symbol file currently known by
18768 @value{GDBN}. Each file is named after its corresponding symbol file,
18769 with @samp{.gdb-index} appended, and is written into the given
18773 Once you have created an index file you can merge it into your symbol
18774 file, here named @file{symfile}, using @command{objcopy}:
18777 $ objcopy --add-section .gdb_index=symfile.gdb-index \
18778 --set-section-flags .gdb_index=readonly symfile symfile
18781 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
18782 sections that have been deprecated. Usually they are deprecated because
18783 they are missing a new feature or have performance issues.
18784 To tell @value{GDBN} to use a deprecated index section anyway
18785 specify @code{set use-deprecated-index-sections on}.
18786 The default is @code{off}.
18787 This can speed up startup, but may result in some functionality being lost.
18788 @xref{Index Section Format}.
18790 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
18791 must be done before gdb reads the file. The following will not work:
18794 $ gdb -ex "set use-deprecated-index-sections on" <program>
18797 Instead you must do, for example,
18800 $ gdb -iex "set use-deprecated-index-sections on" <program>
18803 There are currently some limitation on indices. They only work when
18804 for DWARF debugging information, not stabs. And, they do not
18805 currently work for programs using Ada.
18807 @node Symbol Errors
18808 @section Errors Reading Symbol Files
18810 While reading a symbol file, @value{GDBN} occasionally encounters problems,
18811 such as symbol types it does not recognize, or known bugs in compiler
18812 output. By default, @value{GDBN} does not notify you of such problems, since
18813 they are relatively common and primarily of interest to people
18814 debugging compilers. If you are interested in seeing information
18815 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
18816 only one message about each such type of problem, no matter how many
18817 times the problem occurs; or you can ask @value{GDBN} to print more messages,
18818 to see how many times the problems occur, with the @code{set
18819 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
18822 The messages currently printed, and their meanings, include:
18825 @item inner block not inside outer block in @var{symbol}
18827 The symbol information shows where symbol scopes begin and end
18828 (such as at the start of a function or a block of statements). This
18829 error indicates that an inner scope block is not fully contained
18830 in its outer scope blocks.
18832 @value{GDBN} circumvents the problem by treating the inner block as if it had
18833 the same scope as the outer block. In the error message, @var{symbol}
18834 may be shown as ``@code{(don't know)}'' if the outer block is not a
18837 @item block at @var{address} out of order
18839 The symbol information for symbol scope blocks should occur in
18840 order of increasing addresses. This error indicates that it does not
18843 @value{GDBN} does not circumvent this problem, and has trouble
18844 locating symbols in the source file whose symbols it is reading. (You
18845 can often determine what source file is affected by specifying
18846 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
18849 @item bad block start address patched
18851 The symbol information for a symbol scope block has a start address
18852 smaller than the address of the preceding source line. This is known
18853 to occur in the SunOS 4.1.1 (and earlier) C compiler.
18855 @value{GDBN} circumvents the problem by treating the symbol scope block as
18856 starting on the previous source line.
18858 @item bad string table offset in symbol @var{n}
18861 Symbol number @var{n} contains a pointer into the string table which is
18862 larger than the size of the string table.
18864 @value{GDBN} circumvents the problem by considering the symbol to have the
18865 name @code{foo}, which may cause other problems if many symbols end up
18868 @item unknown symbol type @code{0x@var{nn}}
18870 The symbol information contains new data types that @value{GDBN} does
18871 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
18872 uncomprehended information, in hexadecimal.
18874 @value{GDBN} circumvents the error by ignoring this symbol information.
18875 This usually allows you to debug your program, though certain symbols
18876 are not accessible. If you encounter such a problem and feel like
18877 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
18878 on @code{complain}, then go up to the function @code{read_dbx_symtab}
18879 and examine @code{*bufp} to see the symbol.
18881 @item stub type has NULL name
18883 @value{GDBN} could not find the full definition for a struct or class.
18885 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
18886 The symbol information for a C@t{++} member function is missing some
18887 information that recent versions of the compiler should have output for
18890 @item info mismatch between compiler and debugger
18892 @value{GDBN} could not parse a type specification output by the compiler.
18897 @section GDB Data Files
18899 @cindex prefix for data files
18900 @value{GDBN} will sometimes read an auxiliary data file. These files
18901 are kept in a directory known as the @dfn{data directory}.
18903 You can set the data directory's name, and view the name @value{GDBN}
18904 is currently using.
18907 @kindex set data-directory
18908 @item set data-directory @var{directory}
18909 Set the directory which @value{GDBN} searches for auxiliary data files
18910 to @var{directory}.
18912 @kindex show data-directory
18913 @item show data-directory
18914 Show the directory @value{GDBN} searches for auxiliary data files.
18917 @cindex default data directory
18918 @cindex @samp{--with-gdb-datadir}
18919 You can set the default data directory by using the configure-time
18920 @samp{--with-gdb-datadir} option. If the data directory is inside
18921 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
18922 @samp{--exec-prefix}), then the default data directory will be updated
18923 automatically if the installed @value{GDBN} is moved to a new
18926 The data directory may also be specified with the
18927 @code{--data-directory} command line option.
18928 @xref{Mode Options}.
18931 @chapter Specifying a Debugging Target
18933 @cindex debugging target
18934 A @dfn{target} is the execution environment occupied by your program.
18936 Often, @value{GDBN} runs in the same host environment as your program;
18937 in that case, the debugging target is specified as a side effect when
18938 you use the @code{file} or @code{core} commands. When you need more
18939 flexibility---for example, running @value{GDBN} on a physically separate
18940 host, or controlling a standalone system over a serial port or a
18941 realtime system over a TCP/IP connection---you can use the @code{target}
18942 command to specify one of the target types configured for @value{GDBN}
18943 (@pxref{Target Commands, ,Commands for Managing Targets}).
18945 @cindex target architecture
18946 It is possible to build @value{GDBN} for several different @dfn{target
18947 architectures}. When @value{GDBN} is built like that, you can choose
18948 one of the available architectures with the @kbd{set architecture}
18952 @kindex set architecture
18953 @kindex show architecture
18954 @item set architecture @var{arch}
18955 This command sets the current target architecture to @var{arch}. The
18956 value of @var{arch} can be @code{"auto"}, in addition to one of the
18957 supported architectures.
18959 @item show architecture
18960 Show the current target architecture.
18962 @item set processor
18964 @kindex set processor
18965 @kindex show processor
18966 These are alias commands for, respectively, @code{set architecture}
18967 and @code{show architecture}.
18971 * Active Targets:: Active targets
18972 * Target Commands:: Commands for managing targets
18973 * Byte Order:: Choosing target byte order
18976 @node Active Targets
18977 @section Active Targets
18979 @cindex stacking targets
18980 @cindex active targets
18981 @cindex multiple targets
18983 There are multiple classes of targets such as: processes, executable files or
18984 recording sessions. Core files belong to the process class, making core file
18985 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
18986 on multiple active targets, one in each class. This allows you to (for
18987 example) start a process and inspect its activity, while still having access to
18988 the executable file after the process finishes. Or if you start process
18989 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
18990 presented a virtual layer of the recording target, while the process target
18991 remains stopped at the chronologically last point of the process execution.
18993 Use the @code{core-file} and @code{exec-file} commands to select a new core
18994 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
18995 specify as a target a process that is already running, use the @code{attach}
18996 command (@pxref{Attach, ,Debugging an Already-running Process}).
18998 @node Target Commands
18999 @section Commands for Managing Targets
19002 @item target @var{type} @var{parameters}
19003 Connects the @value{GDBN} host environment to a target machine or
19004 process. A target is typically a protocol for talking to debugging
19005 facilities. You use the argument @var{type} to specify the type or
19006 protocol of the target machine.
19008 Further @var{parameters} are interpreted by the target protocol, but
19009 typically include things like device names or host names to connect
19010 with, process numbers, and baud rates.
19012 The @code{target} command does not repeat if you press @key{RET} again
19013 after executing the command.
19015 @kindex help target
19017 Displays the names of all targets available. To display targets
19018 currently selected, use either @code{info target} or @code{info files}
19019 (@pxref{Files, ,Commands to Specify Files}).
19021 @item help target @var{name}
19022 Describe a particular target, including any parameters necessary to
19025 @kindex set gnutarget
19026 @item set gnutarget @var{args}
19027 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
19028 knows whether it is reading an @dfn{executable},
19029 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
19030 with the @code{set gnutarget} command. Unlike most @code{target} commands,
19031 with @code{gnutarget} the @code{target} refers to a program, not a machine.
19034 @emph{Warning:} To specify a file format with @code{set gnutarget},
19035 you must know the actual BFD name.
19039 @xref{Files, , Commands to Specify Files}.
19041 @kindex show gnutarget
19042 @item show gnutarget
19043 Use the @code{show gnutarget} command to display what file format
19044 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
19045 @value{GDBN} will determine the file format for each file automatically,
19046 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
19049 @cindex common targets
19050 Here are some common targets (available, or not, depending on the GDB
19055 @item target exec @var{program}
19056 @cindex executable file target
19057 An executable file. @samp{target exec @var{program}} is the same as
19058 @samp{exec-file @var{program}}.
19060 @item target core @var{filename}
19061 @cindex core dump file target
19062 A core dump file. @samp{target core @var{filename}} is the same as
19063 @samp{core-file @var{filename}}.
19065 @item target remote @var{medium}
19066 @cindex remote target
19067 A remote system connected to @value{GDBN} via a serial line or network
19068 connection. This command tells @value{GDBN} to use its own remote
19069 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
19071 For example, if you have a board connected to @file{/dev/ttya} on the
19072 machine running @value{GDBN}, you could say:
19075 target remote /dev/ttya
19078 @code{target remote} supports the @code{load} command. This is only
19079 useful if you have some other way of getting the stub to the target
19080 system, and you can put it somewhere in memory where it won't get
19081 clobbered by the download.
19083 @item target sim @r{[}@var{simargs}@r{]} @dots{}
19084 @cindex built-in simulator target
19085 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
19093 works; however, you cannot assume that a specific memory map, device
19094 drivers, or even basic I/O is available, although some simulators do
19095 provide these. For info about any processor-specific simulator details,
19096 see the appropriate section in @ref{Embedded Processors, ,Embedded
19099 @item target native
19100 @cindex native target
19101 Setup for local/native process debugging. Useful to make the
19102 @code{run} command spawn native processes (likewise @code{attach},
19103 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
19104 (@pxref{set auto-connect-native-target}).
19108 Different targets are available on different configurations of @value{GDBN};
19109 your configuration may have more or fewer targets.
19111 Many remote targets require you to download the executable's code once
19112 you've successfully established a connection. You may wish to control
19113 various aspects of this process.
19118 @kindex set hash@r{, for remote monitors}
19119 @cindex hash mark while downloading
19120 This command controls whether a hash mark @samp{#} is displayed while
19121 downloading a file to the remote monitor. If on, a hash mark is
19122 displayed after each S-record is successfully downloaded to the
19126 @kindex show hash@r{, for remote monitors}
19127 Show the current status of displaying the hash mark.
19129 @item set debug monitor
19130 @kindex set debug monitor
19131 @cindex display remote monitor communications
19132 Enable or disable display of communications messages between
19133 @value{GDBN} and the remote monitor.
19135 @item show debug monitor
19136 @kindex show debug monitor
19137 Show the current status of displaying communications between
19138 @value{GDBN} and the remote monitor.
19143 @kindex load @var{filename}
19144 @item load @var{filename}
19146 Depending on what remote debugging facilities are configured into
19147 @value{GDBN}, the @code{load} command may be available. Where it exists, it
19148 is meant to make @var{filename} (an executable) available for debugging
19149 on the remote system---by downloading, or dynamic linking, for example.
19150 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
19151 the @code{add-symbol-file} command.
19153 If your @value{GDBN} does not have a @code{load} command, attempting to
19154 execute it gets the error message ``@code{You can't do that when your
19155 target is @dots{}}''
19157 The file is loaded at whatever address is specified in the executable.
19158 For some object file formats, you can specify the load address when you
19159 link the program; for other formats, like a.out, the object file format
19160 specifies a fixed address.
19161 @c FIXME! This would be a good place for an xref to the GNU linker doc.
19163 Depending on the remote side capabilities, @value{GDBN} may be able to
19164 load programs into flash memory.
19166 @code{load} does not repeat if you press @key{RET} again after using it.
19170 @section Choosing Target Byte Order
19172 @cindex choosing target byte order
19173 @cindex target byte order
19175 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
19176 offer the ability to run either big-endian or little-endian byte
19177 orders. Usually the executable or symbol will include a bit to
19178 designate the endian-ness, and you will not need to worry about
19179 which to use. However, you may still find it useful to adjust
19180 @value{GDBN}'s idea of processor endian-ness manually.
19184 @item set endian big
19185 Instruct @value{GDBN} to assume the target is big-endian.
19187 @item set endian little
19188 Instruct @value{GDBN} to assume the target is little-endian.
19190 @item set endian auto
19191 Instruct @value{GDBN} to use the byte order associated with the
19195 Display @value{GDBN}'s current idea of the target byte order.
19199 Note that these commands merely adjust interpretation of symbolic
19200 data on the host, and that they have absolutely no effect on the
19204 @node Remote Debugging
19205 @chapter Debugging Remote Programs
19206 @cindex remote debugging
19208 If you are trying to debug a program running on a machine that cannot run
19209 @value{GDBN} in the usual way, it is often useful to use remote debugging.
19210 For example, you might use remote debugging on an operating system kernel,
19211 or on a small system which does not have a general purpose operating system
19212 powerful enough to run a full-featured debugger.
19214 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
19215 to make this work with particular debugging targets. In addition,
19216 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
19217 but not specific to any particular target system) which you can use if you
19218 write the remote stubs---the code that runs on the remote system to
19219 communicate with @value{GDBN}.
19221 Other remote targets may be available in your
19222 configuration of @value{GDBN}; use @code{help target} to list them.
19225 * Connecting:: Connecting to a remote target
19226 * File Transfer:: Sending files to a remote system
19227 * Server:: Using the gdbserver program
19228 * Remote Configuration:: Remote configuration
19229 * Remote Stub:: Implementing a remote stub
19233 @section Connecting to a Remote Target
19235 @value{GDBN} needs an unstripped copy of your program to access symbol
19236 and debugging information. Some remote targets (@pxref{qXfer
19237 executable filename read}, and @pxref{Host I/O Packets}) allow
19238 @value{GDBN} to access program files over the same connection used to
19239 communicate with @value{GDBN}. With such a target, if the remote
19240 program is unstripped, the only command you need is @code{target
19241 remote}. Otherwise, start up @value{GDBN} using the name of the local
19242 unstripped copy of your program as the first argument, or use the
19243 @code{file} command.
19245 @cindex @code{target remote}
19246 @value{GDBN} can communicate with the target over a serial line, or
19247 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
19248 each case, @value{GDBN} uses the same protocol for debugging your
19249 program; only the medium carrying the debugging packets varies. The
19250 @code{target remote} command establishes a connection to the target.
19251 Its arguments indicate which medium to use:
19255 @item target remote @var{serial-device}
19256 @cindex serial line, @code{target remote}
19257 Use @var{serial-device} to communicate with the target. For example,
19258 to use a serial line connected to the device named @file{/dev/ttyb}:
19261 target remote /dev/ttyb
19264 If you're using a serial line, you may want to give @value{GDBN} the
19265 @samp{--baud} option, or use the @code{set serial baud} command
19266 (@pxref{Remote Configuration, set serial baud}) before the
19267 @code{target} command.
19269 @item target remote @code{@var{host}:@var{port}}
19270 @itemx target remote @code{tcp:@var{host}:@var{port}}
19271 @cindex @acronym{TCP} port, @code{target remote}
19272 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
19273 The @var{host} may be either a host name or a numeric @acronym{IP}
19274 address; @var{port} must be a decimal number. The @var{host} could be
19275 the target machine itself, if it is directly connected to the net, or
19276 it might be a terminal server which in turn has a serial line to the
19279 For example, to connect to port 2828 on a terminal server named
19283 target remote manyfarms:2828
19286 If your remote target is actually running on the same machine as your
19287 debugger session (e.g.@: a simulator for your target running on the
19288 same host), you can omit the hostname. For example, to connect to
19289 port 1234 on your local machine:
19292 target remote :1234
19296 Note that the colon is still required here.
19298 @item target remote @code{udp:@var{host}:@var{port}}
19299 @cindex @acronym{UDP} port, @code{target remote}
19300 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
19301 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
19304 target remote udp:manyfarms:2828
19307 When using a @acronym{UDP} connection for remote debugging, you should
19308 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
19309 can silently drop packets on busy or unreliable networks, which will
19310 cause havoc with your debugging session.
19312 @item target remote | @var{command}
19313 @cindex pipe, @code{target remote} to
19314 Run @var{command} in the background and communicate with it using a
19315 pipe. The @var{command} is a shell command, to be parsed and expanded
19316 by the system's command shell, @code{/bin/sh}; it should expect remote
19317 protocol packets on its standard input, and send replies on its
19318 standard output. You could use this to run a stand-alone simulator
19319 that speaks the remote debugging protocol, to make net connections
19320 using programs like @code{ssh}, or for other similar tricks.
19322 If @var{command} closes its standard output (perhaps by exiting),
19323 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
19324 program has already exited, this will have no effect.)
19328 Once the connection has been established, you can use all the usual
19329 commands to examine and change data. The remote program is already
19330 running; you can use @kbd{step} and @kbd{continue}, and you do not
19331 need to use @kbd{run}.
19333 @cindex interrupting remote programs
19334 @cindex remote programs, interrupting
19335 Whenever @value{GDBN} is waiting for the remote program, if you type the
19336 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
19337 program. This may or may not succeed, depending in part on the hardware
19338 and the serial drivers the remote system uses. If you type the
19339 interrupt character once again, @value{GDBN} displays this prompt:
19342 Interrupted while waiting for the program.
19343 Give up (and stop debugging it)? (y or n)
19346 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
19347 (If you decide you want to try again later, you can use @samp{target
19348 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
19349 goes back to waiting.
19352 @kindex detach (remote)
19354 When you have finished debugging the remote program, you can use the
19355 @code{detach} command to release it from @value{GDBN} control.
19356 Detaching from the target normally resumes its execution, but the results
19357 will depend on your particular remote stub. After the @code{detach}
19358 command, @value{GDBN} is free to connect to another target.
19362 The @code{disconnect} command behaves like @code{detach}, except that
19363 the target is generally not resumed. It will wait for @value{GDBN}
19364 (this instance or another one) to connect and continue debugging. After
19365 the @code{disconnect} command, @value{GDBN} is again free to connect to
19368 @cindex send command to remote monitor
19369 @cindex extend @value{GDBN} for remote targets
19370 @cindex add new commands for external monitor
19372 @item monitor @var{cmd}
19373 This command allows you to send arbitrary commands directly to the
19374 remote monitor. Since @value{GDBN} doesn't care about the commands it
19375 sends like this, this command is the way to extend @value{GDBN}---you
19376 can add new commands that only the external monitor will understand
19380 @node File Transfer
19381 @section Sending files to a remote system
19382 @cindex remote target, file transfer
19383 @cindex file transfer
19384 @cindex sending files to remote systems
19386 Some remote targets offer the ability to transfer files over the same
19387 connection used to communicate with @value{GDBN}. This is convenient
19388 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
19389 running @code{gdbserver} over a network interface. For other targets,
19390 e.g.@: embedded devices with only a single serial port, this may be
19391 the only way to upload or download files.
19393 Not all remote targets support these commands.
19397 @item remote put @var{hostfile} @var{targetfile}
19398 Copy file @var{hostfile} from the host system (the machine running
19399 @value{GDBN}) to @var{targetfile} on the target system.
19402 @item remote get @var{targetfile} @var{hostfile}
19403 Copy file @var{targetfile} from the target system to @var{hostfile}
19404 on the host system.
19406 @kindex remote delete
19407 @item remote delete @var{targetfile}
19408 Delete @var{targetfile} from the target system.
19413 @section Using the @code{gdbserver} Program
19416 @cindex remote connection without stubs
19417 @code{gdbserver} is a control program for Unix-like systems, which
19418 allows you to connect your program with a remote @value{GDBN} via
19419 @code{target remote}---but without linking in the usual debugging stub.
19421 @code{gdbserver} is not a complete replacement for the debugging stubs,
19422 because it requires essentially the same operating-system facilities
19423 that @value{GDBN} itself does. In fact, a system that can run
19424 @code{gdbserver} to connect to a remote @value{GDBN} could also run
19425 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
19426 because it is a much smaller program than @value{GDBN} itself. It is
19427 also easier to port than all of @value{GDBN}, so you may be able to get
19428 started more quickly on a new system by using @code{gdbserver}.
19429 Finally, if you develop code for real-time systems, you may find that
19430 the tradeoffs involved in real-time operation make it more convenient to
19431 do as much development work as possible on another system, for example
19432 by cross-compiling. You can use @code{gdbserver} to make a similar
19433 choice for debugging.
19435 @value{GDBN} and @code{gdbserver} communicate via either a serial line
19436 or a TCP connection, using the standard @value{GDBN} remote serial
19440 @emph{Warning:} @code{gdbserver} does not have any built-in security.
19441 Do not run @code{gdbserver} connected to any public network; a
19442 @value{GDBN} connection to @code{gdbserver} provides access to the
19443 target system with the same privileges as the user running
19447 @subsection Running @code{gdbserver}
19448 @cindex arguments, to @code{gdbserver}
19449 @cindex @code{gdbserver}, command-line arguments
19451 Run @code{gdbserver} on the target system. You need a copy of the
19452 program you want to debug, including any libraries it requires.
19453 @code{gdbserver} does not need your program's symbol table, so you can
19454 strip the program if necessary to save space. @value{GDBN} on the host
19455 system does all the symbol handling.
19457 To use the server, you must tell it how to communicate with @value{GDBN};
19458 the name of your program; and the arguments for your program. The usual
19462 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
19465 @var{comm} is either a device name (to use a serial line), or a TCP
19466 hostname and portnumber, or @code{-} or @code{stdio} to use
19467 stdin/stdout of @code{gdbserver}.
19468 For example, to debug Emacs with the argument
19469 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
19473 target> gdbserver /dev/com1 emacs foo.txt
19476 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
19479 To use a TCP connection instead of a serial line:
19482 target> gdbserver host:2345 emacs foo.txt
19485 The only difference from the previous example is the first argument,
19486 specifying that you are communicating with the host @value{GDBN} via
19487 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
19488 expect a TCP connection from machine @samp{host} to local TCP port 2345.
19489 (Currently, the @samp{host} part is ignored.) You can choose any number
19490 you want for the port number as long as it does not conflict with any
19491 TCP ports already in use on the target system (for example, @code{23} is
19492 reserved for @code{telnet}).@footnote{If you choose a port number that
19493 conflicts with another service, @code{gdbserver} prints an error message
19494 and exits.} You must use the same port number with the host @value{GDBN}
19495 @code{target remote} command.
19497 The @code{stdio} connection is useful when starting @code{gdbserver}
19501 (gdb) target remote | ssh -T hostname gdbserver - hello
19504 The @samp{-T} option to ssh is provided because we don't need a remote pty,
19505 and we don't want escape-character handling. Ssh does this by default when
19506 a command is provided, the flag is provided to make it explicit.
19507 You could elide it if you want to.
19509 Programs started with stdio-connected gdbserver have @file{/dev/null} for
19510 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
19511 display through a pipe connected to gdbserver.
19512 Both @code{stdout} and @code{stderr} use the same pipe.
19514 @subsubsection Attaching to a Running Program
19515 @cindex attach to a program, @code{gdbserver}
19516 @cindex @option{--attach}, @code{gdbserver} option
19518 On some targets, @code{gdbserver} can also attach to running programs.
19519 This is accomplished via the @code{--attach} argument. The syntax is:
19522 target> gdbserver --attach @var{comm} @var{pid}
19525 @var{pid} is the process ID of a currently running process. It isn't necessary
19526 to point @code{gdbserver} at a binary for the running process.
19529 You can debug processes by name instead of process ID if your target has the
19530 @code{pidof} utility:
19533 target> gdbserver --attach @var{comm} `pidof @var{program}`
19536 In case more than one copy of @var{program} is running, or @var{program}
19537 has multiple threads, most versions of @code{pidof} support the
19538 @code{-s} option to only return the first process ID.
19540 @subsubsection Multi-Process Mode for @code{gdbserver}
19541 @cindex @code{gdbserver}, multiple processes
19542 @cindex multiple processes with @code{gdbserver}
19544 When you connect to @code{gdbserver} using @code{target remote},
19545 @code{gdbserver} debugs the specified program only once. When the
19546 program exits, or you detach from it, @value{GDBN} closes the connection
19547 and @code{gdbserver} exits.
19549 If you connect using @kbd{target extended-remote}, @code{gdbserver}
19550 enters multi-process mode. When the debugged program exits, or you
19551 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
19552 though no program is running. The @code{run} and @code{attach}
19553 commands instruct @code{gdbserver} to run or attach to a new program.
19554 The @code{run} command uses @code{set remote exec-file} (@pxref{set
19555 remote exec-file}) to select the program to run. Command line
19556 arguments are supported, except for wildcard expansion and I/O
19557 redirection (@pxref{Arguments}).
19559 @cindex @option{--multi}, @code{gdbserver} option
19560 To start @code{gdbserver} without supplying an initial command to run
19561 or process ID to attach, use the @option{--multi} command line option.
19562 Then you can connect using @kbd{target extended-remote} and start
19563 the program you want to debug.
19565 In multi-process mode @code{gdbserver} does not automatically exit unless you
19566 use the option @option{--once}. You can terminate it by using
19567 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
19568 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
19569 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
19570 @option{--multi} option to @code{gdbserver} has no influence on that.
19572 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
19574 This section applies only when @code{gdbserver} is run to listen on a TCP port.
19576 @code{gdbserver} normally terminates after all of its debugged processes have
19577 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
19578 extended-remote}, @code{gdbserver} stays running even with no processes left.
19579 @value{GDBN} normally terminates the spawned debugged process on its exit,
19580 which normally also terminates @code{gdbserver} in the @kbd{target remote}
19581 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
19582 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
19583 stays running even in the @kbd{target remote} mode.
19585 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
19586 Such reconnecting is useful for features like @ref{disconnected tracing}. For
19587 completeness, at most one @value{GDBN} can be connected at a time.
19589 @cindex @option{--once}, @code{gdbserver} option
19590 By default, @code{gdbserver} keeps the listening TCP port open, so that
19591 subsequent connections are possible. However, if you start @code{gdbserver}
19592 with the @option{--once} option, it will stop listening for any further
19593 connection attempts after connecting to the first @value{GDBN} session. This
19594 means no further connections to @code{gdbserver} will be possible after the
19595 first one. It also means @code{gdbserver} will terminate after the first
19596 connection with remote @value{GDBN} has closed, even for unexpectedly closed
19597 connections and even in the @kbd{target extended-remote} mode. The
19598 @option{--once} option allows reusing the same port number for connecting to
19599 multiple instances of @code{gdbserver} running on the same host, since each
19600 instance closes its port after the first connection.
19602 @anchor{Other Command-Line Arguments for gdbserver}
19603 @subsubsection Other Command-Line Arguments for @code{gdbserver}
19605 @cindex @option{--debug}, @code{gdbserver} option
19606 The @option{--debug} option tells @code{gdbserver} to display extra
19607 status information about the debugging process.
19608 @cindex @option{--remote-debug}, @code{gdbserver} option
19609 The @option{--remote-debug} option tells @code{gdbserver} to display
19610 remote protocol debug output. These options are intended for
19611 @code{gdbserver} development and for bug reports to the developers.
19613 @cindex @option{--debug-format}, @code{gdbserver} option
19614 The @option{--debug-format=option1[,option2,...]} option tells
19615 @code{gdbserver} to include additional information in each output.
19616 Possible options are:
19620 Turn off all extra information in debugging output.
19622 Turn on all extra information in debugging output.
19624 Include a timestamp in each line of debugging output.
19627 Options are processed in order. Thus, for example, if @option{none}
19628 appears last then no additional information is added to debugging output.
19630 @cindex @option{--wrapper}, @code{gdbserver} option
19631 The @option{--wrapper} option specifies a wrapper to launch programs
19632 for debugging. The option should be followed by the name of the
19633 wrapper, then any command-line arguments to pass to the wrapper, then
19634 @kbd{--} indicating the end of the wrapper arguments.
19636 @code{gdbserver} runs the specified wrapper program with a combined
19637 command line including the wrapper arguments, then the name of the
19638 program to debug, then any arguments to the program. The wrapper
19639 runs until it executes your program, and then @value{GDBN} gains control.
19641 You can use any program that eventually calls @code{execve} with
19642 its arguments as a wrapper. Several standard Unix utilities do
19643 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
19644 with @code{exec "$@@"} will also work.
19646 For example, you can use @code{env} to pass an environment variable to
19647 the debugged program, without setting the variable in @code{gdbserver}'s
19651 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
19654 @subsection Connecting to @code{gdbserver}
19656 Run @value{GDBN} on the host system.
19658 First make sure you have the necessary symbol files. Load symbols for
19659 your application using the @code{file} command before you connect. Use
19660 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
19661 was compiled with the correct sysroot using @code{--with-sysroot}).
19663 The symbol file and target libraries must exactly match the executable
19664 and libraries on the target, with one exception: the files on the host
19665 system should not be stripped, even if the files on the target system
19666 are. Mismatched or missing files will lead to confusing results
19667 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
19668 files may also prevent @code{gdbserver} from debugging multi-threaded
19671 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
19672 For TCP connections, you must start up @code{gdbserver} prior to using
19673 the @code{target remote} command. Otherwise you may get an error whose
19674 text depends on the host system, but which usually looks something like
19675 @samp{Connection refused}. Don't use the @code{load}
19676 command in @value{GDBN} when using @code{gdbserver}, since the program is
19677 already on the target.
19679 @subsection Monitor Commands for @code{gdbserver}
19680 @cindex monitor commands, for @code{gdbserver}
19681 @anchor{Monitor Commands for gdbserver}
19683 During a @value{GDBN} session using @code{gdbserver}, you can use the
19684 @code{monitor} command to send special requests to @code{gdbserver}.
19685 Here are the available commands.
19689 List the available monitor commands.
19691 @item monitor set debug 0
19692 @itemx monitor set debug 1
19693 Disable or enable general debugging messages.
19695 @item monitor set remote-debug 0
19696 @itemx monitor set remote-debug 1
19697 Disable or enable specific debugging messages associated with the remote
19698 protocol (@pxref{Remote Protocol}).
19700 @item monitor set debug-format option1@r{[},option2,...@r{]}
19701 Specify additional text to add to debugging messages.
19702 Possible options are:
19706 Turn off all extra information in debugging output.
19708 Turn on all extra information in debugging output.
19710 Include a timestamp in each line of debugging output.
19713 Options are processed in order. Thus, for example, if @option{none}
19714 appears last then no additional information is added to debugging output.
19716 @item monitor set libthread-db-search-path [PATH]
19717 @cindex gdbserver, search path for @code{libthread_db}
19718 When this command is issued, @var{path} is a colon-separated list of
19719 directories to search for @code{libthread_db} (@pxref{Threads,,set
19720 libthread-db-search-path}). If you omit @var{path},
19721 @samp{libthread-db-search-path} will be reset to its default value.
19723 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
19724 not supported in @code{gdbserver}.
19727 Tell gdbserver to exit immediately. This command should be followed by
19728 @code{disconnect} to close the debugging session. @code{gdbserver} will
19729 detach from any attached processes and kill any processes it created.
19730 Use @code{monitor exit} to terminate @code{gdbserver} at the end
19731 of a multi-process mode debug session.
19735 @subsection Tracepoints support in @code{gdbserver}
19736 @cindex tracepoints support in @code{gdbserver}
19738 On some targets, @code{gdbserver} supports tracepoints, fast
19739 tracepoints and static tracepoints.
19741 For fast or static tracepoints to work, a special library called the
19742 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
19743 This library is built and distributed as an integral part of
19744 @code{gdbserver}. In addition, support for static tracepoints
19745 requires building the in-process agent library with static tracepoints
19746 support. At present, the UST (LTTng Userspace Tracer,
19747 @url{http://lttng.org/ust}) tracing engine is supported. This support
19748 is automatically available if UST development headers are found in the
19749 standard include path when @code{gdbserver} is built, or if
19750 @code{gdbserver} was explicitly configured using @option{--with-ust}
19751 to point at such headers. You can explicitly disable the support
19752 using @option{--with-ust=no}.
19754 There are several ways to load the in-process agent in your program:
19757 @item Specifying it as dependency at link time
19759 You can link your program dynamically with the in-process agent
19760 library. On most systems, this is accomplished by adding
19761 @code{-linproctrace} to the link command.
19763 @item Using the system's preloading mechanisms
19765 You can force loading the in-process agent at startup time by using
19766 your system's support for preloading shared libraries. Many Unixes
19767 support the concept of preloading user defined libraries. In most
19768 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
19769 in the environment. See also the description of @code{gdbserver}'s
19770 @option{--wrapper} command line option.
19772 @item Using @value{GDBN} to force loading the agent at run time
19774 On some systems, you can force the inferior to load a shared library,
19775 by calling a dynamic loader function in the inferior that takes care
19776 of dynamically looking up and loading a shared library. On most Unix
19777 systems, the function is @code{dlopen}. You'll use the @code{call}
19778 command for that. For example:
19781 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
19784 Note that on most Unix systems, for the @code{dlopen} function to be
19785 available, the program needs to be linked with @code{-ldl}.
19788 On systems that have a userspace dynamic loader, like most Unix
19789 systems, when you connect to @code{gdbserver} using @code{target
19790 remote}, you'll find that the program is stopped at the dynamic
19791 loader's entry point, and no shared library has been loaded in the
19792 program's address space yet, including the in-process agent. In that
19793 case, before being able to use any of the fast or static tracepoints
19794 features, you need to let the loader run and load the shared
19795 libraries. The simplest way to do that is to run the program to the
19796 main procedure. E.g., if debugging a C or C@t{++} program, start
19797 @code{gdbserver} like so:
19800 $ gdbserver :9999 myprogram
19803 Start GDB and connect to @code{gdbserver} like so, and run to main:
19807 (@value{GDBP}) target remote myhost:9999
19808 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
19809 (@value{GDBP}) b main
19810 (@value{GDBP}) continue
19813 The in-process tracing agent library should now be loaded into the
19814 process; you can confirm it with the @code{info sharedlibrary}
19815 command, which will list @file{libinproctrace.so} as loaded in the
19816 process. You are now ready to install fast tracepoints, list static
19817 tracepoint markers, probe static tracepoints markers, and start
19820 @node Remote Configuration
19821 @section Remote Configuration
19824 @kindex show remote
19825 This section documents the configuration options available when
19826 debugging remote programs. For the options related to the File I/O
19827 extensions of the remote protocol, see @ref{system,
19828 system-call-allowed}.
19831 @item set remoteaddresssize @var{bits}
19832 @cindex address size for remote targets
19833 @cindex bits in remote address
19834 Set the maximum size of address in a memory packet to the specified
19835 number of bits. @value{GDBN} will mask off the address bits above
19836 that number, when it passes addresses to the remote target. The
19837 default value is the number of bits in the target's address.
19839 @item show remoteaddresssize
19840 Show the current value of remote address size in bits.
19842 @item set serial baud @var{n}
19843 @cindex baud rate for remote targets
19844 Set the baud rate for the remote serial I/O to @var{n} baud. The
19845 value is used to set the speed of the serial port used for debugging
19848 @item show serial baud
19849 Show the current speed of the remote connection.
19851 @item set serial parity @var{parity}
19852 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
19853 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
19855 @item show serial parity
19856 Show the current parity of the serial port.
19858 @item set remotebreak
19859 @cindex interrupt remote programs
19860 @cindex BREAK signal instead of Ctrl-C
19861 @anchor{set remotebreak}
19862 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
19863 when you type @kbd{Ctrl-c} to interrupt the program running
19864 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
19865 character instead. The default is off, since most remote systems
19866 expect to see @samp{Ctrl-C} as the interrupt signal.
19868 @item show remotebreak
19869 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
19870 interrupt the remote program.
19872 @item set remoteflow on
19873 @itemx set remoteflow off
19874 @kindex set remoteflow
19875 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
19876 on the serial port used to communicate to the remote target.
19878 @item show remoteflow
19879 @kindex show remoteflow
19880 Show the current setting of hardware flow control.
19882 @item set remotelogbase @var{base}
19883 Set the base (a.k.a.@: radix) of logging serial protocol
19884 communications to @var{base}. Supported values of @var{base} are:
19885 @code{ascii}, @code{octal}, and @code{hex}. The default is
19888 @item show remotelogbase
19889 Show the current setting of the radix for logging remote serial
19892 @item set remotelogfile @var{file}
19893 @cindex record serial communications on file
19894 Record remote serial communications on the named @var{file}. The
19895 default is not to record at all.
19897 @item show remotelogfile.
19898 Show the current setting of the file name on which to record the
19899 serial communications.
19901 @item set remotetimeout @var{num}
19902 @cindex timeout for serial communications
19903 @cindex remote timeout
19904 Set the timeout limit to wait for the remote target to respond to
19905 @var{num} seconds. The default is 2 seconds.
19907 @item show remotetimeout
19908 Show the current number of seconds to wait for the remote target
19911 @cindex limit hardware breakpoints and watchpoints
19912 @cindex remote target, limit break- and watchpoints
19913 @anchor{set remote hardware-watchpoint-limit}
19914 @anchor{set remote hardware-breakpoint-limit}
19915 @item set remote hardware-watchpoint-limit @var{limit}
19916 @itemx set remote hardware-breakpoint-limit @var{limit}
19917 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
19918 watchpoints. A limit of -1, the default, is treated as unlimited.
19920 @cindex limit hardware watchpoints length
19921 @cindex remote target, limit watchpoints length
19922 @anchor{set remote hardware-watchpoint-length-limit}
19923 @item set remote hardware-watchpoint-length-limit @var{limit}
19924 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
19925 a remote hardware watchpoint. A limit of -1, the default, is treated
19928 @item show remote hardware-watchpoint-length-limit
19929 Show the current limit (in bytes) of the maximum length of
19930 a remote hardware watchpoint.
19932 @item set remote exec-file @var{filename}
19933 @itemx show remote exec-file
19934 @anchor{set remote exec-file}
19935 @cindex executable file, for remote target
19936 Select the file used for @code{run} with @code{target
19937 extended-remote}. This should be set to a filename valid on the
19938 target system. If it is not set, the target will use a default
19939 filename (e.g.@: the last program run).
19941 @item set remote interrupt-sequence
19942 @cindex interrupt remote programs
19943 @cindex select Ctrl-C, BREAK or BREAK-g
19944 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
19945 @samp{BREAK-g} as the
19946 sequence to the remote target in order to interrupt the execution.
19947 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
19948 is high level of serial line for some certain time.
19949 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
19950 It is @code{BREAK} signal followed by character @code{g}.
19952 @item show interrupt-sequence
19953 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
19954 is sent by @value{GDBN} to interrupt the remote program.
19955 @code{BREAK-g} is BREAK signal followed by @code{g} and
19956 also known as Magic SysRq g.
19958 @item set remote interrupt-on-connect
19959 @cindex send interrupt-sequence on start
19960 Specify whether interrupt-sequence is sent to remote target when
19961 @value{GDBN} connects to it. This is mostly needed when you debug
19962 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
19963 which is known as Magic SysRq g in order to connect @value{GDBN}.
19965 @item show interrupt-on-connect
19966 Show whether interrupt-sequence is sent
19967 to remote target when @value{GDBN} connects to it.
19971 @item set tcp auto-retry on
19972 @cindex auto-retry, for remote TCP target
19973 Enable auto-retry for remote TCP connections. This is useful if the remote
19974 debugging agent is launched in parallel with @value{GDBN}; there is a race
19975 condition because the agent may not become ready to accept the connection
19976 before @value{GDBN} attempts to connect. When auto-retry is
19977 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
19978 to establish the connection using the timeout specified by
19979 @code{set tcp connect-timeout}.
19981 @item set tcp auto-retry off
19982 Do not auto-retry failed TCP connections.
19984 @item show tcp auto-retry
19985 Show the current auto-retry setting.
19987 @item set tcp connect-timeout @var{seconds}
19988 @itemx set tcp connect-timeout unlimited
19989 @cindex connection timeout, for remote TCP target
19990 @cindex timeout, for remote target connection
19991 Set the timeout for establishing a TCP connection to the remote target to
19992 @var{seconds}. The timeout affects both polling to retry failed connections
19993 (enabled by @code{set tcp auto-retry on}) and waiting for connections
19994 that are merely slow to complete, and represents an approximate cumulative
19995 value. If @var{seconds} is @code{unlimited}, there is no timeout and
19996 @value{GDBN} will keep attempting to establish a connection forever,
19997 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
19999 @item show tcp connect-timeout
20000 Show the current connection timeout setting.
20003 @cindex remote packets, enabling and disabling
20004 The @value{GDBN} remote protocol autodetects the packets supported by
20005 your debugging stub. If you need to override the autodetection, you
20006 can use these commands to enable or disable individual packets. Each
20007 packet can be set to @samp{on} (the remote target supports this
20008 packet), @samp{off} (the remote target does not support this packet),
20009 or @samp{auto} (detect remote target support for this packet). They
20010 all default to @samp{auto}. For more information about each packet,
20011 see @ref{Remote Protocol}.
20013 During normal use, you should not have to use any of these commands.
20014 If you do, that may be a bug in your remote debugging stub, or a bug
20015 in @value{GDBN}. You may want to report the problem to the
20016 @value{GDBN} developers.
20018 For each packet @var{name}, the command to enable or disable the
20019 packet is @code{set remote @var{name}-packet}. The available settings
20022 @multitable @columnfractions 0.28 0.32 0.25
20025 @tab Related Features
20027 @item @code{fetch-register}
20029 @tab @code{info registers}
20031 @item @code{set-register}
20035 @item @code{binary-download}
20037 @tab @code{load}, @code{set}
20039 @item @code{read-aux-vector}
20040 @tab @code{qXfer:auxv:read}
20041 @tab @code{info auxv}
20043 @item @code{symbol-lookup}
20044 @tab @code{qSymbol}
20045 @tab Detecting multiple threads
20047 @item @code{attach}
20048 @tab @code{vAttach}
20051 @item @code{verbose-resume}
20053 @tab Stepping or resuming multiple threads
20059 @item @code{software-breakpoint}
20063 @item @code{hardware-breakpoint}
20067 @item @code{write-watchpoint}
20071 @item @code{read-watchpoint}
20075 @item @code{access-watchpoint}
20079 @item @code{pid-to-exec-file}
20080 @tab @code{qXfer:exec-file:read}
20081 @tab @code{attach}, @code{run}
20083 @item @code{target-features}
20084 @tab @code{qXfer:features:read}
20085 @tab @code{set architecture}
20087 @item @code{library-info}
20088 @tab @code{qXfer:libraries:read}
20089 @tab @code{info sharedlibrary}
20091 @item @code{memory-map}
20092 @tab @code{qXfer:memory-map:read}
20093 @tab @code{info mem}
20095 @item @code{read-sdata-object}
20096 @tab @code{qXfer:sdata:read}
20097 @tab @code{print $_sdata}
20099 @item @code{read-spu-object}
20100 @tab @code{qXfer:spu:read}
20101 @tab @code{info spu}
20103 @item @code{write-spu-object}
20104 @tab @code{qXfer:spu:write}
20105 @tab @code{info spu}
20107 @item @code{read-siginfo-object}
20108 @tab @code{qXfer:siginfo:read}
20109 @tab @code{print $_siginfo}
20111 @item @code{write-siginfo-object}
20112 @tab @code{qXfer:siginfo:write}
20113 @tab @code{set $_siginfo}
20115 @item @code{threads}
20116 @tab @code{qXfer:threads:read}
20117 @tab @code{info threads}
20119 @item @code{get-thread-local-@*storage-address}
20120 @tab @code{qGetTLSAddr}
20121 @tab Displaying @code{__thread} variables
20123 @item @code{get-thread-information-block-address}
20124 @tab @code{qGetTIBAddr}
20125 @tab Display MS-Windows Thread Information Block.
20127 @item @code{search-memory}
20128 @tab @code{qSearch:memory}
20131 @item @code{supported-packets}
20132 @tab @code{qSupported}
20133 @tab Remote communications parameters
20135 @item @code{pass-signals}
20136 @tab @code{QPassSignals}
20137 @tab @code{handle @var{signal}}
20139 @item @code{program-signals}
20140 @tab @code{QProgramSignals}
20141 @tab @code{handle @var{signal}}
20143 @item @code{hostio-close-packet}
20144 @tab @code{vFile:close}
20145 @tab @code{remote get}, @code{remote put}
20147 @item @code{hostio-open-packet}
20148 @tab @code{vFile:open}
20149 @tab @code{remote get}, @code{remote put}
20151 @item @code{hostio-pread-packet}
20152 @tab @code{vFile:pread}
20153 @tab @code{remote get}, @code{remote put}
20155 @item @code{hostio-pwrite-packet}
20156 @tab @code{vFile:pwrite}
20157 @tab @code{remote get}, @code{remote put}
20159 @item @code{hostio-unlink-packet}
20160 @tab @code{vFile:unlink}
20161 @tab @code{remote delete}
20163 @item @code{hostio-readlink-packet}
20164 @tab @code{vFile:readlink}
20167 @item @code{hostio-fstat-packet}
20168 @tab @code{vFile:fstat}
20171 @item @code{hostio-setfs-packet}
20172 @tab @code{vFile:setfs}
20175 @item @code{noack-packet}
20176 @tab @code{QStartNoAckMode}
20177 @tab Packet acknowledgment
20179 @item @code{osdata}
20180 @tab @code{qXfer:osdata:read}
20181 @tab @code{info os}
20183 @item @code{query-attached}
20184 @tab @code{qAttached}
20185 @tab Querying remote process attach state.
20187 @item @code{trace-buffer-size}
20188 @tab @code{QTBuffer:size}
20189 @tab @code{set trace-buffer-size}
20191 @item @code{trace-status}
20192 @tab @code{qTStatus}
20193 @tab @code{tstatus}
20195 @item @code{traceframe-info}
20196 @tab @code{qXfer:traceframe-info:read}
20197 @tab Traceframe info
20199 @item @code{install-in-trace}
20200 @tab @code{InstallInTrace}
20201 @tab Install tracepoint in tracing
20203 @item @code{disable-randomization}
20204 @tab @code{QDisableRandomization}
20205 @tab @code{set disable-randomization}
20207 @item @code{conditional-breakpoints-packet}
20208 @tab @code{Z0 and Z1}
20209 @tab @code{Support for target-side breakpoint condition evaluation}
20211 @item @code{multiprocess-extensions}
20212 @tab @code{multiprocess extensions}
20213 @tab Debug multiple processes and remote process PID awareness
20215 @item @code{swbreak-feature}
20216 @tab @code{swbreak stop reason}
20219 @item @code{hwbreak-feature}
20220 @tab @code{hwbreak stop reason}
20223 @item @code{fork-event-feature}
20224 @tab @code{fork stop reason}
20227 @item @code{vfork-event-feature}
20228 @tab @code{vfork stop reason}
20231 @item @code{exec-event-feature}
20232 @tab @code{exec stop reason}
20238 @section Implementing a Remote Stub
20240 @cindex debugging stub, example
20241 @cindex remote stub, example
20242 @cindex stub example, remote debugging
20243 The stub files provided with @value{GDBN} implement the target side of the
20244 communication protocol, and the @value{GDBN} side is implemented in the
20245 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
20246 these subroutines to communicate, and ignore the details. (If you're
20247 implementing your own stub file, you can still ignore the details: start
20248 with one of the existing stub files. @file{sparc-stub.c} is the best
20249 organized, and therefore the easiest to read.)
20251 @cindex remote serial debugging, overview
20252 To debug a program running on another machine (the debugging
20253 @dfn{target} machine), you must first arrange for all the usual
20254 prerequisites for the program to run by itself. For example, for a C
20259 A startup routine to set up the C runtime environment; these usually
20260 have a name like @file{crt0}. The startup routine may be supplied by
20261 your hardware supplier, or you may have to write your own.
20264 A C subroutine library to support your program's
20265 subroutine calls, notably managing input and output.
20268 A way of getting your program to the other machine---for example, a
20269 download program. These are often supplied by the hardware
20270 manufacturer, but you may have to write your own from hardware
20274 The next step is to arrange for your program to use a serial port to
20275 communicate with the machine where @value{GDBN} is running (the @dfn{host}
20276 machine). In general terms, the scheme looks like this:
20280 @value{GDBN} already understands how to use this protocol; when everything
20281 else is set up, you can simply use the @samp{target remote} command
20282 (@pxref{Targets,,Specifying a Debugging Target}).
20284 @item On the target,
20285 you must link with your program a few special-purpose subroutines that
20286 implement the @value{GDBN} remote serial protocol. The file containing these
20287 subroutines is called a @dfn{debugging stub}.
20289 On certain remote targets, you can use an auxiliary program
20290 @code{gdbserver} instead of linking a stub into your program.
20291 @xref{Server,,Using the @code{gdbserver} Program}, for details.
20294 The debugging stub is specific to the architecture of the remote
20295 machine; for example, use @file{sparc-stub.c} to debug programs on
20298 @cindex remote serial stub list
20299 These working remote stubs are distributed with @value{GDBN}:
20304 @cindex @file{i386-stub.c}
20307 For Intel 386 and compatible architectures.
20310 @cindex @file{m68k-stub.c}
20311 @cindex Motorola 680x0
20313 For Motorola 680x0 architectures.
20316 @cindex @file{sh-stub.c}
20319 For Renesas SH architectures.
20322 @cindex @file{sparc-stub.c}
20324 For @sc{sparc} architectures.
20326 @item sparcl-stub.c
20327 @cindex @file{sparcl-stub.c}
20330 For Fujitsu @sc{sparclite} architectures.
20334 The @file{README} file in the @value{GDBN} distribution may list other
20335 recently added stubs.
20338 * Stub Contents:: What the stub can do for you
20339 * Bootstrapping:: What you must do for the stub
20340 * Debug Session:: Putting it all together
20343 @node Stub Contents
20344 @subsection What the Stub Can Do for You
20346 @cindex remote serial stub
20347 The debugging stub for your architecture supplies these three
20351 @item set_debug_traps
20352 @findex set_debug_traps
20353 @cindex remote serial stub, initialization
20354 This routine arranges for @code{handle_exception} to run when your
20355 program stops. You must call this subroutine explicitly in your
20356 program's startup code.
20358 @item handle_exception
20359 @findex handle_exception
20360 @cindex remote serial stub, main routine
20361 This is the central workhorse, but your program never calls it
20362 explicitly---the setup code arranges for @code{handle_exception} to
20363 run when a trap is triggered.
20365 @code{handle_exception} takes control when your program stops during
20366 execution (for example, on a breakpoint), and mediates communications
20367 with @value{GDBN} on the host machine. This is where the communications
20368 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
20369 representative on the target machine. It begins by sending summary
20370 information on the state of your program, then continues to execute,
20371 retrieving and transmitting any information @value{GDBN} needs, until you
20372 execute a @value{GDBN} command that makes your program resume; at that point,
20373 @code{handle_exception} returns control to your own code on the target
20377 @cindex @code{breakpoint} subroutine, remote
20378 Use this auxiliary subroutine to make your program contain a
20379 breakpoint. Depending on the particular situation, this may be the only
20380 way for @value{GDBN} to get control. For instance, if your target
20381 machine has some sort of interrupt button, you won't need to call this;
20382 pressing the interrupt button transfers control to
20383 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
20384 simply receiving characters on the serial port may also trigger a trap;
20385 again, in that situation, you don't need to call @code{breakpoint} from
20386 your own program---simply running @samp{target remote} from the host
20387 @value{GDBN} session gets control.
20389 Call @code{breakpoint} if none of these is true, or if you simply want
20390 to make certain your program stops at a predetermined point for the
20391 start of your debugging session.
20394 @node Bootstrapping
20395 @subsection What You Must Do for the Stub
20397 @cindex remote stub, support routines
20398 The debugging stubs that come with @value{GDBN} are set up for a particular
20399 chip architecture, but they have no information about the rest of your
20400 debugging target machine.
20402 First of all you need to tell the stub how to communicate with the
20406 @item int getDebugChar()
20407 @findex getDebugChar
20408 Write this subroutine to read a single character from the serial port.
20409 It may be identical to @code{getchar} for your target system; a
20410 different name is used to allow you to distinguish the two if you wish.
20412 @item void putDebugChar(int)
20413 @findex putDebugChar
20414 Write this subroutine to write a single character to the serial port.
20415 It may be identical to @code{putchar} for your target system; a
20416 different name is used to allow you to distinguish the two if you wish.
20419 @cindex control C, and remote debugging
20420 @cindex interrupting remote targets
20421 If you want @value{GDBN} to be able to stop your program while it is
20422 running, you need to use an interrupt-driven serial driver, and arrange
20423 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
20424 character). That is the character which @value{GDBN} uses to tell the
20425 remote system to stop.
20427 Getting the debugging target to return the proper status to @value{GDBN}
20428 probably requires changes to the standard stub; one quick and dirty way
20429 is to just execute a breakpoint instruction (the ``dirty'' part is that
20430 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
20432 Other routines you need to supply are:
20435 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
20436 @findex exceptionHandler
20437 Write this function to install @var{exception_address} in the exception
20438 handling tables. You need to do this because the stub does not have any
20439 way of knowing what the exception handling tables on your target system
20440 are like (for example, the processor's table might be in @sc{rom},
20441 containing entries which point to a table in @sc{ram}).
20442 The @var{exception_number} specifies the exception which should be changed;
20443 its meaning is architecture-dependent (for example, different numbers
20444 might represent divide by zero, misaligned access, etc). When this
20445 exception occurs, control should be transferred directly to
20446 @var{exception_address}, and the processor state (stack, registers,
20447 and so on) should be just as it is when a processor exception occurs. So if
20448 you want to use a jump instruction to reach @var{exception_address}, it
20449 should be a simple jump, not a jump to subroutine.
20451 For the 386, @var{exception_address} should be installed as an interrupt
20452 gate so that interrupts are masked while the handler runs. The gate
20453 should be at privilege level 0 (the most privileged level). The
20454 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
20455 help from @code{exceptionHandler}.
20457 @item void flush_i_cache()
20458 @findex flush_i_cache
20459 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
20460 instruction cache, if any, on your target machine. If there is no
20461 instruction cache, this subroutine may be a no-op.
20463 On target machines that have instruction caches, @value{GDBN} requires this
20464 function to make certain that the state of your program is stable.
20468 You must also make sure this library routine is available:
20471 @item void *memset(void *, int, int)
20473 This is the standard library function @code{memset} that sets an area of
20474 memory to a known value. If you have one of the free versions of
20475 @code{libc.a}, @code{memset} can be found there; otherwise, you must
20476 either obtain it from your hardware manufacturer, or write your own.
20479 If you do not use the GNU C compiler, you may need other standard
20480 library subroutines as well; this varies from one stub to another,
20481 but in general the stubs are likely to use any of the common library
20482 subroutines which @code{@value{NGCC}} generates as inline code.
20485 @node Debug Session
20486 @subsection Putting it All Together
20488 @cindex remote serial debugging summary
20489 In summary, when your program is ready to debug, you must follow these
20494 Make sure you have defined the supporting low-level routines
20495 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
20497 @code{getDebugChar}, @code{putDebugChar},
20498 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
20502 Insert these lines in your program's startup code, before the main
20503 procedure is called:
20510 On some machines, when a breakpoint trap is raised, the hardware
20511 automatically makes the PC point to the instruction after the
20512 breakpoint. If your machine doesn't do that, you may need to adjust
20513 @code{handle_exception} to arrange for it to return to the instruction
20514 after the breakpoint on this first invocation, so that your program
20515 doesn't keep hitting the initial breakpoint instead of making
20519 For the 680x0 stub only, you need to provide a variable called
20520 @code{exceptionHook}. Normally you just use:
20523 void (*exceptionHook)() = 0;
20527 but if before calling @code{set_debug_traps}, you set it to point to a
20528 function in your program, that function is called when
20529 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
20530 error). The function indicated by @code{exceptionHook} is called with
20531 one parameter: an @code{int} which is the exception number.
20534 Compile and link together: your program, the @value{GDBN} debugging stub for
20535 your target architecture, and the supporting subroutines.
20538 Make sure you have a serial connection between your target machine and
20539 the @value{GDBN} host, and identify the serial port on the host.
20542 @c The "remote" target now provides a `load' command, so we should
20543 @c document that. FIXME.
20544 Download your program to your target machine (or get it there by
20545 whatever means the manufacturer provides), and start it.
20548 Start @value{GDBN} on the host, and connect to the target
20549 (@pxref{Connecting,,Connecting to a Remote Target}).
20553 @node Configurations
20554 @chapter Configuration-Specific Information
20556 While nearly all @value{GDBN} commands are available for all native and
20557 cross versions of the debugger, there are some exceptions. This chapter
20558 describes things that are only available in certain configurations.
20560 There are three major categories of configurations: native
20561 configurations, where the host and target are the same, embedded
20562 operating system configurations, which are usually the same for several
20563 different processor architectures, and bare embedded processors, which
20564 are quite different from each other.
20569 * Embedded Processors::
20576 This section describes details specific to particular native
20581 * BSD libkvm Interface:: Debugging BSD kernel memory images
20582 * SVR4 Process Information:: SVR4 process information
20583 * DJGPP Native:: Features specific to the DJGPP port
20584 * Cygwin Native:: Features specific to the Cygwin port
20585 * Hurd Native:: Features specific to @sc{gnu} Hurd
20586 * Darwin:: Features specific to Darwin
20592 On HP-UX systems, if you refer to a function or variable name that
20593 begins with a dollar sign, @value{GDBN} searches for a user or system
20594 name first, before it searches for a convenience variable.
20597 @node BSD libkvm Interface
20598 @subsection BSD libkvm Interface
20601 @cindex kernel memory image
20602 @cindex kernel crash dump
20604 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
20605 interface that provides a uniform interface for accessing kernel virtual
20606 memory images, including live systems and crash dumps. @value{GDBN}
20607 uses this interface to allow you to debug live kernels and kernel crash
20608 dumps on many native BSD configurations. This is implemented as a
20609 special @code{kvm} debugging target. For debugging a live system, load
20610 the currently running kernel into @value{GDBN} and connect to the
20614 (@value{GDBP}) @b{target kvm}
20617 For debugging crash dumps, provide the file name of the crash dump as an
20621 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
20624 Once connected to the @code{kvm} target, the following commands are
20630 Set current context from the @dfn{Process Control Block} (PCB) address.
20633 Set current context from proc address. This command isn't available on
20634 modern FreeBSD systems.
20637 @node SVR4 Process Information
20638 @subsection SVR4 Process Information
20640 @cindex examine process image
20641 @cindex process info via @file{/proc}
20643 Many versions of SVR4 and compatible systems provide a facility called
20644 @samp{/proc} that can be used to examine the image of a running
20645 process using file-system subroutines.
20647 If @value{GDBN} is configured for an operating system with this
20648 facility, the command @code{info proc} is available to report
20649 information about the process running your program, or about any
20650 process running on your system. This includes, as of this writing,
20651 @sc{gnu}/Linux and Solaris, but not HP-UX, for example.
20653 This command may also work on core files that were created on a system
20654 that has the @samp{/proc} facility.
20660 @itemx info proc @var{process-id}
20661 Summarize available information about any running process. If a
20662 process ID is specified by @var{process-id}, display information about
20663 that process; otherwise display information about the program being
20664 debugged. The summary includes the debugged process ID, the command
20665 line used to invoke it, its current working directory, and its
20666 executable file's absolute file name.
20668 On some systems, @var{process-id} can be of the form
20669 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
20670 within a process. If the optional @var{pid} part is missing, it means
20671 a thread from the process being debugged (the leading @samp{/} still
20672 needs to be present, or else @value{GDBN} will interpret the number as
20673 a process ID rather than a thread ID).
20675 @item info proc cmdline
20676 @cindex info proc cmdline
20677 Show the original command line of the process. This command is
20678 specific to @sc{gnu}/Linux.
20680 @item info proc cwd
20681 @cindex info proc cwd
20682 Show the current working directory of the process. This command is
20683 specific to @sc{gnu}/Linux.
20685 @item info proc exe
20686 @cindex info proc exe
20687 Show the name of executable of the process. This command is specific
20690 @item info proc mappings
20691 @cindex memory address space mappings
20692 Report the memory address space ranges accessible in the program, with
20693 information on whether the process has read, write, or execute access
20694 rights to each range. On @sc{gnu}/Linux systems, each memory range
20695 includes the object file which is mapped to that range, instead of the
20696 memory access rights to that range.
20698 @item info proc stat
20699 @itemx info proc status
20700 @cindex process detailed status information
20701 These subcommands are specific to @sc{gnu}/Linux systems. They show
20702 the process-related information, including the user ID and group ID;
20703 how many threads are there in the process; its virtual memory usage;
20704 the signals that are pending, blocked, and ignored; its TTY; its
20705 consumption of system and user time; its stack size; its @samp{nice}
20706 value; etc. For more information, see the @samp{proc} man page
20707 (type @kbd{man 5 proc} from your shell prompt).
20709 @item info proc all
20710 Show all the information about the process described under all of the
20711 above @code{info proc} subcommands.
20714 @comment These sub-options of 'info proc' were not included when
20715 @comment procfs.c was re-written. Keep their descriptions around
20716 @comment against the day when someone finds the time to put them back in.
20717 @kindex info proc times
20718 @item info proc times
20719 Starting time, user CPU time, and system CPU time for your program and
20722 @kindex info proc id
20724 Report on the process IDs related to your program: its own process ID,
20725 the ID of its parent, the process group ID, and the session ID.
20728 @item set procfs-trace
20729 @kindex set procfs-trace
20730 @cindex @code{procfs} API calls
20731 This command enables and disables tracing of @code{procfs} API calls.
20733 @item show procfs-trace
20734 @kindex show procfs-trace
20735 Show the current state of @code{procfs} API call tracing.
20737 @item set procfs-file @var{file}
20738 @kindex set procfs-file
20739 Tell @value{GDBN} to write @code{procfs} API trace to the named
20740 @var{file}. @value{GDBN} appends the trace info to the previous
20741 contents of the file. The default is to display the trace on the
20744 @item show procfs-file
20745 @kindex show procfs-file
20746 Show the file to which @code{procfs} API trace is written.
20748 @item proc-trace-entry
20749 @itemx proc-trace-exit
20750 @itemx proc-untrace-entry
20751 @itemx proc-untrace-exit
20752 @kindex proc-trace-entry
20753 @kindex proc-trace-exit
20754 @kindex proc-untrace-entry
20755 @kindex proc-untrace-exit
20756 These commands enable and disable tracing of entries into and exits
20757 from the @code{syscall} interface.
20760 @kindex info pidlist
20761 @cindex process list, QNX Neutrino
20762 For QNX Neutrino only, this command displays the list of all the
20763 processes and all the threads within each process.
20766 @kindex info meminfo
20767 @cindex mapinfo list, QNX Neutrino
20768 For QNX Neutrino only, this command displays the list of all mapinfos.
20772 @subsection Features for Debugging @sc{djgpp} Programs
20773 @cindex @sc{djgpp} debugging
20774 @cindex native @sc{djgpp} debugging
20775 @cindex MS-DOS-specific commands
20778 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
20779 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
20780 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
20781 top of real-mode DOS systems and their emulations.
20783 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
20784 defines a few commands specific to the @sc{djgpp} port. This
20785 subsection describes those commands.
20790 This is a prefix of @sc{djgpp}-specific commands which print
20791 information about the target system and important OS structures.
20794 @cindex MS-DOS system info
20795 @cindex free memory information (MS-DOS)
20796 @item info dos sysinfo
20797 This command displays assorted information about the underlying
20798 platform: the CPU type and features, the OS version and flavor, the
20799 DPMI version, and the available conventional and DPMI memory.
20804 @cindex segment descriptor tables
20805 @cindex descriptor tables display
20807 @itemx info dos ldt
20808 @itemx info dos idt
20809 These 3 commands display entries from, respectively, Global, Local,
20810 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
20811 tables are data structures which store a descriptor for each segment
20812 that is currently in use. The segment's selector is an index into a
20813 descriptor table; the table entry for that index holds the
20814 descriptor's base address and limit, and its attributes and access
20817 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
20818 segment (used for both data and the stack), and a DOS segment (which
20819 allows access to DOS/BIOS data structures and absolute addresses in
20820 conventional memory). However, the DPMI host will usually define
20821 additional segments in order to support the DPMI environment.
20823 @cindex garbled pointers
20824 These commands allow to display entries from the descriptor tables.
20825 Without an argument, all entries from the specified table are
20826 displayed. An argument, which should be an integer expression, means
20827 display a single entry whose index is given by the argument. For
20828 example, here's a convenient way to display information about the
20829 debugged program's data segment:
20832 @exdent @code{(@value{GDBP}) info dos ldt $ds}
20833 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
20837 This comes in handy when you want to see whether a pointer is outside
20838 the data segment's limit (i.e.@: @dfn{garbled}).
20840 @cindex page tables display (MS-DOS)
20842 @itemx info dos pte
20843 These two commands display entries from, respectively, the Page
20844 Directory and the Page Tables. Page Directories and Page Tables are
20845 data structures which control how virtual memory addresses are mapped
20846 into physical addresses. A Page Table includes an entry for every
20847 page of memory that is mapped into the program's address space; there
20848 may be several Page Tables, each one holding up to 4096 entries. A
20849 Page Directory has up to 4096 entries, one each for every Page Table
20850 that is currently in use.
20852 Without an argument, @kbd{info dos pde} displays the entire Page
20853 Directory, and @kbd{info dos pte} displays all the entries in all of
20854 the Page Tables. An argument, an integer expression, given to the
20855 @kbd{info dos pde} command means display only that entry from the Page
20856 Directory table. An argument given to the @kbd{info dos pte} command
20857 means display entries from a single Page Table, the one pointed to by
20858 the specified entry in the Page Directory.
20860 @cindex direct memory access (DMA) on MS-DOS
20861 These commands are useful when your program uses @dfn{DMA} (Direct
20862 Memory Access), which needs physical addresses to program the DMA
20865 These commands are supported only with some DPMI servers.
20867 @cindex physical address from linear address
20868 @item info dos address-pte @var{addr}
20869 This command displays the Page Table entry for a specified linear
20870 address. The argument @var{addr} is a linear address which should
20871 already have the appropriate segment's base address added to it,
20872 because this command accepts addresses which may belong to @emph{any}
20873 segment. For example, here's how to display the Page Table entry for
20874 the page where a variable @code{i} is stored:
20877 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
20878 @exdent @code{Page Table entry for address 0x11a00d30:}
20879 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
20883 This says that @code{i} is stored at offset @code{0xd30} from the page
20884 whose physical base address is @code{0x02698000}, and shows all the
20885 attributes of that page.
20887 Note that you must cast the addresses of variables to a @code{char *},
20888 since otherwise the value of @code{__djgpp_base_address}, the base
20889 address of all variables and functions in a @sc{djgpp} program, will
20890 be added using the rules of C pointer arithmetics: if @code{i} is
20891 declared an @code{int}, @value{GDBN} will add 4 times the value of
20892 @code{__djgpp_base_address} to the address of @code{i}.
20894 Here's another example, it displays the Page Table entry for the
20898 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
20899 @exdent @code{Page Table entry for address 0x29110:}
20900 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
20904 (The @code{+ 3} offset is because the transfer buffer's address is the
20905 3rd member of the @code{_go32_info_block} structure.) The output
20906 clearly shows that this DPMI server maps the addresses in conventional
20907 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
20908 linear (@code{0x29110}) addresses are identical.
20910 This command is supported only with some DPMI servers.
20913 @cindex DOS serial data link, remote debugging
20914 In addition to native debugging, the DJGPP port supports remote
20915 debugging via a serial data link. The following commands are specific
20916 to remote serial debugging in the DJGPP port of @value{GDBN}.
20919 @kindex set com1base
20920 @kindex set com1irq
20921 @kindex set com2base
20922 @kindex set com2irq
20923 @kindex set com3base
20924 @kindex set com3irq
20925 @kindex set com4base
20926 @kindex set com4irq
20927 @item set com1base @var{addr}
20928 This command sets the base I/O port address of the @file{COM1} serial
20931 @item set com1irq @var{irq}
20932 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
20933 for the @file{COM1} serial port.
20935 There are similar commands @samp{set com2base}, @samp{set com3irq},
20936 etc.@: for setting the port address and the @code{IRQ} lines for the
20939 @kindex show com1base
20940 @kindex show com1irq
20941 @kindex show com2base
20942 @kindex show com2irq
20943 @kindex show com3base
20944 @kindex show com3irq
20945 @kindex show com4base
20946 @kindex show com4irq
20947 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
20948 display the current settings of the base address and the @code{IRQ}
20949 lines used by the COM ports.
20952 @kindex info serial
20953 @cindex DOS serial port status
20954 This command prints the status of the 4 DOS serial ports. For each
20955 port, it prints whether it's active or not, its I/O base address and
20956 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
20957 counts of various errors encountered so far.
20961 @node Cygwin Native
20962 @subsection Features for Debugging MS Windows PE Executables
20963 @cindex MS Windows debugging
20964 @cindex native Cygwin debugging
20965 @cindex Cygwin-specific commands
20967 @value{GDBN} supports native debugging of MS Windows programs, including
20968 DLLs with and without symbolic debugging information.
20970 @cindex Ctrl-BREAK, MS-Windows
20971 @cindex interrupt debuggee on MS-Windows
20972 MS-Windows programs that call @code{SetConsoleMode} to switch off the
20973 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
20974 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
20975 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
20976 sequence, which can be used to interrupt the debuggee even if it
20979 There are various additional Cygwin-specific commands, described in
20980 this section. Working with DLLs that have no debugging symbols is
20981 described in @ref{Non-debug DLL Symbols}.
20986 This is a prefix of MS Windows-specific commands which print
20987 information about the target system and important OS structures.
20989 @item info w32 selector
20990 This command displays information returned by
20991 the Win32 API @code{GetThreadSelectorEntry} function.
20992 It takes an optional argument that is evaluated to
20993 a long value to give the information about this given selector.
20994 Without argument, this command displays information
20995 about the six segment registers.
20997 @item info w32 thread-information-block
20998 This command displays thread specific information stored in the
20999 Thread Information Block (readable on the X86 CPU family using @code{$fs}
21000 selector for 32-bit programs and @code{$gs} for 64-bit programs).
21002 @kindex set cygwin-exceptions
21003 @cindex debugging the Cygwin DLL
21004 @cindex Cygwin DLL, debugging
21005 @item set cygwin-exceptions @var{mode}
21006 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
21007 happen inside the Cygwin DLL. If @var{mode} is @code{off},
21008 @value{GDBN} will delay recognition of exceptions, and may ignore some
21009 exceptions which seem to be caused by internal Cygwin DLL
21010 ``bookkeeping''. This option is meant primarily for debugging the
21011 Cygwin DLL itself; the default value is @code{off} to avoid annoying
21012 @value{GDBN} users with false @code{SIGSEGV} signals.
21014 @kindex show cygwin-exceptions
21015 @item show cygwin-exceptions
21016 Displays whether @value{GDBN} will break on exceptions that happen
21017 inside the Cygwin DLL itself.
21019 @kindex set new-console
21020 @item set new-console @var{mode}
21021 If @var{mode} is @code{on} the debuggee will
21022 be started in a new console on next start.
21023 If @var{mode} is @code{off}, the debuggee will
21024 be started in the same console as the debugger.
21026 @kindex show new-console
21027 @item show new-console
21028 Displays whether a new console is used
21029 when the debuggee is started.
21031 @kindex set new-group
21032 @item set new-group @var{mode}
21033 This boolean value controls whether the debuggee should
21034 start a new group or stay in the same group as the debugger.
21035 This affects the way the Windows OS handles
21038 @kindex show new-group
21039 @item show new-group
21040 Displays current value of new-group boolean.
21042 @kindex set debugevents
21043 @item set debugevents
21044 This boolean value adds debug output concerning kernel events related
21045 to the debuggee seen by the debugger. This includes events that
21046 signal thread and process creation and exit, DLL loading and
21047 unloading, console interrupts, and debugging messages produced by the
21048 Windows @code{OutputDebugString} API call.
21050 @kindex set debugexec
21051 @item set debugexec
21052 This boolean value adds debug output concerning execute events
21053 (such as resume thread) seen by the debugger.
21055 @kindex set debugexceptions
21056 @item set debugexceptions
21057 This boolean value adds debug output concerning exceptions in the
21058 debuggee seen by the debugger.
21060 @kindex set debugmemory
21061 @item set debugmemory
21062 This boolean value adds debug output concerning debuggee memory reads
21063 and writes by the debugger.
21067 This boolean values specifies whether the debuggee is called
21068 via a shell or directly (default value is on).
21072 Displays if the debuggee will be started with a shell.
21077 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
21080 @node Non-debug DLL Symbols
21081 @subsubsection Support for DLLs without Debugging Symbols
21082 @cindex DLLs with no debugging symbols
21083 @cindex Minimal symbols and DLLs
21085 Very often on windows, some of the DLLs that your program relies on do
21086 not include symbolic debugging information (for example,
21087 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
21088 symbols in a DLL, it relies on the minimal amount of symbolic
21089 information contained in the DLL's export table. This section
21090 describes working with such symbols, known internally to @value{GDBN} as
21091 ``minimal symbols''.
21093 Note that before the debugged program has started execution, no DLLs
21094 will have been loaded. The easiest way around this problem is simply to
21095 start the program --- either by setting a breakpoint or letting the
21096 program run once to completion.
21098 @subsubsection DLL Name Prefixes
21100 In keeping with the naming conventions used by the Microsoft debugging
21101 tools, DLL export symbols are made available with a prefix based on the
21102 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
21103 also entered into the symbol table, so @code{CreateFileA} is often
21104 sufficient. In some cases there will be name clashes within a program
21105 (particularly if the executable itself includes full debugging symbols)
21106 necessitating the use of the fully qualified name when referring to the
21107 contents of the DLL. Use single-quotes around the name to avoid the
21108 exclamation mark (``!'') being interpreted as a language operator.
21110 Note that the internal name of the DLL may be all upper-case, even
21111 though the file name of the DLL is lower-case, or vice-versa. Since
21112 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
21113 some confusion. If in doubt, try the @code{info functions} and
21114 @code{info variables} commands or even @code{maint print msymbols}
21115 (@pxref{Symbols}). Here's an example:
21118 (@value{GDBP}) info function CreateFileA
21119 All functions matching regular expression "CreateFileA":
21121 Non-debugging symbols:
21122 0x77e885f4 CreateFileA
21123 0x77e885f4 KERNEL32!CreateFileA
21127 (@value{GDBP}) info function !
21128 All functions matching regular expression "!":
21130 Non-debugging symbols:
21131 0x6100114c cygwin1!__assert
21132 0x61004034 cygwin1!_dll_crt0@@0
21133 0x61004240 cygwin1!dll_crt0(per_process *)
21137 @subsubsection Working with Minimal Symbols
21139 Symbols extracted from a DLL's export table do not contain very much
21140 type information. All that @value{GDBN} can do is guess whether a symbol
21141 refers to a function or variable depending on the linker section that
21142 contains the symbol. Also note that the actual contents of the memory
21143 contained in a DLL are not available unless the program is running. This
21144 means that you cannot examine the contents of a variable or disassemble
21145 a function within a DLL without a running program.
21147 Variables are generally treated as pointers and dereferenced
21148 automatically. For this reason, it is often necessary to prefix a
21149 variable name with the address-of operator (``&'') and provide explicit
21150 type information in the command. Here's an example of the type of
21154 (@value{GDBP}) print 'cygwin1!__argv'
21159 (@value{GDBP}) x 'cygwin1!__argv'
21160 0x10021610: "\230y\""
21163 And two possible solutions:
21166 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
21167 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
21171 (@value{GDBP}) x/2x &'cygwin1!__argv'
21172 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
21173 (@value{GDBP}) x/x 0x10021608
21174 0x10021608: 0x0022fd98
21175 (@value{GDBP}) x/s 0x0022fd98
21176 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
21179 Setting a break point within a DLL is possible even before the program
21180 starts execution. However, under these circumstances, @value{GDBN} can't
21181 examine the initial instructions of the function in order to skip the
21182 function's frame set-up code. You can work around this by using ``*&''
21183 to set the breakpoint at a raw memory address:
21186 (@value{GDBP}) break *&'python22!PyOS_Readline'
21187 Breakpoint 1 at 0x1e04eff0
21190 The author of these extensions is not entirely convinced that setting a
21191 break point within a shared DLL like @file{kernel32.dll} is completely
21195 @subsection Commands Specific to @sc{gnu} Hurd Systems
21196 @cindex @sc{gnu} Hurd debugging
21198 This subsection describes @value{GDBN} commands specific to the
21199 @sc{gnu} Hurd native debugging.
21204 @kindex set signals@r{, Hurd command}
21205 @kindex set sigs@r{, Hurd command}
21206 This command toggles the state of inferior signal interception by
21207 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
21208 affected by this command. @code{sigs} is a shorthand alias for
21213 @kindex show signals@r{, Hurd command}
21214 @kindex show sigs@r{, Hurd command}
21215 Show the current state of intercepting inferior's signals.
21217 @item set signal-thread
21218 @itemx set sigthread
21219 @kindex set signal-thread
21220 @kindex set sigthread
21221 This command tells @value{GDBN} which thread is the @code{libc} signal
21222 thread. That thread is run when a signal is delivered to a running
21223 process. @code{set sigthread} is the shorthand alias of @code{set
21226 @item show signal-thread
21227 @itemx show sigthread
21228 @kindex show signal-thread
21229 @kindex show sigthread
21230 These two commands show which thread will run when the inferior is
21231 delivered a signal.
21234 @kindex set stopped@r{, Hurd command}
21235 This commands tells @value{GDBN} that the inferior process is stopped,
21236 as with the @code{SIGSTOP} signal. The stopped process can be
21237 continued by delivering a signal to it.
21240 @kindex show stopped@r{, Hurd command}
21241 This command shows whether @value{GDBN} thinks the debuggee is
21244 @item set exceptions
21245 @kindex set exceptions@r{, Hurd command}
21246 Use this command to turn off trapping of exceptions in the inferior.
21247 When exception trapping is off, neither breakpoints nor
21248 single-stepping will work. To restore the default, set exception
21251 @item show exceptions
21252 @kindex show exceptions@r{, Hurd command}
21253 Show the current state of trapping exceptions in the inferior.
21255 @item set task pause
21256 @kindex set task@r{, Hurd commands}
21257 @cindex task attributes (@sc{gnu} Hurd)
21258 @cindex pause current task (@sc{gnu} Hurd)
21259 This command toggles task suspension when @value{GDBN} has control.
21260 Setting it to on takes effect immediately, and the task is suspended
21261 whenever @value{GDBN} gets control. Setting it to off will take
21262 effect the next time the inferior is continued. If this option is set
21263 to off, you can use @code{set thread default pause on} or @code{set
21264 thread pause on} (see below) to pause individual threads.
21266 @item show task pause
21267 @kindex show task@r{, Hurd commands}
21268 Show the current state of task suspension.
21270 @item set task detach-suspend-count
21271 @cindex task suspend count
21272 @cindex detach from task, @sc{gnu} Hurd
21273 This command sets the suspend count the task will be left with when
21274 @value{GDBN} detaches from it.
21276 @item show task detach-suspend-count
21277 Show the suspend count the task will be left with when detaching.
21279 @item set task exception-port
21280 @itemx set task excp
21281 @cindex task exception port, @sc{gnu} Hurd
21282 This command sets the task exception port to which @value{GDBN} will
21283 forward exceptions. The argument should be the value of the @dfn{send
21284 rights} of the task. @code{set task excp} is a shorthand alias.
21286 @item set noninvasive
21287 @cindex noninvasive task options
21288 This command switches @value{GDBN} to a mode that is the least
21289 invasive as far as interfering with the inferior is concerned. This
21290 is the same as using @code{set task pause}, @code{set exceptions}, and
21291 @code{set signals} to values opposite to the defaults.
21293 @item info send-rights
21294 @itemx info receive-rights
21295 @itemx info port-rights
21296 @itemx info port-sets
21297 @itemx info dead-names
21300 @cindex send rights, @sc{gnu} Hurd
21301 @cindex receive rights, @sc{gnu} Hurd
21302 @cindex port rights, @sc{gnu} Hurd
21303 @cindex port sets, @sc{gnu} Hurd
21304 @cindex dead names, @sc{gnu} Hurd
21305 These commands display information about, respectively, send rights,
21306 receive rights, port rights, port sets, and dead names of a task.
21307 There are also shorthand aliases: @code{info ports} for @code{info
21308 port-rights} and @code{info psets} for @code{info port-sets}.
21310 @item set thread pause
21311 @kindex set thread@r{, Hurd command}
21312 @cindex thread properties, @sc{gnu} Hurd
21313 @cindex pause current thread (@sc{gnu} Hurd)
21314 This command toggles current thread suspension when @value{GDBN} has
21315 control. Setting it to on takes effect immediately, and the current
21316 thread is suspended whenever @value{GDBN} gets control. Setting it to
21317 off will take effect the next time the inferior is continued.
21318 Normally, this command has no effect, since when @value{GDBN} has
21319 control, the whole task is suspended. However, if you used @code{set
21320 task pause off} (see above), this command comes in handy to suspend
21321 only the current thread.
21323 @item show thread pause
21324 @kindex show thread@r{, Hurd command}
21325 This command shows the state of current thread suspension.
21327 @item set thread run
21328 This command sets whether the current thread is allowed to run.
21330 @item show thread run
21331 Show whether the current thread is allowed to run.
21333 @item set thread detach-suspend-count
21334 @cindex thread suspend count, @sc{gnu} Hurd
21335 @cindex detach from thread, @sc{gnu} Hurd
21336 This command sets the suspend count @value{GDBN} will leave on a
21337 thread when detaching. This number is relative to the suspend count
21338 found by @value{GDBN} when it notices the thread; use @code{set thread
21339 takeover-suspend-count} to force it to an absolute value.
21341 @item show thread detach-suspend-count
21342 Show the suspend count @value{GDBN} will leave on the thread when
21345 @item set thread exception-port
21346 @itemx set thread excp
21347 Set the thread exception port to which to forward exceptions. This
21348 overrides the port set by @code{set task exception-port} (see above).
21349 @code{set thread excp} is the shorthand alias.
21351 @item set thread takeover-suspend-count
21352 Normally, @value{GDBN}'s thread suspend counts are relative to the
21353 value @value{GDBN} finds when it notices each thread. This command
21354 changes the suspend counts to be absolute instead.
21356 @item set thread default
21357 @itemx show thread default
21358 @cindex thread default settings, @sc{gnu} Hurd
21359 Each of the above @code{set thread} commands has a @code{set thread
21360 default} counterpart (e.g., @code{set thread default pause}, @code{set
21361 thread default exception-port}, etc.). The @code{thread default}
21362 variety of commands sets the default thread properties for all
21363 threads; you can then change the properties of individual threads with
21364 the non-default commands.
21371 @value{GDBN} provides the following commands specific to the Darwin target:
21374 @item set debug darwin @var{num}
21375 @kindex set debug darwin
21376 When set to a non zero value, enables debugging messages specific to
21377 the Darwin support. Higher values produce more verbose output.
21379 @item show debug darwin
21380 @kindex show debug darwin
21381 Show the current state of Darwin messages.
21383 @item set debug mach-o @var{num}
21384 @kindex set debug mach-o
21385 When set to a non zero value, enables debugging messages while
21386 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
21387 file format used on Darwin for object and executable files.) Higher
21388 values produce more verbose output. This is a command to diagnose
21389 problems internal to @value{GDBN} and should not be needed in normal
21392 @item show debug mach-o
21393 @kindex show debug mach-o
21394 Show the current state of Mach-O file messages.
21396 @item set mach-exceptions on
21397 @itemx set mach-exceptions off
21398 @kindex set mach-exceptions
21399 On Darwin, faults are first reported as a Mach exception and are then
21400 mapped to a Posix signal. Use this command to turn on trapping of
21401 Mach exceptions in the inferior. This might be sometimes useful to
21402 better understand the cause of a fault. The default is off.
21404 @item show mach-exceptions
21405 @kindex show mach-exceptions
21406 Show the current state of exceptions trapping.
21411 @section Embedded Operating Systems
21413 This section describes configurations involving the debugging of
21414 embedded operating systems that are available for several different
21417 @value{GDBN} includes the ability to debug programs running on
21418 various real-time operating systems.
21420 @node Embedded Processors
21421 @section Embedded Processors
21423 This section goes into details specific to particular embedded
21426 @cindex send command to simulator
21427 Whenever a specific embedded processor has a simulator, @value{GDBN}
21428 allows to send an arbitrary command to the simulator.
21431 @item sim @var{command}
21432 @kindex sim@r{, a command}
21433 Send an arbitrary @var{command} string to the simulator. Consult the
21434 documentation for the specific simulator in use for information about
21435 acceptable commands.
21441 * M32R/SDI:: Renesas M32R/SDI
21442 * M68K:: Motorola M68K
21443 * MicroBlaze:: Xilinx MicroBlaze
21444 * MIPS Embedded:: MIPS Embedded
21445 * PowerPC Embedded:: PowerPC Embedded
21448 * Super-H:: Renesas Super-H
21454 @value{GDBN} provides the following ARM-specific commands:
21457 @item set arm disassembler
21459 This commands selects from a list of disassembly styles. The
21460 @code{"std"} style is the standard style.
21462 @item show arm disassembler
21464 Show the current disassembly style.
21466 @item set arm apcs32
21467 @cindex ARM 32-bit mode
21468 This command toggles ARM operation mode between 32-bit and 26-bit.
21470 @item show arm apcs32
21471 Display the current usage of the ARM 32-bit mode.
21473 @item set arm fpu @var{fputype}
21474 This command sets the ARM floating-point unit (FPU) type. The
21475 argument @var{fputype} can be one of these:
21479 Determine the FPU type by querying the OS ABI.
21481 Software FPU, with mixed-endian doubles on little-endian ARM
21484 GCC-compiled FPA co-processor.
21486 Software FPU with pure-endian doubles.
21492 Show the current type of the FPU.
21495 This command forces @value{GDBN} to use the specified ABI.
21498 Show the currently used ABI.
21500 @item set arm fallback-mode (arm|thumb|auto)
21501 @value{GDBN} uses the symbol table, when available, to determine
21502 whether instructions are ARM or Thumb. This command controls
21503 @value{GDBN}'s default behavior when the symbol table is not
21504 available. The default is @samp{auto}, which causes @value{GDBN} to
21505 use the current execution mode (from the @code{T} bit in the @code{CPSR}
21508 @item show arm fallback-mode
21509 Show the current fallback instruction mode.
21511 @item set arm force-mode (arm|thumb|auto)
21512 This command overrides use of the symbol table to determine whether
21513 instructions are ARM or Thumb. The default is @samp{auto}, which
21514 causes @value{GDBN} to use the symbol table and then the setting
21515 of @samp{set arm fallback-mode}.
21517 @item show arm force-mode
21518 Show the current forced instruction mode.
21520 @item set debug arm
21521 Toggle whether to display ARM-specific debugging messages from the ARM
21522 target support subsystem.
21524 @item show debug arm
21525 Show whether ARM-specific debugging messages are enabled.
21529 @item target sim @r{[}@var{simargs}@r{]} @dots{}
21530 The @value{GDBN} ARM simulator accepts the following optional arguments.
21533 @item --swi-support=@var{type}
21534 Tell the simulator which SWI interfaces to support. The argument
21535 @var{type} may be a comma separated list of the following values.
21536 The default value is @code{all}.
21549 @subsection Renesas M32R/SDI
21551 The following commands are available for M32R/SDI:
21556 @cindex reset SDI connection, M32R
21557 This command resets the SDI connection.
21561 This command shows the SDI connection status.
21564 @kindex debug_chaos
21565 @cindex M32R/Chaos debugging
21566 Instructs the remote that M32R/Chaos debugging is to be used.
21568 @item use_debug_dma
21569 @kindex use_debug_dma
21570 Instructs the remote to use the DEBUG_DMA method of accessing memory.
21573 @kindex use_mon_code
21574 Instructs the remote to use the MON_CODE method of accessing memory.
21577 @kindex use_ib_break
21578 Instructs the remote to set breakpoints by IB break.
21580 @item use_dbt_break
21581 @kindex use_dbt_break
21582 Instructs the remote to set breakpoints by DBT.
21588 The Motorola m68k configuration includes ColdFire support.
21591 @subsection MicroBlaze
21592 @cindex Xilinx MicroBlaze
21593 @cindex XMD, Xilinx Microprocessor Debugger
21595 The MicroBlaze is a soft-core processor supported on various Xilinx
21596 FPGAs, such as Spartan or Virtex series. Boards with these processors
21597 usually have JTAG ports which connect to a host system running the Xilinx
21598 Embedded Development Kit (EDK) or Software Development Kit (SDK).
21599 This host system is used to download the configuration bitstream to
21600 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
21601 communicates with the target board using the JTAG interface and
21602 presents a @code{gdbserver} interface to the board. By default
21603 @code{xmd} uses port @code{1234}. (While it is possible to change
21604 this default port, it requires the use of undocumented @code{xmd}
21605 commands. Contact Xilinx support if you need to do this.)
21607 Use these GDB commands to connect to the MicroBlaze target processor.
21610 @item target remote :1234
21611 Use this command to connect to the target if you are running @value{GDBN}
21612 on the same system as @code{xmd}.
21614 @item target remote @var{xmd-host}:1234
21615 Use this command to connect to the target if it is connected to @code{xmd}
21616 running on a different system named @var{xmd-host}.
21619 Use this command to download a program to the MicroBlaze target.
21621 @item set debug microblaze @var{n}
21622 Enable MicroBlaze-specific debugging messages if non-zero.
21624 @item show debug microblaze @var{n}
21625 Show MicroBlaze-specific debugging level.
21628 @node MIPS Embedded
21629 @subsection @acronym{MIPS} Embedded
21631 @cindex @acronym{MIPS} boards
21632 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
21633 @acronym{MIPS} board attached to a serial line. This is available when
21634 you configure @value{GDBN} with @samp{--target=mips-elf}.
21637 Use these @value{GDBN} commands to specify the connection to your target board:
21640 @item target mips @var{port}
21641 @kindex target mips @var{port}
21642 To run a program on the board, start up @code{@value{GDBP}} with the
21643 name of your program as the argument. To connect to the board, use the
21644 command @samp{target mips @var{port}}, where @var{port} is the name of
21645 the serial port connected to the board. If the program has not already
21646 been downloaded to the board, you may use the @code{load} command to
21647 download it. You can then use all the usual @value{GDBN} commands.
21649 For example, this sequence connects to the target board through a serial
21650 port, and loads and runs a program called @var{prog} through the
21654 host$ @value{GDBP} @var{prog}
21655 @value{GDBN} is free software and @dots{}
21656 (@value{GDBP}) target mips /dev/ttyb
21657 (@value{GDBP}) load @var{prog}
21661 @item target mips @var{hostname}:@var{portnumber}
21662 On some @value{GDBN} host configurations, you can specify a TCP
21663 connection (for instance, to a serial line managed by a terminal
21664 concentrator) instead of a serial port, using the syntax
21665 @samp{@var{hostname}:@var{portnumber}}.
21667 @item target pmon @var{port}
21668 @kindex target pmon @var{port}
21671 @item target ddb @var{port}
21672 @kindex target ddb @var{port}
21673 NEC's DDB variant of PMON for Vr4300.
21675 @item target lsi @var{port}
21676 @kindex target lsi @var{port}
21677 LSI variant of PMON.
21683 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
21686 @item set mipsfpu double
21687 @itemx set mipsfpu single
21688 @itemx set mipsfpu none
21689 @itemx set mipsfpu auto
21690 @itemx show mipsfpu
21691 @kindex set mipsfpu
21692 @kindex show mipsfpu
21693 @cindex @acronym{MIPS} remote floating point
21694 @cindex floating point, @acronym{MIPS} remote
21695 If your target board does not support the @acronym{MIPS} floating point
21696 coprocessor, you should use the command @samp{set mipsfpu none} (if you
21697 need this, you may wish to put the command in your @value{GDBN} init
21698 file). This tells @value{GDBN} how to find the return value of
21699 functions which return floating point values. It also allows
21700 @value{GDBN} to avoid saving the floating point registers when calling
21701 functions on the board. If you are using a floating point coprocessor
21702 with only single precision floating point support, as on the @sc{r4650}
21703 processor, use the command @samp{set mipsfpu single}. The default
21704 double precision floating point coprocessor may be selected using
21705 @samp{set mipsfpu double}.
21707 In previous versions the only choices were double precision or no
21708 floating point, so @samp{set mipsfpu on} will select double precision
21709 and @samp{set mipsfpu off} will select no floating point.
21711 As usual, you can inquire about the @code{mipsfpu} variable with
21712 @samp{show mipsfpu}.
21714 @item set timeout @var{seconds}
21715 @itemx set retransmit-timeout @var{seconds}
21716 @itemx show timeout
21717 @itemx show retransmit-timeout
21718 @cindex @code{timeout}, @acronym{MIPS} protocol
21719 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
21720 @kindex set timeout
21721 @kindex show timeout
21722 @kindex set retransmit-timeout
21723 @kindex show retransmit-timeout
21724 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
21725 remote protocol, with the @code{set timeout @var{seconds}} command. The
21726 default is 5 seconds. Similarly, you can control the timeout used while
21727 waiting for an acknowledgment of a packet with the @code{set
21728 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
21729 You can inspect both values with @code{show timeout} and @code{show
21730 retransmit-timeout}. (These commands are @emph{only} available when
21731 @value{GDBN} is configured for @samp{--target=mips-elf}.)
21733 The timeout set by @code{set timeout} does not apply when @value{GDBN}
21734 is waiting for your program to stop. In that case, @value{GDBN} waits
21735 forever because it has no way of knowing how long the program is going
21736 to run before stopping.
21738 @item set syn-garbage-limit @var{num}
21739 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
21740 @cindex synchronize with remote @acronym{MIPS} target
21741 Limit the maximum number of characters @value{GDBN} should ignore when
21742 it tries to synchronize with the remote target. The default is 10
21743 characters. Setting the limit to -1 means there's no limit.
21745 @item show syn-garbage-limit
21746 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
21747 Show the current limit on the number of characters to ignore when
21748 trying to synchronize with the remote system.
21750 @item set monitor-prompt @var{prompt}
21751 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
21752 @cindex remote monitor prompt
21753 Tell @value{GDBN} to expect the specified @var{prompt} string from the
21754 remote monitor. The default depends on the target:
21764 @item show monitor-prompt
21765 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
21766 Show the current strings @value{GDBN} expects as the prompt from the
21769 @item set monitor-warnings
21770 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
21771 Enable or disable monitor warnings about hardware breakpoints. This
21772 has effect only for the @code{lsi} target. When on, @value{GDBN} will
21773 display warning messages whose codes are returned by the @code{lsi}
21774 PMON monitor for breakpoint commands.
21776 @item show monitor-warnings
21777 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
21778 Show the current setting of printing monitor warnings.
21780 @item pmon @var{command}
21781 @kindex pmon@r{, @acronym{MIPS} remote}
21782 @cindex send PMON command
21783 This command allows sending an arbitrary @var{command} string to the
21784 monitor. The monitor must be in debug mode for this to work.
21787 @node PowerPC Embedded
21788 @subsection PowerPC Embedded
21790 @cindex DVC register
21791 @value{GDBN} supports using the DVC (Data Value Compare) register to
21792 implement in hardware simple hardware watchpoint conditions of the form:
21795 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
21796 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
21799 The DVC register will be automatically used when @value{GDBN} detects
21800 such pattern in a condition expression, and the created watchpoint uses one
21801 debug register (either the @code{exact-watchpoints} option is on and the
21802 variable is scalar, or the variable has a length of one byte). This feature
21803 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
21806 When running on PowerPC embedded processors, @value{GDBN} automatically uses
21807 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
21808 in which case watchpoints using only one debug register are created when
21809 watching variables of scalar types.
21811 You can create an artificial array to watch an arbitrary memory
21812 region using one of the following commands (@pxref{Expressions}):
21815 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
21816 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
21819 PowerPC embedded processors support masked watchpoints. See the discussion
21820 about the @code{mask} argument in @ref{Set Watchpoints}.
21822 @cindex ranged breakpoint
21823 PowerPC embedded processors support hardware accelerated
21824 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
21825 the inferior whenever it executes an instruction at any address within
21826 the range it specifies. To set a ranged breakpoint in @value{GDBN},
21827 use the @code{break-range} command.
21829 @value{GDBN} provides the following PowerPC-specific commands:
21832 @kindex break-range
21833 @item break-range @var{start-location}, @var{end-location}
21834 Set a breakpoint for an address range given by
21835 @var{start-location} and @var{end-location}, which can specify a function name,
21836 a line number, an offset of lines from the current line or from the start
21837 location, or an address of an instruction (see @ref{Specify Location},
21838 for a list of all the possible ways to specify a @var{location}.)
21839 The breakpoint will stop execution of the inferior whenever it
21840 executes an instruction at any address within the specified range,
21841 (including @var{start-location} and @var{end-location}.)
21843 @kindex set powerpc
21844 @item set powerpc soft-float
21845 @itemx show powerpc soft-float
21846 Force @value{GDBN} to use (or not use) a software floating point calling
21847 convention. By default, @value{GDBN} selects the calling convention based
21848 on the selected architecture and the provided executable file.
21850 @item set powerpc vector-abi
21851 @itemx show powerpc vector-abi
21852 Force @value{GDBN} to use the specified calling convention for vector
21853 arguments and return values. The valid options are @samp{auto};
21854 @samp{generic}, to avoid vector registers even if they are present;
21855 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
21856 registers. By default, @value{GDBN} selects the calling convention
21857 based on the selected architecture and the provided executable file.
21859 @item set powerpc exact-watchpoints
21860 @itemx show powerpc exact-watchpoints
21861 Allow @value{GDBN} to use only one debug register when watching a variable
21862 of scalar type, thus assuming that the variable is accessed through the
21863 address of its first byte.
21868 @subsection Atmel AVR
21871 When configured for debugging the Atmel AVR, @value{GDBN} supports the
21872 following AVR-specific commands:
21875 @item info io_registers
21876 @kindex info io_registers@r{, AVR}
21877 @cindex I/O registers (Atmel AVR)
21878 This command displays information about the AVR I/O registers. For
21879 each register, @value{GDBN} prints its number and value.
21886 When configured for debugging CRIS, @value{GDBN} provides the
21887 following CRIS-specific commands:
21890 @item set cris-version @var{ver}
21891 @cindex CRIS version
21892 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
21893 The CRIS version affects register names and sizes. This command is useful in
21894 case autodetection of the CRIS version fails.
21896 @item show cris-version
21897 Show the current CRIS version.
21899 @item set cris-dwarf2-cfi
21900 @cindex DWARF-2 CFI and CRIS
21901 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
21902 Change to @samp{off} when using @code{gcc-cris} whose version is below
21905 @item show cris-dwarf2-cfi
21906 Show the current state of using DWARF-2 CFI.
21908 @item set cris-mode @var{mode}
21910 Set the current CRIS mode to @var{mode}. It should only be changed when
21911 debugging in guru mode, in which case it should be set to
21912 @samp{guru} (the default is @samp{normal}).
21914 @item show cris-mode
21915 Show the current CRIS mode.
21919 @subsection Renesas Super-H
21922 For the Renesas Super-H processor, @value{GDBN} provides these
21926 @item set sh calling-convention @var{convention}
21927 @kindex set sh calling-convention
21928 Set the calling-convention used when calling functions from @value{GDBN}.
21929 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
21930 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
21931 convention. If the DWARF-2 information of the called function specifies
21932 that the function follows the Renesas calling convention, the function
21933 is called using the Renesas calling convention. If the calling convention
21934 is set to @samp{renesas}, the Renesas calling convention is always used,
21935 regardless of the DWARF-2 information. This can be used to override the
21936 default of @samp{gcc} if debug information is missing, or the compiler
21937 does not emit the DWARF-2 calling convention entry for a function.
21939 @item show sh calling-convention
21940 @kindex show sh calling-convention
21941 Show the current calling convention setting.
21946 @node Architectures
21947 @section Architectures
21949 This section describes characteristics of architectures that affect
21950 all uses of @value{GDBN} with the architecture, both native and cross.
21957 * HPPA:: HP PA architecture
21958 * SPU:: Cell Broadband Engine SPU architecture
21964 @subsection AArch64
21965 @cindex AArch64 support
21967 When @value{GDBN} is debugging the AArch64 architecture, it provides the
21968 following special commands:
21971 @item set debug aarch64
21972 @kindex set debug aarch64
21973 This command determines whether AArch64 architecture-specific debugging
21974 messages are to be displayed.
21976 @item show debug aarch64
21977 Show whether AArch64 debugging messages are displayed.
21982 @subsection x86 Architecture-specific Issues
21985 @item set struct-convention @var{mode}
21986 @kindex set struct-convention
21987 @cindex struct return convention
21988 @cindex struct/union returned in registers
21989 Set the convention used by the inferior to return @code{struct}s and
21990 @code{union}s from functions to @var{mode}. Possible values of
21991 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
21992 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
21993 are returned on the stack, while @code{"reg"} means that a
21994 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
21995 be returned in a register.
21997 @item show struct-convention
21998 @kindex show struct-convention
21999 Show the current setting of the convention to return @code{struct}s
22004 @subsubsection Intel(R) @dfn{Memory Protection Extensions} (MPX).
22005 @cindex Intel(R) Memory Protection Extensions (MPX).
22007 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
22008 @footnote{The register named with capital letters represent the architecture
22009 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
22010 which are the lower bound and upper bound. Bounds are effective addresses or
22011 memory locations. The upper bounds are architecturally represented in 1's
22012 complement form. A bound having lower bound = 0, and upper bound = 0
22013 (1's complement of all bits set) will allow access to the entire address space.
22015 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
22016 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
22017 display the upper bound performing the complement of one operation on the
22018 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
22019 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
22020 can also be noted that the upper bounds are inclusive.
22022 As an example, assume that the register BND0 holds bounds for a pointer having
22023 access allowed for the range between 0x32 and 0x71. The values present on
22024 bnd0raw and bnd registers are presented as follows:
22027 bnd0raw = @{0x32, 0xffffffff8e@}
22028 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
22031 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
22032 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
22033 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
22034 Python, the display includes the memory size, in bits, accessible to
22037 Bounds can also be stored in bounds tables, which are stored in
22038 application memory. These tables store bounds for pointers by specifying
22039 the bounds pointer's value along with its bounds. Evaluating and changing
22040 bounds located in bound tables is therefore interesting while investigating
22041 bugs on MPX context. @value{GDBN} provides commands for this purpose:
22044 @item show mpx bound @var{pointer}
22045 @kindex show mpx bound
22046 Display bounds of the given @var{pointer}.
22048 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
22049 @kindex set mpx bound
22050 Set the bounds of a pointer in the bound table.
22051 This command takes three parameters: @var{pointer} is the pointers
22052 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
22053 for lower and upper bounds respectively.
22059 See the following section.
22062 @subsection @acronym{MIPS}
22064 @cindex stack on Alpha
22065 @cindex stack on @acronym{MIPS}
22066 @cindex Alpha stack
22067 @cindex @acronym{MIPS} stack
22068 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
22069 sometimes requires @value{GDBN} to search backward in the object code to
22070 find the beginning of a function.
22072 @cindex response time, @acronym{MIPS} debugging
22073 To improve response time (especially for embedded applications, where
22074 @value{GDBN} may be restricted to a slow serial line for this search)
22075 you may want to limit the size of this search, using one of these
22079 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
22080 @item set heuristic-fence-post @var{limit}
22081 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
22082 search for the beginning of a function. A value of @var{0} (the
22083 default) means there is no limit. However, except for @var{0}, the
22084 larger the limit the more bytes @code{heuristic-fence-post} must search
22085 and therefore the longer it takes to run. You should only need to use
22086 this command when debugging a stripped executable.
22088 @item show heuristic-fence-post
22089 Display the current limit.
22093 These commands are available @emph{only} when @value{GDBN} is configured
22094 for debugging programs on Alpha or @acronym{MIPS} processors.
22096 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
22100 @item set mips abi @var{arg}
22101 @kindex set mips abi
22102 @cindex set ABI for @acronym{MIPS}
22103 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
22104 values of @var{arg} are:
22108 The default ABI associated with the current binary (this is the
22118 @item show mips abi
22119 @kindex show mips abi
22120 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
22122 @item set mips compression @var{arg}
22123 @kindex set mips compression
22124 @cindex code compression, @acronym{MIPS}
22125 Tell @value{GDBN} which @acronym{MIPS} compressed
22126 @acronym{ISA, Instruction Set Architecture} encoding is used by the
22127 inferior. @value{GDBN} uses this for code disassembly and other
22128 internal interpretation purposes. This setting is only referred to
22129 when no executable has been associated with the debugging session or
22130 the executable does not provide information about the encoding it uses.
22131 Otherwise this setting is automatically updated from information
22132 provided by the executable.
22134 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
22135 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
22136 executables containing @acronym{MIPS16} code frequently are not
22137 identified as such.
22139 This setting is ``sticky''; that is, it retains its value across
22140 debugging sessions until reset either explicitly with this command or
22141 implicitly from an executable.
22143 The compiler and/or assembler typically add symbol table annotations to
22144 identify functions compiled for the @acronym{MIPS16} or
22145 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
22146 are present, @value{GDBN} uses them in preference to the global
22147 compressed @acronym{ISA} encoding setting.
22149 @item show mips compression
22150 @kindex show mips compression
22151 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
22152 @value{GDBN} to debug the inferior.
22155 @itemx show mipsfpu
22156 @xref{MIPS Embedded, set mipsfpu}.
22158 @item set mips mask-address @var{arg}
22159 @kindex set mips mask-address
22160 @cindex @acronym{MIPS} addresses, masking
22161 This command determines whether the most-significant 32 bits of 64-bit
22162 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
22163 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
22164 setting, which lets @value{GDBN} determine the correct value.
22166 @item show mips mask-address
22167 @kindex show mips mask-address
22168 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
22171 @item set remote-mips64-transfers-32bit-regs
22172 @kindex set remote-mips64-transfers-32bit-regs
22173 This command controls compatibility with 64-bit @acronym{MIPS} targets that
22174 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
22175 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
22176 and 64 bits for other registers, set this option to @samp{on}.
22178 @item show remote-mips64-transfers-32bit-regs
22179 @kindex show remote-mips64-transfers-32bit-regs
22180 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
22182 @item set debug mips
22183 @kindex set debug mips
22184 This command turns on and off debugging messages for the @acronym{MIPS}-specific
22185 target code in @value{GDBN}.
22187 @item show debug mips
22188 @kindex show debug mips
22189 Show the current setting of @acronym{MIPS} debugging messages.
22195 @cindex HPPA support
22197 When @value{GDBN} is debugging the HP PA architecture, it provides the
22198 following special commands:
22201 @item set debug hppa
22202 @kindex set debug hppa
22203 This command determines whether HPPA architecture-specific debugging
22204 messages are to be displayed.
22206 @item show debug hppa
22207 Show whether HPPA debugging messages are displayed.
22209 @item maint print unwind @var{address}
22210 @kindex maint print unwind@r{, HPPA}
22211 This command displays the contents of the unwind table entry at the
22212 given @var{address}.
22218 @subsection Cell Broadband Engine SPU architecture
22219 @cindex Cell Broadband Engine
22222 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
22223 it provides the following special commands:
22226 @item info spu event
22228 Display SPU event facility status. Shows current event mask
22229 and pending event status.
22231 @item info spu signal
22232 Display SPU signal notification facility status. Shows pending
22233 signal-control word and signal notification mode of both signal
22234 notification channels.
22236 @item info spu mailbox
22237 Display SPU mailbox facility status. Shows all pending entries,
22238 in order of processing, in each of the SPU Write Outbound,
22239 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
22242 Display MFC DMA status. Shows all pending commands in the MFC
22243 DMA queue. For each entry, opcode, tag, class IDs, effective
22244 and local store addresses and transfer size are shown.
22246 @item info spu proxydma
22247 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
22248 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
22249 and local store addresses and transfer size are shown.
22253 When @value{GDBN} is debugging a combined PowerPC/SPU application
22254 on the Cell Broadband Engine, it provides in addition the following
22258 @item set spu stop-on-load @var{arg}
22260 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
22261 will give control to the user when a new SPE thread enters its @code{main}
22262 function. The default is @code{off}.
22264 @item show spu stop-on-load
22266 Show whether to stop for new SPE threads.
22268 @item set spu auto-flush-cache @var{arg}
22269 Set whether to automatically flush the software-managed cache. When set to
22270 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
22271 cache to be flushed whenever SPE execution stops. This provides a consistent
22272 view of PowerPC memory that is accessed via the cache. If an application
22273 does not use the software-managed cache, this option has no effect.
22275 @item show spu auto-flush-cache
22276 Show whether to automatically flush the software-managed cache.
22281 @subsection PowerPC
22282 @cindex PowerPC architecture
22284 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
22285 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
22286 numbers stored in the floating point registers. These values must be stored
22287 in two consecutive registers, always starting at an even register like
22288 @code{f0} or @code{f2}.
22290 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
22291 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
22292 @code{f2} and @code{f3} for @code{$dl1} and so on.
22294 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
22295 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
22298 @subsection Nios II
22299 @cindex Nios II architecture
22301 When @value{GDBN} is debugging the Nios II architecture,
22302 it provides the following special commands:
22306 @item set debug nios2
22307 @kindex set debug nios2
22308 This command turns on and off debugging messages for the Nios II
22309 target code in @value{GDBN}.
22311 @item show debug nios2
22312 @kindex show debug nios2
22313 Show the current setting of Nios II debugging messages.
22316 @node Controlling GDB
22317 @chapter Controlling @value{GDBN}
22319 You can alter the way @value{GDBN} interacts with you by using the
22320 @code{set} command. For commands controlling how @value{GDBN} displays
22321 data, see @ref{Print Settings, ,Print Settings}. Other settings are
22326 * Editing:: Command editing
22327 * Command History:: Command history
22328 * Screen Size:: Screen size
22329 * Numbers:: Numbers
22330 * ABI:: Configuring the current ABI
22331 * Auto-loading:: Automatically loading associated files
22332 * Messages/Warnings:: Optional warnings and messages
22333 * Debugging Output:: Optional messages about internal happenings
22334 * Other Misc Settings:: Other Miscellaneous Settings
22342 @value{GDBN} indicates its readiness to read a command by printing a string
22343 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
22344 can change the prompt string with the @code{set prompt} command. For
22345 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
22346 the prompt in one of the @value{GDBN} sessions so that you can always tell
22347 which one you are talking to.
22349 @emph{Note:} @code{set prompt} does not add a space for you after the
22350 prompt you set. This allows you to set a prompt which ends in a space
22351 or a prompt that does not.
22355 @item set prompt @var{newprompt}
22356 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
22358 @kindex show prompt
22360 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
22363 Versions of @value{GDBN} that ship with Python scripting enabled have
22364 prompt extensions. The commands for interacting with these extensions
22368 @kindex set extended-prompt
22369 @item set extended-prompt @var{prompt}
22370 Set an extended prompt that allows for substitutions.
22371 @xref{gdb.prompt}, for a list of escape sequences that can be used for
22372 substitution. Any escape sequences specified as part of the prompt
22373 string are replaced with the corresponding strings each time the prompt
22379 set extended-prompt Current working directory: \w (gdb)
22382 Note that when an extended-prompt is set, it takes control of the
22383 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
22385 @kindex show extended-prompt
22386 @item show extended-prompt
22387 Prints the extended prompt. Any escape sequences specified as part of
22388 the prompt string with @code{set extended-prompt}, are replaced with the
22389 corresponding strings each time the prompt is displayed.
22393 @section Command Editing
22395 @cindex command line editing
22397 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
22398 @sc{gnu} library provides consistent behavior for programs which provide a
22399 command line interface to the user. Advantages are @sc{gnu} Emacs-style
22400 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
22401 substitution, and a storage and recall of command history across
22402 debugging sessions.
22404 You may control the behavior of command line editing in @value{GDBN} with the
22405 command @code{set}.
22408 @kindex set editing
22411 @itemx set editing on
22412 Enable command line editing (enabled by default).
22414 @item set editing off
22415 Disable command line editing.
22417 @kindex show editing
22419 Show whether command line editing is enabled.
22422 @ifset SYSTEM_READLINE
22423 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
22425 @ifclear SYSTEM_READLINE
22426 @xref{Command Line Editing},
22428 for more details about the Readline
22429 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
22430 encouraged to read that chapter.
22432 @node Command History
22433 @section Command History
22434 @cindex command history
22436 @value{GDBN} can keep track of the commands you type during your
22437 debugging sessions, so that you can be certain of precisely what
22438 happened. Use these commands to manage the @value{GDBN} command
22441 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
22442 package, to provide the history facility.
22443 @ifset SYSTEM_READLINE
22444 @xref{Using History Interactively, , , history, GNU History Library},
22446 @ifclear SYSTEM_READLINE
22447 @xref{Using History Interactively},
22449 for the detailed description of the History library.
22451 To issue a command to @value{GDBN} without affecting certain aspects of
22452 the state which is seen by users, prefix it with @samp{server }
22453 (@pxref{Server Prefix}). This
22454 means that this command will not affect the command history, nor will it
22455 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
22456 pressed on a line by itself.
22458 @cindex @code{server}, command prefix
22459 The server prefix does not affect the recording of values into the value
22460 history; to print a value without recording it into the value history,
22461 use the @code{output} command instead of the @code{print} command.
22463 Here is the description of @value{GDBN} commands related to command
22467 @cindex history substitution
22468 @cindex history file
22469 @kindex set history filename
22470 @cindex @env{GDBHISTFILE}, environment variable
22471 @item set history filename @var{fname}
22472 Set the name of the @value{GDBN} command history file to @var{fname}.
22473 This is the file where @value{GDBN} reads an initial command history
22474 list, and where it writes the command history from this session when it
22475 exits. You can access this list through history expansion or through
22476 the history command editing characters listed below. This file defaults
22477 to the value of the environment variable @code{GDBHISTFILE}, or to
22478 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
22481 @cindex save command history
22482 @kindex set history save
22483 @item set history save
22484 @itemx set history save on
22485 Record command history in a file, whose name may be specified with the
22486 @code{set history filename} command. By default, this option is disabled.
22488 @item set history save off
22489 Stop recording command history in a file.
22491 @cindex history size
22492 @kindex set history size
22493 @cindex @env{GDBHISTSIZE}, environment variable
22494 @item set history size @var{size}
22495 @itemx set history size unlimited
22496 Set the number of commands which @value{GDBN} keeps in its history list.
22497 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
22498 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
22499 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
22500 either a negative number or the empty string, then the number of commands
22501 @value{GDBN} keeps in the history list is unlimited.
22503 @cindex remove duplicate history
22504 @kindex set history remove-duplicates
22505 @item set history remove-duplicates @var{count}
22506 @itemx set history remove-duplicates unlimited
22507 Control the removal of duplicate history entries in the command history list.
22508 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
22509 history entries and remove the first entry that is a duplicate of the current
22510 entry being added to the command history list. If @var{count} is
22511 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
22512 removal of duplicate history entries is disabled.
22514 Only history entries added during the current session are considered for
22515 removal. This option is set to 0 by default.
22519 History expansion assigns special meaning to the character @kbd{!}.
22520 @ifset SYSTEM_READLINE
22521 @xref{Event Designators, , , history, GNU History Library},
22523 @ifclear SYSTEM_READLINE
22524 @xref{Event Designators},
22528 @cindex history expansion, turn on/off
22529 Since @kbd{!} is also the logical not operator in C, history expansion
22530 is off by default. If you decide to enable history expansion with the
22531 @code{set history expansion on} command, you may sometimes need to
22532 follow @kbd{!} (when it is used as logical not, in an expression) with
22533 a space or a tab to prevent it from being expanded. The readline
22534 history facilities do not attempt substitution on the strings
22535 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
22537 The commands to control history expansion are:
22540 @item set history expansion on
22541 @itemx set history expansion
22542 @kindex set history expansion
22543 Enable history expansion. History expansion is off by default.
22545 @item set history expansion off
22546 Disable history expansion.
22549 @kindex show history
22551 @itemx show history filename
22552 @itemx show history save
22553 @itemx show history size
22554 @itemx show history expansion
22555 These commands display the state of the @value{GDBN} history parameters.
22556 @code{show history} by itself displays all four states.
22561 @kindex show commands
22562 @cindex show last commands
22563 @cindex display command history
22564 @item show commands
22565 Display the last ten commands in the command history.
22567 @item show commands @var{n}
22568 Print ten commands centered on command number @var{n}.
22570 @item show commands +
22571 Print ten commands just after the commands last printed.
22575 @section Screen Size
22576 @cindex size of screen
22577 @cindex screen size
22580 @cindex pauses in output
22582 Certain commands to @value{GDBN} may produce large amounts of
22583 information output to the screen. To help you read all of it,
22584 @value{GDBN} pauses and asks you for input at the end of each page of
22585 output. Type @key{RET} when you want to continue the output, or @kbd{q}
22586 to discard the remaining output. Also, the screen width setting
22587 determines when to wrap lines of output. Depending on what is being
22588 printed, @value{GDBN} tries to break the line at a readable place,
22589 rather than simply letting it overflow onto the following line.
22591 Normally @value{GDBN} knows the size of the screen from the terminal
22592 driver software. For example, on Unix @value{GDBN} uses the termcap data base
22593 together with the value of the @code{TERM} environment variable and the
22594 @code{stty rows} and @code{stty cols} settings. If this is not correct,
22595 you can override it with the @code{set height} and @code{set
22602 @kindex show height
22603 @item set height @var{lpp}
22604 @itemx set height unlimited
22606 @itemx set width @var{cpl}
22607 @itemx set width unlimited
22609 These @code{set} commands specify a screen height of @var{lpp} lines and
22610 a screen width of @var{cpl} characters. The associated @code{show}
22611 commands display the current settings.
22613 If you specify a height of either @code{unlimited} or zero lines,
22614 @value{GDBN} does not pause during output no matter how long the
22615 output is. This is useful if output is to a file or to an editor
22618 Likewise, you can specify @samp{set width unlimited} or @samp{set
22619 width 0} to prevent @value{GDBN} from wrapping its output.
22621 @item set pagination on
22622 @itemx set pagination off
22623 @kindex set pagination
22624 Turn the output pagination on or off; the default is on. Turning
22625 pagination off is the alternative to @code{set height unlimited}. Note that
22626 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
22627 Options, -batch}) also automatically disables pagination.
22629 @item show pagination
22630 @kindex show pagination
22631 Show the current pagination mode.
22636 @cindex number representation
22637 @cindex entering numbers
22639 You can always enter numbers in octal, decimal, or hexadecimal in
22640 @value{GDBN} by the usual conventions: octal numbers begin with
22641 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
22642 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
22643 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
22644 10; likewise, the default display for numbers---when no particular
22645 format is specified---is base 10. You can change the default base for
22646 both input and output with the commands described below.
22649 @kindex set input-radix
22650 @item set input-radix @var{base}
22651 Set the default base for numeric input. Supported choices
22652 for @var{base} are decimal 8, 10, or 16. The base must itself be
22653 specified either unambiguously or using the current input radix; for
22657 set input-radix 012
22658 set input-radix 10.
22659 set input-radix 0xa
22663 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
22664 leaves the input radix unchanged, no matter what it was, since
22665 @samp{10}, being without any leading or trailing signs of its base, is
22666 interpreted in the current radix. Thus, if the current radix is 16,
22667 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
22670 @kindex set output-radix
22671 @item set output-radix @var{base}
22672 Set the default base for numeric display. Supported choices
22673 for @var{base} are decimal 8, 10, or 16. The base must itself be
22674 specified either unambiguously or using the current input radix.
22676 @kindex show input-radix
22677 @item show input-radix
22678 Display the current default base for numeric input.
22680 @kindex show output-radix
22681 @item show output-radix
22682 Display the current default base for numeric display.
22684 @item set radix @r{[}@var{base}@r{]}
22688 These commands set and show the default base for both input and output
22689 of numbers. @code{set radix} sets the radix of input and output to
22690 the same base; without an argument, it resets the radix back to its
22691 default value of 10.
22696 @section Configuring the Current ABI
22698 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
22699 application automatically. However, sometimes you need to override its
22700 conclusions. Use these commands to manage @value{GDBN}'s view of the
22706 @cindex Newlib OS ABI and its influence on the longjmp handling
22708 One @value{GDBN} configuration can debug binaries for multiple operating
22709 system targets, either via remote debugging or native emulation.
22710 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
22711 but you can override its conclusion using the @code{set osabi} command.
22712 One example where this is useful is in debugging of binaries which use
22713 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
22714 not have the same identifying marks that the standard C library for your
22717 When @value{GDBN} is debugging the AArch64 architecture, it provides a
22718 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
22719 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
22720 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
22724 Show the OS ABI currently in use.
22727 With no argument, show the list of registered available OS ABI's.
22729 @item set osabi @var{abi}
22730 Set the current OS ABI to @var{abi}.
22733 @cindex float promotion
22735 Generally, the way that an argument of type @code{float} is passed to a
22736 function depends on whether the function is prototyped. For a prototyped
22737 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
22738 according to the architecture's convention for @code{float}. For unprototyped
22739 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
22740 @code{double} and then passed.
22742 Unfortunately, some forms of debug information do not reliably indicate whether
22743 a function is prototyped. If @value{GDBN} calls a function that is not marked
22744 as prototyped, it consults @kbd{set coerce-float-to-double}.
22747 @kindex set coerce-float-to-double
22748 @item set coerce-float-to-double
22749 @itemx set coerce-float-to-double on
22750 Arguments of type @code{float} will be promoted to @code{double} when passed
22751 to an unprototyped function. This is the default setting.
22753 @item set coerce-float-to-double off
22754 Arguments of type @code{float} will be passed directly to unprototyped
22757 @kindex show coerce-float-to-double
22758 @item show coerce-float-to-double
22759 Show the current setting of promoting @code{float} to @code{double}.
22763 @kindex show cp-abi
22764 @value{GDBN} needs to know the ABI used for your program's C@t{++}
22765 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
22766 used to build your application. @value{GDBN} only fully supports
22767 programs with a single C@t{++} ABI; if your program contains code using
22768 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
22769 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
22770 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
22771 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
22772 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
22773 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
22778 Show the C@t{++} ABI currently in use.
22781 With no argument, show the list of supported C@t{++} ABI's.
22783 @item set cp-abi @var{abi}
22784 @itemx set cp-abi auto
22785 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
22789 @section Automatically loading associated files
22790 @cindex auto-loading
22792 @value{GDBN} sometimes reads files with commands and settings automatically,
22793 without being explicitly told so by the user. We call this feature
22794 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
22795 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
22796 results or introduce security risks (e.g., if the file comes from untrusted
22800 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
22801 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
22803 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
22804 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
22807 There are various kinds of files @value{GDBN} can automatically load.
22808 In addition to these files, @value{GDBN} supports auto-loading code written
22809 in various extension languages. @xref{Auto-loading extensions}.
22811 Note that loading of these associated files (including the local @file{.gdbinit}
22812 file) requires accordingly configured @code{auto-load safe-path}
22813 (@pxref{Auto-loading safe path}).
22815 For these reasons, @value{GDBN} includes commands and options to let you
22816 control when to auto-load files and which files should be auto-loaded.
22819 @anchor{set auto-load off}
22820 @kindex set auto-load off
22821 @item set auto-load off
22822 Globally disable loading of all auto-loaded files.
22823 You may want to use this command with the @samp{-iex} option
22824 (@pxref{Option -init-eval-command}) such as:
22826 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
22829 Be aware that system init file (@pxref{System-wide configuration})
22830 and init files from your home directory (@pxref{Home Directory Init File})
22831 still get read (as they come from generally trusted directories).
22832 To prevent @value{GDBN} from auto-loading even those init files, use the
22833 @option{-nx} option (@pxref{Mode Options}), in addition to
22834 @code{set auto-load no}.
22836 @anchor{show auto-load}
22837 @kindex show auto-load
22838 @item show auto-load
22839 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
22843 (gdb) show auto-load
22844 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
22845 libthread-db: Auto-loading of inferior specific libthread_db is on.
22846 local-gdbinit: Auto-loading of .gdbinit script from current directory
22848 python-scripts: Auto-loading of Python scripts is on.
22849 safe-path: List of directories from which it is safe to auto-load files
22850 is $debugdir:$datadir/auto-load.
22851 scripts-directory: List of directories from which to load auto-loaded scripts
22852 is $debugdir:$datadir/auto-load.
22855 @anchor{info auto-load}
22856 @kindex info auto-load
22857 @item info auto-load
22858 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
22862 (gdb) info auto-load
22865 Yes /home/user/gdb/gdb-gdb.gdb
22866 libthread-db: No auto-loaded libthread-db.
22867 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
22871 Yes /home/user/gdb/gdb-gdb.py
22875 These are @value{GDBN} control commands for the auto-loading:
22877 @multitable @columnfractions .5 .5
22878 @item @xref{set auto-load off}.
22879 @tab Disable auto-loading globally.
22880 @item @xref{show auto-load}.
22881 @tab Show setting of all kinds of files.
22882 @item @xref{info auto-load}.
22883 @tab Show state of all kinds of files.
22884 @item @xref{set auto-load gdb-scripts}.
22885 @tab Control for @value{GDBN} command scripts.
22886 @item @xref{show auto-load gdb-scripts}.
22887 @tab Show setting of @value{GDBN} command scripts.
22888 @item @xref{info auto-load gdb-scripts}.
22889 @tab Show state of @value{GDBN} command scripts.
22890 @item @xref{set auto-load python-scripts}.
22891 @tab Control for @value{GDBN} Python scripts.
22892 @item @xref{show auto-load python-scripts}.
22893 @tab Show setting of @value{GDBN} Python scripts.
22894 @item @xref{info auto-load python-scripts}.
22895 @tab Show state of @value{GDBN} Python scripts.
22896 @item @xref{set auto-load guile-scripts}.
22897 @tab Control for @value{GDBN} Guile scripts.
22898 @item @xref{show auto-load guile-scripts}.
22899 @tab Show setting of @value{GDBN} Guile scripts.
22900 @item @xref{info auto-load guile-scripts}.
22901 @tab Show state of @value{GDBN} Guile scripts.
22902 @item @xref{set auto-load scripts-directory}.
22903 @tab Control for @value{GDBN} auto-loaded scripts location.
22904 @item @xref{show auto-load scripts-directory}.
22905 @tab Show @value{GDBN} auto-loaded scripts location.
22906 @item @xref{add-auto-load-scripts-directory}.
22907 @tab Add directory for auto-loaded scripts location list.
22908 @item @xref{set auto-load local-gdbinit}.
22909 @tab Control for init file in the current directory.
22910 @item @xref{show auto-load local-gdbinit}.
22911 @tab Show setting of init file in the current directory.
22912 @item @xref{info auto-load local-gdbinit}.
22913 @tab Show state of init file in the current directory.
22914 @item @xref{set auto-load libthread-db}.
22915 @tab Control for thread debugging library.
22916 @item @xref{show auto-load libthread-db}.
22917 @tab Show setting of thread debugging library.
22918 @item @xref{info auto-load libthread-db}.
22919 @tab Show state of thread debugging library.
22920 @item @xref{set auto-load safe-path}.
22921 @tab Control directories trusted for automatic loading.
22922 @item @xref{show auto-load safe-path}.
22923 @tab Show directories trusted for automatic loading.
22924 @item @xref{add-auto-load-safe-path}.
22925 @tab Add directory trusted for automatic loading.
22928 @node Init File in the Current Directory
22929 @subsection Automatically loading init file in the current directory
22930 @cindex auto-loading init file in the current directory
22932 By default, @value{GDBN} reads and executes the canned sequences of commands
22933 from init file (if any) in the current working directory,
22934 see @ref{Init File in the Current Directory during Startup}.
22936 Note that loading of this local @file{.gdbinit} file also requires accordingly
22937 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22940 @anchor{set auto-load local-gdbinit}
22941 @kindex set auto-load local-gdbinit
22942 @item set auto-load local-gdbinit [on|off]
22943 Enable or disable the auto-loading of canned sequences of commands
22944 (@pxref{Sequences}) found in init file in the current directory.
22946 @anchor{show auto-load local-gdbinit}
22947 @kindex show auto-load local-gdbinit
22948 @item show auto-load local-gdbinit
22949 Show whether auto-loading of canned sequences of commands from init file in the
22950 current directory is enabled or disabled.
22952 @anchor{info auto-load local-gdbinit}
22953 @kindex info auto-load local-gdbinit
22954 @item info auto-load local-gdbinit
22955 Print whether canned sequences of commands from init file in the
22956 current directory have been auto-loaded.
22959 @node libthread_db.so.1 file
22960 @subsection Automatically loading thread debugging library
22961 @cindex auto-loading libthread_db.so.1
22963 This feature is currently present only on @sc{gnu}/Linux native hosts.
22965 @value{GDBN} reads in some cases thread debugging library from places specific
22966 to the inferior (@pxref{set libthread-db-search-path}).
22968 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
22969 without checking this @samp{set auto-load libthread-db} switch as system
22970 libraries have to be trusted in general. In all other cases of
22971 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
22972 auto-load libthread-db} is enabled before trying to open such thread debugging
22975 Note that loading of this debugging library also requires accordingly configured
22976 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22979 @anchor{set auto-load libthread-db}
22980 @kindex set auto-load libthread-db
22981 @item set auto-load libthread-db [on|off]
22982 Enable or disable the auto-loading of inferior specific thread debugging library.
22984 @anchor{show auto-load libthread-db}
22985 @kindex show auto-load libthread-db
22986 @item show auto-load libthread-db
22987 Show whether auto-loading of inferior specific thread debugging library is
22988 enabled or disabled.
22990 @anchor{info auto-load libthread-db}
22991 @kindex info auto-load libthread-db
22992 @item info auto-load libthread-db
22993 Print the list of all loaded inferior specific thread debugging libraries and
22994 for each such library print list of inferior @var{pid}s using it.
22997 @node Auto-loading safe path
22998 @subsection Security restriction for auto-loading
22999 @cindex auto-loading safe-path
23001 As the files of inferior can come from untrusted source (such as submitted by
23002 an application user) @value{GDBN} does not always load any files automatically.
23003 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
23004 directories trusted for loading files not explicitly requested by user.
23005 Each directory can also be a shell wildcard pattern.
23007 If the path is not set properly you will see a warning and the file will not
23012 Reading symbols from /home/user/gdb/gdb...done.
23013 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
23014 declined by your `auto-load safe-path' set
23015 to "$debugdir:$datadir/auto-load".
23016 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
23017 declined by your `auto-load safe-path' set
23018 to "$debugdir:$datadir/auto-load".
23022 To instruct @value{GDBN} to go ahead and use the init files anyway,
23023 invoke @value{GDBN} like this:
23026 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
23029 The list of trusted directories is controlled by the following commands:
23032 @anchor{set auto-load safe-path}
23033 @kindex set auto-load safe-path
23034 @item set auto-load safe-path @r{[}@var{directories}@r{]}
23035 Set the list of directories (and their subdirectories) trusted for automatic
23036 loading and execution of scripts. You can also enter a specific trusted file.
23037 Each directory can also be a shell wildcard pattern; wildcards do not match
23038 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
23039 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
23040 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
23041 its default value as specified during @value{GDBN} compilation.
23043 The list of directories uses path separator (@samp{:} on GNU and Unix
23044 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
23045 to the @env{PATH} environment variable.
23047 @anchor{show auto-load safe-path}
23048 @kindex show auto-load safe-path
23049 @item show auto-load safe-path
23050 Show the list of directories trusted for automatic loading and execution of
23053 @anchor{add-auto-load-safe-path}
23054 @kindex add-auto-load-safe-path
23055 @item add-auto-load-safe-path
23056 Add an entry (or list of entries) to the list of directories trusted for
23057 automatic loading and execution of scripts. Multiple entries may be delimited
23058 by the host platform path separator in use.
23061 This variable defaults to what @code{--with-auto-load-dir} has been configured
23062 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
23063 substitution applies the same as for @ref{set auto-load scripts-directory}.
23064 The default @code{set auto-load safe-path} value can be also overriden by
23065 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
23067 Setting this variable to @file{/} disables this security protection,
23068 corresponding @value{GDBN} configuration option is
23069 @option{--without-auto-load-safe-path}.
23070 This variable is supposed to be set to the system directories writable by the
23071 system superuser only. Users can add their source directories in init files in
23072 their home directories (@pxref{Home Directory Init File}). See also deprecated
23073 init file in the current directory
23074 (@pxref{Init File in the Current Directory during Startup}).
23076 To force @value{GDBN} to load the files it declined to load in the previous
23077 example, you could use one of the following ways:
23080 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
23081 Specify this trusted directory (or a file) as additional component of the list.
23082 You have to specify also any existing directories displayed by
23083 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
23085 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
23086 Specify this directory as in the previous case but just for a single
23087 @value{GDBN} session.
23089 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
23090 Disable auto-loading safety for a single @value{GDBN} session.
23091 This assumes all the files you debug during this @value{GDBN} session will come
23092 from trusted sources.
23094 @item @kbd{./configure --without-auto-load-safe-path}
23095 During compilation of @value{GDBN} you may disable any auto-loading safety.
23096 This assumes all the files you will ever debug with this @value{GDBN} come from
23100 On the other hand you can also explicitly forbid automatic files loading which
23101 also suppresses any such warning messages:
23104 @item @kbd{gdb -iex "set auto-load no" @dots{}}
23105 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
23107 @item @file{~/.gdbinit}: @samp{set auto-load no}
23108 Disable auto-loading globally for the user
23109 (@pxref{Home Directory Init File}). While it is improbable, you could also
23110 use system init file instead (@pxref{System-wide configuration}).
23113 This setting applies to the file names as entered by user. If no entry matches
23114 @value{GDBN} tries as a last resort to also resolve all the file names into
23115 their canonical form (typically resolving symbolic links) and compare the
23116 entries again. @value{GDBN} already canonicalizes most of the filenames on its
23117 own before starting the comparison so a canonical form of directories is
23118 recommended to be entered.
23120 @node Auto-loading verbose mode
23121 @subsection Displaying files tried for auto-load
23122 @cindex auto-loading verbose mode
23124 For better visibility of all the file locations where you can place scripts to
23125 be auto-loaded with inferior --- or to protect yourself against accidental
23126 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
23127 all the files attempted to be loaded. Both existing and non-existing files may
23130 For example the list of directories from which it is safe to auto-load files
23131 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
23132 may not be too obvious while setting it up.
23135 (gdb) set debug auto-load on
23136 (gdb) file ~/src/t/true
23137 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
23138 for objfile "/tmp/true".
23139 auto-load: Updating directories of "/usr:/opt".
23140 auto-load: Using directory "/usr".
23141 auto-load: Using directory "/opt".
23142 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
23143 by your `auto-load safe-path' set to "/usr:/opt".
23147 @anchor{set debug auto-load}
23148 @kindex set debug auto-load
23149 @item set debug auto-load [on|off]
23150 Set whether to print the filenames attempted to be auto-loaded.
23152 @anchor{show debug auto-load}
23153 @kindex show debug auto-load
23154 @item show debug auto-load
23155 Show whether printing of the filenames attempted to be auto-loaded is turned
23159 @node Messages/Warnings
23160 @section Optional Warnings and Messages
23162 @cindex verbose operation
23163 @cindex optional warnings
23164 By default, @value{GDBN} is silent about its inner workings. If you are
23165 running on a slow machine, you may want to use the @code{set verbose}
23166 command. This makes @value{GDBN} tell you when it does a lengthy
23167 internal operation, so you will not think it has crashed.
23169 Currently, the messages controlled by @code{set verbose} are those
23170 which announce that the symbol table for a source file is being read;
23171 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
23174 @kindex set verbose
23175 @item set verbose on
23176 Enables @value{GDBN} output of certain informational messages.
23178 @item set verbose off
23179 Disables @value{GDBN} output of certain informational messages.
23181 @kindex show verbose
23183 Displays whether @code{set verbose} is on or off.
23186 By default, if @value{GDBN} encounters bugs in the symbol table of an
23187 object file, it is silent; but if you are debugging a compiler, you may
23188 find this information useful (@pxref{Symbol Errors, ,Errors Reading
23193 @kindex set complaints
23194 @item set complaints @var{limit}
23195 Permits @value{GDBN} to output @var{limit} complaints about each type of
23196 unusual symbols before becoming silent about the problem. Set
23197 @var{limit} to zero to suppress all complaints; set it to a large number
23198 to prevent complaints from being suppressed.
23200 @kindex show complaints
23201 @item show complaints
23202 Displays how many symbol complaints @value{GDBN} is permitted to produce.
23206 @anchor{confirmation requests}
23207 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
23208 lot of stupid questions to confirm certain commands. For example, if
23209 you try to run a program which is already running:
23213 The program being debugged has been started already.
23214 Start it from the beginning? (y or n)
23217 If you are willing to unflinchingly face the consequences of your own
23218 commands, you can disable this ``feature'':
23222 @kindex set confirm
23224 @cindex confirmation
23225 @cindex stupid questions
23226 @item set confirm off
23227 Disables confirmation requests. Note that running @value{GDBN} with
23228 the @option{--batch} option (@pxref{Mode Options, -batch}) also
23229 automatically disables confirmation requests.
23231 @item set confirm on
23232 Enables confirmation requests (the default).
23234 @kindex show confirm
23236 Displays state of confirmation requests.
23240 @cindex command tracing
23241 If you need to debug user-defined commands or sourced files you may find it
23242 useful to enable @dfn{command tracing}. In this mode each command will be
23243 printed as it is executed, prefixed with one or more @samp{+} symbols, the
23244 quantity denoting the call depth of each command.
23247 @kindex set trace-commands
23248 @cindex command scripts, debugging
23249 @item set trace-commands on
23250 Enable command tracing.
23251 @item set trace-commands off
23252 Disable command tracing.
23253 @item show trace-commands
23254 Display the current state of command tracing.
23257 @node Debugging Output
23258 @section Optional Messages about Internal Happenings
23259 @cindex optional debugging messages
23261 @value{GDBN} has commands that enable optional debugging messages from
23262 various @value{GDBN} subsystems; normally these commands are of
23263 interest to @value{GDBN} maintainers, or when reporting a bug. This
23264 section documents those commands.
23267 @kindex set exec-done-display
23268 @item set exec-done-display
23269 Turns on or off the notification of asynchronous commands'
23270 completion. When on, @value{GDBN} will print a message when an
23271 asynchronous command finishes its execution. The default is off.
23272 @kindex show exec-done-display
23273 @item show exec-done-display
23274 Displays the current setting of asynchronous command completion
23277 @cindex ARM AArch64
23278 @item set debug aarch64
23279 Turns on or off display of debugging messages related to ARM AArch64.
23280 The default is off.
23282 @item show debug aarch64
23283 Displays the current state of displaying debugging messages related to
23285 @cindex gdbarch debugging info
23286 @cindex architecture debugging info
23287 @item set debug arch
23288 Turns on or off display of gdbarch debugging info. The default is off
23289 @item show debug arch
23290 Displays the current state of displaying gdbarch debugging info.
23291 @item set debug aix-solib
23292 @cindex AIX shared library debugging
23293 Control display of debugging messages from the AIX shared library
23294 support module. The default is off.
23295 @item show debug aix-thread
23296 Show the current state of displaying AIX shared library debugging messages.
23297 @item set debug aix-thread
23298 @cindex AIX threads
23299 Display debugging messages about inner workings of the AIX thread
23301 @item show debug aix-thread
23302 Show the current state of AIX thread debugging info display.
23303 @item set debug check-physname
23305 Check the results of the ``physname'' computation. When reading DWARF
23306 debugging information for C@t{++}, @value{GDBN} attempts to compute
23307 each entity's name. @value{GDBN} can do this computation in two
23308 different ways, depending on exactly what information is present.
23309 When enabled, this setting causes @value{GDBN} to compute the names
23310 both ways and display any discrepancies.
23311 @item show debug check-physname
23312 Show the current state of ``physname'' checking.
23313 @item set debug coff-pe-read
23314 @cindex COFF/PE exported symbols
23315 Control display of debugging messages related to reading of COFF/PE
23316 exported symbols. The default is off.
23317 @item show debug coff-pe-read
23318 Displays the current state of displaying debugging messages related to
23319 reading of COFF/PE exported symbols.
23320 @item set debug dwarf-die
23322 Dump DWARF DIEs after they are read in.
23323 The value is the number of nesting levels to print.
23324 A value of zero turns off the display.
23325 @item show debug dwarf-die
23326 Show the current state of DWARF DIE debugging.
23327 @item set debug dwarf-line
23328 @cindex DWARF Line Tables
23329 Turns on or off display of debugging messages related to reading
23330 DWARF line tables. The default is 0 (off).
23331 A value of 1 provides basic information.
23332 A value greater than 1 provides more verbose information.
23333 @item show debug dwarf-line
23334 Show the current state of DWARF line table debugging.
23335 @item set debug dwarf-read
23336 @cindex DWARF Reading
23337 Turns on or off display of debugging messages related to reading
23338 DWARF debug info. The default is 0 (off).
23339 A value of 1 provides basic information.
23340 A value greater than 1 provides more verbose information.
23341 @item show debug dwarf-read
23342 Show the current state of DWARF reader debugging.
23343 @item set debug displaced
23344 @cindex displaced stepping debugging info
23345 Turns on or off display of @value{GDBN} debugging info for the
23346 displaced stepping support. The default is off.
23347 @item show debug displaced
23348 Displays the current state of displaying @value{GDBN} debugging info
23349 related to displaced stepping.
23350 @item set debug event
23351 @cindex event debugging info
23352 Turns on or off display of @value{GDBN} event debugging info. The
23354 @item show debug event
23355 Displays the current state of displaying @value{GDBN} event debugging
23357 @item set debug expression
23358 @cindex expression debugging info
23359 Turns on or off display of debugging info about @value{GDBN}
23360 expression parsing. The default is off.
23361 @item show debug expression
23362 Displays the current state of displaying debugging info about
23363 @value{GDBN} expression parsing.
23364 @item set debug frame
23365 @cindex frame debugging info
23366 Turns on or off display of @value{GDBN} frame debugging info. The
23368 @item show debug frame
23369 Displays the current state of displaying @value{GDBN} frame debugging
23371 @item set debug gnu-nat
23372 @cindex @sc{gnu}/Hurd debug messages
23373 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
23374 @item show debug gnu-nat
23375 Show the current state of @sc{gnu}/Hurd debugging messages.
23376 @item set debug infrun
23377 @cindex inferior debugging info
23378 Turns on or off display of @value{GDBN} debugging info for running the inferior.
23379 The default is off. @file{infrun.c} contains GDB's runtime state machine used
23380 for implementing operations such as single-stepping the inferior.
23381 @item show debug infrun
23382 Displays the current state of @value{GDBN} inferior debugging.
23383 @item set debug jit
23384 @cindex just-in-time compilation, debugging messages
23385 Turns on or off debugging messages from JIT debug support.
23386 @item show debug jit
23387 Displays the current state of @value{GDBN} JIT debugging.
23388 @item set debug lin-lwp
23389 @cindex @sc{gnu}/Linux LWP debug messages
23390 @cindex Linux lightweight processes
23391 Turns on or off debugging messages from the Linux LWP debug support.
23392 @item show debug lin-lwp
23393 Show the current state of Linux LWP debugging messages.
23394 @item set debug linux-namespaces
23395 @cindex @sc{gnu}/Linux namespaces debug messages
23396 Turns on or off debugging messages from the Linux namespaces debug support.
23397 @item show debug linux-namespaces
23398 Show the current state of Linux namespaces debugging messages.
23399 @item set debug mach-o
23400 @cindex Mach-O symbols processing
23401 Control display of debugging messages related to Mach-O symbols
23402 processing. The default is off.
23403 @item show debug mach-o
23404 Displays the current state of displaying debugging messages related to
23405 reading of COFF/PE exported symbols.
23406 @item set debug notification
23407 @cindex remote async notification debugging info
23408 Turns on or off debugging messages about remote async notification.
23409 The default is off.
23410 @item show debug notification
23411 Displays the current state of remote async notification debugging messages.
23412 @item set debug observer
23413 @cindex observer debugging info
23414 Turns on or off display of @value{GDBN} observer debugging. This
23415 includes info such as the notification of observable events.
23416 @item show debug observer
23417 Displays the current state of observer debugging.
23418 @item set debug overload
23419 @cindex C@t{++} overload debugging info
23420 Turns on or off display of @value{GDBN} C@t{++} overload debugging
23421 info. This includes info such as ranking of functions, etc. The default
23423 @item show debug overload
23424 Displays the current state of displaying @value{GDBN} C@t{++} overload
23426 @cindex expression parser, debugging info
23427 @cindex debug expression parser
23428 @item set debug parser
23429 Turns on or off the display of expression parser debugging output.
23430 Internally, this sets the @code{yydebug} variable in the expression
23431 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
23432 details. The default is off.
23433 @item show debug parser
23434 Show the current state of expression parser debugging.
23435 @cindex packets, reporting on stdout
23436 @cindex serial connections, debugging
23437 @cindex debug remote protocol
23438 @cindex remote protocol debugging
23439 @cindex display remote packets
23440 @item set debug remote
23441 Turns on or off display of reports on all packets sent back and forth across
23442 the serial line to the remote machine. The info is printed on the
23443 @value{GDBN} standard output stream. The default is off.
23444 @item show debug remote
23445 Displays the state of display of remote packets.
23446 @item set debug serial
23447 Turns on or off display of @value{GDBN} serial debugging info. The
23449 @item show debug serial
23450 Displays the current state of displaying @value{GDBN} serial debugging
23452 @item set debug solib-frv
23453 @cindex FR-V shared-library debugging
23454 Turns on or off debugging messages for FR-V shared-library code.
23455 @item show debug solib-frv
23456 Display the current state of FR-V shared-library code debugging
23458 @item set debug symbol-lookup
23459 @cindex symbol lookup
23460 Turns on or off display of debugging messages related to symbol lookup.
23461 The default is 0 (off).
23462 A value of 1 provides basic information.
23463 A value greater than 1 provides more verbose information.
23464 @item show debug symbol-lookup
23465 Show the current state of symbol lookup debugging messages.
23466 @item set debug symfile
23467 @cindex symbol file functions
23468 Turns on or off display of debugging messages related to symbol file functions.
23469 The default is off. @xref{Files}.
23470 @item show debug symfile
23471 Show the current state of symbol file debugging messages.
23472 @item set debug symtab-create
23473 @cindex symbol table creation
23474 Turns on or off display of debugging messages related to symbol table creation.
23475 The default is 0 (off).
23476 A value of 1 provides basic information.
23477 A value greater than 1 provides more verbose information.
23478 @item show debug symtab-create
23479 Show the current state of symbol table creation debugging.
23480 @item set debug target
23481 @cindex target debugging info
23482 Turns on or off display of @value{GDBN} target debugging info. This info
23483 includes what is going on at the target level of GDB, as it happens. The
23484 default is 0. Set it to 1 to track events, and to 2 to also track the
23485 value of large memory transfers.
23486 @item show debug target
23487 Displays the current state of displaying @value{GDBN} target debugging
23489 @item set debug timestamp
23490 @cindex timestampping debugging info
23491 Turns on or off display of timestamps with @value{GDBN} debugging info.
23492 When enabled, seconds and microseconds are displayed before each debugging
23494 @item show debug timestamp
23495 Displays the current state of displaying timestamps with @value{GDBN}
23497 @item set debug varobj
23498 @cindex variable object debugging info
23499 Turns on or off display of @value{GDBN} variable object debugging
23500 info. The default is off.
23501 @item show debug varobj
23502 Displays the current state of displaying @value{GDBN} variable object
23504 @item set debug xml
23505 @cindex XML parser debugging
23506 Turns on or off debugging messages for built-in XML parsers.
23507 @item show debug xml
23508 Displays the current state of XML debugging messages.
23511 @node Other Misc Settings
23512 @section Other Miscellaneous Settings
23513 @cindex miscellaneous settings
23516 @kindex set interactive-mode
23517 @item set interactive-mode
23518 If @code{on}, forces @value{GDBN} to assume that GDB was started
23519 in a terminal. In practice, this means that @value{GDBN} should wait
23520 for the user to answer queries generated by commands entered at
23521 the command prompt. If @code{off}, forces @value{GDBN} to operate
23522 in the opposite mode, and it uses the default answers to all queries.
23523 If @code{auto} (the default), @value{GDBN} tries to determine whether
23524 its standard input is a terminal, and works in interactive-mode if it
23525 is, non-interactively otherwise.
23527 In the vast majority of cases, the debugger should be able to guess
23528 correctly which mode should be used. But this setting can be useful
23529 in certain specific cases, such as running a MinGW @value{GDBN}
23530 inside a cygwin window.
23532 @kindex show interactive-mode
23533 @item show interactive-mode
23534 Displays whether the debugger is operating in interactive mode or not.
23537 @node Extending GDB
23538 @chapter Extending @value{GDBN}
23539 @cindex extending GDB
23541 @value{GDBN} provides several mechanisms for extension.
23542 @value{GDBN} also provides the ability to automatically load
23543 extensions when it reads a file for debugging. This allows the
23544 user to automatically customize @value{GDBN} for the program
23548 * Sequences:: Canned Sequences of @value{GDBN} Commands
23549 * Python:: Extending @value{GDBN} using Python
23550 * Guile:: Extending @value{GDBN} using Guile
23551 * Auto-loading extensions:: Automatically loading extensions
23552 * Multiple Extension Languages:: Working with multiple extension languages
23553 * Aliases:: Creating new spellings of existing commands
23556 To facilitate the use of extension languages, @value{GDBN} is capable
23557 of evaluating the contents of a file. When doing so, @value{GDBN}
23558 can recognize which extension language is being used by looking at
23559 the filename extension. Files with an unrecognized filename extension
23560 are always treated as a @value{GDBN} Command Files.
23561 @xref{Command Files,, Command files}.
23563 You can control how @value{GDBN} evaluates these files with the following
23567 @kindex set script-extension
23568 @kindex show script-extension
23569 @item set script-extension off
23570 All scripts are always evaluated as @value{GDBN} Command Files.
23572 @item set script-extension soft
23573 The debugger determines the scripting language based on filename
23574 extension. If this scripting language is supported, @value{GDBN}
23575 evaluates the script using that language. Otherwise, it evaluates
23576 the file as a @value{GDBN} Command File.
23578 @item set script-extension strict
23579 The debugger determines the scripting language based on filename
23580 extension, and evaluates the script using that language. If the
23581 language is not supported, then the evaluation fails.
23583 @item show script-extension
23584 Display the current value of the @code{script-extension} option.
23589 @section Canned Sequences of Commands
23591 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
23592 Command Lists}), @value{GDBN} provides two ways to store sequences of
23593 commands for execution as a unit: user-defined commands and command
23597 * Define:: How to define your own commands
23598 * Hooks:: Hooks for user-defined commands
23599 * Command Files:: How to write scripts of commands to be stored in a file
23600 * Output:: Commands for controlled output
23601 * Auto-loading sequences:: Controlling auto-loaded command files
23605 @subsection User-defined Commands
23607 @cindex user-defined command
23608 @cindex arguments, to user-defined commands
23609 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
23610 which you assign a new name as a command. This is done with the
23611 @code{define} command. User commands may accept up to 10 arguments
23612 separated by whitespace. Arguments are accessed within the user command
23613 via @code{$arg0@dots{}$arg9}. A trivial example:
23617 print $arg0 + $arg1 + $arg2
23622 To execute the command use:
23629 This defines the command @code{adder}, which prints the sum of
23630 its three arguments. Note the arguments are text substitutions, so they may
23631 reference variables, use complex expressions, or even perform inferior
23634 @cindex argument count in user-defined commands
23635 @cindex how many arguments (user-defined commands)
23636 In addition, @code{$argc} may be used to find out how many arguments have
23637 been passed. This expands to a number in the range 0@dots{}10.
23642 print $arg0 + $arg1
23645 print $arg0 + $arg1 + $arg2
23653 @item define @var{commandname}
23654 Define a command named @var{commandname}. If there is already a command
23655 by that name, you are asked to confirm that you want to redefine it.
23656 The argument @var{commandname} may be a bare command name consisting of letters,
23657 numbers, dashes, and underscores. It may also start with any predefined
23658 prefix command. For example, @samp{define target my-target} creates
23659 a user-defined @samp{target my-target} command.
23661 The definition of the command is made up of other @value{GDBN} command lines,
23662 which are given following the @code{define} command. The end of these
23663 commands is marked by a line containing @code{end}.
23666 @kindex end@r{ (user-defined commands)}
23667 @item document @var{commandname}
23668 Document the user-defined command @var{commandname}, so that it can be
23669 accessed by @code{help}. The command @var{commandname} must already be
23670 defined. This command reads lines of documentation just as @code{define}
23671 reads the lines of the command definition, ending with @code{end}.
23672 After the @code{document} command is finished, @code{help} on command
23673 @var{commandname} displays the documentation you have written.
23675 You may use the @code{document} command again to change the
23676 documentation of a command. Redefining the command with @code{define}
23677 does not change the documentation.
23679 @kindex dont-repeat
23680 @cindex don't repeat command
23682 Used inside a user-defined command, this tells @value{GDBN} that this
23683 command should not be repeated when the user hits @key{RET}
23684 (@pxref{Command Syntax, repeat last command}).
23686 @kindex help user-defined
23687 @item help user-defined
23688 List all user-defined commands and all python commands defined in class
23689 COMAND_USER. The first line of the documentation or docstring is
23694 @itemx show user @var{commandname}
23695 Display the @value{GDBN} commands used to define @var{commandname} (but
23696 not its documentation). If no @var{commandname} is given, display the
23697 definitions for all user-defined commands.
23698 This does not work for user-defined python commands.
23700 @cindex infinite recursion in user-defined commands
23701 @kindex show max-user-call-depth
23702 @kindex set max-user-call-depth
23703 @item show max-user-call-depth
23704 @itemx set max-user-call-depth
23705 The value of @code{max-user-call-depth} controls how many recursion
23706 levels are allowed in user-defined commands before @value{GDBN} suspects an
23707 infinite recursion and aborts the command.
23708 This does not apply to user-defined python commands.
23711 In addition to the above commands, user-defined commands frequently
23712 use control flow commands, described in @ref{Command Files}.
23714 When user-defined commands are executed, the
23715 commands of the definition are not printed. An error in any command
23716 stops execution of the user-defined command.
23718 If used interactively, commands that would ask for confirmation proceed
23719 without asking when used inside a user-defined command. Many @value{GDBN}
23720 commands that normally print messages to say what they are doing omit the
23721 messages when used in a user-defined command.
23724 @subsection User-defined Command Hooks
23725 @cindex command hooks
23726 @cindex hooks, for commands
23727 @cindex hooks, pre-command
23730 You may define @dfn{hooks}, which are a special kind of user-defined
23731 command. Whenever you run the command @samp{foo}, if the user-defined
23732 command @samp{hook-foo} exists, it is executed (with no arguments)
23733 before that command.
23735 @cindex hooks, post-command
23737 A hook may also be defined which is run after the command you executed.
23738 Whenever you run the command @samp{foo}, if the user-defined command
23739 @samp{hookpost-foo} exists, it is executed (with no arguments) after
23740 that command. Post-execution hooks may exist simultaneously with
23741 pre-execution hooks, for the same command.
23743 It is valid for a hook to call the command which it hooks. If this
23744 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
23746 @c It would be nice if hookpost could be passed a parameter indicating
23747 @c if the command it hooks executed properly or not. FIXME!
23749 @kindex stop@r{, a pseudo-command}
23750 In addition, a pseudo-command, @samp{stop} exists. Defining
23751 (@samp{hook-stop}) makes the associated commands execute every time
23752 execution stops in your program: before breakpoint commands are run,
23753 displays are printed, or the stack frame is printed.
23755 For example, to ignore @code{SIGALRM} signals while
23756 single-stepping, but treat them normally during normal execution,
23761 handle SIGALRM nopass
23765 handle SIGALRM pass
23768 define hook-continue
23769 handle SIGALRM pass
23773 As a further example, to hook at the beginning and end of the @code{echo}
23774 command, and to add extra text to the beginning and end of the message,
23782 define hookpost-echo
23786 (@value{GDBP}) echo Hello World
23787 <<<---Hello World--->>>
23792 You can define a hook for any single-word command in @value{GDBN}, but
23793 not for command aliases; you should define a hook for the basic command
23794 name, e.g.@: @code{backtrace} rather than @code{bt}.
23795 @c FIXME! So how does Joe User discover whether a command is an alias
23797 You can hook a multi-word command by adding @code{hook-} or
23798 @code{hookpost-} to the last word of the command, e.g.@:
23799 @samp{define target hook-remote} to add a hook to @samp{target remote}.
23801 If an error occurs during the execution of your hook, execution of
23802 @value{GDBN} commands stops and @value{GDBN} issues a prompt
23803 (before the command that you actually typed had a chance to run).
23805 If you try to define a hook which does not match any known command, you
23806 get a warning from the @code{define} command.
23808 @node Command Files
23809 @subsection Command Files
23811 @cindex command files
23812 @cindex scripting commands
23813 A command file for @value{GDBN} is a text file made of lines that are
23814 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
23815 also be included. An empty line in a command file does nothing; it
23816 does not mean to repeat the last command, as it would from the
23819 You can request the execution of a command file with the @code{source}
23820 command. Note that the @code{source} command is also used to evaluate
23821 scripts that are not Command Files. The exact behavior can be configured
23822 using the @code{script-extension} setting.
23823 @xref{Extending GDB,, Extending GDB}.
23827 @cindex execute commands from a file
23828 @item source [-s] [-v] @var{filename}
23829 Execute the command file @var{filename}.
23832 The lines in a command file are generally executed sequentially,
23833 unless the order of execution is changed by one of the
23834 @emph{flow-control commands} described below. The commands are not
23835 printed as they are executed. An error in any command terminates
23836 execution of the command file and control is returned to the console.
23838 @value{GDBN} first searches for @var{filename} in the current directory.
23839 If the file is not found there, and @var{filename} does not specify a
23840 directory, then @value{GDBN} also looks for the file on the source search path
23841 (specified with the @samp{directory} command);
23842 except that @file{$cdir} is not searched because the compilation directory
23843 is not relevant to scripts.
23845 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
23846 on the search path even if @var{filename} specifies a directory.
23847 The search is done by appending @var{filename} to each element of the
23848 search path. So, for example, if @var{filename} is @file{mylib/myscript}
23849 and the search path contains @file{/home/user} then @value{GDBN} will
23850 look for the script @file{/home/user/mylib/myscript}.
23851 The search is also done if @var{filename} is an absolute path.
23852 For example, if @var{filename} is @file{/tmp/myscript} and
23853 the search path contains @file{/home/user} then @value{GDBN} will
23854 look for the script @file{/home/user/tmp/myscript}.
23855 For DOS-like systems, if @var{filename} contains a drive specification,
23856 it is stripped before concatenation. For example, if @var{filename} is
23857 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
23858 will look for the script @file{c:/tmp/myscript}.
23860 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
23861 each command as it is executed. The option must be given before
23862 @var{filename}, and is interpreted as part of the filename anywhere else.
23864 Commands that would ask for confirmation if used interactively proceed
23865 without asking when used in a command file. Many @value{GDBN} commands that
23866 normally print messages to say what they are doing omit the messages
23867 when called from command files.
23869 @value{GDBN} also accepts command input from standard input. In this
23870 mode, normal output goes to standard output and error output goes to
23871 standard error. Errors in a command file supplied on standard input do
23872 not terminate execution of the command file---execution continues with
23876 gdb < cmds > log 2>&1
23879 (The syntax above will vary depending on the shell used.) This example
23880 will execute commands from the file @file{cmds}. All output and errors
23881 would be directed to @file{log}.
23883 Since commands stored on command files tend to be more general than
23884 commands typed interactively, they frequently need to deal with
23885 complicated situations, such as different or unexpected values of
23886 variables and symbols, changes in how the program being debugged is
23887 built, etc. @value{GDBN} provides a set of flow-control commands to
23888 deal with these complexities. Using these commands, you can write
23889 complex scripts that loop over data structures, execute commands
23890 conditionally, etc.
23897 This command allows to include in your script conditionally executed
23898 commands. The @code{if} command takes a single argument, which is an
23899 expression to evaluate. It is followed by a series of commands that
23900 are executed only if the expression is true (its value is nonzero).
23901 There can then optionally be an @code{else} line, followed by a series
23902 of commands that are only executed if the expression was false. The
23903 end of the list is marked by a line containing @code{end}.
23907 This command allows to write loops. Its syntax is similar to
23908 @code{if}: the command takes a single argument, which is an expression
23909 to evaluate, and must be followed by the commands to execute, one per
23910 line, terminated by an @code{end}. These commands are called the
23911 @dfn{body} of the loop. The commands in the body of @code{while} are
23912 executed repeatedly as long as the expression evaluates to true.
23916 This command exits the @code{while} loop in whose body it is included.
23917 Execution of the script continues after that @code{while}s @code{end}
23920 @kindex loop_continue
23921 @item loop_continue
23922 This command skips the execution of the rest of the body of commands
23923 in the @code{while} loop in whose body it is included. Execution
23924 branches to the beginning of the @code{while} loop, where it evaluates
23925 the controlling expression.
23927 @kindex end@r{ (if/else/while commands)}
23929 Terminate the block of commands that are the body of @code{if},
23930 @code{else}, or @code{while} flow-control commands.
23935 @subsection Commands for Controlled Output
23937 During the execution of a command file or a user-defined command, normal
23938 @value{GDBN} output is suppressed; the only output that appears is what is
23939 explicitly printed by the commands in the definition. This section
23940 describes three commands useful for generating exactly the output you
23945 @item echo @var{text}
23946 @c I do not consider backslash-space a standard C escape sequence
23947 @c because it is not in ANSI.
23948 Print @var{text}. Nonprinting characters can be included in
23949 @var{text} using C escape sequences, such as @samp{\n} to print a
23950 newline. @strong{No newline is printed unless you specify one.}
23951 In addition to the standard C escape sequences, a backslash followed
23952 by a space stands for a space. This is useful for displaying a
23953 string with spaces at the beginning or the end, since leading and
23954 trailing spaces are otherwise trimmed from all arguments.
23955 To print @samp{@w{ }and foo =@w{ }}, use the command
23956 @samp{echo \@w{ }and foo = \@w{ }}.
23958 A backslash at the end of @var{text} can be used, as in C, to continue
23959 the command onto subsequent lines. For example,
23962 echo This is some text\n\
23963 which is continued\n\
23964 onto several lines.\n
23967 produces the same output as
23970 echo This is some text\n
23971 echo which is continued\n
23972 echo onto several lines.\n
23976 @item output @var{expression}
23977 Print the value of @var{expression} and nothing but that value: no
23978 newlines, no @samp{$@var{nn} = }. The value is not entered in the
23979 value history either. @xref{Expressions, ,Expressions}, for more information
23982 @item output/@var{fmt} @var{expression}
23983 Print the value of @var{expression} in format @var{fmt}. You can use
23984 the same formats as for @code{print}. @xref{Output Formats,,Output
23985 Formats}, for more information.
23988 @item printf @var{template}, @var{expressions}@dots{}
23989 Print the values of one or more @var{expressions} under the control of
23990 the string @var{template}. To print several values, make
23991 @var{expressions} be a comma-separated list of individual expressions,
23992 which may be either numbers or pointers. Their values are printed as
23993 specified by @var{template}, exactly as a C program would do by
23994 executing the code below:
23997 printf (@var{template}, @var{expressions}@dots{});
24000 As in @code{C} @code{printf}, ordinary characters in @var{template}
24001 are printed verbatim, while @dfn{conversion specification} introduced
24002 by the @samp{%} character cause subsequent @var{expressions} to be
24003 evaluated, their values converted and formatted according to type and
24004 style information encoded in the conversion specifications, and then
24007 For example, you can print two values in hex like this:
24010 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
24013 @code{printf} supports all the standard @code{C} conversion
24014 specifications, including the flags and modifiers between the @samp{%}
24015 character and the conversion letter, with the following exceptions:
24019 The argument-ordering modifiers, such as @samp{2$}, are not supported.
24022 The modifier @samp{*} is not supported for specifying precision or
24026 The @samp{'} flag (for separation of digits into groups according to
24027 @code{LC_NUMERIC'}) is not supported.
24030 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
24034 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
24037 The conversion letters @samp{a} and @samp{A} are not supported.
24041 Note that the @samp{ll} type modifier is supported only if the
24042 underlying @code{C} implementation used to build @value{GDBN} supports
24043 the @code{long long int} type, and the @samp{L} type modifier is
24044 supported only if @code{long double} type is available.
24046 As in @code{C}, @code{printf} supports simple backslash-escape
24047 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
24048 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
24049 single character. Octal and hexadecimal escape sequences are not
24052 Additionally, @code{printf} supports conversion specifications for DFP
24053 (@dfn{Decimal Floating Point}) types using the following length modifiers
24054 together with a floating point specifier.
24059 @samp{H} for printing @code{Decimal32} types.
24062 @samp{D} for printing @code{Decimal64} types.
24065 @samp{DD} for printing @code{Decimal128} types.
24068 If the underlying @code{C} implementation used to build @value{GDBN} has
24069 support for the three length modifiers for DFP types, other modifiers
24070 such as width and precision will also be available for @value{GDBN} to use.
24072 In case there is no such @code{C} support, no additional modifiers will be
24073 available and the value will be printed in the standard way.
24075 Here's an example of printing DFP types using the above conversion letters:
24077 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
24081 @item eval @var{template}, @var{expressions}@dots{}
24082 Convert the values of one or more @var{expressions} under the control of
24083 the string @var{template} to a command line, and call it.
24087 @node Auto-loading sequences
24088 @subsection Controlling auto-loading native @value{GDBN} scripts
24089 @cindex native script auto-loading
24091 When a new object file is read (for example, due to the @code{file}
24092 command, or because the inferior has loaded a shared library),
24093 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
24094 @xref{Auto-loading extensions}.
24096 Auto-loading can be enabled or disabled,
24097 and the list of auto-loaded scripts can be printed.
24100 @anchor{set auto-load gdb-scripts}
24101 @kindex set auto-load gdb-scripts
24102 @item set auto-load gdb-scripts [on|off]
24103 Enable or disable the auto-loading of canned sequences of commands scripts.
24105 @anchor{show auto-load gdb-scripts}
24106 @kindex show auto-load gdb-scripts
24107 @item show auto-load gdb-scripts
24108 Show whether auto-loading of canned sequences of commands scripts is enabled or
24111 @anchor{info auto-load gdb-scripts}
24112 @kindex info auto-load gdb-scripts
24113 @cindex print list of auto-loaded canned sequences of commands scripts
24114 @item info auto-load gdb-scripts [@var{regexp}]
24115 Print the list of all canned sequences of commands scripts that @value{GDBN}
24119 If @var{regexp} is supplied only canned sequences of commands scripts with
24120 matching names are printed.
24122 @c Python docs live in a separate file.
24123 @include python.texi
24125 @c Guile docs live in a separate file.
24126 @include guile.texi
24128 @node Auto-loading extensions
24129 @section Auto-loading extensions
24130 @cindex auto-loading extensions
24132 @value{GDBN} provides two mechanisms for automatically loading extensions
24133 when a new object file is read (for example, due to the @code{file}
24134 command, or because the inferior has loaded a shared library):
24135 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
24136 section of modern file formats like ELF.
24139 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
24140 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
24141 * Which flavor to choose?::
24144 The auto-loading feature is useful for supplying application-specific
24145 debugging commands and features.
24147 Auto-loading can be enabled or disabled,
24148 and the list of auto-loaded scripts can be printed.
24149 See the @samp{auto-loading} section of each extension language
24150 for more information.
24151 For @value{GDBN} command files see @ref{Auto-loading sequences}.
24152 For Python files see @ref{Python Auto-loading}.
24154 Note that loading of this script file also requires accordingly configured
24155 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24157 @node objfile-gdbdotext file
24158 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
24159 @cindex @file{@var{objfile}-gdb.gdb}
24160 @cindex @file{@var{objfile}-gdb.py}
24161 @cindex @file{@var{objfile}-gdb.scm}
24163 When a new object file is read, @value{GDBN} looks for a file named
24164 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
24165 where @var{objfile} is the object file's name and
24166 where @var{ext} is the file extension for the extension language:
24169 @item @file{@var{objfile}-gdb.gdb}
24170 GDB's own command language
24171 @item @file{@var{objfile}-gdb.py}
24173 @item @file{@var{objfile}-gdb.scm}
24177 @var{script-name} is formed by ensuring that the file name of @var{objfile}
24178 is absolute, following all symlinks, and resolving @code{.} and @code{..}
24179 components, and appending the @file{-gdb.@var{ext}} suffix.
24180 If this file exists and is readable, @value{GDBN} will evaluate it as a
24181 script in the specified extension language.
24183 If this file does not exist, then @value{GDBN} will look for
24184 @var{script-name} file in all of the directories as specified below.
24186 Note that loading of these files requires an accordingly configured
24187 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24189 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
24190 scripts normally according to its @file{.exe} filename. But if no scripts are
24191 found @value{GDBN} also tries script filenames matching the object file without
24192 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
24193 is attempted on any platform. This makes the script filenames compatible
24194 between Unix and MS-Windows hosts.
24197 @anchor{set auto-load scripts-directory}
24198 @kindex set auto-load scripts-directory
24199 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
24200 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
24201 may be delimited by the host platform path separator in use
24202 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
24204 Each entry here needs to be covered also by the security setting
24205 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
24207 @anchor{with-auto-load-dir}
24208 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
24209 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
24210 configuration option @option{--with-auto-load-dir}.
24212 Any reference to @file{$debugdir} will get replaced by
24213 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
24214 reference to @file{$datadir} will get replaced by @var{data-directory} which is
24215 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
24216 @file{$datadir} must be placed as a directory component --- either alone or
24217 delimited by @file{/} or @file{\} directory separators, depending on the host
24220 The list of directories uses path separator (@samp{:} on GNU and Unix
24221 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
24222 to the @env{PATH} environment variable.
24224 @anchor{show auto-load scripts-directory}
24225 @kindex show auto-load scripts-directory
24226 @item show auto-load scripts-directory
24227 Show @value{GDBN} auto-loaded scripts location.
24229 @anchor{add-auto-load-scripts-directory}
24230 @kindex add-auto-load-scripts-directory
24231 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
24232 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
24233 Multiple entries may be delimited by the host platform path separator in use.
24236 @value{GDBN} does not track which files it has already auto-loaded this way.
24237 @value{GDBN} will load the associated script every time the corresponding
24238 @var{objfile} is opened.
24239 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
24240 is evaluated more than once.
24242 @node dotdebug_gdb_scripts section
24243 @subsection The @code{.debug_gdb_scripts} section
24244 @cindex @code{.debug_gdb_scripts} section
24246 For systems using file formats like ELF and COFF,
24247 when @value{GDBN} loads a new object file
24248 it will look for a special section named @code{.debug_gdb_scripts}.
24249 If this section exists, its contents is a list of null-terminated entries
24250 specifying scripts to load. Each entry begins with a non-null prefix byte that
24251 specifies the kind of entry, typically the extension language and whether the
24252 script is in a file or inlined in @code{.debug_gdb_scripts}.
24254 The following entries are supported:
24257 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
24258 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
24259 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
24260 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
24263 @subsubsection Script File Entries
24265 If the entry specifies a file, @value{GDBN} will look for the file first
24266 in the current directory and then along the source search path
24267 (@pxref{Source Path, ,Specifying Source Directories}),
24268 except that @file{$cdir} is not searched, since the compilation
24269 directory is not relevant to scripts.
24271 File entries can be placed in section @code{.debug_gdb_scripts} with,
24272 for example, this GCC macro for Python scripts.
24275 /* Note: The "MS" section flags are to remove duplicates. */
24276 #define DEFINE_GDB_PY_SCRIPT(script_name) \
24278 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
24279 .byte 1 /* Python */\n\
24280 .asciz \"" script_name "\"\n\
24286 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
24287 Then one can reference the macro in a header or source file like this:
24290 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
24293 The script name may include directories if desired.
24295 Note that loading of this script file also requires accordingly configured
24296 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24298 If the macro invocation is put in a header, any application or library
24299 using this header will get a reference to the specified script,
24300 and with the use of @code{"MS"} attributes on the section, the linker
24301 will remove duplicates.
24303 @subsubsection Script Text Entries
24305 Script text entries allow to put the executable script in the entry
24306 itself instead of loading it from a file.
24307 The first line of the entry, everything after the prefix byte and up to
24308 the first newline (@code{0xa}) character, is the script name, and must not
24309 contain any kind of space character, e.g., spaces or tabs.
24310 The rest of the entry, up to the trailing null byte, is the script to
24311 execute in the specified language. The name needs to be unique among
24312 all script names, as @value{GDBN} executes each script only once based
24315 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
24319 #include "symcat.h"
24320 #include "gdb/section-scripts.h"
24322 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
24323 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
24324 ".ascii \"gdb.inlined-script\\n\"\n"
24325 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
24326 ".ascii \" def __init__ (self):\\n\"\n"
24327 ".ascii \" super (test_cmd, self).__init__ ("
24328 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
24329 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
24330 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
24331 ".ascii \"test_cmd ()\\n\"\n"
24337 Loading of inlined scripts requires a properly configured
24338 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24339 The path to specify in @code{auto-load safe-path} is the path of the file
24340 containing the @code{.debug_gdb_scripts} section.
24342 @node Which flavor to choose?
24343 @subsection Which flavor to choose?
24345 Given the multiple ways of auto-loading extensions, it might not always
24346 be clear which one to choose. This section provides some guidance.
24349 Benefits of the @file{-gdb.@var{ext}} way:
24353 Can be used with file formats that don't support multiple sections.
24356 Ease of finding scripts for public libraries.
24358 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
24359 in the source search path.
24360 For publicly installed libraries, e.g., @file{libstdc++}, there typically
24361 isn't a source directory in which to find the script.
24364 Doesn't require source code additions.
24368 Benefits of the @code{.debug_gdb_scripts} way:
24372 Works with static linking.
24374 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
24375 trigger their loading. When an application is statically linked the only
24376 objfile available is the executable, and it is cumbersome to attach all the
24377 scripts from all the input libraries to the executable's
24378 @file{-gdb.@var{ext}} script.
24381 Works with classes that are entirely inlined.
24383 Some classes can be entirely inlined, and thus there may not be an associated
24384 shared library to attach a @file{-gdb.@var{ext}} script to.
24387 Scripts needn't be copied out of the source tree.
24389 In some circumstances, apps can be built out of large collections of internal
24390 libraries, and the build infrastructure necessary to install the
24391 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
24392 cumbersome. It may be easier to specify the scripts in the
24393 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
24394 top of the source tree to the source search path.
24397 @node Multiple Extension Languages
24398 @section Multiple Extension Languages
24400 The Guile and Python extension languages do not share any state,
24401 and generally do not interfere with each other.
24402 There are some things to be aware of, however.
24404 @subsection Python comes first
24406 Python was @value{GDBN}'s first extension language, and to avoid breaking
24407 existing behaviour Python comes first. This is generally solved by the
24408 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
24409 extension languages, and when it makes a call to an extension language,
24410 (say to pretty-print a value), it tries each in turn until an extension
24411 language indicates it has performed the request (e.g., has returned the
24412 pretty-printed form of a value).
24413 This extends to errors while performing such requests: If an error happens
24414 while, for example, trying to pretty-print an object then the error is
24415 reported and any following extension languages are not tried.
24418 @section Creating new spellings of existing commands
24419 @cindex aliases for commands
24421 It is often useful to define alternate spellings of existing commands.
24422 For example, if a new @value{GDBN} command defined in Python has
24423 a long name to type, it is handy to have an abbreviated version of it
24424 that involves less typing.
24426 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
24427 of the @samp{step} command even though it is otherwise an ambiguous
24428 abbreviation of other commands like @samp{set} and @samp{show}.
24430 Aliases are also used to provide shortened or more common versions
24431 of multi-word commands. For example, @value{GDBN} provides the
24432 @samp{tty} alias of the @samp{set inferior-tty} command.
24434 You can define a new alias with the @samp{alias} command.
24439 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
24443 @var{ALIAS} specifies the name of the new alias.
24444 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
24447 @var{COMMAND} specifies the name of an existing command
24448 that is being aliased.
24450 The @samp{-a} option specifies that the new alias is an abbreviation
24451 of the command. Abbreviations are not shown in command
24452 lists displayed by the @samp{help} command.
24454 The @samp{--} option specifies the end of options,
24455 and is useful when @var{ALIAS} begins with a dash.
24457 Here is a simple example showing how to make an abbreviation
24458 of a command so that there is less to type.
24459 Suppose you were tired of typing @samp{disas}, the current
24460 shortest unambiguous abbreviation of the @samp{disassemble} command
24461 and you wanted an even shorter version named @samp{di}.
24462 The following will accomplish this.
24465 (gdb) alias -a di = disas
24468 Note that aliases are different from user-defined commands.
24469 With a user-defined command, you also need to write documentation
24470 for it with the @samp{document} command.
24471 An alias automatically picks up the documentation of the existing command.
24473 Here is an example where we make @samp{elms} an abbreviation of
24474 @samp{elements} in the @samp{set print elements} command.
24475 This is to show that you can make an abbreviation of any part
24479 (gdb) alias -a set print elms = set print elements
24480 (gdb) alias -a show print elms = show print elements
24481 (gdb) set p elms 20
24483 Limit on string chars or array elements to print is 200.
24486 Note that if you are defining an alias of a @samp{set} command,
24487 and you want to have an alias for the corresponding @samp{show}
24488 command, then you need to define the latter separately.
24490 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
24491 @var{ALIAS}, just as they are normally.
24494 (gdb) alias -a set pr elms = set p ele
24497 Finally, here is an example showing the creation of a one word
24498 alias for a more complex command.
24499 This creates alias @samp{spe} of the command @samp{set print elements}.
24502 (gdb) alias spe = set print elements
24507 @chapter Command Interpreters
24508 @cindex command interpreters
24510 @value{GDBN} supports multiple command interpreters, and some command
24511 infrastructure to allow users or user interface writers to switch
24512 between interpreters or run commands in other interpreters.
24514 @value{GDBN} currently supports two command interpreters, the console
24515 interpreter (sometimes called the command-line interpreter or @sc{cli})
24516 and the machine interface interpreter (or @sc{gdb/mi}). This manual
24517 describes both of these interfaces in great detail.
24519 By default, @value{GDBN} will start with the console interpreter.
24520 However, the user may choose to start @value{GDBN} with another
24521 interpreter by specifying the @option{-i} or @option{--interpreter}
24522 startup options. Defined interpreters include:
24526 @cindex console interpreter
24527 The traditional console or command-line interpreter. This is the most often
24528 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
24529 @value{GDBN} will use this interpreter.
24532 @cindex mi interpreter
24533 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
24534 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
24535 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
24539 @cindex mi2 interpreter
24540 The current @sc{gdb/mi} interface.
24543 @cindex mi1 interpreter
24544 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
24548 @cindex invoke another interpreter
24549 The interpreter being used by @value{GDBN} may not be dynamically
24550 switched at runtime. Although possible, this could lead to a very
24551 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
24552 enters the command "interpreter-set console" in a console view,
24553 @value{GDBN} would switch to using the console interpreter, rendering
24554 the IDE inoperable!
24556 @kindex interpreter-exec
24557 Although you may only choose a single interpreter at startup, you may execute
24558 commands in any interpreter from the current interpreter using the appropriate
24559 command. If you are running the console interpreter, simply use the
24560 @code{interpreter-exec} command:
24563 interpreter-exec mi "-data-list-register-names"
24566 @sc{gdb/mi} has a similar command, although it is only available in versions of
24567 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
24570 @chapter @value{GDBN} Text User Interface
24572 @cindex Text User Interface
24575 * TUI Overview:: TUI overview
24576 * TUI Keys:: TUI key bindings
24577 * TUI Single Key Mode:: TUI single key mode
24578 * TUI Commands:: TUI-specific commands
24579 * TUI Configuration:: TUI configuration variables
24582 The @value{GDBN} Text User Interface (TUI) is a terminal
24583 interface which uses the @code{curses} library to show the source
24584 file, the assembly output, the program registers and @value{GDBN}
24585 commands in separate text windows. The TUI mode is supported only
24586 on platforms where a suitable version of the @code{curses} library
24589 The TUI mode is enabled by default when you invoke @value{GDBN} as
24590 @samp{@value{GDBP} -tui}.
24591 You can also switch in and out of TUI mode while @value{GDBN} runs by
24592 using various TUI commands and key bindings, such as @command{tui
24593 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
24594 @ref{TUI Keys, ,TUI Key Bindings}.
24597 @section TUI Overview
24599 In TUI mode, @value{GDBN} can display several text windows:
24603 This window is the @value{GDBN} command window with the @value{GDBN}
24604 prompt and the @value{GDBN} output. The @value{GDBN} input is still
24605 managed using readline.
24608 The source window shows the source file of the program. The current
24609 line and active breakpoints are displayed in this window.
24612 The assembly window shows the disassembly output of the program.
24615 This window shows the processor registers. Registers are highlighted
24616 when their values change.
24619 The source and assembly windows show the current program position
24620 by highlighting the current line and marking it with a @samp{>} marker.
24621 Breakpoints are indicated with two markers. The first marker
24622 indicates the breakpoint type:
24626 Breakpoint which was hit at least once.
24629 Breakpoint which was never hit.
24632 Hardware breakpoint which was hit at least once.
24635 Hardware breakpoint which was never hit.
24638 The second marker indicates whether the breakpoint is enabled or not:
24642 Breakpoint is enabled.
24645 Breakpoint is disabled.
24648 The source, assembly and register windows are updated when the current
24649 thread changes, when the frame changes, or when the program counter
24652 These windows are not all visible at the same time. The command
24653 window is always visible. The others can be arranged in several
24664 source and assembly,
24667 source and registers, or
24670 assembly and registers.
24673 A status line above the command window shows the following information:
24677 Indicates the current @value{GDBN} target.
24678 (@pxref{Targets, ,Specifying a Debugging Target}).
24681 Gives the current process or thread number.
24682 When no process is being debugged, this field is set to @code{No process}.
24685 Gives the current function name for the selected frame.
24686 The name is demangled if demangling is turned on (@pxref{Print Settings}).
24687 When there is no symbol corresponding to the current program counter,
24688 the string @code{??} is displayed.
24691 Indicates the current line number for the selected frame.
24692 When the current line number is not known, the string @code{??} is displayed.
24695 Indicates the current program counter address.
24699 @section TUI Key Bindings
24700 @cindex TUI key bindings
24702 The TUI installs several key bindings in the readline keymaps
24703 @ifset SYSTEM_READLINE
24704 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
24706 @ifclear SYSTEM_READLINE
24707 (@pxref{Command Line Editing}).
24709 The following key bindings are installed for both TUI mode and the
24710 @value{GDBN} standard mode.
24719 Enter or leave the TUI mode. When leaving the TUI mode,
24720 the curses window management stops and @value{GDBN} operates using
24721 its standard mode, writing on the terminal directly. When reentering
24722 the TUI mode, control is given back to the curses windows.
24723 The screen is then refreshed.
24727 Use a TUI layout with only one window. The layout will
24728 either be @samp{source} or @samp{assembly}. When the TUI mode
24729 is not active, it will switch to the TUI mode.
24731 Think of this key binding as the Emacs @kbd{C-x 1} binding.
24735 Use a TUI layout with at least two windows. When the current
24736 layout already has two windows, the next layout with two windows is used.
24737 When a new layout is chosen, one window will always be common to the
24738 previous layout and the new one.
24740 Think of it as the Emacs @kbd{C-x 2} binding.
24744 Change the active window. The TUI associates several key bindings
24745 (like scrolling and arrow keys) with the active window. This command
24746 gives the focus to the next TUI window.
24748 Think of it as the Emacs @kbd{C-x o} binding.
24752 Switch in and out of the TUI SingleKey mode that binds single
24753 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
24756 The following key bindings only work in the TUI mode:
24761 Scroll the active window one page up.
24765 Scroll the active window one page down.
24769 Scroll the active window one line up.
24773 Scroll the active window one line down.
24777 Scroll the active window one column left.
24781 Scroll the active window one column right.
24785 Refresh the screen.
24788 Because the arrow keys scroll the active window in the TUI mode, they
24789 are not available for their normal use by readline unless the command
24790 window has the focus. When another window is active, you must use
24791 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
24792 and @kbd{C-f} to control the command window.
24794 @node TUI Single Key Mode
24795 @section TUI Single Key Mode
24796 @cindex TUI single key mode
24798 The TUI also provides a @dfn{SingleKey} mode, which binds several
24799 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
24800 switch into this mode, where the following key bindings are used:
24803 @kindex c @r{(SingleKey TUI key)}
24807 @kindex d @r{(SingleKey TUI key)}
24811 @kindex f @r{(SingleKey TUI key)}
24815 @kindex n @r{(SingleKey TUI key)}
24819 @kindex q @r{(SingleKey TUI key)}
24821 exit the SingleKey mode.
24823 @kindex r @r{(SingleKey TUI key)}
24827 @kindex s @r{(SingleKey TUI key)}
24831 @kindex u @r{(SingleKey TUI key)}
24835 @kindex v @r{(SingleKey TUI key)}
24839 @kindex w @r{(SingleKey TUI key)}
24844 Other keys temporarily switch to the @value{GDBN} command prompt.
24845 The key that was pressed is inserted in the editing buffer so that
24846 it is possible to type most @value{GDBN} commands without interaction
24847 with the TUI SingleKey mode. Once the command is entered the TUI
24848 SingleKey mode is restored. The only way to permanently leave
24849 this mode is by typing @kbd{q} or @kbd{C-x s}.
24853 @section TUI-specific Commands
24854 @cindex TUI commands
24856 The TUI has specific commands to control the text windows.
24857 These commands are always available, even when @value{GDBN} is not in
24858 the TUI mode. When @value{GDBN} is in the standard mode, most
24859 of these commands will automatically switch to the TUI mode.
24861 Note that if @value{GDBN}'s @code{stdout} is not connected to a
24862 terminal, or @value{GDBN} has been started with the machine interface
24863 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
24864 these commands will fail with an error, because it would not be
24865 possible or desirable to enable curses window management.
24870 Activate TUI mode. The last active TUI window layout will be used if
24871 TUI mode has prevsiouly been used in the current debugging session,
24872 otherwise a default layout is used.
24875 @kindex tui disable
24876 Disable TUI mode, returning to the console interpreter.
24880 List and give the size of all displayed windows.
24882 @item layout @var{name}
24884 Changes which TUI windows are displayed. In each layout the command
24885 window is always displayed, the @var{name} parameter controls which
24886 additional windows are displayed, and can be any of the following:
24890 Display the next layout.
24893 Display the previous layout.
24896 Display the source and command windows.
24899 Display the assembly and command windows.
24902 Display the source, assembly, and command windows.
24905 When in @code{src} layout display the register, source, and command
24906 windows. When in @code{asm} or @code{split} layout display the
24907 register, assembler, and command windows.
24910 @item focus @var{name}
24912 Changes which TUI window is currently active for scrolling. The
24913 @var{name} parameter can be any of the following:
24917 Make the next window active for scrolling.
24920 Make the previous window active for scrolling.
24923 Make the source window active for scrolling.
24926 Make the assembly window active for scrolling.
24929 Make the register window active for scrolling.
24932 Make the command window active for scrolling.
24937 Refresh the screen. This is similar to typing @kbd{C-L}.
24939 @item tui reg @var{group}
24941 Changes the register group displayed in the tui register window to
24942 @var{group}. If the register window is not currently displayed this
24943 command will cause the register window to be displayed. The list of
24944 register groups, as well as their order is target specific. The
24945 following groups are available on most targets:
24948 Repeatedly selecting this group will cause the display to cycle
24949 through all of the available register groups.
24952 Repeatedly selecting this group will cause the display to cycle
24953 through all of the available register groups in the reverse order to
24957 Display the general registers.
24959 Display the floating point registers.
24961 Display the system registers.
24963 Display the vector registers.
24965 Display all registers.
24970 Update the source window and the current execution point.
24972 @item winheight @var{name} +@var{count}
24973 @itemx winheight @var{name} -@var{count}
24975 Change the height of the window @var{name} by @var{count}
24976 lines. Positive counts increase the height, while negative counts
24977 decrease it. The @var{name} parameter can be one of @code{src} (the
24978 source window), @code{cmd} (the command window), @code{asm} (the
24979 disassembly window), or @code{regs} (the register display window).
24981 @item tabset @var{nchars}
24983 Set the width of tab stops to be @var{nchars} characters. This
24984 setting affects the display of TAB characters in the source and
24988 @node TUI Configuration
24989 @section TUI Configuration Variables
24990 @cindex TUI configuration variables
24992 Several configuration variables control the appearance of TUI windows.
24995 @item set tui border-kind @var{kind}
24996 @kindex set tui border-kind
24997 Select the border appearance for the source, assembly and register windows.
24998 The possible values are the following:
25001 Use a space character to draw the border.
25004 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
25007 Use the Alternate Character Set to draw the border. The border is
25008 drawn using character line graphics if the terminal supports them.
25011 @item set tui border-mode @var{mode}
25012 @kindex set tui border-mode
25013 @itemx set tui active-border-mode @var{mode}
25014 @kindex set tui active-border-mode
25015 Select the display attributes for the borders of the inactive windows
25016 or the active window. The @var{mode} can be one of the following:
25019 Use normal attributes to display the border.
25025 Use reverse video mode.
25028 Use half bright mode.
25030 @item half-standout
25031 Use half bright and standout mode.
25034 Use extra bright or bold mode.
25036 @item bold-standout
25037 Use extra bright or bold and standout mode.
25042 @chapter Using @value{GDBN} under @sc{gnu} Emacs
25045 @cindex @sc{gnu} Emacs
25046 A special interface allows you to use @sc{gnu} Emacs to view (and
25047 edit) the source files for the program you are debugging with
25050 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
25051 executable file you want to debug as an argument. This command starts
25052 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
25053 created Emacs buffer.
25054 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
25056 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
25061 All ``terminal'' input and output goes through an Emacs buffer, called
25064 This applies both to @value{GDBN} commands and their output, and to the input
25065 and output done by the program you are debugging.
25067 This is useful because it means that you can copy the text of previous
25068 commands and input them again; you can even use parts of the output
25071 All the facilities of Emacs' Shell mode are available for interacting
25072 with your program. In particular, you can send signals the usual
25073 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
25077 @value{GDBN} displays source code through Emacs.
25079 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
25080 source file for that frame and puts an arrow (@samp{=>}) at the
25081 left margin of the current line. Emacs uses a separate buffer for
25082 source display, and splits the screen to show both your @value{GDBN} session
25085 Explicit @value{GDBN} @code{list} or search commands still produce output as
25086 usual, but you probably have no reason to use them from Emacs.
25089 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
25090 a graphical mode, enabled by default, which provides further buffers
25091 that can control the execution and describe the state of your program.
25092 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
25094 If you specify an absolute file name when prompted for the @kbd{M-x
25095 gdb} argument, then Emacs sets your current working directory to where
25096 your program resides. If you only specify the file name, then Emacs
25097 sets your current working directory to the directory associated
25098 with the previous buffer. In this case, @value{GDBN} may find your
25099 program by searching your environment's @code{PATH} variable, but on
25100 some operating systems it might not find the source. So, although the
25101 @value{GDBN} input and output session proceeds normally, the auxiliary
25102 buffer does not display the current source and line of execution.
25104 The initial working directory of @value{GDBN} is printed on the top
25105 line of the GUD buffer and this serves as a default for the commands
25106 that specify files for @value{GDBN} to operate on. @xref{Files,
25107 ,Commands to Specify Files}.
25109 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
25110 need to call @value{GDBN} by a different name (for example, if you
25111 keep several configurations around, with different names) you can
25112 customize the Emacs variable @code{gud-gdb-command-name} to run the
25115 In the GUD buffer, you can use these special Emacs commands in
25116 addition to the standard Shell mode commands:
25120 Describe the features of Emacs' GUD Mode.
25123 Execute to another source line, like the @value{GDBN} @code{step} command; also
25124 update the display window to show the current file and location.
25127 Execute to next source line in this function, skipping all function
25128 calls, like the @value{GDBN} @code{next} command. Then update the display window
25129 to show the current file and location.
25132 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
25133 display window accordingly.
25136 Execute until exit from the selected stack frame, like the @value{GDBN}
25137 @code{finish} command.
25140 Continue execution of your program, like the @value{GDBN} @code{continue}
25144 Go up the number of frames indicated by the numeric argument
25145 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
25146 like the @value{GDBN} @code{up} command.
25149 Go down the number of frames indicated by the numeric argument, like the
25150 @value{GDBN} @code{down} command.
25153 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
25154 tells @value{GDBN} to set a breakpoint on the source line point is on.
25156 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
25157 separate frame which shows a backtrace when the GUD buffer is current.
25158 Move point to any frame in the stack and type @key{RET} to make it
25159 become the current frame and display the associated source in the
25160 source buffer. Alternatively, click @kbd{Mouse-2} to make the
25161 selected frame become the current one. In graphical mode, the
25162 speedbar displays watch expressions.
25164 If you accidentally delete the source-display buffer, an easy way to get
25165 it back is to type the command @code{f} in the @value{GDBN} buffer, to
25166 request a frame display; when you run under Emacs, this recreates
25167 the source buffer if necessary to show you the context of the current
25170 The source files displayed in Emacs are in ordinary Emacs buffers
25171 which are visiting the source files in the usual way. You can edit
25172 the files with these buffers if you wish; but keep in mind that @value{GDBN}
25173 communicates with Emacs in terms of line numbers. If you add or
25174 delete lines from the text, the line numbers that @value{GDBN} knows cease
25175 to correspond properly with the code.
25177 A more detailed description of Emacs' interaction with @value{GDBN} is
25178 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
25182 @chapter The @sc{gdb/mi} Interface
25184 @unnumberedsec Function and Purpose
25186 @cindex @sc{gdb/mi}, its purpose
25187 @sc{gdb/mi} is a line based machine oriented text interface to
25188 @value{GDBN} and is activated by specifying using the
25189 @option{--interpreter} command line option (@pxref{Mode Options}). It
25190 is specifically intended to support the development of systems which
25191 use the debugger as just one small component of a larger system.
25193 This chapter is a specification of the @sc{gdb/mi} interface. It is written
25194 in the form of a reference manual.
25196 Note that @sc{gdb/mi} is still under construction, so some of the
25197 features described below are incomplete and subject to change
25198 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
25200 @unnumberedsec Notation and Terminology
25202 @cindex notational conventions, for @sc{gdb/mi}
25203 This chapter uses the following notation:
25207 @code{|} separates two alternatives.
25210 @code{[ @var{something} ]} indicates that @var{something} is optional:
25211 it may or may not be given.
25214 @code{( @var{group} )*} means that @var{group} inside the parentheses
25215 may repeat zero or more times.
25218 @code{( @var{group} )+} means that @var{group} inside the parentheses
25219 may repeat one or more times.
25222 @code{"@var{string}"} means a literal @var{string}.
25226 @heading Dependencies
25230 * GDB/MI General Design::
25231 * GDB/MI Command Syntax::
25232 * GDB/MI Compatibility with CLI::
25233 * GDB/MI Development and Front Ends::
25234 * GDB/MI Output Records::
25235 * GDB/MI Simple Examples::
25236 * GDB/MI Command Description Format::
25237 * GDB/MI Breakpoint Commands::
25238 * GDB/MI Catchpoint Commands::
25239 * GDB/MI Program Context::
25240 * GDB/MI Thread Commands::
25241 * GDB/MI Ada Tasking Commands::
25242 * GDB/MI Program Execution::
25243 * GDB/MI Stack Manipulation::
25244 * GDB/MI Variable Objects::
25245 * GDB/MI Data Manipulation::
25246 * GDB/MI Tracepoint Commands::
25247 * GDB/MI Symbol Query::
25248 * GDB/MI File Commands::
25250 * GDB/MI Kod Commands::
25251 * GDB/MI Memory Overlay Commands::
25252 * GDB/MI Signal Handling Commands::
25254 * GDB/MI Target Manipulation::
25255 * GDB/MI File Transfer Commands::
25256 * GDB/MI Ada Exceptions Commands::
25257 * GDB/MI Support Commands::
25258 * GDB/MI Miscellaneous Commands::
25261 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25262 @node GDB/MI General Design
25263 @section @sc{gdb/mi} General Design
25264 @cindex GDB/MI General Design
25266 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
25267 parts---commands sent to @value{GDBN}, responses to those commands
25268 and notifications. Each command results in exactly one response,
25269 indicating either successful completion of the command, or an error.
25270 For the commands that do not resume the target, the response contains the
25271 requested information. For the commands that resume the target, the
25272 response only indicates whether the target was successfully resumed.
25273 Notifications is the mechanism for reporting changes in the state of the
25274 target, or in @value{GDBN} state, that cannot conveniently be associated with
25275 a command and reported as part of that command response.
25277 The important examples of notifications are:
25281 Exec notifications. These are used to report changes in
25282 target state---when a target is resumed, or stopped. It would not
25283 be feasible to include this information in response of resuming
25284 commands, because one resume commands can result in multiple events in
25285 different threads. Also, quite some time may pass before any event
25286 happens in the target, while a frontend needs to know whether the resuming
25287 command itself was successfully executed.
25290 Console output, and status notifications. Console output
25291 notifications are used to report output of CLI commands, as well as
25292 diagnostics for other commands. Status notifications are used to
25293 report the progress of a long-running operation. Naturally, including
25294 this information in command response would mean no output is produced
25295 until the command is finished, which is undesirable.
25298 General notifications. Commands may have various side effects on
25299 the @value{GDBN} or target state beyond their official purpose. For example,
25300 a command may change the selected thread. Although such changes can
25301 be included in command response, using notification allows for more
25302 orthogonal frontend design.
25306 There's no guarantee that whenever an MI command reports an error,
25307 @value{GDBN} or the target are in any specific state, and especially,
25308 the state is not reverted to the state before the MI command was
25309 processed. Therefore, whenever an MI command results in an error,
25310 we recommend that the frontend refreshes all the information shown in
25311 the user interface.
25315 * Context management::
25316 * Asynchronous and non-stop modes::
25320 @node Context management
25321 @subsection Context management
25323 @subsubsection Threads and Frames
25325 In most cases when @value{GDBN} accesses the target, this access is
25326 done in context of a specific thread and frame (@pxref{Frames}).
25327 Often, even when accessing global data, the target requires that a thread
25328 be specified. The CLI interface maintains the selected thread and frame,
25329 and supplies them to target on each command. This is convenient,
25330 because a command line user would not want to specify that information
25331 explicitly on each command, and because user interacts with
25332 @value{GDBN} via a single terminal, so no confusion is possible as
25333 to what thread and frame are the current ones.
25335 In the case of MI, the concept of selected thread and frame is less
25336 useful. First, a frontend can easily remember this information
25337 itself. Second, a graphical frontend can have more than one window,
25338 each one used for debugging a different thread, and the frontend might
25339 want to access additional threads for internal purposes. This
25340 increases the risk that by relying on implicitly selected thread, the
25341 frontend may be operating on a wrong one. Therefore, each MI command
25342 should explicitly specify which thread and frame to operate on. To
25343 make it possible, each MI command accepts the @samp{--thread} and
25344 @samp{--frame} options, the value to each is @value{GDBN} identifier
25345 for thread and frame to operate on.
25347 Usually, each top-level window in a frontend allows the user to select
25348 a thread and a frame, and remembers the user selection for further
25349 operations. However, in some cases @value{GDBN} may suggest that the
25350 current thread be changed. For example, when stopping on a breakpoint
25351 it is reasonable to switch to the thread where breakpoint is hit. For
25352 another example, if the user issues the CLI @samp{thread} command via
25353 the frontend, it is desirable to change the frontend's selected thread to the
25354 one specified by user. @value{GDBN} communicates the suggestion to
25355 change current thread using the @samp{=thread-selected} notification.
25356 No such notification is available for the selected frame at the moment.
25358 Note that historically, MI shares the selected thread with CLI, so
25359 frontends used the @code{-thread-select} to execute commands in the
25360 right context. However, getting this to work right is cumbersome. The
25361 simplest way is for frontend to emit @code{-thread-select} command
25362 before every command. This doubles the number of commands that need
25363 to be sent. The alternative approach is to suppress @code{-thread-select}
25364 if the selected thread in @value{GDBN} is supposed to be identical to the
25365 thread the frontend wants to operate on. However, getting this
25366 optimization right can be tricky. In particular, if the frontend
25367 sends several commands to @value{GDBN}, and one of the commands changes the
25368 selected thread, then the behaviour of subsequent commands will
25369 change. So, a frontend should either wait for response from such
25370 problematic commands, or explicitly add @code{-thread-select} for
25371 all subsequent commands. No frontend is known to do this exactly
25372 right, so it is suggested to just always pass the @samp{--thread} and
25373 @samp{--frame} options.
25375 @subsubsection Language
25377 The execution of several commands depends on which language is selected.
25378 By default, the current language (@pxref{show language}) is used.
25379 But for commands known to be language-sensitive, it is recommended
25380 to use the @samp{--language} option. This option takes one argument,
25381 which is the name of the language to use while executing the command.
25385 -data-evaluate-expression --language c "sizeof (void*)"
25390 The valid language names are the same names accepted by the
25391 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
25392 @samp{local} or @samp{unknown}.
25394 @node Asynchronous and non-stop modes
25395 @subsection Asynchronous command execution and non-stop mode
25397 On some targets, @value{GDBN} is capable of processing MI commands
25398 even while the target is running. This is called @dfn{asynchronous
25399 command execution} (@pxref{Background Execution}). The frontend may
25400 specify a preferrence for asynchronous execution using the
25401 @code{-gdb-set mi-async 1} command, which should be emitted before
25402 either running the executable or attaching to the target. After the
25403 frontend has started the executable or attached to the target, it can
25404 find if asynchronous execution is enabled using the
25405 @code{-list-target-features} command.
25408 @item -gdb-set mi-async on
25409 @item -gdb-set mi-async off
25410 Set whether MI is in asynchronous mode.
25412 When @code{off}, which is the default, MI execution commands (e.g.,
25413 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
25414 for the program to stop before processing further commands.
25416 When @code{on}, MI execution commands are background execution
25417 commands (e.g., @code{-exec-continue} becomes the equivalent of the
25418 @code{c&} CLI command), and so @value{GDBN} is capable of processing
25419 MI commands even while the target is running.
25421 @item -gdb-show mi-async
25422 Show whether MI asynchronous mode is enabled.
25425 Note: In @value{GDBN} version 7.7 and earlier, this option was called
25426 @code{target-async} instead of @code{mi-async}, and it had the effect
25427 of both putting MI in asynchronous mode and making CLI background
25428 commands possible. CLI background commands are now always possible
25429 ``out of the box'' if the target supports them. The old spelling is
25430 kept as a deprecated alias for backwards compatibility.
25432 Even if @value{GDBN} can accept a command while target is running,
25433 many commands that access the target do not work when the target is
25434 running. Therefore, asynchronous command execution is most useful
25435 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
25436 it is possible to examine the state of one thread, while other threads
25439 When a given thread is running, MI commands that try to access the
25440 target in the context of that thread may not work, or may work only on
25441 some targets. In particular, commands that try to operate on thread's
25442 stack will not work, on any target. Commands that read memory, or
25443 modify breakpoints, may work or not work, depending on the target. Note
25444 that even commands that operate on global state, such as @code{print},
25445 @code{set}, and breakpoint commands, still access the target in the
25446 context of a specific thread, so frontend should try to find a
25447 stopped thread and perform the operation on that thread (using the
25448 @samp{--thread} option).
25450 Which commands will work in the context of a running thread is
25451 highly target dependent. However, the two commands
25452 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
25453 to find the state of a thread, will always work.
25455 @node Thread groups
25456 @subsection Thread groups
25457 @value{GDBN} may be used to debug several processes at the same time.
25458 On some platfroms, @value{GDBN} may support debugging of several
25459 hardware systems, each one having several cores with several different
25460 processes running on each core. This section describes the MI
25461 mechanism to support such debugging scenarios.
25463 The key observation is that regardless of the structure of the
25464 target, MI can have a global list of threads, because most commands that
25465 accept the @samp{--thread} option do not need to know what process that
25466 thread belongs to. Therefore, it is not necessary to introduce
25467 neither additional @samp{--process} option, nor an notion of the
25468 current process in the MI interface. The only strictly new feature
25469 that is required is the ability to find how the threads are grouped
25472 To allow the user to discover such grouping, and to support arbitrary
25473 hierarchy of machines/cores/processes, MI introduces the concept of a
25474 @dfn{thread group}. Thread group is a collection of threads and other
25475 thread groups. A thread group always has a string identifier, a type,
25476 and may have additional attributes specific to the type. A new
25477 command, @code{-list-thread-groups}, returns the list of top-level
25478 thread groups, which correspond to processes that @value{GDBN} is
25479 debugging at the moment. By passing an identifier of a thread group
25480 to the @code{-list-thread-groups} command, it is possible to obtain
25481 the members of specific thread group.
25483 To allow the user to easily discover processes, and other objects, he
25484 wishes to debug, a concept of @dfn{available thread group} is
25485 introduced. Available thread group is an thread group that
25486 @value{GDBN} is not debugging, but that can be attached to, using the
25487 @code{-target-attach} command. The list of available top-level thread
25488 groups can be obtained using @samp{-list-thread-groups --available}.
25489 In general, the content of a thread group may be only retrieved only
25490 after attaching to that thread group.
25492 Thread groups are related to inferiors (@pxref{Inferiors and
25493 Programs}). Each inferior corresponds to a thread group of a special
25494 type @samp{process}, and some additional operations are permitted on
25495 such thread groups.
25497 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25498 @node GDB/MI Command Syntax
25499 @section @sc{gdb/mi} Command Syntax
25502 * GDB/MI Input Syntax::
25503 * GDB/MI Output Syntax::
25506 @node GDB/MI Input Syntax
25507 @subsection @sc{gdb/mi} Input Syntax
25509 @cindex input syntax for @sc{gdb/mi}
25510 @cindex @sc{gdb/mi}, input syntax
25512 @item @var{command} @expansion{}
25513 @code{@var{cli-command} | @var{mi-command}}
25515 @item @var{cli-command} @expansion{}
25516 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
25517 @var{cli-command} is any existing @value{GDBN} CLI command.
25519 @item @var{mi-command} @expansion{}
25520 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
25521 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
25523 @item @var{token} @expansion{}
25524 "any sequence of digits"
25526 @item @var{option} @expansion{}
25527 @code{"-" @var{parameter} [ " " @var{parameter} ]}
25529 @item @var{parameter} @expansion{}
25530 @code{@var{non-blank-sequence} | @var{c-string}}
25532 @item @var{operation} @expansion{}
25533 @emph{any of the operations described in this chapter}
25535 @item @var{non-blank-sequence} @expansion{}
25536 @emph{anything, provided it doesn't contain special characters such as
25537 "-", @var{nl}, """ and of course " "}
25539 @item @var{c-string} @expansion{}
25540 @code{""" @var{seven-bit-iso-c-string-content} """}
25542 @item @var{nl} @expansion{}
25551 The CLI commands are still handled by the @sc{mi} interpreter; their
25552 output is described below.
25555 The @code{@var{token}}, when present, is passed back when the command
25559 Some @sc{mi} commands accept optional arguments as part of the parameter
25560 list. Each option is identified by a leading @samp{-} (dash) and may be
25561 followed by an optional argument parameter. Options occur first in the
25562 parameter list and can be delimited from normal parameters using
25563 @samp{--} (this is useful when some parameters begin with a dash).
25570 We want easy access to the existing CLI syntax (for debugging).
25573 We want it to be easy to spot a @sc{mi} operation.
25576 @node GDB/MI Output Syntax
25577 @subsection @sc{gdb/mi} Output Syntax
25579 @cindex output syntax of @sc{gdb/mi}
25580 @cindex @sc{gdb/mi}, output syntax
25581 The output from @sc{gdb/mi} consists of zero or more out-of-band records
25582 followed, optionally, by a single result record. This result record
25583 is for the most recent command. The sequence of output records is
25584 terminated by @samp{(gdb)}.
25586 If an input command was prefixed with a @code{@var{token}} then the
25587 corresponding output for that command will also be prefixed by that same
25591 @item @var{output} @expansion{}
25592 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
25594 @item @var{result-record} @expansion{}
25595 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
25597 @item @var{out-of-band-record} @expansion{}
25598 @code{@var{async-record} | @var{stream-record}}
25600 @item @var{async-record} @expansion{}
25601 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
25603 @item @var{exec-async-output} @expansion{}
25604 @code{[ @var{token} ] "*" @var{async-output nl}}
25606 @item @var{status-async-output} @expansion{}
25607 @code{[ @var{token} ] "+" @var{async-output nl}}
25609 @item @var{notify-async-output} @expansion{}
25610 @code{[ @var{token} ] "=" @var{async-output nl}}
25612 @item @var{async-output} @expansion{}
25613 @code{@var{async-class} ( "," @var{result} )*}
25615 @item @var{result-class} @expansion{}
25616 @code{"done" | "running" | "connected" | "error" | "exit"}
25618 @item @var{async-class} @expansion{}
25619 @code{"stopped" | @var{others}} (where @var{others} will be added
25620 depending on the needs---this is still in development).
25622 @item @var{result} @expansion{}
25623 @code{ @var{variable} "=" @var{value}}
25625 @item @var{variable} @expansion{}
25626 @code{ @var{string} }
25628 @item @var{value} @expansion{}
25629 @code{ @var{const} | @var{tuple} | @var{list} }
25631 @item @var{const} @expansion{}
25632 @code{@var{c-string}}
25634 @item @var{tuple} @expansion{}
25635 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
25637 @item @var{list} @expansion{}
25638 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
25639 @var{result} ( "," @var{result} )* "]" }
25641 @item @var{stream-record} @expansion{}
25642 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
25644 @item @var{console-stream-output} @expansion{}
25645 @code{"~" @var{c-string nl}}
25647 @item @var{target-stream-output} @expansion{}
25648 @code{"@@" @var{c-string nl}}
25650 @item @var{log-stream-output} @expansion{}
25651 @code{"&" @var{c-string nl}}
25653 @item @var{nl} @expansion{}
25656 @item @var{token} @expansion{}
25657 @emph{any sequence of digits}.
25665 All output sequences end in a single line containing a period.
25668 The @code{@var{token}} is from the corresponding request. Note that
25669 for all async output, while the token is allowed by the grammar and
25670 may be output by future versions of @value{GDBN} for select async
25671 output messages, it is generally omitted. Frontends should treat
25672 all async output as reporting general changes in the state of the
25673 target and there should be no need to associate async output to any
25677 @cindex status output in @sc{gdb/mi}
25678 @var{status-async-output} contains on-going status information about the
25679 progress of a slow operation. It can be discarded. All status output is
25680 prefixed by @samp{+}.
25683 @cindex async output in @sc{gdb/mi}
25684 @var{exec-async-output} contains asynchronous state change on the target
25685 (stopped, started, disappeared). All async output is prefixed by
25689 @cindex notify output in @sc{gdb/mi}
25690 @var{notify-async-output} contains supplementary information that the
25691 client should handle (e.g., a new breakpoint information). All notify
25692 output is prefixed by @samp{=}.
25695 @cindex console output in @sc{gdb/mi}
25696 @var{console-stream-output} is output that should be displayed as is in the
25697 console. It is the textual response to a CLI command. All the console
25698 output is prefixed by @samp{~}.
25701 @cindex target output in @sc{gdb/mi}
25702 @var{target-stream-output} is the output produced by the target program.
25703 All the target output is prefixed by @samp{@@}.
25706 @cindex log output in @sc{gdb/mi}
25707 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
25708 instance messages that should be displayed as part of an error log. All
25709 the log output is prefixed by @samp{&}.
25712 @cindex list output in @sc{gdb/mi}
25713 New @sc{gdb/mi} commands should only output @var{lists} containing
25719 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
25720 details about the various output records.
25722 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25723 @node GDB/MI Compatibility with CLI
25724 @section @sc{gdb/mi} Compatibility with CLI
25726 @cindex compatibility, @sc{gdb/mi} and CLI
25727 @cindex @sc{gdb/mi}, compatibility with CLI
25729 For the developers convenience CLI commands can be entered directly,
25730 but there may be some unexpected behaviour. For example, commands
25731 that query the user will behave as if the user replied yes, breakpoint
25732 command lists are not executed and some CLI commands, such as
25733 @code{if}, @code{when} and @code{define}, prompt for further input with
25734 @samp{>}, which is not valid MI output.
25736 This feature may be removed at some stage in the future and it is
25737 recommended that front ends use the @code{-interpreter-exec} command
25738 (@pxref{-interpreter-exec}).
25740 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25741 @node GDB/MI Development and Front Ends
25742 @section @sc{gdb/mi} Development and Front Ends
25743 @cindex @sc{gdb/mi} development
25745 The application which takes the MI output and presents the state of the
25746 program being debugged to the user is called a @dfn{front end}.
25748 Although @sc{gdb/mi} is still incomplete, it is currently being used
25749 by a variety of front ends to @value{GDBN}. This makes it difficult
25750 to introduce new functionality without breaking existing usage. This
25751 section tries to minimize the problems by describing how the protocol
25754 Some changes in MI need not break a carefully designed front end, and
25755 for these the MI version will remain unchanged. The following is a
25756 list of changes that may occur within one level, so front ends should
25757 parse MI output in a way that can handle them:
25761 New MI commands may be added.
25764 New fields may be added to the output of any MI command.
25767 The range of values for fields with specified values, e.g.,
25768 @code{in_scope} (@pxref{-var-update}) may be extended.
25770 @c The format of field's content e.g type prefix, may change so parse it
25771 @c at your own risk. Yes, in general?
25773 @c The order of fields may change? Shouldn't really matter but it might
25774 @c resolve inconsistencies.
25777 If the changes are likely to break front ends, the MI version level
25778 will be increased by one. This will allow the front end to parse the
25779 output according to the MI version. Apart from mi0, new versions of
25780 @value{GDBN} will not support old versions of MI and it will be the
25781 responsibility of the front end to work with the new one.
25783 @c Starting with mi3, add a new command -mi-version that prints the MI
25786 The best way to avoid unexpected changes in MI that might break your front
25787 end is to make your project known to @value{GDBN} developers and
25788 follow development on @email{gdb@@sourceware.org} and
25789 @email{gdb-patches@@sourceware.org}.
25790 @cindex mailing lists
25792 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25793 @node GDB/MI Output Records
25794 @section @sc{gdb/mi} Output Records
25797 * GDB/MI Result Records::
25798 * GDB/MI Stream Records::
25799 * GDB/MI Async Records::
25800 * GDB/MI Breakpoint Information::
25801 * GDB/MI Frame Information::
25802 * GDB/MI Thread Information::
25803 * GDB/MI Ada Exception Information::
25806 @node GDB/MI Result Records
25807 @subsection @sc{gdb/mi} Result Records
25809 @cindex result records in @sc{gdb/mi}
25810 @cindex @sc{gdb/mi}, result records
25811 In addition to a number of out-of-band notifications, the response to a
25812 @sc{gdb/mi} command includes one of the following result indications:
25816 @item "^done" [ "," @var{results} ]
25817 The synchronous operation was successful, @code{@var{results}} are the return
25822 This result record is equivalent to @samp{^done}. Historically, it
25823 was output instead of @samp{^done} if the command has resumed the
25824 target. This behaviour is maintained for backward compatibility, but
25825 all frontends should treat @samp{^done} and @samp{^running}
25826 identically and rely on the @samp{*running} output record to determine
25827 which threads are resumed.
25831 @value{GDBN} has connected to a remote target.
25833 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
25835 The operation failed. The @code{msg=@var{c-string}} variable contains
25836 the corresponding error message.
25838 If present, the @code{code=@var{c-string}} variable provides an error
25839 code on which consumers can rely on to detect the corresponding
25840 error condition. At present, only one error code is defined:
25843 @item "undefined-command"
25844 Indicates that the command causing the error does not exist.
25849 @value{GDBN} has terminated.
25853 @node GDB/MI Stream Records
25854 @subsection @sc{gdb/mi} Stream Records
25856 @cindex @sc{gdb/mi}, stream records
25857 @cindex stream records in @sc{gdb/mi}
25858 @value{GDBN} internally maintains a number of output streams: the console, the
25859 target, and the log. The output intended for each of these streams is
25860 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
25862 Each stream record begins with a unique @dfn{prefix character} which
25863 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
25864 Syntax}). In addition to the prefix, each stream record contains a
25865 @code{@var{string-output}}. This is either raw text (with an implicit new
25866 line) or a quoted C string (which does not contain an implicit newline).
25869 @item "~" @var{string-output}
25870 The console output stream contains text that should be displayed in the
25871 CLI console window. It contains the textual responses to CLI commands.
25873 @item "@@" @var{string-output}
25874 The target output stream contains any textual output from the running
25875 target. This is only present when GDB's event loop is truly
25876 asynchronous, which is currently only the case for remote targets.
25878 @item "&" @var{string-output}
25879 The log stream contains debugging messages being produced by @value{GDBN}'s
25883 @node GDB/MI Async Records
25884 @subsection @sc{gdb/mi} Async Records
25886 @cindex async records in @sc{gdb/mi}
25887 @cindex @sc{gdb/mi}, async records
25888 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
25889 additional changes that have occurred. Those changes can either be a
25890 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
25891 target activity (e.g., target stopped).
25893 The following is the list of possible async records:
25897 @item *running,thread-id="@var{thread}"
25898 The target is now running. The @var{thread} field tells which
25899 specific thread is now running, and can be @samp{all} if all threads
25900 are running. The frontend should assume that no interaction with a
25901 running thread is possible after this notification is produced.
25902 The frontend should not assume that this notification is output
25903 only once for any command. @value{GDBN} may emit this notification
25904 several times, either for different threads, because it cannot resume
25905 all threads together, or even for a single thread, if the thread must
25906 be stepped though some code before letting it run freely.
25908 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
25909 The target has stopped. The @var{reason} field can have one of the
25913 @item breakpoint-hit
25914 A breakpoint was reached.
25915 @item watchpoint-trigger
25916 A watchpoint was triggered.
25917 @item read-watchpoint-trigger
25918 A read watchpoint was triggered.
25919 @item access-watchpoint-trigger
25920 An access watchpoint was triggered.
25921 @item function-finished
25922 An -exec-finish or similar CLI command was accomplished.
25923 @item location-reached
25924 An -exec-until or similar CLI command was accomplished.
25925 @item watchpoint-scope
25926 A watchpoint has gone out of scope.
25927 @item end-stepping-range
25928 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
25929 similar CLI command was accomplished.
25930 @item exited-signalled
25931 The inferior exited because of a signal.
25933 The inferior exited.
25934 @item exited-normally
25935 The inferior exited normally.
25936 @item signal-received
25937 A signal was received by the inferior.
25939 The inferior has stopped due to a library being loaded or unloaded.
25940 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
25941 set or when a @code{catch load} or @code{catch unload} catchpoint is
25942 in use (@pxref{Set Catchpoints}).
25944 The inferior has forked. This is reported when @code{catch fork}
25945 (@pxref{Set Catchpoints}) has been used.
25947 The inferior has vforked. This is reported in when @code{catch vfork}
25948 (@pxref{Set Catchpoints}) has been used.
25949 @item syscall-entry
25950 The inferior entered a system call. This is reported when @code{catch
25951 syscall} (@pxref{Set Catchpoints}) has been used.
25952 @item syscall-return
25953 The inferior returned from a system call. This is reported when
25954 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
25956 The inferior called @code{exec}. This is reported when @code{catch exec}
25957 (@pxref{Set Catchpoints}) has been used.
25960 The @var{id} field identifies the thread that directly caused the stop
25961 -- for example by hitting a breakpoint. Depending on whether all-stop
25962 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
25963 stop all threads, or only the thread that directly triggered the stop.
25964 If all threads are stopped, the @var{stopped} field will have the
25965 value of @code{"all"}. Otherwise, the value of the @var{stopped}
25966 field will be a list of thread identifiers. Presently, this list will
25967 always include a single thread, but frontend should be prepared to see
25968 several threads in the list. The @var{core} field reports the
25969 processor core on which the stop event has happened. This field may be absent
25970 if such information is not available.
25972 @item =thread-group-added,id="@var{id}"
25973 @itemx =thread-group-removed,id="@var{id}"
25974 A thread group was either added or removed. The @var{id} field
25975 contains the @value{GDBN} identifier of the thread group. When a thread
25976 group is added, it generally might not be associated with a running
25977 process. When a thread group is removed, its id becomes invalid and
25978 cannot be used in any way.
25980 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
25981 A thread group became associated with a running program,
25982 either because the program was just started or the thread group
25983 was attached to a program. The @var{id} field contains the
25984 @value{GDBN} identifier of the thread group. The @var{pid} field
25985 contains process identifier, specific to the operating system.
25987 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
25988 A thread group is no longer associated with a running program,
25989 either because the program has exited, or because it was detached
25990 from. The @var{id} field contains the @value{GDBN} identifier of the
25991 thread group. The @var{code} field is the exit code of the inferior; it exists
25992 only when the inferior exited with some code.
25994 @item =thread-created,id="@var{id}",group-id="@var{gid}"
25995 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
25996 A thread either was created, or has exited. The @var{id} field
25997 contains the @value{GDBN} identifier of the thread. The @var{gid}
25998 field identifies the thread group this thread belongs to.
26000 @item =thread-selected,id="@var{id}"
26001 Informs that the selected thread was changed as result of the last
26002 command. This notification is not emitted as result of @code{-thread-select}
26003 command but is emitted whenever an MI command that is not documented
26004 to change the selected thread actually changes it. In particular,
26005 invoking, directly or indirectly (via user-defined command), the CLI
26006 @code{thread} command, will generate this notification.
26008 We suggest that in response to this notification, front ends
26009 highlight the selected thread and cause subsequent commands to apply to
26012 @item =library-loaded,...
26013 Reports that a new library file was loaded by the program. This
26014 notification has 4 fields---@var{id}, @var{target-name},
26015 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
26016 opaque identifier of the library. For remote debugging case,
26017 @var{target-name} and @var{host-name} fields give the name of the
26018 library file on the target, and on the host respectively. For native
26019 debugging, both those fields have the same value. The
26020 @var{symbols-loaded} field is emitted only for backward compatibility
26021 and should not be relied on to convey any useful information. The
26022 @var{thread-group} field, if present, specifies the id of the thread
26023 group in whose context the library was loaded. If the field is
26024 absent, it means the library was loaded in the context of all present
26027 @item =library-unloaded,...
26028 Reports that a library was unloaded by the program. This notification
26029 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
26030 the same meaning as for the @code{=library-loaded} notification.
26031 The @var{thread-group} field, if present, specifies the id of the
26032 thread group in whose context the library was unloaded. If the field is
26033 absent, it means the library was unloaded in the context of all present
26036 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
26037 @itemx =traceframe-changed,end
26038 Reports that the trace frame was changed and its new number is
26039 @var{tfnum}. The number of the tracepoint associated with this trace
26040 frame is @var{tpnum}.
26042 @item =tsv-created,name=@var{name},initial=@var{initial}
26043 Reports that the new trace state variable @var{name} is created with
26044 initial value @var{initial}.
26046 @item =tsv-deleted,name=@var{name}
26047 @itemx =tsv-deleted
26048 Reports that the trace state variable @var{name} is deleted or all
26049 trace state variables are deleted.
26051 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
26052 Reports that the trace state variable @var{name} is modified with
26053 the initial value @var{initial}. The current value @var{current} of
26054 trace state variable is optional and is reported if the current
26055 value of trace state variable is known.
26057 @item =breakpoint-created,bkpt=@{...@}
26058 @itemx =breakpoint-modified,bkpt=@{...@}
26059 @itemx =breakpoint-deleted,id=@var{number}
26060 Reports that a breakpoint was created, modified, or deleted,
26061 respectively. Only user-visible breakpoints are reported to the MI
26064 The @var{bkpt} argument is of the same form as returned by the various
26065 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
26066 @var{number} is the ordinal number of the breakpoint.
26068 Note that if a breakpoint is emitted in the result record of a
26069 command, then it will not also be emitted in an async record.
26071 @item =record-started,thread-group="@var{id}"
26072 @itemx =record-stopped,thread-group="@var{id}"
26073 Execution log recording was either started or stopped on an
26074 inferior. The @var{id} is the @value{GDBN} identifier of the thread
26075 group corresponding to the affected inferior.
26077 @item =cmd-param-changed,param=@var{param},value=@var{value}
26078 Reports that a parameter of the command @code{set @var{param}} is
26079 changed to @var{value}. In the multi-word @code{set} command,
26080 the @var{param} is the whole parameter list to @code{set} command.
26081 For example, In command @code{set check type on}, @var{param}
26082 is @code{check type} and @var{value} is @code{on}.
26084 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
26085 Reports that bytes from @var{addr} to @var{data} + @var{len} were
26086 written in an inferior. The @var{id} is the identifier of the
26087 thread group corresponding to the affected inferior. The optional
26088 @code{type="code"} part is reported if the memory written to holds
26092 @node GDB/MI Breakpoint Information
26093 @subsection @sc{gdb/mi} Breakpoint Information
26095 When @value{GDBN} reports information about a breakpoint, a
26096 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
26101 The breakpoint number. For a breakpoint that represents one location
26102 of a multi-location breakpoint, this will be a dotted pair, like
26106 The type of the breakpoint. For ordinary breakpoints this will be
26107 @samp{breakpoint}, but many values are possible.
26110 If the type of the breakpoint is @samp{catchpoint}, then this
26111 indicates the exact type of catchpoint.
26114 This is the breakpoint disposition---either @samp{del}, meaning that
26115 the breakpoint will be deleted at the next stop, or @samp{keep},
26116 meaning that the breakpoint will not be deleted.
26119 This indicates whether the breakpoint is enabled, in which case the
26120 value is @samp{y}, or disabled, in which case the value is @samp{n}.
26121 Note that this is not the same as the field @code{enable}.
26124 The address of the breakpoint. This may be a hexidecimal number,
26125 giving the address; or the string @samp{<PENDING>}, for a pending
26126 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
26127 multiple locations. This field will not be present if no address can
26128 be determined. For example, a watchpoint does not have an address.
26131 If known, the function in which the breakpoint appears.
26132 If not known, this field is not present.
26135 The name of the source file which contains this function, if known.
26136 If not known, this field is not present.
26139 The full file name of the source file which contains this function, if
26140 known. If not known, this field is not present.
26143 The line number at which this breakpoint appears, if known.
26144 If not known, this field is not present.
26147 If the source file is not known, this field may be provided. If
26148 provided, this holds the address of the breakpoint, possibly followed
26152 If this breakpoint is pending, this field is present and holds the
26153 text used to set the breakpoint, as entered by the user.
26156 Where this breakpoint's condition is evaluated, either @samp{host} or
26160 If this is a thread-specific breakpoint, then this identifies the
26161 thread in which the breakpoint can trigger.
26164 If this breakpoint is restricted to a particular Ada task, then this
26165 field will hold the task identifier.
26168 If the breakpoint is conditional, this is the condition expression.
26171 The ignore count of the breakpoint.
26174 The enable count of the breakpoint.
26176 @item traceframe-usage
26179 @item static-tracepoint-marker-string-id
26180 For a static tracepoint, the name of the static tracepoint marker.
26183 For a masked watchpoint, this is the mask.
26186 A tracepoint's pass count.
26188 @item original-location
26189 The location of the breakpoint as originally specified by the user.
26190 This field is optional.
26193 The number of times the breakpoint has been hit.
26196 This field is only given for tracepoints. This is either @samp{y},
26197 meaning that the tracepoint is installed, or @samp{n}, meaning that it
26201 Some extra data, the exact contents of which are type-dependent.
26205 For example, here is what the output of @code{-break-insert}
26206 (@pxref{GDB/MI Breakpoint Commands}) might be:
26209 -> -break-insert main
26210 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26211 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26212 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26217 @node GDB/MI Frame Information
26218 @subsection @sc{gdb/mi} Frame Information
26220 Response from many MI commands includes an information about stack
26221 frame. This information is a tuple that may have the following
26226 The level of the stack frame. The innermost frame has the level of
26227 zero. This field is always present.
26230 The name of the function corresponding to the frame. This field may
26231 be absent if @value{GDBN} is unable to determine the function name.
26234 The code address for the frame. This field is always present.
26237 The name of the source files that correspond to the frame's code
26238 address. This field may be absent.
26241 The source line corresponding to the frames' code address. This field
26245 The name of the binary file (either executable or shared library) the
26246 corresponds to the frame's code address. This field may be absent.
26250 @node GDB/MI Thread Information
26251 @subsection @sc{gdb/mi} Thread Information
26253 Whenever @value{GDBN} has to report an information about a thread, it
26254 uses a tuple with the following fields:
26258 The numeric id assigned to the thread by @value{GDBN}. This field is
26262 Target-specific string identifying the thread. This field is always present.
26265 Additional information about the thread provided by the target.
26266 It is supposed to be human-readable and not interpreted by the
26267 frontend. This field is optional.
26270 Either @samp{stopped} or @samp{running}, depending on whether the
26271 thread is presently running. This field is always present.
26274 The value of this field is an integer number of the processor core the
26275 thread was last seen on. This field is optional.
26278 @node GDB/MI Ada Exception Information
26279 @subsection @sc{gdb/mi} Ada Exception Information
26281 Whenever a @code{*stopped} record is emitted because the program
26282 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
26283 @value{GDBN} provides the name of the exception that was raised via
26284 the @code{exception-name} field.
26286 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26287 @node GDB/MI Simple Examples
26288 @section Simple Examples of @sc{gdb/mi} Interaction
26289 @cindex @sc{gdb/mi}, simple examples
26291 This subsection presents several simple examples of interaction using
26292 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
26293 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
26294 the output received from @sc{gdb/mi}.
26296 Note the line breaks shown in the examples are here only for
26297 readability, they don't appear in the real output.
26299 @subheading Setting a Breakpoint
26301 Setting a breakpoint generates synchronous output which contains detailed
26302 information of the breakpoint.
26305 -> -break-insert main
26306 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26307 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26308 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26313 @subheading Program Execution
26315 Program execution generates asynchronous records and MI gives the
26316 reason that execution stopped.
26322 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
26323 frame=@{addr="0x08048564",func="main",
26324 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
26325 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
26330 <- *stopped,reason="exited-normally"
26334 @subheading Quitting @value{GDBN}
26336 Quitting @value{GDBN} just prints the result class @samp{^exit}.
26344 Please note that @samp{^exit} is printed immediately, but it might
26345 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
26346 performs necessary cleanups, including killing programs being debugged
26347 or disconnecting from debug hardware, so the frontend should wait till
26348 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
26349 fails to exit in reasonable time.
26351 @subheading A Bad Command
26353 Here's what happens if you pass a non-existent command:
26357 <- ^error,msg="Undefined MI command: rubbish"
26362 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26363 @node GDB/MI Command Description Format
26364 @section @sc{gdb/mi} Command Description Format
26366 The remaining sections describe blocks of commands. Each block of
26367 commands is laid out in a fashion similar to this section.
26369 @subheading Motivation
26371 The motivation for this collection of commands.
26373 @subheading Introduction
26375 A brief introduction to this collection of commands as a whole.
26377 @subheading Commands
26379 For each command in the block, the following is described:
26381 @subsubheading Synopsis
26384 -command @var{args}@dots{}
26387 @subsubheading Result
26389 @subsubheading @value{GDBN} Command
26391 The corresponding @value{GDBN} CLI command(s), if any.
26393 @subsubheading Example
26395 Example(s) formatted for readability. Some of the described commands have
26396 not been implemented yet and these are labeled N.A.@: (not available).
26399 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26400 @node GDB/MI Breakpoint Commands
26401 @section @sc{gdb/mi} Breakpoint Commands
26403 @cindex breakpoint commands for @sc{gdb/mi}
26404 @cindex @sc{gdb/mi}, breakpoint commands
26405 This section documents @sc{gdb/mi} commands for manipulating
26408 @subheading The @code{-break-after} Command
26409 @findex -break-after
26411 @subsubheading Synopsis
26414 -break-after @var{number} @var{count}
26417 The breakpoint number @var{number} is not in effect until it has been
26418 hit @var{count} times. To see how this is reflected in the output of
26419 the @samp{-break-list} command, see the description of the
26420 @samp{-break-list} command below.
26422 @subsubheading @value{GDBN} Command
26424 The corresponding @value{GDBN} command is @samp{ignore}.
26426 @subsubheading Example
26431 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26432 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26433 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26441 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26442 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26443 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26444 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26445 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26446 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26447 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26448 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26449 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26450 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
26455 @subheading The @code{-break-catch} Command
26456 @findex -break-catch
26459 @subheading The @code{-break-commands} Command
26460 @findex -break-commands
26462 @subsubheading Synopsis
26465 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
26468 Specifies the CLI commands that should be executed when breakpoint
26469 @var{number} is hit. The parameters @var{command1} to @var{commandN}
26470 are the commands. If no command is specified, any previously-set
26471 commands are cleared. @xref{Break Commands}. Typical use of this
26472 functionality is tracing a program, that is, printing of values of
26473 some variables whenever breakpoint is hit and then continuing.
26475 @subsubheading @value{GDBN} Command
26477 The corresponding @value{GDBN} command is @samp{commands}.
26479 @subsubheading Example
26484 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26485 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26486 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26489 -break-commands 1 "print v" "continue"
26494 @subheading The @code{-break-condition} Command
26495 @findex -break-condition
26497 @subsubheading Synopsis
26500 -break-condition @var{number} @var{expr}
26503 Breakpoint @var{number} will stop the program only if the condition in
26504 @var{expr} is true. The condition becomes part of the
26505 @samp{-break-list} output (see the description of the @samp{-break-list}
26508 @subsubheading @value{GDBN} Command
26510 The corresponding @value{GDBN} command is @samp{condition}.
26512 @subsubheading Example
26516 -break-condition 1 1
26520 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26521 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26522 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26523 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26524 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26525 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26526 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26527 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26528 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26529 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
26533 @subheading The @code{-break-delete} Command
26534 @findex -break-delete
26536 @subsubheading Synopsis
26539 -break-delete ( @var{breakpoint} )+
26542 Delete the breakpoint(s) whose number(s) are specified in the argument
26543 list. This is obviously reflected in the breakpoint list.
26545 @subsubheading @value{GDBN} Command
26547 The corresponding @value{GDBN} command is @samp{delete}.
26549 @subsubheading Example
26557 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26558 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26559 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26560 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26561 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26562 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26563 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26568 @subheading The @code{-break-disable} Command
26569 @findex -break-disable
26571 @subsubheading Synopsis
26574 -break-disable ( @var{breakpoint} )+
26577 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
26578 break list is now set to @samp{n} for the named @var{breakpoint}(s).
26580 @subsubheading @value{GDBN} Command
26582 The corresponding @value{GDBN} command is @samp{disable}.
26584 @subsubheading Example
26592 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26593 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26594 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26595 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26596 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26597 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26598 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26599 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
26600 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26601 line="5",thread-groups=["i1"],times="0"@}]@}
26605 @subheading The @code{-break-enable} Command
26606 @findex -break-enable
26608 @subsubheading Synopsis
26611 -break-enable ( @var{breakpoint} )+
26614 Enable (previously disabled) @var{breakpoint}(s).
26616 @subsubheading @value{GDBN} Command
26618 The corresponding @value{GDBN} command is @samp{enable}.
26620 @subsubheading Example
26628 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26629 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26630 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26631 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26632 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26633 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26634 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26635 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26636 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26637 line="5",thread-groups=["i1"],times="0"@}]@}
26641 @subheading The @code{-break-info} Command
26642 @findex -break-info
26644 @subsubheading Synopsis
26647 -break-info @var{breakpoint}
26651 Get information about a single breakpoint.
26653 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
26654 Information}, for details on the format of each breakpoint in the
26657 @subsubheading @value{GDBN} Command
26659 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
26661 @subsubheading Example
26664 @subheading The @code{-break-insert} Command
26665 @findex -break-insert
26666 @anchor{-break-insert}
26668 @subsubheading Synopsis
26671 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
26672 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26673 [ -p @var{thread-id} ] [ @var{location} ]
26677 If specified, @var{location}, can be one of:
26680 @item linespec location
26681 A linespec location. @xref{Linespec Locations}.
26683 @item explicit location
26684 An explicit location. @sc{gdb/mi} explicit locations are
26685 analogous to the CLI's explicit locations using the option names
26686 listed below. @xref{Explicit Locations}.
26689 @item --source @var{filename}
26690 The source file name of the location. This option requires the use
26691 of either @samp{--function} or @samp{--line}.
26693 @item --function @var{function}
26694 The name of a function or method.
26696 @item --label @var{label}
26697 The name of a label.
26699 @item --line @var{lineoffset}
26700 An absolute or relative line offset from the start of the location.
26703 @item address location
26704 An address location, *@var{address}. @xref{Address Locations}.
26708 The possible optional parameters of this command are:
26712 Insert a temporary breakpoint.
26714 Insert a hardware breakpoint.
26716 If @var{location} cannot be parsed (for example if it
26717 refers to unknown files or functions), create a pending
26718 breakpoint. Without this flag, @value{GDBN} will report
26719 an error, and won't create a breakpoint, if @var{location}
26722 Create a disabled breakpoint.
26724 Create a tracepoint. @xref{Tracepoints}. When this parameter
26725 is used together with @samp{-h}, a fast tracepoint is created.
26726 @item -c @var{condition}
26727 Make the breakpoint conditional on @var{condition}.
26728 @item -i @var{ignore-count}
26729 Initialize the @var{ignore-count}.
26730 @item -p @var{thread-id}
26731 Restrict the breakpoint to the specified @var{thread-id}.
26734 @subsubheading Result
26736 @xref{GDB/MI Breakpoint Information}, for details on the format of the
26737 resulting breakpoint.
26739 Note: this format is open to change.
26740 @c An out-of-band breakpoint instead of part of the result?
26742 @subsubheading @value{GDBN} Command
26744 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
26745 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
26747 @subsubheading Example
26752 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
26753 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
26756 -break-insert -t foo
26757 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
26758 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
26762 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26763 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26764 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26765 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26766 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26767 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26768 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26769 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26770 addr="0x0001072c", func="main",file="recursive2.c",
26771 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
26773 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
26774 addr="0x00010774",func="foo",file="recursive2.c",
26775 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
26778 @c -break-insert -r foo.*
26779 @c ~int foo(int, int);
26780 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
26781 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
26786 @subheading The @code{-dprintf-insert} Command
26787 @findex -dprintf-insert
26789 @subsubheading Synopsis
26792 -dprintf-insert [ -t ] [ -f ] [ -d ]
26793 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26794 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
26799 If supplied, @var{location} may be specified the same way as for
26800 the @code{-break-insert} command. @xref{-break-insert}.
26802 The possible optional parameters of this command are:
26806 Insert a temporary breakpoint.
26808 If @var{location} cannot be parsed (for example, if it
26809 refers to unknown files or functions), create a pending
26810 breakpoint. Without this flag, @value{GDBN} will report
26811 an error, and won't create a breakpoint, if @var{location}
26814 Create a disabled breakpoint.
26815 @item -c @var{condition}
26816 Make the breakpoint conditional on @var{condition}.
26817 @item -i @var{ignore-count}
26818 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
26819 to @var{ignore-count}.
26820 @item -p @var{thread-id}
26821 Restrict the breakpoint to the specified @var{thread-id}.
26824 @subsubheading Result
26826 @xref{GDB/MI Breakpoint Information}, for details on the format of the
26827 resulting breakpoint.
26829 @c An out-of-band breakpoint instead of part of the result?
26831 @subsubheading @value{GDBN} Command
26833 The corresponding @value{GDBN} command is @samp{dprintf}.
26835 @subsubheading Example
26839 4-dprintf-insert foo "At foo entry\n"
26840 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
26841 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
26842 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
26843 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
26844 original-location="foo"@}
26846 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
26847 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
26848 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
26849 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
26850 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
26851 original-location="mi-dprintf.c:26"@}
26855 @subheading The @code{-break-list} Command
26856 @findex -break-list
26858 @subsubheading Synopsis
26864 Displays the list of inserted breakpoints, showing the following fields:
26868 number of the breakpoint
26870 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
26872 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
26875 is the breakpoint enabled or no: @samp{y} or @samp{n}
26877 memory location at which the breakpoint is set
26879 logical location of the breakpoint, expressed by function name, file
26881 @item Thread-groups
26882 list of thread groups to which this breakpoint applies
26884 number of times the breakpoint has been hit
26887 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
26888 @code{body} field is an empty list.
26890 @subsubheading @value{GDBN} Command
26892 The corresponding @value{GDBN} command is @samp{info break}.
26894 @subsubheading Example
26899 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26900 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26901 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26902 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26903 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26904 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26905 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26906 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26907 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
26909 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26910 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
26911 line="13",thread-groups=["i1"],times="0"@}]@}
26915 Here's an example of the result when there are no breakpoints:
26920 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26921 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26922 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26923 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26924 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26925 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26926 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26931 @subheading The @code{-break-passcount} Command
26932 @findex -break-passcount
26934 @subsubheading Synopsis
26937 -break-passcount @var{tracepoint-number} @var{passcount}
26940 Set the passcount for tracepoint @var{tracepoint-number} to
26941 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
26942 is not a tracepoint, error is emitted. This corresponds to CLI
26943 command @samp{passcount}.
26945 @subheading The @code{-break-watch} Command
26946 @findex -break-watch
26948 @subsubheading Synopsis
26951 -break-watch [ -a | -r ]
26954 Create a watchpoint. With the @samp{-a} option it will create an
26955 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
26956 read from or on a write to the memory location. With the @samp{-r}
26957 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
26958 trigger only when the memory location is accessed for reading. Without
26959 either of the options, the watchpoint created is a regular watchpoint,
26960 i.e., it will trigger when the memory location is accessed for writing.
26961 @xref{Set Watchpoints, , Setting Watchpoints}.
26963 Note that @samp{-break-list} will report a single list of watchpoints and
26964 breakpoints inserted.
26966 @subsubheading @value{GDBN} Command
26968 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
26971 @subsubheading Example
26973 Setting a watchpoint on a variable in the @code{main} function:
26978 ^done,wpt=@{number="2",exp="x"@}
26983 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
26984 value=@{old="-268439212",new="55"@},
26985 frame=@{func="main",args=[],file="recursive2.c",
26986 fullname="/home/foo/bar/recursive2.c",line="5"@}
26990 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
26991 the program execution twice: first for the variable changing value, then
26992 for the watchpoint going out of scope.
26997 ^done,wpt=@{number="5",exp="C"@}
27002 *stopped,reason="watchpoint-trigger",
27003 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
27004 frame=@{func="callee4",args=[],
27005 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27006 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27011 *stopped,reason="watchpoint-scope",wpnum="5",
27012 frame=@{func="callee3",args=[@{name="strarg",
27013 value="0x11940 \"A string argument.\""@}],
27014 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27015 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27019 Listing breakpoints and watchpoints, at different points in the program
27020 execution. Note that once the watchpoint goes out of scope, it is
27026 ^done,wpt=@{number="2",exp="C"@}
27029 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27030 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27031 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27032 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27033 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27034 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27035 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27036 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27037 addr="0x00010734",func="callee4",
27038 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27039 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
27041 bkpt=@{number="2",type="watchpoint",disp="keep",
27042 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
27047 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
27048 value=@{old="-276895068",new="3"@},
27049 frame=@{func="callee4",args=[],
27050 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27051 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27054 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27055 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27056 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27057 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27058 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27059 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27060 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27061 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27062 addr="0x00010734",func="callee4",
27063 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27064 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
27066 bkpt=@{number="2",type="watchpoint",disp="keep",
27067 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
27071 ^done,reason="watchpoint-scope",wpnum="2",
27072 frame=@{func="callee3",args=[@{name="strarg",
27073 value="0x11940 \"A string argument.\""@}],
27074 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27075 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27078 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27079 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27080 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27081 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27082 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27083 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27084 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27085 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27086 addr="0x00010734",func="callee4",
27087 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27088 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
27089 thread-groups=["i1"],times="1"@}]@}
27094 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27095 @node GDB/MI Catchpoint Commands
27096 @section @sc{gdb/mi} Catchpoint Commands
27098 This section documents @sc{gdb/mi} commands for manipulating
27102 * Shared Library GDB/MI Catchpoint Commands::
27103 * Ada Exception GDB/MI Catchpoint Commands::
27106 @node Shared Library GDB/MI Catchpoint Commands
27107 @subsection Shared Library @sc{gdb/mi} Catchpoints
27109 @subheading The @code{-catch-load} Command
27110 @findex -catch-load
27112 @subsubheading Synopsis
27115 -catch-load [ -t ] [ -d ] @var{regexp}
27118 Add a catchpoint for library load events. If the @samp{-t} option is used,
27119 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27120 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
27121 in a disabled state. The @samp{regexp} argument is a regular
27122 expression used to match the name of the loaded library.
27125 @subsubheading @value{GDBN} Command
27127 The corresponding @value{GDBN} command is @samp{catch load}.
27129 @subsubheading Example
27132 -catch-load -t foo.so
27133 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
27134 what="load of library matching foo.so",catch-type="load",times="0"@}
27139 @subheading The @code{-catch-unload} Command
27140 @findex -catch-unload
27142 @subsubheading Synopsis
27145 -catch-unload [ -t ] [ -d ] @var{regexp}
27148 Add a catchpoint for library unload events. If the @samp{-t} option is
27149 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27150 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
27151 created in a disabled state. The @samp{regexp} argument is a regular
27152 expression used to match the name of the unloaded library.
27154 @subsubheading @value{GDBN} Command
27156 The corresponding @value{GDBN} command is @samp{catch unload}.
27158 @subsubheading Example
27161 -catch-unload -d bar.so
27162 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
27163 what="load of library matching bar.so",catch-type="unload",times="0"@}
27167 @node Ada Exception GDB/MI Catchpoint Commands
27168 @subsection Ada Exception @sc{gdb/mi} Catchpoints
27170 The following @sc{gdb/mi} commands can be used to create catchpoints
27171 that stop the execution when Ada exceptions are being raised.
27173 @subheading The @code{-catch-assert} Command
27174 @findex -catch-assert
27176 @subsubheading Synopsis
27179 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
27182 Add a catchpoint for failed Ada assertions.
27184 The possible optional parameters for this command are:
27187 @item -c @var{condition}
27188 Make the catchpoint conditional on @var{condition}.
27190 Create a disabled catchpoint.
27192 Create a temporary catchpoint.
27195 @subsubheading @value{GDBN} Command
27197 The corresponding @value{GDBN} command is @samp{catch assert}.
27199 @subsubheading Example
27203 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
27204 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
27205 thread-groups=["i1"],times="0",
27206 original-location="__gnat_debug_raise_assert_failure"@}
27210 @subheading The @code{-catch-exception} Command
27211 @findex -catch-exception
27213 @subsubheading Synopsis
27216 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
27220 Add a catchpoint stopping when Ada exceptions are raised.
27221 By default, the command stops the program when any Ada exception
27222 gets raised. But it is also possible, by using some of the
27223 optional parameters described below, to create more selective
27226 The possible optional parameters for this command are:
27229 @item -c @var{condition}
27230 Make the catchpoint conditional on @var{condition}.
27232 Create a disabled catchpoint.
27233 @item -e @var{exception-name}
27234 Only stop when @var{exception-name} is raised. This option cannot
27235 be used combined with @samp{-u}.
27237 Create a temporary catchpoint.
27239 Stop only when an unhandled exception gets raised. This option
27240 cannot be used combined with @samp{-e}.
27243 @subsubheading @value{GDBN} Command
27245 The corresponding @value{GDBN} commands are @samp{catch exception}
27246 and @samp{catch exception unhandled}.
27248 @subsubheading Example
27251 -catch-exception -e Program_Error
27252 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
27253 enabled="y",addr="0x0000000000404874",
27254 what="`Program_Error' Ada exception", thread-groups=["i1"],
27255 times="0",original-location="__gnat_debug_raise_exception"@}
27259 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27260 @node GDB/MI Program Context
27261 @section @sc{gdb/mi} Program Context
27263 @subheading The @code{-exec-arguments} Command
27264 @findex -exec-arguments
27267 @subsubheading Synopsis
27270 -exec-arguments @var{args}
27273 Set the inferior program arguments, to be used in the next
27276 @subsubheading @value{GDBN} Command
27278 The corresponding @value{GDBN} command is @samp{set args}.
27280 @subsubheading Example
27284 -exec-arguments -v word
27291 @subheading The @code{-exec-show-arguments} Command
27292 @findex -exec-show-arguments
27294 @subsubheading Synopsis
27297 -exec-show-arguments
27300 Print the arguments of the program.
27302 @subsubheading @value{GDBN} Command
27304 The corresponding @value{GDBN} command is @samp{show args}.
27306 @subsubheading Example
27311 @subheading The @code{-environment-cd} Command
27312 @findex -environment-cd
27314 @subsubheading Synopsis
27317 -environment-cd @var{pathdir}
27320 Set @value{GDBN}'s working directory.
27322 @subsubheading @value{GDBN} Command
27324 The corresponding @value{GDBN} command is @samp{cd}.
27326 @subsubheading Example
27330 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27336 @subheading The @code{-environment-directory} Command
27337 @findex -environment-directory
27339 @subsubheading Synopsis
27342 -environment-directory [ -r ] [ @var{pathdir} ]+
27345 Add directories @var{pathdir} to beginning of search path for source files.
27346 If the @samp{-r} option is used, the search path is reset to the default
27347 search path. If directories @var{pathdir} are supplied in addition to the
27348 @samp{-r} option, the search path is first reset and then addition
27350 Multiple directories may be specified, separated by blanks. Specifying
27351 multiple directories in a single command
27352 results in the directories added to the beginning of the
27353 search path in the same order they were presented in the command.
27354 If blanks are needed as
27355 part of a directory name, double-quotes should be used around
27356 the name. In the command output, the path will show up separated
27357 by the system directory-separator character. The directory-separator
27358 character must not be used
27359 in any directory name.
27360 If no directories are specified, the current search path is displayed.
27362 @subsubheading @value{GDBN} Command
27364 The corresponding @value{GDBN} command is @samp{dir}.
27366 @subsubheading Example
27370 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27371 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27373 -environment-directory ""
27374 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27376 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
27377 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
27379 -environment-directory -r
27380 ^done,source-path="$cdir:$cwd"
27385 @subheading The @code{-environment-path} Command
27386 @findex -environment-path
27388 @subsubheading Synopsis
27391 -environment-path [ -r ] [ @var{pathdir} ]+
27394 Add directories @var{pathdir} to beginning of search path for object files.
27395 If the @samp{-r} option is used, the search path is reset to the original
27396 search path that existed at gdb start-up. If directories @var{pathdir} are
27397 supplied in addition to the
27398 @samp{-r} option, the search path is first reset and then addition
27400 Multiple directories may be specified, separated by blanks. Specifying
27401 multiple directories in a single command
27402 results in the directories added to the beginning of the
27403 search path in the same order they were presented in the command.
27404 If blanks are needed as
27405 part of a directory name, double-quotes should be used around
27406 the name. In the command output, the path will show up separated
27407 by the system directory-separator character. The directory-separator
27408 character must not be used
27409 in any directory name.
27410 If no directories are specified, the current path is displayed.
27413 @subsubheading @value{GDBN} Command
27415 The corresponding @value{GDBN} command is @samp{path}.
27417 @subsubheading Example
27422 ^done,path="/usr/bin"
27424 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
27425 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
27427 -environment-path -r /usr/local/bin
27428 ^done,path="/usr/local/bin:/usr/bin"
27433 @subheading The @code{-environment-pwd} Command
27434 @findex -environment-pwd
27436 @subsubheading Synopsis
27442 Show the current working directory.
27444 @subsubheading @value{GDBN} Command
27446 The corresponding @value{GDBN} command is @samp{pwd}.
27448 @subsubheading Example
27453 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
27457 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27458 @node GDB/MI Thread Commands
27459 @section @sc{gdb/mi} Thread Commands
27462 @subheading The @code{-thread-info} Command
27463 @findex -thread-info
27465 @subsubheading Synopsis
27468 -thread-info [ @var{thread-id} ]
27471 Reports information about either a specific thread, if
27472 the @var{thread-id} parameter is present, or about all
27473 threads. When printing information about all threads,
27474 also reports the current thread.
27476 @subsubheading @value{GDBN} Command
27478 The @samp{info thread} command prints the same information
27481 @subsubheading Result
27483 The result is a list of threads. The following attributes are
27484 defined for a given thread:
27488 This field exists only for the current thread. It has the value @samp{*}.
27491 The identifier that @value{GDBN} uses to refer to the thread.
27494 The identifier that the target uses to refer to the thread.
27497 Extra information about the thread, in a target-specific format. This
27501 The name of the thread. If the user specified a name using the
27502 @code{thread name} command, then this name is given. Otherwise, if
27503 @value{GDBN} can extract the thread name from the target, then that
27504 name is given. If @value{GDBN} cannot find the thread name, then this
27508 The stack frame currently executing in the thread.
27511 The thread's state. The @samp{state} field may have the following
27516 The thread is stopped. Frame information is available for stopped
27520 The thread is running. There's no frame information for running
27526 If @value{GDBN} can find the CPU core on which this thread is running,
27527 then this field is the core identifier. This field is optional.
27531 @subsubheading Example
27536 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
27537 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
27538 args=[]@},state="running"@},
27539 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
27540 frame=@{level="0",addr="0x0804891f",func="foo",
27541 args=[@{name="i",value="10"@}],
27542 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
27543 state="running"@}],
27544 current-thread-id="1"
27548 @subheading The @code{-thread-list-ids} Command
27549 @findex -thread-list-ids
27551 @subsubheading Synopsis
27557 Produces a list of the currently known @value{GDBN} thread ids. At the
27558 end of the list it also prints the total number of such threads.
27560 This command is retained for historical reasons, the
27561 @code{-thread-info} command should be used instead.
27563 @subsubheading @value{GDBN} Command
27565 Part of @samp{info threads} supplies the same information.
27567 @subsubheading Example
27572 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27573 current-thread-id="1",number-of-threads="3"
27578 @subheading The @code{-thread-select} Command
27579 @findex -thread-select
27581 @subsubheading Synopsis
27584 -thread-select @var{threadnum}
27587 Make @var{threadnum} the current thread. It prints the number of the new
27588 current thread, and the topmost frame for that thread.
27590 This command is deprecated in favor of explicitly using the
27591 @samp{--thread} option to each command.
27593 @subsubheading @value{GDBN} Command
27595 The corresponding @value{GDBN} command is @samp{thread}.
27597 @subsubheading Example
27604 *stopped,reason="end-stepping-range",thread-id="2",line="187",
27605 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
27609 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27610 number-of-threads="3"
27613 ^done,new-thread-id="3",
27614 frame=@{level="0",func="vprintf",
27615 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
27616 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
27620 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27621 @node GDB/MI Ada Tasking Commands
27622 @section @sc{gdb/mi} Ada Tasking Commands
27624 @subheading The @code{-ada-task-info} Command
27625 @findex -ada-task-info
27627 @subsubheading Synopsis
27630 -ada-task-info [ @var{task-id} ]
27633 Reports information about either a specific Ada task, if the
27634 @var{task-id} parameter is present, or about all Ada tasks.
27636 @subsubheading @value{GDBN} Command
27638 The @samp{info tasks} command prints the same information
27639 about all Ada tasks (@pxref{Ada Tasks}).
27641 @subsubheading Result
27643 The result is a table of Ada tasks. The following columns are
27644 defined for each Ada task:
27648 This field exists only for the current thread. It has the value @samp{*}.
27651 The identifier that @value{GDBN} uses to refer to the Ada task.
27654 The identifier that the target uses to refer to the Ada task.
27657 The identifier of the thread corresponding to the Ada task.
27659 This field should always exist, as Ada tasks are always implemented
27660 on top of a thread. But if @value{GDBN} cannot find this corresponding
27661 thread for any reason, the field is omitted.
27664 This field exists only when the task was created by another task.
27665 In this case, it provides the ID of the parent task.
27668 The base priority of the task.
27671 The current state of the task. For a detailed description of the
27672 possible states, see @ref{Ada Tasks}.
27675 The name of the task.
27679 @subsubheading Example
27683 ^done,tasks=@{nr_rows="3",nr_cols="8",
27684 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
27685 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
27686 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
27687 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
27688 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
27689 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
27690 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
27691 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
27692 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
27693 state="Child Termination Wait",name="main_task"@}]@}
27697 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27698 @node GDB/MI Program Execution
27699 @section @sc{gdb/mi} Program Execution
27701 These are the asynchronous commands which generate the out-of-band
27702 record @samp{*stopped}. Currently @value{GDBN} only really executes
27703 asynchronously with remote targets and this interaction is mimicked in
27706 @subheading The @code{-exec-continue} Command
27707 @findex -exec-continue
27709 @subsubheading Synopsis
27712 -exec-continue [--reverse] [--all|--thread-group N]
27715 Resumes the execution of the inferior program, which will continue
27716 to execute until it reaches a debugger stop event. If the
27717 @samp{--reverse} option is specified, execution resumes in reverse until
27718 it reaches a stop event. Stop events may include
27721 breakpoints or watchpoints
27723 signals or exceptions
27725 the end of the process (or its beginning under @samp{--reverse})
27727 the end or beginning of a replay log if one is being used.
27729 In all-stop mode (@pxref{All-Stop
27730 Mode}), may resume only one thread, or all threads, depending on the
27731 value of the @samp{scheduler-locking} variable. If @samp{--all} is
27732 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
27733 ignored in all-stop mode. If the @samp{--thread-group} options is
27734 specified, then all threads in that thread group are resumed.
27736 @subsubheading @value{GDBN} Command
27738 The corresponding @value{GDBN} corresponding is @samp{continue}.
27740 @subsubheading Example
27747 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
27748 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
27754 @subheading The @code{-exec-finish} Command
27755 @findex -exec-finish
27757 @subsubheading Synopsis
27760 -exec-finish [--reverse]
27763 Resumes the execution of the inferior program until the current
27764 function is exited. Displays the results returned by the function.
27765 If the @samp{--reverse} option is specified, resumes the reverse
27766 execution of the inferior program until the point where current
27767 function was called.
27769 @subsubheading @value{GDBN} Command
27771 The corresponding @value{GDBN} command is @samp{finish}.
27773 @subsubheading Example
27775 Function returning @code{void}.
27782 *stopped,reason="function-finished",frame=@{func="main",args=[],
27783 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
27787 Function returning other than @code{void}. The name of the internal
27788 @value{GDBN} variable storing the result is printed, together with the
27795 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
27796 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
27797 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27798 gdb-result-var="$1",return-value="0"
27803 @subheading The @code{-exec-interrupt} Command
27804 @findex -exec-interrupt
27806 @subsubheading Synopsis
27809 -exec-interrupt [--all|--thread-group N]
27812 Interrupts the background execution of the target. Note how the token
27813 associated with the stop message is the one for the execution command
27814 that has been interrupted. The token for the interrupt itself only
27815 appears in the @samp{^done} output. If the user is trying to
27816 interrupt a non-running program, an error message will be printed.
27818 Note that when asynchronous execution is enabled, this command is
27819 asynchronous just like other execution commands. That is, first the
27820 @samp{^done} response will be printed, and the target stop will be
27821 reported after that using the @samp{*stopped} notification.
27823 In non-stop mode, only the context thread is interrupted by default.
27824 All threads (in all inferiors) will be interrupted if the
27825 @samp{--all} option is specified. If the @samp{--thread-group}
27826 option is specified, all threads in that group will be interrupted.
27828 @subsubheading @value{GDBN} Command
27830 The corresponding @value{GDBN} command is @samp{interrupt}.
27832 @subsubheading Example
27843 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
27844 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
27845 fullname="/home/foo/bar/try.c",line="13"@}
27850 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
27854 @subheading The @code{-exec-jump} Command
27857 @subsubheading Synopsis
27860 -exec-jump @var{location}
27863 Resumes execution of the inferior program at the location specified by
27864 parameter. @xref{Specify Location}, for a description of the
27865 different forms of @var{location}.
27867 @subsubheading @value{GDBN} Command
27869 The corresponding @value{GDBN} command is @samp{jump}.
27871 @subsubheading Example
27874 -exec-jump foo.c:10
27875 *running,thread-id="all"
27880 @subheading The @code{-exec-next} Command
27883 @subsubheading Synopsis
27886 -exec-next [--reverse]
27889 Resumes execution of the inferior program, stopping when the beginning
27890 of the next source line is reached.
27892 If the @samp{--reverse} option is specified, resumes reverse execution
27893 of the inferior program, stopping at the beginning of the previous
27894 source line. If you issue this command on the first line of a
27895 function, it will take you back to the caller of that function, to the
27896 source line where the function was called.
27899 @subsubheading @value{GDBN} Command
27901 The corresponding @value{GDBN} command is @samp{next}.
27903 @subsubheading Example
27909 *stopped,reason="end-stepping-range",line="8",file="hello.c"
27914 @subheading The @code{-exec-next-instruction} Command
27915 @findex -exec-next-instruction
27917 @subsubheading Synopsis
27920 -exec-next-instruction [--reverse]
27923 Executes one machine instruction. If the instruction is a function
27924 call, continues until the function returns. If the program stops at an
27925 instruction in the middle of a source line, the address will be
27928 If the @samp{--reverse} option is specified, resumes reverse execution
27929 of the inferior program, stopping at the previous instruction. If the
27930 previously executed instruction was a return from another function,
27931 it will continue to execute in reverse until the call to that function
27932 (from the current stack frame) is reached.
27934 @subsubheading @value{GDBN} Command
27936 The corresponding @value{GDBN} command is @samp{nexti}.
27938 @subsubheading Example
27942 -exec-next-instruction
27946 *stopped,reason="end-stepping-range",
27947 addr="0x000100d4",line="5",file="hello.c"
27952 @subheading The @code{-exec-return} Command
27953 @findex -exec-return
27955 @subsubheading Synopsis
27961 Makes current function return immediately. Doesn't execute the inferior.
27962 Displays the new current frame.
27964 @subsubheading @value{GDBN} Command
27966 The corresponding @value{GDBN} command is @samp{return}.
27968 @subsubheading Example
27972 200-break-insert callee4
27973 200^done,bkpt=@{number="1",addr="0x00010734",
27974 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27979 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27980 frame=@{func="callee4",args=[],
27981 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27982 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27988 111^done,frame=@{level="0",func="callee3",
27989 args=[@{name="strarg",
27990 value="0x11940 \"A string argument.\""@}],
27991 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27992 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27997 @subheading The @code{-exec-run} Command
28000 @subsubheading Synopsis
28003 -exec-run [ --all | --thread-group N ] [ --start ]
28006 Starts execution of the inferior from the beginning. The inferior
28007 executes until either a breakpoint is encountered or the program
28008 exits. In the latter case the output will include an exit code, if
28009 the program has exited exceptionally.
28011 When neither the @samp{--all} nor the @samp{--thread-group} option
28012 is specified, the current inferior is started. If the
28013 @samp{--thread-group} option is specified, it should refer to a thread
28014 group of type @samp{process}, and that thread group will be started.
28015 If the @samp{--all} option is specified, then all inferiors will be started.
28017 Using the @samp{--start} option instructs the debugger to stop
28018 the execution at the start of the inferior's main subprogram,
28019 following the same behavior as the @code{start} command
28020 (@pxref{Starting}).
28022 @subsubheading @value{GDBN} Command
28024 The corresponding @value{GDBN} command is @samp{run}.
28026 @subsubheading Examples
28031 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
28036 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28037 frame=@{func="main",args=[],file="recursive2.c",
28038 fullname="/home/foo/bar/recursive2.c",line="4"@}
28043 Program exited normally:
28051 *stopped,reason="exited-normally"
28056 Program exited exceptionally:
28064 *stopped,reason="exited",exit-code="01"
28068 Another way the program can terminate is if it receives a signal such as
28069 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
28073 *stopped,reason="exited-signalled",signal-name="SIGINT",
28074 signal-meaning="Interrupt"
28078 @c @subheading -exec-signal
28081 @subheading The @code{-exec-step} Command
28084 @subsubheading Synopsis
28087 -exec-step [--reverse]
28090 Resumes execution of the inferior program, stopping when the beginning
28091 of the next source line is reached, if the next source line is not a
28092 function call. If it is, stop at the first instruction of the called
28093 function. If the @samp{--reverse} option is specified, resumes reverse
28094 execution of the inferior program, stopping at the beginning of the
28095 previously executed source line.
28097 @subsubheading @value{GDBN} Command
28099 The corresponding @value{GDBN} command is @samp{step}.
28101 @subsubheading Example
28103 Stepping into a function:
28109 *stopped,reason="end-stepping-range",
28110 frame=@{func="foo",args=[@{name="a",value="10"@},
28111 @{name="b",value="0"@}],file="recursive2.c",
28112 fullname="/home/foo/bar/recursive2.c",line="11"@}
28122 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
28127 @subheading The @code{-exec-step-instruction} Command
28128 @findex -exec-step-instruction
28130 @subsubheading Synopsis
28133 -exec-step-instruction [--reverse]
28136 Resumes the inferior which executes one machine instruction. If the
28137 @samp{--reverse} option is specified, resumes reverse execution of the
28138 inferior program, stopping at the previously executed instruction.
28139 The output, once @value{GDBN} has stopped, will vary depending on
28140 whether we have stopped in the middle of a source line or not. In the
28141 former case, the address at which the program stopped will be printed
28144 @subsubheading @value{GDBN} Command
28146 The corresponding @value{GDBN} command is @samp{stepi}.
28148 @subsubheading Example
28152 -exec-step-instruction
28156 *stopped,reason="end-stepping-range",
28157 frame=@{func="foo",args=[],file="try.c",
28158 fullname="/home/foo/bar/try.c",line="10"@}
28160 -exec-step-instruction
28164 *stopped,reason="end-stepping-range",
28165 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
28166 fullname="/home/foo/bar/try.c",line="10"@}
28171 @subheading The @code{-exec-until} Command
28172 @findex -exec-until
28174 @subsubheading Synopsis
28177 -exec-until [ @var{location} ]
28180 Executes the inferior until the @var{location} specified in the
28181 argument is reached. If there is no argument, the inferior executes
28182 until a source line greater than the current one is reached. The
28183 reason for stopping in this case will be @samp{location-reached}.
28185 @subsubheading @value{GDBN} Command
28187 The corresponding @value{GDBN} command is @samp{until}.
28189 @subsubheading Example
28193 -exec-until recursive2.c:6
28197 *stopped,reason="location-reached",frame=@{func="main",args=[],
28198 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
28203 @subheading -file-clear
28204 Is this going away????
28207 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28208 @node GDB/MI Stack Manipulation
28209 @section @sc{gdb/mi} Stack Manipulation Commands
28211 @subheading The @code{-enable-frame-filters} Command
28212 @findex -enable-frame-filters
28215 -enable-frame-filters
28218 @value{GDBN} allows Python-based frame filters to affect the output of
28219 the MI commands relating to stack traces. As there is no way to
28220 implement this in a fully backward-compatible way, a front end must
28221 request that this functionality be enabled.
28223 Once enabled, this feature cannot be disabled.
28225 Note that if Python support has not been compiled into @value{GDBN},
28226 this command will still succeed (and do nothing).
28228 @subheading The @code{-stack-info-frame} Command
28229 @findex -stack-info-frame
28231 @subsubheading Synopsis
28237 Get info on the selected frame.
28239 @subsubheading @value{GDBN} Command
28241 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
28242 (without arguments).
28244 @subsubheading Example
28249 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
28250 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28251 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
28255 @subheading The @code{-stack-info-depth} Command
28256 @findex -stack-info-depth
28258 @subsubheading Synopsis
28261 -stack-info-depth [ @var{max-depth} ]
28264 Return the depth of the stack. If the integer argument @var{max-depth}
28265 is specified, do not count beyond @var{max-depth} frames.
28267 @subsubheading @value{GDBN} Command
28269 There's no equivalent @value{GDBN} command.
28271 @subsubheading Example
28273 For a stack with frame levels 0 through 11:
28280 -stack-info-depth 4
28283 -stack-info-depth 12
28286 -stack-info-depth 11
28289 -stack-info-depth 13
28294 @anchor{-stack-list-arguments}
28295 @subheading The @code{-stack-list-arguments} Command
28296 @findex -stack-list-arguments
28298 @subsubheading Synopsis
28301 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28302 [ @var{low-frame} @var{high-frame} ]
28305 Display a list of the arguments for the frames between @var{low-frame}
28306 and @var{high-frame} (inclusive). If @var{low-frame} and
28307 @var{high-frame} are not provided, list the arguments for the whole
28308 call stack. If the two arguments are equal, show the single frame
28309 at the corresponding level. It is an error if @var{low-frame} is
28310 larger than the actual number of frames. On the other hand,
28311 @var{high-frame} may be larger than the actual number of frames, in
28312 which case only existing frames will be returned.
28314 If @var{print-values} is 0 or @code{--no-values}, print only the names of
28315 the variables; if it is 1 or @code{--all-values}, print also their
28316 values; and if it is 2 or @code{--simple-values}, print the name,
28317 type and value for simple data types, and the name and type for arrays,
28318 structures and unions. If the option @code{--no-frame-filters} is
28319 supplied, then Python frame filters will not be executed.
28321 If the @code{--skip-unavailable} option is specified, arguments that
28322 are not available are not listed. Partially available arguments
28323 are still displayed, however.
28325 Use of this command to obtain arguments in a single frame is
28326 deprecated in favor of the @samp{-stack-list-variables} command.
28328 @subsubheading @value{GDBN} Command
28330 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
28331 @samp{gdb_get_args} command which partially overlaps with the
28332 functionality of @samp{-stack-list-arguments}.
28334 @subsubheading Example
28341 frame=@{level="0",addr="0x00010734",func="callee4",
28342 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28343 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
28344 frame=@{level="1",addr="0x0001076c",func="callee3",
28345 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28346 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
28347 frame=@{level="2",addr="0x0001078c",func="callee2",
28348 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28349 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
28350 frame=@{level="3",addr="0x000107b4",func="callee1",
28351 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28352 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
28353 frame=@{level="4",addr="0x000107e0",func="main",
28354 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28355 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
28357 -stack-list-arguments 0
28360 frame=@{level="0",args=[]@},
28361 frame=@{level="1",args=[name="strarg"]@},
28362 frame=@{level="2",args=[name="intarg",name="strarg"]@},
28363 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
28364 frame=@{level="4",args=[]@}]
28366 -stack-list-arguments 1
28369 frame=@{level="0",args=[]@},
28371 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28372 frame=@{level="2",args=[
28373 @{name="intarg",value="2"@},
28374 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28375 @{frame=@{level="3",args=[
28376 @{name="intarg",value="2"@},
28377 @{name="strarg",value="0x11940 \"A string argument.\""@},
28378 @{name="fltarg",value="3.5"@}]@},
28379 frame=@{level="4",args=[]@}]
28381 -stack-list-arguments 0 2 2
28382 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
28384 -stack-list-arguments 1 2 2
28385 ^done,stack-args=[frame=@{level="2",
28386 args=[@{name="intarg",value="2"@},
28387 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
28391 @c @subheading -stack-list-exception-handlers
28394 @anchor{-stack-list-frames}
28395 @subheading The @code{-stack-list-frames} Command
28396 @findex -stack-list-frames
28398 @subsubheading Synopsis
28401 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
28404 List the frames currently on the stack. For each frame it displays the
28409 The frame number, 0 being the topmost frame, i.e., the innermost function.
28411 The @code{$pc} value for that frame.
28415 File name of the source file where the function lives.
28416 @item @var{fullname}
28417 The full file name of the source file where the function lives.
28419 Line number corresponding to the @code{$pc}.
28421 The shared library where this function is defined. This is only given
28422 if the frame's function is not known.
28425 If invoked without arguments, this command prints a backtrace for the
28426 whole stack. If given two integer arguments, it shows the frames whose
28427 levels are between the two arguments (inclusive). If the two arguments
28428 are equal, it shows the single frame at the corresponding level. It is
28429 an error if @var{low-frame} is larger than the actual number of
28430 frames. On the other hand, @var{high-frame} may be larger than the
28431 actual number of frames, in which case only existing frames will be
28432 returned. If the option @code{--no-frame-filters} is supplied, then
28433 Python frame filters will not be executed.
28435 @subsubheading @value{GDBN} Command
28437 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
28439 @subsubheading Example
28441 Full stack backtrace:
28447 [frame=@{level="0",addr="0x0001076c",func="foo",
28448 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
28449 frame=@{level="1",addr="0x000107a4",func="foo",
28450 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28451 frame=@{level="2",addr="0x000107a4",func="foo",
28452 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28453 frame=@{level="3",addr="0x000107a4",func="foo",
28454 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28455 frame=@{level="4",addr="0x000107a4",func="foo",
28456 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28457 frame=@{level="5",addr="0x000107a4",func="foo",
28458 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28459 frame=@{level="6",addr="0x000107a4",func="foo",
28460 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28461 frame=@{level="7",addr="0x000107a4",func="foo",
28462 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28463 frame=@{level="8",addr="0x000107a4",func="foo",
28464 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28465 frame=@{level="9",addr="0x000107a4",func="foo",
28466 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28467 frame=@{level="10",addr="0x000107a4",func="foo",
28468 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28469 frame=@{level="11",addr="0x00010738",func="main",
28470 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
28474 Show frames between @var{low_frame} and @var{high_frame}:
28478 -stack-list-frames 3 5
28480 [frame=@{level="3",addr="0x000107a4",func="foo",
28481 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28482 frame=@{level="4",addr="0x000107a4",func="foo",
28483 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28484 frame=@{level="5",addr="0x000107a4",func="foo",
28485 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28489 Show a single frame:
28493 -stack-list-frames 3 3
28495 [frame=@{level="3",addr="0x000107a4",func="foo",
28496 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28501 @subheading The @code{-stack-list-locals} Command
28502 @findex -stack-list-locals
28503 @anchor{-stack-list-locals}
28505 @subsubheading Synopsis
28508 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28511 Display the local variable names for the selected frame. If
28512 @var{print-values} is 0 or @code{--no-values}, print only the names of
28513 the variables; if it is 1 or @code{--all-values}, print also their
28514 values; and if it is 2 or @code{--simple-values}, print the name,
28515 type and value for simple data types, and the name and type for arrays,
28516 structures and unions. In this last case, a frontend can immediately
28517 display the value of simple data types and create variable objects for
28518 other data types when the user wishes to explore their values in
28519 more detail. If the option @code{--no-frame-filters} is supplied, then
28520 Python frame filters will not be executed.
28522 If the @code{--skip-unavailable} option is specified, local variables
28523 that are not available are not listed. Partially available local
28524 variables are still displayed, however.
28526 This command is deprecated in favor of the
28527 @samp{-stack-list-variables} command.
28529 @subsubheading @value{GDBN} Command
28531 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
28533 @subsubheading Example
28537 -stack-list-locals 0
28538 ^done,locals=[name="A",name="B",name="C"]
28540 -stack-list-locals --all-values
28541 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
28542 @{name="C",value="@{1, 2, 3@}"@}]
28543 -stack-list-locals --simple-values
28544 ^done,locals=[@{name="A",type="int",value="1"@},
28545 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
28549 @anchor{-stack-list-variables}
28550 @subheading The @code{-stack-list-variables} Command
28551 @findex -stack-list-variables
28553 @subsubheading Synopsis
28556 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28559 Display the names of local variables and function arguments for the selected frame. If
28560 @var{print-values} is 0 or @code{--no-values}, print only the names of
28561 the variables; if it is 1 or @code{--all-values}, print also their
28562 values; and if it is 2 or @code{--simple-values}, print the name,
28563 type and value for simple data types, and the name and type for arrays,
28564 structures and unions. If the option @code{--no-frame-filters} is
28565 supplied, then Python frame filters will not be executed.
28567 If the @code{--skip-unavailable} option is specified, local variables
28568 and arguments that are not available are not listed. Partially
28569 available arguments and local variables are still displayed, however.
28571 @subsubheading Example
28575 -stack-list-variables --thread 1 --frame 0 --all-values
28576 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
28581 @subheading The @code{-stack-select-frame} Command
28582 @findex -stack-select-frame
28584 @subsubheading Synopsis
28587 -stack-select-frame @var{framenum}
28590 Change the selected frame. Select a different frame @var{framenum} on
28593 This command in deprecated in favor of passing the @samp{--frame}
28594 option to every command.
28596 @subsubheading @value{GDBN} Command
28598 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
28599 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
28601 @subsubheading Example
28605 -stack-select-frame 2
28610 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28611 @node GDB/MI Variable Objects
28612 @section @sc{gdb/mi} Variable Objects
28616 @subheading Motivation for Variable Objects in @sc{gdb/mi}
28618 For the implementation of a variable debugger window (locals, watched
28619 expressions, etc.), we are proposing the adaptation of the existing code
28620 used by @code{Insight}.
28622 The two main reasons for that are:
28626 It has been proven in practice (it is already on its second generation).
28629 It will shorten development time (needless to say how important it is
28633 The original interface was designed to be used by Tcl code, so it was
28634 slightly changed so it could be used through @sc{gdb/mi}. This section
28635 describes the @sc{gdb/mi} operations that will be available and gives some
28636 hints about their use.
28638 @emph{Note}: In addition to the set of operations described here, we
28639 expect the @sc{gui} implementation of a variable window to require, at
28640 least, the following operations:
28643 @item @code{-gdb-show} @code{output-radix}
28644 @item @code{-stack-list-arguments}
28645 @item @code{-stack-list-locals}
28646 @item @code{-stack-select-frame}
28651 @subheading Introduction to Variable Objects
28653 @cindex variable objects in @sc{gdb/mi}
28655 Variable objects are "object-oriented" MI interface for examining and
28656 changing values of expressions. Unlike some other MI interfaces that
28657 work with expressions, variable objects are specifically designed for
28658 simple and efficient presentation in the frontend. A variable object
28659 is identified by string name. When a variable object is created, the
28660 frontend specifies the expression for that variable object. The
28661 expression can be a simple variable, or it can be an arbitrary complex
28662 expression, and can even involve CPU registers. After creating a
28663 variable object, the frontend can invoke other variable object
28664 operations---for example to obtain or change the value of a variable
28665 object, or to change display format.
28667 Variable objects have hierarchical tree structure. Any variable object
28668 that corresponds to a composite type, such as structure in C, has
28669 a number of child variable objects, for example corresponding to each
28670 element of a structure. A child variable object can itself have
28671 children, recursively. Recursion ends when we reach
28672 leaf variable objects, which always have built-in types. Child variable
28673 objects are created only by explicit request, so if a frontend
28674 is not interested in the children of a particular variable object, no
28675 child will be created.
28677 For a leaf variable object it is possible to obtain its value as a
28678 string, or set the value from a string. String value can be also
28679 obtained for a non-leaf variable object, but it's generally a string
28680 that only indicates the type of the object, and does not list its
28681 contents. Assignment to a non-leaf variable object is not allowed.
28683 A frontend does not need to read the values of all variable objects each time
28684 the program stops. Instead, MI provides an update command that lists all
28685 variable objects whose values has changed since the last update
28686 operation. This considerably reduces the amount of data that must
28687 be transferred to the frontend. As noted above, children variable
28688 objects are created on demand, and only leaf variable objects have a
28689 real value. As result, gdb will read target memory only for leaf
28690 variables that frontend has created.
28692 The automatic update is not always desirable. For example, a frontend
28693 might want to keep a value of some expression for future reference,
28694 and never update it. For another example, fetching memory is
28695 relatively slow for embedded targets, so a frontend might want
28696 to disable automatic update for the variables that are either not
28697 visible on the screen, or ``closed''. This is possible using so
28698 called ``frozen variable objects''. Such variable objects are never
28699 implicitly updated.
28701 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
28702 fixed variable object, the expression is parsed when the variable
28703 object is created, including associating identifiers to specific
28704 variables. The meaning of expression never changes. For a floating
28705 variable object the values of variables whose names appear in the
28706 expressions are re-evaluated every time in the context of the current
28707 frame. Consider this example:
28712 struct work_state state;
28719 If a fixed variable object for the @code{state} variable is created in
28720 this function, and we enter the recursive call, the variable
28721 object will report the value of @code{state} in the top-level
28722 @code{do_work} invocation. On the other hand, a floating variable
28723 object will report the value of @code{state} in the current frame.
28725 If an expression specified when creating a fixed variable object
28726 refers to a local variable, the variable object becomes bound to the
28727 thread and frame in which the variable object is created. When such
28728 variable object is updated, @value{GDBN} makes sure that the
28729 thread/frame combination the variable object is bound to still exists,
28730 and re-evaluates the variable object in context of that thread/frame.
28732 The following is the complete set of @sc{gdb/mi} operations defined to
28733 access this functionality:
28735 @multitable @columnfractions .4 .6
28736 @item @strong{Operation}
28737 @tab @strong{Description}
28739 @item @code{-enable-pretty-printing}
28740 @tab enable Python-based pretty-printing
28741 @item @code{-var-create}
28742 @tab create a variable object
28743 @item @code{-var-delete}
28744 @tab delete the variable object and/or its children
28745 @item @code{-var-set-format}
28746 @tab set the display format of this variable
28747 @item @code{-var-show-format}
28748 @tab show the display format of this variable
28749 @item @code{-var-info-num-children}
28750 @tab tells how many children this object has
28751 @item @code{-var-list-children}
28752 @tab return a list of the object's children
28753 @item @code{-var-info-type}
28754 @tab show the type of this variable object
28755 @item @code{-var-info-expression}
28756 @tab print parent-relative expression that this variable object represents
28757 @item @code{-var-info-path-expression}
28758 @tab print full expression that this variable object represents
28759 @item @code{-var-show-attributes}
28760 @tab is this variable editable? does it exist here?
28761 @item @code{-var-evaluate-expression}
28762 @tab get the value of this variable
28763 @item @code{-var-assign}
28764 @tab set the value of this variable
28765 @item @code{-var-update}
28766 @tab update the variable and its children
28767 @item @code{-var-set-frozen}
28768 @tab set frozeness attribute
28769 @item @code{-var-set-update-range}
28770 @tab set range of children to display on update
28773 In the next subsection we describe each operation in detail and suggest
28774 how it can be used.
28776 @subheading Description And Use of Operations on Variable Objects
28778 @subheading The @code{-enable-pretty-printing} Command
28779 @findex -enable-pretty-printing
28782 -enable-pretty-printing
28785 @value{GDBN} allows Python-based visualizers to affect the output of the
28786 MI variable object commands. However, because there was no way to
28787 implement this in a fully backward-compatible way, a front end must
28788 request that this functionality be enabled.
28790 Once enabled, this feature cannot be disabled.
28792 Note that if Python support has not been compiled into @value{GDBN},
28793 this command will still succeed (and do nothing).
28795 This feature is currently (as of @value{GDBN} 7.0) experimental, and
28796 may work differently in future versions of @value{GDBN}.
28798 @subheading The @code{-var-create} Command
28799 @findex -var-create
28801 @subsubheading Synopsis
28804 -var-create @{@var{name} | "-"@}
28805 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
28808 This operation creates a variable object, which allows the monitoring of
28809 a variable, the result of an expression, a memory cell or a CPU
28812 The @var{name} parameter is the string by which the object can be
28813 referenced. It must be unique. If @samp{-} is specified, the varobj
28814 system will generate a string ``varNNNNNN'' automatically. It will be
28815 unique provided that one does not specify @var{name} of that format.
28816 The command fails if a duplicate name is found.
28818 The frame under which the expression should be evaluated can be
28819 specified by @var{frame-addr}. A @samp{*} indicates that the current
28820 frame should be used. A @samp{@@} indicates that a floating variable
28821 object must be created.
28823 @var{expression} is any expression valid on the current language set (must not
28824 begin with a @samp{*}), or one of the following:
28828 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
28831 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
28834 @samp{$@var{regname}} --- a CPU register name
28837 @cindex dynamic varobj
28838 A varobj's contents may be provided by a Python-based pretty-printer. In this
28839 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
28840 have slightly different semantics in some cases. If the
28841 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
28842 will never create a dynamic varobj. This ensures backward
28843 compatibility for existing clients.
28845 @subsubheading Result
28847 This operation returns attributes of the newly-created varobj. These
28852 The name of the varobj.
28855 The number of children of the varobj. This number is not necessarily
28856 reliable for a dynamic varobj. Instead, you must examine the
28857 @samp{has_more} attribute.
28860 The varobj's scalar value. For a varobj whose type is some sort of
28861 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
28862 will not be interesting.
28865 The varobj's type. This is a string representation of the type, as
28866 would be printed by the @value{GDBN} CLI. If @samp{print object}
28867 (@pxref{Print Settings, set print object}) is set to @code{on}, the
28868 @emph{actual} (derived) type of the object is shown rather than the
28869 @emph{declared} one.
28872 If a variable object is bound to a specific thread, then this is the
28873 thread's identifier.
28876 For a dynamic varobj, this indicates whether there appear to be any
28877 children available. For a non-dynamic varobj, this will be 0.
28880 This attribute will be present and have the value @samp{1} if the
28881 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28882 then this attribute will not be present.
28885 A dynamic varobj can supply a display hint to the front end. The
28886 value comes directly from the Python pretty-printer object's
28887 @code{display_hint} method. @xref{Pretty Printing API}.
28890 Typical output will look like this:
28893 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
28894 has_more="@var{has_more}"
28898 @subheading The @code{-var-delete} Command
28899 @findex -var-delete
28901 @subsubheading Synopsis
28904 -var-delete [ -c ] @var{name}
28907 Deletes a previously created variable object and all of its children.
28908 With the @samp{-c} option, just deletes the children.
28910 Returns an error if the object @var{name} is not found.
28913 @subheading The @code{-var-set-format} Command
28914 @findex -var-set-format
28916 @subsubheading Synopsis
28919 -var-set-format @var{name} @var{format-spec}
28922 Sets the output format for the value of the object @var{name} to be
28925 @anchor{-var-set-format}
28926 The syntax for the @var{format-spec} is as follows:
28929 @var{format-spec} @expansion{}
28930 @{binary | decimal | hexadecimal | octal | natural@}
28933 The natural format is the default format choosen automatically
28934 based on the variable type (like decimal for an @code{int}, hex
28935 for pointers, etc.).
28937 For a variable with children, the format is set only on the
28938 variable itself, and the children are not affected.
28940 @subheading The @code{-var-show-format} Command
28941 @findex -var-show-format
28943 @subsubheading Synopsis
28946 -var-show-format @var{name}
28949 Returns the format used to display the value of the object @var{name}.
28952 @var{format} @expansion{}
28957 @subheading The @code{-var-info-num-children} Command
28958 @findex -var-info-num-children
28960 @subsubheading Synopsis
28963 -var-info-num-children @var{name}
28966 Returns the number of children of a variable object @var{name}:
28972 Note that this number is not completely reliable for a dynamic varobj.
28973 It will return the current number of children, but more children may
28977 @subheading The @code{-var-list-children} Command
28978 @findex -var-list-children
28980 @subsubheading Synopsis
28983 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
28985 @anchor{-var-list-children}
28987 Return a list of the children of the specified variable object and
28988 create variable objects for them, if they do not already exist. With
28989 a single argument or if @var{print-values} has a value of 0 or
28990 @code{--no-values}, print only the names of the variables; if
28991 @var{print-values} is 1 or @code{--all-values}, also print their
28992 values; and if it is 2 or @code{--simple-values} print the name and
28993 value for simple data types and just the name for arrays, structures
28996 @var{from} and @var{to}, if specified, indicate the range of children
28997 to report. If @var{from} or @var{to} is less than zero, the range is
28998 reset and all children will be reported. Otherwise, children starting
28999 at @var{from} (zero-based) and up to and excluding @var{to} will be
29002 If a child range is requested, it will only affect the current call to
29003 @code{-var-list-children}, but not future calls to @code{-var-update}.
29004 For this, you must instead use @code{-var-set-update-range}. The
29005 intent of this approach is to enable a front end to implement any
29006 update approach it likes; for example, scrolling a view may cause the
29007 front end to request more children with @code{-var-list-children}, and
29008 then the front end could call @code{-var-set-update-range} with a
29009 different range to ensure that future updates are restricted to just
29012 For each child the following results are returned:
29017 Name of the variable object created for this child.
29020 The expression to be shown to the user by the front end to designate this child.
29021 For example this may be the name of a structure member.
29023 For a dynamic varobj, this value cannot be used to form an
29024 expression. There is no way to do this at all with a dynamic varobj.
29026 For C/C@t{++} structures there are several pseudo children returned to
29027 designate access qualifiers. For these pseudo children @var{exp} is
29028 @samp{public}, @samp{private}, or @samp{protected}. In this case the
29029 type and value are not present.
29031 A dynamic varobj will not report the access qualifying
29032 pseudo-children, regardless of the language. This information is not
29033 available at all with a dynamic varobj.
29036 Number of children this child has. For a dynamic varobj, this will be
29040 The type of the child. If @samp{print object}
29041 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29042 @emph{actual} (derived) type of the object is shown rather than the
29043 @emph{declared} one.
29046 If values were requested, this is the value.
29049 If this variable object is associated with a thread, this is the thread id.
29050 Otherwise this result is not present.
29053 If the variable object is frozen, this variable will be present with a value of 1.
29056 A dynamic varobj can supply a display hint to the front end. The
29057 value comes directly from the Python pretty-printer object's
29058 @code{display_hint} method. @xref{Pretty Printing API}.
29061 This attribute will be present and have the value @samp{1} if the
29062 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29063 then this attribute will not be present.
29067 The result may have its own attributes:
29071 A dynamic varobj can supply a display hint to the front end. The
29072 value comes directly from the Python pretty-printer object's
29073 @code{display_hint} method. @xref{Pretty Printing API}.
29076 This is an integer attribute which is nonzero if there are children
29077 remaining after the end of the selected range.
29080 @subsubheading Example
29084 -var-list-children n
29085 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29086 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
29088 -var-list-children --all-values n
29089 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29090 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
29094 @subheading The @code{-var-info-type} Command
29095 @findex -var-info-type
29097 @subsubheading Synopsis
29100 -var-info-type @var{name}
29103 Returns the type of the specified variable @var{name}. The type is
29104 returned as a string in the same format as it is output by the
29108 type=@var{typename}
29112 @subheading The @code{-var-info-expression} Command
29113 @findex -var-info-expression
29115 @subsubheading Synopsis
29118 -var-info-expression @var{name}
29121 Returns a string that is suitable for presenting this
29122 variable object in user interface. The string is generally
29123 not valid expression in the current language, and cannot be evaluated.
29125 For example, if @code{a} is an array, and variable object
29126 @code{A} was created for @code{a}, then we'll get this output:
29129 (gdb) -var-info-expression A.1
29130 ^done,lang="C",exp="1"
29134 Here, the value of @code{lang} is the language name, which can be
29135 found in @ref{Supported Languages}.
29137 Note that the output of the @code{-var-list-children} command also
29138 includes those expressions, so the @code{-var-info-expression} command
29141 @subheading The @code{-var-info-path-expression} Command
29142 @findex -var-info-path-expression
29144 @subsubheading Synopsis
29147 -var-info-path-expression @var{name}
29150 Returns an expression that can be evaluated in the current
29151 context and will yield the same value that a variable object has.
29152 Compare this with the @code{-var-info-expression} command, which
29153 result can be used only for UI presentation. Typical use of
29154 the @code{-var-info-path-expression} command is creating a
29155 watchpoint from a variable object.
29157 This command is currently not valid for children of a dynamic varobj,
29158 and will give an error when invoked on one.
29160 For example, suppose @code{C} is a C@t{++} class, derived from class
29161 @code{Base}, and that the @code{Base} class has a member called
29162 @code{m_size}. Assume a variable @code{c} is has the type of
29163 @code{C} and a variable object @code{C} was created for variable
29164 @code{c}. Then, we'll get this output:
29166 (gdb) -var-info-path-expression C.Base.public.m_size
29167 ^done,path_expr=((Base)c).m_size)
29170 @subheading The @code{-var-show-attributes} Command
29171 @findex -var-show-attributes
29173 @subsubheading Synopsis
29176 -var-show-attributes @var{name}
29179 List attributes of the specified variable object @var{name}:
29182 status=@var{attr} [ ( ,@var{attr} )* ]
29186 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
29188 @subheading The @code{-var-evaluate-expression} Command
29189 @findex -var-evaluate-expression
29191 @subsubheading Synopsis
29194 -var-evaluate-expression [-f @var{format-spec}] @var{name}
29197 Evaluates the expression that is represented by the specified variable
29198 object and returns its value as a string. The format of the string
29199 can be specified with the @samp{-f} option. The possible values of
29200 this option are the same as for @code{-var-set-format}
29201 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
29202 the current display format will be used. The current display format
29203 can be changed using the @code{-var-set-format} command.
29209 Note that one must invoke @code{-var-list-children} for a variable
29210 before the value of a child variable can be evaluated.
29212 @subheading The @code{-var-assign} Command
29213 @findex -var-assign
29215 @subsubheading Synopsis
29218 -var-assign @var{name} @var{expression}
29221 Assigns the value of @var{expression} to the variable object specified
29222 by @var{name}. The object must be @samp{editable}. If the variable's
29223 value is altered by the assign, the variable will show up in any
29224 subsequent @code{-var-update} list.
29226 @subsubheading Example
29234 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
29238 @subheading The @code{-var-update} Command
29239 @findex -var-update
29241 @subsubheading Synopsis
29244 -var-update [@var{print-values}] @{@var{name} | "*"@}
29247 Reevaluate the expressions corresponding to the variable object
29248 @var{name} and all its direct and indirect children, and return the
29249 list of variable objects whose values have changed; @var{name} must
29250 be a root variable object. Here, ``changed'' means that the result of
29251 @code{-var-evaluate-expression} before and after the
29252 @code{-var-update} is different. If @samp{*} is used as the variable
29253 object names, all existing variable objects are updated, except
29254 for frozen ones (@pxref{-var-set-frozen}). The option
29255 @var{print-values} determines whether both names and values, or just
29256 names are printed. The possible values of this option are the same
29257 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
29258 recommended to use the @samp{--all-values} option, to reduce the
29259 number of MI commands needed on each program stop.
29261 With the @samp{*} parameter, if a variable object is bound to a
29262 currently running thread, it will not be updated, without any
29265 If @code{-var-set-update-range} was previously used on a varobj, then
29266 only the selected range of children will be reported.
29268 @code{-var-update} reports all the changed varobjs in a tuple named
29271 Each item in the change list is itself a tuple holding:
29275 The name of the varobj.
29278 If values were requested for this update, then this field will be
29279 present and will hold the value of the varobj.
29282 @anchor{-var-update}
29283 This field is a string which may take one of three values:
29287 The variable object's current value is valid.
29290 The variable object does not currently hold a valid value but it may
29291 hold one in the future if its associated expression comes back into
29295 The variable object no longer holds a valid value.
29296 This can occur when the executable file being debugged has changed,
29297 either through recompilation or by using the @value{GDBN} @code{file}
29298 command. The front end should normally choose to delete these variable
29302 In the future new values may be added to this list so the front should
29303 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
29306 This is only present if the varobj is still valid. If the type
29307 changed, then this will be the string @samp{true}; otherwise it will
29310 When a varobj's type changes, its children are also likely to have
29311 become incorrect. Therefore, the varobj's children are automatically
29312 deleted when this attribute is @samp{true}. Also, the varobj's update
29313 range, when set using the @code{-var-set-update-range} command, is
29317 If the varobj's type changed, then this field will be present and will
29320 @item new_num_children
29321 For a dynamic varobj, if the number of children changed, or if the
29322 type changed, this will be the new number of children.
29324 The @samp{numchild} field in other varobj responses is generally not
29325 valid for a dynamic varobj -- it will show the number of children that
29326 @value{GDBN} knows about, but because dynamic varobjs lazily
29327 instantiate their children, this will not reflect the number of
29328 children which may be available.
29330 The @samp{new_num_children} attribute only reports changes to the
29331 number of children known by @value{GDBN}. This is the only way to
29332 detect whether an update has removed children (which necessarily can
29333 only happen at the end of the update range).
29336 The display hint, if any.
29339 This is an integer value, which will be 1 if there are more children
29340 available outside the varobj's update range.
29343 This attribute will be present and have the value @samp{1} if the
29344 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29345 then this attribute will not be present.
29348 If new children were added to a dynamic varobj within the selected
29349 update range (as set by @code{-var-set-update-range}), then they will
29350 be listed in this attribute.
29353 @subsubheading Example
29360 -var-update --all-values var1
29361 ^done,changelist=[@{name="var1",value="3",in_scope="true",
29362 type_changed="false"@}]
29366 @subheading The @code{-var-set-frozen} Command
29367 @findex -var-set-frozen
29368 @anchor{-var-set-frozen}
29370 @subsubheading Synopsis
29373 -var-set-frozen @var{name} @var{flag}
29376 Set the frozenness flag on the variable object @var{name}. The
29377 @var{flag} parameter should be either @samp{1} to make the variable
29378 frozen or @samp{0} to make it unfrozen. If a variable object is
29379 frozen, then neither itself, nor any of its children, are
29380 implicitly updated by @code{-var-update} of
29381 a parent variable or by @code{-var-update *}. Only
29382 @code{-var-update} of the variable itself will update its value and
29383 values of its children. After a variable object is unfrozen, it is
29384 implicitly updated by all subsequent @code{-var-update} operations.
29385 Unfreezing a variable does not update it, only subsequent
29386 @code{-var-update} does.
29388 @subsubheading Example
29392 -var-set-frozen V 1
29397 @subheading The @code{-var-set-update-range} command
29398 @findex -var-set-update-range
29399 @anchor{-var-set-update-range}
29401 @subsubheading Synopsis
29404 -var-set-update-range @var{name} @var{from} @var{to}
29407 Set the range of children to be returned by future invocations of
29408 @code{-var-update}.
29410 @var{from} and @var{to} indicate the range of children to report. If
29411 @var{from} or @var{to} is less than zero, the range is reset and all
29412 children will be reported. Otherwise, children starting at @var{from}
29413 (zero-based) and up to and excluding @var{to} will be reported.
29415 @subsubheading Example
29419 -var-set-update-range V 1 2
29423 @subheading The @code{-var-set-visualizer} command
29424 @findex -var-set-visualizer
29425 @anchor{-var-set-visualizer}
29427 @subsubheading Synopsis
29430 -var-set-visualizer @var{name} @var{visualizer}
29433 Set a visualizer for the variable object @var{name}.
29435 @var{visualizer} is the visualizer to use. The special value
29436 @samp{None} means to disable any visualizer in use.
29438 If not @samp{None}, @var{visualizer} must be a Python expression.
29439 This expression must evaluate to a callable object which accepts a
29440 single argument. @value{GDBN} will call this object with the value of
29441 the varobj @var{name} as an argument (this is done so that the same
29442 Python pretty-printing code can be used for both the CLI and MI).
29443 When called, this object must return an object which conforms to the
29444 pretty-printing interface (@pxref{Pretty Printing API}).
29446 The pre-defined function @code{gdb.default_visualizer} may be used to
29447 select a visualizer by following the built-in process
29448 (@pxref{Selecting Pretty-Printers}). This is done automatically when
29449 a varobj is created, and so ordinarily is not needed.
29451 This feature is only available if Python support is enabled. The MI
29452 command @code{-list-features} (@pxref{GDB/MI Support Commands})
29453 can be used to check this.
29455 @subsubheading Example
29457 Resetting the visualizer:
29461 -var-set-visualizer V None
29465 Reselecting the default (type-based) visualizer:
29469 -var-set-visualizer V gdb.default_visualizer
29473 Suppose @code{SomeClass} is a visualizer class. A lambda expression
29474 can be used to instantiate this class for a varobj:
29478 -var-set-visualizer V "lambda val: SomeClass()"
29482 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29483 @node GDB/MI Data Manipulation
29484 @section @sc{gdb/mi} Data Manipulation
29486 @cindex data manipulation, in @sc{gdb/mi}
29487 @cindex @sc{gdb/mi}, data manipulation
29488 This section describes the @sc{gdb/mi} commands that manipulate data:
29489 examine memory and registers, evaluate expressions, etc.
29491 For details about what an addressable memory unit is,
29492 @pxref{addressable memory unit}.
29494 @c REMOVED FROM THE INTERFACE.
29495 @c @subheading -data-assign
29496 @c Change the value of a program variable. Plenty of side effects.
29497 @c @subsubheading GDB Command
29499 @c @subsubheading Example
29502 @subheading The @code{-data-disassemble} Command
29503 @findex -data-disassemble
29505 @subsubheading Synopsis
29509 [ -s @var{start-addr} -e @var{end-addr} ]
29510 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
29518 @item @var{start-addr}
29519 is the beginning address (or @code{$pc})
29520 @item @var{end-addr}
29522 @item @var{filename}
29523 is the name of the file to disassemble
29524 @item @var{linenum}
29525 is the line number to disassemble around
29527 is the number of disassembly lines to be produced. If it is -1,
29528 the whole function will be disassembled, in case no @var{end-addr} is
29529 specified. If @var{end-addr} is specified as a non-zero value, and
29530 @var{lines} is lower than the number of disassembly lines between
29531 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
29532 displayed; if @var{lines} is higher than the number of lines between
29533 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
29538 @item 0 disassembly only
29539 @item 1 mixed source and disassembly (deprecated)
29540 @item 2 disassembly with raw opcodes
29541 @item 3 mixed source and disassembly with raw opcodes (deprecated)
29542 @item 4 mixed source and disassembly
29543 @item 5 mixed source and disassembly with raw opcodes
29546 Modes 1 and 3 are deprecated. The output is ``source centric''
29547 which hasn't proved useful in practice.
29548 @xref{Machine Code}, for a discussion of the difference between
29549 @code{/m} and @code{/s} output of the @code{disassemble} command.
29552 @subsubheading Result
29554 The result of the @code{-data-disassemble} command will be a list named
29555 @samp{asm_insns}, the contents of this list depend on the @var{mode}
29556 used with the @code{-data-disassemble} command.
29558 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
29563 The address at which this instruction was disassembled.
29566 The name of the function this instruction is within.
29569 The decimal offset in bytes from the start of @samp{func-name}.
29572 The text disassembly for this @samp{address}.
29575 This field is only present for modes 2, 3 and 5. This contains the raw opcode
29576 bytes for the @samp{inst} field.
29580 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
29581 @samp{src_and_asm_line}, each of which has the following fields:
29585 The line number within @samp{file}.
29588 The file name from the compilation unit. This might be an absolute
29589 file name or a relative file name depending on the compile command
29593 Absolute file name of @samp{file}. It is converted to a canonical form
29594 using the source file search path
29595 (@pxref{Source Path, ,Specifying Source Directories})
29596 and after resolving all the symbolic links.
29598 If the source file is not found this field will contain the path as
29599 present in the debug information.
29601 @item line_asm_insn
29602 This is a list of tuples containing the disassembly for @samp{line} in
29603 @samp{file}. The fields of each tuple are the same as for
29604 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
29605 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
29610 Note that whatever included in the @samp{inst} field, is not
29611 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
29614 @subsubheading @value{GDBN} Command
29616 The corresponding @value{GDBN} command is @samp{disassemble}.
29618 @subsubheading Example
29620 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
29624 -data-disassemble -s $pc -e "$pc + 20" -- 0
29627 @{address="0x000107c0",func-name="main",offset="4",
29628 inst="mov 2, %o0"@},
29629 @{address="0x000107c4",func-name="main",offset="8",
29630 inst="sethi %hi(0x11800), %o2"@},
29631 @{address="0x000107c8",func-name="main",offset="12",
29632 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
29633 @{address="0x000107cc",func-name="main",offset="16",
29634 inst="sethi %hi(0x11800), %o2"@},
29635 @{address="0x000107d0",func-name="main",offset="20",
29636 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
29640 Disassemble the whole @code{main} function. Line 32 is part of
29644 -data-disassemble -f basics.c -l 32 -- 0
29646 @{address="0x000107bc",func-name="main",offset="0",
29647 inst="save %sp, -112, %sp"@},
29648 @{address="0x000107c0",func-name="main",offset="4",
29649 inst="mov 2, %o0"@},
29650 @{address="0x000107c4",func-name="main",offset="8",
29651 inst="sethi %hi(0x11800), %o2"@},
29653 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
29654 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
29658 Disassemble 3 instructions from the start of @code{main}:
29662 -data-disassemble -f basics.c -l 32 -n 3 -- 0
29664 @{address="0x000107bc",func-name="main",offset="0",
29665 inst="save %sp, -112, %sp"@},
29666 @{address="0x000107c0",func-name="main",offset="4",
29667 inst="mov 2, %o0"@},
29668 @{address="0x000107c4",func-name="main",offset="8",
29669 inst="sethi %hi(0x11800), %o2"@}]
29673 Disassemble 3 instructions from the start of @code{main} in mixed mode:
29677 -data-disassemble -f basics.c -l 32 -n 3 -- 1
29679 src_and_asm_line=@{line="31",
29680 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
29681 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
29682 line_asm_insn=[@{address="0x000107bc",
29683 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
29684 src_and_asm_line=@{line="32",
29685 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
29686 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
29687 line_asm_insn=[@{address="0x000107c0",
29688 func-name="main",offset="4",inst="mov 2, %o0"@},
29689 @{address="0x000107c4",func-name="main",offset="8",
29690 inst="sethi %hi(0x11800), %o2"@}]@}]
29695 @subheading The @code{-data-evaluate-expression} Command
29696 @findex -data-evaluate-expression
29698 @subsubheading Synopsis
29701 -data-evaluate-expression @var{expr}
29704 Evaluate @var{expr} as an expression. The expression could contain an
29705 inferior function call. The function call will execute synchronously.
29706 If the expression contains spaces, it must be enclosed in double quotes.
29708 @subsubheading @value{GDBN} Command
29710 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
29711 @samp{call}. In @code{gdbtk} only, there's a corresponding
29712 @samp{gdb_eval} command.
29714 @subsubheading Example
29716 In the following example, the numbers that precede the commands are the
29717 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
29718 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
29722 211-data-evaluate-expression A
29725 311-data-evaluate-expression &A
29726 311^done,value="0xefffeb7c"
29728 411-data-evaluate-expression A+3
29731 511-data-evaluate-expression "A + 3"
29737 @subheading The @code{-data-list-changed-registers} Command
29738 @findex -data-list-changed-registers
29740 @subsubheading Synopsis
29743 -data-list-changed-registers
29746 Display a list of the registers that have changed.
29748 @subsubheading @value{GDBN} Command
29750 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
29751 has the corresponding command @samp{gdb_changed_register_list}.
29753 @subsubheading Example
29755 On a PPC MBX board:
29763 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
29764 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
29767 -data-list-changed-registers
29768 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
29769 "10","11","13","14","15","16","17","18","19","20","21","22","23",
29770 "24","25","26","27","28","30","31","64","65","66","67","69"]
29775 @subheading The @code{-data-list-register-names} Command
29776 @findex -data-list-register-names
29778 @subsubheading Synopsis
29781 -data-list-register-names [ ( @var{regno} )+ ]
29784 Show a list of register names for the current target. If no arguments
29785 are given, it shows a list of the names of all the registers. If
29786 integer numbers are given as arguments, it will print a list of the
29787 names of the registers corresponding to the arguments. To ensure
29788 consistency between a register name and its number, the output list may
29789 include empty register names.
29791 @subsubheading @value{GDBN} Command
29793 @value{GDBN} does not have a command which corresponds to
29794 @samp{-data-list-register-names}. In @code{gdbtk} there is a
29795 corresponding command @samp{gdb_regnames}.
29797 @subsubheading Example
29799 For the PPC MBX board:
29802 -data-list-register-names
29803 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
29804 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
29805 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
29806 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
29807 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
29808 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
29809 "", "pc","ps","cr","lr","ctr","xer"]
29811 -data-list-register-names 1 2 3
29812 ^done,register-names=["r1","r2","r3"]
29816 @subheading The @code{-data-list-register-values} Command
29817 @findex -data-list-register-values
29819 @subsubheading Synopsis
29822 -data-list-register-values
29823 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
29826 Display the registers' contents. The format according to which the
29827 registers' contents are to be returned is given by @var{fmt}, followed
29828 by an optional list of numbers specifying the registers to display. A
29829 missing list of numbers indicates that the contents of all the
29830 registers must be returned. The @code{--skip-unavailable} option
29831 indicates that only the available registers are to be returned.
29833 Allowed formats for @var{fmt} are:
29850 @subsubheading @value{GDBN} Command
29852 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
29853 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
29855 @subsubheading Example
29857 For a PPC MBX board (note: line breaks are for readability only, they
29858 don't appear in the actual output):
29862 -data-list-register-values r 64 65
29863 ^done,register-values=[@{number="64",value="0xfe00a300"@},
29864 @{number="65",value="0x00029002"@}]
29866 -data-list-register-values x
29867 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
29868 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
29869 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
29870 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
29871 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
29872 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
29873 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
29874 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
29875 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
29876 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
29877 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
29878 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
29879 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
29880 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
29881 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
29882 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
29883 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
29884 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
29885 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
29886 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
29887 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
29888 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
29889 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
29890 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
29891 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
29892 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
29893 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
29894 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
29895 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
29896 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
29897 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
29898 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
29899 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
29900 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
29901 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
29902 @{number="69",value="0x20002b03"@}]
29907 @subheading The @code{-data-read-memory} Command
29908 @findex -data-read-memory
29910 This command is deprecated, use @code{-data-read-memory-bytes} instead.
29912 @subsubheading Synopsis
29915 -data-read-memory [ -o @var{byte-offset} ]
29916 @var{address} @var{word-format} @var{word-size}
29917 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
29924 @item @var{address}
29925 An expression specifying the address of the first memory word to be
29926 read. Complex expressions containing embedded white space should be
29927 quoted using the C convention.
29929 @item @var{word-format}
29930 The format to be used to print the memory words. The notation is the
29931 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
29934 @item @var{word-size}
29935 The size of each memory word in bytes.
29937 @item @var{nr-rows}
29938 The number of rows in the output table.
29940 @item @var{nr-cols}
29941 The number of columns in the output table.
29944 If present, indicates that each row should include an @sc{ascii} dump. The
29945 value of @var{aschar} is used as a padding character when a byte is not a
29946 member of the printable @sc{ascii} character set (printable @sc{ascii}
29947 characters are those whose code is between 32 and 126, inclusively).
29949 @item @var{byte-offset}
29950 An offset to add to the @var{address} before fetching memory.
29953 This command displays memory contents as a table of @var{nr-rows} by
29954 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
29955 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
29956 (returned as @samp{total-bytes}). Should less than the requested number
29957 of bytes be returned by the target, the missing words are identified
29958 using @samp{N/A}. The number of bytes read from the target is returned
29959 in @samp{nr-bytes} and the starting address used to read memory in
29962 The address of the next/previous row or page is available in
29963 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
29966 @subsubheading @value{GDBN} Command
29968 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
29969 @samp{gdb_get_mem} memory read command.
29971 @subsubheading Example
29973 Read six bytes of memory starting at @code{bytes+6} but then offset by
29974 @code{-6} bytes. Format as three rows of two columns. One byte per
29975 word. Display each word in hex.
29979 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
29980 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
29981 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
29982 prev-page="0x0000138a",memory=[
29983 @{addr="0x00001390",data=["0x00","0x01"]@},
29984 @{addr="0x00001392",data=["0x02","0x03"]@},
29985 @{addr="0x00001394",data=["0x04","0x05"]@}]
29989 Read two bytes of memory starting at address @code{shorts + 64} and
29990 display as a single word formatted in decimal.
29994 5-data-read-memory shorts+64 d 2 1 1
29995 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
29996 next-row="0x00001512",prev-row="0x0000150e",
29997 next-page="0x00001512",prev-page="0x0000150e",memory=[
29998 @{addr="0x00001510",data=["128"]@}]
30002 Read thirty two bytes of memory starting at @code{bytes+16} and format
30003 as eight rows of four columns. Include a string encoding with @samp{x}
30004 used as the non-printable character.
30008 4-data-read-memory bytes+16 x 1 8 4 x
30009 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
30010 next-row="0x000013c0",prev-row="0x0000139c",
30011 next-page="0x000013c0",prev-page="0x00001380",memory=[
30012 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
30013 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
30014 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
30015 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
30016 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
30017 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
30018 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
30019 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
30023 @subheading The @code{-data-read-memory-bytes} Command
30024 @findex -data-read-memory-bytes
30026 @subsubheading Synopsis
30029 -data-read-memory-bytes [ -o @var{offset} ]
30030 @var{address} @var{count}
30037 @item @var{address}
30038 An expression specifying the address of the first addressable memory unit
30039 to be read. Complex expressions containing embedded white space should be
30040 quoted using the C convention.
30043 The number of addressable memory units to read. This should be an integer
30047 The offset relative to @var{address} at which to start reading. This
30048 should be an integer literal. This option is provided so that a frontend
30049 is not required to first evaluate address and then perform address
30050 arithmetics itself.
30054 This command attempts to read all accessible memory regions in the
30055 specified range. First, all regions marked as unreadable in the memory
30056 map (if one is defined) will be skipped. @xref{Memory Region
30057 Attributes}. Second, @value{GDBN} will attempt to read the remaining
30058 regions. For each one, if reading full region results in an errors,
30059 @value{GDBN} will try to read a subset of the region.
30061 In general, every single memory unit in the region may be readable or not,
30062 and the only way to read every readable unit is to try a read at
30063 every address, which is not practical. Therefore, @value{GDBN} will
30064 attempt to read all accessible memory units at either beginning or the end
30065 of the region, using a binary division scheme. This heuristic works
30066 well for reading accross a memory map boundary. Note that if a region
30067 has a readable range that is neither at the beginning or the end,
30068 @value{GDBN} will not read it.
30070 The result record (@pxref{GDB/MI Result Records}) that is output of
30071 the command includes a field named @samp{memory} whose content is a
30072 list of tuples. Each tuple represent a successfully read memory block
30073 and has the following fields:
30077 The start address of the memory block, as hexadecimal literal.
30080 The end address of the memory block, as hexadecimal literal.
30083 The offset of the memory block, as hexadecimal literal, relative to
30084 the start address passed to @code{-data-read-memory-bytes}.
30087 The contents of the memory block, in hex.
30093 @subsubheading @value{GDBN} Command
30095 The corresponding @value{GDBN} command is @samp{x}.
30097 @subsubheading Example
30101 -data-read-memory-bytes &a 10
30102 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
30104 contents="01000000020000000300"@}]
30109 @subheading The @code{-data-write-memory-bytes} Command
30110 @findex -data-write-memory-bytes
30112 @subsubheading Synopsis
30115 -data-write-memory-bytes @var{address} @var{contents}
30116 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
30123 @item @var{address}
30124 An expression specifying the address of the first addressable memory unit
30125 to be written. Complex expressions containing embedded white space should
30126 be quoted using the C convention.
30128 @item @var{contents}
30129 The hex-encoded data to write. It is an error if @var{contents} does
30130 not represent an integral number of addressable memory units.
30133 Optional argument indicating the number of addressable memory units to be
30134 written. If @var{count} is greater than @var{contents}' length,
30135 @value{GDBN} will repeatedly write @var{contents} until it fills
30136 @var{count} memory units.
30140 @subsubheading @value{GDBN} Command
30142 There's no corresponding @value{GDBN} command.
30144 @subsubheading Example
30148 -data-write-memory-bytes &a "aabbccdd"
30155 -data-write-memory-bytes &a "aabbccdd" 16e
30160 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30161 @node GDB/MI Tracepoint Commands
30162 @section @sc{gdb/mi} Tracepoint Commands
30164 The commands defined in this section implement MI support for
30165 tracepoints. For detailed introduction, see @ref{Tracepoints}.
30167 @subheading The @code{-trace-find} Command
30168 @findex -trace-find
30170 @subsubheading Synopsis
30173 -trace-find @var{mode} [@var{parameters}@dots{}]
30176 Find a trace frame using criteria defined by @var{mode} and
30177 @var{parameters}. The following table lists permissible
30178 modes and their parameters. For details of operation, see @ref{tfind}.
30183 No parameters are required. Stops examining trace frames.
30186 An integer is required as parameter. Selects tracepoint frame with
30189 @item tracepoint-number
30190 An integer is required as parameter. Finds next
30191 trace frame that corresponds to tracepoint with the specified number.
30194 An address is required as parameter. Finds
30195 next trace frame that corresponds to any tracepoint at the specified
30198 @item pc-inside-range
30199 Two addresses are required as parameters. Finds next trace
30200 frame that corresponds to a tracepoint at an address inside the
30201 specified range. Both bounds are considered to be inside the range.
30203 @item pc-outside-range
30204 Two addresses are required as parameters. Finds
30205 next trace frame that corresponds to a tracepoint at an address outside
30206 the specified range. Both bounds are considered to be inside the range.
30209 Line specification is required as parameter. @xref{Specify Location}.
30210 Finds next trace frame that corresponds to a tracepoint at
30211 the specified location.
30215 If @samp{none} was passed as @var{mode}, the response does not
30216 have fields. Otherwise, the response may have the following fields:
30220 This field has either @samp{0} or @samp{1} as the value, depending
30221 on whether a matching tracepoint was found.
30224 The index of the found traceframe. This field is present iff
30225 the @samp{found} field has value of @samp{1}.
30228 The index of the found tracepoint. This field is present iff
30229 the @samp{found} field has value of @samp{1}.
30232 The information about the frame corresponding to the found trace
30233 frame. This field is present only if a trace frame was found.
30234 @xref{GDB/MI Frame Information}, for description of this field.
30238 @subsubheading @value{GDBN} Command
30240 The corresponding @value{GDBN} command is @samp{tfind}.
30242 @subheading -trace-define-variable
30243 @findex -trace-define-variable
30245 @subsubheading Synopsis
30248 -trace-define-variable @var{name} [ @var{value} ]
30251 Create trace variable @var{name} if it does not exist. If
30252 @var{value} is specified, sets the initial value of the specified
30253 trace variable to that value. Note that the @var{name} should start
30254 with the @samp{$} character.
30256 @subsubheading @value{GDBN} Command
30258 The corresponding @value{GDBN} command is @samp{tvariable}.
30260 @subheading The @code{-trace-frame-collected} Command
30261 @findex -trace-frame-collected
30263 @subsubheading Synopsis
30266 -trace-frame-collected
30267 [--var-print-values @var{var_pval}]
30268 [--comp-print-values @var{comp_pval}]
30269 [--registers-format @var{regformat}]
30270 [--memory-contents]
30273 This command returns the set of collected objects, register names,
30274 trace state variable names, memory ranges and computed expressions
30275 that have been collected at a particular trace frame. The optional
30276 parameters to the command affect the output format in different ways.
30277 See the output description table below for more details.
30279 The reported names can be used in the normal manner to create
30280 varobjs and inspect the objects themselves. The items returned by
30281 this command are categorized so that it is clear which is a variable,
30282 which is a register, which is a trace state variable, which is a
30283 memory range and which is a computed expression.
30285 For instance, if the actions were
30287 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
30288 collect *(int*)0xaf02bef0@@40
30292 the object collected in its entirety would be @code{myVar}. The
30293 object @code{myArray} would be partially collected, because only the
30294 element at index @code{myIndex} would be collected. The remaining
30295 objects would be computed expressions.
30297 An example output would be:
30301 -trace-frame-collected
30303 explicit-variables=[@{name="myVar",value="1"@}],
30304 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
30305 @{name="myObj.field",value="0"@},
30306 @{name="myPtr->field",value="1"@},
30307 @{name="myCount + 2",value="3"@},
30308 @{name="$tvar1 + 1",value="43970027"@}],
30309 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
30310 @{number="1",value="0x0"@},
30311 @{number="2",value="0x4"@},
30313 @{number="125",value="0x0"@}],
30314 tvars=[@{name="$tvar1",current="43970026"@}],
30315 memory=[@{address="0x0000000000602264",length="4"@},
30316 @{address="0x0000000000615bc0",length="4"@}]
30323 @item explicit-variables
30324 The set of objects that have been collected in their entirety (as
30325 opposed to collecting just a few elements of an array or a few struct
30326 members). For each object, its name and value are printed.
30327 The @code{--var-print-values} option affects how or whether the value
30328 field is output. If @var{var_pval} is 0, then print only the names;
30329 if it is 1, print also their values; and if it is 2, print the name,
30330 type and value for simple data types, and the name and type for
30331 arrays, structures and unions.
30333 @item computed-expressions
30334 The set of computed expressions that have been collected at the
30335 current trace frame. The @code{--comp-print-values} option affects
30336 this set like the @code{--var-print-values} option affects the
30337 @code{explicit-variables} set. See above.
30340 The registers that have been collected at the current trace frame.
30341 For each register collected, the name and current value are returned.
30342 The value is formatted according to the @code{--registers-format}
30343 option. See the @command{-data-list-register-values} command for a
30344 list of the allowed formats. The default is @samp{x}.
30347 The trace state variables that have been collected at the current
30348 trace frame. For each trace state variable collected, the name and
30349 current value are returned.
30352 The set of memory ranges that have been collected at the current trace
30353 frame. Its content is a list of tuples. Each tuple represents a
30354 collected memory range and has the following fields:
30358 The start address of the memory range, as hexadecimal literal.
30361 The length of the memory range, as decimal literal.
30364 The contents of the memory block, in hex. This field is only present
30365 if the @code{--memory-contents} option is specified.
30371 @subsubheading @value{GDBN} Command
30373 There is no corresponding @value{GDBN} command.
30375 @subsubheading Example
30377 @subheading -trace-list-variables
30378 @findex -trace-list-variables
30380 @subsubheading Synopsis
30383 -trace-list-variables
30386 Return a table of all defined trace variables. Each element of the
30387 table has the following fields:
30391 The name of the trace variable. This field is always present.
30394 The initial value. This is a 64-bit signed integer. This
30395 field is always present.
30398 The value the trace variable has at the moment. This is a 64-bit
30399 signed integer. This field is absent iff current value is
30400 not defined, for example if the trace was never run, or is
30405 @subsubheading @value{GDBN} Command
30407 The corresponding @value{GDBN} command is @samp{tvariables}.
30409 @subsubheading Example
30413 -trace-list-variables
30414 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
30415 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
30416 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
30417 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
30418 body=[variable=@{name="$trace_timestamp",initial="0"@}
30419 variable=@{name="$foo",initial="10",current="15"@}]@}
30423 @subheading -trace-save
30424 @findex -trace-save
30426 @subsubheading Synopsis
30429 -trace-save [-r ] @var{filename}
30432 Saves the collected trace data to @var{filename}. Without the
30433 @samp{-r} option, the data is downloaded from the target and saved
30434 in a local file. With the @samp{-r} option the target is asked
30435 to perform the save.
30437 @subsubheading @value{GDBN} Command
30439 The corresponding @value{GDBN} command is @samp{tsave}.
30442 @subheading -trace-start
30443 @findex -trace-start
30445 @subsubheading Synopsis
30451 Starts a tracing experiments. The result of this command does not
30454 @subsubheading @value{GDBN} Command
30456 The corresponding @value{GDBN} command is @samp{tstart}.
30458 @subheading -trace-status
30459 @findex -trace-status
30461 @subsubheading Synopsis
30467 Obtains the status of a tracing experiment. The result may include
30468 the following fields:
30473 May have a value of either @samp{0}, when no tracing operations are
30474 supported, @samp{1}, when all tracing operations are supported, or
30475 @samp{file} when examining trace file. In the latter case, examining
30476 of trace frame is possible but new tracing experiement cannot be
30477 started. This field is always present.
30480 May have a value of either @samp{0} or @samp{1} depending on whether
30481 tracing experiement is in progress on target. This field is present
30482 if @samp{supported} field is not @samp{0}.
30485 Report the reason why the tracing was stopped last time. This field
30486 may be absent iff tracing was never stopped on target yet. The
30487 value of @samp{request} means the tracing was stopped as result of
30488 the @code{-trace-stop} command. The value of @samp{overflow} means
30489 the tracing buffer is full. The value of @samp{disconnection} means
30490 tracing was automatically stopped when @value{GDBN} has disconnected.
30491 The value of @samp{passcount} means tracing was stopped when a
30492 tracepoint was passed a maximal number of times for that tracepoint.
30493 This field is present if @samp{supported} field is not @samp{0}.
30495 @item stopping-tracepoint
30496 The number of tracepoint whose passcount as exceeded. This field is
30497 present iff the @samp{stop-reason} field has the value of
30501 @itemx frames-created
30502 The @samp{frames} field is a count of the total number of trace frames
30503 in the trace buffer, while @samp{frames-created} is the total created
30504 during the run, including ones that were discarded, such as when a
30505 circular trace buffer filled up. Both fields are optional.
30509 These fields tell the current size of the tracing buffer and the
30510 remaining space. These fields are optional.
30513 The value of the circular trace buffer flag. @code{1} means that the
30514 trace buffer is circular and old trace frames will be discarded if
30515 necessary to make room, @code{0} means that the trace buffer is linear
30519 The value of the disconnected tracing flag. @code{1} means that
30520 tracing will continue after @value{GDBN} disconnects, @code{0} means
30521 that the trace run will stop.
30524 The filename of the trace file being examined. This field is
30525 optional, and only present when examining a trace file.
30529 @subsubheading @value{GDBN} Command
30531 The corresponding @value{GDBN} command is @samp{tstatus}.
30533 @subheading -trace-stop
30534 @findex -trace-stop
30536 @subsubheading Synopsis
30542 Stops a tracing experiment. The result of this command has the same
30543 fields as @code{-trace-status}, except that the @samp{supported} and
30544 @samp{running} fields are not output.
30546 @subsubheading @value{GDBN} Command
30548 The corresponding @value{GDBN} command is @samp{tstop}.
30551 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30552 @node GDB/MI Symbol Query
30553 @section @sc{gdb/mi} Symbol Query Commands
30557 @subheading The @code{-symbol-info-address} Command
30558 @findex -symbol-info-address
30560 @subsubheading Synopsis
30563 -symbol-info-address @var{symbol}
30566 Describe where @var{symbol} is stored.
30568 @subsubheading @value{GDBN} Command
30570 The corresponding @value{GDBN} command is @samp{info address}.
30572 @subsubheading Example
30576 @subheading The @code{-symbol-info-file} Command
30577 @findex -symbol-info-file
30579 @subsubheading Synopsis
30585 Show the file for the symbol.
30587 @subsubheading @value{GDBN} Command
30589 There's no equivalent @value{GDBN} command. @code{gdbtk} has
30590 @samp{gdb_find_file}.
30592 @subsubheading Example
30596 @subheading The @code{-symbol-info-function} Command
30597 @findex -symbol-info-function
30599 @subsubheading Synopsis
30602 -symbol-info-function
30605 Show which function the symbol lives in.
30607 @subsubheading @value{GDBN} Command
30609 @samp{gdb_get_function} in @code{gdbtk}.
30611 @subsubheading Example
30615 @subheading The @code{-symbol-info-line} Command
30616 @findex -symbol-info-line
30618 @subsubheading Synopsis
30624 Show the core addresses of the code for a source line.
30626 @subsubheading @value{GDBN} Command
30628 The corresponding @value{GDBN} command is @samp{info line}.
30629 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
30631 @subsubheading Example
30635 @subheading The @code{-symbol-info-symbol} Command
30636 @findex -symbol-info-symbol
30638 @subsubheading Synopsis
30641 -symbol-info-symbol @var{addr}
30644 Describe what symbol is at location @var{addr}.
30646 @subsubheading @value{GDBN} Command
30648 The corresponding @value{GDBN} command is @samp{info symbol}.
30650 @subsubheading Example
30654 @subheading The @code{-symbol-list-functions} Command
30655 @findex -symbol-list-functions
30657 @subsubheading Synopsis
30660 -symbol-list-functions
30663 List the functions in the executable.
30665 @subsubheading @value{GDBN} Command
30667 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
30668 @samp{gdb_search} in @code{gdbtk}.
30670 @subsubheading Example
30675 @subheading The @code{-symbol-list-lines} Command
30676 @findex -symbol-list-lines
30678 @subsubheading Synopsis
30681 -symbol-list-lines @var{filename}
30684 Print the list of lines that contain code and their associated program
30685 addresses for the given source filename. The entries are sorted in
30686 ascending PC order.
30688 @subsubheading @value{GDBN} Command
30690 There is no corresponding @value{GDBN} command.
30692 @subsubheading Example
30695 -symbol-list-lines basics.c
30696 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
30702 @subheading The @code{-symbol-list-types} Command
30703 @findex -symbol-list-types
30705 @subsubheading Synopsis
30711 List all the type names.
30713 @subsubheading @value{GDBN} Command
30715 The corresponding commands are @samp{info types} in @value{GDBN},
30716 @samp{gdb_search} in @code{gdbtk}.
30718 @subsubheading Example
30722 @subheading The @code{-symbol-list-variables} Command
30723 @findex -symbol-list-variables
30725 @subsubheading Synopsis
30728 -symbol-list-variables
30731 List all the global and static variable names.
30733 @subsubheading @value{GDBN} Command
30735 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
30737 @subsubheading Example
30741 @subheading The @code{-symbol-locate} Command
30742 @findex -symbol-locate
30744 @subsubheading Synopsis
30750 @subsubheading @value{GDBN} Command
30752 @samp{gdb_loc} in @code{gdbtk}.
30754 @subsubheading Example
30758 @subheading The @code{-symbol-type} Command
30759 @findex -symbol-type
30761 @subsubheading Synopsis
30764 -symbol-type @var{variable}
30767 Show type of @var{variable}.
30769 @subsubheading @value{GDBN} Command
30771 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
30772 @samp{gdb_obj_variable}.
30774 @subsubheading Example
30779 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30780 @node GDB/MI File Commands
30781 @section @sc{gdb/mi} File Commands
30783 This section describes the GDB/MI commands to specify executable file names
30784 and to read in and obtain symbol table information.
30786 @subheading The @code{-file-exec-and-symbols} Command
30787 @findex -file-exec-and-symbols
30789 @subsubheading Synopsis
30792 -file-exec-and-symbols @var{file}
30795 Specify the executable file to be debugged. This file is the one from
30796 which the symbol table is also read. If no file is specified, the
30797 command clears the executable and symbol information. If breakpoints
30798 are set when using this command with no arguments, @value{GDBN} will produce
30799 error messages. Otherwise, no output is produced, except a completion
30802 @subsubheading @value{GDBN} Command
30804 The corresponding @value{GDBN} command is @samp{file}.
30806 @subsubheading Example
30810 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30816 @subheading The @code{-file-exec-file} Command
30817 @findex -file-exec-file
30819 @subsubheading Synopsis
30822 -file-exec-file @var{file}
30825 Specify the executable file to be debugged. Unlike
30826 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
30827 from this file. If used without argument, @value{GDBN} clears the information
30828 about the executable file. No output is produced, except a completion
30831 @subsubheading @value{GDBN} Command
30833 The corresponding @value{GDBN} command is @samp{exec-file}.
30835 @subsubheading Example
30839 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30846 @subheading The @code{-file-list-exec-sections} Command
30847 @findex -file-list-exec-sections
30849 @subsubheading Synopsis
30852 -file-list-exec-sections
30855 List the sections of the current executable file.
30857 @subsubheading @value{GDBN} Command
30859 The @value{GDBN} command @samp{info file} shows, among the rest, the same
30860 information as this command. @code{gdbtk} has a corresponding command
30861 @samp{gdb_load_info}.
30863 @subsubheading Example
30868 @subheading The @code{-file-list-exec-source-file} Command
30869 @findex -file-list-exec-source-file
30871 @subsubheading Synopsis
30874 -file-list-exec-source-file
30877 List the line number, the current source file, and the absolute path
30878 to the current source file for the current executable. The macro
30879 information field has a value of @samp{1} or @samp{0} depending on
30880 whether or not the file includes preprocessor macro information.
30882 @subsubheading @value{GDBN} Command
30884 The @value{GDBN} equivalent is @samp{info source}
30886 @subsubheading Example
30890 123-file-list-exec-source-file
30891 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
30896 @subheading The @code{-file-list-exec-source-files} Command
30897 @findex -file-list-exec-source-files
30899 @subsubheading Synopsis
30902 -file-list-exec-source-files
30905 List the source files for the current executable.
30907 It will always output both the filename and fullname (absolute file
30908 name) of a source file.
30910 @subsubheading @value{GDBN} Command
30912 The @value{GDBN} equivalent is @samp{info sources}.
30913 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
30915 @subsubheading Example
30918 -file-list-exec-source-files
30920 @{file=foo.c,fullname=/home/foo.c@},
30921 @{file=/home/bar.c,fullname=/home/bar.c@},
30922 @{file=gdb_could_not_find_fullpath.c@}]
30927 @subheading The @code{-file-list-shared-libraries} Command
30928 @findex -file-list-shared-libraries
30930 @subsubheading Synopsis
30933 -file-list-shared-libraries
30936 List the shared libraries in the program.
30938 @subsubheading @value{GDBN} Command
30940 The corresponding @value{GDBN} command is @samp{info shared}.
30942 @subsubheading Example
30946 @subheading The @code{-file-list-symbol-files} Command
30947 @findex -file-list-symbol-files
30949 @subsubheading Synopsis
30952 -file-list-symbol-files
30957 @subsubheading @value{GDBN} Command
30959 The corresponding @value{GDBN} command is @samp{info file} (part of it).
30961 @subsubheading Example
30966 @subheading The @code{-file-symbol-file} Command
30967 @findex -file-symbol-file
30969 @subsubheading Synopsis
30972 -file-symbol-file @var{file}
30975 Read symbol table info from the specified @var{file} argument. When
30976 used without arguments, clears @value{GDBN}'s symbol table info. No output is
30977 produced, except for a completion notification.
30979 @subsubheading @value{GDBN} Command
30981 The corresponding @value{GDBN} command is @samp{symbol-file}.
30983 @subsubheading Example
30987 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30993 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30994 @node GDB/MI Memory Overlay Commands
30995 @section @sc{gdb/mi} Memory Overlay Commands
30997 The memory overlay commands are not implemented.
30999 @c @subheading -overlay-auto
31001 @c @subheading -overlay-list-mapping-state
31003 @c @subheading -overlay-list-overlays
31005 @c @subheading -overlay-map
31007 @c @subheading -overlay-off
31009 @c @subheading -overlay-on
31011 @c @subheading -overlay-unmap
31013 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31014 @node GDB/MI Signal Handling Commands
31015 @section @sc{gdb/mi} Signal Handling Commands
31017 Signal handling commands are not implemented.
31019 @c @subheading -signal-handle
31021 @c @subheading -signal-list-handle-actions
31023 @c @subheading -signal-list-signal-types
31027 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31028 @node GDB/MI Target Manipulation
31029 @section @sc{gdb/mi} Target Manipulation Commands
31032 @subheading The @code{-target-attach} Command
31033 @findex -target-attach
31035 @subsubheading Synopsis
31038 -target-attach @var{pid} | @var{gid} | @var{file}
31041 Attach to a process @var{pid} or a file @var{file} outside of
31042 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
31043 group, the id previously returned by
31044 @samp{-list-thread-groups --available} must be used.
31046 @subsubheading @value{GDBN} Command
31048 The corresponding @value{GDBN} command is @samp{attach}.
31050 @subsubheading Example
31054 =thread-created,id="1"
31055 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
31061 @subheading The @code{-target-compare-sections} Command
31062 @findex -target-compare-sections
31064 @subsubheading Synopsis
31067 -target-compare-sections [ @var{section} ]
31070 Compare data of section @var{section} on target to the exec file.
31071 Without the argument, all sections are compared.
31073 @subsubheading @value{GDBN} Command
31075 The @value{GDBN} equivalent is @samp{compare-sections}.
31077 @subsubheading Example
31082 @subheading The @code{-target-detach} Command
31083 @findex -target-detach
31085 @subsubheading Synopsis
31088 -target-detach [ @var{pid} | @var{gid} ]
31091 Detach from the remote target which normally resumes its execution.
31092 If either @var{pid} or @var{gid} is specified, detaches from either
31093 the specified process, or specified thread group. There's no output.
31095 @subsubheading @value{GDBN} Command
31097 The corresponding @value{GDBN} command is @samp{detach}.
31099 @subsubheading Example
31109 @subheading The @code{-target-disconnect} Command
31110 @findex -target-disconnect
31112 @subsubheading Synopsis
31118 Disconnect from the remote target. There's no output and the target is
31119 generally not resumed.
31121 @subsubheading @value{GDBN} Command
31123 The corresponding @value{GDBN} command is @samp{disconnect}.
31125 @subsubheading Example
31135 @subheading The @code{-target-download} Command
31136 @findex -target-download
31138 @subsubheading Synopsis
31144 Loads the executable onto the remote target.
31145 It prints out an update message every half second, which includes the fields:
31149 The name of the section.
31151 The size of what has been sent so far for that section.
31153 The size of the section.
31155 The total size of what was sent so far (the current and the previous sections).
31157 The size of the overall executable to download.
31161 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
31162 @sc{gdb/mi} Output Syntax}).
31164 In addition, it prints the name and size of the sections, as they are
31165 downloaded. These messages include the following fields:
31169 The name of the section.
31171 The size of the section.
31173 The size of the overall executable to download.
31177 At the end, a summary is printed.
31179 @subsubheading @value{GDBN} Command
31181 The corresponding @value{GDBN} command is @samp{load}.
31183 @subsubheading Example
31185 Note: each status message appears on a single line. Here the messages
31186 have been broken down so that they can fit onto a page.
31191 +download,@{section=".text",section-size="6668",total-size="9880"@}
31192 +download,@{section=".text",section-sent="512",section-size="6668",
31193 total-sent="512",total-size="9880"@}
31194 +download,@{section=".text",section-sent="1024",section-size="6668",
31195 total-sent="1024",total-size="9880"@}
31196 +download,@{section=".text",section-sent="1536",section-size="6668",
31197 total-sent="1536",total-size="9880"@}
31198 +download,@{section=".text",section-sent="2048",section-size="6668",
31199 total-sent="2048",total-size="9880"@}
31200 +download,@{section=".text",section-sent="2560",section-size="6668",
31201 total-sent="2560",total-size="9880"@}
31202 +download,@{section=".text",section-sent="3072",section-size="6668",
31203 total-sent="3072",total-size="9880"@}
31204 +download,@{section=".text",section-sent="3584",section-size="6668",
31205 total-sent="3584",total-size="9880"@}
31206 +download,@{section=".text",section-sent="4096",section-size="6668",
31207 total-sent="4096",total-size="9880"@}
31208 +download,@{section=".text",section-sent="4608",section-size="6668",
31209 total-sent="4608",total-size="9880"@}
31210 +download,@{section=".text",section-sent="5120",section-size="6668",
31211 total-sent="5120",total-size="9880"@}
31212 +download,@{section=".text",section-sent="5632",section-size="6668",
31213 total-sent="5632",total-size="9880"@}
31214 +download,@{section=".text",section-sent="6144",section-size="6668",
31215 total-sent="6144",total-size="9880"@}
31216 +download,@{section=".text",section-sent="6656",section-size="6668",
31217 total-sent="6656",total-size="9880"@}
31218 +download,@{section=".init",section-size="28",total-size="9880"@}
31219 +download,@{section=".fini",section-size="28",total-size="9880"@}
31220 +download,@{section=".data",section-size="3156",total-size="9880"@}
31221 +download,@{section=".data",section-sent="512",section-size="3156",
31222 total-sent="7236",total-size="9880"@}
31223 +download,@{section=".data",section-sent="1024",section-size="3156",
31224 total-sent="7748",total-size="9880"@}
31225 +download,@{section=".data",section-sent="1536",section-size="3156",
31226 total-sent="8260",total-size="9880"@}
31227 +download,@{section=".data",section-sent="2048",section-size="3156",
31228 total-sent="8772",total-size="9880"@}
31229 +download,@{section=".data",section-sent="2560",section-size="3156",
31230 total-sent="9284",total-size="9880"@}
31231 +download,@{section=".data",section-sent="3072",section-size="3156",
31232 total-sent="9796",total-size="9880"@}
31233 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
31240 @subheading The @code{-target-exec-status} Command
31241 @findex -target-exec-status
31243 @subsubheading Synopsis
31246 -target-exec-status
31249 Provide information on the state of the target (whether it is running or
31250 not, for instance).
31252 @subsubheading @value{GDBN} Command
31254 There's no equivalent @value{GDBN} command.
31256 @subsubheading Example
31260 @subheading The @code{-target-list-available-targets} Command
31261 @findex -target-list-available-targets
31263 @subsubheading Synopsis
31266 -target-list-available-targets
31269 List the possible targets to connect to.
31271 @subsubheading @value{GDBN} Command
31273 The corresponding @value{GDBN} command is @samp{help target}.
31275 @subsubheading Example
31279 @subheading The @code{-target-list-current-targets} Command
31280 @findex -target-list-current-targets
31282 @subsubheading Synopsis
31285 -target-list-current-targets
31288 Describe the current target.
31290 @subsubheading @value{GDBN} Command
31292 The corresponding information is printed by @samp{info file} (among
31295 @subsubheading Example
31299 @subheading The @code{-target-list-parameters} Command
31300 @findex -target-list-parameters
31302 @subsubheading Synopsis
31305 -target-list-parameters
31311 @subsubheading @value{GDBN} Command
31315 @subsubheading Example
31319 @subheading The @code{-target-select} Command
31320 @findex -target-select
31322 @subsubheading Synopsis
31325 -target-select @var{type} @var{parameters @dots{}}
31328 Connect @value{GDBN} to the remote target. This command takes two args:
31332 The type of target, for instance @samp{remote}, etc.
31333 @item @var{parameters}
31334 Device names, host names and the like. @xref{Target Commands, ,
31335 Commands for Managing Targets}, for more details.
31338 The output is a connection notification, followed by the address at
31339 which the target program is, in the following form:
31342 ^connected,addr="@var{address}",func="@var{function name}",
31343 args=[@var{arg list}]
31346 @subsubheading @value{GDBN} Command
31348 The corresponding @value{GDBN} command is @samp{target}.
31350 @subsubheading Example
31354 -target-select remote /dev/ttya
31355 ^connected,addr="0xfe00a300",func="??",args=[]
31359 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31360 @node GDB/MI File Transfer Commands
31361 @section @sc{gdb/mi} File Transfer Commands
31364 @subheading The @code{-target-file-put} Command
31365 @findex -target-file-put
31367 @subsubheading Synopsis
31370 -target-file-put @var{hostfile} @var{targetfile}
31373 Copy file @var{hostfile} from the host system (the machine running
31374 @value{GDBN}) to @var{targetfile} on the target system.
31376 @subsubheading @value{GDBN} Command
31378 The corresponding @value{GDBN} command is @samp{remote put}.
31380 @subsubheading Example
31384 -target-file-put localfile remotefile
31390 @subheading The @code{-target-file-get} Command
31391 @findex -target-file-get
31393 @subsubheading Synopsis
31396 -target-file-get @var{targetfile} @var{hostfile}
31399 Copy file @var{targetfile} from the target system to @var{hostfile}
31400 on the host system.
31402 @subsubheading @value{GDBN} Command
31404 The corresponding @value{GDBN} command is @samp{remote get}.
31406 @subsubheading Example
31410 -target-file-get remotefile localfile
31416 @subheading The @code{-target-file-delete} Command
31417 @findex -target-file-delete
31419 @subsubheading Synopsis
31422 -target-file-delete @var{targetfile}
31425 Delete @var{targetfile} from the target system.
31427 @subsubheading @value{GDBN} Command
31429 The corresponding @value{GDBN} command is @samp{remote delete}.
31431 @subsubheading Example
31435 -target-file-delete remotefile
31441 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31442 @node GDB/MI Ada Exceptions Commands
31443 @section Ada Exceptions @sc{gdb/mi} Commands
31445 @subheading The @code{-info-ada-exceptions} Command
31446 @findex -info-ada-exceptions
31448 @subsubheading Synopsis
31451 -info-ada-exceptions [ @var{regexp}]
31454 List all Ada exceptions defined within the program being debugged.
31455 With a regular expression @var{regexp}, only those exceptions whose
31456 names match @var{regexp} are listed.
31458 @subsubheading @value{GDBN} Command
31460 The corresponding @value{GDBN} command is @samp{info exceptions}.
31462 @subsubheading Result
31464 The result is a table of Ada exceptions. The following columns are
31465 defined for each exception:
31469 The name of the exception.
31472 The address of the exception.
31476 @subsubheading Example
31479 -info-ada-exceptions aint
31480 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
31481 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
31482 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
31483 body=[@{name="constraint_error",address="0x0000000000613da0"@},
31484 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
31487 @subheading Catching Ada Exceptions
31489 The commands describing how to ask @value{GDBN} to stop when a program
31490 raises an exception are described at @ref{Ada Exception GDB/MI
31491 Catchpoint Commands}.
31494 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31495 @node GDB/MI Support Commands
31496 @section @sc{gdb/mi} Support Commands
31498 Since new commands and features get regularly added to @sc{gdb/mi},
31499 some commands are available to help front-ends query the debugger
31500 about support for these capabilities. Similarly, it is also possible
31501 to query @value{GDBN} about target support of certain features.
31503 @subheading The @code{-info-gdb-mi-command} Command
31504 @cindex @code{-info-gdb-mi-command}
31505 @findex -info-gdb-mi-command
31507 @subsubheading Synopsis
31510 -info-gdb-mi-command @var{cmd_name}
31513 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
31515 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
31516 is technically not part of the command name (@pxref{GDB/MI Input
31517 Syntax}), and thus should be omitted in @var{cmd_name}. However,
31518 for ease of use, this command also accepts the form with the leading
31521 @subsubheading @value{GDBN} Command
31523 There is no corresponding @value{GDBN} command.
31525 @subsubheading Result
31527 The result is a tuple. There is currently only one field:
31531 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
31532 @code{"false"} otherwise.
31536 @subsubheading Example
31538 Here is an example where the @sc{gdb/mi} command does not exist:
31541 -info-gdb-mi-command unsupported-command
31542 ^done,command=@{exists="false"@}
31546 And here is an example where the @sc{gdb/mi} command is known
31550 -info-gdb-mi-command symbol-list-lines
31551 ^done,command=@{exists="true"@}
31554 @subheading The @code{-list-features} Command
31555 @findex -list-features
31556 @cindex supported @sc{gdb/mi} features, list
31558 Returns a list of particular features of the MI protocol that
31559 this version of gdb implements. A feature can be a command,
31560 or a new field in an output of some command, or even an
31561 important bugfix. While a frontend can sometimes detect presence
31562 of a feature at runtime, it is easier to perform detection at debugger
31565 The command returns a list of strings, with each string naming an
31566 available feature. Each returned string is just a name, it does not
31567 have any internal structure. The list of possible feature names
31573 (gdb) -list-features
31574 ^done,result=["feature1","feature2"]
31577 The current list of features is:
31580 @item frozen-varobjs
31581 Indicates support for the @code{-var-set-frozen} command, as well
31582 as possible presense of the @code{frozen} field in the output
31583 of @code{-varobj-create}.
31584 @item pending-breakpoints
31585 Indicates support for the @option{-f} option to the @code{-break-insert}
31588 Indicates Python scripting support, Python-based
31589 pretty-printing commands, and possible presence of the
31590 @samp{display_hint} field in the output of @code{-var-list-children}
31592 Indicates support for the @code{-thread-info} command.
31593 @item data-read-memory-bytes
31594 Indicates support for the @code{-data-read-memory-bytes} and the
31595 @code{-data-write-memory-bytes} commands.
31596 @item breakpoint-notifications
31597 Indicates that changes to breakpoints and breakpoints created via the
31598 CLI will be announced via async records.
31599 @item ada-task-info
31600 Indicates support for the @code{-ada-task-info} command.
31601 @item language-option
31602 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
31603 option (@pxref{Context management}).
31604 @item info-gdb-mi-command
31605 Indicates support for the @code{-info-gdb-mi-command} command.
31606 @item undefined-command-error-code
31607 Indicates support for the "undefined-command" error code in error result
31608 records, produced when trying to execute an undefined @sc{gdb/mi} command
31609 (@pxref{GDB/MI Result Records}).
31610 @item exec-run-start-option
31611 Indicates that the @code{-exec-run} command supports the @option{--start}
31612 option (@pxref{GDB/MI Program Execution}).
31615 @subheading The @code{-list-target-features} Command
31616 @findex -list-target-features
31618 Returns a list of particular features that are supported by the
31619 target. Those features affect the permitted MI commands, but
31620 unlike the features reported by the @code{-list-features} command, the
31621 features depend on which target GDB is using at the moment. Whenever
31622 a target can change, due to commands such as @code{-target-select},
31623 @code{-target-attach} or @code{-exec-run}, the list of target features
31624 may change, and the frontend should obtain it again.
31628 (gdb) -list-target-features
31629 ^done,result=["async"]
31632 The current list of features is:
31636 Indicates that the target is capable of asynchronous command
31637 execution, which means that @value{GDBN} will accept further commands
31638 while the target is running.
31641 Indicates that the target is capable of reverse execution.
31642 @xref{Reverse Execution}, for more information.
31646 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31647 @node GDB/MI Miscellaneous Commands
31648 @section Miscellaneous @sc{gdb/mi} Commands
31650 @c @subheading -gdb-complete
31652 @subheading The @code{-gdb-exit} Command
31655 @subsubheading Synopsis
31661 Exit @value{GDBN} immediately.
31663 @subsubheading @value{GDBN} Command
31665 Approximately corresponds to @samp{quit}.
31667 @subsubheading Example
31677 @subheading The @code{-exec-abort} Command
31678 @findex -exec-abort
31680 @subsubheading Synopsis
31686 Kill the inferior running program.
31688 @subsubheading @value{GDBN} Command
31690 The corresponding @value{GDBN} command is @samp{kill}.
31692 @subsubheading Example
31697 @subheading The @code{-gdb-set} Command
31700 @subsubheading Synopsis
31706 Set an internal @value{GDBN} variable.
31707 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
31709 @subsubheading @value{GDBN} Command
31711 The corresponding @value{GDBN} command is @samp{set}.
31713 @subsubheading Example
31723 @subheading The @code{-gdb-show} Command
31726 @subsubheading Synopsis
31732 Show the current value of a @value{GDBN} variable.
31734 @subsubheading @value{GDBN} Command
31736 The corresponding @value{GDBN} command is @samp{show}.
31738 @subsubheading Example
31747 @c @subheading -gdb-source
31750 @subheading The @code{-gdb-version} Command
31751 @findex -gdb-version
31753 @subsubheading Synopsis
31759 Show version information for @value{GDBN}. Used mostly in testing.
31761 @subsubheading @value{GDBN} Command
31763 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
31764 default shows this information when you start an interactive session.
31766 @subsubheading Example
31768 @c This example modifies the actual output from GDB to avoid overfull
31774 ~Copyright 2000 Free Software Foundation, Inc.
31775 ~GDB is free software, covered by the GNU General Public License, and
31776 ~you are welcome to change it and/or distribute copies of it under
31777 ~ certain conditions.
31778 ~Type "show copying" to see the conditions.
31779 ~There is absolutely no warranty for GDB. Type "show warranty" for
31781 ~This GDB was configured as
31782 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
31787 @subheading The @code{-list-thread-groups} Command
31788 @findex -list-thread-groups
31790 @subheading Synopsis
31793 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
31796 Lists thread groups (@pxref{Thread groups}). When a single thread
31797 group is passed as the argument, lists the children of that group.
31798 When several thread group are passed, lists information about those
31799 thread groups. Without any parameters, lists information about all
31800 top-level thread groups.
31802 Normally, thread groups that are being debugged are reported.
31803 With the @samp{--available} option, @value{GDBN} reports thread groups
31804 available on the target.
31806 The output of this command may have either a @samp{threads} result or
31807 a @samp{groups} result. The @samp{thread} result has a list of tuples
31808 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
31809 Information}). The @samp{groups} result has a list of tuples as value,
31810 each tuple describing a thread group. If top-level groups are
31811 requested (that is, no parameter is passed), or when several groups
31812 are passed, the output always has a @samp{groups} result. The format
31813 of the @samp{group} result is described below.
31815 To reduce the number of roundtrips it's possible to list thread groups
31816 together with their children, by passing the @samp{--recurse} option
31817 and the recursion depth. Presently, only recursion depth of 1 is
31818 permitted. If this option is present, then every reported thread group
31819 will also include its children, either as @samp{group} or
31820 @samp{threads} field.
31822 In general, any combination of option and parameters is permitted, with
31823 the following caveats:
31827 When a single thread group is passed, the output will typically
31828 be the @samp{threads} result. Because threads may not contain
31829 anything, the @samp{recurse} option will be ignored.
31832 When the @samp{--available} option is passed, limited information may
31833 be available. In particular, the list of threads of a process might
31834 be inaccessible. Further, specifying specific thread groups might
31835 not give any performance advantage over listing all thread groups.
31836 The frontend should assume that @samp{-list-thread-groups --available}
31837 is always an expensive operation and cache the results.
31841 The @samp{groups} result is a list of tuples, where each tuple may
31842 have the following fields:
31846 Identifier of the thread group. This field is always present.
31847 The identifier is an opaque string; frontends should not try to
31848 convert it to an integer, even though it might look like one.
31851 The type of the thread group. At present, only @samp{process} is a
31855 The target-specific process identifier. This field is only present
31856 for thread groups of type @samp{process} and only if the process exists.
31859 The exit code of this group's last exited thread, formatted in octal.
31860 This field is only present for thread groups of type @samp{process} and
31861 only if the process is not running.
31864 The number of children this thread group has. This field may be
31865 absent for an available thread group.
31868 This field has a list of tuples as value, each tuple describing a
31869 thread. It may be present if the @samp{--recurse} option is
31870 specified, and it's actually possible to obtain the threads.
31873 This field is a list of integers, each identifying a core that one
31874 thread of the group is running on. This field may be absent if
31875 such information is not available.
31878 The name of the executable file that corresponds to this thread group.
31879 The field is only present for thread groups of type @samp{process},
31880 and only if there is a corresponding executable file.
31884 @subheading Example
31888 -list-thread-groups
31889 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
31890 -list-thread-groups 17
31891 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31892 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
31893 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31894 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
31895 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
31896 -list-thread-groups --available
31897 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
31898 -list-thread-groups --available --recurse 1
31899 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31900 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31901 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
31902 -list-thread-groups --available --recurse 1 17 18
31903 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31904 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31905 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
31908 @subheading The @code{-info-os} Command
31911 @subsubheading Synopsis
31914 -info-os [ @var{type} ]
31917 If no argument is supplied, the command returns a table of available
31918 operating-system-specific information types. If one of these types is
31919 supplied as an argument @var{type}, then the command returns a table
31920 of data of that type.
31922 The types of information available depend on the target operating
31925 @subsubheading @value{GDBN} Command
31927 The corresponding @value{GDBN} command is @samp{info os}.
31929 @subsubheading Example
31931 When run on a @sc{gnu}/Linux system, the output will look something
31937 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
31938 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
31939 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
31940 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
31941 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
31943 item=@{col0="files",col1="Listing of all file descriptors",
31944 col2="File descriptors"@},
31945 item=@{col0="modules",col1="Listing of all loaded kernel modules",
31946 col2="Kernel modules"@},
31947 item=@{col0="msg",col1="Listing of all message queues",
31948 col2="Message queues"@},
31949 item=@{col0="processes",col1="Listing of all processes",
31950 col2="Processes"@},
31951 item=@{col0="procgroups",col1="Listing of all process groups",
31952 col2="Process groups"@},
31953 item=@{col0="semaphores",col1="Listing of all semaphores",
31954 col2="Semaphores"@},
31955 item=@{col0="shm",col1="Listing of all shared-memory regions",
31956 col2="Shared-memory regions"@},
31957 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
31959 item=@{col0="threads",col1="Listing of all threads",
31963 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
31964 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
31965 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
31966 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
31967 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
31968 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
31969 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
31970 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
31972 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
31973 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
31977 (Note that the MI output here includes a @code{"Title"} column that
31978 does not appear in command-line @code{info os}; this column is useful
31979 for MI clients that want to enumerate the types of data, such as in a
31980 popup menu, but is needless clutter on the command line, and
31981 @code{info os} omits it.)
31983 @subheading The @code{-add-inferior} Command
31984 @findex -add-inferior
31986 @subheading Synopsis
31992 Creates a new inferior (@pxref{Inferiors and Programs}). The created
31993 inferior is not associated with any executable. Such association may
31994 be established with the @samp{-file-exec-and-symbols} command
31995 (@pxref{GDB/MI File Commands}). The command response has a single
31996 field, @samp{inferior}, whose value is the identifier of the
31997 thread group corresponding to the new inferior.
31999 @subheading Example
32004 ^done,inferior="i3"
32007 @subheading The @code{-interpreter-exec} Command
32008 @findex -interpreter-exec
32010 @subheading Synopsis
32013 -interpreter-exec @var{interpreter} @var{command}
32015 @anchor{-interpreter-exec}
32017 Execute the specified @var{command} in the given @var{interpreter}.
32019 @subheading @value{GDBN} Command
32021 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
32023 @subheading Example
32027 -interpreter-exec console "break main"
32028 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
32029 &"During symbol reading, bad structure-type format.\n"
32030 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
32035 @subheading The @code{-inferior-tty-set} Command
32036 @findex -inferior-tty-set
32038 @subheading Synopsis
32041 -inferior-tty-set /dev/pts/1
32044 Set terminal for future runs of the program being debugged.
32046 @subheading @value{GDBN} Command
32048 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
32050 @subheading Example
32054 -inferior-tty-set /dev/pts/1
32059 @subheading The @code{-inferior-tty-show} Command
32060 @findex -inferior-tty-show
32062 @subheading Synopsis
32068 Show terminal for future runs of program being debugged.
32070 @subheading @value{GDBN} Command
32072 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
32074 @subheading Example
32078 -inferior-tty-set /dev/pts/1
32082 ^done,inferior_tty_terminal="/dev/pts/1"
32086 @subheading The @code{-enable-timings} Command
32087 @findex -enable-timings
32089 @subheading Synopsis
32092 -enable-timings [yes | no]
32095 Toggle the printing of the wallclock, user and system times for an MI
32096 command as a field in its output. This command is to help frontend
32097 developers optimize the performance of their code. No argument is
32098 equivalent to @samp{yes}.
32100 @subheading @value{GDBN} Command
32104 @subheading Example
32112 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
32113 addr="0x080484ed",func="main",file="myprog.c",
32114 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
32116 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
32124 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
32125 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
32126 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
32127 fullname="/home/nickrob/myprog.c",line="73"@}
32132 @chapter @value{GDBN} Annotations
32134 This chapter describes annotations in @value{GDBN}. Annotations were
32135 designed to interface @value{GDBN} to graphical user interfaces or other
32136 similar programs which want to interact with @value{GDBN} at a
32137 relatively high level.
32139 The annotation mechanism has largely been superseded by @sc{gdb/mi}
32143 This is Edition @value{EDITION}, @value{DATE}.
32147 * Annotations Overview:: What annotations are; the general syntax.
32148 * Server Prefix:: Issuing a command without affecting user state.
32149 * Prompting:: Annotations marking @value{GDBN}'s need for input.
32150 * Errors:: Annotations for error messages.
32151 * Invalidation:: Some annotations describe things now invalid.
32152 * Annotations for Running::
32153 Whether the program is running, how it stopped, etc.
32154 * Source Annotations:: Annotations describing source code.
32157 @node Annotations Overview
32158 @section What is an Annotation?
32159 @cindex annotations
32161 Annotations start with a newline character, two @samp{control-z}
32162 characters, and the name of the annotation. If there is no additional
32163 information associated with this annotation, the name of the annotation
32164 is followed immediately by a newline. If there is additional
32165 information, the name of the annotation is followed by a space, the
32166 additional information, and a newline. The additional information
32167 cannot contain newline characters.
32169 Any output not beginning with a newline and two @samp{control-z}
32170 characters denotes literal output from @value{GDBN}. Currently there is
32171 no need for @value{GDBN} to output a newline followed by two
32172 @samp{control-z} characters, but if there was such a need, the
32173 annotations could be extended with an @samp{escape} annotation which
32174 means those three characters as output.
32176 The annotation @var{level}, which is specified using the
32177 @option{--annotate} command line option (@pxref{Mode Options}), controls
32178 how much information @value{GDBN} prints together with its prompt,
32179 values of expressions, source lines, and other types of output. Level 0
32180 is for no annotations, level 1 is for use when @value{GDBN} is run as a
32181 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
32182 for programs that control @value{GDBN}, and level 2 annotations have
32183 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
32184 Interface, annotate, GDB's Obsolete Annotations}).
32187 @kindex set annotate
32188 @item set annotate @var{level}
32189 The @value{GDBN} command @code{set annotate} sets the level of
32190 annotations to the specified @var{level}.
32192 @item show annotate
32193 @kindex show annotate
32194 Show the current annotation level.
32197 This chapter describes level 3 annotations.
32199 A simple example of starting up @value{GDBN} with annotations is:
32202 $ @kbd{gdb --annotate=3}
32204 Copyright 2003 Free Software Foundation, Inc.
32205 GDB is free software, covered by the GNU General Public License,
32206 and you are welcome to change it and/or distribute copies of it
32207 under certain conditions.
32208 Type "show copying" to see the conditions.
32209 There is absolutely no warranty for GDB. Type "show warranty"
32211 This GDB was configured as "i386-pc-linux-gnu"
32222 Here @samp{quit} is input to @value{GDBN}; the rest is output from
32223 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
32224 denotes a @samp{control-z} character) are annotations; the rest is
32225 output from @value{GDBN}.
32227 @node Server Prefix
32228 @section The Server Prefix
32229 @cindex server prefix
32231 If you prefix a command with @samp{server } then it will not affect
32232 the command history, nor will it affect @value{GDBN}'s notion of which
32233 command to repeat if @key{RET} is pressed on a line by itself. This
32234 means that commands can be run behind a user's back by a front-end in
32235 a transparent manner.
32237 The @code{server } prefix does not affect the recording of values into
32238 the value history; to print a value without recording it into the
32239 value history, use the @code{output} command instead of the
32240 @code{print} command.
32242 Using this prefix also disables confirmation requests
32243 (@pxref{confirmation requests}).
32246 @section Annotation for @value{GDBN} Input
32248 @cindex annotations for prompts
32249 When @value{GDBN} prompts for input, it annotates this fact so it is possible
32250 to know when to send output, when the output from a given command is
32253 Different kinds of input each have a different @dfn{input type}. Each
32254 input type has three annotations: a @code{pre-} annotation, which
32255 denotes the beginning of any prompt which is being output, a plain
32256 annotation, which denotes the end of the prompt, and then a @code{post-}
32257 annotation which denotes the end of any echo which may (or may not) be
32258 associated with the input. For example, the @code{prompt} input type
32259 features the following annotations:
32267 The input types are
32270 @findex pre-prompt annotation
32271 @findex prompt annotation
32272 @findex post-prompt annotation
32274 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
32276 @findex pre-commands annotation
32277 @findex commands annotation
32278 @findex post-commands annotation
32280 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
32281 command. The annotations are repeated for each command which is input.
32283 @findex pre-overload-choice annotation
32284 @findex overload-choice annotation
32285 @findex post-overload-choice annotation
32286 @item overload-choice
32287 When @value{GDBN} wants the user to select between various overloaded functions.
32289 @findex pre-query annotation
32290 @findex query annotation
32291 @findex post-query annotation
32293 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
32295 @findex pre-prompt-for-continue annotation
32296 @findex prompt-for-continue annotation
32297 @findex post-prompt-for-continue annotation
32298 @item prompt-for-continue
32299 When @value{GDBN} is asking the user to press return to continue. Note: Don't
32300 expect this to work well; instead use @code{set height 0} to disable
32301 prompting. This is because the counting of lines is buggy in the
32302 presence of annotations.
32307 @cindex annotations for errors, warnings and interrupts
32309 @findex quit annotation
32314 This annotation occurs right before @value{GDBN} responds to an interrupt.
32316 @findex error annotation
32321 This annotation occurs right before @value{GDBN} responds to an error.
32323 Quit and error annotations indicate that any annotations which @value{GDBN} was
32324 in the middle of may end abruptly. For example, if a
32325 @code{value-history-begin} annotation is followed by a @code{error}, one
32326 cannot expect to receive the matching @code{value-history-end}. One
32327 cannot expect not to receive it either, however; an error annotation
32328 does not necessarily mean that @value{GDBN} is immediately returning all the way
32331 @findex error-begin annotation
32332 A quit or error annotation may be preceded by
32338 Any output between that and the quit or error annotation is the error
32341 Warning messages are not yet annotated.
32342 @c If we want to change that, need to fix warning(), type_error(),
32343 @c range_error(), and possibly other places.
32346 @section Invalidation Notices
32348 @cindex annotations for invalidation messages
32349 The following annotations say that certain pieces of state may have
32353 @findex frames-invalid annotation
32354 @item ^Z^Zframes-invalid
32356 The frames (for example, output from the @code{backtrace} command) may
32359 @findex breakpoints-invalid annotation
32360 @item ^Z^Zbreakpoints-invalid
32362 The breakpoints may have changed. For example, the user just added or
32363 deleted a breakpoint.
32366 @node Annotations for Running
32367 @section Running the Program
32368 @cindex annotations for running programs
32370 @findex starting annotation
32371 @findex stopping annotation
32372 When the program starts executing due to a @value{GDBN} command such as
32373 @code{step} or @code{continue},
32379 is output. When the program stops,
32385 is output. Before the @code{stopped} annotation, a variety of
32386 annotations describe how the program stopped.
32389 @findex exited annotation
32390 @item ^Z^Zexited @var{exit-status}
32391 The program exited, and @var{exit-status} is the exit status (zero for
32392 successful exit, otherwise nonzero).
32394 @findex signalled annotation
32395 @findex signal-name annotation
32396 @findex signal-name-end annotation
32397 @findex signal-string annotation
32398 @findex signal-string-end annotation
32399 @item ^Z^Zsignalled
32400 The program exited with a signal. After the @code{^Z^Zsignalled}, the
32401 annotation continues:
32407 ^Z^Zsignal-name-end
32411 ^Z^Zsignal-string-end
32416 where @var{name} is the name of the signal, such as @code{SIGILL} or
32417 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
32418 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
32419 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
32420 user's benefit and have no particular format.
32422 @findex signal annotation
32424 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
32425 just saying that the program received the signal, not that it was
32426 terminated with it.
32428 @findex breakpoint annotation
32429 @item ^Z^Zbreakpoint @var{number}
32430 The program hit breakpoint number @var{number}.
32432 @findex watchpoint annotation
32433 @item ^Z^Zwatchpoint @var{number}
32434 The program hit watchpoint number @var{number}.
32437 @node Source Annotations
32438 @section Displaying Source
32439 @cindex annotations for source display
32441 @findex source annotation
32442 The following annotation is used instead of displaying source code:
32445 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
32448 where @var{filename} is an absolute file name indicating which source
32449 file, @var{line} is the line number within that file (where 1 is the
32450 first line in the file), @var{character} is the character position
32451 within the file (where 0 is the first character in the file) (for most
32452 debug formats this will necessarily point to the beginning of a line),
32453 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
32454 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
32455 @var{addr} is the address in the target program associated with the
32456 source which is being displayed. The @var{addr} is in the form @samp{0x}
32457 followed by one or more lowercase hex digits (note that this does not
32458 depend on the language).
32460 @node JIT Interface
32461 @chapter JIT Compilation Interface
32462 @cindex just-in-time compilation
32463 @cindex JIT compilation interface
32465 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
32466 interface. A JIT compiler is a program or library that generates native
32467 executable code at runtime and executes it, usually in order to achieve good
32468 performance while maintaining platform independence.
32470 Programs that use JIT compilation are normally difficult to debug because
32471 portions of their code are generated at runtime, instead of being loaded from
32472 object files, which is where @value{GDBN} normally finds the program's symbols
32473 and debug information. In order to debug programs that use JIT compilation,
32474 @value{GDBN} has an interface that allows the program to register in-memory
32475 symbol files with @value{GDBN} at runtime.
32477 If you are using @value{GDBN} to debug a program that uses this interface, then
32478 it should work transparently so long as you have not stripped the binary. If
32479 you are developing a JIT compiler, then the interface is documented in the rest
32480 of this chapter. At this time, the only known client of this interface is the
32483 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
32484 JIT compiler communicates with @value{GDBN} by writing data into a global
32485 variable and calling a fuction at a well-known symbol. When @value{GDBN}
32486 attaches, it reads a linked list of symbol files from the global variable to
32487 find existing code, and puts a breakpoint in the function so that it can find
32488 out about additional code.
32491 * Declarations:: Relevant C struct declarations
32492 * Registering Code:: Steps to register code
32493 * Unregistering Code:: Steps to unregister code
32494 * Custom Debug Info:: Emit debug information in a custom format
32498 @section JIT Declarations
32500 These are the relevant struct declarations that a C program should include to
32501 implement the interface:
32511 struct jit_code_entry
32513 struct jit_code_entry *next_entry;
32514 struct jit_code_entry *prev_entry;
32515 const char *symfile_addr;
32516 uint64_t symfile_size;
32519 struct jit_descriptor
32522 /* This type should be jit_actions_t, but we use uint32_t
32523 to be explicit about the bitwidth. */
32524 uint32_t action_flag;
32525 struct jit_code_entry *relevant_entry;
32526 struct jit_code_entry *first_entry;
32529 /* GDB puts a breakpoint in this function. */
32530 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
32532 /* Make sure to specify the version statically, because the
32533 debugger may check the version before we can set it. */
32534 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
32537 If the JIT is multi-threaded, then it is important that the JIT synchronize any
32538 modifications to this global data properly, which can easily be done by putting
32539 a global mutex around modifications to these structures.
32541 @node Registering Code
32542 @section Registering Code
32544 To register code with @value{GDBN}, the JIT should follow this protocol:
32548 Generate an object file in memory with symbols and other desired debug
32549 information. The file must include the virtual addresses of the sections.
32552 Create a code entry for the file, which gives the start and size of the symbol
32556 Add it to the linked list in the JIT descriptor.
32559 Point the relevant_entry field of the descriptor at the entry.
32562 Set @code{action_flag} to @code{JIT_REGISTER} and call
32563 @code{__jit_debug_register_code}.
32566 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
32567 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
32568 new code. However, the linked list must still be maintained in order to allow
32569 @value{GDBN} to attach to a running process and still find the symbol files.
32571 @node Unregistering Code
32572 @section Unregistering Code
32574 If code is freed, then the JIT should use the following protocol:
32578 Remove the code entry corresponding to the code from the linked list.
32581 Point the @code{relevant_entry} field of the descriptor at the code entry.
32584 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
32585 @code{__jit_debug_register_code}.
32588 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
32589 and the JIT will leak the memory used for the associated symbol files.
32591 @node Custom Debug Info
32592 @section Custom Debug Info
32593 @cindex custom JIT debug info
32594 @cindex JIT debug info reader
32596 Generating debug information in platform-native file formats (like ELF
32597 or COFF) may be an overkill for JIT compilers; especially if all the
32598 debug info is used for is displaying a meaningful backtrace. The
32599 issue can be resolved by having the JIT writers decide on a debug info
32600 format and also provide a reader that parses the debug info generated
32601 by the JIT compiler. This section gives a brief overview on writing
32602 such a parser. More specific details can be found in the source file
32603 @file{gdb/jit-reader.in}, which is also installed as a header at
32604 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
32606 The reader is implemented as a shared object (so this functionality is
32607 not available on platforms which don't allow loading shared objects at
32608 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
32609 @code{jit-reader-unload} are provided, to be used to load and unload
32610 the readers from a preconfigured directory. Once loaded, the shared
32611 object is used the parse the debug information emitted by the JIT
32615 * Using JIT Debug Info Readers:: How to use supplied readers correctly
32616 * Writing JIT Debug Info Readers:: Creating a debug-info reader
32619 @node Using JIT Debug Info Readers
32620 @subsection Using JIT Debug Info Readers
32621 @kindex jit-reader-load
32622 @kindex jit-reader-unload
32624 Readers can be loaded and unloaded using the @code{jit-reader-load}
32625 and @code{jit-reader-unload} commands.
32628 @item jit-reader-load @var{reader}
32629 Load the JIT reader named @var{reader}, which is a shared
32630 object specified as either an absolute or a relative file name. In
32631 the latter case, @value{GDBN} will try to load the reader from a
32632 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
32633 system (here @var{libdir} is the system library directory, often
32634 @file{/usr/local/lib}).
32636 Only one reader can be active at a time; trying to load a second
32637 reader when one is already loaded will result in @value{GDBN}
32638 reporting an error. A new JIT reader can be loaded by first unloading
32639 the current one using @code{jit-reader-unload} and then invoking
32640 @code{jit-reader-load}.
32642 @item jit-reader-unload
32643 Unload the currently loaded JIT reader.
32647 @node Writing JIT Debug Info Readers
32648 @subsection Writing JIT Debug Info Readers
32649 @cindex writing JIT debug info readers
32651 As mentioned, a reader is essentially a shared object conforming to a
32652 certain ABI. This ABI is described in @file{jit-reader.h}.
32654 @file{jit-reader.h} defines the structures, macros and functions
32655 required to write a reader. It is installed (along with
32656 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
32657 the system include directory.
32659 Readers need to be released under a GPL compatible license. A reader
32660 can be declared as released under such a license by placing the macro
32661 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
32663 The entry point for readers is the symbol @code{gdb_init_reader},
32664 which is expected to be a function with the prototype
32666 @findex gdb_init_reader
32668 extern struct gdb_reader_funcs *gdb_init_reader (void);
32671 @cindex @code{struct gdb_reader_funcs}
32673 @code{struct gdb_reader_funcs} contains a set of pointers to callback
32674 functions. These functions are executed to read the debug info
32675 generated by the JIT compiler (@code{read}), to unwind stack frames
32676 (@code{unwind}) and to create canonical frame IDs
32677 (@code{get_Frame_id}). It also has a callback that is called when the
32678 reader is being unloaded (@code{destroy}). The struct looks like this
32681 struct gdb_reader_funcs
32683 /* Must be set to GDB_READER_INTERFACE_VERSION. */
32684 int reader_version;
32686 /* For use by the reader. */
32689 gdb_read_debug_info *read;
32690 gdb_unwind_frame *unwind;
32691 gdb_get_frame_id *get_frame_id;
32692 gdb_destroy_reader *destroy;
32696 @cindex @code{struct gdb_symbol_callbacks}
32697 @cindex @code{struct gdb_unwind_callbacks}
32699 The callbacks are provided with another set of callbacks by
32700 @value{GDBN} to do their job. For @code{read}, these callbacks are
32701 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
32702 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
32703 @code{struct gdb_symbol_callbacks} has callbacks to create new object
32704 files and new symbol tables inside those object files. @code{struct
32705 gdb_unwind_callbacks} has callbacks to read registers off the current
32706 frame and to write out the values of the registers in the previous
32707 frame. Both have a callback (@code{target_read}) to read bytes off the
32708 target's address space.
32710 @node In-Process Agent
32711 @chapter In-Process Agent
32712 @cindex debugging agent
32713 The traditional debugging model is conceptually low-speed, but works fine,
32714 because most bugs can be reproduced in debugging-mode execution. However,
32715 as multi-core or many-core processors are becoming mainstream, and
32716 multi-threaded programs become more and more popular, there should be more
32717 and more bugs that only manifest themselves at normal-mode execution, for
32718 example, thread races, because debugger's interference with the program's
32719 timing may conceal the bugs. On the other hand, in some applications,
32720 it is not feasible for the debugger to interrupt the program's execution
32721 long enough for the developer to learn anything helpful about its behavior.
32722 If the program's correctness depends on its real-time behavior, delays
32723 introduced by a debugger might cause the program to fail, even when the
32724 code itself is correct. It is useful to be able to observe the program's
32725 behavior without interrupting it.
32727 Therefore, traditional debugging model is too intrusive to reproduce
32728 some bugs. In order to reduce the interference with the program, we can
32729 reduce the number of operations performed by debugger. The
32730 @dfn{In-Process Agent}, a shared library, is running within the same
32731 process with inferior, and is able to perform some debugging operations
32732 itself. As a result, debugger is only involved when necessary, and
32733 performance of debugging can be improved accordingly. Note that
32734 interference with program can be reduced but can't be removed completely,
32735 because the in-process agent will still stop or slow down the program.
32737 The in-process agent can interpret and execute Agent Expressions
32738 (@pxref{Agent Expressions}) during performing debugging operations. The
32739 agent expressions can be used for different purposes, such as collecting
32740 data in tracepoints, and condition evaluation in breakpoints.
32742 @anchor{Control Agent}
32743 You can control whether the in-process agent is used as an aid for
32744 debugging with the following commands:
32747 @kindex set agent on
32749 Causes the in-process agent to perform some operations on behalf of the
32750 debugger. Just which operations requested by the user will be done
32751 by the in-process agent depends on the its capabilities. For example,
32752 if you request to evaluate breakpoint conditions in the in-process agent,
32753 and the in-process agent has such capability as well, then breakpoint
32754 conditions will be evaluated in the in-process agent.
32756 @kindex set agent off
32757 @item set agent off
32758 Disables execution of debugging operations by the in-process agent. All
32759 of the operations will be performed by @value{GDBN}.
32763 Display the current setting of execution of debugging operations by
32764 the in-process agent.
32768 * In-Process Agent Protocol::
32771 @node In-Process Agent Protocol
32772 @section In-Process Agent Protocol
32773 @cindex in-process agent protocol
32775 The in-process agent is able to communicate with both @value{GDBN} and
32776 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
32777 used for communications between @value{GDBN} or GDBserver and the IPA.
32778 In general, @value{GDBN} or GDBserver sends commands
32779 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
32780 in-process agent replies back with the return result of the command, or
32781 some other information. The data sent to in-process agent is composed
32782 of primitive data types, such as 4-byte or 8-byte type, and composite
32783 types, which are called objects (@pxref{IPA Protocol Objects}).
32786 * IPA Protocol Objects::
32787 * IPA Protocol Commands::
32790 @node IPA Protocol Objects
32791 @subsection IPA Protocol Objects
32792 @cindex ipa protocol objects
32794 The commands sent to and results received from agent may contain some
32795 complex data types called @dfn{objects}.
32797 The in-process agent is running on the same machine with @value{GDBN}
32798 or GDBserver, so it doesn't have to handle as much differences between
32799 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
32800 However, there are still some differences of two ends in two processes:
32804 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
32805 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
32807 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
32808 GDBserver is compiled with one, and in-process agent is compiled with
32812 Here are the IPA Protocol Objects:
32816 agent expression object. It represents an agent expression
32817 (@pxref{Agent Expressions}).
32818 @anchor{agent expression object}
32820 tracepoint action object. It represents a tracepoint action
32821 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
32822 memory, static trace data and to evaluate expression.
32823 @anchor{tracepoint action object}
32825 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
32826 @anchor{tracepoint object}
32830 The following table describes important attributes of each IPA protocol
32833 @multitable @columnfractions .30 .20 .50
32834 @headitem Name @tab Size @tab Description
32835 @item @emph{agent expression object} @tab @tab
32836 @item length @tab 4 @tab length of bytes code
32837 @item byte code @tab @var{length} @tab contents of byte code
32838 @item @emph{tracepoint action for collecting memory} @tab @tab
32839 @item 'M' @tab 1 @tab type of tracepoint action
32840 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
32841 address of the lowest byte to collect, otherwise @var{addr} is the offset
32842 of @var{basereg} for memory collecting.
32843 @item len @tab 8 @tab length of memory for collecting
32844 @item basereg @tab 4 @tab the register number containing the starting
32845 memory address for collecting.
32846 @item @emph{tracepoint action for collecting registers} @tab @tab
32847 @item 'R' @tab 1 @tab type of tracepoint action
32848 @item @emph{tracepoint action for collecting static trace data} @tab @tab
32849 @item 'L' @tab 1 @tab type of tracepoint action
32850 @item @emph{tracepoint action for expression evaluation} @tab @tab
32851 @item 'X' @tab 1 @tab type of tracepoint action
32852 @item agent expression @tab length of @tab @ref{agent expression object}
32853 @item @emph{tracepoint object} @tab @tab
32854 @item number @tab 4 @tab number of tracepoint
32855 @item address @tab 8 @tab address of tracepoint inserted on
32856 @item type @tab 4 @tab type of tracepoint
32857 @item enabled @tab 1 @tab enable or disable of tracepoint
32858 @item step_count @tab 8 @tab step
32859 @item pass_count @tab 8 @tab pass
32860 @item numactions @tab 4 @tab number of tracepoint actions
32861 @item hit count @tab 8 @tab hit count
32862 @item trace frame usage @tab 8 @tab trace frame usage
32863 @item compiled_cond @tab 8 @tab compiled condition
32864 @item orig_size @tab 8 @tab orig size
32865 @item condition @tab 4 if condition is NULL otherwise length of
32866 @ref{agent expression object}
32867 @tab zero if condition is NULL, otherwise is
32868 @ref{agent expression object}
32869 @item actions @tab variable
32870 @tab numactions number of @ref{tracepoint action object}
32873 @node IPA Protocol Commands
32874 @subsection IPA Protocol Commands
32875 @cindex ipa protocol commands
32877 The spaces in each command are delimiters to ease reading this commands
32878 specification. They don't exist in real commands.
32882 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
32883 Installs a new fast tracepoint described by @var{tracepoint_object}
32884 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
32885 head of @dfn{jumppad}, which is used to jump to data collection routine
32890 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
32891 @var{target_address} is address of tracepoint in the inferior.
32892 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
32893 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
32894 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
32895 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
32902 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
32903 is about to kill inferiors.
32911 @item probe_marker_at:@var{address}
32912 Asks in-process agent to probe the marker at @var{address}.
32919 @item unprobe_marker_at:@var{address}
32920 Asks in-process agent to unprobe the marker at @var{address}.
32924 @chapter Reporting Bugs in @value{GDBN}
32925 @cindex bugs in @value{GDBN}
32926 @cindex reporting bugs in @value{GDBN}
32928 Your bug reports play an essential role in making @value{GDBN} reliable.
32930 Reporting a bug may help you by bringing a solution to your problem, or it
32931 may not. But in any case the principal function of a bug report is to help
32932 the entire community by making the next version of @value{GDBN} work better. Bug
32933 reports are your contribution to the maintenance of @value{GDBN}.
32935 In order for a bug report to serve its purpose, you must include the
32936 information that enables us to fix the bug.
32939 * Bug Criteria:: Have you found a bug?
32940 * Bug Reporting:: How to report bugs
32944 @section Have You Found a Bug?
32945 @cindex bug criteria
32947 If you are not sure whether you have found a bug, here are some guidelines:
32950 @cindex fatal signal
32951 @cindex debugger crash
32952 @cindex crash of debugger
32954 If the debugger gets a fatal signal, for any input whatever, that is a
32955 @value{GDBN} bug. Reliable debuggers never crash.
32957 @cindex error on valid input
32959 If @value{GDBN} produces an error message for valid input, that is a
32960 bug. (Note that if you're cross debugging, the problem may also be
32961 somewhere in the connection to the target.)
32963 @cindex invalid input
32965 If @value{GDBN} does not produce an error message for invalid input,
32966 that is a bug. However, you should note that your idea of
32967 ``invalid input'' might be our idea of ``an extension'' or ``support
32968 for traditional practice''.
32971 If you are an experienced user of debugging tools, your suggestions
32972 for improvement of @value{GDBN} are welcome in any case.
32975 @node Bug Reporting
32976 @section How to Report Bugs
32977 @cindex bug reports
32978 @cindex @value{GDBN} bugs, reporting
32980 A number of companies and individuals offer support for @sc{gnu} products.
32981 If you obtained @value{GDBN} from a support organization, we recommend you
32982 contact that organization first.
32984 You can find contact information for many support companies and
32985 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
32987 @c should add a web page ref...
32990 @ifset BUGURL_DEFAULT
32991 In any event, we also recommend that you submit bug reports for
32992 @value{GDBN}. The preferred method is to submit them directly using
32993 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
32994 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
32997 @strong{Do not send bug reports to @samp{info-gdb}, or to
32998 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
32999 not want to receive bug reports. Those that do have arranged to receive
33002 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
33003 serves as a repeater. The mailing list and the newsgroup carry exactly
33004 the same messages. Often people think of posting bug reports to the
33005 newsgroup instead of mailing them. This appears to work, but it has one
33006 problem which can be crucial: a newsgroup posting often lacks a mail
33007 path back to the sender. Thus, if we need to ask for more information,
33008 we may be unable to reach you. For this reason, it is better to send
33009 bug reports to the mailing list.
33011 @ifclear BUGURL_DEFAULT
33012 In any event, we also recommend that you submit bug reports for
33013 @value{GDBN} to @value{BUGURL}.
33017 The fundamental principle of reporting bugs usefully is this:
33018 @strong{report all the facts}. If you are not sure whether to state a
33019 fact or leave it out, state it!
33021 Often people omit facts because they think they know what causes the
33022 problem and assume that some details do not matter. Thus, you might
33023 assume that the name of the variable you use in an example does not matter.
33024 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
33025 stray memory reference which happens to fetch from the location where that
33026 name is stored in memory; perhaps, if the name were different, the contents
33027 of that location would fool the debugger into doing the right thing despite
33028 the bug. Play it safe and give a specific, complete example. That is the
33029 easiest thing for you to do, and the most helpful.
33031 Keep in mind that the purpose of a bug report is to enable us to fix the
33032 bug. It may be that the bug has been reported previously, but neither
33033 you nor we can know that unless your bug report is complete and
33036 Sometimes people give a few sketchy facts and ask, ``Does this ring a
33037 bell?'' Those bug reports are useless, and we urge everyone to
33038 @emph{refuse to respond to them} except to chide the sender to report
33041 To enable us to fix the bug, you should include all these things:
33045 The version of @value{GDBN}. @value{GDBN} announces it if you start
33046 with no arguments; you can also print it at any time using @code{show
33049 Without this, we will not know whether there is any point in looking for
33050 the bug in the current version of @value{GDBN}.
33053 The type of machine you are using, and the operating system name and
33057 The details of the @value{GDBN} build-time configuration.
33058 @value{GDBN} shows these details if you invoke it with the
33059 @option{--configuration} command-line option, or if you type
33060 @code{show configuration} at @value{GDBN}'s prompt.
33063 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
33064 ``@value{GCC}--2.8.1''.
33067 What compiler (and its version) was used to compile the program you are
33068 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
33069 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
33070 to get this information; for other compilers, see the documentation for
33074 The command arguments you gave the compiler to compile your example and
33075 observe the bug. For example, did you use @samp{-O}? To guarantee
33076 you will not omit something important, list them all. A copy of the
33077 Makefile (or the output from make) is sufficient.
33079 If we were to try to guess the arguments, we would probably guess wrong
33080 and then we might not encounter the bug.
33083 A complete input script, and all necessary source files, that will
33087 A description of what behavior you observe that you believe is
33088 incorrect. For example, ``It gets a fatal signal.''
33090 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
33091 will certainly notice it. But if the bug is incorrect output, we might
33092 not notice unless it is glaringly wrong. You might as well not give us
33093 a chance to make a mistake.
33095 Even if the problem you experience is a fatal signal, you should still
33096 say so explicitly. Suppose something strange is going on, such as, your
33097 copy of @value{GDBN} is out of synch, or you have encountered a bug in
33098 the C library on your system. (This has happened!) Your copy might
33099 crash and ours would not. If you told us to expect a crash, then when
33100 ours fails to crash, we would know that the bug was not happening for
33101 us. If you had not told us to expect a crash, then we would not be able
33102 to draw any conclusion from our observations.
33105 @cindex recording a session script
33106 To collect all this information, you can use a session recording program
33107 such as @command{script}, which is available on many Unix systems.
33108 Just run your @value{GDBN} session inside @command{script} and then
33109 include the @file{typescript} file with your bug report.
33111 Another way to record a @value{GDBN} session is to run @value{GDBN}
33112 inside Emacs and then save the entire buffer to a file.
33115 If you wish to suggest changes to the @value{GDBN} source, send us context
33116 diffs. If you even discuss something in the @value{GDBN} source, refer to
33117 it by context, not by line number.
33119 The line numbers in our development sources will not match those in your
33120 sources. Your line numbers would convey no useful information to us.
33124 Here are some things that are not necessary:
33128 A description of the envelope of the bug.
33130 Often people who encounter a bug spend a lot of time investigating
33131 which changes to the input file will make the bug go away and which
33132 changes will not affect it.
33134 This is often time consuming and not very useful, because the way we
33135 will find the bug is by running a single example under the debugger
33136 with breakpoints, not by pure deduction from a series of examples.
33137 We recommend that you save your time for something else.
33139 Of course, if you can find a simpler example to report @emph{instead}
33140 of the original one, that is a convenience for us. Errors in the
33141 output will be easier to spot, running under the debugger will take
33142 less time, and so on.
33144 However, simplification is not vital; if you do not want to do this,
33145 report the bug anyway and send us the entire test case you used.
33148 A patch for the bug.
33150 A patch for the bug does help us if it is a good one. But do not omit
33151 the necessary information, such as the test case, on the assumption that
33152 a patch is all we need. We might see problems with your patch and decide
33153 to fix the problem another way, or we might not understand it at all.
33155 Sometimes with a program as complicated as @value{GDBN} it is very hard to
33156 construct an example that will make the program follow a certain path
33157 through the code. If you do not send us the example, we will not be able
33158 to construct one, so we will not be able to verify that the bug is fixed.
33160 And if we cannot understand what bug you are trying to fix, or why your
33161 patch should be an improvement, we will not install it. A test case will
33162 help us to understand.
33165 A guess about what the bug is or what it depends on.
33167 Such guesses are usually wrong. Even we cannot guess right about such
33168 things without first using the debugger to find the facts.
33171 @c The readline documentation is distributed with the readline code
33172 @c and consists of the two following files:
33175 @c Use -I with makeinfo to point to the appropriate directory,
33176 @c environment var TEXINPUTS with TeX.
33177 @ifclear SYSTEM_READLINE
33178 @include rluser.texi
33179 @include hsuser.texi
33183 @appendix In Memoriam
33185 The @value{GDBN} project mourns the loss of the following long-time
33190 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
33191 to Free Software in general. Outside of @value{GDBN}, he was known in
33192 the Amiga world for his series of Fish Disks, and the GeekGadget project.
33194 @item Michael Snyder
33195 Michael was one of the Global Maintainers of the @value{GDBN} project,
33196 with contributions recorded as early as 1996, until 2011. In addition
33197 to his day to day participation, he was a large driving force behind
33198 adding Reverse Debugging to @value{GDBN}.
33201 Beyond their technical contributions to the project, they were also
33202 enjoyable members of the Free Software Community. We will miss them.
33204 @node Formatting Documentation
33205 @appendix Formatting Documentation
33207 @cindex @value{GDBN} reference card
33208 @cindex reference card
33209 The @value{GDBN} 4 release includes an already-formatted reference card, ready
33210 for printing with PostScript or Ghostscript, in the @file{gdb}
33211 subdirectory of the main source directory@footnote{In
33212 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
33213 release.}. If you can use PostScript or Ghostscript with your printer,
33214 you can print the reference card immediately with @file{refcard.ps}.
33216 The release also includes the source for the reference card. You
33217 can format it, using @TeX{}, by typing:
33223 The @value{GDBN} reference card is designed to print in @dfn{landscape}
33224 mode on US ``letter'' size paper;
33225 that is, on a sheet 11 inches wide by 8.5 inches
33226 high. You will need to specify this form of printing as an option to
33227 your @sc{dvi} output program.
33229 @cindex documentation
33231 All the documentation for @value{GDBN} comes as part of the machine-readable
33232 distribution. The documentation is written in Texinfo format, which is
33233 a documentation system that uses a single source file to produce both
33234 on-line information and a printed manual. You can use one of the Info
33235 formatting commands to create the on-line version of the documentation
33236 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
33238 @value{GDBN} includes an already formatted copy of the on-line Info
33239 version of this manual in the @file{gdb} subdirectory. The main Info
33240 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
33241 subordinate files matching @samp{gdb.info*} in the same directory. If
33242 necessary, you can print out these files, or read them with any editor;
33243 but they are easier to read using the @code{info} subsystem in @sc{gnu}
33244 Emacs or the standalone @code{info} program, available as part of the
33245 @sc{gnu} Texinfo distribution.
33247 If you want to format these Info files yourself, you need one of the
33248 Info formatting programs, such as @code{texinfo-format-buffer} or
33251 If you have @code{makeinfo} installed, and are in the top level
33252 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
33253 version @value{GDBVN}), you can make the Info file by typing:
33260 If you want to typeset and print copies of this manual, you need @TeX{},
33261 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
33262 Texinfo definitions file.
33264 @TeX{} is a typesetting program; it does not print files directly, but
33265 produces output files called @sc{dvi} files. To print a typeset
33266 document, you need a program to print @sc{dvi} files. If your system
33267 has @TeX{} installed, chances are it has such a program. The precise
33268 command to use depends on your system; @kbd{lpr -d} is common; another
33269 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
33270 require a file name without any extension or a @samp{.dvi} extension.
33272 @TeX{} also requires a macro definitions file called
33273 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
33274 written in Texinfo format. On its own, @TeX{} cannot either read or
33275 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
33276 and is located in the @file{gdb-@var{version-number}/texinfo}
33279 If you have @TeX{} and a @sc{dvi} printer program installed, you can
33280 typeset and print this manual. First switch to the @file{gdb}
33281 subdirectory of the main source directory (for example, to
33282 @file{gdb-@value{GDBVN}/gdb}) and type:
33288 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
33290 @node Installing GDB
33291 @appendix Installing @value{GDBN}
33292 @cindex installation
33295 * Requirements:: Requirements for building @value{GDBN}
33296 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
33297 * Separate Objdir:: Compiling @value{GDBN} in another directory
33298 * Config Names:: Specifying names for hosts and targets
33299 * Configure Options:: Summary of options for configure
33300 * System-wide configuration:: Having a system-wide init file
33304 @section Requirements for Building @value{GDBN}
33305 @cindex building @value{GDBN}, requirements for
33307 Building @value{GDBN} requires various tools and packages to be available.
33308 Other packages will be used only if they are found.
33310 @heading Tools/Packages Necessary for Building @value{GDBN}
33312 @item ISO C90 compiler
33313 @value{GDBN} is written in ISO C90. It should be buildable with any
33314 working C90 compiler, e.g.@: GCC.
33318 @heading Tools/Packages Optional for Building @value{GDBN}
33322 @value{GDBN} can use the Expat XML parsing library. This library may be
33323 included with your operating system distribution; if it is not, you
33324 can get the latest version from @url{http://expat.sourceforge.net}.
33325 The @file{configure} script will search for this library in several
33326 standard locations; if it is installed in an unusual path, you can
33327 use the @option{--with-libexpat-prefix} option to specify its location.
33333 Remote protocol memory maps (@pxref{Memory Map Format})
33335 Target descriptions (@pxref{Target Descriptions})
33337 Remote shared library lists (@xref{Library List Format},
33338 or alternatively @pxref{Library List Format for SVR4 Targets})
33340 MS-Windows shared libraries (@pxref{Shared Libraries})
33342 Traceframe info (@pxref{Traceframe Info Format})
33344 Branch trace (@pxref{Branch Trace Format},
33345 @pxref{Branch Trace Configuration Format})
33349 @cindex compressed debug sections
33350 @value{GDBN} will use the @samp{zlib} library, if available, to read
33351 compressed debug sections. Some linkers, such as GNU gold, are capable
33352 of producing binaries with compressed debug sections. If @value{GDBN}
33353 is compiled with @samp{zlib}, it will be able to read the debug
33354 information in such binaries.
33356 The @samp{zlib} library is likely included with your operating system
33357 distribution; if it is not, you can get the latest version from
33358 @url{http://zlib.net}.
33361 @value{GDBN}'s features related to character sets (@pxref{Character
33362 Sets}) require a functioning @code{iconv} implementation. If you are
33363 on a GNU system, then this is provided by the GNU C Library. Some
33364 other systems also provide a working @code{iconv}.
33366 If @value{GDBN} is using the @code{iconv} program which is installed
33367 in a non-standard place, you will need to tell @value{GDBN} where to find it.
33368 This is done with @option{--with-iconv-bin} which specifies the
33369 directory that contains the @code{iconv} program.
33371 On systems without @code{iconv}, you can install GNU Libiconv. If you
33372 have previously installed Libiconv, you can use the
33373 @option{--with-libiconv-prefix} option to configure.
33375 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
33376 arrange to build Libiconv if a directory named @file{libiconv} appears
33377 in the top-most source directory. If Libiconv is built this way, and
33378 if the operating system does not provide a suitable @code{iconv}
33379 implementation, then the just-built library will automatically be used
33380 by @value{GDBN}. One easy way to set this up is to download GNU
33381 Libiconv, unpack it, and then rename the directory holding the
33382 Libiconv source code to @samp{libiconv}.
33385 @node Running Configure
33386 @section Invoking the @value{GDBN} @file{configure} Script
33387 @cindex configuring @value{GDBN}
33388 @value{GDBN} comes with a @file{configure} script that automates the process
33389 of preparing @value{GDBN} for installation; you can then use @code{make} to
33390 build the @code{gdb} program.
33392 @c irrelevant in info file; it's as current as the code it lives with.
33393 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
33394 look at the @file{README} file in the sources; we may have improved the
33395 installation procedures since publishing this manual.}
33398 The @value{GDBN} distribution includes all the source code you need for
33399 @value{GDBN} in a single directory, whose name is usually composed by
33400 appending the version number to @samp{gdb}.
33402 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
33403 @file{gdb-@value{GDBVN}} directory. That directory contains:
33406 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
33407 script for configuring @value{GDBN} and all its supporting libraries
33409 @item gdb-@value{GDBVN}/gdb
33410 the source specific to @value{GDBN} itself
33412 @item gdb-@value{GDBVN}/bfd
33413 source for the Binary File Descriptor library
33415 @item gdb-@value{GDBVN}/include
33416 @sc{gnu} include files
33418 @item gdb-@value{GDBVN}/libiberty
33419 source for the @samp{-liberty} free software library
33421 @item gdb-@value{GDBVN}/opcodes
33422 source for the library of opcode tables and disassemblers
33424 @item gdb-@value{GDBVN}/readline
33425 source for the @sc{gnu} command-line interface
33427 @item gdb-@value{GDBVN}/glob
33428 source for the @sc{gnu} filename pattern-matching subroutine
33430 @item gdb-@value{GDBVN}/mmalloc
33431 source for the @sc{gnu} memory-mapped malloc package
33434 The simplest way to configure and build @value{GDBN} is to run @file{configure}
33435 from the @file{gdb-@var{version-number}} source directory, which in
33436 this example is the @file{gdb-@value{GDBVN}} directory.
33438 First switch to the @file{gdb-@var{version-number}} source directory
33439 if you are not already in it; then run @file{configure}. Pass the
33440 identifier for the platform on which @value{GDBN} will run as an
33446 cd gdb-@value{GDBVN}
33447 ./configure @var{host}
33452 where @var{host} is an identifier such as @samp{sun4} or
33453 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
33454 (You can often leave off @var{host}; @file{configure} tries to guess the
33455 correct value by examining your system.)
33457 Running @samp{configure @var{host}} and then running @code{make} builds the
33458 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
33459 libraries, then @code{gdb} itself. The configured source files, and the
33460 binaries, are left in the corresponding source directories.
33463 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
33464 system does not recognize this automatically when you run a different
33465 shell, you may need to run @code{sh} on it explicitly:
33468 sh configure @var{host}
33471 If you run @file{configure} from a directory that contains source
33472 directories for multiple libraries or programs, such as the
33473 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
33475 creates configuration files for every directory level underneath (unless
33476 you tell it not to, with the @samp{--norecursion} option).
33478 You should run the @file{configure} script from the top directory in the
33479 source tree, the @file{gdb-@var{version-number}} directory. If you run
33480 @file{configure} from one of the subdirectories, you will configure only
33481 that subdirectory. That is usually not what you want. In particular,
33482 if you run the first @file{configure} from the @file{gdb} subdirectory
33483 of the @file{gdb-@var{version-number}} directory, you will omit the
33484 configuration of @file{bfd}, @file{readline}, and other sibling
33485 directories of the @file{gdb} subdirectory. This leads to build errors
33486 about missing include files such as @file{bfd/bfd.h}.
33488 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
33489 However, you should make sure that the shell on your path (named by
33490 the @samp{SHELL} environment variable) is publicly readable. Remember
33491 that @value{GDBN} uses the shell to start your program---some systems refuse to
33492 let @value{GDBN} debug child processes whose programs are not readable.
33494 @node Separate Objdir
33495 @section Compiling @value{GDBN} in Another Directory
33497 If you want to run @value{GDBN} versions for several host or target machines,
33498 you need a different @code{gdb} compiled for each combination of
33499 host and target. @file{configure} is designed to make this easy by
33500 allowing you to generate each configuration in a separate subdirectory,
33501 rather than in the source directory. If your @code{make} program
33502 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
33503 @code{make} in each of these directories builds the @code{gdb}
33504 program specified there.
33506 To build @code{gdb} in a separate directory, run @file{configure}
33507 with the @samp{--srcdir} option to specify where to find the source.
33508 (You also need to specify a path to find @file{configure}
33509 itself from your working directory. If the path to @file{configure}
33510 would be the same as the argument to @samp{--srcdir}, you can leave out
33511 the @samp{--srcdir} option; it is assumed.)
33513 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
33514 separate directory for a Sun 4 like this:
33518 cd gdb-@value{GDBVN}
33521 ../gdb-@value{GDBVN}/configure sun4
33526 When @file{configure} builds a configuration using a remote source
33527 directory, it creates a tree for the binaries with the same structure
33528 (and using the same names) as the tree under the source directory. In
33529 the example, you'd find the Sun 4 library @file{libiberty.a} in the
33530 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
33531 @file{gdb-sun4/gdb}.
33533 Make sure that your path to the @file{configure} script has just one
33534 instance of @file{gdb} in it. If your path to @file{configure} looks
33535 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
33536 one subdirectory of @value{GDBN}, not the whole package. This leads to
33537 build errors about missing include files such as @file{bfd/bfd.h}.
33539 One popular reason to build several @value{GDBN} configurations in separate
33540 directories is to configure @value{GDBN} for cross-compiling (where
33541 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
33542 programs that run on another machine---the @dfn{target}).
33543 You specify a cross-debugging target by
33544 giving the @samp{--target=@var{target}} option to @file{configure}.
33546 When you run @code{make} to build a program or library, you must run
33547 it in a configured directory---whatever directory you were in when you
33548 called @file{configure} (or one of its subdirectories).
33550 The @code{Makefile} that @file{configure} generates in each source
33551 directory also runs recursively. If you type @code{make} in a source
33552 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
33553 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
33554 will build all the required libraries, and then build GDB.
33556 When you have multiple hosts or targets configured in separate
33557 directories, you can run @code{make} on them in parallel (for example,
33558 if they are NFS-mounted on each of the hosts); they will not interfere
33562 @section Specifying Names for Hosts and Targets
33564 The specifications used for hosts and targets in the @file{configure}
33565 script are based on a three-part naming scheme, but some short predefined
33566 aliases are also supported. The full naming scheme encodes three pieces
33567 of information in the following pattern:
33570 @var{architecture}-@var{vendor}-@var{os}
33573 For example, you can use the alias @code{sun4} as a @var{host} argument,
33574 or as the value for @var{target} in a @code{--target=@var{target}}
33575 option. The equivalent full name is @samp{sparc-sun-sunos4}.
33577 The @file{configure} script accompanying @value{GDBN} does not provide
33578 any query facility to list all supported host and target names or
33579 aliases. @file{configure} calls the Bourne shell script
33580 @code{config.sub} to map abbreviations to full names; you can read the
33581 script, if you wish, or you can use it to test your guesses on
33582 abbreviations---for example:
33585 % sh config.sub i386-linux
33587 % sh config.sub alpha-linux
33588 alpha-unknown-linux-gnu
33589 % sh config.sub hp9k700
33591 % sh config.sub sun4
33592 sparc-sun-sunos4.1.1
33593 % sh config.sub sun3
33594 m68k-sun-sunos4.1.1
33595 % sh config.sub i986v
33596 Invalid configuration `i986v': machine `i986v' not recognized
33600 @code{config.sub} is also distributed in the @value{GDBN} source
33601 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
33603 @node Configure Options
33604 @section @file{configure} Options
33606 Here is a summary of the @file{configure} options and arguments that
33607 are most often useful for building @value{GDBN}. @file{configure} also has
33608 several other options not listed here. @inforef{What Configure
33609 Does,,configure.info}, for a full explanation of @file{configure}.
33612 configure @r{[}--help@r{]}
33613 @r{[}--prefix=@var{dir}@r{]}
33614 @r{[}--exec-prefix=@var{dir}@r{]}
33615 @r{[}--srcdir=@var{dirname}@r{]}
33616 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
33617 @r{[}--target=@var{target}@r{]}
33622 You may introduce options with a single @samp{-} rather than
33623 @samp{--} if you prefer; but you may abbreviate option names if you use
33628 Display a quick summary of how to invoke @file{configure}.
33630 @item --prefix=@var{dir}
33631 Configure the source to install programs and files under directory
33634 @item --exec-prefix=@var{dir}
33635 Configure the source to install programs under directory
33638 @c avoid splitting the warning from the explanation:
33640 @item --srcdir=@var{dirname}
33641 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
33642 @code{make} that implements the @code{VPATH} feature.}@*
33643 Use this option to make configurations in directories separate from the
33644 @value{GDBN} source directories. Among other things, you can use this to
33645 build (or maintain) several configurations simultaneously, in separate
33646 directories. @file{configure} writes configuration-specific files in
33647 the current directory, but arranges for them to use the source in the
33648 directory @var{dirname}. @file{configure} creates directories under
33649 the working directory in parallel to the source directories below
33652 @item --norecursion
33653 Configure only the directory level where @file{configure} is executed; do not
33654 propagate configuration to subdirectories.
33656 @item --target=@var{target}
33657 Configure @value{GDBN} for cross-debugging programs running on the specified
33658 @var{target}. Without this option, @value{GDBN} is configured to debug
33659 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
33661 There is no convenient way to generate a list of all available targets.
33663 @item @var{host} @dots{}
33664 Configure @value{GDBN} to run on the specified @var{host}.
33666 There is no convenient way to generate a list of all available hosts.
33669 There are many other options available as well, but they are generally
33670 needed for special purposes only.
33672 @node System-wide configuration
33673 @section System-wide configuration and settings
33674 @cindex system-wide init file
33676 @value{GDBN} can be configured to have a system-wide init file;
33677 this file will be read and executed at startup (@pxref{Startup, , What
33678 @value{GDBN} does during startup}).
33680 Here is the corresponding configure option:
33683 @item --with-system-gdbinit=@var{file}
33684 Specify that the default location of the system-wide init file is
33688 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
33689 it may be subject to relocation. Two possible cases:
33693 If the default location of this init file contains @file{$prefix},
33694 it will be subject to relocation. Suppose that the configure options
33695 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
33696 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
33697 init file is looked for as @file{$install/etc/gdbinit} instead of
33698 @file{$prefix/etc/gdbinit}.
33701 By contrast, if the default location does not contain the prefix,
33702 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
33703 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
33704 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
33705 wherever @value{GDBN} is installed.
33708 If the configured location of the system-wide init file (as given by the
33709 @option{--with-system-gdbinit} option at configure time) is in the
33710 data-directory (as specified by @option{--with-gdb-datadir} at configure
33711 time) or in one of its subdirectories, then @value{GDBN} will look for the
33712 system-wide init file in the directory specified by the
33713 @option{--data-directory} command-line option.
33714 Note that the system-wide init file is only read once, during @value{GDBN}
33715 initialization. If the data-directory is changed after @value{GDBN} has
33716 started with the @code{set data-directory} command, the file will not be
33720 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
33723 @node System-wide Configuration Scripts
33724 @subsection Installed System-wide Configuration Scripts
33725 @cindex system-wide configuration scripts
33727 The @file{system-gdbinit} directory, located inside the data-directory
33728 (as specified by @option{--with-gdb-datadir} at configure time) contains
33729 a number of scripts which can be used as system-wide init files. To
33730 automatically source those scripts at startup, @value{GDBN} should be
33731 configured with @option{--with-system-gdbinit}. Otherwise, any user
33732 should be able to source them by hand as needed.
33734 The following scripts are currently available:
33737 @item @file{elinos.py}
33739 @cindex ELinOS system-wide configuration script
33740 This script is useful when debugging a program on an ELinOS target.
33741 It takes advantage of the environment variables defined in a standard
33742 ELinOS environment in order to determine the location of the system
33743 shared libraries, and then sets the @samp{solib-absolute-prefix}
33744 and @samp{solib-search-path} variables appropriately.
33746 @item @file{wrs-linux.py}
33747 @pindex wrs-linux.py
33748 @cindex Wind River Linux system-wide configuration script
33749 This script is useful when debugging a program on a target running
33750 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
33751 the host-side sysroot used by the target system.
33755 @node Maintenance Commands
33756 @appendix Maintenance Commands
33757 @cindex maintenance commands
33758 @cindex internal commands
33760 In addition to commands intended for @value{GDBN} users, @value{GDBN}
33761 includes a number of commands intended for @value{GDBN} developers,
33762 that are not documented elsewhere in this manual. These commands are
33763 provided here for reference. (For commands that turn on debugging
33764 messages, see @ref{Debugging Output}.)
33767 @kindex maint agent
33768 @kindex maint agent-eval
33769 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
33770 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
33771 Translate the given @var{expression} into remote agent bytecodes.
33772 This command is useful for debugging the Agent Expression mechanism
33773 (@pxref{Agent Expressions}). The @samp{agent} version produces an
33774 expression useful for data collection, such as by tracepoints, while
33775 @samp{maint agent-eval} produces an expression that evaluates directly
33776 to a result. For instance, a collection expression for @code{globa +
33777 globb} will include bytecodes to record four bytes of memory at each
33778 of the addresses of @code{globa} and @code{globb}, while discarding
33779 the result of the addition, while an evaluation expression will do the
33780 addition and return the sum.
33781 If @code{-at} is given, generate remote agent bytecode for @var{location}.
33782 If not, generate remote agent bytecode for current frame PC address.
33784 @kindex maint agent-printf
33785 @item maint agent-printf @var{format},@var{expr},...
33786 Translate the given format string and list of argument expressions
33787 into remote agent bytecodes and display them as a disassembled list.
33788 This command is useful for debugging the agent version of dynamic
33789 printf (@pxref{Dynamic Printf}).
33791 @kindex maint info breakpoints
33792 @item @anchor{maint info breakpoints}maint info breakpoints
33793 Using the same format as @samp{info breakpoints}, display both the
33794 breakpoints you've set explicitly, and those @value{GDBN} is using for
33795 internal purposes. Internal breakpoints are shown with negative
33796 breakpoint numbers. The type column identifies what kind of breakpoint
33801 Normal, explicitly set breakpoint.
33804 Normal, explicitly set watchpoint.
33807 Internal breakpoint, used to handle correctly stepping through
33808 @code{longjmp} calls.
33810 @item longjmp resume
33811 Internal breakpoint at the target of a @code{longjmp}.
33814 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
33817 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
33820 Shared library events.
33824 @kindex maint info btrace
33825 @item maint info btrace
33826 Pint information about raw branch tracing data.
33828 @kindex maint btrace packet-history
33829 @item maint btrace packet-history
33830 Print the raw branch trace packets that are used to compute the
33831 execution history for the @samp{record btrace} command. Both the
33832 information and the format in which it is printed depend on the btrace
33837 For the BTS recording format, print a list of blocks of sequential
33838 code. For each block, the following information is printed:
33842 Newer blocks have higher numbers. The oldest block has number zero.
33843 @item Lowest @samp{PC}
33844 @item Highest @samp{PC}
33848 For the Intel(R) Processor Trace recording format, print a list of
33849 Intel(R) Processor Trace packets. For each packet, the following
33850 information is printed:
33853 @item Packet number
33854 Newer packets have higher numbers. The oldest packet has number zero.
33856 The packet's offset in the trace stream.
33857 @item Packet opcode and payload
33861 @kindex maint btrace clear-packet-history
33862 @item maint btrace clear-packet-history
33863 Discards the cached packet history printed by the @samp{maint btrace
33864 packet-history} command. The history will be computed again when
33867 @kindex maint btrace clear
33868 @item maint btrace clear
33869 Discard the branch trace data. The data will be fetched anew and the
33870 branch trace will be recomputed when needed.
33872 This implicitly truncates the branch trace to a single branch trace
33873 buffer. When updating branch trace incrementally, the branch trace
33874 available to @value{GDBN} may be bigger than a single branch trace
33877 @kindex maint set btrace pt skip-pad
33878 @item maint set btrace pt skip-pad
33879 @kindex maint show btrace pt skip-pad
33880 @item maint show btrace pt skip-pad
33881 Control whether @value{GDBN} will skip PAD packets when computing the
33884 @kindex set displaced-stepping
33885 @kindex show displaced-stepping
33886 @cindex displaced stepping support
33887 @cindex out-of-line single-stepping
33888 @item set displaced-stepping
33889 @itemx show displaced-stepping
33890 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
33891 if the target supports it. Displaced stepping is a way to single-step
33892 over breakpoints without removing them from the inferior, by executing
33893 an out-of-line copy of the instruction that was originally at the
33894 breakpoint location. It is also known as out-of-line single-stepping.
33897 @item set displaced-stepping on
33898 If the target architecture supports it, @value{GDBN} will use
33899 displaced stepping to step over breakpoints.
33901 @item set displaced-stepping off
33902 @value{GDBN} will not use displaced stepping to step over breakpoints,
33903 even if such is supported by the target architecture.
33905 @cindex non-stop mode, and @samp{set displaced-stepping}
33906 @item set displaced-stepping auto
33907 This is the default mode. @value{GDBN} will use displaced stepping
33908 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
33909 architecture supports displaced stepping.
33912 @kindex maint check-psymtabs
33913 @item maint check-psymtabs
33914 Check the consistency of currently expanded psymtabs versus symtabs.
33915 Use this to check, for example, whether a symbol is in one but not the other.
33917 @kindex maint check-symtabs
33918 @item maint check-symtabs
33919 Check the consistency of currently expanded symtabs.
33921 @kindex maint expand-symtabs
33922 @item maint expand-symtabs [@var{regexp}]
33923 Expand symbol tables.
33924 If @var{regexp} is specified, only expand symbol tables for file
33925 names matching @var{regexp}.
33927 @kindex maint set catch-demangler-crashes
33928 @kindex maint show catch-demangler-crashes
33929 @cindex demangler crashes
33930 @item maint set catch-demangler-crashes [on|off]
33931 @itemx maint show catch-demangler-crashes
33932 Control whether @value{GDBN} should attempt to catch crashes in the
33933 symbol name demangler. The default is to attempt to catch crashes.
33934 If enabled, the first time a crash is caught, a core file is created,
33935 the offending symbol is displayed and the user is presented with the
33936 option to terminate the current session.
33938 @kindex maint cplus first_component
33939 @item maint cplus first_component @var{name}
33940 Print the first C@t{++} class/namespace component of @var{name}.
33942 @kindex maint cplus namespace
33943 @item maint cplus namespace
33944 Print the list of possible C@t{++} namespaces.
33946 @kindex maint deprecate
33947 @kindex maint undeprecate
33948 @cindex deprecated commands
33949 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
33950 @itemx maint undeprecate @var{command}
33951 Deprecate or undeprecate the named @var{command}. Deprecated commands
33952 cause @value{GDBN} to issue a warning when you use them. The optional
33953 argument @var{replacement} says which newer command should be used in
33954 favor of the deprecated one; if it is given, @value{GDBN} will mention
33955 the replacement as part of the warning.
33957 @kindex maint dump-me
33958 @item maint dump-me
33959 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
33960 Cause a fatal signal in the debugger and force it to dump its core.
33961 This is supported only on systems which support aborting a program
33962 with the @code{SIGQUIT} signal.
33964 @kindex maint internal-error
33965 @kindex maint internal-warning
33966 @kindex maint demangler-warning
33967 @cindex demangler crashes
33968 @item maint internal-error @r{[}@var{message-text}@r{]}
33969 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
33970 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
33972 Cause @value{GDBN} to call the internal function @code{internal_error},
33973 @code{internal_warning} or @code{demangler_warning} and hence behave
33974 as though an internal problem has been detected. In addition to
33975 reporting the internal problem, these functions give the user the
33976 opportunity to either quit @value{GDBN} or (for @code{internal_error}
33977 and @code{internal_warning}) create a core file of the current
33978 @value{GDBN} session.
33980 These commands take an optional parameter @var{message-text} that is
33981 used as the text of the error or warning message.
33983 Here's an example of using @code{internal-error}:
33986 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
33987 @dots{}/maint.c:121: internal-error: testing, 1, 2
33988 A problem internal to GDB has been detected. Further
33989 debugging may prove unreliable.
33990 Quit this debugging session? (y or n) @kbd{n}
33991 Create a core file? (y or n) @kbd{n}
33995 @cindex @value{GDBN} internal error
33996 @cindex internal errors, control of @value{GDBN} behavior
33997 @cindex demangler crashes
33999 @kindex maint set internal-error
34000 @kindex maint show internal-error
34001 @kindex maint set internal-warning
34002 @kindex maint show internal-warning
34003 @kindex maint set demangler-warning
34004 @kindex maint show demangler-warning
34005 @item maint set internal-error @var{action} [ask|yes|no]
34006 @itemx maint show internal-error @var{action}
34007 @itemx maint set internal-warning @var{action} [ask|yes|no]
34008 @itemx maint show internal-warning @var{action}
34009 @itemx maint set demangler-warning @var{action} [ask|yes|no]
34010 @itemx maint show demangler-warning @var{action}
34011 When @value{GDBN} reports an internal problem (error or warning) it
34012 gives the user the opportunity to both quit @value{GDBN} and create a
34013 core file of the current @value{GDBN} session. These commands let you
34014 override the default behaviour for each particular @var{action},
34015 described in the table below.
34019 You can specify that @value{GDBN} should always (yes) or never (no)
34020 quit. The default is to ask the user what to do.
34023 You can specify that @value{GDBN} should always (yes) or never (no)
34024 create a core file. The default is to ask the user what to do. Note
34025 that there is no @code{corefile} option for @code{demangler-warning}:
34026 demangler warnings always create a core file and this cannot be
34030 @kindex maint packet
34031 @item maint packet @var{text}
34032 If @value{GDBN} is talking to an inferior via the serial protocol,
34033 then this command sends the string @var{text} to the inferior, and
34034 displays the response packet. @value{GDBN} supplies the initial
34035 @samp{$} character, the terminating @samp{#} character, and the
34038 @kindex maint print architecture
34039 @item maint print architecture @r{[}@var{file}@r{]}
34040 Print the entire architecture configuration. The optional argument
34041 @var{file} names the file where the output goes.
34043 @kindex maint print c-tdesc
34044 @item maint print c-tdesc
34045 Print the current target description (@pxref{Target Descriptions}) as
34046 a C source file. The created source file can be used in @value{GDBN}
34047 when an XML parser is not available to parse the description.
34049 @kindex maint print dummy-frames
34050 @item maint print dummy-frames
34051 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
34054 (@value{GDBP}) @kbd{b add}
34056 (@value{GDBP}) @kbd{print add(2,3)}
34057 Breakpoint 2, add (a=2, b=3) at @dots{}
34059 The program being debugged stopped while in a function called from GDB.
34061 (@value{GDBP}) @kbd{maint print dummy-frames}
34062 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
34066 Takes an optional file parameter.
34068 @kindex maint print registers
34069 @kindex maint print raw-registers
34070 @kindex maint print cooked-registers
34071 @kindex maint print register-groups
34072 @kindex maint print remote-registers
34073 @item maint print registers @r{[}@var{file}@r{]}
34074 @itemx maint print raw-registers @r{[}@var{file}@r{]}
34075 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
34076 @itemx maint print register-groups @r{[}@var{file}@r{]}
34077 @itemx maint print remote-registers @r{[}@var{file}@r{]}
34078 Print @value{GDBN}'s internal register data structures.
34080 The command @code{maint print raw-registers} includes the contents of
34081 the raw register cache; the command @code{maint print
34082 cooked-registers} includes the (cooked) value of all registers,
34083 including registers which aren't available on the target nor visible
34084 to user; the command @code{maint print register-groups} includes the
34085 groups that each register is a member of; and the command @code{maint
34086 print remote-registers} includes the remote target's register numbers
34087 and offsets in the `G' packets.
34089 These commands take an optional parameter, a file name to which to
34090 write the information.
34092 @kindex maint print reggroups
34093 @item maint print reggroups @r{[}@var{file}@r{]}
34094 Print @value{GDBN}'s internal register group data structures. The
34095 optional argument @var{file} tells to what file to write the
34098 The register groups info looks like this:
34101 (@value{GDBP}) @kbd{maint print reggroups}
34114 This command forces @value{GDBN} to flush its internal register cache.
34116 @kindex maint print objfiles
34117 @cindex info for known object files
34118 @item maint print objfiles @r{[}@var{regexp}@r{]}
34119 Print a dump of all known object files.
34120 If @var{regexp} is specified, only print object files whose names
34121 match @var{regexp}. For each object file, this command prints its name,
34122 address in memory, and all of its psymtabs and symtabs.
34124 @kindex maint print user-registers
34125 @cindex user registers
34126 @item maint print user-registers
34127 List all currently available @dfn{user registers}. User registers
34128 typically provide alternate names for actual hardware registers. They
34129 include the four ``standard'' registers @code{$fp}, @code{$pc},
34130 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
34131 registers can be used in expressions in the same way as the canonical
34132 register names, but only the latter are listed by the @code{info
34133 registers} and @code{maint print registers} commands.
34135 @kindex maint print section-scripts
34136 @cindex info for known .debug_gdb_scripts-loaded scripts
34137 @item maint print section-scripts [@var{regexp}]
34138 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
34139 If @var{regexp} is specified, only print scripts loaded by object files
34140 matching @var{regexp}.
34141 For each script, this command prints its name as specified in the objfile,
34142 and the full path if known.
34143 @xref{dotdebug_gdb_scripts section}.
34145 @kindex maint print statistics
34146 @cindex bcache statistics
34147 @item maint print statistics
34148 This command prints, for each object file in the program, various data
34149 about that object file followed by the byte cache (@dfn{bcache})
34150 statistics for the object file. The objfile data includes the number
34151 of minimal, partial, full, and stabs symbols, the number of types
34152 defined by the objfile, the number of as yet unexpanded psym tables,
34153 the number of line tables and string tables, and the amount of memory
34154 used by the various tables. The bcache statistics include the counts,
34155 sizes, and counts of duplicates of all and unique objects, max,
34156 average, and median entry size, total memory used and its overhead and
34157 savings, and various measures of the hash table size and chain
34160 @kindex maint print target-stack
34161 @cindex target stack description
34162 @item maint print target-stack
34163 A @dfn{target} is an interface between the debugger and a particular
34164 kind of file or process. Targets can be stacked in @dfn{strata},
34165 so that more than one target can potentially respond to a request.
34166 In particular, memory accesses will walk down the stack of targets
34167 until they find a target that is interested in handling that particular
34170 This command prints a short description of each layer that was pushed on
34171 the @dfn{target stack}, starting from the top layer down to the bottom one.
34173 @kindex maint print type
34174 @cindex type chain of a data type
34175 @item maint print type @var{expr}
34176 Print the type chain for a type specified by @var{expr}. The argument
34177 can be either a type name or a symbol. If it is a symbol, the type of
34178 that symbol is described. The type chain produced by this command is
34179 a recursive definition of the data type as stored in @value{GDBN}'s
34180 data structures, including its flags and contained types.
34182 @kindex maint set dwarf always-disassemble
34183 @kindex maint show dwarf always-disassemble
34184 @item maint set dwarf always-disassemble
34185 @item maint show dwarf always-disassemble
34186 Control the behavior of @code{info address} when using DWARF debugging
34189 The default is @code{off}, which means that @value{GDBN} should try to
34190 describe a variable's location in an easily readable format. When
34191 @code{on}, @value{GDBN} will instead display the DWARF location
34192 expression in an assembly-like format. Note that some locations are
34193 too complex for @value{GDBN} to describe simply; in this case you will
34194 always see the disassembly form.
34196 Here is an example of the resulting disassembly:
34199 (gdb) info addr argc
34200 Symbol "argc" is a complex DWARF expression:
34204 For more information on these expressions, see
34205 @uref{http://www.dwarfstd.org/, the DWARF standard}.
34207 @kindex maint set dwarf max-cache-age
34208 @kindex maint show dwarf max-cache-age
34209 @item maint set dwarf max-cache-age
34210 @itemx maint show dwarf max-cache-age
34211 Control the DWARF compilation unit cache.
34213 @cindex DWARF compilation units cache
34214 In object files with inter-compilation-unit references, such as those
34215 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
34216 reader needs to frequently refer to previously read compilation units.
34217 This setting controls how long a compilation unit will remain in the
34218 cache if it is not referenced. A higher limit means that cached
34219 compilation units will be stored in memory longer, and more total
34220 memory will be used. Setting it to zero disables caching, which will
34221 slow down @value{GDBN} startup, but reduce memory consumption.
34223 @kindex maint set profile
34224 @kindex maint show profile
34225 @cindex profiling GDB
34226 @item maint set profile
34227 @itemx maint show profile
34228 Control profiling of @value{GDBN}.
34230 Profiling will be disabled until you use the @samp{maint set profile}
34231 command to enable it. When you enable profiling, the system will begin
34232 collecting timing and execution count data; when you disable profiling or
34233 exit @value{GDBN}, the results will be written to a log file. Remember that
34234 if you use profiling, @value{GDBN} will overwrite the profiling log file
34235 (often called @file{gmon.out}). If you have a record of important profiling
34236 data in a @file{gmon.out} file, be sure to move it to a safe location.
34238 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
34239 compiled with the @samp{-pg} compiler option.
34241 @kindex maint set show-debug-regs
34242 @kindex maint show show-debug-regs
34243 @cindex hardware debug registers
34244 @item maint set show-debug-regs
34245 @itemx maint show show-debug-regs
34246 Control whether to show variables that mirror the hardware debug
34247 registers. Use @code{on} to enable, @code{off} to disable. If
34248 enabled, the debug registers values are shown when @value{GDBN} inserts or
34249 removes a hardware breakpoint or watchpoint, and when the inferior
34250 triggers a hardware-assisted breakpoint or watchpoint.
34252 @kindex maint set show-all-tib
34253 @kindex maint show show-all-tib
34254 @item maint set show-all-tib
34255 @itemx maint show show-all-tib
34256 Control whether to show all non zero areas within a 1k block starting
34257 at thread local base, when using the @samp{info w32 thread-information-block}
34260 @kindex maint set target-async
34261 @kindex maint show target-async
34262 @item maint set target-async
34263 @itemx maint show target-async
34264 This controls whether @value{GDBN} targets operate in synchronous or
34265 asynchronous mode (@pxref{Background Execution}). Normally the
34266 default is asynchronous, if it is available; but this can be changed
34267 to more easily debug problems occurring only in synchronous mode.
34269 @kindex maint set target-non-stop @var{mode} [on|off|auto]
34270 @kindex maint show target-non-stop
34271 @item maint set target-non-stop
34272 @itemx maint show target-non-stop
34274 This controls whether @value{GDBN} targets always operate in non-stop
34275 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
34276 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
34277 if supported by the target.
34280 @item maint set target-non-stop auto
34281 This is the default mode. @value{GDBN} controls the target in
34282 non-stop mode if the target supports it.
34284 @item maint set target-non-stop on
34285 @value{GDBN} controls the target in non-stop mode even if the target
34286 does not indicate support.
34288 @item maint set target-non-stop off
34289 @value{GDBN} does not control the target in non-stop mode even if the
34290 target supports it.
34293 @kindex maint set per-command
34294 @kindex maint show per-command
34295 @item maint set per-command
34296 @itemx maint show per-command
34297 @cindex resources used by commands
34299 @value{GDBN} can display the resources used by each command.
34300 This is useful in debugging performance problems.
34303 @item maint set per-command space [on|off]
34304 @itemx maint show per-command space
34305 Enable or disable the printing of the memory used by GDB for each command.
34306 If enabled, @value{GDBN} will display how much memory each command
34307 took, following the command's own output.
34308 This can also be requested by invoking @value{GDBN} with the
34309 @option{--statistics} command-line switch (@pxref{Mode Options}).
34311 @item maint set per-command time [on|off]
34312 @itemx maint show per-command time
34313 Enable or disable the printing of the execution time of @value{GDBN}
34315 If enabled, @value{GDBN} will display how much time it
34316 took to execute each command, following the command's own output.
34317 Both CPU time and wallclock time are printed.
34318 Printing both is useful when trying to determine whether the cost is
34319 CPU or, e.g., disk/network latency.
34320 Note that the CPU time printed is for @value{GDBN} only, it does not include
34321 the execution time of the inferior because there's no mechanism currently
34322 to compute how much time was spent by @value{GDBN} and how much time was
34323 spent by the program been debugged.
34324 This can also be requested by invoking @value{GDBN} with the
34325 @option{--statistics} command-line switch (@pxref{Mode Options}).
34327 @item maint set per-command symtab [on|off]
34328 @itemx maint show per-command symtab
34329 Enable or disable the printing of basic symbol table statistics
34331 If enabled, @value{GDBN} will display the following information:
34335 number of symbol tables
34337 number of primary symbol tables
34339 number of blocks in the blockvector
34343 @kindex maint space
34344 @cindex memory used by commands
34345 @item maint space @var{value}
34346 An alias for @code{maint set per-command space}.
34347 A non-zero value enables it, zero disables it.
34350 @cindex time of command execution
34351 @item maint time @var{value}
34352 An alias for @code{maint set per-command time}.
34353 A non-zero value enables it, zero disables it.
34355 @kindex maint translate-address
34356 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
34357 Find the symbol stored at the location specified by the address
34358 @var{addr} and an optional section name @var{section}. If found,
34359 @value{GDBN} prints the name of the closest symbol and an offset from
34360 the symbol's location to the specified address. This is similar to
34361 the @code{info address} command (@pxref{Symbols}), except that this
34362 command also allows to find symbols in other sections.
34364 If section was not specified, the section in which the symbol was found
34365 is also printed. For dynamically linked executables, the name of
34366 executable or shared library containing the symbol is printed as well.
34370 The following command is useful for non-interactive invocations of
34371 @value{GDBN}, such as in the test suite.
34374 @item set watchdog @var{nsec}
34375 @kindex set watchdog
34376 @cindex watchdog timer
34377 @cindex timeout for commands
34378 Set the maximum number of seconds @value{GDBN} will wait for the
34379 target operation to finish. If this time expires, @value{GDBN}
34380 reports and error and the command is aborted.
34382 @item show watchdog
34383 Show the current setting of the target wait timeout.
34386 @node Remote Protocol
34387 @appendix @value{GDBN} Remote Serial Protocol
34392 * Stop Reply Packets::
34393 * General Query Packets::
34394 * Architecture-Specific Protocol Details::
34395 * Tracepoint Packets::
34396 * Host I/O Packets::
34398 * Notification Packets::
34399 * Remote Non-Stop::
34400 * Packet Acknowledgment::
34402 * File-I/O Remote Protocol Extension::
34403 * Library List Format::
34404 * Library List Format for SVR4 Targets::
34405 * Memory Map Format::
34406 * Thread List Format::
34407 * Traceframe Info Format::
34408 * Branch Trace Format::
34409 * Branch Trace Configuration Format::
34415 There may be occasions when you need to know something about the
34416 protocol---for example, if there is only one serial port to your target
34417 machine, you might want your program to do something special if it
34418 recognizes a packet meant for @value{GDBN}.
34420 In the examples below, @samp{->} and @samp{<-} are used to indicate
34421 transmitted and received data, respectively.
34423 @cindex protocol, @value{GDBN} remote serial
34424 @cindex serial protocol, @value{GDBN} remote
34425 @cindex remote serial protocol
34426 All @value{GDBN} commands and responses (other than acknowledgments
34427 and notifications, see @ref{Notification Packets}) are sent as a
34428 @var{packet}. A @var{packet} is introduced with the character
34429 @samp{$}, the actual @var{packet-data}, and the terminating character
34430 @samp{#} followed by a two-digit @var{checksum}:
34433 @code{$}@var{packet-data}@code{#}@var{checksum}
34437 @cindex checksum, for @value{GDBN} remote
34439 The two-digit @var{checksum} is computed as the modulo 256 sum of all
34440 characters between the leading @samp{$} and the trailing @samp{#} (an
34441 eight bit unsigned checksum).
34443 Implementors should note that prior to @value{GDBN} 5.0 the protocol
34444 specification also included an optional two-digit @var{sequence-id}:
34447 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
34450 @cindex sequence-id, for @value{GDBN} remote
34452 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
34453 has never output @var{sequence-id}s. Stubs that handle packets added
34454 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
34456 When either the host or the target machine receives a packet, the first
34457 response expected is an acknowledgment: either @samp{+} (to indicate
34458 the package was received correctly) or @samp{-} (to request
34462 -> @code{$}@var{packet-data}@code{#}@var{checksum}
34467 The @samp{+}/@samp{-} acknowledgments can be disabled
34468 once a connection is established.
34469 @xref{Packet Acknowledgment}, for details.
34471 The host (@value{GDBN}) sends @var{command}s, and the target (the
34472 debugging stub incorporated in your program) sends a @var{response}. In
34473 the case of step and continue @var{command}s, the response is only sent
34474 when the operation has completed, and the target has again stopped all
34475 threads in all attached processes. This is the default all-stop mode
34476 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
34477 execution mode; see @ref{Remote Non-Stop}, for details.
34479 @var{packet-data} consists of a sequence of characters with the
34480 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
34483 @cindex remote protocol, field separator
34484 Fields within the packet should be separated using @samp{,} @samp{;} or
34485 @samp{:}. Except where otherwise noted all numbers are represented in
34486 @sc{hex} with leading zeros suppressed.
34488 Implementors should note that prior to @value{GDBN} 5.0, the character
34489 @samp{:} could not appear as the third character in a packet (as it
34490 would potentially conflict with the @var{sequence-id}).
34492 @cindex remote protocol, binary data
34493 @anchor{Binary Data}
34494 Binary data in most packets is encoded either as two hexadecimal
34495 digits per byte of binary data. This allowed the traditional remote
34496 protocol to work over connections which were only seven-bit clean.
34497 Some packets designed more recently assume an eight-bit clean
34498 connection, and use a more efficient encoding to send and receive
34501 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
34502 as an escape character. Any escaped byte is transmitted as the escape
34503 character followed by the original character XORed with @code{0x20}.
34504 For example, the byte @code{0x7d} would be transmitted as the two
34505 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
34506 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
34507 @samp{@}}) must always be escaped. Responses sent by the stub
34508 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
34509 is not interpreted as the start of a run-length encoded sequence
34512 Response @var{data} can be run-length encoded to save space.
34513 Run-length encoding replaces runs of identical characters with one
34514 instance of the repeated character, followed by a @samp{*} and a
34515 repeat count. The repeat count is itself sent encoded, to avoid
34516 binary characters in @var{data}: a value of @var{n} is sent as
34517 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
34518 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
34519 code 32) for a repeat count of 3. (This is because run-length
34520 encoding starts to win for counts 3 or more.) Thus, for example,
34521 @samp{0* } is a run-length encoding of ``0000'': the space character
34522 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
34525 The printable characters @samp{#} and @samp{$} or with a numeric value
34526 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
34527 seven repeats (@samp{$}) can be expanded using a repeat count of only
34528 five (@samp{"}). For example, @samp{00000000} can be encoded as
34531 The error response returned for some packets includes a two character
34532 error number. That number is not well defined.
34534 @cindex empty response, for unsupported packets
34535 For any @var{command} not supported by the stub, an empty response
34536 (@samp{$#00}) should be returned. That way it is possible to extend the
34537 protocol. A newer @value{GDBN} can tell if a packet is supported based
34540 At a minimum, a stub is required to support the @samp{g} and @samp{G}
34541 commands for register access, and the @samp{m} and @samp{M} commands
34542 for memory access. Stubs that only control single-threaded targets
34543 can implement run control with the @samp{c} (continue), and @samp{s}
34544 (step) commands. Stubs that support multi-threading targets should
34545 support the @samp{vCont} command. All other commands are optional.
34550 The following table provides a complete list of all currently defined
34551 @var{command}s and their corresponding response @var{data}.
34552 @xref{File-I/O Remote Protocol Extension}, for details about the File
34553 I/O extension of the remote protocol.
34555 Each packet's description has a template showing the packet's overall
34556 syntax, followed by an explanation of the packet's meaning. We
34557 include spaces in some of the templates for clarity; these are not
34558 part of the packet's syntax. No @value{GDBN} packet uses spaces to
34559 separate its components. For example, a template like @samp{foo
34560 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
34561 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
34562 @var{baz}. @value{GDBN} does not transmit a space character between the
34563 @samp{foo} and the @var{bar}, or between the @var{bar} and the
34566 @cindex @var{thread-id}, in remote protocol
34567 @anchor{thread-id syntax}
34568 Several packets and replies include a @var{thread-id} field to identify
34569 a thread. Normally these are positive numbers with a target-specific
34570 interpretation, formatted as big-endian hex strings. A @var{thread-id}
34571 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
34574 In addition, the remote protocol supports a multiprocess feature in
34575 which the @var{thread-id} syntax is extended to optionally include both
34576 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
34577 The @var{pid} (process) and @var{tid} (thread) components each have the
34578 format described above: a positive number with target-specific
34579 interpretation formatted as a big-endian hex string, literal @samp{-1}
34580 to indicate all processes or threads (respectively), or @samp{0} to
34581 indicate an arbitrary process or thread. Specifying just a process, as
34582 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
34583 error to specify all processes but a specific thread, such as
34584 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
34585 for those packets and replies explicitly documented to include a process
34586 ID, rather than a @var{thread-id}.
34588 The multiprocess @var{thread-id} syntax extensions are only used if both
34589 @value{GDBN} and the stub report support for the @samp{multiprocess}
34590 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
34593 Note that all packet forms beginning with an upper- or lower-case
34594 letter, other than those described here, are reserved for future use.
34596 Here are the packet descriptions.
34601 @cindex @samp{!} packet
34602 @anchor{extended mode}
34603 Enable extended mode. In extended mode, the remote server is made
34604 persistent. The @samp{R} packet is used to restart the program being
34610 The remote target both supports and has enabled extended mode.
34614 @cindex @samp{?} packet
34616 Indicate the reason the target halted. The reply is the same as for
34617 step and continue. This packet has a special interpretation when the
34618 target is in non-stop mode; see @ref{Remote Non-Stop}.
34621 @xref{Stop Reply Packets}, for the reply specifications.
34623 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
34624 @cindex @samp{A} packet
34625 Initialized @code{argv[]} array passed into program. @var{arglen}
34626 specifies the number of bytes in the hex encoded byte stream
34627 @var{arg}. See @code{gdbserver} for more details.
34632 The arguments were set.
34638 @cindex @samp{b} packet
34639 (Don't use this packet; its behavior is not well-defined.)
34640 Change the serial line speed to @var{baud}.
34642 JTC: @emph{When does the transport layer state change? When it's
34643 received, or after the ACK is transmitted. In either case, there are
34644 problems if the command or the acknowledgment packet is dropped.}
34646 Stan: @emph{If people really wanted to add something like this, and get
34647 it working for the first time, they ought to modify ser-unix.c to send
34648 some kind of out-of-band message to a specially-setup stub and have the
34649 switch happen "in between" packets, so that from remote protocol's point
34650 of view, nothing actually happened.}
34652 @item B @var{addr},@var{mode}
34653 @cindex @samp{B} packet
34654 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
34655 breakpoint at @var{addr}.
34657 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
34658 (@pxref{insert breakpoint or watchpoint packet}).
34660 @cindex @samp{bc} packet
34663 Backward continue. Execute the target system in reverse. No parameter.
34664 @xref{Reverse Execution}, for more information.
34667 @xref{Stop Reply Packets}, for the reply specifications.
34669 @cindex @samp{bs} packet
34672 Backward single step. Execute one instruction in reverse. No parameter.
34673 @xref{Reverse Execution}, for more information.
34676 @xref{Stop Reply Packets}, for the reply specifications.
34678 @item c @r{[}@var{addr}@r{]}
34679 @cindex @samp{c} packet
34680 Continue at @var{addr}, which is the address to resume. If @var{addr}
34681 is omitted, resume at current address.
34683 This packet is deprecated for multi-threading support. @xref{vCont
34687 @xref{Stop Reply Packets}, for the reply specifications.
34689 @item C @var{sig}@r{[};@var{addr}@r{]}
34690 @cindex @samp{C} packet
34691 Continue with signal @var{sig} (hex signal number). If
34692 @samp{;@var{addr}} is omitted, resume at same address.
34694 This packet is deprecated for multi-threading support. @xref{vCont
34698 @xref{Stop Reply Packets}, for the reply specifications.
34701 @cindex @samp{d} packet
34704 Don't use this packet; instead, define a general set packet
34705 (@pxref{General Query Packets}).
34709 @cindex @samp{D} packet
34710 The first form of the packet is used to detach @value{GDBN} from the
34711 remote system. It is sent to the remote target
34712 before @value{GDBN} disconnects via the @code{detach} command.
34714 The second form, including a process ID, is used when multiprocess
34715 protocol extensions are enabled (@pxref{multiprocess extensions}), to
34716 detach only a specific process. The @var{pid} is specified as a
34717 big-endian hex string.
34727 @item F @var{RC},@var{EE},@var{CF};@var{XX}
34728 @cindex @samp{F} packet
34729 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
34730 This is part of the File-I/O protocol extension. @xref{File-I/O
34731 Remote Protocol Extension}, for the specification.
34734 @anchor{read registers packet}
34735 @cindex @samp{g} packet
34736 Read general registers.
34740 @item @var{XX@dots{}}
34741 Each byte of register data is described by two hex digits. The bytes
34742 with the register are transmitted in target byte order. The size of
34743 each register and their position within the @samp{g} packet are
34744 determined by the @value{GDBN} internal gdbarch functions
34745 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
34746 specification of several standard @samp{g} packets is specified below.
34748 When reading registers from a trace frame (@pxref{Analyze Collected
34749 Data,,Using the Collected Data}), the stub may also return a string of
34750 literal @samp{x}'s in place of the register data digits, to indicate
34751 that the corresponding register has not been collected, thus its value
34752 is unavailable. For example, for an architecture with 4 registers of
34753 4 bytes each, the following reply indicates to @value{GDBN} that
34754 registers 0 and 2 have not been collected, while registers 1 and 3
34755 have been collected, and both have zero value:
34759 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
34766 @item G @var{XX@dots{}}
34767 @cindex @samp{G} packet
34768 Write general registers. @xref{read registers packet}, for a
34769 description of the @var{XX@dots{}} data.
34779 @item H @var{op} @var{thread-id}
34780 @cindex @samp{H} packet
34781 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
34782 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
34783 should be @samp{c} for step and continue operations (note that this
34784 is deprecated, supporting the @samp{vCont} command is a better
34785 option), and @samp{g} for other operations. The thread designator
34786 @var{thread-id} has the format and interpretation described in
34787 @ref{thread-id syntax}.
34798 @c 'H': How restrictive (or permissive) is the thread model. If a
34799 @c thread is selected and stopped, are other threads allowed
34800 @c to continue to execute? As I mentioned above, I think the
34801 @c semantics of each command when a thread is selected must be
34802 @c described. For example:
34804 @c 'g': If the stub supports threads and a specific thread is
34805 @c selected, returns the register block from that thread;
34806 @c otherwise returns current registers.
34808 @c 'G' If the stub supports threads and a specific thread is
34809 @c selected, sets the registers of the register block of
34810 @c that thread; otherwise sets current registers.
34812 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
34813 @anchor{cycle step packet}
34814 @cindex @samp{i} packet
34815 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
34816 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
34817 step starting at that address.
34820 @cindex @samp{I} packet
34821 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
34825 @cindex @samp{k} packet
34828 The exact effect of this packet is not specified.
34830 For a bare-metal target, it may power cycle or reset the target
34831 system. For that reason, the @samp{k} packet has no reply.
34833 For a single-process target, it may kill that process if possible.
34835 A multiple-process target may choose to kill just one process, or all
34836 that are under @value{GDBN}'s control. For more precise control, use
34837 the vKill packet (@pxref{vKill packet}).
34839 If the target system immediately closes the connection in response to
34840 @samp{k}, @value{GDBN} does not consider the lack of packet
34841 acknowledgment to be an error, and assumes the kill was successful.
34843 If connected using @kbd{target extended-remote}, and the target does
34844 not close the connection in response to a kill request, @value{GDBN}
34845 probes the target state as if a new connection was opened
34846 (@pxref{? packet}).
34848 @item m @var{addr},@var{length}
34849 @cindex @samp{m} packet
34850 Read @var{length} addressable memory units starting at address @var{addr}
34851 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
34852 any particular boundary.
34854 The stub need not use any particular size or alignment when gathering
34855 data from memory for the response; even if @var{addr} is word-aligned
34856 and @var{length} is a multiple of the word size, the stub is free to
34857 use byte accesses, or not. For this reason, this packet may not be
34858 suitable for accessing memory-mapped I/O devices.
34859 @cindex alignment of remote memory accesses
34860 @cindex size of remote memory accesses
34861 @cindex memory, alignment and size of remote accesses
34865 @item @var{XX@dots{}}
34866 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
34867 The reply may contain fewer addressable memory units than requested if the
34868 server was able to read only part of the region of memory.
34873 @item M @var{addr},@var{length}:@var{XX@dots{}}
34874 @cindex @samp{M} packet
34875 Write @var{length} addressable memory units starting at address @var{addr}
34876 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
34877 byte is transmitted as a two-digit hexadecimal number.
34884 for an error (this includes the case where only part of the data was
34889 @cindex @samp{p} packet
34890 Read the value of register @var{n}; @var{n} is in hex.
34891 @xref{read registers packet}, for a description of how the returned
34892 register value is encoded.
34896 @item @var{XX@dots{}}
34897 the register's value
34901 Indicating an unrecognized @var{query}.
34904 @item P @var{n@dots{}}=@var{r@dots{}}
34905 @anchor{write register packet}
34906 @cindex @samp{P} packet
34907 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
34908 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
34909 digits for each byte in the register (target byte order).
34919 @item q @var{name} @var{params}@dots{}
34920 @itemx Q @var{name} @var{params}@dots{}
34921 @cindex @samp{q} packet
34922 @cindex @samp{Q} packet
34923 General query (@samp{q}) and set (@samp{Q}). These packets are
34924 described fully in @ref{General Query Packets}.
34927 @cindex @samp{r} packet
34928 Reset the entire system.
34930 Don't use this packet; use the @samp{R} packet instead.
34933 @cindex @samp{R} packet
34934 Restart the program being debugged. The @var{XX}, while needed, is ignored.
34935 This packet is only available in extended mode (@pxref{extended mode}).
34937 The @samp{R} packet has no reply.
34939 @item s @r{[}@var{addr}@r{]}
34940 @cindex @samp{s} packet
34941 Single step, resuming at @var{addr}. If
34942 @var{addr} is omitted, resume at same address.
34944 This packet is deprecated for multi-threading support. @xref{vCont
34948 @xref{Stop Reply Packets}, for the reply specifications.
34950 @item S @var{sig}@r{[};@var{addr}@r{]}
34951 @anchor{step with signal packet}
34952 @cindex @samp{S} packet
34953 Step with signal. This is analogous to the @samp{C} packet, but
34954 requests a single-step, rather than a normal resumption of execution.
34956 This packet is deprecated for multi-threading support. @xref{vCont
34960 @xref{Stop Reply Packets}, for the reply specifications.
34962 @item t @var{addr}:@var{PP},@var{MM}
34963 @cindex @samp{t} packet
34964 Search backwards starting at address @var{addr} for a match with pattern
34965 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
34966 There must be at least 3 digits in @var{addr}.
34968 @item T @var{thread-id}
34969 @cindex @samp{T} packet
34970 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
34975 thread is still alive
34981 Packets starting with @samp{v} are identified by a multi-letter name,
34982 up to the first @samp{;} or @samp{?} (or the end of the packet).
34984 @item vAttach;@var{pid}
34985 @cindex @samp{vAttach} packet
34986 Attach to a new process with the specified process ID @var{pid}.
34987 The process ID is a
34988 hexadecimal integer identifying the process. In all-stop mode, all
34989 threads in the attached process are stopped; in non-stop mode, it may be
34990 attached without being stopped if that is supported by the target.
34992 @c In non-stop mode, on a successful vAttach, the stub should set the
34993 @c current thread to a thread of the newly-attached process. After
34994 @c attaching, GDB queries for the attached process's thread ID with qC.
34995 @c Also note that, from a user perspective, whether or not the
34996 @c target is stopped on attach in non-stop mode depends on whether you
34997 @c use the foreground or background version of the attach command, not
34998 @c on what vAttach does; GDB does the right thing with respect to either
34999 @c stopping or restarting threads.
35001 This packet is only available in extended mode (@pxref{extended mode}).
35007 @item @r{Any stop packet}
35008 for success in all-stop mode (@pxref{Stop Reply Packets})
35010 for success in non-stop mode (@pxref{Remote Non-Stop})
35013 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
35014 @cindex @samp{vCont} packet
35015 @anchor{vCont packet}
35016 Resume the inferior, specifying different actions for each thread.
35017 If an action is specified with no @var{thread-id}, then it is applied to any
35018 threads that don't have a specific action specified; if no default action is
35019 specified then other threads should remain stopped in all-stop mode and
35020 in their current state in non-stop mode.
35021 Specifying multiple
35022 default actions is an error; specifying no actions is also an error.
35023 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
35025 Currently supported actions are:
35031 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
35035 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
35038 @item r @var{start},@var{end}
35039 Step once, and then keep stepping as long as the thread stops at
35040 addresses between @var{start} (inclusive) and @var{end} (exclusive).
35041 The remote stub reports a stop reply when either the thread goes out
35042 of the range or is stopped due to an unrelated reason, such as hitting
35043 a breakpoint. @xref{range stepping}.
35045 If the range is empty (@var{start} == @var{end}), then the action
35046 becomes equivalent to the @samp{s} action. In other words,
35047 single-step once, and report the stop (even if the stepped instruction
35048 jumps to @var{start}).
35050 (A stop reply may be sent at any point even if the PC is still within
35051 the stepping range; for example, it is valid to implement this packet
35052 in a degenerate way as a single instruction step operation.)
35056 The optional argument @var{addr} normally associated with the
35057 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
35058 not supported in @samp{vCont}.
35060 The @samp{t} action is only relevant in non-stop mode
35061 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
35062 A stop reply should be generated for any affected thread not already stopped.
35063 When a thread is stopped by means of a @samp{t} action,
35064 the corresponding stop reply should indicate that the thread has stopped with
35065 signal @samp{0}, regardless of whether the target uses some other signal
35066 as an implementation detail.
35068 The stub must support @samp{vCont} if it reports support for
35069 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
35070 this case @samp{vCont} actions can be specified to apply to all threads
35071 in a process by using the @samp{p@var{pid}.-1} form of the
35075 @xref{Stop Reply Packets}, for the reply specifications.
35078 @cindex @samp{vCont?} packet
35079 Request a list of actions supported by the @samp{vCont} packet.
35083 @item vCont@r{[};@var{action}@dots{}@r{]}
35084 The @samp{vCont} packet is supported. Each @var{action} is a supported
35085 command in the @samp{vCont} packet.
35087 The @samp{vCont} packet is not supported.
35090 @item vFile:@var{operation}:@var{parameter}@dots{}
35091 @cindex @samp{vFile} packet
35092 Perform a file operation on the target system. For details,
35093 see @ref{Host I/O Packets}.
35095 @item vFlashErase:@var{addr},@var{length}
35096 @cindex @samp{vFlashErase} packet
35097 Direct the stub to erase @var{length} bytes of flash starting at
35098 @var{addr}. The region may enclose any number of flash blocks, but
35099 its start and end must fall on block boundaries, as indicated by the
35100 flash block size appearing in the memory map (@pxref{Memory Map
35101 Format}). @value{GDBN} groups flash memory programming operations
35102 together, and sends a @samp{vFlashDone} request after each group; the
35103 stub is allowed to delay erase operation until the @samp{vFlashDone}
35104 packet is received.
35114 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
35115 @cindex @samp{vFlashWrite} packet
35116 Direct the stub to write data to flash address @var{addr}. The data
35117 is passed in binary form using the same encoding as for the @samp{X}
35118 packet (@pxref{Binary Data}). The memory ranges specified by
35119 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
35120 not overlap, and must appear in order of increasing addresses
35121 (although @samp{vFlashErase} packets for higher addresses may already
35122 have been received; the ordering is guaranteed only between
35123 @samp{vFlashWrite} packets). If a packet writes to an address that was
35124 neither erased by a preceding @samp{vFlashErase} packet nor by some other
35125 target-specific method, the results are unpredictable.
35133 for vFlashWrite addressing non-flash memory
35139 @cindex @samp{vFlashDone} packet
35140 Indicate to the stub that flash programming operation is finished.
35141 The stub is permitted to delay or batch the effects of a group of
35142 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
35143 @samp{vFlashDone} packet is received. The contents of the affected
35144 regions of flash memory are unpredictable until the @samp{vFlashDone}
35145 request is completed.
35147 @item vKill;@var{pid}
35148 @cindex @samp{vKill} packet
35149 @anchor{vKill packet}
35150 Kill the process with the specified process ID @var{pid}, which is a
35151 hexadecimal integer identifying the process. This packet is used in
35152 preference to @samp{k} when multiprocess protocol extensions are
35153 supported; see @ref{multiprocess extensions}.
35163 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
35164 @cindex @samp{vRun} packet
35165 Run the program @var{filename}, passing it each @var{argument} on its
35166 command line. The file and arguments are hex-encoded strings. If
35167 @var{filename} is an empty string, the stub may use a default program
35168 (e.g.@: the last program run). The program is created in the stopped
35171 @c FIXME: What about non-stop mode?
35173 This packet is only available in extended mode (@pxref{extended mode}).
35179 @item @r{Any stop packet}
35180 for success (@pxref{Stop Reply Packets})
35184 @cindex @samp{vStopped} packet
35185 @xref{Notification Packets}.
35187 @item X @var{addr},@var{length}:@var{XX@dots{}}
35189 @cindex @samp{X} packet
35190 Write data to memory, where the data is transmitted in binary.
35191 Memory is specified by its address @var{addr} and number of addressable memory
35192 units @var{length} (@pxref{addressable memory unit});
35193 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
35203 @item z @var{type},@var{addr},@var{kind}
35204 @itemx Z @var{type},@var{addr},@var{kind}
35205 @anchor{insert breakpoint or watchpoint packet}
35206 @cindex @samp{z} packet
35207 @cindex @samp{Z} packets
35208 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
35209 watchpoint starting at address @var{address} of kind @var{kind}.
35211 Each breakpoint and watchpoint packet @var{type} is documented
35214 @emph{Implementation notes: A remote target shall return an empty string
35215 for an unrecognized breakpoint or watchpoint packet @var{type}. A
35216 remote target shall support either both or neither of a given
35217 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
35218 avoid potential problems with duplicate packets, the operations should
35219 be implemented in an idempotent way.}
35221 @item z0,@var{addr},@var{kind}
35222 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
35223 @cindex @samp{z0} packet
35224 @cindex @samp{Z0} packet
35225 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
35226 @var{addr} of type @var{kind}.
35228 A memory breakpoint is implemented by replacing the instruction at
35229 @var{addr} with a software breakpoint or trap instruction. The
35230 @var{kind} is target-specific and typically indicates the size of
35231 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
35232 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
35233 architectures have additional meanings for @var{kind};
35234 @var{cond_list} is an optional list of conditional expressions in bytecode
35235 form that should be evaluated on the target's side. These are the
35236 conditions that should be taken into consideration when deciding if
35237 the breakpoint trigger should be reported back to @var{GDBN}.
35239 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
35240 for how to best report a memory breakpoint event to @value{GDBN}.
35242 The @var{cond_list} parameter is comprised of a series of expressions,
35243 concatenated without separators. Each expression has the following form:
35247 @item X @var{len},@var{expr}
35248 @var{len} is the length of the bytecode expression and @var{expr} is the
35249 actual conditional expression in bytecode form.
35253 The optional @var{cmd_list} parameter introduces commands that may be
35254 run on the target, rather than being reported back to @value{GDBN}.
35255 The parameter starts with a numeric flag @var{persist}; if the flag is
35256 nonzero, then the breakpoint may remain active and the commands
35257 continue to be run even when @value{GDBN} disconnects from the target.
35258 Following this flag is a series of expressions concatenated with no
35259 separators. Each expression has the following form:
35263 @item X @var{len},@var{expr}
35264 @var{len} is the length of the bytecode expression and @var{expr} is the
35265 actual conditional expression in bytecode form.
35269 see @ref{Architecture-Specific Protocol Details}.
35271 @emph{Implementation note: It is possible for a target to copy or move
35272 code that contains memory breakpoints (e.g., when implementing
35273 overlays). The behavior of this packet, in the presence of such a
35274 target, is not defined.}
35286 @item z1,@var{addr},@var{kind}
35287 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
35288 @cindex @samp{z1} packet
35289 @cindex @samp{Z1} packet
35290 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
35291 address @var{addr}.
35293 A hardware breakpoint is implemented using a mechanism that is not
35294 dependant on being able to modify the target's memory. The @var{kind}
35295 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
35297 @emph{Implementation note: A hardware breakpoint is not affected by code
35310 @item z2,@var{addr},@var{kind}
35311 @itemx Z2,@var{addr},@var{kind}
35312 @cindex @samp{z2} packet
35313 @cindex @samp{Z2} packet
35314 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
35315 The number of bytes to watch is specified by @var{kind}.
35327 @item z3,@var{addr},@var{kind}
35328 @itemx Z3,@var{addr},@var{kind}
35329 @cindex @samp{z3} packet
35330 @cindex @samp{Z3} packet
35331 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
35332 The number of bytes to watch is specified by @var{kind}.
35344 @item z4,@var{addr},@var{kind}
35345 @itemx Z4,@var{addr},@var{kind}
35346 @cindex @samp{z4} packet
35347 @cindex @samp{Z4} packet
35348 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
35349 The number of bytes to watch is specified by @var{kind}.
35363 @node Stop Reply Packets
35364 @section Stop Reply Packets
35365 @cindex stop reply packets
35367 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
35368 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
35369 receive any of the below as a reply. Except for @samp{?}
35370 and @samp{vStopped}, that reply is only returned
35371 when the target halts. In the below the exact meaning of @dfn{signal
35372 number} is defined by the header @file{include/gdb/signals.h} in the
35373 @value{GDBN} source code.
35375 As in the description of request packets, we include spaces in the
35376 reply templates for clarity; these are not part of the reply packet's
35377 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
35383 The program received signal number @var{AA} (a two-digit hexadecimal
35384 number). This is equivalent to a @samp{T} response with no
35385 @var{n}:@var{r} pairs.
35387 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
35388 @cindex @samp{T} packet reply
35389 The program received signal number @var{AA} (a two-digit hexadecimal
35390 number). This is equivalent to an @samp{S} response, except that the
35391 @samp{@var{n}:@var{r}} pairs can carry values of important registers
35392 and other information directly in the stop reply packet, reducing
35393 round-trip latency. Single-step and breakpoint traps are reported
35394 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
35398 If @var{n} is a hexadecimal number, it is a register number, and the
35399 corresponding @var{r} gives that register's value. The data @var{r} is a
35400 series of bytes in target byte order, with each byte given by a
35401 two-digit hex number.
35404 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
35405 the stopped thread, as specified in @ref{thread-id syntax}.
35408 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
35409 the core on which the stop event was detected.
35412 If @var{n} is a recognized @dfn{stop reason}, it describes a more
35413 specific event that stopped the target. The currently defined stop
35414 reasons are listed below. The @var{aa} should be @samp{05}, the trap
35415 signal. At most one stop reason should be present.
35418 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
35419 and go on to the next; this allows us to extend the protocol in the
35423 The currently defined stop reasons are:
35429 The packet indicates a watchpoint hit, and @var{r} is the data address, in
35432 @cindex shared library events, remote reply
35434 The packet indicates that the loaded libraries have changed.
35435 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
35436 list of loaded libraries. The @var{r} part is ignored.
35438 @cindex replay log events, remote reply
35440 The packet indicates that the target cannot continue replaying
35441 logged execution events, because it has reached the end (or the
35442 beginning when executing backward) of the log. The value of @var{r}
35443 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
35444 for more information.
35447 @anchor{swbreak stop reason}
35448 The packet indicates a memory breakpoint instruction was executed,
35449 irrespective of whether it was @value{GDBN} that planted the
35450 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
35451 part must be left empty.
35453 On some architectures, such as x86, at the architecture level, when a
35454 breakpoint instruction executes the program counter points at the
35455 breakpoint address plus an offset. On such targets, the stub is
35456 responsible for adjusting the PC to point back at the breakpoint
35459 This packet should not be sent by default; older @value{GDBN} versions
35460 did not support it. @value{GDBN} requests it, by supplying an
35461 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35462 remote stub must also supply the appropriate @samp{qSupported} feature
35463 indicating support.
35465 This packet is required for correct non-stop mode operation.
35468 The packet indicates the target stopped for a hardware breakpoint.
35469 The @var{r} part must be left empty.
35471 The same remarks about @samp{qSupported} and non-stop mode above
35474 @cindex fork events, remote reply
35476 The packet indicates that @code{fork} was called, and @var{r}
35477 is the thread ID of the new child process. Refer to
35478 @ref{thread-id syntax} for the format of the @var{thread-id}
35479 field. This packet is only applicable to targets that support
35482 This packet should not be sent by default; older @value{GDBN} versions
35483 did not support it. @value{GDBN} requests it, by supplying an
35484 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35485 remote stub must also supply the appropriate @samp{qSupported} feature
35486 indicating support.
35488 @cindex vfork events, remote reply
35490 The packet indicates that @code{vfork} was called, and @var{r}
35491 is the thread ID of the new child process. Refer to
35492 @ref{thread-id syntax} for the format of the @var{thread-id}
35493 field. This packet is only applicable to targets that support
35496 This packet should not be sent by default; older @value{GDBN} versions
35497 did not support it. @value{GDBN} requests it, by supplying an
35498 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35499 remote stub must also supply the appropriate @samp{qSupported} feature
35500 indicating support.
35502 @cindex vforkdone events, remote reply
35504 The packet indicates that a child process created by a vfork
35505 has either called @code{exec} or terminated, so that the
35506 address spaces of the parent and child process are no longer
35507 shared. The @var{r} part is ignored. This packet is only
35508 applicable to targets that support vforkdone events.
35510 This packet should not be sent by default; older @value{GDBN} versions
35511 did not support it. @value{GDBN} requests it, by supplying an
35512 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35513 remote stub must also supply the appropriate @samp{qSupported} feature
35514 indicating support.
35516 @cindex exec events, remote reply
35518 The packet indicates that @code{execve} was called, and @var{r}
35519 is the absolute pathname of the file that was executed, in hex.
35520 This packet is only applicable to targets that support exec events.
35522 This packet should not be sent by default; older @value{GDBN} versions
35523 did not support it. @value{GDBN} requests it, by supplying an
35524 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35525 remote stub must also supply the appropriate @samp{qSupported} feature
35526 indicating support.
35531 @itemx W @var{AA} ; process:@var{pid}
35532 The process exited, and @var{AA} is the exit status. This is only
35533 applicable to certain targets.
35535 The second form of the response, including the process ID of the exited
35536 process, can be used only when @value{GDBN} has reported support for
35537 multiprocess protocol extensions; see @ref{multiprocess extensions}.
35538 The @var{pid} is formatted as a big-endian hex string.
35541 @itemx X @var{AA} ; process:@var{pid}
35542 The process terminated with signal @var{AA}.
35544 The second form of the response, including the process ID of the
35545 terminated process, can be used only when @value{GDBN} has reported
35546 support for multiprocess protocol extensions; see @ref{multiprocess
35547 extensions}. The @var{pid} is formatted as a big-endian hex string.
35549 @item O @var{XX}@dots{}
35550 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
35551 written as the program's console output. This can happen at any time
35552 while the program is running and the debugger should continue to wait
35553 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
35555 @item F @var{call-id},@var{parameter}@dots{}
35556 @var{call-id} is the identifier which says which host system call should
35557 be called. This is just the name of the function. Translation into the
35558 correct system call is only applicable as it's defined in @value{GDBN}.
35559 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
35562 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
35563 this very system call.
35565 The target replies with this packet when it expects @value{GDBN} to
35566 call a host system call on behalf of the target. @value{GDBN} replies
35567 with an appropriate @samp{F} packet and keeps up waiting for the next
35568 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
35569 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
35570 Protocol Extension}, for more details.
35574 @node General Query Packets
35575 @section General Query Packets
35576 @cindex remote query requests
35578 Packets starting with @samp{q} are @dfn{general query packets};
35579 packets starting with @samp{Q} are @dfn{general set packets}. General
35580 query and set packets are a semi-unified form for retrieving and
35581 sending information to and from the stub.
35583 The initial letter of a query or set packet is followed by a name
35584 indicating what sort of thing the packet applies to. For example,
35585 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
35586 definitions with the stub. These packet names follow some
35591 The name must not contain commas, colons or semicolons.
35593 Most @value{GDBN} query and set packets have a leading upper case
35596 The names of custom vendor packets should use a company prefix, in
35597 lower case, followed by a period. For example, packets designed at
35598 the Acme Corporation might begin with @samp{qacme.foo} (for querying
35599 foos) or @samp{Qacme.bar} (for setting bars).
35602 The name of a query or set packet should be separated from any
35603 parameters by a @samp{:}; the parameters themselves should be
35604 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
35605 full packet name, and check for a separator or the end of the packet,
35606 in case two packet names share a common prefix. New packets should not begin
35607 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
35608 packets predate these conventions, and have arguments without any terminator
35609 for the packet name; we suspect they are in widespread use in places that
35610 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
35611 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
35614 Like the descriptions of the other packets, each description here
35615 has a template showing the packet's overall syntax, followed by an
35616 explanation of the packet's meaning. We include spaces in some of the
35617 templates for clarity; these are not part of the packet's syntax. No
35618 @value{GDBN} packet uses spaces to separate its components.
35620 Here are the currently defined query and set packets:
35626 Turn on or off the agent as a helper to perform some debugging operations
35627 delegated from @value{GDBN} (@pxref{Control Agent}).
35629 @item QAllow:@var{op}:@var{val}@dots{}
35630 @cindex @samp{QAllow} packet
35631 Specify which operations @value{GDBN} expects to request of the
35632 target, as a semicolon-separated list of operation name and value
35633 pairs. Possible values for @var{op} include @samp{WriteReg},
35634 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
35635 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
35636 indicating that @value{GDBN} will not request the operation, or 1,
35637 indicating that it may. (The target can then use this to set up its
35638 own internals optimally, for instance if the debugger never expects to
35639 insert breakpoints, it may not need to install its own trap handler.)
35642 @cindex current thread, remote request
35643 @cindex @samp{qC} packet
35644 Return the current thread ID.
35648 @item QC @var{thread-id}
35649 Where @var{thread-id} is a thread ID as documented in
35650 @ref{thread-id syntax}.
35651 @item @r{(anything else)}
35652 Any other reply implies the old thread ID.
35655 @item qCRC:@var{addr},@var{length}
35656 @cindex CRC of memory block, remote request
35657 @cindex @samp{qCRC} packet
35658 @anchor{qCRC packet}
35659 Compute the CRC checksum of a block of memory using CRC-32 defined in
35660 IEEE 802.3. The CRC is computed byte at a time, taking the most
35661 significant bit of each byte first. The initial pattern code
35662 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
35664 @emph{Note:} This is the same CRC used in validating separate debug
35665 files (@pxref{Separate Debug Files, , Debugging Information in Separate
35666 Files}). However the algorithm is slightly different. When validating
35667 separate debug files, the CRC is computed taking the @emph{least}
35668 significant bit of each byte first, and the final result is inverted to
35669 detect trailing zeros.
35674 An error (such as memory fault)
35675 @item C @var{crc32}
35676 The specified memory region's checksum is @var{crc32}.
35679 @item QDisableRandomization:@var{value}
35680 @cindex disable address space randomization, remote request
35681 @cindex @samp{QDisableRandomization} packet
35682 Some target operating systems will randomize the virtual address space
35683 of the inferior process as a security feature, but provide a feature
35684 to disable such randomization, e.g.@: to allow for a more deterministic
35685 debugging experience. On such systems, this packet with a @var{value}
35686 of 1 directs the target to disable address space randomization for
35687 processes subsequently started via @samp{vRun} packets, while a packet
35688 with a @var{value} of 0 tells the target to enable address space
35691 This packet is only available in extended mode (@pxref{extended mode}).
35696 The request succeeded.
35699 An error occurred. The error number @var{nn} is given as hex digits.
35702 An empty reply indicates that @samp{QDisableRandomization} is not supported
35706 This packet is not probed by default; the remote stub must request it,
35707 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35708 This should only be done on targets that actually support disabling
35709 address space randomization.
35712 @itemx qsThreadInfo
35713 @cindex list active threads, remote request
35714 @cindex @samp{qfThreadInfo} packet
35715 @cindex @samp{qsThreadInfo} packet
35716 Obtain a list of all active thread IDs from the target (OS). Since there
35717 may be too many active threads to fit into one reply packet, this query
35718 works iteratively: it may require more than one query/reply sequence to
35719 obtain the entire list of threads. The first query of the sequence will
35720 be the @samp{qfThreadInfo} query; subsequent queries in the
35721 sequence will be the @samp{qsThreadInfo} query.
35723 NOTE: This packet replaces the @samp{qL} query (see below).
35727 @item m @var{thread-id}
35729 @item m @var{thread-id},@var{thread-id}@dots{}
35730 a comma-separated list of thread IDs
35732 (lower case letter @samp{L}) denotes end of list.
35735 In response to each query, the target will reply with a list of one or
35736 more thread IDs, separated by commas.
35737 @value{GDBN} will respond to each reply with a request for more thread
35738 ids (using the @samp{qs} form of the query), until the target responds
35739 with @samp{l} (lower-case ell, for @dfn{last}).
35740 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
35743 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
35744 initial connection with the remote target, and the very first thread ID
35745 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
35746 message. Therefore, the stub should ensure that the first thread ID in
35747 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
35749 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
35750 @cindex get thread-local storage address, remote request
35751 @cindex @samp{qGetTLSAddr} packet
35752 Fetch the address associated with thread local storage specified
35753 by @var{thread-id}, @var{offset}, and @var{lm}.
35755 @var{thread-id} is the thread ID associated with the
35756 thread for which to fetch the TLS address. @xref{thread-id syntax}.
35758 @var{offset} is the (big endian, hex encoded) offset associated with the
35759 thread local variable. (This offset is obtained from the debug
35760 information associated with the variable.)
35762 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
35763 load module associated with the thread local storage. For example,
35764 a @sc{gnu}/Linux system will pass the link map address of the shared
35765 object associated with the thread local storage under consideration.
35766 Other operating environments may choose to represent the load module
35767 differently, so the precise meaning of this parameter will vary.
35771 @item @var{XX}@dots{}
35772 Hex encoded (big endian) bytes representing the address of the thread
35773 local storage requested.
35776 An error occurred. The error number @var{nn} is given as hex digits.
35779 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
35782 @item qGetTIBAddr:@var{thread-id}
35783 @cindex get thread information block address
35784 @cindex @samp{qGetTIBAddr} packet
35785 Fetch address of the Windows OS specific Thread Information Block.
35787 @var{thread-id} is the thread ID associated with the thread.
35791 @item @var{XX}@dots{}
35792 Hex encoded (big endian) bytes representing the linear address of the
35793 thread information block.
35796 An error occured. This means that either the thread was not found, or the
35797 address could not be retrieved.
35800 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
35803 @item qL @var{startflag} @var{threadcount} @var{nextthread}
35804 Obtain thread information from RTOS. Where: @var{startflag} (one hex
35805 digit) is one to indicate the first query and zero to indicate a
35806 subsequent query; @var{threadcount} (two hex digits) is the maximum
35807 number of threads the response packet can contain; and @var{nextthread}
35808 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
35809 returned in the response as @var{argthread}.
35811 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
35815 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
35816 Where: @var{count} (two hex digits) is the number of threads being
35817 returned; @var{done} (one hex digit) is zero to indicate more threads
35818 and one indicates no further threads; @var{argthreadid} (eight hex
35819 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
35820 is a sequence of thread IDs, @var{threadid} (eight hex
35821 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
35825 @cindex section offsets, remote request
35826 @cindex @samp{qOffsets} packet
35827 Get section offsets that the target used when relocating the downloaded
35832 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
35833 Relocate the @code{Text} section by @var{xxx} from its original address.
35834 Relocate the @code{Data} section by @var{yyy} from its original address.
35835 If the object file format provides segment information (e.g.@: @sc{elf}
35836 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
35837 segments by the supplied offsets.
35839 @emph{Note: while a @code{Bss} offset may be included in the response,
35840 @value{GDBN} ignores this and instead applies the @code{Data} offset
35841 to the @code{Bss} section.}
35843 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
35844 Relocate the first segment of the object file, which conventionally
35845 contains program code, to a starting address of @var{xxx}. If
35846 @samp{DataSeg} is specified, relocate the second segment, which
35847 conventionally contains modifiable data, to a starting address of
35848 @var{yyy}. @value{GDBN} will report an error if the object file
35849 does not contain segment information, or does not contain at least
35850 as many segments as mentioned in the reply. Extra segments are
35851 kept at fixed offsets relative to the last relocated segment.
35854 @item qP @var{mode} @var{thread-id}
35855 @cindex thread information, remote request
35856 @cindex @samp{qP} packet
35857 Returns information on @var{thread-id}. Where: @var{mode} is a hex
35858 encoded 32 bit mode; @var{thread-id} is a thread ID
35859 (@pxref{thread-id syntax}).
35861 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
35864 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
35868 @cindex non-stop mode, remote request
35869 @cindex @samp{QNonStop} packet
35871 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
35872 @xref{Remote Non-Stop}, for more information.
35877 The request succeeded.
35880 An error occurred. The error number @var{nn} is given as hex digits.
35883 An empty reply indicates that @samp{QNonStop} is not supported by
35887 This packet is not probed by default; the remote stub must request it,
35888 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35889 Use of this packet is controlled by the @code{set non-stop} command;
35890 @pxref{Non-Stop Mode}.
35892 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
35893 @cindex pass signals to inferior, remote request
35894 @cindex @samp{QPassSignals} packet
35895 @anchor{QPassSignals}
35896 Each listed @var{signal} should be passed directly to the inferior process.
35897 Signals are numbered identically to continue packets and stop replies
35898 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
35899 strictly greater than the previous item. These signals do not need to stop
35900 the inferior, or be reported to @value{GDBN}. All other signals should be
35901 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
35902 combine; any earlier @samp{QPassSignals} list is completely replaced by the
35903 new list. This packet improves performance when using @samp{handle
35904 @var{signal} nostop noprint pass}.
35909 The request succeeded.
35912 An error occurred. The error number @var{nn} is given as hex digits.
35915 An empty reply indicates that @samp{QPassSignals} is not supported by
35919 Use of this packet is controlled by the @code{set remote pass-signals}
35920 command (@pxref{Remote Configuration, set remote pass-signals}).
35921 This packet is not probed by default; the remote stub must request it,
35922 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35924 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
35925 @cindex signals the inferior may see, remote request
35926 @cindex @samp{QProgramSignals} packet
35927 @anchor{QProgramSignals}
35928 Each listed @var{signal} may be delivered to the inferior process.
35929 Others should be silently discarded.
35931 In some cases, the remote stub may need to decide whether to deliver a
35932 signal to the program or not without @value{GDBN} involvement. One
35933 example of that is while detaching --- the program's threads may have
35934 stopped for signals that haven't yet had a chance of being reported to
35935 @value{GDBN}, and so the remote stub can use the signal list specified
35936 by this packet to know whether to deliver or ignore those pending
35939 This does not influence whether to deliver a signal as requested by a
35940 resumption packet (@pxref{vCont packet}).
35942 Signals are numbered identically to continue packets and stop replies
35943 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
35944 strictly greater than the previous item. Multiple
35945 @samp{QProgramSignals} packets do not combine; any earlier
35946 @samp{QProgramSignals} list is completely replaced by the new list.
35951 The request succeeded.
35954 An error occurred. The error number @var{nn} is given as hex digits.
35957 An empty reply indicates that @samp{QProgramSignals} is not supported
35961 Use of this packet is controlled by the @code{set remote program-signals}
35962 command (@pxref{Remote Configuration, set remote program-signals}).
35963 This packet is not probed by default; the remote stub must request it,
35964 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35966 @item qRcmd,@var{command}
35967 @cindex execute remote command, remote request
35968 @cindex @samp{qRcmd} packet
35969 @var{command} (hex encoded) is passed to the local interpreter for
35970 execution. Invalid commands should be reported using the output
35971 string. Before the final result packet, the target may also respond
35972 with a number of intermediate @samp{O@var{output}} console output
35973 packets. @emph{Implementors should note that providing access to a
35974 stubs's interpreter may have security implications}.
35979 A command response with no output.
35981 A command response with the hex encoded output string @var{OUTPUT}.
35983 Indicate a badly formed request.
35985 An empty reply indicates that @samp{qRcmd} is not recognized.
35988 (Note that the @code{qRcmd} packet's name is separated from the
35989 command by a @samp{,}, not a @samp{:}, contrary to the naming
35990 conventions above. Please don't use this packet as a model for new
35993 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
35994 @cindex searching memory, in remote debugging
35996 @cindex @samp{qSearch:memory} packet
35998 @cindex @samp{qSearch memory} packet
35999 @anchor{qSearch memory}
36000 Search @var{length} bytes at @var{address} for @var{search-pattern}.
36001 Both @var{address} and @var{length} are encoded in hex;
36002 @var{search-pattern} is a sequence of bytes, also hex encoded.
36007 The pattern was not found.
36009 The pattern was found at @var{address}.
36011 A badly formed request or an error was encountered while searching memory.
36013 An empty reply indicates that @samp{qSearch:memory} is not recognized.
36016 @item QStartNoAckMode
36017 @cindex @samp{QStartNoAckMode} packet
36018 @anchor{QStartNoAckMode}
36019 Request that the remote stub disable the normal @samp{+}/@samp{-}
36020 protocol acknowledgments (@pxref{Packet Acknowledgment}).
36025 The stub has switched to no-acknowledgment mode.
36026 @value{GDBN} acknowledges this reponse,
36027 but neither the stub nor @value{GDBN} shall send or expect further
36028 @samp{+}/@samp{-} acknowledgments in the current connection.
36030 An empty reply indicates that the stub does not support no-acknowledgment mode.
36033 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
36034 @cindex supported packets, remote query
36035 @cindex features of the remote protocol
36036 @cindex @samp{qSupported} packet
36037 @anchor{qSupported}
36038 Tell the remote stub about features supported by @value{GDBN}, and
36039 query the stub for features it supports. This packet allows
36040 @value{GDBN} and the remote stub to take advantage of each others'
36041 features. @samp{qSupported} also consolidates multiple feature probes
36042 at startup, to improve @value{GDBN} performance---a single larger
36043 packet performs better than multiple smaller probe packets on
36044 high-latency links. Some features may enable behavior which must not
36045 be on by default, e.g.@: because it would confuse older clients or
36046 stubs. Other features may describe packets which could be
36047 automatically probed for, but are not. These features must be
36048 reported before @value{GDBN} will use them. This ``default
36049 unsupported'' behavior is not appropriate for all packets, but it
36050 helps to keep the initial connection time under control with new
36051 versions of @value{GDBN} which support increasing numbers of packets.
36055 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
36056 The stub supports or does not support each returned @var{stubfeature},
36057 depending on the form of each @var{stubfeature} (see below for the
36060 An empty reply indicates that @samp{qSupported} is not recognized,
36061 or that no features needed to be reported to @value{GDBN}.
36064 The allowed forms for each feature (either a @var{gdbfeature} in the
36065 @samp{qSupported} packet, or a @var{stubfeature} in the response)
36069 @item @var{name}=@var{value}
36070 The remote protocol feature @var{name} is supported, and associated
36071 with the specified @var{value}. The format of @var{value} depends
36072 on the feature, but it must not include a semicolon.
36074 The remote protocol feature @var{name} is supported, and does not
36075 need an associated value.
36077 The remote protocol feature @var{name} is not supported.
36079 The remote protocol feature @var{name} may be supported, and
36080 @value{GDBN} should auto-detect support in some other way when it is
36081 needed. This form will not be used for @var{gdbfeature} notifications,
36082 but may be used for @var{stubfeature} responses.
36085 Whenever the stub receives a @samp{qSupported} request, the
36086 supplied set of @value{GDBN} features should override any previous
36087 request. This allows @value{GDBN} to put the stub in a known
36088 state, even if the stub had previously been communicating with
36089 a different version of @value{GDBN}.
36091 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
36096 This feature indicates whether @value{GDBN} supports multiprocess
36097 extensions to the remote protocol. @value{GDBN} does not use such
36098 extensions unless the stub also reports that it supports them by
36099 including @samp{multiprocess+} in its @samp{qSupported} reply.
36100 @xref{multiprocess extensions}, for details.
36103 This feature indicates that @value{GDBN} supports the XML target
36104 description. If the stub sees @samp{xmlRegisters=} with target
36105 specific strings separated by a comma, it will report register
36109 This feature indicates whether @value{GDBN} supports the
36110 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
36111 instruction reply packet}).
36114 This feature indicates whether @value{GDBN} supports the swbreak stop
36115 reason in stop replies. @xref{swbreak stop reason}, for details.
36118 This feature indicates whether @value{GDBN} supports the hwbreak stop
36119 reason in stop replies. @xref{swbreak stop reason}, for details.
36122 This feature indicates whether @value{GDBN} supports fork event
36123 extensions to the remote protocol. @value{GDBN} does not use such
36124 extensions unless the stub also reports that it supports them by
36125 including @samp{fork-events+} in its @samp{qSupported} reply.
36128 This feature indicates whether @value{GDBN} supports vfork event
36129 extensions to the remote protocol. @value{GDBN} does not use such
36130 extensions unless the stub also reports that it supports them by
36131 including @samp{vfork-events+} in its @samp{qSupported} reply.
36134 This feature indicates whether @value{GDBN} supports exec event
36135 extensions to the remote protocol. @value{GDBN} does not use such
36136 extensions unless the stub also reports that it supports them by
36137 including @samp{exec-events+} in its @samp{qSupported} reply.
36139 @item vContSupported
36140 This feature indicates whether @value{GDBN} wants to know the
36141 supported actions in the reply to @samp{vCont?} packet.
36144 Stubs should ignore any unknown values for
36145 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
36146 packet supports receiving packets of unlimited length (earlier
36147 versions of @value{GDBN} may reject overly long responses). Additional values
36148 for @var{gdbfeature} may be defined in the future to let the stub take
36149 advantage of new features in @value{GDBN}, e.g.@: incompatible
36150 improvements in the remote protocol---the @samp{multiprocess} feature is
36151 an example of such a feature. The stub's reply should be independent
36152 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
36153 describes all the features it supports, and then the stub replies with
36154 all the features it supports.
36156 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
36157 responses, as long as each response uses one of the standard forms.
36159 Some features are flags. A stub which supports a flag feature
36160 should respond with a @samp{+} form response. Other features
36161 require values, and the stub should respond with an @samp{=}
36164 Each feature has a default value, which @value{GDBN} will use if
36165 @samp{qSupported} is not available or if the feature is not mentioned
36166 in the @samp{qSupported} response. The default values are fixed; a
36167 stub is free to omit any feature responses that match the defaults.
36169 Not all features can be probed, but for those which can, the probing
36170 mechanism is useful: in some cases, a stub's internal
36171 architecture may not allow the protocol layer to know some information
36172 about the underlying target in advance. This is especially common in
36173 stubs which may be configured for multiple targets.
36175 These are the currently defined stub features and their properties:
36177 @multitable @columnfractions 0.35 0.2 0.12 0.2
36178 @c NOTE: The first row should be @headitem, but we do not yet require
36179 @c a new enough version of Texinfo (4.7) to use @headitem.
36181 @tab Value Required
36185 @item @samp{PacketSize}
36190 @item @samp{qXfer:auxv:read}
36195 @item @samp{qXfer:btrace:read}
36200 @item @samp{qXfer:btrace-conf:read}
36205 @item @samp{qXfer:exec-file:read}
36210 @item @samp{qXfer:features:read}
36215 @item @samp{qXfer:libraries:read}
36220 @item @samp{qXfer:libraries-svr4:read}
36225 @item @samp{augmented-libraries-svr4-read}
36230 @item @samp{qXfer:memory-map:read}
36235 @item @samp{qXfer:sdata:read}
36240 @item @samp{qXfer:spu:read}
36245 @item @samp{qXfer:spu:write}
36250 @item @samp{qXfer:siginfo:read}
36255 @item @samp{qXfer:siginfo:write}
36260 @item @samp{qXfer:threads:read}
36265 @item @samp{qXfer:traceframe-info:read}
36270 @item @samp{qXfer:uib:read}
36275 @item @samp{qXfer:fdpic:read}
36280 @item @samp{Qbtrace:off}
36285 @item @samp{Qbtrace:bts}
36290 @item @samp{Qbtrace:pt}
36295 @item @samp{Qbtrace-conf:bts:size}
36300 @item @samp{Qbtrace-conf:pt:size}
36305 @item @samp{QNonStop}
36310 @item @samp{QPassSignals}
36315 @item @samp{QStartNoAckMode}
36320 @item @samp{multiprocess}
36325 @item @samp{ConditionalBreakpoints}
36330 @item @samp{ConditionalTracepoints}
36335 @item @samp{ReverseContinue}
36340 @item @samp{ReverseStep}
36345 @item @samp{TracepointSource}
36350 @item @samp{QAgent}
36355 @item @samp{QAllow}
36360 @item @samp{QDisableRandomization}
36365 @item @samp{EnableDisableTracepoints}
36370 @item @samp{QTBuffer:size}
36375 @item @samp{tracenz}
36380 @item @samp{BreakpointCommands}
36385 @item @samp{swbreak}
36390 @item @samp{hwbreak}
36395 @item @samp{fork-events}
36400 @item @samp{vfork-events}
36405 @item @samp{exec-events}
36412 These are the currently defined stub features, in more detail:
36415 @cindex packet size, remote protocol
36416 @item PacketSize=@var{bytes}
36417 The remote stub can accept packets up to at least @var{bytes} in
36418 length. @value{GDBN} will send packets up to this size for bulk
36419 transfers, and will never send larger packets. This is a limit on the
36420 data characters in the packet, including the frame and checksum.
36421 There is no trailing NUL byte in a remote protocol packet; if the stub
36422 stores packets in a NUL-terminated format, it should allow an extra
36423 byte in its buffer for the NUL. If this stub feature is not supported,
36424 @value{GDBN} guesses based on the size of the @samp{g} packet response.
36426 @item qXfer:auxv:read
36427 The remote stub understands the @samp{qXfer:auxv:read} packet
36428 (@pxref{qXfer auxiliary vector read}).
36430 @item qXfer:btrace:read
36431 The remote stub understands the @samp{qXfer:btrace:read}
36432 packet (@pxref{qXfer btrace read}).
36434 @item qXfer:btrace-conf:read
36435 The remote stub understands the @samp{qXfer:btrace-conf:read}
36436 packet (@pxref{qXfer btrace-conf read}).
36438 @item qXfer:exec-file:read
36439 The remote stub understands the @samp{qXfer:exec-file:read} packet
36440 (@pxref{qXfer executable filename read}).
36442 @item qXfer:features:read
36443 The remote stub understands the @samp{qXfer:features:read} packet
36444 (@pxref{qXfer target description read}).
36446 @item qXfer:libraries:read
36447 The remote stub understands the @samp{qXfer:libraries:read} packet
36448 (@pxref{qXfer library list read}).
36450 @item qXfer:libraries-svr4:read
36451 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
36452 (@pxref{qXfer svr4 library list read}).
36454 @item augmented-libraries-svr4-read
36455 The remote stub understands the augmented form of the
36456 @samp{qXfer:libraries-svr4:read} packet
36457 (@pxref{qXfer svr4 library list read}).
36459 @item qXfer:memory-map:read
36460 The remote stub understands the @samp{qXfer:memory-map:read} packet
36461 (@pxref{qXfer memory map read}).
36463 @item qXfer:sdata:read
36464 The remote stub understands the @samp{qXfer:sdata:read} packet
36465 (@pxref{qXfer sdata read}).
36467 @item qXfer:spu:read
36468 The remote stub understands the @samp{qXfer:spu:read} packet
36469 (@pxref{qXfer spu read}).
36471 @item qXfer:spu:write
36472 The remote stub understands the @samp{qXfer:spu:write} packet
36473 (@pxref{qXfer spu write}).
36475 @item qXfer:siginfo:read
36476 The remote stub understands the @samp{qXfer:siginfo:read} packet
36477 (@pxref{qXfer siginfo read}).
36479 @item qXfer:siginfo:write
36480 The remote stub understands the @samp{qXfer:siginfo:write} packet
36481 (@pxref{qXfer siginfo write}).
36483 @item qXfer:threads:read
36484 The remote stub understands the @samp{qXfer:threads:read} packet
36485 (@pxref{qXfer threads read}).
36487 @item qXfer:traceframe-info:read
36488 The remote stub understands the @samp{qXfer:traceframe-info:read}
36489 packet (@pxref{qXfer traceframe info read}).
36491 @item qXfer:uib:read
36492 The remote stub understands the @samp{qXfer:uib:read}
36493 packet (@pxref{qXfer unwind info block}).
36495 @item qXfer:fdpic:read
36496 The remote stub understands the @samp{qXfer:fdpic:read}
36497 packet (@pxref{qXfer fdpic loadmap read}).
36500 The remote stub understands the @samp{QNonStop} packet
36501 (@pxref{QNonStop}).
36504 The remote stub understands the @samp{QPassSignals} packet
36505 (@pxref{QPassSignals}).
36507 @item QStartNoAckMode
36508 The remote stub understands the @samp{QStartNoAckMode} packet and
36509 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
36512 @anchor{multiprocess extensions}
36513 @cindex multiprocess extensions, in remote protocol
36514 The remote stub understands the multiprocess extensions to the remote
36515 protocol syntax. The multiprocess extensions affect the syntax of
36516 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
36517 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
36518 replies. Note that reporting this feature indicates support for the
36519 syntactic extensions only, not that the stub necessarily supports
36520 debugging of more than one process at a time. The stub must not use
36521 multiprocess extensions in packet replies unless @value{GDBN} has also
36522 indicated it supports them in its @samp{qSupported} request.
36524 @item qXfer:osdata:read
36525 The remote stub understands the @samp{qXfer:osdata:read} packet
36526 ((@pxref{qXfer osdata read}).
36528 @item ConditionalBreakpoints
36529 The target accepts and implements evaluation of conditional expressions
36530 defined for breakpoints. The target will only report breakpoint triggers
36531 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
36533 @item ConditionalTracepoints
36534 The remote stub accepts and implements conditional expressions defined
36535 for tracepoints (@pxref{Tracepoint Conditions}).
36537 @item ReverseContinue
36538 The remote stub accepts and implements the reverse continue packet
36542 The remote stub accepts and implements the reverse step packet
36545 @item TracepointSource
36546 The remote stub understands the @samp{QTDPsrc} packet that supplies
36547 the source form of tracepoint definitions.
36550 The remote stub understands the @samp{QAgent} packet.
36553 The remote stub understands the @samp{QAllow} packet.
36555 @item QDisableRandomization
36556 The remote stub understands the @samp{QDisableRandomization} packet.
36558 @item StaticTracepoint
36559 @cindex static tracepoints, in remote protocol
36560 The remote stub supports static tracepoints.
36562 @item InstallInTrace
36563 @anchor{install tracepoint in tracing}
36564 The remote stub supports installing tracepoint in tracing.
36566 @item EnableDisableTracepoints
36567 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
36568 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
36569 to be enabled and disabled while a trace experiment is running.
36571 @item QTBuffer:size
36572 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
36573 packet that allows to change the size of the trace buffer.
36576 @cindex string tracing, in remote protocol
36577 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
36578 See @ref{Bytecode Descriptions} for details about the bytecode.
36580 @item BreakpointCommands
36581 @cindex breakpoint commands, in remote protocol
36582 The remote stub supports running a breakpoint's command list itself,
36583 rather than reporting the hit to @value{GDBN}.
36586 The remote stub understands the @samp{Qbtrace:off} packet.
36589 The remote stub understands the @samp{Qbtrace:bts} packet.
36592 The remote stub understands the @samp{Qbtrace:pt} packet.
36594 @item Qbtrace-conf:bts:size
36595 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
36597 @item Qbtrace-conf:pt:size
36598 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
36601 The remote stub reports the @samp{swbreak} stop reason for memory
36605 The remote stub reports the @samp{hwbreak} stop reason for hardware
36609 The remote stub reports the @samp{fork} stop reason for fork events.
36612 The remote stub reports the @samp{vfork} stop reason for vfork events
36613 and vforkdone events.
36616 The remote stub reports the @samp{exec} stop reason for exec events.
36618 @item vContSupported
36619 The remote stub reports the supported actions in the reply to
36620 @samp{vCont?} packet.
36625 @cindex symbol lookup, remote request
36626 @cindex @samp{qSymbol} packet
36627 Notify the target that @value{GDBN} is prepared to serve symbol lookup
36628 requests. Accept requests from the target for the values of symbols.
36633 The target does not need to look up any (more) symbols.
36634 @item qSymbol:@var{sym_name}
36635 The target requests the value of symbol @var{sym_name} (hex encoded).
36636 @value{GDBN} may provide the value by using the
36637 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
36641 @item qSymbol:@var{sym_value}:@var{sym_name}
36642 Set the value of @var{sym_name} to @var{sym_value}.
36644 @var{sym_name} (hex encoded) is the name of a symbol whose value the
36645 target has previously requested.
36647 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
36648 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
36654 The target does not need to look up any (more) symbols.
36655 @item qSymbol:@var{sym_name}
36656 The target requests the value of a new symbol @var{sym_name} (hex
36657 encoded). @value{GDBN} will continue to supply the values of symbols
36658 (if available), until the target ceases to request them.
36663 @itemx QTDisconnected
36670 @itemx qTMinFTPILen
36672 @xref{Tracepoint Packets}.
36674 @item qThreadExtraInfo,@var{thread-id}
36675 @cindex thread attributes info, remote request
36676 @cindex @samp{qThreadExtraInfo} packet
36677 Obtain from the target OS a printable string description of thread
36678 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
36679 for the forms of @var{thread-id}. This
36680 string may contain anything that the target OS thinks is interesting
36681 for @value{GDBN} to tell the user about the thread. The string is
36682 displayed in @value{GDBN}'s @code{info threads} display. Some
36683 examples of possible thread extra info strings are @samp{Runnable}, or
36684 @samp{Blocked on Mutex}.
36688 @item @var{XX}@dots{}
36689 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
36690 comprising the printable string containing the extra information about
36691 the thread's attributes.
36694 (Note that the @code{qThreadExtraInfo} packet's name is separated from
36695 the command by a @samp{,}, not a @samp{:}, contrary to the naming
36696 conventions above. Please don't use this packet as a model for new
36715 @xref{Tracepoint Packets}.
36717 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
36718 @cindex read special object, remote request
36719 @cindex @samp{qXfer} packet
36720 @anchor{qXfer read}
36721 Read uninterpreted bytes from the target's special data area
36722 identified by the keyword @var{object}. Request @var{length} bytes
36723 starting at @var{offset} bytes into the data. The content and
36724 encoding of @var{annex} is specific to @var{object}; it can supply
36725 additional details about what data to access.
36727 Here are the specific requests of this form defined so far. All
36728 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
36729 formats, listed below.
36732 @item qXfer:auxv:read::@var{offset},@var{length}
36733 @anchor{qXfer auxiliary vector read}
36734 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
36735 auxiliary vector}. Note @var{annex} must be empty.
36737 This packet is not probed by default; the remote stub must request it,
36738 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36740 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
36741 @anchor{qXfer btrace read}
36743 Return a description of the current branch trace.
36744 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
36745 packet may have one of the following values:
36749 Returns all available branch trace.
36752 Returns all available branch trace if the branch trace changed since
36753 the last read request.
36756 Returns the new branch trace since the last read request. Adds a new
36757 block to the end of the trace that begins at zero and ends at the source
36758 location of the first branch in the trace buffer. This extra block is
36759 used to stitch traces together.
36761 If the trace buffer overflowed, returns an error indicating the overflow.
36764 This packet is not probed by default; the remote stub must request it
36765 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36767 @item qXfer:btrace-conf:read::@var{offset},@var{length}
36768 @anchor{qXfer btrace-conf read}
36770 Return a description of the current branch trace configuration.
36771 @xref{Branch Trace Configuration Format}.
36773 This packet is not probed by default; the remote stub must request it
36774 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36776 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
36777 @anchor{qXfer executable filename read}
36778 Return the full absolute name of the file that was executed to create
36779 a process running on the remote system. The annex specifies the
36780 numeric process ID of the process to query, encoded as a hexadecimal
36781 number. If the annex part is empty the remote stub should return the
36782 filename corresponding to the currently executing process.
36784 This packet is not probed by default; the remote stub must request it,
36785 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36787 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
36788 @anchor{qXfer target description read}
36789 Access the @dfn{target description}. @xref{Target Descriptions}. The
36790 annex specifies which XML document to access. The main description is
36791 always loaded from the @samp{target.xml} annex.
36793 This packet is not probed by default; the remote stub must request it,
36794 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36796 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
36797 @anchor{qXfer library list read}
36798 Access the target's list of loaded libraries. @xref{Library List Format}.
36799 The annex part of the generic @samp{qXfer} packet must be empty
36800 (@pxref{qXfer read}).
36802 Targets which maintain a list of libraries in the program's memory do
36803 not need to implement this packet; it is designed for platforms where
36804 the operating system manages the list of loaded libraries.
36806 This packet is not probed by default; the remote stub must request it,
36807 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36809 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
36810 @anchor{qXfer svr4 library list read}
36811 Access the target's list of loaded libraries when the target is an SVR4
36812 platform. @xref{Library List Format for SVR4 Targets}. The annex part
36813 of the generic @samp{qXfer} packet must be empty unless the remote
36814 stub indicated it supports the augmented form of this packet
36815 by supplying an appropriate @samp{qSupported} response
36816 (@pxref{qXfer read}, @ref{qSupported}).
36818 This packet is optional for better performance on SVR4 targets.
36819 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
36821 This packet is not probed by default; the remote stub must request it,
36822 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36824 If the remote stub indicates it supports the augmented form of this
36825 packet then the annex part of the generic @samp{qXfer} packet may
36826 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
36827 arguments. The currently supported arguments are:
36830 @item start=@var{address}
36831 A hexadecimal number specifying the address of the @samp{struct
36832 link_map} to start reading the library list from. If unset or zero
36833 then the first @samp{struct link_map} in the library list will be
36834 chosen as the starting point.
36836 @item prev=@var{address}
36837 A hexadecimal number specifying the address of the @samp{struct
36838 link_map} immediately preceding the @samp{struct link_map}
36839 specified by the @samp{start} argument. If unset or zero then
36840 the remote stub will expect that no @samp{struct link_map}
36841 exists prior to the starting point.
36845 Arguments that are not understood by the remote stub will be silently
36848 @item qXfer:memory-map:read::@var{offset},@var{length}
36849 @anchor{qXfer memory map read}
36850 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
36851 annex part of the generic @samp{qXfer} packet must be empty
36852 (@pxref{qXfer read}).
36854 This packet is not probed by default; the remote stub must request it,
36855 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36857 @item qXfer:sdata:read::@var{offset},@var{length}
36858 @anchor{qXfer sdata read}
36860 Read contents of the extra collected static tracepoint marker
36861 information. The annex part of the generic @samp{qXfer} packet must
36862 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
36865 This packet is not probed by default; the remote stub must request it,
36866 by supplying an appropriate @samp{qSupported} response
36867 (@pxref{qSupported}).
36869 @item qXfer:siginfo:read::@var{offset},@var{length}
36870 @anchor{qXfer siginfo read}
36871 Read contents of the extra signal information on the target
36872 system. The annex part of the generic @samp{qXfer} packet must be
36873 empty (@pxref{qXfer read}).
36875 This packet is not probed by default; the remote stub must request it,
36876 by supplying an appropriate @samp{qSupported} response
36877 (@pxref{qSupported}).
36879 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
36880 @anchor{qXfer spu read}
36881 Read contents of an @code{spufs} file on the target system. The
36882 annex specifies which file to read; it must be of the form
36883 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
36884 in the target process, and @var{name} identifes the @code{spufs} file
36885 in that context to be accessed.
36887 This packet is not probed by default; the remote stub must request it,
36888 by supplying an appropriate @samp{qSupported} response
36889 (@pxref{qSupported}).
36891 @item qXfer:threads:read::@var{offset},@var{length}
36892 @anchor{qXfer threads read}
36893 Access the list of threads on target. @xref{Thread List Format}. The
36894 annex part of the generic @samp{qXfer} packet must be empty
36895 (@pxref{qXfer read}).
36897 This packet is not probed by default; the remote stub must request it,
36898 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36900 @item qXfer:traceframe-info:read::@var{offset},@var{length}
36901 @anchor{qXfer traceframe info read}
36903 Return a description of the current traceframe's contents.
36904 @xref{Traceframe Info Format}. The annex part of the generic
36905 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
36907 This packet is not probed by default; the remote stub must request it,
36908 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36910 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
36911 @anchor{qXfer unwind info block}
36913 Return the unwind information block for @var{pc}. This packet is used
36914 on OpenVMS/ia64 to ask the kernel unwind information.
36916 This packet is not probed by default.
36918 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
36919 @anchor{qXfer fdpic loadmap read}
36920 Read contents of @code{loadmap}s on the target system. The
36921 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
36922 executable @code{loadmap} or interpreter @code{loadmap} to read.
36924 This packet is not probed by default; the remote stub must request it,
36925 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36927 @item qXfer:osdata:read::@var{offset},@var{length}
36928 @anchor{qXfer osdata read}
36929 Access the target's @dfn{operating system information}.
36930 @xref{Operating System Information}.
36937 Data @var{data} (@pxref{Binary Data}) has been read from the
36938 target. There may be more data at a higher address (although
36939 it is permitted to return @samp{m} even for the last valid
36940 block of data, as long as at least one byte of data was read).
36941 It is possible for @var{data} to have fewer bytes than the @var{length} in the
36945 Data @var{data} (@pxref{Binary Data}) has been read from the target.
36946 There is no more data to be read. It is possible for @var{data} to
36947 have fewer bytes than the @var{length} in the request.
36950 The @var{offset} in the request is at the end of the data.
36951 There is no more data to be read.
36954 The request was malformed, or @var{annex} was invalid.
36957 The offset was invalid, or there was an error encountered reading the data.
36958 The @var{nn} part is a hex-encoded @code{errno} value.
36961 An empty reply indicates the @var{object} string was not recognized by
36962 the stub, or that the object does not support reading.
36965 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
36966 @cindex write data into object, remote request
36967 @anchor{qXfer write}
36968 Write uninterpreted bytes into the target's special data area
36969 identified by the keyword @var{object}, starting at @var{offset} bytes
36970 into the data. The binary-encoded data (@pxref{Binary Data}) to be
36971 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
36972 is specific to @var{object}; it can supply additional details about what data
36975 Here are the specific requests of this form defined so far. All
36976 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
36977 formats, listed below.
36980 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
36981 @anchor{qXfer siginfo write}
36982 Write @var{data} to the extra signal information on the target system.
36983 The annex part of the generic @samp{qXfer} packet must be
36984 empty (@pxref{qXfer write}).
36986 This packet is not probed by default; the remote stub must request it,
36987 by supplying an appropriate @samp{qSupported} response
36988 (@pxref{qSupported}).
36990 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
36991 @anchor{qXfer spu write}
36992 Write @var{data} to an @code{spufs} file on the target system. The
36993 annex specifies which file to write; it must be of the form
36994 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
36995 in the target process, and @var{name} identifes the @code{spufs} file
36996 in that context to be accessed.
36998 This packet is not probed by default; the remote stub must request it,
36999 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37005 @var{nn} (hex encoded) is the number of bytes written.
37006 This may be fewer bytes than supplied in the request.
37009 The request was malformed, or @var{annex} was invalid.
37012 The offset was invalid, or there was an error encountered writing the data.
37013 The @var{nn} part is a hex-encoded @code{errno} value.
37016 An empty reply indicates the @var{object} string was not
37017 recognized by the stub, or that the object does not support writing.
37020 @item qXfer:@var{object}:@var{operation}:@dots{}
37021 Requests of this form may be added in the future. When a stub does
37022 not recognize the @var{object} keyword, or its support for
37023 @var{object} does not recognize the @var{operation} keyword, the stub
37024 must respond with an empty packet.
37026 @item qAttached:@var{pid}
37027 @cindex query attached, remote request
37028 @cindex @samp{qAttached} packet
37029 Return an indication of whether the remote server attached to an
37030 existing process or created a new process. When the multiprocess
37031 protocol extensions are supported (@pxref{multiprocess extensions}),
37032 @var{pid} is an integer in hexadecimal format identifying the target
37033 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
37034 the query packet will be simplified as @samp{qAttached}.
37036 This query is used, for example, to know whether the remote process
37037 should be detached or killed when a @value{GDBN} session is ended with
37038 the @code{quit} command.
37043 The remote server attached to an existing process.
37045 The remote server created a new process.
37047 A badly formed request or an error was encountered.
37051 Enable branch tracing for the current thread using Branch Trace Store.
37056 Branch tracing has been enabled.
37058 A badly formed request or an error was encountered.
37062 Enable branch tracing for the current thread using Intel(R) Processor Trace.
37067 Branch tracing has been enabled.
37069 A badly formed request or an error was encountered.
37073 Disable branch tracing for the current thread.
37078 Branch tracing has been disabled.
37080 A badly formed request or an error was encountered.
37083 @item Qbtrace-conf:bts:size=@var{value}
37084 Set the requested ring buffer size for new threads that use the
37085 btrace recording method in bts format.
37090 The ring buffer size has been set.
37092 A badly formed request or an error was encountered.
37095 @item Qbtrace-conf:pt:size=@var{value}
37096 Set the requested ring buffer size for new threads that use the
37097 btrace recording method in pt format.
37102 The ring buffer size has been set.
37104 A badly formed request or an error was encountered.
37109 @node Architecture-Specific Protocol Details
37110 @section Architecture-Specific Protocol Details
37112 This section describes how the remote protocol is applied to specific
37113 target architectures. Also see @ref{Standard Target Features}, for
37114 details of XML target descriptions for each architecture.
37117 * ARM-Specific Protocol Details::
37118 * MIPS-Specific Protocol Details::
37121 @node ARM-Specific Protocol Details
37122 @subsection @acronym{ARM}-specific Protocol Details
37125 * ARM Breakpoint Kinds::
37128 @node ARM Breakpoint Kinds
37129 @subsubsection @acronym{ARM} Breakpoint Kinds
37130 @cindex breakpoint kinds, @acronym{ARM}
37132 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37137 16-bit Thumb mode breakpoint.
37140 32-bit Thumb mode (Thumb-2) breakpoint.
37143 32-bit @acronym{ARM} mode breakpoint.
37147 @node MIPS-Specific Protocol Details
37148 @subsection @acronym{MIPS}-specific Protocol Details
37151 * MIPS Register packet Format::
37152 * MIPS Breakpoint Kinds::
37155 @node MIPS Register packet Format
37156 @subsubsection @acronym{MIPS} Register Packet Format
37157 @cindex register packet format, @acronym{MIPS}
37159 The following @code{g}/@code{G} packets have previously been defined.
37160 In the below, some thirty-two bit registers are transferred as
37161 sixty-four bits. Those registers should be zero/sign extended (which?)
37162 to fill the space allocated. Register bytes are transferred in target
37163 byte order. The two nibbles within a register byte are transferred
37164 most-significant -- least-significant.
37169 All registers are transferred as thirty-two bit quantities in the order:
37170 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
37171 registers; fsr; fir; fp.
37174 All registers are transferred as sixty-four bit quantities (including
37175 thirty-two bit registers such as @code{sr}). The ordering is the same
37180 @node MIPS Breakpoint Kinds
37181 @subsubsection @acronym{MIPS} Breakpoint Kinds
37182 @cindex breakpoint kinds, @acronym{MIPS}
37184 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37189 16-bit @acronym{MIPS16} mode breakpoint.
37192 16-bit @acronym{microMIPS} mode breakpoint.
37195 32-bit standard @acronym{MIPS} mode breakpoint.
37198 32-bit @acronym{microMIPS} mode breakpoint.
37202 @node Tracepoint Packets
37203 @section Tracepoint Packets
37204 @cindex tracepoint packets
37205 @cindex packets, tracepoint
37207 Here we describe the packets @value{GDBN} uses to implement
37208 tracepoints (@pxref{Tracepoints}).
37212 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
37213 @cindex @samp{QTDP} packet
37214 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
37215 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
37216 the tracepoint is disabled. The @var{step} gives the tracepoint's step
37217 count, and @var{pass} gives its pass count. If an @samp{F} is present,
37218 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
37219 the number of bytes that the target should copy elsewhere to make room
37220 for the tracepoint. If an @samp{X} is present, it introduces a
37221 tracepoint condition, which consists of a hexadecimal length, followed
37222 by a comma and hex-encoded bytes, in a manner similar to action
37223 encodings as described below. If the trailing @samp{-} is present,
37224 further @samp{QTDP} packets will follow to specify this tracepoint's
37230 The packet was understood and carried out.
37232 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
37234 The packet was not recognized.
37237 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
37238 Define actions to be taken when a tracepoint is hit. The @var{n} and
37239 @var{addr} must be the same as in the initial @samp{QTDP} packet for
37240 this tracepoint. This packet may only be sent immediately after
37241 another @samp{QTDP} packet that ended with a @samp{-}. If the
37242 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
37243 specifying more actions for this tracepoint.
37245 In the series of action packets for a given tracepoint, at most one
37246 can have an @samp{S} before its first @var{action}. If such a packet
37247 is sent, it and the following packets define ``while-stepping''
37248 actions. Any prior packets define ordinary actions --- that is, those
37249 taken when the tracepoint is first hit. If no action packet has an
37250 @samp{S}, then all the packets in the series specify ordinary
37251 tracepoint actions.
37253 The @samp{@var{action}@dots{}} portion of the packet is a series of
37254 actions, concatenated without separators. Each action has one of the
37260 Collect the registers whose bits are set in @var{mask},
37261 a hexadecimal number whose @var{i}'th bit is set if register number
37262 @var{i} should be collected. (The least significant bit is numbered
37263 zero.) Note that @var{mask} may be any number of digits long; it may
37264 not fit in a 32-bit word.
37266 @item M @var{basereg},@var{offset},@var{len}
37267 Collect @var{len} bytes of memory starting at the address in register
37268 number @var{basereg}, plus @var{offset}. If @var{basereg} is
37269 @samp{-1}, then the range has a fixed address: @var{offset} is the
37270 address of the lowest byte to collect. The @var{basereg},
37271 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
37272 values (the @samp{-1} value for @var{basereg} is a special case).
37274 @item X @var{len},@var{expr}
37275 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
37276 it directs. The agent expression @var{expr} is as described in
37277 @ref{Agent Expressions}. Each byte of the expression is encoded as a
37278 two-digit hex number in the packet; @var{len} is the number of bytes
37279 in the expression (and thus one-half the number of hex digits in the
37284 Any number of actions may be packed together in a single @samp{QTDP}
37285 packet, as long as the packet does not exceed the maximum packet
37286 length (400 bytes, for many stubs). There may be only one @samp{R}
37287 action per tracepoint, and it must precede any @samp{M} or @samp{X}
37288 actions. Any registers referred to by @samp{M} and @samp{X} actions
37289 must be collected by a preceding @samp{R} action. (The
37290 ``while-stepping'' actions are treated as if they were attached to a
37291 separate tracepoint, as far as these restrictions are concerned.)
37296 The packet was understood and carried out.
37298 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
37300 The packet was not recognized.
37303 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
37304 @cindex @samp{QTDPsrc} packet
37305 Specify a source string of tracepoint @var{n} at address @var{addr}.
37306 This is useful to get accurate reproduction of the tracepoints
37307 originally downloaded at the beginning of the trace run. The @var{type}
37308 is the name of the tracepoint part, such as @samp{cond} for the
37309 tracepoint's conditional expression (see below for a list of types), while
37310 @var{bytes} is the string, encoded in hexadecimal.
37312 @var{start} is the offset of the @var{bytes} within the overall source
37313 string, while @var{slen} is the total length of the source string.
37314 This is intended for handling source strings that are longer than will
37315 fit in a single packet.
37316 @c Add detailed example when this info is moved into a dedicated
37317 @c tracepoint descriptions section.
37319 The available string types are @samp{at} for the location,
37320 @samp{cond} for the conditional, and @samp{cmd} for an action command.
37321 @value{GDBN} sends a separate packet for each command in the action
37322 list, in the same order in which the commands are stored in the list.
37324 The target does not need to do anything with source strings except
37325 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
37328 Although this packet is optional, and @value{GDBN} will only send it
37329 if the target replies with @samp{TracepointSource} @xref{General
37330 Query Packets}, it makes both disconnected tracing and trace files
37331 much easier to use. Otherwise the user must be careful that the
37332 tracepoints in effect while looking at trace frames are identical to
37333 the ones in effect during the trace run; even a small discrepancy
37334 could cause @samp{tdump} not to work, or a particular trace frame not
37337 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
37338 @cindex define trace state variable, remote request
37339 @cindex @samp{QTDV} packet
37340 Create a new trace state variable, number @var{n}, with an initial
37341 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
37342 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
37343 the option of not using this packet for initial values of zero; the
37344 target should simply create the trace state variables as they are
37345 mentioned in expressions. The value @var{builtin} should be 1 (one)
37346 if the trace state variable is builtin and 0 (zero) if it is not builtin.
37347 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
37348 @samp{qTsV} packet had it set. The contents of @var{name} is the
37349 hex-encoded name (without the leading @samp{$}) of the trace state
37352 @item QTFrame:@var{n}
37353 @cindex @samp{QTFrame} packet
37354 Select the @var{n}'th tracepoint frame from the buffer, and use the
37355 register and memory contents recorded there to answer subsequent
37356 request packets from @value{GDBN}.
37358 A successful reply from the stub indicates that the stub has found the
37359 requested frame. The response is a series of parts, concatenated
37360 without separators, describing the frame we selected. Each part has
37361 one of the following forms:
37365 The selected frame is number @var{n} in the trace frame buffer;
37366 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
37367 was no frame matching the criteria in the request packet.
37370 The selected trace frame records a hit of tracepoint number @var{t};
37371 @var{t} is a hexadecimal number.
37375 @item QTFrame:pc:@var{addr}
37376 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37377 currently selected frame whose PC is @var{addr};
37378 @var{addr} is a hexadecimal number.
37380 @item QTFrame:tdp:@var{t}
37381 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37382 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
37383 is a hexadecimal number.
37385 @item QTFrame:range:@var{start}:@var{end}
37386 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37387 currently selected frame whose PC is between @var{start} (inclusive)
37388 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
37391 @item QTFrame:outside:@var{start}:@var{end}
37392 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
37393 frame @emph{outside} the given range of addresses (exclusive).
37396 @cindex @samp{qTMinFTPILen} packet
37397 This packet requests the minimum length of instruction at which a fast
37398 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
37399 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
37400 it depends on the target system being able to create trampolines in
37401 the first 64K of memory, which might or might not be possible for that
37402 system. So the reply to this packet will be 4 if it is able to
37409 The minimum instruction length is currently unknown.
37411 The minimum instruction length is @var{length}, where @var{length}
37412 is a hexadecimal number greater or equal to 1. A reply
37413 of 1 means that a fast tracepoint may be placed on any instruction
37414 regardless of size.
37416 An error has occurred.
37418 An empty reply indicates that the request is not supported by the stub.
37422 @cindex @samp{QTStart} packet
37423 Begin the tracepoint experiment. Begin collecting data from
37424 tracepoint hits in the trace frame buffer. This packet supports the
37425 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
37426 instruction reply packet}).
37429 @cindex @samp{QTStop} packet
37430 End the tracepoint experiment. Stop collecting trace frames.
37432 @item QTEnable:@var{n}:@var{addr}
37434 @cindex @samp{QTEnable} packet
37435 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
37436 experiment. If the tracepoint was previously disabled, then collection
37437 of data from it will resume.
37439 @item QTDisable:@var{n}:@var{addr}
37441 @cindex @samp{QTDisable} packet
37442 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
37443 experiment. No more data will be collected from the tracepoint unless
37444 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
37447 @cindex @samp{QTinit} packet
37448 Clear the table of tracepoints, and empty the trace frame buffer.
37450 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
37451 @cindex @samp{QTro} packet
37452 Establish the given ranges of memory as ``transparent''. The stub
37453 will answer requests for these ranges from memory's current contents,
37454 if they were not collected as part of the tracepoint hit.
37456 @value{GDBN} uses this to mark read-only regions of memory, like those
37457 containing program code. Since these areas never change, they should
37458 still have the same contents they did when the tracepoint was hit, so
37459 there's no reason for the stub to refuse to provide their contents.
37461 @item QTDisconnected:@var{value}
37462 @cindex @samp{QTDisconnected} packet
37463 Set the choice to what to do with the tracing run when @value{GDBN}
37464 disconnects from the target. A @var{value} of 1 directs the target to
37465 continue the tracing run, while 0 tells the target to stop tracing if
37466 @value{GDBN} is no longer in the picture.
37469 @cindex @samp{qTStatus} packet
37470 Ask the stub if there is a trace experiment running right now.
37472 The reply has the form:
37476 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
37477 @var{running} is a single digit @code{1} if the trace is presently
37478 running, or @code{0} if not. It is followed by semicolon-separated
37479 optional fields that an agent may use to report additional status.
37483 If the trace is not running, the agent may report any of several
37484 explanations as one of the optional fields:
37489 No trace has been run yet.
37491 @item tstop[:@var{text}]:0
37492 The trace was stopped by a user-originated stop command. The optional
37493 @var{text} field is a user-supplied string supplied as part of the
37494 stop command (for instance, an explanation of why the trace was
37495 stopped manually). It is hex-encoded.
37498 The trace stopped because the trace buffer filled up.
37500 @item tdisconnected:0
37501 The trace stopped because @value{GDBN} disconnected from the target.
37503 @item tpasscount:@var{tpnum}
37504 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
37506 @item terror:@var{text}:@var{tpnum}
37507 The trace stopped because tracepoint @var{tpnum} had an error. The
37508 string @var{text} is available to describe the nature of the error
37509 (for instance, a divide by zero in the condition expression); it
37513 The trace stopped for some other reason.
37517 Additional optional fields supply statistical and other information.
37518 Although not required, they are extremely useful for users monitoring
37519 the progress of a trace run. If a trace has stopped, and these
37520 numbers are reported, they must reflect the state of the just-stopped
37525 @item tframes:@var{n}
37526 The number of trace frames in the buffer.
37528 @item tcreated:@var{n}
37529 The total number of trace frames created during the run. This may
37530 be larger than the trace frame count, if the buffer is circular.
37532 @item tsize:@var{n}
37533 The total size of the trace buffer, in bytes.
37535 @item tfree:@var{n}
37536 The number of bytes still unused in the buffer.
37538 @item circular:@var{n}
37539 The value of the circular trace buffer flag. @code{1} means that the
37540 trace buffer is circular and old trace frames will be discarded if
37541 necessary to make room, @code{0} means that the trace buffer is linear
37544 @item disconn:@var{n}
37545 The value of the disconnected tracing flag. @code{1} means that
37546 tracing will continue after @value{GDBN} disconnects, @code{0} means
37547 that the trace run will stop.
37551 @item qTP:@var{tp}:@var{addr}
37552 @cindex tracepoint status, remote request
37553 @cindex @samp{qTP} packet
37554 Ask the stub for the current state of tracepoint number @var{tp} at
37555 address @var{addr}.
37559 @item V@var{hits}:@var{usage}
37560 The tracepoint has been hit @var{hits} times so far during the trace
37561 run, and accounts for @var{usage} in the trace buffer. Note that
37562 @code{while-stepping} steps are not counted as separate hits, but the
37563 steps' space consumption is added into the usage number.
37567 @item qTV:@var{var}
37568 @cindex trace state variable value, remote request
37569 @cindex @samp{qTV} packet
37570 Ask the stub for the value of the trace state variable number @var{var}.
37575 The value of the variable is @var{value}. This will be the current
37576 value of the variable if the user is examining a running target, or a
37577 saved value if the variable was collected in the trace frame that the
37578 user is looking at. Note that multiple requests may result in
37579 different reply values, such as when requesting values while the
37580 program is running.
37583 The value of the variable is unknown. This would occur, for example,
37584 if the user is examining a trace frame in which the requested variable
37589 @cindex @samp{qTfP} packet
37591 @cindex @samp{qTsP} packet
37592 These packets request data about tracepoints that are being used by
37593 the target. @value{GDBN} sends @code{qTfP} to get the first piece
37594 of data, and multiple @code{qTsP} to get additional pieces. Replies
37595 to these packets generally take the form of the @code{QTDP} packets
37596 that define tracepoints. (FIXME add detailed syntax)
37599 @cindex @samp{qTfV} packet
37601 @cindex @samp{qTsV} packet
37602 These packets request data about trace state variables that are on the
37603 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
37604 and multiple @code{qTsV} to get additional variables. Replies to
37605 these packets follow the syntax of the @code{QTDV} packets that define
37606 trace state variables.
37612 @cindex @samp{qTfSTM} packet
37613 @cindex @samp{qTsSTM} packet
37614 These packets request data about static tracepoint markers that exist
37615 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
37616 first piece of data, and multiple @code{qTsSTM} to get additional
37617 pieces. Replies to these packets take the following form:
37621 @item m @var{address}:@var{id}:@var{extra}
37623 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
37624 a comma-separated list of markers
37626 (lower case letter @samp{L}) denotes end of list.
37628 An error occurred. The error number @var{nn} is given as hex digits.
37630 An empty reply indicates that the request is not supported by the
37634 The @var{address} is encoded in hex;
37635 @var{id} and @var{extra} are strings encoded in hex.
37637 In response to each query, the target will reply with a list of one or
37638 more markers, separated by commas. @value{GDBN} will respond to each
37639 reply with a request for more markers (using the @samp{qs} form of the
37640 query), until the target responds with @samp{l} (lower-case ell, for
37643 @item qTSTMat:@var{address}
37645 @cindex @samp{qTSTMat} packet
37646 This packets requests data about static tracepoint markers in the
37647 target program at @var{address}. Replies to this packet follow the
37648 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
37649 tracepoint markers.
37651 @item QTSave:@var{filename}
37652 @cindex @samp{QTSave} packet
37653 This packet directs the target to save trace data to the file name
37654 @var{filename} in the target's filesystem. The @var{filename} is encoded
37655 as a hex string; the interpretation of the file name (relative vs
37656 absolute, wild cards, etc) is up to the target.
37658 @item qTBuffer:@var{offset},@var{len}
37659 @cindex @samp{qTBuffer} packet
37660 Return up to @var{len} bytes of the current contents of trace buffer,
37661 starting at @var{offset}. The trace buffer is treated as if it were
37662 a contiguous collection of traceframes, as per the trace file format.
37663 The reply consists as many hex-encoded bytes as the target can deliver
37664 in a packet; it is not an error to return fewer than were asked for.
37665 A reply consisting of just @code{l} indicates that no bytes are
37668 @item QTBuffer:circular:@var{value}
37669 This packet directs the target to use a circular trace buffer if
37670 @var{value} is 1, or a linear buffer if the value is 0.
37672 @item QTBuffer:size:@var{size}
37673 @anchor{QTBuffer-size}
37674 @cindex @samp{QTBuffer size} packet
37675 This packet directs the target to make the trace buffer be of size
37676 @var{size} if possible. A value of @code{-1} tells the target to
37677 use whatever size it prefers.
37679 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
37680 @cindex @samp{QTNotes} packet
37681 This packet adds optional textual notes to the trace run. Allowable
37682 types include @code{user}, @code{notes}, and @code{tstop}, the
37683 @var{text} fields are arbitrary strings, hex-encoded.
37687 @subsection Relocate instruction reply packet
37688 When installing fast tracepoints in memory, the target may need to
37689 relocate the instruction currently at the tracepoint address to a
37690 different address in memory. For most instructions, a simple copy is
37691 enough, but, for example, call instructions that implicitly push the
37692 return address on the stack, and relative branches or other
37693 PC-relative instructions require offset adjustment, so that the effect
37694 of executing the instruction at a different address is the same as if
37695 it had executed in the original location.
37697 In response to several of the tracepoint packets, the target may also
37698 respond with a number of intermediate @samp{qRelocInsn} request
37699 packets before the final result packet, to have @value{GDBN} handle
37700 this relocation operation. If a packet supports this mechanism, its
37701 documentation will explicitly say so. See for example the above
37702 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
37703 format of the request is:
37706 @item qRelocInsn:@var{from};@var{to}
37708 This requests @value{GDBN} to copy instruction at address @var{from}
37709 to address @var{to}, possibly adjusted so that executing the
37710 instruction at @var{to} has the same effect as executing it at
37711 @var{from}. @value{GDBN} writes the adjusted instruction to target
37712 memory starting at @var{to}.
37717 @item qRelocInsn:@var{adjusted_size}
37718 Informs the stub the relocation is complete. The @var{adjusted_size} is
37719 the length in bytes of resulting relocated instruction sequence.
37721 A badly formed request was detected, or an error was encountered while
37722 relocating the instruction.
37725 @node Host I/O Packets
37726 @section Host I/O Packets
37727 @cindex Host I/O, remote protocol
37728 @cindex file transfer, remote protocol
37730 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
37731 operations on the far side of a remote link. For example, Host I/O is
37732 used to upload and download files to a remote target with its own
37733 filesystem. Host I/O uses the same constant values and data structure
37734 layout as the target-initiated File-I/O protocol. However, the
37735 Host I/O packets are structured differently. The target-initiated
37736 protocol relies on target memory to store parameters and buffers.
37737 Host I/O requests are initiated by @value{GDBN}, and the
37738 target's memory is not involved. @xref{File-I/O Remote Protocol
37739 Extension}, for more details on the target-initiated protocol.
37741 The Host I/O request packets all encode a single operation along with
37742 its arguments. They have this format:
37746 @item vFile:@var{operation}: @var{parameter}@dots{}
37747 @var{operation} is the name of the particular request; the target
37748 should compare the entire packet name up to the second colon when checking
37749 for a supported operation. The format of @var{parameter} depends on
37750 the operation. Numbers are always passed in hexadecimal. Negative
37751 numbers have an explicit minus sign (i.e.@: two's complement is not
37752 used). Strings (e.g.@: filenames) are encoded as a series of
37753 hexadecimal bytes. The last argument to a system call may be a
37754 buffer of escaped binary data (@pxref{Binary Data}).
37758 The valid responses to Host I/O packets are:
37762 @item F @var{result} [, @var{errno}] [; @var{attachment}]
37763 @var{result} is the integer value returned by this operation, usually
37764 non-negative for success and -1 for errors. If an error has occured,
37765 @var{errno} will be included in the result specifying a
37766 value defined by the File-I/O protocol (@pxref{Errno Values}). For
37767 operations which return data, @var{attachment} supplies the data as a
37768 binary buffer. Binary buffers in response packets are escaped in the
37769 normal way (@pxref{Binary Data}). See the individual packet
37770 documentation for the interpretation of @var{result} and
37774 An empty response indicates that this operation is not recognized.
37778 These are the supported Host I/O operations:
37781 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
37782 Open a file at @var{filename} and return a file descriptor for it, or
37783 return -1 if an error occurs. The @var{filename} is a string,
37784 @var{flags} is an integer indicating a mask of open flags
37785 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
37786 of mode bits to use if the file is created (@pxref{mode_t Values}).
37787 @xref{open}, for details of the open flags and mode values.
37789 @item vFile:close: @var{fd}
37790 Close the open file corresponding to @var{fd} and return 0, or
37791 -1 if an error occurs.
37793 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
37794 Read data from the open file corresponding to @var{fd}. Up to
37795 @var{count} bytes will be read from the file, starting at @var{offset}
37796 relative to the start of the file. The target may read fewer bytes;
37797 common reasons include packet size limits and an end-of-file
37798 condition. The number of bytes read is returned. Zero should only be
37799 returned for a successful read at the end of the file, or if
37800 @var{count} was zero.
37802 The data read should be returned as a binary attachment on success.
37803 If zero bytes were read, the response should include an empty binary
37804 attachment (i.e.@: a trailing semicolon). The return value is the
37805 number of target bytes read; the binary attachment may be longer if
37806 some characters were escaped.
37808 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
37809 Write @var{data} (a binary buffer) to the open file corresponding
37810 to @var{fd}. Start the write at @var{offset} from the start of the
37811 file. Unlike many @code{write} system calls, there is no
37812 separate @var{count} argument; the length of @var{data} in the
37813 packet is used. @samp{vFile:write} returns the number of bytes written,
37814 which may be shorter than the length of @var{data}, or -1 if an
37817 @item vFile:fstat: @var{fd}
37818 Get information about the open file corresponding to @var{fd}.
37819 On success the information is returned as a binary attachment
37820 and the return value is the size of this attachment in bytes.
37821 If an error occurs the return value is -1. The format of the
37822 returned binary attachment is as described in @ref{struct stat}.
37824 @item vFile:unlink: @var{filename}
37825 Delete the file at @var{filename} on the target. Return 0,
37826 or -1 if an error occurs. The @var{filename} is a string.
37828 @item vFile:readlink: @var{filename}
37829 Read value of symbolic link @var{filename} on the target. Return
37830 the number of bytes read, or -1 if an error occurs.
37832 The data read should be returned as a binary attachment on success.
37833 If zero bytes were read, the response should include an empty binary
37834 attachment (i.e.@: a trailing semicolon). The return value is the
37835 number of target bytes read; the binary attachment may be longer if
37836 some characters were escaped.
37838 @item vFile:setfs: @var{pid}
37839 Select the filesystem on which @code{vFile} operations with
37840 @var{filename} arguments will operate. This is required for
37841 @value{GDBN} to be able to access files on remote targets where
37842 the remote stub does not share a common filesystem with the
37845 If @var{pid} is nonzero, select the filesystem as seen by process
37846 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
37847 the remote stub. Return 0 on success, or -1 if an error occurs.
37848 If @code{vFile:setfs:} indicates success, the selected filesystem
37849 remains selected until the next successful @code{vFile:setfs:}
37855 @section Interrupts
37856 @cindex interrupts (remote protocol)
37858 When a program on the remote target is running, @value{GDBN} may
37859 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
37860 a @code{BREAK} followed by @code{g},
37861 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
37863 The precise meaning of @code{BREAK} is defined by the transport
37864 mechanism and may, in fact, be undefined. @value{GDBN} does not
37865 currently define a @code{BREAK} mechanism for any of the network
37866 interfaces except for TCP, in which case @value{GDBN} sends the
37867 @code{telnet} BREAK sequence.
37869 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
37870 transport mechanisms. It is represented by sending the single byte
37871 @code{0x03} without any of the usual packet overhead described in
37872 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
37873 transmitted as part of a packet, it is considered to be packet data
37874 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
37875 (@pxref{X packet}), used for binary downloads, may include an unescaped
37876 @code{0x03} as part of its packet.
37878 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
37879 When Linux kernel receives this sequence from serial port,
37880 it stops execution and connects to gdb.
37882 Stubs are not required to recognize these interrupt mechanisms and the
37883 precise meaning associated with receipt of the interrupt is
37884 implementation defined. If the target supports debugging of multiple
37885 threads and/or processes, it should attempt to interrupt all
37886 currently-executing threads and processes.
37887 If the stub is successful at interrupting the
37888 running program, it should send one of the stop
37889 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
37890 of successfully stopping the program in all-stop mode, and a stop reply
37891 for each stopped thread in non-stop mode.
37892 Interrupts received while the
37893 program is stopped are discarded.
37895 @node Notification Packets
37896 @section Notification Packets
37897 @cindex notification packets
37898 @cindex packets, notification
37900 The @value{GDBN} remote serial protocol includes @dfn{notifications},
37901 packets that require no acknowledgment. Both the GDB and the stub
37902 may send notifications (although the only notifications defined at
37903 present are sent by the stub). Notifications carry information
37904 without incurring the round-trip latency of an acknowledgment, and so
37905 are useful for low-impact communications where occasional packet loss
37908 A notification packet has the form @samp{% @var{data} #
37909 @var{checksum}}, where @var{data} is the content of the notification,
37910 and @var{checksum} is a checksum of @var{data}, computed and formatted
37911 as for ordinary @value{GDBN} packets. A notification's @var{data}
37912 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
37913 receiving a notification, the recipient sends no @samp{+} or @samp{-}
37914 to acknowledge the notification's receipt or to report its corruption.
37916 Every notification's @var{data} begins with a name, which contains no
37917 colon characters, followed by a colon character.
37919 Recipients should silently ignore corrupted notifications and
37920 notifications they do not understand. Recipients should restart
37921 timeout periods on receipt of a well-formed notification, whether or
37922 not they understand it.
37924 Senders should only send the notifications described here when this
37925 protocol description specifies that they are permitted. In the
37926 future, we may extend the protocol to permit existing notifications in
37927 new contexts; this rule helps older senders avoid confusing newer
37930 (Older versions of @value{GDBN} ignore bytes received until they see
37931 the @samp{$} byte that begins an ordinary packet, so new stubs may
37932 transmit notifications without fear of confusing older clients. There
37933 are no notifications defined for @value{GDBN} to send at the moment, but we
37934 assume that most older stubs would ignore them, as well.)
37936 Each notification is comprised of three parts:
37938 @item @var{name}:@var{event}
37939 The notification packet is sent by the side that initiates the
37940 exchange (currently, only the stub does that), with @var{event}
37941 carrying the specific information about the notification, and
37942 @var{name} specifying the name of the notification.
37944 The acknowledge sent by the other side, usually @value{GDBN}, to
37945 acknowledge the exchange and request the event.
37948 The purpose of an asynchronous notification mechanism is to report to
37949 @value{GDBN} that something interesting happened in the remote stub.
37951 The remote stub may send notification @var{name}:@var{event}
37952 at any time, but @value{GDBN} acknowledges the notification when
37953 appropriate. The notification event is pending before @value{GDBN}
37954 acknowledges. Only one notification at a time may be pending; if
37955 additional events occur before @value{GDBN} has acknowledged the
37956 previous notification, they must be queued by the stub for later
37957 synchronous transmission in response to @var{ack} packets from
37958 @value{GDBN}. Because the notification mechanism is unreliable,
37959 the stub is permitted to resend a notification if it believes
37960 @value{GDBN} may not have received it.
37962 Specifically, notifications may appear when @value{GDBN} is not
37963 otherwise reading input from the stub, or when @value{GDBN} is
37964 expecting to read a normal synchronous response or a
37965 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
37966 Notification packets are distinct from any other communication from
37967 the stub so there is no ambiguity.
37969 After receiving a notification, @value{GDBN} shall acknowledge it by
37970 sending a @var{ack} packet as a regular, synchronous request to the
37971 stub. Such acknowledgment is not required to happen immediately, as
37972 @value{GDBN} is permitted to send other, unrelated packets to the
37973 stub first, which the stub should process normally.
37975 Upon receiving a @var{ack} packet, if the stub has other queued
37976 events to report to @value{GDBN}, it shall respond by sending a
37977 normal @var{event}. @value{GDBN} shall then send another @var{ack}
37978 packet to solicit further responses; again, it is permitted to send
37979 other, unrelated packets as well which the stub should process
37982 If the stub receives a @var{ack} packet and there are no additional
37983 @var{event} to report, the stub shall return an @samp{OK} response.
37984 At this point, @value{GDBN} has finished processing a notification
37985 and the stub has completed sending any queued events. @value{GDBN}
37986 won't accept any new notifications until the final @samp{OK} is
37987 received . If further notification events occur, the stub shall send
37988 a new notification, @value{GDBN} shall accept the notification, and
37989 the process shall be repeated.
37991 The process of asynchronous notification can be illustrated by the
37994 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
37997 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
37999 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
38004 The following notifications are defined:
38005 @multitable @columnfractions 0.12 0.12 0.38 0.38
38014 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
38015 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
38016 for information on how these notifications are acknowledged by
38018 @tab Report an asynchronous stop event in non-stop mode.
38022 @node Remote Non-Stop
38023 @section Remote Protocol Support for Non-Stop Mode
38025 @value{GDBN}'s remote protocol supports non-stop debugging of
38026 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
38027 supports non-stop mode, it should report that to @value{GDBN} by including
38028 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
38030 @value{GDBN} typically sends a @samp{QNonStop} packet only when
38031 establishing a new connection with the stub. Entering non-stop mode
38032 does not alter the state of any currently-running threads, but targets
38033 must stop all threads in any already-attached processes when entering
38034 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
38035 probe the target state after a mode change.
38037 In non-stop mode, when an attached process encounters an event that
38038 would otherwise be reported with a stop reply, it uses the
38039 asynchronous notification mechanism (@pxref{Notification Packets}) to
38040 inform @value{GDBN}. In contrast to all-stop mode, where all threads
38041 in all processes are stopped when a stop reply is sent, in non-stop
38042 mode only the thread reporting the stop event is stopped. That is,
38043 when reporting a @samp{S} or @samp{T} response to indicate completion
38044 of a step operation, hitting a breakpoint, or a fault, only the
38045 affected thread is stopped; any other still-running threads continue
38046 to run. When reporting a @samp{W} or @samp{X} response, all running
38047 threads belonging to other attached processes continue to run.
38049 In non-stop mode, the target shall respond to the @samp{?} packet as
38050 follows. First, any incomplete stop reply notification/@samp{vStopped}
38051 sequence in progress is abandoned. The target must begin a new
38052 sequence reporting stop events for all stopped threads, whether or not
38053 it has previously reported those events to @value{GDBN}. The first
38054 stop reply is sent as a synchronous reply to the @samp{?} packet, and
38055 subsequent stop replies are sent as responses to @samp{vStopped} packets
38056 using the mechanism described above. The target must not send
38057 asynchronous stop reply notifications until the sequence is complete.
38058 If all threads are running when the target receives the @samp{?} packet,
38059 or if the target is not attached to any process, it shall respond
38062 If the stub supports non-stop mode, it should also support the
38063 @samp{swbreak} stop reason if software breakpoints are supported, and
38064 the @samp{hwbreak} stop reason if hardware breakpoints are supported
38065 (@pxref{swbreak stop reason}). This is because given the asynchronous
38066 nature of non-stop mode, between the time a thread hits a breakpoint
38067 and the time the event is finally processed by @value{GDBN}, the
38068 breakpoint may have already been removed from the target. Due to
38069 this, @value{GDBN} needs to be able to tell whether a trap stop was
38070 caused by a delayed breakpoint event, which should be ignored, as
38071 opposed to a random trap signal, which should be reported to the user.
38072 Note the @samp{swbreak} feature implies that the target is responsible
38073 for adjusting the PC when a software breakpoint triggers, if
38074 necessary, such as on the x86 architecture.
38076 @node Packet Acknowledgment
38077 @section Packet Acknowledgment
38079 @cindex acknowledgment, for @value{GDBN} remote
38080 @cindex packet acknowledgment, for @value{GDBN} remote
38081 By default, when either the host or the target machine receives a packet,
38082 the first response expected is an acknowledgment: either @samp{+} (to indicate
38083 the package was received correctly) or @samp{-} (to request retransmission).
38084 This mechanism allows the @value{GDBN} remote protocol to operate over
38085 unreliable transport mechanisms, such as a serial line.
38087 In cases where the transport mechanism is itself reliable (such as a pipe or
38088 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
38089 It may be desirable to disable them in that case to reduce communication
38090 overhead, or for other reasons. This can be accomplished by means of the
38091 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
38093 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
38094 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
38095 and response format still includes the normal checksum, as described in
38096 @ref{Overview}, but the checksum may be ignored by the receiver.
38098 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
38099 no-acknowledgment mode, it should report that to @value{GDBN}
38100 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
38101 @pxref{qSupported}.
38102 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
38103 disabled via the @code{set remote noack-packet off} command
38104 (@pxref{Remote Configuration}),
38105 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
38106 Only then may the stub actually turn off packet acknowledgments.
38107 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
38108 response, which can be safely ignored by the stub.
38110 Note that @code{set remote noack-packet} command only affects negotiation
38111 between @value{GDBN} and the stub when subsequent connections are made;
38112 it does not affect the protocol acknowledgment state for any current
38114 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
38115 new connection is established,
38116 there is also no protocol request to re-enable the acknowledgments
38117 for the current connection, once disabled.
38122 Example sequence of a target being re-started. Notice how the restart
38123 does not get any direct output:
38128 @emph{target restarts}
38131 <- @code{T001:1234123412341234}
38135 Example sequence of a target being stepped by a single instruction:
38138 -> @code{G1445@dots{}}
38143 <- @code{T001:1234123412341234}
38147 <- @code{1455@dots{}}
38151 @node File-I/O Remote Protocol Extension
38152 @section File-I/O Remote Protocol Extension
38153 @cindex File-I/O remote protocol extension
38156 * File-I/O Overview::
38157 * Protocol Basics::
38158 * The F Request Packet::
38159 * The F Reply Packet::
38160 * The Ctrl-C Message::
38162 * List of Supported Calls::
38163 * Protocol-specific Representation of Datatypes::
38165 * File-I/O Examples::
38168 @node File-I/O Overview
38169 @subsection File-I/O Overview
38170 @cindex file-i/o overview
38172 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
38173 target to use the host's file system and console I/O to perform various
38174 system calls. System calls on the target system are translated into a
38175 remote protocol packet to the host system, which then performs the needed
38176 actions and returns a response packet to the target system.
38177 This simulates file system operations even on targets that lack file systems.
38179 The protocol is defined to be independent of both the host and target systems.
38180 It uses its own internal representation of datatypes and values. Both
38181 @value{GDBN} and the target's @value{GDBN} stub are responsible for
38182 translating the system-dependent value representations into the internal
38183 protocol representations when data is transmitted.
38185 The communication is synchronous. A system call is possible only when
38186 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
38187 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
38188 the target is stopped to allow deterministic access to the target's
38189 memory. Therefore File-I/O is not interruptible by target signals. On
38190 the other hand, it is possible to interrupt File-I/O by a user interrupt
38191 (@samp{Ctrl-C}) within @value{GDBN}.
38193 The target's request to perform a host system call does not finish
38194 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
38195 after finishing the system call, the target returns to continuing the
38196 previous activity (continue, step). No additional continue or step
38197 request from @value{GDBN} is required.
38200 (@value{GDBP}) continue
38201 <- target requests 'system call X'
38202 target is stopped, @value{GDBN} executes system call
38203 -> @value{GDBN} returns result
38204 ... target continues, @value{GDBN} returns to wait for the target
38205 <- target hits breakpoint and sends a Txx packet
38208 The protocol only supports I/O on the console and to regular files on
38209 the host file system. Character or block special devices, pipes,
38210 named pipes, sockets or any other communication method on the host
38211 system are not supported by this protocol.
38213 File I/O is not supported in non-stop mode.
38215 @node Protocol Basics
38216 @subsection Protocol Basics
38217 @cindex protocol basics, file-i/o
38219 The File-I/O protocol uses the @code{F} packet as the request as well
38220 as reply packet. Since a File-I/O system call can only occur when
38221 @value{GDBN} is waiting for a response from the continuing or stepping target,
38222 the File-I/O request is a reply that @value{GDBN} has to expect as a result
38223 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
38224 This @code{F} packet contains all information needed to allow @value{GDBN}
38225 to call the appropriate host system call:
38229 A unique identifier for the requested system call.
38232 All parameters to the system call. Pointers are given as addresses
38233 in the target memory address space. Pointers to strings are given as
38234 pointer/length pair. Numerical values are given as they are.
38235 Numerical control flags are given in a protocol-specific representation.
38239 At this point, @value{GDBN} has to perform the following actions.
38243 If the parameters include pointer values to data needed as input to a
38244 system call, @value{GDBN} requests this data from the target with a
38245 standard @code{m} packet request. This additional communication has to be
38246 expected by the target implementation and is handled as any other @code{m}
38250 @value{GDBN} translates all value from protocol representation to host
38251 representation as needed. Datatypes are coerced into the host types.
38254 @value{GDBN} calls the system call.
38257 It then coerces datatypes back to protocol representation.
38260 If the system call is expected to return data in buffer space specified
38261 by pointer parameters to the call, the data is transmitted to the
38262 target using a @code{M} or @code{X} packet. This packet has to be expected
38263 by the target implementation and is handled as any other @code{M} or @code{X}
38268 Eventually @value{GDBN} replies with another @code{F} packet which contains all
38269 necessary information for the target to continue. This at least contains
38276 @code{errno}, if has been changed by the system call.
38283 After having done the needed type and value coercion, the target continues
38284 the latest continue or step action.
38286 @node The F Request Packet
38287 @subsection The @code{F} Request Packet
38288 @cindex file-i/o request packet
38289 @cindex @code{F} request packet
38291 The @code{F} request packet has the following format:
38294 @item F@var{call-id},@var{parameter@dots{}}
38296 @var{call-id} is the identifier to indicate the host system call to be called.
38297 This is just the name of the function.
38299 @var{parameter@dots{}} are the parameters to the system call.
38300 Parameters are hexadecimal integer values, either the actual values in case
38301 of scalar datatypes, pointers to target buffer space in case of compound
38302 datatypes and unspecified memory areas, or pointer/length pairs in case
38303 of string parameters. These are appended to the @var{call-id} as a
38304 comma-delimited list. All values are transmitted in ASCII
38305 string representation, pointer/length pairs separated by a slash.
38311 @node The F Reply Packet
38312 @subsection The @code{F} Reply Packet
38313 @cindex file-i/o reply packet
38314 @cindex @code{F} reply packet
38316 The @code{F} reply packet has the following format:
38320 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
38322 @var{retcode} is the return code of the system call as hexadecimal value.
38324 @var{errno} is the @code{errno} set by the call, in protocol-specific
38326 This parameter can be omitted if the call was successful.
38328 @var{Ctrl-C flag} is only sent if the user requested a break. In this
38329 case, @var{errno} must be sent as well, even if the call was successful.
38330 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
38337 or, if the call was interrupted before the host call has been performed:
38344 assuming 4 is the protocol-specific representation of @code{EINTR}.
38349 @node The Ctrl-C Message
38350 @subsection The @samp{Ctrl-C} Message
38351 @cindex ctrl-c message, in file-i/o protocol
38353 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
38354 reply packet (@pxref{The F Reply Packet}),
38355 the target should behave as if it had
38356 gotten a break message. The meaning for the target is ``system call
38357 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
38358 (as with a break message) and return to @value{GDBN} with a @code{T02}
38361 It's important for the target to know in which
38362 state the system call was interrupted. There are two possible cases:
38366 The system call hasn't been performed on the host yet.
38369 The system call on the host has been finished.
38373 These two states can be distinguished by the target by the value of the
38374 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
38375 call hasn't been performed. This is equivalent to the @code{EINTR} handling
38376 on POSIX systems. In any other case, the target may presume that the
38377 system call has been finished --- successfully or not --- and should behave
38378 as if the break message arrived right after the system call.
38380 @value{GDBN} must behave reliably. If the system call has not been called
38381 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
38382 @code{errno} in the packet. If the system call on the host has been finished
38383 before the user requests a break, the full action must be finished by
38384 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
38385 The @code{F} packet may only be sent when either nothing has happened
38386 or the full action has been completed.
38389 @subsection Console I/O
38390 @cindex console i/o as part of file-i/o
38392 By default and if not explicitly closed by the target system, the file
38393 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
38394 on the @value{GDBN} console is handled as any other file output operation
38395 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
38396 by @value{GDBN} so that after the target read request from file descriptor
38397 0 all following typing is buffered until either one of the following
38402 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
38404 system call is treated as finished.
38407 The user presses @key{RET}. This is treated as end of input with a trailing
38411 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
38412 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
38416 If the user has typed more characters than fit in the buffer given to
38417 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
38418 either another @code{read(0, @dots{})} is requested by the target, or debugging
38419 is stopped at the user's request.
38422 @node List of Supported Calls
38423 @subsection List of Supported Calls
38424 @cindex list of supported file-i/o calls
38441 @unnumberedsubsubsec open
38442 @cindex open, file-i/o system call
38447 int open(const char *pathname, int flags);
38448 int open(const char *pathname, int flags, mode_t mode);
38452 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
38455 @var{flags} is the bitwise @code{OR} of the following values:
38459 If the file does not exist it will be created. The host
38460 rules apply as far as file ownership and time stamps
38464 When used with @code{O_CREAT}, if the file already exists it is
38465 an error and open() fails.
38468 If the file already exists and the open mode allows
38469 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
38470 truncated to zero length.
38473 The file is opened in append mode.
38476 The file is opened for reading only.
38479 The file is opened for writing only.
38482 The file is opened for reading and writing.
38486 Other bits are silently ignored.
38490 @var{mode} is the bitwise @code{OR} of the following values:
38494 User has read permission.
38497 User has write permission.
38500 Group has read permission.
38503 Group has write permission.
38506 Others have read permission.
38509 Others have write permission.
38513 Other bits are silently ignored.
38516 @item Return value:
38517 @code{open} returns the new file descriptor or -1 if an error
38524 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
38527 @var{pathname} refers to a directory.
38530 The requested access is not allowed.
38533 @var{pathname} was too long.
38536 A directory component in @var{pathname} does not exist.
38539 @var{pathname} refers to a device, pipe, named pipe or socket.
38542 @var{pathname} refers to a file on a read-only filesystem and
38543 write access was requested.
38546 @var{pathname} is an invalid pointer value.
38549 No space on device to create the file.
38552 The process already has the maximum number of files open.
38555 The limit on the total number of files open on the system
38559 The call was interrupted by the user.
38565 @unnumberedsubsubsec close
38566 @cindex close, file-i/o system call
38575 @samp{Fclose,@var{fd}}
38577 @item Return value:
38578 @code{close} returns zero on success, or -1 if an error occurred.
38584 @var{fd} isn't a valid open file descriptor.
38587 The call was interrupted by the user.
38593 @unnumberedsubsubsec read
38594 @cindex read, file-i/o system call
38599 int read(int fd, void *buf, unsigned int count);
38603 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
38605 @item Return value:
38606 On success, the number of bytes read is returned.
38607 Zero indicates end of file. If count is zero, read
38608 returns zero as well. On error, -1 is returned.
38614 @var{fd} is not a valid file descriptor or is not open for
38618 @var{bufptr} is an invalid pointer value.
38621 The call was interrupted by the user.
38627 @unnumberedsubsubsec write
38628 @cindex write, file-i/o system call
38633 int write(int fd, const void *buf, unsigned int count);
38637 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
38639 @item Return value:
38640 On success, the number of bytes written are returned.
38641 Zero indicates nothing was written. On error, -1
38648 @var{fd} is not a valid file descriptor or is not open for
38652 @var{bufptr} is an invalid pointer value.
38655 An attempt was made to write a file that exceeds the
38656 host-specific maximum file size allowed.
38659 No space on device to write the data.
38662 The call was interrupted by the user.
38668 @unnumberedsubsubsec lseek
38669 @cindex lseek, file-i/o system call
38674 long lseek (int fd, long offset, int flag);
38678 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
38680 @var{flag} is one of:
38684 The offset is set to @var{offset} bytes.
38687 The offset is set to its current location plus @var{offset}
38691 The offset is set to the size of the file plus @var{offset}
38695 @item Return value:
38696 On success, the resulting unsigned offset in bytes from
38697 the beginning of the file is returned. Otherwise, a
38698 value of -1 is returned.
38704 @var{fd} is not a valid open file descriptor.
38707 @var{fd} is associated with the @value{GDBN} console.
38710 @var{flag} is not a proper value.
38713 The call was interrupted by the user.
38719 @unnumberedsubsubsec rename
38720 @cindex rename, file-i/o system call
38725 int rename(const char *oldpath, const char *newpath);
38729 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
38731 @item Return value:
38732 On success, zero is returned. On error, -1 is returned.
38738 @var{newpath} is an existing directory, but @var{oldpath} is not a
38742 @var{newpath} is a non-empty directory.
38745 @var{oldpath} or @var{newpath} is a directory that is in use by some
38749 An attempt was made to make a directory a subdirectory
38753 A component used as a directory in @var{oldpath} or new
38754 path is not a directory. Or @var{oldpath} is a directory
38755 and @var{newpath} exists but is not a directory.
38758 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
38761 No access to the file or the path of the file.
38765 @var{oldpath} or @var{newpath} was too long.
38768 A directory component in @var{oldpath} or @var{newpath} does not exist.
38771 The file is on a read-only filesystem.
38774 The device containing the file has no room for the new
38778 The call was interrupted by the user.
38784 @unnumberedsubsubsec unlink
38785 @cindex unlink, file-i/o system call
38790 int unlink(const char *pathname);
38794 @samp{Funlink,@var{pathnameptr}/@var{len}}
38796 @item Return value:
38797 On success, zero is returned. On error, -1 is returned.
38803 No access to the file or the path of the file.
38806 The system does not allow unlinking of directories.
38809 The file @var{pathname} cannot be unlinked because it's
38810 being used by another process.
38813 @var{pathnameptr} is an invalid pointer value.
38816 @var{pathname} was too long.
38819 A directory component in @var{pathname} does not exist.
38822 A component of the path is not a directory.
38825 The file is on a read-only filesystem.
38828 The call was interrupted by the user.
38834 @unnumberedsubsubsec stat/fstat
38835 @cindex fstat, file-i/o system call
38836 @cindex stat, file-i/o system call
38841 int stat(const char *pathname, struct stat *buf);
38842 int fstat(int fd, struct stat *buf);
38846 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
38847 @samp{Ffstat,@var{fd},@var{bufptr}}
38849 @item Return value:
38850 On success, zero is returned. On error, -1 is returned.
38856 @var{fd} is not a valid open file.
38859 A directory component in @var{pathname} does not exist or the
38860 path is an empty string.
38863 A component of the path is not a directory.
38866 @var{pathnameptr} is an invalid pointer value.
38869 No access to the file or the path of the file.
38872 @var{pathname} was too long.
38875 The call was interrupted by the user.
38881 @unnumberedsubsubsec gettimeofday
38882 @cindex gettimeofday, file-i/o system call
38887 int gettimeofday(struct timeval *tv, void *tz);
38891 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
38893 @item Return value:
38894 On success, 0 is returned, -1 otherwise.
38900 @var{tz} is a non-NULL pointer.
38903 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
38909 @unnumberedsubsubsec isatty
38910 @cindex isatty, file-i/o system call
38915 int isatty(int fd);
38919 @samp{Fisatty,@var{fd}}
38921 @item Return value:
38922 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
38928 The call was interrupted by the user.
38933 Note that the @code{isatty} call is treated as a special case: it returns
38934 1 to the target if the file descriptor is attached
38935 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
38936 would require implementing @code{ioctl} and would be more complex than
38941 @unnumberedsubsubsec system
38942 @cindex system, file-i/o system call
38947 int system(const char *command);
38951 @samp{Fsystem,@var{commandptr}/@var{len}}
38953 @item Return value:
38954 If @var{len} is zero, the return value indicates whether a shell is
38955 available. A zero return value indicates a shell is not available.
38956 For non-zero @var{len}, the value returned is -1 on error and the
38957 return status of the command otherwise. Only the exit status of the
38958 command is returned, which is extracted from the host's @code{system}
38959 return value by calling @code{WEXITSTATUS(retval)}. In case
38960 @file{/bin/sh} could not be executed, 127 is returned.
38966 The call was interrupted by the user.
38971 @value{GDBN} takes over the full task of calling the necessary host calls
38972 to perform the @code{system} call. The return value of @code{system} on
38973 the host is simplified before it's returned
38974 to the target. Any termination signal information from the child process
38975 is discarded, and the return value consists
38976 entirely of the exit status of the called command.
38978 Due to security concerns, the @code{system} call is by default refused
38979 by @value{GDBN}. The user has to allow this call explicitly with the
38980 @code{set remote system-call-allowed 1} command.
38983 @item set remote system-call-allowed
38984 @kindex set remote system-call-allowed
38985 Control whether to allow the @code{system} calls in the File I/O
38986 protocol for the remote target. The default is zero (disabled).
38988 @item show remote system-call-allowed
38989 @kindex show remote system-call-allowed
38990 Show whether the @code{system} calls are allowed in the File I/O
38994 @node Protocol-specific Representation of Datatypes
38995 @subsection Protocol-specific Representation of Datatypes
38996 @cindex protocol-specific representation of datatypes, in file-i/o protocol
38999 * Integral Datatypes::
39001 * Memory Transfer::
39006 @node Integral Datatypes
39007 @unnumberedsubsubsec Integral Datatypes
39008 @cindex integral datatypes, in file-i/o protocol
39010 The integral datatypes used in the system calls are @code{int},
39011 @code{unsigned int}, @code{long}, @code{unsigned long},
39012 @code{mode_t}, and @code{time_t}.
39014 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
39015 implemented as 32 bit values in this protocol.
39017 @code{long} and @code{unsigned long} are implemented as 64 bit types.
39019 @xref{Limits}, for corresponding MIN and MAX values (similar to those
39020 in @file{limits.h}) to allow range checking on host and target.
39022 @code{time_t} datatypes are defined as seconds since the Epoch.
39024 All integral datatypes transferred as part of a memory read or write of a
39025 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
39028 @node Pointer Values
39029 @unnumberedsubsubsec Pointer Values
39030 @cindex pointer values, in file-i/o protocol
39032 Pointers to target data are transmitted as they are. An exception
39033 is made for pointers to buffers for which the length isn't
39034 transmitted as part of the function call, namely strings. Strings
39035 are transmitted as a pointer/length pair, both as hex values, e.g.@:
39042 which is a pointer to data of length 18 bytes at position 0x1aaf.
39043 The length is defined as the full string length in bytes, including
39044 the trailing null byte. For example, the string @code{"hello world"}
39045 at address 0x123456 is transmitted as
39051 @node Memory Transfer
39052 @unnumberedsubsubsec Memory Transfer
39053 @cindex memory transfer, in file-i/o protocol
39055 Structured data which is transferred using a memory read or write (for
39056 example, a @code{struct stat}) is expected to be in a protocol-specific format
39057 with all scalar multibyte datatypes being big endian. Translation to
39058 this representation needs to be done both by the target before the @code{F}
39059 packet is sent, and by @value{GDBN} before
39060 it transfers memory to the target. Transferred pointers to structured
39061 data should point to the already-coerced data at any time.
39065 @unnumberedsubsubsec struct stat
39066 @cindex struct stat, in file-i/o protocol
39068 The buffer of type @code{struct stat} used by the target and @value{GDBN}
39069 is defined as follows:
39073 unsigned int st_dev; /* device */
39074 unsigned int st_ino; /* inode */
39075 mode_t st_mode; /* protection */
39076 unsigned int st_nlink; /* number of hard links */
39077 unsigned int st_uid; /* user ID of owner */
39078 unsigned int st_gid; /* group ID of owner */
39079 unsigned int st_rdev; /* device type (if inode device) */
39080 unsigned long st_size; /* total size, in bytes */
39081 unsigned long st_blksize; /* blocksize for filesystem I/O */
39082 unsigned long st_blocks; /* number of blocks allocated */
39083 time_t st_atime; /* time of last access */
39084 time_t st_mtime; /* time of last modification */
39085 time_t st_ctime; /* time of last change */
39089 The integral datatypes conform to the definitions given in the
39090 appropriate section (see @ref{Integral Datatypes}, for details) so this
39091 structure is of size 64 bytes.
39093 The values of several fields have a restricted meaning and/or
39099 A value of 0 represents a file, 1 the console.
39102 No valid meaning for the target. Transmitted unchanged.
39105 Valid mode bits are described in @ref{Constants}. Any other
39106 bits have currently no meaning for the target.
39111 No valid meaning for the target. Transmitted unchanged.
39116 These values have a host and file system dependent
39117 accuracy. Especially on Windows hosts, the file system may not
39118 support exact timing values.
39121 The target gets a @code{struct stat} of the above representation and is
39122 responsible for coercing it to the target representation before
39125 Note that due to size differences between the host, target, and protocol
39126 representations of @code{struct stat} members, these members could eventually
39127 get truncated on the target.
39129 @node struct timeval
39130 @unnumberedsubsubsec struct timeval
39131 @cindex struct timeval, in file-i/o protocol
39133 The buffer of type @code{struct timeval} used by the File-I/O protocol
39134 is defined as follows:
39138 time_t tv_sec; /* second */
39139 long tv_usec; /* microsecond */
39143 The integral datatypes conform to the definitions given in the
39144 appropriate section (see @ref{Integral Datatypes}, for details) so this
39145 structure is of size 8 bytes.
39148 @subsection Constants
39149 @cindex constants, in file-i/o protocol
39151 The following values are used for the constants inside of the
39152 protocol. @value{GDBN} and target are responsible for translating these
39153 values before and after the call as needed.
39164 @unnumberedsubsubsec Open Flags
39165 @cindex open flags, in file-i/o protocol
39167 All values are given in hexadecimal representation.
39179 @node mode_t Values
39180 @unnumberedsubsubsec mode_t Values
39181 @cindex mode_t values, in file-i/o protocol
39183 All values are given in octal representation.
39200 @unnumberedsubsubsec Errno Values
39201 @cindex errno values, in file-i/o protocol
39203 All values are given in decimal representation.
39228 @code{EUNKNOWN} is used as a fallback error value if a host system returns
39229 any error value not in the list of supported error numbers.
39232 @unnumberedsubsubsec Lseek Flags
39233 @cindex lseek flags, in file-i/o protocol
39242 @unnumberedsubsubsec Limits
39243 @cindex limits, in file-i/o protocol
39245 All values are given in decimal representation.
39248 INT_MIN -2147483648
39250 UINT_MAX 4294967295
39251 LONG_MIN -9223372036854775808
39252 LONG_MAX 9223372036854775807
39253 ULONG_MAX 18446744073709551615
39256 @node File-I/O Examples
39257 @subsection File-I/O Examples
39258 @cindex file-i/o examples
39260 Example sequence of a write call, file descriptor 3, buffer is at target
39261 address 0x1234, 6 bytes should be written:
39264 <- @code{Fwrite,3,1234,6}
39265 @emph{request memory read from target}
39268 @emph{return "6 bytes written"}
39272 Example sequence of a read call, file descriptor 3, buffer is at target
39273 address 0x1234, 6 bytes should be read:
39276 <- @code{Fread,3,1234,6}
39277 @emph{request memory write to target}
39278 -> @code{X1234,6:XXXXXX}
39279 @emph{return "6 bytes read"}
39283 Example sequence of a read call, call fails on the host due to invalid
39284 file descriptor (@code{EBADF}):
39287 <- @code{Fread,3,1234,6}
39291 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
39295 <- @code{Fread,3,1234,6}
39300 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
39304 <- @code{Fread,3,1234,6}
39305 -> @code{X1234,6:XXXXXX}
39309 @node Library List Format
39310 @section Library List Format
39311 @cindex library list format, remote protocol
39313 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
39314 same process as your application to manage libraries. In this case,
39315 @value{GDBN} can use the loader's symbol table and normal memory
39316 operations to maintain a list of shared libraries. On other
39317 platforms, the operating system manages loaded libraries.
39318 @value{GDBN} can not retrieve the list of currently loaded libraries
39319 through memory operations, so it uses the @samp{qXfer:libraries:read}
39320 packet (@pxref{qXfer library list read}) instead. The remote stub
39321 queries the target's operating system and reports which libraries
39324 The @samp{qXfer:libraries:read} packet returns an XML document which
39325 lists loaded libraries and their offsets. Each library has an
39326 associated name and one or more segment or section base addresses,
39327 which report where the library was loaded in memory.
39329 For the common case of libraries that are fully linked binaries, the
39330 library should have a list of segments. If the target supports
39331 dynamic linking of a relocatable object file, its library XML element
39332 should instead include a list of allocated sections. The segment or
39333 section bases are start addresses, not relocation offsets; they do not
39334 depend on the library's link-time base addresses.
39336 @value{GDBN} must be linked with the Expat library to support XML
39337 library lists. @xref{Expat}.
39339 A simple memory map, with one loaded library relocated by a single
39340 offset, looks like this:
39344 <library name="/lib/libc.so.6">
39345 <segment address="0x10000000"/>
39350 Another simple memory map, with one loaded library with three
39351 allocated sections (.text, .data, .bss), looks like this:
39355 <library name="sharedlib.o">
39356 <section address="0x10000000"/>
39357 <section address="0x20000000"/>
39358 <section address="0x30000000"/>
39363 The format of a library list is described by this DTD:
39366 <!-- library-list: Root element with versioning -->
39367 <!ELEMENT library-list (library)*>
39368 <!ATTLIST library-list version CDATA #FIXED "1.0">
39369 <!ELEMENT library (segment*, section*)>
39370 <!ATTLIST library name CDATA #REQUIRED>
39371 <!ELEMENT segment EMPTY>
39372 <!ATTLIST segment address CDATA #REQUIRED>
39373 <!ELEMENT section EMPTY>
39374 <!ATTLIST section address CDATA #REQUIRED>
39377 In addition, segments and section descriptors cannot be mixed within a
39378 single library element, and you must supply at least one segment or
39379 section for each library.
39381 @node Library List Format for SVR4 Targets
39382 @section Library List Format for SVR4 Targets
39383 @cindex library list format, remote protocol
39385 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
39386 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
39387 shared libraries. Still a special library list provided by this packet is
39388 more efficient for the @value{GDBN} remote protocol.
39390 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
39391 loaded libraries and their SVR4 linker parameters. For each library on SVR4
39392 target, the following parameters are reported:
39396 @code{name}, the absolute file name from the @code{l_name} field of
39397 @code{struct link_map}.
39399 @code{lm} with address of @code{struct link_map} used for TLS
39400 (Thread Local Storage) access.
39402 @code{l_addr}, the displacement as read from the field @code{l_addr} of
39403 @code{struct link_map}. For prelinked libraries this is not an absolute
39404 memory address. It is a displacement of absolute memory address against
39405 address the file was prelinked to during the library load.
39407 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
39410 Additionally the single @code{main-lm} attribute specifies address of
39411 @code{struct link_map} used for the main executable. This parameter is used
39412 for TLS access and its presence is optional.
39414 @value{GDBN} must be linked with the Expat library to support XML
39415 SVR4 library lists. @xref{Expat}.
39417 A simple memory map, with two loaded libraries (which do not use prelink),
39421 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
39422 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
39424 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
39426 </library-list-svr>
39429 The format of an SVR4 library list is described by this DTD:
39432 <!-- library-list-svr4: Root element with versioning -->
39433 <!ELEMENT library-list-svr4 (library)*>
39434 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
39435 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
39436 <!ELEMENT library EMPTY>
39437 <!ATTLIST library name CDATA #REQUIRED>
39438 <!ATTLIST library lm CDATA #REQUIRED>
39439 <!ATTLIST library l_addr CDATA #REQUIRED>
39440 <!ATTLIST library l_ld CDATA #REQUIRED>
39443 @node Memory Map Format
39444 @section Memory Map Format
39445 @cindex memory map format
39447 To be able to write into flash memory, @value{GDBN} needs to obtain a
39448 memory map from the target. This section describes the format of the
39451 The memory map is obtained using the @samp{qXfer:memory-map:read}
39452 (@pxref{qXfer memory map read}) packet and is an XML document that
39453 lists memory regions.
39455 @value{GDBN} must be linked with the Expat library to support XML
39456 memory maps. @xref{Expat}.
39458 The top-level structure of the document is shown below:
39461 <?xml version="1.0"?>
39462 <!DOCTYPE memory-map
39463 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
39464 "http://sourceware.org/gdb/gdb-memory-map.dtd">
39470 Each region can be either:
39475 A region of RAM starting at @var{addr} and extending for @var{length}
39479 <memory type="ram" start="@var{addr}" length="@var{length}"/>
39484 A region of read-only memory:
39487 <memory type="rom" start="@var{addr}" length="@var{length}"/>
39492 A region of flash memory, with erasure blocks @var{blocksize}
39496 <memory type="flash" start="@var{addr}" length="@var{length}">
39497 <property name="blocksize">@var{blocksize}</property>
39503 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
39504 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
39505 packets to write to addresses in such ranges.
39507 The formal DTD for memory map format is given below:
39510 <!-- ................................................... -->
39511 <!-- Memory Map XML DTD ................................ -->
39512 <!-- File: memory-map.dtd .............................. -->
39513 <!-- .................................... .............. -->
39514 <!-- memory-map.dtd -->
39515 <!-- memory-map: Root element with versioning -->
39516 <!ELEMENT memory-map (memory | property)>
39517 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
39518 <!ELEMENT memory (property)>
39519 <!-- memory: Specifies a memory region,
39520 and its type, or device. -->
39521 <!ATTLIST memory type CDATA #REQUIRED
39522 start CDATA #REQUIRED
39523 length CDATA #REQUIRED
39524 device CDATA #IMPLIED>
39525 <!-- property: Generic attribute tag -->
39526 <!ELEMENT property (#PCDATA | property)*>
39527 <!ATTLIST property name CDATA #REQUIRED>
39530 @node Thread List Format
39531 @section Thread List Format
39532 @cindex thread list format
39534 To efficiently update the list of threads and their attributes,
39535 @value{GDBN} issues the @samp{qXfer:threads:read} packet
39536 (@pxref{qXfer threads read}) and obtains the XML document with
39537 the following structure:
39540 <?xml version="1.0"?>
39542 <thread id="id" core="0">
39543 ... description ...
39548 Each @samp{thread} element must have the @samp{id} attribute that
39549 identifies the thread (@pxref{thread-id syntax}). The
39550 @samp{core} attribute, if present, specifies which processor core
39551 the thread was last executing on. The content of the of @samp{thread}
39552 element is interpreted as human-readable auxilliary information.
39554 @node Traceframe Info Format
39555 @section Traceframe Info Format
39556 @cindex traceframe info format
39558 To be able to know which objects in the inferior can be examined when
39559 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
39560 memory ranges, registers and trace state variables that have been
39561 collected in a traceframe.
39563 This list is obtained using the @samp{qXfer:traceframe-info:read}
39564 (@pxref{qXfer traceframe info read}) packet and is an XML document.
39566 @value{GDBN} must be linked with the Expat library to support XML
39567 traceframe info discovery. @xref{Expat}.
39569 The top-level structure of the document is shown below:
39572 <?xml version="1.0"?>
39573 <!DOCTYPE traceframe-info
39574 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
39575 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
39581 Each traceframe block can be either:
39586 A region of collected memory starting at @var{addr} and extending for
39587 @var{length} bytes from there:
39590 <memory start="@var{addr}" length="@var{length}"/>
39594 A block indicating trace state variable numbered @var{number} has been
39598 <tvar id="@var{number}"/>
39603 The formal DTD for the traceframe info format is given below:
39606 <!ELEMENT traceframe-info (memory | tvar)* >
39607 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
39609 <!ELEMENT memory EMPTY>
39610 <!ATTLIST memory start CDATA #REQUIRED
39611 length CDATA #REQUIRED>
39613 <!ATTLIST tvar id CDATA #REQUIRED>
39616 @node Branch Trace Format
39617 @section Branch Trace Format
39618 @cindex branch trace format
39620 In order to display the branch trace of an inferior thread,
39621 @value{GDBN} needs to obtain the list of branches. This list is
39622 represented as list of sequential code blocks that are connected via
39623 branches. The code in each block has been executed sequentially.
39625 This list is obtained using the @samp{qXfer:btrace:read}
39626 (@pxref{qXfer btrace read}) packet and is an XML document.
39628 @value{GDBN} must be linked with the Expat library to support XML
39629 traceframe info discovery. @xref{Expat}.
39631 The top-level structure of the document is shown below:
39634 <?xml version="1.0"?>
39636 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
39637 "http://sourceware.org/gdb/gdb-btrace.dtd">
39646 A block of sequentially executed instructions starting at @var{begin}
39647 and ending at @var{end}:
39650 <block begin="@var{begin}" end="@var{end}"/>
39655 The formal DTD for the branch trace format is given below:
39658 <!ELEMENT btrace (block* | pt) >
39659 <!ATTLIST btrace version CDATA #FIXED "1.0">
39661 <!ELEMENT block EMPTY>
39662 <!ATTLIST block begin CDATA #REQUIRED
39663 end CDATA #REQUIRED>
39665 <!ELEMENT pt (pt-config?, raw?)>
39667 <!ELEMENT pt-config (cpu?)>
39669 <!ELEMENT cpu EMPTY>
39670 <!ATTLIST cpu vendor CDATA #REQUIRED
39671 family CDATA #REQUIRED
39672 model CDATA #REQUIRED
39673 stepping CDATA #REQUIRED>
39675 <!ELEMENT raw (#PCDATA)>
39678 @node Branch Trace Configuration Format
39679 @section Branch Trace Configuration Format
39680 @cindex branch trace configuration format
39682 For each inferior thread, @value{GDBN} can obtain the branch trace
39683 configuration using the @samp{qXfer:btrace-conf:read}
39684 (@pxref{qXfer btrace-conf read}) packet.
39686 The configuration describes the branch trace format and configuration
39687 settings for that format. The following information is described:
39691 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
39694 The size of the @acronym{BTS} ring buffer in bytes.
39697 This thread uses the @dfn{Intel(R) Processor Trace} (@acronym{Intel(R)
39701 The size of the @acronym{Intel(R) PT} ring buffer in bytes.
39705 @value{GDBN} must be linked with the Expat library to support XML
39706 branch trace configuration discovery. @xref{Expat}.
39708 The formal DTD for the branch trace configuration format is given below:
39711 <!ELEMENT btrace-conf (bts?, pt?)>
39712 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
39714 <!ELEMENT bts EMPTY>
39715 <!ATTLIST bts size CDATA #IMPLIED>
39717 <!ELEMENT pt EMPTY>
39718 <!ATTLIST pt size CDATA #IMPLIED>
39721 @include agentexpr.texi
39723 @node Target Descriptions
39724 @appendix Target Descriptions
39725 @cindex target descriptions
39727 One of the challenges of using @value{GDBN} to debug embedded systems
39728 is that there are so many minor variants of each processor
39729 architecture in use. It is common practice for vendors to start with
39730 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
39731 and then make changes to adapt it to a particular market niche. Some
39732 architectures have hundreds of variants, available from dozens of
39733 vendors. This leads to a number of problems:
39737 With so many different customized processors, it is difficult for
39738 the @value{GDBN} maintainers to keep up with the changes.
39740 Since individual variants may have short lifetimes or limited
39741 audiences, it may not be worthwhile to carry information about every
39742 variant in the @value{GDBN} source tree.
39744 When @value{GDBN} does support the architecture of the embedded system
39745 at hand, the task of finding the correct architecture name to give the
39746 @command{set architecture} command can be error-prone.
39749 To address these problems, the @value{GDBN} remote protocol allows a
39750 target system to not only identify itself to @value{GDBN}, but to
39751 actually describe its own features. This lets @value{GDBN} support
39752 processor variants it has never seen before --- to the extent that the
39753 descriptions are accurate, and that @value{GDBN} understands them.
39755 @value{GDBN} must be linked with the Expat library to support XML
39756 target descriptions. @xref{Expat}.
39759 * Retrieving Descriptions:: How descriptions are fetched from a target.
39760 * Target Description Format:: The contents of a target description.
39761 * Predefined Target Types:: Standard types available for target
39763 * Standard Target Features:: Features @value{GDBN} knows about.
39766 @node Retrieving Descriptions
39767 @section Retrieving Descriptions
39769 Target descriptions can be read from the target automatically, or
39770 specified by the user manually. The default behavior is to read the
39771 description from the target. @value{GDBN} retrieves it via the remote
39772 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
39773 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
39774 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
39775 XML document, of the form described in @ref{Target Description
39778 Alternatively, you can specify a file to read for the target description.
39779 If a file is set, the target will not be queried. The commands to
39780 specify a file are:
39783 @cindex set tdesc filename
39784 @item set tdesc filename @var{path}
39785 Read the target description from @var{path}.
39787 @cindex unset tdesc filename
39788 @item unset tdesc filename
39789 Do not read the XML target description from a file. @value{GDBN}
39790 will use the description supplied by the current target.
39792 @cindex show tdesc filename
39793 @item show tdesc filename
39794 Show the filename to read for a target description, if any.
39798 @node Target Description Format
39799 @section Target Description Format
39800 @cindex target descriptions, XML format
39802 A target description annex is an @uref{http://www.w3.org/XML/, XML}
39803 document which complies with the Document Type Definition provided in
39804 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
39805 means you can use generally available tools like @command{xmllint} to
39806 check that your feature descriptions are well-formed and valid.
39807 However, to help people unfamiliar with XML write descriptions for
39808 their targets, we also describe the grammar here.
39810 Target descriptions can identify the architecture of the remote target
39811 and (for some architectures) provide information about custom register
39812 sets. They can also identify the OS ABI of the remote target.
39813 @value{GDBN} can use this information to autoconfigure for your
39814 target, or to warn you if you connect to an unsupported target.
39816 Here is a simple target description:
39819 <target version="1.0">
39820 <architecture>i386:x86-64</architecture>
39825 This minimal description only says that the target uses
39826 the x86-64 architecture.
39828 A target description has the following overall form, with [ ] marking
39829 optional elements and @dots{} marking repeatable elements. The elements
39830 are explained further below.
39833 <?xml version="1.0"?>
39834 <!DOCTYPE target SYSTEM "gdb-target.dtd">
39835 <target version="1.0">
39836 @r{[}@var{architecture}@r{]}
39837 @r{[}@var{osabi}@r{]}
39838 @r{[}@var{compatible}@r{]}
39839 @r{[}@var{feature}@dots{}@r{]}
39844 The description is generally insensitive to whitespace and line
39845 breaks, under the usual common-sense rules. The XML version
39846 declaration and document type declaration can generally be omitted
39847 (@value{GDBN} does not require them), but specifying them may be
39848 useful for XML validation tools. The @samp{version} attribute for
39849 @samp{<target>} may also be omitted, but we recommend
39850 including it; if future versions of @value{GDBN} use an incompatible
39851 revision of @file{gdb-target.dtd}, they will detect and report
39852 the version mismatch.
39854 @subsection Inclusion
39855 @cindex target descriptions, inclusion
39858 @cindex <xi:include>
39861 It can sometimes be valuable to split a target description up into
39862 several different annexes, either for organizational purposes, or to
39863 share files between different possible target descriptions. You can
39864 divide a description into multiple files by replacing any element of
39865 the target description with an inclusion directive of the form:
39868 <xi:include href="@var{document}"/>
39872 When @value{GDBN} encounters an element of this form, it will retrieve
39873 the named XML @var{document}, and replace the inclusion directive with
39874 the contents of that document. If the current description was read
39875 using @samp{qXfer}, then so will be the included document;
39876 @var{document} will be interpreted as the name of an annex. If the
39877 current description was read from a file, @value{GDBN} will look for
39878 @var{document} as a file in the same directory where it found the
39879 original description.
39881 @subsection Architecture
39882 @cindex <architecture>
39884 An @samp{<architecture>} element has this form:
39887 <architecture>@var{arch}</architecture>
39890 @var{arch} is one of the architectures from the set accepted by
39891 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
39894 @cindex @code{<osabi>}
39896 This optional field was introduced in @value{GDBN} version 7.0.
39897 Previous versions of @value{GDBN} ignore it.
39899 An @samp{<osabi>} element has this form:
39902 <osabi>@var{abi-name}</osabi>
39905 @var{abi-name} is an OS ABI name from the same selection accepted by
39906 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
39908 @subsection Compatible Architecture
39909 @cindex @code{<compatible>}
39911 This optional field was introduced in @value{GDBN} version 7.0.
39912 Previous versions of @value{GDBN} ignore it.
39914 A @samp{<compatible>} element has this form:
39917 <compatible>@var{arch}</compatible>
39920 @var{arch} is one of the architectures from the set accepted by
39921 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
39923 A @samp{<compatible>} element is used to specify that the target
39924 is able to run binaries in some other than the main target architecture
39925 given by the @samp{<architecture>} element. For example, on the
39926 Cell Broadband Engine, the main architecture is @code{powerpc:common}
39927 or @code{powerpc:common64}, but the system is able to run binaries
39928 in the @code{spu} architecture as well. The way to describe this
39929 capability with @samp{<compatible>} is as follows:
39932 <architecture>powerpc:common</architecture>
39933 <compatible>spu</compatible>
39936 @subsection Features
39939 Each @samp{<feature>} describes some logical portion of the target
39940 system. Features are currently used to describe available CPU
39941 registers and the types of their contents. A @samp{<feature>} element
39945 <feature name="@var{name}">
39946 @r{[}@var{type}@dots{}@r{]}
39952 Each feature's name should be unique within the description. The name
39953 of a feature does not matter unless @value{GDBN} has some special
39954 knowledge of the contents of that feature; if it does, the feature
39955 should have its standard name. @xref{Standard Target Features}.
39959 Any register's value is a collection of bits which @value{GDBN} must
39960 interpret. The default interpretation is a two's complement integer,
39961 but other types can be requested by name in the register description.
39962 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
39963 Target Types}), and the description can define additional composite types.
39965 Each type element must have an @samp{id} attribute, which gives
39966 a unique (within the containing @samp{<feature>}) name to the type.
39967 Types must be defined before they are used.
39970 Some targets offer vector registers, which can be treated as arrays
39971 of scalar elements. These types are written as @samp{<vector>} elements,
39972 specifying the array element type, @var{type}, and the number of elements,
39976 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
39980 If a register's value is usefully viewed in multiple ways, define it
39981 with a union type containing the useful representations. The
39982 @samp{<union>} element contains one or more @samp{<field>} elements,
39983 each of which has a @var{name} and a @var{type}:
39986 <union id="@var{id}">
39987 <field name="@var{name}" type="@var{type}"/>
39993 If a register's value is composed from several separate values, define
39994 it with a structure type. There are two forms of the @samp{<struct>}
39995 element; a @samp{<struct>} element must either contain only bitfields
39996 or contain no bitfields. If the structure contains only bitfields,
39997 its total size in bytes must be specified, each bitfield must have an
39998 explicit start and end, and bitfields are automatically assigned an
39999 integer type. The field's @var{start} should be less than or
40000 equal to its @var{end}, and zero represents the least significant bit.
40003 <struct id="@var{id}" size="@var{size}">
40004 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40009 If the structure contains no bitfields, then each field has an
40010 explicit type, and no implicit padding is added.
40013 <struct id="@var{id}">
40014 <field name="@var{name}" type="@var{type}"/>
40020 If a register's value is a series of single-bit flags, define it with
40021 a flags type. The @samp{<flags>} element has an explicit @var{size}
40022 and contains one or more @samp{<field>} elements. Each field has a
40023 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
40027 <flags id="@var{id}" size="@var{size}">
40028 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40033 @subsection Registers
40036 Each register is represented as an element with this form:
40039 <reg name="@var{name}"
40040 bitsize="@var{size}"
40041 @r{[}regnum="@var{num}"@r{]}
40042 @r{[}save-restore="@var{save-restore}"@r{]}
40043 @r{[}type="@var{type}"@r{]}
40044 @r{[}group="@var{group}"@r{]}/>
40048 The components are as follows:
40053 The register's name; it must be unique within the target description.
40056 The register's size, in bits.
40059 The register's number. If omitted, a register's number is one greater
40060 than that of the previous register (either in the current feature or in
40061 a preceding feature); the first register in the target description
40062 defaults to zero. This register number is used to read or write
40063 the register; e.g.@: it is used in the remote @code{p} and @code{P}
40064 packets, and registers appear in the @code{g} and @code{G} packets
40065 in order of increasing register number.
40068 Whether the register should be preserved across inferior function
40069 calls; this must be either @code{yes} or @code{no}. The default is
40070 @code{yes}, which is appropriate for most registers except for
40071 some system control registers; this is not related to the target's
40075 The type of the register. It may be a predefined type, a type
40076 defined in the current feature, or one of the special types @code{int}
40077 and @code{float}. @code{int} is an integer type of the correct size
40078 for @var{bitsize}, and @code{float} is a floating point type (in the
40079 architecture's normal floating point format) of the correct size for
40080 @var{bitsize}. The default is @code{int}.
40083 The register group to which this register belongs. It must
40084 be either @code{general}, @code{float}, or @code{vector}. If no
40085 @var{group} is specified, @value{GDBN} will not display the register
40086 in @code{info registers}.
40090 @node Predefined Target Types
40091 @section Predefined Target Types
40092 @cindex target descriptions, predefined types
40094 Type definitions in the self-description can build up composite types
40095 from basic building blocks, but can not define fundamental types. Instead,
40096 standard identifiers are provided by @value{GDBN} for the fundamental
40097 types. The currently supported types are:
40106 Signed integer types holding the specified number of bits.
40113 Unsigned integer types holding the specified number of bits.
40117 Pointers to unspecified code and data. The program counter and
40118 any dedicated return address register may be marked as code
40119 pointers; printing a code pointer converts it into a symbolic
40120 address. The stack pointer and any dedicated address registers
40121 may be marked as data pointers.
40124 Single precision IEEE floating point.
40127 Double precision IEEE floating point.
40130 The 12-byte extended precision format used by ARM FPA registers.
40133 The 10-byte extended precision format used by x87 registers.
40136 32bit @sc{eflags} register used by x86.
40139 32bit @sc{mxcsr} register used by x86.
40143 @node Standard Target Features
40144 @section Standard Target Features
40145 @cindex target descriptions, standard features
40147 A target description must contain either no registers or all the
40148 target's registers. If the description contains no registers, then
40149 @value{GDBN} will assume a default register layout, selected based on
40150 the architecture. If the description contains any registers, the
40151 default layout will not be used; the standard registers must be
40152 described in the target description, in such a way that @value{GDBN}
40153 can recognize them.
40155 This is accomplished by giving specific names to feature elements
40156 which contain standard registers. @value{GDBN} will look for features
40157 with those names and verify that they contain the expected registers;
40158 if any known feature is missing required registers, or if any required
40159 feature is missing, @value{GDBN} will reject the target
40160 description. You can add additional registers to any of the
40161 standard features --- @value{GDBN} will display them just as if
40162 they were added to an unrecognized feature.
40164 This section lists the known features and their expected contents.
40165 Sample XML documents for these features are included in the
40166 @value{GDBN} source tree, in the directory @file{gdb/features}.
40168 Names recognized by @value{GDBN} should include the name of the
40169 company or organization which selected the name, and the overall
40170 architecture to which the feature applies; so e.g.@: the feature
40171 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
40173 The names of registers are not case sensitive for the purpose
40174 of recognizing standard features, but @value{GDBN} will only display
40175 registers using the capitalization used in the description.
40178 * AArch64 Features::
40181 * MicroBlaze Features::
40184 * Nios II Features::
40185 * PowerPC Features::
40186 * S/390 and System z Features::
40191 @node AArch64 Features
40192 @subsection AArch64 Features
40193 @cindex target descriptions, AArch64 features
40195 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
40196 targets. It should contain registers @samp{x0} through @samp{x30},
40197 @samp{sp}, @samp{pc}, and @samp{cpsr}.
40199 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
40200 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
40204 @subsection ARM Features
40205 @cindex target descriptions, ARM features
40207 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
40209 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
40210 @samp{lr}, @samp{pc}, and @samp{cpsr}.
40212 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
40213 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
40214 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
40217 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
40218 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
40220 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
40221 it should contain at least registers @samp{wR0} through @samp{wR15} and
40222 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
40223 @samp{wCSSF}, and @samp{wCASF} registers are optional.
40225 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
40226 should contain at least registers @samp{d0} through @samp{d15}. If
40227 they are present, @samp{d16} through @samp{d31} should also be included.
40228 @value{GDBN} will synthesize the single-precision registers from
40229 halves of the double-precision registers.
40231 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
40232 need to contain registers; it instructs @value{GDBN} to display the
40233 VFP double-precision registers as vectors and to synthesize the
40234 quad-precision registers from pairs of double-precision registers.
40235 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
40236 be present and include 32 double-precision registers.
40238 @node i386 Features
40239 @subsection i386 Features
40240 @cindex target descriptions, i386 features
40242 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
40243 targets. It should describe the following registers:
40247 @samp{eax} through @samp{edi} plus @samp{eip} for i386
40249 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
40251 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
40252 @samp{fs}, @samp{gs}
40254 @samp{st0} through @samp{st7}
40256 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
40257 @samp{foseg}, @samp{fooff} and @samp{fop}
40260 The register sets may be different, depending on the target.
40262 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
40263 describe registers:
40267 @samp{xmm0} through @samp{xmm7} for i386
40269 @samp{xmm0} through @samp{xmm15} for amd64
40274 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
40275 @samp{org.gnu.gdb.i386.sse} feature. It should
40276 describe the upper 128 bits of @sc{ymm} registers:
40280 @samp{ymm0h} through @samp{ymm7h} for i386
40282 @samp{ymm0h} through @samp{ymm15h} for amd64
40285 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel(R)
40286 Memory Protection Extension (MPX). It should describe the following registers:
40290 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
40292 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
40295 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
40296 describe a single register, @samp{orig_eax}.
40298 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
40299 @samp{org.gnu.gdb.i386.avx} feature. It should
40300 describe additional @sc{xmm} registers:
40304 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
40307 It should describe the upper 128 bits of additional @sc{ymm} registers:
40311 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
40315 describe the upper 256 bits of @sc{zmm} registers:
40319 @samp{zmm0h} through @samp{zmm7h} for i386.
40321 @samp{zmm0h} through @samp{zmm15h} for amd64.
40325 describe the additional @sc{zmm} registers:
40329 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
40332 @node MicroBlaze Features
40333 @subsection MicroBlaze Features
40334 @cindex target descriptions, MicroBlaze features
40336 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
40337 targets. It should contain registers @samp{r0} through @samp{r31},
40338 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
40339 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
40340 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
40342 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
40343 If present, it should contain registers @samp{rshr} and @samp{rslr}
40345 @node MIPS Features
40346 @subsection @acronym{MIPS} Features
40347 @cindex target descriptions, @acronym{MIPS} features
40349 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
40350 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
40351 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
40354 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
40355 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
40356 registers. They may be 32-bit or 64-bit depending on the target.
40358 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
40359 it may be optional in a future version of @value{GDBN}. It should
40360 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
40361 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
40363 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
40364 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
40365 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
40366 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
40368 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
40369 contain a single register, @samp{restart}, which is used by the
40370 Linux kernel to control restartable syscalls.
40372 @node M68K Features
40373 @subsection M68K Features
40374 @cindex target descriptions, M68K features
40377 @item @samp{org.gnu.gdb.m68k.core}
40378 @itemx @samp{org.gnu.gdb.coldfire.core}
40379 @itemx @samp{org.gnu.gdb.fido.core}
40380 One of those features must be always present.
40381 The feature that is present determines which flavor of m68k is
40382 used. The feature that is present should contain registers
40383 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
40384 @samp{sp}, @samp{ps} and @samp{pc}.
40386 @item @samp{org.gnu.gdb.coldfire.fp}
40387 This feature is optional. If present, it should contain registers
40388 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
40392 @node Nios II Features
40393 @subsection Nios II Features
40394 @cindex target descriptions, Nios II features
40396 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
40397 targets. It should contain the 32 core registers (@samp{zero},
40398 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
40399 @samp{pc}, and the 16 control registers (@samp{status} through
40402 @node PowerPC Features
40403 @subsection PowerPC Features
40404 @cindex target descriptions, PowerPC features
40406 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
40407 targets. It should contain registers @samp{r0} through @samp{r31},
40408 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
40409 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
40411 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
40412 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
40414 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
40415 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
40418 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
40419 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
40420 will combine these registers with the floating point registers
40421 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
40422 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
40423 through @samp{vs63}, the set of vector registers for POWER7.
40425 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
40426 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
40427 @samp{spefscr}. SPE targets should provide 32-bit registers in
40428 @samp{org.gnu.gdb.power.core} and provide the upper halves in
40429 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
40430 these to present registers @samp{ev0} through @samp{ev31} to the
40433 @node S/390 and System z Features
40434 @subsection S/390 and System z Features
40435 @cindex target descriptions, S/390 features
40436 @cindex target descriptions, System z features
40438 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
40439 System z targets. It should contain the PSW and the 16 general
40440 registers. In particular, System z targets should provide the 64-bit
40441 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
40442 S/390 targets should provide the 32-bit versions of these registers.
40443 A System z target that runs in 31-bit addressing mode should provide
40444 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
40445 register's upper halves @samp{r0h} through @samp{r15h}, and their
40446 lower halves @samp{r0l} through @samp{r15l}.
40448 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
40449 contain the 64-bit registers @samp{f0} through @samp{f15}, and
40452 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
40453 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
40455 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
40456 contain the register @samp{orig_r2}, which is 64-bit wide on System z
40457 targets and 32-bit otherwise. In addition, the feature may contain
40458 the @samp{last_break} register, whose width depends on the addressing
40459 mode, as well as the @samp{system_call} register, which is always
40462 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
40463 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
40464 @samp{atia}, and @samp{tr0} through @samp{tr15}.
40466 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
40467 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
40468 combined by @value{GDBN} with the floating point registers @samp{f0}
40469 through @samp{f15} to present the 128-bit wide vector registers
40470 @samp{v0} through @samp{v15}. In addition, this feature should
40471 contain the 128-bit wide vector registers @samp{v16} through
40474 @node TIC6x Features
40475 @subsection TMS320C6x Features
40476 @cindex target descriptions, TIC6x features
40477 @cindex target descriptions, TMS320C6x features
40478 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
40479 targets. It should contain registers @samp{A0} through @samp{A15},
40480 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
40482 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
40483 contain registers @samp{A16} through @samp{A31} and @samp{B16}
40484 through @samp{B31}.
40486 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
40487 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
40489 @node Operating System Information
40490 @appendix Operating System Information
40491 @cindex operating system information
40497 Users of @value{GDBN} often wish to obtain information about the state of
40498 the operating system running on the target---for example the list of
40499 processes, or the list of open files. This section describes the
40500 mechanism that makes it possible. This mechanism is similar to the
40501 target features mechanism (@pxref{Target Descriptions}), but focuses
40502 on a different aspect of target.
40504 Operating system information is retrived from the target via the
40505 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
40506 read}). The object name in the request should be @samp{osdata}, and
40507 the @var{annex} identifies the data to be fetched.
40510 @appendixsection Process list
40511 @cindex operating system information, process list
40513 When requesting the process list, the @var{annex} field in the
40514 @samp{qXfer} request should be @samp{processes}. The returned data is
40515 an XML document. The formal syntax of this document is defined in
40516 @file{gdb/features/osdata.dtd}.
40518 An example document is:
40521 <?xml version="1.0"?>
40522 <!DOCTYPE target SYSTEM "osdata.dtd">
40523 <osdata type="processes">
40525 <column name="pid">1</column>
40526 <column name="user">root</column>
40527 <column name="command">/sbin/init</column>
40528 <column name="cores">1,2,3</column>
40533 Each item should include a column whose name is @samp{pid}. The value
40534 of that column should identify the process on the target. The
40535 @samp{user} and @samp{command} columns are optional, and will be
40536 displayed by @value{GDBN}. The @samp{cores} column, if present,
40537 should contain a comma-separated list of cores that this process
40538 is running on. Target may provide additional columns,
40539 which @value{GDBN} currently ignores.
40541 @node Trace File Format
40542 @appendix Trace File Format
40543 @cindex trace file format
40545 The trace file comes in three parts: a header, a textual description
40546 section, and a trace frame section with binary data.
40548 The header has the form @code{\x7fTRACE0\n}. The first byte is
40549 @code{0x7f} so as to indicate that the file contains binary data,
40550 while the @code{0} is a version number that may have different values
40553 The description section consists of multiple lines of @sc{ascii} text
40554 separated by newline characters (@code{0xa}). The lines may include a
40555 variety of optional descriptive or context-setting information, such
40556 as tracepoint definitions or register set size. @value{GDBN} will
40557 ignore any line that it does not recognize. An empty line marks the end
40560 @c FIXME add some specific types of data
40562 The trace frame section consists of a number of consecutive frames.
40563 Each frame begins with a two-byte tracepoint number, followed by a
40564 four-byte size giving the amount of data in the frame. The data in
40565 the frame consists of a number of blocks, each introduced by a
40566 character indicating its type (at least register, memory, and trace
40567 state variable). The data in this section is raw binary, not a
40568 hexadecimal or other encoding; its endianness matches the target's
40571 @c FIXME bi-arch may require endianness/arch info in description section
40574 @item R @var{bytes}
40575 Register block. The number and ordering of bytes matches that of a
40576 @code{g} packet in the remote protocol. Note that these are the
40577 actual bytes, in target order and @value{GDBN} register order, not a
40578 hexadecimal encoding.
40580 @item M @var{address} @var{length} @var{bytes}...
40581 Memory block. This is a contiguous block of memory, at the 8-byte
40582 address @var{address}, with a 2-byte length @var{length}, followed by
40583 @var{length} bytes.
40585 @item V @var{number} @var{value}
40586 Trace state variable block. This records the 8-byte signed value
40587 @var{value} of trace state variable numbered @var{number}.
40591 Future enhancements of the trace file format may include additional types
40594 @node Index Section Format
40595 @appendix @code{.gdb_index} section format
40596 @cindex .gdb_index section format
40597 @cindex index section format
40599 This section documents the index section that is created by @code{save
40600 gdb-index} (@pxref{Index Files}). The index section is
40601 DWARF-specific; some knowledge of DWARF is assumed in this
40604 The mapped index file format is designed to be directly
40605 @code{mmap}able on any architecture. In most cases, a datum is
40606 represented using a little-endian 32-bit integer value, called an
40607 @code{offset_type}. Big endian machines must byte-swap the values
40608 before using them. Exceptions to this rule are noted. The data is
40609 laid out such that alignment is always respected.
40611 A mapped index consists of several areas, laid out in order.
40615 The file header. This is a sequence of values, of @code{offset_type}
40616 unless otherwise noted:
40620 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
40621 Version 4 uses a different hashing function from versions 5 and 6.
40622 Version 6 includes symbols for inlined functions, whereas versions 4
40623 and 5 do not. Version 7 adds attributes to the CU indices in the
40624 symbol table. Version 8 specifies that symbols from DWARF type units
40625 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
40626 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
40628 @value{GDBN} will only read version 4, 5, or 6 indices
40629 by specifying @code{set use-deprecated-index-sections on}.
40630 GDB has a workaround for potentially broken version 7 indices so it is
40631 currently not flagged as deprecated.
40634 The offset, from the start of the file, of the CU list.
40637 The offset, from the start of the file, of the types CU list. Note
40638 that this area can be empty, in which case this offset will be equal
40639 to the next offset.
40642 The offset, from the start of the file, of the address area.
40645 The offset, from the start of the file, of the symbol table.
40648 The offset, from the start of the file, of the constant pool.
40652 The CU list. This is a sequence of pairs of 64-bit little-endian
40653 values, sorted by the CU offset. The first element in each pair is
40654 the offset of a CU in the @code{.debug_info} section. The second
40655 element in each pair is the length of that CU. References to a CU
40656 elsewhere in the map are done using a CU index, which is just the
40657 0-based index into this table. Note that if there are type CUs, then
40658 conceptually CUs and type CUs form a single list for the purposes of
40662 The types CU list. This is a sequence of triplets of 64-bit
40663 little-endian values. In a triplet, the first value is the CU offset,
40664 the second value is the type offset in the CU, and the third value is
40665 the type signature. The types CU list is not sorted.
40668 The address area. The address area consists of a sequence of address
40669 entries. Each address entry has three elements:
40673 The low address. This is a 64-bit little-endian value.
40676 The high address. This is a 64-bit little-endian value. Like
40677 @code{DW_AT_high_pc}, the value is one byte beyond the end.
40680 The CU index. This is an @code{offset_type} value.
40684 The symbol table. This is an open-addressed hash table. The size of
40685 the hash table is always a power of 2.
40687 Each slot in the hash table consists of a pair of @code{offset_type}
40688 values. The first value is the offset of the symbol's name in the
40689 constant pool. The second value is the offset of the CU vector in the
40692 If both values are 0, then this slot in the hash table is empty. This
40693 is ok because while 0 is a valid constant pool index, it cannot be a
40694 valid index for both a string and a CU vector.
40696 The hash value for a table entry is computed by applying an
40697 iterative hash function to the symbol's name. Starting with an
40698 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
40699 the string is incorporated into the hash using the formula depending on the
40704 The formula is @code{r = r * 67 + c - 113}.
40706 @item Versions 5 to 7
40707 The formula is @code{r = r * 67 + tolower (c) - 113}.
40710 The terminating @samp{\0} is not incorporated into the hash.
40712 The step size used in the hash table is computed via
40713 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
40714 value, and @samp{size} is the size of the hash table. The step size
40715 is used to find the next candidate slot when handling a hash
40718 The names of C@t{++} symbols in the hash table are canonicalized. We
40719 don't currently have a simple description of the canonicalization
40720 algorithm; if you intend to create new index sections, you must read
40724 The constant pool. This is simply a bunch of bytes. It is organized
40725 so that alignment is correct: CU vectors are stored first, followed by
40728 A CU vector in the constant pool is a sequence of @code{offset_type}
40729 values. The first value is the number of CU indices in the vector.
40730 Each subsequent value is the index and symbol attributes of a CU in
40731 the CU list. This element in the hash table is used to indicate which
40732 CUs define the symbol and how the symbol is used.
40733 See below for the format of each CU index+attributes entry.
40735 A string in the constant pool is zero-terminated.
40738 Attributes were added to CU index values in @code{.gdb_index} version 7.
40739 If a symbol has multiple uses within a CU then there is one
40740 CU index+attributes value for each use.
40742 The format of each CU index+attributes entry is as follows
40748 This is the index of the CU in the CU list.
40750 These bits are reserved for future purposes and must be zero.
40752 The kind of the symbol in the CU.
40756 This value is reserved and should not be used.
40757 By reserving zero the full @code{offset_type} value is backwards compatible
40758 with previous versions of the index.
40760 The symbol is a type.
40762 The symbol is a variable or an enum value.
40764 The symbol is a function.
40766 Any other kind of symbol.
40768 These values are reserved.
40772 This bit is zero if the value is global and one if it is static.
40774 The determination of whether a symbol is global or static is complicated.
40775 The authorative reference is the file @file{dwarf2read.c} in
40776 @value{GDBN} sources.
40780 This pseudo-code describes the computation of a symbol's kind and
40781 global/static attributes in the index.
40784 is_external = get_attribute (die, DW_AT_external);
40785 language = get_attribute (cu_die, DW_AT_language);
40788 case DW_TAG_typedef:
40789 case DW_TAG_base_type:
40790 case DW_TAG_subrange_type:
40794 case DW_TAG_enumerator:
40796 is_static = (language != CPLUS && language != JAVA);
40798 case DW_TAG_subprogram:
40800 is_static = ! (is_external || language == ADA);
40802 case DW_TAG_constant:
40804 is_static = ! is_external;
40806 case DW_TAG_variable:
40808 is_static = ! is_external;
40810 case DW_TAG_namespace:
40814 case DW_TAG_class_type:
40815 case DW_TAG_interface_type:
40816 case DW_TAG_structure_type:
40817 case DW_TAG_union_type:
40818 case DW_TAG_enumeration_type:
40820 is_static = (language != CPLUS && language != JAVA);
40828 @appendix Manual pages
40832 * gdb man:: The GNU Debugger man page
40833 * gdbserver man:: Remote Server for the GNU Debugger man page
40834 * gcore man:: Generate a core file of a running program
40835 * gdbinit man:: gdbinit scripts
40841 @c man title gdb The GNU Debugger
40843 @c man begin SYNOPSIS gdb
40844 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
40845 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
40846 [@option{-b}@w{ }@var{bps}]
40847 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
40848 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
40849 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
40850 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
40851 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
40854 @c man begin DESCRIPTION gdb
40855 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
40856 going on ``inside'' another program while it executes -- or what another
40857 program was doing at the moment it crashed.
40859 @value{GDBN} can do four main kinds of things (plus other things in support of
40860 these) to help you catch bugs in the act:
40864 Start your program, specifying anything that might affect its behavior.
40867 Make your program stop on specified conditions.
40870 Examine what has happened, when your program has stopped.
40873 Change things in your program, so you can experiment with correcting the
40874 effects of one bug and go on to learn about another.
40877 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
40880 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
40881 commands from the terminal until you tell it to exit with the @value{GDBN}
40882 command @code{quit}. You can get online help from @value{GDBN} itself
40883 by using the command @code{help}.
40885 You can run @code{gdb} with no arguments or options; but the most
40886 usual way to start @value{GDBN} is with one argument or two, specifying an
40887 executable program as the argument:
40893 You can also start with both an executable program and a core file specified:
40899 You can, instead, specify a process ID as a second argument, if you want
40900 to debug a running process:
40908 would attach @value{GDBN} to process @code{1234} (unless you also have a file
40909 named @file{1234}; @value{GDBN} does check for a core file first).
40910 With option @option{-p} you can omit the @var{program} filename.
40912 Here are some of the most frequently needed @value{GDBN} commands:
40914 @c pod2man highlights the right hand side of the @item lines.
40916 @item break [@var{file}:]@var{functiop}
40917 Set a breakpoint at @var{function} (in @var{file}).
40919 @item run [@var{arglist}]
40920 Start your program (with @var{arglist}, if specified).
40923 Backtrace: display the program stack.
40925 @item print @var{expr}
40926 Display the value of an expression.
40929 Continue running your program (after stopping, e.g. at a breakpoint).
40932 Execute next program line (after stopping); step @emph{over} any
40933 function calls in the line.
40935 @item edit [@var{file}:]@var{function}
40936 look at the program line where it is presently stopped.
40938 @item list [@var{file}:]@var{function}
40939 type the text of the program in the vicinity of where it is presently stopped.
40942 Execute next program line (after stopping); step @emph{into} any
40943 function calls in the line.
40945 @item help [@var{name}]
40946 Show information about @value{GDBN} command @var{name}, or general information
40947 about using @value{GDBN}.
40950 Exit from @value{GDBN}.
40954 For full details on @value{GDBN},
40955 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40956 by Richard M. Stallman and Roland H. Pesch. The same text is available online
40957 as the @code{gdb} entry in the @code{info} program.
40961 @c man begin OPTIONS gdb
40962 Any arguments other than options specify an executable
40963 file and core file (or process ID); that is, the first argument
40964 encountered with no
40965 associated option flag is equivalent to a @option{-se} option, and the second,
40966 if any, is equivalent to a @option{-c} option if it's the name of a file.
40968 both long and short forms; both are shown here. The long forms are also
40969 recognized if you truncate them, so long as enough of the option is
40970 present to be unambiguous. (If you prefer, you can flag option
40971 arguments with @option{+} rather than @option{-}, though we illustrate the
40972 more usual convention.)
40974 All the options and command line arguments you give are processed
40975 in sequential order. The order makes a difference when the @option{-x}
40981 List all options, with brief explanations.
40983 @item -symbols=@var{file}
40984 @itemx -s @var{file}
40985 Read symbol table from file @var{file}.
40988 Enable writing into executable and core files.
40990 @item -exec=@var{file}
40991 @itemx -e @var{file}
40992 Use file @var{file} as the executable file to execute when
40993 appropriate, and for examining pure data in conjunction with a core
40996 @item -se=@var{file}
40997 Read symbol table from file @var{file} and use it as the executable
41000 @item -core=@var{file}
41001 @itemx -c @var{file}
41002 Use file @var{file} as a core dump to examine.
41004 @item -command=@var{file}
41005 @itemx -x @var{file}
41006 Execute @value{GDBN} commands from file @var{file}.
41008 @item -ex @var{command}
41009 Execute given @value{GDBN} @var{command}.
41011 @item -directory=@var{directory}
41012 @itemx -d @var{directory}
41013 Add @var{directory} to the path to search for source files.
41016 Do not execute commands from @file{~/.gdbinit}.
41020 Do not execute commands from any @file{.gdbinit} initialization files.
41024 ``Quiet''. Do not print the introductory and copyright messages. These
41025 messages are also suppressed in batch mode.
41028 Run in batch mode. Exit with status @code{0} after processing all the command
41029 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
41030 Exit with nonzero status if an error occurs in executing the @value{GDBN}
41031 commands in the command files.
41033 Batch mode may be useful for running @value{GDBN} as a filter, for example to
41034 download and run a program on another computer; in order to make this
41035 more useful, the message
41038 Program exited normally.
41042 (which is ordinarily issued whenever a program running under @value{GDBN} control
41043 terminates) is not issued when running in batch mode.
41045 @item -cd=@var{directory}
41046 Run @value{GDBN} using @var{directory} as its working directory,
41047 instead of the current directory.
41051 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
41052 @value{GDBN} to output the full file name and line number in a standard,
41053 recognizable fashion each time a stack frame is displayed (which
41054 includes each time the program stops). This recognizable format looks
41055 like two @samp{\032} characters, followed by the file name, line number
41056 and character position separated by colons, and a newline. The
41057 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
41058 characters as a signal to display the source code for the frame.
41061 Set the line speed (baud rate or bits per second) of any serial
41062 interface used by @value{GDBN} for remote debugging.
41064 @item -tty=@var{device}
41065 Run using @var{device} for your program's standard input and output.
41069 @c man begin SEEALSO gdb
41071 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41072 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41073 documentation are properly installed at your site, the command
41080 should give you access to the complete manual.
41082 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41083 Richard M. Stallman and Roland H. Pesch, July 1991.
41087 @node gdbserver man
41088 @heading gdbserver man
41090 @c man title gdbserver Remote Server for the GNU Debugger
41092 @c man begin SYNOPSIS gdbserver
41093 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
41095 gdbserver --attach @var{comm} @var{pid}
41097 gdbserver --multi @var{comm}
41101 @c man begin DESCRIPTION gdbserver
41102 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
41103 than the one which is running the program being debugged.
41106 @subheading Usage (server (target) side)
41109 Usage (server (target) side):
41112 First, you need to have a copy of the program you want to debug put onto
41113 the target system. The program can be stripped to save space if needed, as
41114 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
41115 the @value{GDBN} running on the host system.
41117 To use the server, you log on to the target system, and run the @command{gdbserver}
41118 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
41119 your program, and (c) its arguments. The general syntax is:
41122 target> gdbserver @var{comm} @var{program} [@var{args} ...]
41125 For example, using a serial port, you might say:
41129 @c @file would wrap it as F</dev/com1>.
41130 target> gdbserver /dev/com1 emacs foo.txt
41133 target> gdbserver @file{/dev/com1} emacs foo.txt
41137 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
41138 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
41139 waits patiently for the host @value{GDBN} to communicate with it.
41141 To use a TCP connection, you could say:
41144 target> gdbserver host:2345 emacs foo.txt
41147 This says pretty much the same thing as the last example, except that we are
41148 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
41149 that we are expecting to see a TCP connection from @code{host} to local TCP port
41150 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
41151 want for the port number as long as it does not conflict with any existing TCP
41152 ports on the target system. This same port number must be used in the host
41153 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
41154 you chose a port number that conflicts with another service, @command{gdbserver} will
41155 print an error message and exit.
41157 @command{gdbserver} can also attach to running programs.
41158 This is accomplished via the @option{--attach} argument. The syntax is:
41161 target> gdbserver --attach @var{comm} @var{pid}
41164 @var{pid} is the process ID of a currently running process. It isn't
41165 necessary to point @command{gdbserver} at a binary for the running process.
41167 To start @code{gdbserver} without supplying an initial command to run
41168 or process ID to attach, use the @option{--multi} command line option.
41169 In such case you should connect using @kbd{target extended-remote} to start
41170 the program you want to debug.
41173 target> gdbserver --multi @var{comm}
41177 @subheading Usage (host side)
41183 You need an unstripped copy of the target program on your host system, since
41184 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
41185 would, with the target program as the first argument. (You may need to use the
41186 @option{--baud} option if the serial line is running at anything except 9600 baud.)
41187 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
41188 new command you need to know about is @code{target remote}
41189 (or @code{target extended-remote}). Its argument is either
41190 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
41191 descriptor. For example:
41195 @c @file would wrap it as F</dev/ttyb>.
41196 (gdb) target remote /dev/ttyb
41199 (gdb) target remote @file{/dev/ttyb}
41204 communicates with the server via serial line @file{/dev/ttyb}, and:
41207 (gdb) target remote the-target:2345
41211 communicates via a TCP connection to port 2345 on host `the-target', where
41212 you previously started up @command{gdbserver} with the same port number. Note that for
41213 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
41214 command, otherwise you may get an error that looks something like
41215 `Connection refused'.
41217 @command{gdbserver} can also debug multiple inferiors at once,
41220 the @value{GDBN} manual in node @code{Inferiors and Programs}
41221 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
41224 @ref{Inferiors and Programs}.
41226 In such case use the @code{extended-remote} @value{GDBN} command variant:
41229 (gdb) target extended-remote the-target:2345
41232 The @command{gdbserver} option @option{--multi} may or may not be used in such
41236 @c man begin OPTIONS gdbserver
41237 There are three different modes for invoking @command{gdbserver}:
41242 Debug a specific program specified by its program name:
41245 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
41248 The @var{comm} parameter specifies how should the server communicate
41249 with @value{GDBN}; it is either a device name (to use a serial line),
41250 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
41251 stdin/stdout of @code{gdbserver}. Specify the name of the program to
41252 debug in @var{prog}. Any remaining arguments will be passed to the
41253 program verbatim. When the program exits, @value{GDBN} will close the
41254 connection, and @code{gdbserver} will exit.
41257 Debug a specific program by specifying the process ID of a running
41261 gdbserver --attach @var{comm} @var{pid}
41264 The @var{comm} parameter is as described above. Supply the process ID
41265 of a running program in @var{pid}; @value{GDBN} will do everything
41266 else. Like with the previous mode, when the process @var{pid} exits,
41267 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
41270 Multi-process mode -- debug more than one program/process:
41273 gdbserver --multi @var{comm}
41276 In this mode, @value{GDBN} can instruct @command{gdbserver} which
41277 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
41278 close the connection when a process being debugged exits, so you can
41279 debug several processes in the same session.
41282 In each of the modes you may specify these options:
41287 List all options, with brief explanations.
41290 This option causes @command{gdbserver} to print its version number and exit.
41293 @command{gdbserver} will attach to a running program. The syntax is:
41296 target> gdbserver --attach @var{comm} @var{pid}
41299 @var{pid} is the process ID of a currently running process. It isn't
41300 necessary to point @command{gdbserver} at a binary for the running process.
41303 To start @code{gdbserver} without supplying an initial command to run
41304 or process ID to attach, use this command line option.
41305 Then you can connect using @kbd{target extended-remote} and start
41306 the program you want to debug. The syntax is:
41309 target> gdbserver --multi @var{comm}
41313 Instruct @code{gdbserver} to display extra status information about the debugging
41315 This option is intended for @code{gdbserver} development and for bug reports to
41318 @item --remote-debug
41319 Instruct @code{gdbserver} to display remote protocol debug output.
41320 This option is intended for @code{gdbserver} development and for bug reports to
41323 @item --debug-format=option1@r{[},option2,...@r{]}
41324 Instruct @code{gdbserver} to include extra information in each line
41325 of debugging output.
41326 @xref{Other Command-Line Arguments for gdbserver}.
41329 Specify a wrapper to launch programs
41330 for debugging. The option should be followed by the name of the
41331 wrapper, then any command-line arguments to pass to the wrapper, then
41332 @kbd{--} indicating the end of the wrapper arguments.
41335 By default, @command{gdbserver} keeps the listening TCP port open, so that
41336 additional connections are possible. However, if you start @code{gdbserver}
41337 with the @option{--once} option, it will stop listening for any further
41338 connection attempts after connecting to the first @value{GDBN} session.
41340 @c --disable-packet is not documented for users.
41342 @c --disable-randomization and --no-disable-randomization are superseded by
41343 @c QDisableRandomization.
41348 @c man begin SEEALSO gdbserver
41350 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41351 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41352 documentation are properly installed at your site, the command
41358 should give you access to the complete manual.
41360 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41361 Richard M. Stallman and Roland H. Pesch, July 1991.
41368 @c man title gcore Generate a core file of a running program
41371 @c man begin SYNOPSIS gcore
41372 gcore [-o @var{filename}] @var{pid}
41376 @c man begin DESCRIPTION gcore
41377 Generate a core dump of a running program with process ID @var{pid}.
41378 Produced file is equivalent to a kernel produced core file as if the process
41379 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
41380 limit). Unlike after a crash, after @command{gcore} the program remains
41381 running without any change.
41384 @c man begin OPTIONS gcore
41386 @item -o @var{filename}
41387 The optional argument
41388 @var{filename} specifies the file name where to put the core dump.
41389 If not specified, the file name defaults to @file{core.@var{pid}},
41390 where @var{pid} is the running program process ID.
41394 @c man begin SEEALSO gcore
41396 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41397 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41398 documentation are properly installed at your site, the command
41405 should give you access to the complete manual.
41407 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41408 Richard M. Stallman and Roland H. Pesch, July 1991.
41415 @c man title gdbinit GDB initialization scripts
41418 @c man begin SYNOPSIS gdbinit
41419 @ifset SYSTEM_GDBINIT
41420 @value{SYSTEM_GDBINIT}
41429 @c man begin DESCRIPTION gdbinit
41430 These files contain @value{GDBN} commands to automatically execute during
41431 @value{GDBN} startup. The lines of contents are canned sequences of commands,
41434 the @value{GDBN} manual in node @code{Sequences}
41435 -- shell command @code{info -f gdb -n Sequences}.
41441 Please read more in
41443 the @value{GDBN} manual in node @code{Startup}
41444 -- shell command @code{info -f gdb -n Startup}.
41451 @ifset SYSTEM_GDBINIT
41452 @item @value{SYSTEM_GDBINIT}
41454 @ifclear SYSTEM_GDBINIT
41455 @item (not enabled with @code{--with-system-gdbinit} during compilation)
41457 System-wide initialization file. It is executed unless user specified
41458 @value{GDBN} option @code{-nx} or @code{-n}.
41461 the @value{GDBN} manual in node @code{System-wide configuration}
41462 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
41465 @ref{System-wide configuration}.
41469 User initialization file. It is executed unless user specified
41470 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
41473 Initialization file for current directory. It may need to be enabled with
41474 @value{GDBN} security command @code{set auto-load local-gdbinit}.
41477 the @value{GDBN} manual in node @code{Init File in the Current Directory}
41478 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
41481 @ref{Init File in the Current Directory}.
41486 @c man begin SEEALSO gdbinit
41488 gdb(1), @code{info -f gdb -n Startup}
41490 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41491 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41492 documentation are properly installed at your site, the command
41498 should give you access to the complete manual.
41500 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41501 Richard M. Stallman and Roland H. Pesch, July 1991.
41507 @node GNU Free Documentation License
41508 @appendix GNU Free Documentation License
41511 @node Concept Index
41512 @unnumbered Concept Index
41516 @node Command and Variable Index
41517 @unnumbered Command, Variable, and Function Index
41522 % I think something like @@colophon should be in texinfo. In the
41524 \long\def\colophon{\hbox to0pt{}\vfill
41525 \centerline{The body of this manual is set in}
41526 \centerline{\fontname\tenrm,}
41527 \centerline{with headings in {\bf\fontname\tenbf}}
41528 \centerline{and examples in {\tt\fontname\tentt}.}
41529 \centerline{{\it\fontname\tenit\/},}
41530 \centerline{{\bf\fontname\tenbf}, and}
41531 \centerline{{\sl\fontname\tensl\/}}
41532 \centerline{are used for emphasis.}\vfill}
41534 % Blame: doc@@cygnus.com, 1991.