1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2014 Free Software Foundation, Inc.
5 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
6 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
23 @c To avoid file-name clashes between index.html and Index.html, when
24 @c the manual is produced on a Posix host and then moved to a
25 @c case-insensitive filesystem (e.g., MS-Windows), we separate the
26 @c indices into two: Concept Index and all the rest.
30 @c readline appendices use @vindex, @findex and @ftable,
31 @c annotate.texi and gdbmi use @findex.
34 @c !!set GDB manual's edition---not the same as GDB version!
35 @c This is updated by GNU Press.
38 @c !!set GDB edit command default editor
41 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
43 @c This is a dir.info fragment to support semi-automated addition of
44 @c manuals to an info tree.
45 @dircategory Software development
47 * Gdb: (gdb). The GNU debugger.
48 * gdbserver: (gdb) Server. The GNU debugging server.
52 @c man begin COPYRIGHT
53 Copyright @copyright{} 1988-2014 Free Software Foundation, Inc.
55 Permission is granted to copy, distribute and/or modify this document
56 under the terms of the GNU Free Documentation License, Version 1.3 or
57 any later version published by the Free Software Foundation; with the
58 Invariant Sections being ``Free Software'' and ``Free Software Needs
59 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
60 and with the Back-Cover Texts as in (a) below.
62 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
63 this GNU Manual. Buying copies from GNU Press supports the FSF in
64 developing GNU and promoting software freedom.''
69 This file documents the @sc{gnu} debugger @value{GDBN}.
71 This is the @value{EDITION} Edition, of @cite{Debugging with
72 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
73 @ifset VERSION_PACKAGE
74 @value{VERSION_PACKAGE}
76 Version @value{GDBVN}.
82 @title Debugging with @value{GDBN}
83 @subtitle The @sc{gnu} Source-Level Debugger
85 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
86 @ifset VERSION_PACKAGE
88 @subtitle @value{VERSION_PACKAGE}
90 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
94 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
95 \hfill {\it Debugging with @value{GDBN}}\par
96 \hfill \TeX{}info \texinfoversion\par
100 @vskip 0pt plus 1filll
101 Published by the Free Software Foundation @*
102 51 Franklin Street, Fifth Floor,
103 Boston, MA 02110-1301, USA@*
104 ISBN 978-0-9831592-3-0 @*
111 @node Top, Summary, (dir), (dir)
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN}
118 @ifset VERSION_PACKAGE
119 @value{VERSION_PACKAGE}
121 Version @value{GDBVN}.
123 Copyright (C) 1988-2014 Free Software Foundation, Inc.
125 This edition of the GDB manual is dedicated to the memory of Fred
126 Fish. Fred was a long-standing contributor to GDB and to Free
127 software in general. We will miss him.
130 * Summary:: Summary of @value{GDBN}
131 * Sample Session:: A sample @value{GDBN} session
133 * Invocation:: Getting in and out of @value{GDBN}
134 * Commands:: @value{GDBN} commands
135 * Running:: Running programs under @value{GDBN}
136 * Stopping:: Stopping and continuing
137 * Reverse Execution:: Running programs backward
138 * Process Record and Replay:: Recording inferior's execution and replaying it
139 * Stack:: Examining the stack
140 * Source:: Examining source files
141 * Data:: Examining data
142 * Optimized Code:: Debugging optimized code
143 * Macros:: Preprocessor Macros
144 * Tracepoints:: Debugging remote targets non-intrusively
145 * Overlays:: Debugging programs that use overlays
147 * Languages:: Using @value{GDBN} with different languages
149 * Symbols:: Examining the symbol table
150 * Altering:: Altering execution
151 * GDB Files:: @value{GDBN} files
152 * Targets:: Specifying a debugging target
153 * Remote Debugging:: Debugging remote programs
154 * Configurations:: Configuration-specific information
155 * Controlling GDB:: Controlling @value{GDBN}
156 * Extending GDB:: Extending @value{GDBN}
157 * Interpreters:: Command Interpreters
158 * TUI:: @value{GDBN} Text User Interface
159 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
160 * GDB/MI:: @value{GDBN}'s Machine Interface.
161 * Annotations:: @value{GDBN}'s annotation interface.
162 * JIT Interface:: Using the JIT debugging interface.
163 * In-Process Agent:: In-Process Agent
165 * GDB Bugs:: Reporting bugs in @value{GDBN}
167 @ifset SYSTEM_READLINE
168 * Command Line Editing: (rluserman). Command Line Editing
169 * Using History Interactively: (history). Using History Interactively
171 @ifclear SYSTEM_READLINE
172 * Command Line Editing:: Command Line Editing
173 * Using History Interactively:: Using History Interactively
175 * In Memoriam:: In Memoriam
176 * Formatting Documentation:: How to format and print @value{GDBN} documentation
177 * Installing GDB:: Installing GDB
178 * Maintenance Commands:: Maintenance Commands
179 * Remote Protocol:: GDB Remote Serial Protocol
180 * Agent Expressions:: The GDB Agent Expression Mechanism
181 * Target Descriptions:: How targets can describe themselves to
183 * Operating System Information:: Getting additional information from
185 * Trace File Format:: GDB trace file format
186 * Index Section Format:: .gdb_index section format
187 * Man Pages:: Manual pages
188 * Copying:: GNU General Public License says
189 how you can copy and share GDB
190 * GNU Free Documentation License:: The license for this documentation
191 * Concept Index:: Index of @value{GDBN} concepts
192 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
193 functions, and Python data types
201 @unnumbered Summary of @value{GDBN}
203 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
204 going on ``inside'' another program while it executes---or what another
205 program was doing at the moment it crashed.
207 @value{GDBN} can do four main kinds of things (plus other things in support of
208 these) to help you catch bugs in the act:
212 Start your program, specifying anything that might affect its behavior.
215 Make your program stop on specified conditions.
218 Examine what has happened, when your program has stopped.
221 Change things in your program, so you can experiment with correcting the
222 effects of one bug and go on to learn about another.
225 You can use @value{GDBN} to debug programs written in C and C@t{++}.
226 For more information, see @ref{Supported Languages,,Supported Languages}.
227 For more information, see @ref{C,,C and C++}.
229 Support for D is partial. For information on D, see
233 Support for Modula-2 is partial. For information on Modula-2, see
234 @ref{Modula-2,,Modula-2}.
236 Support for OpenCL C is partial. For information on OpenCL C, see
237 @ref{OpenCL C,,OpenCL C}.
240 Debugging Pascal programs which use sets, subranges, file variables, or
241 nested functions does not currently work. @value{GDBN} does not support
242 entering expressions, printing values, or similar features using Pascal
246 @value{GDBN} can be used to debug programs written in Fortran, although
247 it may be necessary to refer to some variables with a trailing
250 @value{GDBN} can be used to debug programs written in Objective-C,
251 using either the Apple/NeXT or the GNU Objective-C runtime.
254 * Free Software:: Freely redistributable software
255 * Free Documentation:: Free Software Needs Free Documentation
256 * Contributors:: Contributors to GDB
260 @unnumberedsec Free Software
262 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
263 General Public License
264 (GPL). The GPL gives you the freedom to copy or adapt a licensed
265 program---but every person getting a copy also gets with it the
266 freedom to modify that copy (which means that they must get access to
267 the source code), and the freedom to distribute further copies.
268 Typical software companies use copyrights to limit your freedoms; the
269 Free Software Foundation uses the GPL to preserve these freedoms.
271 Fundamentally, the General Public License is a license which says that
272 you have these freedoms and that you cannot take these freedoms away
275 @node Free Documentation
276 @unnumberedsec Free Software Needs Free Documentation
278 The biggest deficiency in the free software community today is not in
279 the software---it is the lack of good free documentation that we can
280 include with the free software. Many of our most important
281 programs do not come with free reference manuals and free introductory
282 texts. Documentation is an essential part of any software package;
283 when an important free software package does not come with a free
284 manual and a free tutorial, that is a major gap. We have many such
287 Consider Perl, for instance. The tutorial manuals that people
288 normally use are non-free. How did this come about? Because the
289 authors of those manuals published them with restrictive terms---no
290 copying, no modification, source files not available---which exclude
291 them from the free software world.
293 That wasn't the first time this sort of thing happened, and it was far
294 from the last. Many times we have heard a GNU user eagerly describe a
295 manual that he is writing, his intended contribution to the community,
296 only to learn that he had ruined everything by signing a publication
297 contract to make it non-free.
299 Free documentation, like free software, is a matter of freedom, not
300 price. The problem with the non-free manual is not that publishers
301 charge a price for printed copies---that in itself is fine. (The Free
302 Software Foundation sells printed copies of manuals, too.) The
303 problem is the restrictions on the use of the manual. Free manuals
304 are available in source code form, and give you permission to copy and
305 modify. Non-free manuals do not allow this.
307 The criteria of freedom for a free manual are roughly the same as for
308 free software. Redistribution (including the normal kinds of
309 commercial redistribution) must be permitted, so that the manual can
310 accompany every copy of the program, both on-line and on paper.
312 Permission for modification of the technical content is crucial too.
313 When people modify the software, adding or changing features, if they
314 are conscientious they will change the manual too---so they can
315 provide accurate and clear documentation for the modified program. A
316 manual that leaves you no choice but to write a new manual to document
317 a changed version of the program is not really available to our
320 Some kinds of limits on the way modification is handled are
321 acceptable. For example, requirements to preserve the original
322 author's copyright notice, the distribution terms, or the list of
323 authors, are ok. It is also no problem to require modified versions
324 to include notice that they were modified. Even entire sections that
325 may not be deleted or changed are acceptable, as long as they deal
326 with nontechnical topics (like this one). These kinds of restrictions
327 are acceptable because they don't obstruct the community's normal use
330 However, it must be possible to modify all the @emph{technical}
331 content of the manual, and then distribute the result in all the usual
332 media, through all the usual channels. Otherwise, the restrictions
333 obstruct the use of the manual, it is not free, and we need another
334 manual to replace it.
336 Please spread the word about this issue. Our community continues to
337 lose manuals to proprietary publishing. If we spread the word that
338 free software needs free reference manuals and free tutorials, perhaps
339 the next person who wants to contribute by writing documentation will
340 realize, before it is too late, that only free manuals contribute to
341 the free software community.
343 If you are writing documentation, please insist on publishing it under
344 the GNU Free Documentation License or another free documentation
345 license. Remember that this decision requires your approval---you
346 don't have to let the publisher decide. Some commercial publishers
347 will use a free license if you insist, but they will not propose the
348 option; it is up to you to raise the issue and say firmly that this is
349 what you want. If the publisher you are dealing with refuses, please
350 try other publishers. If you're not sure whether a proposed license
351 is free, write to @email{licensing@@gnu.org}.
353 You can encourage commercial publishers to sell more free, copylefted
354 manuals and tutorials by buying them, and particularly by buying
355 copies from the publishers that paid for their writing or for major
356 improvements. Meanwhile, try to avoid buying non-free documentation
357 at all. Check the distribution terms of a manual before you buy it,
358 and insist that whoever seeks your business must respect your freedom.
359 Check the history of the book, and try to reward the publishers that
360 have paid or pay the authors to work on it.
362 The Free Software Foundation maintains a list of free documentation
363 published by other publishers, at
364 @url{http://www.fsf.org/doc/other-free-books.html}.
367 @unnumberedsec Contributors to @value{GDBN}
369 Richard Stallman was the original author of @value{GDBN}, and of many
370 other @sc{gnu} programs. Many others have contributed to its
371 development. This section attempts to credit major contributors. One
372 of the virtues of free software is that everyone is free to contribute
373 to it; with regret, we cannot actually acknowledge everyone here. The
374 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
375 blow-by-blow account.
377 Changes much prior to version 2.0 are lost in the mists of time.
380 @emph{Plea:} Additions to this section are particularly welcome. If you
381 or your friends (or enemies, to be evenhanded) have been unfairly
382 omitted from this list, we would like to add your names!
385 So that they may not regard their many labors as thankless, we
386 particularly thank those who shepherded @value{GDBN} through major
388 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
389 Jim Blandy (release 4.18);
390 Jason Molenda (release 4.17);
391 Stan Shebs (release 4.14);
392 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
393 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
394 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
395 Jim Kingdon (releases 3.5, 3.4, and 3.3);
396 and Randy Smith (releases 3.2, 3.1, and 3.0).
398 Richard Stallman, assisted at various times by Peter TerMaat, Chris
399 Hanson, and Richard Mlynarik, handled releases through 2.8.
401 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
402 in @value{GDBN}, with significant additional contributions from Per
403 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
404 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
405 much general update work leading to release 3.0).
407 @value{GDBN} uses the BFD subroutine library to examine multiple
408 object-file formats; BFD was a joint project of David V.
409 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
411 David Johnson wrote the original COFF support; Pace Willison did
412 the original support for encapsulated COFF.
414 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
416 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
417 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
419 Jean-Daniel Fekete contributed Sun 386i support.
420 Chris Hanson improved the HP9000 support.
421 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
422 David Johnson contributed Encore Umax support.
423 Jyrki Kuoppala contributed Altos 3068 support.
424 Jeff Law contributed HP PA and SOM support.
425 Keith Packard contributed NS32K support.
426 Doug Rabson contributed Acorn Risc Machine support.
427 Bob Rusk contributed Harris Nighthawk CX-UX support.
428 Chris Smith contributed Convex support (and Fortran debugging).
429 Jonathan Stone contributed Pyramid support.
430 Michael Tiemann contributed SPARC support.
431 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
432 Pace Willison contributed Intel 386 support.
433 Jay Vosburgh contributed Symmetry support.
434 Marko Mlinar contributed OpenRISC 1000 support.
436 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
438 Rich Schaefer and Peter Schauer helped with support of SunOS shared
441 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
442 about several machine instruction sets.
444 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
445 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
446 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
447 and RDI targets, respectively.
449 Brian Fox is the author of the readline libraries providing
450 command-line editing and command history.
452 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
453 Modula-2 support, and contributed the Languages chapter of this manual.
455 Fred Fish wrote most of the support for Unix System Vr4.
456 He also enhanced the command-completion support to cover C@t{++} overloaded
459 Hitachi America (now Renesas America), Ltd. sponsored the support for
460 H8/300, H8/500, and Super-H processors.
462 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
464 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
467 Toshiba sponsored the support for the TX39 Mips processor.
469 Matsushita sponsored the support for the MN10200 and MN10300 processors.
471 Fujitsu sponsored the support for SPARClite and FR30 processors.
473 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
476 Michael Snyder added support for tracepoints.
478 Stu Grossman wrote gdbserver.
480 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
481 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
483 The following people at the Hewlett-Packard Company contributed
484 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
485 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
486 compiler, and the Text User Interface (nee Terminal User Interface):
487 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
488 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
489 provided HP-specific information in this manual.
491 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
492 Robert Hoehne made significant contributions to the DJGPP port.
494 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
495 development since 1991. Cygnus engineers who have worked on @value{GDBN}
496 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
497 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
498 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
499 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
500 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
501 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
502 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
503 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
504 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
505 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
506 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
507 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
508 Zuhn have made contributions both large and small.
510 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
511 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
513 Jim Blandy added support for preprocessor macros, while working for Red
516 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
517 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
518 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
519 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
520 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
521 with the migration of old architectures to this new framework.
523 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
524 unwinder framework, this consisting of a fresh new design featuring
525 frame IDs, independent frame sniffers, and the sentinel frame. Mark
526 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
527 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
528 trad unwinders. The architecture-specific changes, each involving a
529 complete rewrite of the architecture's frame code, were carried out by
530 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
531 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
532 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
533 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
536 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
537 Tensilica, Inc.@: contributed support for Xtensa processors. Others
538 who have worked on the Xtensa port of @value{GDBN} in the past include
539 Steve Tjiang, John Newlin, and Scott Foehner.
541 Michael Eager and staff of Xilinx, Inc., contributed support for the
542 Xilinx MicroBlaze architecture.
545 @chapter A Sample @value{GDBN} Session
547 You can use this manual at your leisure to read all about @value{GDBN}.
548 However, a handful of commands are enough to get started using the
549 debugger. This chapter illustrates those commands.
552 In this sample session, we emphasize user input like this: @b{input},
553 to make it easier to pick out from the surrounding output.
556 @c FIXME: this example may not be appropriate for some configs, where
557 @c FIXME...primary interest is in remote use.
559 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
560 processor) exhibits the following bug: sometimes, when we change its
561 quote strings from the default, the commands used to capture one macro
562 definition within another stop working. In the following short @code{m4}
563 session, we define a macro @code{foo} which expands to @code{0000}; we
564 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
565 same thing. However, when we change the open quote string to
566 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
567 procedure fails to define a new synonym @code{baz}:
576 @b{define(bar,defn(`foo'))}
580 @b{changequote(<QUOTE>,<UNQUOTE>)}
582 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
585 m4: End of input: 0: fatal error: EOF in string
589 Let us use @value{GDBN} to try to see what is going on.
592 $ @b{@value{GDBP} m4}
593 @c FIXME: this falsifies the exact text played out, to permit smallbook
594 @c FIXME... format to come out better.
595 @value{GDBN} is free software and you are welcome to distribute copies
596 of it under certain conditions; type "show copying" to see
598 There is absolutely no warranty for @value{GDBN}; type "show warranty"
601 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
606 @value{GDBN} reads only enough symbol data to know where to find the
607 rest when needed; as a result, the first prompt comes up very quickly.
608 We now tell @value{GDBN} to use a narrower display width than usual, so
609 that examples fit in this manual.
612 (@value{GDBP}) @b{set width 70}
616 We need to see how the @code{m4} built-in @code{changequote} works.
617 Having looked at the source, we know the relevant subroutine is
618 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
619 @code{break} command.
622 (@value{GDBP}) @b{break m4_changequote}
623 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
627 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
628 control; as long as control does not reach the @code{m4_changequote}
629 subroutine, the program runs as usual:
632 (@value{GDBP}) @b{run}
633 Starting program: /work/Editorial/gdb/gnu/m4/m4
641 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
642 suspends execution of @code{m4}, displaying information about the
643 context where it stops.
646 @b{changequote(<QUOTE>,<UNQUOTE>)}
648 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
650 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
654 Now we use the command @code{n} (@code{next}) to advance execution to
655 the next line of the current function.
659 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
664 @code{set_quotes} looks like a promising subroutine. We can go into it
665 by using the command @code{s} (@code{step}) instead of @code{next}.
666 @code{step} goes to the next line to be executed in @emph{any}
667 subroutine, so it steps into @code{set_quotes}.
671 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
673 530 if (lquote != def_lquote)
677 The display that shows the subroutine where @code{m4} is now
678 suspended (and its arguments) is called a stack frame display. It
679 shows a summary of the stack. We can use the @code{backtrace}
680 command (which can also be spelled @code{bt}), to see where we are
681 in the stack as a whole: the @code{backtrace} command displays a
682 stack frame for each active subroutine.
685 (@value{GDBP}) @b{bt}
686 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
688 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
690 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
691 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
693 #4 0x79dc in expand_input () at macro.c:40
694 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
698 We step through a few more lines to see what happens. The first two
699 times, we can use @samp{s}; the next two times we use @code{n} to avoid
700 falling into the @code{xstrdup} subroutine.
704 0x3b5c 532 if (rquote != def_rquote)
706 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
707 def_lquote : xstrdup(lq);
709 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
712 538 len_lquote = strlen(rquote);
716 The last line displayed looks a little odd; we can examine the variables
717 @code{lquote} and @code{rquote} to see if they are in fact the new left
718 and right quotes we specified. We use the command @code{p}
719 (@code{print}) to see their values.
722 (@value{GDBP}) @b{p lquote}
723 $1 = 0x35d40 "<QUOTE>"
724 (@value{GDBP}) @b{p rquote}
725 $2 = 0x35d50 "<UNQUOTE>"
729 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
730 To look at some context, we can display ten lines of source
731 surrounding the current line with the @code{l} (@code{list}) command.
737 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
739 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
742 538 len_lquote = strlen(rquote);
743 539 len_rquote = strlen(lquote);
750 Let us step past the two lines that set @code{len_lquote} and
751 @code{len_rquote}, and then examine the values of those variables.
755 539 len_rquote = strlen(lquote);
758 (@value{GDBP}) @b{p len_lquote}
760 (@value{GDBP}) @b{p len_rquote}
765 That certainly looks wrong, assuming @code{len_lquote} and
766 @code{len_rquote} are meant to be the lengths of @code{lquote} and
767 @code{rquote} respectively. We can set them to better values using
768 the @code{p} command, since it can print the value of
769 any expression---and that expression can include subroutine calls and
773 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
775 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
780 Is that enough to fix the problem of using the new quotes with the
781 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
782 executing with the @code{c} (@code{continue}) command, and then try the
783 example that caused trouble initially:
789 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
796 Success! The new quotes now work just as well as the default ones. The
797 problem seems to have been just the two typos defining the wrong
798 lengths. We allow @code{m4} exit by giving it an EOF as input:
802 Program exited normally.
806 The message @samp{Program exited normally.} is from @value{GDBN}; it
807 indicates @code{m4} has finished executing. We can end our @value{GDBN}
808 session with the @value{GDBN} @code{quit} command.
811 (@value{GDBP}) @b{quit}
815 @chapter Getting In and Out of @value{GDBN}
817 This chapter discusses how to start @value{GDBN}, and how to get out of it.
821 type @samp{@value{GDBP}} to start @value{GDBN}.
823 type @kbd{quit} or @kbd{Ctrl-d} to exit.
827 * Invoking GDB:: How to start @value{GDBN}
828 * Quitting GDB:: How to quit @value{GDBN}
829 * Shell Commands:: How to use shell commands inside @value{GDBN}
830 * Logging Output:: How to log @value{GDBN}'s output to a file
834 @section Invoking @value{GDBN}
836 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
837 @value{GDBN} reads commands from the terminal until you tell it to exit.
839 You can also run @code{@value{GDBP}} with a variety of arguments and options,
840 to specify more of your debugging environment at the outset.
842 The command-line options described here are designed
843 to cover a variety of situations; in some environments, some of these
844 options may effectively be unavailable.
846 The most usual way to start @value{GDBN} is with one argument,
847 specifying an executable program:
850 @value{GDBP} @var{program}
854 You can also start with both an executable program and a core file
858 @value{GDBP} @var{program} @var{core}
861 You can, instead, specify a process ID as a second argument, if you want
862 to debug a running process:
865 @value{GDBP} @var{program} 1234
869 would attach @value{GDBN} to process @code{1234} (unless you also have a file
870 named @file{1234}; @value{GDBN} does check for a core file first).
872 Taking advantage of the second command-line argument requires a fairly
873 complete operating system; when you use @value{GDBN} as a remote
874 debugger attached to a bare board, there may not be any notion of
875 ``process'', and there is often no way to get a core dump. @value{GDBN}
876 will warn you if it is unable to attach or to read core dumps.
878 You can optionally have @code{@value{GDBP}} pass any arguments after the
879 executable file to the inferior using @code{--args}. This option stops
882 @value{GDBP} --args gcc -O2 -c foo.c
884 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
885 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
887 You can run @code{@value{GDBP}} without printing the front material, which describes
888 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
895 You can further control how @value{GDBN} starts up by using command-line
896 options. @value{GDBN} itself can remind you of the options available.
906 to display all available options and briefly describe their use
907 (@samp{@value{GDBP} -h} is a shorter equivalent).
909 All options and command line arguments you give are processed
910 in sequential order. The order makes a difference when the
911 @samp{-x} option is used.
915 * File Options:: Choosing files
916 * Mode Options:: Choosing modes
917 * Startup:: What @value{GDBN} does during startup
921 @subsection Choosing Files
923 When @value{GDBN} starts, it reads any arguments other than options as
924 specifying an executable file and core file (or process ID). This is
925 the same as if the arguments were specified by the @samp{-se} and
926 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
927 first argument that does not have an associated option flag as
928 equivalent to the @samp{-se} option followed by that argument; and the
929 second argument that does not have an associated option flag, if any, as
930 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
931 If the second argument begins with a decimal digit, @value{GDBN} will
932 first attempt to attach to it as a process, and if that fails, attempt
933 to open it as a corefile. If you have a corefile whose name begins with
934 a digit, you can prevent @value{GDBN} from treating it as a pid by
935 prefixing it with @file{./}, e.g.@: @file{./12345}.
937 If @value{GDBN} has not been configured to included core file support,
938 such as for most embedded targets, then it will complain about a second
939 argument and ignore it.
941 Many options have both long and short forms; both are shown in the
942 following list. @value{GDBN} also recognizes the long forms if you truncate
943 them, so long as enough of the option is present to be unambiguous.
944 (If you prefer, you can flag option arguments with @samp{--} rather
945 than @samp{-}, though we illustrate the more usual convention.)
947 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
948 @c way, both those who look for -foo and --foo in the index, will find
952 @item -symbols @var{file}
954 @cindex @code{--symbols}
956 Read symbol table from file @var{file}.
958 @item -exec @var{file}
960 @cindex @code{--exec}
962 Use file @var{file} as the executable file to execute when appropriate,
963 and for examining pure data in conjunction with a core dump.
967 Read symbol table from file @var{file} and use it as the executable
970 @item -core @var{file}
972 @cindex @code{--core}
974 Use file @var{file} as a core dump to examine.
976 @item -pid @var{number}
977 @itemx -p @var{number}
980 Connect to process ID @var{number}, as with the @code{attach} command.
982 @item -command @var{file}
984 @cindex @code{--command}
986 Execute commands from file @var{file}. The contents of this file is
987 evaluated exactly as the @code{source} command would.
988 @xref{Command Files,, Command files}.
990 @item -eval-command @var{command}
991 @itemx -ex @var{command}
992 @cindex @code{--eval-command}
994 Execute a single @value{GDBN} command.
996 This option may be used multiple times to call multiple commands. It may
997 also be interleaved with @samp{-command} as required.
1000 @value{GDBP} -ex 'target sim' -ex 'load' \
1001 -x setbreakpoints -ex 'run' a.out
1004 @item -init-command @var{file}
1005 @itemx -ix @var{file}
1006 @cindex @code{--init-command}
1008 Execute commands from file @var{file} before loading the inferior (but
1009 after loading gdbinit files).
1012 @item -init-eval-command @var{command}
1013 @itemx -iex @var{command}
1014 @cindex @code{--init-eval-command}
1016 Execute a single @value{GDBN} command before loading the inferior (but
1017 after loading gdbinit files).
1020 @item -directory @var{directory}
1021 @itemx -d @var{directory}
1022 @cindex @code{--directory}
1024 Add @var{directory} to the path to search for source and script files.
1028 @cindex @code{--readnow}
1030 Read each symbol file's entire symbol table immediately, rather than
1031 the default, which is to read it incrementally as it is needed.
1032 This makes startup slower, but makes future operations faster.
1037 @subsection Choosing Modes
1039 You can run @value{GDBN} in various alternative modes---for example, in
1040 batch mode or quiet mode.
1048 Do not execute commands found in any initialization file.
1049 There are three init files, loaded in the following order:
1052 @item @file{system.gdbinit}
1053 This is the system-wide init file.
1054 Its location is specified with the @code{--with-system-gdbinit}
1055 configure option (@pxref{System-wide configuration}).
1056 It is loaded first when @value{GDBN} starts, before command line options
1057 have been processed.
1058 @item @file{~/.gdbinit}
1059 This is the init file in your home directory.
1060 It is loaded next, after @file{system.gdbinit}, and before
1061 command options have been processed.
1062 @item @file{./.gdbinit}
1063 This is the init file in the current directory.
1064 It is loaded last, after command line options other than @code{-x} and
1065 @code{-ex} have been processed. Command line options @code{-x} and
1066 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1069 For further documentation on startup processing, @xref{Startup}.
1070 For documentation on how to write command files,
1071 @xref{Command Files,,Command Files}.
1076 Do not execute commands found in @file{~/.gdbinit}, the init file
1077 in your home directory.
1083 @cindex @code{--quiet}
1084 @cindex @code{--silent}
1086 ``Quiet''. Do not print the introductory and copyright messages. These
1087 messages are also suppressed in batch mode.
1090 @cindex @code{--batch}
1091 Run in batch mode. Exit with status @code{0} after processing all the
1092 command files specified with @samp{-x} (and all commands from
1093 initialization files, if not inhibited with @samp{-n}). Exit with
1094 nonzero status if an error occurs in executing the @value{GDBN} commands
1095 in the command files. Batch mode also disables pagination, sets unlimited
1096 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1097 off} were in effect (@pxref{Messages/Warnings}).
1099 Batch mode may be useful for running @value{GDBN} as a filter, for
1100 example to download and run a program on another computer; in order to
1101 make this more useful, the message
1104 Program exited normally.
1108 (which is ordinarily issued whenever a program running under
1109 @value{GDBN} control terminates) is not issued when running in batch
1113 @cindex @code{--batch-silent}
1114 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1115 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1116 unaffected). This is much quieter than @samp{-silent} and would be useless
1117 for an interactive session.
1119 This is particularly useful when using targets that give @samp{Loading section}
1120 messages, for example.
1122 Note that targets that give their output via @value{GDBN}, as opposed to
1123 writing directly to @code{stdout}, will also be made silent.
1125 @item -return-child-result
1126 @cindex @code{--return-child-result}
1127 The return code from @value{GDBN} will be the return code from the child
1128 process (the process being debugged), with the following exceptions:
1132 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1133 internal error. In this case the exit code is the same as it would have been
1134 without @samp{-return-child-result}.
1136 The user quits with an explicit value. E.g., @samp{quit 1}.
1138 The child process never runs, or is not allowed to terminate, in which case
1139 the exit code will be -1.
1142 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1143 when @value{GDBN} is being used as a remote program loader or simulator
1148 @cindex @code{--nowindows}
1150 ``No windows''. If @value{GDBN} comes with a graphical user interface
1151 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1152 interface. If no GUI is available, this option has no effect.
1156 @cindex @code{--windows}
1158 If @value{GDBN} includes a GUI, then this option requires it to be
1161 @item -cd @var{directory}
1163 Run @value{GDBN} using @var{directory} as its working directory,
1164 instead of the current directory.
1166 @item -data-directory @var{directory}
1167 @itemx -D @var{directory}
1168 @cindex @code{--data-directory}
1170 Run @value{GDBN} using @var{directory} as its data directory.
1171 The data directory is where @value{GDBN} searches for its
1172 auxiliary files. @xref{Data Files}.
1176 @cindex @code{--fullname}
1178 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1179 subprocess. It tells @value{GDBN} to output the full file name and line
1180 number in a standard, recognizable fashion each time a stack frame is
1181 displayed (which includes each time your program stops). This
1182 recognizable format looks like two @samp{\032} characters, followed by
1183 the file name, line number and character position separated by colons,
1184 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1185 @samp{\032} characters as a signal to display the source code for the
1188 @item -annotate @var{level}
1189 @cindex @code{--annotate}
1190 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1191 effect is identical to using @samp{set annotate @var{level}}
1192 (@pxref{Annotations}). The annotation @var{level} controls how much
1193 information @value{GDBN} prints together with its prompt, values of
1194 expressions, source lines, and other types of output. Level 0 is the
1195 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1196 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1197 that control @value{GDBN}, and level 2 has been deprecated.
1199 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1203 @cindex @code{--args}
1204 Change interpretation of command line so that arguments following the
1205 executable file are passed as command line arguments to the inferior.
1206 This option stops option processing.
1208 @item -baud @var{bps}
1210 @cindex @code{--baud}
1212 Set the line speed (baud rate or bits per second) of any serial
1213 interface used by @value{GDBN} for remote debugging.
1215 @item -l @var{timeout}
1217 Set the timeout (in seconds) of any communication used by @value{GDBN}
1218 for remote debugging.
1220 @item -tty @var{device}
1221 @itemx -t @var{device}
1222 @cindex @code{--tty}
1224 Run using @var{device} for your program's standard input and output.
1225 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1227 @c resolve the situation of these eventually
1229 @cindex @code{--tui}
1230 Activate the @dfn{Text User Interface} when starting. The Text User
1231 Interface manages several text windows on the terminal, showing
1232 source, assembly, registers and @value{GDBN} command outputs
1233 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1234 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1235 Using @value{GDBN} under @sc{gnu} Emacs}).
1238 @c @cindex @code{--xdb}
1239 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1240 @c For information, see the file @file{xdb_trans.html}, which is usually
1241 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1244 @item -interpreter @var{interp}
1245 @cindex @code{--interpreter}
1246 Use the interpreter @var{interp} for interface with the controlling
1247 program or device. This option is meant to be set by programs which
1248 communicate with @value{GDBN} using it as a back end.
1249 @xref{Interpreters, , Command Interpreters}.
1251 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1252 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1253 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1254 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1255 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1256 @sc{gdb/mi} interfaces are no longer supported.
1259 @cindex @code{--write}
1260 Open the executable and core files for both reading and writing. This
1261 is equivalent to the @samp{set write on} command inside @value{GDBN}
1265 @cindex @code{--statistics}
1266 This option causes @value{GDBN} to print statistics about time and
1267 memory usage after it completes each command and returns to the prompt.
1270 @cindex @code{--version}
1271 This option causes @value{GDBN} to print its version number and
1272 no-warranty blurb, and exit.
1274 @item -configuration
1275 @cindex @code{--configuration}
1276 This option causes @value{GDBN} to print details about its build-time
1277 configuration parameters, and then exit. These details can be
1278 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1283 @subsection What @value{GDBN} Does During Startup
1284 @cindex @value{GDBN} startup
1286 Here's the description of what @value{GDBN} does during session startup:
1290 Sets up the command interpreter as specified by the command line
1291 (@pxref{Mode Options, interpreter}).
1295 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1296 used when building @value{GDBN}; @pxref{System-wide configuration,
1297 ,System-wide configuration and settings}) and executes all the commands in
1300 @anchor{Home Directory Init File}
1302 Reads the init file (if any) in your home directory@footnote{On
1303 DOS/Windows systems, the home directory is the one pointed to by the
1304 @code{HOME} environment variable.} and executes all the commands in
1307 @anchor{Option -init-eval-command}
1309 Executes commands and command files specified by the @samp{-iex} and
1310 @samp{-ix} options in their specified order. Usually you should use the
1311 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1312 settings before @value{GDBN} init files get executed and before inferior
1316 Processes command line options and operands.
1318 @anchor{Init File in the Current Directory during Startup}
1320 Reads and executes the commands from init file (if any) in the current
1321 working directory as long as @samp{set auto-load local-gdbinit} is set to
1322 @samp{on} (@pxref{Init File in the Current Directory}).
1323 This is only done if the current directory is
1324 different from your home directory. Thus, you can have more than one
1325 init file, one generic in your home directory, and another, specific
1326 to the program you are debugging, in the directory where you invoke
1330 If the command line specified a program to debug, or a process to
1331 attach to, or a core file, @value{GDBN} loads any auto-loaded
1332 scripts provided for the program or for its loaded shared libraries.
1333 @xref{Auto-loading}.
1335 If you wish to disable the auto-loading during startup,
1336 you must do something like the following:
1339 $ gdb -iex "set auto-load python-scripts off" myprogram
1342 Option @samp{-ex} does not work because the auto-loading is then turned
1346 Executes commands and command files specified by the @samp{-ex} and
1347 @samp{-x} options in their specified order. @xref{Command Files}, for
1348 more details about @value{GDBN} command files.
1351 Reads the command history recorded in the @dfn{history file}.
1352 @xref{Command History}, for more details about the command history and the
1353 files where @value{GDBN} records it.
1356 Init files use the same syntax as @dfn{command files} (@pxref{Command
1357 Files}) and are processed by @value{GDBN} in the same way. The init
1358 file in your home directory can set options (such as @samp{set
1359 complaints}) that affect subsequent processing of command line options
1360 and operands. Init files are not executed if you use the @samp{-nx}
1361 option (@pxref{Mode Options, ,Choosing Modes}).
1363 To display the list of init files loaded by gdb at startup, you
1364 can use @kbd{gdb --help}.
1366 @cindex init file name
1367 @cindex @file{.gdbinit}
1368 @cindex @file{gdb.ini}
1369 The @value{GDBN} init files are normally called @file{.gdbinit}.
1370 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1371 the limitations of file names imposed by DOS filesystems. The Windows
1372 port of @value{GDBN} uses the standard name, but if it finds a
1373 @file{gdb.ini} file in your home directory, it warns you about that
1374 and suggests to rename the file to the standard name.
1378 @section Quitting @value{GDBN}
1379 @cindex exiting @value{GDBN}
1380 @cindex leaving @value{GDBN}
1383 @kindex quit @r{[}@var{expression}@r{]}
1384 @kindex q @r{(@code{quit})}
1385 @item quit @r{[}@var{expression}@r{]}
1387 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1388 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1389 do not supply @var{expression}, @value{GDBN} will terminate normally;
1390 otherwise it will terminate using the result of @var{expression} as the
1395 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1396 terminates the action of any @value{GDBN} command that is in progress and
1397 returns to @value{GDBN} command level. It is safe to type the interrupt
1398 character at any time because @value{GDBN} does not allow it to take effect
1399 until a time when it is safe.
1401 If you have been using @value{GDBN} to control an attached process or
1402 device, you can release it with the @code{detach} command
1403 (@pxref{Attach, ,Debugging an Already-running Process}).
1405 @node Shell Commands
1406 @section Shell Commands
1408 If you need to execute occasional shell commands during your
1409 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1410 just use the @code{shell} command.
1415 @cindex shell escape
1416 @item shell @var{command-string}
1417 @itemx !@var{command-string}
1418 Invoke a standard shell to execute @var{command-string}.
1419 Note that no space is needed between @code{!} and @var{command-string}.
1420 If it exists, the environment variable @code{SHELL} determines which
1421 shell to run. Otherwise @value{GDBN} uses the default shell
1422 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1425 The utility @code{make} is often needed in development environments.
1426 You do not have to use the @code{shell} command for this purpose in
1431 @cindex calling make
1432 @item make @var{make-args}
1433 Execute the @code{make} program with the specified
1434 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1437 @node Logging Output
1438 @section Logging Output
1439 @cindex logging @value{GDBN} output
1440 @cindex save @value{GDBN} output to a file
1442 You may want to save the output of @value{GDBN} commands to a file.
1443 There are several commands to control @value{GDBN}'s logging.
1447 @item set logging on
1449 @item set logging off
1451 @cindex logging file name
1452 @item set logging file @var{file}
1453 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1454 @item set logging overwrite [on|off]
1455 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1456 you want @code{set logging on} to overwrite the logfile instead.
1457 @item set logging redirect [on|off]
1458 By default, @value{GDBN} output will go to both the terminal and the logfile.
1459 Set @code{redirect} if you want output to go only to the log file.
1460 @kindex show logging
1462 Show the current values of the logging settings.
1466 @chapter @value{GDBN} Commands
1468 You can abbreviate a @value{GDBN} command to the first few letters of the command
1469 name, if that abbreviation is unambiguous; and you can repeat certain
1470 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1471 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1472 show you the alternatives available, if there is more than one possibility).
1475 * Command Syntax:: How to give commands to @value{GDBN}
1476 * Completion:: Command completion
1477 * Help:: How to ask @value{GDBN} for help
1480 @node Command Syntax
1481 @section Command Syntax
1483 A @value{GDBN} command is a single line of input. There is no limit on
1484 how long it can be. It starts with a command name, which is followed by
1485 arguments whose meaning depends on the command name. For example, the
1486 command @code{step} accepts an argument which is the number of times to
1487 step, as in @samp{step 5}. You can also use the @code{step} command
1488 with no arguments. Some commands do not allow any arguments.
1490 @cindex abbreviation
1491 @value{GDBN} command names may always be truncated if that abbreviation is
1492 unambiguous. Other possible command abbreviations are listed in the
1493 documentation for individual commands. In some cases, even ambiguous
1494 abbreviations are allowed; for example, @code{s} is specially defined as
1495 equivalent to @code{step} even though there are other commands whose
1496 names start with @code{s}. You can test abbreviations by using them as
1497 arguments to the @code{help} command.
1499 @cindex repeating commands
1500 @kindex RET @r{(repeat last command)}
1501 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1502 repeat the previous command. Certain commands (for example, @code{run})
1503 will not repeat this way; these are commands whose unintentional
1504 repetition might cause trouble and which you are unlikely to want to
1505 repeat. User-defined commands can disable this feature; see
1506 @ref{Define, dont-repeat}.
1508 The @code{list} and @code{x} commands, when you repeat them with
1509 @key{RET}, construct new arguments rather than repeating
1510 exactly as typed. This permits easy scanning of source or memory.
1512 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1513 output, in a way similar to the common utility @code{more}
1514 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1515 @key{RET} too many in this situation, @value{GDBN} disables command
1516 repetition after any command that generates this sort of display.
1518 @kindex # @r{(a comment)}
1520 Any text from a @kbd{#} to the end of the line is a comment; it does
1521 nothing. This is useful mainly in command files (@pxref{Command
1522 Files,,Command Files}).
1524 @cindex repeating command sequences
1525 @kindex Ctrl-o @r{(operate-and-get-next)}
1526 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1527 commands. This command accepts the current line, like @key{RET}, and
1528 then fetches the next line relative to the current line from the history
1532 @section Command Completion
1535 @cindex word completion
1536 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1537 only one possibility; it can also show you what the valid possibilities
1538 are for the next word in a command, at any time. This works for @value{GDBN}
1539 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1541 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1542 of a word. If there is only one possibility, @value{GDBN} fills in the
1543 word, and waits for you to finish the command (or press @key{RET} to
1544 enter it). For example, if you type
1546 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1547 @c complete accuracy in these examples; space introduced for clarity.
1548 @c If texinfo enhancements make it unnecessary, it would be nice to
1549 @c replace " @key" by "@key" in the following...
1551 (@value{GDBP}) info bre @key{TAB}
1555 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1556 the only @code{info} subcommand beginning with @samp{bre}:
1559 (@value{GDBP}) info breakpoints
1563 You can either press @key{RET} at this point, to run the @code{info
1564 breakpoints} command, or backspace and enter something else, if
1565 @samp{breakpoints} does not look like the command you expected. (If you
1566 were sure you wanted @code{info breakpoints} in the first place, you
1567 might as well just type @key{RET} immediately after @samp{info bre},
1568 to exploit command abbreviations rather than command completion).
1570 If there is more than one possibility for the next word when you press
1571 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1572 characters and try again, or just press @key{TAB} a second time;
1573 @value{GDBN} displays all the possible completions for that word. For
1574 example, you might want to set a breakpoint on a subroutine whose name
1575 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1576 just sounds the bell. Typing @key{TAB} again displays all the
1577 function names in your program that begin with those characters, for
1581 (@value{GDBP}) b make_ @key{TAB}
1582 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1583 make_a_section_from_file make_environ
1584 make_abs_section make_function_type
1585 make_blockvector make_pointer_type
1586 make_cleanup make_reference_type
1587 make_command make_symbol_completion_list
1588 (@value{GDBP}) b make_
1592 After displaying the available possibilities, @value{GDBN} copies your
1593 partial input (@samp{b make_} in the example) so you can finish the
1596 If you just want to see the list of alternatives in the first place, you
1597 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1598 means @kbd{@key{META} ?}. You can type this either by holding down a
1599 key designated as the @key{META} shift on your keyboard (if there is
1600 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1602 @cindex quotes in commands
1603 @cindex completion of quoted strings
1604 Sometimes the string you need, while logically a ``word'', may contain
1605 parentheses or other characters that @value{GDBN} normally excludes from
1606 its notion of a word. To permit word completion to work in this
1607 situation, you may enclose words in @code{'} (single quote marks) in
1608 @value{GDBN} commands.
1610 The most likely situation where you might need this is in typing the
1611 name of a C@t{++} function. This is because C@t{++} allows function
1612 overloading (multiple definitions of the same function, distinguished
1613 by argument type). For example, when you want to set a breakpoint you
1614 may need to distinguish whether you mean the version of @code{name}
1615 that takes an @code{int} parameter, @code{name(int)}, or the version
1616 that takes a @code{float} parameter, @code{name(float)}. To use the
1617 word-completion facilities in this situation, type a single quote
1618 @code{'} at the beginning of the function name. This alerts
1619 @value{GDBN} that it may need to consider more information than usual
1620 when you press @key{TAB} or @kbd{M-?} to request word completion:
1623 (@value{GDBP}) b 'bubble( @kbd{M-?}
1624 bubble(double,double) bubble(int,int)
1625 (@value{GDBP}) b 'bubble(
1628 In some cases, @value{GDBN} can tell that completing a name requires using
1629 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1630 completing as much as it can) if you do not type the quote in the first
1634 (@value{GDBP}) b bub @key{TAB}
1635 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1636 (@value{GDBP}) b 'bubble(
1640 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1641 you have not yet started typing the argument list when you ask for
1642 completion on an overloaded symbol.
1644 For more information about overloaded functions, see @ref{C Plus Plus
1645 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1646 overload-resolution off} to disable overload resolution;
1647 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1649 @cindex completion of structure field names
1650 @cindex structure field name completion
1651 @cindex completion of union field names
1652 @cindex union field name completion
1653 When completing in an expression which looks up a field in a
1654 structure, @value{GDBN} also tries@footnote{The completer can be
1655 confused by certain kinds of invalid expressions. Also, it only
1656 examines the static type of the expression, not the dynamic type.} to
1657 limit completions to the field names available in the type of the
1661 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1662 magic to_fputs to_rewind
1663 to_data to_isatty to_write
1664 to_delete to_put to_write_async_safe
1669 This is because the @code{gdb_stdout} is a variable of the type
1670 @code{struct ui_file} that is defined in @value{GDBN} sources as
1677 ui_file_flush_ftype *to_flush;
1678 ui_file_write_ftype *to_write;
1679 ui_file_write_async_safe_ftype *to_write_async_safe;
1680 ui_file_fputs_ftype *to_fputs;
1681 ui_file_read_ftype *to_read;
1682 ui_file_delete_ftype *to_delete;
1683 ui_file_isatty_ftype *to_isatty;
1684 ui_file_rewind_ftype *to_rewind;
1685 ui_file_put_ftype *to_put;
1692 @section Getting Help
1693 @cindex online documentation
1696 You can always ask @value{GDBN} itself for information on its commands,
1697 using the command @code{help}.
1700 @kindex h @r{(@code{help})}
1703 You can use @code{help} (abbreviated @code{h}) with no arguments to
1704 display a short list of named classes of commands:
1708 List of classes of commands:
1710 aliases -- Aliases of other commands
1711 breakpoints -- Making program stop at certain points
1712 data -- Examining data
1713 files -- Specifying and examining files
1714 internals -- Maintenance commands
1715 obscure -- Obscure features
1716 running -- Running the program
1717 stack -- Examining the stack
1718 status -- Status inquiries
1719 support -- Support facilities
1720 tracepoints -- Tracing of program execution without
1721 stopping the program
1722 user-defined -- User-defined commands
1724 Type "help" followed by a class name for a list of
1725 commands in that class.
1726 Type "help" followed by command name for full
1728 Command name abbreviations are allowed if unambiguous.
1731 @c the above line break eliminates huge line overfull...
1733 @item help @var{class}
1734 Using one of the general help classes as an argument, you can get a
1735 list of the individual commands in that class. For example, here is the
1736 help display for the class @code{status}:
1739 (@value{GDBP}) help status
1744 @c Line break in "show" line falsifies real output, but needed
1745 @c to fit in smallbook page size.
1746 info -- Generic command for showing things
1747 about the program being debugged
1748 show -- Generic command for showing things
1751 Type "help" followed by command name for full
1753 Command name abbreviations are allowed if unambiguous.
1757 @item help @var{command}
1758 With a command name as @code{help} argument, @value{GDBN} displays a
1759 short paragraph on how to use that command.
1762 @item apropos @var{args}
1763 The @code{apropos} command searches through all of the @value{GDBN}
1764 commands, and their documentation, for the regular expression specified in
1765 @var{args}. It prints out all matches found. For example:
1776 alias -- Define a new command that is an alias of an existing command
1777 aliases -- Aliases of other commands
1778 d -- Delete some breakpoints or auto-display expressions
1779 del -- Delete some breakpoints or auto-display expressions
1780 delete -- Delete some breakpoints or auto-display expressions
1785 @item complete @var{args}
1786 The @code{complete @var{args}} command lists all the possible completions
1787 for the beginning of a command. Use @var{args} to specify the beginning of the
1788 command you want completed. For example:
1794 @noindent results in:
1805 @noindent This is intended for use by @sc{gnu} Emacs.
1808 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1809 and @code{show} to inquire about the state of your program, or the state
1810 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1811 manual introduces each of them in the appropriate context. The listings
1812 under @code{info} and under @code{show} in the Command, Variable, and
1813 Function Index point to all the sub-commands. @xref{Command and Variable
1819 @kindex i @r{(@code{info})}
1821 This command (abbreviated @code{i}) is for describing the state of your
1822 program. For example, you can show the arguments passed to a function
1823 with @code{info args}, list the registers currently in use with @code{info
1824 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1825 You can get a complete list of the @code{info} sub-commands with
1826 @w{@code{help info}}.
1830 You can assign the result of an expression to an environment variable with
1831 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1832 @code{set prompt $}.
1836 In contrast to @code{info}, @code{show} is for describing the state of
1837 @value{GDBN} itself.
1838 You can change most of the things you can @code{show}, by using the
1839 related command @code{set}; for example, you can control what number
1840 system is used for displays with @code{set radix}, or simply inquire
1841 which is currently in use with @code{show radix}.
1844 To display all the settable parameters and their current
1845 values, you can use @code{show} with no arguments; you may also use
1846 @code{info set}. Both commands produce the same display.
1847 @c FIXME: "info set" violates the rule that "info" is for state of
1848 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1849 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1853 Here are several miscellaneous @code{show} subcommands, all of which are
1854 exceptional in lacking corresponding @code{set} commands:
1857 @kindex show version
1858 @cindex @value{GDBN} version number
1860 Show what version of @value{GDBN} is running. You should include this
1861 information in @value{GDBN} bug-reports. If multiple versions of
1862 @value{GDBN} are in use at your site, you may need to determine which
1863 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1864 commands are introduced, and old ones may wither away. Also, many
1865 system vendors ship variant versions of @value{GDBN}, and there are
1866 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1867 The version number is the same as the one announced when you start
1870 @kindex show copying
1871 @kindex info copying
1872 @cindex display @value{GDBN} copyright
1875 Display information about permission for copying @value{GDBN}.
1877 @kindex show warranty
1878 @kindex info warranty
1880 @itemx info warranty
1881 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1882 if your version of @value{GDBN} comes with one.
1884 @kindex show configuration
1885 @item show configuration
1886 Display detailed information about the way @value{GDBN} was configured
1887 when it was built. This displays the optional arguments passed to the
1888 @file{configure} script and also configuration parameters detected
1889 automatically by @command{configure}. When reporting a @value{GDBN}
1890 bug (@pxref{GDB Bugs}), it is important to include this information in
1896 @chapter Running Programs Under @value{GDBN}
1898 When you run a program under @value{GDBN}, you must first generate
1899 debugging information when you compile it.
1901 You may start @value{GDBN} with its arguments, if any, in an environment
1902 of your choice. If you are doing native debugging, you may redirect
1903 your program's input and output, debug an already running process, or
1904 kill a child process.
1907 * Compilation:: Compiling for debugging
1908 * Starting:: Starting your program
1909 * Arguments:: Your program's arguments
1910 * Environment:: Your program's environment
1912 * Working Directory:: Your program's working directory
1913 * Input/Output:: Your program's input and output
1914 * Attach:: Debugging an already-running process
1915 * Kill Process:: Killing the child process
1917 * Inferiors and Programs:: Debugging multiple inferiors and programs
1918 * Threads:: Debugging programs with multiple threads
1919 * Forks:: Debugging forks
1920 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1924 @section Compiling for Debugging
1926 In order to debug a program effectively, you need to generate
1927 debugging information when you compile it. This debugging information
1928 is stored in the object file; it describes the data type of each
1929 variable or function and the correspondence between source line numbers
1930 and addresses in the executable code.
1932 To request debugging information, specify the @samp{-g} option when you run
1935 Programs that are to be shipped to your customers are compiled with
1936 optimizations, using the @samp{-O} compiler option. However, some
1937 compilers are unable to handle the @samp{-g} and @samp{-O} options
1938 together. Using those compilers, you cannot generate optimized
1939 executables containing debugging information.
1941 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1942 without @samp{-O}, making it possible to debug optimized code. We
1943 recommend that you @emph{always} use @samp{-g} whenever you compile a
1944 program. You may think your program is correct, but there is no sense
1945 in pushing your luck. For more information, see @ref{Optimized Code}.
1947 Older versions of the @sc{gnu} C compiler permitted a variant option
1948 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1949 format; if your @sc{gnu} C compiler has this option, do not use it.
1951 @value{GDBN} knows about preprocessor macros and can show you their
1952 expansion (@pxref{Macros}). Most compilers do not include information
1953 about preprocessor macros in the debugging information if you specify
1954 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1955 the @sc{gnu} C compiler, provides macro information if you are using
1956 the DWARF debugging format, and specify the option @option{-g3}.
1958 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1959 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1960 information on @value{NGCC} options affecting debug information.
1962 You will have the best debugging experience if you use the latest
1963 version of the DWARF debugging format that your compiler supports.
1964 DWARF is currently the most expressive and best supported debugging
1965 format in @value{GDBN}.
1969 @section Starting your Program
1975 @kindex r @r{(@code{run})}
1978 Use the @code{run} command to start your program under @value{GDBN}.
1979 You must first specify the program name (except on VxWorks) with an
1980 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1981 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1982 (@pxref{Files, ,Commands to Specify Files}).
1986 If you are running your program in an execution environment that
1987 supports processes, @code{run} creates an inferior process and makes
1988 that process run your program. In some environments without processes,
1989 @code{run} jumps to the start of your program. Other targets,
1990 like @samp{remote}, are always running. If you get an error
1991 message like this one:
1994 The "remote" target does not support "run".
1995 Try "help target" or "continue".
1999 then use @code{continue} to run your program. You may need @code{load}
2000 first (@pxref{load}).
2002 The execution of a program is affected by certain information it
2003 receives from its superior. @value{GDBN} provides ways to specify this
2004 information, which you must do @emph{before} starting your program. (You
2005 can change it after starting your program, but such changes only affect
2006 your program the next time you start it.) This information may be
2007 divided into four categories:
2010 @item The @emph{arguments.}
2011 Specify the arguments to give your program as the arguments of the
2012 @code{run} command. If a shell is available on your target, the shell
2013 is used to pass the arguments, so that you may use normal conventions
2014 (such as wildcard expansion or variable substitution) in describing
2016 In Unix systems, you can control which shell is used with the
2017 @code{SHELL} environment variable. If you do not define @code{SHELL},
2018 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2019 use of any shell with the @code{set startup-with-shell} command (see
2022 @item The @emph{environment.}
2023 Your program normally inherits its environment from @value{GDBN}, but you can
2024 use the @value{GDBN} commands @code{set environment} and @code{unset
2025 environment} to change parts of the environment that affect
2026 your program. @xref{Environment, ,Your Program's Environment}.
2028 @item The @emph{working directory.}
2029 Your program inherits its working directory from @value{GDBN}. You can set
2030 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
2031 @xref{Working Directory, ,Your Program's Working Directory}.
2033 @item The @emph{standard input and output.}
2034 Your program normally uses the same device for standard input and
2035 standard output as @value{GDBN} is using. You can redirect input and output
2036 in the @code{run} command line, or you can use the @code{tty} command to
2037 set a different device for your program.
2038 @xref{Input/Output, ,Your Program's Input and Output}.
2041 @emph{Warning:} While input and output redirection work, you cannot use
2042 pipes to pass the output of the program you are debugging to another
2043 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2047 When you issue the @code{run} command, your program begins to execute
2048 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2049 of how to arrange for your program to stop. Once your program has
2050 stopped, you may call functions in your program, using the @code{print}
2051 or @code{call} commands. @xref{Data, ,Examining Data}.
2053 If the modification time of your symbol file has changed since the last
2054 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2055 table, and reads it again. When it does this, @value{GDBN} tries to retain
2056 your current breakpoints.
2061 @cindex run to main procedure
2062 The name of the main procedure can vary from language to language.
2063 With C or C@t{++}, the main procedure name is always @code{main}, but
2064 other languages such as Ada do not require a specific name for their
2065 main procedure. The debugger provides a convenient way to start the
2066 execution of the program and to stop at the beginning of the main
2067 procedure, depending on the language used.
2069 The @samp{start} command does the equivalent of setting a temporary
2070 breakpoint at the beginning of the main procedure and then invoking
2071 the @samp{run} command.
2073 @cindex elaboration phase
2074 Some programs contain an @dfn{elaboration} phase where some startup code is
2075 executed before the main procedure is called. This depends on the
2076 languages used to write your program. In C@t{++}, for instance,
2077 constructors for static and global objects are executed before
2078 @code{main} is called. It is therefore possible that the debugger stops
2079 before reaching the main procedure. However, the temporary breakpoint
2080 will remain to halt execution.
2082 Specify the arguments to give to your program as arguments to the
2083 @samp{start} command. These arguments will be given verbatim to the
2084 underlying @samp{run} command. Note that the same arguments will be
2085 reused if no argument is provided during subsequent calls to
2086 @samp{start} or @samp{run}.
2088 It is sometimes necessary to debug the program during elaboration. In
2089 these cases, using the @code{start} command would stop the execution of
2090 your program too late, as the program would have already completed the
2091 elaboration phase. Under these circumstances, insert breakpoints in your
2092 elaboration code before running your program.
2094 @anchor{set exec-wrapper}
2095 @kindex set exec-wrapper
2096 @item set exec-wrapper @var{wrapper}
2097 @itemx show exec-wrapper
2098 @itemx unset exec-wrapper
2099 When @samp{exec-wrapper} is set, the specified wrapper is used to
2100 launch programs for debugging. @value{GDBN} starts your program
2101 with a shell command of the form @kbd{exec @var{wrapper}
2102 @var{program}}. Quoting is added to @var{program} and its
2103 arguments, but not to @var{wrapper}, so you should add quotes if
2104 appropriate for your shell. The wrapper runs until it executes
2105 your program, and then @value{GDBN} takes control.
2107 You can use any program that eventually calls @code{execve} with
2108 its arguments as a wrapper. Several standard Unix utilities do
2109 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2110 with @code{exec "$@@"} will also work.
2112 For example, you can use @code{env} to pass an environment variable to
2113 the debugged program, without setting the variable in your shell's
2117 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2121 This command is available when debugging locally on most targets, excluding
2122 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2124 @kindex set startup-with-shell
2125 @item set startup-with-shell
2126 @itemx set startup-with-shell on
2127 @itemx set startup-with-shell off
2128 @itemx show set startup-with-shell
2129 On Unix systems, by default, if a shell is available on your target,
2130 @value{GDBN}) uses it to start your program. Arguments of the
2131 @code{run} command are passed to the shell, which does variable
2132 substitution, expands wildcard characters and performs redirection of
2133 I/O. In some circumstances, it may be useful to disable such use of a
2134 shell, for example, when debugging the shell itself or diagnosing
2135 startup failures such as:
2139 Starting program: ./a.out
2140 During startup program terminated with signal SIGSEGV, Segmentation fault.
2144 which indicates the shell or the wrapper specified with
2145 @samp{exec-wrapper} crashed, not your program. Most often, this is
2146 caused by something odd in your shell's non-interactive mode
2147 initialization file---such as @file{.cshrc} for C-shell,
2148 $@file{.zshenv} for the Z shell, or the file specified in the
2149 @samp{BASH_ENV} environment variable for BASH.
2151 @kindex set disable-randomization
2152 @item set disable-randomization
2153 @itemx set disable-randomization on
2154 This option (enabled by default in @value{GDBN}) will turn off the native
2155 randomization of the virtual address space of the started program. This option
2156 is useful for multiple debugging sessions to make the execution better
2157 reproducible and memory addresses reusable across debugging sessions.
2159 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2160 On @sc{gnu}/Linux you can get the same behavior using
2163 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2166 @item set disable-randomization off
2167 Leave the behavior of the started executable unchanged. Some bugs rear their
2168 ugly heads only when the program is loaded at certain addresses. If your bug
2169 disappears when you run the program under @value{GDBN}, that might be because
2170 @value{GDBN} by default disables the address randomization on platforms, such
2171 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2172 disable-randomization off} to try to reproduce such elusive bugs.
2174 On targets where it is available, virtual address space randomization
2175 protects the programs against certain kinds of security attacks. In these
2176 cases the attacker needs to know the exact location of a concrete executable
2177 code. Randomizing its location makes it impossible to inject jumps misusing
2178 a code at its expected addresses.
2180 Prelinking shared libraries provides a startup performance advantage but it
2181 makes addresses in these libraries predictable for privileged processes by
2182 having just unprivileged access at the target system. Reading the shared
2183 library binary gives enough information for assembling the malicious code
2184 misusing it. Still even a prelinked shared library can get loaded at a new
2185 random address just requiring the regular relocation process during the
2186 startup. Shared libraries not already prelinked are always loaded at
2187 a randomly chosen address.
2189 Position independent executables (PIE) contain position independent code
2190 similar to the shared libraries and therefore such executables get loaded at
2191 a randomly chosen address upon startup. PIE executables always load even
2192 already prelinked shared libraries at a random address. You can build such
2193 executable using @command{gcc -fPIE -pie}.
2195 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2196 (as long as the randomization is enabled).
2198 @item show disable-randomization
2199 Show the current setting of the explicit disable of the native randomization of
2200 the virtual address space of the started program.
2205 @section Your Program's Arguments
2207 @cindex arguments (to your program)
2208 The arguments to your program can be specified by the arguments of the
2210 They are passed to a shell, which expands wildcard characters and
2211 performs redirection of I/O, and thence to your program. Your
2212 @code{SHELL} environment variable (if it exists) specifies what shell
2213 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2214 the default shell (@file{/bin/sh} on Unix).
2216 On non-Unix systems, the program is usually invoked directly by
2217 @value{GDBN}, which emulates I/O redirection via the appropriate system
2218 calls, and the wildcard characters are expanded by the startup code of
2219 the program, not by the shell.
2221 @code{run} with no arguments uses the same arguments used by the previous
2222 @code{run}, or those set by the @code{set args} command.
2227 Specify the arguments to be used the next time your program is run. If
2228 @code{set args} has no arguments, @code{run} executes your program
2229 with no arguments. Once you have run your program with arguments,
2230 using @code{set args} before the next @code{run} is the only way to run
2231 it again without arguments.
2235 Show the arguments to give your program when it is started.
2239 @section Your Program's Environment
2241 @cindex environment (of your program)
2242 The @dfn{environment} consists of a set of environment variables and
2243 their values. Environment variables conventionally record such things as
2244 your user name, your home directory, your terminal type, and your search
2245 path for programs to run. Usually you set up environment variables with
2246 the shell and they are inherited by all the other programs you run. When
2247 debugging, it can be useful to try running your program with a modified
2248 environment without having to start @value{GDBN} over again.
2252 @item path @var{directory}
2253 Add @var{directory} to the front of the @code{PATH} environment variable
2254 (the search path for executables) that will be passed to your program.
2255 The value of @code{PATH} used by @value{GDBN} does not change.
2256 You may specify several directory names, separated by whitespace or by a
2257 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2258 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2259 is moved to the front, so it is searched sooner.
2261 You can use the string @samp{$cwd} to refer to whatever is the current
2262 working directory at the time @value{GDBN} searches the path. If you
2263 use @samp{.} instead, it refers to the directory where you executed the
2264 @code{path} command. @value{GDBN} replaces @samp{.} in the
2265 @var{directory} argument (with the current path) before adding
2266 @var{directory} to the search path.
2267 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2268 @c document that, since repeating it would be a no-op.
2272 Display the list of search paths for executables (the @code{PATH}
2273 environment variable).
2275 @kindex show environment
2276 @item show environment @r{[}@var{varname}@r{]}
2277 Print the value of environment variable @var{varname} to be given to
2278 your program when it starts. If you do not supply @var{varname},
2279 print the names and values of all environment variables to be given to
2280 your program. You can abbreviate @code{environment} as @code{env}.
2282 @kindex set environment
2283 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2284 Set environment variable @var{varname} to @var{value}. The value
2285 changes for your program (and the shell @value{GDBN} uses to launch
2286 it), not for @value{GDBN} itself. @var{value} may be any string; the
2287 values of environment variables are just strings, and any
2288 interpretation is supplied by your program itself. The @var{value}
2289 parameter is optional; if it is eliminated, the variable is set to a
2291 @c "any string" here does not include leading, trailing
2292 @c blanks. Gnu asks: does anyone care?
2294 For example, this command:
2301 tells the debugged program, when subsequently run, that its user is named
2302 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2303 are not actually required.)
2305 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2306 which also inherits the environment set with @code{set environment}.
2307 If necessary, you can avoid that by using the @samp{env} program as a
2308 wrapper instead of using @code{set environment}. @xref{set
2309 exec-wrapper}, for an example doing just that.
2311 @kindex unset environment
2312 @item unset environment @var{varname}
2313 Remove variable @var{varname} from the environment to be passed to your
2314 program. This is different from @samp{set env @var{varname} =};
2315 @code{unset environment} removes the variable from the environment,
2316 rather than assigning it an empty value.
2319 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2320 the shell indicated by your @code{SHELL} environment variable if it
2321 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2322 names a shell that runs an initialization file when started
2323 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2324 for the Z shell, or the file specified in the @samp{BASH_ENV}
2325 environment variable for BASH---any variables you set in that file
2326 affect your program. You may wish to move setting of environment
2327 variables to files that are only run when you sign on, such as
2328 @file{.login} or @file{.profile}.
2330 @node Working Directory
2331 @section Your Program's Working Directory
2333 @cindex working directory (of your program)
2334 Each time you start your program with @code{run}, it inherits its
2335 working directory from the current working directory of @value{GDBN}.
2336 The @value{GDBN} working directory is initially whatever it inherited
2337 from its parent process (typically the shell), but you can specify a new
2338 working directory in @value{GDBN} with the @code{cd} command.
2340 The @value{GDBN} working directory also serves as a default for the commands
2341 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2346 @cindex change working directory
2347 @item cd @r{[}@var{directory}@r{]}
2348 Set the @value{GDBN} working directory to @var{directory}. If not
2349 given, @var{directory} uses @file{'~'}.
2353 Print the @value{GDBN} working directory.
2356 It is generally impossible to find the current working directory of
2357 the process being debugged (since a program can change its directory
2358 during its run). If you work on a system where @value{GDBN} is
2359 configured with the @file{/proc} support, you can use the @code{info
2360 proc} command (@pxref{SVR4 Process Information}) to find out the
2361 current working directory of the debuggee.
2364 @section Your Program's Input and Output
2369 By default, the program you run under @value{GDBN} does input and output to
2370 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2371 to its own terminal modes to interact with you, but it records the terminal
2372 modes your program was using and switches back to them when you continue
2373 running your program.
2376 @kindex info terminal
2378 Displays information recorded by @value{GDBN} about the terminal modes your
2382 You can redirect your program's input and/or output using shell
2383 redirection with the @code{run} command. For example,
2390 starts your program, diverting its output to the file @file{outfile}.
2393 @cindex controlling terminal
2394 Another way to specify where your program should do input and output is
2395 with the @code{tty} command. This command accepts a file name as
2396 argument, and causes this file to be the default for future @code{run}
2397 commands. It also resets the controlling terminal for the child
2398 process, for future @code{run} commands. For example,
2405 directs that processes started with subsequent @code{run} commands
2406 default to do input and output on the terminal @file{/dev/ttyb} and have
2407 that as their controlling terminal.
2409 An explicit redirection in @code{run} overrides the @code{tty} command's
2410 effect on the input/output device, but not its effect on the controlling
2413 When you use the @code{tty} command or redirect input in the @code{run}
2414 command, only the input @emph{for your program} is affected. The input
2415 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2416 for @code{set inferior-tty}.
2418 @cindex inferior tty
2419 @cindex set inferior controlling terminal
2420 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2421 display the name of the terminal that will be used for future runs of your
2425 @item set inferior-tty /dev/ttyb
2426 @kindex set inferior-tty
2427 Set the tty for the program being debugged to /dev/ttyb.
2429 @item show inferior-tty
2430 @kindex show inferior-tty
2431 Show the current tty for the program being debugged.
2435 @section Debugging an Already-running Process
2440 @item attach @var{process-id}
2441 This command attaches to a running process---one that was started
2442 outside @value{GDBN}. (@code{info files} shows your active
2443 targets.) The command takes as argument a process ID. The usual way to
2444 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2445 or with the @samp{jobs -l} shell command.
2447 @code{attach} does not repeat if you press @key{RET} a second time after
2448 executing the command.
2451 To use @code{attach}, your program must be running in an environment
2452 which supports processes; for example, @code{attach} does not work for
2453 programs on bare-board targets that lack an operating system. You must
2454 also have permission to send the process a signal.
2456 When you use @code{attach}, the debugger finds the program running in
2457 the process first by looking in the current working directory, then (if
2458 the program is not found) by using the source file search path
2459 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2460 the @code{file} command to load the program. @xref{Files, ,Commands to
2463 The first thing @value{GDBN} does after arranging to debug the specified
2464 process is to stop it. You can examine and modify an attached process
2465 with all the @value{GDBN} commands that are ordinarily available when
2466 you start processes with @code{run}. You can insert breakpoints; you
2467 can step and continue; you can modify storage. If you would rather the
2468 process continue running, you may use the @code{continue} command after
2469 attaching @value{GDBN} to the process.
2474 When you have finished debugging the attached process, you can use the
2475 @code{detach} command to release it from @value{GDBN} control. Detaching
2476 the process continues its execution. After the @code{detach} command,
2477 that process and @value{GDBN} become completely independent once more, and you
2478 are ready to @code{attach} another process or start one with @code{run}.
2479 @code{detach} does not repeat if you press @key{RET} again after
2480 executing the command.
2483 If you exit @value{GDBN} while you have an attached process, you detach
2484 that process. If you use the @code{run} command, you kill that process.
2485 By default, @value{GDBN} asks for confirmation if you try to do either of these
2486 things; you can control whether or not you need to confirm by using the
2487 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2491 @section Killing the Child Process
2496 Kill the child process in which your program is running under @value{GDBN}.
2499 This command is useful if you wish to debug a core dump instead of a
2500 running process. @value{GDBN} ignores any core dump file while your program
2503 On some operating systems, a program cannot be executed outside @value{GDBN}
2504 while you have breakpoints set on it inside @value{GDBN}. You can use the
2505 @code{kill} command in this situation to permit running your program
2506 outside the debugger.
2508 The @code{kill} command is also useful if you wish to recompile and
2509 relink your program, since on many systems it is impossible to modify an
2510 executable file while it is running in a process. In this case, when you
2511 next type @code{run}, @value{GDBN} notices that the file has changed, and
2512 reads the symbol table again (while trying to preserve your current
2513 breakpoint settings).
2515 @node Inferiors and Programs
2516 @section Debugging Multiple Inferiors and Programs
2518 @value{GDBN} lets you run and debug multiple programs in a single
2519 session. In addition, @value{GDBN} on some systems may let you run
2520 several programs simultaneously (otherwise you have to exit from one
2521 before starting another). In the most general case, you can have
2522 multiple threads of execution in each of multiple processes, launched
2523 from multiple executables.
2526 @value{GDBN} represents the state of each program execution with an
2527 object called an @dfn{inferior}. An inferior typically corresponds to
2528 a process, but is more general and applies also to targets that do not
2529 have processes. Inferiors may be created before a process runs, and
2530 may be retained after a process exits. Inferiors have unique
2531 identifiers that are different from process ids. Usually each
2532 inferior will also have its own distinct address space, although some
2533 embedded targets may have several inferiors running in different parts
2534 of a single address space. Each inferior may in turn have multiple
2535 threads running in it.
2537 To find out what inferiors exist at any moment, use @w{@code{info
2541 @kindex info inferiors
2542 @item info inferiors
2543 Print a list of all inferiors currently being managed by @value{GDBN}.
2545 @value{GDBN} displays for each inferior (in this order):
2549 the inferior number assigned by @value{GDBN}
2552 the target system's inferior identifier
2555 the name of the executable the inferior is running.
2560 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2561 indicates the current inferior.
2565 @c end table here to get a little more width for example
2568 (@value{GDBP}) info inferiors
2569 Num Description Executable
2570 2 process 2307 hello
2571 * 1 process 3401 goodbye
2574 To switch focus between inferiors, use the @code{inferior} command:
2577 @kindex inferior @var{infno}
2578 @item inferior @var{infno}
2579 Make inferior number @var{infno} the current inferior. The argument
2580 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2581 in the first field of the @samp{info inferiors} display.
2585 You can get multiple executables into a debugging session via the
2586 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2587 systems @value{GDBN} can add inferiors to the debug session
2588 automatically by following calls to @code{fork} and @code{exec}. To
2589 remove inferiors from the debugging session use the
2590 @w{@code{remove-inferiors}} command.
2593 @kindex add-inferior
2594 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2595 Adds @var{n} inferiors to be run using @var{executable} as the
2596 executable. @var{n} defaults to 1. If no executable is specified,
2597 the inferiors begins empty, with no program. You can still assign or
2598 change the program assigned to the inferior at any time by using the
2599 @code{file} command with the executable name as its argument.
2601 @kindex clone-inferior
2602 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2603 Adds @var{n} inferiors ready to execute the same program as inferior
2604 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2605 number of the current inferior. This is a convenient command when you
2606 want to run another instance of the inferior you are debugging.
2609 (@value{GDBP}) info inferiors
2610 Num Description Executable
2611 * 1 process 29964 helloworld
2612 (@value{GDBP}) clone-inferior
2615 (@value{GDBP}) info inferiors
2616 Num Description Executable
2618 * 1 process 29964 helloworld
2621 You can now simply switch focus to inferior 2 and run it.
2623 @kindex remove-inferiors
2624 @item remove-inferiors @var{infno}@dots{}
2625 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2626 possible to remove an inferior that is running with this command. For
2627 those, use the @code{kill} or @code{detach} command first.
2631 To quit debugging one of the running inferiors that is not the current
2632 inferior, you can either detach from it by using the @w{@code{detach
2633 inferior}} command (allowing it to run independently), or kill it
2634 using the @w{@code{kill inferiors}} command:
2637 @kindex detach inferiors @var{infno}@dots{}
2638 @item detach inferior @var{infno}@dots{}
2639 Detach from the inferior or inferiors identified by @value{GDBN}
2640 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2641 still stays on the list of inferiors shown by @code{info inferiors},
2642 but its Description will show @samp{<null>}.
2644 @kindex kill inferiors @var{infno}@dots{}
2645 @item kill inferiors @var{infno}@dots{}
2646 Kill the inferior or inferiors identified by @value{GDBN} inferior
2647 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2648 stays on the list of inferiors shown by @code{info inferiors}, but its
2649 Description will show @samp{<null>}.
2652 After the successful completion of a command such as @code{detach},
2653 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2654 a normal process exit, the inferior is still valid and listed with
2655 @code{info inferiors}, ready to be restarted.
2658 To be notified when inferiors are started or exit under @value{GDBN}'s
2659 control use @w{@code{set print inferior-events}}:
2662 @kindex set print inferior-events
2663 @cindex print messages on inferior start and exit
2664 @item set print inferior-events
2665 @itemx set print inferior-events on
2666 @itemx set print inferior-events off
2667 The @code{set print inferior-events} command allows you to enable or
2668 disable printing of messages when @value{GDBN} notices that new
2669 inferiors have started or that inferiors have exited or have been
2670 detached. By default, these messages will not be printed.
2672 @kindex show print inferior-events
2673 @item show print inferior-events
2674 Show whether messages will be printed when @value{GDBN} detects that
2675 inferiors have started, exited or have been detached.
2678 Many commands will work the same with multiple programs as with a
2679 single program: e.g., @code{print myglobal} will simply display the
2680 value of @code{myglobal} in the current inferior.
2683 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2684 get more info about the relationship of inferiors, programs, address
2685 spaces in a debug session. You can do that with the @w{@code{maint
2686 info program-spaces}} command.
2689 @kindex maint info program-spaces
2690 @item maint info program-spaces
2691 Print a list of all program spaces currently being managed by
2694 @value{GDBN} displays for each program space (in this order):
2698 the program space number assigned by @value{GDBN}
2701 the name of the executable loaded into the program space, with e.g.,
2702 the @code{file} command.
2707 An asterisk @samp{*} preceding the @value{GDBN} program space number
2708 indicates the current program space.
2710 In addition, below each program space line, @value{GDBN} prints extra
2711 information that isn't suitable to display in tabular form. For
2712 example, the list of inferiors bound to the program space.
2715 (@value{GDBP}) maint info program-spaces
2718 Bound inferiors: ID 1 (process 21561)
2722 Here we can see that no inferior is running the program @code{hello},
2723 while @code{process 21561} is running the program @code{goodbye}. On
2724 some targets, it is possible that multiple inferiors are bound to the
2725 same program space. The most common example is that of debugging both
2726 the parent and child processes of a @code{vfork} call. For example,
2729 (@value{GDBP}) maint info program-spaces
2732 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2735 Here, both inferior 2 and inferior 1 are running in the same program
2736 space as a result of inferior 1 having executed a @code{vfork} call.
2740 @section Debugging Programs with Multiple Threads
2742 @cindex threads of execution
2743 @cindex multiple threads
2744 @cindex switching threads
2745 In some operating systems, such as HP-UX and Solaris, a single program
2746 may have more than one @dfn{thread} of execution. The precise semantics
2747 of threads differ from one operating system to another, but in general
2748 the threads of a single program are akin to multiple processes---except
2749 that they share one address space (that is, they can all examine and
2750 modify the same variables). On the other hand, each thread has its own
2751 registers and execution stack, and perhaps private memory.
2753 @value{GDBN} provides these facilities for debugging multi-thread
2757 @item automatic notification of new threads
2758 @item @samp{thread @var{threadno}}, a command to switch among threads
2759 @item @samp{info threads}, a command to inquire about existing threads
2760 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2761 a command to apply a command to a list of threads
2762 @item thread-specific breakpoints
2763 @item @samp{set print thread-events}, which controls printing of
2764 messages on thread start and exit.
2765 @item @samp{set libthread-db-search-path @var{path}}, which lets
2766 the user specify which @code{libthread_db} to use if the default choice
2767 isn't compatible with the program.
2771 @emph{Warning:} These facilities are not yet available on every
2772 @value{GDBN} configuration where the operating system supports threads.
2773 If your @value{GDBN} does not support threads, these commands have no
2774 effect. For example, a system without thread support shows no output
2775 from @samp{info threads}, and always rejects the @code{thread} command,
2779 (@value{GDBP}) info threads
2780 (@value{GDBP}) thread 1
2781 Thread ID 1 not known. Use the "info threads" command to
2782 see the IDs of currently known threads.
2784 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2785 @c doesn't support threads"?
2788 @cindex focus of debugging
2789 @cindex current thread
2790 The @value{GDBN} thread debugging facility allows you to observe all
2791 threads while your program runs---but whenever @value{GDBN} takes
2792 control, one thread in particular is always the focus of debugging.
2793 This thread is called the @dfn{current thread}. Debugging commands show
2794 program information from the perspective of the current thread.
2796 @cindex @code{New} @var{systag} message
2797 @cindex thread identifier (system)
2798 @c FIXME-implementors!! It would be more helpful if the [New...] message
2799 @c included GDB's numeric thread handle, so you could just go to that
2800 @c thread without first checking `info threads'.
2801 Whenever @value{GDBN} detects a new thread in your program, it displays
2802 the target system's identification for the thread with a message in the
2803 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2804 whose form varies depending on the particular system. For example, on
2805 @sc{gnu}/Linux, you might see
2808 [New Thread 0x41e02940 (LWP 25582)]
2812 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2813 the @var{systag} is simply something like @samp{process 368}, with no
2816 @c FIXME!! (1) Does the [New...] message appear even for the very first
2817 @c thread of a program, or does it only appear for the
2818 @c second---i.e.@: when it becomes obvious we have a multithread
2820 @c (2) *Is* there necessarily a first thread always? Or do some
2821 @c multithread systems permit starting a program with multiple
2822 @c threads ab initio?
2824 @cindex thread number
2825 @cindex thread identifier (GDB)
2826 For debugging purposes, @value{GDBN} associates its own thread
2827 number---always a single integer---with each thread in your program.
2830 @kindex info threads
2831 @item info threads @r{[}@var{id}@dots{}@r{]}
2832 Display a summary of all threads currently in your program. Optional
2833 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2834 means to print information only about the specified thread or threads.
2835 @value{GDBN} displays for each thread (in this order):
2839 the thread number assigned by @value{GDBN}
2842 the target system's thread identifier (@var{systag})
2845 the thread's name, if one is known. A thread can either be named by
2846 the user (see @code{thread name}, below), or, in some cases, by the
2850 the current stack frame summary for that thread
2854 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2855 indicates the current thread.
2859 @c end table here to get a little more width for example
2862 (@value{GDBP}) info threads
2864 3 process 35 thread 27 0x34e5 in sigpause ()
2865 2 process 35 thread 23 0x34e5 in sigpause ()
2866 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2870 On Solaris, you can display more information about user threads with a
2871 Solaris-specific command:
2874 @item maint info sol-threads
2875 @kindex maint info sol-threads
2876 @cindex thread info (Solaris)
2877 Display info on Solaris user threads.
2881 @kindex thread @var{threadno}
2882 @item thread @var{threadno}
2883 Make thread number @var{threadno} the current thread. The command
2884 argument @var{threadno} is the internal @value{GDBN} thread number, as
2885 shown in the first field of the @samp{info threads} display.
2886 @value{GDBN} responds by displaying the system identifier of the thread
2887 you selected, and its current stack frame summary:
2890 (@value{GDBP}) thread 2
2891 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2892 #0 some_function (ignore=0x0) at example.c:8
2893 8 printf ("hello\n");
2897 As with the @samp{[New @dots{}]} message, the form of the text after
2898 @samp{Switching to} depends on your system's conventions for identifying
2901 @vindex $_thread@r{, convenience variable}
2902 The debugger convenience variable @samp{$_thread} contains the number
2903 of the current thread. You may find this useful in writing breakpoint
2904 conditional expressions, command scripts, and so forth. See
2905 @xref{Convenience Vars,, Convenience Variables}, for general
2906 information on convenience variables.
2908 @kindex thread apply
2909 @cindex apply command to several threads
2910 @item thread apply [@var{threadno} | all] @var{command}
2911 The @code{thread apply} command allows you to apply the named
2912 @var{command} to one or more threads. Specify the numbers of the
2913 threads that you want affected with the command argument
2914 @var{threadno}. It can be a single thread number, one of the numbers
2915 shown in the first field of the @samp{info threads} display; or it
2916 could be a range of thread numbers, as in @code{2-4}. To apply a
2917 command to all threads, type @kbd{thread apply all @var{command}}.
2920 @cindex name a thread
2921 @item thread name [@var{name}]
2922 This command assigns a name to the current thread. If no argument is
2923 given, any existing user-specified name is removed. The thread name
2924 appears in the @samp{info threads} display.
2926 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2927 determine the name of the thread as given by the OS. On these
2928 systems, a name specified with @samp{thread name} will override the
2929 system-give name, and removing the user-specified name will cause
2930 @value{GDBN} to once again display the system-specified name.
2933 @cindex search for a thread
2934 @item thread find [@var{regexp}]
2935 Search for and display thread ids whose name or @var{systag}
2936 matches the supplied regular expression.
2938 As well as being the complement to the @samp{thread name} command,
2939 this command also allows you to identify a thread by its target
2940 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2944 (@value{GDBN}) thread find 26688
2945 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2946 (@value{GDBN}) info thread 4
2948 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
2951 @kindex set print thread-events
2952 @cindex print messages on thread start and exit
2953 @item set print thread-events
2954 @itemx set print thread-events on
2955 @itemx set print thread-events off
2956 The @code{set print thread-events} command allows you to enable or
2957 disable printing of messages when @value{GDBN} notices that new threads have
2958 started or that threads have exited. By default, these messages will
2959 be printed if detection of these events is supported by the target.
2960 Note that these messages cannot be disabled on all targets.
2962 @kindex show print thread-events
2963 @item show print thread-events
2964 Show whether messages will be printed when @value{GDBN} detects that threads
2965 have started and exited.
2968 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2969 more information about how @value{GDBN} behaves when you stop and start
2970 programs with multiple threads.
2972 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2973 watchpoints in programs with multiple threads.
2975 @anchor{set libthread-db-search-path}
2977 @kindex set libthread-db-search-path
2978 @cindex search path for @code{libthread_db}
2979 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2980 If this variable is set, @var{path} is a colon-separated list of
2981 directories @value{GDBN} will use to search for @code{libthread_db}.
2982 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2983 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
2984 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
2987 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2988 @code{libthread_db} library to obtain information about threads in the
2989 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2990 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
2991 specific thread debugging library loading is enabled
2992 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
2994 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
2995 refers to the default system directories that are
2996 normally searched for loading shared libraries. The @samp{$sdir} entry
2997 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
2998 (@pxref{libthread_db.so.1 file}).
3000 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3001 refers to the directory from which @code{libpthread}
3002 was loaded in the inferior process.
3004 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3005 @value{GDBN} attempts to initialize it with the current inferior process.
3006 If this initialization fails (which could happen because of a version
3007 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3008 will unload @code{libthread_db}, and continue with the next directory.
3009 If none of @code{libthread_db} libraries initialize successfully,
3010 @value{GDBN} will issue a warning and thread debugging will be disabled.
3012 Setting @code{libthread-db-search-path} is currently implemented
3013 only on some platforms.
3015 @kindex show libthread-db-search-path
3016 @item show libthread-db-search-path
3017 Display current libthread_db search path.
3019 @kindex set debug libthread-db
3020 @kindex show debug libthread-db
3021 @cindex debugging @code{libthread_db}
3022 @item set debug libthread-db
3023 @itemx show debug libthread-db
3024 Turns on or off display of @code{libthread_db}-related events.
3025 Use @code{1} to enable, @code{0} to disable.
3029 @section Debugging Forks
3031 @cindex fork, debugging programs which call
3032 @cindex multiple processes
3033 @cindex processes, multiple
3034 On most systems, @value{GDBN} has no special support for debugging
3035 programs which create additional processes using the @code{fork}
3036 function. When a program forks, @value{GDBN} will continue to debug the
3037 parent process and the child process will run unimpeded. If you have
3038 set a breakpoint in any code which the child then executes, the child
3039 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3040 will cause it to terminate.
3042 However, if you want to debug the child process there is a workaround
3043 which isn't too painful. Put a call to @code{sleep} in the code which
3044 the child process executes after the fork. It may be useful to sleep
3045 only if a certain environment variable is set, or a certain file exists,
3046 so that the delay need not occur when you don't want to run @value{GDBN}
3047 on the child. While the child is sleeping, use the @code{ps} program to
3048 get its process ID. Then tell @value{GDBN} (a new invocation of
3049 @value{GDBN} if you are also debugging the parent process) to attach to
3050 the child process (@pxref{Attach}). From that point on you can debug
3051 the child process just like any other process which you attached to.
3053 On some systems, @value{GDBN} provides support for debugging programs that
3054 create additional processes using the @code{fork} or @code{vfork} functions.
3055 Currently, the only platforms with this feature are HP-UX (11.x and later
3056 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
3058 By default, when a program forks, @value{GDBN} will continue to debug
3059 the parent process and the child process will run unimpeded.
3061 If you want to follow the child process instead of the parent process,
3062 use the command @w{@code{set follow-fork-mode}}.
3065 @kindex set follow-fork-mode
3066 @item set follow-fork-mode @var{mode}
3067 Set the debugger response to a program call of @code{fork} or
3068 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3069 process. The @var{mode} argument can be:
3073 The original process is debugged after a fork. The child process runs
3074 unimpeded. This is the default.
3077 The new process is debugged after a fork. The parent process runs
3082 @kindex show follow-fork-mode
3083 @item show follow-fork-mode
3084 Display the current debugger response to a @code{fork} or @code{vfork} call.
3087 @cindex debugging multiple processes
3088 On Linux, if you want to debug both the parent and child processes, use the
3089 command @w{@code{set detach-on-fork}}.
3092 @kindex set detach-on-fork
3093 @item set detach-on-fork @var{mode}
3094 Tells gdb whether to detach one of the processes after a fork, or
3095 retain debugger control over them both.
3099 The child process (or parent process, depending on the value of
3100 @code{follow-fork-mode}) will be detached and allowed to run
3101 independently. This is the default.
3104 Both processes will be held under the control of @value{GDBN}.
3105 One process (child or parent, depending on the value of
3106 @code{follow-fork-mode}) is debugged as usual, while the other
3111 @kindex show detach-on-fork
3112 @item show detach-on-fork
3113 Show whether detach-on-fork mode is on/off.
3116 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3117 will retain control of all forked processes (including nested forks).
3118 You can list the forked processes under the control of @value{GDBN} by
3119 using the @w{@code{info inferiors}} command, and switch from one fork
3120 to another by using the @code{inferior} command (@pxref{Inferiors and
3121 Programs, ,Debugging Multiple Inferiors and Programs}).
3123 To quit debugging one of the forked processes, you can either detach
3124 from it by using the @w{@code{detach inferiors}} command (allowing it
3125 to run independently), or kill it using the @w{@code{kill inferiors}}
3126 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3129 If you ask to debug a child process and a @code{vfork} is followed by an
3130 @code{exec}, @value{GDBN} executes the new target up to the first
3131 breakpoint in the new target. If you have a breakpoint set on
3132 @code{main} in your original program, the breakpoint will also be set on
3133 the child process's @code{main}.
3135 On some systems, when a child process is spawned by @code{vfork}, you
3136 cannot debug the child or parent until an @code{exec} call completes.
3138 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3139 call executes, the new target restarts. To restart the parent
3140 process, use the @code{file} command with the parent executable name
3141 as its argument. By default, after an @code{exec} call executes,
3142 @value{GDBN} discards the symbols of the previous executable image.
3143 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3147 @kindex set follow-exec-mode
3148 @item set follow-exec-mode @var{mode}
3150 Set debugger response to a program call of @code{exec}. An
3151 @code{exec} call replaces the program image of a process.
3153 @code{follow-exec-mode} can be:
3157 @value{GDBN} creates a new inferior and rebinds the process to this
3158 new inferior. The program the process was running before the
3159 @code{exec} call can be restarted afterwards by restarting the
3165 (@value{GDBP}) info inferiors
3167 Id Description Executable
3170 process 12020 is executing new program: prog2
3171 Program exited normally.
3172 (@value{GDBP}) info inferiors
3173 Id Description Executable
3179 @value{GDBN} keeps the process bound to the same inferior. The new
3180 executable image replaces the previous executable loaded in the
3181 inferior. Restarting the inferior after the @code{exec} call, with
3182 e.g., the @code{run} command, restarts the executable the process was
3183 running after the @code{exec} call. This is the default mode.
3188 (@value{GDBP}) info inferiors
3189 Id Description Executable
3192 process 12020 is executing new program: prog2
3193 Program exited normally.
3194 (@value{GDBP}) info inferiors
3195 Id Description Executable
3202 You can use the @code{catch} command to make @value{GDBN} stop whenever
3203 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3204 Catchpoints, ,Setting Catchpoints}.
3206 @node Checkpoint/Restart
3207 @section Setting a @emph{Bookmark} to Return to Later
3212 @cindex snapshot of a process
3213 @cindex rewind program state
3215 On certain operating systems@footnote{Currently, only
3216 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3217 program's state, called a @dfn{checkpoint}, and come back to it
3220 Returning to a checkpoint effectively undoes everything that has
3221 happened in the program since the @code{checkpoint} was saved. This
3222 includes changes in memory, registers, and even (within some limits)
3223 system state. Effectively, it is like going back in time to the
3224 moment when the checkpoint was saved.
3226 Thus, if you're stepping thru a program and you think you're
3227 getting close to the point where things go wrong, you can save
3228 a checkpoint. Then, if you accidentally go too far and miss
3229 the critical statement, instead of having to restart your program
3230 from the beginning, you can just go back to the checkpoint and
3231 start again from there.
3233 This can be especially useful if it takes a lot of time or
3234 steps to reach the point where you think the bug occurs.
3236 To use the @code{checkpoint}/@code{restart} method of debugging:
3241 Save a snapshot of the debugged program's current execution state.
3242 The @code{checkpoint} command takes no arguments, but each checkpoint
3243 is assigned a small integer id, similar to a breakpoint id.
3245 @kindex info checkpoints
3246 @item info checkpoints
3247 List the checkpoints that have been saved in the current debugging
3248 session. For each checkpoint, the following information will be
3255 @item Source line, or label
3258 @kindex restart @var{checkpoint-id}
3259 @item restart @var{checkpoint-id}
3260 Restore the program state that was saved as checkpoint number
3261 @var{checkpoint-id}. All program variables, registers, stack frames
3262 etc.@: will be returned to the values that they had when the checkpoint
3263 was saved. In essence, gdb will ``wind back the clock'' to the point
3264 in time when the checkpoint was saved.
3266 Note that breakpoints, @value{GDBN} variables, command history etc.
3267 are not affected by restoring a checkpoint. In general, a checkpoint
3268 only restores things that reside in the program being debugged, not in
3271 @kindex delete checkpoint @var{checkpoint-id}
3272 @item delete checkpoint @var{checkpoint-id}
3273 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3277 Returning to a previously saved checkpoint will restore the user state
3278 of the program being debugged, plus a significant subset of the system
3279 (OS) state, including file pointers. It won't ``un-write'' data from
3280 a file, but it will rewind the file pointer to the previous location,
3281 so that the previously written data can be overwritten. For files
3282 opened in read mode, the pointer will also be restored so that the
3283 previously read data can be read again.
3285 Of course, characters that have been sent to a printer (or other
3286 external device) cannot be ``snatched back'', and characters received
3287 from eg.@: a serial device can be removed from internal program buffers,
3288 but they cannot be ``pushed back'' into the serial pipeline, ready to
3289 be received again. Similarly, the actual contents of files that have
3290 been changed cannot be restored (at this time).
3292 However, within those constraints, you actually can ``rewind'' your
3293 program to a previously saved point in time, and begin debugging it
3294 again --- and you can change the course of events so as to debug a
3295 different execution path this time.
3297 @cindex checkpoints and process id
3298 Finally, there is one bit of internal program state that will be
3299 different when you return to a checkpoint --- the program's process
3300 id. Each checkpoint will have a unique process id (or @var{pid}),
3301 and each will be different from the program's original @var{pid}.
3302 If your program has saved a local copy of its process id, this could
3303 potentially pose a problem.
3305 @subsection A Non-obvious Benefit of Using Checkpoints
3307 On some systems such as @sc{gnu}/Linux, address space randomization
3308 is performed on new processes for security reasons. This makes it
3309 difficult or impossible to set a breakpoint, or watchpoint, on an
3310 absolute address if you have to restart the program, since the
3311 absolute location of a symbol will change from one execution to the
3314 A checkpoint, however, is an @emph{identical} copy of a process.
3315 Therefore if you create a checkpoint at (eg.@:) the start of main,
3316 and simply return to that checkpoint instead of restarting the
3317 process, you can avoid the effects of address randomization and
3318 your symbols will all stay in the same place.
3321 @chapter Stopping and Continuing
3323 The principal purposes of using a debugger are so that you can stop your
3324 program before it terminates; or so that, if your program runs into
3325 trouble, you can investigate and find out why.
3327 Inside @value{GDBN}, your program may stop for any of several reasons,
3328 such as a signal, a breakpoint, or reaching a new line after a
3329 @value{GDBN} command such as @code{step}. You may then examine and
3330 change variables, set new breakpoints or remove old ones, and then
3331 continue execution. Usually, the messages shown by @value{GDBN} provide
3332 ample explanation of the status of your program---but you can also
3333 explicitly request this information at any time.
3336 @kindex info program
3338 Display information about the status of your program: whether it is
3339 running or not, what process it is, and why it stopped.
3343 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3344 * Continuing and Stepping:: Resuming execution
3345 * Skipping Over Functions and Files::
3346 Skipping over functions and files
3348 * Thread Stops:: Stopping and starting multi-thread programs
3352 @section Breakpoints, Watchpoints, and Catchpoints
3355 A @dfn{breakpoint} makes your program stop whenever a certain point in
3356 the program is reached. For each breakpoint, you can add conditions to
3357 control in finer detail whether your program stops. You can set
3358 breakpoints with the @code{break} command and its variants (@pxref{Set
3359 Breaks, ,Setting Breakpoints}), to specify the place where your program
3360 should stop by line number, function name or exact address in the
3363 On some systems, you can set breakpoints in shared libraries before
3364 the executable is run. There is a minor limitation on HP-UX systems:
3365 you must wait until the executable is run in order to set breakpoints
3366 in shared library routines that are not called directly by the program
3367 (for example, routines that are arguments in a @code{pthread_create}
3371 @cindex data breakpoints
3372 @cindex memory tracing
3373 @cindex breakpoint on memory address
3374 @cindex breakpoint on variable modification
3375 A @dfn{watchpoint} is a special breakpoint that stops your program
3376 when the value of an expression changes. The expression may be a value
3377 of a variable, or it could involve values of one or more variables
3378 combined by operators, such as @samp{a + b}. This is sometimes called
3379 @dfn{data breakpoints}. You must use a different command to set
3380 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3381 from that, you can manage a watchpoint like any other breakpoint: you
3382 enable, disable, and delete both breakpoints and watchpoints using the
3385 You can arrange to have values from your program displayed automatically
3386 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3390 @cindex breakpoint on events
3391 A @dfn{catchpoint} is another special breakpoint that stops your program
3392 when a certain kind of event occurs, such as the throwing of a C@t{++}
3393 exception or the loading of a library. As with watchpoints, you use a
3394 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3395 Catchpoints}), but aside from that, you can manage a catchpoint like any
3396 other breakpoint. (To stop when your program receives a signal, use the
3397 @code{handle} command; see @ref{Signals, ,Signals}.)
3399 @cindex breakpoint numbers
3400 @cindex numbers for breakpoints
3401 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3402 catchpoint when you create it; these numbers are successive integers
3403 starting with one. In many of the commands for controlling various
3404 features of breakpoints you use the breakpoint number to say which
3405 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3406 @dfn{disabled}; if disabled, it has no effect on your program until you
3409 @cindex breakpoint ranges
3410 @cindex ranges of breakpoints
3411 Some @value{GDBN} commands accept a range of breakpoints on which to
3412 operate. A breakpoint range is either a single breakpoint number, like
3413 @samp{5}, or two such numbers, in increasing order, separated by a
3414 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3415 all breakpoints in that range are operated on.
3418 * Set Breaks:: Setting breakpoints
3419 * Set Watchpoints:: Setting watchpoints
3420 * Set Catchpoints:: Setting catchpoints
3421 * Delete Breaks:: Deleting breakpoints
3422 * Disabling:: Disabling breakpoints
3423 * Conditions:: Break conditions
3424 * Break Commands:: Breakpoint command lists
3425 * Dynamic Printf:: Dynamic printf
3426 * Save Breakpoints:: How to save breakpoints in a file
3427 * Static Probe Points:: Listing static probe points
3428 * Error in Breakpoints:: ``Cannot insert breakpoints''
3429 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3433 @subsection Setting Breakpoints
3435 @c FIXME LMB what does GDB do if no code on line of breakpt?
3436 @c consider in particular declaration with/without initialization.
3438 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3441 @kindex b @r{(@code{break})}
3442 @vindex $bpnum@r{, convenience variable}
3443 @cindex latest breakpoint
3444 Breakpoints are set with the @code{break} command (abbreviated
3445 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3446 number of the breakpoint you've set most recently; see @ref{Convenience
3447 Vars,, Convenience Variables}, for a discussion of what you can do with
3448 convenience variables.
3451 @item break @var{location}
3452 Set a breakpoint at the given @var{location}, which can specify a
3453 function name, a line number, or an address of an instruction.
3454 (@xref{Specify Location}, for a list of all the possible ways to
3455 specify a @var{location}.) The breakpoint will stop your program just
3456 before it executes any of the code in the specified @var{location}.
3458 When using source languages that permit overloading of symbols, such as
3459 C@t{++}, a function name may refer to more than one possible place to break.
3460 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3463 It is also possible to insert a breakpoint that will stop the program
3464 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3465 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3468 When called without any arguments, @code{break} sets a breakpoint at
3469 the next instruction to be executed in the selected stack frame
3470 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3471 innermost, this makes your program stop as soon as control
3472 returns to that frame. This is similar to the effect of a
3473 @code{finish} command in the frame inside the selected frame---except
3474 that @code{finish} does not leave an active breakpoint. If you use
3475 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3476 the next time it reaches the current location; this may be useful
3479 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3480 least one instruction has been executed. If it did not do this, you
3481 would be unable to proceed past a breakpoint without first disabling the
3482 breakpoint. This rule applies whether or not the breakpoint already
3483 existed when your program stopped.
3485 @item break @dots{} if @var{cond}
3486 Set a breakpoint with condition @var{cond}; evaluate the expression
3487 @var{cond} each time the breakpoint is reached, and stop only if the
3488 value is nonzero---that is, if @var{cond} evaluates as true.
3489 @samp{@dots{}} stands for one of the possible arguments described
3490 above (or no argument) specifying where to break. @xref{Conditions,
3491 ,Break Conditions}, for more information on breakpoint conditions.
3494 @item tbreak @var{args}
3495 Set a breakpoint enabled only for one stop. @var{args} are the
3496 same as for the @code{break} command, and the breakpoint is set in the same
3497 way, but the breakpoint is automatically deleted after the first time your
3498 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3501 @cindex hardware breakpoints
3502 @item hbreak @var{args}
3503 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3504 @code{break} command and the breakpoint is set in the same way, but the
3505 breakpoint requires hardware support and some target hardware may not
3506 have this support. The main purpose of this is EPROM/ROM code
3507 debugging, so you can set a breakpoint at an instruction without
3508 changing the instruction. This can be used with the new trap-generation
3509 provided by SPARClite DSU and most x86-based targets. These targets
3510 will generate traps when a program accesses some data or instruction
3511 address that is assigned to the debug registers. However the hardware
3512 breakpoint registers can take a limited number of breakpoints. For
3513 example, on the DSU, only two data breakpoints can be set at a time, and
3514 @value{GDBN} will reject this command if more than two are used. Delete
3515 or disable unused hardware breakpoints before setting new ones
3516 (@pxref{Disabling, ,Disabling Breakpoints}).
3517 @xref{Conditions, ,Break Conditions}.
3518 For remote targets, you can restrict the number of hardware
3519 breakpoints @value{GDBN} will use, see @ref{set remote
3520 hardware-breakpoint-limit}.
3523 @item thbreak @var{args}
3524 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3525 are the same as for the @code{hbreak} command and the breakpoint is set in
3526 the same way. However, like the @code{tbreak} command,
3527 the breakpoint is automatically deleted after the
3528 first time your program stops there. Also, like the @code{hbreak}
3529 command, the breakpoint requires hardware support and some target hardware
3530 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3531 See also @ref{Conditions, ,Break Conditions}.
3534 @cindex regular expression
3535 @cindex breakpoints at functions matching a regexp
3536 @cindex set breakpoints in many functions
3537 @item rbreak @var{regex}
3538 Set breakpoints on all functions matching the regular expression
3539 @var{regex}. This command sets an unconditional breakpoint on all
3540 matches, printing a list of all breakpoints it set. Once these
3541 breakpoints are set, they are treated just like the breakpoints set with
3542 the @code{break} command. You can delete them, disable them, or make
3543 them conditional the same way as any other breakpoint.
3545 The syntax of the regular expression is the standard one used with tools
3546 like @file{grep}. Note that this is different from the syntax used by
3547 shells, so for instance @code{foo*} matches all functions that include
3548 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3549 @code{.*} leading and trailing the regular expression you supply, so to
3550 match only functions that begin with @code{foo}, use @code{^foo}.
3552 @cindex non-member C@t{++} functions, set breakpoint in
3553 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3554 breakpoints on overloaded functions that are not members of any special
3557 @cindex set breakpoints on all functions
3558 The @code{rbreak} command can be used to set breakpoints in
3559 @strong{all} the functions in a program, like this:
3562 (@value{GDBP}) rbreak .
3565 @item rbreak @var{file}:@var{regex}
3566 If @code{rbreak} is called with a filename qualification, it limits
3567 the search for functions matching the given regular expression to the
3568 specified @var{file}. This can be used, for example, to set breakpoints on
3569 every function in a given file:
3572 (@value{GDBP}) rbreak file.c:.
3575 The colon separating the filename qualifier from the regex may
3576 optionally be surrounded by spaces.
3578 @kindex info breakpoints
3579 @cindex @code{$_} and @code{info breakpoints}
3580 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3581 @itemx info break @r{[}@var{n}@dots{}@r{]}
3582 Print a table of all breakpoints, watchpoints, and catchpoints set and
3583 not deleted. Optional argument @var{n} means print information only
3584 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3585 For each breakpoint, following columns are printed:
3588 @item Breakpoint Numbers
3590 Breakpoint, watchpoint, or catchpoint.
3592 Whether the breakpoint is marked to be disabled or deleted when hit.
3593 @item Enabled or Disabled
3594 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3595 that are not enabled.
3597 Where the breakpoint is in your program, as a memory address. For a
3598 pending breakpoint whose address is not yet known, this field will
3599 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3600 library that has the symbol or line referred by breakpoint is loaded.
3601 See below for details. A breakpoint with several locations will
3602 have @samp{<MULTIPLE>} in this field---see below for details.
3604 Where the breakpoint is in the source for your program, as a file and
3605 line number. For a pending breakpoint, the original string passed to
3606 the breakpoint command will be listed as it cannot be resolved until
3607 the appropriate shared library is loaded in the future.
3611 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3612 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3613 @value{GDBN} on the host's side. If it is ``target'', then the condition
3614 is evaluated by the target. The @code{info break} command shows
3615 the condition on the line following the affected breakpoint, together with
3616 its condition evaluation mode in between parentheses.
3618 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3619 allowed to have a condition specified for it. The condition is not parsed for
3620 validity until a shared library is loaded that allows the pending
3621 breakpoint to resolve to a valid location.
3624 @code{info break} with a breakpoint
3625 number @var{n} as argument lists only that breakpoint. The
3626 convenience variable @code{$_} and the default examining-address for
3627 the @code{x} command are set to the address of the last breakpoint
3628 listed (@pxref{Memory, ,Examining Memory}).
3631 @code{info break} displays a count of the number of times the breakpoint
3632 has been hit. This is especially useful in conjunction with the
3633 @code{ignore} command. You can ignore a large number of breakpoint
3634 hits, look at the breakpoint info to see how many times the breakpoint
3635 was hit, and then run again, ignoring one less than that number. This
3636 will get you quickly to the last hit of that breakpoint.
3639 For a breakpoints with an enable count (xref) greater than 1,
3640 @code{info break} also displays that count.
3644 @value{GDBN} allows you to set any number of breakpoints at the same place in
3645 your program. There is nothing silly or meaningless about this. When
3646 the breakpoints are conditional, this is even useful
3647 (@pxref{Conditions, ,Break Conditions}).
3649 @cindex multiple locations, breakpoints
3650 @cindex breakpoints, multiple locations
3651 It is possible that a breakpoint corresponds to several locations
3652 in your program. Examples of this situation are:
3656 Multiple functions in the program may have the same name.
3659 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3660 instances of the function body, used in different cases.
3663 For a C@t{++} template function, a given line in the function can
3664 correspond to any number of instantiations.
3667 For an inlined function, a given source line can correspond to
3668 several places where that function is inlined.
3671 In all those cases, @value{GDBN} will insert a breakpoint at all
3672 the relevant locations.
3674 A breakpoint with multiple locations is displayed in the breakpoint
3675 table using several rows---one header row, followed by one row for
3676 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3677 address column. The rows for individual locations contain the actual
3678 addresses for locations, and show the functions to which those
3679 locations belong. The number column for a location is of the form
3680 @var{breakpoint-number}.@var{location-number}.
3685 Num Type Disp Enb Address What
3686 1 breakpoint keep y <MULTIPLE>
3688 breakpoint already hit 1 time
3689 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3690 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3693 Each location can be individually enabled or disabled by passing
3694 @var{breakpoint-number}.@var{location-number} as argument to the
3695 @code{enable} and @code{disable} commands. Note that you cannot
3696 delete the individual locations from the list, you can only delete the
3697 entire list of locations that belong to their parent breakpoint (with
3698 the @kbd{delete @var{num}} command, where @var{num} is the number of
3699 the parent breakpoint, 1 in the above example). Disabling or enabling
3700 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3701 that belong to that breakpoint.
3703 @cindex pending breakpoints
3704 It's quite common to have a breakpoint inside a shared library.
3705 Shared libraries can be loaded and unloaded explicitly,
3706 and possibly repeatedly, as the program is executed. To support
3707 this use case, @value{GDBN} updates breakpoint locations whenever
3708 any shared library is loaded or unloaded. Typically, you would
3709 set a breakpoint in a shared library at the beginning of your
3710 debugging session, when the library is not loaded, and when the
3711 symbols from the library are not available. When you try to set
3712 breakpoint, @value{GDBN} will ask you if you want to set
3713 a so called @dfn{pending breakpoint}---breakpoint whose address
3714 is not yet resolved.
3716 After the program is run, whenever a new shared library is loaded,
3717 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3718 shared library contains the symbol or line referred to by some
3719 pending breakpoint, that breakpoint is resolved and becomes an
3720 ordinary breakpoint. When a library is unloaded, all breakpoints
3721 that refer to its symbols or source lines become pending again.
3723 This logic works for breakpoints with multiple locations, too. For
3724 example, if you have a breakpoint in a C@t{++} template function, and
3725 a newly loaded shared library has an instantiation of that template,
3726 a new location is added to the list of locations for the breakpoint.
3728 Except for having unresolved address, pending breakpoints do not
3729 differ from regular breakpoints. You can set conditions or commands,
3730 enable and disable them and perform other breakpoint operations.
3732 @value{GDBN} provides some additional commands for controlling what
3733 happens when the @samp{break} command cannot resolve breakpoint
3734 address specification to an address:
3736 @kindex set breakpoint pending
3737 @kindex show breakpoint pending
3739 @item set breakpoint pending auto
3740 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3741 location, it queries you whether a pending breakpoint should be created.
3743 @item set breakpoint pending on
3744 This indicates that an unrecognized breakpoint location should automatically
3745 result in a pending breakpoint being created.
3747 @item set breakpoint pending off
3748 This indicates that pending breakpoints are not to be created. Any
3749 unrecognized breakpoint location results in an error. This setting does
3750 not affect any pending breakpoints previously created.
3752 @item show breakpoint pending
3753 Show the current behavior setting for creating pending breakpoints.
3756 The settings above only affect the @code{break} command and its
3757 variants. Once breakpoint is set, it will be automatically updated
3758 as shared libraries are loaded and unloaded.
3760 @cindex automatic hardware breakpoints
3761 For some targets, @value{GDBN} can automatically decide if hardware or
3762 software breakpoints should be used, depending on whether the
3763 breakpoint address is read-only or read-write. This applies to
3764 breakpoints set with the @code{break} command as well as to internal
3765 breakpoints set by commands like @code{next} and @code{finish}. For
3766 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3769 You can control this automatic behaviour with the following commands::
3771 @kindex set breakpoint auto-hw
3772 @kindex show breakpoint auto-hw
3774 @item set breakpoint auto-hw on
3775 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3776 will try to use the target memory map to decide if software or hardware
3777 breakpoint must be used.
3779 @item set breakpoint auto-hw off
3780 This indicates @value{GDBN} should not automatically select breakpoint
3781 type. If the target provides a memory map, @value{GDBN} will warn when
3782 trying to set software breakpoint at a read-only address.
3785 @value{GDBN} normally implements breakpoints by replacing the program code
3786 at the breakpoint address with a special instruction, which, when
3787 executed, given control to the debugger. By default, the program
3788 code is so modified only when the program is resumed. As soon as
3789 the program stops, @value{GDBN} restores the original instructions. This
3790 behaviour guards against leaving breakpoints inserted in the
3791 target should gdb abrubptly disconnect. However, with slow remote
3792 targets, inserting and removing breakpoint can reduce the performance.
3793 This behavior can be controlled with the following commands::
3795 @kindex set breakpoint always-inserted
3796 @kindex show breakpoint always-inserted
3798 @item set breakpoint always-inserted off
3799 All breakpoints, including newly added by the user, are inserted in
3800 the target only when the target is resumed. All breakpoints are
3801 removed from the target when it stops.
3803 @item set breakpoint always-inserted on
3804 Causes all breakpoints to be inserted in the target at all times. If
3805 the user adds a new breakpoint, or changes an existing breakpoint, the
3806 breakpoints in the target are updated immediately. A breakpoint is
3807 removed from the target only when breakpoint itself is removed.
3809 @cindex non-stop mode, and @code{breakpoint always-inserted}
3810 @item set breakpoint always-inserted auto
3811 This is the default mode. If @value{GDBN} is controlling the inferior
3812 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3813 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3814 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3815 @code{breakpoint always-inserted} mode is off.
3818 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3819 when a breakpoint breaks. If the condition is true, then the process being
3820 debugged stops, otherwise the process is resumed.
3822 If the target supports evaluating conditions on its end, @value{GDBN} may
3823 download the breakpoint, together with its conditions, to it.
3825 This feature can be controlled via the following commands:
3827 @kindex set breakpoint condition-evaluation
3828 @kindex show breakpoint condition-evaluation
3830 @item set breakpoint condition-evaluation host
3831 This option commands @value{GDBN} to evaluate the breakpoint
3832 conditions on the host's side. Unconditional breakpoints are sent to
3833 the target which in turn receives the triggers and reports them back to GDB
3834 for condition evaluation. This is the standard evaluation mode.
3836 @item set breakpoint condition-evaluation target
3837 This option commands @value{GDBN} to download breakpoint conditions
3838 to the target at the moment of their insertion. The target
3839 is responsible for evaluating the conditional expression and reporting
3840 breakpoint stop events back to @value{GDBN} whenever the condition
3841 is true. Due to limitations of target-side evaluation, some conditions
3842 cannot be evaluated there, e.g., conditions that depend on local data
3843 that is only known to the host. Examples include
3844 conditional expressions involving convenience variables, complex types
3845 that cannot be handled by the agent expression parser and expressions
3846 that are too long to be sent over to the target, specially when the
3847 target is a remote system. In these cases, the conditions will be
3848 evaluated by @value{GDBN}.
3850 @item set breakpoint condition-evaluation auto
3851 This is the default mode. If the target supports evaluating breakpoint
3852 conditions on its end, @value{GDBN} will download breakpoint conditions to
3853 the target (limitations mentioned previously apply). If the target does
3854 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3855 to evaluating all these conditions on the host's side.
3859 @cindex negative breakpoint numbers
3860 @cindex internal @value{GDBN} breakpoints
3861 @value{GDBN} itself sometimes sets breakpoints in your program for
3862 special purposes, such as proper handling of @code{longjmp} (in C
3863 programs). These internal breakpoints are assigned negative numbers,
3864 starting with @code{-1}; @samp{info breakpoints} does not display them.
3865 You can see these breakpoints with the @value{GDBN} maintenance command
3866 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3869 @node Set Watchpoints
3870 @subsection Setting Watchpoints
3872 @cindex setting watchpoints
3873 You can use a watchpoint to stop execution whenever the value of an
3874 expression changes, without having to predict a particular place where
3875 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3876 The expression may be as simple as the value of a single variable, or
3877 as complex as many variables combined by operators. Examples include:
3881 A reference to the value of a single variable.
3884 An address cast to an appropriate data type. For example,
3885 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3886 address (assuming an @code{int} occupies 4 bytes).
3889 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3890 expression can use any operators valid in the program's native
3891 language (@pxref{Languages}).
3894 You can set a watchpoint on an expression even if the expression can
3895 not be evaluated yet. For instance, you can set a watchpoint on
3896 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3897 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3898 the expression produces a valid value. If the expression becomes
3899 valid in some other way than changing a variable (e.g.@: if the memory
3900 pointed to by @samp{*global_ptr} becomes readable as the result of a
3901 @code{malloc} call), @value{GDBN} may not stop until the next time
3902 the expression changes.
3904 @cindex software watchpoints
3905 @cindex hardware watchpoints
3906 Depending on your system, watchpoints may be implemented in software or
3907 hardware. @value{GDBN} does software watchpointing by single-stepping your
3908 program and testing the variable's value each time, which is hundreds of
3909 times slower than normal execution. (But this may still be worth it, to
3910 catch errors where you have no clue what part of your program is the
3913 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3914 x86-based targets, @value{GDBN} includes support for hardware
3915 watchpoints, which do not slow down the running of your program.
3919 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3920 Set a watchpoint for an expression. @value{GDBN} will break when the
3921 expression @var{expr} is written into by the program and its value
3922 changes. The simplest (and the most popular) use of this command is
3923 to watch the value of a single variable:
3926 (@value{GDBP}) watch foo
3929 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3930 argument, @value{GDBN} breaks only when the thread identified by
3931 @var{threadnum} changes the value of @var{expr}. If any other threads
3932 change the value of @var{expr}, @value{GDBN} will not break. Note
3933 that watchpoints restricted to a single thread in this way only work
3934 with Hardware Watchpoints.
3936 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3937 (see below). The @code{-location} argument tells @value{GDBN} to
3938 instead watch the memory referred to by @var{expr}. In this case,
3939 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3940 and watch the memory at that address. The type of the result is used
3941 to determine the size of the watched memory. If the expression's
3942 result does not have an address, then @value{GDBN} will print an
3945 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3946 of masked watchpoints, if the current architecture supports this
3947 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3948 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3949 to an address to watch. The mask specifies that some bits of an address
3950 (the bits which are reset in the mask) should be ignored when matching
3951 the address accessed by the inferior against the watchpoint address.
3952 Thus, a masked watchpoint watches many addresses simultaneously---those
3953 addresses whose unmasked bits are identical to the unmasked bits in the
3954 watchpoint address. The @code{mask} argument implies @code{-location}.
3958 (@value{GDBP}) watch foo mask 0xffff00ff
3959 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
3963 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3964 Set a watchpoint that will break when the value of @var{expr} is read
3968 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3969 Set a watchpoint that will break when @var{expr} is either read from
3970 or written into by the program.
3972 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
3973 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
3974 This command prints a list of watchpoints, using the same format as
3975 @code{info break} (@pxref{Set Breaks}).
3978 If you watch for a change in a numerically entered address you need to
3979 dereference it, as the address itself is just a constant number which will
3980 never change. @value{GDBN} refuses to create a watchpoint that watches
3981 a never-changing value:
3984 (@value{GDBP}) watch 0x600850
3985 Cannot watch constant value 0x600850.
3986 (@value{GDBP}) watch *(int *) 0x600850
3987 Watchpoint 1: *(int *) 6293584
3990 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3991 watchpoints execute very quickly, and the debugger reports a change in
3992 value at the exact instruction where the change occurs. If @value{GDBN}
3993 cannot set a hardware watchpoint, it sets a software watchpoint, which
3994 executes more slowly and reports the change in value at the next
3995 @emph{statement}, not the instruction, after the change occurs.
3997 @cindex use only software watchpoints
3998 You can force @value{GDBN} to use only software watchpoints with the
3999 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4000 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4001 the underlying system supports them. (Note that hardware-assisted
4002 watchpoints that were set @emph{before} setting
4003 @code{can-use-hw-watchpoints} to zero will still use the hardware
4004 mechanism of watching expression values.)
4007 @item set can-use-hw-watchpoints
4008 @kindex set can-use-hw-watchpoints
4009 Set whether or not to use hardware watchpoints.
4011 @item show can-use-hw-watchpoints
4012 @kindex show can-use-hw-watchpoints
4013 Show the current mode of using hardware watchpoints.
4016 For remote targets, you can restrict the number of hardware
4017 watchpoints @value{GDBN} will use, see @ref{set remote
4018 hardware-breakpoint-limit}.
4020 When you issue the @code{watch} command, @value{GDBN} reports
4023 Hardware watchpoint @var{num}: @var{expr}
4027 if it was able to set a hardware watchpoint.
4029 Currently, the @code{awatch} and @code{rwatch} commands can only set
4030 hardware watchpoints, because accesses to data that don't change the
4031 value of the watched expression cannot be detected without examining
4032 every instruction as it is being executed, and @value{GDBN} does not do
4033 that currently. If @value{GDBN} finds that it is unable to set a
4034 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4035 will print a message like this:
4038 Expression cannot be implemented with read/access watchpoint.
4041 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4042 data type of the watched expression is wider than what a hardware
4043 watchpoint on the target machine can handle. For example, some systems
4044 can only watch regions that are up to 4 bytes wide; on such systems you
4045 cannot set hardware watchpoints for an expression that yields a
4046 double-precision floating-point number (which is typically 8 bytes
4047 wide). As a work-around, it might be possible to break the large region
4048 into a series of smaller ones and watch them with separate watchpoints.
4050 If you set too many hardware watchpoints, @value{GDBN} might be unable
4051 to insert all of them when you resume the execution of your program.
4052 Since the precise number of active watchpoints is unknown until such
4053 time as the program is about to be resumed, @value{GDBN} might not be
4054 able to warn you about this when you set the watchpoints, and the
4055 warning will be printed only when the program is resumed:
4058 Hardware watchpoint @var{num}: Could not insert watchpoint
4062 If this happens, delete or disable some of the watchpoints.
4064 Watching complex expressions that reference many variables can also
4065 exhaust the resources available for hardware-assisted watchpoints.
4066 That's because @value{GDBN} needs to watch every variable in the
4067 expression with separately allocated resources.
4069 If you call a function interactively using @code{print} or @code{call},
4070 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4071 kind of breakpoint or the call completes.
4073 @value{GDBN} automatically deletes watchpoints that watch local
4074 (automatic) variables, or expressions that involve such variables, when
4075 they go out of scope, that is, when the execution leaves the block in
4076 which these variables were defined. In particular, when the program
4077 being debugged terminates, @emph{all} local variables go out of scope,
4078 and so only watchpoints that watch global variables remain set. If you
4079 rerun the program, you will need to set all such watchpoints again. One
4080 way of doing that would be to set a code breakpoint at the entry to the
4081 @code{main} function and when it breaks, set all the watchpoints.
4083 @cindex watchpoints and threads
4084 @cindex threads and watchpoints
4085 In multi-threaded programs, watchpoints will detect changes to the
4086 watched expression from every thread.
4089 @emph{Warning:} In multi-threaded programs, software watchpoints
4090 have only limited usefulness. If @value{GDBN} creates a software
4091 watchpoint, it can only watch the value of an expression @emph{in a
4092 single thread}. If you are confident that the expression can only
4093 change due to the current thread's activity (and if you are also
4094 confident that no other thread can become current), then you can use
4095 software watchpoints as usual. However, @value{GDBN} may not notice
4096 when a non-current thread's activity changes the expression. (Hardware
4097 watchpoints, in contrast, watch an expression in all threads.)
4100 @xref{set remote hardware-watchpoint-limit}.
4102 @node Set Catchpoints
4103 @subsection Setting Catchpoints
4104 @cindex catchpoints, setting
4105 @cindex exception handlers
4106 @cindex event handling
4108 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4109 kinds of program events, such as C@t{++} exceptions or the loading of a
4110 shared library. Use the @code{catch} command to set a catchpoint.
4114 @item catch @var{event}
4115 Stop when @var{event} occurs. @var{event} can be any of the following:
4118 @item throw @r{[}@var{regexp}@r{]}
4119 @itemx rethrow @r{[}@var{regexp}@r{]}
4120 @itemx catch @r{[}@var{regexp}@r{]}
4122 @kindex catch rethrow
4124 @cindex stop on C@t{++} exceptions
4125 The throwing, re-throwing, or catching of a C@t{++} exception.
4127 If @var{regexp} is given, then only exceptions whose type matches the
4128 regular expression will be caught.
4130 @vindex $_exception@r{, convenience variable}
4131 The convenience variable @code{$_exception} is available at an
4132 exception-related catchpoint, on some systems. This holds the
4133 exception being thrown.
4135 There are currently some limitations to C@t{++} exception handling in
4140 The support for these commands is system-dependent. Currently, only
4141 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4145 The regular expression feature and the @code{$_exception} convenience
4146 variable rely on the presence of some SDT probes in @code{libstdc++}.
4147 If these probes are not present, then these features cannot be used.
4148 These probes were first available in the GCC 4.8 release, but whether
4149 or not they are available in your GCC also depends on how it was
4153 The @code{$_exception} convenience variable is only valid at the
4154 instruction at which an exception-related catchpoint is set.
4157 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4158 location in the system library which implements runtime exception
4159 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4160 (@pxref{Selection}) to get to your code.
4163 If you call a function interactively, @value{GDBN} normally returns
4164 control to you when the function has finished executing. If the call
4165 raises an exception, however, the call may bypass the mechanism that
4166 returns control to you and cause your program either to abort or to
4167 simply continue running until it hits a breakpoint, catches a signal
4168 that @value{GDBN} is listening for, or exits. This is the case even if
4169 you set a catchpoint for the exception; catchpoints on exceptions are
4170 disabled within interactive calls. @xref{Calling}, for information on
4171 controlling this with @code{set unwind-on-terminating-exception}.
4174 You cannot raise an exception interactively.
4177 You cannot install an exception handler interactively.
4181 @kindex catch exception
4182 @cindex Ada exception catching
4183 @cindex catch Ada exceptions
4184 An Ada exception being raised. If an exception name is specified
4185 at the end of the command (eg @code{catch exception Program_Error}),
4186 the debugger will stop only when this specific exception is raised.
4187 Otherwise, the debugger stops execution when any Ada exception is raised.
4189 When inserting an exception catchpoint on a user-defined exception whose
4190 name is identical to one of the exceptions defined by the language, the
4191 fully qualified name must be used as the exception name. Otherwise,
4192 @value{GDBN} will assume that it should stop on the pre-defined exception
4193 rather than the user-defined one. For instance, assuming an exception
4194 called @code{Constraint_Error} is defined in package @code{Pck}, then
4195 the command to use to catch such exceptions is @kbd{catch exception
4196 Pck.Constraint_Error}.
4198 @item exception unhandled
4199 @kindex catch exception unhandled
4200 An exception that was raised but is not handled by the program.
4203 @kindex catch assert
4204 A failed Ada assertion.
4208 @cindex break on fork/exec
4209 A call to @code{exec}. This is currently only available for HP-UX
4213 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4214 @kindex catch syscall
4215 @cindex break on a system call.
4216 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4217 syscall is a mechanism for application programs to request a service
4218 from the operating system (OS) or one of the OS system services.
4219 @value{GDBN} can catch some or all of the syscalls issued by the
4220 debuggee, and show the related information for each syscall. If no
4221 argument is specified, calls to and returns from all system calls
4224 @var{name} can be any system call name that is valid for the
4225 underlying OS. Just what syscalls are valid depends on the OS. On
4226 GNU and Unix systems, you can find the full list of valid syscall
4227 names on @file{/usr/include/asm/unistd.h}.
4229 @c For MS-Windows, the syscall names and the corresponding numbers
4230 @c can be found, e.g., on this URL:
4231 @c http://www.metasploit.com/users/opcode/syscalls.html
4232 @c but we don't support Windows syscalls yet.
4234 Normally, @value{GDBN} knows in advance which syscalls are valid for
4235 each OS, so you can use the @value{GDBN} command-line completion
4236 facilities (@pxref{Completion,, command completion}) to list the
4239 You may also specify the system call numerically. A syscall's
4240 number is the value passed to the OS's syscall dispatcher to
4241 identify the requested service. When you specify the syscall by its
4242 name, @value{GDBN} uses its database of syscalls to convert the name
4243 into the corresponding numeric code, but using the number directly
4244 may be useful if @value{GDBN}'s database does not have the complete
4245 list of syscalls on your system (e.g., because @value{GDBN} lags
4246 behind the OS upgrades).
4248 The example below illustrates how this command works if you don't provide
4252 (@value{GDBP}) catch syscall
4253 Catchpoint 1 (syscall)
4255 Starting program: /tmp/catch-syscall
4257 Catchpoint 1 (call to syscall 'close'), \
4258 0xffffe424 in __kernel_vsyscall ()
4262 Catchpoint 1 (returned from syscall 'close'), \
4263 0xffffe424 in __kernel_vsyscall ()
4267 Here is an example of catching a system call by name:
4270 (@value{GDBP}) catch syscall chroot
4271 Catchpoint 1 (syscall 'chroot' [61])
4273 Starting program: /tmp/catch-syscall
4275 Catchpoint 1 (call to syscall 'chroot'), \
4276 0xffffe424 in __kernel_vsyscall ()
4280 Catchpoint 1 (returned from syscall 'chroot'), \
4281 0xffffe424 in __kernel_vsyscall ()
4285 An example of specifying a system call numerically. In the case
4286 below, the syscall number has a corresponding entry in the XML
4287 file, so @value{GDBN} finds its name and prints it:
4290 (@value{GDBP}) catch syscall 252
4291 Catchpoint 1 (syscall(s) 'exit_group')
4293 Starting program: /tmp/catch-syscall
4295 Catchpoint 1 (call to syscall 'exit_group'), \
4296 0xffffe424 in __kernel_vsyscall ()
4300 Program exited normally.
4304 However, there can be situations when there is no corresponding name
4305 in XML file for that syscall number. In this case, @value{GDBN} prints
4306 a warning message saying that it was not able to find the syscall name,
4307 but the catchpoint will be set anyway. See the example below:
4310 (@value{GDBP}) catch syscall 764
4311 warning: The number '764' does not represent a known syscall.
4312 Catchpoint 2 (syscall 764)
4316 If you configure @value{GDBN} using the @samp{--without-expat} option,
4317 it will not be able to display syscall names. Also, if your
4318 architecture does not have an XML file describing its system calls,
4319 you will not be able to see the syscall names. It is important to
4320 notice that these two features are used for accessing the syscall
4321 name database. In either case, you will see a warning like this:
4324 (@value{GDBP}) catch syscall
4325 warning: Could not open "syscalls/i386-linux.xml"
4326 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4327 GDB will not be able to display syscall names.
4328 Catchpoint 1 (syscall)
4332 Of course, the file name will change depending on your architecture and system.
4334 Still using the example above, you can also try to catch a syscall by its
4335 number. In this case, you would see something like:
4338 (@value{GDBP}) catch syscall 252
4339 Catchpoint 1 (syscall(s) 252)
4342 Again, in this case @value{GDBN} would not be able to display syscall's names.
4346 A call to @code{fork}. This is currently only available for HP-UX
4351 A call to @code{vfork}. This is currently only available for HP-UX
4354 @item load @r{[}regexp@r{]}
4355 @itemx unload @r{[}regexp@r{]}
4357 @kindex catch unload
4358 The loading or unloading of a shared library. If @var{regexp} is
4359 given, then the catchpoint will stop only if the regular expression
4360 matches one of the affected libraries.
4362 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4363 @kindex catch signal
4364 The delivery of a signal.
4366 With no arguments, this catchpoint will catch any signal that is not
4367 used internally by @value{GDBN}, specifically, all signals except
4368 @samp{SIGTRAP} and @samp{SIGINT}.
4370 With the argument @samp{all}, all signals, including those used by
4371 @value{GDBN}, will be caught. This argument cannot be used with other
4374 Otherwise, the arguments are a list of signal names as given to
4375 @code{handle} (@pxref{Signals}). Only signals specified in this list
4378 One reason that @code{catch signal} can be more useful than
4379 @code{handle} is that you can attach commands and conditions to the
4382 When a signal is caught by a catchpoint, the signal's @code{stop} and
4383 @code{print} settings, as specified by @code{handle}, are ignored.
4384 However, whether the signal is still delivered to the inferior depends
4385 on the @code{pass} setting; this can be changed in the catchpoint's
4390 @item tcatch @var{event}
4392 Set a catchpoint that is enabled only for one stop. The catchpoint is
4393 automatically deleted after the first time the event is caught.
4397 Use the @code{info break} command to list the current catchpoints.
4401 @subsection Deleting Breakpoints
4403 @cindex clearing breakpoints, watchpoints, catchpoints
4404 @cindex deleting breakpoints, watchpoints, catchpoints
4405 It is often necessary to eliminate a breakpoint, watchpoint, or
4406 catchpoint once it has done its job and you no longer want your program
4407 to stop there. This is called @dfn{deleting} the breakpoint. A
4408 breakpoint that has been deleted no longer exists; it is forgotten.
4410 With the @code{clear} command you can delete breakpoints according to
4411 where they are in your program. With the @code{delete} command you can
4412 delete individual breakpoints, watchpoints, or catchpoints by specifying
4413 their breakpoint numbers.
4415 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4416 automatically ignores breakpoints on the first instruction to be executed
4417 when you continue execution without changing the execution address.
4422 Delete any breakpoints at the next instruction to be executed in the
4423 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4424 the innermost frame is selected, this is a good way to delete a
4425 breakpoint where your program just stopped.
4427 @item clear @var{location}
4428 Delete any breakpoints set at the specified @var{location}.
4429 @xref{Specify Location}, for the various forms of @var{location}; the
4430 most useful ones are listed below:
4433 @item clear @var{function}
4434 @itemx clear @var{filename}:@var{function}
4435 Delete any breakpoints set at entry to the named @var{function}.
4437 @item clear @var{linenum}
4438 @itemx clear @var{filename}:@var{linenum}
4439 Delete any breakpoints set at or within the code of the specified
4440 @var{linenum} of the specified @var{filename}.
4443 @cindex delete breakpoints
4445 @kindex d @r{(@code{delete})}
4446 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4447 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4448 ranges specified as arguments. If no argument is specified, delete all
4449 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4450 confirm off}). You can abbreviate this command as @code{d}.
4454 @subsection Disabling Breakpoints
4456 @cindex enable/disable a breakpoint
4457 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4458 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4459 it had been deleted, but remembers the information on the breakpoint so
4460 that you can @dfn{enable} it again later.
4462 You disable and enable breakpoints, watchpoints, and catchpoints with
4463 the @code{enable} and @code{disable} commands, optionally specifying
4464 one or more breakpoint numbers as arguments. Use @code{info break} to
4465 print a list of all breakpoints, watchpoints, and catchpoints if you
4466 do not know which numbers to use.
4468 Disabling and enabling a breakpoint that has multiple locations
4469 affects all of its locations.
4471 A breakpoint, watchpoint, or catchpoint can have any of several
4472 different states of enablement:
4476 Enabled. The breakpoint stops your program. A breakpoint set
4477 with the @code{break} command starts out in this state.
4479 Disabled. The breakpoint has no effect on your program.
4481 Enabled once. The breakpoint stops your program, but then becomes
4484 Enabled for a count. The breakpoint stops your program for the next
4485 N times, then becomes disabled.
4487 Enabled for deletion. The breakpoint stops your program, but
4488 immediately after it does so it is deleted permanently. A breakpoint
4489 set with the @code{tbreak} command starts out in this state.
4492 You can use the following commands to enable or disable breakpoints,
4493 watchpoints, and catchpoints:
4497 @kindex dis @r{(@code{disable})}
4498 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4499 Disable the specified breakpoints---or all breakpoints, if none are
4500 listed. A disabled breakpoint has no effect but is not forgotten. All
4501 options such as ignore-counts, conditions and commands are remembered in
4502 case the breakpoint is enabled again later. You may abbreviate
4503 @code{disable} as @code{dis}.
4506 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4507 Enable the specified breakpoints (or all defined breakpoints). They
4508 become effective once again in stopping your program.
4510 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4511 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4512 of these breakpoints immediately after stopping your program.
4514 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4515 Enable the specified breakpoints temporarily. @value{GDBN} records
4516 @var{count} with each of the specified breakpoints, and decrements a
4517 breakpoint's count when it is hit. When any count reaches 0,
4518 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4519 count (@pxref{Conditions, ,Break Conditions}), that will be
4520 decremented to 0 before @var{count} is affected.
4522 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4523 Enable the specified breakpoints to work once, then die. @value{GDBN}
4524 deletes any of these breakpoints as soon as your program stops there.
4525 Breakpoints set by the @code{tbreak} command start out in this state.
4528 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4529 @c confusing: tbreak is also initially enabled.
4530 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4531 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4532 subsequently, they become disabled or enabled only when you use one of
4533 the commands above. (The command @code{until} can set and delete a
4534 breakpoint of its own, but it does not change the state of your other
4535 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4539 @subsection Break Conditions
4540 @cindex conditional breakpoints
4541 @cindex breakpoint conditions
4543 @c FIXME what is scope of break condition expr? Context where wanted?
4544 @c in particular for a watchpoint?
4545 The simplest sort of breakpoint breaks every time your program reaches a
4546 specified place. You can also specify a @dfn{condition} for a
4547 breakpoint. A condition is just a Boolean expression in your
4548 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4549 a condition evaluates the expression each time your program reaches it,
4550 and your program stops only if the condition is @emph{true}.
4552 This is the converse of using assertions for program validation; in that
4553 situation, you want to stop when the assertion is violated---that is,
4554 when the condition is false. In C, if you want to test an assertion expressed
4555 by the condition @var{assert}, you should set the condition
4556 @samp{! @var{assert}} on the appropriate breakpoint.
4558 Conditions are also accepted for watchpoints; you may not need them,
4559 since a watchpoint is inspecting the value of an expression anyhow---but
4560 it might be simpler, say, to just set a watchpoint on a variable name,
4561 and specify a condition that tests whether the new value is an interesting
4564 Break conditions can have side effects, and may even call functions in
4565 your program. This can be useful, for example, to activate functions
4566 that log program progress, or to use your own print functions to
4567 format special data structures. The effects are completely predictable
4568 unless there is another enabled breakpoint at the same address. (In
4569 that case, @value{GDBN} might see the other breakpoint first and stop your
4570 program without checking the condition of this one.) Note that
4571 breakpoint commands are usually more convenient and flexible than break
4573 purpose of performing side effects when a breakpoint is reached
4574 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4576 Breakpoint conditions can also be evaluated on the target's side if
4577 the target supports it. Instead of evaluating the conditions locally,
4578 @value{GDBN} encodes the expression into an agent expression
4579 (@pxref{Agent Expressions}) suitable for execution on the target,
4580 independently of @value{GDBN}. Global variables become raw memory
4581 locations, locals become stack accesses, and so forth.
4583 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4584 when its condition evaluates to true. This mechanism may provide faster
4585 response times depending on the performance characteristics of the target
4586 since it does not need to keep @value{GDBN} informed about
4587 every breakpoint trigger, even those with false conditions.
4589 Break conditions can be specified when a breakpoint is set, by using
4590 @samp{if} in the arguments to the @code{break} command. @xref{Set
4591 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4592 with the @code{condition} command.
4594 You can also use the @code{if} keyword with the @code{watch} command.
4595 The @code{catch} command does not recognize the @code{if} keyword;
4596 @code{condition} is the only way to impose a further condition on a
4601 @item condition @var{bnum} @var{expression}
4602 Specify @var{expression} as the break condition for breakpoint,
4603 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4604 breakpoint @var{bnum} stops your program only if the value of
4605 @var{expression} is true (nonzero, in C). When you use
4606 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4607 syntactic correctness, and to determine whether symbols in it have
4608 referents in the context of your breakpoint. If @var{expression} uses
4609 symbols not referenced in the context of the breakpoint, @value{GDBN}
4610 prints an error message:
4613 No symbol "foo" in current context.
4618 not actually evaluate @var{expression} at the time the @code{condition}
4619 command (or a command that sets a breakpoint with a condition, like
4620 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4622 @item condition @var{bnum}
4623 Remove the condition from breakpoint number @var{bnum}. It becomes
4624 an ordinary unconditional breakpoint.
4627 @cindex ignore count (of breakpoint)
4628 A special case of a breakpoint condition is to stop only when the
4629 breakpoint has been reached a certain number of times. This is so
4630 useful that there is a special way to do it, using the @dfn{ignore
4631 count} of the breakpoint. Every breakpoint has an ignore count, which
4632 is an integer. Most of the time, the ignore count is zero, and
4633 therefore has no effect. But if your program reaches a breakpoint whose
4634 ignore count is positive, then instead of stopping, it just decrements
4635 the ignore count by one and continues. As a result, if the ignore count
4636 value is @var{n}, the breakpoint does not stop the next @var{n} times
4637 your program reaches it.
4641 @item ignore @var{bnum} @var{count}
4642 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4643 The next @var{count} times the breakpoint is reached, your program's
4644 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4647 To make the breakpoint stop the next time it is reached, specify
4650 When you use @code{continue} to resume execution of your program from a
4651 breakpoint, you can specify an ignore count directly as an argument to
4652 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4653 Stepping,,Continuing and Stepping}.
4655 If a breakpoint has a positive ignore count and a condition, the
4656 condition is not checked. Once the ignore count reaches zero,
4657 @value{GDBN} resumes checking the condition.
4659 You could achieve the effect of the ignore count with a condition such
4660 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4661 is decremented each time. @xref{Convenience Vars, ,Convenience
4665 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4668 @node Break Commands
4669 @subsection Breakpoint Command Lists
4671 @cindex breakpoint commands
4672 You can give any breakpoint (or watchpoint or catchpoint) a series of
4673 commands to execute when your program stops due to that breakpoint. For
4674 example, you might want to print the values of certain expressions, or
4675 enable other breakpoints.
4679 @kindex end@r{ (breakpoint commands)}
4680 @item commands @r{[}@var{range}@dots{}@r{]}
4681 @itemx @dots{} @var{command-list} @dots{}
4683 Specify a list of commands for the given breakpoints. The commands
4684 themselves appear on the following lines. Type a line containing just
4685 @code{end} to terminate the commands.
4687 To remove all commands from a breakpoint, type @code{commands} and
4688 follow it immediately with @code{end}; that is, give no commands.
4690 With no argument, @code{commands} refers to the last breakpoint,
4691 watchpoint, or catchpoint set (not to the breakpoint most recently
4692 encountered). If the most recent breakpoints were set with a single
4693 command, then the @code{commands} will apply to all the breakpoints
4694 set by that command. This applies to breakpoints set by
4695 @code{rbreak}, and also applies when a single @code{break} command
4696 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4700 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4701 disabled within a @var{command-list}.
4703 You can use breakpoint commands to start your program up again. Simply
4704 use the @code{continue} command, or @code{step}, or any other command
4705 that resumes execution.
4707 Any other commands in the command list, after a command that resumes
4708 execution, are ignored. This is because any time you resume execution
4709 (even with a simple @code{next} or @code{step}), you may encounter
4710 another breakpoint---which could have its own command list, leading to
4711 ambiguities about which list to execute.
4714 If the first command you specify in a command list is @code{silent}, the
4715 usual message about stopping at a breakpoint is not printed. This may
4716 be desirable for breakpoints that are to print a specific message and
4717 then continue. If none of the remaining commands print anything, you
4718 see no sign that the breakpoint was reached. @code{silent} is
4719 meaningful only at the beginning of a breakpoint command list.
4721 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4722 print precisely controlled output, and are often useful in silent
4723 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4725 For example, here is how you could use breakpoint commands to print the
4726 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4732 printf "x is %d\n",x
4737 One application for breakpoint commands is to compensate for one bug so
4738 you can test for another. Put a breakpoint just after the erroneous line
4739 of code, give it a condition to detect the case in which something
4740 erroneous has been done, and give it commands to assign correct values
4741 to any variables that need them. End with the @code{continue} command
4742 so that your program does not stop, and start with the @code{silent}
4743 command so that no output is produced. Here is an example:
4754 @node Dynamic Printf
4755 @subsection Dynamic Printf
4757 @cindex dynamic printf
4759 The dynamic printf command @code{dprintf} combines a breakpoint with
4760 formatted printing of your program's data to give you the effect of
4761 inserting @code{printf} calls into your program on-the-fly, without
4762 having to recompile it.
4764 In its most basic form, the output goes to the GDB console. However,
4765 you can set the variable @code{dprintf-style} for alternate handling.
4766 For instance, you can ask to format the output by calling your
4767 program's @code{printf} function. This has the advantage that the
4768 characters go to the program's output device, so they can recorded in
4769 redirects to files and so forth.
4771 If you are doing remote debugging with a stub or agent, you can also
4772 ask to have the printf handled by the remote agent. In addition to
4773 ensuring that the output goes to the remote program's device along
4774 with any other output the program might produce, you can also ask that
4775 the dprintf remain active even after disconnecting from the remote
4776 target. Using the stub/agent is also more efficient, as it can do
4777 everything without needing to communicate with @value{GDBN}.
4781 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4782 Whenever execution reaches @var{location}, print the values of one or
4783 more @var{expressions} under the control of the string @var{template}.
4784 To print several values, separate them with commas.
4786 @item set dprintf-style @var{style}
4787 Set the dprintf output to be handled in one of several different
4788 styles enumerated below. A change of style affects all existing
4789 dynamic printfs immediately. (If you need individual control over the
4790 print commands, simply define normal breakpoints with
4791 explicitly-supplied command lists.)
4794 @kindex dprintf-style gdb
4795 Handle the output using the @value{GDBN} @code{printf} command.
4798 @kindex dprintf-style call
4799 Handle the output by calling a function in your program (normally
4803 @kindex dprintf-style agent
4804 Have the remote debugging agent (such as @code{gdbserver}) handle
4805 the output itself. This style is only available for agents that
4806 support running commands on the target.
4808 @item set dprintf-function @var{function}
4809 Set the function to call if the dprintf style is @code{call}. By
4810 default its value is @code{printf}. You may set it to any expression.
4811 that @value{GDBN} can evaluate to a function, as per the @code{call}
4814 @item set dprintf-channel @var{channel}
4815 Set a ``channel'' for dprintf. If set to a non-empty value,
4816 @value{GDBN} will evaluate it as an expression and pass the result as
4817 a first argument to the @code{dprintf-function}, in the manner of
4818 @code{fprintf} and similar functions. Otherwise, the dprintf format
4819 string will be the first argument, in the manner of @code{printf}.
4821 As an example, if you wanted @code{dprintf} output to go to a logfile
4822 that is a standard I/O stream assigned to the variable @code{mylog},
4823 you could do the following:
4826 (gdb) set dprintf-style call
4827 (gdb) set dprintf-function fprintf
4828 (gdb) set dprintf-channel mylog
4829 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4830 Dprintf 1 at 0x123456: file main.c, line 25.
4832 1 dprintf keep y 0x00123456 in main at main.c:25
4833 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
4838 Note that the @code{info break} displays the dynamic printf commands
4839 as normal breakpoint commands; you can thus easily see the effect of
4840 the variable settings.
4842 @item set disconnected-dprintf on
4843 @itemx set disconnected-dprintf off
4844 @kindex set disconnected-dprintf
4845 Choose whether @code{dprintf} commands should continue to run if
4846 @value{GDBN} has disconnected from the target. This only applies
4847 if the @code{dprintf-style} is @code{agent}.
4849 @item show disconnected-dprintf off
4850 @kindex show disconnected-dprintf
4851 Show the current choice for disconnected @code{dprintf}.
4855 @value{GDBN} does not check the validity of function and channel,
4856 relying on you to supply values that are meaningful for the contexts
4857 in which they are being used. For instance, the function and channel
4858 may be the values of local variables, but if that is the case, then
4859 all enabled dynamic prints must be at locations within the scope of
4860 those locals. If evaluation fails, @value{GDBN} will report an error.
4862 @node Save Breakpoints
4863 @subsection How to save breakpoints to a file
4865 To save breakpoint definitions to a file use the @w{@code{save
4866 breakpoints}} command.
4869 @kindex save breakpoints
4870 @cindex save breakpoints to a file for future sessions
4871 @item save breakpoints [@var{filename}]
4872 This command saves all current breakpoint definitions together with
4873 their commands and ignore counts, into a file @file{@var{filename}}
4874 suitable for use in a later debugging session. This includes all
4875 types of breakpoints (breakpoints, watchpoints, catchpoints,
4876 tracepoints). To read the saved breakpoint definitions, use the
4877 @code{source} command (@pxref{Command Files}). Note that watchpoints
4878 with expressions involving local variables may fail to be recreated
4879 because it may not be possible to access the context where the
4880 watchpoint is valid anymore. Because the saved breakpoint definitions
4881 are simply a sequence of @value{GDBN} commands that recreate the
4882 breakpoints, you can edit the file in your favorite editing program,
4883 and remove the breakpoint definitions you're not interested in, or
4884 that can no longer be recreated.
4887 @node Static Probe Points
4888 @subsection Static Probe Points
4890 @cindex static probe point, SystemTap
4891 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
4892 for Statically Defined Tracing, and the probes are designed to have a tiny
4893 runtime code and data footprint, and no dynamic relocations. They are
4894 usable from assembly, C and C@t{++} languages. See
4895 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
4896 for a good reference on how the @acronym{SDT} probes are implemented.
4898 Currently, @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
4899 @acronym{SDT} probes are supported on ELF-compatible systems. See
4900 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
4901 for more information on how to add @code{SystemTap} @acronym{SDT} probes
4902 in your applications.
4904 @cindex semaphores on static probe points
4905 Some probes have an associated semaphore variable; for instance, this
4906 happens automatically if you defined your probe using a DTrace-style
4907 @file{.d} file. If your probe has a semaphore, @value{GDBN} will
4908 automatically enable it when you specify a breakpoint using the
4909 @samp{-probe-stap} notation. But, if you put a breakpoint at a probe's
4910 location by some other method (e.g., @code{break file:line}), then
4911 @value{GDBN} will not automatically set the semaphore.
4913 You can examine the available static static probes using @code{info
4914 probes}, with optional arguments:
4918 @item info probes stap @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
4919 If given, @var{provider} is a regular expression used to match against provider
4920 names when selecting which probes to list. If omitted, probes by all
4921 probes from all providers are listed.
4923 If given, @var{name} is a regular expression to match against probe names
4924 when selecting which probes to list. If omitted, probe names are not
4925 considered when deciding whether to display them.
4927 If given, @var{objfile} is a regular expression used to select which
4928 object files (executable or shared libraries) to examine. If not
4929 given, all object files are considered.
4931 @item info probes all
4932 List the available static probes, from all types.
4935 @vindex $_probe_arg@r{, convenience variable}
4936 A probe may specify up to twelve arguments. These are available at the
4937 point at which the probe is defined---that is, when the current PC is
4938 at the probe's location. The arguments are available using the
4939 convenience variables (@pxref{Convenience Vars})
4940 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. Each probe argument is
4941 an integer of the appropriate size; types are not preserved. The
4942 convenience variable @code{$_probe_argc} holds the number of arguments
4943 at the current probe point.
4945 These variables are always available, but attempts to access them at
4946 any location other than a probe point will cause @value{GDBN} to give
4950 @c @ifclear BARETARGET
4951 @node Error in Breakpoints
4952 @subsection ``Cannot insert breakpoints''
4954 If you request too many active hardware-assisted breakpoints and
4955 watchpoints, you will see this error message:
4957 @c FIXME: the precise wording of this message may change; the relevant
4958 @c source change is not committed yet (Sep 3, 1999).
4960 Stopped; cannot insert breakpoints.
4961 You may have requested too many hardware breakpoints and watchpoints.
4965 This message is printed when you attempt to resume the program, since
4966 only then @value{GDBN} knows exactly how many hardware breakpoints and
4967 watchpoints it needs to insert.
4969 When this message is printed, you need to disable or remove some of the
4970 hardware-assisted breakpoints and watchpoints, and then continue.
4972 @node Breakpoint-related Warnings
4973 @subsection ``Breakpoint address adjusted...''
4974 @cindex breakpoint address adjusted
4976 Some processor architectures place constraints on the addresses at
4977 which breakpoints may be placed. For architectures thus constrained,
4978 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4979 with the constraints dictated by the architecture.
4981 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4982 a VLIW architecture in which a number of RISC-like instructions may be
4983 bundled together for parallel execution. The FR-V architecture
4984 constrains the location of a breakpoint instruction within such a
4985 bundle to the instruction with the lowest address. @value{GDBN}
4986 honors this constraint by adjusting a breakpoint's address to the
4987 first in the bundle.
4989 It is not uncommon for optimized code to have bundles which contain
4990 instructions from different source statements, thus it may happen that
4991 a breakpoint's address will be adjusted from one source statement to
4992 another. Since this adjustment may significantly alter @value{GDBN}'s
4993 breakpoint related behavior from what the user expects, a warning is
4994 printed when the breakpoint is first set and also when the breakpoint
4997 A warning like the one below is printed when setting a breakpoint
4998 that's been subject to address adjustment:
5001 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5004 Such warnings are printed both for user settable and @value{GDBN}'s
5005 internal breakpoints. If you see one of these warnings, you should
5006 verify that a breakpoint set at the adjusted address will have the
5007 desired affect. If not, the breakpoint in question may be removed and
5008 other breakpoints may be set which will have the desired behavior.
5009 E.g., it may be sufficient to place the breakpoint at a later
5010 instruction. A conditional breakpoint may also be useful in some
5011 cases to prevent the breakpoint from triggering too often.
5013 @value{GDBN} will also issue a warning when stopping at one of these
5014 adjusted breakpoints:
5017 warning: Breakpoint 1 address previously adjusted from 0x00010414
5021 When this warning is encountered, it may be too late to take remedial
5022 action except in cases where the breakpoint is hit earlier or more
5023 frequently than expected.
5025 @node Continuing and Stepping
5026 @section Continuing and Stepping
5030 @cindex resuming execution
5031 @dfn{Continuing} means resuming program execution until your program
5032 completes normally. In contrast, @dfn{stepping} means executing just
5033 one more ``step'' of your program, where ``step'' may mean either one
5034 line of source code, or one machine instruction (depending on what
5035 particular command you use). Either when continuing or when stepping,
5036 your program may stop even sooner, due to a breakpoint or a signal. (If
5037 it stops due to a signal, you may want to use @code{handle}, or use
5038 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
5042 @kindex c @r{(@code{continue})}
5043 @kindex fg @r{(resume foreground execution)}
5044 @item continue @r{[}@var{ignore-count}@r{]}
5045 @itemx c @r{[}@var{ignore-count}@r{]}
5046 @itemx fg @r{[}@var{ignore-count}@r{]}
5047 Resume program execution, at the address where your program last stopped;
5048 any breakpoints set at that address are bypassed. The optional argument
5049 @var{ignore-count} allows you to specify a further number of times to
5050 ignore a breakpoint at this location; its effect is like that of
5051 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5053 The argument @var{ignore-count} is meaningful only when your program
5054 stopped due to a breakpoint. At other times, the argument to
5055 @code{continue} is ignored.
5057 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5058 debugged program is deemed to be the foreground program) are provided
5059 purely for convenience, and have exactly the same behavior as
5063 To resume execution at a different place, you can use @code{return}
5064 (@pxref{Returning, ,Returning from a Function}) to go back to the
5065 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5066 Different Address}) to go to an arbitrary location in your program.
5068 A typical technique for using stepping is to set a breakpoint
5069 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5070 beginning of the function or the section of your program where a problem
5071 is believed to lie, run your program until it stops at that breakpoint,
5072 and then step through the suspect area, examining the variables that are
5073 interesting, until you see the problem happen.
5077 @kindex s @r{(@code{step})}
5079 Continue running your program until control reaches a different source
5080 line, then stop it and return control to @value{GDBN}. This command is
5081 abbreviated @code{s}.
5084 @c "without debugging information" is imprecise; actually "without line
5085 @c numbers in the debugging information". (gcc -g1 has debugging info but
5086 @c not line numbers). But it seems complex to try to make that
5087 @c distinction here.
5088 @emph{Warning:} If you use the @code{step} command while control is
5089 within a function that was compiled without debugging information,
5090 execution proceeds until control reaches a function that does have
5091 debugging information. Likewise, it will not step into a function which
5092 is compiled without debugging information. To step through functions
5093 without debugging information, use the @code{stepi} command, described
5097 The @code{step} command only stops at the first instruction of a source
5098 line. This prevents the multiple stops that could otherwise occur in
5099 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5100 to stop if a function that has debugging information is called within
5101 the line. In other words, @code{step} @emph{steps inside} any functions
5102 called within the line.
5104 Also, the @code{step} command only enters a function if there is line
5105 number information for the function. Otherwise it acts like the
5106 @code{next} command. This avoids problems when using @code{cc -gl}
5107 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5108 was any debugging information about the routine.
5110 @item step @var{count}
5111 Continue running as in @code{step}, but do so @var{count} times. If a
5112 breakpoint is reached, or a signal not related to stepping occurs before
5113 @var{count} steps, stepping stops right away.
5116 @kindex n @r{(@code{next})}
5117 @item next @r{[}@var{count}@r{]}
5118 Continue to the next source line in the current (innermost) stack frame.
5119 This is similar to @code{step}, but function calls that appear within
5120 the line of code are executed without stopping. Execution stops when
5121 control reaches a different line of code at the original stack level
5122 that was executing when you gave the @code{next} command. This command
5123 is abbreviated @code{n}.
5125 An argument @var{count} is a repeat count, as for @code{step}.
5128 @c FIX ME!! Do we delete this, or is there a way it fits in with
5129 @c the following paragraph? --- Vctoria
5131 @c @code{next} within a function that lacks debugging information acts like
5132 @c @code{step}, but any function calls appearing within the code of the
5133 @c function are executed without stopping.
5135 The @code{next} command only stops at the first instruction of a
5136 source line. This prevents multiple stops that could otherwise occur in
5137 @code{switch} statements, @code{for} loops, etc.
5139 @kindex set step-mode
5141 @cindex functions without line info, and stepping
5142 @cindex stepping into functions with no line info
5143 @itemx set step-mode on
5144 The @code{set step-mode on} command causes the @code{step} command to
5145 stop at the first instruction of a function which contains no debug line
5146 information rather than stepping over it.
5148 This is useful in cases where you may be interested in inspecting the
5149 machine instructions of a function which has no symbolic info and do not
5150 want @value{GDBN} to automatically skip over this function.
5152 @item set step-mode off
5153 Causes the @code{step} command to step over any functions which contains no
5154 debug information. This is the default.
5156 @item show step-mode
5157 Show whether @value{GDBN} will stop in or step over functions without
5158 source line debug information.
5161 @kindex fin @r{(@code{finish})}
5163 Continue running until just after function in the selected stack frame
5164 returns. Print the returned value (if any). This command can be
5165 abbreviated as @code{fin}.
5167 Contrast this with the @code{return} command (@pxref{Returning,
5168 ,Returning from a Function}).
5171 @kindex u @r{(@code{until})}
5172 @cindex run until specified location
5175 Continue running until a source line past the current line, in the
5176 current stack frame, is reached. This command is used to avoid single
5177 stepping through a loop more than once. It is like the @code{next}
5178 command, except that when @code{until} encounters a jump, it
5179 automatically continues execution until the program counter is greater
5180 than the address of the jump.
5182 This means that when you reach the end of a loop after single stepping
5183 though it, @code{until} makes your program continue execution until it
5184 exits the loop. In contrast, a @code{next} command at the end of a loop
5185 simply steps back to the beginning of the loop, which forces you to step
5186 through the next iteration.
5188 @code{until} always stops your program if it attempts to exit the current
5191 @code{until} may produce somewhat counterintuitive results if the order
5192 of machine code does not match the order of the source lines. For
5193 example, in the following excerpt from a debugging session, the @code{f}
5194 (@code{frame}) command shows that execution is stopped at line
5195 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5199 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5201 (@value{GDBP}) until
5202 195 for ( ; argc > 0; NEXTARG) @{
5205 This happened because, for execution efficiency, the compiler had
5206 generated code for the loop closure test at the end, rather than the
5207 start, of the loop---even though the test in a C @code{for}-loop is
5208 written before the body of the loop. The @code{until} command appeared
5209 to step back to the beginning of the loop when it advanced to this
5210 expression; however, it has not really gone to an earlier
5211 statement---not in terms of the actual machine code.
5213 @code{until} with no argument works by means of single
5214 instruction stepping, and hence is slower than @code{until} with an
5217 @item until @var{location}
5218 @itemx u @var{location}
5219 Continue running your program until either the specified location is
5220 reached, or the current stack frame returns. @var{location} is any of
5221 the forms described in @ref{Specify Location}.
5222 This form of the command uses temporary breakpoints, and
5223 hence is quicker than @code{until} without an argument. The specified
5224 location is actually reached only if it is in the current frame. This
5225 implies that @code{until} can be used to skip over recursive function
5226 invocations. For instance in the code below, if the current location is
5227 line @code{96}, issuing @code{until 99} will execute the program up to
5228 line @code{99} in the same invocation of factorial, i.e., after the inner
5229 invocations have returned.
5232 94 int factorial (int value)
5234 96 if (value > 1) @{
5235 97 value *= factorial (value - 1);
5242 @kindex advance @var{location}
5243 @item advance @var{location}
5244 Continue running the program up to the given @var{location}. An argument is
5245 required, which should be of one of the forms described in
5246 @ref{Specify Location}.
5247 Execution will also stop upon exit from the current stack
5248 frame. This command is similar to @code{until}, but @code{advance} will
5249 not skip over recursive function calls, and the target location doesn't
5250 have to be in the same frame as the current one.
5254 @kindex si @r{(@code{stepi})}
5256 @itemx stepi @var{arg}
5258 Execute one machine instruction, then stop and return to the debugger.
5260 It is often useful to do @samp{display/i $pc} when stepping by machine
5261 instructions. This makes @value{GDBN} automatically display the next
5262 instruction to be executed, each time your program stops. @xref{Auto
5263 Display,, Automatic Display}.
5265 An argument is a repeat count, as in @code{step}.
5269 @kindex ni @r{(@code{nexti})}
5271 @itemx nexti @var{arg}
5273 Execute one machine instruction, but if it is a function call,
5274 proceed until the function returns.
5276 An argument is a repeat count, as in @code{next}.
5280 @anchor{range stepping}
5281 @cindex range stepping
5282 @cindex target-assisted range stepping
5283 By default, and if available, @value{GDBN} makes use of
5284 target-assisted @dfn{range stepping}. In other words, whenever you
5285 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5286 tells the target to step the corresponding range of instruction
5287 addresses instead of issuing multiple single-steps. This speeds up
5288 line stepping, particularly for remote targets. Ideally, there should
5289 be no reason you would want to turn range stepping off. However, it's
5290 possible that a bug in the debug info, a bug in the remote stub (for
5291 remote targets), or even a bug in @value{GDBN} could make line
5292 stepping behave incorrectly when target-assisted range stepping is
5293 enabled. You can use the following command to turn off range stepping
5297 @kindex set range-stepping
5298 @kindex show range-stepping
5299 @item set range-stepping
5300 @itemx show range-stepping
5301 Control whether range stepping is enabled.
5303 If @code{on}, and the target supports it, @value{GDBN} tells the
5304 target to step a range of addresses itself, instead of issuing
5305 multiple single-steps. If @code{off}, @value{GDBN} always issues
5306 single-steps, even if range stepping is supported by the target. The
5307 default is @code{on}.
5311 @node Skipping Over Functions and Files
5312 @section Skipping Over Functions and Files
5313 @cindex skipping over functions and files
5315 The program you are debugging may contain some functions which are
5316 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
5317 skip a function or all functions in a file when stepping.
5319 For example, consider the following C function:
5330 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5331 are not interested in stepping through @code{boring}. If you run @code{step}
5332 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5333 step over both @code{foo} and @code{boring}!
5335 One solution is to @code{step} into @code{boring} and use the @code{finish}
5336 command to immediately exit it. But this can become tedious if @code{boring}
5337 is called from many places.
5339 A more flexible solution is to execute @kbd{skip boring}. This instructs
5340 @value{GDBN} never to step into @code{boring}. Now when you execute
5341 @code{step} at line 103, you'll step over @code{boring} and directly into
5344 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5345 example, @code{skip file boring.c}.
5348 @kindex skip function
5349 @item skip @r{[}@var{linespec}@r{]}
5350 @itemx skip function @r{[}@var{linespec}@r{]}
5351 After running this command, the function named by @var{linespec} or the
5352 function containing the line named by @var{linespec} will be skipped over when
5353 stepping. @xref{Specify Location}.
5355 If you do not specify @var{linespec}, the function you're currently debugging
5358 (If you have a function called @code{file} that you want to skip, use
5359 @kbd{skip function file}.)
5362 @item skip file @r{[}@var{filename}@r{]}
5363 After running this command, any function whose source lives in @var{filename}
5364 will be skipped over when stepping.
5366 If you do not specify @var{filename}, functions whose source lives in the file
5367 you're currently debugging will be skipped.
5370 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5371 These are the commands for managing your list of skips:
5375 @item info skip @r{[}@var{range}@r{]}
5376 Print details about the specified skip(s). If @var{range} is not specified,
5377 print a table with details about all functions and files marked for skipping.
5378 @code{info skip} prints the following information about each skip:
5382 A number identifying this skip.
5384 The type of this skip, either @samp{function} or @samp{file}.
5385 @item Enabled or Disabled
5386 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5388 For function skips, this column indicates the address in memory of the function
5389 being skipped. If you've set a function skip on a function which has not yet
5390 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5391 which has the function is loaded, @code{info skip} will show the function's
5394 For file skips, this field contains the filename being skipped. For functions
5395 skips, this field contains the function name and its line number in the file
5396 where it is defined.
5400 @item skip delete @r{[}@var{range}@r{]}
5401 Delete the specified skip(s). If @var{range} is not specified, delete all
5405 @item skip enable @r{[}@var{range}@r{]}
5406 Enable the specified skip(s). If @var{range} is not specified, enable all
5409 @kindex skip disable
5410 @item skip disable @r{[}@var{range}@r{]}
5411 Disable the specified skip(s). If @var{range} is not specified, disable all
5420 A signal is an asynchronous event that can happen in a program. The
5421 operating system defines the possible kinds of signals, and gives each
5422 kind a name and a number. For example, in Unix @code{SIGINT} is the
5423 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5424 @code{SIGSEGV} is the signal a program gets from referencing a place in
5425 memory far away from all the areas in use; @code{SIGALRM} occurs when
5426 the alarm clock timer goes off (which happens only if your program has
5427 requested an alarm).
5429 @cindex fatal signals
5430 Some signals, including @code{SIGALRM}, are a normal part of the
5431 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5432 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5433 program has not specified in advance some other way to handle the signal.
5434 @code{SIGINT} does not indicate an error in your program, but it is normally
5435 fatal so it can carry out the purpose of the interrupt: to kill the program.
5437 @value{GDBN} has the ability to detect any occurrence of a signal in your
5438 program. You can tell @value{GDBN} in advance what to do for each kind of
5441 @cindex handling signals
5442 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5443 @code{SIGALRM} be silently passed to your program
5444 (so as not to interfere with their role in the program's functioning)
5445 but to stop your program immediately whenever an error signal happens.
5446 You can change these settings with the @code{handle} command.
5449 @kindex info signals
5453 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5454 handle each one. You can use this to see the signal numbers of all
5455 the defined types of signals.
5457 @item info signals @var{sig}
5458 Similar, but print information only about the specified signal number.
5460 @code{info handle} is an alias for @code{info signals}.
5462 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5463 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5464 for details about this command.
5467 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5468 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
5469 can be the number of a signal or its name (with or without the
5470 @samp{SIG} at the beginning); a list of signal numbers of the form
5471 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5472 known signals. Optional arguments @var{keywords}, described below,
5473 say what change to make.
5477 The keywords allowed by the @code{handle} command can be abbreviated.
5478 Their full names are:
5482 @value{GDBN} should not stop your program when this signal happens. It may
5483 still print a message telling you that the signal has come in.
5486 @value{GDBN} should stop your program when this signal happens. This implies
5487 the @code{print} keyword as well.
5490 @value{GDBN} should print a message when this signal happens.
5493 @value{GDBN} should not mention the occurrence of the signal at all. This
5494 implies the @code{nostop} keyword as well.
5498 @value{GDBN} should allow your program to see this signal; your program
5499 can handle the signal, or else it may terminate if the signal is fatal
5500 and not handled. @code{pass} and @code{noignore} are synonyms.
5504 @value{GDBN} should not allow your program to see this signal.
5505 @code{nopass} and @code{ignore} are synonyms.
5509 When a signal stops your program, the signal is not visible to the
5511 continue. Your program sees the signal then, if @code{pass} is in
5512 effect for the signal in question @emph{at that time}. In other words,
5513 after @value{GDBN} reports a signal, you can use the @code{handle}
5514 command with @code{pass} or @code{nopass} to control whether your
5515 program sees that signal when you continue.
5517 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5518 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5519 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5522 You can also use the @code{signal} command to prevent your program from
5523 seeing a signal, or cause it to see a signal it normally would not see,
5524 or to give it any signal at any time. For example, if your program stopped
5525 due to some sort of memory reference error, you might store correct
5526 values into the erroneous variables and continue, hoping to see more
5527 execution; but your program would probably terminate immediately as
5528 a result of the fatal signal once it saw the signal. To prevent this,
5529 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5532 @cindex extra signal information
5533 @anchor{extra signal information}
5535 On some targets, @value{GDBN} can inspect extra signal information
5536 associated with the intercepted signal, before it is actually
5537 delivered to the program being debugged. This information is exported
5538 by the convenience variable @code{$_siginfo}, and consists of data
5539 that is passed by the kernel to the signal handler at the time of the
5540 receipt of a signal. The data type of the information itself is
5541 target dependent. You can see the data type using the @code{ptype
5542 $_siginfo} command. On Unix systems, it typically corresponds to the
5543 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5546 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5547 referenced address that raised a segmentation fault.
5551 (@value{GDBP}) continue
5552 Program received signal SIGSEGV, Segmentation fault.
5553 0x0000000000400766 in main ()
5555 (@value{GDBP}) ptype $_siginfo
5562 struct @{...@} _kill;
5563 struct @{...@} _timer;
5565 struct @{...@} _sigchld;
5566 struct @{...@} _sigfault;
5567 struct @{...@} _sigpoll;
5570 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5574 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5575 $1 = (void *) 0x7ffff7ff7000
5579 Depending on target support, @code{$_siginfo} may also be writable.
5582 @section Stopping and Starting Multi-thread Programs
5584 @cindex stopped threads
5585 @cindex threads, stopped
5587 @cindex continuing threads
5588 @cindex threads, continuing
5590 @value{GDBN} supports debugging programs with multiple threads
5591 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5592 are two modes of controlling execution of your program within the
5593 debugger. In the default mode, referred to as @dfn{all-stop mode},
5594 when any thread in your program stops (for example, at a breakpoint
5595 or while being stepped), all other threads in the program are also stopped by
5596 @value{GDBN}. On some targets, @value{GDBN} also supports
5597 @dfn{non-stop mode}, in which other threads can continue to run freely while
5598 you examine the stopped thread in the debugger.
5601 * All-Stop Mode:: All threads stop when GDB takes control
5602 * Non-Stop Mode:: Other threads continue to execute
5603 * Background Execution:: Running your program asynchronously
5604 * Thread-Specific Breakpoints:: Controlling breakpoints
5605 * Interrupted System Calls:: GDB may interfere with system calls
5606 * Observer Mode:: GDB does not alter program behavior
5610 @subsection All-Stop Mode
5612 @cindex all-stop mode
5614 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5615 @emph{all} threads of execution stop, not just the current thread. This
5616 allows you to examine the overall state of the program, including
5617 switching between threads, without worrying that things may change
5620 Conversely, whenever you restart the program, @emph{all} threads start
5621 executing. @emph{This is true even when single-stepping} with commands
5622 like @code{step} or @code{next}.
5624 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5625 Since thread scheduling is up to your debugging target's operating
5626 system (not controlled by @value{GDBN}), other threads may
5627 execute more than one statement while the current thread completes a
5628 single step. Moreover, in general other threads stop in the middle of a
5629 statement, rather than at a clean statement boundary, when the program
5632 You might even find your program stopped in another thread after
5633 continuing or even single-stepping. This happens whenever some other
5634 thread runs into a breakpoint, a signal, or an exception before the
5635 first thread completes whatever you requested.
5637 @cindex automatic thread selection
5638 @cindex switching threads automatically
5639 @cindex threads, automatic switching
5640 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5641 signal, it automatically selects the thread where that breakpoint or
5642 signal happened. @value{GDBN} alerts you to the context switch with a
5643 message such as @samp{[Switching to Thread @var{n}]} to identify the
5646 On some OSes, you can modify @value{GDBN}'s default behavior by
5647 locking the OS scheduler to allow only a single thread to run.
5650 @item set scheduler-locking @var{mode}
5651 @cindex scheduler locking mode
5652 @cindex lock scheduler
5653 Set the scheduler locking mode. If it is @code{off}, then there is no
5654 locking and any thread may run at any time. If @code{on}, then only the
5655 current thread may run when the inferior is resumed. The @code{step}
5656 mode optimizes for single-stepping; it prevents other threads
5657 from preempting the current thread while you are stepping, so that
5658 the focus of debugging does not change unexpectedly.
5659 Other threads only rarely (or never) get a chance to run
5660 when you step. They are more likely to run when you @samp{next} over a
5661 function call, and they are completely free to run when you use commands
5662 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5663 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5664 the current thread away from the thread that you are debugging.
5666 @item show scheduler-locking
5667 Display the current scheduler locking mode.
5670 @cindex resume threads of multiple processes simultaneously
5671 By default, when you issue one of the execution commands such as
5672 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5673 threads of the current inferior to run. For example, if @value{GDBN}
5674 is attached to two inferiors, each with two threads, the
5675 @code{continue} command resumes only the two threads of the current
5676 inferior. This is useful, for example, when you debug a program that
5677 forks and you want to hold the parent stopped (so that, for instance,
5678 it doesn't run to exit), while you debug the child. In other
5679 situations, you may not be interested in inspecting the current state
5680 of any of the processes @value{GDBN} is attached to, and you may want
5681 to resume them all until some breakpoint is hit. In the latter case,
5682 you can instruct @value{GDBN} to allow all threads of all the
5683 inferiors to run with the @w{@code{set schedule-multiple}} command.
5686 @kindex set schedule-multiple
5687 @item set schedule-multiple
5688 Set the mode for allowing threads of multiple processes to be resumed
5689 when an execution command is issued. When @code{on}, all threads of
5690 all processes are allowed to run. When @code{off}, only the threads
5691 of the current process are resumed. The default is @code{off}. The
5692 @code{scheduler-locking} mode takes precedence when set to @code{on},
5693 or while you are stepping and set to @code{step}.
5695 @item show schedule-multiple
5696 Display the current mode for resuming the execution of threads of
5701 @subsection Non-Stop Mode
5703 @cindex non-stop mode
5705 @c This section is really only a place-holder, and needs to be expanded
5706 @c with more details.
5708 For some multi-threaded targets, @value{GDBN} supports an optional
5709 mode of operation in which you can examine stopped program threads in
5710 the debugger while other threads continue to execute freely. This
5711 minimizes intrusion when debugging live systems, such as programs
5712 where some threads have real-time constraints or must continue to
5713 respond to external events. This is referred to as @dfn{non-stop} mode.
5715 In non-stop mode, when a thread stops to report a debugging event,
5716 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5717 threads as well, in contrast to the all-stop mode behavior. Additionally,
5718 execution commands such as @code{continue} and @code{step} apply by default
5719 only to the current thread in non-stop mode, rather than all threads as
5720 in all-stop mode. This allows you to control threads explicitly in
5721 ways that are not possible in all-stop mode --- for example, stepping
5722 one thread while allowing others to run freely, stepping
5723 one thread while holding all others stopped, or stepping several threads
5724 independently and simultaneously.
5726 To enter non-stop mode, use this sequence of commands before you run
5727 or attach to your program:
5730 # Enable the async interface.
5733 # If using the CLI, pagination breaks non-stop.
5736 # Finally, turn it on!
5740 You can use these commands to manipulate the non-stop mode setting:
5743 @kindex set non-stop
5744 @item set non-stop on
5745 Enable selection of non-stop mode.
5746 @item set non-stop off
5747 Disable selection of non-stop mode.
5748 @kindex show non-stop
5750 Show the current non-stop enablement setting.
5753 Note these commands only reflect whether non-stop mode is enabled,
5754 not whether the currently-executing program is being run in non-stop mode.
5755 In particular, the @code{set non-stop} preference is only consulted when
5756 @value{GDBN} starts or connects to the target program, and it is generally
5757 not possible to switch modes once debugging has started. Furthermore,
5758 since not all targets support non-stop mode, even when you have enabled
5759 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5762 In non-stop mode, all execution commands apply only to the current thread
5763 by default. That is, @code{continue} only continues one thread.
5764 To continue all threads, issue @code{continue -a} or @code{c -a}.
5766 You can use @value{GDBN}'s background execution commands
5767 (@pxref{Background Execution}) to run some threads in the background
5768 while you continue to examine or step others from @value{GDBN}.
5769 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5770 always executed asynchronously in non-stop mode.
5772 Suspending execution is done with the @code{interrupt} command when
5773 running in the background, or @kbd{Ctrl-c} during foreground execution.
5774 In all-stop mode, this stops the whole process;
5775 but in non-stop mode the interrupt applies only to the current thread.
5776 To stop the whole program, use @code{interrupt -a}.
5778 Other execution commands do not currently support the @code{-a} option.
5780 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5781 that thread current, as it does in all-stop mode. This is because the
5782 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5783 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5784 changed to a different thread just as you entered a command to operate on the
5785 previously current thread.
5787 @node Background Execution
5788 @subsection Background Execution
5790 @cindex foreground execution
5791 @cindex background execution
5792 @cindex asynchronous execution
5793 @cindex execution, foreground, background and asynchronous
5795 @value{GDBN}'s execution commands have two variants: the normal
5796 foreground (synchronous) behavior, and a background
5797 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5798 the program to report that some thread has stopped before prompting for
5799 another command. In background execution, @value{GDBN} immediately gives
5800 a command prompt so that you can issue other commands while your program runs.
5802 You need to explicitly enable asynchronous mode before you can use
5803 background execution commands. You can use these commands to
5804 manipulate the asynchronous mode setting:
5807 @kindex set target-async
5808 @item set target-async on
5809 Enable asynchronous mode.
5810 @item set target-async off
5811 Disable asynchronous mode.
5812 @kindex show target-async
5813 @item show target-async
5814 Show the current target-async setting.
5817 If the target doesn't support async mode, @value{GDBN} issues an error
5818 message if you attempt to use the background execution commands.
5820 To specify background execution, add a @code{&} to the command. For example,
5821 the background form of the @code{continue} command is @code{continue&}, or
5822 just @code{c&}. The execution commands that accept background execution
5828 @xref{Starting, , Starting your Program}.
5832 @xref{Attach, , Debugging an Already-running Process}.
5836 @xref{Continuing and Stepping, step}.
5840 @xref{Continuing and Stepping, stepi}.
5844 @xref{Continuing and Stepping, next}.
5848 @xref{Continuing and Stepping, nexti}.
5852 @xref{Continuing and Stepping, continue}.
5856 @xref{Continuing and Stepping, finish}.
5860 @xref{Continuing and Stepping, until}.
5864 Background execution is especially useful in conjunction with non-stop
5865 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5866 However, you can also use these commands in the normal all-stop mode with
5867 the restriction that you cannot issue another execution command until the
5868 previous one finishes. Examples of commands that are valid in all-stop
5869 mode while the program is running include @code{help} and @code{info break}.
5871 You can interrupt your program while it is running in the background by
5872 using the @code{interrupt} command.
5879 Suspend execution of the running program. In all-stop mode,
5880 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5881 only the current thread. To stop the whole program in non-stop mode,
5882 use @code{interrupt -a}.
5885 @node Thread-Specific Breakpoints
5886 @subsection Thread-Specific Breakpoints
5888 When your program has multiple threads (@pxref{Threads,, Debugging
5889 Programs with Multiple Threads}), you can choose whether to set
5890 breakpoints on all threads, or on a particular thread.
5893 @cindex breakpoints and threads
5894 @cindex thread breakpoints
5895 @kindex break @dots{} thread @var{threadno}
5896 @item break @var{linespec} thread @var{threadno}
5897 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5898 @var{linespec} specifies source lines; there are several ways of
5899 writing them (@pxref{Specify Location}), but the effect is always to
5900 specify some source line.
5902 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5903 to specify that you only want @value{GDBN} to stop the program when a
5904 particular thread reaches this breakpoint. @var{threadno} is one of the
5905 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5906 column of the @samp{info threads} display.
5908 If you do not specify @samp{thread @var{threadno}} when you set a
5909 breakpoint, the breakpoint applies to @emph{all} threads of your
5912 You can use the @code{thread} qualifier on conditional breakpoints as
5913 well; in this case, place @samp{thread @var{threadno}} before or
5914 after the breakpoint condition, like this:
5917 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5922 Thread-specific breakpoints are automatically deleted when
5923 @value{GDBN} detects the corresponding thread is no longer in the
5924 thread list. For example:
5928 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
5931 There are several ways for a thread to disappear, such as a regular
5932 thread exit, but also when you detach from the process with the
5933 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
5934 Process}), or if @value{GDBN} loses the remote connection
5935 (@pxref{Remote Debugging}), etc. Note that with some targets,
5936 @value{GDBN} is only able to detect a thread has exited when the user
5937 explictly asks for the thread list with the @code{info threads}
5940 @node Interrupted System Calls
5941 @subsection Interrupted System Calls
5943 @cindex thread breakpoints and system calls
5944 @cindex system calls and thread breakpoints
5945 @cindex premature return from system calls
5946 There is an unfortunate side effect when using @value{GDBN} to debug
5947 multi-threaded programs. If one thread stops for a
5948 breakpoint, or for some other reason, and another thread is blocked in a
5949 system call, then the system call may return prematurely. This is a
5950 consequence of the interaction between multiple threads and the signals
5951 that @value{GDBN} uses to implement breakpoints and other events that
5954 To handle this problem, your program should check the return value of
5955 each system call and react appropriately. This is good programming
5958 For example, do not write code like this:
5964 The call to @code{sleep} will return early if a different thread stops
5965 at a breakpoint or for some other reason.
5967 Instead, write this:
5972 unslept = sleep (unslept);
5975 A system call is allowed to return early, so the system is still
5976 conforming to its specification. But @value{GDBN} does cause your
5977 multi-threaded program to behave differently than it would without
5980 Also, @value{GDBN} uses internal breakpoints in the thread library to
5981 monitor certain events such as thread creation and thread destruction.
5982 When such an event happens, a system call in another thread may return
5983 prematurely, even though your program does not appear to stop.
5986 @subsection Observer Mode
5988 If you want to build on non-stop mode and observe program behavior
5989 without any chance of disruption by @value{GDBN}, you can set
5990 variables to disable all of the debugger's attempts to modify state,
5991 whether by writing memory, inserting breakpoints, etc. These operate
5992 at a low level, intercepting operations from all commands.
5994 When all of these are set to @code{off}, then @value{GDBN} is said to
5995 be @dfn{observer mode}. As a convenience, the variable
5996 @code{observer} can be set to disable these, plus enable non-stop
5999 Note that @value{GDBN} will not prevent you from making nonsensical
6000 combinations of these settings. For instance, if you have enabled
6001 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6002 then breakpoints that work by writing trap instructions into the code
6003 stream will still not be able to be placed.
6008 @item set observer on
6009 @itemx set observer off
6010 When set to @code{on}, this disables all the permission variables
6011 below (except for @code{insert-fast-tracepoints}), plus enables
6012 non-stop debugging. Setting this to @code{off} switches back to
6013 normal debugging, though remaining in non-stop mode.
6016 Show whether observer mode is on or off.
6018 @kindex may-write-registers
6019 @item set may-write-registers on
6020 @itemx set may-write-registers off
6021 This controls whether @value{GDBN} will attempt to alter the values of
6022 registers, such as with assignment expressions in @code{print}, or the
6023 @code{jump} command. It defaults to @code{on}.
6025 @item show may-write-registers
6026 Show the current permission to write registers.
6028 @kindex may-write-memory
6029 @item set may-write-memory on
6030 @itemx set may-write-memory off
6031 This controls whether @value{GDBN} will attempt to alter the contents
6032 of memory, such as with assignment expressions in @code{print}. It
6033 defaults to @code{on}.
6035 @item show may-write-memory
6036 Show the current permission to write memory.
6038 @kindex may-insert-breakpoints
6039 @item set may-insert-breakpoints on
6040 @itemx set may-insert-breakpoints off
6041 This controls whether @value{GDBN} will attempt to insert breakpoints.
6042 This affects all breakpoints, including internal breakpoints defined
6043 by @value{GDBN}. It defaults to @code{on}.
6045 @item show may-insert-breakpoints
6046 Show the current permission to insert breakpoints.
6048 @kindex may-insert-tracepoints
6049 @item set may-insert-tracepoints on
6050 @itemx set may-insert-tracepoints off
6051 This controls whether @value{GDBN} will attempt to insert (regular)
6052 tracepoints at the beginning of a tracing experiment. It affects only
6053 non-fast tracepoints, fast tracepoints being under the control of
6054 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6056 @item show may-insert-tracepoints
6057 Show the current permission to insert tracepoints.
6059 @kindex may-insert-fast-tracepoints
6060 @item set may-insert-fast-tracepoints on
6061 @itemx set may-insert-fast-tracepoints off
6062 This controls whether @value{GDBN} will attempt to insert fast
6063 tracepoints at the beginning of a tracing experiment. It affects only
6064 fast tracepoints, regular (non-fast) tracepoints being under the
6065 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6067 @item show may-insert-fast-tracepoints
6068 Show the current permission to insert fast tracepoints.
6070 @kindex may-interrupt
6071 @item set may-interrupt on
6072 @itemx set may-interrupt off
6073 This controls whether @value{GDBN} will attempt to interrupt or stop
6074 program execution. When this variable is @code{off}, the
6075 @code{interrupt} command will have no effect, nor will
6076 @kbd{Ctrl-c}. It defaults to @code{on}.
6078 @item show may-interrupt
6079 Show the current permission to interrupt or stop the program.
6083 @node Reverse Execution
6084 @chapter Running programs backward
6085 @cindex reverse execution
6086 @cindex running programs backward
6088 When you are debugging a program, it is not unusual to realize that
6089 you have gone too far, and some event of interest has already happened.
6090 If the target environment supports it, @value{GDBN} can allow you to
6091 ``rewind'' the program by running it backward.
6093 A target environment that supports reverse execution should be able
6094 to ``undo'' the changes in machine state that have taken place as the
6095 program was executing normally. Variables, registers etc.@: should
6096 revert to their previous values. Obviously this requires a great
6097 deal of sophistication on the part of the target environment; not
6098 all target environments can support reverse execution.
6100 When a program is executed in reverse, the instructions that
6101 have most recently been executed are ``un-executed'', in reverse
6102 order. The program counter runs backward, following the previous
6103 thread of execution in reverse. As each instruction is ``un-executed'',
6104 the values of memory and/or registers that were changed by that
6105 instruction are reverted to their previous states. After executing
6106 a piece of source code in reverse, all side effects of that code
6107 should be ``undone'', and all variables should be returned to their
6108 prior values@footnote{
6109 Note that some side effects are easier to undo than others. For instance,
6110 memory and registers are relatively easy, but device I/O is hard. Some
6111 targets may be able undo things like device I/O, and some may not.
6113 The contract between @value{GDBN} and the reverse executing target
6114 requires only that the target do something reasonable when
6115 @value{GDBN} tells it to execute backwards, and then report the
6116 results back to @value{GDBN}. Whatever the target reports back to
6117 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6118 assumes that the memory and registers that the target reports are in a
6119 consistant state, but @value{GDBN} accepts whatever it is given.
6122 If you are debugging in a target environment that supports
6123 reverse execution, @value{GDBN} provides the following commands.
6126 @kindex reverse-continue
6127 @kindex rc @r{(@code{reverse-continue})}
6128 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6129 @itemx rc @r{[}@var{ignore-count}@r{]}
6130 Beginning at the point where your program last stopped, start executing
6131 in reverse. Reverse execution will stop for breakpoints and synchronous
6132 exceptions (signals), just like normal execution. Behavior of
6133 asynchronous signals depends on the target environment.
6135 @kindex reverse-step
6136 @kindex rs @r{(@code{step})}
6137 @item reverse-step @r{[}@var{count}@r{]}
6138 Run the program backward until control reaches the start of a
6139 different source line; then stop it, and return control to @value{GDBN}.
6141 Like the @code{step} command, @code{reverse-step} will only stop
6142 at the beginning of a source line. It ``un-executes'' the previously
6143 executed source line. If the previous source line included calls to
6144 debuggable functions, @code{reverse-step} will step (backward) into
6145 the called function, stopping at the beginning of the @emph{last}
6146 statement in the called function (typically a return statement).
6148 Also, as with the @code{step} command, if non-debuggable functions are
6149 called, @code{reverse-step} will run thru them backward without stopping.
6151 @kindex reverse-stepi
6152 @kindex rsi @r{(@code{reverse-stepi})}
6153 @item reverse-stepi @r{[}@var{count}@r{]}
6154 Reverse-execute one machine instruction. Note that the instruction
6155 to be reverse-executed is @emph{not} the one pointed to by the program
6156 counter, but the instruction executed prior to that one. For instance,
6157 if the last instruction was a jump, @code{reverse-stepi} will take you
6158 back from the destination of the jump to the jump instruction itself.
6160 @kindex reverse-next
6161 @kindex rn @r{(@code{reverse-next})}
6162 @item reverse-next @r{[}@var{count}@r{]}
6163 Run backward to the beginning of the previous line executed in
6164 the current (innermost) stack frame. If the line contains function
6165 calls, they will be ``un-executed'' without stopping. Starting from
6166 the first line of a function, @code{reverse-next} will take you back
6167 to the caller of that function, @emph{before} the function was called,
6168 just as the normal @code{next} command would take you from the last
6169 line of a function back to its return to its caller
6170 @footnote{Unless the code is too heavily optimized.}.
6172 @kindex reverse-nexti
6173 @kindex rni @r{(@code{reverse-nexti})}
6174 @item reverse-nexti @r{[}@var{count}@r{]}
6175 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6176 in reverse, except that called functions are ``un-executed'' atomically.
6177 That is, if the previously executed instruction was a return from
6178 another function, @code{reverse-nexti} will continue to execute
6179 in reverse until the call to that function (from the current stack
6182 @kindex reverse-finish
6183 @item reverse-finish
6184 Just as the @code{finish} command takes you to the point where the
6185 current function returns, @code{reverse-finish} takes you to the point
6186 where it was called. Instead of ending up at the end of the current
6187 function invocation, you end up at the beginning.
6189 @kindex set exec-direction
6190 @item set exec-direction
6191 Set the direction of target execution.
6192 @item set exec-direction reverse
6193 @cindex execute forward or backward in time
6194 @value{GDBN} will perform all execution commands in reverse, until the
6195 exec-direction mode is changed to ``forward''. Affected commands include
6196 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6197 command cannot be used in reverse mode.
6198 @item set exec-direction forward
6199 @value{GDBN} will perform all execution commands in the normal fashion.
6200 This is the default.
6204 @node Process Record and Replay
6205 @chapter Recording Inferior's Execution and Replaying It
6206 @cindex process record and replay
6207 @cindex recording inferior's execution and replaying it
6209 On some platforms, @value{GDBN} provides a special @dfn{process record
6210 and replay} target that can record a log of the process execution, and
6211 replay it later with both forward and reverse execution commands.
6214 When this target is in use, if the execution log includes the record
6215 for the next instruction, @value{GDBN} will debug in @dfn{replay
6216 mode}. In the replay mode, the inferior does not really execute code
6217 instructions. Instead, all the events that normally happen during
6218 code execution are taken from the execution log. While code is not
6219 really executed in replay mode, the values of registers (including the
6220 program counter register) and the memory of the inferior are still
6221 changed as they normally would. Their contents are taken from the
6225 If the record for the next instruction is not in the execution log,
6226 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6227 inferior executes normally, and @value{GDBN} records the execution log
6230 The process record and replay target supports reverse execution
6231 (@pxref{Reverse Execution}), even if the platform on which the
6232 inferior runs does not. However, the reverse execution is limited in
6233 this case by the range of the instructions recorded in the execution
6234 log. In other words, reverse execution on platforms that don't
6235 support it directly can only be done in the replay mode.
6237 When debugging in the reverse direction, @value{GDBN} will work in
6238 replay mode as long as the execution log includes the record for the
6239 previous instruction; otherwise, it will work in record mode, if the
6240 platform supports reverse execution, or stop if not.
6242 For architecture environments that support process record and replay,
6243 @value{GDBN} provides the following commands:
6246 @kindex target record
6247 @kindex target record-full
6248 @kindex target record-btrace
6251 @kindex record btrace
6255 @item record @var{method}
6256 This command starts the process record and replay target. The
6257 recording method can be specified as parameter. Without a parameter
6258 the command uses the @code{full} recording method. The following
6259 recording methods are available:
6263 Full record/replay recording using @value{GDBN}'s software record and
6264 replay implementation. This method allows replaying and reverse
6268 Hardware-supported instruction recording. This method does not record
6269 data. Further, the data is collected in a ring buffer so old data will
6270 be overwritten when the buffer is full. It allows limited replay and
6273 This recording method may not be available on all processors.
6276 The process record and replay target can only debug a process that is
6277 already running. Therefore, you need first to start the process with
6278 the @kbd{run} or @kbd{start} commands, and then start the recording
6279 with the @kbd{record @var{method}} command.
6281 Both @code{record @var{method}} and @code{rec @var{method}} are
6282 aliases of @code{target record-@var{method}}.
6284 @cindex displaced stepping, and process record and replay
6285 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6286 will be automatically disabled when process record and replay target
6287 is started. That's because the process record and replay target
6288 doesn't support displaced stepping.
6290 @cindex non-stop mode, and process record and replay
6291 @cindex asynchronous execution, and process record and replay
6292 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6293 the asynchronous execution mode (@pxref{Background Execution}), not
6294 all recording methods are available. The @code{full} recording method
6295 does not support these two modes.
6300 Stop the process record and replay target. When process record and
6301 replay target stops, the entire execution log will be deleted and the
6302 inferior will either be terminated, or will remain in its final state.
6304 When you stop the process record and replay target in record mode (at
6305 the end of the execution log), the inferior will be stopped at the
6306 next instruction that would have been recorded. In other words, if
6307 you record for a while and then stop recording, the inferior process
6308 will be left in the same state as if the recording never happened.
6310 On the other hand, if the process record and replay target is stopped
6311 while in replay mode (that is, not at the end of the execution log,
6312 but at some earlier point), the inferior process will become ``live''
6313 at that earlier state, and it will then be possible to continue the
6314 usual ``live'' debugging of the process from that state.
6316 When the inferior process exits, or @value{GDBN} detaches from it,
6317 process record and replay target will automatically stop itself.
6321 Go to a specific location in the execution log. There are several
6322 ways to specify the location to go to:
6325 @item record goto begin
6326 @itemx record goto start
6327 Go to the beginning of the execution log.
6329 @item record goto end
6330 Go to the end of the execution log.
6332 @item record goto @var{n}
6333 Go to instruction number @var{n} in the execution log.
6337 @item record save @var{filename}
6338 Save the execution log to a file @file{@var{filename}}.
6339 Default filename is @file{gdb_record.@var{process_id}}, where
6340 @var{process_id} is the process ID of the inferior.
6342 This command may not be available for all recording methods.
6344 @kindex record restore
6345 @item record restore @var{filename}
6346 Restore the execution log from a file @file{@var{filename}}.
6347 File must have been created with @code{record save}.
6349 @kindex set record full
6350 @item set record full insn-number-max @var{limit}
6351 @itemx set record full insn-number-max unlimited
6352 Set the limit of instructions to be recorded for the @code{full}
6353 recording method. Default value is 200000.
6355 If @var{limit} is a positive number, then @value{GDBN} will start
6356 deleting instructions from the log once the number of the record
6357 instructions becomes greater than @var{limit}. For every new recorded
6358 instruction, @value{GDBN} will delete the earliest recorded
6359 instruction to keep the number of recorded instructions at the limit.
6360 (Since deleting recorded instructions loses information, @value{GDBN}
6361 lets you control what happens when the limit is reached, by means of
6362 the @code{stop-at-limit} option, described below.)
6364 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6365 delete recorded instructions from the execution log. The number of
6366 recorded instructions is limited only by the available memory.
6368 @kindex show record full
6369 @item show record full insn-number-max
6370 Show the limit of instructions to be recorded with the @code{full}
6373 @item set record full stop-at-limit
6374 Control the behavior of the @code{full} recording method when the
6375 number of recorded instructions reaches the limit. If ON (the
6376 default), @value{GDBN} will stop when the limit is reached for the
6377 first time and ask you whether you want to stop the inferior or
6378 continue running it and recording the execution log. If you decide
6379 to continue recording, each new recorded instruction will cause the
6380 oldest one to be deleted.
6382 If this option is OFF, @value{GDBN} will automatically delete the
6383 oldest record to make room for each new one, without asking.
6385 @item show record full stop-at-limit
6386 Show the current setting of @code{stop-at-limit}.
6388 @item set record full memory-query
6389 Control the behavior when @value{GDBN} is unable to record memory
6390 changes caused by an instruction for the @code{full} recording method.
6391 If ON, @value{GDBN} will query whether to stop the inferior in that
6394 If this option is OFF (the default), @value{GDBN} will automatically
6395 ignore the effect of such instructions on memory. Later, when
6396 @value{GDBN} replays this execution log, it will mark the log of this
6397 instruction as not accessible, and it will not affect the replay
6400 @item show record full memory-query
6401 Show the current setting of @code{memory-query}.
6405 Show various statistics about the recording depending on the recording
6410 For the @code{full} recording method, it shows the state of process
6411 record and its in-memory execution log buffer, including:
6415 Whether in record mode or replay mode.
6417 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6419 Highest recorded instruction number.
6421 Current instruction about to be replayed (if in replay mode).
6423 Number of instructions contained in the execution log.
6425 Maximum number of instructions that may be contained in the execution log.
6429 For the @code{btrace} recording method, it shows the number of
6430 instructions that have been recorded and the number of blocks of
6431 sequential control-flow that is formed by the recorded instructions.
6434 @kindex record delete
6437 When record target runs in replay mode (``in the past''), delete the
6438 subsequent execution log and begin to record a new execution log starting
6439 from the current address. This means you will abandon the previously
6440 recorded ``future'' and begin recording a new ``future''.
6442 @kindex record instruction-history
6443 @kindex rec instruction-history
6444 @item record instruction-history
6445 Disassembles instructions from the recorded execution log. By
6446 default, ten instructions are disassembled. This can be changed using
6447 the @code{set record instruction-history-size} command. Instructions
6448 are printed in execution order. There are several ways to specify
6449 what part of the execution log to disassemble:
6452 @item record instruction-history @var{insn}
6453 Disassembles ten instructions starting from instruction number
6456 @item record instruction-history @var{insn}, +/-@var{n}
6457 Disassembles @var{n} instructions around instruction number
6458 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6459 @var{n} instructions after instruction number @var{insn}. If
6460 @var{n} is preceded with @code{-}, disassembles @var{n}
6461 instructions before instruction number @var{insn}.
6463 @item record instruction-history
6464 Disassembles ten more instructions after the last disassembly.
6466 @item record instruction-history -
6467 Disassembles ten more instructions before the last disassembly.
6469 @item record instruction-history @var{begin} @var{end}
6470 Disassembles instructions beginning with instruction number
6471 @var{begin} until instruction number @var{end}. The instruction
6472 number @var{end} is included.
6475 This command may not be available for all recording methods.
6478 @item set record instruction-history-size @var{size}
6479 @itemx set record instruction-history-size unlimited
6480 Define how many instructions to disassemble in the @code{record
6481 instruction-history} command. The default value is 10.
6482 A @var{size} of @code{unlimited} means unlimited instructions.
6485 @item show record instruction-history-size
6486 Show how many instructions to disassemble in the @code{record
6487 instruction-history} command.
6489 @kindex record function-call-history
6490 @kindex rec function-call-history
6491 @item record function-call-history
6492 Prints the execution history at function granularity. It prints one
6493 line for each sequence of instructions that belong to the same
6494 function giving the name of that function, the source lines
6495 for this instruction sequence (if the @code{/l} modifier is
6496 specified), and the instructions numbers that form the sequence (if
6497 the @code{/i} modifier is specified). The function names are indented
6498 to reflect the call stack depth if the @code{/c} modifier is
6499 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
6503 (@value{GDBP}) @b{list 1, 10}
6514 (@value{GDBP}) @b{record function-call-history /ilc}
6515 1 bar inst 1,4 at foo.c:6,8
6516 2 foo inst 5,10 at foo.c:2,3
6517 3 bar inst 11,13 at foo.c:9,10
6520 By default, ten lines are printed. This can be changed using the
6521 @code{set record function-call-history-size} command. Functions are
6522 printed in execution order. There are several ways to specify what
6526 @item record function-call-history @var{func}
6527 Prints ten functions starting from function number @var{func}.
6529 @item record function-call-history @var{func}, +/-@var{n}
6530 Prints @var{n} functions around function number @var{func}. If
6531 @var{n} is preceded with @code{+}, prints @var{n} functions after
6532 function number @var{func}. If @var{n} is preceded with @code{-},
6533 prints @var{n} functions before function number @var{func}.
6535 @item record function-call-history
6536 Prints ten more functions after the last ten-line print.
6538 @item record function-call-history -
6539 Prints ten more functions before the last ten-line print.
6541 @item record function-call-history @var{begin} @var{end}
6542 Prints functions beginning with function number @var{begin} until
6543 function number @var{end}. The function number @var{end} is included.
6546 This command may not be available for all recording methods.
6548 @item set record function-call-history-size @var{size}
6549 @itemx set record function-call-history-size unlimited
6550 Define how many lines to print in the
6551 @code{record function-call-history} command. The default value is 10.
6552 A size of @code{unlimited} means unlimited lines.
6554 @item show record function-call-history-size
6555 Show how many lines to print in the
6556 @code{record function-call-history} command.
6561 @chapter Examining the Stack
6563 When your program has stopped, the first thing you need to know is where it
6564 stopped and how it got there.
6567 Each time your program performs a function call, information about the call
6569 That information includes the location of the call in your program,
6570 the arguments of the call,
6571 and the local variables of the function being called.
6572 The information is saved in a block of data called a @dfn{stack frame}.
6573 The stack frames are allocated in a region of memory called the @dfn{call
6576 When your program stops, the @value{GDBN} commands for examining the
6577 stack allow you to see all of this information.
6579 @cindex selected frame
6580 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6581 @value{GDBN} commands refer implicitly to the selected frame. In
6582 particular, whenever you ask @value{GDBN} for the value of a variable in
6583 your program, the value is found in the selected frame. There are
6584 special @value{GDBN} commands to select whichever frame you are
6585 interested in. @xref{Selection, ,Selecting a Frame}.
6587 When your program stops, @value{GDBN} automatically selects the
6588 currently executing frame and describes it briefly, similar to the
6589 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6592 * Frames:: Stack frames
6593 * Backtrace:: Backtraces
6594 * Frame Filter Management:: Managing frame filters
6595 * Selection:: Selecting a frame
6596 * Frame Info:: Information on a frame
6601 @section Stack Frames
6603 @cindex frame, definition
6605 The call stack is divided up into contiguous pieces called @dfn{stack
6606 frames}, or @dfn{frames} for short; each frame is the data associated
6607 with one call to one function. The frame contains the arguments given
6608 to the function, the function's local variables, and the address at
6609 which the function is executing.
6611 @cindex initial frame
6612 @cindex outermost frame
6613 @cindex innermost frame
6614 When your program is started, the stack has only one frame, that of the
6615 function @code{main}. This is called the @dfn{initial} frame or the
6616 @dfn{outermost} frame. Each time a function is called, a new frame is
6617 made. Each time a function returns, the frame for that function invocation
6618 is eliminated. If a function is recursive, there can be many frames for
6619 the same function. The frame for the function in which execution is
6620 actually occurring is called the @dfn{innermost} frame. This is the most
6621 recently created of all the stack frames that still exist.
6623 @cindex frame pointer
6624 Inside your program, stack frames are identified by their addresses. A
6625 stack frame consists of many bytes, each of which has its own address; each
6626 kind of computer has a convention for choosing one byte whose
6627 address serves as the address of the frame. Usually this address is kept
6628 in a register called the @dfn{frame pointer register}
6629 (@pxref{Registers, $fp}) while execution is going on in that frame.
6631 @cindex frame number
6632 @value{GDBN} assigns numbers to all existing stack frames, starting with
6633 zero for the innermost frame, one for the frame that called it,
6634 and so on upward. These numbers do not really exist in your program;
6635 they are assigned by @value{GDBN} to give you a way of designating stack
6636 frames in @value{GDBN} commands.
6638 @c The -fomit-frame-pointer below perennially causes hbox overflow
6639 @c underflow problems.
6640 @cindex frameless execution
6641 Some compilers provide a way to compile functions so that they operate
6642 without stack frames. (For example, the @value{NGCC} option
6644 @samp{-fomit-frame-pointer}
6646 generates functions without a frame.)
6647 This is occasionally done with heavily used library functions to save
6648 the frame setup time. @value{GDBN} has limited facilities for dealing
6649 with these function invocations. If the innermost function invocation
6650 has no stack frame, @value{GDBN} nevertheless regards it as though
6651 it had a separate frame, which is numbered zero as usual, allowing
6652 correct tracing of the function call chain. However, @value{GDBN} has
6653 no provision for frameless functions elsewhere in the stack.
6656 @kindex frame@r{, command}
6657 @cindex current stack frame
6658 @item frame @var{args}
6659 The @code{frame} command allows you to move from one stack frame to another,
6660 and to print the stack frame you select. @var{args} may be either the
6661 address of the frame or the stack frame number. Without an argument,
6662 @code{frame} prints the current stack frame.
6664 @kindex select-frame
6665 @cindex selecting frame silently
6667 The @code{select-frame} command allows you to move from one stack frame
6668 to another without printing the frame. This is the silent version of
6676 @cindex call stack traces
6677 A backtrace is a summary of how your program got where it is. It shows one
6678 line per frame, for many frames, starting with the currently executing
6679 frame (frame zero), followed by its caller (frame one), and on up the
6682 @anchor{backtrace-command}
6685 @kindex bt @r{(@code{backtrace})}
6688 Print a backtrace of the entire stack: one line per frame for all
6689 frames in the stack.
6691 You can stop the backtrace at any time by typing the system interrupt
6692 character, normally @kbd{Ctrl-c}.
6694 @item backtrace @var{n}
6696 Similar, but print only the innermost @var{n} frames.
6698 @item backtrace -@var{n}
6700 Similar, but print only the outermost @var{n} frames.
6702 @item backtrace full
6704 @itemx bt full @var{n}
6705 @itemx bt full -@var{n}
6706 Print the values of the local variables also. @var{n} specifies the
6707 number of frames to print, as described above.
6709 @item backtrace no-filters
6710 @itemx bt no-filters
6711 @itemx bt no-filters @var{n}
6712 @itemx bt no-filters -@var{n}
6713 @itemx bt no-filters full
6714 @itemx bt no-filters full @var{n}
6715 @itemx bt no-filters full -@var{n}
6716 Do not run Python frame filters on this backtrace. @xref{Frame
6717 Filter API}, for more information. Additionally use @ref{disable
6718 frame-filter all} to turn off all frame filters. This is only
6719 relevant when @value{GDBN} has been configured with @code{Python}
6725 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6726 are additional aliases for @code{backtrace}.
6728 @cindex multiple threads, backtrace
6729 In a multi-threaded program, @value{GDBN} by default shows the
6730 backtrace only for the current thread. To display the backtrace for
6731 several or all of the threads, use the command @code{thread apply}
6732 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6733 apply all backtrace}, @value{GDBN} will display the backtrace for all
6734 the threads; this is handy when you debug a core dump of a
6735 multi-threaded program.
6737 Each line in the backtrace shows the frame number and the function name.
6738 The program counter value is also shown---unless you use @code{set
6739 print address off}. The backtrace also shows the source file name and
6740 line number, as well as the arguments to the function. The program
6741 counter value is omitted if it is at the beginning of the code for that
6744 Here is an example of a backtrace. It was made with the command
6745 @samp{bt 3}, so it shows the innermost three frames.
6749 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6751 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6752 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6754 (More stack frames follow...)
6759 The display for frame zero does not begin with a program counter
6760 value, indicating that your program has stopped at the beginning of the
6761 code for line @code{993} of @code{builtin.c}.
6764 The value of parameter @code{data} in frame 1 has been replaced by
6765 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6766 only if it is a scalar (integer, pointer, enumeration, etc). See command
6767 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6768 on how to configure the way function parameter values are printed.
6770 @cindex optimized out, in backtrace
6771 @cindex function call arguments, optimized out
6772 If your program was compiled with optimizations, some compilers will
6773 optimize away arguments passed to functions if those arguments are
6774 never used after the call. Such optimizations generate code that
6775 passes arguments through registers, but doesn't store those arguments
6776 in the stack frame. @value{GDBN} has no way of displaying such
6777 arguments in stack frames other than the innermost one. Here's what
6778 such a backtrace might look like:
6782 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6784 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6785 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6787 (More stack frames follow...)
6792 The values of arguments that were not saved in their stack frames are
6793 shown as @samp{<optimized out>}.
6795 If you need to display the values of such optimized-out arguments,
6796 either deduce that from other variables whose values depend on the one
6797 you are interested in, or recompile without optimizations.
6799 @cindex backtrace beyond @code{main} function
6800 @cindex program entry point
6801 @cindex startup code, and backtrace
6802 Most programs have a standard user entry point---a place where system
6803 libraries and startup code transition into user code. For C this is
6804 @code{main}@footnote{
6805 Note that embedded programs (the so-called ``free-standing''
6806 environment) are not required to have a @code{main} function as the
6807 entry point. They could even have multiple entry points.}.
6808 When @value{GDBN} finds the entry function in a backtrace
6809 it will terminate the backtrace, to avoid tracing into highly
6810 system-specific (and generally uninteresting) code.
6812 If you need to examine the startup code, or limit the number of levels
6813 in a backtrace, you can change this behavior:
6816 @item set backtrace past-main
6817 @itemx set backtrace past-main on
6818 @kindex set backtrace
6819 Backtraces will continue past the user entry point.
6821 @item set backtrace past-main off
6822 Backtraces will stop when they encounter the user entry point. This is the
6825 @item show backtrace past-main
6826 @kindex show backtrace
6827 Display the current user entry point backtrace policy.
6829 @item set backtrace past-entry
6830 @itemx set backtrace past-entry on
6831 Backtraces will continue past the internal entry point of an application.
6832 This entry point is encoded by the linker when the application is built,
6833 and is likely before the user entry point @code{main} (or equivalent) is called.
6835 @item set backtrace past-entry off
6836 Backtraces will stop when they encounter the internal entry point of an
6837 application. This is the default.
6839 @item show backtrace past-entry
6840 Display the current internal entry point backtrace policy.
6842 @item set backtrace limit @var{n}
6843 @itemx set backtrace limit 0
6844 @itemx set backtrace limit unlimited
6845 @cindex backtrace limit
6846 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
6847 or zero means unlimited levels.
6849 @item show backtrace limit
6850 Display the current limit on backtrace levels.
6853 You can control how file names are displayed.
6856 @item set filename-display
6857 @itemx set filename-display relative
6858 @cindex filename-display
6859 Display file names relative to the compilation directory. This is the default.
6861 @item set filename-display basename
6862 Display only basename of a filename.
6864 @item set filename-display absolute
6865 Display an absolute filename.
6867 @item show filename-display
6868 Show the current way to display filenames.
6871 @node Frame Filter Management
6872 @section Management of Frame Filters.
6873 @cindex managing frame filters
6875 Frame filters are Python based utilities to manage and decorate the
6876 output of frames. @xref{Frame Filter API}, for further information.
6878 Managing frame filters is performed by several commands available
6879 within @value{GDBN}, detailed here.
6882 @kindex info frame-filter
6883 @item info frame-filter
6884 Print a list of installed frame filters from all dictionaries, showing
6885 their name, priority and enabled status.
6887 @kindex disable frame-filter
6888 @anchor{disable frame-filter all}
6889 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
6890 Disable a frame filter in the dictionary matching
6891 @var{filter-dictionary}, or @code{all}, and @var{filter-name}.
6892 @var{filter-dictionary} may be @code{all}, @code{global},
6893 @code{progspace} or the name of the object file where the frame filter
6894 dictionary resides. When @code{all} is specified, all frame filters
6895 across all dictionaries are disabled. @var{filter-name} is the name
6896 of the frame filter and is used when @code{all} is not the option for
6897 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
6898 may be enabled again later.
6900 @kindex enable frame-filter
6901 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
6902 Enable a frame filter in the dictionary matching
6903 @var{filter-dictionary}, or @code{all}, and @var{filter-name}.
6904 @var{filter-dictionary} may be @code{all}, @code{global},
6905 @code{progspace} or the name of the object file where the frame filter
6906 dictionary resides. When @code{all} is specified, all frame filters across
6907 all dictionaries are enabled. @var{filter-name} is the name of the frame
6908 filter and is used when @code{all} is not the option for
6909 @var{filter-dictionary}.
6914 (gdb) info frame-filter
6916 global frame-filters:
6917 Priority Enabled Name
6918 1000 No PrimaryFunctionFilter
6921 progspace /build/test frame-filters:
6922 Priority Enabled Name
6923 100 Yes ProgspaceFilter
6925 objfile /build/test frame-filters:
6926 Priority Enabled Name
6927 999 Yes BuildProgra Filter
6929 (gdb) disable frame-filter /build/test BuildProgramFilter
6930 (gdb) info frame-filter
6932 global frame-filters:
6933 Priority Enabled Name
6934 1000 No PrimaryFunctionFilter
6937 progspace /build/test frame-filters:
6938 Priority Enabled Name
6939 100 Yes ProgspaceFilter
6941 objfile /build/test frame-filters:
6942 Priority Enabled Name
6943 999 No BuildProgramFilter
6945 (gdb) enable frame-filter global PrimaryFunctionFilter
6946 (gdb) info frame-filter
6948 global frame-filters:
6949 Priority Enabled Name
6950 1000 Yes PrimaryFunctionFilter
6953 progspace /build/test frame-filters:
6954 Priority Enabled Name
6955 100 Yes ProgspaceFilter
6957 objfile /build/test frame-filters:
6958 Priority Enabled Name
6959 999 No BuildProgramFilter
6962 @kindex set frame-filter priority
6963 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
6964 Set the @var{priority} of a frame filter in the dictionary matching
6965 @var{filter-dictionary}, and the frame filter name matching
6966 @var{filter-name}. @var{filter-dictionary} may be @code{global},
6967 @code{progspace} or the name of the object file where the frame filter
6968 dictionary resides. @var{priority} is an integer.
6970 @kindex show frame-filter priority
6971 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
6972 Show the @var{priority} of a frame filter in the dictionary matching
6973 @var{filter-dictionary}, and the frame filter name matching
6974 @var{filter-name}. @var{filter-dictionary} may be @code{global},
6975 @code{progspace} or the name of the object file where the frame filter
6981 (gdb) info frame-filter
6983 global frame-filters:
6984 Priority Enabled Name
6985 1000 Yes PrimaryFunctionFilter
6988 progspace /build/test frame-filters:
6989 Priority Enabled Name
6990 100 Yes ProgspaceFilter
6992 objfile /build/test frame-filters:
6993 Priority Enabled Name
6994 999 No BuildProgramFilter
6996 (gdb) set frame-filter priority global Reverse 50
6997 (gdb) info frame-filter
6999 global frame-filters:
7000 Priority Enabled Name
7001 1000 Yes PrimaryFunctionFilter
7004 progspace /build/test frame-filters:
7005 Priority Enabled Name
7006 100 Yes ProgspaceFilter
7008 objfile /build/test frame-filters:
7009 Priority Enabled Name
7010 999 No BuildProgramFilter
7015 @section Selecting a Frame
7017 Most commands for examining the stack and other data in your program work on
7018 whichever stack frame is selected at the moment. Here are the commands for
7019 selecting a stack frame; all of them finish by printing a brief description
7020 of the stack frame just selected.
7023 @kindex frame@r{, selecting}
7024 @kindex f @r{(@code{frame})}
7027 Select frame number @var{n}. Recall that frame zero is the innermost
7028 (currently executing) frame, frame one is the frame that called the
7029 innermost one, and so on. The highest-numbered frame is the one for
7032 @item frame @var{addr}
7034 Select the frame at address @var{addr}. This is useful mainly if the
7035 chaining of stack frames has been damaged by a bug, making it
7036 impossible for @value{GDBN} to assign numbers properly to all frames. In
7037 addition, this can be useful when your program has multiple stacks and
7038 switches between them.
7040 On the SPARC architecture, @code{frame} needs two addresses to
7041 select an arbitrary frame: a frame pointer and a stack pointer.
7043 On the @acronym{MIPS} and Alpha architecture, it needs two addresses: a stack
7044 pointer and a program counter.
7046 On the 29k architecture, it needs three addresses: a register stack
7047 pointer, a program counter, and a memory stack pointer.
7051 Move @var{n} frames up the stack. For positive numbers @var{n}, this
7052 advances toward the outermost frame, to higher frame numbers, to frames
7053 that have existed longer. @var{n} defaults to one.
7056 @kindex do @r{(@code{down})}
7058 Move @var{n} frames down the stack. For positive numbers @var{n}, this
7059 advances toward the innermost frame, to lower frame numbers, to frames
7060 that were created more recently. @var{n} defaults to one. You may
7061 abbreviate @code{down} as @code{do}.
7064 All of these commands end by printing two lines of output describing the
7065 frame. The first line shows the frame number, the function name, the
7066 arguments, and the source file and line number of execution in that
7067 frame. The second line shows the text of that source line.
7075 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7077 10 read_input_file (argv[i]);
7081 After such a printout, the @code{list} command with no arguments
7082 prints ten lines centered on the point of execution in the frame.
7083 You can also edit the program at the point of execution with your favorite
7084 editing program by typing @code{edit}.
7085 @xref{List, ,Printing Source Lines},
7089 @kindex down-silently
7091 @item up-silently @var{n}
7092 @itemx down-silently @var{n}
7093 These two commands are variants of @code{up} and @code{down},
7094 respectively; they differ in that they do their work silently, without
7095 causing display of the new frame. They are intended primarily for use
7096 in @value{GDBN} command scripts, where the output might be unnecessary and
7101 @section Information About a Frame
7103 There are several other commands to print information about the selected
7109 When used without any argument, this command does not change which
7110 frame is selected, but prints a brief description of the currently
7111 selected stack frame. It can be abbreviated @code{f}. With an
7112 argument, this command is used to select a stack frame.
7113 @xref{Selection, ,Selecting a Frame}.
7116 @kindex info f @r{(@code{info frame})}
7119 This command prints a verbose description of the selected stack frame,
7124 the address of the frame
7126 the address of the next frame down (called by this frame)
7128 the address of the next frame up (caller of this frame)
7130 the language in which the source code corresponding to this frame is written
7132 the address of the frame's arguments
7134 the address of the frame's local variables
7136 the program counter saved in it (the address of execution in the caller frame)
7138 which registers were saved in the frame
7141 @noindent The verbose description is useful when
7142 something has gone wrong that has made the stack format fail to fit
7143 the usual conventions.
7145 @item info frame @var{addr}
7146 @itemx info f @var{addr}
7147 Print a verbose description of the frame at address @var{addr}, without
7148 selecting that frame. The selected frame remains unchanged by this
7149 command. This requires the same kind of address (more than one for some
7150 architectures) that you specify in the @code{frame} command.
7151 @xref{Selection, ,Selecting a Frame}.
7155 Print the arguments of the selected frame, each on a separate line.
7159 Print the local variables of the selected frame, each on a separate
7160 line. These are all variables (declared either static or automatic)
7161 accessible at the point of execution of the selected frame.
7167 @chapter Examining Source Files
7169 @value{GDBN} can print parts of your program's source, since the debugging
7170 information recorded in the program tells @value{GDBN} what source files were
7171 used to build it. When your program stops, @value{GDBN} spontaneously prints
7172 the line where it stopped. Likewise, when you select a stack frame
7173 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7174 execution in that frame has stopped. You can print other portions of
7175 source files by explicit command.
7177 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7178 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7179 @value{GDBN} under @sc{gnu} Emacs}.
7182 * List:: Printing source lines
7183 * Specify Location:: How to specify code locations
7184 * Edit:: Editing source files
7185 * Search:: Searching source files
7186 * Source Path:: Specifying source directories
7187 * Machine Code:: Source and machine code
7191 @section Printing Source Lines
7194 @kindex l @r{(@code{list})}
7195 To print lines from a source file, use the @code{list} command
7196 (abbreviated @code{l}). By default, ten lines are printed.
7197 There are several ways to specify what part of the file you want to
7198 print; see @ref{Specify Location}, for the full list.
7200 Here are the forms of the @code{list} command most commonly used:
7203 @item list @var{linenum}
7204 Print lines centered around line number @var{linenum} in the
7205 current source file.
7207 @item list @var{function}
7208 Print lines centered around the beginning of function
7212 Print more lines. If the last lines printed were printed with a
7213 @code{list} command, this prints lines following the last lines
7214 printed; however, if the last line printed was a solitary line printed
7215 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7216 Stack}), this prints lines centered around that line.
7219 Print lines just before the lines last printed.
7222 @cindex @code{list}, how many lines to display
7223 By default, @value{GDBN} prints ten source lines with any of these forms of
7224 the @code{list} command. You can change this using @code{set listsize}:
7227 @kindex set listsize
7228 @item set listsize @var{count}
7229 @itemx set listsize unlimited
7230 Make the @code{list} command display @var{count} source lines (unless
7231 the @code{list} argument explicitly specifies some other number).
7232 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7234 @kindex show listsize
7236 Display the number of lines that @code{list} prints.
7239 Repeating a @code{list} command with @key{RET} discards the argument,
7240 so it is equivalent to typing just @code{list}. This is more useful
7241 than listing the same lines again. An exception is made for an
7242 argument of @samp{-}; that argument is preserved in repetition so that
7243 each repetition moves up in the source file.
7245 In general, the @code{list} command expects you to supply zero, one or two
7246 @dfn{linespecs}. Linespecs specify source lines; there are several ways
7247 of writing them (@pxref{Specify Location}), but the effect is always
7248 to specify some source line.
7250 Here is a complete description of the possible arguments for @code{list}:
7253 @item list @var{linespec}
7254 Print lines centered around the line specified by @var{linespec}.
7256 @item list @var{first},@var{last}
7257 Print lines from @var{first} to @var{last}. Both arguments are
7258 linespecs. When a @code{list} command has two linespecs, and the
7259 source file of the second linespec is omitted, this refers to
7260 the same source file as the first linespec.
7262 @item list ,@var{last}
7263 Print lines ending with @var{last}.
7265 @item list @var{first},
7266 Print lines starting with @var{first}.
7269 Print lines just after the lines last printed.
7272 Print lines just before the lines last printed.
7275 As described in the preceding table.
7278 @node Specify Location
7279 @section Specifying a Location
7280 @cindex specifying location
7283 Several @value{GDBN} commands accept arguments that specify a location
7284 of your program's code. Since @value{GDBN} is a source-level
7285 debugger, a location usually specifies some line in the source code;
7286 for that reason, locations are also known as @dfn{linespecs}.
7288 Here are all the different ways of specifying a code location that
7289 @value{GDBN} understands:
7293 Specifies the line number @var{linenum} of the current source file.
7296 @itemx +@var{offset}
7297 Specifies the line @var{offset} lines before or after the @dfn{current
7298 line}. For the @code{list} command, the current line is the last one
7299 printed; for the breakpoint commands, this is the line at which
7300 execution stopped in the currently selected @dfn{stack frame}
7301 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7302 used as the second of the two linespecs in a @code{list} command,
7303 this specifies the line @var{offset} lines up or down from the first
7306 @item @var{filename}:@var{linenum}
7307 Specifies the line @var{linenum} in the source file @var{filename}.
7308 If @var{filename} is a relative file name, then it will match any
7309 source file name with the same trailing components. For example, if
7310 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7311 name of @file{/build/trunk/gcc/expr.c}, but not
7312 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7314 @item @var{function}
7315 Specifies the line that begins the body of the function @var{function}.
7316 For example, in C, this is the line with the open brace.
7318 @item @var{function}:@var{label}
7319 Specifies the line where @var{label} appears in @var{function}.
7321 @item @var{filename}:@var{function}
7322 Specifies the line that begins the body of the function @var{function}
7323 in the file @var{filename}. You only need the file name with a
7324 function name to avoid ambiguity when there are identically named
7325 functions in different source files.
7328 Specifies the line at which the label named @var{label} appears.
7329 @value{GDBN} searches for the label in the function corresponding to
7330 the currently selected stack frame. If there is no current selected
7331 stack frame (for instance, if the inferior is not running), then
7332 @value{GDBN} will not search for a label.
7334 @item *@var{address}
7335 Specifies the program address @var{address}. For line-oriented
7336 commands, such as @code{list} and @code{edit}, this specifies a source
7337 line that contains @var{address}. For @code{break} and other
7338 breakpoint oriented commands, this can be used to set breakpoints in
7339 parts of your program which do not have debugging information or
7342 Here @var{address} may be any expression valid in the current working
7343 language (@pxref{Languages, working language}) that specifies a code
7344 address. In addition, as a convenience, @value{GDBN} extends the
7345 semantics of expressions used in locations to cover the situations
7346 that frequently happen during debugging. Here are the various forms
7350 @item @var{expression}
7351 Any expression valid in the current working language.
7353 @item @var{funcaddr}
7354 An address of a function or procedure derived from its name. In C,
7355 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
7356 simply the function's name @var{function} (and actually a special case
7357 of a valid expression). In Pascal and Modula-2, this is
7358 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7359 (although the Pascal form also works).
7361 This form specifies the address of the function's first instruction,
7362 before the stack frame and arguments have been set up.
7364 @item '@var{filename}'::@var{funcaddr}
7365 Like @var{funcaddr} above, but also specifies the name of the source
7366 file explicitly. This is useful if the name of the function does not
7367 specify the function unambiguously, e.g., if there are several
7368 functions with identical names in different source files.
7371 @cindex breakpoint at static probe point
7372 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7373 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7374 applications to embed static probes. @xref{Static Probe Points}, for more
7375 information on finding and using static probes. This form of linespec
7376 specifies the location of such a static probe.
7378 If @var{objfile} is given, only probes coming from that shared library
7379 or executable matching @var{objfile} as a regular expression are considered.
7380 If @var{provider} is given, then only probes from that provider are considered.
7381 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7382 each one of those probes.
7388 @section Editing Source Files
7389 @cindex editing source files
7392 @kindex e @r{(@code{edit})}
7393 To edit the lines in a source file, use the @code{edit} command.
7394 The editing program of your choice
7395 is invoked with the current line set to
7396 the active line in the program.
7397 Alternatively, there are several ways to specify what part of the file you
7398 want to print if you want to see other parts of the program:
7401 @item edit @var{location}
7402 Edit the source file specified by @code{location}. Editing starts at
7403 that @var{location}, e.g., at the specified source line of the
7404 specified file. @xref{Specify Location}, for all the possible forms
7405 of the @var{location} argument; here are the forms of the @code{edit}
7406 command most commonly used:
7409 @item edit @var{number}
7410 Edit the current source file with @var{number} as the active line number.
7412 @item edit @var{function}
7413 Edit the file containing @var{function} at the beginning of its definition.
7418 @subsection Choosing your Editor
7419 You can customize @value{GDBN} to use any editor you want
7421 The only restriction is that your editor (say @code{ex}), recognizes the
7422 following command-line syntax:
7424 ex +@var{number} file
7426 The optional numeric value +@var{number} specifies the number of the line in
7427 the file where to start editing.}.
7428 By default, it is @file{@value{EDITOR}}, but you can change this
7429 by setting the environment variable @code{EDITOR} before using
7430 @value{GDBN}. For example, to configure @value{GDBN} to use the
7431 @code{vi} editor, you could use these commands with the @code{sh} shell:
7437 or in the @code{csh} shell,
7439 setenv EDITOR /usr/bin/vi
7444 @section Searching Source Files
7445 @cindex searching source files
7447 There are two commands for searching through the current source file for a
7452 @kindex forward-search
7453 @kindex fo @r{(@code{forward-search})}
7454 @item forward-search @var{regexp}
7455 @itemx search @var{regexp}
7456 The command @samp{forward-search @var{regexp}} checks each line,
7457 starting with the one following the last line listed, for a match for
7458 @var{regexp}. It lists the line that is found. You can use the
7459 synonym @samp{search @var{regexp}} or abbreviate the command name as
7462 @kindex reverse-search
7463 @item reverse-search @var{regexp}
7464 The command @samp{reverse-search @var{regexp}} checks each line, starting
7465 with the one before the last line listed and going backward, for a match
7466 for @var{regexp}. It lists the line that is found. You can abbreviate
7467 this command as @code{rev}.
7471 @section Specifying Source Directories
7474 @cindex directories for source files
7475 Executable programs sometimes do not record the directories of the source
7476 files from which they were compiled, just the names. Even when they do,
7477 the directories could be moved between the compilation and your debugging
7478 session. @value{GDBN} has a list of directories to search for source files;
7479 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
7480 it tries all the directories in the list, in the order they are present
7481 in the list, until it finds a file with the desired name.
7483 For example, suppose an executable references the file
7484 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
7485 @file{/mnt/cross}. The file is first looked up literally; if this
7486 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
7487 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
7488 message is printed. @value{GDBN} does not look up the parts of the
7489 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
7490 Likewise, the subdirectories of the source path are not searched: if
7491 the source path is @file{/mnt/cross}, and the binary refers to
7492 @file{foo.c}, @value{GDBN} would not find it under
7493 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7495 Plain file names, relative file names with leading directories, file
7496 names containing dots, etc.@: are all treated as described above; for
7497 instance, if the source path is @file{/mnt/cross}, and the source file
7498 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7499 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7500 that---@file{/mnt/cross/foo.c}.
7502 Note that the executable search path is @emph{not} used to locate the
7505 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7506 any information it has cached about where source files are found and where
7507 each line is in the file.
7511 When you start @value{GDBN}, its source path includes only @samp{cdir}
7512 and @samp{cwd}, in that order.
7513 To add other directories, use the @code{directory} command.
7515 The search path is used to find both program source files and @value{GDBN}
7516 script files (read using the @samp{-command} option and @samp{source} command).
7518 In addition to the source path, @value{GDBN} provides a set of commands
7519 that manage a list of source path substitution rules. A @dfn{substitution
7520 rule} specifies how to rewrite source directories stored in the program's
7521 debug information in case the sources were moved to a different
7522 directory between compilation and debugging. A rule is made of
7523 two strings, the first specifying what needs to be rewritten in
7524 the path, and the second specifying how it should be rewritten.
7525 In @ref{set substitute-path}, we name these two parts @var{from} and
7526 @var{to} respectively. @value{GDBN} does a simple string replacement
7527 of @var{from} with @var{to} at the start of the directory part of the
7528 source file name, and uses that result instead of the original file
7529 name to look up the sources.
7531 Using the previous example, suppose the @file{foo-1.0} tree has been
7532 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7533 @value{GDBN} to replace @file{/usr/src} in all source path names with
7534 @file{/mnt/cross}. The first lookup will then be
7535 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7536 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7537 substitution rule, use the @code{set substitute-path} command
7538 (@pxref{set substitute-path}).
7540 To avoid unexpected substitution results, a rule is applied only if the
7541 @var{from} part of the directory name ends at a directory separator.
7542 For instance, a rule substituting @file{/usr/source} into
7543 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7544 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7545 is applied only at the beginning of the directory name, this rule will
7546 not be applied to @file{/root/usr/source/baz.c} either.
7548 In many cases, you can achieve the same result using the @code{directory}
7549 command. However, @code{set substitute-path} can be more efficient in
7550 the case where the sources are organized in a complex tree with multiple
7551 subdirectories. With the @code{directory} command, you need to add each
7552 subdirectory of your project. If you moved the entire tree while
7553 preserving its internal organization, then @code{set substitute-path}
7554 allows you to direct the debugger to all the sources with one single
7557 @code{set substitute-path} is also more than just a shortcut command.
7558 The source path is only used if the file at the original location no
7559 longer exists. On the other hand, @code{set substitute-path} modifies
7560 the debugger behavior to look at the rewritten location instead. So, if
7561 for any reason a source file that is not relevant to your executable is
7562 located at the original location, a substitution rule is the only
7563 method available to point @value{GDBN} at the new location.
7565 @cindex @samp{--with-relocated-sources}
7566 @cindex default source path substitution
7567 You can configure a default source path substitution rule by
7568 configuring @value{GDBN} with the
7569 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7570 should be the name of a directory under @value{GDBN}'s configured
7571 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7572 directory names in debug information under @var{dir} will be adjusted
7573 automatically if the installed @value{GDBN} is moved to a new
7574 location. This is useful if @value{GDBN}, libraries or executables
7575 with debug information and corresponding source code are being moved
7579 @item directory @var{dirname} @dots{}
7580 @item dir @var{dirname} @dots{}
7581 Add directory @var{dirname} to the front of the source path. Several
7582 directory names may be given to this command, separated by @samp{:}
7583 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7584 part of absolute file names) or
7585 whitespace. You may specify a directory that is already in the source
7586 path; this moves it forward, so @value{GDBN} searches it sooner.
7590 @vindex $cdir@r{, convenience variable}
7591 @vindex $cwd@r{, convenience variable}
7592 @cindex compilation directory
7593 @cindex current directory
7594 @cindex working directory
7595 @cindex directory, current
7596 @cindex directory, compilation
7597 You can use the string @samp{$cdir} to refer to the compilation
7598 directory (if one is recorded), and @samp{$cwd} to refer to the current
7599 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7600 tracks the current working directory as it changes during your @value{GDBN}
7601 session, while the latter is immediately expanded to the current
7602 directory at the time you add an entry to the source path.
7605 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7607 @c RET-repeat for @code{directory} is explicitly disabled, but since
7608 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7610 @item set directories @var{path-list}
7611 @kindex set directories
7612 Set the source path to @var{path-list}.
7613 @samp{$cdir:$cwd} are added if missing.
7615 @item show directories
7616 @kindex show directories
7617 Print the source path: show which directories it contains.
7619 @anchor{set substitute-path}
7620 @item set substitute-path @var{from} @var{to}
7621 @kindex set substitute-path
7622 Define a source path substitution rule, and add it at the end of the
7623 current list of existing substitution rules. If a rule with the same
7624 @var{from} was already defined, then the old rule is also deleted.
7626 For example, if the file @file{/foo/bar/baz.c} was moved to
7627 @file{/mnt/cross/baz.c}, then the command
7630 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
7634 will tell @value{GDBN} to replace @samp{/usr/src} with
7635 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7636 @file{baz.c} even though it was moved.
7638 In the case when more than one substitution rule have been defined,
7639 the rules are evaluated one by one in the order where they have been
7640 defined. The first one matching, if any, is selected to perform
7643 For instance, if we had entered the following commands:
7646 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
7647 (@value{GDBP}) set substitute-path /usr/src /mnt/src
7651 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
7652 @file{/mnt/include/defs.h} by using the first rule. However, it would
7653 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
7654 @file{/mnt/src/lib/foo.c}.
7657 @item unset substitute-path [path]
7658 @kindex unset substitute-path
7659 If a path is specified, search the current list of substitution rules
7660 for a rule that would rewrite that path. Delete that rule if found.
7661 A warning is emitted by the debugger if no rule could be found.
7663 If no path is specified, then all substitution rules are deleted.
7665 @item show substitute-path [path]
7666 @kindex show substitute-path
7667 If a path is specified, then print the source path substitution rule
7668 which would rewrite that path, if any.
7670 If no path is specified, then print all existing source path substitution
7675 If your source path is cluttered with directories that are no longer of
7676 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
7677 versions of source. You can correct the situation as follows:
7681 Use @code{directory} with no argument to reset the source path to its default value.
7684 Use @code{directory} with suitable arguments to reinstall the
7685 directories you want in the source path. You can add all the
7686 directories in one command.
7690 @section Source and Machine Code
7691 @cindex source line and its code address
7693 You can use the command @code{info line} to map source lines to program
7694 addresses (and vice versa), and the command @code{disassemble} to display
7695 a range of addresses as machine instructions. You can use the command
7696 @code{set disassemble-next-line} to set whether to disassemble next
7697 source line when execution stops. When run under @sc{gnu} Emacs
7698 mode, the @code{info line} command causes the arrow to point to the
7699 line specified. Also, @code{info line} prints addresses in symbolic form as
7704 @item info line @var{linespec}
7705 Print the starting and ending addresses of the compiled code for
7706 source line @var{linespec}. You can specify source lines in any of
7707 the ways documented in @ref{Specify Location}.
7710 For example, we can use @code{info line} to discover the location of
7711 the object code for the first line of function
7712 @code{m4_changequote}:
7714 @c FIXME: I think this example should also show the addresses in
7715 @c symbolic form, as they usually would be displayed.
7717 (@value{GDBP}) info line m4_changequote
7718 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
7722 @cindex code address and its source line
7723 We can also inquire (using @code{*@var{addr}} as the form for
7724 @var{linespec}) what source line covers a particular address:
7726 (@value{GDBP}) info line *0x63ff
7727 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
7730 @cindex @code{$_} and @code{info line}
7731 @cindex @code{x} command, default address
7732 @kindex x@r{(examine), and} info line
7733 After @code{info line}, the default address for the @code{x} command
7734 is changed to the starting address of the line, so that @samp{x/i} is
7735 sufficient to begin examining the machine code (@pxref{Memory,
7736 ,Examining Memory}). Also, this address is saved as the value of the
7737 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
7742 @cindex assembly instructions
7743 @cindex instructions, assembly
7744 @cindex machine instructions
7745 @cindex listing machine instructions
7747 @itemx disassemble /m
7748 @itemx disassemble /r
7749 This specialized command dumps a range of memory as machine
7750 instructions. It can also print mixed source+disassembly by specifying
7751 the @code{/m} modifier and print the raw instructions in hex as well as
7752 in symbolic form by specifying the @code{/r}.
7753 The default memory range is the function surrounding the
7754 program counter of the selected frame. A single argument to this
7755 command is a program counter value; @value{GDBN} dumps the function
7756 surrounding this value. When two arguments are given, they should
7757 be separated by a comma, possibly surrounded by whitespace. The
7758 arguments specify a range of addresses to dump, in one of two forms:
7761 @item @var{start},@var{end}
7762 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
7763 @item @var{start},+@var{length}
7764 the addresses from @var{start} (inclusive) to
7765 @code{@var{start}+@var{length}} (exclusive).
7769 When 2 arguments are specified, the name of the function is also
7770 printed (since there could be several functions in the given range).
7772 The argument(s) can be any expression yielding a numeric value, such as
7773 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
7775 If the range of memory being disassembled contains current program counter,
7776 the instruction at that location is shown with a @code{=>} marker.
7779 The following example shows the disassembly of a range of addresses of
7780 HP PA-RISC 2.0 code:
7783 (@value{GDBP}) disas 0x32c4, 0x32e4
7784 Dump of assembler code from 0x32c4 to 0x32e4:
7785 0x32c4 <main+204>: addil 0,dp
7786 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
7787 0x32cc <main+212>: ldil 0x3000,r31
7788 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
7789 0x32d4 <main+220>: ldo 0(r31),rp
7790 0x32d8 <main+224>: addil -0x800,dp
7791 0x32dc <main+228>: ldo 0x588(r1),r26
7792 0x32e0 <main+232>: ldil 0x3000,r31
7793 End of assembler dump.
7796 Here is an example showing mixed source+assembly for Intel x86, when the
7797 program is stopped just after function prologue:
7800 (@value{GDBP}) disas /m main
7801 Dump of assembler code for function main:
7803 0x08048330 <+0>: push %ebp
7804 0x08048331 <+1>: mov %esp,%ebp
7805 0x08048333 <+3>: sub $0x8,%esp
7806 0x08048336 <+6>: and $0xfffffff0,%esp
7807 0x08048339 <+9>: sub $0x10,%esp
7809 6 printf ("Hello.\n");
7810 => 0x0804833c <+12>: movl $0x8048440,(%esp)
7811 0x08048343 <+19>: call 0x8048284 <puts@@plt>
7815 0x08048348 <+24>: mov $0x0,%eax
7816 0x0804834d <+29>: leave
7817 0x0804834e <+30>: ret
7819 End of assembler dump.
7822 Here is another example showing raw instructions in hex for AMD x86-64,
7825 (gdb) disas /r 0x400281,+10
7826 Dump of assembler code from 0x400281 to 0x40028b:
7827 0x0000000000400281: 38 36 cmp %dh,(%rsi)
7828 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
7829 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
7830 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7831 End of assembler dump.
7834 Addresses cannot be specified as a linespec (@pxref{Specify Location}).
7835 So, for example, if you want to disassemble function @code{bar}
7836 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
7837 and not @samp{disassemble foo.c:bar}.
7839 Some architectures have more than one commonly-used set of instruction
7840 mnemonics or other syntax.
7842 For programs that were dynamically linked and use shared libraries,
7843 instructions that call functions or branch to locations in the shared
7844 libraries might show a seemingly bogus location---it's actually a
7845 location of the relocation table. On some architectures, @value{GDBN}
7846 might be able to resolve these to actual function names.
7849 @kindex set disassembly-flavor
7850 @cindex Intel disassembly flavor
7851 @cindex AT&T disassembly flavor
7852 @item set disassembly-flavor @var{instruction-set}
7853 Select the instruction set to use when disassembling the
7854 program via the @code{disassemble} or @code{x/i} commands.
7856 Currently this command is only defined for the Intel x86 family. You
7857 can set @var{instruction-set} to either @code{intel} or @code{att}.
7858 The default is @code{att}, the AT&T flavor used by default by Unix
7859 assemblers for x86-based targets.
7861 @kindex show disassembly-flavor
7862 @item show disassembly-flavor
7863 Show the current setting of the disassembly flavor.
7867 @kindex set disassemble-next-line
7868 @kindex show disassemble-next-line
7869 @item set disassemble-next-line
7870 @itemx show disassemble-next-line
7871 Control whether or not @value{GDBN} will disassemble the next source
7872 line or instruction when execution stops. If ON, @value{GDBN} will
7873 display disassembly of the next source line when execution of the
7874 program being debugged stops. This is @emph{in addition} to
7875 displaying the source line itself, which @value{GDBN} always does if
7876 possible. If the next source line cannot be displayed for some reason
7877 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7878 info in the debug info), @value{GDBN} will display disassembly of the
7879 next @emph{instruction} instead of showing the next source line. If
7880 AUTO, @value{GDBN} will display disassembly of next instruction only
7881 if the source line cannot be displayed. This setting causes
7882 @value{GDBN} to display some feedback when you step through a function
7883 with no line info or whose source file is unavailable. The default is
7884 OFF, which means never display the disassembly of the next line or
7890 @chapter Examining Data
7892 @cindex printing data
7893 @cindex examining data
7896 The usual way to examine data in your program is with the @code{print}
7897 command (abbreviated @code{p}), or its synonym @code{inspect}. It
7898 evaluates and prints the value of an expression of the language your
7899 program is written in (@pxref{Languages, ,Using @value{GDBN} with
7900 Different Languages}). It may also print the expression using a
7901 Python-based pretty-printer (@pxref{Pretty Printing}).
7904 @item print @var{expr}
7905 @itemx print /@var{f} @var{expr}
7906 @var{expr} is an expression (in the source language). By default the
7907 value of @var{expr} is printed in a format appropriate to its data type;
7908 you can choose a different format by specifying @samp{/@var{f}}, where
7909 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
7913 @itemx print /@var{f}
7914 @cindex reprint the last value
7915 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
7916 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
7917 conveniently inspect the same value in an alternative format.
7920 A more low-level way of examining data is with the @code{x} command.
7921 It examines data in memory at a specified address and prints it in a
7922 specified format. @xref{Memory, ,Examining Memory}.
7924 If you are interested in information about types, or about how the
7925 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
7926 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7929 @cindex exploring hierarchical data structures
7931 Another way of examining values of expressions and type information is
7932 through the Python extension command @code{explore} (available only if
7933 the @value{GDBN} build is configured with @code{--with-python}). It
7934 offers an interactive way to start at the highest level (or, the most
7935 abstract level) of the data type of an expression (or, the data type
7936 itself) and explore all the way down to leaf scalar values/fields
7937 embedded in the higher level data types.
7940 @item explore @var{arg}
7941 @var{arg} is either an expression (in the source language), or a type
7942 visible in the current context of the program being debugged.
7945 The working of the @code{explore} command can be illustrated with an
7946 example. If a data type @code{struct ComplexStruct} is defined in your
7956 struct ComplexStruct
7958 struct SimpleStruct *ss_p;
7964 followed by variable declarations as
7967 struct SimpleStruct ss = @{ 10, 1.11 @};
7968 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
7972 then, the value of the variable @code{cs} can be explored using the
7973 @code{explore} command as follows.
7977 The value of `cs' is a struct/class of type `struct ComplexStruct' with
7978 the following fields:
7980 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
7981 arr = <Enter 1 to explore this field of type `int [10]'>
7983 Enter the field number of choice:
7987 Since the fields of @code{cs} are not scalar values, you are being
7988 prompted to chose the field you want to explore. Let's say you choose
7989 the field @code{ss_p} by entering @code{0}. Then, since this field is a
7990 pointer, you will be asked if it is pointing to a single value. From
7991 the declaration of @code{cs} above, it is indeed pointing to a single
7992 value, hence you enter @code{y}. If you enter @code{n}, then you will
7993 be asked if it were pointing to an array of values, in which case this
7994 field will be explored as if it were an array.
7997 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
7998 Continue exploring it as a pointer to a single value [y/n]: y
7999 The value of `*(cs.ss_p)' is a struct/class of type `struct
8000 SimpleStruct' with the following fields:
8002 i = 10 .. (Value of type `int')
8003 d = 1.1100000000000001 .. (Value of type `double')
8005 Press enter to return to parent value:
8009 If the field @code{arr} of @code{cs} was chosen for exploration by
8010 entering @code{1} earlier, then since it is as array, you will be
8011 prompted to enter the index of the element in the array that you want
8015 `cs.arr' is an array of `int'.
8016 Enter the index of the element you want to explore in `cs.arr': 5
8018 `(cs.arr)[5]' is a scalar value of type `int'.
8022 Press enter to return to parent value:
8025 In general, at any stage of exploration, you can go deeper towards the
8026 leaf values by responding to the prompts appropriately, or hit the
8027 return key to return to the enclosing data structure (the @i{higher}
8028 level data structure).
8030 Similar to exploring values, you can use the @code{explore} command to
8031 explore types. Instead of specifying a value (which is typically a
8032 variable name or an expression valid in the current context of the
8033 program being debugged), you specify a type name. If you consider the
8034 same example as above, your can explore the type
8035 @code{struct ComplexStruct} by passing the argument
8036 @code{struct ComplexStruct} to the @code{explore} command.
8039 (gdb) explore struct ComplexStruct
8043 By responding to the prompts appropriately in the subsequent interactive
8044 session, you can explore the type @code{struct ComplexStruct} in a
8045 manner similar to how the value @code{cs} was explored in the above
8048 The @code{explore} command also has two sub-commands,
8049 @code{explore value} and @code{explore type}. The former sub-command is
8050 a way to explicitly specify that value exploration of the argument is
8051 being invoked, while the latter is a way to explicitly specify that type
8052 exploration of the argument is being invoked.
8055 @item explore value @var{expr}
8056 @cindex explore value
8057 This sub-command of @code{explore} explores the value of the
8058 expression @var{expr} (if @var{expr} is an expression valid in the
8059 current context of the program being debugged). The behavior of this
8060 command is identical to that of the behavior of the @code{explore}
8061 command being passed the argument @var{expr}.
8063 @item explore type @var{arg}
8064 @cindex explore type
8065 This sub-command of @code{explore} explores the type of @var{arg} (if
8066 @var{arg} is a type visible in the current context of program being
8067 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8068 is an expression valid in the current context of the program being
8069 debugged). If @var{arg} is a type, then the behavior of this command is
8070 identical to that of the @code{explore} command being passed the
8071 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8072 this command will be identical to that of the @code{explore} command
8073 being passed the type of @var{arg} as the argument.
8077 * Expressions:: Expressions
8078 * Ambiguous Expressions:: Ambiguous Expressions
8079 * Variables:: Program variables
8080 * Arrays:: Artificial arrays
8081 * Output Formats:: Output formats
8082 * Memory:: Examining memory
8083 * Auto Display:: Automatic display
8084 * Print Settings:: Print settings
8085 * Pretty Printing:: Python pretty printing
8086 * Value History:: Value history
8087 * Convenience Vars:: Convenience variables
8088 * Convenience Funs:: Convenience functions
8089 * Registers:: Registers
8090 * Floating Point Hardware:: Floating point hardware
8091 * Vector Unit:: Vector Unit
8092 * OS Information:: Auxiliary data provided by operating system
8093 * Memory Region Attributes:: Memory region attributes
8094 * Dump/Restore Files:: Copy between memory and a file
8095 * Core File Generation:: Cause a program dump its core
8096 * Character Sets:: Debugging programs that use a different
8097 character set than GDB does
8098 * Caching Target Data:: Data caching for targets
8099 * Searching Memory:: Searching memory for a sequence of bytes
8103 @section Expressions
8106 @code{print} and many other @value{GDBN} commands accept an expression and
8107 compute its value. Any kind of constant, variable or operator defined
8108 by the programming language you are using is valid in an expression in
8109 @value{GDBN}. This includes conditional expressions, function calls,
8110 casts, and string constants. It also includes preprocessor macros, if
8111 you compiled your program to include this information; see
8114 @cindex arrays in expressions
8115 @value{GDBN} supports array constants in expressions input by
8116 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8117 you can use the command @code{print @{1, 2, 3@}} to create an array
8118 of three integers. If you pass an array to a function or assign it
8119 to a program variable, @value{GDBN} copies the array to memory that
8120 is @code{malloc}ed in the target program.
8122 Because C is so widespread, most of the expressions shown in examples in
8123 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8124 Languages}, for information on how to use expressions in other
8127 In this section, we discuss operators that you can use in @value{GDBN}
8128 expressions regardless of your programming language.
8130 @cindex casts, in expressions
8131 Casts are supported in all languages, not just in C, because it is so
8132 useful to cast a number into a pointer in order to examine a structure
8133 at that address in memory.
8134 @c FIXME: casts supported---Mod2 true?
8136 @value{GDBN} supports these operators, in addition to those common
8137 to programming languages:
8141 @samp{@@} is a binary operator for treating parts of memory as arrays.
8142 @xref{Arrays, ,Artificial Arrays}, for more information.
8145 @samp{::} allows you to specify a variable in terms of the file or
8146 function where it is defined. @xref{Variables, ,Program Variables}.
8148 @cindex @{@var{type}@}
8149 @cindex type casting memory
8150 @cindex memory, viewing as typed object
8151 @cindex casts, to view memory
8152 @item @{@var{type}@} @var{addr}
8153 Refers to an object of type @var{type} stored at address @var{addr} in
8154 memory. @var{addr} may be any expression whose value is an integer or
8155 pointer (but parentheses are required around binary operators, just as in
8156 a cast). This construct is allowed regardless of what kind of data is
8157 normally supposed to reside at @var{addr}.
8160 @node Ambiguous Expressions
8161 @section Ambiguous Expressions
8162 @cindex ambiguous expressions
8164 Expressions can sometimes contain some ambiguous elements. For instance,
8165 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8166 a single function name to be defined several times, for application in
8167 different contexts. This is called @dfn{overloading}. Another example
8168 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8169 templates and is typically instantiated several times, resulting in
8170 the same function name being defined in different contexts.
8172 In some cases and depending on the language, it is possible to adjust
8173 the expression to remove the ambiguity. For instance in C@t{++}, you
8174 can specify the signature of the function you want to break on, as in
8175 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8176 qualified name of your function often makes the expression unambiguous
8179 When an ambiguity that needs to be resolved is detected, the debugger
8180 has the capability to display a menu of numbered choices for each
8181 possibility, and then waits for the selection with the prompt @samp{>}.
8182 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
8183 aborts the current command. If the command in which the expression was
8184 used allows more than one choice to be selected, the next option in the
8185 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
8188 For example, the following session excerpt shows an attempt to set a
8189 breakpoint at the overloaded symbol @code{String::after}.
8190 We choose three particular definitions of that function name:
8192 @c FIXME! This is likely to change to show arg type lists, at least
8195 (@value{GDBP}) b String::after
8198 [2] file:String.cc; line number:867
8199 [3] file:String.cc; line number:860
8200 [4] file:String.cc; line number:875
8201 [5] file:String.cc; line number:853
8202 [6] file:String.cc; line number:846
8203 [7] file:String.cc; line number:735
8205 Breakpoint 1 at 0xb26c: file String.cc, line 867.
8206 Breakpoint 2 at 0xb344: file String.cc, line 875.
8207 Breakpoint 3 at 0xafcc: file String.cc, line 846.
8208 Multiple breakpoints were set.
8209 Use the "delete" command to delete unwanted
8216 @kindex set multiple-symbols
8217 @item set multiple-symbols @var{mode}
8218 @cindex multiple-symbols menu
8220 This option allows you to adjust the debugger behavior when an expression
8223 By default, @var{mode} is set to @code{all}. If the command with which
8224 the expression is used allows more than one choice, then @value{GDBN}
8225 automatically selects all possible choices. For instance, inserting
8226 a breakpoint on a function using an ambiguous name results in a breakpoint
8227 inserted on each possible match. However, if a unique choice must be made,
8228 then @value{GDBN} uses the menu to help you disambiguate the expression.
8229 For instance, printing the address of an overloaded function will result
8230 in the use of the menu.
8232 When @var{mode} is set to @code{ask}, the debugger always uses the menu
8233 when an ambiguity is detected.
8235 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
8236 an error due to the ambiguity and the command is aborted.
8238 @kindex show multiple-symbols
8239 @item show multiple-symbols
8240 Show the current value of the @code{multiple-symbols} setting.
8244 @section Program Variables
8246 The most common kind of expression to use is the name of a variable
8249 Variables in expressions are understood in the selected stack frame
8250 (@pxref{Selection, ,Selecting a Frame}); they must be either:
8254 global (or file-static)
8261 visible according to the scope rules of the
8262 programming language from the point of execution in that frame
8265 @noindent This means that in the function
8280 you can examine and use the variable @code{a} whenever your program is
8281 executing within the function @code{foo}, but you can only use or
8282 examine the variable @code{b} while your program is executing inside
8283 the block where @code{b} is declared.
8285 @cindex variable name conflict
8286 There is an exception: you can refer to a variable or function whose
8287 scope is a single source file even if the current execution point is not
8288 in this file. But it is possible to have more than one such variable or
8289 function with the same name (in different source files). If that
8290 happens, referring to that name has unpredictable effects. If you wish,
8291 you can specify a static variable in a particular function or file by
8292 using the colon-colon (@code{::}) notation:
8294 @cindex colon-colon, context for variables/functions
8296 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
8297 @cindex @code{::}, context for variables/functions
8300 @var{file}::@var{variable}
8301 @var{function}::@var{variable}
8305 Here @var{file} or @var{function} is the name of the context for the
8306 static @var{variable}. In the case of file names, you can use quotes to
8307 make sure @value{GDBN} parses the file name as a single word---for example,
8308 to print a global value of @code{x} defined in @file{f2.c}:
8311 (@value{GDBP}) p 'f2.c'::x
8314 The @code{::} notation is normally used for referring to
8315 static variables, since you typically disambiguate uses of local variables
8316 in functions by selecting the appropriate frame and using the
8317 simple name of the variable. However, you may also use this notation
8318 to refer to local variables in frames enclosing the selected frame:
8327 process (a); /* Stop here */
8338 For example, if there is a breakpoint at the commented line,
8339 here is what you might see
8340 when the program stops after executing the call @code{bar(0)}:
8345 (@value{GDBP}) p bar::a
8348 #2 0x080483d0 in foo (a=5) at foobar.c:12
8351 (@value{GDBP}) p bar::a
8355 @cindex C@t{++} scope resolution
8356 These uses of @samp{::} are very rarely in conflict with the very
8357 similar use of the same notation in C@t{++}. When they are in
8358 conflict, the C@t{++} meaning takes precedence; however, this can be
8359 overridden by quoting the file or function name with single quotes.
8361 For example, suppose the program is stopped in a method of a class
8362 that has a field named @code{includefile}, and there is also an
8363 include file named @file{includefile} that defines a variable,
8367 (@value{GDBP}) p includefile
8369 (@value{GDBP}) p includefile::some_global
8370 A syntax error in expression, near `'.
8371 (@value{GDBP}) p 'includefile'::some_global
8375 @cindex wrong values
8376 @cindex variable values, wrong
8377 @cindex function entry/exit, wrong values of variables
8378 @cindex optimized code, wrong values of variables
8380 @emph{Warning:} Occasionally, a local variable may appear to have the
8381 wrong value at certain points in a function---just after entry to a new
8382 scope, and just before exit.
8384 You may see this problem when you are stepping by machine instructions.
8385 This is because, on most machines, it takes more than one instruction to
8386 set up a stack frame (including local variable definitions); if you are
8387 stepping by machine instructions, variables may appear to have the wrong
8388 values until the stack frame is completely built. On exit, it usually
8389 also takes more than one machine instruction to destroy a stack frame;
8390 after you begin stepping through that group of instructions, local
8391 variable definitions may be gone.
8393 This may also happen when the compiler does significant optimizations.
8394 To be sure of always seeing accurate values, turn off all optimization
8397 @cindex ``No symbol "foo" in current context''
8398 Another possible effect of compiler optimizations is to optimize
8399 unused variables out of existence, or assign variables to registers (as
8400 opposed to memory addresses). Depending on the support for such cases
8401 offered by the debug info format used by the compiler, @value{GDBN}
8402 might not be able to display values for such local variables. If that
8403 happens, @value{GDBN} will print a message like this:
8406 No symbol "foo" in current context.
8409 To solve such problems, either recompile without optimizations, or use a
8410 different debug info format, if the compiler supports several such
8411 formats. @xref{Compilation}, for more information on choosing compiler
8412 options. @xref{C, ,C and C@t{++}}, for more information about debug
8413 info formats that are best suited to C@t{++} programs.
8415 If you ask to print an object whose contents are unknown to
8416 @value{GDBN}, e.g., because its data type is not completely specified
8417 by the debug information, @value{GDBN} will say @samp{<incomplete
8418 type>}. @xref{Symbols, incomplete type}, for more about this.
8420 If you append @kbd{@@entry} string to a function parameter name you get its
8421 value at the time the function got called. If the value is not available an
8422 error message is printed. Entry values are available only with some compilers.
8423 Entry values are normally also printed at the function parameter list according
8424 to @ref{set print entry-values}.
8427 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
8433 (gdb) print i@@entry
8437 Strings are identified as arrays of @code{char} values without specified
8438 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
8439 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
8440 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
8441 defines literal string type @code{"char"} as @code{char} without a sign.
8446 signed char var1[] = "A";
8449 You get during debugging
8454 $2 = @{65 'A', 0 '\0'@}
8458 @section Artificial Arrays
8460 @cindex artificial array
8462 @kindex @@@r{, referencing memory as an array}
8463 It is often useful to print out several successive objects of the
8464 same type in memory; a section of an array, or an array of
8465 dynamically determined size for which only a pointer exists in the
8468 You can do this by referring to a contiguous span of memory as an
8469 @dfn{artificial array}, using the binary operator @samp{@@}. The left
8470 operand of @samp{@@} should be the first element of the desired array
8471 and be an individual object. The right operand should be the desired length
8472 of the array. The result is an array value whose elements are all of
8473 the type of the left argument. The first element is actually the left
8474 argument; the second element comes from bytes of memory immediately
8475 following those that hold the first element, and so on. Here is an
8476 example. If a program says
8479 int *array = (int *) malloc (len * sizeof (int));
8483 you can print the contents of @code{array} with
8489 The left operand of @samp{@@} must reside in memory. Array values made
8490 with @samp{@@} in this way behave just like other arrays in terms of
8491 subscripting, and are coerced to pointers when used in expressions.
8492 Artificial arrays most often appear in expressions via the value history
8493 (@pxref{Value History, ,Value History}), after printing one out.
8495 Another way to create an artificial array is to use a cast.
8496 This re-interprets a value as if it were an array.
8497 The value need not be in memory:
8499 (@value{GDBP}) p/x (short[2])0x12345678
8500 $1 = @{0x1234, 0x5678@}
8503 As a convenience, if you leave the array length out (as in
8504 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
8505 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
8507 (@value{GDBP}) p/x (short[])0x12345678
8508 $2 = @{0x1234, 0x5678@}
8511 Sometimes the artificial array mechanism is not quite enough; in
8512 moderately complex data structures, the elements of interest may not
8513 actually be adjacent---for example, if you are interested in the values
8514 of pointers in an array. One useful work-around in this situation is
8515 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8516 Variables}) as a counter in an expression that prints the first
8517 interesting value, and then repeat that expression via @key{RET}. For
8518 instance, suppose you have an array @code{dtab} of pointers to
8519 structures, and you are interested in the values of a field @code{fv}
8520 in each structure. Here is an example of what you might type:
8530 @node Output Formats
8531 @section Output Formats
8533 @cindex formatted output
8534 @cindex output formats
8535 By default, @value{GDBN} prints a value according to its data type. Sometimes
8536 this is not what you want. For example, you might want to print a number
8537 in hex, or a pointer in decimal. Or you might want to view data in memory
8538 at a certain address as a character string or as an instruction. To do
8539 these things, specify an @dfn{output format} when you print a value.
8541 The simplest use of output formats is to say how to print a value
8542 already computed. This is done by starting the arguments of the
8543 @code{print} command with a slash and a format letter. The format
8544 letters supported are:
8548 Regard the bits of the value as an integer, and print the integer in
8552 Print as integer in signed decimal.
8555 Print as integer in unsigned decimal.
8558 Print as integer in octal.
8561 Print as integer in binary. The letter @samp{t} stands for ``two''.
8562 @footnote{@samp{b} cannot be used because these format letters are also
8563 used with the @code{x} command, where @samp{b} stands for ``byte'';
8564 see @ref{Memory,,Examining Memory}.}
8567 @cindex unknown address, locating
8568 @cindex locate address
8569 Print as an address, both absolute in hexadecimal and as an offset from
8570 the nearest preceding symbol. You can use this format used to discover
8571 where (in what function) an unknown address is located:
8574 (@value{GDBP}) p/a 0x54320
8575 $3 = 0x54320 <_initialize_vx+396>
8579 The command @code{info symbol 0x54320} yields similar results.
8580 @xref{Symbols, info symbol}.
8583 Regard as an integer and print it as a character constant. This
8584 prints both the numerical value and its character representation. The
8585 character representation is replaced with the octal escape @samp{\nnn}
8586 for characters outside the 7-bit @sc{ascii} range.
8588 Without this format, @value{GDBN} displays @code{char},
8589 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
8590 constants. Single-byte members of vectors are displayed as integer
8594 Regard the bits of the value as a floating point number and print
8595 using typical floating point syntax.
8598 @cindex printing strings
8599 @cindex printing byte arrays
8600 Regard as a string, if possible. With this format, pointers to single-byte
8601 data are displayed as null-terminated strings and arrays of single-byte data
8602 are displayed as fixed-length strings. Other values are displayed in their
8605 Without this format, @value{GDBN} displays pointers to and arrays of
8606 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
8607 strings. Single-byte members of a vector are displayed as an integer
8611 Like @samp{x} formatting, the value is treated as an integer and
8612 printed as hexadecimal, but leading zeros are printed to pad the value
8613 to the size of the integer type.
8616 @cindex raw printing
8617 Print using the @samp{raw} formatting. By default, @value{GDBN} will
8618 use a Python-based pretty-printer, if one is available (@pxref{Pretty
8619 Printing}). This typically results in a higher-level display of the
8620 value's contents. The @samp{r} format bypasses any Python
8621 pretty-printer which might exist.
8624 For example, to print the program counter in hex (@pxref{Registers}), type
8631 Note that no space is required before the slash; this is because command
8632 names in @value{GDBN} cannot contain a slash.
8634 To reprint the last value in the value history with a different format,
8635 you can use the @code{print} command with just a format and no
8636 expression. For example, @samp{p/x} reprints the last value in hex.
8639 @section Examining Memory
8641 You can use the command @code{x} (for ``examine'') to examine memory in
8642 any of several formats, independently of your program's data types.
8644 @cindex examining memory
8646 @kindex x @r{(examine memory)}
8647 @item x/@var{nfu} @var{addr}
8650 Use the @code{x} command to examine memory.
8653 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
8654 much memory to display and how to format it; @var{addr} is an
8655 expression giving the address where you want to start displaying memory.
8656 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
8657 Several commands set convenient defaults for @var{addr}.
8660 @item @var{n}, the repeat count
8661 The repeat count is a decimal integer; the default is 1. It specifies
8662 how much memory (counting by units @var{u}) to display.
8663 @c This really is **decimal**; unaffected by 'set radix' as of GDB
8666 @item @var{f}, the display format
8667 The display format is one of the formats used by @code{print}
8668 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
8669 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
8670 The default is @samp{x} (hexadecimal) initially. The default changes
8671 each time you use either @code{x} or @code{print}.
8673 @item @var{u}, the unit size
8674 The unit size is any of
8680 Halfwords (two bytes).
8682 Words (four bytes). This is the initial default.
8684 Giant words (eight bytes).
8687 Each time you specify a unit size with @code{x}, that size becomes the
8688 default unit the next time you use @code{x}. For the @samp{i} format,
8689 the unit size is ignored and is normally not written. For the @samp{s} format,
8690 the unit size defaults to @samp{b}, unless it is explicitly given.
8691 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
8692 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
8693 Note that the results depend on the programming language of the
8694 current compilation unit. If the language is C, the @samp{s}
8695 modifier will use the UTF-16 encoding while @samp{w} will use
8696 UTF-32. The encoding is set by the programming language and cannot
8699 @item @var{addr}, starting display address
8700 @var{addr} is the address where you want @value{GDBN} to begin displaying
8701 memory. The expression need not have a pointer value (though it may);
8702 it is always interpreted as an integer address of a byte of memory.
8703 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
8704 @var{addr} is usually just after the last address examined---but several
8705 other commands also set the default address: @code{info breakpoints} (to
8706 the address of the last breakpoint listed), @code{info line} (to the
8707 starting address of a line), and @code{print} (if you use it to display
8708 a value from memory).
8711 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
8712 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
8713 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
8714 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
8715 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
8717 Since the letters indicating unit sizes are all distinct from the
8718 letters specifying output formats, you do not have to remember whether
8719 unit size or format comes first; either order works. The output
8720 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
8721 (However, the count @var{n} must come first; @samp{wx4} does not work.)
8723 Even though the unit size @var{u} is ignored for the formats @samp{s}
8724 and @samp{i}, you might still want to use a count @var{n}; for example,
8725 @samp{3i} specifies that you want to see three machine instructions,
8726 including any operands. For convenience, especially when used with
8727 the @code{display} command, the @samp{i} format also prints branch delay
8728 slot instructions, if any, beyond the count specified, which immediately
8729 follow the last instruction that is within the count. The command
8730 @code{disassemble} gives an alternative way of inspecting machine
8731 instructions; see @ref{Machine Code,,Source and Machine Code}.
8733 All the defaults for the arguments to @code{x} are designed to make it
8734 easy to continue scanning memory with minimal specifications each time
8735 you use @code{x}. For example, after you have inspected three machine
8736 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
8737 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
8738 the repeat count @var{n} is used again; the other arguments default as
8739 for successive uses of @code{x}.
8741 When examining machine instructions, the instruction at current program
8742 counter is shown with a @code{=>} marker. For example:
8745 (@value{GDBP}) x/5i $pc-6
8746 0x804837f <main+11>: mov %esp,%ebp
8747 0x8048381 <main+13>: push %ecx
8748 0x8048382 <main+14>: sub $0x4,%esp
8749 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
8750 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
8753 @cindex @code{$_}, @code{$__}, and value history
8754 The addresses and contents printed by the @code{x} command are not saved
8755 in the value history because there is often too much of them and they
8756 would get in the way. Instead, @value{GDBN} makes these values available for
8757 subsequent use in expressions as values of the convenience variables
8758 @code{$_} and @code{$__}. After an @code{x} command, the last address
8759 examined is available for use in expressions in the convenience variable
8760 @code{$_}. The contents of that address, as examined, are available in
8761 the convenience variable @code{$__}.
8763 If the @code{x} command has a repeat count, the address and contents saved
8764 are from the last memory unit printed; this is not the same as the last
8765 address printed if several units were printed on the last line of output.
8767 @cindex remote memory comparison
8768 @cindex verify remote memory image
8769 When you are debugging a program running on a remote target machine
8770 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
8771 remote machine's memory against the executable file you downloaded to
8772 the target. The @code{compare-sections} command is provided for such
8776 @kindex compare-sections
8777 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
8778 Compare the data of a loadable section @var{section-name} in the
8779 executable file of the program being debugged with the same section in
8780 the remote machine's memory, and report any mismatches. With no
8781 arguments, compares all loadable sections. With an argument of
8782 @code{-r}, compares all loadable read-only sections. This command's
8783 availability depends on the target's support for the @code{"qCRC"}
8788 @section Automatic Display
8789 @cindex automatic display
8790 @cindex display of expressions
8792 If you find that you want to print the value of an expression frequently
8793 (to see how it changes), you might want to add it to the @dfn{automatic
8794 display list} so that @value{GDBN} prints its value each time your program stops.
8795 Each expression added to the list is given a number to identify it;
8796 to remove an expression from the list, you specify that number.
8797 The automatic display looks like this:
8801 3: bar[5] = (struct hack *) 0x3804
8805 This display shows item numbers, expressions and their current values. As with
8806 displays you request manually using @code{x} or @code{print}, you can
8807 specify the output format you prefer; in fact, @code{display} decides
8808 whether to use @code{print} or @code{x} depending your format
8809 specification---it uses @code{x} if you specify either the @samp{i}
8810 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
8814 @item display @var{expr}
8815 Add the expression @var{expr} to the list of expressions to display
8816 each time your program stops. @xref{Expressions, ,Expressions}.
8818 @code{display} does not repeat if you press @key{RET} again after using it.
8820 @item display/@var{fmt} @var{expr}
8821 For @var{fmt} specifying only a display format and not a size or
8822 count, add the expression @var{expr} to the auto-display list but
8823 arrange to display it each time in the specified format @var{fmt}.
8824 @xref{Output Formats,,Output Formats}.
8826 @item display/@var{fmt} @var{addr}
8827 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
8828 number of units, add the expression @var{addr} as a memory address to
8829 be examined each time your program stops. Examining means in effect
8830 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
8833 For example, @samp{display/i $pc} can be helpful, to see the machine
8834 instruction about to be executed each time execution stops (@samp{$pc}
8835 is a common name for the program counter; @pxref{Registers, ,Registers}).
8838 @kindex delete display
8840 @item undisplay @var{dnums}@dots{}
8841 @itemx delete display @var{dnums}@dots{}
8842 Remove items from the list of expressions to display. Specify the
8843 numbers of the displays that you want affected with the command
8844 argument @var{dnums}. It can be a single display number, one of the
8845 numbers shown in the first field of the @samp{info display} display;
8846 or it could be a range of display numbers, as in @code{2-4}.
8848 @code{undisplay} does not repeat if you press @key{RET} after using it.
8849 (Otherwise you would just get the error @samp{No display number @dots{}}.)
8851 @kindex disable display
8852 @item disable display @var{dnums}@dots{}
8853 Disable the display of item numbers @var{dnums}. A disabled display
8854 item is not printed automatically, but is not forgotten. It may be
8855 enabled again later. Specify the numbers of the displays that you
8856 want affected with the command argument @var{dnums}. It can be a
8857 single display number, one of the numbers shown in the first field of
8858 the @samp{info display} display; or it could be a range of display
8859 numbers, as in @code{2-4}.
8861 @kindex enable display
8862 @item enable display @var{dnums}@dots{}
8863 Enable display of item numbers @var{dnums}. It becomes effective once
8864 again in auto display of its expression, until you specify otherwise.
8865 Specify the numbers of the displays that you want affected with the
8866 command argument @var{dnums}. It can be a single display number, one
8867 of the numbers shown in the first field of the @samp{info display}
8868 display; or it could be a range of display numbers, as in @code{2-4}.
8871 Display the current values of the expressions on the list, just as is
8872 done when your program stops.
8874 @kindex info display
8876 Print the list of expressions previously set up to display
8877 automatically, each one with its item number, but without showing the
8878 values. This includes disabled expressions, which are marked as such.
8879 It also includes expressions which would not be displayed right now
8880 because they refer to automatic variables not currently available.
8883 @cindex display disabled out of scope
8884 If a display expression refers to local variables, then it does not make
8885 sense outside the lexical context for which it was set up. Such an
8886 expression is disabled when execution enters a context where one of its
8887 variables is not defined. For example, if you give the command
8888 @code{display last_char} while inside a function with an argument
8889 @code{last_char}, @value{GDBN} displays this argument while your program
8890 continues to stop inside that function. When it stops elsewhere---where
8891 there is no variable @code{last_char}---the display is disabled
8892 automatically. The next time your program stops where @code{last_char}
8893 is meaningful, you can enable the display expression once again.
8895 @node Print Settings
8896 @section Print Settings
8898 @cindex format options
8899 @cindex print settings
8900 @value{GDBN} provides the following ways to control how arrays, structures,
8901 and symbols are printed.
8904 These settings are useful for debugging programs in any language:
8908 @item set print address
8909 @itemx set print address on
8910 @cindex print/don't print memory addresses
8911 @value{GDBN} prints memory addresses showing the location of stack
8912 traces, structure values, pointer values, breakpoints, and so forth,
8913 even when it also displays the contents of those addresses. The default
8914 is @code{on}. For example, this is what a stack frame display looks like with
8915 @code{set print address on}:
8920 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
8922 530 if (lquote != def_lquote)
8926 @item set print address off
8927 Do not print addresses when displaying their contents. For example,
8928 this is the same stack frame displayed with @code{set print address off}:
8932 (@value{GDBP}) set print addr off
8934 #0 set_quotes (lq="<<", rq=">>") at input.c:530
8935 530 if (lquote != def_lquote)
8939 You can use @samp{set print address off} to eliminate all machine
8940 dependent displays from the @value{GDBN} interface. For example, with
8941 @code{print address off}, you should get the same text for backtraces on
8942 all machines---whether or not they involve pointer arguments.
8945 @item show print address
8946 Show whether or not addresses are to be printed.
8949 When @value{GDBN} prints a symbolic address, it normally prints the
8950 closest earlier symbol plus an offset. If that symbol does not uniquely
8951 identify the address (for example, it is a name whose scope is a single
8952 source file), you may need to clarify. One way to do this is with
8953 @code{info line}, for example @samp{info line *0x4537}. Alternately,
8954 you can set @value{GDBN} to print the source file and line number when
8955 it prints a symbolic address:
8958 @item set print symbol-filename on
8959 @cindex source file and line of a symbol
8960 @cindex symbol, source file and line
8961 Tell @value{GDBN} to print the source file name and line number of a
8962 symbol in the symbolic form of an address.
8964 @item set print symbol-filename off
8965 Do not print source file name and line number of a symbol. This is the
8968 @item show print symbol-filename
8969 Show whether or not @value{GDBN} will print the source file name and
8970 line number of a symbol in the symbolic form of an address.
8973 Another situation where it is helpful to show symbol filenames and line
8974 numbers is when disassembling code; @value{GDBN} shows you the line
8975 number and source file that corresponds to each instruction.
8977 Also, you may wish to see the symbolic form only if the address being
8978 printed is reasonably close to the closest earlier symbol:
8981 @item set print max-symbolic-offset @var{max-offset}
8982 @itemx set print max-symbolic-offset unlimited
8983 @cindex maximum value for offset of closest symbol
8984 Tell @value{GDBN} to only display the symbolic form of an address if the
8985 offset between the closest earlier symbol and the address is less than
8986 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
8987 to always print the symbolic form of an address if any symbol precedes
8988 it. Zero is equivalent to @code{unlimited}.
8990 @item show print max-symbolic-offset
8991 Ask how large the maximum offset is that @value{GDBN} prints in a
8995 @cindex wild pointer, interpreting
8996 @cindex pointer, finding referent
8997 If you have a pointer and you are not sure where it points, try
8998 @samp{set print symbol-filename on}. Then you can determine the name
8999 and source file location of the variable where it points, using
9000 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
9001 For example, here @value{GDBN} shows that a variable @code{ptt} points
9002 at another variable @code{t}, defined in @file{hi2.c}:
9005 (@value{GDBP}) set print symbol-filename on
9006 (@value{GDBP}) p/a ptt
9007 $4 = 0xe008 <t in hi2.c>
9011 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
9012 does not show the symbol name and filename of the referent, even with
9013 the appropriate @code{set print} options turned on.
9016 You can also enable @samp{/a}-like formatting all the time using
9017 @samp{set print symbol on}:
9020 @item set print symbol on
9021 Tell @value{GDBN} to print the symbol corresponding to an address, if
9024 @item set print symbol off
9025 Tell @value{GDBN} not to print the symbol corresponding to an
9026 address. In this mode, @value{GDBN} will still print the symbol
9027 corresponding to pointers to functions. This is the default.
9029 @item show print symbol
9030 Show whether @value{GDBN} will display the symbol corresponding to an
9034 Other settings control how different kinds of objects are printed:
9037 @item set print array
9038 @itemx set print array on
9039 @cindex pretty print arrays
9040 Pretty print arrays. This format is more convenient to read,
9041 but uses more space. The default is off.
9043 @item set print array off
9044 Return to compressed format for arrays.
9046 @item show print array
9047 Show whether compressed or pretty format is selected for displaying
9050 @cindex print array indexes
9051 @item set print array-indexes
9052 @itemx set print array-indexes on
9053 Print the index of each element when displaying arrays. May be more
9054 convenient to locate a given element in the array or quickly find the
9055 index of a given element in that printed array. The default is off.
9057 @item set print array-indexes off
9058 Stop printing element indexes when displaying arrays.
9060 @item show print array-indexes
9061 Show whether the index of each element is printed when displaying
9064 @item set print elements @var{number-of-elements}
9065 @itemx set print elements unlimited
9066 @cindex number of array elements to print
9067 @cindex limit on number of printed array elements
9068 Set a limit on how many elements of an array @value{GDBN} will print.
9069 If @value{GDBN} is printing a large array, it stops printing after it has
9070 printed the number of elements set by the @code{set print elements} command.
9071 This limit also applies to the display of strings.
9072 When @value{GDBN} starts, this limit is set to 200.
9073 Setting @var{number-of-elements} to @code{unlimited} or zero means
9074 that the number of elements to print is unlimited.
9076 @item show print elements
9077 Display the number of elements of a large array that @value{GDBN} will print.
9078 If the number is 0, then the printing is unlimited.
9080 @item set print frame-arguments @var{value}
9081 @kindex set print frame-arguments
9082 @cindex printing frame argument values
9083 @cindex print all frame argument values
9084 @cindex print frame argument values for scalars only
9085 @cindex do not print frame argument values
9086 This command allows to control how the values of arguments are printed
9087 when the debugger prints a frame (@pxref{Frames}). The possible
9092 The values of all arguments are printed.
9095 Print the value of an argument only if it is a scalar. The value of more
9096 complex arguments such as arrays, structures, unions, etc, is replaced
9097 by @code{@dots{}}. This is the default. Here is an example where
9098 only scalar arguments are shown:
9101 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9106 None of the argument values are printed. Instead, the value of each argument
9107 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9110 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9115 By default, only scalar arguments are printed. This command can be used
9116 to configure the debugger to print the value of all arguments, regardless
9117 of their type. However, it is often advantageous to not print the value
9118 of more complex parameters. For instance, it reduces the amount of
9119 information printed in each frame, making the backtrace more readable.
9120 Also, it improves performance when displaying Ada frames, because
9121 the computation of large arguments can sometimes be CPU-intensive,
9122 especially in large applications. Setting @code{print frame-arguments}
9123 to @code{scalars} (the default) or @code{none} avoids this computation,
9124 thus speeding up the display of each Ada frame.
9126 @item show print frame-arguments
9127 Show how the value of arguments should be displayed when printing a frame.
9129 @item set print raw frame-arguments on
9130 Print frame arguments in raw, non pretty-printed, form.
9132 @item set print raw frame-arguments off
9133 Print frame arguments in pretty-printed form, if there is a pretty-printer
9134 for the value (@pxref{Pretty Printing}),
9135 otherwise print the value in raw form.
9136 This is the default.
9138 @item show print raw frame-arguments
9139 Show whether to print frame arguments in raw form.
9141 @anchor{set print entry-values}
9142 @item set print entry-values @var{value}
9143 @kindex set print entry-values
9144 Set printing of frame argument values at function entry. In some cases
9145 @value{GDBN} can determine the value of function argument which was passed by
9146 the function caller, even if the value was modified inside the called function
9147 and therefore is different. With optimized code, the current value could be
9148 unavailable, but the entry value may still be known.
9150 The default value is @code{default} (see below for its description). Older
9151 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
9152 this feature will behave in the @code{default} setting the same way as with the
9155 This functionality is currently supported only by DWARF 2 debugging format and
9156 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9157 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9160 The @var{value} parameter can be one of the following:
9164 Print only actual parameter values, never print values from function entry
9168 #0 different (val=6)
9169 #0 lost (val=<optimized out>)
9171 #0 invalid (val=<optimized out>)
9175 Print only parameter values from function entry point. The actual parameter
9176 values are never printed.
9178 #0 equal (val@@entry=5)
9179 #0 different (val@@entry=5)
9180 #0 lost (val@@entry=5)
9181 #0 born (val@@entry=<optimized out>)
9182 #0 invalid (val@@entry=<optimized out>)
9186 Print only parameter values from function entry point. If value from function
9187 entry point is not known while the actual value is known, print the actual
9188 value for such parameter.
9190 #0 equal (val@@entry=5)
9191 #0 different (val@@entry=5)
9192 #0 lost (val@@entry=5)
9194 #0 invalid (val@@entry=<optimized out>)
9198 Print actual parameter values. If actual parameter value is not known while
9199 value from function entry point is known, print the entry point value for such
9203 #0 different (val=6)
9204 #0 lost (val@@entry=5)
9206 #0 invalid (val=<optimized out>)
9210 Always print both the actual parameter value and its value from function entry
9211 point, even if values of one or both are not available due to compiler
9214 #0 equal (val=5, val@@entry=5)
9215 #0 different (val=6, val@@entry=5)
9216 #0 lost (val=<optimized out>, val@@entry=5)
9217 #0 born (val=10, val@@entry=<optimized out>)
9218 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
9222 Print the actual parameter value if it is known and also its value from
9223 function entry point if it is known. If neither is known, print for the actual
9224 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
9225 values are known and identical, print the shortened
9226 @code{param=param@@entry=VALUE} notation.
9228 #0 equal (val=val@@entry=5)
9229 #0 different (val=6, val@@entry=5)
9230 #0 lost (val@@entry=5)
9232 #0 invalid (val=<optimized out>)
9236 Always print the actual parameter value. Print also its value from function
9237 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
9238 if both values are known and identical, print the shortened
9239 @code{param=param@@entry=VALUE} notation.
9241 #0 equal (val=val@@entry=5)
9242 #0 different (val=6, val@@entry=5)
9243 #0 lost (val=<optimized out>, val@@entry=5)
9245 #0 invalid (val=<optimized out>)
9249 For analysis messages on possible failures of frame argument values at function
9250 entry resolution see @ref{set debug entry-values}.
9252 @item show print entry-values
9253 Show the method being used for printing of frame argument values at function
9256 @item set print repeats @var{number-of-repeats}
9257 @itemx set print repeats unlimited
9258 @cindex repeated array elements
9259 Set the threshold for suppressing display of repeated array
9260 elements. When the number of consecutive identical elements of an
9261 array exceeds the threshold, @value{GDBN} prints the string
9262 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
9263 identical repetitions, instead of displaying the identical elements
9264 themselves. Setting the threshold to @code{unlimited} or zero will
9265 cause all elements to be individually printed. The default threshold
9268 @item show print repeats
9269 Display the current threshold for printing repeated identical
9272 @item set print null-stop
9273 @cindex @sc{null} elements in arrays
9274 Cause @value{GDBN} to stop printing the characters of an array when the first
9275 @sc{null} is encountered. This is useful when large arrays actually
9276 contain only short strings.
9279 @item show print null-stop
9280 Show whether @value{GDBN} stops printing an array on the first
9281 @sc{null} character.
9283 @item set print pretty on
9284 @cindex print structures in indented form
9285 @cindex indentation in structure display
9286 Cause @value{GDBN} to print structures in an indented format with one member
9287 per line, like this:
9302 @item set print pretty off
9303 Cause @value{GDBN} to print structures in a compact format, like this:
9307 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
9308 meat = 0x54 "Pork"@}
9313 This is the default format.
9315 @item show print pretty
9316 Show which format @value{GDBN} is using to print structures.
9318 @item set print sevenbit-strings on
9319 @cindex eight-bit characters in strings
9320 @cindex octal escapes in strings
9321 Print using only seven-bit characters; if this option is set,
9322 @value{GDBN} displays any eight-bit characters (in strings or
9323 character values) using the notation @code{\}@var{nnn}. This setting is
9324 best if you are working in English (@sc{ascii}) and you use the
9325 high-order bit of characters as a marker or ``meta'' bit.
9327 @item set print sevenbit-strings off
9328 Print full eight-bit characters. This allows the use of more
9329 international character sets, and is the default.
9331 @item show print sevenbit-strings
9332 Show whether or not @value{GDBN} is printing only seven-bit characters.
9334 @item set print union on
9335 @cindex unions in structures, printing
9336 Tell @value{GDBN} to print unions which are contained in structures
9337 and other unions. This is the default setting.
9339 @item set print union off
9340 Tell @value{GDBN} not to print unions which are contained in
9341 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
9344 @item show print union
9345 Ask @value{GDBN} whether or not it will print unions which are contained in
9346 structures and other unions.
9348 For example, given the declarations
9351 typedef enum @{Tree, Bug@} Species;
9352 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
9353 typedef enum @{Caterpillar, Cocoon, Butterfly@}
9364 struct thing foo = @{Tree, @{Acorn@}@};
9368 with @code{set print union on} in effect @samp{p foo} would print
9371 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
9375 and with @code{set print union off} in effect it would print
9378 $1 = @{it = Tree, form = @{...@}@}
9382 @code{set print union} affects programs written in C-like languages
9388 These settings are of interest when debugging C@t{++} programs:
9391 @cindex demangling C@t{++} names
9392 @item set print demangle
9393 @itemx set print demangle on
9394 Print C@t{++} names in their source form rather than in the encoded
9395 (``mangled'') form passed to the assembler and linker for type-safe
9396 linkage. The default is on.
9398 @item show print demangle
9399 Show whether C@t{++} names are printed in mangled or demangled form.
9401 @item set print asm-demangle
9402 @itemx set print asm-demangle on
9403 Print C@t{++} names in their source form rather than their mangled form, even
9404 in assembler code printouts such as instruction disassemblies.
9407 @item show print asm-demangle
9408 Show whether C@t{++} names in assembly listings are printed in mangled
9411 @cindex C@t{++} symbol decoding style
9412 @cindex symbol decoding style, C@t{++}
9413 @kindex set demangle-style
9414 @item set demangle-style @var{style}
9415 Choose among several encoding schemes used by different compilers to
9416 represent C@t{++} names. The choices for @var{style} are currently:
9420 Allow @value{GDBN} to choose a decoding style by inspecting your program.
9421 This is the default.
9424 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
9427 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
9430 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
9433 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
9434 @strong{Warning:} this setting alone is not sufficient to allow
9435 debugging @code{cfront}-generated executables. @value{GDBN} would
9436 require further enhancement to permit that.
9439 If you omit @var{style}, you will see a list of possible formats.
9441 @item show demangle-style
9442 Display the encoding style currently in use for decoding C@t{++} symbols.
9444 @item set print object
9445 @itemx set print object on
9446 @cindex derived type of an object, printing
9447 @cindex display derived types
9448 When displaying a pointer to an object, identify the @emph{actual}
9449 (derived) type of the object rather than the @emph{declared} type, using
9450 the virtual function table. Note that the virtual function table is
9451 required---this feature can only work for objects that have run-time
9452 type identification; a single virtual method in the object's declared
9453 type is sufficient. Note that this setting is also taken into account when
9454 working with variable objects via MI (@pxref{GDB/MI}).
9456 @item set print object off
9457 Display only the declared type of objects, without reference to the
9458 virtual function table. This is the default setting.
9460 @item show print object
9461 Show whether actual, or declared, object types are displayed.
9463 @item set print static-members
9464 @itemx set print static-members on
9465 @cindex static members of C@t{++} objects
9466 Print static members when displaying a C@t{++} object. The default is on.
9468 @item set print static-members off
9469 Do not print static members when displaying a C@t{++} object.
9471 @item show print static-members
9472 Show whether C@t{++} static members are printed or not.
9474 @item set print pascal_static-members
9475 @itemx set print pascal_static-members on
9476 @cindex static members of Pascal objects
9477 @cindex Pascal objects, static members display
9478 Print static members when displaying a Pascal object. The default is on.
9480 @item set print pascal_static-members off
9481 Do not print static members when displaying a Pascal object.
9483 @item show print pascal_static-members
9484 Show whether Pascal static members are printed or not.
9486 @c These don't work with HP ANSI C++ yet.
9487 @item set print vtbl
9488 @itemx set print vtbl on
9489 @cindex pretty print C@t{++} virtual function tables
9490 @cindex virtual functions (C@t{++}) display
9491 @cindex VTBL display
9492 Pretty print C@t{++} virtual function tables. The default is off.
9493 (The @code{vtbl} commands do not work on programs compiled with the HP
9494 ANSI C@t{++} compiler (@code{aCC}).)
9496 @item set print vtbl off
9497 Do not pretty print C@t{++} virtual function tables.
9499 @item show print vtbl
9500 Show whether C@t{++} virtual function tables are pretty printed, or not.
9503 @node Pretty Printing
9504 @section Pretty Printing
9506 @value{GDBN} provides a mechanism to allow pretty-printing of values using
9507 Python code. It greatly simplifies the display of complex objects. This
9508 mechanism works for both MI and the CLI.
9511 * Pretty-Printer Introduction:: Introduction to pretty-printers
9512 * Pretty-Printer Example:: An example pretty-printer
9513 * Pretty-Printer Commands:: Pretty-printer commands
9516 @node Pretty-Printer Introduction
9517 @subsection Pretty-Printer Introduction
9519 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
9520 registered for the value. If there is then @value{GDBN} invokes the
9521 pretty-printer to print the value. Otherwise the value is printed normally.
9523 Pretty-printers are normally named. This makes them easy to manage.
9524 The @samp{info pretty-printer} command will list all the installed
9525 pretty-printers with their names.
9526 If a pretty-printer can handle multiple data types, then its
9527 @dfn{subprinters} are the printers for the individual data types.
9528 Each such subprinter has its own name.
9529 The format of the name is @var{printer-name};@var{subprinter-name}.
9531 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
9532 Typically they are automatically loaded and registered when the corresponding
9533 debug information is loaded, thus making them available without having to
9534 do anything special.
9536 There are three places where a pretty-printer can be registered.
9540 Pretty-printers registered globally are available when debugging
9544 Pretty-printers registered with a program space are available only
9545 when debugging that program.
9546 @xref{Progspaces In Python}, for more details on program spaces in Python.
9549 Pretty-printers registered with an objfile are loaded and unloaded
9550 with the corresponding objfile (e.g., shared library).
9551 @xref{Objfiles In Python}, for more details on objfiles in Python.
9554 @xref{Selecting Pretty-Printers}, for further information on how
9555 pretty-printers are selected,
9557 @xref{Writing a Pretty-Printer}, for implementing pretty printers
9560 @node Pretty-Printer Example
9561 @subsection Pretty-Printer Example
9563 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
9566 (@value{GDBP}) print s
9568 static npos = 4294967295,
9570 <std::allocator<char>> = @{
9571 <__gnu_cxx::new_allocator<char>> = @{
9572 <No data fields>@}, <No data fields>
9574 members of std::basic_string<char, std::char_traits<char>,
9575 std::allocator<char> >::_Alloc_hider:
9576 _M_p = 0x804a014 "abcd"
9581 With a pretty-printer for @code{std::string} only the contents are printed:
9584 (@value{GDBP}) print s
9588 @node Pretty-Printer Commands
9589 @subsection Pretty-Printer Commands
9590 @cindex pretty-printer commands
9593 @kindex info pretty-printer
9594 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9595 Print the list of installed pretty-printers.
9596 This includes disabled pretty-printers, which are marked as such.
9598 @var{object-regexp} is a regular expression matching the objects
9599 whose pretty-printers to list.
9600 Objects can be @code{global}, the program space's file
9601 (@pxref{Progspaces In Python}),
9602 and the object files within that program space (@pxref{Objfiles In Python}).
9603 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
9604 looks up a printer from these three objects.
9606 @var{name-regexp} is a regular expression matching the name of the printers
9609 @kindex disable pretty-printer
9610 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9611 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9612 A disabled pretty-printer is not forgotten, it may be enabled again later.
9614 @kindex enable pretty-printer
9615 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9616 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9621 Suppose we have three pretty-printers installed: one from library1.so
9622 named @code{foo} that prints objects of type @code{foo}, and
9623 another from library2.so named @code{bar} that prints two types of objects,
9624 @code{bar1} and @code{bar2}.
9627 (gdb) info pretty-printer
9634 (gdb) info pretty-printer library2
9639 (gdb) disable pretty-printer library1
9641 2 of 3 printers enabled
9642 (gdb) info pretty-printer
9649 (gdb) disable pretty-printer library2 bar:bar1
9651 1 of 3 printers enabled
9652 (gdb) info pretty-printer library2
9659 (gdb) disable pretty-printer library2 bar
9661 0 of 3 printers enabled
9662 (gdb) info pretty-printer library2
9671 Note that for @code{bar} the entire printer can be disabled,
9672 as can each individual subprinter.
9675 @section Value History
9677 @cindex value history
9678 @cindex history of values printed by @value{GDBN}
9679 Values printed by the @code{print} command are saved in the @value{GDBN}
9680 @dfn{value history}. This allows you to refer to them in other expressions.
9681 Values are kept until the symbol table is re-read or discarded
9682 (for example with the @code{file} or @code{symbol-file} commands).
9683 When the symbol table changes, the value history is discarded,
9684 since the values may contain pointers back to the types defined in the
9689 @cindex history number
9690 The values printed are given @dfn{history numbers} by which you can
9691 refer to them. These are successive integers starting with one.
9692 @code{print} shows you the history number assigned to a value by
9693 printing @samp{$@var{num} = } before the value; here @var{num} is the
9696 To refer to any previous value, use @samp{$} followed by the value's
9697 history number. The way @code{print} labels its output is designed to
9698 remind you of this. Just @code{$} refers to the most recent value in
9699 the history, and @code{$$} refers to the value before that.
9700 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
9701 is the value just prior to @code{$$}, @code{$$1} is equivalent to
9702 @code{$$}, and @code{$$0} is equivalent to @code{$}.
9704 For example, suppose you have just printed a pointer to a structure and
9705 want to see the contents of the structure. It suffices to type
9711 If you have a chain of structures where the component @code{next} points
9712 to the next one, you can print the contents of the next one with this:
9719 You can print successive links in the chain by repeating this
9720 command---which you can do by just typing @key{RET}.
9722 Note that the history records values, not expressions. If the value of
9723 @code{x} is 4 and you type these commands:
9731 then the value recorded in the value history by the @code{print} command
9732 remains 4 even though the value of @code{x} has changed.
9737 Print the last ten values in the value history, with their item numbers.
9738 This is like @samp{p@ $$9} repeated ten times, except that @code{show
9739 values} does not change the history.
9741 @item show values @var{n}
9742 Print ten history values centered on history item number @var{n}.
9745 Print ten history values just after the values last printed. If no more
9746 values are available, @code{show values +} produces no display.
9749 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
9750 same effect as @samp{show values +}.
9752 @node Convenience Vars
9753 @section Convenience Variables
9755 @cindex convenience variables
9756 @cindex user-defined variables
9757 @value{GDBN} provides @dfn{convenience variables} that you can use within
9758 @value{GDBN} to hold on to a value and refer to it later. These variables
9759 exist entirely within @value{GDBN}; they are not part of your program, and
9760 setting a convenience variable has no direct effect on further execution
9761 of your program. That is why you can use them freely.
9763 Convenience variables are prefixed with @samp{$}. Any name preceded by
9764 @samp{$} can be used for a convenience variable, unless it is one of
9765 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
9766 (Value history references, in contrast, are @emph{numbers} preceded
9767 by @samp{$}. @xref{Value History, ,Value History}.)
9769 You can save a value in a convenience variable with an assignment
9770 expression, just as you would set a variable in your program.
9774 set $foo = *object_ptr
9778 would save in @code{$foo} the value contained in the object pointed to by
9781 Using a convenience variable for the first time creates it, but its
9782 value is @code{void} until you assign a new value. You can alter the
9783 value with another assignment at any time.
9785 Convenience variables have no fixed types. You can assign a convenience
9786 variable any type of value, including structures and arrays, even if
9787 that variable already has a value of a different type. The convenience
9788 variable, when used as an expression, has the type of its current value.
9791 @kindex show convenience
9792 @cindex show all user variables and functions
9793 @item show convenience
9794 Print a list of convenience variables used so far, and their values,
9795 as well as a list of the convenience functions.
9796 Abbreviated @code{show conv}.
9798 @kindex init-if-undefined
9799 @cindex convenience variables, initializing
9800 @item init-if-undefined $@var{variable} = @var{expression}
9801 Set a convenience variable if it has not already been set. This is useful
9802 for user-defined commands that keep some state. It is similar, in concept,
9803 to using local static variables with initializers in C (except that
9804 convenience variables are global). It can also be used to allow users to
9805 override default values used in a command script.
9807 If the variable is already defined then the expression is not evaluated so
9808 any side-effects do not occur.
9811 One of the ways to use a convenience variable is as a counter to be
9812 incremented or a pointer to be advanced. For example, to print
9813 a field from successive elements of an array of structures:
9817 print bar[$i++]->contents
9821 Repeat that command by typing @key{RET}.
9823 Some convenience variables are created automatically by @value{GDBN} and given
9824 values likely to be useful.
9827 @vindex $_@r{, convenience variable}
9829 The variable @code{$_} is automatically set by the @code{x} command to
9830 the last address examined (@pxref{Memory, ,Examining Memory}). Other
9831 commands which provide a default address for @code{x} to examine also
9832 set @code{$_} to that address; these commands include @code{info line}
9833 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
9834 except when set by the @code{x} command, in which case it is a pointer
9835 to the type of @code{$__}.
9837 @vindex $__@r{, convenience variable}
9839 The variable @code{$__} is automatically set by the @code{x} command
9840 to the value found in the last address examined. Its type is chosen
9841 to match the format in which the data was printed.
9844 @vindex $_exitcode@r{, convenience variable}
9845 When the program being debugged terminates normally, @value{GDBN}
9846 automatically sets this variable to the exit code of the program, and
9847 resets @code{$_exitsignal} to @code{void}.
9850 @vindex $_exitsignal@r{, convenience variable}
9851 When the program being debugged dies due to an uncaught signal,
9852 @value{GDBN} automatically sets this variable to that signal's number,
9853 and resets @code{$_exitcode} to @code{void}.
9855 To distinguish between whether the program being debugged has exited
9856 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
9857 @code{$_exitsignal} is not @code{void}), the convenience function
9858 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
9859 Functions}). For example, considering the following source code:
9865 main (int argc, char *argv[])
9872 A valid way of telling whether the program being debugged has exited
9873 or signalled would be:
9876 (@value{GDBP}) define has_exited_or_signalled
9877 Type commands for definition of ``has_exited_or_signalled''.
9878 End with a line saying just ``end''.
9879 >if $_isvoid ($_exitsignal)
9880 >echo The program has exited\n
9882 >echo The program has signalled\n
9888 Program terminated with signal SIGALRM, Alarm clock.
9889 The program no longer exists.
9890 (@value{GDBP}) has_exited_or_signalled
9891 The program has signalled
9894 As can be seen, @value{GDBN} correctly informs that the program being
9895 debugged has signalled, since it calls @code{raise} and raises a
9896 @code{SIGALRM} signal. If the program being debugged had not called
9897 @code{raise}, then @value{GDBN} would report a normal exit:
9900 (@value{GDBP}) has_exited_or_signalled
9901 The program has exited
9905 The variable @code{$_exception} is set to the exception object being
9906 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
9909 @itemx $_probe_arg0@dots{}$_probe_arg11
9910 Arguments to a static probe. @xref{Static Probe Points}.
9913 @vindex $_sdata@r{, inspect, convenience variable}
9914 The variable @code{$_sdata} contains extra collected static tracepoint
9915 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
9916 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
9917 if extra static tracepoint data has not been collected.
9920 @vindex $_siginfo@r{, convenience variable}
9921 The variable @code{$_siginfo} contains extra signal information
9922 (@pxref{extra signal information}). Note that @code{$_siginfo}
9923 could be empty, if the application has not yet received any signals.
9924 For example, it will be empty before you execute the @code{run} command.
9927 @vindex $_tlb@r{, convenience variable}
9928 The variable @code{$_tlb} is automatically set when debugging
9929 applications running on MS-Windows in native mode or connected to
9930 gdbserver that supports the @code{qGetTIBAddr} request.
9931 @xref{General Query Packets}.
9932 This variable contains the address of the thread information block.
9936 On HP-UX systems, if you refer to a function or variable name that
9937 begins with a dollar sign, @value{GDBN} searches for a user or system
9938 name first, before it searches for a convenience variable.
9940 @node Convenience Funs
9941 @section Convenience Functions
9943 @cindex convenience functions
9944 @value{GDBN} also supplies some @dfn{convenience functions}. These
9945 have a syntax similar to convenience variables. A convenience
9946 function can be used in an expression just like an ordinary function;
9947 however, a convenience function is implemented internally to
9950 These functions do not require @value{GDBN} to be configured with
9951 @code{Python} support, which means that they are always available.
9955 @item $_isvoid (@var{expr})
9956 @findex $_isvoid@r{, convenience function}
9957 Return one if the expression @var{expr} is @code{void}. Otherwise it
9960 A @code{void} expression is an expression where the type of the result
9961 is @code{void}. For example, you can examine a convenience variable
9962 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
9966 (@value{GDBP}) print $_exitcode
9968 (@value{GDBP}) print $_isvoid ($_exitcode)
9971 Starting program: ./a.out
9972 [Inferior 1 (process 29572) exited normally]
9973 (@value{GDBP}) print $_exitcode
9975 (@value{GDBP}) print $_isvoid ($_exitcode)
9979 In the example above, we used @code{$_isvoid} to check whether
9980 @code{$_exitcode} is @code{void} before and after the execution of the
9981 program being debugged. Before the execution there is no exit code to
9982 be examined, therefore @code{$_exitcode} is @code{void}. After the
9983 execution the program being debugged returned zero, therefore
9984 @code{$_exitcode} is zero, which means that it is not @code{void}
9987 The @code{void} expression can also be a call of a function from the
9988 program being debugged. For example, given the following function:
9997 The result of calling it inside @value{GDBN} is @code{void}:
10000 (@value{GDBP}) print foo ()
10002 (@value{GDBP}) print $_isvoid (foo ())
10004 (@value{GDBP}) set $v = foo ()
10005 (@value{GDBP}) print $v
10007 (@value{GDBP}) print $_isvoid ($v)
10013 These functions require @value{GDBN} to be configured with
10014 @code{Python} support.
10018 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10019 @findex $_memeq@r{, convenience function}
10020 Returns one if the @var{length} bytes at the addresses given by
10021 @var{buf1} and @var{buf2} are equal.
10022 Otherwise it returns zero.
10024 @item $_regex(@var{str}, @var{regex})
10025 @findex $_regex@r{, convenience function}
10026 Returns one if the string @var{str} matches the regular expression
10027 @var{regex}. Otherwise it returns zero.
10028 The syntax of the regular expression is that specified by @code{Python}'s
10029 regular expression support.
10031 @item $_streq(@var{str1}, @var{str2})
10032 @findex $_streq@r{, convenience function}
10033 Returns one if the strings @var{str1} and @var{str2} are equal.
10034 Otherwise it returns zero.
10036 @item $_strlen(@var{str})
10037 @findex $_strlen@r{, convenience function}
10038 Returns the length of string @var{str}.
10042 @value{GDBN} provides the ability to list and get help on
10043 convenience functions.
10046 @item help function
10047 @kindex help function
10048 @cindex show all convenience functions
10049 Print a list of all convenience functions.
10056 You can refer to machine register contents, in expressions, as variables
10057 with names starting with @samp{$}. The names of registers are different
10058 for each machine; use @code{info registers} to see the names used on
10062 @kindex info registers
10063 @item info registers
10064 Print the names and values of all registers except floating-point
10065 and vector registers (in the selected stack frame).
10067 @kindex info all-registers
10068 @cindex floating point registers
10069 @item info all-registers
10070 Print the names and values of all registers, including floating-point
10071 and vector registers (in the selected stack frame).
10073 @item info registers @var{regname} @dots{}
10074 Print the @dfn{relativized} value of each specified register @var{regname}.
10075 As discussed in detail below, register values are normally relative to
10076 the selected stack frame. @var{regname} may be any register name valid on
10077 the machine you are using, with or without the initial @samp{$}.
10080 @cindex stack pointer register
10081 @cindex program counter register
10082 @cindex process status register
10083 @cindex frame pointer register
10084 @cindex standard registers
10085 @value{GDBN} has four ``standard'' register names that are available (in
10086 expressions) on most machines---whenever they do not conflict with an
10087 architecture's canonical mnemonics for registers. The register names
10088 @code{$pc} and @code{$sp} are used for the program counter register and
10089 the stack pointer. @code{$fp} is used for a register that contains a
10090 pointer to the current stack frame, and @code{$ps} is used for a
10091 register that contains the processor status. For example,
10092 you could print the program counter in hex with
10099 or print the instruction to be executed next with
10106 or add four to the stack pointer@footnote{This is a way of removing
10107 one word from the stack, on machines where stacks grow downward in
10108 memory (most machines, nowadays). This assumes that the innermost
10109 stack frame is selected; setting @code{$sp} is not allowed when other
10110 stack frames are selected. To pop entire frames off the stack,
10111 regardless of machine architecture, use @code{return};
10112 see @ref{Returning, ,Returning from a Function}.} with
10118 Whenever possible, these four standard register names are available on
10119 your machine even though the machine has different canonical mnemonics,
10120 so long as there is no conflict. The @code{info registers} command
10121 shows the canonical names. For example, on the SPARC, @code{info
10122 registers} displays the processor status register as @code{$psr} but you
10123 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
10124 is an alias for the @sc{eflags} register.
10126 @value{GDBN} always considers the contents of an ordinary register as an
10127 integer when the register is examined in this way. Some machines have
10128 special registers which can hold nothing but floating point; these
10129 registers are considered to have floating point values. There is no way
10130 to refer to the contents of an ordinary register as floating point value
10131 (although you can @emph{print} it as a floating point value with
10132 @samp{print/f $@var{regname}}).
10134 Some registers have distinct ``raw'' and ``virtual'' data formats. This
10135 means that the data format in which the register contents are saved by
10136 the operating system is not the same one that your program normally
10137 sees. For example, the registers of the 68881 floating point
10138 coprocessor are always saved in ``extended'' (raw) format, but all C
10139 programs expect to work with ``double'' (virtual) format. In such
10140 cases, @value{GDBN} normally works with the virtual format only (the format
10141 that makes sense for your program), but the @code{info registers} command
10142 prints the data in both formats.
10144 @cindex SSE registers (x86)
10145 @cindex MMX registers (x86)
10146 Some machines have special registers whose contents can be interpreted
10147 in several different ways. For example, modern x86-based machines
10148 have SSE and MMX registers that can hold several values packed
10149 together in several different formats. @value{GDBN} refers to such
10150 registers in @code{struct} notation:
10153 (@value{GDBP}) print $xmm1
10155 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
10156 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
10157 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
10158 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
10159 v4_int32 = @{0, 20657912, 11, 13@},
10160 v2_int64 = @{88725056443645952, 55834574859@},
10161 uint128 = 0x0000000d0000000b013b36f800000000
10166 To set values of such registers, you need to tell @value{GDBN} which
10167 view of the register you wish to change, as if you were assigning
10168 value to a @code{struct} member:
10171 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
10174 Normally, register values are relative to the selected stack frame
10175 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
10176 value that the register would contain if all stack frames farther in
10177 were exited and their saved registers restored. In order to see the
10178 true contents of hardware registers, you must select the innermost
10179 frame (with @samp{frame 0}).
10181 @cindex caller-saved registers
10182 @cindex call-clobbered registers
10183 @cindex volatile registers
10184 @cindex <not saved> values
10185 Usually ABIs reserve some registers as not needed to be saved by the
10186 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
10187 registers). It may therefore not be possible for @value{GDBN} to know
10188 the value a register had before the call (in other words, in the outer
10189 frame), if the register value has since been changed by the callee.
10190 @value{GDBN} tries to deduce where the inner frame saved
10191 (``callee-saved'') registers, from the debug info, unwind info, or the
10192 machine code generated by your compiler. If some register is not
10193 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
10194 its own knowledge of the ABI, or because the debug/unwind info
10195 explicitly says the register's value is undefined), @value{GDBN}
10196 displays @w{@samp{<not saved>}} as the register's value. With targets
10197 that @value{GDBN} has no knowledge of the register saving convention,
10198 if a register was not saved by the callee, then its value and location
10199 in the outer frame are assumed to be the same of the inner frame.
10200 This is usually harmless, because if the register is call-clobbered,
10201 the caller either does not care what is in the register after the
10202 call, or has code to restore the value that it does care about. Note,
10203 however, that if you change such a register in the outer frame, you
10204 may also be affecting the inner frame. Also, the more ``outer'' the
10205 frame is you're looking at, the more likely a call-clobbered
10206 register's value is to be wrong, in the sense that it doesn't actually
10207 represent the value the register had just before the call.
10209 @node Floating Point Hardware
10210 @section Floating Point Hardware
10211 @cindex floating point
10213 Depending on the configuration, @value{GDBN} may be able to give
10214 you more information about the status of the floating point hardware.
10219 Display hardware-dependent information about the floating
10220 point unit. The exact contents and layout vary depending on the
10221 floating point chip. Currently, @samp{info float} is supported on
10222 the ARM and x86 machines.
10226 @section Vector Unit
10227 @cindex vector unit
10229 Depending on the configuration, @value{GDBN} may be able to give you
10230 more information about the status of the vector unit.
10233 @kindex info vector
10235 Display information about the vector unit. The exact contents and
10236 layout vary depending on the hardware.
10239 @node OS Information
10240 @section Operating System Auxiliary Information
10241 @cindex OS information
10243 @value{GDBN} provides interfaces to useful OS facilities that can help
10244 you debug your program.
10246 @cindex auxiliary vector
10247 @cindex vector, auxiliary
10248 Some operating systems supply an @dfn{auxiliary vector} to programs at
10249 startup. This is akin to the arguments and environment that you
10250 specify for a program, but contains a system-dependent variety of
10251 binary values that tell system libraries important details about the
10252 hardware, operating system, and process. Each value's purpose is
10253 identified by an integer tag; the meanings are well-known but system-specific.
10254 Depending on the configuration and operating system facilities,
10255 @value{GDBN} may be able to show you this information. For remote
10256 targets, this functionality may further depend on the remote stub's
10257 support of the @samp{qXfer:auxv:read} packet, see
10258 @ref{qXfer auxiliary vector read}.
10263 Display the auxiliary vector of the inferior, which can be either a
10264 live process or a core dump file. @value{GDBN} prints each tag value
10265 numerically, and also shows names and text descriptions for recognized
10266 tags. Some values in the vector are numbers, some bit masks, and some
10267 pointers to strings or other data. @value{GDBN} displays each value in the
10268 most appropriate form for a recognized tag, and in hexadecimal for
10269 an unrecognized tag.
10272 On some targets, @value{GDBN} can access operating system-specific
10273 information and show it to you. The types of information available
10274 will differ depending on the type of operating system running on the
10275 target. The mechanism used to fetch the data is described in
10276 @ref{Operating System Information}. For remote targets, this
10277 functionality depends on the remote stub's support of the
10278 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
10282 @item info os @var{infotype}
10284 Display OS information of the requested type.
10286 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
10288 @anchor{linux info os infotypes}
10290 @kindex info os processes
10292 Display the list of processes on the target. For each process,
10293 @value{GDBN} prints the process identifier, the name of the user, the
10294 command corresponding to the process, and the list of processor cores
10295 that the process is currently running on. (To understand what these
10296 properties mean, for this and the following info types, please consult
10297 the general @sc{gnu}/Linux documentation.)
10299 @kindex info os procgroups
10301 Display the list of process groups on the target. For each process,
10302 @value{GDBN} prints the identifier of the process group that it belongs
10303 to, the command corresponding to the process group leader, the process
10304 identifier, and the command line of the process. The list is sorted
10305 first by the process group identifier, then by the process identifier,
10306 so that processes belonging to the same process group are grouped together
10307 and the process group leader is listed first.
10309 @kindex info os threads
10311 Display the list of threads running on the target. For each thread,
10312 @value{GDBN} prints the identifier of the process that the thread
10313 belongs to, the command of the process, the thread identifier, and the
10314 processor core that it is currently running on. The main thread of a
10315 process is not listed.
10317 @kindex info os files
10319 Display the list of open file descriptors on the target. For each
10320 file descriptor, @value{GDBN} prints the identifier of the process
10321 owning the descriptor, the command of the owning process, the value
10322 of the descriptor, and the target of the descriptor.
10324 @kindex info os sockets
10326 Display the list of Internet-domain sockets on the target. For each
10327 socket, @value{GDBN} prints the address and port of the local and
10328 remote endpoints, the current state of the connection, the creator of
10329 the socket, the IP address family of the socket, and the type of the
10332 @kindex info os shm
10334 Display the list of all System V shared-memory regions on the target.
10335 For each shared-memory region, @value{GDBN} prints the region key,
10336 the shared-memory identifier, the access permissions, the size of the
10337 region, the process that created the region, the process that last
10338 attached to or detached from the region, the current number of live
10339 attaches to the region, and the times at which the region was last
10340 attached to, detach from, and changed.
10342 @kindex info os semaphores
10344 Display the list of all System V semaphore sets on the target. For each
10345 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
10346 set identifier, the access permissions, the number of semaphores in the
10347 set, the user and group of the owner and creator of the semaphore set,
10348 and the times at which the semaphore set was operated upon and changed.
10350 @kindex info os msg
10352 Display the list of all System V message queues on the target. For each
10353 message queue, @value{GDBN} prints the message queue key, the message
10354 queue identifier, the access permissions, the current number of bytes
10355 on the queue, the current number of messages on the queue, the processes
10356 that last sent and received a message on the queue, the user and group
10357 of the owner and creator of the message queue, the times at which a
10358 message was last sent and received on the queue, and the time at which
10359 the message queue was last changed.
10361 @kindex info os modules
10363 Display the list of all loaded kernel modules on the target. For each
10364 module, @value{GDBN} prints the module name, the size of the module in
10365 bytes, the number of times the module is used, the dependencies of the
10366 module, the status of the module, and the address of the loaded module
10371 If @var{infotype} is omitted, then list the possible values for
10372 @var{infotype} and the kind of OS information available for each
10373 @var{infotype}. If the target does not return a list of possible
10374 types, this command will report an error.
10377 @node Memory Region Attributes
10378 @section Memory Region Attributes
10379 @cindex memory region attributes
10381 @dfn{Memory region attributes} allow you to describe special handling
10382 required by regions of your target's memory. @value{GDBN} uses
10383 attributes to determine whether to allow certain types of memory
10384 accesses; whether to use specific width accesses; and whether to cache
10385 target memory. By default the description of memory regions is
10386 fetched from the target (if the current target supports this), but the
10387 user can override the fetched regions.
10389 Defined memory regions can be individually enabled and disabled. When a
10390 memory region is disabled, @value{GDBN} uses the default attributes when
10391 accessing memory in that region. Similarly, if no memory regions have
10392 been defined, @value{GDBN} uses the default attributes when accessing
10395 When a memory region is defined, it is given a number to identify it;
10396 to enable, disable, or remove a memory region, you specify that number.
10400 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
10401 Define a memory region bounded by @var{lower} and @var{upper} with
10402 attributes @var{attributes}@dots{}, and add it to the list of regions
10403 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
10404 case: it is treated as the target's maximum memory address.
10405 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
10408 Discard any user changes to the memory regions and use target-supplied
10409 regions, if available, or no regions if the target does not support.
10412 @item delete mem @var{nums}@dots{}
10413 Remove memory regions @var{nums}@dots{} from the list of regions
10414 monitored by @value{GDBN}.
10416 @kindex disable mem
10417 @item disable mem @var{nums}@dots{}
10418 Disable monitoring of memory regions @var{nums}@dots{}.
10419 A disabled memory region is not forgotten.
10420 It may be enabled again later.
10423 @item enable mem @var{nums}@dots{}
10424 Enable monitoring of memory regions @var{nums}@dots{}.
10428 Print a table of all defined memory regions, with the following columns
10432 @item Memory Region Number
10433 @item Enabled or Disabled.
10434 Enabled memory regions are marked with @samp{y}.
10435 Disabled memory regions are marked with @samp{n}.
10438 The address defining the inclusive lower bound of the memory region.
10441 The address defining the exclusive upper bound of the memory region.
10444 The list of attributes set for this memory region.
10449 @subsection Attributes
10451 @subsubsection Memory Access Mode
10452 The access mode attributes set whether @value{GDBN} may make read or
10453 write accesses to a memory region.
10455 While these attributes prevent @value{GDBN} from performing invalid
10456 memory accesses, they do nothing to prevent the target system, I/O DMA,
10457 etc.@: from accessing memory.
10461 Memory is read only.
10463 Memory is write only.
10465 Memory is read/write. This is the default.
10468 @subsubsection Memory Access Size
10469 The access size attribute tells @value{GDBN} to use specific sized
10470 accesses in the memory region. Often memory mapped device registers
10471 require specific sized accesses. If no access size attribute is
10472 specified, @value{GDBN} may use accesses of any size.
10476 Use 8 bit memory accesses.
10478 Use 16 bit memory accesses.
10480 Use 32 bit memory accesses.
10482 Use 64 bit memory accesses.
10485 @c @subsubsection Hardware/Software Breakpoints
10486 @c The hardware/software breakpoint attributes set whether @value{GDBN}
10487 @c will use hardware or software breakpoints for the internal breakpoints
10488 @c used by the step, next, finish, until, etc. commands.
10492 @c Always use hardware breakpoints
10493 @c @item swbreak (default)
10496 @subsubsection Data Cache
10497 The data cache attributes set whether @value{GDBN} will cache target
10498 memory. While this generally improves performance by reducing debug
10499 protocol overhead, it can lead to incorrect results because @value{GDBN}
10500 does not know about volatile variables or memory mapped device
10505 Enable @value{GDBN} to cache target memory.
10507 Disable @value{GDBN} from caching target memory. This is the default.
10510 @subsection Memory Access Checking
10511 @value{GDBN} can be instructed to refuse accesses to memory that is
10512 not explicitly described. This can be useful if accessing such
10513 regions has undesired effects for a specific target, or to provide
10514 better error checking. The following commands control this behaviour.
10517 @kindex set mem inaccessible-by-default
10518 @item set mem inaccessible-by-default [on|off]
10519 If @code{on} is specified, make @value{GDBN} treat memory not
10520 explicitly described by the memory ranges as non-existent and refuse accesses
10521 to such memory. The checks are only performed if there's at least one
10522 memory range defined. If @code{off} is specified, make @value{GDBN}
10523 treat the memory not explicitly described by the memory ranges as RAM.
10524 The default value is @code{on}.
10525 @kindex show mem inaccessible-by-default
10526 @item show mem inaccessible-by-default
10527 Show the current handling of accesses to unknown memory.
10531 @c @subsubsection Memory Write Verification
10532 @c The memory write verification attributes set whether @value{GDBN}
10533 @c will re-reads data after each write to verify the write was successful.
10537 @c @item noverify (default)
10540 @node Dump/Restore Files
10541 @section Copy Between Memory and a File
10542 @cindex dump/restore files
10543 @cindex append data to a file
10544 @cindex dump data to a file
10545 @cindex restore data from a file
10547 You can use the commands @code{dump}, @code{append}, and
10548 @code{restore} to copy data between target memory and a file. The
10549 @code{dump} and @code{append} commands write data to a file, and the
10550 @code{restore} command reads data from a file back into the inferior's
10551 memory. Files may be in binary, Motorola S-record, Intel hex, or
10552 Tektronix Hex format; however, @value{GDBN} can only append to binary
10558 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10559 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
10560 Dump the contents of memory from @var{start_addr} to @var{end_addr},
10561 or the value of @var{expr}, to @var{filename} in the given format.
10563 The @var{format} parameter may be any one of:
10570 Motorola S-record format.
10572 Tektronix Hex format.
10575 @value{GDBN} uses the same definitions of these formats as the
10576 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
10577 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
10581 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10582 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
10583 Append the contents of memory from @var{start_addr} to @var{end_addr},
10584 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
10585 (@value{GDBN} can only append data to files in raw binary form.)
10588 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
10589 Restore the contents of file @var{filename} into memory. The
10590 @code{restore} command can automatically recognize any known @sc{bfd}
10591 file format, except for raw binary. To restore a raw binary file you
10592 must specify the optional keyword @code{binary} after the filename.
10594 If @var{bias} is non-zero, its value will be added to the addresses
10595 contained in the file. Binary files always start at address zero, so
10596 they will be restored at address @var{bias}. Other bfd files have
10597 a built-in location; they will be restored at offset @var{bias}
10598 from that location.
10600 If @var{start} and/or @var{end} are non-zero, then only data between
10601 file offset @var{start} and file offset @var{end} will be restored.
10602 These offsets are relative to the addresses in the file, before
10603 the @var{bias} argument is applied.
10607 @node Core File Generation
10608 @section How to Produce a Core File from Your Program
10609 @cindex dump core from inferior
10611 A @dfn{core file} or @dfn{core dump} is a file that records the memory
10612 image of a running process and its process status (register values
10613 etc.). Its primary use is post-mortem debugging of a program that
10614 crashed while it ran outside a debugger. A program that crashes
10615 automatically produces a core file, unless this feature is disabled by
10616 the user. @xref{Files}, for information on invoking @value{GDBN} in
10617 the post-mortem debugging mode.
10619 Occasionally, you may wish to produce a core file of the program you
10620 are debugging in order to preserve a snapshot of its state.
10621 @value{GDBN} has a special command for that.
10625 @kindex generate-core-file
10626 @item generate-core-file [@var{file}]
10627 @itemx gcore [@var{file}]
10628 Produce a core dump of the inferior process. The optional argument
10629 @var{file} specifies the file name where to put the core dump. If not
10630 specified, the file name defaults to @file{core.@var{pid}}, where
10631 @var{pid} is the inferior process ID.
10633 Note that this command is implemented only for some systems (as of
10634 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
10637 @node Character Sets
10638 @section Character Sets
10639 @cindex character sets
10641 @cindex translating between character sets
10642 @cindex host character set
10643 @cindex target character set
10645 If the program you are debugging uses a different character set to
10646 represent characters and strings than the one @value{GDBN} uses itself,
10647 @value{GDBN} can automatically translate between the character sets for
10648 you. The character set @value{GDBN} uses we call the @dfn{host
10649 character set}; the one the inferior program uses we call the
10650 @dfn{target character set}.
10652 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
10653 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
10654 remote protocol (@pxref{Remote Debugging}) to debug a program
10655 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
10656 then the host character set is Latin-1, and the target character set is
10657 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
10658 target-charset EBCDIC-US}, then @value{GDBN} translates between
10659 @sc{ebcdic} and Latin 1 as you print character or string values, or use
10660 character and string literals in expressions.
10662 @value{GDBN} has no way to automatically recognize which character set
10663 the inferior program uses; you must tell it, using the @code{set
10664 target-charset} command, described below.
10666 Here are the commands for controlling @value{GDBN}'s character set
10670 @item set target-charset @var{charset}
10671 @kindex set target-charset
10672 Set the current target character set to @var{charset}. To display the
10673 list of supported target character sets, type
10674 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
10676 @item set host-charset @var{charset}
10677 @kindex set host-charset
10678 Set the current host character set to @var{charset}.
10680 By default, @value{GDBN} uses a host character set appropriate to the
10681 system it is running on; you can override that default using the
10682 @code{set host-charset} command. On some systems, @value{GDBN} cannot
10683 automatically determine the appropriate host character set. In this
10684 case, @value{GDBN} uses @samp{UTF-8}.
10686 @value{GDBN} can only use certain character sets as its host character
10687 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
10688 @value{GDBN} will list the host character sets it supports.
10690 @item set charset @var{charset}
10691 @kindex set charset
10692 Set the current host and target character sets to @var{charset}. As
10693 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
10694 @value{GDBN} will list the names of the character sets that can be used
10695 for both host and target.
10698 @kindex show charset
10699 Show the names of the current host and target character sets.
10701 @item show host-charset
10702 @kindex show host-charset
10703 Show the name of the current host character set.
10705 @item show target-charset
10706 @kindex show target-charset
10707 Show the name of the current target character set.
10709 @item set target-wide-charset @var{charset}
10710 @kindex set target-wide-charset
10711 Set the current target's wide character set to @var{charset}. This is
10712 the character set used by the target's @code{wchar_t} type. To
10713 display the list of supported wide character sets, type
10714 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
10716 @item show target-wide-charset
10717 @kindex show target-wide-charset
10718 Show the name of the current target's wide character set.
10721 Here is an example of @value{GDBN}'s character set support in action.
10722 Assume that the following source code has been placed in the file
10723 @file{charset-test.c}:
10729 = @{72, 101, 108, 108, 111, 44, 32, 119,
10730 111, 114, 108, 100, 33, 10, 0@};
10731 char ibm1047_hello[]
10732 = @{200, 133, 147, 147, 150, 107, 64, 166,
10733 150, 153, 147, 132, 90, 37, 0@};
10737 printf ("Hello, world!\n");
10741 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
10742 containing the string @samp{Hello, world!} followed by a newline,
10743 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
10745 We compile the program, and invoke the debugger on it:
10748 $ gcc -g charset-test.c -o charset-test
10749 $ gdb -nw charset-test
10750 GNU gdb 2001-12-19-cvs
10751 Copyright 2001 Free Software Foundation, Inc.
10756 We can use the @code{show charset} command to see what character sets
10757 @value{GDBN} is currently using to interpret and display characters and
10761 (@value{GDBP}) show charset
10762 The current host and target character set is `ISO-8859-1'.
10766 For the sake of printing this manual, let's use @sc{ascii} as our
10767 initial character set:
10769 (@value{GDBP}) set charset ASCII
10770 (@value{GDBP}) show charset
10771 The current host and target character set is `ASCII'.
10775 Let's assume that @sc{ascii} is indeed the correct character set for our
10776 host system --- in other words, let's assume that if @value{GDBN} prints
10777 characters using the @sc{ascii} character set, our terminal will display
10778 them properly. Since our current target character set is also
10779 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
10782 (@value{GDBP}) print ascii_hello
10783 $1 = 0x401698 "Hello, world!\n"
10784 (@value{GDBP}) print ascii_hello[0]
10789 @value{GDBN} uses the target character set for character and string
10790 literals you use in expressions:
10793 (@value{GDBP}) print '+'
10798 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
10801 @value{GDBN} relies on the user to tell it which character set the
10802 target program uses. If we print @code{ibm1047_hello} while our target
10803 character set is still @sc{ascii}, we get jibberish:
10806 (@value{GDBP}) print ibm1047_hello
10807 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
10808 (@value{GDBP}) print ibm1047_hello[0]
10813 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
10814 @value{GDBN} tells us the character sets it supports:
10817 (@value{GDBP}) set target-charset
10818 ASCII EBCDIC-US IBM1047 ISO-8859-1
10819 (@value{GDBP}) set target-charset
10822 We can select @sc{ibm1047} as our target character set, and examine the
10823 program's strings again. Now the @sc{ascii} string is wrong, but
10824 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
10825 target character set, @sc{ibm1047}, to the host character set,
10826 @sc{ascii}, and they display correctly:
10829 (@value{GDBP}) set target-charset IBM1047
10830 (@value{GDBP}) show charset
10831 The current host character set is `ASCII'.
10832 The current target character set is `IBM1047'.
10833 (@value{GDBP}) print ascii_hello
10834 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
10835 (@value{GDBP}) print ascii_hello[0]
10837 (@value{GDBP}) print ibm1047_hello
10838 $8 = 0x4016a8 "Hello, world!\n"
10839 (@value{GDBP}) print ibm1047_hello[0]
10844 As above, @value{GDBN} uses the target character set for character and
10845 string literals you use in expressions:
10848 (@value{GDBP}) print '+'
10853 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
10856 @node Caching Target Data
10857 @section Caching Data of Targets
10858 @cindex caching data of targets
10860 @value{GDBN} caches data exchanged between the debugger and a target.
10861 Each cache is associated with the address space of the inferior.
10862 @xref{Inferiors and Programs}, about inferior and address space.
10863 Such caching generally improves performance in remote debugging
10864 (@pxref{Remote Debugging}), because it reduces the overhead of the
10865 remote protocol by bundling memory reads and writes into large chunks.
10866 Unfortunately, simply caching everything would lead to incorrect results,
10867 since @value{GDBN} does not necessarily know anything about volatile
10868 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
10869 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
10871 Therefore, by default, @value{GDBN} only caches data
10872 known to be on the stack@footnote{In non-stop mode, it is moderately
10873 rare for a running thread to modify the stack of a stopped thread
10874 in a way that would interfere with a backtrace, and caching of
10875 stack reads provides a significant speed up of remote backtraces.} or
10876 in the code segment.
10877 Other regions of memory can be explicitly marked as
10878 cacheable; @pxref{Memory Region Attributes}.
10881 @kindex set remotecache
10882 @item set remotecache on
10883 @itemx set remotecache off
10884 This option no longer does anything; it exists for compatibility
10887 @kindex show remotecache
10888 @item show remotecache
10889 Show the current state of the obsolete remotecache flag.
10891 @kindex set stack-cache
10892 @item set stack-cache on
10893 @itemx set stack-cache off
10894 Enable or disable caching of stack accesses. When @code{on}, use
10895 caching. By default, this option is @code{on}.
10897 @kindex show stack-cache
10898 @item show stack-cache
10899 Show the current state of data caching for memory accesses.
10901 @kindex set code-cache
10902 @item set code-cache on
10903 @itemx set code-cache off
10904 Enable or disable caching of code segment accesses. When @code{on},
10905 use caching. By default, this option is @code{on}. This improves
10906 performance of disassembly in remote debugging.
10908 @kindex show code-cache
10909 @item show code-cache
10910 Show the current state of target memory cache for code segment
10913 @kindex info dcache
10914 @item info dcache @r{[}line@r{]}
10915 Print the information about the performance of data cache of the
10916 current inferior's address space. The information displayed
10917 includes the dcache width and depth, and for each cache line, its
10918 number, address, and how many times it was referenced. This
10919 command is useful for debugging the data cache operation.
10921 If a line number is specified, the contents of that line will be
10924 @item set dcache size @var{size}
10925 @cindex dcache size
10926 @kindex set dcache size
10927 Set maximum number of entries in dcache (dcache depth above).
10929 @item set dcache line-size @var{line-size}
10930 @cindex dcache line-size
10931 @kindex set dcache line-size
10932 Set number of bytes each dcache entry caches (dcache width above).
10933 Must be a power of 2.
10935 @item show dcache size
10936 @kindex show dcache size
10937 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
10939 @item show dcache line-size
10940 @kindex show dcache line-size
10941 Show default size of dcache lines.
10945 @node Searching Memory
10946 @section Search Memory
10947 @cindex searching memory
10949 Memory can be searched for a particular sequence of bytes with the
10950 @code{find} command.
10954 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10955 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10956 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
10957 etc. The search begins at address @var{start_addr} and continues for either
10958 @var{len} bytes or through to @var{end_addr} inclusive.
10961 @var{s} and @var{n} are optional parameters.
10962 They may be specified in either order, apart or together.
10965 @item @var{s}, search query size
10966 The size of each search query value.
10972 halfwords (two bytes)
10976 giant words (eight bytes)
10979 All values are interpreted in the current language.
10980 This means, for example, that if the current source language is C/C@t{++}
10981 then searching for the string ``hello'' includes the trailing '\0'.
10983 If the value size is not specified, it is taken from the
10984 value's type in the current language.
10985 This is useful when one wants to specify the search
10986 pattern as a mixture of types.
10987 Note that this means, for example, that in the case of C-like languages
10988 a search for an untyped 0x42 will search for @samp{(int) 0x42}
10989 which is typically four bytes.
10991 @item @var{n}, maximum number of finds
10992 The maximum number of matches to print. The default is to print all finds.
10995 You can use strings as search values. Quote them with double-quotes
10997 The string value is copied into the search pattern byte by byte,
10998 regardless of the endianness of the target and the size specification.
11000 The address of each match found is printed as well as a count of the
11001 number of matches found.
11003 The address of the last value found is stored in convenience variable
11005 A count of the number of matches is stored in @samp{$numfound}.
11007 For example, if stopped at the @code{printf} in this function:
11013 static char hello[] = "hello-hello";
11014 static struct @{ char c; short s; int i; @}
11015 __attribute__ ((packed)) mixed
11016 = @{ 'c', 0x1234, 0x87654321 @};
11017 printf ("%s\n", hello);
11022 you get during debugging:
11025 (gdb) find &hello[0], +sizeof(hello), "hello"
11026 0x804956d <hello.1620+6>
11028 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
11029 0x8049567 <hello.1620>
11030 0x804956d <hello.1620+6>
11032 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
11033 0x8049567 <hello.1620>
11035 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
11036 0x8049560 <mixed.1625>
11038 (gdb) print $numfound
11041 $2 = (void *) 0x8049560
11044 @node Optimized Code
11045 @chapter Debugging Optimized Code
11046 @cindex optimized code, debugging
11047 @cindex debugging optimized code
11049 Almost all compilers support optimization. With optimization
11050 disabled, the compiler generates assembly code that corresponds
11051 directly to your source code, in a simplistic way. As the compiler
11052 applies more powerful optimizations, the generated assembly code
11053 diverges from your original source code. With help from debugging
11054 information generated by the compiler, @value{GDBN} can map from
11055 the running program back to constructs from your original source.
11057 @value{GDBN} is more accurate with optimization disabled. If you
11058 can recompile without optimization, it is easier to follow the
11059 progress of your program during debugging. But, there are many cases
11060 where you may need to debug an optimized version.
11062 When you debug a program compiled with @samp{-g -O}, remember that the
11063 optimizer has rearranged your code; the debugger shows you what is
11064 really there. Do not be too surprised when the execution path does not
11065 exactly match your source file! An extreme example: if you define a
11066 variable, but never use it, @value{GDBN} never sees that
11067 variable---because the compiler optimizes it out of existence.
11069 Some things do not work as well with @samp{-g -O} as with just
11070 @samp{-g}, particularly on machines with instruction scheduling. If in
11071 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
11072 please report it to us as a bug (including a test case!).
11073 @xref{Variables}, for more information about debugging optimized code.
11076 * Inline Functions:: How @value{GDBN} presents inlining
11077 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
11080 @node Inline Functions
11081 @section Inline Functions
11082 @cindex inline functions, debugging
11084 @dfn{Inlining} is an optimization that inserts a copy of the function
11085 body directly at each call site, instead of jumping to a shared
11086 routine. @value{GDBN} displays inlined functions just like
11087 non-inlined functions. They appear in backtraces. You can view their
11088 arguments and local variables, step into them with @code{step}, skip
11089 them with @code{next}, and escape from them with @code{finish}.
11090 You can check whether a function was inlined by using the
11091 @code{info frame} command.
11093 For @value{GDBN} to support inlined functions, the compiler must
11094 record information about inlining in the debug information ---
11095 @value{NGCC} using the @sc{dwarf 2} format does this, and several
11096 other compilers do also. @value{GDBN} only supports inlined functions
11097 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
11098 do not emit two required attributes (@samp{DW_AT_call_file} and
11099 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
11100 function calls with earlier versions of @value{NGCC}. It instead
11101 displays the arguments and local variables of inlined functions as
11102 local variables in the caller.
11104 The body of an inlined function is directly included at its call site;
11105 unlike a non-inlined function, there are no instructions devoted to
11106 the call. @value{GDBN} still pretends that the call site and the
11107 start of the inlined function are different instructions. Stepping to
11108 the call site shows the call site, and then stepping again shows
11109 the first line of the inlined function, even though no additional
11110 instructions are executed.
11112 This makes source-level debugging much clearer; you can see both the
11113 context of the call and then the effect of the call. Only stepping by
11114 a single instruction using @code{stepi} or @code{nexti} does not do
11115 this; single instruction steps always show the inlined body.
11117 There are some ways that @value{GDBN} does not pretend that inlined
11118 function calls are the same as normal calls:
11122 Setting breakpoints at the call site of an inlined function may not
11123 work, because the call site does not contain any code. @value{GDBN}
11124 may incorrectly move the breakpoint to the next line of the enclosing
11125 function, after the call. This limitation will be removed in a future
11126 version of @value{GDBN}; until then, set a breakpoint on an earlier line
11127 or inside the inlined function instead.
11130 @value{GDBN} cannot locate the return value of inlined calls after
11131 using the @code{finish} command. This is a limitation of compiler-generated
11132 debugging information; after @code{finish}, you can step to the next line
11133 and print a variable where your program stored the return value.
11137 @node Tail Call Frames
11138 @section Tail Call Frames
11139 @cindex tail call frames, debugging
11141 Function @code{B} can call function @code{C} in its very last statement. In
11142 unoptimized compilation the call of @code{C} is immediately followed by return
11143 instruction at the end of @code{B} code. Optimizing compiler may replace the
11144 call and return in function @code{B} into one jump to function @code{C}
11145 instead. Such use of a jump instruction is called @dfn{tail call}.
11147 During execution of function @code{C}, there will be no indication in the
11148 function call stack frames that it was tail-called from @code{B}. If function
11149 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
11150 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
11151 some cases @value{GDBN} can determine that @code{C} was tail-called from
11152 @code{B}, and it will then create fictitious call frame for that, with the
11153 return address set up as if @code{B} called @code{C} normally.
11155 This functionality is currently supported only by DWARF 2 debugging format and
11156 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
11157 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11160 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
11161 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
11165 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
11167 Stack level 1, frame at 0x7fffffffda30:
11168 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
11169 tail call frame, caller of frame at 0x7fffffffda30
11170 source language c++.
11171 Arglist at unknown address.
11172 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
11175 The detection of all the possible code path executions can find them ambiguous.
11176 There is no execution history stored (possible @ref{Reverse Execution} is never
11177 used for this purpose) and the last known caller could have reached the known
11178 callee by multiple different jump sequences. In such case @value{GDBN} still
11179 tries to show at least all the unambiguous top tail callers and all the
11180 unambiguous bottom tail calees, if any.
11183 @anchor{set debug entry-values}
11184 @item set debug entry-values
11185 @kindex set debug entry-values
11186 When set to on, enables printing of analysis messages for both frame argument
11187 values at function entry and tail calls. It will show all the possible valid
11188 tail calls code paths it has considered. It will also print the intersection
11189 of them with the final unambiguous (possibly partial or even empty) code path
11192 @item show debug entry-values
11193 @kindex show debug entry-values
11194 Show the current state of analysis messages printing for both frame argument
11195 values at function entry and tail calls.
11198 The analysis messages for tail calls can for example show why the virtual tail
11199 call frame for function @code{c} has not been recognized (due to the indirect
11200 reference by variable @code{x}):
11203 static void __attribute__((noinline, noclone)) c (void);
11204 void (*x) (void) = c;
11205 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11206 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
11207 int main (void) @{ x (); return 0; @}
11209 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
11210 DW_TAG_GNU_call_site 0x40039a in main
11212 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11215 #1 0x000000000040039a in main () at t.c:5
11218 Another possibility is an ambiguous virtual tail call frames resolution:
11222 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
11223 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
11224 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
11225 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
11226 static void __attribute__((noinline, noclone)) b (void)
11227 @{ if (i) c (); else e (); @}
11228 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
11229 int main (void) @{ a (); return 0; @}
11231 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
11232 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
11233 tailcall: reduced: 0x4004d2(a) |
11236 #1 0x00000000004004d2 in a () at t.c:8
11237 #2 0x0000000000400395 in main () at t.c:9
11240 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
11241 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
11243 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
11244 @ifset HAVE_MAKEINFO_CLICK
11245 @set ARROW @click{}
11246 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
11247 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
11249 @ifclear HAVE_MAKEINFO_CLICK
11251 @set CALLSEQ1B @value{CALLSEQ1A}
11252 @set CALLSEQ2B @value{CALLSEQ2A}
11255 Frames #0 and #2 are real, #1 is a virtual tail call frame.
11256 The code can have possible execution paths @value{CALLSEQ1B} or
11257 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
11259 @code{initial:} state shows some random possible calling sequence @value{GDBN}
11260 has found. It then finds another possible calling sequcen - that one is
11261 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
11262 printed as the @code{reduced:} calling sequence. That one could have many
11263 futher @code{compare:} and @code{reduced:} statements as long as there remain
11264 any non-ambiguous sequence entries.
11266 For the frame of function @code{b} in both cases there are different possible
11267 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
11268 also ambigous. The only non-ambiguous frame is the one for function @code{a},
11269 therefore this one is displayed to the user while the ambiguous frames are
11272 There can be also reasons why printing of frame argument values at function
11277 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
11278 static void __attribute__((noinline, noclone)) a (int i);
11279 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
11280 static void __attribute__((noinline, noclone)) a (int i)
11281 @{ if (i) b (i - 1); else c (0); @}
11282 int main (void) @{ a (5); return 0; @}
11285 #0 c (i=i@@entry=0) at t.c:2
11286 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
11287 function "a" at 0x400420 can call itself via tail calls
11288 i=<optimized out>) at t.c:6
11289 #2 0x000000000040036e in main () at t.c:7
11292 @value{GDBN} cannot find out from the inferior state if and how many times did
11293 function @code{a} call itself (via function @code{b}) as these calls would be
11294 tail calls. Such tail calls would modify thue @code{i} variable, therefore
11295 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
11296 prints @code{<optimized out>} instead.
11299 @chapter C Preprocessor Macros
11301 Some languages, such as C and C@t{++}, provide a way to define and invoke
11302 ``preprocessor macros'' which expand into strings of tokens.
11303 @value{GDBN} can evaluate expressions containing macro invocations, show
11304 the result of macro expansion, and show a macro's definition, including
11305 where it was defined.
11307 You may need to compile your program specially to provide @value{GDBN}
11308 with information about preprocessor macros. Most compilers do not
11309 include macros in their debugging information, even when you compile
11310 with the @option{-g} flag. @xref{Compilation}.
11312 A program may define a macro at one point, remove that definition later,
11313 and then provide a different definition after that. Thus, at different
11314 points in the program, a macro may have different definitions, or have
11315 no definition at all. If there is a current stack frame, @value{GDBN}
11316 uses the macros in scope at that frame's source code line. Otherwise,
11317 @value{GDBN} uses the macros in scope at the current listing location;
11320 Whenever @value{GDBN} evaluates an expression, it always expands any
11321 macro invocations present in the expression. @value{GDBN} also provides
11322 the following commands for working with macros explicitly.
11326 @kindex macro expand
11327 @cindex macro expansion, showing the results of preprocessor
11328 @cindex preprocessor macro expansion, showing the results of
11329 @cindex expanding preprocessor macros
11330 @item macro expand @var{expression}
11331 @itemx macro exp @var{expression}
11332 Show the results of expanding all preprocessor macro invocations in
11333 @var{expression}. Since @value{GDBN} simply expands macros, but does
11334 not parse the result, @var{expression} need not be a valid expression;
11335 it can be any string of tokens.
11338 @item macro expand-once @var{expression}
11339 @itemx macro exp1 @var{expression}
11340 @cindex expand macro once
11341 @i{(This command is not yet implemented.)} Show the results of
11342 expanding those preprocessor macro invocations that appear explicitly in
11343 @var{expression}. Macro invocations appearing in that expansion are
11344 left unchanged. This command allows you to see the effect of a
11345 particular macro more clearly, without being confused by further
11346 expansions. Since @value{GDBN} simply expands macros, but does not
11347 parse the result, @var{expression} need not be a valid expression; it
11348 can be any string of tokens.
11351 @cindex macro definition, showing
11352 @cindex definition of a macro, showing
11353 @cindex macros, from debug info
11354 @item info macro [-a|-all] [--] @var{macro}
11355 Show the current definition or all definitions of the named @var{macro},
11356 and describe the source location or compiler command-line where that
11357 definition was established. The optional double dash is to signify the end of
11358 argument processing and the beginning of @var{macro} for non C-like macros where
11359 the macro may begin with a hyphen.
11361 @kindex info macros
11362 @item info macros @var{linespec}
11363 Show all macro definitions that are in effect at the location specified
11364 by @var{linespec}, and describe the source location or compiler
11365 command-line where those definitions were established.
11367 @kindex macro define
11368 @cindex user-defined macros
11369 @cindex defining macros interactively
11370 @cindex macros, user-defined
11371 @item macro define @var{macro} @var{replacement-list}
11372 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
11373 Introduce a definition for a preprocessor macro named @var{macro},
11374 invocations of which are replaced by the tokens given in
11375 @var{replacement-list}. The first form of this command defines an
11376 ``object-like'' macro, which takes no arguments; the second form
11377 defines a ``function-like'' macro, which takes the arguments given in
11380 A definition introduced by this command is in scope in every
11381 expression evaluated in @value{GDBN}, until it is removed with the
11382 @code{macro undef} command, described below. The definition overrides
11383 all definitions for @var{macro} present in the program being debugged,
11384 as well as any previous user-supplied definition.
11386 @kindex macro undef
11387 @item macro undef @var{macro}
11388 Remove any user-supplied definition for the macro named @var{macro}.
11389 This command only affects definitions provided with the @code{macro
11390 define} command, described above; it cannot remove definitions present
11391 in the program being debugged.
11395 List all the macros defined using the @code{macro define} command.
11398 @cindex macros, example of debugging with
11399 Here is a transcript showing the above commands in action. First, we
11400 show our source files:
11405 #include "sample.h"
11408 #define ADD(x) (M + x)
11413 printf ("Hello, world!\n");
11415 printf ("We're so creative.\n");
11417 printf ("Goodbye, world!\n");
11424 Now, we compile the program using the @sc{gnu} C compiler,
11425 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
11426 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
11427 and @option{-gdwarf-4}; we recommend always choosing the most recent
11428 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
11429 includes information about preprocessor macros in the debugging
11433 $ gcc -gdwarf-2 -g3 sample.c -o sample
11437 Now, we start @value{GDBN} on our sample program:
11441 GNU gdb 2002-05-06-cvs
11442 Copyright 2002 Free Software Foundation, Inc.
11443 GDB is free software, @dots{}
11447 We can expand macros and examine their definitions, even when the
11448 program is not running. @value{GDBN} uses the current listing position
11449 to decide which macro definitions are in scope:
11452 (@value{GDBP}) list main
11455 5 #define ADD(x) (M + x)
11460 10 printf ("Hello, world!\n");
11462 12 printf ("We're so creative.\n");
11463 (@value{GDBP}) info macro ADD
11464 Defined at /home/jimb/gdb/macros/play/sample.c:5
11465 #define ADD(x) (M + x)
11466 (@value{GDBP}) info macro Q
11467 Defined at /home/jimb/gdb/macros/play/sample.h:1
11468 included at /home/jimb/gdb/macros/play/sample.c:2
11470 (@value{GDBP}) macro expand ADD(1)
11471 expands to: (42 + 1)
11472 (@value{GDBP}) macro expand-once ADD(1)
11473 expands to: once (M + 1)
11477 In the example above, note that @code{macro expand-once} expands only
11478 the macro invocation explicit in the original text --- the invocation of
11479 @code{ADD} --- but does not expand the invocation of the macro @code{M},
11480 which was introduced by @code{ADD}.
11482 Once the program is running, @value{GDBN} uses the macro definitions in
11483 force at the source line of the current stack frame:
11486 (@value{GDBP}) break main
11487 Breakpoint 1 at 0x8048370: file sample.c, line 10.
11489 Starting program: /home/jimb/gdb/macros/play/sample
11491 Breakpoint 1, main () at sample.c:10
11492 10 printf ("Hello, world!\n");
11496 At line 10, the definition of the macro @code{N} at line 9 is in force:
11499 (@value{GDBP}) info macro N
11500 Defined at /home/jimb/gdb/macros/play/sample.c:9
11502 (@value{GDBP}) macro expand N Q M
11503 expands to: 28 < 42
11504 (@value{GDBP}) print N Q M
11509 As we step over directives that remove @code{N}'s definition, and then
11510 give it a new definition, @value{GDBN} finds the definition (or lack
11511 thereof) in force at each point:
11514 (@value{GDBP}) next
11516 12 printf ("We're so creative.\n");
11517 (@value{GDBP}) info macro N
11518 The symbol `N' has no definition as a C/C++ preprocessor macro
11519 at /home/jimb/gdb/macros/play/sample.c:12
11520 (@value{GDBP}) next
11522 14 printf ("Goodbye, world!\n");
11523 (@value{GDBP}) info macro N
11524 Defined at /home/jimb/gdb/macros/play/sample.c:13
11526 (@value{GDBP}) macro expand N Q M
11527 expands to: 1729 < 42
11528 (@value{GDBP}) print N Q M
11533 In addition to source files, macros can be defined on the compilation command
11534 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
11535 such a way, @value{GDBN} displays the location of their definition as line zero
11536 of the source file submitted to the compiler.
11539 (@value{GDBP}) info macro __STDC__
11540 Defined at /home/jimb/gdb/macros/play/sample.c:0
11547 @chapter Tracepoints
11548 @c This chapter is based on the documentation written by Michael
11549 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
11551 @cindex tracepoints
11552 In some applications, it is not feasible for the debugger to interrupt
11553 the program's execution long enough for the developer to learn
11554 anything helpful about its behavior. If the program's correctness
11555 depends on its real-time behavior, delays introduced by a debugger
11556 might cause the program to change its behavior drastically, or perhaps
11557 fail, even when the code itself is correct. It is useful to be able
11558 to observe the program's behavior without interrupting it.
11560 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
11561 specify locations in the program, called @dfn{tracepoints}, and
11562 arbitrary expressions to evaluate when those tracepoints are reached.
11563 Later, using the @code{tfind} command, you can examine the values
11564 those expressions had when the program hit the tracepoints. The
11565 expressions may also denote objects in memory---structures or arrays,
11566 for example---whose values @value{GDBN} should record; while visiting
11567 a particular tracepoint, you may inspect those objects as if they were
11568 in memory at that moment. However, because @value{GDBN} records these
11569 values without interacting with you, it can do so quickly and
11570 unobtrusively, hopefully not disturbing the program's behavior.
11572 The tracepoint facility is currently available only for remote
11573 targets. @xref{Targets}. In addition, your remote target must know
11574 how to collect trace data. This functionality is implemented in the
11575 remote stub; however, none of the stubs distributed with @value{GDBN}
11576 support tracepoints as of this writing. The format of the remote
11577 packets used to implement tracepoints are described in @ref{Tracepoint
11580 It is also possible to get trace data from a file, in a manner reminiscent
11581 of corefiles; you specify the filename, and use @code{tfind} to search
11582 through the file. @xref{Trace Files}, for more details.
11584 This chapter describes the tracepoint commands and features.
11587 * Set Tracepoints::
11588 * Analyze Collected Data::
11589 * Tracepoint Variables::
11593 @node Set Tracepoints
11594 @section Commands to Set Tracepoints
11596 Before running such a @dfn{trace experiment}, an arbitrary number of
11597 tracepoints can be set. A tracepoint is actually a special type of
11598 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
11599 standard breakpoint commands. For instance, as with breakpoints,
11600 tracepoint numbers are successive integers starting from one, and many
11601 of the commands associated with tracepoints take the tracepoint number
11602 as their argument, to identify which tracepoint to work on.
11604 For each tracepoint, you can specify, in advance, some arbitrary set
11605 of data that you want the target to collect in the trace buffer when
11606 it hits that tracepoint. The collected data can include registers,
11607 local variables, or global data. Later, you can use @value{GDBN}
11608 commands to examine the values these data had at the time the
11609 tracepoint was hit.
11611 Tracepoints do not support every breakpoint feature. Ignore counts on
11612 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
11613 commands when they are hit. Tracepoints may not be thread-specific
11616 @cindex fast tracepoints
11617 Some targets may support @dfn{fast tracepoints}, which are inserted in
11618 a different way (such as with a jump instead of a trap), that is
11619 faster but possibly restricted in where they may be installed.
11621 @cindex static tracepoints
11622 @cindex markers, static tracepoints
11623 @cindex probing markers, static tracepoints
11624 Regular and fast tracepoints are dynamic tracing facilities, meaning
11625 that they can be used to insert tracepoints at (almost) any location
11626 in the target. Some targets may also support controlling @dfn{static
11627 tracepoints} from @value{GDBN}. With static tracing, a set of
11628 instrumentation points, also known as @dfn{markers}, are embedded in
11629 the target program, and can be activated or deactivated by name or
11630 address. These are usually placed at locations which facilitate
11631 investigating what the target is actually doing. @value{GDBN}'s
11632 support for static tracing includes being able to list instrumentation
11633 points, and attach them with @value{GDBN} defined high level
11634 tracepoints that expose the whole range of convenience of
11635 @value{GDBN}'s tracepoints support. Namely, support for collecting
11636 registers values and values of global or local (to the instrumentation
11637 point) variables; tracepoint conditions and trace state variables.
11638 The act of installing a @value{GDBN} static tracepoint on an
11639 instrumentation point, or marker, is referred to as @dfn{probing} a
11640 static tracepoint marker.
11642 @code{gdbserver} supports tracepoints on some target systems.
11643 @xref{Server,,Tracepoints support in @code{gdbserver}}.
11645 This section describes commands to set tracepoints and associated
11646 conditions and actions.
11649 * Create and Delete Tracepoints::
11650 * Enable and Disable Tracepoints::
11651 * Tracepoint Passcounts::
11652 * Tracepoint Conditions::
11653 * Trace State Variables::
11654 * Tracepoint Actions::
11655 * Listing Tracepoints::
11656 * Listing Static Tracepoint Markers::
11657 * Starting and Stopping Trace Experiments::
11658 * Tracepoint Restrictions::
11661 @node Create and Delete Tracepoints
11662 @subsection Create and Delete Tracepoints
11665 @cindex set tracepoint
11667 @item trace @var{location}
11668 The @code{trace} command is very similar to the @code{break} command.
11669 Its argument @var{location} can be a source line, a function name, or
11670 an address in the target program. @xref{Specify Location}. The
11671 @code{trace} command defines a tracepoint, which is a point in the
11672 target program where the debugger will briefly stop, collect some
11673 data, and then allow the program to continue. Setting a tracepoint or
11674 changing its actions takes effect immediately if the remote stub
11675 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
11677 If remote stub doesn't support the @samp{InstallInTrace} feature, all
11678 these changes don't take effect until the next @code{tstart}
11679 command, and once a trace experiment is running, further changes will
11680 not have any effect until the next trace experiment starts. In addition,
11681 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
11682 address is not yet resolved. (This is similar to pending breakpoints.)
11683 Pending tracepoints are not downloaded to the target and not installed
11684 until they are resolved. The resolution of pending tracepoints requires
11685 @value{GDBN} support---when debugging with the remote target, and
11686 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
11687 tracing}), pending tracepoints can not be resolved (and downloaded to
11688 the remote stub) while @value{GDBN} is disconnected.
11690 Here are some examples of using the @code{trace} command:
11693 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
11695 (@value{GDBP}) @b{trace +2} // 2 lines forward
11697 (@value{GDBP}) @b{trace my_function} // first source line of function
11699 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
11701 (@value{GDBP}) @b{trace *0x2117c4} // an address
11705 You can abbreviate @code{trace} as @code{tr}.
11707 @item trace @var{location} if @var{cond}
11708 Set a tracepoint with condition @var{cond}; evaluate the expression
11709 @var{cond} each time the tracepoint is reached, and collect data only
11710 if the value is nonzero---that is, if @var{cond} evaluates as true.
11711 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
11712 information on tracepoint conditions.
11714 @item ftrace @var{location} [ if @var{cond} ]
11715 @cindex set fast tracepoint
11716 @cindex fast tracepoints, setting
11718 The @code{ftrace} command sets a fast tracepoint. For targets that
11719 support them, fast tracepoints will use a more efficient but possibly
11720 less general technique to trigger data collection, such as a jump
11721 instruction instead of a trap, or some sort of hardware support. It
11722 may not be possible to create a fast tracepoint at the desired
11723 location, in which case the command will exit with an explanatory
11726 @value{GDBN} handles arguments to @code{ftrace} exactly as for
11729 On 32-bit x86-architecture systems, fast tracepoints normally need to
11730 be placed at an instruction that is 5 bytes or longer, but can be
11731 placed at 4-byte instructions if the low 64K of memory of the target
11732 program is available to install trampolines. Some Unix-type systems,
11733 such as @sc{gnu}/Linux, exclude low addresses from the program's
11734 address space; but for instance with the Linux kernel it is possible
11735 to let @value{GDBN} use this area by doing a @command{sysctl} command
11736 to set the @code{mmap_min_addr} kernel parameter, as in
11739 sudo sysctl -w vm.mmap_min_addr=32768
11743 which sets the low address to 32K, which leaves plenty of room for
11744 trampolines. The minimum address should be set to a page boundary.
11746 @item strace @var{location} [ if @var{cond} ]
11747 @cindex set static tracepoint
11748 @cindex static tracepoints, setting
11749 @cindex probe static tracepoint marker
11751 The @code{strace} command sets a static tracepoint. For targets that
11752 support it, setting a static tracepoint probes a static
11753 instrumentation point, or marker, found at @var{location}. It may not
11754 be possible to set a static tracepoint at the desired location, in
11755 which case the command will exit with an explanatory message.
11757 @value{GDBN} handles arguments to @code{strace} exactly as for
11758 @code{trace}, with the addition that the user can also specify
11759 @code{-m @var{marker}} as @var{location}. This probes the marker
11760 identified by the @var{marker} string identifier. This identifier
11761 depends on the static tracepoint backend library your program is
11762 using. You can find all the marker identifiers in the @samp{ID} field
11763 of the @code{info static-tracepoint-markers} command output.
11764 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
11765 Markers}. For example, in the following small program using the UST
11771 trace_mark(ust, bar33, "str %s", "FOOBAZ");
11776 the marker id is composed of joining the first two arguments to the
11777 @code{trace_mark} call with a slash, which translates to:
11780 (@value{GDBP}) info static-tracepoint-markers
11781 Cnt Enb ID Address What
11782 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
11788 so you may probe the marker above with:
11791 (@value{GDBP}) strace -m ust/bar33
11794 Static tracepoints accept an extra collect action --- @code{collect
11795 $_sdata}. This collects arbitrary user data passed in the probe point
11796 call to the tracing library. In the UST example above, you'll see
11797 that the third argument to @code{trace_mark} is a printf-like format
11798 string. The user data is then the result of running that formating
11799 string against the following arguments. Note that @code{info
11800 static-tracepoint-markers} command output lists that format string in
11801 the @samp{Data:} field.
11803 You can inspect this data when analyzing the trace buffer, by printing
11804 the $_sdata variable like any other variable available to
11805 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
11808 @cindex last tracepoint number
11809 @cindex recent tracepoint number
11810 @cindex tracepoint number
11811 The convenience variable @code{$tpnum} records the tracepoint number
11812 of the most recently set tracepoint.
11814 @kindex delete tracepoint
11815 @cindex tracepoint deletion
11816 @item delete tracepoint @r{[}@var{num}@r{]}
11817 Permanently delete one or more tracepoints. With no argument, the
11818 default is to delete all tracepoints. Note that the regular
11819 @code{delete} command can remove tracepoints also.
11824 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
11826 (@value{GDBP}) @b{delete trace} // remove all tracepoints
11830 You can abbreviate this command as @code{del tr}.
11833 @node Enable and Disable Tracepoints
11834 @subsection Enable and Disable Tracepoints
11836 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
11839 @kindex disable tracepoint
11840 @item disable tracepoint @r{[}@var{num}@r{]}
11841 Disable tracepoint @var{num}, or all tracepoints if no argument
11842 @var{num} is given. A disabled tracepoint will have no effect during
11843 a trace experiment, but it is not forgotten. You can re-enable
11844 a disabled tracepoint using the @code{enable tracepoint} command.
11845 If the command is issued during a trace experiment and the debug target
11846 has support for disabling tracepoints during a trace experiment, then the
11847 change will be effective immediately. Otherwise, it will be applied to the
11848 next trace experiment.
11850 @kindex enable tracepoint
11851 @item enable tracepoint @r{[}@var{num}@r{]}
11852 Enable tracepoint @var{num}, or all tracepoints. If this command is
11853 issued during a trace experiment and the debug target supports enabling
11854 tracepoints during a trace experiment, then the enabled tracepoints will
11855 become effective immediately. Otherwise, they will become effective the
11856 next time a trace experiment is run.
11859 @node Tracepoint Passcounts
11860 @subsection Tracepoint Passcounts
11864 @cindex tracepoint pass count
11865 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
11866 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
11867 automatically stop a trace experiment. If a tracepoint's passcount is
11868 @var{n}, then the trace experiment will be automatically stopped on
11869 the @var{n}'th time that tracepoint is hit. If the tracepoint number
11870 @var{num} is not specified, the @code{passcount} command sets the
11871 passcount of the most recently defined tracepoint. If no passcount is
11872 given, the trace experiment will run until stopped explicitly by the
11878 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
11879 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
11881 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
11882 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
11883 (@value{GDBP}) @b{trace foo}
11884 (@value{GDBP}) @b{pass 3}
11885 (@value{GDBP}) @b{trace bar}
11886 (@value{GDBP}) @b{pass 2}
11887 (@value{GDBP}) @b{trace baz}
11888 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
11889 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
11890 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
11891 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
11895 @node Tracepoint Conditions
11896 @subsection Tracepoint Conditions
11897 @cindex conditional tracepoints
11898 @cindex tracepoint conditions
11900 The simplest sort of tracepoint collects data every time your program
11901 reaches a specified place. You can also specify a @dfn{condition} for
11902 a tracepoint. A condition is just a Boolean expression in your
11903 programming language (@pxref{Expressions, ,Expressions}). A
11904 tracepoint with a condition evaluates the expression each time your
11905 program reaches it, and data collection happens only if the condition
11908 Tracepoint conditions can be specified when a tracepoint is set, by
11909 using @samp{if} in the arguments to the @code{trace} command.
11910 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
11911 also be set or changed at any time with the @code{condition} command,
11912 just as with breakpoints.
11914 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
11915 the conditional expression itself. Instead, @value{GDBN} encodes the
11916 expression into an agent expression (@pxref{Agent Expressions})
11917 suitable for execution on the target, independently of @value{GDBN}.
11918 Global variables become raw memory locations, locals become stack
11919 accesses, and so forth.
11921 For instance, suppose you have a function that is usually called
11922 frequently, but should not be called after an error has occurred. You
11923 could use the following tracepoint command to collect data about calls
11924 of that function that happen while the error code is propagating
11925 through the program; an unconditional tracepoint could end up
11926 collecting thousands of useless trace frames that you would have to
11930 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
11933 @node Trace State Variables
11934 @subsection Trace State Variables
11935 @cindex trace state variables
11937 A @dfn{trace state variable} is a special type of variable that is
11938 created and managed by target-side code. The syntax is the same as
11939 that for GDB's convenience variables (a string prefixed with ``$''),
11940 but they are stored on the target. They must be created explicitly,
11941 using a @code{tvariable} command. They are always 64-bit signed
11944 Trace state variables are remembered by @value{GDBN}, and downloaded
11945 to the target along with tracepoint information when the trace
11946 experiment starts. There are no intrinsic limits on the number of
11947 trace state variables, beyond memory limitations of the target.
11949 @cindex convenience variables, and trace state variables
11950 Although trace state variables are managed by the target, you can use
11951 them in print commands and expressions as if they were convenience
11952 variables; @value{GDBN} will get the current value from the target
11953 while the trace experiment is running. Trace state variables share
11954 the same namespace as other ``$'' variables, which means that you
11955 cannot have trace state variables with names like @code{$23} or
11956 @code{$pc}, nor can you have a trace state variable and a convenience
11957 variable with the same name.
11961 @item tvariable $@var{name} [ = @var{expression} ]
11963 The @code{tvariable} command creates a new trace state variable named
11964 @code{$@var{name}}, and optionally gives it an initial value of
11965 @var{expression}. @var{expression} is evaluated when this command is
11966 entered; the result will be converted to an integer if possible,
11967 otherwise @value{GDBN} will report an error. A subsequent
11968 @code{tvariable} command specifying the same name does not create a
11969 variable, but instead assigns the supplied initial value to the
11970 existing variable of that name, overwriting any previous initial
11971 value. The default initial value is 0.
11973 @item info tvariables
11974 @kindex info tvariables
11975 List all the trace state variables along with their initial values.
11976 Their current values may also be displayed, if the trace experiment is
11979 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
11980 @kindex delete tvariable
11981 Delete the given trace state variables, or all of them if no arguments
11986 @node Tracepoint Actions
11987 @subsection Tracepoint Action Lists
11991 @cindex tracepoint actions
11992 @item actions @r{[}@var{num}@r{]}
11993 This command will prompt for a list of actions to be taken when the
11994 tracepoint is hit. If the tracepoint number @var{num} is not
11995 specified, this command sets the actions for the one that was most
11996 recently defined (so that you can define a tracepoint and then say
11997 @code{actions} without bothering about its number). You specify the
11998 actions themselves on the following lines, one action at a time, and
11999 terminate the actions list with a line containing just @code{end}. So
12000 far, the only defined actions are @code{collect}, @code{teval}, and
12001 @code{while-stepping}.
12003 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
12004 Commands, ,Breakpoint Command Lists}), except that only the defined
12005 actions are allowed; any other @value{GDBN} command is rejected.
12007 @cindex remove actions from a tracepoint
12008 To remove all actions from a tracepoint, type @samp{actions @var{num}}
12009 and follow it immediately with @samp{end}.
12012 (@value{GDBP}) @b{collect @var{data}} // collect some data
12014 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
12016 (@value{GDBP}) @b{end} // signals the end of actions.
12019 In the following example, the action list begins with @code{collect}
12020 commands indicating the things to be collected when the tracepoint is
12021 hit. Then, in order to single-step and collect additional data
12022 following the tracepoint, a @code{while-stepping} command is used,
12023 followed by the list of things to be collected after each step in a
12024 sequence of single steps. The @code{while-stepping} command is
12025 terminated by its own separate @code{end} command. Lastly, the action
12026 list is terminated by an @code{end} command.
12029 (@value{GDBP}) @b{trace foo}
12030 (@value{GDBP}) @b{actions}
12031 Enter actions for tracepoint 1, one per line:
12034 > while-stepping 12
12035 > collect $pc, arr[i]
12040 @kindex collect @r{(tracepoints)}
12041 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
12042 Collect values of the given expressions when the tracepoint is hit.
12043 This command accepts a comma-separated list of any valid expressions.
12044 In addition to global, static, or local variables, the following
12045 special arguments are supported:
12049 Collect all registers.
12052 Collect all function arguments.
12055 Collect all local variables.
12058 Collect the return address. This is helpful if you want to see more
12062 Collects the number of arguments from the static probe at which the
12063 tracepoint is located.
12064 @xref{Static Probe Points}.
12066 @item $_probe_arg@var{n}
12067 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
12068 from the static probe at which the tracepoint is located.
12069 @xref{Static Probe Points}.
12072 @vindex $_sdata@r{, collect}
12073 Collect static tracepoint marker specific data. Only available for
12074 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
12075 Lists}. On the UST static tracepoints library backend, an
12076 instrumentation point resembles a @code{printf} function call. The
12077 tracing library is able to collect user specified data formatted to a
12078 character string using the format provided by the programmer that
12079 instrumented the program. Other backends have similar mechanisms.
12080 Here's an example of a UST marker call:
12083 const char master_name[] = "$your_name";
12084 trace_mark(channel1, marker1, "hello %s", master_name)
12087 In this case, collecting @code{$_sdata} collects the string
12088 @samp{hello $yourname}. When analyzing the trace buffer, you can
12089 inspect @samp{$_sdata} like any other variable available to
12093 You can give several consecutive @code{collect} commands, each one
12094 with a single argument, or one @code{collect} command with several
12095 arguments separated by commas; the effect is the same.
12097 The optional @var{mods} changes the usual handling of the arguments.
12098 @code{s} requests that pointers to chars be handled as strings, in
12099 particular collecting the contents of the memory being pointed at, up
12100 to the first zero. The upper bound is by default the value of the
12101 @code{print elements} variable; if @code{s} is followed by a decimal
12102 number, that is the upper bound instead. So for instance
12103 @samp{collect/s25 mystr} collects as many as 25 characters at
12106 The command @code{info scope} (@pxref{Symbols, info scope}) is
12107 particularly useful for figuring out what data to collect.
12109 @kindex teval @r{(tracepoints)}
12110 @item teval @var{expr1}, @var{expr2}, @dots{}
12111 Evaluate the given expressions when the tracepoint is hit. This
12112 command accepts a comma-separated list of expressions. The results
12113 are discarded, so this is mainly useful for assigning values to trace
12114 state variables (@pxref{Trace State Variables}) without adding those
12115 values to the trace buffer, as would be the case if the @code{collect}
12118 @kindex while-stepping @r{(tracepoints)}
12119 @item while-stepping @var{n}
12120 Perform @var{n} single-step instruction traces after the tracepoint,
12121 collecting new data after each step. The @code{while-stepping}
12122 command is followed by the list of what to collect while stepping
12123 (followed by its own @code{end} command):
12126 > while-stepping 12
12127 > collect $regs, myglobal
12133 Note that @code{$pc} is not automatically collected by
12134 @code{while-stepping}; you need to explicitly collect that register if
12135 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
12138 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
12139 @kindex set default-collect
12140 @cindex default collection action
12141 This variable is a list of expressions to collect at each tracepoint
12142 hit. It is effectively an additional @code{collect} action prepended
12143 to every tracepoint action list. The expressions are parsed
12144 individually for each tracepoint, so for instance a variable named
12145 @code{xyz} may be interpreted as a global for one tracepoint, and a
12146 local for another, as appropriate to the tracepoint's location.
12148 @item show default-collect
12149 @kindex show default-collect
12150 Show the list of expressions that are collected by default at each
12155 @node Listing Tracepoints
12156 @subsection Listing Tracepoints
12159 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
12160 @kindex info tp @r{[}@var{n}@dots{}@r{]}
12161 @cindex information about tracepoints
12162 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
12163 Display information about the tracepoint @var{num}. If you don't
12164 specify a tracepoint number, displays information about all the
12165 tracepoints defined so far. The format is similar to that used for
12166 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
12167 command, simply restricting itself to tracepoints.
12169 A tracepoint's listing may include additional information specific to
12174 its passcount as given by the @code{passcount @var{n}} command
12177 the state about installed on target of each location
12181 (@value{GDBP}) @b{info trace}
12182 Num Type Disp Enb Address What
12183 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
12185 collect globfoo, $regs
12190 2 tracepoint keep y <MULTIPLE>
12192 2.1 y 0x0804859c in func4 at change-loc.h:35
12193 installed on target
12194 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
12195 installed on target
12196 2.3 y <PENDING> set_tracepoint
12197 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
12198 not installed on target
12203 This command can be abbreviated @code{info tp}.
12206 @node Listing Static Tracepoint Markers
12207 @subsection Listing Static Tracepoint Markers
12210 @kindex info static-tracepoint-markers
12211 @cindex information about static tracepoint markers
12212 @item info static-tracepoint-markers
12213 Display information about all static tracepoint markers defined in the
12216 For each marker, the following columns are printed:
12220 An incrementing counter, output to help readability. This is not a
12223 The marker ID, as reported by the target.
12224 @item Enabled or Disabled
12225 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
12226 that are not enabled.
12228 Where the marker is in your program, as a memory address.
12230 Where the marker is in the source for your program, as a file and line
12231 number. If the debug information included in the program does not
12232 allow @value{GDBN} to locate the source of the marker, this column
12233 will be left blank.
12237 In addition, the following information may be printed for each marker:
12241 User data passed to the tracing library by the marker call. In the
12242 UST backend, this is the format string passed as argument to the
12244 @item Static tracepoints probing the marker
12245 The list of static tracepoints attached to the marker.
12249 (@value{GDBP}) info static-tracepoint-markers
12250 Cnt ID Enb Address What
12251 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
12252 Data: number1 %d number2 %d
12253 Probed by static tracepoints: #2
12254 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
12260 @node Starting and Stopping Trace Experiments
12261 @subsection Starting and Stopping Trace Experiments
12264 @kindex tstart [ @var{notes} ]
12265 @cindex start a new trace experiment
12266 @cindex collected data discarded
12268 This command starts the trace experiment, and begins collecting data.
12269 It has the side effect of discarding all the data collected in the
12270 trace buffer during the previous trace experiment. If any arguments
12271 are supplied, they are taken as a note and stored with the trace
12272 experiment's state. The notes may be arbitrary text, and are
12273 especially useful with disconnected tracing in a multi-user context;
12274 the notes can explain what the trace is doing, supply user contact
12275 information, and so forth.
12277 @kindex tstop [ @var{notes} ]
12278 @cindex stop a running trace experiment
12280 This command stops the trace experiment. If any arguments are
12281 supplied, they are recorded with the experiment as a note. This is
12282 useful if you are stopping a trace started by someone else, for
12283 instance if the trace is interfering with the system's behavior and
12284 needs to be stopped quickly.
12286 @strong{Note}: a trace experiment and data collection may stop
12287 automatically if any tracepoint's passcount is reached
12288 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
12291 @cindex status of trace data collection
12292 @cindex trace experiment, status of
12294 This command displays the status of the current trace data
12298 Here is an example of the commands we described so far:
12301 (@value{GDBP}) @b{trace gdb_c_test}
12302 (@value{GDBP}) @b{actions}
12303 Enter actions for tracepoint #1, one per line.
12304 > collect $regs,$locals,$args
12305 > while-stepping 11
12309 (@value{GDBP}) @b{tstart}
12310 [time passes @dots{}]
12311 (@value{GDBP}) @b{tstop}
12314 @anchor{disconnected tracing}
12315 @cindex disconnected tracing
12316 You can choose to continue running the trace experiment even if
12317 @value{GDBN} disconnects from the target, voluntarily or
12318 involuntarily. For commands such as @code{detach}, the debugger will
12319 ask what you want to do with the trace. But for unexpected
12320 terminations (@value{GDBN} crash, network outage), it would be
12321 unfortunate to lose hard-won trace data, so the variable
12322 @code{disconnected-tracing} lets you decide whether the trace should
12323 continue running without @value{GDBN}.
12326 @item set disconnected-tracing on
12327 @itemx set disconnected-tracing off
12328 @kindex set disconnected-tracing
12329 Choose whether a tracing run should continue to run if @value{GDBN}
12330 has disconnected from the target. Note that @code{detach} or
12331 @code{quit} will ask you directly what to do about a running trace no
12332 matter what this variable's setting, so the variable is mainly useful
12333 for handling unexpected situations, such as loss of the network.
12335 @item show disconnected-tracing
12336 @kindex show disconnected-tracing
12337 Show the current choice for disconnected tracing.
12341 When you reconnect to the target, the trace experiment may or may not
12342 still be running; it might have filled the trace buffer in the
12343 meantime, or stopped for one of the other reasons. If it is running,
12344 it will continue after reconnection.
12346 Upon reconnection, the target will upload information about the
12347 tracepoints in effect. @value{GDBN} will then compare that
12348 information to the set of tracepoints currently defined, and attempt
12349 to match them up, allowing for the possibility that the numbers may
12350 have changed due to creation and deletion in the meantime. If one of
12351 the target's tracepoints does not match any in @value{GDBN}, the
12352 debugger will create a new tracepoint, so that you have a number with
12353 which to specify that tracepoint. This matching-up process is
12354 necessarily heuristic, and it may result in useless tracepoints being
12355 created; you may simply delete them if they are of no use.
12357 @cindex circular trace buffer
12358 If your target agent supports a @dfn{circular trace buffer}, then you
12359 can run a trace experiment indefinitely without filling the trace
12360 buffer; when space runs out, the agent deletes already-collected trace
12361 frames, oldest first, until there is enough room to continue
12362 collecting. This is especially useful if your tracepoints are being
12363 hit too often, and your trace gets terminated prematurely because the
12364 buffer is full. To ask for a circular trace buffer, simply set
12365 @samp{circular-trace-buffer} to on. You can set this at any time,
12366 including during tracing; if the agent can do it, it will change
12367 buffer handling on the fly, otherwise it will not take effect until
12371 @item set circular-trace-buffer on
12372 @itemx set circular-trace-buffer off
12373 @kindex set circular-trace-buffer
12374 Choose whether a tracing run should use a linear or circular buffer
12375 for trace data. A linear buffer will not lose any trace data, but may
12376 fill up prematurely, while a circular buffer will discard old trace
12377 data, but it will have always room for the latest tracepoint hits.
12379 @item show circular-trace-buffer
12380 @kindex show circular-trace-buffer
12381 Show the current choice for the trace buffer. Note that this may not
12382 match the agent's current buffer handling, nor is it guaranteed to
12383 match the setting that might have been in effect during a past run,
12384 for instance if you are looking at frames from a trace file.
12389 @item set trace-buffer-size @var{n}
12390 @itemx set trace-buffer-size unlimited
12391 @kindex set trace-buffer-size
12392 Request that the target use a trace buffer of @var{n} bytes. Not all
12393 targets will honor the request; they may have a compiled-in size for
12394 the trace buffer, or some other limitation. Set to a value of
12395 @code{unlimited} or @code{-1} to let the target use whatever size it
12396 likes. This is also the default.
12398 @item show trace-buffer-size
12399 @kindex show trace-buffer-size
12400 Show the current requested size for the trace buffer. Note that this
12401 will only match the actual size if the target supports size-setting,
12402 and was able to handle the requested size. For instance, if the
12403 target can only change buffer size between runs, this variable will
12404 not reflect the change until the next run starts. Use @code{tstatus}
12405 to get a report of the actual buffer size.
12409 @item set trace-user @var{text}
12410 @kindex set trace-user
12412 @item show trace-user
12413 @kindex show trace-user
12415 @item set trace-notes @var{text}
12416 @kindex set trace-notes
12417 Set the trace run's notes.
12419 @item show trace-notes
12420 @kindex show trace-notes
12421 Show the trace run's notes.
12423 @item set trace-stop-notes @var{text}
12424 @kindex set trace-stop-notes
12425 Set the trace run's stop notes. The handling of the note is as for
12426 @code{tstop} arguments; the set command is convenient way to fix a
12427 stop note that is mistaken or incomplete.
12429 @item show trace-stop-notes
12430 @kindex show trace-stop-notes
12431 Show the trace run's stop notes.
12435 @node Tracepoint Restrictions
12436 @subsection Tracepoint Restrictions
12438 @cindex tracepoint restrictions
12439 There are a number of restrictions on the use of tracepoints. As
12440 described above, tracepoint data gathering occurs on the target
12441 without interaction from @value{GDBN}. Thus the full capabilities of
12442 the debugger are not available during data gathering, and then at data
12443 examination time, you will be limited by only having what was
12444 collected. The following items describe some common problems, but it
12445 is not exhaustive, and you may run into additional difficulties not
12451 Tracepoint expressions are intended to gather objects (lvalues). Thus
12452 the full flexibility of GDB's expression evaluator is not available.
12453 You cannot call functions, cast objects to aggregate types, access
12454 convenience variables or modify values (except by assignment to trace
12455 state variables). Some language features may implicitly call
12456 functions (for instance Objective-C fields with accessors), and therefore
12457 cannot be collected either.
12460 Collection of local variables, either individually or in bulk with
12461 @code{$locals} or @code{$args}, during @code{while-stepping} may
12462 behave erratically. The stepping action may enter a new scope (for
12463 instance by stepping into a function), or the location of the variable
12464 may change (for instance it is loaded into a register). The
12465 tracepoint data recorded uses the location information for the
12466 variables that is correct for the tracepoint location. When the
12467 tracepoint is created, it is not possible, in general, to determine
12468 where the steps of a @code{while-stepping} sequence will advance the
12469 program---particularly if a conditional branch is stepped.
12472 Collection of an incompletely-initialized or partially-destroyed object
12473 may result in something that @value{GDBN} cannot display, or displays
12474 in a misleading way.
12477 When @value{GDBN} displays a pointer to character it automatically
12478 dereferences the pointer to also display characters of the string
12479 being pointed to. However, collecting the pointer during tracing does
12480 not automatically collect the string. You need to explicitly
12481 dereference the pointer and provide size information if you want to
12482 collect not only the pointer, but the memory pointed to. For example,
12483 @code{*ptr@@50} can be used to collect the 50 element array pointed to
12487 It is not possible to collect a complete stack backtrace at a
12488 tracepoint. Instead, you may collect the registers and a few hundred
12489 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
12490 (adjust to use the name of the actual stack pointer register on your
12491 target architecture, and the amount of stack you wish to capture).
12492 Then the @code{backtrace} command will show a partial backtrace when
12493 using a trace frame. The number of stack frames that can be examined
12494 depends on the sizes of the frames in the collected stack. Note that
12495 if you ask for a block so large that it goes past the bottom of the
12496 stack, the target agent may report an error trying to read from an
12500 If you do not collect registers at a tracepoint, @value{GDBN} can
12501 infer that the value of @code{$pc} must be the same as the address of
12502 the tracepoint and use that when you are looking at a trace frame
12503 for that tracepoint. However, this cannot work if the tracepoint has
12504 multiple locations (for instance if it was set in a function that was
12505 inlined), or if it has a @code{while-stepping} loop. In those cases
12506 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
12511 @node Analyze Collected Data
12512 @section Using the Collected Data
12514 After the tracepoint experiment ends, you use @value{GDBN} commands
12515 for examining the trace data. The basic idea is that each tracepoint
12516 collects a trace @dfn{snapshot} every time it is hit and another
12517 snapshot every time it single-steps. All these snapshots are
12518 consecutively numbered from zero and go into a buffer, and you can
12519 examine them later. The way you examine them is to @dfn{focus} on a
12520 specific trace snapshot. When the remote stub is focused on a trace
12521 snapshot, it will respond to all @value{GDBN} requests for memory and
12522 registers by reading from the buffer which belongs to that snapshot,
12523 rather than from @emph{real} memory or registers of the program being
12524 debugged. This means that @strong{all} @value{GDBN} commands
12525 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
12526 behave as if we were currently debugging the program state as it was
12527 when the tracepoint occurred. Any requests for data that are not in
12528 the buffer will fail.
12531 * tfind:: How to select a trace snapshot
12532 * tdump:: How to display all data for a snapshot
12533 * save tracepoints:: How to save tracepoints for a future run
12537 @subsection @code{tfind @var{n}}
12540 @cindex select trace snapshot
12541 @cindex find trace snapshot
12542 The basic command for selecting a trace snapshot from the buffer is
12543 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
12544 counting from zero. If no argument @var{n} is given, the next
12545 snapshot is selected.
12547 Here are the various forms of using the @code{tfind} command.
12551 Find the first snapshot in the buffer. This is a synonym for
12552 @code{tfind 0} (since 0 is the number of the first snapshot).
12555 Stop debugging trace snapshots, resume @emph{live} debugging.
12558 Same as @samp{tfind none}.
12561 No argument means find the next trace snapshot.
12564 Find the previous trace snapshot before the current one. This permits
12565 retracing earlier steps.
12567 @item tfind tracepoint @var{num}
12568 Find the next snapshot associated with tracepoint @var{num}. Search
12569 proceeds forward from the last examined trace snapshot. If no
12570 argument @var{num} is given, it means find the next snapshot collected
12571 for the same tracepoint as the current snapshot.
12573 @item tfind pc @var{addr}
12574 Find the next snapshot associated with the value @var{addr} of the
12575 program counter. Search proceeds forward from the last examined trace
12576 snapshot. If no argument @var{addr} is given, it means find the next
12577 snapshot with the same value of PC as the current snapshot.
12579 @item tfind outside @var{addr1}, @var{addr2}
12580 Find the next snapshot whose PC is outside the given range of
12581 addresses (exclusive).
12583 @item tfind range @var{addr1}, @var{addr2}
12584 Find the next snapshot whose PC is between @var{addr1} and
12585 @var{addr2} (inclusive).
12587 @item tfind line @r{[}@var{file}:@r{]}@var{n}
12588 Find the next snapshot associated with the source line @var{n}. If
12589 the optional argument @var{file} is given, refer to line @var{n} in
12590 that source file. Search proceeds forward from the last examined
12591 trace snapshot. If no argument @var{n} is given, it means find the
12592 next line other than the one currently being examined; thus saying
12593 @code{tfind line} repeatedly can appear to have the same effect as
12594 stepping from line to line in a @emph{live} debugging session.
12597 The default arguments for the @code{tfind} commands are specifically
12598 designed to make it easy to scan through the trace buffer. For
12599 instance, @code{tfind} with no argument selects the next trace
12600 snapshot, and @code{tfind -} with no argument selects the previous
12601 trace snapshot. So, by giving one @code{tfind} command, and then
12602 simply hitting @key{RET} repeatedly you can examine all the trace
12603 snapshots in order. Or, by saying @code{tfind -} and then hitting
12604 @key{RET} repeatedly you can examine the snapshots in reverse order.
12605 The @code{tfind line} command with no argument selects the snapshot
12606 for the next source line executed. The @code{tfind pc} command with
12607 no argument selects the next snapshot with the same program counter
12608 (PC) as the current frame. The @code{tfind tracepoint} command with
12609 no argument selects the next trace snapshot collected by the same
12610 tracepoint as the current one.
12612 In addition to letting you scan through the trace buffer manually,
12613 these commands make it easy to construct @value{GDBN} scripts that
12614 scan through the trace buffer and print out whatever collected data
12615 you are interested in. Thus, if we want to examine the PC, FP, and SP
12616 registers from each trace frame in the buffer, we can say this:
12619 (@value{GDBP}) @b{tfind start}
12620 (@value{GDBP}) @b{while ($trace_frame != -1)}
12621 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
12622 $trace_frame, $pc, $sp, $fp
12626 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
12627 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
12628 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
12629 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
12630 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
12631 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
12632 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
12633 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
12634 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
12635 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
12636 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
12639 Or, if we want to examine the variable @code{X} at each source line in
12643 (@value{GDBP}) @b{tfind start}
12644 (@value{GDBP}) @b{while ($trace_frame != -1)}
12645 > printf "Frame %d, X == %d\n", $trace_frame, X
12655 @subsection @code{tdump}
12657 @cindex dump all data collected at tracepoint
12658 @cindex tracepoint data, display
12660 This command takes no arguments. It prints all the data collected at
12661 the current trace snapshot.
12664 (@value{GDBP}) @b{trace 444}
12665 (@value{GDBP}) @b{actions}
12666 Enter actions for tracepoint #2, one per line:
12667 > collect $regs, $locals, $args, gdb_long_test
12670 (@value{GDBP}) @b{tstart}
12672 (@value{GDBP}) @b{tfind line 444}
12673 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
12675 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
12677 (@value{GDBP}) @b{tdump}
12678 Data collected at tracepoint 2, trace frame 1:
12679 d0 0xc4aa0085 -995491707
12683 d4 0x71aea3d 119204413
12686 d7 0x380035 3670069
12687 a0 0x19e24a 1696330
12688 a1 0x3000668 50333288
12690 a3 0x322000 3284992
12691 a4 0x3000698 50333336
12692 a5 0x1ad3cc 1758156
12693 fp 0x30bf3c 0x30bf3c
12694 sp 0x30bf34 0x30bf34
12696 pc 0x20b2c8 0x20b2c8
12700 p = 0x20e5b4 "gdb-test"
12707 gdb_long_test = 17 '\021'
12712 @code{tdump} works by scanning the tracepoint's current collection
12713 actions and printing the value of each expression listed. So
12714 @code{tdump} can fail, if after a run, you change the tracepoint's
12715 actions to mention variables that were not collected during the run.
12717 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
12718 uses the collected value of @code{$pc} to distinguish between trace
12719 frames that were collected at the tracepoint hit, and frames that were
12720 collected while stepping. This allows it to correctly choose whether
12721 to display the basic list of collections, or the collections from the
12722 body of the while-stepping loop. However, if @code{$pc} was not collected,
12723 then @code{tdump} will always attempt to dump using the basic collection
12724 list, and may fail if a while-stepping frame does not include all the
12725 same data that is collected at the tracepoint hit.
12726 @c This is getting pretty arcane, example would be good.
12728 @node save tracepoints
12729 @subsection @code{save tracepoints @var{filename}}
12730 @kindex save tracepoints
12731 @kindex save-tracepoints
12732 @cindex save tracepoints for future sessions
12734 This command saves all current tracepoint definitions together with
12735 their actions and passcounts, into a file @file{@var{filename}}
12736 suitable for use in a later debugging session. To read the saved
12737 tracepoint definitions, use the @code{source} command (@pxref{Command
12738 Files}). The @w{@code{save-tracepoints}} command is a deprecated
12739 alias for @w{@code{save tracepoints}}
12741 @node Tracepoint Variables
12742 @section Convenience Variables for Tracepoints
12743 @cindex tracepoint variables
12744 @cindex convenience variables for tracepoints
12747 @vindex $trace_frame
12748 @item (int) $trace_frame
12749 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
12750 snapshot is selected.
12752 @vindex $tracepoint
12753 @item (int) $tracepoint
12754 The tracepoint for the current trace snapshot.
12756 @vindex $trace_line
12757 @item (int) $trace_line
12758 The line number for the current trace snapshot.
12760 @vindex $trace_file
12761 @item (char []) $trace_file
12762 The source file for the current trace snapshot.
12764 @vindex $trace_func
12765 @item (char []) $trace_func
12766 The name of the function containing @code{$tracepoint}.
12769 Note: @code{$trace_file} is not suitable for use in @code{printf},
12770 use @code{output} instead.
12772 Here's a simple example of using these convenience variables for
12773 stepping through all the trace snapshots and printing some of their
12774 data. Note that these are not the same as trace state variables,
12775 which are managed by the target.
12778 (@value{GDBP}) @b{tfind start}
12780 (@value{GDBP}) @b{while $trace_frame != -1}
12781 > output $trace_file
12782 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
12788 @section Using Trace Files
12789 @cindex trace files
12791 In some situations, the target running a trace experiment may no
12792 longer be available; perhaps it crashed, or the hardware was needed
12793 for a different activity. To handle these cases, you can arrange to
12794 dump the trace data into a file, and later use that file as a source
12795 of trace data, via the @code{target tfile} command.
12800 @item tsave [ -r ] @var{filename}
12801 @itemx tsave [-ctf] @var{dirname}
12802 Save the trace data to @var{filename}. By default, this command
12803 assumes that @var{filename} refers to the host filesystem, so if
12804 necessary @value{GDBN} will copy raw trace data up from the target and
12805 then save it. If the target supports it, you can also supply the
12806 optional argument @code{-r} (``remote'') to direct the target to save
12807 the data directly into @var{filename} in its own filesystem, which may be
12808 more efficient if the trace buffer is very large. (Note, however, that
12809 @code{target tfile} can only read from files accessible to the host.)
12810 By default, this command will save trace frame in tfile format.
12811 You can supply the optional argument @code{-ctf} to save date in CTF
12812 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
12813 that can be shared by multiple debugging and tracing tools. Please go to
12814 @indicateurl{http://www.efficios.com/ctf} to get more information.
12816 @kindex target tfile
12820 @item target tfile @var{filename}
12821 @itemx target ctf @var{dirname}
12822 Use the file named @var{filename} or directory named @var{dirname} as
12823 a source of trace data. Commands that examine data work as they do with
12824 a live target, but it is not possible to run any new trace experiments.
12825 @code{tstatus} will report the state of the trace run at the moment
12826 the data was saved, as well as the current trace frame you are examining.
12827 @var{filename} or @var{dirname} must be on a filesystem accessible to
12831 (@value{GDBP}) target ctf ctf.ctf
12832 (@value{GDBP}) tfind
12833 Found trace frame 0, tracepoint 2
12834 39 ++a; /* set tracepoint 1 here */
12835 (@value{GDBP}) tdump
12836 Data collected at tracepoint 2, trace frame 0:
12840 c = @{"123", "456", "789", "123", "456", "789"@}
12841 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
12849 @chapter Debugging Programs That Use Overlays
12852 If your program is too large to fit completely in your target system's
12853 memory, you can sometimes use @dfn{overlays} to work around this
12854 problem. @value{GDBN} provides some support for debugging programs that
12858 * How Overlays Work:: A general explanation of overlays.
12859 * Overlay Commands:: Managing overlays in @value{GDBN}.
12860 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
12861 mapped by asking the inferior.
12862 * Overlay Sample Program:: A sample program using overlays.
12865 @node How Overlays Work
12866 @section How Overlays Work
12867 @cindex mapped overlays
12868 @cindex unmapped overlays
12869 @cindex load address, overlay's
12870 @cindex mapped address
12871 @cindex overlay area
12873 Suppose you have a computer whose instruction address space is only 64
12874 kilobytes long, but which has much more memory which can be accessed by
12875 other means: special instructions, segment registers, or memory
12876 management hardware, for example. Suppose further that you want to
12877 adapt a program which is larger than 64 kilobytes to run on this system.
12879 One solution is to identify modules of your program which are relatively
12880 independent, and need not call each other directly; call these modules
12881 @dfn{overlays}. Separate the overlays from the main program, and place
12882 their machine code in the larger memory. Place your main program in
12883 instruction memory, but leave at least enough space there to hold the
12884 largest overlay as well.
12886 Now, to call a function located in an overlay, you must first copy that
12887 overlay's machine code from the large memory into the space set aside
12888 for it in the instruction memory, and then jump to its entry point
12891 @c NB: In the below the mapped area's size is greater or equal to the
12892 @c size of all overlays. This is intentional to remind the developer
12893 @c that overlays don't necessarily need to be the same size.
12897 Data Instruction Larger
12898 Address Space Address Space Address Space
12899 +-----------+ +-----------+ +-----------+
12901 +-----------+ +-----------+ +-----------+<-- overlay 1
12902 | program | | main | .----| overlay 1 | load address
12903 | variables | | program | | +-----------+
12904 | and heap | | | | | |
12905 +-----------+ | | | +-----------+<-- overlay 2
12906 | | +-----------+ | | | load address
12907 +-----------+ | | | .-| overlay 2 |
12909 mapped --->+-----------+ | | +-----------+
12910 address | | | | | |
12911 | overlay | <-' | | |
12912 | area | <---' +-----------+<-- overlay 3
12913 | | <---. | | load address
12914 +-----------+ `--| overlay 3 |
12921 @anchor{A code overlay}A code overlay
12925 The diagram (@pxref{A code overlay}) shows a system with separate data
12926 and instruction address spaces. To map an overlay, the program copies
12927 its code from the larger address space to the instruction address space.
12928 Since the overlays shown here all use the same mapped address, only one
12929 may be mapped at a time. For a system with a single address space for
12930 data and instructions, the diagram would be similar, except that the
12931 program variables and heap would share an address space with the main
12932 program and the overlay area.
12934 An overlay loaded into instruction memory and ready for use is called a
12935 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
12936 instruction memory. An overlay not present (or only partially present)
12937 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
12938 is its address in the larger memory. The mapped address is also called
12939 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
12940 called the @dfn{load memory address}, or @dfn{LMA}.
12942 Unfortunately, overlays are not a completely transparent way to adapt a
12943 program to limited instruction memory. They introduce a new set of
12944 global constraints you must keep in mind as you design your program:
12949 Before calling or returning to a function in an overlay, your program
12950 must make sure that overlay is actually mapped. Otherwise, the call or
12951 return will transfer control to the right address, but in the wrong
12952 overlay, and your program will probably crash.
12955 If the process of mapping an overlay is expensive on your system, you
12956 will need to choose your overlays carefully to minimize their effect on
12957 your program's performance.
12960 The executable file you load onto your system must contain each
12961 overlay's instructions, appearing at the overlay's load address, not its
12962 mapped address. However, each overlay's instructions must be relocated
12963 and its symbols defined as if the overlay were at its mapped address.
12964 You can use GNU linker scripts to specify different load and relocation
12965 addresses for pieces of your program; see @ref{Overlay Description,,,
12966 ld.info, Using ld: the GNU linker}.
12969 The procedure for loading executable files onto your system must be able
12970 to load their contents into the larger address space as well as the
12971 instruction and data spaces.
12975 The overlay system described above is rather simple, and could be
12976 improved in many ways:
12981 If your system has suitable bank switch registers or memory management
12982 hardware, you could use those facilities to make an overlay's load area
12983 contents simply appear at their mapped address in instruction space.
12984 This would probably be faster than copying the overlay to its mapped
12985 area in the usual way.
12988 If your overlays are small enough, you could set aside more than one
12989 overlay area, and have more than one overlay mapped at a time.
12992 You can use overlays to manage data, as well as instructions. In
12993 general, data overlays are even less transparent to your design than
12994 code overlays: whereas code overlays only require care when you call or
12995 return to functions, data overlays require care every time you access
12996 the data. Also, if you change the contents of a data overlay, you
12997 must copy its contents back out to its load address before you can copy a
12998 different data overlay into the same mapped area.
13003 @node Overlay Commands
13004 @section Overlay Commands
13006 To use @value{GDBN}'s overlay support, each overlay in your program must
13007 correspond to a separate section of the executable file. The section's
13008 virtual memory address and load memory address must be the overlay's
13009 mapped and load addresses. Identifying overlays with sections allows
13010 @value{GDBN} to determine the appropriate address of a function or
13011 variable, depending on whether the overlay is mapped or not.
13013 @value{GDBN}'s overlay commands all start with the word @code{overlay};
13014 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
13019 Disable @value{GDBN}'s overlay support. When overlay support is
13020 disabled, @value{GDBN} assumes that all functions and variables are
13021 always present at their mapped addresses. By default, @value{GDBN}'s
13022 overlay support is disabled.
13024 @item overlay manual
13025 @cindex manual overlay debugging
13026 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
13027 relies on you to tell it which overlays are mapped, and which are not,
13028 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
13029 commands described below.
13031 @item overlay map-overlay @var{overlay}
13032 @itemx overlay map @var{overlay}
13033 @cindex map an overlay
13034 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
13035 be the name of the object file section containing the overlay. When an
13036 overlay is mapped, @value{GDBN} assumes it can find the overlay's
13037 functions and variables at their mapped addresses. @value{GDBN} assumes
13038 that any other overlays whose mapped ranges overlap that of
13039 @var{overlay} are now unmapped.
13041 @item overlay unmap-overlay @var{overlay}
13042 @itemx overlay unmap @var{overlay}
13043 @cindex unmap an overlay
13044 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
13045 must be the name of the object file section containing the overlay.
13046 When an overlay is unmapped, @value{GDBN} assumes it can find the
13047 overlay's functions and variables at their load addresses.
13050 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
13051 consults a data structure the overlay manager maintains in the inferior
13052 to see which overlays are mapped. For details, see @ref{Automatic
13053 Overlay Debugging}.
13055 @item overlay load-target
13056 @itemx overlay load
13057 @cindex reloading the overlay table
13058 Re-read the overlay table from the inferior. Normally, @value{GDBN}
13059 re-reads the table @value{GDBN} automatically each time the inferior
13060 stops, so this command should only be necessary if you have changed the
13061 overlay mapping yourself using @value{GDBN}. This command is only
13062 useful when using automatic overlay debugging.
13064 @item overlay list-overlays
13065 @itemx overlay list
13066 @cindex listing mapped overlays
13067 Display a list of the overlays currently mapped, along with their mapped
13068 addresses, load addresses, and sizes.
13072 Normally, when @value{GDBN} prints a code address, it includes the name
13073 of the function the address falls in:
13076 (@value{GDBP}) print main
13077 $3 = @{int ()@} 0x11a0 <main>
13080 When overlay debugging is enabled, @value{GDBN} recognizes code in
13081 unmapped overlays, and prints the names of unmapped functions with
13082 asterisks around them. For example, if @code{foo} is a function in an
13083 unmapped overlay, @value{GDBN} prints it this way:
13086 (@value{GDBP}) overlay list
13087 No sections are mapped.
13088 (@value{GDBP}) print foo
13089 $5 = @{int (int)@} 0x100000 <*foo*>
13092 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
13096 (@value{GDBP}) overlay list
13097 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
13098 mapped at 0x1016 - 0x104a
13099 (@value{GDBP}) print foo
13100 $6 = @{int (int)@} 0x1016 <foo>
13103 When overlay debugging is enabled, @value{GDBN} can find the correct
13104 address for functions and variables in an overlay, whether or not the
13105 overlay is mapped. This allows most @value{GDBN} commands, like
13106 @code{break} and @code{disassemble}, to work normally, even on unmapped
13107 code. However, @value{GDBN}'s breakpoint support has some limitations:
13111 @cindex breakpoints in overlays
13112 @cindex overlays, setting breakpoints in
13113 You can set breakpoints in functions in unmapped overlays, as long as
13114 @value{GDBN} can write to the overlay at its load address.
13116 @value{GDBN} can not set hardware or simulator-based breakpoints in
13117 unmapped overlays. However, if you set a breakpoint at the end of your
13118 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
13119 you are using manual overlay management), @value{GDBN} will re-set its
13120 breakpoints properly.
13124 @node Automatic Overlay Debugging
13125 @section Automatic Overlay Debugging
13126 @cindex automatic overlay debugging
13128 @value{GDBN} can automatically track which overlays are mapped and which
13129 are not, given some simple co-operation from the overlay manager in the
13130 inferior. If you enable automatic overlay debugging with the
13131 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
13132 looks in the inferior's memory for certain variables describing the
13133 current state of the overlays.
13135 Here are the variables your overlay manager must define to support
13136 @value{GDBN}'s automatic overlay debugging:
13140 @item @code{_ovly_table}:
13141 This variable must be an array of the following structures:
13146 /* The overlay's mapped address. */
13149 /* The size of the overlay, in bytes. */
13150 unsigned long size;
13152 /* The overlay's load address. */
13155 /* Non-zero if the overlay is currently mapped;
13157 unsigned long mapped;
13161 @item @code{_novlys}:
13162 This variable must be a four-byte signed integer, holding the total
13163 number of elements in @code{_ovly_table}.
13167 To decide whether a particular overlay is mapped or not, @value{GDBN}
13168 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
13169 @code{lma} members equal the VMA and LMA of the overlay's section in the
13170 executable file. When @value{GDBN} finds a matching entry, it consults
13171 the entry's @code{mapped} member to determine whether the overlay is
13174 In addition, your overlay manager may define a function called
13175 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
13176 will silently set a breakpoint there. If the overlay manager then
13177 calls this function whenever it has changed the overlay table, this
13178 will enable @value{GDBN} to accurately keep track of which overlays
13179 are in program memory, and update any breakpoints that may be set
13180 in overlays. This will allow breakpoints to work even if the
13181 overlays are kept in ROM or other non-writable memory while they
13182 are not being executed.
13184 @node Overlay Sample Program
13185 @section Overlay Sample Program
13186 @cindex overlay example program
13188 When linking a program which uses overlays, you must place the overlays
13189 at their load addresses, while relocating them to run at their mapped
13190 addresses. To do this, you must write a linker script (@pxref{Overlay
13191 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
13192 since linker scripts are specific to a particular host system, target
13193 architecture, and target memory layout, this manual cannot provide
13194 portable sample code demonstrating @value{GDBN}'s overlay support.
13196 However, the @value{GDBN} source distribution does contain an overlaid
13197 program, with linker scripts for a few systems, as part of its test
13198 suite. The program consists of the following files from
13199 @file{gdb/testsuite/gdb.base}:
13203 The main program file.
13205 A simple overlay manager, used by @file{overlays.c}.
13210 Overlay modules, loaded and used by @file{overlays.c}.
13213 Linker scripts for linking the test program on the @code{d10v-elf}
13214 and @code{m32r-elf} targets.
13217 You can build the test program using the @code{d10v-elf} GCC
13218 cross-compiler like this:
13221 $ d10v-elf-gcc -g -c overlays.c
13222 $ d10v-elf-gcc -g -c ovlymgr.c
13223 $ d10v-elf-gcc -g -c foo.c
13224 $ d10v-elf-gcc -g -c bar.c
13225 $ d10v-elf-gcc -g -c baz.c
13226 $ d10v-elf-gcc -g -c grbx.c
13227 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
13228 baz.o grbx.o -Wl,-Td10v.ld -o overlays
13231 The build process is identical for any other architecture, except that
13232 you must substitute the appropriate compiler and linker script for the
13233 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
13237 @chapter Using @value{GDBN} with Different Languages
13240 Although programming languages generally have common aspects, they are
13241 rarely expressed in the same manner. For instance, in ANSI C,
13242 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
13243 Modula-2, it is accomplished by @code{p^}. Values can also be
13244 represented (and displayed) differently. Hex numbers in C appear as
13245 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
13247 @cindex working language
13248 Language-specific information is built into @value{GDBN} for some languages,
13249 allowing you to express operations like the above in your program's
13250 native language, and allowing @value{GDBN} to output values in a manner
13251 consistent with the syntax of your program's native language. The
13252 language you use to build expressions is called the @dfn{working
13256 * Setting:: Switching between source languages
13257 * Show:: Displaying the language
13258 * Checks:: Type and range checks
13259 * Supported Languages:: Supported languages
13260 * Unsupported Languages:: Unsupported languages
13264 @section Switching Between Source Languages
13266 There are two ways to control the working language---either have @value{GDBN}
13267 set it automatically, or select it manually yourself. You can use the
13268 @code{set language} command for either purpose. On startup, @value{GDBN}
13269 defaults to setting the language automatically. The working language is
13270 used to determine how expressions you type are interpreted, how values
13273 In addition to the working language, every source file that
13274 @value{GDBN} knows about has its own working language. For some object
13275 file formats, the compiler might indicate which language a particular
13276 source file is in. However, most of the time @value{GDBN} infers the
13277 language from the name of the file. The language of a source file
13278 controls whether C@t{++} names are demangled---this way @code{backtrace} can
13279 show each frame appropriately for its own language. There is no way to
13280 set the language of a source file from within @value{GDBN}, but you can
13281 set the language associated with a filename extension. @xref{Show, ,
13282 Displaying the Language}.
13284 This is most commonly a problem when you use a program, such
13285 as @code{cfront} or @code{f2c}, that generates C but is written in
13286 another language. In that case, make the
13287 program use @code{#line} directives in its C output; that way
13288 @value{GDBN} will know the correct language of the source code of the original
13289 program, and will display that source code, not the generated C code.
13292 * Filenames:: Filename extensions and languages.
13293 * Manually:: Setting the working language manually
13294 * Automatically:: Having @value{GDBN} infer the source language
13298 @subsection List of Filename Extensions and Languages
13300 If a source file name ends in one of the following extensions, then
13301 @value{GDBN} infers that its language is the one indicated.
13319 C@t{++} source file
13325 Objective-C source file
13329 Fortran source file
13332 Modula-2 source file
13336 Assembler source file. This actually behaves almost like C, but
13337 @value{GDBN} does not skip over function prologues when stepping.
13340 In addition, you may set the language associated with a filename
13341 extension. @xref{Show, , Displaying the Language}.
13344 @subsection Setting the Working Language
13346 If you allow @value{GDBN} to set the language automatically,
13347 expressions are interpreted the same way in your debugging session and
13350 @kindex set language
13351 If you wish, you may set the language manually. To do this, issue the
13352 command @samp{set language @var{lang}}, where @var{lang} is the name of
13353 a language, such as
13354 @code{c} or @code{modula-2}.
13355 For a list of the supported languages, type @samp{set language}.
13357 Setting the language manually prevents @value{GDBN} from updating the working
13358 language automatically. This can lead to confusion if you try
13359 to debug a program when the working language is not the same as the
13360 source language, when an expression is acceptable to both
13361 languages---but means different things. For instance, if the current
13362 source file were written in C, and @value{GDBN} was parsing Modula-2, a
13370 might not have the effect you intended. In C, this means to add
13371 @code{b} and @code{c} and place the result in @code{a}. The result
13372 printed would be the value of @code{a}. In Modula-2, this means to compare
13373 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
13375 @node Automatically
13376 @subsection Having @value{GDBN} Infer the Source Language
13378 To have @value{GDBN} set the working language automatically, use
13379 @samp{set language local} or @samp{set language auto}. @value{GDBN}
13380 then infers the working language. That is, when your program stops in a
13381 frame (usually by encountering a breakpoint), @value{GDBN} sets the
13382 working language to the language recorded for the function in that
13383 frame. If the language for a frame is unknown (that is, if the function
13384 or block corresponding to the frame was defined in a source file that
13385 does not have a recognized extension), the current working language is
13386 not changed, and @value{GDBN} issues a warning.
13388 This may not seem necessary for most programs, which are written
13389 entirely in one source language. However, program modules and libraries
13390 written in one source language can be used by a main program written in
13391 a different source language. Using @samp{set language auto} in this
13392 case frees you from having to set the working language manually.
13395 @section Displaying the Language
13397 The following commands help you find out which language is the
13398 working language, and also what language source files were written in.
13401 @item show language
13402 @anchor{show language}
13403 @kindex show language
13404 Display the current working language. This is the
13405 language you can use with commands such as @code{print} to
13406 build and compute expressions that may involve variables in your program.
13409 @kindex info frame@r{, show the source language}
13410 Display the source language for this frame. This language becomes the
13411 working language if you use an identifier from this frame.
13412 @xref{Frame Info, ,Information about a Frame}, to identify the other
13413 information listed here.
13416 @kindex info source@r{, show the source language}
13417 Display the source language of this source file.
13418 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
13419 information listed here.
13422 In unusual circumstances, you may have source files with extensions
13423 not in the standard list. You can then set the extension associated
13424 with a language explicitly:
13427 @item set extension-language @var{ext} @var{language}
13428 @kindex set extension-language
13429 Tell @value{GDBN} that source files with extension @var{ext} are to be
13430 assumed as written in the source language @var{language}.
13432 @item info extensions
13433 @kindex info extensions
13434 List all the filename extensions and the associated languages.
13438 @section Type and Range Checking
13440 Some languages are designed to guard you against making seemingly common
13441 errors through a series of compile- and run-time checks. These include
13442 checking the type of arguments to functions and operators and making
13443 sure mathematical overflows are caught at run time. Checks such as
13444 these help to ensure a program's correctness once it has been compiled
13445 by eliminating type mismatches and providing active checks for range
13446 errors when your program is running.
13448 By default @value{GDBN} checks for these errors according to the
13449 rules of the current source language. Although @value{GDBN} does not check
13450 the statements in your program, it can check expressions entered directly
13451 into @value{GDBN} for evaluation via the @code{print} command, for example.
13454 * Type Checking:: An overview of type checking
13455 * Range Checking:: An overview of range checking
13458 @cindex type checking
13459 @cindex checks, type
13460 @node Type Checking
13461 @subsection An Overview of Type Checking
13463 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
13464 arguments to operators and functions have to be of the correct type,
13465 otherwise an error occurs. These checks prevent type mismatch
13466 errors from ever causing any run-time problems. For example,
13469 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
13471 (@value{GDBP}) print obj.my_method (0)
13474 (@value{GDBP}) print obj.my_method (0x1234)
13475 Cannot resolve method klass::my_method to any overloaded instance
13478 The second example fails because in C@t{++} the integer constant
13479 @samp{0x1234} is not type-compatible with the pointer parameter type.
13481 For the expressions you use in @value{GDBN} commands, you can tell
13482 @value{GDBN} to not enforce strict type checking or
13483 to treat any mismatches as errors and abandon the expression;
13484 When type checking is disabled, @value{GDBN} successfully evaluates
13485 expressions like the second example above.
13487 Even if type checking is off, there may be other reasons
13488 related to type that prevent @value{GDBN} from evaluating an expression.
13489 For instance, @value{GDBN} does not know how to add an @code{int} and
13490 a @code{struct foo}. These particular type errors have nothing to do
13491 with the language in use and usually arise from expressions which make
13492 little sense to evaluate anyway.
13494 @value{GDBN} provides some additional commands for controlling type checking:
13496 @kindex set check type
13497 @kindex show check type
13499 @item set check type on
13500 @itemx set check type off
13501 Set strict type checking on or off. If any type mismatches occur in
13502 evaluating an expression while type checking is on, @value{GDBN} prints a
13503 message and aborts evaluation of the expression.
13505 @item show check type
13506 Show the current setting of type checking and whether @value{GDBN}
13507 is enforcing strict type checking rules.
13510 @cindex range checking
13511 @cindex checks, range
13512 @node Range Checking
13513 @subsection An Overview of Range Checking
13515 In some languages (such as Modula-2), it is an error to exceed the
13516 bounds of a type; this is enforced with run-time checks. Such range
13517 checking is meant to ensure program correctness by making sure
13518 computations do not overflow, or indices on an array element access do
13519 not exceed the bounds of the array.
13521 For expressions you use in @value{GDBN} commands, you can tell
13522 @value{GDBN} to treat range errors in one of three ways: ignore them,
13523 always treat them as errors and abandon the expression, or issue
13524 warnings but evaluate the expression anyway.
13526 A range error can result from numerical overflow, from exceeding an
13527 array index bound, or when you type a constant that is not a member
13528 of any type. Some languages, however, do not treat overflows as an
13529 error. In many implementations of C, mathematical overflow causes the
13530 result to ``wrap around'' to lower values---for example, if @var{m} is
13531 the largest integer value, and @var{s} is the smallest, then
13534 @var{m} + 1 @result{} @var{s}
13537 This, too, is specific to individual languages, and in some cases
13538 specific to individual compilers or machines. @xref{Supported Languages, ,
13539 Supported Languages}, for further details on specific languages.
13541 @value{GDBN} provides some additional commands for controlling the range checker:
13543 @kindex set check range
13544 @kindex show check range
13546 @item set check range auto
13547 Set range checking on or off based on the current working language.
13548 @xref{Supported Languages, ,Supported Languages}, for the default settings for
13551 @item set check range on
13552 @itemx set check range off
13553 Set range checking on or off, overriding the default setting for the
13554 current working language. A warning is issued if the setting does not
13555 match the language default. If a range error occurs and range checking is on,
13556 then a message is printed and evaluation of the expression is aborted.
13558 @item set check range warn
13559 Output messages when the @value{GDBN} range checker detects a range error,
13560 but attempt to evaluate the expression anyway. Evaluating the
13561 expression may still be impossible for other reasons, such as accessing
13562 memory that the process does not own (a typical example from many Unix
13566 Show the current setting of the range checker, and whether or not it is
13567 being set automatically by @value{GDBN}.
13570 @node Supported Languages
13571 @section Supported Languages
13573 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
13574 OpenCL C, Pascal, assembly, Modula-2, and Ada.
13575 @c This is false ...
13576 Some @value{GDBN} features may be used in expressions regardless of the
13577 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
13578 and the @samp{@{type@}addr} construct (@pxref{Expressions,
13579 ,Expressions}) can be used with the constructs of any supported
13582 The following sections detail to what degree each source language is
13583 supported by @value{GDBN}. These sections are not meant to be language
13584 tutorials or references, but serve only as a reference guide to what the
13585 @value{GDBN} expression parser accepts, and what input and output
13586 formats should look like for different languages. There are many good
13587 books written on each of these languages; please look to these for a
13588 language reference or tutorial.
13591 * C:: C and C@t{++}
13594 * Objective-C:: Objective-C
13595 * OpenCL C:: OpenCL C
13596 * Fortran:: Fortran
13598 * Modula-2:: Modula-2
13603 @subsection C and C@t{++}
13605 @cindex C and C@t{++}
13606 @cindex expressions in C or C@t{++}
13608 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
13609 to both languages. Whenever this is the case, we discuss those languages
13613 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
13614 @cindex @sc{gnu} C@t{++}
13615 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
13616 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
13617 effectively, you must compile your C@t{++} programs with a supported
13618 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
13619 compiler (@code{aCC}).
13622 * C Operators:: C and C@t{++} operators
13623 * C Constants:: C and C@t{++} constants
13624 * C Plus Plus Expressions:: C@t{++} expressions
13625 * C Defaults:: Default settings for C and C@t{++}
13626 * C Checks:: C and C@t{++} type and range checks
13627 * Debugging C:: @value{GDBN} and C
13628 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
13629 * Decimal Floating Point:: Numbers in Decimal Floating Point format
13633 @subsubsection C and C@t{++} Operators
13635 @cindex C and C@t{++} operators
13637 Operators must be defined on values of specific types. For instance,
13638 @code{+} is defined on numbers, but not on structures. Operators are
13639 often defined on groups of types.
13641 For the purposes of C and C@t{++}, the following definitions hold:
13646 @emph{Integral types} include @code{int} with any of its storage-class
13647 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
13650 @emph{Floating-point types} include @code{float}, @code{double}, and
13651 @code{long double} (if supported by the target platform).
13654 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
13657 @emph{Scalar types} include all of the above.
13662 The following operators are supported. They are listed here
13663 in order of increasing precedence:
13667 The comma or sequencing operator. Expressions in a comma-separated list
13668 are evaluated from left to right, with the result of the entire
13669 expression being the last expression evaluated.
13672 Assignment. The value of an assignment expression is the value
13673 assigned. Defined on scalar types.
13676 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
13677 and translated to @w{@code{@var{a} = @var{a op b}}}.
13678 @w{@code{@var{op}=}} and @code{=} have the same precedence.
13679 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
13680 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
13683 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
13684 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
13688 Logical @sc{or}. Defined on integral types.
13691 Logical @sc{and}. Defined on integral types.
13694 Bitwise @sc{or}. Defined on integral types.
13697 Bitwise exclusive-@sc{or}. Defined on integral types.
13700 Bitwise @sc{and}. Defined on integral types.
13703 Equality and inequality. Defined on scalar types. The value of these
13704 expressions is 0 for false and non-zero for true.
13706 @item <@r{, }>@r{, }<=@r{, }>=
13707 Less than, greater than, less than or equal, greater than or equal.
13708 Defined on scalar types. The value of these expressions is 0 for false
13709 and non-zero for true.
13712 left shift, and right shift. Defined on integral types.
13715 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13718 Addition and subtraction. Defined on integral types, floating-point types and
13721 @item *@r{, }/@r{, }%
13722 Multiplication, division, and modulus. Multiplication and division are
13723 defined on integral and floating-point types. Modulus is defined on
13727 Increment and decrement. When appearing before a variable, the
13728 operation is performed before the variable is used in an expression;
13729 when appearing after it, the variable's value is used before the
13730 operation takes place.
13733 Pointer dereferencing. Defined on pointer types. Same precedence as
13737 Address operator. Defined on variables. Same precedence as @code{++}.
13739 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
13740 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
13741 to examine the address
13742 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
13746 Negative. Defined on integral and floating-point types. Same
13747 precedence as @code{++}.
13750 Logical negation. Defined on integral types. Same precedence as
13754 Bitwise complement operator. Defined on integral types. Same precedence as
13759 Structure member, and pointer-to-structure member. For convenience,
13760 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
13761 pointer based on the stored type information.
13762 Defined on @code{struct} and @code{union} data.
13765 Dereferences of pointers to members.
13768 Array indexing. @code{@var{a}[@var{i}]} is defined as
13769 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
13772 Function parameter list. Same precedence as @code{->}.
13775 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
13776 and @code{class} types.
13779 Doubled colons also represent the @value{GDBN} scope operator
13780 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
13784 If an operator is redefined in the user code, @value{GDBN} usually
13785 attempts to invoke the redefined version instead of using the operator's
13786 predefined meaning.
13789 @subsubsection C and C@t{++} Constants
13791 @cindex C and C@t{++} constants
13793 @value{GDBN} allows you to express the constants of C and C@t{++} in the
13798 Integer constants are a sequence of digits. Octal constants are
13799 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
13800 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
13801 @samp{l}, specifying that the constant should be treated as a
13805 Floating point constants are a sequence of digits, followed by a decimal
13806 point, followed by a sequence of digits, and optionally followed by an
13807 exponent. An exponent is of the form:
13808 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
13809 sequence of digits. The @samp{+} is optional for positive exponents.
13810 A floating-point constant may also end with a letter @samp{f} or
13811 @samp{F}, specifying that the constant should be treated as being of
13812 the @code{float} (as opposed to the default @code{double}) type; or with
13813 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
13817 Enumerated constants consist of enumerated identifiers, or their
13818 integral equivalents.
13821 Character constants are a single character surrounded by single quotes
13822 (@code{'}), or a number---the ordinal value of the corresponding character
13823 (usually its @sc{ascii} value). Within quotes, the single character may
13824 be represented by a letter or by @dfn{escape sequences}, which are of
13825 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
13826 of the character's ordinal value; or of the form @samp{\@var{x}}, where
13827 @samp{@var{x}} is a predefined special character---for example,
13828 @samp{\n} for newline.
13830 Wide character constants can be written by prefixing a character
13831 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
13832 form of @samp{x}. The target wide character set is used when
13833 computing the value of this constant (@pxref{Character Sets}).
13836 String constants are a sequence of character constants surrounded by
13837 double quotes (@code{"}). Any valid character constant (as described
13838 above) may appear. Double quotes within the string must be preceded by
13839 a backslash, so for instance @samp{"a\"b'c"} is a string of five
13842 Wide string constants can be written by prefixing a string constant
13843 with @samp{L}, as in C. The target wide character set is used when
13844 computing the value of this constant (@pxref{Character Sets}).
13847 Pointer constants are an integral value. You can also write pointers
13848 to constants using the C operator @samp{&}.
13851 Array constants are comma-separated lists surrounded by braces @samp{@{}
13852 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
13853 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
13854 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
13857 @node C Plus Plus Expressions
13858 @subsubsection C@t{++} Expressions
13860 @cindex expressions in C@t{++}
13861 @value{GDBN} expression handling can interpret most C@t{++} expressions.
13863 @cindex debugging C@t{++} programs
13864 @cindex C@t{++} compilers
13865 @cindex debug formats and C@t{++}
13866 @cindex @value{NGCC} and C@t{++}
13868 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
13869 the proper compiler and the proper debug format. Currently,
13870 @value{GDBN} works best when debugging C@t{++} code that is compiled
13871 with the most recent version of @value{NGCC} possible. The DWARF
13872 debugging format is preferred; @value{NGCC} defaults to this on most
13873 popular platforms. Other compilers and/or debug formats are likely to
13874 work badly or not at all when using @value{GDBN} to debug C@t{++}
13875 code. @xref{Compilation}.
13880 @cindex member functions
13882 Member function calls are allowed; you can use expressions like
13885 count = aml->GetOriginal(x, y)
13888 @vindex this@r{, inside C@t{++} member functions}
13889 @cindex namespace in C@t{++}
13891 While a member function is active (in the selected stack frame), your
13892 expressions have the same namespace available as the member function;
13893 that is, @value{GDBN} allows implicit references to the class instance
13894 pointer @code{this} following the same rules as C@t{++}. @code{using}
13895 declarations in the current scope are also respected by @value{GDBN}.
13897 @cindex call overloaded functions
13898 @cindex overloaded functions, calling
13899 @cindex type conversions in C@t{++}
13901 You can call overloaded functions; @value{GDBN} resolves the function
13902 call to the right definition, with some restrictions. @value{GDBN} does not
13903 perform overload resolution involving user-defined type conversions,
13904 calls to constructors, or instantiations of templates that do not exist
13905 in the program. It also cannot handle ellipsis argument lists or
13908 It does perform integral conversions and promotions, floating-point
13909 promotions, arithmetic conversions, pointer conversions, conversions of
13910 class objects to base classes, and standard conversions such as those of
13911 functions or arrays to pointers; it requires an exact match on the
13912 number of function arguments.
13914 Overload resolution is always performed, unless you have specified
13915 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
13916 ,@value{GDBN} Features for C@t{++}}.
13918 You must specify @code{set overload-resolution off} in order to use an
13919 explicit function signature to call an overloaded function, as in
13921 p 'foo(char,int)'('x', 13)
13924 The @value{GDBN} command-completion facility can simplify this;
13925 see @ref{Completion, ,Command Completion}.
13927 @cindex reference declarations
13929 @value{GDBN} understands variables declared as C@t{++} references; you can use
13930 them in expressions just as you do in C@t{++} source---they are automatically
13933 In the parameter list shown when @value{GDBN} displays a frame, the values of
13934 reference variables are not displayed (unlike other variables); this
13935 avoids clutter, since references are often used for large structures.
13936 The @emph{address} of a reference variable is always shown, unless
13937 you have specified @samp{set print address off}.
13940 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
13941 expressions can use it just as expressions in your program do. Since
13942 one scope may be defined in another, you can use @code{::} repeatedly if
13943 necessary, for example in an expression like
13944 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
13945 resolving name scope by reference to source files, in both C and C@t{++}
13946 debugging (@pxref{Variables, ,Program Variables}).
13949 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
13954 @subsubsection C and C@t{++} Defaults
13956 @cindex C and C@t{++} defaults
13958 If you allow @value{GDBN} to set range checking automatically, it
13959 defaults to @code{off} whenever the working language changes to
13960 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
13961 selects the working language.
13963 If you allow @value{GDBN} to set the language automatically, it
13964 recognizes source files whose names end with @file{.c}, @file{.C}, or
13965 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
13966 these files, it sets the working language to C or C@t{++}.
13967 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
13968 for further details.
13971 @subsubsection C and C@t{++} Type and Range Checks
13973 @cindex C and C@t{++} checks
13975 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
13976 checking is used. However, if you turn type checking off, @value{GDBN}
13977 will allow certain non-standard conversions, such as promoting integer
13978 constants to pointers.
13980 Range checking, if turned on, is done on mathematical operations. Array
13981 indices are not checked, since they are often used to index a pointer
13982 that is not itself an array.
13985 @subsubsection @value{GDBN} and C
13987 The @code{set print union} and @code{show print union} commands apply to
13988 the @code{union} type. When set to @samp{on}, any @code{union} that is
13989 inside a @code{struct} or @code{class} is also printed. Otherwise, it
13990 appears as @samp{@{...@}}.
13992 The @code{@@} operator aids in the debugging of dynamic arrays, formed
13993 with pointers and a memory allocation function. @xref{Expressions,
13996 @node Debugging C Plus Plus
13997 @subsubsection @value{GDBN} Features for C@t{++}
13999 @cindex commands for C@t{++}
14001 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
14002 designed specifically for use with C@t{++}. Here is a summary:
14005 @cindex break in overloaded functions
14006 @item @r{breakpoint menus}
14007 When you want a breakpoint in a function whose name is overloaded,
14008 @value{GDBN} has the capability to display a menu of possible breakpoint
14009 locations to help you specify which function definition you want.
14010 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
14012 @cindex overloading in C@t{++}
14013 @item rbreak @var{regex}
14014 Setting breakpoints using regular expressions is helpful for setting
14015 breakpoints on overloaded functions that are not members of any special
14017 @xref{Set Breaks, ,Setting Breakpoints}.
14019 @cindex C@t{++} exception handling
14021 @itemx catch rethrow
14023 Debug C@t{++} exception handling using these commands. @xref{Set
14024 Catchpoints, , Setting Catchpoints}.
14026 @cindex inheritance
14027 @item ptype @var{typename}
14028 Print inheritance relationships as well as other information for type
14030 @xref{Symbols, ,Examining the Symbol Table}.
14032 @item info vtbl @var{expression}.
14033 The @code{info vtbl} command can be used to display the virtual
14034 method tables of the object computed by @var{expression}. This shows
14035 one entry per virtual table; there may be multiple virtual tables when
14036 multiple inheritance is in use.
14038 @cindex C@t{++} symbol display
14039 @item set print demangle
14040 @itemx show print demangle
14041 @itemx set print asm-demangle
14042 @itemx show print asm-demangle
14043 Control whether C@t{++} symbols display in their source form, both when
14044 displaying code as C@t{++} source and when displaying disassemblies.
14045 @xref{Print Settings, ,Print Settings}.
14047 @item set print object
14048 @itemx show print object
14049 Choose whether to print derived (actual) or declared types of objects.
14050 @xref{Print Settings, ,Print Settings}.
14052 @item set print vtbl
14053 @itemx show print vtbl
14054 Control the format for printing virtual function tables.
14055 @xref{Print Settings, ,Print Settings}.
14056 (The @code{vtbl} commands do not work on programs compiled with the HP
14057 ANSI C@t{++} compiler (@code{aCC}).)
14059 @kindex set overload-resolution
14060 @cindex overloaded functions, overload resolution
14061 @item set overload-resolution on
14062 Enable overload resolution for C@t{++} expression evaluation. The default
14063 is on. For overloaded functions, @value{GDBN} evaluates the arguments
14064 and searches for a function whose signature matches the argument types,
14065 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
14066 Expressions, ,C@t{++} Expressions}, for details).
14067 If it cannot find a match, it emits a message.
14069 @item set overload-resolution off
14070 Disable overload resolution for C@t{++} expression evaluation. For
14071 overloaded functions that are not class member functions, @value{GDBN}
14072 chooses the first function of the specified name that it finds in the
14073 symbol table, whether or not its arguments are of the correct type. For
14074 overloaded functions that are class member functions, @value{GDBN}
14075 searches for a function whose signature @emph{exactly} matches the
14078 @kindex show overload-resolution
14079 @item show overload-resolution
14080 Show the current setting of overload resolution.
14082 @item @r{Overloaded symbol names}
14083 You can specify a particular definition of an overloaded symbol, using
14084 the same notation that is used to declare such symbols in C@t{++}: type
14085 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
14086 also use the @value{GDBN} command-line word completion facilities to list the
14087 available choices, or to finish the type list for you.
14088 @xref{Completion,, Command Completion}, for details on how to do this.
14091 @node Decimal Floating Point
14092 @subsubsection Decimal Floating Point format
14093 @cindex decimal floating point format
14095 @value{GDBN} can examine, set and perform computations with numbers in
14096 decimal floating point format, which in the C language correspond to the
14097 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
14098 specified by the extension to support decimal floating-point arithmetic.
14100 There are two encodings in use, depending on the architecture: BID (Binary
14101 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
14102 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
14105 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
14106 to manipulate decimal floating point numbers, it is not possible to convert
14107 (using a cast, for example) integers wider than 32-bit to decimal float.
14109 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
14110 point computations, error checking in decimal float operations ignores
14111 underflow, overflow and divide by zero exceptions.
14113 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
14114 to inspect @code{_Decimal128} values stored in floating point registers.
14115 See @ref{PowerPC,,PowerPC} for more details.
14121 @value{GDBN} can be used to debug programs written in D and compiled with
14122 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
14123 specific feature --- dynamic arrays.
14128 @cindex Go (programming language)
14129 @value{GDBN} can be used to debug programs written in Go and compiled with
14130 @file{gccgo} or @file{6g} compilers.
14132 Here is a summary of the Go-specific features and restrictions:
14135 @cindex current Go package
14136 @item The current Go package
14137 The name of the current package does not need to be specified when
14138 specifying global variables and functions.
14140 For example, given the program:
14144 var myglob = "Shall we?"
14150 When stopped inside @code{main} either of these work:
14154 (gdb) p main.myglob
14157 @cindex builtin Go types
14158 @item Builtin Go types
14159 The @code{string} type is recognized by @value{GDBN} and is printed
14162 @cindex builtin Go functions
14163 @item Builtin Go functions
14164 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
14165 function and handles it internally.
14167 @cindex restrictions on Go expressions
14168 @item Restrictions on Go expressions
14169 All Go operators are supported except @code{&^}.
14170 The Go @code{_} ``blank identifier'' is not supported.
14171 Automatic dereferencing of pointers is not supported.
14175 @subsection Objective-C
14177 @cindex Objective-C
14178 This section provides information about some commands and command
14179 options that are useful for debugging Objective-C code. See also
14180 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
14181 few more commands specific to Objective-C support.
14184 * Method Names in Commands::
14185 * The Print Command with Objective-C::
14188 @node Method Names in Commands
14189 @subsubsection Method Names in Commands
14191 The following commands have been extended to accept Objective-C method
14192 names as line specifications:
14194 @kindex clear@r{, and Objective-C}
14195 @kindex break@r{, and Objective-C}
14196 @kindex info line@r{, and Objective-C}
14197 @kindex jump@r{, and Objective-C}
14198 @kindex list@r{, and Objective-C}
14202 @item @code{info line}
14207 A fully qualified Objective-C method name is specified as
14210 -[@var{Class} @var{methodName}]
14213 where the minus sign is used to indicate an instance method and a
14214 plus sign (not shown) is used to indicate a class method. The class
14215 name @var{Class} and method name @var{methodName} are enclosed in
14216 brackets, similar to the way messages are specified in Objective-C
14217 source code. For example, to set a breakpoint at the @code{create}
14218 instance method of class @code{Fruit} in the program currently being
14222 break -[Fruit create]
14225 To list ten program lines around the @code{initialize} class method,
14229 list +[NSText initialize]
14232 In the current version of @value{GDBN}, the plus or minus sign is
14233 required. In future versions of @value{GDBN}, the plus or minus
14234 sign will be optional, but you can use it to narrow the search. It
14235 is also possible to specify just a method name:
14241 You must specify the complete method name, including any colons. If
14242 your program's source files contain more than one @code{create} method,
14243 you'll be presented with a numbered list of classes that implement that
14244 method. Indicate your choice by number, or type @samp{0} to exit if
14247 As another example, to clear a breakpoint established at the
14248 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
14251 clear -[NSWindow makeKeyAndOrderFront:]
14254 @node The Print Command with Objective-C
14255 @subsubsection The Print Command With Objective-C
14256 @cindex Objective-C, print objects
14257 @kindex print-object
14258 @kindex po @r{(@code{print-object})}
14260 The print command has also been extended to accept methods. For example:
14263 print -[@var{object} hash]
14266 @cindex print an Objective-C object description
14267 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
14269 will tell @value{GDBN} to send the @code{hash} message to @var{object}
14270 and print the result. Also, an additional command has been added,
14271 @code{print-object} or @code{po} for short, which is meant to print
14272 the description of an object. However, this command may only work
14273 with certain Objective-C libraries that have a particular hook
14274 function, @code{_NSPrintForDebugger}, defined.
14277 @subsection OpenCL C
14280 This section provides information about @value{GDBN}s OpenCL C support.
14283 * OpenCL C Datatypes::
14284 * OpenCL C Expressions::
14285 * OpenCL C Operators::
14288 @node OpenCL C Datatypes
14289 @subsubsection OpenCL C Datatypes
14291 @cindex OpenCL C Datatypes
14292 @value{GDBN} supports the builtin scalar and vector datatypes specified
14293 by OpenCL 1.1. In addition the half- and double-precision floating point
14294 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
14295 extensions are also known to @value{GDBN}.
14297 @node OpenCL C Expressions
14298 @subsubsection OpenCL C Expressions
14300 @cindex OpenCL C Expressions
14301 @value{GDBN} supports accesses to vector components including the access as
14302 lvalue where possible. Since OpenCL C is based on C99 most C expressions
14303 supported by @value{GDBN} can be used as well.
14305 @node OpenCL C Operators
14306 @subsubsection OpenCL C Operators
14308 @cindex OpenCL C Operators
14309 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
14313 @subsection Fortran
14314 @cindex Fortran-specific support in @value{GDBN}
14316 @value{GDBN} can be used to debug programs written in Fortran, but it
14317 currently supports only the features of Fortran 77 language.
14319 @cindex trailing underscore, in Fortran symbols
14320 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
14321 among them) append an underscore to the names of variables and
14322 functions. When you debug programs compiled by those compilers, you
14323 will need to refer to variables and functions with a trailing
14327 * Fortran Operators:: Fortran operators and expressions
14328 * Fortran Defaults:: Default settings for Fortran
14329 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
14332 @node Fortran Operators
14333 @subsubsection Fortran Operators and Expressions
14335 @cindex Fortran operators and expressions
14337 Operators must be defined on values of specific types. For instance,
14338 @code{+} is defined on numbers, but not on characters or other non-
14339 arithmetic types. Operators are often defined on groups of types.
14343 The exponentiation operator. It raises the first operand to the power
14347 The range operator. Normally used in the form of array(low:high) to
14348 represent a section of array.
14351 The access component operator. Normally used to access elements in derived
14352 types. Also suitable for unions. As unions aren't part of regular Fortran,
14353 this can only happen when accessing a register that uses a gdbarch-defined
14357 @node Fortran Defaults
14358 @subsubsection Fortran Defaults
14360 @cindex Fortran Defaults
14362 Fortran symbols are usually case-insensitive, so @value{GDBN} by
14363 default uses case-insensitive matches for Fortran symbols. You can
14364 change that with the @samp{set case-insensitive} command, see
14365 @ref{Symbols}, for the details.
14367 @node Special Fortran Commands
14368 @subsubsection Special Fortran Commands
14370 @cindex Special Fortran commands
14372 @value{GDBN} has some commands to support Fortran-specific features,
14373 such as displaying common blocks.
14376 @cindex @code{COMMON} blocks, Fortran
14377 @kindex info common
14378 @item info common @r{[}@var{common-name}@r{]}
14379 This command prints the values contained in the Fortran @code{COMMON}
14380 block whose name is @var{common-name}. With no argument, the names of
14381 all @code{COMMON} blocks visible at the current program location are
14388 @cindex Pascal support in @value{GDBN}, limitations
14389 Debugging Pascal programs which use sets, subranges, file variables, or
14390 nested functions does not currently work. @value{GDBN} does not support
14391 entering expressions, printing values, or similar features using Pascal
14394 The Pascal-specific command @code{set print pascal_static-members}
14395 controls whether static members of Pascal objects are displayed.
14396 @xref{Print Settings, pascal_static-members}.
14399 @subsection Modula-2
14401 @cindex Modula-2, @value{GDBN} support
14403 The extensions made to @value{GDBN} to support Modula-2 only support
14404 output from the @sc{gnu} Modula-2 compiler (which is currently being
14405 developed). Other Modula-2 compilers are not currently supported, and
14406 attempting to debug executables produced by them is most likely
14407 to give an error as @value{GDBN} reads in the executable's symbol
14410 @cindex expressions in Modula-2
14412 * M2 Operators:: Built-in operators
14413 * Built-In Func/Proc:: Built-in functions and procedures
14414 * M2 Constants:: Modula-2 constants
14415 * M2 Types:: Modula-2 types
14416 * M2 Defaults:: Default settings for Modula-2
14417 * Deviations:: Deviations from standard Modula-2
14418 * M2 Checks:: Modula-2 type and range checks
14419 * M2 Scope:: The scope operators @code{::} and @code{.}
14420 * GDB/M2:: @value{GDBN} and Modula-2
14424 @subsubsection Operators
14425 @cindex Modula-2 operators
14427 Operators must be defined on values of specific types. For instance,
14428 @code{+} is defined on numbers, but not on structures. Operators are
14429 often defined on groups of types. For the purposes of Modula-2, the
14430 following definitions hold:
14435 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
14439 @emph{Character types} consist of @code{CHAR} and its subranges.
14442 @emph{Floating-point types} consist of @code{REAL}.
14445 @emph{Pointer types} consist of anything declared as @code{POINTER TO
14449 @emph{Scalar types} consist of all of the above.
14452 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
14455 @emph{Boolean types} consist of @code{BOOLEAN}.
14459 The following operators are supported, and appear in order of
14460 increasing precedence:
14464 Function argument or array index separator.
14467 Assignment. The value of @var{var} @code{:=} @var{value} is
14471 Less than, greater than on integral, floating-point, or enumerated
14475 Less than or equal to, greater than or equal to
14476 on integral, floating-point and enumerated types, or set inclusion on
14477 set types. Same precedence as @code{<}.
14479 @item =@r{, }<>@r{, }#
14480 Equality and two ways of expressing inequality, valid on scalar types.
14481 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
14482 available for inequality, since @code{#} conflicts with the script
14486 Set membership. Defined on set types and the types of their members.
14487 Same precedence as @code{<}.
14490 Boolean disjunction. Defined on boolean types.
14493 Boolean conjunction. Defined on boolean types.
14496 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14499 Addition and subtraction on integral and floating-point types, or union
14500 and difference on set types.
14503 Multiplication on integral and floating-point types, or set intersection
14507 Division on floating-point types, or symmetric set difference on set
14508 types. Same precedence as @code{*}.
14511 Integer division and remainder. Defined on integral types. Same
14512 precedence as @code{*}.
14515 Negative. Defined on @code{INTEGER} and @code{REAL} data.
14518 Pointer dereferencing. Defined on pointer types.
14521 Boolean negation. Defined on boolean types. Same precedence as
14525 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
14526 precedence as @code{^}.
14529 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
14532 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
14536 @value{GDBN} and Modula-2 scope operators.
14540 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
14541 treats the use of the operator @code{IN}, or the use of operators
14542 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
14543 @code{<=}, and @code{>=} on sets as an error.
14547 @node Built-In Func/Proc
14548 @subsubsection Built-in Functions and Procedures
14549 @cindex Modula-2 built-ins
14551 Modula-2 also makes available several built-in procedures and functions.
14552 In describing these, the following metavariables are used:
14557 represents an @code{ARRAY} variable.
14560 represents a @code{CHAR} constant or variable.
14563 represents a variable or constant of integral type.
14566 represents an identifier that belongs to a set. Generally used in the
14567 same function with the metavariable @var{s}. The type of @var{s} should
14568 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
14571 represents a variable or constant of integral or floating-point type.
14574 represents a variable or constant of floating-point type.
14580 represents a variable.
14583 represents a variable or constant of one of many types. See the
14584 explanation of the function for details.
14587 All Modula-2 built-in procedures also return a result, described below.
14591 Returns the absolute value of @var{n}.
14594 If @var{c} is a lower case letter, it returns its upper case
14595 equivalent, otherwise it returns its argument.
14598 Returns the character whose ordinal value is @var{i}.
14601 Decrements the value in the variable @var{v} by one. Returns the new value.
14603 @item DEC(@var{v},@var{i})
14604 Decrements the value in the variable @var{v} by @var{i}. Returns the
14607 @item EXCL(@var{m},@var{s})
14608 Removes the element @var{m} from the set @var{s}. Returns the new
14611 @item FLOAT(@var{i})
14612 Returns the floating point equivalent of the integer @var{i}.
14614 @item HIGH(@var{a})
14615 Returns the index of the last member of @var{a}.
14618 Increments the value in the variable @var{v} by one. Returns the new value.
14620 @item INC(@var{v},@var{i})
14621 Increments the value in the variable @var{v} by @var{i}. Returns the
14624 @item INCL(@var{m},@var{s})
14625 Adds the element @var{m} to the set @var{s} if it is not already
14626 there. Returns the new set.
14629 Returns the maximum value of the type @var{t}.
14632 Returns the minimum value of the type @var{t}.
14635 Returns boolean TRUE if @var{i} is an odd number.
14638 Returns the ordinal value of its argument. For example, the ordinal
14639 value of a character is its @sc{ascii} value (on machines supporting the
14640 @sc{ascii} character set). @var{x} must be of an ordered type, which include
14641 integral, character and enumerated types.
14643 @item SIZE(@var{x})
14644 Returns the size of its argument. @var{x} can be a variable or a type.
14646 @item TRUNC(@var{r})
14647 Returns the integral part of @var{r}.
14649 @item TSIZE(@var{x})
14650 Returns the size of its argument. @var{x} can be a variable or a type.
14652 @item VAL(@var{t},@var{i})
14653 Returns the member of the type @var{t} whose ordinal value is @var{i}.
14657 @emph{Warning:} Sets and their operations are not yet supported, so
14658 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
14662 @cindex Modula-2 constants
14664 @subsubsection Constants
14666 @value{GDBN} allows you to express the constants of Modula-2 in the following
14672 Integer constants are simply a sequence of digits. When used in an
14673 expression, a constant is interpreted to be type-compatible with the
14674 rest of the expression. Hexadecimal integers are specified by a
14675 trailing @samp{H}, and octal integers by a trailing @samp{B}.
14678 Floating point constants appear as a sequence of digits, followed by a
14679 decimal point and another sequence of digits. An optional exponent can
14680 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
14681 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
14682 digits of the floating point constant must be valid decimal (base 10)
14686 Character constants consist of a single character enclosed by a pair of
14687 like quotes, either single (@code{'}) or double (@code{"}). They may
14688 also be expressed by their ordinal value (their @sc{ascii} value, usually)
14689 followed by a @samp{C}.
14692 String constants consist of a sequence of characters enclosed by a
14693 pair of like quotes, either single (@code{'}) or double (@code{"}).
14694 Escape sequences in the style of C are also allowed. @xref{C
14695 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
14699 Enumerated constants consist of an enumerated identifier.
14702 Boolean constants consist of the identifiers @code{TRUE} and
14706 Pointer constants consist of integral values only.
14709 Set constants are not yet supported.
14713 @subsubsection Modula-2 Types
14714 @cindex Modula-2 types
14716 Currently @value{GDBN} can print the following data types in Modula-2
14717 syntax: array types, record types, set types, pointer types, procedure
14718 types, enumerated types, subrange types and base types. You can also
14719 print the contents of variables declared using these type.
14720 This section gives a number of simple source code examples together with
14721 sample @value{GDBN} sessions.
14723 The first example contains the following section of code:
14732 and you can request @value{GDBN} to interrogate the type and value of
14733 @code{r} and @code{s}.
14736 (@value{GDBP}) print s
14738 (@value{GDBP}) ptype s
14740 (@value{GDBP}) print r
14742 (@value{GDBP}) ptype r
14747 Likewise if your source code declares @code{s} as:
14751 s: SET ['A'..'Z'] ;
14755 then you may query the type of @code{s} by:
14758 (@value{GDBP}) ptype s
14759 type = SET ['A'..'Z']
14763 Note that at present you cannot interactively manipulate set
14764 expressions using the debugger.
14766 The following example shows how you might declare an array in Modula-2
14767 and how you can interact with @value{GDBN} to print its type and contents:
14771 s: ARRAY [-10..10] OF CHAR ;
14775 (@value{GDBP}) ptype s
14776 ARRAY [-10..10] OF CHAR
14779 Note that the array handling is not yet complete and although the type
14780 is printed correctly, expression handling still assumes that all
14781 arrays have a lower bound of zero and not @code{-10} as in the example
14784 Here are some more type related Modula-2 examples:
14788 colour = (blue, red, yellow, green) ;
14789 t = [blue..yellow] ;
14797 The @value{GDBN} interaction shows how you can query the data type
14798 and value of a variable.
14801 (@value{GDBP}) print s
14803 (@value{GDBP}) ptype t
14804 type = [blue..yellow]
14808 In this example a Modula-2 array is declared and its contents
14809 displayed. Observe that the contents are written in the same way as
14810 their @code{C} counterparts.
14814 s: ARRAY [1..5] OF CARDINAL ;
14820 (@value{GDBP}) print s
14821 $1 = @{1, 0, 0, 0, 0@}
14822 (@value{GDBP}) ptype s
14823 type = ARRAY [1..5] OF CARDINAL
14826 The Modula-2 language interface to @value{GDBN} also understands
14827 pointer types as shown in this example:
14831 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
14838 and you can request that @value{GDBN} describes the type of @code{s}.
14841 (@value{GDBP}) ptype s
14842 type = POINTER TO ARRAY [1..5] OF CARDINAL
14845 @value{GDBN} handles compound types as we can see in this example.
14846 Here we combine array types, record types, pointer types and subrange
14857 myarray = ARRAY myrange OF CARDINAL ;
14858 myrange = [-2..2] ;
14860 s: POINTER TO ARRAY myrange OF foo ;
14864 and you can ask @value{GDBN} to describe the type of @code{s} as shown
14868 (@value{GDBP}) ptype s
14869 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
14872 f3 : ARRAY [-2..2] OF CARDINAL;
14877 @subsubsection Modula-2 Defaults
14878 @cindex Modula-2 defaults
14880 If type and range checking are set automatically by @value{GDBN}, they
14881 both default to @code{on} whenever the working language changes to
14882 Modula-2. This happens regardless of whether you or @value{GDBN}
14883 selected the working language.
14885 If you allow @value{GDBN} to set the language automatically, then entering
14886 code compiled from a file whose name ends with @file{.mod} sets the
14887 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
14888 Infer the Source Language}, for further details.
14891 @subsubsection Deviations from Standard Modula-2
14892 @cindex Modula-2, deviations from
14894 A few changes have been made to make Modula-2 programs easier to debug.
14895 This is done primarily via loosening its type strictness:
14899 Unlike in standard Modula-2, pointer constants can be formed by
14900 integers. This allows you to modify pointer variables during
14901 debugging. (In standard Modula-2, the actual address contained in a
14902 pointer variable is hidden from you; it can only be modified
14903 through direct assignment to another pointer variable or expression that
14904 returned a pointer.)
14907 C escape sequences can be used in strings and characters to represent
14908 non-printable characters. @value{GDBN} prints out strings with these
14909 escape sequences embedded. Single non-printable characters are
14910 printed using the @samp{CHR(@var{nnn})} format.
14913 The assignment operator (@code{:=}) returns the value of its right-hand
14917 All built-in procedures both modify @emph{and} return their argument.
14921 @subsubsection Modula-2 Type and Range Checks
14922 @cindex Modula-2 checks
14925 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
14928 @c FIXME remove warning when type/range checks added
14930 @value{GDBN} considers two Modula-2 variables type equivalent if:
14934 They are of types that have been declared equivalent via a @code{TYPE
14935 @var{t1} = @var{t2}} statement
14938 They have been declared on the same line. (Note: This is true of the
14939 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
14942 As long as type checking is enabled, any attempt to combine variables
14943 whose types are not equivalent is an error.
14945 Range checking is done on all mathematical operations, assignment, array
14946 index bounds, and all built-in functions and procedures.
14949 @subsubsection The Scope Operators @code{::} and @code{.}
14951 @cindex @code{.}, Modula-2 scope operator
14952 @cindex colon, doubled as scope operator
14954 @vindex colon-colon@r{, in Modula-2}
14955 @c Info cannot handle :: but TeX can.
14958 @vindex ::@r{, in Modula-2}
14961 There are a few subtle differences between the Modula-2 scope operator
14962 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
14967 @var{module} . @var{id}
14968 @var{scope} :: @var{id}
14972 where @var{scope} is the name of a module or a procedure,
14973 @var{module} the name of a module, and @var{id} is any declared
14974 identifier within your program, except another module.
14976 Using the @code{::} operator makes @value{GDBN} search the scope
14977 specified by @var{scope} for the identifier @var{id}. If it is not
14978 found in the specified scope, then @value{GDBN} searches all scopes
14979 enclosing the one specified by @var{scope}.
14981 Using the @code{.} operator makes @value{GDBN} search the current scope for
14982 the identifier specified by @var{id} that was imported from the
14983 definition module specified by @var{module}. With this operator, it is
14984 an error if the identifier @var{id} was not imported from definition
14985 module @var{module}, or if @var{id} is not an identifier in
14989 @subsubsection @value{GDBN} and Modula-2
14991 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
14992 Five subcommands of @code{set print} and @code{show print} apply
14993 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
14994 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
14995 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
14996 analogue in Modula-2.
14998 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
14999 with any language, is not useful with Modula-2. Its
15000 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
15001 created in Modula-2 as they can in C or C@t{++}. However, because an
15002 address can be specified by an integral constant, the construct
15003 @samp{@{@var{type}@}@var{adrexp}} is still useful.
15005 @cindex @code{#} in Modula-2
15006 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
15007 interpreted as the beginning of a comment. Use @code{<>} instead.
15013 The extensions made to @value{GDBN} for Ada only support
15014 output from the @sc{gnu} Ada (GNAT) compiler.
15015 Other Ada compilers are not currently supported, and
15016 attempting to debug executables produced by them is most likely
15020 @cindex expressions in Ada
15022 * Ada Mode Intro:: General remarks on the Ada syntax
15023 and semantics supported by Ada mode
15025 * Omissions from Ada:: Restrictions on the Ada expression syntax.
15026 * Additions to Ada:: Extensions of the Ada expression syntax.
15027 * Stopping Before Main Program:: Debugging the program during elaboration.
15028 * Ada Exceptions:: Ada Exceptions
15029 * Ada Tasks:: Listing and setting breakpoints in tasks.
15030 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
15031 * Ravenscar Profile:: Tasking Support when using the Ravenscar
15033 * Ada Glitches:: Known peculiarities of Ada mode.
15036 @node Ada Mode Intro
15037 @subsubsection Introduction
15038 @cindex Ada mode, general
15040 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
15041 syntax, with some extensions.
15042 The philosophy behind the design of this subset is
15046 That @value{GDBN} should provide basic literals and access to operations for
15047 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
15048 leaving more sophisticated computations to subprograms written into the
15049 program (which therefore may be called from @value{GDBN}).
15052 That type safety and strict adherence to Ada language restrictions
15053 are not particularly important to the @value{GDBN} user.
15056 That brevity is important to the @value{GDBN} user.
15059 Thus, for brevity, the debugger acts as if all names declared in
15060 user-written packages are directly visible, even if they are not visible
15061 according to Ada rules, thus making it unnecessary to fully qualify most
15062 names with their packages, regardless of context. Where this causes
15063 ambiguity, @value{GDBN} asks the user's intent.
15065 The debugger will start in Ada mode if it detects an Ada main program.
15066 As for other languages, it will enter Ada mode when stopped in a program that
15067 was translated from an Ada source file.
15069 While in Ada mode, you may use `@t{--}' for comments. This is useful
15070 mostly for documenting command files. The standard @value{GDBN} comment
15071 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
15072 middle (to allow based literals).
15074 The debugger supports limited overloading. Given a subprogram call in which
15075 the function symbol has multiple definitions, it will use the number of
15076 actual parameters and some information about their types to attempt to narrow
15077 the set of definitions. It also makes very limited use of context, preferring
15078 procedures to functions in the context of the @code{call} command, and
15079 functions to procedures elsewhere.
15081 @node Omissions from Ada
15082 @subsubsection Omissions from Ada
15083 @cindex Ada, omissions from
15085 Here are the notable omissions from the subset:
15089 Only a subset of the attributes are supported:
15093 @t{'First}, @t{'Last}, and @t{'Length}
15094 on array objects (not on types and subtypes).
15097 @t{'Min} and @t{'Max}.
15100 @t{'Pos} and @t{'Val}.
15106 @t{'Range} on array objects (not subtypes), but only as the right
15107 operand of the membership (@code{in}) operator.
15110 @t{'Access}, @t{'Unchecked_Access}, and
15111 @t{'Unrestricted_Access} (a GNAT extension).
15119 @code{Characters.Latin_1} are not available and
15120 concatenation is not implemented. Thus, escape characters in strings are
15121 not currently available.
15124 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
15125 equality of representations. They will generally work correctly
15126 for strings and arrays whose elements have integer or enumeration types.
15127 They may not work correctly for arrays whose element
15128 types have user-defined equality, for arrays of real values
15129 (in particular, IEEE-conformant floating point, because of negative
15130 zeroes and NaNs), and for arrays whose elements contain unused bits with
15131 indeterminate values.
15134 The other component-by-component array operations (@code{and}, @code{or},
15135 @code{xor}, @code{not}, and relational tests other than equality)
15136 are not implemented.
15139 @cindex array aggregates (Ada)
15140 @cindex record aggregates (Ada)
15141 @cindex aggregates (Ada)
15142 There is limited support for array and record aggregates. They are
15143 permitted only on the right sides of assignments, as in these examples:
15146 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
15147 (@value{GDBP}) set An_Array := (1, others => 0)
15148 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
15149 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
15150 (@value{GDBP}) set A_Record := (1, "Peter", True);
15151 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
15155 discriminant's value by assigning an aggregate has an
15156 undefined effect if that discriminant is used within the record.
15157 However, you can first modify discriminants by directly assigning to
15158 them (which normally would not be allowed in Ada), and then performing an
15159 aggregate assignment. For example, given a variable @code{A_Rec}
15160 declared to have a type such as:
15163 type Rec (Len : Small_Integer := 0) is record
15165 Vals : IntArray (1 .. Len);
15169 you can assign a value with a different size of @code{Vals} with two
15173 (@value{GDBP}) set A_Rec.Len := 4
15174 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
15177 As this example also illustrates, @value{GDBN} is very loose about the usual
15178 rules concerning aggregates. You may leave out some of the
15179 components of an array or record aggregate (such as the @code{Len}
15180 component in the assignment to @code{A_Rec} above); they will retain their
15181 original values upon assignment. You may freely use dynamic values as
15182 indices in component associations. You may even use overlapping or
15183 redundant component associations, although which component values are
15184 assigned in such cases is not defined.
15187 Calls to dispatching subprograms are not implemented.
15190 The overloading algorithm is much more limited (i.e., less selective)
15191 than that of real Ada. It makes only limited use of the context in
15192 which a subexpression appears to resolve its meaning, and it is much
15193 looser in its rules for allowing type matches. As a result, some
15194 function calls will be ambiguous, and the user will be asked to choose
15195 the proper resolution.
15198 The @code{new} operator is not implemented.
15201 Entry calls are not implemented.
15204 Aside from printing, arithmetic operations on the native VAX floating-point
15205 formats are not supported.
15208 It is not possible to slice a packed array.
15211 The names @code{True} and @code{False}, when not part of a qualified name,
15212 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
15214 Should your program
15215 redefine these names in a package or procedure (at best a dubious practice),
15216 you will have to use fully qualified names to access their new definitions.
15219 @node Additions to Ada
15220 @subsubsection Additions to Ada
15221 @cindex Ada, deviations from
15223 As it does for other languages, @value{GDBN} makes certain generic
15224 extensions to Ada (@pxref{Expressions}):
15228 If the expression @var{E} is a variable residing in memory (typically
15229 a local variable or array element) and @var{N} is a positive integer,
15230 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
15231 @var{N}-1 adjacent variables following it in memory as an array. In
15232 Ada, this operator is generally not necessary, since its prime use is
15233 in displaying parts of an array, and slicing will usually do this in
15234 Ada. However, there are occasional uses when debugging programs in
15235 which certain debugging information has been optimized away.
15238 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
15239 appears in function or file @var{B}.'' When @var{B} is a file name,
15240 you must typically surround it in single quotes.
15243 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
15244 @var{type} that appears at address @var{addr}.''
15247 A name starting with @samp{$} is a convenience variable
15248 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
15251 In addition, @value{GDBN} provides a few other shortcuts and outright
15252 additions specific to Ada:
15256 The assignment statement is allowed as an expression, returning
15257 its right-hand operand as its value. Thus, you may enter
15260 (@value{GDBP}) set x := y + 3
15261 (@value{GDBP}) print A(tmp := y + 1)
15265 The semicolon is allowed as an ``operator,'' returning as its value
15266 the value of its right-hand operand.
15267 This allows, for example,
15268 complex conditional breaks:
15271 (@value{GDBP}) break f
15272 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
15276 Rather than use catenation and symbolic character names to introduce special
15277 characters into strings, one may instead use a special bracket notation,
15278 which is also used to print strings. A sequence of characters of the form
15279 @samp{["@var{XX}"]} within a string or character literal denotes the
15280 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
15281 sequence of characters @samp{["""]} also denotes a single quotation mark
15282 in strings. For example,
15284 "One line.["0a"]Next line.["0a"]"
15287 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
15291 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
15292 @t{'Max} is optional (and is ignored in any case). For example, it is valid
15296 (@value{GDBP}) print 'max(x, y)
15300 When printing arrays, @value{GDBN} uses positional notation when the
15301 array has a lower bound of 1, and uses a modified named notation otherwise.
15302 For example, a one-dimensional array of three integers with a lower bound
15303 of 3 might print as
15310 That is, in contrast to valid Ada, only the first component has a @code{=>}
15314 You may abbreviate attributes in expressions with any unique,
15315 multi-character subsequence of
15316 their names (an exact match gets preference).
15317 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
15318 in place of @t{a'length}.
15321 @cindex quoting Ada internal identifiers
15322 Since Ada is case-insensitive, the debugger normally maps identifiers you type
15323 to lower case. The GNAT compiler uses upper-case characters for
15324 some of its internal identifiers, which are normally of no interest to users.
15325 For the rare occasions when you actually have to look at them,
15326 enclose them in angle brackets to avoid the lower-case mapping.
15329 (@value{GDBP}) print <JMPBUF_SAVE>[0]
15333 Printing an object of class-wide type or dereferencing an
15334 access-to-class-wide value will display all the components of the object's
15335 specific type (as indicated by its run-time tag). Likewise, component
15336 selection on such a value will operate on the specific type of the
15341 @node Stopping Before Main Program
15342 @subsubsection Stopping at the Very Beginning
15344 @cindex breakpointing Ada elaboration code
15345 It is sometimes necessary to debug the program during elaboration, and
15346 before reaching the main procedure.
15347 As defined in the Ada Reference
15348 Manual, the elaboration code is invoked from a procedure called
15349 @code{adainit}. To run your program up to the beginning of
15350 elaboration, simply use the following two commands:
15351 @code{tbreak adainit} and @code{run}.
15353 @node Ada Exceptions
15354 @subsubsection Ada Exceptions
15356 A command is provided to list all Ada exceptions:
15359 @kindex info exceptions
15360 @item info exceptions
15361 @itemx info exceptions @var{regexp}
15362 The @code{info exceptions} command allows you to list all Ada exceptions
15363 defined within the program being debugged, as well as their addresses.
15364 With a regular expression, @var{regexp}, as argument, only those exceptions
15365 whose names match @var{regexp} are listed.
15368 Below is a small example, showing how the command can be used, first
15369 without argument, and next with a regular expression passed as an
15373 (@value{GDBP}) info exceptions
15374 All defined Ada exceptions:
15375 constraint_error: 0x613da0
15376 program_error: 0x613d20
15377 storage_error: 0x613ce0
15378 tasking_error: 0x613ca0
15379 const.aint_global_e: 0x613b00
15380 (@value{GDBP}) info exceptions const.aint
15381 All Ada exceptions matching regular expression "const.aint":
15382 constraint_error: 0x613da0
15383 const.aint_global_e: 0x613b00
15386 It is also possible to ask @value{GDBN} to stop your program's execution
15387 when an exception is raised. For more details, see @ref{Set Catchpoints}.
15390 @subsubsection Extensions for Ada Tasks
15391 @cindex Ada, tasking
15393 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
15394 @value{GDBN} provides the following task-related commands:
15399 This command shows a list of current Ada tasks, as in the following example:
15406 (@value{GDBP}) info tasks
15407 ID TID P-ID Pri State Name
15408 1 8088000 0 15 Child Activation Wait main_task
15409 2 80a4000 1 15 Accept Statement b
15410 3 809a800 1 15 Child Activation Wait a
15411 * 4 80ae800 3 15 Runnable c
15416 In this listing, the asterisk before the last task indicates it to be the
15417 task currently being inspected.
15421 Represents @value{GDBN}'s internal task number.
15427 The parent's task ID (@value{GDBN}'s internal task number).
15430 The base priority of the task.
15433 Current state of the task.
15437 The task has been created but has not been activated. It cannot be
15441 The task is not blocked for any reason known to Ada. (It may be waiting
15442 for a mutex, though.) It is conceptually "executing" in normal mode.
15445 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
15446 that were waiting on terminate alternatives have been awakened and have
15447 terminated themselves.
15449 @item Child Activation Wait
15450 The task is waiting for created tasks to complete activation.
15452 @item Accept Statement
15453 The task is waiting on an accept or selective wait statement.
15455 @item Waiting on entry call
15456 The task is waiting on an entry call.
15458 @item Async Select Wait
15459 The task is waiting to start the abortable part of an asynchronous
15463 The task is waiting on a select statement with only a delay
15466 @item Child Termination Wait
15467 The task is sleeping having completed a master within itself, and is
15468 waiting for the tasks dependent on that master to become terminated or
15469 waiting on a terminate Phase.
15471 @item Wait Child in Term Alt
15472 The task is sleeping waiting for tasks on terminate alternatives to
15473 finish terminating.
15475 @item Accepting RV with @var{taskno}
15476 The task is accepting a rendez-vous with the task @var{taskno}.
15480 Name of the task in the program.
15484 @kindex info task @var{taskno}
15485 @item info task @var{taskno}
15486 This command shows detailled informations on the specified task, as in
15487 the following example:
15492 (@value{GDBP}) info tasks
15493 ID TID P-ID Pri State Name
15494 1 8077880 0 15 Child Activation Wait main_task
15495 * 2 807c468 1 15 Runnable task_1
15496 (@value{GDBP}) info task 2
15497 Ada Task: 0x807c468
15500 Parent: 1 (main_task)
15506 @kindex task@r{ (Ada)}
15507 @cindex current Ada task ID
15508 This command prints the ID of the current task.
15514 (@value{GDBP}) info tasks
15515 ID TID P-ID Pri State Name
15516 1 8077870 0 15 Child Activation Wait main_task
15517 * 2 807c458 1 15 Runnable t
15518 (@value{GDBP}) task
15519 [Current task is 2]
15522 @item task @var{taskno}
15523 @cindex Ada task switching
15524 This command is like the @code{thread @var{threadno}}
15525 command (@pxref{Threads}). It switches the context of debugging
15526 from the current task to the given task.
15532 (@value{GDBP}) info tasks
15533 ID TID P-ID Pri State Name
15534 1 8077870 0 15 Child Activation Wait main_task
15535 * 2 807c458 1 15 Runnable t
15536 (@value{GDBP}) task 1
15537 [Switching to task 1]
15538 #0 0x8067726 in pthread_cond_wait ()
15540 #0 0x8067726 in pthread_cond_wait ()
15541 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
15542 #2 0x805cb63 in system.task_primitives.operations.sleep ()
15543 #3 0x806153e in system.tasking.stages.activate_tasks ()
15544 #4 0x804aacc in un () at un.adb:5
15547 @item break @var{linespec} task @var{taskno}
15548 @itemx break @var{linespec} task @var{taskno} if @dots{}
15549 @cindex breakpoints and tasks, in Ada
15550 @cindex task breakpoints, in Ada
15551 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
15552 These commands are like the @code{break @dots{} thread @dots{}}
15553 command (@pxref{Thread Stops}).
15554 @var{linespec} specifies source lines, as described
15555 in @ref{Specify Location}.
15557 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
15558 to specify that you only want @value{GDBN} to stop the program when a
15559 particular Ada task reaches this breakpoint. @var{taskno} is one of the
15560 numeric task identifiers assigned by @value{GDBN}, shown in the first
15561 column of the @samp{info tasks} display.
15563 If you do not specify @samp{task @var{taskno}} when you set a
15564 breakpoint, the breakpoint applies to @emph{all} tasks of your
15567 You can use the @code{task} qualifier on conditional breakpoints as
15568 well; in this case, place @samp{task @var{taskno}} before the
15569 breakpoint condition (before the @code{if}).
15577 (@value{GDBP}) info tasks
15578 ID TID P-ID Pri State Name
15579 1 140022020 0 15 Child Activation Wait main_task
15580 2 140045060 1 15 Accept/Select Wait t2
15581 3 140044840 1 15 Runnable t1
15582 * 4 140056040 1 15 Runnable t3
15583 (@value{GDBP}) b 15 task 2
15584 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
15585 (@value{GDBP}) cont
15590 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
15592 (@value{GDBP}) info tasks
15593 ID TID P-ID Pri State Name
15594 1 140022020 0 15 Child Activation Wait main_task
15595 * 2 140045060 1 15 Runnable t2
15596 3 140044840 1 15 Runnable t1
15597 4 140056040 1 15 Delay Sleep t3
15601 @node Ada Tasks and Core Files
15602 @subsubsection Tasking Support when Debugging Core Files
15603 @cindex Ada tasking and core file debugging
15605 When inspecting a core file, as opposed to debugging a live program,
15606 tasking support may be limited or even unavailable, depending on
15607 the platform being used.
15608 For instance, on x86-linux, the list of tasks is available, but task
15609 switching is not supported. On Tru64, however, task switching will work
15612 On certain platforms, including Tru64, the debugger needs to perform some
15613 memory writes in order to provide Ada tasking support. When inspecting
15614 a core file, this means that the core file must be opened with read-write
15615 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
15616 Under these circumstances, you should make a backup copy of the core
15617 file before inspecting it with @value{GDBN}.
15619 @node Ravenscar Profile
15620 @subsubsection Tasking Support when using the Ravenscar Profile
15621 @cindex Ravenscar Profile
15623 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
15624 specifically designed for systems with safety-critical real-time
15628 @kindex set ravenscar task-switching on
15629 @cindex task switching with program using Ravenscar Profile
15630 @item set ravenscar task-switching on
15631 Allows task switching when debugging a program that uses the Ravenscar
15632 Profile. This is the default.
15634 @kindex set ravenscar task-switching off
15635 @item set ravenscar task-switching off
15636 Turn off task switching when debugging a program that uses the Ravenscar
15637 Profile. This is mostly intended to disable the code that adds support
15638 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
15639 the Ravenscar runtime is preventing @value{GDBN} from working properly.
15640 To be effective, this command should be run before the program is started.
15642 @kindex show ravenscar task-switching
15643 @item show ravenscar task-switching
15644 Show whether it is possible to switch from task to task in a program
15645 using the Ravenscar Profile.
15650 @subsubsection Known Peculiarities of Ada Mode
15651 @cindex Ada, problems
15653 Besides the omissions listed previously (@pxref{Omissions from Ada}),
15654 we know of several problems with and limitations of Ada mode in
15656 some of which will be fixed with planned future releases of the debugger
15657 and the GNU Ada compiler.
15661 Static constants that the compiler chooses not to materialize as objects in
15662 storage are invisible to the debugger.
15665 Named parameter associations in function argument lists are ignored (the
15666 argument lists are treated as positional).
15669 Many useful library packages are currently invisible to the debugger.
15672 Fixed-point arithmetic, conversions, input, and output is carried out using
15673 floating-point arithmetic, and may give results that only approximate those on
15677 The GNAT compiler never generates the prefix @code{Standard} for any of
15678 the standard symbols defined by the Ada language. @value{GDBN} knows about
15679 this: it will strip the prefix from names when you use it, and will never
15680 look for a name you have so qualified among local symbols, nor match against
15681 symbols in other packages or subprograms. If you have
15682 defined entities anywhere in your program other than parameters and
15683 local variables whose simple names match names in @code{Standard},
15684 GNAT's lack of qualification here can cause confusion. When this happens,
15685 you can usually resolve the confusion
15686 by qualifying the problematic names with package
15687 @code{Standard} explicitly.
15690 Older versions of the compiler sometimes generate erroneous debugging
15691 information, resulting in the debugger incorrectly printing the value
15692 of affected entities. In some cases, the debugger is able to work
15693 around an issue automatically. In other cases, the debugger is able
15694 to work around the issue, but the work-around has to be specifically
15697 @kindex set ada trust-PAD-over-XVS
15698 @kindex show ada trust-PAD-over-XVS
15701 @item set ada trust-PAD-over-XVS on
15702 Configure GDB to strictly follow the GNAT encoding when computing the
15703 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
15704 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
15705 a complete description of the encoding used by the GNAT compiler).
15706 This is the default.
15708 @item set ada trust-PAD-over-XVS off
15709 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
15710 sometimes prints the wrong value for certain entities, changing @code{ada
15711 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
15712 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
15713 @code{off}, but this incurs a slight performance penalty, so it is
15714 recommended to leave this setting to @code{on} unless necessary.
15718 @cindex GNAT descriptive types
15719 @cindex GNAT encoding
15720 Internally, the debugger also relies on the compiler following a number
15721 of conventions known as the @samp{GNAT Encoding}, all documented in
15722 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
15723 how the debugging information should be generated for certain types.
15724 In particular, this convention makes use of @dfn{descriptive types},
15725 which are artificial types generated purely to help the debugger.
15727 These encodings were defined at a time when the debugging information
15728 format used was not powerful enough to describe some of the more complex
15729 types available in Ada. Since DWARF allows us to express nearly all
15730 Ada features, the long-term goal is to slowly replace these descriptive
15731 types by their pure DWARF equivalent. To facilitate that transition,
15732 a new maintenance option is available to force the debugger to ignore
15733 those descriptive types. It allows the user to quickly evaluate how
15734 well @value{GDBN} works without them.
15738 @kindex maint ada set ignore-descriptive-types
15739 @item maintenance ada set ignore-descriptive-types [on|off]
15740 Control whether the debugger should ignore descriptive types.
15741 The default is not to ignore descriptives types (@code{off}).
15743 @kindex maint ada show ignore-descriptive-types
15744 @item maintenance ada show ignore-descriptive-types
15745 Show if descriptive types are ignored by @value{GDBN}.
15749 @node Unsupported Languages
15750 @section Unsupported Languages
15752 @cindex unsupported languages
15753 @cindex minimal language
15754 In addition to the other fully-supported programming languages,
15755 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
15756 It does not represent a real programming language, but provides a set
15757 of capabilities close to what the C or assembly languages provide.
15758 This should allow most simple operations to be performed while debugging
15759 an application that uses a language currently not supported by @value{GDBN}.
15761 If the language is set to @code{auto}, @value{GDBN} will automatically
15762 select this language if the current frame corresponds to an unsupported
15766 @chapter Examining the Symbol Table
15768 The commands described in this chapter allow you to inquire about the
15769 symbols (names of variables, functions and types) defined in your
15770 program. This information is inherent in the text of your program and
15771 does not change as your program executes. @value{GDBN} finds it in your
15772 program's symbol table, in the file indicated when you started @value{GDBN}
15773 (@pxref{File Options, ,Choosing Files}), or by one of the
15774 file-management commands (@pxref{Files, ,Commands to Specify Files}).
15776 @cindex symbol names
15777 @cindex names of symbols
15778 @cindex quoting names
15779 Occasionally, you may need to refer to symbols that contain unusual
15780 characters, which @value{GDBN} ordinarily treats as word delimiters. The
15781 most frequent case is in referring to static variables in other
15782 source files (@pxref{Variables,,Program Variables}). File names
15783 are recorded in object files as debugging symbols, but @value{GDBN} would
15784 ordinarily parse a typical file name, like @file{foo.c}, as the three words
15785 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
15786 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
15793 looks up the value of @code{x} in the scope of the file @file{foo.c}.
15796 @cindex case-insensitive symbol names
15797 @cindex case sensitivity in symbol names
15798 @kindex set case-sensitive
15799 @item set case-sensitive on
15800 @itemx set case-sensitive off
15801 @itemx set case-sensitive auto
15802 Normally, when @value{GDBN} looks up symbols, it matches their names
15803 with case sensitivity determined by the current source language.
15804 Occasionally, you may wish to control that. The command @code{set
15805 case-sensitive} lets you do that by specifying @code{on} for
15806 case-sensitive matches or @code{off} for case-insensitive ones. If
15807 you specify @code{auto}, case sensitivity is reset to the default
15808 suitable for the source language. The default is case-sensitive
15809 matches for all languages except for Fortran, for which the default is
15810 case-insensitive matches.
15812 @kindex show case-sensitive
15813 @item show case-sensitive
15814 This command shows the current setting of case sensitivity for symbols
15817 @kindex set print type methods
15818 @item set print type methods
15819 @itemx set print type methods on
15820 @itemx set print type methods off
15821 Normally, when @value{GDBN} prints a class, it displays any methods
15822 declared in that class. You can control this behavior either by
15823 passing the appropriate flag to @code{ptype}, or using @command{set
15824 print type methods}. Specifying @code{on} will cause @value{GDBN} to
15825 display the methods; this is the default. Specifying @code{off} will
15826 cause @value{GDBN} to omit the methods.
15828 @kindex show print type methods
15829 @item show print type methods
15830 This command shows the current setting of method display when printing
15833 @kindex set print type typedefs
15834 @item set print type typedefs
15835 @itemx set print type typedefs on
15836 @itemx set print type typedefs off
15838 Normally, when @value{GDBN} prints a class, it displays any typedefs
15839 defined in that class. You can control this behavior either by
15840 passing the appropriate flag to @code{ptype}, or using @command{set
15841 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
15842 display the typedef definitions; this is the default. Specifying
15843 @code{off} will cause @value{GDBN} to omit the typedef definitions.
15844 Note that this controls whether the typedef definition itself is
15845 printed, not whether typedef names are substituted when printing other
15848 @kindex show print type typedefs
15849 @item show print type typedefs
15850 This command shows the current setting of typedef display when
15853 @kindex info address
15854 @cindex address of a symbol
15855 @item info address @var{symbol}
15856 Describe where the data for @var{symbol} is stored. For a register
15857 variable, this says which register it is kept in. For a non-register
15858 local variable, this prints the stack-frame offset at which the variable
15861 Note the contrast with @samp{print &@var{symbol}}, which does not work
15862 at all for a register variable, and for a stack local variable prints
15863 the exact address of the current instantiation of the variable.
15865 @kindex info symbol
15866 @cindex symbol from address
15867 @cindex closest symbol and offset for an address
15868 @item info symbol @var{addr}
15869 Print the name of a symbol which is stored at the address @var{addr}.
15870 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
15871 nearest symbol and an offset from it:
15874 (@value{GDBP}) info symbol 0x54320
15875 _initialize_vx + 396 in section .text
15879 This is the opposite of the @code{info address} command. You can use
15880 it to find out the name of a variable or a function given its address.
15882 For dynamically linked executables, the name of executable or shared
15883 library containing the symbol is also printed:
15886 (@value{GDBP}) info symbol 0x400225
15887 _start + 5 in section .text of /tmp/a.out
15888 (@value{GDBP}) info symbol 0x2aaaac2811cf
15889 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
15893 @item whatis[/@var{flags}] [@var{arg}]
15894 Print the data type of @var{arg}, which can be either an expression
15895 or a name of a data type. With no argument, print the data type of
15896 @code{$}, the last value in the value history.
15898 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
15899 is not actually evaluated, and any side-effecting operations (such as
15900 assignments or function calls) inside it do not take place.
15902 If @var{arg} is a variable or an expression, @code{whatis} prints its
15903 literal type as it is used in the source code. If the type was
15904 defined using a @code{typedef}, @code{whatis} will @emph{not} print
15905 the data type underlying the @code{typedef}. If the type of the
15906 variable or the expression is a compound data type, such as
15907 @code{struct} or @code{class}, @code{whatis} never prints their
15908 fields or methods. It just prints the @code{struct}/@code{class}
15909 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
15910 such a compound data type, use @code{ptype}.
15912 If @var{arg} is a type name that was defined using @code{typedef},
15913 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
15914 Unrolling means that @code{whatis} will show the underlying type used
15915 in the @code{typedef} declaration of @var{arg}. However, if that
15916 underlying type is also a @code{typedef}, @code{whatis} will not
15919 For C code, the type names may also have the form @samp{class
15920 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
15921 @var{union-tag}} or @samp{enum @var{enum-tag}}.
15923 @var{flags} can be used to modify how the type is displayed.
15924 Available flags are:
15928 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
15929 parameters and typedefs defined in a class when printing the class'
15930 members. The @code{/r} flag disables this.
15933 Do not print methods defined in the class.
15936 Print methods defined in the class. This is the default, but the flag
15937 exists in case you change the default with @command{set print type methods}.
15940 Do not print typedefs defined in the class. Note that this controls
15941 whether the typedef definition itself is printed, not whether typedef
15942 names are substituted when printing other types.
15945 Print typedefs defined in the class. This is the default, but the flag
15946 exists in case you change the default with @command{set print type typedefs}.
15950 @item ptype[/@var{flags}] [@var{arg}]
15951 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
15952 detailed description of the type, instead of just the name of the type.
15953 @xref{Expressions, ,Expressions}.
15955 Contrary to @code{whatis}, @code{ptype} always unrolls any
15956 @code{typedef}s in its argument declaration, whether the argument is
15957 a variable, expression, or a data type. This means that @code{ptype}
15958 of a variable or an expression will not print literally its type as
15959 present in the source code---use @code{whatis} for that. @code{typedef}s at
15960 the pointer or reference targets are also unrolled. Only @code{typedef}s of
15961 fields, methods and inner @code{class typedef}s of @code{struct}s,
15962 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
15964 For example, for this variable declaration:
15967 typedef double real_t;
15968 struct complex @{ real_t real; double imag; @};
15969 typedef struct complex complex_t;
15971 real_t *real_pointer_var;
15975 the two commands give this output:
15979 (@value{GDBP}) whatis var
15981 (@value{GDBP}) ptype var
15982 type = struct complex @{
15986 (@value{GDBP}) whatis complex_t
15987 type = struct complex
15988 (@value{GDBP}) whatis struct complex
15989 type = struct complex
15990 (@value{GDBP}) ptype struct complex
15991 type = struct complex @{
15995 (@value{GDBP}) whatis real_pointer_var
15997 (@value{GDBP}) ptype real_pointer_var
16003 As with @code{whatis}, using @code{ptype} without an argument refers to
16004 the type of @code{$}, the last value in the value history.
16006 @cindex incomplete type
16007 Sometimes, programs use opaque data types or incomplete specifications
16008 of complex data structure. If the debug information included in the
16009 program does not allow @value{GDBN} to display a full declaration of
16010 the data type, it will say @samp{<incomplete type>}. For example,
16011 given these declarations:
16015 struct foo *fooptr;
16019 but no definition for @code{struct foo} itself, @value{GDBN} will say:
16022 (@value{GDBP}) ptype foo
16023 $1 = <incomplete type>
16027 ``Incomplete type'' is C terminology for data types that are not
16028 completely specified.
16031 @item info types @var{regexp}
16033 Print a brief description of all types whose names match the regular
16034 expression @var{regexp} (or all types in your program, if you supply
16035 no argument). Each complete typename is matched as though it were a
16036 complete line; thus, @samp{i type value} gives information on all
16037 types in your program whose names include the string @code{value}, but
16038 @samp{i type ^value$} gives information only on types whose complete
16039 name is @code{value}.
16041 This command differs from @code{ptype} in two ways: first, like
16042 @code{whatis}, it does not print a detailed description; second, it
16043 lists all source files where a type is defined.
16045 @kindex info type-printers
16046 @item info type-printers
16047 Versions of @value{GDBN} that ship with Python scripting enabled may
16048 have ``type printers'' available. When using @command{ptype} or
16049 @command{whatis}, these printers are consulted when the name of a type
16050 is needed. @xref{Type Printing API}, for more information on writing
16053 @code{info type-printers} displays all the available type printers.
16055 @kindex enable type-printer
16056 @kindex disable type-printer
16057 @item enable type-printer @var{name}@dots{}
16058 @item disable type-printer @var{name}@dots{}
16059 These commands can be used to enable or disable type printers.
16062 @cindex local variables
16063 @item info scope @var{location}
16064 List all the variables local to a particular scope. This command
16065 accepts a @var{location} argument---a function name, a source line, or
16066 an address preceded by a @samp{*}, and prints all the variables local
16067 to the scope defined by that location. (@xref{Specify Location}, for
16068 details about supported forms of @var{location}.) For example:
16071 (@value{GDBP}) @b{info scope command_line_handler}
16072 Scope for command_line_handler:
16073 Symbol rl is an argument at stack/frame offset 8, length 4.
16074 Symbol linebuffer is in static storage at address 0x150a18, length 4.
16075 Symbol linelength is in static storage at address 0x150a1c, length 4.
16076 Symbol p is a local variable in register $esi, length 4.
16077 Symbol p1 is a local variable in register $ebx, length 4.
16078 Symbol nline is a local variable in register $edx, length 4.
16079 Symbol repeat is a local variable at frame offset -8, length 4.
16083 This command is especially useful for determining what data to collect
16084 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
16087 @kindex info source
16089 Show information about the current source file---that is, the source file for
16090 the function containing the current point of execution:
16093 the name of the source file, and the directory containing it,
16095 the directory it was compiled in,
16097 its length, in lines,
16099 which programming language it is written in,
16101 whether the executable includes debugging information for that file, and
16102 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
16104 whether the debugging information includes information about
16105 preprocessor macros.
16109 @kindex info sources
16111 Print the names of all source files in your program for which there is
16112 debugging information, organized into two lists: files whose symbols
16113 have already been read, and files whose symbols will be read when needed.
16115 @kindex info functions
16116 @item info functions
16117 Print the names and data types of all defined functions.
16119 @item info functions @var{regexp}
16120 Print the names and data types of all defined functions
16121 whose names contain a match for regular expression @var{regexp}.
16122 Thus, @samp{info fun step} finds all functions whose names
16123 include @code{step}; @samp{info fun ^step} finds those whose names
16124 start with @code{step}. If a function name contains characters
16125 that conflict with the regular expression language (e.g.@:
16126 @samp{operator*()}), they may be quoted with a backslash.
16128 @kindex info variables
16129 @item info variables
16130 Print the names and data types of all variables that are defined
16131 outside of functions (i.e.@: excluding local variables).
16133 @item info variables @var{regexp}
16134 Print the names and data types of all variables (except for local
16135 variables) whose names contain a match for regular expression
16138 @kindex info classes
16139 @cindex Objective-C, classes and selectors
16141 @itemx info classes @var{regexp}
16142 Display all Objective-C classes in your program, or
16143 (with the @var{regexp} argument) all those matching a particular regular
16146 @kindex info selectors
16147 @item info selectors
16148 @itemx info selectors @var{regexp}
16149 Display all Objective-C selectors in your program, or
16150 (with the @var{regexp} argument) all those matching a particular regular
16154 This was never implemented.
16155 @kindex info methods
16157 @itemx info methods @var{regexp}
16158 The @code{info methods} command permits the user to examine all defined
16159 methods within C@t{++} program, or (with the @var{regexp} argument) a
16160 specific set of methods found in the various C@t{++} classes. Many
16161 C@t{++} classes provide a large number of methods. Thus, the output
16162 from the @code{ptype} command can be overwhelming and hard to use. The
16163 @code{info-methods} command filters the methods, printing only those
16164 which match the regular-expression @var{regexp}.
16167 @cindex opaque data types
16168 @kindex set opaque-type-resolution
16169 @item set opaque-type-resolution on
16170 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
16171 declared as a pointer to a @code{struct}, @code{class}, or
16172 @code{union}---for example, @code{struct MyType *}---that is used in one
16173 source file although the full declaration of @code{struct MyType} is in
16174 another source file. The default is on.
16176 A change in the setting of this subcommand will not take effect until
16177 the next time symbols for a file are loaded.
16179 @item set opaque-type-resolution off
16180 Tell @value{GDBN} not to resolve opaque types. In this case, the type
16181 is printed as follows:
16183 @{<no data fields>@}
16186 @kindex show opaque-type-resolution
16187 @item show opaque-type-resolution
16188 Show whether opaque types are resolved or not.
16190 @kindex set print symbol-loading
16191 @cindex print messages when symbols are loaded
16192 @item set print symbol-loading
16193 @itemx set print symbol-loading full
16194 @itemx set print symbol-loading brief
16195 @itemx set print symbol-loading off
16196 The @code{set print symbol-loading} command allows you to control the
16197 printing of messages when @value{GDBN} loads symbol information.
16198 By default a message is printed for the executable and one for each
16199 shared library, and normally this is what you want. However, when
16200 debugging apps with large numbers of shared libraries these messages
16202 When set to @code{brief} a message is printed for each executable,
16203 and when @value{GDBN} loads a collection of shared libraries at once
16204 it will only print one message regardless of the number of shared
16205 libraries. When set to @code{off} no messages are printed.
16207 @kindex show print symbol-loading
16208 @item show print symbol-loading
16209 Show whether messages will be printed when a @value{GDBN} command
16210 entered from the keyboard causes symbol information to be loaded.
16212 @kindex maint print symbols
16213 @cindex symbol dump
16214 @kindex maint print psymbols
16215 @cindex partial symbol dump
16216 @kindex maint print msymbols
16217 @cindex minimal symbol dump
16218 @item maint print symbols @var{filename}
16219 @itemx maint print psymbols @var{filename}
16220 @itemx maint print msymbols @var{filename}
16221 Write a dump of debugging symbol data into the file @var{filename}.
16222 These commands are used to debug the @value{GDBN} symbol-reading code. Only
16223 symbols with debugging data are included. If you use @samp{maint print
16224 symbols}, @value{GDBN} includes all the symbols for which it has already
16225 collected full details: that is, @var{filename} reflects symbols for
16226 only those files whose symbols @value{GDBN} has read. You can use the
16227 command @code{info sources} to find out which files these are. If you
16228 use @samp{maint print psymbols} instead, the dump shows information about
16229 symbols that @value{GDBN} only knows partially---that is, symbols defined in
16230 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
16231 @samp{maint print msymbols} dumps just the minimal symbol information
16232 required for each object file from which @value{GDBN} has read some symbols.
16233 @xref{Files, ,Commands to Specify Files}, for a discussion of how
16234 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
16236 @kindex maint info symtabs
16237 @kindex maint info psymtabs
16238 @cindex listing @value{GDBN}'s internal symbol tables
16239 @cindex symbol tables, listing @value{GDBN}'s internal
16240 @cindex full symbol tables, listing @value{GDBN}'s internal
16241 @cindex partial symbol tables, listing @value{GDBN}'s internal
16242 @item maint info symtabs @r{[} @var{regexp} @r{]}
16243 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
16245 List the @code{struct symtab} or @code{struct partial_symtab}
16246 structures whose names match @var{regexp}. If @var{regexp} is not
16247 given, list them all. The output includes expressions which you can
16248 copy into a @value{GDBN} debugging this one to examine a particular
16249 structure in more detail. For example:
16252 (@value{GDBP}) maint info psymtabs dwarf2read
16253 @{ objfile /home/gnu/build/gdb/gdb
16254 ((struct objfile *) 0x82e69d0)
16255 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
16256 ((struct partial_symtab *) 0x8474b10)
16259 text addresses 0x814d3c8 -- 0x8158074
16260 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
16261 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
16262 dependencies (none)
16265 (@value{GDBP}) maint info symtabs
16269 We see that there is one partial symbol table whose filename contains
16270 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
16271 and we see that @value{GDBN} has not read in any symtabs yet at all.
16272 If we set a breakpoint on a function, that will cause @value{GDBN} to
16273 read the symtab for the compilation unit containing that function:
16276 (@value{GDBP}) break dwarf2_psymtab_to_symtab
16277 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
16279 (@value{GDBP}) maint info symtabs
16280 @{ objfile /home/gnu/build/gdb/gdb
16281 ((struct objfile *) 0x82e69d0)
16282 @{ symtab /home/gnu/src/gdb/dwarf2read.c
16283 ((struct symtab *) 0x86c1f38)
16286 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
16287 linetable ((struct linetable *) 0x8370fa0)
16288 debugformat DWARF 2
16297 @chapter Altering Execution
16299 Once you think you have found an error in your program, you might want to
16300 find out for certain whether correcting the apparent error would lead to
16301 correct results in the rest of the run. You can find the answer by
16302 experiment, using the @value{GDBN} features for altering execution of the
16305 For example, you can store new values into variables or memory
16306 locations, give your program a signal, restart it at a different
16307 address, or even return prematurely from a function.
16310 * Assignment:: Assignment to variables
16311 * Jumping:: Continuing at a different address
16312 * Signaling:: Giving your program a signal
16313 * Returning:: Returning from a function
16314 * Calling:: Calling your program's functions
16315 * Patching:: Patching your program
16319 @section Assignment to Variables
16322 @cindex setting variables
16323 To alter the value of a variable, evaluate an assignment expression.
16324 @xref{Expressions, ,Expressions}. For example,
16331 stores the value 4 into the variable @code{x}, and then prints the
16332 value of the assignment expression (which is 4).
16333 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
16334 information on operators in supported languages.
16336 @kindex set variable
16337 @cindex variables, setting
16338 If you are not interested in seeing the value of the assignment, use the
16339 @code{set} command instead of the @code{print} command. @code{set} is
16340 really the same as @code{print} except that the expression's value is
16341 not printed and is not put in the value history (@pxref{Value History,
16342 ,Value History}). The expression is evaluated only for its effects.
16344 If the beginning of the argument string of the @code{set} command
16345 appears identical to a @code{set} subcommand, use the @code{set
16346 variable} command instead of just @code{set}. This command is identical
16347 to @code{set} except for its lack of subcommands. For example, if your
16348 program has a variable @code{width}, you get an error if you try to set
16349 a new value with just @samp{set width=13}, because @value{GDBN} has the
16350 command @code{set width}:
16353 (@value{GDBP}) whatis width
16355 (@value{GDBP}) p width
16357 (@value{GDBP}) set width=47
16358 Invalid syntax in expression.
16362 The invalid expression, of course, is @samp{=47}. In
16363 order to actually set the program's variable @code{width}, use
16366 (@value{GDBP}) set var width=47
16369 Because the @code{set} command has many subcommands that can conflict
16370 with the names of program variables, it is a good idea to use the
16371 @code{set variable} command instead of just @code{set}. For example, if
16372 your program has a variable @code{g}, you run into problems if you try
16373 to set a new value with just @samp{set g=4}, because @value{GDBN} has
16374 the command @code{set gnutarget}, abbreviated @code{set g}:
16378 (@value{GDBP}) whatis g
16382 (@value{GDBP}) set g=4
16386 The program being debugged has been started already.
16387 Start it from the beginning? (y or n) y
16388 Starting program: /home/smith/cc_progs/a.out
16389 "/home/smith/cc_progs/a.out": can't open to read symbols:
16390 Invalid bfd target.
16391 (@value{GDBP}) show g
16392 The current BFD target is "=4".
16397 The program variable @code{g} did not change, and you silently set the
16398 @code{gnutarget} to an invalid value. In order to set the variable
16402 (@value{GDBP}) set var g=4
16405 @value{GDBN} allows more implicit conversions in assignments than C; you can
16406 freely store an integer value into a pointer variable or vice versa,
16407 and you can convert any structure to any other structure that is the
16408 same length or shorter.
16409 @comment FIXME: how do structs align/pad in these conversions?
16410 @comment /doc@cygnus.com 18dec1990
16412 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
16413 construct to generate a value of specified type at a specified address
16414 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
16415 to memory location @code{0x83040} as an integer (which implies a certain size
16416 and representation in memory), and
16419 set @{int@}0x83040 = 4
16423 stores the value 4 into that memory location.
16426 @section Continuing at a Different Address
16428 Ordinarily, when you continue your program, you do so at the place where
16429 it stopped, with the @code{continue} command. You can instead continue at
16430 an address of your own choosing, with the following commands:
16434 @kindex j @r{(@code{jump})}
16435 @item jump @var{linespec}
16436 @itemx j @var{linespec}
16437 @itemx jump @var{location}
16438 @itemx j @var{location}
16439 Resume execution at line @var{linespec} or at address given by
16440 @var{location}. Execution stops again immediately if there is a
16441 breakpoint there. @xref{Specify Location}, for a description of the
16442 different forms of @var{linespec} and @var{location}. It is common
16443 practice to use the @code{tbreak} command in conjunction with
16444 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
16446 The @code{jump} command does not change the current stack frame, or
16447 the stack pointer, or the contents of any memory location or any
16448 register other than the program counter. If line @var{linespec} is in
16449 a different function from the one currently executing, the results may
16450 be bizarre if the two functions expect different patterns of arguments or
16451 of local variables. For this reason, the @code{jump} command requests
16452 confirmation if the specified line is not in the function currently
16453 executing. However, even bizarre results are predictable if you are
16454 well acquainted with the machine-language code of your program.
16457 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
16458 On many systems, you can get much the same effect as the @code{jump}
16459 command by storing a new value into the register @code{$pc}. The
16460 difference is that this does not start your program running; it only
16461 changes the address of where it @emph{will} run when you continue. For
16469 makes the next @code{continue} command or stepping command execute at
16470 address @code{0x485}, rather than at the address where your program stopped.
16471 @xref{Continuing and Stepping, ,Continuing and Stepping}.
16473 The most common occasion to use the @code{jump} command is to back
16474 up---perhaps with more breakpoints set---over a portion of a program
16475 that has already executed, in order to examine its execution in more
16480 @section Giving your Program a Signal
16481 @cindex deliver a signal to a program
16485 @item signal @var{signal}
16486 Resume execution where your program stopped, but immediately give it the
16487 signal @var{signal}. @var{signal} can be the name or the number of a
16488 signal. For example, on many systems @code{signal 2} and @code{signal
16489 SIGINT} are both ways of sending an interrupt signal.
16491 Alternatively, if @var{signal} is zero, continue execution without
16492 giving a signal. This is useful when your program stopped on account of
16493 a signal and would ordinarily see the signal when resumed with the
16494 @code{continue} command; @samp{signal 0} causes it to resume without a
16497 @code{signal} does not repeat when you press @key{RET} a second time
16498 after executing the command.
16502 Invoking the @code{signal} command is not the same as invoking the
16503 @code{kill} utility from the shell. Sending a signal with @code{kill}
16504 causes @value{GDBN} to decide what to do with the signal depending on
16505 the signal handling tables (@pxref{Signals}). The @code{signal} command
16506 passes the signal directly to your program.
16510 @section Returning from a Function
16513 @cindex returning from a function
16516 @itemx return @var{expression}
16517 You can cancel execution of a function call with the @code{return}
16518 command. If you give an
16519 @var{expression} argument, its value is used as the function's return
16523 When you use @code{return}, @value{GDBN} discards the selected stack frame
16524 (and all frames within it). You can think of this as making the
16525 discarded frame return prematurely. If you wish to specify a value to
16526 be returned, give that value as the argument to @code{return}.
16528 This pops the selected stack frame (@pxref{Selection, ,Selecting a
16529 Frame}), and any other frames inside of it, leaving its caller as the
16530 innermost remaining frame. That frame becomes selected. The
16531 specified value is stored in the registers used for returning values
16534 The @code{return} command does not resume execution; it leaves the
16535 program stopped in the state that would exist if the function had just
16536 returned. In contrast, the @code{finish} command (@pxref{Continuing
16537 and Stepping, ,Continuing and Stepping}) resumes execution until the
16538 selected stack frame returns naturally.
16540 @value{GDBN} needs to know how the @var{expression} argument should be set for
16541 the inferior. The concrete registers assignment depends on the OS ABI and the
16542 type being returned by the selected stack frame. For example it is common for
16543 OS ABI to return floating point values in FPU registers while integer values in
16544 CPU registers. Still some ABIs return even floating point values in CPU
16545 registers. Larger integer widths (such as @code{long long int}) also have
16546 specific placement rules. @value{GDBN} already knows the OS ABI from its
16547 current target so it needs to find out also the type being returned to make the
16548 assignment into the right register(s).
16550 Normally, the selected stack frame has debug info. @value{GDBN} will always
16551 use the debug info instead of the implicit type of @var{expression} when the
16552 debug info is available. For example, if you type @kbd{return -1}, and the
16553 function in the current stack frame is declared to return a @code{long long
16554 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
16555 into a @code{long long int}:
16558 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
16560 (@value{GDBP}) return -1
16561 Make func return now? (y or n) y
16562 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
16563 43 printf ("result=%lld\n", func ());
16567 However, if the selected stack frame does not have a debug info, e.g., if the
16568 function was compiled without debug info, @value{GDBN} has to find out the type
16569 to return from user. Specifying a different type by mistake may set the value
16570 in different inferior registers than the caller code expects. For example,
16571 typing @kbd{return -1} with its implicit type @code{int} would set only a part
16572 of a @code{long long int} result for a debug info less function (on 32-bit
16573 architectures). Therefore the user is required to specify the return type by
16574 an appropriate cast explicitly:
16577 Breakpoint 2, 0x0040050b in func ()
16578 (@value{GDBP}) return -1
16579 Return value type not available for selected stack frame.
16580 Please use an explicit cast of the value to return.
16581 (@value{GDBP}) return (long long int) -1
16582 Make selected stack frame return now? (y or n) y
16583 #0 0x00400526 in main ()
16588 @section Calling Program Functions
16591 @cindex calling functions
16592 @cindex inferior functions, calling
16593 @item print @var{expr}
16594 Evaluate the expression @var{expr} and display the resulting value.
16595 @var{expr} may include calls to functions in the program being
16599 @item call @var{expr}
16600 Evaluate the expression @var{expr} without displaying @code{void}
16603 You can use this variant of the @code{print} command if you want to
16604 execute a function from your program that does not return anything
16605 (a.k.a.@: @dfn{a void function}), but without cluttering the output
16606 with @code{void} returned values that @value{GDBN} will otherwise
16607 print. If the result is not void, it is printed and saved in the
16611 It is possible for the function you call via the @code{print} or
16612 @code{call} command to generate a signal (e.g., if there's a bug in
16613 the function, or if you passed it incorrect arguments). What happens
16614 in that case is controlled by the @code{set unwindonsignal} command.
16616 Similarly, with a C@t{++} program it is possible for the function you
16617 call via the @code{print} or @code{call} command to generate an
16618 exception that is not handled due to the constraints of the dummy
16619 frame. In this case, any exception that is raised in the frame, but has
16620 an out-of-frame exception handler will not be found. GDB builds a
16621 dummy-frame for the inferior function call, and the unwinder cannot
16622 seek for exception handlers outside of this dummy-frame. What happens
16623 in that case is controlled by the
16624 @code{set unwind-on-terminating-exception} command.
16627 @item set unwindonsignal
16628 @kindex set unwindonsignal
16629 @cindex unwind stack in called functions
16630 @cindex call dummy stack unwinding
16631 Set unwinding of the stack if a signal is received while in a function
16632 that @value{GDBN} called in the program being debugged. If set to on,
16633 @value{GDBN} unwinds the stack it created for the call and restores
16634 the context to what it was before the call. If set to off (the
16635 default), @value{GDBN} stops in the frame where the signal was
16638 @item show unwindonsignal
16639 @kindex show unwindonsignal
16640 Show the current setting of stack unwinding in the functions called by
16643 @item set unwind-on-terminating-exception
16644 @kindex set unwind-on-terminating-exception
16645 @cindex unwind stack in called functions with unhandled exceptions
16646 @cindex call dummy stack unwinding on unhandled exception.
16647 Set unwinding of the stack if a C@t{++} exception is raised, but left
16648 unhandled while in a function that @value{GDBN} called in the program being
16649 debugged. If set to on (the default), @value{GDBN} unwinds the stack
16650 it created for the call and restores the context to what it was before
16651 the call. If set to off, @value{GDBN} the exception is delivered to
16652 the default C@t{++} exception handler and the inferior terminated.
16654 @item show unwind-on-terminating-exception
16655 @kindex show unwind-on-terminating-exception
16656 Show the current setting of stack unwinding in the functions called by
16661 @cindex weak alias functions
16662 Sometimes, a function you wish to call is actually a @dfn{weak alias}
16663 for another function. In such case, @value{GDBN} might not pick up
16664 the type information, including the types of the function arguments,
16665 which causes @value{GDBN} to call the inferior function incorrectly.
16666 As a result, the called function will function erroneously and may
16667 even crash. A solution to that is to use the name of the aliased
16671 @section Patching Programs
16673 @cindex patching binaries
16674 @cindex writing into executables
16675 @cindex writing into corefiles
16677 By default, @value{GDBN} opens the file containing your program's
16678 executable code (or the corefile) read-only. This prevents accidental
16679 alterations to machine code; but it also prevents you from intentionally
16680 patching your program's binary.
16682 If you'd like to be able to patch the binary, you can specify that
16683 explicitly with the @code{set write} command. For example, you might
16684 want to turn on internal debugging flags, or even to make emergency
16690 @itemx set write off
16691 If you specify @samp{set write on}, @value{GDBN} opens executable and
16692 core files for both reading and writing; if you specify @kbd{set write
16693 off} (the default), @value{GDBN} opens them read-only.
16695 If you have already loaded a file, you must load it again (using the
16696 @code{exec-file} or @code{core-file} command) after changing @code{set
16697 write}, for your new setting to take effect.
16701 Display whether executable files and core files are opened for writing
16702 as well as reading.
16706 @chapter @value{GDBN} Files
16708 @value{GDBN} needs to know the file name of the program to be debugged,
16709 both in order to read its symbol table and in order to start your
16710 program. To debug a core dump of a previous run, you must also tell
16711 @value{GDBN} the name of the core dump file.
16714 * Files:: Commands to specify files
16715 * Separate Debug Files:: Debugging information in separate files
16716 * MiniDebugInfo:: Debugging information in a special section
16717 * Index Files:: Index files speed up GDB
16718 * Symbol Errors:: Errors reading symbol files
16719 * Data Files:: GDB data files
16723 @section Commands to Specify Files
16725 @cindex symbol table
16726 @cindex core dump file
16728 You may want to specify executable and core dump file names. The usual
16729 way to do this is at start-up time, using the arguments to
16730 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
16731 Out of @value{GDBN}}).
16733 Occasionally it is necessary to change to a different file during a
16734 @value{GDBN} session. Or you may run @value{GDBN} and forget to
16735 specify a file you want to use. Or you are debugging a remote target
16736 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
16737 Program}). In these situations the @value{GDBN} commands to specify
16738 new files are useful.
16741 @cindex executable file
16743 @item file @var{filename}
16744 Use @var{filename} as the program to be debugged. It is read for its
16745 symbols and for the contents of pure memory. It is also the program
16746 executed when you use the @code{run} command. If you do not specify a
16747 directory and the file is not found in the @value{GDBN} working directory,
16748 @value{GDBN} uses the environment variable @code{PATH} as a list of
16749 directories to search, just as the shell does when looking for a program
16750 to run. You can change the value of this variable, for both @value{GDBN}
16751 and your program, using the @code{path} command.
16753 @cindex unlinked object files
16754 @cindex patching object files
16755 You can load unlinked object @file{.o} files into @value{GDBN} using
16756 the @code{file} command. You will not be able to ``run'' an object
16757 file, but you can disassemble functions and inspect variables. Also,
16758 if the underlying BFD functionality supports it, you could use
16759 @kbd{gdb -write} to patch object files using this technique. Note
16760 that @value{GDBN} can neither interpret nor modify relocations in this
16761 case, so branches and some initialized variables will appear to go to
16762 the wrong place. But this feature is still handy from time to time.
16765 @code{file} with no argument makes @value{GDBN} discard any information it
16766 has on both executable file and the symbol table.
16769 @item exec-file @r{[} @var{filename} @r{]}
16770 Specify that the program to be run (but not the symbol table) is found
16771 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
16772 if necessary to locate your program. Omitting @var{filename} means to
16773 discard information on the executable file.
16775 @kindex symbol-file
16776 @item symbol-file @r{[} @var{filename} @r{]}
16777 Read symbol table information from file @var{filename}. @code{PATH} is
16778 searched when necessary. Use the @code{file} command to get both symbol
16779 table and program to run from the same file.
16781 @code{symbol-file} with no argument clears out @value{GDBN} information on your
16782 program's symbol table.
16784 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
16785 some breakpoints and auto-display expressions. This is because they may
16786 contain pointers to the internal data recording symbols and data types,
16787 which are part of the old symbol table data being discarded inside
16790 @code{symbol-file} does not repeat if you press @key{RET} again after
16793 When @value{GDBN} is configured for a particular environment, it
16794 understands debugging information in whatever format is the standard
16795 generated for that environment; you may use either a @sc{gnu} compiler, or
16796 other compilers that adhere to the local conventions.
16797 Best results are usually obtained from @sc{gnu} compilers; for example,
16798 using @code{@value{NGCC}} you can generate debugging information for
16801 For most kinds of object files, with the exception of old SVR3 systems
16802 using COFF, the @code{symbol-file} command does not normally read the
16803 symbol table in full right away. Instead, it scans the symbol table
16804 quickly to find which source files and which symbols are present. The
16805 details are read later, one source file at a time, as they are needed.
16807 The purpose of this two-stage reading strategy is to make @value{GDBN}
16808 start up faster. For the most part, it is invisible except for
16809 occasional pauses while the symbol table details for a particular source
16810 file are being read. (The @code{set verbose} command can turn these
16811 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
16812 Warnings and Messages}.)
16814 We have not implemented the two-stage strategy for COFF yet. When the
16815 symbol table is stored in COFF format, @code{symbol-file} reads the
16816 symbol table data in full right away. Note that ``stabs-in-COFF''
16817 still does the two-stage strategy, since the debug info is actually
16821 @cindex reading symbols immediately
16822 @cindex symbols, reading immediately
16823 @item symbol-file @r{[} -readnow @r{]} @var{filename}
16824 @itemx file @r{[} -readnow @r{]} @var{filename}
16825 You can override the @value{GDBN} two-stage strategy for reading symbol
16826 tables by using the @samp{-readnow} option with any of the commands that
16827 load symbol table information, if you want to be sure @value{GDBN} has the
16828 entire symbol table available.
16830 @c FIXME: for now no mention of directories, since this seems to be in
16831 @c flux. 13mar1992 status is that in theory GDB would look either in
16832 @c current dir or in same dir as myprog; but issues like competing
16833 @c GDB's, or clutter in system dirs, mean that in practice right now
16834 @c only current dir is used. FFish says maybe a special GDB hierarchy
16835 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
16839 @item core-file @r{[}@var{filename}@r{]}
16841 Specify the whereabouts of a core dump file to be used as the ``contents
16842 of memory''. Traditionally, core files contain only some parts of the
16843 address space of the process that generated them; @value{GDBN} can access the
16844 executable file itself for other parts.
16846 @code{core-file} with no argument specifies that no core file is
16849 Note that the core file is ignored when your program is actually running
16850 under @value{GDBN}. So, if you have been running your program and you
16851 wish to debug a core file instead, you must kill the subprocess in which
16852 the program is running. To do this, use the @code{kill} command
16853 (@pxref{Kill Process, ,Killing the Child Process}).
16855 @kindex add-symbol-file
16856 @cindex dynamic linking
16857 @item add-symbol-file @var{filename} @var{address}
16858 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
16859 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
16860 The @code{add-symbol-file} command reads additional symbol table
16861 information from the file @var{filename}. You would use this command
16862 when @var{filename} has been dynamically loaded (by some other means)
16863 into the program that is running. @var{address} should be the memory
16864 address at which the file has been loaded; @value{GDBN} cannot figure
16865 this out for itself. You can additionally specify an arbitrary number
16866 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
16867 section name and base address for that section. You can specify any
16868 @var{address} as an expression.
16870 The symbol table of the file @var{filename} is added to the symbol table
16871 originally read with the @code{symbol-file} command. You can use the
16872 @code{add-symbol-file} command any number of times; the new symbol data
16873 thus read is kept in addition to the old.
16875 Changes can be reverted using the command @code{remove-symbol-file}.
16877 @cindex relocatable object files, reading symbols from
16878 @cindex object files, relocatable, reading symbols from
16879 @cindex reading symbols from relocatable object files
16880 @cindex symbols, reading from relocatable object files
16881 @cindex @file{.o} files, reading symbols from
16882 Although @var{filename} is typically a shared library file, an
16883 executable file, or some other object file which has been fully
16884 relocated for loading into a process, you can also load symbolic
16885 information from relocatable @file{.o} files, as long as:
16889 the file's symbolic information refers only to linker symbols defined in
16890 that file, not to symbols defined by other object files,
16892 every section the file's symbolic information refers to has actually
16893 been loaded into the inferior, as it appears in the file, and
16895 you can determine the address at which every section was loaded, and
16896 provide these to the @code{add-symbol-file} command.
16900 Some embedded operating systems, like Sun Chorus and VxWorks, can load
16901 relocatable files into an already running program; such systems
16902 typically make the requirements above easy to meet. However, it's
16903 important to recognize that many native systems use complex link
16904 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
16905 assembly, for example) that make the requirements difficult to meet. In
16906 general, one cannot assume that using @code{add-symbol-file} to read a
16907 relocatable object file's symbolic information will have the same effect
16908 as linking the relocatable object file into the program in the normal
16911 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
16913 @kindex remove-symbol-file
16914 @item remove-symbol-file @var{filename}
16915 @item remove-symbol-file -a @var{address}
16916 Remove a symbol file added via the @code{add-symbol-file} command. The
16917 file to remove can be identified by its @var{filename} or by an @var{address}
16918 that lies within the boundaries of this symbol file in memory. Example:
16921 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
16922 add symbol table from file "/home/user/gdb/mylib.so" at
16923 .text_addr = 0x7ffff7ff9480
16925 Reading symbols from /home/user/gdb/mylib.so...done.
16926 (gdb) remove-symbol-file -a 0x7ffff7ff9480
16927 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
16932 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
16934 @kindex add-symbol-file-from-memory
16935 @cindex @code{syscall DSO}
16936 @cindex load symbols from memory
16937 @item add-symbol-file-from-memory @var{address}
16938 Load symbols from the given @var{address} in a dynamically loaded
16939 object file whose image is mapped directly into the inferior's memory.
16940 For example, the Linux kernel maps a @code{syscall DSO} into each
16941 process's address space; this DSO provides kernel-specific code for
16942 some system calls. The argument can be any expression whose
16943 evaluation yields the address of the file's shared object file header.
16944 For this command to work, you must have used @code{symbol-file} or
16945 @code{exec-file} commands in advance.
16947 @kindex add-shared-symbol-files
16949 @item add-shared-symbol-files @var{library-file}
16950 @itemx assf @var{library-file}
16951 This command is deprecated and will be removed in future versions
16952 of @value{GDBN}. Use the @code{sharedlibrary} command instead.
16954 The @code{add-shared-symbol-files} command can currently be used only
16955 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
16956 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
16957 @value{GDBN} automatically looks for shared libraries, however if
16958 @value{GDBN} does not find yours, you can invoke
16959 @code{add-shared-symbol-files}. It takes one argument: the shared
16960 library's file name. @code{assf} is a shorthand alias for
16961 @code{add-shared-symbol-files}.
16964 @item section @var{section} @var{addr}
16965 The @code{section} command changes the base address of the named
16966 @var{section} of the exec file to @var{addr}. This can be used if the
16967 exec file does not contain section addresses, (such as in the
16968 @code{a.out} format), or when the addresses specified in the file
16969 itself are wrong. Each section must be changed separately. The
16970 @code{info files} command, described below, lists all the sections and
16974 @kindex info target
16977 @code{info files} and @code{info target} are synonymous; both print the
16978 current target (@pxref{Targets, ,Specifying a Debugging Target}),
16979 including the names of the executable and core dump files currently in
16980 use by @value{GDBN}, and the files from which symbols were loaded. The
16981 command @code{help target} lists all possible targets rather than
16984 @kindex maint info sections
16985 @item maint info sections
16986 Another command that can give you extra information about program sections
16987 is @code{maint info sections}. In addition to the section information
16988 displayed by @code{info files}, this command displays the flags and file
16989 offset of each section in the executable and core dump files. In addition,
16990 @code{maint info sections} provides the following command options (which
16991 may be arbitrarily combined):
16995 Display sections for all loaded object files, including shared libraries.
16996 @item @var{sections}
16997 Display info only for named @var{sections}.
16998 @item @var{section-flags}
16999 Display info only for sections for which @var{section-flags} are true.
17000 The section flags that @value{GDBN} currently knows about are:
17003 Section will have space allocated in the process when loaded.
17004 Set for all sections except those containing debug information.
17006 Section will be loaded from the file into the child process memory.
17007 Set for pre-initialized code and data, clear for @code{.bss} sections.
17009 Section needs to be relocated before loading.
17011 Section cannot be modified by the child process.
17013 Section contains executable code only.
17015 Section contains data only (no executable code).
17017 Section will reside in ROM.
17019 Section contains data for constructor/destructor lists.
17021 Section is not empty.
17023 An instruction to the linker to not output the section.
17024 @item COFF_SHARED_LIBRARY
17025 A notification to the linker that the section contains
17026 COFF shared library information.
17028 Section contains common symbols.
17031 @kindex set trust-readonly-sections
17032 @cindex read-only sections
17033 @item set trust-readonly-sections on
17034 Tell @value{GDBN} that readonly sections in your object file
17035 really are read-only (i.e.@: that their contents will not change).
17036 In that case, @value{GDBN} can fetch values from these sections
17037 out of the object file, rather than from the target program.
17038 For some targets (notably embedded ones), this can be a significant
17039 enhancement to debugging performance.
17041 The default is off.
17043 @item set trust-readonly-sections off
17044 Tell @value{GDBN} not to trust readonly sections. This means that
17045 the contents of the section might change while the program is running,
17046 and must therefore be fetched from the target when needed.
17048 @item show trust-readonly-sections
17049 Show the current setting of trusting readonly sections.
17052 All file-specifying commands allow both absolute and relative file names
17053 as arguments. @value{GDBN} always converts the file name to an absolute file
17054 name and remembers it that way.
17056 @cindex shared libraries
17057 @anchor{Shared Libraries}
17058 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
17059 and IBM RS/6000 AIX shared libraries.
17061 On MS-Windows @value{GDBN} must be linked with the Expat library to support
17062 shared libraries. @xref{Expat}.
17064 @value{GDBN} automatically loads symbol definitions from shared libraries
17065 when you use the @code{run} command, or when you examine a core file.
17066 (Before you issue the @code{run} command, @value{GDBN} does not understand
17067 references to a function in a shared library, however---unless you are
17068 debugging a core file).
17070 On HP-UX, if the program loads a library explicitly, @value{GDBN}
17071 automatically loads the symbols at the time of the @code{shl_load} call.
17073 @c FIXME: some @value{GDBN} release may permit some refs to undef
17074 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
17075 @c FIXME...lib; check this from time to time when updating manual
17077 There are times, however, when you may wish to not automatically load
17078 symbol definitions from shared libraries, such as when they are
17079 particularly large or there are many of them.
17081 To control the automatic loading of shared library symbols, use the
17085 @kindex set auto-solib-add
17086 @item set auto-solib-add @var{mode}
17087 If @var{mode} is @code{on}, symbols from all shared object libraries
17088 will be loaded automatically when the inferior begins execution, you
17089 attach to an independently started inferior, or when the dynamic linker
17090 informs @value{GDBN} that a new library has been loaded. If @var{mode}
17091 is @code{off}, symbols must be loaded manually, using the
17092 @code{sharedlibrary} command. The default value is @code{on}.
17094 @cindex memory used for symbol tables
17095 If your program uses lots of shared libraries with debug info that
17096 takes large amounts of memory, you can decrease the @value{GDBN}
17097 memory footprint by preventing it from automatically loading the
17098 symbols from shared libraries. To that end, type @kbd{set
17099 auto-solib-add off} before running the inferior, then load each
17100 library whose debug symbols you do need with @kbd{sharedlibrary
17101 @var{regexp}}, where @var{regexp} is a regular expression that matches
17102 the libraries whose symbols you want to be loaded.
17104 @kindex show auto-solib-add
17105 @item show auto-solib-add
17106 Display the current autoloading mode.
17109 @cindex load shared library
17110 To explicitly load shared library symbols, use the @code{sharedlibrary}
17114 @kindex info sharedlibrary
17116 @item info share @var{regex}
17117 @itemx info sharedlibrary @var{regex}
17118 Print the names of the shared libraries which are currently loaded
17119 that match @var{regex}. If @var{regex} is omitted then print
17120 all shared libraries that are loaded.
17122 @kindex sharedlibrary
17124 @item sharedlibrary @var{regex}
17125 @itemx share @var{regex}
17126 Load shared object library symbols for files matching a
17127 Unix regular expression.
17128 As with files loaded automatically, it only loads shared libraries
17129 required by your program for a core file or after typing @code{run}. If
17130 @var{regex} is omitted all shared libraries required by your program are
17133 @item nosharedlibrary
17134 @kindex nosharedlibrary
17135 @cindex unload symbols from shared libraries
17136 Unload all shared object library symbols. This discards all symbols
17137 that have been loaded from all shared libraries. Symbols from shared
17138 libraries that were loaded by explicit user requests are not
17142 Sometimes you may wish that @value{GDBN} stops and gives you control
17143 when any of shared library events happen. The best way to do this is
17144 to use @code{catch load} and @code{catch unload} (@pxref{Set
17147 @value{GDBN} also supports the the @code{set stop-on-solib-events}
17148 command for this. This command exists for historical reasons. It is
17149 less useful than setting a catchpoint, because it does not allow for
17150 conditions or commands as a catchpoint does.
17153 @item set stop-on-solib-events
17154 @kindex set stop-on-solib-events
17155 This command controls whether @value{GDBN} should give you control
17156 when the dynamic linker notifies it about some shared library event.
17157 The most common event of interest is loading or unloading of a new
17160 @item show stop-on-solib-events
17161 @kindex show stop-on-solib-events
17162 Show whether @value{GDBN} stops and gives you control when shared
17163 library events happen.
17166 Shared libraries are also supported in many cross or remote debugging
17167 configurations. @value{GDBN} needs to have access to the target's libraries;
17168 this can be accomplished either by providing copies of the libraries
17169 on the host system, or by asking @value{GDBN} to automatically retrieve the
17170 libraries from the target. If copies of the target libraries are
17171 provided, they need to be the same as the target libraries, although the
17172 copies on the target can be stripped as long as the copies on the host are
17175 @cindex where to look for shared libraries
17176 For remote debugging, you need to tell @value{GDBN} where the target
17177 libraries are, so that it can load the correct copies---otherwise, it
17178 may try to load the host's libraries. @value{GDBN} has two variables
17179 to specify the search directories for target libraries.
17182 @cindex prefix for shared library file names
17183 @cindex system root, alternate
17184 @kindex set solib-absolute-prefix
17185 @kindex set sysroot
17186 @item set sysroot @var{path}
17187 Use @var{path} as the system root for the program being debugged. Any
17188 absolute shared library paths will be prefixed with @var{path}; many
17189 runtime loaders store the absolute paths to the shared library in the
17190 target program's memory. If you use @code{set sysroot} to find shared
17191 libraries, they need to be laid out in the same way that they are on
17192 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
17195 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
17196 retrieve the target libraries from the remote system. This is only
17197 supported when using a remote target that supports the @code{remote get}
17198 command (@pxref{File Transfer,,Sending files to a remote system}).
17199 The part of @var{path} following the initial @file{remote:}
17200 (if present) is used as system root prefix on the remote file system.
17201 @footnote{If you want to specify a local system root using a directory
17202 that happens to be named @file{remote:}, you need to use some equivalent
17203 variant of the name like @file{./remote:}.}
17205 For targets with an MS-DOS based filesystem, such as MS-Windows and
17206 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
17207 absolute file name with @var{path}. But first, on Unix hosts,
17208 @value{GDBN} converts all backslash directory separators into forward
17209 slashes, because the backslash is not a directory separator on Unix:
17212 c:\foo\bar.dll @result{} c:/foo/bar.dll
17215 Then, @value{GDBN} attempts prefixing the target file name with
17216 @var{path}, and looks for the resulting file name in the host file
17220 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
17223 If that does not find the shared library, @value{GDBN} tries removing
17224 the @samp{:} character from the drive spec, both for convenience, and,
17225 for the case of the host file system not supporting file names with
17229 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
17232 This makes it possible to have a system root that mirrors a target
17233 with more than one drive. E.g., you may want to setup your local
17234 copies of the target system shared libraries like so (note @samp{c} vs
17238 @file{/path/to/sysroot/c/sys/bin/foo.dll}
17239 @file{/path/to/sysroot/c/sys/bin/bar.dll}
17240 @file{/path/to/sysroot/z/sys/bin/bar.dll}
17244 and point the system root at @file{/path/to/sysroot}, so that
17245 @value{GDBN} can find the correct copies of both
17246 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
17248 If that still does not find the shared library, @value{GDBN} tries
17249 removing the whole drive spec from the target file name:
17252 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
17255 This last lookup makes it possible to not care about the drive name,
17256 if you don't want or need to.
17258 The @code{set solib-absolute-prefix} command is an alias for @code{set
17261 @cindex default system root
17262 @cindex @samp{--with-sysroot}
17263 You can set the default system root by using the configure-time
17264 @samp{--with-sysroot} option. If the system root is inside
17265 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17266 @samp{--exec-prefix}), then the default system root will be updated
17267 automatically if the installed @value{GDBN} is moved to a new
17270 @kindex show sysroot
17272 Display the current shared library prefix.
17274 @kindex set solib-search-path
17275 @item set solib-search-path @var{path}
17276 If this variable is set, @var{path} is a colon-separated list of
17277 directories to search for shared libraries. @samp{solib-search-path}
17278 is used after @samp{sysroot} fails to locate the library, or if the
17279 path to the library is relative instead of absolute. If you want to
17280 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
17281 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
17282 finding your host's libraries. @samp{sysroot} is preferred; setting
17283 it to a nonexistent directory may interfere with automatic loading
17284 of shared library symbols.
17286 @kindex show solib-search-path
17287 @item show solib-search-path
17288 Display the current shared library search path.
17290 @cindex DOS file-name semantics of file names.
17291 @kindex set target-file-system-kind (unix|dos-based|auto)
17292 @kindex show target-file-system-kind
17293 @item set target-file-system-kind @var{kind}
17294 Set assumed file system kind for target reported file names.
17296 Shared library file names as reported by the target system may not
17297 make sense as is on the system @value{GDBN} is running on. For
17298 example, when remote debugging a target that has MS-DOS based file
17299 system semantics, from a Unix host, the target may be reporting to
17300 @value{GDBN} a list of loaded shared libraries with file names such as
17301 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
17302 drive letters, so the @samp{c:\} prefix is not normally understood as
17303 indicating an absolute file name, and neither is the backslash
17304 normally considered a directory separator character. In that case,
17305 the native file system would interpret this whole absolute file name
17306 as a relative file name with no directory components. This would make
17307 it impossible to point @value{GDBN} at a copy of the remote target's
17308 shared libraries on the host using @code{set sysroot}, and impractical
17309 with @code{set solib-search-path}. Setting
17310 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
17311 to interpret such file names similarly to how the target would, and to
17312 map them to file names valid on @value{GDBN}'s native file system
17313 semantics. The value of @var{kind} can be @code{"auto"}, in addition
17314 to one of the supported file system kinds. In that case, @value{GDBN}
17315 tries to determine the appropriate file system variant based on the
17316 current target's operating system (@pxref{ABI, ,Configuring the
17317 Current ABI}). The supported file system settings are:
17321 Instruct @value{GDBN} to assume the target file system is of Unix
17322 kind. Only file names starting the forward slash (@samp{/}) character
17323 are considered absolute, and the directory separator character is also
17327 Instruct @value{GDBN} to assume the target file system is DOS based.
17328 File names starting with either a forward slash, or a drive letter
17329 followed by a colon (e.g., @samp{c:}), are considered absolute, and
17330 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
17331 considered directory separators.
17334 Instruct @value{GDBN} to use the file system kind associated with the
17335 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
17336 This is the default.
17340 @cindex file name canonicalization
17341 @cindex base name differences
17342 When processing file names provided by the user, @value{GDBN}
17343 frequently needs to compare them to the file names recorded in the
17344 program's debug info. Normally, @value{GDBN} compares just the
17345 @dfn{base names} of the files as strings, which is reasonably fast
17346 even for very large programs. (The base name of a file is the last
17347 portion of its name, after stripping all the leading directories.)
17348 This shortcut in comparison is based upon the assumption that files
17349 cannot have more than one base name. This is usually true, but
17350 references to files that use symlinks or similar filesystem
17351 facilities violate that assumption. If your program records files
17352 using such facilities, or if you provide file names to @value{GDBN}
17353 using symlinks etc., you can set @code{basenames-may-differ} to
17354 @code{true} to instruct @value{GDBN} to completely canonicalize each
17355 pair of file names it needs to compare. This will make file-name
17356 comparisons accurate, but at a price of a significant slowdown.
17359 @item set basenames-may-differ
17360 @kindex set basenames-may-differ
17361 Set whether a source file may have multiple base names.
17363 @item show basenames-may-differ
17364 @kindex show basenames-may-differ
17365 Show whether a source file may have multiple base names.
17368 @node Separate Debug Files
17369 @section Debugging Information in Separate Files
17370 @cindex separate debugging information files
17371 @cindex debugging information in separate files
17372 @cindex @file{.debug} subdirectories
17373 @cindex debugging information directory, global
17374 @cindex global debugging information directories
17375 @cindex build ID, and separate debugging files
17376 @cindex @file{.build-id} directory
17378 @value{GDBN} allows you to put a program's debugging information in a
17379 file separate from the executable itself, in a way that allows
17380 @value{GDBN} to find and load the debugging information automatically.
17381 Since debugging information can be very large---sometimes larger
17382 than the executable code itself---some systems distribute debugging
17383 information for their executables in separate files, which users can
17384 install only when they need to debug a problem.
17386 @value{GDBN} supports two ways of specifying the separate debug info
17391 The executable contains a @dfn{debug link} that specifies the name of
17392 the separate debug info file. The separate debug file's name is
17393 usually @file{@var{executable}.debug}, where @var{executable} is the
17394 name of the corresponding executable file without leading directories
17395 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
17396 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
17397 checksum for the debug file, which @value{GDBN} uses to validate that
17398 the executable and the debug file came from the same build.
17401 The executable contains a @dfn{build ID}, a unique bit string that is
17402 also present in the corresponding debug info file. (This is supported
17403 only on some operating systems, notably those which use the ELF format
17404 for binary files and the @sc{gnu} Binutils.) For more details about
17405 this feature, see the description of the @option{--build-id}
17406 command-line option in @ref{Options, , Command Line Options, ld.info,
17407 The GNU Linker}. The debug info file's name is not specified
17408 explicitly by the build ID, but can be computed from the build ID, see
17412 Depending on the way the debug info file is specified, @value{GDBN}
17413 uses two different methods of looking for the debug file:
17417 For the ``debug link'' method, @value{GDBN} looks up the named file in
17418 the directory of the executable file, then in a subdirectory of that
17419 directory named @file{.debug}, and finally under each one of the global debug
17420 directories, in a subdirectory whose name is identical to the leading
17421 directories of the executable's absolute file name.
17424 For the ``build ID'' method, @value{GDBN} looks in the
17425 @file{.build-id} subdirectory of each one of the global debug directories for
17426 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
17427 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
17428 are the rest of the bit string. (Real build ID strings are 32 or more
17429 hex characters, not 10.)
17432 So, for example, suppose you ask @value{GDBN} to debug
17433 @file{/usr/bin/ls}, which has a debug link that specifies the
17434 file @file{ls.debug}, and a build ID whose value in hex is
17435 @code{abcdef1234}. If the list of the global debug directories includes
17436 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
17437 debug information files, in the indicated order:
17441 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
17443 @file{/usr/bin/ls.debug}
17445 @file{/usr/bin/.debug/ls.debug}
17447 @file{/usr/lib/debug/usr/bin/ls.debug}.
17450 @anchor{debug-file-directory}
17451 Global debugging info directories default to what is set by @value{GDBN}
17452 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
17453 you can also set the global debugging info directories, and view the list
17454 @value{GDBN} is currently using.
17458 @kindex set debug-file-directory
17459 @item set debug-file-directory @var{directories}
17460 Set the directories which @value{GDBN} searches for separate debugging
17461 information files to @var{directory}. Multiple path components can be set
17462 concatenating them by a path separator.
17464 @kindex show debug-file-directory
17465 @item show debug-file-directory
17466 Show the directories @value{GDBN} searches for separate debugging
17471 @cindex @code{.gnu_debuglink} sections
17472 @cindex debug link sections
17473 A debug link is a special section of the executable file named
17474 @code{.gnu_debuglink}. The section must contain:
17478 A filename, with any leading directory components removed, followed by
17481 zero to three bytes of padding, as needed to reach the next four-byte
17482 boundary within the section, and
17484 a four-byte CRC checksum, stored in the same endianness used for the
17485 executable file itself. The checksum is computed on the debugging
17486 information file's full contents by the function given below, passing
17487 zero as the @var{crc} argument.
17490 Any executable file format can carry a debug link, as long as it can
17491 contain a section named @code{.gnu_debuglink} with the contents
17494 @cindex @code{.note.gnu.build-id} sections
17495 @cindex build ID sections
17496 The build ID is a special section in the executable file (and in other
17497 ELF binary files that @value{GDBN} may consider). This section is
17498 often named @code{.note.gnu.build-id}, but that name is not mandatory.
17499 It contains unique identification for the built files---the ID remains
17500 the same across multiple builds of the same build tree. The default
17501 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
17502 content for the build ID string. The same section with an identical
17503 value is present in the original built binary with symbols, in its
17504 stripped variant, and in the separate debugging information file.
17506 The debugging information file itself should be an ordinary
17507 executable, containing a full set of linker symbols, sections, and
17508 debugging information. The sections of the debugging information file
17509 should have the same names, addresses, and sizes as the original file,
17510 but they need not contain any data---much like a @code{.bss} section
17511 in an ordinary executable.
17513 The @sc{gnu} binary utilities (Binutils) package includes the
17514 @samp{objcopy} utility that can produce
17515 the separated executable / debugging information file pairs using the
17516 following commands:
17519 @kbd{objcopy --only-keep-debug foo foo.debug}
17524 These commands remove the debugging
17525 information from the executable file @file{foo} and place it in the file
17526 @file{foo.debug}. You can use the first, second or both methods to link the
17531 The debug link method needs the following additional command to also leave
17532 behind a debug link in @file{foo}:
17535 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
17538 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
17539 a version of the @code{strip} command such that the command @kbd{strip foo -f
17540 foo.debug} has the same functionality as the two @code{objcopy} commands and
17541 the @code{ln -s} command above, together.
17544 Build ID gets embedded into the main executable using @code{ld --build-id} or
17545 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
17546 compatibility fixes for debug files separation are present in @sc{gnu} binary
17547 utilities (Binutils) package since version 2.18.
17552 @cindex CRC algorithm definition
17553 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
17554 IEEE 802.3 using the polynomial:
17556 @c TexInfo requires naked braces for multi-digit exponents for Tex
17557 @c output, but this causes HTML output to barf. HTML has to be set using
17558 @c raw commands. So we end up having to specify this equation in 2
17563 <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>
17564 + <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
17570 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
17571 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
17575 The function is computed byte at a time, taking the least
17576 significant bit of each byte first. The initial pattern
17577 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
17578 the final result is inverted to ensure trailing zeros also affect the
17581 @emph{Note:} This is the same CRC polynomial as used in handling the
17582 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
17583 , @value{GDBN} Remote Serial Protocol}). However in the
17584 case of the Remote Serial Protocol, the CRC is computed @emph{most}
17585 significant bit first, and the result is not inverted, so trailing
17586 zeros have no effect on the CRC value.
17588 To complete the description, we show below the code of the function
17589 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
17590 initially supplied @code{crc} argument means that an initial call to
17591 this function passing in zero will start computing the CRC using
17594 @kindex gnu_debuglink_crc32
17597 gnu_debuglink_crc32 (unsigned long crc,
17598 unsigned char *buf, size_t len)
17600 static const unsigned long crc32_table[256] =
17602 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
17603 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
17604 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
17605 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
17606 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
17607 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
17608 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
17609 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
17610 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
17611 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
17612 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
17613 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
17614 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
17615 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
17616 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
17617 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
17618 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
17619 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
17620 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
17621 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
17622 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
17623 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
17624 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
17625 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
17626 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
17627 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
17628 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
17629 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
17630 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
17631 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
17632 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
17633 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
17634 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
17635 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
17636 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
17637 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
17638 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
17639 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
17640 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
17641 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
17642 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
17643 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
17644 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
17645 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
17646 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
17647 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
17648 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
17649 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
17650 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
17651 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
17652 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
17655 unsigned char *end;
17657 crc = ~crc & 0xffffffff;
17658 for (end = buf + len; buf < end; ++buf)
17659 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
17660 return ~crc & 0xffffffff;
17665 This computation does not apply to the ``build ID'' method.
17667 @node MiniDebugInfo
17668 @section Debugging information in a special section
17669 @cindex separate debug sections
17670 @cindex @samp{.gnu_debugdata} section
17672 Some systems ship pre-built executables and libraries that have a
17673 special @samp{.gnu_debugdata} section. This feature is called
17674 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
17675 is used to supply extra symbols for backtraces.
17677 The intent of this section is to provide extra minimal debugging
17678 information for use in simple backtraces. It is not intended to be a
17679 replacement for full separate debugging information (@pxref{Separate
17680 Debug Files}). The example below shows the intended use; however,
17681 @value{GDBN} does not currently put restrictions on what sort of
17682 debugging information might be included in the section.
17684 @value{GDBN} has support for this extension. If the section exists,
17685 then it is used provided that no other source of debugging information
17686 can be found, and that @value{GDBN} was configured with LZMA support.
17688 This section can be easily created using @command{objcopy} and other
17689 standard utilities:
17692 # Extract the dynamic symbols from the main binary, there is no need
17693 # to also have these in the normal symbol table.
17694 nm -D @var{binary} --format=posix --defined-only \
17695 | awk '@{ print $1 @}' | sort > dynsyms
17697 # Extract all the text (i.e. function) symbols from the debuginfo.
17698 # (Note that we actually also accept "D" symbols, for the benefit
17699 # of platforms like PowerPC64 that use function descriptors.)
17700 nm @var{binary} --format=posix --defined-only \
17701 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
17704 # Keep all the function symbols not already in the dynamic symbol
17706 comm -13 dynsyms funcsyms > keep_symbols
17708 # Separate full debug info into debug binary.
17709 objcopy --only-keep-debug @var{binary} debug
17711 # Copy the full debuginfo, keeping only a minimal set of symbols and
17712 # removing some unnecessary sections.
17713 objcopy -S --remove-section .gdb_index --remove-section .comment \
17714 --keep-symbols=keep_symbols debug mini_debuginfo
17716 # Drop the full debug info from the original binary.
17717 strip --strip-all -R .comment @var{binary}
17719 # Inject the compressed data into the .gnu_debugdata section of the
17722 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
17726 @section Index Files Speed Up @value{GDBN}
17727 @cindex index files
17728 @cindex @samp{.gdb_index} section
17730 When @value{GDBN} finds a symbol file, it scans the symbols in the
17731 file in order to construct an internal symbol table. This lets most
17732 @value{GDBN} operations work quickly---at the cost of a delay early
17733 on. For large programs, this delay can be quite lengthy, so
17734 @value{GDBN} provides a way to build an index, which speeds up
17737 The index is stored as a section in the symbol file. @value{GDBN} can
17738 write the index to a file, then you can put it into the symbol file
17739 using @command{objcopy}.
17741 To create an index file, use the @code{save gdb-index} command:
17744 @item save gdb-index @var{directory}
17745 @kindex save gdb-index
17746 Create an index file for each symbol file currently known by
17747 @value{GDBN}. Each file is named after its corresponding symbol file,
17748 with @samp{.gdb-index} appended, and is written into the given
17752 Once you have created an index file you can merge it into your symbol
17753 file, here named @file{symfile}, using @command{objcopy}:
17756 $ objcopy --add-section .gdb_index=symfile.gdb-index \
17757 --set-section-flags .gdb_index=readonly symfile symfile
17760 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
17761 sections that have been deprecated. Usually they are deprecated because
17762 they are missing a new feature or have performance issues.
17763 To tell @value{GDBN} to use a deprecated index section anyway
17764 specify @code{set use-deprecated-index-sections on}.
17765 The default is @code{off}.
17766 This can speed up startup, but may result in some functionality being lost.
17767 @xref{Index Section Format}.
17769 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
17770 must be done before gdb reads the file. The following will not work:
17773 $ gdb -ex "set use-deprecated-index-sections on" <program>
17776 Instead you must do, for example,
17779 $ gdb -iex "set use-deprecated-index-sections on" <program>
17782 There are currently some limitation on indices. They only work when
17783 for DWARF debugging information, not stabs. And, they do not
17784 currently work for programs using Ada.
17786 @node Symbol Errors
17787 @section Errors Reading Symbol Files
17789 While reading a symbol file, @value{GDBN} occasionally encounters problems,
17790 such as symbol types it does not recognize, or known bugs in compiler
17791 output. By default, @value{GDBN} does not notify you of such problems, since
17792 they are relatively common and primarily of interest to people
17793 debugging compilers. If you are interested in seeing information
17794 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
17795 only one message about each such type of problem, no matter how many
17796 times the problem occurs; or you can ask @value{GDBN} to print more messages,
17797 to see how many times the problems occur, with the @code{set
17798 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
17801 The messages currently printed, and their meanings, include:
17804 @item inner block not inside outer block in @var{symbol}
17806 The symbol information shows where symbol scopes begin and end
17807 (such as at the start of a function or a block of statements). This
17808 error indicates that an inner scope block is not fully contained
17809 in its outer scope blocks.
17811 @value{GDBN} circumvents the problem by treating the inner block as if it had
17812 the same scope as the outer block. In the error message, @var{symbol}
17813 may be shown as ``@code{(don't know)}'' if the outer block is not a
17816 @item block at @var{address} out of order
17818 The symbol information for symbol scope blocks should occur in
17819 order of increasing addresses. This error indicates that it does not
17822 @value{GDBN} does not circumvent this problem, and has trouble
17823 locating symbols in the source file whose symbols it is reading. (You
17824 can often determine what source file is affected by specifying
17825 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
17828 @item bad block start address patched
17830 The symbol information for a symbol scope block has a start address
17831 smaller than the address of the preceding source line. This is known
17832 to occur in the SunOS 4.1.1 (and earlier) C compiler.
17834 @value{GDBN} circumvents the problem by treating the symbol scope block as
17835 starting on the previous source line.
17837 @item bad string table offset in symbol @var{n}
17840 Symbol number @var{n} contains a pointer into the string table which is
17841 larger than the size of the string table.
17843 @value{GDBN} circumvents the problem by considering the symbol to have the
17844 name @code{foo}, which may cause other problems if many symbols end up
17847 @item unknown symbol type @code{0x@var{nn}}
17849 The symbol information contains new data types that @value{GDBN} does
17850 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
17851 uncomprehended information, in hexadecimal.
17853 @value{GDBN} circumvents the error by ignoring this symbol information.
17854 This usually allows you to debug your program, though certain symbols
17855 are not accessible. If you encounter such a problem and feel like
17856 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
17857 on @code{complain}, then go up to the function @code{read_dbx_symtab}
17858 and examine @code{*bufp} to see the symbol.
17860 @item stub type has NULL name
17862 @value{GDBN} could not find the full definition for a struct or class.
17864 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
17865 The symbol information for a C@t{++} member function is missing some
17866 information that recent versions of the compiler should have output for
17869 @item info mismatch between compiler and debugger
17871 @value{GDBN} could not parse a type specification output by the compiler.
17876 @section GDB Data Files
17878 @cindex prefix for data files
17879 @value{GDBN} will sometimes read an auxiliary data file. These files
17880 are kept in a directory known as the @dfn{data directory}.
17882 You can set the data directory's name, and view the name @value{GDBN}
17883 is currently using.
17886 @kindex set data-directory
17887 @item set data-directory @var{directory}
17888 Set the directory which @value{GDBN} searches for auxiliary data files
17889 to @var{directory}.
17891 @kindex show data-directory
17892 @item show data-directory
17893 Show the directory @value{GDBN} searches for auxiliary data files.
17896 @cindex default data directory
17897 @cindex @samp{--with-gdb-datadir}
17898 You can set the default data directory by using the configure-time
17899 @samp{--with-gdb-datadir} option. If the data directory is inside
17900 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17901 @samp{--exec-prefix}), then the default data directory will be updated
17902 automatically if the installed @value{GDBN} is moved to a new
17905 The data directory may also be specified with the
17906 @code{--data-directory} command line option.
17907 @xref{Mode Options}.
17910 @chapter Specifying a Debugging Target
17912 @cindex debugging target
17913 A @dfn{target} is the execution environment occupied by your program.
17915 Often, @value{GDBN} runs in the same host environment as your program;
17916 in that case, the debugging target is specified as a side effect when
17917 you use the @code{file} or @code{core} commands. When you need more
17918 flexibility---for example, running @value{GDBN} on a physically separate
17919 host, or controlling a standalone system over a serial port or a
17920 realtime system over a TCP/IP connection---you can use the @code{target}
17921 command to specify one of the target types configured for @value{GDBN}
17922 (@pxref{Target Commands, ,Commands for Managing Targets}).
17924 @cindex target architecture
17925 It is possible to build @value{GDBN} for several different @dfn{target
17926 architectures}. When @value{GDBN} is built like that, you can choose
17927 one of the available architectures with the @kbd{set architecture}
17931 @kindex set architecture
17932 @kindex show architecture
17933 @item set architecture @var{arch}
17934 This command sets the current target architecture to @var{arch}. The
17935 value of @var{arch} can be @code{"auto"}, in addition to one of the
17936 supported architectures.
17938 @item show architecture
17939 Show the current target architecture.
17941 @item set processor
17943 @kindex set processor
17944 @kindex show processor
17945 These are alias commands for, respectively, @code{set architecture}
17946 and @code{show architecture}.
17950 * Active Targets:: Active targets
17951 * Target Commands:: Commands for managing targets
17952 * Byte Order:: Choosing target byte order
17955 @node Active Targets
17956 @section Active Targets
17958 @cindex stacking targets
17959 @cindex active targets
17960 @cindex multiple targets
17962 There are multiple classes of targets such as: processes, executable files or
17963 recording sessions. Core files belong to the process class, making core file
17964 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
17965 on multiple active targets, one in each class. This allows you to (for
17966 example) start a process and inspect its activity, while still having access to
17967 the executable file after the process finishes. Or if you start process
17968 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
17969 presented a virtual layer of the recording target, while the process target
17970 remains stopped at the chronologically last point of the process execution.
17972 Use the @code{core-file} and @code{exec-file} commands to select a new core
17973 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
17974 specify as a target a process that is already running, use the @code{attach}
17975 command (@pxref{Attach, ,Debugging an Already-running Process}).
17977 @node Target Commands
17978 @section Commands for Managing Targets
17981 @item target @var{type} @var{parameters}
17982 Connects the @value{GDBN} host environment to a target machine or
17983 process. A target is typically a protocol for talking to debugging
17984 facilities. You use the argument @var{type} to specify the type or
17985 protocol of the target machine.
17987 Further @var{parameters} are interpreted by the target protocol, but
17988 typically include things like device names or host names to connect
17989 with, process numbers, and baud rates.
17991 The @code{target} command does not repeat if you press @key{RET} again
17992 after executing the command.
17994 @kindex help target
17996 Displays the names of all targets available. To display targets
17997 currently selected, use either @code{info target} or @code{info files}
17998 (@pxref{Files, ,Commands to Specify Files}).
18000 @item help target @var{name}
18001 Describe a particular target, including any parameters necessary to
18004 @kindex set gnutarget
18005 @item set gnutarget @var{args}
18006 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
18007 knows whether it is reading an @dfn{executable},
18008 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
18009 with the @code{set gnutarget} command. Unlike most @code{target} commands,
18010 with @code{gnutarget} the @code{target} refers to a program, not a machine.
18013 @emph{Warning:} To specify a file format with @code{set gnutarget},
18014 you must know the actual BFD name.
18018 @xref{Files, , Commands to Specify Files}.
18020 @kindex show gnutarget
18021 @item show gnutarget
18022 Use the @code{show gnutarget} command to display what file format
18023 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
18024 @value{GDBN} will determine the file format for each file automatically,
18025 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
18028 @cindex common targets
18029 Here are some common targets (available, or not, depending on the GDB
18034 @item target exec @var{program}
18035 @cindex executable file target
18036 An executable file. @samp{target exec @var{program}} is the same as
18037 @samp{exec-file @var{program}}.
18039 @item target core @var{filename}
18040 @cindex core dump file target
18041 A core dump file. @samp{target core @var{filename}} is the same as
18042 @samp{core-file @var{filename}}.
18044 @item target remote @var{medium}
18045 @cindex remote target
18046 A remote system connected to @value{GDBN} via a serial line or network
18047 connection. This command tells @value{GDBN} to use its own remote
18048 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
18050 For example, if you have a board connected to @file{/dev/ttya} on the
18051 machine running @value{GDBN}, you could say:
18054 target remote /dev/ttya
18057 @code{target remote} supports the @code{load} command. This is only
18058 useful if you have some other way of getting the stub to the target
18059 system, and you can put it somewhere in memory where it won't get
18060 clobbered by the download.
18062 @item target sim @r{[}@var{simargs}@r{]} @dots{}
18063 @cindex built-in simulator target
18064 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
18072 works; however, you cannot assume that a specific memory map, device
18073 drivers, or even basic I/O is available, although some simulators do
18074 provide these. For info about any processor-specific simulator details,
18075 see the appropriate section in @ref{Embedded Processors, ,Embedded
18080 Different targets are available on different configurations of @value{GDBN};
18081 your configuration may have more or fewer targets.
18083 Many remote targets require you to download the executable's code once
18084 you've successfully established a connection. You may wish to control
18085 various aspects of this process.
18090 @kindex set hash@r{, for remote monitors}
18091 @cindex hash mark while downloading
18092 This command controls whether a hash mark @samp{#} is displayed while
18093 downloading a file to the remote monitor. If on, a hash mark is
18094 displayed after each S-record is successfully downloaded to the
18098 @kindex show hash@r{, for remote monitors}
18099 Show the current status of displaying the hash mark.
18101 @item set debug monitor
18102 @kindex set debug monitor
18103 @cindex display remote monitor communications
18104 Enable or disable display of communications messages between
18105 @value{GDBN} and the remote monitor.
18107 @item show debug monitor
18108 @kindex show debug monitor
18109 Show the current status of displaying communications between
18110 @value{GDBN} and the remote monitor.
18115 @kindex load @var{filename}
18116 @item load @var{filename}
18118 Depending on what remote debugging facilities are configured into
18119 @value{GDBN}, the @code{load} command may be available. Where it exists, it
18120 is meant to make @var{filename} (an executable) available for debugging
18121 on the remote system---by downloading, or dynamic linking, for example.
18122 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
18123 the @code{add-symbol-file} command.
18125 If your @value{GDBN} does not have a @code{load} command, attempting to
18126 execute it gets the error message ``@code{You can't do that when your
18127 target is @dots{}}''
18129 The file is loaded at whatever address is specified in the executable.
18130 For some object file formats, you can specify the load address when you
18131 link the program; for other formats, like a.out, the object file format
18132 specifies a fixed address.
18133 @c FIXME! This would be a good place for an xref to the GNU linker doc.
18135 Depending on the remote side capabilities, @value{GDBN} may be able to
18136 load programs into flash memory.
18138 @code{load} does not repeat if you press @key{RET} again after using it.
18142 @section Choosing Target Byte Order
18144 @cindex choosing target byte order
18145 @cindex target byte order
18147 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
18148 offer the ability to run either big-endian or little-endian byte
18149 orders. Usually the executable or symbol will include a bit to
18150 designate the endian-ness, and you will not need to worry about
18151 which to use. However, you may still find it useful to adjust
18152 @value{GDBN}'s idea of processor endian-ness manually.
18156 @item set endian big
18157 Instruct @value{GDBN} to assume the target is big-endian.
18159 @item set endian little
18160 Instruct @value{GDBN} to assume the target is little-endian.
18162 @item set endian auto
18163 Instruct @value{GDBN} to use the byte order associated with the
18167 Display @value{GDBN}'s current idea of the target byte order.
18171 Note that these commands merely adjust interpretation of symbolic
18172 data on the host, and that they have absolutely no effect on the
18176 @node Remote Debugging
18177 @chapter Debugging Remote Programs
18178 @cindex remote debugging
18180 If you are trying to debug a program running on a machine that cannot run
18181 @value{GDBN} in the usual way, it is often useful to use remote debugging.
18182 For example, you might use remote debugging on an operating system kernel,
18183 or on a small system which does not have a general purpose operating system
18184 powerful enough to run a full-featured debugger.
18186 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
18187 to make this work with particular debugging targets. In addition,
18188 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
18189 but not specific to any particular target system) which you can use if you
18190 write the remote stubs---the code that runs on the remote system to
18191 communicate with @value{GDBN}.
18193 Other remote targets may be available in your
18194 configuration of @value{GDBN}; use @code{help target} to list them.
18197 * Connecting:: Connecting to a remote target
18198 * File Transfer:: Sending files to a remote system
18199 * Server:: Using the gdbserver program
18200 * Remote Configuration:: Remote configuration
18201 * Remote Stub:: Implementing a remote stub
18205 @section Connecting to a Remote Target
18207 On the @value{GDBN} host machine, you will need an unstripped copy of
18208 your program, since @value{GDBN} needs symbol and debugging information.
18209 Start up @value{GDBN} as usual, using the name of the local copy of your
18210 program as the first argument.
18212 @cindex @code{target remote}
18213 @value{GDBN} can communicate with the target over a serial line, or
18214 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
18215 each case, @value{GDBN} uses the same protocol for debugging your
18216 program; only the medium carrying the debugging packets varies. The
18217 @code{target remote} command establishes a connection to the target.
18218 Its arguments indicate which medium to use:
18222 @item target remote @var{serial-device}
18223 @cindex serial line, @code{target remote}
18224 Use @var{serial-device} to communicate with the target. For example,
18225 to use a serial line connected to the device named @file{/dev/ttyb}:
18228 target remote /dev/ttyb
18231 If you're using a serial line, you may want to give @value{GDBN} the
18232 @samp{--baud} option, or use the @code{set serial baud} command
18233 (@pxref{Remote Configuration, set serial baud}) before the
18234 @code{target} command.
18236 @item target remote @code{@var{host}:@var{port}}
18237 @itemx target remote @code{tcp:@var{host}:@var{port}}
18238 @cindex @acronym{TCP} port, @code{target remote}
18239 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
18240 The @var{host} may be either a host name or a numeric @acronym{IP}
18241 address; @var{port} must be a decimal number. The @var{host} could be
18242 the target machine itself, if it is directly connected to the net, or
18243 it might be a terminal server which in turn has a serial line to the
18246 For example, to connect to port 2828 on a terminal server named
18250 target remote manyfarms:2828
18253 If your remote target is actually running on the same machine as your
18254 debugger session (e.g.@: a simulator for your target running on the
18255 same host), you can omit the hostname. For example, to connect to
18256 port 1234 on your local machine:
18259 target remote :1234
18263 Note that the colon is still required here.
18265 @item target remote @code{udp:@var{host}:@var{port}}
18266 @cindex @acronym{UDP} port, @code{target remote}
18267 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
18268 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
18271 target remote udp:manyfarms:2828
18274 When using a @acronym{UDP} connection for remote debugging, you should
18275 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
18276 can silently drop packets on busy or unreliable networks, which will
18277 cause havoc with your debugging session.
18279 @item target remote | @var{command}
18280 @cindex pipe, @code{target remote} to
18281 Run @var{command} in the background and communicate with it using a
18282 pipe. The @var{command} is a shell command, to be parsed and expanded
18283 by the system's command shell, @code{/bin/sh}; it should expect remote
18284 protocol packets on its standard input, and send replies on its
18285 standard output. You could use this to run a stand-alone simulator
18286 that speaks the remote debugging protocol, to make net connections
18287 using programs like @code{ssh}, or for other similar tricks.
18289 If @var{command} closes its standard output (perhaps by exiting),
18290 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
18291 program has already exited, this will have no effect.)
18295 Once the connection has been established, you can use all the usual
18296 commands to examine and change data. The remote program is already
18297 running; you can use @kbd{step} and @kbd{continue}, and you do not
18298 need to use @kbd{run}.
18300 @cindex interrupting remote programs
18301 @cindex remote programs, interrupting
18302 Whenever @value{GDBN} is waiting for the remote program, if you type the
18303 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
18304 program. This may or may not succeed, depending in part on the hardware
18305 and the serial drivers the remote system uses. If you type the
18306 interrupt character once again, @value{GDBN} displays this prompt:
18309 Interrupted while waiting for the program.
18310 Give up (and stop debugging it)? (y or n)
18313 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
18314 (If you decide you want to try again later, you can use @samp{target
18315 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
18316 goes back to waiting.
18319 @kindex detach (remote)
18321 When you have finished debugging the remote program, you can use the
18322 @code{detach} command to release it from @value{GDBN} control.
18323 Detaching from the target normally resumes its execution, but the results
18324 will depend on your particular remote stub. After the @code{detach}
18325 command, @value{GDBN} is free to connect to another target.
18329 The @code{disconnect} command behaves like @code{detach}, except that
18330 the target is generally not resumed. It will wait for @value{GDBN}
18331 (this instance or another one) to connect and continue debugging. After
18332 the @code{disconnect} command, @value{GDBN} is again free to connect to
18335 @cindex send command to remote monitor
18336 @cindex extend @value{GDBN} for remote targets
18337 @cindex add new commands for external monitor
18339 @item monitor @var{cmd}
18340 This command allows you to send arbitrary commands directly to the
18341 remote monitor. Since @value{GDBN} doesn't care about the commands it
18342 sends like this, this command is the way to extend @value{GDBN}---you
18343 can add new commands that only the external monitor will understand
18347 @node File Transfer
18348 @section Sending files to a remote system
18349 @cindex remote target, file transfer
18350 @cindex file transfer
18351 @cindex sending files to remote systems
18353 Some remote targets offer the ability to transfer files over the same
18354 connection used to communicate with @value{GDBN}. This is convenient
18355 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
18356 running @code{gdbserver} over a network interface. For other targets,
18357 e.g.@: embedded devices with only a single serial port, this may be
18358 the only way to upload or download files.
18360 Not all remote targets support these commands.
18364 @item remote put @var{hostfile} @var{targetfile}
18365 Copy file @var{hostfile} from the host system (the machine running
18366 @value{GDBN}) to @var{targetfile} on the target system.
18369 @item remote get @var{targetfile} @var{hostfile}
18370 Copy file @var{targetfile} from the target system to @var{hostfile}
18371 on the host system.
18373 @kindex remote delete
18374 @item remote delete @var{targetfile}
18375 Delete @var{targetfile} from the target system.
18380 @section Using the @code{gdbserver} Program
18383 @cindex remote connection without stubs
18384 @code{gdbserver} is a control program for Unix-like systems, which
18385 allows you to connect your program with a remote @value{GDBN} via
18386 @code{target remote}---but without linking in the usual debugging stub.
18388 @code{gdbserver} is not a complete replacement for the debugging stubs,
18389 because it requires essentially the same operating-system facilities
18390 that @value{GDBN} itself does. In fact, a system that can run
18391 @code{gdbserver} to connect to a remote @value{GDBN} could also run
18392 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
18393 because it is a much smaller program than @value{GDBN} itself. It is
18394 also easier to port than all of @value{GDBN}, so you may be able to get
18395 started more quickly on a new system by using @code{gdbserver}.
18396 Finally, if you develop code for real-time systems, you may find that
18397 the tradeoffs involved in real-time operation make it more convenient to
18398 do as much development work as possible on another system, for example
18399 by cross-compiling. You can use @code{gdbserver} to make a similar
18400 choice for debugging.
18402 @value{GDBN} and @code{gdbserver} communicate via either a serial line
18403 or a TCP connection, using the standard @value{GDBN} remote serial
18407 @emph{Warning:} @code{gdbserver} does not have any built-in security.
18408 Do not run @code{gdbserver} connected to any public network; a
18409 @value{GDBN} connection to @code{gdbserver} provides access to the
18410 target system with the same privileges as the user running
18414 @subsection Running @code{gdbserver}
18415 @cindex arguments, to @code{gdbserver}
18416 @cindex @code{gdbserver}, command-line arguments
18418 Run @code{gdbserver} on the target system. You need a copy of the
18419 program you want to debug, including any libraries it requires.
18420 @code{gdbserver} does not need your program's symbol table, so you can
18421 strip the program if necessary to save space. @value{GDBN} on the host
18422 system does all the symbol handling.
18424 To use the server, you must tell it how to communicate with @value{GDBN};
18425 the name of your program; and the arguments for your program. The usual
18429 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
18432 @var{comm} is either a device name (to use a serial line), or a TCP
18433 hostname and portnumber, or @code{-} or @code{stdio} to use
18434 stdin/stdout of @code{gdbserver}.
18435 For example, to debug Emacs with the argument
18436 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
18440 target> gdbserver /dev/com1 emacs foo.txt
18443 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
18446 To use a TCP connection instead of a serial line:
18449 target> gdbserver host:2345 emacs foo.txt
18452 The only difference from the previous example is the first argument,
18453 specifying that you are communicating with the host @value{GDBN} via
18454 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
18455 expect a TCP connection from machine @samp{host} to local TCP port 2345.
18456 (Currently, the @samp{host} part is ignored.) You can choose any number
18457 you want for the port number as long as it does not conflict with any
18458 TCP ports already in use on the target system (for example, @code{23} is
18459 reserved for @code{telnet}).@footnote{If you choose a port number that
18460 conflicts with another service, @code{gdbserver} prints an error message
18461 and exits.} You must use the same port number with the host @value{GDBN}
18462 @code{target remote} command.
18464 The @code{stdio} connection is useful when starting @code{gdbserver}
18468 (gdb) target remote | ssh -T hostname gdbserver - hello
18471 The @samp{-T} option to ssh is provided because we don't need a remote pty,
18472 and we don't want escape-character handling. Ssh does this by default when
18473 a command is provided, the flag is provided to make it explicit.
18474 You could elide it if you want to.
18476 Programs started with stdio-connected gdbserver have @file{/dev/null} for
18477 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
18478 display through a pipe connected to gdbserver.
18479 Both @code{stdout} and @code{stderr} use the same pipe.
18481 @subsubsection Attaching to a Running Program
18482 @cindex attach to a program, @code{gdbserver}
18483 @cindex @option{--attach}, @code{gdbserver} option
18485 On some targets, @code{gdbserver} can also attach to running programs.
18486 This is accomplished via the @code{--attach} argument. The syntax is:
18489 target> gdbserver --attach @var{comm} @var{pid}
18492 @var{pid} is the process ID of a currently running process. It isn't necessary
18493 to point @code{gdbserver} at a binary for the running process.
18496 You can debug processes by name instead of process ID if your target has the
18497 @code{pidof} utility:
18500 target> gdbserver --attach @var{comm} `pidof @var{program}`
18503 In case more than one copy of @var{program} is running, or @var{program}
18504 has multiple threads, most versions of @code{pidof} support the
18505 @code{-s} option to only return the first process ID.
18507 @subsubsection Multi-Process Mode for @code{gdbserver}
18508 @cindex @code{gdbserver}, multiple processes
18509 @cindex multiple processes with @code{gdbserver}
18511 When you connect to @code{gdbserver} using @code{target remote},
18512 @code{gdbserver} debugs the specified program only once. When the
18513 program exits, or you detach from it, @value{GDBN} closes the connection
18514 and @code{gdbserver} exits.
18516 If you connect using @kbd{target extended-remote}, @code{gdbserver}
18517 enters multi-process mode. When the debugged program exits, or you
18518 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
18519 though no program is running. The @code{run} and @code{attach}
18520 commands instruct @code{gdbserver} to run or attach to a new program.
18521 The @code{run} command uses @code{set remote exec-file} (@pxref{set
18522 remote exec-file}) to select the program to run. Command line
18523 arguments are supported, except for wildcard expansion and I/O
18524 redirection (@pxref{Arguments}).
18526 @cindex @option{--multi}, @code{gdbserver} option
18527 To start @code{gdbserver} without supplying an initial command to run
18528 or process ID to attach, use the @option{--multi} command line option.
18529 Then you can connect using @kbd{target extended-remote} and start
18530 the program you want to debug.
18532 In multi-process mode @code{gdbserver} does not automatically exit unless you
18533 use the option @option{--once}. You can terminate it by using
18534 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
18535 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
18536 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
18537 @option{--multi} option to @code{gdbserver} has no influence on that.
18539 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
18541 This section applies only when @code{gdbserver} is run to listen on a TCP port.
18543 @code{gdbserver} normally terminates after all of its debugged processes have
18544 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
18545 extended-remote}, @code{gdbserver} stays running even with no processes left.
18546 @value{GDBN} normally terminates the spawned debugged process on its exit,
18547 which normally also terminates @code{gdbserver} in the @kbd{target remote}
18548 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
18549 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
18550 stays running even in the @kbd{target remote} mode.
18552 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
18553 Such reconnecting is useful for features like @ref{disconnected tracing}. For
18554 completeness, at most one @value{GDBN} can be connected at a time.
18556 @cindex @option{--once}, @code{gdbserver} option
18557 By default, @code{gdbserver} keeps the listening TCP port open, so that
18558 subsequent connections are possible. However, if you start @code{gdbserver}
18559 with the @option{--once} option, it will stop listening for any further
18560 connection attempts after connecting to the first @value{GDBN} session. This
18561 means no further connections to @code{gdbserver} will be possible after the
18562 first one. It also means @code{gdbserver} will terminate after the first
18563 connection with remote @value{GDBN} has closed, even for unexpectedly closed
18564 connections and even in the @kbd{target extended-remote} mode. The
18565 @option{--once} option allows reusing the same port number for connecting to
18566 multiple instances of @code{gdbserver} running on the same host, since each
18567 instance closes its port after the first connection.
18569 @anchor{Other Command-Line Arguments for gdbserver}
18570 @subsubsection Other Command-Line Arguments for @code{gdbserver}
18572 @cindex @option{--debug}, @code{gdbserver} option
18573 The @option{--debug} option tells @code{gdbserver} to display extra
18574 status information about the debugging process.
18575 @cindex @option{--remote-debug}, @code{gdbserver} option
18576 The @option{--remote-debug} option tells @code{gdbserver} to display
18577 remote protocol debug output. These options are intended for
18578 @code{gdbserver} development and for bug reports to the developers.
18580 @cindex @option{--debug-format}, @code{gdbserver} option
18581 The @option{--debug-format=option1[,option2,...]} option tells
18582 @code{gdbserver} to include additional information in each output.
18583 Possible options are:
18587 Turn off all extra information in debugging output.
18589 Turn on all extra information in debugging output.
18591 Include a timestamp in each line of debugging output.
18594 Options are processed in order. Thus, for example, if @option{none}
18595 appears last then no additional information is added to debugging output.
18597 @cindex @option{--wrapper}, @code{gdbserver} option
18598 The @option{--wrapper} option specifies a wrapper to launch programs
18599 for debugging. The option should be followed by the name of the
18600 wrapper, then any command-line arguments to pass to the wrapper, then
18601 @kbd{--} indicating the end of the wrapper arguments.
18603 @code{gdbserver} runs the specified wrapper program with a combined
18604 command line including the wrapper arguments, then the name of the
18605 program to debug, then any arguments to the program. The wrapper
18606 runs until it executes your program, and then @value{GDBN} gains control.
18608 You can use any program that eventually calls @code{execve} with
18609 its arguments as a wrapper. Several standard Unix utilities do
18610 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
18611 with @code{exec "$@@"} will also work.
18613 For example, you can use @code{env} to pass an environment variable to
18614 the debugged program, without setting the variable in @code{gdbserver}'s
18618 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
18621 @subsection Connecting to @code{gdbserver}
18623 Run @value{GDBN} on the host system.
18625 First make sure you have the necessary symbol files. Load symbols for
18626 your application using the @code{file} command before you connect. Use
18627 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
18628 was compiled with the correct sysroot using @code{--with-sysroot}).
18630 The symbol file and target libraries must exactly match the executable
18631 and libraries on the target, with one exception: the files on the host
18632 system should not be stripped, even if the files on the target system
18633 are. Mismatched or missing files will lead to confusing results
18634 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
18635 files may also prevent @code{gdbserver} from debugging multi-threaded
18638 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
18639 For TCP connections, you must start up @code{gdbserver} prior to using
18640 the @code{target remote} command. Otherwise you may get an error whose
18641 text depends on the host system, but which usually looks something like
18642 @samp{Connection refused}. Don't use the @code{load}
18643 command in @value{GDBN} when using @code{gdbserver}, since the program is
18644 already on the target.
18646 @subsection Monitor Commands for @code{gdbserver}
18647 @cindex monitor commands, for @code{gdbserver}
18648 @anchor{Monitor Commands for gdbserver}
18650 During a @value{GDBN} session using @code{gdbserver}, you can use the
18651 @code{monitor} command to send special requests to @code{gdbserver}.
18652 Here are the available commands.
18656 List the available monitor commands.
18658 @item monitor set debug 0
18659 @itemx monitor set debug 1
18660 Disable or enable general debugging messages.
18662 @item monitor set remote-debug 0
18663 @itemx monitor set remote-debug 1
18664 Disable or enable specific debugging messages associated with the remote
18665 protocol (@pxref{Remote Protocol}).
18667 @item monitor set debug-format option1@r{[},option2,...@r{]}
18668 Specify additional text to add to debugging messages.
18669 Possible options are:
18673 Turn off all extra information in debugging output.
18675 Turn on all extra information in debugging output.
18677 Include a timestamp in each line of debugging output.
18680 Options are processed in order. Thus, for example, if @option{none}
18681 appears last then no additional information is added to debugging output.
18683 @item monitor set libthread-db-search-path [PATH]
18684 @cindex gdbserver, search path for @code{libthread_db}
18685 When this command is issued, @var{path} is a colon-separated list of
18686 directories to search for @code{libthread_db} (@pxref{Threads,,set
18687 libthread-db-search-path}). If you omit @var{path},
18688 @samp{libthread-db-search-path} will be reset to its default value.
18690 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
18691 not supported in @code{gdbserver}.
18694 Tell gdbserver to exit immediately. This command should be followed by
18695 @code{disconnect} to close the debugging session. @code{gdbserver} will
18696 detach from any attached processes and kill any processes it created.
18697 Use @code{monitor exit} to terminate @code{gdbserver} at the end
18698 of a multi-process mode debug session.
18702 @subsection Tracepoints support in @code{gdbserver}
18703 @cindex tracepoints support in @code{gdbserver}
18705 On some targets, @code{gdbserver} supports tracepoints, fast
18706 tracepoints and static tracepoints.
18708 For fast or static tracepoints to work, a special library called the
18709 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
18710 This library is built and distributed as an integral part of
18711 @code{gdbserver}. In addition, support for static tracepoints
18712 requires building the in-process agent library with static tracepoints
18713 support. At present, the UST (LTTng Userspace Tracer,
18714 @url{http://lttng.org/ust}) tracing engine is supported. This support
18715 is automatically available if UST development headers are found in the
18716 standard include path when @code{gdbserver} is built, or if
18717 @code{gdbserver} was explicitly configured using @option{--with-ust}
18718 to point at such headers. You can explicitly disable the support
18719 using @option{--with-ust=no}.
18721 There are several ways to load the in-process agent in your program:
18724 @item Specifying it as dependency at link time
18726 You can link your program dynamically with the in-process agent
18727 library. On most systems, this is accomplished by adding
18728 @code{-linproctrace} to the link command.
18730 @item Using the system's preloading mechanisms
18732 You can force loading the in-process agent at startup time by using
18733 your system's support for preloading shared libraries. Many Unixes
18734 support the concept of preloading user defined libraries. In most
18735 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
18736 in the environment. See also the description of @code{gdbserver}'s
18737 @option{--wrapper} command line option.
18739 @item Using @value{GDBN} to force loading the agent at run time
18741 On some systems, you can force the inferior to load a shared library,
18742 by calling a dynamic loader function in the inferior that takes care
18743 of dynamically looking up and loading a shared library. On most Unix
18744 systems, the function is @code{dlopen}. You'll use the @code{call}
18745 command for that. For example:
18748 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
18751 Note that on most Unix systems, for the @code{dlopen} function to be
18752 available, the program needs to be linked with @code{-ldl}.
18755 On systems that have a userspace dynamic loader, like most Unix
18756 systems, when you connect to @code{gdbserver} using @code{target
18757 remote}, you'll find that the program is stopped at the dynamic
18758 loader's entry point, and no shared library has been loaded in the
18759 program's address space yet, including the in-process agent. In that
18760 case, before being able to use any of the fast or static tracepoints
18761 features, you need to let the loader run and load the shared
18762 libraries. The simplest way to do that is to run the program to the
18763 main procedure. E.g., if debugging a C or C@t{++} program, start
18764 @code{gdbserver} like so:
18767 $ gdbserver :9999 myprogram
18770 Start GDB and connect to @code{gdbserver} like so, and run to main:
18774 (@value{GDBP}) target remote myhost:9999
18775 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
18776 (@value{GDBP}) b main
18777 (@value{GDBP}) continue
18780 The in-process tracing agent library should now be loaded into the
18781 process; you can confirm it with the @code{info sharedlibrary}
18782 command, which will list @file{libinproctrace.so} as loaded in the
18783 process. You are now ready to install fast tracepoints, list static
18784 tracepoint markers, probe static tracepoints markers, and start
18787 @node Remote Configuration
18788 @section Remote Configuration
18791 @kindex show remote
18792 This section documents the configuration options available when
18793 debugging remote programs. For the options related to the File I/O
18794 extensions of the remote protocol, see @ref{system,
18795 system-call-allowed}.
18798 @item set remoteaddresssize @var{bits}
18799 @cindex address size for remote targets
18800 @cindex bits in remote address
18801 Set the maximum size of address in a memory packet to the specified
18802 number of bits. @value{GDBN} will mask off the address bits above
18803 that number, when it passes addresses to the remote target. The
18804 default value is the number of bits in the target's address.
18806 @item show remoteaddresssize
18807 Show the current value of remote address size in bits.
18809 @item set serial baud @var{n}
18810 @cindex baud rate for remote targets
18811 Set the baud rate for the remote serial I/O to @var{n} baud. The
18812 value is used to set the speed of the serial port used for debugging
18815 @item show serial baud
18816 Show the current speed of the remote connection.
18818 @item set remotebreak
18819 @cindex interrupt remote programs
18820 @cindex BREAK signal instead of Ctrl-C
18821 @anchor{set remotebreak}
18822 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
18823 when you type @kbd{Ctrl-c} to interrupt the program running
18824 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
18825 character instead. The default is off, since most remote systems
18826 expect to see @samp{Ctrl-C} as the interrupt signal.
18828 @item show remotebreak
18829 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
18830 interrupt the remote program.
18832 @item set remoteflow on
18833 @itemx set remoteflow off
18834 @kindex set remoteflow
18835 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
18836 on the serial port used to communicate to the remote target.
18838 @item show remoteflow
18839 @kindex show remoteflow
18840 Show the current setting of hardware flow control.
18842 @item set remotelogbase @var{base}
18843 Set the base (a.k.a.@: radix) of logging serial protocol
18844 communications to @var{base}. Supported values of @var{base} are:
18845 @code{ascii}, @code{octal}, and @code{hex}. The default is
18848 @item show remotelogbase
18849 Show the current setting of the radix for logging remote serial
18852 @item set remotelogfile @var{file}
18853 @cindex record serial communications on file
18854 Record remote serial communications on the named @var{file}. The
18855 default is not to record at all.
18857 @item show remotelogfile.
18858 Show the current setting of the file name on which to record the
18859 serial communications.
18861 @item set remotetimeout @var{num}
18862 @cindex timeout for serial communications
18863 @cindex remote timeout
18864 Set the timeout limit to wait for the remote target to respond to
18865 @var{num} seconds. The default is 2 seconds.
18867 @item show remotetimeout
18868 Show the current number of seconds to wait for the remote target
18871 @cindex limit hardware breakpoints and watchpoints
18872 @cindex remote target, limit break- and watchpoints
18873 @anchor{set remote hardware-watchpoint-limit}
18874 @anchor{set remote hardware-breakpoint-limit}
18875 @item set remote hardware-watchpoint-limit @var{limit}
18876 @itemx set remote hardware-breakpoint-limit @var{limit}
18877 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
18878 watchpoints. A limit of -1, the default, is treated as unlimited.
18880 @cindex limit hardware watchpoints length
18881 @cindex remote target, limit watchpoints length
18882 @anchor{set remote hardware-watchpoint-length-limit}
18883 @item set remote hardware-watchpoint-length-limit @var{limit}
18884 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
18885 a remote hardware watchpoint. A limit of -1, the default, is treated
18888 @item show remote hardware-watchpoint-length-limit
18889 Show the current limit (in bytes) of the maximum length of
18890 a remote hardware watchpoint.
18892 @item set remote exec-file @var{filename}
18893 @itemx show remote exec-file
18894 @anchor{set remote exec-file}
18895 @cindex executable file, for remote target
18896 Select the file used for @code{run} with @code{target
18897 extended-remote}. This should be set to a filename valid on the
18898 target system. If it is not set, the target will use a default
18899 filename (e.g.@: the last program run).
18901 @item set remote interrupt-sequence
18902 @cindex interrupt remote programs
18903 @cindex select Ctrl-C, BREAK or BREAK-g
18904 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
18905 @samp{BREAK-g} as the
18906 sequence to the remote target in order to interrupt the execution.
18907 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
18908 is high level of serial line for some certain time.
18909 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
18910 It is @code{BREAK} signal followed by character @code{g}.
18912 @item show interrupt-sequence
18913 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
18914 is sent by @value{GDBN} to interrupt the remote program.
18915 @code{BREAK-g} is BREAK signal followed by @code{g} and
18916 also known as Magic SysRq g.
18918 @item set remote interrupt-on-connect
18919 @cindex send interrupt-sequence on start
18920 Specify whether interrupt-sequence is sent to remote target when
18921 @value{GDBN} connects to it. This is mostly needed when you debug
18922 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
18923 which is known as Magic SysRq g in order to connect @value{GDBN}.
18925 @item show interrupt-on-connect
18926 Show whether interrupt-sequence is sent
18927 to remote target when @value{GDBN} connects to it.
18931 @item set tcp auto-retry on
18932 @cindex auto-retry, for remote TCP target
18933 Enable auto-retry for remote TCP connections. This is useful if the remote
18934 debugging agent is launched in parallel with @value{GDBN}; there is a race
18935 condition because the agent may not become ready to accept the connection
18936 before @value{GDBN} attempts to connect. When auto-retry is
18937 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
18938 to establish the connection using the timeout specified by
18939 @code{set tcp connect-timeout}.
18941 @item set tcp auto-retry off
18942 Do not auto-retry failed TCP connections.
18944 @item show tcp auto-retry
18945 Show the current auto-retry setting.
18947 @item set tcp connect-timeout @var{seconds}
18948 @itemx set tcp connect-timeout unlimited
18949 @cindex connection timeout, for remote TCP target
18950 @cindex timeout, for remote target connection
18951 Set the timeout for establishing a TCP connection to the remote target to
18952 @var{seconds}. The timeout affects both polling to retry failed connections
18953 (enabled by @code{set tcp auto-retry on}) and waiting for connections
18954 that are merely slow to complete, and represents an approximate cumulative
18955 value. If @var{seconds} is @code{unlimited}, there is no timeout and
18956 @value{GDBN} will keep attempting to establish a connection forever,
18957 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
18959 @item show tcp connect-timeout
18960 Show the current connection timeout setting.
18963 @cindex remote packets, enabling and disabling
18964 The @value{GDBN} remote protocol autodetects the packets supported by
18965 your debugging stub. If you need to override the autodetection, you
18966 can use these commands to enable or disable individual packets. Each
18967 packet can be set to @samp{on} (the remote target supports this
18968 packet), @samp{off} (the remote target does not support this packet),
18969 or @samp{auto} (detect remote target support for this packet). They
18970 all default to @samp{auto}. For more information about each packet,
18971 see @ref{Remote Protocol}.
18973 During normal use, you should not have to use any of these commands.
18974 If you do, that may be a bug in your remote debugging stub, or a bug
18975 in @value{GDBN}. You may want to report the problem to the
18976 @value{GDBN} developers.
18978 For each packet @var{name}, the command to enable or disable the
18979 packet is @code{set remote @var{name}-packet}. The available settings
18982 @multitable @columnfractions 0.28 0.32 0.25
18985 @tab Related Features
18987 @item @code{fetch-register}
18989 @tab @code{info registers}
18991 @item @code{set-register}
18995 @item @code{binary-download}
18997 @tab @code{load}, @code{set}
18999 @item @code{read-aux-vector}
19000 @tab @code{qXfer:auxv:read}
19001 @tab @code{info auxv}
19003 @item @code{symbol-lookup}
19004 @tab @code{qSymbol}
19005 @tab Detecting multiple threads
19007 @item @code{attach}
19008 @tab @code{vAttach}
19011 @item @code{verbose-resume}
19013 @tab Stepping or resuming multiple threads
19019 @item @code{software-breakpoint}
19023 @item @code{hardware-breakpoint}
19027 @item @code{write-watchpoint}
19031 @item @code{read-watchpoint}
19035 @item @code{access-watchpoint}
19039 @item @code{target-features}
19040 @tab @code{qXfer:features:read}
19041 @tab @code{set architecture}
19043 @item @code{library-info}
19044 @tab @code{qXfer:libraries:read}
19045 @tab @code{info sharedlibrary}
19047 @item @code{memory-map}
19048 @tab @code{qXfer:memory-map:read}
19049 @tab @code{info mem}
19051 @item @code{read-sdata-object}
19052 @tab @code{qXfer:sdata:read}
19053 @tab @code{print $_sdata}
19055 @item @code{read-spu-object}
19056 @tab @code{qXfer:spu:read}
19057 @tab @code{info spu}
19059 @item @code{write-spu-object}
19060 @tab @code{qXfer:spu:write}
19061 @tab @code{info spu}
19063 @item @code{read-siginfo-object}
19064 @tab @code{qXfer:siginfo:read}
19065 @tab @code{print $_siginfo}
19067 @item @code{write-siginfo-object}
19068 @tab @code{qXfer:siginfo:write}
19069 @tab @code{set $_siginfo}
19071 @item @code{threads}
19072 @tab @code{qXfer:threads:read}
19073 @tab @code{info threads}
19075 @item @code{get-thread-local-@*storage-address}
19076 @tab @code{qGetTLSAddr}
19077 @tab Displaying @code{__thread} variables
19079 @item @code{get-thread-information-block-address}
19080 @tab @code{qGetTIBAddr}
19081 @tab Display MS-Windows Thread Information Block.
19083 @item @code{search-memory}
19084 @tab @code{qSearch:memory}
19087 @item @code{supported-packets}
19088 @tab @code{qSupported}
19089 @tab Remote communications parameters
19091 @item @code{pass-signals}
19092 @tab @code{QPassSignals}
19093 @tab @code{handle @var{signal}}
19095 @item @code{program-signals}
19096 @tab @code{QProgramSignals}
19097 @tab @code{handle @var{signal}}
19099 @item @code{hostio-close-packet}
19100 @tab @code{vFile:close}
19101 @tab @code{remote get}, @code{remote put}
19103 @item @code{hostio-open-packet}
19104 @tab @code{vFile:open}
19105 @tab @code{remote get}, @code{remote put}
19107 @item @code{hostio-pread-packet}
19108 @tab @code{vFile:pread}
19109 @tab @code{remote get}, @code{remote put}
19111 @item @code{hostio-pwrite-packet}
19112 @tab @code{vFile:pwrite}
19113 @tab @code{remote get}, @code{remote put}
19115 @item @code{hostio-unlink-packet}
19116 @tab @code{vFile:unlink}
19117 @tab @code{remote delete}
19119 @item @code{hostio-readlink-packet}
19120 @tab @code{vFile:readlink}
19123 @item @code{noack-packet}
19124 @tab @code{QStartNoAckMode}
19125 @tab Packet acknowledgment
19127 @item @code{osdata}
19128 @tab @code{qXfer:osdata:read}
19129 @tab @code{info os}
19131 @item @code{query-attached}
19132 @tab @code{qAttached}
19133 @tab Querying remote process attach state.
19135 @item @code{trace-buffer-size}
19136 @tab @code{QTBuffer:size}
19137 @tab @code{set trace-buffer-size}
19139 @item @code{trace-status}
19140 @tab @code{qTStatus}
19141 @tab @code{tstatus}
19143 @item @code{traceframe-info}
19144 @tab @code{qXfer:traceframe-info:read}
19145 @tab Traceframe info
19147 @item @code{install-in-trace}
19148 @tab @code{InstallInTrace}
19149 @tab Install tracepoint in tracing
19151 @item @code{disable-randomization}
19152 @tab @code{QDisableRandomization}
19153 @tab @code{set disable-randomization}
19155 @item @code{conditional-breakpoints-packet}
19156 @tab @code{Z0 and Z1}
19157 @tab @code{Support for target-side breakpoint condition evaluation}
19161 @section Implementing a Remote Stub
19163 @cindex debugging stub, example
19164 @cindex remote stub, example
19165 @cindex stub example, remote debugging
19166 The stub files provided with @value{GDBN} implement the target side of the
19167 communication protocol, and the @value{GDBN} side is implemented in the
19168 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
19169 these subroutines to communicate, and ignore the details. (If you're
19170 implementing your own stub file, you can still ignore the details: start
19171 with one of the existing stub files. @file{sparc-stub.c} is the best
19172 organized, and therefore the easiest to read.)
19174 @cindex remote serial debugging, overview
19175 To debug a program running on another machine (the debugging
19176 @dfn{target} machine), you must first arrange for all the usual
19177 prerequisites for the program to run by itself. For example, for a C
19182 A startup routine to set up the C runtime environment; these usually
19183 have a name like @file{crt0}. The startup routine may be supplied by
19184 your hardware supplier, or you may have to write your own.
19187 A C subroutine library to support your program's
19188 subroutine calls, notably managing input and output.
19191 A way of getting your program to the other machine---for example, a
19192 download program. These are often supplied by the hardware
19193 manufacturer, but you may have to write your own from hardware
19197 The next step is to arrange for your program to use a serial port to
19198 communicate with the machine where @value{GDBN} is running (the @dfn{host}
19199 machine). In general terms, the scheme looks like this:
19203 @value{GDBN} already understands how to use this protocol; when everything
19204 else is set up, you can simply use the @samp{target remote} command
19205 (@pxref{Targets,,Specifying a Debugging Target}).
19207 @item On the target,
19208 you must link with your program a few special-purpose subroutines that
19209 implement the @value{GDBN} remote serial protocol. The file containing these
19210 subroutines is called a @dfn{debugging stub}.
19212 On certain remote targets, you can use an auxiliary program
19213 @code{gdbserver} instead of linking a stub into your program.
19214 @xref{Server,,Using the @code{gdbserver} Program}, for details.
19217 The debugging stub is specific to the architecture of the remote
19218 machine; for example, use @file{sparc-stub.c} to debug programs on
19221 @cindex remote serial stub list
19222 These working remote stubs are distributed with @value{GDBN}:
19227 @cindex @file{i386-stub.c}
19230 For Intel 386 and compatible architectures.
19233 @cindex @file{m68k-stub.c}
19234 @cindex Motorola 680x0
19236 For Motorola 680x0 architectures.
19239 @cindex @file{sh-stub.c}
19242 For Renesas SH architectures.
19245 @cindex @file{sparc-stub.c}
19247 For @sc{sparc} architectures.
19249 @item sparcl-stub.c
19250 @cindex @file{sparcl-stub.c}
19253 For Fujitsu @sc{sparclite} architectures.
19257 The @file{README} file in the @value{GDBN} distribution may list other
19258 recently added stubs.
19261 * Stub Contents:: What the stub can do for you
19262 * Bootstrapping:: What you must do for the stub
19263 * Debug Session:: Putting it all together
19266 @node Stub Contents
19267 @subsection What the Stub Can Do for You
19269 @cindex remote serial stub
19270 The debugging stub for your architecture supplies these three
19274 @item set_debug_traps
19275 @findex set_debug_traps
19276 @cindex remote serial stub, initialization
19277 This routine arranges for @code{handle_exception} to run when your
19278 program stops. You must call this subroutine explicitly in your
19279 program's startup code.
19281 @item handle_exception
19282 @findex handle_exception
19283 @cindex remote serial stub, main routine
19284 This is the central workhorse, but your program never calls it
19285 explicitly---the setup code arranges for @code{handle_exception} to
19286 run when a trap is triggered.
19288 @code{handle_exception} takes control when your program stops during
19289 execution (for example, on a breakpoint), and mediates communications
19290 with @value{GDBN} on the host machine. This is where the communications
19291 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
19292 representative on the target machine. It begins by sending summary
19293 information on the state of your program, then continues to execute,
19294 retrieving and transmitting any information @value{GDBN} needs, until you
19295 execute a @value{GDBN} command that makes your program resume; at that point,
19296 @code{handle_exception} returns control to your own code on the target
19300 @cindex @code{breakpoint} subroutine, remote
19301 Use this auxiliary subroutine to make your program contain a
19302 breakpoint. Depending on the particular situation, this may be the only
19303 way for @value{GDBN} to get control. For instance, if your target
19304 machine has some sort of interrupt button, you won't need to call this;
19305 pressing the interrupt button transfers control to
19306 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
19307 simply receiving characters on the serial port may also trigger a trap;
19308 again, in that situation, you don't need to call @code{breakpoint} from
19309 your own program---simply running @samp{target remote} from the host
19310 @value{GDBN} session gets control.
19312 Call @code{breakpoint} if none of these is true, or if you simply want
19313 to make certain your program stops at a predetermined point for the
19314 start of your debugging session.
19317 @node Bootstrapping
19318 @subsection What You Must Do for the Stub
19320 @cindex remote stub, support routines
19321 The debugging stubs that come with @value{GDBN} are set up for a particular
19322 chip architecture, but they have no information about the rest of your
19323 debugging target machine.
19325 First of all you need to tell the stub how to communicate with the
19329 @item int getDebugChar()
19330 @findex getDebugChar
19331 Write this subroutine to read a single character from the serial port.
19332 It may be identical to @code{getchar} for your target system; a
19333 different name is used to allow you to distinguish the two if you wish.
19335 @item void putDebugChar(int)
19336 @findex putDebugChar
19337 Write this subroutine to write a single character to the serial port.
19338 It may be identical to @code{putchar} for your target system; a
19339 different name is used to allow you to distinguish the two if you wish.
19342 @cindex control C, and remote debugging
19343 @cindex interrupting remote targets
19344 If you want @value{GDBN} to be able to stop your program while it is
19345 running, you need to use an interrupt-driven serial driver, and arrange
19346 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
19347 character). That is the character which @value{GDBN} uses to tell the
19348 remote system to stop.
19350 Getting the debugging target to return the proper status to @value{GDBN}
19351 probably requires changes to the standard stub; one quick and dirty way
19352 is to just execute a breakpoint instruction (the ``dirty'' part is that
19353 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
19355 Other routines you need to supply are:
19358 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
19359 @findex exceptionHandler
19360 Write this function to install @var{exception_address} in the exception
19361 handling tables. You need to do this because the stub does not have any
19362 way of knowing what the exception handling tables on your target system
19363 are like (for example, the processor's table might be in @sc{rom},
19364 containing entries which point to a table in @sc{ram}).
19365 @var{exception_number} is the exception number which should be changed;
19366 its meaning is architecture-dependent (for example, different numbers
19367 might represent divide by zero, misaligned access, etc). When this
19368 exception occurs, control should be transferred directly to
19369 @var{exception_address}, and the processor state (stack, registers,
19370 and so on) should be just as it is when a processor exception occurs. So if
19371 you want to use a jump instruction to reach @var{exception_address}, it
19372 should be a simple jump, not a jump to subroutine.
19374 For the 386, @var{exception_address} should be installed as an interrupt
19375 gate so that interrupts are masked while the handler runs. The gate
19376 should be at privilege level 0 (the most privileged level). The
19377 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
19378 help from @code{exceptionHandler}.
19380 @item void flush_i_cache()
19381 @findex flush_i_cache
19382 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
19383 instruction cache, if any, on your target machine. If there is no
19384 instruction cache, this subroutine may be a no-op.
19386 On target machines that have instruction caches, @value{GDBN} requires this
19387 function to make certain that the state of your program is stable.
19391 You must also make sure this library routine is available:
19394 @item void *memset(void *, int, int)
19396 This is the standard library function @code{memset} that sets an area of
19397 memory to a known value. If you have one of the free versions of
19398 @code{libc.a}, @code{memset} can be found there; otherwise, you must
19399 either obtain it from your hardware manufacturer, or write your own.
19402 If you do not use the GNU C compiler, you may need other standard
19403 library subroutines as well; this varies from one stub to another,
19404 but in general the stubs are likely to use any of the common library
19405 subroutines which @code{@value{NGCC}} generates as inline code.
19408 @node Debug Session
19409 @subsection Putting it All Together
19411 @cindex remote serial debugging summary
19412 In summary, when your program is ready to debug, you must follow these
19417 Make sure you have defined the supporting low-level routines
19418 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
19420 @code{getDebugChar}, @code{putDebugChar},
19421 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
19425 Insert these lines in your program's startup code, before the main
19426 procedure is called:
19433 On some machines, when a breakpoint trap is raised, the hardware
19434 automatically makes the PC point to the instruction after the
19435 breakpoint. If your machine doesn't do that, you may need to adjust
19436 @code{handle_exception} to arrange for it to return to the instruction
19437 after the breakpoint on this first invocation, so that your program
19438 doesn't keep hitting the initial breakpoint instead of making
19442 For the 680x0 stub only, you need to provide a variable called
19443 @code{exceptionHook}. Normally you just use:
19446 void (*exceptionHook)() = 0;
19450 but if before calling @code{set_debug_traps}, you set it to point to a
19451 function in your program, that function is called when
19452 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
19453 error). The function indicated by @code{exceptionHook} is called with
19454 one parameter: an @code{int} which is the exception number.
19457 Compile and link together: your program, the @value{GDBN} debugging stub for
19458 your target architecture, and the supporting subroutines.
19461 Make sure you have a serial connection between your target machine and
19462 the @value{GDBN} host, and identify the serial port on the host.
19465 @c The "remote" target now provides a `load' command, so we should
19466 @c document that. FIXME.
19467 Download your program to your target machine (or get it there by
19468 whatever means the manufacturer provides), and start it.
19471 Start @value{GDBN} on the host, and connect to the target
19472 (@pxref{Connecting,,Connecting to a Remote Target}).
19476 @node Configurations
19477 @chapter Configuration-Specific Information
19479 While nearly all @value{GDBN} commands are available for all native and
19480 cross versions of the debugger, there are some exceptions. This chapter
19481 describes things that are only available in certain configurations.
19483 There are three major categories of configurations: native
19484 configurations, where the host and target are the same, embedded
19485 operating system configurations, which are usually the same for several
19486 different processor architectures, and bare embedded processors, which
19487 are quite different from each other.
19492 * Embedded Processors::
19499 This section describes details specific to particular native
19504 * BSD libkvm Interface:: Debugging BSD kernel memory images
19505 * SVR4 Process Information:: SVR4 process information
19506 * DJGPP Native:: Features specific to the DJGPP port
19507 * Cygwin Native:: Features specific to the Cygwin port
19508 * Hurd Native:: Features specific to @sc{gnu} Hurd
19509 * Darwin:: Features specific to Darwin
19515 On HP-UX systems, if you refer to a function or variable name that
19516 begins with a dollar sign, @value{GDBN} searches for a user or system
19517 name first, before it searches for a convenience variable.
19520 @node BSD libkvm Interface
19521 @subsection BSD libkvm Interface
19524 @cindex kernel memory image
19525 @cindex kernel crash dump
19527 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
19528 interface that provides a uniform interface for accessing kernel virtual
19529 memory images, including live systems and crash dumps. @value{GDBN}
19530 uses this interface to allow you to debug live kernels and kernel crash
19531 dumps on many native BSD configurations. This is implemented as a
19532 special @code{kvm} debugging target. For debugging a live system, load
19533 the currently running kernel into @value{GDBN} and connect to the
19537 (@value{GDBP}) @b{target kvm}
19540 For debugging crash dumps, provide the file name of the crash dump as an
19544 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
19547 Once connected to the @code{kvm} target, the following commands are
19553 Set current context from the @dfn{Process Control Block} (PCB) address.
19556 Set current context from proc address. This command isn't available on
19557 modern FreeBSD systems.
19560 @node SVR4 Process Information
19561 @subsection SVR4 Process Information
19563 @cindex examine process image
19564 @cindex process info via @file{/proc}
19566 Many versions of SVR4 and compatible systems provide a facility called
19567 @samp{/proc} that can be used to examine the image of a running
19568 process using file-system subroutines.
19570 If @value{GDBN} is configured for an operating system with this
19571 facility, the command @code{info proc} is available to report
19572 information about the process running your program, or about any
19573 process running on your system. This includes, as of this writing,
19574 @sc{gnu}/Linux, OSF/1 (Digital Unix), Solaris, and Irix, but
19575 not HP-UX, for example.
19577 This command may also work on core files that were created on a system
19578 that has the @samp{/proc} facility.
19584 @itemx info proc @var{process-id}
19585 Summarize available information about any running process. If a
19586 process ID is specified by @var{process-id}, display information about
19587 that process; otherwise display information about the program being
19588 debugged. The summary includes the debugged process ID, the command
19589 line used to invoke it, its current working directory, and its
19590 executable file's absolute file name.
19592 On some systems, @var{process-id} can be of the form
19593 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
19594 within a process. If the optional @var{pid} part is missing, it means
19595 a thread from the process being debugged (the leading @samp{/} still
19596 needs to be present, or else @value{GDBN} will interpret the number as
19597 a process ID rather than a thread ID).
19599 @item info proc cmdline
19600 @cindex info proc cmdline
19601 Show the original command line of the process. This command is
19602 specific to @sc{gnu}/Linux.
19604 @item info proc cwd
19605 @cindex info proc cwd
19606 Show the current working directory of the process. This command is
19607 specific to @sc{gnu}/Linux.
19609 @item info proc exe
19610 @cindex info proc exe
19611 Show the name of executable of the process. This command is specific
19614 @item info proc mappings
19615 @cindex memory address space mappings
19616 Report the memory address space ranges accessible in the program, with
19617 information on whether the process has read, write, or execute access
19618 rights to each range. On @sc{gnu}/Linux systems, each memory range
19619 includes the object file which is mapped to that range, instead of the
19620 memory access rights to that range.
19622 @item info proc stat
19623 @itemx info proc status
19624 @cindex process detailed status information
19625 These subcommands are specific to @sc{gnu}/Linux systems. They show
19626 the process-related information, including the user ID and group ID;
19627 how many threads are there in the process; its virtual memory usage;
19628 the signals that are pending, blocked, and ignored; its TTY; its
19629 consumption of system and user time; its stack size; its @samp{nice}
19630 value; etc. For more information, see the @samp{proc} man page
19631 (type @kbd{man 5 proc} from your shell prompt).
19633 @item info proc all
19634 Show all the information about the process described under all of the
19635 above @code{info proc} subcommands.
19638 @comment These sub-options of 'info proc' were not included when
19639 @comment procfs.c was re-written. Keep their descriptions around
19640 @comment against the day when someone finds the time to put them back in.
19641 @kindex info proc times
19642 @item info proc times
19643 Starting time, user CPU time, and system CPU time for your program and
19646 @kindex info proc id
19648 Report on the process IDs related to your program: its own process ID,
19649 the ID of its parent, the process group ID, and the session ID.
19652 @item set procfs-trace
19653 @kindex set procfs-trace
19654 @cindex @code{procfs} API calls
19655 This command enables and disables tracing of @code{procfs} API calls.
19657 @item show procfs-trace
19658 @kindex show procfs-trace
19659 Show the current state of @code{procfs} API call tracing.
19661 @item set procfs-file @var{file}
19662 @kindex set procfs-file
19663 Tell @value{GDBN} to write @code{procfs} API trace to the named
19664 @var{file}. @value{GDBN} appends the trace info to the previous
19665 contents of the file. The default is to display the trace on the
19668 @item show procfs-file
19669 @kindex show procfs-file
19670 Show the file to which @code{procfs} API trace is written.
19672 @item proc-trace-entry
19673 @itemx proc-trace-exit
19674 @itemx proc-untrace-entry
19675 @itemx proc-untrace-exit
19676 @kindex proc-trace-entry
19677 @kindex proc-trace-exit
19678 @kindex proc-untrace-entry
19679 @kindex proc-untrace-exit
19680 These commands enable and disable tracing of entries into and exits
19681 from the @code{syscall} interface.
19684 @kindex info pidlist
19685 @cindex process list, QNX Neutrino
19686 For QNX Neutrino only, this command displays the list of all the
19687 processes and all the threads within each process.
19690 @kindex info meminfo
19691 @cindex mapinfo list, QNX Neutrino
19692 For QNX Neutrino only, this command displays the list of all mapinfos.
19696 @subsection Features for Debugging @sc{djgpp} Programs
19697 @cindex @sc{djgpp} debugging
19698 @cindex native @sc{djgpp} debugging
19699 @cindex MS-DOS-specific commands
19702 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
19703 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
19704 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
19705 top of real-mode DOS systems and their emulations.
19707 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
19708 defines a few commands specific to the @sc{djgpp} port. This
19709 subsection describes those commands.
19714 This is a prefix of @sc{djgpp}-specific commands which print
19715 information about the target system and important OS structures.
19718 @cindex MS-DOS system info
19719 @cindex free memory information (MS-DOS)
19720 @item info dos sysinfo
19721 This command displays assorted information about the underlying
19722 platform: the CPU type and features, the OS version and flavor, the
19723 DPMI version, and the available conventional and DPMI memory.
19728 @cindex segment descriptor tables
19729 @cindex descriptor tables display
19731 @itemx info dos ldt
19732 @itemx info dos idt
19733 These 3 commands display entries from, respectively, Global, Local,
19734 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
19735 tables are data structures which store a descriptor for each segment
19736 that is currently in use. The segment's selector is an index into a
19737 descriptor table; the table entry for that index holds the
19738 descriptor's base address and limit, and its attributes and access
19741 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
19742 segment (used for both data and the stack), and a DOS segment (which
19743 allows access to DOS/BIOS data structures and absolute addresses in
19744 conventional memory). However, the DPMI host will usually define
19745 additional segments in order to support the DPMI environment.
19747 @cindex garbled pointers
19748 These commands allow to display entries from the descriptor tables.
19749 Without an argument, all entries from the specified table are
19750 displayed. An argument, which should be an integer expression, means
19751 display a single entry whose index is given by the argument. For
19752 example, here's a convenient way to display information about the
19753 debugged program's data segment:
19756 @exdent @code{(@value{GDBP}) info dos ldt $ds}
19757 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
19761 This comes in handy when you want to see whether a pointer is outside
19762 the data segment's limit (i.e.@: @dfn{garbled}).
19764 @cindex page tables display (MS-DOS)
19766 @itemx info dos pte
19767 These two commands display entries from, respectively, the Page
19768 Directory and the Page Tables. Page Directories and Page Tables are
19769 data structures which control how virtual memory addresses are mapped
19770 into physical addresses. A Page Table includes an entry for every
19771 page of memory that is mapped into the program's address space; there
19772 may be several Page Tables, each one holding up to 4096 entries. A
19773 Page Directory has up to 4096 entries, one each for every Page Table
19774 that is currently in use.
19776 Without an argument, @kbd{info dos pde} displays the entire Page
19777 Directory, and @kbd{info dos pte} displays all the entries in all of
19778 the Page Tables. An argument, an integer expression, given to the
19779 @kbd{info dos pde} command means display only that entry from the Page
19780 Directory table. An argument given to the @kbd{info dos pte} command
19781 means display entries from a single Page Table, the one pointed to by
19782 the specified entry in the Page Directory.
19784 @cindex direct memory access (DMA) on MS-DOS
19785 These commands are useful when your program uses @dfn{DMA} (Direct
19786 Memory Access), which needs physical addresses to program the DMA
19789 These commands are supported only with some DPMI servers.
19791 @cindex physical address from linear address
19792 @item info dos address-pte @var{addr}
19793 This command displays the Page Table entry for a specified linear
19794 address. The argument @var{addr} is a linear address which should
19795 already have the appropriate segment's base address added to it,
19796 because this command accepts addresses which may belong to @emph{any}
19797 segment. For example, here's how to display the Page Table entry for
19798 the page where a variable @code{i} is stored:
19801 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
19802 @exdent @code{Page Table entry for address 0x11a00d30:}
19803 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
19807 This says that @code{i} is stored at offset @code{0xd30} from the page
19808 whose physical base address is @code{0x02698000}, and shows all the
19809 attributes of that page.
19811 Note that you must cast the addresses of variables to a @code{char *},
19812 since otherwise the value of @code{__djgpp_base_address}, the base
19813 address of all variables and functions in a @sc{djgpp} program, will
19814 be added using the rules of C pointer arithmetics: if @code{i} is
19815 declared an @code{int}, @value{GDBN} will add 4 times the value of
19816 @code{__djgpp_base_address} to the address of @code{i}.
19818 Here's another example, it displays the Page Table entry for the
19822 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
19823 @exdent @code{Page Table entry for address 0x29110:}
19824 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
19828 (The @code{+ 3} offset is because the transfer buffer's address is the
19829 3rd member of the @code{_go32_info_block} structure.) The output
19830 clearly shows that this DPMI server maps the addresses in conventional
19831 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
19832 linear (@code{0x29110}) addresses are identical.
19834 This command is supported only with some DPMI servers.
19837 @cindex DOS serial data link, remote debugging
19838 In addition to native debugging, the DJGPP port supports remote
19839 debugging via a serial data link. The following commands are specific
19840 to remote serial debugging in the DJGPP port of @value{GDBN}.
19843 @kindex set com1base
19844 @kindex set com1irq
19845 @kindex set com2base
19846 @kindex set com2irq
19847 @kindex set com3base
19848 @kindex set com3irq
19849 @kindex set com4base
19850 @kindex set com4irq
19851 @item set com1base @var{addr}
19852 This command sets the base I/O port address of the @file{COM1} serial
19855 @item set com1irq @var{irq}
19856 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
19857 for the @file{COM1} serial port.
19859 There are similar commands @samp{set com2base}, @samp{set com3irq},
19860 etc.@: for setting the port address and the @code{IRQ} lines for the
19863 @kindex show com1base
19864 @kindex show com1irq
19865 @kindex show com2base
19866 @kindex show com2irq
19867 @kindex show com3base
19868 @kindex show com3irq
19869 @kindex show com4base
19870 @kindex show com4irq
19871 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
19872 display the current settings of the base address and the @code{IRQ}
19873 lines used by the COM ports.
19876 @kindex info serial
19877 @cindex DOS serial port status
19878 This command prints the status of the 4 DOS serial ports. For each
19879 port, it prints whether it's active or not, its I/O base address and
19880 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
19881 counts of various errors encountered so far.
19885 @node Cygwin Native
19886 @subsection Features for Debugging MS Windows PE Executables
19887 @cindex MS Windows debugging
19888 @cindex native Cygwin debugging
19889 @cindex Cygwin-specific commands
19891 @value{GDBN} supports native debugging of MS Windows programs, including
19892 DLLs with and without symbolic debugging information.
19894 @cindex Ctrl-BREAK, MS-Windows
19895 @cindex interrupt debuggee on MS-Windows
19896 MS-Windows programs that call @code{SetConsoleMode} to switch off the
19897 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
19898 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
19899 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
19900 sequence, which can be used to interrupt the debuggee even if it
19903 There are various additional Cygwin-specific commands, described in
19904 this section. Working with DLLs that have no debugging symbols is
19905 described in @ref{Non-debug DLL Symbols}.
19910 This is a prefix of MS Windows-specific commands which print
19911 information about the target system and important OS structures.
19913 @item info w32 selector
19914 This command displays information returned by
19915 the Win32 API @code{GetThreadSelectorEntry} function.
19916 It takes an optional argument that is evaluated to
19917 a long value to give the information about this given selector.
19918 Without argument, this command displays information
19919 about the six segment registers.
19921 @item info w32 thread-information-block
19922 This command displays thread specific information stored in the
19923 Thread Information Block (readable on the X86 CPU family using @code{$fs}
19924 selector for 32-bit programs and @code{$gs} for 64-bit programs).
19928 This is a Cygwin-specific alias of @code{info shared}.
19930 @kindex dll-symbols
19932 This command is deprecated and will be removed in future versions
19933 of @value{GDBN}. Use the @code{sharedlibrary} command instead.
19935 This command loads symbols from a dll similarly to
19936 add-sym command but without the need to specify a base address.
19938 @kindex set cygwin-exceptions
19939 @cindex debugging the Cygwin DLL
19940 @cindex Cygwin DLL, debugging
19941 @item set cygwin-exceptions @var{mode}
19942 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
19943 happen inside the Cygwin DLL. If @var{mode} is @code{off},
19944 @value{GDBN} will delay recognition of exceptions, and may ignore some
19945 exceptions which seem to be caused by internal Cygwin DLL
19946 ``bookkeeping''. This option is meant primarily for debugging the
19947 Cygwin DLL itself; the default value is @code{off} to avoid annoying
19948 @value{GDBN} users with false @code{SIGSEGV} signals.
19950 @kindex show cygwin-exceptions
19951 @item show cygwin-exceptions
19952 Displays whether @value{GDBN} will break on exceptions that happen
19953 inside the Cygwin DLL itself.
19955 @kindex set new-console
19956 @item set new-console @var{mode}
19957 If @var{mode} is @code{on} the debuggee will
19958 be started in a new console on next start.
19959 If @var{mode} is @code{off}, the debuggee will
19960 be started in the same console as the debugger.
19962 @kindex show new-console
19963 @item show new-console
19964 Displays whether a new console is used
19965 when the debuggee is started.
19967 @kindex set new-group
19968 @item set new-group @var{mode}
19969 This boolean value controls whether the debuggee should
19970 start a new group or stay in the same group as the debugger.
19971 This affects the way the Windows OS handles
19974 @kindex show new-group
19975 @item show new-group
19976 Displays current value of new-group boolean.
19978 @kindex set debugevents
19979 @item set debugevents
19980 This boolean value adds debug output concerning kernel events related
19981 to the debuggee seen by the debugger. This includes events that
19982 signal thread and process creation and exit, DLL loading and
19983 unloading, console interrupts, and debugging messages produced by the
19984 Windows @code{OutputDebugString} API call.
19986 @kindex set debugexec
19987 @item set debugexec
19988 This boolean value adds debug output concerning execute events
19989 (such as resume thread) seen by the debugger.
19991 @kindex set debugexceptions
19992 @item set debugexceptions
19993 This boolean value adds debug output concerning exceptions in the
19994 debuggee seen by the debugger.
19996 @kindex set debugmemory
19997 @item set debugmemory
19998 This boolean value adds debug output concerning debuggee memory reads
19999 and writes by the debugger.
20003 This boolean values specifies whether the debuggee is called
20004 via a shell or directly (default value is on).
20008 Displays if the debuggee will be started with a shell.
20013 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
20016 @node Non-debug DLL Symbols
20017 @subsubsection Support for DLLs without Debugging Symbols
20018 @cindex DLLs with no debugging symbols
20019 @cindex Minimal symbols and DLLs
20021 Very often on windows, some of the DLLs that your program relies on do
20022 not include symbolic debugging information (for example,
20023 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
20024 symbols in a DLL, it relies on the minimal amount of symbolic
20025 information contained in the DLL's export table. This section
20026 describes working with such symbols, known internally to @value{GDBN} as
20027 ``minimal symbols''.
20029 Note that before the debugged program has started execution, no DLLs
20030 will have been loaded. The easiest way around this problem is simply to
20031 start the program --- either by setting a breakpoint or letting the
20032 program run once to completion.
20034 @subsubsection DLL Name Prefixes
20036 In keeping with the naming conventions used by the Microsoft debugging
20037 tools, DLL export symbols are made available with a prefix based on the
20038 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
20039 also entered into the symbol table, so @code{CreateFileA} is often
20040 sufficient. In some cases there will be name clashes within a program
20041 (particularly if the executable itself includes full debugging symbols)
20042 necessitating the use of the fully qualified name when referring to the
20043 contents of the DLL. Use single-quotes around the name to avoid the
20044 exclamation mark (``!'') being interpreted as a language operator.
20046 Note that the internal name of the DLL may be all upper-case, even
20047 though the file name of the DLL is lower-case, or vice-versa. Since
20048 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
20049 some confusion. If in doubt, try the @code{info functions} and
20050 @code{info variables} commands or even @code{maint print msymbols}
20051 (@pxref{Symbols}). Here's an example:
20054 (@value{GDBP}) info function CreateFileA
20055 All functions matching regular expression "CreateFileA":
20057 Non-debugging symbols:
20058 0x77e885f4 CreateFileA
20059 0x77e885f4 KERNEL32!CreateFileA
20063 (@value{GDBP}) info function !
20064 All functions matching regular expression "!":
20066 Non-debugging symbols:
20067 0x6100114c cygwin1!__assert
20068 0x61004034 cygwin1!_dll_crt0@@0
20069 0x61004240 cygwin1!dll_crt0(per_process *)
20073 @subsubsection Working with Minimal Symbols
20075 Symbols extracted from a DLL's export table do not contain very much
20076 type information. All that @value{GDBN} can do is guess whether a symbol
20077 refers to a function or variable depending on the linker section that
20078 contains the symbol. Also note that the actual contents of the memory
20079 contained in a DLL are not available unless the program is running. This
20080 means that you cannot examine the contents of a variable or disassemble
20081 a function within a DLL without a running program.
20083 Variables are generally treated as pointers and dereferenced
20084 automatically. For this reason, it is often necessary to prefix a
20085 variable name with the address-of operator (``&'') and provide explicit
20086 type information in the command. Here's an example of the type of
20090 (@value{GDBP}) print 'cygwin1!__argv'
20095 (@value{GDBP}) x 'cygwin1!__argv'
20096 0x10021610: "\230y\""
20099 And two possible solutions:
20102 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
20103 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
20107 (@value{GDBP}) x/2x &'cygwin1!__argv'
20108 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
20109 (@value{GDBP}) x/x 0x10021608
20110 0x10021608: 0x0022fd98
20111 (@value{GDBP}) x/s 0x0022fd98
20112 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
20115 Setting a break point within a DLL is possible even before the program
20116 starts execution. However, under these circumstances, @value{GDBN} can't
20117 examine the initial instructions of the function in order to skip the
20118 function's frame set-up code. You can work around this by using ``*&''
20119 to set the breakpoint at a raw memory address:
20122 (@value{GDBP}) break *&'python22!PyOS_Readline'
20123 Breakpoint 1 at 0x1e04eff0
20126 The author of these extensions is not entirely convinced that setting a
20127 break point within a shared DLL like @file{kernel32.dll} is completely
20131 @subsection Commands Specific to @sc{gnu} Hurd Systems
20132 @cindex @sc{gnu} Hurd debugging
20134 This subsection describes @value{GDBN} commands specific to the
20135 @sc{gnu} Hurd native debugging.
20140 @kindex set signals@r{, Hurd command}
20141 @kindex set sigs@r{, Hurd command}
20142 This command toggles the state of inferior signal interception by
20143 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
20144 affected by this command. @code{sigs} is a shorthand alias for
20149 @kindex show signals@r{, Hurd command}
20150 @kindex show sigs@r{, Hurd command}
20151 Show the current state of intercepting inferior's signals.
20153 @item set signal-thread
20154 @itemx set sigthread
20155 @kindex set signal-thread
20156 @kindex set sigthread
20157 This command tells @value{GDBN} which thread is the @code{libc} signal
20158 thread. That thread is run when a signal is delivered to a running
20159 process. @code{set sigthread} is the shorthand alias of @code{set
20162 @item show signal-thread
20163 @itemx show sigthread
20164 @kindex show signal-thread
20165 @kindex show sigthread
20166 These two commands show which thread will run when the inferior is
20167 delivered a signal.
20170 @kindex set stopped@r{, Hurd command}
20171 This commands tells @value{GDBN} that the inferior process is stopped,
20172 as with the @code{SIGSTOP} signal. The stopped process can be
20173 continued by delivering a signal to it.
20176 @kindex show stopped@r{, Hurd command}
20177 This command shows whether @value{GDBN} thinks the debuggee is
20180 @item set exceptions
20181 @kindex set exceptions@r{, Hurd command}
20182 Use this command to turn off trapping of exceptions in the inferior.
20183 When exception trapping is off, neither breakpoints nor
20184 single-stepping will work. To restore the default, set exception
20187 @item show exceptions
20188 @kindex show exceptions@r{, Hurd command}
20189 Show the current state of trapping exceptions in the inferior.
20191 @item set task pause
20192 @kindex set task@r{, Hurd commands}
20193 @cindex task attributes (@sc{gnu} Hurd)
20194 @cindex pause current task (@sc{gnu} Hurd)
20195 This command toggles task suspension when @value{GDBN} has control.
20196 Setting it to on takes effect immediately, and the task is suspended
20197 whenever @value{GDBN} gets control. Setting it to off will take
20198 effect the next time the inferior is continued. If this option is set
20199 to off, you can use @code{set thread default pause on} or @code{set
20200 thread pause on} (see below) to pause individual threads.
20202 @item show task pause
20203 @kindex show task@r{, Hurd commands}
20204 Show the current state of task suspension.
20206 @item set task detach-suspend-count
20207 @cindex task suspend count
20208 @cindex detach from task, @sc{gnu} Hurd
20209 This command sets the suspend count the task will be left with when
20210 @value{GDBN} detaches from it.
20212 @item show task detach-suspend-count
20213 Show the suspend count the task will be left with when detaching.
20215 @item set task exception-port
20216 @itemx set task excp
20217 @cindex task exception port, @sc{gnu} Hurd
20218 This command sets the task exception port to which @value{GDBN} will
20219 forward exceptions. The argument should be the value of the @dfn{send
20220 rights} of the task. @code{set task excp} is a shorthand alias.
20222 @item set noninvasive
20223 @cindex noninvasive task options
20224 This command switches @value{GDBN} to a mode that is the least
20225 invasive as far as interfering with the inferior is concerned. This
20226 is the same as using @code{set task pause}, @code{set exceptions}, and
20227 @code{set signals} to values opposite to the defaults.
20229 @item info send-rights
20230 @itemx info receive-rights
20231 @itemx info port-rights
20232 @itemx info port-sets
20233 @itemx info dead-names
20236 @cindex send rights, @sc{gnu} Hurd
20237 @cindex receive rights, @sc{gnu} Hurd
20238 @cindex port rights, @sc{gnu} Hurd
20239 @cindex port sets, @sc{gnu} Hurd
20240 @cindex dead names, @sc{gnu} Hurd
20241 These commands display information about, respectively, send rights,
20242 receive rights, port rights, port sets, and dead names of a task.
20243 There are also shorthand aliases: @code{info ports} for @code{info
20244 port-rights} and @code{info psets} for @code{info port-sets}.
20246 @item set thread pause
20247 @kindex set thread@r{, Hurd command}
20248 @cindex thread properties, @sc{gnu} Hurd
20249 @cindex pause current thread (@sc{gnu} Hurd)
20250 This command toggles current thread suspension when @value{GDBN} has
20251 control. Setting it to on takes effect immediately, and the current
20252 thread is suspended whenever @value{GDBN} gets control. Setting it to
20253 off will take effect the next time the inferior is continued.
20254 Normally, this command has no effect, since when @value{GDBN} has
20255 control, the whole task is suspended. However, if you used @code{set
20256 task pause off} (see above), this command comes in handy to suspend
20257 only the current thread.
20259 @item show thread pause
20260 @kindex show thread@r{, Hurd command}
20261 This command shows the state of current thread suspension.
20263 @item set thread run
20264 This command sets whether the current thread is allowed to run.
20266 @item show thread run
20267 Show whether the current thread is allowed to run.
20269 @item set thread detach-suspend-count
20270 @cindex thread suspend count, @sc{gnu} Hurd
20271 @cindex detach from thread, @sc{gnu} Hurd
20272 This command sets the suspend count @value{GDBN} will leave on a
20273 thread when detaching. This number is relative to the suspend count
20274 found by @value{GDBN} when it notices the thread; use @code{set thread
20275 takeover-suspend-count} to force it to an absolute value.
20277 @item show thread detach-suspend-count
20278 Show the suspend count @value{GDBN} will leave on the thread when
20281 @item set thread exception-port
20282 @itemx set thread excp
20283 Set the thread exception port to which to forward exceptions. This
20284 overrides the port set by @code{set task exception-port} (see above).
20285 @code{set thread excp} is the shorthand alias.
20287 @item set thread takeover-suspend-count
20288 Normally, @value{GDBN}'s thread suspend counts are relative to the
20289 value @value{GDBN} finds when it notices each thread. This command
20290 changes the suspend counts to be absolute instead.
20292 @item set thread default
20293 @itemx show thread default
20294 @cindex thread default settings, @sc{gnu} Hurd
20295 Each of the above @code{set thread} commands has a @code{set thread
20296 default} counterpart (e.g., @code{set thread default pause}, @code{set
20297 thread default exception-port}, etc.). The @code{thread default}
20298 variety of commands sets the default thread properties for all
20299 threads; you can then change the properties of individual threads with
20300 the non-default commands.
20307 @value{GDBN} provides the following commands specific to the Darwin target:
20310 @item set debug darwin @var{num}
20311 @kindex set debug darwin
20312 When set to a non zero value, enables debugging messages specific to
20313 the Darwin support. Higher values produce more verbose output.
20315 @item show debug darwin
20316 @kindex show debug darwin
20317 Show the current state of Darwin messages.
20319 @item set debug mach-o @var{num}
20320 @kindex set debug mach-o
20321 When set to a non zero value, enables debugging messages while
20322 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
20323 file format used on Darwin for object and executable files.) Higher
20324 values produce more verbose output. This is a command to diagnose
20325 problems internal to @value{GDBN} and should not be needed in normal
20328 @item show debug mach-o
20329 @kindex show debug mach-o
20330 Show the current state of Mach-O file messages.
20332 @item set mach-exceptions on
20333 @itemx set mach-exceptions off
20334 @kindex set mach-exceptions
20335 On Darwin, faults are first reported as a Mach exception and are then
20336 mapped to a Posix signal. Use this command to turn on trapping of
20337 Mach exceptions in the inferior. This might be sometimes useful to
20338 better understand the cause of a fault. The default is off.
20340 @item show mach-exceptions
20341 @kindex show mach-exceptions
20342 Show the current state of exceptions trapping.
20347 @section Embedded Operating Systems
20349 This section describes configurations involving the debugging of
20350 embedded operating systems that are available for several different
20354 * VxWorks:: Using @value{GDBN} with VxWorks
20357 @value{GDBN} includes the ability to debug programs running on
20358 various real-time operating systems.
20361 @subsection Using @value{GDBN} with VxWorks
20367 @kindex target vxworks
20368 @item target vxworks @var{machinename}
20369 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
20370 is the target system's machine name or IP address.
20374 On VxWorks, @code{load} links @var{filename} dynamically on the
20375 current target system as well as adding its symbols in @value{GDBN}.
20377 @value{GDBN} enables developers to spawn and debug tasks running on networked
20378 VxWorks targets from a Unix host. Already-running tasks spawned from
20379 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
20380 both the Unix host and on the VxWorks target. The program
20381 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
20382 installed with the name @code{vxgdb}, to distinguish it from a
20383 @value{GDBN} for debugging programs on the host itself.)
20386 @item VxWorks-timeout @var{args}
20387 @kindex vxworks-timeout
20388 All VxWorks-based targets now support the option @code{vxworks-timeout}.
20389 This option is set by the user, and @var{args} represents the number of
20390 seconds @value{GDBN} waits for responses to rpc's. You might use this if
20391 your VxWorks target is a slow software simulator or is on the far side
20392 of a thin network line.
20395 The following information on connecting to VxWorks was current when
20396 this manual was produced; newer releases of VxWorks may use revised
20399 @findex INCLUDE_RDB
20400 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
20401 to include the remote debugging interface routines in the VxWorks
20402 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
20403 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
20404 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
20405 source debugging task @code{tRdbTask} when VxWorks is booted. For more
20406 information on configuring and remaking VxWorks, see the manufacturer's
20408 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
20410 Once you have included @file{rdb.a} in your VxWorks system image and set
20411 your Unix execution search path to find @value{GDBN}, you are ready to
20412 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
20413 @code{vxgdb}, depending on your installation).
20415 @value{GDBN} comes up showing the prompt:
20422 * VxWorks Connection:: Connecting to VxWorks
20423 * VxWorks Download:: VxWorks download
20424 * VxWorks Attach:: Running tasks
20427 @node VxWorks Connection
20428 @subsubsection Connecting to VxWorks
20430 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
20431 network. To connect to a target whose host name is ``@code{tt}'', type:
20434 (vxgdb) target vxworks tt
20438 @value{GDBN} displays messages like these:
20441 Attaching remote machine across net...
20446 @value{GDBN} then attempts to read the symbol tables of any object modules
20447 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
20448 these files by searching the directories listed in the command search
20449 path (@pxref{Environment, ,Your Program's Environment}); if it fails
20450 to find an object file, it displays a message such as:
20453 prog.o: No such file or directory.
20456 When this happens, add the appropriate directory to the search path with
20457 the @value{GDBN} command @code{path}, and execute the @code{target}
20460 @node VxWorks Download
20461 @subsubsection VxWorks Download
20463 @cindex download to VxWorks
20464 If you have connected to the VxWorks target and you want to debug an
20465 object that has not yet been loaded, you can use the @value{GDBN}
20466 @code{load} command to download a file from Unix to VxWorks
20467 incrementally. The object file given as an argument to the @code{load}
20468 command is actually opened twice: first by the VxWorks target in order
20469 to download the code, then by @value{GDBN} in order to read the symbol
20470 table. This can lead to problems if the current working directories on
20471 the two systems differ. If both systems have NFS mounted the same
20472 filesystems, you can avoid these problems by using absolute paths.
20473 Otherwise, it is simplest to set the working directory on both systems
20474 to the directory in which the object file resides, and then to reference
20475 the file by its name, without any path. For instance, a program
20476 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
20477 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
20478 program, type this on VxWorks:
20481 -> cd "@var{vxpath}/vw/demo/rdb"
20485 Then, in @value{GDBN}, type:
20488 (vxgdb) cd @var{hostpath}/vw/demo/rdb
20489 (vxgdb) load prog.o
20492 @value{GDBN} displays a response similar to this:
20495 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
20498 You can also use the @code{load} command to reload an object module
20499 after editing and recompiling the corresponding source file. Note that
20500 this makes @value{GDBN} delete all currently-defined breakpoints,
20501 auto-displays, and convenience variables, and to clear the value
20502 history. (This is necessary in order to preserve the integrity of
20503 debugger's data structures that reference the target system's symbol
20506 @node VxWorks Attach
20507 @subsubsection Running Tasks
20509 @cindex running VxWorks tasks
20510 You can also attach to an existing task using the @code{attach} command as
20514 (vxgdb) attach @var{task}
20518 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
20519 or suspended when you attach to it. Running tasks are suspended at
20520 the time of attachment.
20522 @node Embedded Processors
20523 @section Embedded Processors
20525 This section goes into details specific to particular embedded
20528 @cindex send command to simulator
20529 Whenever a specific embedded processor has a simulator, @value{GDBN}
20530 allows to send an arbitrary command to the simulator.
20533 @item sim @var{command}
20534 @kindex sim@r{, a command}
20535 Send an arbitrary @var{command} string to the simulator. Consult the
20536 documentation for the specific simulator in use for information about
20537 acceptable commands.
20543 * M32R/D:: Renesas M32R/D
20544 * M68K:: Motorola M68K
20545 * MicroBlaze:: Xilinx MicroBlaze
20546 * MIPS Embedded:: MIPS Embedded
20547 * PowerPC Embedded:: PowerPC Embedded
20548 * PA:: HP PA Embedded
20549 * Sparclet:: Tsqware Sparclet
20550 * Sparclite:: Fujitsu Sparclite
20551 * Z8000:: Zilog Z8000
20554 * Super-H:: Renesas Super-H
20563 @item target rdi @var{dev}
20564 ARM Angel monitor, via RDI library interface to ADP protocol. You may
20565 use this target to communicate with both boards running the Angel
20566 monitor, or with the EmbeddedICE JTAG debug device.
20569 @item target rdp @var{dev}
20574 @value{GDBN} provides the following ARM-specific commands:
20577 @item set arm disassembler
20579 This commands selects from a list of disassembly styles. The
20580 @code{"std"} style is the standard style.
20582 @item show arm disassembler
20584 Show the current disassembly style.
20586 @item set arm apcs32
20587 @cindex ARM 32-bit mode
20588 This command toggles ARM operation mode between 32-bit and 26-bit.
20590 @item show arm apcs32
20591 Display the current usage of the ARM 32-bit mode.
20593 @item set arm fpu @var{fputype}
20594 This command sets the ARM floating-point unit (FPU) type. The
20595 argument @var{fputype} can be one of these:
20599 Determine the FPU type by querying the OS ABI.
20601 Software FPU, with mixed-endian doubles on little-endian ARM
20604 GCC-compiled FPA co-processor.
20606 Software FPU with pure-endian doubles.
20612 Show the current type of the FPU.
20615 This command forces @value{GDBN} to use the specified ABI.
20618 Show the currently used ABI.
20620 @item set arm fallback-mode (arm|thumb|auto)
20621 @value{GDBN} uses the symbol table, when available, to determine
20622 whether instructions are ARM or Thumb. This command controls
20623 @value{GDBN}'s default behavior when the symbol table is not
20624 available. The default is @samp{auto}, which causes @value{GDBN} to
20625 use the current execution mode (from the @code{T} bit in the @code{CPSR}
20628 @item show arm fallback-mode
20629 Show the current fallback instruction mode.
20631 @item set arm force-mode (arm|thumb|auto)
20632 This command overrides use of the symbol table to determine whether
20633 instructions are ARM or Thumb. The default is @samp{auto}, which
20634 causes @value{GDBN} to use the symbol table and then the setting
20635 of @samp{set arm fallback-mode}.
20637 @item show arm force-mode
20638 Show the current forced instruction mode.
20640 @item set debug arm
20641 Toggle whether to display ARM-specific debugging messages from the ARM
20642 target support subsystem.
20644 @item show debug arm
20645 Show whether ARM-specific debugging messages are enabled.
20648 The following commands are available when an ARM target is debugged
20649 using the RDI interface:
20652 @item rdilogfile @r{[}@var{file}@r{]}
20654 @cindex ADP (Angel Debugger Protocol) logging
20655 Set the filename for the ADP (Angel Debugger Protocol) packet log.
20656 With an argument, sets the log file to the specified @var{file}. With
20657 no argument, show the current log file name. The default log file is
20660 @item rdilogenable @r{[}@var{arg}@r{]}
20661 @kindex rdilogenable
20662 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
20663 enables logging, with an argument 0 or @code{"no"} disables it. With
20664 no arguments displays the current setting. When logging is enabled,
20665 ADP packets exchanged between @value{GDBN} and the RDI target device
20666 are logged to a file.
20668 @item set rdiromatzero
20669 @kindex set rdiromatzero
20670 @cindex ROM at zero address, RDI
20671 Tell @value{GDBN} whether the target has ROM at address 0. If on,
20672 vector catching is disabled, so that zero address can be used. If off
20673 (the default), vector catching is enabled. For this command to take
20674 effect, it needs to be invoked prior to the @code{target rdi} command.
20676 @item show rdiromatzero
20677 @kindex show rdiromatzero
20678 Show the current setting of ROM at zero address.
20680 @item set rdiheartbeat
20681 @kindex set rdiheartbeat
20682 @cindex RDI heartbeat
20683 Enable or disable RDI heartbeat packets. It is not recommended to
20684 turn on this option, since it confuses ARM and EPI JTAG interface, as
20685 well as the Angel monitor.
20687 @item show rdiheartbeat
20688 @kindex show rdiheartbeat
20689 Show the setting of RDI heartbeat packets.
20693 @item target sim @r{[}@var{simargs}@r{]} @dots{}
20694 The @value{GDBN} ARM simulator accepts the following optional arguments.
20697 @item --swi-support=@var{type}
20698 Tell the simulator which SWI interfaces to support.
20699 @var{type} may be a comma separated list of the following values.
20700 The default value is @code{all}.
20713 @subsection Renesas M32R/D and M32R/SDI
20716 @kindex target m32r
20717 @item target m32r @var{dev}
20718 Renesas M32R/D ROM monitor.
20720 @kindex target m32rsdi
20721 @item target m32rsdi @var{dev}
20722 Renesas M32R SDI server, connected via parallel port to the board.
20725 The following @value{GDBN} commands are specific to the M32R monitor:
20728 @item set download-path @var{path}
20729 @kindex set download-path
20730 @cindex find downloadable @sc{srec} files (M32R)
20731 Set the default path for finding downloadable @sc{srec} files.
20733 @item show download-path
20734 @kindex show download-path
20735 Show the default path for downloadable @sc{srec} files.
20737 @item set board-address @var{addr}
20738 @kindex set board-address
20739 @cindex M32-EVA target board address
20740 Set the IP address for the M32R-EVA target board.
20742 @item show board-address
20743 @kindex show board-address
20744 Show the current IP address of the target board.
20746 @item set server-address @var{addr}
20747 @kindex set server-address
20748 @cindex download server address (M32R)
20749 Set the IP address for the download server, which is the @value{GDBN}'s
20752 @item show server-address
20753 @kindex show server-address
20754 Display the IP address of the download server.
20756 @item upload @r{[}@var{file}@r{]}
20757 @kindex upload@r{, M32R}
20758 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
20759 upload capability. If no @var{file} argument is given, the current
20760 executable file is uploaded.
20762 @item tload @r{[}@var{file}@r{]}
20763 @kindex tload@r{, M32R}
20764 Test the @code{upload} command.
20767 The following commands are available for M32R/SDI:
20772 @cindex reset SDI connection, M32R
20773 This command resets the SDI connection.
20777 This command shows the SDI connection status.
20780 @kindex debug_chaos
20781 @cindex M32R/Chaos debugging
20782 Instructs the remote that M32R/Chaos debugging is to be used.
20784 @item use_debug_dma
20785 @kindex use_debug_dma
20786 Instructs the remote to use the DEBUG_DMA method of accessing memory.
20789 @kindex use_mon_code
20790 Instructs the remote to use the MON_CODE method of accessing memory.
20793 @kindex use_ib_break
20794 Instructs the remote to set breakpoints by IB break.
20796 @item use_dbt_break
20797 @kindex use_dbt_break
20798 Instructs the remote to set breakpoints by DBT.
20804 The Motorola m68k configuration includes ColdFire support, and a
20805 target command for the following ROM monitor.
20809 @kindex target dbug
20810 @item target dbug @var{dev}
20811 dBUG ROM monitor for Motorola ColdFire.
20816 @subsection MicroBlaze
20817 @cindex Xilinx MicroBlaze
20818 @cindex XMD, Xilinx Microprocessor Debugger
20820 The MicroBlaze is a soft-core processor supported on various Xilinx
20821 FPGAs, such as Spartan or Virtex series. Boards with these processors
20822 usually have JTAG ports which connect to a host system running the Xilinx
20823 Embedded Development Kit (EDK) or Software Development Kit (SDK).
20824 This host system is used to download the configuration bitstream to
20825 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
20826 communicates with the target board using the JTAG interface and
20827 presents a @code{gdbserver} interface to the board. By default
20828 @code{xmd} uses port @code{1234}. (While it is possible to change
20829 this default port, it requires the use of undocumented @code{xmd}
20830 commands. Contact Xilinx support if you need to do this.)
20832 Use these GDB commands to connect to the MicroBlaze target processor.
20835 @item target remote :1234
20836 Use this command to connect to the target if you are running @value{GDBN}
20837 on the same system as @code{xmd}.
20839 @item target remote @var{xmd-host}:1234
20840 Use this command to connect to the target if it is connected to @code{xmd}
20841 running on a different system named @var{xmd-host}.
20844 Use this command to download a program to the MicroBlaze target.
20846 @item set debug microblaze @var{n}
20847 Enable MicroBlaze-specific debugging messages if non-zero.
20849 @item show debug microblaze @var{n}
20850 Show MicroBlaze-specific debugging level.
20853 @node MIPS Embedded
20854 @subsection @acronym{MIPS} Embedded
20856 @cindex @acronym{MIPS} boards
20857 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
20858 @acronym{MIPS} board attached to a serial line. This is available when
20859 you configure @value{GDBN} with @samp{--target=mips-elf}.
20862 Use these @value{GDBN} commands to specify the connection to your target board:
20865 @item target mips @var{port}
20866 @kindex target mips @var{port}
20867 To run a program on the board, start up @code{@value{GDBP}} with the
20868 name of your program as the argument. To connect to the board, use the
20869 command @samp{target mips @var{port}}, where @var{port} is the name of
20870 the serial port connected to the board. If the program has not already
20871 been downloaded to the board, you may use the @code{load} command to
20872 download it. You can then use all the usual @value{GDBN} commands.
20874 For example, this sequence connects to the target board through a serial
20875 port, and loads and runs a program called @var{prog} through the
20879 host$ @value{GDBP} @var{prog}
20880 @value{GDBN} is free software and @dots{}
20881 (@value{GDBP}) target mips /dev/ttyb
20882 (@value{GDBP}) load @var{prog}
20886 @item target mips @var{hostname}:@var{portnumber}
20887 On some @value{GDBN} host configurations, you can specify a TCP
20888 connection (for instance, to a serial line managed by a terminal
20889 concentrator) instead of a serial port, using the syntax
20890 @samp{@var{hostname}:@var{portnumber}}.
20892 @item target pmon @var{port}
20893 @kindex target pmon @var{port}
20896 @item target ddb @var{port}
20897 @kindex target ddb @var{port}
20898 NEC's DDB variant of PMON for Vr4300.
20900 @item target lsi @var{port}
20901 @kindex target lsi @var{port}
20902 LSI variant of PMON.
20904 @kindex target r3900
20905 @item target r3900 @var{dev}
20906 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
20908 @kindex target array
20909 @item target array @var{dev}
20910 Array Tech LSI33K RAID controller board.
20916 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
20919 @item set mipsfpu double
20920 @itemx set mipsfpu single
20921 @itemx set mipsfpu none
20922 @itemx set mipsfpu auto
20923 @itemx show mipsfpu
20924 @kindex set mipsfpu
20925 @kindex show mipsfpu
20926 @cindex @acronym{MIPS} remote floating point
20927 @cindex floating point, @acronym{MIPS} remote
20928 If your target board does not support the @acronym{MIPS} floating point
20929 coprocessor, you should use the command @samp{set mipsfpu none} (if you
20930 need this, you may wish to put the command in your @value{GDBN} init
20931 file). This tells @value{GDBN} how to find the return value of
20932 functions which return floating point values. It also allows
20933 @value{GDBN} to avoid saving the floating point registers when calling
20934 functions on the board. If you are using a floating point coprocessor
20935 with only single precision floating point support, as on the @sc{r4650}
20936 processor, use the command @samp{set mipsfpu single}. The default
20937 double precision floating point coprocessor may be selected using
20938 @samp{set mipsfpu double}.
20940 In previous versions the only choices were double precision or no
20941 floating point, so @samp{set mipsfpu on} will select double precision
20942 and @samp{set mipsfpu off} will select no floating point.
20944 As usual, you can inquire about the @code{mipsfpu} variable with
20945 @samp{show mipsfpu}.
20947 @item set timeout @var{seconds}
20948 @itemx set retransmit-timeout @var{seconds}
20949 @itemx show timeout
20950 @itemx show retransmit-timeout
20951 @cindex @code{timeout}, @acronym{MIPS} protocol
20952 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
20953 @kindex set timeout
20954 @kindex show timeout
20955 @kindex set retransmit-timeout
20956 @kindex show retransmit-timeout
20957 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
20958 remote protocol, with the @code{set timeout @var{seconds}} command. The
20959 default is 5 seconds. Similarly, you can control the timeout used while
20960 waiting for an acknowledgment of a packet with the @code{set
20961 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
20962 You can inspect both values with @code{show timeout} and @code{show
20963 retransmit-timeout}. (These commands are @emph{only} available when
20964 @value{GDBN} is configured for @samp{--target=mips-elf}.)
20966 The timeout set by @code{set timeout} does not apply when @value{GDBN}
20967 is waiting for your program to stop. In that case, @value{GDBN} waits
20968 forever because it has no way of knowing how long the program is going
20969 to run before stopping.
20971 @item set syn-garbage-limit @var{num}
20972 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
20973 @cindex synchronize with remote @acronym{MIPS} target
20974 Limit the maximum number of characters @value{GDBN} should ignore when
20975 it tries to synchronize with the remote target. The default is 10
20976 characters. Setting the limit to -1 means there's no limit.
20978 @item show syn-garbage-limit
20979 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
20980 Show the current limit on the number of characters to ignore when
20981 trying to synchronize with the remote system.
20983 @item set monitor-prompt @var{prompt}
20984 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
20985 @cindex remote monitor prompt
20986 Tell @value{GDBN} to expect the specified @var{prompt} string from the
20987 remote monitor. The default depends on the target:
20997 @item show monitor-prompt
20998 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
20999 Show the current strings @value{GDBN} expects as the prompt from the
21002 @item set monitor-warnings
21003 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
21004 Enable or disable monitor warnings about hardware breakpoints. This
21005 has effect only for the @code{lsi} target. When on, @value{GDBN} will
21006 display warning messages whose codes are returned by the @code{lsi}
21007 PMON monitor for breakpoint commands.
21009 @item show monitor-warnings
21010 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
21011 Show the current setting of printing monitor warnings.
21013 @item pmon @var{command}
21014 @kindex pmon@r{, @acronym{MIPS} remote}
21015 @cindex send PMON command
21016 This command allows sending an arbitrary @var{command} string to the
21017 monitor. The monitor must be in debug mode for this to work.
21020 @node PowerPC Embedded
21021 @subsection PowerPC Embedded
21023 @cindex DVC register
21024 @value{GDBN} supports using the DVC (Data Value Compare) register to
21025 implement in hardware simple hardware watchpoint conditions of the form:
21028 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
21029 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
21032 The DVC register will be automatically used when @value{GDBN} detects
21033 such pattern in a condition expression, and the created watchpoint uses one
21034 debug register (either the @code{exact-watchpoints} option is on and the
21035 variable is scalar, or the variable has a length of one byte). This feature
21036 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
21039 When running on PowerPC embedded processors, @value{GDBN} automatically uses
21040 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
21041 in which case watchpoints using only one debug register are created when
21042 watching variables of scalar types.
21044 You can create an artificial array to watch an arbitrary memory
21045 region using one of the following commands (@pxref{Expressions}):
21048 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
21049 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
21052 PowerPC embedded processors support masked watchpoints. See the discussion
21053 about the @code{mask} argument in @ref{Set Watchpoints}.
21055 @cindex ranged breakpoint
21056 PowerPC embedded processors support hardware accelerated
21057 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
21058 the inferior whenever it executes an instruction at any address within
21059 the range it specifies. To set a ranged breakpoint in @value{GDBN},
21060 use the @code{break-range} command.
21062 @value{GDBN} provides the following PowerPC-specific commands:
21065 @kindex break-range
21066 @item break-range @var{start-location}, @var{end-location}
21067 Set a breakpoint for an address range.
21068 @var{start-location} and @var{end-location} can specify a function name,
21069 a line number, an offset of lines from the current line or from the start
21070 location, or an address of an instruction (see @ref{Specify Location},
21071 for a list of all the possible ways to specify a @var{location}.)
21072 The breakpoint will stop execution of the inferior whenever it
21073 executes an instruction at any address within the specified range,
21074 (including @var{start-location} and @var{end-location}.)
21076 @kindex set powerpc
21077 @item set powerpc soft-float
21078 @itemx show powerpc soft-float
21079 Force @value{GDBN} to use (or not use) a software floating point calling
21080 convention. By default, @value{GDBN} selects the calling convention based
21081 on the selected architecture and the provided executable file.
21083 @item set powerpc vector-abi
21084 @itemx show powerpc vector-abi
21085 Force @value{GDBN} to use the specified calling convention for vector
21086 arguments and return values. The valid options are @samp{auto};
21087 @samp{generic}, to avoid vector registers even if they are present;
21088 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
21089 registers. By default, @value{GDBN} selects the calling convention
21090 based on the selected architecture and the provided executable file.
21092 @item set powerpc exact-watchpoints
21093 @itemx show powerpc exact-watchpoints
21094 Allow @value{GDBN} to use only one debug register when watching a variable
21095 of scalar type, thus assuming that the variable is accessed through the
21096 address of its first byte.
21098 @kindex target dink32
21099 @item target dink32 @var{dev}
21100 DINK32 ROM monitor.
21102 @kindex target ppcbug
21103 @item target ppcbug @var{dev}
21104 @kindex target ppcbug1
21105 @item target ppcbug1 @var{dev}
21106 PPCBUG ROM monitor for PowerPC.
21109 @item target sds @var{dev}
21110 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
21113 @cindex SDS protocol
21114 The following commands specific to the SDS protocol are supported
21118 @item set sdstimeout @var{nsec}
21119 @kindex set sdstimeout
21120 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
21121 default is 2 seconds.
21123 @item show sdstimeout
21124 @kindex show sdstimeout
21125 Show the current value of the SDS timeout.
21127 @item sds @var{command}
21128 @kindex sds@r{, a command}
21129 Send the specified @var{command} string to the SDS monitor.
21134 @subsection HP PA Embedded
21138 @kindex target op50n
21139 @item target op50n @var{dev}
21140 OP50N monitor, running on an OKI HPPA board.
21142 @kindex target w89k
21143 @item target w89k @var{dev}
21144 W89K monitor, running on a Winbond HPPA board.
21149 @subsection Tsqware Sparclet
21153 @value{GDBN} enables developers to debug tasks running on
21154 Sparclet targets from a Unix host.
21155 @value{GDBN} uses code that runs on
21156 both the Unix host and on the Sparclet target. The program
21157 @code{@value{GDBP}} is installed and executed on the Unix host.
21160 @item remotetimeout @var{args}
21161 @kindex remotetimeout
21162 @value{GDBN} supports the option @code{remotetimeout}.
21163 This option is set by the user, and @var{args} represents the number of
21164 seconds @value{GDBN} waits for responses.
21167 @cindex compiling, on Sparclet
21168 When compiling for debugging, include the options @samp{-g} to get debug
21169 information and @samp{-Ttext} to relocate the program to where you wish to
21170 load it on the target. You may also want to add the options @samp{-n} or
21171 @samp{-N} in order to reduce the size of the sections. Example:
21174 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
21177 You can use @code{objdump} to verify that the addresses are what you intended:
21180 sparclet-aout-objdump --headers --syms prog
21183 @cindex running, on Sparclet
21185 your Unix execution search path to find @value{GDBN}, you are ready to
21186 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
21187 (or @code{sparclet-aout-gdb}, depending on your installation).
21189 @value{GDBN} comes up showing the prompt:
21196 * Sparclet File:: Setting the file to debug
21197 * Sparclet Connection:: Connecting to Sparclet
21198 * Sparclet Download:: Sparclet download
21199 * Sparclet Execution:: Running and debugging
21202 @node Sparclet File
21203 @subsubsection Setting File to Debug
21205 The @value{GDBN} command @code{file} lets you choose with program to debug.
21208 (gdbslet) file prog
21212 @value{GDBN} then attempts to read the symbol table of @file{prog}.
21213 @value{GDBN} locates
21214 the file by searching the directories listed in the command search
21216 If the file was compiled with debug information (option @samp{-g}), source
21217 files will be searched as well.
21218 @value{GDBN} locates
21219 the source files by searching the directories listed in the directory search
21220 path (@pxref{Environment, ,Your Program's Environment}).
21222 to find a file, it displays a message such as:
21225 prog: No such file or directory.
21228 When this happens, add the appropriate directories to the search paths with
21229 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
21230 @code{target} command again.
21232 @node Sparclet Connection
21233 @subsubsection Connecting to Sparclet
21235 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
21236 To connect to a target on serial port ``@code{ttya}'', type:
21239 (gdbslet) target sparclet /dev/ttya
21240 Remote target sparclet connected to /dev/ttya
21241 main () at ../prog.c:3
21245 @value{GDBN} displays messages like these:
21251 @node Sparclet Download
21252 @subsubsection Sparclet Download
21254 @cindex download to Sparclet
21255 Once connected to the Sparclet target,
21256 you can use the @value{GDBN}
21257 @code{load} command to download the file from the host to the target.
21258 The file name and load offset should be given as arguments to the @code{load}
21260 Since the file format is aout, the program must be loaded to the starting
21261 address. You can use @code{objdump} to find out what this value is. The load
21262 offset is an offset which is added to the VMA (virtual memory address)
21263 of each of the file's sections.
21264 For instance, if the program
21265 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
21266 and bss at 0x12010170, in @value{GDBN}, type:
21269 (gdbslet) load prog 0x12010000
21270 Loading section .text, size 0xdb0 vma 0x12010000
21273 If the code is loaded at a different address then what the program was linked
21274 to, you may need to use the @code{section} and @code{add-symbol-file} commands
21275 to tell @value{GDBN} where to map the symbol table.
21277 @node Sparclet Execution
21278 @subsubsection Running and Debugging
21280 @cindex running and debugging Sparclet programs
21281 You can now begin debugging the task using @value{GDBN}'s execution control
21282 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
21283 manual for the list of commands.
21287 Breakpoint 1 at 0x12010000: file prog.c, line 3.
21289 Starting program: prog
21290 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
21291 3 char *symarg = 0;
21293 4 char *execarg = "hello!";
21298 @subsection Fujitsu Sparclite
21302 @kindex target sparclite
21303 @item target sparclite @var{dev}
21304 Fujitsu sparclite boards, used only for the purpose of loading.
21305 You must use an additional command to debug the program.
21306 For example: target remote @var{dev} using @value{GDBN} standard
21312 @subsection Zilog Z8000
21315 @cindex simulator, Z8000
21316 @cindex Zilog Z8000 simulator
21318 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
21321 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
21322 unsegmented variant of the Z8000 architecture) or the Z8001 (the
21323 segmented variant). The simulator recognizes which architecture is
21324 appropriate by inspecting the object code.
21327 @item target sim @var{args}
21329 @kindex target sim@r{, with Z8000}
21330 Debug programs on a simulated CPU. If the simulator supports setup
21331 options, specify them via @var{args}.
21335 After specifying this target, you can debug programs for the simulated
21336 CPU in the same style as programs for your host computer; use the
21337 @code{file} command to load a new program image, the @code{run} command
21338 to run your program, and so on.
21340 As well as making available all the usual machine registers
21341 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
21342 additional items of information as specially named registers:
21347 Counts clock-ticks in the simulator.
21350 Counts instructions run in the simulator.
21353 Execution time in 60ths of a second.
21357 You can refer to these values in @value{GDBN} expressions with the usual
21358 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
21359 conditional breakpoint that suspends only after at least 5000
21360 simulated clock ticks.
21363 @subsection Atmel AVR
21366 When configured for debugging the Atmel AVR, @value{GDBN} supports the
21367 following AVR-specific commands:
21370 @item info io_registers
21371 @kindex info io_registers@r{, AVR}
21372 @cindex I/O registers (Atmel AVR)
21373 This command displays information about the AVR I/O registers. For
21374 each register, @value{GDBN} prints its number and value.
21381 When configured for debugging CRIS, @value{GDBN} provides the
21382 following CRIS-specific commands:
21385 @item set cris-version @var{ver}
21386 @cindex CRIS version
21387 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
21388 The CRIS version affects register names and sizes. This command is useful in
21389 case autodetection of the CRIS version fails.
21391 @item show cris-version
21392 Show the current CRIS version.
21394 @item set cris-dwarf2-cfi
21395 @cindex DWARF-2 CFI and CRIS
21396 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
21397 Change to @samp{off} when using @code{gcc-cris} whose version is below
21400 @item show cris-dwarf2-cfi
21401 Show the current state of using DWARF-2 CFI.
21403 @item set cris-mode @var{mode}
21405 Set the current CRIS mode to @var{mode}. It should only be changed when
21406 debugging in guru mode, in which case it should be set to
21407 @samp{guru} (the default is @samp{normal}).
21409 @item show cris-mode
21410 Show the current CRIS mode.
21414 @subsection Renesas Super-H
21417 For the Renesas Super-H processor, @value{GDBN} provides these
21421 @item set sh calling-convention @var{convention}
21422 @kindex set sh calling-convention
21423 Set the calling-convention used when calling functions from @value{GDBN}.
21424 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
21425 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
21426 convention. If the DWARF-2 information of the called function specifies
21427 that the function follows the Renesas calling convention, the function
21428 is called using the Renesas calling convention. If the calling convention
21429 is set to @samp{renesas}, the Renesas calling convention is always used,
21430 regardless of the DWARF-2 information. This can be used to override the
21431 default of @samp{gcc} if debug information is missing, or the compiler
21432 does not emit the DWARF-2 calling convention entry for a function.
21434 @item show sh calling-convention
21435 @kindex show sh calling-convention
21436 Show the current calling convention setting.
21441 @node Architectures
21442 @section Architectures
21444 This section describes characteristics of architectures that affect
21445 all uses of @value{GDBN} with the architecture, both native and cross.
21452 * HPPA:: HP PA architecture
21453 * SPU:: Cell Broadband Engine SPU architecture
21459 @subsection AArch64
21460 @cindex AArch64 support
21462 When @value{GDBN} is debugging the AArch64 architecture, it provides the
21463 following special commands:
21466 @item set debug aarch64
21467 @kindex set debug aarch64
21468 This command determines whether AArch64 architecture-specific debugging
21469 messages are to be displayed.
21471 @item show debug aarch64
21472 Show whether AArch64 debugging messages are displayed.
21477 @subsection x86 Architecture-specific Issues
21480 @item set struct-convention @var{mode}
21481 @kindex set struct-convention
21482 @cindex struct return convention
21483 @cindex struct/union returned in registers
21484 Set the convention used by the inferior to return @code{struct}s and
21485 @code{union}s from functions to @var{mode}. Possible values of
21486 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
21487 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
21488 are returned on the stack, while @code{"reg"} means that a
21489 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
21490 be returned in a register.
21492 @item show struct-convention
21493 @kindex show struct-convention
21494 Show the current setting of the convention to return @code{struct}s
21498 @subsubsection Intel(R) @dfn{Memory Protection Extensions} (MPX).
21499 @cindex Intel(R) Memory Protection Extensions (MPX).
21501 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
21502 @footnote{The register named with capital letters represent the architecture
21503 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
21504 which are the lower bound and upper bound. Bounds are effective addresses or
21505 memory locations. The upper bounds are architecturally represented in 1's
21506 complement form. A bound having lower bound = 0, and upper bound = 0
21507 (1's complement of all bits set) will allow access to the entire address space.
21509 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
21510 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
21511 display the upper bound performing the complement of one operation on the
21512 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
21513 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
21514 can also be noted that the upper bounds are inclusive.
21516 As an example, assume that the register BND0 holds bounds for a pointer having
21517 access allowed for the range between 0x32 and 0x71. The values present on
21518 bnd0raw and bnd registers are presented as follows:
21521 bnd0raw = @{0x32, 0xffffffff8e@}
21522 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
21525 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
21526 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
21527 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
21528 Python, the display includes the memory size, in bits, accessible to
21534 See the following section.
21537 @subsection @acronym{MIPS}
21539 @cindex stack on Alpha
21540 @cindex stack on @acronym{MIPS}
21541 @cindex Alpha stack
21542 @cindex @acronym{MIPS} stack
21543 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
21544 sometimes requires @value{GDBN} to search backward in the object code to
21545 find the beginning of a function.
21547 @cindex response time, @acronym{MIPS} debugging
21548 To improve response time (especially for embedded applications, where
21549 @value{GDBN} may be restricted to a slow serial line for this search)
21550 you may want to limit the size of this search, using one of these
21554 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
21555 @item set heuristic-fence-post @var{limit}
21556 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
21557 search for the beginning of a function. A value of @var{0} (the
21558 default) means there is no limit. However, except for @var{0}, the
21559 larger the limit the more bytes @code{heuristic-fence-post} must search
21560 and therefore the longer it takes to run. You should only need to use
21561 this command when debugging a stripped executable.
21563 @item show heuristic-fence-post
21564 Display the current limit.
21568 These commands are available @emph{only} when @value{GDBN} is configured
21569 for debugging programs on Alpha or @acronym{MIPS} processors.
21571 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
21575 @item set mips abi @var{arg}
21576 @kindex set mips abi
21577 @cindex set ABI for @acronym{MIPS}
21578 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
21579 values of @var{arg} are:
21583 The default ABI associated with the current binary (this is the
21593 @item show mips abi
21594 @kindex show mips abi
21595 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
21597 @item set mips compression @var{arg}
21598 @kindex set mips compression
21599 @cindex code compression, @acronym{MIPS}
21600 Tell @value{GDBN} which @acronym{MIPS} compressed
21601 @acronym{ISA, Instruction Set Architecture} encoding is used by the
21602 inferior. @value{GDBN} uses this for code disassembly and other
21603 internal interpretation purposes. This setting is only referred to
21604 when no executable has been associated with the debugging session or
21605 the executable does not provide information about the encoding it uses.
21606 Otherwise this setting is automatically updated from information
21607 provided by the executable.
21609 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
21610 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
21611 executables containing @acronym{MIPS16} code frequently are not
21612 identified as such.
21614 This setting is ``sticky''; that is, it retains its value across
21615 debugging sessions until reset either explicitly with this command or
21616 implicitly from an executable.
21618 The compiler and/or assembler typically add symbol table annotations to
21619 identify functions compiled for the @acronym{MIPS16} or
21620 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
21621 are present, @value{GDBN} uses them in preference to the global
21622 compressed @acronym{ISA} encoding setting.
21624 @item show mips compression
21625 @kindex show mips compression
21626 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
21627 @value{GDBN} to debug the inferior.
21630 @itemx show mipsfpu
21631 @xref{MIPS Embedded, set mipsfpu}.
21633 @item set mips mask-address @var{arg}
21634 @kindex set mips mask-address
21635 @cindex @acronym{MIPS} addresses, masking
21636 This command determines whether the most-significant 32 bits of 64-bit
21637 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
21638 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
21639 setting, which lets @value{GDBN} determine the correct value.
21641 @item show mips mask-address
21642 @kindex show mips mask-address
21643 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
21646 @item set remote-mips64-transfers-32bit-regs
21647 @kindex set remote-mips64-transfers-32bit-regs
21648 This command controls compatibility with 64-bit @acronym{MIPS} targets that
21649 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
21650 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
21651 and 64 bits for other registers, set this option to @samp{on}.
21653 @item show remote-mips64-transfers-32bit-regs
21654 @kindex show remote-mips64-transfers-32bit-regs
21655 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
21657 @item set debug mips
21658 @kindex set debug mips
21659 This command turns on and off debugging messages for the @acronym{MIPS}-specific
21660 target code in @value{GDBN}.
21662 @item show debug mips
21663 @kindex show debug mips
21664 Show the current setting of @acronym{MIPS} debugging messages.
21670 @cindex HPPA support
21672 When @value{GDBN} is debugging the HP PA architecture, it provides the
21673 following special commands:
21676 @item set debug hppa
21677 @kindex set debug hppa
21678 This command determines whether HPPA architecture-specific debugging
21679 messages are to be displayed.
21681 @item show debug hppa
21682 Show whether HPPA debugging messages are displayed.
21684 @item maint print unwind @var{address}
21685 @kindex maint print unwind@r{, HPPA}
21686 This command displays the contents of the unwind table entry at the
21687 given @var{address}.
21693 @subsection Cell Broadband Engine SPU architecture
21694 @cindex Cell Broadband Engine
21697 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
21698 it provides the following special commands:
21701 @item info spu event
21703 Display SPU event facility status. Shows current event mask
21704 and pending event status.
21706 @item info spu signal
21707 Display SPU signal notification facility status. Shows pending
21708 signal-control word and signal notification mode of both signal
21709 notification channels.
21711 @item info spu mailbox
21712 Display SPU mailbox facility status. Shows all pending entries,
21713 in order of processing, in each of the SPU Write Outbound,
21714 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
21717 Display MFC DMA status. Shows all pending commands in the MFC
21718 DMA queue. For each entry, opcode, tag, class IDs, effective
21719 and local store addresses and transfer size are shown.
21721 @item info spu proxydma
21722 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
21723 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
21724 and local store addresses and transfer size are shown.
21728 When @value{GDBN} is debugging a combined PowerPC/SPU application
21729 on the Cell Broadband Engine, it provides in addition the following
21733 @item set spu stop-on-load @var{arg}
21735 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
21736 will give control to the user when a new SPE thread enters its @code{main}
21737 function. The default is @code{off}.
21739 @item show spu stop-on-load
21741 Show whether to stop for new SPE threads.
21743 @item set spu auto-flush-cache @var{arg}
21744 Set whether to automatically flush the software-managed cache. When set to
21745 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
21746 cache to be flushed whenever SPE execution stops. This provides a consistent
21747 view of PowerPC memory that is accessed via the cache. If an application
21748 does not use the software-managed cache, this option has no effect.
21750 @item show spu auto-flush-cache
21751 Show whether to automatically flush the software-managed cache.
21756 @subsection PowerPC
21757 @cindex PowerPC architecture
21759 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
21760 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
21761 numbers stored in the floating point registers. These values must be stored
21762 in two consecutive registers, always starting at an even register like
21763 @code{f0} or @code{f2}.
21765 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
21766 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
21767 @code{f2} and @code{f3} for @code{$dl1} and so on.
21769 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
21770 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
21773 @subsection Nios II
21774 @cindex Nios II architecture
21776 When @value{GDBN} is debugging the Nios II architecture,
21777 it provides the following special commands:
21781 @item set debug nios2
21782 @kindex set debug nios2
21783 This command turns on and off debugging messages for the Nios II
21784 target code in @value{GDBN}.
21786 @item show debug nios2
21787 @kindex show debug nios2
21788 Show the current setting of Nios II debugging messages.
21791 @node Controlling GDB
21792 @chapter Controlling @value{GDBN}
21794 You can alter the way @value{GDBN} interacts with you by using the
21795 @code{set} command. For commands controlling how @value{GDBN} displays
21796 data, see @ref{Print Settings, ,Print Settings}. Other settings are
21801 * Editing:: Command editing
21802 * Command History:: Command history
21803 * Screen Size:: Screen size
21804 * Numbers:: Numbers
21805 * ABI:: Configuring the current ABI
21806 * Auto-loading:: Automatically loading associated files
21807 * Messages/Warnings:: Optional warnings and messages
21808 * Debugging Output:: Optional messages about internal happenings
21809 * Other Misc Settings:: Other Miscellaneous Settings
21817 @value{GDBN} indicates its readiness to read a command by printing a string
21818 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
21819 can change the prompt string with the @code{set prompt} command. For
21820 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
21821 the prompt in one of the @value{GDBN} sessions so that you can always tell
21822 which one you are talking to.
21824 @emph{Note:} @code{set prompt} does not add a space for you after the
21825 prompt you set. This allows you to set a prompt which ends in a space
21826 or a prompt that does not.
21830 @item set prompt @var{newprompt}
21831 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
21833 @kindex show prompt
21835 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
21838 Versions of @value{GDBN} that ship with Python scripting enabled have
21839 prompt extensions. The commands for interacting with these extensions
21843 @kindex set extended-prompt
21844 @item set extended-prompt @var{prompt}
21845 Set an extended prompt that allows for substitutions.
21846 @xref{gdb.prompt}, for a list of escape sequences that can be used for
21847 substitution. Any escape sequences specified as part of the prompt
21848 string are replaced with the corresponding strings each time the prompt
21854 set extended-prompt Current working directory: \w (gdb)
21857 Note that when an extended-prompt is set, it takes control of the
21858 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
21860 @kindex show extended-prompt
21861 @item show extended-prompt
21862 Prints the extended prompt. Any escape sequences specified as part of
21863 the prompt string with @code{set extended-prompt}, are replaced with the
21864 corresponding strings each time the prompt is displayed.
21868 @section Command Editing
21870 @cindex command line editing
21872 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
21873 @sc{gnu} library provides consistent behavior for programs which provide a
21874 command line interface to the user. Advantages are @sc{gnu} Emacs-style
21875 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
21876 substitution, and a storage and recall of command history across
21877 debugging sessions.
21879 You may control the behavior of command line editing in @value{GDBN} with the
21880 command @code{set}.
21883 @kindex set editing
21886 @itemx set editing on
21887 Enable command line editing (enabled by default).
21889 @item set editing off
21890 Disable command line editing.
21892 @kindex show editing
21894 Show whether command line editing is enabled.
21897 @ifset SYSTEM_READLINE
21898 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
21900 @ifclear SYSTEM_READLINE
21901 @xref{Command Line Editing},
21903 for more details about the Readline
21904 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
21905 encouraged to read that chapter.
21907 @node Command History
21908 @section Command History
21909 @cindex command history
21911 @value{GDBN} can keep track of the commands you type during your
21912 debugging sessions, so that you can be certain of precisely what
21913 happened. Use these commands to manage the @value{GDBN} command
21916 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
21917 package, to provide the history facility.
21918 @ifset SYSTEM_READLINE
21919 @xref{Using History Interactively, , , history, GNU History Library},
21921 @ifclear SYSTEM_READLINE
21922 @xref{Using History Interactively},
21924 for the detailed description of the History library.
21926 To issue a command to @value{GDBN} without affecting certain aspects of
21927 the state which is seen by users, prefix it with @samp{server }
21928 (@pxref{Server Prefix}). This
21929 means that this command will not affect the command history, nor will it
21930 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
21931 pressed on a line by itself.
21933 @cindex @code{server}, command prefix
21934 The server prefix does not affect the recording of values into the value
21935 history; to print a value without recording it into the value history,
21936 use the @code{output} command instead of the @code{print} command.
21938 Here is the description of @value{GDBN} commands related to command
21942 @cindex history substitution
21943 @cindex history file
21944 @kindex set history filename
21945 @cindex @env{GDBHISTFILE}, environment variable
21946 @item set history filename @var{fname}
21947 Set the name of the @value{GDBN} command history file to @var{fname}.
21948 This is the file where @value{GDBN} reads an initial command history
21949 list, and where it writes the command history from this session when it
21950 exits. You can access this list through history expansion or through
21951 the history command editing characters listed below. This file defaults
21952 to the value of the environment variable @code{GDBHISTFILE}, or to
21953 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
21956 @cindex save command history
21957 @kindex set history save
21958 @item set history save
21959 @itemx set history save on
21960 Record command history in a file, whose name may be specified with the
21961 @code{set history filename} command. By default, this option is disabled.
21963 @item set history save off
21964 Stop recording command history in a file.
21966 @cindex history size
21967 @kindex set history size
21968 @cindex @env{HISTSIZE}, environment variable
21969 @item set history size @var{size}
21970 @itemx set history size unlimited
21971 Set the number of commands which @value{GDBN} keeps in its history list.
21972 This defaults to the value of the environment variable
21973 @code{HISTSIZE}, or to 256 if this variable is not set. If @var{size}
21974 is @code{unlimited}, the number of commands @value{GDBN} keeps in the
21975 history list is unlimited.
21978 History expansion assigns special meaning to the character @kbd{!}.
21979 @ifset SYSTEM_READLINE
21980 @xref{Event Designators, , , history, GNU History Library},
21982 @ifclear SYSTEM_READLINE
21983 @xref{Event Designators},
21987 @cindex history expansion, turn on/off
21988 Since @kbd{!} is also the logical not operator in C, history expansion
21989 is off by default. If you decide to enable history expansion with the
21990 @code{set history expansion on} command, you may sometimes need to
21991 follow @kbd{!} (when it is used as logical not, in an expression) with
21992 a space or a tab to prevent it from being expanded. The readline
21993 history facilities do not attempt substitution on the strings
21994 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
21996 The commands to control history expansion are:
21999 @item set history expansion on
22000 @itemx set history expansion
22001 @kindex set history expansion
22002 Enable history expansion. History expansion is off by default.
22004 @item set history expansion off
22005 Disable history expansion.
22008 @kindex show history
22010 @itemx show history filename
22011 @itemx show history save
22012 @itemx show history size
22013 @itemx show history expansion
22014 These commands display the state of the @value{GDBN} history parameters.
22015 @code{show history} by itself displays all four states.
22020 @kindex show commands
22021 @cindex show last commands
22022 @cindex display command history
22023 @item show commands
22024 Display the last ten commands in the command history.
22026 @item show commands @var{n}
22027 Print ten commands centered on command number @var{n}.
22029 @item show commands +
22030 Print ten commands just after the commands last printed.
22034 @section Screen Size
22035 @cindex size of screen
22036 @cindex pauses in output
22038 Certain commands to @value{GDBN} may produce large amounts of
22039 information output to the screen. To help you read all of it,
22040 @value{GDBN} pauses and asks you for input at the end of each page of
22041 output. Type @key{RET} when you want to continue the output, or @kbd{q}
22042 to discard the remaining output. Also, the screen width setting
22043 determines when to wrap lines of output. Depending on what is being
22044 printed, @value{GDBN} tries to break the line at a readable place,
22045 rather than simply letting it overflow onto the following line.
22047 Normally @value{GDBN} knows the size of the screen from the terminal
22048 driver software. For example, on Unix @value{GDBN} uses the termcap data base
22049 together with the value of the @code{TERM} environment variable and the
22050 @code{stty rows} and @code{stty cols} settings. If this is not correct,
22051 you can override it with the @code{set height} and @code{set
22058 @kindex show height
22059 @item set height @var{lpp}
22060 @itemx set height unlimited
22062 @itemx set width @var{cpl}
22063 @itemx set width unlimited
22065 These @code{set} commands specify a screen height of @var{lpp} lines and
22066 a screen width of @var{cpl} characters. The associated @code{show}
22067 commands display the current settings.
22069 If you specify a height of either @code{unlimited} or zero lines,
22070 @value{GDBN} does not pause during output no matter how long the
22071 output is. This is useful if output is to a file or to an editor
22074 Likewise, you can specify @samp{set width unlimited} or @samp{set
22075 width 0} to prevent @value{GDBN} from wrapping its output.
22077 @item set pagination on
22078 @itemx set pagination off
22079 @kindex set pagination
22080 Turn the output pagination on or off; the default is on. Turning
22081 pagination off is the alternative to @code{set height unlimited}. Note that
22082 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
22083 Options, -batch}) also automatically disables pagination.
22085 @item show pagination
22086 @kindex show pagination
22087 Show the current pagination mode.
22092 @cindex number representation
22093 @cindex entering numbers
22095 You can always enter numbers in octal, decimal, or hexadecimal in
22096 @value{GDBN} by the usual conventions: octal numbers begin with
22097 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
22098 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
22099 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
22100 10; likewise, the default display for numbers---when no particular
22101 format is specified---is base 10. You can change the default base for
22102 both input and output with the commands described below.
22105 @kindex set input-radix
22106 @item set input-radix @var{base}
22107 Set the default base for numeric input. Supported choices
22108 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
22109 specified either unambiguously or using the current input radix; for
22113 set input-radix 012
22114 set input-radix 10.
22115 set input-radix 0xa
22119 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
22120 leaves the input radix unchanged, no matter what it was, since
22121 @samp{10}, being without any leading or trailing signs of its base, is
22122 interpreted in the current radix. Thus, if the current radix is 16,
22123 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
22126 @kindex set output-radix
22127 @item set output-radix @var{base}
22128 Set the default base for numeric display. Supported choices
22129 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
22130 specified either unambiguously or using the current input radix.
22132 @kindex show input-radix
22133 @item show input-radix
22134 Display the current default base for numeric input.
22136 @kindex show output-radix
22137 @item show output-radix
22138 Display the current default base for numeric display.
22140 @item set radix @r{[}@var{base}@r{]}
22144 These commands set and show the default base for both input and output
22145 of numbers. @code{set radix} sets the radix of input and output to
22146 the same base; without an argument, it resets the radix back to its
22147 default value of 10.
22152 @section Configuring the Current ABI
22154 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
22155 application automatically. However, sometimes you need to override its
22156 conclusions. Use these commands to manage @value{GDBN}'s view of the
22162 @cindex Newlib OS ABI and its influence on the longjmp handling
22164 One @value{GDBN} configuration can debug binaries for multiple operating
22165 system targets, either via remote debugging or native emulation.
22166 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
22167 but you can override its conclusion using the @code{set osabi} command.
22168 One example where this is useful is in debugging of binaries which use
22169 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
22170 not have the same identifying marks that the standard C library for your
22173 When @value{GDBN} is debugging the AArch64 architecture, it provides a
22174 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
22175 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
22176 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
22180 Show the OS ABI currently in use.
22183 With no argument, show the list of registered available OS ABI's.
22185 @item set osabi @var{abi}
22186 Set the current OS ABI to @var{abi}.
22189 @cindex float promotion
22191 Generally, the way that an argument of type @code{float} is passed to a
22192 function depends on whether the function is prototyped. For a prototyped
22193 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
22194 according to the architecture's convention for @code{float}. For unprototyped
22195 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
22196 @code{double} and then passed.
22198 Unfortunately, some forms of debug information do not reliably indicate whether
22199 a function is prototyped. If @value{GDBN} calls a function that is not marked
22200 as prototyped, it consults @kbd{set coerce-float-to-double}.
22203 @kindex set coerce-float-to-double
22204 @item set coerce-float-to-double
22205 @itemx set coerce-float-to-double on
22206 Arguments of type @code{float} will be promoted to @code{double} when passed
22207 to an unprototyped function. This is the default setting.
22209 @item set coerce-float-to-double off
22210 Arguments of type @code{float} will be passed directly to unprototyped
22213 @kindex show coerce-float-to-double
22214 @item show coerce-float-to-double
22215 Show the current setting of promoting @code{float} to @code{double}.
22219 @kindex show cp-abi
22220 @value{GDBN} needs to know the ABI used for your program's C@t{++}
22221 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
22222 used to build your application. @value{GDBN} only fully supports
22223 programs with a single C@t{++} ABI; if your program contains code using
22224 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
22225 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
22226 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
22227 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
22228 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
22229 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
22234 Show the C@t{++} ABI currently in use.
22237 With no argument, show the list of supported C@t{++} ABI's.
22239 @item set cp-abi @var{abi}
22240 @itemx set cp-abi auto
22241 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
22245 @section Automatically loading associated files
22246 @cindex auto-loading
22248 @value{GDBN} sometimes reads files with commands and settings automatically,
22249 without being explicitly told so by the user. We call this feature
22250 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
22251 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
22252 results or introduce security risks (e.g., if the file comes from untrusted
22256 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
22257 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
22259 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
22260 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
22263 There are various kinds of files @value{GDBN} can automatically load.
22264 In addition to these files, @value{GDBN} supports auto-loading code written
22265 in various extension languages. @xref{Auto-loading extensions}.
22267 Note that loading of these associated files (including the local @file{.gdbinit}
22268 file) requires accordingly configured @code{auto-load safe-path}
22269 (@pxref{Auto-loading safe path}).
22271 For these reasons, @value{GDBN} includes commands and options to let you
22272 control when to auto-load files and which files should be auto-loaded.
22275 @anchor{set auto-load off}
22276 @kindex set auto-load off
22277 @item set auto-load off
22278 Globally disable loading of all auto-loaded files.
22279 You may want to use this command with the @samp{-iex} option
22280 (@pxref{Option -init-eval-command}) such as:
22282 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
22285 Be aware that system init file (@pxref{System-wide configuration})
22286 and init files from your home directory (@pxref{Home Directory Init File})
22287 still get read (as they come from generally trusted directories).
22288 To prevent @value{GDBN} from auto-loading even those init files, use the
22289 @option{-nx} option (@pxref{Mode Options}), in addition to
22290 @code{set auto-load no}.
22292 @anchor{show auto-load}
22293 @kindex show auto-load
22294 @item show auto-load
22295 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
22299 (gdb) show auto-load
22300 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
22301 libthread-db: Auto-loading of inferior specific libthread_db is on.
22302 local-gdbinit: Auto-loading of .gdbinit script from current directory
22304 python-scripts: Auto-loading of Python scripts is on.
22305 safe-path: List of directories from which it is safe to auto-load files
22306 is $debugdir:$datadir/auto-load.
22307 scripts-directory: List of directories from which to load auto-loaded scripts
22308 is $debugdir:$datadir/auto-load.
22311 @anchor{info auto-load}
22312 @kindex info auto-load
22313 @item info auto-load
22314 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
22318 (gdb) info auto-load
22321 Yes /home/user/gdb/gdb-gdb.gdb
22322 libthread-db: No auto-loaded libthread-db.
22323 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
22327 Yes /home/user/gdb/gdb-gdb.py
22331 These are @value{GDBN} control commands for the auto-loading:
22333 @multitable @columnfractions .5 .5
22334 @item @xref{set auto-load off}.
22335 @tab Disable auto-loading globally.
22336 @item @xref{show auto-load}.
22337 @tab Show setting of all kinds of files.
22338 @item @xref{info auto-load}.
22339 @tab Show state of all kinds of files.
22340 @item @xref{set auto-load gdb-scripts}.
22341 @tab Control for @value{GDBN} command scripts.
22342 @item @xref{show auto-load gdb-scripts}.
22343 @tab Show setting of @value{GDBN} command scripts.
22344 @item @xref{info auto-load gdb-scripts}.
22345 @tab Show state of @value{GDBN} command scripts.
22346 @item @xref{set auto-load python-scripts}.
22347 @tab Control for @value{GDBN} Python scripts.
22348 @item @xref{show auto-load python-scripts}.
22349 @tab Show setting of @value{GDBN} Python scripts.
22350 @item @xref{info auto-load python-scripts}.
22351 @tab Show state of @value{GDBN} Python scripts.
22352 @item @xref{set auto-load guile-scripts}.
22353 @tab Control for @value{GDBN} Guile scripts.
22354 @item @xref{show auto-load guile-scripts}.
22355 @tab Show setting of @value{GDBN} Guile scripts.
22356 @item @xref{info auto-load guile-scripts}.
22357 @tab Show state of @value{GDBN} Guile scripts.
22358 @item @xref{set auto-load scripts-directory}.
22359 @tab Control for @value{GDBN} auto-loaded scripts location.
22360 @item @xref{show auto-load scripts-directory}.
22361 @tab Show @value{GDBN} auto-loaded scripts location.
22362 @item @xref{set auto-load local-gdbinit}.
22363 @tab Control for init file in the current directory.
22364 @item @xref{show auto-load local-gdbinit}.
22365 @tab Show setting of init file in the current directory.
22366 @item @xref{info auto-load local-gdbinit}.
22367 @tab Show state of init file in the current directory.
22368 @item @xref{set auto-load libthread-db}.
22369 @tab Control for thread debugging library.
22370 @item @xref{show auto-load libthread-db}.
22371 @tab Show setting of thread debugging library.
22372 @item @xref{info auto-load libthread-db}.
22373 @tab Show state of thread debugging library.
22374 @item @xref{set auto-load safe-path}.
22375 @tab Control directories trusted for automatic loading.
22376 @item @xref{show auto-load safe-path}.
22377 @tab Show directories trusted for automatic loading.
22378 @item @xref{add-auto-load-safe-path}.
22379 @tab Add directory trusted for automatic loading.
22382 @node Init File in the Current Directory
22383 @subsection Automatically loading init file in the current directory
22384 @cindex auto-loading init file in the current directory
22386 By default, @value{GDBN} reads and executes the canned sequences of commands
22387 from init file (if any) in the current working directory,
22388 see @ref{Init File in the Current Directory during Startup}.
22390 Note that loading of this local @file{.gdbinit} file also requires accordingly
22391 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22394 @anchor{set auto-load local-gdbinit}
22395 @kindex set auto-load local-gdbinit
22396 @item set auto-load local-gdbinit [on|off]
22397 Enable or disable the auto-loading of canned sequences of commands
22398 (@pxref{Sequences}) found in init file in the current directory.
22400 @anchor{show auto-load local-gdbinit}
22401 @kindex show auto-load local-gdbinit
22402 @item show auto-load local-gdbinit
22403 Show whether auto-loading of canned sequences of commands from init file in the
22404 current directory is enabled or disabled.
22406 @anchor{info auto-load local-gdbinit}
22407 @kindex info auto-load local-gdbinit
22408 @item info auto-load local-gdbinit
22409 Print whether canned sequences of commands from init file in the
22410 current directory have been auto-loaded.
22413 @node libthread_db.so.1 file
22414 @subsection Automatically loading thread debugging library
22415 @cindex auto-loading libthread_db.so.1
22417 This feature is currently present only on @sc{gnu}/Linux native hosts.
22419 @value{GDBN} reads in some cases thread debugging library from places specific
22420 to the inferior (@pxref{set libthread-db-search-path}).
22422 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
22423 without checking this @samp{set auto-load libthread-db} switch as system
22424 libraries have to be trusted in general. In all other cases of
22425 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
22426 auto-load libthread-db} is enabled before trying to open such thread debugging
22429 Note that loading of this debugging library also requires accordingly configured
22430 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22433 @anchor{set auto-load libthread-db}
22434 @kindex set auto-load libthread-db
22435 @item set auto-load libthread-db [on|off]
22436 Enable or disable the auto-loading of inferior specific thread debugging library.
22438 @anchor{show auto-load libthread-db}
22439 @kindex show auto-load libthread-db
22440 @item show auto-load libthread-db
22441 Show whether auto-loading of inferior specific thread debugging library is
22442 enabled or disabled.
22444 @anchor{info auto-load libthread-db}
22445 @kindex info auto-load libthread-db
22446 @item info auto-load libthread-db
22447 Print the list of all loaded inferior specific thread debugging libraries and
22448 for each such library print list of inferior @var{pid}s using it.
22451 @node Auto-loading safe path
22452 @subsection Security restriction for auto-loading
22453 @cindex auto-loading safe-path
22455 As the files of inferior can come from untrusted source (such as submitted by
22456 an application user) @value{GDBN} does not always load any files automatically.
22457 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
22458 directories trusted for loading files not explicitly requested by user.
22459 Each directory can also be a shell wildcard pattern.
22461 If the path is not set properly you will see a warning and the file will not
22466 Reading symbols from /home/user/gdb/gdb...done.
22467 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
22468 declined by your `auto-load safe-path' set
22469 to "$debugdir:$datadir/auto-load".
22470 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
22471 declined by your `auto-load safe-path' set
22472 to "$debugdir:$datadir/auto-load".
22476 To instruct @value{GDBN} to go ahead and use the init files anyway,
22477 invoke @value{GDBN} like this:
22480 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
22483 The list of trusted directories is controlled by the following commands:
22486 @anchor{set auto-load safe-path}
22487 @kindex set auto-load safe-path
22488 @item set auto-load safe-path @r{[}@var{directories}@r{]}
22489 Set the list of directories (and their subdirectories) trusted for automatic
22490 loading and execution of scripts. You can also enter a specific trusted file.
22491 Each directory can also be a shell wildcard pattern; wildcards do not match
22492 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
22493 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
22494 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
22495 its default value as specified during @value{GDBN} compilation.
22497 The list of directories uses path separator (@samp{:} on GNU and Unix
22498 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
22499 to the @env{PATH} environment variable.
22501 @anchor{show auto-load safe-path}
22502 @kindex show auto-load safe-path
22503 @item show auto-load safe-path
22504 Show the list of directories trusted for automatic loading and execution of
22507 @anchor{add-auto-load-safe-path}
22508 @kindex add-auto-load-safe-path
22509 @item add-auto-load-safe-path
22510 Add an entry (or list of entries) the list of directories trusted for automatic
22511 loading and execution of scripts. Multiple entries may be delimited by the
22512 host platform path separator in use.
22515 This variable defaults to what @code{--with-auto-load-dir} has been configured
22516 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
22517 substitution applies the same as for @ref{set auto-load scripts-directory}.
22518 The default @code{set auto-load safe-path} value can be also overriden by
22519 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
22521 Setting this variable to @file{/} disables this security protection,
22522 corresponding @value{GDBN} configuration option is
22523 @option{--without-auto-load-safe-path}.
22524 This variable is supposed to be set to the system directories writable by the
22525 system superuser only. Users can add their source directories in init files in
22526 their home directories (@pxref{Home Directory Init File}). See also deprecated
22527 init file in the current directory
22528 (@pxref{Init File in the Current Directory during Startup}).
22530 To force @value{GDBN} to load the files it declined to load in the previous
22531 example, you could use one of the following ways:
22534 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
22535 Specify this trusted directory (or a file) as additional component of the list.
22536 You have to specify also any existing directories displayed by
22537 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
22539 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
22540 Specify this directory as in the previous case but just for a single
22541 @value{GDBN} session.
22543 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
22544 Disable auto-loading safety for a single @value{GDBN} session.
22545 This assumes all the files you debug during this @value{GDBN} session will come
22546 from trusted sources.
22548 @item @kbd{./configure --without-auto-load-safe-path}
22549 During compilation of @value{GDBN} you may disable any auto-loading safety.
22550 This assumes all the files you will ever debug with this @value{GDBN} come from
22554 On the other hand you can also explicitly forbid automatic files loading which
22555 also suppresses any such warning messages:
22558 @item @kbd{gdb -iex "set auto-load no" @dots{}}
22559 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
22561 @item @file{~/.gdbinit}: @samp{set auto-load no}
22562 Disable auto-loading globally for the user
22563 (@pxref{Home Directory Init File}). While it is improbable, you could also
22564 use system init file instead (@pxref{System-wide configuration}).
22567 This setting applies to the file names as entered by user. If no entry matches
22568 @value{GDBN} tries as a last resort to also resolve all the file names into
22569 their canonical form (typically resolving symbolic links) and compare the
22570 entries again. @value{GDBN} already canonicalizes most of the filenames on its
22571 own before starting the comparison so a canonical form of directories is
22572 recommended to be entered.
22574 @node Auto-loading verbose mode
22575 @subsection Displaying files tried for auto-load
22576 @cindex auto-loading verbose mode
22578 For better visibility of all the file locations where you can place scripts to
22579 be auto-loaded with inferior --- or to protect yourself against accidental
22580 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
22581 all the files attempted to be loaded. Both existing and non-existing files may
22584 For example the list of directories from which it is safe to auto-load files
22585 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
22586 may not be too obvious while setting it up.
22589 (gdb) set debug auto-load on
22590 (gdb) file ~/src/t/true
22591 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
22592 for objfile "/tmp/true".
22593 auto-load: Updating directories of "/usr:/opt".
22594 auto-load: Using directory "/usr".
22595 auto-load: Using directory "/opt".
22596 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
22597 by your `auto-load safe-path' set to "/usr:/opt".
22601 @anchor{set debug auto-load}
22602 @kindex set debug auto-load
22603 @item set debug auto-load [on|off]
22604 Set whether to print the filenames attempted to be auto-loaded.
22606 @anchor{show debug auto-load}
22607 @kindex show debug auto-load
22608 @item show debug auto-load
22609 Show whether printing of the filenames attempted to be auto-loaded is turned
22613 @node Messages/Warnings
22614 @section Optional Warnings and Messages
22616 @cindex verbose operation
22617 @cindex optional warnings
22618 By default, @value{GDBN} is silent about its inner workings. If you are
22619 running on a slow machine, you may want to use the @code{set verbose}
22620 command. This makes @value{GDBN} tell you when it does a lengthy
22621 internal operation, so you will not think it has crashed.
22623 Currently, the messages controlled by @code{set verbose} are those
22624 which announce that the symbol table for a source file is being read;
22625 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
22628 @kindex set verbose
22629 @item set verbose on
22630 Enables @value{GDBN} output of certain informational messages.
22632 @item set verbose off
22633 Disables @value{GDBN} output of certain informational messages.
22635 @kindex show verbose
22637 Displays whether @code{set verbose} is on or off.
22640 By default, if @value{GDBN} encounters bugs in the symbol table of an
22641 object file, it is silent; but if you are debugging a compiler, you may
22642 find this information useful (@pxref{Symbol Errors, ,Errors Reading
22647 @kindex set complaints
22648 @item set complaints @var{limit}
22649 Permits @value{GDBN} to output @var{limit} complaints about each type of
22650 unusual symbols before becoming silent about the problem. Set
22651 @var{limit} to zero to suppress all complaints; set it to a large number
22652 to prevent complaints from being suppressed.
22654 @kindex show complaints
22655 @item show complaints
22656 Displays how many symbol complaints @value{GDBN} is permitted to produce.
22660 @anchor{confirmation requests}
22661 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
22662 lot of stupid questions to confirm certain commands. For example, if
22663 you try to run a program which is already running:
22667 The program being debugged has been started already.
22668 Start it from the beginning? (y or n)
22671 If you are willing to unflinchingly face the consequences of your own
22672 commands, you can disable this ``feature'':
22676 @kindex set confirm
22678 @cindex confirmation
22679 @cindex stupid questions
22680 @item set confirm off
22681 Disables confirmation requests. Note that running @value{GDBN} with
22682 the @option{--batch} option (@pxref{Mode Options, -batch}) also
22683 automatically disables confirmation requests.
22685 @item set confirm on
22686 Enables confirmation requests (the default).
22688 @kindex show confirm
22690 Displays state of confirmation requests.
22694 @cindex command tracing
22695 If you need to debug user-defined commands or sourced files you may find it
22696 useful to enable @dfn{command tracing}. In this mode each command will be
22697 printed as it is executed, prefixed with one or more @samp{+} symbols, the
22698 quantity denoting the call depth of each command.
22701 @kindex set trace-commands
22702 @cindex command scripts, debugging
22703 @item set trace-commands on
22704 Enable command tracing.
22705 @item set trace-commands off
22706 Disable command tracing.
22707 @item show trace-commands
22708 Display the current state of command tracing.
22711 @node Debugging Output
22712 @section Optional Messages about Internal Happenings
22713 @cindex optional debugging messages
22715 @value{GDBN} has commands that enable optional debugging messages from
22716 various @value{GDBN} subsystems; normally these commands are of
22717 interest to @value{GDBN} maintainers, or when reporting a bug. This
22718 section documents those commands.
22721 @kindex set exec-done-display
22722 @item set exec-done-display
22723 Turns on or off the notification of asynchronous commands'
22724 completion. When on, @value{GDBN} will print a message when an
22725 asynchronous command finishes its execution. The default is off.
22726 @kindex show exec-done-display
22727 @item show exec-done-display
22728 Displays the current setting of asynchronous command completion
22731 @cindex ARM AArch64
22732 @item set debug aarch64
22733 Turns on or off display of debugging messages related to ARM AArch64.
22734 The default is off.
22736 @item show debug aarch64
22737 Displays the current state of displaying debugging messages related to
22739 @cindex gdbarch debugging info
22740 @cindex architecture debugging info
22741 @item set debug arch
22742 Turns on or off display of gdbarch debugging info. The default is off
22743 @item show debug arch
22744 Displays the current state of displaying gdbarch debugging info.
22745 @item set debug aix-solib
22746 @cindex AIX shared library debugging
22747 Control display of debugging messages from the AIX shared library
22748 support module. The default is off.
22749 @item show debug aix-thread
22750 Show the current state of displaying AIX shared library debugging messages.
22751 @item set debug aix-thread
22752 @cindex AIX threads
22753 Display debugging messages about inner workings of the AIX thread
22755 @item show debug aix-thread
22756 Show the current state of AIX thread debugging info display.
22757 @item set debug check-physname
22759 Check the results of the ``physname'' computation. When reading DWARF
22760 debugging information for C@t{++}, @value{GDBN} attempts to compute
22761 each entity's name. @value{GDBN} can do this computation in two
22762 different ways, depending on exactly what information is present.
22763 When enabled, this setting causes @value{GDBN} to compute the names
22764 both ways and display any discrepancies.
22765 @item show debug check-physname
22766 Show the current state of ``physname'' checking.
22767 @item set debug coff-pe-read
22768 @cindex COFF/PE exported symbols
22769 Control display of debugging messages related to reading of COFF/PE
22770 exported symbols. The default is off.
22771 @item show debug coff-pe-read
22772 Displays the current state of displaying debugging messages related to
22773 reading of COFF/PE exported symbols.
22774 @item set debug dwarf2-die
22775 @cindex DWARF2 DIEs
22776 Dump DWARF2 DIEs after they are read in.
22777 The value is the number of nesting levels to print.
22778 A value of zero turns off the display.
22779 @item show debug dwarf2-die
22780 Show the current state of DWARF2 DIE debugging.
22781 @item set debug dwarf2-read
22782 @cindex DWARF2 Reading
22783 Turns on or off display of debugging messages related to reading
22784 DWARF debug info. The default is 0 (off).
22785 A value of 1 provides basic information.
22786 A value greater than 1 provides more verbose information.
22787 @item show debug dwarf2-read
22788 Show the current state of DWARF2 reader debugging.
22789 @item set debug displaced
22790 @cindex displaced stepping debugging info
22791 Turns on or off display of @value{GDBN} debugging info for the
22792 displaced stepping support. The default is off.
22793 @item show debug displaced
22794 Displays the current state of displaying @value{GDBN} debugging info
22795 related to displaced stepping.
22796 @item set debug event
22797 @cindex event debugging info
22798 Turns on or off display of @value{GDBN} event debugging info. The
22800 @item show debug event
22801 Displays the current state of displaying @value{GDBN} event debugging
22803 @item set debug expression
22804 @cindex expression debugging info
22805 Turns on or off display of debugging info about @value{GDBN}
22806 expression parsing. The default is off.
22807 @item show debug expression
22808 Displays the current state of displaying debugging info about
22809 @value{GDBN} expression parsing.
22810 @item set debug frame
22811 @cindex frame debugging info
22812 Turns on or off display of @value{GDBN} frame debugging info. The
22814 @item show debug frame
22815 Displays the current state of displaying @value{GDBN} frame debugging
22817 @item set debug gnu-nat
22818 @cindex @sc{gnu}/Hurd debug messages
22819 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
22820 @item show debug gnu-nat
22821 Show the current state of @sc{gnu}/Hurd debugging messages.
22822 @item set debug infrun
22823 @cindex inferior debugging info
22824 Turns on or off display of @value{GDBN} debugging info for running the inferior.
22825 The default is off. @file{infrun.c} contains GDB's runtime state machine used
22826 for implementing operations such as single-stepping the inferior.
22827 @item show debug infrun
22828 Displays the current state of @value{GDBN} inferior debugging.
22829 @item set debug jit
22830 @cindex just-in-time compilation, debugging messages
22831 Turns on or off debugging messages from JIT debug support.
22832 @item show debug jit
22833 Displays the current state of @value{GDBN} JIT debugging.
22834 @item set debug lin-lwp
22835 @cindex @sc{gnu}/Linux LWP debug messages
22836 @cindex Linux lightweight processes
22837 Turns on or off debugging messages from the Linux LWP debug support.
22838 @item show debug lin-lwp
22839 Show the current state of Linux LWP debugging messages.
22840 @item set debug mach-o
22841 @cindex Mach-O symbols processing
22842 Control display of debugging messages related to Mach-O symbols
22843 processing. The default is off.
22844 @item show debug mach-o
22845 Displays the current state of displaying debugging messages related to
22846 reading of COFF/PE exported symbols.
22847 @item set debug notification
22848 @cindex remote async notification debugging info
22849 Turns on or off debugging messages about remote async notification.
22850 The default is off.
22851 @item show debug notification
22852 Displays the current state of remote async notification debugging messages.
22853 @item set debug observer
22854 @cindex observer debugging info
22855 Turns on or off display of @value{GDBN} observer debugging. This
22856 includes info such as the notification of observable events.
22857 @item show debug observer
22858 Displays the current state of observer debugging.
22859 @item set debug overload
22860 @cindex C@t{++} overload debugging info
22861 Turns on or off display of @value{GDBN} C@t{++} overload debugging
22862 info. This includes info such as ranking of functions, etc. The default
22864 @item show debug overload
22865 Displays the current state of displaying @value{GDBN} C@t{++} overload
22867 @cindex expression parser, debugging info
22868 @cindex debug expression parser
22869 @item set debug parser
22870 Turns on or off the display of expression parser debugging output.
22871 Internally, this sets the @code{yydebug} variable in the expression
22872 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
22873 details. The default is off.
22874 @item show debug parser
22875 Show the current state of expression parser debugging.
22876 @cindex packets, reporting on stdout
22877 @cindex serial connections, debugging
22878 @cindex debug remote protocol
22879 @cindex remote protocol debugging
22880 @cindex display remote packets
22881 @item set debug remote
22882 Turns on or off display of reports on all packets sent back and forth across
22883 the serial line to the remote machine. The info is printed on the
22884 @value{GDBN} standard output stream. The default is off.
22885 @item show debug remote
22886 Displays the state of display of remote packets.
22887 @item set debug serial
22888 Turns on or off display of @value{GDBN} serial debugging info. The
22890 @item show debug serial
22891 Displays the current state of displaying @value{GDBN} serial debugging
22893 @item set debug solib-frv
22894 @cindex FR-V shared-library debugging
22895 Turns on or off debugging messages for FR-V shared-library code.
22896 @item show debug solib-frv
22897 Display the current state of FR-V shared-library code debugging
22899 @item set debug symfile
22900 @cindex symbol file functions
22901 Turns on or off display of debugging messages related to symbol file functions.
22902 The default is off. @xref{Files}.
22903 @item show debug symfile
22904 Show the current state of symbol file debugging messages.
22905 @item set debug symtab-create
22906 @cindex symbol table creation
22907 Turns on or off display of debugging messages related to symbol table creation.
22908 The default is 0 (off).
22909 A value of 1 provides basic information.
22910 A value greater than 1 provides more verbose information.
22911 @item show debug symtab-create
22912 Show the current state of symbol table creation debugging.
22913 @item set debug target
22914 @cindex target debugging info
22915 Turns on or off display of @value{GDBN} target debugging info. This info
22916 includes what is going on at the target level of GDB, as it happens. The
22917 default is 0. Set it to 1 to track events, and to 2 to also track the
22918 value of large memory transfers. Changes to this flag do not take effect
22919 until the next time you connect to a target or use the @code{run} command.
22920 @item show debug target
22921 Displays the current state of displaying @value{GDBN} target debugging
22923 @item set debug timestamp
22924 @cindex timestampping debugging info
22925 Turns on or off display of timestamps with @value{GDBN} debugging info.
22926 When enabled, seconds and microseconds are displayed before each debugging
22928 @item show debug timestamp
22929 Displays the current state of displaying timestamps with @value{GDBN}
22931 @item set debug varobj
22932 @cindex variable object debugging info
22933 Turns on or off display of @value{GDBN} variable object debugging
22934 info. The default is off.
22935 @item show debug varobj
22936 Displays the current state of displaying @value{GDBN} variable object
22938 @item set debug xml
22939 @cindex XML parser debugging
22940 Turns on or off debugging messages for built-in XML parsers.
22941 @item show debug xml
22942 Displays the current state of XML debugging messages.
22945 @node Other Misc Settings
22946 @section Other Miscellaneous Settings
22947 @cindex miscellaneous settings
22950 @kindex set interactive-mode
22951 @item set interactive-mode
22952 If @code{on}, forces @value{GDBN} to assume that GDB was started
22953 in a terminal. In practice, this means that @value{GDBN} should wait
22954 for the user to answer queries generated by commands entered at
22955 the command prompt. If @code{off}, forces @value{GDBN} to operate
22956 in the opposite mode, and it uses the default answers to all queries.
22957 If @code{auto} (the default), @value{GDBN} tries to determine whether
22958 its standard input is a terminal, and works in interactive-mode if it
22959 is, non-interactively otherwise.
22961 In the vast majority of cases, the debugger should be able to guess
22962 correctly which mode should be used. But this setting can be useful
22963 in certain specific cases, such as running a MinGW @value{GDBN}
22964 inside a cygwin window.
22966 @kindex show interactive-mode
22967 @item show interactive-mode
22968 Displays whether the debugger is operating in interactive mode or not.
22971 @node Extending GDB
22972 @chapter Extending @value{GDBN}
22973 @cindex extending GDB
22975 @value{GDBN} provides several mechanisms for extension.
22976 @value{GDBN} also provides the ability to automatically load
22977 extensions when it reads a file for debugging. This allows the
22978 user to automatically customize @value{GDBN} for the program
22982 * Sequences:: Canned Sequences of @value{GDBN} Commands
22983 * Python:: Extending @value{GDBN} using Python
22984 * Guile:: Extending @value{GDBN} using Guile
22985 * Auto-loading extensions:: Automatically loading extensions
22986 * Multiple Extension Languages:: Working with multiple extension languages
22987 * Aliases:: Creating new spellings of existing commands
22990 To facilitate the use of extension languages, @value{GDBN} is capable
22991 of evaluating the contents of a file. When doing so, @value{GDBN}
22992 can recognize which extension language is being used by looking at
22993 the filename extension. Files with an unrecognized filename extension
22994 are always treated as a @value{GDBN} Command Files.
22995 @xref{Command Files,, Command files}.
22997 You can control how @value{GDBN} evaluates these files with the following
23001 @kindex set script-extension
23002 @kindex show script-extension
23003 @item set script-extension off
23004 All scripts are always evaluated as @value{GDBN} Command Files.
23006 @item set script-extension soft
23007 The debugger determines the scripting language based on filename
23008 extension. If this scripting language is supported, @value{GDBN}
23009 evaluates the script using that language. Otherwise, it evaluates
23010 the file as a @value{GDBN} Command File.
23012 @item set script-extension strict
23013 The debugger determines the scripting language based on filename
23014 extension, and evaluates the script using that language. If the
23015 language is not supported, then the evaluation fails.
23017 @item show script-extension
23018 Display the current value of the @code{script-extension} option.
23023 @section Canned Sequences of Commands
23025 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
23026 Command Lists}), @value{GDBN} provides two ways to store sequences of
23027 commands for execution as a unit: user-defined commands and command
23031 * Define:: How to define your own commands
23032 * Hooks:: Hooks for user-defined commands
23033 * Command Files:: How to write scripts of commands to be stored in a file
23034 * Output:: Commands for controlled output
23035 * Auto-loading sequences:: Controlling auto-loaded command files
23039 @subsection User-defined Commands
23041 @cindex user-defined command
23042 @cindex arguments, to user-defined commands
23043 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
23044 which you assign a new name as a command. This is done with the
23045 @code{define} command. User commands may accept up to 10 arguments
23046 separated by whitespace. Arguments are accessed within the user command
23047 via @code{$arg0@dots{}$arg9}. A trivial example:
23051 print $arg0 + $arg1 + $arg2
23056 To execute the command use:
23063 This defines the command @code{adder}, which prints the sum of
23064 its three arguments. Note the arguments are text substitutions, so they may
23065 reference variables, use complex expressions, or even perform inferior
23068 @cindex argument count in user-defined commands
23069 @cindex how many arguments (user-defined commands)
23070 In addition, @code{$argc} may be used to find out how many arguments have
23071 been passed. This expands to a number in the range 0@dots{}10.
23076 print $arg0 + $arg1
23079 print $arg0 + $arg1 + $arg2
23087 @item define @var{commandname}
23088 Define a command named @var{commandname}. If there is already a command
23089 by that name, you are asked to confirm that you want to redefine it.
23090 @var{commandname} may be a bare command name consisting of letters,
23091 numbers, dashes, and underscores. It may also start with any predefined
23092 prefix command. For example, @samp{define target my-target} creates
23093 a user-defined @samp{target my-target} command.
23095 The definition of the command is made up of other @value{GDBN} command lines,
23096 which are given following the @code{define} command. The end of these
23097 commands is marked by a line containing @code{end}.
23100 @kindex end@r{ (user-defined commands)}
23101 @item document @var{commandname}
23102 Document the user-defined command @var{commandname}, so that it can be
23103 accessed by @code{help}. The command @var{commandname} must already be
23104 defined. This command reads lines of documentation just as @code{define}
23105 reads the lines of the command definition, ending with @code{end}.
23106 After the @code{document} command is finished, @code{help} on command
23107 @var{commandname} displays the documentation you have written.
23109 You may use the @code{document} command again to change the
23110 documentation of a command. Redefining the command with @code{define}
23111 does not change the documentation.
23113 @kindex dont-repeat
23114 @cindex don't repeat command
23116 Used inside a user-defined command, this tells @value{GDBN} that this
23117 command should not be repeated when the user hits @key{RET}
23118 (@pxref{Command Syntax, repeat last command}).
23120 @kindex help user-defined
23121 @item help user-defined
23122 List all user-defined commands and all python commands defined in class
23123 COMAND_USER. The first line of the documentation or docstring is
23128 @itemx show user @var{commandname}
23129 Display the @value{GDBN} commands used to define @var{commandname} (but
23130 not its documentation). If no @var{commandname} is given, display the
23131 definitions for all user-defined commands.
23132 This does not work for user-defined python commands.
23134 @cindex infinite recursion in user-defined commands
23135 @kindex show max-user-call-depth
23136 @kindex set max-user-call-depth
23137 @item show max-user-call-depth
23138 @itemx set max-user-call-depth
23139 The value of @code{max-user-call-depth} controls how many recursion
23140 levels are allowed in user-defined commands before @value{GDBN} suspects an
23141 infinite recursion and aborts the command.
23142 This does not apply to user-defined python commands.
23145 In addition to the above commands, user-defined commands frequently
23146 use control flow commands, described in @ref{Command Files}.
23148 When user-defined commands are executed, the
23149 commands of the definition are not printed. An error in any command
23150 stops execution of the user-defined command.
23152 If used interactively, commands that would ask for confirmation proceed
23153 without asking when used inside a user-defined command. Many @value{GDBN}
23154 commands that normally print messages to say what they are doing omit the
23155 messages when used in a user-defined command.
23158 @subsection User-defined Command Hooks
23159 @cindex command hooks
23160 @cindex hooks, for commands
23161 @cindex hooks, pre-command
23164 You may define @dfn{hooks}, which are a special kind of user-defined
23165 command. Whenever you run the command @samp{foo}, if the user-defined
23166 command @samp{hook-foo} exists, it is executed (with no arguments)
23167 before that command.
23169 @cindex hooks, post-command
23171 A hook may also be defined which is run after the command you executed.
23172 Whenever you run the command @samp{foo}, if the user-defined command
23173 @samp{hookpost-foo} exists, it is executed (with no arguments) after
23174 that command. Post-execution hooks may exist simultaneously with
23175 pre-execution hooks, for the same command.
23177 It is valid for a hook to call the command which it hooks. If this
23178 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
23180 @c It would be nice if hookpost could be passed a parameter indicating
23181 @c if the command it hooks executed properly or not. FIXME!
23183 @kindex stop@r{, a pseudo-command}
23184 In addition, a pseudo-command, @samp{stop} exists. Defining
23185 (@samp{hook-stop}) makes the associated commands execute every time
23186 execution stops in your program: before breakpoint commands are run,
23187 displays are printed, or the stack frame is printed.
23189 For example, to ignore @code{SIGALRM} signals while
23190 single-stepping, but treat them normally during normal execution,
23195 handle SIGALRM nopass
23199 handle SIGALRM pass
23202 define hook-continue
23203 handle SIGALRM pass
23207 As a further example, to hook at the beginning and end of the @code{echo}
23208 command, and to add extra text to the beginning and end of the message,
23216 define hookpost-echo
23220 (@value{GDBP}) echo Hello World
23221 <<<---Hello World--->>>
23226 You can define a hook for any single-word command in @value{GDBN}, but
23227 not for command aliases; you should define a hook for the basic command
23228 name, e.g.@: @code{backtrace} rather than @code{bt}.
23229 @c FIXME! So how does Joe User discover whether a command is an alias
23231 You can hook a multi-word command by adding @code{hook-} or
23232 @code{hookpost-} to the last word of the command, e.g.@:
23233 @samp{define target hook-remote} to add a hook to @samp{target remote}.
23235 If an error occurs during the execution of your hook, execution of
23236 @value{GDBN} commands stops and @value{GDBN} issues a prompt
23237 (before the command that you actually typed had a chance to run).
23239 If you try to define a hook which does not match any known command, you
23240 get a warning from the @code{define} command.
23242 @node Command Files
23243 @subsection Command Files
23245 @cindex command files
23246 @cindex scripting commands
23247 A command file for @value{GDBN} is a text file made of lines that are
23248 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
23249 also be included. An empty line in a command file does nothing; it
23250 does not mean to repeat the last command, as it would from the
23253 You can request the execution of a command file with the @code{source}
23254 command. Note that the @code{source} command is also used to evaluate
23255 scripts that are not Command Files. The exact behavior can be configured
23256 using the @code{script-extension} setting.
23257 @xref{Extending GDB,, Extending GDB}.
23261 @cindex execute commands from a file
23262 @item source [-s] [-v] @var{filename}
23263 Execute the command file @var{filename}.
23266 The lines in a command file are generally executed sequentially,
23267 unless the order of execution is changed by one of the
23268 @emph{flow-control commands} described below. The commands are not
23269 printed as they are executed. An error in any command terminates
23270 execution of the command file and control is returned to the console.
23272 @value{GDBN} first searches for @var{filename} in the current directory.
23273 If the file is not found there, and @var{filename} does not specify a
23274 directory, then @value{GDBN} also looks for the file on the source search path
23275 (specified with the @samp{directory} command);
23276 except that @file{$cdir} is not searched because the compilation directory
23277 is not relevant to scripts.
23279 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
23280 on the search path even if @var{filename} specifies a directory.
23281 The search is done by appending @var{filename} to each element of the
23282 search path. So, for example, if @var{filename} is @file{mylib/myscript}
23283 and the search path contains @file{/home/user} then @value{GDBN} will
23284 look for the script @file{/home/user/mylib/myscript}.
23285 The search is also done if @var{filename} is an absolute path.
23286 For example, if @var{filename} is @file{/tmp/myscript} and
23287 the search path contains @file{/home/user} then @value{GDBN} will
23288 look for the script @file{/home/user/tmp/myscript}.
23289 For DOS-like systems, if @var{filename} contains a drive specification,
23290 it is stripped before concatenation. For example, if @var{filename} is
23291 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
23292 will look for the script @file{c:/tmp/myscript}.
23294 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
23295 each command as it is executed. The option must be given before
23296 @var{filename}, and is interpreted as part of the filename anywhere else.
23298 Commands that would ask for confirmation if used interactively proceed
23299 without asking when used in a command file. Many @value{GDBN} commands that
23300 normally print messages to say what they are doing omit the messages
23301 when called from command files.
23303 @value{GDBN} also accepts command input from standard input. In this
23304 mode, normal output goes to standard output and error output goes to
23305 standard error. Errors in a command file supplied on standard input do
23306 not terminate execution of the command file---execution continues with
23310 gdb < cmds > log 2>&1
23313 (The syntax above will vary depending on the shell used.) This example
23314 will execute commands from the file @file{cmds}. All output and errors
23315 would be directed to @file{log}.
23317 Since commands stored on command files tend to be more general than
23318 commands typed interactively, they frequently need to deal with
23319 complicated situations, such as different or unexpected values of
23320 variables and symbols, changes in how the program being debugged is
23321 built, etc. @value{GDBN} provides a set of flow-control commands to
23322 deal with these complexities. Using these commands, you can write
23323 complex scripts that loop over data structures, execute commands
23324 conditionally, etc.
23331 This command allows to include in your script conditionally executed
23332 commands. The @code{if} command takes a single argument, which is an
23333 expression to evaluate. It is followed by a series of commands that
23334 are executed only if the expression is true (its value is nonzero).
23335 There can then optionally be an @code{else} line, followed by a series
23336 of commands that are only executed if the expression was false. The
23337 end of the list is marked by a line containing @code{end}.
23341 This command allows to write loops. Its syntax is similar to
23342 @code{if}: the command takes a single argument, which is an expression
23343 to evaluate, and must be followed by the commands to execute, one per
23344 line, terminated by an @code{end}. These commands are called the
23345 @dfn{body} of the loop. The commands in the body of @code{while} are
23346 executed repeatedly as long as the expression evaluates to true.
23350 This command exits the @code{while} loop in whose body it is included.
23351 Execution of the script continues after that @code{while}s @code{end}
23354 @kindex loop_continue
23355 @item loop_continue
23356 This command skips the execution of the rest of the body of commands
23357 in the @code{while} loop in whose body it is included. Execution
23358 branches to the beginning of the @code{while} loop, where it evaluates
23359 the controlling expression.
23361 @kindex end@r{ (if/else/while commands)}
23363 Terminate the block of commands that are the body of @code{if},
23364 @code{else}, or @code{while} flow-control commands.
23369 @subsection Commands for Controlled Output
23371 During the execution of a command file or a user-defined command, normal
23372 @value{GDBN} output is suppressed; the only output that appears is what is
23373 explicitly printed by the commands in the definition. This section
23374 describes three commands useful for generating exactly the output you
23379 @item echo @var{text}
23380 @c I do not consider backslash-space a standard C escape sequence
23381 @c because it is not in ANSI.
23382 Print @var{text}. Nonprinting characters can be included in
23383 @var{text} using C escape sequences, such as @samp{\n} to print a
23384 newline. @strong{No newline is printed unless you specify one.}
23385 In addition to the standard C escape sequences, a backslash followed
23386 by a space stands for a space. This is useful for displaying a
23387 string with spaces at the beginning or the end, since leading and
23388 trailing spaces are otherwise trimmed from all arguments.
23389 To print @samp{@w{ }and foo =@w{ }}, use the command
23390 @samp{echo \@w{ }and foo = \@w{ }}.
23392 A backslash at the end of @var{text} can be used, as in C, to continue
23393 the command onto subsequent lines. For example,
23396 echo This is some text\n\
23397 which is continued\n\
23398 onto several lines.\n
23401 produces the same output as
23404 echo This is some text\n
23405 echo which is continued\n
23406 echo onto several lines.\n
23410 @item output @var{expression}
23411 Print the value of @var{expression} and nothing but that value: no
23412 newlines, no @samp{$@var{nn} = }. The value is not entered in the
23413 value history either. @xref{Expressions, ,Expressions}, for more information
23416 @item output/@var{fmt} @var{expression}
23417 Print the value of @var{expression} in format @var{fmt}. You can use
23418 the same formats as for @code{print}. @xref{Output Formats,,Output
23419 Formats}, for more information.
23422 @item printf @var{template}, @var{expressions}@dots{}
23423 Print the values of one or more @var{expressions} under the control of
23424 the string @var{template}. To print several values, make
23425 @var{expressions} be a comma-separated list of individual expressions,
23426 which may be either numbers or pointers. Their values are printed as
23427 specified by @var{template}, exactly as a C program would do by
23428 executing the code below:
23431 printf (@var{template}, @var{expressions}@dots{});
23434 As in @code{C} @code{printf}, ordinary characters in @var{template}
23435 are printed verbatim, while @dfn{conversion specification} introduced
23436 by the @samp{%} character cause subsequent @var{expressions} to be
23437 evaluated, their values converted and formatted according to type and
23438 style information encoded in the conversion specifications, and then
23441 For example, you can print two values in hex like this:
23444 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
23447 @code{printf} supports all the standard @code{C} conversion
23448 specifications, including the flags and modifiers between the @samp{%}
23449 character and the conversion letter, with the following exceptions:
23453 The argument-ordering modifiers, such as @samp{2$}, are not supported.
23456 The modifier @samp{*} is not supported for specifying precision or
23460 The @samp{'} flag (for separation of digits into groups according to
23461 @code{LC_NUMERIC'}) is not supported.
23464 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
23468 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
23471 The conversion letters @samp{a} and @samp{A} are not supported.
23475 Note that the @samp{ll} type modifier is supported only if the
23476 underlying @code{C} implementation used to build @value{GDBN} supports
23477 the @code{long long int} type, and the @samp{L} type modifier is
23478 supported only if @code{long double} type is available.
23480 As in @code{C}, @code{printf} supports simple backslash-escape
23481 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
23482 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
23483 single character. Octal and hexadecimal escape sequences are not
23486 Additionally, @code{printf} supports conversion specifications for DFP
23487 (@dfn{Decimal Floating Point}) types using the following length modifiers
23488 together with a floating point specifier.
23493 @samp{H} for printing @code{Decimal32} types.
23496 @samp{D} for printing @code{Decimal64} types.
23499 @samp{DD} for printing @code{Decimal128} types.
23502 If the underlying @code{C} implementation used to build @value{GDBN} has
23503 support for the three length modifiers for DFP types, other modifiers
23504 such as width and precision will also be available for @value{GDBN} to use.
23506 In case there is no such @code{C} support, no additional modifiers will be
23507 available and the value will be printed in the standard way.
23509 Here's an example of printing DFP types using the above conversion letters:
23511 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
23515 @item eval @var{template}, @var{expressions}@dots{}
23516 Convert the values of one or more @var{expressions} under the control of
23517 the string @var{template} to a command line, and call it.
23521 @node Auto-loading sequences
23522 @subsection Controlling auto-loading native @value{GDBN} scripts
23523 @cindex native script auto-loading
23525 When a new object file is read (for example, due to the @code{file}
23526 command, or because the inferior has loaded a shared library),
23527 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
23528 @xref{Auto-loading extensions}.
23530 Auto-loading can be enabled or disabled,
23531 and the list of auto-loaded scripts can be printed.
23534 @anchor{set auto-load gdb-scripts}
23535 @kindex set auto-load gdb-scripts
23536 @item set auto-load gdb-scripts [on|off]
23537 Enable or disable the auto-loading of canned sequences of commands scripts.
23539 @anchor{show auto-load gdb-scripts}
23540 @kindex show auto-load gdb-scripts
23541 @item show auto-load gdb-scripts
23542 Show whether auto-loading of canned sequences of commands scripts is enabled or
23545 @anchor{info auto-load gdb-scripts}
23546 @kindex info auto-load gdb-scripts
23547 @cindex print list of auto-loaded canned sequences of commands scripts
23548 @item info auto-load gdb-scripts [@var{regexp}]
23549 Print the list of all canned sequences of commands scripts that @value{GDBN}
23553 If @var{regexp} is supplied only canned sequences of commands scripts with
23554 matching names are printed.
23556 @c Python docs live in a separate file.
23557 @include python.texi
23559 @c Guile docs live in a separate file.
23560 @include guile.texi
23562 @node Auto-loading extensions
23563 @section Auto-loading extensions
23564 @cindex auto-loading extensions
23566 @value{GDBN} provides two mechanisms for automatically loading extensions
23567 when a new object file is read (for example, due to the @code{file}
23568 command, or because the inferior has loaded a shared library):
23569 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
23570 section of modern file formats like ELF.
23573 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
23574 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
23575 * Which flavor to choose?::
23578 The auto-loading feature is useful for supplying application-specific
23579 debugging commands and features.
23581 Auto-loading can be enabled or disabled,
23582 and the list of auto-loaded scripts can be printed.
23583 See the @samp{auto-loading} section of each extension language
23584 for more information.
23585 For @value{GDBN} command files see @ref{Auto-loading sequences}.
23586 For Python files see @ref{Python Auto-loading}.
23588 Note that loading of this script file also requires accordingly configured
23589 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23591 @node objfile-gdbdotext file
23592 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
23593 @cindex @file{@var{objfile}-gdb.gdb}
23594 @cindex @file{@var{objfile}-gdb.py}
23595 @cindex @file{@var{objfile}-gdb.scm}
23597 When a new object file is read, @value{GDBN} looks for a file named
23598 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
23599 where @var{objfile} is the object file's name and
23600 where @var{ext} is the file extension for the extension language:
23603 @item @file{@var{objfile}-gdb.gdb}
23604 GDB's own command language
23605 @item @file{@var{objfile}-gdb.py}
23607 @item @file{@var{objfile}-gdb.scm}
23611 @var{script-name} is formed by ensuring that the file name of @var{objfile}
23612 is absolute, following all symlinks, and resolving @code{.} and @code{..}
23613 components, and appending the @file{-gdb.@var{ext}} suffix.
23614 If this file exists and is readable, @value{GDBN} will evaluate it as a
23615 script in the specified extension language.
23617 If this file does not exist, then @value{GDBN} will look for
23618 @var{script-name} file in all of the directories as specified below.
23620 Note that loading of these files requires an accordingly configured
23621 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23623 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
23624 scripts normally according to its @file{.exe} filename. But if no scripts are
23625 found @value{GDBN} also tries script filenames matching the object file without
23626 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
23627 is attempted on any platform. This makes the script filenames compatible
23628 between Unix and MS-Windows hosts.
23631 @anchor{set auto-load scripts-directory}
23632 @kindex set auto-load scripts-directory
23633 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
23634 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
23635 may be delimited by the host platform path separator in use
23636 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
23638 Each entry here needs to be covered also by the security setting
23639 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
23641 @anchor{with-auto-load-dir}
23642 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
23643 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
23644 configuration option @option{--with-auto-load-dir}.
23646 Any reference to @file{$debugdir} will get replaced by
23647 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
23648 reference to @file{$datadir} will get replaced by @var{data-directory} which is
23649 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
23650 @file{$datadir} must be placed as a directory component --- either alone or
23651 delimited by @file{/} or @file{\} directory separators, depending on the host
23654 The list of directories uses path separator (@samp{:} on GNU and Unix
23655 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
23656 to the @env{PATH} environment variable.
23658 @anchor{show auto-load scripts-directory}
23659 @kindex show auto-load scripts-directory
23660 @item show auto-load scripts-directory
23661 Show @value{GDBN} auto-loaded scripts location.
23664 @value{GDBN} does not track which files it has already auto-loaded this way.
23665 @value{GDBN} will load the associated script every time the corresponding
23666 @var{objfile} is opened.
23667 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
23668 is evaluated more than once.
23670 @node dotdebug_gdb_scripts section
23671 @subsection The @code{.debug_gdb_scripts} section
23672 @cindex @code{.debug_gdb_scripts} section
23674 For systems using file formats like ELF and COFF,
23675 when @value{GDBN} loads a new object file
23676 it will look for a special section named @code{.debug_gdb_scripts}.
23677 If this section exists, its contents is a list of NUL-terminated names
23678 of scripts to load. Each entry begins with a non-NULL prefix byte that
23679 specifies the kind of entry, typically the extension language.
23681 @value{GDBN} will look for each specified script file first in the
23682 current directory and then along the source search path
23683 (@pxref{Source Path, ,Specifying Source Directories}),
23684 except that @file{$cdir} is not searched, since the compilation
23685 directory is not relevant to scripts.
23687 Entries can be placed in section @code{.debug_gdb_scripts} with,
23688 for example, this GCC macro for Python scripts.
23691 /* Note: The "MS" section flags are to remove duplicates. */
23692 #define DEFINE_GDB_PY_SCRIPT(script_name) \
23694 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
23695 .byte 1 /* Python */\n\
23696 .asciz \"" script_name "\"\n\
23702 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
23703 Then one can reference the macro in a header or source file like this:
23706 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
23709 The script name may include directories if desired.
23711 Note that loading of this script file also requires accordingly configured
23712 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23714 If the macro invocation is put in a header, any application or library
23715 using this header will get a reference to the specified script,
23716 and with the use of @code{"MS"} attributes on the section, the linker
23717 will remove duplicates.
23719 @node Which flavor to choose?
23720 @subsection Which flavor to choose?
23722 Given the multiple ways of auto-loading extensions, it might not always
23723 be clear which one to choose. This section provides some guidance.
23726 Benefits of the @file{-gdb.@var{ext}} way:
23730 Can be used with file formats that don't support multiple sections.
23733 Ease of finding scripts for public libraries.
23735 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
23736 in the source search path.
23737 For publicly installed libraries, e.g., @file{libstdc++}, there typically
23738 isn't a source directory in which to find the script.
23741 Doesn't require source code additions.
23745 Benefits of the @code{.debug_gdb_scripts} way:
23749 Works with static linking.
23751 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
23752 trigger their loading. When an application is statically linked the only
23753 objfile available is the executable, and it is cumbersome to attach all the
23754 scripts from all the input libraries to the executable's
23755 @file{-gdb.@var{ext}} script.
23758 Works with classes that are entirely inlined.
23760 Some classes can be entirely inlined, and thus there may not be an associated
23761 shared library to attach a @file{-gdb.@var{ext}} script to.
23764 Scripts needn't be copied out of the source tree.
23766 In some circumstances, apps can be built out of large collections of internal
23767 libraries, and the build infrastructure necessary to install the
23768 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
23769 cumbersome. It may be easier to specify the scripts in the
23770 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
23771 top of the source tree to the source search path.
23774 @node Multiple Extension Languages
23775 @section Multiple Extension Languages
23777 The Guile and Python extension languages do not share any state,
23778 and generally do not interfere with each other.
23779 There are some things to be aware of, however.
23781 @subsection Python comes first
23783 Python was @value{GDBN}'s first extension language, and to avoid breaking
23784 existing behaviour Python comes first. This is generally solved by the
23785 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
23786 extension languages, and when it makes a call to an extension language,
23787 (say to pretty-print a value), it tries each in turn until an extension
23788 language indicates it has performed the request (e.g., has returned the
23789 pretty-printed form of a value).
23790 This extends to errors while performing such requests: If an error happens
23791 while, for example, trying to pretty-print an object then the error is
23792 reported and any following extension languages are not tried.
23795 @section Creating new spellings of existing commands
23796 @cindex aliases for commands
23798 It is often useful to define alternate spellings of existing commands.
23799 For example, if a new @value{GDBN} command defined in Python has
23800 a long name to type, it is handy to have an abbreviated version of it
23801 that involves less typing.
23803 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
23804 of the @samp{step} command even though it is otherwise an ambiguous
23805 abbreviation of other commands like @samp{set} and @samp{show}.
23807 Aliases are also used to provide shortened or more common versions
23808 of multi-word commands. For example, @value{GDBN} provides the
23809 @samp{tty} alias of the @samp{set inferior-tty} command.
23811 You can define a new alias with the @samp{alias} command.
23816 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
23820 @var{ALIAS} specifies the name of the new alias.
23821 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
23824 @var{COMMAND} specifies the name of an existing command
23825 that is being aliased.
23827 The @samp{-a} option specifies that the new alias is an abbreviation
23828 of the command. Abbreviations are not shown in command
23829 lists displayed by the @samp{help} command.
23831 The @samp{--} option specifies the end of options,
23832 and is useful when @var{ALIAS} begins with a dash.
23834 Here is a simple example showing how to make an abbreviation
23835 of a command so that there is less to type.
23836 Suppose you were tired of typing @samp{disas}, the current
23837 shortest unambiguous abbreviation of the @samp{disassemble} command
23838 and you wanted an even shorter version named @samp{di}.
23839 The following will accomplish this.
23842 (gdb) alias -a di = disas
23845 Note that aliases are different from user-defined commands.
23846 With a user-defined command, you also need to write documentation
23847 for it with the @samp{document} command.
23848 An alias automatically picks up the documentation of the existing command.
23850 Here is an example where we make @samp{elms} an abbreviation of
23851 @samp{elements} in the @samp{set print elements} command.
23852 This is to show that you can make an abbreviation of any part
23856 (gdb) alias -a set print elms = set print elements
23857 (gdb) alias -a show print elms = show print elements
23858 (gdb) set p elms 20
23860 Limit on string chars or array elements to print is 200.
23863 Note that if you are defining an alias of a @samp{set} command,
23864 and you want to have an alias for the corresponding @samp{show}
23865 command, then you need to define the latter separately.
23867 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
23868 @var{ALIAS}, just as they are normally.
23871 (gdb) alias -a set pr elms = set p ele
23874 Finally, here is an example showing the creation of a one word
23875 alias for a more complex command.
23876 This creates alias @samp{spe} of the command @samp{set print elements}.
23879 (gdb) alias spe = set print elements
23884 @chapter Command Interpreters
23885 @cindex command interpreters
23887 @value{GDBN} supports multiple command interpreters, and some command
23888 infrastructure to allow users or user interface writers to switch
23889 between interpreters or run commands in other interpreters.
23891 @value{GDBN} currently supports two command interpreters, the console
23892 interpreter (sometimes called the command-line interpreter or @sc{cli})
23893 and the machine interface interpreter (or @sc{gdb/mi}). This manual
23894 describes both of these interfaces in great detail.
23896 By default, @value{GDBN} will start with the console interpreter.
23897 However, the user may choose to start @value{GDBN} with another
23898 interpreter by specifying the @option{-i} or @option{--interpreter}
23899 startup options. Defined interpreters include:
23903 @cindex console interpreter
23904 The traditional console or command-line interpreter. This is the most often
23905 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
23906 @value{GDBN} will use this interpreter.
23909 @cindex mi interpreter
23910 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
23911 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
23912 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
23916 @cindex mi2 interpreter
23917 The current @sc{gdb/mi} interface.
23920 @cindex mi1 interpreter
23921 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
23925 @cindex invoke another interpreter
23926 The interpreter being used by @value{GDBN} may not be dynamically
23927 switched at runtime. Although possible, this could lead to a very
23928 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
23929 enters the command "interpreter-set console" in a console view,
23930 @value{GDBN} would switch to using the console interpreter, rendering
23931 the IDE inoperable!
23933 @kindex interpreter-exec
23934 Although you may only choose a single interpreter at startup, you may execute
23935 commands in any interpreter from the current interpreter using the appropriate
23936 command. If you are running the console interpreter, simply use the
23937 @code{interpreter-exec} command:
23940 interpreter-exec mi "-data-list-register-names"
23943 @sc{gdb/mi} has a similar command, although it is only available in versions of
23944 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
23947 @chapter @value{GDBN} Text User Interface
23949 @cindex Text User Interface
23952 * TUI Overview:: TUI overview
23953 * TUI Keys:: TUI key bindings
23954 * TUI Single Key Mode:: TUI single key mode
23955 * TUI Commands:: TUI-specific commands
23956 * TUI Configuration:: TUI configuration variables
23959 The @value{GDBN} Text User Interface (TUI) is a terminal
23960 interface which uses the @code{curses} library to show the source
23961 file, the assembly output, the program registers and @value{GDBN}
23962 commands in separate text windows. The TUI mode is supported only
23963 on platforms where a suitable version of the @code{curses} library
23966 The TUI mode is enabled by default when you invoke @value{GDBN} as
23967 @samp{@value{GDBP} -tui}.
23968 You can also switch in and out of TUI mode while @value{GDBN} runs by
23969 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
23970 @xref{TUI Keys, ,TUI Key Bindings}.
23973 @section TUI Overview
23975 In TUI mode, @value{GDBN} can display several text windows:
23979 This window is the @value{GDBN} command window with the @value{GDBN}
23980 prompt and the @value{GDBN} output. The @value{GDBN} input is still
23981 managed using readline.
23984 The source window shows the source file of the program. The current
23985 line and active breakpoints are displayed in this window.
23988 The assembly window shows the disassembly output of the program.
23991 This window shows the processor registers. Registers are highlighted
23992 when their values change.
23995 The source and assembly windows show the current program position
23996 by highlighting the current line and marking it with a @samp{>} marker.
23997 Breakpoints are indicated with two markers. The first marker
23998 indicates the breakpoint type:
24002 Breakpoint which was hit at least once.
24005 Breakpoint which was never hit.
24008 Hardware breakpoint which was hit at least once.
24011 Hardware breakpoint which was never hit.
24014 The second marker indicates whether the breakpoint is enabled or not:
24018 Breakpoint is enabled.
24021 Breakpoint is disabled.
24024 The source, assembly and register windows are updated when the current
24025 thread changes, when the frame changes, or when the program counter
24028 These windows are not all visible at the same time. The command
24029 window is always visible. The others can be arranged in several
24040 source and assembly,
24043 source and registers, or
24046 assembly and registers.
24049 A status line above the command window shows the following information:
24053 Indicates the current @value{GDBN} target.
24054 (@pxref{Targets, ,Specifying a Debugging Target}).
24057 Gives the current process or thread number.
24058 When no process is being debugged, this field is set to @code{No process}.
24061 Gives the current function name for the selected frame.
24062 The name is demangled if demangling is turned on (@pxref{Print Settings}).
24063 When there is no symbol corresponding to the current program counter,
24064 the string @code{??} is displayed.
24067 Indicates the current line number for the selected frame.
24068 When the current line number is not known, the string @code{??} is displayed.
24071 Indicates the current program counter address.
24075 @section TUI Key Bindings
24076 @cindex TUI key bindings
24078 The TUI installs several key bindings in the readline keymaps
24079 @ifset SYSTEM_READLINE
24080 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
24082 @ifclear SYSTEM_READLINE
24083 (@pxref{Command Line Editing}).
24085 The following key bindings are installed for both TUI mode and the
24086 @value{GDBN} standard mode.
24095 Enter or leave the TUI mode. When leaving the TUI mode,
24096 the curses window management stops and @value{GDBN} operates using
24097 its standard mode, writing on the terminal directly. When reentering
24098 the TUI mode, control is given back to the curses windows.
24099 The screen is then refreshed.
24103 Use a TUI layout with only one window. The layout will
24104 either be @samp{source} or @samp{assembly}. When the TUI mode
24105 is not active, it will switch to the TUI mode.
24107 Think of this key binding as the Emacs @kbd{C-x 1} binding.
24111 Use a TUI layout with at least two windows. When the current
24112 layout already has two windows, the next layout with two windows is used.
24113 When a new layout is chosen, one window will always be common to the
24114 previous layout and the new one.
24116 Think of it as the Emacs @kbd{C-x 2} binding.
24120 Change the active window. The TUI associates several key bindings
24121 (like scrolling and arrow keys) with the active window. This command
24122 gives the focus to the next TUI window.
24124 Think of it as the Emacs @kbd{C-x o} binding.
24128 Switch in and out of the TUI SingleKey mode that binds single
24129 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
24132 The following key bindings only work in the TUI mode:
24137 Scroll the active window one page up.
24141 Scroll the active window one page down.
24145 Scroll the active window one line up.
24149 Scroll the active window one line down.
24153 Scroll the active window one column left.
24157 Scroll the active window one column right.
24161 Refresh the screen.
24164 Because the arrow keys scroll the active window in the TUI mode, they
24165 are not available for their normal use by readline unless the command
24166 window has the focus. When another window is active, you must use
24167 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
24168 and @kbd{C-f} to control the command window.
24170 @node TUI Single Key Mode
24171 @section TUI Single Key Mode
24172 @cindex TUI single key mode
24174 The TUI also provides a @dfn{SingleKey} mode, which binds several
24175 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
24176 switch into this mode, where the following key bindings are used:
24179 @kindex c @r{(SingleKey TUI key)}
24183 @kindex d @r{(SingleKey TUI key)}
24187 @kindex f @r{(SingleKey TUI key)}
24191 @kindex n @r{(SingleKey TUI key)}
24195 @kindex q @r{(SingleKey TUI key)}
24197 exit the SingleKey mode.
24199 @kindex r @r{(SingleKey TUI key)}
24203 @kindex s @r{(SingleKey TUI key)}
24207 @kindex u @r{(SingleKey TUI key)}
24211 @kindex v @r{(SingleKey TUI key)}
24215 @kindex w @r{(SingleKey TUI key)}
24220 Other keys temporarily switch to the @value{GDBN} command prompt.
24221 The key that was pressed is inserted in the editing buffer so that
24222 it is possible to type most @value{GDBN} commands without interaction
24223 with the TUI SingleKey mode. Once the command is entered the TUI
24224 SingleKey mode is restored. The only way to permanently leave
24225 this mode is by typing @kbd{q} or @kbd{C-x s}.
24229 @section TUI-specific Commands
24230 @cindex TUI commands
24232 The TUI has specific commands to control the text windows.
24233 These commands are always available, even when @value{GDBN} is not in
24234 the TUI mode. When @value{GDBN} is in the standard mode, most
24235 of these commands will automatically switch to the TUI mode.
24237 Note that if @value{GDBN}'s @code{stdout} is not connected to a
24238 terminal, or @value{GDBN} has been started with the machine interface
24239 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
24240 these commands will fail with an error, because it would not be
24241 possible or desirable to enable curses window management.
24246 List and give the size of all displayed windows.
24250 Display the next layout.
24253 Display the previous layout.
24256 Display the source window only.
24259 Display the assembly window only.
24262 Display the source and assembly window.
24265 Display the register window together with the source or assembly window.
24269 Make the next window active for scrolling.
24272 Make the previous window active for scrolling.
24275 Make the source window active for scrolling.
24278 Make the assembly window active for scrolling.
24281 Make the register window active for scrolling.
24284 Make the command window active for scrolling.
24288 Refresh the screen. This is similar to typing @kbd{C-L}.
24290 @item tui reg float
24292 Show the floating point registers in the register window.
24294 @item tui reg general
24295 Show the general registers in the register window.
24298 Show the next register group. The list of register groups as well as
24299 their order is target specific. The predefined register groups are the
24300 following: @code{general}, @code{float}, @code{system}, @code{vector},
24301 @code{all}, @code{save}, @code{restore}.
24303 @item tui reg system
24304 Show the system registers in the register window.
24308 Update the source window and the current execution point.
24310 @item winheight @var{name} +@var{count}
24311 @itemx winheight @var{name} -@var{count}
24313 Change the height of the window @var{name} by @var{count}
24314 lines. Positive counts increase the height, while negative counts
24317 @item tabset @var{nchars}
24319 Set the width of tab stops to be @var{nchars} characters.
24322 @node TUI Configuration
24323 @section TUI Configuration Variables
24324 @cindex TUI configuration variables
24326 Several configuration variables control the appearance of TUI windows.
24329 @item set tui border-kind @var{kind}
24330 @kindex set tui border-kind
24331 Select the border appearance for the source, assembly and register windows.
24332 The possible values are the following:
24335 Use a space character to draw the border.
24338 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
24341 Use the Alternate Character Set to draw the border. The border is
24342 drawn using character line graphics if the terminal supports them.
24345 @item set tui border-mode @var{mode}
24346 @kindex set tui border-mode
24347 @itemx set tui active-border-mode @var{mode}
24348 @kindex set tui active-border-mode
24349 Select the display attributes for the borders of the inactive windows
24350 or the active window. The @var{mode} can be one of the following:
24353 Use normal attributes to display the border.
24359 Use reverse video mode.
24362 Use half bright mode.
24364 @item half-standout
24365 Use half bright and standout mode.
24368 Use extra bright or bold mode.
24370 @item bold-standout
24371 Use extra bright or bold and standout mode.
24376 @chapter Using @value{GDBN} under @sc{gnu} Emacs
24379 @cindex @sc{gnu} Emacs
24380 A special interface allows you to use @sc{gnu} Emacs to view (and
24381 edit) the source files for the program you are debugging with
24384 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
24385 executable file you want to debug as an argument. This command starts
24386 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
24387 created Emacs buffer.
24388 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
24390 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
24395 All ``terminal'' input and output goes through an Emacs buffer, called
24398 This applies both to @value{GDBN} commands and their output, and to the input
24399 and output done by the program you are debugging.
24401 This is useful because it means that you can copy the text of previous
24402 commands and input them again; you can even use parts of the output
24405 All the facilities of Emacs' Shell mode are available for interacting
24406 with your program. In particular, you can send signals the usual
24407 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
24411 @value{GDBN} displays source code through Emacs.
24413 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
24414 source file for that frame and puts an arrow (@samp{=>}) at the
24415 left margin of the current line. Emacs uses a separate buffer for
24416 source display, and splits the screen to show both your @value{GDBN} session
24419 Explicit @value{GDBN} @code{list} or search commands still produce output as
24420 usual, but you probably have no reason to use them from Emacs.
24423 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
24424 a graphical mode, enabled by default, which provides further buffers
24425 that can control the execution and describe the state of your program.
24426 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
24428 If you specify an absolute file name when prompted for the @kbd{M-x
24429 gdb} argument, then Emacs sets your current working directory to where
24430 your program resides. If you only specify the file name, then Emacs
24431 sets your current working directory to the directory associated
24432 with the previous buffer. In this case, @value{GDBN} may find your
24433 program by searching your environment's @code{PATH} variable, but on
24434 some operating systems it might not find the source. So, although the
24435 @value{GDBN} input and output session proceeds normally, the auxiliary
24436 buffer does not display the current source and line of execution.
24438 The initial working directory of @value{GDBN} is printed on the top
24439 line of the GUD buffer and this serves as a default for the commands
24440 that specify files for @value{GDBN} to operate on. @xref{Files,
24441 ,Commands to Specify Files}.
24443 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
24444 need to call @value{GDBN} by a different name (for example, if you
24445 keep several configurations around, with different names) you can
24446 customize the Emacs variable @code{gud-gdb-command-name} to run the
24449 In the GUD buffer, you can use these special Emacs commands in
24450 addition to the standard Shell mode commands:
24454 Describe the features of Emacs' GUD Mode.
24457 Execute to another source line, like the @value{GDBN} @code{step} command; also
24458 update the display window to show the current file and location.
24461 Execute to next source line in this function, skipping all function
24462 calls, like the @value{GDBN} @code{next} command. Then update the display window
24463 to show the current file and location.
24466 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
24467 display window accordingly.
24470 Execute until exit from the selected stack frame, like the @value{GDBN}
24471 @code{finish} command.
24474 Continue execution of your program, like the @value{GDBN} @code{continue}
24478 Go up the number of frames indicated by the numeric argument
24479 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
24480 like the @value{GDBN} @code{up} command.
24483 Go down the number of frames indicated by the numeric argument, like the
24484 @value{GDBN} @code{down} command.
24487 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
24488 tells @value{GDBN} to set a breakpoint on the source line point is on.
24490 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
24491 separate frame which shows a backtrace when the GUD buffer is current.
24492 Move point to any frame in the stack and type @key{RET} to make it
24493 become the current frame and display the associated source in the
24494 source buffer. Alternatively, click @kbd{Mouse-2} to make the
24495 selected frame become the current one. In graphical mode, the
24496 speedbar displays watch expressions.
24498 If you accidentally delete the source-display buffer, an easy way to get
24499 it back is to type the command @code{f} in the @value{GDBN} buffer, to
24500 request a frame display; when you run under Emacs, this recreates
24501 the source buffer if necessary to show you the context of the current
24504 The source files displayed in Emacs are in ordinary Emacs buffers
24505 which are visiting the source files in the usual way. You can edit
24506 the files with these buffers if you wish; but keep in mind that @value{GDBN}
24507 communicates with Emacs in terms of line numbers. If you add or
24508 delete lines from the text, the line numbers that @value{GDBN} knows cease
24509 to correspond properly with the code.
24511 A more detailed description of Emacs' interaction with @value{GDBN} is
24512 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
24516 @chapter The @sc{gdb/mi} Interface
24518 @unnumberedsec Function and Purpose
24520 @cindex @sc{gdb/mi}, its purpose
24521 @sc{gdb/mi} is a line based machine oriented text interface to
24522 @value{GDBN} and is activated by specifying using the
24523 @option{--interpreter} command line option (@pxref{Mode Options}). It
24524 is specifically intended to support the development of systems which
24525 use the debugger as just one small component of a larger system.
24527 This chapter is a specification of the @sc{gdb/mi} interface. It is written
24528 in the form of a reference manual.
24530 Note that @sc{gdb/mi} is still under construction, so some of the
24531 features described below are incomplete and subject to change
24532 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
24534 @unnumberedsec Notation and Terminology
24536 @cindex notational conventions, for @sc{gdb/mi}
24537 This chapter uses the following notation:
24541 @code{|} separates two alternatives.
24544 @code{[ @var{something} ]} indicates that @var{something} is optional:
24545 it may or may not be given.
24548 @code{( @var{group} )*} means that @var{group} inside the parentheses
24549 may repeat zero or more times.
24552 @code{( @var{group} )+} means that @var{group} inside the parentheses
24553 may repeat one or more times.
24556 @code{"@var{string}"} means a literal @var{string}.
24560 @heading Dependencies
24564 * GDB/MI General Design::
24565 * GDB/MI Command Syntax::
24566 * GDB/MI Compatibility with CLI::
24567 * GDB/MI Development and Front Ends::
24568 * GDB/MI Output Records::
24569 * GDB/MI Simple Examples::
24570 * GDB/MI Command Description Format::
24571 * GDB/MI Breakpoint Commands::
24572 * GDB/MI Catchpoint Commands::
24573 * GDB/MI Program Context::
24574 * GDB/MI Thread Commands::
24575 * GDB/MI Ada Tasking Commands::
24576 * GDB/MI Program Execution::
24577 * GDB/MI Stack Manipulation::
24578 * GDB/MI Variable Objects::
24579 * GDB/MI Data Manipulation::
24580 * GDB/MI Tracepoint Commands::
24581 * GDB/MI Symbol Query::
24582 * GDB/MI File Commands::
24584 * GDB/MI Kod Commands::
24585 * GDB/MI Memory Overlay Commands::
24586 * GDB/MI Signal Handling Commands::
24588 * GDB/MI Target Manipulation::
24589 * GDB/MI File Transfer Commands::
24590 * GDB/MI Ada Exceptions Commands::
24591 * GDB/MI Support Commands::
24592 * GDB/MI Miscellaneous Commands::
24595 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24596 @node GDB/MI General Design
24597 @section @sc{gdb/mi} General Design
24598 @cindex GDB/MI General Design
24600 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
24601 parts---commands sent to @value{GDBN}, responses to those commands
24602 and notifications. Each command results in exactly one response,
24603 indicating either successful completion of the command, or an error.
24604 For the commands that do not resume the target, the response contains the
24605 requested information. For the commands that resume the target, the
24606 response only indicates whether the target was successfully resumed.
24607 Notifications is the mechanism for reporting changes in the state of the
24608 target, or in @value{GDBN} state, that cannot conveniently be associated with
24609 a command and reported as part of that command response.
24611 The important examples of notifications are:
24615 Exec notifications. These are used to report changes in
24616 target state---when a target is resumed, or stopped. It would not
24617 be feasible to include this information in response of resuming
24618 commands, because one resume commands can result in multiple events in
24619 different threads. Also, quite some time may pass before any event
24620 happens in the target, while a frontend needs to know whether the resuming
24621 command itself was successfully executed.
24624 Console output, and status notifications. Console output
24625 notifications are used to report output of CLI commands, as well as
24626 diagnostics for other commands. Status notifications are used to
24627 report the progress of a long-running operation. Naturally, including
24628 this information in command response would mean no output is produced
24629 until the command is finished, which is undesirable.
24632 General notifications. Commands may have various side effects on
24633 the @value{GDBN} or target state beyond their official purpose. For example,
24634 a command may change the selected thread. Although such changes can
24635 be included in command response, using notification allows for more
24636 orthogonal frontend design.
24640 There's no guarantee that whenever an MI command reports an error,
24641 @value{GDBN} or the target are in any specific state, and especially,
24642 the state is not reverted to the state before the MI command was
24643 processed. Therefore, whenever an MI command results in an error,
24644 we recommend that the frontend refreshes all the information shown in
24645 the user interface.
24649 * Context management::
24650 * Asynchronous and non-stop modes::
24654 @node Context management
24655 @subsection Context management
24657 @subsubsection Threads and Frames
24659 In most cases when @value{GDBN} accesses the target, this access is
24660 done in context of a specific thread and frame (@pxref{Frames}).
24661 Often, even when accessing global data, the target requires that a thread
24662 be specified. The CLI interface maintains the selected thread and frame,
24663 and supplies them to target on each command. This is convenient,
24664 because a command line user would not want to specify that information
24665 explicitly on each command, and because user interacts with
24666 @value{GDBN} via a single terminal, so no confusion is possible as
24667 to what thread and frame are the current ones.
24669 In the case of MI, the concept of selected thread and frame is less
24670 useful. First, a frontend can easily remember this information
24671 itself. Second, a graphical frontend can have more than one window,
24672 each one used for debugging a different thread, and the frontend might
24673 want to access additional threads for internal purposes. This
24674 increases the risk that by relying on implicitly selected thread, the
24675 frontend may be operating on a wrong one. Therefore, each MI command
24676 should explicitly specify which thread and frame to operate on. To
24677 make it possible, each MI command accepts the @samp{--thread} and
24678 @samp{--frame} options, the value to each is @value{GDBN} identifier
24679 for thread and frame to operate on.
24681 Usually, each top-level window in a frontend allows the user to select
24682 a thread and a frame, and remembers the user selection for further
24683 operations. However, in some cases @value{GDBN} may suggest that the
24684 current thread be changed. For example, when stopping on a breakpoint
24685 it is reasonable to switch to the thread where breakpoint is hit. For
24686 another example, if the user issues the CLI @samp{thread} command via
24687 the frontend, it is desirable to change the frontend's selected thread to the
24688 one specified by user. @value{GDBN} communicates the suggestion to
24689 change current thread using the @samp{=thread-selected} notification.
24690 No such notification is available for the selected frame at the moment.
24692 Note that historically, MI shares the selected thread with CLI, so
24693 frontends used the @code{-thread-select} to execute commands in the
24694 right context. However, getting this to work right is cumbersome. The
24695 simplest way is for frontend to emit @code{-thread-select} command
24696 before every command. This doubles the number of commands that need
24697 to be sent. The alternative approach is to suppress @code{-thread-select}
24698 if the selected thread in @value{GDBN} is supposed to be identical to the
24699 thread the frontend wants to operate on. However, getting this
24700 optimization right can be tricky. In particular, if the frontend
24701 sends several commands to @value{GDBN}, and one of the commands changes the
24702 selected thread, then the behaviour of subsequent commands will
24703 change. So, a frontend should either wait for response from such
24704 problematic commands, or explicitly add @code{-thread-select} for
24705 all subsequent commands. No frontend is known to do this exactly
24706 right, so it is suggested to just always pass the @samp{--thread} and
24707 @samp{--frame} options.
24709 @subsubsection Language
24711 The execution of several commands depends on which language is selected.
24712 By default, the current language (@pxref{show language}) is used.
24713 But for commands known to be language-sensitive, it is recommended
24714 to use the @samp{--language} option. This option takes one argument,
24715 which is the name of the language to use while executing the command.
24719 -data-evaluate-expression --language c "sizeof (void*)"
24724 The valid language names are the same names accepted by the
24725 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
24726 @samp{local} or @samp{unknown}.
24728 @node Asynchronous and non-stop modes
24729 @subsection Asynchronous command execution and non-stop mode
24731 On some targets, @value{GDBN} is capable of processing MI commands
24732 even while the target is running. This is called @dfn{asynchronous
24733 command execution} (@pxref{Background Execution}). The frontend may
24734 specify a preferrence for asynchronous execution using the
24735 @code{-gdb-set target-async 1} command, which should be emitted before
24736 either running the executable or attaching to the target. After the
24737 frontend has started the executable or attached to the target, it can
24738 find if asynchronous execution is enabled using the
24739 @code{-list-target-features} command.
24741 Even if @value{GDBN} can accept a command while target is running,
24742 many commands that access the target do not work when the target is
24743 running. Therefore, asynchronous command execution is most useful
24744 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
24745 it is possible to examine the state of one thread, while other threads
24748 When a given thread is running, MI commands that try to access the
24749 target in the context of that thread may not work, or may work only on
24750 some targets. In particular, commands that try to operate on thread's
24751 stack will not work, on any target. Commands that read memory, or
24752 modify breakpoints, may work or not work, depending on the target. Note
24753 that even commands that operate on global state, such as @code{print},
24754 @code{set}, and breakpoint commands, still access the target in the
24755 context of a specific thread, so frontend should try to find a
24756 stopped thread and perform the operation on that thread (using the
24757 @samp{--thread} option).
24759 Which commands will work in the context of a running thread is
24760 highly target dependent. However, the two commands
24761 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
24762 to find the state of a thread, will always work.
24764 @node Thread groups
24765 @subsection Thread groups
24766 @value{GDBN} may be used to debug several processes at the same time.
24767 On some platfroms, @value{GDBN} may support debugging of several
24768 hardware systems, each one having several cores with several different
24769 processes running on each core. This section describes the MI
24770 mechanism to support such debugging scenarios.
24772 The key observation is that regardless of the structure of the
24773 target, MI can have a global list of threads, because most commands that
24774 accept the @samp{--thread} option do not need to know what process that
24775 thread belongs to. Therefore, it is not necessary to introduce
24776 neither additional @samp{--process} option, nor an notion of the
24777 current process in the MI interface. The only strictly new feature
24778 that is required is the ability to find how the threads are grouped
24781 To allow the user to discover such grouping, and to support arbitrary
24782 hierarchy of machines/cores/processes, MI introduces the concept of a
24783 @dfn{thread group}. Thread group is a collection of threads and other
24784 thread groups. A thread group always has a string identifier, a type,
24785 and may have additional attributes specific to the type. A new
24786 command, @code{-list-thread-groups}, returns the list of top-level
24787 thread groups, which correspond to processes that @value{GDBN} is
24788 debugging at the moment. By passing an identifier of a thread group
24789 to the @code{-list-thread-groups} command, it is possible to obtain
24790 the members of specific thread group.
24792 To allow the user to easily discover processes, and other objects, he
24793 wishes to debug, a concept of @dfn{available thread group} is
24794 introduced. Available thread group is an thread group that
24795 @value{GDBN} is not debugging, but that can be attached to, using the
24796 @code{-target-attach} command. The list of available top-level thread
24797 groups can be obtained using @samp{-list-thread-groups --available}.
24798 In general, the content of a thread group may be only retrieved only
24799 after attaching to that thread group.
24801 Thread groups are related to inferiors (@pxref{Inferiors and
24802 Programs}). Each inferior corresponds to a thread group of a special
24803 type @samp{process}, and some additional operations are permitted on
24804 such thread groups.
24806 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24807 @node GDB/MI Command Syntax
24808 @section @sc{gdb/mi} Command Syntax
24811 * GDB/MI Input Syntax::
24812 * GDB/MI Output Syntax::
24815 @node GDB/MI Input Syntax
24816 @subsection @sc{gdb/mi} Input Syntax
24818 @cindex input syntax for @sc{gdb/mi}
24819 @cindex @sc{gdb/mi}, input syntax
24821 @item @var{command} @expansion{}
24822 @code{@var{cli-command} | @var{mi-command}}
24824 @item @var{cli-command} @expansion{}
24825 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
24826 @var{cli-command} is any existing @value{GDBN} CLI command.
24828 @item @var{mi-command} @expansion{}
24829 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
24830 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
24832 @item @var{token} @expansion{}
24833 "any sequence of digits"
24835 @item @var{option} @expansion{}
24836 @code{"-" @var{parameter} [ " " @var{parameter} ]}
24838 @item @var{parameter} @expansion{}
24839 @code{@var{non-blank-sequence} | @var{c-string}}
24841 @item @var{operation} @expansion{}
24842 @emph{any of the operations described in this chapter}
24844 @item @var{non-blank-sequence} @expansion{}
24845 @emph{anything, provided it doesn't contain special characters such as
24846 "-", @var{nl}, """ and of course " "}
24848 @item @var{c-string} @expansion{}
24849 @code{""" @var{seven-bit-iso-c-string-content} """}
24851 @item @var{nl} @expansion{}
24860 The CLI commands are still handled by the @sc{mi} interpreter; their
24861 output is described below.
24864 The @code{@var{token}}, when present, is passed back when the command
24868 Some @sc{mi} commands accept optional arguments as part of the parameter
24869 list. Each option is identified by a leading @samp{-} (dash) and may be
24870 followed by an optional argument parameter. Options occur first in the
24871 parameter list and can be delimited from normal parameters using
24872 @samp{--} (this is useful when some parameters begin with a dash).
24879 We want easy access to the existing CLI syntax (for debugging).
24882 We want it to be easy to spot a @sc{mi} operation.
24885 @node GDB/MI Output Syntax
24886 @subsection @sc{gdb/mi} Output Syntax
24888 @cindex output syntax of @sc{gdb/mi}
24889 @cindex @sc{gdb/mi}, output syntax
24890 The output from @sc{gdb/mi} consists of zero or more out-of-band records
24891 followed, optionally, by a single result record. This result record
24892 is for the most recent command. The sequence of output records is
24893 terminated by @samp{(gdb)}.
24895 If an input command was prefixed with a @code{@var{token}} then the
24896 corresponding output for that command will also be prefixed by that same
24900 @item @var{output} @expansion{}
24901 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
24903 @item @var{result-record} @expansion{}
24904 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
24906 @item @var{out-of-band-record} @expansion{}
24907 @code{@var{async-record} | @var{stream-record}}
24909 @item @var{async-record} @expansion{}
24910 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
24912 @item @var{exec-async-output} @expansion{}
24913 @code{[ @var{token} ] "*" @var{async-output nl}}
24915 @item @var{status-async-output} @expansion{}
24916 @code{[ @var{token} ] "+" @var{async-output nl}}
24918 @item @var{notify-async-output} @expansion{}
24919 @code{[ @var{token} ] "=" @var{async-output nl}}
24921 @item @var{async-output} @expansion{}
24922 @code{@var{async-class} ( "," @var{result} )*}
24924 @item @var{result-class} @expansion{}
24925 @code{"done" | "running" | "connected" | "error" | "exit"}
24927 @item @var{async-class} @expansion{}
24928 @code{"stopped" | @var{others}} (where @var{others} will be added
24929 depending on the needs---this is still in development).
24931 @item @var{result} @expansion{}
24932 @code{ @var{variable} "=" @var{value}}
24934 @item @var{variable} @expansion{}
24935 @code{ @var{string} }
24937 @item @var{value} @expansion{}
24938 @code{ @var{const} | @var{tuple} | @var{list} }
24940 @item @var{const} @expansion{}
24941 @code{@var{c-string}}
24943 @item @var{tuple} @expansion{}
24944 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
24946 @item @var{list} @expansion{}
24947 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
24948 @var{result} ( "," @var{result} )* "]" }
24950 @item @var{stream-record} @expansion{}
24951 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
24953 @item @var{console-stream-output} @expansion{}
24954 @code{"~" @var{c-string nl}}
24956 @item @var{target-stream-output} @expansion{}
24957 @code{"@@" @var{c-string nl}}
24959 @item @var{log-stream-output} @expansion{}
24960 @code{"&" @var{c-string nl}}
24962 @item @var{nl} @expansion{}
24965 @item @var{token} @expansion{}
24966 @emph{any sequence of digits}.
24974 All output sequences end in a single line containing a period.
24977 The @code{@var{token}} is from the corresponding request. Note that
24978 for all async output, while the token is allowed by the grammar and
24979 may be output by future versions of @value{GDBN} for select async
24980 output messages, it is generally omitted. Frontends should treat
24981 all async output as reporting general changes in the state of the
24982 target and there should be no need to associate async output to any
24986 @cindex status output in @sc{gdb/mi}
24987 @var{status-async-output} contains on-going status information about the
24988 progress of a slow operation. It can be discarded. All status output is
24989 prefixed by @samp{+}.
24992 @cindex async output in @sc{gdb/mi}
24993 @var{exec-async-output} contains asynchronous state change on the target
24994 (stopped, started, disappeared). All async output is prefixed by
24998 @cindex notify output in @sc{gdb/mi}
24999 @var{notify-async-output} contains supplementary information that the
25000 client should handle (e.g., a new breakpoint information). All notify
25001 output is prefixed by @samp{=}.
25004 @cindex console output in @sc{gdb/mi}
25005 @var{console-stream-output} is output that should be displayed as is in the
25006 console. It is the textual response to a CLI command. All the console
25007 output is prefixed by @samp{~}.
25010 @cindex target output in @sc{gdb/mi}
25011 @var{target-stream-output} is the output produced by the target program.
25012 All the target output is prefixed by @samp{@@}.
25015 @cindex log output in @sc{gdb/mi}
25016 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
25017 instance messages that should be displayed as part of an error log. All
25018 the log output is prefixed by @samp{&}.
25021 @cindex list output in @sc{gdb/mi}
25022 New @sc{gdb/mi} commands should only output @var{lists} containing
25028 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
25029 details about the various output records.
25031 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25032 @node GDB/MI Compatibility with CLI
25033 @section @sc{gdb/mi} Compatibility with CLI
25035 @cindex compatibility, @sc{gdb/mi} and CLI
25036 @cindex @sc{gdb/mi}, compatibility with CLI
25038 For the developers convenience CLI commands can be entered directly,
25039 but there may be some unexpected behaviour. For example, commands
25040 that query the user will behave as if the user replied yes, breakpoint
25041 command lists are not executed and some CLI commands, such as
25042 @code{if}, @code{when} and @code{define}, prompt for further input with
25043 @samp{>}, which is not valid MI output.
25045 This feature may be removed at some stage in the future and it is
25046 recommended that front ends use the @code{-interpreter-exec} command
25047 (@pxref{-interpreter-exec}).
25049 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25050 @node GDB/MI Development and Front Ends
25051 @section @sc{gdb/mi} Development and Front Ends
25052 @cindex @sc{gdb/mi} development
25054 The application which takes the MI output and presents the state of the
25055 program being debugged to the user is called a @dfn{front end}.
25057 Although @sc{gdb/mi} is still incomplete, it is currently being used
25058 by a variety of front ends to @value{GDBN}. This makes it difficult
25059 to introduce new functionality without breaking existing usage. This
25060 section tries to minimize the problems by describing how the protocol
25063 Some changes in MI need not break a carefully designed front end, and
25064 for these the MI version will remain unchanged. The following is a
25065 list of changes that may occur within one level, so front ends should
25066 parse MI output in a way that can handle them:
25070 New MI commands may be added.
25073 New fields may be added to the output of any MI command.
25076 The range of values for fields with specified values, e.g.,
25077 @code{in_scope} (@pxref{-var-update}) may be extended.
25079 @c The format of field's content e.g type prefix, may change so parse it
25080 @c at your own risk. Yes, in general?
25082 @c The order of fields may change? Shouldn't really matter but it might
25083 @c resolve inconsistencies.
25086 If the changes are likely to break front ends, the MI version level
25087 will be increased by one. This will allow the front end to parse the
25088 output according to the MI version. Apart from mi0, new versions of
25089 @value{GDBN} will not support old versions of MI and it will be the
25090 responsibility of the front end to work with the new one.
25092 @c Starting with mi3, add a new command -mi-version that prints the MI
25095 The best way to avoid unexpected changes in MI that might break your front
25096 end is to make your project known to @value{GDBN} developers and
25097 follow development on @email{gdb@@sourceware.org} and
25098 @email{gdb-patches@@sourceware.org}.
25099 @cindex mailing lists
25101 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25102 @node GDB/MI Output Records
25103 @section @sc{gdb/mi} Output Records
25106 * GDB/MI Result Records::
25107 * GDB/MI Stream Records::
25108 * GDB/MI Async Records::
25109 * GDB/MI Breakpoint Information::
25110 * GDB/MI Frame Information::
25111 * GDB/MI Thread Information::
25112 * GDB/MI Ada Exception Information::
25115 @node GDB/MI Result Records
25116 @subsection @sc{gdb/mi} Result Records
25118 @cindex result records in @sc{gdb/mi}
25119 @cindex @sc{gdb/mi}, result records
25120 In addition to a number of out-of-band notifications, the response to a
25121 @sc{gdb/mi} command includes one of the following result indications:
25125 @item "^done" [ "," @var{results} ]
25126 The synchronous operation was successful, @code{@var{results}} are the return
25131 This result record is equivalent to @samp{^done}. Historically, it
25132 was output instead of @samp{^done} if the command has resumed the
25133 target. This behaviour is maintained for backward compatibility, but
25134 all frontends should treat @samp{^done} and @samp{^running}
25135 identically and rely on the @samp{*running} output record to determine
25136 which threads are resumed.
25140 @value{GDBN} has connected to a remote target.
25142 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
25144 The operation failed. The @code{msg=@var{c-string}} variable contains
25145 the corresponding error message.
25147 If present, the @code{code=@var{c-string}} variable provides an error
25148 code on which consumers can rely on to detect the corresponding
25149 error condition. At present, only one error code is defined:
25152 @item "undefined-command"
25153 Indicates that the command causing the error does not exist.
25158 @value{GDBN} has terminated.
25162 @node GDB/MI Stream Records
25163 @subsection @sc{gdb/mi} Stream Records
25165 @cindex @sc{gdb/mi}, stream records
25166 @cindex stream records in @sc{gdb/mi}
25167 @value{GDBN} internally maintains a number of output streams: the console, the
25168 target, and the log. The output intended for each of these streams is
25169 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
25171 Each stream record begins with a unique @dfn{prefix character} which
25172 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
25173 Syntax}). In addition to the prefix, each stream record contains a
25174 @code{@var{string-output}}. This is either raw text (with an implicit new
25175 line) or a quoted C string (which does not contain an implicit newline).
25178 @item "~" @var{string-output}
25179 The console output stream contains text that should be displayed in the
25180 CLI console window. It contains the textual responses to CLI commands.
25182 @item "@@" @var{string-output}
25183 The target output stream contains any textual output from the running
25184 target. This is only present when GDB's event loop is truly
25185 asynchronous, which is currently only the case for remote targets.
25187 @item "&" @var{string-output}
25188 The log stream contains debugging messages being produced by @value{GDBN}'s
25192 @node GDB/MI Async Records
25193 @subsection @sc{gdb/mi} Async Records
25195 @cindex async records in @sc{gdb/mi}
25196 @cindex @sc{gdb/mi}, async records
25197 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
25198 additional changes that have occurred. Those changes can either be a
25199 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
25200 target activity (e.g., target stopped).
25202 The following is the list of possible async records:
25206 @item *running,thread-id="@var{thread}"
25207 The target is now running. The @var{thread} field tells which
25208 specific thread is now running, and can be @samp{all} if all threads
25209 are running. The frontend should assume that no interaction with a
25210 running thread is possible after this notification is produced.
25211 The frontend should not assume that this notification is output
25212 only once for any command. @value{GDBN} may emit this notification
25213 several times, either for different threads, because it cannot resume
25214 all threads together, or even for a single thread, if the thread must
25215 be stepped though some code before letting it run freely.
25217 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
25218 The target has stopped. The @var{reason} field can have one of the
25222 @item breakpoint-hit
25223 A breakpoint was reached.
25224 @item watchpoint-trigger
25225 A watchpoint was triggered.
25226 @item read-watchpoint-trigger
25227 A read watchpoint was triggered.
25228 @item access-watchpoint-trigger
25229 An access watchpoint was triggered.
25230 @item function-finished
25231 An -exec-finish or similar CLI command was accomplished.
25232 @item location-reached
25233 An -exec-until or similar CLI command was accomplished.
25234 @item watchpoint-scope
25235 A watchpoint has gone out of scope.
25236 @item end-stepping-range
25237 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
25238 similar CLI command was accomplished.
25239 @item exited-signalled
25240 The inferior exited because of a signal.
25242 The inferior exited.
25243 @item exited-normally
25244 The inferior exited normally.
25245 @item signal-received
25246 A signal was received by the inferior.
25248 The inferior has stopped due to a library being loaded or unloaded.
25249 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
25250 set or when a @code{catch load} or @code{catch unload} catchpoint is
25251 in use (@pxref{Set Catchpoints}).
25253 The inferior has forked. This is reported when @code{catch fork}
25254 (@pxref{Set Catchpoints}) has been used.
25256 The inferior has vforked. This is reported in when @code{catch vfork}
25257 (@pxref{Set Catchpoints}) has been used.
25258 @item syscall-entry
25259 The inferior entered a system call. This is reported when @code{catch
25260 syscall} (@pxref{Set Catchpoints}) has been used.
25261 @item syscall-entry
25262 The inferior returned from a system call. This is reported when
25263 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
25265 The inferior called @code{exec}. This is reported when @code{catch exec}
25266 (@pxref{Set Catchpoints}) has been used.
25269 The @var{id} field identifies the thread that directly caused the stop
25270 -- for example by hitting a breakpoint. Depending on whether all-stop
25271 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
25272 stop all threads, or only the thread that directly triggered the stop.
25273 If all threads are stopped, the @var{stopped} field will have the
25274 value of @code{"all"}. Otherwise, the value of the @var{stopped}
25275 field will be a list of thread identifiers. Presently, this list will
25276 always include a single thread, but frontend should be prepared to see
25277 several threads in the list. The @var{core} field reports the
25278 processor core on which the stop event has happened. This field may be absent
25279 if such information is not available.
25281 @item =thread-group-added,id="@var{id}"
25282 @itemx =thread-group-removed,id="@var{id}"
25283 A thread group was either added or removed. The @var{id} field
25284 contains the @value{GDBN} identifier of the thread group. When a thread
25285 group is added, it generally might not be associated with a running
25286 process. When a thread group is removed, its id becomes invalid and
25287 cannot be used in any way.
25289 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
25290 A thread group became associated with a running program,
25291 either because the program was just started or the thread group
25292 was attached to a program. The @var{id} field contains the
25293 @value{GDBN} identifier of the thread group. The @var{pid} field
25294 contains process identifier, specific to the operating system.
25296 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
25297 A thread group is no longer associated with a running program,
25298 either because the program has exited, or because it was detached
25299 from. The @var{id} field contains the @value{GDBN} identifier of the
25300 thread group. @var{code} is the exit code of the inferior; it exists
25301 only when the inferior exited with some code.
25303 @item =thread-created,id="@var{id}",group-id="@var{gid}"
25304 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
25305 A thread either was created, or has exited. The @var{id} field
25306 contains the @value{GDBN} identifier of the thread. The @var{gid}
25307 field identifies the thread group this thread belongs to.
25309 @item =thread-selected,id="@var{id}"
25310 Informs that the selected thread was changed as result of the last
25311 command. This notification is not emitted as result of @code{-thread-select}
25312 command but is emitted whenever an MI command that is not documented
25313 to change the selected thread actually changes it. In particular,
25314 invoking, directly or indirectly (via user-defined command), the CLI
25315 @code{thread} command, will generate this notification.
25317 We suggest that in response to this notification, front ends
25318 highlight the selected thread and cause subsequent commands to apply to
25321 @item =library-loaded,...
25322 Reports that a new library file was loaded by the program. This
25323 notification has 4 fields---@var{id}, @var{target-name},
25324 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
25325 opaque identifier of the library. For remote debugging case,
25326 @var{target-name} and @var{host-name} fields give the name of the
25327 library file on the target, and on the host respectively. For native
25328 debugging, both those fields have the same value. The
25329 @var{symbols-loaded} field is emitted only for backward compatibility
25330 and should not be relied on to convey any useful information. The
25331 @var{thread-group} field, if present, specifies the id of the thread
25332 group in whose context the library was loaded. If the field is
25333 absent, it means the library was loaded in the context of all present
25336 @item =library-unloaded,...
25337 Reports that a library was unloaded by the program. This notification
25338 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
25339 the same meaning as for the @code{=library-loaded} notification.
25340 The @var{thread-group} field, if present, specifies the id of the
25341 thread group in whose context the library was unloaded. If the field is
25342 absent, it means the library was unloaded in the context of all present
25345 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
25346 @itemx =traceframe-changed,end
25347 Reports that the trace frame was changed and its new number is
25348 @var{tfnum}. The number of the tracepoint associated with this trace
25349 frame is @var{tpnum}.
25351 @item =tsv-created,name=@var{name},initial=@var{initial}
25352 Reports that the new trace state variable @var{name} is created with
25353 initial value @var{initial}.
25355 @item =tsv-deleted,name=@var{name}
25356 @itemx =tsv-deleted
25357 Reports that the trace state variable @var{name} is deleted or all
25358 trace state variables are deleted.
25360 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
25361 Reports that the trace state variable @var{name} is modified with
25362 the initial value @var{initial}. The current value @var{current} of
25363 trace state variable is optional and is reported if the current
25364 value of trace state variable is known.
25366 @item =breakpoint-created,bkpt=@{...@}
25367 @itemx =breakpoint-modified,bkpt=@{...@}
25368 @itemx =breakpoint-deleted,id=@var{number}
25369 Reports that a breakpoint was created, modified, or deleted,
25370 respectively. Only user-visible breakpoints are reported to the MI
25373 The @var{bkpt} argument is of the same form as returned by the various
25374 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
25375 @var{number} is the ordinal number of the breakpoint.
25377 Note that if a breakpoint is emitted in the result record of a
25378 command, then it will not also be emitted in an async record.
25380 @item =record-started,thread-group="@var{id}"
25381 @itemx =record-stopped,thread-group="@var{id}"
25382 Execution log recording was either started or stopped on an
25383 inferior. The @var{id} is the @value{GDBN} identifier of the thread
25384 group corresponding to the affected inferior.
25386 @item =cmd-param-changed,param=@var{param},value=@var{value}
25387 Reports that a parameter of the command @code{set @var{param}} is
25388 changed to @var{value}. In the multi-word @code{set} command,
25389 the @var{param} is the whole parameter list to @code{set} command.
25390 For example, In command @code{set check type on}, @var{param}
25391 is @code{check type} and @var{value} is @code{on}.
25393 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
25394 Reports that bytes from @var{addr} to @var{data} + @var{len} were
25395 written in an inferior. The @var{id} is the identifier of the
25396 thread group corresponding to the affected inferior. The optional
25397 @code{type="code"} part is reported if the memory written to holds
25401 @node GDB/MI Breakpoint Information
25402 @subsection @sc{gdb/mi} Breakpoint Information
25404 When @value{GDBN} reports information about a breakpoint, a
25405 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
25410 The breakpoint number. For a breakpoint that represents one location
25411 of a multi-location breakpoint, this will be a dotted pair, like
25415 The type of the breakpoint. For ordinary breakpoints this will be
25416 @samp{breakpoint}, but many values are possible.
25419 If the type of the breakpoint is @samp{catchpoint}, then this
25420 indicates the exact type of catchpoint.
25423 This is the breakpoint disposition---either @samp{del}, meaning that
25424 the breakpoint will be deleted at the next stop, or @samp{keep},
25425 meaning that the breakpoint will not be deleted.
25428 This indicates whether the breakpoint is enabled, in which case the
25429 value is @samp{y}, or disabled, in which case the value is @samp{n}.
25430 Note that this is not the same as the field @code{enable}.
25433 The address of the breakpoint. This may be a hexidecimal number,
25434 giving the address; or the string @samp{<PENDING>}, for a pending
25435 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
25436 multiple locations. This field will not be present if no address can
25437 be determined. For example, a watchpoint does not have an address.
25440 If known, the function in which the breakpoint appears.
25441 If not known, this field is not present.
25444 The name of the source file which contains this function, if known.
25445 If not known, this field is not present.
25448 The full file name of the source file which contains this function, if
25449 known. If not known, this field is not present.
25452 The line number at which this breakpoint appears, if known.
25453 If not known, this field is not present.
25456 If the source file is not known, this field may be provided. If
25457 provided, this holds the address of the breakpoint, possibly followed
25461 If this breakpoint is pending, this field is present and holds the
25462 text used to set the breakpoint, as entered by the user.
25465 Where this breakpoint's condition is evaluated, either @samp{host} or
25469 If this is a thread-specific breakpoint, then this identifies the
25470 thread in which the breakpoint can trigger.
25473 If this breakpoint is restricted to a particular Ada task, then this
25474 field will hold the task identifier.
25477 If the breakpoint is conditional, this is the condition expression.
25480 The ignore count of the breakpoint.
25483 The enable count of the breakpoint.
25485 @item traceframe-usage
25488 @item static-tracepoint-marker-string-id
25489 For a static tracepoint, the name of the static tracepoint marker.
25492 For a masked watchpoint, this is the mask.
25495 A tracepoint's pass count.
25497 @item original-location
25498 The location of the breakpoint as originally specified by the user.
25499 This field is optional.
25502 The number of times the breakpoint has been hit.
25505 This field is only given for tracepoints. This is either @samp{y},
25506 meaning that the tracepoint is installed, or @samp{n}, meaning that it
25510 Some extra data, the exact contents of which are type-dependent.
25514 For example, here is what the output of @code{-break-insert}
25515 (@pxref{GDB/MI Breakpoint Commands}) might be:
25518 -> -break-insert main
25519 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25520 enabled="y",addr="0x08048564",func="main",file="myprog.c",
25521 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
25526 @node GDB/MI Frame Information
25527 @subsection @sc{gdb/mi} Frame Information
25529 Response from many MI commands includes an information about stack
25530 frame. This information is a tuple that may have the following
25535 The level of the stack frame. The innermost frame has the level of
25536 zero. This field is always present.
25539 The name of the function corresponding to the frame. This field may
25540 be absent if @value{GDBN} is unable to determine the function name.
25543 The code address for the frame. This field is always present.
25546 The name of the source files that correspond to the frame's code
25547 address. This field may be absent.
25550 The source line corresponding to the frames' code address. This field
25554 The name of the binary file (either executable or shared library) the
25555 corresponds to the frame's code address. This field may be absent.
25559 @node GDB/MI Thread Information
25560 @subsection @sc{gdb/mi} Thread Information
25562 Whenever @value{GDBN} has to report an information about a thread, it
25563 uses a tuple with the following fields:
25567 The numeric id assigned to the thread by @value{GDBN}. This field is
25571 Target-specific string identifying the thread. This field is always present.
25574 Additional information about the thread provided by the target.
25575 It is supposed to be human-readable and not interpreted by the
25576 frontend. This field is optional.
25579 Either @samp{stopped} or @samp{running}, depending on whether the
25580 thread is presently running. This field is always present.
25583 The value of this field is an integer number of the processor core the
25584 thread was last seen on. This field is optional.
25587 @node GDB/MI Ada Exception Information
25588 @subsection @sc{gdb/mi} Ada Exception Information
25590 Whenever a @code{*stopped} record is emitted because the program
25591 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
25592 @value{GDBN} provides the name of the exception that was raised via
25593 the @code{exception-name} field.
25595 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25596 @node GDB/MI Simple Examples
25597 @section Simple Examples of @sc{gdb/mi} Interaction
25598 @cindex @sc{gdb/mi}, simple examples
25600 This subsection presents several simple examples of interaction using
25601 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
25602 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
25603 the output received from @sc{gdb/mi}.
25605 Note the line breaks shown in the examples are here only for
25606 readability, they don't appear in the real output.
25608 @subheading Setting a Breakpoint
25610 Setting a breakpoint generates synchronous output which contains detailed
25611 information of the breakpoint.
25614 -> -break-insert main
25615 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25616 enabled="y",addr="0x08048564",func="main",file="myprog.c",
25617 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
25622 @subheading Program Execution
25624 Program execution generates asynchronous records and MI gives the
25625 reason that execution stopped.
25631 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
25632 frame=@{addr="0x08048564",func="main",
25633 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
25634 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
25639 <- *stopped,reason="exited-normally"
25643 @subheading Quitting @value{GDBN}
25645 Quitting @value{GDBN} just prints the result class @samp{^exit}.
25653 Please note that @samp{^exit} is printed immediately, but it might
25654 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
25655 performs necessary cleanups, including killing programs being debugged
25656 or disconnecting from debug hardware, so the frontend should wait till
25657 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
25658 fails to exit in reasonable time.
25660 @subheading A Bad Command
25662 Here's what happens if you pass a non-existent command:
25666 <- ^error,msg="Undefined MI command: rubbish"
25671 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25672 @node GDB/MI Command Description Format
25673 @section @sc{gdb/mi} Command Description Format
25675 The remaining sections describe blocks of commands. Each block of
25676 commands is laid out in a fashion similar to this section.
25678 @subheading Motivation
25680 The motivation for this collection of commands.
25682 @subheading Introduction
25684 A brief introduction to this collection of commands as a whole.
25686 @subheading Commands
25688 For each command in the block, the following is described:
25690 @subsubheading Synopsis
25693 -command @var{args}@dots{}
25696 @subsubheading Result
25698 @subsubheading @value{GDBN} Command
25700 The corresponding @value{GDBN} CLI command(s), if any.
25702 @subsubheading Example
25704 Example(s) formatted for readability. Some of the described commands have
25705 not been implemented yet and these are labeled N.A.@: (not available).
25708 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25709 @node GDB/MI Breakpoint Commands
25710 @section @sc{gdb/mi} Breakpoint Commands
25712 @cindex breakpoint commands for @sc{gdb/mi}
25713 @cindex @sc{gdb/mi}, breakpoint commands
25714 This section documents @sc{gdb/mi} commands for manipulating
25717 @subheading The @code{-break-after} Command
25718 @findex -break-after
25720 @subsubheading Synopsis
25723 -break-after @var{number} @var{count}
25726 The breakpoint number @var{number} is not in effect until it has been
25727 hit @var{count} times. To see how this is reflected in the output of
25728 the @samp{-break-list} command, see the description of the
25729 @samp{-break-list} command below.
25731 @subsubheading @value{GDBN} Command
25733 The corresponding @value{GDBN} command is @samp{ignore}.
25735 @subsubheading Example
25740 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25741 enabled="y",addr="0x000100d0",func="main",file="hello.c",
25742 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
25750 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25751 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25752 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25753 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25754 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25755 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25756 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25757 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25758 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25759 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
25764 @subheading The @code{-break-catch} Command
25765 @findex -break-catch
25768 @subheading The @code{-break-commands} Command
25769 @findex -break-commands
25771 @subsubheading Synopsis
25774 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
25777 Specifies the CLI commands that should be executed when breakpoint
25778 @var{number} is hit. The parameters @var{command1} to @var{commandN}
25779 are the commands. If no command is specified, any previously-set
25780 commands are cleared. @xref{Break Commands}. Typical use of this
25781 functionality is tracing a program, that is, printing of values of
25782 some variables whenever breakpoint is hit and then continuing.
25784 @subsubheading @value{GDBN} Command
25786 The corresponding @value{GDBN} command is @samp{commands}.
25788 @subsubheading Example
25793 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25794 enabled="y",addr="0x000100d0",func="main",file="hello.c",
25795 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
25798 -break-commands 1 "print v" "continue"
25803 @subheading The @code{-break-condition} Command
25804 @findex -break-condition
25806 @subsubheading Synopsis
25809 -break-condition @var{number} @var{expr}
25812 Breakpoint @var{number} will stop the program only if the condition in
25813 @var{expr} is true. The condition becomes part of the
25814 @samp{-break-list} output (see the description of the @samp{-break-list}
25817 @subsubheading @value{GDBN} Command
25819 The corresponding @value{GDBN} command is @samp{condition}.
25821 @subsubheading Example
25825 -break-condition 1 1
25829 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25830 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25831 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25832 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25833 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25834 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25835 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25836 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25837 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25838 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
25842 @subheading The @code{-break-delete} Command
25843 @findex -break-delete
25845 @subsubheading Synopsis
25848 -break-delete ( @var{breakpoint} )+
25851 Delete the breakpoint(s) whose number(s) are specified in the argument
25852 list. This is obviously reflected in the breakpoint list.
25854 @subsubheading @value{GDBN} Command
25856 The corresponding @value{GDBN} command is @samp{delete}.
25858 @subsubheading Example
25866 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
25867 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25868 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25869 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25870 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25871 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25872 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25877 @subheading The @code{-break-disable} Command
25878 @findex -break-disable
25880 @subsubheading Synopsis
25883 -break-disable ( @var{breakpoint} )+
25886 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
25887 break list is now set to @samp{n} for the named @var{breakpoint}(s).
25889 @subsubheading @value{GDBN} Command
25891 The corresponding @value{GDBN} command is @samp{disable}.
25893 @subsubheading Example
25901 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25902 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25903 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25904 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25905 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25906 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25907 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25908 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
25909 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25910 line="5",thread-groups=["i1"],times="0"@}]@}
25914 @subheading The @code{-break-enable} Command
25915 @findex -break-enable
25917 @subsubheading Synopsis
25920 -break-enable ( @var{breakpoint} )+
25923 Enable (previously disabled) @var{breakpoint}(s).
25925 @subsubheading @value{GDBN} Command
25927 The corresponding @value{GDBN} command is @samp{enable}.
25929 @subsubheading Example
25937 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25938 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25939 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25940 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25941 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25942 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25943 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25944 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
25945 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25946 line="5",thread-groups=["i1"],times="0"@}]@}
25950 @subheading The @code{-break-info} Command
25951 @findex -break-info
25953 @subsubheading Synopsis
25956 -break-info @var{breakpoint}
25960 Get information about a single breakpoint.
25962 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
25963 Information}, for details on the format of each breakpoint in the
25966 @subsubheading @value{GDBN} Command
25968 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
25970 @subsubheading Example
25973 @subheading The @code{-break-insert} Command
25974 @findex -break-insert
25976 @subsubheading Synopsis
25979 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
25980 [ -c @var{condition} ] [ -i @var{ignore-count} ]
25981 [ -p @var{thread-id} ] [ @var{location} ]
25985 If specified, @var{location}, can be one of:
25992 @item filename:linenum
25993 @item filename:function
25997 The possible optional parameters of this command are:
26001 Insert a temporary breakpoint.
26003 Insert a hardware breakpoint.
26005 If @var{location} cannot be parsed (for example if it
26006 refers to unknown files or functions), create a pending
26007 breakpoint. Without this flag, @value{GDBN} will report
26008 an error, and won't create a breakpoint, if @var{location}
26011 Create a disabled breakpoint.
26013 Create a tracepoint. @xref{Tracepoints}. When this parameter
26014 is used together with @samp{-h}, a fast tracepoint is created.
26015 @item -c @var{condition}
26016 Make the breakpoint conditional on @var{condition}.
26017 @item -i @var{ignore-count}
26018 Initialize the @var{ignore-count}.
26019 @item -p @var{thread-id}
26020 Restrict the breakpoint to the specified @var{thread-id}.
26023 @subsubheading Result
26025 @xref{GDB/MI Breakpoint Information}, for details on the format of the
26026 resulting breakpoint.
26028 Note: this format is open to change.
26029 @c An out-of-band breakpoint instead of part of the result?
26031 @subsubheading @value{GDBN} Command
26033 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
26034 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
26036 @subsubheading Example
26041 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
26042 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
26045 -break-insert -t foo
26046 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
26047 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
26051 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26052 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26053 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26054 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26055 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26056 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26057 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26058 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26059 addr="0x0001072c", func="main",file="recursive2.c",
26060 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
26062 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
26063 addr="0x00010774",func="foo",file="recursive2.c",
26064 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
26067 @c -break-insert -r foo.*
26068 @c ~int foo(int, int);
26069 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
26070 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
26075 @subheading The @code{-dprintf-insert} Command
26076 @findex -dprintf-insert
26078 @subsubheading Synopsis
26081 -dprintf-insert [ -t ] [ -f ] [ -d ]
26082 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26083 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
26088 If specified, @var{location}, can be one of:
26091 @item @var{function}
26094 @c @item @var{linenum}
26095 @item @var{filename}:@var{linenum}
26096 @item @var{filename}:function
26097 @item *@var{address}
26100 The possible optional parameters of this command are:
26104 Insert a temporary breakpoint.
26106 If @var{location} cannot be parsed (for example, if it
26107 refers to unknown files or functions), create a pending
26108 breakpoint. Without this flag, @value{GDBN} will report
26109 an error, and won't create a breakpoint, if @var{location}
26112 Create a disabled breakpoint.
26113 @item -c @var{condition}
26114 Make the breakpoint conditional on @var{condition}.
26115 @item -i @var{ignore-count}
26116 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
26117 to @var{ignore-count}.
26118 @item -p @var{thread-id}
26119 Restrict the breakpoint to the specified @var{thread-id}.
26122 @subsubheading Result
26124 @xref{GDB/MI Breakpoint Information}, for details on the format of the
26125 resulting breakpoint.
26127 @c An out-of-band breakpoint instead of part of the result?
26129 @subsubheading @value{GDBN} Command
26131 The corresponding @value{GDBN} command is @samp{dprintf}.
26133 @subsubheading Example
26137 4-dprintf-insert foo "At foo entry\n"
26138 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
26139 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
26140 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
26141 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
26142 original-location="foo"@}
26144 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
26145 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
26146 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
26147 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
26148 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
26149 original-location="mi-dprintf.c:26"@}
26153 @subheading The @code{-break-list} Command
26154 @findex -break-list
26156 @subsubheading Synopsis
26162 Displays the list of inserted breakpoints, showing the following fields:
26166 number of the breakpoint
26168 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
26170 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
26173 is the breakpoint enabled or no: @samp{y} or @samp{n}
26175 memory location at which the breakpoint is set
26177 logical location of the breakpoint, expressed by function name, file
26179 @item Thread-groups
26180 list of thread groups to which this breakpoint applies
26182 number of times the breakpoint has been hit
26185 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
26186 @code{body} field is an empty list.
26188 @subsubheading @value{GDBN} Command
26190 The corresponding @value{GDBN} command is @samp{info break}.
26192 @subsubheading Example
26197 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26198 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26199 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26200 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26201 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26202 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26203 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26204 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26205 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
26207 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26208 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
26209 line="13",thread-groups=["i1"],times="0"@}]@}
26213 Here's an example of the result when there are no breakpoints:
26218 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26219 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26220 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26221 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26222 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26223 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26224 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26229 @subheading The @code{-break-passcount} Command
26230 @findex -break-passcount
26232 @subsubheading Synopsis
26235 -break-passcount @var{tracepoint-number} @var{passcount}
26238 Set the passcount for tracepoint @var{tracepoint-number} to
26239 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
26240 is not a tracepoint, error is emitted. This corresponds to CLI
26241 command @samp{passcount}.
26243 @subheading The @code{-break-watch} Command
26244 @findex -break-watch
26246 @subsubheading Synopsis
26249 -break-watch [ -a | -r ]
26252 Create a watchpoint. With the @samp{-a} option it will create an
26253 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
26254 read from or on a write to the memory location. With the @samp{-r}
26255 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
26256 trigger only when the memory location is accessed for reading. Without
26257 either of the options, the watchpoint created is a regular watchpoint,
26258 i.e., it will trigger when the memory location is accessed for writing.
26259 @xref{Set Watchpoints, , Setting Watchpoints}.
26261 Note that @samp{-break-list} will report a single list of watchpoints and
26262 breakpoints inserted.
26264 @subsubheading @value{GDBN} Command
26266 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
26269 @subsubheading Example
26271 Setting a watchpoint on a variable in the @code{main} function:
26276 ^done,wpt=@{number="2",exp="x"@}
26281 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
26282 value=@{old="-268439212",new="55"@},
26283 frame=@{func="main",args=[],file="recursive2.c",
26284 fullname="/home/foo/bar/recursive2.c",line="5"@}
26288 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
26289 the program execution twice: first for the variable changing value, then
26290 for the watchpoint going out of scope.
26295 ^done,wpt=@{number="5",exp="C"@}
26300 *stopped,reason="watchpoint-trigger",
26301 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
26302 frame=@{func="callee4",args=[],
26303 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26304 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
26309 *stopped,reason="watchpoint-scope",wpnum="5",
26310 frame=@{func="callee3",args=[@{name="strarg",
26311 value="0x11940 \"A string argument.\""@}],
26312 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26313 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26317 Listing breakpoints and watchpoints, at different points in the program
26318 execution. Note that once the watchpoint goes out of scope, it is
26324 ^done,wpt=@{number="2",exp="C"@}
26327 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26328 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26329 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26330 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26331 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26332 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26333 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26334 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26335 addr="0x00010734",func="callee4",
26336 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26337 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
26339 bkpt=@{number="2",type="watchpoint",disp="keep",
26340 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
26345 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
26346 value=@{old="-276895068",new="3"@},
26347 frame=@{func="callee4",args=[],
26348 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26349 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
26352 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26353 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26354 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26355 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26356 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26357 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26358 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26359 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26360 addr="0x00010734",func="callee4",
26361 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26362 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
26364 bkpt=@{number="2",type="watchpoint",disp="keep",
26365 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
26369 ^done,reason="watchpoint-scope",wpnum="2",
26370 frame=@{func="callee3",args=[@{name="strarg",
26371 value="0x11940 \"A string argument.\""@}],
26372 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26373 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26376 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26377 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26378 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26379 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26380 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26381 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26382 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26383 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26384 addr="0x00010734",func="callee4",
26385 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26386 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
26387 thread-groups=["i1"],times="1"@}]@}
26392 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26393 @node GDB/MI Catchpoint Commands
26394 @section @sc{gdb/mi} Catchpoint Commands
26396 This section documents @sc{gdb/mi} commands for manipulating
26400 * Shared Library GDB/MI Catchpoint Commands::
26401 * Ada Exception GDB/MI Catchpoint Commands::
26404 @node Shared Library GDB/MI Catchpoint Commands
26405 @subsection Shared Library @sc{gdb/mi} Catchpoints
26407 @subheading The @code{-catch-load} Command
26408 @findex -catch-load
26410 @subsubheading Synopsis
26413 -catch-load [ -t ] [ -d ] @var{regexp}
26416 Add a catchpoint for library load events. If the @samp{-t} option is used,
26417 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
26418 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
26419 in a disabled state. The @samp{regexp} argument is a regular
26420 expression used to match the name of the loaded library.
26423 @subsubheading @value{GDBN} Command
26425 The corresponding @value{GDBN} command is @samp{catch load}.
26427 @subsubheading Example
26430 -catch-load -t foo.so
26431 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
26432 what="load of library matching foo.so",catch-type="load",times="0"@}
26437 @subheading The @code{-catch-unload} Command
26438 @findex -catch-unload
26440 @subsubheading Synopsis
26443 -catch-unload [ -t ] [ -d ] @var{regexp}
26446 Add a catchpoint for library unload events. If the @samp{-t} option is
26447 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
26448 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
26449 created in a disabled state. The @samp{regexp} argument is a regular
26450 expression used to match the name of the unloaded library.
26452 @subsubheading @value{GDBN} Command
26454 The corresponding @value{GDBN} command is @samp{catch unload}.
26456 @subsubheading Example
26459 -catch-unload -d bar.so
26460 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
26461 what="load of library matching bar.so",catch-type="unload",times="0"@}
26465 @node Ada Exception GDB/MI Catchpoint Commands
26466 @subsection Ada Exception @sc{gdb/mi} Catchpoints
26468 The following @sc{gdb/mi} commands can be used to create catchpoints
26469 that stop the execution when Ada exceptions are being raised.
26471 @subheading The @code{-catch-assert} Command
26472 @findex -catch-assert
26474 @subsubheading Synopsis
26477 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
26480 Add a catchpoint for failed Ada assertions.
26482 The possible optional parameters for this command are:
26485 @item -c @var{condition}
26486 Make the catchpoint conditional on @var{condition}.
26488 Create a disabled catchpoint.
26490 Create a temporary catchpoint.
26493 @subsubheading @value{GDBN} Command
26495 The corresponding @value{GDBN} command is @samp{catch assert}.
26497 @subsubheading Example
26501 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
26502 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
26503 thread-groups=["i1"],times="0",
26504 original-location="__gnat_debug_raise_assert_failure"@}
26508 @subheading The @code{-catch-exception} Command
26509 @findex -catch-exception
26511 @subsubheading Synopsis
26514 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
26518 Add a catchpoint stopping when Ada exceptions are raised.
26519 By default, the command stops the program when any Ada exception
26520 gets raised. But it is also possible, by using some of the
26521 optional parameters described below, to create more selective
26524 The possible optional parameters for this command are:
26527 @item -c @var{condition}
26528 Make the catchpoint conditional on @var{condition}.
26530 Create a disabled catchpoint.
26531 @item -e @var{exception-name}
26532 Only stop when @var{exception-name} is raised. This option cannot
26533 be used combined with @samp{-u}.
26535 Create a temporary catchpoint.
26537 Stop only when an unhandled exception gets raised. This option
26538 cannot be used combined with @samp{-e}.
26541 @subsubheading @value{GDBN} Command
26543 The corresponding @value{GDBN} commands are @samp{catch exception}
26544 and @samp{catch exception unhandled}.
26546 @subsubheading Example
26549 -catch-exception -e Program_Error
26550 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
26551 enabled="y",addr="0x0000000000404874",
26552 what="`Program_Error' Ada exception", thread-groups=["i1"],
26553 times="0",original-location="__gnat_debug_raise_exception"@}
26557 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26558 @node GDB/MI Program Context
26559 @section @sc{gdb/mi} Program Context
26561 @subheading The @code{-exec-arguments} Command
26562 @findex -exec-arguments
26565 @subsubheading Synopsis
26568 -exec-arguments @var{args}
26571 Set the inferior program arguments, to be used in the next
26574 @subsubheading @value{GDBN} Command
26576 The corresponding @value{GDBN} command is @samp{set args}.
26578 @subsubheading Example
26582 -exec-arguments -v word
26589 @subheading The @code{-exec-show-arguments} Command
26590 @findex -exec-show-arguments
26592 @subsubheading Synopsis
26595 -exec-show-arguments
26598 Print the arguments of the program.
26600 @subsubheading @value{GDBN} Command
26602 The corresponding @value{GDBN} command is @samp{show args}.
26604 @subsubheading Example
26609 @subheading The @code{-environment-cd} Command
26610 @findex -environment-cd
26612 @subsubheading Synopsis
26615 -environment-cd @var{pathdir}
26618 Set @value{GDBN}'s working directory.
26620 @subsubheading @value{GDBN} Command
26622 The corresponding @value{GDBN} command is @samp{cd}.
26624 @subsubheading Example
26628 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
26634 @subheading The @code{-environment-directory} Command
26635 @findex -environment-directory
26637 @subsubheading Synopsis
26640 -environment-directory [ -r ] [ @var{pathdir} ]+
26643 Add directories @var{pathdir} to beginning of search path for source files.
26644 If the @samp{-r} option is used, the search path is reset to the default
26645 search path. If directories @var{pathdir} are supplied in addition to the
26646 @samp{-r} option, the search path is first reset and then addition
26648 Multiple directories may be specified, separated by blanks. Specifying
26649 multiple directories in a single command
26650 results in the directories added to the beginning of the
26651 search path in the same order they were presented in the command.
26652 If blanks are needed as
26653 part of a directory name, double-quotes should be used around
26654 the name. In the command output, the path will show up separated
26655 by the system directory-separator character. The directory-separator
26656 character must not be used
26657 in any directory name.
26658 If no directories are specified, the current search path is displayed.
26660 @subsubheading @value{GDBN} Command
26662 The corresponding @value{GDBN} command is @samp{dir}.
26664 @subsubheading Example
26668 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
26669 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
26671 -environment-directory ""
26672 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
26674 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
26675 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
26677 -environment-directory -r
26678 ^done,source-path="$cdir:$cwd"
26683 @subheading The @code{-environment-path} Command
26684 @findex -environment-path
26686 @subsubheading Synopsis
26689 -environment-path [ -r ] [ @var{pathdir} ]+
26692 Add directories @var{pathdir} to beginning of search path for object files.
26693 If the @samp{-r} option is used, the search path is reset to the original
26694 search path that existed at gdb start-up. If directories @var{pathdir} are
26695 supplied in addition to the
26696 @samp{-r} option, the search path is first reset and then addition
26698 Multiple directories may be specified, separated by blanks. Specifying
26699 multiple directories in a single command
26700 results in the directories added to the beginning of the
26701 search path in the same order they were presented in the command.
26702 If blanks are needed as
26703 part of a directory name, double-quotes should be used around
26704 the name. In the command output, the path will show up separated
26705 by the system directory-separator character. The directory-separator
26706 character must not be used
26707 in any directory name.
26708 If no directories are specified, the current path is displayed.
26711 @subsubheading @value{GDBN} Command
26713 The corresponding @value{GDBN} command is @samp{path}.
26715 @subsubheading Example
26720 ^done,path="/usr/bin"
26722 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
26723 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
26725 -environment-path -r /usr/local/bin
26726 ^done,path="/usr/local/bin:/usr/bin"
26731 @subheading The @code{-environment-pwd} Command
26732 @findex -environment-pwd
26734 @subsubheading Synopsis
26740 Show the current working directory.
26742 @subsubheading @value{GDBN} Command
26744 The corresponding @value{GDBN} command is @samp{pwd}.
26746 @subsubheading Example
26751 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
26755 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26756 @node GDB/MI Thread Commands
26757 @section @sc{gdb/mi} Thread Commands
26760 @subheading The @code{-thread-info} Command
26761 @findex -thread-info
26763 @subsubheading Synopsis
26766 -thread-info [ @var{thread-id} ]
26769 Reports information about either a specific thread, if
26770 the @var{thread-id} parameter is present, or about all
26771 threads. When printing information about all threads,
26772 also reports the current thread.
26774 @subsubheading @value{GDBN} Command
26776 The @samp{info thread} command prints the same information
26779 @subsubheading Result
26781 The result is a list of threads. The following attributes are
26782 defined for a given thread:
26786 This field exists only for the current thread. It has the value @samp{*}.
26789 The identifier that @value{GDBN} uses to refer to the thread.
26792 The identifier that the target uses to refer to the thread.
26795 Extra information about the thread, in a target-specific format. This
26799 The name of the thread. If the user specified a name using the
26800 @code{thread name} command, then this name is given. Otherwise, if
26801 @value{GDBN} can extract the thread name from the target, then that
26802 name is given. If @value{GDBN} cannot find the thread name, then this
26806 The stack frame currently executing in the thread.
26809 The thread's state. The @samp{state} field may have the following
26814 The thread is stopped. Frame information is available for stopped
26818 The thread is running. There's no frame information for running
26824 If @value{GDBN} can find the CPU core on which this thread is running,
26825 then this field is the core identifier. This field is optional.
26829 @subsubheading Example
26834 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
26835 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
26836 args=[]@},state="running"@},
26837 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
26838 frame=@{level="0",addr="0x0804891f",func="foo",
26839 args=[@{name="i",value="10"@}],
26840 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
26841 state="running"@}],
26842 current-thread-id="1"
26846 @subheading The @code{-thread-list-ids} Command
26847 @findex -thread-list-ids
26849 @subsubheading Synopsis
26855 Produces a list of the currently known @value{GDBN} thread ids. At the
26856 end of the list it also prints the total number of such threads.
26858 This command is retained for historical reasons, the
26859 @code{-thread-info} command should be used instead.
26861 @subsubheading @value{GDBN} Command
26863 Part of @samp{info threads} supplies the same information.
26865 @subsubheading Example
26870 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
26871 current-thread-id="1",number-of-threads="3"
26876 @subheading The @code{-thread-select} Command
26877 @findex -thread-select
26879 @subsubheading Synopsis
26882 -thread-select @var{threadnum}
26885 Make @var{threadnum} the current thread. It prints the number of the new
26886 current thread, and the topmost frame for that thread.
26888 This command is deprecated in favor of explicitly using the
26889 @samp{--thread} option to each command.
26891 @subsubheading @value{GDBN} Command
26893 The corresponding @value{GDBN} command is @samp{thread}.
26895 @subsubheading Example
26902 *stopped,reason="end-stepping-range",thread-id="2",line="187",
26903 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
26907 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
26908 number-of-threads="3"
26911 ^done,new-thread-id="3",
26912 frame=@{level="0",func="vprintf",
26913 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
26914 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
26918 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26919 @node GDB/MI Ada Tasking Commands
26920 @section @sc{gdb/mi} Ada Tasking Commands
26922 @subheading The @code{-ada-task-info} Command
26923 @findex -ada-task-info
26925 @subsubheading Synopsis
26928 -ada-task-info [ @var{task-id} ]
26931 Reports information about either a specific Ada task, if the
26932 @var{task-id} parameter is present, or about all Ada tasks.
26934 @subsubheading @value{GDBN} Command
26936 The @samp{info tasks} command prints the same information
26937 about all Ada tasks (@pxref{Ada Tasks}).
26939 @subsubheading Result
26941 The result is a table of Ada tasks. The following columns are
26942 defined for each Ada task:
26946 This field exists only for the current thread. It has the value @samp{*}.
26949 The identifier that @value{GDBN} uses to refer to the Ada task.
26952 The identifier that the target uses to refer to the Ada task.
26955 The identifier of the thread corresponding to the Ada task.
26957 This field should always exist, as Ada tasks are always implemented
26958 on top of a thread. But if @value{GDBN} cannot find this corresponding
26959 thread for any reason, the field is omitted.
26962 This field exists only when the task was created by another task.
26963 In this case, it provides the ID of the parent task.
26966 The base priority of the task.
26969 The current state of the task. For a detailed description of the
26970 possible states, see @ref{Ada Tasks}.
26973 The name of the task.
26977 @subsubheading Example
26981 ^done,tasks=@{nr_rows="3",nr_cols="8",
26982 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
26983 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
26984 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
26985 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
26986 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
26987 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
26988 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
26989 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
26990 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
26991 state="Child Termination Wait",name="main_task"@}]@}
26995 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26996 @node GDB/MI Program Execution
26997 @section @sc{gdb/mi} Program Execution
26999 These are the asynchronous commands which generate the out-of-band
27000 record @samp{*stopped}. Currently @value{GDBN} only really executes
27001 asynchronously with remote targets and this interaction is mimicked in
27004 @subheading The @code{-exec-continue} Command
27005 @findex -exec-continue
27007 @subsubheading Synopsis
27010 -exec-continue [--reverse] [--all|--thread-group N]
27013 Resumes the execution of the inferior program, which will continue
27014 to execute until it reaches a debugger stop event. If the
27015 @samp{--reverse} option is specified, execution resumes in reverse until
27016 it reaches a stop event. Stop events may include
27019 breakpoints or watchpoints
27021 signals or exceptions
27023 the end of the process (or its beginning under @samp{--reverse})
27025 the end or beginning of a replay log if one is being used.
27027 In all-stop mode (@pxref{All-Stop
27028 Mode}), may resume only one thread, or all threads, depending on the
27029 value of the @samp{scheduler-locking} variable. If @samp{--all} is
27030 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
27031 ignored in all-stop mode. If the @samp{--thread-group} options is
27032 specified, then all threads in that thread group are resumed.
27034 @subsubheading @value{GDBN} Command
27036 The corresponding @value{GDBN} corresponding is @samp{continue}.
27038 @subsubheading Example
27045 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
27046 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
27052 @subheading The @code{-exec-finish} Command
27053 @findex -exec-finish
27055 @subsubheading Synopsis
27058 -exec-finish [--reverse]
27061 Resumes the execution of the inferior program until the current
27062 function is exited. Displays the results returned by the function.
27063 If the @samp{--reverse} option is specified, resumes the reverse
27064 execution of the inferior program until the point where current
27065 function was called.
27067 @subsubheading @value{GDBN} Command
27069 The corresponding @value{GDBN} command is @samp{finish}.
27071 @subsubheading Example
27073 Function returning @code{void}.
27080 *stopped,reason="function-finished",frame=@{func="main",args=[],
27081 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
27085 Function returning other than @code{void}. The name of the internal
27086 @value{GDBN} variable storing the result is printed, together with the
27093 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
27094 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
27095 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27096 gdb-result-var="$1",return-value="0"
27101 @subheading The @code{-exec-interrupt} Command
27102 @findex -exec-interrupt
27104 @subsubheading Synopsis
27107 -exec-interrupt [--all|--thread-group N]
27110 Interrupts the background execution of the target. Note how the token
27111 associated with the stop message is the one for the execution command
27112 that has been interrupted. The token for the interrupt itself only
27113 appears in the @samp{^done} output. If the user is trying to
27114 interrupt a non-running program, an error message will be printed.
27116 Note that when asynchronous execution is enabled, this command is
27117 asynchronous just like other execution commands. That is, first the
27118 @samp{^done} response will be printed, and the target stop will be
27119 reported after that using the @samp{*stopped} notification.
27121 In non-stop mode, only the context thread is interrupted by default.
27122 All threads (in all inferiors) will be interrupted if the
27123 @samp{--all} option is specified. If the @samp{--thread-group}
27124 option is specified, all threads in that group will be interrupted.
27126 @subsubheading @value{GDBN} Command
27128 The corresponding @value{GDBN} command is @samp{interrupt}.
27130 @subsubheading Example
27141 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
27142 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
27143 fullname="/home/foo/bar/try.c",line="13"@}
27148 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
27152 @subheading The @code{-exec-jump} Command
27155 @subsubheading Synopsis
27158 -exec-jump @var{location}
27161 Resumes execution of the inferior program at the location specified by
27162 parameter. @xref{Specify Location}, for a description of the
27163 different forms of @var{location}.
27165 @subsubheading @value{GDBN} Command
27167 The corresponding @value{GDBN} command is @samp{jump}.
27169 @subsubheading Example
27172 -exec-jump foo.c:10
27173 *running,thread-id="all"
27178 @subheading The @code{-exec-next} Command
27181 @subsubheading Synopsis
27184 -exec-next [--reverse]
27187 Resumes execution of the inferior program, stopping when the beginning
27188 of the next source line is reached.
27190 If the @samp{--reverse} option is specified, resumes reverse execution
27191 of the inferior program, stopping at the beginning of the previous
27192 source line. If you issue this command on the first line of a
27193 function, it will take you back to the caller of that function, to the
27194 source line where the function was called.
27197 @subsubheading @value{GDBN} Command
27199 The corresponding @value{GDBN} command is @samp{next}.
27201 @subsubheading Example
27207 *stopped,reason="end-stepping-range",line="8",file="hello.c"
27212 @subheading The @code{-exec-next-instruction} Command
27213 @findex -exec-next-instruction
27215 @subsubheading Synopsis
27218 -exec-next-instruction [--reverse]
27221 Executes one machine instruction. If the instruction is a function
27222 call, continues until the function returns. If the program stops at an
27223 instruction in the middle of a source line, the address will be
27226 If the @samp{--reverse} option is specified, resumes reverse execution
27227 of the inferior program, stopping at the previous instruction. If the
27228 previously executed instruction was a return from another function,
27229 it will continue to execute in reverse until the call to that function
27230 (from the current stack frame) is reached.
27232 @subsubheading @value{GDBN} Command
27234 The corresponding @value{GDBN} command is @samp{nexti}.
27236 @subsubheading Example
27240 -exec-next-instruction
27244 *stopped,reason="end-stepping-range",
27245 addr="0x000100d4",line="5",file="hello.c"
27250 @subheading The @code{-exec-return} Command
27251 @findex -exec-return
27253 @subsubheading Synopsis
27259 Makes current function return immediately. Doesn't execute the inferior.
27260 Displays the new current frame.
27262 @subsubheading @value{GDBN} Command
27264 The corresponding @value{GDBN} command is @samp{return}.
27266 @subsubheading Example
27270 200-break-insert callee4
27271 200^done,bkpt=@{number="1",addr="0x00010734",
27272 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27277 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27278 frame=@{func="callee4",args=[],
27279 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27280 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27286 111^done,frame=@{level="0",func="callee3",
27287 args=[@{name="strarg",
27288 value="0x11940 \"A string argument.\""@}],
27289 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27290 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27295 @subheading The @code{-exec-run} Command
27298 @subsubheading Synopsis
27301 -exec-run [ --all | --thread-group N ] [ --start ]
27304 Starts execution of the inferior from the beginning. The inferior
27305 executes until either a breakpoint is encountered or the program
27306 exits. In the latter case the output will include an exit code, if
27307 the program has exited exceptionally.
27309 When neither the @samp{--all} nor the @samp{--thread-group} option
27310 is specified, the current inferior is started. If the
27311 @samp{--thread-group} option is specified, it should refer to a thread
27312 group of type @samp{process}, and that thread group will be started.
27313 If the @samp{--all} option is specified, then all inferiors will be started.
27315 Using the @samp{--start} option instructs the debugger to stop
27316 the execution at the start of the inferior's main subprogram,
27317 following the same behavior as the @code{start} command
27318 (@pxref{Starting}).
27320 @subsubheading @value{GDBN} Command
27322 The corresponding @value{GDBN} command is @samp{run}.
27324 @subsubheading Examples
27329 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
27334 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27335 frame=@{func="main",args=[],file="recursive2.c",
27336 fullname="/home/foo/bar/recursive2.c",line="4"@}
27341 Program exited normally:
27349 *stopped,reason="exited-normally"
27354 Program exited exceptionally:
27362 *stopped,reason="exited",exit-code="01"
27366 Another way the program can terminate is if it receives a signal such as
27367 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
27371 *stopped,reason="exited-signalled",signal-name="SIGINT",
27372 signal-meaning="Interrupt"
27376 @c @subheading -exec-signal
27379 @subheading The @code{-exec-step} Command
27382 @subsubheading Synopsis
27385 -exec-step [--reverse]
27388 Resumes execution of the inferior program, stopping when the beginning
27389 of the next source line is reached, if the next source line is not a
27390 function call. If it is, stop at the first instruction of the called
27391 function. If the @samp{--reverse} option is specified, resumes reverse
27392 execution of the inferior program, stopping at the beginning of the
27393 previously executed source line.
27395 @subsubheading @value{GDBN} Command
27397 The corresponding @value{GDBN} command is @samp{step}.
27399 @subsubheading Example
27401 Stepping into a function:
27407 *stopped,reason="end-stepping-range",
27408 frame=@{func="foo",args=[@{name="a",value="10"@},
27409 @{name="b",value="0"@}],file="recursive2.c",
27410 fullname="/home/foo/bar/recursive2.c",line="11"@}
27420 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
27425 @subheading The @code{-exec-step-instruction} Command
27426 @findex -exec-step-instruction
27428 @subsubheading Synopsis
27431 -exec-step-instruction [--reverse]
27434 Resumes the inferior which executes one machine instruction. If the
27435 @samp{--reverse} option is specified, resumes reverse execution of the
27436 inferior program, stopping at the previously executed instruction.
27437 The output, once @value{GDBN} has stopped, will vary depending on
27438 whether we have stopped in the middle of a source line or not. In the
27439 former case, the address at which the program stopped will be printed
27442 @subsubheading @value{GDBN} Command
27444 The corresponding @value{GDBN} command is @samp{stepi}.
27446 @subsubheading Example
27450 -exec-step-instruction
27454 *stopped,reason="end-stepping-range",
27455 frame=@{func="foo",args=[],file="try.c",
27456 fullname="/home/foo/bar/try.c",line="10"@}
27458 -exec-step-instruction
27462 *stopped,reason="end-stepping-range",
27463 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
27464 fullname="/home/foo/bar/try.c",line="10"@}
27469 @subheading The @code{-exec-until} Command
27470 @findex -exec-until
27472 @subsubheading Synopsis
27475 -exec-until [ @var{location} ]
27478 Executes the inferior until the @var{location} specified in the
27479 argument is reached. If there is no argument, the inferior executes
27480 until a source line greater than the current one is reached. The
27481 reason for stopping in this case will be @samp{location-reached}.
27483 @subsubheading @value{GDBN} Command
27485 The corresponding @value{GDBN} command is @samp{until}.
27487 @subsubheading Example
27491 -exec-until recursive2.c:6
27495 *stopped,reason="location-reached",frame=@{func="main",args=[],
27496 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
27501 @subheading -file-clear
27502 Is this going away????
27505 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27506 @node GDB/MI Stack Manipulation
27507 @section @sc{gdb/mi} Stack Manipulation Commands
27509 @subheading The @code{-enable-frame-filters} Command
27510 @findex -enable-frame-filters
27513 -enable-frame-filters
27516 @value{GDBN} allows Python-based frame filters to affect the output of
27517 the MI commands relating to stack traces. As there is no way to
27518 implement this in a fully backward-compatible way, a front end must
27519 request that this functionality be enabled.
27521 Once enabled, this feature cannot be disabled.
27523 Note that if Python support has not been compiled into @value{GDBN},
27524 this command will still succeed (and do nothing).
27526 @subheading The @code{-stack-info-frame} Command
27527 @findex -stack-info-frame
27529 @subsubheading Synopsis
27535 Get info on the selected frame.
27537 @subsubheading @value{GDBN} Command
27539 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
27540 (without arguments).
27542 @subsubheading Example
27547 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
27548 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27549 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
27553 @subheading The @code{-stack-info-depth} Command
27554 @findex -stack-info-depth
27556 @subsubheading Synopsis
27559 -stack-info-depth [ @var{max-depth} ]
27562 Return the depth of the stack. If the integer argument @var{max-depth}
27563 is specified, do not count beyond @var{max-depth} frames.
27565 @subsubheading @value{GDBN} Command
27567 There's no equivalent @value{GDBN} command.
27569 @subsubheading Example
27571 For a stack with frame levels 0 through 11:
27578 -stack-info-depth 4
27581 -stack-info-depth 12
27584 -stack-info-depth 11
27587 -stack-info-depth 13
27592 @anchor{-stack-list-arguments}
27593 @subheading The @code{-stack-list-arguments} Command
27594 @findex -stack-list-arguments
27596 @subsubheading Synopsis
27599 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
27600 [ @var{low-frame} @var{high-frame} ]
27603 Display a list of the arguments for the frames between @var{low-frame}
27604 and @var{high-frame} (inclusive). If @var{low-frame} and
27605 @var{high-frame} are not provided, list the arguments for the whole
27606 call stack. If the two arguments are equal, show the single frame
27607 at the corresponding level. It is an error if @var{low-frame} is
27608 larger than the actual number of frames. On the other hand,
27609 @var{high-frame} may be larger than the actual number of frames, in
27610 which case only existing frames will be returned.
27612 If @var{print-values} is 0 or @code{--no-values}, print only the names of
27613 the variables; if it is 1 or @code{--all-values}, print also their
27614 values; and if it is 2 or @code{--simple-values}, print the name,
27615 type and value for simple data types, and the name and type for arrays,
27616 structures and unions. If the option @code{--no-frame-filters} is
27617 supplied, then Python frame filters will not be executed.
27619 If the @code{--skip-unavailable} option is specified, arguments that
27620 are not available are not listed. Partially available arguments
27621 are still displayed, however.
27623 Use of this command to obtain arguments in a single frame is
27624 deprecated in favor of the @samp{-stack-list-variables} command.
27626 @subsubheading @value{GDBN} Command
27628 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
27629 @samp{gdb_get_args} command which partially overlaps with the
27630 functionality of @samp{-stack-list-arguments}.
27632 @subsubheading Example
27639 frame=@{level="0",addr="0x00010734",func="callee4",
27640 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27641 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
27642 frame=@{level="1",addr="0x0001076c",func="callee3",
27643 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27644 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
27645 frame=@{level="2",addr="0x0001078c",func="callee2",
27646 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27647 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
27648 frame=@{level="3",addr="0x000107b4",func="callee1",
27649 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27650 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
27651 frame=@{level="4",addr="0x000107e0",func="main",
27652 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27653 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
27655 -stack-list-arguments 0
27658 frame=@{level="0",args=[]@},
27659 frame=@{level="1",args=[name="strarg"]@},
27660 frame=@{level="2",args=[name="intarg",name="strarg"]@},
27661 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
27662 frame=@{level="4",args=[]@}]
27664 -stack-list-arguments 1
27667 frame=@{level="0",args=[]@},
27669 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
27670 frame=@{level="2",args=[
27671 @{name="intarg",value="2"@},
27672 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
27673 @{frame=@{level="3",args=[
27674 @{name="intarg",value="2"@},
27675 @{name="strarg",value="0x11940 \"A string argument.\""@},
27676 @{name="fltarg",value="3.5"@}]@},
27677 frame=@{level="4",args=[]@}]
27679 -stack-list-arguments 0 2 2
27680 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
27682 -stack-list-arguments 1 2 2
27683 ^done,stack-args=[frame=@{level="2",
27684 args=[@{name="intarg",value="2"@},
27685 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
27689 @c @subheading -stack-list-exception-handlers
27692 @anchor{-stack-list-frames}
27693 @subheading The @code{-stack-list-frames} Command
27694 @findex -stack-list-frames
27696 @subsubheading Synopsis
27699 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
27702 List the frames currently on the stack. For each frame it displays the
27707 The frame number, 0 being the topmost frame, i.e., the innermost function.
27709 The @code{$pc} value for that frame.
27713 File name of the source file where the function lives.
27714 @item @var{fullname}
27715 The full file name of the source file where the function lives.
27717 Line number corresponding to the @code{$pc}.
27719 The shared library where this function is defined. This is only given
27720 if the frame's function is not known.
27723 If invoked without arguments, this command prints a backtrace for the
27724 whole stack. If given two integer arguments, it shows the frames whose
27725 levels are between the two arguments (inclusive). If the two arguments
27726 are equal, it shows the single frame at the corresponding level. It is
27727 an error if @var{low-frame} is larger than the actual number of
27728 frames. On the other hand, @var{high-frame} may be larger than the
27729 actual number of frames, in which case only existing frames will be
27730 returned. If the option @code{--no-frame-filters} is supplied, then
27731 Python frame filters will not be executed.
27733 @subsubheading @value{GDBN} Command
27735 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
27737 @subsubheading Example
27739 Full stack backtrace:
27745 [frame=@{level="0",addr="0x0001076c",func="foo",
27746 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
27747 frame=@{level="1",addr="0x000107a4",func="foo",
27748 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27749 frame=@{level="2",addr="0x000107a4",func="foo",
27750 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27751 frame=@{level="3",addr="0x000107a4",func="foo",
27752 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27753 frame=@{level="4",addr="0x000107a4",func="foo",
27754 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27755 frame=@{level="5",addr="0x000107a4",func="foo",
27756 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27757 frame=@{level="6",addr="0x000107a4",func="foo",
27758 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27759 frame=@{level="7",addr="0x000107a4",func="foo",
27760 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27761 frame=@{level="8",addr="0x000107a4",func="foo",
27762 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27763 frame=@{level="9",addr="0x000107a4",func="foo",
27764 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27765 frame=@{level="10",addr="0x000107a4",func="foo",
27766 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27767 frame=@{level="11",addr="0x00010738",func="main",
27768 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
27772 Show frames between @var{low_frame} and @var{high_frame}:
27776 -stack-list-frames 3 5
27778 [frame=@{level="3",addr="0x000107a4",func="foo",
27779 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27780 frame=@{level="4",addr="0x000107a4",func="foo",
27781 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27782 frame=@{level="5",addr="0x000107a4",func="foo",
27783 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
27787 Show a single frame:
27791 -stack-list-frames 3 3
27793 [frame=@{level="3",addr="0x000107a4",func="foo",
27794 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
27799 @subheading The @code{-stack-list-locals} Command
27800 @findex -stack-list-locals
27801 @anchor{-stack-list-locals}
27803 @subsubheading Synopsis
27806 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
27809 Display the local variable names for the selected frame. If
27810 @var{print-values} is 0 or @code{--no-values}, print only the names of
27811 the variables; if it is 1 or @code{--all-values}, print also their
27812 values; and if it is 2 or @code{--simple-values}, print the name,
27813 type and value for simple data types, and the name and type for arrays,
27814 structures and unions. In this last case, a frontend can immediately
27815 display the value of simple data types and create variable objects for
27816 other data types when the user wishes to explore their values in
27817 more detail. If the option @code{--no-frame-filters} is supplied, then
27818 Python frame filters will not be executed.
27820 If the @code{--skip-unavailable} option is specified, local variables
27821 that are not available are not listed. Partially available local
27822 variables are still displayed, however.
27824 This command is deprecated in favor of the
27825 @samp{-stack-list-variables} command.
27827 @subsubheading @value{GDBN} Command
27829 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
27831 @subsubheading Example
27835 -stack-list-locals 0
27836 ^done,locals=[name="A",name="B",name="C"]
27838 -stack-list-locals --all-values
27839 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
27840 @{name="C",value="@{1, 2, 3@}"@}]
27841 -stack-list-locals --simple-values
27842 ^done,locals=[@{name="A",type="int",value="1"@},
27843 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
27847 @anchor{-stack-list-variables}
27848 @subheading The @code{-stack-list-variables} Command
27849 @findex -stack-list-variables
27851 @subsubheading Synopsis
27854 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
27857 Display the names of local variables and function arguments for the selected frame. If
27858 @var{print-values} is 0 or @code{--no-values}, print only the names of
27859 the variables; if it is 1 or @code{--all-values}, print also their
27860 values; and if it is 2 or @code{--simple-values}, print the name,
27861 type and value for simple data types, and the name and type for arrays,
27862 structures and unions. If the option @code{--no-frame-filters} is
27863 supplied, then Python frame filters will not be executed.
27865 If the @code{--skip-unavailable} option is specified, local variables
27866 and arguments that are not available are not listed. Partially
27867 available arguments and local variables are still displayed, however.
27869 @subsubheading Example
27873 -stack-list-variables --thread 1 --frame 0 --all-values
27874 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
27879 @subheading The @code{-stack-select-frame} Command
27880 @findex -stack-select-frame
27882 @subsubheading Synopsis
27885 -stack-select-frame @var{framenum}
27888 Change the selected frame. Select a different frame @var{framenum} on
27891 This command in deprecated in favor of passing the @samp{--frame}
27892 option to every command.
27894 @subsubheading @value{GDBN} Command
27896 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
27897 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
27899 @subsubheading Example
27903 -stack-select-frame 2
27908 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27909 @node GDB/MI Variable Objects
27910 @section @sc{gdb/mi} Variable Objects
27914 @subheading Motivation for Variable Objects in @sc{gdb/mi}
27916 For the implementation of a variable debugger window (locals, watched
27917 expressions, etc.), we are proposing the adaptation of the existing code
27918 used by @code{Insight}.
27920 The two main reasons for that are:
27924 It has been proven in practice (it is already on its second generation).
27927 It will shorten development time (needless to say how important it is
27931 The original interface was designed to be used by Tcl code, so it was
27932 slightly changed so it could be used through @sc{gdb/mi}. This section
27933 describes the @sc{gdb/mi} operations that will be available and gives some
27934 hints about their use.
27936 @emph{Note}: In addition to the set of operations described here, we
27937 expect the @sc{gui} implementation of a variable window to require, at
27938 least, the following operations:
27941 @item @code{-gdb-show} @code{output-radix}
27942 @item @code{-stack-list-arguments}
27943 @item @code{-stack-list-locals}
27944 @item @code{-stack-select-frame}
27949 @subheading Introduction to Variable Objects
27951 @cindex variable objects in @sc{gdb/mi}
27953 Variable objects are "object-oriented" MI interface for examining and
27954 changing values of expressions. Unlike some other MI interfaces that
27955 work with expressions, variable objects are specifically designed for
27956 simple and efficient presentation in the frontend. A variable object
27957 is identified by string name. When a variable object is created, the
27958 frontend specifies the expression for that variable object. The
27959 expression can be a simple variable, or it can be an arbitrary complex
27960 expression, and can even involve CPU registers. After creating a
27961 variable object, the frontend can invoke other variable object
27962 operations---for example to obtain or change the value of a variable
27963 object, or to change display format.
27965 Variable objects have hierarchical tree structure. Any variable object
27966 that corresponds to a composite type, such as structure in C, has
27967 a number of child variable objects, for example corresponding to each
27968 element of a structure. A child variable object can itself have
27969 children, recursively. Recursion ends when we reach
27970 leaf variable objects, which always have built-in types. Child variable
27971 objects are created only by explicit request, so if a frontend
27972 is not interested in the children of a particular variable object, no
27973 child will be created.
27975 For a leaf variable object it is possible to obtain its value as a
27976 string, or set the value from a string. String value can be also
27977 obtained for a non-leaf variable object, but it's generally a string
27978 that only indicates the type of the object, and does not list its
27979 contents. Assignment to a non-leaf variable object is not allowed.
27981 A frontend does not need to read the values of all variable objects each time
27982 the program stops. Instead, MI provides an update command that lists all
27983 variable objects whose values has changed since the last update
27984 operation. This considerably reduces the amount of data that must
27985 be transferred to the frontend. As noted above, children variable
27986 objects are created on demand, and only leaf variable objects have a
27987 real value. As result, gdb will read target memory only for leaf
27988 variables that frontend has created.
27990 The automatic update is not always desirable. For example, a frontend
27991 might want to keep a value of some expression for future reference,
27992 and never update it. For another example, fetching memory is
27993 relatively slow for embedded targets, so a frontend might want
27994 to disable automatic update for the variables that are either not
27995 visible on the screen, or ``closed''. This is possible using so
27996 called ``frozen variable objects''. Such variable objects are never
27997 implicitly updated.
27999 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
28000 fixed variable object, the expression is parsed when the variable
28001 object is created, including associating identifiers to specific
28002 variables. The meaning of expression never changes. For a floating
28003 variable object the values of variables whose names appear in the
28004 expressions are re-evaluated every time in the context of the current
28005 frame. Consider this example:
28010 struct work_state state;
28017 If a fixed variable object for the @code{state} variable is created in
28018 this function, and we enter the recursive call, the variable
28019 object will report the value of @code{state} in the top-level
28020 @code{do_work} invocation. On the other hand, a floating variable
28021 object will report the value of @code{state} in the current frame.
28023 If an expression specified when creating a fixed variable object
28024 refers to a local variable, the variable object becomes bound to the
28025 thread and frame in which the variable object is created. When such
28026 variable object is updated, @value{GDBN} makes sure that the
28027 thread/frame combination the variable object is bound to still exists,
28028 and re-evaluates the variable object in context of that thread/frame.
28030 The following is the complete set of @sc{gdb/mi} operations defined to
28031 access this functionality:
28033 @multitable @columnfractions .4 .6
28034 @item @strong{Operation}
28035 @tab @strong{Description}
28037 @item @code{-enable-pretty-printing}
28038 @tab enable Python-based pretty-printing
28039 @item @code{-var-create}
28040 @tab create a variable object
28041 @item @code{-var-delete}
28042 @tab delete the variable object and/or its children
28043 @item @code{-var-set-format}
28044 @tab set the display format of this variable
28045 @item @code{-var-show-format}
28046 @tab show the display format of this variable
28047 @item @code{-var-info-num-children}
28048 @tab tells how many children this object has
28049 @item @code{-var-list-children}
28050 @tab return a list of the object's children
28051 @item @code{-var-info-type}
28052 @tab show the type of this variable object
28053 @item @code{-var-info-expression}
28054 @tab print parent-relative expression that this variable object represents
28055 @item @code{-var-info-path-expression}
28056 @tab print full expression that this variable object represents
28057 @item @code{-var-show-attributes}
28058 @tab is this variable editable? does it exist here?
28059 @item @code{-var-evaluate-expression}
28060 @tab get the value of this variable
28061 @item @code{-var-assign}
28062 @tab set the value of this variable
28063 @item @code{-var-update}
28064 @tab update the variable and its children
28065 @item @code{-var-set-frozen}
28066 @tab set frozeness attribute
28067 @item @code{-var-set-update-range}
28068 @tab set range of children to display on update
28071 In the next subsection we describe each operation in detail and suggest
28072 how it can be used.
28074 @subheading Description And Use of Operations on Variable Objects
28076 @subheading The @code{-enable-pretty-printing} Command
28077 @findex -enable-pretty-printing
28080 -enable-pretty-printing
28083 @value{GDBN} allows Python-based visualizers to affect the output of the
28084 MI variable object commands. However, because there was no way to
28085 implement this in a fully backward-compatible way, a front end must
28086 request that this functionality be enabled.
28088 Once enabled, this feature cannot be disabled.
28090 Note that if Python support has not been compiled into @value{GDBN},
28091 this command will still succeed (and do nothing).
28093 This feature is currently (as of @value{GDBN} 7.0) experimental, and
28094 may work differently in future versions of @value{GDBN}.
28096 @subheading The @code{-var-create} Command
28097 @findex -var-create
28099 @subsubheading Synopsis
28102 -var-create @{@var{name} | "-"@}
28103 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
28106 This operation creates a variable object, which allows the monitoring of
28107 a variable, the result of an expression, a memory cell or a CPU
28110 The @var{name} parameter is the string by which the object can be
28111 referenced. It must be unique. If @samp{-} is specified, the varobj
28112 system will generate a string ``varNNNNNN'' automatically. It will be
28113 unique provided that one does not specify @var{name} of that format.
28114 The command fails if a duplicate name is found.
28116 The frame under which the expression should be evaluated can be
28117 specified by @var{frame-addr}. A @samp{*} indicates that the current
28118 frame should be used. A @samp{@@} indicates that a floating variable
28119 object must be created.
28121 @var{expression} is any expression valid on the current language set (must not
28122 begin with a @samp{*}), or one of the following:
28126 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
28129 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
28132 @samp{$@var{regname}} --- a CPU register name
28135 @cindex dynamic varobj
28136 A varobj's contents may be provided by a Python-based pretty-printer. In this
28137 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
28138 have slightly different semantics in some cases. If the
28139 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
28140 will never create a dynamic varobj. This ensures backward
28141 compatibility for existing clients.
28143 @subsubheading Result
28145 This operation returns attributes of the newly-created varobj. These
28150 The name of the varobj.
28153 The number of children of the varobj. This number is not necessarily
28154 reliable for a dynamic varobj. Instead, you must examine the
28155 @samp{has_more} attribute.
28158 The varobj's scalar value. For a varobj whose type is some sort of
28159 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
28160 will not be interesting.
28163 The varobj's type. This is a string representation of the type, as
28164 would be printed by the @value{GDBN} CLI. If @samp{print object}
28165 (@pxref{Print Settings, set print object}) is set to @code{on}, the
28166 @emph{actual} (derived) type of the object is shown rather than the
28167 @emph{declared} one.
28170 If a variable object is bound to a specific thread, then this is the
28171 thread's identifier.
28174 For a dynamic varobj, this indicates whether there appear to be any
28175 children available. For a non-dynamic varobj, this will be 0.
28178 This attribute will be present and have the value @samp{1} if the
28179 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28180 then this attribute will not be present.
28183 A dynamic varobj can supply a display hint to the front end. The
28184 value comes directly from the Python pretty-printer object's
28185 @code{display_hint} method. @xref{Pretty Printing API}.
28188 Typical output will look like this:
28191 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
28192 has_more="@var{has_more}"
28196 @subheading The @code{-var-delete} Command
28197 @findex -var-delete
28199 @subsubheading Synopsis
28202 -var-delete [ -c ] @var{name}
28205 Deletes a previously created variable object and all of its children.
28206 With the @samp{-c} option, just deletes the children.
28208 Returns an error if the object @var{name} is not found.
28211 @subheading The @code{-var-set-format} Command
28212 @findex -var-set-format
28214 @subsubheading Synopsis
28217 -var-set-format @var{name} @var{format-spec}
28220 Sets the output format for the value of the object @var{name} to be
28223 @anchor{-var-set-format}
28224 The syntax for the @var{format-spec} is as follows:
28227 @var{format-spec} @expansion{}
28228 @{binary | decimal | hexadecimal | octal | natural@}
28231 The natural format is the default format choosen automatically
28232 based on the variable type (like decimal for an @code{int}, hex
28233 for pointers, etc.).
28235 For a variable with children, the format is set only on the
28236 variable itself, and the children are not affected.
28238 @subheading The @code{-var-show-format} Command
28239 @findex -var-show-format
28241 @subsubheading Synopsis
28244 -var-show-format @var{name}
28247 Returns the format used to display the value of the object @var{name}.
28250 @var{format} @expansion{}
28255 @subheading The @code{-var-info-num-children} Command
28256 @findex -var-info-num-children
28258 @subsubheading Synopsis
28261 -var-info-num-children @var{name}
28264 Returns the number of children of a variable object @var{name}:
28270 Note that this number is not completely reliable for a dynamic varobj.
28271 It will return the current number of children, but more children may
28275 @subheading The @code{-var-list-children} Command
28276 @findex -var-list-children
28278 @subsubheading Synopsis
28281 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
28283 @anchor{-var-list-children}
28285 Return a list of the children of the specified variable object and
28286 create variable objects for them, if they do not already exist. With
28287 a single argument or if @var{print-values} has a value of 0 or
28288 @code{--no-values}, print only the names of the variables; if
28289 @var{print-values} is 1 or @code{--all-values}, also print their
28290 values; and if it is 2 or @code{--simple-values} print the name and
28291 value for simple data types and just the name for arrays, structures
28294 @var{from} and @var{to}, if specified, indicate the range of children
28295 to report. If @var{from} or @var{to} is less than zero, the range is
28296 reset and all children will be reported. Otherwise, children starting
28297 at @var{from} (zero-based) and up to and excluding @var{to} will be
28300 If a child range is requested, it will only affect the current call to
28301 @code{-var-list-children}, but not future calls to @code{-var-update}.
28302 For this, you must instead use @code{-var-set-update-range}. The
28303 intent of this approach is to enable a front end to implement any
28304 update approach it likes; for example, scrolling a view may cause the
28305 front end to request more children with @code{-var-list-children}, and
28306 then the front end could call @code{-var-set-update-range} with a
28307 different range to ensure that future updates are restricted to just
28310 For each child the following results are returned:
28315 Name of the variable object created for this child.
28318 The expression to be shown to the user by the front end to designate this child.
28319 For example this may be the name of a structure member.
28321 For a dynamic varobj, this value cannot be used to form an
28322 expression. There is no way to do this at all with a dynamic varobj.
28324 For C/C@t{++} structures there are several pseudo children returned to
28325 designate access qualifiers. For these pseudo children @var{exp} is
28326 @samp{public}, @samp{private}, or @samp{protected}. In this case the
28327 type and value are not present.
28329 A dynamic varobj will not report the access qualifying
28330 pseudo-children, regardless of the language. This information is not
28331 available at all with a dynamic varobj.
28334 Number of children this child has. For a dynamic varobj, this will be
28338 The type of the child. If @samp{print object}
28339 (@pxref{Print Settings, set print object}) is set to @code{on}, the
28340 @emph{actual} (derived) type of the object is shown rather than the
28341 @emph{declared} one.
28344 If values were requested, this is the value.
28347 If this variable object is associated with a thread, this is the thread id.
28348 Otherwise this result is not present.
28351 If the variable object is frozen, this variable will be present with a value of 1.
28354 A dynamic varobj can supply a display hint to the front end. The
28355 value comes directly from the Python pretty-printer object's
28356 @code{display_hint} method. @xref{Pretty Printing API}.
28359 This attribute will be present and have the value @samp{1} if the
28360 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28361 then this attribute will not be present.
28365 The result may have its own attributes:
28369 A dynamic varobj can supply a display hint to the front end. The
28370 value comes directly from the Python pretty-printer object's
28371 @code{display_hint} method. @xref{Pretty Printing API}.
28374 This is an integer attribute which is nonzero if there are children
28375 remaining after the end of the selected range.
28378 @subsubheading Example
28382 -var-list-children n
28383 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28384 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
28386 -var-list-children --all-values n
28387 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28388 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
28392 @subheading The @code{-var-info-type} Command
28393 @findex -var-info-type
28395 @subsubheading Synopsis
28398 -var-info-type @var{name}
28401 Returns the type of the specified variable @var{name}. The type is
28402 returned as a string in the same format as it is output by the
28406 type=@var{typename}
28410 @subheading The @code{-var-info-expression} Command
28411 @findex -var-info-expression
28413 @subsubheading Synopsis
28416 -var-info-expression @var{name}
28419 Returns a string that is suitable for presenting this
28420 variable object in user interface. The string is generally
28421 not valid expression in the current language, and cannot be evaluated.
28423 For example, if @code{a} is an array, and variable object
28424 @code{A} was created for @code{a}, then we'll get this output:
28427 (gdb) -var-info-expression A.1
28428 ^done,lang="C",exp="1"
28432 Here, the value of @code{lang} is the language name, which can be
28433 found in @ref{Supported Languages}.
28435 Note that the output of the @code{-var-list-children} command also
28436 includes those expressions, so the @code{-var-info-expression} command
28439 @subheading The @code{-var-info-path-expression} Command
28440 @findex -var-info-path-expression
28442 @subsubheading Synopsis
28445 -var-info-path-expression @var{name}
28448 Returns an expression that can be evaluated in the current
28449 context and will yield the same value that a variable object has.
28450 Compare this with the @code{-var-info-expression} command, which
28451 result can be used only for UI presentation. Typical use of
28452 the @code{-var-info-path-expression} command is creating a
28453 watchpoint from a variable object.
28455 This command is currently not valid for children of a dynamic varobj,
28456 and will give an error when invoked on one.
28458 For example, suppose @code{C} is a C@t{++} class, derived from class
28459 @code{Base}, and that the @code{Base} class has a member called
28460 @code{m_size}. Assume a variable @code{c} is has the type of
28461 @code{C} and a variable object @code{C} was created for variable
28462 @code{c}. Then, we'll get this output:
28464 (gdb) -var-info-path-expression C.Base.public.m_size
28465 ^done,path_expr=((Base)c).m_size)
28468 @subheading The @code{-var-show-attributes} Command
28469 @findex -var-show-attributes
28471 @subsubheading Synopsis
28474 -var-show-attributes @var{name}
28477 List attributes of the specified variable object @var{name}:
28480 status=@var{attr} [ ( ,@var{attr} )* ]
28484 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
28486 @subheading The @code{-var-evaluate-expression} Command
28487 @findex -var-evaluate-expression
28489 @subsubheading Synopsis
28492 -var-evaluate-expression [-f @var{format-spec}] @var{name}
28495 Evaluates the expression that is represented by the specified variable
28496 object and returns its value as a string. The format of the string
28497 can be specified with the @samp{-f} option. The possible values of
28498 this option are the same as for @code{-var-set-format}
28499 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
28500 the current display format will be used. The current display format
28501 can be changed using the @code{-var-set-format} command.
28507 Note that one must invoke @code{-var-list-children} for a variable
28508 before the value of a child variable can be evaluated.
28510 @subheading The @code{-var-assign} Command
28511 @findex -var-assign
28513 @subsubheading Synopsis
28516 -var-assign @var{name} @var{expression}
28519 Assigns the value of @var{expression} to the variable object specified
28520 by @var{name}. The object must be @samp{editable}. If the variable's
28521 value is altered by the assign, the variable will show up in any
28522 subsequent @code{-var-update} list.
28524 @subsubheading Example
28532 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
28536 @subheading The @code{-var-update} Command
28537 @findex -var-update
28539 @subsubheading Synopsis
28542 -var-update [@var{print-values}] @{@var{name} | "*"@}
28545 Reevaluate the expressions corresponding to the variable object
28546 @var{name} and all its direct and indirect children, and return the
28547 list of variable objects whose values have changed; @var{name} must
28548 be a root variable object. Here, ``changed'' means that the result of
28549 @code{-var-evaluate-expression} before and after the
28550 @code{-var-update} is different. If @samp{*} is used as the variable
28551 object names, all existing variable objects are updated, except
28552 for frozen ones (@pxref{-var-set-frozen}). The option
28553 @var{print-values} determines whether both names and values, or just
28554 names are printed. The possible values of this option are the same
28555 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
28556 recommended to use the @samp{--all-values} option, to reduce the
28557 number of MI commands needed on each program stop.
28559 With the @samp{*} parameter, if a variable object is bound to a
28560 currently running thread, it will not be updated, without any
28563 If @code{-var-set-update-range} was previously used on a varobj, then
28564 only the selected range of children will be reported.
28566 @code{-var-update} reports all the changed varobjs in a tuple named
28569 Each item in the change list is itself a tuple holding:
28573 The name of the varobj.
28576 If values were requested for this update, then this field will be
28577 present and will hold the value of the varobj.
28580 @anchor{-var-update}
28581 This field is a string which may take one of three values:
28585 The variable object's current value is valid.
28588 The variable object does not currently hold a valid value but it may
28589 hold one in the future if its associated expression comes back into
28593 The variable object no longer holds a valid value.
28594 This can occur when the executable file being debugged has changed,
28595 either through recompilation or by using the @value{GDBN} @code{file}
28596 command. The front end should normally choose to delete these variable
28600 In the future new values may be added to this list so the front should
28601 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
28604 This is only present if the varobj is still valid. If the type
28605 changed, then this will be the string @samp{true}; otherwise it will
28608 When a varobj's type changes, its children are also likely to have
28609 become incorrect. Therefore, the varobj's children are automatically
28610 deleted when this attribute is @samp{true}. Also, the varobj's update
28611 range, when set using the @code{-var-set-update-range} command, is
28615 If the varobj's type changed, then this field will be present and will
28618 @item new_num_children
28619 For a dynamic varobj, if the number of children changed, or if the
28620 type changed, this will be the new number of children.
28622 The @samp{numchild} field in other varobj responses is generally not
28623 valid for a dynamic varobj -- it will show the number of children that
28624 @value{GDBN} knows about, but because dynamic varobjs lazily
28625 instantiate their children, this will not reflect the number of
28626 children which may be available.
28628 The @samp{new_num_children} attribute only reports changes to the
28629 number of children known by @value{GDBN}. This is the only way to
28630 detect whether an update has removed children (which necessarily can
28631 only happen at the end of the update range).
28634 The display hint, if any.
28637 This is an integer value, which will be 1 if there are more children
28638 available outside the varobj's update range.
28641 This attribute will be present and have the value @samp{1} if the
28642 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28643 then this attribute will not be present.
28646 If new children were added to a dynamic varobj within the selected
28647 update range (as set by @code{-var-set-update-range}), then they will
28648 be listed in this attribute.
28651 @subsubheading Example
28658 -var-update --all-values var1
28659 ^done,changelist=[@{name="var1",value="3",in_scope="true",
28660 type_changed="false"@}]
28664 @subheading The @code{-var-set-frozen} Command
28665 @findex -var-set-frozen
28666 @anchor{-var-set-frozen}
28668 @subsubheading Synopsis
28671 -var-set-frozen @var{name} @var{flag}
28674 Set the frozenness flag on the variable object @var{name}. The
28675 @var{flag} parameter should be either @samp{1} to make the variable
28676 frozen or @samp{0} to make it unfrozen. If a variable object is
28677 frozen, then neither itself, nor any of its children, are
28678 implicitly updated by @code{-var-update} of
28679 a parent variable or by @code{-var-update *}. Only
28680 @code{-var-update} of the variable itself will update its value and
28681 values of its children. After a variable object is unfrozen, it is
28682 implicitly updated by all subsequent @code{-var-update} operations.
28683 Unfreezing a variable does not update it, only subsequent
28684 @code{-var-update} does.
28686 @subsubheading Example
28690 -var-set-frozen V 1
28695 @subheading The @code{-var-set-update-range} command
28696 @findex -var-set-update-range
28697 @anchor{-var-set-update-range}
28699 @subsubheading Synopsis
28702 -var-set-update-range @var{name} @var{from} @var{to}
28705 Set the range of children to be returned by future invocations of
28706 @code{-var-update}.
28708 @var{from} and @var{to} indicate the range of children to report. If
28709 @var{from} or @var{to} is less than zero, the range is reset and all
28710 children will be reported. Otherwise, children starting at @var{from}
28711 (zero-based) and up to and excluding @var{to} will be reported.
28713 @subsubheading Example
28717 -var-set-update-range V 1 2
28721 @subheading The @code{-var-set-visualizer} command
28722 @findex -var-set-visualizer
28723 @anchor{-var-set-visualizer}
28725 @subsubheading Synopsis
28728 -var-set-visualizer @var{name} @var{visualizer}
28731 Set a visualizer for the variable object @var{name}.
28733 @var{visualizer} is the visualizer to use. The special value
28734 @samp{None} means to disable any visualizer in use.
28736 If not @samp{None}, @var{visualizer} must be a Python expression.
28737 This expression must evaluate to a callable object which accepts a
28738 single argument. @value{GDBN} will call this object with the value of
28739 the varobj @var{name} as an argument (this is done so that the same
28740 Python pretty-printing code can be used for both the CLI and MI).
28741 When called, this object must return an object which conforms to the
28742 pretty-printing interface (@pxref{Pretty Printing API}).
28744 The pre-defined function @code{gdb.default_visualizer} may be used to
28745 select a visualizer by following the built-in process
28746 (@pxref{Selecting Pretty-Printers}). This is done automatically when
28747 a varobj is created, and so ordinarily is not needed.
28749 This feature is only available if Python support is enabled. The MI
28750 command @code{-list-features} (@pxref{GDB/MI Support Commands})
28751 can be used to check this.
28753 @subsubheading Example
28755 Resetting the visualizer:
28759 -var-set-visualizer V None
28763 Reselecting the default (type-based) visualizer:
28767 -var-set-visualizer V gdb.default_visualizer
28771 Suppose @code{SomeClass} is a visualizer class. A lambda expression
28772 can be used to instantiate this class for a varobj:
28776 -var-set-visualizer V "lambda val: SomeClass()"
28780 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28781 @node GDB/MI Data Manipulation
28782 @section @sc{gdb/mi} Data Manipulation
28784 @cindex data manipulation, in @sc{gdb/mi}
28785 @cindex @sc{gdb/mi}, data manipulation
28786 This section describes the @sc{gdb/mi} commands that manipulate data:
28787 examine memory and registers, evaluate expressions, etc.
28789 @c REMOVED FROM THE INTERFACE.
28790 @c @subheading -data-assign
28791 @c Change the value of a program variable. Plenty of side effects.
28792 @c @subsubheading GDB Command
28794 @c @subsubheading Example
28797 @subheading The @code{-data-disassemble} Command
28798 @findex -data-disassemble
28800 @subsubheading Synopsis
28804 [ -s @var{start-addr} -e @var{end-addr} ]
28805 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
28813 @item @var{start-addr}
28814 is the beginning address (or @code{$pc})
28815 @item @var{end-addr}
28817 @item @var{filename}
28818 is the name of the file to disassemble
28819 @item @var{linenum}
28820 is the line number to disassemble around
28822 is the number of disassembly lines to be produced. If it is -1,
28823 the whole function will be disassembled, in case no @var{end-addr} is
28824 specified. If @var{end-addr} is specified as a non-zero value, and
28825 @var{lines} is lower than the number of disassembly lines between
28826 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
28827 displayed; if @var{lines} is higher than the number of lines between
28828 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
28831 is either 0 (meaning only disassembly), 1 (meaning mixed source and
28832 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
28833 mixed source and disassembly with raw opcodes).
28836 @subsubheading Result
28838 The result of the @code{-data-disassemble} command will be a list named
28839 @samp{asm_insns}, the contents of this list depend on the @var{mode}
28840 used with the @code{-data-disassemble} command.
28842 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
28847 The address at which this instruction was disassembled.
28850 The name of the function this instruction is within.
28853 The decimal offset in bytes from the start of @samp{func-name}.
28856 The text disassembly for this @samp{address}.
28859 This field is only present for mode 2. This contains the raw opcode
28860 bytes for the @samp{inst} field.
28864 For modes 1 and 3 the @samp{asm_insns} list contains tuples named
28865 @samp{src_and_asm_line}, each of which has the following fields:
28869 The line number within @samp{file}.
28872 The file name from the compilation unit. This might be an absolute
28873 file name or a relative file name depending on the compile command
28877 Absolute file name of @samp{file}. It is converted to a canonical form
28878 using the source file search path
28879 (@pxref{Source Path, ,Specifying Source Directories})
28880 and after resolving all the symbolic links.
28882 If the source file is not found this field will contain the path as
28883 present in the debug information.
28885 @item line_asm_insn
28886 This is a list of tuples containing the disassembly for @samp{line} in
28887 @samp{file}. The fields of each tuple are the same as for
28888 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
28889 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
28894 Note that whatever included in the @samp{inst} field, is not
28895 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
28898 @subsubheading @value{GDBN} Command
28900 The corresponding @value{GDBN} command is @samp{disassemble}.
28902 @subsubheading Example
28904 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
28908 -data-disassemble -s $pc -e "$pc + 20" -- 0
28911 @{address="0x000107c0",func-name="main",offset="4",
28912 inst="mov 2, %o0"@},
28913 @{address="0x000107c4",func-name="main",offset="8",
28914 inst="sethi %hi(0x11800), %o2"@},
28915 @{address="0x000107c8",func-name="main",offset="12",
28916 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
28917 @{address="0x000107cc",func-name="main",offset="16",
28918 inst="sethi %hi(0x11800), %o2"@},
28919 @{address="0x000107d0",func-name="main",offset="20",
28920 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
28924 Disassemble the whole @code{main} function. Line 32 is part of
28928 -data-disassemble -f basics.c -l 32 -- 0
28930 @{address="0x000107bc",func-name="main",offset="0",
28931 inst="save %sp, -112, %sp"@},
28932 @{address="0x000107c0",func-name="main",offset="4",
28933 inst="mov 2, %o0"@},
28934 @{address="0x000107c4",func-name="main",offset="8",
28935 inst="sethi %hi(0x11800), %o2"@},
28937 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
28938 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
28942 Disassemble 3 instructions from the start of @code{main}:
28946 -data-disassemble -f basics.c -l 32 -n 3 -- 0
28948 @{address="0x000107bc",func-name="main",offset="0",
28949 inst="save %sp, -112, %sp"@},
28950 @{address="0x000107c0",func-name="main",offset="4",
28951 inst="mov 2, %o0"@},
28952 @{address="0x000107c4",func-name="main",offset="8",
28953 inst="sethi %hi(0x11800), %o2"@}]
28957 Disassemble 3 instructions from the start of @code{main} in mixed mode:
28961 -data-disassemble -f basics.c -l 32 -n 3 -- 1
28963 src_and_asm_line=@{line="31",
28964 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
28965 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
28966 line_asm_insn=[@{address="0x000107bc",
28967 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
28968 src_and_asm_line=@{line="32",
28969 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
28970 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
28971 line_asm_insn=[@{address="0x000107c0",
28972 func-name="main",offset="4",inst="mov 2, %o0"@},
28973 @{address="0x000107c4",func-name="main",offset="8",
28974 inst="sethi %hi(0x11800), %o2"@}]@}]
28979 @subheading The @code{-data-evaluate-expression} Command
28980 @findex -data-evaluate-expression
28982 @subsubheading Synopsis
28985 -data-evaluate-expression @var{expr}
28988 Evaluate @var{expr} as an expression. The expression could contain an
28989 inferior function call. The function call will execute synchronously.
28990 If the expression contains spaces, it must be enclosed in double quotes.
28992 @subsubheading @value{GDBN} Command
28994 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
28995 @samp{call}. In @code{gdbtk} only, there's a corresponding
28996 @samp{gdb_eval} command.
28998 @subsubheading Example
29000 In the following example, the numbers that precede the commands are the
29001 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
29002 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
29006 211-data-evaluate-expression A
29009 311-data-evaluate-expression &A
29010 311^done,value="0xefffeb7c"
29012 411-data-evaluate-expression A+3
29015 511-data-evaluate-expression "A + 3"
29021 @subheading The @code{-data-list-changed-registers} Command
29022 @findex -data-list-changed-registers
29024 @subsubheading Synopsis
29027 -data-list-changed-registers
29030 Display a list of the registers that have changed.
29032 @subsubheading @value{GDBN} Command
29034 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
29035 has the corresponding command @samp{gdb_changed_register_list}.
29037 @subsubheading Example
29039 On a PPC MBX board:
29047 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
29048 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
29051 -data-list-changed-registers
29052 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
29053 "10","11","13","14","15","16","17","18","19","20","21","22","23",
29054 "24","25","26","27","28","30","31","64","65","66","67","69"]
29059 @subheading The @code{-data-list-register-names} Command
29060 @findex -data-list-register-names
29062 @subsubheading Synopsis
29065 -data-list-register-names [ ( @var{regno} )+ ]
29068 Show a list of register names for the current target. If no arguments
29069 are given, it shows a list of the names of all the registers. If
29070 integer numbers are given as arguments, it will print a list of the
29071 names of the registers corresponding to the arguments. To ensure
29072 consistency between a register name and its number, the output list may
29073 include empty register names.
29075 @subsubheading @value{GDBN} Command
29077 @value{GDBN} does not have a command which corresponds to
29078 @samp{-data-list-register-names}. In @code{gdbtk} there is a
29079 corresponding command @samp{gdb_regnames}.
29081 @subsubheading Example
29083 For the PPC MBX board:
29086 -data-list-register-names
29087 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
29088 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
29089 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
29090 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
29091 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
29092 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
29093 "", "pc","ps","cr","lr","ctr","xer"]
29095 -data-list-register-names 1 2 3
29096 ^done,register-names=["r1","r2","r3"]
29100 @subheading The @code{-data-list-register-values} Command
29101 @findex -data-list-register-values
29103 @subsubheading Synopsis
29106 -data-list-register-values
29107 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
29110 Display the registers' contents. @var{fmt} is the format according to
29111 which the registers' contents are to be returned, followed by an optional
29112 list of numbers specifying the registers to display. A missing list of
29113 numbers indicates that the contents of all the registers must be
29114 returned. The @code{--skip-unavailable} option indicates that only
29115 the available registers are to be returned.
29117 Allowed formats for @var{fmt} are:
29134 @subsubheading @value{GDBN} Command
29136 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
29137 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
29139 @subsubheading Example
29141 For a PPC MBX board (note: line breaks are for readability only, they
29142 don't appear in the actual output):
29146 -data-list-register-values r 64 65
29147 ^done,register-values=[@{number="64",value="0xfe00a300"@},
29148 @{number="65",value="0x00029002"@}]
29150 -data-list-register-values x
29151 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
29152 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
29153 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
29154 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
29155 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
29156 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
29157 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
29158 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
29159 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
29160 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
29161 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
29162 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
29163 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
29164 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
29165 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
29166 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
29167 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
29168 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
29169 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
29170 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
29171 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
29172 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
29173 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
29174 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
29175 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
29176 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
29177 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
29178 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
29179 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
29180 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
29181 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
29182 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
29183 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
29184 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
29185 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
29186 @{number="69",value="0x20002b03"@}]
29191 @subheading The @code{-data-read-memory} Command
29192 @findex -data-read-memory
29194 This command is deprecated, use @code{-data-read-memory-bytes} instead.
29196 @subsubheading Synopsis
29199 -data-read-memory [ -o @var{byte-offset} ]
29200 @var{address} @var{word-format} @var{word-size}
29201 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
29208 @item @var{address}
29209 An expression specifying the address of the first memory word to be
29210 read. Complex expressions containing embedded white space should be
29211 quoted using the C convention.
29213 @item @var{word-format}
29214 The format to be used to print the memory words. The notation is the
29215 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
29218 @item @var{word-size}
29219 The size of each memory word in bytes.
29221 @item @var{nr-rows}
29222 The number of rows in the output table.
29224 @item @var{nr-cols}
29225 The number of columns in the output table.
29228 If present, indicates that each row should include an @sc{ascii} dump. The
29229 value of @var{aschar} is used as a padding character when a byte is not a
29230 member of the printable @sc{ascii} character set (printable @sc{ascii}
29231 characters are those whose code is between 32 and 126, inclusively).
29233 @item @var{byte-offset}
29234 An offset to add to the @var{address} before fetching memory.
29237 This command displays memory contents as a table of @var{nr-rows} by
29238 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
29239 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
29240 (returned as @samp{total-bytes}). Should less than the requested number
29241 of bytes be returned by the target, the missing words are identified
29242 using @samp{N/A}. The number of bytes read from the target is returned
29243 in @samp{nr-bytes} and the starting address used to read memory in
29246 The address of the next/previous row or page is available in
29247 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
29250 @subsubheading @value{GDBN} Command
29252 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
29253 @samp{gdb_get_mem} memory read command.
29255 @subsubheading Example
29257 Read six bytes of memory starting at @code{bytes+6} but then offset by
29258 @code{-6} bytes. Format as three rows of two columns. One byte per
29259 word. Display each word in hex.
29263 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
29264 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
29265 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
29266 prev-page="0x0000138a",memory=[
29267 @{addr="0x00001390",data=["0x00","0x01"]@},
29268 @{addr="0x00001392",data=["0x02","0x03"]@},
29269 @{addr="0x00001394",data=["0x04","0x05"]@}]
29273 Read two bytes of memory starting at address @code{shorts + 64} and
29274 display as a single word formatted in decimal.
29278 5-data-read-memory shorts+64 d 2 1 1
29279 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
29280 next-row="0x00001512",prev-row="0x0000150e",
29281 next-page="0x00001512",prev-page="0x0000150e",memory=[
29282 @{addr="0x00001510",data=["128"]@}]
29286 Read thirty two bytes of memory starting at @code{bytes+16} and format
29287 as eight rows of four columns. Include a string encoding with @samp{x}
29288 used as the non-printable character.
29292 4-data-read-memory bytes+16 x 1 8 4 x
29293 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
29294 next-row="0x000013c0",prev-row="0x0000139c",
29295 next-page="0x000013c0",prev-page="0x00001380",memory=[
29296 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
29297 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
29298 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
29299 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
29300 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
29301 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
29302 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
29303 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
29307 @subheading The @code{-data-read-memory-bytes} Command
29308 @findex -data-read-memory-bytes
29310 @subsubheading Synopsis
29313 -data-read-memory-bytes [ -o @var{byte-offset} ]
29314 @var{address} @var{count}
29321 @item @var{address}
29322 An expression specifying the address of the first memory word to be
29323 read. Complex expressions containing embedded white space should be
29324 quoted using the C convention.
29327 The number of bytes to read. This should be an integer literal.
29329 @item @var{byte-offset}
29330 The offsets in bytes relative to @var{address} at which to start
29331 reading. This should be an integer literal. This option is provided
29332 so that a frontend is not required to first evaluate address and then
29333 perform address arithmetics itself.
29337 This command attempts to read all accessible memory regions in the
29338 specified range. First, all regions marked as unreadable in the memory
29339 map (if one is defined) will be skipped. @xref{Memory Region
29340 Attributes}. Second, @value{GDBN} will attempt to read the remaining
29341 regions. For each one, if reading full region results in an errors,
29342 @value{GDBN} will try to read a subset of the region.
29344 In general, every single byte in the region may be readable or not,
29345 and the only way to read every readable byte is to try a read at
29346 every address, which is not practical. Therefore, @value{GDBN} will
29347 attempt to read all accessible bytes at either beginning or the end
29348 of the region, using a binary division scheme. This heuristic works
29349 well for reading accross a memory map boundary. Note that if a region
29350 has a readable range that is neither at the beginning or the end,
29351 @value{GDBN} will not read it.
29353 The result record (@pxref{GDB/MI Result Records}) that is output of
29354 the command includes a field named @samp{memory} whose content is a
29355 list of tuples. Each tuple represent a successfully read memory block
29356 and has the following fields:
29360 The start address of the memory block, as hexadecimal literal.
29363 The end address of the memory block, as hexadecimal literal.
29366 The offset of the memory block, as hexadecimal literal, relative to
29367 the start address passed to @code{-data-read-memory-bytes}.
29370 The contents of the memory block, in hex.
29376 @subsubheading @value{GDBN} Command
29378 The corresponding @value{GDBN} command is @samp{x}.
29380 @subsubheading Example
29384 -data-read-memory-bytes &a 10
29385 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
29387 contents="01000000020000000300"@}]
29392 @subheading The @code{-data-write-memory-bytes} Command
29393 @findex -data-write-memory-bytes
29395 @subsubheading Synopsis
29398 -data-write-memory-bytes @var{address} @var{contents}
29399 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
29406 @item @var{address}
29407 An expression specifying the address of the first memory word to be
29408 read. Complex expressions containing embedded white space should be
29409 quoted using the C convention.
29411 @item @var{contents}
29412 The hex-encoded bytes to write.
29415 Optional argument indicating the number of bytes to be written. If @var{count}
29416 is greater than @var{contents}' length, @value{GDBN} will repeatedly
29417 write @var{contents} until it fills @var{count} bytes.
29421 @subsubheading @value{GDBN} Command
29423 There's no corresponding @value{GDBN} command.
29425 @subsubheading Example
29429 -data-write-memory-bytes &a "aabbccdd"
29436 -data-write-memory-bytes &a "aabbccdd" 16e
29441 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29442 @node GDB/MI Tracepoint Commands
29443 @section @sc{gdb/mi} Tracepoint Commands
29445 The commands defined in this section implement MI support for
29446 tracepoints. For detailed introduction, see @ref{Tracepoints}.
29448 @subheading The @code{-trace-find} Command
29449 @findex -trace-find
29451 @subsubheading Synopsis
29454 -trace-find @var{mode} [@var{parameters}@dots{}]
29457 Find a trace frame using criteria defined by @var{mode} and
29458 @var{parameters}. The following table lists permissible
29459 modes and their parameters. For details of operation, see @ref{tfind}.
29464 No parameters are required. Stops examining trace frames.
29467 An integer is required as parameter. Selects tracepoint frame with
29470 @item tracepoint-number
29471 An integer is required as parameter. Finds next
29472 trace frame that corresponds to tracepoint with the specified number.
29475 An address is required as parameter. Finds
29476 next trace frame that corresponds to any tracepoint at the specified
29479 @item pc-inside-range
29480 Two addresses are required as parameters. Finds next trace
29481 frame that corresponds to a tracepoint at an address inside the
29482 specified range. Both bounds are considered to be inside the range.
29484 @item pc-outside-range
29485 Two addresses are required as parameters. Finds
29486 next trace frame that corresponds to a tracepoint at an address outside
29487 the specified range. Both bounds are considered to be inside the range.
29490 Line specification is required as parameter. @xref{Specify Location}.
29491 Finds next trace frame that corresponds to a tracepoint at
29492 the specified location.
29496 If @samp{none} was passed as @var{mode}, the response does not
29497 have fields. Otherwise, the response may have the following fields:
29501 This field has either @samp{0} or @samp{1} as the value, depending
29502 on whether a matching tracepoint was found.
29505 The index of the found traceframe. This field is present iff
29506 the @samp{found} field has value of @samp{1}.
29509 The index of the found tracepoint. This field is present iff
29510 the @samp{found} field has value of @samp{1}.
29513 The information about the frame corresponding to the found trace
29514 frame. This field is present only if a trace frame was found.
29515 @xref{GDB/MI Frame Information}, for description of this field.
29519 @subsubheading @value{GDBN} Command
29521 The corresponding @value{GDBN} command is @samp{tfind}.
29523 @subheading -trace-define-variable
29524 @findex -trace-define-variable
29526 @subsubheading Synopsis
29529 -trace-define-variable @var{name} [ @var{value} ]
29532 Create trace variable @var{name} if it does not exist. If
29533 @var{value} is specified, sets the initial value of the specified
29534 trace variable to that value. Note that the @var{name} should start
29535 with the @samp{$} character.
29537 @subsubheading @value{GDBN} Command
29539 The corresponding @value{GDBN} command is @samp{tvariable}.
29541 @subheading The @code{-trace-frame-collected} Command
29542 @findex -trace-frame-collected
29544 @subsubheading Synopsis
29547 -trace-frame-collected
29548 [--var-print-values @var{var_pval}]
29549 [--comp-print-values @var{comp_pval}]
29550 [--registers-format @var{regformat}]
29551 [--memory-contents]
29554 This command returns the set of collected objects, register names,
29555 trace state variable names, memory ranges and computed expressions
29556 that have been collected at a particular trace frame. The optional
29557 parameters to the command affect the output format in different ways.
29558 See the output description table below for more details.
29560 The reported names can be used in the normal manner to create
29561 varobjs and inspect the objects themselves. The items returned by
29562 this command are categorized so that it is clear which is a variable,
29563 which is a register, which is a trace state variable, which is a
29564 memory range and which is a computed expression.
29566 For instance, if the actions were
29568 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
29569 collect *(int*)0xaf02bef0@@40
29573 the object collected in its entirety would be @code{myVar}. The
29574 object @code{myArray} would be partially collected, because only the
29575 element at index @code{myIndex} would be collected. The remaining
29576 objects would be computed expressions.
29578 An example output would be:
29582 -trace-frame-collected
29584 explicit-variables=[@{name="myVar",value="1"@}],
29585 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
29586 @{name="myObj.field",value="0"@},
29587 @{name="myPtr->field",value="1"@},
29588 @{name="myCount + 2",value="3"@},
29589 @{name="$tvar1 + 1",value="43970027"@}],
29590 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
29591 @{number="1",value="0x0"@},
29592 @{number="2",value="0x4"@},
29594 @{number="125",value="0x0"@}],
29595 tvars=[@{name="$tvar1",current="43970026"@}],
29596 memory=[@{address="0x0000000000602264",length="4"@},
29597 @{address="0x0000000000615bc0",length="4"@}]
29604 @item explicit-variables
29605 The set of objects that have been collected in their entirety (as
29606 opposed to collecting just a few elements of an array or a few struct
29607 members). For each object, its name and value are printed.
29608 The @code{--var-print-values} option affects how or whether the value
29609 field is output. If @var{var_pval} is 0, then print only the names;
29610 if it is 1, print also their values; and if it is 2, print the name,
29611 type and value for simple data types, and the name and type for
29612 arrays, structures and unions.
29614 @item computed-expressions
29615 The set of computed expressions that have been collected at the
29616 current trace frame. The @code{--comp-print-values} option affects
29617 this set like the @code{--var-print-values} option affects the
29618 @code{explicit-variables} set. See above.
29621 The registers that have been collected at the current trace frame.
29622 For each register collected, the name and current value are returned.
29623 The value is formatted according to the @code{--registers-format}
29624 option. See the @command{-data-list-register-values} command for a
29625 list of the allowed formats. The default is @samp{x}.
29628 The trace state variables that have been collected at the current
29629 trace frame. For each trace state variable collected, the name and
29630 current value are returned.
29633 The set of memory ranges that have been collected at the current trace
29634 frame. Its content is a list of tuples. Each tuple represents a
29635 collected memory range and has the following fields:
29639 The start address of the memory range, as hexadecimal literal.
29642 The length of the memory range, as decimal literal.
29645 The contents of the memory block, in hex. This field is only present
29646 if the @code{--memory-contents} option is specified.
29652 @subsubheading @value{GDBN} Command
29654 There is no corresponding @value{GDBN} command.
29656 @subsubheading Example
29658 @subheading -trace-list-variables
29659 @findex -trace-list-variables
29661 @subsubheading Synopsis
29664 -trace-list-variables
29667 Return a table of all defined trace variables. Each element of the
29668 table has the following fields:
29672 The name of the trace variable. This field is always present.
29675 The initial value. This is a 64-bit signed integer. This
29676 field is always present.
29679 The value the trace variable has at the moment. This is a 64-bit
29680 signed integer. This field is absent iff current value is
29681 not defined, for example if the trace was never run, or is
29686 @subsubheading @value{GDBN} Command
29688 The corresponding @value{GDBN} command is @samp{tvariables}.
29690 @subsubheading Example
29694 -trace-list-variables
29695 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
29696 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
29697 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
29698 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
29699 body=[variable=@{name="$trace_timestamp",initial="0"@}
29700 variable=@{name="$foo",initial="10",current="15"@}]@}
29704 @subheading -trace-save
29705 @findex -trace-save
29707 @subsubheading Synopsis
29710 -trace-save [-r ] @var{filename}
29713 Saves the collected trace data to @var{filename}. Without the
29714 @samp{-r} option, the data is downloaded from the target and saved
29715 in a local file. With the @samp{-r} option the target is asked
29716 to perform the save.
29718 @subsubheading @value{GDBN} Command
29720 The corresponding @value{GDBN} command is @samp{tsave}.
29723 @subheading -trace-start
29724 @findex -trace-start
29726 @subsubheading Synopsis
29732 Starts a tracing experiments. The result of this command does not
29735 @subsubheading @value{GDBN} Command
29737 The corresponding @value{GDBN} command is @samp{tstart}.
29739 @subheading -trace-status
29740 @findex -trace-status
29742 @subsubheading Synopsis
29748 Obtains the status of a tracing experiment. The result may include
29749 the following fields:
29754 May have a value of either @samp{0}, when no tracing operations are
29755 supported, @samp{1}, when all tracing operations are supported, or
29756 @samp{file} when examining trace file. In the latter case, examining
29757 of trace frame is possible but new tracing experiement cannot be
29758 started. This field is always present.
29761 May have a value of either @samp{0} or @samp{1} depending on whether
29762 tracing experiement is in progress on target. This field is present
29763 if @samp{supported} field is not @samp{0}.
29766 Report the reason why the tracing was stopped last time. This field
29767 may be absent iff tracing was never stopped on target yet. The
29768 value of @samp{request} means the tracing was stopped as result of
29769 the @code{-trace-stop} command. The value of @samp{overflow} means
29770 the tracing buffer is full. The value of @samp{disconnection} means
29771 tracing was automatically stopped when @value{GDBN} has disconnected.
29772 The value of @samp{passcount} means tracing was stopped when a
29773 tracepoint was passed a maximal number of times for that tracepoint.
29774 This field is present if @samp{supported} field is not @samp{0}.
29776 @item stopping-tracepoint
29777 The number of tracepoint whose passcount as exceeded. This field is
29778 present iff the @samp{stop-reason} field has the value of
29782 @itemx frames-created
29783 The @samp{frames} field is a count of the total number of trace frames
29784 in the trace buffer, while @samp{frames-created} is the total created
29785 during the run, including ones that were discarded, such as when a
29786 circular trace buffer filled up. Both fields are optional.
29790 These fields tell the current size of the tracing buffer and the
29791 remaining space. These fields are optional.
29794 The value of the circular trace buffer flag. @code{1} means that the
29795 trace buffer is circular and old trace frames will be discarded if
29796 necessary to make room, @code{0} means that the trace buffer is linear
29800 The value of the disconnected tracing flag. @code{1} means that
29801 tracing will continue after @value{GDBN} disconnects, @code{0} means
29802 that the trace run will stop.
29805 The filename of the trace file being examined. This field is
29806 optional, and only present when examining a trace file.
29810 @subsubheading @value{GDBN} Command
29812 The corresponding @value{GDBN} command is @samp{tstatus}.
29814 @subheading -trace-stop
29815 @findex -trace-stop
29817 @subsubheading Synopsis
29823 Stops a tracing experiment. The result of this command has the same
29824 fields as @code{-trace-status}, except that the @samp{supported} and
29825 @samp{running} fields are not output.
29827 @subsubheading @value{GDBN} Command
29829 The corresponding @value{GDBN} command is @samp{tstop}.
29832 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29833 @node GDB/MI Symbol Query
29834 @section @sc{gdb/mi} Symbol Query Commands
29838 @subheading The @code{-symbol-info-address} Command
29839 @findex -symbol-info-address
29841 @subsubheading Synopsis
29844 -symbol-info-address @var{symbol}
29847 Describe where @var{symbol} is stored.
29849 @subsubheading @value{GDBN} Command
29851 The corresponding @value{GDBN} command is @samp{info address}.
29853 @subsubheading Example
29857 @subheading The @code{-symbol-info-file} Command
29858 @findex -symbol-info-file
29860 @subsubheading Synopsis
29866 Show the file for the symbol.
29868 @subsubheading @value{GDBN} Command
29870 There's no equivalent @value{GDBN} command. @code{gdbtk} has
29871 @samp{gdb_find_file}.
29873 @subsubheading Example
29877 @subheading The @code{-symbol-info-function} Command
29878 @findex -symbol-info-function
29880 @subsubheading Synopsis
29883 -symbol-info-function
29886 Show which function the symbol lives in.
29888 @subsubheading @value{GDBN} Command
29890 @samp{gdb_get_function} in @code{gdbtk}.
29892 @subsubheading Example
29896 @subheading The @code{-symbol-info-line} Command
29897 @findex -symbol-info-line
29899 @subsubheading Synopsis
29905 Show the core addresses of the code for a source line.
29907 @subsubheading @value{GDBN} Command
29909 The corresponding @value{GDBN} command is @samp{info line}.
29910 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
29912 @subsubheading Example
29916 @subheading The @code{-symbol-info-symbol} Command
29917 @findex -symbol-info-symbol
29919 @subsubheading Synopsis
29922 -symbol-info-symbol @var{addr}
29925 Describe what symbol is at location @var{addr}.
29927 @subsubheading @value{GDBN} Command
29929 The corresponding @value{GDBN} command is @samp{info symbol}.
29931 @subsubheading Example
29935 @subheading The @code{-symbol-list-functions} Command
29936 @findex -symbol-list-functions
29938 @subsubheading Synopsis
29941 -symbol-list-functions
29944 List the functions in the executable.
29946 @subsubheading @value{GDBN} Command
29948 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
29949 @samp{gdb_search} in @code{gdbtk}.
29951 @subsubheading Example
29956 @subheading The @code{-symbol-list-lines} Command
29957 @findex -symbol-list-lines
29959 @subsubheading Synopsis
29962 -symbol-list-lines @var{filename}
29965 Print the list of lines that contain code and their associated program
29966 addresses for the given source filename. The entries are sorted in
29967 ascending PC order.
29969 @subsubheading @value{GDBN} Command
29971 There is no corresponding @value{GDBN} command.
29973 @subsubheading Example
29976 -symbol-list-lines basics.c
29977 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
29983 @subheading The @code{-symbol-list-types} Command
29984 @findex -symbol-list-types
29986 @subsubheading Synopsis
29992 List all the type names.
29994 @subsubheading @value{GDBN} Command
29996 The corresponding commands are @samp{info types} in @value{GDBN},
29997 @samp{gdb_search} in @code{gdbtk}.
29999 @subsubheading Example
30003 @subheading The @code{-symbol-list-variables} Command
30004 @findex -symbol-list-variables
30006 @subsubheading Synopsis
30009 -symbol-list-variables
30012 List all the global and static variable names.
30014 @subsubheading @value{GDBN} Command
30016 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
30018 @subsubheading Example
30022 @subheading The @code{-symbol-locate} Command
30023 @findex -symbol-locate
30025 @subsubheading Synopsis
30031 @subsubheading @value{GDBN} Command
30033 @samp{gdb_loc} in @code{gdbtk}.
30035 @subsubheading Example
30039 @subheading The @code{-symbol-type} Command
30040 @findex -symbol-type
30042 @subsubheading Synopsis
30045 -symbol-type @var{variable}
30048 Show type of @var{variable}.
30050 @subsubheading @value{GDBN} Command
30052 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
30053 @samp{gdb_obj_variable}.
30055 @subsubheading Example
30060 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30061 @node GDB/MI File Commands
30062 @section @sc{gdb/mi} File Commands
30064 This section describes the GDB/MI commands to specify executable file names
30065 and to read in and obtain symbol table information.
30067 @subheading The @code{-file-exec-and-symbols} Command
30068 @findex -file-exec-and-symbols
30070 @subsubheading Synopsis
30073 -file-exec-and-symbols @var{file}
30076 Specify the executable file to be debugged. This file is the one from
30077 which the symbol table is also read. If no file is specified, the
30078 command clears the executable and symbol information. If breakpoints
30079 are set when using this command with no arguments, @value{GDBN} will produce
30080 error messages. Otherwise, no output is produced, except a completion
30083 @subsubheading @value{GDBN} Command
30085 The corresponding @value{GDBN} command is @samp{file}.
30087 @subsubheading Example
30091 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30097 @subheading The @code{-file-exec-file} Command
30098 @findex -file-exec-file
30100 @subsubheading Synopsis
30103 -file-exec-file @var{file}
30106 Specify the executable file to be debugged. Unlike
30107 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
30108 from this file. If used without argument, @value{GDBN} clears the information
30109 about the executable file. No output is produced, except a completion
30112 @subsubheading @value{GDBN} Command
30114 The corresponding @value{GDBN} command is @samp{exec-file}.
30116 @subsubheading Example
30120 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30127 @subheading The @code{-file-list-exec-sections} Command
30128 @findex -file-list-exec-sections
30130 @subsubheading Synopsis
30133 -file-list-exec-sections
30136 List the sections of the current executable file.
30138 @subsubheading @value{GDBN} Command
30140 The @value{GDBN} command @samp{info file} shows, among the rest, the same
30141 information as this command. @code{gdbtk} has a corresponding command
30142 @samp{gdb_load_info}.
30144 @subsubheading Example
30149 @subheading The @code{-file-list-exec-source-file} Command
30150 @findex -file-list-exec-source-file
30152 @subsubheading Synopsis
30155 -file-list-exec-source-file
30158 List the line number, the current source file, and the absolute path
30159 to the current source file for the current executable. The macro
30160 information field has a value of @samp{1} or @samp{0} depending on
30161 whether or not the file includes preprocessor macro information.
30163 @subsubheading @value{GDBN} Command
30165 The @value{GDBN} equivalent is @samp{info source}
30167 @subsubheading Example
30171 123-file-list-exec-source-file
30172 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
30177 @subheading The @code{-file-list-exec-source-files} Command
30178 @findex -file-list-exec-source-files
30180 @subsubheading Synopsis
30183 -file-list-exec-source-files
30186 List the source files for the current executable.
30188 It will always output both the filename and fullname (absolute file
30189 name) of a source file.
30191 @subsubheading @value{GDBN} Command
30193 The @value{GDBN} equivalent is @samp{info sources}.
30194 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
30196 @subsubheading Example
30199 -file-list-exec-source-files
30201 @{file=foo.c,fullname=/home/foo.c@},
30202 @{file=/home/bar.c,fullname=/home/bar.c@},
30203 @{file=gdb_could_not_find_fullpath.c@}]
30208 @subheading The @code{-file-list-shared-libraries} Command
30209 @findex -file-list-shared-libraries
30211 @subsubheading Synopsis
30214 -file-list-shared-libraries
30217 List the shared libraries in the program.
30219 @subsubheading @value{GDBN} Command
30221 The corresponding @value{GDBN} command is @samp{info shared}.
30223 @subsubheading Example
30227 @subheading The @code{-file-list-symbol-files} Command
30228 @findex -file-list-symbol-files
30230 @subsubheading Synopsis
30233 -file-list-symbol-files
30238 @subsubheading @value{GDBN} Command
30240 The corresponding @value{GDBN} command is @samp{info file} (part of it).
30242 @subsubheading Example
30247 @subheading The @code{-file-symbol-file} Command
30248 @findex -file-symbol-file
30250 @subsubheading Synopsis
30253 -file-symbol-file @var{file}
30256 Read symbol table info from the specified @var{file} argument. When
30257 used without arguments, clears @value{GDBN}'s symbol table info. No output is
30258 produced, except for a completion notification.
30260 @subsubheading @value{GDBN} Command
30262 The corresponding @value{GDBN} command is @samp{symbol-file}.
30264 @subsubheading Example
30268 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30274 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30275 @node GDB/MI Memory Overlay Commands
30276 @section @sc{gdb/mi} Memory Overlay Commands
30278 The memory overlay commands are not implemented.
30280 @c @subheading -overlay-auto
30282 @c @subheading -overlay-list-mapping-state
30284 @c @subheading -overlay-list-overlays
30286 @c @subheading -overlay-map
30288 @c @subheading -overlay-off
30290 @c @subheading -overlay-on
30292 @c @subheading -overlay-unmap
30294 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30295 @node GDB/MI Signal Handling Commands
30296 @section @sc{gdb/mi} Signal Handling Commands
30298 Signal handling commands are not implemented.
30300 @c @subheading -signal-handle
30302 @c @subheading -signal-list-handle-actions
30304 @c @subheading -signal-list-signal-types
30308 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30309 @node GDB/MI Target Manipulation
30310 @section @sc{gdb/mi} Target Manipulation Commands
30313 @subheading The @code{-target-attach} Command
30314 @findex -target-attach
30316 @subsubheading Synopsis
30319 -target-attach @var{pid} | @var{gid} | @var{file}
30322 Attach to a process @var{pid} or a file @var{file} outside of
30323 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
30324 group, the id previously returned by
30325 @samp{-list-thread-groups --available} must be used.
30327 @subsubheading @value{GDBN} Command
30329 The corresponding @value{GDBN} command is @samp{attach}.
30331 @subsubheading Example
30335 =thread-created,id="1"
30336 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
30342 @subheading The @code{-target-compare-sections} Command
30343 @findex -target-compare-sections
30345 @subsubheading Synopsis
30348 -target-compare-sections [ @var{section} ]
30351 Compare data of section @var{section} on target to the exec file.
30352 Without the argument, all sections are compared.
30354 @subsubheading @value{GDBN} Command
30356 The @value{GDBN} equivalent is @samp{compare-sections}.
30358 @subsubheading Example
30363 @subheading The @code{-target-detach} Command
30364 @findex -target-detach
30366 @subsubheading Synopsis
30369 -target-detach [ @var{pid} | @var{gid} ]
30372 Detach from the remote target which normally resumes its execution.
30373 If either @var{pid} or @var{gid} is specified, detaches from either
30374 the specified process, or specified thread group. There's no output.
30376 @subsubheading @value{GDBN} Command
30378 The corresponding @value{GDBN} command is @samp{detach}.
30380 @subsubheading Example
30390 @subheading The @code{-target-disconnect} Command
30391 @findex -target-disconnect
30393 @subsubheading Synopsis
30399 Disconnect from the remote target. There's no output and the target is
30400 generally not resumed.
30402 @subsubheading @value{GDBN} Command
30404 The corresponding @value{GDBN} command is @samp{disconnect}.
30406 @subsubheading Example
30416 @subheading The @code{-target-download} Command
30417 @findex -target-download
30419 @subsubheading Synopsis
30425 Loads the executable onto the remote target.
30426 It prints out an update message every half second, which includes the fields:
30430 The name of the section.
30432 The size of what has been sent so far for that section.
30434 The size of the section.
30436 The total size of what was sent so far (the current and the previous sections).
30438 The size of the overall executable to download.
30442 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
30443 @sc{gdb/mi} Output Syntax}).
30445 In addition, it prints the name and size of the sections, as they are
30446 downloaded. These messages include the following fields:
30450 The name of the section.
30452 The size of the section.
30454 The size of the overall executable to download.
30458 At the end, a summary is printed.
30460 @subsubheading @value{GDBN} Command
30462 The corresponding @value{GDBN} command is @samp{load}.
30464 @subsubheading Example
30466 Note: each status message appears on a single line. Here the messages
30467 have been broken down so that they can fit onto a page.
30472 +download,@{section=".text",section-size="6668",total-size="9880"@}
30473 +download,@{section=".text",section-sent="512",section-size="6668",
30474 total-sent="512",total-size="9880"@}
30475 +download,@{section=".text",section-sent="1024",section-size="6668",
30476 total-sent="1024",total-size="9880"@}
30477 +download,@{section=".text",section-sent="1536",section-size="6668",
30478 total-sent="1536",total-size="9880"@}
30479 +download,@{section=".text",section-sent="2048",section-size="6668",
30480 total-sent="2048",total-size="9880"@}
30481 +download,@{section=".text",section-sent="2560",section-size="6668",
30482 total-sent="2560",total-size="9880"@}
30483 +download,@{section=".text",section-sent="3072",section-size="6668",
30484 total-sent="3072",total-size="9880"@}
30485 +download,@{section=".text",section-sent="3584",section-size="6668",
30486 total-sent="3584",total-size="9880"@}
30487 +download,@{section=".text",section-sent="4096",section-size="6668",
30488 total-sent="4096",total-size="9880"@}
30489 +download,@{section=".text",section-sent="4608",section-size="6668",
30490 total-sent="4608",total-size="9880"@}
30491 +download,@{section=".text",section-sent="5120",section-size="6668",
30492 total-sent="5120",total-size="9880"@}
30493 +download,@{section=".text",section-sent="5632",section-size="6668",
30494 total-sent="5632",total-size="9880"@}
30495 +download,@{section=".text",section-sent="6144",section-size="6668",
30496 total-sent="6144",total-size="9880"@}
30497 +download,@{section=".text",section-sent="6656",section-size="6668",
30498 total-sent="6656",total-size="9880"@}
30499 +download,@{section=".init",section-size="28",total-size="9880"@}
30500 +download,@{section=".fini",section-size="28",total-size="9880"@}
30501 +download,@{section=".data",section-size="3156",total-size="9880"@}
30502 +download,@{section=".data",section-sent="512",section-size="3156",
30503 total-sent="7236",total-size="9880"@}
30504 +download,@{section=".data",section-sent="1024",section-size="3156",
30505 total-sent="7748",total-size="9880"@}
30506 +download,@{section=".data",section-sent="1536",section-size="3156",
30507 total-sent="8260",total-size="9880"@}
30508 +download,@{section=".data",section-sent="2048",section-size="3156",
30509 total-sent="8772",total-size="9880"@}
30510 +download,@{section=".data",section-sent="2560",section-size="3156",
30511 total-sent="9284",total-size="9880"@}
30512 +download,@{section=".data",section-sent="3072",section-size="3156",
30513 total-sent="9796",total-size="9880"@}
30514 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
30521 @subheading The @code{-target-exec-status} Command
30522 @findex -target-exec-status
30524 @subsubheading Synopsis
30527 -target-exec-status
30530 Provide information on the state of the target (whether it is running or
30531 not, for instance).
30533 @subsubheading @value{GDBN} Command
30535 There's no equivalent @value{GDBN} command.
30537 @subsubheading Example
30541 @subheading The @code{-target-list-available-targets} Command
30542 @findex -target-list-available-targets
30544 @subsubheading Synopsis
30547 -target-list-available-targets
30550 List the possible targets to connect to.
30552 @subsubheading @value{GDBN} Command
30554 The corresponding @value{GDBN} command is @samp{help target}.
30556 @subsubheading Example
30560 @subheading The @code{-target-list-current-targets} Command
30561 @findex -target-list-current-targets
30563 @subsubheading Synopsis
30566 -target-list-current-targets
30569 Describe the current target.
30571 @subsubheading @value{GDBN} Command
30573 The corresponding information is printed by @samp{info file} (among
30576 @subsubheading Example
30580 @subheading The @code{-target-list-parameters} Command
30581 @findex -target-list-parameters
30583 @subsubheading Synopsis
30586 -target-list-parameters
30592 @subsubheading @value{GDBN} Command
30596 @subsubheading Example
30600 @subheading The @code{-target-select} Command
30601 @findex -target-select
30603 @subsubheading Synopsis
30606 -target-select @var{type} @var{parameters @dots{}}
30609 Connect @value{GDBN} to the remote target. This command takes two args:
30613 The type of target, for instance @samp{remote}, etc.
30614 @item @var{parameters}
30615 Device names, host names and the like. @xref{Target Commands, ,
30616 Commands for Managing Targets}, for more details.
30619 The output is a connection notification, followed by the address at
30620 which the target program is, in the following form:
30623 ^connected,addr="@var{address}",func="@var{function name}",
30624 args=[@var{arg list}]
30627 @subsubheading @value{GDBN} Command
30629 The corresponding @value{GDBN} command is @samp{target}.
30631 @subsubheading Example
30635 -target-select remote /dev/ttya
30636 ^connected,addr="0xfe00a300",func="??",args=[]
30640 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30641 @node GDB/MI File Transfer Commands
30642 @section @sc{gdb/mi} File Transfer Commands
30645 @subheading The @code{-target-file-put} Command
30646 @findex -target-file-put
30648 @subsubheading Synopsis
30651 -target-file-put @var{hostfile} @var{targetfile}
30654 Copy file @var{hostfile} from the host system (the machine running
30655 @value{GDBN}) to @var{targetfile} on the target system.
30657 @subsubheading @value{GDBN} Command
30659 The corresponding @value{GDBN} command is @samp{remote put}.
30661 @subsubheading Example
30665 -target-file-put localfile remotefile
30671 @subheading The @code{-target-file-get} Command
30672 @findex -target-file-get
30674 @subsubheading Synopsis
30677 -target-file-get @var{targetfile} @var{hostfile}
30680 Copy file @var{targetfile} from the target system to @var{hostfile}
30681 on the host system.
30683 @subsubheading @value{GDBN} Command
30685 The corresponding @value{GDBN} command is @samp{remote get}.
30687 @subsubheading Example
30691 -target-file-get remotefile localfile
30697 @subheading The @code{-target-file-delete} Command
30698 @findex -target-file-delete
30700 @subsubheading Synopsis
30703 -target-file-delete @var{targetfile}
30706 Delete @var{targetfile} from the target system.
30708 @subsubheading @value{GDBN} Command
30710 The corresponding @value{GDBN} command is @samp{remote delete}.
30712 @subsubheading Example
30716 -target-file-delete remotefile
30722 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30723 @node GDB/MI Ada Exceptions Commands
30724 @section Ada Exceptions @sc{gdb/mi} Commands
30726 @subheading The @code{-info-ada-exceptions} Command
30727 @findex -info-ada-exceptions
30729 @subsubheading Synopsis
30732 -info-ada-exceptions [ @var{regexp}]
30735 List all Ada exceptions defined within the program being debugged.
30736 With a regular expression @var{regexp}, only those exceptions whose
30737 names match @var{regexp} are listed.
30739 @subsubheading @value{GDBN} Command
30741 The corresponding @value{GDBN} command is @samp{info exceptions}.
30743 @subsubheading Result
30745 The result is a table of Ada exceptions. The following columns are
30746 defined for each exception:
30750 The name of the exception.
30753 The address of the exception.
30757 @subsubheading Example
30760 -info-ada-exceptions aint
30761 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
30762 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
30763 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
30764 body=[@{name="constraint_error",address="0x0000000000613da0"@},
30765 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
30768 @subheading Catching Ada Exceptions
30770 The commands describing how to ask @value{GDBN} to stop when a program
30771 raises an exception are described at @ref{Ada Exception GDB/MI
30772 Catchpoint Commands}.
30775 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30776 @node GDB/MI Support Commands
30777 @section @sc{gdb/mi} Support Commands
30779 Since new commands and features get regularly added to @sc{gdb/mi},
30780 some commands are available to help front-ends query the debugger
30781 about support for these capabilities. Similarly, it is also possible
30782 to query @value{GDBN} about target support of certain features.
30784 @subheading The @code{-info-gdb-mi-command} Command
30785 @cindex @code{-info-gdb-mi-command}
30786 @findex -info-gdb-mi-command
30788 @subsubheading Synopsis
30791 -info-gdb-mi-command @var{cmd_name}
30794 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
30796 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
30797 is technically not part of the command name (@pxref{GDB/MI Input
30798 Syntax}), and thus should be omitted in @var{cmd_name}. However,
30799 for ease of use, this command also accepts the form with the leading
30802 @subsubheading @value{GDBN} Command
30804 There is no corresponding @value{GDBN} command.
30806 @subsubheading Result
30808 The result is a tuple. There is currently only one field:
30812 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
30813 @code{"false"} otherwise.
30817 @subsubheading Example
30819 Here is an example where the @sc{gdb/mi} command does not exist:
30822 -info-gdb-mi-command unsupported-command
30823 ^done,command=@{exists="false"@}
30827 And here is an example where the @sc{gdb/mi} command is known
30831 -info-gdb-mi-command symbol-list-lines
30832 ^done,command=@{exists="true"@}
30835 @subheading The @code{-list-features} Command
30836 @findex -list-features
30837 @cindex supported @sc{gdb/mi} features, list
30839 Returns a list of particular features of the MI protocol that
30840 this version of gdb implements. A feature can be a command,
30841 or a new field in an output of some command, or even an
30842 important bugfix. While a frontend can sometimes detect presence
30843 of a feature at runtime, it is easier to perform detection at debugger
30846 The command returns a list of strings, with each string naming an
30847 available feature. Each returned string is just a name, it does not
30848 have any internal structure. The list of possible feature names
30854 (gdb) -list-features
30855 ^done,result=["feature1","feature2"]
30858 The current list of features is:
30861 @item frozen-varobjs
30862 Indicates support for the @code{-var-set-frozen} command, as well
30863 as possible presense of the @code{frozen} field in the output
30864 of @code{-varobj-create}.
30865 @item pending-breakpoints
30866 Indicates support for the @option{-f} option to the @code{-break-insert}
30869 Indicates Python scripting support, Python-based
30870 pretty-printing commands, and possible presence of the
30871 @samp{display_hint} field in the output of @code{-var-list-children}
30873 Indicates support for the @code{-thread-info} command.
30874 @item data-read-memory-bytes
30875 Indicates support for the @code{-data-read-memory-bytes} and the
30876 @code{-data-write-memory-bytes} commands.
30877 @item breakpoint-notifications
30878 Indicates that changes to breakpoints and breakpoints created via the
30879 CLI will be announced via async records.
30880 @item ada-task-info
30881 Indicates support for the @code{-ada-task-info} command.
30882 @item language-option
30883 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
30884 option (@pxref{Context management}).
30885 @item info-gdb-mi-command
30886 Indicates support for the @code{-info-gdb-mi-command} command.
30887 @item undefined-command-error-code
30888 Indicates support for the "undefined-command" error code in error result
30889 records, produced when trying to execute an undefined @sc{gdb/mi} command
30890 (@pxref{GDB/MI Result Records}).
30891 @item exec-run-start-option
30892 Indicates that the @code{-exec-run} command supports the @option{--start}
30893 option (@pxref{GDB/MI Program Execution}).
30896 @subheading The @code{-list-target-features} Command
30897 @findex -list-target-features
30899 Returns a list of particular features that are supported by the
30900 target. Those features affect the permitted MI commands, but
30901 unlike the features reported by the @code{-list-features} command, the
30902 features depend on which target GDB is using at the moment. Whenever
30903 a target can change, due to commands such as @code{-target-select},
30904 @code{-target-attach} or @code{-exec-run}, the list of target features
30905 may change, and the frontend should obtain it again.
30909 (gdb) -list-target-features
30910 ^done,result=["async"]
30913 The current list of features is:
30917 Indicates that the target is capable of asynchronous command
30918 execution, which means that @value{GDBN} will accept further commands
30919 while the target is running.
30922 Indicates that the target is capable of reverse execution.
30923 @xref{Reverse Execution}, for more information.
30927 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30928 @node GDB/MI Miscellaneous Commands
30929 @section Miscellaneous @sc{gdb/mi} Commands
30931 @c @subheading -gdb-complete
30933 @subheading The @code{-gdb-exit} Command
30936 @subsubheading Synopsis
30942 Exit @value{GDBN} immediately.
30944 @subsubheading @value{GDBN} Command
30946 Approximately corresponds to @samp{quit}.
30948 @subsubheading Example
30958 @subheading The @code{-exec-abort} Command
30959 @findex -exec-abort
30961 @subsubheading Synopsis
30967 Kill the inferior running program.
30969 @subsubheading @value{GDBN} Command
30971 The corresponding @value{GDBN} command is @samp{kill}.
30973 @subsubheading Example
30978 @subheading The @code{-gdb-set} Command
30981 @subsubheading Synopsis
30987 Set an internal @value{GDBN} variable.
30988 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
30990 @subsubheading @value{GDBN} Command
30992 The corresponding @value{GDBN} command is @samp{set}.
30994 @subsubheading Example
31004 @subheading The @code{-gdb-show} Command
31007 @subsubheading Synopsis
31013 Show the current value of a @value{GDBN} variable.
31015 @subsubheading @value{GDBN} Command
31017 The corresponding @value{GDBN} command is @samp{show}.
31019 @subsubheading Example
31028 @c @subheading -gdb-source
31031 @subheading The @code{-gdb-version} Command
31032 @findex -gdb-version
31034 @subsubheading Synopsis
31040 Show version information for @value{GDBN}. Used mostly in testing.
31042 @subsubheading @value{GDBN} Command
31044 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
31045 default shows this information when you start an interactive session.
31047 @subsubheading Example
31049 @c This example modifies the actual output from GDB to avoid overfull
31055 ~Copyright 2000 Free Software Foundation, Inc.
31056 ~GDB is free software, covered by the GNU General Public License, and
31057 ~you are welcome to change it and/or distribute copies of it under
31058 ~ certain conditions.
31059 ~Type "show copying" to see the conditions.
31060 ~There is absolutely no warranty for GDB. Type "show warranty" for
31062 ~This GDB was configured as
31063 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
31068 @subheading The @code{-list-thread-groups} Command
31069 @findex -list-thread-groups
31071 @subheading Synopsis
31074 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
31077 Lists thread groups (@pxref{Thread groups}). When a single thread
31078 group is passed as the argument, lists the children of that group.
31079 When several thread group are passed, lists information about those
31080 thread groups. Without any parameters, lists information about all
31081 top-level thread groups.
31083 Normally, thread groups that are being debugged are reported.
31084 With the @samp{--available} option, @value{GDBN} reports thread groups
31085 available on the target.
31087 The output of this command may have either a @samp{threads} result or
31088 a @samp{groups} result. The @samp{thread} result has a list of tuples
31089 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
31090 Information}). The @samp{groups} result has a list of tuples as value,
31091 each tuple describing a thread group. If top-level groups are
31092 requested (that is, no parameter is passed), or when several groups
31093 are passed, the output always has a @samp{groups} result. The format
31094 of the @samp{group} result is described below.
31096 To reduce the number of roundtrips it's possible to list thread groups
31097 together with their children, by passing the @samp{--recurse} option
31098 and the recursion depth. Presently, only recursion depth of 1 is
31099 permitted. If this option is present, then every reported thread group
31100 will also include its children, either as @samp{group} or
31101 @samp{threads} field.
31103 In general, any combination of option and parameters is permitted, with
31104 the following caveats:
31108 When a single thread group is passed, the output will typically
31109 be the @samp{threads} result. Because threads may not contain
31110 anything, the @samp{recurse} option will be ignored.
31113 When the @samp{--available} option is passed, limited information may
31114 be available. In particular, the list of threads of a process might
31115 be inaccessible. Further, specifying specific thread groups might
31116 not give any performance advantage over listing all thread groups.
31117 The frontend should assume that @samp{-list-thread-groups --available}
31118 is always an expensive operation and cache the results.
31122 The @samp{groups} result is a list of tuples, where each tuple may
31123 have the following fields:
31127 Identifier of the thread group. This field is always present.
31128 The identifier is an opaque string; frontends should not try to
31129 convert it to an integer, even though it might look like one.
31132 The type of the thread group. At present, only @samp{process} is a
31136 The target-specific process identifier. This field is only present
31137 for thread groups of type @samp{process} and only if the process exists.
31140 The number of children this thread group has. This field may be
31141 absent for an available thread group.
31144 This field has a list of tuples as value, each tuple describing a
31145 thread. It may be present if the @samp{--recurse} option is
31146 specified, and it's actually possible to obtain the threads.
31149 This field is a list of integers, each identifying a core that one
31150 thread of the group is running on. This field may be absent if
31151 such information is not available.
31154 The name of the executable file that corresponds to this thread group.
31155 The field is only present for thread groups of type @samp{process},
31156 and only if there is a corresponding executable file.
31160 @subheading Example
31164 -list-thread-groups
31165 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
31166 -list-thread-groups 17
31167 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31168 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
31169 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31170 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
31171 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
31172 -list-thread-groups --available
31173 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
31174 -list-thread-groups --available --recurse 1
31175 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31176 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31177 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
31178 -list-thread-groups --available --recurse 1 17 18
31179 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31180 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31181 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
31184 @subheading The @code{-info-os} Command
31187 @subsubheading Synopsis
31190 -info-os [ @var{type} ]
31193 If no argument is supplied, the command returns a table of available
31194 operating-system-specific information types. If one of these types is
31195 supplied as an argument @var{type}, then the command returns a table
31196 of data of that type.
31198 The types of information available depend on the target operating
31201 @subsubheading @value{GDBN} Command
31203 The corresponding @value{GDBN} command is @samp{info os}.
31205 @subsubheading Example
31207 When run on a @sc{gnu}/Linux system, the output will look something
31213 ^done,OSDataTable=@{nr_rows="9",nr_cols="3",
31214 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
31215 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
31216 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
31217 body=[item=@{col0="processes",col1="Listing of all processes",
31218 col2="Processes"@},
31219 item=@{col0="procgroups",col1="Listing of all process groups",
31220 col2="Process groups"@},
31221 item=@{col0="threads",col1="Listing of all threads",
31223 item=@{col0="files",col1="Listing of all file descriptors",
31224 col2="File descriptors"@},
31225 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
31227 item=@{col0="shm",col1="Listing of all shared-memory regions",
31228 col2="Shared-memory regions"@},
31229 item=@{col0="semaphores",col1="Listing of all semaphores",
31230 col2="Semaphores"@},
31231 item=@{col0="msg",col1="Listing of all message queues",
31232 col2="Message queues"@},
31233 item=@{col0="modules",col1="Listing of all loaded kernel modules",
31234 col2="Kernel modules"@}]@}
31237 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
31238 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
31239 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
31240 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
31241 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
31242 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
31243 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
31244 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
31246 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
31247 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
31251 (Note that the MI output here includes a @code{"Title"} column that
31252 does not appear in command-line @code{info os}; this column is useful
31253 for MI clients that want to enumerate the types of data, such as in a
31254 popup menu, but is needless clutter on the command line, and
31255 @code{info os} omits it.)
31257 @subheading The @code{-add-inferior} Command
31258 @findex -add-inferior
31260 @subheading Synopsis
31266 Creates a new inferior (@pxref{Inferiors and Programs}). The created
31267 inferior is not associated with any executable. Such association may
31268 be established with the @samp{-file-exec-and-symbols} command
31269 (@pxref{GDB/MI File Commands}). The command response has a single
31270 field, @samp{inferior}, whose value is the identifier of the
31271 thread group corresponding to the new inferior.
31273 @subheading Example
31278 ^done,inferior="i3"
31281 @subheading The @code{-interpreter-exec} Command
31282 @findex -interpreter-exec
31284 @subheading Synopsis
31287 -interpreter-exec @var{interpreter} @var{command}
31289 @anchor{-interpreter-exec}
31291 Execute the specified @var{command} in the given @var{interpreter}.
31293 @subheading @value{GDBN} Command
31295 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
31297 @subheading Example
31301 -interpreter-exec console "break main"
31302 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
31303 &"During symbol reading, bad structure-type format.\n"
31304 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
31309 @subheading The @code{-inferior-tty-set} Command
31310 @findex -inferior-tty-set
31312 @subheading Synopsis
31315 -inferior-tty-set /dev/pts/1
31318 Set terminal for future runs of the program being debugged.
31320 @subheading @value{GDBN} Command
31322 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
31324 @subheading Example
31328 -inferior-tty-set /dev/pts/1
31333 @subheading The @code{-inferior-tty-show} Command
31334 @findex -inferior-tty-show
31336 @subheading Synopsis
31342 Show terminal for future runs of program being debugged.
31344 @subheading @value{GDBN} Command
31346 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
31348 @subheading Example
31352 -inferior-tty-set /dev/pts/1
31356 ^done,inferior_tty_terminal="/dev/pts/1"
31360 @subheading The @code{-enable-timings} Command
31361 @findex -enable-timings
31363 @subheading Synopsis
31366 -enable-timings [yes | no]
31369 Toggle the printing of the wallclock, user and system times for an MI
31370 command as a field in its output. This command is to help frontend
31371 developers optimize the performance of their code. No argument is
31372 equivalent to @samp{yes}.
31374 @subheading @value{GDBN} Command
31378 @subheading Example
31386 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31387 addr="0x080484ed",func="main",file="myprog.c",
31388 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
31390 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
31398 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
31399 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
31400 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
31401 fullname="/home/nickrob/myprog.c",line="73"@}
31406 @chapter @value{GDBN} Annotations
31408 This chapter describes annotations in @value{GDBN}. Annotations were
31409 designed to interface @value{GDBN} to graphical user interfaces or other
31410 similar programs which want to interact with @value{GDBN} at a
31411 relatively high level.
31413 The annotation mechanism has largely been superseded by @sc{gdb/mi}
31417 This is Edition @value{EDITION}, @value{DATE}.
31421 * Annotations Overview:: What annotations are; the general syntax.
31422 * Server Prefix:: Issuing a command without affecting user state.
31423 * Prompting:: Annotations marking @value{GDBN}'s need for input.
31424 * Errors:: Annotations for error messages.
31425 * Invalidation:: Some annotations describe things now invalid.
31426 * Annotations for Running::
31427 Whether the program is running, how it stopped, etc.
31428 * Source Annotations:: Annotations describing source code.
31431 @node Annotations Overview
31432 @section What is an Annotation?
31433 @cindex annotations
31435 Annotations start with a newline character, two @samp{control-z}
31436 characters, and the name of the annotation. If there is no additional
31437 information associated with this annotation, the name of the annotation
31438 is followed immediately by a newline. If there is additional
31439 information, the name of the annotation is followed by a space, the
31440 additional information, and a newline. The additional information
31441 cannot contain newline characters.
31443 Any output not beginning with a newline and two @samp{control-z}
31444 characters denotes literal output from @value{GDBN}. Currently there is
31445 no need for @value{GDBN} to output a newline followed by two
31446 @samp{control-z} characters, but if there was such a need, the
31447 annotations could be extended with an @samp{escape} annotation which
31448 means those three characters as output.
31450 The annotation @var{level}, which is specified using the
31451 @option{--annotate} command line option (@pxref{Mode Options}), controls
31452 how much information @value{GDBN} prints together with its prompt,
31453 values of expressions, source lines, and other types of output. Level 0
31454 is for no annotations, level 1 is for use when @value{GDBN} is run as a
31455 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
31456 for programs that control @value{GDBN}, and level 2 annotations have
31457 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
31458 Interface, annotate, GDB's Obsolete Annotations}).
31461 @kindex set annotate
31462 @item set annotate @var{level}
31463 The @value{GDBN} command @code{set annotate} sets the level of
31464 annotations to the specified @var{level}.
31466 @item show annotate
31467 @kindex show annotate
31468 Show the current annotation level.
31471 This chapter describes level 3 annotations.
31473 A simple example of starting up @value{GDBN} with annotations is:
31476 $ @kbd{gdb --annotate=3}
31478 Copyright 2003 Free Software Foundation, Inc.
31479 GDB is free software, covered by the GNU General Public License,
31480 and you are welcome to change it and/or distribute copies of it
31481 under certain conditions.
31482 Type "show copying" to see the conditions.
31483 There is absolutely no warranty for GDB. Type "show warranty"
31485 This GDB was configured as "i386-pc-linux-gnu"
31496 Here @samp{quit} is input to @value{GDBN}; the rest is output from
31497 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
31498 denotes a @samp{control-z} character) are annotations; the rest is
31499 output from @value{GDBN}.
31501 @node Server Prefix
31502 @section The Server Prefix
31503 @cindex server prefix
31505 If you prefix a command with @samp{server } then it will not affect
31506 the command history, nor will it affect @value{GDBN}'s notion of which
31507 command to repeat if @key{RET} is pressed on a line by itself. This
31508 means that commands can be run behind a user's back by a front-end in
31509 a transparent manner.
31511 The @code{server } prefix does not affect the recording of values into
31512 the value history; to print a value without recording it into the
31513 value history, use the @code{output} command instead of the
31514 @code{print} command.
31516 Using this prefix also disables confirmation requests
31517 (@pxref{confirmation requests}).
31520 @section Annotation for @value{GDBN} Input
31522 @cindex annotations for prompts
31523 When @value{GDBN} prompts for input, it annotates this fact so it is possible
31524 to know when to send output, when the output from a given command is
31527 Different kinds of input each have a different @dfn{input type}. Each
31528 input type has three annotations: a @code{pre-} annotation, which
31529 denotes the beginning of any prompt which is being output, a plain
31530 annotation, which denotes the end of the prompt, and then a @code{post-}
31531 annotation which denotes the end of any echo which may (or may not) be
31532 associated with the input. For example, the @code{prompt} input type
31533 features the following annotations:
31541 The input types are
31544 @findex pre-prompt annotation
31545 @findex prompt annotation
31546 @findex post-prompt annotation
31548 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
31550 @findex pre-commands annotation
31551 @findex commands annotation
31552 @findex post-commands annotation
31554 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
31555 command. The annotations are repeated for each command which is input.
31557 @findex pre-overload-choice annotation
31558 @findex overload-choice annotation
31559 @findex post-overload-choice annotation
31560 @item overload-choice
31561 When @value{GDBN} wants the user to select between various overloaded functions.
31563 @findex pre-query annotation
31564 @findex query annotation
31565 @findex post-query annotation
31567 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
31569 @findex pre-prompt-for-continue annotation
31570 @findex prompt-for-continue annotation
31571 @findex post-prompt-for-continue annotation
31572 @item prompt-for-continue
31573 When @value{GDBN} is asking the user to press return to continue. Note: Don't
31574 expect this to work well; instead use @code{set height 0} to disable
31575 prompting. This is because the counting of lines is buggy in the
31576 presence of annotations.
31581 @cindex annotations for errors, warnings and interrupts
31583 @findex quit annotation
31588 This annotation occurs right before @value{GDBN} responds to an interrupt.
31590 @findex error annotation
31595 This annotation occurs right before @value{GDBN} responds to an error.
31597 Quit and error annotations indicate that any annotations which @value{GDBN} was
31598 in the middle of may end abruptly. For example, if a
31599 @code{value-history-begin} annotation is followed by a @code{error}, one
31600 cannot expect to receive the matching @code{value-history-end}. One
31601 cannot expect not to receive it either, however; an error annotation
31602 does not necessarily mean that @value{GDBN} is immediately returning all the way
31605 @findex error-begin annotation
31606 A quit or error annotation may be preceded by
31612 Any output between that and the quit or error annotation is the error
31615 Warning messages are not yet annotated.
31616 @c If we want to change that, need to fix warning(), type_error(),
31617 @c range_error(), and possibly other places.
31620 @section Invalidation Notices
31622 @cindex annotations for invalidation messages
31623 The following annotations say that certain pieces of state may have
31627 @findex frames-invalid annotation
31628 @item ^Z^Zframes-invalid
31630 The frames (for example, output from the @code{backtrace} command) may
31633 @findex breakpoints-invalid annotation
31634 @item ^Z^Zbreakpoints-invalid
31636 The breakpoints may have changed. For example, the user just added or
31637 deleted a breakpoint.
31640 @node Annotations for Running
31641 @section Running the Program
31642 @cindex annotations for running programs
31644 @findex starting annotation
31645 @findex stopping annotation
31646 When the program starts executing due to a @value{GDBN} command such as
31647 @code{step} or @code{continue},
31653 is output. When the program stops,
31659 is output. Before the @code{stopped} annotation, a variety of
31660 annotations describe how the program stopped.
31663 @findex exited annotation
31664 @item ^Z^Zexited @var{exit-status}
31665 The program exited, and @var{exit-status} is the exit status (zero for
31666 successful exit, otherwise nonzero).
31668 @findex signalled annotation
31669 @findex signal-name annotation
31670 @findex signal-name-end annotation
31671 @findex signal-string annotation
31672 @findex signal-string-end annotation
31673 @item ^Z^Zsignalled
31674 The program exited with a signal. After the @code{^Z^Zsignalled}, the
31675 annotation continues:
31681 ^Z^Zsignal-name-end
31685 ^Z^Zsignal-string-end
31690 where @var{name} is the name of the signal, such as @code{SIGILL} or
31691 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
31692 as @code{Illegal Instruction} or @code{Segmentation fault}.
31693 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
31694 user's benefit and have no particular format.
31696 @findex signal annotation
31698 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
31699 just saying that the program received the signal, not that it was
31700 terminated with it.
31702 @findex breakpoint annotation
31703 @item ^Z^Zbreakpoint @var{number}
31704 The program hit breakpoint number @var{number}.
31706 @findex watchpoint annotation
31707 @item ^Z^Zwatchpoint @var{number}
31708 The program hit watchpoint number @var{number}.
31711 @node Source Annotations
31712 @section Displaying Source
31713 @cindex annotations for source display
31715 @findex source annotation
31716 The following annotation is used instead of displaying source code:
31719 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
31722 where @var{filename} is an absolute file name indicating which source
31723 file, @var{line} is the line number within that file (where 1 is the
31724 first line in the file), @var{character} is the character position
31725 within the file (where 0 is the first character in the file) (for most
31726 debug formats this will necessarily point to the beginning of a line),
31727 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
31728 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
31729 @var{addr} is the address in the target program associated with the
31730 source which is being displayed. @var{addr} is in the form @samp{0x}
31731 followed by one or more lowercase hex digits (note that this does not
31732 depend on the language).
31734 @node JIT Interface
31735 @chapter JIT Compilation Interface
31736 @cindex just-in-time compilation
31737 @cindex JIT compilation interface
31739 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
31740 interface. A JIT compiler is a program or library that generates native
31741 executable code at runtime and executes it, usually in order to achieve good
31742 performance while maintaining platform independence.
31744 Programs that use JIT compilation are normally difficult to debug because
31745 portions of their code are generated at runtime, instead of being loaded from
31746 object files, which is where @value{GDBN} normally finds the program's symbols
31747 and debug information. In order to debug programs that use JIT compilation,
31748 @value{GDBN} has an interface that allows the program to register in-memory
31749 symbol files with @value{GDBN} at runtime.
31751 If you are using @value{GDBN} to debug a program that uses this interface, then
31752 it should work transparently so long as you have not stripped the binary. If
31753 you are developing a JIT compiler, then the interface is documented in the rest
31754 of this chapter. At this time, the only known client of this interface is the
31757 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
31758 JIT compiler communicates with @value{GDBN} by writing data into a global
31759 variable and calling a fuction at a well-known symbol. When @value{GDBN}
31760 attaches, it reads a linked list of symbol files from the global variable to
31761 find existing code, and puts a breakpoint in the function so that it can find
31762 out about additional code.
31765 * Declarations:: Relevant C struct declarations
31766 * Registering Code:: Steps to register code
31767 * Unregistering Code:: Steps to unregister code
31768 * Custom Debug Info:: Emit debug information in a custom format
31772 @section JIT Declarations
31774 These are the relevant struct declarations that a C program should include to
31775 implement the interface:
31785 struct jit_code_entry
31787 struct jit_code_entry *next_entry;
31788 struct jit_code_entry *prev_entry;
31789 const char *symfile_addr;
31790 uint64_t symfile_size;
31793 struct jit_descriptor
31796 /* This type should be jit_actions_t, but we use uint32_t
31797 to be explicit about the bitwidth. */
31798 uint32_t action_flag;
31799 struct jit_code_entry *relevant_entry;
31800 struct jit_code_entry *first_entry;
31803 /* GDB puts a breakpoint in this function. */
31804 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
31806 /* Make sure to specify the version statically, because the
31807 debugger may check the version before we can set it. */
31808 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
31811 If the JIT is multi-threaded, then it is important that the JIT synchronize any
31812 modifications to this global data properly, which can easily be done by putting
31813 a global mutex around modifications to these structures.
31815 @node Registering Code
31816 @section Registering Code
31818 To register code with @value{GDBN}, the JIT should follow this protocol:
31822 Generate an object file in memory with symbols and other desired debug
31823 information. The file must include the virtual addresses of the sections.
31826 Create a code entry for the file, which gives the start and size of the symbol
31830 Add it to the linked list in the JIT descriptor.
31833 Point the relevant_entry field of the descriptor at the entry.
31836 Set @code{action_flag} to @code{JIT_REGISTER} and call
31837 @code{__jit_debug_register_code}.
31840 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
31841 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
31842 new code. However, the linked list must still be maintained in order to allow
31843 @value{GDBN} to attach to a running process and still find the symbol files.
31845 @node Unregistering Code
31846 @section Unregistering Code
31848 If code is freed, then the JIT should use the following protocol:
31852 Remove the code entry corresponding to the code from the linked list.
31855 Point the @code{relevant_entry} field of the descriptor at the code entry.
31858 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
31859 @code{__jit_debug_register_code}.
31862 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
31863 and the JIT will leak the memory used for the associated symbol files.
31865 @node Custom Debug Info
31866 @section Custom Debug Info
31867 @cindex custom JIT debug info
31868 @cindex JIT debug info reader
31870 Generating debug information in platform-native file formats (like ELF
31871 or COFF) may be an overkill for JIT compilers; especially if all the
31872 debug info is used for is displaying a meaningful backtrace. The
31873 issue can be resolved by having the JIT writers decide on a debug info
31874 format and also provide a reader that parses the debug info generated
31875 by the JIT compiler. This section gives a brief overview on writing
31876 such a parser. More specific details can be found in the source file
31877 @file{gdb/jit-reader.in}, which is also installed as a header at
31878 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
31880 The reader is implemented as a shared object (so this functionality is
31881 not available on platforms which don't allow loading shared objects at
31882 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
31883 @code{jit-reader-unload} are provided, to be used to load and unload
31884 the readers from a preconfigured directory. Once loaded, the shared
31885 object is used the parse the debug information emitted by the JIT
31889 * Using JIT Debug Info Readers:: How to use supplied readers correctly
31890 * Writing JIT Debug Info Readers:: Creating a debug-info reader
31893 @node Using JIT Debug Info Readers
31894 @subsection Using JIT Debug Info Readers
31895 @kindex jit-reader-load
31896 @kindex jit-reader-unload
31898 Readers can be loaded and unloaded using the @code{jit-reader-load}
31899 and @code{jit-reader-unload} commands.
31902 @item jit-reader-load @var{reader}
31903 Load the JIT reader named @var{reader}. @var{reader} is a shared
31904 object specified as either an absolute or a relative file name. In
31905 the latter case, @value{GDBN} will try to load the reader from a
31906 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
31907 system (here @var{libdir} is the system library directory, often
31908 @file{/usr/local/lib}).
31910 Only one reader can be active at a time; trying to load a second
31911 reader when one is already loaded will result in @value{GDBN}
31912 reporting an error. A new JIT reader can be loaded by first unloading
31913 the current one using @code{jit-reader-unload} and then invoking
31914 @code{jit-reader-load}.
31916 @item jit-reader-unload
31917 Unload the currently loaded JIT reader.
31921 @node Writing JIT Debug Info Readers
31922 @subsection Writing JIT Debug Info Readers
31923 @cindex writing JIT debug info readers
31925 As mentioned, a reader is essentially a shared object conforming to a
31926 certain ABI. This ABI is described in @file{jit-reader.h}.
31928 @file{jit-reader.h} defines the structures, macros and functions
31929 required to write a reader. It is installed (along with
31930 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
31931 the system include directory.
31933 Readers need to be released under a GPL compatible license. A reader
31934 can be declared as released under such a license by placing the macro
31935 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
31937 The entry point for readers is the symbol @code{gdb_init_reader},
31938 which is expected to be a function with the prototype
31940 @findex gdb_init_reader
31942 extern struct gdb_reader_funcs *gdb_init_reader (void);
31945 @cindex @code{struct gdb_reader_funcs}
31947 @code{struct gdb_reader_funcs} contains a set of pointers to callback
31948 functions. These functions are executed to read the debug info
31949 generated by the JIT compiler (@code{read}), to unwind stack frames
31950 (@code{unwind}) and to create canonical frame IDs
31951 (@code{get_Frame_id}). It also has a callback that is called when the
31952 reader is being unloaded (@code{destroy}). The struct looks like this
31955 struct gdb_reader_funcs
31957 /* Must be set to GDB_READER_INTERFACE_VERSION. */
31958 int reader_version;
31960 /* For use by the reader. */
31963 gdb_read_debug_info *read;
31964 gdb_unwind_frame *unwind;
31965 gdb_get_frame_id *get_frame_id;
31966 gdb_destroy_reader *destroy;
31970 @cindex @code{struct gdb_symbol_callbacks}
31971 @cindex @code{struct gdb_unwind_callbacks}
31973 The callbacks are provided with another set of callbacks by
31974 @value{GDBN} to do their job. For @code{read}, these callbacks are
31975 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
31976 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
31977 @code{struct gdb_symbol_callbacks} has callbacks to create new object
31978 files and new symbol tables inside those object files. @code{struct
31979 gdb_unwind_callbacks} has callbacks to read registers off the current
31980 frame and to write out the values of the registers in the previous
31981 frame. Both have a callback (@code{target_read}) to read bytes off the
31982 target's address space.
31984 @node In-Process Agent
31985 @chapter In-Process Agent
31986 @cindex debugging agent
31987 The traditional debugging model is conceptually low-speed, but works fine,
31988 because most bugs can be reproduced in debugging-mode execution. However,
31989 as multi-core or many-core processors are becoming mainstream, and
31990 multi-threaded programs become more and more popular, there should be more
31991 and more bugs that only manifest themselves at normal-mode execution, for
31992 example, thread races, because debugger's interference with the program's
31993 timing may conceal the bugs. On the other hand, in some applications,
31994 it is not feasible for the debugger to interrupt the program's execution
31995 long enough for the developer to learn anything helpful about its behavior.
31996 If the program's correctness depends on its real-time behavior, delays
31997 introduced by a debugger might cause the program to fail, even when the
31998 code itself is correct. It is useful to be able to observe the program's
31999 behavior without interrupting it.
32001 Therefore, traditional debugging model is too intrusive to reproduce
32002 some bugs. In order to reduce the interference with the program, we can
32003 reduce the number of operations performed by debugger. The
32004 @dfn{In-Process Agent}, a shared library, is running within the same
32005 process with inferior, and is able to perform some debugging operations
32006 itself. As a result, debugger is only involved when necessary, and
32007 performance of debugging can be improved accordingly. Note that
32008 interference with program can be reduced but can't be removed completely,
32009 because the in-process agent will still stop or slow down the program.
32011 The in-process agent can interpret and execute Agent Expressions
32012 (@pxref{Agent Expressions}) during performing debugging operations. The
32013 agent expressions can be used for different purposes, such as collecting
32014 data in tracepoints, and condition evaluation in breakpoints.
32016 @anchor{Control Agent}
32017 You can control whether the in-process agent is used as an aid for
32018 debugging with the following commands:
32021 @kindex set agent on
32023 Causes the in-process agent to perform some operations on behalf of the
32024 debugger. Just which operations requested by the user will be done
32025 by the in-process agent depends on the its capabilities. For example,
32026 if you request to evaluate breakpoint conditions in the in-process agent,
32027 and the in-process agent has such capability as well, then breakpoint
32028 conditions will be evaluated in the in-process agent.
32030 @kindex set agent off
32031 @item set agent off
32032 Disables execution of debugging operations by the in-process agent. All
32033 of the operations will be performed by @value{GDBN}.
32037 Display the current setting of execution of debugging operations by
32038 the in-process agent.
32042 * In-Process Agent Protocol::
32045 @node In-Process Agent Protocol
32046 @section In-Process Agent Protocol
32047 @cindex in-process agent protocol
32049 The in-process agent is able to communicate with both @value{GDBN} and
32050 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
32051 used for communications between @value{GDBN} or GDBserver and the IPA.
32052 In general, @value{GDBN} or GDBserver sends commands
32053 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
32054 in-process agent replies back with the return result of the command, or
32055 some other information. The data sent to in-process agent is composed
32056 of primitive data types, such as 4-byte or 8-byte type, and composite
32057 types, which are called objects (@pxref{IPA Protocol Objects}).
32060 * IPA Protocol Objects::
32061 * IPA Protocol Commands::
32064 @node IPA Protocol Objects
32065 @subsection IPA Protocol Objects
32066 @cindex ipa protocol objects
32068 The commands sent to and results received from agent may contain some
32069 complex data types called @dfn{objects}.
32071 The in-process agent is running on the same machine with @value{GDBN}
32072 or GDBserver, so it doesn't have to handle as much differences between
32073 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
32074 However, there are still some differences of two ends in two processes:
32078 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
32079 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
32081 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
32082 GDBserver is compiled with one, and in-process agent is compiled with
32086 Here are the IPA Protocol Objects:
32090 agent expression object. It represents an agent expression
32091 (@pxref{Agent Expressions}).
32092 @anchor{agent expression object}
32094 tracepoint action object. It represents a tracepoint action
32095 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
32096 memory, static trace data and to evaluate expression.
32097 @anchor{tracepoint action object}
32099 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
32100 @anchor{tracepoint object}
32104 The following table describes important attributes of each IPA protocol
32107 @multitable @columnfractions .30 .20 .50
32108 @headitem Name @tab Size @tab Description
32109 @item @emph{agent expression object} @tab @tab
32110 @item length @tab 4 @tab length of bytes code
32111 @item byte code @tab @var{length} @tab contents of byte code
32112 @item @emph{tracepoint action for collecting memory} @tab @tab
32113 @item 'M' @tab 1 @tab type of tracepoint action
32114 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
32115 address of the lowest byte to collect, otherwise @var{addr} is the offset
32116 of @var{basereg} for memory collecting.
32117 @item len @tab 8 @tab length of memory for collecting
32118 @item basereg @tab 4 @tab the register number containing the starting
32119 memory address for collecting.
32120 @item @emph{tracepoint action for collecting registers} @tab @tab
32121 @item 'R' @tab 1 @tab type of tracepoint action
32122 @item @emph{tracepoint action for collecting static trace data} @tab @tab
32123 @item 'L' @tab 1 @tab type of tracepoint action
32124 @item @emph{tracepoint action for expression evaluation} @tab @tab
32125 @item 'X' @tab 1 @tab type of tracepoint action
32126 @item agent expression @tab length of @tab @ref{agent expression object}
32127 @item @emph{tracepoint object} @tab @tab
32128 @item number @tab 4 @tab number of tracepoint
32129 @item address @tab 8 @tab address of tracepoint inserted on
32130 @item type @tab 4 @tab type of tracepoint
32131 @item enabled @tab 1 @tab enable or disable of tracepoint
32132 @item step_count @tab 8 @tab step
32133 @item pass_count @tab 8 @tab pass
32134 @item numactions @tab 4 @tab number of tracepoint actions
32135 @item hit count @tab 8 @tab hit count
32136 @item trace frame usage @tab 8 @tab trace frame usage
32137 @item compiled_cond @tab 8 @tab compiled condition
32138 @item orig_size @tab 8 @tab orig size
32139 @item condition @tab 4 if condition is NULL otherwise length of
32140 @ref{agent expression object}
32141 @tab zero if condition is NULL, otherwise is
32142 @ref{agent expression object}
32143 @item actions @tab variable
32144 @tab numactions number of @ref{tracepoint action object}
32147 @node IPA Protocol Commands
32148 @subsection IPA Protocol Commands
32149 @cindex ipa protocol commands
32151 The spaces in each command are delimiters to ease reading this commands
32152 specification. They don't exist in real commands.
32156 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
32157 Installs a new fast tracepoint described by @var{tracepoint_object}
32158 (@pxref{tracepoint object}). @var{gdb_jump_pad_head}, 8-byte long, is the
32159 head of @dfn{jumppad}, which is used to jump to data collection routine
32164 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
32165 @var{target_address} is address of tracepoint in the inferior.
32166 @var{gdb_jump_pad_head} is updated head of jumppad. Both of
32167 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
32168 @var{fjump} contains a sequence of instructions jump to jumppad entry.
32169 @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
32176 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
32177 is about to kill inferiors.
32185 @item probe_marker_at:@var{address}
32186 Asks in-process agent to probe the marker at @var{address}.
32193 @item unprobe_marker_at:@var{address}
32194 Asks in-process agent to unprobe the marker at @var{address}.
32198 @chapter Reporting Bugs in @value{GDBN}
32199 @cindex bugs in @value{GDBN}
32200 @cindex reporting bugs in @value{GDBN}
32202 Your bug reports play an essential role in making @value{GDBN} reliable.
32204 Reporting a bug may help you by bringing a solution to your problem, or it
32205 may not. But in any case the principal function of a bug report is to help
32206 the entire community by making the next version of @value{GDBN} work better. Bug
32207 reports are your contribution to the maintenance of @value{GDBN}.
32209 In order for a bug report to serve its purpose, you must include the
32210 information that enables us to fix the bug.
32213 * Bug Criteria:: Have you found a bug?
32214 * Bug Reporting:: How to report bugs
32218 @section Have You Found a Bug?
32219 @cindex bug criteria
32221 If you are not sure whether you have found a bug, here are some guidelines:
32224 @cindex fatal signal
32225 @cindex debugger crash
32226 @cindex crash of debugger
32228 If the debugger gets a fatal signal, for any input whatever, that is a
32229 @value{GDBN} bug. Reliable debuggers never crash.
32231 @cindex error on valid input
32233 If @value{GDBN} produces an error message for valid input, that is a
32234 bug. (Note that if you're cross debugging, the problem may also be
32235 somewhere in the connection to the target.)
32237 @cindex invalid input
32239 If @value{GDBN} does not produce an error message for invalid input,
32240 that is a bug. However, you should note that your idea of
32241 ``invalid input'' might be our idea of ``an extension'' or ``support
32242 for traditional practice''.
32245 If you are an experienced user of debugging tools, your suggestions
32246 for improvement of @value{GDBN} are welcome in any case.
32249 @node Bug Reporting
32250 @section How to Report Bugs
32251 @cindex bug reports
32252 @cindex @value{GDBN} bugs, reporting
32254 A number of companies and individuals offer support for @sc{gnu} products.
32255 If you obtained @value{GDBN} from a support organization, we recommend you
32256 contact that organization first.
32258 You can find contact information for many support companies and
32259 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
32261 @c should add a web page ref...
32264 @ifset BUGURL_DEFAULT
32265 In any event, we also recommend that you submit bug reports for
32266 @value{GDBN}. The preferred method is to submit them directly using
32267 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
32268 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
32271 @strong{Do not send bug reports to @samp{info-gdb}, or to
32272 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
32273 not want to receive bug reports. Those that do have arranged to receive
32276 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
32277 serves as a repeater. The mailing list and the newsgroup carry exactly
32278 the same messages. Often people think of posting bug reports to the
32279 newsgroup instead of mailing them. This appears to work, but it has one
32280 problem which can be crucial: a newsgroup posting often lacks a mail
32281 path back to the sender. Thus, if we need to ask for more information,
32282 we may be unable to reach you. For this reason, it is better to send
32283 bug reports to the mailing list.
32285 @ifclear BUGURL_DEFAULT
32286 In any event, we also recommend that you submit bug reports for
32287 @value{GDBN} to @value{BUGURL}.
32291 The fundamental principle of reporting bugs usefully is this:
32292 @strong{report all the facts}. If you are not sure whether to state a
32293 fact or leave it out, state it!
32295 Often people omit facts because they think they know what causes the
32296 problem and assume that some details do not matter. Thus, you might
32297 assume that the name of the variable you use in an example does not matter.
32298 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
32299 stray memory reference which happens to fetch from the location where that
32300 name is stored in memory; perhaps, if the name were different, the contents
32301 of that location would fool the debugger into doing the right thing despite
32302 the bug. Play it safe and give a specific, complete example. That is the
32303 easiest thing for you to do, and the most helpful.
32305 Keep in mind that the purpose of a bug report is to enable us to fix the
32306 bug. It may be that the bug has been reported previously, but neither
32307 you nor we can know that unless your bug report is complete and
32310 Sometimes people give a few sketchy facts and ask, ``Does this ring a
32311 bell?'' Those bug reports are useless, and we urge everyone to
32312 @emph{refuse to respond to them} except to chide the sender to report
32315 To enable us to fix the bug, you should include all these things:
32319 The version of @value{GDBN}. @value{GDBN} announces it if you start
32320 with no arguments; you can also print it at any time using @code{show
32323 Without this, we will not know whether there is any point in looking for
32324 the bug in the current version of @value{GDBN}.
32327 The type of machine you are using, and the operating system name and
32331 The details of the @value{GDBN} build-time configuration.
32332 @value{GDBN} shows these details if you invoke it with the
32333 @option{--configuration} command-line option, or if you type
32334 @code{show configuration} at @value{GDBN}'s prompt.
32337 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
32338 ``@value{GCC}--2.8.1''.
32341 What compiler (and its version) was used to compile the program you are
32342 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
32343 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
32344 to get this information; for other compilers, see the documentation for
32348 The command arguments you gave the compiler to compile your example and
32349 observe the bug. For example, did you use @samp{-O}? To guarantee
32350 you will not omit something important, list them all. A copy of the
32351 Makefile (or the output from make) is sufficient.
32353 If we were to try to guess the arguments, we would probably guess wrong
32354 and then we might not encounter the bug.
32357 A complete input script, and all necessary source files, that will
32361 A description of what behavior you observe that you believe is
32362 incorrect. For example, ``It gets a fatal signal.''
32364 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
32365 will certainly notice it. But if the bug is incorrect output, we might
32366 not notice unless it is glaringly wrong. You might as well not give us
32367 a chance to make a mistake.
32369 Even if the problem you experience is a fatal signal, you should still
32370 say so explicitly. Suppose something strange is going on, such as, your
32371 copy of @value{GDBN} is out of synch, or you have encountered a bug in
32372 the C library on your system. (This has happened!) Your copy might
32373 crash and ours would not. If you told us to expect a crash, then when
32374 ours fails to crash, we would know that the bug was not happening for
32375 us. If you had not told us to expect a crash, then we would not be able
32376 to draw any conclusion from our observations.
32379 @cindex recording a session script
32380 To collect all this information, you can use a session recording program
32381 such as @command{script}, which is available on many Unix systems.
32382 Just run your @value{GDBN} session inside @command{script} and then
32383 include the @file{typescript} file with your bug report.
32385 Another way to record a @value{GDBN} session is to run @value{GDBN}
32386 inside Emacs and then save the entire buffer to a file.
32389 If you wish to suggest changes to the @value{GDBN} source, send us context
32390 diffs. If you even discuss something in the @value{GDBN} source, refer to
32391 it by context, not by line number.
32393 The line numbers in our development sources will not match those in your
32394 sources. Your line numbers would convey no useful information to us.
32398 Here are some things that are not necessary:
32402 A description of the envelope of the bug.
32404 Often people who encounter a bug spend a lot of time investigating
32405 which changes to the input file will make the bug go away and which
32406 changes will not affect it.
32408 This is often time consuming and not very useful, because the way we
32409 will find the bug is by running a single example under the debugger
32410 with breakpoints, not by pure deduction from a series of examples.
32411 We recommend that you save your time for something else.
32413 Of course, if you can find a simpler example to report @emph{instead}
32414 of the original one, that is a convenience for us. Errors in the
32415 output will be easier to spot, running under the debugger will take
32416 less time, and so on.
32418 However, simplification is not vital; if you do not want to do this,
32419 report the bug anyway and send us the entire test case you used.
32422 A patch for the bug.
32424 A patch for the bug does help us if it is a good one. But do not omit
32425 the necessary information, such as the test case, on the assumption that
32426 a patch is all we need. We might see problems with your patch and decide
32427 to fix the problem another way, or we might not understand it at all.
32429 Sometimes with a program as complicated as @value{GDBN} it is very hard to
32430 construct an example that will make the program follow a certain path
32431 through the code. If you do not send us the example, we will not be able
32432 to construct one, so we will not be able to verify that the bug is fixed.
32434 And if we cannot understand what bug you are trying to fix, or why your
32435 patch should be an improvement, we will not install it. A test case will
32436 help us to understand.
32439 A guess about what the bug is or what it depends on.
32441 Such guesses are usually wrong. Even we cannot guess right about such
32442 things without first using the debugger to find the facts.
32445 @c The readline documentation is distributed with the readline code
32446 @c and consists of the two following files:
32449 @c Use -I with makeinfo to point to the appropriate directory,
32450 @c environment var TEXINPUTS with TeX.
32451 @ifclear SYSTEM_READLINE
32452 @include rluser.texi
32453 @include hsuser.texi
32457 @appendix In Memoriam
32459 The @value{GDBN} project mourns the loss of the following long-time
32464 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
32465 to Free Software in general. Outside of @value{GDBN}, he was known in
32466 the Amiga world for his series of Fish Disks, and the GeekGadget project.
32468 @item Michael Snyder
32469 Michael was one of the Global Maintainers of the @value{GDBN} project,
32470 with contributions recorded as early as 1996, until 2011. In addition
32471 to his day to day participation, he was a large driving force behind
32472 adding Reverse Debugging to @value{GDBN}.
32475 Beyond their technical contributions to the project, they were also
32476 enjoyable members of the Free Software Community. We will miss them.
32478 @node Formatting Documentation
32479 @appendix Formatting Documentation
32481 @cindex @value{GDBN} reference card
32482 @cindex reference card
32483 The @value{GDBN} 4 release includes an already-formatted reference card, ready
32484 for printing with PostScript or Ghostscript, in the @file{gdb}
32485 subdirectory of the main source directory@footnote{In
32486 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
32487 release.}. If you can use PostScript or Ghostscript with your printer,
32488 you can print the reference card immediately with @file{refcard.ps}.
32490 The release also includes the source for the reference card. You
32491 can format it, using @TeX{}, by typing:
32497 The @value{GDBN} reference card is designed to print in @dfn{landscape}
32498 mode on US ``letter'' size paper;
32499 that is, on a sheet 11 inches wide by 8.5 inches
32500 high. You will need to specify this form of printing as an option to
32501 your @sc{dvi} output program.
32503 @cindex documentation
32505 All the documentation for @value{GDBN} comes as part of the machine-readable
32506 distribution. The documentation is written in Texinfo format, which is
32507 a documentation system that uses a single source file to produce both
32508 on-line information and a printed manual. You can use one of the Info
32509 formatting commands to create the on-line version of the documentation
32510 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
32512 @value{GDBN} includes an already formatted copy of the on-line Info
32513 version of this manual in the @file{gdb} subdirectory. The main Info
32514 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
32515 subordinate files matching @samp{gdb.info*} in the same directory. If
32516 necessary, you can print out these files, or read them with any editor;
32517 but they are easier to read using the @code{info} subsystem in @sc{gnu}
32518 Emacs or the standalone @code{info} program, available as part of the
32519 @sc{gnu} Texinfo distribution.
32521 If you want to format these Info files yourself, you need one of the
32522 Info formatting programs, such as @code{texinfo-format-buffer} or
32525 If you have @code{makeinfo} installed, and are in the top level
32526 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
32527 version @value{GDBVN}), you can make the Info file by typing:
32534 If you want to typeset and print copies of this manual, you need @TeX{},
32535 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
32536 Texinfo definitions file.
32538 @TeX{} is a typesetting program; it does not print files directly, but
32539 produces output files called @sc{dvi} files. To print a typeset
32540 document, you need a program to print @sc{dvi} files. If your system
32541 has @TeX{} installed, chances are it has such a program. The precise
32542 command to use depends on your system; @kbd{lpr -d} is common; another
32543 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
32544 require a file name without any extension or a @samp{.dvi} extension.
32546 @TeX{} also requires a macro definitions file called
32547 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
32548 written in Texinfo format. On its own, @TeX{} cannot either read or
32549 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
32550 and is located in the @file{gdb-@var{version-number}/texinfo}
32553 If you have @TeX{} and a @sc{dvi} printer program installed, you can
32554 typeset and print this manual. First switch to the @file{gdb}
32555 subdirectory of the main source directory (for example, to
32556 @file{gdb-@value{GDBVN}/gdb}) and type:
32562 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
32564 @node Installing GDB
32565 @appendix Installing @value{GDBN}
32566 @cindex installation
32569 * Requirements:: Requirements for building @value{GDBN}
32570 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
32571 * Separate Objdir:: Compiling @value{GDBN} in another directory
32572 * Config Names:: Specifying names for hosts and targets
32573 * Configure Options:: Summary of options for configure
32574 * System-wide configuration:: Having a system-wide init file
32578 @section Requirements for Building @value{GDBN}
32579 @cindex building @value{GDBN}, requirements for
32581 Building @value{GDBN} requires various tools and packages to be available.
32582 Other packages will be used only if they are found.
32584 @heading Tools/Packages Necessary for Building @value{GDBN}
32586 @item ISO C90 compiler
32587 @value{GDBN} is written in ISO C90. It should be buildable with any
32588 working C90 compiler, e.g.@: GCC.
32592 @heading Tools/Packages Optional for Building @value{GDBN}
32596 @value{GDBN} can use the Expat XML parsing library. This library may be
32597 included with your operating system distribution; if it is not, you
32598 can get the latest version from @url{http://expat.sourceforge.net}.
32599 The @file{configure} script will search for this library in several
32600 standard locations; if it is installed in an unusual path, you can
32601 use the @option{--with-libexpat-prefix} option to specify its location.
32607 Remote protocol memory maps (@pxref{Memory Map Format})
32609 Target descriptions (@pxref{Target Descriptions})
32611 Remote shared library lists (@xref{Library List Format},
32612 or alternatively @pxref{Library List Format for SVR4 Targets})
32614 MS-Windows shared libraries (@pxref{Shared Libraries})
32616 Traceframe info (@pxref{Traceframe Info Format})
32618 Branch trace (@pxref{Branch Trace Format})
32622 @cindex compressed debug sections
32623 @value{GDBN} will use the @samp{zlib} library, if available, to read
32624 compressed debug sections. Some linkers, such as GNU gold, are capable
32625 of producing binaries with compressed debug sections. If @value{GDBN}
32626 is compiled with @samp{zlib}, it will be able to read the debug
32627 information in such binaries.
32629 The @samp{zlib} library is likely included with your operating system
32630 distribution; if it is not, you can get the latest version from
32631 @url{http://zlib.net}.
32634 @value{GDBN}'s features related to character sets (@pxref{Character
32635 Sets}) require a functioning @code{iconv} implementation. If you are
32636 on a GNU system, then this is provided by the GNU C Library. Some
32637 other systems also provide a working @code{iconv}.
32639 If @value{GDBN} is using the @code{iconv} program which is installed
32640 in a non-standard place, you will need to tell @value{GDBN} where to find it.
32641 This is done with @option{--with-iconv-bin} which specifies the
32642 directory that contains the @code{iconv} program.
32644 On systems without @code{iconv}, you can install GNU Libiconv. If you
32645 have previously installed Libiconv, you can use the
32646 @option{--with-libiconv-prefix} option to configure.
32648 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
32649 arrange to build Libiconv if a directory named @file{libiconv} appears
32650 in the top-most source directory. If Libiconv is built this way, and
32651 if the operating system does not provide a suitable @code{iconv}
32652 implementation, then the just-built library will automatically be used
32653 by @value{GDBN}. One easy way to set this up is to download GNU
32654 Libiconv, unpack it, and then rename the directory holding the
32655 Libiconv source code to @samp{libiconv}.
32658 @node Running Configure
32659 @section Invoking the @value{GDBN} @file{configure} Script
32660 @cindex configuring @value{GDBN}
32661 @value{GDBN} comes with a @file{configure} script that automates the process
32662 of preparing @value{GDBN} for installation; you can then use @code{make} to
32663 build the @code{gdb} program.
32665 @c irrelevant in info file; it's as current as the code it lives with.
32666 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
32667 look at the @file{README} file in the sources; we may have improved the
32668 installation procedures since publishing this manual.}
32671 The @value{GDBN} distribution includes all the source code you need for
32672 @value{GDBN} in a single directory, whose name is usually composed by
32673 appending the version number to @samp{gdb}.
32675 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
32676 @file{gdb-@value{GDBVN}} directory. That directory contains:
32679 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
32680 script for configuring @value{GDBN} and all its supporting libraries
32682 @item gdb-@value{GDBVN}/gdb
32683 the source specific to @value{GDBN} itself
32685 @item gdb-@value{GDBVN}/bfd
32686 source for the Binary File Descriptor library
32688 @item gdb-@value{GDBVN}/include
32689 @sc{gnu} include files
32691 @item gdb-@value{GDBVN}/libiberty
32692 source for the @samp{-liberty} free software library
32694 @item gdb-@value{GDBVN}/opcodes
32695 source for the library of opcode tables and disassemblers
32697 @item gdb-@value{GDBVN}/readline
32698 source for the @sc{gnu} command-line interface
32700 @item gdb-@value{GDBVN}/glob
32701 source for the @sc{gnu} filename pattern-matching subroutine
32703 @item gdb-@value{GDBVN}/mmalloc
32704 source for the @sc{gnu} memory-mapped malloc package
32707 The simplest way to configure and build @value{GDBN} is to run @file{configure}
32708 from the @file{gdb-@var{version-number}} source directory, which in
32709 this example is the @file{gdb-@value{GDBVN}} directory.
32711 First switch to the @file{gdb-@var{version-number}} source directory
32712 if you are not already in it; then run @file{configure}. Pass the
32713 identifier for the platform on which @value{GDBN} will run as an
32719 cd gdb-@value{GDBVN}
32720 ./configure @var{host}
32725 where @var{host} is an identifier such as @samp{sun4} or
32726 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
32727 (You can often leave off @var{host}; @file{configure} tries to guess the
32728 correct value by examining your system.)
32730 Running @samp{configure @var{host}} and then running @code{make} builds the
32731 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
32732 libraries, then @code{gdb} itself. The configured source files, and the
32733 binaries, are left in the corresponding source directories.
32736 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
32737 system does not recognize this automatically when you run a different
32738 shell, you may need to run @code{sh} on it explicitly:
32741 sh configure @var{host}
32744 If you run @file{configure} from a directory that contains source
32745 directories for multiple libraries or programs, such as the
32746 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
32748 creates configuration files for every directory level underneath (unless
32749 you tell it not to, with the @samp{--norecursion} option).
32751 You should run the @file{configure} script from the top directory in the
32752 source tree, the @file{gdb-@var{version-number}} directory. If you run
32753 @file{configure} from one of the subdirectories, you will configure only
32754 that subdirectory. That is usually not what you want. In particular,
32755 if you run the first @file{configure} from the @file{gdb} subdirectory
32756 of the @file{gdb-@var{version-number}} directory, you will omit the
32757 configuration of @file{bfd}, @file{readline}, and other sibling
32758 directories of the @file{gdb} subdirectory. This leads to build errors
32759 about missing include files such as @file{bfd/bfd.h}.
32761 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
32762 However, you should make sure that the shell on your path (named by
32763 the @samp{SHELL} environment variable) is publicly readable. Remember
32764 that @value{GDBN} uses the shell to start your program---some systems refuse to
32765 let @value{GDBN} debug child processes whose programs are not readable.
32767 @node Separate Objdir
32768 @section Compiling @value{GDBN} in Another Directory
32770 If you want to run @value{GDBN} versions for several host or target machines,
32771 you need a different @code{gdb} compiled for each combination of
32772 host and target. @file{configure} is designed to make this easy by
32773 allowing you to generate each configuration in a separate subdirectory,
32774 rather than in the source directory. If your @code{make} program
32775 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
32776 @code{make} in each of these directories builds the @code{gdb}
32777 program specified there.
32779 To build @code{gdb} in a separate directory, run @file{configure}
32780 with the @samp{--srcdir} option to specify where to find the source.
32781 (You also need to specify a path to find @file{configure}
32782 itself from your working directory. If the path to @file{configure}
32783 would be the same as the argument to @samp{--srcdir}, you can leave out
32784 the @samp{--srcdir} option; it is assumed.)
32786 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
32787 separate directory for a Sun 4 like this:
32791 cd gdb-@value{GDBVN}
32794 ../gdb-@value{GDBVN}/configure sun4
32799 When @file{configure} builds a configuration using a remote source
32800 directory, it creates a tree for the binaries with the same structure
32801 (and using the same names) as the tree under the source directory. In
32802 the example, you'd find the Sun 4 library @file{libiberty.a} in the
32803 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
32804 @file{gdb-sun4/gdb}.
32806 Make sure that your path to the @file{configure} script has just one
32807 instance of @file{gdb} in it. If your path to @file{configure} looks
32808 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
32809 one subdirectory of @value{GDBN}, not the whole package. This leads to
32810 build errors about missing include files such as @file{bfd/bfd.h}.
32812 One popular reason to build several @value{GDBN} configurations in separate
32813 directories is to configure @value{GDBN} for cross-compiling (where
32814 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
32815 programs that run on another machine---the @dfn{target}).
32816 You specify a cross-debugging target by
32817 giving the @samp{--target=@var{target}} option to @file{configure}.
32819 When you run @code{make} to build a program or library, you must run
32820 it in a configured directory---whatever directory you were in when you
32821 called @file{configure} (or one of its subdirectories).
32823 The @code{Makefile} that @file{configure} generates in each source
32824 directory also runs recursively. If you type @code{make} in a source
32825 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
32826 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
32827 will build all the required libraries, and then build GDB.
32829 When you have multiple hosts or targets configured in separate
32830 directories, you can run @code{make} on them in parallel (for example,
32831 if they are NFS-mounted on each of the hosts); they will not interfere
32835 @section Specifying Names for Hosts and Targets
32837 The specifications used for hosts and targets in the @file{configure}
32838 script are based on a three-part naming scheme, but some short predefined
32839 aliases are also supported. The full naming scheme encodes three pieces
32840 of information in the following pattern:
32843 @var{architecture}-@var{vendor}-@var{os}
32846 For example, you can use the alias @code{sun4} as a @var{host} argument,
32847 or as the value for @var{target} in a @code{--target=@var{target}}
32848 option. The equivalent full name is @samp{sparc-sun-sunos4}.
32850 The @file{configure} script accompanying @value{GDBN} does not provide
32851 any query facility to list all supported host and target names or
32852 aliases. @file{configure} calls the Bourne shell script
32853 @code{config.sub} to map abbreviations to full names; you can read the
32854 script, if you wish, or you can use it to test your guesses on
32855 abbreviations---for example:
32858 % sh config.sub i386-linux
32860 % sh config.sub alpha-linux
32861 alpha-unknown-linux-gnu
32862 % sh config.sub hp9k700
32864 % sh config.sub sun4
32865 sparc-sun-sunos4.1.1
32866 % sh config.sub sun3
32867 m68k-sun-sunos4.1.1
32868 % sh config.sub i986v
32869 Invalid configuration `i986v': machine `i986v' not recognized
32873 @code{config.sub} is also distributed in the @value{GDBN} source
32874 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
32876 @node Configure Options
32877 @section @file{configure} Options
32879 Here is a summary of the @file{configure} options and arguments that
32880 are most often useful for building @value{GDBN}. @file{configure} also has
32881 several other options not listed here. @inforef{What Configure
32882 Does,,configure.info}, for a full explanation of @file{configure}.
32885 configure @r{[}--help@r{]}
32886 @r{[}--prefix=@var{dir}@r{]}
32887 @r{[}--exec-prefix=@var{dir}@r{]}
32888 @r{[}--srcdir=@var{dirname}@r{]}
32889 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
32890 @r{[}--target=@var{target}@r{]}
32895 You may introduce options with a single @samp{-} rather than
32896 @samp{--} if you prefer; but you may abbreviate option names if you use
32901 Display a quick summary of how to invoke @file{configure}.
32903 @item --prefix=@var{dir}
32904 Configure the source to install programs and files under directory
32907 @item --exec-prefix=@var{dir}
32908 Configure the source to install programs under directory
32911 @c avoid splitting the warning from the explanation:
32913 @item --srcdir=@var{dirname}
32914 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
32915 @code{make} that implements the @code{VPATH} feature.}@*
32916 Use this option to make configurations in directories separate from the
32917 @value{GDBN} source directories. Among other things, you can use this to
32918 build (or maintain) several configurations simultaneously, in separate
32919 directories. @file{configure} writes configuration-specific files in
32920 the current directory, but arranges for them to use the source in the
32921 directory @var{dirname}. @file{configure} creates directories under
32922 the working directory in parallel to the source directories below
32925 @item --norecursion
32926 Configure only the directory level where @file{configure} is executed; do not
32927 propagate configuration to subdirectories.
32929 @item --target=@var{target}
32930 Configure @value{GDBN} for cross-debugging programs running on the specified
32931 @var{target}. Without this option, @value{GDBN} is configured to debug
32932 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
32934 There is no convenient way to generate a list of all available targets.
32936 @item @var{host} @dots{}
32937 Configure @value{GDBN} to run on the specified @var{host}.
32939 There is no convenient way to generate a list of all available hosts.
32942 There are many other options available as well, but they are generally
32943 needed for special purposes only.
32945 @node System-wide configuration
32946 @section System-wide configuration and settings
32947 @cindex system-wide init file
32949 @value{GDBN} can be configured to have a system-wide init file;
32950 this file will be read and executed at startup (@pxref{Startup, , What
32951 @value{GDBN} does during startup}).
32953 Here is the corresponding configure option:
32956 @item --with-system-gdbinit=@var{file}
32957 Specify that the default location of the system-wide init file is
32961 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
32962 it may be subject to relocation. Two possible cases:
32966 If the default location of this init file contains @file{$prefix},
32967 it will be subject to relocation. Suppose that the configure options
32968 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
32969 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
32970 init file is looked for as @file{$install/etc/gdbinit} instead of
32971 @file{$prefix/etc/gdbinit}.
32974 By contrast, if the default location does not contain the prefix,
32975 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
32976 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
32977 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
32978 wherever @value{GDBN} is installed.
32981 If the configured location of the system-wide init file (as given by the
32982 @option{--with-system-gdbinit} option at configure time) is in the
32983 data-directory (as specified by @option{--with-gdb-datadir} at configure
32984 time) or in one of its subdirectories, then @value{GDBN} will look for the
32985 system-wide init file in the directory specified by the
32986 @option{--data-directory} command-line option.
32987 Note that the system-wide init file is only read once, during @value{GDBN}
32988 initialization. If the data-directory is changed after @value{GDBN} has
32989 started with the @code{set data-directory} command, the file will not be
32993 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
32996 @node System-wide Configuration Scripts
32997 @subsection Installed System-wide Configuration Scripts
32998 @cindex system-wide configuration scripts
33000 The @file{system-gdbinit} directory, located inside the data-directory
33001 (as specified by @option{--with-gdb-datadir} at configure time) contains
33002 a number of scripts which can be used as system-wide init files. To
33003 automatically source those scripts at startup, @value{GDBN} should be
33004 configured with @option{--with-system-gdbinit}. Otherwise, any user
33005 should be able to source them by hand as needed.
33007 The following scripts are currently available:
33010 @item @file{elinos.py}
33012 @cindex ELinOS system-wide configuration script
33013 This script is useful when debugging a program on an ELinOS target.
33014 It takes advantage of the environment variables defined in a standard
33015 ELinOS environment in order to determine the location of the system
33016 shared libraries, and then sets the @samp{solib-absolute-prefix}
33017 and @samp{solib-search-path} variables appropriately.
33019 @item @file{wrs-linux.py}
33020 @pindex wrs-linux.py
33021 @cindex Wind River Linux system-wide configuration script
33022 This script is useful when debugging a program on a target running
33023 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
33024 the host-side sysroot used by the target system.
33028 @node Maintenance Commands
33029 @appendix Maintenance Commands
33030 @cindex maintenance commands
33031 @cindex internal commands
33033 In addition to commands intended for @value{GDBN} users, @value{GDBN}
33034 includes a number of commands intended for @value{GDBN} developers,
33035 that are not documented elsewhere in this manual. These commands are
33036 provided here for reference. (For commands that turn on debugging
33037 messages, see @ref{Debugging Output}.)
33040 @kindex maint agent
33041 @kindex maint agent-eval
33042 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
33043 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
33044 Translate the given @var{expression} into remote agent bytecodes.
33045 This command is useful for debugging the Agent Expression mechanism
33046 (@pxref{Agent Expressions}). The @samp{agent} version produces an
33047 expression useful for data collection, such as by tracepoints, while
33048 @samp{maint agent-eval} produces an expression that evaluates directly
33049 to a result. For instance, a collection expression for @code{globa +
33050 globb} will include bytecodes to record four bytes of memory at each
33051 of the addresses of @code{globa} and @code{globb}, while discarding
33052 the result of the addition, while an evaluation expression will do the
33053 addition and return the sum.
33054 If @code{-at} is given, generate remote agent bytecode for @var{location}.
33055 If not, generate remote agent bytecode for current frame PC address.
33057 @kindex maint agent-printf
33058 @item maint agent-printf @var{format},@var{expr},...
33059 Translate the given format string and list of argument expressions
33060 into remote agent bytecodes and display them as a disassembled list.
33061 This command is useful for debugging the agent version of dynamic
33062 printf (@pxref{Dynamic Printf}).
33064 @kindex maint info breakpoints
33065 @item @anchor{maint info breakpoints}maint info breakpoints
33066 Using the same format as @samp{info breakpoints}, display both the
33067 breakpoints you've set explicitly, and those @value{GDBN} is using for
33068 internal purposes. Internal breakpoints are shown with negative
33069 breakpoint numbers. The type column identifies what kind of breakpoint
33074 Normal, explicitly set breakpoint.
33077 Normal, explicitly set watchpoint.
33080 Internal breakpoint, used to handle correctly stepping through
33081 @code{longjmp} calls.
33083 @item longjmp resume
33084 Internal breakpoint at the target of a @code{longjmp}.
33087 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
33090 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
33093 Shared library events.
33097 @kindex maint info bfds
33098 @item maint info bfds
33099 This prints information about each @code{bfd} object that is known to
33100 @value{GDBN}. @xref{Top, , BFD, bfd, The Binary File Descriptor Library}.
33102 @kindex set displaced-stepping
33103 @kindex show displaced-stepping
33104 @cindex displaced stepping support
33105 @cindex out-of-line single-stepping
33106 @item set displaced-stepping
33107 @itemx show displaced-stepping
33108 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
33109 if the target supports it. Displaced stepping is a way to single-step
33110 over breakpoints without removing them from the inferior, by executing
33111 an out-of-line copy of the instruction that was originally at the
33112 breakpoint location. It is also known as out-of-line single-stepping.
33115 @item set displaced-stepping on
33116 If the target architecture supports it, @value{GDBN} will use
33117 displaced stepping to step over breakpoints.
33119 @item set displaced-stepping off
33120 @value{GDBN} will not use displaced stepping to step over breakpoints,
33121 even if such is supported by the target architecture.
33123 @cindex non-stop mode, and @samp{set displaced-stepping}
33124 @item set displaced-stepping auto
33125 This is the default mode. @value{GDBN} will use displaced stepping
33126 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
33127 architecture supports displaced stepping.
33130 @kindex maint check-psymtabs
33131 @item maint check-psymtabs
33132 Check the consistency of currently expanded psymtabs versus symtabs.
33133 Use this to check, for example, whether a symbol is in one but not the other.
33135 @kindex maint check-symtabs
33136 @item maint check-symtabs
33137 Check the consistency of currently expanded symtabs.
33139 @kindex maint expand-symtabs
33140 @item maint expand-symtabs [@var{regexp}]
33141 Expand symbol tables.
33142 If @var{regexp} is specified, only expand symbol tables for file
33143 names matching @var{regexp}.
33145 @kindex maint cplus first_component
33146 @item maint cplus first_component @var{name}
33147 Print the first C@t{++} class/namespace component of @var{name}.
33149 @kindex maint cplus namespace
33150 @item maint cplus namespace
33151 Print the list of possible C@t{++} namespaces.
33153 @kindex maint demangle
33154 @item maint demangle @var{name}
33155 Demangle a C@t{++} or Objective-C mangled @var{name}.
33157 @kindex maint deprecate
33158 @kindex maint undeprecate
33159 @cindex deprecated commands
33160 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
33161 @itemx maint undeprecate @var{command}
33162 Deprecate or undeprecate the named @var{command}. Deprecated commands
33163 cause @value{GDBN} to issue a warning when you use them. The optional
33164 argument @var{replacement} says which newer command should be used in
33165 favor of the deprecated one; if it is given, @value{GDBN} will mention
33166 the replacement as part of the warning.
33168 @kindex maint dump-me
33169 @item maint dump-me
33170 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
33171 Cause a fatal signal in the debugger and force it to dump its core.
33172 This is supported only on systems which support aborting a program
33173 with the @code{SIGQUIT} signal.
33175 @kindex maint internal-error
33176 @kindex maint internal-warning
33177 @item maint internal-error @r{[}@var{message-text}@r{]}
33178 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
33179 Cause @value{GDBN} to call the internal function @code{internal_error}
33180 or @code{internal_warning} and hence behave as though an internal error
33181 or internal warning has been detected. In addition to reporting the
33182 internal problem, these functions give the user the opportunity to
33183 either quit @value{GDBN} or create a core file of the current
33184 @value{GDBN} session.
33186 These commands take an optional parameter @var{message-text} that is
33187 used as the text of the error or warning message.
33189 Here's an example of using @code{internal-error}:
33192 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
33193 @dots{}/maint.c:121: internal-error: testing, 1, 2
33194 A problem internal to GDB has been detected. Further
33195 debugging may prove unreliable.
33196 Quit this debugging session? (y or n) @kbd{n}
33197 Create a core file? (y or n) @kbd{n}
33201 @cindex @value{GDBN} internal error
33202 @cindex internal errors, control of @value{GDBN} behavior
33204 @kindex maint set internal-error
33205 @kindex maint show internal-error
33206 @kindex maint set internal-warning
33207 @kindex maint show internal-warning
33208 @item maint set internal-error @var{action} [ask|yes|no]
33209 @itemx maint show internal-error @var{action}
33210 @itemx maint set internal-warning @var{action} [ask|yes|no]
33211 @itemx maint show internal-warning @var{action}
33212 When @value{GDBN} reports an internal problem (error or warning) it
33213 gives the user the opportunity to both quit @value{GDBN} and create a
33214 core file of the current @value{GDBN} session. These commands let you
33215 override the default behaviour for each particular @var{action},
33216 described in the table below.
33220 You can specify that @value{GDBN} should always (yes) or never (no)
33221 quit. The default is to ask the user what to do.
33224 You can specify that @value{GDBN} should always (yes) or never (no)
33225 create a core file. The default is to ask the user what to do.
33228 @kindex maint packet
33229 @item maint packet @var{text}
33230 If @value{GDBN} is talking to an inferior via the serial protocol,
33231 then this command sends the string @var{text} to the inferior, and
33232 displays the response packet. @value{GDBN} supplies the initial
33233 @samp{$} character, the terminating @samp{#} character, and the
33236 @kindex maint print architecture
33237 @item maint print architecture @r{[}@var{file}@r{]}
33238 Print the entire architecture configuration. The optional argument
33239 @var{file} names the file where the output goes.
33241 @kindex maint print c-tdesc
33242 @item maint print c-tdesc
33243 Print the current target description (@pxref{Target Descriptions}) as
33244 a C source file. The created source file can be used in @value{GDBN}
33245 when an XML parser is not available to parse the description.
33247 @kindex maint print dummy-frames
33248 @item maint print dummy-frames
33249 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
33252 (@value{GDBP}) @kbd{b add}
33254 (@value{GDBP}) @kbd{print add(2,3)}
33255 Breakpoint 2, add (a=2, b=3) at @dots{}
33257 The program being debugged stopped while in a function called from GDB.
33259 (@value{GDBP}) @kbd{maint print dummy-frames}
33260 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
33261 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
33262 call_lo=0x01014000 call_hi=0x01014001
33266 Takes an optional file parameter.
33268 @kindex maint print registers
33269 @kindex maint print raw-registers
33270 @kindex maint print cooked-registers
33271 @kindex maint print register-groups
33272 @kindex maint print remote-registers
33273 @item maint print registers @r{[}@var{file}@r{]}
33274 @itemx maint print raw-registers @r{[}@var{file}@r{]}
33275 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
33276 @itemx maint print register-groups @r{[}@var{file}@r{]}
33277 @itemx maint print remote-registers @r{[}@var{file}@r{]}
33278 Print @value{GDBN}'s internal register data structures.
33280 The command @code{maint print raw-registers} includes the contents of
33281 the raw register cache; the command @code{maint print
33282 cooked-registers} includes the (cooked) value of all registers,
33283 including registers which aren't available on the target nor visible
33284 to user; the command @code{maint print register-groups} includes the
33285 groups that each register is a member of; and the command @code{maint
33286 print remote-registers} includes the remote target's register numbers
33287 and offsets in the `G' packets.
33289 These commands take an optional parameter, a file name to which to
33290 write the information.
33292 @kindex maint print reggroups
33293 @item maint print reggroups @r{[}@var{file}@r{]}
33294 Print @value{GDBN}'s internal register group data structures. The
33295 optional argument @var{file} tells to what file to write the
33298 The register groups info looks like this:
33301 (@value{GDBP}) @kbd{maint print reggroups}
33314 This command forces @value{GDBN} to flush its internal register cache.
33316 @kindex maint print objfiles
33317 @cindex info for known object files
33318 @item maint print objfiles @r{[}@var{regexp}@r{]}
33319 Print a dump of all known object files.
33320 If @var{regexp} is specified, only print object files whose names
33321 match @var{regexp}. For each object file, this command prints its name,
33322 address in memory, and all of its psymtabs and symtabs.
33324 @kindex maint print section-scripts
33325 @cindex info for known .debug_gdb_scripts-loaded scripts
33326 @item maint print section-scripts [@var{regexp}]
33327 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
33328 If @var{regexp} is specified, only print scripts loaded by object files
33329 matching @var{regexp}.
33330 For each script, this command prints its name as specified in the objfile,
33331 and the full path if known.
33332 @xref{dotdebug_gdb_scripts section}.
33334 @kindex maint print statistics
33335 @cindex bcache statistics
33336 @item maint print statistics
33337 This command prints, for each object file in the program, various data
33338 about that object file followed by the byte cache (@dfn{bcache})
33339 statistics for the object file. The objfile data includes the number
33340 of minimal, partial, full, and stabs symbols, the number of types
33341 defined by the objfile, the number of as yet unexpanded psym tables,
33342 the number of line tables and string tables, and the amount of memory
33343 used by the various tables. The bcache statistics include the counts,
33344 sizes, and counts of duplicates of all and unique objects, max,
33345 average, and median entry size, total memory used and its overhead and
33346 savings, and various measures of the hash table size and chain
33349 @kindex maint print target-stack
33350 @cindex target stack description
33351 @item maint print target-stack
33352 A @dfn{target} is an interface between the debugger and a particular
33353 kind of file or process. Targets can be stacked in @dfn{strata},
33354 so that more than one target can potentially respond to a request.
33355 In particular, memory accesses will walk down the stack of targets
33356 until they find a target that is interested in handling that particular
33359 This command prints a short description of each layer that was pushed on
33360 the @dfn{target stack}, starting from the top layer down to the bottom one.
33362 @kindex maint print type
33363 @cindex type chain of a data type
33364 @item maint print type @var{expr}
33365 Print the type chain for a type specified by @var{expr}. The argument
33366 can be either a type name or a symbol. If it is a symbol, the type of
33367 that symbol is described. The type chain produced by this command is
33368 a recursive definition of the data type as stored in @value{GDBN}'s
33369 data structures, including its flags and contained types.
33371 @kindex maint set dwarf2 always-disassemble
33372 @kindex maint show dwarf2 always-disassemble
33373 @item maint set dwarf2 always-disassemble
33374 @item maint show dwarf2 always-disassemble
33375 Control the behavior of @code{info address} when using DWARF debugging
33378 The default is @code{off}, which means that @value{GDBN} should try to
33379 describe a variable's location in an easily readable format. When
33380 @code{on}, @value{GDBN} will instead display the DWARF location
33381 expression in an assembly-like format. Note that some locations are
33382 too complex for @value{GDBN} to describe simply; in this case you will
33383 always see the disassembly form.
33385 Here is an example of the resulting disassembly:
33388 (gdb) info addr argc
33389 Symbol "argc" is a complex DWARF expression:
33393 For more information on these expressions, see
33394 @uref{http://www.dwarfstd.org/, the DWARF standard}.
33396 @kindex maint set dwarf2 max-cache-age
33397 @kindex maint show dwarf2 max-cache-age
33398 @item maint set dwarf2 max-cache-age
33399 @itemx maint show dwarf2 max-cache-age
33400 Control the DWARF 2 compilation unit cache.
33402 @cindex DWARF 2 compilation units cache
33403 In object files with inter-compilation-unit references, such as those
33404 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
33405 reader needs to frequently refer to previously read compilation units.
33406 This setting controls how long a compilation unit will remain in the
33407 cache if it is not referenced. A higher limit means that cached
33408 compilation units will be stored in memory longer, and more total
33409 memory will be used. Setting it to zero disables caching, which will
33410 slow down @value{GDBN} startup, but reduce memory consumption.
33412 @kindex maint set profile
33413 @kindex maint show profile
33414 @cindex profiling GDB
33415 @item maint set profile
33416 @itemx maint show profile
33417 Control profiling of @value{GDBN}.
33419 Profiling will be disabled until you use the @samp{maint set profile}
33420 command to enable it. When you enable profiling, the system will begin
33421 collecting timing and execution count data; when you disable profiling or
33422 exit @value{GDBN}, the results will be written to a log file. Remember that
33423 if you use profiling, @value{GDBN} will overwrite the profiling log file
33424 (often called @file{gmon.out}). If you have a record of important profiling
33425 data in a @file{gmon.out} file, be sure to move it to a safe location.
33427 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
33428 compiled with the @samp{-pg} compiler option.
33430 @kindex maint set show-debug-regs
33431 @kindex maint show show-debug-regs
33432 @cindex hardware debug registers
33433 @item maint set show-debug-regs
33434 @itemx maint show show-debug-regs
33435 Control whether to show variables that mirror the hardware debug
33436 registers. Use @code{on} to enable, @code{off} to disable. If
33437 enabled, the debug registers values are shown when @value{GDBN} inserts or
33438 removes a hardware breakpoint or watchpoint, and when the inferior
33439 triggers a hardware-assisted breakpoint or watchpoint.
33441 @kindex maint set show-all-tib
33442 @kindex maint show show-all-tib
33443 @item maint set show-all-tib
33444 @itemx maint show show-all-tib
33445 Control whether to show all non zero areas within a 1k block starting
33446 at thread local base, when using the @samp{info w32 thread-information-block}
33449 @kindex maint set per-command
33450 @kindex maint show per-command
33451 @item maint set per-command
33452 @itemx maint show per-command
33453 @cindex resources used by commands
33455 @value{GDBN} can display the resources used by each command.
33456 This is useful in debugging performance problems.
33459 @item maint set per-command space [on|off]
33460 @itemx maint show per-command space
33461 Enable or disable the printing of the memory used by GDB for each command.
33462 If enabled, @value{GDBN} will display how much memory each command
33463 took, following the command's own output.
33464 This can also be requested by invoking @value{GDBN} with the
33465 @option{--statistics} command-line switch (@pxref{Mode Options}).
33467 @item maint set per-command time [on|off]
33468 @itemx maint show per-command time
33469 Enable or disable the printing of the execution time of @value{GDBN}
33471 If enabled, @value{GDBN} will display how much time it
33472 took to execute each command, following the command's own output.
33473 Both CPU time and wallclock time are printed.
33474 Printing both is useful when trying to determine whether the cost is
33475 CPU or, e.g., disk/network latency.
33476 Note that the CPU time printed is for @value{GDBN} only, it does not include
33477 the execution time of the inferior because there's no mechanism currently
33478 to compute how much time was spent by @value{GDBN} and how much time was
33479 spent by the program been debugged.
33480 This can also be requested by invoking @value{GDBN} with the
33481 @option{--statistics} command-line switch (@pxref{Mode Options}).
33483 @item maint set per-command symtab [on|off]
33484 @itemx maint show per-command symtab
33485 Enable or disable the printing of basic symbol table statistics
33487 If enabled, @value{GDBN} will display the following information:
33491 number of symbol tables
33493 number of primary symbol tables
33495 number of blocks in the blockvector
33499 @kindex maint space
33500 @cindex memory used by commands
33501 @item maint space @var{value}
33502 An alias for @code{maint set per-command space}.
33503 A non-zero value enables it, zero disables it.
33506 @cindex time of command execution
33507 @item maint time @var{value}
33508 An alias for @code{maint set per-command time}.
33509 A non-zero value enables it, zero disables it.
33511 @kindex maint translate-address
33512 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
33513 Find the symbol stored at the location specified by the address
33514 @var{addr} and an optional section name @var{section}. If found,
33515 @value{GDBN} prints the name of the closest symbol and an offset from
33516 the symbol's location to the specified address. This is similar to
33517 the @code{info address} command (@pxref{Symbols}), except that this
33518 command also allows to find symbols in other sections.
33520 If section was not specified, the section in which the symbol was found
33521 is also printed. For dynamically linked executables, the name of
33522 executable or shared library containing the symbol is printed as well.
33526 The following command is useful for non-interactive invocations of
33527 @value{GDBN}, such as in the test suite.
33530 @item set watchdog @var{nsec}
33531 @kindex set watchdog
33532 @cindex watchdog timer
33533 @cindex timeout for commands
33534 Set the maximum number of seconds @value{GDBN} will wait for the
33535 target operation to finish. If this time expires, @value{GDBN}
33536 reports and error and the command is aborted.
33538 @item show watchdog
33539 Show the current setting of the target wait timeout.
33542 @node Remote Protocol
33543 @appendix @value{GDBN} Remote Serial Protocol
33548 * Stop Reply Packets::
33549 * General Query Packets::
33550 * Architecture-Specific Protocol Details::
33551 * Tracepoint Packets::
33552 * Host I/O Packets::
33554 * Notification Packets::
33555 * Remote Non-Stop::
33556 * Packet Acknowledgment::
33558 * File-I/O Remote Protocol Extension::
33559 * Library List Format::
33560 * Library List Format for SVR4 Targets::
33561 * Memory Map Format::
33562 * Thread List Format::
33563 * Traceframe Info Format::
33564 * Branch Trace Format::
33570 There may be occasions when you need to know something about the
33571 protocol---for example, if there is only one serial port to your target
33572 machine, you might want your program to do something special if it
33573 recognizes a packet meant for @value{GDBN}.
33575 In the examples below, @samp{->} and @samp{<-} are used to indicate
33576 transmitted and received data, respectively.
33578 @cindex protocol, @value{GDBN} remote serial
33579 @cindex serial protocol, @value{GDBN} remote
33580 @cindex remote serial protocol
33581 All @value{GDBN} commands and responses (other than acknowledgments
33582 and notifications, see @ref{Notification Packets}) are sent as a
33583 @var{packet}. A @var{packet} is introduced with the character
33584 @samp{$}, the actual @var{packet-data}, and the terminating character
33585 @samp{#} followed by a two-digit @var{checksum}:
33588 @code{$}@var{packet-data}@code{#}@var{checksum}
33592 @cindex checksum, for @value{GDBN} remote
33594 The two-digit @var{checksum} is computed as the modulo 256 sum of all
33595 characters between the leading @samp{$} and the trailing @samp{#} (an
33596 eight bit unsigned checksum).
33598 Implementors should note that prior to @value{GDBN} 5.0 the protocol
33599 specification also included an optional two-digit @var{sequence-id}:
33602 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
33605 @cindex sequence-id, for @value{GDBN} remote
33607 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
33608 has never output @var{sequence-id}s. Stubs that handle packets added
33609 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
33611 When either the host or the target machine receives a packet, the first
33612 response expected is an acknowledgment: either @samp{+} (to indicate
33613 the package was received correctly) or @samp{-} (to request
33617 -> @code{$}@var{packet-data}@code{#}@var{checksum}
33622 The @samp{+}/@samp{-} acknowledgments can be disabled
33623 once a connection is established.
33624 @xref{Packet Acknowledgment}, for details.
33626 The host (@value{GDBN}) sends @var{command}s, and the target (the
33627 debugging stub incorporated in your program) sends a @var{response}. In
33628 the case of step and continue @var{command}s, the response is only sent
33629 when the operation has completed, and the target has again stopped all
33630 threads in all attached processes. This is the default all-stop mode
33631 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
33632 execution mode; see @ref{Remote Non-Stop}, for details.
33634 @var{packet-data} consists of a sequence of characters with the
33635 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
33638 @cindex remote protocol, field separator
33639 Fields within the packet should be separated using @samp{,} @samp{;} or
33640 @samp{:}. Except where otherwise noted all numbers are represented in
33641 @sc{hex} with leading zeros suppressed.
33643 Implementors should note that prior to @value{GDBN} 5.0, the character
33644 @samp{:} could not appear as the third character in a packet (as it
33645 would potentially conflict with the @var{sequence-id}).
33647 @cindex remote protocol, binary data
33648 @anchor{Binary Data}
33649 Binary data in most packets is encoded either as two hexadecimal
33650 digits per byte of binary data. This allowed the traditional remote
33651 protocol to work over connections which were only seven-bit clean.
33652 Some packets designed more recently assume an eight-bit clean
33653 connection, and use a more efficient encoding to send and receive
33656 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
33657 as an escape character. Any escaped byte is transmitted as the escape
33658 character followed by the original character XORed with @code{0x20}.
33659 For example, the byte @code{0x7d} would be transmitted as the two
33660 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
33661 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
33662 @samp{@}}) must always be escaped. Responses sent by the stub
33663 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
33664 is not interpreted as the start of a run-length encoded sequence
33667 Response @var{data} can be run-length encoded to save space.
33668 Run-length encoding replaces runs of identical characters with one
33669 instance of the repeated character, followed by a @samp{*} and a
33670 repeat count. The repeat count is itself sent encoded, to avoid
33671 binary characters in @var{data}: a value of @var{n} is sent as
33672 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
33673 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
33674 code 32) for a repeat count of 3. (This is because run-length
33675 encoding starts to win for counts 3 or more.) Thus, for example,
33676 @samp{0* } is a run-length encoding of ``0000'': the space character
33677 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
33680 The printable characters @samp{#} and @samp{$} or with a numeric value
33681 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
33682 seven repeats (@samp{$}) can be expanded using a repeat count of only
33683 five (@samp{"}). For example, @samp{00000000} can be encoded as
33686 The error response returned for some packets includes a two character
33687 error number. That number is not well defined.
33689 @cindex empty response, for unsupported packets
33690 For any @var{command} not supported by the stub, an empty response
33691 (@samp{$#00}) should be returned. That way it is possible to extend the
33692 protocol. A newer @value{GDBN} can tell if a packet is supported based
33695 At a minimum, a stub is required to support the @samp{g} and @samp{G}
33696 commands for register access, and the @samp{m} and @samp{M} commands
33697 for memory access. Stubs that only control single-threaded targets
33698 can implement run control with the @samp{c} (continue), and @samp{s}
33699 (step) commands. Stubs that support multi-threading targets should
33700 support the @samp{vCont} command. All other commands are optional.
33705 The following table provides a complete list of all currently defined
33706 @var{command}s and their corresponding response @var{data}.
33707 @xref{File-I/O Remote Protocol Extension}, for details about the File
33708 I/O extension of the remote protocol.
33710 Each packet's description has a template showing the packet's overall
33711 syntax, followed by an explanation of the packet's meaning. We
33712 include spaces in some of the templates for clarity; these are not
33713 part of the packet's syntax. No @value{GDBN} packet uses spaces to
33714 separate its components. For example, a template like @samp{foo
33715 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
33716 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
33717 @var{baz}. @value{GDBN} does not transmit a space character between the
33718 @samp{foo} and the @var{bar}, or between the @var{bar} and the
33721 @cindex @var{thread-id}, in remote protocol
33722 @anchor{thread-id syntax}
33723 Several packets and replies include a @var{thread-id} field to identify
33724 a thread. Normally these are positive numbers with a target-specific
33725 interpretation, formatted as big-endian hex strings. A @var{thread-id}
33726 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
33729 In addition, the remote protocol supports a multiprocess feature in
33730 which the @var{thread-id} syntax is extended to optionally include both
33731 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
33732 The @var{pid} (process) and @var{tid} (thread) components each have the
33733 format described above: a positive number with target-specific
33734 interpretation formatted as a big-endian hex string, literal @samp{-1}
33735 to indicate all processes or threads (respectively), or @samp{0} to
33736 indicate an arbitrary process or thread. Specifying just a process, as
33737 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
33738 error to specify all processes but a specific thread, such as
33739 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
33740 for those packets and replies explicitly documented to include a process
33741 ID, rather than a @var{thread-id}.
33743 The multiprocess @var{thread-id} syntax extensions are only used if both
33744 @value{GDBN} and the stub report support for the @samp{multiprocess}
33745 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
33748 Note that all packet forms beginning with an upper- or lower-case
33749 letter, other than those described here, are reserved for future use.
33751 Here are the packet descriptions.
33756 @cindex @samp{!} packet
33757 @anchor{extended mode}
33758 Enable extended mode. In extended mode, the remote server is made
33759 persistent. The @samp{R} packet is used to restart the program being
33765 The remote target both supports and has enabled extended mode.
33769 @cindex @samp{?} packet
33771 Indicate the reason the target halted. The reply is the same as for
33772 step and continue. This packet has a special interpretation when the
33773 target is in non-stop mode; see @ref{Remote Non-Stop}.
33776 @xref{Stop Reply Packets}, for the reply specifications.
33778 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
33779 @cindex @samp{A} packet
33780 Initialized @code{argv[]} array passed into program. @var{arglen}
33781 specifies the number of bytes in the hex encoded byte stream
33782 @var{arg}. See @code{gdbserver} for more details.
33787 The arguments were set.
33793 @cindex @samp{b} packet
33794 (Don't use this packet; its behavior is not well-defined.)
33795 Change the serial line speed to @var{baud}.
33797 JTC: @emph{When does the transport layer state change? When it's
33798 received, or after the ACK is transmitted. In either case, there are
33799 problems if the command or the acknowledgment packet is dropped.}
33801 Stan: @emph{If people really wanted to add something like this, and get
33802 it working for the first time, they ought to modify ser-unix.c to send
33803 some kind of out-of-band message to a specially-setup stub and have the
33804 switch happen "in between" packets, so that from remote protocol's point
33805 of view, nothing actually happened.}
33807 @item B @var{addr},@var{mode}
33808 @cindex @samp{B} packet
33809 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
33810 breakpoint at @var{addr}.
33812 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
33813 (@pxref{insert breakpoint or watchpoint packet}).
33815 @cindex @samp{bc} packet
33818 Backward continue. Execute the target system in reverse. No parameter.
33819 @xref{Reverse Execution}, for more information.
33822 @xref{Stop Reply Packets}, for the reply specifications.
33824 @cindex @samp{bs} packet
33827 Backward single step. Execute one instruction in reverse. No parameter.
33828 @xref{Reverse Execution}, for more information.
33831 @xref{Stop Reply Packets}, for the reply specifications.
33833 @item c @r{[}@var{addr}@r{]}
33834 @cindex @samp{c} packet
33835 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
33836 resume at current address.
33838 This packet is deprecated for multi-threading support. @xref{vCont
33842 @xref{Stop Reply Packets}, for the reply specifications.
33844 @item C @var{sig}@r{[};@var{addr}@r{]}
33845 @cindex @samp{C} packet
33846 Continue with signal @var{sig} (hex signal number). If
33847 @samp{;@var{addr}} is omitted, resume at same address.
33849 This packet is deprecated for multi-threading support. @xref{vCont
33853 @xref{Stop Reply Packets}, for the reply specifications.
33856 @cindex @samp{d} packet
33859 Don't use this packet; instead, define a general set packet
33860 (@pxref{General Query Packets}).
33864 @cindex @samp{D} packet
33865 The first form of the packet is used to detach @value{GDBN} from the
33866 remote system. It is sent to the remote target
33867 before @value{GDBN} disconnects via the @code{detach} command.
33869 The second form, including a process ID, is used when multiprocess
33870 protocol extensions are enabled (@pxref{multiprocess extensions}), to
33871 detach only a specific process. The @var{pid} is specified as a
33872 big-endian hex string.
33882 @item F @var{RC},@var{EE},@var{CF};@var{XX}
33883 @cindex @samp{F} packet
33884 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
33885 This is part of the File-I/O protocol extension. @xref{File-I/O
33886 Remote Protocol Extension}, for the specification.
33889 @anchor{read registers packet}
33890 @cindex @samp{g} packet
33891 Read general registers.
33895 @item @var{XX@dots{}}
33896 Each byte of register data is described by two hex digits. The bytes
33897 with the register are transmitted in target byte order. The size of
33898 each register and their position within the @samp{g} packet are
33899 determined by the @value{GDBN} internal gdbarch functions
33900 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
33901 specification of several standard @samp{g} packets is specified below.
33903 When reading registers from a trace frame (@pxref{Analyze Collected
33904 Data,,Using the Collected Data}), the stub may also return a string of
33905 literal @samp{x}'s in place of the register data digits, to indicate
33906 that the corresponding register has not been collected, thus its value
33907 is unavailable. For example, for an architecture with 4 registers of
33908 4 bytes each, the following reply indicates to @value{GDBN} that
33909 registers 0 and 2 have not been collected, while registers 1 and 3
33910 have been collected, and both have zero value:
33914 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
33921 @item G @var{XX@dots{}}
33922 @cindex @samp{G} packet
33923 Write general registers. @xref{read registers packet}, for a
33924 description of the @var{XX@dots{}} data.
33934 @item H @var{op} @var{thread-id}
33935 @cindex @samp{H} packet
33936 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
33937 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
33938 it should be @samp{c} for step and continue operations (note that this
33939 is deprecated, supporting the @samp{vCont} command is a better
33940 option), @samp{g} for other operations. The thread designator
33941 @var{thread-id} has the format and interpretation described in
33942 @ref{thread-id syntax}.
33953 @c 'H': How restrictive (or permissive) is the thread model. If a
33954 @c thread is selected and stopped, are other threads allowed
33955 @c to continue to execute? As I mentioned above, I think the
33956 @c semantics of each command when a thread is selected must be
33957 @c described. For example:
33959 @c 'g': If the stub supports threads and a specific thread is
33960 @c selected, returns the register block from that thread;
33961 @c otherwise returns current registers.
33963 @c 'G' If the stub supports threads and a specific thread is
33964 @c selected, sets the registers of the register block of
33965 @c that thread; otherwise sets current registers.
33967 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
33968 @anchor{cycle step packet}
33969 @cindex @samp{i} packet
33970 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
33971 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
33972 step starting at that address.
33975 @cindex @samp{I} packet
33976 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
33980 @cindex @samp{k} packet
33983 The exact effect of this packet is not specified.
33985 For a bare-metal target, it may power cycle or reset the target
33986 system. For that reason, the @samp{k} packet has no reply.
33988 For a single-process target, it may kill that process if possible.
33990 A multiple-process target may choose to kill just one process, or all
33991 that are under @value{GDBN}'s control. For more precise control, use
33992 the vKill packet (@pxref{vKill packet}).
33994 If the target system immediately closes the connection in response to
33995 @samp{k}, @value{GDBN} does not consider the lack of packet
33996 acknowledgment to be an error, and assumes the kill was successful.
33998 If connected using @kbd{target extended-remote}, and the target does
33999 not close the connection in response to a kill request, @value{GDBN}
34000 probes the target state as if a new connection was opened
34001 (@pxref{? packet}).
34003 @item m @var{addr},@var{length}
34004 @cindex @samp{m} packet
34005 Read @var{length} bytes of memory starting at address @var{addr}.
34006 Note that @var{addr} may not be aligned to any particular boundary.
34008 The stub need not use any particular size or alignment when gathering
34009 data from memory for the response; even if @var{addr} is word-aligned
34010 and @var{length} is a multiple of the word size, the stub is free to
34011 use byte accesses, or not. For this reason, this packet may not be
34012 suitable for accessing memory-mapped I/O devices.
34013 @cindex alignment of remote memory accesses
34014 @cindex size of remote memory accesses
34015 @cindex memory, alignment and size of remote accesses
34019 @item @var{XX@dots{}}
34020 Memory contents; each byte is transmitted as a two-digit hexadecimal
34021 number. The reply may contain fewer bytes than requested if the
34022 server was able to read only part of the region of memory.
34027 @item M @var{addr},@var{length}:@var{XX@dots{}}
34028 @cindex @samp{M} packet
34029 Write @var{length} bytes of memory starting at address @var{addr}.
34030 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
34031 hexadecimal number.
34038 for an error (this includes the case where only part of the data was
34043 @cindex @samp{p} packet
34044 Read the value of register @var{n}; @var{n} is in hex.
34045 @xref{read registers packet}, for a description of how the returned
34046 register value is encoded.
34050 @item @var{XX@dots{}}
34051 the register's value
34055 Indicating an unrecognized @var{query}.
34058 @item P @var{n@dots{}}=@var{r@dots{}}
34059 @anchor{write register packet}
34060 @cindex @samp{P} packet
34061 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
34062 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
34063 digits for each byte in the register (target byte order).
34073 @item q @var{name} @var{params}@dots{}
34074 @itemx Q @var{name} @var{params}@dots{}
34075 @cindex @samp{q} packet
34076 @cindex @samp{Q} packet
34077 General query (@samp{q}) and set (@samp{Q}). These packets are
34078 described fully in @ref{General Query Packets}.
34081 @cindex @samp{r} packet
34082 Reset the entire system.
34084 Don't use this packet; use the @samp{R} packet instead.
34087 @cindex @samp{R} packet
34088 Restart the program being debugged. @var{XX}, while needed, is ignored.
34089 This packet is only available in extended mode (@pxref{extended mode}).
34091 The @samp{R} packet has no reply.
34093 @item s @r{[}@var{addr}@r{]}
34094 @cindex @samp{s} packet
34095 Single step. @var{addr} is the address at which to resume. If
34096 @var{addr} is omitted, resume at same address.
34098 This packet is deprecated for multi-threading support. @xref{vCont
34102 @xref{Stop Reply Packets}, for the reply specifications.
34104 @item S @var{sig}@r{[};@var{addr}@r{]}
34105 @anchor{step with signal packet}
34106 @cindex @samp{S} packet
34107 Step with signal. This is analogous to the @samp{C} packet, but
34108 requests a single-step, rather than a normal resumption of execution.
34110 This packet is deprecated for multi-threading support. @xref{vCont
34114 @xref{Stop Reply Packets}, for the reply specifications.
34116 @item t @var{addr}:@var{PP},@var{MM}
34117 @cindex @samp{t} packet
34118 Search backwards starting at address @var{addr} for a match with pattern
34119 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
34120 @var{addr} must be at least 3 digits.
34122 @item T @var{thread-id}
34123 @cindex @samp{T} packet
34124 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
34129 thread is still alive
34135 Packets starting with @samp{v} are identified by a multi-letter name,
34136 up to the first @samp{;} or @samp{?} (or the end of the packet).
34138 @item vAttach;@var{pid}
34139 @cindex @samp{vAttach} packet
34140 Attach to a new process with the specified process ID @var{pid}.
34141 The process ID is a
34142 hexadecimal integer identifying the process. In all-stop mode, all
34143 threads in the attached process are stopped; in non-stop mode, it may be
34144 attached without being stopped if that is supported by the target.
34146 @c In non-stop mode, on a successful vAttach, the stub should set the
34147 @c current thread to a thread of the newly-attached process. After
34148 @c attaching, GDB queries for the attached process's thread ID with qC.
34149 @c Also note that, from a user perspective, whether or not the
34150 @c target is stopped on attach in non-stop mode depends on whether you
34151 @c use the foreground or background version of the attach command, not
34152 @c on what vAttach does; GDB does the right thing with respect to either
34153 @c stopping or restarting threads.
34155 This packet is only available in extended mode (@pxref{extended mode}).
34161 @item @r{Any stop packet}
34162 for success in all-stop mode (@pxref{Stop Reply Packets})
34164 for success in non-stop mode (@pxref{Remote Non-Stop})
34167 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
34168 @cindex @samp{vCont} packet
34169 @anchor{vCont packet}
34170 Resume the inferior, specifying different actions for each thread.
34171 If an action is specified with no @var{thread-id}, then it is applied to any
34172 threads that don't have a specific action specified; if no default action is
34173 specified then other threads should remain stopped in all-stop mode and
34174 in their current state in non-stop mode.
34175 Specifying multiple
34176 default actions is an error; specifying no actions is also an error.
34177 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
34179 Currently supported actions are:
34185 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
34189 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
34192 @item r @var{start},@var{end}
34193 Step once, and then keep stepping as long as the thread stops at
34194 addresses between @var{start} (inclusive) and @var{end} (exclusive).
34195 The remote stub reports a stop reply when either the thread goes out
34196 of the range or is stopped due to an unrelated reason, such as hitting
34197 a breakpoint. @xref{range stepping}.
34199 If the range is empty (@var{start} == @var{end}), then the action
34200 becomes equivalent to the @samp{s} action. In other words,
34201 single-step once, and report the stop (even if the stepped instruction
34202 jumps to @var{start}).
34204 (A stop reply may be sent at any point even if the PC is still within
34205 the stepping range; for example, it is valid to implement this packet
34206 in a degenerate way as a single instruction step operation.)
34210 The optional argument @var{addr} normally associated with the
34211 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
34212 not supported in @samp{vCont}.
34214 The @samp{t} action is only relevant in non-stop mode
34215 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
34216 A stop reply should be generated for any affected thread not already stopped.
34217 When a thread is stopped by means of a @samp{t} action,
34218 the corresponding stop reply should indicate that the thread has stopped with
34219 signal @samp{0}, regardless of whether the target uses some other signal
34220 as an implementation detail.
34222 The stub must support @samp{vCont} if it reports support for
34223 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
34224 this case @samp{vCont} actions can be specified to apply to all threads
34225 in a process by using the @samp{p@var{pid}.-1} form of the
34229 @xref{Stop Reply Packets}, for the reply specifications.
34232 @cindex @samp{vCont?} packet
34233 Request a list of actions supported by the @samp{vCont} packet.
34237 @item vCont@r{[};@var{action}@dots{}@r{]}
34238 The @samp{vCont} packet is supported. Each @var{action} is a supported
34239 command in the @samp{vCont} packet.
34241 The @samp{vCont} packet is not supported.
34244 @item vFile:@var{operation}:@var{parameter}@dots{}
34245 @cindex @samp{vFile} packet
34246 Perform a file operation on the target system. For details,
34247 see @ref{Host I/O Packets}.
34249 @item vFlashErase:@var{addr},@var{length}
34250 @cindex @samp{vFlashErase} packet
34251 Direct the stub to erase @var{length} bytes of flash starting at
34252 @var{addr}. The region may enclose any number of flash blocks, but
34253 its start and end must fall on block boundaries, as indicated by the
34254 flash block size appearing in the memory map (@pxref{Memory Map
34255 Format}). @value{GDBN} groups flash memory programming operations
34256 together, and sends a @samp{vFlashDone} request after each group; the
34257 stub is allowed to delay erase operation until the @samp{vFlashDone}
34258 packet is received.
34268 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
34269 @cindex @samp{vFlashWrite} packet
34270 Direct the stub to write data to flash address @var{addr}. The data
34271 is passed in binary form using the same encoding as for the @samp{X}
34272 packet (@pxref{Binary Data}). The memory ranges specified by
34273 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
34274 not overlap, and must appear in order of increasing addresses
34275 (although @samp{vFlashErase} packets for higher addresses may already
34276 have been received; the ordering is guaranteed only between
34277 @samp{vFlashWrite} packets). If a packet writes to an address that was
34278 neither erased by a preceding @samp{vFlashErase} packet nor by some other
34279 target-specific method, the results are unpredictable.
34287 for vFlashWrite addressing non-flash memory
34293 @cindex @samp{vFlashDone} packet
34294 Indicate to the stub that flash programming operation is finished.
34295 The stub is permitted to delay or batch the effects of a group of
34296 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
34297 @samp{vFlashDone} packet is received. The contents of the affected
34298 regions of flash memory are unpredictable until the @samp{vFlashDone}
34299 request is completed.
34301 @item vKill;@var{pid}
34302 @cindex @samp{vKill} packet
34303 @anchor{vKill packet}
34304 Kill the process with the specified process ID. @var{pid} is a
34305 hexadecimal integer identifying the process. This packet is used in
34306 preference to @samp{k} when multiprocess protocol extensions are
34307 supported; see @ref{multiprocess extensions}.
34317 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
34318 @cindex @samp{vRun} packet
34319 Run the program @var{filename}, passing it each @var{argument} on its
34320 command line. The file and arguments are hex-encoded strings. If
34321 @var{filename} is an empty string, the stub may use a default program
34322 (e.g.@: the last program run). The program is created in the stopped
34325 @c FIXME: What about non-stop mode?
34327 This packet is only available in extended mode (@pxref{extended mode}).
34333 @item @r{Any stop packet}
34334 for success (@pxref{Stop Reply Packets})
34338 @cindex @samp{vStopped} packet
34339 @xref{Notification Packets}.
34341 @item X @var{addr},@var{length}:@var{XX@dots{}}
34343 @cindex @samp{X} packet
34344 Write data to memory, where the data is transmitted in binary.
34345 @var{addr} is address, @var{length} is number of bytes,
34346 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
34356 @item z @var{type},@var{addr},@var{kind}
34357 @itemx Z @var{type},@var{addr},@var{kind}
34358 @anchor{insert breakpoint or watchpoint packet}
34359 @cindex @samp{z} packet
34360 @cindex @samp{Z} packets
34361 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
34362 watchpoint starting at address @var{address} of kind @var{kind}.
34364 Each breakpoint and watchpoint packet @var{type} is documented
34367 @emph{Implementation notes: A remote target shall return an empty string
34368 for an unrecognized breakpoint or watchpoint packet @var{type}. A
34369 remote target shall support either both or neither of a given
34370 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
34371 avoid potential problems with duplicate packets, the operations should
34372 be implemented in an idempotent way.}
34374 @item z0,@var{addr},@var{kind}
34375 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
34376 @cindex @samp{z0} packet
34377 @cindex @samp{Z0} packet
34378 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
34379 @var{addr} of type @var{kind}.
34381 A memory breakpoint is implemented by replacing the instruction at
34382 @var{addr} with a software breakpoint or trap instruction. The
34383 @var{kind} is target-specific and typically indicates the size of
34384 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
34385 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
34386 architectures have additional meanings for @var{kind};
34387 @var{cond_list} is an optional list of conditional expressions in bytecode
34388 form that should be evaluated on the target's side. These are the
34389 conditions that should be taken into consideration when deciding if
34390 the breakpoint trigger should be reported back to @var{GDBN}.
34392 The @var{cond_list} parameter is comprised of a series of expressions,
34393 concatenated without separators. Each expression has the following form:
34397 @item X @var{len},@var{expr}
34398 @var{len} is the length of the bytecode expression and @var{expr} is the
34399 actual conditional expression in bytecode form.
34403 The optional @var{cmd_list} parameter introduces commands that may be
34404 run on the target, rather than being reported back to @value{GDBN}.
34405 The parameter starts with a numeric flag @var{persist}; if the flag is
34406 nonzero, then the breakpoint may remain active and the commands
34407 continue to be run even when @value{GDBN} disconnects from the target.
34408 Following this flag is a series of expressions concatenated with no
34409 separators. Each expression has the following form:
34413 @item X @var{len},@var{expr}
34414 @var{len} is the length of the bytecode expression and @var{expr} is the
34415 actual conditional expression in bytecode form.
34419 see @ref{Architecture-Specific Protocol Details}.
34421 @emph{Implementation note: It is possible for a target to copy or move
34422 code that contains memory breakpoints (e.g., when implementing
34423 overlays). The behavior of this packet, in the presence of such a
34424 target, is not defined.}
34436 @item z1,@var{addr},@var{kind}
34437 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
34438 @cindex @samp{z1} packet
34439 @cindex @samp{Z1} packet
34440 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
34441 address @var{addr}.
34443 A hardware breakpoint is implemented using a mechanism that is not
34444 dependant on being able to modify the target's memory. @var{kind}
34445 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
34447 @emph{Implementation note: A hardware breakpoint is not affected by code
34460 @item z2,@var{addr},@var{kind}
34461 @itemx Z2,@var{addr},@var{kind}
34462 @cindex @samp{z2} packet
34463 @cindex @samp{Z2} packet
34464 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
34465 @var{kind} is interpreted as the number of bytes to watch.
34477 @item z3,@var{addr},@var{kind}
34478 @itemx Z3,@var{addr},@var{kind}
34479 @cindex @samp{z3} packet
34480 @cindex @samp{Z3} packet
34481 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
34482 @var{kind} is interpreted as the number of bytes to watch.
34494 @item z4,@var{addr},@var{kind}
34495 @itemx Z4,@var{addr},@var{kind}
34496 @cindex @samp{z4} packet
34497 @cindex @samp{Z4} packet
34498 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
34499 @var{kind} is interpreted as the number of bytes to watch.
34513 @node Stop Reply Packets
34514 @section Stop Reply Packets
34515 @cindex stop reply packets
34517 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
34518 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
34519 receive any of the below as a reply. Except for @samp{?}
34520 and @samp{vStopped}, that reply is only returned
34521 when the target halts. In the below the exact meaning of @dfn{signal
34522 number} is defined by the header @file{include/gdb/signals.h} in the
34523 @value{GDBN} source code.
34525 As in the description of request packets, we include spaces in the
34526 reply templates for clarity; these are not part of the reply packet's
34527 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
34533 The program received signal number @var{AA} (a two-digit hexadecimal
34534 number). This is equivalent to a @samp{T} response with no
34535 @var{n}:@var{r} pairs.
34537 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
34538 @cindex @samp{T} packet reply
34539 The program received signal number @var{AA} (a two-digit hexadecimal
34540 number). This is equivalent to an @samp{S} response, except that the
34541 @samp{@var{n}:@var{r}} pairs can carry values of important registers
34542 and other information directly in the stop reply packet, reducing
34543 round-trip latency. Single-step and breakpoint traps are reported
34544 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
34548 If @var{n} is a hexadecimal number, it is a register number, and the
34549 corresponding @var{r} gives that register's value. @var{r} is a
34550 series of bytes in target byte order, with each byte given by a
34551 two-digit hex number.
34554 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
34555 the stopped thread, as specified in @ref{thread-id syntax}.
34558 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
34559 the core on which the stop event was detected.
34562 If @var{n} is a recognized @dfn{stop reason}, it describes a more
34563 specific event that stopped the target. The currently defined stop
34564 reasons are listed below. @var{aa} should be @samp{05}, the trap
34565 signal. At most one stop reason should be present.
34568 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
34569 and go on to the next; this allows us to extend the protocol in the
34573 The currently defined stop reasons are:
34579 The packet indicates a watchpoint hit, and @var{r} is the data address, in
34582 @cindex shared library events, remote reply
34584 The packet indicates that the loaded libraries have changed.
34585 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
34586 list of loaded libraries. @var{r} is ignored.
34588 @cindex replay log events, remote reply
34590 The packet indicates that the target cannot continue replaying
34591 logged execution events, because it has reached the end (or the
34592 beginning when executing backward) of the log. The value of @var{r}
34593 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
34594 for more information.
34598 @itemx W @var{AA} ; process:@var{pid}
34599 The process exited, and @var{AA} is the exit status. This is only
34600 applicable to certain targets.
34602 The second form of the response, including the process ID of the exited
34603 process, can be used only when @value{GDBN} has reported support for
34604 multiprocess protocol extensions; see @ref{multiprocess extensions}.
34605 The @var{pid} is formatted as a big-endian hex string.
34608 @itemx X @var{AA} ; process:@var{pid}
34609 The process terminated with signal @var{AA}.
34611 The second form of the response, including the process ID of the
34612 terminated process, can be used only when @value{GDBN} has reported
34613 support for multiprocess protocol extensions; see @ref{multiprocess
34614 extensions}. The @var{pid} is formatted as a big-endian hex string.
34616 @item O @var{XX}@dots{}
34617 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
34618 written as the program's console output. This can happen at any time
34619 while the program is running and the debugger should continue to wait
34620 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
34622 @item F @var{call-id},@var{parameter}@dots{}
34623 @var{call-id} is the identifier which says which host system call should
34624 be called. This is just the name of the function. Translation into the
34625 correct system call is only applicable as it's defined in @value{GDBN}.
34626 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
34629 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
34630 this very system call.
34632 The target replies with this packet when it expects @value{GDBN} to
34633 call a host system call on behalf of the target. @value{GDBN} replies
34634 with an appropriate @samp{F} packet and keeps up waiting for the next
34635 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
34636 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
34637 Protocol Extension}, for more details.
34641 @node General Query Packets
34642 @section General Query Packets
34643 @cindex remote query requests
34645 Packets starting with @samp{q} are @dfn{general query packets};
34646 packets starting with @samp{Q} are @dfn{general set packets}. General
34647 query and set packets are a semi-unified form for retrieving and
34648 sending information to and from the stub.
34650 The initial letter of a query or set packet is followed by a name
34651 indicating what sort of thing the packet applies to. For example,
34652 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
34653 definitions with the stub. These packet names follow some
34658 The name must not contain commas, colons or semicolons.
34660 Most @value{GDBN} query and set packets have a leading upper case
34663 The names of custom vendor packets should use a company prefix, in
34664 lower case, followed by a period. For example, packets designed at
34665 the Acme Corporation might begin with @samp{qacme.foo} (for querying
34666 foos) or @samp{Qacme.bar} (for setting bars).
34669 The name of a query or set packet should be separated from any
34670 parameters by a @samp{:}; the parameters themselves should be
34671 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
34672 full packet name, and check for a separator or the end of the packet,
34673 in case two packet names share a common prefix. New packets should not begin
34674 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
34675 packets predate these conventions, and have arguments without any terminator
34676 for the packet name; we suspect they are in widespread use in places that
34677 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
34678 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
34681 Like the descriptions of the other packets, each description here
34682 has a template showing the packet's overall syntax, followed by an
34683 explanation of the packet's meaning. We include spaces in some of the
34684 templates for clarity; these are not part of the packet's syntax. No
34685 @value{GDBN} packet uses spaces to separate its components.
34687 Here are the currently defined query and set packets:
34693 Turn on or off the agent as a helper to perform some debugging operations
34694 delegated from @value{GDBN} (@pxref{Control Agent}).
34696 @item QAllow:@var{op}:@var{val}@dots{}
34697 @cindex @samp{QAllow} packet
34698 Specify which operations @value{GDBN} expects to request of the
34699 target, as a semicolon-separated list of operation name and value
34700 pairs. Possible values for @var{op} include @samp{WriteReg},
34701 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
34702 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
34703 indicating that @value{GDBN} will not request the operation, or 1,
34704 indicating that it may. (The target can then use this to set up its
34705 own internals optimally, for instance if the debugger never expects to
34706 insert breakpoints, it may not need to install its own trap handler.)
34709 @cindex current thread, remote request
34710 @cindex @samp{qC} packet
34711 Return the current thread ID.
34715 @item QC @var{thread-id}
34716 Where @var{thread-id} is a thread ID as documented in
34717 @ref{thread-id syntax}.
34718 @item @r{(anything else)}
34719 Any other reply implies the old thread ID.
34722 @item qCRC:@var{addr},@var{length}
34723 @cindex CRC of memory block, remote request
34724 @cindex @samp{qCRC} packet
34725 Compute the CRC checksum of a block of memory using CRC-32 defined in
34726 IEEE 802.3. The CRC is computed byte at a time, taking the most
34727 significant bit of each byte first. The initial pattern code
34728 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
34730 @emph{Note:} This is the same CRC used in validating separate debug
34731 files (@pxref{Separate Debug Files, , Debugging Information in Separate
34732 Files}). However the algorithm is slightly different. When validating
34733 separate debug files, the CRC is computed taking the @emph{least}
34734 significant bit of each byte first, and the final result is inverted to
34735 detect trailing zeros.
34740 An error (such as memory fault)
34741 @item C @var{crc32}
34742 The specified memory region's checksum is @var{crc32}.
34745 @item QDisableRandomization:@var{value}
34746 @cindex disable address space randomization, remote request
34747 @cindex @samp{QDisableRandomization} packet
34748 Some target operating systems will randomize the virtual address space
34749 of the inferior process as a security feature, but provide a feature
34750 to disable such randomization, e.g.@: to allow for a more deterministic
34751 debugging experience. On such systems, this packet with a @var{value}
34752 of 1 directs the target to disable address space randomization for
34753 processes subsequently started via @samp{vRun} packets, while a packet
34754 with a @var{value} of 0 tells the target to enable address space
34757 This packet is only available in extended mode (@pxref{extended mode}).
34762 The request succeeded.
34765 An error occurred. @var{nn} are hex digits.
34768 An empty reply indicates that @samp{QDisableRandomization} is not supported
34772 This packet is not probed by default; the remote stub must request it,
34773 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34774 This should only be done on targets that actually support disabling
34775 address space randomization.
34778 @itemx qsThreadInfo
34779 @cindex list active threads, remote request
34780 @cindex @samp{qfThreadInfo} packet
34781 @cindex @samp{qsThreadInfo} packet
34782 Obtain a list of all active thread IDs from the target (OS). Since there
34783 may be too many active threads to fit into one reply packet, this query
34784 works iteratively: it may require more than one query/reply sequence to
34785 obtain the entire list of threads. The first query of the sequence will
34786 be the @samp{qfThreadInfo} query; subsequent queries in the
34787 sequence will be the @samp{qsThreadInfo} query.
34789 NOTE: This packet replaces the @samp{qL} query (see below).
34793 @item m @var{thread-id}
34795 @item m @var{thread-id},@var{thread-id}@dots{}
34796 a comma-separated list of thread IDs
34798 (lower case letter @samp{L}) denotes end of list.
34801 In response to each query, the target will reply with a list of one or
34802 more thread IDs, separated by commas.
34803 @value{GDBN} will respond to each reply with a request for more thread
34804 ids (using the @samp{qs} form of the query), until the target responds
34805 with @samp{l} (lower-case ell, for @dfn{last}).
34806 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
34809 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
34810 initial connection with the remote target, and the very first thread ID
34811 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
34812 message. Therefore, the stub should ensure that the first thread ID in
34813 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
34815 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
34816 @cindex get thread-local storage address, remote request
34817 @cindex @samp{qGetTLSAddr} packet
34818 Fetch the address associated with thread local storage specified
34819 by @var{thread-id}, @var{offset}, and @var{lm}.
34821 @var{thread-id} is the thread ID associated with the
34822 thread for which to fetch the TLS address. @xref{thread-id syntax}.
34824 @var{offset} is the (big endian, hex encoded) offset associated with the
34825 thread local variable. (This offset is obtained from the debug
34826 information associated with the variable.)
34828 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
34829 load module associated with the thread local storage. For example,
34830 a @sc{gnu}/Linux system will pass the link map address of the shared
34831 object associated with the thread local storage under consideration.
34832 Other operating environments may choose to represent the load module
34833 differently, so the precise meaning of this parameter will vary.
34837 @item @var{XX}@dots{}
34838 Hex encoded (big endian) bytes representing the address of the thread
34839 local storage requested.
34842 An error occurred. @var{nn} are hex digits.
34845 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
34848 @item qGetTIBAddr:@var{thread-id}
34849 @cindex get thread information block address
34850 @cindex @samp{qGetTIBAddr} packet
34851 Fetch address of the Windows OS specific Thread Information Block.
34853 @var{thread-id} is the thread ID associated with the thread.
34857 @item @var{XX}@dots{}
34858 Hex encoded (big endian) bytes representing the linear address of the
34859 thread information block.
34862 An error occured. This means that either the thread was not found, or the
34863 address could not be retrieved.
34866 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
34869 @item qL @var{startflag} @var{threadcount} @var{nextthread}
34870 Obtain thread information from RTOS. Where: @var{startflag} (one hex
34871 digit) is one to indicate the first query and zero to indicate a
34872 subsequent query; @var{threadcount} (two hex digits) is the maximum
34873 number of threads the response packet can contain; and @var{nextthread}
34874 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
34875 returned in the response as @var{argthread}.
34877 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
34881 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
34882 Where: @var{count} (two hex digits) is the number of threads being
34883 returned; @var{done} (one hex digit) is zero to indicate more threads
34884 and one indicates no further threads; @var{argthreadid} (eight hex
34885 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
34886 is a sequence of thread IDs from the target. @var{threadid} (eight hex
34887 digits). See @code{remote.c:parse_threadlist_response()}.
34891 @cindex section offsets, remote request
34892 @cindex @samp{qOffsets} packet
34893 Get section offsets that the target used when relocating the downloaded
34898 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
34899 Relocate the @code{Text} section by @var{xxx} from its original address.
34900 Relocate the @code{Data} section by @var{yyy} from its original address.
34901 If the object file format provides segment information (e.g.@: @sc{elf}
34902 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
34903 segments by the supplied offsets.
34905 @emph{Note: while a @code{Bss} offset may be included in the response,
34906 @value{GDBN} ignores this and instead applies the @code{Data} offset
34907 to the @code{Bss} section.}
34909 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
34910 Relocate the first segment of the object file, which conventionally
34911 contains program code, to a starting address of @var{xxx}. If
34912 @samp{DataSeg} is specified, relocate the second segment, which
34913 conventionally contains modifiable data, to a starting address of
34914 @var{yyy}. @value{GDBN} will report an error if the object file
34915 does not contain segment information, or does not contain at least
34916 as many segments as mentioned in the reply. Extra segments are
34917 kept at fixed offsets relative to the last relocated segment.
34920 @item qP @var{mode} @var{thread-id}
34921 @cindex thread information, remote request
34922 @cindex @samp{qP} packet
34923 Returns information on @var{thread-id}. Where: @var{mode} is a hex
34924 encoded 32 bit mode; @var{thread-id} is a thread ID
34925 (@pxref{thread-id syntax}).
34927 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
34930 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
34934 @cindex non-stop mode, remote request
34935 @cindex @samp{QNonStop} packet
34937 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
34938 @xref{Remote Non-Stop}, for more information.
34943 The request succeeded.
34946 An error occurred. @var{nn} are hex digits.
34949 An empty reply indicates that @samp{QNonStop} is not supported by
34953 This packet is not probed by default; the remote stub must request it,
34954 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34955 Use of this packet is controlled by the @code{set non-stop} command;
34956 @pxref{Non-Stop Mode}.
34958 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
34959 @cindex pass signals to inferior, remote request
34960 @cindex @samp{QPassSignals} packet
34961 @anchor{QPassSignals}
34962 Each listed @var{signal} should be passed directly to the inferior process.
34963 Signals are numbered identically to continue packets and stop replies
34964 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
34965 strictly greater than the previous item. These signals do not need to stop
34966 the inferior, or be reported to @value{GDBN}. All other signals should be
34967 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
34968 combine; any earlier @samp{QPassSignals} list is completely replaced by the
34969 new list. This packet improves performance when using @samp{handle
34970 @var{signal} nostop noprint pass}.
34975 The request succeeded.
34978 An error occurred. @var{nn} are hex digits.
34981 An empty reply indicates that @samp{QPassSignals} is not supported by
34985 Use of this packet is controlled by the @code{set remote pass-signals}
34986 command (@pxref{Remote Configuration, set remote pass-signals}).
34987 This packet is not probed by default; the remote stub must request it,
34988 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34990 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
34991 @cindex signals the inferior may see, remote request
34992 @cindex @samp{QProgramSignals} packet
34993 @anchor{QProgramSignals}
34994 Each listed @var{signal} may be delivered to the inferior process.
34995 Others should be silently discarded.
34997 In some cases, the remote stub may need to decide whether to deliver a
34998 signal to the program or not without @value{GDBN} involvement. One
34999 example of that is while detaching --- the program's threads may have
35000 stopped for signals that haven't yet had a chance of being reported to
35001 @value{GDBN}, and so the remote stub can use the signal list specified
35002 by this packet to know whether to deliver or ignore those pending
35005 This does not influence whether to deliver a signal as requested by a
35006 resumption packet (@pxref{vCont packet}).
35008 Signals are numbered identically to continue packets and stop replies
35009 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
35010 strictly greater than the previous item. Multiple
35011 @samp{QProgramSignals} packets do not combine; any earlier
35012 @samp{QProgramSignals} list is completely replaced by the new list.
35017 The request succeeded.
35020 An error occurred. @var{nn} are hex digits.
35023 An empty reply indicates that @samp{QProgramSignals} is not supported
35027 Use of this packet is controlled by the @code{set remote program-signals}
35028 command (@pxref{Remote Configuration, set remote program-signals}).
35029 This packet is not probed by default; the remote stub must request it,
35030 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35032 @item qRcmd,@var{command}
35033 @cindex execute remote command, remote request
35034 @cindex @samp{qRcmd} packet
35035 @var{command} (hex encoded) is passed to the local interpreter for
35036 execution. Invalid commands should be reported using the output
35037 string. Before the final result packet, the target may also respond
35038 with a number of intermediate @samp{O@var{output}} console output
35039 packets. @emph{Implementors should note that providing access to a
35040 stubs's interpreter may have security implications}.
35045 A command response with no output.
35047 A command response with the hex encoded output string @var{OUTPUT}.
35049 Indicate a badly formed request.
35051 An empty reply indicates that @samp{qRcmd} is not recognized.
35054 (Note that the @code{qRcmd} packet's name is separated from the
35055 command by a @samp{,}, not a @samp{:}, contrary to the naming
35056 conventions above. Please don't use this packet as a model for new
35059 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
35060 @cindex searching memory, in remote debugging
35062 @cindex @samp{qSearch:memory} packet
35064 @cindex @samp{qSearch memory} packet
35065 @anchor{qSearch memory}
35066 Search @var{length} bytes at @var{address} for @var{search-pattern}.
35067 @var{address} and @var{length} are encoded in hex.
35068 @var{search-pattern} is a sequence of bytes, hex encoded.
35073 The pattern was not found.
35075 The pattern was found at @var{address}.
35077 A badly formed request or an error was encountered while searching memory.
35079 An empty reply indicates that @samp{qSearch:memory} is not recognized.
35082 @item QStartNoAckMode
35083 @cindex @samp{QStartNoAckMode} packet
35084 @anchor{QStartNoAckMode}
35085 Request that the remote stub disable the normal @samp{+}/@samp{-}
35086 protocol acknowledgments (@pxref{Packet Acknowledgment}).
35091 The stub has switched to no-acknowledgment mode.
35092 @value{GDBN} acknowledges this reponse,
35093 but neither the stub nor @value{GDBN} shall send or expect further
35094 @samp{+}/@samp{-} acknowledgments in the current connection.
35096 An empty reply indicates that the stub does not support no-acknowledgment mode.
35099 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
35100 @cindex supported packets, remote query
35101 @cindex features of the remote protocol
35102 @cindex @samp{qSupported} packet
35103 @anchor{qSupported}
35104 Tell the remote stub about features supported by @value{GDBN}, and
35105 query the stub for features it supports. This packet allows
35106 @value{GDBN} and the remote stub to take advantage of each others'
35107 features. @samp{qSupported} also consolidates multiple feature probes
35108 at startup, to improve @value{GDBN} performance---a single larger
35109 packet performs better than multiple smaller probe packets on
35110 high-latency links. Some features may enable behavior which must not
35111 be on by default, e.g.@: because it would confuse older clients or
35112 stubs. Other features may describe packets which could be
35113 automatically probed for, but are not. These features must be
35114 reported before @value{GDBN} will use them. This ``default
35115 unsupported'' behavior is not appropriate for all packets, but it
35116 helps to keep the initial connection time under control with new
35117 versions of @value{GDBN} which support increasing numbers of packets.
35121 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
35122 The stub supports or does not support each returned @var{stubfeature},
35123 depending on the form of each @var{stubfeature} (see below for the
35126 An empty reply indicates that @samp{qSupported} is not recognized,
35127 or that no features needed to be reported to @value{GDBN}.
35130 The allowed forms for each feature (either a @var{gdbfeature} in the
35131 @samp{qSupported} packet, or a @var{stubfeature} in the response)
35135 @item @var{name}=@var{value}
35136 The remote protocol feature @var{name} is supported, and associated
35137 with the specified @var{value}. The format of @var{value} depends
35138 on the feature, but it must not include a semicolon.
35140 The remote protocol feature @var{name} is supported, and does not
35141 need an associated value.
35143 The remote protocol feature @var{name} is not supported.
35145 The remote protocol feature @var{name} may be supported, and
35146 @value{GDBN} should auto-detect support in some other way when it is
35147 needed. This form will not be used for @var{gdbfeature} notifications,
35148 but may be used for @var{stubfeature} responses.
35151 Whenever the stub receives a @samp{qSupported} request, the
35152 supplied set of @value{GDBN} features should override any previous
35153 request. This allows @value{GDBN} to put the stub in a known
35154 state, even if the stub had previously been communicating with
35155 a different version of @value{GDBN}.
35157 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
35162 This feature indicates whether @value{GDBN} supports multiprocess
35163 extensions to the remote protocol. @value{GDBN} does not use such
35164 extensions unless the stub also reports that it supports them by
35165 including @samp{multiprocess+} in its @samp{qSupported} reply.
35166 @xref{multiprocess extensions}, for details.
35169 This feature indicates that @value{GDBN} supports the XML target
35170 description. If the stub sees @samp{xmlRegisters=} with target
35171 specific strings separated by a comma, it will report register
35175 This feature indicates whether @value{GDBN} supports the
35176 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
35177 instruction reply packet}).
35180 Stubs should ignore any unknown values for
35181 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
35182 packet supports receiving packets of unlimited length (earlier
35183 versions of @value{GDBN} may reject overly long responses). Additional values
35184 for @var{gdbfeature} may be defined in the future to let the stub take
35185 advantage of new features in @value{GDBN}, e.g.@: incompatible
35186 improvements in the remote protocol---the @samp{multiprocess} feature is
35187 an example of such a feature. The stub's reply should be independent
35188 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
35189 describes all the features it supports, and then the stub replies with
35190 all the features it supports.
35192 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
35193 responses, as long as each response uses one of the standard forms.
35195 Some features are flags. A stub which supports a flag feature
35196 should respond with a @samp{+} form response. Other features
35197 require values, and the stub should respond with an @samp{=}
35200 Each feature has a default value, which @value{GDBN} will use if
35201 @samp{qSupported} is not available or if the feature is not mentioned
35202 in the @samp{qSupported} response. The default values are fixed; a
35203 stub is free to omit any feature responses that match the defaults.
35205 Not all features can be probed, but for those which can, the probing
35206 mechanism is useful: in some cases, a stub's internal
35207 architecture may not allow the protocol layer to know some information
35208 about the underlying target in advance. This is especially common in
35209 stubs which may be configured for multiple targets.
35211 These are the currently defined stub features and their properties:
35213 @multitable @columnfractions 0.35 0.2 0.12 0.2
35214 @c NOTE: The first row should be @headitem, but we do not yet require
35215 @c a new enough version of Texinfo (4.7) to use @headitem.
35217 @tab Value Required
35221 @item @samp{PacketSize}
35226 @item @samp{qXfer:auxv:read}
35231 @item @samp{qXfer:btrace:read}
35236 @item @samp{qXfer:features:read}
35241 @item @samp{qXfer:libraries:read}
35246 @item @samp{qXfer:libraries-svr4:read}
35251 @item @samp{augmented-libraries-svr4-read}
35256 @item @samp{qXfer:memory-map:read}
35261 @item @samp{qXfer:sdata:read}
35266 @item @samp{qXfer:spu:read}
35271 @item @samp{qXfer:spu:write}
35276 @item @samp{qXfer:siginfo:read}
35281 @item @samp{qXfer:siginfo:write}
35286 @item @samp{qXfer:threads:read}
35291 @item @samp{qXfer:traceframe-info:read}
35296 @item @samp{qXfer:uib:read}
35301 @item @samp{qXfer:fdpic:read}
35306 @item @samp{Qbtrace:off}
35311 @item @samp{Qbtrace:bts}
35316 @item @samp{QNonStop}
35321 @item @samp{QPassSignals}
35326 @item @samp{QStartNoAckMode}
35331 @item @samp{multiprocess}
35336 @item @samp{ConditionalBreakpoints}
35341 @item @samp{ConditionalTracepoints}
35346 @item @samp{ReverseContinue}
35351 @item @samp{ReverseStep}
35356 @item @samp{TracepointSource}
35361 @item @samp{QAgent}
35366 @item @samp{QAllow}
35371 @item @samp{QDisableRandomization}
35376 @item @samp{EnableDisableTracepoints}
35381 @item @samp{QTBuffer:size}
35386 @item @samp{tracenz}
35391 @item @samp{BreakpointCommands}
35398 These are the currently defined stub features, in more detail:
35401 @cindex packet size, remote protocol
35402 @item PacketSize=@var{bytes}
35403 The remote stub can accept packets up to at least @var{bytes} in
35404 length. @value{GDBN} will send packets up to this size for bulk
35405 transfers, and will never send larger packets. This is a limit on the
35406 data characters in the packet, including the frame and checksum.
35407 There is no trailing NUL byte in a remote protocol packet; if the stub
35408 stores packets in a NUL-terminated format, it should allow an extra
35409 byte in its buffer for the NUL. If this stub feature is not supported,
35410 @value{GDBN} guesses based on the size of the @samp{g} packet response.
35412 @item qXfer:auxv:read
35413 The remote stub understands the @samp{qXfer:auxv:read} packet
35414 (@pxref{qXfer auxiliary vector read}).
35416 @item qXfer:btrace:read
35417 The remote stub understands the @samp{qXfer:btrace:read}
35418 packet (@pxref{qXfer btrace read}).
35420 @item qXfer:features:read
35421 The remote stub understands the @samp{qXfer:features:read} packet
35422 (@pxref{qXfer target description read}).
35424 @item qXfer:libraries:read
35425 The remote stub understands the @samp{qXfer:libraries:read} packet
35426 (@pxref{qXfer library list read}).
35428 @item qXfer:libraries-svr4:read
35429 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
35430 (@pxref{qXfer svr4 library list read}).
35432 @item augmented-libraries-svr4-read
35433 The remote stub understands the augmented form of the
35434 @samp{qXfer:libraries-svr4:read} packet
35435 (@pxref{qXfer svr4 library list read}).
35437 @item qXfer:memory-map:read
35438 The remote stub understands the @samp{qXfer:memory-map:read} packet
35439 (@pxref{qXfer memory map read}).
35441 @item qXfer:sdata:read
35442 The remote stub understands the @samp{qXfer:sdata:read} packet
35443 (@pxref{qXfer sdata read}).
35445 @item qXfer:spu:read
35446 The remote stub understands the @samp{qXfer:spu:read} packet
35447 (@pxref{qXfer spu read}).
35449 @item qXfer:spu:write
35450 The remote stub understands the @samp{qXfer:spu:write} packet
35451 (@pxref{qXfer spu write}).
35453 @item qXfer:siginfo:read
35454 The remote stub understands the @samp{qXfer:siginfo:read} packet
35455 (@pxref{qXfer siginfo read}).
35457 @item qXfer:siginfo:write
35458 The remote stub understands the @samp{qXfer:siginfo:write} packet
35459 (@pxref{qXfer siginfo write}).
35461 @item qXfer:threads:read
35462 The remote stub understands the @samp{qXfer:threads:read} packet
35463 (@pxref{qXfer threads read}).
35465 @item qXfer:traceframe-info:read
35466 The remote stub understands the @samp{qXfer:traceframe-info:read}
35467 packet (@pxref{qXfer traceframe info read}).
35469 @item qXfer:uib:read
35470 The remote stub understands the @samp{qXfer:uib:read}
35471 packet (@pxref{qXfer unwind info block}).
35473 @item qXfer:fdpic:read
35474 The remote stub understands the @samp{qXfer:fdpic:read}
35475 packet (@pxref{qXfer fdpic loadmap read}).
35478 The remote stub understands the @samp{QNonStop} packet
35479 (@pxref{QNonStop}).
35482 The remote stub understands the @samp{QPassSignals} packet
35483 (@pxref{QPassSignals}).
35485 @item QStartNoAckMode
35486 The remote stub understands the @samp{QStartNoAckMode} packet and
35487 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
35490 @anchor{multiprocess extensions}
35491 @cindex multiprocess extensions, in remote protocol
35492 The remote stub understands the multiprocess extensions to the remote
35493 protocol syntax. The multiprocess extensions affect the syntax of
35494 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
35495 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
35496 replies. Note that reporting this feature indicates support for the
35497 syntactic extensions only, not that the stub necessarily supports
35498 debugging of more than one process at a time. The stub must not use
35499 multiprocess extensions in packet replies unless @value{GDBN} has also
35500 indicated it supports them in its @samp{qSupported} request.
35502 @item qXfer:osdata:read
35503 The remote stub understands the @samp{qXfer:osdata:read} packet
35504 ((@pxref{qXfer osdata read}).
35506 @item ConditionalBreakpoints
35507 The target accepts and implements evaluation of conditional expressions
35508 defined for breakpoints. The target will only report breakpoint triggers
35509 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
35511 @item ConditionalTracepoints
35512 The remote stub accepts and implements conditional expressions defined
35513 for tracepoints (@pxref{Tracepoint Conditions}).
35515 @item ReverseContinue
35516 The remote stub accepts and implements the reverse continue packet
35520 The remote stub accepts and implements the reverse step packet
35523 @item TracepointSource
35524 The remote stub understands the @samp{QTDPsrc} packet that supplies
35525 the source form of tracepoint definitions.
35528 The remote stub understands the @samp{QAgent} packet.
35531 The remote stub understands the @samp{QAllow} packet.
35533 @item QDisableRandomization
35534 The remote stub understands the @samp{QDisableRandomization} packet.
35536 @item StaticTracepoint
35537 @cindex static tracepoints, in remote protocol
35538 The remote stub supports static tracepoints.
35540 @item InstallInTrace
35541 @anchor{install tracepoint in tracing}
35542 The remote stub supports installing tracepoint in tracing.
35544 @item EnableDisableTracepoints
35545 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
35546 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
35547 to be enabled and disabled while a trace experiment is running.
35549 @item QTBuffer:size
35550 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
35551 packet that allows to change the size of the trace buffer.
35554 @cindex string tracing, in remote protocol
35555 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
35556 See @ref{Bytecode Descriptions} for details about the bytecode.
35558 @item BreakpointCommands
35559 @cindex breakpoint commands, in remote protocol
35560 The remote stub supports running a breakpoint's command list itself,
35561 rather than reporting the hit to @value{GDBN}.
35564 The remote stub understands the @samp{Qbtrace:off} packet.
35567 The remote stub understands the @samp{Qbtrace:bts} packet.
35572 @cindex symbol lookup, remote request
35573 @cindex @samp{qSymbol} packet
35574 Notify the target that @value{GDBN} is prepared to serve symbol lookup
35575 requests. Accept requests from the target for the values of symbols.
35580 The target does not need to look up any (more) symbols.
35581 @item qSymbol:@var{sym_name}
35582 The target requests the value of symbol @var{sym_name} (hex encoded).
35583 @value{GDBN} may provide the value by using the
35584 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
35588 @item qSymbol:@var{sym_value}:@var{sym_name}
35589 Set the value of @var{sym_name} to @var{sym_value}.
35591 @var{sym_name} (hex encoded) is the name of a symbol whose value the
35592 target has previously requested.
35594 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
35595 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
35601 The target does not need to look up any (more) symbols.
35602 @item qSymbol:@var{sym_name}
35603 The target requests the value of a new symbol @var{sym_name} (hex
35604 encoded). @value{GDBN} will continue to supply the values of symbols
35605 (if available), until the target ceases to request them.
35610 @itemx QTDisconnected
35617 @itemx qTMinFTPILen
35619 @xref{Tracepoint Packets}.
35621 @item qThreadExtraInfo,@var{thread-id}
35622 @cindex thread attributes info, remote request
35623 @cindex @samp{qThreadExtraInfo} packet
35624 Obtain a printable string description of a thread's attributes from
35625 the target OS. @var{thread-id} is a thread ID;
35626 see @ref{thread-id syntax}. This
35627 string may contain anything that the target OS thinks is interesting
35628 for @value{GDBN} to tell the user about the thread. The string is
35629 displayed in @value{GDBN}'s @code{info threads} display. Some
35630 examples of possible thread extra info strings are @samp{Runnable}, or
35631 @samp{Blocked on Mutex}.
35635 @item @var{XX}@dots{}
35636 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
35637 comprising the printable string containing the extra information about
35638 the thread's attributes.
35641 (Note that the @code{qThreadExtraInfo} packet's name is separated from
35642 the command by a @samp{,}, not a @samp{:}, contrary to the naming
35643 conventions above. Please don't use this packet as a model for new
35662 @xref{Tracepoint Packets}.
35664 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
35665 @cindex read special object, remote request
35666 @cindex @samp{qXfer} packet
35667 @anchor{qXfer read}
35668 Read uninterpreted bytes from the target's special data area
35669 identified by the keyword @var{object}. Request @var{length} bytes
35670 starting at @var{offset} bytes into the data. The content and
35671 encoding of @var{annex} is specific to @var{object}; it can supply
35672 additional details about what data to access.
35674 Here are the specific requests of this form defined so far. All
35675 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
35676 formats, listed below.
35679 @item qXfer:auxv:read::@var{offset},@var{length}
35680 @anchor{qXfer auxiliary vector read}
35681 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
35682 auxiliary vector}. Note @var{annex} must be empty.
35684 This packet is not probed by default; the remote stub must request it,
35685 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35687 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
35688 @anchor{qXfer btrace read}
35690 Return a description of the current branch trace.
35691 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
35692 packet may have one of the following values:
35696 Returns all available branch trace.
35699 Returns all available branch trace if the branch trace changed since
35700 the last read request.
35703 Returns the new branch trace since the last read request. Adds a new
35704 block to the end of the trace that begins at zero and ends at the source
35705 location of the first branch in the trace buffer. This extra block is
35706 used to stitch traces together.
35708 If the trace buffer overflowed, returns an error indicating the overflow.
35711 This packet is not probed by default; the remote stub must request it
35712 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35714 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
35715 @anchor{qXfer target description read}
35716 Access the @dfn{target description}. @xref{Target Descriptions}. The
35717 annex specifies which XML document to access. The main description is
35718 always loaded from the @samp{target.xml} annex.
35720 This packet is not probed by default; the remote stub must request it,
35721 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35723 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
35724 @anchor{qXfer library list read}
35725 Access the target's list of loaded libraries. @xref{Library List Format}.
35726 The annex part of the generic @samp{qXfer} packet must be empty
35727 (@pxref{qXfer read}).
35729 Targets which maintain a list of libraries in the program's memory do
35730 not need to implement this packet; it is designed for platforms where
35731 the operating system manages the list of loaded libraries.
35733 This packet is not probed by default; the remote stub must request it,
35734 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35736 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
35737 @anchor{qXfer svr4 library list read}
35738 Access the target's list of loaded libraries when the target is an SVR4
35739 platform. @xref{Library List Format for SVR4 Targets}. The annex part
35740 of the generic @samp{qXfer} packet must be empty unless the remote
35741 stub indicated it supports the augmented form of this packet
35742 by supplying an appropriate @samp{qSupported} response
35743 (@pxref{qXfer read}, @ref{qSupported}).
35745 This packet is optional for better performance on SVR4 targets.
35746 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
35748 This packet is not probed by default; the remote stub must request it,
35749 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35751 If the remote stub indicates it supports the augmented form of this
35752 packet then the annex part of the generic @samp{qXfer} packet may
35753 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
35754 arguments. The currently supported arguments are:
35757 @item start=@var{address}
35758 A hexadecimal number specifying the address of the @samp{struct
35759 link_map} to start reading the library list from. If unset or zero
35760 then the first @samp{struct link_map} in the library list will be
35761 chosen as the starting point.
35763 @item prev=@var{address}
35764 A hexadecimal number specifying the address of the @samp{struct
35765 link_map} immediately preceding the @samp{struct link_map}
35766 specified by the @samp{start} argument. If unset or zero then
35767 the remote stub will expect that no @samp{struct link_map}
35768 exists prior to the starting point.
35772 Arguments that are not understood by the remote stub will be silently
35775 @item qXfer:memory-map:read::@var{offset},@var{length}
35776 @anchor{qXfer memory map read}
35777 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
35778 annex part of the generic @samp{qXfer} packet must be empty
35779 (@pxref{qXfer read}).
35781 This packet is not probed by default; the remote stub must request it,
35782 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35784 @item qXfer:sdata:read::@var{offset},@var{length}
35785 @anchor{qXfer sdata read}
35787 Read contents of the extra collected static tracepoint marker
35788 information. The annex part of the generic @samp{qXfer} packet must
35789 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
35792 This packet is not probed by default; the remote stub must request it,
35793 by supplying an appropriate @samp{qSupported} response
35794 (@pxref{qSupported}).
35796 @item qXfer:siginfo:read::@var{offset},@var{length}
35797 @anchor{qXfer siginfo read}
35798 Read contents of the extra signal information on the target
35799 system. The annex part of the generic @samp{qXfer} packet must be
35800 empty (@pxref{qXfer read}).
35802 This packet is not probed by default; the remote stub must request it,
35803 by supplying an appropriate @samp{qSupported} response
35804 (@pxref{qSupported}).
35806 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
35807 @anchor{qXfer spu read}
35808 Read contents of an @code{spufs} file on the target system. The
35809 annex specifies which file to read; it must be of the form
35810 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
35811 in the target process, and @var{name} identifes the @code{spufs} file
35812 in that context to be accessed.
35814 This packet is not probed by default; the remote stub must request it,
35815 by supplying an appropriate @samp{qSupported} response
35816 (@pxref{qSupported}).
35818 @item qXfer:threads:read::@var{offset},@var{length}
35819 @anchor{qXfer threads read}
35820 Access the list of threads on target. @xref{Thread List Format}. The
35821 annex part of the generic @samp{qXfer} packet must be empty
35822 (@pxref{qXfer read}).
35824 This packet is not probed by default; the remote stub must request it,
35825 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35827 @item qXfer:traceframe-info:read::@var{offset},@var{length}
35828 @anchor{qXfer traceframe info read}
35830 Return a description of the current traceframe's contents.
35831 @xref{Traceframe Info Format}. The annex part of the generic
35832 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
35834 This packet is not probed by default; the remote stub must request it,
35835 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35837 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
35838 @anchor{qXfer unwind info block}
35840 Return the unwind information block for @var{pc}. This packet is used
35841 on OpenVMS/ia64 to ask the kernel unwind information.
35843 This packet is not probed by default.
35845 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
35846 @anchor{qXfer fdpic loadmap read}
35847 Read contents of @code{loadmap}s on the target system. The
35848 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
35849 executable @code{loadmap} or interpreter @code{loadmap} to read.
35851 This packet is not probed by default; the remote stub must request it,
35852 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35854 @item qXfer:osdata:read::@var{offset},@var{length}
35855 @anchor{qXfer osdata read}
35856 Access the target's @dfn{operating system information}.
35857 @xref{Operating System Information}.
35864 Data @var{data} (@pxref{Binary Data}) has been read from the
35865 target. There may be more data at a higher address (although
35866 it is permitted to return @samp{m} even for the last valid
35867 block of data, as long as at least one byte of data was read).
35868 @var{data} may have fewer bytes than the @var{length} in the
35872 Data @var{data} (@pxref{Binary Data}) has been read from the target.
35873 There is no more data to be read. @var{data} may have fewer bytes
35874 than the @var{length} in the request.
35877 The @var{offset} in the request is at the end of the data.
35878 There is no more data to be read.
35881 The request was malformed, or @var{annex} was invalid.
35884 The offset was invalid, or there was an error encountered reading the data.
35885 @var{nn} is a hex-encoded @code{errno} value.
35888 An empty reply indicates the @var{object} string was not recognized by
35889 the stub, or that the object does not support reading.
35892 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
35893 @cindex write data into object, remote request
35894 @anchor{qXfer write}
35895 Write uninterpreted bytes into the target's special data area
35896 identified by the keyword @var{object}, starting at @var{offset} bytes
35897 into the data. @var{data}@dots{} is the binary-encoded data
35898 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
35899 is specific to @var{object}; it can supply additional details about what data
35902 Here are the specific requests of this form defined so far. All
35903 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
35904 formats, listed below.
35907 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
35908 @anchor{qXfer siginfo write}
35909 Write @var{data} to the extra signal information on the target system.
35910 The annex part of the generic @samp{qXfer} packet must be
35911 empty (@pxref{qXfer write}).
35913 This packet is not probed by default; the remote stub must request it,
35914 by supplying an appropriate @samp{qSupported} response
35915 (@pxref{qSupported}).
35917 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
35918 @anchor{qXfer spu write}
35919 Write @var{data} to an @code{spufs} file on the target system. The
35920 annex specifies which file to write; it must be of the form
35921 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
35922 in the target process, and @var{name} identifes the @code{spufs} file
35923 in that context to be accessed.
35925 This packet is not probed by default; the remote stub must request it,
35926 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35932 @var{nn} (hex encoded) is the number of bytes written.
35933 This may be fewer bytes than supplied in the request.
35936 The request was malformed, or @var{annex} was invalid.
35939 The offset was invalid, or there was an error encountered writing the data.
35940 @var{nn} is a hex-encoded @code{errno} value.
35943 An empty reply indicates the @var{object} string was not
35944 recognized by the stub, or that the object does not support writing.
35947 @item qXfer:@var{object}:@var{operation}:@dots{}
35948 Requests of this form may be added in the future. When a stub does
35949 not recognize the @var{object} keyword, or its support for
35950 @var{object} does not recognize the @var{operation} keyword, the stub
35951 must respond with an empty packet.
35953 @item qAttached:@var{pid}
35954 @cindex query attached, remote request
35955 @cindex @samp{qAttached} packet
35956 Return an indication of whether the remote server attached to an
35957 existing process or created a new process. When the multiprocess
35958 protocol extensions are supported (@pxref{multiprocess extensions}),
35959 @var{pid} is an integer in hexadecimal format identifying the target
35960 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
35961 the query packet will be simplified as @samp{qAttached}.
35963 This query is used, for example, to know whether the remote process
35964 should be detached or killed when a @value{GDBN} session is ended with
35965 the @code{quit} command.
35970 The remote server attached to an existing process.
35972 The remote server created a new process.
35974 A badly formed request or an error was encountered.
35978 Enable branch tracing for the current thread using bts tracing.
35983 Branch tracing has been enabled.
35985 A badly formed request or an error was encountered.
35989 Disable branch tracing for the current thread.
35994 Branch tracing has been disabled.
35996 A badly formed request or an error was encountered.
36001 @node Architecture-Specific Protocol Details
36002 @section Architecture-Specific Protocol Details
36004 This section describes how the remote protocol is applied to specific
36005 target architectures. Also see @ref{Standard Target Features}, for
36006 details of XML target descriptions for each architecture.
36009 * ARM-Specific Protocol Details::
36010 * MIPS-Specific Protocol Details::
36013 @node ARM-Specific Protocol Details
36014 @subsection @acronym{ARM}-specific Protocol Details
36017 * ARM Breakpoint Kinds::
36020 @node ARM Breakpoint Kinds
36021 @subsubsection @acronym{ARM} Breakpoint Kinds
36022 @cindex breakpoint kinds, @acronym{ARM}
36024 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
36029 16-bit Thumb mode breakpoint.
36032 32-bit Thumb mode (Thumb-2) breakpoint.
36035 32-bit @acronym{ARM} mode breakpoint.
36039 @node MIPS-Specific Protocol Details
36040 @subsection @acronym{MIPS}-specific Protocol Details
36043 * MIPS Register packet Format::
36044 * MIPS Breakpoint Kinds::
36047 @node MIPS Register packet Format
36048 @subsubsection @acronym{MIPS} Register Packet Format
36049 @cindex register packet format, @acronym{MIPS}
36051 The following @code{g}/@code{G} packets have previously been defined.
36052 In the below, some thirty-two bit registers are transferred as
36053 sixty-four bits. Those registers should be zero/sign extended (which?)
36054 to fill the space allocated. Register bytes are transferred in target
36055 byte order. The two nibbles within a register byte are transferred
36056 most-significant -- least-significant.
36061 All registers are transferred as thirty-two bit quantities in the order:
36062 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
36063 registers; fsr; fir; fp.
36066 All registers are transferred as sixty-four bit quantities (including
36067 thirty-two bit registers such as @code{sr}). The ordering is the same
36072 @node MIPS Breakpoint Kinds
36073 @subsubsection @acronym{MIPS} Breakpoint Kinds
36074 @cindex breakpoint kinds, @acronym{MIPS}
36076 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
36081 16-bit @acronym{MIPS16} mode breakpoint.
36084 16-bit @acronym{microMIPS} mode breakpoint.
36087 32-bit standard @acronym{MIPS} mode breakpoint.
36090 32-bit @acronym{microMIPS} mode breakpoint.
36094 @node Tracepoint Packets
36095 @section Tracepoint Packets
36096 @cindex tracepoint packets
36097 @cindex packets, tracepoint
36099 Here we describe the packets @value{GDBN} uses to implement
36100 tracepoints (@pxref{Tracepoints}).
36104 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
36105 @cindex @samp{QTDP} packet
36106 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
36107 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
36108 the tracepoint is disabled. @var{step} is the tracepoint's step
36109 count, and @var{pass} is its pass count. If an @samp{F} is present,
36110 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
36111 the number of bytes that the target should copy elsewhere to make room
36112 for the tracepoint. If an @samp{X} is present, it introduces a
36113 tracepoint condition, which consists of a hexadecimal length, followed
36114 by a comma and hex-encoded bytes, in a manner similar to action
36115 encodings as described below. If the trailing @samp{-} is present,
36116 further @samp{QTDP} packets will follow to specify this tracepoint's
36122 The packet was understood and carried out.
36124 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
36126 The packet was not recognized.
36129 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
36130 Define actions to be taken when a tracepoint is hit. @var{n} and
36131 @var{addr} must be the same as in the initial @samp{QTDP} packet for
36132 this tracepoint. This packet may only be sent immediately after
36133 another @samp{QTDP} packet that ended with a @samp{-}. If the
36134 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
36135 specifying more actions for this tracepoint.
36137 In the series of action packets for a given tracepoint, at most one
36138 can have an @samp{S} before its first @var{action}. If such a packet
36139 is sent, it and the following packets define ``while-stepping''
36140 actions. Any prior packets define ordinary actions --- that is, those
36141 taken when the tracepoint is first hit. If no action packet has an
36142 @samp{S}, then all the packets in the series specify ordinary
36143 tracepoint actions.
36145 The @samp{@var{action}@dots{}} portion of the packet is a series of
36146 actions, concatenated without separators. Each action has one of the
36152 Collect the registers whose bits are set in @var{mask}. @var{mask} is
36153 a hexadecimal number whose @var{i}'th bit is set if register number
36154 @var{i} should be collected. (The least significant bit is numbered
36155 zero.) Note that @var{mask} may be any number of digits long; it may
36156 not fit in a 32-bit word.
36158 @item M @var{basereg},@var{offset},@var{len}
36159 Collect @var{len} bytes of memory starting at the address in register
36160 number @var{basereg}, plus @var{offset}. If @var{basereg} is
36161 @samp{-1}, then the range has a fixed address: @var{offset} is the
36162 address of the lowest byte to collect. The @var{basereg},
36163 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
36164 values (the @samp{-1} value for @var{basereg} is a special case).
36166 @item X @var{len},@var{expr}
36167 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
36168 it directs. @var{expr} is an agent expression, as described in
36169 @ref{Agent Expressions}. Each byte of the expression is encoded as a
36170 two-digit hex number in the packet; @var{len} is the number of bytes
36171 in the expression (and thus one-half the number of hex digits in the
36176 Any number of actions may be packed together in a single @samp{QTDP}
36177 packet, as long as the packet does not exceed the maximum packet
36178 length (400 bytes, for many stubs). There may be only one @samp{R}
36179 action per tracepoint, and it must precede any @samp{M} or @samp{X}
36180 actions. Any registers referred to by @samp{M} and @samp{X} actions
36181 must be collected by a preceding @samp{R} action. (The
36182 ``while-stepping'' actions are treated as if they were attached to a
36183 separate tracepoint, as far as these restrictions are concerned.)
36188 The packet was understood and carried out.
36190 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
36192 The packet was not recognized.
36195 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
36196 @cindex @samp{QTDPsrc} packet
36197 Specify a source string of tracepoint @var{n} at address @var{addr}.
36198 This is useful to get accurate reproduction of the tracepoints
36199 originally downloaded at the beginning of the trace run. @var{type}
36200 is the name of the tracepoint part, such as @samp{cond} for the
36201 tracepoint's conditional expression (see below for a list of types), while
36202 @var{bytes} is the string, encoded in hexadecimal.
36204 @var{start} is the offset of the @var{bytes} within the overall source
36205 string, while @var{slen} is the total length of the source string.
36206 This is intended for handling source strings that are longer than will
36207 fit in a single packet.
36208 @c Add detailed example when this info is moved into a dedicated
36209 @c tracepoint descriptions section.
36211 The available string types are @samp{at} for the location,
36212 @samp{cond} for the conditional, and @samp{cmd} for an action command.
36213 @value{GDBN} sends a separate packet for each command in the action
36214 list, in the same order in which the commands are stored in the list.
36216 The target does not need to do anything with source strings except
36217 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
36220 Although this packet is optional, and @value{GDBN} will only send it
36221 if the target replies with @samp{TracepointSource} @xref{General
36222 Query Packets}, it makes both disconnected tracing and trace files
36223 much easier to use. Otherwise the user must be careful that the
36224 tracepoints in effect while looking at trace frames are identical to
36225 the ones in effect during the trace run; even a small discrepancy
36226 could cause @samp{tdump} not to work, or a particular trace frame not
36229 @item QTDV:@var{n}:@var{value}
36230 @cindex define trace state variable, remote request
36231 @cindex @samp{QTDV} packet
36232 Create a new trace state variable, number @var{n}, with an initial
36233 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
36234 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
36235 the option of not using this packet for initial values of zero; the
36236 target should simply create the trace state variables as they are
36237 mentioned in expressions.
36239 @item QTFrame:@var{n}
36240 @cindex @samp{QTFrame} packet
36241 Select the @var{n}'th tracepoint frame from the buffer, and use the
36242 register and memory contents recorded there to answer subsequent
36243 request packets from @value{GDBN}.
36245 A successful reply from the stub indicates that the stub has found the
36246 requested frame. The response is a series of parts, concatenated
36247 without separators, describing the frame we selected. Each part has
36248 one of the following forms:
36252 The selected frame is number @var{n} in the trace frame buffer;
36253 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
36254 was no frame matching the criteria in the request packet.
36257 The selected trace frame records a hit of tracepoint number @var{t};
36258 @var{t} is a hexadecimal number.
36262 @item QTFrame:pc:@var{addr}
36263 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36264 currently selected frame whose PC is @var{addr};
36265 @var{addr} is a hexadecimal number.
36267 @item QTFrame:tdp:@var{t}
36268 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36269 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
36270 is a hexadecimal number.
36272 @item QTFrame:range:@var{start}:@var{end}
36273 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36274 currently selected frame whose PC is between @var{start} (inclusive)
36275 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
36278 @item QTFrame:outside:@var{start}:@var{end}
36279 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
36280 frame @emph{outside} the given range of addresses (exclusive).
36283 @cindex @samp{qTMinFTPILen} packet
36284 This packet requests the minimum length of instruction at which a fast
36285 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
36286 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
36287 it depends on the target system being able to create trampolines in
36288 the first 64K of memory, which might or might not be possible for that
36289 system. So the reply to this packet will be 4 if it is able to
36296 The minimum instruction length is currently unknown.
36298 The minimum instruction length is @var{length}, where @var{length} is greater
36299 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
36300 that a fast tracepoint may be placed on any instruction regardless of size.
36302 An error has occurred.
36304 An empty reply indicates that the request is not supported by the stub.
36308 @cindex @samp{QTStart} packet
36309 Begin the tracepoint experiment. Begin collecting data from
36310 tracepoint hits in the trace frame buffer. This packet supports the
36311 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
36312 instruction reply packet}).
36315 @cindex @samp{QTStop} packet
36316 End the tracepoint experiment. Stop collecting trace frames.
36318 @item QTEnable:@var{n}:@var{addr}
36320 @cindex @samp{QTEnable} packet
36321 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
36322 experiment. If the tracepoint was previously disabled, then collection
36323 of data from it will resume.
36325 @item QTDisable:@var{n}:@var{addr}
36327 @cindex @samp{QTDisable} packet
36328 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
36329 experiment. No more data will be collected from the tracepoint unless
36330 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
36333 @cindex @samp{QTinit} packet
36334 Clear the table of tracepoints, and empty the trace frame buffer.
36336 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
36337 @cindex @samp{QTro} packet
36338 Establish the given ranges of memory as ``transparent''. The stub
36339 will answer requests for these ranges from memory's current contents,
36340 if they were not collected as part of the tracepoint hit.
36342 @value{GDBN} uses this to mark read-only regions of memory, like those
36343 containing program code. Since these areas never change, they should
36344 still have the same contents they did when the tracepoint was hit, so
36345 there's no reason for the stub to refuse to provide their contents.
36347 @item QTDisconnected:@var{value}
36348 @cindex @samp{QTDisconnected} packet
36349 Set the choice to what to do with the tracing run when @value{GDBN}
36350 disconnects from the target. A @var{value} of 1 directs the target to
36351 continue the tracing run, while 0 tells the target to stop tracing if
36352 @value{GDBN} is no longer in the picture.
36355 @cindex @samp{qTStatus} packet
36356 Ask the stub if there is a trace experiment running right now.
36358 The reply has the form:
36362 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
36363 @var{running} is a single digit @code{1} if the trace is presently
36364 running, or @code{0} if not. It is followed by semicolon-separated
36365 optional fields that an agent may use to report additional status.
36369 If the trace is not running, the agent may report any of several
36370 explanations as one of the optional fields:
36375 No trace has been run yet.
36377 @item tstop[:@var{text}]:0
36378 The trace was stopped by a user-originated stop command. The optional
36379 @var{text} field is a user-supplied string supplied as part of the
36380 stop command (for instance, an explanation of why the trace was
36381 stopped manually). It is hex-encoded.
36384 The trace stopped because the trace buffer filled up.
36386 @item tdisconnected:0
36387 The trace stopped because @value{GDBN} disconnected from the target.
36389 @item tpasscount:@var{tpnum}
36390 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
36392 @item terror:@var{text}:@var{tpnum}
36393 The trace stopped because tracepoint @var{tpnum} had an error. The
36394 string @var{text} is available to describe the nature of the error
36395 (for instance, a divide by zero in the condition expression).
36396 @var{text} is hex encoded.
36399 The trace stopped for some other reason.
36403 Additional optional fields supply statistical and other information.
36404 Although not required, they are extremely useful for users monitoring
36405 the progress of a trace run. If a trace has stopped, and these
36406 numbers are reported, they must reflect the state of the just-stopped
36411 @item tframes:@var{n}
36412 The number of trace frames in the buffer.
36414 @item tcreated:@var{n}
36415 The total number of trace frames created during the run. This may
36416 be larger than the trace frame count, if the buffer is circular.
36418 @item tsize:@var{n}
36419 The total size of the trace buffer, in bytes.
36421 @item tfree:@var{n}
36422 The number of bytes still unused in the buffer.
36424 @item circular:@var{n}
36425 The value of the circular trace buffer flag. @code{1} means that the
36426 trace buffer is circular and old trace frames will be discarded if
36427 necessary to make room, @code{0} means that the trace buffer is linear
36430 @item disconn:@var{n}
36431 The value of the disconnected tracing flag. @code{1} means that
36432 tracing will continue after @value{GDBN} disconnects, @code{0} means
36433 that the trace run will stop.
36437 @item qTP:@var{tp}:@var{addr}
36438 @cindex tracepoint status, remote request
36439 @cindex @samp{qTP} packet
36440 Ask the stub for the current state of tracepoint number @var{tp} at
36441 address @var{addr}.
36445 @item V@var{hits}:@var{usage}
36446 The tracepoint has been hit @var{hits} times so far during the trace
36447 run, and accounts for @var{usage} in the trace buffer. Note that
36448 @code{while-stepping} steps are not counted as separate hits, but the
36449 steps' space consumption is added into the usage number.
36453 @item qTV:@var{var}
36454 @cindex trace state variable value, remote request
36455 @cindex @samp{qTV} packet
36456 Ask the stub for the value of the trace state variable number @var{var}.
36461 The value of the variable is @var{value}. This will be the current
36462 value of the variable if the user is examining a running target, or a
36463 saved value if the variable was collected in the trace frame that the
36464 user is looking at. Note that multiple requests may result in
36465 different reply values, such as when requesting values while the
36466 program is running.
36469 The value of the variable is unknown. This would occur, for example,
36470 if the user is examining a trace frame in which the requested variable
36475 @cindex @samp{qTfP} packet
36477 @cindex @samp{qTsP} packet
36478 These packets request data about tracepoints that are being used by
36479 the target. @value{GDBN} sends @code{qTfP} to get the first piece
36480 of data, and multiple @code{qTsP} to get additional pieces. Replies
36481 to these packets generally take the form of the @code{QTDP} packets
36482 that define tracepoints. (FIXME add detailed syntax)
36485 @cindex @samp{qTfV} packet
36487 @cindex @samp{qTsV} packet
36488 These packets request data about trace state variables that are on the
36489 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
36490 and multiple @code{qTsV} to get additional variables. Replies to
36491 these packets follow the syntax of the @code{QTDV} packets that define
36492 trace state variables.
36498 @cindex @samp{qTfSTM} packet
36499 @cindex @samp{qTsSTM} packet
36500 These packets request data about static tracepoint markers that exist
36501 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
36502 first piece of data, and multiple @code{qTsSTM} to get additional
36503 pieces. Replies to these packets take the following form:
36507 @item m @var{address}:@var{id}:@var{extra}
36509 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
36510 a comma-separated list of markers
36512 (lower case letter @samp{L}) denotes end of list.
36514 An error occurred. @var{nn} are hex digits.
36516 An empty reply indicates that the request is not supported by the
36520 @var{address} is encoded in hex.
36521 @var{id} and @var{extra} are strings encoded in hex.
36523 In response to each query, the target will reply with a list of one or
36524 more markers, separated by commas. @value{GDBN} will respond to each
36525 reply with a request for more markers (using the @samp{qs} form of the
36526 query), until the target responds with @samp{l} (lower-case ell, for
36529 @item qTSTMat:@var{address}
36531 @cindex @samp{qTSTMat} packet
36532 This packets requests data about static tracepoint markers in the
36533 target program at @var{address}. Replies to this packet follow the
36534 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
36535 tracepoint markers.
36537 @item QTSave:@var{filename}
36538 @cindex @samp{QTSave} packet
36539 This packet directs the target to save trace data to the file name
36540 @var{filename} in the target's filesystem. @var{filename} is encoded
36541 as a hex string; the interpretation of the file name (relative vs
36542 absolute, wild cards, etc) is up to the target.
36544 @item qTBuffer:@var{offset},@var{len}
36545 @cindex @samp{qTBuffer} packet
36546 Return up to @var{len} bytes of the current contents of trace buffer,
36547 starting at @var{offset}. The trace buffer is treated as if it were
36548 a contiguous collection of traceframes, as per the trace file format.
36549 The reply consists as many hex-encoded bytes as the target can deliver
36550 in a packet; it is not an error to return fewer than were asked for.
36551 A reply consisting of just @code{l} indicates that no bytes are
36554 @item QTBuffer:circular:@var{value}
36555 This packet directs the target to use a circular trace buffer if
36556 @var{value} is 1, or a linear buffer if the value is 0.
36558 @item QTBuffer:size:@var{size}
36559 @anchor{QTBuffer-size}
36560 @cindex @samp{QTBuffer size} packet
36561 This packet directs the target to make the trace buffer be of size
36562 @var{size} if possible. A value of @code{-1} tells the target to
36563 use whatever size it prefers.
36565 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
36566 @cindex @samp{QTNotes} packet
36567 This packet adds optional textual notes to the trace run. Allowable
36568 types include @code{user}, @code{notes}, and @code{tstop}, the
36569 @var{text} fields are arbitrary strings, hex-encoded.
36573 @subsection Relocate instruction reply packet
36574 When installing fast tracepoints in memory, the target may need to
36575 relocate the instruction currently at the tracepoint address to a
36576 different address in memory. For most instructions, a simple copy is
36577 enough, but, for example, call instructions that implicitly push the
36578 return address on the stack, and relative branches or other
36579 PC-relative instructions require offset adjustment, so that the effect
36580 of executing the instruction at a different address is the same as if
36581 it had executed in the original location.
36583 In response to several of the tracepoint packets, the target may also
36584 respond with a number of intermediate @samp{qRelocInsn} request
36585 packets before the final result packet, to have @value{GDBN} handle
36586 this relocation operation. If a packet supports this mechanism, its
36587 documentation will explicitly say so. See for example the above
36588 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
36589 format of the request is:
36592 @item qRelocInsn:@var{from};@var{to}
36594 This requests @value{GDBN} to copy instruction at address @var{from}
36595 to address @var{to}, possibly adjusted so that executing the
36596 instruction at @var{to} has the same effect as executing it at
36597 @var{from}. @value{GDBN} writes the adjusted instruction to target
36598 memory starting at @var{to}.
36603 @item qRelocInsn:@var{adjusted_size}
36604 Informs the stub the relocation is complete. @var{adjusted_size} is
36605 the length in bytes of resulting relocated instruction sequence.
36607 A badly formed request was detected, or an error was encountered while
36608 relocating the instruction.
36611 @node Host I/O Packets
36612 @section Host I/O Packets
36613 @cindex Host I/O, remote protocol
36614 @cindex file transfer, remote protocol
36616 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
36617 operations on the far side of a remote link. For example, Host I/O is
36618 used to upload and download files to a remote target with its own
36619 filesystem. Host I/O uses the same constant values and data structure
36620 layout as the target-initiated File-I/O protocol. However, the
36621 Host I/O packets are structured differently. The target-initiated
36622 protocol relies on target memory to store parameters and buffers.
36623 Host I/O requests are initiated by @value{GDBN}, and the
36624 target's memory is not involved. @xref{File-I/O Remote Protocol
36625 Extension}, for more details on the target-initiated protocol.
36627 The Host I/O request packets all encode a single operation along with
36628 its arguments. They have this format:
36632 @item vFile:@var{operation}: @var{parameter}@dots{}
36633 @var{operation} is the name of the particular request; the target
36634 should compare the entire packet name up to the second colon when checking
36635 for a supported operation. The format of @var{parameter} depends on
36636 the operation. Numbers are always passed in hexadecimal. Negative
36637 numbers have an explicit minus sign (i.e.@: two's complement is not
36638 used). Strings (e.g.@: filenames) are encoded as a series of
36639 hexadecimal bytes. The last argument to a system call may be a
36640 buffer of escaped binary data (@pxref{Binary Data}).
36644 The valid responses to Host I/O packets are:
36648 @item F @var{result} [, @var{errno}] [; @var{attachment}]
36649 @var{result} is the integer value returned by this operation, usually
36650 non-negative for success and -1 for errors. If an error has occured,
36651 @var{errno} will be included in the result. @var{errno} will have a
36652 value defined by the File-I/O protocol (@pxref{Errno Values}). For
36653 operations which return data, @var{attachment} supplies the data as a
36654 binary buffer. Binary buffers in response packets are escaped in the
36655 normal way (@pxref{Binary Data}). See the individual packet
36656 documentation for the interpretation of @var{result} and
36660 An empty response indicates that this operation is not recognized.
36664 These are the supported Host I/O operations:
36667 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
36668 Open a file at @var{pathname} and return a file descriptor for it, or
36669 return -1 if an error occurs. @var{pathname} is a string,
36670 @var{flags} is an integer indicating a mask of open flags
36671 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
36672 of mode bits to use if the file is created (@pxref{mode_t Values}).
36673 @xref{open}, for details of the open flags and mode values.
36675 @item vFile:close: @var{fd}
36676 Close the open file corresponding to @var{fd} and return 0, or
36677 -1 if an error occurs.
36679 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
36680 Read data from the open file corresponding to @var{fd}. Up to
36681 @var{count} bytes will be read from the file, starting at @var{offset}
36682 relative to the start of the file. The target may read fewer bytes;
36683 common reasons include packet size limits and an end-of-file
36684 condition. The number of bytes read is returned. Zero should only be
36685 returned for a successful read at the end of the file, or if
36686 @var{count} was zero.
36688 The data read should be returned as a binary attachment on success.
36689 If zero bytes were read, the response should include an empty binary
36690 attachment (i.e.@: a trailing semicolon). The return value is the
36691 number of target bytes read; the binary attachment may be longer if
36692 some characters were escaped.
36694 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
36695 Write @var{data} (a binary buffer) to the open file corresponding
36696 to @var{fd}. Start the write at @var{offset} from the start of the
36697 file. Unlike many @code{write} system calls, there is no
36698 separate @var{count} argument; the length of @var{data} in the
36699 packet is used. @samp{vFile:write} returns the number of bytes written,
36700 which may be shorter than the length of @var{data}, or -1 if an
36703 @item vFile:unlink: @var{pathname}
36704 Delete the file at @var{pathname} on the target. Return 0,
36705 or -1 if an error occurs. @var{pathname} is a string.
36707 @item vFile:readlink: @var{filename}
36708 Read value of symbolic link @var{filename} on the target. Return
36709 the number of bytes read, or -1 if an error occurs.
36711 The data read should be returned as a binary attachment on success.
36712 If zero bytes were read, the response should include an empty binary
36713 attachment (i.e.@: a trailing semicolon). The return value is the
36714 number of target bytes read; the binary attachment may be longer if
36715 some characters were escaped.
36720 @section Interrupts
36721 @cindex interrupts (remote protocol)
36723 When a program on the remote target is running, @value{GDBN} may
36724 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
36725 a @code{BREAK} followed by @code{g},
36726 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
36728 The precise meaning of @code{BREAK} is defined by the transport
36729 mechanism and may, in fact, be undefined. @value{GDBN} does not
36730 currently define a @code{BREAK} mechanism for any of the network
36731 interfaces except for TCP, in which case @value{GDBN} sends the
36732 @code{telnet} BREAK sequence.
36734 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
36735 transport mechanisms. It is represented by sending the single byte
36736 @code{0x03} without any of the usual packet overhead described in
36737 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
36738 transmitted as part of a packet, it is considered to be packet data
36739 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
36740 (@pxref{X packet}), used for binary downloads, may include an unescaped
36741 @code{0x03} as part of its packet.
36743 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
36744 When Linux kernel receives this sequence from serial port,
36745 it stops execution and connects to gdb.
36747 Stubs are not required to recognize these interrupt mechanisms and the
36748 precise meaning associated with receipt of the interrupt is
36749 implementation defined. If the target supports debugging of multiple
36750 threads and/or processes, it should attempt to interrupt all
36751 currently-executing threads and processes.
36752 If the stub is successful at interrupting the
36753 running program, it should send one of the stop
36754 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
36755 of successfully stopping the program in all-stop mode, and a stop reply
36756 for each stopped thread in non-stop mode.
36757 Interrupts received while the
36758 program is stopped are discarded.
36760 @node Notification Packets
36761 @section Notification Packets
36762 @cindex notification packets
36763 @cindex packets, notification
36765 The @value{GDBN} remote serial protocol includes @dfn{notifications},
36766 packets that require no acknowledgment. Both the GDB and the stub
36767 may send notifications (although the only notifications defined at
36768 present are sent by the stub). Notifications carry information
36769 without incurring the round-trip latency of an acknowledgment, and so
36770 are useful for low-impact communications where occasional packet loss
36773 A notification packet has the form @samp{% @var{data} #
36774 @var{checksum}}, where @var{data} is the content of the notification,
36775 and @var{checksum} is a checksum of @var{data}, computed and formatted
36776 as for ordinary @value{GDBN} packets. A notification's @var{data}
36777 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
36778 receiving a notification, the recipient sends no @samp{+} or @samp{-}
36779 to acknowledge the notification's receipt or to report its corruption.
36781 Every notification's @var{data} begins with a name, which contains no
36782 colon characters, followed by a colon character.
36784 Recipients should silently ignore corrupted notifications and
36785 notifications they do not understand. Recipients should restart
36786 timeout periods on receipt of a well-formed notification, whether or
36787 not they understand it.
36789 Senders should only send the notifications described here when this
36790 protocol description specifies that they are permitted. In the
36791 future, we may extend the protocol to permit existing notifications in
36792 new contexts; this rule helps older senders avoid confusing newer
36795 (Older versions of @value{GDBN} ignore bytes received until they see
36796 the @samp{$} byte that begins an ordinary packet, so new stubs may
36797 transmit notifications without fear of confusing older clients. There
36798 are no notifications defined for @value{GDBN} to send at the moment, but we
36799 assume that most older stubs would ignore them, as well.)
36801 Each notification is comprised of three parts:
36803 @item @var{name}:@var{event}
36804 The notification packet is sent by the side that initiates the
36805 exchange (currently, only the stub does that), with @var{event}
36806 carrying the specific information about the notification.
36807 @var{name} is the name of the notification.
36809 The acknowledge sent by the other side, usually @value{GDBN}, to
36810 acknowledge the exchange and request the event.
36813 The purpose of an asynchronous notification mechanism is to report to
36814 @value{GDBN} that something interesting happened in the remote stub.
36816 The remote stub may send notification @var{name}:@var{event}
36817 at any time, but @value{GDBN} acknowledges the notification when
36818 appropriate. The notification event is pending before @value{GDBN}
36819 acknowledges. Only one notification at a time may be pending; if
36820 additional events occur before @value{GDBN} has acknowledged the
36821 previous notification, they must be queued by the stub for later
36822 synchronous transmission in response to @var{ack} packets from
36823 @value{GDBN}. Because the notification mechanism is unreliable,
36824 the stub is permitted to resend a notification if it believes
36825 @value{GDBN} may not have received it.
36827 Specifically, notifications may appear when @value{GDBN} is not
36828 otherwise reading input from the stub, or when @value{GDBN} is
36829 expecting to read a normal synchronous response or a
36830 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
36831 Notification packets are distinct from any other communication from
36832 the stub so there is no ambiguity.
36834 After receiving a notification, @value{GDBN} shall acknowledge it by
36835 sending a @var{ack} packet as a regular, synchronous request to the
36836 stub. Such acknowledgment is not required to happen immediately, as
36837 @value{GDBN} is permitted to send other, unrelated packets to the
36838 stub first, which the stub should process normally.
36840 Upon receiving a @var{ack} packet, if the stub has other queued
36841 events to report to @value{GDBN}, it shall respond by sending a
36842 normal @var{event}. @value{GDBN} shall then send another @var{ack}
36843 packet to solicit further responses; again, it is permitted to send
36844 other, unrelated packets as well which the stub should process
36847 If the stub receives a @var{ack} packet and there are no additional
36848 @var{event} to report, the stub shall return an @samp{OK} response.
36849 At this point, @value{GDBN} has finished processing a notification
36850 and the stub has completed sending any queued events. @value{GDBN}
36851 won't accept any new notifications until the final @samp{OK} is
36852 received . If further notification events occur, the stub shall send
36853 a new notification, @value{GDBN} shall accept the notification, and
36854 the process shall be repeated.
36856 The process of asynchronous notification can be illustrated by the
36859 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
36862 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
36864 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
36869 The following notifications are defined:
36870 @multitable @columnfractions 0.12 0.12 0.38 0.38
36879 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
36880 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
36881 for information on how these notifications are acknowledged by
36883 @tab Report an asynchronous stop event in non-stop mode.
36887 @node Remote Non-Stop
36888 @section Remote Protocol Support for Non-Stop Mode
36890 @value{GDBN}'s remote protocol supports non-stop debugging of
36891 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
36892 supports non-stop mode, it should report that to @value{GDBN} by including
36893 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
36895 @value{GDBN} typically sends a @samp{QNonStop} packet only when
36896 establishing a new connection with the stub. Entering non-stop mode
36897 does not alter the state of any currently-running threads, but targets
36898 must stop all threads in any already-attached processes when entering
36899 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
36900 probe the target state after a mode change.
36902 In non-stop mode, when an attached process encounters an event that
36903 would otherwise be reported with a stop reply, it uses the
36904 asynchronous notification mechanism (@pxref{Notification Packets}) to
36905 inform @value{GDBN}. In contrast to all-stop mode, where all threads
36906 in all processes are stopped when a stop reply is sent, in non-stop
36907 mode only the thread reporting the stop event is stopped. That is,
36908 when reporting a @samp{S} or @samp{T} response to indicate completion
36909 of a step operation, hitting a breakpoint, or a fault, only the
36910 affected thread is stopped; any other still-running threads continue
36911 to run. When reporting a @samp{W} or @samp{X} response, all running
36912 threads belonging to other attached processes continue to run.
36914 In non-stop mode, the target shall respond to the @samp{?} packet as
36915 follows. First, any incomplete stop reply notification/@samp{vStopped}
36916 sequence in progress is abandoned. The target must begin a new
36917 sequence reporting stop events for all stopped threads, whether or not
36918 it has previously reported those events to @value{GDBN}. The first
36919 stop reply is sent as a synchronous reply to the @samp{?} packet, and
36920 subsequent stop replies are sent as responses to @samp{vStopped} packets
36921 using the mechanism described above. The target must not send
36922 asynchronous stop reply notifications until the sequence is complete.
36923 If all threads are running when the target receives the @samp{?} packet,
36924 or if the target is not attached to any process, it shall respond
36927 @node Packet Acknowledgment
36928 @section Packet Acknowledgment
36930 @cindex acknowledgment, for @value{GDBN} remote
36931 @cindex packet acknowledgment, for @value{GDBN} remote
36932 By default, when either the host or the target machine receives a packet,
36933 the first response expected is an acknowledgment: either @samp{+} (to indicate
36934 the package was received correctly) or @samp{-} (to request retransmission).
36935 This mechanism allows the @value{GDBN} remote protocol to operate over
36936 unreliable transport mechanisms, such as a serial line.
36938 In cases where the transport mechanism is itself reliable (such as a pipe or
36939 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
36940 It may be desirable to disable them in that case to reduce communication
36941 overhead, or for other reasons. This can be accomplished by means of the
36942 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
36944 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
36945 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
36946 and response format still includes the normal checksum, as described in
36947 @ref{Overview}, but the checksum may be ignored by the receiver.
36949 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
36950 no-acknowledgment mode, it should report that to @value{GDBN}
36951 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
36952 @pxref{qSupported}.
36953 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
36954 disabled via the @code{set remote noack-packet off} command
36955 (@pxref{Remote Configuration}),
36956 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
36957 Only then may the stub actually turn off packet acknowledgments.
36958 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
36959 response, which can be safely ignored by the stub.
36961 Note that @code{set remote noack-packet} command only affects negotiation
36962 between @value{GDBN} and the stub when subsequent connections are made;
36963 it does not affect the protocol acknowledgment state for any current
36965 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
36966 new connection is established,
36967 there is also no protocol request to re-enable the acknowledgments
36968 for the current connection, once disabled.
36973 Example sequence of a target being re-started. Notice how the restart
36974 does not get any direct output:
36979 @emph{target restarts}
36982 <- @code{T001:1234123412341234}
36986 Example sequence of a target being stepped by a single instruction:
36989 -> @code{G1445@dots{}}
36994 <- @code{T001:1234123412341234}
36998 <- @code{1455@dots{}}
37002 @node File-I/O Remote Protocol Extension
37003 @section File-I/O Remote Protocol Extension
37004 @cindex File-I/O remote protocol extension
37007 * File-I/O Overview::
37008 * Protocol Basics::
37009 * The F Request Packet::
37010 * The F Reply Packet::
37011 * The Ctrl-C Message::
37013 * List of Supported Calls::
37014 * Protocol-specific Representation of Datatypes::
37016 * File-I/O Examples::
37019 @node File-I/O Overview
37020 @subsection File-I/O Overview
37021 @cindex file-i/o overview
37023 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
37024 target to use the host's file system and console I/O to perform various
37025 system calls. System calls on the target system are translated into a
37026 remote protocol packet to the host system, which then performs the needed
37027 actions and returns a response packet to the target system.
37028 This simulates file system operations even on targets that lack file systems.
37030 The protocol is defined to be independent of both the host and target systems.
37031 It uses its own internal representation of datatypes and values. Both
37032 @value{GDBN} and the target's @value{GDBN} stub are responsible for
37033 translating the system-dependent value representations into the internal
37034 protocol representations when data is transmitted.
37036 The communication is synchronous. A system call is possible only when
37037 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
37038 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
37039 the target is stopped to allow deterministic access to the target's
37040 memory. Therefore File-I/O is not interruptible by target signals. On
37041 the other hand, it is possible to interrupt File-I/O by a user interrupt
37042 (@samp{Ctrl-C}) within @value{GDBN}.
37044 The target's request to perform a host system call does not finish
37045 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
37046 after finishing the system call, the target returns to continuing the
37047 previous activity (continue, step). No additional continue or step
37048 request from @value{GDBN} is required.
37051 (@value{GDBP}) continue
37052 <- target requests 'system call X'
37053 target is stopped, @value{GDBN} executes system call
37054 -> @value{GDBN} returns result
37055 ... target continues, @value{GDBN} returns to wait for the target
37056 <- target hits breakpoint and sends a Txx packet
37059 The protocol only supports I/O on the console and to regular files on
37060 the host file system. Character or block special devices, pipes,
37061 named pipes, sockets or any other communication method on the host
37062 system are not supported by this protocol.
37064 File I/O is not supported in non-stop mode.
37066 @node Protocol Basics
37067 @subsection Protocol Basics
37068 @cindex protocol basics, file-i/o
37070 The File-I/O protocol uses the @code{F} packet as the request as well
37071 as reply packet. Since a File-I/O system call can only occur when
37072 @value{GDBN} is waiting for a response from the continuing or stepping target,
37073 the File-I/O request is a reply that @value{GDBN} has to expect as a result
37074 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
37075 This @code{F} packet contains all information needed to allow @value{GDBN}
37076 to call the appropriate host system call:
37080 A unique identifier for the requested system call.
37083 All parameters to the system call. Pointers are given as addresses
37084 in the target memory address space. Pointers to strings are given as
37085 pointer/length pair. Numerical values are given as they are.
37086 Numerical control flags are given in a protocol-specific representation.
37090 At this point, @value{GDBN} has to perform the following actions.
37094 If the parameters include pointer values to data needed as input to a
37095 system call, @value{GDBN} requests this data from the target with a
37096 standard @code{m} packet request. This additional communication has to be
37097 expected by the target implementation and is handled as any other @code{m}
37101 @value{GDBN} translates all value from protocol representation to host
37102 representation as needed. Datatypes are coerced into the host types.
37105 @value{GDBN} calls the system call.
37108 It then coerces datatypes back to protocol representation.
37111 If the system call is expected to return data in buffer space specified
37112 by pointer parameters to the call, the data is transmitted to the
37113 target using a @code{M} or @code{X} packet. This packet has to be expected
37114 by the target implementation and is handled as any other @code{M} or @code{X}
37119 Eventually @value{GDBN} replies with another @code{F} packet which contains all
37120 necessary information for the target to continue. This at least contains
37127 @code{errno}, if has been changed by the system call.
37134 After having done the needed type and value coercion, the target continues
37135 the latest continue or step action.
37137 @node The F Request Packet
37138 @subsection The @code{F} Request Packet
37139 @cindex file-i/o request packet
37140 @cindex @code{F} request packet
37142 The @code{F} request packet has the following format:
37145 @item F@var{call-id},@var{parameter@dots{}}
37147 @var{call-id} is the identifier to indicate the host system call to be called.
37148 This is just the name of the function.
37150 @var{parameter@dots{}} are the parameters to the system call.
37151 Parameters are hexadecimal integer values, either the actual values in case
37152 of scalar datatypes, pointers to target buffer space in case of compound
37153 datatypes and unspecified memory areas, or pointer/length pairs in case
37154 of string parameters. These are appended to the @var{call-id} as a
37155 comma-delimited list. All values are transmitted in ASCII
37156 string representation, pointer/length pairs separated by a slash.
37162 @node The F Reply Packet
37163 @subsection The @code{F} Reply Packet
37164 @cindex file-i/o reply packet
37165 @cindex @code{F} reply packet
37167 The @code{F} reply packet has the following format:
37171 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
37173 @var{retcode} is the return code of the system call as hexadecimal value.
37175 @var{errno} is the @code{errno} set by the call, in protocol-specific
37177 This parameter can be omitted if the call was successful.
37179 @var{Ctrl-C flag} is only sent if the user requested a break. In this
37180 case, @var{errno} must be sent as well, even if the call was successful.
37181 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
37188 or, if the call was interrupted before the host call has been performed:
37195 assuming 4 is the protocol-specific representation of @code{EINTR}.
37200 @node The Ctrl-C Message
37201 @subsection The @samp{Ctrl-C} Message
37202 @cindex ctrl-c message, in file-i/o protocol
37204 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
37205 reply packet (@pxref{The F Reply Packet}),
37206 the target should behave as if it had
37207 gotten a break message. The meaning for the target is ``system call
37208 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
37209 (as with a break message) and return to @value{GDBN} with a @code{T02}
37212 It's important for the target to know in which
37213 state the system call was interrupted. There are two possible cases:
37217 The system call hasn't been performed on the host yet.
37220 The system call on the host has been finished.
37224 These two states can be distinguished by the target by the value of the
37225 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
37226 call hasn't been performed. This is equivalent to the @code{EINTR} handling
37227 on POSIX systems. In any other case, the target may presume that the
37228 system call has been finished --- successfully or not --- and should behave
37229 as if the break message arrived right after the system call.
37231 @value{GDBN} must behave reliably. If the system call has not been called
37232 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
37233 @code{errno} in the packet. If the system call on the host has been finished
37234 before the user requests a break, the full action must be finished by
37235 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
37236 The @code{F} packet may only be sent when either nothing has happened
37237 or the full action has been completed.
37240 @subsection Console I/O
37241 @cindex console i/o as part of file-i/o
37243 By default and if not explicitly closed by the target system, the file
37244 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
37245 on the @value{GDBN} console is handled as any other file output operation
37246 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
37247 by @value{GDBN} so that after the target read request from file descriptor
37248 0 all following typing is buffered until either one of the following
37253 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
37255 system call is treated as finished.
37258 The user presses @key{RET}. This is treated as end of input with a trailing
37262 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
37263 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
37267 If the user has typed more characters than fit in the buffer given to
37268 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
37269 either another @code{read(0, @dots{})} is requested by the target, or debugging
37270 is stopped at the user's request.
37273 @node List of Supported Calls
37274 @subsection List of Supported Calls
37275 @cindex list of supported file-i/o calls
37292 @unnumberedsubsubsec open
37293 @cindex open, file-i/o system call
37298 int open(const char *pathname, int flags);
37299 int open(const char *pathname, int flags, mode_t mode);
37303 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
37306 @var{flags} is the bitwise @code{OR} of the following values:
37310 If the file does not exist it will be created. The host
37311 rules apply as far as file ownership and time stamps
37315 When used with @code{O_CREAT}, if the file already exists it is
37316 an error and open() fails.
37319 If the file already exists and the open mode allows
37320 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
37321 truncated to zero length.
37324 The file is opened in append mode.
37327 The file is opened for reading only.
37330 The file is opened for writing only.
37333 The file is opened for reading and writing.
37337 Other bits are silently ignored.
37341 @var{mode} is the bitwise @code{OR} of the following values:
37345 User has read permission.
37348 User has write permission.
37351 Group has read permission.
37354 Group has write permission.
37357 Others have read permission.
37360 Others have write permission.
37364 Other bits are silently ignored.
37367 @item Return value:
37368 @code{open} returns the new file descriptor or -1 if an error
37375 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
37378 @var{pathname} refers to a directory.
37381 The requested access is not allowed.
37384 @var{pathname} was too long.
37387 A directory component in @var{pathname} does not exist.
37390 @var{pathname} refers to a device, pipe, named pipe or socket.
37393 @var{pathname} refers to a file on a read-only filesystem and
37394 write access was requested.
37397 @var{pathname} is an invalid pointer value.
37400 No space on device to create the file.
37403 The process already has the maximum number of files open.
37406 The limit on the total number of files open on the system
37410 The call was interrupted by the user.
37416 @unnumberedsubsubsec close
37417 @cindex close, file-i/o system call
37426 @samp{Fclose,@var{fd}}
37428 @item Return value:
37429 @code{close} returns zero on success, or -1 if an error occurred.
37435 @var{fd} isn't a valid open file descriptor.
37438 The call was interrupted by the user.
37444 @unnumberedsubsubsec read
37445 @cindex read, file-i/o system call
37450 int read(int fd, void *buf, unsigned int count);
37454 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
37456 @item Return value:
37457 On success, the number of bytes read is returned.
37458 Zero indicates end of file. If count is zero, read
37459 returns zero as well. On error, -1 is returned.
37465 @var{fd} is not a valid file descriptor or is not open for
37469 @var{bufptr} is an invalid pointer value.
37472 The call was interrupted by the user.
37478 @unnumberedsubsubsec write
37479 @cindex write, file-i/o system call
37484 int write(int fd, const void *buf, unsigned int count);
37488 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
37490 @item Return value:
37491 On success, the number of bytes written are returned.
37492 Zero indicates nothing was written. On error, -1
37499 @var{fd} is not a valid file descriptor or is not open for
37503 @var{bufptr} is an invalid pointer value.
37506 An attempt was made to write a file that exceeds the
37507 host-specific maximum file size allowed.
37510 No space on device to write the data.
37513 The call was interrupted by the user.
37519 @unnumberedsubsubsec lseek
37520 @cindex lseek, file-i/o system call
37525 long lseek (int fd, long offset, int flag);
37529 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
37531 @var{flag} is one of:
37535 The offset is set to @var{offset} bytes.
37538 The offset is set to its current location plus @var{offset}
37542 The offset is set to the size of the file plus @var{offset}
37546 @item Return value:
37547 On success, the resulting unsigned offset in bytes from
37548 the beginning of the file is returned. Otherwise, a
37549 value of -1 is returned.
37555 @var{fd} is not a valid open file descriptor.
37558 @var{fd} is associated with the @value{GDBN} console.
37561 @var{flag} is not a proper value.
37564 The call was interrupted by the user.
37570 @unnumberedsubsubsec rename
37571 @cindex rename, file-i/o system call
37576 int rename(const char *oldpath, const char *newpath);
37580 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
37582 @item Return value:
37583 On success, zero is returned. On error, -1 is returned.
37589 @var{newpath} is an existing directory, but @var{oldpath} is not a
37593 @var{newpath} is a non-empty directory.
37596 @var{oldpath} or @var{newpath} is a directory that is in use by some
37600 An attempt was made to make a directory a subdirectory
37604 A component used as a directory in @var{oldpath} or new
37605 path is not a directory. Or @var{oldpath} is a directory
37606 and @var{newpath} exists but is not a directory.
37609 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
37612 No access to the file or the path of the file.
37616 @var{oldpath} or @var{newpath} was too long.
37619 A directory component in @var{oldpath} or @var{newpath} does not exist.
37622 The file is on a read-only filesystem.
37625 The device containing the file has no room for the new
37629 The call was interrupted by the user.
37635 @unnumberedsubsubsec unlink
37636 @cindex unlink, file-i/o system call
37641 int unlink(const char *pathname);
37645 @samp{Funlink,@var{pathnameptr}/@var{len}}
37647 @item Return value:
37648 On success, zero is returned. On error, -1 is returned.
37654 No access to the file or the path of the file.
37657 The system does not allow unlinking of directories.
37660 The file @var{pathname} cannot be unlinked because it's
37661 being used by another process.
37664 @var{pathnameptr} is an invalid pointer value.
37667 @var{pathname} was too long.
37670 A directory component in @var{pathname} does not exist.
37673 A component of the path is not a directory.
37676 The file is on a read-only filesystem.
37679 The call was interrupted by the user.
37685 @unnumberedsubsubsec stat/fstat
37686 @cindex fstat, file-i/o system call
37687 @cindex stat, file-i/o system call
37692 int stat(const char *pathname, struct stat *buf);
37693 int fstat(int fd, struct stat *buf);
37697 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
37698 @samp{Ffstat,@var{fd},@var{bufptr}}
37700 @item Return value:
37701 On success, zero is returned. On error, -1 is returned.
37707 @var{fd} is not a valid open file.
37710 A directory component in @var{pathname} does not exist or the
37711 path is an empty string.
37714 A component of the path is not a directory.
37717 @var{pathnameptr} is an invalid pointer value.
37720 No access to the file or the path of the file.
37723 @var{pathname} was too long.
37726 The call was interrupted by the user.
37732 @unnumberedsubsubsec gettimeofday
37733 @cindex gettimeofday, file-i/o system call
37738 int gettimeofday(struct timeval *tv, void *tz);
37742 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
37744 @item Return value:
37745 On success, 0 is returned, -1 otherwise.
37751 @var{tz} is a non-NULL pointer.
37754 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
37760 @unnumberedsubsubsec isatty
37761 @cindex isatty, file-i/o system call
37766 int isatty(int fd);
37770 @samp{Fisatty,@var{fd}}
37772 @item Return value:
37773 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
37779 The call was interrupted by the user.
37784 Note that the @code{isatty} call is treated as a special case: it returns
37785 1 to the target if the file descriptor is attached
37786 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
37787 would require implementing @code{ioctl} and would be more complex than
37792 @unnumberedsubsubsec system
37793 @cindex system, file-i/o system call
37798 int system(const char *command);
37802 @samp{Fsystem,@var{commandptr}/@var{len}}
37804 @item Return value:
37805 If @var{len} is zero, the return value indicates whether a shell is
37806 available. A zero return value indicates a shell is not available.
37807 For non-zero @var{len}, the value returned is -1 on error and the
37808 return status of the command otherwise. Only the exit status of the
37809 command is returned, which is extracted from the host's @code{system}
37810 return value by calling @code{WEXITSTATUS(retval)}. In case
37811 @file{/bin/sh} could not be executed, 127 is returned.
37817 The call was interrupted by the user.
37822 @value{GDBN} takes over the full task of calling the necessary host calls
37823 to perform the @code{system} call. The return value of @code{system} on
37824 the host is simplified before it's returned
37825 to the target. Any termination signal information from the child process
37826 is discarded, and the return value consists
37827 entirely of the exit status of the called command.
37829 Due to security concerns, the @code{system} call is by default refused
37830 by @value{GDBN}. The user has to allow this call explicitly with the
37831 @code{set remote system-call-allowed 1} command.
37834 @item set remote system-call-allowed
37835 @kindex set remote system-call-allowed
37836 Control whether to allow the @code{system} calls in the File I/O
37837 protocol for the remote target. The default is zero (disabled).
37839 @item show remote system-call-allowed
37840 @kindex show remote system-call-allowed
37841 Show whether the @code{system} calls are allowed in the File I/O
37845 @node Protocol-specific Representation of Datatypes
37846 @subsection Protocol-specific Representation of Datatypes
37847 @cindex protocol-specific representation of datatypes, in file-i/o protocol
37850 * Integral Datatypes::
37852 * Memory Transfer::
37857 @node Integral Datatypes
37858 @unnumberedsubsubsec Integral Datatypes
37859 @cindex integral datatypes, in file-i/o protocol
37861 The integral datatypes used in the system calls are @code{int},
37862 @code{unsigned int}, @code{long}, @code{unsigned long},
37863 @code{mode_t}, and @code{time_t}.
37865 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
37866 implemented as 32 bit values in this protocol.
37868 @code{long} and @code{unsigned long} are implemented as 64 bit types.
37870 @xref{Limits}, for corresponding MIN and MAX values (similar to those
37871 in @file{limits.h}) to allow range checking on host and target.
37873 @code{time_t} datatypes are defined as seconds since the Epoch.
37875 All integral datatypes transferred as part of a memory read or write of a
37876 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
37879 @node Pointer Values
37880 @unnumberedsubsubsec Pointer Values
37881 @cindex pointer values, in file-i/o protocol
37883 Pointers to target data are transmitted as they are. An exception
37884 is made for pointers to buffers for which the length isn't
37885 transmitted as part of the function call, namely strings. Strings
37886 are transmitted as a pointer/length pair, both as hex values, e.g.@:
37893 which is a pointer to data of length 18 bytes at position 0x1aaf.
37894 The length is defined as the full string length in bytes, including
37895 the trailing null byte. For example, the string @code{"hello world"}
37896 at address 0x123456 is transmitted as
37902 @node Memory Transfer
37903 @unnumberedsubsubsec Memory Transfer
37904 @cindex memory transfer, in file-i/o protocol
37906 Structured data which is transferred using a memory read or write (for
37907 example, a @code{struct stat}) is expected to be in a protocol-specific format
37908 with all scalar multibyte datatypes being big endian. Translation to
37909 this representation needs to be done both by the target before the @code{F}
37910 packet is sent, and by @value{GDBN} before
37911 it transfers memory to the target. Transferred pointers to structured
37912 data should point to the already-coerced data at any time.
37916 @unnumberedsubsubsec struct stat
37917 @cindex struct stat, in file-i/o protocol
37919 The buffer of type @code{struct stat} used by the target and @value{GDBN}
37920 is defined as follows:
37924 unsigned int st_dev; /* device */
37925 unsigned int st_ino; /* inode */
37926 mode_t st_mode; /* protection */
37927 unsigned int st_nlink; /* number of hard links */
37928 unsigned int st_uid; /* user ID of owner */
37929 unsigned int st_gid; /* group ID of owner */
37930 unsigned int st_rdev; /* device type (if inode device) */
37931 unsigned long st_size; /* total size, in bytes */
37932 unsigned long st_blksize; /* blocksize for filesystem I/O */
37933 unsigned long st_blocks; /* number of blocks allocated */
37934 time_t st_atime; /* time of last access */
37935 time_t st_mtime; /* time of last modification */
37936 time_t st_ctime; /* time of last change */
37940 The integral datatypes conform to the definitions given in the
37941 appropriate section (see @ref{Integral Datatypes}, for details) so this
37942 structure is of size 64 bytes.
37944 The values of several fields have a restricted meaning and/or
37950 A value of 0 represents a file, 1 the console.
37953 No valid meaning for the target. Transmitted unchanged.
37956 Valid mode bits are described in @ref{Constants}. Any other
37957 bits have currently no meaning for the target.
37962 No valid meaning for the target. Transmitted unchanged.
37967 These values have a host and file system dependent
37968 accuracy. Especially on Windows hosts, the file system may not
37969 support exact timing values.
37972 The target gets a @code{struct stat} of the above representation and is
37973 responsible for coercing it to the target representation before
37976 Note that due to size differences between the host, target, and protocol
37977 representations of @code{struct stat} members, these members could eventually
37978 get truncated on the target.
37980 @node struct timeval
37981 @unnumberedsubsubsec struct timeval
37982 @cindex struct timeval, in file-i/o protocol
37984 The buffer of type @code{struct timeval} used by the File-I/O protocol
37985 is defined as follows:
37989 time_t tv_sec; /* second */
37990 long tv_usec; /* microsecond */
37994 The integral datatypes conform to the definitions given in the
37995 appropriate section (see @ref{Integral Datatypes}, for details) so this
37996 structure is of size 8 bytes.
37999 @subsection Constants
38000 @cindex constants, in file-i/o protocol
38002 The following values are used for the constants inside of the
38003 protocol. @value{GDBN} and target are responsible for translating these
38004 values before and after the call as needed.
38015 @unnumberedsubsubsec Open Flags
38016 @cindex open flags, in file-i/o protocol
38018 All values are given in hexadecimal representation.
38030 @node mode_t Values
38031 @unnumberedsubsubsec mode_t Values
38032 @cindex mode_t values, in file-i/o protocol
38034 All values are given in octal representation.
38051 @unnumberedsubsubsec Errno Values
38052 @cindex errno values, in file-i/o protocol
38054 All values are given in decimal representation.
38079 @code{EUNKNOWN} is used as a fallback error value if a host system returns
38080 any error value not in the list of supported error numbers.
38083 @unnumberedsubsubsec Lseek Flags
38084 @cindex lseek flags, in file-i/o protocol
38093 @unnumberedsubsubsec Limits
38094 @cindex limits, in file-i/o protocol
38096 All values are given in decimal representation.
38099 INT_MIN -2147483648
38101 UINT_MAX 4294967295
38102 LONG_MIN -9223372036854775808
38103 LONG_MAX 9223372036854775807
38104 ULONG_MAX 18446744073709551615
38107 @node File-I/O Examples
38108 @subsection File-I/O Examples
38109 @cindex file-i/o examples
38111 Example sequence of a write call, file descriptor 3, buffer is at target
38112 address 0x1234, 6 bytes should be written:
38115 <- @code{Fwrite,3,1234,6}
38116 @emph{request memory read from target}
38119 @emph{return "6 bytes written"}
38123 Example sequence of a read call, file descriptor 3, buffer is at target
38124 address 0x1234, 6 bytes should be read:
38127 <- @code{Fread,3,1234,6}
38128 @emph{request memory write to target}
38129 -> @code{X1234,6:XXXXXX}
38130 @emph{return "6 bytes read"}
38134 Example sequence of a read call, call fails on the host due to invalid
38135 file descriptor (@code{EBADF}):
38138 <- @code{Fread,3,1234,6}
38142 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
38146 <- @code{Fread,3,1234,6}
38151 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
38155 <- @code{Fread,3,1234,6}
38156 -> @code{X1234,6:XXXXXX}
38160 @node Library List Format
38161 @section Library List Format
38162 @cindex library list format, remote protocol
38164 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
38165 same process as your application to manage libraries. In this case,
38166 @value{GDBN} can use the loader's symbol table and normal memory
38167 operations to maintain a list of shared libraries. On other
38168 platforms, the operating system manages loaded libraries.
38169 @value{GDBN} can not retrieve the list of currently loaded libraries
38170 through memory operations, so it uses the @samp{qXfer:libraries:read}
38171 packet (@pxref{qXfer library list read}) instead. The remote stub
38172 queries the target's operating system and reports which libraries
38175 The @samp{qXfer:libraries:read} packet returns an XML document which
38176 lists loaded libraries and their offsets. Each library has an
38177 associated name and one or more segment or section base addresses,
38178 which report where the library was loaded in memory.
38180 For the common case of libraries that are fully linked binaries, the
38181 library should have a list of segments. If the target supports
38182 dynamic linking of a relocatable object file, its library XML element
38183 should instead include a list of allocated sections. The segment or
38184 section bases are start addresses, not relocation offsets; they do not
38185 depend on the library's link-time base addresses.
38187 @value{GDBN} must be linked with the Expat library to support XML
38188 library lists. @xref{Expat}.
38190 A simple memory map, with one loaded library relocated by a single
38191 offset, looks like this:
38195 <library name="/lib/libc.so.6">
38196 <segment address="0x10000000"/>
38201 Another simple memory map, with one loaded library with three
38202 allocated sections (.text, .data, .bss), looks like this:
38206 <library name="sharedlib.o">
38207 <section address="0x10000000"/>
38208 <section address="0x20000000"/>
38209 <section address="0x30000000"/>
38214 The format of a library list is described by this DTD:
38217 <!-- library-list: Root element with versioning -->
38218 <!ELEMENT library-list (library)*>
38219 <!ATTLIST library-list version CDATA #FIXED "1.0">
38220 <!ELEMENT library (segment*, section*)>
38221 <!ATTLIST library name CDATA #REQUIRED>
38222 <!ELEMENT segment EMPTY>
38223 <!ATTLIST segment address CDATA #REQUIRED>
38224 <!ELEMENT section EMPTY>
38225 <!ATTLIST section address CDATA #REQUIRED>
38228 In addition, segments and section descriptors cannot be mixed within a
38229 single library element, and you must supply at least one segment or
38230 section for each library.
38232 @node Library List Format for SVR4 Targets
38233 @section Library List Format for SVR4 Targets
38234 @cindex library list format, remote protocol
38236 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
38237 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
38238 shared libraries. Still a special library list provided by this packet is
38239 more efficient for the @value{GDBN} remote protocol.
38241 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
38242 loaded libraries and their SVR4 linker parameters. For each library on SVR4
38243 target, the following parameters are reported:
38247 @code{name}, the absolute file name from the @code{l_name} field of
38248 @code{struct link_map}.
38250 @code{lm} with address of @code{struct link_map} used for TLS
38251 (Thread Local Storage) access.
38253 @code{l_addr}, the displacement as read from the field @code{l_addr} of
38254 @code{struct link_map}. For prelinked libraries this is not an absolute
38255 memory address. It is a displacement of absolute memory address against
38256 address the file was prelinked to during the library load.
38258 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
38261 Additionally the single @code{main-lm} attribute specifies address of
38262 @code{struct link_map} used for the main executable. This parameter is used
38263 for TLS access and its presence is optional.
38265 @value{GDBN} must be linked with the Expat library to support XML
38266 SVR4 library lists. @xref{Expat}.
38268 A simple memory map, with two loaded libraries (which do not use prelink),
38272 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
38273 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
38275 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
38277 </library-list-svr>
38280 The format of an SVR4 library list is described by this DTD:
38283 <!-- library-list-svr4: Root element with versioning -->
38284 <!ELEMENT library-list-svr4 (library)*>
38285 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
38286 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
38287 <!ELEMENT library EMPTY>
38288 <!ATTLIST library name CDATA #REQUIRED>
38289 <!ATTLIST library lm CDATA #REQUIRED>
38290 <!ATTLIST library l_addr CDATA #REQUIRED>
38291 <!ATTLIST library l_ld CDATA #REQUIRED>
38294 @node Memory Map Format
38295 @section Memory Map Format
38296 @cindex memory map format
38298 To be able to write into flash memory, @value{GDBN} needs to obtain a
38299 memory map from the target. This section describes the format of the
38302 The memory map is obtained using the @samp{qXfer:memory-map:read}
38303 (@pxref{qXfer memory map read}) packet and is an XML document that
38304 lists memory regions.
38306 @value{GDBN} must be linked with the Expat library to support XML
38307 memory maps. @xref{Expat}.
38309 The top-level structure of the document is shown below:
38312 <?xml version="1.0"?>
38313 <!DOCTYPE memory-map
38314 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
38315 "http://sourceware.org/gdb/gdb-memory-map.dtd">
38321 Each region can be either:
38326 A region of RAM starting at @var{addr} and extending for @var{length}
38330 <memory type="ram" start="@var{addr}" length="@var{length}"/>
38335 A region of read-only memory:
38338 <memory type="rom" start="@var{addr}" length="@var{length}"/>
38343 A region of flash memory, with erasure blocks @var{blocksize}
38347 <memory type="flash" start="@var{addr}" length="@var{length}">
38348 <property name="blocksize">@var{blocksize}</property>
38354 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
38355 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
38356 packets to write to addresses in such ranges.
38358 The formal DTD for memory map format is given below:
38361 <!-- ................................................... -->
38362 <!-- Memory Map XML DTD ................................ -->
38363 <!-- File: memory-map.dtd .............................. -->
38364 <!-- .................................... .............. -->
38365 <!-- memory-map.dtd -->
38366 <!-- memory-map: Root element with versioning -->
38367 <!ELEMENT memory-map (memory | property)>
38368 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
38369 <!ELEMENT memory (property)>
38370 <!-- memory: Specifies a memory region,
38371 and its type, or device. -->
38372 <!ATTLIST memory type CDATA #REQUIRED
38373 start CDATA #REQUIRED
38374 length CDATA #REQUIRED
38375 device CDATA #IMPLIED>
38376 <!-- property: Generic attribute tag -->
38377 <!ELEMENT property (#PCDATA | property)*>
38378 <!ATTLIST property name CDATA #REQUIRED>
38381 @node Thread List Format
38382 @section Thread List Format
38383 @cindex thread list format
38385 To efficiently update the list of threads and their attributes,
38386 @value{GDBN} issues the @samp{qXfer:threads:read} packet
38387 (@pxref{qXfer threads read}) and obtains the XML document with
38388 the following structure:
38391 <?xml version="1.0"?>
38393 <thread id="id" core="0">
38394 ... description ...
38399 Each @samp{thread} element must have the @samp{id} attribute that
38400 identifies the thread (@pxref{thread-id syntax}). The
38401 @samp{core} attribute, if present, specifies which processor core
38402 the thread was last executing on. The content of the of @samp{thread}
38403 element is interpreted as human-readable auxilliary information.
38405 @node Traceframe Info Format
38406 @section Traceframe Info Format
38407 @cindex traceframe info format
38409 To be able to know which objects in the inferior can be examined when
38410 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
38411 memory ranges, registers and trace state variables that have been
38412 collected in a traceframe.
38414 This list is obtained using the @samp{qXfer:traceframe-info:read}
38415 (@pxref{qXfer traceframe info read}) packet and is an XML document.
38417 @value{GDBN} must be linked with the Expat library to support XML
38418 traceframe info discovery. @xref{Expat}.
38420 The top-level structure of the document is shown below:
38423 <?xml version="1.0"?>
38424 <!DOCTYPE traceframe-info
38425 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
38426 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
38432 Each traceframe block can be either:
38437 A region of collected memory starting at @var{addr} and extending for
38438 @var{length} bytes from there:
38441 <memory start="@var{addr}" length="@var{length}"/>
38445 A block indicating trace state variable numbered @var{number} has been
38449 <tvar id="@var{number}"/>
38454 The formal DTD for the traceframe info format is given below:
38457 <!ELEMENT traceframe-info (memory | tvar)* >
38458 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
38460 <!ELEMENT memory EMPTY>
38461 <!ATTLIST memory start CDATA #REQUIRED
38462 length CDATA #REQUIRED>
38464 <!ATTLIST tvar id CDATA #REQUIRED>
38467 @node Branch Trace Format
38468 @section Branch Trace Format
38469 @cindex branch trace format
38471 In order to display the branch trace of an inferior thread,
38472 @value{GDBN} needs to obtain the list of branches. This list is
38473 represented as list of sequential code blocks that are connected via
38474 branches. The code in each block has been executed sequentially.
38476 This list is obtained using the @samp{qXfer:btrace:read}
38477 (@pxref{qXfer btrace read}) packet and is an XML document.
38479 @value{GDBN} must be linked with the Expat library to support XML
38480 traceframe info discovery. @xref{Expat}.
38482 The top-level structure of the document is shown below:
38485 <?xml version="1.0"?>
38487 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
38488 "http://sourceware.org/gdb/gdb-btrace.dtd">
38497 A block of sequentially executed instructions starting at @var{begin}
38498 and ending at @var{end}:
38501 <block begin="@var{begin}" end="@var{end}"/>
38506 The formal DTD for the branch trace format is given below:
38509 <!ELEMENT btrace (block)* >
38510 <!ATTLIST btrace version CDATA #FIXED "1.0">
38512 <!ELEMENT block EMPTY>
38513 <!ATTLIST block begin CDATA #REQUIRED
38514 end CDATA #REQUIRED>
38517 @include agentexpr.texi
38519 @node Target Descriptions
38520 @appendix Target Descriptions
38521 @cindex target descriptions
38523 One of the challenges of using @value{GDBN} to debug embedded systems
38524 is that there are so many minor variants of each processor
38525 architecture in use. It is common practice for vendors to start with
38526 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
38527 and then make changes to adapt it to a particular market niche. Some
38528 architectures have hundreds of variants, available from dozens of
38529 vendors. This leads to a number of problems:
38533 With so many different customized processors, it is difficult for
38534 the @value{GDBN} maintainers to keep up with the changes.
38536 Since individual variants may have short lifetimes or limited
38537 audiences, it may not be worthwhile to carry information about every
38538 variant in the @value{GDBN} source tree.
38540 When @value{GDBN} does support the architecture of the embedded system
38541 at hand, the task of finding the correct architecture name to give the
38542 @command{set architecture} command can be error-prone.
38545 To address these problems, the @value{GDBN} remote protocol allows a
38546 target system to not only identify itself to @value{GDBN}, but to
38547 actually describe its own features. This lets @value{GDBN} support
38548 processor variants it has never seen before --- to the extent that the
38549 descriptions are accurate, and that @value{GDBN} understands them.
38551 @value{GDBN} must be linked with the Expat library to support XML
38552 target descriptions. @xref{Expat}.
38555 * Retrieving Descriptions:: How descriptions are fetched from a target.
38556 * Target Description Format:: The contents of a target description.
38557 * Predefined Target Types:: Standard types available for target
38559 * Standard Target Features:: Features @value{GDBN} knows about.
38562 @node Retrieving Descriptions
38563 @section Retrieving Descriptions
38565 Target descriptions can be read from the target automatically, or
38566 specified by the user manually. The default behavior is to read the
38567 description from the target. @value{GDBN} retrieves it via the remote
38568 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
38569 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
38570 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
38571 XML document, of the form described in @ref{Target Description
38574 Alternatively, you can specify a file to read for the target description.
38575 If a file is set, the target will not be queried. The commands to
38576 specify a file are:
38579 @cindex set tdesc filename
38580 @item set tdesc filename @var{path}
38581 Read the target description from @var{path}.
38583 @cindex unset tdesc filename
38584 @item unset tdesc filename
38585 Do not read the XML target description from a file. @value{GDBN}
38586 will use the description supplied by the current target.
38588 @cindex show tdesc filename
38589 @item show tdesc filename
38590 Show the filename to read for a target description, if any.
38594 @node Target Description Format
38595 @section Target Description Format
38596 @cindex target descriptions, XML format
38598 A target description annex is an @uref{http://www.w3.org/XML/, XML}
38599 document which complies with the Document Type Definition provided in
38600 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
38601 means you can use generally available tools like @command{xmllint} to
38602 check that your feature descriptions are well-formed and valid.
38603 However, to help people unfamiliar with XML write descriptions for
38604 their targets, we also describe the grammar here.
38606 Target descriptions can identify the architecture of the remote target
38607 and (for some architectures) provide information about custom register
38608 sets. They can also identify the OS ABI of the remote target.
38609 @value{GDBN} can use this information to autoconfigure for your
38610 target, or to warn you if you connect to an unsupported target.
38612 Here is a simple target description:
38615 <target version="1.0">
38616 <architecture>i386:x86-64</architecture>
38621 This minimal description only says that the target uses
38622 the x86-64 architecture.
38624 A target description has the following overall form, with [ ] marking
38625 optional elements and @dots{} marking repeatable elements. The elements
38626 are explained further below.
38629 <?xml version="1.0"?>
38630 <!DOCTYPE target SYSTEM "gdb-target.dtd">
38631 <target version="1.0">
38632 @r{[}@var{architecture}@r{]}
38633 @r{[}@var{osabi}@r{]}
38634 @r{[}@var{compatible}@r{]}
38635 @r{[}@var{feature}@dots{}@r{]}
38640 The description is generally insensitive to whitespace and line
38641 breaks, under the usual common-sense rules. The XML version
38642 declaration and document type declaration can generally be omitted
38643 (@value{GDBN} does not require them), but specifying them may be
38644 useful for XML validation tools. The @samp{version} attribute for
38645 @samp{<target>} may also be omitted, but we recommend
38646 including it; if future versions of @value{GDBN} use an incompatible
38647 revision of @file{gdb-target.dtd}, they will detect and report
38648 the version mismatch.
38650 @subsection Inclusion
38651 @cindex target descriptions, inclusion
38654 @cindex <xi:include>
38657 It can sometimes be valuable to split a target description up into
38658 several different annexes, either for organizational purposes, or to
38659 share files between different possible target descriptions. You can
38660 divide a description into multiple files by replacing any element of
38661 the target description with an inclusion directive of the form:
38664 <xi:include href="@var{document}"/>
38668 When @value{GDBN} encounters an element of this form, it will retrieve
38669 the named XML @var{document}, and replace the inclusion directive with
38670 the contents of that document. If the current description was read
38671 using @samp{qXfer}, then so will be the included document;
38672 @var{document} will be interpreted as the name of an annex. If the
38673 current description was read from a file, @value{GDBN} will look for
38674 @var{document} as a file in the same directory where it found the
38675 original description.
38677 @subsection Architecture
38678 @cindex <architecture>
38680 An @samp{<architecture>} element has this form:
38683 <architecture>@var{arch}</architecture>
38686 @var{arch} is one of the architectures from the set accepted by
38687 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
38690 @cindex @code{<osabi>}
38692 This optional field was introduced in @value{GDBN} version 7.0.
38693 Previous versions of @value{GDBN} ignore it.
38695 An @samp{<osabi>} element has this form:
38698 <osabi>@var{abi-name}</osabi>
38701 @var{abi-name} is an OS ABI name from the same selection accepted by
38702 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
38704 @subsection Compatible Architecture
38705 @cindex @code{<compatible>}
38707 This optional field was introduced in @value{GDBN} version 7.0.
38708 Previous versions of @value{GDBN} ignore it.
38710 A @samp{<compatible>} element has this form:
38713 <compatible>@var{arch}</compatible>
38716 @var{arch} is one of the architectures from the set accepted by
38717 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
38719 A @samp{<compatible>} element is used to specify that the target
38720 is able to run binaries in some other than the main target architecture
38721 given by the @samp{<architecture>} element. For example, on the
38722 Cell Broadband Engine, the main architecture is @code{powerpc:common}
38723 or @code{powerpc:common64}, but the system is able to run binaries
38724 in the @code{spu} architecture as well. The way to describe this
38725 capability with @samp{<compatible>} is as follows:
38728 <architecture>powerpc:common</architecture>
38729 <compatible>spu</compatible>
38732 @subsection Features
38735 Each @samp{<feature>} describes some logical portion of the target
38736 system. Features are currently used to describe available CPU
38737 registers and the types of their contents. A @samp{<feature>} element
38741 <feature name="@var{name}">
38742 @r{[}@var{type}@dots{}@r{]}
38748 Each feature's name should be unique within the description. The name
38749 of a feature does not matter unless @value{GDBN} has some special
38750 knowledge of the contents of that feature; if it does, the feature
38751 should have its standard name. @xref{Standard Target Features}.
38755 Any register's value is a collection of bits which @value{GDBN} must
38756 interpret. The default interpretation is a two's complement integer,
38757 but other types can be requested by name in the register description.
38758 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
38759 Target Types}), and the description can define additional composite types.
38761 Each type element must have an @samp{id} attribute, which gives
38762 a unique (within the containing @samp{<feature>}) name to the type.
38763 Types must be defined before they are used.
38766 Some targets offer vector registers, which can be treated as arrays
38767 of scalar elements. These types are written as @samp{<vector>} elements,
38768 specifying the array element type, @var{type}, and the number of elements,
38772 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
38776 If a register's value is usefully viewed in multiple ways, define it
38777 with a union type containing the useful representations. The
38778 @samp{<union>} element contains one or more @samp{<field>} elements,
38779 each of which has a @var{name} and a @var{type}:
38782 <union id="@var{id}">
38783 <field name="@var{name}" type="@var{type}"/>
38789 If a register's value is composed from several separate values, define
38790 it with a structure type. There are two forms of the @samp{<struct>}
38791 element; a @samp{<struct>} element must either contain only bitfields
38792 or contain no bitfields. If the structure contains only bitfields,
38793 its total size in bytes must be specified, each bitfield must have an
38794 explicit start and end, and bitfields are automatically assigned an
38795 integer type. The field's @var{start} should be less than or
38796 equal to its @var{end}, and zero represents the least significant bit.
38799 <struct id="@var{id}" size="@var{size}">
38800 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
38805 If the structure contains no bitfields, then each field has an
38806 explicit type, and no implicit padding is added.
38809 <struct id="@var{id}">
38810 <field name="@var{name}" type="@var{type}"/>
38816 If a register's value is a series of single-bit flags, define it with
38817 a flags type. The @samp{<flags>} element has an explicit @var{size}
38818 and contains one or more @samp{<field>} elements. Each field has a
38819 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
38823 <flags id="@var{id}" size="@var{size}">
38824 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
38829 @subsection Registers
38832 Each register is represented as an element with this form:
38835 <reg name="@var{name}"
38836 bitsize="@var{size}"
38837 @r{[}regnum="@var{num}"@r{]}
38838 @r{[}save-restore="@var{save-restore}"@r{]}
38839 @r{[}type="@var{type}"@r{]}
38840 @r{[}group="@var{group}"@r{]}/>
38844 The components are as follows:
38849 The register's name; it must be unique within the target description.
38852 The register's size, in bits.
38855 The register's number. If omitted, a register's number is one greater
38856 than that of the previous register (either in the current feature or in
38857 a preceding feature); the first register in the target description
38858 defaults to zero. This register number is used to read or write
38859 the register; e.g.@: it is used in the remote @code{p} and @code{P}
38860 packets, and registers appear in the @code{g} and @code{G} packets
38861 in order of increasing register number.
38864 Whether the register should be preserved across inferior function
38865 calls; this must be either @code{yes} or @code{no}. The default is
38866 @code{yes}, which is appropriate for most registers except for
38867 some system control registers; this is not related to the target's
38871 The type of the register. @var{type} may be a predefined type, a type
38872 defined in the current feature, or one of the special types @code{int}
38873 and @code{float}. @code{int} is an integer type of the correct size
38874 for @var{bitsize}, and @code{float} is a floating point type (in the
38875 architecture's normal floating point format) of the correct size for
38876 @var{bitsize}. The default is @code{int}.
38879 The register group to which this register belongs. @var{group} must
38880 be either @code{general}, @code{float}, or @code{vector}. If no
38881 @var{group} is specified, @value{GDBN} will not display the register
38882 in @code{info registers}.
38886 @node Predefined Target Types
38887 @section Predefined Target Types
38888 @cindex target descriptions, predefined types
38890 Type definitions in the self-description can build up composite types
38891 from basic building blocks, but can not define fundamental types. Instead,
38892 standard identifiers are provided by @value{GDBN} for the fundamental
38893 types. The currently supported types are:
38902 Signed integer types holding the specified number of bits.
38909 Unsigned integer types holding the specified number of bits.
38913 Pointers to unspecified code and data. The program counter and
38914 any dedicated return address register may be marked as code
38915 pointers; printing a code pointer converts it into a symbolic
38916 address. The stack pointer and any dedicated address registers
38917 may be marked as data pointers.
38920 Single precision IEEE floating point.
38923 Double precision IEEE floating point.
38926 The 12-byte extended precision format used by ARM FPA registers.
38929 The 10-byte extended precision format used by x87 registers.
38932 32bit @sc{eflags} register used by x86.
38935 32bit @sc{mxcsr} register used by x86.
38939 @node Standard Target Features
38940 @section Standard Target Features
38941 @cindex target descriptions, standard features
38943 A target description must contain either no registers or all the
38944 target's registers. If the description contains no registers, then
38945 @value{GDBN} will assume a default register layout, selected based on
38946 the architecture. If the description contains any registers, the
38947 default layout will not be used; the standard registers must be
38948 described in the target description, in such a way that @value{GDBN}
38949 can recognize them.
38951 This is accomplished by giving specific names to feature elements
38952 which contain standard registers. @value{GDBN} will look for features
38953 with those names and verify that they contain the expected registers;
38954 if any known feature is missing required registers, or if any required
38955 feature is missing, @value{GDBN} will reject the target
38956 description. You can add additional registers to any of the
38957 standard features --- @value{GDBN} will display them just as if
38958 they were added to an unrecognized feature.
38960 This section lists the known features and their expected contents.
38961 Sample XML documents for these features are included in the
38962 @value{GDBN} source tree, in the directory @file{gdb/features}.
38964 Names recognized by @value{GDBN} should include the name of the
38965 company or organization which selected the name, and the overall
38966 architecture to which the feature applies; so e.g.@: the feature
38967 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
38969 The names of registers are not case sensitive for the purpose
38970 of recognizing standard features, but @value{GDBN} will only display
38971 registers using the capitalization used in the description.
38974 * AArch64 Features::
38979 * Nios II Features::
38980 * PowerPC Features::
38981 * S/390 and System z Features::
38986 @node AArch64 Features
38987 @subsection AArch64 Features
38988 @cindex target descriptions, AArch64 features
38990 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
38991 targets. It should contain registers @samp{x0} through @samp{x30},
38992 @samp{sp}, @samp{pc}, and @samp{cpsr}.
38994 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
38995 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
38999 @subsection ARM Features
39000 @cindex target descriptions, ARM features
39002 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
39004 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
39005 @samp{lr}, @samp{pc}, and @samp{cpsr}.
39007 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
39008 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
39009 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
39012 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
39013 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
39015 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
39016 it should contain at least registers @samp{wR0} through @samp{wR15} and
39017 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
39018 @samp{wCSSF}, and @samp{wCASF} registers are optional.
39020 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
39021 should contain at least registers @samp{d0} through @samp{d15}. If
39022 they are present, @samp{d16} through @samp{d31} should also be included.
39023 @value{GDBN} will synthesize the single-precision registers from
39024 halves of the double-precision registers.
39026 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
39027 need to contain registers; it instructs @value{GDBN} to display the
39028 VFP double-precision registers as vectors and to synthesize the
39029 quad-precision registers from pairs of double-precision registers.
39030 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
39031 be present and include 32 double-precision registers.
39033 @node i386 Features
39034 @subsection i386 Features
39035 @cindex target descriptions, i386 features
39037 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
39038 targets. It should describe the following registers:
39042 @samp{eax} through @samp{edi} plus @samp{eip} for i386
39044 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
39046 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
39047 @samp{fs}, @samp{gs}
39049 @samp{st0} through @samp{st7}
39051 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
39052 @samp{foseg}, @samp{fooff} and @samp{fop}
39055 The register sets may be different, depending on the target.
39057 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
39058 describe registers:
39062 @samp{xmm0} through @samp{xmm7} for i386
39064 @samp{xmm0} through @samp{xmm15} for amd64
39069 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
39070 @samp{org.gnu.gdb.i386.sse} feature. It should
39071 describe the upper 128 bits of @sc{ymm} registers:
39075 @samp{ymm0h} through @samp{ymm7h} for i386
39077 @samp{ymm0h} through @samp{ymm15h} for amd64
39080 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel(R)
39081 Memory Protection Extension (MPX). It should describe the following registers:
39085 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
39087 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
39090 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
39091 describe a single register, @samp{orig_eax}.
39093 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
39094 @samp{org.gnu.gdb.i386.avx} feature. It should
39095 describe additional @sc{xmm} registers:
39099 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
39102 It should describe the upper 128 bits of additional @sc{ymm} registers:
39106 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
39110 describe the upper 256 bits of @sc{zmm} registers:
39114 @samp{zmm0h} through @samp{zmm7h} for i386.
39116 @samp{zmm0h} through @samp{zmm15h} for amd64.
39120 describe the additional @sc{zmm} registers:
39124 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
39127 @node MIPS Features
39128 @subsection @acronym{MIPS} Features
39129 @cindex target descriptions, @acronym{MIPS} features
39131 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
39132 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
39133 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
39136 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
39137 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
39138 registers. They may be 32-bit or 64-bit depending on the target.
39140 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
39141 it may be optional in a future version of @value{GDBN}. It should
39142 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
39143 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
39145 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
39146 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
39147 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
39148 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
39150 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
39151 contain a single register, @samp{restart}, which is used by the
39152 Linux kernel to control restartable syscalls.
39154 @node M68K Features
39155 @subsection M68K Features
39156 @cindex target descriptions, M68K features
39159 @item @samp{org.gnu.gdb.m68k.core}
39160 @itemx @samp{org.gnu.gdb.coldfire.core}
39161 @itemx @samp{org.gnu.gdb.fido.core}
39162 One of those features must be always present.
39163 The feature that is present determines which flavor of m68k is
39164 used. The feature that is present should contain registers
39165 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
39166 @samp{sp}, @samp{ps} and @samp{pc}.
39168 @item @samp{org.gnu.gdb.coldfire.fp}
39169 This feature is optional. If present, it should contain registers
39170 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
39174 @node Nios II Features
39175 @subsection Nios II Features
39176 @cindex target descriptions, Nios II features
39178 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
39179 targets. It should contain the 32 core registers (@samp{zero},
39180 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
39181 @samp{pc}, and the 16 control registers (@samp{status} through
39184 @node PowerPC Features
39185 @subsection PowerPC Features
39186 @cindex target descriptions, PowerPC features
39188 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
39189 targets. It should contain registers @samp{r0} through @samp{r31},
39190 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
39191 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
39193 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
39194 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
39196 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
39197 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
39200 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
39201 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
39202 will combine these registers with the floating point registers
39203 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
39204 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
39205 through @samp{vs63}, the set of vector registers for POWER7.
39207 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
39208 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
39209 @samp{spefscr}. SPE targets should provide 32-bit registers in
39210 @samp{org.gnu.gdb.power.core} and provide the upper halves in
39211 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
39212 these to present registers @samp{ev0} through @samp{ev31} to the
39215 @node S/390 and System z Features
39216 @subsection S/390 and System z Features
39217 @cindex target descriptions, S/390 features
39218 @cindex target descriptions, System z features
39220 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
39221 System z targets. It should contain the PSW and the 16 general
39222 registers. In particular, System z targets should provide the 64-bit
39223 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
39224 S/390 targets should provide the 32-bit versions of these registers.
39225 A System z target that runs in 31-bit addressing mode should provide
39226 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
39227 register's upper halves @samp{r0h} through @samp{r15h}, and their
39228 lower halves @samp{r0l} through @samp{r15l}.
39230 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
39231 contain the 64-bit registers @samp{f0} through @samp{f15}, and
39234 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
39235 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
39237 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
39238 contain the register @samp{orig_r2}, which is 64-bit wide on System z
39239 targets and 32-bit otherwise. In addition, the feature may contain
39240 the @samp{last_break} register, whose width depends on the addressing
39241 mode, as well as the @samp{system_call} register, which is always
39244 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
39245 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
39246 @samp{atia}, and @samp{tr0} through @samp{tr15}.
39248 @node TIC6x Features
39249 @subsection TMS320C6x Features
39250 @cindex target descriptions, TIC6x features
39251 @cindex target descriptions, TMS320C6x features
39252 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
39253 targets. It should contain registers @samp{A0} through @samp{A15},
39254 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
39256 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
39257 contain registers @samp{A16} through @samp{A31} and @samp{B16}
39258 through @samp{B31}.
39260 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
39261 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
39263 @node Operating System Information
39264 @appendix Operating System Information
39265 @cindex operating system information
39271 Users of @value{GDBN} often wish to obtain information about the state of
39272 the operating system running on the target---for example the list of
39273 processes, or the list of open files. This section describes the
39274 mechanism that makes it possible. This mechanism is similar to the
39275 target features mechanism (@pxref{Target Descriptions}), but focuses
39276 on a different aspect of target.
39278 Operating system information is retrived from the target via the
39279 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
39280 read}). The object name in the request should be @samp{osdata}, and
39281 the @var{annex} identifies the data to be fetched.
39284 @appendixsection Process list
39285 @cindex operating system information, process list
39287 When requesting the process list, the @var{annex} field in the
39288 @samp{qXfer} request should be @samp{processes}. The returned data is
39289 an XML document. The formal syntax of this document is defined in
39290 @file{gdb/features/osdata.dtd}.
39292 An example document is:
39295 <?xml version="1.0"?>
39296 <!DOCTYPE target SYSTEM "osdata.dtd">
39297 <osdata type="processes">
39299 <column name="pid">1</column>
39300 <column name="user">root</column>
39301 <column name="command">/sbin/init</column>
39302 <column name="cores">1,2,3</column>
39307 Each item should include a column whose name is @samp{pid}. The value
39308 of that column should identify the process on the target. The
39309 @samp{user} and @samp{command} columns are optional, and will be
39310 displayed by @value{GDBN}. The @samp{cores} column, if present,
39311 should contain a comma-separated list of cores that this process
39312 is running on. Target may provide additional columns,
39313 which @value{GDBN} currently ignores.
39315 @node Trace File Format
39316 @appendix Trace File Format
39317 @cindex trace file format
39319 The trace file comes in three parts: a header, a textual description
39320 section, and a trace frame section with binary data.
39322 The header has the form @code{\x7fTRACE0\n}. The first byte is
39323 @code{0x7f} so as to indicate that the file contains binary data,
39324 while the @code{0} is a version number that may have different values
39327 The description section consists of multiple lines of @sc{ascii} text
39328 separated by newline characters (@code{0xa}). The lines may include a
39329 variety of optional descriptive or context-setting information, such
39330 as tracepoint definitions or register set size. @value{GDBN} will
39331 ignore any line that it does not recognize. An empty line marks the end
39334 @c FIXME add some specific types of data
39336 The trace frame section consists of a number of consecutive frames.
39337 Each frame begins with a two-byte tracepoint number, followed by a
39338 four-byte size giving the amount of data in the frame. The data in
39339 the frame consists of a number of blocks, each introduced by a
39340 character indicating its type (at least register, memory, and trace
39341 state variable). The data in this section is raw binary, not a
39342 hexadecimal or other encoding; its endianness matches the target's
39345 @c FIXME bi-arch may require endianness/arch info in description section
39348 @item R @var{bytes}
39349 Register block. The number and ordering of bytes matches that of a
39350 @code{g} packet in the remote protocol. Note that these are the
39351 actual bytes, in target order and @value{GDBN} register order, not a
39352 hexadecimal encoding.
39354 @item M @var{address} @var{length} @var{bytes}...
39355 Memory block. This is a contiguous block of memory, at the 8-byte
39356 address @var{address}, with a 2-byte length @var{length}, followed by
39357 @var{length} bytes.
39359 @item V @var{number} @var{value}
39360 Trace state variable block. This records the 8-byte signed value
39361 @var{value} of trace state variable numbered @var{number}.
39365 Future enhancements of the trace file format may include additional types
39368 @node Index Section Format
39369 @appendix @code{.gdb_index} section format
39370 @cindex .gdb_index section format
39371 @cindex index section format
39373 This section documents the index section that is created by @code{save
39374 gdb-index} (@pxref{Index Files}). The index section is
39375 DWARF-specific; some knowledge of DWARF is assumed in this
39378 The mapped index file format is designed to be directly
39379 @code{mmap}able on any architecture. In most cases, a datum is
39380 represented using a little-endian 32-bit integer value, called an
39381 @code{offset_type}. Big endian machines must byte-swap the values
39382 before using them. Exceptions to this rule are noted. The data is
39383 laid out such that alignment is always respected.
39385 A mapped index consists of several areas, laid out in order.
39389 The file header. This is a sequence of values, of @code{offset_type}
39390 unless otherwise noted:
39394 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
39395 Version 4 uses a different hashing function from versions 5 and 6.
39396 Version 6 includes symbols for inlined functions, whereas versions 4
39397 and 5 do not. Version 7 adds attributes to the CU indices in the
39398 symbol table. Version 8 specifies that symbols from DWARF type units
39399 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
39400 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
39402 @value{GDBN} will only read version 4, 5, or 6 indices
39403 by specifying @code{set use-deprecated-index-sections on}.
39404 GDB has a workaround for potentially broken version 7 indices so it is
39405 currently not flagged as deprecated.
39408 The offset, from the start of the file, of the CU list.
39411 The offset, from the start of the file, of the types CU list. Note
39412 that this area can be empty, in which case this offset will be equal
39413 to the next offset.
39416 The offset, from the start of the file, of the address area.
39419 The offset, from the start of the file, of the symbol table.
39422 The offset, from the start of the file, of the constant pool.
39426 The CU list. This is a sequence of pairs of 64-bit little-endian
39427 values, sorted by the CU offset. The first element in each pair is
39428 the offset of a CU in the @code{.debug_info} section. The second
39429 element in each pair is the length of that CU. References to a CU
39430 elsewhere in the map are done using a CU index, which is just the
39431 0-based index into this table. Note that if there are type CUs, then
39432 conceptually CUs and type CUs form a single list for the purposes of
39436 The types CU list. This is a sequence of triplets of 64-bit
39437 little-endian values. In a triplet, the first value is the CU offset,
39438 the second value is the type offset in the CU, and the third value is
39439 the type signature. The types CU list is not sorted.
39442 The address area. The address area consists of a sequence of address
39443 entries. Each address entry has three elements:
39447 The low address. This is a 64-bit little-endian value.
39450 The high address. This is a 64-bit little-endian value. Like
39451 @code{DW_AT_high_pc}, the value is one byte beyond the end.
39454 The CU index. This is an @code{offset_type} value.
39458 The symbol table. This is an open-addressed hash table. The size of
39459 the hash table is always a power of 2.
39461 Each slot in the hash table consists of a pair of @code{offset_type}
39462 values. The first value is the offset of the symbol's name in the
39463 constant pool. The second value is the offset of the CU vector in the
39466 If both values are 0, then this slot in the hash table is empty. This
39467 is ok because while 0 is a valid constant pool index, it cannot be a
39468 valid index for both a string and a CU vector.
39470 The hash value for a table entry is computed by applying an
39471 iterative hash function to the symbol's name. Starting with an
39472 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
39473 the string is incorporated into the hash using the formula depending on the
39478 The formula is @code{r = r * 67 + c - 113}.
39480 @item Versions 5 to 7
39481 The formula is @code{r = r * 67 + tolower (c) - 113}.
39484 The terminating @samp{\0} is not incorporated into the hash.
39486 The step size used in the hash table is computed via
39487 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
39488 value, and @samp{size} is the size of the hash table. The step size
39489 is used to find the next candidate slot when handling a hash
39492 The names of C@t{++} symbols in the hash table are canonicalized. We
39493 don't currently have a simple description of the canonicalization
39494 algorithm; if you intend to create new index sections, you must read
39498 The constant pool. This is simply a bunch of bytes. It is organized
39499 so that alignment is correct: CU vectors are stored first, followed by
39502 A CU vector in the constant pool is a sequence of @code{offset_type}
39503 values. The first value is the number of CU indices in the vector.
39504 Each subsequent value is the index and symbol attributes of a CU in
39505 the CU list. This element in the hash table is used to indicate which
39506 CUs define the symbol and how the symbol is used.
39507 See below for the format of each CU index+attributes entry.
39509 A string in the constant pool is zero-terminated.
39512 Attributes were added to CU index values in @code{.gdb_index} version 7.
39513 If a symbol has multiple uses within a CU then there is one
39514 CU index+attributes value for each use.
39516 The format of each CU index+attributes entry is as follows
39522 This is the index of the CU in the CU list.
39524 These bits are reserved for future purposes and must be zero.
39526 The kind of the symbol in the CU.
39530 This value is reserved and should not be used.
39531 By reserving zero the full @code{offset_type} value is backwards compatible
39532 with previous versions of the index.
39534 The symbol is a type.
39536 The symbol is a variable or an enum value.
39538 The symbol is a function.
39540 Any other kind of symbol.
39542 These values are reserved.
39546 This bit is zero if the value is global and one if it is static.
39548 The determination of whether a symbol is global or static is complicated.
39549 The authorative reference is the file @file{dwarf2read.c} in
39550 @value{GDBN} sources.
39554 This pseudo-code describes the computation of a symbol's kind and
39555 global/static attributes in the index.
39558 is_external = get_attribute (die, DW_AT_external);
39559 language = get_attribute (cu_die, DW_AT_language);
39562 case DW_TAG_typedef:
39563 case DW_TAG_base_type:
39564 case DW_TAG_subrange_type:
39568 case DW_TAG_enumerator:
39570 is_static = (language != CPLUS && language != JAVA);
39572 case DW_TAG_subprogram:
39574 is_static = ! (is_external || language == ADA);
39576 case DW_TAG_constant:
39578 is_static = ! is_external;
39580 case DW_TAG_variable:
39582 is_static = ! is_external;
39584 case DW_TAG_namespace:
39588 case DW_TAG_class_type:
39589 case DW_TAG_interface_type:
39590 case DW_TAG_structure_type:
39591 case DW_TAG_union_type:
39592 case DW_TAG_enumeration_type:
39594 is_static = (language != CPLUS && language != JAVA);
39602 @appendix Manual pages
39606 * gdb man:: The GNU Debugger man page
39607 * gdbserver man:: Remote Server for the GNU Debugger man page
39608 * gcore man:: Generate a core file of a running program
39609 * gdbinit man:: gdbinit scripts
39615 @c man title gdb The GNU Debugger
39617 @c man begin SYNOPSIS gdb
39618 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
39619 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
39620 [@option{-b}@w{ }@var{bps}]
39621 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
39622 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
39623 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
39624 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
39625 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
39628 @c man begin DESCRIPTION gdb
39629 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
39630 going on ``inside'' another program while it executes -- or what another
39631 program was doing at the moment it crashed.
39633 @value{GDBN} can do four main kinds of things (plus other things in support of
39634 these) to help you catch bugs in the act:
39638 Start your program, specifying anything that might affect its behavior.
39641 Make your program stop on specified conditions.
39644 Examine what has happened, when your program has stopped.
39647 Change things in your program, so you can experiment with correcting the
39648 effects of one bug and go on to learn about another.
39651 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
39654 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
39655 commands from the terminal until you tell it to exit with the @value{GDBN}
39656 command @code{quit}. You can get online help from @value{GDBN} itself
39657 by using the command @code{help}.
39659 You can run @code{gdb} with no arguments or options; but the most
39660 usual way to start @value{GDBN} is with one argument or two, specifying an
39661 executable program as the argument:
39667 You can also start with both an executable program and a core file specified:
39673 You can, instead, specify a process ID as a second argument, if you want
39674 to debug a running process:
39682 would attach @value{GDBN} to process @code{1234} (unless you also have a file
39683 named @file{1234}; @value{GDBN} does check for a core file first).
39684 With option @option{-p} you can omit the @var{program} filename.
39686 Here are some of the most frequently needed @value{GDBN} commands:
39688 @c pod2man highlights the right hand side of the @item lines.
39690 @item break [@var{file}:]@var{functiop}
39691 Set a breakpoint at @var{function} (in @var{file}).
39693 @item run [@var{arglist}]
39694 Start your program (with @var{arglist}, if specified).
39697 Backtrace: display the program stack.
39699 @item print @var{expr}
39700 Display the value of an expression.
39703 Continue running your program (after stopping, e.g. at a breakpoint).
39706 Execute next program line (after stopping); step @emph{over} any
39707 function calls in the line.
39709 @item edit [@var{file}:]@var{function}
39710 look at the program line where it is presently stopped.
39712 @item list [@var{file}:]@var{function}
39713 type the text of the program in the vicinity of where it is presently stopped.
39716 Execute next program line (after stopping); step @emph{into} any
39717 function calls in the line.
39719 @item help [@var{name}]
39720 Show information about @value{GDBN} command @var{name}, or general information
39721 about using @value{GDBN}.
39724 Exit from @value{GDBN}.
39728 For full details on @value{GDBN},
39729 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
39730 by Richard M. Stallman and Roland H. Pesch. The same text is available online
39731 as the @code{gdb} entry in the @code{info} program.
39735 @c man begin OPTIONS gdb
39736 Any arguments other than options specify an executable
39737 file and core file (or process ID); that is, the first argument
39738 encountered with no
39739 associated option flag is equivalent to a @option{-se} option, and the second,
39740 if any, is equivalent to a @option{-c} option if it's the name of a file.
39742 both long and short forms; both are shown here. The long forms are also
39743 recognized if you truncate them, so long as enough of the option is
39744 present to be unambiguous. (If you prefer, you can flag option
39745 arguments with @option{+} rather than @option{-}, though we illustrate the
39746 more usual convention.)
39748 All the options and command line arguments you give are processed
39749 in sequential order. The order makes a difference when the @option{-x}
39755 List all options, with brief explanations.
39757 @item -symbols=@var{file}
39758 @itemx -s @var{file}
39759 Read symbol table from file @var{file}.
39762 Enable writing into executable and core files.
39764 @item -exec=@var{file}
39765 @itemx -e @var{file}
39766 Use file @var{file} as the executable file to execute when
39767 appropriate, and for examining pure data in conjunction with a core
39770 @item -se=@var{file}
39771 Read symbol table from file @var{file} and use it as the executable
39774 @item -core=@var{file}
39775 @itemx -c @var{file}
39776 Use file @var{file} as a core dump to examine.
39778 @item -command=@var{file}
39779 @itemx -x @var{file}
39780 Execute @value{GDBN} commands from file @var{file}.
39782 @item -ex @var{command}
39783 Execute given @value{GDBN} @var{command}.
39785 @item -directory=@var{directory}
39786 @itemx -d @var{directory}
39787 Add @var{directory} to the path to search for source files.
39790 Do not execute commands from @file{~/.gdbinit}.
39794 Do not execute commands from any @file{.gdbinit} initialization files.
39798 ``Quiet''. Do not print the introductory and copyright messages. These
39799 messages are also suppressed in batch mode.
39802 Run in batch mode. Exit with status @code{0} after processing all the command
39803 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
39804 Exit with nonzero status if an error occurs in executing the @value{GDBN}
39805 commands in the command files.
39807 Batch mode may be useful for running @value{GDBN} as a filter, for example to
39808 download and run a program on another computer; in order to make this
39809 more useful, the message
39812 Program exited normally.
39816 (which is ordinarily issued whenever a program running under @value{GDBN} control
39817 terminates) is not issued when running in batch mode.
39819 @item -cd=@var{directory}
39820 Run @value{GDBN} using @var{directory} as its working directory,
39821 instead of the current directory.
39825 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
39826 @value{GDBN} to output the full file name and line number in a standard,
39827 recognizable fashion each time a stack frame is displayed (which
39828 includes each time the program stops). This recognizable format looks
39829 like two @samp{\032} characters, followed by the file name, line number
39830 and character position separated by colons, and a newline. The
39831 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
39832 characters as a signal to display the source code for the frame.
39835 Set the line speed (baud rate or bits per second) of any serial
39836 interface used by @value{GDBN} for remote debugging.
39838 @item -tty=@var{device}
39839 Run using @var{device} for your program's standard input and output.
39843 @c man begin SEEALSO gdb
39845 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
39846 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
39847 documentation are properly installed at your site, the command
39854 should give you access to the complete manual.
39856 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
39857 Richard M. Stallman and Roland H. Pesch, July 1991.
39861 @node gdbserver man
39862 @heading gdbserver man
39864 @c man title gdbserver Remote Server for the GNU Debugger
39866 @c man begin SYNOPSIS gdbserver
39867 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
39869 gdbserver --attach @var{comm} @var{pid}
39871 gdbserver --multi @var{comm}
39875 @c man begin DESCRIPTION gdbserver
39876 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
39877 than the one which is running the program being debugged.
39880 @subheading Usage (server (target) side)
39883 Usage (server (target) side):
39886 First, you need to have a copy of the program you want to debug put onto
39887 the target system. The program can be stripped to save space if needed, as
39888 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
39889 the @value{GDBN} running on the host system.
39891 To use the server, you log on to the target system, and run the @command{gdbserver}
39892 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
39893 your program, and (c) its arguments. The general syntax is:
39896 target> gdbserver @var{comm} @var{program} [@var{args} ...]
39899 For example, using a serial port, you might say:
39903 @c @file would wrap it as F</dev/com1>.
39904 target> gdbserver /dev/com1 emacs foo.txt
39907 target> gdbserver @file{/dev/com1} emacs foo.txt
39911 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
39912 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
39913 waits patiently for the host @value{GDBN} to communicate with it.
39915 To use a TCP connection, you could say:
39918 target> gdbserver host:2345 emacs foo.txt
39921 This says pretty much the same thing as the last example, except that we are
39922 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
39923 that we are expecting to see a TCP connection from @code{host} to local TCP port
39924 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
39925 want for the port number as long as it does not conflict with any existing TCP
39926 ports on the target system. This same port number must be used in the host
39927 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
39928 you chose a port number that conflicts with another service, @command{gdbserver} will
39929 print an error message and exit.
39931 @command{gdbserver} can also attach to running programs.
39932 This is accomplished via the @option{--attach} argument. The syntax is:
39935 target> gdbserver --attach @var{comm} @var{pid}
39938 @var{pid} is the process ID of a currently running process. It isn't
39939 necessary to point @command{gdbserver} at a binary for the running process.
39941 To start @code{gdbserver} without supplying an initial command to run
39942 or process ID to attach, use the @option{--multi} command line option.
39943 In such case you should connect using @kbd{target extended-remote} to start
39944 the program you want to debug.
39947 target> gdbserver --multi @var{comm}
39951 @subheading Usage (host side)
39957 You need an unstripped copy of the target program on your host system, since
39958 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
39959 would, with the target program as the first argument. (You may need to use the
39960 @option{--baud} option if the serial line is running at anything except 9600 baud.)
39961 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
39962 new command you need to know about is @code{target remote}
39963 (or @code{target extended-remote}). Its argument is either
39964 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
39965 descriptor. For example:
39969 @c @file would wrap it as F</dev/ttyb>.
39970 (gdb) target remote /dev/ttyb
39973 (gdb) target remote @file{/dev/ttyb}
39978 communicates with the server via serial line @file{/dev/ttyb}, and:
39981 (gdb) target remote the-target:2345
39985 communicates via a TCP connection to port 2345 on host `the-target', where
39986 you previously started up @command{gdbserver} with the same port number. Note that for
39987 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
39988 command, otherwise you may get an error that looks something like
39989 `Connection refused'.
39991 @command{gdbserver} can also debug multiple inferiors at once,
39994 the @value{GDBN} manual in node @code{Inferiors and Programs}
39995 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
39998 @ref{Inferiors and Programs}.
40000 In such case use the @code{extended-remote} @value{GDBN} command variant:
40003 (gdb) target extended-remote the-target:2345
40006 The @command{gdbserver} option @option{--multi} may or may not be used in such
40010 @c man begin OPTIONS gdbserver
40011 There are three different modes for invoking @command{gdbserver}:
40016 Debug a specific program specified by its program name:
40019 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
40022 The @var{comm} parameter specifies how should the server communicate
40023 with @value{GDBN}; it is either a device name (to use a serial line),
40024 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
40025 stdin/stdout of @code{gdbserver}. Specify the name of the program to
40026 debug in @var{prog}. Any remaining arguments will be passed to the
40027 program verbatim. When the program exits, @value{GDBN} will close the
40028 connection, and @code{gdbserver} will exit.
40031 Debug a specific program by specifying the process ID of a running
40035 gdbserver --attach @var{comm} @var{pid}
40038 The @var{comm} parameter is as described above. Supply the process ID
40039 of a running program in @var{pid}; @value{GDBN} will do everything
40040 else. Like with the previous mode, when the process @var{pid} exits,
40041 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
40044 Multi-process mode -- debug more than one program/process:
40047 gdbserver --multi @var{comm}
40050 In this mode, @value{GDBN} can instruct @command{gdbserver} which
40051 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
40052 close the connection when a process being debugged exits, so you can
40053 debug several processes in the same session.
40056 In each of the modes you may specify these options:
40061 List all options, with brief explanations.
40064 This option causes @command{gdbserver} to print its version number and exit.
40067 @command{gdbserver} will attach to a running program. The syntax is:
40070 target> gdbserver --attach @var{comm} @var{pid}
40073 @var{pid} is the process ID of a currently running process. It isn't
40074 necessary to point @command{gdbserver} at a binary for the running process.
40077 To start @code{gdbserver} without supplying an initial command to run
40078 or process ID to attach, use this command line option.
40079 Then you can connect using @kbd{target extended-remote} and start
40080 the program you want to debug. The syntax is:
40083 target> gdbserver --multi @var{comm}
40087 Instruct @code{gdbserver} to display extra status information about the debugging
40089 This option is intended for @code{gdbserver} development and for bug reports to
40092 @item --remote-debug
40093 Instruct @code{gdbserver} to display remote protocol debug output.
40094 This option is intended for @code{gdbserver} development and for bug reports to
40097 @item --debug-format=option1@r{[},option2,...@r{]}
40098 Instruct @code{gdbserver} to include extra information in each line
40099 of debugging output.
40100 @xref{Other Command-Line Arguments for gdbserver}.
40103 Specify a wrapper to launch programs
40104 for debugging. The option should be followed by the name of the
40105 wrapper, then any command-line arguments to pass to the wrapper, then
40106 @kbd{--} indicating the end of the wrapper arguments.
40109 By default, @command{gdbserver} keeps the listening TCP port open, so that
40110 additional connections are possible. However, if you start @code{gdbserver}
40111 with the @option{--once} option, it will stop listening for any further
40112 connection attempts after connecting to the first @value{GDBN} session.
40114 @c --disable-packet is not documented for users.
40116 @c --disable-randomization and --no-disable-randomization are superseded by
40117 @c QDisableRandomization.
40122 @c man begin SEEALSO gdbserver
40124 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
40125 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
40126 documentation are properly installed at your site, the command
40132 should give you access to the complete manual.
40134 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40135 Richard M. Stallman and Roland H. Pesch, July 1991.
40142 @c man title gcore Generate a core file of a running program
40145 @c man begin SYNOPSIS gcore
40146 gcore [-o @var{filename}] @var{pid}
40150 @c man begin DESCRIPTION gcore
40151 Generate a core dump of a running program with process ID @var{pid}.
40152 Produced file is equivalent to a kernel produced core file as if the process
40153 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
40154 limit). Unlike after a crash, after @command{gcore} the program remains
40155 running without any change.
40158 @c man begin OPTIONS gcore
40160 @item -o @var{filename}
40161 The optional argument
40162 @var{filename} specifies the file name where to put the core dump.
40163 If not specified, the file name defaults to @file{core.@var{pid}},
40164 where @var{pid} is the running program process ID.
40168 @c man begin SEEALSO gcore
40170 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
40171 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
40172 documentation are properly installed at your site, the command
40179 should give you access to the complete manual.
40181 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40182 Richard M. Stallman and Roland H. Pesch, July 1991.
40189 @c man title gdbinit GDB initialization scripts
40192 @c man begin SYNOPSIS gdbinit
40193 @ifset SYSTEM_GDBINIT
40194 @value{SYSTEM_GDBINIT}
40203 @c man begin DESCRIPTION gdbinit
40204 These files contain @value{GDBN} commands to automatically execute during
40205 @value{GDBN} startup. The lines of contents are canned sequences of commands,
40208 the @value{GDBN} manual in node @code{Sequences}
40209 -- shell command @code{info -f gdb -n Sequences}.
40215 Please read more in
40217 the @value{GDBN} manual in node @code{Startup}
40218 -- shell command @code{info -f gdb -n Startup}.
40225 @ifset SYSTEM_GDBINIT
40226 @item @value{SYSTEM_GDBINIT}
40228 @ifclear SYSTEM_GDBINIT
40229 @item (not enabled with @code{--with-system-gdbinit} during compilation)
40231 System-wide initialization file. It is executed unless user specified
40232 @value{GDBN} option @code{-nx} or @code{-n}.
40235 the @value{GDBN} manual in node @code{System-wide configuration}
40236 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
40239 @ref{System-wide configuration}.
40243 User initialization file. It is executed unless user specified
40244 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
40247 Initialization file for current directory. It may need to be enabled with
40248 @value{GDBN} security command @code{set auto-load local-gdbinit}.
40251 the @value{GDBN} manual in node @code{Init File in the Current Directory}
40252 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
40255 @ref{Init File in the Current Directory}.
40260 @c man begin SEEALSO gdbinit
40262 gdb(1), @code{info -f gdb -n Startup}
40264 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
40265 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
40266 documentation are properly installed at your site, the command
40272 should give you access to the complete manual.
40274 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40275 Richard M. Stallman and Roland H. Pesch, July 1991.
40281 @node GNU Free Documentation License
40282 @appendix GNU Free Documentation License
40285 @node Concept Index
40286 @unnumbered Concept Index
40290 @node Command and Variable Index
40291 @unnumbered Command, Variable, and Function Index
40296 % I think something like @@colophon should be in texinfo. In the
40298 \long\def\colophon{\hbox to0pt{}\vfill
40299 \centerline{The body of this manual is set in}
40300 \centerline{\fontname\tenrm,}
40301 \centerline{with headings in {\bf\fontname\tenbf}}
40302 \centerline{and examples in {\tt\fontname\tentt}.}
40303 \centerline{{\it\fontname\tenit\/},}
40304 \centerline{{\bf\fontname\tenbf}, and}
40305 \centerline{{\sl\fontname\tensl\/}}
40306 \centerline{are used for emphasis.}\vfill}
40308 % Blame: doc@@cygnus.com, 1991.