1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2015 Free Software Foundation, Inc.
5 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
6 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
23 @c To avoid file-name clashes between index.html and Index.html, when
24 @c the manual is produced on a Posix host and then moved to a
25 @c case-insensitive filesystem (e.g., MS-Windows), we separate the
26 @c indices into two: Concept Index and all the rest.
30 @c readline appendices use @vindex, @findex and @ftable,
31 @c annotate.texi and gdbmi use @findex.
34 @c !!set GDB manual's edition---not the same as GDB version!
35 @c This is updated by GNU Press.
38 @c !!set GDB edit command default editor
41 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
43 @c This is a dir.info fragment to support semi-automated addition of
44 @c manuals to an info tree.
45 @dircategory Software development
47 * Gdb: (gdb). The GNU debugger.
48 * gdbserver: (gdb) Server. The GNU debugging server.
52 @c man begin COPYRIGHT
53 Copyright @copyright{} 1988-2015 Free Software Foundation, Inc.
55 Permission is granted to copy, distribute and/or modify this document
56 under the terms of the GNU Free Documentation License, Version 1.3 or
57 any later version published by the Free Software Foundation; with the
58 Invariant Sections being ``Free Software'' and ``Free Software Needs
59 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
60 and with the Back-Cover Texts as in (a) below.
62 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
63 this GNU Manual. Buying copies from GNU Press supports the FSF in
64 developing GNU and promoting software freedom.''
69 This file documents the @sc{gnu} debugger @value{GDBN}.
71 This is the @value{EDITION} Edition, of @cite{Debugging with
72 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
73 @ifset VERSION_PACKAGE
74 @value{VERSION_PACKAGE}
76 Version @value{GDBVN}.
82 @title Debugging with @value{GDBN}
83 @subtitle The @sc{gnu} Source-Level Debugger
85 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
86 @ifset VERSION_PACKAGE
88 @subtitle @value{VERSION_PACKAGE}
90 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
94 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
95 \hfill {\it Debugging with @value{GDBN}}\par
96 \hfill \TeX{}info \texinfoversion\par
100 @vskip 0pt plus 1filll
101 Published by the Free Software Foundation @*
102 51 Franklin Street, Fifth Floor,
103 Boston, MA 02110-1301, USA@*
104 ISBN 978-0-9831592-3-0 @*
111 @node Top, Summary, (dir), (dir)
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN}
118 @ifset VERSION_PACKAGE
119 @value{VERSION_PACKAGE}
121 Version @value{GDBVN}.
123 Copyright (C) 1988-2015 Free Software Foundation, Inc.
125 This edition of the GDB manual is dedicated to the memory of Fred
126 Fish. Fred was a long-standing contributor to GDB and to Free
127 software in general. We will miss him.
130 * Summary:: Summary of @value{GDBN}
131 * Sample Session:: A sample @value{GDBN} session
133 * Invocation:: Getting in and out of @value{GDBN}
134 * Commands:: @value{GDBN} commands
135 * Running:: Running programs under @value{GDBN}
136 * Stopping:: Stopping and continuing
137 * Reverse Execution:: Running programs backward
138 * Process Record and Replay:: Recording inferior's execution and replaying it
139 * Stack:: Examining the stack
140 * Source:: Examining source files
141 * Data:: Examining data
142 * Optimized Code:: Debugging optimized code
143 * Macros:: Preprocessor Macros
144 * Tracepoints:: Debugging remote targets non-intrusively
145 * Overlays:: Debugging programs that use overlays
147 * Languages:: Using @value{GDBN} with different languages
149 * Symbols:: Examining the symbol table
150 * Altering:: Altering execution
151 * GDB Files:: @value{GDBN} files
152 * Targets:: Specifying a debugging target
153 * Remote Debugging:: Debugging remote programs
154 * Configurations:: Configuration-specific information
155 * Controlling GDB:: Controlling @value{GDBN}
156 * Extending GDB:: Extending @value{GDBN}
157 * Interpreters:: Command Interpreters
158 * TUI:: @value{GDBN} Text User Interface
159 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
160 * GDB/MI:: @value{GDBN}'s Machine Interface.
161 * Annotations:: @value{GDBN}'s annotation interface.
162 * JIT Interface:: Using the JIT debugging interface.
163 * In-Process Agent:: In-Process Agent
165 * GDB Bugs:: Reporting bugs in @value{GDBN}
167 @ifset SYSTEM_READLINE
168 * Command Line Editing: (rluserman). Command Line Editing
169 * Using History Interactively: (history). Using History Interactively
171 @ifclear SYSTEM_READLINE
172 * Command Line Editing:: Command Line Editing
173 * Using History Interactively:: Using History Interactively
175 * In Memoriam:: In Memoriam
176 * Formatting Documentation:: How to format and print @value{GDBN} documentation
177 * Installing GDB:: Installing GDB
178 * Maintenance Commands:: Maintenance Commands
179 * Remote Protocol:: GDB Remote Serial Protocol
180 * Agent Expressions:: The GDB Agent Expression Mechanism
181 * Target Descriptions:: How targets can describe themselves to
183 * Operating System Information:: Getting additional information from
185 * Trace File Format:: GDB trace file format
186 * Index Section Format:: .gdb_index section format
187 * Man Pages:: Manual pages
188 * Copying:: GNU General Public License says
189 how you can copy and share GDB
190 * GNU Free Documentation License:: The license for this documentation
191 * Concept Index:: Index of @value{GDBN} concepts
192 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
193 functions, and Python data types
201 @unnumbered Summary of @value{GDBN}
203 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
204 going on ``inside'' another program while it executes---or what another
205 program was doing at the moment it crashed.
207 @value{GDBN} can do four main kinds of things (plus other things in support of
208 these) to help you catch bugs in the act:
212 Start your program, specifying anything that might affect its behavior.
215 Make your program stop on specified conditions.
218 Examine what has happened, when your program has stopped.
221 Change things in your program, so you can experiment with correcting the
222 effects of one bug and go on to learn about another.
225 You can use @value{GDBN} to debug programs written in C and C@t{++}.
226 For more information, see @ref{Supported Languages,,Supported Languages}.
227 For more information, see @ref{C,,C and C++}.
229 Support for D is partial. For information on D, see
233 Support for Modula-2 is partial. For information on Modula-2, see
234 @ref{Modula-2,,Modula-2}.
236 Support for OpenCL C is partial. For information on OpenCL C, see
237 @ref{OpenCL C,,OpenCL C}.
240 Debugging Pascal programs which use sets, subranges, file variables, or
241 nested functions does not currently work. @value{GDBN} does not support
242 entering expressions, printing values, or similar features using Pascal
246 @value{GDBN} can be used to debug programs written in Fortran, although
247 it may be necessary to refer to some variables with a trailing
250 @value{GDBN} can be used to debug programs written in Objective-C,
251 using either the Apple/NeXT or the GNU Objective-C runtime.
254 * Free Software:: Freely redistributable software
255 * Free Documentation:: Free Software Needs Free Documentation
256 * Contributors:: Contributors to GDB
260 @unnumberedsec Free Software
262 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
263 General Public License
264 (GPL). The GPL gives you the freedom to copy or adapt a licensed
265 program---but every person getting a copy also gets with it the
266 freedom to modify that copy (which means that they must get access to
267 the source code), and the freedom to distribute further copies.
268 Typical software companies use copyrights to limit your freedoms; the
269 Free Software Foundation uses the GPL to preserve these freedoms.
271 Fundamentally, the General Public License is a license which says that
272 you have these freedoms and that you cannot take these freedoms away
275 @node Free Documentation
276 @unnumberedsec Free Software Needs Free Documentation
278 The biggest deficiency in the free software community today is not in
279 the software---it is the lack of good free documentation that we can
280 include with the free software. Many of our most important
281 programs do not come with free reference manuals and free introductory
282 texts. Documentation is an essential part of any software package;
283 when an important free software package does not come with a free
284 manual and a free tutorial, that is a major gap. We have many such
287 Consider Perl, for instance. The tutorial manuals that people
288 normally use are non-free. How did this come about? Because the
289 authors of those manuals published them with restrictive terms---no
290 copying, no modification, source files not available---which exclude
291 them from the free software world.
293 That wasn't the first time this sort of thing happened, and it was far
294 from the last. Many times we have heard a GNU user eagerly describe a
295 manual that he is writing, his intended contribution to the community,
296 only to learn that he had ruined everything by signing a publication
297 contract to make it non-free.
299 Free documentation, like free software, is a matter of freedom, not
300 price. The problem with the non-free manual is not that publishers
301 charge a price for printed copies---that in itself is fine. (The Free
302 Software Foundation sells printed copies of manuals, too.) The
303 problem is the restrictions on the use of the manual. Free manuals
304 are available in source code form, and give you permission to copy and
305 modify. Non-free manuals do not allow this.
307 The criteria of freedom for a free manual are roughly the same as for
308 free software. Redistribution (including the normal kinds of
309 commercial redistribution) must be permitted, so that the manual can
310 accompany every copy of the program, both on-line and on paper.
312 Permission for modification of the technical content is crucial too.
313 When people modify the software, adding or changing features, if they
314 are conscientious they will change the manual too---so they can
315 provide accurate and clear documentation for the modified program. A
316 manual that leaves you no choice but to write a new manual to document
317 a changed version of the program is not really available to our
320 Some kinds of limits on the way modification is handled are
321 acceptable. For example, requirements to preserve the original
322 author's copyright notice, the distribution terms, or the list of
323 authors, are ok. It is also no problem to require modified versions
324 to include notice that they were modified. Even entire sections that
325 may not be deleted or changed are acceptable, as long as they deal
326 with nontechnical topics (like this one). These kinds of restrictions
327 are acceptable because they don't obstruct the community's normal use
330 However, it must be possible to modify all the @emph{technical}
331 content of the manual, and then distribute the result in all the usual
332 media, through all the usual channels. Otherwise, the restrictions
333 obstruct the use of the manual, it is not free, and we need another
334 manual to replace it.
336 Please spread the word about this issue. Our community continues to
337 lose manuals to proprietary publishing. If we spread the word that
338 free software needs free reference manuals and free tutorials, perhaps
339 the next person who wants to contribute by writing documentation will
340 realize, before it is too late, that only free manuals contribute to
341 the free software community.
343 If you are writing documentation, please insist on publishing it under
344 the GNU Free Documentation License or another free documentation
345 license. Remember that this decision requires your approval---you
346 don't have to let the publisher decide. Some commercial publishers
347 will use a free license if you insist, but they will not propose the
348 option; it is up to you to raise the issue and say firmly that this is
349 what you want. If the publisher you are dealing with refuses, please
350 try other publishers. If you're not sure whether a proposed license
351 is free, write to @email{licensing@@gnu.org}.
353 You can encourage commercial publishers to sell more free, copylefted
354 manuals and tutorials by buying them, and particularly by buying
355 copies from the publishers that paid for their writing or for major
356 improvements. Meanwhile, try to avoid buying non-free documentation
357 at all. Check the distribution terms of a manual before you buy it,
358 and insist that whoever seeks your business must respect your freedom.
359 Check the history of the book, and try to reward the publishers that
360 have paid or pay the authors to work on it.
362 The Free Software Foundation maintains a list of free documentation
363 published by other publishers, at
364 @url{http://www.fsf.org/doc/other-free-books.html}.
367 @unnumberedsec Contributors to @value{GDBN}
369 Richard Stallman was the original author of @value{GDBN}, and of many
370 other @sc{gnu} programs. Many others have contributed to its
371 development. This section attempts to credit major contributors. One
372 of the virtues of free software is that everyone is free to contribute
373 to it; with regret, we cannot actually acknowledge everyone here. The
374 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
375 blow-by-blow account.
377 Changes much prior to version 2.0 are lost in the mists of time.
380 @emph{Plea:} Additions to this section are particularly welcome. If you
381 or your friends (or enemies, to be evenhanded) have been unfairly
382 omitted from this list, we would like to add your names!
385 So that they may not regard their many labors as thankless, we
386 particularly thank those who shepherded @value{GDBN} through major
388 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
389 Jim Blandy (release 4.18);
390 Jason Molenda (release 4.17);
391 Stan Shebs (release 4.14);
392 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
393 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
394 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
395 Jim Kingdon (releases 3.5, 3.4, and 3.3);
396 and Randy Smith (releases 3.2, 3.1, and 3.0).
398 Richard Stallman, assisted at various times by Peter TerMaat, Chris
399 Hanson, and Richard Mlynarik, handled releases through 2.8.
401 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
402 in @value{GDBN}, with significant additional contributions from Per
403 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
404 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
405 much general update work leading to release 3.0).
407 @value{GDBN} uses the BFD subroutine library to examine multiple
408 object-file formats; BFD was a joint project of David V.
409 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
411 David Johnson wrote the original COFF support; Pace Willison did
412 the original support for encapsulated COFF.
414 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
416 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
417 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
419 Jean-Daniel Fekete contributed Sun 386i support.
420 Chris Hanson improved the HP9000 support.
421 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
422 David Johnson contributed Encore Umax support.
423 Jyrki Kuoppala contributed Altos 3068 support.
424 Jeff Law contributed HP PA and SOM support.
425 Keith Packard contributed NS32K support.
426 Doug Rabson contributed Acorn Risc Machine support.
427 Bob Rusk contributed Harris Nighthawk CX-UX support.
428 Chris Smith contributed Convex support (and Fortran debugging).
429 Jonathan Stone contributed Pyramid support.
430 Michael Tiemann contributed SPARC support.
431 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
432 Pace Willison contributed Intel 386 support.
433 Jay Vosburgh contributed Symmetry support.
434 Marko Mlinar contributed OpenRISC 1000 support.
436 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
438 Rich Schaefer and Peter Schauer helped with support of SunOS shared
441 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
442 about several machine instruction sets.
444 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
445 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
446 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
447 and RDI targets, respectively.
449 Brian Fox is the author of the readline libraries providing
450 command-line editing and command history.
452 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
453 Modula-2 support, and contributed the Languages chapter of this manual.
455 Fred Fish wrote most of the support for Unix System Vr4.
456 He also enhanced the command-completion support to cover C@t{++} overloaded
459 Hitachi America (now Renesas America), Ltd. sponsored the support for
460 H8/300, H8/500, and Super-H processors.
462 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
464 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
467 Toshiba sponsored the support for the TX39 Mips processor.
469 Matsushita sponsored the support for the MN10200 and MN10300 processors.
471 Fujitsu sponsored the support for SPARClite and FR30 processors.
473 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
476 Michael Snyder added support for tracepoints.
478 Stu Grossman wrote gdbserver.
480 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
481 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
483 The following people at the Hewlett-Packard Company contributed
484 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
485 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
486 compiler, and the Text User Interface (nee Terminal User Interface):
487 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
488 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
489 provided HP-specific information in this manual.
491 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
492 Robert Hoehne made significant contributions to the DJGPP port.
494 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
495 development since 1991. Cygnus engineers who have worked on @value{GDBN}
496 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
497 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
498 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
499 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
500 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
501 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
502 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
503 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
504 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
505 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
506 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
507 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
508 Zuhn have made contributions both large and small.
510 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
511 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
513 Jim Blandy added support for preprocessor macros, while working for Red
516 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
517 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
518 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
519 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
520 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
521 with the migration of old architectures to this new framework.
523 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
524 unwinder framework, this consisting of a fresh new design featuring
525 frame IDs, independent frame sniffers, and the sentinel frame. Mark
526 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
527 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
528 trad unwinders. The architecture-specific changes, each involving a
529 complete rewrite of the architecture's frame code, were carried out by
530 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
531 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
532 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
533 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
536 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
537 Tensilica, Inc.@: contributed support for Xtensa processors. Others
538 who have worked on the Xtensa port of @value{GDBN} in the past include
539 Steve Tjiang, John Newlin, and Scott Foehner.
541 Michael Eager and staff of Xilinx, Inc., contributed support for the
542 Xilinx MicroBlaze architecture.
545 @chapter A Sample @value{GDBN} Session
547 You can use this manual at your leisure to read all about @value{GDBN}.
548 However, a handful of commands are enough to get started using the
549 debugger. This chapter illustrates those commands.
552 In this sample session, we emphasize user input like this: @b{input},
553 to make it easier to pick out from the surrounding output.
556 @c FIXME: this example may not be appropriate for some configs, where
557 @c FIXME...primary interest is in remote use.
559 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
560 processor) exhibits the following bug: sometimes, when we change its
561 quote strings from the default, the commands used to capture one macro
562 definition within another stop working. In the following short @code{m4}
563 session, we define a macro @code{foo} which expands to @code{0000}; we
564 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
565 same thing. However, when we change the open quote string to
566 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
567 procedure fails to define a new synonym @code{baz}:
576 @b{define(bar,defn(`foo'))}
580 @b{changequote(<QUOTE>,<UNQUOTE>)}
582 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
585 m4: End of input: 0: fatal error: EOF in string
589 Let us use @value{GDBN} to try to see what is going on.
592 $ @b{@value{GDBP} m4}
593 @c FIXME: this falsifies the exact text played out, to permit smallbook
594 @c FIXME... format to come out better.
595 @value{GDBN} is free software and you are welcome to distribute copies
596 of it under certain conditions; type "show copying" to see
598 There is absolutely no warranty for @value{GDBN}; type "show warranty"
601 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
606 @value{GDBN} reads only enough symbol data to know where to find the
607 rest when needed; as a result, the first prompt comes up very quickly.
608 We now tell @value{GDBN} to use a narrower display width than usual, so
609 that examples fit in this manual.
612 (@value{GDBP}) @b{set width 70}
616 We need to see how the @code{m4} built-in @code{changequote} works.
617 Having looked at the source, we know the relevant subroutine is
618 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
619 @code{break} command.
622 (@value{GDBP}) @b{break m4_changequote}
623 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
627 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
628 control; as long as control does not reach the @code{m4_changequote}
629 subroutine, the program runs as usual:
632 (@value{GDBP}) @b{run}
633 Starting program: /work/Editorial/gdb/gnu/m4/m4
641 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
642 suspends execution of @code{m4}, displaying information about the
643 context where it stops.
646 @b{changequote(<QUOTE>,<UNQUOTE>)}
648 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
650 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
654 Now we use the command @code{n} (@code{next}) to advance execution to
655 the next line of the current function.
659 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
664 @code{set_quotes} looks like a promising subroutine. We can go into it
665 by using the command @code{s} (@code{step}) instead of @code{next}.
666 @code{step} goes to the next line to be executed in @emph{any}
667 subroutine, so it steps into @code{set_quotes}.
671 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
673 530 if (lquote != def_lquote)
677 The display that shows the subroutine where @code{m4} is now
678 suspended (and its arguments) is called a stack frame display. It
679 shows a summary of the stack. We can use the @code{backtrace}
680 command (which can also be spelled @code{bt}), to see where we are
681 in the stack as a whole: the @code{backtrace} command displays a
682 stack frame for each active subroutine.
685 (@value{GDBP}) @b{bt}
686 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
688 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
690 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
691 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
693 #4 0x79dc in expand_input () at macro.c:40
694 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
698 We step through a few more lines to see what happens. The first two
699 times, we can use @samp{s}; the next two times we use @code{n} to avoid
700 falling into the @code{xstrdup} subroutine.
704 0x3b5c 532 if (rquote != def_rquote)
706 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
707 def_lquote : xstrdup(lq);
709 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
712 538 len_lquote = strlen(rquote);
716 The last line displayed looks a little odd; we can examine the variables
717 @code{lquote} and @code{rquote} to see if they are in fact the new left
718 and right quotes we specified. We use the command @code{p}
719 (@code{print}) to see their values.
722 (@value{GDBP}) @b{p lquote}
723 $1 = 0x35d40 "<QUOTE>"
724 (@value{GDBP}) @b{p rquote}
725 $2 = 0x35d50 "<UNQUOTE>"
729 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
730 To look at some context, we can display ten lines of source
731 surrounding the current line with the @code{l} (@code{list}) command.
737 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
739 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
742 538 len_lquote = strlen(rquote);
743 539 len_rquote = strlen(lquote);
750 Let us step past the two lines that set @code{len_lquote} and
751 @code{len_rquote}, and then examine the values of those variables.
755 539 len_rquote = strlen(lquote);
758 (@value{GDBP}) @b{p len_lquote}
760 (@value{GDBP}) @b{p len_rquote}
765 That certainly looks wrong, assuming @code{len_lquote} and
766 @code{len_rquote} are meant to be the lengths of @code{lquote} and
767 @code{rquote} respectively. We can set them to better values using
768 the @code{p} command, since it can print the value of
769 any expression---and that expression can include subroutine calls and
773 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
775 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
780 Is that enough to fix the problem of using the new quotes with the
781 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
782 executing with the @code{c} (@code{continue}) command, and then try the
783 example that caused trouble initially:
789 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
796 Success! The new quotes now work just as well as the default ones. The
797 problem seems to have been just the two typos defining the wrong
798 lengths. We allow @code{m4} exit by giving it an EOF as input:
802 Program exited normally.
806 The message @samp{Program exited normally.} is from @value{GDBN}; it
807 indicates @code{m4} has finished executing. We can end our @value{GDBN}
808 session with the @value{GDBN} @code{quit} command.
811 (@value{GDBP}) @b{quit}
815 @chapter Getting In and Out of @value{GDBN}
817 This chapter discusses how to start @value{GDBN}, and how to get out of it.
821 type @samp{@value{GDBP}} to start @value{GDBN}.
823 type @kbd{quit} or @kbd{Ctrl-d} to exit.
827 * Invoking GDB:: How to start @value{GDBN}
828 * Quitting GDB:: How to quit @value{GDBN}
829 * Shell Commands:: How to use shell commands inside @value{GDBN}
830 * Logging Output:: How to log @value{GDBN}'s output to a file
834 @section Invoking @value{GDBN}
836 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
837 @value{GDBN} reads commands from the terminal until you tell it to exit.
839 You can also run @code{@value{GDBP}} with a variety of arguments and options,
840 to specify more of your debugging environment at the outset.
842 The command-line options described here are designed
843 to cover a variety of situations; in some environments, some of these
844 options may effectively be unavailable.
846 The most usual way to start @value{GDBN} is with one argument,
847 specifying an executable program:
850 @value{GDBP} @var{program}
854 You can also start with both an executable program and a core file
858 @value{GDBP} @var{program} @var{core}
861 You can, instead, specify a process ID as a second argument, if you want
862 to debug a running process:
865 @value{GDBP} @var{program} 1234
869 would attach @value{GDBN} to process @code{1234} (unless you also have a file
870 named @file{1234}; @value{GDBN} does check for a core file first).
872 Taking advantage of the second command-line argument requires a fairly
873 complete operating system; when you use @value{GDBN} as a remote
874 debugger attached to a bare board, there may not be any notion of
875 ``process'', and there is often no way to get a core dump. @value{GDBN}
876 will warn you if it is unable to attach or to read core dumps.
878 You can optionally have @code{@value{GDBP}} pass any arguments after the
879 executable file to the inferior using @code{--args}. This option stops
882 @value{GDBP} --args gcc -O2 -c foo.c
884 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
885 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
887 You can run @code{@value{GDBP}} without printing the front material, which describes
888 @value{GDBN}'s non-warranty, by specifying @code{--silent}
889 (or @code{-q}/@code{--quiet}):
892 @value{GDBP} --silent
896 You can further control how @value{GDBN} starts up by using command-line
897 options. @value{GDBN} itself can remind you of the options available.
907 to display all available options and briefly describe their use
908 (@samp{@value{GDBP} -h} is a shorter equivalent).
910 All options and command line arguments you give are processed
911 in sequential order. The order makes a difference when the
912 @samp{-x} option is used.
916 * File Options:: Choosing files
917 * Mode Options:: Choosing modes
918 * Startup:: What @value{GDBN} does during startup
922 @subsection Choosing Files
924 When @value{GDBN} starts, it reads any arguments other than options as
925 specifying an executable file and core file (or process ID). This is
926 the same as if the arguments were specified by the @samp{-se} and
927 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
928 first argument that does not have an associated option flag as
929 equivalent to the @samp{-se} option followed by that argument; and the
930 second argument that does not have an associated option flag, if any, as
931 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
932 If the second argument begins with a decimal digit, @value{GDBN} will
933 first attempt to attach to it as a process, and if that fails, attempt
934 to open it as a corefile. If you have a corefile whose name begins with
935 a digit, you can prevent @value{GDBN} from treating it as a pid by
936 prefixing it with @file{./}, e.g.@: @file{./12345}.
938 If @value{GDBN} has not been configured to included core file support,
939 such as for most embedded targets, then it will complain about a second
940 argument and ignore it.
942 Many options have both long and short forms; both are shown in the
943 following list. @value{GDBN} also recognizes the long forms if you truncate
944 them, so long as enough of the option is present to be unambiguous.
945 (If you prefer, you can flag option arguments with @samp{--} rather
946 than @samp{-}, though we illustrate the more usual convention.)
948 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
949 @c way, both those who look for -foo and --foo in the index, will find
953 @item -symbols @var{file}
955 @cindex @code{--symbols}
957 Read symbol table from file @var{file}.
959 @item -exec @var{file}
961 @cindex @code{--exec}
963 Use file @var{file} as the executable file to execute when appropriate,
964 and for examining pure data in conjunction with a core dump.
968 Read symbol table from file @var{file} and use it as the executable
971 @item -core @var{file}
973 @cindex @code{--core}
975 Use file @var{file} as a core dump to examine.
977 @item -pid @var{number}
978 @itemx -p @var{number}
981 Connect to process ID @var{number}, as with the @code{attach} command.
983 @item -command @var{file}
985 @cindex @code{--command}
987 Execute commands from file @var{file}. The contents of this file is
988 evaluated exactly as the @code{source} command would.
989 @xref{Command Files,, Command files}.
991 @item -eval-command @var{command}
992 @itemx -ex @var{command}
993 @cindex @code{--eval-command}
995 Execute a single @value{GDBN} command.
997 This option may be used multiple times to call multiple commands. It may
998 also be interleaved with @samp{-command} as required.
1001 @value{GDBP} -ex 'target sim' -ex 'load' \
1002 -x setbreakpoints -ex 'run' a.out
1005 @item -init-command @var{file}
1006 @itemx -ix @var{file}
1007 @cindex @code{--init-command}
1009 Execute commands from file @var{file} before loading the inferior (but
1010 after loading gdbinit files).
1013 @item -init-eval-command @var{command}
1014 @itemx -iex @var{command}
1015 @cindex @code{--init-eval-command}
1017 Execute a single @value{GDBN} command before loading the inferior (but
1018 after loading gdbinit files).
1021 @item -directory @var{directory}
1022 @itemx -d @var{directory}
1023 @cindex @code{--directory}
1025 Add @var{directory} to the path to search for source and script files.
1029 @cindex @code{--readnow}
1031 Read each symbol file's entire symbol table immediately, rather than
1032 the default, which is to read it incrementally as it is needed.
1033 This makes startup slower, but makes future operations faster.
1038 @subsection Choosing Modes
1040 You can run @value{GDBN} in various alternative modes---for example, in
1041 batch mode or quiet mode.
1049 Do not execute commands found in any initialization file.
1050 There are three init files, loaded in the following order:
1053 @item @file{system.gdbinit}
1054 This is the system-wide init file.
1055 Its location is specified with the @code{--with-system-gdbinit}
1056 configure option (@pxref{System-wide configuration}).
1057 It is loaded first when @value{GDBN} starts, before command line options
1058 have been processed.
1059 @item @file{~/.gdbinit}
1060 This is the init file in your home directory.
1061 It is loaded next, after @file{system.gdbinit}, and before
1062 command options have been processed.
1063 @item @file{./.gdbinit}
1064 This is the init file in the current directory.
1065 It is loaded last, after command line options other than @code{-x} and
1066 @code{-ex} have been processed. Command line options @code{-x} and
1067 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1070 For further documentation on startup processing, @xref{Startup}.
1071 For documentation on how to write command files,
1072 @xref{Command Files,,Command Files}.
1077 Do not execute commands found in @file{~/.gdbinit}, the init file
1078 in your home directory.
1084 @cindex @code{--quiet}
1085 @cindex @code{--silent}
1087 ``Quiet''. Do not print the introductory and copyright messages. These
1088 messages are also suppressed in batch mode.
1091 @cindex @code{--batch}
1092 Run in batch mode. Exit with status @code{0} after processing all the
1093 command files specified with @samp{-x} (and all commands from
1094 initialization files, if not inhibited with @samp{-n}). Exit with
1095 nonzero status if an error occurs in executing the @value{GDBN} commands
1096 in the command files. Batch mode also disables pagination, sets unlimited
1097 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1098 off} were in effect (@pxref{Messages/Warnings}).
1100 Batch mode may be useful for running @value{GDBN} as a filter, for
1101 example to download and run a program on another computer; in order to
1102 make this more useful, the message
1105 Program exited normally.
1109 (which is ordinarily issued whenever a program running under
1110 @value{GDBN} control terminates) is not issued when running in batch
1114 @cindex @code{--batch-silent}
1115 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1116 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1117 unaffected). This is much quieter than @samp{-silent} and would be useless
1118 for an interactive session.
1120 This is particularly useful when using targets that give @samp{Loading section}
1121 messages, for example.
1123 Note that targets that give their output via @value{GDBN}, as opposed to
1124 writing directly to @code{stdout}, will also be made silent.
1126 @item -return-child-result
1127 @cindex @code{--return-child-result}
1128 The return code from @value{GDBN} will be the return code from the child
1129 process (the process being debugged), with the following exceptions:
1133 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1134 internal error. In this case the exit code is the same as it would have been
1135 without @samp{-return-child-result}.
1137 The user quits with an explicit value. E.g., @samp{quit 1}.
1139 The child process never runs, or is not allowed to terminate, in which case
1140 the exit code will be -1.
1143 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1144 when @value{GDBN} is being used as a remote program loader or simulator
1149 @cindex @code{--nowindows}
1151 ``No windows''. If @value{GDBN} comes with a graphical user interface
1152 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1153 interface. If no GUI is available, this option has no effect.
1157 @cindex @code{--windows}
1159 If @value{GDBN} includes a GUI, then this option requires it to be
1162 @item -cd @var{directory}
1164 Run @value{GDBN} using @var{directory} as its working directory,
1165 instead of the current directory.
1167 @item -data-directory @var{directory}
1168 @itemx -D @var{directory}
1169 @cindex @code{--data-directory}
1171 Run @value{GDBN} using @var{directory} as its data directory.
1172 The data directory is where @value{GDBN} searches for its
1173 auxiliary files. @xref{Data Files}.
1177 @cindex @code{--fullname}
1179 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1180 subprocess. It tells @value{GDBN} to output the full file name and line
1181 number in a standard, recognizable fashion each time a stack frame is
1182 displayed (which includes each time your program stops). This
1183 recognizable format looks like two @samp{\032} characters, followed by
1184 the file name, line number and character position separated by colons,
1185 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1186 @samp{\032} characters as a signal to display the source code for the
1189 @item -annotate @var{level}
1190 @cindex @code{--annotate}
1191 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1192 effect is identical to using @samp{set annotate @var{level}}
1193 (@pxref{Annotations}). The annotation @var{level} controls how much
1194 information @value{GDBN} prints together with its prompt, values of
1195 expressions, source lines, and other types of output. Level 0 is the
1196 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1197 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1198 that control @value{GDBN}, and level 2 has been deprecated.
1200 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1204 @cindex @code{--args}
1205 Change interpretation of command line so that arguments following the
1206 executable file are passed as command line arguments to the inferior.
1207 This option stops option processing.
1209 @item -baud @var{bps}
1211 @cindex @code{--baud}
1213 Set the line speed (baud rate or bits per second) of any serial
1214 interface used by @value{GDBN} for remote debugging.
1216 @item -l @var{timeout}
1218 Set the timeout (in seconds) of any communication used by @value{GDBN}
1219 for remote debugging.
1221 @item -tty @var{device}
1222 @itemx -t @var{device}
1223 @cindex @code{--tty}
1225 Run using @var{device} for your program's standard input and output.
1226 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1228 @c resolve the situation of these eventually
1230 @cindex @code{--tui}
1231 Activate the @dfn{Text User Interface} when starting. The Text User
1232 Interface manages several text windows on the terminal, showing
1233 source, assembly, registers and @value{GDBN} command outputs
1234 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1235 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1236 Using @value{GDBN} under @sc{gnu} Emacs}).
1239 @c @cindex @code{--xdb}
1240 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1241 @c For information, see the file @file{xdb_trans.html}, which is usually
1242 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1245 @item -interpreter @var{interp}
1246 @cindex @code{--interpreter}
1247 Use the interpreter @var{interp} for interface with the controlling
1248 program or device. This option is meant to be set by programs which
1249 communicate with @value{GDBN} using it as a back end.
1250 @xref{Interpreters, , Command Interpreters}.
1252 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1253 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1254 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1255 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1256 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1257 @sc{gdb/mi} interfaces are no longer supported.
1260 @cindex @code{--write}
1261 Open the executable and core files for both reading and writing. This
1262 is equivalent to the @samp{set write on} command inside @value{GDBN}
1266 @cindex @code{--statistics}
1267 This option causes @value{GDBN} to print statistics about time and
1268 memory usage after it completes each command and returns to the prompt.
1271 @cindex @code{--version}
1272 This option causes @value{GDBN} to print its version number and
1273 no-warranty blurb, and exit.
1275 @item -configuration
1276 @cindex @code{--configuration}
1277 This option causes @value{GDBN} to print details about its build-time
1278 configuration parameters, and then exit. These details can be
1279 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1284 @subsection What @value{GDBN} Does During Startup
1285 @cindex @value{GDBN} startup
1287 Here's the description of what @value{GDBN} does during session startup:
1291 Sets up the command interpreter as specified by the command line
1292 (@pxref{Mode Options, interpreter}).
1296 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1297 used when building @value{GDBN}; @pxref{System-wide configuration,
1298 ,System-wide configuration and settings}) and executes all the commands in
1301 @anchor{Home Directory Init File}
1303 Reads the init file (if any) in your home directory@footnote{On
1304 DOS/Windows systems, the home directory is the one pointed to by the
1305 @code{HOME} environment variable.} and executes all the commands in
1308 @anchor{Option -init-eval-command}
1310 Executes commands and command files specified by the @samp{-iex} and
1311 @samp{-ix} options in their specified order. Usually you should use the
1312 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1313 settings before @value{GDBN} init files get executed and before inferior
1317 Processes command line options and operands.
1319 @anchor{Init File in the Current Directory during Startup}
1321 Reads and executes the commands from init file (if any) in the current
1322 working directory as long as @samp{set auto-load local-gdbinit} is set to
1323 @samp{on} (@pxref{Init File in the Current Directory}).
1324 This is only done if the current directory is
1325 different from your home directory. Thus, you can have more than one
1326 init file, one generic in your home directory, and another, specific
1327 to the program you are debugging, in the directory where you invoke
1331 If the command line specified a program to debug, or a process to
1332 attach to, or a core file, @value{GDBN} loads any auto-loaded
1333 scripts provided for the program or for its loaded shared libraries.
1334 @xref{Auto-loading}.
1336 If you wish to disable the auto-loading during startup,
1337 you must do something like the following:
1340 $ gdb -iex "set auto-load python-scripts off" myprogram
1343 Option @samp{-ex} does not work because the auto-loading is then turned
1347 Executes commands and command files specified by the @samp{-ex} and
1348 @samp{-x} options in their specified order. @xref{Command Files}, for
1349 more details about @value{GDBN} command files.
1352 Reads the command history recorded in the @dfn{history file}.
1353 @xref{Command History}, for more details about the command history and the
1354 files where @value{GDBN} records it.
1357 Init files use the same syntax as @dfn{command files} (@pxref{Command
1358 Files}) and are processed by @value{GDBN} in the same way. The init
1359 file in your home directory can set options (such as @samp{set
1360 complaints}) that affect subsequent processing of command line options
1361 and operands. Init files are not executed if you use the @samp{-nx}
1362 option (@pxref{Mode Options, ,Choosing Modes}).
1364 To display the list of init files loaded by gdb at startup, you
1365 can use @kbd{gdb --help}.
1367 @cindex init file name
1368 @cindex @file{.gdbinit}
1369 @cindex @file{gdb.ini}
1370 The @value{GDBN} init files are normally called @file{.gdbinit}.
1371 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1372 the limitations of file names imposed by DOS filesystems. The Windows
1373 port of @value{GDBN} uses the standard name, but if it finds a
1374 @file{gdb.ini} file in your home directory, it warns you about that
1375 and suggests to rename the file to the standard name.
1379 @section Quitting @value{GDBN}
1380 @cindex exiting @value{GDBN}
1381 @cindex leaving @value{GDBN}
1384 @kindex quit @r{[}@var{expression}@r{]}
1385 @kindex q @r{(@code{quit})}
1386 @item quit @r{[}@var{expression}@r{]}
1388 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1389 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1390 do not supply @var{expression}, @value{GDBN} will terminate normally;
1391 otherwise it will terminate using the result of @var{expression} as the
1396 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1397 terminates the action of any @value{GDBN} command that is in progress and
1398 returns to @value{GDBN} command level. It is safe to type the interrupt
1399 character at any time because @value{GDBN} does not allow it to take effect
1400 until a time when it is safe.
1402 If you have been using @value{GDBN} to control an attached process or
1403 device, you can release it with the @code{detach} command
1404 (@pxref{Attach, ,Debugging an Already-running Process}).
1406 @node Shell Commands
1407 @section Shell Commands
1409 If you need to execute occasional shell commands during your
1410 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1411 just use the @code{shell} command.
1416 @cindex shell escape
1417 @item shell @var{command-string}
1418 @itemx !@var{command-string}
1419 Invoke a standard shell to execute @var{command-string}.
1420 Note that no space is needed between @code{!} and @var{command-string}.
1421 If it exists, the environment variable @code{SHELL} determines which
1422 shell to run. Otherwise @value{GDBN} uses the default shell
1423 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1426 The utility @code{make} is often needed in development environments.
1427 You do not have to use the @code{shell} command for this purpose in
1432 @cindex calling make
1433 @item make @var{make-args}
1434 Execute the @code{make} program with the specified
1435 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1438 @node Logging Output
1439 @section Logging Output
1440 @cindex logging @value{GDBN} output
1441 @cindex save @value{GDBN} output to a file
1443 You may want to save the output of @value{GDBN} commands to a file.
1444 There are several commands to control @value{GDBN}'s logging.
1448 @item set logging on
1450 @item set logging off
1452 @cindex logging file name
1453 @item set logging file @var{file}
1454 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1455 @item set logging overwrite [on|off]
1456 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1457 you want @code{set logging on} to overwrite the logfile instead.
1458 @item set logging redirect [on|off]
1459 By default, @value{GDBN} output will go to both the terminal and the logfile.
1460 Set @code{redirect} if you want output to go only to the log file.
1461 @kindex show logging
1463 Show the current values of the logging settings.
1467 @chapter @value{GDBN} Commands
1469 You can abbreviate a @value{GDBN} command to the first few letters of the command
1470 name, if that abbreviation is unambiguous; and you can repeat certain
1471 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1472 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1473 show you the alternatives available, if there is more than one possibility).
1476 * Command Syntax:: How to give commands to @value{GDBN}
1477 * Completion:: Command completion
1478 * Help:: How to ask @value{GDBN} for help
1481 @node Command Syntax
1482 @section Command Syntax
1484 A @value{GDBN} command is a single line of input. There is no limit on
1485 how long it can be. It starts with a command name, which is followed by
1486 arguments whose meaning depends on the command name. For example, the
1487 command @code{step} accepts an argument which is the number of times to
1488 step, as in @samp{step 5}. You can also use the @code{step} command
1489 with no arguments. Some commands do not allow any arguments.
1491 @cindex abbreviation
1492 @value{GDBN} command names may always be truncated if that abbreviation is
1493 unambiguous. Other possible command abbreviations are listed in the
1494 documentation for individual commands. In some cases, even ambiguous
1495 abbreviations are allowed; for example, @code{s} is specially defined as
1496 equivalent to @code{step} even though there are other commands whose
1497 names start with @code{s}. You can test abbreviations by using them as
1498 arguments to the @code{help} command.
1500 @cindex repeating commands
1501 @kindex RET @r{(repeat last command)}
1502 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1503 repeat the previous command. Certain commands (for example, @code{run})
1504 will not repeat this way; these are commands whose unintentional
1505 repetition might cause trouble and which you are unlikely to want to
1506 repeat. User-defined commands can disable this feature; see
1507 @ref{Define, dont-repeat}.
1509 The @code{list} and @code{x} commands, when you repeat them with
1510 @key{RET}, construct new arguments rather than repeating
1511 exactly as typed. This permits easy scanning of source or memory.
1513 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1514 output, in a way similar to the common utility @code{more}
1515 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1516 @key{RET} too many in this situation, @value{GDBN} disables command
1517 repetition after any command that generates this sort of display.
1519 @kindex # @r{(a comment)}
1521 Any text from a @kbd{#} to the end of the line is a comment; it does
1522 nothing. This is useful mainly in command files (@pxref{Command
1523 Files,,Command Files}).
1525 @cindex repeating command sequences
1526 @kindex Ctrl-o @r{(operate-and-get-next)}
1527 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1528 commands. This command accepts the current line, like @key{RET}, and
1529 then fetches the next line relative to the current line from the history
1533 @section Command Completion
1536 @cindex word completion
1537 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1538 only one possibility; it can also show you what the valid possibilities
1539 are for the next word in a command, at any time. This works for @value{GDBN}
1540 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1542 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1543 of a word. If there is only one possibility, @value{GDBN} fills in the
1544 word, and waits for you to finish the command (or press @key{RET} to
1545 enter it). For example, if you type
1547 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1548 @c complete accuracy in these examples; space introduced for clarity.
1549 @c If texinfo enhancements make it unnecessary, it would be nice to
1550 @c replace " @key" by "@key" in the following...
1552 (@value{GDBP}) info bre @key{TAB}
1556 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1557 the only @code{info} subcommand beginning with @samp{bre}:
1560 (@value{GDBP}) info breakpoints
1564 You can either press @key{RET} at this point, to run the @code{info
1565 breakpoints} command, or backspace and enter something else, if
1566 @samp{breakpoints} does not look like the command you expected. (If you
1567 were sure you wanted @code{info breakpoints} in the first place, you
1568 might as well just type @key{RET} immediately after @samp{info bre},
1569 to exploit command abbreviations rather than command completion).
1571 If there is more than one possibility for the next word when you press
1572 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1573 characters and try again, or just press @key{TAB} a second time;
1574 @value{GDBN} displays all the possible completions for that word. For
1575 example, you might want to set a breakpoint on a subroutine whose name
1576 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1577 just sounds the bell. Typing @key{TAB} again displays all the
1578 function names in your program that begin with those characters, for
1582 (@value{GDBP}) b make_ @key{TAB}
1583 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1584 make_a_section_from_file make_environ
1585 make_abs_section make_function_type
1586 make_blockvector make_pointer_type
1587 make_cleanup make_reference_type
1588 make_command make_symbol_completion_list
1589 (@value{GDBP}) b make_
1593 After displaying the available possibilities, @value{GDBN} copies your
1594 partial input (@samp{b make_} in the example) so you can finish the
1597 If you just want to see the list of alternatives in the first place, you
1598 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1599 means @kbd{@key{META} ?}. You can type this either by holding down a
1600 key designated as the @key{META} shift on your keyboard (if there is
1601 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1603 If the number of possible completions is large, @value{GDBN} will
1604 print as much of the list as it has collected, as well as a message
1605 indicating that the list may be truncated.
1608 (@value{GDBP}) b m@key{TAB}@key{TAB}
1610 <... the rest of the possible completions ...>
1611 *** List may be truncated, max-completions reached. ***
1616 This behavior can be controlled with the following commands:
1619 @kindex set max-completions
1620 @item set max-completions @var{limit}
1621 @itemx set max-completions unlimited
1622 Set the maximum number of completion candidates. @value{GDBN} will
1623 stop looking for more completions once it collects this many candidates.
1624 This is useful when completing on things like function names as collecting
1625 all the possible candidates can be time consuming.
1626 The default value is 200. A value of zero disables tab-completion.
1627 Note that setting either no limit or a very large limit can make
1629 @kindex show max-completions
1630 @item show max-completions
1631 Show the maximum number of candidates that @value{GDBN} will collect and show
1635 @cindex quotes in commands
1636 @cindex completion of quoted strings
1637 Sometimes the string you need, while logically a ``word'', may contain
1638 parentheses or other characters that @value{GDBN} normally excludes from
1639 its notion of a word. To permit word completion to work in this
1640 situation, you may enclose words in @code{'} (single quote marks) in
1641 @value{GDBN} commands.
1643 The most likely situation where you might need this is in typing the
1644 name of a C@t{++} function. This is because C@t{++} allows function
1645 overloading (multiple definitions of the same function, distinguished
1646 by argument type). For example, when you want to set a breakpoint you
1647 may need to distinguish whether you mean the version of @code{name}
1648 that takes an @code{int} parameter, @code{name(int)}, or the version
1649 that takes a @code{float} parameter, @code{name(float)}. To use the
1650 word-completion facilities in this situation, type a single quote
1651 @code{'} at the beginning of the function name. This alerts
1652 @value{GDBN} that it may need to consider more information than usual
1653 when you press @key{TAB} or @kbd{M-?} to request word completion:
1656 (@value{GDBP}) b 'bubble( @kbd{M-?}
1657 bubble(double,double) bubble(int,int)
1658 (@value{GDBP}) b 'bubble(
1661 In some cases, @value{GDBN} can tell that completing a name requires using
1662 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1663 completing as much as it can) if you do not type the quote in the first
1667 (@value{GDBP}) b bub @key{TAB}
1668 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1669 (@value{GDBP}) b 'bubble(
1673 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1674 you have not yet started typing the argument list when you ask for
1675 completion on an overloaded symbol.
1677 For more information about overloaded functions, see @ref{C Plus Plus
1678 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1679 overload-resolution off} to disable overload resolution;
1680 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1682 @cindex completion of structure field names
1683 @cindex structure field name completion
1684 @cindex completion of union field names
1685 @cindex union field name completion
1686 When completing in an expression which looks up a field in a
1687 structure, @value{GDBN} also tries@footnote{The completer can be
1688 confused by certain kinds of invalid expressions. Also, it only
1689 examines the static type of the expression, not the dynamic type.} to
1690 limit completions to the field names available in the type of the
1694 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1695 magic to_fputs to_rewind
1696 to_data to_isatty to_write
1697 to_delete to_put to_write_async_safe
1702 This is because the @code{gdb_stdout} is a variable of the type
1703 @code{struct ui_file} that is defined in @value{GDBN} sources as
1710 ui_file_flush_ftype *to_flush;
1711 ui_file_write_ftype *to_write;
1712 ui_file_write_async_safe_ftype *to_write_async_safe;
1713 ui_file_fputs_ftype *to_fputs;
1714 ui_file_read_ftype *to_read;
1715 ui_file_delete_ftype *to_delete;
1716 ui_file_isatty_ftype *to_isatty;
1717 ui_file_rewind_ftype *to_rewind;
1718 ui_file_put_ftype *to_put;
1725 @section Getting Help
1726 @cindex online documentation
1729 You can always ask @value{GDBN} itself for information on its commands,
1730 using the command @code{help}.
1733 @kindex h @r{(@code{help})}
1736 You can use @code{help} (abbreviated @code{h}) with no arguments to
1737 display a short list of named classes of commands:
1741 List of classes of commands:
1743 aliases -- Aliases of other commands
1744 breakpoints -- Making program stop at certain points
1745 data -- Examining data
1746 files -- Specifying and examining files
1747 internals -- Maintenance commands
1748 obscure -- Obscure features
1749 running -- Running the program
1750 stack -- Examining the stack
1751 status -- Status inquiries
1752 support -- Support facilities
1753 tracepoints -- Tracing of program execution without
1754 stopping the program
1755 user-defined -- User-defined commands
1757 Type "help" followed by a class name for a list of
1758 commands in that class.
1759 Type "help" followed by command name for full
1761 Command name abbreviations are allowed if unambiguous.
1764 @c the above line break eliminates huge line overfull...
1766 @item help @var{class}
1767 Using one of the general help classes as an argument, you can get a
1768 list of the individual commands in that class. For example, here is the
1769 help display for the class @code{status}:
1772 (@value{GDBP}) help status
1777 @c Line break in "show" line falsifies real output, but needed
1778 @c to fit in smallbook page size.
1779 info -- Generic command for showing things
1780 about the program being debugged
1781 show -- Generic command for showing things
1784 Type "help" followed by command name for full
1786 Command name abbreviations are allowed if unambiguous.
1790 @item help @var{command}
1791 With a command name as @code{help} argument, @value{GDBN} displays a
1792 short paragraph on how to use that command.
1795 @item apropos @var{args}
1796 The @code{apropos} command searches through all of the @value{GDBN}
1797 commands, and their documentation, for the regular expression specified in
1798 @var{args}. It prints out all matches found. For example:
1809 alias -- Define a new command that is an alias of an existing command
1810 aliases -- Aliases of other commands
1811 d -- Delete some breakpoints or auto-display expressions
1812 del -- Delete some breakpoints or auto-display expressions
1813 delete -- Delete some breakpoints or auto-display expressions
1818 @item complete @var{args}
1819 The @code{complete @var{args}} command lists all the possible completions
1820 for the beginning of a command. Use @var{args} to specify the beginning of the
1821 command you want completed. For example:
1827 @noindent results in:
1838 @noindent This is intended for use by @sc{gnu} Emacs.
1841 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1842 and @code{show} to inquire about the state of your program, or the state
1843 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1844 manual introduces each of them in the appropriate context. The listings
1845 under @code{info} and under @code{show} in the Command, Variable, and
1846 Function Index point to all the sub-commands. @xref{Command and Variable
1852 @kindex i @r{(@code{info})}
1854 This command (abbreviated @code{i}) is for describing the state of your
1855 program. For example, you can show the arguments passed to a function
1856 with @code{info args}, list the registers currently in use with @code{info
1857 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1858 You can get a complete list of the @code{info} sub-commands with
1859 @w{@code{help info}}.
1863 You can assign the result of an expression to an environment variable with
1864 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1865 @code{set prompt $}.
1869 In contrast to @code{info}, @code{show} is for describing the state of
1870 @value{GDBN} itself.
1871 You can change most of the things you can @code{show}, by using the
1872 related command @code{set}; for example, you can control what number
1873 system is used for displays with @code{set radix}, or simply inquire
1874 which is currently in use with @code{show radix}.
1877 To display all the settable parameters and their current
1878 values, you can use @code{show} with no arguments; you may also use
1879 @code{info set}. Both commands produce the same display.
1880 @c FIXME: "info set" violates the rule that "info" is for state of
1881 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1882 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1886 Here are several miscellaneous @code{show} subcommands, all of which are
1887 exceptional in lacking corresponding @code{set} commands:
1890 @kindex show version
1891 @cindex @value{GDBN} version number
1893 Show what version of @value{GDBN} is running. You should include this
1894 information in @value{GDBN} bug-reports. If multiple versions of
1895 @value{GDBN} are in use at your site, you may need to determine which
1896 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1897 commands are introduced, and old ones may wither away. Also, many
1898 system vendors ship variant versions of @value{GDBN}, and there are
1899 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1900 The version number is the same as the one announced when you start
1903 @kindex show copying
1904 @kindex info copying
1905 @cindex display @value{GDBN} copyright
1908 Display information about permission for copying @value{GDBN}.
1910 @kindex show warranty
1911 @kindex info warranty
1913 @itemx info warranty
1914 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1915 if your version of @value{GDBN} comes with one.
1917 @kindex show configuration
1918 @item show configuration
1919 Display detailed information about the way @value{GDBN} was configured
1920 when it was built. This displays the optional arguments passed to the
1921 @file{configure} script and also configuration parameters detected
1922 automatically by @command{configure}. When reporting a @value{GDBN}
1923 bug (@pxref{GDB Bugs}), it is important to include this information in
1929 @chapter Running Programs Under @value{GDBN}
1931 When you run a program under @value{GDBN}, you must first generate
1932 debugging information when you compile it.
1934 You may start @value{GDBN} with its arguments, if any, in an environment
1935 of your choice. If you are doing native debugging, you may redirect
1936 your program's input and output, debug an already running process, or
1937 kill a child process.
1940 * Compilation:: Compiling for debugging
1941 * Starting:: Starting your program
1942 * Arguments:: Your program's arguments
1943 * Environment:: Your program's environment
1945 * Working Directory:: Your program's working directory
1946 * Input/Output:: Your program's input and output
1947 * Attach:: Debugging an already-running process
1948 * Kill Process:: Killing the child process
1950 * Inferiors and Programs:: Debugging multiple inferiors and programs
1951 * Threads:: Debugging programs with multiple threads
1952 * Forks:: Debugging forks
1953 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1957 @section Compiling for Debugging
1959 In order to debug a program effectively, you need to generate
1960 debugging information when you compile it. This debugging information
1961 is stored in the object file; it describes the data type of each
1962 variable or function and the correspondence between source line numbers
1963 and addresses in the executable code.
1965 To request debugging information, specify the @samp{-g} option when you run
1968 Programs that are to be shipped to your customers are compiled with
1969 optimizations, using the @samp{-O} compiler option. However, some
1970 compilers are unable to handle the @samp{-g} and @samp{-O} options
1971 together. Using those compilers, you cannot generate optimized
1972 executables containing debugging information.
1974 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1975 without @samp{-O}, making it possible to debug optimized code. We
1976 recommend that you @emph{always} use @samp{-g} whenever you compile a
1977 program. You may think your program is correct, but there is no sense
1978 in pushing your luck. For more information, see @ref{Optimized Code}.
1980 Older versions of the @sc{gnu} C compiler permitted a variant option
1981 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1982 format; if your @sc{gnu} C compiler has this option, do not use it.
1984 @value{GDBN} knows about preprocessor macros and can show you their
1985 expansion (@pxref{Macros}). Most compilers do not include information
1986 about preprocessor macros in the debugging information if you specify
1987 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1988 the @sc{gnu} C compiler, provides macro information if you are using
1989 the DWARF debugging format, and specify the option @option{-g3}.
1991 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1992 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1993 information on @value{NGCC} options affecting debug information.
1995 You will have the best debugging experience if you use the latest
1996 version of the DWARF debugging format that your compiler supports.
1997 DWARF is currently the most expressive and best supported debugging
1998 format in @value{GDBN}.
2002 @section Starting your Program
2008 @kindex r @r{(@code{run})}
2011 Use the @code{run} command to start your program under @value{GDBN}.
2012 You must first specify the program name with an argument to
2013 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2014 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2015 command (@pxref{Files, ,Commands to Specify Files}).
2019 If you are running your program in an execution environment that
2020 supports processes, @code{run} creates an inferior process and makes
2021 that process run your program. In some environments without processes,
2022 @code{run} jumps to the start of your program. Other targets,
2023 like @samp{remote}, are always running. If you get an error
2024 message like this one:
2027 The "remote" target does not support "run".
2028 Try "help target" or "continue".
2032 then use @code{continue} to run your program. You may need @code{load}
2033 first (@pxref{load}).
2035 The execution of a program is affected by certain information it
2036 receives from its superior. @value{GDBN} provides ways to specify this
2037 information, which you must do @emph{before} starting your program. (You
2038 can change it after starting your program, but such changes only affect
2039 your program the next time you start it.) This information may be
2040 divided into four categories:
2043 @item The @emph{arguments.}
2044 Specify the arguments to give your program as the arguments of the
2045 @code{run} command. If a shell is available on your target, the shell
2046 is used to pass the arguments, so that you may use normal conventions
2047 (such as wildcard expansion or variable substitution) in describing
2049 In Unix systems, you can control which shell is used with the
2050 @code{SHELL} environment variable. If you do not define @code{SHELL},
2051 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2052 use of any shell with the @code{set startup-with-shell} command (see
2055 @item The @emph{environment.}
2056 Your program normally inherits its environment from @value{GDBN}, but you can
2057 use the @value{GDBN} commands @code{set environment} and @code{unset
2058 environment} to change parts of the environment that affect
2059 your program. @xref{Environment, ,Your Program's Environment}.
2061 @item The @emph{working directory.}
2062 Your program inherits its working directory from @value{GDBN}. You can set
2063 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
2064 @xref{Working Directory, ,Your Program's Working Directory}.
2066 @item The @emph{standard input and output.}
2067 Your program normally uses the same device for standard input and
2068 standard output as @value{GDBN} is using. You can redirect input and output
2069 in the @code{run} command line, or you can use the @code{tty} command to
2070 set a different device for your program.
2071 @xref{Input/Output, ,Your Program's Input and Output}.
2074 @emph{Warning:} While input and output redirection work, you cannot use
2075 pipes to pass the output of the program you are debugging to another
2076 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2080 When you issue the @code{run} command, your program begins to execute
2081 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2082 of how to arrange for your program to stop. Once your program has
2083 stopped, you may call functions in your program, using the @code{print}
2084 or @code{call} commands. @xref{Data, ,Examining Data}.
2086 If the modification time of your symbol file has changed since the last
2087 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2088 table, and reads it again. When it does this, @value{GDBN} tries to retain
2089 your current breakpoints.
2094 @cindex run to main procedure
2095 The name of the main procedure can vary from language to language.
2096 With C or C@t{++}, the main procedure name is always @code{main}, but
2097 other languages such as Ada do not require a specific name for their
2098 main procedure. The debugger provides a convenient way to start the
2099 execution of the program and to stop at the beginning of the main
2100 procedure, depending on the language used.
2102 The @samp{start} command does the equivalent of setting a temporary
2103 breakpoint at the beginning of the main procedure and then invoking
2104 the @samp{run} command.
2106 @cindex elaboration phase
2107 Some programs contain an @dfn{elaboration} phase where some startup code is
2108 executed before the main procedure is called. This depends on the
2109 languages used to write your program. In C@t{++}, for instance,
2110 constructors for static and global objects are executed before
2111 @code{main} is called. It is therefore possible that the debugger stops
2112 before reaching the main procedure. However, the temporary breakpoint
2113 will remain to halt execution.
2115 Specify the arguments to give to your program as arguments to the
2116 @samp{start} command. These arguments will be given verbatim to the
2117 underlying @samp{run} command. Note that the same arguments will be
2118 reused if no argument is provided during subsequent calls to
2119 @samp{start} or @samp{run}.
2121 It is sometimes necessary to debug the program during elaboration. In
2122 these cases, using the @code{start} command would stop the execution of
2123 your program too late, as the program would have already completed the
2124 elaboration phase. Under these circumstances, insert breakpoints in your
2125 elaboration code before running your program.
2127 @anchor{set exec-wrapper}
2128 @kindex set exec-wrapper
2129 @item set exec-wrapper @var{wrapper}
2130 @itemx show exec-wrapper
2131 @itemx unset exec-wrapper
2132 When @samp{exec-wrapper} is set, the specified wrapper is used to
2133 launch programs for debugging. @value{GDBN} starts your program
2134 with a shell command of the form @kbd{exec @var{wrapper}
2135 @var{program}}. Quoting is added to @var{program} and its
2136 arguments, but not to @var{wrapper}, so you should add quotes if
2137 appropriate for your shell. The wrapper runs until it executes
2138 your program, and then @value{GDBN} takes control.
2140 You can use any program that eventually calls @code{execve} with
2141 its arguments as a wrapper. Several standard Unix utilities do
2142 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2143 with @code{exec "$@@"} will also work.
2145 For example, you can use @code{env} to pass an environment variable to
2146 the debugged program, without setting the variable in your shell's
2150 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2154 This command is available when debugging locally on most targets, excluding
2155 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2157 @kindex set startup-with-shell
2158 @item set startup-with-shell
2159 @itemx set startup-with-shell on
2160 @itemx set startup-with-shell off
2161 @itemx show set startup-with-shell
2162 On Unix systems, by default, if a shell is available on your target,
2163 @value{GDBN}) uses it to start your program. Arguments of the
2164 @code{run} command are passed to the shell, which does variable
2165 substitution, expands wildcard characters and performs redirection of
2166 I/O. In some circumstances, it may be useful to disable such use of a
2167 shell, for example, when debugging the shell itself or diagnosing
2168 startup failures such as:
2172 Starting program: ./a.out
2173 During startup program terminated with signal SIGSEGV, Segmentation fault.
2177 which indicates the shell or the wrapper specified with
2178 @samp{exec-wrapper} crashed, not your program. Most often, this is
2179 caused by something odd in your shell's non-interactive mode
2180 initialization file---such as @file{.cshrc} for C-shell,
2181 $@file{.zshenv} for the Z shell, or the file specified in the
2182 @samp{BASH_ENV} environment variable for BASH.
2184 @anchor{set auto-connect-native-target}
2185 @kindex set auto-connect-native-target
2186 @item set auto-connect-native-target
2187 @itemx set auto-connect-native-target on
2188 @itemx set auto-connect-native-target off
2189 @itemx show auto-connect-native-target
2191 By default, if not connected to any target yet (e.g., with
2192 @code{target remote}), the @code{run} command starts your program as a
2193 native process under @value{GDBN}, on your local machine. If you're
2194 sure you don't want to debug programs on your local machine, you can
2195 tell @value{GDBN} to not connect to the native target automatically
2196 with the @code{set auto-connect-native-target off} command.
2198 If @code{on}, which is the default, and if @value{GDBN} is not
2199 connected to a target already, the @code{run} command automaticaly
2200 connects to the native target, if one is available.
2202 If @code{off}, and if @value{GDBN} is not connected to a target
2203 already, the @code{run} command fails with an error:
2207 Don't know how to run. Try "help target".
2210 If @value{GDBN} is already connected to a target, @value{GDBN} always
2211 uses it with the @code{run} command.
2213 In any case, you can explicitly connect to the native target with the
2214 @code{target native} command. For example,
2217 (@value{GDBP}) set auto-connect-native-target off
2219 Don't know how to run. Try "help target".
2220 (@value{GDBP}) target native
2222 Starting program: ./a.out
2223 [Inferior 1 (process 10421) exited normally]
2226 In case you connected explicitly to the @code{native} target,
2227 @value{GDBN} remains connected even if all inferiors exit, ready for
2228 the next @code{run} command. Use the @code{disconnect} command to
2231 Examples of other commands that likewise respect the
2232 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2233 proc}, @code{info os}.
2235 @kindex set disable-randomization
2236 @item set disable-randomization
2237 @itemx set disable-randomization on
2238 This option (enabled by default in @value{GDBN}) will turn off the native
2239 randomization of the virtual address space of the started program. This option
2240 is useful for multiple debugging sessions to make the execution better
2241 reproducible and memory addresses reusable across debugging sessions.
2243 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2244 On @sc{gnu}/Linux you can get the same behavior using
2247 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2250 @item set disable-randomization off
2251 Leave the behavior of the started executable unchanged. Some bugs rear their
2252 ugly heads only when the program is loaded at certain addresses. If your bug
2253 disappears when you run the program under @value{GDBN}, that might be because
2254 @value{GDBN} by default disables the address randomization on platforms, such
2255 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2256 disable-randomization off} to try to reproduce such elusive bugs.
2258 On targets where it is available, virtual address space randomization
2259 protects the programs against certain kinds of security attacks. In these
2260 cases the attacker needs to know the exact location of a concrete executable
2261 code. Randomizing its location makes it impossible to inject jumps misusing
2262 a code at its expected addresses.
2264 Prelinking shared libraries provides a startup performance advantage but it
2265 makes addresses in these libraries predictable for privileged processes by
2266 having just unprivileged access at the target system. Reading the shared
2267 library binary gives enough information for assembling the malicious code
2268 misusing it. Still even a prelinked shared library can get loaded at a new
2269 random address just requiring the regular relocation process during the
2270 startup. Shared libraries not already prelinked are always loaded at
2271 a randomly chosen address.
2273 Position independent executables (PIE) contain position independent code
2274 similar to the shared libraries and therefore such executables get loaded at
2275 a randomly chosen address upon startup. PIE executables always load even
2276 already prelinked shared libraries at a random address. You can build such
2277 executable using @command{gcc -fPIE -pie}.
2279 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2280 (as long as the randomization is enabled).
2282 @item show disable-randomization
2283 Show the current setting of the explicit disable of the native randomization of
2284 the virtual address space of the started program.
2289 @section Your Program's Arguments
2291 @cindex arguments (to your program)
2292 The arguments to your program can be specified by the arguments of the
2294 They are passed to a shell, which expands wildcard characters and
2295 performs redirection of I/O, and thence to your program. Your
2296 @code{SHELL} environment variable (if it exists) specifies what shell
2297 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2298 the default shell (@file{/bin/sh} on Unix).
2300 On non-Unix systems, the program is usually invoked directly by
2301 @value{GDBN}, which emulates I/O redirection via the appropriate system
2302 calls, and the wildcard characters are expanded by the startup code of
2303 the program, not by the shell.
2305 @code{run} with no arguments uses the same arguments used by the previous
2306 @code{run}, or those set by the @code{set args} command.
2311 Specify the arguments to be used the next time your program is run. If
2312 @code{set args} has no arguments, @code{run} executes your program
2313 with no arguments. Once you have run your program with arguments,
2314 using @code{set args} before the next @code{run} is the only way to run
2315 it again without arguments.
2319 Show the arguments to give your program when it is started.
2323 @section Your Program's Environment
2325 @cindex environment (of your program)
2326 The @dfn{environment} consists of a set of environment variables and
2327 their values. Environment variables conventionally record such things as
2328 your user name, your home directory, your terminal type, and your search
2329 path for programs to run. Usually you set up environment variables with
2330 the shell and they are inherited by all the other programs you run. When
2331 debugging, it can be useful to try running your program with a modified
2332 environment without having to start @value{GDBN} over again.
2336 @item path @var{directory}
2337 Add @var{directory} to the front of the @code{PATH} environment variable
2338 (the search path for executables) that will be passed to your program.
2339 The value of @code{PATH} used by @value{GDBN} does not change.
2340 You may specify several directory names, separated by whitespace or by a
2341 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2342 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2343 is moved to the front, so it is searched sooner.
2345 You can use the string @samp{$cwd} to refer to whatever is the current
2346 working directory at the time @value{GDBN} searches the path. If you
2347 use @samp{.} instead, it refers to the directory where you executed the
2348 @code{path} command. @value{GDBN} replaces @samp{.} in the
2349 @var{directory} argument (with the current path) before adding
2350 @var{directory} to the search path.
2351 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2352 @c document that, since repeating it would be a no-op.
2356 Display the list of search paths for executables (the @code{PATH}
2357 environment variable).
2359 @kindex show environment
2360 @item show environment @r{[}@var{varname}@r{]}
2361 Print the value of environment variable @var{varname} to be given to
2362 your program when it starts. If you do not supply @var{varname},
2363 print the names and values of all environment variables to be given to
2364 your program. You can abbreviate @code{environment} as @code{env}.
2366 @kindex set environment
2367 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2368 Set environment variable @var{varname} to @var{value}. The value
2369 changes for your program (and the shell @value{GDBN} uses to launch
2370 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2371 values of environment variables are just strings, and any
2372 interpretation is supplied by your program itself. The @var{value}
2373 parameter is optional; if it is eliminated, the variable is set to a
2375 @c "any string" here does not include leading, trailing
2376 @c blanks. Gnu asks: does anyone care?
2378 For example, this command:
2385 tells the debugged program, when subsequently run, that its user is named
2386 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2387 are not actually required.)
2389 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2390 which also inherits the environment set with @code{set environment}.
2391 If necessary, you can avoid that by using the @samp{env} program as a
2392 wrapper instead of using @code{set environment}. @xref{set
2393 exec-wrapper}, for an example doing just that.
2395 @kindex unset environment
2396 @item unset environment @var{varname}
2397 Remove variable @var{varname} from the environment to be passed to your
2398 program. This is different from @samp{set env @var{varname} =};
2399 @code{unset environment} removes the variable from the environment,
2400 rather than assigning it an empty value.
2403 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2404 the shell indicated by your @code{SHELL} environment variable if it
2405 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2406 names a shell that runs an initialization file when started
2407 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2408 for the Z shell, or the file specified in the @samp{BASH_ENV}
2409 environment variable for BASH---any variables you set in that file
2410 affect your program. You may wish to move setting of environment
2411 variables to files that are only run when you sign on, such as
2412 @file{.login} or @file{.profile}.
2414 @node Working Directory
2415 @section Your Program's Working Directory
2417 @cindex working directory (of your program)
2418 Each time you start your program with @code{run}, it inherits its
2419 working directory from the current working directory of @value{GDBN}.
2420 The @value{GDBN} working directory is initially whatever it inherited
2421 from its parent process (typically the shell), but you can specify a new
2422 working directory in @value{GDBN} with the @code{cd} command.
2424 The @value{GDBN} working directory also serves as a default for the commands
2425 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2430 @cindex change working directory
2431 @item cd @r{[}@var{directory}@r{]}
2432 Set the @value{GDBN} working directory to @var{directory}. If not
2433 given, @var{directory} uses @file{'~'}.
2437 Print the @value{GDBN} working directory.
2440 It is generally impossible to find the current working directory of
2441 the process being debugged (since a program can change its directory
2442 during its run). If you work on a system where @value{GDBN} is
2443 configured with the @file{/proc} support, you can use the @code{info
2444 proc} command (@pxref{SVR4 Process Information}) to find out the
2445 current working directory of the debuggee.
2448 @section Your Program's Input and Output
2453 By default, the program you run under @value{GDBN} does input and output to
2454 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2455 to its own terminal modes to interact with you, but it records the terminal
2456 modes your program was using and switches back to them when you continue
2457 running your program.
2460 @kindex info terminal
2462 Displays information recorded by @value{GDBN} about the terminal modes your
2466 You can redirect your program's input and/or output using shell
2467 redirection with the @code{run} command. For example,
2474 starts your program, diverting its output to the file @file{outfile}.
2477 @cindex controlling terminal
2478 Another way to specify where your program should do input and output is
2479 with the @code{tty} command. This command accepts a file name as
2480 argument, and causes this file to be the default for future @code{run}
2481 commands. It also resets the controlling terminal for the child
2482 process, for future @code{run} commands. For example,
2489 directs that processes started with subsequent @code{run} commands
2490 default to do input and output on the terminal @file{/dev/ttyb} and have
2491 that as their controlling terminal.
2493 An explicit redirection in @code{run} overrides the @code{tty} command's
2494 effect on the input/output device, but not its effect on the controlling
2497 When you use the @code{tty} command or redirect input in the @code{run}
2498 command, only the input @emph{for your program} is affected. The input
2499 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2500 for @code{set inferior-tty}.
2502 @cindex inferior tty
2503 @cindex set inferior controlling terminal
2504 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2505 display the name of the terminal that will be used for future runs of your
2509 @item set inferior-tty /dev/ttyb
2510 @kindex set inferior-tty
2511 Set the tty for the program being debugged to /dev/ttyb.
2513 @item show inferior-tty
2514 @kindex show inferior-tty
2515 Show the current tty for the program being debugged.
2519 @section Debugging an Already-running Process
2524 @item attach @var{process-id}
2525 This command attaches to a running process---one that was started
2526 outside @value{GDBN}. (@code{info files} shows your active
2527 targets.) The command takes as argument a process ID. The usual way to
2528 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2529 or with the @samp{jobs -l} shell command.
2531 @code{attach} does not repeat if you press @key{RET} a second time after
2532 executing the command.
2535 To use @code{attach}, your program must be running in an environment
2536 which supports processes; for example, @code{attach} does not work for
2537 programs on bare-board targets that lack an operating system. You must
2538 also have permission to send the process a signal.
2540 When you use @code{attach}, the debugger finds the program running in
2541 the process first by looking in the current working directory, then (if
2542 the program is not found) by using the source file search path
2543 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2544 the @code{file} command to load the program. @xref{Files, ,Commands to
2547 The first thing @value{GDBN} does after arranging to debug the specified
2548 process is to stop it. You can examine and modify an attached process
2549 with all the @value{GDBN} commands that are ordinarily available when
2550 you start processes with @code{run}. You can insert breakpoints; you
2551 can step and continue; you can modify storage. If you would rather the
2552 process continue running, you may use the @code{continue} command after
2553 attaching @value{GDBN} to the process.
2558 When you have finished debugging the attached process, you can use the
2559 @code{detach} command to release it from @value{GDBN} control. Detaching
2560 the process continues its execution. After the @code{detach} command,
2561 that process and @value{GDBN} become completely independent once more, and you
2562 are ready to @code{attach} another process or start one with @code{run}.
2563 @code{detach} does not repeat if you press @key{RET} again after
2564 executing the command.
2567 If you exit @value{GDBN} while you have an attached process, you detach
2568 that process. If you use the @code{run} command, you kill that process.
2569 By default, @value{GDBN} asks for confirmation if you try to do either of these
2570 things; you can control whether or not you need to confirm by using the
2571 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2575 @section Killing the Child Process
2580 Kill the child process in which your program is running under @value{GDBN}.
2583 This command is useful if you wish to debug a core dump instead of a
2584 running process. @value{GDBN} ignores any core dump file while your program
2587 On some operating systems, a program cannot be executed outside @value{GDBN}
2588 while you have breakpoints set on it inside @value{GDBN}. You can use the
2589 @code{kill} command in this situation to permit running your program
2590 outside the debugger.
2592 The @code{kill} command is also useful if you wish to recompile and
2593 relink your program, since on many systems it is impossible to modify an
2594 executable file while it is running in a process. In this case, when you
2595 next type @code{run}, @value{GDBN} notices that the file has changed, and
2596 reads the symbol table again (while trying to preserve your current
2597 breakpoint settings).
2599 @node Inferiors and Programs
2600 @section Debugging Multiple Inferiors and Programs
2602 @value{GDBN} lets you run and debug multiple programs in a single
2603 session. In addition, @value{GDBN} on some systems may let you run
2604 several programs simultaneously (otherwise you have to exit from one
2605 before starting another). In the most general case, you can have
2606 multiple threads of execution in each of multiple processes, launched
2607 from multiple executables.
2610 @value{GDBN} represents the state of each program execution with an
2611 object called an @dfn{inferior}. An inferior typically corresponds to
2612 a process, but is more general and applies also to targets that do not
2613 have processes. Inferiors may be created before a process runs, and
2614 may be retained after a process exits. Inferiors have unique
2615 identifiers that are different from process ids. Usually each
2616 inferior will also have its own distinct address space, although some
2617 embedded targets may have several inferiors running in different parts
2618 of a single address space. Each inferior may in turn have multiple
2619 threads running in it.
2621 To find out what inferiors exist at any moment, use @w{@code{info
2625 @kindex info inferiors
2626 @item info inferiors
2627 Print a list of all inferiors currently being managed by @value{GDBN}.
2629 @value{GDBN} displays for each inferior (in this order):
2633 the inferior number assigned by @value{GDBN}
2636 the target system's inferior identifier
2639 the name of the executable the inferior is running.
2644 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2645 indicates the current inferior.
2649 @c end table here to get a little more width for example
2652 (@value{GDBP}) info inferiors
2653 Num Description Executable
2654 2 process 2307 hello
2655 * 1 process 3401 goodbye
2658 To switch focus between inferiors, use the @code{inferior} command:
2661 @kindex inferior @var{infno}
2662 @item inferior @var{infno}
2663 Make inferior number @var{infno} the current inferior. The argument
2664 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2665 in the first field of the @samp{info inferiors} display.
2669 You can get multiple executables into a debugging session via the
2670 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2671 systems @value{GDBN} can add inferiors to the debug session
2672 automatically by following calls to @code{fork} and @code{exec}. To
2673 remove inferiors from the debugging session use the
2674 @w{@code{remove-inferiors}} command.
2677 @kindex add-inferior
2678 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2679 Adds @var{n} inferiors to be run using @var{executable} as the
2680 executable; @var{n} defaults to 1. If no executable is specified,
2681 the inferiors begins empty, with no program. You can still assign or
2682 change the program assigned to the inferior at any time by using the
2683 @code{file} command with the executable name as its argument.
2685 @kindex clone-inferior
2686 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2687 Adds @var{n} inferiors ready to execute the same program as inferior
2688 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
2689 number of the current inferior. This is a convenient command when you
2690 want to run another instance of the inferior you are debugging.
2693 (@value{GDBP}) info inferiors
2694 Num Description Executable
2695 * 1 process 29964 helloworld
2696 (@value{GDBP}) clone-inferior
2699 (@value{GDBP}) info inferiors
2700 Num Description Executable
2702 * 1 process 29964 helloworld
2705 You can now simply switch focus to inferior 2 and run it.
2707 @kindex remove-inferiors
2708 @item remove-inferiors @var{infno}@dots{}
2709 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2710 possible to remove an inferior that is running with this command. For
2711 those, use the @code{kill} or @code{detach} command first.
2715 To quit debugging one of the running inferiors that is not the current
2716 inferior, you can either detach from it by using the @w{@code{detach
2717 inferior}} command (allowing it to run independently), or kill it
2718 using the @w{@code{kill inferiors}} command:
2721 @kindex detach inferiors @var{infno}@dots{}
2722 @item detach inferior @var{infno}@dots{}
2723 Detach from the inferior or inferiors identified by @value{GDBN}
2724 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2725 still stays on the list of inferiors shown by @code{info inferiors},
2726 but its Description will show @samp{<null>}.
2728 @kindex kill inferiors @var{infno}@dots{}
2729 @item kill inferiors @var{infno}@dots{}
2730 Kill the inferior or inferiors identified by @value{GDBN} inferior
2731 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2732 stays on the list of inferiors shown by @code{info inferiors}, but its
2733 Description will show @samp{<null>}.
2736 After the successful completion of a command such as @code{detach},
2737 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2738 a normal process exit, the inferior is still valid and listed with
2739 @code{info inferiors}, ready to be restarted.
2742 To be notified when inferiors are started or exit under @value{GDBN}'s
2743 control use @w{@code{set print inferior-events}}:
2746 @kindex set print inferior-events
2747 @cindex print messages on inferior start and exit
2748 @item set print inferior-events
2749 @itemx set print inferior-events on
2750 @itemx set print inferior-events off
2751 The @code{set print inferior-events} command allows you to enable or
2752 disable printing of messages when @value{GDBN} notices that new
2753 inferiors have started or that inferiors have exited or have been
2754 detached. By default, these messages will not be printed.
2756 @kindex show print inferior-events
2757 @item show print inferior-events
2758 Show whether messages will be printed when @value{GDBN} detects that
2759 inferiors have started, exited or have been detached.
2762 Many commands will work the same with multiple programs as with a
2763 single program: e.g., @code{print myglobal} will simply display the
2764 value of @code{myglobal} in the current inferior.
2767 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2768 get more info about the relationship of inferiors, programs, address
2769 spaces in a debug session. You can do that with the @w{@code{maint
2770 info program-spaces}} command.
2773 @kindex maint info program-spaces
2774 @item maint info program-spaces
2775 Print a list of all program spaces currently being managed by
2778 @value{GDBN} displays for each program space (in this order):
2782 the program space number assigned by @value{GDBN}
2785 the name of the executable loaded into the program space, with e.g.,
2786 the @code{file} command.
2791 An asterisk @samp{*} preceding the @value{GDBN} program space number
2792 indicates the current program space.
2794 In addition, below each program space line, @value{GDBN} prints extra
2795 information that isn't suitable to display in tabular form. For
2796 example, the list of inferiors bound to the program space.
2799 (@value{GDBP}) maint info program-spaces
2802 Bound inferiors: ID 1 (process 21561)
2806 Here we can see that no inferior is running the program @code{hello},
2807 while @code{process 21561} is running the program @code{goodbye}. On
2808 some targets, it is possible that multiple inferiors are bound to the
2809 same program space. The most common example is that of debugging both
2810 the parent and child processes of a @code{vfork} call. For example,
2813 (@value{GDBP}) maint info program-spaces
2816 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2819 Here, both inferior 2 and inferior 1 are running in the same program
2820 space as a result of inferior 1 having executed a @code{vfork} call.
2824 @section Debugging Programs with Multiple Threads
2826 @cindex threads of execution
2827 @cindex multiple threads
2828 @cindex switching threads
2829 In some operating systems, such as HP-UX and Solaris, a single program
2830 may have more than one @dfn{thread} of execution. The precise semantics
2831 of threads differ from one operating system to another, but in general
2832 the threads of a single program are akin to multiple processes---except
2833 that they share one address space (that is, they can all examine and
2834 modify the same variables). On the other hand, each thread has its own
2835 registers and execution stack, and perhaps private memory.
2837 @value{GDBN} provides these facilities for debugging multi-thread
2841 @item automatic notification of new threads
2842 @item @samp{thread @var{threadno}}, a command to switch among threads
2843 @item @samp{info threads}, a command to inquire about existing threads
2844 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2845 a command to apply a command to a list of threads
2846 @item thread-specific breakpoints
2847 @item @samp{set print thread-events}, which controls printing of
2848 messages on thread start and exit.
2849 @item @samp{set libthread-db-search-path @var{path}}, which lets
2850 the user specify which @code{libthread_db} to use if the default choice
2851 isn't compatible with the program.
2855 @emph{Warning:} These facilities are not yet available on every
2856 @value{GDBN} configuration where the operating system supports threads.
2857 If your @value{GDBN} does not support threads, these commands have no
2858 effect. For example, a system without thread support shows no output
2859 from @samp{info threads}, and always rejects the @code{thread} command,
2863 (@value{GDBP}) info threads
2864 (@value{GDBP}) thread 1
2865 Thread ID 1 not known. Use the "info threads" command to
2866 see the IDs of currently known threads.
2868 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2869 @c doesn't support threads"?
2872 @cindex focus of debugging
2873 @cindex current thread
2874 The @value{GDBN} thread debugging facility allows you to observe all
2875 threads while your program runs---but whenever @value{GDBN} takes
2876 control, one thread in particular is always the focus of debugging.
2877 This thread is called the @dfn{current thread}. Debugging commands show
2878 program information from the perspective of the current thread.
2880 @cindex @code{New} @var{systag} message
2881 @cindex thread identifier (system)
2882 @c FIXME-implementors!! It would be more helpful if the [New...] message
2883 @c included GDB's numeric thread handle, so you could just go to that
2884 @c thread without first checking `info threads'.
2885 Whenever @value{GDBN} detects a new thread in your program, it displays
2886 the target system's identification for the thread with a message in the
2887 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
2888 whose form varies depending on the particular system. For example, on
2889 @sc{gnu}/Linux, you might see
2892 [New Thread 0x41e02940 (LWP 25582)]
2896 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2897 the @var{systag} is simply something like @samp{process 368}, with no
2900 @c FIXME!! (1) Does the [New...] message appear even for the very first
2901 @c thread of a program, or does it only appear for the
2902 @c second---i.e.@: when it becomes obvious we have a multithread
2904 @c (2) *Is* there necessarily a first thread always? Or do some
2905 @c multithread systems permit starting a program with multiple
2906 @c threads ab initio?
2908 @cindex thread number
2909 @cindex thread identifier (GDB)
2910 For debugging purposes, @value{GDBN} associates its own thread
2911 number---always a single integer---with each thread in your program.
2914 @kindex info threads
2915 @item info threads @r{[}@var{id}@dots{}@r{]}
2916 Display a summary of all threads currently in your program. Optional
2917 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2918 means to print information only about the specified thread or threads.
2919 @value{GDBN} displays for each thread (in this order):
2923 the thread number assigned by @value{GDBN}
2926 the target system's thread identifier (@var{systag})
2929 the thread's name, if one is known. A thread can either be named by
2930 the user (see @code{thread name}, below), or, in some cases, by the
2934 the current stack frame summary for that thread
2938 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2939 indicates the current thread.
2943 @c end table here to get a little more width for example
2946 (@value{GDBP}) info threads
2948 3 process 35 thread 27 0x34e5 in sigpause ()
2949 2 process 35 thread 23 0x34e5 in sigpause ()
2950 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2954 On Solaris, you can display more information about user threads with a
2955 Solaris-specific command:
2958 @item maint info sol-threads
2959 @kindex maint info sol-threads
2960 @cindex thread info (Solaris)
2961 Display info on Solaris user threads.
2965 @kindex thread @var{threadno}
2966 @item thread @var{threadno}
2967 Make thread number @var{threadno} the current thread. The command
2968 argument @var{threadno} is the internal @value{GDBN} thread number, as
2969 shown in the first field of the @samp{info threads} display.
2970 @value{GDBN} responds by displaying the system identifier of the thread
2971 you selected, and its current stack frame summary:
2974 (@value{GDBP}) thread 2
2975 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2976 #0 some_function (ignore=0x0) at example.c:8
2977 8 printf ("hello\n");
2981 As with the @samp{[New @dots{}]} message, the form of the text after
2982 @samp{Switching to} depends on your system's conventions for identifying
2985 @vindex $_thread@r{, convenience variable}
2986 The debugger convenience variable @samp{$_thread} contains the number
2987 of the current thread. You may find this useful in writing breakpoint
2988 conditional expressions, command scripts, and so forth. See
2989 @xref{Convenience Vars,, Convenience Variables}, for general
2990 information on convenience variables.
2992 @kindex thread apply
2993 @cindex apply command to several threads
2994 @item thread apply [@var{threadno} | all [-ascending]] @var{command}
2995 The @code{thread apply} command allows you to apply the named
2996 @var{command} to one or more threads. Specify the numbers of the
2997 threads that you want affected with the command argument
2998 @var{threadno}. It can be a single thread number, one of the numbers
2999 shown in the first field of the @samp{info threads} display; or it
3000 could be a range of thread numbers, as in @code{2-4}. To apply
3001 a command to all threads in descending order, type @kbd{thread apply all
3002 @var{command}}. To apply a command to all threads in ascending order,
3003 type @kbd{thread apply all -ascending @var{command}}.
3007 @cindex name a thread
3008 @item thread name [@var{name}]
3009 This command assigns a name to the current thread. If no argument is
3010 given, any existing user-specified name is removed. The thread name
3011 appears in the @samp{info threads} display.
3013 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3014 determine the name of the thread as given by the OS. On these
3015 systems, a name specified with @samp{thread name} will override the
3016 system-give name, and removing the user-specified name will cause
3017 @value{GDBN} to once again display the system-specified name.
3020 @cindex search for a thread
3021 @item thread find [@var{regexp}]
3022 Search for and display thread ids whose name or @var{systag}
3023 matches the supplied regular expression.
3025 As well as being the complement to the @samp{thread name} command,
3026 this command also allows you to identify a thread by its target
3027 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3031 (@value{GDBN}) thread find 26688
3032 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3033 (@value{GDBN}) info thread 4
3035 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3038 @kindex set print thread-events
3039 @cindex print messages on thread start and exit
3040 @item set print thread-events
3041 @itemx set print thread-events on
3042 @itemx set print thread-events off
3043 The @code{set print thread-events} command allows you to enable or
3044 disable printing of messages when @value{GDBN} notices that new threads have
3045 started or that threads have exited. By default, these messages will
3046 be printed if detection of these events is supported by the target.
3047 Note that these messages cannot be disabled on all targets.
3049 @kindex show print thread-events
3050 @item show print thread-events
3051 Show whether messages will be printed when @value{GDBN} detects that threads
3052 have started and exited.
3055 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3056 more information about how @value{GDBN} behaves when you stop and start
3057 programs with multiple threads.
3059 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3060 watchpoints in programs with multiple threads.
3062 @anchor{set libthread-db-search-path}
3064 @kindex set libthread-db-search-path
3065 @cindex search path for @code{libthread_db}
3066 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3067 If this variable is set, @var{path} is a colon-separated list of
3068 directories @value{GDBN} will use to search for @code{libthread_db}.
3069 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3070 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3071 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3074 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3075 @code{libthread_db} library to obtain information about threads in the
3076 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3077 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3078 specific thread debugging library loading is enabled
3079 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3081 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3082 refers to the default system directories that are
3083 normally searched for loading shared libraries. The @samp{$sdir} entry
3084 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3085 (@pxref{libthread_db.so.1 file}).
3087 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3088 refers to the directory from which @code{libpthread}
3089 was loaded in the inferior process.
3091 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3092 @value{GDBN} attempts to initialize it with the current inferior process.
3093 If this initialization fails (which could happen because of a version
3094 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3095 will unload @code{libthread_db}, and continue with the next directory.
3096 If none of @code{libthread_db} libraries initialize successfully,
3097 @value{GDBN} will issue a warning and thread debugging will be disabled.
3099 Setting @code{libthread-db-search-path} is currently implemented
3100 only on some platforms.
3102 @kindex show libthread-db-search-path
3103 @item show libthread-db-search-path
3104 Display current libthread_db search path.
3106 @kindex set debug libthread-db
3107 @kindex show debug libthread-db
3108 @cindex debugging @code{libthread_db}
3109 @item set debug libthread-db
3110 @itemx show debug libthread-db
3111 Turns on or off display of @code{libthread_db}-related events.
3112 Use @code{1} to enable, @code{0} to disable.
3116 @section Debugging Forks
3118 @cindex fork, debugging programs which call
3119 @cindex multiple processes
3120 @cindex processes, multiple
3121 On most systems, @value{GDBN} has no special support for debugging
3122 programs which create additional processes using the @code{fork}
3123 function. When a program forks, @value{GDBN} will continue to debug the
3124 parent process and the child process will run unimpeded. If you have
3125 set a breakpoint in any code which the child then executes, the child
3126 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3127 will cause it to terminate.
3129 However, if you want to debug the child process there is a workaround
3130 which isn't too painful. Put a call to @code{sleep} in the code which
3131 the child process executes after the fork. It may be useful to sleep
3132 only if a certain environment variable is set, or a certain file exists,
3133 so that the delay need not occur when you don't want to run @value{GDBN}
3134 on the child. While the child is sleeping, use the @code{ps} program to
3135 get its process ID. Then tell @value{GDBN} (a new invocation of
3136 @value{GDBN} if you are also debugging the parent process) to attach to
3137 the child process (@pxref{Attach}). From that point on you can debug
3138 the child process just like any other process which you attached to.
3140 On some systems, @value{GDBN} provides support for debugging programs that
3141 create additional processes using the @code{fork} or @code{vfork} functions.
3142 Currently, the only platforms with this feature are HP-UX (11.x and later
3143 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
3145 By default, when a program forks, @value{GDBN} will continue to debug
3146 the parent process and the child process will run unimpeded.
3148 If you want to follow the child process instead of the parent process,
3149 use the command @w{@code{set follow-fork-mode}}.
3152 @kindex set follow-fork-mode
3153 @item set follow-fork-mode @var{mode}
3154 Set the debugger response to a program call of @code{fork} or
3155 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3156 process. The @var{mode} argument can be:
3160 The original process is debugged after a fork. The child process runs
3161 unimpeded. This is the default.
3164 The new process is debugged after a fork. The parent process runs
3169 @kindex show follow-fork-mode
3170 @item show follow-fork-mode
3171 Display the current debugger response to a @code{fork} or @code{vfork} call.
3174 @cindex debugging multiple processes
3175 On Linux, if you want to debug both the parent and child processes, use the
3176 command @w{@code{set detach-on-fork}}.
3179 @kindex set detach-on-fork
3180 @item set detach-on-fork @var{mode}
3181 Tells gdb whether to detach one of the processes after a fork, or
3182 retain debugger control over them both.
3186 The child process (or parent process, depending on the value of
3187 @code{follow-fork-mode}) will be detached and allowed to run
3188 independently. This is the default.
3191 Both processes will be held under the control of @value{GDBN}.
3192 One process (child or parent, depending on the value of
3193 @code{follow-fork-mode}) is debugged as usual, while the other
3198 @kindex show detach-on-fork
3199 @item show detach-on-fork
3200 Show whether detach-on-fork mode is on/off.
3203 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3204 will retain control of all forked processes (including nested forks).
3205 You can list the forked processes under the control of @value{GDBN} by
3206 using the @w{@code{info inferiors}} command, and switch from one fork
3207 to another by using the @code{inferior} command (@pxref{Inferiors and
3208 Programs, ,Debugging Multiple Inferiors and Programs}).
3210 To quit debugging one of the forked processes, you can either detach
3211 from it by using the @w{@code{detach inferiors}} command (allowing it
3212 to run independently), or kill it using the @w{@code{kill inferiors}}
3213 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3216 If you ask to debug a child process and a @code{vfork} is followed by an
3217 @code{exec}, @value{GDBN} executes the new target up to the first
3218 breakpoint in the new target. If you have a breakpoint set on
3219 @code{main} in your original program, the breakpoint will also be set on
3220 the child process's @code{main}.
3222 On some systems, when a child process is spawned by @code{vfork}, you
3223 cannot debug the child or parent until an @code{exec} call completes.
3225 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3226 call executes, the new target restarts. To restart the parent
3227 process, use the @code{file} command with the parent executable name
3228 as its argument. By default, after an @code{exec} call executes,
3229 @value{GDBN} discards the symbols of the previous executable image.
3230 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3234 @kindex set follow-exec-mode
3235 @item set follow-exec-mode @var{mode}
3237 Set debugger response to a program call of @code{exec}. An
3238 @code{exec} call replaces the program image of a process.
3240 @code{follow-exec-mode} can be:
3244 @value{GDBN} creates a new inferior and rebinds the process to this
3245 new inferior. The program the process was running before the
3246 @code{exec} call can be restarted afterwards by restarting the
3252 (@value{GDBP}) info inferiors
3254 Id Description Executable
3257 process 12020 is executing new program: prog2
3258 Program exited normally.
3259 (@value{GDBP}) info inferiors
3260 Id Description Executable
3266 @value{GDBN} keeps the process bound to the same inferior. The new
3267 executable image replaces the previous executable loaded in the
3268 inferior. Restarting the inferior after the @code{exec} call, with
3269 e.g., the @code{run} command, restarts the executable the process was
3270 running after the @code{exec} call. This is the default mode.
3275 (@value{GDBP}) info inferiors
3276 Id Description Executable
3279 process 12020 is executing new program: prog2
3280 Program exited normally.
3281 (@value{GDBP}) info inferiors
3282 Id Description Executable
3289 You can use the @code{catch} command to make @value{GDBN} stop whenever
3290 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3291 Catchpoints, ,Setting Catchpoints}.
3293 @node Checkpoint/Restart
3294 @section Setting a @emph{Bookmark} to Return to Later
3299 @cindex snapshot of a process
3300 @cindex rewind program state
3302 On certain operating systems@footnote{Currently, only
3303 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3304 program's state, called a @dfn{checkpoint}, and come back to it
3307 Returning to a checkpoint effectively undoes everything that has
3308 happened in the program since the @code{checkpoint} was saved. This
3309 includes changes in memory, registers, and even (within some limits)
3310 system state. Effectively, it is like going back in time to the
3311 moment when the checkpoint was saved.
3313 Thus, if you're stepping thru a program and you think you're
3314 getting close to the point where things go wrong, you can save
3315 a checkpoint. Then, if you accidentally go too far and miss
3316 the critical statement, instead of having to restart your program
3317 from the beginning, you can just go back to the checkpoint and
3318 start again from there.
3320 This can be especially useful if it takes a lot of time or
3321 steps to reach the point where you think the bug occurs.
3323 To use the @code{checkpoint}/@code{restart} method of debugging:
3328 Save a snapshot of the debugged program's current execution state.
3329 The @code{checkpoint} command takes no arguments, but each checkpoint
3330 is assigned a small integer id, similar to a breakpoint id.
3332 @kindex info checkpoints
3333 @item info checkpoints
3334 List the checkpoints that have been saved in the current debugging
3335 session. For each checkpoint, the following information will be
3342 @item Source line, or label
3345 @kindex restart @var{checkpoint-id}
3346 @item restart @var{checkpoint-id}
3347 Restore the program state that was saved as checkpoint number
3348 @var{checkpoint-id}. All program variables, registers, stack frames
3349 etc.@: will be returned to the values that they had when the checkpoint
3350 was saved. In essence, gdb will ``wind back the clock'' to the point
3351 in time when the checkpoint was saved.
3353 Note that breakpoints, @value{GDBN} variables, command history etc.
3354 are not affected by restoring a checkpoint. In general, a checkpoint
3355 only restores things that reside in the program being debugged, not in
3358 @kindex delete checkpoint @var{checkpoint-id}
3359 @item delete checkpoint @var{checkpoint-id}
3360 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3364 Returning to a previously saved checkpoint will restore the user state
3365 of the program being debugged, plus a significant subset of the system
3366 (OS) state, including file pointers. It won't ``un-write'' data from
3367 a file, but it will rewind the file pointer to the previous location,
3368 so that the previously written data can be overwritten. For files
3369 opened in read mode, the pointer will also be restored so that the
3370 previously read data can be read again.
3372 Of course, characters that have been sent to a printer (or other
3373 external device) cannot be ``snatched back'', and characters received
3374 from eg.@: a serial device can be removed from internal program buffers,
3375 but they cannot be ``pushed back'' into the serial pipeline, ready to
3376 be received again. Similarly, the actual contents of files that have
3377 been changed cannot be restored (at this time).
3379 However, within those constraints, you actually can ``rewind'' your
3380 program to a previously saved point in time, and begin debugging it
3381 again --- and you can change the course of events so as to debug a
3382 different execution path this time.
3384 @cindex checkpoints and process id
3385 Finally, there is one bit of internal program state that will be
3386 different when you return to a checkpoint --- the program's process
3387 id. Each checkpoint will have a unique process id (or @var{pid}),
3388 and each will be different from the program's original @var{pid}.
3389 If your program has saved a local copy of its process id, this could
3390 potentially pose a problem.
3392 @subsection A Non-obvious Benefit of Using Checkpoints
3394 On some systems such as @sc{gnu}/Linux, address space randomization
3395 is performed on new processes for security reasons. This makes it
3396 difficult or impossible to set a breakpoint, or watchpoint, on an
3397 absolute address if you have to restart the program, since the
3398 absolute location of a symbol will change from one execution to the
3401 A checkpoint, however, is an @emph{identical} copy of a process.
3402 Therefore if you create a checkpoint at (eg.@:) the start of main,
3403 and simply return to that checkpoint instead of restarting the
3404 process, you can avoid the effects of address randomization and
3405 your symbols will all stay in the same place.
3408 @chapter Stopping and Continuing
3410 The principal purposes of using a debugger are so that you can stop your
3411 program before it terminates; or so that, if your program runs into
3412 trouble, you can investigate and find out why.
3414 Inside @value{GDBN}, your program may stop for any of several reasons,
3415 such as a signal, a breakpoint, or reaching a new line after a
3416 @value{GDBN} command such as @code{step}. You may then examine and
3417 change variables, set new breakpoints or remove old ones, and then
3418 continue execution. Usually, the messages shown by @value{GDBN} provide
3419 ample explanation of the status of your program---but you can also
3420 explicitly request this information at any time.
3423 @kindex info program
3425 Display information about the status of your program: whether it is
3426 running or not, what process it is, and why it stopped.
3430 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3431 * Continuing and Stepping:: Resuming execution
3432 * Skipping Over Functions and Files::
3433 Skipping over functions and files
3435 * Thread Stops:: Stopping and starting multi-thread programs
3439 @section Breakpoints, Watchpoints, and Catchpoints
3442 A @dfn{breakpoint} makes your program stop whenever a certain point in
3443 the program is reached. For each breakpoint, you can add conditions to
3444 control in finer detail whether your program stops. You can set
3445 breakpoints with the @code{break} command and its variants (@pxref{Set
3446 Breaks, ,Setting Breakpoints}), to specify the place where your program
3447 should stop by line number, function name or exact address in the
3450 On some systems, you can set breakpoints in shared libraries before
3451 the executable is run. There is a minor limitation on HP-UX systems:
3452 you must wait until the executable is run in order to set breakpoints
3453 in shared library routines that are not called directly by the program
3454 (for example, routines that are arguments in a @code{pthread_create}
3458 @cindex data breakpoints
3459 @cindex memory tracing
3460 @cindex breakpoint on memory address
3461 @cindex breakpoint on variable modification
3462 A @dfn{watchpoint} is a special breakpoint that stops your program
3463 when the value of an expression changes. The expression may be a value
3464 of a variable, or it could involve values of one or more variables
3465 combined by operators, such as @samp{a + b}. This is sometimes called
3466 @dfn{data breakpoints}. You must use a different command to set
3467 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3468 from that, you can manage a watchpoint like any other breakpoint: you
3469 enable, disable, and delete both breakpoints and watchpoints using the
3472 You can arrange to have values from your program displayed automatically
3473 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3477 @cindex breakpoint on events
3478 A @dfn{catchpoint} is another special breakpoint that stops your program
3479 when a certain kind of event occurs, such as the throwing of a C@t{++}
3480 exception or the loading of a library. As with watchpoints, you use a
3481 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3482 Catchpoints}), but aside from that, you can manage a catchpoint like any
3483 other breakpoint. (To stop when your program receives a signal, use the
3484 @code{handle} command; see @ref{Signals, ,Signals}.)
3486 @cindex breakpoint numbers
3487 @cindex numbers for breakpoints
3488 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3489 catchpoint when you create it; these numbers are successive integers
3490 starting with one. In many of the commands for controlling various
3491 features of breakpoints you use the breakpoint number to say which
3492 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3493 @dfn{disabled}; if disabled, it has no effect on your program until you
3496 @cindex breakpoint ranges
3497 @cindex ranges of breakpoints
3498 Some @value{GDBN} commands accept a range of breakpoints on which to
3499 operate. A breakpoint range is either a single breakpoint number, like
3500 @samp{5}, or two such numbers, in increasing order, separated by a
3501 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3502 all breakpoints in that range are operated on.
3505 * Set Breaks:: Setting breakpoints
3506 * Set Watchpoints:: Setting watchpoints
3507 * Set Catchpoints:: Setting catchpoints
3508 * Delete Breaks:: Deleting breakpoints
3509 * Disabling:: Disabling breakpoints
3510 * Conditions:: Break conditions
3511 * Break Commands:: Breakpoint command lists
3512 * Dynamic Printf:: Dynamic printf
3513 * Save Breakpoints:: How to save breakpoints in a file
3514 * Static Probe Points:: Listing static probe points
3515 * Error in Breakpoints:: ``Cannot insert breakpoints''
3516 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3520 @subsection Setting Breakpoints
3522 @c FIXME LMB what does GDB do if no code on line of breakpt?
3523 @c consider in particular declaration with/without initialization.
3525 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3528 @kindex b @r{(@code{break})}
3529 @vindex $bpnum@r{, convenience variable}
3530 @cindex latest breakpoint
3531 Breakpoints are set with the @code{break} command (abbreviated
3532 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3533 number of the breakpoint you've set most recently; see @ref{Convenience
3534 Vars,, Convenience Variables}, for a discussion of what you can do with
3535 convenience variables.
3538 @item break @var{location}
3539 Set a breakpoint at the given @var{location}, which can specify a
3540 function name, a line number, or an address of an instruction.
3541 (@xref{Specify Location}, for a list of all the possible ways to
3542 specify a @var{location}.) The breakpoint will stop your program just
3543 before it executes any of the code in the specified @var{location}.
3545 When using source languages that permit overloading of symbols, such as
3546 C@t{++}, a function name may refer to more than one possible place to break.
3547 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3550 It is also possible to insert a breakpoint that will stop the program
3551 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3552 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3555 When called without any arguments, @code{break} sets a breakpoint at
3556 the next instruction to be executed in the selected stack frame
3557 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3558 innermost, this makes your program stop as soon as control
3559 returns to that frame. This is similar to the effect of a
3560 @code{finish} command in the frame inside the selected frame---except
3561 that @code{finish} does not leave an active breakpoint. If you use
3562 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3563 the next time it reaches the current location; this may be useful
3566 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3567 least one instruction has been executed. If it did not do this, you
3568 would be unable to proceed past a breakpoint without first disabling the
3569 breakpoint. This rule applies whether or not the breakpoint already
3570 existed when your program stopped.
3572 @item break @dots{} if @var{cond}
3573 Set a breakpoint with condition @var{cond}; evaluate the expression
3574 @var{cond} each time the breakpoint is reached, and stop only if the
3575 value is nonzero---that is, if @var{cond} evaluates as true.
3576 @samp{@dots{}} stands for one of the possible arguments described
3577 above (or no argument) specifying where to break. @xref{Conditions,
3578 ,Break Conditions}, for more information on breakpoint conditions.
3581 @item tbreak @var{args}
3582 Set a breakpoint enabled only for one stop. The @var{args} are the
3583 same as for the @code{break} command, and the breakpoint is set in the same
3584 way, but the breakpoint is automatically deleted after the first time your
3585 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3588 @cindex hardware breakpoints
3589 @item hbreak @var{args}
3590 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
3591 @code{break} command and the breakpoint is set in the same way, but the
3592 breakpoint requires hardware support and some target hardware may not
3593 have this support. The main purpose of this is EPROM/ROM code
3594 debugging, so you can set a breakpoint at an instruction without
3595 changing the instruction. This can be used with the new trap-generation
3596 provided by SPARClite DSU and most x86-based targets. These targets
3597 will generate traps when a program accesses some data or instruction
3598 address that is assigned to the debug registers. However the hardware
3599 breakpoint registers can take a limited number of breakpoints. For
3600 example, on the DSU, only two data breakpoints can be set at a time, and
3601 @value{GDBN} will reject this command if more than two are used. Delete
3602 or disable unused hardware breakpoints before setting new ones
3603 (@pxref{Disabling, ,Disabling Breakpoints}).
3604 @xref{Conditions, ,Break Conditions}.
3605 For remote targets, you can restrict the number of hardware
3606 breakpoints @value{GDBN} will use, see @ref{set remote
3607 hardware-breakpoint-limit}.
3610 @item thbreak @var{args}
3611 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
3612 are the same as for the @code{hbreak} command and the breakpoint is set in
3613 the same way. However, like the @code{tbreak} command,
3614 the breakpoint is automatically deleted after the
3615 first time your program stops there. Also, like the @code{hbreak}
3616 command, the breakpoint requires hardware support and some target hardware
3617 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3618 See also @ref{Conditions, ,Break Conditions}.
3621 @cindex regular expression
3622 @cindex breakpoints at functions matching a regexp
3623 @cindex set breakpoints in many functions
3624 @item rbreak @var{regex}
3625 Set breakpoints on all functions matching the regular expression
3626 @var{regex}. This command sets an unconditional breakpoint on all
3627 matches, printing a list of all breakpoints it set. Once these
3628 breakpoints are set, they are treated just like the breakpoints set with
3629 the @code{break} command. You can delete them, disable them, or make
3630 them conditional the same way as any other breakpoint.
3632 The syntax of the regular expression is the standard one used with tools
3633 like @file{grep}. Note that this is different from the syntax used by
3634 shells, so for instance @code{foo*} matches all functions that include
3635 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3636 @code{.*} leading and trailing the regular expression you supply, so to
3637 match only functions that begin with @code{foo}, use @code{^foo}.
3639 @cindex non-member C@t{++} functions, set breakpoint in
3640 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3641 breakpoints on overloaded functions that are not members of any special
3644 @cindex set breakpoints on all functions
3645 The @code{rbreak} command can be used to set breakpoints in
3646 @strong{all} the functions in a program, like this:
3649 (@value{GDBP}) rbreak .
3652 @item rbreak @var{file}:@var{regex}
3653 If @code{rbreak} is called with a filename qualification, it limits
3654 the search for functions matching the given regular expression to the
3655 specified @var{file}. This can be used, for example, to set breakpoints on
3656 every function in a given file:
3659 (@value{GDBP}) rbreak file.c:.
3662 The colon separating the filename qualifier from the regex may
3663 optionally be surrounded by spaces.
3665 @kindex info breakpoints
3666 @cindex @code{$_} and @code{info breakpoints}
3667 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3668 @itemx info break @r{[}@var{n}@dots{}@r{]}
3669 Print a table of all breakpoints, watchpoints, and catchpoints set and
3670 not deleted. Optional argument @var{n} means print information only
3671 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3672 For each breakpoint, following columns are printed:
3675 @item Breakpoint Numbers
3677 Breakpoint, watchpoint, or catchpoint.
3679 Whether the breakpoint is marked to be disabled or deleted when hit.
3680 @item Enabled or Disabled
3681 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3682 that are not enabled.
3684 Where the breakpoint is in your program, as a memory address. For a
3685 pending breakpoint whose address is not yet known, this field will
3686 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3687 library that has the symbol or line referred by breakpoint is loaded.
3688 See below for details. A breakpoint with several locations will
3689 have @samp{<MULTIPLE>} in this field---see below for details.
3691 Where the breakpoint is in the source for your program, as a file and
3692 line number. For a pending breakpoint, the original string passed to
3693 the breakpoint command will be listed as it cannot be resolved until
3694 the appropriate shared library is loaded in the future.
3698 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3699 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3700 @value{GDBN} on the host's side. If it is ``target'', then the condition
3701 is evaluated by the target. The @code{info break} command shows
3702 the condition on the line following the affected breakpoint, together with
3703 its condition evaluation mode in between parentheses.
3705 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3706 allowed to have a condition specified for it. The condition is not parsed for
3707 validity until a shared library is loaded that allows the pending
3708 breakpoint to resolve to a valid location.
3711 @code{info break} with a breakpoint
3712 number @var{n} as argument lists only that breakpoint. The
3713 convenience variable @code{$_} and the default examining-address for
3714 the @code{x} command are set to the address of the last breakpoint
3715 listed (@pxref{Memory, ,Examining Memory}).
3718 @code{info break} displays a count of the number of times the breakpoint
3719 has been hit. This is especially useful in conjunction with the
3720 @code{ignore} command. You can ignore a large number of breakpoint
3721 hits, look at the breakpoint info to see how many times the breakpoint
3722 was hit, and then run again, ignoring one less than that number. This
3723 will get you quickly to the last hit of that breakpoint.
3726 For a breakpoints with an enable count (xref) greater than 1,
3727 @code{info break} also displays that count.
3731 @value{GDBN} allows you to set any number of breakpoints at the same place in
3732 your program. There is nothing silly or meaningless about this. When
3733 the breakpoints are conditional, this is even useful
3734 (@pxref{Conditions, ,Break Conditions}).
3736 @cindex multiple locations, breakpoints
3737 @cindex breakpoints, multiple locations
3738 It is possible that a breakpoint corresponds to several locations
3739 in your program. Examples of this situation are:
3743 Multiple functions in the program may have the same name.
3746 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3747 instances of the function body, used in different cases.
3750 For a C@t{++} template function, a given line in the function can
3751 correspond to any number of instantiations.
3754 For an inlined function, a given source line can correspond to
3755 several places where that function is inlined.
3758 In all those cases, @value{GDBN} will insert a breakpoint at all
3759 the relevant locations.
3761 A breakpoint with multiple locations is displayed in the breakpoint
3762 table using several rows---one header row, followed by one row for
3763 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3764 address column. The rows for individual locations contain the actual
3765 addresses for locations, and show the functions to which those
3766 locations belong. The number column for a location is of the form
3767 @var{breakpoint-number}.@var{location-number}.
3772 Num Type Disp Enb Address What
3773 1 breakpoint keep y <MULTIPLE>
3775 breakpoint already hit 1 time
3776 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3777 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3780 Each location can be individually enabled or disabled by passing
3781 @var{breakpoint-number}.@var{location-number} as argument to the
3782 @code{enable} and @code{disable} commands. Note that you cannot
3783 delete the individual locations from the list, you can only delete the
3784 entire list of locations that belong to their parent breakpoint (with
3785 the @kbd{delete @var{num}} command, where @var{num} is the number of
3786 the parent breakpoint, 1 in the above example). Disabling or enabling
3787 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3788 that belong to that breakpoint.
3790 @cindex pending breakpoints
3791 It's quite common to have a breakpoint inside a shared library.
3792 Shared libraries can be loaded and unloaded explicitly,
3793 and possibly repeatedly, as the program is executed. To support
3794 this use case, @value{GDBN} updates breakpoint locations whenever
3795 any shared library is loaded or unloaded. Typically, you would
3796 set a breakpoint in a shared library at the beginning of your
3797 debugging session, when the library is not loaded, and when the
3798 symbols from the library are not available. When you try to set
3799 breakpoint, @value{GDBN} will ask you if you want to set
3800 a so called @dfn{pending breakpoint}---breakpoint whose address
3801 is not yet resolved.
3803 After the program is run, whenever a new shared library is loaded,
3804 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3805 shared library contains the symbol or line referred to by some
3806 pending breakpoint, that breakpoint is resolved and becomes an
3807 ordinary breakpoint. When a library is unloaded, all breakpoints
3808 that refer to its symbols or source lines become pending again.
3810 This logic works for breakpoints with multiple locations, too. For
3811 example, if you have a breakpoint in a C@t{++} template function, and
3812 a newly loaded shared library has an instantiation of that template,
3813 a new location is added to the list of locations for the breakpoint.
3815 Except for having unresolved address, pending breakpoints do not
3816 differ from regular breakpoints. You can set conditions or commands,
3817 enable and disable them and perform other breakpoint operations.
3819 @value{GDBN} provides some additional commands for controlling what
3820 happens when the @samp{break} command cannot resolve breakpoint
3821 address specification to an address:
3823 @kindex set breakpoint pending
3824 @kindex show breakpoint pending
3826 @item set breakpoint pending auto
3827 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3828 location, it queries you whether a pending breakpoint should be created.
3830 @item set breakpoint pending on
3831 This indicates that an unrecognized breakpoint location should automatically
3832 result in a pending breakpoint being created.
3834 @item set breakpoint pending off
3835 This indicates that pending breakpoints are not to be created. Any
3836 unrecognized breakpoint location results in an error. This setting does
3837 not affect any pending breakpoints previously created.
3839 @item show breakpoint pending
3840 Show the current behavior setting for creating pending breakpoints.
3843 The settings above only affect the @code{break} command and its
3844 variants. Once breakpoint is set, it will be automatically updated
3845 as shared libraries are loaded and unloaded.
3847 @cindex automatic hardware breakpoints
3848 For some targets, @value{GDBN} can automatically decide if hardware or
3849 software breakpoints should be used, depending on whether the
3850 breakpoint address is read-only or read-write. This applies to
3851 breakpoints set with the @code{break} command as well as to internal
3852 breakpoints set by commands like @code{next} and @code{finish}. For
3853 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3856 You can control this automatic behaviour with the following commands::
3858 @kindex set breakpoint auto-hw
3859 @kindex show breakpoint auto-hw
3861 @item set breakpoint auto-hw on
3862 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3863 will try to use the target memory map to decide if software or hardware
3864 breakpoint must be used.
3866 @item set breakpoint auto-hw off
3867 This indicates @value{GDBN} should not automatically select breakpoint
3868 type. If the target provides a memory map, @value{GDBN} will warn when
3869 trying to set software breakpoint at a read-only address.
3872 @value{GDBN} normally implements breakpoints by replacing the program code
3873 at the breakpoint address with a special instruction, which, when
3874 executed, given control to the debugger. By default, the program
3875 code is so modified only when the program is resumed. As soon as
3876 the program stops, @value{GDBN} restores the original instructions. This
3877 behaviour guards against leaving breakpoints inserted in the
3878 target should gdb abrubptly disconnect. However, with slow remote
3879 targets, inserting and removing breakpoint can reduce the performance.
3880 This behavior can be controlled with the following commands::
3882 @kindex set breakpoint always-inserted
3883 @kindex show breakpoint always-inserted
3885 @item set breakpoint always-inserted off
3886 All breakpoints, including newly added by the user, are inserted in
3887 the target only when the target is resumed. All breakpoints are
3888 removed from the target when it stops. This is the default mode.
3890 @item set breakpoint always-inserted on
3891 Causes all breakpoints to be inserted in the target at all times. If
3892 the user adds a new breakpoint, or changes an existing breakpoint, the
3893 breakpoints in the target are updated immediately. A breakpoint is
3894 removed from the target only when breakpoint itself is deleted.
3897 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3898 when a breakpoint breaks. If the condition is true, then the process being
3899 debugged stops, otherwise the process is resumed.
3901 If the target supports evaluating conditions on its end, @value{GDBN} may
3902 download the breakpoint, together with its conditions, to it.
3904 This feature can be controlled via the following commands:
3906 @kindex set breakpoint condition-evaluation
3907 @kindex show breakpoint condition-evaluation
3909 @item set breakpoint condition-evaluation host
3910 This option commands @value{GDBN} to evaluate the breakpoint
3911 conditions on the host's side. Unconditional breakpoints are sent to
3912 the target which in turn receives the triggers and reports them back to GDB
3913 for condition evaluation. This is the standard evaluation mode.
3915 @item set breakpoint condition-evaluation target
3916 This option commands @value{GDBN} to download breakpoint conditions
3917 to the target at the moment of their insertion. The target
3918 is responsible for evaluating the conditional expression and reporting
3919 breakpoint stop events back to @value{GDBN} whenever the condition
3920 is true. Due to limitations of target-side evaluation, some conditions
3921 cannot be evaluated there, e.g., conditions that depend on local data
3922 that is only known to the host. Examples include
3923 conditional expressions involving convenience variables, complex types
3924 that cannot be handled by the agent expression parser and expressions
3925 that are too long to be sent over to the target, specially when the
3926 target is a remote system. In these cases, the conditions will be
3927 evaluated by @value{GDBN}.
3929 @item set breakpoint condition-evaluation auto
3930 This is the default mode. If the target supports evaluating breakpoint
3931 conditions on its end, @value{GDBN} will download breakpoint conditions to
3932 the target (limitations mentioned previously apply). If the target does
3933 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3934 to evaluating all these conditions on the host's side.
3938 @cindex negative breakpoint numbers
3939 @cindex internal @value{GDBN} breakpoints
3940 @value{GDBN} itself sometimes sets breakpoints in your program for
3941 special purposes, such as proper handling of @code{longjmp} (in C
3942 programs). These internal breakpoints are assigned negative numbers,
3943 starting with @code{-1}; @samp{info breakpoints} does not display them.
3944 You can see these breakpoints with the @value{GDBN} maintenance command
3945 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3948 @node Set Watchpoints
3949 @subsection Setting Watchpoints
3951 @cindex setting watchpoints
3952 You can use a watchpoint to stop execution whenever the value of an
3953 expression changes, without having to predict a particular place where
3954 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3955 The expression may be as simple as the value of a single variable, or
3956 as complex as many variables combined by operators. Examples include:
3960 A reference to the value of a single variable.
3963 An address cast to an appropriate data type. For example,
3964 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3965 address (assuming an @code{int} occupies 4 bytes).
3968 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3969 expression can use any operators valid in the program's native
3970 language (@pxref{Languages}).
3973 You can set a watchpoint on an expression even if the expression can
3974 not be evaluated yet. For instance, you can set a watchpoint on
3975 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3976 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3977 the expression produces a valid value. If the expression becomes
3978 valid in some other way than changing a variable (e.g.@: if the memory
3979 pointed to by @samp{*global_ptr} becomes readable as the result of a
3980 @code{malloc} call), @value{GDBN} may not stop until the next time
3981 the expression changes.
3983 @cindex software watchpoints
3984 @cindex hardware watchpoints
3985 Depending on your system, watchpoints may be implemented in software or
3986 hardware. @value{GDBN} does software watchpointing by single-stepping your
3987 program and testing the variable's value each time, which is hundreds of
3988 times slower than normal execution. (But this may still be worth it, to
3989 catch errors where you have no clue what part of your program is the
3992 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3993 x86-based targets, @value{GDBN} includes support for hardware
3994 watchpoints, which do not slow down the running of your program.
3998 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3999 Set a watchpoint for an expression. @value{GDBN} will break when the
4000 expression @var{expr} is written into by the program and its value
4001 changes. The simplest (and the most popular) use of this command is
4002 to watch the value of a single variable:
4005 (@value{GDBP}) watch foo
4008 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
4009 argument, @value{GDBN} breaks only when the thread identified by
4010 @var{threadnum} changes the value of @var{expr}. If any other threads
4011 change the value of @var{expr}, @value{GDBN} will not break. Note
4012 that watchpoints restricted to a single thread in this way only work
4013 with Hardware Watchpoints.
4015 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4016 (see below). The @code{-location} argument tells @value{GDBN} to
4017 instead watch the memory referred to by @var{expr}. In this case,
4018 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4019 and watch the memory at that address. The type of the result is used
4020 to determine the size of the watched memory. If the expression's
4021 result does not have an address, then @value{GDBN} will print an
4024 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4025 of masked watchpoints, if the current architecture supports this
4026 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4027 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4028 to an address to watch. The mask specifies that some bits of an address
4029 (the bits which are reset in the mask) should be ignored when matching
4030 the address accessed by the inferior against the watchpoint address.
4031 Thus, a masked watchpoint watches many addresses simultaneously---those
4032 addresses whose unmasked bits are identical to the unmasked bits in the
4033 watchpoint address. The @code{mask} argument implies @code{-location}.
4037 (@value{GDBP}) watch foo mask 0xffff00ff
4038 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4042 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
4043 Set a watchpoint that will break when the value of @var{expr} is read
4047 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
4048 Set a watchpoint that will break when @var{expr} is either read from
4049 or written into by the program.
4051 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
4052 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
4053 This command prints a list of watchpoints, using the same format as
4054 @code{info break} (@pxref{Set Breaks}).
4057 If you watch for a change in a numerically entered address you need to
4058 dereference it, as the address itself is just a constant number which will
4059 never change. @value{GDBN} refuses to create a watchpoint that watches
4060 a never-changing value:
4063 (@value{GDBP}) watch 0x600850
4064 Cannot watch constant value 0x600850.
4065 (@value{GDBP}) watch *(int *) 0x600850
4066 Watchpoint 1: *(int *) 6293584
4069 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4070 watchpoints execute very quickly, and the debugger reports a change in
4071 value at the exact instruction where the change occurs. If @value{GDBN}
4072 cannot set a hardware watchpoint, it sets a software watchpoint, which
4073 executes more slowly and reports the change in value at the next
4074 @emph{statement}, not the instruction, after the change occurs.
4076 @cindex use only software watchpoints
4077 You can force @value{GDBN} to use only software watchpoints with the
4078 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4079 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4080 the underlying system supports them. (Note that hardware-assisted
4081 watchpoints that were set @emph{before} setting
4082 @code{can-use-hw-watchpoints} to zero will still use the hardware
4083 mechanism of watching expression values.)
4086 @item set can-use-hw-watchpoints
4087 @kindex set can-use-hw-watchpoints
4088 Set whether or not to use hardware watchpoints.
4090 @item show can-use-hw-watchpoints
4091 @kindex show can-use-hw-watchpoints
4092 Show the current mode of using hardware watchpoints.
4095 For remote targets, you can restrict the number of hardware
4096 watchpoints @value{GDBN} will use, see @ref{set remote
4097 hardware-breakpoint-limit}.
4099 When you issue the @code{watch} command, @value{GDBN} reports
4102 Hardware watchpoint @var{num}: @var{expr}
4106 if it was able to set a hardware watchpoint.
4108 Currently, the @code{awatch} and @code{rwatch} commands can only set
4109 hardware watchpoints, because accesses to data that don't change the
4110 value of the watched expression cannot be detected without examining
4111 every instruction as it is being executed, and @value{GDBN} does not do
4112 that currently. If @value{GDBN} finds that it is unable to set a
4113 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4114 will print a message like this:
4117 Expression cannot be implemented with read/access watchpoint.
4120 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4121 data type of the watched expression is wider than what a hardware
4122 watchpoint on the target machine can handle. For example, some systems
4123 can only watch regions that are up to 4 bytes wide; on such systems you
4124 cannot set hardware watchpoints for an expression that yields a
4125 double-precision floating-point number (which is typically 8 bytes
4126 wide). As a work-around, it might be possible to break the large region
4127 into a series of smaller ones and watch them with separate watchpoints.
4129 If you set too many hardware watchpoints, @value{GDBN} might be unable
4130 to insert all of them when you resume the execution of your program.
4131 Since the precise number of active watchpoints is unknown until such
4132 time as the program is about to be resumed, @value{GDBN} might not be
4133 able to warn you about this when you set the watchpoints, and the
4134 warning will be printed only when the program is resumed:
4137 Hardware watchpoint @var{num}: Could not insert watchpoint
4141 If this happens, delete or disable some of the watchpoints.
4143 Watching complex expressions that reference many variables can also
4144 exhaust the resources available for hardware-assisted watchpoints.
4145 That's because @value{GDBN} needs to watch every variable in the
4146 expression with separately allocated resources.
4148 If you call a function interactively using @code{print} or @code{call},
4149 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4150 kind of breakpoint or the call completes.
4152 @value{GDBN} automatically deletes watchpoints that watch local
4153 (automatic) variables, or expressions that involve such variables, when
4154 they go out of scope, that is, when the execution leaves the block in
4155 which these variables were defined. In particular, when the program
4156 being debugged terminates, @emph{all} local variables go out of scope,
4157 and so only watchpoints that watch global variables remain set. If you
4158 rerun the program, you will need to set all such watchpoints again. One
4159 way of doing that would be to set a code breakpoint at the entry to the
4160 @code{main} function and when it breaks, set all the watchpoints.
4162 @cindex watchpoints and threads
4163 @cindex threads and watchpoints
4164 In multi-threaded programs, watchpoints will detect changes to the
4165 watched expression from every thread.
4168 @emph{Warning:} In multi-threaded programs, software watchpoints
4169 have only limited usefulness. If @value{GDBN} creates a software
4170 watchpoint, it can only watch the value of an expression @emph{in a
4171 single thread}. If you are confident that the expression can only
4172 change due to the current thread's activity (and if you are also
4173 confident that no other thread can become current), then you can use
4174 software watchpoints as usual. However, @value{GDBN} may not notice
4175 when a non-current thread's activity changes the expression. (Hardware
4176 watchpoints, in contrast, watch an expression in all threads.)
4179 @xref{set remote hardware-watchpoint-limit}.
4181 @node Set Catchpoints
4182 @subsection Setting Catchpoints
4183 @cindex catchpoints, setting
4184 @cindex exception handlers
4185 @cindex event handling
4187 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4188 kinds of program events, such as C@t{++} exceptions or the loading of a
4189 shared library. Use the @code{catch} command to set a catchpoint.
4193 @item catch @var{event}
4194 Stop when @var{event} occurs. The @var{event} can be any of the following:
4197 @item throw @r{[}@var{regexp}@r{]}
4198 @itemx rethrow @r{[}@var{regexp}@r{]}
4199 @itemx catch @r{[}@var{regexp}@r{]}
4201 @kindex catch rethrow
4203 @cindex stop on C@t{++} exceptions
4204 The throwing, re-throwing, or catching of a C@t{++} exception.
4206 If @var{regexp} is given, then only exceptions whose type matches the
4207 regular expression will be caught.
4209 @vindex $_exception@r{, convenience variable}
4210 The convenience variable @code{$_exception} is available at an
4211 exception-related catchpoint, on some systems. This holds the
4212 exception being thrown.
4214 There are currently some limitations to C@t{++} exception handling in
4219 The support for these commands is system-dependent. Currently, only
4220 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4224 The regular expression feature and the @code{$_exception} convenience
4225 variable rely on the presence of some SDT probes in @code{libstdc++}.
4226 If these probes are not present, then these features cannot be used.
4227 These probes were first available in the GCC 4.8 release, but whether
4228 or not they are available in your GCC also depends on how it was
4232 The @code{$_exception} convenience variable is only valid at the
4233 instruction at which an exception-related catchpoint is set.
4236 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4237 location in the system library which implements runtime exception
4238 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4239 (@pxref{Selection}) to get to your code.
4242 If you call a function interactively, @value{GDBN} normally returns
4243 control to you when the function has finished executing. If the call
4244 raises an exception, however, the call may bypass the mechanism that
4245 returns control to you and cause your program either to abort or to
4246 simply continue running until it hits a breakpoint, catches a signal
4247 that @value{GDBN} is listening for, or exits. This is the case even if
4248 you set a catchpoint for the exception; catchpoints on exceptions are
4249 disabled within interactive calls. @xref{Calling}, for information on
4250 controlling this with @code{set unwind-on-terminating-exception}.
4253 You cannot raise an exception interactively.
4256 You cannot install an exception handler interactively.
4260 @kindex catch exception
4261 @cindex Ada exception catching
4262 @cindex catch Ada exceptions
4263 An Ada exception being raised. If an exception name is specified
4264 at the end of the command (eg @code{catch exception Program_Error}),
4265 the debugger will stop only when this specific exception is raised.
4266 Otherwise, the debugger stops execution when any Ada exception is raised.
4268 When inserting an exception catchpoint on a user-defined exception whose
4269 name is identical to one of the exceptions defined by the language, the
4270 fully qualified name must be used as the exception name. Otherwise,
4271 @value{GDBN} will assume that it should stop on the pre-defined exception
4272 rather than the user-defined one. For instance, assuming an exception
4273 called @code{Constraint_Error} is defined in package @code{Pck}, then
4274 the command to use to catch such exceptions is @kbd{catch exception
4275 Pck.Constraint_Error}.
4277 @item exception unhandled
4278 @kindex catch exception unhandled
4279 An exception that was raised but is not handled by the program.
4282 @kindex catch assert
4283 A failed Ada assertion.
4287 @cindex break on fork/exec
4288 A call to @code{exec}. This is currently only available for HP-UX
4292 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4293 @kindex catch syscall
4294 @cindex break on a system call.
4295 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4296 syscall is a mechanism for application programs to request a service
4297 from the operating system (OS) or one of the OS system services.
4298 @value{GDBN} can catch some or all of the syscalls issued by the
4299 debuggee, and show the related information for each syscall. If no
4300 argument is specified, calls to and returns from all system calls
4303 @var{name} can be any system call name that is valid for the
4304 underlying OS. Just what syscalls are valid depends on the OS. On
4305 GNU and Unix systems, you can find the full list of valid syscall
4306 names on @file{/usr/include/asm/unistd.h}.
4308 @c For MS-Windows, the syscall names and the corresponding numbers
4309 @c can be found, e.g., on this URL:
4310 @c http://www.metasploit.com/users/opcode/syscalls.html
4311 @c but we don't support Windows syscalls yet.
4313 Normally, @value{GDBN} knows in advance which syscalls are valid for
4314 each OS, so you can use the @value{GDBN} command-line completion
4315 facilities (@pxref{Completion,, command completion}) to list the
4318 You may also specify the system call numerically. A syscall's
4319 number is the value passed to the OS's syscall dispatcher to
4320 identify the requested service. When you specify the syscall by its
4321 name, @value{GDBN} uses its database of syscalls to convert the name
4322 into the corresponding numeric code, but using the number directly
4323 may be useful if @value{GDBN}'s database does not have the complete
4324 list of syscalls on your system (e.g., because @value{GDBN} lags
4325 behind the OS upgrades).
4327 The example below illustrates how this command works if you don't provide
4331 (@value{GDBP}) catch syscall
4332 Catchpoint 1 (syscall)
4334 Starting program: /tmp/catch-syscall
4336 Catchpoint 1 (call to syscall 'close'), \
4337 0xffffe424 in __kernel_vsyscall ()
4341 Catchpoint 1 (returned from syscall 'close'), \
4342 0xffffe424 in __kernel_vsyscall ()
4346 Here is an example of catching a system call by name:
4349 (@value{GDBP}) catch syscall chroot
4350 Catchpoint 1 (syscall 'chroot' [61])
4352 Starting program: /tmp/catch-syscall
4354 Catchpoint 1 (call to syscall 'chroot'), \
4355 0xffffe424 in __kernel_vsyscall ()
4359 Catchpoint 1 (returned from syscall 'chroot'), \
4360 0xffffe424 in __kernel_vsyscall ()
4364 An example of specifying a system call numerically. In the case
4365 below, the syscall number has a corresponding entry in the XML
4366 file, so @value{GDBN} finds its name and prints it:
4369 (@value{GDBP}) catch syscall 252
4370 Catchpoint 1 (syscall(s) 'exit_group')
4372 Starting program: /tmp/catch-syscall
4374 Catchpoint 1 (call to syscall 'exit_group'), \
4375 0xffffe424 in __kernel_vsyscall ()
4379 Program exited normally.
4383 However, there can be situations when there is no corresponding name
4384 in XML file for that syscall number. In this case, @value{GDBN} prints
4385 a warning message saying that it was not able to find the syscall name,
4386 but the catchpoint will be set anyway. See the example below:
4389 (@value{GDBP}) catch syscall 764
4390 warning: The number '764' does not represent a known syscall.
4391 Catchpoint 2 (syscall 764)
4395 If you configure @value{GDBN} using the @samp{--without-expat} option,
4396 it will not be able to display syscall names. Also, if your
4397 architecture does not have an XML file describing its system calls,
4398 you will not be able to see the syscall names. It is important to
4399 notice that these two features are used for accessing the syscall
4400 name database. In either case, you will see a warning like this:
4403 (@value{GDBP}) catch syscall
4404 warning: Could not open "syscalls/i386-linux.xml"
4405 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4406 GDB will not be able to display syscall names.
4407 Catchpoint 1 (syscall)
4411 Of course, the file name will change depending on your architecture and system.
4413 Still using the example above, you can also try to catch a syscall by its
4414 number. In this case, you would see something like:
4417 (@value{GDBP}) catch syscall 252
4418 Catchpoint 1 (syscall(s) 252)
4421 Again, in this case @value{GDBN} would not be able to display syscall's names.
4425 A call to @code{fork}. This is currently only available for HP-UX
4430 A call to @code{vfork}. This is currently only available for HP-UX
4433 @item load @r{[}regexp@r{]}
4434 @itemx unload @r{[}regexp@r{]}
4436 @kindex catch unload
4437 The loading or unloading of a shared library. If @var{regexp} is
4438 given, then the catchpoint will stop only if the regular expression
4439 matches one of the affected libraries.
4441 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4442 @kindex catch signal
4443 The delivery of a signal.
4445 With no arguments, this catchpoint will catch any signal that is not
4446 used internally by @value{GDBN}, specifically, all signals except
4447 @samp{SIGTRAP} and @samp{SIGINT}.
4449 With the argument @samp{all}, all signals, including those used by
4450 @value{GDBN}, will be caught. This argument cannot be used with other
4453 Otherwise, the arguments are a list of signal names as given to
4454 @code{handle} (@pxref{Signals}). Only signals specified in this list
4457 One reason that @code{catch signal} can be more useful than
4458 @code{handle} is that you can attach commands and conditions to the
4461 When a signal is caught by a catchpoint, the signal's @code{stop} and
4462 @code{print} settings, as specified by @code{handle}, are ignored.
4463 However, whether the signal is still delivered to the inferior depends
4464 on the @code{pass} setting; this can be changed in the catchpoint's
4469 @item tcatch @var{event}
4471 Set a catchpoint that is enabled only for one stop. The catchpoint is
4472 automatically deleted after the first time the event is caught.
4476 Use the @code{info break} command to list the current catchpoints.
4480 @subsection Deleting Breakpoints
4482 @cindex clearing breakpoints, watchpoints, catchpoints
4483 @cindex deleting breakpoints, watchpoints, catchpoints
4484 It is often necessary to eliminate a breakpoint, watchpoint, or
4485 catchpoint once it has done its job and you no longer want your program
4486 to stop there. This is called @dfn{deleting} the breakpoint. A
4487 breakpoint that has been deleted no longer exists; it is forgotten.
4489 With the @code{clear} command you can delete breakpoints according to
4490 where they are in your program. With the @code{delete} command you can
4491 delete individual breakpoints, watchpoints, or catchpoints by specifying
4492 their breakpoint numbers.
4494 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4495 automatically ignores breakpoints on the first instruction to be executed
4496 when you continue execution without changing the execution address.
4501 Delete any breakpoints at the next instruction to be executed in the
4502 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4503 the innermost frame is selected, this is a good way to delete a
4504 breakpoint where your program just stopped.
4506 @item clear @var{location}
4507 Delete any breakpoints set at the specified @var{location}.
4508 @xref{Specify Location}, for the various forms of @var{location}; the
4509 most useful ones are listed below:
4512 @item clear @var{function}
4513 @itemx clear @var{filename}:@var{function}
4514 Delete any breakpoints set at entry to the named @var{function}.
4516 @item clear @var{linenum}
4517 @itemx clear @var{filename}:@var{linenum}
4518 Delete any breakpoints set at or within the code of the specified
4519 @var{linenum} of the specified @var{filename}.
4522 @cindex delete breakpoints
4524 @kindex d @r{(@code{delete})}
4525 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4526 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4527 ranges specified as arguments. If no argument is specified, delete all
4528 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4529 confirm off}). You can abbreviate this command as @code{d}.
4533 @subsection Disabling Breakpoints
4535 @cindex enable/disable a breakpoint
4536 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4537 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4538 it had been deleted, but remembers the information on the breakpoint so
4539 that you can @dfn{enable} it again later.
4541 You disable and enable breakpoints, watchpoints, and catchpoints with
4542 the @code{enable} and @code{disable} commands, optionally specifying
4543 one or more breakpoint numbers as arguments. Use @code{info break} to
4544 print a list of all breakpoints, watchpoints, and catchpoints if you
4545 do not know which numbers to use.
4547 Disabling and enabling a breakpoint that has multiple locations
4548 affects all of its locations.
4550 A breakpoint, watchpoint, or catchpoint can have any of several
4551 different states of enablement:
4555 Enabled. The breakpoint stops your program. A breakpoint set
4556 with the @code{break} command starts out in this state.
4558 Disabled. The breakpoint has no effect on your program.
4560 Enabled once. The breakpoint stops your program, but then becomes
4563 Enabled for a count. The breakpoint stops your program for the next
4564 N times, then becomes disabled.
4566 Enabled for deletion. The breakpoint stops your program, but
4567 immediately after it does so it is deleted permanently. A breakpoint
4568 set with the @code{tbreak} command starts out in this state.
4571 You can use the following commands to enable or disable breakpoints,
4572 watchpoints, and catchpoints:
4576 @kindex dis @r{(@code{disable})}
4577 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4578 Disable the specified breakpoints---or all breakpoints, if none are
4579 listed. A disabled breakpoint has no effect but is not forgotten. All
4580 options such as ignore-counts, conditions and commands are remembered in
4581 case the breakpoint is enabled again later. You may abbreviate
4582 @code{disable} as @code{dis}.
4585 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4586 Enable the specified breakpoints (or all defined breakpoints). They
4587 become effective once again in stopping your program.
4589 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4590 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4591 of these breakpoints immediately after stopping your program.
4593 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4594 Enable the specified breakpoints temporarily. @value{GDBN} records
4595 @var{count} with each of the specified breakpoints, and decrements a
4596 breakpoint's count when it is hit. When any count reaches 0,
4597 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4598 count (@pxref{Conditions, ,Break Conditions}), that will be
4599 decremented to 0 before @var{count} is affected.
4601 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4602 Enable the specified breakpoints to work once, then die. @value{GDBN}
4603 deletes any of these breakpoints as soon as your program stops there.
4604 Breakpoints set by the @code{tbreak} command start out in this state.
4607 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4608 @c confusing: tbreak is also initially enabled.
4609 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4610 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4611 subsequently, they become disabled or enabled only when you use one of
4612 the commands above. (The command @code{until} can set and delete a
4613 breakpoint of its own, but it does not change the state of your other
4614 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4618 @subsection Break Conditions
4619 @cindex conditional breakpoints
4620 @cindex breakpoint conditions
4622 @c FIXME what is scope of break condition expr? Context where wanted?
4623 @c in particular for a watchpoint?
4624 The simplest sort of breakpoint breaks every time your program reaches a
4625 specified place. You can also specify a @dfn{condition} for a
4626 breakpoint. A condition is just a Boolean expression in your
4627 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4628 a condition evaluates the expression each time your program reaches it,
4629 and your program stops only if the condition is @emph{true}.
4631 This is the converse of using assertions for program validation; in that
4632 situation, you want to stop when the assertion is violated---that is,
4633 when the condition is false. In C, if you want to test an assertion expressed
4634 by the condition @var{assert}, you should set the condition
4635 @samp{! @var{assert}} on the appropriate breakpoint.
4637 Conditions are also accepted for watchpoints; you may not need them,
4638 since a watchpoint is inspecting the value of an expression anyhow---but
4639 it might be simpler, say, to just set a watchpoint on a variable name,
4640 and specify a condition that tests whether the new value is an interesting
4643 Break conditions can have side effects, and may even call functions in
4644 your program. This can be useful, for example, to activate functions
4645 that log program progress, or to use your own print functions to
4646 format special data structures. The effects are completely predictable
4647 unless there is another enabled breakpoint at the same address. (In
4648 that case, @value{GDBN} might see the other breakpoint first and stop your
4649 program without checking the condition of this one.) Note that
4650 breakpoint commands are usually more convenient and flexible than break
4652 purpose of performing side effects when a breakpoint is reached
4653 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4655 Breakpoint conditions can also be evaluated on the target's side if
4656 the target supports it. Instead of evaluating the conditions locally,
4657 @value{GDBN} encodes the expression into an agent expression
4658 (@pxref{Agent Expressions}) suitable for execution on the target,
4659 independently of @value{GDBN}. Global variables become raw memory
4660 locations, locals become stack accesses, and so forth.
4662 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4663 when its condition evaluates to true. This mechanism may provide faster
4664 response times depending on the performance characteristics of the target
4665 since it does not need to keep @value{GDBN} informed about
4666 every breakpoint trigger, even those with false conditions.
4668 Break conditions can be specified when a breakpoint is set, by using
4669 @samp{if} in the arguments to the @code{break} command. @xref{Set
4670 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4671 with the @code{condition} command.
4673 You can also use the @code{if} keyword with the @code{watch} command.
4674 The @code{catch} command does not recognize the @code{if} keyword;
4675 @code{condition} is the only way to impose a further condition on a
4680 @item condition @var{bnum} @var{expression}
4681 Specify @var{expression} as the break condition for breakpoint,
4682 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4683 breakpoint @var{bnum} stops your program only if the value of
4684 @var{expression} is true (nonzero, in C). When you use
4685 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4686 syntactic correctness, and to determine whether symbols in it have
4687 referents in the context of your breakpoint. If @var{expression} uses
4688 symbols not referenced in the context of the breakpoint, @value{GDBN}
4689 prints an error message:
4692 No symbol "foo" in current context.
4697 not actually evaluate @var{expression} at the time the @code{condition}
4698 command (or a command that sets a breakpoint with a condition, like
4699 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4701 @item condition @var{bnum}
4702 Remove the condition from breakpoint number @var{bnum}. It becomes
4703 an ordinary unconditional breakpoint.
4706 @cindex ignore count (of breakpoint)
4707 A special case of a breakpoint condition is to stop only when the
4708 breakpoint has been reached a certain number of times. This is so
4709 useful that there is a special way to do it, using the @dfn{ignore
4710 count} of the breakpoint. Every breakpoint has an ignore count, which
4711 is an integer. Most of the time, the ignore count is zero, and
4712 therefore has no effect. But if your program reaches a breakpoint whose
4713 ignore count is positive, then instead of stopping, it just decrements
4714 the ignore count by one and continues. As a result, if the ignore count
4715 value is @var{n}, the breakpoint does not stop the next @var{n} times
4716 your program reaches it.
4720 @item ignore @var{bnum} @var{count}
4721 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4722 The next @var{count} times the breakpoint is reached, your program's
4723 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4726 To make the breakpoint stop the next time it is reached, specify
4729 When you use @code{continue} to resume execution of your program from a
4730 breakpoint, you can specify an ignore count directly as an argument to
4731 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4732 Stepping,,Continuing and Stepping}.
4734 If a breakpoint has a positive ignore count and a condition, the
4735 condition is not checked. Once the ignore count reaches zero,
4736 @value{GDBN} resumes checking the condition.
4738 You could achieve the effect of the ignore count with a condition such
4739 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4740 is decremented each time. @xref{Convenience Vars, ,Convenience
4744 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4747 @node Break Commands
4748 @subsection Breakpoint Command Lists
4750 @cindex breakpoint commands
4751 You can give any breakpoint (or watchpoint or catchpoint) a series of
4752 commands to execute when your program stops due to that breakpoint. For
4753 example, you might want to print the values of certain expressions, or
4754 enable other breakpoints.
4758 @kindex end@r{ (breakpoint commands)}
4759 @item commands @r{[}@var{range}@dots{}@r{]}
4760 @itemx @dots{} @var{command-list} @dots{}
4762 Specify a list of commands for the given breakpoints. The commands
4763 themselves appear on the following lines. Type a line containing just
4764 @code{end} to terminate the commands.
4766 To remove all commands from a breakpoint, type @code{commands} and
4767 follow it immediately with @code{end}; that is, give no commands.
4769 With no argument, @code{commands} refers to the last breakpoint,
4770 watchpoint, or catchpoint set (not to the breakpoint most recently
4771 encountered). If the most recent breakpoints were set with a single
4772 command, then the @code{commands} will apply to all the breakpoints
4773 set by that command. This applies to breakpoints set by
4774 @code{rbreak}, and also applies when a single @code{break} command
4775 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4779 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4780 disabled within a @var{command-list}.
4782 You can use breakpoint commands to start your program up again. Simply
4783 use the @code{continue} command, or @code{step}, or any other command
4784 that resumes execution.
4786 Any other commands in the command list, after a command that resumes
4787 execution, are ignored. This is because any time you resume execution
4788 (even with a simple @code{next} or @code{step}), you may encounter
4789 another breakpoint---which could have its own command list, leading to
4790 ambiguities about which list to execute.
4793 If the first command you specify in a command list is @code{silent}, the
4794 usual message about stopping at a breakpoint is not printed. This may
4795 be desirable for breakpoints that are to print a specific message and
4796 then continue. If none of the remaining commands print anything, you
4797 see no sign that the breakpoint was reached. @code{silent} is
4798 meaningful only at the beginning of a breakpoint command list.
4800 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4801 print precisely controlled output, and are often useful in silent
4802 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4804 For example, here is how you could use breakpoint commands to print the
4805 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4811 printf "x is %d\n",x
4816 One application for breakpoint commands is to compensate for one bug so
4817 you can test for another. Put a breakpoint just after the erroneous line
4818 of code, give it a condition to detect the case in which something
4819 erroneous has been done, and give it commands to assign correct values
4820 to any variables that need them. End with the @code{continue} command
4821 so that your program does not stop, and start with the @code{silent}
4822 command so that no output is produced. Here is an example:
4833 @node Dynamic Printf
4834 @subsection Dynamic Printf
4836 @cindex dynamic printf
4838 The dynamic printf command @code{dprintf} combines a breakpoint with
4839 formatted printing of your program's data to give you the effect of
4840 inserting @code{printf} calls into your program on-the-fly, without
4841 having to recompile it.
4843 In its most basic form, the output goes to the GDB console. However,
4844 you can set the variable @code{dprintf-style} for alternate handling.
4845 For instance, you can ask to format the output by calling your
4846 program's @code{printf} function. This has the advantage that the
4847 characters go to the program's output device, so they can recorded in
4848 redirects to files and so forth.
4850 If you are doing remote debugging with a stub or agent, you can also
4851 ask to have the printf handled by the remote agent. In addition to
4852 ensuring that the output goes to the remote program's device along
4853 with any other output the program might produce, you can also ask that
4854 the dprintf remain active even after disconnecting from the remote
4855 target. Using the stub/agent is also more efficient, as it can do
4856 everything without needing to communicate with @value{GDBN}.
4860 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4861 Whenever execution reaches @var{location}, print the values of one or
4862 more @var{expressions} under the control of the string @var{template}.
4863 To print several values, separate them with commas.
4865 @item set dprintf-style @var{style}
4866 Set the dprintf output to be handled in one of several different
4867 styles enumerated below. A change of style affects all existing
4868 dynamic printfs immediately. (If you need individual control over the
4869 print commands, simply define normal breakpoints with
4870 explicitly-supplied command lists.)
4873 @kindex dprintf-style gdb
4874 Handle the output using the @value{GDBN} @code{printf} command.
4877 @kindex dprintf-style call
4878 Handle the output by calling a function in your program (normally
4882 @kindex dprintf-style agent
4883 Have the remote debugging agent (such as @code{gdbserver}) handle
4884 the output itself. This style is only available for agents that
4885 support running commands on the target.
4887 @item set dprintf-function @var{function}
4888 Set the function to call if the dprintf style is @code{call}. By
4889 default its value is @code{printf}. You may set it to any expression.
4890 that @value{GDBN} can evaluate to a function, as per the @code{call}
4893 @item set dprintf-channel @var{channel}
4894 Set a ``channel'' for dprintf. If set to a non-empty value,
4895 @value{GDBN} will evaluate it as an expression and pass the result as
4896 a first argument to the @code{dprintf-function}, in the manner of
4897 @code{fprintf} and similar functions. Otherwise, the dprintf format
4898 string will be the first argument, in the manner of @code{printf}.
4900 As an example, if you wanted @code{dprintf} output to go to a logfile
4901 that is a standard I/O stream assigned to the variable @code{mylog},
4902 you could do the following:
4905 (gdb) set dprintf-style call
4906 (gdb) set dprintf-function fprintf
4907 (gdb) set dprintf-channel mylog
4908 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4909 Dprintf 1 at 0x123456: file main.c, line 25.
4911 1 dprintf keep y 0x00123456 in main at main.c:25
4912 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
4917 Note that the @code{info break} displays the dynamic printf commands
4918 as normal breakpoint commands; you can thus easily see the effect of
4919 the variable settings.
4921 @item set disconnected-dprintf on
4922 @itemx set disconnected-dprintf off
4923 @kindex set disconnected-dprintf
4924 Choose whether @code{dprintf} commands should continue to run if
4925 @value{GDBN} has disconnected from the target. This only applies
4926 if the @code{dprintf-style} is @code{agent}.
4928 @item show disconnected-dprintf off
4929 @kindex show disconnected-dprintf
4930 Show the current choice for disconnected @code{dprintf}.
4934 @value{GDBN} does not check the validity of function and channel,
4935 relying on you to supply values that are meaningful for the contexts
4936 in which they are being used. For instance, the function and channel
4937 may be the values of local variables, but if that is the case, then
4938 all enabled dynamic prints must be at locations within the scope of
4939 those locals. If evaluation fails, @value{GDBN} will report an error.
4941 @node Save Breakpoints
4942 @subsection How to save breakpoints to a file
4944 To save breakpoint definitions to a file use the @w{@code{save
4945 breakpoints}} command.
4948 @kindex save breakpoints
4949 @cindex save breakpoints to a file for future sessions
4950 @item save breakpoints [@var{filename}]
4951 This command saves all current breakpoint definitions together with
4952 their commands and ignore counts, into a file @file{@var{filename}}
4953 suitable for use in a later debugging session. This includes all
4954 types of breakpoints (breakpoints, watchpoints, catchpoints,
4955 tracepoints). To read the saved breakpoint definitions, use the
4956 @code{source} command (@pxref{Command Files}). Note that watchpoints
4957 with expressions involving local variables may fail to be recreated
4958 because it may not be possible to access the context where the
4959 watchpoint is valid anymore. Because the saved breakpoint definitions
4960 are simply a sequence of @value{GDBN} commands that recreate the
4961 breakpoints, you can edit the file in your favorite editing program,
4962 and remove the breakpoint definitions you're not interested in, or
4963 that can no longer be recreated.
4966 @node Static Probe Points
4967 @subsection Static Probe Points
4969 @cindex static probe point, SystemTap
4970 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
4971 for Statically Defined Tracing, and the probes are designed to have a tiny
4972 runtime code and data footprint, and no dynamic relocations. They are
4973 usable from assembly, C and C@t{++} languages. See
4974 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
4975 for a good reference on how the @acronym{SDT} probes are implemented.
4977 Currently, @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
4978 @acronym{SDT} probes are supported on ELF-compatible systems. See
4979 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
4980 for more information on how to add @code{SystemTap} @acronym{SDT} probes
4981 in your applications.
4983 @cindex semaphores on static probe points
4984 Some probes have an associated semaphore variable; for instance, this
4985 happens automatically if you defined your probe using a DTrace-style
4986 @file{.d} file. If your probe has a semaphore, @value{GDBN} will
4987 automatically enable it when you specify a breakpoint using the
4988 @samp{-probe-stap} notation. But, if you put a breakpoint at a probe's
4989 location by some other method (e.g., @code{break file:line}), then
4990 @value{GDBN} will not automatically set the semaphore.
4992 You can examine the available static static probes using @code{info
4993 probes}, with optional arguments:
4997 @item info probes stap @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
4998 If given, @var{provider} is a regular expression used to match against provider
4999 names when selecting which probes to list. If omitted, probes by all
5000 probes from all providers are listed.
5002 If given, @var{name} is a regular expression to match against probe names
5003 when selecting which probes to list. If omitted, probe names are not
5004 considered when deciding whether to display them.
5006 If given, @var{objfile} is a regular expression used to select which
5007 object files (executable or shared libraries) to examine. If not
5008 given, all object files are considered.
5010 @item info probes all
5011 List the available static probes, from all types.
5014 @vindex $_probe_arg@r{, convenience variable}
5015 A probe may specify up to twelve arguments. These are available at the
5016 point at which the probe is defined---that is, when the current PC is
5017 at the probe's location. The arguments are available using the
5018 convenience variables (@pxref{Convenience Vars})
5019 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. Each probe argument is
5020 an integer of the appropriate size; types are not preserved. The
5021 convenience variable @code{$_probe_argc} holds the number of arguments
5022 at the current probe point.
5024 These variables are always available, but attempts to access them at
5025 any location other than a probe point will cause @value{GDBN} to give
5029 @c @ifclear BARETARGET
5030 @node Error in Breakpoints
5031 @subsection ``Cannot insert breakpoints''
5033 If you request too many active hardware-assisted breakpoints and
5034 watchpoints, you will see this error message:
5036 @c FIXME: the precise wording of this message may change; the relevant
5037 @c source change is not committed yet (Sep 3, 1999).
5039 Stopped; cannot insert breakpoints.
5040 You may have requested too many hardware breakpoints and watchpoints.
5044 This message is printed when you attempt to resume the program, since
5045 only then @value{GDBN} knows exactly how many hardware breakpoints and
5046 watchpoints it needs to insert.
5048 When this message is printed, you need to disable or remove some of the
5049 hardware-assisted breakpoints and watchpoints, and then continue.
5051 @node Breakpoint-related Warnings
5052 @subsection ``Breakpoint address adjusted...''
5053 @cindex breakpoint address adjusted
5055 Some processor architectures place constraints on the addresses at
5056 which breakpoints may be placed. For architectures thus constrained,
5057 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5058 with the constraints dictated by the architecture.
5060 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5061 a VLIW architecture in which a number of RISC-like instructions may be
5062 bundled together for parallel execution. The FR-V architecture
5063 constrains the location of a breakpoint instruction within such a
5064 bundle to the instruction with the lowest address. @value{GDBN}
5065 honors this constraint by adjusting a breakpoint's address to the
5066 first in the bundle.
5068 It is not uncommon for optimized code to have bundles which contain
5069 instructions from different source statements, thus it may happen that
5070 a breakpoint's address will be adjusted from one source statement to
5071 another. Since this adjustment may significantly alter @value{GDBN}'s
5072 breakpoint related behavior from what the user expects, a warning is
5073 printed when the breakpoint is first set and also when the breakpoint
5076 A warning like the one below is printed when setting a breakpoint
5077 that's been subject to address adjustment:
5080 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5083 Such warnings are printed both for user settable and @value{GDBN}'s
5084 internal breakpoints. If you see one of these warnings, you should
5085 verify that a breakpoint set at the adjusted address will have the
5086 desired affect. If not, the breakpoint in question may be removed and
5087 other breakpoints may be set which will have the desired behavior.
5088 E.g., it may be sufficient to place the breakpoint at a later
5089 instruction. A conditional breakpoint may also be useful in some
5090 cases to prevent the breakpoint from triggering too often.
5092 @value{GDBN} will also issue a warning when stopping at one of these
5093 adjusted breakpoints:
5096 warning: Breakpoint 1 address previously adjusted from 0x00010414
5100 When this warning is encountered, it may be too late to take remedial
5101 action except in cases where the breakpoint is hit earlier or more
5102 frequently than expected.
5104 @node Continuing and Stepping
5105 @section Continuing and Stepping
5109 @cindex resuming execution
5110 @dfn{Continuing} means resuming program execution until your program
5111 completes normally. In contrast, @dfn{stepping} means executing just
5112 one more ``step'' of your program, where ``step'' may mean either one
5113 line of source code, or one machine instruction (depending on what
5114 particular command you use). Either when continuing or when stepping,
5115 your program may stop even sooner, due to a breakpoint or a signal. (If
5116 it stops due to a signal, you may want to use @code{handle}, or use
5117 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5118 or you may step into the signal's handler (@pxref{stepping and signal
5123 @kindex c @r{(@code{continue})}
5124 @kindex fg @r{(resume foreground execution)}
5125 @item continue @r{[}@var{ignore-count}@r{]}
5126 @itemx c @r{[}@var{ignore-count}@r{]}
5127 @itemx fg @r{[}@var{ignore-count}@r{]}
5128 Resume program execution, at the address where your program last stopped;
5129 any breakpoints set at that address are bypassed. The optional argument
5130 @var{ignore-count} allows you to specify a further number of times to
5131 ignore a breakpoint at this location; its effect is like that of
5132 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5134 The argument @var{ignore-count} is meaningful only when your program
5135 stopped due to a breakpoint. At other times, the argument to
5136 @code{continue} is ignored.
5138 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5139 debugged program is deemed to be the foreground program) are provided
5140 purely for convenience, and have exactly the same behavior as
5144 To resume execution at a different place, you can use @code{return}
5145 (@pxref{Returning, ,Returning from a Function}) to go back to the
5146 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5147 Different Address}) to go to an arbitrary location in your program.
5149 A typical technique for using stepping is to set a breakpoint
5150 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5151 beginning of the function or the section of your program where a problem
5152 is believed to lie, run your program until it stops at that breakpoint,
5153 and then step through the suspect area, examining the variables that are
5154 interesting, until you see the problem happen.
5158 @kindex s @r{(@code{step})}
5160 Continue running your program until control reaches a different source
5161 line, then stop it and return control to @value{GDBN}. This command is
5162 abbreviated @code{s}.
5165 @c "without debugging information" is imprecise; actually "without line
5166 @c numbers in the debugging information". (gcc -g1 has debugging info but
5167 @c not line numbers). But it seems complex to try to make that
5168 @c distinction here.
5169 @emph{Warning:} If you use the @code{step} command while control is
5170 within a function that was compiled without debugging information,
5171 execution proceeds until control reaches a function that does have
5172 debugging information. Likewise, it will not step into a function which
5173 is compiled without debugging information. To step through functions
5174 without debugging information, use the @code{stepi} command, described
5178 The @code{step} command only stops at the first instruction of a source
5179 line. This prevents the multiple stops that could otherwise occur in
5180 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5181 to stop if a function that has debugging information is called within
5182 the line. In other words, @code{step} @emph{steps inside} any functions
5183 called within the line.
5185 Also, the @code{step} command only enters a function if there is line
5186 number information for the function. Otherwise it acts like the
5187 @code{next} command. This avoids problems when using @code{cc -gl}
5188 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5189 was any debugging information about the routine.
5191 @item step @var{count}
5192 Continue running as in @code{step}, but do so @var{count} times. If a
5193 breakpoint is reached, or a signal not related to stepping occurs before
5194 @var{count} steps, stepping stops right away.
5197 @kindex n @r{(@code{next})}
5198 @item next @r{[}@var{count}@r{]}
5199 Continue to the next source line in the current (innermost) stack frame.
5200 This is similar to @code{step}, but function calls that appear within
5201 the line of code are executed without stopping. Execution stops when
5202 control reaches a different line of code at the original stack level
5203 that was executing when you gave the @code{next} command. This command
5204 is abbreviated @code{n}.
5206 An argument @var{count} is a repeat count, as for @code{step}.
5209 @c FIX ME!! Do we delete this, or is there a way it fits in with
5210 @c the following paragraph? --- Vctoria
5212 @c @code{next} within a function that lacks debugging information acts like
5213 @c @code{step}, but any function calls appearing within the code of the
5214 @c function are executed without stopping.
5216 The @code{next} command only stops at the first instruction of a
5217 source line. This prevents multiple stops that could otherwise occur in
5218 @code{switch} statements, @code{for} loops, etc.
5220 @kindex set step-mode
5222 @cindex functions without line info, and stepping
5223 @cindex stepping into functions with no line info
5224 @itemx set step-mode on
5225 The @code{set step-mode on} command causes the @code{step} command to
5226 stop at the first instruction of a function which contains no debug line
5227 information rather than stepping over it.
5229 This is useful in cases where you may be interested in inspecting the
5230 machine instructions of a function which has no symbolic info and do not
5231 want @value{GDBN} to automatically skip over this function.
5233 @item set step-mode off
5234 Causes the @code{step} command to step over any functions which contains no
5235 debug information. This is the default.
5237 @item show step-mode
5238 Show whether @value{GDBN} will stop in or step over functions without
5239 source line debug information.
5242 @kindex fin @r{(@code{finish})}
5244 Continue running until just after function in the selected stack frame
5245 returns. Print the returned value (if any). This command can be
5246 abbreviated as @code{fin}.
5248 Contrast this with the @code{return} command (@pxref{Returning,
5249 ,Returning from a Function}).
5252 @kindex u @r{(@code{until})}
5253 @cindex run until specified location
5256 Continue running until a source line past the current line, in the
5257 current stack frame, is reached. This command is used to avoid single
5258 stepping through a loop more than once. It is like the @code{next}
5259 command, except that when @code{until} encounters a jump, it
5260 automatically continues execution until the program counter is greater
5261 than the address of the jump.
5263 This means that when you reach the end of a loop after single stepping
5264 though it, @code{until} makes your program continue execution until it
5265 exits the loop. In contrast, a @code{next} command at the end of a loop
5266 simply steps back to the beginning of the loop, which forces you to step
5267 through the next iteration.
5269 @code{until} always stops your program if it attempts to exit the current
5272 @code{until} may produce somewhat counterintuitive results if the order
5273 of machine code does not match the order of the source lines. For
5274 example, in the following excerpt from a debugging session, the @code{f}
5275 (@code{frame}) command shows that execution is stopped at line
5276 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5280 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5282 (@value{GDBP}) until
5283 195 for ( ; argc > 0; NEXTARG) @{
5286 This happened because, for execution efficiency, the compiler had
5287 generated code for the loop closure test at the end, rather than the
5288 start, of the loop---even though the test in a C @code{for}-loop is
5289 written before the body of the loop. The @code{until} command appeared
5290 to step back to the beginning of the loop when it advanced to this
5291 expression; however, it has not really gone to an earlier
5292 statement---not in terms of the actual machine code.
5294 @code{until} with no argument works by means of single
5295 instruction stepping, and hence is slower than @code{until} with an
5298 @item until @var{location}
5299 @itemx u @var{location}
5300 Continue running your program until either the specified @var{location} is
5301 reached, or the current stack frame returns. The location is any of
5302 the forms described in @ref{Specify Location}.
5303 This form of the command uses temporary breakpoints, and
5304 hence is quicker than @code{until} without an argument. The specified
5305 location is actually reached only if it is in the current frame. This
5306 implies that @code{until} can be used to skip over recursive function
5307 invocations. For instance in the code below, if the current location is
5308 line @code{96}, issuing @code{until 99} will execute the program up to
5309 line @code{99} in the same invocation of factorial, i.e., after the inner
5310 invocations have returned.
5313 94 int factorial (int value)
5315 96 if (value > 1) @{
5316 97 value *= factorial (value - 1);
5323 @kindex advance @var{location}
5324 @item advance @var{location}
5325 Continue running the program up to the given @var{location}. An argument is
5326 required, which should be of one of the forms described in
5327 @ref{Specify Location}.
5328 Execution will also stop upon exit from the current stack
5329 frame. This command is similar to @code{until}, but @code{advance} will
5330 not skip over recursive function calls, and the target location doesn't
5331 have to be in the same frame as the current one.
5335 @kindex si @r{(@code{stepi})}
5337 @itemx stepi @var{arg}
5339 Execute one machine instruction, then stop and return to the debugger.
5341 It is often useful to do @samp{display/i $pc} when stepping by machine
5342 instructions. This makes @value{GDBN} automatically display the next
5343 instruction to be executed, each time your program stops. @xref{Auto
5344 Display,, Automatic Display}.
5346 An argument is a repeat count, as in @code{step}.
5350 @kindex ni @r{(@code{nexti})}
5352 @itemx nexti @var{arg}
5354 Execute one machine instruction, but if it is a function call,
5355 proceed until the function returns.
5357 An argument is a repeat count, as in @code{next}.
5361 @anchor{range stepping}
5362 @cindex range stepping
5363 @cindex target-assisted range stepping
5364 By default, and if available, @value{GDBN} makes use of
5365 target-assisted @dfn{range stepping}. In other words, whenever you
5366 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5367 tells the target to step the corresponding range of instruction
5368 addresses instead of issuing multiple single-steps. This speeds up
5369 line stepping, particularly for remote targets. Ideally, there should
5370 be no reason you would want to turn range stepping off. However, it's
5371 possible that a bug in the debug info, a bug in the remote stub (for
5372 remote targets), or even a bug in @value{GDBN} could make line
5373 stepping behave incorrectly when target-assisted range stepping is
5374 enabled. You can use the following command to turn off range stepping
5378 @kindex set range-stepping
5379 @kindex show range-stepping
5380 @item set range-stepping
5381 @itemx show range-stepping
5382 Control whether range stepping is enabled.
5384 If @code{on}, and the target supports it, @value{GDBN} tells the
5385 target to step a range of addresses itself, instead of issuing
5386 multiple single-steps. If @code{off}, @value{GDBN} always issues
5387 single-steps, even if range stepping is supported by the target. The
5388 default is @code{on}.
5392 @node Skipping Over Functions and Files
5393 @section Skipping Over Functions and Files
5394 @cindex skipping over functions and files
5396 The program you are debugging may contain some functions which are
5397 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
5398 skip a function or all functions in a file when stepping.
5400 For example, consider the following C function:
5411 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5412 are not interested in stepping through @code{boring}. If you run @code{step}
5413 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5414 step over both @code{foo} and @code{boring}!
5416 One solution is to @code{step} into @code{boring} and use the @code{finish}
5417 command to immediately exit it. But this can become tedious if @code{boring}
5418 is called from many places.
5420 A more flexible solution is to execute @kbd{skip boring}. This instructs
5421 @value{GDBN} never to step into @code{boring}. Now when you execute
5422 @code{step} at line 103, you'll step over @code{boring} and directly into
5425 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5426 example, @code{skip file boring.c}.
5429 @kindex skip function
5430 @item skip @r{[}@var{linespec}@r{]}
5431 @itemx skip function @r{[}@var{linespec}@r{]}
5432 After running this command, the function named by @var{linespec} or the
5433 function containing the line named by @var{linespec} will be skipped over when
5434 stepping. @xref{Specify Location}.
5436 If you do not specify @var{linespec}, the function you're currently debugging
5439 (If you have a function called @code{file} that you want to skip, use
5440 @kbd{skip function file}.)
5443 @item skip file @r{[}@var{filename}@r{]}
5444 After running this command, any function whose source lives in @var{filename}
5445 will be skipped over when stepping.
5447 If you do not specify @var{filename}, functions whose source lives in the file
5448 you're currently debugging will be skipped.
5451 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5452 These are the commands for managing your list of skips:
5456 @item info skip @r{[}@var{range}@r{]}
5457 Print details about the specified skip(s). If @var{range} is not specified,
5458 print a table with details about all functions and files marked for skipping.
5459 @code{info skip} prints the following information about each skip:
5463 A number identifying this skip.
5465 The type of this skip, either @samp{function} or @samp{file}.
5466 @item Enabled or Disabled
5467 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5469 For function skips, this column indicates the address in memory of the function
5470 being skipped. If you've set a function skip on a function which has not yet
5471 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5472 which has the function is loaded, @code{info skip} will show the function's
5475 For file skips, this field contains the filename being skipped. For functions
5476 skips, this field contains the function name and its line number in the file
5477 where it is defined.
5481 @item skip delete @r{[}@var{range}@r{]}
5482 Delete the specified skip(s). If @var{range} is not specified, delete all
5486 @item skip enable @r{[}@var{range}@r{]}
5487 Enable the specified skip(s). If @var{range} is not specified, enable all
5490 @kindex skip disable
5491 @item skip disable @r{[}@var{range}@r{]}
5492 Disable the specified skip(s). If @var{range} is not specified, disable all
5501 A signal is an asynchronous event that can happen in a program. The
5502 operating system defines the possible kinds of signals, and gives each
5503 kind a name and a number. For example, in Unix @code{SIGINT} is the
5504 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5505 @code{SIGSEGV} is the signal a program gets from referencing a place in
5506 memory far away from all the areas in use; @code{SIGALRM} occurs when
5507 the alarm clock timer goes off (which happens only if your program has
5508 requested an alarm).
5510 @cindex fatal signals
5511 Some signals, including @code{SIGALRM}, are a normal part of the
5512 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5513 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5514 program has not specified in advance some other way to handle the signal.
5515 @code{SIGINT} does not indicate an error in your program, but it is normally
5516 fatal so it can carry out the purpose of the interrupt: to kill the program.
5518 @value{GDBN} has the ability to detect any occurrence of a signal in your
5519 program. You can tell @value{GDBN} in advance what to do for each kind of
5522 @cindex handling signals
5523 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5524 @code{SIGALRM} be silently passed to your program
5525 (so as not to interfere with their role in the program's functioning)
5526 but to stop your program immediately whenever an error signal happens.
5527 You can change these settings with the @code{handle} command.
5530 @kindex info signals
5534 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5535 handle each one. You can use this to see the signal numbers of all
5536 the defined types of signals.
5538 @item info signals @var{sig}
5539 Similar, but print information only about the specified signal number.
5541 @code{info handle} is an alias for @code{info signals}.
5543 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5544 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5545 for details about this command.
5548 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5549 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5550 can be the number of a signal or its name (with or without the
5551 @samp{SIG} at the beginning); a list of signal numbers of the form
5552 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5553 known signals. Optional arguments @var{keywords}, described below,
5554 say what change to make.
5558 The keywords allowed by the @code{handle} command can be abbreviated.
5559 Their full names are:
5563 @value{GDBN} should not stop your program when this signal happens. It may
5564 still print a message telling you that the signal has come in.
5567 @value{GDBN} should stop your program when this signal happens. This implies
5568 the @code{print} keyword as well.
5571 @value{GDBN} should print a message when this signal happens.
5574 @value{GDBN} should not mention the occurrence of the signal at all. This
5575 implies the @code{nostop} keyword as well.
5579 @value{GDBN} should allow your program to see this signal; your program
5580 can handle the signal, or else it may terminate if the signal is fatal
5581 and not handled. @code{pass} and @code{noignore} are synonyms.
5585 @value{GDBN} should not allow your program to see this signal.
5586 @code{nopass} and @code{ignore} are synonyms.
5590 When a signal stops your program, the signal is not visible to the
5592 continue. Your program sees the signal then, if @code{pass} is in
5593 effect for the signal in question @emph{at that time}. In other words,
5594 after @value{GDBN} reports a signal, you can use the @code{handle}
5595 command with @code{pass} or @code{nopass} to control whether your
5596 program sees that signal when you continue.
5598 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5599 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5600 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5603 You can also use the @code{signal} command to prevent your program from
5604 seeing a signal, or cause it to see a signal it normally would not see,
5605 or to give it any signal at any time. For example, if your program stopped
5606 due to some sort of memory reference error, you might store correct
5607 values into the erroneous variables and continue, hoping to see more
5608 execution; but your program would probably terminate immediately as
5609 a result of the fatal signal once it saw the signal. To prevent this,
5610 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5613 @cindex stepping and signal handlers
5614 @anchor{stepping and signal handlers}
5616 @value{GDBN} optimizes for stepping the mainline code. If a signal
5617 that has @code{handle nostop} and @code{handle pass} set arrives while
5618 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
5619 in progress, @value{GDBN} lets the signal handler run and then resumes
5620 stepping the mainline code once the signal handler returns. In other
5621 words, @value{GDBN} steps over the signal handler. This prevents
5622 signals that you've specified as not interesting (with @code{handle
5623 nostop}) from changing the focus of debugging unexpectedly. Note that
5624 the signal handler itself may still hit a breakpoint, stop for another
5625 signal that has @code{handle stop} in effect, or for any other event
5626 that normally results in stopping the stepping command sooner. Also
5627 note that @value{GDBN} still informs you that the program received a
5628 signal if @code{handle print} is set.
5630 @anchor{stepping into signal handlers}
5632 If you set @code{handle pass} for a signal, and your program sets up a
5633 handler for it, then issuing a stepping command, such as @code{step}
5634 or @code{stepi}, when your program is stopped due to the signal will
5635 step @emph{into} the signal handler (if the target supports that).
5637 Likewise, if you use the @code{queue-signal} command to queue a signal
5638 to be delivered to the current thread when execution of the thread
5639 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
5640 stepping command will step into the signal handler.
5642 Here's an example, using @code{stepi} to step to the first instruction
5643 of @code{SIGUSR1}'s handler:
5646 (@value{GDBP}) handle SIGUSR1
5647 Signal Stop Print Pass to program Description
5648 SIGUSR1 Yes Yes Yes User defined signal 1
5652 Program received signal SIGUSR1, User defined signal 1.
5653 main () sigusr1.c:28
5656 sigusr1_handler () at sigusr1.c:9
5660 The same, but using @code{queue-signal} instead of waiting for the
5661 program to receive the signal first:
5666 (@value{GDBP}) queue-signal SIGUSR1
5668 sigusr1_handler () at sigusr1.c:9
5673 @cindex extra signal information
5674 @anchor{extra signal information}
5676 On some targets, @value{GDBN} can inspect extra signal information
5677 associated with the intercepted signal, before it is actually
5678 delivered to the program being debugged. This information is exported
5679 by the convenience variable @code{$_siginfo}, and consists of data
5680 that is passed by the kernel to the signal handler at the time of the
5681 receipt of a signal. The data type of the information itself is
5682 target dependent. You can see the data type using the @code{ptype
5683 $_siginfo} command. On Unix systems, it typically corresponds to the
5684 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5687 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5688 referenced address that raised a segmentation fault.
5692 (@value{GDBP}) continue
5693 Program received signal SIGSEGV, Segmentation fault.
5694 0x0000000000400766 in main ()
5696 (@value{GDBP}) ptype $_siginfo
5703 struct @{...@} _kill;
5704 struct @{...@} _timer;
5706 struct @{...@} _sigchld;
5707 struct @{...@} _sigfault;
5708 struct @{...@} _sigpoll;
5711 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5715 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5716 $1 = (void *) 0x7ffff7ff7000
5720 Depending on target support, @code{$_siginfo} may also be writable.
5723 @section Stopping and Starting Multi-thread Programs
5725 @cindex stopped threads
5726 @cindex threads, stopped
5728 @cindex continuing threads
5729 @cindex threads, continuing
5731 @value{GDBN} supports debugging programs with multiple threads
5732 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5733 are two modes of controlling execution of your program within the
5734 debugger. In the default mode, referred to as @dfn{all-stop mode},
5735 when any thread in your program stops (for example, at a breakpoint
5736 or while being stepped), all other threads in the program are also stopped by
5737 @value{GDBN}. On some targets, @value{GDBN} also supports
5738 @dfn{non-stop mode}, in which other threads can continue to run freely while
5739 you examine the stopped thread in the debugger.
5742 * All-Stop Mode:: All threads stop when GDB takes control
5743 * Non-Stop Mode:: Other threads continue to execute
5744 * Background Execution:: Running your program asynchronously
5745 * Thread-Specific Breakpoints:: Controlling breakpoints
5746 * Interrupted System Calls:: GDB may interfere with system calls
5747 * Observer Mode:: GDB does not alter program behavior
5751 @subsection All-Stop Mode
5753 @cindex all-stop mode
5755 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5756 @emph{all} threads of execution stop, not just the current thread. This
5757 allows you to examine the overall state of the program, including
5758 switching between threads, without worrying that things may change
5761 Conversely, whenever you restart the program, @emph{all} threads start
5762 executing. @emph{This is true even when single-stepping} with commands
5763 like @code{step} or @code{next}.
5765 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5766 Since thread scheduling is up to your debugging target's operating
5767 system (not controlled by @value{GDBN}), other threads may
5768 execute more than one statement while the current thread completes a
5769 single step. Moreover, in general other threads stop in the middle of a
5770 statement, rather than at a clean statement boundary, when the program
5773 You might even find your program stopped in another thread after
5774 continuing or even single-stepping. This happens whenever some other
5775 thread runs into a breakpoint, a signal, or an exception before the
5776 first thread completes whatever you requested.
5778 @cindex automatic thread selection
5779 @cindex switching threads automatically
5780 @cindex threads, automatic switching
5781 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5782 signal, it automatically selects the thread where that breakpoint or
5783 signal happened. @value{GDBN} alerts you to the context switch with a
5784 message such as @samp{[Switching to Thread @var{n}]} to identify the
5787 On some OSes, you can modify @value{GDBN}'s default behavior by
5788 locking the OS scheduler to allow only a single thread to run.
5791 @item set scheduler-locking @var{mode}
5792 @cindex scheduler locking mode
5793 @cindex lock scheduler
5794 Set the scheduler locking mode. If it is @code{off}, then there is no
5795 locking and any thread may run at any time. If @code{on}, then only the
5796 current thread may run when the inferior is resumed. The @code{step}
5797 mode optimizes for single-stepping; it prevents other threads
5798 from preempting the current thread while you are stepping, so that
5799 the focus of debugging does not change unexpectedly.
5800 Other threads only rarely (or never) get a chance to run
5801 when you step. They are more likely to run when you @samp{next} over a
5802 function call, and they are completely free to run when you use commands
5803 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5804 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5805 the current thread away from the thread that you are debugging.
5807 @item show scheduler-locking
5808 Display the current scheduler locking mode.
5811 @cindex resume threads of multiple processes simultaneously
5812 By default, when you issue one of the execution commands such as
5813 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5814 threads of the current inferior to run. For example, if @value{GDBN}
5815 is attached to two inferiors, each with two threads, the
5816 @code{continue} command resumes only the two threads of the current
5817 inferior. This is useful, for example, when you debug a program that
5818 forks and you want to hold the parent stopped (so that, for instance,
5819 it doesn't run to exit), while you debug the child. In other
5820 situations, you may not be interested in inspecting the current state
5821 of any of the processes @value{GDBN} is attached to, and you may want
5822 to resume them all until some breakpoint is hit. In the latter case,
5823 you can instruct @value{GDBN} to allow all threads of all the
5824 inferiors to run with the @w{@code{set schedule-multiple}} command.
5827 @kindex set schedule-multiple
5828 @item set schedule-multiple
5829 Set the mode for allowing threads of multiple processes to be resumed
5830 when an execution command is issued. When @code{on}, all threads of
5831 all processes are allowed to run. When @code{off}, only the threads
5832 of the current process are resumed. The default is @code{off}. The
5833 @code{scheduler-locking} mode takes precedence when set to @code{on},
5834 or while you are stepping and set to @code{step}.
5836 @item show schedule-multiple
5837 Display the current mode for resuming the execution of threads of
5842 @subsection Non-Stop Mode
5844 @cindex non-stop mode
5846 @c This section is really only a place-holder, and needs to be expanded
5847 @c with more details.
5849 For some multi-threaded targets, @value{GDBN} supports an optional
5850 mode of operation in which you can examine stopped program threads in
5851 the debugger while other threads continue to execute freely. This
5852 minimizes intrusion when debugging live systems, such as programs
5853 where some threads have real-time constraints or must continue to
5854 respond to external events. This is referred to as @dfn{non-stop} mode.
5856 In non-stop mode, when a thread stops to report a debugging event,
5857 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5858 threads as well, in contrast to the all-stop mode behavior. Additionally,
5859 execution commands such as @code{continue} and @code{step} apply by default
5860 only to the current thread in non-stop mode, rather than all threads as
5861 in all-stop mode. This allows you to control threads explicitly in
5862 ways that are not possible in all-stop mode --- for example, stepping
5863 one thread while allowing others to run freely, stepping
5864 one thread while holding all others stopped, or stepping several threads
5865 independently and simultaneously.
5867 To enter non-stop mode, use this sequence of commands before you run
5868 or attach to your program:
5871 # If using the CLI, pagination breaks non-stop.
5874 # Finally, turn it on!
5878 You can use these commands to manipulate the non-stop mode setting:
5881 @kindex set non-stop
5882 @item set non-stop on
5883 Enable selection of non-stop mode.
5884 @item set non-stop off
5885 Disable selection of non-stop mode.
5886 @kindex show non-stop
5888 Show the current non-stop enablement setting.
5891 Note these commands only reflect whether non-stop mode is enabled,
5892 not whether the currently-executing program is being run in non-stop mode.
5893 In particular, the @code{set non-stop} preference is only consulted when
5894 @value{GDBN} starts or connects to the target program, and it is generally
5895 not possible to switch modes once debugging has started. Furthermore,
5896 since not all targets support non-stop mode, even when you have enabled
5897 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5900 In non-stop mode, all execution commands apply only to the current thread
5901 by default. That is, @code{continue} only continues one thread.
5902 To continue all threads, issue @code{continue -a} or @code{c -a}.
5904 You can use @value{GDBN}'s background execution commands
5905 (@pxref{Background Execution}) to run some threads in the background
5906 while you continue to examine or step others from @value{GDBN}.
5907 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5908 always executed asynchronously in non-stop mode.
5910 Suspending execution is done with the @code{interrupt} command when
5911 running in the background, or @kbd{Ctrl-c} during foreground execution.
5912 In all-stop mode, this stops the whole process;
5913 but in non-stop mode the interrupt applies only to the current thread.
5914 To stop the whole program, use @code{interrupt -a}.
5916 Other execution commands do not currently support the @code{-a} option.
5918 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5919 that thread current, as it does in all-stop mode. This is because the
5920 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5921 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5922 changed to a different thread just as you entered a command to operate on the
5923 previously current thread.
5925 @node Background Execution
5926 @subsection Background Execution
5928 @cindex foreground execution
5929 @cindex background execution
5930 @cindex asynchronous execution
5931 @cindex execution, foreground, background and asynchronous
5933 @value{GDBN}'s execution commands have two variants: the normal
5934 foreground (synchronous) behavior, and a background
5935 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5936 the program to report that some thread has stopped before prompting for
5937 another command. In background execution, @value{GDBN} immediately gives
5938 a command prompt so that you can issue other commands while your program runs.
5940 If the target doesn't support async mode, @value{GDBN} issues an error
5941 message if you attempt to use the background execution commands.
5943 To specify background execution, add a @code{&} to the command. For example,
5944 the background form of the @code{continue} command is @code{continue&}, or
5945 just @code{c&}. The execution commands that accept background execution
5951 @xref{Starting, , Starting your Program}.
5955 @xref{Attach, , Debugging an Already-running Process}.
5959 @xref{Continuing and Stepping, step}.
5963 @xref{Continuing and Stepping, stepi}.
5967 @xref{Continuing and Stepping, next}.
5971 @xref{Continuing and Stepping, nexti}.
5975 @xref{Continuing and Stepping, continue}.
5979 @xref{Continuing and Stepping, finish}.
5983 @xref{Continuing and Stepping, until}.
5987 Background execution is especially useful in conjunction with non-stop
5988 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5989 However, you can also use these commands in the normal all-stop mode with
5990 the restriction that you cannot issue another execution command until the
5991 previous one finishes. Examples of commands that are valid in all-stop
5992 mode while the program is running include @code{help} and @code{info break}.
5994 You can interrupt your program while it is running in the background by
5995 using the @code{interrupt} command.
6002 Suspend execution of the running program. In all-stop mode,
6003 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6004 only the current thread. To stop the whole program in non-stop mode,
6005 use @code{interrupt -a}.
6008 @node Thread-Specific Breakpoints
6009 @subsection Thread-Specific Breakpoints
6011 When your program has multiple threads (@pxref{Threads,, Debugging
6012 Programs with Multiple Threads}), you can choose whether to set
6013 breakpoints on all threads, or on a particular thread.
6016 @cindex breakpoints and threads
6017 @cindex thread breakpoints
6018 @kindex break @dots{} thread @var{threadno}
6019 @item break @var{linespec} thread @var{threadno}
6020 @itemx break @var{linespec} thread @var{threadno} if @dots{}
6021 @var{linespec} specifies source lines; there are several ways of
6022 writing them (@pxref{Specify Location}), but the effect is always to
6023 specify some source line.
6025 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
6026 to specify that you only want @value{GDBN} to stop the program when a
6027 particular thread reaches this breakpoint. The @var{threadno} specifier
6028 is one of the numeric thread identifiers assigned by @value{GDBN}, shown
6029 in the first column of the @samp{info threads} display.
6031 If you do not specify @samp{thread @var{threadno}} when you set a
6032 breakpoint, the breakpoint applies to @emph{all} threads of your
6035 You can use the @code{thread} qualifier on conditional breakpoints as
6036 well; in this case, place @samp{thread @var{threadno}} before or
6037 after the breakpoint condition, like this:
6040 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6045 Thread-specific breakpoints are automatically deleted when
6046 @value{GDBN} detects the corresponding thread is no longer in the
6047 thread list. For example:
6051 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6054 There are several ways for a thread to disappear, such as a regular
6055 thread exit, but also when you detach from the process with the
6056 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6057 Process}), or if @value{GDBN} loses the remote connection
6058 (@pxref{Remote Debugging}), etc. Note that with some targets,
6059 @value{GDBN} is only able to detect a thread has exited when the user
6060 explictly asks for the thread list with the @code{info threads}
6063 @node Interrupted System Calls
6064 @subsection Interrupted System Calls
6066 @cindex thread breakpoints and system calls
6067 @cindex system calls and thread breakpoints
6068 @cindex premature return from system calls
6069 There is an unfortunate side effect when using @value{GDBN} to debug
6070 multi-threaded programs. If one thread stops for a
6071 breakpoint, or for some other reason, and another thread is blocked in a
6072 system call, then the system call may return prematurely. This is a
6073 consequence of the interaction between multiple threads and the signals
6074 that @value{GDBN} uses to implement breakpoints and other events that
6077 To handle this problem, your program should check the return value of
6078 each system call and react appropriately. This is good programming
6081 For example, do not write code like this:
6087 The call to @code{sleep} will return early if a different thread stops
6088 at a breakpoint or for some other reason.
6090 Instead, write this:
6095 unslept = sleep (unslept);
6098 A system call is allowed to return early, so the system is still
6099 conforming to its specification. But @value{GDBN} does cause your
6100 multi-threaded program to behave differently than it would without
6103 Also, @value{GDBN} uses internal breakpoints in the thread library to
6104 monitor certain events such as thread creation and thread destruction.
6105 When such an event happens, a system call in another thread may return
6106 prematurely, even though your program does not appear to stop.
6109 @subsection Observer Mode
6111 If you want to build on non-stop mode and observe program behavior
6112 without any chance of disruption by @value{GDBN}, you can set
6113 variables to disable all of the debugger's attempts to modify state,
6114 whether by writing memory, inserting breakpoints, etc. These operate
6115 at a low level, intercepting operations from all commands.
6117 When all of these are set to @code{off}, then @value{GDBN} is said to
6118 be @dfn{observer mode}. As a convenience, the variable
6119 @code{observer} can be set to disable these, plus enable non-stop
6122 Note that @value{GDBN} will not prevent you from making nonsensical
6123 combinations of these settings. For instance, if you have enabled
6124 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6125 then breakpoints that work by writing trap instructions into the code
6126 stream will still not be able to be placed.
6131 @item set observer on
6132 @itemx set observer off
6133 When set to @code{on}, this disables all the permission variables
6134 below (except for @code{insert-fast-tracepoints}), plus enables
6135 non-stop debugging. Setting this to @code{off} switches back to
6136 normal debugging, though remaining in non-stop mode.
6139 Show whether observer mode is on or off.
6141 @kindex may-write-registers
6142 @item set may-write-registers on
6143 @itemx set may-write-registers off
6144 This controls whether @value{GDBN} will attempt to alter the values of
6145 registers, such as with assignment expressions in @code{print}, or the
6146 @code{jump} command. It defaults to @code{on}.
6148 @item show may-write-registers
6149 Show the current permission to write registers.
6151 @kindex may-write-memory
6152 @item set may-write-memory on
6153 @itemx set may-write-memory off
6154 This controls whether @value{GDBN} will attempt to alter the contents
6155 of memory, such as with assignment expressions in @code{print}. It
6156 defaults to @code{on}.
6158 @item show may-write-memory
6159 Show the current permission to write memory.
6161 @kindex may-insert-breakpoints
6162 @item set may-insert-breakpoints on
6163 @itemx set may-insert-breakpoints off
6164 This controls whether @value{GDBN} will attempt to insert breakpoints.
6165 This affects all breakpoints, including internal breakpoints defined
6166 by @value{GDBN}. It defaults to @code{on}.
6168 @item show may-insert-breakpoints
6169 Show the current permission to insert breakpoints.
6171 @kindex may-insert-tracepoints
6172 @item set may-insert-tracepoints on
6173 @itemx set may-insert-tracepoints off
6174 This controls whether @value{GDBN} will attempt to insert (regular)
6175 tracepoints at the beginning of a tracing experiment. It affects only
6176 non-fast tracepoints, fast tracepoints being under the control of
6177 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6179 @item show may-insert-tracepoints
6180 Show the current permission to insert tracepoints.
6182 @kindex may-insert-fast-tracepoints
6183 @item set may-insert-fast-tracepoints on
6184 @itemx set may-insert-fast-tracepoints off
6185 This controls whether @value{GDBN} will attempt to insert fast
6186 tracepoints at the beginning of a tracing experiment. It affects only
6187 fast tracepoints, regular (non-fast) tracepoints being under the
6188 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6190 @item show may-insert-fast-tracepoints
6191 Show the current permission to insert fast tracepoints.
6193 @kindex may-interrupt
6194 @item set may-interrupt on
6195 @itemx set may-interrupt off
6196 This controls whether @value{GDBN} will attempt to interrupt or stop
6197 program execution. When this variable is @code{off}, the
6198 @code{interrupt} command will have no effect, nor will
6199 @kbd{Ctrl-c}. It defaults to @code{on}.
6201 @item show may-interrupt
6202 Show the current permission to interrupt or stop the program.
6206 @node Reverse Execution
6207 @chapter Running programs backward
6208 @cindex reverse execution
6209 @cindex running programs backward
6211 When you are debugging a program, it is not unusual to realize that
6212 you have gone too far, and some event of interest has already happened.
6213 If the target environment supports it, @value{GDBN} can allow you to
6214 ``rewind'' the program by running it backward.
6216 A target environment that supports reverse execution should be able
6217 to ``undo'' the changes in machine state that have taken place as the
6218 program was executing normally. Variables, registers etc.@: should
6219 revert to their previous values. Obviously this requires a great
6220 deal of sophistication on the part of the target environment; not
6221 all target environments can support reverse execution.
6223 When a program is executed in reverse, the instructions that
6224 have most recently been executed are ``un-executed'', in reverse
6225 order. The program counter runs backward, following the previous
6226 thread of execution in reverse. As each instruction is ``un-executed'',
6227 the values of memory and/or registers that were changed by that
6228 instruction are reverted to their previous states. After executing
6229 a piece of source code in reverse, all side effects of that code
6230 should be ``undone'', and all variables should be returned to their
6231 prior values@footnote{
6232 Note that some side effects are easier to undo than others. For instance,
6233 memory and registers are relatively easy, but device I/O is hard. Some
6234 targets may be able undo things like device I/O, and some may not.
6236 The contract between @value{GDBN} and the reverse executing target
6237 requires only that the target do something reasonable when
6238 @value{GDBN} tells it to execute backwards, and then report the
6239 results back to @value{GDBN}. Whatever the target reports back to
6240 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6241 assumes that the memory and registers that the target reports are in a
6242 consistant state, but @value{GDBN} accepts whatever it is given.
6245 If you are debugging in a target environment that supports
6246 reverse execution, @value{GDBN} provides the following commands.
6249 @kindex reverse-continue
6250 @kindex rc @r{(@code{reverse-continue})}
6251 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6252 @itemx rc @r{[}@var{ignore-count}@r{]}
6253 Beginning at the point where your program last stopped, start executing
6254 in reverse. Reverse execution will stop for breakpoints and synchronous
6255 exceptions (signals), just like normal execution. Behavior of
6256 asynchronous signals depends on the target environment.
6258 @kindex reverse-step
6259 @kindex rs @r{(@code{step})}
6260 @item reverse-step @r{[}@var{count}@r{]}
6261 Run the program backward until control reaches the start of a
6262 different source line; then stop it, and return control to @value{GDBN}.
6264 Like the @code{step} command, @code{reverse-step} will only stop
6265 at the beginning of a source line. It ``un-executes'' the previously
6266 executed source line. If the previous source line included calls to
6267 debuggable functions, @code{reverse-step} will step (backward) into
6268 the called function, stopping at the beginning of the @emph{last}
6269 statement in the called function (typically a return statement).
6271 Also, as with the @code{step} command, if non-debuggable functions are
6272 called, @code{reverse-step} will run thru them backward without stopping.
6274 @kindex reverse-stepi
6275 @kindex rsi @r{(@code{reverse-stepi})}
6276 @item reverse-stepi @r{[}@var{count}@r{]}
6277 Reverse-execute one machine instruction. Note that the instruction
6278 to be reverse-executed is @emph{not} the one pointed to by the program
6279 counter, but the instruction executed prior to that one. For instance,
6280 if the last instruction was a jump, @code{reverse-stepi} will take you
6281 back from the destination of the jump to the jump instruction itself.
6283 @kindex reverse-next
6284 @kindex rn @r{(@code{reverse-next})}
6285 @item reverse-next @r{[}@var{count}@r{]}
6286 Run backward to the beginning of the previous line executed in
6287 the current (innermost) stack frame. If the line contains function
6288 calls, they will be ``un-executed'' without stopping. Starting from
6289 the first line of a function, @code{reverse-next} will take you back
6290 to the caller of that function, @emph{before} the function was called,
6291 just as the normal @code{next} command would take you from the last
6292 line of a function back to its return to its caller
6293 @footnote{Unless the code is too heavily optimized.}.
6295 @kindex reverse-nexti
6296 @kindex rni @r{(@code{reverse-nexti})}
6297 @item reverse-nexti @r{[}@var{count}@r{]}
6298 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6299 in reverse, except that called functions are ``un-executed'' atomically.
6300 That is, if the previously executed instruction was a return from
6301 another function, @code{reverse-nexti} will continue to execute
6302 in reverse until the call to that function (from the current stack
6305 @kindex reverse-finish
6306 @item reverse-finish
6307 Just as the @code{finish} command takes you to the point where the
6308 current function returns, @code{reverse-finish} takes you to the point
6309 where it was called. Instead of ending up at the end of the current
6310 function invocation, you end up at the beginning.
6312 @kindex set exec-direction
6313 @item set exec-direction
6314 Set the direction of target execution.
6315 @item set exec-direction reverse
6316 @cindex execute forward or backward in time
6317 @value{GDBN} will perform all execution commands in reverse, until the
6318 exec-direction mode is changed to ``forward''. Affected commands include
6319 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6320 command cannot be used in reverse mode.
6321 @item set exec-direction forward
6322 @value{GDBN} will perform all execution commands in the normal fashion.
6323 This is the default.
6327 @node Process Record and Replay
6328 @chapter Recording Inferior's Execution and Replaying It
6329 @cindex process record and replay
6330 @cindex recording inferior's execution and replaying it
6332 On some platforms, @value{GDBN} provides a special @dfn{process record
6333 and replay} target that can record a log of the process execution, and
6334 replay it later with both forward and reverse execution commands.
6337 When this target is in use, if the execution log includes the record
6338 for the next instruction, @value{GDBN} will debug in @dfn{replay
6339 mode}. In the replay mode, the inferior does not really execute code
6340 instructions. Instead, all the events that normally happen during
6341 code execution are taken from the execution log. While code is not
6342 really executed in replay mode, the values of registers (including the
6343 program counter register) and the memory of the inferior are still
6344 changed as they normally would. Their contents are taken from the
6348 If the record for the next instruction is not in the execution log,
6349 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6350 inferior executes normally, and @value{GDBN} records the execution log
6353 The process record and replay target supports reverse execution
6354 (@pxref{Reverse Execution}), even if the platform on which the
6355 inferior runs does not. However, the reverse execution is limited in
6356 this case by the range of the instructions recorded in the execution
6357 log. In other words, reverse execution on platforms that don't
6358 support it directly can only be done in the replay mode.
6360 When debugging in the reverse direction, @value{GDBN} will work in
6361 replay mode as long as the execution log includes the record for the
6362 previous instruction; otherwise, it will work in record mode, if the
6363 platform supports reverse execution, or stop if not.
6365 For architecture environments that support process record and replay,
6366 @value{GDBN} provides the following commands:
6369 @kindex target record
6370 @kindex target record-full
6371 @kindex target record-btrace
6374 @kindex record btrace
6375 @kindex record btrace bts
6380 @kindex rec btrace bts
6382 @item record @var{method}
6383 This command starts the process record and replay target. The
6384 recording method can be specified as parameter. Without a parameter
6385 the command uses the @code{full} recording method. The following
6386 recording methods are available:
6390 Full record/replay recording using @value{GDBN}'s software record and
6391 replay implementation. This method allows replaying and reverse
6394 @item btrace @var{format}
6395 Hardware-supported instruction recording. This method does not record
6396 data. Further, the data is collected in a ring buffer so old data will
6397 be overwritten when the buffer is full. It allows limited replay and
6400 The recording format can be specified as parameter. Without a parameter
6401 the command chooses the recording format. The following recording
6402 formats are available:
6406 @cindex branch trace store
6407 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
6408 this format, the processor stores a from/to record for each executed
6409 branch in the btrace ring buffer.
6412 Not all recording formats may be available on all processors.
6415 The process record and replay target can only debug a process that is
6416 already running. Therefore, you need first to start the process with
6417 the @kbd{run} or @kbd{start} commands, and then start the recording
6418 with the @kbd{record @var{method}} command.
6420 Both @code{record @var{method}} and @code{rec @var{method}} are
6421 aliases of @code{target record-@var{method}}.
6423 @cindex displaced stepping, and process record and replay
6424 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6425 will be automatically disabled when process record and replay target
6426 is started. That's because the process record and replay target
6427 doesn't support displaced stepping.
6429 @cindex non-stop mode, and process record and replay
6430 @cindex asynchronous execution, and process record and replay
6431 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6432 the asynchronous execution mode (@pxref{Background Execution}), not
6433 all recording methods are available. The @code{full} recording method
6434 does not support these two modes.
6439 Stop the process record and replay target. When process record and
6440 replay target stops, the entire execution log will be deleted and the
6441 inferior will either be terminated, or will remain in its final state.
6443 When you stop the process record and replay target in record mode (at
6444 the end of the execution log), the inferior will be stopped at the
6445 next instruction that would have been recorded. In other words, if
6446 you record for a while and then stop recording, the inferior process
6447 will be left in the same state as if the recording never happened.
6449 On the other hand, if the process record and replay target is stopped
6450 while in replay mode (that is, not at the end of the execution log,
6451 but at some earlier point), the inferior process will become ``live''
6452 at that earlier state, and it will then be possible to continue the
6453 usual ``live'' debugging of the process from that state.
6455 When the inferior process exits, or @value{GDBN} detaches from it,
6456 process record and replay target will automatically stop itself.
6460 Go to a specific location in the execution log. There are several
6461 ways to specify the location to go to:
6464 @item record goto begin
6465 @itemx record goto start
6466 Go to the beginning of the execution log.
6468 @item record goto end
6469 Go to the end of the execution log.
6471 @item record goto @var{n}
6472 Go to instruction number @var{n} in the execution log.
6476 @item record save @var{filename}
6477 Save the execution log to a file @file{@var{filename}}.
6478 Default filename is @file{gdb_record.@var{process_id}}, where
6479 @var{process_id} is the process ID of the inferior.
6481 This command may not be available for all recording methods.
6483 @kindex record restore
6484 @item record restore @var{filename}
6485 Restore the execution log from a file @file{@var{filename}}.
6486 File must have been created with @code{record save}.
6488 @kindex set record full
6489 @item set record full insn-number-max @var{limit}
6490 @itemx set record full insn-number-max unlimited
6491 Set the limit of instructions to be recorded for the @code{full}
6492 recording method. Default value is 200000.
6494 If @var{limit} is a positive number, then @value{GDBN} will start
6495 deleting instructions from the log once the number of the record
6496 instructions becomes greater than @var{limit}. For every new recorded
6497 instruction, @value{GDBN} will delete the earliest recorded
6498 instruction to keep the number of recorded instructions at the limit.
6499 (Since deleting recorded instructions loses information, @value{GDBN}
6500 lets you control what happens when the limit is reached, by means of
6501 the @code{stop-at-limit} option, described below.)
6503 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6504 delete recorded instructions from the execution log. The number of
6505 recorded instructions is limited only by the available memory.
6507 @kindex show record full
6508 @item show record full insn-number-max
6509 Show the limit of instructions to be recorded with the @code{full}
6512 @item set record full stop-at-limit
6513 Control the behavior of the @code{full} recording method when the
6514 number of recorded instructions reaches the limit. If ON (the
6515 default), @value{GDBN} will stop when the limit is reached for the
6516 first time and ask you whether you want to stop the inferior or
6517 continue running it and recording the execution log. If you decide
6518 to continue recording, each new recorded instruction will cause the
6519 oldest one to be deleted.
6521 If this option is OFF, @value{GDBN} will automatically delete the
6522 oldest record to make room for each new one, without asking.
6524 @item show record full stop-at-limit
6525 Show the current setting of @code{stop-at-limit}.
6527 @item set record full memory-query
6528 Control the behavior when @value{GDBN} is unable to record memory
6529 changes caused by an instruction for the @code{full} recording method.
6530 If ON, @value{GDBN} will query whether to stop the inferior in that
6533 If this option is OFF (the default), @value{GDBN} will automatically
6534 ignore the effect of such instructions on memory. Later, when
6535 @value{GDBN} replays this execution log, it will mark the log of this
6536 instruction as not accessible, and it will not affect the replay
6539 @item show record full memory-query
6540 Show the current setting of @code{memory-query}.
6542 @kindex set record btrace
6543 The @code{btrace} record target does not trace data. As a
6544 convenience, when replaying, @value{GDBN} reads read-only memory off
6545 the live program directly, assuming that the addresses of the
6546 read-only areas don't change. This for example makes it possible to
6547 disassemble code while replaying, but not to print variables.
6548 In some cases, being able to inspect variables might be useful.
6549 You can use the following command for that:
6551 @item set record btrace replay-memory-access
6552 Control the behavior of the @code{btrace} recording method when
6553 accessing memory during replay. If @code{read-only} (the default),
6554 @value{GDBN} will only allow accesses to read-only memory.
6555 If @code{read-write}, @value{GDBN} will allow accesses to read-only
6556 and to read-write memory. Beware that the accessed memory corresponds
6557 to the live target and not necessarily to the current replay
6560 @kindex show record btrace
6561 @item show record btrace replay-memory-access
6562 Show the current setting of @code{replay-memory-access}.
6566 Show various statistics about the recording depending on the recording
6571 For the @code{full} recording method, it shows the state of process
6572 record and its in-memory execution log buffer, including:
6576 Whether in record mode or replay mode.
6578 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6580 Highest recorded instruction number.
6582 Current instruction about to be replayed (if in replay mode).
6584 Number of instructions contained in the execution log.
6586 Maximum number of instructions that may be contained in the execution log.
6590 For the @code{btrace} recording method, it shows the recording format,
6591 the number of instructions that have been recorded and the number of blocks
6592 of sequential control-flow that is formed by the recorded instructions.
6595 @kindex record delete
6598 When record target runs in replay mode (``in the past''), delete the
6599 subsequent execution log and begin to record a new execution log starting
6600 from the current address. This means you will abandon the previously
6601 recorded ``future'' and begin recording a new ``future''.
6603 @kindex record instruction-history
6604 @kindex rec instruction-history
6605 @item record instruction-history
6606 Disassembles instructions from the recorded execution log. By
6607 default, ten instructions are disassembled. This can be changed using
6608 the @code{set record instruction-history-size} command. Instructions
6609 are printed in execution order. There are several ways to specify
6610 what part of the execution log to disassemble:
6613 @item record instruction-history @var{insn}
6614 Disassembles ten instructions starting from instruction number
6617 @item record instruction-history @var{insn}, +/-@var{n}
6618 Disassembles @var{n} instructions around instruction number
6619 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6620 @var{n} instructions after instruction number @var{insn}. If
6621 @var{n} is preceded with @code{-}, disassembles @var{n}
6622 instructions before instruction number @var{insn}.
6624 @item record instruction-history
6625 Disassembles ten more instructions after the last disassembly.
6627 @item record instruction-history -
6628 Disassembles ten more instructions before the last disassembly.
6630 @item record instruction-history @var{begin} @var{end}
6631 Disassembles instructions beginning with instruction number
6632 @var{begin} until instruction number @var{end}. The instruction
6633 number @var{end} is included.
6636 This command may not be available for all recording methods.
6639 @item set record instruction-history-size @var{size}
6640 @itemx set record instruction-history-size unlimited
6641 Define how many instructions to disassemble in the @code{record
6642 instruction-history} command. The default value is 10.
6643 A @var{size} of @code{unlimited} means unlimited instructions.
6646 @item show record instruction-history-size
6647 Show how many instructions to disassemble in the @code{record
6648 instruction-history} command.
6650 @kindex record function-call-history
6651 @kindex rec function-call-history
6652 @item record function-call-history
6653 Prints the execution history at function granularity. It prints one
6654 line for each sequence of instructions that belong to the same
6655 function giving the name of that function, the source lines
6656 for this instruction sequence (if the @code{/l} modifier is
6657 specified), and the instructions numbers that form the sequence (if
6658 the @code{/i} modifier is specified). The function names are indented
6659 to reflect the call stack depth if the @code{/c} modifier is
6660 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
6664 (@value{GDBP}) @b{list 1, 10}
6675 (@value{GDBP}) @b{record function-call-history /ilc}
6676 1 bar inst 1,4 at foo.c:6,8
6677 2 foo inst 5,10 at foo.c:2,3
6678 3 bar inst 11,13 at foo.c:9,10
6681 By default, ten lines are printed. This can be changed using the
6682 @code{set record function-call-history-size} command. Functions are
6683 printed in execution order. There are several ways to specify what
6687 @item record function-call-history @var{func}
6688 Prints ten functions starting from function number @var{func}.
6690 @item record function-call-history @var{func}, +/-@var{n}
6691 Prints @var{n} functions around function number @var{func}. If
6692 @var{n} is preceded with @code{+}, prints @var{n} functions after
6693 function number @var{func}. If @var{n} is preceded with @code{-},
6694 prints @var{n} functions before function number @var{func}.
6696 @item record function-call-history
6697 Prints ten more functions after the last ten-line print.
6699 @item record function-call-history -
6700 Prints ten more functions before the last ten-line print.
6702 @item record function-call-history @var{begin} @var{end}
6703 Prints functions beginning with function number @var{begin} until
6704 function number @var{end}. The function number @var{end} is included.
6707 This command may not be available for all recording methods.
6709 @item set record function-call-history-size @var{size}
6710 @itemx set record function-call-history-size unlimited
6711 Define how many lines to print in the
6712 @code{record function-call-history} command. The default value is 10.
6713 A size of @code{unlimited} means unlimited lines.
6715 @item show record function-call-history-size
6716 Show how many lines to print in the
6717 @code{record function-call-history} command.
6722 @chapter Examining the Stack
6724 When your program has stopped, the first thing you need to know is where it
6725 stopped and how it got there.
6728 Each time your program performs a function call, information about the call
6730 That information includes the location of the call in your program,
6731 the arguments of the call,
6732 and the local variables of the function being called.
6733 The information is saved in a block of data called a @dfn{stack frame}.
6734 The stack frames are allocated in a region of memory called the @dfn{call
6737 When your program stops, the @value{GDBN} commands for examining the
6738 stack allow you to see all of this information.
6740 @cindex selected frame
6741 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6742 @value{GDBN} commands refer implicitly to the selected frame. In
6743 particular, whenever you ask @value{GDBN} for the value of a variable in
6744 your program, the value is found in the selected frame. There are
6745 special @value{GDBN} commands to select whichever frame you are
6746 interested in. @xref{Selection, ,Selecting a Frame}.
6748 When your program stops, @value{GDBN} automatically selects the
6749 currently executing frame and describes it briefly, similar to the
6750 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6753 * Frames:: Stack frames
6754 * Backtrace:: Backtraces
6755 * Frame Filter Management:: Managing frame filters
6756 * Selection:: Selecting a frame
6757 * Frame Info:: Information on a frame
6762 @section Stack Frames
6764 @cindex frame, definition
6766 The call stack is divided up into contiguous pieces called @dfn{stack
6767 frames}, or @dfn{frames} for short; each frame is the data associated
6768 with one call to one function. The frame contains the arguments given
6769 to the function, the function's local variables, and the address at
6770 which the function is executing.
6772 @cindex initial frame
6773 @cindex outermost frame
6774 @cindex innermost frame
6775 When your program is started, the stack has only one frame, that of the
6776 function @code{main}. This is called the @dfn{initial} frame or the
6777 @dfn{outermost} frame. Each time a function is called, a new frame is
6778 made. Each time a function returns, the frame for that function invocation
6779 is eliminated. If a function is recursive, there can be many frames for
6780 the same function. The frame for the function in which execution is
6781 actually occurring is called the @dfn{innermost} frame. This is the most
6782 recently created of all the stack frames that still exist.
6784 @cindex frame pointer
6785 Inside your program, stack frames are identified by their addresses. A
6786 stack frame consists of many bytes, each of which has its own address; each
6787 kind of computer has a convention for choosing one byte whose
6788 address serves as the address of the frame. Usually this address is kept
6789 in a register called the @dfn{frame pointer register}
6790 (@pxref{Registers, $fp}) while execution is going on in that frame.
6792 @cindex frame number
6793 @value{GDBN} assigns numbers to all existing stack frames, starting with
6794 zero for the innermost frame, one for the frame that called it,
6795 and so on upward. These numbers do not really exist in your program;
6796 they are assigned by @value{GDBN} to give you a way of designating stack
6797 frames in @value{GDBN} commands.
6799 @c The -fomit-frame-pointer below perennially causes hbox overflow
6800 @c underflow problems.
6801 @cindex frameless execution
6802 Some compilers provide a way to compile functions so that they operate
6803 without stack frames. (For example, the @value{NGCC} option
6805 @samp{-fomit-frame-pointer}
6807 generates functions without a frame.)
6808 This is occasionally done with heavily used library functions to save
6809 the frame setup time. @value{GDBN} has limited facilities for dealing
6810 with these function invocations. If the innermost function invocation
6811 has no stack frame, @value{GDBN} nevertheless regards it as though
6812 it had a separate frame, which is numbered zero as usual, allowing
6813 correct tracing of the function call chain. However, @value{GDBN} has
6814 no provision for frameless functions elsewhere in the stack.
6817 @kindex frame@r{, command}
6818 @cindex current stack frame
6819 @item frame @r{[}@var{framespec}@r{]}
6820 The @code{frame} command allows you to move from one stack frame to another,
6821 and to print the stack frame you select. The @var{framespec} may be either the
6822 address of the frame or the stack frame number. Without an argument,
6823 @code{frame} prints the current stack frame.
6825 @kindex select-frame
6826 @cindex selecting frame silently
6828 The @code{select-frame} command allows you to move from one stack frame
6829 to another without printing the frame. This is the silent version of
6837 @cindex call stack traces
6838 A backtrace is a summary of how your program got where it is. It shows one
6839 line per frame, for many frames, starting with the currently executing
6840 frame (frame zero), followed by its caller (frame one), and on up the
6843 @anchor{backtrace-command}
6846 @kindex bt @r{(@code{backtrace})}
6849 Print a backtrace of the entire stack: one line per frame for all
6850 frames in the stack.
6852 You can stop the backtrace at any time by typing the system interrupt
6853 character, normally @kbd{Ctrl-c}.
6855 @item backtrace @var{n}
6857 Similar, but print only the innermost @var{n} frames.
6859 @item backtrace -@var{n}
6861 Similar, but print only the outermost @var{n} frames.
6863 @item backtrace full
6865 @itemx bt full @var{n}
6866 @itemx bt full -@var{n}
6867 Print the values of the local variables also. As described above,
6868 @var{n} specifies the number of frames to print.
6870 @item backtrace no-filters
6871 @itemx bt no-filters
6872 @itemx bt no-filters @var{n}
6873 @itemx bt no-filters -@var{n}
6874 @itemx bt no-filters full
6875 @itemx bt no-filters full @var{n}
6876 @itemx bt no-filters full -@var{n}
6877 Do not run Python frame filters on this backtrace. @xref{Frame
6878 Filter API}, for more information. Additionally use @ref{disable
6879 frame-filter all} to turn off all frame filters. This is only
6880 relevant when @value{GDBN} has been configured with @code{Python}
6886 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6887 are additional aliases for @code{backtrace}.
6889 @cindex multiple threads, backtrace
6890 In a multi-threaded program, @value{GDBN} by default shows the
6891 backtrace only for the current thread. To display the backtrace for
6892 several or all of the threads, use the command @code{thread apply}
6893 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6894 apply all backtrace}, @value{GDBN} will display the backtrace for all
6895 the threads; this is handy when you debug a core dump of a
6896 multi-threaded program.
6898 Each line in the backtrace shows the frame number and the function name.
6899 The program counter value is also shown---unless you use @code{set
6900 print address off}. The backtrace also shows the source file name and
6901 line number, as well as the arguments to the function. The program
6902 counter value is omitted if it is at the beginning of the code for that
6905 Here is an example of a backtrace. It was made with the command
6906 @samp{bt 3}, so it shows the innermost three frames.
6910 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6912 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6913 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6915 (More stack frames follow...)
6920 The display for frame zero does not begin with a program counter
6921 value, indicating that your program has stopped at the beginning of the
6922 code for line @code{993} of @code{builtin.c}.
6925 The value of parameter @code{data} in frame 1 has been replaced by
6926 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6927 only if it is a scalar (integer, pointer, enumeration, etc). See command
6928 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6929 on how to configure the way function parameter values are printed.
6931 @cindex optimized out, in backtrace
6932 @cindex function call arguments, optimized out
6933 If your program was compiled with optimizations, some compilers will
6934 optimize away arguments passed to functions if those arguments are
6935 never used after the call. Such optimizations generate code that
6936 passes arguments through registers, but doesn't store those arguments
6937 in the stack frame. @value{GDBN} has no way of displaying such
6938 arguments in stack frames other than the innermost one. Here's what
6939 such a backtrace might look like:
6943 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6945 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6946 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6948 (More stack frames follow...)
6953 The values of arguments that were not saved in their stack frames are
6954 shown as @samp{<optimized out>}.
6956 If you need to display the values of such optimized-out arguments,
6957 either deduce that from other variables whose values depend on the one
6958 you are interested in, or recompile without optimizations.
6960 @cindex backtrace beyond @code{main} function
6961 @cindex program entry point
6962 @cindex startup code, and backtrace
6963 Most programs have a standard user entry point---a place where system
6964 libraries and startup code transition into user code. For C this is
6965 @code{main}@footnote{
6966 Note that embedded programs (the so-called ``free-standing''
6967 environment) are not required to have a @code{main} function as the
6968 entry point. They could even have multiple entry points.}.
6969 When @value{GDBN} finds the entry function in a backtrace
6970 it will terminate the backtrace, to avoid tracing into highly
6971 system-specific (and generally uninteresting) code.
6973 If you need to examine the startup code, or limit the number of levels
6974 in a backtrace, you can change this behavior:
6977 @item set backtrace past-main
6978 @itemx set backtrace past-main on
6979 @kindex set backtrace
6980 Backtraces will continue past the user entry point.
6982 @item set backtrace past-main off
6983 Backtraces will stop when they encounter the user entry point. This is the
6986 @item show backtrace past-main
6987 @kindex show backtrace
6988 Display the current user entry point backtrace policy.
6990 @item set backtrace past-entry
6991 @itemx set backtrace past-entry on
6992 Backtraces will continue past the internal entry point of an application.
6993 This entry point is encoded by the linker when the application is built,
6994 and is likely before the user entry point @code{main} (or equivalent) is called.
6996 @item set backtrace past-entry off
6997 Backtraces will stop when they encounter the internal entry point of an
6998 application. This is the default.
7000 @item show backtrace past-entry
7001 Display the current internal entry point backtrace policy.
7003 @item set backtrace limit @var{n}
7004 @itemx set backtrace limit 0
7005 @itemx set backtrace limit unlimited
7006 @cindex backtrace limit
7007 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7008 or zero means unlimited levels.
7010 @item show backtrace limit
7011 Display the current limit on backtrace levels.
7014 You can control how file names are displayed.
7017 @item set filename-display
7018 @itemx set filename-display relative
7019 @cindex filename-display
7020 Display file names relative to the compilation directory. This is the default.
7022 @item set filename-display basename
7023 Display only basename of a filename.
7025 @item set filename-display absolute
7026 Display an absolute filename.
7028 @item show filename-display
7029 Show the current way to display filenames.
7032 @node Frame Filter Management
7033 @section Management of Frame Filters.
7034 @cindex managing frame filters
7036 Frame filters are Python based utilities to manage and decorate the
7037 output of frames. @xref{Frame Filter API}, for further information.
7039 Managing frame filters is performed by several commands available
7040 within @value{GDBN}, detailed here.
7043 @kindex info frame-filter
7044 @item info frame-filter
7045 Print a list of installed frame filters from all dictionaries, showing
7046 their name, priority and enabled status.
7048 @kindex disable frame-filter
7049 @anchor{disable frame-filter all}
7050 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
7051 Disable a frame filter in the dictionary matching
7052 @var{filter-dictionary} and @var{filter-name}. The
7053 @var{filter-dictionary} may be @code{all}, @code{global},
7054 @code{progspace}, or the name of the object file where the frame filter
7055 dictionary resides. When @code{all} is specified, all frame filters
7056 across all dictionaries are disabled. The @var{filter-name} is the name
7057 of the frame filter and is used when @code{all} is not the option for
7058 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
7059 may be enabled again later.
7061 @kindex enable frame-filter
7062 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
7063 Enable a frame filter in the dictionary matching
7064 @var{filter-dictionary} and @var{filter-name}. The
7065 @var{filter-dictionary} may be @code{all}, @code{global},
7066 @code{progspace} or the name of the object file where the frame filter
7067 dictionary resides. When @code{all} is specified, all frame filters across
7068 all dictionaries are enabled. The @var{filter-name} is the name of the frame
7069 filter and is used when @code{all} is not the option for
7070 @var{filter-dictionary}.
7075 (gdb) info frame-filter
7077 global frame-filters:
7078 Priority Enabled Name
7079 1000 No PrimaryFunctionFilter
7082 progspace /build/test frame-filters:
7083 Priority Enabled Name
7084 100 Yes ProgspaceFilter
7086 objfile /build/test frame-filters:
7087 Priority Enabled Name
7088 999 Yes BuildProgra Filter
7090 (gdb) disable frame-filter /build/test BuildProgramFilter
7091 (gdb) info frame-filter
7093 global frame-filters:
7094 Priority Enabled Name
7095 1000 No PrimaryFunctionFilter
7098 progspace /build/test frame-filters:
7099 Priority Enabled Name
7100 100 Yes ProgspaceFilter
7102 objfile /build/test frame-filters:
7103 Priority Enabled Name
7104 999 No BuildProgramFilter
7106 (gdb) enable frame-filter global PrimaryFunctionFilter
7107 (gdb) info frame-filter
7109 global frame-filters:
7110 Priority Enabled Name
7111 1000 Yes PrimaryFunctionFilter
7114 progspace /build/test frame-filters:
7115 Priority Enabled Name
7116 100 Yes ProgspaceFilter
7118 objfile /build/test frame-filters:
7119 Priority Enabled Name
7120 999 No BuildProgramFilter
7123 @kindex set frame-filter priority
7124 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
7125 Set the @var{priority} of a frame filter in the dictionary matching
7126 @var{filter-dictionary}, and the frame filter name matching
7127 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7128 @code{progspace} or the name of the object file where the frame filter
7129 dictionary resides. The @var{priority} is an integer.
7131 @kindex show frame-filter priority
7132 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
7133 Show the @var{priority} of a frame filter in the dictionary matching
7134 @var{filter-dictionary}, and the frame filter name matching
7135 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7136 @code{progspace} or the name of the object file where the frame filter
7142 (gdb) info frame-filter
7144 global frame-filters:
7145 Priority Enabled Name
7146 1000 Yes PrimaryFunctionFilter
7149 progspace /build/test frame-filters:
7150 Priority Enabled Name
7151 100 Yes ProgspaceFilter
7153 objfile /build/test frame-filters:
7154 Priority Enabled Name
7155 999 No BuildProgramFilter
7157 (gdb) set frame-filter priority global Reverse 50
7158 (gdb) info frame-filter
7160 global frame-filters:
7161 Priority Enabled Name
7162 1000 Yes PrimaryFunctionFilter
7165 progspace /build/test frame-filters:
7166 Priority Enabled Name
7167 100 Yes ProgspaceFilter
7169 objfile /build/test frame-filters:
7170 Priority Enabled Name
7171 999 No BuildProgramFilter
7176 @section Selecting a Frame
7178 Most commands for examining the stack and other data in your program work on
7179 whichever stack frame is selected at the moment. Here are the commands for
7180 selecting a stack frame; all of them finish by printing a brief description
7181 of the stack frame just selected.
7184 @kindex frame@r{, selecting}
7185 @kindex f @r{(@code{frame})}
7188 Select frame number @var{n}. Recall that frame zero is the innermost
7189 (currently executing) frame, frame one is the frame that called the
7190 innermost one, and so on. The highest-numbered frame is the one for
7193 @item frame @var{addr}
7195 Select the frame at address @var{addr}. This is useful mainly if the
7196 chaining of stack frames has been damaged by a bug, making it
7197 impossible for @value{GDBN} to assign numbers properly to all frames. In
7198 addition, this can be useful when your program has multiple stacks and
7199 switches between them.
7201 On the SPARC architecture, @code{frame} needs two addresses to
7202 select an arbitrary frame: a frame pointer and a stack pointer.
7204 On the @acronym{MIPS} and Alpha architecture, it needs two addresses: a stack
7205 pointer and a program counter.
7207 On the 29k architecture, it needs three addresses: a register stack
7208 pointer, a program counter, and a memory stack pointer.
7212 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7213 numbers @var{n}, this advances toward the outermost frame, to higher
7214 frame numbers, to frames that have existed longer.
7217 @kindex do @r{(@code{down})}
7219 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7220 positive numbers @var{n}, this advances toward the innermost frame, to
7221 lower frame numbers, to frames that were created more recently.
7222 You may abbreviate @code{down} as @code{do}.
7225 All of these commands end by printing two lines of output describing the
7226 frame. The first line shows the frame number, the function name, the
7227 arguments, and the source file and line number of execution in that
7228 frame. The second line shows the text of that source line.
7236 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7238 10 read_input_file (argv[i]);
7242 After such a printout, the @code{list} command with no arguments
7243 prints ten lines centered on the point of execution in the frame.
7244 You can also edit the program at the point of execution with your favorite
7245 editing program by typing @code{edit}.
7246 @xref{List, ,Printing Source Lines},
7250 @kindex down-silently
7252 @item up-silently @var{n}
7253 @itemx down-silently @var{n}
7254 These two commands are variants of @code{up} and @code{down},
7255 respectively; they differ in that they do their work silently, without
7256 causing display of the new frame. They are intended primarily for use
7257 in @value{GDBN} command scripts, where the output might be unnecessary and
7262 @section Information About a Frame
7264 There are several other commands to print information about the selected
7270 When used without any argument, this command does not change which
7271 frame is selected, but prints a brief description of the currently
7272 selected stack frame. It can be abbreviated @code{f}. With an
7273 argument, this command is used to select a stack frame.
7274 @xref{Selection, ,Selecting a Frame}.
7277 @kindex info f @r{(@code{info frame})}
7280 This command prints a verbose description of the selected stack frame,
7285 the address of the frame
7287 the address of the next frame down (called by this frame)
7289 the address of the next frame up (caller of this frame)
7291 the language in which the source code corresponding to this frame is written
7293 the address of the frame's arguments
7295 the address of the frame's local variables
7297 the program counter saved in it (the address of execution in the caller frame)
7299 which registers were saved in the frame
7302 @noindent The verbose description is useful when
7303 something has gone wrong that has made the stack format fail to fit
7304 the usual conventions.
7306 @item info frame @var{addr}
7307 @itemx info f @var{addr}
7308 Print a verbose description of the frame at address @var{addr}, without
7309 selecting that frame. The selected frame remains unchanged by this
7310 command. This requires the same kind of address (more than one for some
7311 architectures) that you specify in the @code{frame} command.
7312 @xref{Selection, ,Selecting a Frame}.
7316 Print the arguments of the selected frame, each on a separate line.
7320 Print the local variables of the selected frame, each on a separate
7321 line. These are all variables (declared either static or automatic)
7322 accessible at the point of execution of the selected frame.
7328 @chapter Examining Source Files
7330 @value{GDBN} can print parts of your program's source, since the debugging
7331 information recorded in the program tells @value{GDBN} what source files were
7332 used to build it. When your program stops, @value{GDBN} spontaneously prints
7333 the line where it stopped. Likewise, when you select a stack frame
7334 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7335 execution in that frame has stopped. You can print other portions of
7336 source files by explicit command.
7338 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7339 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7340 @value{GDBN} under @sc{gnu} Emacs}.
7343 * List:: Printing source lines
7344 * Specify Location:: How to specify code locations
7345 * Edit:: Editing source files
7346 * Search:: Searching source files
7347 * Source Path:: Specifying source directories
7348 * Machine Code:: Source and machine code
7352 @section Printing Source Lines
7355 @kindex l @r{(@code{list})}
7356 To print lines from a source file, use the @code{list} command
7357 (abbreviated @code{l}). By default, ten lines are printed.
7358 There are several ways to specify what part of the file you want to
7359 print; see @ref{Specify Location}, for the full list.
7361 Here are the forms of the @code{list} command most commonly used:
7364 @item list @var{linenum}
7365 Print lines centered around line number @var{linenum} in the
7366 current source file.
7368 @item list @var{function}
7369 Print lines centered around the beginning of function
7373 Print more lines. If the last lines printed were printed with a
7374 @code{list} command, this prints lines following the last lines
7375 printed; however, if the last line printed was a solitary line printed
7376 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7377 Stack}), this prints lines centered around that line.
7380 Print lines just before the lines last printed.
7383 @cindex @code{list}, how many lines to display
7384 By default, @value{GDBN} prints ten source lines with any of these forms of
7385 the @code{list} command. You can change this using @code{set listsize}:
7388 @kindex set listsize
7389 @item set listsize @var{count}
7390 @itemx set listsize unlimited
7391 Make the @code{list} command display @var{count} source lines (unless
7392 the @code{list} argument explicitly specifies some other number).
7393 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7395 @kindex show listsize
7397 Display the number of lines that @code{list} prints.
7400 Repeating a @code{list} command with @key{RET} discards the argument,
7401 so it is equivalent to typing just @code{list}. This is more useful
7402 than listing the same lines again. An exception is made for an
7403 argument of @samp{-}; that argument is preserved in repetition so that
7404 each repetition moves up in the source file.
7406 In general, the @code{list} command expects you to supply zero, one or two
7407 @dfn{linespecs}. Linespecs specify source lines; there are several ways
7408 of writing them (@pxref{Specify Location}), but the effect is always
7409 to specify some source line.
7411 Here is a complete description of the possible arguments for @code{list}:
7414 @item list @var{linespec}
7415 Print lines centered around the line specified by @var{linespec}.
7417 @item list @var{first},@var{last}
7418 Print lines from @var{first} to @var{last}. Both arguments are
7419 linespecs. When a @code{list} command has two linespecs, and the
7420 source file of the second linespec is omitted, this refers to
7421 the same source file as the first linespec.
7423 @item list ,@var{last}
7424 Print lines ending with @var{last}.
7426 @item list @var{first},
7427 Print lines starting with @var{first}.
7430 Print lines just after the lines last printed.
7433 Print lines just before the lines last printed.
7436 As described in the preceding table.
7439 @node Specify Location
7440 @section Specifying a Location
7441 @cindex specifying location
7444 Several @value{GDBN} commands accept arguments that specify a location
7445 of your program's code. Since @value{GDBN} is a source-level
7446 debugger, a location usually specifies some line in the source code;
7447 for that reason, locations are also known as @dfn{linespecs}.
7449 Here are all the different ways of specifying a code location that
7450 @value{GDBN} understands:
7454 Specifies the line number @var{linenum} of the current source file.
7457 @itemx +@var{offset}
7458 Specifies the line @var{offset} lines before or after the @dfn{current
7459 line}. For the @code{list} command, the current line is the last one
7460 printed; for the breakpoint commands, this is the line at which
7461 execution stopped in the currently selected @dfn{stack frame}
7462 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7463 used as the second of the two linespecs in a @code{list} command,
7464 this specifies the line @var{offset} lines up or down from the first
7467 @item @var{filename}:@var{linenum}
7468 Specifies the line @var{linenum} in the source file @var{filename}.
7469 If @var{filename} is a relative file name, then it will match any
7470 source file name with the same trailing components. For example, if
7471 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7472 name of @file{/build/trunk/gcc/expr.c}, but not
7473 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7475 @item @var{function}
7476 Specifies the line that begins the body of the function @var{function}.
7477 For example, in C, this is the line with the open brace.
7479 @item @var{function}:@var{label}
7480 Specifies the line where @var{label} appears in @var{function}.
7482 @item @var{filename}:@var{function}
7483 Specifies the line that begins the body of the function @var{function}
7484 in the file @var{filename}. You only need the file name with a
7485 function name to avoid ambiguity when there are identically named
7486 functions in different source files.
7489 Specifies the line at which the label named @var{label} appears.
7490 @value{GDBN} searches for the label in the function corresponding to
7491 the currently selected stack frame. If there is no current selected
7492 stack frame (for instance, if the inferior is not running), then
7493 @value{GDBN} will not search for a label.
7495 @item *@var{address}
7496 Specifies the program address @var{address}. For line-oriented
7497 commands, such as @code{list} and @code{edit}, this specifies a source
7498 line that contains @var{address}. For @code{break} and other
7499 breakpoint oriented commands, this can be used to set breakpoints in
7500 parts of your program which do not have debugging information or
7503 Here @var{address} may be any expression valid in the current working
7504 language (@pxref{Languages, working language}) that specifies a code
7505 address. In addition, as a convenience, @value{GDBN} extends the
7506 semantics of expressions used in locations to cover the situations
7507 that frequently happen during debugging. Here are the various forms
7511 @item @var{expression}
7512 Any expression valid in the current working language.
7514 @item @var{funcaddr}
7515 An address of a function or procedure derived from its name. In C,
7516 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
7517 simply the function's name @var{function} (and actually a special case
7518 of a valid expression). In Pascal and Modula-2, this is
7519 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7520 (although the Pascal form also works).
7522 This form specifies the address of the function's first instruction,
7523 before the stack frame and arguments have been set up.
7525 @item '@var{filename}'::@var{funcaddr}
7526 Like @var{funcaddr} above, but also specifies the name of the source
7527 file explicitly. This is useful if the name of the function does not
7528 specify the function unambiguously, e.g., if there are several
7529 functions with identical names in different source files.
7532 @cindex breakpoint at static probe point
7533 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7534 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7535 applications to embed static probes. @xref{Static Probe Points}, for more
7536 information on finding and using static probes. This form of linespec
7537 specifies the location of such a static probe.
7539 If @var{objfile} is given, only probes coming from that shared library
7540 or executable matching @var{objfile} as a regular expression are considered.
7541 If @var{provider} is given, then only probes from that provider are considered.
7542 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7543 each one of those probes.
7549 @section Editing Source Files
7550 @cindex editing source files
7553 @kindex e @r{(@code{edit})}
7554 To edit the lines in a source file, use the @code{edit} command.
7555 The editing program of your choice
7556 is invoked with the current line set to
7557 the active line in the program.
7558 Alternatively, there are several ways to specify what part of the file you
7559 want to print if you want to see other parts of the program:
7562 @item edit @var{location}
7563 Edit the source file specified by @code{location}. Editing starts at
7564 that @var{location}, e.g., at the specified source line of the
7565 specified file. @xref{Specify Location}, for all the possible forms
7566 of the @var{location} argument; here are the forms of the @code{edit}
7567 command most commonly used:
7570 @item edit @var{number}
7571 Edit the current source file with @var{number} as the active line number.
7573 @item edit @var{function}
7574 Edit the file containing @var{function} at the beginning of its definition.
7579 @subsection Choosing your Editor
7580 You can customize @value{GDBN} to use any editor you want
7582 The only restriction is that your editor (say @code{ex}), recognizes the
7583 following command-line syntax:
7585 ex +@var{number} file
7587 The optional numeric value +@var{number} specifies the number of the line in
7588 the file where to start editing.}.
7589 By default, it is @file{@value{EDITOR}}, but you can change this
7590 by setting the environment variable @code{EDITOR} before using
7591 @value{GDBN}. For example, to configure @value{GDBN} to use the
7592 @code{vi} editor, you could use these commands with the @code{sh} shell:
7598 or in the @code{csh} shell,
7600 setenv EDITOR /usr/bin/vi
7605 @section Searching Source Files
7606 @cindex searching source files
7608 There are two commands for searching through the current source file for a
7613 @kindex forward-search
7614 @kindex fo @r{(@code{forward-search})}
7615 @item forward-search @var{regexp}
7616 @itemx search @var{regexp}
7617 The command @samp{forward-search @var{regexp}} checks each line,
7618 starting with the one following the last line listed, for a match for
7619 @var{regexp}. It lists the line that is found. You can use the
7620 synonym @samp{search @var{regexp}} or abbreviate the command name as
7623 @kindex reverse-search
7624 @item reverse-search @var{regexp}
7625 The command @samp{reverse-search @var{regexp}} checks each line, starting
7626 with the one before the last line listed and going backward, for a match
7627 for @var{regexp}. It lists the line that is found. You can abbreviate
7628 this command as @code{rev}.
7632 @section Specifying Source Directories
7635 @cindex directories for source files
7636 Executable programs sometimes do not record the directories of the source
7637 files from which they were compiled, just the names. Even when they do,
7638 the directories could be moved between the compilation and your debugging
7639 session. @value{GDBN} has a list of directories to search for source files;
7640 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
7641 it tries all the directories in the list, in the order they are present
7642 in the list, until it finds a file with the desired name.
7644 For example, suppose an executable references the file
7645 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
7646 @file{/mnt/cross}. The file is first looked up literally; if this
7647 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
7648 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
7649 message is printed. @value{GDBN} does not look up the parts of the
7650 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
7651 Likewise, the subdirectories of the source path are not searched: if
7652 the source path is @file{/mnt/cross}, and the binary refers to
7653 @file{foo.c}, @value{GDBN} would not find it under
7654 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7656 Plain file names, relative file names with leading directories, file
7657 names containing dots, etc.@: are all treated as described above; for
7658 instance, if the source path is @file{/mnt/cross}, and the source file
7659 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7660 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7661 that---@file{/mnt/cross/foo.c}.
7663 Note that the executable search path is @emph{not} used to locate the
7666 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7667 any information it has cached about where source files are found and where
7668 each line is in the file.
7672 When you start @value{GDBN}, its source path includes only @samp{cdir}
7673 and @samp{cwd}, in that order.
7674 To add other directories, use the @code{directory} command.
7676 The search path is used to find both program source files and @value{GDBN}
7677 script files (read using the @samp{-command} option and @samp{source} command).
7679 In addition to the source path, @value{GDBN} provides a set of commands
7680 that manage a list of source path substitution rules. A @dfn{substitution
7681 rule} specifies how to rewrite source directories stored in the program's
7682 debug information in case the sources were moved to a different
7683 directory between compilation and debugging. A rule is made of
7684 two strings, the first specifying what needs to be rewritten in
7685 the path, and the second specifying how it should be rewritten.
7686 In @ref{set substitute-path}, we name these two parts @var{from} and
7687 @var{to} respectively. @value{GDBN} does a simple string replacement
7688 of @var{from} with @var{to} at the start of the directory part of the
7689 source file name, and uses that result instead of the original file
7690 name to look up the sources.
7692 Using the previous example, suppose the @file{foo-1.0} tree has been
7693 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7694 @value{GDBN} to replace @file{/usr/src} in all source path names with
7695 @file{/mnt/cross}. The first lookup will then be
7696 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7697 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7698 substitution rule, use the @code{set substitute-path} command
7699 (@pxref{set substitute-path}).
7701 To avoid unexpected substitution results, a rule is applied only if the
7702 @var{from} part of the directory name ends at a directory separator.
7703 For instance, a rule substituting @file{/usr/source} into
7704 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7705 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7706 is applied only at the beginning of the directory name, this rule will
7707 not be applied to @file{/root/usr/source/baz.c} either.
7709 In many cases, you can achieve the same result using the @code{directory}
7710 command. However, @code{set substitute-path} can be more efficient in
7711 the case where the sources are organized in a complex tree with multiple
7712 subdirectories. With the @code{directory} command, you need to add each
7713 subdirectory of your project. If you moved the entire tree while
7714 preserving its internal organization, then @code{set substitute-path}
7715 allows you to direct the debugger to all the sources with one single
7718 @code{set substitute-path} is also more than just a shortcut command.
7719 The source path is only used if the file at the original location no
7720 longer exists. On the other hand, @code{set substitute-path} modifies
7721 the debugger behavior to look at the rewritten location instead. So, if
7722 for any reason a source file that is not relevant to your executable is
7723 located at the original location, a substitution rule is the only
7724 method available to point @value{GDBN} at the new location.
7726 @cindex @samp{--with-relocated-sources}
7727 @cindex default source path substitution
7728 You can configure a default source path substitution rule by
7729 configuring @value{GDBN} with the
7730 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7731 should be the name of a directory under @value{GDBN}'s configured
7732 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7733 directory names in debug information under @var{dir} will be adjusted
7734 automatically if the installed @value{GDBN} is moved to a new
7735 location. This is useful if @value{GDBN}, libraries or executables
7736 with debug information and corresponding source code are being moved
7740 @item directory @var{dirname} @dots{}
7741 @item dir @var{dirname} @dots{}
7742 Add directory @var{dirname} to the front of the source path. Several
7743 directory names may be given to this command, separated by @samp{:}
7744 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7745 part of absolute file names) or
7746 whitespace. You may specify a directory that is already in the source
7747 path; this moves it forward, so @value{GDBN} searches it sooner.
7751 @vindex $cdir@r{, convenience variable}
7752 @vindex $cwd@r{, convenience variable}
7753 @cindex compilation directory
7754 @cindex current directory
7755 @cindex working directory
7756 @cindex directory, current
7757 @cindex directory, compilation
7758 You can use the string @samp{$cdir} to refer to the compilation
7759 directory (if one is recorded), and @samp{$cwd} to refer to the current
7760 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7761 tracks the current working directory as it changes during your @value{GDBN}
7762 session, while the latter is immediately expanded to the current
7763 directory at the time you add an entry to the source path.
7766 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7768 @c RET-repeat for @code{directory} is explicitly disabled, but since
7769 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7771 @item set directories @var{path-list}
7772 @kindex set directories
7773 Set the source path to @var{path-list}.
7774 @samp{$cdir:$cwd} are added if missing.
7776 @item show directories
7777 @kindex show directories
7778 Print the source path: show which directories it contains.
7780 @anchor{set substitute-path}
7781 @item set substitute-path @var{from} @var{to}
7782 @kindex set substitute-path
7783 Define a source path substitution rule, and add it at the end of the
7784 current list of existing substitution rules. If a rule with the same
7785 @var{from} was already defined, then the old rule is also deleted.
7787 For example, if the file @file{/foo/bar/baz.c} was moved to
7788 @file{/mnt/cross/baz.c}, then the command
7791 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
7795 will tell @value{GDBN} to replace @samp{/usr/src} with
7796 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7797 @file{baz.c} even though it was moved.
7799 In the case when more than one substitution rule have been defined,
7800 the rules are evaluated one by one in the order where they have been
7801 defined. The first one matching, if any, is selected to perform
7804 For instance, if we had entered the following commands:
7807 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
7808 (@value{GDBP}) set substitute-path /usr/src /mnt/src
7812 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
7813 @file{/mnt/include/defs.h} by using the first rule. However, it would
7814 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
7815 @file{/mnt/src/lib/foo.c}.
7818 @item unset substitute-path [path]
7819 @kindex unset substitute-path
7820 If a path is specified, search the current list of substitution rules
7821 for a rule that would rewrite that path. Delete that rule if found.
7822 A warning is emitted by the debugger if no rule could be found.
7824 If no path is specified, then all substitution rules are deleted.
7826 @item show substitute-path [path]
7827 @kindex show substitute-path
7828 If a path is specified, then print the source path substitution rule
7829 which would rewrite that path, if any.
7831 If no path is specified, then print all existing source path substitution
7836 If your source path is cluttered with directories that are no longer of
7837 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
7838 versions of source. You can correct the situation as follows:
7842 Use @code{directory} with no argument to reset the source path to its default value.
7845 Use @code{directory} with suitable arguments to reinstall the
7846 directories you want in the source path. You can add all the
7847 directories in one command.
7851 @section Source and Machine Code
7852 @cindex source line and its code address
7854 You can use the command @code{info line} to map source lines to program
7855 addresses (and vice versa), and the command @code{disassemble} to display
7856 a range of addresses as machine instructions. You can use the command
7857 @code{set disassemble-next-line} to set whether to disassemble next
7858 source line when execution stops. When run under @sc{gnu} Emacs
7859 mode, the @code{info line} command causes the arrow to point to the
7860 line specified. Also, @code{info line} prints addresses in symbolic form as
7865 @item info line @var{linespec}
7866 Print the starting and ending addresses of the compiled code for
7867 source line @var{linespec}. You can specify source lines in any of
7868 the ways documented in @ref{Specify Location}.
7871 For example, we can use @code{info line} to discover the location of
7872 the object code for the first line of function
7873 @code{m4_changequote}:
7875 @c FIXME: I think this example should also show the addresses in
7876 @c symbolic form, as they usually would be displayed.
7878 (@value{GDBP}) info line m4_changequote
7879 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
7883 @cindex code address and its source line
7884 We can also inquire (using @code{*@var{addr}} as the form for
7885 @var{linespec}) what source line covers a particular address:
7887 (@value{GDBP}) info line *0x63ff
7888 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
7891 @cindex @code{$_} and @code{info line}
7892 @cindex @code{x} command, default address
7893 @kindex x@r{(examine), and} info line
7894 After @code{info line}, the default address for the @code{x} command
7895 is changed to the starting address of the line, so that @samp{x/i} is
7896 sufficient to begin examining the machine code (@pxref{Memory,
7897 ,Examining Memory}). Also, this address is saved as the value of the
7898 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
7903 @cindex assembly instructions
7904 @cindex instructions, assembly
7905 @cindex machine instructions
7906 @cindex listing machine instructions
7908 @itemx disassemble /m
7909 @itemx disassemble /r
7910 This specialized command dumps a range of memory as machine
7911 instructions. It can also print mixed source+disassembly by specifying
7912 the @code{/m} modifier and print the raw instructions in hex as well as
7913 in symbolic form by specifying the @code{/r}.
7914 The default memory range is the function surrounding the
7915 program counter of the selected frame. A single argument to this
7916 command is a program counter value; @value{GDBN} dumps the function
7917 surrounding this value. When two arguments are given, they should
7918 be separated by a comma, possibly surrounded by whitespace. The
7919 arguments specify a range of addresses to dump, in one of two forms:
7922 @item @var{start},@var{end}
7923 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
7924 @item @var{start},+@var{length}
7925 the addresses from @var{start} (inclusive) to
7926 @code{@var{start}+@var{length}} (exclusive).
7930 When 2 arguments are specified, the name of the function is also
7931 printed (since there could be several functions in the given range).
7933 The argument(s) can be any expression yielding a numeric value, such as
7934 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
7936 If the range of memory being disassembled contains current program counter,
7937 the instruction at that location is shown with a @code{=>} marker.
7940 The following example shows the disassembly of a range of addresses of
7941 HP PA-RISC 2.0 code:
7944 (@value{GDBP}) disas 0x32c4, 0x32e4
7945 Dump of assembler code from 0x32c4 to 0x32e4:
7946 0x32c4 <main+204>: addil 0,dp
7947 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
7948 0x32cc <main+212>: ldil 0x3000,r31
7949 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
7950 0x32d4 <main+220>: ldo 0(r31),rp
7951 0x32d8 <main+224>: addil -0x800,dp
7952 0x32dc <main+228>: ldo 0x588(r1),r26
7953 0x32e0 <main+232>: ldil 0x3000,r31
7954 End of assembler dump.
7957 Here is an example showing mixed source+assembly for Intel x86, when the
7958 program is stopped just after function prologue:
7961 (@value{GDBP}) disas /m main
7962 Dump of assembler code for function main:
7964 0x08048330 <+0>: push %ebp
7965 0x08048331 <+1>: mov %esp,%ebp
7966 0x08048333 <+3>: sub $0x8,%esp
7967 0x08048336 <+6>: and $0xfffffff0,%esp
7968 0x08048339 <+9>: sub $0x10,%esp
7970 6 printf ("Hello.\n");
7971 => 0x0804833c <+12>: movl $0x8048440,(%esp)
7972 0x08048343 <+19>: call 0x8048284 <puts@@plt>
7976 0x08048348 <+24>: mov $0x0,%eax
7977 0x0804834d <+29>: leave
7978 0x0804834e <+30>: ret
7980 End of assembler dump.
7983 Here is another example showing raw instructions in hex for AMD x86-64,
7986 (gdb) disas /r 0x400281,+10
7987 Dump of assembler code from 0x400281 to 0x40028b:
7988 0x0000000000400281: 38 36 cmp %dh,(%rsi)
7989 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
7990 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
7991 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7992 End of assembler dump.
7995 Addresses cannot be specified as a linespec (@pxref{Specify Location}).
7996 So, for example, if you want to disassemble function @code{bar}
7997 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
7998 and not @samp{disassemble foo.c:bar}.
8000 Some architectures have more than one commonly-used set of instruction
8001 mnemonics or other syntax.
8003 For programs that were dynamically linked and use shared libraries,
8004 instructions that call functions or branch to locations in the shared
8005 libraries might show a seemingly bogus location---it's actually a
8006 location of the relocation table. On some architectures, @value{GDBN}
8007 might be able to resolve these to actual function names.
8010 @kindex set disassembly-flavor
8011 @cindex Intel disassembly flavor
8012 @cindex AT&T disassembly flavor
8013 @item set disassembly-flavor @var{instruction-set}
8014 Select the instruction set to use when disassembling the
8015 program via the @code{disassemble} or @code{x/i} commands.
8017 Currently this command is only defined for the Intel x86 family. You
8018 can set @var{instruction-set} to either @code{intel} or @code{att}.
8019 The default is @code{att}, the AT&T flavor used by default by Unix
8020 assemblers for x86-based targets.
8022 @kindex show disassembly-flavor
8023 @item show disassembly-flavor
8024 Show the current setting of the disassembly flavor.
8028 @kindex set disassemble-next-line
8029 @kindex show disassemble-next-line
8030 @item set disassemble-next-line
8031 @itemx show disassemble-next-line
8032 Control whether or not @value{GDBN} will disassemble the next source
8033 line or instruction when execution stops. If ON, @value{GDBN} will
8034 display disassembly of the next source line when execution of the
8035 program being debugged stops. This is @emph{in addition} to
8036 displaying the source line itself, which @value{GDBN} always does if
8037 possible. If the next source line cannot be displayed for some reason
8038 (e.g., if @value{GDBN} cannot find the source file, or there's no line
8039 info in the debug info), @value{GDBN} will display disassembly of the
8040 next @emph{instruction} instead of showing the next source line. If
8041 AUTO, @value{GDBN} will display disassembly of next instruction only
8042 if the source line cannot be displayed. This setting causes
8043 @value{GDBN} to display some feedback when you step through a function
8044 with no line info or whose source file is unavailable. The default is
8045 OFF, which means never display the disassembly of the next line or
8051 @chapter Examining Data
8053 @cindex printing data
8054 @cindex examining data
8057 The usual way to examine data in your program is with the @code{print}
8058 command (abbreviated @code{p}), or its synonym @code{inspect}. It
8059 evaluates and prints the value of an expression of the language your
8060 program is written in (@pxref{Languages, ,Using @value{GDBN} with
8061 Different Languages}). It may also print the expression using a
8062 Python-based pretty-printer (@pxref{Pretty Printing}).
8065 @item print @var{expr}
8066 @itemx print /@var{f} @var{expr}
8067 @var{expr} is an expression (in the source language). By default the
8068 value of @var{expr} is printed in a format appropriate to its data type;
8069 you can choose a different format by specifying @samp{/@var{f}}, where
8070 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
8074 @itemx print /@var{f}
8075 @cindex reprint the last value
8076 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
8077 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
8078 conveniently inspect the same value in an alternative format.
8081 A more low-level way of examining data is with the @code{x} command.
8082 It examines data in memory at a specified address and prints it in a
8083 specified format. @xref{Memory, ,Examining Memory}.
8085 If you are interested in information about types, or about how the
8086 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
8087 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
8090 @cindex exploring hierarchical data structures
8092 Another way of examining values of expressions and type information is
8093 through the Python extension command @code{explore} (available only if
8094 the @value{GDBN} build is configured with @code{--with-python}). It
8095 offers an interactive way to start at the highest level (or, the most
8096 abstract level) of the data type of an expression (or, the data type
8097 itself) and explore all the way down to leaf scalar values/fields
8098 embedded in the higher level data types.
8101 @item explore @var{arg}
8102 @var{arg} is either an expression (in the source language), or a type
8103 visible in the current context of the program being debugged.
8106 The working of the @code{explore} command can be illustrated with an
8107 example. If a data type @code{struct ComplexStruct} is defined in your
8117 struct ComplexStruct
8119 struct SimpleStruct *ss_p;
8125 followed by variable declarations as
8128 struct SimpleStruct ss = @{ 10, 1.11 @};
8129 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
8133 then, the value of the variable @code{cs} can be explored using the
8134 @code{explore} command as follows.
8138 The value of `cs' is a struct/class of type `struct ComplexStruct' with
8139 the following fields:
8141 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
8142 arr = <Enter 1 to explore this field of type `int [10]'>
8144 Enter the field number of choice:
8148 Since the fields of @code{cs} are not scalar values, you are being
8149 prompted to chose the field you want to explore. Let's say you choose
8150 the field @code{ss_p} by entering @code{0}. Then, since this field is a
8151 pointer, you will be asked if it is pointing to a single value. From
8152 the declaration of @code{cs} above, it is indeed pointing to a single
8153 value, hence you enter @code{y}. If you enter @code{n}, then you will
8154 be asked if it were pointing to an array of values, in which case this
8155 field will be explored as if it were an array.
8158 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
8159 Continue exploring it as a pointer to a single value [y/n]: y
8160 The value of `*(cs.ss_p)' is a struct/class of type `struct
8161 SimpleStruct' with the following fields:
8163 i = 10 .. (Value of type `int')
8164 d = 1.1100000000000001 .. (Value of type `double')
8166 Press enter to return to parent value:
8170 If the field @code{arr} of @code{cs} was chosen for exploration by
8171 entering @code{1} earlier, then since it is as array, you will be
8172 prompted to enter the index of the element in the array that you want
8176 `cs.arr' is an array of `int'.
8177 Enter the index of the element you want to explore in `cs.arr': 5
8179 `(cs.arr)[5]' is a scalar value of type `int'.
8183 Press enter to return to parent value:
8186 In general, at any stage of exploration, you can go deeper towards the
8187 leaf values by responding to the prompts appropriately, or hit the
8188 return key to return to the enclosing data structure (the @i{higher}
8189 level data structure).
8191 Similar to exploring values, you can use the @code{explore} command to
8192 explore types. Instead of specifying a value (which is typically a
8193 variable name or an expression valid in the current context of the
8194 program being debugged), you specify a type name. If you consider the
8195 same example as above, your can explore the type
8196 @code{struct ComplexStruct} by passing the argument
8197 @code{struct ComplexStruct} to the @code{explore} command.
8200 (gdb) explore struct ComplexStruct
8204 By responding to the prompts appropriately in the subsequent interactive
8205 session, you can explore the type @code{struct ComplexStruct} in a
8206 manner similar to how the value @code{cs} was explored in the above
8209 The @code{explore} command also has two sub-commands,
8210 @code{explore value} and @code{explore type}. The former sub-command is
8211 a way to explicitly specify that value exploration of the argument is
8212 being invoked, while the latter is a way to explicitly specify that type
8213 exploration of the argument is being invoked.
8216 @item explore value @var{expr}
8217 @cindex explore value
8218 This sub-command of @code{explore} explores the value of the
8219 expression @var{expr} (if @var{expr} is an expression valid in the
8220 current context of the program being debugged). The behavior of this
8221 command is identical to that of the behavior of the @code{explore}
8222 command being passed the argument @var{expr}.
8224 @item explore type @var{arg}
8225 @cindex explore type
8226 This sub-command of @code{explore} explores the type of @var{arg} (if
8227 @var{arg} is a type visible in the current context of program being
8228 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8229 is an expression valid in the current context of the program being
8230 debugged). If @var{arg} is a type, then the behavior of this command is
8231 identical to that of the @code{explore} command being passed the
8232 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8233 this command will be identical to that of the @code{explore} command
8234 being passed the type of @var{arg} as the argument.
8238 * Expressions:: Expressions
8239 * Ambiguous Expressions:: Ambiguous Expressions
8240 * Variables:: Program variables
8241 * Arrays:: Artificial arrays
8242 * Output Formats:: Output formats
8243 * Memory:: Examining memory
8244 * Auto Display:: Automatic display
8245 * Print Settings:: Print settings
8246 * Pretty Printing:: Python pretty printing
8247 * Value History:: Value history
8248 * Convenience Vars:: Convenience variables
8249 * Convenience Funs:: Convenience functions
8250 * Registers:: Registers
8251 * Floating Point Hardware:: Floating point hardware
8252 * Vector Unit:: Vector Unit
8253 * OS Information:: Auxiliary data provided by operating system
8254 * Memory Region Attributes:: Memory region attributes
8255 * Dump/Restore Files:: Copy between memory and a file
8256 * Core File Generation:: Cause a program dump its core
8257 * Character Sets:: Debugging programs that use a different
8258 character set than GDB does
8259 * Caching Target Data:: Data caching for targets
8260 * Searching Memory:: Searching memory for a sequence of bytes
8264 @section Expressions
8267 @code{print} and many other @value{GDBN} commands accept an expression and
8268 compute its value. Any kind of constant, variable or operator defined
8269 by the programming language you are using is valid in an expression in
8270 @value{GDBN}. This includes conditional expressions, function calls,
8271 casts, and string constants. It also includes preprocessor macros, if
8272 you compiled your program to include this information; see
8275 @cindex arrays in expressions
8276 @value{GDBN} supports array constants in expressions input by
8277 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8278 you can use the command @code{print @{1, 2, 3@}} to create an array
8279 of three integers. If you pass an array to a function or assign it
8280 to a program variable, @value{GDBN} copies the array to memory that
8281 is @code{malloc}ed in the target program.
8283 Because C is so widespread, most of the expressions shown in examples in
8284 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8285 Languages}, for information on how to use expressions in other
8288 In this section, we discuss operators that you can use in @value{GDBN}
8289 expressions regardless of your programming language.
8291 @cindex casts, in expressions
8292 Casts are supported in all languages, not just in C, because it is so
8293 useful to cast a number into a pointer in order to examine a structure
8294 at that address in memory.
8295 @c FIXME: casts supported---Mod2 true?
8297 @value{GDBN} supports these operators, in addition to those common
8298 to programming languages:
8302 @samp{@@} is a binary operator for treating parts of memory as arrays.
8303 @xref{Arrays, ,Artificial Arrays}, for more information.
8306 @samp{::} allows you to specify a variable in terms of the file or
8307 function where it is defined. @xref{Variables, ,Program Variables}.
8309 @cindex @{@var{type}@}
8310 @cindex type casting memory
8311 @cindex memory, viewing as typed object
8312 @cindex casts, to view memory
8313 @item @{@var{type}@} @var{addr}
8314 Refers to an object of type @var{type} stored at address @var{addr} in
8315 memory. The address @var{addr} may be any expression whose value is
8316 an integer or pointer (but parentheses are required around binary
8317 operators, just as in a cast). This construct is allowed regardless
8318 of what kind of data is normally supposed to reside at @var{addr}.
8321 @node Ambiguous Expressions
8322 @section Ambiguous Expressions
8323 @cindex ambiguous expressions
8325 Expressions can sometimes contain some ambiguous elements. For instance,
8326 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8327 a single function name to be defined several times, for application in
8328 different contexts. This is called @dfn{overloading}. Another example
8329 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8330 templates and is typically instantiated several times, resulting in
8331 the same function name being defined in different contexts.
8333 In some cases and depending on the language, it is possible to adjust
8334 the expression to remove the ambiguity. For instance in C@t{++}, you
8335 can specify the signature of the function you want to break on, as in
8336 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8337 qualified name of your function often makes the expression unambiguous
8340 When an ambiguity that needs to be resolved is detected, the debugger
8341 has the capability to display a menu of numbered choices for each
8342 possibility, and then waits for the selection with the prompt @samp{>}.
8343 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
8344 aborts the current command. If the command in which the expression was
8345 used allows more than one choice to be selected, the next option in the
8346 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
8349 For example, the following session excerpt shows an attempt to set a
8350 breakpoint at the overloaded symbol @code{String::after}.
8351 We choose three particular definitions of that function name:
8353 @c FIXME! This is likely to change to show arg type lists, at least
8356 (@value{GDBP}) b String::after
8359 [2] file:String.cc; line number:867
8360 [3] file:String.cc; line number:860
8361 [4] file:String.cc; line number:875
8362 [5] file:String.cc; line number:853
8363 [6] file:String.cc; line number:846
8364 [7] file:String.cc; line number:735
8366 Breakpoint 1 at 0xb26c: file String.cc, line 867.
8367 Breakpoint 2 at 0xb344: file String.cc, line 875.
8368 Breakpoint 3 at 0xafcc: file String.cc, line 846.
8369 Multiple breakpoints were set.
8370 Use the "delete" command to delete unwanted
8377 @kindex set multiple-symbols
8378 @item set multiple-symbols @var{mode}
8379 @cindex multiple-symbols menu
8381 This option allows you to adjust the debugger behavior when an expression
8384 By default, @var{mode} is set to @code{all}. If the command with which
8385 the expression is used allows more than one choice, then @value{GDBN}
8386 automatically selects all possible choices. For instance, inserting
8387 a breakpoint on a function using an ambiguous name results in a breakpoint
8388 inserted on each possible match. However, if a unique choice must be made,
8389 then @value{GDBN} uses the menu to help you disambiguate the expression.
8390 For instance, printing the address of an overloaded function will result
8391 in the use of the menu.
8393 When @var{mode} is set to @code{ask}, the debugger always uses the menu
8394 when an ambiguity is detected.
8396 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
8397 an error due to the ambiguity and the command is aborted.
8399 @kindex show multiple-symbols
8400 @item show multiple-symbols
8401 Show the current value of the @code{multiple-symbols} setting.
8405 @section Program Variables
8407 The most common kind of expression to use is the name of a variable
8410 Variables in expressions are understood in the selected stack frame
8411 (@pxref{Selection, ,Selecting a Frame}); they must be either:
8415 global (or file-static)
8422 visible according to the scope rules of the
8423 programming language from the point of execution in that frame
8426 @noindent This means that in the function
8441 you can examine and use the variable @code{a} whenever your program is
8442 executing within the function @code{foo}, but you can only use or
8443 examine the variable @code{b} while your program is executing inside
8444 the block where @code{b} is declared.
8446 @cindex variable name conflict
8447 There is an exception: you can refer to a variable or function whose
8448 scope is a single source file even if the current execution point is not
8449 in this file. But it is possible to have more than one such variable or
8450 function with the same name (in different source files). If that
8451 happens, referring to that name has unpredictable effects. If you wish,
8452 you can specify a static variable in a particular function or file by
8453 using the colon-colon (@code{::}) notation:
8455 @cindex colon-colon, context for variables/functions
8457 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
8458 @cindex @code{::}, context for variables/functions
8461 @var{file}::@var{variable}
8462 @var{function}::@var{variable}
8466 Here @var{file} or @var{function} is the name of the context for the
8467 static @var{variable}. In the case of file names, you can use quotes to
8468 make sure @value{GDBN} parses the file name as a single word---for example,
8469 to print a global value of @code{x} defined in @file{f2.c}:
8472 (@value{GDBP}) p 'f2.c'::x
8475 The @code{::} notation is normally used for referring to
8476 static variables, since you typically disambiguate uses of local variables
8477 in functions by selecting the appropriate frame and using the
8478 simple name of the variable. However, you may also use this notation
8479 to refer to local variables in frames enclosing the selected frame:
8488 process (a); /* Stop here */
8499 For example, if there is a breakpoint at the commented line,
8500 here is what you might see
8501 when the program stops after executing the call @code{bar(0)}:
8506 (@value{GDBP}) p bar::a
8509 #2 0x080483d0 in foo (a=5) at foobar.c:12
8512 (@value{GDBP}) p bar::a
8516 @cindex C@t{++} scope resolution
8517 These uses of @samp{::} are very rarely in conflict with the very
8518 similar use of the same notation in C@t{++}. When they are in
8519 conflict, the C@t{++} meaning takes precedence; however, this can be
8520 overridden by quoting the file or function name with single quotes.
8522 For example, suppose the program is stopped in a method of a class
8523 that has a field named @code{includefile}, and there is also an
8524 include file named @file{includefile} that defines a variable,
8528 (@value{GDBP}) p includefile
8530 (@value{GDBP}) p includefile::some_global
8531 A syntax error in expression, near `'.
8532 (@value{GDBP}) p 'includefile'::some_global
8536 @cindex wrong values
8537 @cindex variable values, wrong
8538 @cindex function entry/exit, wrong values of variables
8539 @cindex optimized code, wrong values of variables
8541 @emph{Warning:} Occasionally, a local variable may appear to have the
8542 wrong value at certain points in a function---just after entry to a new
8543 scope, and just before exit.
8545 You may see this problem when you are stepping by machine instructions.
8546 This is because, on most machines, it takes more than one instruction to
8547 set up a stack frame (including local variable definitions); if you are
8548 stepping by machine instructions, variables may appear to have the wrong
8549 values until the stack frame is completely built. On exit, it usually
8550 also takes more than one machine instruction to destroy a stack frame;
8551 after you begin stepping through that group of instructions, local
8552 variable definitions may be gone.
8554 This may also happen when the compiler does significant optimizations.
8555 To be sure of always seeing accurate values, turn off all optimization
8558 @cindex ``No symbol "foo" in current context''
8559 Another possible effect of compiler optimizations is to optimize
8560 unused variables out of existence, or assign variables to registers (as
8561 opposed to memory addresses). Depending on the support for such cases
8562 offered by the debug info format used by the compiler, @value{GDBN}
8563 might not be able to display values for such local variables. If that
8564 happens, @value{GDBN} will print a message like this:
8567 No symbol "foo" in current context.
8570 To solve such problems, either recompile without optimizations, or use a
8571 different debug info format, if the compiler supports several such
8572 formats. @xref{Compilation}, for more information on choosing compiler
8573 options. @xref{C, ,C and C@t{++}}, for more information about debug
8574 info formats that are best suited to C@t{++} programs.
8576 If you ask to print an object whose contents are unknown to
8577 @value{GDBN}, e.g., because its data type is not completely specified
8578 by the debug information, @value{GDBN} will say @samp{<incomplete
8579 type>}. @xref{Symbols, incomplete type}, for more about this.
8581 If you append @kbd{@@entry} string to a function parameter name you get its
8582 value at the time the function got called. If the value is not available an
8583 error message is printed. Entry values are available only with some compilers.
8584 Entry values are normally also printed at the function parameter list according
8585 to @ref{set print entry-values}.
8588 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
8594 (gdb) print i@@entry
8598 Strings are identified as arrays of @code{char} values without specified
8599 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
8600 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
8601 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
8602 defines literal string type @code{"char"} as @code{char} without a sign.
8607 signed char var1[] = "A";
8610 You get during debugging
8615 $2 = @{65 'A', 0 '\0'@}
8619 @section Artificial Arrays
8621 @cindex artificial array
8623 @kindex @@@r{, referencing memory as an array}
8624 It is often useful to print out several successive objects of the
8625 same type in memory; a section of an array, or an array of
8626 dynamically determined size for which only a pointer exists in the
8629 You can do this by referring to a contiguous span of memory as an
8630 @dfn{artificial array}, using the binary operator @samp{@@}. The left
8631 operand of @samp{@@} should be the first element of the desired array
8632 and be an individual object. The right operand should be the desired length
8633 of the array. The result is an array value whose elements are all of
8634 the type of the left argument. The first element is actually the left
8635 argument; the second element comes from bytes of memory immediately
8636 following those that hold the first element, and so on. Here is an
8637 example. If a program says
8640 int *array = (int *) malloc (len * sizeof (int));
8644 you can print the contents of @code{array} with
8650 The left operand of @samp{@@} must reside in memory. Array values made
8651 with @samp{@@} in this way behave just like other arrays in terms of
8652 subscripting, and are coerced to pointers when used in expressions.
8653 Artificial arrays most often appear in expressions via the value history
8654 (@pxref{Value History, ,Value History}), after printing one out.
8656 Another way to create an artificial array is to use a cast.
8657 This re-interprets a value as if it were an array.
8658 The value need not be in memory:
8660 (@value{GDBP}) p/x (short[2])0x12345678
8661 $1 = @{0x1234, 0x5678@}
8664 As a convenience, if you leave the array length out (as in
8665 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
8666 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
8668 (@value{GDBP}) p/x (short[])0x12345678
8669 $2 = @{0x1234, 0x5678@}
8672 Sometimes the artificial array mechanism is not quite enough; in
8673 moderately complex data structures, the elements of interest may not
8674 actually be adjacent---for example, if you are interested in the values
8675 of pointers in an array. One useful work-around in this situation is
8676 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8677 Variables}) as a counter in an expression that prints the first
8678 interesting value, and then repeat that expression via @key{RET}. For
8679 instance, suppose you have an array @code{dtab} of pointers to
8680 structures, and you are interested in the values of a field @code{fv}
8681 in each structure. Here is an example of what you might type:
8691 @node Output Formats
8692 @section Output Formats
8694 @cindex formatted output
8695 @cindex output formats
8696 By default, @value{GDBN} prints a value according to its data type. Sometimes
8697 this is not what you want. For example, you might want to print a number
8698 in hex, or a pointer in decimal. Or you might want to view data in memory
8699 at a certain address as a character string or as an instruction. To do
8700 these things, specify an @dfn{output format} when you print a value.
8702 The simplest use of output formats is to say how to print a value
8703 already computed. This is done by starting the arguments of the
8704 @code{print} command with a slash and a format letter. The format
8705 letters supported are:
8709 Regard the bits of the value as an integer, and print the integer in
8713 Print as integer in signed decimal.
8716 Print as integer in unsigned decimal.
8719 Print as integer in octal.
8722 Print as integer in binary. The letter @samp{t} stands for ``two''.
8723 @footnote{@samp{b} cannot be used because these format letters are also
8724 used with the @code{x} command, where @samp{b} stands for ``byte'';
8725 see @ref{Memory,,Examining Memory}.}
8728 @cindex unknown address, locating
8729 @cindex locate address
8730 Print as an address, both absolute in hexadecimal and as an offset from
8731 the nearest preceding symbol. You can use this format used to discover
8732 where (in what function) an unknown address is located:
8735 (@value{GDBP}) p/a 0x54320
8736 $3 = 0x54320 <_initialize_vx+396>
8740 The command @code{info symbol 0x54320} yields similar results.
8741 @xref{Symbols, info symbol}.
8744 Regard as an integer and print it as a character constant. This
8745 prints both the numerical value and its character representation. The
8746 character representation is replaced with the octal escape @samp{\nnn}
8747 for characters outside the 7-bit @sc{ascii} range.
8749 Without this format, @value{GDBN} displays @code{char},
8750 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
8751 constants. Single-byte members of vectors are displayed as integer
8755 Regard the bits of the value as a floating point number and print
8756 using typical floating point syntax.
8759 @cindex printing strings
8760 @cindex printing byte arrays
8761 Regard as a string, if possible. With this format, pointers to single-byte
8762 data are displayed as null-terminated strings and arrays of single-byte data
8763 are displayed as fixed-length strings. Other values are displayed in their
8766 Without this format, @value{GDBN} displays pointers to and arrays of
8767 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
8768 strings. Single-byte members of a vector are displayed as an integer
8772 Like @samp{x} formatting, the value is treated as an integer and
8773 printed as hexadecimal, but leading zeros are printed to pad the value
8774 to the size of the integer type.
8777 @cindex raw printing
8778 Print using the @samp{raw} formatting. By default, @value{GDBN} will
8779 use a Python-based pretty-printer, if one is available (@pxref{Pretty
8780 Printing}). This typically results in a higher-level display of the
8781 value's contents. The @samp{r} format bypasses any Python
8782 pretty-printer which might exist.
8785 For example, to print the program counter in hex (@pxref{Registers}), type
8792 Note that no space is required before the slash; this is because command
8793 names in @value{GDBN} cannot contain a slash.
8795 To reprint the last value in the value history with a different format,
8796 you can use the @code{print} command with just a format and no
8797 expression. For example, @samp{p/x} reprints the last value in hex.
8800 @section Examining Memory
8802 You can use the command @code{x} (for ``examine'') to examine memory in
8803 any of several formats, independently of your program's data types.
8805 @cindex examining memory
8807 @kindex x @r{(examine memory)}
8808 @item x/@var{nfu} @var{addr}
8811 Use the @code{x} command to examine memory.
8814 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
8815 much memory to display and how to format it; @var{addr} is an
8816 expression giving the address where you want to start displaying memory.
8817 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
8818 Several commands set convenient defaults for @var{addr}.
8821 @item @var{n}, the repeat count
8822 The repeat count is a decimal integer; the default is 1. It specifies
8823 how much memory (counting by units @var{u}) to display.
8824 @c This really is **decimal**; unaffected by 'set radix' as of GDB
8827 @item @var{f}, the display format
8828 The display format is one of the formats used by @code{print}
8829 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
8830 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
8831 The default is @samp{x} (hexadecimal) initially. The default changes
8832 each time you use either @code{x} or @code{print}.
8834 @item @var{u}, the unit size
8835 The unit size is any of
8841 Halfwords (two bytes).
8843 Words (four bytes). This is the initial default.
8845 Giant words (eight bytes).
8848 Each time you specify a unit size with @code{x}, that size becomes the
8849 default unit the next time you use @code{x}. For the @samp{i} format,
8850 the unit size is ignored and is normally not written. For the @samp{s} format,
8851 the unit size defaults to @samp{b}, unless it is explicitly given.
8852 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
8853 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
8854 Note that the results depend on the programming language of the
8855 current compilation unit. If the language is C, the @samp{s}
8856 modifier will use the UTF-16 encoding while @samp{w} will use
8857 UTF-32. The encoding is set by the programming language and cannot
8860 @item @var{addr}, starting display address
8861 @var{addr} is the address where you want @value{GDBN} to begin displaying
8862 memory. The expression need not have a pointer value (though it may);
8863 it is always interpreted as an integer address of a byte of memory.
8864 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
8865 @var{addr} is usually just after the last address examined---but several
8866 other commands also set the default address: @code{info breakpoints} (to
8867 the address of the last breakpoint listed), @code{info line} (to the
8868 starting address of a line), and @code{print} (if you use it to display
8869 a value from memory).
8872 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
8873 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
8874 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
8875 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
8876 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
8878 Since the letters indicating unit sizes are all distinct from the
8879 letters specifying output formats, you do not have to remember whether
8880 unit size or format comes first; either order works. The output
8881 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
8882 (However, the count @var{n} must come first; @samp{wx4} does not work.)
8884 Even though the unit size @var{u} is ignored for the formats @samp{s}
8885 and @samp{i}, you might still want to use a count @var{n}; for example,
8886 @samp{3i} specifies that you want to see three machine instructions,
8887 including any operands. For convenience, especially when used with
8888 the @code{display} command, the @samp{i} format also prints branch delay
8889 slot instructions, if any, beyond the count specified, which immediately
8890 follow the last instruction that is within the count. The command
8891 @code{disassemble} gives an alternative way of inspecting machine
8892 instructions; see @ref{Machine Code,,Source and Machine Code}.
8894 All the defaults for the arguments to @code{x} are designed to make it
8895 easy to continue scanning memory with minimal specifications each time
8896 you use @code{x}. For example, after you have inspected three machine
8897 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
8898 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
8899 the repeat count @var{n} is used again; the other arguments default as
8900 for successive uses of @code{x}.
8902 When examining machine instructions, the instruction at current program
8903 counter is shown with a @code{=>} marker. For example:
8906 (@value{GDBP}) x/5i $pc-6
8907 0x804837f <main+11>: mov %esp,%ebp
8908 0x8048381 <main+13>: push %ecx
8909 0x8048382 <main+14>: sub $0x4,%esp
8910 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
8911 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
8914 @cindex @code{$_}, @code{$__}, and value history
8915 The addresses and contents printed by the @code{x} command are not saved
8916 in the value history because there is often too much of them and they
8917 would get in the way. Instead, @value{GDBN} makes these values available for
8918 subsequent use in expressions as values of the convenience variables
8919 @code{$_} and @code{$__}. After an @code{x} command, the last address
8920 examined is available for use in expressions in the convenience variable
8921 @code{$_}. The contents of that address, as examined, are available in
8922 the convenience variable @code{$__}.
8924 If the @code{x} command has a repeat count, the address and contents saved
8925 are from the last memory unit printed; this is not the same as the last
8926 address printed if several units were printed on the last line of output.
8928 @cindex remote memory comparison
8929 @cindex target memory comparison
8930 @cindex verify remote memory image
8931 @cindex verify target memory image
8932 When you are debugging a program running on a remote target machine
8933 (@pxref{Remote Debugging}), you may wish to verify the program's image
8934 in the remote machine's memory against the executable file you
8935 downloaded to the target. Or, on any target, you may want to check
8936 whether the program has corrupted its own read-only sections. The
8937 @code{compare-sections} command is provided for such situations.
8940 @kindex compare-sections
8941 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
8942 Compare the data of a loadable section @var{section-name} in the
8943 executable file of the program being debugged with the same section in
8944 the target machine's memory, and report any mismatches. With no
8945 arguments, compares all loadable sections. With an argument of
8946 @code{-r}, compares all loadable read-only sections.
8948 Note: for remote targets, this command can be accelerated if the
8949 target supports computing the CRC checksum of a block of memory
8950 (@pxref{qCRC packet}).
8954 @section Automatic Display
8955 @cindex automatic display
8956 @cindex display of expressions
8958 If you find that you want to print the value of an expression frequently
8959 (to see how it changes), you might want to add it to the @dfn{automatic
8960 display list} so that @value{GDBN} prints its value each time your program stops.
8961 Each expression added to the list is given a number to identify it;
8962 to remove an expression from the list, you specify that number.
8963 The automatic display looks like this:
8967 3: bar[5] = (struct hack *) 0x3804
8971 This display shows item numbers, expressions and their current values. As with
8972 displays you request manually using @code{x} or @code{print}, you can
8973 specify the output format you prefer; in fact, @code{display} decides
8974 whether to use @code{print} or @code{x} depending your format
8975 specification---it uses @code{x} if you specify either the @samp{i}
8976 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
8980 @item display @var{expr}
8981 Add the expression @var{expr} to the list of expressions to display
8982 each time your program stops. @xref{Expressions, ,Expressions}.
8984 @code{display} does not repeat if you press @key{RET} again after using it.
8986 @item display/@var{fmt} @var{expr}
8987 For @var{fmt} specifying only a display format and not a size or
8988 count, add the expression @var{expr} to the auto-display list but
8989 arrange to display it each time in the specified format @var{fmt}.
8990 @xref{Output Formats,,Output Formats}.
8992 @item display/@var{fmt} @var{addr}
8993 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
8994 number of units, add the expression @var{addr} as a memory address to
8995 be examined each time your program stops. Examining means in effect
8996 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
8999 For example, @samp{display/i $pc} can be helpful, to see the machine
9000 instruction about to be executed each time execution stops (@samp{$pc}
9001 is a common name for the program counter; @pxref{Registers, ,Registers}).
9004 @kindex delete display
9006 @item undisplay @var{dnums}@dots{}
9007 @itemx delete display @var{dnums}@dots{}
9008 Remove items from the list of expressions to display. Specify the
9009 numbers of the displays that you want affected with the command
9010 argument @var{dnums}. It can be a single display number, one of the
9011 numbers shown in the first field of the @samp{info display} display;
9012 or it could be a range of display numbers, as in @code{2-4}.
9014 @code{undisplay} does not repeat if you press @key{RET} after using it.
9015 (Otherwise you would just get the error @samp{No display number @dots{}}.)
9017 @kindex disable display
9018 @item disable display @var{dnums}@dots{}
9019 Disable the display of item numbers @var{dnums}. A disabled display
9020 item is not printed automatically, but is not forgotten. It may be
9021 enabled again later. Specify the numbers of the displays that you
9022 want affected with the command argument @var{dnums}. It can be a
9023 single display number, one of the numbers shown in the first field of
9024 the @samp{info display} display; or it could be a range of display
9025 numbers, as in @code{2-4}.
9027 @kindex enable display
9028 @item enable display @var{dnums}@dots{}
9029 Enable display of item numbers @var{dnums}. It becomes effective once
9030 again in auto display of its expression, until you specify otherwise.
9031 Specify the numbers of the displays that you want affected with the
9032 command argument @var{dnums}. It can be a single display number, one
9033 of the numbers shown in the first field of the @samp{info display}
9034 display; or it could be a range of display numbers, as in @code{2-4}.
9037 Display the current values of the expressions on the list, just as is
9038 done when your program stops.
9040 @kindex info display
9042 Print the list of expressions previously set up to display
9043 automatically, each one with its item number, but without showing the
9044 values. This includes disabled expressions, which are marked as such.
9045 It also includes expressions which would not be displayed right now
9046 because they refer to automatic variables not currently available.
9049 @cindex display disabled out of scope
9050 If a display expression refers to local variables, then it does not make
9051 sense outside the lexical context for which it was set up. Such an
9052 expression is disabled when execution enters a context where one of its
9053 variables is not defined. For example, if you give the command
9054 @code{display last_char} while inside a function with an argument
9055 @code{last_char}, @value{GDBN} displays this argument while your program
9056 continues to stop inside that function. When it stops elsewhere---where
9057 there is no variable @code{last_char}---the display is disabled
9058 automatically. The next time your program stops where @code{last_char}
9059 is meaningful, you can enable the display expression once again.
9061 @node Print Settings
9062 @section Print Settings
9064 @cindex format options
9065 @cindex print settings
9066 @value{GDBN} provides the following ways to control how arrays, structures,
9067 and symbols are printed.
9070 These settings are useful for debugging programs in any language:
9074 @item set print address
9075 @itemx set print address on
9076 @cindex print/don't print memory addresses
9077 @value{GDBN} prints memory addresses showing the location of stack
9078 traces, structure values, pointer values, breakpoints, and so forth,
9079 even when it also displays the contents of those addresses. The default
9080 is @code{on}. For example, this is what a stack frame display looks like with
9081 @code{set print address on}:
9086 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
9088 530 if (lquote != def_lquote)
9092 @item set print address off
9093 Do not print addresses when displaying their contents. For example,
9094 this is the same stack frame displayed with @code{set print address off}:
9098 (@value{GDBP}) set print addr off
9100 #0 set_quotes (lq="<<", rq=">>") at input.c:530
9101 530 if (lquote != def_lquote)
9105 You can use @samp{set print address off} to eliminate all machine
9106 dependent displays from the @value{GDBN} interface. For example, with
9107 @code{print address off}, you should get the same text for backtraces on
9108 all machines---whether or not they involve pointer arguments.
9111 @item show print address
9112 Show whether or not addresses are to be printed.
9115 When @value{GDBN} prints a symbolic address, it normally prints the
9116 closest earlier symbol plus an offset. If that symbol does not uniquely
9117 identify the address (for example, it is a name whose scope is a single
9118 source file), you may need to clarify. One way to do this is with
9119 @code{info line}, for example @samp{info line *0x4537}. Alternately,
9120 you can set @value{GDBN} to print the source file and line number when
9121 it prints a symbolic address:
9124 @item set print symbol-filename on
9125 @cindex source file and line of a symbol
9126 @cindex symbol, source file and line
9127 Tell @value{GDBN} to print the source file name and line number of a
9128 symbol in the symbolic form of an address.
9130 @item set print symbol-filename off
9131 Do not print source file name and line number of a symbol. This is the
9134 @item show print symbol-filename
9135 Show whether or not @value{GDBN} will print the source file name and
9136 line number of a symbol in the symbolic form of an address.
9139 Another situation where it is helpful to show symbol filenames and line
9140 numbers is when disassembling code; @value{GDBN} shows you the line
9141 number and source file that corresponds to each instruction.
9143 Also, you may wish to see the symbolic form only if the address being
9144 printed is reasonably close to the closest earlier symbol:
9147 @item set print max-symbolic-offset @var{max-offset}
9148 @itemx set print max-symbolic-offset unlimited
9149 @cindex maximum value for offset of closest symbol
9150 Tell @value{GDBN} to only display the symbolic form of an address if the
9151 offset between the closest earlier symbol and the address is less than
9152 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
9153 to always print the symbolic form of an address if any symbol precedes
9154 it. Zero is equivalent to @code{unlimited}.
9156 @item show print max-symbolic-offset
9157 Ask how large the maximum offset is that @value{GDBN} prints in a
9161 @cindex wild pointer, interpreting
9162 @cindex pointer, finding referent
9163 If you have a pointer and you are not sure where it points, try
9164 @samp{set print symbol-filename on}. Then you can determine the name
9165 and source file location of the variable where it points, using
9166 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
9167 For example, here @value{GDBN} shows that a variable @code{ptt} points
9168 at another variable @code{t}, defined in @file{hi2.c}:
9171 (@value{GDBP}) set print symbol-filename on
9172 (@value{GDBP}) p/a ptt
9173 $4 = 0xe008 <t in hi2.c>
9177 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
9178 does not show the symbol name and filename of the referent, even with
9179 the appropriate @code{set print} options turned on.
9182 You can also enable @samp{/a}-like formatting all the time using
9183 @samp{set print symbol on}:
9186 @item set print symbol on
9187 Tell @value{GDBN} to print the symbol corresponding to an address, if
9190 @item set print symbol off
9191 Tell @value{GDBN} not to print the symbol corresponding to an
9192 address. In this mode, @value{GDBN} will still print the symbol
9193 corresponding to pointers to functions. This is the default.
9195 @item show print symbol
9196 Show whether @value{GDBN} will display the symbol corresponding to an
9200 Other settings control how different kinds of objects are printed:
9203 @item set print array
9204 @itemx set print array on
9205 @cindex pretty print arrays
9206 Pretty print arrays. This format is more convenient to read,
9207 but uses more space. The default is off.
9209 @item set print array off
9210 Return to compressed format for arrays.
9212 @item show print array
9213 Show whether compressed or pretty format is selected for displaying
9216 @cindex print array indexes
9217 @item set print array-indexes
9218 @itemx set print array-indexes on
9219 Print the index of each element when displaying arrays. May be more
9220 convenient to locate a given element in the array or quickly find the
9221 index of a given element in that printed array. The default is off.
9223 @item set print array-indexes off
9224 Stop printing element indexes when displaying arrays.
9226 @item show print array-indexes
9227 Show whether the index of each element is printed when displaying
9230 @item set print elements @var{number-of-elements}
9231 @itemx set print elements unlimited
9232 @cindex number of array elements to print
9233 @cindex limit on number of printed array elements
9234 Set a limit on how many elements of an array @value{GDBN} will print.
9235 If @value{GDBN} is printing a large array, it stops printing after it has
9236 printed the number of elements set by the @code{set print elements} command.
9237 This limit also applies to the display of strings.
9238 When @value{GDBN} starts, this limit is set to 200.
9239 Setting @var{number-of-elements} to @code{unlimited} or zero means
9240 that the number of elements to print is unlimited.
9242 @item show print elements
9243 Display the number of elements of a large array that @value{GDBN} will print.
9244 If the number is 0, then the printing is unlimited.
9246 @item set print frame-arguments @var{value}
9247 @kindex set print frame-arguments
9248 @cindex printing frame argument values
9249 @cindex print all frame argument values
9250 @cindex print frame argument values for scalars only
9251 @cindex do not print frame argument values
9252 This command allows to control how the values of arguments are printed
9253 when the debugger prints a frame (@pxref{Frames}). The possible
9258 The values of all arguments are printed.
9261 Print the value of an argument only if it is a scalar. The value of more
9262 complex arguments such as arrays, structures, unions, etc, is replaced
9263 by @code{@dots{}}. This is the default. Here is an example where
9264 only scalar arguments are shown:
9267 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9272 None of the argument values are printed. Instead, the value of each argument
9273 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9276 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9281 By default, only scalar arguments are printed. This command can be used
9282 to configure the debugger to print the value of all arguments, regardless
9283 of their type. However, it is often advantageous to not print the value
9284 of more complex parameters. For instance, it reduces the amount of
9285 information printed in each frame, making the backtrace more readable.
9286 Also, it improves performance when displaying Ada frames, because
9287 the computation of large arguments can sometimes be CPU-intensive,
9288 especially in large applications. Setting @code{print frame-arguments}
9289 to @code{scalars} (the default) or @code{none} avoids this computation,
9290 thus speeding up the display of each Ada frame.
9292 @item show print frame-arguments
9293 Show how the value of arguments should be displayed when printing a frame.
9295 @item set print raw frame-arguments on
9296 Print frame arguments in raw, non pretty-printed, form.
9298 @item set print raw frame-arguments off
9299 Print frame arguments in pretty-printed form, if there is a pretty-printer
9300 for the value (@pxref{Pretty Printing}),
9301 otherwise print the value in raw form.
9302 This is the default.
9304 @item show print raw frame-arguments
9305 Show whether to print frame arguments in raw form.
9307 @anchor{set print entry-values}
9308 @item set print entry-values @var{value}
9309 @kindex set print entry-values
9310 Set printing of frame argument values at function entry. In some cases
9311 @value{GDBN} can determine the value of function argument which was passed by
9312 the function caller, even if the value was modified inside the called function
9313 and therefore is different. With optimized code, the current value could be
9314 unavailable, but the entry value may still be known.
9316 The default value is @code{default} (see below for its description). Older
9317 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
9318 this feature will behave in the @code{default} setting the same way as with the
9321 This functionality is currently supported only by DWARF 2 debugging format and
9322 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9323 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9326 The @var{value} parameter can be one of the following:
9330 Print only actual parameter values, never print values from function entry
9334 #0 different (val=6)
9335 #0 lost (val=<optimized out>)
9337 #0 invalid (val=<optimized out>)
9341 Print only parameter values from function entry point. The actual parameter
9342 values are never printed.
9344 #0 equal (val@@entry=5)
9345 #0 different (val@@entry=5)
9346 #0 lost (val@@entry=5)
9347 #0 born (val@@entry=<optimized out>)
9348 #0 invalid (val@@entry=<optimized out>)
9352 Print only parameter values from function entry point. If value from function
9353 entry point is not known while the actual value is known, print the actual
9354 value for such parameter.
9356 #0 equal (val@@entry=5)
9357 #0 different (val@@entry=5)
9358 #0 lost (val@@entry=5)
9360 #0 invalid (val@@entry=<optimized out>)
9364 Print actual parameter values. If actual parameter value is not known while
9365 value from function entry point is known, print the entry point value for such
9369 #0 different (val=6)
9370 #0 lost (val@@entry=5)
9372 #0 invalid (val=<optimized out>)
9376 Always print both the actual parameter value and its value from function entry
9377 point, even if values of one or both are not available due to compiler
9380 #0 equal (val=5, val@@entry=5)
9381 #0 different (val=6, val@@entry=5)
9382 #0 lost (val=<optimized out>, val@@entry=5)
9383 #0 born (val=10, val@@entry=<optimized out>)
9384 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
9388 Print the actual parameter value if it is known and also its value from
9389 function entry point if it is known. If neither is known, print for the actual
9390 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
9391 values are known and identical, print the shortened
9392 @code{param=param@@entry=VALUE} notation.
9394 #0 equal (val=val@@entry=5)
9395 #0 different (val=6, val@@entry=5)
9396 #0 lost (val@@entry=5)
9398 #0 invalid (val=<optimized out>)
9402 Always print the actual parameter value. Print also its value from function
9403 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
9404 if both values are known and identical, print the shortened
9405 @code{param=param@@entry=VALUE} notation.
9407 #0 equal (val=val@@entry=5)
9408 #0 different (val=6, val@@entry=5)
9409 #0 lost (val=<optimized out>, val@@entry=5)
9411 #0 invalid (val=<optimized out>)
9415 For analysis messages on possible failures of frame argument values at function
9416 entry resolution see @ref{set debug entry-values}.
9418 @item show print entry-values
9419 Show the method being used for printing of frame argument values at function
9422 @item set print repeats @var{number-of-repeats}
9423 @itemx set print repeats unlimited
9424 @cindex repeated array elements
9425 Set the threshold for suppressing display of repeated array
9426 elements. When the number of consecutive identical elements of an
9427 array exceeds the threshold, @value{GDBN} prints the string
9428 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
9429 identical repetitions, instead of displaying the identical elements
9430 themselves. Setting the threshold to @code{unlimited} or zero will
9431 cause all elements to be individually printed. The default threshold
9434 @item show print repeats
9435 Display the current threshold for printing repeated identical
9438 @item set print null-stop
9439 @cindex @sc{null} elements in arrays
9440 Cause @value{GDBN} to stop printing the characters of an array when the first
9441 @sc{null} is encountered. This is useful when large arrays actually
9442 contain only short strings.
9445 @item show print null-stop
9446 Show whether @value{GDBN} stops printing an array on the first
9447 @sc{null} character.
9449 @item set print pretty on
9450 @cindex print structures in indented form
9451 @cindex indentation in structure display
9452 Cause @value{GDBN} to print structures in an indented format with one member
9453 per line, like this:
9468 @item set print pretty off
9469 Cause @value{GDBN} to print structures in a compact format, like this:
9473 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
9474 meat = 0x54 "Pork"@}
9479 This is the default format.
9481 @item show print pretty
9482 Show which format @value{GDBN} is using to print structures.
9484 @item set print sevenbit-strings on
9485 @cindex eight-bit characters in strings
9486 @cindex octal escapes in strings
9487 Print using only seven-bit characters; if this option is set,
9488 @value{GDBN} displays any eight-bit characters (in strings or
9489 character values) using the notation @code{\}@var{nnn}. This setting is
9490 best if you are working in English (@sc{ascii}) and you use the
9491 high-order bit of characters as a marker or ``meta'' bit.
9493 @item set print sevenbit-strings off
9494 Print full eight-bit characters. This allows the use of more
9495 international character sets, and is the default.
9497 @item show print sevenbit-strings
9498 Show whether or not @value{GDBN} is printing only seven-bit characters.
9500 @item set print union on
9501 @cindex unions in structures, printing
9502 Tell @value{GDBN} to print unions which are contained in structures
9503 and other unions. This is the default setting.
9505 @item set print union off
9506 Tell @value{GDBN} not to print unions which are contained in
9507 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
9510 @item show print union
9511 Ask @value{GDBN} whether or not it will print unions which are contained in
9512 structures and other unions.
9514 For example, given the declarations
9517 typedef enum @{Tree, Bug@} Species;
9518 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
9519 typedef enum @{Caterpillar, Cocoon, Butterfly@}
9530 struct thing foo = @{Tree, @{Acorn@}@};
9534 with @code{set print union on} in effect @samp{p foo} would print
9537 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
9541 and with @code{set print union off} in effect it would print
9544 $1 = @{it = Tree, form = @{...@}@}
9548 @code{set print union} affects programs written in C-like languages
9554 These settings are of interest when debugging C@t{++} programs:
9557 @cindex demangling C@t{++} names
9558 @item set print demangle
9559 @itemx set print demangle on
9560 Print C@t{++} names in their source form rather than in the encoded
9561 (``mangled'') form passed to the assembler and linker for type-safe
9562 linkage. The default is on.
9564 @item show print demangle
9565 Show whether C@t{++} names are printed in mangled or demangled form.
9567 @item set print asm-demangle
9568 @itemx set print asm-demangle on
9569 Print C@t{++} names in their source form rather than their mangled form, even
9570 in assembler code printouts such as instruction disassemblies.
9573 @item show print asm-demangle
9574 Show whether C@t{++} names in assembly listings are printed in mangled
9577 @cindex C@t{++} symbol decoding style
9578 @cindex symbol decoding style, C@t{++}
9579 @kindex set demangle-style
9580 @item set demangle-style @var{style}
9581 Choose among several encoding schemes used by different compilers to
9582 represent C@t{++} names. The choices for @var{style} are currently:
9586 Allow @value{GDBN} to choose a decoding style by inspecting your program.
9587 This is the default.
9590 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
9593 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
9596 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
9599 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
9600 @strong{Warning:} this setting alone is not sufficient to allow
9601 debugging @code{cfront}-generated executables. @value{GDBN} would
9602 require further enhancement to permit that.
9605 If you omit @var{style}, you will see a list of possible formats.
9607 @item show demangle-style
9608 Display the encoding style currently in use for decoding C@t{++} symbols.
9610 @item set print object
9611 @itemx set print object on
9612 @cindex derived type of an object, printing
9613 @cindex display derived types
9614 When displaying a pointer to an object, identify the @emph{actual}
9615 (derived) type of the object rather than the @emph{declared} type, using
9616 the virtual function table. Note that the virtual function table is
9617 required---this feature can only work for objects that have run-time
9618 type identification; a single virtual method in the object's declared
9619 type is sufficient. Note that this setting is also taken into account when
9620 working with variable objects via MI (@pxref{GDB/MI}).
9622 @item set print object off
9623 Display only the declared type of objects, without reference to the
9624 virtual function table. This is the default setting.
9626 @item show print object
9627 Show whether actual, or declared, object types are displayed.
9629 @item set print static-members
9630 @itemx set print static-members on
9631 @cindex static members of C@t{++} objects
9632 Print static members when displaying a C@t{++} object. The default is on.
9634 @item set print static-members off
9635 Do not print static members when displaying a C@t{++} object.
9637 @item show print static-members
9638 Show whether C@t{++} static members are printed or not.
9640 @item set print pascal_static-members
9641 @itemx set print pascal_static-members on
9642 @cindex static members of Pascal objects
9643 @cindex Pascal objects, static members display
9644 Print static members when displaying a Pascal object. The default is on.
9646 @item set print pascal_static-members off
9647 Do not print static members when displaying a Pascal object.
9649 @item show print pascal_static-members
9650 Show whether Pascal static members are printed or not.
9652 @c These don't work with HP ANSI C++ yet.
9653 @item set print vtbl
9654 @itemx set print vtbl on
9655 @cindex pretty print C@t{++} virtual function tables
9656 @cindex virtual functions (C@t{++}) display
9657 @cindex VTBL display
9658 Pretty print C@t{++} virtual function tables. The default is off.
9659 (The @code{vtbl} commands do not work on programs compiled with the HP
9660 ANSI C@t{++} compiler (@code{aCC}).)
9662 @item set print vtbl off
9663 Do not pretty print C@t{++} virtual function tables.
9665 @item show print vtbl
9666 Show whether C@t{++} virtual function tables are pretty printed, or not.
9669 @node Pretty Printing
9670 @section Pretty Printing
9672 @value{GDBN} provides a mechanism to allow pretty-printing of values using
9673 Python code. It greatly simplifies the display of complex objects. This
9674 mechanism works for both MI and the CLI.
9677 * Pretty-Printer Introduction:: Introduction to pretty-printers
9678 * Pretty-Printer Example:: An example pretty-printer
9679 * Pretty-Printer Commands:: Pretty-printer commands
9682 @node Pretty-Printer Introduction
9683 @subsection Pretty-Printer Introduction
9685 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
9686 registered for the value. If there is then @value{GDBN} invokes the
9687 pretty-printer to print the value. Otherwise the value is printed normally.
9689 Pretty-printers are normally named. This makes them easy to manage.
9690 The @samp{info pretty-printer} command will list all the installed
9691 pretty-printers with their names.
9692 If a pretty-printer can handle multiple data types, then its
9693 @dfn{subprinters} are the printers for the individual data types.
9694 Each such subprinter has its own name.
9695 The format of the name is @var{printer-name};@var{subprinter-name}.
9697 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
9698 Typically they are automatically loaded and registered when the corresponding
9699 debug information is loaded, thus making them available without having to
9700 do anything special.
9702 There are three places where a pretty-printer can be registered.
9706 Pretty-printers registered globally are available when debugging
9710 Pretty-printers registered with a program space are available only
9711 when debugging that program.
9712 @xref{Progspaces In Python}, for more details on program spaces in Python.
9715 Pretty-printers registered with an objfile are loaded and unloaded
9716 with the corresponding objfile (e.g., shared library).
9717 @xref{Objfiles In Python}, for more details on objfiles in Python.
9720 @xref{Selecting Pretty-Printers}, for further information on how
9721 pretty-printers are selected,
9723 @xref{Writing a Pretty-Printer}, for implementing pretty printers
9726 @node Pretty-Printer Example
9727 @subsection Pretty-Printer Example
9729 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
9732 (@value{GDBP}) print s
9734 static npos = 4294967295,
9736 <std::allocator<char>> = @{
9737 <__gnu_cxx::new_allocator<char>> = @{
9738 <No data fields>@}, <No data fields>
9740 members of std::basic_string<char, std::char_traits<char>,
9741 std::allocator<char> >::_Alloc_hider:
9742 _M_p = 0x804a014 "abcd"
9747 With a pretty-printer for @code{std::string} only the contents are printed:
9750 (@value{GDBP}) print s
9754 @node Pretty-Printer Commands
9755 @subsection Pretty-Printer Commands
9756 @cindex pretty-printer commands
9759 @kindex info pretty-printer
9760 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9761 Print the list of installed pretty-printers.
9762 This includes disabled pretty-printers, which are marked as such.
9764 @var{object-regexp} is a regular expression matching the objects
9765 whose pretty-printers to list.
9766 Objects can be @code{global}, the program space's file
9767 (@pxref{Progspaces In Python}),
9768 and the object files within that program space (@pxref{Objfiles In Python}).
9769 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
9770 looks up a printer from these three objects.
9772 @var{name-regexp} is a regular expression matching the name of the printers
9775 @kindex disable pretty-printer
9776 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9777 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9778 A disabled pretty-printer is not forgotten, it may be enabled again later.
9780 @kindex enable pretty-printer
9781 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9782 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9787 Suppose we have three pretty-printers installed: one from library1.so
9788 named @code{foo} that prints objects of type @code{foo}, and
9789 another from library2.so named @code{bar} that prints two types of objects,
9790 @code{bar1} and @code{bar2}.
9793 (gdb) info pretty-printer
9800 (gdb) info pretty-printer library2
9805 (gdb) disable pretty-printer library1
9807 2 of 3 printers enabled
9808 (gdb) info pretty-printer
9815 (gdb) disable pretty-printer library2 bar:bar1
9817 1 of 3 printers enabled
9818 (gdb) info pretty-printer library2
9825 (gdb) disable pretty-printer library2 bar
9827 0 of 3 printers enabled
9828 (gdb) info pretty-printer library2
9837 Note that for @code{bar} the entire printer can be disabled,
9838 as can each individual subprinter.
9841 @section Value History
9843 @cindex value history
9844 @cindex history of values printed by @value{GDBN}
9845 Values printed by the @code{print} command are saved in the @value{GDBN}
9846 @dfn{value history}. This allows you to refer to them in other expressions.
9847 Values are kept until the symbol table is re-read or discarded
9848 (for example with the @code{file} or @code{symbol-file} commands).
9849 When the symbol table changes, the value history is discarded,
9850 since the values may contain pointers back to the types defined in the
9855 @cindex history number
9856 The values printed are given @dfn{history numbers} by which you can
9857 refer to them. These are successive integers starting with one.
9858 @code{print} shows you the history number assigned to a value by
9859 printing @samp{$@var{num} = } before the value; here @var{num} is the
9862 To refer to any previous value, use @samp{$} followed by the value's
9863 history number. The way @code{print} labels its output is designed to
9864 remind you of this. Just @code{$} refers to the most recent value in
9865 the history, and @code{$$} refers to the value before that.
9866 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
9867 is the value just prior to @code{$$}, @code{$$1} is equivalent to
9868 @code{$$}, and @code{$$0} is equivalent to @code{$}.
9870 For example, suppose you have just printed a pointer to a structure and
9871 want to see the contents of the structure. It suffices to type
9877 If you have a chain of structures where the component @code{next} points
9878 to the next one, you can print the contents of the next one with this:
9885 You can print successive links in the chain by repeating this
9886 command---which you can do by just typing @key{RET}.
9888 Note that the history records values, not expressions. If the value of
9889 @code{x} is 4 and you type these commands:
9897 then the value recorded in the value history by the @code{print} command
9898 remains 4 even though the value of @code{x} has changed.
9903 Print the last ten values in the value history, with their item numbers.
9904 This is like @samp{p@ $$9} repeated ten times, except that @code{show
9905 values} does not change the history.
9907 @item show values @var{n}
9908 Print ten history values centered on history item number @var{n}.
9911 Print ten history values just after the values last printed. If no more
9912 values are available, @code{show values +} produces no display.
9915 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
9916 same effect as @samp{show values +}.
9918 @node Convenience Vars
9919 @section Convenience Variables
9921 @cindex convenience variables
9922 @cindex user-defined variables
9923 @value{GDBN} provides @dfn{convenience variables} that you can use within
9924 @value{GDBN} to hold on to a value and refer to it later. These variables
9925 exist entirely within @value{GDBN}; they are not part of your program, and
9926 setting a convenience variable has no direct effect on further execution
9927 of your program. That is why you can use them freely.
9929 Convenience variables are prefixed with @samp{$}. Any name preceded by
9930 @samp{$} can be used for a convenience variable, unless it is one of
9931 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
9932 (Value history references, in contrast, are @emph{numbers} preceded
9933 by @samp{$}. @xref{Value History, ,Value History}.)
9935 You can save a value in a convenience variable with an assignment
9936 expression, just as you would set a variable in your program.
9940 set $foo = *object_ptr
9944 would save in @code{$foo} the value contained in the object pointed to by
9947 Using a convenience variable for the first time creates it, but its
9948 value is @code{void} until you assign a new value. You can alter the
9949 value with another assignment at any time.
9951 Convenience variables have no fixed types. You can assign a convenience
9952 variable any type of value, including structures and arrays, even if
9953 that variable already has a value of a different type. The convenience
9954 variable, when used as an expression, has the type of its current value.
9957 @kindex show convenience
9958 @cindex show all user variables and functions
9959 @item show convenience
9960 Print a list of convenience variables used so far, and their values,
9961 as well as a list of the convenience functions.
9962 Abbreviated @code{show conv}.
9964 @kindex init-if-undefined
9965 @cindex convenience variables, initializing
9966 @item init-if-undefined $@var{variable} = @var{expression}
9967 Set a convenience variable if it has not already been set. This is useful
9968 for user-defined commands that keep some state. It is similar, in concept,
9969 to using local static variables with initializers in C (except that
9970 convenience variables are global). It can also be used to allow users to
9971 override default values used in a command script.
9973 If the variable is already defined then the expression is not evaluated so
9974 any side-effects do not occur.
9977 One of the ways to use a convenience variable is as a counter to be
9978 incremented or a pointer to be advanced. For example, to print
9979 a field from successive elements of an array of structures:
9983 print bar[$i++]->contents
9987 Repeat that command by typing @key{RET}.
9989 Some convenience variables are created automatically by @value{GDBN} and given
9990 values likely to be useful.
9993 @vindex $_@r{, convenience variable}
9995 The variable @code{$_} is automatically set by the @code{x} command to
9996 the last address examined (@pxref{Memory, ,Examining Memory}). Other
9997 commands which provide a default address for @code{x} to examine also
9998 set @code{$_} to that address; these commands include @code{info line}
9999 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
10000 except when set by the @code{x} command, in which case it is a pointer
10001 to the type of @code{$__}.
10003 @vindex $__@r{, convenience variable}
10005 The variable @code{$__} is automatically set by the @code{x} command
10006 to the value found in the last address examined. Its type is chosen
10007 to match the format in which the data was printed.
10010 @vindex $_exitcode@r{, convenience variable}
10011 When the program being debugged terminates normally, @value{GDBN}
10012 automatically sets this variable to the exit code of the program, and
10013 resets @code{$_exitsignal} to @code{void}.
10016 @vindex $_exitsignal@r{, convenience variable}
10017 When the program being debugged dies due to an uncaught signal,
10018 @value{GDBN} automatically sets this variable to that signal's number,
10019 and resets @code{$_exitcode} to @code{void}.
10021 To distinguish between whether the program being debugged has exited
10022 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
10023 @code{$_exitsignal} is not @code{void}), the convenience function
10024 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
10025 Functions}). For example, considering the following source code:
10028 #include <signal.h>
10031 main (int argc, char *argv[])
10038 A valid way of telling whether the program being debugged has exited
10039 or signalled would be:
10042 (@value{GDBP}) define has_exited_or_signalled
10043 Type commands for definition of ``has_exited_or_signalled''.
10044 End with a line saying just ``end''.
10045 >if $_isvoid ($_exitsignal)
10046 >echo The program has exited\n
10048 >echo The program has signalled\n
10054 Program terminated with signal SIGALRM, Alarm clock.
10055 The program no longer exists.
10056 (@value{GDBP}) has_exited_or_signalled
10057 The program has signalled
10060 As can be seen, @value{GDBN} correctly informs that the program being
10061 debugged has signalled, since it calls @code{raise} and raises a
10062 @code{SIGALRM} signal. If the program being debugged had not called
10063 @code{raise}, then @value{GDBN} would report a normal exit:
10066 (@value{GDBP}) has_exited_or_signalled
10067 The program has exited
10071 The variable @code{$_exception} is set to the exception object being
10072 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
10075 @itemx $_probe_arg0@dots{}$_probe_arg11
10076 Arguments to a static probe. @xref{Static Probe Points}.
10079 @vindex $_sdata@r{, inspect, convenience variable}
10080 The variable @code{$_sdata} contains extra collected static tracepoint
10081 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
10082 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
10083 if extra static tracepoint data has not been collected.
10086 @vindex $_siginfo@r{, convenience variable}
10087 The variable @code{$_siginfo} contains extra signal information
10088 (@pxref{extra signal information}). Note that @code{$_siginfo}
10089 could be empty, if the application has not yet received any signals.
10090 For example, it will be empty before you execute the @code{run} command.
10093 @vindex $_tlb@r{, convenience variable}
10094 The variable @code{$_tlb} is automatically set when debugging
10095 applications running on MS-Windows in native mode or connected to
10096 gdbserver that supports the @code{qGetTIBAddr} request.
10097 @xref{General Query Packets}.
10098 This variable contains the address of the thread information block.
10102 On HP-UX systems, if you refer to a function or variable name that
10103 begins with a dollar sign, @value{GDBN} searches for a user or system
10104 name first, before it searches for a convenience variable.
10106 @node Convenience Funs
10107 @section Convenience Functions
10109 @cindex convenience functions
10110 @value{GDBN} also supplies some @dfn{convenience functions}. These
10111 have a syntax similar to convenience variables. A convenience
10112 function can be used in an expression just like an ordinary function;
10113 however, a convenience function is implemented internally to
10116 These functions do not require @value{GDBN} to be configured with
10117 @code{Python} support, which means that they are always available.
10121 @item $_isvoid (@var{expr})
10122 @findex $_isvoid@r{, convenience function}
10123 Return one if the expression @var{expr} is @code{void}. Otherwise it
10126 A @code{void} expression is an expression where the type of the result
10127 is @code{void}. For example, you can examine a convenience variable
10128 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
10132 (@value{GDBP}) print $_exitcode
10134 (@value{GDBP}) print $_isvoid ($_exitcode)
10137 Starting program: ./a.out
10138 [Inferior 1 (process 29572) exited normally]
10139 (@value{GDBP}) print $_exitcode
10141 (@value{GDBP}) print $_isvoid ($_exitcode)
10145 In the example above, we used @code{$_isvoid} to check whether
10146 @code{$_exitcode} is @code{void} before and after the execution of the
10147 program being debugged. Before the execution there is no exit code to
10148 be examined, therefore @code{$_exitcode} is @code{void}. After the
10149 execution the program being debugged returned zero, therefore
10150 @code{$_exitcode} is zero, which means that it is not @code{void}
10153 The @code{void} expression can also be a call of a function from the
10154 program being debugged. For example, given the following function:
10163 The result of calling it inside @value{GDBN} is @code{void}:
10166 (@value{GDBP}) print foo ()
10168 (@value{GDBP}) print $_isvoid (foo ())
10170 (@value{GDBP}) set $v = foo ()
10171 (@value{GDBP}) print $v
10173 (@value{GDBP}) print $_isvoid ($v)
10179 These functions require @value{GDBN} to be configured with
10180 @code{Python} support.
10184 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10185 @findex $_memeq@r{, convenience function}
10186 Returns one if the @var{length} bytes at the addresses given by
10187 @var{buf1} and @var{buf2} are equal.
10188 Otherwise it returns zero.
10190 @item $_regex(@var{str}, @var{regex})
10191 @findex $_regex@r{, convenience function}
10192 Returns one if the string @var{str} matches the regular expression
10193 @var{regex}. Otherwise it returns zero.
10194 The syntax of the regular expression is that specified by @code{Python}'s
10195 regular expression support.
10197 @item $_streq(@var{str1}, @var{str2})
10198 @findex $_streq@r{, convenience function}
10199 Returns one if the strings @var{str1} and @var{str2} are equal.
10200 Otherwise it returns zero.
10202 @item $_strlen(@var{str})
10203 @findex $_strlen@r{, convenience function}
10204 Returns the length of string @var{str}.
10206 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10207 @findex $_caller_is@r{, convenience function}
10208 Returns one if the calling function's name is equal to @var{name}.
10209 Otherwise it returns zero.
10211 If the optional argument @var{number_of_frames} is provided,
10212 it is the number of frames up in the stack to look.
10220 at testsuite/gdb.python/py-caller-is.c:21
10221 #1 0x00000000004005a0 in middle_func ()
10222 at testsuite/gdb.python/py-caller-is.c:27
10223 #2 0x00000000004005ab in top_func ()
10224 at testsuite/gdb.python/py-caller-is.c:33
10225 #3 0x00000000004005b6 in main ()
10226 at testsuite/gdb.python/py-caller-is.c:39
10227 (gdb) print $_caller_is ("middle_func")
10229 (gdb) print $_caller_is ("top_func", 2)
10233 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10234 @findex $_caller_matches@r{, convenience function}
10235 Returns one if the calling function's name matches the regular expression
10236 @var{regexp}. Otherwise it returns zero.
10238 If the optional argument @var{number_of_frames} is provided,
10239 it is the number of frames up in the stack to look.
10242 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10243 @findex $_any_caller_is@r{, convenience function}
10244 Returns one if any calling function's name is equal to @var{name}.
10245 Otherwise it returns zero.
10247 If the optional argument @var{number_of_frames} is provided,
10248 it is the number of frames up in the stack to look.
10251 This function differs from @code{$_caller_is} in that this function
10252 checks all stack frames from the immediate caller to the frame specified
10253 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
10254 frame specified by @var{number_of_frames}.
10256 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10257 @findex $_any_caller_matches@r{, convenience function}
10258 Returns one if any calling function's name matches the regular expression
10259 @var{regexp}. Otherwise it returns zero.
10261 If the optional argument @var{number_of_frames} is provided,
10262 it is the number of frames up in the stack to look.
10265 This function differs from @code{$_caller_matches} in that this function
10266 checks all stack frames from the immediate caller to the frame specified
10267 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
10268 frame specified by @var{number_of_frames}.
10272 @value{GDBN} provides the ability to list and get help on
10273 convenience functions.
10276 @item help function
10277 @kindex help function
10278 @cindex show all convenience functions
10279 Print a list of all convenience functions.
10286 You can refer to machine register contents, in expressions, as variables
10287 with names starting with @samp{$}. The names of registers are different
10288 for each machine; use @code{info registers} to see the names used on
10292 @kindex info registers
10293 @item info registers
10294 Print the names and values of all registers except floating-point
10295 and vector registers (in the selected stack frame).
10297 @kindex info all-registers
10298 @cindex floating point registers
10299 @item info all-registers
10300 Print the names and values of all registers, including floating-point
10301 and vector registers (in the selected stack frame).
10303 @item info registers @var{regname} @dots{}
10304 Print the @dfn{relativized} value of each specified register @var{regname}.
10305 As discussed in detail below, register values are normally relative to
10306 the selected stack frame. The @var{regname} may be any register name valid on
10307 the machine you are using, with or without the initial @samp{$}.
10310 @anchor{standard registers}
10311 @cindex stack pointer register
10312 @cindex program counter register
10313 @cindex process status register
10314 @cindex frame pointer register
10315 @cindex standard registers
10316 @value{GDBN} has four ``standard'' register names that are available (in
10317 expressions) on most machines---whenever they do not conflict with an
10318 architecture's canonical mnemonics for registers. The register names
10319 @code{$pc} and @code{$sp} are used for the program counter register and
10320 the stack pointer. @code{$fp} is used for a register that contains a
10321 pointer to the current stack frame, and @code{$ps} is used for a
10322 register that contains the processor status. For example,
10323 you could print the program counter in hex with
10330 or print the instruction to be executed next with
10337 or add four to the stack pointer@footnote{This is a way of removing
10338 one word from the stack, on machines where stacks grow downward in
10339 memory (most machines, nowadays). This assumes that the innermost
10340 stack frame is selected; setting @code{$sp} is not allowed when other
10341 stack frames are selected. To pop entire frames off the stack,
10342 regardless of machine architecture, use @code{return};
10343 see @ref{Returning, ,Returning from a Function}.} with
10349 Whenever possible, these four standard register names are available on
10350 your machine even though the machine has different canonical mnemonics,
10351 so long as there is no conflict. The @code{info registers} command
10352 shows the canonical names. For example, on the SPARC, @code{info
10353 registers} displays the processor status register as @code{$psr} but you
10354 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
10355 is an alias for the @sc{eflags} register.
10357 @value{GDBN} always considers the contents of an ordinary register as an
10358 integer when the register is examined in this way. Some machines have
10359 special registers which can hold nothing but floating point; these
10360 registers are considered to have floating point values. There is no way
10361 to refer to the contents of an ordinary register as floating point value
10362 (although you can @emph{print} it as a floating point value with
10363 @samp{print/f $@var{regname}}).
10365 Some registers have distinct ``raw'' and ``virtual'' data formats. This
10366 means that the data format in which the register contents are saved by
10367 the operating system is not the same one that your program normally
10368 sees. For example, the registers of the 68881 floating point
10369 coprocessor are always saved in ``extended'' (raw) format, but all C
10370 programs expect to work with ``double'' (virtual) format. In such
10371 cases, @value{GDBN} normally works with the virtual format only (the format
10372 that makes sense for your program), but the @code{info registers} command
10373 prints the data in both formats.
10375 @cindex SSE registers (x86)
10376 @cindex MMX registers (x86)
10377 Some machines have special registers whose contents can be interpreted
10378 in several different ways. For example, modern x86-based machines
10379 have SSE and MMX registers that can hold several values packed
10380 together in several different formats. @value{GDBN} refers to such
10381 registers in @code{struct} notation:
10384 (@value{GDBP}) print $xmm1
10386 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
10387 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
10388 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
10389 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
10390 v4_int32 = @{0, 20657912, 11, 13@},
10391 v2_int64 = @{88725056443645952, 55834574859@},
10392 uint128 = 0x0000000d0000000b013b36f800000000
10397 To set values of such registers, you need to tell @value{GDBN} which
10398 view of the register you wish to change, as if you were assigning
10399 value to a @code{struct} member:
10402 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
10405 Normally, register values are relative to the selected stack frame
10406 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
10407 value that the register would contain if all stack frames farther in
10408 were exited and their saved registers restored. In order to see the
10409 true contents of hardware registers, you must select the innermost
10410 frame (with @samp{frame 0}).
10412 @cindex caller-saved registers
10413 @cindex call-clobbered registers
10414 @cindex volatile registers
10415 @cindex <not saved> values
10416 Usually ABIs reserve some registers as not needed to be saved by the
10417 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
10418 registers). It may therefore not be possible for @value{GDBN} to know
10419 the value a register had before the call (in other words, in the outer
10420 frame), if the register value has since been changed by the callee.
10421 @value{GDBN} tries to deduce where the inner frame saved
10422 (``callee-saved'') registers, from the debug info, unwind info, or the
10423 machine code generated by your compiler. If some register is not
10424 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
10425 its own knowledge of the ABI, or because the debug/unwind info
10426 explicitly says the register's value is undefined), @value{GDBN}
10427 displays @w{@samp{<not saved>}} as the register's value. With targets
10428 that @value{GDBN} has no knowledge of the register saving convention,
10429 if a register was not saved by the callee, then its value and location
10430 in the outer frame are assumed to be the same of the inner frame.
10431 This is usually harmless, because if the register is call-clobbered,
10432 the caller either does not care what is in the register after the
10433 call, or has code to restore the value that it does care about. Note,
10434 however, that if you change such a register in the outer frame, you
10435 may also be affecting the inner frame. Also, the more ``outer'' the
10436 frame is you're looking at, the more likely a call-clobbered
10437 register's value is to be wrong, in the sense that it doesn't actually
10438 represent the value the register had just before the call.
10440 @node Floating Point Hardware
10441 @section Floating Point Hardware
10442 @cindex floating point
10444 Depending on the configuration, @value{GDBN} may be able to give
10445 you more information about the status of the floating point hardware.
10450 Display hardware-dependent information about the floating
10451 point unit. The exact contents and layout vary depending on the
10452 floating point chip. Currently, @samp{info float} is supported on
10453 the ARM and x86 machines.
10457 @section Vector Unit
10458 @cindex vector unit
10460 Depending on the configuration, @value{GDBN} may be able to give you
10461 more information about the status of the vector unit.
10464 @kindex info vector
10466 Display information about the vector unit. The exact contents and
10467 layout vary depending on the hardware.
10470 @node OS Information
10471 @section Operating System Auxiliary Information
10472 @cindex OS information
10474 @value{GDBN} provides interfaces to useful OS facilities that can help
10475 you debug your program.
10477 @cindex auxiliary vector
10478 @cindex vector, auxiliary
10479 Some operating systems supply an @dfn{auxiliary vector} to programs at
10480 startup. This is akin to the arguments and environment that you
10481 specify for a program, but contains a system-dependent variety of
10482 binary values that tell system libraries important details about the
10483 hardware, operating system, and process. Each value's purpose is
10484 identified by an integer tag; the meanings are well-known but system-specific.
10485 Depending on the configuration and operating system facilities,
10486 @value{GDBN} may be able to show you this information. For remote
10487 targets, this functionality may further depend on the remote stub's
10488 support of the @samp{qXfer:auxv:read} packet, see
10489 @ref{qXfer auxiliary vector read}.
10494 Display the auxiliary vector of the inferior, which can be either a
10495 live process or a core dump file. @value{GDBN} prints each tag value
10496 numerically, and also shows names and text descriptions for recognized
10497 tags. Some values in the vector are numbers, some bit masks, and some
10498 pointers to strings or other data. @value{GDBN} displays each value in the
10499 most appropriate form for a recognized tag, and in hexadecimal for
10500 an unrecognized tag.
10503 On some targets, @value{GDBN} can access operating system-specific
10504 information and show it to you. The types of information available
10505 will differ depending on the type of operating system running on the
10506 target. The mechanism used to fetch the data is described in
10507 @ref{Operating System Information}. For remote targets, this
10508 functionality depends on the remote stub's support of the
10509 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
10513 @item info os @var{infotype}
10515 Display OS information of the requested type.
10517 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
10519 @anchor{linux info os infotypes}
10521 @kindex info os processes
10523 Display the list of processes on the target. For each process,
10524 @value{GDBN} prints the process identifier, the name of the user, the
10525 command corresponding to the process, and the list of processor cores
10526 that the process is currently running on. (To understand what these
10527 properties mean, for this and the following info types, please consult
10528 the general @sc{gnu}/Linux documentation.)
10530 @kindex info os procgroups
10532 Display the list of process groups on the target. For each process,
10533 @value{GDBN} prints the identifier of the process group that it belongs
10534 to, the command corresponding to the process group leader, the process
10535 identifier, and the command line of the process. The list is sorted
10536 first by the process group identifier, then by the process identifier,
10537 so that processes belonging to the same process group are grouped together
10538 and the process group leader is listed first.
10540 @kindex info os threads
10542 Display the list of threads running on the target. For each thread,
10543 @value{GDBN} prints the identifier of the process that the thread
10544 belongs to, the command of the process, the thread identifier, and the
10545 processor core that it is currently running on. The main thread of a
10546 process is not listed.
10548 @kindex info os files
10550 Display the list of open file descriptors on the target. For each
10551 file descriptor, @value{GDBN} prints the identifier of the process
10552 owning the descriptor, the command of the owning process, the value
10553 of the descriptor, and the target of the descriptor.
10555 @kindex info os sockets
10557 Display the list of Internet-domain sockets on the target. For each
10558 socket, @value{GDBN} prints the address and port of the local and
10559 remote endpoints, the current state of the connection, the creator of
10560 the socket, the IP address family of the socket, and the type of the
10563 @kindex info os shm
10565 Display the list of all System V shared-memory regions on the target.
10566 For each shared-memory region, @value{GDBN} prints the region key,
10567 the shared-memory identifier, the access permissions, the size of the
10568 region, the process that created the region, the process that last
10569 attached to or detached from the region, the current number of live
10570 attaches to the region, and the times at which the region was last
10571 attached to, detach from, and changed.
10573 @kindex info os semaphores
10575 Display the list of all System V semaphore sets on the target. For each
10576 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
10577 set identifier, the access permissions, the number of semaphores in the
10578 set, the user and group of the owner and creator of the semaphore set,
10579 and the times at which the semaphore set was operated upon and changed.
10581 @kindex info os msg
10583 Display the list of all System V message queues on the target. For each
10584 message queue, @value{GDBN} prints the message queue key, the message
10585 queue identifier, the access permissions, the current number of bytes
10586 on the queue, the current number of messages on the queue, the processes
10587 that last sent and received a message on the queue, the user and group
10588 of the owner and creator of the message queue, the times at which a
10589 message was last sent and received on the queue, and the time at which
10590 the message queue was last changed.
10592 @kindex info os modules
10594 Display the list of all loaded kernel modules on the target. For each
10595 module, @value{GDBN} prints the module name, the size of the module in
10596 bytes, the number of times the module is used, the dependencies of the
10597 module, the status of the module, and the address of the loaded module
10602 If @var{infotype} is omitted, then list the possible values for
10603 @var{infotype} and the kind of OS information available for each
10604 @var{infotype}. If the target does not return a list of possible
10605 types, this command will report an error.
10608 @node Memory Region Attributes
10609 @section Memory Region Attributes
10610 @cindex memory region attributes
10612 @dfn{Memory region attributes} allow you to describe special handling
10613 required by regions of your target's memory. @value{GDBN} uses
10614 attributes to determine whether to allow certain types of memory
10615 accesses; whether to use specific width accesses; and whether to cache
10616 target memory. By default the description of memory regions is
10617 fetched from the target (if the current target supports this), but the
10618 user can override the fetched regions.
10620 Defined memory regions can be individually enabled and disabled. When a
10621 memory region is disabled, @value{GDBN} uses the default attributes when
10622 accessing memory in that region. Similarly, if no memory regions have
10623 been defined, @value{GDBN} uses the default attributes when accessing
10626 When a memory region is defined, it is given a number to identify it;
10627 to enable, disable, or remove a memory region, you specify that number.
10631 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
10632 Define a memory region bounded by @var{lower} and @var{upper} with
10633 attributes @var{attributes}@dots{}, and add it to the list of regions
10634 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
10635 case: it is treated as the target's maximum memory address.
10636 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
10639 Discard any user changes to the memory regions and use target-supplied
10640 regions, if available, or no regions if the target does not support.
10643 @item delete mem @var{nums}@dots{}
10644 Remove memory regions @var{nums}@dots{} from the list of regions
10645 monitored by @value{GDBN}.
10647 @kindex disable mem
10648 @item disable mem @var{nums}@dots{}
10649 Disable monitoring of memory regions @var{nums}@dots{}.
10650 A disabled memory region is not forgotten.
10651 It may be enabled again later.
10654 @item enable mem @var{nums}@dots{}
10655 Enable monitoring of memory regions @var{nums}@dots{}.
10659 Print a table of all defined memory regions, with the following columns
10663 @item Memory Region Number
10664 @item Enabled or Disabled.
10665 Enabled memory regions are marked with @samp{y}.
10666 Disabled memory regions are marked with @samp{n}.
10669 The address defining the inclusive lower bound of the memory region.
10672 The address defining the exclusive upper bound of the memory region.
10675 The list of attributes set for this memory region.
10680 @subsection Attributes
10682 @subsubsection Memory Access Mode
10683 The access mode attributes set whether @value{GDBN} may make read or
10684 write accesses to a memory region.
10686 While these attributes prevent @value{GDBN} from performing invalid
10687 memory accesses, they do nothing to prevent the target system, I/O DMA,
10688 etc.@: from accessing memory.
10692 Memory is read only.
10694 Memory is write only.
10696 Memory is read/write. This is the default.
10699 @subsubsection Memory Access Size
10700 The access size attribute tells @value{GDBN} to use specific sized
10701 accesses in the memory region. Often memory mapped device registers
10702 require specific sized accesses. If no access size attribute is
10703 specified, @value{GDBN} may use accesses of any size.
10707 Use 8 bit memory accesses.
10709 Use 16 bit memory accesses.
10711 Use 32 bit memory accesses.
10713 Use 64 bit memory accesses.
10716 @c @subsubsection Hardware/Software Breakpoints
10717 @c The hardware/software breakpoint attributes set whether @value{GDBN}
10718 @c will use hardware or software breakpoints for the internal breakpoints
10719 @c used by the step, next, finish, until, etc. commands.
10723 @c Always use hardware breakpoints
10724 @c @item swbreak (default)
10727 @subsubsection Data Cache
10728 The data cache attributes set whether @value{GDBN} will cache target
10729 memory. While this generally improves performance by reducing debug
10730 protocol overhead, it can lead to incorrect results because @value{GDBN}
10731 does not know about volatile variables or memory mapped device
10736 Enable @value{GDBN} to cache target memory.
10738 Disable @value{GDBN} from caching target memory. This is the default.
10741 @subsection Memory Access Checking
10742 @value{GDBN} can be instructed to refuse accesses to memory that is
10743 not explicitly described. This can be useful if accessing such
10744 regions has undesired effects for a specific target, or to provide
10745 better error checking. The following commands control this behaviour.
10748 @kindex set mem inaccessible-by-default
10749 @item set mem inaccessible-by-default [on|off]
10750 If @code{on} is specified, make @value{GDBN} treat memory not
10751 explicitly described by the memory ranges as non-existent and refuse accesses
10752 to such memory. The checks are only performed if there's at least one
10753 memory range defined. If @code{off} is specified, make @value{GDBN}
10754 treat the memory not explicitly described by the memory ranges as RAM.
10755 The default value is @code{on}.
10756 @kindex show mem inaccessible-by-default
10757 @item show mem inaccessible-by-default
10758 Show the current handling of accesses to unknown memory.
10762 @c @subsubsection Memory Write Verification
10763 @c The memory write verification attributes set whether @value{GDBN}
10764 @c will re-reads data after each write to verify the write was successful.
10768 @c @item noverify (default)
10771 @node Dump/Restore Files
10772 @section Copy Between Memory and a File
10773 @cindex dump/restore files
10774 @cindex append data to a file
10775 @cindex dump data to a file
10776 @cindex restore data from a file
10778 You can use the commands @code{dump}, @code{append}, and
10779 @code{restore} to copy data between target memory and a file. The
10780 @code{dump} and @code{append} commands write data to a file, and the
10781 @code{restore} command reads data from a file back into the inferior's
10782 memory. Files may be in binary, Motorola S-record, Intel hex, or
10783 Tektronix Hex format; however, @value{GDBN} can only append to binary
10789 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10790 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
10791 Dump the contents of memory from @var{start_addr} to @var{end_addr},
10792 or the value of @var{expr}, to @var{filename} in the given format.
10794 The @var{format} parameter may be any one of:
10801 Motorola S-record format.
10803 Tektronix Hex format.
10806 @value{GDBN} uses the same definitions of these formats as the
10807 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
10808 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
10812 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10813 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
10814 Append the contents of memory from @var{start_addr} to @var{end_addr},
10815 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
10816 (@value{GDBN} can only append data to files in raw binary form.)
10819 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
10820 Restore the contents of file @var{filename} into memory. The
10821 @code{restore} command can automatically recognize any known @sc{bfd}
10822 file format, except for raw binary. To restore a raw binary file you
10823 must specify the optional keyword @code{binary} after the filename.
10825 If @var{bias} is non-zero, its value will be added to the addresses
10826 contained in the file. Binary files always start at address zero, so
10827 they will be restored at address @var{bias}. Other bfd files have
10828 a built-in location; they will be restored at offset @var{bias}
10829 from that location.
10831 If @var{start} and/or @var{end} are non-zero, then only data between
10832 file offset @var{start} and file offset @var{end} will be restored.
10833 These offsets are relative to the addresses in the file, before
10834 the @var{bias} argument is applied.
10838 @node Core File Generation
10839 @section How to Produce a Core File from Your Program
10840 @cindex dump core from inferior
10842 A @dfn{core file} or @dfn{core dump} is a file that records the memory
10843 image of a running process and its process status (register values
10844 etc.). Its primary use is post-mortem debugging of a program that
10845 crashed while it ran outside a debugger. A program that crashes
10846 automatically produces a core file, unless this feature is disabled by
10847 the user. @xref{Files}, for information on invoking @value{GDBN} in
10848 the post-mortem debugging mode.
10850 Occasionally, you may wish to produce a core file of the program you
10851 are debugging in order to preserve a snapshot of its state.
10852 @value{GDBN} has a special command for that.
10856 @kindex generate-core-file
10857 @item generate-core-file [@var{file}]
10858 @itemx gcore [@var{file}]
10859 Produce a core dump of the inferior process. The optional argument
10860 @var{file} specifies the file name where to put the core dump. If not
10861 specified, the file name defaults to @file{core.@var{pid}}, where
10862 @var{pid} is the inferior process ID.
10864 Note that this command is implemented only for some systems (as of
10865 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
10868 @node Character Sets
10869 @section Character Sets
10870 @cindex character sets
10872 @cindex translating between character sets
10873 @cindex host character set
10874 @cindex target character set
10876 If the program you are debugging uses a different character set to
10877 represent characters and strings than the one @value{GDBN} uses itself,
10878 @value{GDBN} can automatically translate between the character sets for
10879 you. The character set @value{GDBN} uses we call the @dfn{host
10880 character set}; the one the inferior program uses we call the
10881 @dfn{target character set}.
10883 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
10884 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
10885 remote protocol (@pxref{Remote Debugging}) to debug a program
10886 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
10887 then the host character set is Latin-1, and the target character set is
10888 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
10889 target-charset EBCDIC-US}, then @value{GDBN} translates between
10890 @sc{ebcdic} and Latin 1 as you print character or string values, or use
10891 character and string literals in expressions.
10893 @value{GDBN} has no way to automatically recognize which character set
10894 the inferior program uses; you must tell it, using the @code{set
10895 target-charset} command, described below.
10897 Here are the commands for controlling @value{GDBN}'s character set
10901 @item set target-charset @var{charset}
10902 @kindex set target-charset
10903 Set the current target character set to @var{charset}. To display the
10904 list of supported target character sets, type
10905 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
10907 @item set host-charset @var{charset}
10908 @kindex set host-charset
10909 Set the current host character set to @var{charset}.
10911 By default, @value{GDBN} uses a host character set appropriate to the
10912 system it is running on; you can override that default using the
10913 @code{set host-charset} command. On some systems, @value{GDBN} cannot
10914 automatically determine the appropriate host character set. In this
10915 case, @value{GDBN} uses @samp{UTF-8}.
10917 @value{GDBN} can only use certain character sets as its host character
10918 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
10919 @value{GDBN} will list the host character sets it supports.
10921 @item set charset @var{charset}
10922 @kindex set charset
10923 Set the current host and target character sets to @var{charset}. As
10924 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
10925 @value{GDBN} will list the names of the character sets that can be used
10926 for both host and target.
10929 @kindex show charset
10930 Show the names of the current host and target character sets.
10932 @item show host-charset
10933 @kindex show host-charset
10934 Show the name of the current host character set.
10936 @item show target-charset
10937 @kindex show target-charset
10938 Show the name of the current target character set.
10940 @item set target-wide-charset @var{charset}
10941 @kindex set target-wide-charset
10942 Set the current target's wide character set to @var{charset}. This is
10943 the character set used by the target's @code{wchar_t} type. To
10944 display the list of supported wide character sets, type
10945 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
10947 @item show target-wide-charset
10948 @kindex show target-wide-charset
10949 Show the name of the current target's wide character set.
10952 Here is an example of @value{GDBN}'s character set support in action.
10953 Assume that the following source code has been placed in the file
10954 @file{charset-test.c}:
10960 = @{72, 101, 108, 108, 111, 44, 32, 119,
10961 111, 114, 108, 100, 33, 10, 0@};
10962 char ibm1047_hello[]
10963 = @{200, 133, 147, 147, 150, 107, 64, 166,
10964 150, 153, 147, 132, 90, 37, 0@};
10968 printf ("Hello, world!\n");
10972 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
10973 containing the string @samp{Hello, world!} followed by a newline,
10974 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
10976 We compile the program, and invoke the debugger on it:
10979 $ gcc -g charset-test.c -o charset-test
10980 $ gdb -nw charset-test
10981 GNU gdb 2001-12-19-cvs
10982 Copyright 2001 Free Software Foundation, Inc.
10987 We can use the @code{show charset} command to see what character sets
10988 @value{GDBN} is currently using to interpret and display characters and
10992 (@value{GDBP}) show charset
10993 The current host and target character set is `ISO-8859-1'.
10997 For the sake of printing this manual, let's use @sc{ascii} as our
10998 initial character set:
11000 (@value{GDBP}) set charset ASCII
11001 (@value{GDBP}) show charset
11002 The current host and target character set is `ASCII'.
11006 Let's assume that @sc{ascii} is indeed the correct character set for our
11007 host system --- in other words, let's assume that if @value{GDBN} prints
11008 characters using the @sc{ascii} character set, our terminal will display
11009 them properly. Since our current target character set is also
11010 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
11013 (@value{GDBP}) print ascii_hello
11014 $1 = 0x401698 "Hello, world!\n"
11015 (@value{GDBP}) print ascii_hello[0]
11020 @value{GDBN} uses the target character set for character and string
11021 literals you use in expressions:
11024 (@value{GDBP}) print '+'
11029 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
11032 @value{GDBN} relies on the user to tell it which character set the
11033 target program uses. If we print @code{ibm1047_hello} while our target
11034 character set is still @sc{ascii}, we get jibberish:
11037 (@value{GDBP}) print ibm1047_hello
11038 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
11039 (@value{GDBP}) print ibm1047_hello[0]
11044 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
11045 @value{GDBN} tells us the character sets it supports:
11048 (@value{GDBP}) set target-charset
11049 ASCII EBCDIC-US IBM1047 ISO-8859-1
11050 (@value{GDBP}) set target-charset
11053 We can select @sc{ibm1047} as our target character set, and examine the
11054 program's strings again. Now the @sc{ascii} string is wrong, but
11055 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
11056 target character set, @sc{ibm1047}, to the host character set,
11057 @sc{ascii}, and they display correctly:
11060 (@value{GDBP}) set target-charset IBM1047
11061 (@value{GDBP}) show charset
11062 The current host character set is `ASCII'.
11063 The current target character set is `IBM1047'.
11064 (@value{GDBP}) print ascii_hello
11065 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
11066 (@value{GDBP}) print ascii_hello[0]
11068 (@value{GDBP}) print ibm1047_hello
11069 $8 = 0x4016a8 "Hello, world!\n"
11070 (@value{GDBP}) print ibm1047_hello[0]
11075 As above, @value{GDBN} uses the target character set for character and
11076 string literals you use in expressions:
11079 (@value{GDBP}) print '+'
11084 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
11087 @node Caching Target Data
11088 @section Caching Data of Targets
11089 @cindex caching data of targets
11091 @value{GDBN} caches data exchanged between the debugger and a target.
11092 Each cache is associated with the address space of the inferior.
11093 @xref{Inferiors and Programs}, about inferior and address space.
11094 Such caching generally improves performance in remote debugging
11095 (@pxref{Remote Debugging}), because it reduces the overhead of the
11096 remote protocol by bundling memory reads and writes into large chunks.
11097 Unfortunately, simply caching everything would lead to incorrect results,
11098 since @value{GDBN} does not necessarily know anything about volatile
11099 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
11100 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
11102 Therefore, by default, @value{GDBN} only caches data
11103 known to be on the stack@footnote{In non-stop mode, it is moderately
11104 rare for a running thread to modify the stack of a stopped thread
11105 in a way that would interfere with a backtrace, and caching of
11106 stack reads provides a significant speed up of remote backtraces.} or
11107 in the code segment.
11108 Other regions of memory can be explicitly marked as
11109 cacheable; @pxref{Memory Region Attributes}.
11112 @kindex set remotecache
11113 @item set remotecache on
11114 @itemx set remotecache off
11115 This option no longer does anything; it exists for compatibility
11118 @kindex show remotecache
11119 @item show remotecache
11120 Show the current state of the obsolete remotecache flag.
11122 @kindex set stack-cache
11123 @item set stack-cache on
11124 @itemx set stack-cache off
11125 Enable or disable caching of stack accesses. When @code{on}, use
11126 caching. By default, this option is @code{on}.
11128 @kindex show stack-cache
11129 @item show stack-cache
11130 Show the current state of data caching for memory accesses.
11132 @kindex set code-cache
11133 @item set code-cache on
11134 @itemx set code-cache off
11135 Enable or disable caching of code segment accesses. When @code{on},
11136 use caching. By default, this option is @code{on}. This improves
11137 performance of disassembly in remote debugging.
11139 @kindex show code-cache
11140 @item show code-cache
11141 Show the current state of target memory cache for code segment
11144 @kindex info dcache
11145 @item info dcache @r{[}line@r{]}
11146 Print the information about the performance of data cache of the
11147 current inferior's address space. The information displayed
11148 includes the dcache width and depth, and for each cache line, its
11149 number, address, and how many times it was referenced. This
11150 command is useful for debugging the data cache operation.
11152 If a line number is specified, the contents of that line will be
11155 @item set dcache size @var{size}
11156 @cindex dcache size
11157 @kindex set dcache size
11158 Set maximum number of entries in dcache (dcache depth above).
11160 @item set dcache line-size @var{line-size}
11161 @cindex dcache line-size
11162 @kindex set dcache line-size
11163 Set number of bytes each dcache entry caches (dcache width above).
11164 Must be a power of 2.
11166 @item show dcache size
11167 @kindex show dcache size
11168 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
11170 @item show dcache line-size
11171 @kindex show dcache line-size
11172 Show default size of dcache lines.
11176 @node Searching Memory
11177 @section Search Memory
11178 @cindex searching memory
11180 Memory can be searched for a particular sequence of bytes with the
11181 @code{find} command.
11185 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11186 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11187 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
11188 etc. The search begins at address @var{start_addr} and continues for either
11189 @var{len} bytes or through to @var{end_addr} inclusive.
11192 @var{s} and @var{n} are optional parameters.
11193 They may be specified in either order, apart or together.
11196 @item @var{s}, search query size
11197 The size of each search query value.
11203 halfwords (two bytes)
11207 giant words (eight bytes)
11210 All values are interpreted in the current language.
11211 This means, for example, that if the current source language is C/C@t{++}
11212 then searching for the string ``hello'' includes the trailing '\0'.
11214 If the value size is not specified, it is taken from the
11215 value's type in the current language.
11216 This is useful when one wants to specify the search
11217 pattern as a mixture of types.
11218 Note that this means, for example, that in the case of C-like languages
11219 a search for an untyped 0x42 will search for @samp{(int) 0x42}
11220 which is typically four bytes.
11222 @item @var{n}, maximum number of finds
11223 The maximum number of matches to print. The default is to print all finds.
11226 You can use strings as search values. Quote them with double-quotes
11228 The string value is copied into the search pattern byte by byte,
11229 regardless of the endianness of the target and the size specification.
11231 The address of each match found is printed as well as a count of the
11232 number of matches found.
11234 The address of the last value found is stored in convenience variable
11236 A count of the number of matches is stored in @samp{$numfound}.
11238 For example, if stopped at the @code{printf} in this function:
11244 static char hello[] = "hello-hello";
11245 static struct @{ char c; short s; int i; @}
11246 __attribute__ ((packed)) mixed
11247 = @{ 'c', 0x1234, 0x87654321 @};
11248 printf ("%s\n", hello);
11253 you get during debugging:
11256 (gdb) find &hello[0], +sizeof(hello), "hello"
11257 0x804956d <hello.1620+6>
11259 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
11260 0x8049567 <hello.1620>
11261 0x804956d <hello.1620+6>
11263 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
11264 0x8049567 <hello.1620>
11266 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
11267 0x8049560 <mixed.1625>
11269 (gdb) print $numfound
11272 $2 = (void *) 0x8049560
11275 @node Optimized Code
11276 @chapter Debugging Optimized Code
11277 @cindex optimized code, debugging
11278 @cindex debugging optimized code
11280 Almost all compilers support optimization. With optimization
11281 disabled, the compiler generates assembly code that corresponds
11282 directly to your source code, in a simplistic way. As the compiler
11283 applies more powerful optimizations, the generated assembly code
11284 diverges from your original source code. With help from debugging
11285 information generated by the compiler, @value{GDBN} can map from
11286 the running program back to constructs from your original source.
11288 @value{GDBN} is more accurate with optimization disabled. If you
11289 can recompile without optimization, it is easier to follow the
11290 progress of your program during debugging. But, there are many cases
11291 where you may need to debug an optimized version.
11293 When you debug a program compiled with @samp{-g -O}, remember that the
11294 optimizer has rearranged your code; the debugger shows you what is
11295 really there. Do not be too surprised when the execution path does not
11296 exactly match your source file! An extreme example: if you define a
11297 variable, but never use it, @value{GDBN} never sees that
11298 variable---because the compiler optimizes it out of existence.
11300 Some things do not work as well with @samp{-g -O} as with just
11301 @samp{-g}, particularly on machines with instruction scheduling. If in
11302 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
11303 please report it to us as a bug (including a test case!).
11304 @xref{Variables}, for more information about debugging optimized code.
11307 * Inline Functions:: How @value{GDBN} presents inlining
11308 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
11311 @node Inline Functions
11312 @section Inline Functions
11313 @cindex inline functions, debugging
11315 @dfn{Inlining} is an optimization that inserts a copy of the function
11316 body directly at each call site, instead of jumping to a shared
11317 routine. @value{GDBN} displays inlined functions just like
11318 non-inlined functions. They appear in backtraces. You can view their
11319 arguments and local variables, step into them with @code{step}, skip
11320 them with @code{next}, and escape from them with @code{finish}.
11321 You can check whether a function was inlined by using the
11322 @code{info frame} command.
11324 For @value{GDBN} to support inlined functions, the compiler must
11325 record information about inlining in the debug information ---
11326 @value{NGCC} using the @sc{dwarf 2} format does this, and several
11327 other compilers do also. @value{GDBN} only supports inlined functions
11328 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
11329 do not emit two required attributes (@samp{DW_AT_call_file} and
11330 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
11331 function calls with earlier versions of @value{NGCC}. It instead
11332 displays the arguments and local variables of inlined functions as
11333 local variables in the caller.
11335 The body of an inlined function is directly included at its call site;
11336 unlike a non-inlined function, there are no instructions devoted to
11337 the call. @value{GDBN} still pretends that the call site and the
11338 start of the inlined function are different instructions. Stepping to
11339 the call site shows the call site, and then stepping again shows
11340 the first line of the inlined function, even though no additional
11341 instructions are executed.
11343 This makes source-level debugging much clearer; you can see both the
11344 context of the call and then the effect of the call. Only stepping by
11345 a single instruction using @code{stepi} or @code{nexti} does not do
11346 this; single instruction steps always show the inlined body.
11348 There are some ways that @value{GDBN} does not pretend that inlined
11349 function calls are the same as normal calls:
11353 Setting breakpoints at the call site of an inlined function may not
11354 work, because the call site does not contain any code. @value{GDBN}
11355 may incorrectly move the breakpoint to the next line of the enclosing
11356 function, after the call. This limitation will be removed in a future
11357 version of @value{GDBN}; until then, set a breakpoint on an earlier line
11358 or inside the inlined function instead.
11361 @value{GDBN} cannot locate the return value of inlined calls after
11362 using the @code{finish} command. This is a limitation of compiler-generated
11363 debugging information; after @code{finish}, you can step to the next line
11364 and print a variable where your program stored the return value.
11368 @node Tail Call Frames
11369 @section Tail Call Frames
11370 @cindex tail call frames, debugging
11372 Function @code{B} can call function @code{C} in its very last statement. In
11373 unoptimized compilation the call of @code{C} is immediately followed by return
11374 instruction at the end of @code{B} code. Optimizing compiler may replace the
11375 call and return in function @code{B} into one jump to function @code{C}
11376 instead. Such use of a jump instruction is called @dfn{tail call}.
11378 During execution of function @code{C}, there will be no indication in the
11379 function call stack frames that it was tail-called from @code{B}. If function
11380 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
11381 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
11382 some cases @value{GDBN} can determine that @code{C} was tail-called from
11383 @code{B}, and it will then create fictitious call frame for that, with the
11384 return address set up as if @code{B} called @code{C} normally.
11386 This functionality is currently supported only by DWARF 2 debugging format and
11387 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
11388 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11391 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
11392 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
11396 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
11398 Stack level 1, frame at 0x7fffffffda30:
11399 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
11400 tail call frame, caller of frame at 0x7fffffffda30
11401 source language c++.
11402 Arglist at unknown address.
11403 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
11406 The detection of all the possible code path executions can find them ambiguous.
11407 There is no execution history stored (possible @ref{Reverse Execution} is never
11408 used for this purpose) and the last known caller could have reached the known
11409 callee by multiple different jump sequences. In such case @value{GDBN} still
11410 tries to show at least all the unambiguous top tail callers and all the
11411 unambiguous bottom tail calees, if any.
11414 @anchor{set debug entry-values}
11415 @item set debug entry-values
11416 @kindex set debug entry-values
11417 When set to on, enables printing of analysis messages for both frame argument
11418 values at function entry and tail calls. It will show all the possible valid
11419 tail calls code paths it has considered. It will also print the intersection
11420 of them with the final unambiguous (possibly partial or even empty) code path
11423 @item show debug entry-values
11424 @kindex show debug entry-values
11425 Show the current state of analysis messages printing for both frame argument
11426 values at function entry and tail calls.
11429 The analysis messages for tail calls can for example show why the virtual tail
11430 call frame for function @code{c} has not been recognized (due to the indirect
11431 reference by variable @code{x}):
11434 static void __attribute__((noinline, noclone)) c (void);
11435 void (*x) (void) = c;
11436 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11437 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
11438 int main (void) @{ x (); return 0; @}
11440 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
11441 DW_TAG_GNU_call_site 0x40039a in main
11443 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11446 #1 0x000000000040039a in main () at t.c:5
11449 Another possibility is an ambiguous virtual tail call frames resolution:
11453 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
11454 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
11455 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
11456 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
11457 static void __attribute__((noinline, noclone)) b (void)
11458 @{ if (i) c (); else e (); @}
11459 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
11460 int main (void) @{ a (); return 0; @}
11462 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
11463 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
11464 tailcall: reduced: 0x4004d2(a) |
11467 #1 0x00000000004004d2 in a () at t.c:8
11468 #2 0x0000000000400395 in main () at t.c:9
11471 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
11472 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
11474 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
11475 @ifset HAVE_MAKEINFO_CLICK
11476 @set ARROW @click{}
11477 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
11478 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
11480 @ifclear HAVE_MAKEINFO_CLICK
11482 @set CALLSEQ1B @value{CALLSEQ1A}
11483 @set CALLSEQ2B @value{CALLSEQ2A}
11486 Frames #0 and #2 are real, #1 is a virtual tail call frame.
11487 The code can have possible execution paths @value{CALLSEQ1B} or
11488 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
11490 @code{initial:} state shows some random possible calling sequence @value{GDBN}
11491 has found. It then finds another possible calling sequcen - that one is
11492 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
11493 printed as the @code{reduced:} calling sequence. That one could have many
11494 futher @code{compare:} and @code{reduced:} statements as long as there remain
11495 any non-ambiguous sequence entries.
11497 For the frame of function @code{b} in both cases there are different possible
11498 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
11499 also ambigous. The only non-ambiguous frame is the one for function @code{a},
11500 therefore this one is displayed to the user while the ambiguous frames are
11503 There can be also reasons why printing of frame argument values at function
11508 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
11509 static void __attribute__((noinline, noclone)) a (int i);
11510 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
11511 static void __attribute__((noinline, noclone)) a (int i)
11512 @{ if (i) b (i - 1); else c (0); @}
11513 int main (void) @{ a (5); return 0; @}
11516 #0 c (i=i@@entry=0) at t.c:2
11517 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
11518 function "a" at 0x400420 can call itself via tail calls
11519 i=<optimized out>) at t.c:6
11520 #2 0x000000000040036e in main () at t.c:7
11523 @value{GDBN} cannot find out from the inferior state if and how many times did
11524 function @code{a} call itself (via function @code{b}) as these calls would be
11525 tail calls. Such tail calls would modify thue @code{i} variable, therefore
11526 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
11527 prints @code{<optimized out>} instead.
11530 @chapter C Preprocessor Macros
11532 Some languages, such as C and C@t{++}, provide a way to define and invoke
11533 ``preprocessor macros'' which expand into strings of tokens.
11534 @value{GDBN} can evaluate expressions containing macro invocations, show
11535 the result of macro expansion, and show a macro's definition, including
11536 where it was defined.
11538 You may need to compile your program specially to provide @value{GDBN}
11539 with information about preprocessor macros. Most compilers do not
11540 include macros in their debugging information, even when you compile
11541 with the @option{-g} flag. @xref{Compilation}.
11543 A program may define a macro at one point, remove that definition later,
11544 and then provide a different definition after that. Thus, at different
11545 points in the program, a macro may have different definitions, or have
11546 no definition at all. If there is a current stack frame, @value{GDBN}
11547 uses the macros in scope at that frame's source code line. Otherwise,
11548 @value{GDBN} uses the macros in scope at the current listing location;
11551 Whenever @value{GDBN} evaluates an expression, it always expands any
11552 macro invocations present in the expression. @value{GDBN} also provides
11553 the following commands for working with macros explicitly.
11557 @kindex macro expand
11558 @cindex macro expansion, showing the results of preprocessor
11559 @cindex preprocessor macro expansion, showing the results of
11560 @cindex expanding preprocessor macros
11561 @item macro expand @var{expression}
11562 @itemx macro exp @var{expression}
11563 Show the results of expanding all preprocessor macro invocations in
11564 @var{expression}. Since @value{GDBN} simply expands macros, but does
11565 not parse the result, @var{expression} need not be a valid expression;
11566 it can be any string of tokens.
11569 @item macro expand-once @var{expression}
11570 @itemx macro exp1 @var{expression}
11571 @cindex expand macro once
11572 @i{(This command is not yet implemented.)} Show the results of
11573 expanding those preprocessor macro invocations that appear explicitly in
11574 @var{expression}. Macro invocations appearing in that expansion are
11575 left unchanged. This command allows you to see the effect of a
11576 particular macro more clearly, without being confused by further
11577 expansions. Since @value{GDBN} simply expands macros, but does not
11578 parse the result, @var{expression} need not be a valid expression; it
11579 can be any string of tokens.
11582 @cindex macro definition, showing
11583 @cindex definition of a macro, showing
11584 @cindex macros, from debug info
11585 @item info macro [-a|-all] [--] @var{macro}
11586 Show the current definition or all definitions of the named @var{macro},
11587 and describe the source location or compiler command-line where that
11588 definition was established. The optional double dash is to signify the end of
11589 argument processing and the beginning of @var{macro} for non C-like macros where
11590 the macro may begin with a hyphen.
11592 @kindex info macros
11593 @item info macros @var{linespec}
11594 Show all macro definitions that are in effect at the location specified
11595 by @var{linespec}, and describe the source location or compiler
11596 command-line where those definitions were established.
11598 @kindex macro define
11599 @cindex user-defined macros
11600 @cindex defining macros interactively
11601 @cindex macros, user-defined
11602 @item macro define @var{macro} @var{replacement-list}
11603 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
11604 Introduce a definition for a preprocessor macro named @var{macro},
11605 invocations of which are replaced by the tokens given in
11606 @var{replacement-list}. The first form of this command defines an
11607 ``object-like'' macro, which takes no arguments; the second form
11608 defines a ``function-like'' macro, which takes the arguments given in
11611 A definition introduced by this command is in scope in every
11612 expression evaluated in @value{GDBN}, until it is removed with the
11613 @code{macro undef} command, described below. The definition overrides
11614 all definitions for @var{macro} present in the program being debugged,
11615 as well as any previous user-supplied definition.
11617 @kindex macro undef
11618 @item macro undef @var{macro}
11619 Remove any user-supplied definition for the macro named @var{macro}.
11620 This command only affects definitions provided with the @code{macro
11621 define} command, described above; it cannot remove definitions present
11622 in the program being debugged.
11626 List all the macros defined using the @code{macro define} command.
11629 @cindex macros, example of debugging with
11630 Here is a transcript showing the above commands in action. First, we
11631 show our source files:
11636 #include "sample.h"
11639 #define ADD(x) (M + x)
11644 printf ("Hello, world!\n");
11646 printf ("We're so creative.\n");
11648 printf ("Goodbye, world!\n");
11655 Now, we compile the program using the @sc{gnu} C compiler,
11656 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
11657 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
11658 and @option{-gdwarf-4}; we recommend always choosing the most recent
11659 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
11660 includes information about preprocessor macros in the debugging
11664 $ gcc -gdwarf-2 -g3 sample.c -o sample
11668 Now, we start @value{GDBN} on our sample program:
11672 GNU gdb 2002-05-06-cvs
11673 Copyright 2002 Free Software Foundation, Inc.
11674 GDB is free software, @dots{}
11678 We can expand macros and examine their definitions, even when the
11679 program is not running. @value{GDBN} uses the current listing position
11680 to decide which macro definitions are in scope:
11683 (@value{GDBP}) list main
11686 5 #define ADD(x) (M + x)
11691 10 printf ("Hello, world!\n");
11693 12 printf ("We're so creative.\n");
11694 (@value{GDBP}) info macro ADD
11695 Defined at /home/jimb/gdb/macros/play/sample.c:5
11696 #define ADD(x) (M + x)
11697 (@value{GDBP}) info macro Q
11698 Defined at /home/jimb/gdb/macros/play/sample.h:1
11699 included at /home/jimb/gdb/macros/play/sample.c:2
11701 (@value{GDBP}) macro expand ADD(1)
11702 expands to: (42 + 1)
11703 (@value{GDBP}) macro expand-once ADD(1)
11704 expands to: once (M + 1)
11708 In the example above, note that @code{macro expand-once} expands only
11709 the macro invocation explicit in the original text --- the invocation of
11710 @code{ADD} --- but does not expand the invocation of the macro @code{M},
11711 which was introduced by @code{ADD}.
11713 Once the program is running, @value{GDBN} uses the macro definitions in
11714 force at the source line of the current stack frame:
11717 (@value{GDBP}) break main
11718 Breakpoint 1 at 0x8048370: file sample.c, line 10.
11720 Starting program: /home/jimb/gdb/macros/play/sample
11722 Breakpoint 1, main () at sample.c:10
11723 10 printf ("Hello, world!\n");
11727 At line 10, the definition of the macro @code{N} at line 9 is in force:
11730 (@value{GDBP}) info macro N
11731 Defined at /home/jimb/gdb/macros/play/sample.c:9
11733 (@value{GDBP}) macro expand N Q M
11734 expands to: 28 < 42
11735 (@value{GDBP}) print N Q M
11740 As we step over directives that remove @code{N}'s definition, and then
11741 give it a new definition, @value{GDBN} finds the definition (or lack
11742 thereof) in force at each point:
11745 (@value{GDBP}) next
11747 12 printf ("We're so creative.\n");
11748 (@value{GDBP}) info macro N
11749 The symbol `N' has no definition as a C/C++ preprocessor macro
11750 at /home/jimb/gdb/macros/play/sample.c:12
11751 (@value{GDBP}) next
11753 14 printf ("Goodbye, world!\n");
11754 (@value{GDBP}) info macro N
11755 Defined at /home/jimb/gdb/macros/play/sample.c:13
11757 (@value{GDBP}) macro expand N Q M
11758 expands to: 1729 < 42
11759 (@value{GDBP}) print N Q M
11764 In addition to source files, macros can be defined on the compilation command
11765 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
11766 such a way, @value{GDBN} displays the location of their definition as line zero
11767 of the source file submitted to the compiler.
11770 (@value{GDBP}) info macro __STDC__
11771 Defined at /home/jimb/gdb/macros/play/sample.c:0
11778 @chapter Tracepoints
11779 @c This chapter is based on the documentation written by Michael
11780 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
11782 @cindex tracepoints
11783 In some applications, it is not feasible for the debugger to interrupt
11784 the program's execution long enough for the developer to learn
11785 anything helpful about its behavior. If the program's correctness
11786 depends on its real-time behavior, delays introduced by a debugger
11787 might cause the program to change its behavior drastically, or perhaps
11788 fail, even when the code itself is correct. It is useful to be able
11789 to observe the program's behavior without interrupting it.
11791 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
11792 specify locations in the program, called @dfn{tracepoints}, and
11793 arbitrary expressions to evaluate when those tracepoints are reached.
11794 Later, using the @code{tfind} command, you can examine the values
11795 those expressions had when the program hit the tracepoints. The
11796 expressions may also denote objects in memory---structures or arrays,
11797 for example---whose values @value{GDBN} should record; while visiting
11798 a particular tracepoint, you may inspect those objects as if they were
11799 in memory at that moment. However, because @value{GDBN} records these
11800 values without interacting with you, it can do so quickly and
11801 unobtrusively, hopefully not disturbing the program's behavior.
11803 The tracepoint facility is currently available only for remote
11804 targets. @xref{Targets}. In addition, your remote target must know
11805 how to collect trace data. This functionality is implemented in the
11806 remote stub; however, none of the stubs distributed with @value{GDBN}
11807 support tracepoints as of this writing. The format of the remote
11808 packets used to implement tracepoints are described in @ref{Tracepoint
11811 It is also possible to get trace data from a file, in a manner reminiscent
11812 of corefiles; you specify the filename, and use @code{tfind} to search
11813 through the file. @xref{Trace Files}, for more details.
11815 This chapter describes the tracepoint commands and features.
11818 * Set Tracepoints::
11819 * Analyze Collected Data::
11820 * Tracepoint Variables::
11824 @node Set Tracepoints
11825 @section Commands to Set Tracepoints
11827 Before running such a @dfn{trace experiment}, an arbitrary number of
11828 tracepoints can be set. A tracepoint is actually a special type of
11829 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
11830 standard breakpoint commands. For instance, as with breakpoints,
11831 tracepoint numbers are successive integers starting from one, and many
11832 of the commands associated with tracepoints take the tracepoint number
11833 as their argument, to identify which tracepoint to work on.
11835 For each tracepoint, you can specify, in advance, some arbitrary set
11836 of data that you want the target to collect in the trace buffer when
11837 it hits that tracepoint. The collected data can include registers,
11838 local variables, or global data. Later, you can use @value{GDBN}
11839 commands to examine the values these data had at the time the
11840 tracepoint was hit.
11842 Tracepoints do not support every breakpoint feature. Ignore counts on
11843 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
11844 commands when they are hit. Tracepoints may not be thread-specific
11847 @cindex fast tracepoints
11848 Some targets may support @dfn{fast tracepoints}, which are inserted in
11849 a different way (such as with a jump instead of a trap), that is
11850 faster but possibly restricted in where they may be installed.
11852 @cindex static tracepoints
11853 @cindex markers, static tracepoints
11854 @cindex probing markers, static tracepoints
11855 Regular and fast tracepoints are dynamic tracing facilities, meaning
11856 that they can be used to insert tracepoints at (almost) any location
11857 in the target. Some targets may also support controlling @dfn{static
11858 tracepoints} from @value{GDBN}. With static tracing, a set of
11859 instrumentation points, also known as @dfn{markers}, are embedded in
11860 the target program, and can be activated or deactivated by name or
11861 address. These are usually placed at locations which facilitate
11862 investigating what the target is actually doing. @value{GDBN}'s
11863 support for static tracing includes being able to list instrumentation
11864 points, and attach them with @value{GDBN} defined high level
11865 tracepoints that expose the whole range of convenience of
11866 @value{GDBN}'s tracepoints support. Namely, support for collecting
11867 registers values and values of global or local (to the instrumentation
11868 point) variables; tracepoint conditions and trace state variables.
11869 The act of installing a @value{GDBN} static tracepoint on an
11870 instrumentation point, or marker, is referred to as @dfn{probing} a
11871 static tracepoint marker.
11873 @code{gdbserver} supports tracepoints on some target systems.
11874 @xref{Server,,Tracepoints support in @code{gdbserver}}.
11876 This section describes commands to set tracepoints and associated
11877 conditions and actions.
11880 * Create and Delete Tracepoints::
11881 * Enable and Disable Tracepoints::
11882 * Tracepoint Passcounts::
11883 * Tracepoint Conditions::
11884 * Trace State Variables::
11885 * Tracepoint Actions::
11886 * Listing Tracepoints::
11887 * Listing Static Tracepoint Markers::
11888 * Starting and Stopping Trace Experiments::
11889 * Tracepoint Restrictions::
11892 @node Create and Delete Tracepoints
11893 @subsection Create and Delete Tracepoints
11896 @cindex set tracepoint
11898 @item trace @var{location}
11899 The @code{trace} command is very similar to the @code{break} command.
11900 Its argument @var{location} can be a source line, a function name, or
11901 an address in the target program. @xref{Specify Location}. The
11902 @code{trace} command defines a tracepoint, which is a point in the
11903 target program where the debugger will briefly stop, collect some
11904 data, and then allow the program to continue. Setting a tracepoint or
11905 changing its actions takes effect immediately if the remote stub
11906 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
11908 If remote stub doesn't support the @samp{InstallInTrace} feature, all
11909 these changes don't take effect until the next @code{tstart}
11910 command, and once a trace experiment is running, further changes will
11911 not have any effect until the next trace experiment starts. In addition,
11912 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
11913 address is not yet resolved. (This is similar to pending breakpoints.)
11914 Pending tracepoints are not downloaded to the target and not installed
11915 until they are resolved. The resolution of pending tracepoints requires
11916 @value{GDBN} support---when debugging with the remote target, and
11917 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
11918 tracing}), pending tracepoints can not be resolved (and downloaded to
11919 the remote stub) while @value{GDBN} is disconnected.
11921 Here are some examples of using the @code{trace} command:
11924 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
11926 (@value{GDBP}) @b{trace +2} // 2 lines forward
11928 (@value{GDBP}) @b{trace my_function} // first source line of function
11930 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
11932 (@value{GDBP}) @b{trace *0x2117c4} // an address
11936 You can abbreviate @code{trace} as @code{tr}.
11938 @item trace @var{location} if @var{cond}
11939 Set a tracepoint with condition @var{cond}; evaluate the expression
11940 @var{cond} each time the tracepoint is reached, and collect data only
11941 if the value is nonzero---that is, if @var{cond} evaluates as true.
11942 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
11943 information on tracepoint conditions.
11945 @item ftrace @var{location} [ if @var{cond} ]
11946 @cindex set fast tracepoint
11947 @cindex fast tracepoints, setting
11949 The @code{ftrace} command sets a fast tracepoint. For targets that
11950 support them, fast tracepoints will use a more efficient but possibly
11951 less general technique to trigger data collection, such as a jump
11952 instruction instead of a trap, or some sort of hardware support. It
11953 may not be possible to create a fast tracepoint at the desired
11954 location, in which case the command will exit with an explanatory
11957 @value{GDBN} handles arguments to @code{ftrace} exactly as for
11960 On 32-bit x86-architecture systems, fast tracepoints normally need to
11961 be placed at an instruction that is 5 bytes or longer, but can be
11962 placed at 4-byte instructions if the low 64K of memory of the target
11963 program is available to install trampolines. Some Unix-type systems,
11964 such as @sc{gnu}/Linux, exclude low addresses from the program's
11965 address space; but for instance with the Linux kernel it is possible
11966 to let @value{GDBN} use this area by doing a @command{sysctl} command
11967 to set the @code{mmap_min_addr} kernel parameter, as in
11970 sudo sysctl -w vm.mmap_min_addr=32768
11974 which sets the low address to 32K, which leaves plenty of room for
11975 trampolines. The minimum address should be set to a page boundary.
11977 @item strace @var{location} [ if @var{cond} ]
11978 @cindex set static tracepoint
11979 @cindex static tracepoints, setting
11980 @cindex probe static tracepoint marker
11982 The @code{strace} command sets a static tracepoint. For targets that
11983 support it, setting a static tracepoint probes a static
11984 instrumentation point, or marker, found at @var{location}. It may not
11985 be possible to set a static tracepoint at the desired location, in
11986 which case the command will exit with an explanatory message.
11988 @value{GDBN} handles arguments to @code{strace} exactly as for
11989 @code{trace}, with the addition that the user can also specify
11990 @code{-m @var{marker}} as @var{location}. This probes the marker
11991 identified by the @var{marker} string identifier. This identifier
11992 depends on the static tracepoint backend library your program is
11993 using. You can find all the marker identifiers in the @samp{ID} field
11994 of the @code{info static-tracepoint-markers} command output.
11995 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
11996 Markers}. For example, in the following small program using the UST
12002 trace_mark(ust, bar33, "str %s", "FOOBAZ");
12007 the marker id is composed of joining the first two arguments to the
12008 @code{trace_mark} call with a slash, which translates to:
12011 (@value{GDBP}) info static-tracepoint-markers
12012 Cnt Enb ID Address What
12013 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
12019 so you may probe the marker above with:
12022 (@value{GDBP}) strace -m ust/bar33
12025 Static tracepoints accept an extra collect action --- @code{collect
12026 $_sdata}. This collects arbitrary user data passed in the probe point
12027 call to the tracing library. In the UST example above, you'll see
12028 that the third argument to @code{trace_mark} is a printf-like format
12029 string. The user data is then the result of running that formating
12030 string against the following arguments. Note that @code{info
12031 static-tracepoint-markers} command output lists that format string in
12032 the @samp{Data:} field.
12034 You can inspect this data when analyzing the trace buffer, by printing
12035 the $_sdata variable like any other variable available to
12036 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
12039 @cindex last tracepoint number
12040 @cindex recent tracepoint number
12041 @cindex tracepoint number
12042 The convenience variable @code{$tpnum} records the tracepoint number
12043 of the most recently set tracepoint.
12045 @kindex delete tracepoint
12046 @cindex tracepoint deletion
12047 @item delete tracepoint @r{[}@var{num}@r{]}
12048 Permanently delete one or more tracepoints. With no argument, the
12049 default is to delete all tracepoints. Note that the regular
12050 @code{delete} command can remove tracepoints also.
12055 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
12057 (@value{GDBP}) @b{delete trace} // remove all tracepoints
12061 You can abbreviate this command as @code{del tr}.
12064 @node Enable and Disable Tracepoints
12065 @subsection Enable and Disable Tracepoints
12067 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
12070 @kindex disable tracepoint
12071 @item disable tracepoint @r{[}@var{num}@r{]}
12072 Disable tracepoint @var{num}, or all tracepoints if no argument
12073 @var{num} is given. A disabled tracepoint will have no effect during
12074 a trace experiment, but it is not forgotten. You can re-enable
12075 a disabled tracepoint using the @code{enable tracepoint} command.
12076 If the command is issued during a trace experiment and the debug target
12077 has support for disabling tracepoints during a trace experiment, then the
12078 change will be effective immediately. Otherwise, it will be applied to the
12079 next trace experiment.
12081 @kindex enable tracepoint
12082 @item enable tracepoint @r{[}@var{num}@r{]}
12083 Enable tracepoint @var{num}, or all tracepoints. If this command is
12084 issued during a trace experiment and the debug target supports enabling
12085 tracepoints during a trace experiment, then the enabled tracepoints will
12086 become effective immediately. Otherwise, they will become effective the
12087 next time a trace experiment is run.
12090 @node Tracepoint Passcounts
12091 @subsection Tracepoint Passcounts
12095 @cindex tracepoint pass count
12096 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
12097 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
12098 automatically stop a trace experiment. If a tracepoint's passcount is
12099 @var{n}, then the trace experiment will be automatically stopped on
12100 the @var{n}'th time that tracepoint is hit. If the tracepoint number
12101 @var{num} is not specified, the @code{passcount} command sets the
12102 passcount of the most recently defined tracepoint. If no passcount is
12103 given, the trace experiment will run until stopped explicitly by the
12109 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
12110 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
12112 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
12113 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
12114 (@value{GDBP}) @b{trace foo}
12115 (@value{GDBP}) @b{pass 3}
12116 (@value{GDBP}) @b{trace bar}
12117 (@value{GDBP}) @b{pass 2}
12118 (@value{GDBP}) @b{trace baz}
12119 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
12120 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
12121 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
12122 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
12126 @node Tracepoint Conditions
12127 @subsection Tracepoint Conditions
12128 @cindex conditional tracepoints
12129 @cindex tracepoint conditions
12131 The simplest sort of tracepoint collects data every time your program
12132 reaches a specified place. You can also specify a @dfn{condition} for
12133 a tracepoint. A condition is just a Boolean expression in your
12134 programming language (@pxref{Expressions, ,Expressions}). A
12135 tracepoint with a condition evaluates the expression each time your
12136 program reaches it, and data collection happens only if the condition
12139 Tracepoint conditions can be specified when a tracepoint is set, by
12140 using @samp{if} in the arguments to the @code{trace} command.
12141 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
12142 also be set or changed at any time with the @code{condition} command,
12143 just as with breakpoints.
12145 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
12146 the conditional expression itself. Instead, @value{GDBN} encodes the
12147 expression into an agent expression (@pxref{Agent Expressions})
12148 suitable for execution on the target, independently of @value{GDBN}.
12149 Global variables become raw memory locations, locals become stack
12150 accesses, and so forth.
12152 For instance, suppose you have a function that is usually called
12153 frequently, but should not be called after an error has occurred. You
12154 could use the following tracepoint command to collect data about calls
12155 of that function that happen while the error code is propagating
12156 through the program; an unconditional tracepoint could end up
12157 collecting thousands of useless trace frames that you would have to
12161 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
12164 @node Trace State Variables
12165 @subsection Trace State Variables
12166 @cindex trace state variables
12168 A @dfn{trace state variable} is a special type of variable that is
12169 created and managed by target-side code. The syntax is the same as
12170 that for GDB's convenience variables (a string prefixed with ``$''),
12171 but they are stored on the target. They must be created explicitly,
12172 using a @code{tvariable} command. They are always 64-bit signed
12175 Trace state variables are remembered by @value{GDBN}, and downloaded
12176 to the target along with tracepoint information when the trace
12177 experiment starts. There are no intrinsic limits on the number of
12178 trace state variables, beyond memory limitations of the target.
12180 @cindex convenience variables, and trace state variables
12181 Although trace state variables are managed by the target, you can use
12182 them in print commands and expressions as if they were convenience
12183 variables; @value{GDBN} will get the current value from the target
12184 while the trace experiment is running. Trace state variables share
12185 the same namespace as other ``$'' variables, which means that you
12186 cannot have trace state variables with names like @code{$23} or
12187 @code{$pc}, nor can you have a trace state variable and a convenience
12188 variable with the same name.
12192 @item tvariable $@var{name} [ = @var{expression} ]
12194 The @code{tvariable} command creates a new trace state variable named
12195 @code{$@var{name}}, and optionally gives it an initial value of
12196 @var{expression}. The @var{expression} is evaluated when this command is
12197 entered; the result will be converted to an integer if possible,
12198 otherwise @value{GDBN} will report an error. A subsequent
12199 @code{tvariable} command specifying the same name does not create a
12200 variable, but instead assigns the supplied initial value to the
12201 existing variable of that name, overwriting any previous initial
12202 value. The default initial value is 0.
12204 @item info tvariables
12205 @kindex info tvariables
12206 List all the trace state variables along with their initial values.
12207 Their current values may also be displayed, if the trace experiment is
12210 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
12211 @kindex delete tvariable
12212 Delete the given trace state variables, or all of them if no arguments
12217 @node Tracepoint Actions
12218 @subsection Tracepoint Action Lists
12222 @cindex tracepoint actions
12223 @item actions @r{[}@var{num}@r{]}
12224 This command will prompt for a list of actions to be taken when the
12225 tracepoint is hit. If the tracepoint number @var{num} is not
12226 specified, this command sets the actions for the one that was most
12227 recently defined (so that you can define a tracepoint and then say
12228 @code{actions} without bothering about its number). You specify the
12229 actions themselves on the following lines, one action at a time, and
12230 terminate the actions list with a line containing just @code{end}. So
12231 far, the only defined actions are @code{collect}, @code{teval}, and
12232 @code{while-stepping}.
12234 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
12235 Commands, ,Breakpoint Command Lists}), except that only the defined
12236 actions are allowed; any other @value{GDBN} command is rejected.
12238 @cindex remove actions from a tracepoint
12239 To remove all actions from a tracepoint, type @samp{actions @var{num}}
12240 and follow it immediately with @samp{end}.
12243 (@value{GDBP}) @b{collect @var{data}} // collect some data
12245 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
12247 (@value{GDBP}) @b{end} // signals the end of actions.
12250 In the following example, the action list begins with @code{collect}
12251 commands indicating the things to be collected when the tracepoint is
12252 hit. Then, in order to single-step and collect additional data
12253 following the tracepoint, a @code{while-stepping} command is used,
12254 followed by the list of things to be collected after each step in a
12255 sequence of single steps. The @code{while-stepping} command is
12256 terminated by its own separate @code{end} command. Lastly, the action
12257 list is terminated by an @code{end} command.
12260 (@value{GDBP}) @b{trace foo}
12261 (@value{GDBP}) @b{actions}
12262 Enter actions for tracepoint 1, one per line:
12265 > while-stepping 12
12266 > collect $pc, arr[i]
12271 @kindex collect @r{(tracepoints)}
12272 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
12273 Collect values of the given expressions when the tracepoint is hit.
12274 This command accepts a comma-separated list of any valid expressions.
12275 In addition to global, static, or local variables, the following
12276 special arguments are supported:
12280 Collect all registers.
12283 Collect all function arguments.
12286 Collect all local variables.
12289 Collect the return address. This is helpful if you want to see more
12293 Collects the number of arguments from the static probe at which the
12294 tracepoint is located.
12295 @xref{Static Probe Points}.
12297 @item $_probe_arg@var{n}
12298 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
12299 from the static probe at which the tracepoint is located.
12300 @xref{Static Probe Points}.
12303 @vindex $_sdata@r{, collect}
12304 Collect static tracepoint marker specific data. Only available for
12305 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
12306 Lists}. On the UST static tracepoints library backend, an
12307 instrumentation point resembles a @code{printf} function call. The
12308 tracing library is able to collect user specified data formatted to a
12309 character string using the format provided by the programmer that
12310 instrumented the program. Other backends have similar mechanisms.
12311 Here's an example of a UST marker call:
12314 const char master_name[] = "$your_name";
12315 trace_mark(channel1, marker1, "hello %s", master_name)
12318 In this case, collecting @code{$_sdata} collects the string
12319 @samp{hello $yourname}. When analyzing the trace buffer, you can
12320 inspect @samp{$_sdata} like any other variable available to
12324 You can give several consecutive @code{collect} commands, each one
12325 with a single argument, or one @code{collect} command with several
12326 arguments separated by commas; the effect is the same.
12328 The optional @var{mods} changes the usual handling of the arguments.
12329 @code{s} requests that pointers to chars be handled as strings, in
12330 particular collecting the contents of the memory being pointed at, up
12331 to the first zero. The upper bound is by default the value of the
12332 @code{print elements} variable; if @code{s} is followed by a decimal
12333 number, that is the upper bound instead. So for instance
12334 @samp{collect/s25 mystr} collects as many as 25 characters at
12337 The command @code{info scope} (@pxref{Symbols, info scope}) is
12338 particularly useful for figuring out what data to collect.
12340 @kindex teval @r{(tracepoints)}
12341 @item teval @var{expr1}, @var{expr2}, @dots{}
12342 Evaluate the given expressions when the tracepoint is hit. This
12343 command accepts a comma-separated list of expressions. The results
12344 are discarded, so this is mainly useful for assigning values to trace
12345 state variables (@pxref{Trace State Variables}) without adding those
12346 values to the trace buffer, as would be the case if the @code{collect}
12349 @kindex while-stepping @r{(tracepoints)}
12350 @item while-stepping @var{n}
12351 Perform @var{n} single-step instruction traces after the tracepoint,
12352 collecting new data after each step. The @code{while-stepping}
12353 command is followed by the list of what to collect while stepping
12354 (followed by its own @code{end} command):
12357 > while-stepping 12
12358 > collect $regs, myglobal
12364 Note that @code{$pc} is not automatically collected by
12365 @code{while-stepping}; you need to explicitly collect that register if
12366 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
12369 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
12370 @kindex set default-collect
12371 @cindex default collection action
12372 This variable is a list of expressions to collect at each tracepoint
12373 hit. It is effectively an additional @code{collect} action prepended
12374 to every tracepoint action list. The expressions are parsed
12375 individually for each tracepoint, so for instance a variable named
12376 @code{xyz} may be interpreted as a global for one tracepoint, and a
12377 local for another, as appropriate to the tracepoint's location.
12379 @item show default-collect
12380 @kindex show default-collect
12381 Show the list of expressions that are collected by default at each
12386 @node Listing Tracepoints
12387 @subsection Listing Tracepoints
12390 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
12391 @kindex info tp @r{[}@var{n}@dots{}@r{]}
12392 @cindex information about tracepoints
12393 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
12394 Display information about the tracepoint @var{num}. If you don't
12395 specify a tracepoint number, displays information about all the
12396 tracepoints defined so far. The format is similar to that used for
12397 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
12398 command, simply restricting itself to tracepoints.
12400 A tracepoint's listing may include additional information specific to
12405 its passcount as given by the @code{passcount @var{n}} command
12408 the state about installed on target of each location
12412 (@value{GDBP}) @b{info trace}
12413 Num Type Disp Enb Address What
12414 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
12416 collect globfoo, $regs
12421 2 tracepoint keep y <MULTIPLE>
12423 2.1 y 0x0804859c in func4 at change-loc.h:35
12424 installed on target
12425 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
12426 installed on target
12427 2.3 y <PENDING> set_tracepoint
12428 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
12429 not installed on target
12434 This command can be abbreviated @code{info tp}.
12437 @node Listing Static Tracepoint Markers
12438 @subsection Listing Static Tracepoint Markers
12441 @kindex info static-tracepoint-markers
12442 @cindex information about static tracepoint markers
12443 @item info static-tracepoint-markers
12444 Display information about all static tracepoint markers defined in the
12447 For each marker, the following columns are printed:
12451 An incrementing counter, output to help readability. This is not a
12454 The marker ID, as reported by the target.
12455 @item Enabled or Disabled
12456 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
12457 that are not enabled.
12459 Where the marker is in your program, as a memory address.
12461 Where the marker is in the source for your program, as a file and line
12462 number. If the debug information included in the program does not
12463 allow @value{GDBN} to locate the source of the marker, this column
12464 will be left blank.
12468 In addition, the following information may be printed for each marker:
12472 User data passed to the tracing library by the marker call. In the
12473 UST backend, this is the format string passed as argument to the
12475 @item Static tracepoints probing the marker
12476 The list of static tracepoints attached to the marker.
12480 (@value{GDBP}) info static-tracepoint-markers
12481 Cnt ID Enb Address What
12482 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
12483 Data: number1 %d number2 %d
12484 Probed by static tracepoints: #2
12485 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
12491 @node Starting and Stopping Trace Experiments
12492 @subsection Starting and Stopping Trace Experiments
12495 @kindex tstart [ @var{notes} ]
12496 @cindex start a new trace experiment
12497 @cindex collected data discarded
12499 This command starts the trace experiment, and begins collecting data.
12500 It has the side effect of discarding all the data collected in the
12501 trace buffer during the previous trace experiment. If any arguments
12502 are supplied, they are taken as a note and stored with the trace
12503 experiment's state. The notes may be arbitrary text, and are
12504 especially useful with disconnected tracing in a multi-user context;
12505 the notes can explain what the trace is doing, supply user contact
12506 information, and so forth.
12508 @kindex tstop [ @var{notes} ]
12509 @cindex stop a running trace experiment
12511 This command stops the trace experiment. If any arguments are
12512 supplied, they are recorded with the experiment as a note. This is
12513 useful if you are stopping a trace started by someone else, for
12514 instance if the trace is interfering with the system's behavior and
12515 needs to be stopped quickly.
12517 @strong{Note}: a trace experiment and data collection may stop
12518 automatically if any tracepoint's passcount is reached
12519 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
12522 @cindex status of trace data collection
12523 @cindex trace experiment, status of
12525 This command displays the status of the current trace data
12529 Here is an example of the commands we described so far:
12532 (@value{GDBP}) @b{trace gdb_c_test}
12533 (@value{GDBP}) @b{actions}
12534 Enter actions for tracepoint #1, one per line.
12535 > collect $regs,$locals,$args
12536 > while-stepping 11
12540 (@value{GDBP}) @b{tstart}
12541 [time passes @dots{}]
12542 (@value{GDBP}) @b{tstop}
12545 @anchor{disconnected tracing}
12546 @cindex disconnected tracing
12547 You can choose to continue running the trace experiment even if
12548 @value{GDBN} disconnects from the target, voluntarily or
12549 involuntarily. For commands such as @code{detach}, the debugger will
12550 ask what you want to do with the trace. But for unexpected
12551 terminations (@value{GDBN} crash, network outage), it would be
12552 unfortunate to lose hard-won trace data, so the variable
12553 @code{disconnected-tracing} lets you decide whether the trace should
12554 continue running without @value{GDBN}.
12557 @item set disconnected-tracing on
12558 @itemx set disconnected-tracing off
12559 @kindex set disconnected-tracing
12560 Choose whether a tracing run should continue to run if @value{GDBN}
12561 has disconnected from the target. Note that @code{detach} or
12562 @code{quit} will ask you directly what to do about a running trace no
12563 matter what this variable's setting, so the variable is mainly useful
12564 for handling unexpected situations, such as loss of the network.
12566 @item show disconnected-tracing
12567 @kindex show disconnected-tracing
12568 Show the current choice for disconnected tracing.
12572 When you reconnect to the target, the trace experiment may or may not
12573 still be running; it might have filled the trace buffer in the
12574 meantime, or stopped for one of the other reasons. If it is running,
12575 it will continue after reconnection.
12577 Upon reconnection, the target will upload information about the
12578 tracepoints in effect. @value{GDBN} will then compare that
12579 information to the set of tracepoints currently defined, and attempt
12580 to match them up, allowing for the possibility that the numbers may
12581 have changed due to creation and deletion in the meantime. If one of
12582 the target's tracepoints does not match any in @value{GDBN}, the
12583 debugger will create a new tracepoint, so that you have a number with
12584 which to specify that tracepoint. This matching-up process is
12585 necessarily heuristic, and it may result in useless tracepoints being
12586 created; you may simply delete them if they are of no use.
12588 @cindex circular trace buffer
12589 If your target agent supports a @dfn{circular trace buffer}, then you
12590 can run a trace experiment indefinitely without filling the trace
12591 buffer; when space runs out, the agent deletes already-collected trace
12592 frames, oldest first, until there is enough room to continue
12593 collecting. This is especially useful if your tracepoints are being
12594 hit too often, and your trace gets terminated prematurely because the
12595 buffer is full. To ask for a circular trace buffer, simply set
12596 @samp{circular-trace-buffer} to on. You can set this at any time,
12597 including during tracing; if the agent can do it, it will change
12598 buffer handling on the fly, otherwise it will not take effect until
12602 @item set circular-trace-buffer on
12603 @itemx set circular-trace-buffer off
12604 @kindex set circular-trace-buffer
12605 Choose whether a tracing run should use a linear or circular buffer
12606 for trace data. A linear buffer will not lose any trace data, but may
12607 fill up prematurely, while a circular buffer will discard old trace
12608 data, but it will have always room for the latest tracepoint hits.
12610 @item show circular-trace-buffer
12611 @kindex show circular-trace-buffer
12612 Show the current choice for the trace buffer. Note that this may not
12613 match the agent's current buffer handling, nor is it guaranteed to
12614 match the setting that might have been in effect during a past run,
12615 for instance if you are looking at frames from a trace file.
12620 @item set trace-buffer-size @var{n}
12621 @itemx set trace-buffer-size unlimited
12622 @kindex set trace-buffer-size
12623 Request that the target use a trace buffer of @var{n} bytes. Not all
12624 targets will honor the request; they may have a compiled-in size for
12625 the trace buffer, or some other limitation. Set to a value of
12626 @code{unlimited} or @code{-1} to let the target use whatever size it
12627 likes. This is also the default.
12629 @item show trace-buffer-size
12630 @kindex show trace-buffer-size
12631 Show the current requested size for the trace buffer. Note that this
12632 will only match the actual size if the target supports size-setting,
12633 and was able to handle the requested size. For instance, if the
12634 target can only change buffer size between runs, this variable will
12635 not reflect the change until the next run starts. Use @code{tstatus}
12636 to get a report of the actual buffer size.
12640 @item set trace-user @var{text}
12641 @kindex set trace-user
12643 @item show trace-user
12644 @kindex show trace-user
12646 @item set trace-notes @var{text}
12647 @kindex set trace-notes
12648 Set the trace run's notes.
12650 @item show trace-notes
12651 @kindex show trace-notes
12652 Show the trace run's notes.
12654 @item set trace-stop-notes @var{text}
12655 @kindex set trace-stop-notes
12656 Set the trace run's stop notes. The handling of the note is as for
12657 @code{tstop} arguments; the set command is convenient way to fix a
12658 stop note that is mistaken or incomplete.
12660 @item show trace-stop-notes
12661 @kindex show trace-stop-notes
12662 Show the trace run's stop notes.
12666 @node Tracepoint Restrictions
12667 @subsection Tracepoint Restrictions
12669 @cindex tracepoint restrictions
12670 There are a number of restrictions on the use of tracepoints. As
12671 described above, tracepoint data gathering occurs on the target
12672 without interaction from @value{GDBN}. Thus the full capabilities of
12673 the debugger are not available during data gathering, and then at data
12674 examination time, you will be limited by only having what was
12675 collected. The following items describe some common problems, but it
12676 is not exhaustive, and you may run into additional difficulties not
12682 Tracepoint expressions are intended to gather objects (lvalues). Thus
12683 the full flexibility of GDB's expression evaluator is not available.
12684 You cannot call functions, cast objects to aggregate types, access
12685 convenience variables or modify values (except by assignment to trace
12686 state variables). Some language features may implicitly call
12687 functions (for instance Objective-C fields with accessors), and therefore
12688 cannot be collected either.
12691 Collection of local variables, either individually or in bulk with
12692 @code{$locals} or @code{$args}, during @code{while-stepping} may
12693 behave erratically. The stepping action may enter a new scope (for
12694 instance by stepping into a function), or the location of the variable
12695 may change (for instance it is loaded into a register). The
12696 tracepoint data recorded uses the location information for the
12697 variables that is correct for the tracepoint location. When the
12698 tracepoint is created, it is not possible, in general, to determine
12699 where the steps of a @code{while-stepping} sequence will advance the
12700 program---particularly if a conditional branch is stepped.
12703 Collection of an incompletely-initialized or partially-destroyed object
12704 may result in something that @value{GDBN} cannot display, or displays
12705 in a misleading way.
12708 When @value{GDBN} displays a pointer to character it automatically
12709 dereferences the pointer to also display characters of the string
12710 being pointed to. However, collecting the pointer during tracing does
12711 not automatically collect the string. You need to explicitly
12712 dereference the pointer and provide size information if you want to
12713 collect not only the pointer, but the memory pointed to. For example,
12714 @code{*ptr@@50} can be used to collect the 50 element array pointed to
12718 It is not possible to collect a complete stack backtrace at a
12719 tracepoint. Instead, you may collect the registers and a few hundred
12720 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
12721 (adjust to use the name of the actual stack pointer register on your
12722 target architecture, and the amount of stack you wish to capture).
12723 Then the @code{backtrace} command will show a partial backtrace when
12724 using a trace frame. The number of stack frames that can be examined
12725 depends on the sizes of the frames in the collected stack. Note that
12726 if you ask for a block so large that it goes past the bottom of the
12727 stack, the target agent may report an error trying to read from an
12731 If you do not collect registers at a tracepoint, @value{GDBN} can
12732 infer that the value of @code{$pc} must be the same as the address of
12733 the tracepoint and use that when you are looking at a trace frame
12734 for that tracepoint. However, this cannot work if the tracepoint has
12735 multiple locations (for instance if it was set in a function that was
12736 inlined), or if it has a @code{while-stepping} loop. In those cases
12737 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
12742 @node Analyze Collected Data
12743 @section Using the Collected Data
12745 After the tracepoint experiment ends, you use @value{GDBN} commands
12746 for examining the trace data. The basic idea is that each tracepoint
12747 collects a trace @dfn{snapshot} every time it is hit and another
12748 snapshot every time it single-steps. All these snapshots are
12749 consecutively numbered from zero and go into a buffer, and you can
12750 examine them later. The way you examine them is to @dfn{focus} on a
12751 specific trace snapshot. When the remote stub is focused on a trace
12752 snapshot, it will respond to all @value{GDBN} requests for memory and
12753 registers by reading from the buffer which belongs to that snapshot,
12754 rather than from @emph{real} memory or registers of the program being
12755 debugged. This means that @strong{all} @value{GDBN} commands
12756 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
12757 behave as if we were currently debugging the program state as it was
12758 when the tracepoint occurred. Any requests for data that are not in
12759 the buffer will fail.
12762 * tfind:: How to select a trace snapshot
12763 * tdump:: How to display all data for a snapshot
12764 * save tracepoints:: How to save tracepoints for a future run
12768 @subsection @code{tfind @var{n}}
12771 @cindex select trace snapshot
12772 @cindex find trace snapshot
12773 The basic command for selecting a trace snapshot from the buffer is
12774 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
12775 counting from zero. If no argument @var{n} is given, the next
12776 snapshot is selected.
12778 Here are the various forms of using the @code{tfind} command.
12782 Find the first snapshot in the buffer. This is a synonym for
12783 @code{tfind 0} (since 0 is the number of the first snapshot).
12786 Stop debugging trace snapshots, resume @emph{live} debugging.
12789 Same as @samp{tfind none}.
12792 No argument means find the next trace snapshot.
12795 Find the previous trace snapshot before the current one. This permits
12796 retracing earlier steps.
12798 @item tfind tracepoint @var{num}
12799 Find the next snapshot associated with tracepoint @var{num}. Search
12800 proceeds forward from the last examined trace snapshot. If no
12801 argument @var{num} is given, it means find the next snapshot collected
12802 for the same tracepoint as the current snapshot.
12804 @item tfind pc @var{addr}
12805 Find the next snapshot associated with the value @var{addr} of the
12806 program counter. Search proceeds forward from the last examined trace
12807 snapshot. If no argument @var{addr} is given, it means find the next
12808 snapshot with the same value of PC as the current snapshot.
12810 @item tfind outside @var{addr1}, @var{addr2}
12811 Find the next snapshot whose PC is outside the given range of
12812 addresses (exclusive).
12814 @item tfind range @var{addr1}, @var{addr2}
12815 Find the next snapshot whose PC is between @var{addr1} and
12816 @var{addr2} (inclusive).
12818 @item tfind line @r{[}@var{file}:@r{]}@var{n}
12819 Find the next snapshot associated with the source line @var{n}. If
12820 the optional argument @var{file} is given, refer to line @var{n} in
12821 that source file. Search proceeds forward from the last examined
12822 trace snapshot. If no argument @var{n} is given, it means find the
12823 next line other than the one currently being examined; thus saying
12824 @code{tfind line} repeatedly can appear to have the same effect as
12825 stepping from line to line in a @emph{live} debugging session.
12828 The default arguments for the @code{tfind} commands are specifically
12829 designed to make it easy to scan through the trace buffer. For
12830 instance, @code{tfind} with no argument selects the next trace
12831 snapshot, and @code{tfind -} with no argument selects the previous
12832 trace snapshot. So, by giving one @code{tfind} command, and then
12833 simply hitting @key{RET} repeatedly you can examine all the trace
12834 snapshots in order. Or, by saying @code{tfind -} and then hitting
12835 @key{RET} repeatedly you can examine the snapshots in reverse order.
12836 The @code{tfind line} command with no argument selects the snapshot
12837 for the next source line executed. The @code{tfind pc} command with
12838 no argument selects the next snapshot with the same program counter
12839 (PC) as the current frame. The @code{tfind tracepoint} command with
12840 no argument selects the next trace snapshot collected by the same
12841 tracepoint as the current one.
12843 In addition to letting you scan through the trace buffer manually,
12844 these commands make it easy to construct @value{GDBN} scripts that
12845 scan through the trace buffer and print out whatever collected data
12846 you are interested in. Thus, if we want to examine the PC, FP, and SP
12847 registers from each trace frame in the buffer, we can say this:
12850 (@value{GDBP}) @b{tfind start}
12851 (@value{GDBP}) @b{while ($trace_frame != -1)}
12852 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
12853 $trace_frame, $pc, $sp, $fp
12857 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
12858 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
12859 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
12860 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
12861 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
12862 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
12863 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
12864 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
12865 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
12866 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
12867 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
12870 Or, if we want to examine the variable @code{X} at each source line in
12874 (@value{GDBP}) @b{tfind start}
12875 (@value{GDBP}) @b{while ($trace_frame != -1)}
12876 > printf "Frame %d, X == %d\n", $trace_frame, X
12886 @subsection @code{tdump}
12888 @cindex dump all data collected at tracepoint
12889 @cindex tracepoint data, display
12891 This command takes no arguments. It prints all the data collected at
12892 the current trace snapshot.
12895 (@value{GDBP}) @b{trace 444}
12896 (@value{GDBP}) @b{actions}
12897 Enter actions for tracepoint #2, one per line:
12898 > collect $regs, $locals, $args, gdb_long_test
12901 (@value{GDBP}) @b{tstart}
12903 (@value{GDBP}) @b{tfind line 444}
12904 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
12906 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
12908 (@value{GDBP}) @b{tdump}
12909 Data collected at tracepoint 2, trace frame 1:
12910 d0 0xc4aa0085 -995491707
12914 d4 0x71aea3d 119204413
12917 d7 0x380035 3670069
12918 a0 0x19e24a 1696330
12919 a1 0x3000668 50333288
12921 a3 0x322000 3284992
12922 a4 0x3000698 50333336
12923 a5 0x1ad3cc 1758156
12924 fp 0x30bf3c 0x30bf3c
12925 sp 0x30bf34 0x30bf34
12927 pc 0x20b2c8 0x20b2c8
12931 p = 0x20e5b4 "gdb-test"
12938 gdb_long_test = 17 '\021'
12943 @code{tdump} works by scanning the tracepoint's current collection
12944 actions and printing the value of each expression listed. So
12945 @code{tdump} can fail, if after a run, you change the tracepoint's
12946 actions to mention variables that were not collected during the run.
12948 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
12949 uses the collected value of @code{$pc} to distinguish between trace
12950 frames that were collected at the tracepoint hit, and frames that were
12951 collected while stepping. This allows it to correctly choose whether
12952 to display the basic list of collections, or the collections from the
12953 body of the while-stepping loop. However, if @code{$pc} was not collected,
12954 then @code{tdump} will always attempt to dump using the basic collection
12955 list, and may fail if a while-stepping frame does not include all the
12956 same data that is collected at the tracepoint hit.
12957 @c This is getting pretty arcane, example would be good.
12959 @node save tracepoints
12960 @subsection @code{save tracepoints @var{filename}}
12961 @kindex save tracepoints
12962 @kindex save-tracepoints
12963 @cindex save tracepoints for future sessions
12965 This command saves all current tracepoint definitions together with
12966 their actions and passcounts, into a file @file{@var{filename}}
12967 suitable for use in a later debugging session. To read the saved
12968 tracepoint definitions, use the @code{source} command (@pxref{Command
12969 Files}). The @w{@code{save-tracepoints}} command is a deprecated
12970 alias for @w{@code{save tracepoints}}
12972 @node Tracepoint Variables
12973 @section Convenience Variables for Tracepoints
12974 @cindex tracepoint variables
12975 @cindex convenience variables for tracepoints
12978 @vindex $trace_frame
12979 @item (int) $trace_frame
12980 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
12981 snapshot is selected.
12983 @vindex $tracepoint
12984 @item (int) $tracepoint
12985 The tracepoint for the current trace snapshot.
12987 @vindex $trace_line
12988 @item (int) $trace_line
12989 The line number for the current trace snapshot.
12991 @vindex $trace_file
12992 @item (char []) $trace_file
12993 The source file for the current trace snapshot.
12995 @vindex $trace_func
12996 @item (char []) $trace_func
12997 The name of the function containing @code{$tracepoint}.
13000 Note: @code{$trace_file} is not suitable for use in @code{printf},
13001 use @code{output} instead.
13003 Here's a simple example of using these convenience variables for
13004 stepping through all the trace snapshots and printing some of their
13005 data. Note that these are not the same as trace state variables,
13006 which are managed by the target.
13009 (@value{GDBP}) @b{tfind start}
13011 (@value{GDBP}) @b{while $trace_frame != -1}
13012 > output $trace_file
13013 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
13019 @section Using Trace Files
13020 @cindex trace files
13022 In some situations, the target running a trace experiment may no
13023 longer be available; perhaps it crashed, or the hardware was needed
13024 for a different activity. To handle these cases, you can arrange to
13025 dump the trace data into a file, and later use that file as a source
13026 of trace data, via the @code{target tfile} command.
13031 @item tsave [ -r ] @var{filename}
13032 @itemx tsave [-ctf] @var{dirname}
13033 Save the trace data to @var{filename}. By default, this command
13034 assumes that @var{filename} refers to the host filesystem, so if
13035 necessary @value{GDBN} will copy raw trace data up from the target and
13036 then save it. If the target supports it, you can also supply the
13037 optional argument @code{-r} (``remote'') to direct the target to save
13038 the data directly into @var{filename} in its own filesystem, which may be
13039 more efficient if the trace buffer is very large. (Note, however, that
13040 @code{target tfile} can only read from files accessible to the host.)
13041 By default, this command will save trace frame in tfile format.
13042 You can supply the optional argument @code{-ctf} to save date in CTF
13043 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
13044 that can be shared by multiple debugging and tracing tools. Please go to
13045 @indicateurl{http://www.efficios.com/ctf} to get more information.
13047 @kindex target tfile
13051 @item target tfile @var{filename}
13052 @itemx target ctf @var{dirname}
13053 Use the file named @var{filename} or directory named @var{dirname} as
13054 a source of trace data. Commands that examine data work as they do with
13055 a live target, but it is not possible to run any new trace experiments.
13056 @code{tstatus} will report the state of the trace run at the moment
13057 the data was saved, as well as the current trace frame you are examining.
13058 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
13062 (@value{GDBP}) target ctf ctf.ctf
13063 (@value{GDBP}) tfind
13064 Found trace frame 0, tracepoint 2
13065 39 ++a; /* set tracepoint 1 here */
13066 (@value{GDBP}) tdump
13067 Data collected at tracepoint 2, trace frame 0:
13071 c = @{"123", "456", "789", "123", "456", "789"@}
13072 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
13080 @chapter Debugging Programs That Use Overlays
13083 If your program is too large to fit completely in your target system's
13084 memory, you can sometimes use @dfn{overlays} to work around this
13085 problem. @value{GDBN} provides some support for debugging programs that
13089 * How Overlays Work:: A general explanation of overlays.
13090 * Overlay Commands:: Managing overlays in @value{GDBN}.
13091 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
13092 mapped by asking the inferior.
13093 * Overlay Sample Program:: A sample program using overlays.
13096 @node How Overlays Work
13097 @section How Overlays Work
13098 @cindex mapped overlays
13099 @cindex unmapped overlays
13100 @cindex load address, overlay's
13101 @cindex mapped address
13102 @cindex overlay area
13104 Suppose you have a computer whose instruction address space is only 64
13105 kilobytes long, but which has much more memory which can be accessed by
13106 other means: special instructions, segment registers, or memory
13107 management hardware, for example. Suppose further that you want to
13108 adapt a program which is larger than 64 kilobytes to run on this system.
13110 One solution is to identify modules of your program which are relatively
13111 independent, and need not call each other directly; call these modules
13112 @dfn{overlays}. Separate the overlays from the main program, and place
13113 their machine code in the larger memory. Place your main program in
13114 instruction memory, but leave at least enough space there to hold the
13115 largest overlay as well.
13117 Now, to call a function located in an overlay, you must first copy that
13118 overlay's machine code from the large memory into the space set aside
13119 for it in the instruction memory, and then jump to its entry point
13122 @c NB: In the below the mapped area's size is greater or equal to the
13123 @c size of all overlays. This is intentional to remind the developer
13124 @c that overlays don't necessarily need to be the same size.
13128 Data Instruction Larger
13129 Address Space Address Space Address Space
13130 +-----------+ +-----------+ +-----------+
13132 +-----------+ +-----------+ +-----------+<-- overlay 1
13133 | program | | main | .----| overlay 1 | load address
13134 | variables | | program | | +-----------+
13135 | and heap | | | | | |
13136 +-----------+ | | | +-----------+<-- overlay 2
13137 | | +-----------+ | | | load address
13138 +-----------+ | | | .-| overlay 2 |
13140 mapped --->+-----------+ | | +-----------+
13141 address | | | | | |
13142 | overlay | <-' | | |
13143 | area | <---' +-----------+<-- overlay 3
13144 | | <---. | | load address
13145 +-----------+ `--| overlay 3 |
13152 @anchor{A code overlay}A code overlay
13156 The diagram (@pxref{A code overlay}) shows a system with separate data
13157 and instruction address spaces. To map an overlay, the program copies
13158 its code from the larger address space to the instruction address space.
13159 Since the overlays shown here all use the same mapped address, only one
13160 may be mapped at a time. For a system with a single address space for
13161 data and instructions, the diagram would be similar, except that the
13162 program variables and heap would share an address space with the main
13163 program and the overlay area.
13165 An overlay loaded into instruction memory and ready for use is called a
13166 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
13167 instruction memory. An overlay not present (or only partially present)
13168 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
13169 is its address in the larger memory. The mapped address is also called
13170 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
13171 called the @dfn{load memory address}, or @dfn{LMA}.
13173 Unfortunately, overlays are not a completely transparent way to adapt a
13174 program to limited instruction memory. They introduce a new set of
13175 global constraints you must keep in mind as you design your program:
13180 Before calling or returning to a function in an overlay, your program
13181 must make sure that overlay is actually mapped. Otherwise, the call or
13182 return will transfer control to the right address, but in the wrong
13183 overlay, and your program will probably crash.
13186 If the process of mapping an overlay is expensive on your system, you
13187 will need to choose your overlays carefully to minimize their effect on
13188 your program's performance.
13191 The executable file you load onto your system must contain each
13192 overlay's instructions, appearing at the overlay's load address, not its
13193 mapped address. However, each overlay's instructions must be relocated
13194 and its symbols defined as if the overlay were at its mapped address.
13195 You can use GNU linker scripts to specify different load and relocation
13196 addresses for pieces of your program; see @ref{Overlay Description,,,
13197 ld.info, Using ld: the GNU linker}.
13200 The procedure for loading executable files onto your system must be able
13201 to load their contents into the larger address space as well as the
13202 instruction and data spaces.
13206 The overlay system described above is rather simple, and could be
13207 improved in many ways:
13212 If your system has suitable bank switch registers or memory management
13213 hardware, you could use those facilities to make an overlay's load area
13214 contents simply appear at their mapped address in instruction space.
13215 This would probably be faster than copying the overlay to its mapped
13216 area in the usual way.
13219 If your overlays are small enough, you could set aside more than one
13220 overlay area, and have more than one overlay mapped at a time.
13223 You can use overlays to manage data, as well as instructions. In
13224 general, data overlays are even less transparent to your design than
13225 code overlays: whereas code overlays only require care when you call or
13226 return to functions, data overlays require care every time you access
13227 the data. Also, if you change the contents of a data overlay, you
13228 must copy its contents back out to its load address before you can copy a
13229 different data overlay into the same mapped area.
13234 @node Overlay Commands
13235 @section Overlay Commands
13237 To use @value{GDBN}'s overlay support, each overlay in your program must
13238 correspond to a separate section of the executable file. The section's
13239 virtual memory address and load memory address must be the overlay's
13240 mapped and load addresses. Identifying overlays with sections allows
13241 @value{GDBN} to determine the appropriate address of a function or
13242 variable, depending on whether the overlay is mapped or not.
13244 @value{GDBN}'s overlay commands all start with the word @code{overlay};
13245 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
13250 Disable @value{GDBN}'s overlay support. When overlay support is
13251 disabled, @value{GDBN} assumes that all functions and variables are
13252 always present at their mapped addresses. By default, @value{GDBN}'s
13253 overlay support is disabled.
13255 @item overlay manual
13256 @cindex manual overlay debugging
13257 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
13258 relies on you to tell it which overlays are mapped, and which are not,
13259 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
13260 commands described below.
13262 @item overlay map-overlay @var{overlay}
13263 @itemx overlay map @var{overlay}
13264 @cindex map an overlay
13265 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
13266 be the name of the object file section containing the overlay. When an
13267 overlay is mapped, @value{GDBN} assumes it can find the overlay's
13268 functions and variables at their mapped addresses. @value{GDBN} assumes
13269 that any other overlays whose mapped ranges overlap that of
13270 @var{overlay} are now unmapped.
13272 @item overlay unmap-overlay @var{overlay}
13273 @itemx overlay unmap @var{overlay}
13274 @cindex unmap an overlay
13275 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
13276 must be the name of the object file section containing the overlay.
13277 When an overlay is unmapped, @value{GDBN} assumes it can find the
13278 overlay's functions and variables at their load addresses.
13281 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
13282 consults a data structure the overlay manager maintains in the inferior
13283 to see which overlays are mapped. For details, see @ref{Automatic
13284 Overlay Debugging}.
13286 @item overlay load-target
13287 @itemx overlay load
13288 @cindex reloading the overlay table
13289 Re-read the overlay table from the inferior. Normally, @value{GDBN}
13290 re-reads the table @value{GDBN} automatically each time the inferior
13291 stops, so this command should only be necessary if you have changed the
13292 overlay mapping yourself using @value{GDBN}. This command is only
13293 useful when using automatic overlay debugging.
13295 @item overlay list-overlays
13296 @itemx overlay list
13297 @cindex listing mapped overlays
13298 Display a list of the overlays currently mapped, along with their mapped
13299 addresses, load addresses, and sizes.
13303 Normally, when @value{GDBN} prints a code address, it includes the name
13304 of the function the address falls in:
13307 (@value{GDBP}) print main
13308 $3 = @{int ()@} 0x11a0 <main>
13311 When overlay debugging is enabled, @value{GDBN} recognizes code in
13312 unmapped overlays, and prints the names of unmapped functions with
13313 asterisks around them. For example, if @code{foo} is a function in an
13314 unmapped overlay, @value{GDBN} prints it this way:
13317 (@value{GDBP}) overlay list
13318 No sections are mapped.
13319 (@value{GDBP}) print foo
13320 $5 = @{int (int)@} 0x100000 <*foo*>
13323 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
13327 (@value{GDBP}) overlay list
13328 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
13329 mapped at 0x1016 - 0x104a
13330 (@value{GDBP}) print foo
13331 $6 = @{int (int)@} 0x1016 <foo>
13334 When overlay debugging is enabled, @value{GDBN} can find the correct
13335 address for functions and variables in an overlay, whether or not the
13336 overlay is mapped. This allows most @value{GDBN} commands, like
13337 @code{break} and @code{disassemble}, to work normally, even on unmapped
13338 code. However, @value{GDBN}'s breakpoint support has some limitations:
13342 @cindex breakpoints in overlays
13343 @cindex overlays, setting breakpoints in
13344 You can set breakpoints in functions in unmapped overlays, as long as
13345 @value{GDBN} can write to the overlay at its load address.
13347 @value{GDBN} can not set hardware or simulator-based breakpoints in
13348 unmapped overlays. However, if you set a breakpoint at the end of your
13349 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
13350 you are using manual overlay management), @value{GDBN} will re-set its
13351 breakpoints properly.
13355 @node Automatic Overlay Debugging
13356 @section Automatic Overlay Debugging
13357 @cindex automatic overlay debugging
13359 @value{GDBN} can automatically track which overlays are mapped and which
13360 are not, given some simple co-operation from the overlay manager in the
13361 inferior. If you enable automatic overlay debugging with the
13362 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
13363 looks in the inferior's memory for certain variables describing the
13364 current state of the overlays.
13366 Here are the variables your overlay manager must define to support
13367 @value{GDBN}'s automatic overlay debugging:
13371 @item @code{_ovly_table}:
13372 This variable must be an array of the following structures:
13377 /* The overlay's mapped address. */
13380 /* The size of the overlay, in bytes. */
13381 unsigned long size;
13383 /* The overlay's load address. */
13386 /* Non-zero if the overlay is currently mapped;
13388 unsigned long mapped;
13392 @item @code{_novlys}:
13393 This variable must be a four-byte signed integer, holding the total
13394 number of elements in @code{_ovly_table}.
13398 To decide whether a particular overlay is mapped or not, @value{GDBN}
13399 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
13400 @code{lma} members equal the VMA and LMA of the overlay's section in the
13401 executable file. When @value{GDBN} finds a matching entry, it consults
13402 the entry's @code{mapped} member to determine whether the overlay is
13405 In addition, your overlay manager may define a function called
13406 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
13407 will silently set a breakpoint there. If the overlay manager then
13408 calls this function whenever it has changed the overlay table, this
13409 will enable @value{GDBN} to accurately keep track of which overlays
13410 are in program memory, and update any breakpoints that may be set
13411 in overlays. This will allow breakpoints to work even if the
13412 overlays are kept in ROM or other non-writable memory while they
13413 are not being executed.
13415 @node Overlay Sample Program
13416 @section Overlay Sample Program
13417 @cindex overlay example program
13419 When linking a program which uses overlays, you must place the overlays
13420 at their load addresses, while relocating them to run at their mapped
13421 addresses. To do this, you must write a linker script (@pxref{Overlay
13422 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
13423 since linker scripts are specific to a particular host system, target
13424 architecture, and target memory layout, this manual cannot provide
13425 portable sample code demonstrating @value{GDBN}'s overlay support.
13427 However, the @value{GDBN} source distribution does contain an overlaid
13428 program, with linker scripts for a few systems, as part of its test
13429 suite. The program consists of the following files from
13430 @file{gdb/testsuite/gdb.base}:
13434 The main program file.
13436 A simple overlay manager, used by @file{overlays.c}.
13441 Overlay modules, loaded and used by @file{overlays.c}.
13444 Linker scripts for linking the test program on the @code{d10v-elf}
13445 and @code{m32r-elf} targets.
13448 You can build the test program using the @code{d10v-elf} GCC
13449 cross-compiler like this:
13452 $ d10v-elf-gcc -g -c overlays.c
13453 $ d10v-elf-gcc -g -c ovlymgr.c
13454 $ d10v-elf-gcc -g -c foo.c
13455 $ d10v-elf-gcc -g -c bar.c
13456 $ d10v-elf-gcc -g -c baz.c
13457 $ d10v-elf-gcc -g -c grbx.c
13458 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
13459 baz.o grbx.o -Wl,-Td10v.ld -o overlays
13462 The build process is identical for any other architecture, except that
13463 you must substitute the appropriate compiler and linker script for the
13464 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
13468 @chapter Using @value{GDBN} with Different Languages
13471 Although programming languages generally have common aspects, they are
13472 rarely expressed in the same manner. For instance, in ANSI C,
13473 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
13474 Modula-2, it is accomplished by @code{p^}. Values can also be
13475 represented (and displayed) differently. Hex numbers in C appear as
13476 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
13478 @cindex working language
13479 Language-specific information is built into @value{GDBN} for some languages,
13480 allowing you to express operations like the above in your program's
13481 native language, and allowing @value{GDBN} to output values in a manner
13482 consistent with the syntax of your program's native language. The
13483 language you use to build expressions is called the @dfn{working
13487 * Setting:: Switching between source languages
13488 * Show:: Displaying the language
13489 * Checks:: Type and range checks
13490 * Supported Languages:: Supported languages
13491 * Unsupported Languages:: Unsupported languages
13495 @section Switching Between Source Languages
13497 There are two ways to control the working language---either have @value{GDBN}
13498 set it automatically, or select it manually yourself. You can use the
13499 @code{set language} command for either purpose. On startup, @value{GDBN}
13500 defaults to setting the language automatically. The working language is
13501 used to determine how expressions you type are interpreted, how values
13504 In addition to the working language, every source file that
13505 @value{GDBN} knows about has its own working language. For some object
13506 file formats, the compiler might indicate which language a particular
13507 source file is in. However, most of the time @value{GDBN} infers the
13508 language from the name of the file. The language of a source file
13509 controls whether C@t{++} names are demangled---this way @code{backtrace} can
13510 show each frame appropriately for its own language. There is no way to
13511 set the language of a source file from within @value{GDBN}, but you can
13512 set the language associated with a filename extension. @xref{Show, ,
13513 Displaying the Language}.
13515 This is most commonly a problem when you use a program, such
13516 as @code{cfront} or @code{f2c}, that generates C but is written in
13517 another language. In that case, make the
13518 program use @code{#line} directives in its C output; that way
13519 @value{GDBN} will know the correct language of the source code of the original
13520 program, and will display that source code, not the generated C code.
13523 * Filenames:: Filename extensions and languages.
13524 * Manually:: Setting the working language manually
13525 * Automatically:: Having @value{GDBN} infer the source language
13529 @subsection List of Filename Extensions and Languages
13531 If a source file name ends in one of the following extensions, then
13532 @value{GDBN} infers that its language is the one indicated.
13550 C@t{++} source file
13556 Objective-C source file
13560 Fortran source file
13563 Modula-2 source file
13567 Assembler source file. This actually behaves almost like C, but
13568 @value{GDBN} does not skip over function prologues when stepping.
13571 In addition, you may set the language associated with a filename
13572 extension. @xref{Show, , Displaying the Language}.
13575 @subsection Setting the Working Language
13577 If you allow @value{GDBN} to set the language automatically,
13578 expressions are interpreted the same way in your debugging session and
13581 @kindex set language
13582 If you wish, you may set the language manually. To do this, issue the
13583 command @samp{set language @var{lang}}, where @var{lang} is the name of
13584 a language, such as
13585 @code{c} or @code{modula-2}.
13586 For a list of the supported languages, type @samp{set language}.
13588 Setting the language manually prevents @value{GDBN} from updating the working
13589 language automatically. This can lead to confusion if you try
13590 to debug a program when the working language is not the same as the
13591 source language, when an expression is acceptable to both
13592 languages---but means different things. For instance, if the current
13593 source file were written in C, and @value{GDBN} was parsing Modula-2, a
13601 might not have the effect you intended. In C, this means to add
13602 @code{b} and @code{c} and place the result in @code{a}. The result
13603 printed would be the value of @code{a}. In Modula-2, this means to compare
13604 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
13606 @node Automatically
13607 @subsection Having @value{GDBN} Infer the Source Language
13609 To have @value{GDBN} set the working language automatically, use
13610 @samp{set language local} or @samp{set language auto}. @value{GDBN}
13611 then infers the working language. That is, when your program stops in a
13612 frame (usually by encountering a breakpoint), @value{GDBN} sets the
13613 working language to the language recorded for the function in that
13614 frame. If the language for a frame is unknown (that is, if the function
13615 or block corresponding to the frame was defined in a source file that
13616 does not have a recognized extension), the current working language is
13617 not changed, and @value{GDBN} issues a warning.
13619 This may not seem necessary for most programs, which are written
13620 entirely in one source language. However, program modules and libraries
13621 written in one source language can be used by a main program written in
13622 a different source language. Using @samp{set language auto} in this
13623 case frees you from having to set the working language manually.
13626 @section Displaying the Language
13628 The following commands help you find out which language is the
13629 working language, and also what language source files were written in.
13632 @item show language
13633 @anchor{show language}
13634 @kindex show language
13635 Display the current working language. This is the
13636 language you can use with commands such as @code{print} to
13637 build and compute expressions that may involve variables in your program.
13640 @kindex info frame@r{, show the source language}
13641 Display the source language for this frame. This language becomes the
13642 working language if you use an identifier from this frame.
13643 @xref{Frame Info, ,Information about a Frame}, to identify the other
13644 information listed here.
13647 @kindex info source@r{, show the source language}
13648 Display the source language of this source file.
13649 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
13650 information listed here.
13653 In unusual circumstances, you may have source files with extensions
13654 not in the standard list. You can then set the extension associated
13655 with a language explicitly:
13658 @item set extension-language @var{ext} @var{language}
13659 @kindex set extension-language
13660 Tell @value{GDBN} that source files with extension @var{ext} are to be
13661 assumed as written in the source language @var{language}.
13663 @item info extensions
13664 @kindex info extensions
13665 List all the filename extensions and the associated languages.
13669 @section Type and Range Checking
13671 Some languages are designed to guard you against making seemingly common
13672 errors through a series of compile- and run-time checks. These include
13673 checking the type of arguments to functions and operators and making
13674 sure mathematical overflows are caught at run time. Checks such as
13675 these help to ensure a program's correctness once it has been compiled
13676 by eliminating type mismatches and providing active checks for range
13677 errors when your program is running.
13679 By default @value{GDBN} checks for these errors according to the
13680 rules of the current source language. Although @value{GDBN} does not check
13681 the statements in your program, it can check expressions entered directly
13682 into @value{GDBN} for evaluation via the @code{print} command, for example.
13685 * Type Checking:: An overview of type checking
13686 * Range Checking:: An overview of range checking
13689 @cindex type checking
13690 @cindex checks, type
13691 @node Type Checking
13692 @subsection An Overview of Type Checking
13694 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
13695 arguments to operators and functions have to be of the correct type,
13696 otherwise an error occurs. These checks prevent type mismatch
13697 errors from ever causing any run-time problems. For example,
13700 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
13702 (@value{GDBP}) print obj.my_method (0)
13705 (@value{GDBP}) print obj.my_method (0x1234)
13706 Cannot resolve method klass::my_method to any overloaded instance
13709 The second example fails because in C@t{++} the integer constant
13710 @samp{0x1234} is not type-compatible with the pointer parameter type.
13712 For the expressions you use in @value{GDBN} commands, you can tell
13713 @value{GDBN} to not enforce strict type checking or
13714 to treat any mismatches as errors and abandon the expression;
13715 When type checking is disabled, @value{GDBN} successfully evaluates
13716 expressions like the second example above.
13718 Even if type checking is off, there may be other reasons
13719 related to type that prevent @value{GDBN} from evaluating an expression.
13720 For instance, @value{GDBN} does not know how to add an @code{int} and
13721 a @code{struct foo}. These particular type errors have nothing to do
13722 with the language in use and usually arise from expressions which make
13723 little sense to evaluate anyway.
13725 @value{GDBN} provides some additional commands for controlling type checking:
13727 @kindex set check type
13728 @kindex show check type
13730 @item set check type on
13731 @itemx set check type off
13732 Set strict type checking on or off. If any type mismatches occur in
13733 evaluating an expression while type checking is on, @value{GDBN} prints a
13734 message and aborts evaluation of the expression.
13736 @item show check type
13737 Show the current setting of type checking and whether @value{GDBN}
13738 is enforcing strict type checking rules.
13741 @cindex range checking
13742 @cindex checks, range
13743 @node Range Checking
13744 @subsection An Overview of Range Checking
13746 In some languages (such as Modula-2), it is an error to exceed the
13747 bounds of a type; this is enforced with run-time checks. Such range
13748 checking is meant to ensure program correctness by making sure
13749 computations do not overflow, or indices on an array element access do
13750 not exceed the bounds of the array.
13752 For expressions you use in @value{GDBN} commands, you can tell
13753 @value{GDBN} to treat range errors in one of three ways: ignore them,
13754 always treat them as errors and abandon the expression, or issue
13755 warnings but evaluate the expression anyway.
13757 A range error can result from numerical overflow, from exceeding an
13758 array index bound, or when you type a constant that is not a member
13759 of any type. Some languages, however, do not treat overflows as an
13760 error. In many implementations of C, mathematical overflow causes the
13761 result to ``wrap around'' to lower values---for example, if @var{m} is
13762 the largest integer value, and @var{s} is the smallest, then
13765 @var{m} + 1 @result{} @var{s}
13768 This, too, is specific to individual languages, and in some cases
13769 specific to individual compilers or machines. @xref{Supported Languages, ,
13770 Supported Languages}, for further details on specific languages.
13772 @value{GDBN} provides some additional commands for controlling the range checker:
13774 @kindex set check range
13775 @kindex show check range
13777 @item set check range auto
13778 Set range checking on or off based on the current working language.
13779 @xref{Supported Languages, ,Supported Languages}, for the default settings for
13782 @item set check range on
13783 @itemx set check range off
13784 Set range checking on or off, overriding the default setting for the
13785 current working language. A warning is issued if the setting does not
13786 match the language default. If a range error occurs and range checking is on,
13787 then a message is printed and evaluation of the expression is aborted.
13789 @item set check range warn
13790 Output messages when the @value{GDBN} range checker detects a range error,
13791 but attempt to evaluate the expression anyway. Evaluating the
13792 expression may still be impossible for other reasons, such as accessing
13793 memory that the process does not own (a typical example from many Unix
13797 Show the current setting of the range checker, and whether or not it is
13798 being set automatically by @value{GDBN}.
13801 @node Supported Languages
13802 @section Supported Languages
13804 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
13805 OpenCL C, Pascal, assembly, Modula-2, and Ada.
13806 @c This is false ...
13807 Some @value{GDBN} features may be used in expressions regardless of the
13808 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
13809 and the @samp{@{type@}addr} construct (@pxref{Expressions,
13810 ,Expressions}) can be used with the constructs of any supported
13813 The following sections detail to what degree each source language is
13814 supported by @value{GDBN}. These sections are not meant to be language
13815 tutorials or references, but serve only as a reference guide to what the
13816 @value{GDBN} expression parser accepts, and what input and output
13817 formats should look like for different languages. There are many good
13818 books written on each of these languages; please look to these for a
13819 language reference or tutorial.
13822 * C:: C and C@t{++}
13825 * Objective-C:: Objective-C
13826 * OpenCL C:: OpenCL C
13827 * Fortran:: Fortran
13829 * Modula-2:: Modula-2
13834 @subsection C and C@t{++}
13836 @cindex C and C@t{++}
13837 @cindex expressions in C or C@t{++}
13839 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
13840 to both languages. Whenever this is the case, we discuss those languages
13844 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
13845 @cindex @sc{gnu} C@t{++}
13846 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
13847 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
13848 effectively, you must compile your C@t{++} programs with a supported
13849 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
13850 compiler (@code{aCC}).
13853 * C Operators:: C and C@t{++} operators
13854 * C Constants:: C and C@t{++} constants
13855 * C Plus Plus Expressions:: C@t{++} expressions
13856 * C Defaults:: Default settings for C and C@t{++}
13857 * C Checks:: C and C@t{++} type and range checks
13858 * Debugging C:: @value{GDBN} and C
13859 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
13860 * Decimal Floating Point:: Numbers in Decimal Floating Point format
13864 @subsubsection C and C@t{++} Operators
13866 @cindex C and C@t{++} operators
13868 Operators must be defined on values of specific types. For instance,
13869 @code{+} is defined on numbers, but not on structures. Operators are
13870 often defined on groups of types.
13872 For the purposes of C and C@t{++}, the following definitions hold:
13877 @emph{Integral types} include @code{int} with any of its storage-class
13878 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
13881 @emph{Floating-point types} include @code{float}, @code{double}, and
13882 @code{long double} (if supported by the target platform).
13885 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
13888 @emph{Scalar types} include all of the above.
13893 The following operators are supported. They are listed here
13894 in order of increasing precedence:
13898 The comma or sequencing operator. Expressions in a comma-separated list
13899 are evaluated from left to right, with the result of the entire
13900 expression being the last expression evaluated.
13903 Assignment. The value of an assignment expression is the value
13904 assigned. Defined on scalar types.
13907 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
13908 and translated to @w{@code{@var{a} = @var{a op b}}}.
13909 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
13910 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
13911 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
13914 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
13915 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
13916 should be of an integral type.
13919 Logical @sc{or}. Defined on integral types.
13922 Logical @sc{and}. Defined on integral types.
13925 Bitwise @sc{or}. Defined on integral types.
13928 Bitwise exclusive-@sc{or}. Defined on integral types.
13931 Bitwise @sc{and}. Defined on integral types.
13934 Equality and inequality. Defined on scalar types. The value of these
13935 expressions is 0 for false and non-zero for true.
13937 @item <@r{, }>@r{, }<=@r{, }>=
13938 Less than, greater than, less than or equal, greater than or equal.
13939 Defined on scalar types. The value of these expressions is 0 for false
13940 and non-zero for true.
13943 left shift, and right shift. Defined on integral types.
13946 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13949 Addition and subtraction. Defined on integral types, floating-point types and
13952 @item *@r{, }/@r{, }%
13953 Multiplication, division, and modulus. Multiplication and division are
13954 defined on integral and floating-point types. Modulus is defined on
13958 Increment and decrement. When appearing before a variable, the
13959 operation is performed before the variable is used in an expression;
13960 when appearing after it, the variable's value is used before the
13961 operation takes place.
13964 Pointer dereferencing. Defined on pointer types. Same precedence as
13968 Address operator. Defined on variables. Same precedence as @code{++}.
13970 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
13971 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
13972 to examine the address
13973 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
13977 Negative. Defined on integral and floating-point types. Same
13978 precedence as @code{++}.
13981 Logical negation. Defined on integral types. Same precedence as
13985 Bitwise complement operator. Defined on integral types. Same precedence as
13990 Structure member, and pointer-to-structure member. For convenience,
13991 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
13992 pointer based on the stored type information.
13993 Defined on @code{struct} and @code{union} data.
13996 Dereferences of pointers to members.
13999 Array indexing. @code{@var{a}[@var{i}]} is defined as
14000 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
14003 Function parameter list. Same precedence as @code{->}.
14006 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
14007 and @code{class} types.
14010 Doubled colons also represent the @value{GDBN} scope operator
14011 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
14015 If an operator is redefined in the user code, @value{GDBN} usually
14016 attempts to invoke the redefined version instead of using the operator's
14017 predefined meaning.
14020 @subsubsection C and C@t{++} Constants
14022 @cindex C and C@t{++} constants
14024 @value{GDBN} allows you to express the constants of C and C@t{++} in the
14029 Integer constants are a sequence of digits. Octal constants are
14030 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
14031 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
14032 @samp{l}, specifying that the constant should be treated as a
14036 Floating point constants are a sequence of digits, followed by a decimal
14037 point, followed by a sequence of digits, and optionally followed by an
14038 exponent. An exponent is of the form:
14039 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
14040 sequence of digits. The @samp{+} is optional for positive exponents.
14041 A floating-point constant may also end with a letter @samp{f} or
14042 @samp{F}, specifying that the constant should be treated as being of
14043 the @code{float} (as opposed to the default @code{double}) type; or with
14044 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
14048 Enumerated constants consist of enumerated identifiers, or their
14049 integral equivalents.
14052 Character constants are a single character surrounded by single quotes
14053 (@code{'}), or a number---the ordinal value of the corresponding character
14054 (usually its @sc{ascii} value). Within quotes, the single character may
14055 be represented by a letter or by @dfn{escape sequences}, which are of
14056 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
14057 of the character's ordinal value; or of the form @samp{\@var{x}}, where
14058 @samp{@var{x}} is a predefined special character---for example,
14059 @samp{\n} for newline.
14061 Wide character constants can be written by prefixing a character
14062 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
14063 form of @samp{x}. The target wide character set is used when
14064 computing the value of this constant (@pxref{Character Sets}).
14067 String constants are a sequence of character constants surrounded by
14068 double quotes (@code{"}). Any valid character constant (as described
14069 above) may appear. Double quotes within the string must be preceded by
14070 a backslash, so for instance @samp{"a\"b'c"} is a string of five
14073 Wide string constants can be written by prefixing a string constant
14074 with @samp{L}, as in C. The target wide character set is used when
14075 computing the value of this constant (@pxref{Character Sets}).
14078 Pointer constants are an integral value. You can also write pointers
14079 to constants using the C operator @samp{&}.
14082 Array constants are comma-separated lists surrounded by braces @samp{@{}
14083 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
14084 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
14085 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
14088 @node C Plus Plus Expressions
14089 @subsubsection C@t{++} Expressions
14091 @cindex expressions in C@t{++}
14092 @value{GDBN} expression handling can interpret most C@t{++} expressions.
14094 @cindex debugging C@t{++} programs
14095 @cindex C@t{++} compilers
14096 @cindex debug formats and C@t{++}
14097 @cindex @value{NGCC} and C@t{++}
14099 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
14100 the proper compiler and the proper debug format. Currently,
14101 @value{GDBN} works best when debugging C@t{++} code that is compiled
14102 with the most recent version of @value{NGCC} possible. The DWARF
14103 debugging format is preferred; @value{NGCC} defaults to this on most
14104 popular platforms. Other compilers and/or debug formats are likely to
14105 work badly or not at all when using @value{GDBN} to debug C@t{++}
14106 code. @xref{Compilation}.
14111 @cindex member functions
14113 Member function calls are allowed; you can use expressions like
14116 count = aml->GetOriginal(x, y)
14119 @vindex this@r{, inside C@t{++} member functions}
14120 @cindex namespace in C@t{++}
14122 While a member function is active (in the selected stack frame), your
14123 expressions have the same namespace available as the member function;
14124 that is, @value{GDBN} allows implicit references to the class instance
14125 pointer @code{this} following the same rules as C@t{++}. @code{using}
14126 declarations in the current scope are also respected by @value{GDBN}.
14128 @cindex call overloaded functions
14129 @cindex overloaded functions, calling
14130 @cindex type conversions in C@t{++}
14132 You can call overloaded functions; @value{GDBN} resolves the function
14133 call to the right definition, with some restrictions. @value{GDBN} does not
14134 perform overload resolution involving user-defined type conversions,
14135 calls to constructors, or instantiations of templates that do not exist
14136 in the program. It also cannot handle ellipsis argument lists or
14139 It does perform integral conversions and promotions, floating-point
14140 promotions, arithmetic conversions, pointer conversions, conversions of
14141 class objects to base classes, and standard conversions such as those of
14142 functions or arrays to pointers; it requires an exact match on the
14143 number of function arguments.
14145 Overload resolution is always performed, unless you have specified
14146 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
14147 ,@value{GDBN} Features for C@t{++}}.
14149 You must specify @code{set overload-resolution off} in order to use an
14150 explicit function signature to call an overloaded function, as in
14152 p 'foo(char,int)'('x', 13)
14155 The @value{GDBN} command-completion facility can simplify this;
14156 see @ref{Completion, ,Command Completion}.
14158 @cindex reference declarations
14160 @value{GDBN} understands variables declared as C@t{++} references; you can use
14161 them in expressions just as you do in C@t{++} source---they are automatically
14164 In the parameter list shown when @value{GDBN} displays a frame, the values of
14165 reference variables are not displayed (unlike other variables); this
14166 avoids clutter, since references are often used for large structures.
14167 The @emph{address} of a reference variable is always shown, unless
14168 you have specified @samp{set print address off}.
14171 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
14172 expressions can use it just as expressions in your program do. Since
14173 one scope may be defined in another, you can use @code{::} repeatedly if
14174 necessary, for example in an expression like
14175 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
14176 resolving name scope by reference to source files, in both C and C@t{++}
14177 debugging (@pxref{Variables, ,Program Variables}).
14180 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
14185 @subsubsection C and C@t{++} Defaults
14187 @cindex C and C@t{++} defaults
14189 If you allow @value{GDBN} to set range checking automatically, it
14190 defaults to @code{off} whenever the working language changes to
14191 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
14192 selects the working language.
14194 If you allow @value{GDBN} to set the language automatically, it
14195 recognizes source files whose names end with @file{.c}, @file{.C}, or
14196 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
14197 these files, it sets the working language to C or C@t{++}.
14198 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
14199 for further details.
14202 @subsubsection C and C@t{++} Type and Range Checks
14204 @cindex C and C@t{++} checks
14206 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
14207 checking is used. However, if you turn type checking off, @value{GDBN}
14208 will allow certain non-standard conversions, such as promoting integer
14209 constants to pointers.
14211 Range checking, if turned on, is done on mathematical operations. Array
14212 indices are not checked, since they are often used to index a pointer
14213 that is not itself an array.
14216 @subsubsection @value{GDBN} and C
14218 The @code{set print union} and @code{show print union} commands apply to
14219 the @code{union} type. When set to @samp{on}, any @code{union} that is
14220 inside a @code{struct} or @code{class} is also printed. Otherwise, it
14221 appears as @samp{@{...@}}.
14223 The @code{@@} operator aids in the debugging of dynamic arrays, formed
14224 with pointers and a memory allocation function. @xref{Expressions,
14227 @node Debugging C Plus Plus
14228 @subsubsection @value{GDBN} Features for C@t{++}
14230 @cindex commands for C@t{++}
14232 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
14233 designed specifically for use with C@t{++}. Here is a summary:
14236 @cindex break in overloaded functions
14237 @item @r{breakpoint menus}
14238 When you want a breakpoint in a function whose name is overloaded,
14239 @value{GDBN} has the capability to display a menu of possible breakpoint
14240 locations to help you specify which function definition you want.
14241 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
14243 @cindex overloading in C@t{++}
14244 @item rbreak @var{regex}
14245 Setting breakpoints using regular expressions is helpful for setting
14246 breakpoints on overloaded functions that are not members of any special
14248 @xref{Set Breaks, ,Setting Breakpoints}.
14250 @cindex C@t{++} exception handling
14252 @itemx catch rethrow
14254 Debug C@t{++} exception handling using these commands. @xref{Set
14255 Catchpoints, , Setting Catchpoints}.
14257 @cindex inheritance
14258 @item ptype @var{typename}
14259 Print inheritance relationships as well as other information for type
14261 @xref{Symbols, ,Examining the Symbol Table}.
14263 @item info vtbl @var{expression}.
14264 The @code{info vtbl} command can be used to display the virtual
14265 method tables of the object computed by @var{expression}. This shows
14266 one entry per virtual table; there may be multiple virtual tables when
14267 multiple inheritance is in use.
14269 @cindex C@t{++} demangling
14270 @item demangle @var{name}
14271 Demangle @var{name}.
14272 @xref{Symbols}, for a more complete description of the @code{demangle} command.
14274 @cindex C@t{++} symbol display
14275 @item set print demangle
14276 @itemx show print demangle
14277 @itemx set print asm-demangle
14278 @itemx show print asm-demangle
14279 Control whether C@t{++} symbols display in their source form, both when
14280 displaying code as C@t{++} source and when displaying disassemblies.
14281 @xref{Print Settings, ,Print Settings}.
14283 @item set print object
14284 @itemx show print object
14285 Choose whether to print derived (actual) or declared types of objects.
14286 @xref{Print Settings, ,Print Settings}.
14288 @item set print vtbl
14289 @itemx show print vtbl
14290 Control the format for printing virtual function tables.
14291 @xref{Print Settings, ,Print Settings}.
14292 (The @code{vtbl} commands do not work on programs compiled with the HP
14293 ANSI C@t{++} compiler (@code{aCC}).)
14295 @kindex set overload-resolution
14296 @cindex overloaded functions, overload resolution
14297 @item set overload-resolution on
14298 Enable overload resolution for C@t{++} expression evaluation. The default
14299 is on. For overloaded functions, @value{GDBN} evaluates the arguments
14300 and searches for a function whose signature matches the argument types,
14301 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
14302 Expressions, ,C@t{++} Expressions}, for details).
14303 If it cannot find a match, it emits a message.
14305 @item set overload-resolution off
14306 Disable overload resolution for C@t{++} expression evaluation. For
14307 overloaded functions that are not class member functions, @value{GDBN}
14308 chooses the first function of the specified name that it finds in the
14309 symbol table, whether or not its arguments are of the correct type. For
14310 overloaded functions that are class member functions, @value{GDBN}
14311 searches for a function whose signature @emph{exactly} matches the
14314 @kindex show overload-resolution
14315 @item show overload-resolution
14316 Show the current setting of overload resolution.
14318 @item @r{Overloaded symbol names}
14319 You can specify a particular definition of an overloaded symbol, using
14320 the same notation that is used to declare such symbols in C@t{++}: type
14321 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
14322 also use the @value{GDBN} command-line word completion facilities to list the
14323 available choices, or to finish the type list for you.
14324 @xref{Completion,, Command Completion}, for details on how to do this.
14327 @node Decimal Floating Point
14328 @subsubsection Decimal Floating Point format
14329 @cindex decimal floating point format
14331 @value{GDBN} can examine, set and perform computations with numbers in
14332 decimal floating point format, which in the C language correspond to the
14333 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
14334 specified by the extension to support decimal floating-point arithmetic.
14336 There are two encodings in use, depending on the architecture: BID (Binary
14337 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
14338 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
14341 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
14342 to manipulate decimal floating point numbers, it is not possible to convert
14343 (using a cast, for example) integers wider than 32-bit to decimal float.
14345 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
14346 point computations, error checking in decimal float operations ignores
14347 underflow, overflow and divide by zero exceptions.
14349 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
14350 to inspect @code{_Decimal128} values stored in floating point registers.
14351 See @ref{PowerPC,,PowerPC} for more details.
14357 @value{GDBN} can be used to debug programs written in D and compiled with
14358 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
14359 specific feature --- dynamic arrays.
14364 @cindex Go (programming language)
14365 @value{GDBN} can be used to debug programs written in Go and compiled with
14366 @file{gccgo} or @file{6g} compilers.
14368 Here is a summary of the Go-specific features and restrictions:
14371 @cindex current Go package
14372 @item The current Go package
14373 The name of the current package does not need to be specified when
14374 specifying global variables and functions.
14376 For example, given the program:
14380 var myglob = "Shall we?"
14386 When stopped inside @code{main} either of these work:
14390 (gdb) p main.myglob
14393 @cindex builtin Go types
14394 @item Builtin Go types
14395 The @code{string} type is recognized by @value{GDBN} and is printed
14398 @cindex builtin Go functions
14399 @item Builtin Go functions
14400 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
14401 function and handles it internally.
14403 @cindex restrictions on Go expressions
14404 @item Restrictions on Go expressions
14405 All Go operators are supported except @code{&^}.
14406 The Go @code{_} ``blank identifier'' is not supported.
14407 Automatic dereferencing of pointers is not supported.
14411 @subsection Objective-C
14413 @cindex Objective-C
14414 This section provides information about some commands and command
14415 options that are useful for debugging Objective-C code. See also
14416 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
14417 few more commands specific to Objective-C support.
14420 * Method Names in Commands::
14421 * The Print Command with Objective-C::
14424 @node Method Names in Commands
14425 @subsubsection Method Names in Commands
14427 The following commands have been extended to accept Objective-C method
14428 names as line specifications:
14430 @kindex clear@r{, and Objective-C}
14431 @kindex break@r{, and Objective-C}
14432 @kindex info line@r{, and Objective-C}
14433 @kindex jump@r{, and Objective-C}
14434 @kindex list@r{, and Objective-C}
14438 @item @code{info line}
14443 A fully qualified Objective-C method name is specified as
14446 -[@var{Class} @var{methodName}]
14449 where the minus sign is used to indicate an instance method and a
14450 plus sign (not shown) is used to indicate a class method. The class
14451 name @var{Class} and method name @var{methodName} are enclosed in
14452 brackets, similar to the way messages are specified in Objective-C
14453 source code. For example, to set a breakpoint at the @code{create}
14454 instance method of class @code{Fruit} in the program currently being
14458 break -[Fruit create]
14461 To list ten program lines around the @code{initialize} class method,
14465 list +[NSText initialize]
14468 In the current version of @value{GDBN}, the plus or minus sign is
14469 required. In future versions of @value{GDBN}, the plus or minus
14470 sign will be optional, but you can use it to narrow the search. It
14471 is also possible to specify just a method name:
14477 You must specify the complete method name, including any colons. If
14478 your program's source files contain more than one @code{create} method,
14479 you'll be presented with a numbered list of classes that implement that
14480 method. Indicate your choice by number, or type @samp{0} to exit if
14483 As another example, to clear a breakpoint established at the
14484 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
14487 clear -[NSWindow makeKeyAndOrderFront:]
14490 @node The Print Command with Objective-C
14491 @subsubsection The Print Command With Objective-C
14492 @cindex Objective-C, print objects
14493 @kindex print-object
14494 @kindex po @r{(@code{print-object})}
14496 The print command has also been extended to accept methods. For example:
14499 print -[@var{object} hash]
14502 @cindex print an Objective-C object description
14503 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
14505 will tell @value{GDBN} to send the @code{hash} message to @var{object}
14506 and print the result. Also, an additional command has been added,
14507 @code{print-object} or @code{po} for short, which is meant to print
14508 the description of an object. However, this command may only work
14509 with certain Objective-C libraries that have a particular hook
14510 function, @code{_NSPrintForDebugger}, defined.
14513 @subsection OpenCL C
14516 This section provides information about @value{GDBN}s OpenCL C support.
14519 * OpenCL C Datatypes::
14520 * OpenCL C Expressions::
14521 * OpenCL C Operators::
14524 @node OpenCL C Datatypes
14525 @subsubsection OpenCL C Datatypes
14527 @cindex OpenCL C Datatypes
14528 @value{GDBN} supports the builtin scalar and vector datatypes specified
14529 by OpenCL 1.1. In addition the half- and double-precision floating point
14530 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
14531 extensions are also known to @value{GDBN}.
14533 @node OpenCL C Expressions
14534 @subsubsection OpenCL C Expressions
14536 @cindex OpenCL C Expressions
14537 @value{GDBN} supports accesses to vector components including the access as
14538 lvalue where possible. Since OpenCL C is based on C99 most C expressions
14539 supported by @value{GDBN} can be used as well.
14541 @node OpenCL C Operators
14542 @subsubsection OpenCL C Operators
14544 @cindex OpenCL C Operators
14545 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
14549 @subsection Fortran
14550 @cindex Fortran-specific support in @value{GDBN}
14552 @value{GDBN} can be used to debug programs written in Fortran, but it
14553 currently supports only the features of Fortran 77 language.
14555 @cindex trailing underscore, in Fortran symbols
14556 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
14557 among them) append an underscore to the names of variables and
14558 functions. When you debug programs compiled by those compilers, you
14559 will need to refer to variables and functions with a trailing
14563 * Fortran Operators:: Fortran operators and expressions
14564 * Fortran Defaults:: Default settings for Fortran
14565 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
14568 @node Fortran Operators
14569 @subsubsection Fortran Operators and Expressions
14571 @cindex Fortran operators and expressions
14573 Operators must be defined on values of specific types. For instance,
14574 @code{+} is defined on numbers, but not on characters or other non-
14575 arithmetic types. Operators are often defined on groups of types.
14579 The exponentiation operator. It raises the first operand to the power
14583 The range operator. Normally used in the form of array(low:high) to
14584 represent a section of array.
14587 The access component operator. Normally used to access elements in derived
14588 types. Also suitable for unions. As unions aren't part of regular Fortran,
14589 this can only happen when accessing a register that uses a gdbarch-defined
14593 @node Fortran Defaults
14594 @subsubsection Fortran Defaults
14596 @cindex Fortran Defaults
14598 Fortran symbols are usually case-insensitive, so @value{GDBN} by
14599 default uses case-insensitive matches for Fortran symbols. You can
14600 change that with the @samp{set case-insensitive} command, see
14601 @ref{Symbols}, for the details.
14603 @node Special Fortran Commands
14604 @subsubsection Special Fortran Commands
14606 @cindex Special Fortran commands
14608 @value{GDBN} has some commands to support Fortran-specific features,
14609 such as displaying common blocks.
14612 @cindex @code{COMMON} blocks, Fortran
14613 @kindex info common
14614 @item info common @r{[}@var{common-name}@r{]}
14615 This command prints the values contained in the Fortran @code{COMMON}
14616 block whose name is @var{common-name}. With no argument, the names of
14617 all @code{COMMON} blocks visible at the current program location are
14624 @cindex Pascal support in @value{GDBN}, limitations
14625 Debugging Pascal programs which use sets, subranges, file variables, or
14626 nested functions does not currently work. @value{GDBN} does not support
14627 entering expressions, printing values, or similar features using Pascal
14630 The Pascal-specific command @code{set print pascal_static-members}
14631 controls whether static members of Pascal objects are displayed.
14632 @xref{Print Settings, pascal_static-members}.
14635 @subsection Modula-2
14637 @cindex Modula-2, @value{GDBN} support
14639 The extensions made to @value{GDBN} to support Modula-2 only support
14640 output from the @sc{gnu} Modula-2 compiler (which is currently being
14641 developed). Other Modula-2 compilers are not currently supported, and
14642 attempting to debug executables produced by them is most likely
14643 to give an error as @value{GDBN} reads in the executable's symbol
14646 @cindex expressions in Modula-2
14648 * M2 Operators:: Built-in operators
14649 * Built-In Func/Proc:: Built-in functions and procedures
14650 * M2 Constants:: Modula-2 constants
14651 * M2 Types:: Modula-2 types
14652 * M2 Defaults:: Default settings for Modula-2
14653 * Deviations:: Deviations from standard Modula-2
14654 * M2 Checks:: Modula-2 type and range checks
14655 * M2 Scope:: The scope operators @code{::} and @code{.}
14656 * GDB/M2:: @value{GDBN} and Modula-2
14660 @subsubsection Operators
14661 @cindex Modula-2 operators
14663 Operators must be defined on values of specific types. For instance,
14664 @code{+} is defined on numbers, but not on structures. Operators are
14665 often defined on groups of types. For the purposes of Modula-2, the
14666 following definitions hold:
14671 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
14675 @emph{Character types} consist of @code{CHAR} and its subranges.
14678 @emph{Floating-point types} consist of @code{REAL}.
14681 @emph{Pointer types} consist of anything declared as @code{POINTER TO
14685 @emph{Scalar types} consist of all of the above.
14688 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
14691 @emph{Boolean types} consist of @code{BOOLEAN}.
14695 The following operators are supported, and appear in order of
14696 increasing precedence:
14700 Function argument or array index separator.
14703 Assignment. The value of @var{var} @code{:=} @var{value} is
14707 Less than, greater than on integral, floating-point, or enumerated
14711 Less than or equal to, greater than or equal to
14712 on integral, floating-point and enumerated types, or set inclusion on
14713 set types. Same precedence as @code{<}.
14715 @item =@r{, }<>@r{, }#
14716 Equality and two ways of expressing inequality, valid on scalar types.
14717 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
14718 available for inequality, since @code{#} conflicts with the script
14722 Set membership. Defined on set types and the types of their members.
14723 Same precedence as @code{<}.
14726 Boolean disjunction. Defined on boolean types.
14729 Boolean conjunction. Defined on boolean types.
14732 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14735 Addition and subtraction on integral and floating-point types, or union
14736 and difference on set types.
14739 Multiplication on integral and floating-point types, or set intersection
14743 Division on floating-point types, or symmetric set difference on set
14744 types. Same precedence as @code{*}.
14747 Integer division and remainder. Defined on integral types. Same
14748 precedence as @code{*}.
14751 Negative. Defined on @code{INTEGER} and @code{REAL} data.
14754 Pointer dereferencing. Defined on pointer types.
14757 Boolean negation. Defined on boolean types. Same precedence as
14761 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
14762 precedence as @code{^}.
14765 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
14768 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
14772 @value{GDBN} and Modula-2 scope operators.
14776 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
14777 treats the use of the operator @code{IN}, or the use of operators
14778 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
14779 @code{<=}, and @code{>=} on sets as an error.
14783 @node Built-In Func/Proc
14784 @subsubsection Built-in Functions and Procedures
14785 @cindex Modula-2 built-ins
14787 Modula-2 also makes available several built-in procedures and functions.
14788 In describing these, the following metavariables are used:
14793 represents an @code{ARRAY} variable.
14796 represents a @code{CHAR} constant or variable.
14799 represents a variable or constant of integral type.
14802 represents an identifier that belongs to a set. Generally used in the
14803 same function with the metavariable @var{s}. The type of @var{s} should
14804 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
14807 represents a variable or constant of integral or floating-point type.
14810 represents a variable or constant of floating-point type.
14816 represents a variable.
14819 represents a variable or constant of one of many types. See the
14820 explanation of the function for details.
14823 All Modula-2 built-in procedures also return a result, described below.
14827 Returns the absolute value of @var{n}.
14830 If @var{c} is a lower case letter, it returns its upper case
14831 equivalent, otherwise it returns its argument.
14834 Returns the character whose ordinal value is @var{i}.
14837 Decrements the value in the variable @var{v} by one. Returns the new value.
14839 @item DEC(@var{v},@var{i})
14840 Decrements the value in the variable @var{v} by @var{i}. Returns the
14843 @item EXCL(@var{m},@var{s})
14844 Removes the element @var{m} from the set @var{s}. Returns the new
14847 @item FLOAT(@var{i})
14848 Returns the floating point equivalent of the integer @var{i}.
14850 @item HIGH(@var{a})
14851 Returns the index of the last member of @var{a}.
14854 Increments the value in the variable @var{v} by one. Returns the new value.
14856 @item INC(@var{v},@var{i})
14857 Increments the value in the variable @var{v} by @var{i}. Returns the
14860 @item INCL(@var{m},@var{s})
14861 Adds the element @var{m} to the set @var{s} if it is not already
14862 there. Returns the new set.
14865 Returns the maximum value of the type @var{t}.
14868 Returns the minimum value of the type @var{t}.
14871 Returns boolean TRUE if @var{i} is an odd number.
14874 Returns the ordinal value of its argument. For example, the ordinal
14875 value of a character is its @sc{ascii} value (on machines supporting
14876 the @sc{ascii} character set). The argument @var{x} must be of an
14877 ordered type, which include integral, character and enumerated types.
14879 @item SIZE(@var{x})
14880 Returns the size of its argument. The argument @var{x} can be a
14881 variable or a type.
14883 @item TRUNC(@var{r})
14884 Returns the integral part of @var{r}.
14886 @item TSIZE(@var{x})
14887 Returns the size of its argument. The argument @var{x} can be a
14888 variable or a type.
14890 @item VAL(@var{t},@var{i})
14891 Returns the member of the type @var{t} whose ordinal value is @var{i}.
14895 @emph{Warning:} Sets and their operations are not yet supported, so
14896 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
14900 @cindex Modula-2 constants
14902 @subsubsection Constants
14904 @value{GDBN} allows you to express the constants of Modula-2 in the following
14910 Integer constants are simply a sequence of digits. When used in an
14911 expression, a constant is interpreted to be type-compatible with the
14912 rest of the expression. Hexadecimal integers are specified by a
14913 trailing @samp{H}, and octal integers by a trailing @samp{B}.
14916 Floating point constants appear as a sequence of digits, followed by a
14917 decimal point and another sequence of digits. An optional exponent can
14918 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
14919 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
14920 digits of the floating point constant must be valid decimal (base 10)
14924 Character constants consist of a single character enclosed by a pair of
14925 like quotes, either single (@code{'}) or double (@code{"}). They may
14926 also be expressed by their ordinal value (their @sc{ascii} value, usually)
14927 followed by a @samp{C}.
14930 String constants consist of a sequence of characters enclosed by a
14931 pair of like quotes, either single (@code{'}) or double (@code{"}).
14932 Escape sequences in the style of C are also allowed. @xref{C
14933 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
14937 Enumerated constants consist of an enumerated identifier.
14940 Boolean constants consist of the identifiers @code{TRUE} and
14944 Pointer constants consist of integral values only.
14947 Set constants are not yet supported.
14951 @subsubsection Modula-2 Types
14952 @cindex Modula-2 types
14954 Currently @value{GDBN} can print the following data types in Modula-2
14955 syntax: array types, record types, set types, pointer types, procedure
14956 types, enumerated types, subrange types and base types. You can also
14957 print the contents of variables declared using these type.
14958 This section gives a number of simple source code examples together with
14959 sample @value{GDBN} sessions.
14961 The first example contains the following section of code:
14970 and you can request @value{GDBN} to interrogate the type and value of
14971 @code{r} and @code{s}.
14974 (@value{GDBP}) print s
14976 (@value{GDBP}) ptype s
14978 (@value{GDBP}) print r
14980 (@value{GDBP}) ptype r
14985 Likewise if your source code declares @code{s} as:
14989 s: SET ['A'..'Z'] ;
14993 then you may query the type of @code{s} by:
14996 (@value{GDBP}) ptype s
14997 type = SET ['A'..'Z']
15001 Note that at present you cannot interactively manipulate set
15002 expressions using the debugger.
15004 The following example shows how you might declare an array in Modula-2
15005 and how you can interact with @value{GDBN} to print its type and contents:
15009 s: ARRAY [-10..10] OF CHAR ;
15013 (@value{GDBP}) ptype s
15014 ARRAY [-10..10] OF CHAR
15017 Note that the array handling is not yet complete and although the type
15018 is printed correctly, expression handling still assumes that all
15019 arrays have a lower bound of zero and not @code{-10} as in the example
15022 Here are some more type related Modula-2 examples:
15026 colour = (blue, red, yellow, green) ;
15027 t = [blue..yellow] ;
15035 The @value{GDBN} interaction shows how you can query the data type
15036 and value of a variable.
15039 (@value{GDBP}) print s
15041 (@value{GDBP}) ptype t
15042 type = [blue..yellow]
15046 In this example a Modula-2 array is declared and its contents
15047 displayed. Observe that the contents are written in the same way as
15048 their @code{C} counterparts.
15052 s: ARRAY [1..5] OF CARDINAL ;
15058 (@value{GDBP}) print s
15059 $1 = @{1, 0, 0, 0, 0@}
15060 (@value{GDBP}) ptype s
15061 type = ARRAY [1..5] OF CARDINAL
15064 The Modula-2 language interface to @value{GDBN} also understands
15065 pointer types as shown in this example:
15069 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
15076 and you can request that @value{GDBN} describes the type of @code{s}.
15079 (@value{GDBP}) ptype s
15080 type = POINTER TO ARRAY [1..5] OF CARDINAL
15083 @value{GDBN} handles compound types as we can see in this example.
15084 Here we combine array types, record types, pointer types and subrange
15095 myarray = ARRAY myrange OF CARDINAL ;
15096 myrange = [-2..2] ;
15098 s: POINTER TO ARRAY myrange OF foo ;
15102 and you can ask @value{GDBN} to describe the type of @code{s} as shown
15106 (@value{GDBP}) ptype s
15107 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
15110 f3 : ARRAY [-2..2] OF CARDINAL;
15115 @subsubsection Modula-2 Defaults
15116 @cindex Modula-2 defaults
15118 If type and range checking are set automatically by @value{GDBN}, they
15119 both default to @code{on} whenever the working language changes to
15120 Modula-2. This happens regardless of whether you or @value{GDBN}
15121 selected the working language.
15123 If you allow @value{GDBN} to set the language automatically, then entering
15124 code compiled from a file whose name ends with @file{.mod} sets the
15125 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
15126 Infer the Source Language}, for further details.
15129 @subsubsection Deviations from Standard Modula-2
15130 @cindex Modula-2, deviations from
15132 A few changes have been made to make Modula-2 programs easier to debug.
15133 This is done primarily via loosening its type strictness:
15137 Unlike in standard Modula-2, pointer constants can be formed by
15138 integers. This allows you to modify pointer variables during
15139 debugging. (In standard Modula-2, the actual address contained in a
15140 pointer variable is hidden from you; it can only be modified
15141 through direct assignment to another pointer variable or expression that
15142 returned a pointer.)
15145 C escape sequences can be used in strings and characters to represent
15146 non-printable characters. @value{GDBN} prints out strings with these
15147 escape sequences embedded. Single non-printable characters are
15148 printed using the @samp{CHR(@var{nnn})} format.
15151 The assignment operator (@code{:=}) returns the value of its right-hand
15155 All built-in procedures both modify @emph{and} return their argument.
15159 @subsubsection Modula-2 Type and Range Checks
15160 @cindex Modula-2 checks
15163 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
15166 @c FIXME remove warning when type/range checks added
15168 @value{GDBN} considers two Modula-2 variables type equivalent if:
15172 They are of types that have been declared equivalent via a @code{TYPE
15173 @var{t1} = @var{t2}} statement
15176 They have been declared on the same line. (Note: This is true of the
15177 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
15180 As long as type checking is enabled, any attempt to combine variables
15181 whose types are not equivalent is an error.
15183 Range checking is done on all mathematical operations, assignment, array
15184 index bounds, and all built-in functions and procedures.
15187 @subsubsection The Scope Operators @code{::} and @code{.}
15189 @cindex @code{.}, Modula-2 scope operator
15190 @cindex colon, doubled as scope operator
15192 @vindex colon-colon@r{, in Modula-2}
15193 @c Info cannot handle :: but TeX can.
15196 @vindex ::@r{, in Modula-2}
15199 There are a few subtle differences between the Modula-2 scope operator
15200 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
15205 @var{module} . @var{id}
15206 @var{scope} :: @var{id}
15210 where @var{scope} is the name of a module or a procedure,
15211 @var{module} the name of a module, and @var{id} is any declared
15212 identifier within your program, except another module.
15214 Using the @code{::} operator makes @value{GDBN} search the scope
15215 specified by @var{scope} for the identifier @var{id}. If it is not
15216 found in the specified scope, then @value{GDBN} searches all scopes
15217 enclosing the one specified by @var{scope}.
15219 Using the @code{.} operator makes @value{GDBN} search the current scope for
15220 the identifier specified by @var{id} that was imported from the
15221 definition module specified by @var{module}. With this operator, it is
15222 an error if the identifier @var{id} was not imported from definition
15223 module @var{module}, or if @var{id} is not an identifier in
15227 @subsubsection @value{GDBN} and Modula-2
15229 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
15230 Five subcommands of @code{set print} and @code{show print} apply
15231 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
15232 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
15233 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
15234 analogue in Modula-2.
15236 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
15237 with any language, is not useful with Modula-2. Its
15238 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
15239 created in Modula-2 as they can in C or C@t{++}. However, because an
15240 address can be specified by an integral constant, the construct
15241 @samp{@{@var{type}@}@var{adrexp}} is still useful.
15243 @cindex @code{#} in Modula-2
15244 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
15245 interpreted as the beginning of a comment. Use @code{<>} instead.
15251 The extensions made to @value{GDBN} for Ada only support
15252 output from the @sc{gnu} Ada (GNAT) compiler.
15253 Other Ada compilers are not currently supported, and
15254 attempting to debug executables produced by them is most likely
15258 @cindex expressions in Ada
15260 * Ada Mode Intro:: General remarks on the Ada syntax
15261 and semantics supported by Ada mode
15263 * Omissions from Ada:: Restrictions on the Ada expression syntax.
15264 * Additions to Ada:: Extensions of the Ada expression syntax.
15265 * Stopping Before Main Program:: Debugging the program during elaboration.
15266 * Ada Exceptions:: Ada Exceptions
15267 * Ada Tasks:: Listing and setting breakpoints in tasks.
15268 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
15269 * Ravenscar Profile:: Tasking Support when using the Ravenscar
15271 * Ada Glitches:: Known peculiarities of Ada mode.
15274 @node Ada Mode Intro
15275 @subsubsection Introduction
15276 @cindex Ada mode, general
15278 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
15279 syntax, with some extensions.
15280 The philosophy behind the design of this subset is
15284 That @value{GDBN} should provide basic literals and access to operations for
15285 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
15286 leaving more sophisticated computations to subprograms written into the
15287 program (which therefore may be called from @value{GDBN}).
15290 That type safety and strict adherence to Ada language restrictions
15291 are not particularly important to the @value{GDBN} user.
15294 That brevity is important to the @value{GDBN} user.
15297 Thus, for brevity, the debugger acts as if all names declared in
15298 user-written packages are directly visible, even if they are not visible
15299 according to Ada rules, thus making it unnecessary to fully qualify most
15300 names with their packages, regardless of context. Where this causes
15301 ambiguity, @value{GDBN} asks the user's intent.
15303 The debugger will start in Ada mode if it detects an Ada main program.
15304 As for other languages, it will enter Ada mode when stopped in a program that
15305 was translated from an Ada source file.
15307 While in Ada mode, you may use `@t{--}' for comments. This is useful
15308 mostly for documenting command files. The standard @value{GDBN} comment
15309 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
15310 middle (to allow based literals).
15312 The debugger supports limited overloading. Given a subprogram call in which
15313 the function symbol has multiple definitions, it will use the number of
15314 actual parameters and some information about their types to attempt to narrow
15315 the set of definitions. It also makes very limited use of context, preferring
15316 procedures to functions in the context of the @code{call} command, and
15317 functions to procedures elsewhere.
15319 @node Omissions from Ada
15320 @subsubsection Omissions from Ada
15321 @cindex Ada, omissions from
15323 Here are the notable omissions from the subset:
15327 Only a subset of the attributes are supported:
15331 @t{'First}, @t{'Last}, and @t{'Length}
15332 on array objects (not on types and subtypes).
15335 @t{'Min} and @t{'Max}.
15338 @t{'Pos} and @t{'Val}.
15344 @t{'Range} on array objects (not subtypes), but only as the right
15345 operand of the membership (@code{in}) operator.
15348 @t{'Access}, @t{'Unchecked_Access}, and
15349 @t{'Unrestricted_Access} (a GNAT extension).
15357 @code{Characters.Latin_1} are not available and
15358 concatenation is not implemented. Thus, escape characters in strings are
15359 not currently available.
15362 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
15363 equality of representations. They will generally work correctly
15364 for strings and arrays whose elements have integer or enumeration types.
15365 They may not work correctly for arrays whose element
15366 types have user-defined equality, for arrays of real values
15367 (in particular, IEEE-conformant floating point, because of negative
15368 zeroes and NaNs), and for arrays whose elements contain unused bits with
15369 indeterminate values.
15372 The other component-by-component array operations (@code{and}, @code{or},
15373 @code{xor}, @code{not}, and relational tests other than equality)
15374 are not implemented.
15377 @cindex array aggregates (Ada)
15378 @cindex record aggregates (Ada)
15379 @cindex aggregates (Ada)
15380 There is limited support for array and record aggregates. They are
15381 permitted only on the right sides of assignments, as in these examples:
15384 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
15385 (@value{GDBP}) set An_Array := (1, others => 0)
15386 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
15387 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
15388 (@value{GDBP}) set A_Record := (1, "Peter", True);
15389 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
15393 discriminant's value by assigning an aggregate has an
15394 undefined effect if that discriminant is used within the record.
15395 However, you can first modify discriminants by directly assigning to
15396 them (which normally would not be allowed in Ada), and then performing an
15397 aggregate assignment. For example, given a variable @code{A_Rec}
15398 declared to have a type such as:
15401 type Rec (Len : Small_Integer := 0) is record
15403 Vals : IntArray (1 .. Len);
15407 you can assign a value with a different size of @code{Vals} with two
15411 (@value{GDBP}) set A_Rec.Len := 4
15412 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
15415 As this example also illustrates, @value{GDBN} is very loose about the usual
15416 rules concerning aggregates. You may leave out some of the
15417 components of an array or record aggregate (such as the @code{Len}
15418 component in the assignment to @code{A_Rec} above); they will retain their
15419 original values upon assignment. You may freely use dynamic values as
15420 indices in component associations. You may even use overlapping or
15421 redundant component associations, although which component values are
15422 assigned in such cases is not defined.
15425 Calls to dispatching subprograms are not implemented.
15428 The overloading algorithm is much more limited (i.e., less selective)
15429 than that of real Ada. It makes only limited use of the context in
15430 which a subexpression appears to resolve its meaning, and it is much
15431 looser in its rules for allowing type matches. As a result, some
15432 function calls will be ambiguous, and the user will be asked to choose
15433 the proper resolution.
15436 The @code{new} operator is not implemented.
15439 Entry calls are not implemented.
15442 Aside from printing, arithmetic operations on the native VAX floating-point
15443 formats are not supported.
15446 It is not possible to slice a packed array.
15449 The names @code{True} and @code{False}, when not part of a qualified name,
15450 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
15452 Should your program
15453 redefine these names in a package or procedure (at best a dubious practice),
15454 you will have to use fully qualified names to access their new definitions.
15457 @node Additions to Ada
15458 @subsubsection Additions to Ada
15459 @cindex Ada, deviations from
15461 As it does for other languages, @value{GDBN} makes certain generic
15462 extensions to Ada (@pxref{Expressions}):
15466 If the expression @var{E} is a variable residing in memory (typically
15467 a local variable or array element) and @var{N} is a positive integer,
15468 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
15469 @var{N}-1 adjacent variables following it in memory as an array. In
15470 Ada, this operator is generally not necessary, since its prime use is
15471 in displaying parts of an array, and slicing will usually do this in
15472 Ada. However, there are occasional uses when debugging programs in
15473 which certain debugging information has been optimized away.
15476 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
15477 appears in function or file @var{B}.'' When @var{B} is a file name,
15478 you must typically surround it in single quotes.
15481 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
15482 @var{type} that appears at address @var{addr}.''
15485 A name starting with @samp{$} is a convenience variable
15486 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
15489 In addition, @value{GDBN} provides a few other shortcuts and outright
15490 additions specific to Ada:
15494 The assignment statement is allowed as an expression, returning
15495 its right-hand operand as its value. Thus, you may enter
15498 (@value{GDBP}) set x := y + 3
15499 (@value{GDBP}) print A(tmp := y + 1)
15503 The semicolon is allowed as an ``operator,'' returning as its value
15504 the value of its right-hand operand.
15505 This allows, for example,
15506 complex conditional breaks:
15509 (@value{GDBP}) break f
15510 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
15514 Rather than use catenation and symbolic character names to introduce special
15515 characters into strings, one may instead use a special bracket notation,
15516 which is also used to print strings. A sequence of characters of the form
15517 @samp{["@var{XX}"]} within a string or character literal denotes the
15518 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
15519 sequence of characters @samp{["""]} also denotes a single quotation mark
15520 in strings. For example,
15522 "One line.["0a"]Next line.["0a"]"
15525 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
15529 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
15530 @t{'Max} is optional (and is ignored in any case). For example, it is valid
15534 (@value{GDBP}) print 'max(x, y)
15538 When printing arrays, @value{GDBN} uses positional notation when the
15539 array has a lower bound of 1, and uses a modified named notation otherwise.
15540 For example, a one-dimensional array of three integers with a lower bound
15541 of 3 might print as
15548 That is, in contrast to valid Ada, only the first component has a @code{=>}
15552 You may abbreviate attributes in expressions with any unique,
15553 multi-character subsequence of
15554 their names (an exact match gets preference).
15555 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
15556 in place of @t{a'length}.
15559 @cindex quoting Ada internal identifiers
15560 Since Ada is case-insensitive, the debugger normally maps identifiers you type
15561 to lower case. The GNAT compiler uses upper-case characters for
15562 some of its internal identifiers, which are normally of no interest to users.
15563 For the rare occasions when you actually have to look at them,
15564 enclose them in angle brackets to avoid the lower-case mapping.
15567 (@value{GDBP}) print <JMPBUF_SAVE>[0]
15571 Printing an object of class-wide type or dereferencing an
15572 access-to-class-wide value will display all the components of the object's
15573 specific type (as indicated by its run-time tag). Likewise, component
15574 selection on such a value will operate on the specific type of the
15579 @node Stopping Before Main Program
15580 @subsubsection Stopping at the Very Beginning
15582 @cindex breakpointing Ada elaboration code
15583 It is sometimes necessary to debug the program during elaboration, and
15584 before reaching the main procedure.
15585 As defined in the Ada Reference
15586 Manual, the elaboration code is invoked from a procedure called
15587 @code{adainit}. To run your program up to the beginning of
15588 elaboration, simply use the following two commands:
15589 @code{tbreak adainit} and @code{run}.
15591 @node Ada Exceptions
15592 @subsubsection Ada Exceptions
15594 A command is provided to list all Ada exceptions:
15597 @kindex info exceptions
15598 @item info exceptions
15599 @itemx info exceptions @var{regexp}
15600 The @code{info exceptions} command allows you to list all Ada exceptions
15601 defined within the program being debugged, as well as their addresses.
15602 With a regular expression, @var{regexp}, as argument, only those exceptions
15603 whose names match @var{regexp} are listed.
15606 Below is a small example, showing how the command can be used, first
15607 without argument, and next with a regular expression passed as an
15611 (@value{GDBP}) info exceptions
15612 All defined Ada exceptions:
15613 constraint_error: 0x613da0
15614 program_error: 0x613d20
15615 storage_error: 0x613ce0
15616 tasking_error: 0x613ca0
15617 const.aint_global_e: 0x613b00
15618 (@value{GDBP}) info exceptions const.aint
15619 All Ada exceptions matching regular expression "const.aint":
15620 constraint_error: 0x613da0
15621 const.aint_global_e: 0x613b00
15624 It is also possible to ask @value{GDBN} to stop your program's execution
15625 when an exception is raised. For more details, see @ref{Set Catchpoints}.
15628 @subsubsection Extensions for Ada Tasks
15629 @cindex Ada, tasking
15631 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
15632 @value{GDBN} provides the following task-related commands:
15637 This command shows a list of current Ada tasks, as in the following example:
15644 (@value{GDBP}) info tasks
15645 ID TID P-ID Pri State Name
15646 1 8088000 0 15 Child Activation Wait main_task
15647 2 80a4000 1 15 Accept Statement b
15648 3 809a800 1 15 Child Activation Wait a
15649 * 4 80ae800 3 15 Runnable c
15654 In this listing, the asterisk before the last task indicates it to be the
15655 task currently being inspected.
15659 Represents @value{GDBN}'s internal task number.
15665 The parent's task ID (@value{GDBN}'s internal task number).
15668 The base priority of the task.
15671 Current state of the task.
15675 The task has been created but has not been activated. It cannot be
15679 The task is not blocked for any reason known to Ada. (It may be waiting
15680 for a mutex, though.) It is conceptually "executing" in normal mode.
15683 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
15684 that were waiting on terminate alternatives have been awakened and have
15685 terminated themselves.
15687 @item Child Activation Wait
15688 The task is waiting for created tasks to complete activation.
15690 @item Accept Statement
15691 The task is waiting on an accept or selective wait statement.
15693 @item Waiting on entry call
15694 The task is waiting on an entry call.
15696 @item Async Select Wait
15697 The task is waiting to start the abortable part of an asynchronous
15701 The task is waiting on a select statement with only a delay
15704 @item Child Termination Wait
15705 The task is sleeping having completed a master within itself, and is
15706 waiting for the tasks dependent on that master to become terminated or
15707 waiting on a terminate Phase.
15709 @item Wait Child in Term Alt
15710 The task is sleeping waiting for tasks on terminate alternatives to
15711 finish terminating.
15713 @item Accepting RV with @var{taskno}
15714 The task is accepting a rendez-vous with the task @var{taskno}.
15718 Name of the task in the program.
15722 @kindex info task @var{taskno}
15723 @item info task @var{taskno}
15724 This command shows detailled informations on the specified task, as in
15725 the following example:
15730 (@value{GDBP}) info tasks
15731 ID TID P-ID Pri State Name
15732 1 8077880 0 15 Child Activation Wait main_task
15733 * 2 807c468 1 15 Runnable task_1
15734 (@value{GDBP}) info task 2
15735 Ada Task: 0x807c468
15738 Parent: 1 (main_task)
15744 @kindex task@r{ (Ada)}
15745 @cindex current Ada task ID
15746 This command prints the ID of the current task.
15752 (@value{GDBP}) info tasks
15753 ID TID P-ID Pri State Name
15754 1 8077870 0 15 Child Activation Wait main_task
15755 * 2 807c458 1 15 Runnable t
15756 (@value{GDBP}) task
15757 [Current task is 2]
15760 @item task @var{taskno}
15761 @cindex Ada task switching
15762 This command is like the @code{thread @var{threadno}}
15763 command (@pxref{Threads}). It switches the context of debugging
15764 from the current task to the given task.
15770 (@value{GDBP}) info tasks
15771 ID TID P-ID Pri State Name
15772 1 8077870 0 15 Child Activation Wait main_task
15773 * 2 807c458 1 15 Runnable t
15774 (@value{GDBP}) task 1
15775 [Switching to task 1]
15776 #0 0x8067726 in pthread_cond_wait ()
15778 #0 0x8067726 in pthread_cond_wait ()
15779 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
15780 #2 0x805cb63 in system.task_primitives.operations.sleep ()
15781 #3 0x806153e in system.tasking.stages.activate_tasks ()
15782 #4 0x804aacc in un () at un.adb:5
15785 @item break @var{linespec} task @var{taskno}
15786 @itemx break @var{linespec} task @var{taskno} if @dots{}
15787 @cindex breakpoints and tasks, in Ada
15788 @cindex task breakpoints, in Ada
15789 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
15790 These commands are like the @code{break @dots{} thread @dots{}}
15791 command (@pxref{Thread Stops}). The
15792 @var{linespec} argument specifies source lines, as described
15793 in @ref{Specify Location}.
15795 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
15796 to specify that you only want @value{GDBN} to stop the program when a
15797 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
15798 numeric task identifiers assigned by @value{GDBN}, shown in the first
15799 column of the @samp{info tasks} display.
15801 If you do not specify @samp{task @var{taskno}} when you set a
15802 breakpoint, the breakpoint applies to @emph{all} tasks of your
15805 You can use the @code{task} qualifier on conditional breakpoints as
15806 well; in this case, place @samp{task @var{taskno}} before the
15807 breakpoint condition (before the @code{if}).
15815 (@value{GDBP}) info tasks
15816 ID TID P-ID Pri State Name
15817 1 140022020 0 15 Child Activation Wait main_task
15818 2 140045060 1 15 Accept/Select Wait t2
15819 3 140044840 1 15 Runnable t1
15820 * 4 140056040 1 15 Runnable t3
15821 (@value{GDBP}) b 15 task 2
15822 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
15823 (@value{GDBP}) cont
15828 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
15830 (@value{GDBP}) info tasks
15831 ID TID P-ID Pri State Name
15832 1 140022020 0 15 Child Activation Wait main_task
15833 * 2 140045060 1 15 Runnable t2
15834 3 140044840 1 15 Runnable t1
15835 4 140056040 1 15 Delay Sleep t3
15839 @node Ada Tasks and Core Files
15840 @subsubsection Tasking Support when Debugging Core Files
15841 @cindex Ada tasking and core file debugging
15843 When inspecting a core file, as opposed to debugging a live program,
15844 tasking support may be limited or even unavailable, depending on
15845 the platform being used.
15846 For instance, on x86-linux, the list of tasks is available, but task
15847 switching is not supported.
15849 On certain platforms, the debugger needs to perform some
15850 memory writes in order to provide Ada tasking support. When inspecting
15851 a core file, this means that the core file must be opened with read-write
15852 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
15853 Under these circumstances, you should make a backup copy of the core
15854 file before inspecting it with @value{GDBN}.
15856 @node Ravenscar Profile
15857 @subsubsection Tasking Support when using the Ravenscar Profile
15858 @cindex Ravenscar Profile
15860 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
15861 specifically designed for systems with safety-critical real-time
15865 @kindex set ravenscar task-switching on
15866 @cindex task switching with program using Ravenscar Profile
15867 @item set ravenscar task-switching on
15868 Allows task switching when debugging a program that uses the Ravenscar
15869 Profile. This is the default.
15871 @kindex set ravenscar task-switching off
15872 @item set ravenscar task-switching off
15873 Turn off task switching when debugging a program that uses the Ravenscar
15874 Profile. This is mostly intended to disable the code that adds support
15875 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
15876 the Ravenscar runtime is preventing @value{GDBN} from working properly.
15877 To be effective, this command should be run before the program is started.
15879 @kindex show ravenscar task-switching
15880 @item show ravenscar task-switching
15881 Show whether it is possible to switch from task to task in a program
15882 using the Ravenscar Profile.
15887 @subsubsection Known Peculiarities of Ada Mode
15888 @cindex Ada, problems
15890 Besides the omissions listed previously (@pxref{Omissions from Ada}),
15891 we know of several problems with and limitations of Ada mode in
15893 some of which will be fixed with planned future releases of the debugger
15894 and the GNU Ada compiler.
15898 Static constants that the compiler chooses not to materialize as objects in
15899 storage are invisible to the debugger.
15902 Named parameter associations in function argument lists are ignored (the
15903 argument lists are treated as positional).
15906 Many useful library packages are currently invisible to the debugger.
15909 Fixed-point arithmetic, conversions, input, and output is carried out using
15910 floating-point arithmetic, and may give results that only approximate those on
15914 The GNAT compiler never generates the prefix @code{Standard} for any of
15915 the standard symbols defined by the Ada language. @value{GDBN} knows about
15916 this: it will strip the prefix from names when you use it, and will never
15917 look for a name you have so qualified among local symbols, nor match against
15918 symbols in other packages or subprograms. If you have
15919 defined entities anywhere in your program other than parameters and
15920 local variables whose simple names match names in @code{Standard},
15921 GNAT's lack of qualification here can cause confusion. When this happens,
15922 you can usually resolve the confusion
15923 by qualifying the problematic names with package
15924 @code{Standard} explicitly.
15927 Older versions of the compiler sometimes generate erroneous debugging
15928 information, resulting in the debugger incorrectly printing the value
15929 of affected entities. In some cases, the debugger is able to work
15930 around an issue automatically. In other cases, the debugger is able
15931 to work around the issue, but the work-around has to be specifically
15934 @kindex set ada trust-PAD-over-XVS
15935 @kindex show ada trust-PAD-over-XVS
15938 @item set ada trust-PAD-over-XVS on
15939 Configure GDB to strictly follow the GNAT encoding when computing the
15940 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
15941 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
15942 a complete description of the encoding used by the GNAT compiler).
15943 This is the default.
15945 @item set ada trust-PAD-over-XVS off
15946 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
15947 sometimes prints the wrong value for certain entities, changing @code{ada
15948 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
15949 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
15950 @code{off}, but this incurs a slight performance penalty, so it is
15951 recommended to leave this setting to @code{on} unless necessary.
15955 @cindex GNAT descriptive types
15956 @cindex GNAT encoding
15957 Internally, the debugger also relies on the compiler following a number
15958 of conventions known as the @samp{GNAT Encoding}, all documented in
15959 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
15960 how the debugging information should be generated for certain types.
15961 In particular, this convention makes use of @dfn{descriptive types},
15962 which are artificial types generated purely to help the debugger.
15964 These encodings were defined at a time when the debugging information
15965 format used was not powerful enough to describe some of the more complex
15966 types available in Ada. Since DWARF allows us to express nearly all
15967 Ada features, the long-term goal is to slowly replace these descriptive
15968 types by their pure DWARF equivalent. To facilitate that transition,
15969 a new maintenance option is available to force the debugger to ignore
15970 those descriptive types. It allows the user to quickly evaluate how
15971 well @value{GDBN} works without them.
15975 @kindex maint ada set ignore-descriptive-types
15976 @item maintenance ada set ignore-descriptive-types [on|off]
15977 Control whether the debugger should ignore descriptive types.
15978 The default is not to ignore descriptives types (@code{off}).
15980 @kindex maint ada show ignore-descriptive-types
15981 @item maintenance ada show ignore-descriptive-types
15982 Show if descriptive types are ignored by @value{GDBN}.
15986 @node Unsupported Languages
15987 @section Unsupported Languages
15989 @cindex unsupported languages
15990 @cindex minimal language
15991 In addition to the other fully-supported programming languages,
15992 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
15993 It does not represent a real programming language, but provides a set
15994 of capabilities close to what the C or assembly languages provide.
15995 This should allow most simple operations to be performed while debugging
15996 an application that uses a language currently not supported by @value{GDBN}.
15998 If the language is set to @code{auto}, @value{GDBN} will automatically
15999 select this language if the current frame corresponds to an unsupported
16003 @chapter Examining the Symbol Table
16005 The commands described in this chapter allow you to inquire about the
16006 symbols (names of variables, functions and types) defined in your
16007 program. This information is inherent in the text of your program and
16008 does not change as your program executes. @value{GDBN} finds it in your
16009 program's symbol table, in the file indicated when you started @value{GDBN}
16010 (@pxref{File Options, ,Choosing Files}), or by one of the
16011 file-management commands (@pxref{Files, ,Commands to Specify Files}).
16013 @cindex symbol names
16014 @cindex names of symbols
16015 @cindex quoting names
16016 Occasionally, you may need to refer to symbols that contain unusual
16017 characters, which @value{GDBN} ordinarily treats as word delimiters. The
16018 most frequent case is in referring to static variables in other
16019 source files (@pxref{Variables,,Program Variables}). File names
16020 are recorded in object files as debugging symbols, but @value{GDBN} would
16021 ordinarily parse a typical file name, like @file{foo.c}, as the three words
16022 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
16023 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
16030 looks up the value of @code{x} in the scope of the file @file{foo.c}.
16033 @cindex case-insensitive symbol names
16034 @cindex case sensitivity in symbol names
16035 @kindex set case-sensitive
16036 @item set case-sensitive on
16037 @itemx set case-sensitive off
16038 @itemx set case-sensitive auto
16039 Normally, when @value{GDBN} looks up symbols, it matches their names
16040 with case sensitivity determined by the current source language.
16041 Occasionally, you may wish to control that. The command @code{set
16042 case-sensitive} lets you do that by specifying @code{on} for
16043 case-sensitive matches or @code{off} for case-insensitive ones. If
16044 you specify @code{auto}, case sensitivity is reset to the default
16045 suitable for the source language. The default is case-sensitive
16046 matches for all languages except for Fortran, for which the default is
16047 case-insensitive matches.
16049 @kindex show case-sensitive
16050 @item show case-sensitive
16051 This command shows the current setting of case sensitivity for symbols
16054 @kindex set print type methods
16055 @item set print type methods
16056 @itemx set print type methods on
16057 @itemx set print type methods off
16058 Normally, when @value{GDBN} prints a class, it displays any methods
16059 declared in that class. You can control this behavior either by
16060 passing the appropriate flag to @code{ptype}, or using @command{set
16061 print type methods}. Specifying @code{on} will cause @value{GDBN} to
16062 display the methods; this is the default. Specifying @code{off} will
16063 cause @value{GDBN} to omit the methods.
16065 @kindex show print type methods
16066 @item show print type methods
16067 This command shows the current setting of method display when printing
16070 @kindex set print type typedefs
16071 @item set print type typedefs
16072 @itemx set print type typedefs on
16073 @itemx set print type typedefs off
16075 Normally, when @value{GDBN} prints a class, it displays any typedefs
16076 defined in that class. You can control this behavior either by
16077 passing the appropriate flag to @code{ptype}, or using @command{set
16078 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
16079 display the typedef definitions; this is the default. Specifying
16080 @code{off} will cause @value{GDBN} to omit the typedef definitions.
16081 Note that this controls whether the typedef definition itself is
16082 printed, not whether typedef names are substituted when printing other
16085 @kindex show print type typedefs
16086 @item show print type typedefs
16087 This command shows the current setting of typedef display when
16090 @kindex info address
16091 @cindex address of a symbol
16092 @item info address @var{symbol}
16093 Describe where the data for @var{symbol} is stored. For a register
16094 variable, this says which register it is kept in. For a non-register
16095 local variable, this prints the stack-frame offset at which the variable
16098 Note the contrast with @samp{print &@var{symbol}}, which does not work
16099 at all for a register variable, and for a stack local variable prints
16100 the exact address of the current instantiation of the variable.
16102 @kindex info symbol
16103 @cindex symbol from address
16104 @cindex closest symbol and offset for an address
16105 @item info symbol @var{addr}
16106 Print the name of a symbol which is stored at the address @var{addr}.
16107 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
16108 nearest symbol and an offset from it:
16111 (@value{GDBP}) info symbol 0x54320
16112 _initialize_vx + 396 in section .text
16116 This is the opposite of the @code{info address} command. You can use
16117 it to find out the name of a variable or a function given its address.
16119 For dynamically linked executables, the name of executable or shared
16120 library containing the symbol is also printed:
16123 (@value{GDBP}) info symbol 0x400225
16124 _start + 5 in section .text of /tmp/a.out
16125 (@value{GDBP}) info symbol 0x2aaaac2811cf
16126 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
16131 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
16132 Demangle @var{name}.
16133 If @var{language} is provided it is the name of the language to demangle
16134 @var{name} in. Otherwise @var{name} is demangled in the current language.
16136 The @samp{--} option specifies the end of options,
16137 and is useful when @var{name} begins with a dash.
16139 The parameter @code{demangle-style} specifies how to interpret the kind
16140 of mangling used. @xref{Print Settings}.
16143 @item whatis[/@var{flags}] [@var{arg}]
16144 Print the data type of @var{arg}, which can be either an expression
16145 or a name of a data type. With no argument, print the data type of
16146 @code{$}, the last value in the value history.
16148 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
16149 is not actually evaluated, and any side-effecting operations (such as
16150 assignments or function calls) inside it do not take place.
16152 If @var{arg} is a variable or an expression, @code{whatis} prints its
16153 literal type as it is used in the source code. If the type was
16154 defined using a @code{typedef}, @code{whatis} will @emph{not} print
16155 the data type underlying the @code{typedef}. If the type of the
16156 variable or the expression is a compound data type, such as
16157 @code{struct} or @code{class}, @code{whatis} never prints their
16158 fields or methods. It just prints the @code{struct}/@code{class}
16159 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
16160 such a compound data type, use @code{ptype}.
16162 If @var{arg} is a type name that was defined using @code{typedef},
16163 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
16164 Unrolling means that @code{whatis} will show the underlying type used
16165 in the @code{typedef} declaration of @var{arg}. However, if that
16166 underlying type is also a @code{typedef}, @code{whatis} will not
16169 For C code, the type names may also have the form @samp{class
16170 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
16171 @var{union-tag}} or @samp{enum @var{enum-tag}}.
16173 @var{flags} can be used to modify how the type is displayed.
16174 Available flags are:
16178 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
16179 parameters and typedefs defined in a class when printing the class'
16180 members. The @code{/r} flag disables this.
16183 Do not print methods defined in the class.
16186 Print methods defined in the class. This is the default, but the flag
16187 exists in case you change the default with @command{set print type methods}.
16190 Do not print typedefs defined in the class. Note that this controls
16191 whether the typedef definition itself is printed, not whether typedef
16192 names are substituted when printing other types.
16195 Print typedefs defined in the class. This is the default, but the flag
16196 exists in case you change the default with @command{set print type typedefs}.
16200 @item ptype[/@var{flags}] [@var{arg}]
16201 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
16202 detailed description of the type, instead of just the name of the type.
16203 @xref{Expressions, ,Expressions}.
16205 Contrary to @code{whatis}, @code{ptype} always unrolls any
16206 @code{typedef}s in its argument declaration, whether the argument is
16207 a variable, expression, or a data type. This means that @code{ptype}
16208 of a variable or an expression will not print literally its type as
16209 present in the source code---use @code{whatis} for that. @code{typedef}s at
16210 the pointer or reference targets are also unrolled. Only @code{typedef}s of
16211 fields, methods and inner @code{class typedef}s of @code{struct}s,
16212 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
16214 For example, for this variable declaration:
16217 typedef double real_t;
16218 struct complex @{ real_t real; double imag; @};
16219 typedef struct complex complex_t;
16221 real_t *real_pointer_var;
16225 the two commands give this output:
16229 (@value{GDBP}) whatis var
16231 (@value{GDBP}) ptype var
16232 type = struct complex @{
16236 (@value{GDBP}) whatis complex_t
16237 type = struct complex
16238 (@value{GDBP}) whatis struct complex
16239 type = struct complex
16240 (@value{GDBP}) ptype struct complex
16241 type = struct complex @{
16245 (@value{GDBP}) whatis real_pointer_var
16247 (@value{GDBP}) ptype real_pointer_var
16253 As with @code{whatis}, using @code{ptype} without an argument refers to
16254 the type of @code{$}, the last value in the value history.
16256 @cindex incomplete type
16257 Sometimes, programs use opaque data types or incomplete specifications
16258 of complex data structure. If the debug information included in the
16259 program does not allow @value{GDBN} to display a full declaration of
16260 the data type, it will say @samp{<incomplete type>}. For example,
16261 given these declarations:
16265 struct foo *fooptr;
16269 but no definition for @code{struct foo} itself, @value{GDBN} will say:
16272 (@value{GDBP}) ptype foo
16273 $1 = <incomplete type>
16277 ``Incomplete type'' is C terminology for data types that are not
16278 completely specified.
16281 @item info types @var{regexp}
16283 Print a brief description of all types whose names match the regular
16284 expression @var{regexp} (or all types in your program, if you supply
16285 no argument). Each complete typename is matched as though it were a
16286 complete line; thus, @samp{i type value} gives information on all
16287 types in your program whose names include the string @code{value}, but
16288 @samp{i type ^value$} gives information only on types whose complete
16289 name is @code{value}.
16291 This command differs from @code{ptype} in two ways: first, like
16292 @code{whatis}, it does not print a detailed description; second, it
16293 lists all source files where a type is defined.
16295 @kindex info type-printers
16296 @item info type-printers
16297 Versions of @value{GDBN} that ship with Python scripting enabled may
16298 have ``type printers'' available. When using @command{ptype} or
16299 @command{whatis}, these printers are consulted when the name of a type
16300 is needed. @xref{Type Printing API}, for more information on writing
16303 @code{info type-printers} displays all the available type printers.
16305 @kindex enable type-printer
16306 @kindex disable type-printer
16307 @item enable type-printer @var{name}@dots{}
16308 @item disable type-printer @var{name}@dots{}
16309 These commands can be used to enable or disable type printers.
16312 @cindex local variables
16313 @item info scope @var{location}
16314 List all the variables local to a particular scope. This command
16315 accepts a @var{location} argument---a function name, a source line, or
16316 an address preceded by a @samp{*}, and prints all the variables local
16317 to the scope defined by that location. (@xref{Specify Location}, for
16318 details about supported forms of @var{location}.) For example:
16321 (@value{GDBP}) @b{info scope command_line_handler}
16322 Scope for command_line_handler:
16323 Symbol rl is an argument at stack/frame offset 8, length 4.
16324 Symbol linebuffer is in static storage at address 0x150a18, length 4.
16325 Symbol linelength is in static storage at address 0x150a1c, length 4.
16326 Symbol p is a local variable in register $esi, length 4.
16327 Symbol p1 is a local variable in register $ebx, length 4.
16328 Symbol nline is a local variable in register $edx, length 4.
16329 Symbol repeat is a local variable at frame offset -8, length 4.
16333 This command is especially useful for determining what data to collect
16334 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
16337 @kindex info source
16339 Show information about the current source file---that is, the source file for
16340 the function containing the current point of execution:
16343 the name of the source file, and the directory containing it,
16345 the directory it was compiled in,
16347 its length, in lines,
16349 which programming language it is written in,
16351 if the debug information provides it, the program that compiled the file
16352 (which may include, e.g., the compiler version and command line arguments),
16354 whether the executable includes debugging information for that file, and
16355 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
16357 whether the debugging information includes information about
16358 preprocessor macros.
16362 @kindex info sources
16364 Print the names of all source files in your program for which there is
16365 debugging information, organized into two lists: files whose symbols
16366 have already been read, and files whose symbols will be read when needed.
16368 @kindex info functions
16369 @item info functions
16370 Print the names and data types of all defined functions.
16372 @item info functions @var{regexp}
16373 Print the names and data types of all defined functions
16374 whose names contain a match for regular expression @var{regexp}.
16375 Thus, @samp{info fun step} finds all functions whose names
16376 include @code{step}; @samp{info fun ^step} finds those whose names
16377 start with @code{step}. If a function name contains characters
16378 that conflict with the regular expression language (e.g.@:
16379 @samp{operator*()}), they may be quoted with a backslash.
16381 @kindex info variables
16382 @item info variables
16383 Print the names and data types of all variables that are defined
16384 outside of functions (i.e.@: excluding local variables).
16386 @item info variables @var{regexp}
16387 Print the names and data types of all variables (except for local
16388 variables) whose names contain a match for regular expression
16391 @kindex info classes
16392 @cindex Objective-C, classes and selectors
16394 @itemx info classes @var{regexp}
16395 Display all Objective-C classes in your program, or
16396 (with the @var{regexp} argument) all those matching a particular regular
16399 @kindex info selectors
16400 @item info selectors
16401 @itemx info selectors @var{regexp}
16402 Display all Objective-C selectors in your program, or
16403 (with the @var{regexp} argument) all those matching a particular regular
16407 This was never implemented.
16408 @kindex info methods
16410 @itemx info methods @var{regexp}
16411 The @code{info methods} command permits the user to examine all defined
16412 methods within C@t{++} program, or (with the @var{regexp} argument) a
16413 specific set of methods found in the various C@t{++} classes. Many
16414 C@t{++} classes provide a large number of methods. Thus, the output
16415 from the @code{ptype} command can be overwhelming and hard to use. The
16416 @code{info-methods} command filters the methods, printing only those
16417 which match the regular-expression @var{regexp}.
16420 @cindex opaque data types
16421 @kindex set opaque-type-resolution
16422 @item set opaque-type-resolution on
16423 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
16424 declared as a pointer to a @code{struct}, @code{class}, or
16425 @code{union}---for example, @code{struct MyType *}---that is used in one
16426 source file although the full declaration of @code{struct MyType} is in
16427 another source file. The default is on.
16429 A change in the setting of this subcommand will not take effect until
16430 the next time symbols for a file are loaded.
16432 @item set opaque-type-resolution off
16433 Tell @value{GDBN} not to resolve opaque types. In this case, the type
16434 is printed as follows:
16436 @{<no data fields>@}
16439 @kindex show opaque-type-resolution
16440 @item show opaque-type-resolution
16441 Show whether opaque types are resolved or not.
16443 @kindex set print symbol-loading
16444 @cindex print messages when symbols are loaded
16445 @item set print symbol-loading
16446 @itemx set print symbol-loading full
16447 @itemx set print symbol-loading brief
16448 @itemx set print symbol-loading off
16449 The @code{set print symbol-loading} command allows you to control the
16450 printing of messages when @value{GDBN} loads symbol information.
16451 By default a message is printed for the executable and one for each
16452 shared library, and normally this is what you want. However, when
16453 debugging apps with large numbers of shared libraries these messages
16455 When set to @code{brief} a message is printed for each executable,
16456 and when @value{GDBN} loads a collection of shared libraries at once
16457 it will only print one message regardless of the number of shared
16458 libraries. When set to @code{off} no messages are printed.
16460 @kindex show print symbol-loading
16461 @item show print symbol-loading
16462 Show whether messages will be printed when a @value{GDBN} command
16463 entered from the keyboard causes symbol information to be loaded.
16465 @kindex maint print symbols
16466 @cindex symbol dump
16467 @kindex maint print psymbols
16468 @cindex partial symbol dump
16469 @kindex maint print msymbols
16470 @cindex minimal symbol dump
16471 @item maint print symbols @var{filename}
16472 @itemx maint print psymbols @var{filename}
16473 @itemx maint print msymbols @var{filename}
16474 Write a dump of debugging symbol data into the file @var{filename}.
16475 These commands are used to debug the @value{GDBN} symbol-reading code. Only
16476 symbols with debugging data are included. If you use @samp{maint print
16477 symbols}, @value{GDBN} includes all the symbols for which it has already
16478 collected full details: that is, @var{filename} reflects symbols for
16479 only those files whose symbols @value{GDBN} has read. You can use the
16480 command @code{info sources} to find out which files these are. If you
16481 use @samp{maint print psymbols} instead, the dump shows information about
16482 symbols that @value{GDBN} only knows partially---that is, symbols defined in
16483 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
16484 @samp{maint print msymbols} dumps just the minimal symbol information
16485 required for each object file from which @value{GDBN} has read some symbols.
16486 @xref{Files, ,Commands to Specify Files}, for a discussion of how
16487 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
16489 @kindex maint info symtabs
16490 @kindex maint info psymtabs
16491 @cindex listing @value{GDBN}'s internal symbol tables
16492 @cindex symbol tables, listing @value{GDBN}'s internal
16493 @cindex full symbol tables, listing @value{GDBN}'s internal
16494 @cindex partial symbol tables, listing @value{GDBN}'s internal
16495 @item maint info symtabs @r{[} @var{regexp} @r{]}
16496 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
16498 List the @code{struct symtab} or @code{struct partial_symtab}
16499 structures whose names match @var{regexp}. If @var{regexp} is not
16500 given, list them all. The output includes expressions which you can
16501 copy into a @value{GDBN} debugging this one to examine a particular
16502 structure in more detail. For example:
16505 (@value{GDBP}) maint info psymtabs dwarf2read
16506 @{ objfile /home/gnu/build/gdb/gdb
16507 ((struct objfile *) 0x82e69d0)
16508 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
16509 ((struct partial_symtab *) 0x8474b10)
16512 text addresses 0x814d3c8 -- 0x8158074
16513 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
16514 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
16515 dependencies (none)
16518 (@value{GDBP}) maint info symtabs
16522 We see that there is one partial symbol table whose filename contains
16523 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
16524 and we see that @value{GDBN} has not read in any symtabs yet at all.
16525 If we set a breakpoint on a function, that will cause @value{GDBN} to
16526 read the symtab for the compilation unit containing that function:
16529 (@value{GDBP}) break dwarf2_psymtab_to_symtab
16530 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
16532 (@value{GDBP}) maint info symtabs
16533 @{ objfile /home/gnu/build/gdb/gdb
16534 ((struct objfile *) 0x82e69d0)
16535 @{ symtab /home/gnu/src/gdb/dwarf2read.c
16536 ((struct symtab *) 0x86c1f38)
16539 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
16540 linetable ((struct linetable *) 0x8370fa0)
16541 debugformat DWARF 2
16547 @kindex maint set symbol-cache-size
16548 @cindex symbol cache size
16549 @item maint set symbol-cache-size @var{size}
16550 Set the size of the symbol cache to @var{size}.
16551 The default size is intended to be good enough for debugging
16552 most applications. This option exists to allow for experimenting
16553 with different sizes.
16555 @kindex maint show symbol-cache-size
16556 @item maint show symbol-cache-size
16557 Show the size of the symbol cache.
16559 @kindex maint print symbol-cache
16560 @cindex symbol cache, printing its contents
16561 @item maint print symbol-cache
16562 Print the contents of the symbol cache.
16563 This is useful when debugging symbol cache issues.
16565 @kindex maint print symbol-cache-statistics
16566 @cindex symbol cache, printing usage statistics
16567 @item maint print symbol-cache-statistics
16568 Print symbol cache usage statistics.
16569 This helps determine how well the cache is being utilized.
16571 @kindex maint flush-symbol-cache
16572 @cindex symbol cache, flushing
16573 @item maint flush-symbol-cache
16574 Flush the contents of the symbol cache, all entries are removed.
16575 This command is useful when debugging the symbol cache.
16576 It is also useful when collecting performance data.
16581 @chapter Altering Execution
16583 Once you think you have found an error in your program, you might want to
16584 find out for certain whether correcting the apparent error would lead to
16585 correct results in the rest of the run. You can find the answer by
16586 experiment, using the @value{GDBN} features for altering execution of the
16589 For example, you can store new values into variables or memory
16590 locations, give your program a signal, restart it at a different
16591 address, or even return prematurely from a function.
16594 * Assignment:: Assignment to variables
16595 * Jumping:: Continuing at a different address
16596 * Signaling:: Giving your program a signal
16597 * Returning:: Returning from a function
16598 * Calling:: Calling your program's functions
16599 * Patching:: Patching your program
16600 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
16604 @section Assignment to Variables
16607 @cindex setting variables
16608 To alter the value of a variable, evaluate an assignment expression.
16609 @xref{Expressions, ,Expressions}. For example,
16616 stores the value 4 into the variable @code{x}, and then prints the
16617 value of the assignment expression (which is 4).
16618 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
16619 information on operators in supported languages.
16621 @kindex set variable
16622 @cindex variables, setting
16623 If you are not interested in seeing the value of the assignment, use the
16624 @code{set} command instead of the @code{print} command. @code{set} is
16625 really the same as @code{print} except that the expression's value is
16626 not printed and is not put in the value history (@pxref{Value History,
16627 ,Value History}). The expression is evaluated only for its effects.
16629 If the beginning of the argument string of the @code{set} command
16630 appears identical to a @code{set} subcommand, use the @code{set
16631 variable} command instead of just @code{set}. This command is identical
16632 to @code{set} except for its lack of subcommands. For example, if your
16633 program has a variable @code{width}, you get an error if you try to set
16634 a new value with just @samp{set width=13}, because @value{GDBN} has the
16635 command @code{set width}:
16638 (@value{GDBP}) whatis width
16640 (@value{GDBP}) p width
16642 (@value{GDBP}) set width=47
16643 Invalid syntax in expression.
16647 The invalid expression, of course, is @samp{=47}. In
16648 order to actually set the program's variable @code{width}, use
16651 (@value{GDBP}) set var width=47
16654 Because the @code{set} command has many subcommands that can conflict
16655 with the names of program variables, it is a good idea to use the
16656 @code{set variable} command instead of just @code{set}. For example, if
16657 your program has a variable @code{g}, you run into problems if you try
16658 to set a new value with just @samp{set g=4}, because @value{GDBN} has
16659 the command @code{set gnutarget}, abbreviated @code{set g}:
16663 (@value{GDBP}) whatis g
16667 (@value{GDBP}) set g=4
16671 The program being debugged has been started already.
16672 Start it from the beginning? (y or n) y
16673 Starting program: /home/smith/cc_progs/a.out
16674 "/home/smith/cc_progs/a.out": can't open to read symbols:
16675 Invalid bfd target.
16676 (@value{GDBP}) show g
16677 The current BFD target is "=4".
16682 The program variable @code{g} did not change, and you silently set the
16683 @code{gnutarget} to an invalid value. In order to set the variable
16687 (@value{GDBP}) set var g=4
16690 @value{GDBN} allows more implicit conversions in assignments than C; you can
16691 freely store an integer value into a pointer variable or vice versa,
16692 and you can convert any structure to any other structure that is the
16693 same length or shorter.
16694 @comment FIXME: how do structs align/pad in these conversions?
16695 @comment /doc@cygnus.com 18dec1990
16697 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
16698 construct to generate a value of specified type at a specified address
16699 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
16700 to memory location @code{0x83040} as an integer (which implies a certain size
16701 and representation in memory), and
16704 set @{int@}0x83040 = 4
16708 stores the value 4 into that memory location.
16711 @section Continuing at a Different Address
16713 Ordinarily, when you continue your program, you do so at the place where
16714 it stopped, with the @code{continue} command. You can instead continue at
16715 an address of your own choosing, with the following commands:
16719 @kindex j @r{(@code{jump})}
16720 @item jump @var{linespec}
16721 @itemx j @var{linespec}
16722 @itemx jump @var{location}
16723 @itemx j @var{location}
16724 Resume execution at line @var{linespec} or at address given by
16725 @var{location}. Execution stops again immediately if there is a
16726 breakpoint there. @xref{Specify Location}, for a description of the
16727 different forms of @var{linespec} and @var{location}. It is common
16728 practice to use the @code{tbreak} command in conjunction with
16729 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
16731 The @code{jump} command does not change the current stack frame, or
16732 the stack pointer, or the contents of any memory location or any
16733 register other than the program counter. If line @var{linespec} is in
16734 a different function from the one currently executing, the results may
16735 be bizarre if the two functions expect different patterns of arguments or
16736 of local variables. For this reason, the @code{jump} command requests
16737 confirmation if the specified line is not in the function currently
16738 executing. However, even bizarre results are predictable if you are
16739 well acquainted with the machine-language code of your program.
16742 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
16743 On many systems, you can get much the same effect as the @code{jump}
16744 command by storing a new value into the register @code{$pc}. The
16745 difference is that this does not start your program running; it only
16746 changes the address of where it @emph{will} run when you continue. For
16754 makes the next @code{continue} command or stepping command execute at
16755 address @code{0x485}, rather than at the address where your program stopped.
16756 @xref{Continuing and Stepping, ,Continuing and Stepping}.
16758 The most common occasion to use the @code{jump} command is to back
16759 up---perhaps with more breakpoints set---over a portion of a program
16760 that has already executed, in order to examine its execution in more
16765 @section Giving your Program a Signal
16766 @cindex deliver a signal to a program
16770 @item signal @var{signal}
16771 Resume execution where your program is stopped, but immediately give it the
16772 signal @var{signal}. The @var{signal} can be the name or the number of a
16773 signal. For example, on many systems @code{signal 2} and @code{signal
16774 SIGINT} are both ways of sending an interrupt signal.
16776 Alternatively, if @var{signal} is zero, continue execution without
16777 giving a signal. This is useful when your program stopped on account of
16778 a signal and would ordinarily see the signal when resumed with the
16779 @code{continue} command; @samp{signal 0} causes it to resume without a
16782 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
16783 delivered to the currently selected thread, not the thread that last
16784 reported a stop. This includes the situation where a thread was
16785 stopped due to a signal. So if you want to continue execution
16786 suppressing the signal that stopped a thread, you should select that
16787 same thread before issuing the @samp{signal 0} command. If you issue
16788 the @samp{signal 0} command with another thread as the selected one,
16789 @value{GDBN} detects that and asks for confirmation.
16791 Invoking the @code{signal} command is not the same as invoking the
16792 @code{kill} utility from the shell. Sending a signal with @code{kill}
16793 causes @value{GDBN} to decide what to do with the signal depending on
16794 the signal handling tables (@pxref{Signals}). The @code{signal} command
16795 passes the signal directly to your program.
16797 @code{signal} does not repeat when you press @key{RET} a second time
16798 after executing the command.
16800 @kindex queue-signal
16801 @item queue-signal @var{signal}
16802 Queue @var{signal} to be delivered immediately to the current thread
16803 when execution of the thread resumes. The @var{signal} can be the name or
16804 the number of a signal. For example, on many systems @code{signal 2} and
16805 @code{signal SIGINT} are both ways of sending an interrupt signal.
16806 The handling of the signal must be set to pass the signal to the program,
16807 otherwise @value{GDBN} will report an error.
16808 You can control the handling of signals from @value{GDBN} with the
16809 @code{handle} command (@pxref{Signals}).
16811 Alternatively, if @var{signal} is zero, any currently queued signal
16812 for the current thread is discarded and when execution resumes no signal
16813 will be delivered. This is useful when your program stopped on account
16814 of a signal and would ordinarily see the signal when resumed with the
16815 @code{continue} command.
16817 This command differs from the @code{signal} command in that the signal
16818 is just queued, execution is not resumed. And @code{queue-signal} cannot
16819 be used to pass a signal whose handling state has been set to @code{nopass}
16824 @xref{stepping into signal handlers}, for information on how stepping
16825 commands behave when the thread has a signal queued.
16828 @section Returning from a Function
16831 @cindex returning from a function
16834 @itemx return @var{expression}
16835 You can cancel execution of a function call with the @code{return}
16836 command. If you give an
16837 @var{expression} argument, its value is used as the function's return
16841 When you use @code{return}, @value{GDBN} discards the selected stack frame
16842 (and all frames within it). You can think of this as making the
16843 discarded frame return prematurely. If you wish to specify a value to
16844 be returned, give that value as the argument to @code{return}.
16846 This pops the selected stack frame (@pxref{Selection, ,Selecting a
16847 Frame}), and any other frames inside of it, leaving its caller as the
16848 innermost remaining frame. That frame becomes selected. The
16849 specified value is stored in the registers used for returning values
16852 The @code{return} command does not resume execution; it leaves the
16853 program stopped in the state that would exist if the function had just
16854 returned. In contrast, the @code{finish} command (@pxref{Continuing
16855 and Stepping, ,Continuing and Stepping}) resumes execution until the
16856 selected stack frame returns naturally.
16858 @value{GDBN} needs to know how the @var{expression} argument should be set for
16859 the inferior. The concrete registers assignment depends on the OS ABI and the
16860 type being returned by the selected stack frame. For example it is common for
16861 OS ABI to return floating point values in FPU registers while integer values in
16862 CPU registers. Still some ABIs return even floating point values in CPU
16863 registers. Larger integer widths (such as @code{long long int}) also have
16864 specific placement rules. @value{GDBN} already knows the OS ABI from its
16865 current target so it needs to find out also the type being returned to make the
16866 assignment into the right register(s).
16868 Normally, the selected stack frame has debug info. @value{GDBN} will always
16869 use the debug info instead of the implicit type of @var{expression} when the
16870 debug info is available. For example, if you type @kbd{return -1}, and the
16871 function in the current stack frame is declared to return a @code{long long
16872 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
16873 into a @code{long long int}:
16876 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
16878 (@value{GDBP}) return -1
16879 Make func return now? (y or n) y
16880 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
16881 43 printf ("result=%lld\n", func ());
16885 However, if the selected stack frame does not have a debug info, e.g., if the
16886 function was compiled without debug info, @value{GDBN} has to find out the type
16887 to return from user. Specifying a different type by mistake may set the value
16888 in different inferior registers than the caller code expects. For example,
16889 typing @kbd{return -1} with its implicit type @code{int} would set only a part
16890 of a @code{long long int} result for a debug info less function (on 32-bit
16891 architectures). Therefore the user is required to specify the return type by
16892 an appropriate cast explicitly:
16895 Breakpoint 2, 0x0040050b in func ()
16896 (@value{GDBP}) return -1
16897 Return value type not available for selected stack frame.
16898 Please use an explicit cast of the value to return.
16899 (@value{GDBP}) return (long long int) -1
16900 Make selected stack frame return now? (y or n) y
16901 #0 0x00400526 in main ()
16906 @section Calling Program Functions
16909 @cindex calling functions
16910 @cindex inferior functions, calling
16911 @item print @var{expr}
16912 Evaluate the expression @var{expr} and display the resulting value.
16913 The expression may include calls to functions in the program being
16917 @item call @var{expr}
16918 Evaluate the expression @var{expr} without displaying @code{void}
16921 You can use this variant of the @code{print} command if you want to
16922 execute a function from your program that does not return anything
16923 (a.k.a.@: @dfn{a void function}), but without cluttering the output
16924 with @code{void} returned values that @value{GDBN} will otherwise
16925 print. If the result is not void, it is printed and saved in the
16929 It is possible for the function you call via the @code{print} or
16930 @code{call} command to generate a signal (e.g., if there's a bug in
16931 the function, or if you passed it incorrect arguments). What happens
16932 in that case is controlled by the @code{set unwindonsignal} command.
16934 Similarly, with a C@t{++} program it is possible for the function you
16935 call via the @code{print} or @code{call} command to generate an
16936 exception that is not handled due to the constraints of the dummy
16937 frame. In this case, any exception that is raised in the frame, but has
16938 an out-of-frame exception handler will not be found. GDB builds a
16939 dummy-frame for the inferior function call, and the unwinder cannot
16940 seek for exception handlers outside of this dummy-frame. What happens
16941 in that case is controlled by the
16942 @code{set unwind-on-terminating-exception} command.
16945 @item set unwindonsignal
16946 @kindex set unwindonsignal
16947 @cindex unwind stack in called functions
16948 @cindex call dummy stack unwinding
16949 Set unwinding of the stack if a signal is received while in a function
16950 that @value{GDBN} called in the program being debugged. If set to on,
16951 @value{GDBN} unwinds the stack it created for the call and restores
16952 the context to what it was before the call. If set to off (the
16953 default), @value{GDBN} stops in the frame where the signal was
16956 @item show unwindonsignal
16957 @kindex show unwindonsignal
16958 Show the current setting of stack unwinding in the functions called by
16961 @item set unwind-on-terminating-exception
16962 @kindex set unwind-on-terminating-exception
16963 @cindex unwind stack in called functions with unhandled exceptions
16964 @cindex call dummy stack unwinding on unhandled exception.
16965 Set unwinding of the stack if a C@t{++} exception is raised, but left
16966 unhandled while in a function that @value{GDBN} called in the program being
16967 debugged. If set to on (the default), @value{GDBN} unwinds the stack
16968 it created for the call and restores the context to what it was before
16969 the call. If set to off, @value{GDBN} the exception is delivered to
16970 the default C@t{++} exception handler and the inferior terminated.
16972 @item show unwind-on-terminating-exception
16973 @kindex show unwind-on-terminating-exception
16974 Show the current setting of stack unwinding in the functions called by
16979 @cindex weak alias functions
16980 Sometimes, a function you wish to call is actually a @dfn{weak alias}
16981 for another function. In such case, @value{GDBN} might not pick up
16982 the type information, including the types of the function arguments,
16983 which causes @value{GDBN} to call the inferior function incorrectly.
16984 As a result, the called function will function erroneously and may
16985 even crash. A solution to that is to use the name of the aliased
16989 @section Patching Programs
16991 @cindex patching binaries
16992 @cindex writing into executables
16993 @cindex writing into corefiles
16995 By default, @value{GDBN} opens the file containing your program's
16996 executable code (or the corefile) read-only. This prevents accidental
16997 alterations to machine code; but it also prevents you from intentionally
16998 patching your program's binary.
17000 If you'd like to be able to patch the binary, you can specify that
17001 explicitly with the @code{set write} command. For example, you might
17002 want to turn on internal debugging flags, or even to make emergency
17008 @itemx set write off
17009 If you specify @samp{set write on}, @value{GDBN} opens executable and
17010 core files for both reading and writing; if you specify @kbd{set write
17011 off} (the default), @value{GDBN} opens them read-only.
17013 If you have already loaded a file, you must load it again (using the
17014 @code{exec-file} or @code{core-file} command) after changing @code{set
17015 write}, for your new setting to take effect.
17019 Display whether executable files and core files are opened for writing
17020 as well as reading.
17023 @node Compiling and Injecting Code
17024 @section Compiling and injecting code in @value{GDBN}
17025 @cindex injecting code
17026 @cindex writing into executables
17027 @cindex compiling code
17029 @value{GDBN} supports on-demand compilation and code injection into
17030 programs running under @value{GDBN}. GCC 5.0 or higher built with
17031 @file{libcc1.so} must be installed for this functionality to be enabled.
17032 This functionality is implemented with the following commands.
17035 @kindex compile code
17036 @item compile code @var{source-code}
17037 @itemx compile code -raw @var{--} @var{source-code}
17038 Compile @var{source-code} with the compiler language found as the current
17039 language in @value{GDBN} (@pxref{Languages}). If compilation and
17040 injection is not supported with the current language specified in
17041 @value{GDBN}, or the compiler does not support this feature, an error
17042 message will be printed. If @var{source-code} compiles and links
17043 successfully, @value{GDBN} will load the object-code emitted,
17044 and execute it within the context of the currently selected inferior.
17045 It is important to note that the compiled code is executed immediately.
17046 After execution, the compiled code is removed from @value{GDBN} and any
17047 new types or variables you have defined will be deleted.
17049 The command allows you to specify @var{source-code} in two ways.
17050 The simplest method is to provide a single line of code to the command.
17054 compile code printf ("hello world\n");
17057 If you specify options on the command line as well as source code, they
17058 may conflict. The @samp{--} delimiter can be used to separate options
17059 from actual source code. E.g.:
17062 compile code -r -- printf ("hello world\n");
17065 Alternatively you can enter source code as multiple lines of text. To
17066 enter this mode, invoke the @samp{compile code} command without any text
17067 following the command. This will start the multiple-line editor and
17068 allow you to type as many lines of source code as required. When you
17069 have completed typing, enter @samp{end} on its own line to exit the
17074 >printf ("hello\n");
17075 >printf ("world\n");
17079 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
17080 provided @var{source-code} in a callable scope. In this case, you must
17081 specify the entry point of the code by defining a function named
17082 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
17083 inferior. Using @samp{-raw} option may be needed for example when
17084 @var{source-code} requires @samp{#include} lines which may conflict with
17085 inferior symbols otherwise.
17087 @kindex compile file
17088 @item compile file @var{filename}
17089 @itemx compile file -raw @var{filename}
17090 Like @code{compile code}, but take the source code from @var{filename}.
17093 compile file /home/user/example.c
17097 @subsection Caveats when using the @code{compile} command
17099 There are a few caveats to keep in mind when using the @code{compile}
17100 command. As the caveats are different per language, the table below
17101 highlights specific issues on a per language basis.
17104 @item C code examples and caveats
17105 When the language in @value{GDBN} is set to @samp{C}, the compiler will
17106 attempt to compile the source code with a @samp{C} compiler. The source
17107 code provided to the @code{compile} command will have much the same
17108 access to variables and types as it normally would if it were part of
17109 the program currently being debugged in @value{GDBN}.
17111 Below is a sample program that forms the basis of the examples that
17112 follow. This program has been compiled and loaded into @value{GDBN},
17113 much like any other normal debugging session.
17116 void function1 (void)
17119 printf ("function 1\n");
17122 void function2 (void)
17137 For the purposes of the examples in this section, the program above has
17138 been compiled, loaded into @value{GDBN}, stopped at the function
17139 @code{main}, and @value{GDBN} is awaiting input from the user.
17141 To access variables and types for any program in @value{GDBN}, the
17142 program must be compiled and packaged with debug information. The
17143 @code{compile} command is not an exception to this rule. Without debug
17144 information, you can still use the @code{compile} command, but you will
17145 be very limited in what variables and types you can access.
17147 So with that in mind, the example above has been compiled with debug
17148 information enabled. The @code{compile} command will have access to
17149 all variables and types (except those that may have been optimized
17150 out). Currently, as @value{GDBN} has stopped the program in the
17151 @code{main} function, the @code{compile} command would have access to
17152 the variable @code{k}. You could invoke the @code{compile} command
17153 and type some source code to set the value of @code{k}. You can also
17154 read it, or do anything with that variable you would normally do in
17155 @code{C}. Be aware that changes to inferior variables in the
17156 @code{compile} command are persistent. In the following example:
17159 compile code k = 3;
17163 the variable @code{k} is now 3. It will retain that value until
17164 something else in the example program changes it, or another
17165 @code{compile} command changes it.
17167 Normal scope and access rules apply to source code compiled and
17168 injected by the @code{compile} command. In the example, the variables
17169 @code{j} and @code{k} are not accessible yet, because the program is
17170 currently stopped in the @code{main} function, where these variables
17171 are not in scope. Therefore, the following command
17174 compile code j = 3;
17178 will result in a compilation error message.
17180 Once the program is continued, execution will bring these variables in
17181 scope, and they will become accessible; then the code you specify via
17182 the @code{compile} command will be able to access them.
17184 You can create variables and types with the @code{compile} command as
17185 part of your source code. Variables and types that are created as part
17186 of the @code{compile} command are not visible to the rest of the program for
17187 the duration of its run. This example is valid:
17190 compile code int ff = 5; printf ("ff is %d\n", ff);
17193 However, if you were to type the following into @value{GDBN} after that
17194 command has completed:
17197 compile code printf ("ff is %d\n'', ff);
17201 a compiler error would be raised as the variable @code{ff} no longer
17202 exists. Object code generated and injected by the @code{compile}
17203 command is removed when its execution ends. Caution is advised
17204 when assigning to program variables values of variables created by the
17205 code submitted to the @code{compile} command. This example is valid:
17208 compile code int ff = 5; k = ff;
17211 The value of the variable @code{ff} is assigned to @code{k}. The variable
17212 @code{k} does not require the existence of @code{ff} to maintain the value
17213 it has been assigned. However, pointers require particular care in
17214 assignment. If the source code compiled with the @code{compile} command
17215 changed the address of a pointer in the example program, perhaps to a
17216 variable created in the @code{compile} command, that pointer would point
17217 to an invalid location when the command exits. The following example
17218 would likely cause issues with your debugged program:
17221 compile code int ff = 5; p = &ff;
17224 In this example, @code{p} would point to @code{ff} when the
17225 @code{compile} command is executing the source code provided to it.
17226 However, as variables in the (example) program persist with their
17227 assigned values, the variable @code{p} would point to an invalid
17228 location when the command exists. A general rule should be followed
17229 in that you should either assign @code{NULL} to any assigned pointers,
17230 or restore a valid location to the pointer before the command exits.
17232 Similar caution must be exercised with any structs, unions, and typedefs
17233 defined in @code{compile} command. Types defined in the @code{compile}
17234 command will no longer be available in the next @code{compile} command.
17235 Therefore, if you cast a variable to a type defined in the
17236 @code{compile} command, care must be taken to ensure that any future
17237 need to resolve the type can be achieved.
17240 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
17241 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
17242 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
17243 Compilation failed.
17244 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
17248 Variables that have been optimized away by the compiler are not
17249 accessible to the code submitted to the @code{compile} command.
17250 Access to those variables will generate a compiler error which @value{GDBN}
17251 will print to the console.
17255 @chapter @value{GDBN} Files
17257 @value{GDBN} needs to know the file name of the program to be debugged,
17258 both in order to read its symbol table and in order to start your
17259 program. To debug a core dump of a previous run, you must also tell
17260 @value{GDBN} the name of the core dump file.
17263 * Files:: Commands to specify files
17264 * Separate Debug Files:: Debugging information in separate files
17265 * MiniDebugInfo:: Debugging information in a special section
17266 * Index Files:: Index files speed up GDB
17267 * Symbol Errors:: Errors reading symbol files
17268 * Data Files:: GDB data files
17272 @section Commands to Specify Files
17274 @cindex symbol table
17275 @cindex core dump file
17277 You may want to specify executable and core dump file names. The usual
17278 way to do this is at start-up time, using the arguments to
17279 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
17280 Out of @value{GDBN}}).
17282 Occasionally it is necessary to change to a different file during a
17283 @value{GDBN} session. Or you may run @value{GDBN} and forget to
17284 specify a file you want to use. Or you are debugging a remote target
17285 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
17286 Program}). In these situations the @value{GDBN} commands to specify
17287 new files are useful.
17290 @cindex executable file
17292 @item file @var{filename}
17293 Use @var{filename} as the program to be debugged. It is read for its
17294 symbols and for the contents of pure memory. It is also the program
17295 executed when you use the @code{run} command. If you do not specify a
17296 directory and the file is not found in the @value{GDBN} working directory,
17297 @value{GDBN} uses the environment variable @code{PATH} as a list of
17298 directories to search, just as the shell does when looking for a program
17299 to run. You can change the value of this variable, for both @value{GDBN}
17300 and your program, using the @code{path} command.
17302 @cindex unlinked object files
17303 @cindex patching object files
17304 You can load unlinked object @file{.o} files into @value{GDBN} using
17305 the @code{file} command. You will not be able to ``run'' an object
17306 file, but you can disassemble functions and inspect variables. Also,
17307 if the underlying BFD functionality supports it, you could use
17308 @kbd{gdb -write} to patch object files using this technique. Note
17309 that @value{GDBN} can neither interpret nor modify relocations in this
17310 case, so branches and some initialized variables will appear to go to
17311 the wrong place. But this feature is still handy from time to time.
17314 @code{file} with no argument makes @value{GDBN} discard any information it
17315 has on both executable file and the symbol table.
17318 @item exec-file @r{[} @var{filename} @r{]}
17319 Specify that the program to be run (but not the symbol table) is found
17320 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
17321 if necessary to locate your program. Omitting @var{filename} means to
17322 discard information on the executable file.
17324 @kindex symbol-file
17325 @item symbol-file @r{[} @var{filename} @r{]}
17326 Read symbol table information from file @var{filename}. @code{PATH} is
17327 searched when necessary. Use the @code{file} command to get both symbol
17328 table and program to run from the same file.
17330 @code{symbol-file} with no argument clears out @value{GDBN} information on your
17331 program's symbol table.
17333 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
17334 some breakpoints and auto-display expressions. This is because they may
17335 contain pointers to the internal data recording symbols and data types,
17336 which are part of the old symbol table data being discarded inside
17339 @code{symbol-file} does not repeat if you press @key{RET} again after
17342 When @value{GDBN} is configured for a particular environment, it
17343 understands debugging information in whatever format is the standard
17344 generated for that environment; you may use either a @sc{gnu} compiler, or
17345 other compilers that adhere to the local conventions.
17346 Best results are usually obtained from @sc{gnu} compilers; for example,
17347 using @code{@value{NGCC}} you can generate debugging information for
17350 For most kinds of object files, with the exception of old SVR3 systems
17351 using COFF, the @code{symbol-file} command does not normally read the
17352 symbol table in full right away. Instead, it scans the symbol table
17353 quickly to find which source files and which symbols are present. The
17354 details are read later, one source file at a time, as they are needed.
17356 The purpose of this two-stage reading strategy is to make @value{GDBN}
17357 start up faster. For the most part, it is invisible except for
17358 occasional pauses while the symbol table details for a particular source
17359 file are being read. (The @code{set verbose} command can turn these
17360 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
17361 Warnings and Messages}.)
17363 We have not implemented the two-stage strategy for COFF yet. When the
17364 symbol table is stored in COFF format, @code{symbol-file} reads the
17365 symbol table data in full right away. Note that ``stabs-in-COFF''
17366 still does the two-stage strategy, since the debug info is actually
17370 @cindex reading symbols immediately
17371 @cindex symbols, reading immediately
17372 @item symbol-file @r{[} -readnow @r{]} @var{filename}
17373 @itemx file @r{[} -readnow @r{]} @var{filename}
17374 You can override the @value{GDBN} two-stage strategy for reading symbol
17375 tables by using the @samp{-readnow} option with any of the commands that
17376 load symbol table information, if you want to be sure @value{GDBN} has the
17377 entire symbol table available.
17379 @c FIXME: for now no mention of directories, since this seems to be in
17380 @c flux. 13mar1992 status is that in theory GDB would look either in
17381 @c current dir or in same dir as myprog; but issues like competing
17382 @c GDB's, or clutter in system dirs, mean that in practice right now
17383 @c only current dir is used. FFish says maybe a special GDB hierarchy
17384 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
17388 @item core-file @r{[}@var{filename}@r{]}
17390 Specify the whereabouts of a core dump file to be used as the ``contents
17391 of memory''. Traditionally, core files contain only some parts of the
17392 address space of the process that generated them; @value{GDBN} can access the
17393 executable file itself for other parts.
17395 @code{core-file} with no argument specifies that no core file is
17398 Note that the core file is ignored when your program is actually running
17399 under @value{GDBN}. So, if you have been running your program and you
17400 wish to debug a core file instead, you must kill the subprocess in which
17401 the program is running. To do this, use the @code{kill} command
17402 (@pxref{Kill Process, ,Killing the Child Process}).
17404 @kindex add-symbol-file
17405 @cindex dynamic linking
17406 @item add-symbol-file @var{filename} @var{address}
17407 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
17408 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
17409 The @code{add-symbol-file} command reads additional symbol table
17410 information from the file @var{filename}. You would use this command
17411 when @var{filename} has been dynamically loaded (by some other means)
17412 into the program that is running. The @var{address} should give the memory
17413 address at which the file has been loaded; @value{GDBN} cannot figure
17414 this out for itself. You can additionally specify an arbitrary number
17415 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
17416 section name and base address for that section. You can specify any
17417 @var{address} as an expression.
17419 The symbol table of the file @var{filename} is added to the symbol table
17420 originally read with the @code{symbol-file} command. You can use the
17421 @code{add-symbol-file} command any number of times; the new symbol data
17422 thus read is kept in addition to the old.
17424 Changes can be reverted using the command @code{remove-symbol-file}.
17426 @cindex relocatable object files, reading symbols from
17427 @cindex object files, relocatable, reading symbols from
17428 @cindex reading symbols from relocatable object files
17429 @cindex symbols, reading from relocatable object files
17430 @cindex @file{.o} files, reading symbols from
17431 Although @var{filename} is typically a shared library file, an
17432 executable file, or some other object file which has been fully
17433 relocated for loading into a process, you can also load symbolic
17434 information from relocatable @file{.o} files, as long as:
17438 the file's symbolic information refers only to linker symbols defined in
17439 that file, not to symbols defined by other object files,
17441 every section the file's symbolic information refers to has actually
17442 been loaded into the inferior, as it appears in the file, and
17444 you can determine the address at which every section was loaded, and
17445 provide these to the @code{add-symbol-file} command.
17449 Some embedded operating systems, like Sun Chorus and VxWorks, can load
17450 relocatable files into an already running program; such systems
17451 typically make the requirements above easy to meet. However, it's
17452 important to recognize that many native systems use complex link
17453 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
17454 assembly, for example) that make the requirements difficult to meet. In
17455 general, one cannot assume that using @code{add-symbol-file} to read a
17456 relocatable object file's symbolic information will have the same effect
17457 as linking the relocatable object file into the program in the normal
17460 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
17462 @kindex remove-symbol-file
17463 @item remove-symbol-file @var{filename}
17464 @item remove-symbol-file -a @var{address}
17465 Remove a symbol file added via the @code{add-symbol-file} command. The
17466 file to remove can be identified by its @var{filename} or by an @var{address}
17467 that lies within the boundaries of this symbol file in memory. Example:
17470 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
17471 add symbol table from file "/home/user/gdb/mylib.so" at
17472 .text_addr = 0x7ffff7ff9480
17474 Reading symbols from /home/user/gdb/mylib.so...done.
17475 (gdb) remove-symbol-file -a 0x7ffff7ff9480
17476 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
17481 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
17483 @kindex add-symbol-file-from-memory
17484 @cindex @code{syscall DSO}
17485 @cindex load symbols from memory
17486 @item add-symbol-file-from-memory @var{address}
17487 Load symbols from the given @var{address} in a dynamically loaded
17488 object file whose image is mapped directly into the inferior's memory.
17489 For example, the Linux kernel maps a @code{syscall DSO} into each
17490 process's address space; this DSO provides kernel-specific code for
17491 some system calls. The argument can be any expression whose
17492 evaluation yields the address of the file's shared object file header.
17493 For this command to work, you must have used @code{symbol-file} or
17494 @code{exec-file} commands in advance.
17497 @item section @var{section} @var{addr}
17498 The @code{section} command changes the base address of the named
17499 @var{section} of the exec file to @var{addr}. This can be used if the
17500 exec file does not contain section addresses, (such as in the
17501 @code{a.out} format), or when the addresses specified in the file
17502 itself are wrong. Each section must be changed separately. The
17503 @code{info files} command, described below, lists all the sections and
17507 @kindex info target
17510 @code{info files} and @code{info target} are synonymous; both print the
17511 current target (@pxref{Targets, ,Specifying a Debugging Target}),
17512 including the names of the executable and core dump files currently in
17513 use by @value{GDBN}, and the files from which symbols were loaded. The
17514 command @code{help target} lists all possible targets rather than
17517 @kindex maint info sections
17518 @item maint info sections
17519 Another command that can give you extra information about program sections
17520 is @code{maint info sections}. In addition to the section information
17521 displayed by @code{info files}, this command displays the flags and file
17522 offset of each section in the executable and core dump files. In addition,
17523 @code{maint info sections} provides the following command options (which
17524 may be arbitrarily combined):
17528 Display sections for all loaded object files, including shared libraries.
17529 @item @var{sections}
17530 Display info only for named @var{sections}.
17531 @item @var{section-flags}
17532 Display info only for sections for which @var{section-flags} are true.
17533 The section flags that @value{GDBN} currently knows about are:
17536 Section will have space allocated in the process when loaded.
17537 Set for all sections except those containing debug information.
17539 Section will be loaded from the file into the child process memory.
17540 Set for pre-initialized code and data, clear for @code{.bss} sections.
17542 Section needs to be relocated before loading.
17544 Section cannot be modified by the child process.
17546 Section contains executable code only.
17548 Section contains data only (no executable code).
17550 Section will reside in ROM.
17552 Section contains data for constructor/destructor lists.
17554 Section is not empty.
17556 An instruction to the linker to not output the section.
17557 @item COFF_SHARED_LIBRARY
17558 A notification to the linker that the section contains
17559 COFF shared library information.
17561 Section contains common symbols.
17564 @kindex set trust-readonly-sections
17565 @cindex read-only sections
17566 @item set trust-readonly-sections on
17567 Tell @value{GDBN} that readonly sections in your object file
17568 really are read-only (i.e.@: that their contents will not change).
17569 In that case, @value{GDBN} can fetch values from these sections
17570 out of the object file, rather than from the target program.
17571 For some targets (notably embedded ones), this can be a significant
17572 enhancement to debugging performance.
17574 The default is off.
17576 @item set trust-readonly-sections off
17577 Tell @value{GDBN} not to trust readonly sections. This means that
17578 the contents of the section might change while the program is running,
17579 and must therefore be fetched from the target when needed.
17581 @item show trust-readonly-sections
17582 Show the current setting of trusting readonly sections.
17585 All file-specifying commands allow both absolute and relative file names
17586 as arguments. @value{GDBN} always converts the file name to an absolute file
17587 name and remembers it that way.
17589 @cindex shared libraries
17590 @anchor{Shared Libraries}
17591 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
17592 and IBM RS/6000 AIX shared libraries.
17594 On MS-Windows @value{GDBN} must be linked with the Expat library to support
17595 shared libraries. @xref{Expat}.
17597 @value{GDBN} automatically loads symbol definitions from shared libraries
17598 when you use the @code{run} command, or when you examine a core file.
17599 (Before you issue the @code{run} command, @value{GDBN} does not understand
17600 references to a function in a shared library, however---unless you are
17601 debugging a core file).
17603 On HP-UX, if the program loads a library explicitly, @value{GDBN}
17604 automatically loads the symbols at the time of the @code{shl_load} call.
17606 @c FIXME: some @value{GDBN} release may permit some refs to undef
17607 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
17608 @c FIXME...lib; check this from time to time when updating manual
17610 There are times, however, when you may wish to not automatically load
17611 symbol definitions from shared libraries, such as when they are
17612 particularly large or there are many of them.
17614 To control the automatic loading of shared library symbols, use the
17618 @kindex set auto-solib-add
17619 @item set auto-solib-add @var{mode}
17620 If @var{mode} is @code{on}, symbols from all shared object libraries
17621 will be loaded automatically when the inferior begins execution, you
17622 attach to an independently started inferior, or when the dynamic linker
17623 informs @value{GDBN} that a new library has been loaded. If @var{mode}
17624 is @code{off}, symbols must be loaded manually, using the
17625 @code{sharedlibrary} command. The default value is @code{on}.
17627 @cindex memory used for symbol tables
17628 If your program uses lots of shared libraries with debug info that
17629 takes large amounts of memory, you can decrease the @value{GDBN}
17630 memory footprint by preventing it from automatically loading the
17631 symbols from shared libraries. To that end, type @kbd{set
17632 auto-solib-add off} before running the inferior, then load each
17633 library whose debug symbols you do need with @kbd{sharedlibrary
17634 @var{regexp}}, where @var{regexp} is a regular expression that matches
17635 the libraries whose symbols you want to be loaded.
17637 @kindex show auto-solib-add
17638 @item show auto-solib-add
17639 Display the current autoloading mode.
17642 @cindex load shared library
17643 To explicitly load shared library symbols, use the @code{sharedlibrary}
17647 @kindex info sharedlibrary
17649 @item info share @var{regex}
17650 @itemx info sharedlibrary @var{regex}
17651 Print the names of the shared libraries which are currently loaded
17652 that match @var{regex}. If @var{regex} is omitted then print
17653 all shared libraries that are loaded.
17655 @kindex sharedlibrary
17657 @item sharedlibrary @var{regex}
17658 @itemx share @var{regex}
17659 Load shared object library symbols for files matching a
17660 Unix regular expression.
17661 As with files loaded automatically, it only loads shared libraries
17662 required by your program for a core file or after typing @code{run}. If
17663 @var{regex} is omitted all shared libraries required by your program are
17666 @item nosharedlibrary
17667 @kindex nosharedlibrary
17668 @cindex unload symbols from shared libraries
17669 Unload all shared object library symbols. This discards all symbols
17670 that have been loaded from all shared libraries. Symbols from shared
17671 libraries that were loaded by explicit user requests are not
17675 Sometimes you may wish that @value{GDBN} stops and gives you control
17676 when any of shared library events happen. The best way to do this is
17677 to use @code{catch load} and @code{catch unload} (@pxref{Set
17680 @value{GDBN} also supports the the @code{set stop-on-solib-events}
17681 command for this. This command exists for historical reasons. It is
17682 less useful than setting a catchpoint, because it does not allow for
17683 conditions or commands as a catchpoint does.
17686 @item set stop-on-solib-events
17687 @kindex set stop-on-solib-events
17688 This command controls whether @value{GDBN} should give you control
17689 when the dynamic linker notifies it about some shared library event.
17690 The most common event of interest is loading or unloading of a new
17693 @item show stop-on-solib-events
17694 @kindex show stop-on-solib-events
17695 Show whether @value{GDBN} stops and gives you control when shared
17696 library events happen.
17699 Shared libraries are also supported in many cross or remote debugging
17700 configurations. @value{GDBN} needs to have access to the target's libraries;
17701 this can be accomplished either by providing copies of the libraries
17702 on the host system, or by asking @value{GDBN} to automatically retrieve the
17703 libraries from the target. If copies of the target libraries are
17704 provided, they need to be the same as the target libraries, although the
17705 copies on the target can be stripped as long as the copies on the host are
17708 @cindex where to look for shared libraries
17709 For remote debugging, you need to tell @value{GDBN} where the target
17710 libraries are, so that it can load the correct copies---otherwise, it
17711 may try to load the host's libraries. @value{GDBN} has two variables
17712 to specify the search directories for target libraries.
17715 @cindex prefix for shared library file names
17716 @cindex system root, alternate
17717 @kindex set solib-absolute-prefix
17718 @kindex set sysroot
17719 @item set sysroot @var{path}
17720 Use @var{path} as the system root for the program being debugged. Any
17721 absolute shared library paths will be prefixed with @var{path}; many
17722 runtime loaders store the absolute paths to the shared library in the
17723 target program's memory. If you use @code{set sysroot} to find shared
17724 libraries, they need to be laid out in the same way that they are on
17725 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
17728 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
17729 retrieve the target libraries from the remote system. This is only
17730 supported when using a remote target that supports the @code{remote get}
17731 command (@pxref{File Transfer,,Sending files to a remote system}).
17732 The part of @var{path} following the initial @file{remote:}
17733 (if present) is used as system root prefix on the remote file system.
17734 @footnote{If you want to specify a local system root using a directory
17735 that happens to be named @file{remote:}, you need to use some equivalent
17736 variant of the name like @file{./remote:}.}
17738 For targets with an MS-DOS based filesystem, such as MS-Windows and
17739 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
17740 absolute file name with @var{path}. But first, on Unix hosts,
17741 @value{GDBN} converts all backslash directory separators into forward
17742 slashes, because the backslash is not a directory separator on Unix:
17745 c:\foo\bar.dll @result{} c:/foo/bar.dll
17748 Then, @value{GDBN} attempts prefixing the target file name with
17749 @var{path}, and looks for the resulting file name in the host file
17753 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
17756 If that does not find the shared library, @value{GDBN} tries removing
17757 the @samp{:} character from the drive spec, both for convenience, and,
17758 for the case of the host file system not supporting file names with
17762 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
17765 This makes it possible to have a system root that mirrors a target
17766 with more than one drive. E.g., you may want to setup your local
17767 copies of the target system shared libraries like so (note @samp{c} vs
17771 @file{/path/to/sysroot/c/sys/bin/foo.dll}
17772 @file{/path/to/sysroot/c/sys/bin/bar.dll}
17773 @file{/path/to/sysroot/z/sys/bin/bar.dll}
17777 and point the system root at @file{/path/to/sysroot}, so that
17778 @value{GDBN} can find the correct copies of both
17779 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
17781 If that still does not find the shared library, @value{GDBN} tries
17782 removing the whole drive spec from the target file name:
17785 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
17788 This last lookup makes it possible to not care about the drive name,
17789 if you don't want or need to.
17791 The @code{set solib-absolute-prefix} command is an alias for @code{set
17794 @cindex default system root
17795 @cindex @samp{--with-sysroot}
17796 You can set the default system root by using the configure-time
17797 @samp{--with-sysroot} option. If the system root is inside
17798 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17799 @samp{--exec-prefix}), then the default system root will be updated
17800 automatically if the installed @value{GDBN} is moved to a new
17803 @kindex show sysroot
17805 Display the current shared library prefix.
17807 @kindex set solib-search-path
17808 @item set solib-search-path @var{path}
17809 If this variable is set, @var{path} is a colon-separated list of
17810 directories to search for shared libraries. @samp{solib-search-path}
17811 is used after @samp{sysroot} fails to locate the library, or if the
17812 path to the library is relative instead of absolute. If you want to
17813 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
17814 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
17815 finding your host's libraries. @samp{sysroot} is preferred; setting
17816 it to a nonexistent directory may interfere with automatic loading
17817 of shared library symbols.
17819 @kindex show solib-search-path
17820 @item show solib-search-path
17821 Display the current shared library search path.
17823 @cindex DOS file-name semantics of file names.
17824 @kindex set target-file-system-kind (unix|dos-based|auto)
17825 @kindex show target-file-system-kind
17826 @item set target-file-system-kind @var{kind}
17827 Set assumed file system kind for target reported file names.
17829 Shared library file names as reported by the target system may not
17830 make sense as is on the system @value{GDBN} is running on. For
17831 example, when remote debugging a target that has MS-DOS based file
17832 system semantics, from a Unix host, the target may be reporting to
17833 @value{GDBN} a list of loaded shared libraries with file names such as
17834 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
17835 drive letters, so the @samp{c:\} prefix is not normally understood as
17836 indicating an absolute file name, and neither is the backslash
17837 normally considered a directory separator character. In that case,
17838 the native file system would interpret this whole absolute file name
17839 as a relative file name with no directory components. This would make
17840 it impossible to point @value{GDBN} at a copy of the remote target's
17841 shared libraries on the host using @code{set sysroot}, and impractical
17842 with @code{set solib-search-path}. Setting
17843 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
17844 to interpret such file names similarly to how the target would, and to
17845 map them to file names valid on @value{GDBN}'s native file system
17846 semantics. The value of @var{kind} can be @code{"auto"}, in addition
17847 to one of the supported file system kinds. In that case, @value{GDBN}
17848 tries to determine the appropriate file system variant based on the
17849 current target's operating system (@pxref{ABI, ,Configuring the
17850 Current ABI}). The supported file system settings are:
17854 Instruct @value{GDBN} to assume the target file system is of Unix
17855 kind. Only file names starting the forward slash (@samp{/}) character
17856 are considered absolute, and the directory separator character is also
17860 Instruct @value{GDBN} to assume the target file system is DOS based.
17861 File names starting with either a forward slash, or a drive letter
17862 followed by a colon (e.g., @samp{c:}), are considered absolute, and
17863 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
17864 considered directory separators.
17867 Instruct @value{GDBN} to use the file system kind associated with the
17868 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
17869 This is the default.
17873 @cindex file name canonicalization
17874 @cindex base name differences
17875 When processing file names provided by the user, @value{GDBN}
17876 frequently needs to compare them to the file names recorded in the
17877 program's debug info. Normally, @value{GDBN} compares just the
17878 @dfn{base names} of the files as strings, which is reasonably fast
17879 even for very large programs. (The base name of a file is the last
17880 portion of its name, after stripping all the leading directories.)
17881 This shortcut in comparison is based upon the assumption that files
17882 cannot have more than one base name. This is usually true, but
17883 references to files that use symlinks or similar filesystem
17884 facilities violate that assumption. If your program records files
17885 using such facilities, or if you provide file names to @value{GDBN}
17886 using symlinks etc., you can set @code{basenames-may-differ} to
17887 @code{true} to instruct @value{GDBN} to completely canonicalize each
17888 pair of file names it needs to compare. This will make file-name
17889 comparisons accurate, but at a price of a significant slowdown.
17892 @item set basenames-may-differ
17893 @kindex set basenames-may-differ
17894 Set whether a source file may have multiple base names.
17896 @item show basenames-may-differ
17897 @kindex show basenames-may-differ
17898 Show whether a source file may have multiple base names.
17901 @node Separate Debug Files
17902 @section Debugging Information in Separate Files
17903 @cindex separate debugging information files
17904 @cindex debugging information in separate files
17905 @cindex @file{.debug} subdirectories
17906 @cindex debugging information directory, global
17907 @cindex global debugging information directories
17908 @cindex build ID, and separate debugging files
17909 @cindex @file{.build-id} directory
17911 @value{GDBN} allows you to put a program's debugging information in a
17912 file separate from the executable itself, in a way that allows
17913 @value{GDBN} to find and load the debugging information automatically.
17914 Since debugging information can be very large---sometimes larger
17915 than the executable code itself---some systems distribute debugging
17916 information for their executables in separate files, which users can
17917 install only when they need to debug a problem.
17919 @value{GDBN} supports two ways of specifying the separate debug info
17924 The executable contains a @dfn{debug link} that specifies the name of
17925 the separate debug info file. The separate debug file's name is
17926 usually @file{@var{executable}.debug}, where @var{executable} is the
17927 name of the corresponding executable file without leading directories
17928 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
17929 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
17930 checksum for the debug file, which @value{GDBN} uses to validate that
17931 the executable and the debug file came from the same build.
17934 The executable contains a @dfn{build ID}, a unique bit string that is
17935 also present in the corresponding debug info file. (This is supported
17936 only on some operating systems, notably those which use the ELF format
17937 for binary files and the @sc{gnu} Binutils.) For more details about
17938 this feature, see the description of the @option{--build-id}
17939 command-line option in @ref{Options, , Command Line Options, ld.info,
17940 The GNU Linker}. The debug info file's name is not specified
17941 explicitly by the build ID, but can be computed from the build ID, see
17945 Depending on the way the debug info file is specified, @value{GDBN}
17946 uses two different methods of looking for the debug file:
17950 For the ``debug link'' method, @value{GDBN} looks up the named file in
17951 the directory of the executable file, then in a subdirectory of that
17952 directory named @file{.debug}, and finally under each one of the global debug
17953 directories, in a subdirectory whose name is identical to the leading
17954 directories of the executable's absolute file name.
17957 For the ``build ID'' method, @value{GDBN} looks in the
17958 @file{.build-id} subdirectory of each one of the global debug directories for
17959 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
17960 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
17961 are the rest of the bit string. (Real build ID strings are 32 or more
17962 hex characters, not 10.)
17965 So, for example, suppose you ask @value{GDBN} to debug
17966 @file{/usr/bin/ls}, which has a debug link that specifies the
17967 file @file{ls.debug}, and a build ID whose value in hex is
17968 @code{abcdef1234}. If the list of the global debug directories includes
17969 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
17970 debug information files, in the indicated order:
17974 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
17976 @file{/usr/bin/ls.debug}
17978 @file{/usr/bin/.debug/ls.debug}
17980 @file{/usr/lib/debug/usr/bin/ls.debug}.
17983 @anchor{debug-file-directory}
17984 Global debugging info directories default to what is set by @value{GDBN}
17985 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
17986 you can also set the global debugging info directories, and view the list
17987 @value{GDBN} is currently using.
17991 @kindex set debug-file-directory
17992 @item set debug-file-directory @var{directories}
17993 Set the directories which @value{GDBN} searches for separate debugging
17994 information files to @var{directory}. Multiple path components can be set
17995 concatenating them by a path separator.
17997 @kindex show debug-file-directory
17998 @item show debug-file-directory
17999 Show the directories @value{GDBN} searches for separate debugging
18004 @cindex @code{.gnu_debuglink} sections
18005 @cindex debug link sections
18006 A debug link is a special section of the executable file named
18007 @code{.gnu_debuglink}. The section must contain:
18011 A filename, with any leading directory components removed, followed by
18014 zero to three bytes of padding, as needed to reach the next four-byte
18015 boundary within the section, and
18017 a four-byte CRC checksum, stored in the same endianness used for the
18018 executable file itself. The checksum is computed on the debugging
18019 information file's full contents by the function given below, passing
18020 zero as the @var{crc} argument.
18023 Any executable file format can carry a debug link, as long as it can
18024 contain a section named @code{.gnu_debuglink} with the contents
18027 @cindex @code{.note.gnu.build-id} sections
18028 @cindex build ID sections
18029 The build ID is a special section in the executable file (and in other
18030 ELF binary files that @value{GDBN} may consider). This section is
18031 often named @code{.note.gnu.build-id}, but that name is not mandatory.
18032 It contains unique identification for the built files---the ID remains
18033 the same across multiple builds of the same build tree. The default
18034 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
18035 content for the build ID string. The same section with an identical
18036 value is present in the original built binary with symbols, in its
18037 stripped variant, and in the separate debugging information file.
18039 The debugging information file itself should be an ordinary
18040 executable, containing a full set of linker symbols, sections, and
18041 debugging information. The sections of the debugging information file
18042 should have the same names, addresses, and sizes as the original file,
18043 but they need not contain any data---much like a @code{.bss} section
18044 in an ordinary executable.
18046 The @sc{gnu} binary utilities (Binutils) package includes the
18047 @samp{objcopy} utility that can produce
18048 the separated executable / debugging information file pairs using the
18049 following commands:
18052 @kbd{objcopy --only-keep-debug foo foo.debug}
18057 These commands remove the debugging
18058 information from the executable file @file{foo} and place it in the file
18059 @file{foo.debug}. You can use the first, second or both methods to link the
18064 The debug link method needs the following additional command to also leave
18065 behind a debug link in @file{foo}:
18068 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
18071 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
18072 a version of the @code{strip} command such that the command @kbd{strip foo -f
18073 foo.debug} has the same functionality as the two @code{objcopy} commands and
18074 the @code{ln -s} command above, together.
18077 Build ID gets embedded into the main executable using @code{ld --build-id} or
18078 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
18079 compatibility fixes for debug files separation are present in @sc{gnu} binary
18080 utilities (Binutils) package since version 2.18.
18085 @cindex CRC algorithm definition
18086 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
18087 IEEE 802.3 using the polynomial:
18089 @c TexInfo requires naked braces for multi-digit exponents for Tex
18090 @c output, but this causes HTML output to barf. HTML has to be set using
18091 @c raw commands. So we end up having to specify this equation in 2
18096 <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>
18097 + <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
18103 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
18104 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
18108 The function is computed byte at a time, taking the least
18109 significant bit of each byte first. The initial pattern
18110 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
18111 the final result is inverted to ensure trailing zeros also affect the
18114 @emph{Note:} This is the same CRC polynomial as used in handling the
18115 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
18116 However in the case of the Remote Serial Protocol, the CRC is computed
18117 @emph{most} significant bit first, and the result is not inverted, so
18118 trailing zeros have no effect on the CRC value.
18120 To complete the description, we show below the code of the function
18121 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
18122 initially supplied @code{crc} argument means that an initial call to
18123 this function passing in zero will start computing the CRC using
18126 @kindex gnu_debuglink_crc32
18129 gnu_debuglink_crc32 (unsigned long crc,
18130 unsigned char *buf, size_t len)
18132 static const unsigned long crc32_table[256] =
18134 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
18135 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
18136 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
18137 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
18138 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
18139 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
18140 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
18141 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
18142 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
18143 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
18144 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
18145 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
18146 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
18147 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
18148 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
18149 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
18150 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
18151 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
18152 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
18153 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
18154 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
18155 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
18156 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
18157 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
18158 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
18159 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
18160 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
18161 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
18162 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
18163 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
18164 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
18165 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
18166 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
18167 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
18168 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
18169 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
18170 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
18171 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
18172 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
18173 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
18174 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
18175 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
18176 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
18177 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
18178 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
18179 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
18180 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
18181 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
18182 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
18183 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
18184 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
18187 unsigned char *end;
18189 crc = ~crc & 0xffffffff;
18190 for (end = buf + len; buf < end; ++buf)
18191 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
18192 return ~crc & 0xffffffff;
18197 This computation does not apply to the ``build ID'' method.
18199 @node MiniDebugInfo
18200 @section Debugging information in a special section
18201 @cindex separate debug sections
18202 @cindex @samp{.gnu_debugdata} section
18204 Some systems ship pre-built executables and libraries that have a
18205 special @samp{.gnu_debugdata} section. This feature is called
18206 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
18207 is used to supply extra symbols for backtraces.
18209 The intent of this section is to provide extra minimal debugging
18210 information for use in simple backtraces. It is not intended to be a
18211 replacement for full separate debugging information (@pxref{Separate
18212 Debug Files}). The example below shows the intended use; however,
18213 @value{GDBN} does not currently put restrictions on what sort of
18214 debugging information might be included in the section.
18216 @value{GDBN} has support for this extension. If the section exists,
18217 then it is used provided that no other source of debugging information
18218 can be found, and that @value{GDBN} was configured with LZMA support.
18220 This section can be easily created using @command{objcopy} and other
18221 standard utilities:
18224 # Extract the dynamic symbols from the main binary, there is no need
18225 # to also have these in the normal symbol table.
18226 nm -D @var{binary} --format=posix --defined-only \
18227 | awk '@{ print $1 @}' | sort > dynsyms
18229 # Extract all the text (i.e. function) symbols from the debuginfo.
18230 # (Note that we actually also accept "D" symbols, for the benefit
18231 # of platforms like PowerPC64 that use function descriptors.)
18232 nm @var{binary} --format=posix --defined-only \
18233 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
18236 # Keep all the function symbols not already in the dynamic symbol
18238 comm -13 dynsyms funcsyms > keep_symbols
18240 # Separate full debug info into debug binary.
18241 objcopy --only-keep-debug @var{binary} debug
18243 # Copy the full debuginfo, keeping only a minimal set of symbols and
18244 # removing some unnecessary sections.
18245 objcopy -S --remove-section .gdb_index --remove-section .comment \
18246 --keep-symbols=keep_symbols debug mini_debuginfo
18248 # Drop the full debug info from the original binary.
18249 strip --strip-all -R .comment @var{binary}
18251 # Inject the compressed data into the .gnu_debugdata section of the
18254 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
18258 @section Index Files Speed Up @value{GDBN}
18259 @cindex index files
18260 @cindex @samp{.gdb_index} section
18262 When @value{GDBN} finds a symbol file, it scans the symbols in the
18263 file in order to construct an internal symbol table. This lets most
18264 @value{GDBN} operations work quickly---at the cost of a delay early
18265 on. For large programs, this delay can be quite lengthy, so
18266 @value{GDBN} provides a way to build an index, which speeds up
18269 The index is stored as a section in the symbol file. @value{GDBN} can
18270 write the index to a file, then you can put it into the symbol file
18271 using @command{objcopy}.
18273 To create an index file, use the @code{save gdb-index} command:
18276 @item save gdb-index @var{directory}
18277 @kindex save gdb-index
18278 Create an index file for each symbol file currently known by
18279 @value{GDBN}. Each file is named after its corresponding symbol file,
18280 with @samp{.gdb-index} appended, and is written into the given
18284 Once you have created an index file you can merge it into your symbol
18285 file, here named @file{symfile}, using @command{objcopy}:
18288 $ objcopy --add-section .gdb_index=symfile.gdb-index \
18289 --set-section-flags .gdb_index=readonly symfile symfile
18292 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
18293 sections that have been deprecated. Usually they are deprecated because
18294 they are missing a new feature or have performance issues.
18295 To tell @value{GDBN} to use a deprecated index section anyway
18296 specify @code{set use-deprecated-index-sections on}.
18297 The default is @code{off}.
18298 This can speed up startup, but may result in some functionality being lost.
18299 @xref{Index Section Format}.
18301 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
18302 must be done before gdb reads the file. The following will not work:
18305 $ gdb -ex "set use-deprecated-index-sections on" <program>
18308 Instead you must do, for example,
18311 $ gdb -iex "set use-deprecated-index-sections on" <program>
18314 There are currently some limitation on indices. They only work when
18315 for DWARF debugging information, not stabs. And, they do not
18316 currently work for programs using Ada.
18318 @node Symbol Errors
18319 @section Errors Reading Symbol Files
18321 While reading a symbol file, @value{GDBN} occasionally encounters problems,
18322 such as symbol types it does not recognize, or known bugs in compiler
18323 output. By default, @value{GDBN} does not notify you of such problems, since
18324 they are relatively common and primarily of interest to people
18325 debugging compilers. If you are interested in seeing information
18326 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
18327 only one message about each such type of problem, no matter how many
18328 times the problem occurs; or you can ask @value{GDBN} to print more messages,
18329 to see how many times the problems occur, with the @code{set
18330 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
18333 The messages currently printed, and their meanings, include:
18336 @item inner block not inside outer block in @var{symbol}
18338 The symbol information shows where symbol scopes begin and end
18339 (such as at the start of a function or a block of statements). This
18340 error indicates that an inner scope block is not fully contained
18341 in its outer scope blocks.
18343 @value{GDBN} circumvents the problem by treating the inner block as if it had
18344 the same scope as the outer block. In the error message, @var{symbol}
18345 may be shown as ``@code{(don't know)}'' if the outer block is not a
18348 @item block at @var{address} out of order
18350 The symbol information for symbol scope blocks should occur in
18351 order of increasing addresses. This error indicates that it does not
18354 @value{GDBN} does not circumvent this problem, and has trouble
18355 locating symbols in the source file whose symbols it is reading. (You
18356 can often determine what source file is affected by specifying
18357 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
18360 @item bad block start address patched
18362 The symbol information for a symbol scope block has a start address
18363 smaller than the address of the preceding source line. This is known
18364 to occur in the SunOS 4.1.1 (and earlier) C compiler.
18366 @value{GDBN} circumvents the problem by treating the symbol scope block as
18367 starting on the previous source line.
18369 @item bad string table offset in symbol @var{n}
18372 Symbol number @var{n} contains a pointer into the string table which is
18373 larger than the size of the string table.
18375 @value{GDBN} circumvents the problem by considering the symbol to have the
18376 name @code{foo}, which may cause other problems if many symbols end up
18379 @item unknown symbol type @code{0x@var{nn}}
18381 The symbol information contains new data types that @value{GDBN} does
18382 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
18383 uncomprehended information, in hexadecimal.
18385 @value{GDBN} circumvents the error by ignoring this symbol information.
18386 This usually allows you to debug your program, though certain symbols
18387 are not accessible. If you encounter such a problem and feel like
18388 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
18389 on @code{complain}, then go up to the function @code{read_dbx_symtab}
18390 and examine @code{*bufp} to see the symbol.
18392 @item stub type has NULL name
18394 @value{GDBN} could not find the full definition for a struct or class.
18396 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
18397 The symbol information for a C@t{++} member function is missing some
18398 information that recent versions of the compiler should have output for
18401 @item info mismatch between compiler and debugger
18403 @value{GDBN} could not parse a type specification output by the compiler.
18408 @section GDB Data Files
18410 @cindex prefix for data files
18411 @value{GDBN} will sometimes read an auxiliary data file. These files
18412 are kept in a directory known as the @dfn{data directory}.
18414 You can set the data directory's name, and view the name @value{GDBN}
18415 is currently using.
18418 @kindex set data-directory
18419 @item set data-directory @var{directory}
18420 Set the directory which @value{GDBN} searches for auxiliary data files
18421 to @var{directory}.
18423 @kindex show data-directory
18424 @item show data-directory
18425 Show the directory @value{GDBN} searches for auxiliary data files.
18428 @cindex default data directory
18429 @cindex @samp{--with-gdb-datadir}
18430 You can set the default data directory by using the configure-time
18431 @samp{--with-gdb-datadir} option. If the data directory is inside
18432 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
18433 @samp{--exec-prefix}), then the default data directory will be updated
18434 automatically if the installed @value{GDBN} is moved to a new
18437 The data directory may also be specified with the
18438 @code{--data-directory} command line option.
18439 @xref{Mode Options}.
18442 @chapter Specifying a Debugging Target
18444 @cindex debugging target
18445 A @dfn{target} is the execution environment occupied by your program.
18447 Often, @value{GDBN} runs in the same host environment as your program;
18448 in that case, the debugging target is specified as a side effect when
18449 you use the @code{file} or @code{core} commands. When you need more
18450 flexibility---for example, running @value{GDBN} on a physically separate
18451 host, or controlling a standalone system over a serial port or a
18452 realtime system over a TCP/IP connection---you can use the @code{target}
18453 command to specify one of the target types configured for @value{GDBN}
18454 (@pxref{Target Commands, ,Commands for Managing Targets}).
18456 @cindex target architecture
18457 It is possible to build @value{GDBN} for several different @dfn{target
18458 architectures}. When @value{GDBN} is built like that, you can choose
18459 one of the available architectures with the @kbd{set architecture}
18463 @kindex set architecture
18464 @kindex show architecture
18465 @item set architecture @var{arch}
18466 This command sets the current target architecture to @var{arch}. The
18467 value of @var{arch} can be @code{"auto"}, in addition to one of the
18468 supported architectures.
18470 @item show architecture
18471 Show the current target architecture.
18473 @item set processor
18475 @kindex set processor
18476 @kindex show processor
18477 These are alias commands for, respectively, @code{set architecture}
18478 and @code{show architecture}.
18482 * Active Targets:: Active targets
18483 * Target Commands:: Commands for managing targets
18484 * Byte Order:: Choosing target byte order
18487 @node Active Targets
18488 @section Active Targets
18490 @cindex stacking targets
18491 @cindex active targets
18492 @cindex multiple targets
18494 There are multiple classes of targets such as: processes, executable files or
18495 recording sessions. Core files belong to the process class, making core file
18496 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
18497 on multiple active targets, one in each class. This allows you to (for
18498 example) start a process and inspect its activity, while still having access to
18499 the executable file after the process finishes. Or if you start process
18500 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
18501 presented a virtual layer of the recording target, while the process target
18502 remains stopped at the chronologically last point of the process execution.
18504 Use the @code{core-file} and @code{exec-file} commands to select a new core
18505 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
18506 specify as a target a process that is already running, use the @code{attach}
18507 command (@pxref{Attach, ,Debugging an Already-running Process}).
18509 @node Target Commands
18510 @section Commands for Managing Targets
18513 @item target @var{type} @var{parameters}
18514 Connects the @value{GDBN} host environment to a target machine or
18515 process. A target is typically a protocol for talking to debugging
18516 facilities. You use the argument @var{type} to specify the type or
18517 protocol of the target machine.
18519 Further @var{parameters} are interpreted by the target protocol, but
18520 typically include things like device names or host names to connect
18521 with, process numbers, and baud rates.
18523 The @code{target} command does not repeat if you press @key{RET} again
18524 after executing the command.
18526 @kindex help target
18528 Displays the names of all targets available. To display targets
18529 currently selected, use either @code{info target} or @code{info files}
18530 (@pxref{Files, ,Commands to Specify Files}).
18532 @item help target @var{name}
18533 Describe a particular target, including any parameters necessary to
18536 @kindex set gnutarget
18537 @item set gnutarget @var{args}
18538 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
18539 knows whether it is reading an @dfn{executable},
18540 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
18541 with the @code{set gnutarget} command. Unlike most @code{target} commands,
18542 with @code{gnutarget} the @code{target} refers to a program, not a machine.
18545 @emph{Warning:} To specify a file format with @code{set gnutarget},
18546 you must know the actual BFD name.
18550 @xref{Files, , Commands to Specify Files}.
18552 @kindex show gnutarget
18553 @item show gnutarget
18554 Use the @code{show gnutarget} command to display what file format
18555 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
18556 @value{GDBN} will determine the file format for each file automatically,
18557 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
18560 @cindex common targets
18561 Here are some common targets (available, or not, depending on the GDB
18566 @item target exec @var{program}
18567 @cindex executable file target
18568 An executable file. @samp{target exec @var{program}} is the same as
18569 @samp{exec-file @var{program}}.
18571 @item target core @var{filename}
18572 @cindex core dump file target
18573 A core dump file. @samp{target core @var{filename}} is the same as
18574 @samp{core-file @var{filename}}.
18576 @item target remote @var{medium}
18577 @cindex remote target
18578 A remote system connected to @value{GDBN} via a serial line or network
18579 connection. This command tells @value{GDBN} to use its own remote
18580 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
18582 For example, if you have a board connected to @file{/dev/ttya} on the
18583 machine running @value{GDBN}, you could say:
18586 target remote /dev/ttya
18589 @code{target remote} supports the @code{load} command. This is only
18590 useful if you have some other way of getting the stub to the target
18591 system, and you can put it somewhere in memory where it won't get
18592 clobbered by the download.
18594 @item target sim @r{[}@var{simargs}@r{]} @dots{}
18595 @cindex built-in simulator target
18596 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
18604 works; however, you cannot assume that a specific memory map, device
18605 drivers, or even basic I/O is available, although some simulators do
18606 provide these. For info about any processor-specific simulator details,
18607 see the appropriate section in @ref{Embedded Processors, ,Embedded
18610 @item target native
18611 @cindex native target
18612 Setup for local/native process debugging. Useful to make the
18613 @code{run} command spawn native processes (likewise @code{attach},
18614 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
18615 (@pxref{set auto-connect-native-target}).
18619 Different targets are available on different configurations of @value{GDBN};
18620 your configuration may have more or fewer targets.
18622 Many remote targets require you to download the executable's code once
18623 you've successfully established a connection. You may wish to control
18624 various aspects of this process.
18629 @kindex set hash@r{, for remote monitors}
18630 @cindex hash mark while downloading
18631 This command controls whether a hash mark @samp{#} is displayed while
18632 downloading a file to the remote monitor. If on, a hash mark is
18633 displayed after each S-record is successfully downloaded to the
18637 @kindex show hash@r{, for remote monitors}
18638 Show the current status of displaying the hash mark.
18640 @item set debug monitor
18641 @kindex set debug monitor
18642 @cindex display remote monitor communications
18643 Enable or disable display of communications messages between
18644 @value{GDBN} and the remote monitor.
18646 @item show debug monitor
18647 @kindex show debug monitor
18648 Show the current status of displaying communications between
18649 @value{GDBN} and the remote monitor.
18654 @kindex load @var{filename}
18655 @item load @var{filename}
18657 Depending on what remote debugging facilities are configured into
18658 @value{GDBN}, the @code{load} command may be available. Where it exists, it
18659 is meant to make @var{filename} (an executable) available for debugging
18660 on the remote system---by downloading, or dynamic linking, for example.
18661 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
18662 the @code{add-symbol-file} command.
18664 If your @value{GDBN} does not have a @code{load} command, attempting to
18665 execute it gets the error message ``@code{You can't do that when your
18666 target is @dots{}}''
18668 The file is loaded at whatever address is specified in the executable.
18669 For some object file formats, you can specify the load address when you
18670 link the program; for other formats, like a.out, the object file format
18671 specifies a fixed address.
18672 @c FIXME! This would be a good place for an xref to the GNU linker doc.
18674 Depending on the remote side capabilities, @value{GDBN} may be able to
18675 load programs into flash memory.
18677 @code{load} does not repeat if you press @key{RET} again after using it.
18681 @section Choosing Target Byte Order
18683 @cindex choosing target byte order
18684 @cindex target byte order
18686 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
18687 offer the ability to run either big-endian or little-endian byte
18688 orders. Usually the executable or symbol will include a bit to
18689 designate the endian-ness, and you will not need to worry about
18690 which to use. However, you may still find it useful to adjust
18691 @value{GDBN}'s idea of processor endian-ness manually.
18695 @item set endian big
18696 Instruct @value{GDBN} to assume the target is big-endian.
18698 @item set endian little
18699 Instruct @value{GDBN} to assume the target is little-endian.
18701 @item set endian auto
18702 Instruct @value{GDBN} to use the byte order associated with the
18706 Display @value{GDBN}'s current idea of the target byte order.
18710 Note that these commands merely adjust interpretation of symbolic
18711 data on the host, and that they have absolutely no effect on the
18715 @node Remote Debugging
18716 @chapter Debugging Remote Programs
18717 @cindex remote debugging
18719 If you are trying to debug a program running on a machine that cannot run
18720 @value{GDBN} in the usual way, it is often useful to use remote debugging.
18721 For example, you might use remote debugging on an operating system kernel,
18722 or on a small system which does not have a general purpose operating system
18723 powerful enough to run a full-featured debugger.
18725 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
18726 to make this work with particular debugging targets. In addition,
18727 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
18728 but not specific to any particular target system) which you can use if you
18729 write the remote stubs---the code that runs on the remote system to
18730 communicate with @value{GDBN}.
18732 Other remote targets may be available in your
18733 configuration of @value{GDBN}; use @code{help target} to list them.
18736 * Connecting:: Connecting to a remote target
18737 * File Transfer:: Sending files to a remote system
18738 * Server:: Using the gdbserver program
18739 * Remote Configuration:: Remote configuration
18740 * Remote Stub:: Implementing a remote stub
18744 @section Connecting to a Remote Target
18746 On the @value{GDBN} host machine, you will need an unstripped copy of
18747 your program, since @value{GDBN} needs symbol and debugging information.
18748 Start up @value{GDBN} as usual, using the name of the local copy of your
18749 program as the first argument.
18751 @cindex @code{target remote}
18752 @value{GDBN} can communicate with the target over a serial line, or
18753 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
18754 each case, @value{GDBN} uses the same protocol for debugging your
18755 program; only the medium carrying the debugging packets varies. The
18756 @code{target remote} command establishes a connection to the target.
18757 Its arguments indicate which medium to use:
18761 @item target remote @var{serial-device}
18762 @cindex serial line, @code{target remote}
18763 Use @var{serial-device} to communicate with the target. For example,
18764 to use a serial line connected to the device named @file{/dev/ttyb}:
18767 target remote /dev/ttyb
18770 If you're using a serial line, you may want to give @value{GDBN} the
18771 @samp{--baud} option, or use the @code{set serial baud} command
18772 (@pxref{Remote Configuration, set serial baud}) before the
18773 @code{target} command.
18775 @item target remote @code{@var{host}:@var{port}}
18776 @itemx target remote @code{tcp:@var{host}:@var{port}}
18777 @cindex @acronym{TCP} port, @code{target remote}
18778 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
18779 The @var{host} may be either a host name or a numeric @acronym{IP}
18780 address; @var{port} must be a decimal number. The @var{host} could be
18781 the target machine itself, if it is directly connected to the net, or
18782 it might be a terminal server which in turn has a serial line to the
18785 For example, to connect to port 2828 on a terminal server named
18789 target remote manyfarms:2828
18792 If your remote target is actually running on the same machine as your
18793 debugger session (e.g.@: a simulator for your target running on the
18794 same host), you can omit the hostname. For example, to connect to
18795 port 1234 on your local machine:
18798 target remote :1234
18802 Note that the colon is still required here.
18804 @item target remote @code{udp:@var{host}:@var{port}}
18805 @cindex @acronym{UDP} port, @code{target remote}
18806 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
18807 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
18810 target remote udp:manyfarms:2828
18813 When using a @acronym{UDP} connection for remote debugging, you should
18814 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
18815 can silently drop packets on busy or unreliable networks, which will
18816 cause havoc with your debugging session.
18818 @item target remote | @var{command}
18819 @cindex pipe, @code{target remote} to
18820 Run @var{command} in the background and communicate with it using a
18821 pipe. The @var{command} is a shell command, to be parsed and expanded
18822 by the system's command shell, @code{/bin/sh}; it should expect remote
18823 protocol packets on its standard input, and send replies on its
18824 standard output. You could use this to run a stand-alone simulator
18825 that speaks the remote debugging protocol, to make net connections
18826 using programs like @code{ssh}, or for other similar tricks.
18828 If @var{command} closes its standard output (perhaps by exiting),
18829 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
18830 program has already exited, this will have no effect.)
18834 Once the connection has been established, you can use all the usual
18835 commands to examine and change data. The remote program is already
18836 running; you can use @kbd{step} and @kbd{continue}, and you do not
18837 need to use @kbd{run}.
18839 @cindex interrupting remote programs
18840 @cindex remote programs, interrupting
18841 Whenever @value{GDBN} is waiting for the remote program, if you type the
18842 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
18843 program. This may or may not succeed, depending in part on the hardware
18844 and the serial drivers the remote system uses. If you type the
18845 interrupt character once again, @value{GDBN} displays this prompt:
18848 Interrupted while waiting for the program.
18849 Give up (and stop debugging it)? (y or n)
18852 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
18853 (If you decide you want to try again later, you can use @samp{target
18854 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
18855 goes back to waiting.
18858 @kindex detach (remote)
18860 When you have finished debugging the remote program, you can use the
18861 @code{detach} command to release it from @value{GDBN} control.
18862 Detaching from the target normally resumes its execution, but the results
18863 will depend on your particular remote stub. After the @code{detach}
18864 command, @value{GDBN} is free to connect to another target.
18868 The @code{disconnect} command behaves like @code{detach}, except that
18869 the target is generally not resumed. It will wait for @value{GDBN}
18870 (this instance or another one) to connect and continue debugging. After
18871 the @code{disconnect} command, @value{GDBN} is again free to connect to
18874 @cindex send command to remote monitor
18875 @cindex extend @value{GDBN} for remote targets
18876 @cindex add new commands for external monitor
18878 @item monitor @var{cmd}
18879 This command allows you to send arbitrary commands directly to the
18880 remote monitor. Since @value{GDBN} doesn't care about the commands it
18881 sends like this, this command is the way to extend @value{GDBN}---you
18882 can add new commands that only the external monitor will understand
18886 @node File Transfer
18887 @section Sending files to a remote system
18888 @cindex remote target, file transfer
18889 @cindex file transfer
18890 @cindex sending files to remote systems
18892 Some remote targets offer the ability to transfer files over the same
18893 connection used to communicate with @value{GDBN}. This is convenient
18894 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
18895 running @code{gdbserver} over a network interface. For other targets,
18896 e.g.@: embedded devices with only a single serial port, this may be
18897 the only way to upload or download files.
18899 Not all remote targets support these commands.
18903 @item remote put @var{hostfile} @var{targetfile}
18904 Copy file @var{hostfile} from the host system (the machine running
18905 @value{GDBN}) to @var{targetfile} on the target system.
18908 @item remote get @var{targetfile} @var{hostfile}
18909 Copy file @var{targetfile} from the target system to @var{hostfile}
18910 on the host system.
18912 @kindex remote delete
18913 @item remote delete @var{targetfile}
18914 Delete @var{targetfile} from the target system.
18919 @section Using the @code{gdbserver} Program
18922 @cindex remote connection without stubs
18923 @code{gdbserver} is a control program for Unix-like systems, which
18924 allows you to connect your program with a remote @value{GDBN} via
18925 @code{target remote}---but without linking in the usual debugging stub.
18927 @code{gdbserver} is not a complete replacement for the debugging stubs,
18928 because it requires essentially the same operating-system facilities
18929 that @value{GDBN} itself does. In fact, a system that can run
18930 @code{gdbserver} to connect to a remote @value{GDBN} could also run
18931 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
18932 because it is a much smaller program than @value{GDBN} itself. It is
18933 also easier to port than all of @value{GDBN}, so you may be able to get
18934 started more quickly on a new system by using @code{gdbserver}.
18935 Finally, if you develop code for real-time systems, you may find that
18936 the tradeoffs involved in real-time operation make it more convenient to
18937 do as much development work as possible on another system, for example
18938 by cross-compiling. You can use @code{gdbserver} to make a similar
18939 choice for debugging.
18941 @value{GDBN} and @code{gdbserver} communicate via either a serial line
18942 or a TCP connection, using the standard @value{GDBN} remote serial
18946 @emph{Warning:} @code{gdbserver} does not have any built-in security.
18947 Do not run @code{gdbserver} connected to any public network; a
18948 @value{GDBN} connection to @code{gdbserver} provides access to the
18949 target system with the same privileges as the user running
18953 @subsection Running @code{gdbserver}
18954 @cindex arguments, to @code{gdbserver}
18955 @cindex @code{gdbserver}, command-line arguments
18957 Run @code{gdbserver} on the target system. You need a copy of the
18958 program you want to debug, including any libraries it requires.
18959 @code{gdbserver} does not need your program's symbol table, so you can
18960 strip the program if necessary to save space. @value{GDBN} on the host
18961 system does all the symbol handling.
18963 To use the server, you must tell it how to communicate with @value{GDBN};
18964 the name of your program; and the arguments for your program. The usual
18968 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
18971 @var{comm} is either a device name (to use a serial line), or a TCP
18972 hostname and portnumber, or @code{-} or @code{stdio} to use
18973 stdin/stdout of @code{gdbserver}.
18974 For example, to debug Emacs with the argument
18975 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
18979 target> gdbserver /dev/com1 emacs foo.txt
18982 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
18985 To use a TCP connection instead of a serial line:
18988 target> gdbserver host:2345 emacs foo.txt
18991 The only difference from the previous example is the first argument,
18992 specifying that you are communicating with the host @value{GDBN} via
18993 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
18994 expect a TCP connection from machine @samp{host} to local TCP port 2345.
18995 (Currently, the @samp{host} part is ignored.) You can choose any number
18996 you want for the port number as long as it does not conflict with any
18997 TCP ports already in use on the target system (for example, @code{23} is
18998 reserved for @code{telnet}).@footnote{If you choose a port number that
18999 conflicts with another service, @code{gdbserver} prints an error message
19000 and exits.} You must use the same port number with the host @value{GDBN}
19001 @code{target remote} command.
19003 The @code{stdio} connection is useful when starting @code{gdbserver}
19007 (gdb) target remote | ssh -T hostname gdbserver - hello
19010 The @samp{-T} option to ssh is provided because we don't need a remote pty,
19011 and we don't want escape-character handling. Ssh does this by default when
19012 a command is provided, the flag is provided to make it explicit.
19013 You could elide it if you want to.
19015 Programs started with stdio-connected gdbserver have @file{/dev/null} for
19016 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
19017 display through a pipe connected to gdbserver.
19018 Both @code{stdout} and @code{stderr} use the same pipe.
19020 @subsubsection Attaching to a Running Program
19021 @cindex attach to a program, @code{gdbserver}
19022 @cindex @option{--attach}, @code{gdbserver} option
19024 On some targets, @code{gdbserver} can also attach to running programs.
19025 This is accomplished via the @code{--attach} argument. The syntax is:
19028 target> gdbserver --attach @var{comm} @var{pid}
19031 @var{pid} is the process ID of a currently running process. It isn't necessary
19032 to point @code{gdbserver} at a binary for the running process.
19035 You can debug processes by name instead of process ID if your target has the
19036 @code{pidof} utility:
19039 target> gdbserver --attach @var{comm} `pidof @var{program}`
19042 In case more than one copy of @var{program} is running, or @var{program}
19043 has multiple threads, most versions of @code{pidof} support the
19044 @code{-s} option to only return the first process ID.
19046 @subsubsection Multi-Process Mode for @code{gdbserver}
19047 @cindex @code{gdbserver}, multiple processes
19048 @cindex multiple processes with @code{gdbserver}
19050 When you connect to @code{gdbserver} using @code{target remote},
19051 @code{gdbserver} debugs the specified program only once. When the
19052 program exits, or you detach from it, @value{GDBN} closes the connection
19053 and @code{gdbserver} exits.
19055 If you connect using @kbd{target extended-remote}, @code{gdbserver}
19056 enters multi-process mode. When the debugged program exits, or you
19057 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
19058 though no program is running. The @code{run} and @code{attach}
19059 commands instruct @code{gdbserver} to run or attach to a new program.
19060 The @code{run} command uses @code{set remote exec-file} (@pxref{set
19061 remote exec-file}) to select the program to run. Command line
19062 arguments are supported, except for wildcard expansion and I/O
19063 redirection (@pxref{Arguments}).
19065 @cindex @option{--multi}, @code{gdbserver} option
19066 To start @code{gdbserver} without supplying an initial command to run
19067 or process ID to attach, use the @option{--multi} command line option.
19068 Then you can connect using @kbd{target extended-remote} and start
19069 the program you want to debug.
19071 In multi-process mode @code{gdbserver} does not automatically exit unless you
19072 use the option @option{--once}. You can terminate it by using
19073 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
19074 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
19075 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
19076 @option{--multi} option to @code{gdbserver} has no influence on that.
19078 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
19080 This section applies only when @code{gdbserver} is run to listen on a TCP port.
19082 @code{gdbserver} normally terminates after all of its debugged processes have
19083 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
19084 extended-remote}, @code{gdbserver} stays running even with no processes left.
19085 @value{GDBN} normally terminates the spawned debugged process on its exit,
19086 which normally also terminates @code{gdbserver} in the @kbd{target remote}
19087 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
19088 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
19089 stays running even in the @kbd{target remote} mode.
19091 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
19092 Such reconnecting is useful for features like @ref{disconnected tracing}. For
19093 completeness, at most one @value{GDBN} can be connected at a time.
19095 @cindex @option{--once}, @code{gdbserver} option
19096 By default, @code{gdbserver} keeps the listening TCP port open, so that
19097 subsequent connections are possible. However, if you start @code{gdbserver}
19098 with the @option{--once} option, it will stop listening for any further
19099 connection attempts after connecting to the first @value{GDBN} session. This
19100 means no further connections to @code{gdbserver} will be possible after the
19101 first one. It also means @code{gdbserver} will terminate after the first
19102 connection with remote @value{GDBN} has closed, even for unexpectedly closed
19103 connections and even in the @kbd{target extended-remote} mode. The
19104 @option{--once} option allows reusing the same port number for connecting to
19105 multiple instances of @code{gdbserver} running on the same host, since each
19106 instance closes its port after the first connection.
19108 @anchor{Other Command-Line Arguments for gdbserver}
19109 @subsubsection Other Command-Line Arguments for @code{gdbserver}
19111 @cindex @option{--debug}, @code{gdbserver} option
19112 The @option{--debug} option tells @code{gdbserver} to display extra
19113 status information about the debugging process.
19114 @cindex @option{--remote-debug}, @code{gdbserver} option
19115 The @option{--remote-debug} option tells @code{gdbserver} to display
19116 remote protocol debug output. These options are intended for
19117 @code{gdbserver} development and for bug reports to the developers.
19119 @cindex @option{--debug-format}, @code{gdbserver} option
19120 The @option{--debug-format=option1[,option2,...]} option tells
19121 @code{gdbserver} to include additional information in each output.
19122 Possible options are:
19126 Turn off all extra information in debugging output.
19128 Turn on all extra information in debugging output.
19130 Include a timestamp in each line of debugging output.
19133 Options are processed in order. Thus, for example, if @option{none}
19134 appears last then no additional information is added to debugging output.
19136 @cindex @option{--wrapper}, @code{gdbserver} option
19137 The @option{--wrapper} option specifies a wrapper to launch programs
19138 for debugging. The option should be followed by the name of the
19139 wrapper, then any command-line arguments to pass to the wrapper, then
19140 @kbd{--} indicating the end of the wrapper arguments.
19142 @code{gdbserver} runs the specified wrapper program with a combined
19143 command line including the wrapper arguments, then the name of the
19144 program to debug, then any arguments to the program. The wrapper
19145 runs until it executes your program, and then @value{GDBN} gains control.
19147 You can use any program that eventually calls @code{execve} with
19148 its arguments as a wrapper. Several standard Unix utilities do
19149 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
19150 with @code{exec "$@@"} will also work.
19152 For example, you can use @code{env} to pass an environment variable to
19153 the debugged program, without setting the variable in @code{gdbserver}'s
19157 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
19160 @subsection Connecting to @code{gdbserver}
19162 Run @value{GDBN} on the host system.
19164 First make sure you have the necessary symbol files. Load symbols for
19165 your application using the @code{file} command before you connect. Use
19166 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
19167 was compiled with the correct sysroot using @code{--with-sysroot}).
19169 The symbol file and target libraries must exactly match the executable
19170 and libraries on the target, with one exception: the files on the host
19171 system should not be stripped, even if the files on the target system
19172 are. Mismatched or missing files will lead to confusing results
19173 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
19174 files may also prevent @code{gdbserver} from debugging multi-threaded
19177 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
19178 For TCP connections, you must start up @code{gdbserver} prior to using
19179 the @code{target remote} command. Otherwise you may get an error whose
19180 text depends on the host system, but which usually looks something like
19181 @samp{Connection refused}. Don't use the @code{load}
19182 command in @value{GDBN} when using @code{gdbserver}, since the program is
19183 already on the target.
19185 @subsection Monitor Commands for @code{gdbserver}
19186 @cindex monitor commands, for @code{gdbserver}
19187 @anchor{Monitor Commands for gdbserver}
19189 During a @value{GDBN} session using @code{gdbserver}, you can use the
19190 @code{monitor} command to send special requests to @code{gdbserver}.
19191 Here are the available commands.
19195 List the available monitor commands.
19197 @item monitor set debug 0
19198 @itemx monitor set debug 1
19199 Disable or enable general debugging messages.
19201 @item monitor set remote-debug 0
19202 @itemx monitor set remote-debug 1
19203 Disable or enable specific debugging messages associated with the remote
19204 protocol (@pxref{Remote Protocol}).
19206 @item monitor set debug-format option1@r{[},option2,...@r{]}
19207 Specify additional text to add to debugging messages.
19208 Possible options are:
19212 Turn off all extra information in debugging output.
19214 Turn on all extra information in debugging output.
19216 Include a timestamp in each line of debugging output.
19219 Options are processed in order. Thus, for example, if @option{none}
19220 appears last then no additional information is added to debugging output.
19222 @item monitor set libthread-db-search-path [PATH]
19223 @cindex gdbserver, search path for @code{libthread_db}
19224 When this command is issued, @var{path} is a colon-separated list of
19225 directories to search for @code{libthread_db} (@pxref{Threads,,set
19226 libthread-db-search-path}). If you omit @var{path},
19227 @samp{libthread-db-search-path} will be reset to its default value.
19229 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
19230 not supported in @code{gdbserver}.
19233 Tell gdbserver to exit immediately. This command should be followed by
19234 @code{disconnect} to close the debugging session. @code{gdbserver} will
19235 detach from any attached processes and kill any processes it created.
19236 Use @code{monitor exit} to terminate @code{gdbserver} at the end
19237 of a multi-process mode debug session.
19241 @subsection Tracepoints support in @code{gdbserver}
19242 @cindex tracepoints support in @code{gdbserver}
19244 On some targets, @code{gdbserver} supports tracepoints, fast
19245 tracepoints and static tracepoints.
19247 For fast or static tracepoints to work, a special library called the
19248 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
19249 This library is built and distributed as an integral part of
19250 @code{gdbserver}. In addition, support for static tracepoints
19251 requires building the in-process agent library with static tracepoints
19252 support. At present, the UST (LTTng Userspace Tracer,
19253 @url{http://lttng.org/ust}) tracing engine is supported. This support
19254 is automatically available if UST development headers are found in the
19255 standard include path when @code{gdbserver} is built, or if
19256 @code{gdbserver} was explicitly configured using @option{--with-ust}
19257 to point at such headers. You can explicitly disable the support
19258 using @option{--with-ust=no}.
19260 There are several ways to load the in-process agent in your program:
19263 @item Specifying it as dependency at link time
19265 You can link your program dynamically with the in-process agent
19266 library. On most systems, this is accomplished by adding
19267 @code{-linproctrace} to the link command.
19269 @item Using the system's preloading mechanisms
19271 You can force loading the in-process agent at startup time by using
19272 your system's support for preloading shared libraries. Many Unixes
19273 support the concept of preloading user defined libraries. In most
19274 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
19275 in the environment. See also the description of @code{gdbserver}'s
19276 @option{--wrapper} command line option.
19278 @item Using @value{GDBN} to force loading the agent at run time
19280 On some systems, you can force the inferior to load a shared library,
19281 by calling a dynamic loader function in the inferior that takes care
19282 of dynamically looking up and loading a shared library. On most Unix
19283 systems, the function is @code{dlopen}. You'll use the @code{call}
19284 command for that. For example:
19287 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
19290 Note that on most Unix systems, for the @code{dlopen} function to be
19291 available, the program needs to be linked with @code{-ldl}.
19294 On systems that have a userspace dynamic loader, like most Unix
19295 systems, when you connect to @code{gdbserver} using @code{target
19296 remote}, you'll find that the program is stopped at the dynamic
19297 loader's entry point, and no shared library has been loaded in the
19298 program's address space yet, including the in-process agent. In that
19299 case, before being able to use any of the fast or static tracepoints
19300 features, you need to let the loader run and load the shared
19301 libraries. The simplest way to do that is to run the program to the
19302 main procedure. E.g., if debugging a C or C@t{++} program, start
19303 @code{gdbserver} like so:
19306 $ gdbserver :9999 myprogram
19309 Start GDB and connect to @code{gdbserver} like so, and run to main:
19313 (@value{GDBP}) target remote myhost:9999
19314 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
19315 (@value{GDBP}) b main
19316 (@value{GDBP}) continue
19319 The in-process tracing agent library should now be loaded into the
19320 process; you can confirm it with the @code{info sharedlibrary}
19321 command, which will list @file{libinproctrace.so} as loaded in the
19322 process. You are now ready to install fast tracepoints, list static
19323 tracepoint markers, probe static tracepoints markers, and start
19326 @node Remote Configuration
19327 @section Remote Configuration
19330 @kindex show remote
19331 This section documents the configuration options available when
19332 debugging remote programs. For the options related to the File I/O
19333 extensions of the remote protocol, see @ref{system,
19334 system-call-allowed}.
19337 @item set remoteaddresssize @var{bits}
19338 @cindex address size for remote targets
19339 @cindex bits in remote address
19340 Set the maximum size of address in a memory packet to the specified
19341 number of bits. @value{GDBN} will mask off the address bits above
19342 that number, when it passes addresses to the remote target. The
19343 default value is the number of bits in the target's address.
19345 @item show remoteaddresssize
19346 Show the current value of remote address size in bits.
19348 @item set serial baud @var{n}
19349 @cindex baud rate for remote targets
19350 Set the baud rate for the remote serial I/O to @var{n} baud. The
19351 value is used to set the speed of the serial port used for debugging
19354 @item show serial baud
19355 Show the current speed of the remote connection.
19357 @item set remotebreak
19358 @cindex interrupt remote programs
19359 @cindex BREAK signal instead of Ctrl-C
19360 @anchor{set remotebreak}
19361 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
19362 when you type @kbd{Ctrl-c} to interrupt the program running
19363 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
19364 character instead. The default is off, since most remote systems
19365 expect to see @samp{Ctrl-C} as the interrupt signal.
19367 @item show remotebreak
19368 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
19369 interrupt the remote program.
19371 @item set remoteflow on
19372 @itemx set remoteflow off
19373 @kindex set remoteflow
19374 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
19375 on the serial port used to communicate to the remote target.
19377 @item show remoteflow
19378 @kindex show remoteflow
19379 Show the current setting of hardware flow control.
19381 @item set remotelogbase @var{base}
19382 Set the base (a.k.a.@: radix) of logging serial protocol
19383 communications to @var{base}. Supported values of @var{base} are:
19384 @code{ascii}, @code{octal}, and @code{hex}. The default is
19387 @item show remotelogbase
19388 Show the current setting of the radix for logging remote serial
19391 @item set remotelogfile @var{file}
19392 @cindex record serial communications on file
19393 Record remote serial communications on the named @var{file}. The
19394 default is not to record at all.
19396 @item show remotelogfile.
19397 Show the current setting of the file name on which to record the
19398 serial communications.
19400 @item set remotetimeout @var{num}
19401 @cindex timeout for serial communications
19402 @cindex remote timeout
19403 Set the timeout limit to wait for the remote target to respond to
19404 @var{num} seconds. The default is 2 seconds.
19406 @item show remotetimeout
19407 Show the current number of seconds to wait for the remote target
19410 @cindex limit hardware breakpoints and watchpoints
19411 @cindex remote target, limit break- and watchpoints
19412 @anchor{set remote hardware-watchpoint-limit}
19413 @anchor{set remote hardware-breakpoint-limit}
19414 @item set remote hardware-watchpoint-limit @var{limit}
19415 @itemx set remote hardware-breakpoint-limit @var{limit}
19416 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
19417 watchpoints. A limit of -1, the default, is treated as unlimited.
19419 @cindex limit hardware watchpoints length
19420 @cindex remote target, limit watchpoints length
19421 @anchor{set remote hardware-watchpoint-length-limit}
19422 @item set remote hardware-watchpoint-length-limit @var{limit}
19423 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
19424 a remote hardware watchpoint. A limit of -1, the default, is treated
19427 @item show remote hardware-watchpoint-length-limit
19428 Show the current limit (in bytes) of the maximum length of
19429 a remote hardware watchpoint.
19431 @item set remote exec-file @var{filename}
19432 @itemx show remote exec-file
19433 @anchor{set remote exec-file}
19434 @cindex executable file, for remote target
19435 Select the file used for @code{run} with @code{target
19436 extended-remote}. This should be set to a filename valid on the
19437 target system. If it is not set, the target will use a default
19438 filename (e.g.@: the last program run).
19440 @item set remote interrupt-sequence
19441 @cindex interrupt remote programs
19442 @cindex select Ctrl-C, BREAK or BREAK-g
19443 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
19444 @samp{BREAK-g} as the
19445 sequence to the remote target in order to interrupt the execution.
19446 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
19447 is high level of serial line for some certain time.
19448 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
19449 It is @code{BREAK} signal followed by character @code{g}.
19451 @item show interrupt-sequence
19452 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
19453 is sent by @value{GDBN} to interrupt the remote program.
19454 @code{BREAK-g} is BREAK signal followed by @code{g} and
19455 also known as Magic SysRq g.
19457 @item set remote interrupt-on-connect
19458 @cindex send interrupt-sequence on start
19459 Specify whether interrupt-sequence is sent to remote target when
19460 @value{GDBN} connects to it. This is mostly needed when you debug
19461 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
19462 which is known as Magic SysRq g in order to connect @value{GDBN}.
19464 @item show interrupt-on-connect
19465 Show whether interrupt-sequence is sent
19466 to remote target when @value{GDBN} connects to it.
19470 @item set tcp auto-retry on
19471 @cindex auto-retry, for remote TCP target
19472 Enable auto-retry for remote TCP connections. This is useful if the remote
19473 debugging agent is launched in parallel with @value{GDBN}; there is a race
19474 condition because the agent may not become ready to accept the connection
19475 before @value{GDBN} attempts to connect. When auto-retry is
19476 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
19477 to establish the connection using the timeout specified by
19478 @code{set tcp connect-timeout}.
19480 @item set tcp auto-retry off
19481 Do not auto-retry failed TCP connections.
19483 @item show tcp auto-retry
19484 Show the current auto-retry setting.
19486 @item set tcp connect-timeout @var{seconds}
19487 @itemx set tcp connect-timeout unlimited
19488 @cindex connection timeout, for remote TCP target
19489 @cindex timeout, for remote target connection
19490 Set the timeout for establishing a TCP connection to the remote target to
19491 @var{seconds}. The timeout affects both polling to retry failed connections
19492 (enabled by @code{set tcp auto-retry on}) and waiting for connections
19493 that are merely slow to complete, and represents an approximate cumulative
19494 value. If @var{seconds} is @code{unlimited}, there is no timeout and
19495 @value{GDBN} will keep attempting to establish a connection forever,
19496 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
19498 @item show tcp connect-timeout
19499 Show the current connection timeout setting.
19502 @cindex remote packets, enabling and disabling
19503 The @value{GDBN} remote protocol autodetects the packets supported by
19504 your debugging stub. If you need to override the autodetection, you
19505 can use these commands to enable or disable individual packets. Each
19506 packet can be set to @samp{on} (the remote target supports this
19507 packet), @samp{off} (the remote target does not support this packet),
19508 or @samp{auto} (detect remote target support for this packet). They
19509 all default to @samp{auto}. For more information about each packet,
19510 see @ref{Remote Protocol}.
19512 During normal use, you should not have to use any of these commands.
19513 If you do, that may be a bug in your remote debugging stub, or a bug
19514 in @value{GDBN}. You may want to report the problem to the
19515 @value{GDBN} developers.
19517 For each packet @var{name}, the command to enable or disable the
19518 packet is @code{set remote @var{name}-packet}. The available settings
19521 @multitable @columnfractions 0.28 0.32 0.25
19524 @tab Related Features
19526 @item @code{fetch-register}
19528 @tab @code{info registers}
19530 @item @code{set-register}
19534 @item @code{binary-download}
19536 @tab @code{load}, @code{set}
19538 @item @code{read-aux-vector}
19539 @tab @code{qXfer:auxv:read}
19540 @tab @code{info auxv}
19542 @item @code{symbol-lookup}
19543 @tab @code{qSymbol}
19544 @tab Detecting multiple threads
19546 @item @code{attach}
19547 @tab @code{vAttach}
19550 @item @code{verbose-resume}
19552 @tab Stepping or resuming multiple threads
19558 @item @code{software-breakpoint}
19562 @item @code{hardware-breakpoint}
19566 @item @code{write-watchpoint}
19570 @item @code{read-watchpoint}
19574 @item @code{access-watchpoint}
19578 @item @code{target-features}
19579 @tab @code{qXfer:features:read}
19580 @tab @code{set architecture}
19582 @item @code{library-info}
19583 @tab @code{qXfer:libraries:read}
19584 @tab @code{info sharedlibrary}
19586 @item @code{memory-map}
19587 @tab @code{qXfer:memory-map:read}
19588 @tab @code{info mem}
19590 @item @code{read-sdata-object}
19591 @tab @code{qXfer:sdata:read}
19592 @tab @code{print $_sdata}
19594 @item @code{read-spu-object}
19595 @tab @code{qXfer:spu:read}
19596 @tab @code{info spu}
19598 @item @code{write-spu-object}
19599 @tab @code{qXfer:spu:write}
19600 @tab @code{info spu}
19602 @item @code{read-siginfo-object}
19603 @tab @code{qXfer:siginfo:read}
19604 @tab @code{print $_siginfo}
19606 @item @code{write-siginfo-object}
19607 @tab @code{qXfer:siginfo:write}
19608 @tab @code{set $_siginfo}
19610 @item @code{threads}
19611 @tab @code{qXfer:threads:read}
19612 @tab @code{info threads}
19614 @item @code{get-thread-local-@*storage-address}
19615 @tab @code{qGetTLSAddr}
19616 @tab Displaying @code{__thread} variables
19618 @item @code{get-thread-information-block-address}
19619 @tab @code{qGetTIBAddr}
19620 @tab Display MS-Windows Thread Information Block.
19622 @item @code{search-memory}
19623 @tab @code{qSearch:memory}
19626 @item @code{supported-packets}
19627 @tab @code{qSupported}
19628 @tab Remote communications parameters
19630 @item @code{pass-signals}
19631 @tab @code{QPassSignals}
19632 @tab @code{handle @var{signal}}
19634 @item @code{program-signals}
19635 @tab @code{QProgramSignals}
19636 @tab @code{handle @var{signal}}
19638 @item @code{hostio-close-packet}
19639 @tab @code{vFile:close}
19640 @tab @code{remote get}, @code{remote put}
19642 @item @code{hostio-open-packet}
19643 @tab @code{vFile:open}
19644 @tab @code{remote get}, @code{remote put}
19646 @item @code{hostio-pread-packet}
19647 @tab @code{vFile:pread}
19648 @tab @code{remote get}, @code{remote put}
19650 @item @code{hostio-pwrite-packet}
19651 @tab @code{vFile:pwrite}
19652 @tab @code{remote get}, @code{remote put}
19654 @item @code{hostio-unlink-packet}
19655 @tab @code{vFile:unlink}
19656 @tab @code{remote delete}
19658 @item @code{hostio-readlink-packet}
19659 @tab @code{vFile:readlink}
19662 @item @code{noack-packet}
19663 @tab @code{QStartNoAckMode}
19664 @tab Packet acknowledgment
19666 @item @code{osdata}
19667 @tab @code{qXfer:osdata:read}
19668 @tab @code{info os}
19670 @item @code{query-attached}
19671 @tab @code{qAttached}
19672 @tab Querying remote process attach state.
19674 @item @code{trace-buffer-size}
19675 @tab @code{QTBuffer:size}
19676 @tab @code{set trace-buffer-size}
19678 @item @code{trace-status}
19679 @tab @code{qTStatus}
19680 @tab @code{tstatus}
19682 @item @code{traceframe-info}
19683 @tab @code{qXfer:traceframe-info:read}
19684 @tab Traceframe info
19686 @item @code{install-in-trace}
19687 @tab @code{InstallInTrace}
19688 @tab Install tracepoint in tracing
19690 @item @code{disable-randomization}
19691 @tab @code{QDisableRandomization}
19692 @tab @code{set disable-randomization}
19694 @item @code{conditional-breakpoints-packet}
19695 @tab @code{Z0 and Z1}
19696 @tab @code{Support for target-side breakpoint condition evaluation}
19700 @section Implementing a Remote Stub
19702 @cindex debugging stub, example
19703 @cindex remote stub, example
19704 @cindex stub example, remote debugging
19705 The stub files provided with @value{GDBN} implement the target side of the
19706 communication protocol, and the @value{GDBN} side is implemented in the
19707 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
19708 these subroutines to communicate, and ignore the details. (If you're
19709 implementing your own stub file, you can still ignore the details: start
19710 with one of the existing stub files. @file{sparc-stub.c} is the best
19711 organized, and therefore the easiest to read.)
19713 @cindex remote serial debugging, overview
19714 To debug a program running on another machine (the debugging
19715 @dfn{target} machine), you must first arrange for all the usual
19716 prerequisites for the program to run by itself. For example, for a C
19721 A startup routine to set up the C runtime environment; these usually
19722 have a name like @file{crt0}. The startup routine may be supplied by
19723 your hardware supplier, or you may have to write your own.
19726 A C subroutine library to support your program's
19727 subroutine calls, notably managing input and output.
19730 A way of getting your program to the other machine---for example, a
19731 download program. These are often supplied by the hardware
19732 manufacturer, but you may have to write your own from hardware
19736 The next step is to arrange for your program to use a serial port to
19737 communicate with the machine where @value{GDBN} is running (the @dfn{host}
19738 machine). In general terms, the scheme looks like this:
19742 @value{GDBN} already understands how to use this protocol; when everything
19743 else is set up, you can simply use the @samp{target remote} command
19744 (@pxref{Targets,,Specifying a Debugging Target}).
19746 @item On the target,
19747 you must link with your program a few special-purpose subroutines that
19748 implement the @value{GDBN} remote serial protocol. The file containing these
19749 subroutines is called a @dfn{debugging stub}.
19751 On certain remote targets, you can use an auxiliary program
19752 @code{gdbserver} instead of linking a stub into your program.
19753 @xref{Server,,Using the @code{gdbserver} Program}, for details.
19756 The debugging stub is specific to the architecture of the remote
19757 machine; for example, use @file{sparc-stub.c} to debug programs on
19760 @cindex remote serial stub list
19761 These working remote stubs are distributed with @value{GDBN}:
19766 @cindex @file{i386-stub.c}
19769 For Intel 386 and compatible architectures.
19772 @cindex @file{m68k-stub.c}
19773 @cindex Motorola 680x0
19775 For Motorola 680x0 architectures.
19778 @cindex @file{sh-stub.c}
19781 For Renesas SH architectures.
19784 @cindex @file{sparc-stub.c}
19786 For @sc{sparc} architectures.
19788 @item sparcl-stub.c
19789 @cindex @file{sparcl-stub.c}
19792 For Fujitsu @sc{sparclite} architectures.
19796 The @file{README} file in the @value{GDBN} distribution may list other
19797 recently added stubs.
19800 * Stub Contents:: What the stub can do for you
19801 * Bootstrapping:: What you must do for the stub
19802 * Debug Session:: Putting it all together
19805 @node Stub Contents
19806 @subsection What the Stub Can Do for You
19808 @cindex remote serial stub
19809 The debugging stub for your architecture supplies these three
19813 @item set_debug_traps
19814 @findex set_debug_traps
19815 @cindex remote serial stub, initialization
19816 This routine arranges for @code{handle_exception} to run when your
19817 program stops. You must call this subroutine explicitly in your
19818 program's startup code.
19820 @item handle_exception
19821 @findex handle_exception
19822 @cindex remote serial stub, main routine
19823 This is the central workhorse, but your program never calls it
19824 explicitly---the setup code arranges for @code{handle_exception} to
19825 run when a trap is triggered.
19827 @code{handle_exception} takes control when your program stops during
19828 execution (for example, on a breakpoint), and mediates communications
19829 with @value{GDBN} on the host machine. This is where the communications
19830 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
19831 representative on the target machine. It begins by sending summary
19832 information on the state of your program, then continues to execute,
19833 retrieving and transmitting any information @value{GDBN} needs, until you
19834 execute a @value{GDBN} command that makes your program resume; at that point,
19835 @code{handle_exception} returns control to your own code on the target
19839 @cindex @code{breakpoint} subroutine, remote
19840 Use this auxiliary subroutine to make your program contain a
19841 breakpoint. Depending on the particular situation, this may be the only
19842 way for @value{GDBN} to get control. For instance, if your target
19843 machine has some sort of interrupt button, you won't need to call this;
19844 pressing the interrupt button transfers control to
19845 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
19846 simply receiving characters on the serial port may also trigger a trap;
19847 again, in that situation, you don't need to call @code{breakpoint} from
19848 your own program---simply running @samp{target remote} from the host
19849 @value{GDBN} session gets control.
19851 Call @code{breakpoint} if none of these is true, or if you simply want
19852 to make certain your program stops at a predetermined point for the
19853 start of your debugging session.
19856 @node Bootstrapping
19857 @subsection What You Must Do for the Stub
19859 @cindex remote stub, support routines
19860 The debugging stubs that come with @value{GDBN} are set up for a particular
19861 chip architecture, but they have no information about the rest of your
19862 debugging target machine.
19864 First of all you need to tell the stub how to communicate with the
19868 @item int getDebugChar()
19869 @findex getDebugChar
19870 Write this subroutine to read a single character from the serial port.
19871 It may be identical to @code{getchar} for your target system; a
19872 different name is used to allow you to distinguish the two if you wish.
19874 @item void putDebugChar(int)
19875 @findex putDebugChar
19876 Write this subroutine to write a single character to the serial port.
19877 It may be identical to @code{putchar} for your target system; a
19878 different name is used to allow you to distinguish the two if you wish.
19881 @cindex control C, and remote debugging
19882 @cindex interrupting remote targets
19883 If you want @value{GDBN} to be able to stop your program while it is
19884 running, you need to use an interrupt-driven serial driver, and arrange
19885 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
19886 character). That is the character which @value{GDBN} uses to tell the
19887 remote system to stop.
19889 Getting the debugging target to return the proper status to @value{GDBN}
19890 probably requires changes to the standard stub; one quick and dirty way
19891 is to just execute a breakpoint instruction (the ``dirty'' part is that
19892 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
19894 Other routines you need to supply are:
19897 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
19898 @findex exceptionHandler
19899 Write this function to install @var{exception_address} in the exception
19900 handling tables. You need to do this because the stub does not have any
19901 way of knowing what the exception handling tables on your target system
19902 are like (for example, the processor's table might be in @sc{rom},
19903 containing entries which point to a table in @sc{ram}).
19904 The @var{exception_number} specifies the exception which should be changed;
19905 its meaning is architecture-dependent (for example, different numbers
19906 might represent divide by zero, misaligned access, etc). When this
19907 exception occurs, control should be transferred directly to
19908 @var{exception_address}, and the processor state (stack, registers,
19909 and so on) should be just as it is when a processor exception occurs. So if
19910 you want to use a jump instruction to reach @var{exception_address}, it
19911 should be a simple jump, not a jump to subroutine.
19913 For the 386, @var{exception_address} should be installed as an interrupt
19914 gate so that interrupts are masked while the handler runs. The gate
19915 should be at privilege level 0 (the most privileged level). The
19916 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
19917 help from @code{exceptionHandler}.
19919 @item void flush_i_cache()
19920 @findex flush_i_cache
19921 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
19922 instruction cache, if any, on your target machine. If there is no
19923 instruction cache, this subroutine may be a no-op.
19925 On target machines that have instruction caches, @value{GDBN} requires this
19926 function to make certain that the state of your program is stable.
19930 You must also make sure this library routine is available:
19933 @item void *memset(void *, int, int)
19935 This is the standard library function @code{memset} that sets an area of
19936 memory to a known value. If you have one of the free versions of
19937 @code{libc.a}, @code{memset} can be found there; otherwise, you must
19938 either obtain it from your hardware manufacturer, or write your own.
19941 If you do not use the GNU C compiler, you may need other standard
19942 library subroutines as well; this varies from one stub to another,
19943 but in general the stubs are likely to use any of the common library
19944 subroutines which @code{@value{NGCC}} generates as inline code.
19947 @node Debug Session
19948 @subsection Putting it All Together
19950 @cindex remote serial debugging summary
19951 In summary, when your program is ready to debug, you must follow these
19956 Make sure you have defined the supporting low-level routines
19957 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
19959 @code{getDebugChar}, @code{putDebugChar},
19960 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
19964 Insert these lines in your program's startup code, before the main
19965 procedure is called:
19972 On some machines, when a breakpoint trap is raised, the hardware
19973 automatically makes the PC point to the instruction after the
19974 breakpoint. If your machine doesn't do that, you may need to adjust
19975 @code{handle_exception} to arrange for it to return to the instruction
19976 after the breakpoint on this first invocation, so that your program
19977 doesn't keep hitting the initial breakpoint instead of making
19981 For the 680x0 stub only, you need to provide a variable called
19982 @code{exceptionHook}. Normally you just use:
19985 void (*exceptionHook)() = 0;
19989 but if before calling @code{set_debug_traps}, you set it to point to a
19990 function in your program, that function is called when
19991 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
19992 error). The function indicated by @code{exceptionHook} is called with
19993 one parameter: an @code{int} which is the exception number.
19996 Compile and link together: your program, the @value{GDBN} debugging stub for
19997 your target architecture, and the supporting subroutines.
20000 Make sure you have a serial connection between your target machine and
20001 the @value{GDBN} host, and identify the serial port on the host.
20004 @c The "remote" target now provides a `load' command, so we should
20005 @c document that. FIXME.
20006 Download your program to your target machine (or get it there by
20007 whatever means the manufacturer provides), and start it.
20010 Start @value{GDBN} on the host, and connect to the target
20011 (@pxref{Connecting,,Connecting to a Remote Target}).
20015 @node Configurations
20016 @chapter Configuration-Specific Information
20018 While nearly all @value{GDBN} commands are available for all native and
20019 cross versions of the debugger, there are some exceptions. This chapter
20020 describes things that are only available in certain configurations.
20022 There are three major categories of configurations: native
20023 configurations, where the host and target are the same, embedded
20024 operating system configurations, which are usually the same for several
20025 different processor architectures, and bare embedded processors, which
20026 are quite different from each other.
20031 * Embedded Processors::
20038 This section describes details specific to particular native
20043 * BSD libkvm Interface:: Debugging BSD kernel memory images
20044 * SVR4 Process Information:: SVR4 process information
20045 * DJGPP Native:: Features specific to the DJGPP port
20046 * Cygwin Native:: Features specific to the Cygwin port
20047 * Hurd Native:: Features specific to @sc{gnu} Hurd
20048 * Darwin:: Features specific to Darwin
20054 On HP-UX systems, if you refer to a function or variable name that
20055 begins with a dollar sign, @value{GDBN} searches for a user or system
20056 name first, before it searches for a convenience variable.
20059 @node BSD libkvm Interface
20060 @subsection BSD libkvm Interface
20063 @cindex kernel memory image
20064 @cindex kernel crash dump
20066 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
20067 interface that provides a uniform interface for accessing kernel virtual
20068 memory images, including live systems and crash dumps. @value{GDBN}
20069 uses this interface to allow you to debug live kernels and kernel crash
20070 dumps on many native BSD configurations. This is implemented as a
20071 special @code{kvm} debugging target. For debugging a live system, load
20072 the currently running kernel into @value{GDBN} and connect to the
20076 (@value{GDBP}) @b{target kvm}
20079 For debugging crash dumps, provide the file name of the crash dump as an
20083 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
20086 Once connected to the @code{kvm} target, the following commands are
20092 Set current context from the @dfn{Process Control Block} (PCB) address.
20095 Set current context from proc address. This command isn't available on
20096 modern FreeBSD systems.
20099 @node SVR4 Process Information
20100 @subsection SVR4 Process Information
20102 @cindex examine process image
20103 @cindex process info via @file{/proc}
20105 Many versions of SVR4 and compatible systems provide a facility called
20106 @samp{/proc} that can be used to examine the image of a running
20107 process using file-system subroutines.
20109 If @value{GDBN} is configured for an operating system with this
20110 facility, the command @code{info proc} is available to report
20111 information about the process running your program, or about any
20112 process running on your system. This includes, as of this writing,
20113 @sc{gnu}/Linux and Solaris, but not HP-UX, for example.
20115 This command may also work on core files that were created on a system
20116 that has the @samp{/proc} facility.
20122 @itemx info proc @var{process-id}
20123 Summarize available information about any running process. If a
20124 process ID is specified by @var{process-id}, display information about
20125 that process; otherwise display information about the program being
20126 debugged. The summary includes the debugged process ID, the command
20127 line used to invoke it, its current working directory, and its
20128 executable file's absolute file name.
20130 On some systems, @var{process-id} can be of the form
20131 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
20132 within a process. If the optional @var{pid} part is missing, it means
20133 a thread from the process being debugged (the leading @samp{/} still
20134 needs to be present, or else @value{GDBN} will interpret the number as
20135 a process ID rather than a thread ID).
20137 @item info proc cmdline
20138 @cindex info proc cmdline
20139 Show the original command line of the process. This command is
20140 specific to @sc{gnu}/Linux.
20142 @item info proc cwd
20143 @cindex info proc cwd
20144 Show the current working directory of the process. This command is
20145 specific to @sc{gnu}/Linux.
20147 @item info proc exe
20148 @cindex info proc exe
20149 Show the name of executable of the process. This command is specific
20152 @item info proc mappings
20153 @cindex memory address space mappings
20154 Report the memory address space ranges accessible in the program, with
20155 information on whether the process has read, write, or execute access
20156 rights to each range. On @sc{gnu}/Linux systems, each memory range
20157 includes the object file which is mapped to that range, instead of the
20158 memory access rights to that range.
20160 @item info proc stat
20161 @itemx info proc status
20162 @cindex process detailed status information
20163 These subcommands are specific to @sc{gnu}/Linux systems. They show
20164 the process-related information, including the user ID and group ID;
20165 how many threads are there in the process; its virtual memory usage;
20166 the signals that are pending, blocked, and ignored; its TTY; its
20167 consumption of system and user time; its stack size; its @samp{nice}
20168 value; etc. For more information, see the @samp{proc} man page
20169 (type @kbd{man 5 proc} from your shell prompt).
20171 @item info proc all
20172 Show all the information about the process described under all of the
20173 above @code{info proc} subcommands.
20176 @comment These sub-options of 'info proc' were not included when
20177 @comment procfs.c was re-written. Keep their descriptions around
20178 @comment against the day when someone finds the time to put them back in.
20179 @kindex info proc times
20180 @item info proc times
20181 Starting time, user CPU time, and system CPU time for your program and
20184 @kindex info proc id
20186 Report on the process IDs related to your program: its own process ID,
20187 the ID of its parent, the process group ID, and the session ID.
20190 @item set procfs-trace
20191 @kindex set procfs-trace
20192 @cindex @code{procfs} API calls
20193 This command enables and disables tracing of @code{procfs} API calls.
20195 @item show procfs-trace
20196 @kindex show procfs-trace
20197 Show the current state of @code{procfs} API call tracing.
20199 @item set procfs-file @var{file}
20200 @kindex set procfs-file
20201 Tell @value{GDBN} to write @code{procfs} API trace to the named
20202 @var{file}. @value{GDBN} appends the trace info to the previous
20203 contents of the file. The default is to display the trace on the
20206 @item show procfs-file
20207 @kindex show procfs-file
20208 Show the file to which @code{procfs} API trace is written.
20210 @item proc-trace-entry
20211 @itemx proc-trace-exit
20212 @itemx proc-untrace-entry
20213 @itemx proc-untrace-exit
20214 @kindex proc-trace-entry
20215 @kindex proc-trace-exit
20216 @kindex proc-untrace-entry
20217 @kindex proc-untrace-exit
20218 These commands enable and disable tracing of entries into and exits
20219 from the @code{syscall} interface.
20222 @kindex info pidlist
20223 @cindex process list, QNX Neutrino
20224 For QNX Neutrino only, this command displays the list of all the
20225 processes and all the threads within each process.
20228 @kindex info meminfo
20229 @cindex mapinfo list, QNX Neutrino
20230 For QNX Neutrino only, this command displays the list of all mapinfos.
20234 @subsection Features for Debugging @sc{djgpp} Programs
20235 @cindex @sc{djgpp} debugging
20236 @cindex native @sc{djgpp} debugging
20237 @cindex MS-DOS-specific commands
20240 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
20241 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
20242 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
20243 top of real-mode DOS systems and their emulations.
20245 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
20246 defines a few commands specific to the @sc{djgpp} port. This
20247 subsection describes those commands.
20252 This is a prefix of @sc{djgpp}-specific commands which print
20253 information about the target system and important OS structures.
20256 @cindex MS-DOS system info
20257 @cindex free memory information (MS-DOS)
20258 @item info dos sysinfo
20259 This command displays assorted information about the underlying
20260 platform: the CPU type and features, the OS version and flavor, the
20261 DPMI version, and the available conventional and DPMI memory.
20266 @cindex segment descriptor tables
20267 @cindex descriptor tables display
20269 @itemx info dos ldt
20270 @itemx info dos idt
20271 These 3 commands display entries from, respectively, Global, Local,
20272 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
20273 tables are data structures which store a descriptor for each segment
20274 that is currently in use. The segment's selector is an index into a
20275 descriptor table; the table entry for that index holds the
20276 descriptor's base address and limit, and its attributes and access
20279 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
20280 segment (used for both data and the stack), and a DOS segment (which
20281 allows access to DOS/BIOS data structures and absolute addresses in
20282 conventional memory). However, the DPMI host will usually define
20283 additional segments in order to support the DPMI environment.
20285 @cindex garbled pointers
20286 These commands allow to display entries from the descriptor tables.
20287 Without an argument, all entries from the specified table are
20288 displayed. An argument, which should be an integer expression, means
20289 display a single entry whose index is given by the argument. For
20290 example, here's a convenient way to display information about the
20291 debugged program's data segment:
20294 @exdent @code{(@value{GDBP}) info dos ldt $ds}
20295 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
20299 This comes in handy when you want to see whether a pointer is outside
20300 the data segment's limit (i.e.@: @dfn{garbled}).
20302 @cindex page tables display (MS-DOS)
20304 @itemx info dos pte
20305 These two commands display entries from, respectively, the Page
20306 Directory and the Page Tables. Page Directories and Page Tables are
20307 data structures which control how virtual memory addresses are mapped
20308 into physical addresses. A Page Table includes an entry for every
20309 page of memory that is mapped into the program's address space; there
20310 may be several Page Tables, each one holding up to 4096 entries. A
20311 Page Directory has up to 4096 entries, one each for every Page Table
20312 that is currently in use.
20314 Without an argument, @kbd{info dos pde} displays the entire Page
20315 Directory, and @kbd{info dos pte} displays all the entries in all of
20316 the Page Tables. An argument, an integer expression, given to the
20317 @kbd{info dos pde} command means display only that entry from the Page
20318 Directory table. An argument given to the @kbd{info dos pte} command
20319 means display entries from a single Page Table, the one pointed to by
20320 the specified entry in the Page Directory.
20322 @cindex direct memory access (DMA) on MS-DOS
20323 These commands are useful when your program uses @dfn{DMA} (Direct
20324 Memory Access), which needs physical addresses to program the DMA
20327 These commands are supported only with some DPMI servers.
20329 @cindex physical address from linear address
20330 @item info dos address-pte @var{addr}
20331 This command displays the Page Table entry for a specified linear
20332 address. The argument @var{addr} is a linear address which should
20333 already have the appropriate segment's base address added to it,
20334 because this command accepts addresses which may belong to @emph{any}
20335 segment. For example, here's how to display the Page Table entry for
20336 the page where a variable @code{i} is stored:
20339 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
20340 @exdent @code{Page Table entry for address 0x11a00d30:}
20341 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
20345 This says that @code{i} is stored at offset @code{0xd30} from the page
20346 whose physical base address is @code{0x02698000}, and shows all the
20347 attributes of that page.
20349 Note that you must cast the addresses of variables to a @code{char *},
20350 since otherwise the value of @code{__djgpp_base_address}, the base
20351 address of all variables and functions in a @sc{djgpp} program, will
20352 be added using the rules of C pointer arithmetics: if @code{i} is
20353 declared an @code{int}, @value{GDBN} will add 4 times the value of
20354 @code{__djgpp_base_address} to the address of @code{i}.
20356 Here's another example, it displays the Page Table entry for the
20360 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
20361 @exdent @code{Page Table entry for address 0x29110:}
20362 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
20366 (The @code{+ 3} offset is because the transfer buffer's address is the
20367 3rd member of the @code{_go32_info_block} structure.) The output
20368 clearly shows that this DPMI server maps the addresses in conventional
20369 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
20370 linear (@code{0x29110}) addresses are identical.
20372 This command is supported only with some DPMI servers.
20375 @cindex DOS serial data link, remote debugging
20376 In addition to native debugging, the DJGPP port supports remote
20377 debugging via a serial data link. The following commands are specific
20378 to remote serial debugging in the DJGPP port of @value{GDBN}.
20381 @kindex set com1base
20382 @kindex set com1irq
20383 @kindex set com2base
20384 @kindex set com2irq
20385 @kindex set com3base
20386 @kindex set com3irq
20387 @kindex set com4base
20388 @kindex set com4irq
20389 @item set com1base @var{addr}
20390 This command sets the base I/O port address of the @file{COM1} serial
20393 @item set com1irq @var{irq}
20394 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
20395 for the @file{COM1} serial port.
20397 There are similar commands @samp{set com2base}, @samp{set com3irq},
20398 etc.@: for setting the port address and the @code{IRQ} lines for the
20401 @kindex show com1base
20402 @kindex show com1irq
20403 @kindex show com2base
20404 @kindex show com2irq
20405 @kindex show com3base
20406 @kindex show com3irq
20407 @kindex show com4base
20408 @kindex show com4irq
20409 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
20410 display the current settings of the base address and the @code{IRQ}
20411 lines used by the COM ports.
20414 @kindex info serial
20415 @cindex DOS serial port status
20416 This command prints the status of the 4 DOS serial ports. For each
20417 port, it prints whether it's active or not, its I/O base address and
20418 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
20419 counts of various errors encountered so far.
20423 @node Cygwin Native
20424 @subsection Features for Debugging MS Windows PE Executables
20425 @cindex MS Windows debugging
20426 @cindex native Cygwin debugging
20427 @cindex Cygwin-specific commands
20429 @value{GDBN} supports native debugging of MS Windows programs, including
20430 DLLs with and without symbolic debugging information.
20432 @cindex Ctrl-BREAK, MS-Windows
20433 @cindex interrupt debuggee on MS-Windows
20434 MS-Windows programs that call @code{SetConsoleMode} to switch off the
20435 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
20436 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
20437 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
20438 sequence, which can be used to interrupt the debuggee even if it
20441 There are various additional Cygwin-specific commands, described in
20442 this section. Working with DLLs that have no debugging symbols is
20443 described in @ref{Non-debug DLL Symbols}.
20448 This is a prefix of MS Windows-specific commands which print
20449 information about the target system and important OS structures.
20451 @item info w32 selector
20452 This command displays information returned by
20453 the Win32 API @code{GetThreadSelectorEntry} function.
20454 It takes an optional argument that is evaluated to
20455 a long value to give the information about this given selector.
20456 Without argument, this command displays information
20457 about the six segment registers.
20459 @item info w32 thread-information-block
20460 This command displays thread specific information stored in the
20461 Thread Information Block (readable on the X86 CPU family using @code{$fs}
20462 selector for 32-bit programs and @code{$gs} for 64-bit programs).
20466 This is a Cygwin-specific alias of @code{info shared}.
20468 @kindex set cygwin-exceptions
20469 @cindex debugging the Cygwin DLL
20470 @cindex Cygwin DLL, debugging
20471 @item set cygwin-exceptions @var{mode}
20472 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
20473 happen inside the Cygwin DLL. If @var{mode} is @code{off},
20474 @value{GDBN} will delay recognition of exceptions, and may ignore some
20475 exceptions which seem to be caused by internal Cygwin DLL
20476 ``bookkeeping''. This option is meant primarily for debugging the
20477 Cygwin DLL itself; the default value is @code{off} to avoid annoying
20478 @value{GDBN} users with false @code{SIGSEGV} signals.
20480 @kindex show cygwin-exceptions
20481 @item show cygwin-exceptions
20482 Displays whether @value{GDBN} will break on exceptions that happen
20483 inside the Cygwin DLL itself.
20485 @kindex set new-console
20486 @item set new-console @var{mode}
20487 If @var{mode} is @code{on} the debuggee will
20488 be started in a new console on next start.
20489 If @var{mode} is @code{off}, the debuggee will
20490 be started in the same console as the debugger.
20492 @kindex show new-console
20493 @item show new-console
20494 Displays whether a new console is used
20495 when the debuggee is started.
20497 @kindex set new-group
20498 @item set new-group @var{mode}
20499 This boolean value controls whether the debuggee should
20500 start a new group or stay in the same group as the debugger.
20501 This affects the way the Windows OS handles
20504 @kindex show new-group
20505 @item show new-group
20506 Displays current value of new-group boolean.
20508 @kindex set debugevents
20509 @item set debugevents
20510 This boolean value adds debug output concerning kernel events related
20511 to the debuggee seen by the debugger. This includes events that
20512 signal thread and process creation and exit, DLL loading and
20513 unloading, console interrupts, and debugging messages produced by the
20514 Windows @code{OutputDebugString} API call.
20516 @kindex set debugexec
20517 @item set debugexec
20518 This boolean value adds debug output concerning execute events
20519 (such as resume thread) seen by the debugger.
20521 @kindex set debugexceptions
20522 @item set debugexceptions
20523 This boolean value adds debug output concerning exceptions in the
20524 debuggee seen by the debugger.
20526 @kindex set debugmemory
20527 @item set debugmemory
20528 This boolean value adds debug output concerning debuggee memory reads
20529 and writes by the debugger.
20533 This boolean values specifies whether the debuggee is called
20534 via a shell or directly (default value is on).
20538 Displays if the debuggee will be started with a shell.
20543 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
20546 @node Non-debug DLL Symbols
20547 @subsubsection Support for DLLs without Debugging Symbols
20548 @cindex DLLs with no debugging symbols
20549 @cindex Minimal symbols and DLLs
20551 Very often on windows, some of the DLLs that your program relies on do
20552 not include symbolic debugging information (for example,
20553 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
20554 symbols in a DLL, it relies on the minimal amount of symbolic
20555 information contained in the DLL's export table. This section
20556 describes working with such symbols, known internally to @value{GDBN} as
20557 ``minimal symbols''.
20559 Note that before the debugged program has started execution, no DLLs
20560 will have been loaded. The easiest way around this problem is simply to
20561 start the program --- either by setting a breakpoint or letting the
20562 program run once to completion.
20564 @subsubsection DLL Name Prefixes
20566 In keeping with the naming conventions used by the Microsoft debugging
20567 tools, DLL export symbols are made available with a prefix based on the
20568 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
20569 also entered into the symbol table, so @code{CreateFileA} is often
20570 sufficient. In some cases there will be name clashes within a program
20571 (particularly if the executable itself includes full debugging symbols)
20572 necessitating the use of the fully qualified name when referring to the
20573 contents of the DLL. Use single-quotes around the name to avoid the
20574 exclamation mark (``!'') being interpreted as a language operator.
20576 Note that the internal name of the DLL may be all upper-case, even
20577 though the file name of the DLL is lower-case, or vice-versa. Since
20578 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
20579 some confusion. If in doubt, try the @code{info functions} and
20580 @code{info variables} commands or even @code{maint print msymbols}
20581 (@pxref{Symbols}). Here's an example:
20584 (@value{GDBP}) info function CreateFileA
20585 All functions matching regular expression "CreateFileA":
20587 Non-debugging symbols:
20588 0x77e885f4 CreateFileA
20589 0x77e885f4 KERNEL32!CreateFileA
20593 (@value{GDBP}) info function !
20594 All functions matching regular expression "!":
20596 Non-debugging symbols:
20597 0x6100114c cygwin1!__assert
20598 0x61004034 cygwin1!_dll_crt0@@0
20599 0x61004240 cygwin1!dll_crt0(per_process *)
20603 @subsubsection Working with Minimal Symbols
20605 Symbols extracted from a DLL's export table do not contain very much
20606 type information. All that @value{GDBN} can do is guess whether a symbol
20607 refers to a function or variable depending on the linker section that
20608 contains the symbol. Also note that the actual contents of the memory
20609 contained in a DLL are not available unless the program is running. This
20610 means that you cannot examine the contents of a variable or disassemble
20611 a function within a DLL without a running program.
20613 Variables are generally treated as pointers and dereferenced
20614 automatically. For this reason, it is often necessary to prefix a
20615 variable name with the address-of operator (``&'') and provide explicit
20616 type information in the command. Here's an example of the type of
20620 (@value{GDBP}) print 'cygwin1!__argv'
20625 (@value{GDBP}) x 'cygwin1!__argv'
20626 0x10021610: "\230y\""
20629 And two possible solutions:
20632 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
20633 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
20637 (@value{GDBP}) x/2x &'cygwin1!__argv'
20638 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
20639 (@value{GDBP}) x/x 0x10021608
20640 0x10021608: 0x0022fd98
20641 (@value{GDBP}) x/s 0x0022fd98
20642 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
20645 Setting a break point within a DLL is possible even before the program
20646 starts execution. However, under these circumstances, @value{GDBN} can't
20647 examine the initial instructions of the function in order to skip the
20648 function's frame set-up code. You can work around this by using ``*&''
20649 to set the breakpoint at a raw memory address:
20652 (@value{GDBP}) break *&'python22!PyOS_Readline'
20653 Breakpoint 1 at 0x1e04eff0
20656 The author of these extensions is not entirely convinced that setting a
20657 break point within a shared DLL like @file{kernel32.dll} is completely
20661 @subsection Commands Specific to @sc{gnu} Hurd Systems
20662 @cindex @sc{gnu} Hurd debugging
20664 This subsection describes @value{GDBN} commands specific to the
20665 @sc{gnu} Hurd native debugging.
20670 @kindex set signals@r{, Hurd command}
20671 @kindex set sigs@r{, Hurd command}
20672 This command toggles the state of inferior signal interception by
20673 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
20674 affected by this command. @code{sigs} is a shorthand alias for
20679 @kindex show signals@r{, Hurd command}
20680 @kindex show sigs@r{, Hurd command}
20681 Show the current state of intercepting inferior's signals.
20683 @item set signal-thread
20684 @itemx set sigthread
20685 @kindex set signal-thread
20686 @kindex set sigthread
20687 This command tells @value{GDBN} which thread is the @code{libc} signal
20688 thread. That thread is run when a signal is delivered to a running
20689 process. @code{set sigthread} is the shorthand alias of @code{set
20692 @item show signal-thread
20693 @itemx show sigthread
20694 @kindex show signal-thread
20695 @kindex show sigthread
20696 These two commands show which thread will run when the inferior is
20697 delivered a signal.
20700 @kindex set stopped@r{, Hurd command}
20701 This commands tells @value{GDBN} that the inferior process is stopped,
20702 as with the @code{SIGSTOP} signal. The stopped process can be
20703 continued by delivering a signal to it.
20706 @kindex show stopped@r{, Hurd command}
20707 This command shows whether @value{GDBN} thinks the debuggee is
20710 @item set exceptions
20711 @kindex set exceptions@r{, Hurd command}
20712 Use this command to turn off trapping of exceptions in the inferior.
20713 When exception trapping is off, neither breakpoints nor
20714 single-stepping will work. To restore the default, set exception
20717 @item show exceptions
20718 @kindex show exceptions@r{, Hurd command}
20719 Show the current state of trapping exceptions in the inferior.
20721 @item set task pause
20722 @kindex set task@r{, Hurd commands}
20723 @cindex task attributes (@sc{gnu} Hurd)
20724 @cindex pause current task (@sc{gnu} Hurd)
20725 This command toggles task suspension when @value{GDBN} has control.
20726 Setting it to on takes effect immediately, and the task is suspended
20727 whenever @value{GDBN} gets control. Setting it to off will take
20728 effect the next time the inferior is continued. If this option is set
20729 to off, you can use @code{set thread default pause on} or @code{set
20730 thread pause on} (see below) to pause individual threads.
20732 @item show task pause
20733 @kindex show task@r{, Hurd commands}
20734 Show the current state of task suspension.
20736 @item set task detach-suspend-count
20737 @cindex task suspend count
20738 @cindex detach from task, @sc{gnu} Hurd
20739 This command sets the suspend count the task will be left with when
20740 @value{GDBN} detaches from it.
20742 @item show task detach-suspend-count
20743 Show the suspend count the task will be left with when detaching.
20745 @item set task exception-port
20746 @itemx set task excp
20747 @cindex task exception port, @sc{gnu} Hurd
20748 This command sets the task exception port to which @value{GDBN} will
20749 forward exceptions. The argument should be the value of the @dfn{send
20750 rights} of the task. @code{set task excp} is a shorthand alias.
20752 @item set noninvasive
20753 @cindex noninvasive task options
20754 This command switches @value{GDBN} to a mode that is the least
20755 invasive as far as interfering with the inferior is concerned. This
20756 is the same as using @code{set task pause}, @code{set exceptions}, and
20757 @code{set signals} to values opposite to the defaults.
20759 @item info send-rights
20760 @itemx info receive-rights
20761 @itemx info port-rights
20762 @itemx info port-sets
20763 @itemx info dead-names
20766 @cindex send rights, @sc{gnu} Hurd
20767 @cindex receive rights, @sc{gnu} Hurd
20768 @cindex port rights, @sc{gnu} Hurd
20769 @cindex port sets, @sc{gnu} Hurd
20770 @cindex dead names, @sc{gnu} Hurd
20771 These commands display information about, respectively, send rights,
20772 receive rights, port rights, port sets, and dead names of a task.
20773 There are also shorthand aliases: @code{info ports} for @code{info
20774 port-rights} and @code{info psets} for @code{info port-sets}.
20776 @item set thread pause
20777 @kindex set thread@r{, Hurd command}
20778 @cindex thread properties, @sc{gnu} Hurd
20779 @cindex pause current thread (@sc{gnu} Hurd)
20780 This command toggles current thread suspension when @value{GDBN} has
20781 control. Setting it to on takes effect immediately, and the current
20782 thread is suspended whenever @value{GDBN} gets control. Setting it to
20783 off will take effect the next time the inferior is continued.
20784 Normally, this command has no effect, since when @value{GDBN} has
20785 control, the whole task is suspended. However, if you used @code{set
20786 task pause off} (see above), this command comes in handy to suspend
20787 only the current thread.
20789 @item show thread pause
20790 @kindex show thread@r{, Hurd command}
20791 This command shows the state of current thread suspension.
20793 @item set thread run
20794 This command sets whether the current thread is allowed to run.
20796 @item show thread run
20797 Show whether the current thread is allowed to run.
20799 @item set thread detach-suspend-count
20800 @cindex thread suspend count, @sc{gnu} Hurd
20801 @cindex detach from thread, @sc{gnu} Hurd
20802 This command sets the suspend count @value{GDBN} will leave on a
20803 thread when detaching. This number is relative to the suspend count
20804 found by @value{GDBN} when it notices the thread; use @code{set thread
20805 takeover-suspend-count} to force it to an absolute value.
20807 @item show thread detach-suspend-count
20808 Show the suspend count @value{GDBN} will leave on the thread when
20811 @item set thread exception-port
20812 @itemx set thread excp
20813 Set the thread exception port to which to forward exceptions. This
20814 overrides the port set by @code{set task exception-port} (see above).
20815 @code{set thread excp} is the shorthand alias.
20817 @item set thread takeover-suspend-count
20818 Normally, @value{GDBN}'s thread suspend counts are relative to the
20819 value @value{GDBN} finds when it notices each thread. This command
20820 changes the suspend counts to be absolute instead.
20822 @item set thread default
20823 @itemx show thread default
20824 @cindex thread default settings, @sc{gnu} Hurd
20825 Each of the above @code{set thread} commands has a @code{set thread
20826 default} counterpart (e.g., @code{set thread default pause}, @code{set
20827 thread default exception-port}, etc.). The @code{thread default}
20828 variety of commands sets the default thread properties for all
20829 threads; you can then change the properties of individual threads with
20830 the non-default commands.
20837 @value{GDBN} provides the following commands specific to the Darwin target:
20840 @item set debug darwin @var{num}
20841 @kindex set debug darwin
20842 When set to a non zero value, enables debugging messages specific to
20843 the Darwin support. Higher values produce more verbose output.
20845 @item show debug darwin
20846 @kindex show debug darwin
20847 Show the current state of Darwin messages.
20849 @item set debug mach-o @var{num}
20850 @kindex set debug mach-o
20851 When set to a non zero value, enables debugging messages while
20852 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
20853 file format used on Darwin for object and executable files.) Higher
20854 values produce more verbose output. This is a command to diagnose
20855 problems internal to @value{GDBN} and should not be needed in normal
20858 @item show debug mach-o
20859 @kindex show debug mach-o
20860 Show the current state of Mach-O file messages.
20862 @item set mach-exceptions on
20863 @itemx set mach-exceptions off
20864 @kindex set mach-exceptions
20865 On Darwin, faults are first reported as a Mach exception and are then
20866 mapped to a Posix signal. Use this command to turn on trapping of
20867 Mach exceptions in the inferior. This might be sometimes useful to
20868 better understand the cause of a fault. The default is off.
20870 @item show mach-exceptions
20871 @kindex show mach-exceptions
20872 Show the current state of exceptions trapping.
20877 @section Embedded Operating Systems
20879 This section describes configurations involving the debugging of
20880 embedded operating systems that are available for several different
20883 @value{GDBN} includes the ability to debug programs running on
20884 various real-time operating systems.
20886 @node Embedded Processors
20887 @section Embedded Processors
20889 This section goes into details specific to particular embedded
20892 @cindex send command to simulator
20893 Whenever a specific embedded processor has a simulator, @value{GDBN}
20894 allows to send an arbitrary command to the simulator.
20897 @item sim @var{command}
20898 @kindex sim@r{, a command}
20899 Send an arbitrary @var{command} string to the simulator. Consult the
20900 documentation for the specific simulator in use for information about
20901 acceptable commands.
20907 * M32R/D:: Renesas M32R/D
20908 * M68K:: Motorola M68K
20909 * MicroBlaze:: Xilinx MicroBlaze
20910 * MIPS Embedded:: MIPS Embedded
20911 * PowerPC Embedded:: PowerPC Embedded
20912 * PA:: HP PA Embedded
20913 * Sparclet:: Tsqware Sparclet
20914 * Sparclite:: Fujitsu Sparclite
20915 * Z8000:: Zilog Z8000
20918 * Super-H:: Renesas Super-H
20927 @item target rdi @var{dev}
20928 ARM Angel monitor, via RDI library interface to ADP protocol. You may
20929 use this target to communicate with both boards running the Angel
20930 monitor, or with the EmbeddedICE JTAG debug device.
20933 @item target rdp @var{dev}
20938 @value{GDBN} provides the following ARM-specific commands:
20941 @item set arm disassembler
20943 This commands selects from a list of disassembly styles. The
20944 @code{"std"} style is the standard style.
20946 @item show arm disassembler
20948 Show the current disassembly style.
20950 @item set arm apcs32
20951 @cindex ARM 32-bit mode
20952 This command toggles ARM operation mode between 32-bit and 26-bit.
20954 @item show arm apcs32
20955 Display the current usage of the ARM 32-bit mode.
20957 @item set arm fpu @var{fputype}
20958 This command sets the ARM floating-point unit (FPU) type. The
20959 argument @var{fputype} can be one of these:
20963 Determine the FPU type by querying the OS ABI.
20965 Software FPU, with mixed-endian doubles on little-endian ARM
20968 GCC-compiled FPA co-processor.
20970 Software FPU with pure-endian doubles.
20976 Show the current type of the FPU.
20979 This command forces @value{GDBN} to use the specified ABI.
20982 Show the currently used ABI.
20984 @item set arm fallback-mode (arm|thumb|auto)
20985 @value{GDBN} uses the symbol table, when available, to determine
20986 whether instructions are ARM or Thumb. This command controls
20987 @value{GDBN}'s default behavior when the symbol table is not
20988 available. The default is @samp{auto}, which causes @value{GDBN} to
20989 use the current execution mode (from the @code{T} bit in the @code{CPSR}
20992 @item show arm fallback-mode
20993 Show the current fallback instruction mode.
20995 @item set arm force-mode (arm|thumb|auto)
20996 This command overrides use of the symbol table to determine whether
20997 instructions are ARM or Thumb. The default is @samp{auto}, which
20998 causes @value{GDBN} to use the symbol table and then the setting
20999 of @samp{set arm fallback-mode}.
21001 @item show arm force-mode
21002 Show the current forced instruction mode.
21004 @item set debug arm
21005 Toggle whether to display ARM-specific debugging messages from the ARM
21006 target support subsystem.
21008 @item show debug arm
21009 Show whether ARM-specific debugging messages are enabled.
21012 The following commands are available when an ARM target is debugged
21013 using the RDI interface:
21016 @item rdilogfile @r{[}@var{file}@r{]}
21018 @cindex ADP (Angel Debugger Protocol) logging
21019 Set the filename for the ADP (Angel Debugger Protocol) packet log.
21020 With an argument, sets the log file to the specified @var{file}. With
21021 no argument, show the current log file name. The default log file is
21024 @item rdilogenable @r{[}@var{arg}@r{]}
21025 @kindex rdilogenable
21026 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
21027 enables logging, with an argument 0 or @code{"no"} disables it. With
21028 no arguments displays the current setting. When logging is enabled,
21029 ADP packets exchanged between @value{GDBN} and the RDI target device
21030 are logged to a file.
21032 @item set rdiromatzero
21033 @kindex set rdiromatzero
21034 @cindex ROM at zero address, RDI
21035 Tell @value{GDBN} whether the target has ROM at address 0. If on,
21036 vector catching is disabled, so that zero address can be used. If off
21037 (the default), vector catching is enabled. For this command to take
21038 effect, it needs to be invoked prior to the @code{target rdi} command.
21040 @item show rdiromatzero
21041 @kindex show rdiromatzero
21042 Show the current setting of ROM at zero address.
21044 @item set rdiheartbeat
21045 @kindex set rdiheartbeat
21046 @cindex RDI heartbeat
21047 Enable or disable RDI heartbeat packets. It is not recommended to
21048 turn on this option, since it confuses ARM and EPI JTAG interface, as
21049 well as the Angel monitor.
21051 @item show rdiheartbeat
21052 @kindex show rdiheartbeat
21053 Show the setting of RDI heartbeat packets.
21057 @item target sim @r{[}@var{simargs}@r{]} @dots{}
21058 The @value{GDBN} ARM simulator accepts the following optional arguments.
21061 @item --swi-support=@var{type}
21062 Tell the simulator which SWI interfaces to support. The argument
21063 @var{type} may be a comma separated list of the following values.
21064 The default value is @code{all}.
21077 @subsection Renesas M32R/D and M32R/SDI
21080 @kindex target m32r
21081 @item target m32r @var{dev}
21082 Renesas M32R/D ROM monitor.
21084 @kindex target m32rsdi
21085 @item target m32rsdi @var{dev}
21086 Renesas M32R SDI server, connected via parallel port to the board.
21089 The following @value{GDBN} commands are specific to the M32R monitor:
21092 @item set download-path @var{path}
21093 @kindex set download-path
21094 @cindex find downloadable @sc{srec} files (M32R)
21095 Set the default path for finding downloadable @sc{srec} files.
21097 @item show download-path
21098 @kindex show download-path
21099 Show the default path for downloadable @sc{srec} files.
21101 @item set board-address @var{addr}
21102 @kindex set board-address
21103 @cindex M32-EVA target board address
21104 Set the IP address for the M32R-EVA target board.
21106 @item show board-address
21107 @kindex show board-address
21108 Show the current IP address of the target board.
21110 @item set server-address @var{addr}
21111 @kindex set server-address
21112 @cindex download server address (M32R)
21113 Set the IP address for the download server, which is the @value{GDBN}'s
21116 @item show server-address
21117 @kindex show server-address
21118 Display the IP address of the download server.
21120 @item upload @r{[}@var{file}@r{]}
21121 @kindex upload@r{, M32R}
21122 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
21123 upload capability. If no @var{file} argument is given, the current
21124 executable file is uploaded.
21126 @item tload @r{[}@var{file}@r{]}
21127 @kindex tload@r{, M32R}
21128 Test the @code{upload} command.
21131 The following commands are available for M32R/SDI:
21136 @cindex reset SDI connection, M32R
21137 This command resets the SDI connection.
21141 This command shows the SDI connection status.
21144 @kindex debug_chaos
21145 @cindex M32R/Chaos debugging
21146 Instructs the remote that M32R/Chaos debugging is to be used.
21148 @item use_debug_dma
21149 @kindex use_debug_dma
21150 Instructs the remote to use the DEBUG_DMA method of accessing memory.
21153 @kindex use_mon_code
21154 Instructs the remote to use the MON_CODE method of accessing memory.
21157 @kindex use_ib_break
21158 Instructs the remote to set breakpoints by IB break.
21160 @item use_dbt_break
21161 @kindex use_dbt_break
21162 Instructs the remote to set breakpoints by DBT.
21168 The Motorola m68k configuration includes ColdFire support, and a
21169 target command for the following ROM monitor.
21173 @kindex target dbug
21174 @item target dbug @var{dev}
21175 dBUG ROM monitor for Motorola ColdFire.
21180 @subsection MicroBlaze
21181 @cindex Xilinx MicroBlaze
21182 @cindex XMD, Xilinx Microprocessor Debugger
21184 The MicroBlaze is a soft-core processor supported on various Xilinx
21185 FPGAs, such as Spartan or Virtex series. Boards with these processors
21186 usually have JTAG ports which connect to a host system running the Xilinx
21187 Embedded Development Kit (EDK) or Software Development Kit (SDK).
21188 This host system is used to download the configuration bitstream to
21189 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
21190 communicates with the target board using the JTAG interface and
21191 presents a @code{gdbserver} interface to the board. By default
21192 @code{xmd} uses port @code{1234}. (While it is possible to change
21193 this default port, it requires the use of undocumented @code{xmd}
21194 commands. Contact Xilinx support if you need to do this.)
21196 Use these GDB commands to connect to the MicroBlaze target processor.
21199 @item target remote :1234
21200 Use this command to connect to the target if you are running @value{GDBN}
21201 on the same system as @code{xmd}.
21203 @item target remote @var{xmd-host}:1234
21204 Use this command to connect to the target if it is connected to @code{xmd}
21205 running on a different system named @var{xmd-host}.
21208 Use this command to download a program to the MicroBlaze target.
21210 @item set debug microblaze @var{n}
21211 Enable MicroBlaze-specific debugging messages if non-zero.
21213 @item show debug microblaze @var{n}
21214 Show MicroBlaze-specific debugging level.
21217 @node MIPS Embedded
21218 @subsection @acronym{MIPS} Embedded
21220 @cindex @acronym{MIPS} boards
21221 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
21222 @acronym{MIPS} board attached to a serial line. This is available when
21223 you configure @value{GDBN} with @samp{--target=mips-elf}.
21226 Use these @value{GDBN} commands to specify the connection to your target board:
21229 @item target mips @var{port}
21230 @kindex target mips @var{port}
21231 To run a program on the board, start up @code{@value{GDBP}} with the
21232 name of your program as the argument. To connect to the board, use the
21233 command @samp{target mips @var{port}}, where @var{port} is the name of
21234 the serial port connected to the board. If the program has not already
21235 been downloaded to the board, you may use the @code{load} command to
21236 download it. You can then use all the usual @value{GDBN} commands.
21238 For example, this sequence connects to the target board through a serial
21239 port, and loads and runs a program called @var{prog} through the
21243 host$ @value{GDBP} @var{prog}
21244 @value{GDBN} is free software and @dots{}
21245 (@value{GDBP}) target mips /dev/ttyb
21246 (@value{GDBP}) load @var{prog}
21250 @item target mips @var{hostname}:@var{portnumber}
21251 On some @value{GDBN} host configurations, you can specify a TCP
21252 connection (for instance, to a serial line managed by a terminal
21253 concentrator) instead of a serial port, using the syntax
21254 @samp{@var{hostname}:@var{portnumber}}.
21256 @item target pmon @var{port}
21257 @kindex target pmon @var{port}
21260 @item target ddb @var{port}
21261 @kindex target ddb @var{port}
21262 NEC's DDB variant of PMON for Vr4300.
21264 @item target lsi @var{port}
21265 @kindex target lsi @var{port}
21266 LSI variant of PMON.
21268 @kindex target r3900
21269 @item target r3900 @var{dev}
21270 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
21272 @kindex target array
21273 @item target array @var{dev}
21274 Array Tech LSI33K RAID controller board.
21280 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
21283 @item set mipsfpu double
21284 @itemx set mipsfpu single
21285 @itemx set mipsfpu none
21286 @itemx set mipsfpu auto
21287 @itemx show mipsfpu
21288 @kindex set mipsfpu
21289 @kindex show mipsfpu
21290 @cindex @acronym{MIPS} remote floating point
21291 @cindex floating point, @acronym{MIPS} remote
21292 If your target board does not support the @acronym{MIPS} floating point
21293 coprocessor, you should use the command @samp{set mipsfpu none} (if you
21294 need this, you may wish to put the command in your @value{GDBN} init
21295 file). This tells @value{GDBN} how to find the return value of
21296 functions which return floating point values. It also allows
21297 @value{GDBN} to avoid saving the floating point registers when calling
21298 functions on the board. If you are using a floating point coprocessor
21299 with only single precision floating point support, as on the @sc{r4650}
21300 processor, use the command @samp{set mipsfpu single}. The default
21301 double precision floating point coprocessor may be selected using
21302 @samp{set mipsfpu double}.
21304 In previous versions the only choices were double precision or no
21305 floating point, so @samp{set mipsfpu on} will select double precision
21306 and @samp{set mipsfpu off} will select no floating point.
21308 As usual, you can inquire about the @code{mipsfpu} variable with
21309 @samp{show mipsfpu}.
21311 @item set timeout @var{seconds}
21312 @itemx set retransmit-timeout @var{seconds}
21313 @itemx show timeout
21314 @itemx show retransmit-timeout
21315 @cindex @code{timeout}, @acronym{MIPS} protocol
21316 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
21317 @kindex set timeout
21318 @kindex show timeout
21319 @kindex set retransmit-timeout
21320 @kindex show retransmit-timeout
21321 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
21322 remote protocol, with the @code{set timeout @var{seconds}} command. The
21323 default is 5 seconds. Similarly, you can control the timeout used while
21324 waiting for an acknowledgment of a packet with the @code{set
21325 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
21326 You can inspect both values with @code{show timeout} and @code{show
21327 retransmit-timeout}. (These commands are @emph{only} available when
21328 @value{GDBN} is configured for @samp{--target=mips-elf}.)
21330 The timeout set by @code{set timeout} does not apply when @value{GDBN}
21331 is waiting for your program to stop. In that case, @value{GDBN} waits
21332 forever because it has no way of knowing how long the program is going
21333 to run before stopping.
21335 @item set syn-garbage-limit @var{num}
21336 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
21337 @cindex synchronize with remote @acronym{MIPS} target
21338 Limit the maximum number of characters @value{GDBN} should ignore when
21339 it tries to synchronize with the remote target. The default is 10
21340 characters. Setting the limit to -1 means there's no limit.
21342 @item show syn-garbage-limit
21343 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
21344 Show the current limit on the number of characters to ignore when
21345 trying to synchronize with the remote system.
21347 @item set monitor-prompt @var{prompt}
21348 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
21349 @cindex remote monitor prompt
21350 Tell @value{GDBN} to expect the specified @var{prompt} string from the
21351 remote monitor. The default depends on the target:
21361 @item show monitor-prompt
21362 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
21363 Show the current strings @value{GDBN} expects as the prompt from the
21366 @item set monitor-warnings
21367 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
21368 Enable or disable monitor warnings about hardware breakpoints. This
21369 has effect only for the @code{lsi} target. When on, @value{GDBN} will
21370 display warning messages whose codes are returned by the @code{lsi}
21371 PMON monitor for breakpoint commands.
21373 @item show monitor-warnings
21374 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
21375 Show the current setting of printing monitor warnings.
21377 @item pmon @var{command}
21378 @kindex pmon@r{, @acronym{MIPS} remote}
21379 @cindex send PMON command
21380 This command allows sending an arbitrary @var{command} string to the
21381 monitor. The monitor must be in debug mode for this to work.
21384 @node PowerPC Embedded
21385 @subsection PowerPC Embedded
21387 @cindex DVC register
21388 @value{GDBN} supports using the DVC (Data Value Compare) register to
21389 implement in hardware simple hardware watchpoint conditions of the form:
21392 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
21393 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
21396 The DVC register will be automatically used when @value{GDBN} detects
21397 such pattern in a condition expression, and the created watchpoint uses one
21398 debug register (either the @code{exact-watchpoints} option is on and the
21399 variable is scalar, or the variable has a length of one byte). This feature
21400 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
21403 When running on PowerPC embedded processors, @value{GDBN} automatically uses
21404 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
21405 in which case watchpoints using only one debug register are created when
21406 watching variables of scalar types.
21408 You can create an artificial array to watch an arbitrary memory
21409 region using one of the following commands (@pxref{Expressions}):
21412 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
21413 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
21416 PowerPC embedded processors support masked watchpoints. See the discussion
21417 about the @code{mask} argument in @ref{Set Watchpoints}.
21419 @cindex ranged breakpoint
21420 PowerPC embedded processors support hardware accelerated
21421 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
21422 the inferior whenever it executes an instruction at any address within
21423 the range it specifies. To set a ranged breakpoint in @value{GDBN},
21424 use the @code{break-range} command.
21426 @value{GDBN} provides the following PowerPC-specific commands:
21429 @kindex break-range
21430 @item break-range @var{start-location}, @var{end-location}
21431 Set a breakpoint for an address range given by
21432 @var{start-location} and @var{end-location}, which can specify a function name,
21433 a line number, an offset of lines from the current line or from the start
21434 location, or an address of an instruction (see @ref{Specify Location},
21435 for a list of all the possible ways to specify a @var{location}.)
21436 The breakpoint will stop execution of the inferior whenever it
21437 executes an instruction at any address within the specified range,
21438 (including @var{start-location} and @var{end-location}.)
21440 @kindex set powerpc
21441 @item set powerpc soft-float
21442 @itemx show powerpc soft-float
21443 Force @value{GDBN} to use (or not use) a software floating point calling
21444 convention. By default, @value{GDBN} selects the calling convention based
21445 on the selected architecture and the provided executable file.
21447 @item set powerpc vector-abi
21448 @itemx show powerpc vector-abi
21449 Force @value{GDBN} to use the specified calling convention for vector
21450 arguments and return values. The valid options are @samp{auto};
21451 @samp{generic}, to avoid vector registers even if they are present;
21452 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
21453 registers. By default, @value{GDBN} selects the calling convention
21454 based on the selected architecture and the provided executable file.
21456 @item set powerpc exact-watchpoints
21457 @itemx show powerpc exact-watchpoints
21458 Allow @value{GDBN} to use only one debug register when watching a variable
21459 of scalar type, thus assuming that the variable is accessed through the
21460 address of its first byte.
21462 @kindex target dink32
21463 @item target dink32 @var{dev}
21464 DINK32 ROM monitor.
21466 @kindex target ppcbug
21467 @item target ppcbug @var{dev}
21468 @kindex target ppcbug1
21469 @item target ppcbug1 @var{dev}
21470 PPCBUG ROM monitor for PowerPC.
21473 @item target sds @var{dev}
21474 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
21477 @cindex SDS protocol
21478 The following commands specific to the SDS protocol are supported
21482 @item set sdstimeout @var{nsec}
21483 @kindex set sdstimeout
21484 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
21485 default is 2 seconds.
21487 @item show sdstimeout
21488 @kindex show sdstimeout
21489 Show the current value of the SDS timeout.
21491 @item sds @var{command}
21492 @kindex sds@r{, a command}
21493 Send the specified @var{command} string to the SDS monitor.
21498 @subsection HP PA Embedded
21502 @kindex target op50n
21503 @item target op50n @var{dev}
21504 OP50N monitor, running on an OKI HPPA board.
21506 @kindex target w89k
21507 @item target w89k @var{dev}
21508 W89K monitor, running on a Winbond HPPA board.
21513 @subsection Tsqware Sparclet
21517 @value{GDBN} enables developers to debug tasks running on
21518 Sparclet targets from a Unix host.
21519 @value{GDBN} uses code that runs on
21520 both the Unix host and on the Sparclet target. The program
21521 @code{@value{GDBP}} is installed and executed on the Unix host.
21524 @item remotetimeout @var{args}
21525 @kindex remotetimeout
21526 @value{GDBN} supports the option @code{remotetimeout}.
21527 This option is set by the user, and @var{args} represents the number of
21528 seconds @value{GDBN} waits for responses.
21531 @cindex compiling, on Sparclet
21532 When compiling for debugging, include the options @samp{-g} to get debug
21533 information and @samp{-Ttext} to relocate the program to where you wish to
21534 load it on the target. You may also want to add the options @samp{-n} or
21535 @samp{-N} in order to reduce the size of the sections. Example:
21538 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
21541 You can use @code{objdump} to verify that the addresses are what you intended:
21544 sparclet-aout-objdump --headers --syms prog
21547 @cindex running, on Sparclet
21549 your Unix execution search path to find @value{GDBN}, you are ready to
21550 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
21551 (or @code{sparclet-aout-gdb}, depending on your installation).
21553 @value{GDBN} comes up showing the prompt:
21560 * Sparclet File:: Setting the file to debug
21561 * Sparclet Connection:: Connecting to Sparclet
21562 * Sparclet Download:: Sparclet download
21563 * Sparclet Execution:: Running and debugging
21566 @node Sparclet File
21567 @subsubsection Setting File to Debug
21569 The @value{GDBN} command @code{file} lets you choose with program to debug.
21572 (gdbslet) file prog
21576 @value{GDBN} then attempts to read the symbol table of @file{prog}.
21577 @value{GDBN} locates
21578 the file by searching the directories listed in the command search
21580 If the file was compiled with debug information (option @samp{-g}), source
21581 files will be searched as well.
21582 @value{GDBN} locates
21583 the source files by searching the directories listed in the directory search
21584 path (@pxref{Environment, ,Your Program's Environment}).
21586 to find a file, it displays a message such as:
21589 prog: No such file or directory.
21592 When this happens, add the appropriate directories to the search paths with
21593 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
21594 @code{target} command again.
21596 @node Sparclet Connection
21597 @subsubsection Connecting to Sparclet
21599 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
21600 To connect to a target on serial port ``@code{ttya}'', type:
21603 (gdbslet) target sparclet /dev/ttya
21604 Remote target sparclet connected to /dev/ttya
21605 main () at ../prog.c:3
21609 @value{GDBN} displays messages like these:
21615 @node Sparclet Download
21616 @subsubsection Sparclet Download
21618 @cindex download to Sparclet
21619 Once connected to the Sparclet target,
21620 you can use the @value{GDBN}
21621 @code{load} command to download the file from the host to the target.
21622 The file name and load offset should be given as arguments to the @code{load}
21624 Since the file format is aout, the program must be loaded to the starting
21625 address. You can use @code{objdump} to find out what this value is. The load
21626 offset is an offset which is added to the VMA (virtual memory address)
21627 of each of the file's sections.
21628 For instance, if the program
21629 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
21630 and bss at 0x12010170, in @value{GDBN}, type:
21633 (gdbslet) load prog 0x12010000
21634 Loading section .text, size 0xdb0 vma 0x12010000
21637 If the code is loaded at a different address then what the program was linked
21638 to, you may need to use the @code{section} and @code{add-symbol-file} commands
21639 to tell @value{GDBN} where to map the symbol table.
21641 @node Sparclet Execution
21642 @subsubsection Running and Debugging
21644 @cindex running and debugging Sparclet programs
21645 You can now begin debugging the task using @value{GDBN}'s execution control
21646 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
21647 manual for the list of commands.
21651 Breakpoint 1 at 0x12010000: file prog.c, line 3.
21653 Starting program: prog
21654 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
21655 3 char *symarg = 0;
21657 4 char *execarg = "hello!";
21662 @subsection Fujitsu Sparclite
21666 @kindex target sparclite
21667 @item target sparclite @var{dev}
21668 Fujitsu sparclite boards, used only for the purpose of loading.
21669 You must use an additional command to debug the program.
21670 For example: target remote @var{dev} using @value{GDBN} standard
21676 @subsection Zilog Z8000
21679 @cindex simulator, Z8000
21680 @cindex Zilog Z8000 simulator
21682 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
21685 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
21686 unsegmented variant of the Z8000 architecture) or the Z8001 (the
21687 segmented variant). The simulator recognizes which architecture is
21688 appropriate by inspecting the object code.
21691 @item target sim @var{args}
21693 @kindex target sim@r{, with Z8000}
21694 Debug programs on a simulated CPU. If the simulator supports setup
21695 options, specify them via @var{args}.
21699 After specifying this target, you can debug programs for the simulated
21700 CPU in the same style as programs for your host computer; use the
21701 @code{file} command to load a new program image, the @code{run} command
21702 to run your program, and so on.
21704 As well as making available all the usual machine registers
21705 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
21706 additional items of information as specially named registers:
21711 Counts clock-ticks in the simulator.
21714 Counts instructions run in the simulator.
21717 Execution time in 60ths of a second.
21721 You can refer to these values in @value{GDBN} expressions with the usual
21722 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
21723 conditional breakpoint that suspends only after at least 5000
21724 simulated clock ticks.
21727 @subsection Atmel AVR
21730 When configured for debugging the Atmel AVR, @value{GDBN} supports the
21731 following AVR-specific commands:
21734 @item info io_registers
21735 @kindex info io_registers@r{, AVR}
21736 @cindex I/O registers (Atmel AVR)
21737 This command displays information about the AVR I/O registers. For
21738 each register, @value{GDBN} prints its number and value.
21745 When configured for debugging CRIS, @value{GDBN} provides the
21746 following CRIS-specific commands:
21749 @item set cris-version @var{ver}
21750 @cindex CRIS version
21751 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
21752 The CRIS version affects register names and sizes. This command is useful in
21753 case autodetection of the CRIS version fails.
21755 @item show cris-version
21756 Show the current CRIS version.
21758 @item set cris-dwarf2-cfi
21759 @cindex DWARF-2 CFI and CRIS
21760 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
21761 Change to @samp{off} when using @code{gcc-cris} whose version is below
21764 @item show cris-dwarf2-cfi
21765 Show the current state of using DWARF-2 CFI.
21767 @item set cris-mode @var{mode}
21769 Set the current CRIS mode to @var{mode}. It should only be changed when
21770 debugging in guru mode, in which case it should be set to
21771 @samp{guru} (the default is @samp{normal}).
21773 @item show cris-mode
21774 Show the current CRIS mode.
21778 @subsection Renesas Super-H
21781 For the Renesas Super-H processor, @value{GDBN} provides these
21785 @item set sh calling-convention @var{convention}
21786 @kindex set sh calling-convention
21787 Set the calling-convention used when calling functions from @value{GDBN}.
21788 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
21789 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
21790 convention. If the DWARF-2 information of the called function specifies
21791 that the function follows the Renesas calling convention, the function
21792 is called using the Renesas calling convention. If the calling convention
21793 is set to @samp{renesas}, the Renesas calling convention is always used,
21794 regardless of the DWARF-2 information. This can be used to override the
21795 default of @samp{gcc} if debug information is missing, or the compiler
21796 does not emit the DWARF-2 calling convention entry for a function.
21798 @item show sh calling-convention
21799 @kindex show sh calling-convention
21800 Show the current calling convention setting.
21805 @node Architectures
21806 @section Architectures
21808 This section describes characteristics of architectures that affect
21809 all uses of @value{GDBN} with the architecture, both native and cross.
21816 * HPPA:: HP PA architecture
21817 * SPU:: Cell Broadband Engine SPU architecture
21823 @subsection AArch64
21824 @cindex AArch64 support
21826 When @value{GDBN} is debugging the AArch64 architecture, it provides the
21827 following special commands:
21830 @item set debug aarch64
21831 @kindex set debug aarch64
21832 This command determines whether AArch64 architecture-specific debugging
21833 messages are to be displayed.
21835 @item show debug aarch64
21836 Show whether AArch64 debugging messages are displayed.
21841 @subsection x86 Architecture-specific Issues
21844 @item set struct-convention @var{mode}
21845 @kindex set struct-convention
21846 @cindex struct return convention
21847 @cindex struct/union returned in registers
21848 Set the convention used by the inferior to return @code{struct}s and
21849 @code{union}s from functions to @var{mode}. Possible values of
21850 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
21851 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
21852 are returned on the stack, while @code{"reg"} means that a
21853 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
21854 be returned in a register.
21856 @item show struct-convention
21857 @kindex show struct-convention
21858 Show the current setting of the convention to return @code{struct}s
21862 @subsubsection Intel(R) @dfn{Memory Protection Extensions} (MPX).
21863 @cindex Intel(R) Memory Protection Extensions (MPX).
21865 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
21866 @footnote{The register named with capital letters represent the architecture
21867 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
21868 which are the lower bound and upper bound. Bounds are effective addresses or
21869 memory locations. The upper bounds are architecturally represented in 1's
21870 complement form. A bound having lower bound = 0, and upper bound = 0
21871 (1's complement of all bits set) will allow access to the entire address space.
21873 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
21874 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
21875 display the upper bound performing the complement of one operation on the
21876 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
21877 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
21878 can also be noted that the upper bounds are inclusive.
21880 As an example, assume that the register BND0 holds bounds for a pointer having
21881 access allowed for the range between 0x32 and 0x71. The values present on
21882 bnd0raw and bnd registers are presented as follows:
21885 bnd0raw = @{0x32, 0xffffffff8e@}
21886 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
21889 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
21890 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
21891 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
21892 Python, the display includes the memory size, in bits, accessible to
21898 See the following section.
21901 @subsection @acronym{MIPS}
21903 @cindex stack on Alpha
21904 @cindex stack on @acronym{MIPS}
21905 @cindex Alpha stack
21906 @cindex @acronym{MIPS} stack
21907 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
21908 sometimes requires @value{GDBN} to search backward in the object code to
21909 find the beginning of a function.
21911 @cindex response time, @acronym{MIPS} debugging
21912 To improve response time (especially for embedded applications, where
21913 @value{GDBN} may be restricted to a slow serial line for this search)
21914 you may want to limit the size of this search, using one of these
21918 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
21919 @item set heuristic-fence-post @var{limit}
21920 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
21921 search for the beginning of a function. A value of @var{0} (the
21922 default) means there is no limit. However, except for @var{0}, the
21923 larger the limit the more bytes @code{heuristic-fence-post} must search
21924 and therefore the longer it takes to run. You should only need to use
21925 this command when debugging a stripped executable.
21927 @item show heuristic-fence-post
21928 Display the current limit.
21932 These commands are available @emph{only} when @value{GDBN} is configured
21933 for debugging programs on Alpha or @acronym{MIPS} processors.
21935 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
21939 @item set mips abi @var{arg}
21940 @kindex set mips abi
21941 @cindex set ABI for @acronym{MIPS}
21942 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
21943 values of @var{arg} are:
21947 The default ABI associated with the current binary (this is the
21957 @item show mips abi
21958 @kindex show mips abi
21959 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
21961 @item set mips compression @var{arg}
21962 @kindex set mips compression
21963 @cindex code compression, @acronym{MIPS}
21964 Tell @value{GDBN} which @acronym{MIPS} compressed
21965 @acronym{ISA, Instruction Set Architecture} encoding is used by the
21966 inferior. @value{GDBN} uses this for code disassembly and other
21967 internal interpretation purposes. This setting is only referred to
21968 when no executable has been associated with the debugging session or
21969 the executable does not provide information about the encoding it uses.
21970 Otherwise this setting is automatically updated from information
21971 provided by the executable.
21973 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
21974 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
21975 executables containing @acronym{MIPS16} code frequently are not
21976 identified as such.
21978 This setting is ``sticky''; that is, it retains its value across
21979 debugging sessions until reset either explicitly with this command or
21980 implicitly from an executable.
21982 The compiler and/or assembler typically add symbol table annotations to
21983 identify functions compiled for the @acronym{MIPS16} or
21984 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
21985 are present, @value{GDBN} uses them in preference to the global
21986 compressed @acronym{ISA} encoding setting.
21988 @item show mips compression
21989 @kindex show mips compression
21990 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
21991 @value{GDBN} to debug the inferior.
21994 @itemx show mipsfpu
21995 @xref{MIPS Embedded, set mipsfpu}.
21997 @item set mips mask-address @var{arg}
21998 @kindex set mips mask-address
21999 @cindex @acronym{MIPS} addresses, masking
22000 This command determines whether the most-significant 32 bits of 64-bit
22001 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
22002 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
22003 setting, which lets @value{GDBN} determine the correct value.
22005 @item show mips mask-address
22006 @kindex show mips mask-address
22007 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
22010 @item set remote-mips64-transfers-32bit-regs
22011 @kindex set remote-mips64-transfers-32bit-regs
22012 This command controls compatibility with 64-bit @acronym{MIPS} targets that
22013 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
22014 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
22015 and 64 bits for other registers, set this option to @samp{on}.
22017 @item show remote-mips64-transfers-32bit-regs
22018 @kindex show remote-mips64-transfers-32bit-regs
22019 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
22021 @item set debug mips
22022 @kindex set debug mips
22023 This command turns on and off debugging messages for the @acronym{MIPS}-specific
22024 target code in @value{GDBN}.
22026 @item show debug mips
22027 @kindex show debug mips
22028 Show the current setting of @acronym{MIPS} debugging messages.
22034 @cindex HPPA support
22036 When @value{GDBN} is debugging the HP PA architecture, it provides the
22037 following special commands:
22040 @item set debug hppa
22041 @kindex set debug hppa
22042 This command determines whether HPPA architecture-specific debugging
22043 messages are to be displayed.
22045 @item show debug hppa
22046 Show whether HPPA debugging messages are displayed.
22048 @item maint print unwind @var{address}
22049 @kindex maint print unwind@r{, HPPA}
22050 This command displays the contents of the unwind table entry at the
22051 given @var{address}.
22057 @subsection Cell Broadband Engine SPU architecture
22058 @cindex Cell Broadband Engine
22061 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
22062 it provides the following special commands:
22065 @item info spu event
22067 Display SPU event facility status. Shows current event mask
22068 and pending event status.
22070 @item info spu signal
22071 Display SPU signal notification facility status. Shows pending
22072 signal-control word and signal notification mode of both signal
22073 notification channels.
22075 @item info spu mailbox
22076 Display SPU mailbox facility status. Shows all pending entries,
22077 in order of processing, in each of the SPU Write Outbound,
22078 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
22081 Display MFC DMA status. Shows all pending commands in the MFC
22082 DMA queue. For each entry, opcode, tag, class IDs, effective
22083 and local store addresses and transfer size are shown.
22085 @item info spu proxydma
22086 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
22087 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
22088 and local store addresses and transfer size are shown.
22092 When @value{GDBN} is debugging a combined PowerPC/SPU application
22093 on the Cell Broadband Engine, it provides in addition the following
22097 @item set spu stop-on-load @var{arg}
22099 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
22100 will give control to the user when a new SPE thread enters its @code{main}
22101 function. The default is @code{off}.
22103 @item show spu stop-on-load
22105 Show whether to stop for new SPE threads.
22107 @item set spu auto-flush-cache @var{arg}
22108 Set whether to automatically flush the software-managed cache. When set to
22109 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
22110 cache to be flushed whenever SPE execution stops. This provides a consistent
22111 view of PowerPC memory that is accessed via the cache. If an application
22112 does not use the software-managed cache, this option has no effect.
22114 @item show spu auto-flush-cache
22115 Show whether to automatically flush the software-managed cache.
22120 @subsection PowerPC
22121 @cindex PowerPC architecture
22123 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
22124 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
22125 numbers stored in the floating point registers. These values must be stored
22126 in two consecutive registers, always starting at an even register like
22127 @code{f0} or @code{f2}.
22129 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
22130 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
22131 @code{f2} and @code{f3} for @code{$dl1} and so on.
22133 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
22134 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
22137 @subsection Nios II
22138 @cindex Nios II architecture
22140 When @value{GDBN} is debugging the Nios II architecture,
22141 it provides the following special commands:
22145 @item set debug nios2
22146 @kindex set debug nios2
22147 This command turns on and off debugging messages for the Nios II
22148 target code in @value{GDBN}.
22150 @item show debug nios2
22151 @kindex show debug nios2
22152 Show the current setting of Nios II debugging messages.
22155 @node Controlling GDB
22156 @chapter Controlling @value{GDBN}
22158 You can alter the way @value{GDBN} interacts with you by using the
22159 @code{set} command. For commands controlling how @value{GDBN} displays
22160 data, see @ref{Print Settings, ,Print Settings}. Other settings are
22165 * Editing:: Command editing
22166 * Command History:: Command history
22167 * Screen Size:: Screen size
22168 * Numbers:: Numbers
22169 * ABI:: Configuring the current ABI
22170 * Auto-loading:: Automatically loading associated files
22171 * Messages/Warnings:: Optional warnings and messages
22172 * Debugging Output:: Optional messages about internal happenings
22173 * Other Misc Settings:: Other Miscellaneous Settings
22181 @value{GDBN} indicates its readiness to read a command by printing a string
22182 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
22183 can change the prompt string with the @code{set prompt} command. For
22184 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
22185 the prompt in one of the @value{GDBN} sessions so that you can always tell
22186 which one you are talking to.
22188 @emph{Note:} @code{set prompt} does not add a space for you after the
22189 prompt you set. This allows you to set a prompt which ends in a space
22190 or a prompt that does not.
22194 @item set prompt @var{newprompt}
22195 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
22197 @kindex show prompt
22199 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
22202 Versions of @value{GDBN} that ship with Python scripting enabled have
22203 prompt extensions. The commands for interacting with these extensions
22207 @kindex set extended-prompt
22208 @item set extended-prompt @var{prompt}
22209 Set an extended prompt that allows for substitutions.
22210 @xref{gdb.prompt}, for a list of escape sequences that can be used for
22211 substitution. Any escape sequences specified as part of the prompt
22212 string are replaced with the corresponding strings each time the prompt
22218 set extended-prompt Current working directory: \w (gdb)
22221 Note that when an extended-prompt is set, it takes control of the
22222 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
22224 @kindex show extended-prompt
22225 @item show extended-prompt
22226 Prints the extended prompt. Any escape sequences specified as part of
22227 the prompt string with @code{set extended-prompt}, are replaced with the
22228 corresponding strings each time the prompt is displayed.
22232 @section Command Editing
22234 @cindex command line editing
22236 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
22237 @sc{gnu} library provides consistent behavior for programs which provide a
22238 command line interface to the user. Advantages are @sc{gnu} Emacs-style
22239 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
22240 substitution, and a storage and recall of command history across
22241 debugging sessions.
22243 You may control the behavior of command line editing in @value{GDBN} with the
22244 command @code{set}.
22247 @kindex set editing
22250 @itemx set editing on
22251 Enable command line editing (enabled by default).
22253 @item set editing off
22254 Disable command line editing.
22256 @kindex show editing
22258 Show whether command line editing is enabled.
22261 @ifset SYSTEM_READLINE
22262 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
22264 @ifclear SYSTEM_READLINE
22265 @xref{Command Line Editing},
22267 for more details about the Readline
22268 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
22269 encouraged to read that chapter.
22271 @node Command History
22272 @section Command History
22273 @cindex command history
22275 @value{GDBN} can keep track of the commands you type during your
22276 debugging sessions, so that you can be certain of precisely what
22277 happened. Use these commands to manage the @value{GDBN} command
22280 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
22281 package, to provide the history facility.
22282 @ifset SYSTEM_READLINE
22283 @xref{Using History Interactively, , , history, GNU History Library},
22285 @ifclear SYSTEM_READLINE
22286 @xref{Using History Interactively},
22288 for the detailed description of the History library.
22290 To issue a command to @value{GDBN} without affecting certain aspects of
22291 the state which is seen by users, prefix it with @samp{server }
22292 (@pxref{Server Prefix}). This
22293 means that this command will not affect the command history, nor will it
22294 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
22295 pressed on a line by itself.
22297 @cindex @code{server}, command prefix
22298 The server prefix does not affect the recording of values into the value
22299 history; to print a value without recording it into the value history,
22300 use the @code{output} command instead of the @code{print} command.
22302 Here is the description of @value{GDBN} commands related to command
22306 @cindex history substitution
22307 @cindex history file
22308 @kindex set history filename
22309 @cindex @env{GDBHISTFILE}, environment variable
22310 @item set history filename @var{fname}
22311 Set the name of the @value{GDBN} command history file to @var{fname}.
22312 This is the file where @value{GDBN} reads an initial command history
22313 list, and where it writes the command history from this session when it
22314 exits. You can access this list through history expansion or through
22315 the history command editing characters listed below. This file defaults
22316 to the value of the environment variable @code{GDBHISTFILE}, or to
22317 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
22320 @cindex save command history
22321 @kindex set history save
22322 @item set history save
22323 @itemx set history save on
22324 Record command history in a file, whose name may be specified with the
22325 @code{set history filename} command. By default, this option is disabled.
22327 @item set history save off
22328 Stop recording command history in a file.
22330 @cindex history size
22331 @kindex set history size
22332 @cindex @env{HISTSIZE}, environment variable
22333 @item set history size @var{size}
22334 @itemx set history size unlimited
22335 Set the number of commands which @value{GDBN} keeps in its history list.
22336 This defaults to the value of the environment variable
22337 @code{HISTSIZE}, or to 256 if this variable is not set. If @var{size}
22338 is @code{unlimited}, the number of commands @value{GDBN} keeps in the
22339 history list is unlimited.
22342 History expansion assigns special meaning to the character @kbd{!}.
22343 @ifset SYSTEM_READLINE
22344 @xref{Event Designators, , , history, GNU History Library},
22346 @ifclear SYSTEM_READLINE
22347 @xref{Event Designators},
22351 @cindex history expansion, turn on/off
22352 Since @kbd{!} is also the logical not operator in C, history expansion
22353 is off by default. If you decide to enable history expansion with the
22354 @code{set history expansion on} command, you may sometimes need to
22355 follow @kbd{!} (when it is used as logical not, in an expression) with
22356 a space or a tab to prevent it from being expanded. The readline
22357 history facilities do not attempt substitution on the strings
22358 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
22360 The commands to control history expansion are:
22363 @item set history expansion on
22364 @itemx set history expansion
22365 @kindex set history expansion
22366 Enable history expansion. History expansion is off by default.
22368 @item set history expansion off
22369 Disable history expansion.
22372 @kindex show history
22374 @itemx show history filename
22375 @itemx show history save
22376 @itemx show history size
22377 @itemx show history expansion
22378 These commands display the state of the @value{GDBN} history parameters.
22379 @code{show history} by itself displays all four states.
22384 @kindex show commands
22385 @cindex show last commands
22386 @cindex display command history
22387 @item show commands
22388 Display the last ten commands in the command history.
22390 @item show commands @var{n}
22391 Print ten commands centered on command number @var{n}.
22393 @item show commands +
22394 Print ten commands just after the commands last printed.
22398 @section Screen Size
22399 @cindex size of screen
22400 @cindex screen size
22403 @cindex pauses in output
22405 Certain commands to @value{GDBN} may produce large amounts of
22406 information output to the screen. To help you read all of it,
22407 @value{GDBN} pauses and asks you for input at the end of each page of
22408 output. Type @key{RET} when you want to continue the output, or @kbd{q}
22409 to discard the remaining output. Also, the screen width setting
22410 determines when to wrap lines of output. Depending on what is being
22411 printed, @value{GDBN} tries to break the line at a readable place,
22412 rather than simply letting it overflow onto the following line.
22414 Normally @value{GDBN} knows the size of the screen from the terminal
22415 driver software. For example, on Unix @value{GDBN} uses the termcap data base
22416 together with the value of the @code{TERM} environment variable and the
22417 @code{stty rows} and @code{stty cols} settings. If this is not correct,
22418 you can override it with the @code{set height} and @code{set
22425 @kindex show height
22426 @item set height @var{lpp}
22427 @itemx set height unlimited
22429 @itemx set width @var{cpl}
22430 @itemx set width unlimited
22432 These @code{set} commands specify a screen height of @var{lpp} lines and
22433 a screen width of @var{cpl} characters. The associated @code{show}
22434 commands display the current settings.
22436 If you specify a height of either @code{unlimited} or zero lines,
22437 @value{GDBN} does not pause during output no matter how long the
22438 output is. This is useful if output is to a file or to an editor
22441 Likewise, you can specify @samp{set width unlimited} or @samp{set
22442 width 0} to prevent @value{GDBN} from wrapping its output.
22444 @item set pagination on
22445 @itemx set pagination off
22446 @kindex set pagination
22447 Turn the output pagination on or off; the default is on. Turning
22448 pagination off is the alternative to @code{set height unlimited}. Note that
22449 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
22450 Options, -batch}) also automatically disables pagination.
22452 @item show pagination
22453 @kindex show pagination
22454 Show the current pagination mode.
22459 @cindex number representation
22460 @cindex entering numbers
22462 You can always enter numbers in octal, decimal, or hexadecimal in
22463 @value{GDBN} by the usual conventions: octal numbers begin with
22464 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
22465 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
22466 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
22467 10; likewise, the default display for numbers---when no particular
22468 format is specified---is base 10. You can change the default base for
22469 both input and output with the commands described below.
22472 @kindex set input-radix
22473 @item set input-radix @var{base}
22474 Set the default base for numeric input. Supported choices
22475 for @var{base} are decimal 8, 10, or 16. The base must itself be
22476 specified either unambiguously or using the current input radix; for
22480 set input-radix 012
22481 set input-radix 10.
22482 set input-radix 0xa
22486 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
22487 leaves the input radix unchanged, no matter what it was, since
22488 @samp{10}, being without any leading or trailing signs of its base, is
22489 interpreted in the current radix. Thus, if the current radix is 16,
22490 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
22493 @kindex set output-radix
22494 @item set output-radix @var{base}
22495 Set the default base for numeric display. Supported choices
22496 for @var{base} are decimal 8, 10, or 16. The base must itself be
22497 specified either unambiguously or using the current input radix.
22499 @kindex show input-radix
22500 @item show input-radix
22501 Display the current default base for numeric input.
22503 @kindex show output-radix
22504 @item show output-radix
22505 Display the current default base for numeric display.
22507 @item set radix @r{[}@var{base}@r{]}
22511 These commands set and show the default base for both input and output
22512 of numbers. @code{set radix} sets the radix of input and output to
22513 the same base; without an argument, it resets the radix back to its
22514 default value of 10.
22519 @section Configuring the Current ABI
22521 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
22522 application automatically. However, sometimes you need to override its
22523 conclusions. Use these commands to manage @value{GDBN}'s view of the
22529 @cindex Newlib OS ABI and its influence on the longjmp handling
22531 One @value{GDBN} configuration can debug binaries for multiple operating
22532 system targets, either via remote debugging or native emulation.
22533 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
22534 but you can override its conclusion using the @code{set osabi} command.
22535 One example where this is useful is in debugging of binaries which use
22536 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
22537 not have the same identifying marks that the standard C library for your
22540 When @value{GDBN} is debugging the AArch64 architecture, it provides a
22541 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
22542 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
22543 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
22547 Show the OS ABI currently in use.
22550 With no argument, show the list of registered available OS ABI's.
22552 @item set osabi @var{abi}
22553 Set the current OS ABI to @var{abi}.
22556 @cindex float promotion
22558 Generally, the way that an argument of type @code{float} is passed to a
22559 function depends on whether the function is prototyped. For a prototyped
22560 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
22561 according to the architecture's convention for @code{float}. For unprototyped
22562 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
22563 @code{double} and then passed.
22565 Unfortunately, some forms of debug information do not reliably indicate whether
22566 a function is prototyped. If @value{GDBN} calls a function that is not marked
22567 as prototyped, it consults @kbd{set coerce-float-to-double}.
22570 @kindex set coerce-float-to-double
22571 @item set coerce-float-to-double
22572 @itemx set coerce-float-to-double on
22573 Arguments of type @code{float} will be promoted to @code{double} when passed
22574 to an unprototyped function. This is the default setting.
22576 @item set coerce-float-to-double off
22577 Arguments of type @code{float} will be passed directly to unprototyped
22580 @kindex show coerce-float-to-double
22581 @item show coerce-float-to-double
22582 Show the current setting of promoting @code{float} to @code{double}.
22586 @kindex show cp-abi
22587 @value{GDBN} needs to know the ABI used for your program's C@t{++}
22588 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
22589 used to build your application. @value{GDBN} only fully supports
22590 programs with a single C@t{++} ABI; if your program contains code using
22591 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
22592 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
22593 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
22594 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
22595 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
22596 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
22601 Show the C@t{++} ABI currently in use.
22604 With no argument, show the list of supported C@t{++} ABI's.
22606 @item set cp-abi @var{abi}
22607 @itemx set cp-abi auto
22608 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
22612 @section Automatically loading associated files
22613 @cindex auto-loading
22615 @value{GDBN} sometimes reads files with commands and settings automatically,
22616 without being explicitly told so by the user. We call this feature
22617 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
22618 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
22619 results or introduce security risks (e.g., if the file comes from untrusted
22623 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
22624 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
22626 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
22627 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
22630 There are various kinds of files @value{GDBN} can automatically load.
22631 In addition to these files, @value{GDBN} supports auto-loading code written
22632 in various extension languages. @xref{Auto-loading extensions}.
22634 Note that loading of these associated files (including the local @file{.gdbinit}
22635 file) requires accordingly configured @code{auto-load safe-path}
22636 (@pxref{Auto-loading safe path}).
22638 For these reasons, @value{GDBN} includes commands and options to let you
22639 control when to auto-load files and which files should be auto-loaded.
22642 @anchor{set auto-load off}
22643 @kindex set auto-load off
22644 @item set auto-load off
22645 Globally disable loading of all auto-loaded files.
22646 You may want to use this command with the @samp{-iex} option
22647 (@pxref{Option -init-eval-command}) such as:
22649 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
22652 Be aware that system init file (@pxref{System-wide configuration})
22653 and init files from your home directory (@pxref{Home Directory Init File})
22654 still get read (as they come from generally trusted directories).
22655 To prevent @value{GDBN} from auto-loading even those init files, use the
22656 @option{-nx} option (@pxref{Mode Options}), in addition to
22657 @code{set auto-load no}.
22659 @anchor{show auto-load}
22660 @kindex show auto-load
22661 @item show auto-load
22662 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
22666 (gdb) show auto-load
22667 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
22668 libthread-db: Auto-loading of inferior specific libthread_db is on.
22669 local-gdbinit: Auto-loading of .gdbinit script from current directory
22671 python-scripts: Auto-loading of Python scripts is on.
22672 safe-path: List of directories from which it is safe to auto-load files
22673 is $debugdir:$datadir/auto-load.
22674 scripts-directory: List of directories from which to load auto-loaded scripts
22675 is $debugdir:$datadir/auto-load.
22678 @anchor{info auto-load}
22679 @kindex info auto-load
22680 @item info auto-load
22681 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
22685 (gdb) info auto-load
22688 Yes /home/user/gdb/gdb-gdb.gdb
22689 libthread-db: No auto-loaded libthread-db.
22690 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
22694 Yes /home/user/gdb/gdb-gdb.py
22698 These are @value{GDBN} control commands for the auto-loading:
22700 @multitable @columnfractions .5 .5
22701 @item @xref{set auto-load off}.
22702 @tab Disable auto-loading globally.
22703 @item @xref{show auto-load}.
22704 @tab Show setting of all kinds of files.
22705 @item @xref{info auto-load}.
22706 @tab Show state of all kinds of files.
22707 @item @xref{set auto-load gdb-scripts}.
22708 @tab Control for @value{GDBN} command scripts.
22709 @item @xref{show auto-load gdb-scripts}.
22710 @tab Show setting of @value{GDBN} command scripts.
22711 @item @xref{info auto-load gdb-scripts}.
22712 @tab Show state of @value{GDBN} command scripts.
22713 @item @xref{set auto-load python-scripts}.
22714 @tab Control for @value{GDBN} Python scripts.
22715 @item @xref{show auto-load python-scripts}.
22716 @tab Show setting of @value{GDBN} Python scripts.
22717 @item @xref{info auto-load python-scripts}.
22718 @tab Show state of @value{GDBN} Python scripts.
22719 @item @xref{set auto-load guile-scripts}.
22720 @tab Control for @value{GDBN} Guile scripts.
22721 @item @xref{show auto-load guile-scripts}.
22722 @tab Show setting of @value{GDBN} Guile scripts.
22723 @item @xref{info auto-load guile-scripts}.
22724 @tab Show state of @value{GDBN} Guile scripts.
22725 @item @xref{set auto-load scripts-directory}.
22726 @tab Control for @value{GDBN} auto-loaded scripts location.
22727 @item @xref{show auto-load scripts-directory}.
22728 @tab Show @value{GDBN} auto-loaded scripts location.
22729 @item @xref{add-auto-load-scripts-directory}.
22730 @tab Add directory for auto-loaded scripts location list.
22731 @item @xref{set auto-load local-gdbinit}.
22732 @tab Control for init file in the current directory.
22733 @item @xref{show auto-load local-gdbinit}.
22734 @tab Show setting of init file in the current directory.
22735 @item @xref{info auto-load local-gdbinit}.
22736 @tab Show state of init file in the current directory.
22737 @item @xref{set auto-load libthread-db}.
22738 @tab Control for thread debugging library.
22739 @item @xref{show auto-load libthread-db}.
22740 @tab Show setting of thread debugging library.
22741 @item @xref{info auto-load libthread-db}.
22742 @tab Show state of thread debugging library.
22743 @item @xref{set auto-load safe-path}.
22744 @tab Control directories trusted for automatic loading.
22745 @item @xref{show auto-load safe-path}.
22746 @tab Show directories trusted for automatic loading.
22747 @item @xref{add-auto-load-safe-path}.
22748 @tab Add directory trusted for automatic loading.
22751 @node Init File in the Current Directory
22752 @subsection Automatically loading init file in the current directory
22753 @cindex auto-loading init file in the current directory
22755 By default, @value{GDBN} reads and executes the canned sequences of commands
22756 from init file (if any) in the current working directory,
22757 see @ref{Init File in the Current Directory during Startup}.
22759 Note that loading of this local @file{.gdbinit} file also requires accordingly
22760 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22763 @anchor{set auto-load local-gdbinit}
22764 @kindex set auto-load local-gdbinit
22765 @item set auto-load local-gdbinit [on|off]
22766 Enable or disable the auto-loading of canned sequences of commands
22767 (@pxref{Sequences}) found in init file in the current directory.
22769 @anchor{show auto-load local-gdbinit}
22770 @kindex show auto-load local-gdbinit
22771 @item show auto-load local-gdbinit
22772 Show whether auto-loading of canned sequences of commands from init file in the
22773 current directory is enabled or disabled.
22775 @anchor{info auto-load local-gdbinit}
22776 @kindex info auto-load local-gdbinit
22777 @item info auto-load local-gdbinit
22778 Print whether canned sequences of commands from init file in the
22779 current directory have been auto-loaded.
22782 @node libthread_db.so.1 file
22783 @subsection Automatically loading thread debugging library
22784 @cindex auto-loading libthread_db.so.1
22786 This feature is currently present only on @sc{gnu}/Linux native hosts.
22788 @value{GDBN} reads in some cases thread debugging library from places specific
22789 to the inferior (@pxref{set libthread-db-search-path}).
22791 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
22792 without checking this @samp{set auto-load libthread-db} switch as system
22793 libraries have to be trusted in general. In all other cases of
22794 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
22795 auto-load libthread-db} is enabled before trying to open such thread debugging
22798 Note that loading of this debugging library also requires accordingly configured
22799 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22802 @anchor{set auto-load libthread-db}
22803 @kindex set auto-load libthread-db
22804 @item set auto-load libthread-db [on|off]
22805 Enable or disable the auto-loading of inferior specific thread debugging library.
22807 @anchor{show auto-load libthread-db}
22808 @kindex show auto-load libthread-db
22809 @item show auto-load libthread-db
22810 Show whether auto-loading of inferior specific thread debugging library is
22811 enabled or disabled.
22813 @anchor{info auto-load libthread-db}
22814 @kindex info auto-load libthread-db
22815 @item info auto-load libthread-db
22816 Print the list of all loaded inferior specific thread debugging libraries and
22817 for each such library print list of inferior @var{pid}s using it.
22820 @node Auto-loading safe path
22821 @subsection Security restriction for auto-loading
22822 @cindex auto-loading safe-path
22824 As the files of inferior can come from untrusted source (such as submitted by
22825 an application user) @value{GDBN} does not always load any files automatically.
22826 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
22827 directories trusted for loading files not explicitly requested by user.
22828 Each directory can also be a shell wildcard pattern.
22830 If the path is not set properly you will see a warning and the file will not
22835 Reading symbols from /home/user/gdb/gdb...done.
22836 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
22837 declined by your `auto-load safe-path' set
22838 to "$debugdir:$datadir/auto-load".
22839 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
22840 declined by your `auto-load safe-path' set
22841 to "$debugdir:$datadir/auto-load".
22845 To instruct @value{GDBN} to go ahead and use the init files anyway,
22846 invoke @value{GDBN} like this:
22849 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
22852 The list of trusted directories is controlled by the following commands:
22855 @anchor{set auto-load safe-path}
22856 @kindex set auto-load safe-path
22857 @item set auto-load safe-path @r{[}@var{directories}@r{]}
22858 Set the list of directories (and their subdirectories) trusted for automatic
22859 loading and execution of scripts. You can also enter a specific trusted file.
22860 Each directory can also be a shell wildcard pattern; wildcards do not match
22861 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
22862 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
22863 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
22864 its default value as specified during @value{GDBN} compilation.
22866 The list of directories uses path separator (@samp{:} on GNU and Unix
22867 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
22868 to the @env{PATH} environment variable.
22870 @anchor{show auto-load safe-path}
22871 @kindex show auto-load safe-path
22872 @item show auto-load safe-path
22873 Show the list of directories trusted for automatic loading and execution of
22876 @anchor{add-auto-load-safe-path}
22877 @kindex add-auto-load-safe-path
22878 @item add-auto-load-safe-path
22879 Add an entry (or list of entries) to the list of directories trusted for
22880 automatic loading and execution of scripts. Multiple entries may be delimited
22881 by the host platform path separator in use.
22884 This variable defaults to what @code{--with-auto-load-dir} has been configured
22885 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
22886 substitution applies the same as for @ref{set auto-load scripts-directory}.
22887 The default @code{set auto-load safe-path} value can be also overriden by
22888 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
22890 Setting this variable to @file{/} disables this security protection,
22891 corresponding @value{GDBN} configuration option is
22892 @option{--without-auto-load-safe-path}.
22893 This variable is supposed to be set to the system directories writable by the
22894 system superuser only. Users can add their source directories in init files in
22895 their home directories (@pxref{Home Directory Init File}). See also deprecated
22896 init file in the current directory
22897 (@pxref{Init File in the Current Directory during Startup}).
22899 To force @value{GDBN} to load the files it declined to load in the previous
22900 example, you could use one of the following ways:
22903 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
22904 Specify this trusted directory (or a file) as additional component of the list.
22905 You have to specify also any existing directories displayed by
22906 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
22908 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
22909 Specify this directory as in the previous case but just for a single
22910 @value{GDBN} session.
22912 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
22913 Disable auto-loading safety for a single @value{GDBN} session.
22914 This assumes all the files you debug during this @value{GDBN} session will come
22915 from trusted sources.
22917 @item @kbd{./configure --without-auto-load-safe-path}
22918 During compilation of @value{GDBN} you may disable any auto-loading safety.
22919 This assumes all the files you will ever debug with this @value{GDBN} come from
22923 On the other hand you can also explicitly forbid automatic files loading which
22924 also suppresses any such warning messages:
22927 @item @kbd{gdb -iex "set auto-load no" @dots{}}
22928 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
22930 @item @file{~/.gdbinit}: @samp{set auto-load no}
22931 Disable auto-loading globally for the user
22932 (@pxref{Home Directory Init File}). While it is improbable, you could also
22933 use system init file instead (@pxref{System-wide configuration}).
22936 This setting applies to the file names as entered by user. If no entry matches
22937 @value{GDBN} tries as a last resort to also resolve all the file names into
22938 their canonical form (typically resolving symbolic links) and compare the
22939 entries again. @value{GDBN} already canonicalizes most of the filenames on its
22940 own before starting the comparison so a canonical form of directories is
22941 recommended to be entered.
22943 @node Auto-loading verbose mode
22944 @subsection Displaying files tried for auto-load
22945 @cindex auto-loading verbose mode
22947 For better visibility of all the file locations where you can place scripts to
22948 be auto-loaded with inferior --- or to protect yourself against accidental
22949 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
22950 all the files attempted to be loaded. Both existing and non-existing files may
22953 For example the list of directories from which it is safe to auto-load files
22954 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
22955 may not be too obvious while setting it up.
22958 (gdb) set debug auto-load on
22959 (gdb) file ~/src/t/true
22960 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
22961 for objfile "/tmp/true".
22962 auto-load: Updating directories of "/usr:/opt".
22963 auto-load: Using directory "/usr".
22964 auto-load: Using directory "/opt".
22965 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
22966 by your `auto-load safe-path' set to "/usr:/opt".
22970 @anchor{set debug auto-load}
22971 @kindex set debug auto-load
22972 @item set debug auto-load [on|off]
22973 Set whether to print the filenames attempted to be auto-loaded.
22975 @anchor{show debug auto-load}
22976 @kindex show debug auto-load
22977 @item show debug auto-load
22978 Show whether printing of the filenames attempted to be auto-loaded is turned
22982 @node Messages/Warnings
22983 @section Optional Warnings and Messages
22985 @cindex verbose operation
22986 @cindex optional warnings
22987 By default, @value{GDBN} is silent about its inner workings. If you are
22988 running on a slow machine, you may want to use the @code{set verbose}
22989 command. This makes @value{GDBN} tell you when it does a lengthy
22990 internal operation, so you will not think it has crashed.
22992 Currently, the messages controlled by @code{set verbose} are those
22993 which announce that the symbol table for a source file is being read;
22994 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
22997 @kindex set verbose
22998 @item set verbose on
22999 Enables @value{GDBN} output of certain informational messages.
23001 @item set verbose off
23002 Disables @value{GDBN} output of certain informational messages.
23004 @kindex show verbose
23006 Displays whether @code{set verbose} is on or off.
23009 By default, if @value{GDBN} encounters bugs in the symbol table of an
23010 object file, it is silent; but if you are debugging a compiler, you may
23011 find this information useful (@pxref{Symbol Errors, ,Errors Reading
23016 @kindex set complaints
23017 @item set complaints @var{limit}
23018 Permits @value{GDBN} to output @var{limit} complaints about each type of
23019 unusual symbols before becoming silent about the problem. Set
23020 @var{limit} to zero to suppress all complaints; set it to a large number
23021 to prevent complaints from being suppressed.
23023 @kindex show complaints
23024 @item show complaints
23025 Displays how many symbol complaints @value{GDBN} is permitted to produce.
23029 @anchor{confirmation requests}
23030 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
23031 lot of stupid questions to confirm certain commands. For example, if
23032 you try to run a program which is already running:
23036 The program being debugged has been started already.
23037 Start it from the beginning? (y or n)
23040 If you are willing to unflinchingly face the consequences of your own
23041 commands, you can disable this ``feature'':
23045 @kindex set confirm
23047 @cindex confirmation
23048 @cindex stupid questions
23049 @item set confirm off
23050 Disables confirmation requests. Note that running @value{GDBN} with
23051 the @option{--batch} option (@pxref{Mode Options, -batch}) also
23052 automatically disables confirmation requests.
23054 @item set confirm on
23055 Enables confirmation requests (the default).
23057 @kindex show confirm
23059 Displays state of confirmation requests.
23063 @cindex command tracing
23064 If you need to debug user-defined commands or sourced files you may find it
23065 useful to enable @dfn{command tracing}. In this mode each command will be
23066 printed as it is executed, prefixed with one or more @samp{+} symbols, the
23067 quantity denoting the call depth of each command.
23070 @kindex set trace-commands
23071 @cindex command scripts, debugging
23072 @item set trace-commands on
23073 Enable command tracing.
23074 @item set trace-commands off
23075 Disable command tracing.
23076 @item show trace-commands
23077 Display the current state of command tracing.
23080 @node Debugging Output
23081 @section Optional Messages about Internal Happenings
23082 @cindex optional debugging messages
23084 @value{GDBN} has commands that enable optional debugging messages from
23085 various @value{GDBN} subsystems; normally these commands are of
23086 interest to @value{GDBN} maintainers, or when reporting a bug. This
23087 section documents those commands.
23090 @kindex set exec-done-display
23091 @item set exec-done-display
23092 Turns on or off the notification of asynchronous commands'
23093 completion. When on, @value{GDBN} will print a message when an
23094 asynchronous command finishes its execution. The default is off.
23095 @kindex show exec-done-display
23096 @item show exec-done-display
23097 Displays the current setting of asynchronous command completion
23100 @cindex ARM AArch64
23101 @item set debug aarch64
23102 Turns on or off display of debugging messages related to ARM AArch64.
23103 The default is off.
23105 @item show debug aarch64
23106 Displays the current state of displaying debugging messages related to
23108 @cindex gdbarch debugging info
23109 @cindex architecture debugging info
23110 @item set debug arch
23111 Turns on or off display of gdbarch debugging info. The default is off
23112 @item show debug arch
23113 Displays the current state of displaying gdbarch debugging info.
23114 @item set debug aix-solib
23115 @cindex AIX shared library debugging
23116 Control display of debugging messages from the AIX shared library
23117 support module. The default is off.
23118 @item show debug aix-thread
23119 Show the current state of displaying AIX shared library debugging messages.
23120 @item set debug aix-thread
23121 @cindex AIX threads
23122 Display debugging messages about inner workings of the AIX thread
23124 @item show debug aix-thread
23125 Show the current state of AIX thread debugging info display.
23126 @item set debug check-physname
23128 Check the results of the ``physname'' computation. When reading DWARF
23129 debugging information for C@t{++}, @value{GDBN} attempts to compute
23130 each entity's name. @value{GDBN} can do this computation in two
23131 different ways, depending on exactly what information is present.
23132 When enabled, this setting causes @value{GDBN} to compute the names
23133 both ways and display any discrepancies.
23134 @item show debug check-physname
23135 Show the current state of ``physname'' checking.
23136 @item set debug coff-pe-read
23137 @cindex COFF/PE exported symbols
23138 Control display of debugging messages related to reading of COFF/PE
23139 exported symbols. The default is off.
23140 @item show debug coff-pe-read
23141 Displays the current state of displaying debugging messages related to
23142 reading of COFF/PE exported symbols.
23143 @item set debug dwarf2-die
23144 @cindex DWARF2 DIEs
23145 Dump DWARF2 DIEs after they are read in.
23146 The value is the number of nesting levels to print.
23147 A value of zero turns off the display.
23148 @item show debug dwarf2-die
23149 Show the current state of DWARF2 DIE debugging.
23150 @item set debug dwarf2-read
23151 @cindex DWARF2 Reading
23152 Turns on or off display of debugging messages related to reading
23153 DWARF debug info. The default is 0 (off).
23154 A value of 1 provides basic information.
23155 A value greater than 1 provides more verbose information.
23156 @item show debug dwarf2-read
23157 Show the current state of DWARF2 reader debugging.
23158 @item set debug displaced
23159 @cindex displaced stepping debugging info
23160 Turns on or off display of @value{GDBN} debugging info for the
23161 displaced stepping support. The default is off.
23162 @item show debug displaced
23163 Displays the current state of displaying @value{GDBN} debugging info
23164 related to displaced stepping.
23165 @item set debug event
23166 @cindex event debugging info
23167 Turns on or off display of @value{GDBN} event debugging info. The
23169 @item show debug event
23170 Displays the current state of displaying @value{GDBN} event debugging
23172 @item set debug expression
23173 @cindex expression debugging info
23174 Turns on or off display of debugging info about @value{GDBN}
23175 expression parsing. The default is off.
23176 @item show debug expression
23177 Displays the current state of displaying debugging info about
23178 @value{GDBN} expression parsing.
23179 @item set debug frame
23180 @cindex frame debugging info
23181 Turns on or off display of @value{GDBN} frame debugging info. The
23183 @item show debug frame
23184 Displays the current state of displaying @value{GDBN} frame debugging
23186 @item set debug gnu-nat
23187 @cindex @sc{gnu}/Hurd debug messages
23188 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
23189 @item show debug gnu-nat
23190 Show the current state of @sc{gnu}/Hurd debugging messages.
23191 @item set debug infrun
23192 @cindex inferior debugging info
23193 Turns on or off display of @value{GDBN} debugging info for running the inferior.
23194 The default is off. @file{infrun.c} contains GDB's runtime state machine used
23195 for implementing operations such as single-stepping the inferior.
23196 @item show debug infrun
23197 Displays the current state of @value{GDBN} inferior debugging.
23198 @item set debug jit
23199 @cindex just-in-time compilation, debugging messages
23200 Turns on or off debugging messages from JIT debug support.
23201 @item show debug jit
23202 Displays the current state of @value{GDBN} JIT debugging.
23203 @item set debug lin-lwp
23204 @cindex @sc{gnu}/Linux LWP debug messages
23205 @cindex Linux lightweight processes
23206 Turns on or off debugging messages from the Linux LWP debug support.
23207 @item show debug lin-lwp
23208 Show the current state of Linux LWP debugging messages.
23209 @item set debug mach-o
23210 @cindex Mach-O symbols processing
23211 Control display of debugging messages related to Mach-O symbols
23212 processing. The default is off.
23213 @item show debug mach-o
23214 Displays the current state of displaying debugging messages related to
23215 reading of COFF/PE exported symbols.
23216 @item set debug notification
23217 @cindex remote async notification debugging info
23218 Turns on or off debugging messages about remote async notification.
23219 The default is off.
23220 @item show debug notification
23221 Displays the current state of remote async notification debugging messages.
23222 @item set debug observer
23223 @cindex observer debugging info
23224 Turns on or off display of @value{GDBN} observer debugging. This
23225 includes info such as the notification of observable events.
23226 @item show debug observer
23227 Displays the current state of observer debugging.
23228 @item set debug overload
23229 @cindex C@t{++} overload debugging info
23230 Turns on or off display of @value{GDBN} C@t{++} overload debugging
23231 info. This includes info such as ranking of functions, etc. The default
23233 @item show debug overload
23234 Displays the current state of displaying @value{GDBN} C@t{++} overload
23236 @cindex expression parser, debugging info
23237 @cindex debug expression parser
23238 @item set debug parser
23239 Turns on or off the display of expression parser debugging output.
23240 Internally, this sets the @code{yydebug} variable in the expression
23241 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
23242 details. The default is off.
23243 @item show debug parser
23244 Show the current state of expression parser debugging.
23245 @cindex packets, reporting on stdout
23246 @cindex serial connections, debugging
23247 @cindex debug remote protocol
23248 @cindex remote protocol debugging
23249 @cindex display remote packets
23250 @item set debug remote
23251 Turns on or off display of reports on all packets sent back and forth across
23252 the serial line to the remote machine. The info is printed on the
23253 @value{GDBN} standard output stream. The default is off.
23254 @item show debug remote
23255 Displays the state of display of remote packets.
23256 @item set debug serial
23257 Turns on or off display of @value{GDBN} serial debugging info. The
23259 @item show debug serial
23260 Displays the current state of displaying @value{GDBN} serial debugging
23262 @item set debug solib-frv
23263 @cindex FR-V shared-library debugging
23264 Turns on or off debugging messages for FR-V shared-library code.
23265 @item show debug solib-frv
23266 Display the current state of FR-V shared-library code debugging
23268 @item set debug symbol-lookup
23269 @cindex symbol lookup
23270 Turns on or off display of debugging messages related to symbol lookup.
23271 The default is 0 (off).
23272 A value of 1 provides basic information.
23273 A value greater than 1 provides more verbose information.
23274 @item show debug symbol-lookup
23275 Show the current state of symbol lookup debugging messages.
23276 @item set debug symfile
23277 @cindex symbol file functions
23278 Turns on or off display of debugging messages related to symbol file functions.
23279 The default is off. @xref{Files}.
23280 @item show debug symfile
23281 Show the current state of symbol file debugging messages.
23282 @item set debug symtab-create
23283 @cindex symbol table creation
23284 Turns on or off display of debugging messages related to symbol table creation.
23285 The default is 0 (off).
23286 A value of 1 provides basic information.
23287 A value greater than 1 provides more verbose information.
23288 @item show debug symtab-create
23289 Show the current state of symbol table creation debugging.
23290 @item set debug target
23291 @cindex target debugging info
23292 Turns on or off display of @value{GDBN} target debugging info. This info
23293 includes what is going on at the target level of GDB, as it happens. The
23294 default is 0. Set it to 1 to track events, and to 2 to also track the
23295 value of large memory transfers.
23296 @item show debug target
23297 Displays the current state of displaying @value{GDBN} target debugging
23299 @item set debug timestamp
23300 @cindex timestampping debugging info
23301 Turns on or off display of timestamps with @value{GDBN} debugging info.
23302 When enabled, seconds and microseconds are displayed before each debugging
23304 @item show debug timestamp
23305 Displays the current state of displaying timestamps with @value{GDBN}
23307 @item set debug varobj
23308 @cindex variable object debugging info
23309 Turns on or off display of @value{GDBN} variable object debugging
23310 info. The default is off.
23311 @item show debug varobj
23312 Displays the current state of displaying @value{GDBN} variable object
23314 @item set debug xml
23315 @cindex XML parser debugging
23316 Turns on or off debugging messages for built-in XML parsers.
23317 @item show debug xml
23318 Displays the current state of XML debugging messages.
23321 @node Other Misc Settings
23322 @section Other Miscellaneous Settings
23323 @cindex miscellaneous settings
23326 @kindex set interactive-mode
23327 @item set interactive-mode
23328 If @code{on}, forces @value{GDBN} to assume that GDB was started
23329 in a terminal. In practice, this means that @value{GDBN} should wait
23330 for the user to answer queries generated by commands entered at
23331 the command prompt. If @code{off}, forces @value{GDBN} to operate
23332 in the opposite mode, and it uses the default answers to all queries.
23333 If @code{auto} (the default), @value{GDBN} tries to determine whether
23334 its standard input is a terminal, and works in interactive-mode if it
23335 is, non-interactively otherwise.
23337 In the vast majority of cases, the debugger should be able to guess
23338 correctly which mode should be used. But this setting can be useful
23339 in certain specific cases, such as running a MinGW @value{GDBN}
23340 inside a cygwin window.
23342 @kindex show interactive-mode
23343 @item show interactive-mode
23344 Displays whether the debugger is operating in interactive mode or not.
23347 @node Extending GDB
23348 @chapter Extending @value{GDBN}
23349 @cindex extending GDB
23351 @value{GDBN} provides several mechanisms for extension.
23352 @value{GDBN} also provides the ability to automatically load
23353 extensions when it reads a file for debugging. This allows the
23354 user to automatically customize @value{GDBN} for the program
23358 * Sequences:: Canned Sequences of @value{GDBN} Commands
23359 * Python:: Extending @value{GDBN} using Python
23360 * Guile:: Extending @value{GDBN} using Guile
23361 * Auto-loading extensions:: Automatically loading extensions
23362 * Multiple Extension Languages:: Working with multiple extension languages
23363 * Aliases:: Creating new spellings of existing commands
23366 To facilitate the use of extension languages, @value{GDBN} is capable
23367 of evaluating the contents of a file. When doing so, @value{GDBN}
23368 can recognize which extension language is being used by looking at
23369 the filename extension. Files with an unrecognized filename extension
23370 are always treated as a @value{GDBN} Command Files.
23371 @xref{Command Files,, Command files}.
23373 You can control how @value{GDBN} evaluates these files with the following
23377 @kindex set script-extension
23378 @kindex show script-extension
23379 @item set script-extension off
23380 All scripts are always evaluated as @value{GDBN} Command Files.
23382 @item set script-extension soft
23383 The debugger determines the scripting language based on filename
23384 extension. If this scripting language is supported, @value{GDBN}
23385 evaluates the script using that language. Otherwise, it evaluates
23386 the file as a @value{GDBN} Command File.
23388 @item set script-extension strict
23389 The debugger determines the scripting language based on filename
23390 extension, and evaluates the script using that language. If the
23391 language is not supported, then the evaluation fails.
23393 @item show script-extension
23394 Display the current value of the @code{script-extension} option.
23399 @section Canned Sequences of Commands
23401 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
23402 Command Lists}), @value{GDBN} provides two ways to store sequences of
23403 commands for execution as a unit: user-defined commands and command
23407 * Define:: How to define your own commands
23408 * Hooks:: Hooks for user-defined commands
23409 * Command Files:: How to write scripts of commands to be stored in a file
23410 * Output:: Commands for controlled output
23411 * Auto-loading sequences:: Controlling auto-loaded command files
23415 @subsection User-defined Commands
23417 @cindex user-defined command
23418 @cindex arguments, to user-defined commands
23419 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
23420 which you assign a new name as a command. This is done with the
23421 @code{define} command. User commands may accept up to 10 arguments
23422 separated by whitespace. Arguments are accessed within the user command
23423 via @code{$arg0@dots{}$arg9}. A trivial example:
23427 print $arg0 + $arg1 + $arg2
23432 To execute the command use:
23439 This defines the command @code{adder}, which prints the sum of
23440 its three arguments. Note the arguments are text substitutions, so they may
23441 reference variables, use complex expressions, or even perform inferior
23444 @cindex argument count in user-defined commands
23445 @cindex how many arguments (user-defined commands)
23446 In addition, @code{$argc} may be used to find out how many arguments have
23447 been passed. This expands to a number in the range 0@dots{}10.
23452 print $arg0 + $arg1
23455 print $arg0 + $arg1 + $arg2
23463 @item define @var{commandname}
23464 Define a command named @var{commandname}. If there is already a command
23465 by that name, you are asked to confirm that you want to redefine it.
23466 The argument @var{commandname} may be a bare command name consisting of letters,
23467 numbers, dashes, and underscores. It may also start with any predefined
23468 prefix command. For example, @samp{define target my-target} creates
23469 a user-defined @samp{target my-target} command.
23471 The definition of the command is made up of other @value{GDBN} command lines,
23472 which are given following the @code{define} command. The end of these
23473 commands is marked by a line containing @code{end}.
23476 @kindex end@r{ (user-defined commands)}
23477 @item document @var{commandname}
23478 Document the user-defined command @var{commandname}, so that it can be
23479 accessed by @code{help}. The command @var{commandname} must already be
23480 defined. This command reads lines of documentation just as @code{define}
23481 reads the lines of the command definition, ending with @code{end}.
23482 After the @code{document} command is finished, @code{help} on command
23483 @var{commandname} displays the documentation you have written.
23485 You may use the @code{document} command again to change the
23486 documentation of a command. Redefining the command with @code{define}
23487 does not change the documentation.
23489 @kindex dont-repeat
23490 @cindex don't repeat command
23492 Used inside a user-defined command, this tells @value{GDBN} that this
23493 command should not be repeated when the user hits @key{RET}
23494 (@pxref{Command Syntax, repeat last command}).
23496 @kindex help user-defined
23497 @item help user-defined
23498 List all user-defined commands and all python commands defined in class
23499 COMAND_USER. The first line of the documentation or docstring is
23504 @itemx show user @var{commandname}
23505 Display the @value{GDBN} commands used to define @var{commandname} (but
23506 not its documentation). If no @var{commandname} is given, display the
23507 definitions for all user-defined commands.
23508 This does not work for user-defined python commands.
23510 @cindex infinite recursion in user-defined commands
23511 @kindex show max-user-call-depth
23512 @kindex set max-user-call-depth
23513 @item show max-user-call-depth
23514 @itemx set max-user-call-depth
23515 The value of @code{max-user-call-depth} controls how many recursion
23516 levels are allowed in user-defined commands before @value{GDBN} suspects an
23517 infinite recursion and aborts the command.
23518 This does not apply to user-defined python commands.
23521 In addition to the above commands, user-defined commands frequently
23522 use control flow commands, described in @ref{Command Files}.
23524 When user-defined commands are executed, the
23525 commands of the definition are not printed. An error in any command
23526 stops execution of the user-defined command.
23528 If used interactively, commands that would ask for confirmation proceed
23529 without asking when used inside a user-defined command. Many @value{GDBN}
23530 commands that normally print messages to say what they are doing omit the
23531 messages when used in a user-defined command.
23534 @subsection User-defined Command Hooks
23535 @cindex command hooks
23536 @cindex hooks, for commands
23537 @cindex hooks, pre-command
23540 You may define @dfn{hooks}, which are a special kind of user-defined
23541 command. Whenever you run the command @samp{foo}, if the user-defined
23542 command @samp{hook-foo} exists, it is executed (with no arguments)
23543 before that command.
23545 @cindex hooks, post-command
23547 A hook may also be defined which is run after the command you executed.
23548 Whenever you run the command @samp{foo}, if the user-defined command
23549 @samp{hookpost-foo} exists, it is executed (with no arguments) after
23550 that command. Post-execution hooks may exist simultaneously with
23551 pre-execution hooks, for the same command.
23553 It is valid for a hook to call the command which it hooks. If this
23554 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
23556 @c It would be nice if hookpost could be passed a parameter indicating
23557 @c if the command it hooks executed properly or not. FIXME!
23559 @kindex stop@r{, a pseudo-command}
23560 In addition, a pseudo-command, @samp{stop} exists. Defining
23561 (@samp{hook-stop}) makes the associated commands execute every time
23562 execution stops in your program: before breakpoint commands are run,
23563 displays are printed, or the stack frame is printed.
23565 For example, to ignore @code{SIGALRM} signals while
23566 single-stepping, but treat them normally during normal execution,
23571 handle SIGALRM nopass
23575 handle SIGALRM pass
23578 define hook-continue
23579 handle SIGALRM pass
23583 As a further example, to hook at the beginning and end of the @code{echo}
23584 command, and to add extra text to the beginning and end of the message,
23592 define hookpost-echo
23596 (@value{GDBP}) echo Hello World
23597 <<<---Hello World--->>>
23602 You can define a hook for any single-word command in @value{GDBN}, but
23603 not for command aliases; you should define a hook for the basic command
23604 name, e.g.@: @code{backtrace} rather than @code{bt}.
23605 @c FIXME! So how does Joe User discover whether a command is an alias
23607 You can hook a multi-word command by adding @code{hook-} or
23608 @code{hookpost-} to the last word of the command, e.g.@:
23609 @samp{define target hook-remote} to add a hook to @samp{target remote}.
23611 If an error occurs during the execution of your hook, execution of
23612 @value{GDBN} commands stops and @value{GDBN} issues a prompt
23613 (before the command that you actually typed had a chance to run).
23615 If you try to define a hook which does not match any known command, you
23616 get a warning from the @code{define} command.
23618 @node Command Files
23619 @subsection Command Files
23621 @cindex command files
23622 @cindex scripting commands
23623 A command file for @value{GDBN} is a text file made of lines that are
23624 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
23625 also be included. An empty line in a command file does nothing; it
23626 does not mean to repeat the last command, as it would from the
23629 You can request the execution of a command file with the @code{source}
23630 command. Note that the @code{source} command is also used to evaluate
23631 scripts that are not Command Files. The exact behavior can be configured
23632 using the @code{script-extension} setting.
23633 @xref{Extending GDB,, Extending GDB}.
23637 @cindex execute commands from a file
23638 @item source [-s] [-v] @var{filename}
23639 Execute the command file @var{filename}.
23642 The lines in a command file are generally executed sequentially,
23643 unless the order of execution is changed by one of the
23644 @emph{flow-control commands} described below. The commands are not
23645 printed as they are executed. An error in any command terminates
23646 execution of the command file and control is returned to the console.
23648 @value{GDBN} first searches for @var{filename} in the current directory.
23649 If the file is not found there, and @var{filename} does not specify a
23650 directory, then @value{GDBN} also looks for the file on the source search path
23651 (specified with the @samp{directory} command);
23652 except that @file{$cdir} is not searched because the compilation directory
23653 is not relevant to scripts.
23655 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
23656 on the search path even if @var{filename} specifies a directory.
23657 The search is done by appending @var{filename} to each element of the
23658 search path. So, for example, if @var{filename} is @file{mylib/myscript}
23659 and the search path contains @file{/home/user} then @value{GDBN} will
23660 look for the script @file{/home/user/mylib/myscript}.
23661 The search is also done if @var{filename} is an absolute path.
23662 For example, if @var{filename} is @file{/tmp/myscript} and
23663 the search path contains @file{/home/user} then @value{GDBN} will
23664 look for the script @file{/home/user/tmp/myscript}.
23665 For DOS-like systems, if @var{filename} contains a drive specification,
23666 it is stripped before concatenation. For example, if @var{filename} is
23667 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
23668 will look for the script @file{c:/tmp/myscript}.
23670 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
23671 each command as it is executed. The option must be given before
23672 @var{filename}, and is interpreted as part of the filename anywhere else.
23674 Commands that would ask for confirmation if used interactively proceed
23675 without asking when used in a command file. Many @value{GDBN} commands that
23676 normally print messages to say what they are doing omit the messages
23677 when called from command files.
23679 @value{GDBN} also accepts command input from standard input. In this
23680 mode, normal output goes to standard output and error output goes to
23681 standard error. Errors in a command file supplied on standard input do
23682 not terminate execution of the command file---execution continues with
23686 gdb < cmds > log 2>&1
23689 (The syntax above will vary depending on the shell used.) This example
23690 will execute commands from the file @file{cmds}. All output and errors
23691 would be directed to @file{log}.
23693 Since commands stored on command files tend to be more general than
23694 commands typed interactively, they frequently need to deal with
23695 complicated situations, such as different or unexpected values of
23696 variables and symbols, changes in how the program being debugged is
23697 built, etc. @value{GDBN} provides a set of flow-control commands to
23698 deal with these complexities. Using these commands, you can write
23699 complex scripts that loop over data structures, execute commands
23700 conditionally, etc.
23707 This command allows to include in your script conditionally executed
23708 commands. The @code{if} command takes a single argument, which is an
23709 expression to evaluate. It is followed by a series of commands that
23710 are executed only if the expression is true (its value is nonzero).
23711 There can then optionally be an @code{else} line, followed by a series
23712 of commands that are only executed if the expression was false. The
23713 end of the list is marked by a line containing @code{end}.
23717 This command allows to write loops. Its syntax is similar to
23718 @code{if}: the command takes a single argument, which is an expression
23719 to evaluate, and must be followed by the commands to execute, one per
23720 line, terminated by an @code{end}. These commands are called the
23721 @dfn{body} of the loop. The commands in the body of @code{while} are
23722 executed repeatedly as long as the expression evaluates to true.
23726 This command exits the @code{while} loop in whose body it is included.
23727 Execution of the script continues after that @code{while}s @code{end}
23730 @kindex loop_continue
23731 @item loop_continue
23732 This command skips the execution of the rest of the body of commands
23733 in the @code{while} loop in whose body it is included. Execution
23734 branches to the beginning of the @code{while} loop, where it evaluates
23735 the controlling expression.
23737 @kindex end@r{ (if/else/while commands)}
23739 Terminate the block of commands that are the body of @code{if},
23740 @code{else}, or @code{while} flow-control commands.
23745 @subsection Commands for Controlled Output
23747 During the execution of a command file or a user-defined command, normal
23748 @value{GDBN} output is suppressed; the only output that appears is what is
23749 explicitly printed by the commands in the definition. This section
23750 describes three commands useful for generating exactly the output you
23755 @item echo @var{text}
23756 @c I do not consider backslash-space a standard C escape sequence
23757 @c because it is not in ANSI.
23758 Print @var{text}. Nonprinting characters can be included in
23759 @var{text} using C escape sequences, such as @samp{\n} to print a
23760 newline. @strong{No newline is printed unless you specify one.}
23761 In addition to the standard C escape sequences, a backslash followed
23762 by a space stands for a space. This is useful for displaying a
23763 string with spaces at the beginning or the end, since leading and
23764 trailing spaces are otherwise trimmed from all arguments.
23765 To print @samp{@w{ }and foo =@w{ }}, use the command
23766 @samp{echo \@w{ }and foo = \@w{ }}.
23768 A backslash at the end of @var{text} can be used, as in C, to continue
23769 the command onto subsequent lines. For example,
23772 echo This is some text\n\
23773 which is continued\n\
23774 onto several lines.\n
23777 produces the same output as
23780 echo This is some text\n
23781 echo which is continued\n
23782 echo onto several lines.\n
23786 @item output @var{expression}
23787 Print the value of @var{expression} and nothing but that value: no
23788 newlines, no @samp{$@var{nn} = }. The value is not entered in the
23789 value history either. @xref{Expressions, ,Expressions}, for more information
23792 @item output/@var{fmt} @var{expression}
23793 Print the value of @var{expression} in format @var{fmt}. You can use
23794 the same formats as for @code{print}. @xref{Output Formats,,Output
23795 Formats}, for more information.
23798 @item printf @var{template}, @var{expressions}@dots{}
23799 Print the values of one or more @var{expressions} under the control of
23800 the string @var{template}. To print several values, make
23801 @var{expressions} be a comma-separated list of individual expressions,
23802 which may be either numbers or pointers. Their values are printed as
23803 specified by @var{template}, exactly as a C program would do by
23804 executing the code below:
23807 printf (@var{template}, @var{expressions}@dots{});
23810 As in @code{C} @code{printf}, ordinary characters in @var{template}
23811 are printed verbatim, while @dfn{conversion specification} introduced
23812 by the @samp{%} character cause subsequent @var{expressions} to be
23813 evaluated, their values converted and formatted according to type and
23814 style information encoded in the conversion specifications, and then
23817 For example, you can print two values in hex like this:
23820 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
23823 @code{printf} supports all the standard @code{C} conversion
23824 specifications, including the flags and modifiers between the @samp{%}
23825 character and the conversion letter, with the following exceptions:
23829 The argument-ordering modifiers, such as @samp{2$}, are not supported.
23832 The modifier @samp{*} is not supported for specifying precision or
23836 The @samp{'} flag (for separation of digits into groups according to
23837 @code{LC_NUMERIC'}) is not supported.
23840 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
23844 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
23847 The conversion letters @samp{a} and @samp{A} are not supported.
23851 Note that the @samp{ll} type modifier is supported only if the
23852 underlying @code{C} implementation used to build @value{GDBN} supports
23853 the @code{long long int} type, and the @samp{L} type modifier is
23854 supported only if @code{long double} type is available.
23856 As in @code{C}, @code{printf} supports simple backslash-escape
23857 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
23858 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
23859 single character. Octal and hexadecimal escape sequences are not
23862 Additionally, @code{printf} supports conversion specifications for DFP
23863 (@dfn{Decimal Floating Point}) types using the following length modifiers
23864 together with a floating point specifier.
23869 @samp{H} for printing @code{Decimal32} types.
23872 @samp{D} for printing @code{Decimal64} types.
23875 @samp{DD} for printing @code{Decimal128} types.
23878 If the underlying @code{C} implementation used to build @value{GDBN} has
23879 support for the three length modifiers for DFP types, other modifiers
23880 such as width and precision will also be available for @value{GDBN} to use.
23882 In case there is no such @code{C} support, no additional modifiers will be
23883 available and the value will be printed in the standard way.
23885 Here's an example of printing DFP types using the above conversion letters:
23887 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
23891 @item eval @var{template}, @var{expressions}@dots{}
23892 Convert the values of one or more @var{expressions} under the control of
23893 the string @var{template} to a command line, and call it.
23897 @node Auto-loading sequences
23898 @subsection Controlling auto-loading native @value{GDBN} scripts
23899 @cindex native script auto-loading
23901 When a new object file is read (for example, due to the @code{file}
23902 command, or because the inferior has loaded a shared library),
23903 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
23904 @xref{Auto-loading extensions}.
23906 Auto-loading can be enabled or disabled,
23907 and the list of auto-loaded scripts can be printed.
23910 @anchor{set auto-load gdb-scripts}
23911 @kindex set auto-load gdb-scripts
23912 @item set auto-load gdb-scripts [on|off]
23913 Enable or disable the auto-loading of canned sequences of commands scripts.
23915 @anchor{show auto-load gdb-scripts}
23916 @kindex show auto-load gdb-scripts
23917 @item show auto-load gdb-scripts
23918 Show whether auto-loading of canned sequences of commands scripts is enabled or
23921 @anchor{info auto-load gdb-scripts}
23922 @kindex info auto-load gdb-scripts
23923 @cindex print list of auto-loaded canned sequences of commands scripts
23924 @item info auto-load gdb-scripts [@var{regexp}]
23925 Print the list of all canned sequences of commands scripts that @value{GDBN}
23929 If @var{regexp} is supplied only canned sequences of commands scripts with
23930 matching names are printed.
23932 @c Python docs live in a separate file.
23933 @include python.texi
23935 @c Guile docs live in a separate file.
23936 @include guile.texi
23938 @node Auto-loading extensions
23939 @section Auto-loading extensions
23940 @cindex auto-loading extensions
23942 @value{GDBN} provides two mechanisms for automatically loading extensions
23943 when a new object file is read (for example, due to the @code{file}
23944 command, or because the inferior has loaded a shared library):
23945 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
23946 section of modern file formats like ELF.
23949 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
23950 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
23951 * Which flavor to choose?::
23954 The auto-loading feature is useful for supplying application-specific
23955 debugging commands and features.
23957 Auto-loading can be enabled or disabled,
23958 and the list of auto-loaded scripts can be printed.
23959 See the @samp{auto-loading} section of each extension language
23960 for more information.
23961 For @value{GDBN} command files see @ref{Auto-loading sequences}.
23962 For Python files see @ref{Python Auto-loading}.
23964 Note that loading of this script file also requires accordingly configured
23965 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23967 @node objfile-gdbdotext file
23968 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
23969 @cindex @file{@var{objfile}-gdb.gdb}
23970 @cindex @file{@var{objfile}-gdb.py}
23971 @cindex @file{@var{objfile}-gdb.scm}
23973 When a new object file is read, @value{GDBN} looks for a file named
23974 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
23975 where @var{objfile} is the object file's name and
23976 where @var{ext} is the file extension for the extension language:
23979 @item @file{@var{objfile}-gdb.gdb}
23980 GDB's own command language
23981 @item @file{@var{objfile}-gdb.py}
23983 @item @file{@var{objfile}-gdb.scm}
23987 @var{script-name} is formed by ensuring that the file name of @var{objfile}
23988 is absolute, following all symlinks, and resolving @code{.} and @code{..}
23989 components, and appending the @file{-gdb.@var{ext}} suffix.
23990 If this file exists and is readable, @value{GDBN} will evaluate it as a
23991 script in the specified extension language.
23993 If this file does not exist, then @value{GDBN} will look for
23994 @var{script-name} file in all of the directories as specified below.
23996 Note that loading of these files requires an accordingly configured
23997 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23999 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
24000 scripts normally according to its @file{.exe} filename. But if no scripts are
24001 found @value{GDBN} also tries script filenames matching the object file without
24002 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
24003 is attempted on any platform. This makes the script filenames compatible
24004 between Unix and MS-Windows hosts.
24007 @anchor{set auto-load scripts-directory}
24008 @kindex set auto-load scripts-directory
24009 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
24010 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
24011 may be delimited by the host platform path separator in use
24012 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
24014 Each entry here needs to be covered also by the security setting
24015 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
24017 @anchor{with-auto-load-dir}
24018 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
24019 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
24020 configuration option @option{--with-auto-load-dir}.
24022 Any reference to @file{$debugdir} will get replaced by
24023 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
24024 reference to @file{$datadir} will get replaced by @var{data-directory} which is
24025 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
24026 @file{$datadir} must be placed as a directory component --- either alone or
24027 delimited by @file{/} or @file{\} directory separators, depending on the host
24030 The list of directories uses path separator (@samp{:} on GNU and Unix
24031 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
24032 to the @env{PATH} environment variable.
24034 @anchor{show auto-load scripts-directory}
24035 @kindex show auto-load scripts-directory
24036 @item show auto-load scripts-directory
24037 Show @value{GDBN} auto-loaded scripts location.
24039 @anchor{add-auto-load-scripts-directory}
24040 @kindex add-auto-load-scripts-directory
24041 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
24042 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
24043 Multiple entries may be delimited by the host platform path separator in use.
24046 @value{GDBN} does not track which files it has already auto-loaded this way.
24047 @value{GDBN} will load the associated script every time the corresponding
24048 @var{objfile} is opened.
24049 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
24050 is evaluated more than once.
24052 @node dotdebug_gdb_scripts section
24053 @subsection The @code{.debug_gdb_scripts} section
24054 @cindex @code{.debug_gdb_scripts} section
24056 For systems using file formats like ELF and COFF,
24057 when @value{GDBN} loads a new object file
24058 it will look for a special section named @code{.debug_gdb_scripts}.
24059 If this section exists, its contents is a list of null-terminated entries
24060 specifying scripts to load. Each entry begins with a non-null prefix byte that
24061 specifies the kind of entry, typically the extension language and whether the
24062 script is in a file or inlined in @code{.debug_gdb_scripts}.
24064 The following entries are supported:
24067 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
24068 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
24069 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
24070 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
24073 @subsubsection Script File Entries
24075 If the entry specifies a file, @value{GDBN} will look for the file first
24076 in the current directory and then along the source search path
24077 (@pxref{Source Path, ,Specifying Source Directories}),
24078 except that @file{$cdir} is not searched, since the compilation
24079 directory is not relevant to scripts.
24081 File entries can be placed in section @code{.debug_gdb_scripts} with,
24082 for example, this GCC macro for Python scripts.
24085 /* Note: The "MS" section flags are to remove duplicates. */
24086 #define DEFINE_GDB_PY_SCRIPT(script_name) \
24088 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
24089 .byte 1 /* Python */\n\
24090 .asciz \"" script_name "\"\n\
24096 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
24097 Then one can reference the macro in a header or source file like this:
24100 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
24103 The script name may include directories if desired.
24105 Note that loading of this script file also requires accordingly configured
24106 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24108 If the macro invocation is put in a header, any application or library
24109 using this header will get a reference to the specified script,
24110 and with the use of @code{"MS"} attributes on the section, the linker
24111 will remove duplicates.
24113 @subsubsection Script Text Entries
24115 Script text entries allow to put the executable script in the entry
24116 itself instead of loading it from a file.
24117 The first line of the entry, everything after the prefix byte and up to
24118 the first newline (@code{0xa}) character, is the script name, and must not
24119 contain any kind of space character, e.g., spaces or tabs.
24120 The rest of the entry, up to the trailing null byte, is the script to
24121 execute in the specified language. The name needs to be unique among
24122 all script names, as @value{GDBN} executes each script only once based
24125 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
24129 #include "symcat.h"
24130 #include "gdb/section-scripts.h"
24132 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
24133 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
24134 ".ascii \"gdb.inlined-script\\n\"\n"
24135 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
24136 ".ascii \" def __init__ (self):\\n\"\n"
24137 ".ascii \" super (test_cmd, self).__init__ ("
24138 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
24139 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
24140 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
24141 ".ascii \"test_cmd ()\\n\"\n"
24147 Loading of inlined scripts requires a properly configured
24148 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24149 The path to specify in @code{auto-load safe-path} is the path of the file
24150 containing the @code{.debug_gdb_scripts} section.
24152 @node Which flavor to choose?
24153 @subsection Which flavor to choose?
24155 Given the multiple ways of auto-loading extensions, it might not always
24156 be clear which one to choose. This section provides some guidance.
24159 Benefits of the @file{-gdb.@var{ext}} way:
24163 Can be used with file formats that don't support multiple sections.
24166 Ease of finding scripts for public libraries.
24168 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
24169 in the source search path.
24170 For publicly installed libraries, e.g., @file{libstdc++}, there typically
24171 isn't a source directory in which to find the script.
24174 Doesn't require source code additions.
24178 Benefits of the @code{.debug_gdb_scripts} way:
24182 Works with static linking.
24184 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
24185 trigger their loading. When an application is statically linked the only
24186 objfile available is the executable, and it is cumbersome to attach all the
24187 scripts from all the input libraries to the executable's
24188 @file{-gdb.@var{ext}} script.
24191 Works with classes that are entirely inlined.
24193 Some classes can be entirely inlined, and thus there may not be an associated
24194 shared library to attach a @file{-gdb.@var{ext}} script to.
24197 Scripts needn't be copied out of the source tree.
24199 In some circumstances, apps can be built out of large collections of internal
24200 libraries, and the build infrastructure necessary to install the
24201 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
24202 cumbersome. It may be easier to specify the scripts in the
24203 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
24204 top of the source tree to the source search path.
24207 @node Multiple Extension Languages
24208 @section Multiple Extension Languages
24210 The Guile and Python extension languages do not share any state,
24211 and generally do not interfere with each other.
24212 There are some things to be aware of, however.
24214 @subsection Python comes first
24216 Python was @value{GDBN}'s first extension language, and to avoid breaking
24217 existing behaviour Python comes first. This is generally solved by the
24218 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
24219 extension languages, and when it makes a call to an extension language,
24220 (say to pretty-print a value), it tries each in turn until an extension
24221 language indicates it has performed the request (e.g., has returned the
24222 pretty-printed form of a value).
24223 This extends to errors while performing such requests: If an error happens
24224 while, for example, trying to pretty-print an object then the error is
24225 reported and any following extension languages are not tried.
24228 @section Creating new spellings of existing commands
24229 @cindex aliases for commands
24231 It is often useful to define alternate spellings of existing commands.
24232 For example, if a new @value{GDBN} command defined in Python has
24233 a long name to type, it is handy to have an abbreviated version of it
24234 that involves less typing.
24236 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
24237 of the @samp{step} command even though it is otherwise an ambiguous
24238 abbreviation of other commands like @samp{set} and @samp{show}.
24240 Aliases are also used to provide shortened or more common versions
24241 of multi-word commands. For example, @value{GDBN} provides the
24242 @samp{tty} alias of the @samp{set inferior-tty} command.
24244 You can define a new alias with the @samp{alias} command.
24249 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
24253 @var{ALIAS} specifies the name of the new alias.
24254 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
24257 @var{COMMAND} specifies the name of an existing command
24258 that is being aliased.
24260 The @samp{-a} option specifies that the new alias is an abbreviation
24261 of the command. Abbreviations are not shown in command
24262 lists displayed by the @samp{help} command.
24264 The @samp{--} option specifies the end of options,
24265 and is useful when @var{ALIAS} begins with a dash.
24267 Here is a simple example showing how to make an abbreviation
24268 of a command so that there is less to type.
24269 Suppose you were tired of typing @samp{disas}, the current
24270 shortest unambiguous abbreviation of the @samp{disassemble} command
24271 and you wanted an even shorter version named @samp{di}.
24272 The following will accomplish this.
24275 (gdb) alias -a di = disas
24278 Note that aliases are different from user-defined commands.
24279 With a user-defined command, you also need to write documentation
24280 for it with the @samp{document} command.
24281 An alias automatically picks up the documentation of the existing command.
24283 Here is an example where we make @samp{elms} an abbreviation of
24284 @samp{elements} in the @samp{set print elements} command.
24285 This is to show that you can make an abbreviation of any part
24289 (gdb) alias -a set print elms = set print elements
24290 (gdb) alias -a show print elms = show print elements
24291 (gdb) set p elms 20
24293 Limit on string chars or array elements to print is 200.
24296 Note that if you are defining an alias of a @samp{set} command,
24297 and you want to have an alias for the corresponding @samp{show}
24298 command, then you need to define the latter separately.
24300 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
24301 @var{ALIAS}, just as they are normally.
24304 (gdb) alias -a set pr elms = set p ele
24307 Finally, here is an example showing the creation of a one word
24308 alias for a more complex command.
24309 This creates alias @samp{spe} of the command @samp{set print elements}.
24312 (gdb) alias spe = set print elements
24317 @chapter Command Interpreters
24318 @cindex command interpreters
24320 @value{GDBN} supports multiple command interpreters, and some command
24321 infrastructure to allow users or user interface writers to switch
24322 between interpreters or run commands in other interpreters.
24324 @value{GDBN} currently supports two command interpreters, the console
24325 interpreter (sometimes called the command-line interpreter or @sc{cli})
24326 and the machine interface interpreter (or @sc{gdb/mi}). This manual
24327 describes both of these interfaces in great detail.
24329 By default, @value{GDBN} will start with the console interpreter.
24330 However, the user may choose to start @value{GDBN} with another
24331 interpreter by specifying the @option{-i} or @option{--interpreter}
24332 startup options. Defined interpreters include:
24336 @cindex console interpreter
24337 The traditional console or command-line interpreter. This is the most often
24338 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
24339 @value{GDBN} will use this interpreter.
24342 @cindex mi interpreter
24343 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
24344 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
24345 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
24349 @cindex mi2 interpreter
24350 The current @sc{gdb/mi} interface.
24353 @cindex mi1 interpreter
24354 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
24358 @cindex invoke another interpreter
24359 The interpreter being used by @value{GDBN} may not be dynamically
24360 switched at runtime. Although possible, this could lead to a very
24361 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
24362 enters the command "interpreter-set console" in a console view,
24363 @value{GDBN} would switch to using the console interpreter, rendering
24364 the IDE inoperable!
24366 @kindex interpreter-exec
24367 Although you may only choose a single interpreter at startup, you may execute
24368 commands in any interpreter from the current interpreter using the appropriate
24369 command. If you are running the console interpreter, simply use the
24370 @code{interpreter-exec} command:
24373 interpreter-exec mi "-data-list-register-names"
24376 @sc{gdb/mi} has a similar command, although it is only available in versions of
24377 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
24380 @chapter @value{GDBN} Text User Interface
24382 @cindex Text User Interface
24385 * TUI Overview:: TUI overview
24386 * TUI Keys:: TUI key bindings
24387 * TUI Single Key Mode:: TUI single key mode
24388 * TUI Commands:: TUI-specific commands
24389 * TUI Configuration:: TUI configuration variables
24392 The @value{GDBN} Text User Interface (TUI) is a terminal
24393 interface which uses the @code{curses} library to show the source
24394 file, the assembly output, the program registers and @value{GDBN}
24395 commands in separate text windows. The TUI mode is supported only
24396 on platforms where a suitable version of the @code{curses} library
24399 The TUI mode is enabled by default when you invoke @value{GDBN} as
24400 @samp{@value{GDBP} -tui}.
24401 You can also switch in and out of TUI mode while @value{GDBN} runs by
24402 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
24403 @xref{TUI Keys, ,TUI Key Bindings}.
24406 @section TUI Overview
24408 In TUI mode, @value{GDBN} can display several text windows:
24412 This window is the @value{GDBN} command window with the @value{GDBN}
24413 prompt and the @value{GDBN} output. The @value{GDBN} input is still
24414 managed using readline.
24417 The source window shows the source file of the program. The current
24418 line and active breakpoints are displayed in this window.
24421 The assembly window shows the disassembly output of the program.
24424 This window shows the processor registers. Registers are highlighted
24425 when their values change.
24428 The source and assembly windows show the current program position
24429 by highlighting the current line and marking it with a @samp{>} marker.
24430 Breakpoints are indicated with two markers. The first marker
24431 indicates the breakpoint type:
24435 Breakpoint which was hit at least once.
24438 Breakpoint which was never hit.
24441 Hardware breakpoint which was hit at least once.
24444 Hardware breakpoint which was never hit.
24447 The second marker indicates whether the breakpoint is enabled or not:
24451 Breakpoint is enabled.
24454 Breakpoint is disabled.
24457 The source, assembly and register windows are updated when the current
24458 thread changes, when the frame changes, or when the program counter
24461 These windows are not all visible at the same time. The command
24462 window is always visible. The others can be arranged in several
24473 source and assembly,
24476 source and registers, or
24479 assembly and registers.
24482 A status line above the command window shows the following information:
24486 Indicates the current @value{GDBN} target.
24487 (@pxref{Targets, ,Specifying a Debugging Target}).
24490 Gives the current process or thread number.
24491 When no process is being debugged, this field is set to @code{No process}.
24494 Gives the current function name for the selected frame.
24495 The name is demangled if demangling is turned on (@pxref{Print Settings}).
24496 When there is no symbol corresponding to the current program counter,
24497 the string @code{??} is displayed.
24500 Indicates the current line number for the selected frame.
24501 When the current line number is not known, the string @code{??} is displayed.
24504 Indicates the current program counter address.
24508 @section TUI Key Bindings
24509 @cindex TUI key bindings
24511 The TUI installs several key bindings in the readline keymaps
24512 @ifset SYSTEM_READLINE
24513 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
24515 @ifclear SYSTEM_READLINE
24516 (@pxref{Command Line Editing}).
24518 The following key bindings are installed for both TUI mode and the
24519 @value{GDBN} standard mode.
24528 Enter or leave the TUI mode. When leaving the TUI mode,
24529 the curses window management stops and @value{GDBN} operates using
24530 its standard mode, writing on the terminal directly. When reentering
24531 the TUI mode, control is given back to the curses windows.
24532 The screen is then refreshed.
24536 Use a TUI layout with only one window. The layout will
24537 either be @samp{source} or @samp{assembly}. When the TUI mode
24538 is not active, it will switch to the TUI mode.
24540 Think of this key binding as the Emacs @kbd{C-x 1} binding.
24544 Use a TUI layout with at least two windows. When the current
24545 layout already has two windows, the next layout with two windows is used.
24546 When a new layout is chosen, one window will always be common to the
24547 previous layout and the new one.
24549 Think of it as the Emacs @kbd{C-x 2} binding.
24553 Change the active window. The TUI associates several key bindings
24554 (like scrolling and arrow keys) with the active window. This command
24555 gives the focus to the next TUI window.
24557 Think of it as the Emacs @kbd{C-x o} binding.
24561 Switch in and out of the TUI SingleKey mode that binds single
24562 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
24565 The following key bindings only work in the TUI mode:
24570 Scroll the active window one page up.
24574 Scroll the active window one page down.
24578 Scroll the active window one line up.
24582 Scroll the active window one line down.
24586 Scroll the active window one column left.
24590 Scroll the active window one column right.
24594 Refresh the screen.
24597 Because the arrow keys scroll the active window in the TUI mode, they
24598 are not available for their normal use by readline unless the command
24599 window has the focus. When another window is active, you must use
24600 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
24601 and @kbd{C-f} to control the command window.
24603 @node TUI Single Key Mode
24604 @section TUI Single Key Mode
24605 @cindex TUI single key mode
24607 The TUI also provides a @dfn{SingleKey} mode, which binds several
24608 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
24609 switch into this mode, where the following key bindings are used:
24612 @kindex c @r{(SingleKey TUI key)}
24616 @kindex d @r{(SingleKey TUI key)}
24620 @kindex f @r{(SingleKey TUI key)}
24624 @kindex n @r{(SingleKey TUI key)}
24628 @kindex q @r{(SingleKey TUI key)}
24630 exit the SingleKey mode.
24632 @kindex r @r{(SingleKey TUI key)}
24636 @kindex s @r{(SingleKey TUI key)}
24640 @kindex u @r{(SingleKey TUI key)}
24644 @kindex v @r{(SingleKey TUI key)}
24648 @kindex w @r{(SingleKey TUI key)}
24653 Other keys temporarily switch to the @value{GDBN} command prompt.
24654 The key that was pressed is inserted in the editing buffer so that
24655 it is possible to type most @value{GDBN} commands without interaction
24656 with the TUI SingleKey mode. Once the command is entered the TUI
24657 SingleKey mode is restored. The only way to permanently leave
24658 this mode is by typing @kbd{q} or @kbd{C-x s}.
24662 @section TUI-specific Commands
24663 @cindex TUI commands
24665 The TUI has specific commands to control the text windows.
24666 These commands are always available, even when @value{GDBN} is not in
24667 the TUI mode. When @value{GDBN} is in the standard mode, most
24668 of these commands will automatically switch to the TUI mode.
24670 Note that if @value{GDBN}'s @code{stdout} is not connected to a
24671 terminal, or @value{GDBN} has been started with the machine interface
24672 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
24673 these commands will fail with an error, because it would not be
24674 possible or desirable to enable curses window management.
24679 List and give the size of all displayed windows.
24683 Display the next layout.
24686 Display the previous layout.
24689 Display the source window only.
24692 Display the assembly window only.
24695 Display the source and assembly window.
24698 Display the register window together with the source or assembly window.
24702 Make the next window active for scrolling.
24705 Make the previous window active for scrolling.
24708 Make the source window active for scrolling.
24711 Make the assembly window active for scrolling.
24714 Make the register window active for scrolling.
24717 Make the command window active for scrolling.
24721 Refresh the screen. This is similar to typing @kbd{C-L}.
24723 @item tui reg float
24725 Show the floating point registers in the register window.
24727 @item tui reg general
24728 Show the general registers in the register window.
24731 Show the next register group. The list of register groups as well as
24732 their order is target specific. The predefined register groups are the
24733 following: @code{general}, @code{float}, @code{system}, @code{vector},
24734 @code{all}, @code{save}, @code{restore}.
24736 @item tui reg system
24737 Show the system registers in the register window.
24741 Update the source window and the current execution point.
24743 @item winheight @var{name} +@var{count}
24744 @itemx winheight @var{name} -@var{count}
24746 Change the height of the window @var{name} by @var{count}
24747 lines. Positive counts increase the height, while negative counts
24748 decrease it. The @var{name} parameter can be one of @code{src} (the
24749 source window), @code{cmd} (the command window), @code{asm} (the
24750 disassembly window), or @code{regs} (the register display window).
24752 @item tabset @var{nchars}
24754 Set the width of tab stops to be @var{nchars} characters. This
24755 setting affects the display of TAB characters in the source and
24759 @node TUI Configuration
24760 @section TUI Configuration Variables
24761 @cindex TUI configuration variables
24763 Several configuration variables control the appearance of TUI windows.
24766 @item set tui border-kind @var{kind}
24767 @kindex set tui border-kind
24768 Select the border appearance for the source, assembly and register windows.
24769 The possible values are the following:
24772 Use a space character to draw the border.
24775 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
24778 Use the Alternate Character Set to draw the border. The border is
24779 drawn using character line graphics if the terminal supports them.
24782 @item set tui border-mode @var{mode}
24783 @kindex set tui border-mode
24784 @itemx set tui active-border-mode @var{mode}
24785 @kindex set tui active-border-mode
24786 Select the display attributes for the borders of the inactive windows
24787 or the active window. The @var{mode} can be one of the following:
24790 Use normal attributes to display the border.
24796 Use reverse video mode.
24799 Use half bright mode.
24801 @item half-standout
24802 Use half bright and standout mode.
24805 Use extra bright or bold mode.
24807 @item bold-standout
24808 Use extra bright or bold and standout mode.
24813 @chapter Using @value{GDBN} under @sc{gnu} Emacs
24816 @cindex @sc{gnu} Emacs
24817 A special interface allows you to use @sc{gnu} Emacs to view (and
24818 edit) the source files for the program you are debugging with
24821 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
24822 executable file you want to debug as an argument. This command starts
24823 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
24824 created Emacs buffer.
24825 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
24827 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
24832 All ``terminal'' input and output goes through an Emacs buffer, called
24835 This applies both to @value{GDBN} commands and their output, and to the input
24836 and output done by the program you are debugging.
24838 This is useful because it means that you can copy the text of previous
24839 commands and input them again; you can even use parts of the output
24842 All the facilities of Emacs' Shell mode are available for interacting
24843 with your program. In particular, you can send signals the usual
24844 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
24848 @value{GDBN} displays source code through Emacs.
24850 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
24851 source file for that frame and puts an arrow (@samp{=>}) at the
24852 left margin of the current line. Emacs uses a separate buffer for
24853 source display, and splits the screen to show both your @value{GDBN} session
24856 Explicit @value{GDBN} @code{list} or search commands still produce output as
24857 usual, but you probably have no reason to use them from Emacs.
24860 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
24861 a graphical mode, enabled by default, which provides further buffers
24862 that can control the execution and describe the state of your program.
24863 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
24865 If you specify an absolute file name when prompted for the @kbd{M-x
24866 gdb} argument, then Emacs sets your current working directory to where
24867 your program resides. If you only specify the file name, then Emacs
24868 sets your current working directory to the directory associated
24869 with the previous buffer. In this case, @value{GDBN} may find your
24870 program by searching your environment's @code{PATH} variable, but on
24871 some operating systems it might not find the source. So, although the
24872 @value{GDBN} input and output session proceeds normally, the auxiliary
24873 buffer does not display the current source and line of execution.
24875 The initial working directory of @value{GDBN} is printed on the top
24876 line of the GUD buffer and this serves as a default for the commands
24877 that specify files for @value{GDBN} to operate on. @xref{Files,
24878 ,Commands to Specify Files}.
24880 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
24881 need to call @value{GDBN} by a different name (for example, if you
24882 keep several configurations around, with different names) you can
24883 customize the Emacs variable @code{gud-gdb-command-name} to run the
24886 In the GUD buffer, you can use these special Emacs commands in
24887 addition to the standard Shell mode commands:
24891 Describe the features of Emacs' GUD Mode.
24894 Execute to another source line, like the @value{GDBN} @code{step} command; also
24895 update the display window to show the current file and location.
24898 Execute to next source line in this function, skipping all function
24899 calls, like the @value{GDBN} @code{next} command. Then update the display window
24900 to show the current file and location.
24903 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
24904 display window accordingly.
24907 Execute until exit from the selected stack frame, like the @value{GDBN}
24908 @code{finish} command.
24911 Continue execution of your program, like the @value{GDBN} @code{continue}
24915 Go up the number of frames indicated by the numeric argument
24916 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
24917 like the @value{GDBN} @code{up} command.
24920 Go down the number of frames indicated by the numeric argument, like the
24921 @value{GDBN} @code{down} command.
24924 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
24925 tells @value{GDBN} to set a breakpoint on the source line point is on.
24927 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
24928 separate frame which shows a backtrace when the GUD buffer is current.
24929 Move point to any frame in the stack and type @key{RET} to make it
24930 become the current frame and display the associated source in the
24931 source buffer. Alternatively, click @kbd{Mouse-2} to make the
24932 selected frame become the current one. In graphical mode, the
24933 speedbar displays watch expressions.
24935 If you accidentally delete the source-display buffer, an easy way to get
24936 it back is to type the command @code{f} in the @value{GDBN} buffer, to
24937 request a frame display; when you run under Emacs, this recreates
24938 the source buffer if necessary to show you the context of the current
24941 The source files displayed in Emacs are in ordinary Emacs buffers
24942 which are visiting the source files in the usual way. You can edit
24943 the files with these buffers if you wish; but keep in mind that @value{GDBN}
24944 communicates with Emacs in terms of line numbers. If you add or
24945 delete lines from the text, the line numbers that @value{GDBN} knows cease
24946 to correspond properly with the code.
24948 A more detailed description of Emacs' interaction with @value{GDBN} is
24949 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
24953 @chapter The @sc{gdb/mi} Interface
24955 @unnumberedsec Function and Purpose
24957 @cindex @sc{gdb/mi}, its purpose
24958 @sc{gdb/mi} is a line based machine oriented text interface to
24959 @value{GDBN} and is activated by specifying using the
24960 @option{--interpreter} command line option (@pxref{Mode Options}). It
24961 is specifically intended to support the development of systems which
24962 use the debugger as just one small component of a larger system.
24964 This chapter is a specification of the @sc{gdb/mi} interface. It is written
24965 in the form of a reference manual.
24967 Note that @sc{gdb/mi} is still under construction, so some of the
24968 features described below are incomplete and subject to change
24969 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
24971 @unnumberedsec Notation and Terminology
24973 @cindex notational conventions, for @sc{gdb/mi}
24974 This chapter uses the following notation:
24978 @code{|} separates two alternatives.
24981 @code{[ @var{something} ]} indicates that @var{something} is optional:
24982 it may or may not be given.
24985 @code{( @var{group} )*} means that @var{group} inside the parentheses
24986 may repeat zero or more times.
24989 @code{( @var{group} )+} means that @var{group} inside the parentheses
24990 may repeat one or more times.
24993 @code{"@var{string}"} means a literal @var{string}.
24997 @heading Dependencies
25001 * GDB/MI General Design::
25002 * GDB/MI Command Syntax::
25003 * GDB/MI Compatibility with CLI::
25004 * GDB/MI Development and Front Ends::
25005 * GDB/MI Output Records::
25006 * GDB/MI Simple Examples::
25007 * GDB/MI Command Description Format::
25008 * GDB/MI Breakpoint Commands::
25009 * GDB/MI Catchpoint Commands::
25010 * GDB/MI Program Context::
25011 * GDB/MI Thread Commands::
25012 * GDB/MI Ada Tasking Commands::
25013 * GDB/MI Program Execution::
25014 * GDB/MI Stack Manipulation::
25015 * GDB/MI Variable Objects::
25016 * GDB/MI Data Manipulation::
25017 * GDB/MI Tracepoint Commands::
25018 * GDB/MI Symbol Query::
25019 * GDB/MI File Commands::
25021 * GDB/MI Kod Commands::
25022 * GDB/MI Memory Overlay Commands::
25023 * GDB/MI Signal Handling Commands::
25025 * GDB/MI Target Manipulation::
25026 * GDB/MI File Transfer Commands::
25027 * GDB/MI Ada Exceptions Commands::
25028 * GDB/MI Support Commands::
25029 * GDB/MI Miscellaneous Commands::
25032 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25033 @node GDB/MI General Design
25034 @section @sc{gdb/mi} General Design
25035 @cindex GDB/MI General Design
25037 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
25038 parts---commands sent to @value{GDBN}, responses to those commands
25039 and notifications. Each command results in exactly one response,
25040 indicating either successful completion of the command, or an error.
25041 For the commands that do not resume the target, the response contains the
25042 requested information. For the commands that resume the target, the
25043 response only indicates whether the target was successfully resumed.
25044 Notifications is the mechanism for reporting changes in the state of the
25045 target, or in @value{GDBN} state, that cannot conveniently be associated with
25046 a command and reported as part of that command response.
25048 The important examples of notifications are:
25052 Exec notifications. These are used to report changes in
25053 target state---when a target is resumed, or stopped. It would not
25054 be feasible to include this information in response of resuming
25055 commands, because one resume commands can result in multiple events in
25056 different threads. Also, quite some time may pass before any event
25057 happens in the target, while a frontend needs to know whether the resuming
25058 command itself was successfully executed.
25061 Console output, and status notifications. Console output
25062 notifications are used to report output of CLI commands, as well as
25063 diagnostics for other commands. Status notifications are used to
25064 report the progress of a long-running operation. Naturally, including
25065 this information in command response would mean no output is produced
25066 until the command is finished, which is undesirable.
25069 General notifications. Commands may have various side effects on
25070 the @value{GDBN} or target state beyond their official purpose. For example,
25071 a command may change the selected thread. Although such changes can
25072 be included in command response, using notification allows for more
25073 orthogonal frontend design.
25077 There's no guarantee that whenever an MI command reports an error,
25078 @value{GDBN} or the target are in any specific state, and especially,
25079 the state is not reverted to the state before the MI command was
25080 processed. Therefore, whenever an MI command results in an error,
25081 we recommend that the frontend refreshes all the information shown in
25082 the user interface.
25086 * Context management::
25087 * Asynchronous and non-stop modes::
25091 @node Context management
25092 @subsection Context management
25094 @subsubsection Threads and Frames
25096 In most cases when @value{GDBN} accesses the target, this access is
25097 done in context of a specific thread and frame (@pxref{Frames}).
25098 Often, even when accessing global data, the target requires that a thread
25099 be specified. The CLI interface maintains the selected thread and frame,
25100 and supplies them to target on each command. This is convenient,
25101 because a command line user would not want to specify that information
25102 explicitly on each command, and because user interacts with
25103 @value{GDBN} via a single terminal, so no confusion is possible as
25104 to what thread and frame are the current ones.
25106 In the case of MI, the concept of selected thread and frame is less
25107 useful. First, a frontend can easily remember this information
25108 itself. Second, a graphical frontend can have more than one window,
25109 each one used for debugging a different thread, and the frontend might
25110 want to access additional threads for internal purposes. This
25111 increases the risk that by relying on implicitly selected thread, the
25112 frontend may be operating on a wrong one. Therefore, each MI command
25113 should explicitly specify which thread and frame to operate on. To
25114 make it possible, each MI command accepts the @samp{--thread} and
25115 @samp{--frame} options, the value to each is @value{GDBN} identifier
25116 for thread and frame to operate on.
25118 Usually, each top-level window in a frontend allows the user to select
25119 a thread and a frame, and remembers the user selection for further
25120 operations. However, in some cases @value{GDBN} may suggest that the
25121 current thread be changed. For example, when stopping on a breakpoint
25122 it is reasonable to switch to the thread where breakpoint is hit. For
25123 another example, if the user issues the CLI @samp{thread} command via
25124 the frontend, it is desirable to change the frontend's selected thread to the
25125 one specified by user. @value{GDBN} communicates the suggestion to
25126 change current thread using the @samp{=thread-selected} notification.
25127 No such notification is available for the selected frame at the moment.
25129 Note that historically, MI shares the selected thread with CLI, so
25130 frontends used the @code{-thread-select} to execute commands in the
25131 right context. However, getting this to work right is cumbersome. The
25132 simplest way is for frontend to emit @code{-thread-select} command
25133 before every command. This doubles the number of commands that need
25134 to be sent. The alternative approach is to suppress @code{-thread-select}
25135 if the selected thread in @value{GDBN} is supposed to be identical to the
25136 thread the frontend wants to operate on. However, getting this
25137 optimization right can be tricky. In particular, if the frontend
25138 sends several commands to @value{GDBN}, and one of the commands changes the
25139 selected thread, then the behaviour of subsequent commands will
25140 change. So, a frontend should either wait for response from such
25141 problematic commands, or explicitly add @code{-thread-select} for
25142 all subsequent commands. No frontend is known to do this exactly
25143 right, so it is suggested to just always pass the @samp{--thread} and
25144 @samp{--frame} options.
25146 @subsubsection Language
25148 The execution of several commands depends on which language is selected.
25149 By default, the current language (@pxref{show language}) is used.
25150 But for commands known to be language-sensitive, it is recommended
25151 to use the @samp{--language} option. This option takes one argument,
25152 which is the name of the language to use while executing the command.
25156 -data-evaluate-expression --language c "sizeof (void*)"
25161 The valid language names are the same names accepted by the
25162 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
25163 @samp{local} or @samp{unknown}.
25165 @node Asynchronous and non-stop modes
25166 @subsection Asynchronous command execution and non-stop mode
25168 On some targets, @value{GDBN} is capable of processing MI commands
25169 even while the target is running. This is called @dfn{asynchronous
25170 command execution} (@pxref{Background Execution}). The frontend may
25171 specify a preferrence for asynchronous execution using the
25172 @code{-gdb-set mi-async 1} command, which should be emitted before
25173 either running the executable or attaching to the target. After the
25174 frontend has started the executable or attached to the target, it can
25175 find if asynchronous execution is enabled using the
25176 @code{-list-target-features} command.
25179 @item -gdb-set mi-async on
25180 @item -gdb-set mi-async off
25181 Set whether MI is in asynchronous mode.
25183 When @code{off}, which is the default, MI execution commands (e.g.,
25184 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
25185 for the program to stop before processing further commands.
25187 When @code{on}, MI execution commands are background execution
25188 commands (e.g., @code{-exec-continue} becomes the equivalent of the
25189 @code{c&} CLI command), and so @value{GDBN} is capable of processing
25190 MI commands even while the target is running.
25192 @item -gdb-show mi-async
25193 Show whether MI asynchronous mode is enabled.
25196 Note: In @value{GDBN} version 7.7 and earlier, this option was called
25197 @code{target-async} instead of @code{mi-async}, and it had the effect
25198 of both putting MI in asynchronous mode and making CLI background
25199 commands possible. CLI background commands are now always possible
25200 ``out of the box'' if the target supports them. The old spelling is
25201 kept as a deprecated alias for backwards compatibility.
25203 Even if @value{GDBN} can accept a command while target is running,
25204 many commands that access the target do not work when the target is
25205 running. Therefore, asynchronous command execution is most useful
25206 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
25207 it is possible to examine the state of one thread, while other threads
25210 When a given thread is running, MI commands that try to access the
25211 target in the context of that thread may not work, or may work only on
25212 some targets. In particular, commands that try to operate on thread's
25213 stack will not work, on any target. Commands that read memory, or
25214 modify breakpoints, may work or not work, depending on the target. Note
25215 that even commands that operate on global state, such as @code{print},
25216 @code{set}, and breakpoint commands, still access the target in the
25217 context of a specific thread, so frontend should try to find a
25218 stopped thread and perform the operation on that thread (using the
25219 @samp{--thread} option).
25221 Which commands will work in the context of a running thread is
25222 highly target dependent. However, the two commands
25223 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
25224 to find the state of a thread, will always work.
25226 @node Thread groups
25227 @subsection Thread groups
25228 @value{GDBN} may be used to debug several processes at the same time.
25229 On some platfroms, @value{GDBN} may support debugging of several
25230 hardware systems, each one having several cores with several different
25231 processes running on each core. This section describes the MI
25232 mechanism to support such debugging scenarios.
25234 The key observation is that regardless of the structure of the
25235 target, MI can have a global list of threads, because most commands that
25236 accept the @samp{--thread} option do not need to know what process that
25237 thread belongs to. Therefore, it is not necessary to introduce
25238 neither additional @samp{--process} option, nor an notion of the
25239 current process in the MI interface. The only strictly new feature
25240 that is required is the ability to find how the threads are grouped
25243 To allow the user to discover such grouping, and to support arbitrary
25244 hierarchy of machines/cores/processes, MI introduces the concept of a
25245 @dfn{thread group}. Thread group is a collection of threads and other
25246 thread groups. A thread group always has a string identifier, a type,
25247 and may have additional attributes specific to the type. A new
25248 command, @code{-list-thread-groups}, returns the list of top-level
25249 thread groups, which correspond to processes that @value{GDBN} is
25250 debugging at the moment. By passing an identifier of a thread group
25251 to the @code{-list-thread-groups} command, it is possible to obtain
25252 the members of specific thread group.
25254 To allow the user to easily discover processes, and other objects, he
25255 wishes to debug, a concept of @dfn{available thread group} is
25256 introduced. Available thread group is an thread group that
25257 @value{GDBN} is not debugging, but that can be attached to, using the
25258 @code{-target-attach} command. The list of available top-level thread
25259 groups can be obtained using @samp{-list-thread-groups --available}.
25260 In general, the content of a thread group may be only retrieved only
25261 after attaching to that thread group.
25263 Thread groups are related to inferiors (@pxref{Inferiors and
25264 Programs}). Each inferior corresponds to a thread group of a special
25265 type @samp{process}, and some additional operations are permitted on
25266 such thread groups.
25268 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25269 @node GDB/MI Command Syntax
25270 @section @sc{gdb/mi} Command Syntax
25273 * GDB/MI Input Syntax::
25274 * GDB/MI Output Syntax::
25277 @node GDB/MI Input Syntax
25278 @subsection @sc{gdb/mi} Input Syntax
25280 @cindex input syntax for @sc{gdb/mi}
25281 @cindex @sc{gdb/mi}, input syntax
25283 @item @var{command} @expansion{}
25284 @code{@var{cli-command} | @var{mi-command}}
25286 @item @var{cli-command} @expansion{}
25287 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
25288 @var{cli-command} is any existing @value{GDBN} CLI command.
25290 @item @var{mi-command} @expansion{}
25291 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
25292 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
25294 @item @var{token} @expansion{}
25295 "any sequence of digits"
25297 @item @var{option} @expansion{}
25298 @code{"-" @var{parameter} [ " " @var{parameter} ]}
25300 @item @var{parameter} @expansion{}
25301 @code{@var{non-blank-sequence} | @var{c-string}}
25303 @item @var{operation} @expansion{}
25304 @emph{any of the operations described in this chapter}
25306 @item @var{non-blank-sequence} @expansion{}
25307 @emph{anything, provided it doesn't contain special characters such as
25308 "-", @var{nl}, """ and of course " "}
25310 @item @var{c-string} @expansion{}
25311 @code{""" @var{seven-bit-iso-c-string-content} """}
25313 @item @var{nl} @expansion{}
25322 The CLI commands are still handled by the @sc{mi} interpreter; their
25323 output is described below.
25326 The @code{@var{token}}, when present, is passed back when the command
25330 Some @sc{mi} commands accept optional arguments as part of the parameter
25331 list. Each option is identified by a leading @samp{-} (dash) and may be
25332 followed by an optional argument parameter. Options occur first in the
25333 parameter list and can be delimited from normal parameters using
25334 @samp{--} (this is useful when some parameters begin with a dash).
25341 We want easy access to the existing CLI syntax (for debugging).
25344 We want it to be easy to spot a @sc{mi} operation.
25347 @node GDB/MI Output Syntax
25348 @subsection @sc{gdb/mi} Output Syntax
25350 @cindex output syntax of @sc{gdb/mi}
25351 @cindex @sc{gdb/mi}, output syntax
25352 The output from @sc{gdb/mi} consists of zero or more out-of-band records
25353 followed, optionally, by a single result record. This result record
25354 is for the most recent command. The sequence of output records is
25355 terminated by @samp{(gdb)}.
25357 If an input command was prefixed with a @code{@var{token}} then the
25358 corresponding output for that command will also be prefixed by that same
25362 @item @var{output} @expansion{}
25363 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
25365 @item @var{result-record} @expansion{}
25366 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
25368 @item @var{out-of-band-record} @expansion{}
25369 @code{@var{async-record} | @var{stream-record}}
25371 @item @var{async-record} @expansion{}
25372 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
25374 @item @var{exec-async-output} @expansion{}
25375 @code{[ @var{token} ] "*" @var{async-output nl}}
25377 @item @var{status-async-output} @expansion{}
25378 @code{[ @var{token} ] "+" @var{async-output nl}}
25380 @item @var{notify-async-output} @expansion{}
25381 @code{[ @var{token} ] "=" @var{async-output nl}}
25383 @item @var{async-output} @expansion{}
25384 @code{@var{async-class} ( "," @var{result} )*}
25386 @item @var{result-class} @expansion{}
25387 @code{"done" | "running" | "connected" | "error" | "exit"}
25389 @item @var{async-class} @expansion{}
25390 @code{"stopped" | @var{others}} (where @var{others} will be added
25391 depending on the needs---this is still in development).
25393 @item @var{result} @expansion{}
25394 @code{ @var{variable} "=" @var{value}}
25396 @item @var{variable} @expansion{}
25397 @code{ @var{string} }
25399 @item @var{value} @expansion{}
25400 @code{ @var{const} | @var{tuple} | @var{list} }
25402 @item @var{const} @expansion{}
25403 @code{@var{c-string}}
25405 @item @var{tuple} @expansion{}
25406 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
25408 @item @var{list} @expansion{}
25409 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
25410 @var{result} ( "," @var{result} )* "]" }
25412 @item @var{stream-record} @expansion{}
25413 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
25415 @item @var{console-stream-output} @expansion{}
25416 @code{"~" @var{c-string nl}}
25418 @item @var{target-stream-output} @expansion{}
25419 @code{"@@" @var{c-string nl}}
25421 @item @var{log-stream-output} @expansion{}
25422 @code{"&" @var{c-string nl}}
25424 @item @var{nl} @expansion{}
25427 @item @var{token} @expansion{}
25428 @emph{any sequence of digits}.
25436 All output sequences end in a single line containing a period.
25439 The @code{@var{token}} is from the corresponding request. Note that
25440 for all async output, while the token is allowed by the grammar and
25441 may be output by future versions of @value{GDBN} for select async
25442 output messages, it is generally omitted. Frontends should treat
25443 all async output as reporting general changes in the state of the
25444 target and there should be no need to associate async output to any
25448 @cindex status output in @sc{gdb/mi}
25449 @var{status-async-output} contains on-going status information about the
25450 progress of a slow operation. It can be discarded. All status output is
25451 prefixed by @samp{+}.
25454 @cindex async output in @sc{gdb/mi}
25455 @var{exec-async-output} contains asynchronous state change on the target
25456 (stopped, started, disappeared). All async output is prefixed by
25460 @cindex notify output in @sc{gdb/mi}
25461 @var{notify-async-output} contains supplementary information that the
25462 client should handle (e.g., a new breakpoint information). All notify
25463 output is prefixed by @samp{=}.
25466 @cindex console output in @sc{gdb/mi}
25467 @var{console-stream-output} is output that should be displayed as is in the
25468 console. It is the textual response to a CLI command. All the console
25469 output is prefixed by @samp{~}.
25472 @cindex target output in @sc{gdb/mi}
25473 @var{target-stream-output} is the output produced by the target program.
25474 All the target output is prefixed by @samp{@@}.
25477 @cindex log output in @sc{gdb/mi}
25478 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
25479 instance messages that should be displayed as part of an error log. All
25480 the log output is prefixed by @samp{&}.
25483 @cindex list output in @sc{gdb/mi}
25484 New @sc{gdb/mi} commands should only output @var{lists} containing
25490 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
25491 details about the various output records.
25493 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25494 @node GDB/MI Compatibility with CLI
25495 @section @sc{gdb/mi} Compatibility with CLI
25497 @cindex compatibility, @sc{gdb/mi} and CLI
25498 @cindex @sc{gdb/mi}, compatibility with CLI
25500 For the developers convenience CLI commands can be entered directly,
25501 but there may be some unexpected behaviour. For example, commands
25502 that query the user will behave as if the user replied yes, breakpoint
25503 command lists are not executed and some CLI commands, such as
25504 @code{if}, @code{when} and @code{define}, prompt for further input with
25505 @samp{>}, which is not valid MI output.
25507 This feature may be removed at some stage in the future and it is
25508 recommended that front ends use the @code{-interpreter-exec} command
25509 (@pxref{-interpreter-exec}).
25511 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25512 @node GDB/MI Development and Front Ends
25513 @section @sc{gdb/mi} Development and Front Ends
25514 @cindex @sc{gdb/mi} development
25516 The application which takes the MI output and presents the state of the
25517 program being debugged to the user is called a @dfn{front end}.
25519 Although @sc{gdb/mi} is still incomplete, it is currently being used
25520 by a variety of front ends to @value{GDBN}. This makes it difficult
25521 to introduce new functionality without breaking existing usage. This
25522 section tries to minimize the problems by describing how the protocol
25525 Some changes in MI need not break a carefully designed front end, and
25526 for these the MI version will remain unchanged. The following is a
25527 list of changes that may occur within one level, so front ends should
25528 parse MI output in a way that can handle them:
25532 New MI commands may be added.
25535 New fields may be added to the output of any MI command.
25538 The range of values for fields with specified values, e.g.,
25539 @code{in_scope} (@pxref{-var-update}) may be extended.
25541 @c The format of field's content e.g type prefix, may change so parse it
25542 @c at your own risk. Yes, in general?
25544 @c The order of fields may change? Shouldn't really matter but it might
25545 @c resolve inconsistencies.
25548 If the changes are likely to break front ends, the MI version level
25549 will be increased by one. This will allow the front end to parse the
25550 output according to the MI version. Apart from mi0, new versions of
25551 @value{GDBN} will not support old versions of MI and it will be the
25552 responsibility of the front end to work with the new one.
25554 @c Starting with mi3, add a new command -mi-version that prints the MI
25557 The best way to avoid unexpected changes in MI that might break your front
25558 end is to make your project known to @value{GDBN} developers and
25559 follow development on @email{gdb@@sourceware.org} and
25560 @email{gdb-patches@@sourceware.org}.
25561 @cindex mailing lists
25563 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25564 @node GDB/MI Output Records
25565 @section @sc{gdb/mi} Output Records
25568 * GDB/MI Result Records::
25569 * GDB/MI Stream Records::
25570 * GDB/MI Async Records::
25571 * GDB/MI Breakpoint Information::
25572 * GDB/MI Frame Information::
25573 * GDB/MI Thread Information::
25574 * GDB/MI Ada Exception Information::
25577 @node GDB/MI Result Records
25578 @subsection @sc{gdb/mi} Result Records
25580 @cindex result records in @sc{gdb/mi}
25581 @cindex @sc{gdb/mi}, result records
25582 In addition to a number of out-of-band notifications, the response to a
25583 @sc{gdb/mi} command includes one of the following result indications:
25587 @item "^done" [ "," @var{results} ]
25588 The synchronous operation was successful, @code{@var{results}} are the return
25593 This result record is equivalent to @samp{^done}. Historically, it
25594 was output instead of @samp{^done} if the command has resumed the
25595 target. This behaviour is maintained for backward compatibility, but
25596 all frontends should treat @samp{^done} and @samp{^running}
25597 identically and rely on the @samp{*running} output record to determine
25598 which threads are resumed.
25602 @value{GDBN} has connected to a remote target.
25604 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
25606 The operation failed. The @code{msg=@var{c-string}} variable contains
25607 the corresponding error message.
25609 If present, the @code{code=@var{c-string}} variable provides an error
25610 code on which consumers can rely on to detect the corresponding
25611 error condition. At present, only one error code is defined:
25614 @item "undefined-command"
25615 Indicates that the command causing the error does not exist.
25620 @value{GDBN} has terminated.
25624 @node GDB/MI Stream Records
25625 @subsection @sc{gdb/mi} Stream Records
25627 @cindex @sc{gdb/mi}, stream records
25628 @cindex stream records in @sc{gdb/mi}
25629 @value{GDBN} internally maintains a number of output streams: the console, the
25630 target, and the log. The output intended for each of these streams is
25631 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
25633 Each stream record begins with a unique @dfn{prefix character} which
25634 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
25635 Syntax}). In addition to the prefix, each stream record contains a
25636 @code{@var{string-output}}. This is either raw text (with an implicit new
25637 line) or a quoted C string (which does not contain an implicit newline).
25640 @item "~" @var{string-output}
25641 The console output stream contains text that should be displayed in the
25642 CLI console window. It contains the textual responses to CLI commands.
25644 @item "@@" @var{string-output}
25645 The target output stream contains any textual output from the running
25646 target. This is only present when GDB's event loop is truly
25647 asynchronous, which is currently only the case for remote targets.
25649 @item "&" @var{string-output}
25650 The log stream contains debugging messages being produced by @value{GDBN}'s
25654 @node GDB/MI Async Records
25655 @subsection @sc{gdb/mi} Async Records
25657 @cindex async records in @sc{gdb/mi}
25658 @cindex @sc{gdb/mi}, async records
25659 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
25660 additional changes that have occurred. Those changes can either be a
25661 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
25662 target activity (e.g., target stopped).
25664 The following is the list of possible async records:
25668 @item *running,thread-id="@var{thread}"
25669 The target is now running. The @var{thread} field tells which
25670 specific thread is now running, and can be @samp{all} if all threads
25671 are running. The frontend should assume that no interaction with a
25672 running thread is possible after this notification is produced.
25673 The frontend should not assume that this notification is output
25674 only once for any command. @value{GDBN} may emit this notification
25675 several times, either for different threads, because it cannot resume
25676 all threads together, or even for a single thread, if the thread must
25677 be stepped though some code before letting it run freely.
25679 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
25680 The target has stopped. The @var{reason} field can have one of the
25684 @item breakpoint-hit
25685 A breakpoint was reached.
25686 @item watchpoint-trigger
25687 A watchpoint was triggered.
25688 @item read-watchpoint-trigger
25689 A read watchpoint was triggered.
25690 @item access-watchpoint-trigger
25691 An access watchpoint was triggered.
25692 @item function-finished
25693 An -exec-finish or similar CLI command was accomplished.
25694 @item location-reached
25695 An -exec-until or similar CLI command was accomplished.
25696 @item watchpoint-scope
25697 A watchpoint has gone out of scope.
25698 @item end-stepping-range
25699 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
25700 similar CLI command was accomplished.
25701 @item exited-signalled
25702 The inferior exited because of a signal.
25704 The inferior exited.
25705 @item exited-normally
25706 The inferior exited normally.
25707 @item signal-received
25708 A signal was received by the inferior.
25710 The inferior has stopped due to a library being loaded or unloaded.
25711 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
25712 set or when a @code{catch load} or @code{catch unload} catchpoint is
25713 in use (@pxref{Set Catchpoints}).
25715 The inferior has forked. This is reported when @code{catch fork}
25716 (@pxref{Set Catchpoints}) has been used.
25718 The inferior has vforked. This is reported in when @code{catch vfork}
25719 (@pxref{Set Catchpoints}) has been used.
25720 @item syscall-entry
25721 The inferior entered a system call. This is reported when @code{catch
25722 syscall} (@pxref{Set Catchpoints}) has been used.
25723 @item syscall-entry
25724 The inferior returned from a system call. This is reported when
25725 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
25727 The inferior called @code{exec}. This is reported when @code{catch exec}
25728 (@pxref{Set Catchpoints}) has been used.
25731 The @var{id} field identifies the thread that directly caused the stop
25732 -- for example by hitting a breakpoint. Depending on whether all-stop
25733 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
25734 stop all threads, or only the thread that directly triggered the stop.
25735 If all threads are stopped, the @var{stopped} field will have the
25736 value of @code{"all"}. Otherwise, the value of the @var{stopped}
25737 field will be a list of thread identifiers. Presently, this list will
25738 always include a single thread, but frontend should be prepared to see
25739 several threads in the list. The @var{core} field reports the
25740 processor core on which the stop event has happened. This field may be absent
25741 if such information is not available.
25743 @item =thread-group-added,id="@var{id}"
25744 @itemx =thread-group-removed,id="@var{id}"
25745 A thread group was either added or removed. The @var{id} field
25746 contains the @value{GDBN} identifier of the thread group. When a thread
25747 group is added, it generally might not be associated with a running
25748 process. When a thread group is removed, its id becomes invalid and
25749 cannot be used in any way.
25751 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
25752 A thread group became associated with a running program,
25753 either because the program was just started or the thread group
25754 was attached to a program. The @var{id} field contains the
25755 @value{GDBN} identifier of the thread group. The @var{pid} field
25756 contains process identifier, specific to the operating system.
25758 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
25759 A thread group is no longer associated with a running program,
25760 either because the program has exited, or because it was detached
25761 from. The @var{id} field contains the @value{GDBN} identifier of the
25762 thread group. The @var{code} field is the exit code of the inferior; it exists
25763 only when the inferior exited with some code.
25765 @item =thread-created,id="@var{id}",group-id="@var{gid}"
25766 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
25767 A thread either was created, or has exited. The @var{id} field
25768 contains the @value{GDBN} identifier of the thread. The @var{gid}
25769 field identifies the thread group this thread belongs to.
25771 @item =thread-selected,id="@var{id}"
25772 Informs that the selected thread was changed as result of the last
25773 command. This notification is not emitted as result of @code{-thread-select}
25774 command but is emitted whenever an MI command that is not documented
25775 to change the selected thread actually changes it. In particular,
25776 invoking, directly or indirectly (via user-defined command), the CLI
25777 @code{thread} command, will generate this notification.
25779 We suggest that in response to this notification, front ends
25780 highlight the selected thread and cause subsequent commands to apply to
25783 @item =library-loaded,...
25784 Reports that a new library file was loaded by the program. This
25785 notification has 4 fields---@var{id}, @var{target-name},
25786 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
25787 opaque identifier of the library. For remote debugging case,
25788 @var{target-name} and @var{host-name} fields give the name of the
25789 library file on the target, and on the host respectively. For native
25790 debugging, both those fields have the same value. The
25791 @var{symbols-loaded} field is emitted only for backward compatibility
25792 and should not be relied on to convey any useful information. The
25793 @var{thread-group} field, if present, specifies the id of the thread
25794 group in whose context the library was loaded. If the field is
25795 absent, it means the library was loaded in the context of all present
25798 @item =library-unloaded,...
25799 Reports that a library was unloaded by the program. This notification
25800 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
25801 the same meaning as for the @code{=library-loaded} notification.
25802 The @var{thread-group} field, if present, specifies the id of the
25803 thread group in whose context the library was unloaded. If the field is
25804 absent, it means the library was unloaded in the context of all present
25807 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
25808 @itemx =traceframe-changed,end
25809 Reports that the trace frame was changed and its new number is
25810 @var{tfnum}. The number of the tracepoint associated with this trace
25811 frame is @var{tpnum}.
25813 @item =tsv-created,name=@var{name},initial=@var{initial}
25814 Reports that the new trace state variable @var{name} is created with
25815 initial value @var{initial}.
25817 @item =tsv-deleted,name=@var{name}
25818 @itemx =tsv-deleted
25819 Reports that the trace state variable @var{name} is deleted or all
25820 trace state variables are deleted.
25822 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
25823 Reports that the trace state variable @var{name} is modified with
25824 the initial value @var{initial}. The current value @var{current} of
25825 trace state variable is optional and is reported if the current
25826 value of trace state variable is known.
25828 @item =breakpoint-created,bkpt=@{...@}
25829 @itemx =breakpoint-modified,bkpt=@{...@}
25830 @itemx =breakpoint-deleted,id=@var{number}
25831 Reports that a breakpoint was created, modified, or deleted,
25832 respectively. Only user-visible breakpoints are reported to the MI
25835 The @var{bkpt} argument is of the same form as returned by the various
25836 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
25837 @var{number} is the ordinal number of the breakpoint.
25839 Note that if a breakpoint is emitted in the result record of a
25840 command, then it will not also be emitted in an async record.
25842 @item =record-started,thread-group="@var{id}"
25843 @itemx =record-stopped,thread-group="@var{id}"
25844 Execution log recording was either started or stopped on an
25845 inferior. The @var{id} is the @value{GDBN} identifier of the thread
25846 group corresponding to the affected inferior.
25848 @item =cmd-param-changed,param=@var{param},value=@var{value}
25849 Reports that a parameter of the command @code{set @var{param}} is
25850 changed to @var{value}. In the multi-word @code{set} command,
25851 the @var{param} is the whole parameter list to @code{set} command.
25852 For example, In command @code{set check type on}, @var{param}
25853 is @code{check type} and @var{value} is @code{on}.
25855 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
25856 Reports that bytes from @var{addr} to @var{data} + @var{len} were
25857 written in an inferior. The @var{id} is the identifier of the
25858 thread group corresponding to the affected inferior. The optional
25859 @code{type="code"} part is reported if the memory written to holds
25863 @node GDB/MI Breakpoint Information
25864 @subsection @sc{gdb/mi} Breakpoint Information
25866 When @value{GDBN} reports information about a breakpoint, a
25867 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
25872 The breakpoint number. For a breakpoint that represents one location
25873 of a multi-location breakpoint, this will be a dotted pair, like
25877 The type of the breakpoint. For ordinary breakpoints this will be
25878 @samp{breakpoint}, but many values are possible.
25881 If the type of the breakpoint is @samp{catchpoint}, then this
25882 indicates the exact type of catchpoint.
25885 This is the breakpoint disposition---either @samp{del}, meaning that
25886 the breakpoint will be deleted at the next stop, or @samp{keep},
25887 meaning that the breakpoint will not be deleted.
25890 This indicates whether the breakpoint is enabled, in which case the
25891 value is @samp{y}, or disabled, in which case the value is @samp{n}.
25892 Note that this is not the same as the field @code{enable}.
25895 The address of the breakpoint. This may be a hexidecimal number,
25896 giving the address; or the string @samp{<PENDING>}, for a pending
25897 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
25898 multiple locations. This field will not be present if no address can
25899 be determined. For example, a watchpoint does not have an address.
25902 If known, the function in which the breakpoint appears.
25903 If not known, this field is not present.
25906 The name of the source file which contains this function, if known.
25907 If not known, this field is not present.
25910 The full file name of the source file which contains this function, if
25911 known. If not known, this field is not present.
25914 The line number at which this breakpoint appears, if known.
25915 If not known, this field is not present.
25918 If the source file is not known, this field may be provided. If
25919 provided, this holds the address of the breakpoint, possibly followed
25923 If this breakpoint is pending, this field is present and holds the
25924 text used to set the breakpoint, as entered by the user.
25927 Where this breakpoint's condition is evaluated, either @samp{host} or
25931 If this is a thread-specific breakpoint, then this identifies the
25932 thread in which the breakpoint can trigger.
25935 If this breakpoint is restricted to a particular Ada task, then this
25936 field will hold the task identifier.
25939 If the breakpoint is conditional, this is the condition expression.
25942 The ignore count of the breakpoint.
25945 The enable count of the breakpoint.
25947 @item traceframe-usage
25950 @item static-tracepoint-marker-string-id
25951 For a static tracepoint, the name of the static tracepoint marker.
25954 For a masked watchpoint, this is the mask.
25957 A tracepoint's pass count.
25959 @item original-location
25960 The location of the breakpoint as originally specified by the user.
25961 This field is optional.
25964 The number of times the breakpoint has been hit.
25967 This field is only given for tracepoints. This is either @samp{y},
25968 meaning that the tracepoint is installed, or @samp{n}, meaning that it
25972 Some extra data, the exact contents of which are type-dependent.
25976 For example, here is what the output of @code{-break-insert}
25977 (@pxref{GDB/MI Breakpoint Commands}) might be:
25980 -> -break-insert main
25981 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25982 enabled="y",addr="0x08048564",func="main",file="myprog.c",
25983 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
25988 @node GDB/MI Frame Information
25989 @subsection @sc{gdb/mi} Frame Information
25991 Response from many MI commands includes an information about stack
25992 frame. This information is a tuple that may have the following
25997 The level of the stack frame. The innermost frame has the level of
25998 zero. This field is always present.
26001 The name of the function corresponding to the frame. This field may
26002 be absent if @value{GDBN} is unable to determine the function name.
26005 The code address for the frame. This field is always present.
26008 The name of the source files that correspond to the frame's code
26009 address. This field may be absent.
26012 The source line corresponding to the frames' code address. This field
26016 The name of the binary file (either executable or shared library) the
26017 corresponds to the frame's code address. This field may be absent.
26021 @node GDB/MI Thread Information
26022 @subsection @sc{gdb/mi} Thread Information
26024 Whenever @value{GDBN} has to report an information about a thread, it
26025 uses a tuple with the following fields:
26029 The numeric id assigned to the thread by @value{GDBN}. This field is
26033 Target-specific string identifying the thread. This field is always present.
26036 Additional information about the thread provided by the target.
26037 It is supposed to be human-readable and not interpreted by the
26038 frontend. This field is optional.
26041 Either @samp{stopped} or @samp{running}, depending on whether the
26042 thread is presently running. This field is always present.
26045 The value of this field is an integer number of the processor core the
26046 thread was last seen on. This field is optional.
26049 @node GDB/MI Ada Exception Information
26050 @subsection @sc{gdb/mi} Ada Exception Information
26052 Whenever a @code{*stopped} record is emitted because the program
26053 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
26054 @value{GDBN} provides the name of the exception that was raised via
26055 the @code{exception-name} field.
26057 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26058 @node GDB/MI Simple Examples
26059 @section Simple Examples of @sc{gdb/mi} Interaction
26060 @cindex @sc{gdb/mi}, simple examples
26062 This subsection presents several simple examples of interaction using
26063 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
26064 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
26065 the output received from @sc{gdb/mi}.
26067 Note the line breaks shown in the examples are here only for
26068 readability, they don't appear in the real output.
26070 @subheading Setting a Breakpoint
26072 Setting a breakpoint generates synchronous output which contains detailed
26073 information of the breakpoint.
26076 -> -break-insert main
26077 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26078 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26079 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26084 @subheading Program Execution
26086 Program execution generates asynchronous records and MI gives the
26087 reason that execution stopped.
26093 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
26094 frame=@{addr="0x08048564",func="main",
26095 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
26096 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
26101 <- *stopped,reason="exited-normally"
26105 @subheading Quitting @value{GDBN}
26107 Quitting @value{GDBN} just prints the result class @samp{^exit}.
26115 Please note that @samp{^exit} is printed immediately, but it might
26116 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
26117 performs necessary cleanups, including killing programs being debugged
26118 or disconnecting from debug hardware, so the frontend should wait till
26119 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
26120 fails to exit in reasonable time.
26122 @subheading A Bad Command
26124 Here's what happens if you pass a non-existent command:
26128 <- ^error,msg="Undefined MI command: rubbish"
26133 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26134 @node GDB/MI Command Description Format
26135 @section @sc{gdb/mi} Command Description Format
26137 The remaining sections describe blocks of commands. Each block of
26138 commands is laid out in a fashion similar to this section.
26140 @subheading Motivation
26142 The motivation for this collection of commands.
26144 @subheading Introduction
26146 A brief introduction to this collection of commands as a whole.
26148 @subheading Commands
26150 For each command in the block, the following is described:
26152 @subsubheading Synopsis
26155 -command @var{args}@dots{}
26158 @subsubheading Result
26160 @subsubheading @value{GDBN} Command
26162 The corresponding @value{GDBN} CLI command(s), if any.
26164 @subsubheading Example
26166 Example(s) formatted for readability. Some of the described commands have
26167 not been implemented yet and these are labeled N.A.@: (not available).
26170 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26171 @node GDB/MI Breakpoint Commands
26172 @section @sc{gdb/mi} Breakpoint Commands
26174 @cindex breakpoint commands for @sc{gdb/mi}
26175 @cindex @sc{gdb/mi}, breakpoint commands
26176 This section documents @sc{gdb/mi} commands for manipulating
26179 @subheading The @code{-break-after} Command
26180 @findex -break-after
26182 @subsubheading Synopsis
26185 -break-after @var{number} @var{count}
26188 The breakpoint number @var{number} is not in effect until it has been
26189 hit @var{count} times. To see how this is reflected in the output of
26190 the @samp{-break-list} command, see the description of the
26191 @samp{-break-list} command below.
26193 @subsubheading @value{GDBN} Command
26195 The corresponding @value{GDBN} command is @samp{ignore}.
26197 @subsubheading Example
26202 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26203 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26204 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26212 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26213 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26214 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26215 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26216 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26217 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26218 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26219 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26220 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26221 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
26226 @subheading The @code{-break-catch} Command
26227 @findex -break-catch
26230 @subheading The @code{-break-commands} Command
26231 @findex -break-commands
26233 @subsubheading Synopsis
26236 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
26239 Specifies the CLI commands that should be executed when breakpoint
26240 @var{number} is hit. The parameters @var{command1} to @var{commandN}
26241 are the commands. If no command is specified, any previously-set
26242 commands are cleared. @xref{Break Commands}. Typical use of this
26243 functionality is tracing a program, that is, printing of values of
26244 some variables whenever breakpoint is hit and then continuing.
26246 @subsubheading @value{GDBN} Command
26248 The corresponding @value{GDBN} command is @samp{commands}.
26250 @subsubheading Example
26255 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26256 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26257 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26260 -break-commands 1 "print v" "continue"
26265 @subheading The @code{-break-condition} Command
26266 @findex -break-condition
26268 @subsubheading Synopsis
26271 -break-condition @var{number} @var{expr}
26274 Breakpoint @var{number} will stop the program only if the condition in
26275 @var{expr} is true. The condition becomes part of the
26276 @samp{-break-list} output (see the description of the @samp{-break-list}
26279 @subsubheading @value{GDBN} Command
26281 The corresponding @value{GDBN} command is @samp{condition}.
26283 @subsubheading Example
26287 -break-condition 1 1
26291 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26292 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26293 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26294 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26295 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26296 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26297 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26298 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26299 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26300 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
26304 @subheading The @code{-break-delete} Command
26305 @findex -break-delete
26307 @subsubheading Synopsis
26310 -break-delete ( @var{breakpoint} )+
26313 Delete the breakpoint(s) whose number(s) are specified in the argument
26314 list. This is obviously reflected in the breakpoint list.
26316 @subsubheading @value{GDBN} Command
26318 The corresponding @value{GDBN} command is @samp{delete}.
26320 @subsubheading Example
26328 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26329 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26330 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26331 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26332 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26333 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26334 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26339 @subheading The @code{-break-disable} Command
26340 @findex -break-disable
26342 @subsubheading Synopsis
26345 -break-disable ( @var{breakpoint} )+
26348 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
26349 break list is now set to @samp{n} for the named @var{breakpoint}(s).
26351 @subsubheading @value{GDBN} Command
26353 The corresponding @value{GDBN} command is @samp{disable}.
26355 @subsubheading Example
26363 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26364 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26365 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26366 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26367 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26368 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26369 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26370 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
26371 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26372 line="5",thread-groups=["i1"],times="0"@}]@}
26376 @subheading The @code{-break-enable} Command
26377 @findex -break-enable
26379 @subsubheading Synopsis
26382 -break-enable ( @var{breakpoint} )+
26385 Enable (previously disabled) @var{breakpoint}(s).
26387 @subsubheading @value{GDBN} Command
26389 The corresponding @value{GDBN} command is @samp{enable}.
26391 @subsubheading Example
26399 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26400 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26401 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26402 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26403 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26404 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26405 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26406 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26407 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26408 line="5",thread-groups=["i1"],times="0"@}]@}
26412 @subheading The @code{-break-info} Command
26413 @findex -break-info
26415 @subsubheading Synopsis
26418 -break-info @var{breakpoint}
26422 Get information about a single breakpoint.
26424 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
26425 Information}, for details on the format of each breakpoint in the
26428 @subsubheading @value{GDBN} Command
26430 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
26432 @subsubheading Example
26435 @subheading The @code{-break-insert} Command
26436 @findex -break-insert
26438 @subsubheading Synopsis
26441 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
26442 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26443 [ -p @var{thread-id} ] [ @var{location} ]
26447 If specified, @var{location}, can be one of:
26454 @item filename:linenum
26455 @item filename:function
26459 The possible optional parameters of this command are:
26463 Insert a temporary breakpoint.
26465 Insert a hardware breakpoint.
26467 If @var{location} cannot be parsed (for example if it
26468 refers to unknown files or functions), create a pending
26469 breakpoint. Without this flag, @value{GDBN} will report
26470 an error, and won't create a breakpoint, if @var{location}
26473 Create a disabled breakpoint.
26475 Create a tracepoint. @xref{Tracepoints}. When this parameter
26476 is used together with @samp{-h}, a fast tracepoint is created.
26477 @item -c @var{condition}
26478 Make the breakpoint conditional on @var{condition}.
26479 @item -i @var{ignore-count}
26480 Initialize the @var{ignore-count}.
26481 @item -p @var{thread-id}
26482 Restrict the breakpoint to the specified @var{thread-id}.
26485 @subsubheading Result
26487 @xref{GDB/MI Breakpoint Information}, for details on the format of the
26488 resulting breakpoint.
26490 Note: this format is open to change.
26491 @c An out-of-band breakpoint instead of part of the result?
26493 @subsubheading @value{GDBN} Command
26495 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
26496 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
26498 @subsubheading Example
26503 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
26504 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
26507 -break-insert -t foo
26508 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
26509 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
26513 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26514 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26515 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26516 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26517 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26518 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26519 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26520 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26521 addr="0x0001072c", func="main",file="recursive2.c",
26522 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
26524 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
26525 addr="0x00010774",func="foo",file="recursive2.c",
26526 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
26529 @c -break-insert -r foo.*
26530 @c ~int foo(int, int);
26531 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
26532 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
26537 @subheading The @code{-dprintf-insert} Command
26538 @findex -dprintf-insert
26540 @subsubheading Synopsis
26543 -dprintf-insert [ -t ] [ -f ] [ -d ]
26544 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26545 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
26550 If specified, @var{location}, can be one of:
26553 @item @var{function}
26556 @c @item @var{linenum}
26557 @item @var{filename}:@var{linenum}
26558 @item @var{filename}:function
26559 @item *@var{address}
26562 The possible optional parameters of this command are:
26566 Insert a temporary breakpoint.
26568 If @var{location} cannot be parsed (for example, if it
26569 refers to unknown files or functions), create a pending
26570 breakpoint. Without this flag, @value{GDBN} will report
26571 an error, and won't create a breakpoint, if @var{location}
26574 Create a disabled breakpoint.
26575 @item -c @var{condition}
26576 Make the breakpoint conditional on @var{condition}.
26577 @item -i @var{ignore-count}
26578 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
26579 to @var{ignore-count}.
26580 @item -p @var{thread-id}
26581 Restrict the breakpoint to the specified @var{thread-id}.
26584 @subsubheading Result
26586 @xref{GDB/MI Breakpoint Information}, for details on the format of the
26587 resulting breakpoint.
26589 @c An out-of-band breakpoint instead of part of the result?
26591 @subsubheading @value{GDBN} Command
26593 The corresponding @value{GDBN} command is @samp{dprintf}.
26595 @subsubheading Example
26599 4-dprintf-insert foo "At foo entry\n"
26600 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
26601 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
26602 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
26603 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
26604 original-location="foo"@}
26606 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
26607 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
26608 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
26609 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
26610 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
26611 original-location="mi-dprintf.c:26"@}
26615 @subheading The @code{-break-list} Command
26616 @findex -break-list
26618 @subsubheading Synopsis
26624 Displays the list of inserted breakpoints, showing the following fields:
26628 number of the breakpoint
26630 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
26632 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
26635 is the breakpoint enabled or no: @samp{y} or @samp{n}
26637 memory location at which the breakpoint is set
26639 logical location of the breakpoint, expressed by function name, file
26641 @item Thread-groups
26642 list of thread groups to which this breakpoint applies
26644 number of times the breakpoint has been hit
26647 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
26648 @code{body} field is an empty list.
26650 @subsubheading @value{GDBN} Command
26652 The corresponding @value{GDBN} command is @samp{info break}.
26654 @subsubheading Example
26659 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26660 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26661 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26662 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26663 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26664 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26665 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26666 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26667 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
26669 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26670 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
26671 line="13",thread-groups=["i1"],times="0"@}]@}
26675 Here's an example of the result when there are no breakpoints:
26680 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26681 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26682 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26683 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26684 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26685 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26686 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26691 @subheading The @code{-break-passcount} Command
26692 @findex -break-passcount
26694 @subsubheading Synopsis
26697 -break-passcount @var{tracepoint-number} @var{passcount}
26700 Set the passcount for tracepoint @var{tracepoint-number} to
26701 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
26702 is not a tracepoint, error is emitted. This corresponds to CLI
26703 command @samp{passcount}.
26705 @subheading The @code{-break-watch} Command
26706 @findex -break-watch
26708 @subsubheading Synopsis
26711 -break-watch [ -a | -r ]
26714 Create a watchpoint. With the @samp{-a} option it will create an
26715 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
26716 read from or on a write to the memory location. With the @samp{-r}
26717 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
26718 trigger only when the memory location is accessed for reading. Without
26719 either of the options, the watchpoint created is a regular watchpoint,
26720 i.e., it will trigger when the memory location is accessed for writing.
26721 @xref{Set Watchpoints, , Setting Watchpoints}.
26723 Note that @samp{-break-list} will report a single list of watchpoints and
26724 breakpoints inserted.
26726 @subsubheading @value{GDBN} Command
26728 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
26731 @subsubheading Example
26733 Setting a watchpoint on a variable in the @code{main} function:
26738 ^done,wpt=@{number="2",exp="x"@}
26743 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
26744 value=@{old="-268439212",new="55"@},
26745 frame=@{func="main",args=[],file="recursive2.c",
26746 fullname="/home/foo/bar/recursive2.c",line="5"@}
26750 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
26751 the program execution twice: first for the variable changing value, then
26752 for the watchpoint going out of scope.
26757 ^done,wpt=@{number="5",exp="C"@}
26762 *stopped,reason="watchpoint-trigger",
26763 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
26764 frame=@{func="callee4",args=[],
26765 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26766 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
26771 *stopped,reason="watchpoint-scope",wpnum="5",
26772 frame=@{func="callee3",args=[@{name="strarg",
26773 value="0x11940 \"A string argument.\""@}],
26774 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26775 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26779 Listing breakpoints and watchpoints, at different points in the program
26780 execution. Note that once the watchpoint goes out of scope, it is
26786 ^done,wpt=@{number="2",exp="C"@}
26789 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26790 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26791 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26792 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26793 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26794 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26795 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26796 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26797 addr="0x00010734",func="callee4",
26798 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26799 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
26801 bkpt=@{number="2",type="watchpoint",disp="keep",
26802 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
26807 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
26808 value=@{old="-276895068",new="3"@},
26809 frame=@{func="callee4",args=[],
26810 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26811 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
26814 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26815 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26816 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26817 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26818 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26819 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26820 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26821 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26822 addr="0x00010734",func="callee4",
26823 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26824 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
26826 bkpt=@{number="2",type="watchpoint",disp="keep",
26827 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
26831 ^done,reason="watchpoint-scope",wpnum="2",
26832 frame=@{func="callee3",args=[@{name="strarg",
26833 value="0x11940 \"A string argument.\""@}],
26834 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26835 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26838 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26839 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26840 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26841 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26842 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26843 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26844 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26845 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26846 addr="0x00010734",func="callee4",
26847 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26848 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
26849 thread-groups=["i1"],times="1"@}]@}
26854 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26855 @node GDB/MI Catchpoint Commands
26856 @section @sc{gdb/mi} Catchpoint Commands
26858 This section documents @sc{gdb/mi} commands for manipulating
26862 * Shared Library GDB/MI Catchpoint Commands::
26863 * Ada Exception GDB/MI Catchpoint Commands::
26866 @node Shared Library GDB/MI Catchpoint Commands
26867 @subsection Shared Library @sc{gdb/mi} Catchpoints
26869 @subheading The @code{-catch-load} Command
26870 @findex -catch-load
26872 @subsubheading Synopsis
26875 -catch-load [ -t ] [ -d ] @var{regexp}
26878 Add a catchpoint for library load events. If the @samp{-t} option is used,
26879 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
26880 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
26881 in a disabled state. The @samp{regexp} argument is a regular
26882 expression used to match the name of the loaded library.
26885 @subsubheading @value{GDBN} Command
26887 The corresponding @value{GDBN} command is @samp{catch load}.
26889 @subsubheading Example
26892 -catch-load -t foo.so
26893 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
26894 what="load of library matching foo.so",catch-type="load",times="0"@}
26899 @subheading The @code{-catch-unload} Command
26900 @findex -catch-unload
26902 @subsubheading Synopsis
26905 -catch-unload [ -t ] [ -d ] @var{regexp}
26908 Add a catchpoint for library unload events. If the @samp{-t} option is
26909 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
26910 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
26911 created in a disabled state. The @samp{regexp} argument is a regular
26912 expression used to match the name of the unloaded library.
26914 @subsubheading @value{GDBN} Command
26916 The corresponding @value{GDBN} command is @samp{catch unload}.
26918 @subsubheading Example
26921 -catch-unload -d bar.so
26922 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
26923 what="load of library matching bar.so",catch-type="unload",times="0"@}
26927 @node Ada Exception GDB/MI Catchpoint Commands
26928 @subsection Ada Exception @sc{gdb/mi} Catchpoints
26930 The following @sc{gdb/mi} commands can be used to create catchpoints
26931 that stop the execution when Ada exceptions are being raised.
26933 @subheading The @code{-catch-assert} Command
26934 @findex -catch-assert
26936 @subsubheading Synopsis
26939 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
26942 Add a catchpoint for failed Ada assertions.
26944 The possible optional parameters for this command are:
26947 @item -c @var{condition}
26948 Make the catchpoint conditional on @var{condition}.
26950 Create a disabled catchpoint.
26952 Create a temporary catchpoint.
26955 @subsubheading @value{GDBN} Command
26957 The corresponding @value{GDBN} command is @samp{catch assert}.
26959 @subsubheading Example
26963 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
26964 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
26965 thread-groups=["i1"],times="0",
26966 original-location="__gnat_debug_raise_assert_failure"@}
26970 @subheading The @code{-catch-exception} Command
26971 @findex -catch-exception
26973 @subsubheading Synopsis
26976 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
26980 Add a catchpoint stopping when Ada exceptions are raised.
26981 By default, the command stops the program when any Ada exception
26982 gets raised. But it is also possible, by using some of the
26983 optional parameters described below, to create more selective
26986 The possible optional parameters for this command are:
26989 @item -c @var{condition}
26990 Make the catchpoint conditional on @var{condition}.
26992 Create a disabled catchpoint.
26993 @item -e @var{exception-name}
26994 Only stop when @var{exception-name} is raised. This option cannot
26995 be used combined with @samp{-u}.
26997 Create a temporary catchpoint.
26999 Stop only when an unhandled exception gets raised. This option
27000 cannot be used combined with @samp{-e}.
27003 @subsubheading @value{GDBN} Command
27005 The corresponding @value{GDBN} commands are @samp{catch exception}
27006 and @samp{catch exception unhandled}.
27008 @subsubheading Example
27011 -catch-exception -e Program_Error
27012 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
27013 enabled="y",addr="0x0000000000404874",
27014 what="`Program_Error' Ada exception", thread-groups=["i1"],
27015 times="0",original-location="__gnat_debug_raise_exception"@}
27019 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27020 @node GDB/MI Program Context
27021 @section @sc{gdb/mi} Program Context
27023 @subheading The @code{-exec-arguments} Command
27024 @findex -exec-arguments
27027 @subsubheading Synopsis
27030 -exec-arguments @var{args}
27033 Set the inferior program arguments, to be used in the next
27036 @subsubheading @value{GDBN} Command
27038 The corresponding @value{GDBN} command is @samp{set args}.
27040 @subsubheading Example
27044 -exec-arguments -v word
27051 @subheading The @code{-exec-show-arguments} Command
27052 @findex -exec-show-arguments
27054 @subsubheading Synopsis
27057 -exec-show-arguments
27060 Print the arguments of the program.
27062 @subsubheading @value{GDBN} Command
27064 The corresponding @value{GDBN} command is @samp{show args}.
27066 @subsubheading Example
27071 @subheading The @code{-environment-cd} Command
27072 @findex -environment-cd
27074 @subsubheading Synopsis
27077 -environment-cd @var{pathdir}
27080 Set @value{GDBN}'s working directory.
27082 @subsubheading @value{GDBN} Command
27084 The corresponding @value{GDBN} command is @samp{cd}.
27086 @subsubheading Example
27090 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27096 @subheading The @code{-environment-directory} Command
27097 @findex -environment-directory
27099 @subsubheading Synopsis
27102 -environment-directory [ -r ] [ @var{pathdir} ]+
27105 Add directories @var{pathdir} to beginning of search path for source files.
27106 If the @samp{-r} option is used, the search path is reset to the default
27107 search path. If directories @var{pathdir} are supplied in addition to the
27108 @samp{-r} option, the search path is first reset and then addition
27110 Multiple directories may be specified, separated by blanks. Specifying
27111 multiple directories in a single command
27112 results in the directories added to the beginning of the
27113 search path in the same order they were presented in the command.
27114 If blanks are needed as
27115 part of a directory name, double-quotes should be used around
27116 the name. In the command output, the path will show up separated
27117 by the system directory-separator character. The directory-separator
27118 character must not be used
27119 in any directory name.
27120 If no directories are specified, the current search path is displayed.
27122 @subsubheading @value{GDBN} Command
27124 The corresponding @value{GDBN} command is @samp{dir}.
27126 @subsubheading Example
27130 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27131 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27133 -environment-directory ""
27134 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27136 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
27137 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
27139 -environment-directory -r
27140 ^done,source-path="$cdir:$cwd"
27145 @subheading The @code{-environment-path} Command
27146 @findex -environment-path
27148 @subsubheading Synopsis
27151 -environment-path [ -r ] [ @var{pathdir} ]+
27154 Add directories @var{pathdir} to beginning of search path for object files.
27155 If the @samp{-r} option is used, the search path is reset to the original
27156 search path that existed at gdb start-up. If directories @var{pathdir} are
27157 supplied in addition to the
27158 @samp{-r} option, the search path is first reset and then addition
27160 Multiple directories may be specified, separated by blanks. Specifying
27161 multiple directories in a single command
27162 results in the directories added to the beginning of the
27163 search path in the same order they were presented in the command.
27164 If blanks are needed as
27165 part of a directory name, double-quotes should be used around
27166 the name. In the command output, the path will show up separated
27167 by the system directory-separator character. The directory-separator
27168 character must not be used
27169 in any directory name.
27170 If no directories are specified, the current path is displayed.
27173 @subsubheading @value{GDBN} Command
27175 The corresponding @value{GDBN} command is @samp{path}.
27177 @subsubheading Example
27182 ^done,path="/usr/bin"
27184 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
27185 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
27187 -environment-path -r /usr/local/bin
27188 ^done,path="/usr/local/bin:/usr/bin"
27193 @subheading The @code{-environment-pwd} Command
27194 @findex -environment-pwd
27196 @subsubheading Synopsis
27202 Show the current working directory.
27204 @subsubheading @value{GDBN} Command
27206 The corresponding @value{GDBN} command is @samp{pwd}.
27208 @subsubheading Example
27213 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
27217 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27218 @node GDB/MI Thread Commands
27219 @section @sc{gdb/mi} Thread Commands
27222 @subheading The @code{-thread-info} Command
27223 @findex -thread-info
27225 @subsubheading Synopsis
27228 -thread-info [ @var{thread-id} ]
27231 Reports information about either a specific thread, if
27232 the @var{thread-id} parameter is present, or about all
27233 threads. When printing information about all threads,
27234 also reports the current thread.
27236 @subsubheading @value{GDBN} Command
27238 The @samp{info thread} command prints the same information
27241 @subsubheading Result
27243 The result is a list of threads. The following attributes are
27244 defined for a given thread:
27248 This field exists only for the current thread. It has the value @samp{*}.
27251 The identifier that @value{GDBN} uses to refer to the thread.
27254 The identifier that the target uses to refer to the thread.
27257 Extra information about the thread, in a target-specific format. This
27261 The name of the thread. If the user specified a name using the
27262 @code{thread name} command, then this name is given. Otherwise, if
27263 @value{GDBN} can extract the thread name from the target, then that
27264 name is given. If @value{GDBN} cannot find the thread name, then this
27268 The stack frame currently executing in the thread.
27271 The thread's state. The @samp{state} field may have the following
27276 The thread is stopped. Frame information is available for stopped
27280 The thread is running. There's no frame information for running
27286 If @value{GDBN} can find the CPU core on which this thread is running,
27287 then this field is the core identifier. This field is optional.
27291 @subsubheading Example
27296 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
27297 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
27298 args=[]@},state="running"@},
27299 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
27300 frame=@{level="0",addr="0x0804891f",func="foo",
27301 args=[@{name="i",value="10"@}],
27302 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
27303 state="running"@}],
27304 current-thread-id="1"
27308 @subheading The @code{-thread-list-ids} Command
27309 @findex -thread-list-ids
27311 @subsubheading Synopsis
27317 Produces a list of the currently known @value{GDBN} thread ids. At the
27318 end of the list it also prints the total number of such threads.
27320 This command is retained for historical reasons, the
27321 @code{-thread-info} command should be used instead.
27323 @subsubheading @value{GDBN} Command
27325 Part of @samp{info threads} supplies the same information.
27327 @subsubheading Example
27332 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27333 current-thread-id="1",number-of-threads="3"
27338 @subheading The @code{-thread-select} Command
27339 @findex -thread-select
27341 @subsubheading Synopsis
27344 -thread-select @var{threadnum}
27347 Make @var{threadnum} the current thread. It prints the number of the new
27348 current thread, and the topmost frame for that thread.
27350 This command is deprecated in favor of explicitly using the
27351 @samp{--thread} option to each command.
27353 @subsubheading @value{GDBN} Command
27355 The corresponding @value{GDBN} command is @samp{thread}.
27357 @subsubheading Example
27364 *stopped,reason="end-stepping-range",thread-id="2",line="187",
27365 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
27369 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27370 number-of-threads="3"
27373 ^done,new-thread-id="3",
27374 frame=@{level="0",func="vprintf",
27375 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
27376 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
27380 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27381 @node GDB/MI Ada Tasking Commands
27382 @section @sc{gdb/mi} Ada Tasking Commands
27384 @subheading The @code{-ada-task-info} Command
27385 @findex -ada-task-info
27387 @subsubheading Synopsis
27390 -ada-task-info [ @var{task-id} ]
27393 Reports information about either a specific Ada task, if the
27394 @var{task-id} parameter is present, or about all Ada tasks.
27396 @subsubheading @value{GDBN} Command
27398 The @samp{info tasks} command prints the same information
27399 about all Ada tasks (@pxref{Ada Tasks}).
27401 @subsubheading Result
27403 The result is a table of Ada tasks. The following columns are
27404 defined for each Ada task:
27408 This field exists only for the current thread. It has the value @samp{*}.
27411 The identifier that @value{GDBN} uses to refer to the Ada task.
27414 The identifier that the target uses to refer to the Ada task.
27417 The identifier of the thread corresponding to the Ada task.
27419 This field should always exist, as Ada tasks are always implemented
27420 on top of a thread. But if @value{GDBN} cannot find this corresponding
27421 thread for any reason, the field is omitted.
27424 This field exists only when the task was created by another task.
27425 In this case, it provides the ID of the parent task.
27428 The base priority of the task.
27431 The current state of the task. For a detailed description of the
27432 possible states, see @ref{Ada Tasks}.
27435 The name of the task.
27439 @subsubheading Example
27443 ^done,tasks=@{nr_rows="3",nr_cols="8",
27444 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
27445 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
27446 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
27447 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
27448 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
27449 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
27450 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
27451 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
27452 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
27453 state="Child Termination Wait",name="main_task"@}]@}
27457 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27458 @node GDB/MI Program Execution
27459 @section @sc{gdb/mi} Program Execution
27461 These are the asynchronous commands which generate the out-of-band
27462 record @samp{*stopped}. Currently @value{GDBN} only really executes
27463 asynchronously with remote targets and this interaction is mimicked in
27466 @subheading The @code{-exec-continue} Command
27467 @findex -exec-continue
27469 @subsubheading Synopsis
27472 -exec-continue [--reverse] [--all|--thread-group N]
27475 Resumes the execution of the inferior program, which will continue
27476 to execute until it reaches a debugger stop event. If the
27477 @samp{--reverse} option is specified, execution resumes in reverse until
27478 it reaches a stop event. Stop events may include
27481 breakpoints or watchpoints
27483 signals or exceptions
27485 the end of the process (or its beginning under @samp{--reverse})
27487 the end or beginning of a replay log if one is being used.
27489 In all-stop mode (@pxref{All-Stop
27490 Mode}), may resume only one thread, or all threads, depending on the
27491 value of the @samp{scheduler-locking} variable. If @samp{--all} is
27492 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
27493 ignored in all-stop mode. If the @samp{--thread-group} options is
27494 specified, then all threads in that thread group are resumed.
27496 @subsubheading @value{GDBN} Command
27498 The corresponding @value{GDBN} corresponding is @samp{continue}.
27500 @subsubheading Example
27507 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
27508 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
27514 @subheading The @code{-exec-finish} Command
27515 @findex -exec-finish
27517 @subsubheading Synopsis
27520 -exec-finish [--reverse]
27523 Resumes the execution of the inferior program until the current
27524 function is exited. Displays the results returned by the function.
27525 If the @samp{--reverse} option is specified, resumes the reverse
27526 execution of the inferior program until the point where current
27527 function was called.
27529 @subsubheading @value{GDBN} Command
27531 The corresponding @value{GDBN} command is @samp{finish}.
27533 @subsubheading Example
27535 Function returning @code{void}.
27542 *stopped,reason="function-finished",frame=@{func="main",args=[],
27543 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
27547 Function returning other than @code{void}. The name of the internal
27548 @value{GDBN} variable storing the result is printed, together with the
27555 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
27556 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
27557 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27558 gdb-result-var="$1",return-value="0"
27563 @subheading The @code{-exec-interrupt} Command
27564 @findex -exec-interrupt
27566 @subsubheading Synopsis
27569 -exec-interrupt [--all|--thread-group N]
27572 Interrupts the background execution of the target. Note how the token
27573 associated with the stop message is the one for the execution command
27574 that has been interrupted. The token for the interrupt itself only
27575 appears in the @samp{^done} output. If the user is trying to
27576 interrupt a non-running program, an error message will be printed.
27578 Note that when asynchronous execution is enabled, this command is
27579 asynchronous just like other execution commands. That is, first the
27580 @samp{^done} response will be printed, and the target stop will be
27581 reported after that using the @samp{*stopped} notification.
27583 In non-stop mode, only the context thread is interrupted by default.
27584 All threads (in all inferiors) will be interrupted if the
27585 @samp{--all} option is specified. If the @samp{--thread-group}
27586 option is specified, all threads in that group will be interrupted.
27588 @subsubheading @value{GDBN} Command
27590 The corresponding @value{GDBN} command is @samp{interrupt}.
27592 @subsubheading Example
27603 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
27604 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
27605 fullname="/home/foo/bar/try.c",line="13"@}
27610 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
27614 @subheading The @code{-exec-jump} Command
27617 @subsubheading Synopsis
27620 -exec-jump @var{location}
27623 Resumes execution of the inferior program at the location specified by
27624 parameter. @xref{Specify Location}, for a description of the
27625 different forms of @var{location}.
27627 @subsubheading @value{GDBN} Command
27629 The corresponding @value{GDBN} command is @samp{jump}.
27631 @subsubheading Example
27634 -exec-jump foo.c:10
27635 *running,thread-id="all"
27640 @subheading The @code{-exec-next} Command
27643 @subsubheading Synopsis
27646 -exec-next [--reverse]
27649 Resumes execution of the inferior program, stopping when the beginning
27650 of the next source line is reached.
27652 If the @samp{--reverse} option is specified, resumes reverse execution
27653 of the inferior program, stopping at the beginning of the previous
27654 source line. If you issue this command on the first line of a
27655 function, it will take you back to the caller of that function, to the
27656 source line where the function was called.
27659 @subsubheading @value{GDBN} Command
27661 The corresponding @value{GDBN} command is @samp{next}.
27663 @subsubheading Example
27669 *stopped,reason="end-stepping-range",line="8",file="hello.c"
27674 @subheading The @code{-exec-next-instruction} Command
27675 @findex -exec-next-instruction
27677 @subsubheading Synopsis
27680 -exec-next-instruction [--reverse]
27683 Executes one machine instruction. If the instruction is a function
27684 call, continues until the function returns. If the program stops at an
27685 instruction in the middle of a source line, the address will be
27688 If the @samp{--reverse} option is specified, resumes reverse execution
27689 of the inferior program, stopping at the previous instruction. If the
27690 previously executed instruction was a return from another function,
27691 it will continue to execute in reverse until the call to that function
27692 (from the current stack frame) is reached.
27694 @subsubheading @value{GDBN} Command
27696 The corresponding @value{GDBN} command is @samp{nexti}.
27698 @subsubheading Example
27702 -exec-next-instruction
27706 *stopped,reason="end-stepping-range",
27707 addr="0x000100d4",line="5",file="hello.c"
27712 @subheading The @code{-exec-return} Command
27713 @findex -exec-return
27715 @subsubheading Synopsis
27721 Makes current function return immediately. Doesn't execute the inferior.
27722 Displays the new current frame.
27724 @subsubheading @value{GDBN} Command
27726 The corresponding @value{GDBN} command is @samp{return}.
27728 @subsubheading Example
27732 200-break-insert callee4
27733 200^done,bkpt=@{number="1",addr="0x00010734",
27734 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27739 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27740 frame=@{func="callee4",args=[],
27741 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27742 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27748 111^done,frame=@{level="0",func="callee3",
27749 args=[@{name="strarg",
27750 value="0x11940 \"A string argument.\""@}],
27751 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27752 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27757 @subheading The @code{-exec-run} Command
27760 @subsubheading Synopsis
27763 -exec-run [ --all | --thread-group N ] [ --start ]
27766 Starts execution of the inferior from the beginning. The inferior
27767 executes until either a breakpoint is encountered or the program
27768 exits. In the latter case the output will include an exit code, if
27769 the program has exited exceptionally.
27771 When neither the @samp{--all} nor the @samp{--thread-group} option
27772 is specified, the current inferior is started. If the
27773 @samp{--thread-group} option is specified, it should refer to a thread
27774 group of type @samp{process}, and that thread group will be started.
27775 If the @samp{--all} option is specified, then all inferiors will be started.
27777 Using the @samp{--start} option instructs the debugger to stop
27778 the execution at the start of the inferior's main subprogram,
27779 following the same behavior as the @code{start} command
27780 (@pxref{Starting}).
27782 @subsubheading @value{GDBN} Command
27784 The corresponding @value{GDBN} command is @samp{run}.
27786 @subsubheading Examples
27791 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
27796 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27797 frame=@{func="main",args=[],file="recursive2.c",
27798 fullname="/home/foo/bar/recursive2.c",line="4"@}
27803 Program exited normally:
27811 *stopped,reason="exited-normally"
27816 Program exited exceptionally:
27824 *stopped,reason="exited",exit-code="01"
27828 Another way the program can terminate is if it receives a signal such as
27829 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
27833 *stopped,reason="exited-signalled",signal-name="SIGINT",
27834 signal-meaning="Interrupt"
27838 @c @subheading -exec-signal
27841 @subheading The @code{-exec-step} Command
27844 @subsubheading Synopsis
27847 -exec-step [--reverse]
27850 Resumes execution of the inferior program, stopping when the beginning
27851 of the next source line is reached, if the next source line is not a
27852 function call. If it is, stop at the first instruction of the called
27853 function. If the @samp{--reverse} option is specified, resumes reverse
27854 execution of the inferior program, stopping at the beginning of the
27855 previously executed source line.
27857 @subsubheading @value{GDBN} Command
27859 The corresponding @value{GDBN} command is @samp{step}.
27861 @subsubheading Example
27863 Stepping into a function:
27869 *stopped,reason="end-stepping-range",
27870 frame=@{func="foo",args=[@{name="a",value="10"@},
27871 @{name="b",value="0"@}],file="recursive2.c",
27872 fullname="/home/foo/bar/recursive2.c",line="11"@}
27882 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
27887 @subheading The @code{-exec-step-instruction} Command
27888 @findex -exec-step-instruction
27890 @subsubheading Synopsis
27893 -exec-step-instruction [--reverse]
27896 Resumes the inferior which executes one machine instruction. If the
27897 @samp{--reverse} option is specified, resumes reverse execution of the
27898 inferior program, stopping at the previously executed instruction.
27899 The output, once @value{GDBN} has stopped, will vary depending on
27900 whether we have stopped in the middle of a source line or not. In the
27901 former case, the address at which the program stopped will be printed
27904 @subsubheading @value{GDBN} Command
27906 The corresponding @value{GDBN} command is @samp{stepi}.
27908 @subsubheading Example
27912 -exec-step-instruction
27916 *stopped,reason="end-stepping-range",
27917 frame=@{func="foo",args=[],file="try.c",
27918 fullname="/home/foo/bar/try.c",line="10"@}
27920 -exec-step-instruction
27924 *stopped,reason="end-stepping-range",
27925 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
27926 fullname="/home/foo/bar/try.c",line="10"@}
27931 @subheading The @code{-exec-until} Command
27932 @findex -exec-until
27934 @subsubheading Synopsis
27937 -exec-until [ @var{location} ]
27940 Executes the inferior until the @var{location} specified in the
27941 argument is reached. If there is no argument, the inferior executes
27942 until a source line greater than the current one is reached. The
27943 reason for stopping in this case will be @samp{location-reached}.
27945 @subsubheading @value{GDBN} Command
27947 The corresponding @value{GDBN} command is @samp{until}.
27949 @subsubheading Example
27953 -exec-until recursive2.c:6
27957 *stopped,reason="location-reached",frame=@{func="main",args=[],
27958 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
27963 @subheading -file-clear
27964 Is this going away????
27967 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27968 @node GDB/MI Stack Manipulation
27969 @section @sc{gdb/mi} Stack Manipulation Commands
27971 @subheading The @code{-enable-frame-filters} Command
27972 @findex -enable-frame-filters
27975 -enable-frame-filters
27978 @value{GDBN} allows Python-based frame filters to affect the output of
27979 the MI commands relating to stack traces. As there is no way to
27980 implement this in a fully backward-compatible way, a front end must
27981 request that this functionality be enabled.
27983 Once enabled, this feature cannot be disabled.
27985 Note that if Python support has not been compiled into @value{GDBN},
27986 this command will still succeed (and do nothing).
27988 @subheading The @code{-stack-info-frame} Command
27989 @findex -stack-info-frame
27991 @subsubheading Synopsis
27997 Get info on the selected frame.
27999 @subsubheading @value{GDBN} Command
28001 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
28002 (without arguments).
28004 @subsubheading Example
28009 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
28010 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28011 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
28015 @subheading The @code{-stack-info-depth} Command
28016 @findex -stack-info-depth
28018 @subsubheading Synopsis
28021 -stack-info-depth [ @var{max-depth} ]
28024 Return the depth of the stack. If the integer argument @var{max-depth}
28025 is specified, do not count beyond @var{max-depth} frames.
28027 @subsubheading @value{GDBN} Command
28029 There's no equivalent @value{GDBN} command.
28031 @subsubheading Example
28033 For a stack with frame levels 0 through 11:
28040 -stack-info-depth 4
28043 -stack-info-depth 12
28046 -stack-info-depth 11
28049 -stack-info-depth 13
28054 @anchor{-stack-list-arguments}
28055 @subheading The @code{-stack-list-arguments} Command
28056 @findex -stack-list-arguments
28058 @subsubheading Synopsis
28061 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28062 [ @var{low-frame} @var{high-frame} ]
28065 Display a list of the arguments for the frames between @var{low-frame}
28066 and @var{high-frame} (inclusive). If @var{low-frame} and
28067 @var{high-frame} are not provided, list the arguments for the whole
28068 call stack. If the two arguments are equal, show the single frame
28069 at the corresponding level. It is an error if @var{low-frame} is
28070 larger than the actual number of frames. On the other hand,
28071 @var{high-frame} may be larger than the actual number of frames, in
28072 which case only existing frames will be returned.
28074 If @var{print-values} is 0 or @code{--no-values}, print only the names of
28075 the variables; if it is 1 or @code{--all-values}, print also their
28076 values; and if it is 2 or @code{--simple-values}, print the name,
28077 type and value for simple data types, and the name and type for arrays,
28078 structures and unions. If the option @code{--no-frame-filters} is
28079 supplied, then Python frame filters will not be executed.
28081 If the @code{--skip-unavailable} option is specified, arguments that
28082 are not available are not listed. Partially available arguments
28083 are still displayed, however.
28085 Use of this command to obtain arguments in a single frame is
28086 deprecated in favor of the @samp{-stack-list-variables} command.
28088 @subsubheading @value{GDBN} Command
28090 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
28091 @samp{gdb_get_args} command which partially overlaps with the
28092 functionality of @samp{-stack-list-arguments}.
28094 @subsubheading Example
28101 frame=@{level="0",addr="0x00010734",func="callee4",
28102 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28103 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
28104 frame=@{level="1",addr="0x0001076c",func="callee3",
28105 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28106 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
28107 frame=@{level="2",addr="0x0001078c",func="callee2",
28108 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28109 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
28110 frame=@{level="3",addr="0x000107b4",func="callee1",
28111 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28112 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
28113 frame=@{level="4",addr="0x000107e0",func="main",
28114 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28115 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
28117 -stack-list-arguments 0
28120 frame=@{level="0",args=[]@},
28121 frame=@{level="1",args=[name="strarg"]@},
28122 frame=@{level="2",args=[name="intarg",name="strarg"]@},
28123 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
28124 frame=@{level="4",args=[]@}]
28126 -stack-list-arguments 1
28129 frame=@{level="0",args=[]@},
28131 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28132 frame=@{level="2",args=[
28133 @{name="intarg",value="2"@},
28134 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28135 @{frame=@{level="3",args=[
28136 @{name="intarg",value="2"@},
28137 @{name="strarg",value="0x11940 \"A string argument.\""@},
28138 @{name="fltarg",value="3.5"@}]@},
28139 frame=@{level="4",args=[]@}]
28141 -stack-list-arguments 0 2 2
28142 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
28144 -stack-list-arguments 1 2 2
28145 ^done,stack-args=[frame=@{level="2",
28146 args=[@{name="intarg",value="2"@},
28147 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
28151 @c @subheading -stack-list-exception-handlers
28154 @anchor{-stack-list-frames}
28155 @subheading The @code{-stack-list-frames} Command
28156 @findex -stack-list-frames
28158 @subsubheading Synopsis
28161 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
28164 List the frames currently on the stack. For each frame it displays the
28169 The frame number, 0 being the topmost frame, i.e., the innermost function.
28171 The @code{$pc} value for that frame.
28175 File name of the source file where the function lives.
28176 @item @var{fullname}
28177 The full file name of the source file where the function lives.
28179 Line number corresponding to the @code{$pc}.
28181 The shared library where this function is defined. This is only given
28182 if the frame's function is not known.
28185 If invoked without arguments, this command prints a backtrace for the
28186 whole stack. If given two integer arguments, it shows the frames whose
28187 levels are between the two arguments (inclusive). If the two arguments
28188 are equal, it shows the single frame at the corresponding level. It is
28189 an error if @var{low-frame} is larger than the actual number of
28190 frames. On the other hand, @var{high-frame} may be larger than the
28191 actual number of frames, in which case only existing frames will be
28192 returned. If the option @code{--no-frame-filters} is supplied, then
28193 Python frame filters will not be executed.
28195 @subsubheading @value{GDBN} Command
28197 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
28199 @subsubheading Example
28201 Full stack backtrace:
28207 [frame=@{level="0",addr="0x0001076c",func="foo",
28208 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
28209 frame=@{level="1",addr="0x000107a4",func="foo",
28210 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28211 frame=@{level="2",addr="0x000107a4",func="foo",
28212 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28213 frame=@{level="3",addr="0x000107a4",func="foo",
28214 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28215 frame=@{level="4",addr="0x000107a4",func="foo",
28216 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28217 frame=@{level="5",addr="0x000107a4",func="foo",
28218 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28219 frame=@{level="6",addr="0x000107a4",func="foo",
28220 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28221 frame=@{level="7",addr="0x000107a4",func="foo",
28222 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28223 frame=@{level="8",addr="0x000107a4",func="foo",
28224 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28225 frame=@{level="9",addr="0x000107a4",func="foo",
28226 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28227 frame=@{level="10",addr="0x000107a4",func="foo",
28228 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28229 frame=@{level="11",addr="0x00010738",func="main",
28230 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
28234 Show frames between @var{low_frame} and @var{high_frame}:
28238 -stack-list-frames 3 5
28240 [frame=@{level="3",addr="0x000107a4",func="foo",
28241 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28242 frame=@{level="4",addr="0x000107a4",func="foo",
28243 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28244 frame=@{level="5",addr="0x000107a4",func="foo",
28245 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28249 Show a single frame:
28253 -stack-list-frames 3 3
28255 [frame=@{level="3",addr="0x000107a4",func="foo",
28256 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28261 @subheading The @code{-stack-list-locals} Command
28262 @findex -stack-list-locals
28263 @anchor{-stack-list-locals}
28265 @subsubheading Synopsis
28268 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28271 Display the local variable names for the selected frame. If
28272 @var{print-values} is 0 or @code{--no-values}, print only the names of
28273 the variables; if it is 1 or @code{--all-values}, print also their
28274 values; and if it is 2 or @code{--simple-values}, print the name,
28275 type and value for simple data types, and the name and type for arrays,
28276 structures and unions. In this last case, a frontend can immediately
28277 display the value of simple data types and create variable objects for
28278 other data types when the user wishes to explore their values in
28279 more detail. If the option @code{--no-frame-filters} is supplied, then
28280 Python frame filters will not be executed.
28282 If the @code{--skip-unavailable} option is specified, local variables
28283 that are not available are not listed. Partially available local
28284 variables are still displayed, however.
28286 This command is deprecated in favor of the
28287 @samp{-stack-list-variables} command.
28289 @subsubheading @value{GDBN} Command
28291 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
28293 @subsubheading Example
28297 -stack-list-locals 0
28298 ^done,locals=[name="A",name="B",name="C"]
28300 -stack-list-locals --all-values
28301 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
28302 @{name="C",value="@{1, 2, 3@}"@}]
28303 -stack-list-locals --simple-values
28304 ^done,locals=[@{name="A",type="int",value="1"@},
28305 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
28309 @anchor{-stack-list-variables}
28310 @subheading The @code{-stack-list-variables} Command
28311 @findex -stack-list-variables
28313 @subsubheading Synopsis
28316 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28319 Display the names of local variables and function arguments for the selected frame. If
28320 @var{print-values} is 0 or @code{--no-values}, print only the names of
28321 the variables; if it is 1 or @code{--all-values}, print also their
28322 values; and if it is 2 or @code{--simple-values}, print the name,
28323 type and value for simple data types, and the name and type for arrays,
28324 structures and unions. If the option @code{--no-frame-filters} is
28325 supplied, then Python frame filters will not be executed.
28327 If the @code{--skip-unavailable} option is specified, local variables
28328 and arguments that are not available are not listed. Partially
28329 available arguments and local variables are still displayed, however.
28331 @subsubheading Example
28335 -stack-list-variables --thread 1 --frame 0 --all-values
28336 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
28341 @subheading The @code{-stack-select-frame} Command
28342 @findex -stack-select-frame
28344 @subsubheading Synopsis
28347 -stack-select-frame @var{framenum}
28350 Change the selected frame. Select a different frame @var{framenum} on
28353 This command in deprecated in favor of passing the @samp{--frame}
28354 option to every command.
28356 @subsubheading @value{GDBN} Command
28358 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
28359 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
28361 @subsubheading Example
28365 -stack-select-frame 2
28370 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28371 @node GDB/MI Variable Objects
28372 @section @sc{gdb/mi} Variable Objects
28376 @subheading Motivation for Variable Objects in @sc{gdb/mi}
28378 For the implementation of a variable debugger window (locals, watched
28379 expressions, etc.), we are proposing the adaptation of the existing code
28380 used by @code{Insight}.
28382 The two main reasons for that are:
28386 It has been proven in practice (it is already on its second generation).
28389 It will shorten development time (needless to say how important it is
28393 The original interface was designed to be used by Tcl code, so it was
28394 slightly changed so it could be used through @sc{gdb/mi}. This section
28395 describes the @sc{gdb/mi} operations that will be available and gives some
28396 hints about their use.
28398 @emph{Note}: In addition to the set of operations described here, we
28399 expect the @sc{gui} implementation of a variable window to require, at
28400 least, the following operations:
28403 @item @code{-gdb-show} @code{output-radix}
28404 @item @code{-stack-list-arguments}
28405 @item @code{-stack-list-locals}
28406 @item @code{-stack-select-frame}
28411 @subheading Introduction to Variable Objects
28413 @cindex variable objects in @sc{gdb/mi}
28415 Variable objects are "object-oriented" MI interface for examining and
28416 changing values of expressions. Unlike some other MI interfaces that
28417 work with expressions, variable objects are specifically designed for
28418 simple and efficient presentation in the frontend. A variable object
28419 is identified by string name. When a variable object is created, the
28420 frontend specifies the expression for that variable object. The
28421 expression can be a simple variable, or it can be an arbitrary complex
28422 expression, and can even involve CPU registers. After creating a
28423 variable object, the frontend can invoke other variable object
28424 operations---for example to obtain or change the value of a variable
28425 object, or to change display format.
28427 Variable objects have hierarchical tree structure. Any variable object
28428 that corresponds to a composite type, such as structure in C, has
28429 a number of child variable objects, for example corresponding to each
28430 element of a structure. A child variable object can itself have
28431 children, recursively. Recursion ends when we reach
28432 leaf variable objects, which always have built-in types. Child variable
28433 objects are created only by explicit request, so if a frontend
28434 is not interested in the children of a particular variable object, no
28435 child will be created.
28437 For a leaf variable object it is possible to obtain its value as a
28438 string, or set the value from a string. String value can be also
28439 obtained for a non-leaf variable object, but it's generally a string
28440 that only indicates the type of the object, and does not list its
28441 contents. Assignment to a non-leaf variable object is not allowed.
28443 A frontend does not need to read the values of all variable objects each time
28444 the program stops. Instead, MI provides an update command that lists all
28445 variable objects whose values has changed since the last update
28446 operation. This considerably reduces the amount of data that must
28447 be transferred to the frontend. As noted above, children variable
28448 objects are created on demand, and only leaf variable objects have a
28449 real value. As result, gdb will read target memory only for leaf
28450 variables that frontend has created.
28452 The automatic update is not always desirable. For example, a frontend
28453 might want to keep a value of some expression for future reference,
28454 and never update it. For another example, fetching memory is
28455 relatively slow for embedded targets, so a frontend might want
28456 to disable automatic update for the variables that are either not
28457 visible on the screen, or ``closed''. This is possible using so
28458 called ``frozen variable objects''. Such variable objects are never
28459 implicitly updated.
28461 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
28462 fixed variable object, the expression is parsed when the variable
28463 object is created, including associating identifiers to specific
28464 variables. The meaning of expression never changes. For a floating
28465 variable object the values of variables whose names appear in the
28466 expressions are re-evaluated every time in the context of the current
28467 frame. Consider this example:
28472 struct work_state state;
28479 If a fixed variable object for the @code{state} variable is created in
28480 this function, and we enter the recursive call, the variable
28481 object will report the value of @code{state} in the top-level
28482 @code{do_work} invocation. On the other hand, a floating variable
28483 object will report the value of @code{state} in the current frame.
28485 If an expression specified when creating a fixed variable object
28486 refers to a local variable, the variable object becomes bound to the
28487 thread and frame in which the variable object is created. When such
28488 variable object is updated, @value{GDBN} makes sure that the
28489 thread/frame combination the variable object is bound to still exists,
28490 and re-evaluates the variable object in context of that thread/frame.
28492 The following is the complete set of @sc{gdb/mi} operations defined to
28493 access this functionality:
28495 @multitable @columnfractions .4 .6
28496 @item @strong{Operation}
28497 @tab @strong{Description}
28499 @item @code{-enable-pretty-printing}
28500 @tab enable Python-based pretty-printing
28501 @item @code{-var-create}
28502 @tab create a variable object
28503 @item @code{-var-delete}
28504 @tab delete the variable object and/or its children
28505 @item @code{-var-set-format}
28506 @tab set the display format of this variable
28507 @item @code{-var-show-format}
28508 @tab show the display format of this variable
28509 @item @code{-var-info-num-children}
28510 @tab tells how many children this object has
28511 @item @code{-var-list-children}
28512 @tab return a list of the object's children
28513 @item @code{-var-info-type}
28514 @tab show the type of this variable object
28515 @item @code{-var-info-expression}
28516 @tab print parent-relative expression that this variable object represents
28517 @item @code{-var-info-path-expression}
28518 @tab print full expression that this variable object represents
28519 @item @code{-var-show-attributes}
28520 @tab is this variable editable? does it exist here?
28521 @item @code{-var-evaluate-expression}
28522 @tab get the value of this variable
28523 @item @code{-var-assign}
28524 @tab set the value of this variable
28525 @item @code{-var-update}
28526 @tab update the variable and its children
28527 @item @code{-var-set-frozen}
28528 @tab set frozeness attribute
28529 @item @code{-var-set-update-range}
28530 @tab set range of children to display on update
28533 In the next subsection we describe each operation in detail and suggest
28534 how it can be used.
28536 @subheading Description And Use of Operations on Variable Objects
28538 @subheading The @code{-enable-pretty-printing} Command
28539 @findex -enable-pretty-printing
28542 -enable-pretty-printing
28545 @value{GDBN} allows Python-based visualizers to affect the output of the
28546 MI variable object commands. However, because there was no way to
28547 implement this in a fully backward-compatible way, a front end must
28548 request that this functionality be enabled.
28550 Once enabled, this feature cannot be disabled.
28552 Note that if Python support has not been compiled into @value{GDBN},
28553 this command will still succeed (and do nothing).
28555 This feature is currently (as of @value{GDBN} 7.0) experimental, and
28556 may work differently in future versions of @value{GDBN}.
28558 @subheading The @code{-var-create} Command
28559 @findex -var-create
28561 @subsubheading Synopsis
28564 -var-create @{@var{name} | "-"@}
28565 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
28568 This operation creates a variable object, which allows the monitoring of
28569 a variable, the result of an expression, a memory cell or a CPU
28572 The @var{name} parameter is the string by which the object can be
28573 referenced. It must be unique. If @samp{-} is specified, the varobj
28574 system will generate a string ``varNNNNNN'' automatically. It will be
28575 unique provided that one does not specify @var{name} of that format.
28576 The command fails if a duplicate name is found.
28578 The frame under which the expression should be evaluated can be
28579 specified by @var{frame-addr}. A @samp{*} indicates that the current
28580 frame should be used. A @samp{@@} indicates that a floating variable
28581 object must be created.
28583 @var{expression} is any expression valid on the current language set (must not
28584 begin with a @samp{*}), or one of the following:
28588 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
28591 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
28594 @samp{$@var{regname}} --- a CPU register name
28597 @cindex dynamic varobj
28598 A varobj's contents may be provided by a Python-based pretty-printer. In this
28599 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
28600 have slightly different semantics in some cases. If the
28601 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
28602 will never create a dynamic varobj. This ensures backward
28603 compatibility for existing clients.
28605 @subsubheading Result
28607 This operation returns attributes of the newly-created varobj. These
28612 The name of the varobj.
28615 The number of children of the varobj. This number is not necessarily
28616 reliable for a dynamic varobj. Instead, you must examine the
28617 @samp{has_more} attribute.
28620 The varobj's scalar value. For a varobj whose type is some sort of
28621 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
28622 will not be interesting.
28625 The varobj's type. This is a string representation of the type, as
28626 would be printed by the @value{GDBN} CLI. If @samp{print object}
28627 (@pxref{Print Settings, set print object}) is set to @code{on}, the
28628 @emph{actual} (derived) type of the object is shown rather than the
28629 @emph{declared} one.
28632 If a variable object is bound to a specific thread, then this is the
28633 thread's identifier.
28636 For a dynamic varobj, this indicates whether there appear to be any
28637 children available. For a non-dynamic varobj, this will be 0.
28640 This attribute will be present and have the value @samp{1} if the
28641 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28642 then this attribute will not be present.
28645 A dynamic varobj can supply a display hint to the front end. The
28646 value comes directly from the Python pretty-printer object's
28647 @code{display_hint} method. @xref{Pretty Printing API}.
28650 Typical output will look like this:
28653 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
28654 has_more="@var{has_more}"
28658 @subheading The @code{-var-delete} Command
28659 @findex -var-delete
28661 @subsubheading Synopsis
28664 -var-delete [ -c ] @var{name}
28667 Deletes a previously created variable object and all of its children.
28668 With the @samp{-c} option, just deletes the children.
28670 Returns an error if the object @var{name} is not found.
28673 @subheading The @code{-var-set-format} Command
28674 @findex -var-set-format
28676 @subsubheading Synopsis
28679 -var-set-format @var{name} @var{format-spec}
28682 Sets the output format for the value of the object @var{name} to be
28685 @anchor{-var-set-format}
28686 The syntax for the @var{format-spec} is as follows:
28689 @var{format-spec} @expansion{}
28690 @{binary | decimal | hexadecimal | octal | natural@}
28693 The natural format is the default format choosen automatically
28694 based on the variable type (like decimal for an @code{int}, hex
28695 for pointers, etc.).
28697 For a variable with children, the format is set only on the
28698 variable itself, and the children are not affected.
28700 @subheading The @code{-var-show-format} Command
28701 @findex -var-show-format
28703 @subsubheading Synopsis
28706 -var-show-format @var{name}
28709 Returns the format used to display the value of the object @var{name}.
28712 @var{format} @expansion{}
28717 @subheading The @code{-var-info-num-children} Command
28718 @findex -var-info-num-children
28720 @subsubheading Synopsis
28723 -var-info-num-children @var{name}
28726 Returns the number of children of a variable object @var{name}:
28732 Note that this number is not completely reliable for a dynamic varobj.
28733 It will return the current number of children, but more children may
28737 @subheading The @code{-var-list-children} Command
28738 @findex -var-list-children
28740 @subsubheading Synopsis
28743 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
28745 @anchor{-var-list-children}
28747 Return a list of the children of the specified variable object and
28748 create variable objects for them, if they do not already exist. With
28749 a single argument or if @var{print-values} has a value of 0 or
28750 @code{--no-values}, print only the names of the variables; if
28751 @var{print-values} is 1 or @code{--all-values}, also print their
28752 values; and if it is 2 or @code{--simple-values} print the name and
28753 value for simple data types and just the name for arrays, structures
28756 @var{from} and @var{to}, if specified, indicate the range of children
28757 to report. If @var{from} or @var{to} is less than zero, the range is
28758 reset and all children will be reported. Otherwise, children starting
28759 at @var{from} (zero-based) and up to and excluding @var{to} will be
28762 If a child range is requested, it will only affect the current call to
28763 @code{-var-list-children}, but not future calls to @code{-var-update}.
28764 For this, you must instead use @code{-var-set-update-range}. The
28765 intent of this approach is to enable a front end to implement any
28766 update approach it likes; for example, scrolling a view may cause the
28767 front end to request more children with @code{-var-list-children}, and
28768 then the front end could call @code{-var-set-update-range} with a
28769 different range to ensure that future updates are restricted to just
28772 For each child the following results are returned:
28777 Name of the variable object created for this child.
28780 The expression to be shown to the user by the front end to designate this child.
28781 For example this may be the name of a structure member.
28783 For a dynamic varobj, this value cannot be used to form an
28784 expression. There is no way to do this at all with a dynamic varobj.
28786 For C/C@t{++} structures there are several pseudo children returned to
28787 designate access qualifiers. For these pseudo children @var{exp} is
28788 @samp{public}, @samp{private}, or @samp{protected}. In this case the
28789 type and value are not present.
28791 A dynamic varobj will not report the access qualifying
28792 pseudo-children, regardless of the language. This information is not
28793 available at all with a dynamic varobj.
28796 Number of children this child has. For a dynamic varobj, this will be
28800 The type of the child. If @samp{print object}
28801 (@pxref{Print Settings, set print object}) is set to @code{on}, the
28802 @emph{actual} (derived) type of the object is shown rather than the
28803 @emph{declared} one.
28806 If values were requested, this is the value.
28809 If this variable object is associated with a thread, this is the thread id.
28810 Otherwise this result is not present.
28813 If the variable object is frozen, this variable will be present with a value of 1.
28816 A dynamic varobj can supply a display hint to the front end. The
28817 value comes directly from the Python pretty-printer object's
28818 @code{display_hint} method. @xref{Pretty Printing API}.
28821 This attribute will be present and have the value @samp{1} if the
28822 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28823 then this attribute will not be present.
28827 The result may have its own attributes:
28831 A dynamic varobj can supply a display hint to the front end. The
28832 value comes directly from the Python pretty-printer object's
28833 @code{display_hint} method. @xref{Pretty Printing API}.
28836 This is an integer attribute which is nonzero if there are children
28837 remaining after the end of the selected range.
28840 @subsubheading Example
28844 -var-list-children n
28845 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28846 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
28848 -var-list-children --all-values n
28849 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28850 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
28854 @subheading The @code{-var-info-type} Command
28855 @findex -var-info-type
28857 @subsubheading Synopsis
28860 -var-info-type @var{name}
28863 Returns the type of the specified variable @var{name}. The type is
28864 returned as a string in the same format as it is output by the
28868 type=@var{typename}
28872 @subheading The @code{-var-info-expression} Command
28873 @findex -var-info-expression
28875 @subsubheading Synopsis
28878 -var-info-expression @var{name}
28881 Returns a string that is suitable for presenting this
28882 variable object in user interface. The string is generally
28883 not valid expression in the current language, and cannot be evaluated.
28885 For example, if @code{a} is an array, and variable object
28886 @code{A} was created for @code{a}, then we'll get this output:
28889 (gdb) -var-info-expression A.1
28890 ^done,lang="C",exp="1"
28894 Here, the value of @code{lang} is the language name, which can be
28895 found in @ref{Supported Languages}.
28897 Note that the output of the @code{-var-list-children} command also
28898 includes those expressions, so the @code{-var-info-expression} command
28901 @subheading The @code{-var-info-path-expression} Command
28902 @findex -var-info-path-expression
28904 @subsubheading Synopsis
28907 -var-info-path-expression @var{name}
28910 Returns an expression that can be evaluated in the current
28911 context and will yield the same value that a variable object has.
28912 Compare this with the @code{-var-info-expression} command, which
28913 result can be used only for UI presentation. Typical use of
28914 the @code{-var-info-path-expression} command is creating a
28915 watchpoint from a variable object.
28917 This command is currently not valid for children of a dynamic varobj,
28918 and will give an error when invoked on one.
28920 For example, suppose @code{C} is a C@t{++} class, derived from class
28921 @code{Base}, and that the @code{Base} class has a member called
28922 @code{m_size}. Assume a variable @code{c} is has the type of
28923 @code{C} and a variable object @code{C} was created for variable
28924 @code{c}. Then, we'll get this output:
28926 (gdb) -var-info-path-expression C.Base.public.m_size
28927 ^done,path_expr=((Base)c).m_size)
28930 @subheading The @code{-var-show-attributes} Command
28931 @findex -var-show-attributes
28933 @subsubheading Synopsis
28936 -var-show-attributes @var{name}
28939 List attributes of the specified variable object @var{name}:
28942 status=@var{attr} [ ( ,@var{attr} )* ]
28946 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
28948 @subheading The @code{-var-evaluate-expression} Command
28949 @findex -var-evaluate-expression
28951 @subsubheading Synopsis
28954 -var-evaluate-expression [-f @var{format-spec}] @var{name}
28957 Evaluates the expression that is represented by the specified variable
28958 object and returns its value as a string. The format of the string
28959 can be specified with the @samp{-f} option. The possible values of
28960 this option are the same as for @code{-var-set-format}
28961 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
28962 the current display format will be used. The current display format
28963 can be changed using the @code{-var-set-format} command.
28969 Note that one must invoke @code{-var-list-children} for a variable
28970 before the value of a child variable can be evaluated.
28972 @subheading The @code{-var-assign} Command
28973 @findex -var-assign
28975 @subsubheading Synopsis
28978 -var-assign @var{name} @var{expression}
28981 Assigns the value of @var{expression} to the variable object specified
28982 by @var{name}. The object must be @samp{editable}. If the variable's
28983 value is altered by the assign, the variable will show up in any
28984 subsequent @code{-var-update} list.
28986 @subsubheading Example
28994 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
28998 @subheading The @code{-var-update} Command
28999 @findex -var-update
29001 @subsubheading Synopsis
29004 -var-update [@var{print-values}] @{@var{name} | "*"@}
29007 Reevaluate the expressions corresponding to the variable object
29008 @var{name} and all its direct and indirect children, and return the
29009 list of variable objects whose values have changed; @var{name} must
29010 be a root variable object. Here, ``changed'' means that the result of
29011 @code{-var-evaluate-expression} before and after the
29012 @code{-var-update} is different. If @samp{*} is used as the variable
29013 object names, all existing variable objects are updated, except
29014 for frozen ones (@pxref{-var-set-frozen}). The option
29015 @var{print-values} determines whether both names and values, or just
29016 names are printed. The possible values of this option are the same
29017 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
29018 recommended to use the @samp{--all-values} option, to reduce the
29019 number of MI commands needed on each program stop.
29021 With the @samp{*} parameter, if a variable object is bound to a
29022 currently running thread, it will not be updated, without any
29025 If @code{-var-set-update-range} was previously used on a varobj, then
29026 only the selected range of children will be reported.
29028 @code{-var-update} reports all the changed varobjs in a tuple named
29031 Each item in the change list is itself a tuple holding:
29035 The name of the varobj.
29038 If values were requested for this update, then this field will be
29039 present and will hold the value of the varobj.
29042 @anchor{-var-update}
29043 This field is a string which may take one of three values:
29047 The variable object's current value is valid.
29050 The variable object does not currently hold a valid value but it may
29051 hold one in the future if its associated expression comes back into
29055 The variable object no longer holds a valid value.
29056 This can occur when the executable file being debugged has changed,
29057 either through recompilation or by using the @value{GDBN} @code{file}
29058 command. The front end should normally choose to delete these variable
29062 In the future new values may be added to this list so the front should
29063 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
29066 This is only present if the varobj is still valid. If the type
29067 changed, then this will be the string @samp{true}; otherwise it will
29070 When a varobj's type changes, its children are also likely to have
29071 become incorrect. Therefore, the varobj's children are automatically
29072 deleted when this attribute is @samp{true}. Also, the varobj's update
29073 range, when set using the @code{-var-set-update-range} command, is
29077 If the varobj's type changed, then this field will be present and will
29080 @item new_num_children
29081 For a dynamic varobj, if the number of children changed, or if the
29082 type changed, this will be the new number of children.
29084 The @samp{numchild} field in other varobj responses is generally not
29085 valid for a dynamic varobj -- it will show the number of children that
29086 @value{GDBN} knows about, but because dynamic varobjs lazily
29087 instantiate their children, this will not reflect the number of
29088 children which may be available.
29090 The @samp{new_num_children} attribute only reports changes to the
29091 number of children known by @value{GDBN}. This is the only way to
29092 detect whether an update has removed children (which necessarily can
29093 only happen at the end of the update range).
29096 The display hint, if any.
29099 This is an integer value, which will be 1 if there are more children
29100 available outside the varobj's update range.
29103 This attribute will be present and have the value @samp{1} if the
29104 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29105 then this attribute will not be present.
29108 If new children were added to a dynamic varobj within the selected
29109 update range (as set by @code{-var-set-update-range}), then they will
29110 be listed in this attribute.
29113 @subsubheading Example
29120 -var-update --all-values var1
29121 ^done,changelist=[@{name="var1",value="3",in_scope="true",
29122 type_changed="false"@}]
29126 @subheading The @code{-var-set-frozen} Command
29127 @findex -var-set-frozen
29128 @anchor{-var-set-frozen}
29130 @subsubheading Synopsis
29133 -var-set-frozen @var{name} @var{flag}
29136 Set the frozenness flag on the variable object @var{name}. The
29137 @var{flag} parameter should be either @samp{1} to make the variable
29138 frozen or @samp{0} to make it unfrozen. If a variable object is
29139 frozen, then neither itself, nor any of its children, are
29140 implicitly updated by @code{-var-update} of
29141 a parent variable or by @code{-var-update *}. Only
29142 @code{-var-update} of the variable itself will update its value and
29143 values of its children. After a variable object is unfrozen, it is
29144 implicitly updated by all subsequent @code{-var-update} operations.
29145 Unfreezing a variable does not update it, only subsequent
29146 @code{-var-update} does.
29148 @subsubheading Example
29152 -var-set-frozen V 1
29157 @subheading The @code{-var-set-update-range} command
29158 @findex -var-set-update-range
29159 @anchor{-var-set-update-range}
29161 @subsubheading Synopsis
29164 -var-set-update-range @var{name} @var{from} @var{to}
29167 Set the range of children to be returned by future invocations of
29168 @code{-var-update}.
29170 @var{from} and @var{to} indicate the range of children to report. If
29171 @var{from} or @var{to} is less than zero, the range is reset and all
29172 children will be reported. Otherwise, children starting at @var{from}
29173 (zero-based) and up to and excluding @var{to} will be reported.
29175 @subsubheading Example
29179 -var-set-update-range V 1 2
29183 @subheading The @code{-var-set-visualizer} command
29184 @findex -var-set-visualizer
29185 @anchor{-var-set-visualizer}
29187 @subsubheading Synopsis
29190 -var-set-visualizer @var{name} @var{visualizer}
29193 Set a visualizer for the variable object @var{name}.
29195 @var{visualizer} is the visualizer to use. The special value
29196 @samp{None} means to disable any visualizer in use.
29198 If not @samp{None}, @var{visualizer} must be a Python expression.
29199 This expression must evaluate to a callable object which accepts a
29200 single argument. @value{GDBN} will call this object with the value of
29201 the varobj @var{name} as an argument (this is done so that the same
29202 Python pretty-printing code can be used for both the CLI and MI).
29203 When called, this object must return an object which conforms to the
29204 pretty-printing interface (@pxref{Pretty Printing API}).
29206 The pre-defined function @code{gdb.default_visualizer} may be used to
29207 select a visualizer by following the built-in process
29208 (@pxref{Selecting Pretty-Printers}). This is done automatically when
29209 a varobj is created, and so ordinarily is not needed.
29211 This feature is only available if Python support is enabled. The MI
29212 command @code{-list-features} (@pxref{GDB/MI Support Commands})
29213 can be used to check this.
29215 @subsubheading Example
29217 Resetting the visualizer:
29221 -var-set-visualizer V None
29225 Reselecting the default (type-based) visualizer:
29229 -var-set-visualizer V gdb.default_visualizer
29233 Suppose @code{SomeClass} is a visualizer class. A lambda expression
29234 can be used to instantiate this class for a varobj:
29238 -var-set-visualizer V "lambda val: SomeClass()"
29242 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29243 @node GDB/MI Data Manipulation
29244 @section @sc{gdb/mi} Data Manipulation
29246 @cindex data manipulation, in @sc{gdb/mi}
29247 @cindex @sc{gdb/mi}, data manipulation
29248 This section describes the @sc{gdb/mi} commands that manipulate data:
29249 examine memory and registers, evaluate expressions, etc.
29251 @c REMOVED FROM THE INTERFACE.
29252 @c @subheading -data-assign
29253 @c Change the value of a program variable. Plenty of side effects.
29254 @c @subsubheading GDB Command
29256 @c @subsubheading Example
29259 @subheading The @code{-data-disassemble} Command
29260 @findex -data-disassemble
29262 @subsubheading Synopsis
29266 [ -s @var{start-addr} -e @var{end-addr} ]
29267 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
29275 @item @var{start-addr}
29276 is the beginning address (or @code{$pc})
29277 @item @var{end-addr}
29279 @item @var{filename}
29280 is the name of the file to disassemble
29281 @item @var{linenum}
29282 is the line number to disassemble around
29284 is the number of disassembly lines to be produced. If it is -1,
29285 the whole function will be disassembled, in case no @var{end-addr} is
29286 specified. If @var{end-addr} is specified as a non-zero value, and
29287 @var{lines} is lower than the number of disassembly lines between
29288 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
29289 displayed; if @var{lines} is higher than the number of lines between
29290 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
29293 is either 0 (meaning only disassembly), 1 (meaning mixed source and
29294 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
29295 mixed source and disassembly with raw opcodes).
29298 @subsubheading Result
29300 The result of the @code{-data-disassemble} command will be a list named
29301 @samp{asm_insns}, the contents of this list depend on the @var{mode}
29302 used with the @code{-data-disassemble} command.
29304 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
29309 The address at which this instruction was disassembled.
29312 The name of the function this instruction is within.
29315 The decimal offset in bytes from the start of @samp{func-name}.
29318 The text disassembly for this @samp{address}.
29321 This field is only present for mode 2. This contains the raw opcode
29322 bytes for the @samp{inst} field.
29326 For modes 1 and 3 the @samp{asm_insns} list contains tuples named
29327 @samp{src_and_asm_line}, each of which has the following fields:
29331 The line number within @samp{file}.
29334 The file name from the compilation unit. This might be an absolute
29335 file name or a relative file name depending on the compile command
29339 Absolute file name of @samp{file}. It is converted to a canonical form
29340 using the source file search path
29341 (@pxref{Source Path, ,Specifying Source Directories})
29342 and after resolving all the symbolic links.
29344 If the source file is not found this field will contain the path as
29345 present in the debug information.
29347 @item line_asm_insn
29348 This is a list of tuples containing the disassembly for @samp{line} in
29349 @samp{file}. The fields of each tuple are the same as for
29350 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
29351 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
29356 Note that whatever included in the @samp{inst} field, is not
29357 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
29360 @subsubheading @value{GDBN} Command
29362 The corresponding @value{GDBN} command is @samp{disassemble}.
29364 @subsubheading Example
29366 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
29370 -data-disassemble -s $pc -e "$pc + 20" -- 0
29373 @{address="0x000107c0",func-name="main",offset="4",
29374 inst="mov 2, %o0"@},
29375 @{address="0x000107c4",func-name="main",offset="8",
29376 inst="sethi %hi(0x11800), %o2"@},
29377 @{address="0x000107c8",func-name="main",offset="12",
29378 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
29379 @{address="0x000107cc",func-name="main",offset="16",
29380 inst="sethi %hi(0x11800), %o2"@},
29381 @{address="0x000107d0",func-name="main",offset="20",
29382 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
29386 Disassemble the whole @code{main} function. Line 32 is part of
29390 -data-disassemble -f basics.c -l 32 -- 0
29392 @{address="0x000107bc",func-name="main",offset="0",
29393 inst="save %sp, -112, %sp"@},
29394 @{address="0x000107c0",func-name="main",offset="4",
29395 inst="mov 2, %o0"@},
29396 @{address="0x000107c4",func-name="main",offset="8",
29397 inst="sethi %hi(0x11800), %o2"@},
29399 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
29400 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
29404 Disassemble 3 instructions from the start of @code{main}:
29408 -data-disassemble -f basics.c -l 32 -n 3 -- 0
29410 @{address="0x000107bc",func-name="main",offset="0",
29411 inst="save %sp, -112, %sp"@},
29412 @{address="0x000107c0",func-name="main",offset="4",
29413 inst="mov 2, %o0"@},
29414 @{address="0x000107c4",func-name="main",offset="8",
29415 inst="sethi %hi(0x11800), %o2"@}]
29419 Disassemble 3 instructions from the start of @code{main} in mixed mode:
29423 -data-disassemble -f basics.c -l 32 -n 3 -- 1
29425 src_and_asm_line=@{line="31",
29426 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
29427 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
29428 line_asm_insn=[@{address="0x000107bc",
29429 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
29430 src_and_asm_line=@{line="32",
29431 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
29432 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
29433 line_asm_insn=[@{address="0x000107c0",
29434 func-name="main",offset="4",inst="mov 2, %o0"@},
29435 @{address="0x000107c4",func-name="main",offset="8",
29436 inst="sethi %hi(0x11800), %o2"@}]@}]
29441 @subheading The @code{-data-evaluate-expression} Command
29442 @findex -data-evaluate-expression
29444 @subsubheading Synopsis
29447 -data-evaluate-expression @var{expr}
29450 Evaluate @var{expr} as an expression. The expression could contain an
29451 inferior function call. The function call will execute synchronously.
29452 If the expression contains spaces, it must be enclosed in double quotes.
29454 @subsubheading @value{GDBN} Command
29456 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
29457 @samp{call}. In @code{gdbtk} only, there's a corresponding
29458 @samp{gdb_eval} command.
29460 @subsubheading Example
29462 In the following example, the numbers that precede the commands are the
29463 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
29464 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
29468 211-data-evaluate-expression A
29471 311-data-evaluate-expression &A
29472 311^done,value="0xefffeb7c"
29474 411-data-evaluate-expression A+3
29477 511-data-evaluate-expression "A + 3"
29483 @subheading The @code{-data-list-changed-registers} Command
29484 @findex -data-list-changed-registers
29486 @subsubheading Synopsis
29489 -data-list-changed-registers
29492 Display a list of the registers that have changed.
29494 @subsubheading @value{GDBN} Command
29496 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
29497 has the corresponding command @samp{gdb_changed_register_list}.
29499 @subsubheading Example
29501 On a PPC MBX board:
29509 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
29510 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
29513 -data-list-changed-registers
29514 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
29515 "10","11","13","14","15","16","17","18","19","20","21","22","23",
29516 "24","25","26","27","28","30","31","64","65","66","67","69"]
29521 @subheading The @code{-data-list-register-names} Command
29522 @findex -data-list-register-names
29524 @subsubheading Synopsis
29527 -data-list-register-names [ ( @var{regno} )+ ]
29530 Show a list of register names for the current target. If no arguments
29531 are given, it shows a list of the names of all the registers. If
29532 integer numbers are given as arguments, it will print a list of the
29533 names of the registers corresponding to the arguments. To ensure
29534 consistency between a register name and its number, the output list may
29535 include empty register names.
29537 @subsubheading @value{GDBN} Command
29539 @value{GDBN} does not have a command which corresponds to
29540 @samp{-data-list-register-names}. In @code{gdbtk} there is a
29541 corresponding command @samp{gdb_regnames}.
29543 @subsubheading Example
29545 For the PPC MBX board:
29548 -data-list-register-names
29549 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
29550 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
29551 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
29552 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
29553 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
29554 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
29555 "", "pc","ps","cr","lr","ctr","xer"]
29557 -data-list-register-names 1 2 3
29558 ^done,register-names=["r1","r2","r3"]
29562 @subheading The @code{-data-list-register-values} Command
29563 @findex -data-list-register-values
29565 @subsubheading Synopsis
29568 -data-list-register-values
29569 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
29572 Display the registers' contents. The format according to which the
29573 registers' contents are to be returned is given by @var{fmt}, followed
29574 by an optional list of numbers specifying the registers to display. A
29575 missing list of numbers indicates that the contents of all the
29576 registers must be returned. The @code{--skip-unavailable} option
29577 indicates that only the available registers are to be returned.
29579 Allowed formats for @var{fmt} are:
29596 @subsubheading @value{GDBN} Command
29598 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
29599 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
29601 @subsubheading Example
29603 For a PPC MBX board (note: line breaks are for readability only, they
29604 don't appear in the actual output):
29608 -data-list-register-values r 64 65
29609 ^done,register-values=[@{number="64",value="0xfe00a300"@},
29610 @{number="65",value="0x00029002"@}]
29612 -data-list-register-values x
29613 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
29614 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
29615 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
29616 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
29617 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
29618 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
29619 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
29620 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
29621 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
29622 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
29623 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
29624 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
29625 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
29626 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
29627 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
29628 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
29629 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
29630 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
29631 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
29632 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
29633 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
29634 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
29635 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
29636 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
29637 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
29638 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
29639 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
29640 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
29641 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
29642 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
29643 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
29644 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
29645 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
29646 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
29647 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
29648 @{number="69",value="0x20002b03"@}]
29653 @subheading The @code{-data-read-memory} Command
29654 @findex -data-read-memory
29656 This command is deprecated, use @code{-data-read-memory-bytes} instead.
29658 @subsubheading Synopsis
29661 -data-read-memory [ -o @var{byte-offset} ]
29662 @var{address} @var{word-format} @var{word-size}
29663 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
29670 @item @var{address}
29671 An expression specifying the address of the first memory word to be
29672 read. Complex expressions containing embedded white space should be
29673 quoted using the C convention.
29675 @item @var{word-format}
29676 The format to be used to print the memory words. The notation is the
29677 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
29680 @item @var{word-size}
29681 The size of each memory word in bytes.
29683 @item @var{nr-rows}
29684 The number of rows in the output table.
29686 @item @var{nr-cols}
29687 The number of columns in the output table.
29690 If present, indicates that each row should include an @sc{ascii} dump. The
29691 value of @var{aschar} is used as a padding character when a byte is not a
29692 member of the printable @sc{ascii} character set (printable @sc{ascii}
29693 characters are those whose code is between 32 and 126, inclusively).
29695 @item @var{byte-offset}
29696 An offset to add to the @var{address} before fetching memory.
29699 This command displays memory contents as a table of @var{nr-rows} by
29700 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
29701 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
29702 (returned as @samp{total-bytes}). Should less than the requested number
29703 of bytes be returned by the target, the missing words are identified
29704 using @samp{N/A}. The number of bytes read from the target is returned
29705 in @samp{nr-bytes} and the starting address used to read memory in
29708 The address of the next/previous row or page is available in
29709 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
29712 @subsubheading @value{GDBN} Command
29714 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
29715 @samp{gdb_get_mem} memory read command.
29717 @subsubheading Example
29719 Read six bytes of memory starting at @code{bytes+6} but then offset by
29720 @code{-6} bytes. Format as three rows of two columns. One byte per
29721 word. Display each word in hex.
29725 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
29726 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
29727 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
29728 prev-page="0x0000138a",memory=[
29729 @{addr="0x00001390",data=["0x00","0x01"]@},
29730 @{addr="0x00001392",data=["0x02","0x03"]@},
29731 @{addr="0x00001394",data=["0x04","0x05"]@}]
29735 Read two bytes of memory starting at address @code{shorts + 64} and
29736 display as a single word formatted in decimal.
29740 5-data-read-memory shorts+64 d 2 1 1
29741 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
29742 next-row="0x00001512",prev-row="0x0000150e",
29743 next-page="0x00001512",prev-page="0x0000150e",memory=[
29744 @{addr="0x00001510",data=["128"]@}]
29748 Read thirty two bytes of memory starting at @code{bytes+16} and format
29749 as eight rows of four columns. Include a string encoding with @samp{x}
29750 used as the non-printable character.
29754 4-data-read-memory bytes+16 x 1 8 4 x
29755 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
29756 next-row="0x000013c0",prev-row="0x0000139c",
29757 next-page="0x000013c0",prev-page="0x00001380",memory=[
29758 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
29759 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
29760 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
29761 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
29762 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
29763 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
29764 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
29765 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
29769 @subheading The @code{-data-read-memory-bytes} Command
29770 @findex -data-read-memory-bytes
29772 @subsubheading Synopsis
29775 -data-read-memory-bytes [ -o @var{byte-offset} ]
29776 @var{address} @var{count}
29783 @item @var{address}
29784 An expression specifying the address of the first memory word to be
29785 read. Complex expressions containing embedded white space should be
29786 quoted using the C convention.
29789 The number of bytes to read. This should be an integer literal.
29791 @item @var{byte-offset}
29792 The offsets in bytes relative to @var{address} at which to start
29793 reading. This should be an integer literal. This option is provided
29794 so that a frontend is not required to first evaluate address and then
29795 perform address arithmetics itself.
29799 This command attempts to read all accessible memory regions in the
29800 specified range. First, all regions marked as unreadable in the memory
29801 map (if one is defined) will be skipped. @xref{Memory Region
29802 Attributes}. Second, @value{GDBN} will attempt to read the remaining
29803 regions. For each one, if reading full region results in an errors,
29804 @value{GDBN} will try to read a subset of the region.
29806 In general, every single byte in the region may be readable or not,
29807 and the only way to read every readable byte is to try a read at
29808 every address, which is not practical. Therefore, @value{GDBN} will
29809 attempt to read all accessible bytes at either beginning or the end
29810 of the region, using a binary division scheme. This heuristic works
29811 well for reading accross a memory map boundary. Note that if a region
29812 has a readable range that is neither at the beginning or the end,
29813 @value{GDBN} will not read it.
29815 The result record (@pxref{GDB/MI Result Records}) that is output of
29816 the command includes a field named @samp{memory} whose content is a
29817 list of tuples. Each tuple represent a successfully read memory block
29818 and has the following fields:
29822 The start address of the memory block, as hexadecimal literal.
29825 The end address of the memory block, as hexadecimal literal.
29828 The offset of the memory block, as hexadecimal literal, relative to
29829 the start address passed to @code{-data-read-memory-bytes}.
29832 The contents of the memory block, in hex.
29838 @subsubheading @value{GDBN} Command
29840 The corresponding @value{GDBN} command is @samp{x}.
29842 @subsubheading Example
29846 -data-read-memory-bytes &a 10
29847 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
29849 contents="01000000020000000300"@}]
29854 @subheading The @code{-data-write-memory-bytes} Command
29855 @findex -data-write-memory-bytes
29857 @subsubheading Synopsis
29860 -data-write-memory-bytes @var{address} @var{contents}
29861 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
29868 @item @var{address}
29869 An expression specifying the address of the first memory word to be
29870 read. Complex expressions containing embedded white space should be
29871 quoted using the C convention.
29873 @item @var{contents}
29874 The hex-encoded bytes to write.
29877 Optional argument indicating the number of bytes to be written. If @var{count}
29878 is greater than @var{contents}' length, @value{GDBN} will repeatedly
29879 write @var{contents} until it fills @var{count} bytes.
29883 @subsubheading @value{GDBN} Command
29885 There's no corresponding @value{GDBN} command.
29887 @subsubheading Example
29891 -data-write-memory-bytes &a "aabbccdd"
29898 -data-write-memory-bytes &a "aabbccdd" 16e
29903 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29904 @node GDB/MI Tracepoint Commands
29905 @section @sc{gdb/mi} Tracepoint Commands
29907 The commands defined in this section implement MI support for
29908 tracepoints. For detailed introduction, see @ref{Tracepoints}.
29910 @subheading The @code{-trace-find} Command
29911 @findex -trace-find
29913 @subsubheading Synopsis
29916 -trace-find @var{mode} [@var{parameters}@dots{}]
29919 Find a trace frame using criteria defined by @var{mode} and
29920 @var{parameters}. The following table lists permissible
29921 modes and their parameters. For details of operation, see @ref{tfind}.
29926 No parameters are required. Stops examining trace frames.
29929 An integer is required as parameter. Selects tracepoint frame with
29932 @item tracepoint-number
29933 An integer is required as parameter. Finds next
29934 trace frame that corresponds to tracepoint with the specified number.
29937 An address is required as parameter. Finds
29938 next trace frame that corresponds to any tracepoint at the specified
29941 @item pc-inside-range
29942 Two addresses are required as parameters. Finds next trace
29943 frame that corresponds to a tracepoint at an address inside the
29944 specified range. Both bounds are considered to be inside the range.
29946 @item pc-outside-range
29947 Two addresses are required as parameters. Finds
29948 next trace frame that corresponds to a tracepoint at an address outside
29949 the specified range. Both bounds are considered to be inside the range.
29952 Line specification is required as parameter. @xref{Specify Location}.
29953 Finds next trace frame that corresponds to a tracepoint at
29954 the specified location.
29958 If @samp{none} was passed as @var{mode}, the response does not
29959 have fields. Otherwise, the response may have the following fields:
29963 This field has either @samp{0} or @samp{1} as the value, depending
29964 on whether a matching tracepoint was found.
29967 The index of the found traceframe. This field is present iff
29968 the @samp{found} field has value of @samp{1}.
29971 The index of the found tracepoint. This field is present iff
29972 the @samp{found} field has value of @samp{1}.
29975 The information about the frame corresponding to the found trace
29976 frame. This field is present only if a trace frame was found.
29977 @xref{GDB/MI Frame Information}, for description of this field.
29981 @subsubheading @value{GDBN} Command
29983 The corresponding @value{GDBN} command is @samp{tfind}.
29985 @subheading -trace-define-variable
29986 @findex -trace-define-variable
29988 @subsubheading Synopsis
29991 -trace-define-variable @var{name} [ @var{value} ]
29994 Create trace variable @var{name} if it does not exist. If
29995 @var{value} is specified, sets the initial value of the specified
29996 trace variable to that value. Note that the @var{name} should start
29997 with the @samp{$} character.
29999 @subsubheading @value{GDBN} Command
30001 The corresponding @value{GDBN} command is @samp{tvariable}.
30003 @subheading The @code{-trace-frame-collected} Command
30004 @findex -trace-frame-collected
30006 @subsubheading Synopsis
30009 -trace-frame-collected
30010 [--var-print-values @var{var_pval}]
30011 [--comp-print-values @var{comp_pval}]
30012 [--registers-format @var{regformat}]
30013 [--memory-contents]
30016 This command returns the set of collected objects, register names,
30017 trace state variable names, memory ranges and computed expressions
30018 that have been collected at a particular trace frame. The optional
30019 parameters to the command affect the output format in different ways.
30020 See the output description table below for more details.
30022 The reported names can be used in the normal manner to create
30023 varobjs and inspect the objects themselves. The items returned by
30024 this command are categorized so that it is clear which is a variable,
30025 which is a register, which is a trace state variable, which is a
30026 memory range and which is a computed expression.
30028 For instance, if the actions were
30030 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
30031 collect *(int*)0xaf02bef0@@40
30035 the object collected in its entirety would be @code{myVar}. The
30036 object @code{myArray} would be partially collected, because only the
30037 element at index @code{myIndex} would be collected. The remaining
30038 objects would be computed expressions.
30040 An example output would be:
30044 -trace-frame-collected
30046 explicit-variables=[@{name="myVar",value="1"@}],
30047 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
30048 @{name="myObj.field",value="0"@},
30049 @{name="myPtr->field",value="1"@},
30050 @{name="myCount + 2",value="3"@},
30051 @{name="$tvar1 + 1",value="43970027"@}],
30052 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
30053 @{number="1",value="0x0"@},
30054 @{number="2",value="0x4"@},
30056 @{number="125",value="0x0"@}],
30057 tvars=[@{name="$tvar1",current="43970026"@}],
30058 memory=[@{address="0x0000000000602264",length="4"@},
30059 @{address="0x0000000000615bc0",length="4"@}]
30066 @item explicit-variables
30067 The set of objects that have been collected in their entirety (as
30068 opposed to collecting just a few elements of an array or a few struct
30069 members). For each object, its name and value are printed.
30070 The @code{--var-print-values} option affects how or whether the value
30071 field is output. If @var{var_pval} is 0, then print only the names;
30072 if it is 1, print also their values; and if it is 2, print the name,
30073 type and value for simple data types, and the name and type for
30074 arrays, structures and unions.
30076 @item computed-expressions
30077 The set of computed expressions that have been collected at the
30078 current trace frame. The @code{--comp-print-values} option affects
30079 this set like the @code{--var-print-values} option affects the
30080 @code{explicit-variables} set. See above.
30083 The registers that have been collected at the current trace frame.
30084 For each register collected, the name and current value are returned.
30085 The value is formatted according to the @code{--registers-format}
30086 option. See the @command{-data-list-register-values} command for a
30087 list of the allowed formats. The default is @samp{x}.
30090 The trace state variables that have been collected at the current
30091 trace frame. For each trace state variable collected, the name and
30092 current value are returned.
30095 The set of memory ranges that have been collected at the current trace
30096 frame. Its content is a list of tuples. Each tuple represents a
30097 collected memory range and has the following fields:
30101 The start address of the memory range, as hexadecimal literal.
30104 The length of the memory range, as decimal literal.
30107 The contents of the memory block, in hex. This field is only present
30108 if the @code{--memory-contents} option is specified.
30114 @subsubheading @value{GDBN} Command
30116 There is no corresponding @value{GDBN} command.
30118 @subsubheading Example
30120 @subheading -trace-list-variables
30121 @findex -trace-list-variables
30123 @subsubheading Synopsis
30126 -trace-list-variables
30129 Return a table of all defined trace variables. Each element of the
30130 table has the following fields:
30134 The name of the trace variable. This field is always present.
30137 The initial value. This is a 64-bit signed integer. This
30138 field is always present.
30141 The value the trace variable has at the moment. This is a 64-bit
30142 signed integer. This field is absent iff current value is
30143 not defined, for example if the trace was never run, or is
30148 @subsubheading @value{GDBN} Command
30150 The corresponding @value{GDBN} command is @samp{tvariables}.
30152 @subsubheading Example
30156 -trace-list-variables
30157 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
30158 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
30159 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
30160 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
30161 body=[variable=@{name="$trace_timestamp",initial="0"@}
30162 variable=@{name="$foo",initial="10",current="15"@}]@}
30166 @subheading -trace-save
30167 @findex -trace-save
30169 @subsubheading Synopsis
30172 -trace-save [-r ] @var{filename}
30175 Saves the collected trace data to @var{filename}. Without the
30176 @samp{-r} option, the data is downloaded from the target and saved
30177 in a local file. With the @samp{-r} option the target is asked
30178 to perform the save.
30180 @subsubheading @value{GDBN} Command
30182 The corresponding @value{GDBN} command is @samp{tsave}.
30185 @subheading -trace-start
30186 @findex -trace-start
30188 @subsubheading Synopsis
30194 Starts a tracing experiments. The result of this command does not
30197 @subsubheading @value{GDBN} Command
30199 The corresponding @value{GDBN} command is @samp{tstart}.
30201 @subheading -trace-status
30202 @findex -trace-status
30204 @subsubheading Synopsis
30210 Obtains the status of a tracing experiment. The result may include
30211 the following fields:
30216 May have a value of either @samp{0}, when no tracing operations are
30217 supported, @samp{1}, when all tracing operations are supported, or
30218 @samp{file} when examining trace file. In the latter case, examining
30219 of trace frame is possible but new tracing experiement cannot be
30220 started. This field is always present.
30223 May have a value of either @samp{0} or @samp{1} depending on whether
30224 tracing experiement is in progress on target. This field is present
30225 if @samp{supported} field is not @samp{0}.
30228 Report the reason why the tracing was stopped last time. This field
30229 may be absent iff tracing was never stopped on target yet. The
30230 value of @samp{request} means the tracing was stopped as result of
30231 the @code{-trace-stop} command. The value of @samp{overflow} means
30232 the tracing buffer is full. The value of @samp{disconnection} means
30233 tracing was automatically stopped when @value{GDBN} has disconnected.
30234 The value of @samp{passcount} means tracing was stopped when a
30235 tracepoint was passed a maximal number of times for that tracepoint.
30236 This field is present if @samp{supported} field is not @samp{0}.
30238 @item stopping-tracepoint
30239 The number of tracepoint whose passcount as exceeded. This field is
30240 present iff the @samp{stop-reason} field has the value of
30244 @itemx frames-created
30245 The @samp{frames} field is a count of the total number of trace frames
30246 in the trace buffer, while @samp{frames-created} is the total created
30247 during the run, including ones that were discarded, such as when a
30248 circular trace buffer filled up. Both fields are optional.
30252 These fields tell the current size of the tracing buffer and the
30253 remaining space. These fields are optional.
30256 The value of the circular trace buffer flag. @code{1} means that the
30257 trace buffer is circular and old trace frames will be discarded if
30258 necessary to make room, @code{0} means that the trace buffer is linear
30262 The value of the disconnected tracing flag. @code{1} means that
30263 tracing will continue after @value{GDBN} disconnects, @code{0} means
30264 that the trace run will stop.
30267 The filename of the trace file being examined. This field is
30268 optional, and only present when examining a trace file.
30272 @subsubheading @value{GDBN} Command
30274 The corresponding @value{GDBN} command is @samp{tstatus}.
30276 @subheading -trace-stop
30277 @findex -trace-stop
30279 @subsubheading Synopsis
30285 Stops a tracing experiment. The result of this command has the same
30286 fields as @code{-trace-status}, except that the @samp{supported} and
30287 @samp{running} fields are not output.
30289 @subsubheading @value{GDBN} Command
30291 The corresponding @value{GDBN} command is @samp{tstop}.
30294 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30295 @node GDB/MI Symbol Query
30296 @section @sc{gdb/mi} Symbol Query Commands
30300 @subheading The @code{-symbol-info-address} Command
30301 @findex -symbol-info-address
30303 @subsubheading Synopsis
30306 -symbol-info-address @var{symbol}
30309 Describe where @var{symbol} is stored.
30311 @subsubheading @value{GDBN} Command
30313 The corresponding @value{GDBN} command is @samp{info address}.
30315 @subsubheading Example
30319 @subheading The @code{-symbol-info-file} Command
30320 @findex -symbol-info-file
30322 @subsubheading Synopsis
30328 Show the file for the symbol.
30330 @subsubheading @value{GDBN} Command
30332 There's no equivalent @value{GDBN} command. @code{gdbtk} has
30333 @samp{gdb_find_file}.
30335 @subsubheading Example
30339 @subheading The @code{-symbol-info-function} Command
30340 @findex -symbol-info-function
30342 @subsubheading Synopsis
30345 -symbol-info-function
30348 Show which function the symbol lives in.
30350 @subsubheading @value{GDBN} Command
30352 @samp{gdb_get_function} in @code{gdbtk}.
30354 @subsubheading Example
30358 @subheading The @code{-symbol-info-line} Command
30359 @findex -symbol-info-line
30361 @subsubheading Synopsis
30367 Show the core addresses of the code for a source line.
30369 @subsubheading @value{GDBN} Command
30371 The corresponding @value{GDBN} command is @samp{info line}.
30372 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
30374 @subsubheading Example
30378 @subheading The @code{-symbol-info-symbol} Command
30379 @findex -symbol-info-symbol
30381 @subsubheading Synopsis
30384 -symbol-info-symbol @var{addr}
30387 Describe what symbol is at location @var{addr}.
30389 @subsubheading @value{GDBN} Command
30391 The corresponding @value{GDBN} command is @samp{info symbol}.
30393 @subsubheading Example
30397 @subheading The @code{-symbol-list-functions} Command
30398 @findex -symbol-list-functions
30400 @subsubheading Synopsis
30403 -symbol-list-functions
30406 List the functions in the executable.
30408 @subsubheading @value{GDBN} Command
30410 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
30411 @samp{gdb_search} in @code{gdbtk}.
30413 @subsubheading Example
30418 @subheading The @code{-symbol-list-lines} Command
30419 @findex -symbol-list-lines
30421 @subsubheading Synopsis
30424 -symbol-list-lines @var{filename}
30427 Print the list of lines that contain code and their associated program
30428 addresses for the given source filename. The entries are sorted in
30429 ascending PC order.
30431 @subsubheading @value{GDBN} Command
30433 There is no corresponding @value{GDBN} command.
30435 @subsubheading Example
30438 -symbol-list-lines basics.c
30439 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
30445 @subheading The @code{-symbol-list-types} Command
30446 @findex -symbol-list-types
30448 @subsubheading Synopsis
30454 List all the type names.
30456 @subsubheading @value{GDBN} Command
30458 The corresponding commands are @samp{info types} in @value{GDBN},
30459 @samp{gdb_search} in @code{gdbtk}.
30461 @subsubheading Example
30465 @subheading The @code{-symbol-list-variables} Command
30466 @findex -symbol-list-variables
30468 @subsubheading Synopsis
30471 -symbol-list-variables
30474 List all the global and static variable names.
30476 @subsubheading @value{GDBN} Command
30478 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
30480 @subsubheading Example
30484 @subheading The @code{-symbol-locate} Command
30485 @findex -symbol-locate
30487 @subsubheading Synopsis
30493 @subsubheading @value{GDBN} Command
30495 @samp{gdb_loc} in @code{gdbtk}.
30497 @subsubheading Example
30501 @subheading The @code{-symbol-type} Command
30502 @findex -symbol-type
30504 @subsubheading Synopsis
30507 -symbol-type @var{variable}
30510 Show type of @var{variable}.
30512 @subsubheading @value{GDBN} Command
30514 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
30515 @samp{gdb_obj_variable}.
30517 @subsubheading Example
30522 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30523 @node GDB/MI File Commands
30524 @section @sc{gdb/mi} File Commands
30526 This section describes the GDB/MI commands to specify executable file names
30527 and to read in and obtain symbol table information.
30529 @subheading The @code{-file-exec-and-symbols} Command
30530 @findex -file-exec-and-symbols
30532 @subsubheading Synopsis
30535 -file-exec-and-symbols @var{file}
30538 Specify the executable file to be debugged. This file is the one from
30539 which the symbol table is also read. If no file is specified, the
30540 command clears the executable and symbol information. If breakpoints
30541 are set when using this command with no arguments, @value{GDBN} will produce
30542 error messages. Otherwise, no output is produced, except a completion
30545 @subsubheading @value{GDBN} Command
30547 The corresponding @value{GDBN} command is @samp{file}.
30549 @subsubheading Example
30553 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30559 @subheading The @code{-file-exec-file} Command
30560 @findex -file-exec-file
30562 @subsubheading Synopsis
30565 -file-exec-file @var{file}
30568 Specify the executable file to be debugged. Unlike
30569 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
30570 from this file. If used without argument, @value{GDBN} clears the information
30571 about the executable file. No output is produced, except a completion
30574 @subsubheading @value{GDBN} Command
30576 The corresponding @value{GDBN} command is @samp{exec-file}.
30578 @subsubheading Example
30582 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30589 @subheading The @code{-file-list-exec-sections} Command
30590 @findex -file-list-exec-sections
30592 @subsubheading Synopsis
30595 -file-list-exec-sections
30598 List the sections of the current executable file.
30600 @subsubheading @value{GDBN} Command
30602 The @value{GDBN} command @samp{info file} shows, among the rest, the same
30603 information as this command. @code{gdbtk} has a corresponding command
30604 @samp{gdb_load_info}.
30606 @subsubheading Example
30611 @subheading The @code{-file-list-exec-source-file} Command
30612 @findex -file-list-exec-source-file
30614 @subsubheading Synopsis
30617 -file-list-exec-source-file
30620 List the line number, the current source file, and the absolute path
30621 to the current source file for the current executable. The macro
30622 information field has a value of @samp{1} or @samp{0} depending on
30623 whether or not the file includes preprocessor macro information.
30625 @subsubheading @value{GDBN} Command
30627 The @value{GDBN} equivalent is @samp{info source}
30629 @subsubheading Example
30633 123-file-list-exec-source-file
30634 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
30639 @subheading The @code{-file-list-exec-source-files} Command
30640 @findex -file-list-exec-source-files
30642 @subsubheading Synopsis
30645 -file-list-exec-source-files
30648 List the source files for the current executable.
30650 It will always output both the filename and fullname (absolute file
30651 name) of a source file.
30653 @subsubheading @value{GDBN} Command
30655 The @value{GDBN} equivalent is @samp{info sources}.
30656 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
30658 @subsubheading Example
30661 -file-list-exec-source-files
30663 @{file=foo.c,fullname=/home/foo.c@},
30664 @{file=/home/bar.c,fullname=/home/bar.c@},
30665 @{file=gdb_could_not_find_fullpath.c@}]
30670 @subheading The @code{-file-list-shared-libraries} Command
30671 @findex -file-list-shared-libraries
30673 @subsubheading Synopsis
30676 -file-list-shared-libraries
30679 List the shared libraries in the program.
30681 @subsubheading @value{GDBN} Command
30683 The corresponding @value{GDBN} command is @samp{info shared}.
30685 @subsubheading Example
30689 @subheading The @code{-file-list-symbol-files} Command
30690 @findex -file-list-symbol-files
30692 @subsubheading Synopsis
30695 -file-list-symbol-files
30700 @subsubheading @value{GDBN} Command
30702 The corresponding @value{GDBN} command is @samp{info file} (part of it).
30704 @subsubheading Example
30709 @subheading The @code{-file-symbol-file} Command
30710 @findex -file-symbol-file
30712 @subsubheading Synopsis
30715 -file-symbol-file @var{file}
30718 Read symbol table info from the specified @var{file} argument. When
30719 used without arguments, clears @value{GDBN}'s symbol table info. No output is
30720 produced, except for a completion notification.
30722 @subsubheading @value{GDBN} Command
30724 The corresponding @value{GDBN} command is @samp{symbol-file}.
30726 @subsubheading Example
30730 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30736 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30737 @node GDB/MI Memory Overlay Commands
30738 @section @sc{gdb/mi} Memory Overlay Commands
30740 The memory overlay commands are not implemented.
30742 @c @subheading -overlay-auto
30744 @c @subheading -overlay-list-mapping-state
30746 @c @subheading -overlay-list-overlays
30748 @c @subheading -overlay-map
30750 @c @subheading -overlay-off
30752 @c @subheading -overlay-on
30754 @c @subheading -overlay-unmap
30756 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30757 @node GDB/MI Signal Handling Commands
30758 @section @sc{gdb/mi} Signal Handling Commands
30760 Signal handling commands are not implemented.
30762 @c @subheading -signal-handle
30764 @c @subheading -signal-list-handle-actions
30766 @c @subheading -signal-list-signal-types
30770 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30771 @node GDB/MI Target Manipulation
30772 @section @sc{gdb/mi} Target Manipulation Commands
30775 @subheading The @code{-target-attach} Command
30776 @findex -target-attach
30778 @subsubheading Synopsis
30781 -target-attach @var{pid} | @var{gid} | @var{file}
30784 Attach to a process @var{pid} or a file @var{file} outside of
30785 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
30786 group, the id previously returned by
30787 @samp{-list-thread-groups --available} must be used.
30789 @subsubheading @value{GDBN} Command
30791 The corresponding @value{GDBN} command is @samp{attach}.
30793 @subsubheading Example
30797 =thread-created,id="1"
30798 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
30804 @subheading The @code{-target-compare-sections} Command
30805 @findex -target-compare-sections
30807 @subsubheading Synopsis
30810 -target-compare-sections [ @var{section} ]
30813 Compare data of section @var{section} on target to the exec file.
30814 Without the argument, all sections are compared.
30816 @subsubheading @value{GDBN} Command
30818 The @value{GDBN} equivalent is @samp{compare-sections}.
30820 @subsubheading Example
30825 @subheading The @code{-target-detach} Command
30826 @findex -target-detach
30828 @subsubheading Synopsis
30831 -target-detach [ @var{pid} | @var{gid} ]
30834 Detach from the remote target which normally resumes its execution.
30835 If either @var{pid} or @var{gid} is specified, detaches from either
30836 the specified process, or specified thread group. There's no output.
30838 @subsubheading @value{GDBN} Command
30840 The corresponding @value{GDBN} command is @samp{detach}.
30842 @subsubheading Example
30852 @subheading The @code{-target-disconnect} Command
30853 @findex -target-disconnect
30855 @subsubheading Synopsis
30861 Disconnect from the remote target. There's no output and the target is
30862 generally not resumed.
30864 @subsubheading @value{GDBN} Command
30866 The corresponding @value{GDBN} command is @samp{disconnect}.
30868 @subsubheading Example
30878 @subheading The @code{-target-download} Command
30879 @findex -target-download
30881 @subsubheading Synopsis
30887 Loads the executable onto the remote target.
30888 It prints out an update message every half second, which includes the fields:
30892 The name of the section.
30894 The size of what has been sent so far for that section.
30896 The size of the section.
30898 The total size of what was sent so far (the current and the previous sections).
30900 The size of the overall executable to download.
30904 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
30905 @sc{gdb/mi} Output Syntax}).
30907 In addition, it prints the name and size of the sections, as they are
30908 downloaded. These messages include the following fields:
30912 The name of the section.
30914 The size of the section.
30916 The size of the overall executable to download.
30920 At the end, a summary is printed.
30922 @subsubheading @value{GDBN} Command
30924 The corresponding @value{GDBN} command is @samp{load}.
30926 @subsubheading Example
30928 Note: each status message appears on a single line. Here the messages
30929 have been broken down so that they can fit onto a page.
30934 +download,@{section=".text",section-size="6668",total-size="9880"@}
30935 +download,@{section=".text",section-sent="512",section-size="6668",
30936 total-sent="512",total-size="9880"@}
30937 +download,@{section=".text",section-sent="1024",section-size="6668",
30938 total-sent="1024",total-size="9880"@}
30939 +download,@{section=".text",section-sent="1536",section-size="6668",
30940 total-sent="1536",total-size="9880"@}
30941 +download,@{section=".text",section-sent="2048",section-size="6668",
30942 total-sent="2048",total-size="9880"@}
30943 +download,@{section=".text",section-sent="2560",section-size="6668",
30944 total-sent="2560",total-size="9880"@}
30945 +download,@{section=".text",section-sent="3072",section-size="6668",
30946 total-sent="3072",total-size="9880"@}
30947 +download,@{section=".text",section-sent="3584",section-size="6668",
30948 total-sent="3584",total-size="9880"@}
30949 +download,@{section=".text",section-sent="4096",section-size="6668",
30950 total-sent="4096",total-size="9880"@}
30951 +download,@{section=".text",section-sent="4608",section-size="6668",
30952 total-sent="4608",total-size="9880"@}
30953 +download,@{section=".text",section-sent="5120",section-size="6668",
30954 total-sent="5120",total-size="9880"@}
30955 +download,@{section=".text",section-sent="5632",section-size="6668",
30956 total-sent="5632",total-size="9880"@}
30957 +download,@{section=".text",section-sent="6144",section-size="6668",
30958 total-sent="6144",total-size="9880"@}
30959 +download,@{section=".text",section-sent="6656",section-size="6668",
30960 total-sent="6656",total-size="9880"@}
30961 +download,@{section=".init",section-size="28",total-size="9880"@}
30962 +download,@{section=".fini",section-size="28",total-size="9880"@}
30963 +download,@{section=".data",section-size="3156",total-size="9880"@}
30964 +download,@{section=".data",section-sent="512",section-size="3156",
30965 total-sent="7236",total-size="9880"@}
30966 +download,@{section=".data",section-sent="1024",section-size="3156",
30967 total-sent="7748",total-size="9880"@}
30968 +download,@{section=".data",section-sent="1536",section-size="3156",
30969 total-sent="8260",total-size="9880"@}
30970 +download,@{section=".data",section-sent="2048",section-size="3156",
30971 total-sent="8772",total-size="9880"@}
30972 +download,@{section=".data",section-sent="2560",section-size="3156",
30973 total-sent="9284",total-size="9880"@}
30974 +download,@{section=".data",section-sent="3072",section-size="3156",
30975 total-sent="9796",total-size="9880"@}
30976 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
30983 @subheading The @code{-target-exec-status} Command
30984 @findex -target-exec-status
30986 @subsubheading Synopsis
30989 -target-exec-status
30992 Provide information on the state of the target (whether it is running or
30993 not, for instance).
30995 @subsubheading @value{GDBN} Command
30997 There's no equivalent @value{GDBN} command.
30999 @subsubheading Example
31003 @subheading The @code{-target-list-available-targets} Command
31004 @findex -target-list-available-targets
31006 @subsubheading Synopsis
31009 -target-list-available-targets
31012 List the possible targets to connect to.
31014 @subsubheading @value{GDBN} Command
31016 The corresponding @value{GDBN} command is @samp{help target}.
31018 @subsubheading Example
31022 @subheading The @code{-target-list-current-targets} Command
31023 @findex -target-list-current-targets
31025 @subsubheading Synopsis
31028 -target-list-current-targets
31031 Describe the current target.
31033 @subsubheading @value{GDBN} Command
31035 The corresponding information is printed by @samp{info file} (among
31038 @subsubheading Example
31042 @subheading The @code{-target-list-parameters} Command
31043 @findex -target-list-parameters
31045 @subsubheading Synopsis
31048 -target-list-parameters
31054 @subsubheading @value{GDBN} Command
31058 @subsubheading Example
31062 @subheading The @code{-target-select} Command
31063 @findex -target-select
31065 @subsubheading Synopsis
31068 -target-select @var{type} @var{parameters @dots{}}
31071 Connect @value{GDBN} to the remote target. This command takes two args:
31075 The type of target, for instance @samp{remote}, etc.
31076 @item @var{parameters}
31077 Device names, host names and the like. @xref{Target Commands, ,
31078 Commands for Managing Targets}, for more details.
31081 The output is a connection notification, followed by the address at
31082 which the target program is, in the following form:
31085 ^connected,addr="@var{address}",func="@var{function name}",
31086 args=[@var{arg list}]
31089 @subsubheading @value{GDBN} Command
31091 The corresponding @value{GDBN} command is @samp{target}.
31093 @subsubheading Example
31097 -target-select remote /dev/ttya
31098 ^connected,addr="0xfe00a300",func="??",args=[]
31102 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31103 @node GDB/MI File Transfer Commands
31104 @section @sc{gdb/mi} File Transfer Commands
31107 @subheading The @code{-target-file-put} Command
31108 @findex -target-file-put
31110 @subsubheading Synopsis
31113 -target-file-put @var{hostfile} @var{targetfile}
31116 Copy file @var{hostfile} from the host system (the machine running
31117 @value{GDBN}) to @var{targetfile} on the target system.
31119 @subsubheading @value{GDBN} Command
31121 The corresponding @value{GDBN} command is @samp{remote put}.
31123 @subsubheading Example
31127 -target-file-put localfile remotefile
31133 @subheading The @code{-target-file-get} Command
31134 @findex -target-file-get
31136 @subsubheading Synopsis
31139 -target-file-get @var{targetfile} @var{hostfile}
31142 Copy file @var{targetfile} from the target system to @var{hostfile}
31143 on the host system.
31145 @subsubheading @value{GDBN} Command
31147 The corresponding @value{GDBN} command is @samp{remote get}.
31149 @subsubheading Example
31153 -target-file-get remotefile localfile
31159 @subheading The @code{-target-file-delete} Command
31160 @findex -target-file-delete
31162 @subsubheading Synopsis
31165 -target-file-delete @var{targetfile}
31168 Delete @var{targetfile} from the target system.
31170 @subsubheading @value{GDBN} Command
31172 The corresponding @value{GDBN} command is @samp{remote delete}.
31174 @subsubheading Example
31178 -target-file-delete remotefile
31184 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31185 @node GDB/MI Ada Exceptions Commands
31186 @section Ada Exceptions @sc{gdb/mi} Commands
31188 @subheading The @code{-info-ada-exceptions} Command
31189 @findex -info-ada-exceptions
31191 @subsubheading Synopsis
31194 -info-ada-exceptions [ @var{regexp}]
31197 List all Ada exceptions defined within the program being debugged.
31198 With a regular expression @var{regexp}, only those exceptions whose
31199 names match @var{regexp} are listed.
31201 @subsubheading @value{GDBN} Command
31203 The corresponding @value{GDBN} command is @samp{info exceptions}.
31205 @subsubheading Result
31207 The result is a table of Ada exceptions. The following columns are
31208 defined for each exception:
31212 The name of the exception.
31215 The address of the exception.
31219 @subsubheading Example
31222 -info-ada-exceptions aint
31223 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
31224 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
31225 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
31226 body=[@{name="constraint_error",address="0x0000000000613da0"@},
31227 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
31230 @subheading Catching Ada Exceptions
31232 The commands describing how to ask @value{GDBN} to stop when a program
31233 raises an exception are described at @ref{Ada Exception GDB/MI
31234 Catchpoint Commands}.
31237 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31238 @node GDB/MI Support Commands
31239 @section @sc{gdb/mi} Support Commands
31241 Since new commands and features get regularly added to @sc{gdb/mi},
31242 some commands are available to help front-ends query the debugger
31243 about support for these capabilities. Similarly, it is also possible
31244 to query @value{GDBN} about target support of certain features.
31246 @subheading The @code{-info-gdb-mi-command} Command
31247 @cindex @code{-info-gdb-mi-command}
31248 @findex -info-gdb-mi-command
31250 @subsubheading Synopsis
31253 -info-gdb-mi-command @var{cmd_name}
31256 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
31258 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
31259 is technically not part of the command name (@pxref{GDB/MI Input
31260 Syntax}), and thus should be omitted in @var{cmd_name}. However,
31261 for ease of use, this command also accepts the form with the leading
31264 @subsubheading @value{GDBN} Command
31266 There is no corresponding @value{GDBN} command.
31268 @subsubheading Result
31270 The result is a tuple. There is currently only one field:
31274 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
31275 @code{"false"} otherwise.
31279 @subsubheading Example
31281 Here is an example where the @sc{gdb/mi} command does not exist:
31284 -info-gdb-mi-command unsupported-command
31285 ^done,command=@{exists="false"@}
31289 And here is an example where the @sc{gdb/mi} command is known
31293 -info-gdb-mi-command symbol-list-lines
31294 ^done,command=@{exists="true"@}
31297 @subheading The @code{-list-features} Command
31298 @findex -list-features
31299 @cindex supported @sc{gdb/mi} features, list
31301 Returns a list of particular features of the MI protocol that
31302 this version of gdb implements. A feature can be a command,
31303 or a new field in an output of some command, or even an
31304 important bugfix. While a frontend can sometimes detect presence
31305 of a feature at runtime, it is easier to perform detection at debugger
31308 The command returns a list of strings, with each string naming an
31309 available feature. Each returned string is just a name, it does not
31310 have any internal structure. The list of possible feature names
31316 (gdb) -list-features
31317 ^done,result=["feature1","feature2"]
31320 The current list of features is:
31323 @item frozen-varobjs
31324 Indicates support for the @code{-var-set-frozen} command, as well
31325 as possible presense of the @code{frozen} field in the output
31326 of @code{-varobj-create}.
31327 @item pending-breakpoints
31328 Indicates support for the @option{-f} option to the @code{-break-insert}
31331 Indicates Python scripting support, Python-based
31332 pretty-printing commands, and possible presence of the
31333 @samp{display_hint} field in the output of @code{-var-list-children}
31335 Indicates support for the @code{-thread-info} command.
31336 @item data-read-memory-bytes
31337 Indicates support for the @code{-data-read-memory-bytes} and the
31338 @code{-data-write-memory-bytes} commands.
31339 @item breakpoint-notifications
31340 Indicates that changes to breakpoints and breakpoints created via the
31341 CLI will be announced via async records.
31342 @item ada-task-info
31343 Indicates support for the @code{-ada-task-info} command.
31344 @item language-option
31345 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
31346 option (@pxref{Context management}).
31347 @item info-gdb-mi-command
31348 Indicates support for the @code{-info-gdb-mi-command} command.
31349 @item undefined-command-error-code
31350 Indicates support for the "undefined-command" error code in error result
31351 records, produced when trying to execute an undefined @sc{gdb/mi} command
31352 (@pxref{GDB/MI Result Records}).
31353 @item exec-run-start-option
31354 Indicates that the @code{-exec-run} command supports the @option{--start}
31355 option (@pxref{GDB/MI Program Execution}).
31358 @subheading The @code{-list-target-features} Command
31359 @findex -list-target-features
31361 Returns a list of particular features that are supported by the
31362 target. Those features affect the permitted MI commands, but
31363 unlike the features reported by the @code{-list-features} command, the
31364 features depend on which target GDB is using at the moment. Whenever
31365 a target can change, due to commands such as @code{-target-select},
31366 @code{-target-attach} or @code{-exec-run}, the list of target features
31367 may change, and the frontend should obtain it again.
31371 (gdb) -list-target-features
31372 ^done,result=["async"]
31375 The current list of features is:
31379 Indicates that the target is capable of asynchronous command
31380 execution, which means that @value{GDBN} will accept further commands
31381 while the target is running.
31384 Indicates that the target is capable of reverse execution.
31385 @xref{Reverse Execution}, for more information.
31389 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31390 @node GDB/MI Miscellaneous Commands
31391 @section Miscellaneous @sc{gdb/mi} Commands
31393 @c @subheading -gdb-complete
31395 @subheading The @code{-gdb-exit} Command
31398 @subsubheading Synopsis
31404 Exit @value{GDBN} immediately.
31406 @subsubheading @value{GDBN} Command
31408 Approximately corresponds to @samp{quit}.
31410 @subsubheading Example
31420 @subheading The @code{-exec-abort} Command
31421 @findex -exec-abort
31423 @subsubheading Synopsis
31429 Kill the inferior running program.
31431 @subsubheading @value{GDBN} Command
31433 The corresponding @value{GDBN} command is @samp{kill}.
31435 @subsubheading Example
31440 @subheading The @code{-gdb-set} Command
31443 @subsubheading Synopsis
31449 Set an internal @value{GDBN} variable.
31450 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
31452 @subsubheading @value{GDBN} Command
31454 The corresponding @value{GDBN} command is @samp{set}.
31456 @subsubheading Example
31466 @subheading The @code{-gdb-show} Command
31469 @subsubheading Synopsis
31475 Show the current value of a @value{GDBN} variable.
31477 @subsubheading @value{GDBN} Command
31479 The corresponding @value{GDBN} command is @samp{show}.
31481 @subsubheading Example
31490 @c @subheading -gdb-source
31493 @subheading The @code{-gdb-version} Command
31494 @findex -gdb-version
31496 @subsubheading Synopsis
31502 Show version information for @value{GDBN}. Used mostly in testing.
31504 @subsubheading @value{GDBN} Command
31506 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
31507 default shows this information when you start an interactive session.
31509 @subsubheading Example
31511 @c This example modifies the actual output from GDB to avoid overfull
31517 ~Copyright 2000 Free Software Foundation, Inc.
31518 ~GDB is free software, covered by the GNU General Public License, and
31519 ~you are welcome to change it and/or distribute copies of it under
31520 ~ certain conditions.
31521 ~Type "show copying" to see the conditions.
31522 ~There is absolutely no warranty for GDB. Type "show warranty" for
31524 ~This GDB was configured as
31525 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
31530 @subheading The @code{-list-thread-groups} Command
31531 @findex -list-thread-groups
31533 @subheading Synopsis
31536 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
31539 Lists thread groups (@pxref{Thread groups}). When a single thread
31540 group is passed as the argument, lists the children of that group.
31541 When several thread group are passed, lists information about those
31542 thread groups. Without any parameters, lists information about all
31543 top-level thread groups.
31545 Normally, thread groups that are being debugged are reported.
31546 With the @samp{--available} option, @value{GDBN} reports thread groups
31547 available on the target.
31549 The output of this command may have either a @samp{threads} result or
31550 a @samp{groups} result. The @samp{thread} result has a list of tuples
31551 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
31552 Information}). The @samp{groups} result has a list of tuples as value,
31553 each tuple describing a thread group. If top-level groups are
31554 requested (that is, no parameter is passed), or when several groups
31555 are passed, the output always has a @samp{groups} result. The format
31556 of the @samp{group} result is described below.
31558 To reduce the number of roundtrips it's possible to list thread groups
31559 together with their children, by passing the @samp{--recurse} option
31560 and the recursion depth. Presently, only recursion depth of 1 is
31561 permitted. If this option is present, then every reported thread group
31562 will also include its children, either as @samp{group} or
31563 @samp{threads} field.
31565 In general, any combination of option and parameters is permitted, with
31566 the following caveats:
31570 When a single thread group is passed, the output will typically
31571 be the @samp{threads} result. Because threads may not contain
31572 anything, the @samp{recurse} option will be ignored.
31575 When the @samp{--available} option is passed, limited information may
31576 be available. In particular, the list of threads of a process might
31577 be inaccessible. Further, specifying specific thread groups might
31578 not give any performance advantage over listing all thread groups.
31579 The frontend should assume that @samp{-list-thread-groups --available}
31580 is always an expensive operation and cache the results.
31584 The @samp{groups} result is a list of tuples, where each tuple may
31585 have the following fields:
31589 Identifier of the thread group. This field is always present.
31590 The identifier is an opaque string; frontends should not try to
31591 convert it to an integer, even though it might look like one.
31594 The type of the thread group. At present, only @samp{process} is a
31598 The target-specific process identifier. This field is only present
31599 for thread groups of type @samp{process} and only if the process exists.
31602 The exit code of this group's last exited thread, formatted in octal.
31603 This field is only present for thread groups of type @samp{process} and
31604 only if the process is not running.
31607 The number of children this thread group has. This field may be
31608 absent for an available thread group.
31611 This field has a list of tuples as value, each tuple describing a
31612 thread. It may be present if the @samp{--recurse} option is
31613 specified, and it's actually possible to obtain the threads.
31616 This field is a list of integers, each identifying a core that one
31617 thread of the group is running on. This field may be absent if
31618 such information is not available.
31621 The name of the executable file that corresponds to this thread group.
31622 The field is only present for thread groups of type @samp{process},
31623 and only if there is a corresponding executable file.
31627 @subheading Example
31631 -list-thread-groups
31632 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
31633 -list-thread-groups 17
31634 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31635 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
31636 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31637 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
31638 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
31639 -list-thread-groups --available
31640 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
31641 -list-thread-groups --available --recurse 1
31642 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31643 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31644 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
31645 -list-thread-groups --available --recurse 1 17 18
31646 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31647 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31648 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
31651 @subheading The @code{-info-os} Command
31654 @subsubheading Synopsis
31657 -info-os [ @var{type} ]
31660 If no argument is supplied, the command returns a table of available
31661 operating-system-specific information types. If one of these types is
31662 supplied as an argument @var{type}, then the command returns a table
31663 of data of that type.
31665 The types of information available depend on the target operating
31668 @subsubheading @value{GDBN} Command
31670 The corresponding @value{GDBN} command is @samp{info os}.
31672 @subsubheading Example
31674 When run on a @sc{gnu}/Linux system, the output will look something
31680 ^done,OSDataTable=@{nr_rows="9",nr_cols="3",
31681 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
31682 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
31683 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
31684 body=[item=@{col0="processes",col1="Listing of all processes",
31685 col2="Processes"@},
31686 item=@{col0="procgroups",col1="Listing of all process groups",
31687 col2="Process groups"@},
31688 item=@{col0="threads",col1="Listing of all threads",
31690 item=@{col0="files",col1="Listing of all file descriptors",
31691 col2="File descriptors"@},
31692 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
31694 item=@{col0="shm",col1="Listing of all shared-memory regions",
31695 col2="Shared-memory regions"@},
31696 item=@{col0="semaphores",col1="Listing of all semaphores",
31697 col2="Semaphores"@},
31698 item=@{col0="msg",col1="Listing of all message queues",
31699 col2="Message queues"@},
31700 item=@{col0="modules",col1="Listing of all loaded kernel modules",
31701 col2="Kernel modules"@}]@}
31704 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
31705 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
31706 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
31707 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
31708 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
31709 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
31710 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
31711 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
31713 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
31714 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
31718 (Note that the MI output here includes a @code{"Title"} column that
31719 does not appear in command-line @code{info os}; this column is useful
31720 for MI clients that want to enumerate the types of data, such as in a
31721 popup menu, but is needless clutter on the command line, and
31722 @code{info os} omits it.)
31724 @subheading The @code{-add-inferior} Command
31725 @findex -add-inferior
31727 @subheading Synopsis
31733 Creates a new inferior (@pxref{Inferiors and Programs}). The created
31734 inferior is not associated with any executable. Such association may
31735 be established with the @samp{-file-exec-and-symbols} command
31736 (@pxref{GDB/MI File Commands}). The command response has a single
31737 field, @samp{inferior}, whose value is the identifier of the
31738 thread group corresponding to the new inferior.
31740 @subheading Example
31745 ^done,inferior="i3"
31748 @subheading The @code{-interpreter-exec} Command
31749 @findex -interpreter-exec
31751 @subheading Synopsis
31754 -interpreter-exec @var{interpreter} @var{command}
31756 @anchor{-interpreter-exec}
31758 Execute the specified @var{command} in the given @var{interpreter}.
31760 @subheading @value{GDBN} Command
31762 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
31764 @subheading Example
31768 -interpreter-exec console "break main"
31769 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
31770 &"During symbol reading, bad structure-type format.\n"
31771 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
31776 @subheading The @code{-inferior-tty-set} Command
31777 @findex -inferior-tty-set
31779 @subheading Synopsis
31782 -inferior-tty-set /dev/pts/1
31785 Set terminal for future runs of the program being debugged.
31787 @subheading @value{GDBN} Command
31789 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
31791 @subheading Example
31795 -inferior-tty-set /dev/pts/1
31800 @subheading The @code{-inferior-tty-show} Command
31801 @findex -inferior-tty-show
31803 @subheading Synopsis
31809 Show terminal for future runs of program being debugged.
31811 @subheading @value{GDBN} Command
31813 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
31815 @subheading Example
31819 -inferior-tty-set /dev/pts/1
31823 ^done,inferior_tty_terminal="/dev/pts/1"
31827 @subheading The @code{-enable-timings} Command
31828 @findex -enable-timings
31830 @subheading Synopsis
31833 -enable-timings [yes | no]
31836 Toggle the printing of the wallclock, user and system times for an MI
31837 command as a field in its output. This command is to help frontend
31838 developers optimize the performance of their code. No argument is
31839 equivalent to @samp{yes}.
31841 @subheading @value{GDBN} Command
31845 @subheading Example
31853 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31854 addr="0x080484ed",func="main",file="myprog.c",
31855 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
31857 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
31865 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
31866 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
31867 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
31868 fullname="/home/nickrob/myprog.c",line="73"@}
31873 @chapter @value{GDBN} Annotations
31875 This chapter describes annotations in @value{GDBN}. Annotations were
31876 designed to interface @value{GDBN} to graphical user interfaces or other
31877 similar programs which want to interact with @value{GDBN} at a
31878 relatively high level.
31880 The annotation mechanism has largely been superseded by @sc{gdb/mi}
31884 This is Edition @value{EDITION}, @value{DATE}.
31888 * Annotations Overview:: What annotations are; the general syntax.
31889 * Server Prefix:: Issuing a command without affecting user state.
31890 * Prompting:: Annotations marking @value{GDBN}'s need for input.
31891 * Errors:: Annotations for error messages.
31892 * Invalidation:: Some annotations describe things now invalid.
31893 * Annotations for Running::
31894 Whether the program is running, how it stopped, etc.
31895 * Source Annotations:: Annotations describing source code.
31898 @node Annotations Overview
31899 @section What is an Annotation?
31900 @cindex annotations
31902 Annotations start with a newline character, two @samp{control-z}
31903 characters, and the name of the annotation. If there is no additional
31904 information associated with this annotation, the name of the annotation
31905 is followed immediately by a newline. If there is additional
31906 information, the name of the annotation is followed by a space, the
31907 additional information, and a newline. The additional information
31908 cannot contain newline characters.
31910 Any output not beginning with a newline and two @samp{control-z}
31911 characters denotes literal output from @value{GDBN}. Currently there is
31912 no need for @value{GDBN} to output a newline followed by two
31913 @samp{control-z} characters, but if there was such a need, the
31914 annotations could be extended with an @samp{escape} annotation which
31915 means those three characters as output.
31917 The annotation @var{level}, which is specified using the
31918 @option{--annotate} command line option (@pxref{Mode Options}), controls
31919 how much information @value{GDBN} prints together with its prompt,
31920 values of expressions, source lines, and other types of output. Level 0
31921 is for no annotations, level 1 is for use when @value{GDBN} is run as a
31922 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
31923 for programs that control @value{GDBN}, and level 2 annotations have
31924 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
31925 Interface, annotate, GDB's Obsolete Annotations}).
31928 @kindex set annotate
31929 @item set annotate @var{level}
31930 The @value{GDBN} command @code{set annotate} sets the level of
31931 annotations to the specified @var{level}.
31933 @item show annotate
31934 @kindex show annotate
31935 Show the current annotation level.
31938 This chapter describes level 3 annotations.
31940 A simple example of starting up @value{GDBN} with annotations is:
31943 $ @kbd{gdb --annotate=3}
31945 Copyright 2003 Free Software Foundation, Inc.
31946 GDB is free software, covered by the GNU General Public License,
31947 and you are welcome to change it and/or distribute copies of it
31948 under certain conditions.
31949 Type "show copying" to see the conditions.
31950 There is absolutely no warranty for GDB. Type "show warranty"
31952 This GDB was configured as "i386-pc-linux-gnu"
31963 Here @samp{quit} is input to @value{GDBN}; the rest is output from
31964 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
31965 denotes a @samp{control-z} character) are annotations; the rest is
31966 output from @value{GDBN}.
31968 @node Server Prefix
31969 @section The Server Prefix
31970 @cindex server prefix
31972 If you prefix a command with @samp{server } then it will not affect
31973 the command history, nor will it affect @value{GDBN}'s notion of which
31974 command to repeat if @key{RET} is pressed on a line by itself. This
31975 means that commands can be run behind a user's back by a front-end in
31976 a transparent manner.
31978 The @code{server } prefix does not affect the recording of values into
31979 the value history; to print a value without recording it into the
31980 value history, use the @code{output} command instead of the
31981 @code{print} command.
31983 Using this prefix also disables confirmation requests
31984 (@pxref{confirmation requests}).
31987 @section Annotation for @value{GDBN} Input
31989 @cindex annotations for prompts
31990 When @value{GDBN} prompts for input, it annotates this fact so it is possible
31991 to know when to send output, when the output from a given command is
31994 Different kinds of input each have a different @dfn{input type}. Each
31995 input type has three annotations: a @code{pre-} annotation, which
31996 denotes the beginning of any prompt which is being output, a plain
31997 annotation, which denotes the end of the prompt, and then a @code{post-}
31998 annotation which denotes the end of any echo which may (or may not) be
31999 associated with the input. For example, the @code{prompt} input type
32000 features the following annotations:
32008 The input types are
32011 @findex pre-prompt annotation
32012 @findex prompt annotation
32013 @findex post-prompt annotation
32015 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
32017 @findex pre-commands annotation
32018 @findex commands annotation
32019 @findex post-commands annotation
32021 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
32022 command. The annotations are repeated for each command which is input.
32024 @findex pre-overload-choice annotation
32025 @findex overload-choice annotation
32026 @findex post-overload-choice annotation
32027 @item overload-choice
32028 When @value{GDBN} wants the user to select between various overloaded functions.
32030 @findex pre-query annotation
32031 @findex query annotation
32032 @findex post-query annotation
32034 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
32036 @findex pre-prompt-for-continue annotation
32037 @findex prompt-for-continue annotation
32038 @findex post-prompt-for-continue annotation
32039 @item prompt-for-continue
32040 When @value{GDBN} is asking the user to press return to continue. Note: Don't
32041 expect this to work well; instead use @code{set height 0} to disable
32042 prompting. This is because the counting of lines is buggy in the
32043 presence of annotations.
32048 @cindex annotations for errors, warnings and interrupts
32050 @findex quit annotation
32055 This annotation occurs right before @value{GDBN} responds to an interrupt.
32057 @findex error annotation
32062 This annotation occurs right before @value{GDBN} responds to an error.
32064 Quit and error annotations indicate that any annotations which @value{GDBN} was
32065 in the middle of may end abruptly. For example, if a
32066 @code{value-history-begin} annotation is followed by a @code{error}, one
32067 cannot expect to receive the matching @code{value-history-end}. One
32068 cannot expect not to receive it either, however; an error annotation
32069 does not necessarily mean that @value{GDBN} is immediately returning all the way
32072 @findex error-begin annotation
32073 A quit or error annotation may be preceded by
32079 Any output between that and the quit or error annotation is the error
32082 Warning messages are not yet annotated.
32083 @c If we want to change that, need to fix warning(), type_error(),
32084 @c range_error(), and possibly other places.
32087 @section Invalidation Notices
32089 @cindex annotations for invalidation messages
32090 The following annotations say that certain pieces of state may have
32094 @findex frames-invalid annotation
32095 @item ^Z^Zframes-invalid
32097 The frames (for example, output from the @code{backtrace} command) may
32100 @findex breakpoints-invalid annotation
32101 @item ^Z^Zbreakpoints-invalid
32103 The breakpoints may have changed. For example, the user just added or
32104 deleted a breakpoint.
32107 @node Annotations for Running
32108 @section Running the Program
32109 @cindex annotations for running programs
32111 @findex starting annotation
32112 @findex stopping annotation
32113 When the program starts executing due to a @value{GDBN} command such as
32114 @code{step} or @code{continue},
32120 is output. When the program stops,
32126 is output. Before the @code{stopped} annotation, a variety of
32127 annotations describe how the program stopped.
32130 @findex exited annotation
32131 @item ^Z^Zexited @var{exit-status}
32132 The program exited, and @var{exit-status} is the exit status (zero for
32133 successful exit, otherwise nonzero).
32135 @findex signalled annotation
32136 @findex signal-name annotation
32137 @findex signal-name-end annotation
32138 @findex signal-string annotation
32139 @findex signal-string-end annotation
32140 @item ^Z^Zsignalled
32141 The program exited with a signal. After the @code{^Z^Zsignalled}, the
32142 annotation continues:
32148 ^Z^Zsignal-name-end
32152 ^Z^Zsignal-string-end
32157 where @var{name} is the name of the signal, such as @code{SIGILL} or
32158 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
32159 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
32160 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
32161 user's benefit and have no particular format.
32163 @findex signal annotation
32165 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
32166 just saying that the program received the signal, not that it was
32167 terminated with it.
32169 @findex breakpoint annotation
32170 @item ^Z^Zbreakpoint @var{number}
32171 The program hit breakpoint number @var{number}.
32173 @findex watchpoint annotation
32174 @item ^Z^Zwatchpoint @var{number}
32175 The program hit watchpoint number @var{number}.
32178 @node Source Annotations
32179 @section Displaying Source
32180 @cindex annotations for source display
32182 @findex source annotation
32183 The following annotation is used instead of displaying source code:
32186 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
32189 where @var{filename} is an absolute file name indicating which source
32190 file, @var{line} is the line number within that file (where 1 is the
32191 first line in the file), @var{character} is the character position
32192 within the file (where 0 is the first character in the file) (for most
32193 debug formats this will necessarily point to the beginning of a line),
32194 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
32195 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
32196 @var{addr} is the address in the target program associated with the
32197 source which is being displayed. The @var{addr} is in the form @samp{0x}
32198 followed by one or more lowercase hex digits (note that this does not
32199 depend on the language).
32201 @node JIT Interface
32202 @chapter JIT Compilation Interface
32203 @cindex just-in-time compilation
32204 @cindex JIT compilation interface
32206 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
32207 interface. A JIT compiler is a program or library that generates native
32208 executable code at runtime and executes it, usually in order to achieve good
32209 performance while maintaining platform independence.
32211 Programs that use JIT compilation are normally difficult to debug because
32212 portions of their code are generated at runtime, instead of being loaded from
32213 object files, which is where @value{GDBN} normally finds the program's symbols
32214 and debug information. In order to debug programs that use JIT compilation,
32215 @value{GDBN} has an interface that allows the program to register in-memory
32216 symbol files with @value{GDBN} at runtime.
32218 If you are using @value{GDBN} to debug a program that uses this interface, then
32219 it should work transparently so long as you have not stripped the binary. If
32220 you are developing a JIT compiler, then the interface is documented in the rest
32221 of this chapter. At this time, the only known client of this interface is the
32224 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
32225 JIT compiler communicates with @value{GDBN} by writing data into a global
32226 variable and calling a fuction at a well-known symbol. When @value{GDBN}
32227 attaches, it reads a linked list of symbol files from the global variable to
32228 find existing code, and puts a breakpoint in the function so that it can find
32229 out about additional code.
32232 * Declarations:: Relevant C struct declarations
32233 * Registering Code:: Steps to register code
32234 * Unregistering Code:: Steps to unregister code
32235 * Custom Debug Info:: Emit debug information in a custom format
32239 @section JIT Declarations
32241 These are the relevant struct declarations that a C program should include to
32242 implement the interface:
32252 struct jit_code_entry
32254 struct jit_code_entry *next_entry;
32255 struct jit_code_entry *prev_entry;
32256 const char *symfile_addr;
32257 uint64_t symfile_size;
32260 struct jit_descriptor
32263 /* This type should be jit_actions_t, but we use uint32_t
32264 to be explicit about the bitwidth. */
32265 uint32_t action_flag;
32266 struct jit_code_entry *relevant_entry;
32267 struct jit_code_entry *first_entry;
32270 /* GDB puts a breakpoint in this function. */
32271 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
32273 /* Make sure to specify the version statically, because the
32274 debugger may check the version before we can set it. */
32275 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
32278 If the JIT is multi-threaded, then it is important that the JIT synchronize any
32279 modifications to this global data properly, which can easily be done by putting
32280 a global mutex around modifications to these structures.
32282 @node Registering Code
32283 @section Registering Code
32285 To register code with @value{GDBN}, the JIT should follow this protocol:
32289 Generate an object file in memory with symbols and other desired debug
32290 information. The file must include the virtual addresses of the sections.
32293 Create a code entry for the file, which gives the start and size of the symbol
32297 Add it to the linked list in the JIT descriptor.
32300 Point the relevant_entry field of the descriptor at the entry.
32303 Set @code{action_flag} to @code{JIT_REGISTER} and call
32304 @code{__jit_debug_register_code}.
32307 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
32308 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
32309 new code. However, the linked list must still be maintained in order to allow
32310 @value{GDBN} to attach to a running process and still find the symbol files.
32312 @node Unregistering Code
32313 @section Unregistering Code
32315 If code is freed, then the JIT should use the following protocol:
32319 Remove the code entry corresponding to the code from the linked list.
32322 Point the @code{relevant_entry} field of the descriptor at the code entry.
32325 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
32326 @code{__jit_debug_register_code}.
32329 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
32330 and the JIT will leak the memory used for the associated symbol files.
32332 @node Custom Debug Info
32333 @section Custom Debug Info
32334 @cindex custom JIT debug info
32335 @cindex JIT debug info reader
32337 Generating debug information in platform-native file formats (like ELF
32338 or COFF) may be an overkill for JIT compilers; especially if all the
32339 debug info is used for is displaying a meaningful backtrace. The
32340 issue can be resolved by having the JIT writers decide on a debug info
32341 format and also provide a reader that parses the debug info generated
32342 by the JIT compiler. This section gives a brief overview on writing
32343 such a parser. More specific details can be found in the source file
32344 @file{gdb/jit-reader.in}, which is also installed as a header at
32345 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
32347 The reader is implemented as a shared object (so this functionality is
32348 not available on platforms which don't allow loading shared objects at
32349 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
32350 @code{jit-reader-unload} are provided, to be used to load and unload
32351 the readers from a preconfigured directory. Once loaded, the shared
32352 object is used the parse the debug information emitted by the JIT
32356 * Using JIT Debug Info Readers:: How to use supplied readers correctly
32357 * Writing JIT Debug Info Readers:: Creating a debug-info reader
32360 @node Using JIT Debug Info Readers
32361 @subsection Using JIT Debug Info Readers
32362 @kindex jit-reader-load
32363 @kindex jit-reader-unload
32365 Readers can be loaded and unloaded using the @code{jit-reader-load}
32366 and @code{jit-reader-unload} commands.
32369 @item jit-reader-load @var{reader}
32370 Load the JIT reader named @var{reader}, which is a shared
32371 object specified as either an absolute or a relative file name. In
32372 the latter case, @value{GDBN} will try to load the reader from a
32373 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
32374 system (here @var{libdir} is the system library directory, often
32375 @file{/usr/local/lib}).
32377 Only one reader can be active at a time; trying to load a second
32378 reader when one is already loaded will result in @value{GDBN}
32379 reporting an error. A new JIT reader can be loaded by first unloading
32380 the current one using @code{jit-reader-unload} and then invoking
32381 @code{jit-reader-load}.
32383 @item jit-reader-unload
32384 Unload the currently loaded JIT reader.
32388 @node Writing JIT Debug Info Readers
32389 @subsection Writing JIT Debug Info Readers
32390 @cindex writing JIT debug info readers
32392 As mentioned, a reader is essentially a shared object conforming to a
32393 certain ABI. This ABI is described in @file{jit-reader.h}.
32395 @file{jit-reader.h} defines the structures, macros and functions
32396 required to write a reader. It is installed (along with
32397 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
32398 the system include directory.
32400 Readers need to be released under a GPL compatible license. A reader
32401 can be declared as released under such a license by placing the macro
32402 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
32404 The entry point for readers is the symbol @code{gdb_init_reader},
32405 which is expected to be a function with the prototype
32407 @findex gdb_init_reader
32409 extern struct gdb_reader_funcs *gdb_init_reader (void);
32412 @cindex @code{struct gdb_reader_funcs}
32414 @code{struct gdb_reader_funcs} contains a set of pointers to callback
32415 functions. These functions are executed to read the debug info
32416 generated by the JIT compiler (@code{read}), to unwind stack frames
32417 (@code{unwind}) and to create canonical frame IDs
32418 (@code{get_Frame_id}). It also has a callback that is called when the
32419 reader is being unloaded (@code{destroy}). The struct looks like this
32422 struct gdb_reader_funcs
32424 /* Must be set to GDB_READER_INTERFACE_VERSION. */
32425 int reader_version;
32427 /* For use by the reader. */
32430 gdb_read_debug_info *read;
32431 gdb_unwind_frame *unwind;
32432 gdb_get_frame_id *get_frame_id;
32433 gdb_destroy_reader *destroy;
32437 @cindex @code{struct gdb_symbol_callbacks}
32438 @cindex @code{struct gdb_unwind_callbacks}
32440 The callbacks are provided with another set of callbacks by
32441 @value{GDBN} to do their job. For @code{read}, these callbacks are
32442 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
32443 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
32444 @code{struct gdb_symbol_callbacks} has callbacks to create new object
32445 files and new symbol tables inside those object files. @code{struct
32446 gdb_unwind_callbacks} has callbacks to read registers off the current
32447 frame and to write out the values of the registers in the previous
32448 frame. Both have a callback (@code{target_read}) to read bytes off the
32449 target's address space.
32451 @node In-Process Agent
32452 @chapter In-Process Agent
32453 @cindex debugging agent
32454 The traditional debugging model is conceptually low-speed, but works fine,
32455 because most bugs can be reproduced in debugging-mode execution. However,
32456 as multi-core or many-core processors are becoming mainstream, and
32457 multi-threaded programs become more and more popular, there should be more
32458 and more bugs that only manifest themselves at normal-mode execution, for
32459 example, thread races, because debugger's interference with the program's
32460 timing may conceal the bugs. On the other hand, in some applications,
32461 it is not feasible for the debugger to interrupt the program's execution
32462 long enough for the developer to learn anything helpful about its behavior.
32463 If the program's correctness depends on its real-time behavior, delays
32464 introduced by a debugger might cause the program to fail, even when the
32465 code itself is correct. It is useful to be able to observe the program's
32466 behavior without interrupting it.
32468 Therefore, traditional debugging model is too intrusive to reproduce
32469 some bugs. In order to reduce the interference with the program, we can
32470 reduce the number of operations performed by debugger. The
32471 @dfn{In-Process Agent}, a shared library, is running within the same
32472 process with inferior, and is able to perform some debugging operations
32473 itself. As a result, debugger is only involved when necessary, and
32474 performance of debugging can be improved accordingly. Note that
32475 interference with program can be reduced but can't be removed completely,
32476 because the in-process agent will still stop or slow down the program.
32478 The in-process agent can interpret and execute Agent Expressions
32479 (@pxref{Agent Expressions}) during performing debugging operations. The
32480 agent expressions can be used for different purposes, such as collecting
32481 data in tracepoints, and condition evaluation in breakpoints.
32483 @anchor{Control Agent}
32484 You can control whether the in-process agent is used as an aid for
32485 debugging with the following commands:
32488 @kindex set agent on
32490 Causes the in-process agent to perform some operations on behalf of the
32491 debugger. Just which operations requested by the user will be done
32492 by the in-process agent depends on the its capabilities. For example,
32493 if you request to evaluate breakpoint conditions in the in-process agent,
32494 and the in-process agent has such capability as well, then breakpoint
32495 conditions will be evaluated in the in-process agent.
32497 @kindex set agent off
32498 @item set agent off
32499 Disables execution of debugging operations by the in-process agent. All
32500 of the operations will be performed by @value{GDBN}.
32504 Display the current setting of execution of debugging operations by
32505 the in-process agent.
32509 * In-Process Agent Protocol::
32512 @node In-Process Agent Protocol
32513 @section In-Process Agent Protocol
32514 @cindex in-process agent protocol
32516 The in-process agent is able to communicate with both @value{GDBN} and
32517 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
32518 used for communications between @value{GDBN} or GDBserver and the IPA.
32519 In general, @value{GDBN} or GDBserver sends commands
32520 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
32521 in-process agent replies back with the return result of the command, or
32522 some other information. The data sent to in-process agent is composed
32523 of primitive data types, such as 4-byte or 8-byte type, and composite
32524 types, which are called objects (@pxref{IPA Protocol Objects}).
32527 * IPA Protocol Objects::
32528 * IPA Protocol Commands::
32531 @node IPA Protocol Objects
32532 @subsection IPA Protocol Objects
32533 @cindex ipa protocol objects
32535 The commands sent to and results received from agent may contain some
32536 complex data types called @dfn{objects}.
32538 The in-process agent is running on the same machine with @value{GDBN}
32539 or GDBserver, so it doesn't have to handle as much differences between
32540 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
32541 However, there are still some differences of two ends in two processes:
32545 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
32546 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
32548 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
32549 GDBserver is compiled with one, and in-process agent is compiled with
32553 Here are the IPA Protocol Objects:
32557 agent expression object. It represents an agent expression
32558 (@pxref{Agent Expressions}).
32559 @anchor{agent expression object}
32561 tracepoint action object. It represents a tracepoint action
32562 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
32563 memory, static trace data and to evaluate expression.
32564 @anchor{tracepoint action object}
32566 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
32567 @anchor{tracepoint object}
32571 The following table describes important attributes of each IPA protocol
32574 @multitable @columnfractions .30 .20 .50
32575 @headitem Name @tab Size @tab Description
32576 @item @emph{agent expression object} @tab @tab
32577 @item length @tab 4 @tab length of bytes code
32578 @item byte code @tab @var{length} @tab contents of byte code
32579 @item @emph{tracepoint action for collecting memory} @tab @tab
32580 @item 'M' @tab 1 @tab type of tracepoint action
32581 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
32582 address of the lowest byte to collect, otherwise @var{addr} is the offset
32583 of @var{basereg} for memory collecting.
32584 @item len @tab 8 @tab length of memory for collecting
32585 @item basereg @tab 4 @tab the register number containing the starting
32586 memory address for collecting.
32587 @item @emph{tracepoint action for collecting registers} @tab @tab
32588 @item 'R' @tab 1 @tab type of tracepoint action
32589 @item @emph{tracepoint action for collecting static trace data} @tab @tab
32590 @item 'L' @tab 1 @tab type of tracepoint action
32591 @item @emph{tracepoint action for expression evaluation} @tab @tab
32592 @item 'X' @tab 1 @tab type of tracepoint action
32593 @item agent expression @tab length of @tab @ref{agent expression object}
32594 @item @emph{tracepoint object} @tab @tab
32595 @item number @tab 4 @tab number of tracepoint
32596 @item address @tab 8 @tab address of tracepoint inserted on
32597 @item type @tab 4 @tab type of tracepoint
32598 @item enabled @tab 1 @tab enable or disable of tracepoint
32599 @item step_count @tab 8 @tab step
32600 @item pass_count @tab 8 @tab pass
32601 @item numactions @tab 4 @tab number of tracepoint actions
32602 @item hit count @tab 8 @tab hit count
32603 @item trace frame usage @tab 8 @tab trace frame usage
32604 @item compiled_cond @tab 8 @tab compiled condition
32605 @item orig_size @tab 8 @tab orig size
32606 @item condition @tab 4 if condition is NULL otherwise length of
32607 @ref{agent expression object}
32608 @tab zero if condition is NULL, otherwise is
32609 @ref{agent expression object}
32610 @item actions @tab variable
32611 @tab numactions number of @ref{tracepoint action object}
32614 @node IPA Protocol Commands
32615 @subsection IPA Protocol Commands
32616 @cindex ipa protocol commands
32618 The spaces in each command are delimiters to ease reading this commands
32619 specification. They don't exist in real commands.
32623 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
32624 Installs a new fast tracepoint described by @var{tracepoint_object}
32625 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
32626 head of @dfn{jumppad}, which is used to jump to data collection routine
32631 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
32632 @var{target_address} is address of tracepoint in the inferior.
32633 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
32634 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
32635 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
32636 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
32643 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
32644 is about to kill inferiors.
32652 @item probe_marker_at:@var{address}
32653 Asks in-process agent to probe the marker at @var{address}.
32660 @item unprobe_marker_at:@var{address}
32661 Asks in-process agent to unprobe the marker at @var{address}.
32665 @chapter Reporting Bugs in @value{GDBN}
32666 @cindex bugs in @value{GDBN}
32667 @cindex reporting bugs in @value{GDBN}
32669 Your bug reports play an essential role in making @value{GDBN} reliable.
32671 Reporting a bug may help you by bringing a solution to your problem, or it
32672 may not. But in any case the principal function of a bug report is to help
32673 the entire community by making the next version of @value{GDBN} work better. Bug
32674 reports are your contribution to the maintenance of @value{GDBN}.
32676 In order for a bug report to serve its purpose, you must include the
32677 information that enables us to fix the bug.
32680 * Bug Criteria:: Have you found a bug?
32681 * Bug Reporting:: How to report bugs
32685 @section Have You Found a Bug?
32686 @cindex bug criteria
32688 If you are not sure whether you have found a bug, here are some guidelines:
32691 @cindex fatal signal
32692 @cindex debugger crash
32693 @cindex crash of debugger
32695 If the debugger gets a fatal signal, for any input whatever, that is a
32696 @value{GDBN} bug. Reliable debuggers never crash.
32698 @cindex error on valid input
32700 If @value{GDBN} produces an error message for valid input, that is a
32701 bug. (Note that if you're cross debugging, the problem may also be
32702 somewhere in the connection to the target.)
32704 @cindex invalid input
32706 If @value{GDBN} does not produce an error message for invalid input,
32707 that is a bug. However, you should note that your idea of
32708 ``invalid input'' might be our idea of ``an extension'' or ``support
32709 for traditional practice''.
32712 If you are an experienced user of debugging tools, your suggestions
32713 for improvement of @value{GDBN} are welcome in any case.
32716 @node Bug Reporting
32717 @section How to Report Bugs
32718 @cindex bug reports
32719 @cindex @value{GDBN} bugs, reporting
32721 A number of companies and individuals offer support for @sc{gnu} products.
32722 If you obtained @value{GDBN} from a support organization, we recommend you
32723 contact that organization first.
32725 You can find contact information for many support companies and
32726 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
32728 @c should add a web page ref...
32731 @ifset BUGURL_DEFAULT
32732 In any event, we also recommend that you submit bug reports for
32733 @value{GDBN}. The preferred method is to submit them directly using
32734 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
32735 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
32738 @strong{Do not send bug reports to @samp{info-gdb}, or to
32739 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
32740 not want to receive bug reports. Those that do have arranged to receive
32743 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
32744 serves as a repeater. The mailing list and the newsgroup carry exactly
32745 the same messages. Often people think of posting bug reports to the
32746 newsgroup instead of mailing them. This appears to work, but it has one
32747 problem which can be crucial: a newsgroup posting often lacks a mail
32748 path back to the sender. Thus, if we need to ask for more information,
32749 we may be unable to reach you. For this reason, it is better to send
32750 bug reports to the mailing list.
32752 @ifclear BUGURL_DEFAULT
32753 In any event, we also recommend that you submit bug reports for
32754 @value{GDBN} to @value{BUGURL}.
32758 The fundamental principle of reporting bugs usefully is this:
32759 @strong{report all the facts}. If you are not sure whether to state a
32760 fact or leave it out, state it!
32762 Often people omit facts because they think they know what causes the
32763 problem and assume that some details do not matter. Thus, you might
32764 assume that the name of the variable you use in an example does not matter.
32765 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
32766 stray memory reference which happens to fetch from the location where that
32767 name is stored in memory; perhaps, if the name were different, the contents
32768 of that location would fool the debugger into doing the right thing despite
32769 the bug. Play it safe and give a specific, complete example. That is the
32770 easiest thing for you to do, and the most helpful.
32772 Keep in mind that the purpose of a bug report is to enable us to fix the
32773 bug. It may be that the bug has been reported previously, but neither
32774 you nor we can know that unless your bug report is complete and
32777 Sometimes people give a few sketchy facts and ask, ``Does this ring a
32778 bell?'' Those bug reports are useless, and we urge everyone to
32779 @emph{refuse to respond to them} except to chide the sender to report
32782 To enable us to fix the bug, you should include all these things:
32786 The version of @value{GDBN}. @value{GDBN} announces it if you start
32787 with no arguments; you can also print it at any time using @code{show
32790 Without this, we will not know whether there is any point in looking for
32791 the bug in the current version of @value{GDBN}.
32794 The type of machine you are using, and the operating system name and
32798 The details of the @value{GDBN} build-time configuration.
32799 @value{GDBN} shows these details if you invoke it with the
32800 @option{--configuration} command-line option, or if you type
32801 @code{show configuration} at @value{GDBN}'s prompt.
32804 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
32805 ``@value{GCC}--2.8.1''.
32808 What compiler (and its version) was used to compile the program you are
32809 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
32810 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
32811 to get this information; for other compilers, see the documentation for
32815 The command arguments you gave the compiler to compile your example and
32816 observe the bug. For example, did you use @samp{-O}? To guarantee
32817 you will not omit something important, list them all. A copy of the
32818 Makefile (or the output from make) is sufficient.
32820 If we were to try to guess the arguments, we would probably guess wrong
32821 and then we might not encounter the bug.
32824 A complete input script, and all necessary source files, that will
32828 A description of what behavior you observe that you believe is
32829 incorrect. For example, ``It gets a fatal signal.''
32831 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
32832 will certainly notice it. But if the bug is incorrect output, we might
32833 not notice unless it is glaringly wrong. You might as well not give us
32834 a chance to make a mistake.
32836 Even if the problem you experience is a fatal signal, you should still
32837 say so explicitly. Suppose something strange is going on, such as, your
32838 copy of @value{GDBN} is out of synch, or you have encountered a bug in
32839 the C library on your system. (This has happened!) Your copy might
32840 crash and ours would not. If you told us to expect a crash, then when
32841 ours fails to crash, we would know that the bug was not happening for
32842 us. If you had not told us to expect a crash, then we would not be able
32843 to draw any conclusion from our observations.
32846 @cindex recording a session script
32847 To collect all this information, you can use a session recording program
32848 such as @command{script}, which is available on many Unix systems.
32849 Just run your @value{GDBN} session inside @command{script} and then
32850 include the @file{typescript} file with your bug report.
32852 Another way to record a @value{GDBN} session is to run @value{GDBN}
32853 inside Emacs and then save the entire buffer to a file.
32856 If you wish to suggest changes to the @value{GDBN} source, send us context
32857 diffs. If you even discuss something in the @value{GDBN} source, refer to
32858 it by context, not by line number.
32860 The line numbers in our development sources will not match those in your
32861 sources. Your line numbers would convey no useful information to us.
32865 Here are some things that are not necessary:
32869 A description of the envelope of the bug.
32871 Often people who encounter a bug spend a lot of time investigating
32872 which changes to the input file will make the bug go away and which
32873 changes will not affect it.
32875 This is often time consuming and not very useful, because the way we
32876 will find the bug is by running a single example under the debugger
32877 with breakpoints, not by pure deduction from a series of examples.
32878 We recommend that you save your time for something else.
32880 Of course, if you can find a simpler example to report @emph{instead}
32881 of the original one, that is a convenience for us. Errors in the
32882 output will be easier to spot, running under the debugger will take
32883 less time, and so on.
32885 However, simplification is not vital; if you do not want to do this,
32886 report the bug anyway and send us the entire test case you used.
32889 A patch for the bug.
32891 A patch for the bug does help us if it is a good one. But do not omit
32892 the necessary information, such as the test case, on the assumption that
32893 a patch is all we need. We might see problems with your patch and decide
32894 to fix the problem another way, or we might not understand it at all.
32896 Sometimes with a program as complicated as @value{GDBN} it is very hard to
32897 construct an example that will make the program follow a certain path
32898 through the code. If you do not send us the example, we will not be able
32899 to construct one, so we will not be able to verify that the bug is fixed.
32901 And if we cannot understand what bug you are trying to fix, or why your
32902 patch should be an improvement, we will not install it. A test case will
32903 help us to understand.
32906 A guess about what the bug is or what it depends on.
32908 Such guesses are usually wrong. Even we cannot guess right about such
32909 things without first using the debugger to find the facts.
32912 @c The readline documentation is distributed with the readline code
32913 @c and consists of the two following files:
32916 @c Use -I with makeinfo to point to the appropriate directory,
32917 @c environment var TEXINPUTS with TeX.
32918 @ifclear SYSTEM_READLINE
32919 @include rluser.texi
32920 @include hsuser.texi
32924 @appendix In Memoriam
32926 The @value{GDBN} project mourns the loss of the following long-time
32931 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
32932 to Free Software in general. Outside of @value{GDBN}, he was known in
32933 the Amiga world for his series of Fish Disks, and the GeekGadget project.
32935 @item Michael Snyder
32936 Michael was one of the Global Maintainers of the @value{GDBN} project,
32937 with contributions recorded as early as 1996, until 2011. In addition
32938 to his day to day participation, he was a large driving force behind
32939 adding Reverse Debugging to @value{GDBN}.
32942 Beyond their technical contributions to the project, they were also
32943 enjoyable members of the Free Software Community. We will miss them.
32945 @node Formatting Documentation
32946 @appendix Formatting Documentation
32948 @cindex @value{GDBN} reference card
32949 @cindex reference card
32950 The @value{GDBN} 4 release includes an already-formatted reference card, ready
32951 for printing with PostScript or Ghostscript, in the @file{gdb}
32952 subdirectory of the main source directory@footnote{In
32953 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
32954 release.}. If you can use PostScript or Ghostscript with your printer,
32955 you can print the reference card immediately with @file{refcard.ps}.
32957 The release also includes the source for the reference card. You
32958 can format it, using @TeX{}, by typing:
32964 The @value{GDBN} reference card is designed to print in @dfn{landscape}
32965 mode on US ``letter'' size paper;
32966 that is, on a sheet 11 inches wide by 8.5 inches
32967 high. You will need to specify this form of printing as an option to
32968 your @sc{dvi} output program.
32970 @cindex documentation
32972 All the documentation for @value{GDBN} comes as part of the machine-readable
32973 distribution. The documentation is written in Texinfo format, which is
32974 a documentation system that uses a single source file to produce both
32975 on-line information and a printed manual. You can use one of the Info
32976 formatting commands to create the on-line version of the documentation
32977 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
32979 @value{GDBN} includes an already formatted copy of the on-line Info
32980 version of this manual in the @file{gdb} subdirectory. The main Info
32981 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
32982 subordinate files matching @samp{gdb.info*} in the same directory. If
32983 necessary, you can print out these files, or read them with any editor;
32984 but they are easier to read using the @code{info} subsystem in @sc{gnu}
32985 Emacs or the standalone @code{info} program, available as part of the
32986 @sc{gnu} Texinfo distribution.
32988 If you want to format these Info files yourself, you need one of the
32989 Info formatting programs, such as @code{texinfo-format-buffer} or
32992 If you have @code{makeinfo} installed, and are in the top level
32993 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
32994 version @value{GDBVN}), you can make the Info file by typing:
33001 If you want to typeset and print copies of this manual, you need @TeX{},
33002 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
33003 Texinfo definitions file.
33005 @TeX{} is a typesetting program; it does not print files directly, but
33006 produces output files called @sc{dvi} files. To print a typeset
33007 document, you need a program to print @sc{dvi} files. If your system
33008 has @TeX{} installed, chances are it has such a program. The precise
33009 command to use depends on your system; @kbd{lpr -d} is common; another
33010 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
33011 require a file name without any extension or a @samp{.dvi} extension.
33013 @TeX{} also requires a macro definitions file called
33014 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
33015 written in Texinfo format. On its own, @TeX{} cannot either read or
33016 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
33017 and is located in the @file{gdb-@var{version-number}/texinfo}
33020 If you have @TeX{} and a @sc{dvi} printer program installed, you can
33021 typeset and print this manual. First switch to the @file{gdb}
33022 subdirectory of the main source directory (for example, to
33023 @file{gdb-@value{GDBVN}/gdb}) and type:
33029 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
33031 @node Installing GDB
33032 @appendix Installing @value{GDBN}
33033 @cindex installation
33036 * Requirements:: Requirements for building @value{GDBN}
33037 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
33038 * Separate Objdir:: Compiling @value{GDBN} in another directory
33039 * Config Names:: Specifying names for hosts and targets
33040 * Configure Options:: Summary of options for configure
33041 * System-wide configuration:: Having a system-wide init file
33045 @section Requirements for Building @value{GDBN}
33046 @cindex building @value{GDBN}, requirements for
33048 Building @value{GDBN} requires various tools and packages to be available.
33049 Other packages will be used only if they are found.
33051 @heading Tools/Packages Necessary for Building @value{GDBN}
33053 @item ISO C90 compiler
33054 @value{GDBN} is written in ISO C90. It should be buildable with any
33055 working C90 compiler, e.g.@: GCC.
33059 @heading Tools/Packages Optional for Building @value{GDBN}
33063 @value{GDBN} can use the Expat XML parsing library. This library may be
33064 included with your operating system distribution; if it is not, you
33065 can get the latest version from @url{http://expat.sourceforge.net}.
33066 The @file{configure} script will search for this library in several
33067 standard locations; if it is installed in an unusual path, you can
33068 use the @option{--with-libexpat-prefix} option to specify its location.
33074 Remote protocol memory maps (@pxref{Memory Map Format})
33076 Target descriptions (@pxref{Target Descriptions})
33078 Remote shared library lists (@xref{Library List Format},
33079 or alternatively @pxref{Library List Format for SVR4 Targets})
33081 MS-Windows shared libraries (@pxref{Shared Libraries})
33083 Traceframe info (@pxref{Traceframe Info Format})
33085 Branch trace (@pxref{Branch Trace Format},
33086 @pxref{Branch Trace Configuration Format})
33090 @cindex compressed debug sections
33091 @value{GDBN} will use the @samp{zlib} library, if available, to read
33092 compressed debug sections. Some linkers, such as GNU gold, are capable
33093 of producing binaries with compressed debug sections. If @value{GDBN}
33094 is compiled with @samp{zlib}, it will be able to read the debug
33095 information in such binaries.
33097 The @samp{zlib} library is likely included with your operating system
33098 distribution; if it is not, you can get the latest version from
33099 @url{http://zlib.net}.
33102 @value{GDBN}'s features related to character sets (@pxref{Character
33103 Sets}) require a functioning @code{iconv} implementation. If you are
33104 on a GNU system, then this is provided by the GNU C Library. Some
33105 other systems also provide a working @code{iconv}.
33107 If @value{GDBN} is using the @code{iconv} program which is installed
33108 in a non-standard place, you will need to tell @value{GDBN} where to find it.
33109 This is done with @option{--with-iconv-bin} which specifies the
33110 directory that contains the @code{iconv} program.
33112 On systems without @code{iconv}, you can install GNU Libiconv. If you
33113 have previously installed Libiconv, you can use the
33114 @option{--with-libiconv-prefix} option to configure.
33116 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
33117 arrange to build Libiconv if a directory named @file{libiconv} appears
33118 in the top-most source directory. If Libiconv is built this way, and
33119 if the operating system does not provide a suitable @code{iconv}
33120 implementation, then the just-built library will automatically be used
33121 by @value{GDBN}. One easy way to set this up is to download GNU
33122 Libiconv, unpack it, and then rename the directory holding the
33123 Libiconv source code to @samp{libiconv}.
33126 @node Running Configure
33127 @section Invoking the @value{GDBN} @file{configure} Script
33128 @cindex configuring @value{GDBN}
33129 @value{GDBN} comes with a @file{configure} script that automates the process
33130 of preparing @value{GDBN} for installation; you can then use @code{make} to
33131 build the @code{gdb} program.
33133 @c irrelevant in info file; it's as current as the code it lives with.
33134 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
33135 look at the @file{README} file in the sources; we may have improved the
33136 installation procedures since publishing this manual.}
33139 The @value{GDBN} distribution includes all the source code you need for
33140 @value{GDBN} in a single directory, whose name is usually composed by
33141 appending the version number to @samp{gdb}.
33143 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
33144 @file{gdb-@value{GDBVN}} directory. That directory contains:
33147 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
33148 script for configuring @value{GDBN} and all its supporting libraries
33150 @item gdb-@value{GDBVN}/gdb
33151 the source specific to @value{GDBN} itself
33153 @item gdb-@value{GDBVN}/bfd
33154 source for the Binary File Descriptor library
33156 @item gdb-@value{GDBVN}/include
33157 @sc{gnu} include files
33159 @item gdb-@value{GDBVN}/libiberty
33160 source for the @samp{-liberty} free software library
33162 @item gdb-@value{GDBVN}/opcodes
33163 source for the library of opcode tables and disassemblers
33165 @item gdb-@value{GDBVN}/readline
33166 source for the @sc{gnu} command-line interface
33168 @item gdb-@value{GDBVN}/glob
33169 source for the @sc{gnu} filename pattern-matching subroutine
33171 @item gdb-@value{GDBVN}/mmalloc
33172 source for the @sc{gnu} memory-mapped malloc package
33175 The simplest way to configure and build @value{GDBN} is to run @file{configure}
33176 from the @file{gdb-@var{version-number}} source directory, which in
33177 this example is the @file{gdb-@value{GDBVN}} directory.
33179 First switch to the @file{gdb-@var{version-number}} source directory
33180 if you are not already in it; then run @file{configure}. Pass the
33181 identifier for the platform on which @value{GDBN} will run as an
33187 cd gdb-@value{GDBVN}
33188 ./configure @var{host}
33193 where @var{host} is an identifier such as @samp{sun4} or
33194 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
33195 (You can often leave off @var{host}; @file{configure} tries to guess the
33196 correct value by examining your system.)
33198 Running @samp{configure @var{host}} and then running @code{make} builds the
33199 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
33200 libraries, then @code{gdb} itself. The configured source files, and the
33201 binaries, are left in the corresponding source directories.
33204 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
33205 system does not recognize this automatically when you run a different
33206 shell, you may need to run @code{sh} on it explicitly:
33209 sh configure @var{host}
33212 If you run @file{configure} from a directory that contains source
33213 directories for multiple libraries or programs, such as the
33214 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
33216 creates configuration files for every directory level underneath (unless
33217 you tell it not to, with the @samp{--norecursion} option).
33219 You should run the @file{configure} script from the top directory in the
33220 source tree, the @file{gdb-@var{version-number}} directory. If you run
33221 @file{configure} from one of the subdirectories, you will configure only
33222 that subdirectory. That is usually not what you want. In particular,
33223 if you run the first @file{configure} from the @file{gdb} subdirectory
33224 of the @file{gdb-@var{version-number}} directory, you will omit the
33225 configuration of @file{bfd}, @file{readline}, and other sibling
33226 directories of the @file{gdb} subdirectory. This leads to build errors
33227 about missing include files such as @file{bfd/bfd.h}.
33229 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
33230 However, you should make sure that the shell on your path (named by
33231 the @samp{SHELL} environment variable) is publicly readable. Remember
33232 that @value{GDBN} uses the shell to start your program---some systems refuse to
33233 let @value{GDBN} debug child processes whose programs are not readable.
33235 @node Separate Objdir
33236 @section Compiling @value{GDBN} in Another Directory
33238 If you want to run @value{GDBN} versions for several host or target machines,
33239 you need a different @code{gdb} compiled for each combination of
33240 host and target. @file{configure} is designed to make this easy by
33241 allowing you to generate each configuration in a separate subdirectory,
33242 rather than in the source directory. If your @code{make} program
33243 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
33244 @code{make} in each of these directories builds the @code{gdb}
33245 program specified there.
33247 To build @code{gdb} in a separate directory, run @file{configure}
33248 with the @samp{--srcdir} option to specify where to find the source.
33249 (You also need to specify a path to find @file{configure}
33250 itself from your working directory. If the path to @file{configure}
33251 would be the same as the argument to @samp{--srcdir}, you can leave out
33252 the @samp{--srcdir} option; it is assumed.)
33254 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
33255 separate directory for a Sun 4 like this:
33259 cd gdb-@value{GDBVN}
33262 ../gdb-@value{GDBVN}/configure sun4
33267 When @file{configure} builds a configuration using a remote source
33268 directory, it creates a tree for the binaries with the same structure
33269 (and using the same names) as the tree under the source directory. In
33270 the example, you'd find the Sun 4 library @file{libiberty.a} in the
33271 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
33272 @file{gdb-sun4/gdb}.
33274 Make sure that your path to the @file{configure} script has just one
33275 instance of @file{gdb} in it. If your path to @file{configure} looks
33276 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
33277 one subdirectory of @value{GDBN}, not the whole package. This leads to
33278 build errors about missing include files such as @file{bfd/bfd.h}.
33280 One popular reason to build several @value{GDBN} configurations in separate
33281 directories is to configure @value{GDBN} for cross-compiling (where
33282 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
33283 programs that run on another machine---the @dfn{target}).
33284 You specify a cross-debugging target by
33285 giving the @samp{--target=@var{target}} option to @file{configure}.
33287 When you run @code{make} to build a program or library, you must run
33288 it in a configured directory---whatever directory you were in when you
33289 called @file{configure} (or one of its subdirectories).
33291 The @code{Makefile} that @file{configure} generates in each source
33292 directory also runs recursively. If you type @code{make} in a source
33293 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
33294 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
33295 will build all the required libraries, and then build GDB.
33297 When you have multiple hosts or targets configured in separate
33298 directories, you can run @code{make} on them in parallel (for example,
33299 if they are NFS-mounted on each of the hosts); they will not interfere
33303 @section Specifying Names for Hosts and Targets
33305 The specifications used for hosts and targets in the @file{configure}
33306 script are based on a three-part naming scheme, but some short predefined
33307 aliases are also supported. The full naming scheme encodes three pieces
33308 of information in the following pattern:
33311 @var{architecture}-@var{vendor}-@var{os}
33314 For example, you can use the alias @code{sun4} as a @var{host} argument,
33315 or as the value for @var{target} in a @code{--target=@var{target}}
33316 option. The equivalent full name is @samp{sparc-sun-sunos4}.
33318 The @file{configure} script accompanying @value{GDBN} does not provide
33319 any query facility to list all supported host and target names or
33320 aliases. @file{configure} calls the Bourne shell script
33321 @code{config.sub} to map abbreviations to full names; you can read the
33322 script, if you wish, or you can use it to test your guesses on
33323 abbreviations---for example:
33326 % sh config.sub i386-linux
33328 % sh config.sub alpha-linux
33329 alpha-unknown-linux-gnu
33330 % sh config.sub hp9k700
33332 % sh config.sub sun4
33333 sparc-sun-sunos4.1.1
33334 % sh config.sub sun3
33335 m68k-sun-sunos4.1.1
33336 % sh config.sub i986v
33337 Invalid configuration `i986v': machine `i986v' not recognized
33341 @code{config.sub} is also distributed in the @value{GDBN} source
33342 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
33344 @node Configure Options
33345 @section @file{configure} Options
33347 Here is a summary of the @file{configure} options and arguments that
33348 are most often useful for building @value{GDBN}. @file{configure} also has
33349 several other options not listed here. @inforef{What Configure
33350 Does,,configure.info}, for a full explanation of @file{configure}.
33353 configure @r{[}--help@r{]}
33354 @r{[}--prefix=@var{dir}@r{]}
33355 @r{[}--exec-prefix=@var{dir}@r{]}
33356 @r{[}--srcdir=@var{dirname}@r{]}
33357 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
33358 @r{[}--target=@var{target}@r{]}
33363 You may introduce options with a single @samp{-} rather than
33364 @samp{--} if you prefer; but you may abbreviate option names if you use
33369 Display a quick summary of how to invoke @file{configure}.
33371 @item --prefix=@var{dir}
33372 Configure the source to install programs and files under directory
33375 @item --exec-prefix=@var{dir}
33376 Configure the source to install programs under directory
33379 @c avoid splitting the warning from the explanation:
33381 @item --srcdir=@var{dirname}
33382 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
33383 @code{make} that implements the @code{VPATH} feature.}@*
33384 Use this option to make configurations in directories separate from the
33385 @value{GDBN} source directories. Among other things, you can use this to
33386 build (or maintain) several configurations simultaneously, in separate
33387 directories. @file{configure} writes configuration-specific files in
33388 the current directory, but arranges for them to use the source in the
33389 directory @var{dirname}. @file{configure} creates directories under
33390 the working directory in parallel to the source directories below
33393 @item --norecursion
33394 Configure only the directory level where @file{configure} is executed; do not
33395 propagate configuration to subdirectories.
33397 @item --target=@var{target}
33398 Configure @value{GDBN} for cross-debugging programs running on the specified
33399 @var{target}. Without this option, @value{GDBN} is configured to debug
33400 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
33402 There is no convenient way to generate a list of all available targets.
33404 @item @var{host} @dots{}
33405 Configure @value{GDBN} to run on the specified @var{host}.
33407 There is no convenient way to generate a list of all available hosts.
33410 There are many other options available as well, but they are generally
33411 needed for special purposes only.
33413 @node System-wide configuration
33414 @section System-wide configuration and settings
33415 @cindex system-wide init file
33417 @value{GDBN} can be configured to have a system-wide init file;
33418 this file will be read and executed at startup (@pxref{Startup, , What
33419 @value{GDBN} does during startup}).
33421 Here is the corresponding configure option:
33424 @item --with-system-gdbinit=@var{file}
33425 Specify that the default location of the system-wide init file is
33429 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
33430 it may be subject to relocation. Two possible cases:
33434 If the default location of this init file contains @file{$prefix},
33435 it will be subject to relocation. Suppose that the configure options
33436 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
33437 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
33438 init file is looked for as @file{$install/etc/gdbinit} instead of
33439 @file{$prefix/etc/gdbinit}.
33442 By contrast, if the default location does not contain the prefix,
33443 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
33444 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
33445 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
33446 wherever @value{GDBN} is installed.
33449 If the configured location of the system-wide init file (as given by the
33450 @option{--with-system-gdbinit} option at configure time) is in the
33451 data-directory (as specified by @option{--with-gdb-datadir} at configure
33452 time) or in one of its subdirectories, then @value{GDBN} will look for the
33453 system-wide init file in the directory specified by the
33454 @option{--data-directory} command-line option.
33455 Note that the system-wide init file is only read once, during @value{GDBN}
33456 initialization. If the data-directory is changed after @value{GDBN} has
33457 started with the @code{set data-directory} command, the file will not be
33461 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
33464 @node System-wide Configuration Scripts
33465 @subsection Installed System-wide Configuration Scripts
33466 @cindex system-wide configuration scripts
33468 The @file{system-gdbinit} directory, located inside the data-directory
33469 (as specified by @option{--with-gdb-datadir} at configure time) contains
33470 a number of scripts which can be used as system-wide init files. To
33471 automatically source those scripts at startup, @value{GDBN} should be
33472 configured with @option{--with-system-gdbinit}. Otherwise, any user
33473 should be able to source them by hand as needed.
33475 The following scripts are currently available:
33478 @item @file{elinos.py}
33480 @cindex ELinOS system-wide configuration script
33481 This script is useful when debugging a program on an ELinOS target.
33482 It takes advantage of the environment variables defined in a standard
33483 ELinOS environment in order to determine the location of the system
33484 shared libraries, and then sets the @samp{solib-absolute-prefix}
33485 and @samp{solib-search-path} variables appropriately.
33487 @item @file{wrs-linux.py}
33488 @pindex wrs-linux.py
33489 @cindex Wind River Linux system-wide configuration script
33490 This script is useful when debugging a program on a target running
33491 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
33492 the host-side sysroot used by the target system.
33496 @node Maintenance Commands
33497 @appendix Maintenance Commands
33498 @cindex maintenance commands
33499 @cindex internal commands
33501 In addition to commands intended for @value{GDBN} users, @value{GDBN}
33502 includes a number of commands intended for @value{GDBN} developers,
33503 that are not documented elsewhere in this manual. These commands are
33504 provided here for reference. (For commands that turn on debugging
33505 messages, see @ref{Debugging Output}.)
33508 @kindex maint agent
33509 @kindex maint agent-eval
33510 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
33511 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
33512 Translate the given @var{expression} into remote agent bytecodes.
33513 This command is useful for debugging the Agent Expression mechanism
33514 (@pxref{Agent Expressions}). The @samp{agent} version produces an
33515 expression useful for data collection, such as by tracepoints, while
33516 @samp{maint agent-eval} produces an expression that evaluates directly
33517 to a result. For instance, a collection expression for @code{globa +
33518 globb} will include bytecodes to record four bytes of memory at each
33519 of the addresses of @code{globa} and @code{globb}, while discarding
33520 the result of the addition, while an evaluation expression will do the
33521 addition and return the sum.
33522 If @code{-at} is given, generate remote agent bytecode for @var{location}.
33523 If not, generate remote agent bytecode for current frame PC address.
33525 @kindex maint agent-printf
33526 @item maint agent-printf @var{format},@var{expr},...
33527 Translate the given format string and list of argument expressions
33528 into remote agent bytecodes and display them as a disassembled list.
33529 This command is useful for debugging the agent version of dynamic
33530 printf (@pxref{Dynamic Printf}).
33532 @kindex maint info breakpoints
33533 @item @anchor{maint info breakpoints}maint info breakpoints
33534 Using the same format as @samp{info breakpoints}, display both the
33535 breakpoints you've set explicitly, and those @value{GDBN} is using for
33536 internal purposes. Internal breakpoints are shown with negative
33537 breakpoint numbers. The type column identifies what kind of breakpoint
33542 Normal, explicitly set breakpoint.
33545 Normal, explicitly set watchpoint.
33548 Internal breakpoint, used to handle correctly stepping through
33549 @code{longjmp} calls.
33551 @item longjmp resume
33552 Internal breakpoint at the target of a @code{longjmp}.
33555 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
33558 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
33561 Shared library events.
33565 @kindex maint info bfds
33566 @item maint info bfds
33567 This prints information about each @code{bfd} object that is known to
33568 @value{GDBN}. @xref{Top, , BFD, bfd, The Binary File Descriptor Library}.
33570 @kindex set displaced-stepping
33571 @kindex show displaced-stepping
33572 @cindex displaced stepping support
33573 @cindex out-of-line single-stepping
33574 @item set displaced-stepping
33575 @itemx show displaced-stepping
33576 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
33577 if the target supports it. Displaced stepping is a way to single-step
33578 over breakpoints without removing them from the inferior, by executing
33579 an out-of-line copy of the instruction that was originally at the
33580 breakpoint location. It is also known as out-of-line single-stepping.
33583 @item set displaced-stepping on
33584 If the target architecture supports it, @value{GDBN} will use
33585 displaced stepping to step over breakpoints.
33587 @item set displaced-stepping off
33588 @value{GDBN} will not use displaced stepping to step over breakpoints,
33589 even if such is supported by the target architecture.
33591 @cindex non-stop mode, and @samp{set displaced-stepping}
33592 @item set displaced-stepping auto
33593 This is the default mode. @value{GDBN} will use displaced stepping
33594 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
33595 architecture supports displaced stepping.
33598 @kindex maint check-psymtabs
33599 @item maint check-psymtabs
33600 Check the consistency of currently expanded psymtabs versus symtabs.
33601 Use this to check, for example, whether a symbol is in one but not the other.
33603 @kindex maint check-symtabs
33604 @item maint check-symtabs
33605 Check the consistency of currently expanded symtabs.
33607 @kindex maint expand-symtabs
33608 @item maint expand-symtabs [@var{regexp}]
33609 Expand symbol tables.
33610 If @var{regexp} is specified, only expand symbol tables for file
33611 names matching @var{regexp}.
33613 @kindex maint set catch-demangler-crashes
33614 @kindex maint show catch-demangler-crashes
33615 @cindex demangler crashes
33616 @item maint set catch-demangler-crashes [on|off]
33617 @itemx maint show catch-demangler-crashes
33618 Control whether @value{GDBN} should attempt to catch crashes in the
33619 symbol name demangler. The default is to attempt to catch crashes.
33620 If enabled, the first time a crash is caught, a core file is created,
33621 the offending symbol is displayed and the user is presented with the
33622 option to terminate the current session.
33624 @kindex maint cplus first_component
33625 @item maint cplus first_component @var{name}
33626 Print the first C@t{++} class/namespace component of @var{name}.
33628 @kindex maint cplus namespace
33629 @item maint cplus namespace
33630 Print the list of possible C@t{++} namespaces.
33632 @kindex maint deprecate
33633 @kindex maint undeprecate
33634 @cindex deprecated commands
33635 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
33636 @itemx maint undeprecate @var{command}
33637 Deprecate or undeprecate the named @var{command}. Deprecated commands
33638 cause @value{GDBN} to issue a warning when you use them. The optional
33639 argument @var{replacement} says which newer command should be used in
33640 favor of the deprecated one; if it is given, @value{GDBN} will mention
33641 the replacement as part of the warning.
33643 @kindex maint dump-me
33644 @item maint dump-me
33645 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
33646 Cause a fatal signal in the debugger and force it to dump its core.
33647 This is supported only on systems which support aborting a program
33648 with the @code{SIGQUIT} signal.
33650 @kindex maint internal-error
33651 @kindex maint internal-warning
33652 @kindex maint demangler-warning
33653 @cindex demangler crashes
33654 @item maint internal-error @r{[}@var{message-text}@r{]}
33655 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
33656 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
33658 Cause @value{GDBN} to call the internal function @code{internal_error},
33659 @code{internal_warning} or @code{demangler_warning} and hence behave
33660 as though an internal problam has been detected. In addition to
33661 reporting the internal problem, these functions give the user the
33662 opportunity to either quit @value{GDBN} or (for @code{internal_error}
33663 and @code{internal_warning}) create a core file of the current
33664 @value{GDBN} session.
33666 These commands take an optional parameter @var{message-text} that is
33667 used as the text of the error or warning message.
33669 Here's an example of using @code{internal-error}:
33672 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
33673 @dots{}/maint.c:121: internal-error: testing, 1, 2
33674 A problem internal to GDB has been detected. Further
33675 debugging may prove unreliable.
33676 Quit this debugging session? (y or n) @kbd{n}
33677 Create a core file? (y or n) @kbd{n}
33681 @cindex @value{GDBN} internal error
33682 @cindex internal errors, control of @value{GDBN} behavior
33683 @cindex demangler crashes
33685 @kindex maint set internal-error
33686 @kindex maint show internal-error
33687 @kindex maint set internal-warning
33688 @kindex maint show internal-warning
33689 @kindex maint set demangler-warning
33690 @kindex maint show demangler-warning
33691 @item maint set internal-error @var{action} [ask|yes|no]
33692 @itemx maint show internal-error @var{action}
33693 @itemx maint set internal-warning @var{action} [ask|yes|no]
33694 @itemx maint show internal-warning @var{action}
33695 @itemx maint set demangler-warning @var{action} [ask|yes|no]
33696 @itemx maint show demangler-warning @var{action}
33697 When @value{GDBN} reports an internal problem (error or warning) it
33698 gives the user the opportunity to both quit @value{GDBN} and create a
33699 core file of the current @value{GDBN} session. These commands let you
33700 override the default behaviour for each particular @var{action},
33701 described in the table below.
33705 You can specify that @value{GDBN} should always (yes) or never (no)
33706 quit. The default is to ask the user what to do.
33709 You can specify that @value{GDBN} should always (yes) or never (no)
33710 create a core file. The default is to ask the user what to do. Note
33711 that there is no @code{corefile} option for @code{demangler-warning}:
33712 demangler warnings always create a core file and this cannot be
33716 @kindex maint packet
33717 @item maint packet @var{text}
33718 If @value{GDBN} is talking to an inferior via the serial protocol,
33719 then this command sends the string @var{text} to the inferior, and
33720 displays the response packet. @value{GDBN} supplies the initial
33721 @samp{$} character, the terminating @samp{#} character, and the
33724 @kindex maint print architecture
33725 @item maint print architecture @r{[}@var{file}@r{]}
33726 Print the entire architecture configuration. The optional argument
33727 @var{file} names the file where the output goes.
33729 @kindex maint print c-tdesc
33730 @item maint print c-tdesc
33731 Print the current target description (@pxref{Target Descriptions}) as
33732 a C source file. The created source file can be used in @value{GDBN}
33733 when an XML parser is not available to parse the description.
33735 @kindex maint print dummy-frames
33736 @item maint print dummy-frames
33737 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
33740 (@value{GDBP}) @kbd{b add}
33742 (@value{GDBP}) @kbd{print add(2,3)}
33743 Breakpoint 2, add (a=2, b=3) at @dots{}
33745 The program being debugged stopped while in a function called from GDB.
33747 (@value{GDBP}) @kbd{maint print dummy-frames}
33748 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
33752 Takes an optional file parameter.
33754 @kindex maint print registers
33755 @kindex maint print raw-registers
33756 @kindex maint print cooked-registers
33757 @kindex maint print register-groups
33758 @kindex maint print remote-registers
33759 @item maint print registers @r{[}@var{file}@r{]}
33760 @itemx maint print raw-registers @r{[}@var{file}@r{]}
33761 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
33762 @itemx maint print register-groups @r{[}@var{file}@r{]}
33763 @itemx maint print remote-registers @r{[}@var{file}@r{]}
33764 Print @value{GDBN}'s internal register data structures.
33766 The command @code{maint print raw-registers} includes the contents of
33767 the raw register cache; the command @code{maint print
33768 cooked-registers} includes the (cooked) value of all registers,
33769 including registers which aren't available on the target nor visible
33770 to user; the command @code{maint print register-groups} includes the
33771 groups that each register is a member of; and the command @code{maint
33772 print remote-registers} includes the remote target's register numbers
33773 and offsets in the `G' packets.
33775 These commands take an optional parameter, a file name to which to
33776 write the information.
33778 @kindex maint print reggroups
33779 @item maint print reggroups @r{[}@var{file}@r{]}
33780 Print @value{GDBN}'s internal register group data structures. The
33781 optional argument @var{file} tells to what file to write the
33784 The register groups info looks like this:
33787 (@value{GDBP}) @kbd{maint print reggroups}
33800 This command forces @value{GDBN} to flush its internal register cache.
33802 @kindex maint print objfiles
33803 @cindex info for known object files
33804 @item maint print objfiles @r{[}@var{regexp}@r{]}
33805 Print a dump of all known object files.
33806 If @var{regexp} is specified, only print object files whose names
33807 match @var{regexp}. For each object file, this command prints its name,
33808 address in memory, and all of its psymtabs and symtabs.
33810 @kindex maint print user-registers
33811 @cindex user registers
33812 @item maint print user-registers
33813 List all currently available @dfn{user registers}. User registers
33814 typically provide alternate names for actual hardware registers. They
33815 include the four ``standard'' registers @code{$fp}, @code{$pc},
33816 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
33817 registers can be used in expressions in the same way as the canonical
33818 register names, but only the latter are listed by the @code{info
33819 registers} and @code{maint print registers} commands.
33821 @kindex maint print section-scripts
33822 @cindex info for known .debug_gdb_scripts-loaded scripts
33823 @item maint print section-scripts [@var{regexp}]
33824 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
33825 If @var{regexp} is specified, only print scripts loaded by object files
33826 matching @var{regexp}.
33827 For each script, this command prints its name as specified in the objfile,
33828 and the full path if known.
33829 @xref{dotdebug_gdb_scripts section}.
33831 @kindex maint print statistics
33832 @cindex bcache statistics
33833 @item maint print statistics
33834 This command prints, for each object file in the program, various data
33835 about that object file followed by the byte cache (@dfn{bcache})
33836 statistics for the object file. The objfile data includes the number
33837 of minimal, partial, full, and stabs symbols, the number of types
33838 defined by the objfile, the number of as yet unexpanded psym tables,
33839 the number of line tables and string tables, and the amount of memory
33840 used by the various tables. The bcache statistics include the counts,
33841 sizes, and counts of duplicates of all and unique objects, max,
33842 average, and median entry size, total memory used and its overhead and
33843 savings, and various measures of the hash table size and chain
33846 @kindex maint print target-stack
33847 @cindex target stack description
33848 @item maint print target-stack
33849 A @dfn{target} is an interface between the debugger and a particular
33850 kind of file or process. Targets can be stacked in @dfn{strata},
33851 so that more than one target can potentially respond to a request.
33852 In particular, memory accesses will walk down the stack of targets
33853 until they find a target that is interested in handling that particular
33856 This command prints a short description of each layer that was pushed on
33857 the @dfn{target stack}, starting from the top layer down to the bottom one.
33859 @kindex maint print type
33860 @cindex type chain of a data type
33861 @item maint print type @var{expr}
33862 Print the type chain for a type specified by @var{expr}. The argument
33863 can be either a type name or a symbol. If it is a symbol, the type of
33864 that symbol is described. The type chain produced by this command is
33865 a recursive definition of the data type as stored in @value{GDBN}'s
33866 data structures, including its flags and contained types.
33868 @kindex maint set dwarf2 always-disassemble
33869 @kindex maint show dwarf2 always-disassemble
33870 @item maint set dwarf2 always-disassemble
33871 @item maint show dwarf2 always-disassemble
33872 Control the behavior of @code{info address} when using DWARF debugging
33875 The default is @code{off}, which means that @value{GDBN} should try to
33876 describe a variable's location in an easily readable format. When
33877 @code{on}, @value{GDBN} will instead display the DWARF location
33878 expression in an assembly-like format. Note that some locations are
33879 too complex for @value{GDBN} to describe simply; in this case you will
33880 always see the disassembly form.
33882 Here is an example of the resulting disassembly:
33885 (gdb) info addr argc
33886 Symbol "argc" is a complex DWARF expression:
33890 For more information on these expressions, see
33891 @uref{http://www.dwarfstd.org/, the DWARF standard}.
33893 @kindex maint set dwarf2 max-cache-age
33894 @kindex maint show dwarf2 max-cache-age
33895 @item maint set dwarf2 max-cache-age
33896 @itemx maint show dwarf2 max-cache-age
33897 Control the DWARF 2 compilation unit cache.
33899 @cindex DWARF 2 compilation units cache
33900 In object files with inter-compilation-unit references, such as those
33901 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
33902 reader needs to frequently refer to previously read compilation units.
33903 This setting controls how long a compilation unit will remain in the
33904 cache if it is not referenced. A higher limit means that cached
33905 compilation units will be stored in memory longer, and more total
33906 memory will be used. Setting it to zero disables caching, which will
33907 slow down @value{GDBN} startup, but reduce memory consumption.
33909 @kindex maint set profile
33910 @kindex maint show profile
33911 @cindex profiling GDB
33912 @item maint set profile
33913 @itemx maint show profile
33914 Control profiling of @value{GDBN}.
33916 Profiling will be disabled until you use the @samp{maint set profile}
33917 command to enable it. When you enable profiling, the system will begin
33918 collecting timing and execution count data; when you disable profiling or
33919 exit @value{GDBN}, the results will be written to a log file. Remember that
33920 if you use profiling, @value{GDBN} will overwrite the profiling log file
33921 (often called @file{gmon.out}). If you have a record of important profiling
33922 data in a @file{gmon.out} file, be sure to move it to a safe location.
33924 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
33925 compiled with the @samp{-pg} compiler option.
33927 @kindex maint set show-debug-regs
33928 @kindex maint show show-debug-regs
33929 @cindex hardware debug registers
33930 @item maint set show-debug-regs
33931 @itemx maint show show-debug-regs
33932 Control whether to show variables that mirror the hardware debug
33933 registers. Use @code{on} to enable, @code{off} to disable. If
33934 enabled, the debug registers values are shown when @value{GDBN} inserts or
33935 removes a hardware breakpoint or watchpoint, and when the inferior
33936 triggers a hardware-assisted breakpoint or watchpoint.
33938 @kindex maint set show-all-tib
33939 @kindex maint show show-all-tib
33940 @item maint set show-all-tib
33941 @itemx maint show show-all-tib
33942 Control whether to show all non zero areas within a 1k block starting
33943 at thread local base, when using the @samp{info w32 thread-information-block}
33946 @kindex maint set target-async
33947 @kindex maint show target-async
33948 @item maint set target-async
33949 @itemx maint show target-async
33950 This controls whether @value{GDBN} targets operate in synchronous or
33951 asynchronous mode (@pxref{Background Execution}). Normally the
33952 default is asynchronous, if it is available; but this can be changed
33953 to more easily debug problems occurring only in synchronous mode.
33955 @kindex maint set per-command
33956 @kindex maint show per-command
33957 @item maint set per-command
33958 @itemx maint show per-command
33959 @cindex resources used by commands
33961 @value{GDBN} can display the resources used by each command.
33962 This is useful in debugging performance problems.
33965 @item maint set per-command space [on|off]
33966 @itemx maint show per-command space
33967 Enable or disable the printing of the memory used by GDB for each command.
33968 If enabled, @value{GDBN} will display how much memory each command
33969 took, following the command's own output.
33970 This can also be requested by invoking @value{GDBN} with the
33971 @option{--statistics} command-line switch (@pxref{Mode Options}).
33973 @item maint set per-command time [on|off]
33974 @itemx maint show per-command time
33975 Enable or disable the printing of the execution time of @value{GDBN}
33977 If enabled, @value{GDBN} will display how much time it
33978 took to execute each command, following the command's own output.
33979 Both CPU time and wallclock time are printed.
33980 Printing both is useful when trying to determine whether the cost is
33981 CPU or, e.g., disk/network latency.
33982 Note that the CPU time printed is for @value{GDBN} only, it does not include
33983 the execution time of the inferior because there's no mechanism currently
33984 to compute how much time was spent by @value{GDBN} and how much time was
33985 spent by the program been debugged.
33986 This can also be requested by invoking @value{GDBN} with the
33987 @option{--statistics} command-line switch (@pxref{Mode Options}).
33989 @item maint set per-command symtab [on|off]
33990 @itemx maint show per-command symtab
33991 Enable or disable the printing of basic symbol table statistics
33993 If enabled, @value{GDBN} will display the following information:
33997 number of symbol tables
33999 number of primary symbol tables
34001 number of blocks in the blockvector
34005 @kindex maint space
34006 @cindex memory used by commands
34007 @item maint space @var{value}
34008 An alias for @code{maint set per-command space}.
34009 A non-zero value enables it, zero disables it.
34012 @cindex time of command execution
34013 @item maint time @var{value}
34014 An alias for @code{maint set per-command time}.
34015 A non-zero value enables it, zero disables it.
34017 @kindex maint translate-address
34018 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
34019 Find the symbol stored at the location specified by the address
34020 @var{addr} and an optional section name @var{section}. If found,
34021 @value{GDBN} prints the name of the closest symbol and an offset from
34022 the symbol's location to the specified address. This is similar to
34023 the @code{info address} command (@pxref{Symbols}), except that this
34024 command also allows to find symbols in other sections.
34026 If section was not specified, the section in which the symbol was found
34027 is also printed. For dynamically linked executables, the name of
34028 executable or shared library containing the symbol is printed as well.
34032 The following command is useful for non-interactive invocations of
34033 @value{GDBN}, such as in the test suite.
34036 @item set watchdog @var{nsec}
34037 @kindex set watchdog
34038 @cindex watchdog timer
34039 @cindex timeout for commands
34040 Set the maximum number of seconds @value{GDBN} will wait for the
34041 target operation to finish. If this time expires, @value{GDBN}
34042 reports and error and the command is aborted.
34044 @item show watchdog
34045 Show the current setting of the target wait timeout.
34048 @node Remote Protocol
34049 @appendix @value{GDBN} Remote Serial Protocol
34054 * Stop Reply Packets::
34055 * General Query Packets::
34056 * Architecture-Specific Protocol Details::
34057 * Tracepoint Packets::
34058 * Host I/O Packets::
34060 * Notification Packets::
34061 * Remote Non-Stop::
34062 * Packet Acknowledgment::
34064 * File-I/O Remote Protocol Extension::
34065 * Library List Format::
34066 * Library List Format for SVR4 Targets::
34067 * Memory Map Format::
34068 * Thread List Format::
34069 * Traceframe Info Format::
34070 * Branch Trace Format::
34071 * Branch Trace Configuration Format::
34077 There may be occasions when you need to know something about the
34078 protocol---for example, if there is only one serial port to your target
34079 machine, you might want your program to do something special if it
34080 recognizes a packet meant for @value{GDBN}.
34082 In the examples below, @samp{->} and @samp{<-} are used to indicate
34083 transmitted and received data, respectively.
34085 @cindex protocol, @value{GDBN} remote serial
34086 @cindex serial protocol, @value{GDBN} remote
34087 @cindex remote serial protocol
34088 All @value{GDBN} commands and responses (other than acknowledgments
34089 and notifications, see @ref{Notification Packets}) are sent as a
34090 @var{packet}. A @var{packet} is introduced with the character
34091 @samp{$}, the actual @var{packet-data}, and the terminating character
34092 @samp{#} followed by a two-digit @var{checksum}:
34095 @code{$}@var{packet-data}@code{#}@var{checksum}
34099 @cindex checksum, for @value{GDBN} remote
34101 The two-digit @var{checksum} is computed as the modulo 256 sum of all
34102 characters between the leading @samp{$} and the trailing @samp{#} (an
34103 eight bit unsigned checksum).
34105 Implementors should note that prior to @value{GDBN} 5.0 the protocol
34106 specification also included an optional two-digit @var{sequence-id}:
34109 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
34112 @cindex sequence-id, for @value{GDBN} remote
34114 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
34115 has never output @var{sequence-id}s. Stubs that handle packets added
34116 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
34118 When either the host or the target machine receives a packet, the first
34119 response expected is an acknowledgment: either @samp{+} (to indicate
34120 the package was received correctly) or @samp{-} (to request
34124 -> @code{$}@var{packet-data}@code{#}@var{checksum}
34129 The @samp{+}/@samp{-} acknowledgments can be disabled
34130 once a connection is established.
34131 @xref{Packet Acknowledgment}, for details.
34133 The host (@value{GDBN}) sends @var{command}s, and the target (the
34134 debugging stub incorporated in your program) sends a @var{response}. In
34135 the case of step and continue @var{command}s, the response is only sent
34136 when the operation has completed, and the target has again stopped all
34137 threads in all attached processes. This is the default all-stop mode
34138 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
34139 execution mode; see @ref{Remote Non-Stop}, for details.
34141 @var{packet-data} consists of a sequence of characters with the
34142 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
34145 @cindex remote protocol, field separator
34146 Fields within the packet should be separated using @samp{,} @samp{;} or
34147 @samp{:}. Except where otherwise noted all numbers are represented in
34148 @sc{hex} with leading zeros suppressed.
34150 Implementors should note that prior to @value{GDBN} 5.0, the character
34151 @samp{:} could not appear as the third character in a packet (as it
34152 would potentially conflict with the @var{sequence-id}).
34154 @cindex remote protocol, binary data
34155 @anchor{Binary Data}
34156 Binary data in most packets is encoded either as two hexadecimal
34157 digits per byte of binary data. This allowed the traditional remote
34158 protocol to work over connections which were only seven-bit clean.
34159 Some packets designed more recently assume an eight-bit clean
34160 connection, and use a more efficient encoding to send and receive
34163 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
34164 as an escape character. Any escaped byte is transmitted as the escape
34165 character followed by the original character XORed with @code{0x20}.
34166 For example, the byte @code{0x7d} would be transmitted as the two
34167 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
34168 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
34169 @samp{@}}) must always be escaped. Responses sent by the stub
34170 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
34171 is not interpreted as the start of a run-length encoded sequence
34174 Response @var{data} can be run-length encoded to save space.
34175 Run-length encoding replaces runs of identical characters with one
34176 instance of the repeated character, followed by a @samp{*} and a
34177 repeat count. The repeat count is itself sent encoded, to avoid
34178 binary characters in @var{data}: a value of @var{n} is sent as
34179 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
34180 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
34181 code 32) for a repeat count of 3. (This is because run-length
34182 encoding starts to win for counts 3 or more.) Thus, for example,
34183 @samp{0* } is a run-length encoding of ``0000'': the space character
34184 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
34187 The printable characters @samp{#} and @samp{$} or with a numeric value
34188 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
34189 seven repeats (@samp{$}) can be expanded using a repeat count of only
34190 five (@samp{"}). For example, @samp{00000000} can be encoded as
34193 The error response returned for some packets includes a two character
34194 error number. That number is not well defined.
34196 @cindex empty response, for unsupported packets
34197 For any @var{command} not supported by the stub, an empty response
34198 (@samp{$#00}) should be returned. That way it is possible to extend the
34199 protocol. A newer @value{GDBN} can tell if a packet is supported based
34202 At a minimum, a stub is required to support the @samp{g} and @samp{G}
34203 commands for register access, and the @samp{m} and @samp{M} commands
34204 for memory access. Stubs that only control single-threaded targets
34205 can implement run control with the @samp{c} (continue), and @samp{s}
34206 (step) commands. Stubs that support multi-threading targets should
34207 support the @samp{vCont} command. All other commands are optional.
34212 The following table provides a complete list of all currently defined
34213 @var{command}s and their corresponding response @var{data}.
34214 @xref{File-I/O Remote Protocol Extension}, for details about the File
34215 I/O extension of the remote protocol.
34217 Each packet's description has a template showing the packet's overall
34218 syntax, followed by an explanation of the packet's meaning. We
34219 include spaces in some of the templates for clarity; these are not
34220 part of the packet's syntax. No @value{GDBN} packet uses spaces to
34221 separate its components. For example, a template like @samp{foo
34222 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
34223 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
34224 @var{baz}. @value{GDBN} does not transmit a space character between the
34225 @samp{foo} and the @var{bar}, or between the @var{bar} and the
34228 @cindex @var{thread-id}, in remote protocol
34229 @anchor{thread-id syntax}
34230 Several packets and replies include a @var{thread-id} field to identify
34231 a thread. Normally these are positive numbers with a target-specific
34232 interpretation, formatted as big-endian hex strings. A @var{thread-id}
34233 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
34236 In addition, the remote protocol supports a multiprocess feature in
34237 which the @var{thread-id} syntax is extended to optionally include both
34238 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
34239 The @var{pid} (process) and @var{tid} (thread) components each have the
34240 format described above: a positive number with target-specific
34241 interpretation formatted as a big-endian hex string, literal @samp{-1}
34242 to indicate all processes or threads (respectively), or @samp{0} to
34243 indicate an arbitrary process or thread. Specifying just a process, as
34244 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
34245 error to specify all processes but a specific thread, such as
34246 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
34247 for those packets and replies explicitly documented to include a process
34248 ID, rather than a @var{thread-id}.
34250 The multiprocess @var{thread-id} syntax extensions are only used if both
34251 @value{GDBN} and the stub report support for the @samp{multiprocess}
34252 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
34255 Note that all packet forms beginning with an upper- or lower-case
34256 letter, other than those described here, are reserved for future use.
34258 Here are the packet descriptions.
34263 @cindex @samp{!} packet
34264 @anchor{extended mode}
34265 Enable extended mode. In extended mode, the remote server is made
34266 persistent. The @samp{R} packet is used to restart the program being
34272 The remote target both supports and has enabled extended mode.
34276 @cindex @samp{?} packet
34278 Indicate the reason the target halted. The reply is the same as for
34279 step and continue. This packet has a special interpretation when the
34280 target is in non-stop mode; see @ref{Remote Non-Stop}.
34283 @xref{Stop Reply Packets}, for the reply specifications.
34285 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
34286 @cindex @samp{A} packet
34287 Initialized @code{argv[]} array passed into program. @var{arglen}
34288 specifies the number of bytes in the hex encoded byte stream
34289 @var{arg}. See @code{gdbserver} for more details.
34294 The arguments were set.
34300 @cindex @samp{b} packet
34301 (Don't use this packet; its behavior is not well-defined.)
34302 Change the serial line speed to @var{baud}.
34304 JTC: @emph{When does the transport layer state change? When it's
34305 received, or after the ACK is transmitted. In either case, there are
34306 problems if the command or the acknowledgment packet is dropped.}
34308 Stan: @emph{If people really wanted to add something like this, and get
34309 it working for the first time, they ought to modify ser-unix.c to send
34310 some kind of out-of-band message to a specially-setup stub and have the
34311 switch happen "in between" packets, so that from remote protocol's point
34312 of view, nothing actually happened.}
34314 @item B @var{addr},@var{mode}
34315 @cindex @samp{B} packet
34316 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
34317 breakpoint at @var{addr}.
34319 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
34320 (@pxref{insert breakpoint or watchpoint packet}).
34322 @cindex @samp{bc} packet
34325 Backward continue. Execute the target system in reverse. No parameter.
34326 @xref{Reverse Execution}, for more information.
34329 @xref{Stop Reply Packets}, for the reply specifications.
34331 @cindex @samp{bs} packet
34334 Backward single step. Execute one instruction in reverse. No parameter.
34335 @xref{Reverse Execution}, for more information.
34338 @xref{Stop Reply Packets}, for the reply specifications.
34340 @item c @r{[}@var{addr}@r{]}
34341 @cindex @samp{c} packet
34342 Continue at @var{addr}, which is the address to resume. If @var{addr}
34343 is omitted, resume at current address.
34345 This packet is deprecated for multi-threading support. @xref{vCont
34349 @xref{Stop Reply Packets}, for the reply specifications.
34351 @item C @var{sig}@r{[};@var{addr}@r{]}
34352 @cindex @samp{C} packet
34353 Continue with signal @var{sig} (hex signal number). If
34354 @samp{;@var{addr}} is omitted, resume at same address.
34356 This packet is deprecated for multi-threading support. @xref{vCont
34360 @xref{Stop Reply Packets}, for the reply specifications.
34363 @cindex @samp{d} packet
34366 Don't use this packet; instead, define a general set packet
34367 (@pxref{General Query Packets}).
34371 @cindex @samp{D} packet
34372 The first form of the packet is used to detach @value{GDBN} from the
34373 remote system. It is sent to the remote target
34374 before @value{GDBN} disconnects via the @code{detach} command.
34376 The second form, including a process ID, is used when multiprocess
34377 protocol extensions are enabled (@pxref{multiprocess extensions}), to
34378 detach only a specific process. The @var{pid} is specified as a
34379 big-endian hex string.
34389 @item F @var{RC},@var{EE},@var{CF};@var{XX}
34390 @cindex @samp{F} packet
34391 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
34392 This is part of the File-I/O protocol extension. @xref{File-I/O
34393 Remote Protocol Extension}, for the specification.
34396 @anchor{read registers packet}
34397 @cindex @samp{g} packet
34398 Read general registers.
34402 @item @var{XX@dots{}}
34403 Each byte of register data is described by two hex digits. The bytes
34404 with the register are transmitted in target byte order. The size of
34405 each register and their position within the @samp{g} packet are
34406 determined by the @value{GDBN} internal gdbarch functions
34407 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
34408 specification of several standard @samp{g} packets is specified below.
34410 When reading registers from a trace frame (@pxref{Analyze Collected
34411 Data,,Using the Collected Data}), the stub may also return a string of
34412 literal @samp{x}'s in place of the register data digits, to indicate
34413 that the corresponding register has not been collected, thus its value
34414 is unavailable. For example, for an architecture with 4 registers of
34415 4 bytes each, the following reply indicates to @value{GDBN} that
34416 registers 0 and 2 have not been collected, while registers 1 and 3
34417 have been collected, and both have zero value:
34421 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
34428 @item G @var{XX@dots{}}
34429 @cindex @samp{G} packet
34430 Write general registers. @xref{read registers packet}, for a
34431 description of the @var{XX@dots{}} data.
34441 @item H @var{op} @var{thread-id}
34442 @cindex @samp{H} packet
34443 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
34444 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
34445 should be @samp{c} for step and continue operations (note that this
34446 is deprecated, supporting the @samp{vCont} command is a better
34447 option), and @samp{g} for other operations. The thread designator
34448 @var{thread-id} has the format and interpretation described in
34449 @ref{thread-id syntax}.
34460 @c 'H': How restrictive (or permissive) is the thread model. If a
34461 @c thread is selected and stopped, are other threads allowed
34462 @c to continue to execute? As I mentioned above, I think the
34463 @c semantics of each command when a thread is selected must be
34464 @c described. For example:
34466 @c 'g': If the stub supports threads and a specific thread is
34467 @c selected, returns the register block from that thread;
34468 @c otherwise returns current registers.
34470 @c 'G' If the stub supports threads and a specific thread is
34471 @c selected, sets the registers of the register block of
34472 @c that thread; otherwise sets current registers.
34474 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
34475 @anchor{cycle step packet}
34476 @cindex @samp{i} packet
34477 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
34478 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
34479 step starting at that address.
34482 @cindex @samp{I} packet
34483 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
34487 @cindex @samp{k} packet
34490 The exact effect of this packet is not specified.
34492 For a bare-metal target, it may power cycle or reset the target
34493 system. For that reason, the @samp{k} packet has no reply.
34495 For a single-process target, it may kill that process if possible.
34497 A multiple-process target may choose to kill just one process, or all
34498 that are under @value{GDBN}'s control. For more precise control, use
34499 the vKill packet (@pxref{vKill packet}).
34501 If the target system immediately closes the connection in response to
34502 @samp{k}, @value{GDBN} does not consider the lack of packet
34503 acknowledgment to be an error, and assumes the kill was successful.
34505 If connected using @kbd{target extended-remote}, and the target does
34506 not close the connection in response to a kill request, @value{GDBN}
34507 probes the target state as if a new connection was opened
34508 (@pxref{? packet}).
34510 @item m @var{addr},@var{length}
34511 @cindex @samp{m} packet
34512 Read @var{length} bytes of memory starting at address @var{addr}.
34513 Note that @var{addr} may not be aligned to any particular boundary.
34515 The stub need not use any particular size or alignment when gathering
34516 data from memory for the response; even if @var{addr} is word-aligned
34517 and @var{length} is a multiple of the word size, the stub is free to
34518 use byte accesses, or not. For this reason, this packet may not be
34519 suitable for accessing memory-mapped I/O devices.
34520 @cindex alignment of remote memory accesses
34521 @cindex size of remote memory accesses
34522 @cindex memory, alignment and size of remote accesses
34526 @item @var{XX@dots{}}
34527 Memory contents; each byte is transmitted as a two-digit hexadecimal
34528 number. The reply may contain fewer bytes than requested if the
34529 server was able to read only part of the region of memory.
34534 @item M @var{addr},@var{length}:@var{XX@dots{}}
34535 @cindex @samp{M} packet
34536 Write @var{length} bytes of memory starting at address @var{addr}.
34537 The data is given by @var{XX@dots{}}; each byte is transmitted as a two-digit
34538 hexadecimal number.
34545 for an error (this includes the case where only part of the data was
34550 @cindex @samp{p} packet
34551 Read the value of register @var{n}; @var{n} is in hex.
34552 @xref{read registers packet}, for a description of how the returned
34553 register value is encoded.
34557 @item @var{XX@dots{}}
34558 the register's value
34562 Indicating an unrecognized @var{query}.
34565 @item P @var{n@dots{}}=@var{r@dots{}}
34566 @anchor{write register packet}
34567 @cindex @samp{P} packet
34568 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
34569 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
34570 digits for each byte in the register (target byte order).
34580 @item q @var{name} @var{params}@dots{}
34581 @itemx Q @var{name} @var{params}@dots{}
34582 @cindex @samp{q} packet
34583 @cindex @samp{Q} packet
34584 General query (@samp{q}) and set (@samp{Q}). These packets are
34585 described fully in @ref{General Query Packets}.
34588 @cindex @samp{r} packet
34589 Reset the entire system.
34591 Don't use this packet; use the @samp{R} packet instead.
34594 @cindex @samp{R} packet
34595 Restart the program being debugged. The @var{XX}, while needed, is ignored.
34596 This packet is only available in extended mode (@pxref{extended mode}).
34598 The @samp{R} packet has no reply.
34600 @item s @r{[}@var{addr}@r{]}
34601 @cindex @samp{s} packet
34602 Single step, resuming at @var{addr}. If
34603 @var{addr} is omitted, resume at same address.
34605 This packet is deprecated for multi-threading support. @xref{vCont
34609 @xref{Stop Reply Packets}, for the reply specifications.
34611 @item S @var{sig}@r{[};@var{addr}@r{]}
34612 @anchor{step with signal packet}
34613 @cindex @samp{S} packet
34614 Step with signal. This is analogous to the @samp{C} packet, but
34615 requests a single-step, rather than a normal resumption of execution.
34617 This packet is deprecated for multi-threading support. @xref{vCont
34621 @xref{Stop Reply Packets}, for the reply specifications.
34623 @item t @var{addr}:@var{PP},@var{MM}
34624 @cindex @samp{t} packet
34625 Search backwards starting at address @var{addr} for a match with pattern
34626 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
34627 There must be at least 3 digits in @var{addr}.
34629 @item T @var{thread-id}
34630 @cindex @samp{T} packet
34631 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
34636 thread is still alive
34642 Packets starting with @samp{v} are identified by a multi-letter name,
34643 up to the first @samp{;} or @samp{?} (or the end of the packet).
34645 @item vAttach;@var{pid}
34646 @cindex @samp{vAttach} packet
34647 Attach to a new process with the specified process ID @var{pid}.
34648 The process ID is a
34649 hexadecimal integer identifying the process. In all-stop mode, all
34650 threads in the attached process are stopped; in non-stop mode, it may be
34651 attached without being stopped if that is supported by the target.
34653 @c In non-stop mode, on a successful vAttach, the stub should set the
34654 @c current thread to a thread of the newly-attached process. After
34655 @c attaching, GDB queries for the attached process's thread ID with qC.
34656 @c Also note that, from a user perspective, whether or not the
34657 @c target is stopped on attach in non-stop mode depends on whether you
34658 @c use the foreground or background version of the attach command, not
34659 @c on what vAttach does; GDB does the right thing with respect to either
34660 @c stopping or restarting threads.
34662 This packet is only available in extended mode (@pxref{extended mode}).
34668 @item @r{Any stop packet}
34669 for success in all-stop mode (@pxref{Stop Reply Packets})
34671 for success in non-stop mode (@pxref{Remote Non-Stop})
34674 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
34675 @cindex @samp{vCont} packet
34676 @anchor{vCont packet}
34677 Resume the inferior, specifying different actions for each thread.
34678 If an action is specified with no @var{thread-id}, then it is applied to any
34679 threads that don't have a specific action specified; if no default action is
34680 specified then other threads should remain stopped in all-stop mode and
34681 in their current state in non-stop mode.
34682 Specifying multiple
34683 default actions is an error; specifying no actions is also an error.
34684 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
34686 Currently supported actions are:
34692 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
34696 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
34699 @item r @var{start},@var{end}
34700 Step once, and then keep stepping as long as the thread stops at
34701 addresses between @var{start} (inclusive) and @var{end} (exclusive).
34702 The remote stub reports a stop reply when either the thread goes out
34703 of the range or is stopped due to an unrelated reason, such as hitting
34704 a breakpoint. @xref{range stepping}.
34706 If the range is empty (@var{start} == @var{end}), then the action
34707 becomes equivalent to the @samp{s} action. In other words,
34708 single-step once, and report the stop (even if the stepped instruction
34709 jumps to @var{start}).
34711 (A stop reply may be sent at any point even if the PC is still within
34712 the stepping range; for example, it is valid to implement this packet
34713 in a degenerate way as a single instruction step operation.)
34717 The optional argument @var{addr} normally associated with the
34718 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
34719 not supported in @samp{vCont}.
34721 The @samp{t} action is only relevant in non-stop mode
34722 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
34723 A stop reply should be generated for any affected thread not already stopped.
34724 When a thread is stopped by means of a @samp{t} action,
34725 the corresponding stop reply should indicate that the thread has stopped with
34726 signal @samp{0}, regardless of whether the target uses some other signal
34727 as an implementation detail.
34729 The stub must support @samp{vCont} if it reports support for
34730 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
34731 this case @samp{vCont} actions can be specified to apply to all threads
34732 in a process by using the @samp{p@var{pid}.-1} form of the
34736 @xref{Stop Reply Packets}, for the reply specifications.
34739 @cindex @samp{vCont?} packet
34740 Request a list of actions supported by the @samp{vCont} packet.
34744 @item vCont@r{[};@var{action}@dots{}@r{]}
34745 The @samp{vCont} packet is supported. Each @var{action} is a supported
34746 command in the @samp{vCont} packet.
34748 The @samp{vCont} packet is not supported.
34751 @item vFile:@var{operation}:@var{parameter}@dots{}
34752 @cindex @samp{vFile} packet
34753 Perform a file operation on the target system. For details,
34754 see @ref{Host I/O Packets}.
34756 @item vFlashErase:@var{addr},@var{length}
34757 @cindex @samp{vFlashErase} packet
34758 Direct the stub to erase @var{length} bytes of flash starting at
34759 @var{addr}. The region may enclose any number of flash blocks, but
34760 its start and end must fall on block boundaries, as indicated by the
34761 flash block size appearing in the memory map (@pxref{Memory Map
34762 Format}). @value{GDBN} groups flash memory programming operations
34763 together, and sends a @samp{vFlashDone} request after each group; the
34764 stub is allowed to delay erase operation until the @samp{vFlashDone}
34765 packet is received.
34775 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
34776 @cindex @samp{vFlashWrite} packet
34777 Direct the stub to write data to flash address @var{addr}. The data
34778 is passed in binary form using the same encoding as for the @samp{X}
34779 packet (@pxref{Binary Data}). The memory ranges specified by
34780 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
34781 not overlap, and must appear in order of increasing addresses
34782 (although @samp{vFlashErase} packets for higher addresses may already
34783 have been received; the ordering is guaranteed only between
34784 @samp{vFlashWrite} packets). If a packet writes to an address that was
34785 neither erased by a preceding @samp{vFlashErase} packet nor by some other
34786 target-specific method, the results are unpredictable.
34794 for vFlashWrite addressing non-flash memory
34800 @cindex @samp{vFlashDone} packet
34801 Indicate to the stub that flash programming operation is finished.
34802 The stub is permitted to delay or batch the effects of a group of
34803 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
34804 @samp{vFlashDone} packet is received. The contents of the affected
34805 regions of flash memory are unpredictable until the @samp{vFlashDone}
34806 request is completed.
34808 @item vKill;@var{pid}
34809 @cindex @samp{vKill} packet
34810 @anchor{vKill packet}
34811 Kill the process with the specified process ID @var{pid}, which is a
34812 hexadecimal integer identifying the process. This packet is used in
34813 preference to @samp{k} when multiprocess protocol extensions are
34814 supported; see @ref{multiprocess extensions}.
34824 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
34825 @cindex @samp{vRun} packet
34826 Run the program @var{filename}, passing it each @var{argument} on its
34827 command line. The file and arguments are hex-encoded strings. If
34828 @var{filename} is an empty string, the stub may use a default program
34829 (e.g.@: the last program run). The program is created in the stopped
34832 @c FIXME: What about non-stop mode?
34834 This packet is only available in extended mode (@pxref{extended mode}).
34840 @item @r{Any stop packet}
34841 for success (@pxref{Stop Reply Packets})
34845 @cindex @samp{vStopped} packet
34846 @xref{Notification Packets}.
34848 @item X @var{addr},@var{length}:@var{XX@dots{}}
34850 @cindex @samp{X} packet
34851 Write data to memory, where the data is transmitted in binary.
34852 Memory is specified by its address @var{addr} and number of bytes @var{length};
34853 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
34863 @item z @var{type},@var{addr},@var{kind}
34864 @itemx Z @var{type},@var{addr},@var{kind}
34865 @anchor{insert breakpoint or watchpoint packet}
34866 @cindex @samp{z} packet
34867 @cindex @samp{Z} packets
34868 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
34869 watchpoint starting at address @var{address} of kind @var{kind}.
34871 Each breakpoint and watchpoint packet @var{type} is documented
34874 @emph{Implementation notes: A remote target shall return an empty string
34875 for an unrecognized breakpoint or watchpoint packet @var{type}. A
34876 remote target shall support either both or neither of a given
34877 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
34878 avoid potential problems with duplicate packets, the operations should
34879 be implemented in an idempotent way.}
34881 @item z0,@var{addr},@var{kind}
34882 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
34883 @cindex @samp{z0} packet
34884 @cindex @samp{Z0} packet
34885 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
34886 @var{addr} of type @var{kind}.
34888 A memory breakpoint is implemented by replacing the instruction at
34889 @var{addr} with a software breakpoint or trap instruction. The
34890 @var{kind} is target-specific and typically indicates the size of
34891 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
34892 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
34893 architectures have additional meanings for @var{kind};
34894 @var{cond_list} is an optional list of conditional expressions in bytecode
34895 form that should be evaluated on the target's side. These are the
34896 conditions that should be taken into consideration when deciding if
34897 the breakpoint trigger should be reported back to @var{GDBN}.
34899 The @var{cond_list} parameter is comprised of a series of expressions,
34900 concatenated without separators. Each expression has the following form:
34904 @item X @var{len},@var{expr}
34905 @var{len} is the length of the bytecode expression and @var{expr} is the
34906 actual conditional expression in bytecode form.
34910 The optional @var{cmd_list} parameter introduces commands that may be
34911 run on the target, rather than being reported back to @value{GDBN}.
34912 The parameter starts with a numeric flag @var{persist}; if the flag is
34913 nonzero, then the breakpoint may remain active and the commands
34914 continue to be run even when @value{GDBN} disconnects from the target.
34915 Following this flag is a series of expressions concatenated with no
34916 separators. Each expression has the following form:
34920 @item X @var{len},@var{expr}
34921 @var{len} is the length of the bytecode expression and @var{expr} is the
34922 actual conditional expression in bytecode form.
34926 see @ref{Architecture-Specific Protocol Details}.
34928 @emph{Implementation note: It is possible for a target to copy or move
34929 code that contains memory breakpoints (e.g., when implementing
34930 overlays). The behavior of this packet, in the presence of such a
34931 target, is not defined.}
34943 @item z1,@var{addr},@var{kind}
34944 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
34945 @cindex @samp{z1} packet
34946 @cindex @samp{Z1} packet
34947 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
34948 address @var{addr}.
34950 A hardware breakpoint is implemented using a mechanism that is not
34951 dependant on being able to modify the target's memory. The @var{kind}
34952 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
34954 @emph{Implementation note: A hardware breakpoint is not affected by code
34967 @item z2,@var{addr},@var{kind}
34968 @itemx Z2,@var{addr},@var{kind}
34969 @cindex @samp{z2} packet
34970 @cindex @samp{Z2} packet
34971 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
34972 The number of bytes to watch is specified by @var{kind}.
34984 @item z3,@var{addr},@var{kind}
34985 @itemx Z3,@var{addr},@var{kind}
34986 @cindex @samp{z3} packet
34987 @cindex @samp{Z3} packet
34988 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
34989 The number of bytes to watch is specified by @var{kind}.
35001 @item z4,@var{addr},@var{kind}
35002 @itemx Z4,@var{addr},@var{kind}
35003 @cindex @samp{z4} packet
35004 @cindex @samp{Z4} packet
35005 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
35006 The number of bytes to watch is specified by @var{kind}.
35020 @node Stop Reply Packets
35021 @section Stop Reply Packets
35022 @cindex stop reply packets
35024 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
35025 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
35026 receive any of the below as a reply. Except for @samp{?}
35027 and @samp{vStopped}, that reply is only returned
35028 when the target halts. In the below the exact meaning of @dfn{signal
35029 number} is defined by the header @file{include/gdb/signals.h} in the
35030 @value{GDBN} source code.
35032 As in the description of request packets, we include spaces in the
35033 reply templates for clarity; these are not part of the reply packet's
35034 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
35040 The program received signal number @var{AA} (a two-digit hexadecimal
35041 number). This is equivalent to a @samp{T} response with no
35042 @var{n}:@var{r} pairs.
35044 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
35045 @cindex @samp{T} packet reply
35046 The program received signal number @var{AA} (a two-digit hexadecimal
35047 number). This is equivalent to an @samp{S} response, except that the
35048 @samp{@var{n}:@var{r}} pairs can carry values of important registers
35049 and other information directly in the stop reply packet, reducing
35050 round-trip latency. Single-step and breakpoint traps are reported
35051 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
35055 If @var{n} is a hexadecimal number, it is a register number, and the
35056 corresponding @var{r} gives that register's value. The data @var{r} is a
35057 series of bytes in target byte order, with each byte given by a
35058 two-digit hex number.
35061 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
35062 the stopped thread, as specified in @ref{thread-id syntax}.
35065 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
35066 the core on which the stop event was detected.
35069 If @var{n} is a recognized @dfn{stop reason}, it describes a more
35070 specific event that stopped the target. The currently defined stop
35071 reasons are listed below. The @var{aa} should be @samp{05}, the trap
35072 signal. At most one stop reason should be present.
35075 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
35076 and go on to the next; this allows us to extend the protocol in the
35080 The currently defined stop reasons are:
35086 The packet indicates a watchpoint hit, and @var{r} is the data address, in
35089 @cindex shared library events, remote reply
35091 The packet indicates that the loaded libraries have changed.
35092 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
35093 list of loaded libraries. The @var{r} part is ignored.
35095 @cindex replay log events, remote reply
35097 The packet indicates that the target cannot continue replaying
35098 logged execution events, because it has reached the end (or the
35099 beginning when executing backward) of the log. The value of @var{r}
35100 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
35101 for more information.
35105 @itemx W @var{AA} ; process:@var{pid}
35106 The process exited, and @var{AA} is the exit status. This is only
35107 applicable to certain targets.
35109 The second form of the response, including the process ID of the exited
35110 process, can be used only when @value{GDBN} has reported support for
35111 multiprocess protocol extensions; see @ref{multiprocess extensions}.
35112 The @var{pid} is formatted as a big-endian hex string.
35115 @itemx X @var{AA} ; process:@var{pid}
35116 The process terminated with signal @var{AA}.
35118 The second form of the response, including the process ID of the
35119 terminated process, can be used only when @value{GDBN} has reported
35120 support for multiprocess protocol extensions; see @ref{multiprocess
35121 extensions}. The @var{pid} is formatted as a big-endian hex string.
35123 @item O @var{XX}@dots{}
35124 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
35125 written as the program's console output. This can happen at any time
35126 while the program is running and the debugger should continue to wait
35127 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
35129 @item F @var{call-id},@var{parameter}@dots{}
35130 @var{call-id} is the identifier which says which host system call should
35131 be called. This is just the name of the function. Translation into the
35132 correct system call is only applicable as it's defined in @value{GDBN}.
35133 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
35136 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
35137 this very system call.
35139 The target replies with this packet when it expects @value{GDBN} to
35140 call a host system call on behalf of the target. @value{GDBN} replies
35141 with an appropriate @samp{F} packet and keeps up waiting for the next
35142 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
35143 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
35144 Protocol Extension}, for more details.
35148 @node General Query Packets
35149 @section General Query Packets
35150 @cindex remote query requests
35152 Packets starting with @samp{q} are @dfn{general query packets};
35153 packets starting with @samp{Q} are @dfn{general set packets}. General
35154 query and set packets are a semi-unified form for retrieving and
35155 sending information to and from the stub.
35157 The initial letter of a query or set packet is followed by a name
35158 indicating what sort of thing the packet applies to. For example,
35159 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
35160 definitions with the stub. These packet names follow some
35165 The name must not contain commas, colons or semicolons.
35167 Most @value{GDBN} query and set packets have a leading upper case
35170 The names of custom vendor packets should use a company prefix, in
35171 lower case, followed by a period. For example, packets designed at
35172 the Acme Corporation might begin with @samp{qacme.foo} (for querying
35173 foos) or @samp{Qacme.bar} (for setting bars).
35176 The name of a query or set packet should be separated from any
35177 parameters by a @samp{:}; the parameters themselves should be
35178 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
35179 full packet name, and check for a separator or the end of the packet,
35180 in case two packet names share a common prefix. New packets should not begin
35181 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
35182 packets predate these conventions, and have arguments without any terminator
35183 for the packet name; we suspect they are in widespread use in places that
35184 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
35185 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
35188 Like the descriptions of the other packets, each description here
35189 has a template showing the packet's overall syntax, followed by an
35190 explanation of the packet's meaning. We include spaces in some of the
35191 templates for clarity; these are not part of the packet's syntax. No
35192 @value{GDBN} packet uses spaces to separate its components.
35194 Here are the currently defined query and set packets:
35200 Turn on or off the agent as a helper to perform some debugging operations
35201 delegated from @value{GDBN} (@pxref{Control Agent}).
35203 @item QAllow:@var{op}:@var{val}@dots{}
35204 @cindex @samp{QAllow} packet
35205 Specify which operations @value{GDBN} expects to request of the
35206 target, as a semicolon-separated list of operation name and value
35207 pairs. Possible values for @var{op} include @samp{WriteReg},
35208 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
35209 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
35210 indicating that @value{GDBN} will not request the operation, or 1,
35211 indicating that it may. (The target can then use this to set up its
35212 own internals optimally, for instance if the debugger never expects to
35213 insert breakpoints, it may not need to install its own trap handler.)
35216 @cindex current thread, remote request
35217 @cindex @samp{qC} packet
35218 Return the current thread ID.
35222 @item QC @var{thread-id}
35223 Where @var{thread-id} is a thread ID as documented in
35224 @ref{thread-id syntax}.
35225 @item @r{(anything else)}
35226 Any other reply implies the old thread ID.
35229 @item qCRC:@var{addr},@var{length}
35230 @cindex CRC of memory block, remote request
35231 @cindex @samp{qCRC} packet
35232 @anchor{qCRC packet}
35233 Compute the CRC checksum of a block of memory using CRC-32 defined in
35234 IEEE 802.3. The CRC is computed byte at a time, taking the most
35235 significant bit of each byte first. The initial pattern code
35236 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
35238 @emph{Note:} This is the same CRC used in validating separate debug
35239 files (@pxref{Separate Debug Files, , Debugging Information in Separate
35240 Files}). However the algorithm is slightly different. When validating
35241 separate debug files, the CRC is computed taking the @emph{least}
35242 significant bit of each byte first, and the final result is inverted to
35243 detect trailing zeros.
35248 An error (such as memory fault)
35249 @item C @var{crc32}
35250 The specified memory region's checksum is @var{crc32}.
35253 @item QDisableRandomization:@var{value}
35254 @cindex disable address space randomization, remote request
35255 @cindex @samp{QDisableRandomization} packet
35256 Some target operating systems will randomize the virtual address space
35257 of the inferior process as a security feature, but provide a feature
35258 to disable such randomization, e.g.@: to allow for a more deterministic
35259 debugging experience. On such systems, this packet with a @var{value}
35260 of 1 directs the target to disable address space randomization for
35261 processes subsequently started via @samp{vRun} packets, while a packet
35262 with a @var{value} of 0 tells the target to enable address space
35265 This packet is only available in extended mode (@pxref{extended mode}).
35270 The request succeeded.
35273 An error occurred. The error number @var{nn} is given as hex digits.
35276 An empty reply indicates that @samp{QDisableRandomization} is not supported
35280 This packet is not probed by default; the remote stub must request it,
35281 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35282 This should only be done on targets that actually support disabling
35283 address space randomization.
35286 @itemx qsThreadInfo
35287 @cindex list active threads, remote request
35288 @cindex @samp{qfThreadInfo} packet
35289 @cindex @samp{qsThreadInfo} packet
35290 Obtain a list of all active thread IDs from the target (OS). Since there
35291 may be too many active threads to fit into one reply packet, this query
35292 works iteratively: it may require more than one query/reply sequence to
35293 obtain the entire list of threads. The first query of the sequence will
35294 be the @samp{qfThreadInfo} query; subsequent queries in the
35295 sequence will be the @samp{qsThreadInfo} query.
35297 NOTE: This packet replaces the @samp{qL} query (see below).
35301 @item m @var{thread-id}
35303 @item m @var{thread-id},@var{thread-id}@dots{}
35304 a comma-separated list of thread IDs
35306 (lower case letter @samp{L}) denotes end of list.
35309 In response to each query, the target will reply with a list of one or
35310 more thread IDs, separated by commas.
35311 @value{GDBN} will respond to each reply with a request for more thread
35312 ids (using the @samp{qs} form of the query), until the target responds
35313 with @samp{l} (lower-case ell, for @dfn{last}).
35314 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
35317 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
35318 initial connection with the remote target, and the very first thread ID
35319 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
35320 message. Therefore, the stub should ensure that the first thread ID in
35321 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
35323 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
35324 @cindex get thread-local storage address, remote request
35325 @cindex @samp{qGetTLSAddr} packet
35326 Fetch the address associated with thread local storage specified
35327 by @var{thread-id}, @var{offset}, and @var{lm}.
35329 @var{thread-id} is the thread ID associated with the
35330 thread for which to fetch the TLS address. @xref{thread-id syntax}.
35332 @var{offset} is the (big endian, hex encoded) offset associated with the
35333 thread local variable. (This offset is obtained from the debug
35334 information associated with the variable.)
35336 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
35337 load module associated with the thread local storage. For example,
35338 a @sc{gnu}/Linux system will pass the link map address of the shared
35339 object associated with the thread local storage under consideration.
35340 Other operating environments may choose to represent the load module
35341 differently, so the precise meaning of this parameter will vary.
35345 @item @var{XX}@dots{}
35346 Hex encoded (big endian) bytes representing the address of the thread
35347 local storage requested.
35350 An error occurred. The error number @var{nn} is given as hex digits.
35353 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
35356 @item qGetTIBAddr:@var{thread-id}
35357 @cindex get thread information block address
35358 @cindex @samp{qGetTIBAddr} packet
35359 Fetch address of the Windows OS specific Thread Information Block.
35361 @var{thread-id} is the thread ID associated with the thread.
35365 @item @var{XX}@dots{}
35366 Hex encoded (big endian) bytes representing the linear address of the
35367 thread information block.
35370 An error occured. This means that either the thread was not found, or the
35371 address could not be retrieved.
35374 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
35377 @item qL @var{startflag} @var{threadcount} @var{nextthread}
35378 Obtain thread information from RTOS. Where: @var{startflag} (one hex
35379 digit) is one to indicate the first query and zero to indicate a
35380 subsequent query; @var{threadcount} (two hex digits) is the maximum
35381 number of threads the response packet can contain; and @var{nextthread}
35382 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
35383 returned in the response as @var{argthread}.
35385 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
35389 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
35390 Where: @var{count} (two hex digits) is the number of threads being
35391 returned; @var{done} (one hex digit) is zero to indicate more threads
35392 and one indicates no further threads; @var{argthreadid} (eight hex
35393 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
35394 is a sequence of thread IDs, @var{threadid} (eight hex
35395 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
35399 @cindex section offsets, remote request
35400 @cindex @samp{qOffsets} packet
35401 Get section offsets that the target used when relocating the downloaded
35406 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
35407 Relocate the @code{Text} section by @var{xxx} from its original address.
35408 Relocate the @code{Data} section by @var{yyy} from its original address.
35409 If the object file format provides segment information (e.g.@: @sc{elf}
35410 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
35411 segments by the supplied offsets.
35413 @emph{Note: while a @code{Bss} offset may be included in the response,
35414 @value{GDBN} ignores this and instead applies the @code{Data} offset
35415 to the @code{Bss} section.}
35417 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
35418 Relocate the first segment of the object file, which conventionally
35419 contains program code, to a starting address of @var{xxx}. If
35420 @samp{DataSeg} is specified, relocate the second segment, which
35421 conventionally contains modifiable data, to a starting address of
35422 @var{yyy}. @value{GDBN} will report an error if the object file
35423 does not contain segment information, or does not contain at least
35424 as many segments as mentioned in the reply. Extra segments are
35425 kept at fixed offsets relative to the last relocated segment.
35428 @item qP @var{mode} @var{thread-id}
35429 @cindex thread information, remote request
35430 @cindex @samp{qP} packet
35431 Returns information on @var{thread-id}. Where: @var{mode} is a hex
35432 encoded 32 bit mode; @var{thread-id} is a thread ID
35433 (@pxref{thread-id syntax}).
35435 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
35438 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
35442 @cindex non-stop mode, remote request
35443 @cindex @samp{QNonStop} packet
35445 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
35446 @xref{Remote Non-Stop}, for more information.
35451 The request succeeded.
35454 An error occurred. The error number @var{nn} is given as hex digits.
35457 An empty reply indicates that @samp{QNonStop} is not supported by
35461 This packet is not probed by default; the remote stub must request it,
35462 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35463 Use of this packet is controlled by the @code{set non-stop} command;
35464 @pxref{Non-Stop Mode}.
35466 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
35467 @cindex pass signals to inferior, remote request
35468 @cindex @samp{QPassSignals} packet
35469 @anchor{QPassSignals}
35470 Each listed @var{signal} should be passed directly to the inferior process.
35471 Signals are numbered identically to continue packets and stop replies
35472 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
35473 strictly greater than the previous item. These signals do not need to stop
35474 the inferior, or be reported to @value{GDBN}. All other signals should be
35475 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
35476 combine; any earlier @samp{QPassSignals} list is completely replaced by the
35477 new list. This packet improves performance when using @samp{handle
35478 @var{signal} nostop noprint pass}.
35483 The request succeeded.
35486 An error occurred. The error number @var{nn} is given as hex digits.
35489 An empty reply indicates that @samp{QPassSignals} is not supported by
35493 Use of this packet is controlled by the @code{set remote pass-signals}
35494 command (@pxref{Remote Configuration, set remote pass-signals}).
35495 This packet is not probed by default; the remote stub must request it,
35496 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35498 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
35499 @cindex signals the inferior may see, remote request
35500 @cindex @samp{QProgramSignals} packet
35501 @anchor{QProgramSignals}
35502 Each listed @var{signal} may be delivered to the inferior process.
35503 Others should be silently discarded.
35505 In some cases, the remote stub may need to decide whether to deliver a
35506 signal to the program or not without @value{GDBN} involvement. One
35507 example of that is while detaching --- the program's threads may have
35508 stopped for signals that haven't yet had a chance of being reported to
35509 @value{GDBN}, and so the remote stub can use the signal list specified
35510 by this packet to know whether to deliver or ignore those pending
35513 This does not influence whether to deliver a signal as requested by a
35514 resumption packet (@pxref{vCont packet}).
35516 Signals are numbered identically to continue packets and stop replies
35517 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
35518 strictly greater than the previous item. Multiple
35519 @samp{QProgramSignals} packets do not combine; any earlier
35520 @samp{QProgramSignals} list is completely replaced by the new list.
35525 The request succeeded.
35528 An error occurred. The error number @var{nn} is given as hex digits.
35531 An empty reply indicates that @samp{QProgramSignals} is not supported
35535 Use of this packet is controlled by the @code{set remote program-signals}
35536 command (@pxref{Remote Configuration, set remote program-signals}).
35537 This packet is not probed by default; the remote stub must request it,
35538 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35540 @item qRcmd,@var{command}
35541 @cindex execute remote command, remote request
35542 @cindex @samp{qRcmd} packet
35543 @var{command} (hex encoded) is passed to the local interpreter for
35544 execution. Invalid commands should be reported using the output
35545 string. Before the final result packet, the target may also respond
35546 with a number of intermediate @samp{O@var{output}} console output
35547 packets. @emph{Implementors should note that providing access to a
35548 stubs's interpreter may have security implications}.
35553 A command response with no output.
35555 A command response with the hex encoded output string @var{OUTPUT}.
35557 Indicate a badly formed request.
35559 An empty reply indicates that @samp{qRcmd} is not recognized.
35562 (Note that the @code{qRcmd} packet's name is separated from the
35563 command by a @samp{,}, not a @samp{:}, contrary to the naming
35564 conventions above. Please don't use this packet as a model for new
35567 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
35568 @cindex searching memory, in remote debugging
35570 @cindex @samp{qSearch:memory} packet
35572 @cindex @samp{qSearch memory} packet
35573 @anchor{qSearch memory}
35574 Search @var{length} bytes at @var{address} for @var{search-pattern}.
35575 Both @var{address} and @var{length} are encoded in hex;
35576 @var{search-pattern} is a sequence of bytes, also hex encoded.
35581 The pattern was not found.
35583 The pattern was found at @var{address}.
35585 A badly formed request or an error was encountered while searching memory.
35587 An empty reply indicates that @samp{qSearch:memory} is not recognized.
35590 @item QStartNoAckMode
35591 @cindex @samp{QStartNoAckMode} packet
35592 @anchor{QStartNoAckMode}
35593 Request that the remote stub disable the normal @samp{+}/@samp{-}
35594 protocol acknowledgments (@pxref{Packet Acknowledgment}).
35599 The stub has switched to no-acknowledgment mode.
35600 @value{GDBN} acknowledges this reponse,
35601 but neither the stub nor @value{GDBN} shall send or expect further
35602 @samp{+}/@samp{-} acknowledgments in the current connection.
35604 An empty reply indicates that the stub does not support no-acknowledgment mode.
35607 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
35608 @cindex supported packets, remote query
35609 @cindex features of the remote protocol
35610 @cindex @samp{qSupported} packet
35611 @anchor{qSupported}
35612 Tell the remote stub about features supported by @value{GDBN}, and
35613 query the stub for features it supports. This packet allows
35614 @value{GDBN} and the remote stub to take advantage of each others'
35615 features. @samp{qSupported} also consolidates multiple feature probes
35616 at startup, to improve @value{GDBN} performance---a single larger
35617 packet performs better than multiple smaller probe packets on
35618 high-latency links. Some features may enable behavior which must not
35619 be on by default, e.g.@: because it would confuse older clients or
35620 stubs. Other features may describe packets which could be
35621 automatically probed for, but are not. These features must be
35622 reported before @value{GDBN} will use them. This ``default
35623 unsupported'' behavior is not appropriate for all packets, but it
35624 helps to keep the initial connection time under control with new
35625 versions of @value{GDBN} which support increasing numbers of packets.
35629 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
35630 The stub supports or does not support each returned @var{stubfeature},
35631 depending on the form of each @var{stubfeature} (see below for the
35634 An empty reply indicates that @samp{qSupported} is not recognized,
35635 or that no features needed to be reported to @value{GDBN}.
35638 The allowed forms for each feature (either a @var{gdbfeature} in the
35639 @samp{qSupported} packet, or a @var{stubfeature} in the response)
35643 @item @var{name}=@var{value}
35644 The remote protocol feature @var{name} is supported, and associated
35645 with the specified @var{value}. The format of @var{value} depends
35646 on the feature, but it must not include a semicolon.
35648 The remote protocol feature @var{name} is supported, and does not
35649 need an associated value.
35651 The remote protocol feature @var{name} is not supported.
35653 The remote protocol feature @var{name} may be supported, and
35654 @value{GDBN} should auto-detect support in some other way when it is
35655 needed. This form will not be used for @var{gdbfeature} notifications,
35656 but may be used for @var{stubfeature} responses.
35659 Whenever the stub receives a @samp{qSupported} request, the
35660 supplied set of @value{GDBN} features should override any previous
35661 request. This allows @value{GDBN} to put the stub in a known
35662 state, even if the stub had previously been communicating with
35663 a different version of @value{GDBN}.
35665 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
35670 This feature indicates whether @value{GDBN} supports multiprocess
35671 extensions to the remote protocol. @value{GDBN} does not use such
35672 extensions unless the stub also reports that it supports them by
35673 including @samp{multiprocess+} in its @samp{qSupported} reply.
35674 @xref{multiprocess extensions}, for details.
35677 This feature indicates that @value{GDBN} supports the XML target
35678 description. If the stub sees @samp{xmlRegisters=} with target
35679 specific strings separated by a comma, it will report register
35683 This feature indicates whether @value{GDBN} supports the
35684 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
35685 instruction reply packet}).
35688 Stubs should ignore any unknown values for
35689 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
35690 packet supports receiving packets of unlimited length (earlier
35691 versions of @value{GDBN} may reject overly long responses). Additional values
35692 for @var{gdbfeature} may be defined in the future to let the stub take
35693 advantage of new features in @value{GDBN}, e.g.@: incompatible
35694 improvements in the remote protocol---the @samp{multiprocess} feature is
35695 an example of such a feature. The stub's reply should be independent
35696 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
35697 describes all the features it supports, and then the stub replies with
35698 all the features it supports.
35700 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
35701 responses, as long as each response uses one of the standard forms.
35703 Some features are flags. A stub which supports a flag feature
35704 should respond with a @samp{+} form response. Other features
35705 require values, and the stub should respond with an @samp{=}
35708 Each feature has a default value, which @value{GDBN} will use if
35709 @samp{qSupported} is not available or if the feature is not mentioned
35710 in the @samp{qSupported} response. The default values are fixed; a
35711 stub is free to omit any feature responses that match the defaults.
35713 Not all features can be probed, but for those which can, the probing
35714 mechanism is useful: in some cases, a stub's internal
35715 architecture may not allow the protocol layer to know some information
35716 about the underlying target in advance. This is especially common in
35717 stubs which may be configured for multiple targets.
35719 These are the currently defined stub features and their properties:
35721 @multitable @columnfractions 0.35 0.2 0.12 0.2
35722 @c NOTE: The first row should be @headitem, but we do not yet require
35723 @c a new enough version of Texinfo (4.7) to use @headitem.
35725 @tab Value Required
35729 @item @samp{PacketSize}
35734 @item @samp{qXfer:auxv:read}
35739 @item @samp{qXfer:btrace:read}
35744 @item @samp{qXfer:btrace-conf:read}
35749 @item @samp{qXfer:features:read}
35754 @item @samp{qXfer:libraries:read}
35759 @item @samp{qXfer:libraries-svr4:read}
35764 @item @samp{augmented-libraries-svr4-read}
35769 @item @samp{qXfer:memory-map:read}
35774 @item @samp{qXfer:sdata:read}
35779 @item @samp{qXfer:spu:read}
35784 @item @samp{qXfer:spu:write}
35789 @item @samp{qXfer:siginfo:read}
35794 @item @samp{qXfer:siginfo:write}
35799 @item @samp{qXfer:threads:read}
35804 @item @samp{qXfer:traceframe-info:read}
35809 @item @samp{qXfer:uib:read}
35814 @item @samp{qXfer:fdpic:read}
35819 @item @samp{Qbtrace:off}
35824 @item @samp{Qbtrace:bts}
35829 @item @samp{QNonStop}
35834 @item @samp{QPassSignals}
35839 @item @samp{QStartNoAckMode}
35844 @item @samp{multiprocess}
35849 @item @samp{ConditionalBreakpoints}
35854 @item @samp{ConditionalTracepoints}
35859 @item @samp{ReverseContinue}
35864 @item @samp{ReverseStep}
35869 @item @samp{TracepointSource}
35874 @item @samp{QAgent}
35879 @item @samp{QAllow}
35884 @item @samp{QDisableRandomization}
35889 @item @samp{EnableDisableTracepoints}
35894 @item @samp{QTBuffer:size}
35899 @item @samp{tracenz}
35904 @item @samp{BreakpointCommands}
35911 These are the currently defined stub features, in more detail:
35914 @cindex packet size, remote protocol
35915 @item PacketSize=@var{bytes}
35916 The remote stub can accept packets up to at least @var{bytes} in
35917 length. @value{GDBN} will send packets up to this size for bulk
35918 transfers, and will never send larger packets. This is a limit on the
35919 data characters in the packet, including the frame and checksum.
35920 There is no trailing NUL byte in a remote protocol packet; if the stub
35921 stores packets in a NUL-terminated format, it should allow an extra
35922 byte in its buffer for the NUL. If this stub feature is not supported,
35923 @value{GDBN} guesses based on the size of the @samp{g} packet response.
35925 @item qXfer:auxv:read
35926 The remote stub understands the @samp{qXfer:auxv:read} packet
35927 (@pxref{qXfer auxiliary vector read}).
35929 @item qXfer:btrace:read
35930 The remote stub understands the @samp{qXfer:btrace:read}
35931 packet (@pxref{qXfer btrace read}).
35933 @item qXfer:btrace-conf:read
35934 The remote stub understands the @samp{qXfer:btrace-conf:read}
35935 packet (@pxref{qXfer btrace-conf read}).
35937 @item qXfer:features:read
35938 The remote stub understands the @samp{qXfer:features:read} packet
35939 (@pxref{qXfer target description read}).
35941 @item qXfer:libraries:read
35942 The remote stub understands the @samp{qXfer:libraries:read} packet
35943 (@pxref{qXfer library list read}).
35945 @item qXfer:libraries-svr4:read
35946 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
35947 (@pxref{qXfer svr4 library list read}).
35949 @item augmented-libraries-svr4-read
35950 The remote stub understands the augmented form of the
35951 @samp{qXfer:libraries-svr4:read} packet
35952 (@pxref{qXfer svr4 library list read}).
35954 @item qXfer:memory-map:read
35955 The remote stub understands the @samp{qXfer:memory-map:read} packet
35956 (@pxref{qXfer memory map read}).
35958 @item qXfer:sdata:read
35959 The remote stub understands the @samp{qXfer:sdata:read} packet
35960 (@pxref{qXfer sdata read}).
35962 @item qXfer:spu:read
35963 The remote stub understands the @samp{qXfer:spu:read} packet
35964 (@pxref{qXfer spu read}).
35966 @item qXfer:spu:write
35967 The remote stub understands the @samp{qXfer:spu:write} packet
35968 (@pxref{qXfer spu write}).
35970 @item qXfer:siginfo:read
35971 The remote stub understands the @samp{qXfer:siginfo:read} packet
35972 (@pxref{qXfer siginfo read}).
35974 @item qXfer:siginfo:write
35975 The remote stub understands the @samp{qXfer:siginfo:write} packet
35976 (@pxref{qXfer siginfo write}).
35978 @item qXfer:threads:read
35979 The remote stub understands the @samp{qXfer:threads:read} packet
35980 (@pxref{qXfer threads read}).
35982 @item qXfer:traceframe-info:read
35983 The remote stub understands the @samp{qXfer:traceframe-info:read}
35984 packet (@pxref{qXfer traceframe info read}).
35986 @item qXfer:uib:read
35987 The remote stub understands the @samp{qXfer:uib:read}
35988 packet (@pxref{qXfer unwind info block}).
35990 @item qXfer:fdpic:read
35991 The remote stub understands the @samp{qXfer:fdpic:read}
35992 packet (@pxref{qXfer fdpic loadmap read}).
35995 The remote stub understands the @samp{QNonStop} packet
35996 (@pxref{QNonStop}).
35999 The remote stub understands the @samp{QPassSignals} packet
36000 (@pxref{QPassSignals}).
36002 @item QStartNoAckMode
36003 The remote stub understands the @samp{QStartNoAckMode} packet and
36004 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
36007 @anchor{multiprocess extensions}
36008 @cindex multiprocess extensions, in remote protocol
36009 The remote stub understands the multiprocess extensions to the remote
36010 protocol syntax. The multiprocess extensions affect the syntax of
36011 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
36012 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
36013 replies. Note that reporting this feature indicates support for the
36014 syntactic extensions only, not that the stub necessarily supports
36015 debugging of more than one process at a time. The stub must not use
36016 multiprocess extensions in packet replies unless @value{GDBN} has also
36017 indicated it supports them in its @samp{qSupported} request.
36019 @item qXfer:osdata:read
36020 The remote stub understands the @samp{qXfer:osdata:read} packet
36021 ((@pxref{qXfer osdata read}).
36023 @item ConditionalBreakpoints
36024 The target accepts and implements evaluation of conditional expressions
36025 defined for breakpoints. The target will only report breakpoint triggers
36026 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
36028 @item ConditionalTracepoints
36029 The remote stub accepts and implements conditional expressions defined
36030 for tracepoints (@pxref{Tracepoint Conditions}).
36032 @item ReverseContinue
36033 The remote stub accepts and implements the reverse continue packet
36037 The remote stub accepts and implements the reverse step packet
36040 @item TracepointSource
36041 The remote stub understands the @samp{QTDPsrc} packet that supplies
36042 the source form of tracepoint definitions.
36045 The remote stub understands the @samp{QAgent} packet.
36048 The remote stub understands the @samp{QAllow} packet.
36050 @item QDisableRandomization
36051 The remote stub understands the @samp{QDisableRandomization} packet.
36053 @item StaticTracepoint
36054 @cindex static tracepoints, in remote protocol
36055 The remote stub supports static tracepoints.
36057 @item InstallInTrace
36058 @anchor{install tracepoint in tracing}
36059 The remote stub supports installing tracepoint in tracing.
36061 @item EnableDisableTracepoints
36062 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
36063 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
36064 to be enabled and disabled while a trace experiment is running.
36066 @item QTBuffer:size
36067 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
36068 packet that allows to change the size of the trace buffer.
36071 @cindex string tracing, in remote protocol
36072 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
36073 See @ref{Bytecode Descriptions} for details about the bytecode.
36075 @item BreakpointCommands
36076 @cindex breakpoint commands, in remote protocol
36077 The remote stub supports running a breakpoint's command list itself,
36078 rather than reporting the hit to @value{GDBN}.
36081 The remote stub understands the @samp{Qbtrace:off} packet.
36084 The remote stub understands the @samp{Qbtrace:bts} packet.
36089 @cindex symbol lookup, remote request
36090 @cindex @samp{qSymbol} packet
36091 Notify the target that @value{GDBN} is prepared to serve symbol lookup
36092 requests. Accept requests from the target for the values of symbols.
36097 The target does not need to look up any (more) symbols.
36098 @item qSymbol:@var{sym_name}
36099 The target requests the value of symbol @var{sym_name} (hex encoded).
36100 @value{GDBN} may provide the value by using the
36101 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
36105 @item qSymbol:@var{sym_value}:@var{sym_name}
36106 Set the value of @var{sym_name} to @var{sym_value}.
36108 @var{sym_name} (hex encoded) is the name of a symbol whose value the
36109 target has previously requested.
36111 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
36112 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
36118 The target does not need to look up any (more) symbols.
36119 @item qSymbol:@var{sym_name}
36120 The target requests the value of a new symbol @var{sym_name} (hex
36121 encoded). @value{GDBN} will continue to supply the values of symbols
36122 (if available), until the target ceases to request them.
36127 @itemx QTDisconnected
36134 @itemx qTMinFTPILen
36136 @xref{Tracepoint Packets}.
36138 @item qThreadExtraInfo,@var{thread-id}
36139 @cindex thread attributes info, remote request
36140 @cindex @samp{qThreadExtraInfo} packet
36141 Obtain from the target OS a printable string description of thread
36142 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
36143 for the forms of @var{thread-id}. This
36144 string may contain anything that the target OS thinks is interesting
36145 for @value{GDBN} to tell the user about the thread. The string is
36146 displayed in @value{GDBN}'s @code{info threads} display. Some
36147 examples of possible thread extra info strings are @samp{Runnable}, or
36148 @samp{Blocked on Mutex}.
36152 @item @var{XX}@dots{}
36153 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
36154 comprising the printable string containing the extra information about
36155 the thread's attributes.
36158 (Note that the @code{qThreadExtraInfo} packet's name is separated from
36159 the command by a @samp{,}, not a @samp{:}, contrary to the naming
36160 conventions above. Please don't use this packet as a model for new
36179 @xref{Tracepoint Packets}.
36181 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
36182 @cindex read special object, remote request
36183 @cindex @samp{qXfer} packet
36184 @anchor{qXfer read}
36185 Read uninterpreted bytes from the target's special data area
36186 identified by the keyword @var{object}. Request @var{length} bytes
36187 starting at @var{offset} bytes into the data. The content and
36188 encoding of @var{annex} is specific to @var{object}; it can supply
36189 additional details about what data to access.
36191 Here are the specific requests of this form defined so far. All
36192 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
36193 formats, listed below.
36196 @item qXfer:auxv:read::@var{offset},@var{length}
36197 @anchor{qXfer auxiliary vector read}
36198 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
36199 auxiliary vector}. Note @var{annex} must be empty.
36201 This packet is not probed by default; the remote stub must request it,
36202 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36204 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
36205 @anchor{qXfer btrace read}
36207 Return a description of the current branch trace.
36208 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
36209 packet may have one of the following values:
36213 Returns all available branch trace.
36216 Returns all available branch trace if the branch trace changed since
36217 the last read request.
36220 Returns the new branch trace since the last read request. Adds a new
36221 block to the end of the trace that begins at zero and ends at the source
36222 location of the first branch in the trace buffer. This extra block is
36223 used to stitch traces together.
36225 If the trace buffer overflowed, returns an error indicating the overflow.
36228 This packet is not probed by default; the remote stub must request it
36229 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36231 @item qXfer:btrace-conf:read::@var{offset},@var{length}
36232 @anchor{qXfer btrace-conf read}
36234 Return a description of the current branch trace configuration.
36235 @xref{Branch Trace Configuration Format}.
36237 This packet is not probed by default; the remote stub must request it
36238 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36240 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
36241 @anchor{qXfer target description read}
36242 Access the @dfn{target description}. @xref{Target Descriptions}. The
36243 annex specifies which XML document to access. The main description is
36244 always loaded from the @samp{target.xml} annex.
36246 This packet is not probed by default; the remote stub must request it,
36247 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36249 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
36250 @anchor{qXfer library list read}
36251 Access the target's list of loaded libraries. @xref{Library List Format}.
36252 The annex part of the generic @samp{qXfer} packet must be empty
36253 (@pxref{qXfer read}).
36255 Targets which maintain a list of libraries in the program's memory do
36256 not need to implement this packet; it is designed for platforms where
36257 the operating system manages the list of loaded libraries.
36259 This packet is not probed by default; the remote stub must request it,
36260 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36262 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
36263 @anchor{qXfer svr4 library list read}
36264 Access the target's list of loaded libraries when the target is an SVR4
36265 platform. @xref{Library List Format for SVR4 Targets}. The annex part
36266 of the generic @samp{qXfer} packet must be empty unless the remote
36267 stub indicated it supports the augmented form of this packet
36268 by supplying an appropriate @samp{qSupported} response
36269 (@pxref{qXfer read}, @ref{qSupported}).
36271 This packet is optional for better performance on SVR4 targets.
36272 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
36274 This packet is not probed by default; the remote stub must request it,
36275 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36277 If the remote stub indicates it supports the augmented form of this
36278 packet then the annex part of the generic @samp{qXfer} packet may
36279 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
36280 arguments. The currently supported arguments are:
36283 @item start=@var{address}
36284 A hexadecimal number specifying the address of the @samp{struct
36285 link_map} to start reading the library list from. If unset or zero
36286 then the first @samp{struct link_map} in the library list will be
36287 chosen as the starting point.
36289 @item prev=@var{address}
36290 A hexadecimal number specifying the address of the @samp{struct
36291 link_map} immediately preceding the @samp{struct link_map}
36292 specified by the @samp{start} argument. If unset or zero then
36293 the remote stub will expect that no @samp{struct link_map}
36294 exists prior to the starting point.
36298 Arguments that are not understood by the remote stub will be silently
36301 @item qXfer:memory-map:read::@var{offset},@var{length}
36302 @anchor{qXfer memory map read}
36303 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
36304 annex part of the generic @samp{qXfer} packet must be empty
36305 (@pxref{qXfer read}).
36307 This packet is not probed by default; the remote stub must request it,
36308 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36310 @item qXfer:sdata:read::@var{offset},@var{length}
36311 @anchor{qXfer sdata read}
36313 Read contents of the extra collected static tracepoint marker
36314 information. The annex part of the generic @samp{qXfer} packet must
36315 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
36318 This packet is not probed by default; the remote stub must request it,
36319 by supplying an appropriate @samp{qSupported} response
36320 (@pxref{qSupported}).
36322 @item qXfer:siginfo:read::@var{offset},@var{length}
36323 @anchor{qXfer siginfo read}
36324 Read contents of the extra signal information on the target
36325 system. The annex part of the generic @samp{qXfer} packet must be
36326 empty (@pxref{qXfer read}).
36328 This packet is not probed by default; the remote stub must request it,
36329 by supplying an appropriate @samp{qSupported} response
36330 (@pxref{qSupported}).
36332 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
36333 @anchor{qXfer spu read}
36334 Read contents of an @code{spufs} file on the target system. The
36335 annex specifies which file to read; it must be of the form
36336 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
36337 in the target process, and @var{name} identifes the @code{spufs} file
36338 in that context to be accessed.
36340 This packet is not probed by default; the remote stub must request it,
36341 by supplying an appropriate @samp{qSupported} response
36342 (@pxref{qSupported}).
36344 @item qXfer:threads:read::@var{offset},@var{length}
36345 @anchor{qXfer threads read}
36346 Access the list of threads on target. @xref{Thread List Format}. The
36347 annex part of the generic @samp{qXfer} packet must be empty
36348 (@pxref{qXfer read}).
36350 This packet is not probed by default; the remote stub must request it,
36351 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36353 @item qXfer:traceframe-info:read::@var{offset},@var{length}
36354 @anchor{qXfer traceframe info read}
36356 Return a description of the current traceframe's contents.
36357 @xref{Traceframe Info Format}. The annex part of the generic
36358 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
36360 This packet is not probed by default; the remote stub must request it,
36361 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36363 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
36364 @anchor{qXfer unwind info block}
36366 Return the unwind information block for @var{pc}. This packet is used
36367 on OpenVMS/ia64 to ask the kernel unwind information.
36369 This packet is not probed by default.
36371 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
36372 @anchor{qXfer fdpic loadmap read}
36373 Read contents of @code{loadmap}s on the target system. The
36374 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
36375 executable @code{loadmap} or interpreter @code{loadmap} to read.
36377 This packet is not probed by default; the remote stub must request it,
36378 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36380 @item qXfer:osdata:read::@var{offset},@var{length}
36381 @anchor{qXfer osdata read}
36382 Access the target's @dfn{operating system information}.
36383 @xref{Operating System Information}.
36390 Data @var{data} (@pxref{Binary Data}) has been read from the
36391 target. There may be more data at a higher address (although
36392 it is permitted to return @samp{m} even for the last valid
36393 block of data, as long as at least one byte of data was read).
36394 It is possible for @var{data} to have fewer bytes than the @var{length} in the
36398 Data @var{data} (@pxref{Binary Data}) has been read from the target.
36399 There is no more data to be read. It is possible for @var{data} to
36400 have fewer bytes than the @var{length} in the request.
36403 The @var{offset} in the request is at the end of the data.
36404 There is no more data to be read.
36407 The request was malformed, or @var{annex} was invalid.
36410 The offset was invalid, or there was an error encountered reading the data.
36411 The @var{nn} part is a hex-encoded @code{errno} value.
36414 An empty reply indicates the @var{object} string was not recognized by
36415 the stub, or that the object does not support reading.
36418 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
36419 @cindex write data into object, remote request
36420 @anchor{qXfer write}
36421 Write uninterpreted bytes into the target's special data area
36422 identified by the keyword @var{object}, starting at @var{offset} bytes
36423 into the data. The binary-encoded data (@pxref{Binary Data}) to be
36424 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
36425 is specific to @var{object}; it can supply additional details about what data
36428 Here are the specific requests of this form defined so far. All
36429 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
36430 formats, listed below.
36433 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
36434 @anchor{qXfer siginfo write}
36435 Write @var{data} to the extra signal information on the target system.
36436 The annex part of the generic @samp{qXfer} packet must be
36437 empty (@pxref{qXfer write}).
36439 This packet is not probed by default; the remote stub must request it,
36440 by supplying an appropriate @samp{qSupported} response
36441 (@pxref{qSupported}).
36443 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
36444 @anchor{qXfer spu write}
36445 Write @var{data} to an @code{spufs} file on the target system. The
36446 annex specifies which file to write; it must be of the form
36447 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
36448 in the target process, and @var{name} identifes the @code{spufs} file
36449 in that context to be accessed.
36451 This packet is not probed by default; the remote stub must request it,
36452 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36458 @var{nn} (hex encoded) is the number of bytes written.
36459 This may be fewer bytes than supplied in the request.
36462 The request was malformed, or @var{annex} was invalid.
36465 The offset was invalid, or there was an error encountered writing the data.
36466 The @var{nn} part is a hex-encoded @code{errno} value.
36469 An empty reply indicates the @var{object} string was not
36470 recognized by the stub, or that the object does not support writing.
36473 @item qXfer:@var{object}:@var{operation}:@dots{}
36474 Requests of this form may be added in the future. When a stub does
36475 not recognize the @var{object} keyword, or its support for
36476 @var{object} does not recognize the @var{operation} keyword, the stub
36477 must respond with an empty packet.
36479 @item qAttached:@var{pid}
36480 @cindex query attached, remote request
36481 @cindex @samp{qAttached} packet
36482 Return an indication of whether the remote server attached to an
36483 existing process or created a new process. When the multiprocess
36484 protocol extensions are supported (@pxref{multiprocess extensions}),
36485 @var{pid} is an integer in hexadecimal format identifying the target
36486 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
36487 the query packet will be simplified as @samp{qAttached}.
36489 This query is used, for example, to know whether the remote process
36490 should be detached or killed when a @value{GDBN} session is ended with
36491 the @code{quit} command.
36496 The remote server attached to an existing process.
36498 The remote server created a new process.
36500 A badly formed request or an error was encountered.
36504 Enable branch tracing for the current thread using bts tracing.
36509 Branch tracing has been enabled.
36511 A badly formed request or an error was encountered.
36515 Disable branch tracing for the current thread.
36520 Branch tracing has been disabled.
36522 A badly formed request or an error was encountered.
36527 @node Architecture-Specific Protocol Details
36528 @section Architecture-Specific Protocol Details
36530 This section describes how the remote protocol is applied to specific
36531 target architectures. Also see @ref{Standard Target Features}, for
36532 details of XML target descriptions for each architecture.
36535 * ARM-Specific Protocol Details::
36536 * MIPS-Specific Protocol Details::
36539 @node ARM-Specific Protocol Details
36540 @subsection @acronym{ARM}-specific Protocol Details
36543 * ARM Breakpoint Kinds::
36546 @node ARM Breakpoint Kinds
36547 @subsubsection @acronym{ARM} Breakpoint Kinds
36548 @cindex breakpoint kinds, @acronym{ARM}
36550 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
36555 16-bit Thumb mode breakpoint.
36558 32-bit Thumb mode (Thumb-2) breakpoint.
36561 32-bit @acronym{ARM} mode breakpoint.
36565 @node MIPS-Specific Protocol Details
36566 @subsection @acronym{MIPS}-specific Protocol Details
36569 * MIPS Register packet Format::
36570 * MIPS Breakpoint Kinds::
36573 @node MIPS Register packet Format
36574 @subsubsection @acronym{MIPS} Register Packet Format
36575 @cindex register packet format, @acronym{MIPS}
36577 The following @code{g}/@code{G} packets have previously been defined.
36578 In the below, some thirty-two bit registers are transferred as
36579 sixty-four bits. Those registers should be zero/sign extended (which?)
36580 to fill the space allocated. Register bytes are transferred in target
36581 byte order. The two nibbles within a register byte are transferred
36582 most-significant -- least-significant.
36587 All registers are transferred as thirty-two bit quantities in the order:
36588 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
36589 registers; fsr; fir; fp.
36592 All registers are transferred as sixty-four bit quantities (including
36593 thirty-two bit registers such as @code{sr}). The ordering is the same
36598 @node MIPS Breakpoint Kinds
36599 @subsubsection @acronym{MIPS} Breakpoint Kinds
36600 @cindex breakpoint kinds, @acronym{MIPS}
36602 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
36607 16-bit @acronym{MIPS16} mode breakpoint.
36610 16-bit @acronym{microMIPS} mode breakpoint.
36613 32-bit standard @acronym{MIPS} mode breakpoint.
36616 32-bit @acronym{microMIPS} mode breakpoint.
36620 @node Tracepoint Packets
36621 @section Tracepoint Packets
36622 @cindex tracepoint packets
36623 @cindex packets, tracepoint
36625 Here we describe the packets @value{GDBN} uses to implement
36626 tracepoints (@pxref{Tracepoints}).
36630 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
36631 @cindex @samp{QTDP} packet
36632 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
36633 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
36634 the tracepoint is disabled. The @var{step} gives the tracepoint's step
36635 count, and @var{pass} gives its pass count. If an @samp{F} is present,
36636 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
36637 the number of bytes that the target should copy elsewhere to make room
36638 for the tracepoint. If an @samp{X} is present, it introduces a
36639 tracepoint condition, which consists of a hexadecimal length, followed
36640 by a comma and hex-encoded bytes, in a manner similar to action
36641 encodings as described below. If the trailing @samp{-} is present,
36642 further @samp{QTDP} packets will follow to specify this tracepoint's
36648 The packet was understood and carried out.
36650 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
36652 The packet was not recognized.
36655 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
36656 Define actions to be taken when a tracepoint is hit. The @var{n} and
36657 @var{addr} must be the same as in the initial @samp{QTDP} packet for
36658 this tracepoint. This packet may only be sent immediately after
36659 another @samp{QTDP} packet that ended with a @samp{-}. If the
36660 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
36661 specifying more actions for this tracepoint.
36663 In the series of action packets for a given tracepoint, at most one
36664 can have an @samp{S} before its first @var{action}. If such a packet
36665 is sent, it and the following packets define ``while-stepping''
36666 actions. Any prior packets define ordinary actions --- that is, those
36667 taken when the tracepoint is first hit. If no action packet has an
36668 @samp{S}, then all the packets in the series specify ordinary
36669 tracepoint actions.
36671 The @samp{@var{action}@dots{}} portion of the packet is a series of
36672 actions, concatenated without separators. Each action has one of the
36678 Collect the registers whose bits are set in @var{mask},
36679 a hexadecimal number whose @var{i}'th bit is set if register number
36680 @var{i} should be collected. (The least significant bit is numbered
36681 zero.) Note that @var{mask} may be any number of digits long; it may
36682 not fit in a 32-bit word.
36684 @item M @var{basereg},@var{offset},@var{len}
36685 Collect @var{len} bytes of memory starting at the address in register
36686 number @var{basereg}, plus @var{offset}. If @var{basereg} is
36687 @samp{-1}, then the range has a fixed address: @var{offset} is the
36688 address of the lowest byte to collect. The @var{basereg},
36689 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
36690 values (the @samp{-1} value for @var{basereg} is a special case).
36692 @item X @var{len},@var{expr}
36693 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
36694 it directs. The agent expression @var{expr} is as described in
36695 @ref{Agent Expressions}. Each byte of the expression is encoded as a
36696 two-digit hex number in the packet; @var{len} is the number of bytes
36697 in the expression (and thus one-half the number of hex digits in the
36702 Any number of actions may be packed together in a single @samp{QTDP}
36703 packet, as long as the packet does not exceed the maximum packet
36704 length (400 bytes, for many stubs). There may be only one @samp{R}
36705 action per tracepoint, and it must precede any @samp{M} or @samp{X}
36706 actions. Any registers referred to by @samp{M} and @samp{X} actions
36707 must be collected by a preceding @samp{R} action. (The
36708 ``while-stepping'' actions are treated as if they were attached to a
36709 separate tracepoint, as far as these restrictions are concerned.)
36714 The packet was understood and carried out.
36716 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
36718 The packet was not recognized.
36721 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
36722 @cindex @samp{QTDPsrc} packet
36723 Specify a source string of tracepoint @var{n} at address @var{addr}.
36724 This is useful to get accurate reproduction of the tracepoints
36725 originally downloaded at the beginning of the trace run. The @var{type}
36726 is the name of the tracepoint part, such as @samp{cond} for the
36727 tracepoint's conditional expression (see below for a list of types), while
36728 @var{bytes} is the string, encoded in hexadecimal.
36730 @var{start} is the offset of the @var{bytes} within the overall source
36731 string, while @var{slen} is the total length of the source string.
36732 This is intended for handling source strings that are longer than will
36733 fit in a single packet.
36734 @c Add detailed example when this info is moved into a dedicated
36735 @c tracepoint descriptions section.
36737 The available string types are @samp{at} for the location,
36738 @samp{cond} for the conditional, and @samp{cmd} for an action command.
36739 @value{GDBN} sends a separate packet for each command in the action
36740 list, in the same order in which the commands are stored in the list.
36742 The target does not need to do anything with source strings except
36743 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
36746 Although this packet is optional, and @value{GDBN} will only send it
36747 if the target replies with @samp{TracepointSource} @xref{General
36748 Query Packets}, it makes both disconnected tracing and trace files
36749 much easier to use. Otherwise the user must be careful that the
36750 tracepoints in effect while looking at trace frames are identical to
36751 the ones in effect during the trace run; even a small discrepancy
36752 could cause @samp{tdump} not to work, or a particular trace frame not
36755 @item QTDV:@var{n}:@var{value}
36756 @cindex define trace state variable, remote request
36757 @cindex @samp{QTDV} packet
36758 Create a new trace state variable, number @var{n}, with an initial
36759 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
36760 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
36761 the option of not using this packet for initial values of zero; the
36762 target should simply create the trace state variables as they are
36763 mentioned in expressions.
36765 @item QTFrame:@var{n}
36766 @cindex @samp{QTFrame} packet
36767 Select the @var{n}'th tracepoint frame from the buffer, and use the
36768 register and memory contents recorded there to answer subsequent
36769 request packets from @value{GDBN}.
36771 A successful reply from the stub indicates that the stub has found the
36772 requested frame. The response is a series of parts, concatenated
36773 without separators, describing the frame we selected. Each part has
36774 one of the following forms:
36778 The selected frame is number @var{n} in the trace frame buffer;
36779 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
36780 was no frame matching the criteria in the request packet.
36783 The selected trace frame records a hit of tracepoint number @var{t};
36784 @var{t} is a hexadecimal number.
36788 @item QTFrame:pc:@var{addr}
36789 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36790 currently selected frame whose PC is @var{addr};
36791 @var{addr} is a hexadecimal number.
36793 @item QTFrame:tdp:@var{t}
36794 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36795 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
36796 is a hexadecimal number.
36798 @item QTFrame:range:@var{start}:@var{end}
36799 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36800 currently selected frame whose PC is between @var{start} (inclusive)
36801 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
36804 @item QTFrame:outside:@var{start}:@var{end}
36805 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
36806 frame @emph{outside} the given range of addresses (exclusive).
36809 @cindex @samp{qTMinFTPILen} packet
36810 This packet requests the minimum length of instruction at which a fast
36811 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
36812 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
36813 it depends on the target system being able to create trampolines in
36814 the first 64K of memory, which might or might not be possible for that
36815 system. So the reply to this packet will be 4 if it is able to
36822 The minimum instruction length is currently unknown.
36824 The minimum instruction length is @var{length}, where @var{length}
36825 is a hexadecimal number greater or equal to 1. A reply
36826 of 1 means that a fast tracepoint may be placed on any instruction
36827 regardless of size.
36829 An error has occurred.
36831 An empty reply indicates that the request is not supported by the stub.
36835 @cindex @samp{QTStart} packet
36836 Begin the tracepoint experiment. Begin collecting data from
36837 tracepoint hits in the trace frame buffer. This packet supports the
36838 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
36839 instruction reply packet}).
36842 @cindex @samp{QTStop} packet
36843 End the tracepoint experiment. Stop collecting trace frames.
36845 @item QTEnable:@var{n}:@var{addr}
36847 @cindex @samp{QTEnable} packet
36848 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
36849 experiment. If the tracepoint was previously disabled, then collection
36850 of data from it will resume.
36852 @item QTDisable:@var{n}:@var{addr}
36854 @cindex @samp{QTDisable} packet
36855 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
36856 experiment. No more data will be collected from the tracepoint unless
36857 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
36860 @cindex @samp{QTinit} packet
36861 Clear the table of tracepoints, and empty the trace frame buffer.
36863 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
36864 @cindex @samp{QTro} packet
36865 Establish the given ranges of memory as ``transparent''. The stub
36866 will answer requests for these ranges from memory's current contents,
36867 if they were not collected as part of the tracepoint hit.
36869 @value{GDBN} uses this to mark read-only regions of memory, like those
36870 containing program code. Since these areas never change, they should
36871 still have the same contents they did when the tracepoint was hit, so
36872 there's no reason for the stub to refuse to provide their contents.
36874 @item QTDisconnected:@var{value}
36875 @cindex @samp{QTDisconnected} packet
36876 Set the choice to what to do with the tracing run when @value{GDBN}
36877 disconnects from the target. A @var{value} of 1 directs the target to
36878 continue the tracing run, while 0 tells the target to stop tracing if
36879 @value{GDBN} is no longer in the picture.
36882 @cindex @samp{qTStatus} packet
36883 Ask the stub if there is a trace experiment running right now.
36885 The reply has the form:
36889 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
36890 @var{running} is a single digit @code{1} if the trace is presently
36891 running, or @code{0} if not. It is followed by semicolon-separated
36892 optional fields that an agent may use to report additional status.
36896 If the trace is not running, the agent may report any of several
36897 explanations as one of the optional fields:
36902 No trace has been run yet.
36904 @item tstop[:@var{text}]:0
36905 The trace was stopped by a user-originated stop command. The optional
36906 @var{text} field is a user-supplied string supplied as part of the
36907 stop command (for instance, an explanation of why the trace was
36908 stopped manually). It is hex-encoded.
36911 The trace stopped because the trace buffer filled up.
36913 @item tdisconnected:0
36914 The trace stopped because @value{GDBN} disconnected from the target.
36916 @item tpasscount:@var{tpnum}
36917 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
36919 @item terror:@var{text}:@var{tpnum}
36920 The trace stopped because tracepoint @var{tpnum} had an error. The
36921 string @var{text} is available to describe the nature of the error
36922 (for instance, a divide by zero in the condition expression); it
36926 The trace stopped for some other reason.
36930 Additional optional fields supply statistical and other information.
36931 Although not required, they are extremely useful for users monitoring
36932 the progress of a trace run. If a trace has stopped, and these
36933 numbers are reported, they must reflect the state of the just-stopped
36938 @item tframes:@var{n}
36939 The number of trace frames in the buffer.
36941 @item tcreated:@var{n}
36942 The total number of trace frames created during the run. This may
36943 be larger than the trace frame count, if the buffer is circular.
36945 @item tsize:@var{n}
36946 The total size of the trace buffer, in bytes.
36948 @item tfree:@var{n}
36949 The number of bytes still unused in the buffer.
36951 @item circular:@var{n}
36952 The value of the circular trace buffer flag. @code{1} means that the
36953 trace buffer is circular and old trace frames will be discarded if
36954 necessary to make room, @code{0} means that the trace buffer is linear
36957 @item disconn:@var{n}
36958 The value of the disconnected tracing flag. @code{1} means that
36959 tracing will continue after @value{GDBN} disconnects, @code{0} means
36960 that the trace run will stop.
36964 @item qTP:@var{tp}:@var{addr}
36965 @cindex tracepoint status, remote request
36966 @cindex @samp{qTP} packet
36967 Ask the stub for the current state of tracepoint number @var{tp} at
36968 address @var{addr}.
36972 @item V@var{hits}:@var{usage}
36973 The tracepoint has been hit @var{hits} times so far during the trace
36974 run, and accounts for @var{usage} in the trace buffer. Note that
36975 @code{while-stepping} steps are not counted as separate hits, but the
36976 steps' space consumption is added into the usage number.
36980 @item qTV:@var{var}
36981 @cindex trace state variable value, remote request
36982 @cindex @samp{qTV} packet
36983 Ask the stub for the value of the trace state variable number @var{var}.
36988 The value of the variable is @var{value}. This will be the current
36989 value of the variable if the user is examining a running target, or a
36990 saved value if the variable was collected in the trace frame that the
36991 user is looking at. Note that multiple requests may result in
36992 different reply values, such as when requesting values while the
36993 program is running.
36996 The value of the variable is unknown. This would occur, for example,
36997 if the user is examining a trace frame in which the requested variable
37002 @cindex @samp{qTfP} packet
37004 @cindex @samp{qTsP} packet
37005 These packets request data about tracepoints that are being used by
37006 the target. @value{GDBN} sends @code{qTfP} to get the first piece
37007 of data, and multiple @code{qTsP} to get additional pieces. Replies
37008 to these packets generally take the form of the @code{QTDP} packets
37009 that define tracepoints. (FIXME add detailed syntax)
37012 @cindex @samp{qTfV} packet
37014 @cindex @samp{qTsV} packet
37015 These packets request data about trace state variables that are on the
37016 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
37017 and multiple @code{qTsV} to get additional variables. Replies to
37018 these packets follow the syntax of the @code{QTDV} packets that define
37019 trace state variables.
37025 @cindex @samp{qTfSTM} packet
37026 @cindex @samp{qTsSTM} packet
37027 These packets request data about static tracepoint markers that exist
37028 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
37029 first piece of data, and multiple @code{qTsSTM} to get additional
37030 pieces. Replies to these packets take the following form:
37034 @item m @var{address}:@var{id}:@var{extra}
37036 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
37037 a comma-separated list of markers
37039 (lower case letter @samp{L}) denotes end of list.
37041 An error occurred. The error number @var{nn} is given as hex digits.
37043 An empty reply indicates that the request is not supported by the
37047 The @var{address} is encoded in hex;
37048 @var{id} and @var{extra} are strings encoded in hex.
37050 In response to each query, the target will reply with a list of one or
37051 more markers, separated by commas. @value{GDBN} will respond to each
37052 reply with a request for more markers (using the @samp{qs} form of the
37053 query), until the target responds with @samp{l} (lower-case ell, for
37056 @item qTSTMat:@var{address}
37058 @cindex @samp{qTSTMat} packet
37059 This packets requests data about static tracepoint markers in the
37060 target program at @var{address}. Replies to this packet follow the
37061 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
37062 tracepoint markers.
37064 @item QTSave:@var{filename}
37065 @cindex @samp{QTSave} packet
37066 This packet directs the target to save trace data to the file name
37067 @var{filename} in the target's filesystem. The @var{filename} is encoded
37068 as a hex string; the interpretation of the file name (relative vs
37069 absolute, wild cards, etc) is up to the target.
37071 @item qTBuffer:@var{offset},@var{len}
37072 @cindex @samp{qTBuffer} packet
37073 Return up to @var{len} bytes of the current contents of trace buffer,
37074 starting at @var{offset}. The trace buffer is treated as if it were
37075 a contiguous collection of traceframes, as per the trace file format.
37076 The reply consists as many hex-encoded bytes as the target can deliver
37077 in a packet; it is not an error to return fewer than were asked for.
37078 A reply consisting of just @code{l} indicates that no bytes are
37081 @item QTBuffer:circular:@var{value}
37082 This packet directs the target to use a circular trace buffer if
37083 @var{value} is 1, or a linear buffer if the value is 0.
37085 @item QTBuffer:size:@var{size}
37086 @anchor{QTBuffer-size}
37087 @cindex @samp{QTBuffer size} packet
37088 This packet directs the target to make the trace buffer be of size
37089 @var{size} if possible. A value of @code{-1} tells the target to
37090 use whatever size it prefers.
37092 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
37093 @cindex @samp{QTNotes} packet
37094 This packet adds optional textual notes to the trace run. Allowable
37095 types include @code{user}, @code{notes}, and @code{tstop}, the
37096 @var{text} fields are arbitrary strings, hex-encoded.
37100 @subsection Relocate instruction reply packet
37101 When installing fast tracepoints in memory, the target may need to
37102 relocate the instruction currently at the tracepoint address to a
37103 different address in memory. For most instructions, a simple copy is
37104 enough, but, for example, call instructions that implicitly push the
37105 return address on the stack, and relative branches or other
37106 PC-relative instructions require offset adjustment, so that the effect
37107 of executing the instruction at a different address is the same as if
37108 it had executed in the original location.
37110 In response to several of the tracepoint packets, the target may also
37111 respond with a number of intermediate @samp{qRelocInsn} request
37112 packets before the final result packet, to have @value{GDBN} handle
37113 this relocation operation. If a packet supports this mechanism, its
37114 documentation will explicitly say so. See for example the above
37115 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
37116 format of the request is:
37119 @item qRelocInsn:@var{from};@var{to}
37121 This requests @value{GDBN} to copy instruction at address @var{from}
37122 to address @var{to}, possibly adjusted so that executing the
37123 instruction at @var{to} has the same effect as executing it at
37124 @var{from}. @value{GDBN} writes the adjusted instruction to target
37125 memory starting at @var{to}.
37130 @item qRelocInsn:@var{adjusted_size}
37131 Informs the stub the relocation is complete. The @var{adjusted_size} is
37132 the length in bytes of resulting relocated instruction sequence.
37134 A badly formed request was detected, or an error was encountered while
37135 relocating the instruction.
37138 @node Host I/O Packets
37139 @section Host I/O Packets
37140 @cindex Host I/O, remote protocol
37141 @cindex file transfer, remote protocol
37143 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
37144 operations on the far side of a remote link. For example, Host I/O is
37145 used to upload and download files to a remote target with its own
37146 filesystem. Host I/O uses the same constant values and data structure
37147 layout as the target-initiated File-I/O protocol. However, the
37148 Host I/O packets are structured differently. The target-initiated
37149 protocol relies on target memory to store parameters and buffers.
37150 Host I/O requests are initiated by @value{GDBN}, and the
37151 target's memory is not involved. @xref{File-I/O Remote Protocol
37152 Extension}, for more details on the target-initiated protocol.
37154 The Host I/O request packets all encode a single operation along with
37155 its arguments. They have this format:
37159 @item vFile:@var{operation}: @var{parameter}@dots{}
37160 @var{operation} is the name of the particular request; the target
37161 should compare the entire packet name up to the second colon when checking
37162 for a supported operation. The format of @var{parameter} depends on
37163 the operation. Numbers are always passed in hexadecimal. Negative
37164 numbers have an explicit minus sign (i.e.@: two's complement is not
37165 used). Strings (e.g.@: filenames) are encoded as a series of
37166 hexadecimal bytes. The last argument to a system call may be a
37167 buffer of escaped binary data (@pxref{Binary Data}).
37171 The valid responses to Host I/O packets are:
37175 @item F @var{result} [, @var{errno}] [; @var{attachment}]
37176 @var{result} is the integer value returned by this operation, usually
37177 non-negative for success and -1 for errors. If an error has occured,
37178 @var{errno} will be included in the result specifying a
37179 value defined by the File-I/O protocol (@pxref{Errno Values}). For
37180 operations which return data, @var{attachment} supplies the data as a
37181 binary buffer. Binary buffers in response packets are escaped in the
37182 normal way (@pxref{Binary Data}). See the individual packet
37183 documentation for the interpretation of @var{result} and
37187 An empty response indicates that this operation is not recognized.
37191 These are the supported Host I/O operations:
37194 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
37195 Open a file at @var{filename} and return a file descriptor for it, or
37196 return -1 if an error occurs. The @var{filename} is a string,
37197 @var{flags} is an integer indicating a mask of open flags
37198 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
37199 of mode bits to use if the file is created (@pxref{mode_t Values}).
37200 @xref{open}, for details of the open flags and mode values.
37202 @item vFile:close: @var{fd}
37203 Close the open file corresponding to @var{fd} and return 0, or
37204 -1 if an error occurs.
37206 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
37207 Read data from the open file corresponding to @var{fd}. Up to
37208 @var{count} bytes will be read from the file, starting at @var{offset}
37209 relative to the start of the file. The target may read fewer bytes;
37210 common reasons include packet size limits and an end-of-file
37211 condition. The number of bytes read is returned. Zero should only be
37212 returned for a successful read at the end of the file, or if
37213 @var{count} was zero.
37215 The data read should be returned as a binary attachment on success.
37216 If zero bytes were read, the response should include an empty binary
37217 attachment (i.e.@: a trailing semicolon). The return value is the
37218 number of target bytes read; the binary attachment may be longer if
37219 some characters were escaped.
37221 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
37222 Write @var{data} (a binary buffer) to the open file corresponding
37223 to @var{fd}. Start the write at @var{offset} from the start of the
37224 file. Unlike many @code{write} system calls, there is no
37225 separate @var{count} argument; the length of @var{data} in the
37226 packet is used. @samp{vFile:write} returns the number of bytes written,
37227 which may be shorter than the length of @var{data}, or -1 if an
37230 @item vFile:unlink: @var{filename}
37231 Delete the file at @var{filename} on the target. Return 0,
37232 or -1 if an error occurs. The @var{filename} is a string.
37234 @item vFile:readlink: @var{filename}
37235 Read value of symbolic link @var{filename} on the target. Return
37236 the number of bytes read, or -1 if an error occurs.
37238 The data read should be returned as a binary attachment on success.
37239 If zero bytes were read, the response should include an empty binary
37240 attachment (i.e.@: a trailing semicolon). The return value is the
37241 number of target bytes read; the binary attachment may be longer if
37242 some characters were escaped.
37247 @section Interrupts
37248 @cindex interrupts (remote protocol)
37250 When a program on the remote target is running, @value{GDBN} may
37251 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
37252 a @code{BREAK} followed by @code{g},
37253 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
37255 The precise meaning of @code{BREAK} is defined by the transport
37256 mechanism and may, in fact, be undefined. @value{GDBN} does not
37257 currently define a @code{BREAK} mechanism for any of the network
37258 interfaces except for TCP, in which case @value{GDBN} sends the
37259 @code{telnet} BREAK sequence.
37261 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
37262 transport mechanisms. It is represented by sending the single byte
37263 @code{0x03} without any of the usual packet overhead described in
37264 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
37265 transmitted as part of a packet, it is considered to be packet data
37266 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
37267 (@pxref{X packet}), used for binary downloads, may include an unescaped
37268 @code{0x03} as part of its packet.
37270 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
37271 When Linux kernel receives this sequence from serial port,
37272 it stops execution and connects to gdb.
37274 Stubs are not required to recognize these interrupt mechanisms and the
37275 precise meaning associated with receipt of the interrupt is
37276 implementation defined. If the target supports debugging of multiple
37277 threads and/or processes, it should attempt to interrupt all
37278 currently-executing threads and processes.
37279 If the stub is successful at interrupting the
37280 running program, it should send one of the stop
37281 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
37282 of successfully stopping the program in all-stop mode, and a stop reply
37283 for each stopped thread in non-stop mode.
37284 Interrupts received while the
37285 program is stopped are discarded.
37287 @node Notification Packets
37288 @section Notification Packets
37289 @cindex notification packets
37290 @cindex packets, notification
37292 The @value{GDBN} remote serial protocol includes @dfn{notifications},
37293 packets that require no acknowledgment. Both the GDB and the stub
37294 may send notifications (although the only notifications defined at
37295 present are sent by the stub). Notifications carry information
37296 without incurring the round-trip latency of an acknowledgment, and so
37297 are useful for low-impact communications where occasional packet loss
37300 A notification packet has the form @samp{% @var{data} #
37301 @var{checksum}}, where @var{data} is the content of the notification,
37302 and @var{checksum} is a checksum of @var{data}, computed and formatted
37303 as for ordinary @value{GDBN} packets. A notification's @var{data}
37304 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
37305 receiving a notification, the recipient sends no @samp{+} or @samp{-}
37306 to acknowledge the notification's receipt or to report its corruption.
37308 Every notification's @var{data} begins with a name, which contains no
37309 colon characters, followed by a colon character.
37311 Recipients should silently ignore corrupted notifications and
37312 notifications they do not understand. Recipients should restart
37313 timeout periods on receipt of a well-formed notification, whether or
37314 not they understand it.
37316 Senders should only send the notifications described here when this
37317 protocol description specifies that they are permitted. In the
37318 future, we may extend the protocol to permit existing notifications in
37319 new contexts; this rule helps older senders avoid confusing newer
37322 (Older versions of @value{GDBN} ignore bytes received until they see
37323 the @samp{$} byte that begins an ordinary packet, so new stubs may
37324 transmit notifications without fear of confusing older clients. There
37325 are no notifications defined for @value{GDBN} to send at the moment, but we
37326 assume that most older stubs would ignore them, as well.)
37328 Each notification is comprised of three parts:
37330 @item @var{name}:@var{event}
37331 The notification packet is sent by the side that initiates the
37332 exchange (currently, only the stub does that), with @var{event}
37333 carrying the specific information about the notification, and
37334 @var{name} specifying the name of the notification.
37336 The acknowledge sent by the other side, usually @value{GDBN}, to
37337 acknowledge the exchange and request the event.
37340 The purpose of an asynchronous notification mechanism is to report to
37341 @value{GDBN} that something interesting happened in the remote stub.
37343 The remote stub may send notification @var{name}:@var{event}
37344 at any time, but @value{GDBN} acknowledges the notification when
37345 appropriate. The notification event is pending before @value{GDBN}
37346 acknowledges. Only one notification at a time may be pending; if
37347 additional events occur before @value{GDBN} has acknowledged the
37348 previous notification, they must be queued by the stub for later
37349 synchronous transmission in response to @var{ack} packets from
37350 @value{GDBN}. Because the notification mechanism is unreliable,
37351 the stub is permitted to resend a notification if it believes
37352 @value{GDBN} may not have received it.
37354 Specifically, notifications may appear when @value{GDBN} is not
37355 otherwise reading input from the stub, or when @value{GDBN} is
37356 expecting to read a normal synchronous response or a
37357 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
37358 Notification packets are distinct from any other communication from
37359 the stub so there is no ambiguity.
37361 After receiving a notification, @value{GDBN} shall acknowledge it by
37362 sending a @var{ack} packet as a regular, synchronous request to the
37363 stub. Such acknowledgment is not required to happen immediately, as
37364 @value{GDBN} is permitted to send other, unrelated packets to the
37365 stub first, which the stub should process normally.
37367 Upon receiving a @var{ack} packet, if the stub has other queued
37368 events to report to @value{GDBN}, it shall respond by sending a
37369 normal @var{event}. @value{GDBN} shall then send another @var{ack}
37370 packet to solicit further responses; again, it is permitted to send
37371 other, unrelated packets as well which the stub should process
37374 If the stub receives a @var{ack} packet and there are no additional
37375 @var{event} to report, the stub shall return an @samp{OK} response.
37376 At this point, @value{GDBN} has finished processing a notification
37377 and the stub has completed sending any queued events. @value{GDBN}
37378 won't accept any new notifications until the final @samp{OK} is
37379 received . If further notification events occur, the stub shall send
37380 a new notification, @value{GDBN} shall accept the notification, and
37381 the process shall be repeated.
37383 The process of asynchronous notification can be illustrated by the
37386 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
37389 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
37391 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
37396 The following notifications are defined:
37397 @multitable @columnfractions 0.12 0.12 0.38 0.38
37406 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
37407 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
37408 for information on how these notifications are acknowledged by
37410 @tab Report an asynchronous stop event in non-stop mode.
37414 @node Remote Non-Stop
37415 @section Remote Protocol Support for Non-Stop Mode
37417 @value{GDBN}'s remote protocol supports non-stop debugging of
37418 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
37419 supports non-stop mode, it should report that to @value{GDBN} by including
37420 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
37422 @value{GDBN} typically sends a @samp{QNonStop} packet only when
37423 establishing a new connection with the stub. Entering non-stop mode
37424 does not alter the state of any currently-running threads, but targets
37425 must stop all threads in any already-attached processes when entering
37426 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
37427 probe the target state after a mode change.
37429 In non-stop mode, when an attached process encounters an event that
37430 would otherwise be reported with a stop reply, it uses the
37431 asynchronous notification mechanism (@pxref{Notification Packets}) to
37432 inform @value{GDBN}. In contrast to all-stop mode, where all threads
37433 in all processes are stopped when a stop reply is sent, in non-stop
37434 mode only the thread reporting the stop event is stopped. That is,
37435 when reporting a @samp{S} or @samp{T} response to indicate completion
37436 of a step operation, hitting a breakpoint, or a fault, only the
37437 affected thread is stopped; any other still-running threads continue
37438 to run. When reporting a @samp{W} or @samp{X} response, all running
37439 threads belonging to other attached processes continue to run.
37441 In non-stop mode, the target shall respond to the @samp{?} packet as
37442 follows. First, any incomplete stop reply notification/@samp{vStopped}
37443 sequence in progress is abandoned. The target must begin a new
37444 sequence reporting stop events for all stopped threads, whether or not
37445 it has previously reported those events to @value{GDBN}. The first
37446 stop reply is sent as a synchronous reply to the @samp{?} packet, and
37447 subsequent stop replies are sent as responses to @samp{vStopped} packets
37448 using the mechanism described above. The target must not send
37449 asynchronous stop reply notifications until the sequence is complete.
37450 If all threads are running when the target receives the @samp{?} packet,
37451 or if the target is not attached to any process, it shall respond
37454 @node Packet Acknowledgment
37455 @section Packet Acknowledgment
37457 @cindex acknowledgment, for @value{GDBN} remote
37458 @cindex packet acknowledgment, for @value{GDBN} remote
37459 By default, when either the host or the target machine receives a packet,
37460 the first response expected is an acknowledgment: either @samp{+} (to indicate
37461 the package was received correctly) or @samp{-} (to request retransmission).
37462 This mechanism allows the @value{GDBN} remote protocol to operate over
37463 unreliable transport mechanisms, such as a serial line.
37465 In cases where the transport mechanism is itself reliable (such as a pipe or
37466 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
37467 It may be desirable to disable them in that case to reduce communication
37468 overhead, or for other reasons. This can be accomplished by means of the
37469 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
37471 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
37472 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
37473 and response format still includes the normal checksum, as described in
37474 @ref{Overview}, but the checksum may be ignored by the receiver.
37476 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
37477 no-acknowledgment mode, it should report that to @value{GDBN}
37478 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
37479 @pxref{qSupported}.
37480 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
37481 disabled via the @code{set remote noack-packet off} command
37482 (@pxref{Remote Configuration}),
37483 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
37484 Only then may the stub actually turn off packet acknowledgments.
37485 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
37486 response, which can be safely ignored by the stub.
37488 Note that @code{set remote noack-packet} command only affects negotiation
37489 between @value{GDBN} and the stub when subsequent connections are made;
37490 it does not affect the protocol acknowledgment state for any current
37492 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
37493 new connection is established,
37494 there is also no protocol request to re-enable the acknowledgments
37495 for the current connection, once disabled.
37500 Example sequence of a target being re-started. Notice how the restart
37501 does not get any direct output:
37506 @emph{target restarts}
37509 <- @code{T001:1234123412341234}
37513 Example sequence of a target being stepped by a single instruction:
37516 -> @code{G1445@dots{}}
37521 <- @code{T001:1234123412341234}
37525 <- @code{1455@dots{}}
37529 @node File-I/O Remote Protocol Extension
37530 @section File-I/O Remote Protocol Extension
37531 @cindex File-I/O remote protocol extension
37534 * File-I/O Overview::
37535 * Protocol Basics::
37536 * The F Request Packet::
37537 * The F Reply Packet::
37538 * The Ctrl-C Message::
37540 * List of Supported Calls::
37541 * Protocol-specific Representation of Datatypes::
37543 * File-I/O Examples::
37546 @node File-I/O Overview
37547 @subsection File-I/O Overview
37548 @cindex file-i/o overview
37550 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
37551 target to use the host's file system and console I/O to perform various
37552 system calls. System calls on the target system are translated into a
37553 remote protocol packet to the host system, which then performs the needed
37554 actions and returns a response packet to the target system.
37555 This simulates file system operations even on targets that lack file systems.
37557 The protocol is defined to be independent of both the host and target systems.
37558 It uses its own internal representation of datatypes and values. Both
37559 @value{GDBN} and the target's @value{GDBN} stub are responsible for
37560 translating the system-dependent value representations into the internal
37561 protocol representations when data is transmitted.
37563 The communication is synchronous. A system call is possible only when
37564 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
37565 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
37566 the target is stopped to allow deterministic access to the target's
37567 memory. Therefore File-I/O is not interruptible by target signals. On
37568 the other hand, it is possible to interrupt File-I/O by a user interrupt
37569 (@samp{Ctrl-C}) within @value{GDBN}.
37571 The target's request to perform a host system call does not finish
37572 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
37573 after finishing the system call, the target returns to continuing the
37574 previous activity (continue, step). No additional continue or step
37575 request from @value{GDBN} is required.
37578 (@value{GDBP}) continue
37579 <- target requests 'system call X'
37580 target is stopped, @value{GDBN} executes system call
37581 -> @value{GDBN} returns result
37582 ... target continues, @value{GDBN} returns to wait for the target
37583 <- target hits breakpoint and sends a Txx packet
37586 The protocol only supports I/O on the console and to regular files on
37587 the host file system. Character or block special devices, pipes,
37588 named pipes, sockets or any other communication method on the host
37589 system are not supported by this protocol.
37591 File I/O is not supported in non-stop mode.
37593 @node Protocol Basics
37594 @subsection Protocol Basics
37595 @cindex protocol basics, file-i/o
37597 The File-I/O protocol uses the @code{F} packet as the request as well
37598 as reply packet. Since a File-I/O system call can only occur when
37599 @value{GDBN} is waiting for a response from the continuing or stepping target,
37600 the File-I/O request is a reply that @value{GDBN} has to expect as a result
37601 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
37602 This @code{F} packet contains all information needed to allow @value{GDBN}
37603 to call the appropriate host system call:
37607 A unique identifier for the requested system call.
37610 All parameters to the system call. Pointers are given as addresses
37611 in the target memory address space. Pointers to strings are given as
37612 pointer/length pair. Numerical values are given as they are.
37613 Numerical control flags are given in a protocol-specific representation.
37617 At this point, @value{GDBN} has to perform the following actions.
37621 If the parameters include pointer values to data needed as input to a
37622 system call, @value{GDBN} requests this data from the target with a
37623 standard @code{m} packet request. This additional communication has to be
37624 expected by the target implementation and is handled as any other @code{m}
37628 @value{GDBN} translates all value from protocol representation to host
37629 representation as needed. Datatypes are coerced into the host types.
37632 @value{GDBN} calls the system call.
37635 It then coerces datatypes back to protocol representation.
37638 If the system call is expected to return data in buffer space specified
37639 by pointer parameters to the call, the data is transmitted to the
37640 target using a @code{M} or @code{X} packet. This packet has to be expected
37641 by the target implementation and is handled as any other @code{M} or @code{X}
37646 Eventually @value{GDBN} replies with another @code{F} packet which contains all
37647 necessary information for the target to continue. This at least contains
37654 @code{errno}, if has been changed by the system call.
37661 After having done the needed type and value coercion, the target continues
37662 the latest continue or step action.
37664 @node The F Request Packet
37665 @subsection The @code{F} Request Packet
37666 @cindex file-i/o request packet
37667 @cindex @code{F} request packet
37669 The @code{F} request packet has the following format:
37672 @item F@var{call-id},@var{parameter@dots{}}
37674 @var{call-id} is the identifier to indicate the host system call to be called.
37675 This is just the name of the function.
37677 @var{parameter@dots{}} are the parameters to the system call.
37678 Parameters are hexadecimal integer values, either the actual values in case
37679 of scalar datatypes, pointers to target buffer space in case of compound
37680 datatypes and unspecified memory areas, or pointer/length pairs in case
37681 of string parameters. These are appended to the @var{call-id} as a
37682 comma-delimited list. All values are transmitted in ASCII
37683 string representation, pointer/length pairs separated by a slash.
37689 @node The F Reply Packet
37690 @subsection The @code{F} Reply Packet
37691 @cindex file-i/o reply packet
37692 @cindex @code{F} reply packet
37694 The @code{F} reply packet has the following format:
37698 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
37700 @var{retcode} is the return code of the system call as hexadecimal value.
37702 @var{errno} is the @code{errno} set by the call, in protocol-specific
37704 This parameter can be omitted if the call was successful.
37706 @var{Ctrl-C flag} is only sent if the user requested a break. In this
37707 case, @var{errno} must be sent as well, even if the call was successful.
37708 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
37715 or, if the call was interrupted before the host call has been performed:
37722 assuming 4 is the protocol-specific representation of @code{EINTR}.
37727 @node The Ctrl-C Message
37728 @subsection The @samp{Ctrl-C} Message
37729 @cindex ctrl-c message, in file-i/o protocol
37731 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
37732 reply packet (@pxref{The F Reply Packet}),
37733 the target should behave as if it had
37734 gotten a break message. The meaning for the target is ``system call
37735 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
37736 (as with a break message) and return to @value{GDBN} with a @code{T02}
37739 It's important for the target to know in which
37740 state the system call was interrupted. There are two possible cases:
37744 The system call hasn't been performed on the host yet.
37747 The system call on the host has been finished.
37751 These two states can be distinguished by the target by the value of the
37752 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
37753 call hasn't been performed. This is equivalent to the @code{EINTR} handling
37754 on POSIX systems. In any other case, the target may presume that the
37755 system call has been finished --- successfully or not --- and should behave
37756 as if the break message arrived right after the system call.
37758 @value{GDBN} must behave reliably. If the system call has not been called
37759 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
37760 @code{errno} in the packet. If the system call on the host has been finished
37761 before the user requests a break, the full action must be finished by
37762 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
37763 The @code{F} packet may only be sent when either nothing has happened
37764 or the full action has been completed.
37767 @subsection Console I/O
37768 @cindex console i/o as part of file-i/o
37770 By default and if not explicitly closed by the target system, the file
37771 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
37772 on the @value{GDBN} console is handled as any other file output operation
37773 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
37774 by @value{GDBN} so that after the target read request from file descriptor
37775 0 all following typing is buffered until either one of the following
37780 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
37782 system call is treated as finished.
37785 The user presses @key{RET}. This is treated as end of input with a trailing
37789 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
37790 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
37794 If the user has typed more characters than fit in the buffer given to
37795 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
37796 either another @code{read(0, @dots{})} is requested by the target, or debugging
37797 is stopped at the user's request.
37800 @node List of Supported Calls
37801 @subsection List of Supported Calls
37802 @cindex list of supported file-i/o calls
37819 @unnumberedsubsubsec open
37820 @cindex open, file-i/o system call
37825 int open(const char *pathname, int flags);
37826 int open(const char *pathname, int flags, mode_t mode);
37830 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
37833 @var{flags} is the bitwise @code{OR} of the following values:
37837 If the file does not exist it will be created. The host
37838 rules apply as far as file ownership and time stamps
37842 When used with @code{O_CREAT}, if the file already exists it is
37843 an error and open() fails.
37846 If the file already exists and the open mode allows
37847 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
37848 truncated to zero length.
37851 The file is opened in append mode.
37854 The file is opened for reading only.
37857 The file is opened for writing only.
37860 The file is opened for reading and writing.
37864 Other bits are silently ignored.
37868 @var{mode} is the bitwise @code{OR} of the following values:
37872 User has read permission.
37875 User has write permission.
37878 Group has read permission.
37881 Group has write permission.
37884 Others have read permission.
37887 Others have write permission.
37891 Other bits are silently ignored.
37894 @item Return value:
37895 @code{open} returns the new file descriptor or -1 if an error
37902 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
37905 @var{pathname} refers to a directory.
37908 The requested access is not allowed.
37911 @var{pathname} was too long.
37914 A directory component in @var{pathname} does not exist.
37917 @var{pathname} refers to a device, pipe, named pipe or socket.
37920 @var{pathname} refers to a file on a read-only filesystem and
37921 write access was requested.
37924 @var{pathname} is an invalid pointer value.
37927 No space on device to create the file.
37930 The process already has the maximum number of files open.
37933 The limit on the total number of files open on the system
37937 The call was interrupted by the user.
37943 @unnumberedsubsubsec close
37944 @cindex close, file-i/o system call
37953 @samp{Fclose,@var{fd}}
37955 @item Return value:
37956 @code{close} returns zero on success, or -1 if an error occurred.
37962 @var{fd} isn't a valid open file descriptor.
37965 The call was interrupted by the user.
37971 @unnumberedsubsubsec read
37972 @cindex read, file-i/o system call
37977 int read(int fd, void *buf, unsigned int count);
37981 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
37983 @item Return value:
37984 On success, the number of bytes read is returned.
37985 Zero indicates end of file. If count is zero, read
37986 returns zero as well. On error, -1 is returned.
37992 @var{fd} is not a valid file descriptor or is not open for
37996 @var{bufptr} is an invalid pointer value.
37999 The call was interrupted by the user.
38005 @unnumberedsubsubsec write
38006 @cindex write, file-i/o system call
38011 int write(int fd, const void *buf, unsigned int count);
38015 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
38017 @item Return value:
38018 On success, the number of bytes written are returned.
38019 Zero indicates nothing was written. On error, -1
38026 @var{fd} is not a valid file descriptor or is not open for
38030 @var{bufptr} is an invalid pointer value.
38033 An attempt was made to write a file that exceeds the
38034 host-specific maximum file size allowed.
38037 No space on device to write the data.
38040 The call was interrupted by the user.
38046 @unnumberedsubsubsec lseek
38047 @cindex lseek, file-i/o system call
38052 long lseek (int fd, long offset, int flag);
38056 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
38058 @var{flag} is one of:
38062 The offset is set to @var{offset} bytes.
38065 The offset is set to its current location plus @var{offset}
38069 The offset is set to the size of the file plus @var{offset}
38073 @item Return value:
38074 On success, the resulting unsigned offset in bytes from
38075 the beginning of the file is returned. Otherwise, a
38076 value of -1 is returned.
38082 @var{fd} is not a valid open file descriptor.
38085 @var{fd} is associated with the @value{GDBN} console.
38088 @var{flag} is not a proper value.
38091 The call was interrupted by the user.
38097 @unnumberedsubsubsec rename
38098 @cindex rename, file-i/o system call
38103 int rename(const char *oldpath, const char *newpath);
38107 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
38109 @item Return value:
38110 On success, zero is returned. On error, -1 is returned.
38116 @var{newpath} is an existing directory, but @var{oldpath} is not a
38120 @var{newpath} is a non-empty directory.
38123 @var{oldpath} or @var{newpath} is a directory that is in use by some
38127 An attempt was made to make a directory a subdirectory
38131 A component used as a directory in @var{oldpath} or new
38132 path is not a directory. Or @var{oldpath} is a directory
38133 and @var{newpath} exists but is not a directory.
38136 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
38139 No access to the file or the path of the file.
38143 @var{oldpath} or @var{newpath} was too long.
38146 A directory component in @var{oldpath} or @var{newpath} does not exist.
38149 The file is on a read-only filesystem.
38152 The device containing the file has no room for the new
38156 The call was interrupted by the user.
38162 @unnumberedsubsubsec unlink
38163 @cindex unlink, file-i/o system call
38168 int unlink(const char *pathname);
38172 @samp{Funlink,@var{pathnameptr}/@var{len}}
38174 @item Return value:
38175 On success, zero is returned. On error, -1 is returned.
38181 No access to the file or the path of the file.
38184 The system does not allow unlinking of directories.
38187 The file @var{pathname} cannot be unlinked because it's
38188 being used by another process.
38191 @var{pathnameptr} is an invalid pointer value.
38194 @var{pathname} was too long.
38197 A directory component in @var{pathname} does not exist.
38200 A component of the path is not a directory.
38203 The file is on a read-only filesystem.
38206 The call was interrupted by the user.
38212 @unnumberedsubsubsec stat/fstat
38213 @cindex fstat, file-i/o system call
38214 @cindex stat, file-i/o system call
38219 int stat(const char *pathname, struct stat *buf);
38220 int fstat(int fd, struct stat *buf);
38224 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
38225 @samp{Ffstat,@var{fd},@var{bufptr}}
38227 @item Return value:
38228 On success, zero is returned. On error, -1 is returned.
38234 @var{fd} is not a valid open file.
38237 A directory component in @var{pathname} does not exist or the
38238 path is an empty string.
38241 A component of the path is not a directory.
38244 @var{pathnameptr} is an invalid pointer value.
38247 No access to the file or the path of the file.
38250 @var{pathname} was too long.
38253 The call was interrupted by the user.
38259 @unnumberedsubsubsec gettimeofday
38260 @cindex gettimeofday, file-i/o system call
38265 int gettimeofday(struct timeval *tv, void *tz);
38269 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
38271 @item Return value:
38272 On success, 0 is returned, -1 otherwise.
38278 @var{tz} is a non-NULL pointer.
38281 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
38287 @unnumberedsubsubsec isatty
38288 @cindex isatty, file-i/o system call
38293 int isatty(int fd);
38297 @samp{Fisatty,@var{fd}}
38299 @item Return value:
38300 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
38306 The call was interrupted by the user.
38311 Note that the @code{isatty} call is treated as a special case: it returns
38312 1 to the target if the file descriptor is attached
38313 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
38314 would require implementing @code{ioctl} and would be more complex than
38319 @unnumberedsubsubsec system
38320 @cindex system, file-i/o system call
38325 int system(const char *command);
38329 @samp{Fsystem,@var{commandptr}/@var{len}}
38331 @item Return value:
38332 If @var{len} is zero, the return value indicates whether a shell is
38333 available. A zero return value indicates a shell is not available.
38334 For non-zero @var{len}, the value returned is -1 on error and the
38335 return status of the command otherwise. Only the exit status of the
38336 command is returned, which is extracted from the host's @code{system}
38337 return value by calling @code{WEXITSTATUS(retval)}. In case
38338 @file{/bin/sh} could not be executed, 127 is returned.
38344 The call was interrupted by the user.
38349 @value{GDBN} takes over the full task of calling the necessary host calls
38350 to perform the @code{system} call. The return value of @code{system} on
38351 the host is simplified before it's returned
38352 to the target. Any termination signal information from the child process
38353 is discarded, and the return value consists
38354 entirely of the exit status of the called command.
38356 Due to security concerns, the @code{system} call is by default refused
38357 by @value{GDBN}. The user has to allow this call explicitly with the
38358 @code{set remote system-call-allowed 1} command.
38361 @item set remote system-call-allowed
38362 @kindex set remote system-call-allowed
38363 Control whether to allow the @code{system} calls in the File I/O
38364 protocol for the remote target. The default is zero (disabled).
38366 @item show remote system-call-allowed
38367 @kindex show remote system-call-allowed
38368 Show whether the @code{system} calls are allowed in the File I/O
38372 @node Protocol-specific Representation of Datatypes
38373 @subsection Protocol-specific Representation of Datatypes
38374 @cindex protocol-specific representation of datatypes, in file-i/o protocol
38377 * Integral Datatypes::
38379 * Memory Transfer::
38384 @node Integral Datatypes
38385 @unnumberedsubsubsec Integral Datatypes
38386 @cindex integral datatypes, in file-i/o protocol
38388 The integral datatypes used in the system calls are @code{int},
38389 @code{unsigned int}, @code{long}, @code{unsigned long},
38390 @code{mode_t}, and @code{time_t}.
38392 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
38393 implemented as 32 bit values in this protocol.
38395 @code{long} and @code{unsigned long} are implemented as 64 bit types.
38397 @xref{Limits}, for corresponding MIN and MAX values (similar to those
38398 in @file{limits.h}) to allow range checking on host and target.
38400 @code{time_t} datatypes are defined as seconds since the Epoch.
38402 All integral datatypes transferred as part of a memory read or write of a
38403 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
38406 @node Pointer Values
38407 @unnumberedsubsubsec Pointer Values
38408 @cindex pointer values, in file-i/o protocol
38410 Pointers to target data are transmitted as they are. An exception
38411 is made for pointers to buffers for which the length isn't
38412 transmitted as part of the function call, namely strings. Strings
38413 are transmitted as a pointer/length pair, both as hex values, e.g.@:
38420 which is a pointer to data of length 18 bytes at position 0x1aaf.
38421 The length is defined as the full string length in bytes, including
38422 the trailing null byte. For example, the string @code{"hello world"}
38423 at address 0x123456 is transmitted as
38429 @node Memory Transfer
38430 @unnumberedsubsubsec Memory Transfer
38431 @cindex memory transfer, in file-i/o protocol
38433 Structured data which is transferred using a memory read or write (for
38434 example, a @code{struct stat}) is expected to be in a protocol-specific format
38435 with all scalar multibyte datatypes being big endian. Translation to
38436 this representation needs to be done both by the target before the @code{F}
38437 packet is sent, and by @value{GDBN} before
38438 it transfers memory to the target. Transferred pointers to structured
38439 data should point to the already-coerced data at any time.
38443 @unnumberedsubsubsec struct stat
38444 @cindex struct stat, in file-i/o protocol
38446 The buffer of type @code{struct stat} used by the target and @value{GDBN}
38447 is defined as follows:
38451 unsigned int st_dev; /* device */
38452 unsigned int st_ino; /* inode */
38453 mode_t st_mode; /* protection */
38454 unsigned int st_nlink; /* number of hard links */
38455 unsigned int st_uid; /* user ID of owner */
38456 unsigned int st_gid; /* group ID of owner */
38457 unsigned int st_rdev; /* device type (if inode device) */
38458 unsigned long st_size; /* total size, in bytes */
38459 unsigned long st_blksize; /* blocksize for filesystem I/O */
38460 unsigned long st_blocks; /* number of blocks allocated */
38461 time_t st_atime; /* time of last access */
38462 time_t st_mtime; /* time of last modification */
38463 time_t st_ctime; /* time of last change */
38467 The integral datatypes conform to the definitions given in the
38468 appropriate section (see @ref{Integral Datatypes}, for details) so this
38469 structure is of size 64 bytes.
38471 The values of several fields have a restricted meaning and/or
38477 A value of 0 represents a file, 1 the console.
38480 No valid meaning for the target. Transmitted unchanged.
38483 Valid mode bits are described in @ref{Constants}. Any other
38484 bits have currently no meaning for the target.
38489 No valid meaning for the target. Transmitted unchanged.
38494 These values have a host and file system dependent
38495 accuracy. Especially on Windows hosts, the file system may not
38496 support exact timing values.
38499 The target gets a @code{struct stat} of the above representation and is
38500 responsible for coercing it to the target representation before
38503 Note that due to size differences between the host, target, and protocol
38504 representations of @code{struct stat} members, these members could eventually
38505 get truncated on the target.
38507 @node struct timeval
38508 @unnumberedsubsubsec struct timeval
38509 @cindex struct timeval, in file-i/o protocol
38511 The buffer of type @code{struct timeval} used by the File-I/O protocol
38512 is defined as follows:
38516 time_t tv_sec; /* second */
38517 long tv_usec; /* microsecond */
38521 The integral datatypes conform to the definitions given in the
38522 appropriate section (see @ref{Integral Datatypes}, for details) so this
38523 structure is of size 8 bytes.
38526 @subsection Constants
38527 @cindex constants, in file-i/o protocol
38529 The following values are used for the constants inside of the
38530 protocol. @value{GDBN} and target are responsible for translating these
38531 values before and after the call as needed.
38542 @unnumberedsubsubsec Open Flags
38543 @cindex open flags, in file-i/o protocol
38545 All values are given in hexadecimal representation.
38557 @node mode_t Values
38558 @unnumberedsubsubsec mode_t Values
38559 @cindex mode_t values, in file-i/o protocol
38561 All values are given in octal representation.
38578 @unnumberedsubsubsec Errno Values
38579 @cindex errno values, in file-i/o protocol
38581 All values are given in decimal representation.
38606 @code{EUNKNOWN} is used as a fallback error value if a host system returns
38607 any error value not in the list of supported error numbers.
38610 @unnumberedsubsubsec Lseek Flags
38611 @cindex lseek flags, in file-i/o protocol
38620 @unnumberedsubsubsec Limits
38621 @cindex limits, in file-i/o protocol
38623 All values are given in decimal representation.
38626 INT_MIN -2147483648
38628 UINT_MAX 4294967295
38629 LONG_MIN -9223372036854775808
38630 LONG_MAX 9223372036854775807
38631 ULONG_MAX 18446744073709551615
38634 @node File-I/O Examples
38635 @subsection File-I/O Examples
38636 @cindex file-i/o examples
38638 Example sequence of a write call, file descriptor 3, buffer is at target
38639 address 0x1234, 6 bytes should be written:
38642 <- @code{Fwrite,3,1234,6}
38643 @emph{request memory read from target}
38646 @emph{return "6 bytes written"}
38650 Example sequence of a read call, file descriptor 3, buffer is at target
38651 address 0x1234, 6 bytes should be read:
38654 <- @code{Fread,3,1234,6}
38655 @emph{request memory write to target}
38656 -> @code{X1234,6:XXXXXX}
38657 @emph{return "6 bytes read"}
38661 Example sequence of a read call, call fails on the host due to invalid
38662 file descriptor (@code{EBADF}):
38665 <- @code{Fread,3,1234,6}
38669 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
38673 <- @code{Fread,3,1234,6}
38678 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
38682 <- @code{Fread,3,1234,6}
38683 -> @code{X1234,6:XXXXXX}
38687 @node Library List Format
38688 @section Library List Format
38689 @cindex library list format, remote protocol
38691 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
38692 same process as your application to manage libraries. In this case,
38693 @value{GDBN} can use the loader's symbol table and normal memory
38694 operations to maintain a list of shared libraries. On other
38695 platforms, the operating system manages loaded libraries.
38696 @value{GDBN} can not retrieve the list of currently loaded libraries
38697 through memory operations, so it uses the @samp{qXfer:libraries:read}
38698 packet (@pxref{qXfer library list read}) instead. The remote stub
38699 queries the target's operating system and reports which libraries
38702 The @samp{qXfer:libraries:read} packet returns an XML document which
38703 lists loaded libraries and their offsets. Each library has an
38704 associated name and one or more segment or section base addresses,
38705 which report where the library was loaded in memory.
38707 For the common case of libraries that are fully linked binaries, the
38708 library should have a list of segments. If the target supports
38709 dynamic linking of a relocatable object file, its library XML element
38710 should instead include a list of allocated sections. The segment or
38711 section bases are start addresses, not relocation offsets; they do not
38712 depend on the library's link-time base addresses.
38714 @value{GDBN} must be linked with the Expat library to support XML
38715 library lists. @xref{Expat}.
38717 A simple memory map, with one loaded library relocated by a single
38718 offset, looks like this:
38722 <library name="/lib/libc.so.6">
38723 <segment address="0x10000000"/>
38728 Another simple memory map, with one loaded library with three
38729 allocated sections (.text, .data, .bss), looks like this:
38733 <library name="sharedlib.o">
38734 <section address="0x10000000"/>
38735 <section address="0x20000000"/>
38736 <section address="0x30000000"/>
38741 The format of a library list is described by this DTD:
38744 <!-- library-list: Root element with versioning -->
38745 <!ELEMENT library-list (library)*>
38746 <!ATTLIST library-list version CDATA #FIXED "1.0">
38747 <!ELEMENT library (segment*, section*)>
38748 <!ATTLIST library name CDATA #REQUIRED>
38749 <!ELEMENT segment EMPTY>
38750 <!ATTLIST segment address CDATA #REQUIRED>
38751 <!ELEMENT section EMPTY>
38752 <!ATTLIST section address CDATA #REQUIRED>
38755 In addition, segments and section descriptors cannot be mixed within a
38756 single library element, and you must supply at least one segment or
38757 section for each library.
38759 @node Library List Format for SVR4 Targets
38760 @section Library List Format for SVR4 Targets
38761 @cindex library list format, remote protocol
38763 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
38764 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
38765 shared libraries. Still a special library list provided by this packet is
38766 more efficient for the @value{GDBN} remote protocol.
38768 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
38769 loaded libraries and their SVR4 linker parameters. For each library on SVR4
38770 target, the following parameters are reported:
38774 @code{name}, the absolute file name from the @code{l_name} field of
38775 @code{struct link_map}.
38777 @code{lm} with address of @code{struct link_map} used for TLS
38778 (Thread Local Storage) access.
38780 @code{l_addr}, the displacement as read from the field @code{l_addr} of
38781 @code{struct link_map}. For prelinked libraries this is not an absolute
38782 memory address. It is a displacement of absolute memory address against
38783 address the file was prelinked to during the library load.
38785 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
38788 Additionally the single @code{main-lm} attribute specifies address of
38789 @code{struct link_map} used for the main executable. This parameter is used
38790 for TLS access and its presence is optional.
38792 @value{GDBN} must be linked with the Expat library to support XML
38793 SVR4 library lists. @xref{Expat}.
38795 A simple memory map, with two loaded libraries (which do not use prelink),
38799 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
38800 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
38802 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
38804 </library-list-svr>
38807 The format of an SVR4 library list is described by this DTD:
38810 <!-- library-list-svr4: Root element with versioning -->
38811 <!ELEMENT library-list-svr4 (library)*>
38812 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
38813 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
38814 <!ELEMENT library EMPTY>
38815 <!ATTLIST library name CDATA #REQUIRED>
38816 <!ATTLIST library lm CDATA #REQUIRED>
38817 <!ATTLIST library l_addr CDATA #REQUIRED>
38818 <!ATTLIST library l_ld CDATA #REQUIRED>
38821 @node Memory Map Format
38822 @section Memory Map Format
38823 @cindex memory map format
38825 To be able to write into flash memory, @value{GDBN} needs to obtain a
38826 memory map from the target. This section describes the format of the
38829 The memory map is obtained using the @samp{qXfer:memory-map:read}
38830 (@pxref{qXfer memory map read}) packet and is an XML document that
38831 lists memory regions.
38833 @value{GDBN} must be linked with the Expat library to support XML
38834 memory maps. @xref{Expat}.
38836 The top-level structure of the document is shown below:
38839 <?xml version="1.0"?>
38840 <!DOCTYPE memory-map
38841 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
38842 "http://sourceware.org/gdb/gdb-memory-map.dtd">
38848 Each region can be either:
38853 A region of RAM starting at @var{addr} and extending for @var{length}
38857 <memory type="ram" start="@var{addr}" length="@var{length}"/>
38862 A region of read-only memory:
38865 <memory type="rom" start="@var{addr}" length="@var{length}"/>
38870 A region of flash memory, with erasure blocks @var{blocksize}
38874 <memory type="flash" start="@var{addr}" length="@var{length}">
38875 <property name="blocksize">@var{blocksize}</property>
38881 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
38882 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
38883 packets to write to addresses in such ranges.
38885 The formal DTD for memory map format is given below:
38888 <!-- ................................................... -->
38889 <!-- Memory Map XML DTD ................................ -->
38890 <!-- File: memory-map.dtd .............................. -->
38891 <!-- .................................... .............. -->
38892 <!-- memory-map.dtd -->
38893 <!-- memory-map: Root element with versioning -->
38894 <!ELEMENT memory-map (memory | property)>
38895 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
38896 <!ELEMENT memory (property)>
38897 <!-- memory: Specifies a memory region,
38898 and its type, or device. -->
38899 <!ATTLIST memory type CDATA #REQUIRED
38900 start CDATA #REQUIRED
38901 length CDATA #REQUIRED
38902 device CDATA #IMPLIED>
38903 <!-- property: Generic attribute tag -->
38904 <!ELEMENT property (#PCDATA | property)*>
38905 <!ATTLIST property name CDATA #REQUIRED>
38908 @node Thread List Format
38909 @section Thread List Format
38910 @cindex thread list format
38912 To efficiently update the list of threads and their attributes,
38913 @value{GDBN} issues the @samp{qXfer:threads:read} packet
38914 (@pxref{qXfer threads read}) and obtains the XML document with
38915 the following structure:
38918 <?xml version="1.0"?>
38920 <thread id="id" core="0">
38921 ... description ...
38926 Each @samp{thread} element must have the @samp{id} attribute that
38927 identifies the thread (@pxref{thread-id syntax}). The
38928 @samp{core} attribute, if present, specifies which processor core
38929 the thread was last executing on. The content of the of @samp{thread}
38930 element is interpreted as human-readable auxilliary information.
38932 @node Traceframe Info Format
38933 @section Traceframe Info Format
38934 @cindex traceframe info format
38936 To be able to know which objects in the inferior can be examined when
38937 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
38938 memory ranges, registers and trace state variables that have been
38939 collected in a traceframe.
38941 This list is obtained using the @samp{qXfer:traceframe-info:read}
38942 (@pxref{qXfer traceframe info read}) packet and is an XML document.
38944 @value{GDBN} must be linked with the Expat library to support XML
38945 traceframe info discovery. @xref{Expat}.
38947 The top-level structure of the document is shown below:
38950 <?xml version="1.0"?>
38951 <!DOCTYPE traceframe-info
38952 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
38953 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
38959 Each traceframe block can be either:
38964 A region of collected memory starting at @var{addr} and extending for
38965 @var{length} bytes from there:
38968 <memory start="@var{addr}" length="@var{length}"/>
38972 A block indicating trace state variable numbered @var{number} has been
38976 <tvar id="@var{number}"/>
38981 The formal DTD for the traceframe info format is given below:
38984 <!ELEMENT traceframe-info (memory | tvar)* >
38985 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
38987 <!ELEMENT memory EMPTY>
38988 <!ATTLIST memory start CDATA #REQUIRED
38989 length CDATA #REQUIRED>
38991 <!ATTLIST tvar id CDATA #REQUIRED>
38994 @node Branch Trace Format
38995 @section Branch Trace Format
38996 @cindex branch trace format
38998 In order to display the branch trace of an inferior thread,
38999 @value{GDBN} needs to obtain the list of branches. This list is
39000 represented as list of sequential code blocks that are connected via
39001 branches. The code in each block has been executed sequentially.
39003 This list is obtained using the @samp{qXfer:btrace:read}
39004 (@pxref{qXfer btrace read}) packet and is an XML document.
39006 @value{GDBN} must be linked with the Expat library to support XML
39007 traceframe info discovery. @xref{Expat}.
39009 The top-level structure of the document is shown below:
39012 <?xml version="1.0"?>
39014 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
39015 "http://sourceware.org/gdb/gdb-btrace.dtd">
39024 A block of sequentially executed instructions starting at @var{begin}
39025 and ending at @var{end}:
39028 <block begin="@var{begin}" end="@var{end}"/>
39033 The formal DTD for the branch trace format is given below:
39036 <!ELEMENT btrace (block)* >
39037 <!ATTLIST btrace version CDATA #FIXED "1.0">
39039 <!ELEMENT block EMPTY>
39040 <!ATTLIST block begin CDATA #REQUIRED
39041 end CDATA #REQUIRED>
39044 @node Branch Trace Configuration Format
39045 @section Branch Trace Configuration Format
39046 @cindex branch trace configuration format
39048 For each inferior thread, @value{GDBN} can obtain the branch trace
39049 configuration using the @samp{qXfer:btrace-conf:read}
39050 (@pxref{qXfer btrace-conf read}) packet.
39052 The configuration describes the branch trace format and configuration
39053 settings for that format.
39055 @value{GDBN} must be linked with the Expat library to support XML
39056 branch trace configuration discovery. @xref{Expat}.
39058 The formal DTD for the branch trace configuration format is given below:
39061 <!ELEMENT btrace-conf (bts?)>
39062 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
39064 <!ELEMENT bts EMPTY>
39067 @include agentexpr.texi
39069 @node Target Descriptions
39070 @appendix Target Descriptions
39071 @cindex target descriptions
39073 One of the challenges of using @value{GDBN} to debug embedded systems
39074 is that there are so many minor variants of each processor
39075 architecture in use. It is common practice for vendors to start with
39076 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
39077 and then make changes to adapt it to a particular market niche. Some
39078 architectures have hundreds of variants, available from dozens of
39079 vendors. This leads to a number of problems:
39083 With so many different customized processors, it is difficult for
39084 the @value{GDBN} maintainers to keep up with the changes.
39086 Since individual variants may have short lifetimes or limited
39087 audiences, it may not be worthwhile to carry information about every
39088 variant in the @value{GDBN} source tree.
39090 When @value{GDBN} does support the architecture of the embedded system
39091 at hand, the task of finding the correct architecture name to give the
39092 @command{set architecture} command can be error-prone.
39095 To address these problems, the @value{GDBN} remote protocol allows a
39096 target system to not only identify itself to @value{GDBN}, but to
39097 actually describe its own features. This lets @value{GDBN} support
39098 processor variants it has never seen before --- to the extent that the
39099 descriptions are accurate, and that @value{GDBN} understands them.
39101 @value{GDBN} must be linked with the Expat library to support XML
39102 target descriptions. @xref{Expat}.
39105 * Retrieving Descriptions:: How descriptions are fetched from a target.
39106 * Target Description Format:: The contents of a target description.
39107 * Predefined Target Types:: Standard types available for target
39109 * Standard Target Features:: Features @value{GDBN} knows about.
39112 @node Retrieving Descriptions
39113 @section Retrieving Descriptions
39115 Target descriptions can be read from the target automatically, or
39116 specified by the user manually. The default behavior is to read the
39117 description from the target. @value{GDBN} retrieves it via the remote
39118 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
39119 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
39120 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
39121 XML document, of the form described in @ref{Target Description
39124 Alternatively, you can specify a file to read for the target description.
39125 If a file is set, the target will not be queried. The commands to
39126 specify a file are:
39129 @cindex set tdesc filename
39130 @item set tdesc filename @var{path}
39131 Read the target description from @var{path}.
39133 @cindex unset tdesc filename
39134 @item unset tdesc filename
39135 Do not read the XML target description from a file. @value{GDBN}
39136 will use the description supplied by the current target.
39138 @cindex show tdesc filename
39139 @item show tdesc filename
39140 Show the filename to read for a target description, if any.
39144 @node Target Description Format
39145 @section Target Description Format
39146 @cindex target descriptions, XML format
39148 A target description annex is an @uref{http://www.w3.org/XML/, XML}
39149 document which complies with the Document Type Definition provided in
39150 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
39151 means you can use generally available tools like @command{xmllint} to
39152 check that your feature descriptions are well-formed and valid.
39153 However, to help people unfamiliar with XML write descriptions for
39154 their targets, we also describe the grammar here.
39156 Target descriptions can identify the architecture of the remote target
39157 and (for some architectures) provide information about custom register
39158 sets. They can also identify the OS ABI of the remote target.
39159 @value{GDBN} can use this information to autoconfigure for your
39160 target, or to warn you if you connect to an unsupported target.
39162 Here is a simple target description:
39165 <target version="1.0">
39166 <architecture>i386:x86-64</architecture>
39171 This minimal description only says that the target uses
39172 the x86-64 architecture.
39174 A target description has the following overall form, with [ ] marking
39175 optional elements and @dots{} marking repeatable elements. The elements
39176 are explained further below.
39179 <?xml version="1.0"?>
39180 <!DOCTYPE target SYSTEM "gdb-target.dtd">
39181 <target version="1.0">
39182 @r{[}@var{architecture}@r{]}
39183 @r{[}@var{osabi}@r{]}
39184 @r{[}@var{compatible}@r{]}
39185 @r{[}@var{feature}@dots{}@r{]}
39190 The description is generally insensitive to whitespace and line
39191 breaks, under the usual common-sense rules. The XML version
39192 declaration and document type declaration can generally be omitted
39193 (@value{GDBN} does not require them), but specifying them may be
39194 useful for XML validation tools. The @samp{version} attribute for
39195 @samp{<target>} may also be omitted, but we recommend
39196 including it; if future versions of @value{GDBN} use an incompatible
39197 revision of @file{gdb-target.dtd}, they will detect and report
39198 the version mismatch.
39200 @subsection Inclusion
39201 @cindex target descriptions, inclusion
39204 @cindex <xi:include>
39207 It can sometimes be valuable to split a target description up into
39208 several different annexes, either for organizational purposes, or to
39209 share files between different possible target descriptions. You can
39210 divide a description into multiple files by replacing any element of
39211 the target description with an inclusion directive of the form:
39214 <xi:include href="@var{document}"/>
39218 When @value{GDBN} encounters an element of this form, it will retrieve
39219 the named XML @var{document}, and replace the inclusion directive with
39220 the contents of that document. If the current description was read
39221 using @samp{qXfer}, then so will be the included document;
39222 @var{document} will be interpreted as the name of an annex. If the
39223 current description was read from a file, @value{GDBN} will look for
39224 @var{document} as a file in the same directory where it found the
39225 original description.
39227 @subsection Architecture
39228 @cindex <architecture>
39230 An @samp{<architecture>} element has this form:
39233 <architecture>@var{arch}</architecture>
39236 @var{arch} is one of the architectures from the set accepted by
39237 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
39240 @cindex @code{<osabi>}
39242 This optional field was introduced in @value{GDBN} version 7.0.
39243 Previous versions of @value{GDBN} ignore it.
39245 An @samp{<osabi>} element has this form:
39248 <osabi>@var{abi-name}</osabi>
39251 @var{abi-name} is an OS ABI name from the same selection accepted by
39252 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
39254 @subsection Compatible Architecture
39255 @cindex @code{<compatible>}
39257 This optional field was introduced in @value{GDBN} version 7.0.
39258 Previous versions of @value{GDBN} ignore it.
39260 A @samp{<compatible>} element has this form:
39263 <compatible>@var{arch}</compatible>
39266 @var{arch} is one of the architectures from the set accepted by
39267 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
39269 A @samp{<compatible>} element is used to specify that the target
39270 is able to run binaries in some other than the main target architecture
39271 given by the @samp{<architecture>} element. For example, on the
39272 Cell Broadband Engine, the main architecture is @code{powerpc:common}
39273 or @code{powerpc:common64}, but the system is able to run binaries
39274 in the @code{spu} architecture as well. The way to describe this
39275 capability with @samp{<compatible>} is as follows:
39278 <architecture>powerpc:common</architecture>
39279 <compatible>spu</compatible>
39282 @subsection Features
39285 Each @samp{<feature>} describes some logical portion of the target
39286 system. Features are currently used to describe available CPU
39287 registers and the types of their contents. A @samp{<feature>} element
39291 <feature name="@var{name}">
39292 @r{[}@var{type}@dots{}@r{]}
39298 Each feature's name should be unique within the description. The name
39299 of a feature does not matter unless @value{GDBN} has some special
39300 knowledge of the contents of that feature; if it does, the feature
39301 should have its standard name. @xref{Standard Target Features}.
39305 Any register's value is a collection of bits which @value{GDBN} must
39306 interpret. The default interpretation is a two's complement integer,
39307 but other types can be requested by name in the register description.
39308 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
39309 Target Types}), and the description can define additional composite types.
39311 Each type element must have an @samp{id} attribute, which gives
39312 a unique (within the containing @samp{<feature>}) name to the type.
39313 Types must be defined before they are used.
39316 Some targets offer vector registers, which can be treated as arrays
39317 of scalar elements. These types are written as @samp{<vector>} elements,
39318 specifying the array element type, @var{type}, and the number of elements,
39322 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
39326 If a register's value is usefully viewed in multiple ways, define it
39327 with a union type containing the useful representations. The
39328 @samp{<union>} element contains one or more @samp{<field>} elements,
39329 each of which has a @var{name} and a @var{type}:
39332 <union id="@var{id}">
39333 <field name="@var{name}" type="@var{type}"/>
39339 If a register's value is composed from several separate values, define
39340 it with a structure type. There are two forms of the @samp{<struct>}
39341 element; a @samp{<struct>} element must either contain only bitfields
39342 or contain no bitfields. If the structure contains only bitfields,
39343 its total size in bytes must be specified, each bitfield must have an
39344 explicit start and end, and bitfields are automatically assigned an
39345 integer type. The field's @var{start} should be less than or
39346 equal to its @var{end}, and zero represents the least significant bit.
39349 <struct id="@var{id}" size="@var{size}">
39350 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
39355 If the structure contains no bitfields, then each field has an
39356 explicit type, and no implicit padding is added.
39359 <struct id="@var{id}">
39360 <field name="@var{name}" type="@var{type}"/>
39366 If a register's value is a series of single-bit flags, define it with
39367 a flags type. The @samp{<flags>} element has an explicit @var{size}
39368 and contains one or more @samp{<field>} elements. Each field has a
39369 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
39373 <flags id="@var{id}" size="@var{size}">
39374 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
39379 @subsection Registers
39382 Each register is represented as an element with this form:
39385 <reg name="@var{name}"
39386 bitsize="@var{size}"
39387 @r{[}regnum="@var{num}"@r{]}
39388 @r{[}save-restore="@var{save-restore}"@r{]}
39389 @r{[}type="@var{type}"@r{]}
39390 @r{[}group="@var{group}"@r{]}/>
39394 The components are as follows:
39399 The register's name; it must be unique within the target description.
39402 The register's size, in bits.
39405 The register's number. If omitted, a register's number is one greater
39406 than that of the previous register (either in the current feature or in
39407 a preceding feature); the first register in the target description
39408 defaults to zero. This register number is used to read or write
39409 the register; e.g.@: it is used in the remote @code{p} and @code{P}
39410 packets, and registers appear in the @code{g} and @code{G} packets
39411 in order of increasing register number.
39414 Whether the register should be preserved across inferior function
39415 calls; this must be either @code{yes} or @code{no}. The default is
39416 @code{yes}, which is appropriate for most registers except for
39417 some system control registers; this is not related to the target's
39421 The type of the register. It may be a predefined type, a type
39422 defined in the current feature, or one of the special types @code{int}
39423 and @code{float}. @code{int} is an integer type of the correct size
39424 for @var{bitsize}, and @code{float} is a floating point type (in the
39425 architecture's normal floating point format) of the correct size for
39426 @var{bitsize}. The default is @code{int}.
39429 The register group to which this register belongs. It must
39430 be either @code{general}, @code{float}, or @code{vector}. If no
39431 @var{group} is specified, @value{GDBN} will not display the register
39432 in @code{info registers}.
39436 @node Predefined Target Types
39437 @section Predefined Target Types
39438 @cindex target descriptions, predefined types
39440 Type definitions in the self-description can build up composite types
39441 from basic building blocks, but can not define fundamental types. Instead,
39442 standard identifiers are provided by @value{GDBN} for the fundamental
39443 types. The currently supported types are:
39452 Signed integer types holding the specified number of bits.
39459 Unsigned integer types holding the specified number of bits.
39463 Pointers to unspecified code and data. The program counter and
39464 any dedicated return address register may be marked as code
39465 pointers; printing a code pointer converts it into a symbolic
39466 address. The stack pointer and any dedicated address registers
39467 may be marked as data pointers.
39470 Single precision IEEE floating point.
39473 Double precision IEEE floating point.
39476 The 12-byte extended precision format used by ARM FPA registers.
39479 The 10-byte extended precision format used by x87 registers.
39482 32bit @sc{eflags} register used by x86.
39485 32bit @sc{mxcsr} register used by x86.
39489 @node Standard Target Features
39490 @section Standard Target Features
39491 @cindex target descriptions, standard features
39493 A target description must contain either no registers or all the
39494 target's registers. If the description contains no registers, then
39495 @value{GDBN} will assume a default register layout, selected based on
39496 the architecture. If the description contains any registers, the
39497 default layout will not be used; the standard registers must be
39498 described in the target description, in such a way that @value{GDBN}
39499 can recognize them.
39501 This is accomplished by giving specific names to feature elements
39502 which contain standard registers. @value{GDBN} will look for features
39503 with those names and verify that they contain the expected registers;
39504 if any known feature is missing required registers, or if any required
39505 feature is missing, @value{GDBN} will reject the target
39506 description. You can add additional registers to any of the
39507 standard features --- @value{GDBN} will display them just as if
39508 they were added to an unrecognized feature.
39510 This section lists the known features and their expected contents.
39511 Sample XML documents for these features are included in the
39512 @value{GDBN} source tree, in the directory @file{gdb/features}.
39514 Names recognized by @value{GDBN} should include the name of the
39515 company or organization which selected the name, and the overall
39516 architecture to which the feature applies; so e.g.@: the feature
39517 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
39519 The names of registers are not case sensitive for the purpose
39520 of recognizing standard features, but @value{GDBN} will only display
39521 registers using the capitalization used in the description.
39524 * AArch64 Features::
39527 * MicroBlaze Features::
39530 * Nios II Features::
39531 * PowerPC Features::
39532 * S/390 and System z Features::
39537 @node AArch64 Features
39538 @subsection AArch64 Features
39539 @cindex target descriptions, AArch64 features
39541 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
39542 targets. It should contain registers @samp{x0} through @samp{x30},
39543 @samp{sp}, @samp{pc}, and @samp{cpsr}.
39545 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
39546 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
39550 @subsection ARM Features
39551 @cindex target descriptions, ARM features
39553 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
39555 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
39556 @samp{lr}, @samp{pc}, and @samp{cpsr}.
39558 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
39559 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
39560 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
39563 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
39564 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
39566 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
39567 it should contain at least registers @samp{wR0} through @samp{wR15} and
39568 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
39569 @samp{wCSSF}, and @samp{wCASF} registers are optional.
39571 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
39572 should contain at least registers @samp{d0} through @samp{d15}. If
39573 they are present, @samp{d16} through @samp{d31} should also be included.
39574 @value{GDBN} will synthesize the single-precision registers from
39575 halves of the double-precision registers.
39577 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
39578 need to contain registers; it instructs @value{GDBN} to display the
39579 VFP double-precision registers as vectors and to synthesize the
39580 quad-precision registers from pairs of double-precision registers.
39581 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
39582 be present and include 32 double-precision registers.
39584 @node i386 Features
39585 @subsection i386 Features
39586 @cindex target descriptions, i386 features
39588 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
39589 targets. It should describe the following registers:
39593 @samp{eax} through @samp{edi} plus @samp{eip} for i386
39595 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
39597 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
39598 @samp{fs}, @samp{gs}
39600 @samp{st0} through @samp{st7}
39602 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
39603 @samp{foseg}, @samp{fooff} and @samp{fop}
39606 The register sets may be different, depending on the target.
39608 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
39609 describe registers:
39613 @samp{xmm0} through @samp{xmm7} for i386
39615 @samp{xmm0} through @samp{xmm15} for amd64
39620 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
39621 @samp{org.gnu.gdb.i386.sse} feature. It should
39622 describe the upper 128 bits of @sc{ymm} registers:
39626 @samp{ymm0h} through @samp{ymm7h} for i386
39628 @samp{ymm0h} through @samp{ymm15h} for amd64
39631 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel(R)
39632 Memory Protection Extension (MPX). It should describe the following registers:
39636 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
39638 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
39641 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
39642 describe a single register, @samp{orig_eax}.
39644 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
39645 @samp{org.gnu.gdb.i386.avx} feature. It should
39646 describe additional @sc{xmm} registers:
39650 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
39653 It should describe the upper 128 bits of additional @sc{ymm} registers:
39657 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
39661 describe the upper 256 bits of @sc{zmm} registers:
39665 @samp{zmm0h} through @samp{zmm7h} for i386.
39667 @samp{zmm0h} through @samp{zmm15h} for amd64.
39671 describe the additional @sc{zmm} registers:
39675 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
39678 @node MicroBlaze Features
39679 @subsection MicroBlaze Features
39680 @cindex target descriptions, MicroBlaze features
39682 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
39683 targets. It should contain registers @samp{r0} through @samp{r31},
39684 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
39685 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
39686 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
39688 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
39689 If present, it should contain registers @samp{rshr} and @samp{rslr}
39691 @node MIPS Features
39692 @subsection @acronym{MIPS} Features
39693 @cindex target descriptions, @acronym{MIPS} features
39695 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
39696 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
39697 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
39700 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
39701 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
39702 registers. They may be 32-bit or 64-bit depending on the target.
39704 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
39705 it may be optional in a future version of @value{GDBN}. It should
39706 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
39707 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
39709 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
39710 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
39711 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
39712 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
39714 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
39715 contain a single register, @samp{restart}, which is used by the
39716 Linux kernel to control restartable syscalls.
39718 @node M68K Features
39719 @subsection M68K Features
39720 @cindex target descriptions, M68K features
39723 @item @samp{org.gnu.gdb.m68k.core}
39724 @itemx @samp{org.gnu.gdb.coldfire.core}
39725 @itemx @samp{org.gnu.gdb.fido.core}
39726 One of those features must be always present.
39727 The feature that is present determines which flavor of m68k is
39728 used. The feature that is present should contain registers
39729 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
39730 @samp{sp}, @samp{ps} and @samp{pc}.
39732 @item @samp{org.gnu.gdb.coldfire.fp}
39733 This feature is optional. If present, it should contain registers
39734 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
39738 @node Nios II Features
39739 @subsection Nios II Features
39740 @cindex target descriptions, Nios II features
39742 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
39743 targets. It should contain the 32 core registers (@samp{zero},
39744 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
39745 @samp{pc}, and the 16 control registers (@samp{status} through
39748 @node PowerPC Features
39749 @subsection PowerPC Features
39750 @cindex target descriptions, PowerPC features
39752 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
39753 targets. It should contain registers @samp{r0} through @samp{r31},
39754 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
39755 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
39757 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
39758 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
39760 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
39761 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
39764 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
39765 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
39766 will combine these registers with the floating point registers
39767 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
39768 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
39769 through @samp{vs63}, the set of vector registers for POWER7.
39771 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
39772 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
39773 @samp{spefscr}. SPE targets should provide 32-bit registers in
39774 @samp{org.gnu.gdb.power.core} and provide the upper halves in
39775 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
39776 these to present registers @samp{ev0} through @samp{ev31} to the
39779 @node S/390 and System z Features
39780 @subsection S/390 and System z Features
39781 @cindex target descriptions, S/390 features
39782 @cindex target descriptions, System z features
39784 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
39785 System z targets. It should contain the PSW and the 16 general
39786 registers. In particular, System z targets should provide the 64-bit
39787 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
39788 S/390 targets should provide the 32-bit versions of these registers.
39789 A System z target that runs in 31-bit addressing mode should provide
39790 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
39791 register's upper halves @samp{r0h} through @samp{r15h}, and their
39792 lower halves @samp{r0l} through @samp{r15l}.
39794 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
39795 contain the 64-bit registers @samp{f0} through @samp{f15}, and
39798 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
39799 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
39801 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
39802 contain the register @samp{orig_r2}, which is 64-bit wide on System z
39803 targets and 32-bit otherwise. In addition, the feature may contain
39804 the @samp{last_break} register, whose width depends on the addressing
39805 mode, as well as the @samp{system_call} register, which is always
39808 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
39809 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
39810 @samp{atia}, and @samp{tr0} through @samp{tr15}.
39812 @node TIC6x Features
39813 @subsection TMS320C6x Features
39814 @cindex target descriptions, TIC6x features
39815 @cindex target descriptions, TMS320C6x features
39816 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
39817 targets. It should contain registers @samp{A0} through @samp{A15},
39818 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
39820 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
39821 contain registers @samp{A16} through @samp{A31} and @samp{B16}
39822 through @samp{B31}.
39824 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
39825 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
39827 @node Operating System Information
39828 @appendix Operating System Information
39829 @cindex operating system information
39835 Users of @value{GDBN} often wish to obtain information about the state of
39836 the operating system running on the target---for example the list of
39837 processes, or the list of open files. This section describes the
39838 mechanism that makes it possible. This mechanism is similar to the
39839 target features mechanism (@pxref{Target Descriptions}), but focuses
39840 on a different aspect of target.
39842 Operating system information is retrived from the target via the
39843 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
39844 read}). The object name in the request should be @samp{osdata}, and
39845 the @var{annex} identifies the data to be fetched.
39848 @appendixsection Process list
39849 @cindex operating system information, process list
39851 When requesting the process list, the @var{annex} field in the
39852 @samp{qXfer} request should be @samp{processes}. The returned data is
39853 an XML document. The formal syntax of this document is defined in
39854 @file{gdb/features/osdata.dtd}.
39856 An example document is:
39859 <?xml version="1.0"?>
39860 <!DOCTYPE target SYSTEM "osdata.dtd">
39861 <osdata type="processes">
39863 <column name="pid">1</column>
39864 <column name="user">root</column>
39865 <column name="command">/sbin/init</column>
39866 <column name="cores">1,2,3</column>
39871 Each item should include a column whose name is @samp{pid}. The value
39872 of that column should identify the process on the target. The
39873 @samp{user} and @samp{command} columns are optional, and will be
39874 displayed by @value{GDBN}. The @samp{cores} column, if present,
39875 should contain a comma-separated list of cores that this process
39876 is running on. Target may provide additional columns,
39877 which @value{GDBN} currently ignores.
39879 @node Trace File Format
39880 @appendix Trace File Format
39881 @cindex trace file format
39883 The trace file comes in three parts: a header, a textual description
39884 section, and a trace frame section with binary data.
39886 The header has the form @code{\x7fTRACE0\n}. The first byte is
39887 @code{0x7f} so as to indicate that the file contains binary data,
39888 while the @code{0} is a version number that may have different values
39891 The description section consists of multiple lines of @sc{ascii} text
39892 separated by newline characters (@code{0xa}). The lines may include a
39893 variety of optional descriptive or context-setting information, such
39894 as tracepoint definitions or register set size. @value{GDBN} will
39895 ignore any line that it does not recognize. An empty line marks the end
39898 @c FIXME add some specific types of data
39900 The trace frame section consists of a number of consecutive frames.
39901 Each frame begins with a two-byte tracepoint number, followed by a
39902 four-byte size giving the amount of data in the frame. The data in
39903 the frame consists of a number of blocks, each introduced by a
39904 character indicating its type (at least register, memory, and trace
39905 state variable). The data in this section is raw binary, not a
39906 hexadecimal or other encoding; its endianness matches the target's
39909 @c FIXME bi-arch may require endianness/arch info in description section
39912 @item R @var{bytes}
39913 Register block. The number and ordering of bytes matches that of a
39914 @code{g} packet in the remote protocol. Note that these are the
39915 actual bytes, in target order and @value{GDBN} register order, not a
39916 hexadecimal encoding.
39918 @item M @var{address} @var{length} @var{bytes}...
39919 Memory block. This is a contiguous block of memory, at the 8-byte
39920 address @var{address}, with a 2-byte length @var{length}, followed by
39921 @var{length} bytes.
39923 @item V @var{number} @var{value}
39924 Trace state variable block. This records the 8-byte signed value
39925 @var{value} of trace state variable numbered @var{number}.
39929 Future enhancements of the trace file format may include additional types
39932 @node Index Section Format
39933 @appendix @code{.gdb_index} section format
39934 @cindex .gdb_index section format
39935 @cindex index section format
39937 This section documents the index section that is created by @code{save
39938 gdb-index} (@pxref{Index Files}). The index section is
39939 DWARF-specific; some knowledge of DWARF is assumed in this
39942 The mapped index file format is designed to be directly
39943 @code{mmap}able on any architecture. In most cases, a datum is
39944 represented using a little-endian 32-bit integer value, called an
39945 @code{offset_type}. Big endian machines must byte-swap the values
39946 before using them. Exceptions to this rule are noted. The data is
39947 laid out such that alignment is always respected.
39949 A mapped index consists of several areas, laid out in order.
39953 The file header. This is a sequence of values, of @code{offset_type}
39954 unless otherwise noted:
39958 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
39959 Version 4 uses a different hashing function from versions 5 and 6.
39960 Version 6 includes symbols for inlined functions, whereas versions 4
39961 and 5 do not. Version 7 adds attributes to the CU indices in the
39962 symbol table. Version 8 specifies that symbols from DWARF type units
39963 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
39964 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
39966 @value{GDBN} will only read version 4, 5, or 6 indices
39967 by specifying @code{set use-deprecated-index-sections on}.
39968 GDB has a workaround for potentially broken version 7 indices so it is
39969 currently not flagged as deprecated.
39972 The offset, from the start of the file, of the CU list.
39975 The offset, from the start of the file, of the types CU list. Note
39976 that this area can be empty, in which case this offset will be equal
39977 to the next offset.
39980 The offset, from the start of the file, of the address area.
39983 The offset, from the start of the file, of the symbol table.
39986 The offset, from the start of the file, of the constant pool.
39990 The CU list. This is a sequence of pairs of 64-bit little-endian
39991 values, sorted by the CU offset. The first element in each pair is
39992 the offset of a CU in the @code{.debug_info} section. The second
39993 element in each pair is the length of that CU. References to a CU
39994 elsewhere in the map are done using a CU index, which is just the
39995 0-based index into this table. Note that if there are type CUs, then
39996 conceptually CUs and type CUs form a single list for the purposes of
40000 The types CU list. This is a sequence of triplets of 64-bit
40001 little-endian values. In a triplet, the first value is the CU offset,
40002 the second value is the type offset in the CU, and the third value is
40003 the type signature. The types CU list is not sorted.
40006 The address area. The address area consists of a sequence of address
40007 entries. Each address entry has three elements:
40011 The low address. This is a 64-bit little-endian value.
40014 The high address. This is a 64-bit little-endian value. Like
40015 @code{DW_AT_high_pc}, the value is one byte beyond the end.
40018 The CU index. This is an @code{offset_type} value.
40022 The symbol table. This is an open-addressed hash table. The size of
40023 the hash table is always a power of 2.
40025 Each slot in the hash table consists of a pair of @code{offset_type}
40026 values. The first value is the offset of the symbol's name in the
40027 constant pool. The second value is the offset of the CU vector in the
40030 If both values are 0, then this slot in the hash table is empty. This
40031 is ok because while 0 is a valid constant pool index, it cannot be a
40032 valid index for both a string and a CU vector.
40034 The hash value for a table entry is computed by applying an
40035 iterative hash function to the symbol's name. Starting with an
40036 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
40037 the string is incorporated into the hash using the formula depending on the
40042 The formula is @code{r = r * 67 + c - 113}.
40044 @item Versions 5 to 7
40045 The formula is @code{r = r * 67 + tolower (c) - 113}.
40048 The terminating @samp{\0} is not incorporated into the hash.
40050 The step size used in the hash table is computed via
40051 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
40052 value, and @samp{size} is the size of the hash table. The step size
40053 is used to find the next candidate slot when handling a hash
40056 The names of C@t{++} symbols in the hash table are canonicalized. We
40057 don't currently have a simple description of the canonicalization
40058 algorithm; if you intend to create new index sections, you must read
40062 The constant pool. This is simply a bunch of bytes. It is organized
40063 so that alignment is correct: CU vectors are stored first, followed by
40066 A CU vector in the constant pool is a sequence of @code{offset_type}
40067 values. The first value is the number of CU indices in the vector.
40068 Each subsequent value is the index and symbol attributes of a CU in
40069 the CU list. This element in the hash table is used to indicate which
40070 CUs define the symbol and how the symbol is used.
40071 See below for the format of each CU index+attributes entry.
40073 A string in the constant pool is zero-terminated.
40076 Attributes were added to CU index values in @code{.gdb_index} version 7.
40077 If a symbol has multiple uses within a CU then there is one
40078 CU index+attributes value for each use.
40080 The format of each CU index+attributes entry is as follows
40086 This is the index of the CU in the CU list.
40088 These bits are reserved for future purposes and must be zero.
40090 The kind of the symbol in the CU.
40094 This value is reserved and should not be used.
40095 By reserving zero the full @code{offset_type} value is backwards compatible
40096 with previous versions of the index.
40098 The symbol is a type.
40100 The symbol is a variable or an enum value.
40102 The symbol is a function.
40104 Any other kind of symbol.
40106 These values are reserved.
40110 This bit is zero if the value is global and one if it is static.
40112 The determination of whether a symbol is global or static is complicated.
40113 The authorative reference is the file @file{dwarf2read.c} in
40114 @value{GDBN} sources.
40118 This pseudo-code describes the computation of a symbol's kind and
40119 global/static attributes in the index.
40122 is_external = get_attribute (die, DW_AT_external);
40123 language = get_attribute (cu_die, DW_AT_language);
40126 case DW_TAG_typedef:
40127 case DW_TAG_base_type:
40128 case DW_TAG_subrange_type:
40132 case DW_TAG_enumerator:
40134 is_static = (language != CPLUS && language != JAVA);
40136 case DW_TAG_subprogram:
40138 is_static = ! (is_external || language == ADA);
40140 case DW_TAG_constant:
40142 is_static = ! is_external;
40144 case DW_TAG_variable:
40146 is_static = ! is_external;
40148 case DW_TAG_namespace:
40152 case DW_TAG_class_type:
40153 case DW_TAG_interface_type:
40154 case DW_TAG_structure_type:
40155 case DW_TAG_union_type:
40156 case DW_TAG_enumeration_type:
40158 is_static = (language != CPLUS && language != JAVA);
40166 @appendix Manual pages
40170 * gdb man:: The GNU Debugger man page
40171 * gdbserver man:: Remote Server for the GNU Debugger man page
40172 * gcore man:: Generate a core file of a running program
40173 * gdbinit man:: gdbinit scripts
40179 @c man title gdb The GNU Debugger
40181 @c man begin SYNOPSIS gdb
40182 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
40183 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
40184 [@option{-b}@w{ }@var{bps}]
40185 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
40186 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
40187 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
40188 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
40189 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
40192 @c man begin DESCRIPTION gdb
40193 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
40194 going on ``inside'' another program while it executes -- or what another
40195 program was doing at the moment it crashed.
40197 @value{GDBN} can do four main kinds of things (plus other things in support of
40198 these) to help you catch bugs in the act:
40202 Start your program, specifying anything that might affect its behavior.
40205 Make your program stop on specified conditions.
40208 Examine what has happened, when your program has stopped.
40211 Change things in your program, so you can experiment with correcting the
40212 effects of one bug and go on to learn about another.
40215 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
40218 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
40219 commands from the terminal until you tell it to exit with the @value{GDBN}
40220 command @code{quit}. You can get online help from @value{GDBN} itself
40221 by using the command @code{help}.
40223 You can run @code{gdb} with no arguments or options; but the most
40224 usual way to start @value{GDBN} is with one argument or two, specifying an
40225 executable program as the argument:
40231 You can also start with both an executable program and a core file specified:
40237 You can, instead, specify a process ID as a second argument, if you want
40238 to debug a running process:
40246 would attach @value{GDBN} to process @code{1234} (unless you also have a file
40247 named @file{1234}; @value{GDBN} does check for a core file first).
40248 With option @option{-p} you can omit the @var{program} filename.
40250 Here are some of the most frequently needed @value{GDBN} commands:
40252 @c pod2man highlights the right hand side of the @item lines.
40254 @item break [@var{file}:]@var{functiop}
40255 Set a breakpoint at @var{function} (in @var{file}).
40257 @item run [@var{arglist}]
40258 Start your program (with @var{arglist}, if specified).
40261 Backtrace: display the program stack.
40263 @item print @var{expr}
40264 Display the value of an expression.
40267 Continue running your program (after stopping, e.g. at a breakpoint).
40270 Execute next program line (after stopping); step @emph{over} any
40271 function calls in the line.
40273 @item edit [@var{file}:]@var{function}
40274 look at the program line where it is presently stopped.
40276 @item list [@var{file}:]@var{function}
40277 type the text of the program in the vicinity of where it is presently stopped.
40280 Execute next program line (after stopping); step @emph{into} any
40281 function calls in the line.
40283 @item help [@var{name}]
40284 Show information about @value{GDBN} command @var{name}, or general information
40285 about using @value{GDBN}.
40288 Exit from @value{GDBN}.
40292 For full details on @value{GDBN},
40293 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40294 by Richard M. Stallman and Roland H. Pesch. The same text is available online
40295 as the @code{gdb} entry in the @code{info} program.
40299 @c man begin OPTIONS gdb
40300 Any arguments other than options specify an executable
40301 file and core file (or process ID); that is, the first argument
40302 encountered with no
40303 associated option flag is equivalent to a @option{-se} option, and the second,
40304 if any, is equivalent to a @option{-c} option if it's the name of a file.
40306 both long and short forms; both are shown here. The long forms are also
40307 recognized if you truncate them, so long as enough of the option is
40308 present to be unambiguous. (If you prefer, you can flag option
40309 arguments with @option{+} rather than @option{-}, though we illustrate the
40310 more usual convention.)
40312 All the options and command line arguments you give are processed
40313 in sequential order. The order makes a difference when the @option{-x}
40319 List all options, with brief explanations.
40321 @item -symbols=@var{file}
40322 @itemx -s @var{file}
40323 Read symbol table from file @var{file}.
40326 Enable writing into executable and core files.
40328 @item -exec=@var{file}
40329 @itemx -e @var{file}
40330 Use file @var{file} as the executable file to execute when
40331 appropriate, and for examining pure data in conjunction with a core
40334 @item -se=@var{file}
40335 Read symbol table from file @var{file} and use it as the executable
40338 @item -core=@var{file}
40339 @itemx -c @var{file}
40340 Use file @var{file} as a core dump to examine.
40342 @item -command=@var{file}
40343 @itemx -x @var{file}
40344 Execute @value{GDBN} commands from file @var{file}.
40346 @item -ex @var{command}
40347 Execute given @value{GDBN} @var{command}.
40349 @item -directory=@var{directory}
40350 @itemx -d @var{directory}
40351 Add @var{directory} to the path to search for source files.
40354 Do not execute commands from @file{~/.gdbinit}.
40358 Do not execute commands from any @file{.gdbinit} initialization files.
40362 ``Quiet''. Do not print the introductory and copyright messages. These
40363 messages are also suppressed in batch mode.
40366 Run in batch mode. Exit with status @code{0} after processing all the command
40367 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
40368 Exit with nonzero status if an error occurs in executing the @value{GDBN}
40369 commands in the command files.
40371 Batch mode may be useful for running @value{GDBN} as a filter, for example to
40372 download and run a program on another computer; in order to make this
40373 more useful, the message
40376 Program exited normally.
40380 (which is ordinarily issued whenever a program running under @value{GDBN} control
40381 terminates) is not issued when running in batch mode.
40383 @item -cd=@var{directory}
40384 Run @value{GDBN} using @var{directory} as its working directory,
40385 instead of the current directory.
40389 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
40390 @value{GDBN} to output the full file name and line number in a standard,
40391 recognizable fashion each time a stack frame is displayed (which
40392 includes each time the program stops). This recognizable format looks
40393 like two @samp{\032} characters, followed by the file name, line number
40394 and character position separated by colons, and a newline. The
40395 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
40396 characters as a signal to display the source code for the frame.
40399 Set the line speed (baud rate or bits per second) of any serial
40400 interface used by @value{GDBN} for remote debugging.
40402 @item -tty=@var{device}
40403 Run using @var{device} for your program's standard input and output.
40407 @c man begin SEEALSO gdb
40409 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
40410 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
40411 documentation are properly installed at your site, the command
40418 should give you access to the complete manual.
40420 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40421 Richard M. Stallman and Roland H. Pesch, July 1991.
40425 @node gdbserver man
40426 @heading gdbserver man
40428 @c man title gdbserver Remote Server for the GNU Debugger
40430 @c man begin SYNOPSIS gdbserver
40431 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
40433 gdbserver --attach @var{comm} @var{pid}
40435 gdbserver --multi @var{comm}
40439 @c man begin DESCRIPTION gdbserver
40440 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
40441 than the one which is running the program being debugged.
40444 @subheading Usage (server (target) side)
40447 Usage (server (target) side):
40450 First, you need to have a copy of the program you want to debug put onto
40451 the target system. The program can be stripped to save space if needed, as
40452 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
40453 the @value{GDBN} running on the host system.
40455 To use the server, you log on to the target system, and run the @command{gdbserver}
40456 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
40457 your program, and (c) its arguments. The general syntax is:
40460 target> gdbserver @var{comm} @var{program} [@var{args} ...]
40463 For example, using a serial port, you might say:
40467 @c @file would wrap it as F</dev/com1>.
40468 target> gdbserver /dev/com1 emacs foo.txt
40471 target> gdbserver @file{/dev/com1} emacs foo.txt
40475 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
40476 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
40477 waits patiently for the host @value{GDBN} to communicate with it.
40479 To use a TCP connection, you could say:
40482 target> gdbserver host:2345 emacs foo.txt
40485 This says pretty much the same thing as the last example, except that we are
40486 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
40487 that we are expecting to see a TCP connection from @code{host} to local TCP port
40488 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
40489 want for the port number as long as it does not conflict with any existing TCP
40490 ports on the target system. This same port number must be used in the host
40491 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
40492 you chose a port number that conflicts with another service, @command{gdbserver} will
40493 print an error message and exit.
40495 @command{gdbserver} can also attach to running programs.
40496 This is accomplished via the @option{--attach} argument. The syntax is:
40499 target> gdbserver --attach @var{comm} @var{pid}
40502 @var{pid} is the process ID of a currently running process. It isn't
40503 necessary to point @command{gdbserver} at a binary for the running process.
40505 To start @code{gdbserver} without supplying an initial command to run
40506 or process ID to attach, use the @option{--multi} command line option.
40507 In such case you should connect using @kbd{target extended-remote} to start
40508 the program you want to debug.
40511 target> gdbserver --multi @var{comm}
40515 @subheading Usage (host side)
40521 You need an unstripped copy of the target program on your host system, since
40522 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
40523 would, with the target program as the first argument. (You may need to use the
40524 @option{--baud} option if the serial line is running at anything except 9600 baud.)
40525 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
40526 new command you need to know about is @code{target remote}
40527 (or @code{target extended-remote}). Its argument is either
40528 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
40529 descriptor. For example:
40533 @c @file would wrap it as F</dev/ttyb>.
40534 (gdb) target remote /dev/ttyb
40537 (gdb) target remote @file{/dev/ttyb}
40542 communicates with the server via serial line @file{/dev/ttyb}, and:
40545 (gdb) target remote the-target:2345
40549 communicates via a TCP connection to port 2345 on host `the-target', where
40550 you previously started up @command{gdbserver} with the same port number. Note that for
40551 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
40552 command, otherwise you may get an error that looks something like
40553 `Connection refused'.
40555 @command{gdbserver} can also debug multiple inferiors at once,
40558 the @value{GDBN} manual in node @code{Inferiors and Programs}
40559 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
40562 @ref{Inferiors and Programs}.
40564 In such case use the @code{extended-remote} @value{GDBN} command variant:
40567 (gdb) target extended-remote the-target:2345
40570 The @command{gdbserver} option @option{--multi} may or may not be used in such
40574 @c man begin OPTIONS gdbserver
40575 There are three different modes for invoking @command{gdbserver}:
40580 Debug a specific program specified by its program name:
40583 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
40586 The @var{comm} parameter specifies how should the server communicate
40587 with @value{GDBN}; it is either a device name (to use a serial line),
40588 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
40589 stdin/stdout of @code{gdbserver}. Specify the name of the program to
40590 debug in @var{prog}. Any remaining arguments will be passed to the
40591 program verbatim. When the program exits, @value{GDBN} will close the
40592 connection, and @code{gdbserver} will exit.
40595 Debug a specific program by specifying the process ID of a running
40599 gdbserver --attach @var{comm} @var{pid}
40602 The @var{comm} parameter is as described above. Supply the process ID
40603 of a running program in @var{pid}; @value{GDBN} will do everything
40604 else. Like with the previous mode, when the process @var{pid} exits,
40605 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
40608 Multi-process mode -- debug more than one program/process:
40611 gdbserver --multi @var{comm}
40614 In this mode, @value{GDBN} can instruct @command{gdbserver} which
40615 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
40616 close the connection when a process being debugged exits, so you can
40617 debug several processes in the same session.
40620 In each of the modes you may specify these options:
40625 List all options, with brief explanations.
40628 This option causes @command{gdbserver} to print its version number and exit.
40631 @command{gdbserver} will attach to a running program. The syntax is:
40634 target> gdbserver --attach @var{comm} @var{pid}
40637 @var{pid} is the process ID of a currently running process. It isn't
40638 necessary to point @command{gdbserver} at a binary for the running process.
40641 To start @code{gdbserver} without supplying an initial command to run
40642 or process ID to attach, use this command line option.
40643 Then you can connect using @kbd{target extended-remote} and start
40644 the program you want to debug. The syntax is:
40647 target> gdbserver --multi @var{comm}
40651 Instruct @code{gdbserver} to display extra status information about the debugging
40653 This option is intended for @code{gdbserver} development and for bug reports to
40656 @item --remote-debug
40657 Instruct @code{gdbserver} to display remote protocol debug output.
40658 This option is intended for @code{gdbserver} development and for bug reports to
40661 @item --debug-format=option1@r{[},option2,...@r{]}
40662 Instruct @code{gdbserver} to include extra information in each line
40663 of debugging output.
40664 @xref{Other Command-Line Arguments for gdbserver}.
40667 Specify a wrapper to launch programs
40668 for debugging. The option should be followed by the name of the
40669 wrapper, then any command-line arguments to pass to the wrapper, then
40670 @kbd{--} indicating the end of the wrapper arguments.
40673 By default, @command{gdbserver} keeps the listening TCP port open, so that
40674 additional connections are possible. However, if you start @code{gdbserver}
40675 with the @option{--once} option, it will stop listening for any further
40676 connection attempts after connecting to the first @value{GDBN} session.
40678 @c --disable-packet is not documented for users.
40680 @c --disable-randomization and --no-disable-randomization are superseded by
40681 @c QDisableRandomization.
40686 @c man begin SEEALSO gdbserver
40688 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
40689 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
40690 documentation are properly installed at your site, the command
40696 should give you access to the complete manual.
40698 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40699 Richard M. Stallman and Roland H. Pesch, July 1991.
40706 @c man title gcore Generate a core file of a running program
40709 @c man begin SYNOPSIS gcore
40710 gcore [-o @var{filename}] @var{pid}
40714 @c man begin DESCRIPTION gcore
40715 Generate a core dump of a running program with process ID @var{pid}.
40716 Produced file is equivalent to a kernel produced core file as if the process
40717 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
40718 limit). Unlike after a crash, after @command{gcore} the program remains
40719 running without any change.
40722 @c man begin OPTIONS gcore
40724 @item -o @var{filename}
40725 The optional argument
40726 @var{filename} specifies the file name where to put the core dump.
40727 If not specified, the file name defaults to @file{core.@var{pid}},
40728 where @var{pid} is the running program process ID.
40732 @c man begin SEEALSO gcore
40734 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
40735 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
40736 documentation are properly installed at your site, the command
40743 should give you access to the complete manual.
40745 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40746 Richard M. Stallman and Roland H. Pesch, July 1991.
40753 @c man title gdbinit GDB initialization scripts
40756 @c man begin SYNOPSIS gdbinit
40757 @ifset SYSTEM_GDBINIT
40758 @value{SYSTEM_GDBINIT}
40767 @c man begin DESCRIPTION gdbinit
40768 These files contain @value{GDBN} commands to automatically execute during
40769 @value{GDBN} startup. The lines of contents are canned sequences of commands,
40772 the @value{GDBN} manual in node @code{Sequences}
40773 -- shell command @code{info -f gdb -n Sequences}.
40779 Please read more in
40781 the @value{GDBN} manual in node @code{Startup}
40782 -- shell command @code{info -f gdb -n Startup}.
40789 @ifset SYSTEM_GDBINIT
40790 @item @value{SYSTEM_GDBINIT}
40792 @ifclear SYSTEM_GDBINIT
40793 @item (not enabled with @code{--with-system-gdbinit} during compilation)
40795 System-wide initialization file. It is executed unless user specified
40796 @value{GDBN} option @code{-nx} or @code{-n}.
40799 the @value{GDBN} manual in node @code{System-wide configuration}
40800 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
40803 @ref{System-wide configuration}.
40807 User initialization file. It is executed unless user specified
40808 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
40811 Initialization file for current directory. It may need to be enabled with
40812 @value{GDBN} security command @code{set auto-load local-gdbinit}.
40815 the @value{GDBN} manual in node @code{Init File in the Current Directory}
40816 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
40819 @ref{Init File in the Current Directory}.
40824 @c man begin SEEALSO gdbinit
40826 gdb(1), @code{info -f gdb -n Startup}
40828 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
40829 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
40830 documentation are properly installed at your site, the command
40836 should give you access to the complete manual.
40838 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40839 Richard M. Stallman and Roland H. Pesch, July 1991.
40845 @node GNU Free Documentation License
40846 @appendix GNU Free Documentation License
40849 @node Concept Index
40850 @unnumbered Concept Index
40854 @node Command and Variable Index
40855 @unnumbered Command, Variable, and Function Index
40860 % I think something like @@colophon should be in texinfo. In the
40862 \long\def\colophon{\hbox to0pt{}\vfill
40863 \centerline{The body of this manual is set in}
40864 \centerline{\fontname\tenrm,}
40865 \centerline{with headings in {\bf\fontname\tenbf}}
40866 \centerline{and examples in {\tt\fontname\tentt}.}
40867 \centerline{{\it\fontname\tenit\/},}
40868 \centerline{{\bf\fontname\tenbf}, and}
40869 \centerline{{\sl\fontname\tensl\/}}
40870 \centerline{are used for emphasis.}\vfill}
40872 % Blame: doc@@cygnus.com, 1991.