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 @cindex quotes in commands
1604 @cindex completion of quoted strings
1605 Sometimes the string you need, while logically a ``word'', may contain
1606 parentheses or other characters that @value{GDBN} normally excludes from
1607 its notion of a word. To permit word completion to work in this
1608 situation, you may enclose words in @code{'} (single quote marks) in
1609 @value{GDBN} commands.
1611 The most likely situation where you might need this is in typing the
1612 name of a C@t{++} function. This is because C@t{++} allows function
1613 overloading (multiple definitions of the same function, distinguished
1614 by argument type). For example, when you want to set a breakpoint you
1615 may need to distinguish whether you mean the version of @code{name}
1616 that takes an @code{int} parameter, @code{name(int)}, or the version
1617 that takes a @code{float} parameter, @code{name(float)}. To use the
1618 word-completion facilities in this situation, type a single quote
1619 @code{'} at the beginning of the function name. This alerts
1620 @value{GDBN} that it may need to consider more information than usual
1621 when you press @key{TAB} or @kbd{M-?} to request word completion:
1624 (@value{GDBP}) b 'bubble( @kbd{M-?}
1625 bubble(double,double) bubble(int,int)
1626 (@value{GDBP}) b 'bubble(
1629 In some cases, @value{GDBN} can tell that completing a name requires using
1630 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1631 completing as much as it can) if you do not type the quote in the first
1635 (@value{GDBP}) b bub @key{TAB}
1636 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1637 (@value{GDBP}) b 'bubble(
1641 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1642 you have not yet started typing the argument list when you ask for
1643 completion on an overloaded symbol.
1645 For more information about overloaded functions, see @ref{C Plus Plus
1646 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1647 overload-resolution off} to disable overload resolution;
1648 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1650 @cindex completion of structure field names
1651 @cindex structure field name completion
1652 @cindex completion of union field names
1653 @cindex union field name completion
1654 When completing in an expression which looks up a field in a
1655 structure, @value{GDBN} also tries@footnote{The completer can be
1656 confused by certain kinds of invalid expressions. Also, it only
1657 examines the static type of the expression, not the dynamic type.} to
1658 limit completions to the field names available in the type of the
1662 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1663 magic to_fputs to_rewind
1664 to_data to_isatty to_write
1665 to_delete to_put to_write_async_safe
1670 This is because the @code{gdb_stdout} is a variable of the type
1671 @code{struct ui_file} that is defined in @value{GDBN} sources as
1678 ui_file_flush_ftype *to_flush;
1679 ui_file_write_ftype *to_write;
1680 ui_file_write_async_safe_ftype *to_write_async_safe;
1681 ui_file_fputs_ftype *to_fputs;
1682 ui_file_read_ftype *to_read;
1683 ui_file_delete_ftype *to_delete;
1684 ui_file_isatty_ftype *to_isatty;
1685 ui_file_rewind_ftype *to_rewind;
1686 ui_file_put_ftype *to_put;
1693 @section Getting Help
1694 @cindex online documentation
1697 You can always ask @value{GDBN} itself for information on its commands,
1698 using the command @code{help}.
1701 @kindex h @r{(@code{help})}
1704 You can use @code{help} (abbreviated @code{h}) with no arguments to
1705 display a short list of named classes of commands:
1709 List of classes of commands:
1711 aliases -- Aliases of other commands
1712 breakpoints -- Making program stop at certain points
1713 data -- Examining data
1714 files -- Specifying and examining files
1715 internals -- Maintenance commands
1716 obscure -- Obscure features
1717 running -- Running the program
1718 stack -- Examining the stack
1719 status -- Status inquiries
1720 support -- Support facilities
1721 tracepoints -- Tracing of program execution without
1722 stopping the program
1723 user-defined -- User-defined commands
1725 Type "help" followed by a class name for a list of
1726 commands in that class.
1727 Type "help" followed by command name for full
1729 Command name abbreviations are allowed if unambiguous.
1732 @c the above line break eliminates huge line overfull...
1734 @item help @var{class}
1735 Using one of the general help classes as an argument, you can get a
1736 list of the individual commands in that class. For example, here is the
1737 help display for the class @code{status}:
1740 (@value{GDBP}) help status
1745 @c Line break in "show" line falsifies real output, but needed
1746 @c to fit in smallbook page size.
1747 info -- Generic command for showing things
1748 about the program being debugged
1749 show -- Generic command for showing things
1752 Type "help" followed by command name for full
1754 Command name abbreviations are allowed if unambiguous.
1758 @item help @var{command}
1759 With a command name as @code{help} argument, @value{GDBN} displays a
1760 short paragraph on how to use that command.
1763 @item apropos @var{args}
1764 The @code{apropos} command searches through all of the @value{GDBN}
1765 commands, and their documentation, for the regular expression specified in
1766 @var{args}. It prints out all matches found. For example:
1777 alias -- Define a new command that is an alias of an existing command
1778 aliases -- Aliases of other commands
1779 d -- Delete some breakpoints or auto-display expressions
1780 del -- Delete some breakpoints or auto-display expressions
1781 delete -- Delete some breakpoints or auto-display expressions
1786 @item complete @var{args}
1787 The @code{complete @var{args}} command lists all the possible completions
1788 for the beginning of a command. Use @var{args} to specify the beginning of the
1789 command you want completed. For example:
1795 @noindent results in:
1806 @noindent This is intended for use by @sc{gnu} Emacs.
1809 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1810 and @code{show} to inquire about the state of your program, or the state
1811 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1812 manual introduces each of them in the appropriate context. The listings
1813 under @code{info} and under @code{show} in the Command, Variable, and
1814 Function Index point to all the sub-commands. @xref{Command and Variable
1820 @kindex i @r{(@code{info})}
1822 This command (abbreviated @code{i}) is for describing the state of your
1823 program. For example, you can show the arguments passed to a function
1824 with @code{info args}, list the registers currently in use with @code{info
1825 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1826 You can get a complete list of the @code{info} sub-commands with
1827 @w{@code{help info}}.
1831 You can assign the result of an expression to an environment variable with
1832 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1833 @code{set prompt $}.
1837 In contrast to @code{info}, @code{show} is for describing the state of
1838 @value{GDBN} itself.
1839 You can change most of the things you can @code{show}, by using the
1840 related command @code{set}; for example, you can control what number
1841 system is used for displays with @code{set radix}, or simply inquire
1842 which is currently in use with @code{show radix}.
1845 To display all the settable parameters and their current
1846 values, you can use @code{show} with no arguments; you may also use
1847 @code{info set}. Both commands produce the same display.
1848 @c FIXME: "info set" violates the rule that "info" is for state of
1849 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1850 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1854 Here are several miscellaneous @code{show} subcommands, all of which are
1855 exceptional in lacking corresponding @code{set} commands:
1858 @kindex show version
1859 @cindex @value{GDBN} version number
1861 Show what version of @value{GDBN} is running. You should include this
1862 information in @value{GDBN} bug-reports. If multiple versions of
1863 @value{GDBN} are in use at your site, you may need to determine which
1864 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1865 commands are introduced, and old ones may wither away. Also, many
1866 system vendors ship variant versions of @value{GDBN}, and there are
1867 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1868 The version number is the same as the one announced when you start
1871 @kindex show copying
1872 @kindex info copying
1873 @cindex display @value{GDBN} copyright
1876 Display information about permission for copying @value{GDBN}.
1878 @kindex show warranty
1879 @kindex info warranty
1881 @itemx info warranty
1882 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1883 if your version of @value{GDBN} comes with one.
1885 @kindex show configuration
1886 @item show configuration
1887 Display detailed information about the way @value{GDBN} was configured
1888 when it was built. This displays the optional arguments passed to the
1889 @file{configure} script and also configuration parameters detected
1890 automatically by @command{configure}. When reporting a @value{GDBN}
1891 bug (@pxref{GDB Bugs}), it is important to include this information in
1897 @chapter Running Programs Under @value{GDBN}
1899 When you run a program under @value{GDBN}, you must first generate
1900 debugging information when you compile it.
1902 You may start @value{GDBN} with its arguments, if any, in an environment
1903 of your choice. If you are doing native debugging, you may redirect
1904 your program's input and output, debug an already running process, or
1905 kill a child process.
1908 * Compilation:: Compiling for debugging
1909 * Starting:: Starting your program
1910 * Arguments:: Your program's arguments
1911 * Environment:: Your program's environment
1913 * Working Directory:: Your program's working directory
1914 * Input/Output:: Your program's input and output
1915 * Attach:: Debugging an already-running process
1916 * Kill Process:: Killing the child process
1918 * Inferiors and Programs:: Debugging multiple inferiors and programs
1919 * Threads:: Debugging programs with multiple threads
1920 * Forks:: Debugging forks
1921 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1925 @section Compiling for Debugging
1927 In order to debug a program effectively, you need to generate
1928 debugging information when you compile it. This debugging information
1929 is stored in the object file; it describes the data type of each
1930 variable or function and the correspondence between source line numbers
1931 and addresses in the executable code.
1933 To request debugging information, specify the @samp{-g} option when you run
1936 Programs that are to be shipped to your customers are compiled with
1937 optimizations, using the @samp{-O} compiler option. However, some
1938 compilers are unable to handle the @samp{-g} and @samp{-O} options
1939 together. Using those compilers, you cannot generate optimized
1940 executables containing debugging information.
1942 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1943 without @samp{-O}, making it possible to debug optimized code. We
1944 recommend that you @emph{always} use @samp{-g} whenever you compile a
1945 program. You may think your program is correct, but there is no sense
1946 in pushing your luck. For more information, see @ref{Optimized Code}.
1948 Older versions of the @sc{gnu} C compiler permitted a variant option
1949 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1950 format; if your @sc{gnu} C compiler has this option, do not use it.
1952 @value{GDBN} knows about preprocessor macros and can show you their
1953 expansion (@pxref{Macros}). Most compilers do not include information
1954 about preprocessor macros in the debugging information if you specify
1955 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1956 the @sc{gnu} C compiler, provides macro information if you are using
1957 the DWARF debugging format, and specify the option @option{-g3}.
1959 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1960 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1961 information on @value{NGCC} options affecting debug information.
1963 You will have the best debugging experience if you use the latest
1964 version of the DWARF debugging format that your compiler supports.
1965 DWARF is currently the most expressive and best supported debugging
1966 format in @value{GDBN}.
1970 @section Starting your Program
1976 @kindex r @r{(@code{run})}
1979 Use the @code{run} command to start your program under @value{GDBN}.
1980 You must first specify the program name with an argument to
1981 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1982 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
1983 command (@pxref{Files, ,Commands to Specify Files}).
1987 If you are running your program in an execution environment that
1988 supports processes, @code{run} creates an inferior process and makes
1989 that process run your program. In some environments without processes,
1990 @code{run} jumps to the start of your program. Other targets,
1991 like @samp{remote}, are always running. If you get an error
1992 message like this one:
1995 The "remote" target does not support "run".
1996 Try "help target" or "continue".
2000 then use @code{continue} to run your program. You may need @code{load}
2001 first (@pxref{load}).
2003 The execution of a program is affected by certain information it
2004 receives from its superior. @value{GDBN} provides ways to specify this
2005 information, which you must do @emph{before} starting your program. (You
2006 can change it after starting your program, but such changes only affect
2007 your program the next time you start it.) This information may be
2008 divided into four categories:
2011 @item The @emph{arguments.}
2012 Specify the arguments to give your program as the arguments of the
2013 @code{run} command. If a shell is available on your target, the shell
2014 is used to pass the arguments, so that you may use normal conventions
2015 (such as wildcard expansion or variable substitution) in describing
2017 In Unix systems, you can control which shell is used with the
2018 @code{SHELL} environment variable. If you do not define @code{SHELL},
2019 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2020 use of any shell with the @code{set startup-with-shell} command (see
2023 @item The @emph{environment.}
2024 Your program normally inherits its environment from @value{GDBN}, but you can
2025 use the @value{GDBN} commands @code{set environment} and @code{unset
2026 environment} to change parts of the environment that affect
2027 your program. @xref{Environment, ,Your Program's Environment}.
2029 @item The @emph{working directory.}
2030 Your program inherits its working directory from @value{GDBN}. You can set
2031 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
2032 @xref{Working Directory, ,Your Program's Working Directory}.
2034 @item The @emph{standard input and output.}
2035 Your program normally uses the same device for standard input and
2036 standard output as @value{GDBN} is using. You can redirect input and output
2037 in the @code{run} command line, or you can use the @code{tty} command to
2038 set a different device for your program.
2039 @xref{Input/Output, ,Your Program's Input and Output}.
2042 @emph{Warning:} While input and output redirection work, you cannot use
2043 pipes to pass the output of the program you are debugging to another
2044 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2048 When you issue the @code{run} command, your program begins to execute
2049 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2050 of how to arrange for your program to stop. Once your program has
2051 stopped, you may call functions in your program, using the @code{print}
2052 or @code{call} commands. @xref{Data, ,Examining Data}.
2054 If the modification time of your symbol file has changed since the last
2055 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2056 table, and reads it again. When it does this, @value{GDBN} tries to retain
2057 your current breakpoints.
2062 @cindex run to main procedure
2063 The name of the main procedure can vary from language to language.
2064 With C or C@t{++}, the main procedure name is always @code{main}, but
2065 other languages such as Ada do not require a specific name for their
2066 main procedure. The debugger provides a convenient way to start the
2067 execution of the program and to stop at the beginning of the main
2068 procedure, depending on the language used.
2070 The @samp{start} command does the equivalent of setting a temporary
2071 breakpoint at the beginning of the main procedure and then invoking
2072 the @samp{run} command.
2074 @cindex elaboration phase
2075 Some programs contain an @dfn{elaboration} phase where some startup code is
2076 executed before the main procedure is called. This depends on the
2077 languages used to write your program. In C@t{++}, for instance,
2078 constructors for static and global objects are executed before
2079 @code{main} is called. It is therefore possible that the debugger stops
2080 before reaching the main procedure. However, the temporary breakpoint
2081 will remain to halt execution.
2083 Specify the arguments to give to your program as arguments to the
2084 @samp{start} command. These arguments will be given verbatim to the
2085 underlying @samp{run} command. Note that the same arguments will be
2086 reused if no argument is provided during subsequent calls to
2087 @samp{start} or @samp{run}.
2089 It is sometimes necessary to debug the program during elaboration. In
2090 these cases, using the @code{start} command would stop the execution of
2091 your program too late, as the program would have already completed the
2092 elaboration phase. Under these circumstances, insert breakpoints in your
2093 elaboration code before running your program.
2095 @anchor{set exec-wrapper}
2096 @kindex set exec-wrapper
2097 @item set exec-wrapper @var{wrapper}
2098 @itemx show exec-wrapper
2099 @itemx unset exec-wrapper
2100 When @samp{exec-wrapper} is set, the specified wrapper is used to
2101 launch programs for debugging. @value{GDBN} starts your program
2102 with a shell command of the form @kbd{exec @var{wrapper}
2103 @var{program}}. Quoting is added to @var{program} and its
2104 arguments, but not to @var{wrapper}, so you should add quotes if
2105 appropriate for your shell. The wrapper runs until it executes
2106 your program, and then @value{GDBN} takes control.
2108 You can use any program that eventually calls @code{execve} with
2109 its arguments as a wrapper. Several standard Unix utilities do
2110 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2111 with @code{exec "$@@"} will also work.
2113 For example, you can use @code{env} to pass an environment variable to
2114 the debugged program, without setting the variable in your shell's
2118 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2122 This command is available when debugging locally on most targets, excluding
2123 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2125 @kindex set startup-with-shell
2126 @item set startup-with-shell
2127 @itemx set startup-with-shell on
2128 @itemx set startup-with-shell off
2129 @itemx show set startup-with-shell
2130 On Unix systems, by default, if a shell is available on your target,
2131 @value{GDBN}) uses it to start your program. Arguments of the
2132 @code{run} command are passed to the shell, which does variable
2133 substitution, expands wildcard characters and performs redirection of
2134 I/O. In some circumstances, it may be useful to disable such use of a
2135 shell, for example, when debugging the shell itself or diagnosing
2136 startup failures such as:
2140 Starting program: ./a.out
2141 During startup program terminated with signal SIGSEGV, Segmentation fault.
2145 which indicates the shell or the wrapper specified with
2146 @samp{exec-wrapper} crashed, not your program. Most often, this is
2147 caused by something odd in your shell's non-interactive mode
2148 initialization file---such as @file{.cshrc} for C-shell,
2149 $@file{.zshenv} for the Z shell, or the file specified in the
2150 @samp{BASH_ENV} environment variable for BASH.
2152 @anchor{set auto-connect-native-target}
2153 @kindex set auto-connect-native-target
2154 @item set auto-connect-native-target
2155 @itemx set auto-connect-native-target on
2156 @itemx set auto-connect-native-target off
2157 @itemx show auto-connect-native-target
2159 By default, if not connected to any target yet (e.g., with
2160 @code{target remote}), the @code{run} command starts your program as a
2161 native process under @value{GDBN}, on your local machine. If you're
2162 sure you don't want to debug programs on your local machine, you can
2163 tell @value{GDBN} to not connect to the native target automatically
2164 with the @code{set auto-connect-native-target off} command.
2166 If @code{on}, which is the default, and if @value{GDBN} is not
2167 connected to a target already, the @code{run} command automaticaly
2168 connects to the native target, if one is available.
2170 If @code{off}, and if @value{GDBN} is not connected to a target
2171 already, the @code{run} command fails with an error:
2175 Don't know how to run. Try "help target".
2178 If @value{GDBN} is already connected to a target, @value{GDBN} always
2179 uses it with the @code{run} command.
2181 In any case, you can explicitly connect to the native target with the
2182 @code{target native} command. For example,
2185 (@value{GDBP}) set auto-connect-native-target off
2187 Don't know how to run. Try "help target".
2188 (@value{GDBP}) target native
2190 Starting program: ./a.out
2191 [Inferior 1 (process 10421) exited normally]
2194 In case you connected explicitly to the @code{native} target,
2195 @value{GDBN} remains connected even if all inferiors exit, ready for
2196 the next @code{run} command. Use the @code{disconnect} command to
2199 Examples of other commands that likewise respect the
2200 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2201 proc}, @code{info os}.
2203 @kindex set disable-randomization
2204 @item set disable-randomization
2205 @itemx set disable-randomization on
2206 This option (enabled by default in @value{GDBN}) will turn off the native
2207 randomization of the virtual address space of the started program. This option
2208 is useful for multiple debugging sessions to make the execution better
2209 reproducible and memory addresses reusable across debugging sessions.
2211 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2212 On @sc{gnu}/Linux you can get the same behavior using
2215 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2218 @item set disable-randomization off
2219 Leave the behavior of the started executable unchanged. Some bugs rear their
2220 ugly heads only when the program is loaded at certain addresses. If your bug
2221 disappears when you run the program under @value{GDBN}, that might be because
2222 @value{GDBN} by default disables the address randomization on platforms, such
2223 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2224 disable-randomization off} to try to reproduce such elusive bugs.
2226 On targets where it is available, virtual address space randomization
2227 protects the programs against certain kinds of security attacks. In these
2228 cases the attacker needs to know the exact location of a concrete executable
2229 code. Randomizing its location makes it impossible to inject jumps misusing
2230 a code at its expected addresses.
2232 Prelinking shared libraries provides a startup performance advantage but it
2233 makes addresses in these libraries predictable for privileged processes by
2234 having just unprivileged access at the target system. Reading the shared
2235 library binary gives enough information for assembling the malicious code
2236 misusing it. Still even a prelinked shared library can get loaded at a new
2237 random address just requiring the regular relocation process during the
2238 startup. Shared libraries not already prelinked are always loaded at
2239 a randomly chosen address.
2241 Position independent executables (PIE) contain position independent code
2242 similar to the shared libraries and therefore such executables get loaded at
2243 a randomly chosen address upon startup. PIE executables always load even
2244 already prelinked shared libraries at a random address. You can build such
2245 executable using @command{gcc -fPIE -pie}.
2247 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2248 (as long as the randomization is enabled).
2250 @item show disable-randomization
2251 Show the current setting of the explicit disable of the native randomization of
2252 the virtual address space of the started program.
2257 @section Your Program's Arguments
2259 @cindex arguments (to your program)
2260 The arguments to your program can be specified by the arguments of the
2262 They are passed to a shell, which expands wildcard characters and
2263 performs redirection of I/O, and thence to your program. Your
2264 @code{SHELL} environment variable (if it exists) specifies what shell
2265 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2266 the default shell (@file{/bin/sh} on Unix).
2268 On non-Unix systems, the program is usually invoked directly by
2269 @value{GDBN}, which emulates I/O redirection via the appropriate system
2270 calls, and the wildcard characters are expanded by the startup code of
2271 the program, not by the shell.
2273 @code{run} with no arguments uses the same arguments used by the previous
2274 @code{run}, or those set by the @code{set args} command.
2279 Specify the arguments to be used the next time your program is run. If
2280 @code{set args} has no arguments, @code{run} executes your program
2281 with no arguments. Once you have run your program with arguments,
2282 using @code{set args} before the next @code{run} is the only way to run
2283 it again without arguments.
2287 Show the arguments to give your program when it is started.
2291 @section Your Program's Environment
2293 @cindex environment (of your program)
2294 The @dfn{environment} consists of a set of environment variables and
2295 their values. Environment variables conventionally record such things as
2296 your user name, your home directory, your terminal type, and your search
2297 path for programs to run. Usually you set up environment variables with
2298 the shell and they are inherited by all the other programs you run. When
2299 debugging, it can be useful to try running your program with a modified
2300 environment without having to start @value{GDBN} over again.
2304 @item path @var{directory}
2305 Add @var{directory} to the front of the @code{PATH} environment variable
2306 (the search path for executables) that will be passed to your program.
2307 The value of @code{PATH} used by @value{GDBN} does not change.
2308 You may specify several directory names, separated by whitespace or by a
2309 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2310 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2311 is moved to the front, so it is searched sooner.
2313 You can use the string @samp{$cwd} to refer to whatever is the current
2314 working directory at the time @value{GDBN} searches the path. If you
2315 use @samp{.} instead, it refers to the directory where you executed the
2316 @code{path} command. @value{GDBN} replaces @samp{.} in the
2317 @var{directory} argument (with the current path) before adding
2318 @var{directory} to the search path.
2319 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2320 @c document that, since repeating it would be a no-op.
2324 Display the list of search paths for executables (the @code{PATH}
2325 environment variable).
2327 @kindex show environment
2328 @item show environment @r{[}@var{varname}@r{]}
2329 Print the value of environment variable @var{varname} to be given to
2330 your program when it starts. If you do not supply @var{varname},
2331 print the names and values of all environment variables to be given to
2332 your program. You can abbreviate @code{environment} as @code{env}.
2334 @kindex set environment
2335 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2336 Set environment variable @var{varname} to @var{value}. The value
2337 changes for your program (and the shell @value{GDBN} uses to launch
2338 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2339 values of environment variables are just strings, and any
2340 interpretation is supplied by your program itself. The @var{value}
2341 parameter is optional; if it is eliminated, the variable is set to a
2343 @c "any string" here does not include leading, trailing
2344 @c blanks. Gnu asks: does anyone care?
2346 For example, this command:
2353 tells the debugged program, when subsequently run, that its user is named
2354 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2355 are not actually required.)
2357 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2358 which also inherits the environment set with @code{set environment}.
2359 If necessary, you can avoid that by using the @samp{env} program as a
2360 wrapper instead of using @code{set environment}. @xref{set
2361 exec-wrapper}, for an example doing just that.
2363 @kindex unset environment
2364 @item unset environment @var{varname}
2365 Remove variable @var{varname} from the environment to be passed to your
2366 program. This is different from @samp{set env @var{varname} =};
2367 @code{unset environment} removes the variable from the environment,
2368 rather than assigning it an empty value.
2371 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2372 the shell indicated by your @code{SHELL} environment variable if it
2373 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2374 names a shell that runs an initialization file when started
2375 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2376 for the Z shell, or the file specified in the @samp{BASH_ENV}
2377 environment variable for BASH---any variables you set in that file
2378 affect your program. You may wish to move setting of environment
2379 variables to files that are only run when you sign on, such as
2380 @file{.login} or @file{.profile}.
2382 @node Working Directory
2383 @section Your Program's Working Directory
2385 @cindex working directory (of your program)
2386 Each time you start your program with @code{run}, it inherits its
2387 working directory from the current working directory of @value{GDBN}.
2388 The @value{GDBN} working directory is initially whatever it inherited
2389 from its parent process (typically the shell), but you can specify a new
2390 working directory in @value{GDBN} with the @code{cd} command.
2392 The @value{GDBN} working directory also serves as a default for the commands
2393 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2398 @cindex change working directory
2399 @item cd @r{[}@var{directory}@r{]}
2400 Set the @value{GDBN} working directory to @var{directory}. If not
2401 given, @var{directory} uses @file{'~'}.
2405 Print the @value{GDBN} working directory.
2408 It is generally impossible to find the current working directory of
2409 the process being debugged (since a program can change its directory
2410 during its run). If you work on a system where @value{GDBN} is
2411 configured with the @file{/proc} support, you can use the @code{info
2412 proc} command (@pxref{SVR4 Process Information}) to find out the
2413 current working directory of the debuggee.
2416 @section Your Program's Input and Output
2421 By default, the program you run under @value{GDBN} does input and output to
2422 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2423 to its own terminal modes to interact with you, but it records the terminal
2424 modes your program was using and switches back to them when you continue
2425 running your program.
2428 @kindex info terminal
2430 Displays information recorded by @value{GDBN} about the terminal modes your
2434 You can redirect your program's input and/or output using shell
2435 redirection with the @code{run} command. For example,
2442 starts your program, diverting its output to the file @file{outfile}.
2445 @cindex controlling terminal
2446 Another way to specify where your program should do input and output is
2447 with the @code{tty} command. This command accepts a file name as
2448 argument, and causes this file to be the default for future @code{run}
2449 commands. It also resets the controlling terminal for the child
2450 process, for future @code{run} commands. For example,
2457 directs that processes started with subsequent @code{run} commands
2458 default to do input and output on the terminal @file{/dev/ttyb} and have
2459 that as their controlling terminal.
2461 An explicit redirection in @code{run} overrides the @code{tty} command's
2462 effect on the input/output device, but not its effect on the controlling
2465 When you use the @code{tty} command or redirect input in the @code{run}
2466 command, only the input @emph{for your program} is affected. The input
2467 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2468 for @code{set inferior-tty}.
2470 @cindex inferior tty
2471 @cindex set inferior controlling terminal
2472 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2473 display the name of the terminal that will be used for future runs of your
2477 @item set inferior-tty /dev/ttyb
2478 @kindex set inferior-tty
2479 Set the tty for the program being debugged to /dev/ttyb.
2481 @item show inferior-tty
2482 @kindex show inferior-tty
2483 Show the current tty for the program being debugged.
2487 @section Debugging an Already-running Process
2492 @item attach @var{process-id}
2493 This command attaches to a running process---one that was started
2494 outside @value{GDBN}. (@code{info files} shows your active
2495 targets.) The command takes as argument a process ID. The usual way to
2496 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2497 or with the @samp{jobs -l} shell command.
2499 @code{attach} does not repeat if you press @key{RET} a second time after
2500 executing the command.
2503 To use @code{attach}, your program must be running in an environment
2504 which supports processes; for example, @code{attach} does not work for
2505 programs on bare-board targets that lack an operating system. You must
2506 also have permission to send the process a signal.
2508 When you use @code{attach}, the debugger finds the program running in
2509 the process first by looking in the current working directory, then (if
2510 the program is not found) by using the source file search path
2511 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2512 the @code{file} command to load the program. @xref{Files, ,Commands to
2515 The first thing @value{GDBN} does after arranging to debug the specified
2516 process is to stop it. You can examine and modify an attached process
2517 with all the @value{GDBN} commands that are ordinarily available when
2518 you start processes with @code{run}. You can insert breakpoints; you
2519 can step and continue; you can modify storage. If you would rather the
2520 process continue running, you may use the @code{continue} command after
2521 attaching @value{GDBN} to the process.
2526 When you have finished debugging the attached process, you can use the
2527 @code{detach} command to release it from @value{GDBN} control. Detaching
2528 the process continues its execution. After the @code{detach} command,
2529 that process and @value{GDBN} become completely independent once more, and you
2530 are ready to @code{attach} another process or start one with @code{run}.
2531 @code{detach} does not repeat if you press @key{RET} again after
2532 executing the command.
2535 If you exit @value{GDBN} while you have an attached process, you detach
2536 that process. If you use the @code{run} command, you kill that process.
2537 By default, @value{GDBN} asks for confirmation if you try to do either of these
2538 things; you can control whether or not you need to confirm by using the
2539 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2543 @section Killing the Child Process
2548 Kill the child process in which your program is running under @value{GDBN}.
2551 This command is useful if you wish to debug a core dump instead of a
2552 running process. @value{GDBN} ignores any core dump file while your program
2555 On some operating systems, a program cannot be executed outside @value{GDBN}
2556 while you have breakpoints set on it inside @value{GDBN}. You can use the
2557 @code{kill} command in this situation to permit running your program
2558 outside the debugger.
2560 The @code{kill} command is also useful if you wish to recompile and
2561 relink your program, since on many systems it is impossible to modify an
2562 executable file while it is running in a process. In this case, when you
2563 next type @code{run}, @value{GDBN} notices that the file has changed, and
2564 reads the symbol table again (while trying to preserve your current
2565 breakpoint settings).
2567 @node Inferiors and Programs
2568 @section Debugging Multiple Inferiors and Programs
2570 @value{GDBN} lets you run and debug multiple programs in a single
2571 session. In addition, @value{GDBN} on some systems may let you run
2572 several programs simultaneously (otherwise you have to exit from one
2573 before starting another). In the most general case, you can have
2574 multiple threads of execution in each of multiple processes, launched
2575 from multiple executables.
2578 @value{GDBN} represents the state of each program execution with an
2579 object called an @dfn{inferior}. An inferior typically corresponds to
2580 a process, but is more general and applies also to targets that do not
2581 have processes. Inferiors may be created before a process runs, and
2582 may be retained after a process exits. Inferiors have unique
2583 identifiers that are different from process ids. Usually each
2584 inferior will also have its own distinct address space, although some
2585 embedded targets may have several inferiors running in different parts
2586 of a single address space. Each inferior may in turn have multiple
2587 threads running in it.
2589 To find out what inferiors exist at any moment, use @w{@code{info
2593 @kindex info inferiors
2594 @item info inferiors
2595 Print a list of all inferiors currently being managed by @value{GDBN}.
2597 @value{GDBN} displays for each inferior (in this order):
2601 the inferior number assigned by @value{GDBN}
2604 the target system's inferior identifier
2607 the name of the executable the inferior is running.
2612 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2613 indicates the current inferior.
2617 @c end table here to get a little more width for example
2620 (@value{GDBP}) info inferiors
2621 Num Description Executable
2622 2 process 2307 hello
2623 * 1 process 3401 goodbye
2626 To switch focus between inferiors, use the @code{inferior} command:
2629 @kindex inferior @var{infno}
2630 @item inferior @var{infno}
2631 Make inferior number @var{infno} the current inferior. The argument
2632 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2633 in the first field of the @samp{info inferiors} display.
2637 You can get multiple executables into a debugging session via the
2638 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2639 systems @value{GDBN} can add inferiors to the debug session
2640 automatically by following calls to @code{fork} and @code{exec}. To
2641 remove inferiors from the debugging session use the
2642 @w{@code{remove-inferiors}} command.
2645 @kindex add-inferior
2646 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2647 Adds @var{n} inferiors to be run using @var{executable} as the
2648 executable; @var{n} defaults to 1. If no executable is specified,
2649 the inferiors begins empty, with no program. You can still assign or
2650 change the program assigned to the inferior at any time by using the
2651 @code{file} command with the executable name as its argument.
2653 @kindex clone-inferior
2654 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2655 Adds @var{n} inferiors ready to execute the same program as inferior
2656 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
2657 number of the current inferior. This is a convenient command when you
2658 want to run another instance of the inferior you are debugging.
2661 (@value{GDBP}) info inferiors
2662 Num Description Executable
2663 * 1 process 29964 helloworld
2664 (@value{GDBP}) clone-inferior
2667 (@value{GDBP}) info inferiors
2668 Num Description Executable
2670 * 1 process 29964 helloworld
2673 You can now simply switch focus to inferior 2 and run it.
2675 @kindex remove-inferiors
2676 @item remove-inferiors @var{infno}@dots{}
2677 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2678 possible to remove an inferior that is running with this command. For
2679 those, use the @code{kill} or @code{detach} command first.
2683 To quit debugging one of the running inferiors that is not the current
2684 inferior, you can either detach from it by using the @w{@code{detach
2685 inferior}} command (allowing it to run independently), or kill it
2686 using the @w{@code{kill inferiors}} command:
2689 @kindex detach inferiors @var{infno}@dots{}
2690 @item detach inferior @var{infno}@dots{}
2691 Detach from the inferior or inferiors identified by @value{GDBN}
2692 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2693 still stays on the list of inferiors shown by @code{info inferiors},
2694 but its Description will show @samp{<null>}.
2696 @kindex kill inferiors @var{infno}@dots{}
2697 @item kill inferiors @var{infno}@dots{}
2698 Kill the inferior or inferiors identified by @value{GDBN} inferior
2699 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2700 stays on the list of inferiors shown by @code{info inferiors}, but its
2701 Description will show @samp{<null>}.
2704 After the successful completion of a command such as @code{detach},
2705 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2706 a normal process exit, the inferior is still valid and listed with
2707 @code{info inferiors}, ready to be restarted.
2710 To be notified when inferiors are started or exit under @value{GDBN}'s
2711 control use @w{@code{set print inferior-events}}:
2714 @kindex set print inferior-events
2715 @cindex print messages on inferior start and exit
2716 @item set print inferior-events
2717 @itemx set print inferior-events on
2718 @itemx set print inferior-events off
2719 The @code{set print inferior-events} command allows you to enable or
2720 disable printing of messages when @value{GDBN} notices that new
2721 inferiors have started or that inferiors have exited or have been
2722 detached. By default, these messages will not be printed.
2724 @kindex show print inferior-events
2725 @item show print inferior-events
2726 Show whether messages will be printed when @value{GDBN} detects that
2727 inferiors have started, exited or have been detached.
2730 Many commands will work the same with multiple programs as with a
2731 single program: e.g., @code{print myglobal} will simply display the
2732 value of @code{myglobal} in the current inferior.
2735 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2736 get more info about the relationship of inferiors, programs, address
2737 spaces in a debug session. You can do that with the @w{@code{maint
2738 info program-spaces}} command.
2741 @kindex maint info program-spaces
2742 @item maint info program-spaces
2743 Print a list of all program spaces currently being managed by
2746 @value{GDBN} displays for each program space (in this order):
2750 the program space number assigned by @value{GDBN}
2753 the name of the executable loaded into the program space, with e.g.,
2754 the @code{file} command.
2759 An asterisk @samp{*} preceding the @value{GDBN} program space number
2760 indicates the current program space.
2762 In addition, below each program space line, @value{GDBN} prints extra
2763 information that isn't suitable to display in tabular form. For
2764 example, the list of inferiors bound to the program space.
2767 (@value{GDBP}) maint info program-spaces
2770 Bound inferiors: ID 1 (process 21561)
2774 Here we can see that no inferior is running the program @code{hello},
2775 while @code{process 21561} is running the program @code{goodbye}. On
2776 some targets, it is possible that multiple inferiors are bound to the
2777 same program space. The most common example is that of debugging both
2778 the parent and child processes of a @code{vfork} call. For example,
2781 (@value{GDBP}) maint info program-spaces
2784 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2787 Here, both inferior 2 and inferior 1 are running in the same program
2788 space as a result of inferior 1 having executed a @code{vfork} call.
2792 @section Debugging Programs with Multiple Threads
2794 @cindex threads of execution
2795 @cindex multiple threads
2796 @cindex switching threads
2797 In some operating systems, such as HP-UX and Solaris, a single program
2798 may have more than one @dfn{thread} of execution. The precise semantics
2799 of threads differ from one operating system to another, but in general
2800 the threads of a single program are akin to multiple processes---except
2801 that they share one address space (that is, they can all examine and
2802 modify the same variables). On the other hand, each thread has its own
2803 registers and execution stack, and perhaps private memory.
2805 @value{GDBN} provides these facilities for debugging multi-thread
2809 @item automatic notification of new threads
2810 @item @samp{thread @var{threadno}}, a command to switch among threads
2811 @item @samp{info threads}, a command to inquire about existing threads
2812 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2813 a command to apply a command to a list of threads
2814 @item thread-specific breakpoints
2815 @item @samp{set print thread-events}, which controls printing of
2816 messages on thread start and exit.
2817 @item @samp{set libthread-db-search-path @var{path}}, which lets
2818 the user specify which @code{libthread_db} to use if the default choice
2819 isn't compatible with the program.
2823 @emph{Warning:} These facilities are not yet available on every
2824 @value{GDBN} configuration where the operating system supports threads.
2825 If your @value{GDBN} does not support threads, these commands have no
2826 effect. For example, a system without thread support shows no output
2827 from @samp{info threads}, and always rejects the @code{thread} command,
2831 (@value{GDBP}) info threads
2832 (@value{GDBP}) thread 1
2833 Thread ID 1 not known. Use the "info threads" command to
2834 see the IDs of currently known threads.
2836 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2837 @c doesn't support threads"?
2840 @cindex focus of debugging
2841 @cindex current thread
2842 The @value{GDBN} thread debugging facility allows you to observe all
2843 threads while your program runs---but whenever @value{GDBN} takes
2844 control, one thread in particular is always the focus of debugging.
2845 This thread is called the @dfn{current thread}. Debugging commands show
2846 program information from the perspective of the current thread.
2848 @cindex @code{New} @var{systag} message
2849 @cindex thread identifier (system)
2850 @c FIXME-implementors!! It would be more helpful if the [New...] message
2851 @c included GDB's numeric thread handle, so you could just go to that
2852 @c thread without first checking `info threads'.
2853 Whenever @value{GDBN} detects a new thread in your program, it displays
2854 the target system's identification for the thread with a message in the
2855 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
2856 whose form varies depending on the particular system. For example, on
2857 @sc{gnu}/Linux, you might see
2860 [New Thread 0x41e02940 (LWP 25582)]
2864 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2865 the @var{systag} is simply something like @samp{process 368}, with no
2868 @c FIXME!! (1) Does the [New...] message appear even for the very first
2869 @c thread of a program, or does it only appear for the
2870 @c second---i.e.@: when it becomes obvious we have a multithread
2872 @c (2) *Is* there necessarily a first thread always? Or do some
2873 @c multithread systems permit starting a program with multiple
2874 @c threads ab initio?
2876 @cindex thread number
2877 @cindex thread identifier (GDB)
2878 For debugging purposes, @value{GDBN} associates its own thread
2879 number---always a single integer---with each thread in your program.
2882 @kindex info threads
2883 @item info threads @r{[}@var{id}@dots{}@r{]}
2884 Display a summary of all threads currently in your program. Optional
2885 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2886 means to print information only about the specified thread or threads.
2887 @value{GDBN} displays for each thread (in this order):
2891 the thread number assigned by @value{GDBN}
2894 the target system's thread identifier (@var{systag})
2897 the thread's name, if one is known. A thread can either be named by
2898 the user (see @code{thread name}, below), or, in some cases, by the
2902 the current stack frame summary for that thread
2906 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2907 indicates the current thread.
2911 @c end table here to get a little more width for example
2914 (@value{GDBP}) info threads
2916 3 process 35 thread 27 0x34e5 in sigpause ()
2917 2 process 35 thread 23 0x34e5 in sigpause ()
2918 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2922 On Solaris, you can display more information about user threads with a
2923 Solaris-specific command:
2926 @item maint info sol-threads
2927 @kindex maint info sol-threads
2928 @cindex thread info (Solaris)
2929 Display info on Solaris user threads.
2933 @kindex thread @var{threadno}
2934 @item thread @var{threadno}
2935 Make thread number @var{threadno} the current thread. The command
2936 argument @var{threadno} is the internal @value{GDBN} thread number, as
2937 shown in the first field of the @samp{info threads} display.
2938 @value{GDBN} responds by displaying the system identifier of the thread
2939 you selected, and its current stack frame summary:
2942 (@value{GDBP}) thread 2
2943 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2944 #0 some_function (ignore=0x0) at example.c:8
2945 8 printf ("hello\n");
2949 As with the @samp{[New @dots{}]} message, the form of the text after
2950 @samp{Switching to} depends on your system's conventions for identifying
2953 @vindex $_thread@r{, convenience variable}
2954 The debugger convenience variable @samp{$_thread} contains the number
2955 of the current thread. You may find this useful in writing breakpoint
2956 conditional expressions, command scripts, and so forth. See
2957 @xref{Convenience Vars,, Convenience Variables}, for general
2958 information on convenience variables.
2960 @kindex thread apply
2961 @cindex apply command to several threads
2962 @item thread apply [@var{threadno} | all [-ascending]] @var{command}
2963 The @code{thread apply} command allows you to apply the named
2964 @var{command} to one or more threads. Specify the numbers of the
2965 threads that you want affected with the command argument
2966 @var{threadno}. It can be a single thread number, one of the numbers
2967 shown in the first field of the @samp{info threads} display; or it
2968 could be a range of thread numbers, as in @code{2-4}. To apply
2969 a command to all threads in descending order, type @kbd{thread apply all
2970 @var{command}}. To apply a command to all threads in ascending order,
2971 type @kbd{thread apply all -ascending @var{command}}.
2975 @cindex name a thread
2976 @item thread name [@var{name}]
2977 This command assigns a name to the current thread. If no argument is
2978 given, any existing user-specified name is removed. The thread name
2979 appears in the @samp{info threads} display.
2981 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2982 determine the name of the thread as given by the OS. On these
2983 systems, a name specified with @samp{thread name} will override the
2984 system-give name, and removing the user-specified name will cause
2985 @value{GDBN} to once again display the system-specified name.
2988 @cindex search for a thread
2989 @item thread find [@var{regexp}]
2990 Search for and display thread ids whose name or @var{systag}
2991 matches the supplied regular expression.
2993 As well as being the complement to the @samp{thread name} command,
2994 this command also allows you to identify a thread by its target
2995 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2999 (@value{GDBN}) thread find 26688
3000 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3001 (@value{GDBN}) info thread 4
3003 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3006 @kindex set print thread-events
3007 @cindex print messages on thread start and exit
3008 @item set print thread-events
3009 @itemx set print thread-events on
3010 @itemx set print thread-events off
3011 The @code{set print thread-events} command allows you to enable or
3012 disable printing of messages when @value{GDBN} notices that new threads have
3013 started or that threads have exited. By default, these messages will
3014 be printed if detection of these events is supported by the target.
3015 Note that these messages cannot be disabled on all targets.
3017 @kindex show print thread-events
3018 @item show print thread-events
3019 Show whether messages will be printed when @value{GDBN} detects that threads
3020 have started and exited.
3023 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3024 more information about how @value{GDBN} behaves when you stop and start
3025 programs with multiple threads.
3027 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3028 watchpoints in programs with multiple threads.
3030 @anchor{set libthread-db-search-path}
3032 @kindex set libthread-db-search-path
3033 @cindex search path for @code{libthread_db}
3034 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3035 If this variable is set, @var{path} is a colon-separated list of
3036 directories @value{GDBN} will use to search for @code{libthread_db}.
3037 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3038 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3039 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3042 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3043 @code{libthread_db} library to obtain information about threads in the
3044 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3045 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3046 specific thread debugging library loading is enabled
3047 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3049 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3050 refers to the default system directories that are
3051 normally searched for loading shared libraries. The @samp{$sdir} entry
3052 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3053 (@pxref{libthread_db.so.1 file}).
3055 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3056 refers to the directory from which @code{libpthread}
3057 was loaded in the inferior process.
3059 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3060 @value{GDBN} attempts to initialize it with the current inferior process.
3061 If this initialization fails (which could happen because of a version
3062 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3063 will unload @code{libthread_db}, and continue with the next directory.
3064 If none of @code{libthread_db} libraries initialize successfully,
3065 @value{GDBN} will issue a warning and thread debugging will be disabled.
3067 Setting @code{libthread-db-search-path} is currently implemented
3068 only on some platforms.
3070 @kindex show libthread-db-search-path
3071 @item show libthread-db-search-path
3072 Display current libthread_db search path.
3074 @kindex set debug libthread-db
3075 @kindex show debug libthread-db
3076 @cindex debugging @code{libthread_db}
3077 @item set debug libthread-db
3078 @itemx show debug libthread-db
3079 Turns on or off display of @code{libthread_db}-related events.
3080 Use @code{1} to enable, @code{0} to disable.
3084 @section Debugging Forks
3086 @cindex fork, debugging programs which call
3087 @cindex multiple processes
3088 @cindex processes, multiple
3089 On most systems, @value{GDBN} has no special support for debugging
3090 programs which create additional processes using the @code{fork}
3091 function. When a program forks, @value{GDBN} will continue to debug the
3092 parent process and the child process will run unimpeded. If you have
3093 set a breakpoint in any code which the child then executes, the child
3094 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3095 will cause it to terminate.
3097 However, if you want to debug the child process there is a workaround
3098 which isn't too painful. Put a call to @code{sleep} in the code which
3099 the child process executes after the fork. It may be useful to sleep
3100 only if a certain environment variable is set, or a certain file exists,
3101 so that the delay need not occur when you don't want to run @value{GDBN}
3102 on the child. While the child is sleeping, use the @code{ps} program to
3103 get its process ID. Then tell @value{GDBN} (a new invocation of
3104 @value{GDBN} if you are also debugging the parent process) to attach to
3105 the child process (@pxref{Attach}). From that point on you can debug
3106 the child process just like any other process which you attached to.
3108 On some systems, @value{GDBN} provides support for debugging programs that
3109 create additional processes using the @code{fork} or @code{vfork} functions.
3110 Currently, the only platforms with this feature are HP-UX (11.x and later
3111 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
3113 By default, when a program forks, @value{GDBN} will continue to debug
3114 the parent process and the child process will run unimpeded.
3116 If you want to follow the child process instead of the parent process,
3117 use the command @w{@code{set follow-fork-mode}}.
3120 @kindex set follow-fork-mode
3121 @item set follow-fork-mode @var{mode}
3122 Set the debugger response to a program call of @code{fork} or
3123 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3124 process. The @var{mode} argument can be:
3128 The original process is debugged after a fork. The child process runs
3129 unimpeded. This is the default.
3132 The new process is debugged after a fork. The parent process runs
3137 @kindex show follow-fork-mode
3138 @item show follow-fork-mode
3139 Display the current debugger response to a @code{fork} or @code{vfork} call.
3142 @cindex debugging multiple processes
3143 On Linux, if you want to debug both the parent and child processes, use the
3144 command @w{@code{set detach-on-fork}}.
3147 @kindex set detach-on-fork
3148 @item set detach-on-fork @var{mode}
3149 Tells gdb whether to detach one of the processes after a fork, or
3150 retain debugger control over them both.
3154 The child process (or parent process, depending on the value of
3155 @code{follow-fork-mode}) will be detached and allowed to run
3156 independently. This is the default.
3159 Both processes will be held under the control of @value{GDBN}.
3160 One process (child or parent, depending on the value of
3161 @code{follow-fork-mode}) is debugged as usual, while the other
3166 @kindex show detach-on-fork
3167 @item show detach-on-fork
3168 Show whether detach-on-fork mode is on/off.
3171 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3172 will retain control of all forked processes (including nested forks).
3173 You can list the forked processes under the control of @value{GDBN} by
3174 using the @w{@code{info inferiors}} command, and switch from one fork
3175 to another by using the @code{inferior} command (@pxref{Inferiors and
3176 Programs, ,Debugging Multiple Inferiors and Programs}).
3178 To quit debugging one of the forked processes, you can either detach
3179 from it by using the @w{@code{detach inferiors}} command (allowing it
3180 to run independently), or kill it using the @w{@code{kill inferiors}}
3181 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3184 If you ask to debug a child process and a @code{vfork} is followed by an
3185 @code{exec}, @value{GDBN} executes the new target up to the first
3186 breakpoint in the new target. If you have a breakpoint set on
3187 @code{main} in your original program, the breakpoint will also be set on
3188 the child process's @code{main}.
3190 On some systems, when a child process is spawned by @code{vfork}, you
3191 cannot debug the child or parent until an @code{exec} call completes.
3193 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3194 call executes, the new target restarts. To restart the parent
3195 process, use the @code{file} command with the parent executable name
3196 as its argument. By default, after an @code{exec} call executes,
3197 @value{GDBN} discards the symbols of the previous executable image.
3198 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3202 @kindex set follow-exec-mode
3203 @item set follow-exec-mode @var{mode}
3205 Set debugger response to a program call of @code{exec}. An
3206 @code{exec} call replaces the program image of a process.
3208 @code{follow-exec-mode} can be:
3212 @value{GDBN} creates a new inferior and rebinds the process to this
3213 new inferior. The program the process was running before the
3214 @code{exec} call can be restarted afterwards by restarting the
3220 (@value{GDBP}) info inferiors
3222 Id Description Executable
3225 process 12020 is executing new program: prog2
3226 Program exited normally.
3227 (@value{GDBP}) info inferiors
3228 Id Description Executable
3234 @value{GDBN} keeps the process bound to the same inferior. The new
3235 executable image replaces the previous executable loaded in the
3236 inferior. Restarting the inferior after the @code{exec} call, with
3237 e.g., the @code{run} command, restarts the executable the process was
3238 running after the @code{exec} call. This is the default mode.
3243 (@value{GDBP}) info inferiors
3244 Id Description Executable
3247 process 12020 is executing new program: prog2
3248 Program exited normally.
3249 (@value{GDBP}) info inferiors
3250 Id Description Executable
3257 You can use the @code{catch} command to make @value{GDBN} stop whenever
3258 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3259 Catchpoints, ,Setting Catchpoints}.
3261 @node Checkpoint/Restart
3262 @section Setting a @emph{Bookmark} to Return to Later
3267 @cindex snapshot of a process
3268 @cindex rewind program state
3270 On certain operating systems@footnote{Currently, only
3271 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3272 program's state, called a @dfn{checkpoint}, and come back to it
3275 Returning to a checkpoint effectively undoes everything that has
3276 happened in the program since the @code{checkpoint} was saved. This
3277 includes changes in memory, registers, and even (within some limits)
3278 system state. Effectively, it is like going back in time to the
3279 moment when the checkpoint was saved.
3281 Thus, if you're stepping thru a program and you think you're
3282 getting close to the point where things go wrong, you can save
3283 a checkpoint. Then, if you accidentally go too far and miss
3284 the critical statement, instead of having to restart your program
3285 from the beginning, you can just go back to the checkpoint and
3286 start again from there.
3288 This can be especially useful if it takes a lot of time or
3289 steps to reach the point where you think the bug occurs.
3291 To use the @code{checkpoint}/@code{restart} method of debugging:
3296 Save a snapshot of the debugged program's current execution state.
3297 The @code{checkpoint} command takes no arguments, but each checkpoint
3298 is assigned a small integer id, similar to a breakpoint id.
3300 @kindex info checkpoints
3301 @item info checkpoints
3302 List the checkpoints that have been saved in the current debugging
3303 session. For each checkpoint, the following information will be
3310 @item Source line, or label
3313 @kindex restart @var{checkpoint-id}
3314 @item restart @var{checkpoint-id}
3315 Restore the program state that was saved as checkpoint number
3316 @var{checkpoint-id}. All program variables, registers, stack frames
3317 etc.@: will be returned to the values that they had when the checkpoint
3318 was saved. In essence, gdb will ``wind back the clock'' to the point
3319 in time when the checkpoint was saved.
3321 Note that breakpoints, @value{GDBN} variables, command history etc.
3322 are not affected by restoring a checkpoint. In general, a checkpoint
3323 only restores things that reside in the program being debugged, not in
3326 @kindex delete checkpoint @var{checkpoint-id}
3327 @item delete checkpoint @var{checkpoint-id}
3328 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3332 Returning to a previously saved checkpoint will restore the user state
3333 of the program being debugged, plus a significant subset of the system
3334 (OS) state, including file pointers. It won't ``un-write'' data from
3335 a file, but it will rewind the file pointer to the previous location,
3336 so that the previously written data can be overwritten. For files
3337 opened in read mode, the pointer will also be restored so that the
3338 previously read data can be read again.
3340 Of course, characters that have been sent to a printer (or other
3341 external device) cannot be ``snatched back'', and characters received
3342 from eg.@: a serial device can be removed from internal program buffers,
3343 but they cannot be ``pushed back'' into the serial pipeline, ready to
3344 be received again. Similarly, the actual contents of files that have
3345 been changed cannot be restored (at this time).
3347 However, within those constraints, you actually can ``rewind'' your
3348 program to a previously saved point in time, and begin debugging it
3349 again --- and you can change the course of events so as to debug a
3350 different execution path this time.
3352 @cindex checkpoints and process id
3353 Finally, there is one bit of internal program state that will be
3354 different when you return to a checkpoint --- the program's process
3355 id. Each checkpoint will have a unique process id (or @var{pid}),
3356 and each will be different from the program's original @var{pid}.
3357 If your program has saved a local copy of its process id, this could
3358 potentially pose a problem.
3360 @subsection A Non-obvious Benefit of Using Checkpoints
3362 On some systems such as @sc{gnu}/Linux, address space randomization
3363 is performed on new processes for security reasons. This makes it
3364 difficult or impossible to set a breakpoint, or watchpoint, on an
3365 absolute address if you have to restart the program, since the
3366 absolute location of a symbol will change from one execution to the
3369 A checkpoint, however, is an @emph{identical} copy of a process.
3370 Therefore if you create a checkpoint at (eg.@:) the start of main,
3371 and simply return to that checkpoint instead of restarting the
3372 process, you can avoid the effects of address randomization and
3373 your symbols will all stay in the same place.
3376 @chapter Stopping and Continuing
3378 The principal purposes of using a debugger are so that you can stop your
3379 program before it terminates; or so that, if your program runs into
3380 trouble, you can investigate and find out why.
3382 Inside @value{GDBN}, your program may stop for any of several reasons,
3383 such as a signal, a breakpoint, or reaching a new line after a
3384 @value{GDBN} command such as @code{step}. You may then examine and
3385 change variables, set new breakpoints or remove old ones, and then
3386 continue execution. Usually, the messages shown by @value{GDBN} provide
3387 ample explanation of the status of your program---but you can also
3388 explicitly request this information at any time.
3391 @kindex info program
3393 Display information about the status of your program: whether it is
3394 running or not, what process it is, and why it stopped.
3398 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3399 * Continuing and Stepping:: Resuming execution
3400 * Skipping Over Functions and Files::
3401 Skipping over functions and files
3403 * Thread Stops:: Stopping and starting multi-thread programs
3407 @section Breakpoints, Watchpoints, and Catchpoints
3410 A @dfn{breakpoint} makes your program stop whenever a certain point in
3411 the program is reached. For each breakpoint, you can add conditions to
3412 control in finer detail whether your program stops. You can set
3413 breakpoints with the @code{break} command and its variants (@pxref{Set
3414 Breaks, ,Setting Breakpoints}), to specify the place where your program
3415 should stop by line number, function name or exact address in the
3418 On some systems, you can set breakpoints in shared libraries before
3419 the executable is run. There is a minor limitation on HP-UX systems:
3420 you must wait until the executable is run in order to set breakpoints
3421 in shared library routines that are not called directly by the program
3422 (for example, routines that are arguments in a @code{pthread_create}
3426 @cindex data breakpoints
3427 @cindex memory tracing
3428 @cindex breakpoint on memory address
3429 @cindex breakpoint on variable modification
3430 A @dfn{watchpoint} is a special breakpoint that stops your program
3431 when the value of an expression changes. The expression may be a value
3432 of a variable, or it could involve values of one or more variables
3433 combined by operators, such as @samp{a + b}. This is sometimes called
3434 @dfn{data breakpoints}. You must use a different command to set
3435 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3436 from that, you can manage a watchpoint like any other breakpoint: you
3437 enable, disable, and delete both breakpoints and watchpoints using the
3440 You can arrange to have values from your program displayed automatically
3441 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3445 @cindex breakpoint on events
3446 A @dfn{catchpoint} is another special breakpoint that stops your program
3447 when a certain kind of event occurs, such as the throwing of a C@t{++}
3448 exception or the loading of a library. As with watchpoints, you use a
3449 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3450 Catchpoints}), but aside from that, you can manage a catchpoint like any
3451 other breakpoint. (To stop when your program receives a signal, use the
3452 @code{handle} command; see @ref{Signals, ,Signals}.)
3454 @cindex breakpoint numbers
3455 @cindex numbers for breakpoints
3456 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3457 catchpoint when you create it; these numbers are successive integers
3458 starting with one. In many of the commands for controlling various
3459 features of breakpoints you use the breakpoint number to say which
3460 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3461 @dfn{disabled}; if disabled, it has no effect on your program until you
3464 @cindex breakpoint ranges
3465 @cindex ranges of breakpoints
3466 Some @value{GDBN} commands accept a range of breakpoints on which to
3467 operate. A breakpoint range is either a single breakpoint number, like
3468 @samp{5}, or two such numbers, in increasing order, separated by a
3469 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3470 all breakpoints in that range are operated on.
3473 * Set Breaks:: Setting breakpoints
3474 * Set Watchpoints:: Setting watchpoints
3475 * Set Catchpoints:: Setting catchpoints
3476 * Delete Breaks:: Deleting breakpoints
3477 * Disabling:: Disabling breakpoints
3478 * Conditions:: Break conditions
3479 * Break Commands:: Breakpoint command lists
3480 * Dynamic Printf:: Dynamic printf
3481 * Save Breakpoints:: How to save breakpoints in a file
3482 * Static Probe Points:: Listing static probe points
3483 * Error in Breakpoints:: ``Cannot insert breakpoints''
3484 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3488 @subsection Setting Breakpoints
3490 @c FIXME LMB what does GDB do if no code on line of breakpt?
3491 @c consider in particular declaration with/without initialization.
3493 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3496 @kindex b @r{(@code{break})}
3497 @vindex $bpnum@r{, convenience variable}
3498 @cindex latest breakpoint
3499 Breakpoints are set with the @code{break} command (abbreviated
3500 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3501 number of the breakpoint you've set most recently; see @ref{Convenience
3502 Vars,, Convenience Variables}, for a discussion of what you can do with
3503 convenience variables.
3506 @item break @var{location}
3507 Set a breakpoint at the given @var{location}, which can specify a
3508 function name, a line number, or an address of an instruction.
3509 (@xref{Specify Location}, for a list of all the possible ways to
3510 specify a @var{location}.) The breakpoint will stop your program just
3511 before it executes any of the code in the specified @var{location}.
3513 When using source languages that permit overloading of symbols, such as
3514 C@t{++}, a function name may refer to more than one possible place to break.
3515 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3518 It is also possible to insert a breakpoint that will stop the program
3519 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3520 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3523 When called without any arguments, @code{break} sets a breakpoint at
3524 the next instruction to be executed in the selected stack frame
3525 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3526 innermost, this makes your program stop as soon as control
3527 returns to that frame. This is similar to the effect of a
3528 @code{finish} command in the frame inside the selected frame---except
3529 that @code{finish} does not leave an active breakpoint. If you use
3530 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3531 the next time it reaches the current location; this may be useful
3534 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3535 least one instruction has been executed. If it did not do this, you
3536 would be unable to proceed past a breakpoint without first disabling the
3537 breakpoint. This rule applies whether or not the breakpoint already
3538 existed when your program stopped.
3540 @item break @dots{} if @var{cond}
3541 Set a breakpoint with condition @var{cond}; evaluate the expression
3542 @var{cond} each time the breakpoint is reached, and stop only if the
3543 value is nonzero---that is, if @var{cond} evaluates as true.
3544 @samp{@dots{}} stands for one of the possible arguments described
3545 above (or no argument) specifying where to break. @xref{Conditions,
3546 ,Break Conditions}, for more information on breakpoint conditions.
3549 @item tbreak @var{args}
3550 Set a breakpoint enabled only for one stop. The @var{args} are the
3551 same as for the @code{break} command, and the breakpoint is set in the same
3552 way, but the breakpoint is automatically deleted after the first time your
3553 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3556 @cindex hardware breakpoints
3557 @item hbreak @var{args}
3558 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
3559 @code{break} command and the breakpoint is set in the same way, but the
3560 breakpoint requires hardware support and some target hardware may not
3561 have this support. The main purpose of this is EPROM/ROM code
3562 debugging, so you can set a breakpoint at an instruction without
3563 changing the instruction. This can be used with the new trap-generation
3564 provided by SPARClite DSU and most x86-based targets. These targets
3565 will generate traps when a program accesses some data or instruction
3566 address that is assigned to the debug registers. However the hardware
3567 breakpoint registers can take a limited number of breakpoints. For
3568 example, on the DSU, only two data breakpoints can be set at a time, and
3569 @value{GDBN} will reject this command if more than two are used. Delete
3570 or disable unused hardware breakpoints before setting new ones
3571 (@pxref{Disabling, ,Disabling Breakpoints}).
3572 @xref{Conditions, ,Break Conditions}.
3573 For remote targets, you can restrict the number of hardware
3574 breakpoints @value{GDBN} will use, see @ref{set remote
3575 hardware-breakpoint-limit}.
3578 @item thbreak @var{args}
3579 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
3580 are the same as for the @code{hbreak} command and the breakpoint is set in
3581 the same way. However, like the @code{tbreak} command,
3582 the breakpoint is automatically deleted after the
3583 first time your program stops there. Also, like the @code{hbreak}
3584 command, the breakpoint requires hardware support and some target hardware
3585 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3586 See also @ref{Conditions, ,Break Conditions}.
3589 @cindex regular expression
3590 @cindex breakpoints at functions matching a regexp
3591 @cindex set breakpoints in many functions
3592 @item rbreak @var{regex}
3593 Set breakpoints on all functions matching the regular expression
3594 @var{regex}. This command sets an unconditional breakpoint on all
3595 matches, printing a list of all breakpoints it set. Once these
3596 breakpoints are set, they are treated just like the breakpoints set with
3597 the @code{break} command. You can delete them, disable them, or make
3598 them conditional the same way as any other breakpoint.
3600 The syntax of the regular expression is the standard one used with tools
3601 like @file{grep}. Note that this is different from the syntax used by
3602 shells, so for instance @code{foo*} matches all functions that include
3603 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3604 @code{.*} leading and trailing the regular expression you supply, so to
3605 match only functions that begin with @code{foo}, use @code{^foo}.
3607 @cindex non-member C@t{++} functions, set breakpoint in
3608 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3609 breakpoints on overloaded functions that are not members of any special
3612 @cindex set breakpoints on all functions
3613 The @code{rbreak} command can be used to set breakpoints in
3614 @strong{all} the functions in a program, like this:
3617 (@value{GDBP}) rbreak .
3620 @item rbreak @var{file}:@var{regex}
3621 If @code{rbreak} is called with a filename qualification, it limits
3622 the search for functions matching the given regular expression to the
3623 specified @var{file}. This can be used, for example, to set breakpoints on
3624 every function in a given file:
3627 (@value{GDBP}) rbreak file.c:.
3630 The colon separating the filename qualifier from the regex may
3631 optionally be surrounded by spaces.
3633 @kindex info breakpoints
3634 @cindex @code{$_} and @code{info breakpoints}
3635 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3636 @itemx info break @r{[}@var{n}@dots{}@r{]}
3637 Print a table of all breakpoints, watchpoints, and catchpoints set and
3638 not deleted. Optional argument @var{n} means print information only
3639 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3640 For each breakpoint, following columns are printed:
3643 @item Breakpoint Numbers
3645 Breakpoint, watchpoint, or catchpoint.
3647 Whether the breakpoint is marked to be disabled or deleted when hit.
3648 @item Enabled or Disabled
3649 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3650 that are not enabled.
3652 Where the breakpoint is in your program, as a memory address. For a
3653 pending breakpoint whose address is not yet known, this field will
3654 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3655 library that has the symbol or line referred by breakpoint is loaded.
3656 See below for details. A breakpoint with several locations will
3657 have @samp{<MULTIPLE>} in this field---see below for details.
3659 Where the breakpoint is in the source for your program, as a file and
3660 line number. For a pending breakpoint, the original string passed to
3661 the breakpoint command will be listed as it cannot be resolved until
3662 the appropriate shared library is loaded in the future.
3666 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3667 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3668 @value{GDBN} on the host's side. If it is ``target'', then the condition
3669 is evaluated by the target. The @code{info break} command shows
3670 the condition on the line following the affected breakpoint, together with
3671 its condition evaluation mode in between parentheses.
3673 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3674 allowed to have a condition specified for it. The condition is not parsed for
3675 validity until a shared library is loaded that allows the pending
3676 breakpoint to resolve to a valid location.
3679 @code{info break} with a breakpoint
3680 number @var{n} as argument lists only that breakpoint. The
3681 convenience variable @code{$_} and the default examining-address for
3682 the @code{x} command are set to the address of the last breakpoint
3683 listed (@pxref{Memory, ,Examining Memory}).
3686 @code{info break} displays a count of the number of times the breakpoint
3687 has been hit. This is especially useful in conjunction with the
3688 @code{ignore} command. You can ignore a large number of breakpoint
3689 hits, look at the breakpoint info to see how many times the breakpoint
3690 was hit, and then run again, ignoring one less than that number. This
3691 will get you quickly to the last hit of that breakpoint.
3694 For a breakpoints with an enable count (xref) greater than 1,
3695 @code{info break} also displays that count.
3699 @value{GDBN} allows you to set any number of breakpoints at the same place in
3700 your program. There is nothing silly or meaningless about this. When
3701 the breakpoints are conditional, this is even useful
3702 (@pxref{Conditions, ,Break Conditions}).
3704 @cindex multiple locations, breakpoints
3705 @cindex breakpoints, multiple locations
3706 It is possible that a breakpoint corresponds to several locations
3707 in your program. Examples of this situation are:
3711 Multiple functions in the program may have the same name.
3714 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3715 instances of the function body, used in different cases.
3718 For a C@t{++} template function, a given line in the function can
3719 correspond to any number of instantiations.
3722 For an inlined function, a given source line can correspond to
3723 several places where that function is inlined.
3726 In all those cases, @value{GDBN} will insert a breakpoint at all
3727 the relevant locations.
3729 A breakpoint with multiple locations is displayed in the breakpoint
3730 table using several rows---one header row, followed by one row for
3731 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3732 address column. The rows for individual locations contain the actual
3733 addresses for locations, and show the functions to which those
3734 locations belong. The number column for a location is of the form
3735 @var{breakpoint-number}.@var{location-number}.
3740 Num Type Disp Enb Address What
3741 1 breakpoint keep y <MULTIPLE>
3743 breakpoint already hit 1 time
3744 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3745 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3748 Each location can be individually enabled or disabled by passing
3749 @var{breakpoint-number}.@var{location-number} as argument to the
3750 @code{enable} and @code{disable} commands. Note that you cannot
3751 delete the individual locations from the list, you can only delete the
3752 entire list of locations that belong to their parent breakpoint (with
3753 the @kbd{delete @var{num}} command, where @var{num} is the number of
3754 the parent breakpoint, 1 in the above example). Disabling or enabling
3755 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3756 that belong to that breakpoint.
3758 @cindex pending breakpoints
3759 It's quite common to have a breakpoint inside a shared library.
3760 Shared libraries can be loaded and unloaded explicitly,
3761 and possibly repeatedly, as the program is executed. To support
3762 this use case, @value{GDBN} updates breakpoint locations whenever
3763 any shared library is loaded or unloaded. Typically, you would
3764 set a breakpoint in a shared library at the beginning of your
3765 debugging session, when the library is not loaded, and when the
3766 symbols from the library are not available. When you try to set
3767 breakpoint, @value{GDBN} will ask you if you want to set
3768 a so called @dfn{pending breakpoint}---breakpoint whose address
3769 is not yet resolved.
3771 After the program is run, whenever a new shared library is loaded,
3772 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3773 shared library contains the symbol or line referred to by some
3774 pending breakpoint, that breakpoint is resolved and becomes an
3775 ordinary breakpoint. When a library is unloaded, all breakpoints
3776 that refer to its symbols or source lines become pending again.
3778 This logic works for breakpoints with multiple locations, too. For
3779 example, if you have a breakpoint in a C@t{++} template function, and
3780 a newly loaded shared library has an instantiation of that template,
3781 a new location is added to the list of locations for the breakpoint.
3783 Except for having unresolved address, pending breakpoints do not
3784 differ from regular breakpoints. You can set conditions or commands,
3785 enable and disable them and perform other breakpoint operations.
3787 @value{GDBN} provides some additional commands for controlling what
3788 happens when the @samp{break} command cannot resolve breakpoint
3789 address specification to an address:
3791 @kindex set breakpoint pending
3792 @kindex show breakpoint pending
3794 @item set breakpoint pending auto
3795 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3796 location, it queries you whether a pending breakpoint should be created.
3798 @item set breakpoint pending on
3799 This indicates that an unrecognized breakpoint location should automatically
3800 result in a pending breakpoint being created.
3802 @item set breakpoint pending off
3803 This indicates that pending breakpoints are not to be created. Any
3804 unrecognized breakpoint location results in an error. This setting does
3805 not affect any pending breakpoints previously created.
3807 @item show breakpoint pending
3808 Show the current behavior setting for creating pending breakpoints.
3811 The settings above only affect the @code{break} command and its
3812 variants. Once breakpoint is set, it will be automatically updated
3813 as shared libraries are loaded and unloaded.
3815 @cindex automatic hardware breakpoints
3816 For some targets, @value{GDBN} can automatically decide if hardware or
3817 software breakpoints should be used, depending on whether the
3818 breakpoint address is read-only or read-write. This applies to
3819 breakpoints set with the @code{break} command as well as to internal
3820 breakpoints set by commands like @code{next} and @code{finish}. For
3821 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3824 You can control this automatic behaviour with the following commands::
3826 @kindex set breakpoint auto-hw
3827 @kindex show breakpoint auto-hw
3829 @item set breakpoint auto-hw on
3830 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3831 will try to use the target memory map to decide if software or hardware
3832 breakpoint must be used.
3834 @item set breakpoint auto-hw off
3835 This indicates @value{GDBN} should not automatically select breakpoint
3836 type. If the target provides a memory map, @value{GDBN} will warn when
3837 trying to set software breakpoint at a read-only address.
3840 @value{GDBN} normally implements breakpoints by replacing the program code
3841 at the breakpoint address with a special instruction, which, when
3842 executed, given control to the debugger. By default, the program
3843 code is so modified only when the program is resumed. As soon as
3844 the program stops, @value{GDBN} restores the original instructions. This
3845 behaviour guards against leaving breakpoints inserted in the
3846 target should gdb abrubptly disconnect. However, with slow remote
3847 targets, inserting and removing breakpoint can reduce the performance.
3848 This behavior can be controlled with the following commands::
3850 @kindex set breakpoint always-inserted
3851 @kindex show breakpoint always-inserted
3853 @item set breakpoint always-inserted off
3854 All breakpoints, including newly added by the user, are inserted in
3855 the target only when the target is resumed. All breakpoints are
3856 removed from the target when it stops. This is the default mode.
3858 @item set breakpoint always-inserted on
3859 Causes all breakpoints to be inserted in the target at all times. If
3860 the user adds a new breakpoint, or changes an existing breakpoint, the
3861 breakpoints in the target are updated immediately. A breakpoint is
3862 removed from the target only when breakpoint itself is deleted.
3865 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3866 when a breakpoint breaks. If the condition is true, then the process being
3867 debugged stops, otherwise the process is resumed.
3869 If the target supports evaluating conditions on its end, @value{GDBN} may
3870 download the breakpoint, together with its conditions, to it.
3872 This feature can be controlled via the following commands:
3874 @kindex set breakpoint condition-evaluation
3875 @kindex show breakpoint condition-evaluation
3877 @item set breakpoint condition-evaluation host
3878 This option commands @value{GDBN} to evaluate the breakpoint
3879 conditions on the host's side. Unconditional breakpoints are sent to
3880 the target which in turn receives the triggers and reports them back to GDB
3881 for condition evaluation. This is the standard evaluation mode.
3883 @item set breakpoint condition-evaluation target
3884 This option commands @value{GDBN} to download breakpoint conditions
3885 to the target at the moment of their insertion. The target
3886 is responsible for evaluating the conditional expression and reporting
3887 breakpoint stop events back to @value{GDBN} whenever the condition
3888 is true. Due to limitations of target-side evaluation, some conditions
3889 cannot be evaluated there, e.g., conditions that depend on local data
3890 that is only known to the host. Examples include
3891 conditional expressions involving convenience variables, complex types
3892 that cannot be handled by the agent expression parser and expressions
3893 that are too long to be sent over to the target, specially when the
3894 target is a remote system. In these cases, the conditions will be
3895 evaluated by @value{GDBN}.
3897 @item set breakpoint condition-evaluation auto
3898 This is the default mode. If the target supports evaluating breakpoint
3899 conditions on its end, @value{GDBN} will download breakpoint conditions to
3900 the target (limitations mentioned previously apply). If the target does
3901 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3902 to evaluating all these conditions on the host's side.
3906 @cindex negative breakpoint numbers
3907 @cindex internal @value{GDBN} breakpoints
3908 @value{GDBN} itself sometimes sets breakpoints in your program for
3909 special purposes, such as proper handling of @code{longjmp} (in C
3910 programs). These internal breakpoints are assigned negative numbers,
3911 starting with @code{-1}; @samp{info breakpoints} does not display them.
3912 You can see these breakpoints with the @value{GDBN} maintenance command
3913 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3916 @node Set Watchpoints
3917 @subsection Setting Watchpoints
3919 @cindex setting watchpoints
3920 You can use a watchpoint to stop execution whenever the value of an
3921 expression changes, without having to predict a particular place where
3922 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3923 The expression may be as simple as the value of a single variable, or
3924 as complex as many variables combined by operators. Examples include:
3928 A reference to the value of a single variable.
3931 An address cast to an appropriate data type. For example,
3932 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3933 address (assuming an @code{int} occupies 4 bytes).
3936 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3937 expression can use any operators valid in the program's native
3938 language (@pxref{Languages}).
3941 You can set a watchpoint on an expression even if the expression can
3942 not be evaluated yet. For instance, you can set a watchpoint on
3943 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3944 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3945 the expression produces a valid value. If the expression becomes
3946 valid in some other way than changing a variable (e.g.@: if the memory
3947 pointed to by @samp{*global_ptr} becomes readable as the result of a
3948 @code{malloc} call), @value{GDBN} may not stop until the next time
3949 the expression changes.
3951 @cindex software watchpoints
3952 @cindex hardware watchpoints
3953 Depending on your system, watchpoints may be implemented in software or
3954 hardware. @value{GDBN} does software watchpointing by single-stepping your
3955 program and testing the variable's value each time, which is hundreds of
3956 times slower than normal execution. (But this may still be worth it, to
3957 catch errors where you have no clue what part of your program is the
3960 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3961 x86-based targets, @value{GDBN} includes support for hardware
3962 watchpoints, which do not slow down the running of your program.
3966 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3967 Set a watchpoint for an expression. @value{GDBN} will break when the
3968 expression @var{expr} is written into by the program and its value
3969 changes. The simplest (and the most popular) use of this command is
3970 to watch the value of a single variable:
3973 (@value{GDBP}) watch foo
3976 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3977 argument, @value{GDBN} breaks only when the thread identified by
3978 @var{threadnum} changes the value of @var{expr}. If any other threads
3979 change the value of @var{expr}, @value{GDBN} will not break. Note
3980 that watchpoints restricted to a single thread in this way only work
3981 with Hardware Watchpoints.
3983 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3984 (see below). The @code{-location} argument tells @value{GDBN} to
3985 instead watch the memory referred to by @var{expr}. In this case,
3986 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3987 and watch the memory at that address. The type of the result is used
3988 to determine the size of the watched memory. If the expression's
3989 result does not have an address, then @value{GDBN} will print an
3992 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3993 of masked watchpoints, if the current architecture supports this
3994 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3995 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3996 to an address to watch. The mask specifies that some bits of an address
3997 (the bits which are reset in the mask) should be ignored when matching
3998 the address accessed by the inferior against the watchpoint address.
3999 Thus, a masked watchpoint watches many addresses simultaneously---those
4000 addresses whose unmasked bits are identical to the unmasked bits in the
4001 watchpoint address. The @code{mask} argument implies @code{-location}.
4005 (@value{GDBP}) watch foo mask 0xffff00ff
4006 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4010 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
4011 Set a watchpoint that will break when the value of @var{expr} is read
4015 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
4016 Set a watchpoint that will break when @var{expr} is either read from
4017 or written into by the program.
4019 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
4020 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
4021 This command prints a list of watchpoints, using the same format as
4022 @code{info break} (@pxref{Set Breaks}).
4025 If you watch for a change in a numerically entered address you need to
4026 dereference it, as the address itself is just a constant number which will
4027 never change. @value{GDBN} refuses to create a watchpoint that watches
4028 a never-changing value:
4031 (@value{GDBP}) watch 0x600850
4032 Cannot watch constant value 0x600850.
4033 (@value{GDBP}) watch *(int *) 0x600850
4034 Watchpoint 1: *(int *) 6293584
4037 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4038 watchpoints execute very quickly, and the debugger reports a change in
4039 value at the exact instruction where the change occurs. If @value{GDBN}
4040 cannot set a hardware watchpoint, it sets a software watchpoint, which
4041 executes more slowly and reports the change in value at the next
4042 @emph{statement}, not the instruction, after the change occurs.
4044 @cindex use only software watchpoints
4045 You can force @value{GDBN} to use only software watchpoints with the
4046 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4047 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4048 the underlying system supports them. (Note that hardware-assisted
4049 watchpoints that were set @emph{before} setting
4050 @code{can-use-hw-watchpoints} to zero will still use the hardware
4051 mechanism of watching expression values.)
4054 @item set can-use-hw-watchpoints
4055 @kindex set can-use-hw-watchpoints
4056 Set whether or not to use hardware watchpoints.
4058 @item show can-use-hw-watchpoints
4059 @kindex show can-use-hw-watchpoints
4060 Show the current mode of using hardware watchpoints.
4063 For remote targets, you can restrict the number of hardware
4064 watchpoints @value{GDBN} will use, see @ref{set remote
4065 hardware-breakpoint-limit}.
4067 When you issue the @code{watch} command, @value{GDBN} reports
4070 Hardware watchpoint @var{num}: @var{expr}
4074 if it was able to set a hardware watchpoint.
4076 Currently, the @code{awatch} and @code{rwatch} commands can only set
4077 hardware watchpoints, because accesses to data that don't change the
4078 value of the watched expression cannot be detected without examining
4079 every instruction as it is being executed, and @value{GDBN} does not do
4080 that currently. If @value{GDBN} finds that it is unable to set a
4081 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4082 will print a message like this:
4085 Expression cannot be implemented with read/access watchpoint.
4088 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4089 data type of the watched expression is wider than what a hardware
4090 watchpoint on the target machine can handle. For example, some systems
4091 can only watch regions that are up to 4 bytes wide; on such systems you
4092 cannot set hardware watchpoints for an expression that yields a
4093 double-precision floating-point number (which is typically 8 bytes
4094 wide). As a work-around, it might be possible to break the large region
4095 into a series of smaller ones and watch them with separate watchpoints.
4097 If you set too many hardware watchpoints, @value{GDBN} might be unable
4098 to insert all of them when you resume the execution of your program.
4099 Since the precise number of active watchpoints is unknown until such
4100 time as the program is about to be resumed, @value{GDBN} might not be
4101 able to warn you about this when you set the watchpoints, and the
4102 warning will be printed only when the program is resumed:
4105 Hardware watchpoint @var{num}: Could not insert watchpoint
4109 If this happens, delete or disable some of the watchpoints.
4111 Watching complex expressions that reference many variables can also
4112 exhaust the resources available for hardware-assisted watchpoints.
4113 That's because @value{GDBN} needs to watch every variable in the
4114 expression with separately allocated resources.
4116 If you call a function interactively using @code{print} or @code{call},
4117 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4118 kind of breakpoint or the call completes.
4120 @value{GDBN} automatically deletes watchpoints that watch local
4121 (automatic) variables, or expressions that involve such variables, when
4122 they go out of scope, that is, when the execution leaves the block in
4123 which these variables were defined. In particular, when the program
4124 being debugged terminates, @emph{all} local variables go out of scope,
4125 and so only watchpoints that watch global variables remain set. If you
4126 rerun the program, you will need to set all such watchpoints again. One
4127 way of doing that would be to set a code breakpoint at the entry to the
4128 @code{main} function and when it breaks, set all the watchpoints.
4130 @cindex watchpoints and threads
4131 @cindex threads and watchpoints
4132 In multi-threaded programs, watchpoints will detect changes to the
4133 watched expression from every thread.
4136 @emph{Warning:} In multi-threaded programs, software watchpoints
4137 have only limited usefulness. If @value{GDBN} creates a software
4138 watchpoint, it can only watch the value of an expression @emph{in a
4139 single thread}. If you are confident that the expression can only
4140 change due to the current thread's activity (and if you are also
4141 confident that no other thread can become current), then you can use
4142 software watchpoints as usual. However, @value{GDBN} may not notice
4143 when a non-current thread's activity changes the expression. (Hardware
4144 watchpoints, in contrast, watch an expression in all threads.)
4147 @xref{set remote hardware-watchpoint-limit}.
4149 @node Set Catchpoints
4150 @subsection Setting Catchpoints
4151 @cindex catchpoints, setting
4152 @cindex exception handlers
4153 @cindex event handling
4155 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4156 kinds of program events, such as C@t{++} exceptions or the loading of a
4157 shared library. Use the @code{catch} command to set a catchpoint.
4161 @item catch @var{event}
4162 Stop when @var{event} occurs. The @var{event} can be any of the following:
4165 @item throw @r{[}@var{regexp}@r{]}
4166 @itemx rethrow @r{[}@var{regexp}@r{]}
4167 @itemx catch @r{[}@var{regexp}@r{]}
4169 @kindex catch rethrow
4171 @cindex stop on C@t{++} exceptions
4172 The throwing, re-throwing, or catching of a C@t{++} exception.
4174 If @var{regexp} is given, then only exceptions whose type matches the
4175 regular expression will be caught.
4177 @vindex $_exception@r{, convenience variable}
4178 The convenience variable @code{$_exception} is available at an
4179 exception-related catchpoint, on some systems. This holds the
4180 exception being thrown.
4182 There are currently some limitations to C@t{++} exception handling in
4187 The support for these commands is system-dependent. Currently, only
4188 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4192 The regular expression feature and the @code{$_exception} convenience
4193 variable rely on the presence of some SDT probes in @code{libstdc++}.
4194 If these probes are not present, then these features cannot be used.
4195 These probes were first available in the GCC 4.8 release, but whether
4196 or not they are available in your GCC also depends on how it was
4200 The @code{$_exception} convenience variable is only valid at the
4201 instruction at which an exception-related catchpoint is set.
4204 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4205 location in the system library which implements runtime exception
4206 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4207 (@pxref{Selection}) to get to your code.
4210 If you call a function interactively, @value{GDBN} normally returns
4211 control to you when the function has finished executing. If the call
4212 raises an exception, however, the call may bypass the mechanism that
4213 returns control to you and cause your program either to abort or to
4214 simply continue running until it hits a breakpoint, catches a signal
4215 that @value{GDBN} is listening for, or exits. This is the case even if
4216 you set a catchpoint for the exception; catchpoints on exceptions are
4217 disabled within interactive calls. @xref{Calling}, for information on
4218 controlling this with @code{set unwind-on-terminating-exception}.
4221 You cannot raise an exception interactively.
4224 You cannot install an exception handler interactively.
4228 @kindex catch exception
4229 @cindex Ada exception catching
4230 @cindex catch Ada exceptions
4231 An Ada exception being raised. If an exception name is specified
4232 at the end of the command (eg @code{catch exception Program_Error}),
4233 the debugger will stop only when this specific exception is raised.
4234 Otherwise, the debugger stops execution when any Ada exception is raised.
4236 When inserting an exception catchpoint on a user-defined exception whose
4237 name is identical to one of the exceptions defined by the language, the
4238 fully qualified name must be used as the exception name. Otherwise,
4239 @value{GDBN} will assume that it should stop on the pre-defined exception
4240 rather than the user-defined one. For instance, assuming an exception
4241 called @code{Constraint_Error} is defined in package @code{Pck}, then
4242 the command to use to catch such exceptions is @kbd{catch exception
4243 Pck.Constraint_Error}.
4245 @item exception unhandled
4246 @kindex catch exception unhandled
4247 An exception that was raised but is not handled by the program.
4250 @kindex catch assert
4251 A failed Ada assertion.
4255 @cindex break on fork/exec
4256 A call to @code{exec}. This is currently only available for HP-UX
4260 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4261 @kindex catch syscall
4262 @cindex break on a system call.
4263 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4264 syscall is a mechanism for application programs to request a service
4265 from the operating system (OS) or one of the OS system services.
4266 @value{GDBN} can catch some or all of the syscalls issued by the
4267 debuggee, and show the related information for each syscall. If no
4268 argument is specified, calls to and returns from all system calls
4271 @var{name} can be any system call name that is valid for the
4272 underlying OS. Just what syscalls are valid depends on the OS. On
4273 GNU and Unix systems, you can find the full list of valid syscall
4274 names on @file{/usr/include/asm/unistd.h}.
4276 @c For MS-Windows, the syscall names and the corresponding numbers
4277 @c can be found, e.g., on this URL:
4278 @c http://www.metasploit.com/users/opcode/syscalls.html
4279 @c but we don't support Windows syscalls yet.
4281 Normally, @value{GDBN} knows in advance which syscalls are valid for
4282 each OS, so you can use the @value{GDBN} command-line completion
4283 facilities (@pxref{Completion,, command completion}) to list the
4286 You may also specify the system call numerically. A syscall's
4287 number is the value passed to the OS's syscall dispatcher to
4288 identify the requested service. When you specify the syscall by its
4289 name, @value{GDBN} uses its database of syscalls to convert the name
4290 into the corresponding numeric code, but using the number directly
4291 may be useful if @value{GDBN}'s database does not have the complete
4292 list of syscalls on your system (e.g., because @value{GDBN} lags
4293 behind the OS upgrades).
4295 The example below illustrates how this command works if you don't provide
4299 (@value{GDBP}) catch syscall
4300 Catchpoint 1 (syscall)
4302 Starting program: /tmp/catch-syscall
4304 Catchpoint 1 (call to syscall 'close'), \
4305 0xffffe424 in __kernel_vsyscall ()
4309 Catchpoint 1 (returned from syscall 'close'), \
4310 0xffffe424 in __kernel_vsyscall ()
4314 Here is an example of catching a system call by name:
4317 (@value{GDBP}) catch syscall chroot
4318 Catchpoint 1 (syscall 'chroot' [61])
4320 Starting program: /tmp/catch-syscall
4322 Catchpoint 1 (call to syscall 'chroot'), \
4323 0xffffe424 in __kernel_vsyscall ()
4327 Catchpoint 1 (returned from syscall 'chroot'), \
4328 0xffffe424 in __kernel_vsyscall ()
4332 An example of specifying a system call numerically. In the case
4333 below, the syscall number has a corresponding entry in the XML
4334 file, so @value{GDBN} finds its name and prints it:
4337 (@value{GDBP}) catch syscall 252
4338 Catchpoint 1 (syscall(s) 'exit_group')
4340 Starting program: /tmp/catch-syscall
4342 Catchpoint 1 (call to syscall 'exit_group'), \
4343 0xffffe424 in __kernel_vsyscall ()
4347 Program exited normally.
4351 However, there can be situations when there is no corresponding name
4352 in XML file for that syscall number. In this case, @value{GDBN} prints
4353 a warning message saying that it was not able to find the syscall name,
4354 but the catchpoint will be set anyway. See the example below:
4357 (@value{GDBP}) catch syscall 764
4358 warning: The number '764' does not represent a known syscall.
4359 Catchpoint 2 (syscall 764)
4363 If you configure @value{GDBN} using the @samp{--without-expat} option,
4364 it will not be able to display syscall names. Also, if your
4365 architecture does not have an XML file describing its system calls,
4366 you will not be able to see the syscall names. It is important to
4367 notice that these two features are used for accessing the syscall
4368 name database. In either case, you will see a warning like this:
4371 (@value{GDBP}) catch syscall
4372 warning: Could not open "syscalls/i386-linux.xml"
4373 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4374 GDB will not be able to display syscall names.
4375 Catchpoint 1 (syscall)
4379 Of course, the file name will change depending on your architecture and system.
4381 Still using the example above, you can also try to catch a syscall by its
4382 number. In this case, you would see something like:
4385 (@value{GDBP}) catch syscall 252
4386 Catchpoint 1 (syscall(s) 252)
4389 Again, in this case @value{GDBN} would not be able to display syscall's names.
4393 A call to @code{fork}. This is currently only available for HP-UX
4398 A call to @code{vfork}. This is currently only available for HP-UX
4401 @item load @r{[}regexp@r{]}
4402 @itemx unload @r{[}regexp@r{]}
4404 @kindex catch unload
4405 The loading or unloading of a shared library. If @var{regexp} is
4406 given, then the catchpoint will stop only if the regular expression
4407 matches one of the affected libraries.
4409 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4410 @kindex catch signal
4411 The delivery of a signal.
4413 With no arguments, this catchpoint will catch any signal that is not
4414 used internally by @value{GDBN}, specifically, all signals except
4415 @samp{SIGTRAP} and @samp{SIGINT}.
4417 With the argument @samp{all}, all signals, including those used by
4418 @value{GDBN}, will be caught. This argument cannot be used with other
4421 Otherwise, the arguments are a list of signal names as given to
4422 @code{handle} (@pxref{Signals}). Only signals specified in this list
4425 One reason that @code{catch signal} can be more useful than
4426 @code{handle} is that you can attach commands and conditions to the
4429 When a signal is caught by a catchpoint, the signal's @code{stop} and
4430 @code{print} settings, as specified by @code{handle}, are ignored.
4431 However, whether the signal is still delivered to the inferior depends
4432 on the @code{pass} setting; this can be changed in the catchpoint's
4437 @item tcatch @var{event}
4439 Set a catchpoint that is enabled only for one stop. The catchpoint is
4440 automatically deleted after the first time the event is caught.
4444 Use the @code{info break} command to list the current catchpoints.
4448 @subsection Deleting Breakpoints
4450 @cindex clearing breakpoints, watchpoints, catchpoints
4451 @cindex deleting breakpoints, watchpoints, catchpoints
4452 It is often necessary to eliminate a breakpoint, watchpoint, or
4453 catchpoint once it has done its job and you no longer want your program
4454 to stop there. This is called @dfn{deleting} the breakpoint. A
4455 breakpoint that has been deleted no longer exists; it is forgotten.
4457 With the @code{clear} command you can delete breakpoints according to
4458 where they are in your program. With the @code{delete} command you can
4459 delete individual breakpoints, watchpoints, or catchpoints by specifying
4460 their breakpoint numbers.
4462 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4463 automatically ignores breakpoints on the first instruction to be executed
4464 when you continue execution without changing the execution address.
4469 Delete any breakpoints at the next instruction to be executed in the
4470 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4471 the innermost frame is selected, this is a good way to delete a
4472 breakpoint where your program just stopped.
4474 @item clear @var{location}
4475 Delete any breakpoints set at the specified @var{location}.
4476 @xref{Specify Location}, for the various forms of @var{location}; the
4477 most useful ones are listed below:
4480 @item clear @var{function}
4481 @itemx clear @var{filename}:@var{function}
4482 Delete any breakpoints set at entry to the named @var{function}.
4484 @item clear @var{linenum}
4485 @itemx clear @var{filename}:@var{linenum}
4486 Delete any breakpoints set at or within the code of the specified
4487 @var{linenum} of the specified @var{filename}.
4490 @cindex delete breakpoints
4492 @kindex d @r{(@code{delete})}
4493 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4494 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4495 ranges specified as arguments. If no argument is specified, delete all
4496 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4497 confirm off}). You can abbreviate this command as @code{d}.
4501 @subsection Disabling Breakpoints
4503 @cindex enable/disable a breakpoint
4504 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4505 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4506 it had been deleted, but remembers the information on the breakpoint so
4507 that you can @dfn{enable} it again later.
4509 You disable and enable breakpoints, watchpoints, and catchpoints with
4510 the @code{enable} and @code{disable} commands, optionally specifying
4511 one or more breakpoint numbers as arguments. Use @code{info break} to
4512 print a list of all breakpoints, watchpoints, and catchpoints if you
4513 do not know which numbers to use.
4515 Disabling and enabling a breakpoint that has multiple locations
4516 affects all of its locations.
4518 A breakpoint, watchpoint, or catchpoint can have any of several
4519 different states of enablement:
4523 Enabled. The breakpoint stops your program. A breakpoint set
4524 with the @code{break} command starts out in this state.
4526 Disabled. The breakpoint has no effect on your program.
4528 Enabled once. The breakpoint stops your program, but then becomes
4531 Enabled for a count. The breakpoint stops your program for the next
4532 N times, then becomes disabled.
4534 Enabled for deletion. The breakpoint stops your program, but
4535 immediately after it does so it is deleted permanently. A breakpoint
4536 set with the @code{tbreak} command starts out in this state.
4539 You can use the following commands to enable or disable breakpoints,
4540 watchpoints, and catchpoints:
4544 @kindex dis @r{(@code{disable})}
4545 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4546 Disable the specified breakpoints---or all breakpoints, if none are
4547 listed. A disabled breakpoint has no effect but is not forgotten. All
4548 options such as ignore-counts, conditions and commands are remembered in
4549 case the breakpoint is enabled again later. You may abbreviate
4550 @code{disable} as @code{dis}.
4553 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4554 Enable the specified breakpoints (or all defined breakpoints). They
4555 become effective once again in stopping your program.
4557 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4558 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4559 of these breakpoints immediately after stopping your program.
4561 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4562 Enable the specified breakpoints temporarily. @value{GDBN} records
4563 @var{count} with each of the specified breakpoints, and decrements a
4564 breakpoint's count when it is hit. When any count reaches 0,
4565 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4566 count (@pxref{Conditions, ,Break Conditions}), that will be
4567 decremented to 0 before @var{count} is affected.
4569 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4570 Enable the specified breakpoints to work once, then die. @value{GDBN}
4571 deletes any of these breakpoints as soon as your program stops there.
4572 Breakpoints set by the @code{tbreak} command start out in this state.
4575 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4576 @c confusing: tbreak is also initially enabled.
4577 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4578 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4579 subsequently, they become disabled or enabled only when you use one of
4580 the commands above. (The command @code{until} can set and delete a
4581 breakpoint of its own, but it does not change the state of your other
4582 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4586 @subsection Break Conditions
4587 @cindex conditional breakpoints
4588 @cindex breakpoint conditions
4590 @c FIXME what is scope of break condition expr? Context where wanted?
4591 @c in particular for a watchpoint?
4592 The simplest sort of breakpoint breaks every time your program reaches a
4593 specified place. You can also specify a @dfn{condition} for a
4594 breakpoint. A condition is just a Boolean expression in your
4595 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4596 a condition evaluates the expression each time your program reaches it,
4597 and your program stops only if the condition is @emph{true}.
4599 This is the converse of using assertions for program validation; in that
4600 situation, you want to stop when the assertion is violated---that is,
4601 when the condition is false. In C, if you want to test an assertion expressed
4602 by the condition @var{assert}, you should set the condition
4603 @samp{! @var{assert}} on the appropriate breakpoint.
4605 Conditions are also accepted for watchpoints; you may not need them,
4606 since a watchpoint is inspecting the value of an expression anyhow---but
4607 it might be simpler, say, to just set a watchpoint on a variable name,
4608 and specify a condition that tests whether the new value is an interesting
4611 Break conditions can have side effects, and may even call functions in
4612 your program. This can be useful, for example, to activate functions
4613 that log program progress, or to use your own print functions to
4614 format special data structures. The effects are completely predictable
4615 unless there is another enabled breakpoint at the same address. (In
4616 that case, @value{GDBN} might see the other breakpoint first and stop your
4617 program without checking the condition of this one.) Note that
4618 breakpoint commands are usually more convenient and flexible than break
4620 purpose of performing side effects when a breakpoint is reached
4621 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4623 Breakpoint conditions can also be evaluated on the target's side if
4624 the target supports it. Instead of evaluating the conditions locally,
4625 @value{GDBN} encodes the expression into an agent expression
4626 (@pxref{Agent Expressions}) suitable for execution on the target,
4627 independently of @value{GDBN}. Global variables become raw memory
4628 locations, locals become stack accesses, and so forth.
4630 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4631 when its condition evaluates to true. This mechanism may provide faster
4632 response times depending on the performance characteristics of the target
4633 since it does not need to keep @value{GDBN} informed about
4634 every breakpoint trigger, even those with false conditions.
4636 Break conditions can be specified when a breakpoint is set, by using
4637 @samp{if} in the arguments to the @code{break} command. @xref{Set
4638 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4639 with the @code{condition} command.
4641 You can also use the @code{if} keyword with the @code{watch} command.
4642 The @code{catch} command does not recognize the @code{if} keyword;
4643 @code{condition} is the only way to impose a further condition on a
4648 @item condition @var{bnum} @var{expression}
4649 Specify @var{expression} as the break condition for breakpoint,
4650 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4651 breakpoint @var{bnum} stops your program only if the value of
4652 @var{expression} is true (nonzero, in C). When you use
4653 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4654 syntactic correctness, and to determine whether symbols in it have
4655 referents in the context of your breakpoint. If @var{expression} uses
4656 symbols not referenced in the context of the breakpoint, @value{GDBN}
4657 prints an error message:
4660 No symbol "foo" in current context.
4665 not actually evaluate @var{expression} at the time the @code{condition}
4666 command (or a command that sets a breakpoint with a condition, like
4667 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4669 @item condition @var{bnum}
4670 Remove the condition from breakpoint number @var{bnum}. It becomes
4671 an ordinary unconditional breakpoint.
4674 @cindex ignore count (of breakpoint)
4675 A special case of a breakpoint condition is to stop only when the
4676 breakpoint has been reached a certain number of times. This is so
4677 useful that there is a special way to do it, using the @dfn{ignore
4678 count} of the breakpoint. Every breakpoint has an ignore count, which
4679 is an integer. Most of the time, the ignore count is zero, and
4680 therefore has no effect. But if your program reaches a breakpoint whose
4681 ignore count is positive, then instead of stopping, it just decrements
4682 the ignore count by one and continues. As a result, if the ignore count
4683 value is @var{n}, the breakpoint does not stop the next @var{n} times
4684 your program reaches it.
4688 @item ignore @var{bnum} @var{count}
4689 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4690 The next @var{count} times the breakpoint is reached, your program's
4691 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4694 To make the breakpoint stop the next time it is reached, specify
4697 When you use @code{continue} to resume execution of your program from a
4698 breakpoint, you can specify an ignore count directly as an argument to
4699 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4700 Stepping,,Continuing and Stepping}.
4702 If a breakpoint has a positive ignore count and a condition, the
4703 condition is not checked. Once the ignore count reaches zero,
4704 @value{GDBN} resumes checking the condition.
4706 You could achieve the effect of the ignore count with a condition such
4707 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4708 is decremented each time. @xref{Convenience Vars, ,Convenience
4712 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4715 @node Break Commands
4716 @subsection Breakpoint Command Lists
4718 @cindex breakpoint commands
4719 You can give any breakpoint (or watchpoint or catchpoint) a series of
4720 commands to execute when your program stops due to that breakpoint. For
4721 example, you might want to print the values of certain expressions, or
4722 enable other breakpoints.
4726 @kindex end@r{ (breakpoint commands)}
4727 @item commands @r{[}@var{range}@dots{}@r{]}
4728 @itemx @dots{} @var{command-list} @dots{}
4730 Specify a list of commands for the given breakpoints. The commands
4731 themselves appear on the following lines. Type a line containing just
4732 @code{end} to terminate the commands.
4734 To remove all commands from a breakpoint, type @code{commands} and
4735 follow it immediately with @code{end}; that is, give no commands.
4737 With no argument, @code{commands} refers to the last breakpoint,
4738 watchpoint, or catchpoint set (not to the breakpoint most recently
4739 encountered). If the most recent breakpoints were set with a single
4740 command, then the @code{commands} will apply to all the breakpoints
4741 set by that command. This applies to breakpoints set by
4742 @code{rbreak}, and also applies when a single @code{break} command
4743 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4747 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4748 disabled within a @var{command-list}.
4750 You can use breakpoint commands to start your program up again. Simply
4751 use the @code{continue} command, or @code{step}, or any other command
4752 that resumes execution.
4754 Any other commands in the command list, after a command that resumes
4755 execution, are ignored. This is because any time you resume execution
4756 (even with a simple @code{next} or @code{step}), you may encounter
4757 another breakpoint---which could have its own command list, leading to
4758 ambiguities about which list to execute.
4761 If the first command you specify in a command list is @code{silent}, the
4762 usual message about stopping at a breakpoint is not printed. This may
4763 be desirable for breakpoints that are to print a specific message and
4764 then continue. If none of the remaining commands print anything, you
4765 see no sign that the breakpoint was reached. @code{silent} is
4766 meaningful only at the beginning of a breakpoint command list.
4768 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4769 print precisely controlled output, and are often useful in silent
4770 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4772 For example, here is how you could use breakpoint commands to print the
4773 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4779 printf "x is %d\n",x
4784 One application for breakpoint commands is to compensate for one bug so
4785 you can test for another. Put a breakpoint just after the erroneous line
4786 of code, give it a condition to detect the case in which something
4787 erroneous has been done, and give it commands to assign correct values
4788 to any variables that need them. End with the @code{continue} command
4789 so that your program does not stop, and start with the @code{silent}
4790 command so that no output is produced. Here is an example:
4801 @node Dynamic Printf
4802 @subsection Dynamic Printf
4804 @cindex dynamic printf
4806 The dynamic printf command @code{dprintf} combines a breakpoint with
4807 formatted printing of your program's data to give you the effect of
4808 inserting @code{printf} calls into your program on-the-fly, without
4809 having to recompile it.
4811 In its most basic form, the output goes to the GDB console. However,
4812 you can set the variable @code{dprintf-style} for alternate handling.
4813 For instance, you can ask to format the output by calling your
4814 program's @code{printf} function. This has the advantage that the
4815 characters go to the program's output device, so they can recorded in
4816 redirects to files and so forth.
4818 If you are doing remote debugging with a stub or agent, you can also
4819 ask to have the printf handled by the remote agent. In addition to
4820 ensuring that the output goes to the remote program's device along
4821 with any other output the program might produce, you can also ask that
4822 the dprintf remain active even after disconnecting from the remote
4823 target. Using the stub/agent is also more efficient, as it can do
4824 everything without needing to communicate with @value{GDBN}.
4828 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4829 Whenever execution reaches @var{location}, print the values of one or
4830 more @var{expressions} under the control of the string @var{template}.
4831 To print several values, separate them with commas.
4833 @item set dprintf-style @var{style}
4834 Set the dprintf output to be handled in one of several different
4835 styles enumerated below. A change of style affects all existing
4836 dynamic printfs immediately. (If you need individual control over the
4837 print commands, simply define normal breakpoints with
4838 explicitly-supplied command lists.)
4841 @kindex dprintf-style gdb
4842 Handle the output using the @value{GDBN} @code{printf} command.
4845 @kindex dprintf-style call
4846 Handle the output by calling a function in your program (normally
4850 @kindex dprintf-style agent
4851 Have the remote debugging agent (such as @code{gdbserver}) handle
4852 the output itself. This style is only available for agents that
4853 support running commands on the target.
4855 @item set dprintf-function @var{function}
4856 Set the function to call if the dprintf style is @code{call}. By
4857 default its value is @code{printf}. You may set it to any expression.
4858 that @value{GDBN} can evaluate to a function, as per the @code{call}
4861 @item set dprintf-channel @var{channel}
4862 Set a ``channel'' for dprintf. If set to a non-empty value,
4863 @value{GDBN} will evaluate it as an expression and pass the result as
4864 a first argument to the @code{dprintf-function}, in the manner of
4865 @code{fprintf} and similar functions. Otherwise, the dprintf format
4866 string will be the first argument, in the manner of @code{printf}.
4868 As an example, if you wanted @code{dprintf} output to go to a logfile
4869 that is a standard I/O stream assigned to the variable @code{mylog},
4870 you could do the following:
4873 (gdb) set dprintf-style call
4874 (gdb) set dprintf-function fprintf
4875 (gdb) set dprintf-channel mylog
4876 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4877 Dprintf 1 at 0x123456: file main.c, line 25.
4879 1 dprintf keep y 0x00123456 in main at main.c:25
4880 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
4885 Note that the @code{info break} displays the dynamic printf commands
4886 as normal breakpoint commands; you can thus easily see the effect of
4887 the variable settings.
4889 @item set disconnected-dprintf on
4890 @itemx set disconnected-dprintf off
4891 @kindex set disconnected-dprintf
4892 Choose whether @code{dprintf} commands should continue to run if
4893 @value{GDBN} has disconnected from the target. This only applies
4894 if the @code{dprintf-style} is @code{agent}.
4896 @item show disconnected-dprintf off
4897 @kindex show disconnected-dprintf
4898 Show the current choice for disconnected @code{dprintf}.
4902 @value{GDBN} does not check the validity of function and channel,
4903 relying on you to supply values that are meaningful for the contexts
4904 in which they are being used. For instance, the function and channel
4905 may be the values of local variables, but if that is the case, then
4906 all enabled dynamic prints must be at locations within the scope of
4907 those locals. If evaluation fails, @value{GDBN} will report an error.
4909 @node Save Breakpoints
4910 @subsection How to save breakpoints to a file
4912 To save breakpoint definitions to a file use the @w{@code{save
4913 breakpoints}} command.
4916 @kindex save breakpoints
4917 @cindex save breakpoints to a file for future sessions
4918 @item save breakpoints [@var{filename}]
4919 This command saves all current breakpoint definitions together with
4920 their commands and ignore counts, into a file @file{@var{filename}}
4921 suitable for use in a later debugging session. This includes all
4922 types of breakpoints (breakpoints, watchpoints, catchpoints,
4923 tracepoints). To read the saved breakpoint definitions, use the
4924 @code{source} command (@pxref{Command Files}). Note that watchpoints
4925 with expressions involving local variables may fail to be recreated
4926 because it may not be possible to access the context where the
4927 watchpoint is valid anymore. Because the saved breakpoint definitions
4928 are simply a sequence of @value{GDBN} commands that recreate the
4929 breakpoints, you can edit the file in your favorite editing program,
4930 and remove the breakpoint definitions you're not interested in, or
4931 that can no longer be recreated.
4934 @node Static Probe Points
4935 @subsection Static Probe Points
4937 @cindex static probe point, SystemTap
4938 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
4939 for Statically Defined Tracing, and the probes are designed to have a tiny
4940 runtime code and data footprint, and no dynamic relocations. They are
4941 usable from assembly, C and C@t{++} languages. See
4942 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
4943 for a good reference on how the @acronym{SDT} probes are implemented.
4945 Currently, @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
4946 @acronym{SDT} probes are supported on ELF-compatible systems. See
4947 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
4948 for more information on how to add @code{SystemTap} @acronym{SDT} probes
4949 in your applications.
4951 @cindex semaphores on static probe points
4952 Some probes have an associated semaphore variable; for instance, this
4953 happens automatically if you defined your probe using a DTrace-style
4954 @file{.d} file. If your probe has a semaphore, @value{GDBN} will
4955 automatically enable it when you specify a breakpoint using the
4956 @samp{-probe-stap} notation. But, if you put a breakpoint at a probe's
4957 location by some other method (e.g., @code{break file:line}), then
4958 @value{GDBN} will not automatically set the semaphore.
4960 You can examine the available static static probes using @code{info
4961 probes}, with optional arguments:
4965 @item info probes stap @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
4966 If given, @var{provider} is a regular expression used to match against provider
4967 names when selecting which probes to list. If omitted, probes by all
4968 probes from all providers are listed.
4970 If given, @var{name} is a regular expression to match against probe names
4971 when selecting which probes to list. If omitted, probe names are not
4972 considered when deciding whether to display them.
4974 If given, @var{objfile} is a regular expression used to select which
4975 object files (executable or shared libraries) to examine. If not
4976 given, all object files are considered.
4978 @item info probes all
4979 List the available static probes, from all types.
4982 @vindex $_probe_arg@r{, convenience variable}
4983 A probe may specify up to twelve arguments. These are available at the
4984 point at which the probe is defined---that is, when the current PC is
4985 at the probe's location. The arguments are available using the
4986 convenience variables (@pxref{Convenience Vars})
4987 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. Each probe argument is
4988 an integer of the appropriate size; types are not preserved. The
4989 convenience variable @code{$_probe_argc} holds the number of arguments
4990 at the current probe point.
4992 These variables are always available, but attempts to access them at
4993 any location other than a probe point will cause @value{GDBN} to give
4997 @c @ifclear BARETARGET
4998 @node Error in Breakpoints
4999 @subsection ``Cannot insert breakpoints''
5001 If you request too many active hardware-assisted breakpoints and
5002 watchpoints, you will see this error message:
5004 @c FIXME: the precise wording of this message may change; the relevant
5005 @c source change is not committed yet (Sep 3, 1999).
5007 Stopped; cannot insert breakpoints.
5008 You may have requested too many hardware breakpoints and watchpoints.
5012 This message is printed when you attempt to resume the program, since
5013 only then @value{GDBN} knows exactly how many hardware breakpoints and
5014 watchpoints it needs to insert.
5016 When this message is printed, you need to disable or remove some of the
5017 hardware-assisted breakpoints and watchpoints, and then continue.
5019 @node Breakpoint-related Warnings
5020 @subsection ``Breakpoint address adjusted...''
5021 @cindex breakpoint address adjusted
5023 Some processor architectures place constraints on the addresses at
5024 which breakpoints may be placed. For architectures thus constrained,
5025 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5026 with the constraints dictated by the architecture.
5028 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5029 a VLIW architecture in which a number of RISC-like instructions may be
5030 bundled together for parallel execution. The FR-V architecture
5031 constrains the location of a breakpoint instruction within such a
5032 bundle to the instruction with the lowest address. @value{GDBN}
5033 honors this constraint by adjusting a breakpoint's address to the
5034 first in the bundle.
5036 It is not uncommon for optimized code to have bundles which contain
5037 instructions from different source statements, thus it may happen that
5038 a breakpoint's address will be adjusted from one source statement to
5039 another. Since this adjustment may significantly alter @value{GDBN}'s
5040 breakpoint related behavior from what the user expects, a warning is
5041 printed when the breakpoint is first set and also when the breakpoint
5044 A warning like the one below is printed when setting a breakpoint
5045 that's been subject to address adjustment:
5048 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5051 Such warnings are printed both for user settable and @value{GDBN}'s
5052 internal breakpoints. If you see one of these warnings, you should
5053 verify that a breakpoint set at the adjusted address will have the
5054 desired affect. If not, the breakpoint in question may be removed and
5055 other breakpoints may be set which will have the desired behavior.
5056 E.g., it may be sufficient to place the breakpoint at a later
5057 instruction. A conditional breakpoint may also be useful in some
5058 cases to prevent the breakpoint from triggering too often.
5060 @value{GDBN} will also issue a warning when stopping at one of these
5061 adjusted breakpoints:
5064 warning: Breakpoint 1 address previously adjusted from 0x00010414
5068 When this warning is encountered, it may be too late to take remedial
5069 action except in cases where the breakpoint is hit earlier or more
5070 frequently than expected.
5072 @node Continuing and Stepping
5073 @section Continuing and Stepping
5077 @cindex resuming execution
5078 @dfn{Continuing} means resuming program execution until your program
5079 completes normally. In contrast, @dfn{stepping} means executing just
5080 one more ``step'' of your program, where ``step'' may mean either one
5081 line of source code, or one machine instruction (depending on what
5082 particular command you use). Either when continuing or when stepping,
5083 your program may stop even sooner, due to a breakpoint or a signal. (If
5084 it stops due to a signal, you may want to use @code{handle}, or use
5085 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5086 or you may step into the signal's handler (@pxref{stepping and signal
5091 @kindex c @r{(@code{continue})}
5092 @kindex fg @r{(resume foreground execution)}
5093 @item continue @r{[}@var{ignore-count}@r{]}
5094 @itemx c @r{[}@var{ignore-count}@r{]}
5095 @itemx fg @r{[}@var{ignore-count}@r{]}
5096 Resume program execution, at the address where your program last stopped;
5097 any breakpoints set at that address are bypassed. The optional argument
5098 @var{ignore-count} allows you to specify a further number of times to
5099 ignore a breakpoint at this location; its effect is like that of
5100 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5102 The argument @var{ignore-count} is meaningful only when your program
5103 stopped due to a breakpoint. At other times, the argument to
5104 @code{continue} is ignored.
5106 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5107 debugged program is deemed to be the foreground program) are provided
5108 purely for convenience, and have exactly the same behavior as
5112 To resume execution at a different place, you can use @code{return}
5113 (@pxref{Returning, ,Returning from a Function}) to go back to the
5114 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5115 Different Address}) to go to an arbitrary location in your program.
5117 A typical technique for using stepping is to set a breakpoint
5118 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5119 beginning of the function or the section of your program where a problem
5120 is believed to lie, run your program until it stops at that breakpoint,
5121 and then step through the suspect area, examining the variables that are
5122 interesting, until you see the problem happen.
5126 @kindex s @r{(@code{step})}
5128 Continue running your program until control reaches a different source
5129 line, then stop it and return control to @value{GDBN}. This command is
5130 abbreviated @code{s}.
5133 @c "without debugging information" is imprecise; actually "without line
5134 @c numbers in the debugging information". (gcc -g1 has debugging info but
5135 @c not line numbers). But it seems complex to try to make that
5136 @c distinction here.
5137 @emph{Warning:} If you use the @code{step} command while control is
5138 within a function that was compiled without debugging information,
5139 execution proceeds until control reaches a function that does have
5140 debugging information. Likewise, it will not step into a function which
5141 is compiled without debugging information. To step through functions
5142 without debugging information, use the @code{stepi} command, described
5146 The @code{step} command only stops at the first instruction of a source
5147 line. This prevents the multiple stops that could otherwise occur in
5148 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5149 to stop if a function that has debugging information is called within
5150 the line. In other words, @code{step} @emph{steps inside} any functions
5151 called within the line.
5153 Also, the @code{step} command only enters a function if there is line
5154 number information for the function. Otherwise it acts like the
5155 @code{next} command. This avoids problems when using @code{cc -gl}
5156 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5157 was any debugging information about the routine.
5159 @item step @var{count}
5160 Continue running as in @code{step}, but do so @var{count} times. If a
5161 breakpoint is reached, or a signal not related to stepping occurs before
5162 @var{count} steps, stepping stops right away.
5165 @kindex n @r{(@code{next})}
5166 @item next @r{[}@var{count}@r{]}
5167 Continue to the next source line in the current (innermost) stack frame.
5168 This is similar to @code{step}, but function calls that appear within
5169 the line of code are executed without stopping. Execution stops when
5170 control reaches a different line of code at the original stack level
5171 that was executing when you gave the @code{next} command. This command
5172 is abbreviated @code{n}.
5174 An argument @var{count} is a repeat count, as for @code{step}.
5177 @c FIX ME!! Do we delete this, or is there a way it fits in with
5178 @c the following paragraph? --- Vctoria
5180 @c @code{next} within a function that lacks debugging information acts like
5181 @c @code{step}, but any function calls appearing within the code of the
5182 @c function are executed without stopping.
5184 The @code{next} command only stops at the first instruction of a
5185 source line. This prevents multiple stops that could otherwise occur in
5186 @code{switch} statements, @code{for} loops, etc.
5188 @kindex set step-mode
5190 @cindex functions without line info, and stepping
5191 @cindex stepping into functions with no line info
5192 @itemx set step-mode on
5193 The @code{set step-mode on} command causes the @code{step} command to
5194 stop at the first instruction of a function which contains no debug line
5195 information rather than stepping over it.
5197 This is useful in cases where you may be interested in inspecting the
5198 machine instructions of a function which has no symbolic info and do not
5199 want @value{GDBN} to automatically skip over this function.
5201 @item set step-mode off
5202 Causes the @code{step} command to step over any functions which contains no
5203 debug information. This is the default.
5205 @item show step-mode
5206 Show whether @value{GDBN} will stop in or step over functions without
5207 source line debug information.
5210 @kindex fin @r{(@code{finish})}
5212 Continue running until just after function in the selected stack frame
5213 returns. Print the returned value (if any). This command can be
5214 abbreviated as @code{fin}.
5216 Contrast this with the @code{return} command (@pxref{Returning,
5217 ,Returning from a Function}).
5220 @kindex u @r{(@code{until})}
5221 @cindex run until specified location
5224 Continue running until a source line past the current line, in the
5225 current stack frame, is reached. This command is used to avoid single
5226 stepping through a loop more than once. It is like the @code{next}
5227 command, except that when @code{until} encounters a jump, it
5228 automatically continues execution until the program counter is greater
5229 than the address of the jump.
5231 This means that when you reach the end of a loop after single stepping
5232 though it, @code{until} makes your program continue execution until it
5233 exits the loop. In contrast, a @code{next} command at the end of a loop
5234 simply steps back to the beginning of the loop, which forces you to step
5235 through the next iteration.
5237 @code{until} always stops your program if it attempts to exit the current
5240 @code{until} may produce somewhat counterintuitive results if the order
5241 of machine code does not match the order of the source lines. For
5242 example, in the following excerpt from a debugging session, the @code{f}
5243 (@code{frame}) command shows that execution is stopped at line
5244 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5248 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5250 (@value{GDBP}) until
5251 195 for ( ; argc > 0; NEXTARG) @{
5254 This happened because, for execution efficiency, the compiler had
5255 generated code for the loop closure test at the end, rather than the
5256 start, of the loop---even though the test in a C @code{for}-loop is
5257 written before the body of the loop. The @code{until} command appeared
5258 to step back to the beginning of the loop when it advanced to this
5259 expression; however, it has not really gone to an earlier
5260 statement---not in terms of the actual machine code.
5262 @code{until} with no argument works by means of single
5263 instruction stepping, and hence is slower than @code{until} with an
5266 @item until @var{location}
5267 @itemx u @var{location}
5268 Continue running your program until either the specified @var{location} is
5269 reached, or the current stack frame returns. The location is any of
5270 the forms described in @ref{Specify Location}.
5271 This form of the command uses temporary breakpoints, and
5272 hence is quicker than @code{until} without an argument. The specified
5273 location is actually reached only if it is in the current frame. This
5274 implies that @code{until} can be used to skip over recursive function
5275 invocations. For instance in the code below, if the current location is
5276 line @code{96}, issuing @code{until 99} will execute the program up to
5277 line @code{99} in the same invocation of factorial, i.e., after the inner
5278 invocations have returned.
5281 94 int factorial (int value)
5283 96 if (value > 1) @{
5284 97 value *= factorial (value - 1);
5291 @kindex advance @var{location}
5292 @item advance @var{location}
5293 Continue running the program up to the given @var{location}. An argument is
5294 required, which should be of one of the forms described in
5295 @ref{Specify Location}.
5296 Execution will also stop upon exit from the current stack
5297 frame. This command is similar to @code{until}, but @code{advance} will
5298 not skip over recursive function calls, and the target location doesn't
5299 have to be in the same frame as the current one.
5303 @kindex si @r{(@code{stepi})}
5305 @itemx stepi @var{arg}
5307 Execute one machine instruction, then stop and return to the debugger.
5309 It is often useful to do @samp{display/i $pc} when stepping by machine
5310 instructions. This makes @value{GDBN} automatically display the next
5311 instruction to be executed, each time your program stops. @xref{Auto
5312 Display,, Automatic Display}.
5314 An argument is a repeat count, as in @code{step}.
5318 @kindex ni @r{(@code{nexti})}
5320 @itemx nexti @var{arg}
5322 Execute one machine instruction, but if it is a function call,
5323 proceed until the function returns.
5325 An argument is a repeat count, as in @code{next}.
5329 @anchor{range stepping}
5330 @cindex range stepping
5331 @cindex target-assisted range stepping
5332 By default, and if available, @value{GDBN} makes use of
5333 target-assisted @dfn{range stepping}. In other words, whenever you
5334 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5335 tells the target to step the corresponding range of instruction
5336 addresses instead of issuing multiple single-steps. This speeds up
5337 line stepping, particularly for remote targets. Ideally, there should
5338 be no reason you would want to turn range stepping off. However, it's
5339 possible that a bug in the debug info, a bug in the remote stub (for
5340 remote targets), or even a bug in @value{GDBN} could make line
5341 stepping behave incorrectly when target-assisted range stepping is
5342 enabled. You can use the following command to turn off range stepping
5346 @kindex set range-stepping
5347 @kindex show range-stepping
5348 @item set range-stepping
5349 @itemx show range-stepping
5350 Control whether range stepping is enabled.
5352 If @code{on}, and the target supports it, @value{GDBN} tells the
5353 target to step a range of addresses itself, instead of issuing
5354 multiple single-steps. If @code{off}, @value{GDBN} always issues
5355 single-steps, even if range stepping is supported by the target. The
5356 default is @code{on}.
5360 @node Skipping Over Functions and Files
5361 @section Skipping Over Functions and Files
5362 @cindex skipping over functions and files
5364 The program you are debugging may contain some functions which are
5365 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
5366 skip a function or all functions in a file when stepping.
5368 For example, consider the following C function:
5379 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5380 are not interested in stepping through @code{boring}. If you run @code{step}
5381 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5382 step over both @code{foo} and @code{boring}!
5384 One solution is to @code{step} into @code{boring} and use the @code{finish}
5385 command to immediately exit it. But this can become tedious if @code{boring}
5386 is called from many places.
5388 A more flexible solution is to execute @kbd{skip boring}. This instructs
5389 @value{GDBN} never to step into @code{boring}. Now when you execute
5390 @code{step} at line 103, you'll step over @code{boring} and directly into
5393 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5394 example, @code{skip file boring.c}.
5397 @kindex skip function
5398 @item skip @r{[}@var{linespec}@r{]}
5399 @itemx skip function @r{[}@var{linespec}@r{]}
5400 After running this command, the function named by @var{linespec} or the
5401 function containing the line named by @var{linespec} will be skipped over when
5402 stepping. @xref{Specify Location}.
5404 If you do not specify @var{linespec}, the function you're currently debugging
5407 (If you have a function called @code{file} that you want to skip, use
5408 @kbd{skip function file}.)
5411 @item skip file @r{[}@var{filename}@r{]}
5412 After running this command, any function whose source lives in @var{filename}
5413 will be skipped over when stepping.
5415 If you do not specify @var{filename}, functions whose source lives in the file
5416 you're currently debugging will be skipped.
5419 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5420 These are the commands for managing your list of skips:
5424 @item info skip @r{[}@var{range}@r{]}
5425 Print details about the specified skip(s). If @var{range} is not specified,
5426 print a table with details about all functions and files marked for skipping.
5427 @code{info skip} prints the following information about each skip:
5431 A number identifying this skip.
5433 The type of this skip, either @samp{function} or @samp{file}.
5434 @item Enabled or Disabled
5435 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5437 For function skips, this column indicates the address in memory of the function
5438 being skipped. If you've set a function skip on a function which has not yet
5439 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5440 which has the function is loaded, @code{info skip} will show the function's
5443 For file skips, this field contains the filename being skipped. For functions
5444 skips, this field contains the function name and its line number in the file
5445 where it is defined.
5449 @item skip delete @r{[}@var{range}@r{]}
5450 Delete the specified skip(s). If @var{range} is not specified, delete all
5454 @item skip enable @r{[}@var{range}@r{]}
5455 Enable the specified skip(s). If @var{range} is not specified, enable all
5458 @kindex skip disable
5459 @item skip disable @r{[}@var{range}@r{]}
5460 Disable the specified skip(s). If @var{range} is not specified, disable all
5469 A signal is an asynchronous event that can happen in a program. The
5470 operating system defines the possible kinds of signals, and gives each
5471 kind a name and a number. For example, in Unix @code{SIGINT} is the
5472 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5473 @code{SIGSEGV} is the signal a program gets from referencing a place in
5474 memory far away from all the areas in use; @code{SIGALRM} occurs when
5475 the alarm clock timer goes off (which happens only if your program has
5476 requested an alarm).
5478 @cindex fatal signals
5479 Some signals, including @code{SIGALRM}, are a normal part of the
5480 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5481 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5482 program has not specified in advance some other way to handle the signal.
5483 @code{SIGINT} does not indicate an error in your program, but it is normally
5484 fatal so it can carry out the purpose of the interrupt: to kill the program.
5486 @value{GDBN} has the ability to detect any occurrence of a signal in your
5487 program. You can tell @value{GDBN} in advance what to do for each kind of
5490 @cindex handling signals
5491 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5492 @code{SIGALRM} be silently passed to your program
5493 (so as not to interfere with their role in the program's functioning)
5494 but to stop your program immediately whenever an error signal happens.
5495 You can change these settings with the @code{handle} command.
5498 @kindex info signals
5502 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5503 handle each one. You can use this to see the signal numbers of all
5504 the defined types of signals.
5506 @item info signals @var{sig}
5507 Similar, but print information only about the specified signal number.
5509 @code{info handle} is an alias for @code{info signals}.
5511 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5512 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5513 for details about this command.
5516 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5517 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5518 can be the number of a signal or its name (with or without the
5519 @samp{SIG} at the beginning); a list of signal numbers of the form
5520 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5521 known signals. Optional arguments @var{keywords}, described below,
5522 say what change to make.
5526 The keywords allowed by the @code{handle} command can be abbreviated.
5527 Their full names are:
5531 @value{GDBN} should not stop your program when this signal happens. It may
5532 still print a message telling you that the signal has come in.
5535 @value{GDBN} should stop your program when this signal happens. This implies
5536 the @code{print} keyword as well.
5539 @value{GDBN} should print a message when this signal happens.
5542 @value{GDBN} should not mention the occurrence of the signal at all. This
5543 implies the @code{nostop} keyword as well.
5547 @value{GDBN} should allow your program to see this signal; your program
5548 can handle the signal, or else it may terminate if the signal is fatal
5549 and not handled. @code{pass} and @code{noignore} are synonyms.
5553 @value{GDBN} should not allow your program to see this signal.
5554 @code{nopass} and @code{ignore} are synonyms.
5558 When a signal stops your program, the signal is not visible to the
5560 continue. Your program sees the signal then, if @code{pass} is in
5561 effect for the signal in question @emph{at that time}. In other words,
5562 after @value{GDBN} reports a signal, you can use the @code{handle}
5563 command with @code{pass} or @code{nopass} to control whether your
5564 program sees that signal when you continue.
5566 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5567 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5568 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5571 You can also use the @code{signal} command to prevent your program from
5572 seeing a signal, or cause it to see a signal it normally would not see,
5573 or to give it any signal at any time. For example, if your program stopped
5574 due to some sort of memory reference error, you might store correct
5575 values into the erroneous variables and continue, hoping to see more
5576 execution; but your program would probably terminate immediately as
5577 a result of the fatal signal once it saw the signal. To prevent this,
5578 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5581 @cindex stepping and signal handlers
5582 @anchor{stepping and signal handlers}
5584 @value{GDBN} optimizes for stepping the mainline code. If a signal
5585 that has @code{handle nostop} and @code{handle pass} set arrives while
5586 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
5587 in progress, @value{GDBN} lets the signal handler run and then resumes
5588 stepping the mainline code once the signal handler returns. In other
5589 words, @value{GDBN} steps over the signal handler. This prevents
5590 signals that you've specified as not interesting (with @code{handle
5591 nostop}) from changing the focus of debugging unexpectedly. Note that
5592 the signal handler itself may still hit a breakpoint, stop for another
5593 signal that has @code{handle stop} in effect, or for any other event
5594 that normally results in stopping the stepping command sooner. Also
5595 note that @value{GDBN} still informs you that the program received a
5596 signal if @code{handle print} is set.
5598 @anchor{stepping into signal handlers}
5600 If you set @code{handle pass} for a signal, and your program sets up a
5601 handler for it, then issuing a stepping command, such as @code{step}
5602 or @code{stepi}, when your program is stopped due to the signal will
5603 step @emph{into} the signal handler (if the target supports that).
5605 Likewise, if you use the @code{queue-signal} command to queue a signal
5606 to be delivered to the current thread when execution of the thread
5607 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
5608 stepping command will step into the signal handler.
5610 Here's an example, using @code{stepi} to step to the first instruction
5611 of @code{SIGUSR1}'s handler:
5614 (@value{GDBP}) handle SIGUSR1
5615 Signal Stop Print Pass to program Description
5616 SIGUSR1 Yes Yes Yes User defined signal 1
5620 Program received signal SIGUSR1, User defined signal 1.
5621 main () sigusr1.c:28
5624 sigusr1_handler () at sigusr1.c:9
5628 The same, but using @code{queue-signal} instead of waiting for the
5629 program to receive the signal first:
5634 (@value{GDBP}) queue-signal SIGUSR1
5636 sigusr1_handler () at sigusr1.c:9
5641 @cindex extra signal information
5642 @anchor{extra signal information}
5644 On some targets, @value{GDBN} can inspect extra signal information
5645 associated with the intercepted signal, before it is actually
5646 delivered to the program being debugged. This information is exported
5647 by the convenience variable @code{$_siginfo}, and consists of data
5648 that is passed by the kernel to the signal handler at the time of the
5649 receipt of a signal. The data type of the information itself is
5650 target dependent. You can see the data type using the @code{ptype
5651 $_siginfo} command. On Unix systems, it typically corresponds to the
5652 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5655 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5656 referenced address that raised a segmentation fault.
5660 (@value{GDBP}) continue
5661 Program received signal SIGSEGV, Segmentation fault.
5662 0x0000000000400766 in main ()
5664 (@value{GDBP}) ptype $_siginfo
5671 struct @{...@} _kill;
5672 struct @{...@} _timer;
5674 struct @{...@} _sigchld;
5675 struct @{...@} _sigfault;
5676 struct @{...@} _sigpoll;
5679 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5683 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5684 $1 = (void *) 0x7ffff7ff7000
5688 Depending on target support, @code{$_siginfo} may also be writable.
5691 @section Stopping and Starting Multi-thread Programs
5693 @cindex stopped threads
5694 @cindex threads, stopped
5696 @cindex continuing threads
5697 @cindex threads, continuing
5699 @value{GDBN} supports debugging programs with multiple threads
5700 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5701 are two modes of controlling execution of your program within the
5702 debugger. In the default mode, referred to as @dfn{all-stop mode},
5703 when any thread in your program stops (for example, at a breakpoint
5704 or while being stepped), all other threads in the program are also stopped by
5705 @value{GDBN}. On some targets, @value{GDBN} also supports
5706 @dfn{non-stop mode}, in which other threads can continue to run freely while
5707 you examine the stopped thread in the debugger.
5710 * All-Stop Mode:: All threads stop when GDB takes control
5711 * Non-Stop Mode:: Other threads continue to execute
5712 * Background Execution:: Running your program asynchronously
5713 * Thread-Specific Breakpoints:: Controlling breakpoints
5714 * Interrupted System Calls:: GDB may interfere with system calls
5715 * Observer Mode:: GDB does not alter program behavior
5719 @subsection All-Stop Mode
5721 @cindex all-stop mode
5723 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5724 @emph{all} threads of execution stop, not just the current thread. This
5725 allows you to examine the overall state of the program, including
5726 switching between threads, without worrying that things may change
5729 Conversely, whenever you restart the program, @emph{all} threads start
5730 executing. @emph{This is true even when single-stepping} with commands
5731 like @code{step} or @code{next}.
5733 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5734 Since thread scheduling is up to your debugging target's operating
5735 system (not controlled by @value{GDBN}), other threads may
5736 execute more than one statement while the current thread completes a
5737 single step. Moreover, in general other threads stop in the middle of a
5738 statement, rather than at a clean statement boundary, when the program
5741 You might even find your program stopped in another thread after
5742 continuing or even single-stepping. This happens whenever some other
5743 thread runs into a breakpoint, a signal, or an exception before the
5744 first thread completes whatever you requested.
5746 @cindex automatic thread selection
5747 @cindex switching threads automatically
5748 @cindex threads, automatic switching
5749 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5750 signal, it automatically selects the thread where that breakpoint or
5751 signal happened. @value{GDBN} alerts you to the context switch with a
5752 message such as @samp{[Switching to Thread @var{n}]} to identify the
5755 On some OSes, you can modify @value{GDBN}'s default behavior by
5756 locking the OS scheduler to allow only a single thread to run.
5759 @item set scheduler-locking @var{mode}
5760 @cindex scheduler locking mode
5761 @cindex lock scheduler
5762 Set the scheduler locking mode. If it is @code{off}, then there is no
5763 locking and any thread may run at any time. If @code{on}, then only the
5764 current thread may run when the inferior is resumed. The @code{step}
5765 mode optimizes for single-stepping; it prevents other threads
5766 from preempting the current thread while you are stepping, so that
5767 the focus of debugging does not change unexpectedly.
5768 Other threads only rarely (or never) get a chance to run
5769 when you step. They are more likely to run when you @samp{next} over a
5770 function call, and they are completely free to run when you use commands
5771 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5772 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5773 the current thread away from the thread that you are debugging.
5775 @item show scheduler-locking
5776 Display the current scheduler locking mode.
5779 @cindex resume threads of multiple processes simultaneously
5780 By default, when you issue one of the execution commands such as
5781 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5782 threads of the current inferior to run. For example, if @value{GDBN}
5783 is attached to two inferiors, each with two threads, the
5784 @code{continue} command resumes only the two threads of the current
5785 inferior. This is useful, for example, when you debug a program that
5786 forks and you want to hold the parent stopped (so that, for instance,
5787 it doesn't run to exit), while you debug the child. In other
5788 situations, you may not be interested in inspecting the current state
5789 of any of the processes @value{GDBN} is attached to, and you may want
5790 to resume them all until some breakpoint is hit. In the latter case,
5791 you can instruct @value{GDBN} to allow all threads of all the
5792 inferiors to run with the @w{@code{set schedule-multiple}} command.
5795 @kindex set schedule-multiple
5796 @item set schedule-multiple
5797 Set the mode for allowing threads of multiple processes to be resumed
5798 when an execution command is issued. When @code{on}, all threads of
5799 all processes are allowed to run. When @code{off}, only the threads
5800 of the current process are resumed. The default is @code{off}. The
5801 @code{scheduler-locking} mode takes precedence when set to @code{on},
5802 or while you are stepping and set to @code{step}.
5804 @item show schedule-multiple
5805 Display the current mode for resuming the execution of threads of
5810 @subsection Non-Stop Mode
5812 @cindex non-stop mode
5814 @c This section is really only a place-holder, and needs to be expanded
5815 @c with more details.
5817 For some multi-threaded targets, @value{GDBN} supports an optional
5818 mode of operation in which you can examine stopped program threads in
5819 the debugger while other threads continue to execute freely. This
5820 minimizes intrusion when debugging live systems, such as programs
5821 where some threads have real-time constraints or must continue to
5822 respond to external events. This is referred to as @dfn{non-stop} mode.
5824 In non-stop mode, when a thread stops to report a debugging event,
5825 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5826 threads as well, in contrast to the all-stop mode behavior. Additionally,
5827 execution commands such as @code{continue} and @code{step} apply by default
5828 only to the current thread in non-stop mode, rather than all threads as
5829 in all-stop mode. This allows you to control threads explicitly in
5830 ways that are not possible in all-stop mode --- for example, stepping
5831 one thread while allowing others to run freely, stepping
5832 one thread while holding all others stopped, or stepping several threads
5833 independently and simultaneously.
5835 To enter non-stop mode, use this sequence of commands before you run
5836 or attach to your program:
5839 # If using the CLI, pagination breaks non-stop.
5842 # Finally, turn it on!
5846 You can use these commands to manipulate the non-stop mode setting:
5849 @kindex set non-stop
5850 @item set non-stop on
5851 Enable selection of non-stop mode.
5852 @item set non-stop off
5853 Disable selection of non-stop mode.
5854 @kindex show non-stop
5856 Show the current non-stop enablement setting.
5859 Note these commands only reflect whether non-stop mode is enabled,
5860 not whether the currently-executing program is being run in non-stop mode.
5861 In particular, the @code{set non-stop} preference is only consulted when
5862 @value{GDBN} starts or connects to the target program, and it is generally
5863 not possible to switch modes once debugging has started. Furthermore,
5864 since not all targets support non-stop mode, even when you have enabled
5865 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5868 In non-stop mode, all execution commands apply only to the current thread
5869 by default. That is, @code{continue} only continues one thread.
5870 To continue all threads, issue @code{continue -a} or @code{c -a}.
5872 You can use @value{GDBN}'s background execution commands
5873 (@pxref{Background Execution}) to run some threads in the background
5874 while you continue to examine or step others from @value{GDBN}.
5875 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5876 always executed asynchronously in non-stop mode.
5878 Suspending execution is done with the @code{interrupt} command when
5879 running in the background, or @kbd{Ctrl-c} during foreground execution.
5880 In all-stop mode, this stops the whole process;
5881 but in non-stop mode the interrupt applies only to the current thread.
5882 To stop the whole program, use @code{interrupt -a}.
5884 Other execution commands do not currently support the @code{-a} option.
5886 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5887 that thread current, as it does in all-stop mode. This is because the
5888 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5889 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5890 changed to a different thread just as you entered a command to operate on the
5891 previously current thread.
5893 @node Background Execution
5894 @subsection Background Execution
5896 @cindex foreground execution
5897 @cindex background execution
5898 @cindex asynchronous execution
5899 @cindex execution, foreground, background and asynchronous
5901 @value{GDBN}'s execution commands have two variants: the normal
5902 foreground (synchronous) behavior, and a background
5903 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5904 the program to report that some thread has stopped before prompting for
5905 another command. In background execution, @value{GDBN} immediately gives
5906 a command prompt so that you can issue other commands while your program runs.
5908 If the target doesn't support async mode, @value{GDBN} issues an error
5909 message if you attempt to use the background execution commands.
5911 To specify background execution, add a @code{&} to the command. For example,
5912 the background form of the @code{continue} command is @code{continue&}, or
5913 just @code{c&}. The execution commands that accept background execution
5919 @xref{Starting, , Starting your Program}.
5923 @xref{Attach, , Debugging an Already-running Process}.
5927 @xref{Continuing and Stepping, step}.
5931 @xref{Continuing and Stepping, stepi}.
5935 @xref{Continuing and Stepping, next}.
5939 @xref{Continuing and Stepping, nexti}.
5943 @xref{Continuing and Stepping, continue}.
5947 @xref{Continuing and Stepping, finish}.
5951 @xref{Continuing and Stepping, until}.
5955 Background execution is especially useful in conjunction with non-stop
5956 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5957 However, you can also use these commands in the normal all-stop mode with
5958 the restriction that you cannot issue another execution command until the
5959 previous one finishes. Examples of commands that are valid in all-stop
5960 mode while the program is running include @code{help} and @code{info break}.
5962 You can interrupt your program while it is running in the background by
5963 using the @code{interrupt} command.
5970 Suspend execution of the running program. In all-stop mode,
5971 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5972 only the current thread. To stop the whole program in non-stop mode,
5973 use @code{interrupt -a}.
5976 @node Thread-Specific Breakpoints
5977 @subsection Thread-Specific Breakpoints
5979 When your program has multiple threads (@pxref{Threads,, Debugging
5980 Programs with Multiple Threads}), you can choose whether to set
5981 breakpoints on all threads, or on a particular thread.
5984 @cindex breakpoints and threads
5985 @cindex thread breakpoints
5986 @kindex break @dots{} thread @var{threadno}
5987 @item break @var{linespec} thread @var{threadno}
5988 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5989 @var{linespec} specifies source lines; there are several ways of
5990 writing them (@pxref{Specify Location}), but the effect is always to
5991 specify some source line.
5993 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5994 to specify that you only want @value{GDBN} to stop the program when a
5995 particular thread reaches this breakpoint. The @var{threadno} specifier
5996 is one of the numeric thread identifiers assigned by @value{GDBN}, shown
5997 in the first column of the @samp{info threads} display.
5999 If you do not specify @samp{thread @var{threadno}} when you set a
6000 breakpoint, the breakpoint applies to @emph{all} threads of your
6003 You can use the @code{thread} qualifier on conditional breakpoints as
6004 well; in this case, place @samp{thread @var{threadno}} before or
6005 after the breakpoint condition, like this:
6008 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6013 Thread-specific breakpoints are automatically deleted when
6014 @value{GDBN} detects the corresponding thread is no longer in the
6015 thread list. For example:
6019 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6022 There are several ways for a thread to disappear, such as a regular
6023 thread exit, but also when you detach from the process with the
6024 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6025 Process}), or if @value{GDBN} loses the remote connection
6026 (@pxref{Remote Debugging}), etc. Note that with some targets,
6027 @value{GDBN} is only able to detect a thread has exited when the user
6028 explictly asks for the thread list with the @code{info threads}
6031 @node Interrupted System Calls
6032 @subsection Interrupted System Calls
6034 @cindex thread breakpoints and system calls
6035 @cindex system calls and thread breakpoints
6036 @cindex premature return from system calls
6037 There is an unfortunate side effect when using @value{GDBN} to debug
6038 multi-threaded programs. If one thread stops for a
6039 breakpoint, or for some other reason, and another thread is blocked in a
6040 system call, then the system call may return prematurely. This is a
6041 consequence of the interaction between multiple threads and the signals
6042 that @value{GDBN} uses to implement breakpoints and other events that
6045 To handle this problem, your program should check the return value of
6046 each system call and react appropriately. This is good programming
6049 For example, do not write code like this:
6055 The call to @code{sleep} will return early if a different thread stops
6056 at a breakpoint or for some other reason.
6058 Instead, write this:
6063 unslept = sleep (unslept);
6066 A system call is allowed to return early, so the system is still
6067 conforming to its specification. But @value{GDBN} does cause your
6068 multi-threaded program to behave differently than it would without
6071 Also, @value{GDBN} uses internal breakpoints in the thread library to
6072 monitor certain events such as thread creation and thread destruction.
6073 When such an event happens, a system call in another thread may return
6074 prematurely, even though your program does not appear to stop.
6077 @subsection Observer Mode
6079 If you want to build on non-stop mode and observe program behavior
6080 without any chance of disruption by @value{GDBN}, you can set
6081 variables to disable all of the debugger's attempts to modify state,
6082 whether by writing memory, inserting breakpoints, etc. These operate
6083 at a low level, intercepting operations from all commands.
6085 When all of these are set to @code{off}, then @value{GDBN} is said to
6086 be @dfn{observer mode}. As a convenience, the variable
6087 @code{observer} can be set to disable these, plus enable non-stop
6090 Note that @value{GDBN} will not prevent you from making nonsensical
6091 combinations of these settings. For instance, if you have enabled
6092 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6093 then breakpoints that work by writing trap instructions into the code
6094 stream will still not be able to be placed.
6099 @item set observer on
6100 @itemx set observer off
6101 When set to @code{on}, this disables all the permission variables
6102 below (except for @code{insert-fast-tracepoints}), plus enables
6103 non-stop debugging. Setting this to @code{off} switches back to
6104 normal debugging, though remaining in non-stop mode.
6107 Show whether observer mode is on or off.
6109 @kindex may-write-registers
6110 @item set may-write-registers on
6111 @itemx set may-write-registers off
6112 This controls whether @value{GDBN} will attempt to alter the values of
6113 registers, such as with assignment expressions in @code{print}, or the
6114 @code{jump} command. It defaults to @code{on}.
6116 @item show may-write-registers
6117 Show the current permission to write registers.
6119 @kindex may-write-memory
6120 @item set may-write-memory on
6121 @itemx set may-write-memory off
6122 This controls whether @value{GDBN} will attempt to alter the contents
6123 of memory, such as with assignment expressions in @code{print}. It
6124 defaults to @code{on}.
6126 @item show may-write-memory
6127 Show the current permission to write memory.
6129 @kindex may-insert-breakpoints
6130 @item set may-insert-breakpoints on
6131 @itemx set may-insert-breakpoints off
6132 This controls whether @value{GDBN} will attempt to insert breakpoints.
6133 This affects all breakpoints, including internal breakpoints defined
6134 by @value{GDBN}. It defaults to @code{on}.
6136 @item show may-insert-breakpoints
6137 Show the current permission to insert breakpoints.
6139 @kindex may-insert-tracepoints
6140 @item set may-insert-tracepoints on
6141 @itemx set may-insert-tracepoints off
6142 This controls whether @value{GDBN} will attempt to insert (regular)
6143 tracepoints at the beginning of a tracing experiment. It affects only
6144 non-fast tracepoints, fast tracepoints being under the control of
6145 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6147 @item show may-insert-tracepoints
6148 Show the current permission to insert tracepoints.
6150 @kindex may-insert-fast-tracepoints
6151 @item set may-insert-fast-tracepoints on
6152 @itemx set may-insert-fast-tracepoints off
6153 This controls whether @value{GDBN} will attempt to insert fast
6154 tracepoints at the beginning of a tracing experiment. It affects only
6155 fast tracepoints, regular (non-fast) tracepoints being under the
6156 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6158 @item show may-insert-fast-tracepoints
6159 Show the current permission to insert fast tracepoints.
6161 @kindex may-interrupt
6162 @item set may-interrupt on
6163 @itemx set may-interrupt off
6164 This controls whether @value{GDBN} will attempt to interrupt or stop
6165 program execution. When this variable is @code{off}, the
6166 @code{interrupt} command will have no effect, nor will
6167 @kbd{Ctrl-c}. It defaults to @code{on}.
6169 @item show may-interrupt
6170 Show the current permission to interrupt or stop the program.
6174 @node Reverse Execution
6175 @chapter Running programs backward
6176 @cindex reverse execution
6177 @cindex running programs backward
6179 When you are debugging a program, it is not unusual to realize that
6180 you have gone too far, and some event of interest has already happened.
6181 If the target environment supports it, @value{GDBN} can allow you to
6182 ``rewind'' the program by running it backward.
6184 A target environment that supports reverse execution should be able
6185 to ``undo'' the changes in machine state that have taken place as the
6186 program was executing normally. Variables, registers etc.@: should
6187 revert to their previous values. Obviously this requires a great
6188 deal of sophistication on the part of the target environment; not
6189 all target environments can support reverse execution.
6191 When a program is executed in reverse, the instructions that
6192 have most recently been executed are ``un-executed'', in reverse
6193 order. The program counter runs backward, following the previous
6194 thread of execution in reverse. As each instruction is ``un-executed'',
6195 the values of memory and/or registers that were changed by that
6196 instruction are reverted to their previous states. After executing
6197 a piece of source code in reverse, all side effects of that code
6198 should be ``undone'', and all variables should be returned to their
6199 prior values@footnote{
6200 Note that some side effects are easier to undo than others. For instance,
6201 memory and registers are relatively easy, but device I/O is hard. Some
6202 targets may be able undo things like device I/O, and some may not.
6204 The contract between @value{GDBN} and the reverse executing target
6205 requires only that the target do something reasonable when
6206 @value{GDBN} tells it to execute backwards, and then report the
6207 results back to @value{GDBN}. Whatever the target reports back to
6208 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6209 assumes that the memory and registers that the target reports are in a
6210 consistant state, but @value{GDBN} accepts whatever it is given.
6213 If you are debugging in a target environment that supports
6214 reverse execution, @value{GDBN} provides the following commands.
6217 @kindex reverse-continue
6218 @kindex rc @r{(@code{reverse-continue})}
6219 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6220 @itemx rc @r{[}@var{ignore-count}@r{]}
6221 Beginning at the point where your program last stopped, start executing
6222 in reverse. Reverse execution will stop for breakpoints and synchronous
6223 exceptions (signals), just like normal execution. Behavior of
6224 asynchronous signals depends on the target environment.
6226 @kindex reverse-step
6227 @kindex rs @r{(@code{step})}
6228 @item reverse-step @r{[}@var{count}@r{]}
6229 Run the program backward until control reaches the start of a
6230 different source line; then stop it, and return control to @value{GDBN}.
6232 Like the @code{step} command, @code{reverse-step} will only stop
6233 at the beginning of a source line. It ``un-executes'' the previously
6234 executed source line. If the previous source line included calls to
6235 debuggable functions, @code{reverse-step} will step (backward) into
6236 the called function, stopping at the beginning of the @emph{last}
6237 statement in the called function (typically a return statement).
6239 Also, as with the @code{step} command, if non-debuggable functions are
6240 called, @code{reverse-step} will run thru them backward without stopping.
6242 @kindex reverse-stepi
6243 @kindex rsi @r{(@code{reverse-stepi})}
6244 @item reverse-stepi @r{[}@var{count}@r{]}
6245 Reverse-execute one machine instruction. Note that the instruction
6246 to be reverse-executed is @emph{not} the one pointed to by the program
6247 counter, but the instruction executed prior to that one. For instance,
6248 if the last instruction was a jump, @code{reverse-stepi} will take you
6249 back from the destination of the jump to the jump instruction itself.
6251 @kindex reverse-next
6252 @kindex rn @r{(@code{reverse-next})}
6253 @item reverse-next @r{[}@var{count}@r{]}
6254 Run backward to the beginning of the previous line executed in
6255 the current (innermost) stack frame. If the line contains function
6256 calls, they will be ``un-executed'' without stopping. Starting from
6257 the first line of a function, @code{reverse-next} will take you back
6258 to the caller of that function, @emph{before} the function was called,
6259 just as the normal @code{next} command would take you from the last
6260 line of a function back to its return to its caller
6261 @footnote{Unless the code is too heavily optimized.}.
6263 @kindex reverse-nexti
6264 @kindex rni @r{(@code{reverse-nexti})}
6265 @item reverse-nexti @r{[}@var{count}@r{]}
6266 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6267 in reverse, except that called functions are ``un-executed'' atomically.
6268 That is, if the previously executed instruction was a return from
6269 another function, @code{reverse-nexti} will continue to execute
6270 in reverse until the call to that function (from the current stack
6273 @kindex reverse-finish
6274 @item reverse-finish
6275 Just as the @code{finish} command takes you to the point where the
6276 current function returns, @code{reverse-finish} takes you to the point
6277 where it was called. Instead of ending up at the end of the current
6278 function invocation, you end up at the beginning.
6280 @kindex set exec-direction
6281 @item set exec-direction
6282 Set the direction of target execution.
6283 @item set exec-direction reverse
6284 @cindex execute forward or backward in time
6285 @value{GDBN} will perform all execution commands in reverse, until the
6286 exec-direction mode is changed to ``forward''. Affected commands include
6287 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6288 command cannot be used in reverse mode.
6289 @item set exec-direction forward
6290 @value{GDBN} will perform all execution commands in the normal fashion.
6291 This is the default.
6295 @node Process Record and Replay
6296 @chapter Recording Inferior's Execution and Replaying It
6297 @cindex process record and replay
6298 @cindex recording inferior's execution and replaying it
6300 On some platforms, @value{GDBN} provides a special @dfn{process record
6301 and replay} target that can record a log of the process execution, and
6302 replay it later with both forward and reverse execution commands.
6305 When this target is in use, if the execution log includes the record
6306 for the next instruction, @value{GDBN} will debug in @dfn{replay
6307 mode}. In the replay mode, the inferior does not really execute code
6308 instructions. Instead, all the events that normally happen during
6309 code execution are taken from the execution log. While code is not
6310 really executed in replay mode, the values of registers (including the
6311 program counter register) and the memory of the inferior are still
6312 changed as they normally would. Their contents are taken from the
6316 If the record for the next instruction is not in the execution log,
6317 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6318 inferior executes normally, and @value{GDBN} records the execution log
6321 The process record and replay target supports reverse execution
6322 (@pxref{Reverse Execution}), even if the platform on which the
6323 inferior runs does not. However, the reverse execution is limited in
6324 this case by the range of the instructions recorded in the execution
6325 log. In other words, reverse execution on platforms that don't
6326 support it directly can only be done in the replay mode.
6328 When debugging in the reverse direction, @value{GDBN} will work in
6329 replay mode as long as the execution log includes the record for the
6330 previous instruction; otherwise, it will work in record mode, if the
6331 platform supports reverse execution, or stop if not.
6333 For architecture environments that support process record and replay,
6334 @value{GDBN} provides the following commands:
6337 @kindex target record
6338 @kindex target record-full
6339 @kindex target record-btrace
6342 @kindex record btrace
6346 @item record @var{method}
6347 This command starts the process record and replay target. The
6348 recording method can be specified as parameter. Without a parameter
6349 the command uses the @code{full} recording method. The following
6350 recording methods are available:
6354 Full record/replay recording using @value{GDBN}'s software record and
6355 replay implementation. This method allows replaying and reverse
6359 Hardware-supported instruction recording. This method does not record
6360 data. Further, the data is collected in a ring buffer so old data will
6361 be overwritten when the buffer is full. It allows limited replay and
6364 This recording method may not be available on all processors.
6367 The process record and replay target can only debug a process that is
6368 already running. Therefore, you need first to start the process with
6369 the @kbd{run} or @kbd{start} commands, and then start the recording
6370 with the @kbd{record @var{method}} command.
6372 Both @code{record @var{method}} and @code{rec @var{method}} are
6373 aliases of @code{target record-@var{method}}.
6375 @cindex displaced stepping, and process record and replay
6376 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6377 will be automatically disabled when process record and replay target
6378 is started. That's because the process record and replay target
6379 doesn't support displaced stepping.
6381 @cindex non-stop mode, and process record and replay
6382 @cindex asynchronous execution, and process record and replay
6383 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6384 the asynchronous execution mode (@pxref{Background Execution}), not
6385 all recording methods are available. The @code{full} recording method
6386 does not support these two modes.
6391 Stop the process record and replay target. When process record and
6392 replay target stops, the entire execution log will be deleted and the
6393 inferior will either be terminated, or will remain in its final state.
6395 When you stop the process record and replay target in record mode (at
6396 the end of the execution log), the inferior will be stopped at the
6397 next instruction that would have been recorded. In other words, if
6398 you record for a while and then stop recording, the inferior process
6399 will be left in the same state as if the recording never happened.
6401 On the other hand, if the process record and replay target is stopped
6402 while in replay mode (that is, not at the end of the execution log,
6403 but at some earlier point), the inferior process will become ``live''
6404 at that earlier state, and it will then be possible to continue the
6405 usual ``live'' debugging of the process from that state.
6407 When the inferior process exits, or @value{GDBN} detaches from it,
6408 process record and replay target will automatically stop itself.
6412 Go to a specific location in the execution log. There are several
6413 ways to specify the location to go to:
6416 @item record goto begin
6417 @itemx record goto start
6418 Go to the beginning of the execution log.
6420 @item record goto end
6421 Go to the end of the execution log.
6423 @item record goto @var{n}
6424 Go to instruction number @var{n} in the execution log.
6428 @item record save @var{filename}
6429 Save the execution log to a file @file{@var{filename}}.
6430 Default filename is @file{gdb_record.@var{process_id}}, where
6431 @var{process_id} is the process ID of the inferior.
6433 This command may not be available for all recording methods.
6435 @kindex record restore
6436 @item record restore @var{filename}
6437 Restore the execution log from a file @file{@var{filename}}.
6438 File must have been created with @code{record save}.
6440 @kindex set record full
6441 @item set record full insn-number-max @var{limit}
6442 @itemx set record full insn-number-max unlimited
6443 Set the limit of instructions to be recorded for the @code{full}
6444 recording method. Default value is 200000.
6446 If @var{limit} is a positive number, then @value{GDBN} will start
6447 deleting instructions from the log once the number of the record
6448 instructions becomes greater than @var{limit}. For every new recorded
6449 instruction, @value{GDBN} will delete the earliest recorded
6450 instruction to keep the number of recorded instructions at the limit.
6451 (Since deleting recorded instructions loses information, @value{GDBN}
6452 lets you control what happens when the limit is reached, by means of
6453 the @code{stop-at-limit} option, described below.)
6455 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6456 delete recorded instructions from the execution log. The number of
6457 recorded instructions is limited only by the available memory.
6459 @kindex show record full
6460 @item show record full insn-number-max
6461 Show the limit of instructions to be recorded with the @code{full}
6464 @item set record full stop-at-limit
6465 Control the behavior of the @code{full} recording method when the
6466 number of recorded instructions reaches the limit. If ON (the
6467 default), @value{GDBN} will stop when the limit is reached for the
6468 first time and ask you whether you want to stop the inferior or
6469 continue running it and recording the execution log. If you decide
6470 to continue recording, each new recorded instruction will cause the
6471 oldest one to be deleted.
6473 If this option is OFF, @value{GDBN} will automatically delete the
6474 oldest record to make room for each new one, without asking.
6476 @item show record full stop-at-limit
6477 Show the current setting of @code{stop-at-limit}.
6479 @item set record full memory-query
6480 Control the behavior when @value{GDBN} is unable to record memory
6481 changes caused by an instruction for the @code{full} recording method.
6482 If ON, @value{GDBN} will query whether to stop the inferior in that
6485 If this option is OFF (the default), @value{GDBN} will automatically
6486 ignore the effect of such instructions on memory. Later, when
6487 @value{GDBN} replays this execution log, it will mark the log of this
6488 instruction as not accessible, and it will not affect the replay
6491 @item show record full memory-query
6492 Show the current setting of @code{memory-query}.
6494 @kindex set record btrace
6495 The @code{btrace} record target does not trace data. As a
6496 convenience, when replaying, @value{GDBN} reads read-only memory off
6497 the live program directly, assuming that the addresses of the
6498 read-only areas don't change. This for example makes it possible to
6499 disassemble code while replaying, but not to print variables.
6500 In some cases, being able to inspect variables might be useful.
6501 You can use the following command for that:
6503 @item set record btrace replay-memory-access
6504 Control the behavior of the @code{btrace} recording method when
6505 accessing memory during replay. If @code{read-only} (the default),
6506 @value{GDBN} will only allow accesses to read-only memory.
6507 If @code{read-write}, @value{GDBN} will allow accesses to read-only
6508 and to read-write memory. Beware that the accessed memory corresponds
6509 to the live target and not necessarily to the current replay
6512 @kindex show record btrace
6513 @item show record btrace replay-memory-access
6514 Show the current setting of @code{replay-memory-access}.
6518 Show various statistics about the recording depending on the recording
6523 For the @code{full} recording method, it shows the state of process
6524 record and its in-memory execution log buffer, including:
6528 Whether in record mode or replay mode.
6530 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6532 Highest recorded instruction number.
6534 Current instruction about to be replayed (if in replay mode).
6536 Number of instructions contained in the execution log.
6538 Maximum number of instructions that may be contained in the execution log.
6542 For the @code{btrace} recording method, it shows the number of
6543 instructions that have been recorded and the number of blocks of
6544 sequential control-flow that is formed by the recorded instructions.
6547 @kindex record delete
6550 When record target runs in replay mode (``in the past''), delete the
6551 subsequent execution log and begin to record a new execution log starting
6552 from the current address. This means you will abandon the previously
6553 recorded ``future'' and begin recording a new ``future''.
6555 @kindex record instruction-history
6556 @kindex rec instruction-history
6557 @item record instruction-history
6558 Disassembles instructions from the recorded execution log. By
6559 default, ten instructions are disassembled. This can be changed using
6560 the @code{set record instruction-history-size} command. Instructions
6561 are printed in execution order. There are several ways to specify
6562 what part of the execution log to disassemble:
6565 @item record instruction-history @var{insn}
6566 Disassembles ten instructions starting from instruction number
6569 @item record instruction-history @var{insn}, +/-@var{n}
6570 Disassembles @var{n} instructions around instruction number
6571 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6572 @var{n} instructions after instruction number @var{insn}. If
6573 @var{n} is preceded with @code{-}, disassembles @var{n}
6574 instructions before instruction number @var{insn}.
6576 @item record instruction-history
6577 Disassembles ten more instructions after the last disassembly.
6579 @item record instruction-history -
6580 Disassembles ten more instructions before the last disassembly.
6582 @item record instruction-history @var{begin} @var{end}
6583 Disassembles instructions beginning with instruction number
6584 @var{begin} until instruction number @var{end}. The instruction
6585 number @var{end} is included.
6588 This command may not be available for all recording methods.
6591 @item set record instruction-history-size @var{size}
6592 @itemx set record instruction-history-size unlimited
6593 Define how many instructions to disassemble in the @code{record
6594 instruction-history} command. The default value is 10.
6595 A @var{size} of @code{unlimited} means unlimited instructions.
6598 @item show record instruction-history-size
6599 Show how many instructions to disassemble in the @code{record
6600 instruction-history} command.
6602 @kindex record function-call-history
6603 @kindex rec function-call-history
6604 @item record function-call-history
6605 Prints the execution history at function granularity. It prints one
6606 line for each sequence of instructions that belong to the same
6607 function giving the name of that function, the source lines
6608 for this instruction sequence (if the @code{/l} modifier is
6609 specified), and the instructions numbers that form the sequence (if
6610 the @code{/i} modifier is specified). The function names are indented
6611 to reflect the call stack depth if the @code{/c} modifier is
6612 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
6616 (@value{GDBP}) @b{list 1, 10}
6627 (@value{GDBP}) @b{record function-call-history /ilc}
6628 1 bar inst 1,4 at foo.c:6,8
6629 2 foo inst 5,10 at foo.c:2,3
6630 3 bar inst 11,13 at foo.c:9,10
6633 By default, ten lines are printed. This can be changed using the
6634 @code{set record function-call-history-size} command. Functions are
6635 printed in execution order. There are several ways to specify what
6639 @item record function-call-history @var{func}
6640 Prints ten functions starting from function number @var{func}.
6642 @item record function-call-history @var{func}, +/-@var{n}
6643 Prints @var{n} functions around function number @var{func}. If
6644 @var{n} is preceded with @code{+}, prints @var{n} functions after
6645 function number @var{func}. If @var{n} is preceded with @code{-},
6646 prints @var{n} functions before function number @var{func}.
6648 @item record function-call-history
6649 Prints ten more functions after the last ten-line print.
6651 @item record function-call-history -
6652 Prints ten more functions before the last ten-line print.
6654 @item record function-call-history @var{begin} @var{end}
6655 Prints functions beginning with function number @var{begin} until
6656 function number @var{end}. The function number @var{end} is included.
6659 This command may not be available for all recording methods.
6661 @item set record function-call-history-size @var{size}
6662 @itemx set record function-call-history-size unlimited
6663 Define how many lines to print in the
6664 @code{record function-call-history} command. The default value is 10.
6665 A size of @code{unlimited} means unlimited lines.
6667 @item show record function-call-history-size
6668 Show how many lines to print in the
6669 @code{record function-call-history} command.
6674 @chapter Examining the Stack
6676 When your program has stopped, the first thing you need to know is where it
6677 stopped and how it got there.
6680 Each time your program performs a function call, information about the call
6682 That information includes the location of the call in your program,
6683 the arguments of the call,
6684 and the local variables of the function being called.
6685 The information is saved in a block of data called a @dfn{stack frame}.
6686 The stack frames are allocated in a region of memory called the @dfn{call
6689 When your program stops, the @value{GDBN} commands for examining the
6690 stack allow you to see all of this information.
6692 @cindex selected frame
6693 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6694 @value{GDBN} commands refer implicitly to the selected frame. In
6695 particular, whenever you ask @value{GDBN} for the value of a variable in
6696 your program, the value is found in the selected frame. There are
6697 special @value{GDBN} commands to select whichever frame you are
6698 interested in. @xref{Selection, ,Selecting a Frame}.
6700 When your program stops, @value{GDBN} automatically selects the
6701 currently executing frame and describes it briefly, similar to the
6702 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6705 * Frames:: Stack frames
6706 * Backtrace:: Backtraces
6707 * Frame Filter Management:: Managing frame filters
6708 * Selection:: Selecting a frame
6709 * Frame Info:: Information on a frame
6714 @section Stack Frames
6716 @cindex frame, definition
6718 The call stack is divided up into contiguous pieces called @dfn{stack
6719 frames}, or @dfn{frames} for short; each frame is the data associated
6720 with one call to one function. The frame contains the arguments given
6721 to the function, the function's local variables, and the address at
6722 which the function is executing.
6724 @cindex initial frame
6725 @cindex outermost frame
6726 @cindex innermost frame
6727 When your program is started, the stack has only one frame, that of the
6728 function @code{main}. This is called the @dfn{initial} frame or the
6729 @dfn{outermost} frame. Each time a function is called, a new frame is
6730 made. Each time a function returns, the frame for that function invocation
6731 is eliminated. If a function is recursive, there can be many frames for
6732 the same function. The frame for the function in which execution is
6733 actually occurring is called the @dfn{innermost} frame. This is the most
6734 recently created of all the stack frames that still exist.
6736 @cindex frame pointer
6737 Inside your program, stack frames are identified by their addresses. A
6738 stack frame consists of many bytes, each of which has its own address; each
6739 kind of computer has a convention for choosing one byte whose
6740 address serves as the address of the frame. Usually this address is kept
6741 in a register called the @dfn{frame pointer register}
6742 (@pxref{Registers, $fp}) while execution is going on in that frame.
6744 @cindex frame number
6745 @value{GDBN} assigns numbers to all existing stack frames, starting with
6746 zero for the innermost frame, one for the frame that called it,
6747 and so on upward. These numbers do not really exist in your program;
6748 they are assigned by @value{GDBN} to give you a way of designating stack
6749 frames in @value{GDBN} commands.
6751 @c The -fomit-frame-pointer below perennially causes hbox overflow
6752 @c underflow problems.
6753 @cindex frameless execution
6754 Some compilers provide a way to compile functions so that they operate
6755 without stack frames. (For example, the @value{NGCC} option
6757 @samp{-fomit-frame-pointer}
6759 generates functions without a frame.)
6760 This is occasionally done with heavily used library functions to save
6761 the frame setup time. @value{GDBN} has limited facilities for dealing
6762 with these function invocations. If the innermost function invocation
6763 has no stack frame, @value{GDBN} nevertheless regards it as though
6764 it had a separate frame, which is numbered zero as usual, allowing
6765 correct tracing of the function call chain. However, @value{GDBN} has
6766 no provision for frameless functions elsewhere in the stack.
6769 @kindex frame@r{, command}
6770 @cindex current stack frame
6771 @item frame @r{[}@var{framespec}@r{]}
6772 The @code{frame} command allows you to move from one stack frame to another,
6773 and to print the stack frame you select. The @var{framespec} may be either the
6774 address of the frame or the stack frame number. Without an argument,
6775 @code{frame} prints the current stack frame.
6777 @kindex select-frame
6778 @cindex selecting frame silently
6780 The @code{select-frame} command allows you to move from one stack frame
6781 to another without printing the frame. This is the silent version of
6789 @cindex call stack traces
6790 A backtrace is a summary of how your program got where it is. It shows one
6791 line per frame, for many frames, starting with the currently executing
6792 frame (frame zero), followed by its caller (frame one), and on up the
6795 @anchor{backtrace-command}
6798 @kindex bt @r{(@code{backtrace})}
6801 Print a backtrace of the entire stack: one line per frame for all
6802 frames in the stack.
6804 You can stop the backtrace at any time by typing the system interrupt
6805 character, normally @kbd{Ctrl-c}.
6807 @item backtrace @var{n}
6809 Similar, but print only the innermost @var{n} frames.
6811 @item backtrace -@var{n}
6813 Similar, but print only the outermost @var{n} frames.
6815 @item backtrace full
6817 @itemx bt full @var{n}
6818 @itemx bt full -@var{n}
6819 Print the values of the local variables also. As described above,
6820 @var{n} specifies the number of frames to print.
6822 @item backtrace no-filters
6823 @itemx bt no-filters
6824 @itemx bt no-filters @var{n}
6825 @itemx bt no-filters -@var{n}
6826 @itemx bt no-filters full
6827 @itemx bt no-filters full @var{n}
6828 @itemx bt no-filters full -@var{n}
6829 Do not run Python frame filters on this backtrace. @xref{Frame
6830 Filter API}, for more information. Additionally use @ref{disable
6831 frame-filter all} to turn off all frame filters. This is only
6832 relevant when @value{GDBN} has been configured with @code{Python}
6838 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6839 are additional aliases for @code{backtrace}.
6841 @cindex multiple threads, backtrace
6842 In a multi-threaded program, @value{GDBN} by default shows the
6843 backtrace only for the current thread. To display the backtrace for
6844 several or all of the threads, use the command @code{thread apply}
6845 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6846 apply all backtrace}, @value{GDBN} will display the backtrace for all
6847 the threads; this is handy when you debug a core dump of a
6848 multi-threaded program.
6850 Each line in the backtrace shows the frame number and the function name.
6851 The program counter value is also shown---unless you use @code{set
6852 print address off}. The backtrace also shows the source file name and
6853 line number, as well as the arguments to the function. The program
6854 counter value is omitted if it is at the beginning of the code for that
6857 Here is an example of a backtrace. It was made with the command
6858 @samp{bt 3}, so it shows the innermost three frames.
6862 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6864 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6865 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6867 (More stack frames follow...)
6872 The display for frame zero does not begin with a program counter
6873 value, indicating that your program has stopped at the beginning of the
6874 code for line @code{993} of @code{builtin.c}.
6877 The value of parameter @code{data} in frame 1 has been replaced by
6878 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6879 only if it is a scalar (integer, pointer, enumeration, etc). See command
6880 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6881 on how to configure the way function parameter values are printed.
6883 @cindex optimized out, in backtrace
6884 @cindex function call arguments, optimized out
6885 If your program was compiled with optimizations, some compilers will
6886 optimize away arguments passed to functions if those arguments are
6887 never used after the call. Such optimizations generate code that
6888 passes arguments through registers, but doesn't store those arguments
6889 in the stack frame. @value{GDBN} has no way of displaying such
6890 arguments in stack frames other than the innermost one. Here's what
6891 such a backtrace might look like:
6895 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6897 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6898 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6900 (More stack frames follow...)
6905 The values of arguments that were not saved in their stack frames are
6906 shown as @samp{<optimized out>}.
6908 If you need to display the values of such optimized-out arguments,
6909 either deduce that from other variables whose values depend on the one
6910 you are interested in, or recompile without optimizations.
6912 @cindex backtrace beyond @code{main} function
6913 @cindex program entry point
6914 @cindex startup code, and backtrace
6915 Most programs have a standard user entry point---a place where system
6916 libraries and startup code transition into user code. For C this is
6917 @code{main}@footnote{
6918 Note that embedded programs (the so-called ``free-standing''
6919 environment) are not required to have a @code{main} function as the
6920 entry point. They could even have multiple entry points.}.
6921 When @value{GDBN} finds the entry function in a backtrace
6922 it will terminate the backtrace, to avoid tracing into highly
6923 system-specific (and generally uninteresting) code.
6925 If you need to examine the startup code, or limit the number of levels
6926 in a backtrace, you can change this behavior:
6929 @item set backtrace past-main
6930 @itemx set backtrace past-main on
6931 @kindex set backtrace
6932 Backtraces will continue past the user entry point.
6934 @item set backtrace past-main off
6935 Backtraces will stop when they encounter the user entry point. This is the
6938 @item show backtrace past-main
6939 @kindex show backtrace
6940 Display the current user entry point backtrace policy.
6942 @item set backtrace past-entry
6943 @itemx set backtrace past-entry on
6944 Backtraces will continue past the internal entry point of an application.
6945 This entry point is encoded by the linker when the application is built,
6946 and is likely before the user entry point @code{main} (or equivalent) is called.
6948 @item set backtrace past-entry off
6949 Backtraces will stop when they encounter the internal entry point of an
6950 application. This is the default.
6952 @item show backtrace past-entry
6953 Display the current internal entry point backtrace policy.
6955 @item set backtrace limit @var{n}
6956 @itemx set backtrace limit 0
6957 @itemx set backtrace limit unlimited
6958 @cindex backtrace limit
6959 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
6960 or zero means unlimited levels.
6962 @item show backtrace limit
6963 Display the current limit on backtrace levels.
6966 You can control how file names are displayed.
6969 @item set filename-display
6970 @itemx set filename-display relative
6971 @cindex filename-display
6972 Display file names relative to the compilation directory. This is the default.
6974 @item set filename-display basename
6975 Display only basename of a filename.
6977 @item set filename-display absolute
6978 Display an absolute filename.
6980 @item show filename-display
6981 Show the current way to display filenames.
6984 @node Frame Filter Management
6985 @section Management of Frame Filters.
6986 @cindex managing frame filters
6988 Frame filters are Python based utilities to manage and decorate the
6989 output of frames. @xref{Frame Filter API}, for further information.
6991 Managing frame filters is performed by several commands available
6992 within @value{GDBN}, detailed here.
6995 @kindex info frame-filter
6996 @item info frame-filter
6997 Print a list of installed frame filters from all dictionaries, showing
6998 their name, priority and enabled status.
7000 @kindex disable frame-filter
7001 @anchor{disable frame-filter all}
7002 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
7003 Disable a frame filter in the dictionary matching
7004 @var{filter-dictionary} and @var{filter-name}. The
7005 @var{filter-dictionary} may be @code{all}, @code{global},
7006 @code{progspace}, or the name of the object file where the frame filter
7007 dictionary resides. When @code{all} is specified, all frame filters
7008 across all dictionaries are disabled. The @var{filter-name} is the name
7009 of the frame filter and is used when @code{all} is not the option for
7010 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
7011 may be enabled again later.
7013 @kindex enable frame-filter
7014 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
7015 Enable a frame filter in the dictionary matching
7016 @var{filter-dictionary} and @var{filter-name}. The
7017 @var{filter-dictionary} may be @code{all}, @code{global},
7018 @code{progspace} or the name of the object file where the frame filter
7019 dictionary resides. When @code{all} is specified, all frame filters across
7020 all dictionaries are enabled. The @var{filter-name} is the name of the frame
7021 filter and is used when @code{all} is not the option for
7022 @var{filter-dictionary}.
7027 (gdb) info frame-filter
7029 global frame-filters:
7030 Priority Enabled Name
7031 1000 No PrimaryFunctionFilter
7034 progspace /build/test frame-filters:
7035 Priority Enabled Name
7036 100 Yes ProgspaceFilter
7038 objfile /build/test frame-filters:
7039 Priority Enabled Name
7040 999 Yes BuildProgra Filter
7042 (gdb) disable frame-filter /build/test BuildProgramFilter
7043 (gdb) info frame-filter
7045 global frame-filters:
7046 Priority Enabled Name
7047 1000 No PrimaryFunctionFilter
7050 progspace /build/test frame-filters:
7051 Priority Enabled Name
7052 100 Yes ProgspaceFilter
7054 objfile /build/test frame-filters:
7055 Priority Enabled Name
7056 999 No BuildProgramFilter
7058 (gdb) enable frame-filter global PrimaryFunctionFilter
7059 (gdb) info frame-filter
7061 global frame-filters:
7062 Priority Enabled Name
7063 1000 Yes PrimaryFunctionFilter
7066 progspace /build/test frame-filters:
7067 Priority Enabled Name
7068 100 Yes ProgspaceFilter
7070 objfile /build/test frame-filters:
7071 Priority Enabled Name
7072 999 No BuildProgramFilter
7075 @kindex set frame-filter priority
7076 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
7077 Set the @var{priority} of a frame filter in the dictionary matching
7078 @var{filter-dictionary}, and the frame filter name matching
7079 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7080 @code{progspace} or the name of the object file where the frame filter
7081 dictionary resides. The @var{priority} is an integer.
7083 @kindex show frame-filter priority
7084 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
7085 Show the @var{priority} of a frame filter in the dictionary matching
7086 @var{filter-dictionary}, and the frame filter name matching
7087 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7088 @code{progspace} or the name of the object file where the frame filter
7094 (gdb) info frame-filter
7096 global frame-filters:
7097 Priority Enabled Name
7098 1000 Yes PrimaryFunctionFilter
7101 progspace /build/test frame-filters:
7102 Priority Enabled Name
7103 100 Yes ProgspaceFilter
7105 objfile /build/test frame-filters:
7106 Priority Enabled Name
7107 999 No BuildProgramFilter
7109 (gdb) set frame-filter priority global Reverse 50
7110 (gdb) info frame-filter
7112 global frame-filters:
7113 Priority Enabled Name
7114 1000 Yes PrimaryFunctionFilter
7117 progspace /build/test frame-filters:
7118 Priority Enabled Name
7119 100 Yes ProgspaceFilter
7121 objfile /build/test frame-filters:
7122 Priority Enabled Name
7123 999 No BuildProgramFilter
7128 @section Selecting a Frame
7130 Most commands for examining the stack and other data in your program work on
7131 whichever stack frame is selected at the moment. Here are the commands for
7132 selecting a stack frame; all of them finish by printing a brief description
7133 of the stack frame just selected.
7136 @kindex frame@r{, selecting}
7137 @kindex f @r{(@code{frame})}
7140 Select frame number @var{n}. Recall that frame zero is the innermost
7141 (currently executing) frame, frame one is the frame that called the
7142 innermost one, and so on. The highest-numbered frame is the one for
7145 @item frame @var{addr}
7147 Select the frame at address @var{addr}. This is useful mainly if the
7148 chaining of stack frames has been damaged by a bug, making it
7149 impossible for @value{GDBN} to assign numbers properly to all frames. In
7150 addition, this can be useful when your program has multiple stacks and
7151 switches between them.
7153 On the SPARC architecture, @code{frame} needs two addresses to
7154 select an arbitrary frame: a frame pointer and a stack pointer.
7156 On the @acronym{MIPS} and Alpha architecture, it needs two addresses: a stack
7157 pointer and a program counter.
7159 On the 29k architecture, it needs three addresses: a register stack
7160 pointer, a program counter, and a memory stack pointer.
7164 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7165 numbers @var{n}, this advances toward the outermost frame, to higher
7166 frame numbers, to frames that have existed longer.
7169 @kindex do @r{(@code{down})}
7171 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7172 positive numbers @var{n}, this advances toward the innermost frame, to
7173 lower frame numbers, to frames that were created more recently.
7174 You may abbreviate @code{down} as @code{do}.
7177 All of these commands end by printing two lines of output describing the
7178 frame. The first line shows the frame number, the function name, the
7179 arguments, and the source file and line number of execution in that
7180 frame. The second line shows the text of that source line.
7188 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7190 10 read_input_file (argv[i]);
7194 After such a printout, the @code{list} command with no arguments
7195 prints ten lines centered on the point of execution in the frame.
7196 You can also edit the program at the point of execution with your favorite
7197 editing program by typing @code{edit}.
7198 @xref{List, ,Printing Source Lines},
7202 @kindex down-silently
7204 @item up-silently @var{n}
7205 @itemx down-silently @var{n}
7206 These two commands are variants of @code{up} and @code{down},
7207 respectively; they differ in that they do their work silently, without
7208 causing display of the new frame. They are intended primarily for use
7209 in @value{GDBN} command scripts, where the output might be unnecessary and
7214 @section Information About a Frame
7216 There are several other commands to print information about the selected
7222 When used without any argument, this command does not change which
7223 frame is selected, but prints a brief description of the currently
7224 selected stack frame. It can be abbreviated @code{f}. With an
7225 argument, this command is used to select a stack frame.
7226 @xref{Selection, ,Selecting a Frame}.
7229 @kindex info f @r{(@code{info frame})}
7232 This command prints a verbose description of the selected stack frame,
7237 the address of the frame
7239 the address of the next frame down (called by this frame)
7241 the address of the next frame up (caller of this frame)
7243 the language in which the source code corresponding to this frame is written
7245 the address of the frame's arguments
7247 the address of the frame's local variables
7249 the program counter saved in it (the address of execution in the caller frame)
7251 which registers were saved in the frame
7254 @noindent The verbose description is useful when
7255 something has gone wrong that has made the stack format fail to fit
7256 the usual conventions.
7258 @item info frame @var{addr}
7259 @itemx info f @var{addr}
7260 Print a verbose description of the frame at address @var{addr}, without
7261 selecting that frame. The selected frame remains unchanged by this
7262 command. This requires the same kind of address (more than one for some
7263 architectures) that you specify in the @code{frame} command.
7264 @xref{Selection, ,Selecting a Frame}.
7268 Print the arguments of the selected frame, each on a separate line.
7272 Print the local variables of the selected frame, each on a separate
7273 line. These are all variables (declared either static or automatic)
7274 accessible at the point of execution of the selected frame.
7280 @chapter Examining Source Files
7282 @value{GDBN} can print parts of your program's source, since the debugging
7283 information recorded in the program tells @value{GDBN} what source files were
7284 used to build it. When your program stops, @value{GDBN} spontaneously prints
7285 the line where it stopped. Likewise, when you select a stack frame
7286 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7287 execution in that frame has stopped. You can print other portions of
7288 source files by explicit command.
7290 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7291 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7292 @value{GDBN} under @sc{gnu} Emacs}.
7295 * List:: Printing source lines
7296 * Specify Location:: How to specify code locations
7297 * Edit:: Editing source files
7298 * Search:: Searching source files
7299 * Source Path:: Specifying source directories
7300 * Machine Code:: Source and machine code
7304 @section Printing Source Lines
7307 @kindex l @r{(@code{list})}
7308 To print lines from a source file, use the @code{list} command
7309 (abbreviated @code{l}). By default, ten lines are printed.
7310 There are several ways to specify what part of the file you want to
7311 print; see @ref{Specify Location}, for the full list.
7313 Here are the forms of the @code{list} command most commonly used:
7316 @item list @var{linenum}
7317 Print lines centered around line number @var{linenum} in the
7318 current source file.
7320 @item list @var{function}
7321 Print lines centered around the beginning of function
7325 Print more lines. If the last lines printed were printed with a
7326 @code{list} command, this prints lines following the last lines
7327 printed; however, if the last line printed was a solitary line printed
7328 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7329 Stack}), this prints lines centered around that line.
7332 Print lines just before the lines last printed.
7335 @cindex @code{list}, how many lines to display
7336 By default, @value{GDBN} prints ten source lines with any of these forms of
7337 the @code{list} command. You can change this using @code{set listsize}:
7340 @kindex set listsize
7341 @item set listsize @var{count}
7342 @itemx set listsize unlimited
7343 Make the @code{list} command display @var{count} source lines (unless
7344 the @code{list} argument explicitly specifies some other number).
7345 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7347 @kindex show listsize
7349 Display the number of lines that @code{list} prints.
7352 Repeating a @code{list} command with @key{RET} discards the argument,
7353 so it is equivalent to typing just @code{list}. This is more useful
7354 than listing the same lines again. An exception is made for an
7355 argument of @samp{-}; that argument is preserved in repetition so that
7356 each repetition moves up in the source file.
7358 In general, the @code{list} command expects you to supply zero, one or two
7359 @dfn{linespecs}. Linespecs specify source lines; there are several ways
7360 of writing them (@pxref{Specify Location}), but the effect is always
7361 to specify some source line.
7363 Here is a complete description of the possible arguments for @code{list}:
7366 @item list @var{linespec}
7367 Print lines centered around the line specified by @var{linespec}.
7369 @item list @var{first},@var{last}
7370 Print lines from @var{first} to @var{last}. Both arguments are
7371 linespecs. When a @code{list} command has two linespecs, and the
7372 source file of the second linespec is omitted, this refers to
7373 the same source file as the first linespec.
7375 @item list ,@var{last}
7376 Print lines ending with @var{last}.
7378 @item list @var{first},
7379 Print lines starting with @var{first}.
7382 Print lines just after the lines last printed.
7385 Print lines just before the lines last printed.
7388 As described in the preceding table.
7391 @node Specify Location
7392 @section Specifying a Location
7393 @cindex specifying location
7396 Several @value{GDBN} commands accept arguments that specify a location
7397 of your program's code. Since @value{GDBN} is a source-level
7398 debugger, a location usually specifies some line in the source code;
7399 for that reason, locations are also known as @dfn{linespecs}.
7401 Here are all the different ways of specifying a code location that
7402 @value{GDBN} understands:
7406 Specifies the line number @var{linenum} of the current source file.
7409 @itemx +@var{offset}
7410 Specifies the line @var{offset} lines before or after the @dfn{current
7411 line}. For the @code{list} command, the current line is the last one
7412 printed; for the breakpoint commands, this is the line at which
7413 execution stopped in the currently selected @dfn{stack frame}
7414 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7415 used as the second of the two linespecs in a @code{list} command,
7416 this specifies the line @var{offset} lines up or down from the first
7419 @item @var{filename}:@var{linenum}
7420 Specifies the line @var{linenum} in the source file @var{filename}.
7421 If @var{filename} is a relative file name, then it will match any
7422 source file name with the same trailing components. For example, if
7423 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7424 name of @file{/build/trunk/gcc/expr.c}, but not
7425 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7427 @item @var{function}
7428 Specifies the line that begins the body of the function @var{function}.
7429 For example, in C, this is the line with the open brace.
7431 @item @var{function}:@var{label}
7432 Specifies the line where @var{label} appears in @var{function}.
7434 @item @var{filename}:@var{function}
7435 Specifies the line that begins the body of the function @var{function}
7436 in the file @var{filename}. You only need the file name with a
7437 function name to avoid ambiguity when there are identically named
7438 functions in different source files.
7441 Specifies the line at which the label named @var{label} appears.
7442 @value{GDBN} searches for the label in the function corresponding to
7443 the currently selected stack frame. If there is no current selected
7444 stack frame (for instance, if the inferior is not running), then
7445 @value{GDBN} will not search for a label.
7447 @item *@var{address}
7448 Specifies the program address @var{address}. For line-oriented
7449 commands, such as @code{list} and @code{edit}, this specifies a source
7450 line that contains @var{address}. For @code{break} and other
7451 breakpoint oriented commands, this can be used to set breakpoints in
7452 parts of your program which do not have debugging information or
7455 Here @var{address} may be any expression valid in the current working
7456 language (@pxref{Languages, working language}) that specifies a code
7457 address. In addition, as a convenience, @value{GDBN} extends the
7458 semantics of expressions used in locations to cover the situations
7459 that frequently happen during debugging. Here are the various forms
7463 @item @var{expression}
7464 Any expression valid in the current working language.
7466 @item @var{funcaddr}
7467 An address of a function or procedure derived from its name. In C,
7468 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
7469 simply the function's name @var{function} (and actually a special case
7470 of a valid expression). In Pascal and Modula-2, this is
7471 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7472 (although the Pascal form also works).
7474 This form specifies the address of the function's first instruction,
7475 before the stack frame and arguments have been set up.
7477 @item '@var{filename}'::@var{funcaddr}
7478 Like @var{funcaddr} above, but also specifies the name of the source
7479 file explicitly. This is useful if the name of the function does not
7480 specify the function unambiguously, e.g., if there are several
7481 functions with identical names in different source files.
7484 @cindex breakpoint at static probe point
7485 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7486 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7487 applications to embed static probes. @xref{Static Probe Points}, for more
7488 information on finding and using static probes. This form of linespec
7489 specifies the location of such a static probe.
7491 If @var{objfile} is given, only probes coming from that shared library
7492 or executable matching @var{objfile} as a regular expression are considered.
7493 If @var{provider} is given, then only probes from that provider are considered.
7494 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7495 each one of those probes.
7501 @section Editing Source Files
7502 @cindex editing source files
7505 @kindex e @r{(@code{edit})}
7506 To edit the lines in a source file, use the @code{edit} command.
7507 The editing program of your choice
7508 is invoked with the current line set to
7509 the active line in the program.
7510 Alternatively, there are several ways to specify what part of the file you
7511 want to print if you want to see other parts of the program:
7514 @item edit @var{location}
7515 Edit the source file specified by @code{location}. Editing starts at
7516 that @var{location}, e.g., at the specified source line of the
7517 specified file. @xref{Specify Location}, for all the possible forms
7518 of the @var{location} argument; here are the forms of the @code{edit}
7519 command most commonly used:
7522 @item edit @var{number}
7523 Edit the current source file with @var{number} as the active line number.
7525 @item edit @var{function}
7526 Edit the file containing @var{function} at the beginning of its definition.
7531 @subsection Choosing your Editor
7532 You can customize @value{GDBN} to use any editor you want
7534 The only restriction is that your editor (say @code{ex}), recognizes the
7535 following command-line syntax:
7537 ex +@var{number} file
7539 The optional numeric value +@var{number} specifies the number of the line in
7540 the file where to start editing.}.
7541 By default, it is @file{@value{EDITOR}}, but you can change this
7542 by setting the environment variable @code{EDITOR} before using
7543 @value{GDBN}. For example, to configure @value{GDBN} to use the
7544 @code{vi} editor, you could use these commands with the @code{sh} shell:
7550 or in the @code{csh} shell,
7552 setenv EDITOR /usr/bin/vi
7557 @section Searching Source Files
7558 @cindex searching source files
7560 There are two commands for searching through the current source file for a
7565 @kindex forward-search
7566 @kindex fo @r{(@code{forward-search})}
7567 @item forward-search @var{regexp}
7568 @itemx search @var{regexp}
7569 The command @samp{forward-search @var{regexp}} checks each line,
7570 starting with the one following the last line listed, for a match for
7571 @var{regexp}. It lists the line that is found. You can use the
7572 synonym @samp{search @var{regexp}} or abbreviate the command name as
7575 @kindex reverse-search
7576 @item reverse-search @var{regexp}
7577 The command @samp{reverse-search @var{regexp}} checks each line, starting
7578 with the one before the last line listed and going backward, for a match
7579 for @var{regexp}. It lists the line that is found. You can abbreviate
7580 this command as @code{rev}.
7584 @section Specifying Source Directories
7587 @cindex directories for source files
7588 Executable programs sometimes do not record the directories of the source
7589 files from which they were compiled, just the names. Even when they do,
7590 the directories could be moved between the compilation and your debugging
7591 session. @value{GDBN} has a list of directories to search for source files;
7592 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
7593 it tries all the directories in the list, in the order they are present
7594 in the list, until it finds a file with the desired name.
7596 For example, suppose an executable references the file
7597 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
7598 @file{/mnt/cross}. The file is first looked up literally; if this
7599 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
7600 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
7601 message is printed. @value{GDBN} does not look up the parts of the
7602 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
7603 Likewise, the subdirectories of the source path are not searched: if
7604 the source path is @file{/mnt/cross}, and the binary refers to
7605 @file{foo.c}, @value{GDBN} would not find it under
7606 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7608 Plain file names, relative file names with leading directories, file
7609 names containing dots, etc.@: are all treated as described above; for
7610 instance, if the source path is @file{/mnt/cross}, and the source file
7611 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7612 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7613 that---@file{/mnt/cross/foo.c}.
7615 Note that the executable search path is @emph{not} used to locate the
7618 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7619 any information it has cached about where source files are found and where
7620 each line is in the file.
7624 When you start @value{GDBN}, its source path includes only @samp{cdir}
7625 and @samp{cwd}, in that order.
7626 To add other directories, use the @code{directory} command.
7628 The search path is used to find both program source files and @value{GDBN}
7629 script files (read using the @samp{-command} option and @samp{source} command).
7631 In addition to the source path, @value{GDBN} provides a set of commands
7632 that manage a list of source path substitution rules. A @dfn{substitution
7633 rule} specifies how to rewrite source directories stored in the program's
7634 debug information in case the sources were moved to a different
7635 directory between compilation and debugging. A rule is made of
7636 two strings, the first specifying what needs to be rewritten in
7637 the path, and the second specifying how it should be rewritten.
7638 In @ref{set substitute-path}, we name these two parts @var{from} and
7639 @var{to} respectively. @value{GDBN} does a simple string replacement
7640 of @var{from} with @var{to} at the start of the directory part of the
7641 source file name, and uses that result instead of the original file
7642 name to look up the sources.
7644 Using the previous example, suppose the @file{foo-1.0} tree has been
7645 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7646 @value{GDBN} to replace @file{/usr/src} in all source path names with
7647 @file{/mnt/cross}. The first lookup will then be
7648 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7649 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7650 substitution rule, use the @code{set substitute-path} command
7651 (@pxref{set substitute-path}).
7653 To avoid unexpected substitution results, a rule is applied only if the
7654 @var{from} part of the directory name ends at a directory separator.
7655 For instance, a rule substituting @file{/usr/source} into
7656 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7657 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7658 is applied only at the beginning of the directory name, this rule will
7659 not be applied to @file{/root/usr/source/baz.c} either.
7661 In many cases, you can achieve the same result using the @code{directory}
7662 command. However, @code{set substitute-path} can be more efficient in
7663 the case where the sources are organized in a complex tree with multiple
7664 subdirectories. With the @code{directory} command, you need to add each
7665 subdirectory of your project. If you moved the entire tree while
7666 preserving its internal organization, then @code{set substitute-path}
7667 allows you to direct the debugger to all the sources with one single
7670 @code{set substitute-path} is also more than just a shortcut command.
7671 The source path is only used if the file at the original location no
7672 longer exists. On the other hand, @code{set substitute-path} modifies
7673 the debugger behavior to look at the rewritten location instead. So, if
7674 for any reason a source file that is not relevant to your executable is
7675 located at the original location, a substitution rule is the only
7676 method available to point @value{GDBN} at the new location.
7678 @cindex @samp{--with-relocated-sources}
7679 @cindex default source path substitution
7680 You can configure a default source path substitution rule by
7681 configuring @value{GDBN} with the
7682 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7683 should be the name of a directory under @value{GDBN}'s configured
7684 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7685 directory names in debug information under @var{dir} will be adjusted
7686 automatically if the installed @value{GDBN} is moved to a new
7687 location. This is useful if @value{GDBN}, libraries or executables
7688 with debug information and corresponding source code are being moved
7692 @item directory @var{dirname} @dots{}
7693 @item dir @var{dirname} @dots{}
7694 Add directory @var{dirname} to the front of the source path. Several
7695 directory names may be given to this command, separated by @samp{:}
7696 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7697 part of absolute file names) or
7698 whitespace. You may specify a directory that is already in the source
7699 path; this moves it forward, so @value{GDBN} searches it sooner.
7703 @vindex $cdir@r{, convenience variable}
7704 @vindex $cwd@r{, convenience variable}
7705 @cindex compilation directory
7706 @cindex current directory
7707 @cindex working directory
7708 @cindex directory, current
7709 @cindex directory, compilation
7710 You can use the string @samp{$cdir} to refer to the compilation
7711 directory (if one is recorded), and @samp{$cwd} to refer to the current
7712 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7713 tracks the current working directory as it changes during your @value{GDBN}
7714 session, while the latter is immediately expanded to the current
7715 directory at the time you add an entry to the source path.
7718 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7720 @c RET-repeat for @code{directory} is explicitly disabled, but since
7721 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7723 @item set directories @var{path-list}
7724 @kindex set directories
7725 Set the source path to @var{path-list}.
7726 @samp{$cdir:$cwd} are added if missing.
7728 @item show directories
7729 @kindex show directories
7730 Print the source path: show which directories it contains.
7732 @anchor{set substitute-path}
7733 @item set substitute-path @var{from} @var{to}
7734 @kindex set substitute-path
7735 Define a source path substitution rule, and add it at the end of the
7736 current list of existing substitution rules. If a rule with the same
7737 @var{from} was already defined, then the old rule is also deleted.
7739 For example, if the file @file{/foo/bar/baz.c} was moved to
7740 @file{/mnt/cross/baz.c}, then the command
7743 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
7747 will tell @value{GDBN} to replace @samp{/usr/src} with
7748 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7749 @file{baz.c} even though it was moved.
7751 In the case when more than one substitution rule have been defined,
7752 the rules are evaluated one by one in the order where they have been
7753 defined. The first one matching, if any, is selected to perform
7756 For instance, if we had entered the following commands:
7759 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
7760 (@value{GDBP}) set substitute-path /usr/src /mnt/src
7764 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
7765 @file{/mnt/include/defs.h} by using the first rule. However, it would
7766 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
7767 @file{/mnt/src/lib/foo.c}.
7770 @item unset substitute-path [path]
7771 @kindex unset substitute-path
7772 If a path is specified, search the current list of substitution rules
7773 for a rule that would rewrite that path. Delete that rule if found.
7774 A warning is emitted by the debugger if no rule could be found.
7776 If no path is specified, then all substitution rules are deleted.
7778 @item show substitute-path [path]
7779 @kindex show substitute-path
7780 If a path is specified, then print the source path substitution rule
7781 which would rewrite that path, if any.
7783 If no path is specified, then print all existing source path substitution
7788 If your source path is cluttered with directories that are no longer of
7789 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
7790 versions of source. You can correct the situation as follows:
7794 Use @code{directory} with no argument to reset the source path to its default value.
7797 Use @code{directory} with suitable arguments to reinstall the
7798 directories you want in the source path. You can add all the
7799 directories in one command.
7803 @section Source and Machine Code
7804 @cindex source line and its code address
7806 You can use the command @code{info line} to map source lines to program
7807 addresses (and vice versa), and the command @code{disassemble} to display
7808 a range of addresses as machine instructions. You can use the command
7809 @code{set disassemble-next-line} to set whether to disassemble next
7810 source line when execution stops. When run under @sc{gnu} Emacs
7811 mode, the @code{info line} command causes the arrow to point to the
7812 line specified. Also, @code{info line} prints addresses in symbolic form as
7817 @item info line @var{linespec}
7818 Print the starting and ending addresses of the compiled code for
7819 source line @var{linespec}. You can specify source lines in any of
7820 the ways documented in @ref{Specify Location}.
7823 For example, we can use @code{info line} to discover the location of
7824 the object code for the first line of function
7825 @code{m4_changequote}:
7827 @c FIXME: I think this example should also show the addresses in
7828 @c symbolic form, as they usually would be displayed.
7830 (@value{GDBP}) info line m4_changequote
7831 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
7835 @cindex code address and its source line
7836 We can also inquire (using @code{*@var{addr}} as the form for
7837 @var{linespec}) what source line covers a particular address:
7839 (@value{GDBP}) info line *0x63ff
7840 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
7843 @cindex @code{$_} and @code{info line}
7844 @cindex @code{x} command, default address
7845 @kindex x@r{(examine), and} info line
7846 After @code{info line}, the default address for the @code{x} command
7847 is changed to the starting address of the line, so that @samp{x/i} is
7848 sufficient to begin examining the machine code (@pxref{Memory,
7849 ,Examining Memory}). Also, this address is saved as the value of the
7850 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
7855 @cindex assembly instructions
7856 @cindex instructions, assembly
7857 @cindex machine instructions
7858 @cindex listing machine instructions
7860 @itemx disassemble /m
7861 @itemx disassemble /r
7862 This specialized command dumps a range of memory as machine
7863 instructions. It can also print mixed source+disassembly by specifying
7864 the @code{/m} modifier and print the raw instructions in hex as well as
7865 in symbolic form by specifying the @code{/r}.
7866 The default memory range is the function surrounding the
7867 program counter of the selected frame. A single argument to this
7868 command is a program counter value; @value{GDBN} dumps the function
7869 surrounding this value. When two arguments are given, they should
7870 be separated by a comma, possibly surrounded by whitespace. The
7871 arguments specify a range of addresses to dump, in one of two forms:
7874 @item @var{start},@var{end}
7875 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
7876 @item @var{start},+@var{length}
7877 the addresses from @var{start} (inclusive) to
7878 @code{@var{start}+@var{length}} (exclusive).
7882 When 2 arguments are specified, the name of the function is also
7883 printed (since there could be several functions in the given range).
7885 The argument(s) can be any expression yielding a numeric value, such as
7886 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
7888 If the range of memory being disassembled contains current program counter,
7889 the instruction at that location is shown with a @code{=>} marker.
7892 The following example shows the disassembly of a range of addresses of
7893 HP PA-RISC 2.0 code:
7896 (@value{GDBP}) disas 0x32c4, 0x32e4
7897 Dump of assembler code from 0x32c4 to 0x32e4:
7898 0x32c4 <main+204>: addil 0,dp
7899 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
7900 0x32cc <main+212>: ldil 0x3000,r31
7901 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
7902 0x32d4 <main+220>: ldo 0(r31),rp
7903 0x32d8 <main+224>: addil -0x800,dp
7904 0x32dc <main+228>: ldo 0x588(r1),r26
7905 0x32e0 <main+232>: ldil 0x3000,r31
7906 End of assembler dump.
7909 Here is an example showing mixed source+assembly for Intel x86, when the
7910 program is stopped just after function prologue:
7913 (@value{GDBP}) disas /m main
7914 Dump of assembler code for function main:
7916 0x08048330 <+0>: push %ebp
7917 0x08048331 <+1>: mov %esp,%ebp
7918 0x08048333 <+3>: sub $0x8,%esp
7919 0x08048336 <+6>: and $0xfffffff0,%esp
7920 0x08048339 <+9>: sub $0x10,%esp
7922 6 printf ("Hello.\n");
7923 => 0x0804833c <+12>: movl $0x8048440,(%esp)
7924 0x08048343 <+19>: call 0x8048284 <puts@@plt>
7928 0x08048348 <+24>: mov $0x0,%eax
7929 0x0804834d <+29>: leave
7930 0x0804834e <+30>: ret
7932 End of assembler dump.
7935 Here is another example showing raw instructions in hex for AMD x86-64,
7938 (gdb) disas /r 0x400281,+10
7939 Dump of assembler code from 0x400281 to 0x40028b:
7940 0x0000000000400281: 38 36 cmp %dh,(%rsi)
7941 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
7942 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
7943 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7944 End of assembler dump.
7947 Addresses cannot be specified as a linespec (@pxref{Specify Location}).
7948 So, for example, if you want to disassemble function @code{bar}
7949 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
7950 and not @samp{disassemble foo.c:bar}.
7952 Some architectures have more than one commonly-used set of instruction
7953 mnemonics or other syntax.
7955 For programs that were dynamically linked and use shared libraries,
7956 instructions that call functions or branch to locations in the shared
7957 libraries might show a seemingly bogus location---it's actually a
7958 location of the relocation table. On some architectures, @value{GDBN}
7959 might be able to resolve these to actual function names.
7962 @kindex set disassembly-flavor
7963 @cindex Intel disassembly flavor
7964 @cindex AT&T disassembly flavor
7965 @item set disassembly-flavor @var{instruction-set}
7966 Select the instruction set to use when disassembling the
7967 program via the @code{disassemble} or @code{x/i} commands.
7969 Currently this command is only defined for the Intel x86 family. You
7970 can set @var{instruction-set} to either @code{intel} or @code{att}.
7971 The default is @code{att}, the AT&T flavor used by default by Unix
7972 assemblers for x86-based targets.
7974 @kindex show disassembly-flavor
7975 @item show disassembly-flavor
7976 Show the current setting of the disassembly flavor.
7980 @kindex set disassemble-next-line
7981 @kindex show disassemble-next-line
7982 @item set disassemble-next-line
7983 @itemx show disassemble-next-line
7984 Control whether or not @value{GDBN} will disassemble the next source
7985 line or instruction when execution stops. If ON, @value{GDBN} will
7986 display disassembly of the next source line when execution of the
7987 program being debugged stops. This is @emph{in addition} to
7988 displaying the source line itself, which @value{GDBN} always does if
7989 possible. If the next source line cannot be displayed for some reason
7990 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7991 info in the debug info), @value{GDBN} will display disassembly of the
7992 next @emph{instruction} instead of showing the next source line. If
7993 AUTO, @value{GDBN} will display disassembly of next instruction only
7994 if the source line cannot be displayed. This setting causes
7995 @value{GDBN} to display some feedback when you step through a function
7996 with no line info or whose source file is unavailable. The default is
7997 OFF, which means never display the disassembly of the next line or
8003 @chapter Examining Data
8005 @cindex printing data
8006 @cindex examining data
8009 The usual way to examine data in your program is with the @code{print}
8010 command (abbreviated @code{p}), or its synonym @code{inspect}. It
8011 evaluates and prints the value of an expression of the language your
8012 program is written in (@pxref{Languages, ,Using @value{GDBN} with
8013 Different Languages}). It may also print the expression using a
8014 Python-based pretty-printer (@pxref{Pretty Printing}).
8017 @item print @var{expr}
8018 @itemx print /@var{f} @var{expr}
8019 @var{expr} is an expression (in the source language). By default the
8020 value of @var{expr} is printed in a format appropriate to its data type;
8021 you can choose a different format by specifying @samp{/@var{f}}, where
8022 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
8026 @itemx print /@var{f}
8027 @cindex reprint the last value
8028 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
8029 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
8030 conveniently inspect the same value in an alternative format.
8033 A more low-level way of examining data is with the @code{x} command.
8034 It examines data in memory at a specified address and prints it in a
8035 specified format. @xref{Memory, ,Examining Memory}.
8037 If you are interested in information about types, or about how the
8038 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
8039 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
8042 @cindex exploring hierarchical data structures
8044 Another way of examining values of expressions and type information is
8045 through the Python extension command @code{explore} (available only if
8046 the @value{GDBN} build is configured with @code{--with-python}). It
8047 offers an interactive way to start at the highest level (or, the most
8048 abstract level) of the data type of an expression (or, the data type
8049 itself) and explore all the way down to leaf scalar values/fields
8050 embedded in the higher level data types.
8053 @item explore @var{arg}
8054 @var{arg} is either an expression (in the source language), or a type
8055 visible in the current context of the program being debugged.
8058 The working of the @code{explore} command can be illustrated with an
8059 example. If a data type @code{struct ComplexStruct} is defined in your
8069 struct ComplexStruct
8071 struct SimpleStruct *ss_p;
8077 followed by variable declarations as
8080 struct SimpleStruct ss = @{ 10, 1.11 @};
8081 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
8085 then, the value of the variable @code{cs} can be explored using the
8086 @code{explore} command as follows.
8090 The value of `cs' is a struct/class of type `struct ComplexStruct' with
8091 the following fields:
8093 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
8094 arr = <Enter 1 to explore this field of type `int [10]'>
8096 Enter the field number of choice:
8100 Since the fields of @code{cs} are not scalar values, you are being
8101 prompted to chose the field you want to explore. Let's say you choose
8102 the field @code{ss_p} by entering @code{0}. Then, since this field is a
8103 pointer, you will be asked if it is pointing to a single value. From
8104 the declaration of @code{cs} above, it is indeed pointing to a single
8105 value, hence you enter @code{y}. If you enter @code{n}, then you will
8106 be asked if it were pointing to an array of values, in which case this
8107 field will be explored as if it were an array.
8110 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
8111 Continue exploring it as a pointer to a single value [y/n]: y
8112 The value of `*(cs.ss_p)' is a struct/class of type `struct
8113 SimpleStruct' with the following fields:
8115 i = 10 .. (Value of type `int')
8116 d = 1.1100000000000001 .. (Value of type `double')
8118 Press enter to return to parent value:
8122 If the field @code{arr} of @code{cs} was chosen for exploration by
8123 entering @code{1} earlier, then since it is as array, you will be
8124 prompted to enter the index of the element in the array that you want
8128 `cs.arr' is an array of `int'.
8129 Enter the index of the element you want to explore in `cs.arr': 5
8131 `(cs.arr)[5]' is a scalar value of type `int'.
8135 Press enter to return to parent value:
8138 In general, at any stage of exploration, you can go deeper towards the
8139 leaf values by responding to the prompts appropriately, or hit the
8140 return key to return to the enclosing data structure (the @i{higher}
8141 level data structure).
8143 Similar to exploring values, you can use the @code{explore} command to
8144 explore types. Instead of specifying a value (which is typically a
8145 variable name or an expression valid in the current context of the
8146 program being debugged), you specify a type name. If you consider the
8147 same example as above, your can explore the type
8148 @code{struct ComplexStruct} by passing the argument
8149 @code{struct ComplexStruct} to the @code{explore} command.
8152 (gdb) explore struct ComplexStruct
8156 By responding to the prompts appropriately in the subsequent interactive
8157 session, you can explore the type @code{struct ComplexStruct} in a
8158 manner similar to how the value @code{cs} was explored in the above
8161 The @code{explore} command also has two sub-commands,
8162 @code{explore value} and @code{explore type}. The former sub-command is
8163 a way to explicitly specify that value exploration of the argument is
8164 being invoked, while the latter is a way to explicitly specify that type
8165 exploration of the argument is being invoked.
8168 @item explore value @var{expr}
8169 @cindex explore value
8170 This sub-command of @code{explore} explores the value of the
8171 expression @var{expr} (if @var{expr} is an expression valid in the
8172 current context of the program being debugged). The behavior of this
8173 command is identical to that of the behavior of the @code{explore}
8174 command being passed the argument @var{expr}.
8176 @item explore type @var{arg}
8177 @cindex explore type
8178 This sub-command of @code{explore} explores the type of @var{arg} (if
8179 @var{arg} is a type visible in the current context of program being
8180 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8181 is an expression valid in the current context of the program being
8182 debugged). If @var{arg} is a type, then the behavior of this command is
8183 identical to that of the @code{explore} command being passed the
8184 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8185 this command will be identical to that of the @code{explore} command
8186 being passed the type of @var{arg} as the argument.
8190 * Expressions:: Expressions
8191 * Ambiguous Expressions:: Ambiguous Expressions
8192 * Variables:: Program variables
8193 * Arrays:: Artificial arrays
8194 * Output Formats:: Output formats
8195 * Memory:: Examining memory
8196 * Auto Display:: Automatic display
8197 * Print Settings:: Print settings
8198 * Pretty Printing:: Python pretty printing
8199 * Value History:: Value history
8200 * Convenience Vars:: Convenience variables
8201 * Convenience Funs:: Convenience functions
8202 * Registers:: Registers
8203 * Floating Point Hardware:: Floating point hardware
8204 * Vector Unit:: Vector Unit
8205 * OS Information:: Auxiliary data provided by operating system
8206 * Memory Region Attributes:: Memory region attributes
8207 * Dump/Restore Files:: Copy between memory and a file
8208 * Core File Generation:: Cause a program dump its core
8209 * Character Sets:: Debugging programs that use a different
8210 character set than GDB does
8211 * Caching Target Data:: Data caching for targets
8212 * Searching Memory:: Searching memory for a sequence of bytes
8216 @section Expressions
8219 @code{print} and many other @value{GDBN} commands accept an expression and
8220 compute its value. Any kind of constant, variable or operator defined
8221 by the programming language you are using is valid in an expression in
8222 @value{GDBN}. This includes conditional expressions, function calls,
8223 casts, and string constants. It also includes preprocessor macros, if
8224 you compiled your program to include this information; see
8227 @cindex arrays in expressions
8228 @value{GDBN} supports array constants in expressions input by
8229 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8230 you can use the command @code{print @{1, 2, 3@}} to create an array
8231 of three integers. If you pass an array to a function or assign it
8232 to a program variable, @value{GDBN} copies the array to memory that
8233 is @code{malloc}ed in the target program.
8235 Because C is so widespread, most of the expressions shown in examples in
8236 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8237 Languages}, for information on how to use expressions in other
8240 In this section, we discuss operators that you can use in @value{GDBN}
8241 expressions regardless of your programming language.
8243 @cindex casts, in expressions
8244 Casts are supported in all languages, not just in C, because it is so
8245 useful to cast a number into a pointer in order to examine a structure
8246 at that address in memory.
8247 @c FIXME: casts supported---Mod2 true?
8249 @value{GDBN} supports these operators, in addition to those common
8250 to programming languages:
8254 @samp{@@} is a binary operator for treating parts of memory as arrays.
8255 @xref{Arrays, ,Artificial Arrays}, for more information.
8258 @samp{::} allows you to specify a variable in terms of the file or
8259 function where it is defined. @xref{Variables, ,Program Variables}.
8261 @cindex @{@var{type}@}
8262 @cindex type casting memory
8263 @cindex memory, viewing as typed object
8264 @cindex casts, to view memory
8265 @item @{@var{type}@} @var{addr}
8266 Refers to an object of type @var{type} stored at address @var{addr} in
8267 memory. The address @var{addr} may be any expression whose value is
8268 an integer or pointer (but parentheses are required around binary
8269 operators, just as in a cast). This construct is allowed regardless
8270 of what kind of data is normally supposed to reside at @var{addr}.
8273 @node Ambiguous Expressions
8274 @section Ambiguous Expressions
8275 @cindex ambiguous expressions
8277 Expressions can sometimes contain some ambiguous elements. For instance,
8278 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8279 a single function name to be defined several times, for application in
8280 different contexts. This is called @dfn{overloading}. Another example
8281 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8282 templates and is typically instantiated several times, resulting in
8283 the same function name being defined in different contexts.
8285 In some cases and depending on the language, it is possible to adjust
8286 the expression to remove the ambiguity. For instance in C@t{++}, you
8287 can specify the signature of the function you want to break on, as in
8288 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8289 qualified name of your function often makes the expression unambiguous
8292 When an ambiguity that needs to be resolved is detected, the debugger
8293 has the capability to display a menu of numbered choices for each
8294 possibility, and then waits for the selection with the prompt @samp{>}.
8295 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
8296 aborts the current command. If the command in which the expression was
8297 used allows more than one choice to be selected, the next option in the
8298 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
8301 For example, the following session excerpt shows an attempt to set a
8302 breakpoint at the overloaded symbol @code{String::after}.
8303 We choose three particular definitions of that function name:
8305 @c FIXME! This is likely to change to show arg type lists, at least
8308 (@value{GDBP}) b String::after
8311 [2] file:String.cc; line number:867
8312 [3] file:String.cc; line number:860
8313 [4] file:String.cc; line number:875
8314 [5] file:String.cc; line number:853
8315 [6] file:String.cc; line number:846
8316 [7] file:String.cc; line number:735
8318 Breakpoint 1 at 0xb26c: file String.cc, line 867.
8319 Breakpoint 2 at 0xb344: file String.cc, line 875.
8320 Breakpoint 3 at 0xafcc: file String.cc, line 846.
8321 Multiple breakpoints were set.
8322 Use the "delete" command to delete unwanted
8329 @kindex set multiple-symbols
8330 @item set multiple-symbols @var{mode}
8331 @cindex multiple-symbols menu
8333 This option allows you to adjust the debugger behavior when an expression
8336 By default, @var{mode} is set to @code{all}. If the command with which
8337 the expression is used allows more than one choice, then @value{GDBN}
8338 automatically selects all possible choices. For instance, inserting
8339 a breakpoint on a function using an ambiguous name results in a breakpoint
8340 inserted on each possible match. However, if a unique choice must be made,
8341 then @value{GDBN} uses the menu to help you disambiguate the expression.
8342 For instance, printing the address of an overloaded function will result
8343 in the use of the menu.
8345 When @var{mode} is set to @code{ask}, the debugger always uses the menu
8346 when an ambiguity is detected.
8348 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
8349 an error due to the ambiguity and the command is aborted.
8351 @kindex show multiple-symbols
8352 @item show multiple-symbols
8353 Show the current value of the @code{multiple-symbols} setting.
8357 @section Program Variables
8359 The most common kind of expression to use is the name of a variable
8362 Variables in expressions are understood in the selected stack frame
8363 (@pxref{Selection, ,Selecting a Frame}); they must be either:
8367 global (or file-static)
8374 visible according to the scope rules of the
8375 programming language from the point of execution in that frame
8378 @noindent This means that in the function
8393 you can examine and use the variable @code{a} whenever your program is
8394 executing within the function @code{foo}, but you can only use or
8395 examine the variable @code{b} while your program is executing inside
8396 the block where @code{b} is declared.
8398 @cindex variable name conflict
8399 There is an exception: you can refer to a variable or function whose
8400 scope is a single source file even if the current execution point is not
8401 in this file. But it is possible to have more than one such variable or
8402 function with the same name (in different source files). If that
8403 happens, referring to that name has unpredictable effects. If you wish,
8404 you can specify a static variable in a particular function or file by
8405 using the colon-colon (@code{::}) notation:
8407 @cindex colon-colon, context for variables/functions
8409 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
8410 @cindex @code{::}, context for variables/functions
8413 @var{file}::@var{variable}
8414 @var{function}::@var{variable}
8418 Here @var{file} or @var{function} is the name of the context for the
8419 static @var{variable}. In the case of file names, you can use quotes to
8420 make sure @value{GDBN} parses the file name as a single word---for example,
8421 to print a global value of @code{x} defined in @file{f2.c}:
8424 (@value{GDBP}) p 'f2.c'::x
8427 The @code{::} notation is normally used for referring to
8428 static variables, since you typically disambiguate uses of local variables
8429 in functions by selecting the appropriate frame and using the
8430 simple name of the variable. However, you may also use this notation
8431 to refer to local variables in frames enclosing the selected frame:
8440 process (a); /* Stop here */
8451 For example, if there is a breakpoint at the commented line,
8452 here is what you might see
8453 when the program stops after executing the call @code{bar(0)}:
8458 (@value{GDBP}) p bar::a
8461 #2 0x080483d0 in foo (a=5) at foobar.c:12
8464 (@value{GDBP}) p bar::a
8468 @cindex C@t{++} scope resolution
8469 These uses of @samp{::} are very rarely in conflict with the very
8470 similar use of the same notation in C@t{++}. When they are in
8471 conflict, the C@t{++} meaning takes precedence; however, this can be
8472 overridden by quoting the file or function name with single quotes.
8474 For example, suppose the program is stopped in a method of a class
8475 that has a field named @code{includefile}, and there is also an
8476 include file named @file{includefile} that defines a variable,
8480 (@value{GDBP}) p includefile
8482 (@value{GDBP}) p includefile::some_global
8483 A syntax error in expression, near `'.
8484 (@value{GDBP}) p 'includefile'::some_global
8488 @cindex wrong values
8489 @cindex variable values, wrong
8490 @cindex function entry/exit, wrong values of variables
8491 @cindex optimized code, wrong values of variables
8493 @emph{Warning:} Occasionally, a local variable may appear to have the
8494 wrong value at certain points in a function---just after entry to a new
8495 scope, and just before exit.
8497 You may see this problem when you are stepping by machine instructions.
8498 This is because, on most machines, it takes more than one instruction to
8499 set up a stack frame (including local variable definitions); if you are
8500 stepping by machine instructions, variables may appear to have the wrong
8501 values until the stack frame is completely built. On exit, it usually
8502 also takes more than one machine instruction to destroy a stack frame;
8503 after you begin stepping through that group of instructions, local
8504 variable definitions may be gone.
8506 This may also happen when the compiler does significant optimizations.
8507 To be sure of always seeing accurate values, turn off all optimization
8510 @cindex ``No symbol "foo" in current context''
8511 Another possible effect of compiler optimizations is to optimize
8512 unused variables out of existence, or assign variables to registers (as
8513 opposed to memory addresses). Depending on the support for such cases
8514 offered by the debug info format used by the compiler, @value{GDBN}
8515 might not be able to display values for such local variables. If that
8516 happens, @value{GDBN} will print a message like this:
8519 No symbol "foo" in current context.
8522 To solve such problems, either recompile without optimizations, or use a
8523 different debug info format, if the compiler supports several such
8524 formats. @xref{Compilation}, for more information on choosing compiler
8525 options. @xref{C, ,C and C@t{++}}, for more information about debug
8526 info formats that are best suited to C@t{++} programs.
8528 If you ask to print an object whose contents are unknown to
8529 @value{GDBN}, e.g., because its data type is not completely specified
8530 by the debug information, @value{GDBN} will say @samp{<incomplete
8531 type>}. @xref{Symbols, incomplete type}, for more about this.
8533 If you append @kbd{@@entry} string to a function parameter name you get its
8534 value at the time the function got called. If the value is not available an
8535 error message is printed. Entry values are available only with some compilers.
8536 Entry values are normally also printed at the function parameter list according
8537 to @ref{set print entry-values}.
8540 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
8546 (gdb) print i@@entry
8550 Strings are identified as arrays of @code{char} values without specified
8551 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
8552 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
8553 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
8554 defines literal string type @code{"char"} as @code{char} without a sign.
8559 signed char var1[] = "A";
8562 You get during debugging
8567 $2 = @{65 'A', 0 '\0'@}
8571 @section Artificial Arrays
8573 @cindex artificial array
8575 @kindex @@@r{, referencing memory as an array}
8576 It is often useful to print out several successive objects of the
8577 same type in memory; a section of an array, or an array of
8578 dynamically determined size for which only a pointer exists in the
8581 You can do this by referring to a contiguous span of memory as an
8582 @dfn{artificial array}, using the binary operator @samp{@@}. The left
8583 operand of @samp{@@} should be the first element of the desired array
8584 and be an individual object. The right operand should be the desired length
8585 of the array. The result is an array value whose elements are all of
8586 the type of the left argument. The first element is actually the left
8587 argument; the second element comes from bytes of memory immediately
8588 following those that hold the first element, and so on. Here is an
8589 example. If a program says
8592 int *array = (int *) malloc (len * sizeof (int));
8596 you can print the contents of @code{array} with
8602 The left operand of @samp{@@} must reside in memory. Array values made
8603 with @samp{@@} in this way behave just like other arrays in terms of
8604 subscripting, and are coerced to pointers when used in expressions.
8605 Artificial arrays most often appear in expressions via the value history
8606 (@pxref{Value History, ,Value History}), after printing one out.
8608 Another way to create an artificial array is to use a cast.
8609 This re-interprets a value as if it were an array.
8610 The value need not be in memory:
8612 (@value{GDBP}) p/x (short[2])0x12345678
8613 $1 = @{0x1234, 0x5678@}
8616 As a convenience, if you leave the array length out (as in
8617 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
8618 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
8620 (@value{GDBP}) p/x (short[])0x12345678
8621 $2 = @{0x1234, 0x5678@}
8624 Sometimes the artificial array mechanism is not quite enough; in
8625 moderately complex data structures, the elements of interest may not
8626 actually be adjacent---for example, if you are interested in the values
8627 of pointers in an array. One useful work-around in this situation is
8628 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8629 Variables}) as a counter in an expression that prints the first
8630 interesting value, and then repeat that expression via @key{RET}. For
8631 instance, suppose you have an array @code{dtab} of pointers to
8632 structures, and you are interested in the values of a field @code{fv}
8633 in each structure. Here is an example of what you might type:
8643 @node Output Formats
8644 @section Output Formats
8646 @cindex formatted output
8647 @cindex output formats
8648 By default, @value{GDBN} prints a value according to its data type. Sometimes
8649 this is not what you want. For example, you might want to print a number
8650 in hex, or a pointer in decimal. Or you might want to view data in memory
8651 at a certain address as a character string or as an instruction. To do
8652 these things, specify an @dfn{output format} when you print a value.
8654 The simplest use of output formats is to say how to print a value
8655 already computed. This is done by starting the arguments of the
8656 @code{print} command with a slash and a format letter. The format
8657 letters supported are:
8661 Regard the bits of the value as an integer, and print the integer in
8665 Print as integer in signed decimal.
8668 Print as integer in unsigned decimal.
8671 Print as integer in octal.
8674 Print as integer in binary. The letter @samp{t} stands for ``two''.
8675 @footnote{@samp{b} cannot be used because these format letters are also
8676 used with the @code{x} command, where @samp{b} stands for ``byte'';
8677 see @ref{Memory,,Examining Memory}.}
8680 @cindex unknown address, locating
8681 @cindex locate address
8682 Print as an address, both absolute in hexadecimal and as an offset from
8683 the nearest preceding symbol. You can use this format used to discover
8684 where (in what function) an unknown address is located:
8687 (@value{GDBP}) p/a 0x54320
8688 $3 = 0x54320 <_initialize_vx+396>
8692 The command @code{info symbol 0x54320} yields similar results.
8693 @xref{Symbols, info symbol}.
8696 Regard as an integer and print it as a character constant. This
8697 prints both the numerical value and its character representation. The
8698 character representation is replaced with the octal escape @samp{\nnn}
8699 for characters outside the 7-bit @sc{ascii} range.
8701 Without this format, @value{GDBN} displays @code{char},
8702 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
8703 constants. Single-byte members of vectors are displayed as integer
8707 Regard the bits of the value as a floating point number and print
8708 using typical floating point syntax.
8711 @cindex printing strings
8712 @cindex printing byte arrays
8713 Regard as a string, if possible. With this format, pointers to single-byte
8714 data are displayed as null-terminated strings and arrays of single-byte data
8715 are displayed as fixed-length strings. Other values are displayed in their
8718 Without this format, @value{GDBN} displays pointers to and arrays of
8719 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
8720 strings. Single-byte members of a vector are displayed as an integer
8724 Like @samp{x} formatting, the value is treated as an integer and
8725 printed as hexadecimal, but leading zeros are printed to pad the value
8726 to the size of the integer type.
8729 @cindex raw printing
8730 Print using the @samp{raw} formatting. By default, @value{GDBN} will
8731 use a Python-based pretty-printer, if one is available (@pxref{Pretty
8732 Printing}). This typically results in a higher-level display of the
8733 value's contents. The @samp{r} format bypasses any Python
8734 pretty-printer which might exist.
8737 For example, to print the program counter in hex (@pxref{Registers}), type
8744 Note that no space is required before the slash; this is because command
8745 names in @value{GDBN} cannot contain a slash.
8747 To reprint the last value in the value history with a different format,
8748 you can use the @code{print} command with just a format and no
8749 expression. For example, @samp{p/x} reprints the last value in hex.
8752 @section Examining Memory
8754 You can use the command @code{x} (for ``examine'') to examine memory in
8755 any of several formats, independently of your program's data types.
8757 @cindex examining memory
8759 @kindex x @r{(examine memory)}
8760 @item x/@var{nfu} @var{addr}
8763 Use the @code{x} command to examine memory.
8766 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
8767 much memory to display and how to format it; @var{addr} is an
8768 expression giving the address where you want to start displaying memory.
8769 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
8770 Several commands set convenient defaults for @var{addr}.
8773 @item @var{n}, the repeat count
8774 The repeat count is a decimal integer; the default is 1. It specifies
8775 how much memory (counting by units @var{u}) to display.
8776 @c This really is **decimal**; unaffected by 'set radix' as of GDB
8779 @item @var{f}, the display format
8780 The display format is one of the formats used by @code{print}
8781 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
8782 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
8783 The default is @samp{x} (hexadecimal) initially. The default changes
8784 each time you use either @code{x} or @code{print}.
8786 @item @var{u}, the unit size
8787 The unit size is any of
8793 Halfwords (two bytes).
8795 Words (four bytes). This is the initial default.
8797 Giant words (eight bytes).
8800 Each time you specify a unit size with @code{x}, that size becomes the
8801 default unit the next time you use @code{x}. For the @samp{i} format,
8802 the unit size is ignored and is normally not written. For the @samp{s} format,
8803 the unit size defaults to @samp{b}, unless it is explicitly given.
8804 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
8805 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
8806 Note that the results depend on the programming language of the
8807 current compilation unit. If the language is C, the @samp{s}
8808 modifier will use the UTF-16 encoding while @samp{w} will use
8809 UTF-32. The encoding is set by the programming language and cannot
8812 @item @var{addr}, starting display address
8813 @var{addr} is the address where you want @value{GDBN} to begin displaying
8814 memory. The expression need not have a pointer value (though it may);
8815 it is always interpreted as an integer address of a byte of memory.
8816 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
8817 @var{addr} is usually just after the last address examined---but several
8818 other commands also set the default address: @code{info breakpoints} (to
8819 the address of the last breakpoint listed), @code{info line} (to the
8820 starting address of a line), and @code{print} (if you use it to display
8821 a value from memory).
8824 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
8825 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
8826 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
8827 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
8828 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
8830 Since the letters indicating unit sizes are all distinct from the
8831 letters specifying output formats, you do not have to remember whether
8832 unit size or format comes first; either order works. The output
8833 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
8834 (However, the count @var{n} must come first; @samp{wx4} does not work.)
8836 Even though the unit size @var{u} is ignored for the formats @samp{s}
8837 and @samp{i}, you might still want to use a count @var{n}; for example,
8838 @samp{3i} specifies that you want to see three machine instructions,
8839 including any operands. For convenience, especially when used with
8840 the @code{display} command, the @samp{i} format also prints branch delay
8841 slot instructions, if any, beyond the count specified, which immediately
8842 follow the last instruction that is within the count. The command
8843 @code{disassemble} gives an alternative way of inspecting machine
8844 instructions; see @ref{Machine Code,,Source and Machine Code}.
8846 All the defaults for the arguments to @code{x} are designed to make it
8847 easy to continue scanning memory with minimal specifications each time
8848 you use @code{x}. For example, after you have inspected three machine
8849 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
8850 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
8851 the repeat count @var{n} is used again; the other arguments default as
8852 for successive uses of @code{x}.
8854 When examining machine instructions, the instruction at current program
8855 counter is shown with a @code{=>} marker. For example:
8858 (@value{GDBP}) x/5i $pc-6
8859 0x804837f <main+11>: mov %esp,%ebp
8860 0x8048381 <main+13>: push %ecx
8861 0x8048382 <main+14>: sub $0x4,%esp
8862 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
8863 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
8866 @cindex @code{$_}, @code{$__}, and value history
8867 The addresses and contents printed by the @code{x} command are not saved
8868 in the value history because there is often too much of them and they
8869 would get in the way. Instead, @value{GDBN} makes these values available for
8870 subsequent use in expressions as values of the convenience variables
8871 @code{$_} and @code{$__}. After an @code{x} command, the last address
8872 examined is available for use in expressions in the convenience variable
8873 @code{$_}. The contents of that address, as examined, are available in
8874 the convenience variable @code{$__}.
8876 If the @code{x} command has a repeat count, the address and contents saved
8877 are from the last memory unit printed; this is not the same as the last
8878 address printed if several units were printed on the last line of output.
8880 @cindex remote memory comparison
8881 @cindex target memory comparison
8882 @cindex verify remote memory image
8883 @cindex verify target memory image
8884 When you are debugging a program running on a remote target machine
8885 (@pxref{Remote Debugging}), you may wish to verify the program's image
8886 in the remote machine's memory against the executable file you
8887 downloaded to the target. Or, on any target, you may want to check
8888 whether the program has corrupted its own read-only sections. The
8889 @code{compare-sections} command is provided for such situations.
8892 @kindex compare-sections
8893 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
8894 Compare the data of a loadable section @var{section-name} in the
8895 executable file of the program being debugged with the same section in
8896 the target machine's memory, and report any mismatches. With no
8897 arguments, compares all loadable sections. With an argument of
8898 @code{-r}, compares all loadable read-only sections.
8900 Note: for remote targets, this command can be accelerated if the
8901 target supports computing the CRC checksum of a block of memory
8902 (@pxref{qCRC packet}).
8906 @section Automatic Display
8907 @cindex automatic display
8908 @cindex display of expressions
8910 If you find that you want to print the value of an expression frequently
8911 (to see how it changes), you might want to add it to the @dfn{automatic
8912 display list} so that @value{GDBN} prints its value each time your program stops.
8913 Each expression added to the list is given a number to identify it;
8914 to remove an expression from the list, you specify that number.
8915 The automatic display looks like this:
8919 3: bar[5] = (struct hack *) 0x3804
8923 This display shows item numbers, expressions and their current values. As with
8924 displays you request manually using @code{x} or @code{print}, you can
8925 specify the output format you prefer; in fact, @code{display} decides
8926 whether to use @code{print} or @code{x} depending your format
8927 specification---it uses @code{x} if you specify either the @samp{i}
8928 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
8932 @item display @var{expr}
8933 Add the expression @var{expr} to the list of expressions to display
8934 each time your program stops. @xref{Expressions, ,Expressions}.
8936 @code{display} does not repeat if you press @key{RET} again after using it.
8938 @item display/@var{fmt} @var{expr}
8939 For @var{fmt} specifying only a display format and not a size or
8940 count, add the expression @var{expr} to the auto-display list but
8941 arrange to display it each time in the specified format @var{fmt}.
8942 @xref{Output Formats,,Output Formats}.
8944 @item display/@var{fmt} @var{addr}
8945 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
8946 number of units, add the expression @var{addr} as a memory address to
8947 be examined each time your program stops. Examining means in effect
8948 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
8951 For example, @samp{display/i $pc} can be helpful, to see the machine
8952 instruction about to be executed each time execution stops (@samp{$pc}
8953 is a common name for the program counter; @pxref{Registers, ,Registers}).
8956 @kindex delete display
8958 @item undisplay @var{dnums}@dots{}
8959 @itemx delete display @var{dnums}@dots{}
8960 Remove items from the list of expressions to display. Specify the
8961 numbers of the displays that you want affected with the command
8962 argument @var{dnums}. It can be a single display number, one of the
8963 numbers shown in the first field of the @samp{info display} display;
8964 or it could be a range of display numbers, as in @code{2-4}.
8966 @code{undisplay} does not repeat if you press @key{RET} after using it.
8967 (Otherwise you would just get the error @samp{No display number @dots{}}.)
8969 @kindex disable display
8970 @item disable display @var{dnums}@dots{}
8971 Disable the display of item numbers @var{dnums}. A disabled display
8972 item is not printed automatically, but is not forgotten. It may be
8973 enabled again later. Specify the numbers of the displays that you
8974 want affected with the command argument @var{dnums}. It can be a
8975 single display number, one of the numbers shown in the first field of
8976 the @samp{info display} display; or it could be a range of display
8977 numbers, as in @code{2-4}.
8979 @kindex enable display
8980 @item enable display @var{dnums}@dots{}
8981 Enable display of item numbers @var{dnums}. It becomes effective once
8982 again in auto display of its expression, until you specify otherwise.
8983 Specify the numbers of the displays that you want affected with the
8984 command argument @var{dnums}. It can be a single display number, one
8985 of the numbers shown in the first field of the @samp{info display}
8986 display; or it could be a range of display numbers, as in @code{2-4}.
8989 Display the current values of the expressions on the list, just as is
8990 done when your program stops.
8992 @kindex info display
8994 Print the list of expressions previously set up to display
8995 automatically, each one with its item number, but without showing the
8996 values. This includes disabled expressions, which are marked as such.
8997 It also includes expressions which would not be displayed right now
8998 because they refer to automatic variables not currently available.
9001 @cindex display disabled out of scope
9002 If a display expression refers to local variables, then it does not make
9003 sense outside the lexical context for which it was set up. Such an
9004 expression is disabled when execution enters a context where one of its
9005 variables is not defined. For example, if you give the command
9006 @code{display last_char} while inside a function with an argument
9007 @code{last_char}, @value{GDBN} displays this argument while your program
9008 continues to stop inside that function. When it stops elsewhere---where
9009 there is no variable @code{last_char}---the display is disabled
9010 automatically. The next time your program stops where @code{last_char}
9011 is meaningful, you can enable the display expression once again.
9013 @node Print Settings
9014 @section Print Settings
9016 @cindex format options
9017 @cindex print settings
9018 @value{GDBN} provides the following ways to control how arrays, structures,
9019 and symbols are printed.
9022 These settings are useful for debugging programs in any language:
9026 @item set print address
9027 @itemx set print address on
9028 @cindex print/don't print memory addresses
9029 @value{GDBN} prints memory addresses showing the location of stack
9030 traces, structure values, pointer values, breakpoints, and so forth,
9031 even when it also displays the contents of those addresses. The default
9032 is @code{on}. For example, this is what a stack frame display looks like with
9033 @code{set print address on}:
9038 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
9040 530 if (lquote != def_lquote)
9044 @item set print address off
9045 Do not print addresses when displaying their contents. For example,
9046 this is the same stack frame displayed with @code{set print address off}:
9050 (@value{GDBP}) set print addr off
9052 #0 set_quotes (lq="<<", rq=">>") at input.c:530
9053 530 if (lquote != def_lquote)
9057 You can use @samp{set print address off} to eliminate all machine
9058 dependent displays from the @value{GDBN} interface. For example, with
9059 @code{print address off}, you should get the same text for backtraces on
9060 all machines---whether or not they involve pointer arguments.
9063 @item show print address
9064 Show whether or not addresses are to be printed.
9067 When @value{GDBN} prints a symbolic address, it normally prints the
9068 closest earlier symbol plus an offset. If that symbol does not uniquely
9069 identify the address (for example, it is a name whose scope is a single
9070 source file), you may need to clarify. One way to do this is with
9071 @code{info line}, for example @samp{info line *0x4537}. Alternately,
9072 you can set @value{GDBN} to print the source file and line number when
9073 it prints a symbolic address:
9076 @item set print symbol-filename on
9077 @cindex source file and line of a symbol
9078 @cindex symbol, source file and line
9079 Tell @value{GDBN} to print the source file name and line number of a
9080 symbol in the symbolic form of an address.
9082 @item set print symbol-filename off
9083 Do not print source file name and line number of a symbol. This is the
9086 @item show print symbol-filename
9087 Show whether or not @value{GDBN} will print the source file name and
9088 line number of a symbol in the symbolic form of an address.
9091 Another situation where it is helpful to show symbol filenames and line
9092 numbers is when disassembling code; @value{GDBN} shows you the line
9093 number and source file that corresponds to each instruction.
9095 Also, you may wish to see the symbolic form only if the address being
9096 printed is reasonably close to the closest earlier symbol:
9099 @item set print max-symbolic-offset @var{max-offset}
9100 @itemx set print max-symbolic-offset unlimited
9101 @cindex maximum value for offset of closest symbol
9102 Tell @value{GDBN} to only display the symbolic form of an address if the
9103 offset between the closest earlier symbol and the address is less than
9104 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
9105 to always print the symbolic form of an address if any symbol precedes
9106 it. Zero is equivalent to @code{unlimited}.
9108 @item show print max-symbolic-offset
9109 Ask how large the maximum offset is that @value{GDBN} prints in a
9113 @cindex wild pointer, interpreting
9114 @cindex pointer, finding referent
9115 If you have a pointer and you are not sure where it points, try
9116 @samp{set print symbol-filename on}. Then you can determine the name
9117 and source file location of the variable where it points, using
9118 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
9119 For example, here @value{GDBN} shows that a variable @code{ptt} points
9120 at another variable @code{t}, defined in @file{hi2.c}:
9123 (@value{GDBP}) set print symbol-filename on
9124 (@value{GDBP}) p/a ptt
9125 $4 = 0xe008 <t in hi2.c>
9129 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
9130 does not show the symbol name and filename of the referent, even with
9131 the appropriate @code{set print} options turned on.
9134 You can also enable @samp{/a}-like formatting all the time using
9135 @samp{set print symbol on}:
9138 @item set print symbol on
9139 Tell @value{GDBN} to print the symbol corresponding to an address, if
9142 @item set print symbol off
9143 Tell @value{GDBN} not to print the symbol corresponding to an
9144 address. In this mode, @value{GDBN} will still print the symbol
9145 corresponding to pointers to functions. This is the default.
9147 @item show print symbol
9148 Show whether @value{GDBN} will display the symbol corresponding to an
9152 Other settings control how different kinds of objects are printed:
9155 @item set print array
9156 @itemx set print array on
9157 @cindex pretty print arrays
9158 Pretty print arrays. This format is more convenient to read,
9159 but uses more space. The default is off.
9161 @item set print array off
9162 Return to compressed format for arrays.
9164 @item show print array
9165 Show whether compressed or pretty format is selected for displaying
9168 @cindex print array indexes
9169 @item set print array-indexes
9170 @itemx set print array-indexes on
9171 Print the index of each element when displaying arrays. May be more
9172 convenient to locate a given element in the array or quickly find the
9173 index of a given element in that printed array. The default is off.
9175 @item set print array-indexes off
9176 Stop printing element indexes when displaying arrays.
9178 @item show print array-indexes
9179 Show whether the index of each element is printed when displaying
9182 @item set print elements @var{number-of-elements}
9183 @itemx set print elements unlimited
9184 @cindex number of array elements to print
9185 @cindex limit on number of printed array elements
9186 Set a limit on how many elements of an array @value{GDBN} will print.
9187 If @value{GDBN} is printing a large array, it stops printing after it has
9188 printed the number of elements set by the @code{set print elements} command.
9189 This limit also applies to the display of strings.
9190 When @value{GDBN} starts, this limit is set to 200.
9191 Setting @var{number-of-elements} to @code{unlimited} or zero means
9192 that the number of elements to print is unlimited.
9194 @item show print elements
9195 Display the number of elements of a large array that @value{GDBN} will print.
9196 If the number is 0, then the printing is unlimited.
9198 @item set print frame-arguments @var{value}
9199 @kindex set print frame-arguments
9200 @cindex printing frame argument values
9201 @cindex print all frame argument values
9202 @cindex print frame argument values for scalars only
9203 @cindex do not print frame argument values
9204 This command allows to control how the values of arguments are printed
9205 when the debugger prints a frame (@pxref{Frames}). The possible
9210 The values of all arguments are printed.
9213 Print the value of an argument only if it is a scalar. The value of more
9214 complex arguments such as arrays, structures, unions, etc, is replaced
9215 by @code{@dots{}}. This is the default. Here is an example where
9216 only scalar arguments are shown:
9219 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9224 None of the argument values are printed. Instead, the value of each argument
9225 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9228 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9233 By default, only scalar arguments are printed. This command can be used
9234 to configure the debugger to print the value of all arguments, regardless
9235 of their type. However, it is often advantageous to not print the value
9236 of more complex parameters. For instance, it reduces the amount of
9237 information printed in each frame, making the backtrace more readable.
9238 Also, it improves performance when displaying Ada frames, because
9239 the computation of large arguments can sometimes be CPU-intensive,
9240 especially in large applications. Setting @code{print frame-arguments}
9241 to @code{scalars} (the default) or @code{none} avoids this computation,
9242 thus speeding up the display of each Ada frame.
9244 @item show print frame-arguments
9245 Show how the value of arguments should be displayed when printing a frame.
9247 @item set print raw frame-arguments on
9248 Print frame arguments in raw, non pretty-printed, form.
9250 @item set print raw frame-arguments off
9251 Print frame arguments in pretty-printed form, if there is a pretty-printer
9252 for the value (@pxref{Pretty Printing}),
9253 otherwise print the value in raw form.
9254 This is the default.
9256 @item show print raw frame-arguments
9257 Show whether to print frame arguments in raw form.
9259 @anchor{set print entry-values}
9260 @item set print entry-values @var{value}
9261 @kindex set print entry-values
9262 Set printing of frame argument values at function entry. In some cases
9263 @value{GDBN} can determine the value of function argument which was passed by
9264 the function caller, even if the value was modified inside the called function
9265 and therefore is different. With optimized code, the current value could be
9266 unavailable, but the entry value may still be known.
9268 The default value is @code{default} (see below for its description). Older
9269 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
9270 this feature will behave in the @code{default} setting the same way as with the
9273 This functionality is currently supported only by DWARF 2 debugging format and
9274 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9275 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9278 The @var{value} parameter can be one of the following:
9282 Print only actual parameter values, never print values from function entry
9286 #0 different (val=6)
9287 #0 lost (val=<optimized out>)
9289 #0 invalid (val=<optimized out>)
9293 Print only parameter values from function entry point. The actual parameter
9294 values are never printed.
9296 #0 equal (val@@entry=5)
9297 #0 different (val@@entry=5)
9298 #0 lost (val@@entry=5)
9299 #0 born (val@@entry=<optimized out>)
9300 #0 invalid (val@@entry=<optimized out>)
9304 Print only parameter values from function entry point. If value from function
9305 entry point is not known while the actual value is known, print the actual
9306 value for such parameter.
9308 #0 equal (val@@entry=5)
9309 #0 different (val@@entry=5)
9310 #0 lost (val@@entry=5)
9312 #0 invalid (val@@entry=<optimized out>)
9316 Print actual parameter values. If actual parameter value is not known while
9317 value from function entry point is known, print the entry point value for such
9321 #0 different (val=6)
9322 #0 lost (val@@entry=5)
9324 #0 invalid (val=<optimized out>)
9328 Always print both the actual parameter value and its value from function entry
9329 point, even if values of one or both are not available due to compiler
9332 #0 equal (val=5, val@@entry=5)
9333 #0 different (val=6, val@@entry=5)
9334 #0 lost (val=<optimized out>, val@@entry=5)
9335 #0 born (val=10, val@@entry=<optimized out>)
9336 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
9340 Print the actual parameter value if it is known and also its value from
9341 function entry point if it is known. If neither is known, print for the actual
9342 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
9343 values are known and identical, print the shortened
9344 @code{param=param@@entry=VALUE} notation.
9346 #0 equal (val=val@@entry=5)
9347 #0 different (val=6, val@@entry=5)
9348 #0 lost (val@@entry=5)
9350 #0 invalid (val=<optimized out>)
9354 Always print the actual parameter value. Print also its value from function
9355 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
9356 if both values are known and identical, print the shortened
9357 @code{param=param@@entry=VALUE} notation.
9359 #0 equal (val=val@@entry=5)
9360 #0 different (val=6, val@@entry=5)
9361 #0 lost (val=<optimized out>, val@@entry=5)
9363 #0 invalid (val=<optimized out>)
9367 For analysis messages on possible failures of frame argument values at function
9368 entry resolution see @ref{set debug entry-values}.
9370 @item show print entry-values
9371 Show the method being used for printing of frame argument values at function
9374 @item set print repeats @var{number-of-repeats}
9375 @itemx set print repeats unlimited
9376 @cindex repeated array elements
9377 Set the threshold for suppressing display of repeated array
9378 elements. When the number of consecutive identical elements of an
9379 array exceeds the threshold, @value{GDBN} prints the string
9380 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
9381 identical repetitions, instead of displaying the identical elements
9382 themselves. Setting the threshold to @code{unlimited} or zero will
9383 cause all elements to be individually printed. The default threshold
9386 @item show print repeats
9387 Display the current threshold for printing repeated identical
9390 @item set print null-stop
9391 @cindex @sc{null} elements in arrays
9392 Cause @value{GDBN} to stop printing the characters of an array when the first
9393 @sc{null} is encountered. This is useful when large arrays actually
9394 contain only short strings.
9397 @item show print null-stop
9398 Show whether @value{GDBN} stops printing an array on the first
9399 @sc{null} character.
9401 @item set print pretty on
9402 @cindex print structures in indented form
9403 @cindex indentation in structure display
9404 Cause @value{GDBN} to print structures in an indented format with one member
9405 per line, like this:
9420 @item set print pretty off
9421 Cause @value{GDBN} to print structures in a compact format, like this:
9425 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
9426 meat = 0x54 "Pork"@}
9431 This is the default format.
9433 @item show print pretty
9434 Show which format @value{GDBN} is using to print structures.
9436 @item set print sevenbit-strings on
9437 @cindex eight-bit characters in strings
9438 @cindex octal escapes in strings
9439 Print using only seven-bit characters; if this option is set,
9440 @value{GDBN} displays any eight-bit characters (in strings or
9441 character values) using the notation @code{\}@var{nnn}. This setting is
9442 best if you are working in English (@sc{ascii}) and you use the
9443 high-order bit of characters as a marker or ``meta'' bit.
9445 @item set print sevenbit-strings off
9446 Print full eight-bit characters. This allows the use of more
9447 international character sets, and is the default.
9449 @item show print sevenbit-strings
9450 Show whether or not @value{GDBN} is printing only seven-bit characters.
9452 @item set print union on
9453 @cindex unions in structures, printing
9454 Tell @value{GDBN} to print unions which are contained in structures
9455 and other unions. This is the default setting.
9457 @item set print union off
9458 Tell @value{GDBN} not to print unions which are contained in
9459 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
9462 @item show print union
9463 Ask @value{GDBN} whether or not it will print unions which are contained in
9464 structures and other unions.
9466 For example, given the declarations
9469 typedef enum @{Tree, Bug@} Species;
9470 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
9471 typedef enum @{Caterpillar, Cocoon, Butterfly@}
9482 struct thing foo = @{Tree, @{Acorn@}@};
9486 with @code{set print union on} in effect @samp{p foo} would print
9489 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
9493 and with @code{set print union off} in effect it would print
9496 $1 = @{it = Tree, form = @{...@}@}
9500 @code{set print union} affects programs written in C-like languages
9506 These settings are of interest when debugging C@t{++} programs:
9509 @cindex demangling C@t{++} names
9510 @item set print demangle
9511 @itemx set print demangle on
9512 Print C@t{++} names in their source form rather than in the encoded
9513 (``mangled'') form passed to the assembler and linker for type-safe
9514 linkage. The default is on.
9516 @item show print demangle
9517 Show whether C@t{++} names are printed in mangled or demangled form.
9519 @item set print asm-demangle
9520 @itemx set print asm-demangle on
9521 Print C@t{++} names in their source form rather than their mangled form, even
9522 in assembler code printouts such as instruction disassemblies.
9525 @item show print asm-demangle
9526 Show whether C@t{++} names in assembly listings are printed in mangled
9529 @cindex C@t{++} symbol decoding style
9530 @cindex symbol decoding style, C@t{++}
9531 @kindex set demangle-style
9532 @item set demangle-style @var{style}
9533 Choose among several encoding schemes used by different compilers to
9534 represent C@t{++} names. The choices for @var{style} are currently:
9538 Allow @value{GDBN} to choose a decoding style by inspecting your program.
9539 This is the default.
9542 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
9545 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
9548 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
9551 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
9552 @strong{Warning:} this setting alone is not sufficient to allow
9553 debugging @code{cfront}-generated executables. @value{GDBN} would
9554 require further enhancement to permit that.
9557 If you omit @var{style}, you will see a list of possible formats.
9559 @item show demangle-style
9560 Display the encoding style currently in use for decoding C@t{++} symbols.
9562 @item set print object
9563 @itemx set print object on
9564 @cindex derived type of an object, printing
9565 @cindex display derived types
9566 When displaying a pointer to an object, identify the @emph{actual}
9567 (derived) type of the object rather than the @emph{declared} type, using
9568 the virtual function table. Note that the virtual function table is
9569 required---this feature can only work for objects that have run-time
9570 type identification; a single virtual method in the object's declared
9571 type is sufficient. Note that this setting is also taken into account when
9572 working with variable objects via MI (@pxref{GDB/MI}).
9574 @item set print object off
9575 Display only the declared type of objects, without reference to the
9576 virtual function table. This is the default setting.
9578 @item show print object
9579 Show whether actual, or declared, object types are displayed.
9581 @item set print static-members
9582 @itemx set print static-members on
9583 @cindex static members of C@t{++} objects
9584 Print static members when displaying a C@t{++} object. The default is on.
9586 @item set print static-members off
9587 Do not print static members when displaying a C@t{++} object.
9589 @item show print static-members
9590 Show whether C@t{++} static members are printed or not.
9592 @item set print pascal_static-members
9593 @itemx set print pascal_static-members on
9594 @cindex static members of Pascal objects
9595 @cindex Pascal objects, static members display
9596 Print static members when displaying a Pascal object. The default is on.
9598 @item set print pascal_static-members off
9599 Do not print static members when displaying a Pascal object.
9601 @item show print pascal_static-members
9602 Show whether Pascal static members are printed or not.
9604 @c These don't work with HP ANSI C++ yet.
9605 @item set print vtbl
9606 @itemx set print vtbl on
9607 @cindex pretty print C@t{++} virtual function tables
9608 @cindex virtual functions (C@t{++}) display
9609 @cindex VTBL display
9610 Pretty print C@t{++} virtual function tables. The default is off.
9611 (The @code{vtbl} commands do not work on programs compiled with the HP
9612 ANSI C@t{++} compiler (@code{aCC}).)
9614 @item set print vtbl off
9615 Do not pretty print C@t{++} virtual function tables.
9617 @item show print vtbl
9618 Show whether C@t{++} virtual function tables are pretty printed, or not.
9621 @node Pretty Printing
9622 @section Pretty Printing
9624 @value{GDBN} provides a mechanism to allow pretty-printing of values using
9625 Python code. It greatly simplifies the display of complex objects. This
9626 mechanism works for both MI and the CLI.
9629 * Pretty-Printer Introduction:: Introduction to pretty-printers
9630 * Pretty-Printer Example:: An example pretty-printer
9631 * Pretty-Printer Commands:: Pretty-printer commands
9634 @node Pretty-Printer Introduction
9635 @subsection Pretty-Printer Introduction
9637 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
9638 registered for the value. If there is then @value{GDBN} invokes the
9639 pretty-printer to print the value. Otherwise the value is printed normally.
9641 Pretty-printers are normally named. This makes them easy to manage.
9642 The @samp{info pretty-printer} command will list all the installed
9643 pretty-printers with their names.
9644 If a pretty-printer can handle multiple data types, then its
9645 @dfn{subprinters} are the printers for the individual data types.
9646 Each such subprinter has its own name.
9647 The format of the name is @var{printer-name};@var{subprinter-name}.
9649 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
9650 Typically they are automatically loaded and registered when the corresponding
9651 debug information is loaded, thus making them available without having to
9652 do anything special.
9654 There are three places where a pretty-printer can be registered.
9658 Pretty-printers registered globally are available when debugging
9662 Pretty-printers registered with a program space are available only
9663 when debugging that program.
9664 @xref{Progspaces In Python}, for more details on program spaces in Python.
9667 Pretty-printers registered with an objfile are loaded and unloaded
9668 with the corresponding objfile (e.g., shared library).
9669 @xref{Objfiles In Python}, for more details on objfiles in Python.
9672 @xref{Selecting Pretty-Printers}, for further information on how
9673 pretty-printers are selected,
9675 @xref{Writing a Pretty-Printer}, for implementing pretty printers
9678 @node Pretty-Printer Example
9679 @subsection Pretty-Printer Example
9681 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
9684 (@value{GDBP}) print s
9686 static npos = 4294967295,
9688 <std::allocator<char>> = @{
9689 <__gnu_cxx::new_allocator<char>> = @{
9690 <No data fields>@}, <No data fields>
9692 members of std::basic_string<char, std::char_traits<char>,
9693 std::allocator<char> >::_Alloc_hider:
9694 _M_p = 0x804a014 "abcd"
9699 With a pretty-printer for @code{std::string} only the contents are printed:
9702 (@value{GDBP}) print s
9706 @node Pretty-Printer Commands
9707 @subsection Pretty-Printer Commands
9708 @cindex pretty-printer commands
9711 @kindex info pretty-printer
9712 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9713 Print the list of installed pretty-printers.
9714 This includes disabled pretty-printers, which are marked as such.
9716 @var{object-regexp} is a regular expression matching the objects
9717 whose pretty-printers to list.
9718 Objects can be @code{global}, the program space's file
9719 (@pxref{Progspaces In Python}),
9720 and the object files within that program space (@pxref{Objfiles In Python}).
9721 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
9722 looks up a printer from these three objects.
9724 @var{name-regexp} is a regular expression matching the name of the printers
9727 @kindex disable pretty-printer
9728 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9729 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9730 A disabled pretty-printer is not forgotten, it may be enabled again later.
9732 @kindex enable pretty-printer
9733 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9734 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9739 Suppose we have three pretty-printers installed: one from library1.so
9740 named @code{foo} that prints objects of type @code{foo}, and
9741 another from library2.so named @code{bar} that prints two types of objects,
9742 @code{bar1} and @code{bar2}.
9745 (gdb) info pretty-printer
9752 (gdb) info pretty-printer library2
9757 (gdb) disable pretty-printer library1
9759 2 of 3 printers enabled
9760 (gdb) info pretty-printer
9767 (gdb) disable pretty-printer library2 bar:bar1
9769 1 of 3 printers enabled
9770 (gdb) info pretty-printer library2
9777 (gdb) disable pretty-printer library2 bar
9779 0 of 3 printers enabled
9780 (gdb) info pretty-printer library2
9789 Note that for @code{bar} the entire printer can be disabled,
9790 as can each individual subprinter.
9793 @section Value History
9795 @cindex value history
9796 @cindex history of values printed by @value{GDBN}
9797 Values printed by the @code{print} command are saved in the @value{GDBN}
9798 @dfn{value history}. This allows you to refer to them in other expressions.
9799 Values are kept until the symbol table is re-read or discarded
9800 (for example with the @code{file} or @code{symbol-file} commands).
9801 When the symbol table changes, the value history is discarded,
9802 since the values may contain pointers back to the types defined in the
9807 @cindex history number
9808 The values printed are given @dfn{history numbers} by which you can
9809 refer to them. These are successive integers starting with one.
9810 @code{print} shows you the history number assigned to a value by
9811 printing @samp{$@var{num} = } before the value; here @var{num} is the
9814 To refer to any previous value, use @samp{$} followed by the value's
9815 history number. The way @code{print} labels its output is designed to
9816 remind you of this. Just @code{$} refers to the most recent value in
9817 the history, and @code{$$} refers to the value before that.
9818 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
9819 is the value just prior to @code{$$}, @code{$$1} is equivalent to
9820 @code{$$}, and @code{$$0} is equivalent to @code{$}.
9822 For example, suppose you have just printed a pointer to a structure and
9823 want to see the contents of the structure. It suffices to type
9829 If you have a chain of structures where the component @code{next} points
9830 to the next one, you can print the contents of the next one with this:
9837 You can print successive links in the chain by repeating this
9838 command---which you can do by just typing @key{RET}.
9840 Note that the history records values, not expressions. If the value of
9841 @code{x} is 4 and you type these commands:
9849 then the value recorded in the value history by the @code{print} command
9850 remains 4 even though the value of @code{x} has changed.
9855 Print the last ten values in the value history, with their item numbers.
9856 This is like @samp{p@ $$9} repeated ten times, except that @code{show
9857 values} does not change the history.
9859 @item show values @var{n}
9860 Print ten history values centered on history item number @var{n}.
9863 Print ten history values just after the values last printed. If no more
9864 values are available, @code{show values +} produces no display.
9867 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
9868 same effect as @samp{show values +}.
9870 @node Convenience Vars
9871 @section Convenience Variables
9873 @cindex convenience variables
9874 @cindex user-defined variables
9875 @value{GDBN} provides @dfn{convenience variables} that you can use within
9876 @value{GDBN} to hold on to a value and refer to it later. These variables
9877 exist entirely within @value{GDBN}; they are not part of your program, and
9878 setting a convenience variable has no direct effect on further execution
9879 of your program. That is why you can use them freely.
9881 Convenience variables are prefixed with @samp{$}. Any name preceded by
9882 @samp{$} can be used for a convenience variable, unless it is one of
9883 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
9884 (Value history references, in contrast, are @emph{numbers} preceded
9885 by @samp{$}. @xref{Value History, ,Value History}.)
9887 You can save a value in a convenience variable with an assignment
9888 expression, just as you would set a variable in your program.
9892 set $foo = *object_ptr
9896 would save in @code{$foo} the value contained in the object pointed to by
9899 Using a convenience variable for the first time creates it, but its
9900 value is @code{void} until you assign a new value. You can alter the
9901 value with another assignment at any time.
9903 Convenience variables have no fixed types. You can assign a convenience
9904 variable any type of value, including structures and arrays, even if
9905 that variable already has a value of a different type. The convenience
9906 variable, when used as an expression, has the type of its current value.
9909 @kindex show convenience
9910 @cindex show all user variables and functions
9911 @item show convenience
9912 Print a list of convenience variables used so far, and their values,
9913 as well as a list of the convenience functions.
9914 Abbreviated @code{show conv}.
9916 @kindex init-if-undefined
9917 @cindex convenience variables, initializing
9918 @item init-if-undefined $@var{variable} = @var{expression}
9919 Set a convenience variable if it has not already been set. This is useful
9920 for user-defined commands that keep some state. It is similar, in concept,
9921 to using local static variables with initializers in C (except that
9922 convenience variables are global). It can also be used to allow users to
9923 override default values used in a command script.
9925 If the variable is already defined then the expression is not evaluated so
9926 any side-effects do not occur.
9929 One of the ways to use a convenience variable is as a counter to be
9930 incremented or a pointer to be advanced. For example, to print
9931 a field from successive elements of an array of structures:
9935 print bar[$i++]->contents
9939 Repeat that command by typing @key{RET}.
9941 Some convenience variables are created automatically by @value{GDBN} and given
9942 values likely to be useful.
9945 @vindex $_@r{, convenience variable}
9947 The variable @code{$_} is automatically set by the @code{x} command to
9948 the last address examined (@pxref{Memory, ,Examining Memory}). Other
9949 commands which provide a default address for @code{x} to examine also
9950 set @code{$_} to that address; these commands include @code{info line}
9951 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
9952 except when set by the @code{x} command, in which case it is a pointer
9953 to the type of @code{$__}.
9955 @vindex $__@r{, convenience variable}
9957 The variable @code{$__} is automatically set by the @code{x} command
9958 to the value found in the last address examined. Its type is chosen
9959 to match the format in which the data was printed.
9962 @vindex $_exitcode@r{, convenience variable}
9963 When the program being debugged terminates normally, @value{GDBN}
9964 automatically sets this variable to the exit code of the program, and
9965 resets @code{$_exitsignal} to @code{void}.
9968 @vindex $_exitsignal@r{, convenience variable}
9969 When the program being debugged dies due to an uncaught signal,
9970 @value{GDBN} automatically sets this variable to that signal's number,
9971 and resets @code{$_exitcode} to @code{void}.
9973 To distinguish between whether the program being debugged has exited
9974 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
9975 @code{$_exitsignal} is not @code{void}), the convenience function
9976 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
9977 Functions}). For example, considering the following source code:
9983 main (int argc, char *argv[])
9990 A valid way of telling whether the program being debugged has exited
9991 or signalled would be:
9994 (@value{GDBP}) define has_exited_or_signalled
9995 Type commands for definition of ``has_exited_or_signalled''.
9996 End with a line saying just ``end''.
9997 >if $_isvoid ($_exitsignal)
9998 >echo The program has exited\n
10000 >echo The program has signalled\n
10006 Program terminated with signal SIGALRM, Alarm clock.
10007 The program no longer exists.
10008 (@value{GDBP}) has_exited_or_signalled
10009 The program has signalled
10012 As can be seen, @value{GDBN} correctly informs that the program being
10013 debugged has signalled, since it calls @code{raise} and raises a
10014 @code{SIGALRM} signal. If the program being debugged had not called
10015 @code{raise}, then @value{GDBN} would report a normal exit:
10018 (@value{GDBP}) has_exited_or_signalled
10019 The program has exited
10023 The variable @code{$_exception} is set to the exception object being
10024 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
10027 @itemx $_probe_arg0@dots{}$_probe_arg11
10028 Arguments to a static probe. @xref{Static Probe Points}.
10031 @vindex $_sdata@r{, inspect, convenience variable}
10032 The variable @code{$_sdata} contains extra collected static tracepoint
10033 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
10034 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
10035 if extra static tracepoint data has not been collected.
10038 @vindex $_siginfo@r{, convenience variable}
10039 The variable @code{$_siginfo} contains extra signal information
10040 (@pxref{extra signal information}). Note that @code{$_siginfo}
10041 could be empty, if the application has not yet received any signals.
10042 For example, it will be empty before you execute the @code{run} command.
10045 @vindex $_tlb@r{, convenience variable}
10046 The variable @code{$_tlb} is automatically set when debugging
10047 applications running on MS-Windows in native mode or connected to
10048 gdbserver that supports the @code{qGetTIBAddr} request.
10049 @xref{General Query Packets}.
10050 This variable contains the address of the thread information block.
10054 On HP-UX systems, if you refer to a function or variable name that
10055 begins with a dollar sign, @value{GDBN} searches for a user or system
10056 name first, before it searches for a convenience variable.
10058 @node Convenience Funs
10059 @section Convenience Functions
10061 @cindex convenience functions
10062 @value{GDBN} also supplies some @dfn{convenience functions}. These
10063 have a syntax similar to convenience variables. A convenience
10064 function can be used in an expression just like an ordinary function;
10065 however, a convenience function is implemented internally to
10068 These functions do not require @value{GDBN} to be configured with
10069 @code{Python} support, which means that they are always available.
10073 @item $_isvoid (@var{expr})
10074 @findex $_isvoid@r{, convenience function}
10075 Return one if the expression @var{expr} is @code{void}. Otherwise it
10078 A @code{void} expression is an expression where the type of the result
10079 is @code{void}. For example, you can examine a convenience variable
10080 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
10084 (@value{GDBP}) print $_exitcode
10086 (@value{GDBP}) print $_isvoid ($_exitcode)
10089 Starting program: ./a.out
10090 [Inferior 1 (process 29572) exited normally]
10091 (@value{GDBP}) print $_exitcode
10093 (@value{GDBP}) print $_isvoid ($_exitcode)
10097 In the example above, we used @code{$_isvoid} to check whether
10098 @code{$_exitcode} is @code{void} before and after the execution of the
10099 program being debugged. Before the execution there is no exit code to
10100 be examined, therefore @code{$_exitcode} is @code{void}. After the
10101 execution the program being debugged returned zero, therefore
10102 @code{$_exitcode} is zero, which means that it is not @code{void}
10105 The @code{void} expression can also be a call of a function from the
10106 program being debugged. For example, given the following function:
10115 The result of calling it inside @value{GDBN} is @code{void}:
10118 (@value{GDBP}) print foo ()
10120 (@value{GDBP}) print $_isvoid (foo ())
10122 (@value{GDBP}) set $v = foo ()
10123 (@value{GDBP}) print $v
10125 (@value{GDBP}) print $_isvoid ($v)
10131 These functions require @value{GDBN} to be configured with
10132 @code{Python} support.
10136 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10137 @findex $_memeq@r{, convenience function}
10138 Returns one if the @var{length} bytes at the addresses given by
10139 @var{buf1} and @var{buf2} are equal.
10140 Otherwise it returns zero.
10142 @item $_regex(@var{str}, @var{regex})
10143 @findex $_regex@r{, convenience function}
10144 Returns one if the string @var{str} matches the regular expression
10145 @var{regex}. Otherwise it returns zero.
10146 The syntax of the regular expression is that specified by @code{Python}'s
10147 regular expression support.
10149 @item $_streq(@var{str1}, @var{str2})
10150 @findex $_streq@r{, convenience function}
10151 Returns one if the strings @var{str1} and @var{str2} are equal.
10152 Otherwise it returns zero.
10154 @item $_strlen(@var{str})
10155 @findex $_strlen@r{, convenience function}
10156 Returns the length of string @var{str}.
10158 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10159 @findex $_caller_is@r{, convenience function}
10160 Returns one if the calling function's name is equal to @var{name}.
10161 Otherwise it returns zero.
10163 If the optional argument @var{number_of_frames} is provided,
10164 it is the number of frames up in the stack to look.
10172 at testsuite/gdb.python/py-caller-is.c:21
10173 #1 0x00000000004005a0 in middle_func ()
10174 at testsuite/gdb.python/py-caller-is.c:27
10175 #2 0x00000000004005ab in top_func ()
10176 at testsuite/gdb.python/py-caller-is.c:33
10177 #3 0x00000000004005b6 in main ()
10178 at testsuite/gdb.python/py-caller-is.c:39
10179 (gdb) print $_caller_is ("middle_func")
10181 (gdb) print $_caller_is ("top_func", 2)
10185 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10186 @findex $_caller_matches@r{, convenience function}
10187 Returns one if the calling function's name matches the regular expression
10188 @var{regexp}. Otherwise it returns zero.
10190 If the optional argument @var{number_of_frames} is provided,
10191 it is the number of frames up in the stack to look.
10194 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10195 @findex $_any_caller_is@r{, convenience function}
10196 Returns one if any calling function's name is equal to @var{name}.
10197 Otherwise it returns zero.
10199 If the optional argument @var{number_of_frames} is provided,
10200 it is the number of frames up in the stack to look.
10203 This function differs from @code{$_caller_is} in that this function
10204 checks all stack frames from the immediate caller to the frame specified
10205 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
10206 frame specified by @var{number_of_frames}.
10208 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10209 @findex $_any_caller_matches@r{, convenience function}
10210 Returns one if any calling function's name matches the regular expression
10211 @var{regexp}. Otherwise it returns zero.
10213 If the optional argument @var{number_of_frames} is provided,
10214 it is the number of frames up in the stack to look.
10217 This function differs from @code{$_caller_matches} in that this function
10218 checks all stack frames from the immediate caller to the frame specified
10219 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
10220 frame specified by @var{number_of_frames}.
10224 @value{GDBN} provides the ability to list and get help on
10225 convenience functions.
10228 @item help function
10229 @kindex help function
10230 @cindex show all convenience functions
10231 Print a list of all convenience functions.
10238 You can refer to machine register contents, in expressions, as variables
10239 with names starting with @samp{$}. The names of registers are different
10240 for each machine; use @code{info registers} to see the names used on
10244 @kindex info registers
10245 @item info registers
10246 Print the names and values of all registers except floating-point
10247 and vector registers (in the selected stack frame).
10249 @kindex info all-registers
10250 @cindex floating point registers
10251 @item info all-registers
10252 Print the names and values of all registers, including floating-point
10253 and vector registers (in the selected stack frame).
10255 @item info registers @var{regname} @dots{}
10256 Print the @dfn{relativized} value of each specified register @var{regname}.
10257 As discussed in detail below, register values are normally relative to
10258 the selected stack frame. The @var{regname} may be any register name valid on
10259 the machine you are using, with or without the initial @samp{$}.
10262 @anchor{standard registers}
10263 @cindex stack pointer register
10264 @cindex program counter register
10265 @cindex process status register
10266 @cindex frame pointer register
10267 @cindex standard registers
10268 @value{GDBN} has four ``standard'' register names that are available (in
10269 expressions) on most machines---whenever they do not conflict with an
10270 architecture's canonical mnemonics for registers. The register names
10271 @code{$pc} and @code{$sp} are used for the program counter register and
10272 the stack pointer. @code{$fp} is used for a register that contains a
10273 pointer to the current stack frame, and @code{$ps} is used for a
10274 register that contains the processor status. For example,
10275 you could print the program counter in hex with
10282 or print the instruction to be executed next with
10289 or add four to the stack pointer@footnote{This is a way of removing
10290 one word from the stack, on machines where stacks grow downward in
10291 memory (most machines, nowadays). This assumes that the innermost
10292 stack frame is selected; setting @code{$sp} is not allowed when other
10293 stack frames are selected. To pop entire frames off the stack,
10294 regardless of machine architecture, use @code{return};
10295 see @ref{Returning, ,Returning from a Function}.} with
10301 Whenever possible, these four standard register names are available on
10302 your machine even though the machine has different canonical mnemonics,
10303 so long as there is no conflict. The @code{info registers} command
10304 shows the canonical names. For example, on the SPARC, @code{info
10305 registers} displays the processor status register as @code{$psr} but you
10306 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
10307 is an alias for the @sc{eflags} register.
10309 @value{GDBN} always considers the contents of an ordinary register as an
10310 integer when the register is examined in this way. Some machines have
10311 special registers which can hold nothing but floating point; these
10312 registers are considered to have floating point values. There is no way
10313 to refer to the contents of an ordinary register as floating point value
10314 (although you can @emph{print} it as a floating point value with
10315 @samp{print/f $@var{regname}}).
10317 Some registers have distinct ``raw'' and ``virtual'' data formats. This
10318 means that the data format in which the register contents are saved by
10319 the operating system is not the same one that your program normally
10320 sees. For example, the registers of the 68881 floating point
10321 coprocessor are always saved in ``extended'' (raw) format, but all C
10322 programs expect to work with ``double'' (virtual) format. In such
10323 cases, @value{GDBN} normally works with the virtual format only (the format
10324 that makes sense for your program), but the @code{info registers} command
10325 prints the data in both formats.
10327 @cindex SSE registers (x86)
10328 @cindex MMX registers (x86)
10329 Some machines have special registers whose contents can be interpreted
10330 in several different ways. For example, modern x86-based machines
10331 have SSE and MMX registers that can hold several values packed
10332 together in several different formats. @value{GDBN} refers to such
10333 registers in @code{struct} notation:
10336 (@value{GDBP}) print $xmm1
10338 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
10339 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
10340 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
10341 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
10342 v4_int32 = @{0, 20657912, 11, 13@},
10343 v2_int64 = @{88725056443645952, 55834574859@},
10344 uint128 = 0x0000000d0000000b013b36f800000000
10349 To set values of such registers, you need to tell @value{GDBN} which
10350 view of the register you wish to change, as if you were assigning
10351 value to a @code{struct} member:
10354 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
10357 Normally, register values are relative to the selected stack frame
10358 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
10359 value that the register would contain if all stack frames farther in
10360 were exited and their saved registers restored. In order to see the
10361 true contents of hardware registers, you must select the innermost
10362 frame (with @samp{frame 0}).
10364 @cindex caller-saved registers
10365 @cindex call-clobbered registers
10366 @cindex volatile registers
10367 @cindex <not saved> values
10368 Usually ABIs reserve some registers as not needed to be saved by the
10369 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
10370 registers). It may therefore not be possible for @value{GDBN} to know
10371 the value a register had before the call (in other words, in the outer
10372 frame), if the register value has since been changed by the callee.
10373 @value{GDBN} tries to deduce where the inner frame saved
10374 (``callee-saved'') registers, from the debug info, unwind info, or the
10375 machine code generated by your compiler. If some register is not
10376 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
10377 its own knowledge of the ABI, or because the debug/unwind info
10378 explicitly says the register's value is undefined), @value{GDBN}
10379 displays @w{@samp{<not saved>}} as the register's value. With targets
10380 that @value{GDBN} has no knowledge of the register saving convention,
10381 if a register was not saved by the callee, then its value and location
10382 in the outer frame are assumed to be the same of the inner frame.
10383 This is usually harmless, because if the register is call-clobbered,
10384 the caller either does not care what is in the register after the
10385 call, or has code to restore the value that it does care about. Note,
10386 however, that if you change such a register in the outer frame, you
10387 may also be affecting the inner frame. Also, the more ``outer'' the
10388 frame is you're looking at, the more likely a call-clobbered
10389 register's value is to be wrong, in the sense that it doesn't actually
10390 represent the value the register had just before the call.
10392 @node Floating Point Hardware
10393 @section Floating Point Hardware
10394 @cindex floating point
10396 Depending on the configuration, @value{GDBN} may be able to give
10397 you more information about the status of the floating point hardware.
10402 Display hardware-dependent information about the floating
10403 point unit. The exact contents and layout vary depending on the
10404 floating point chip. Currently, @samp{info float} is supported on
10405 the ARM and x86 machines.
10409 @section Vector Unit
10410 @cindex vector unit
10412 Depending on the configuration, @value{GDBN} may be able to give you
10413 more information about the status of the vector unit.
10416 @kindex info vector
10418 Display information about the vector unit. The exact contents and
10419 layout vary depending on the hardware.
10422 @node OS Information
10423 @section Operating System Auxiliary Information
10424 @cindex OS information
10426 @value{GDBN} provides interfaces to useful OS facilities that can help
10427 you debug your program.
10429 @cindex auxiliary vector
10430 @cindex vector, auxiliary
10431 Some operating systems supply an @dfn{auxiliary vector} to programs at
10432 startup. This is akin to the arguments and environment that you
10433 specify for a program, but contains a system-dependent variety of
10434 binary values that tell system libraries important details about the
10435 hardware, operating system, and process. Each value's purpose is
10436 identified by an integer tag; the meanings are well-known but system-specific.
10437 Depending on the configuration and operating system facilities,
10438 @value{GDBN} may be able to show you this information. For remote
10439 targets, this functionality may further depend on the remote stub's
10440 support of the @samp{qXfer:auxv:read} packet, see
10441 @ref{qXfer auxiliary vector read}.
10446 Display the auxiliary vector of the inferior, which can be either a
10447 live process or a core dump file. @value{GDBN} prints each tag value
10448 numerically, and also shows names and text descriptions for recognized
10449 tags. Some values in the vector are numbers, some bit masks, and some
10450 pointers to strings or other data. @value{GDBN} displays each value in the
10451 most appropriate form for a recognized tag, and in hexadecimal for
10452 an unrecognized tag.
10455 On some targets, @value{GDBN} can access operating system-specific
10456 information and show it to you. The types of information available
10457 will differ depending on the type of operating system running on the
10458 target. The mechanism used to fetch the data is described in
10459 @ref{Operating System Information}. For remote targets, this
10460 functionality depends on the remote stub's support of the
10461 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
10465 @item info os @var{infotype}
10467 Display OS information of the requested type.
10469 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
10471 @anchor{linux info os infotypes}
10473 @kindex info os processes
10475 Display the list of processes on the target. For each process,
10476 @value{GDBN} prints the process identifier, the name of the user, the
10477 command corresponding to the process, and the list of processor cores
10478 that the process is currently running on. (To understand what these
10479 properties mean, for this and the following info types, please consult
10480 the general @sc{gnu}/Linux documentation.)
10482 @kindex info os procgroups
10484 Display the list of process groups on the target. For each process,
10485 @value{GDBN} prints the identifier of the process group that it belongs
10486 to, the command corresponding to the process group leader, the process
10487 identifier, and the command line of the process. The list is sorted
10488 first by the process group identifier, then by the process identifier,
10489 so that processes belonging to the same process group are grouped together
10490 and the process group leader is listed first.
10492 @kindex info os threads
10494 Display the list of threads running on the target. For each thread,
10495 @value{GDBN} prints the identifier of the process that the thread
10496 belongs to, the command of the process, the thread identifier, and the
10497 processor core that it is currently running on. The main thread of a
10498 process is not listed.
10500 @kindex info os files
10502 Display the list of open file descriptors on the target. For each
10503 file descriptor, @value{GDBN} prints the identifier of the process
10504 owning the descriptor, the command of the owning process, the value
10505 of the descriptor, and the target of the descriptor.
10507 @kindex info os sockets
10509 Display the list of Internet-domain sockets on the target. For each
10510 socket, @value{GDBN} prints the address and port of the local and
10511 remote endpoints, the current state of the connection, the creator of
10512 the socket, the IP address family of the socket, and the type of the
10515 @kindex info os shm
10517 Display the list of all System V shared-memory regions on the target.
10518 For each shared-memory region, @value{GDBN} prints the region key,
10519 the shared-memory identifier, the access permissions, the size of the
10520 region, the process that created the region, the process that last
10521 attached to or detached from the region, the current number of live
10522 attaches to the region, and the times at which the region was last
10523 attached to, detach from, and changed.
10525 @kindex info os semaphores
10527 Display the list of all System V semaphore sets on the target. For each
10528 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
10529 set identifier, the access permissions, the number of semaphores in the
10530 set, the user and group of the owner and creator of the semaphore set,
10531 and the times at which the semaphore set was operated upon and changed.
10533 @kindex info os msg
10535 Display the list of all System V message queues on the target. For each
10536 message queue, @value{GDBN} prints the message queue key, the message
10537 queue identifier, the access permissions, the current number of bytes
10538 on the queue, the current number of messages on the queue, the processes
10539 that last sent and received a message on the queue, the user and group
10540 of the owner and creator of the message queue, the times at which a
10541 message was last sent and received on the queue, and the time at which
10542 the message queue was last changed.
10544 @kindex info os modules
10546 Display the list of all loaded kernel modules on the target. For each
10547 module, @value{GDBN} prints the module name, the size of the module in
10548 bytes, the number of times the module is used, the dependencies of the
10549 module, the status of the module, and the address of the loaded module
10554 If @var{infotype} is omitted, then list the possible values for
10555 @var{infotype} and the kind of OS information available for each
10556 @var{infotype}. If the target does not return a list of possible
10557 types, this command will report an error.
10560 @node Memory Region Attributes
10561 @section Memory Region Attributes
10562 @cindex memory region attributes
10564 @dfn{Memory region attributes} allow you to describe special handling
10565 required by regions of your target's memory. @value{GDBN} uses
10566 attributes to determine whether to allow certain types of memory
10567 accesses; whether to use specific width accesses; and whether to cache
10568 target memory. By default the description of memory regions is
10569 fetched from the target (if the current target supports this), but the
10570 user can override the fetched regions.
10572 Defined memory regions can be individually enabled and disabled. When a
10573 memory region is disabled, @value{GDBN} uses the default attributes when
10574 accessing memory in that region. Similarly, if no memory regions have
10575 been defined, @value{GDBN} uses the default attributes when accessing
10578 When a memory region is defined, it is given a number to identify it;
10579 to enable, disable, or remove a memory region, you specify that number.
10583 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
10584 Define a memory region bounded by @var{lower} and @var{upper} with
10585 attributes @var{attributes}@dots{}, and add it to the list of regions
10586 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
10587 case: it is treated as the target's maximum memory address.
10588 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
10591 Discard any user changes to the memory regions and use target-supplied
10592 regions, if available, or no regions if the target does not support.
10595 @item delete mem @var{nums}@dots{}
10596 Remove memory regions @var{nums}@dots{} from the list of regions
10597 monitored by @value{GDBN}.
10599 @kindex disable mem
10600 @item disable mem @var{nums}@dots{}
10601 Disable monitoring of memory regions @var{nums}@dots{}.
10602 A disabled memory region is not forgotten.
10603 It may be enabled again later.
10606 @item enable mem @var{nums}@dots{}
10607 Enable monitoring of memory regions @var{nums}@dots{}.
10611 Print a table of all defined memory regions, with the following columns
10615 @item Memory Region Number
10616 @item Enabled or Disabled.
10617 Enabled memory regions are marked with @samp{y}.
10618 Disabled memory regions are marked with @samp{n}.
10621 The address defining the inclusive lower bound of the memory region.
10624 The address defining the exclusive upper bound of the memory region.
10627 The list of attributes set for this memory region.
10632 @subsection Attributes
10634 @subsubsection Memory Access Mode
10635 The access mode attributes set whether @value{GDBN} may make read or
10636 write accesses to a memory region.
10638 While these attributes prevent @value{GDBN} from performing invalid
10639 memory accesses, they do nothing to prevent the target system, I/O DMA,
10640 etc.@: from accessing memory.
10644 Memory is read only.
10646 Memory is write only.
10648 Memory is read/write. This is the default.
10651 @subsubsection Memory Access Size
10652 The access size attribute tells @value{GDBN} to use specific sized
10653 accesses in the memory region. Often memory mapped device registers
10654 require specific sized accesses. If no access size attribute is
10655 specified, @value{GDBN} may use accesses of any size.
10659 Use 8 bit memory accesses.
10661 Use 16 bit memory accesses.
10663 Use 32 bit memory accesses.
10665 Use 64 bit memory accesses.
10668 @c @subsubsection Hardware/Software Breakpoints
10669 @c The hardware/software breakpoint attributes set whether @value{GDBN}
10670 @c will use hardware or software breakpoints for the internal breakpoints
10671 @c used by the step, next, finish, until, etc. commands.
10675 @c Always use hardware breakpoints
10676 @c @item swbreak (default)
10679 @subsubsection Data Cache
10680 The data cache attributes set whether @value{GDBN} will cache target
10681 memory. While this generally improves performance by reducing debug
10682 protocol overhead, it can lead to incorrect results because @value{GDBN}
10683 does not know about volatile variables or memory mapped device
10688 Enable @value{GDBN} to cache target memory.
10690 Disable @value{GDBN} from caching target memory. This is the default.
10693 @subsection Memory Access Checking
10694 @value{GDBN} can be instructed to refuse accesses to memory that is
10695 not explicitly described. This can be useful if accessing such
10696 regions has undesired effects for a specific target, or to provide
10697 better error checking. The following commands control this behaviour.
10700 @kindex set mem inaccessible-by-default
10701 @item set mem inaccessible-by-default [on|off]
10702 If @code{on} is specified, make @value{GDBN} treat memory not
10703 explicitly described by the memory ranges as non-existent and refuse accesses
10704 to such memory. The checks are only performed if there's at least one
10705 memory range defined. If @code{off} is specified, make @value{GDBN}
10706 treat the memory not explicitly described by the memory ranges as RAM.
10707 The default value is @code{on}.
10708 @kindex show mem inaccessible-by-default
10709 @item show mem inaccessible-by-default
10710 Show the current handling of accesses to unknown memory.
10714 @c @subsubsection Memory Write Verification
10715 @c The memory write verification attributes set whether @value{GDBN}
10716 @c will re-reads data after each write to verify the write was successful.
10720 @c @item noverify (default)
10723 @node Dump/Restore Files
10724 @section Copy Between Memory and a File
10725 @cindex dump/restore files
10726 @cindex append data to a file
10727 @cindex dump data to a file
10728 @cindex restore data from a file
10730 You can use the commands @code{dump}, @code{append}, and
10731 @code{restore} to copy data between target memory and a file. The
10732 @code{dump} and @code{append} commands write data to a file, and the
10733 @code{restore} command reads data from a file back into the inferior's
10734 memory. Files may be in binary, Motorola S-record, Intel hex, or
10735 Tektronix Hex format; however, @value{GDBN} can only append to binary
10741 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10742 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
10743 Dump the contents of memory from @var{start_addr} to @var{end_addr},
10744 or the value of @var{expr}, to @var{filename} in the given format.
10746 The @var{format} parameter may be any one of:
10753 Motorola S-record format.
10755 Tektronix Hex format.
10758 @value{GDBN} uses the same definitions of these formats as the
10759 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
10760 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
10764 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10765 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
10766 Append the contents of memory from @var{start_addr} to @var{end_addr},
10767 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
10768 (@value{GDBN} can only append data to files in raw binary form.)
10771 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
10772 Restore the contents of file @var{filename} into memory. The
10773 @code{restore} command can automatically recognize any known @sc{bfd}
10774 file format, except for raw binary. To restore a raw binary file you
10775 must specify the optional keyword @code{binary} after the filename.
10777 If @var{bias} is non-zero, its value will be added to the addresses
10778 contained in the file. Binary files always start at address zero, so
10779 they will be restored at address @var{bias}. Other bfd files have
10780 a built-in location; they will be restored at offset @var{bias}
10781 from that location.
10783 If @var{start} and/or @var{end} are non-zero, then only data between
10784 file offset @var{start} and file offset @var{end} will be restored.
10785 These offsets are relative to the addresses in the file, before
10786 the @var{bias} argument is applied.
10790 @node Core File Generation
10791 @section How to Produce a Core File from Your Program
10792 @cindex dump core from inferior
10794 A @dfn{core file} or @dfn{core dump} is a file that records the memory
10795 image of a running process and its process status (register values
10796 etc.). Its primary use is post-mortem debugging of a program that
10797 crashed while it ran outside a debugger. A program that crashes
10798 automatically produces a core file, unless this feature is disabled by
10799 the user. @xref{Files}, for information on invoking @value{GDBN} in
10800 the post-mortem debugging mode.
10802 Occasionally, you may wish to produce a core file of the program you
10803 are debugging in order to preserve a snapshot of its state.
10804 @value{GDBN} has a special command for that.
10808 @kindex generate-core-file
10809 @item generate-core-file [@var{file}]
10810 @itemx gcore [@var{file}]
10811 Produce a core dump of the inferior process. The optional argument
10812 @var{file} specifies the file name where to put the core dump. If not
10813 specified, the file name defaults to @file{core.@var{pid}}, where
10814 @var{pid} is the inferior process ID.
10816 Note that this command is implemented only for some systems (as of
10817 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
10820 @node Character Sets
10821 @section Character Sets
10822 @cindex character sets
10824 @cindex translating between character sets
10825 @cindex host character set
10826 @cindex target character set
10828 If the program you are debugging uses a different character set to
10829 represent characters and strings than the one @value{GDBN} uses itself,
10830 @value{GDBN} can automatically translate between the character sets for
10831 you. The character set @value{GDBN} uses we call the @dfn{host
10832 character set}; the one the inferior program uses we call the
10833 @dfn{target character set}.
10835 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
10836 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
10837 remote protocol (@pxref{Remote Debugging}) to debug a program
10838 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
10839 then the host character set is Latin-1, and the target character set is
10840 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
10841 target-charset EBCDIC-US}, then @value{GDBN} translates between
10842 @sc{ebcdic} and Latin 1 as you print character or string values, or use
10843 character and string literals in expressions.
10845 @value{GDBN} has no way to automatically recognize which character set
10846 the inferior program uses; you must tell it, using the @code{set
10847 target-charset} command, described below.
10849 Here are the commands for controlling @value{GDBN}'s character set
10853 @item set target-charset @var{charset}
10854 @kindex set target-charset
10855 Set the current target character set to @var{charset}. To display the
10856 list of supported target character sets, type
10857 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
10859 @item set host-charset @var{charset}
10860 @kindex set host-charset
10861 Set the current host character set to @var{charset}.
10863 By default, @value{GDBN} uses a host character set appropriate to the
10864 system it is running on; you can override that default using the
10865 @code{set host-charset} command. On some systems, @value{GDBN} cannot
10866 automatically determine the appropriate host character set. In this
10867 case, @value{GDBN} uses @samp{UTF-8}.
10869 @value{GDBN} can only use certain character sets as its host character
10870 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
10871 @value{GDBN} will list the host character sets it supports.
10873 @item set charset @var{charset}
10874 @kindex set charset
10875 Set the current host and target character sets to @var{charset}. As
10876 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
10877 @value{GDBN} will list the names of the character sets that can be used
10878 for both host and target.
10881 @kindex show charset
10882 Show the names of the current host and target character sets.
10884 @item show host-charset
10885 @kindex show host-charset
10886 Show the name of the current host character set.
10888 @item show target-charset
10889 @kindex show target-charset
10890 Show the name of the current target character set.
10892 @item set target-wide-charset @var{charset}
10893 @kindex set target-wide-charset
10894 Set the current target's wide character set to @var{charset}. This is
10895 the character set used by the target's @code{wchar_t} type. To
10896 display the list of supported wide character sets, type
10897 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
10899 @item show target-wide-charset
10900 @kindex show target-wide-charset
10901 Show the name of the current target's wide character set.
10904 Here is an example of @value{GDBN}'s character set support in action.
10905 Assume that the following source code has been placed in the file
10906 @file{charset-test.c}:
10912 = @{72, 101, 108, 108, 111, 44, 32, 119,
10913 111, 114, 108, 100, 33, 10, 0@};
10914 char ibm1047_hello[]
10915 = @{200, 133, 147, 147, 150, 107, 64, 166,
10916 150, 153, 147, 132, 90, 37, 0@};
10920 printf ("Hello, world!\n");
10924 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
10925 containing the string @samp{Hello, world!} followed by a newline,
10926 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
10928 We compile the program, and invoke the debugger on it:
10931 $ gcc -g charset-test.c -o charset-test
10932 $ gdb -nw charset-test
10933 GNU gdb 2001-12-19-cvs
10934 Copyright 2001 Free Software Foundation, Inc.
10939 We can use the @code{show charset} command to see what character sets
10940 @value{GDBN} is currently using to interpret and display characters and
10944 (@value{GDBP}) show charset
10945 The current host and target character set is `ISO-8859-1'.
10949 For the sake of printing this manual, let's use @sc{ascii} as our
10950 initial character set:
10952 (@value{GDBP}) set charset ASCII
10953 (@value{GDBP}) show charset
10954 The current host and target character set is `ASCII'.
10958 Let's assume that @sc{ascii} is indeed the correct character set for our
10959 host system --- in other words, let's assume that if @value{GDBN} prints
10960 characters using the @sc{ascii} character set, our terminal will display
10961 them properly. Since our current target character set is also
10962 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
10965 (@value{GDBP}) print ascii_hello
10966 $1 = 0x401698 "Hello, world!\n"
10967 (@value{GDBP}) print ascii_hello[0]
10972 @value{GDBN} uses the target character set for character and string
10973 literals you use in expressions:
10976 (@value{GDBP}) print '+'
10981 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
10984 @value{GDBN} relies on the user to tell it which character set the
10985 target program uses. If we print @code{ibm1047_hello} while our target
10986 character set is still @sc{ascii}, we get jibberish:
10989 (@value{GDBP}) print ibm1047_hello
10990 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
10991 (@value{GDBP}) print ibm1047_hello[0]
10996 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
10997 @value{GDBN} tells us the character sets it supports:
11000 (@value{GDBP}) set target-charset
11001 ASCII EBCDIC-US IBM1047 ISO-8859-1
11002 (@value{GDBP}) set target-charset
11005 We can select @sc{ibm1047} as our target character set, and examine the
11006 program's strings again. Now the @sc{ascii} string is wrong, but
11007 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
11008 target character set, @sc{ibm1047}, to the host character set,
11009 @sc{ascii}, and they display correctly:
11012 (@value{GDBP}) set target-charset IBM1047
11013 (@value{GDBP}) show charset
11014 The current host character set is `ASCII'.
11015 The current target character set is `IBM1047'.
11016 (@value{GDBP}) print ascii_hello
11017 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
11018 (@value{GDBP}) print ascii_hello[0]
11020 (@value{GDBP}) print ibm1047_hello
11021 $8 = 0x4016a8 "Hello, world!\n"
11022 (@value{GDBP}) print ibm1047_hello[0]
11027 As above, @value{GDBN} uses the target character set for character and
11028 string literals you use in expressions:
11031 (@value{GDBP}) print '+'
11036 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
11039 @node Caching Target Data
11040 @section Caching Data of Targets
11041 @cindex caching data of targets
11043 @value{GDBN} caches data exchanged between the debugger and a target.
11044 Each cache is associated with the address space of the inferior.
11045 @xref{Inferiors and Programs}, about inferior and address space.
11046 Such caching generally improves performance in remote debugging
11047 (@pxref{Remote Debugging}), because it reduces the overhead of the
11048 remote protocol by bundling memory reads and writes into large chunks.
11049 Unfortunately, simply caching everything would lead to incorrect results,
11050 since @value{GDBN} does not necessarily know anything about volatile
11051 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
11052 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
11054 Therefore, by default, @value{GDBN} only caches data
11055 known to be on the stack@footnote{In non-stop mode, it is moderately
11056 rare for a running thread to modify the stack of a stopped thread
11057 in a way that would interfere with a backtrace, and caching of
11058 stack reads provides a significant speed up of remote backtraces.} or
11059 in the code segment.
11060 Other regions of memory can be explicitly marked as
11061 cacheable; @pxref{Memory Region Attributes}.
11064 @kindex set remotecache
11065 @item set remotecache on
11066 @itemx set remotecache off
11067 This option no longer does anything; it exists for compatibility
11070 @kindex show remotecache
11071 @item show remotecache
11072 Show the current state of the obsolete remotecache flag.
11074 @kindex set stack-cache
11075 @item set stack-cache on
11076 @itemx set stack-cache off
11077 Enable or disable caching of stack accesses. When @code{on}, use
11078 caching. By default, this option is @code{on}.
11080 @kindex show stack-cache
11081 @item show stack-cache
11082 Show the current state of data caching for memory accesses.
11084 @kindex set code-cache
11085 @item set code-cache on
11086 @itemx set code-cache off
11087 Enable or disable caching of code segment accesses. When @code{on},
11088 use caching. By default, this option is @code{on}. This improves
11089 performance of disassembly in remote debugging.
11091 @kindex show code-cache
11092 @item show code-cache
11093 Show the current state of target memory cache for code segment
11096 @kindex info dcache
11097 @item info dcache @r{[}line@r{]}
11098 Print the information about the performance of data cache of the
11099 current inferior's address space. The information displayed
11100 includes the dcache width and depth, and for each cache line, its
11101 number, address, and how many times it was referenced. This
11102 command is useful for debugging the data cache operation.
11104 If a line number is specified, the contents of that line will be
11107 @item set dcache size @var{size}
11108 @cindex dcache size
11109 @kindex set dcache size
11110 Set maximum number of entries in dcache (dcache depth above).
11112 @item set dcache line-size @var{line-size}
11113 @cindex dcache line-size
11114 @kindex set dcache line-size
11115 Set number of bytes each dcache entry caches (dcache width above).
11116 Must be a power of 2.
11118 @item show dcache size
11119 @kindex show dcache size
11120 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
11122 @item show dcache line-size
11123 @kindex show dcache line-size
11124 Show default size of dcache lines.
11128 @node Searching Memory
11129 @section Search Memory
11130 @cindex searching memory
11132 Memory can be searched for a particular sequence of bytes with the
11133 @code{find} command.
11137 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11138 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11139 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
11140 etc. The search begins at address @var{start_addr} and continues for either
11141 @var{len} bytes or through to @var{end_addr} inclusive.
11144 @var{s} and @var{n} are optional parameters.
11145 They may be specified in either order, apart or together.
11148 @item @var{s}, search query size
11149 The size of each search query value.
11155 halfwords (two bytes)
11159 giant words (eight bytes)
11162 All values are interpreted in the current language.
11163 This means, for example, that if the current source language is C/C@t{++}
11164 then searching for the string ``hello'' includes the trailing '\0'.
11166 If the value size is not specified, it is taken from the
11167 value's type in the current language.
11168 This is useful when one wants to specify the search
11169 pattern as a mixture of types.
11170 Note that this means, for example, that in the case of C-like languages
11171 a search for an untyped 0x42 will search for @samp{(int) 0x42}
11172 which is typically four bytes.
11174 @item @var{n}, maximum number of finds
11175 The maximum number of matches to print. The default is to print all finds.
11178 You can use strings as search values. Quote them with double-quotes
11180 The string value is copied into the search pattern byte by byte,
11181 regardless of the endianness of the target and the size specification.
11183 The address of each match found is printed as well as a count of the
11184 number of matches found.
11186 The address of the last value found is stored in convenience variable
11188 A count of the number of matches is stored in @samp{$numfound}.
11190 For example, if stopped at the @code{printf} in this function:
11196 static char hello[] = "hello-hello";
11197 static struct @{ char c; short s; int i; @}
11198 __attribute__ ((packed)) mixed
11199 = @{ 'c', 0x1234, 0x87654321 @};
11200 printf ("%s\n", hello);
11205 you get during debugging:
11208 (gdb) find &hello[0], +sizeof(hello), "hello"
11209 0x804956d <hello.1620+6>
11211 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
11212 0x8049567 <hello.1620>
11213 0x804956d <hello.1620+6>
11215 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
11216 0x8049567 <hello.1620>
11218 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
11219 0x8049560 <mixed.1625>
11221 (gdb) print $numfound
11224 $2 = (void *) 0x8049560
11227 @node Optimized Code
11228 @chapter Debugging Optimized Code
11229 @cindex optimized code, debugging
11230 @cindex debugging optimized code
11232 Almost all compilers support optimization. With optimization
11233 disabled, the compiler generates assembly code that corresponds
11234 directly to your source code, in a simplistic way. As the compiler
11235 applies more powerful optimizations, the generated assembly code
11236 diverges from your original source code. With help from debugging
11237 information generated by the compiler, @value{GDBN} can map from
11238 the running program back to constructs from your original source.
11240 @value{GDBN} is more accurate with optimization disabled. If you
11241 can recompile without optimization, it is easier to follow the
11242 progress of your program during debugging. But, there are many cases
11243 where you may need to debug an optimized version.
11245 When you debug a program compiled with @samp{-g -O}, remember that the
11246 optimizer has rearranged your code; the debugger shows you what is
11247 really there. Do not be too surprised when the execution path does not
11248 exactly match your source file! An extreme example: if you define a
11249 variable, but never use it, @value{GDBN} never sees that
11250 variable---because the compiler optimizes it out of existence.
11252 Some things do not work as well with @samp{-g -O} as with just
11253 @samp{-g}, particularly on machines with instruction scheduling. If in
11254 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
11255 please report it to us as a bug (including a test case!).
11256 @xref{Variables}, for more information about debugging optimized code.
11259 * Inline Functions:: How @value{GDBN} presents inlining
11260 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
11263 @node Inline Functions
11264 @section Inline Functions
11265 @cindex inline functions, debugging
11267 @dfn{Inlining} is an optimization that inserts a copy of the function
11268 body directly at each call site, instead of jumping to a shared
11269 routine. @value{GDBN} displays inlined functions just like
11270 non-inlined functions. They appear in backtraces. You can view their
11271 arguments and local variables, step into them with @code{step}, skip
11272 them with @code{next}, and escape from them with @code{finish}.
11273 You can check whether a function was inlined by using the
11274 @code{info frame} command.
11276 For @value{GDBN} to support inlined functions, the compiler must
11277 record information about inlining in the debug information ---
11278 @value{NGCC} using the @sc{dwarf 2} format does this, and several
11279 other compilers do also. @value{GDBN} only supports inlined functions
11280 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
11281 do not emit two required attributes (@samp{DW_AT_call_file} and
11282 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
11283 function calls with earlier versions of @value{NGCC}. It instead
11284 displays the arguments and local variables of inlined functions as
11285 local variables in the caller.
11287 The body of an inlined function is directly included at its call site;
11288 unlike a non-inlined function, there are no instructions devoted to
11289 the call. @value{GDBN} still pretends that the call site and the
11290 start of the inlined function are different instructions. Stepping to
11291 the call site shows the call site, and then stepping again shows
11292 the first line of the inlined function, even though no additional
11293 instructions are executed.
11295 This makes source-level debugging much clearer; you can see both the
11296 context of the call and then the effect of the call. Only stepping by
11297 a single instruction using @code{stepi} or @code{nexti} does not do
11298 this; single instruction steps always show the inlined body.
11300 There are some ways that @value{GDBN} does not pretend that inlined
11301 function calls are the same as normal calls:
11305 Setting breakpoints at the call site of an inlined function may not
11306 work, because the call site does not contain any code. @value{GDBN}
11307 may incorrectly move the breakpoint to the next line of the enclosing
11308 function, after the call. This limitation will be removed in a future
11309 version of @value{GDBN}; until then, set a breakpoint on an earlier line
11310 or inside the inlined function instead.
11313 @value{GDBN} cannot locate the return value of inlined calls after
11314 using the @code{finish} command. This is a limitation of compiler-generated
11315 debugging information; after @code{finish}, you can step to the next line
11316 and print a variable where your program stored the return value.
11320 @node Tail Call Frames
11321 @section Tail Call Frames
11322 @cindex tail call frames, debugging
11324 Function @code{B} can call function @code{C} in its very last statement. In
11325 unoptimized compilation the call of @code{C} is immediately followed by return
11326 instruction at the end of @code{B} code. Optimizing compiler may replace the
11327 call and return in function @code{B} into one jump to function @code{C}
11328 instead. Such use of a jump instruction is called @dfn{tail call}.
11330 During execution of function @code{C}, there will be no indication in the
11331 function call stack frames that it was tail-called from @code{B}. If function
11332 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
11333 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
11334 some cases @value{GDBN} can determine that @code{C} was tail-called from
11335 @code{B}, and it will then create fictitious call frame for that, with the
11336 return address set up as if @code{B} called @code{C} normally.
11338 This functionality is currently supported only by DWARF 2 debugging format and
11339 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
11340 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11343 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
11344 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
11348 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
11350 Stack level 1, frame at 0x7fffffffda30:
11351 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
11352 tail call frame, caller of frame at 0x7fffffffda30
11353 source language c++.
11354 Arglist at unknown address.
11355 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
11358 The detection of all the possible code path executions can find them ambiguous.
11359 There is no execution history stored (possible @ref{Reverse Execution} is never
11360 used for this purpose) and the last known caller could have reached the known
11361 callee by multiple different jump sequences. In such case @value{GDBN} still
11362 tries to show at least all the unambiguous top tail callers and all the
11363 unambiguous bottom tail calees, if any.
11366 @anchor{set debug entry-values}
11367 @item set debug entry-values
11368 @kindex set debug entry-values
11369 When set to on, enables printing of analysis messages for both frame argument
11370 values at function entry and tail calls. It will show all the possible valid
11371 tail calls code paths it has considered. It will also print the intersection
11372 of them with the final unambiguous (possibly partial or even empty) code path
11375 @item show debug entry-values
11376 @kindex show debug entry-values
11377 Show the current state of analysis messages printing for both frame argument
11378 values at function entry and tail calls.
11381 The analysis messages for tail calls can for example show why the virtual tail
11382 call frame for function @code{c} has not been recognized (due to the indirect
11383 reference by variable @code{x}):
11386 static void __attribute__((noinline, noclone)) c (void);
11387 void (*x) (void) = c;
11388 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11389 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
11390 int main (void) @{ x (); return 0; @}
11392 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
11393 DW_TAG_GNU_call_site 0x40039a in main
11395 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11398 #1 0x000000000040039a in main () at t.c:5
11401 Another possibility is an ambiguous virtual tail call frames resolution:
11405 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
11406 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
11407 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
11408 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
11409 static void __attribute__((noinline, noclone)) b (void)
11410 @{ if (i) c (); else e (); @}
11411 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
11412 int main (void) @{ a (); return 0; @}
11414 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
11415 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
11416 tailcall: reduced: 0x4004d2(a) |
11419 #1 0x00000000004004d2 in a () at t.c:8
11420 #2 0x0000000000400395 in main () at t.c:9
11423 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
11424 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
11426 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
11427 @ifset HAVE_MAKEINFO_CLICK
11428 @set ARROW @click{}
11429 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
11430 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
11432 @ifclear HAVE_MAKEINFO_CLICK
11434 @set CALLSEQ1B @value{CALLSEQ1A}
11435 @set CALLSEQ2B @value{CALLSEQ2A}
11438 Frames #0 and #2 are real, #1 is a virtual tail call frame.
11439 The code can have possible execution paths @value{CALLSEQ1B} or
11440 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
11442 @code{initial:} state shows some random possible calling sequence @value{GDBN}
11443 has found. It then finds another possible calling sequcen - that one is
11444 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
11445 printed as the @code{reduced:} calling sequence. That one could have many
11446 futher @code{compare:} and @code{reduced:} statements as long as there remain
11447 any non-ambiguous sequence entries.
11449 For the frame of function @code{b} in both cases there are different possible
11450 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
11451 also ambigous. The only non-ambiguous frame is the one for function @code{a},
11452 therefore this one is displayed to the user while the ambiguous frames are
11455 There can be also reasons why printing of frame argument values at function
11460 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
11461 static void __attribute__((noinline, noclone)) a (int i);
11462 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
11463 static void __attribute__((noinline, noclone)) a (int i)
11464 @{ if (i) b (i - 1); else c (0); @}
11465 int main (void) @{ a (5); return 0; @}
11468 #0 c (i=i@@entry=0) at t.c:2
11469 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
11470 function "a" at 0x400420 can call itself via tail calls
11471 i=<optimized out>) at t.c:6
11472 #2 0x000000000040036e in main () at t.c:7
11475 @value{GDBN} cannot find out from the inferior state if and how many times did
11476 function @code{a} call itself (via function @code{b}) as these calls would be
11477 tail calls. Such tail calls would modify thue @code{i} variable, therefore
11478 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
11479 prints @code{<optimized out>} instead.
11482 @chapter C Preprocessor Macros
11484 Some languages, such as C and C@t{++}, provide a way to define and invoke
11485 ``preprocessor macros'' which expand into strings of tokens.
11486 @value{GDBN} can evaluate expressions containing macro invocations, show
11487 the result of macro expansion, and show a macro's definition, including
11488 where it was defined.
11490 You may need to compile your program specially to provide @value{GDBN}
11491 with information about preprocessor macros. Most compilers do not
11492 include macros in their debugging information, even when you compile
11493 with the @option{-g} flag. @xref{Compilation}.
11495 A program may define a macro at one point, remove that definition later,
11496 and then provide a different definition after that. Thus, at different
11497 points in the program, a macro may have different definitions, or have
11498 no definition at all. If there is a current stack frame, @value{GDBN}
11499 uses the macros in scope at that frame's source code line. Otherwise,
11500 @value{GDBN} uses the macros in scope at the current listing location;
11503 Whenever @value{GDBN} evaluates an expression, it always expands any
11504 macro invocations present in the expression. @value{GDBN} also provides
11505 the following commands for working with macros explicitly.
11509 @kindex macro expand
11510 @cindex macro expansion, showing the results of preprocessor
11511 @cindex preprocessor macro expansion, showing the results of
11512 @cindex expanding preprocessor macros
11513 @item macro expand @var{expression}
11514 @itemx macro exp @var{expression}
11515 Show the results of expanding all preprocessor macro invocations in
11516 @var{expression}. Since @value{GDBN} simply expands macros, but does
11517 not parse the result, @var{expression} need not be a valid expression;
11518 it can be any string of tokens.
11521 @item macro expand-once @var{expression}
11522 @itemx macro exp1 @var{expression}
11523 @cindex expand macro once
11524 @i{(This command is not yet implemented.)} Show the results of
11525 expanding those preprocessor macro invocations that appear explicitly in
11526 @var{expression}. Macro invocations appearing in that expansion are
11527 left unchanged. This command allows you to see the effect of a
11528 particular macro more clearly, without being confused by further
11529 expansions. Since @value{GDBN} simply expands macros, but does not
11530 parse the result, @var{expression} need not be a valid expression; it
11531 can be any string of tokens.
11534 @cindex macro definition, showing
11535 @cindex definition of a macro, showing
11536 @cindex macros, from debug info
11537 @item info macro [-a|-all] [--] @var{macro}
11538 Show the current definition or all definitions of the named @var{macro},
11539 and describe the source location or compiler command-line where that
11540 definition was established. The optional double dash is to signify the end of
11541 argument processing and the beginning of @var{macro} for non C-like macros where
11542 the macro may begin with a hyphen.
11544 @kindex info macros
11545 @item info macros @var{linespec}
11546 Show all macro definitions that are in effect at the location specified
11547 by @var{linespec}, and describe the source location or compiler
11548 command-line where those definitions were established.
11550 @kindex macro define
11551 @cindex user-defined macros
11552 @cindex defining macros interactively
11553 @cindex macros, user-defined
11554 @item macro define @var{macro} @var{replacement-list}
11555 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
11556 Introduce a definition for a preprocessor macro named @var{macro},
11557 invocations of which are replaced by the tokens given in
11558 @var{replacement-list}. The first form of this command defines an
11559 ``object-like'' macro, which takes no arguments; the second form
11560 defines a ``function-like'' macro, which takes the arguments given in
11563 A definition introduced by this command is in scope in every
11564 expression evaluated in @value{GDBN}, until it is removed with the
11565 @code{macro undef} command, described below. The definition overrides
11566 all definitions for @var{macro} present in the program being debugged,
11567 as well as any previous user-supplied definition.
11569 @kindex macro undef
11570 @item macro undef @var{macro}
11571 Remove any user-supplied definition for the macro named @var{macro}.
11572 This command only affects definitions provided with the @code{macro
11573 define} command, described above; it cannot remove definitions present
11574 in the program being debugged.
11578 List all the macros defined using the @code{macro define} command.
11581 @cindex macros, example of debugging with
11582 Here is a transcript showing the above commands in action. First, we
11583 show our source files:
11588 #include "sample.h"
11591 #define ADD(x) (M + x)
11596 printf ("Hello, world!\n");
11598 printf ("We're so creative.\n");
11600 printf ("Goodbye, world!\n");
11607 Now, we compile the program using the @sc{gnu} C compiler,
11608 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
11609 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
11610 and @option{-gdwarf-4}; we recommend always choosing the most recent
11611 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
11612 includes information about preprocessor macros in the debugging
11616 $ gcc -gdwarf-2 -g3 sample.c -o sample
11620 Now, we start @value{GDBN} on our sample program:
11624 GNU gdb 2002-05-06-cvs
11625 Copyright 2002 Free Software Foundation, Inc.
11626 GDB is free software, @dots{}
11630 We can expand macros and examine their definitions, even when the
11631 program is not running. @value{GDBN} uses the current listing position
11632 to decide which macro definitions are in scope:
11635 (@value{GDBP}) list main
11638 5 #define ADD(x) (M + x)
11643 10 printf ("Hello, world!\n");
11645 12 printf ("We're so creative.\n");
11646 (@value{GDBP}) info macro ADD
11647 Defined at /home/jimb/gdb/macros/play/sample.c:5
11648 #define ADD(x) (M + x)
11649 (@value{GDBP}) info macro Q
11650 Defined at /home/jimb/gdb/macros/play/sample.h:1
11651 included at /home/jimb/gdb/macros/play/sample.c:2
11653 (@value{GDBP}) macro expand ADD(1)
11654 expands to: (42 + 1)
11655 (@value{GDBP}) macro expand-once ADD(1)
11656 expands to: once (M + 1)
11660 In the example above, note that @code{macro expand-once} expands only
11661 the macro invocation explicit in the original text --- the invocation of
11662 @code{ADD} --- but does not expand the invocation of the macro @code{M},
11663 which was introduced by @code{ADD}.
11665 Once the program is running, @value{GDBN} uses the macro definitions in
11666 force at the source line of the current stack frame:
11669 (@value{GDBP}) break main
11670 Breakpoint 1 at 0x8048370: file sample.c, line 10.
11672 Starting program: /home/jimb/gdb/macros/play/sample
11674 Breakpoint 1, main () at sample.c:10
11675 10 printf ("Hello, world!\n");
11679 At line 10, the definition of the macro @code{N} at line 9 is in force:
11682 (@value{GDBP}) info macro N
11683 Defined at /home/jimb/gdb/macros/play/sample.c:9
11685 (@value{GDBP}) macro expand N Q M
11686 expands to: 28 < 42
11687 (@value{GDBP}) print N Q M
11692 As we step over directives that remove @code{N}'s definition, and then
11693 give it a new definition, @value{GDBN} finds the definition (or lack
11694 thereof) in force at each point:
11697 (@value{GDBP}) next
11699 12 printf ("We're so creative.\n");
11700 (@value{GDBP}) info macro N
11701 The symbol `N' has no definition as a C/C++ preprocessor macro
11702 at /home/jimb/gdb/macros/play/sample.c:12
11703 (@value{GDBP}) next
11705 14 printf ("Goodbye, world!\n");
11706 (@value{GDBP}) info macro N
11707 Defined at /home/jimb/gdb/macros/play/sample.c:13
11709 (@value{GDBP}) macro expand N Q M
11710 expands to: 1729 < 42
11711 (@value{GDBP}) print N Q M
11716 In addition to source files, macros can be defined on the compilation command
11717 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
11718 such a way, @value{GDBN} displays the location of their definition as line zero
11719 of the source file submitted to the compiler.
11722 (@value{GDBP}) info macro __STDC__
11723 Defined at /home/jimb/gdb/macros/play/sample.c:0
11730 @chapter Tracepoints
11731 @c This chapter is based on the documentation written by Michael
11732 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
11734 @cindex tracepoints
11735 In some applications, it is not feasible for the debugger to interrupt
11736 the program's execution long enough for the developer to learn
11737 anything helpful about its behavior. If the program's correctness
11738 depends on its real-time behavior, delays introduced by a debugger
11739 might cause the program to change its behavior drastically, or perhaps
11740 fail, even when the code itself is correct. It is useful to be able
11741 to observe the program's behavior without interrupting it.
11743 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
11744 specify locations in the program, called @dfn{tracepoints}, and
11745 arbitrary expressions to evaluate when those tracepoints are reached.
11746 Later, using the @code{tfind} command, you can examine the values
11747 those expressions had when the program hit the tracepoints. The
11748 expressions may also denote objects in memory---structures or arrays,
11749 for example---whose values @value{GDBN} should record; while visiting
11750 a particular tracepoint, you may inspect those objects as if they were
11751 in memory at that moment. However, because @value{GDBN} records these
11752 values without interacting with you, it can do so quickly and
11753 unobtrusively, hopefully not disturbing the program's behavior.
11755 The tracepoint facility is currently available only for remote
11756 targets. @xref{Targets}. In addition, your remote target must know
11757 how to collect trace data. This functionality is implemented in the
11758 remote stub; however, none of the stubs distributed with @value{GDBN}
11759 support tracepoints as of this writing. The format of the remote
11760 packets used to implement tracepoints are described in @ref{Tracepoint
11763 It is also possible to get trace data from a file, in a manner reminiscent
11764 of corefiles; you specify the filename, and use @code{tfind} to search
11765 through the file. @xref{Trace Files}, for more details.
11767 This chapter describes the tracepoint commands and features.
11770 * Set Tracepoints::
11771 * Analyze Collected Data::
11772 * Tracepoint Variables::
11776 @node Set Tracepoints
11777 @section Commands to Set Tracepoints
11779 Before running such a @dfn{trace experiment}, an arbitrary number of
11780 tracepoints can be set. A tracepoint is actually a special type of
11781 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
11782 standard breakpoint commands. For instance, as with breakpoints,
11783 tracepoint numbers are successive integers starting from one, and many
11784 of the commands associated with tracepoints take the tracepoint number
11785 as their argument, to identify which tracepoint to work on.
11787 For each tracepoint, you can specify, in advance, some arbitrary set
11788 of data that you want the target to collect in the trace buffer when
11789 it hits that tracepoint. The collected data can include registers,
11790 local variables, or global data. Later, you can use @value{GDBN}
11791 commands to examine the values these data had at the time the
11792 tracepoint was hit.
11794 Tracepoints do not support every breakpoint feature. Ignore counts on
11795 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
11796 commands when they are hit. Tracepoints may not be thread-specific
11799 @cindex fast tracepoints
11800 Some targets may support @dfn{fast tracepoints}, which are inserted in
11801 a different way (such as with a jump instead of a trap), that is
11802 faster but possibly restricted in where they may be installed.
11804 @cindex static tracepoints
11805 @cindex markers, static tracepoints
11806 @cindex probing markers, static tracepoints
11807 Regular and fast tracepoints are dynamic tracing facilities, meaning
11808 that they can be used to insert tracepoints at (almost) any location
11809 in the target. Some targets may also support controlling @dfn{static
11810 tracepoints} from @value{GDBN}. With static tracing, a set of
11811 instrumentation points, also known as @dfn{markers}, are embedded in
11812 the target program, and can be activated or deactivated by name or
11813 address. These are usually placed at locations which facilitate
11814 investigating what the target is actually doing. @value{GDBN}'s
11815 support for static tracing includes being able to list instrumentation
11816 points, and attach them with @value{GDBN} defined high level
11817 tracepoints that expose the whole range of convenience of
11818 @value{GDBN}'s tracepoints support. Namely, support for collecting
11819 registers values and values of global or local (to the instrumentation
11820 point) variables; tracepoint conditions and trace state variables.
11821 The act of installing a @value{GDBN} static tracepoint on an
11822 instrumentation point, or marker, is referred to as @dfn{probing} a
11823 static tracepoint marker.
11825 @code{gdbserver} supports tracepoints on some target systems.
11826 @xref{Server,,Tracepoints support in @code{gdbserver}}.
11828 This section describes commands to set tracepoints and associated
11829 conditions and actions.
11832 * Create and Delete Tracepoints::
11833 * Enable and Disable Tracepoints::
11834 * Tracepoint Passcounts::
11835 * Tracepoint Conditions::
11836 * Trace State Variables::
11837 * Tracepoint Actions::
11838 * Listing Tracepoints::
11839 * Listing Static Tracepoint Markers::
11840 * Starting and Stopping Trace Experiments::
11841 * Tracepoint Restrictions::
11844 @node Create and Delete Tracepoints
11845 @subsection Create and Delete Tracepoints
11848 @cindex set tracepoint
11850 @item trace @var{location}
11851 The @code{trace} command is very similar to the @code{break} command.
11852 Its argument @var{location} can be a source line, a function name, or
11853 an address in the target program. @xref{Specify Location}. The
11854 @code{trace} command defines a tracepoint, which is a point in the
11855 target program where the debugger will briefly stop, collect some
11856 data, and then allow the program to continue. Setting a tracepoint or
11857 changing its actions takes effect immediately if the remote stub
11858 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
11860 If remote stub doesn't support the @samp{InstallInTrace} feature, all
11861 these changes don't take effect until the next @code{tstart}
11862 command, and once a trace experiment is running, further changes will
11863 not have any effect until the next trace experiment starts. In addition,
11864 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
11865 address is not yet resolved. (This is similar to pending breakpoints.)
11866 Pending tracepoints are not downloaded to the target and not installed
11867 until they are resolved. The resolution of pending tracepoints requires
11868 @value{GDBN} support---when debugging with the remote target, and
11869 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
11870 tracing}), pending tracepoints can not be resolved (and downloaded to
11871 the remote stub) while @value{GDBN} is disconnected.
11873 Here are some examples of using the @code{trace} command:
11876 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
11878 (@value{GDBP}) @b{trace +2} // 2 lines forward
11880 (@value{GDBP}) @b{trace my_function} // first source line of function
11882 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
11884 (@value{GDBP}) @b{trace *0x2117c4} // an address
11888 You can abbreviate @code{trace} as @code{tr}.
11890 @item trace @var{location} if @var{cond}
11891 Set a tracepoint with condition @var{cond}; evaluate the expression
11892 @var{cond} each time the tracepoint is reached, and collect data only
11893 if the value is nonzero---that is, if @var{cond} evaluates as true.
11894 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
11895 information on tracepoint conditions.
11897 @item ftrace @var{location} [ if @var{cond} ]
11898 @cindex set fast tracepoint
11899 @cindex fast tracepoints, setting
11901 The @code{ftrace} command sets a fast tracepoint. For targets that
11902 support them, fast tracepoints will use a more efficient but possibly
11903 less general technique to trigger data collection, such as a jump
11904 instruction instead of a trap, or some sort of hardware support. It
11905 may not be possible to create a fast tracepoint at the desired
11906 location, in which case the command will exit with an explanatory
11909 @value{GDBN} handles arguments to @code{ftrace} exactly as for
11912 On 32-bit x86-architecture systems, fast tracepoints normally need to
11913 be placed at an instruction that is 5 bytes or longer, but can be
11914 placed at 4-byte instructions if the low 64K of memory of the target
11915 program is available to install trampolines. Some Unix-type systems,
11916 such as @sc{gnu}/Linux, exclude low addresses from the program's
11917 address space; but for instance with the Linux kernel it is possible
11918 to let @value{GDBN} use this area by doing a @command{sysctl} command
11919 to set the @code{mmap_min_addr} kernel parameter, as in
11922 sudo sysctl -w vm.mmap_min_addr=32768
11926 which sets the low address to 32K, which leaves plenty of room for
11927 trampolines. The minimum address should be set to a page boundary.
11929 @item strace @var{location} [ if @var{cond} ]
11930 @cindex set static tracepoint
11931 @cindex static tracepoints, setting
11932 @cindex probe static tracepoint marker
11934 The @code{strace} command sets a static tracepoint. For targets that
11935 support it, setting a static tracepoint probes a static
11936 instrumentation point, or marker, found at @var{location}. It may not
11937 be possible to set a static tracepoint at the desired location, in
11938 which case the command will exit with an explanatory message.
11940 @value{GDBN} handles arguments to @code{strace} exactly as for
11941 @code{trace}, with the addition that the user can also specify
11942 @code{-m @var{marker}} as @var{location}. This probes the marker
11943 identified by the @var{marker} string identifier. This identifier
11944 depends on the static tracepoint backend library your program is
11945 using. You can find all the marker identifiers in the @samp{ID} field
11946 of the @code{info static-tracepoint-markers} command output.
11947 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
11948 Markers}. For example, in the following small program using the UST
11954 trace_mark(ust, bar33, "str %s", "FOOBAZ");
11959 the marker id is composed of joining the first two arguments to the
11960 @code{trace_mark} call with a slash, which translates to:
11963 (@value{GDBP}) info static-tracepoint-markers
11964 Cnt Enb ID Address What
11965 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
11971 so you may probe the marker above with:
11974 (@value{GDBP}) strace -m ust/bar33
11977 Static tracepoints accept an extra collect action --- @code{collect
11978 $_sdata}. This collects arbitrary user data passed in the probe point
11979 call to the tracing library. In the UST example above, you'll see
11980 that the third argument to @code{trace_mark} is a printf-like format
11981 string. The user data is then the result of running that formating
11982 string against the following arguments. Note that @code{info
11983 static-tracepoint-markers} command output lists that format string in
11984 the @samp{Data:} field.
11986 You can inspect this data when analyzing the trace buffer, by printing
11987 the $_sdata variable like any other variable available to
11988 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
11991 @cindex last tracepoint number
11992 @cindex recent tracepoint number
11993 @cindex tracepoint number
11994 The convenience variable @code{$tpnum} records the tracepoint number
11995 of the most recently set tracepoint.
11997 @kindex delete tracepoint
11998 @cindex tracepoint deletion
11999 @item delete tracepoint @r{[}@var{num}@r{]}
12000 Permanently delete one or more tracepoints. With no argument, the
12001 default is to delete all tracepoints. Note that the regular
12002 @code{delete} command can remove tracepoints also.
12007 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
12009 (@value{GDBP}) @b{delete trace} // remove all tracepoints
12013 You can abbreviate this command as @code{del tr}.
12016 @node Enable and Disable Tracepoints
12017 @subsection Enable and Disable Tracepoints
12019 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
12022 @kindex disable tracepoint
12023 @item disable tracepoint @r{[}@var{num}@r{]}
12024 Disable tracepoint @var{num}, or all tracepoints if no argument
12025 @var{num} is given. A disabled tracepoint will have no effect during
12026 a trace experiment, but it is not forgotten. You can re-enable
12027 a disabled tracepoint using the @code{enable tracepoint} command.
12028 If the command is issued during a trace experiment and the debug target
12029 has support for disabling tracepoints during a trace experiment, then the
12030 change will be effective immediately. Otherwise, it will be applied to the
12031 next trace experiment.
12033 @kindex enable tracepoint
12034 @item enable tracepoint @r{[}@var{num}@r{]}
12035 Enable tracepoint @var{num}, or all tracepoints. If this command is
12036 issued during a trace experiment and the debug target supports enabling
12037 tracepoints during a trace experiment, then the enabled tracepoints will
12038 become effective immediately. Otherwise, they will become effective the
12039 next time a trace experiment is run.
12042 @node Tracepoint Passcounts
12043 @subsection Tracepoint Passcounts
12047 @cindex tracepoint pass count
12048 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
12049 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
12050 automatically stop a trace experiment. If a tracepoint's passcount is
12051 @var{n}, then the trace experiment will be automatically stopped on
12052 the @var{n}'th time that tracepoint is hit. If the tracepoint number
12053 @var{num} is not specified, the @code{passcount} command sets the
12054 passcount of the most recently defined tracepoint. If no passcount is
12055 given, the trace experiment will run until stopped explicitly by the
12061 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
12062 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
12064 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
12065 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
12066 (@value{GDBP}) @b{trace foo}
12067 (@value{GDBP}) @b{pass 3}
12068 (@value{GDBP}) @b{trace bar}
12069 (@value{GDBP}) @b{pass 2}
12070 (@value{GDBP}) @b{trace baz}
12071 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
12072 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
12073 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
12074 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
12078 @node Tracepoint Conditions
12079 @subsection Tracepoint Conditions
12080 @cindex conditional tracepoints
12081 @cindex tracepoint conditions
12083 The simplest sort of tracepoint collects data every time your program
12084 reaches a specified place. You can also specify a @dfn{condition} for
12085 a tracepoint. A condition is just a Boolean expression in your
12086 programming language (@pxref{Expressions, ,Expressions}). A
12087 tracepoint with a condition evaluates the expression each time your
12088 program reaches it, and data collection happens only if the condition
12091 Tracepoint conditions can be specified when a tracepoint is set, by
12092 using @samp{if} in the arguments to the @code{trace} command.
12093 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
12094 also be set or changed at any time with the @code{condition} command,
12095 just as with breakpoints.
12097 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
12098 the conditional expression itself. Instead, @value{GDBN} encodes the
12099 expression into an agent expression (@pxref{Agent Expressions})
12100 suitable for execution on the target, independently of @value{GDBN}.
12101 Global variables become raw memory locations, locals become stack
12102 accesses, and so forth.
12104 For instance, suppose you have a function that is usually called
12105 frequently, but should not be called after an error has occurred. You
12106 could use the following tracepoint command to collect data about calls
12107 of that function that happen while the error code is propagating
12108 through the program; an unconditional tracepoint could end up
12109 collecting thousands of useless trace frames that you would have to
12113 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
12116 @node Trace State Variables
12117 @subsection Trace State Variables
12118 @cindex trace state variables
12120 A @dfn{trace state variable} is a special type of variable that is
12121 created and managed by target-side code. The syntax is the same as
12122 that for GDB's convenience variables (a string prefixed with ``$''),
12123 but they are stored on the target. They must be created explicitly,
12124 using a @code{tvariable} command. They are always 64-bit signed
12127 Trace state variables are remembered by @value{GDBN}, and downloaded
12128 to the target along with tracepoint information when the trace
12129 experiment starts. There are no intrinsic limits on the number of
12130 trace state variables, beyond memory limitations of the target.
12132 @cindex convenience variables, and trace state variables
12133 Although trace state variables are managed by the target, you can use
12134 them in print commands and expressions as if they were convenience
12135 variables; @value{GDBN} will get the current value from the target
12136 while the trace experiment is running. Trace state variables share
12137 the same namespace as other ``$'' variables, which means that you
12138 cannot have trace state variables with names like @code{$23} or
12139 @code{$pc}, nor can you have a trace state variable and a convenience
12140 variable with the same name.
12144 @item tvariable $@var{name} [ = @var{expression} ]
12146 The @code{tvariable} command creates a new trace state variable named
12147 @code{$@var{name}}, and optionally gives it an initial value of
12148 @var{expression}. The @var{expression} is evaluated when this command is
12149 entered; the result will be converted to an integer if possible,
12150 otherwise @value{GDBN} will report an error. A subsequent
12151 @code{tvariable} command specifying the same name does not create a
12152 variable, but instead assigns the supplied initial value to the
12153 existing variable of that name, overwriting any previous initial
12154 value. The default initial value is 0.
12156 @item info tvariables
12157 @kindex info tvariables
12158 List all the trace state variables along with their initial values.
12159 Their current values may also be displayed, if the trace experiment is
12162 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
12163 @kindex delete tvariable
12164 Delete the given trace state variables, or all of them if no arguments
12169 @node Tracepoint Actions
12170 @subsection Tracepoint Action Lists
12174 @cindex tracepoint actions
12175 @item actions @r{[}@var{num}@r{]}
12176 This command will prompt for a list of actions to be taken when the
12177 tracepoint is hit. If the tracepoint number @var{num} is not
12178 specified, this command sets the actions for the one that was most
12179 recently defined (so that you can define a tracepoint and then say
12180 @code{actions} without bothering about its number). You specify the
12181 actions themselves on the following lines, one action at a time, and
12182 terminate the actions list with a line containing just @code{end}. So
12183 far, the only defined actions are @code{collect}, @code{teval}, and
12184 @code{while-stepping}.
12186 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
12187 Commands, ,Breakpoint Command Lists}), except that only the defined
12188 actions are allowed; any other @value{GDBN} command is rejected.
12190 @cindex remove actions from a tracepoint
12191 To remove all actions from a tracepoint, type @samp{actions @var{num}}
12192 and follow it immediately with @samp{end}.
12195 (@value{GDBP}) @b{collect @var{data}} // collect some data
12197 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
12199 (@value{GDBP}) @b{end} // signals the end of actions.
12202 In the following example, the action list begins with @code{collect}
12203 commands indicating the things to be collected when the tracepoint is
12204 hit. Then, in order to single-step and collect additional data
12205 following the tracepoint, a @code{while-stepping} command is used,
12206 followed by the list of things to be collected after each step in a
12207 sequence of single steps. The @code{while-stepping} command is
12208 terminated by its own separate @code{end} command. Lastly, the action
12209 list is terminated by an @code{end} command.
12212 (@value{GDBP}) @b{trace foo}
12213 (@value{GDBP}) @b{actions}
12214 Enter actions for tracepoint 1, one per line:
12217 > while-stepping 12
12218 > collect $pc, arr[i]
12223 @kindex collect @r{(tracepoints)}
12224 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
12225 Collect values of the given expressions when the tracepoint is hit.
12226 This command accepts a comma-separated list of any valid expressions.
12227 In addition to global, static, or local variables, the following
12228 special arguments are supported:
12232 Collect all registers.
12235 Collect all function arguments.
12238 Collect all local variables.
12241 Collect the return address. This is helpful if you want to see more
12245 Collects the number of arguments from the static probe at which the
12246 tracepoint is located.
12247 @xref{Static Probe Points}.
12249 @item $_probe_arg@var{n}
12250 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
12251 from the static probe at which the tracepoint is located.
12252 @xref{Static Probe Points}.
12255 @vindex $_sdata@r{, collect}
12256 Collect static tracepoint marker specific data. Only available for
12257 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
12258 Lists}. On the UST static tracepoints library backend, an
12259 instrumentation point resembles a @code{printf} function call. The
12260 tracing library is able to collect user specified data formatted to a
12261 character string using the format provided by the programmer that
12262 instrumented the program. Other backends have similar mechanisms.
12263 Here's an example of a UST marker call:
12266 const char master_name[] = "$your_name";
12267 trace_mark(channel1, marker1, "hello %s", master_name)
12270 In this case, collecting @code{$_sdata} collects the string
12271 @samp{hello $yourname}. When analyzing the trace buffer, you can
12272 inspect @samp{$_sdata} like any other variable available to
12276 You can give several consecutive @code{collect} commands, each one
12277 with a single argument, or one @code{collect} command with several
12278 arguments separated by commas; the effect is the same.
12280 The optional @var{mods} changes the usual handling of the arguments.
12281 @code{s} requests that pointers to chars be handled as strings, in
12282 particular collecting the contents of the memory being pointed at, up
12283 to the first zero. The upper bound is by default the value of the
12284 @code{print elements} variable; if @code{s} is followed by a decimal
12285 number, that is the upper bound instead. So for instance
12286 @samp{collect/s25 mystr} collects as many as 25 characters at
12289 The command @code{info scope} (@pxref{Symbols, info scope}) is
12290 particularly useful for figuring out what data to collect.
12292 @kindex teval @r{(tracepoints)}
12293 @item teval @var{expr1}, @var{expr2}, @dots{}
12294 Evaluate the given expressions when the tracepoint is hit. This
12295 command accepts a comma-separated list of expressions. The results
12296 are discarded, so this is mainly useful for assigning values to trace
12297 state variables (@pxref{Trace State Variables}) without adding those
12298 values to the trace buffer, as would be the case if the @code{collect}
12301 @kindex while-stepping @r{(tracepoints)}
12302 @item while-stepping @var{n}
12303 Perform @var{n} single-step instruction traces after the tracepoint,
12304 collecting new data after each step. The @code{while-stepping}
12305 command is followed by the list of what to collect while stepping
12306 (followed by its own @code{end} command):
12309 > while-stepping 12
12310 > collect $regs, myglobal
12316 Note that @code{$pc} is not automatically collected by
12317 @code{while-stepping}; you need to explicitly collect that register if
12318 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
12321 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
12322 @kindex set default-collect
12323 @cindex default collection action
12324 This variable is a list of expressions to collect at each tracepoint
12325 hit. It is effectively an additional @code{collect} action prepended
12326 to every tracepoint action list. The expressions are parsed
12327 individually for each tracepoint, so for instance a variable named
12328 @code{xyz} may be interpreted as a global for one tracepoint, and a
12329 local for another, as appropriate to the tracepoint's location.
12331 @item show default-collect
12332 @kindex show default-collect
12333 Show the list of expressions that are collected by default at each
12338 @node Listing Tracepoints
12339 @subsection Listing Tracepoints
12342 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
12343 @kindex info tp @r{[}@var{n}@dots{}@r{]}
12344 @cindex information about tracepoints
12345 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
12346 Display information about the tracepoint @var{num}. If you don't
12347 specify a tracepoint number, displays information about all the
12348 tracepoints defined so far. The format is similar to that used for
12349 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
12350 command, simply restricting itself to tracepoints.
12352 A tracepoint's listing may include additional information specific to
12357 its passcount as given by the @code{passcount @var{n}} command
12360 the state about installed on target of each location
12364 (@value{GDBP}) @b{info trace}
12365 Num Type Disp Enb Address What
12366 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
12368 collect globfoo, $regs
12373 2 tracepoint keep y <MULTIPLE>
12375 2.1 y 0x0804859c in func4 at change-loc.h:35
12376 installed on target
12377 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
12378 installed on target
12379 2.3 y <PENDING> set_tracepoint
12380 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
12381 not installed on target
12386 This command can be abbreviated @code{info tp}.
12389 @node Listing Static Tracepoint Markers
12390 @subsection Listing Static Tracepoint Markers
12393 @kindex info static-tracepoint-markers
12394 @cindex information about static tracepoint markers
12395 @item info static-tracepoint-markers
12396 Display information about all static tracepoint markers defined in the
12399 For each marker, the following columns are printed:
12403 An incrementing counter, output to help readability. This is not a
12406 The marker ID, as reported by the target.
12407 @item Enabled or Disabled
12408 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
12409 that are not enabled.
12411 Where the marker is in your program, as a memory address.
12413 Where the marker is in the source for your program, as a file and line
12414 number. If the debug information included in the program does not
12415 allow @value{GDBN} to locate the source of the marker, this column
12416 will be left blank.
12420 In addition, the following information may be printed for each marker:
12424 User data passed to the tracing library by the marker call. In the
12425 UST backend, this is the format string passed as argument to the
12427 @item Static tracepoints probing the marker
12428 The list of static tracepoints attached to the marker.
12432 (@value{GDBP}) info static-tracepoint-markers
12433 Cnt ID Enb Address What
12434 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
12435 Data: number1 %d number2 %d
12436 Probed by static tracepoints: #2
12437 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
12443 @node Starting and Stopping Trace Experiments
12444 @subsection Starting and Stopping Trace Experiments
12447 @kindex tstart [ @var{notes} ]
12448 @cindex start a new trace experiment
12449 @cindex collected data discarded
12451 This command starts the trace experiment, and begins collecting data.
12452 It has the side effect of discarding all the data collected in the
12453 trace buffer during the previous trace experiment. If any arguments
12454 are supplied, they are taken as a note and stored with the trace
12455 experiment's state. The notes may be arbitrary text, and are
12456 especially useful with disconnected tracing in a multi-user context;
12457 the notes can explain what the trace is doing, supply user contact
12458 information, and so forth.
12460 @kindex tstop [ @var{notes} ]
12461 @cindex stop a running trace experiment
12463 This command stops the trace experiment. If any arguments are
12464 supplied, they are recorded with the experiment as a note. This is
12465 useful if you are stopping a trace started by someone else, for
12466 instance if the trace is interfering with the system's behavior and
12467 needs to be stopped quickly.
12469 @strong{Note}: a trace experiment and data collection may stop
12470 automatically if any tracepoint's passcount is reached
12471 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
12474 @cindex status of trace data collection
12475 @cindex trace experiment, status of
12477 This command displays the status of the current trace data
12481 Here is an example of the commands we described so far:
12484 (@value{GDBP}) @b{trace gdb_c_test}
12485 (@value{GDBP}) @b{actions}
12486 Enter actions for tracepoint #1, one per line.
12487 > collect $regs,$locals,$args
12488 > while-stepping 11
12492 (@value{GDBP}) @b{tstart}
12493 [time passes @dots{}]
12494 (@value{GDBP}) @b{tstop}
12497 @anchor{disconnected tracing}
12498 @cindex disconnected tracing
12499 You can choose to continue running the trace experiment even if
12500 @value{GDBN} disconnects from the target, voluntarily or
12501 involuntarily. For commands such as @code{detach}, the debugger will
12502 ask what you want to do with the trace. But for unexpected
12503 terminations (@value{GDBN} crash, network outage), it would be
12504 unfortunate to lose hard-won trace data, so the variable
12505 @code{disconnected-tracing} lets you decide whether the trace should
12506 continue running without @value{GDBN}.
12509 @item set disconnected-tracing on
12510 @itemx set disconnected-tracing off
12511 @kindex set disconnected-tracing
12512 Choose whether a tracing run should continue to run if @value{GDBN}
12513 has disconnected from the target. Note that @code{detach} or
12514 @code{quit} will ask you directly what to do about a running trace no
12515 matter what this variable's setting, so the variable is mainly useful
12516 for handling unexpected situations, such as loss of the network.
12518 @item show disconnected-tracing
12519 @kindex show disconnected-tracing
12520 Show the current choice for disconnected tracing.
12524 When you reconnect to the target, the trace experiment may or may not
12525 still be running; it might have filled the trace buffer in the
12526 meantime, or stopped for one of the other reasons. If it is running,
12527 it will continue after reconnection.
12529 Upon reconnection, the target will upload information about the
12530 tracepoints in effect. @value{GDBN} will then compare that
12531 information to the set of tracepoints currently defined, and attempt
12532 to match them up, allowing for the possibility that the numbers may
12533 have changed due to creation and deletion in the meantime. If one of
12534 the target's tracepoints does not match any in @value{GDBN}, the
12535 debugger will create a new tracepoint, so that you have a number with
12536 which to specify that tracepoint. This matching-up process is
12537 necessarily heuristic, and it may result in useless tracepoints being
12538 created; you may simply delete them if they are of no use.
12540 @cindex circular trace buffer
12541 If your target agent supports a @dfn{circular trace buffer}, then you
12542 can run a trace experiment indefinitely without filling the trace
12543 buffer; when space runs out, the agent deletes already-collected trace
12544 frames, oldest first, until there is enough room to continue
12545 collecting. This is especially useful if your tracepoints are being
12546 hit too often, and your trace gets terminated prematurely because the
12547 buffer is full. To ask for a circular trace buffer, simply set
12548 @samp{circular-trace-buffer} to on. You can set this at any time,
12549 including during tracing; if the agent can do it, it will change
12550 buffer handling on the fly, otherwise it will not take effect until
12554 @item set circular-trace-buffer on
12555 @itemx set circular-trace-buffer off
12556 @kindex set circular-trace-buffer
12557 Choose whether a tracing run should use a linear or circular buffer
12558 for trace data. A linear buffer will not lose any trace data, but may
12559 fill up prematurely, while a circular buffer will discard old trace
12560 data, but it will have always room for the latest tracepoint hits.
12562 @item show circular-trace-buffer
12563 @kindex show circular-trace-buffer
12564 Show the current choice for the trace buffer. Note that this may not
12565 match the agent's current buffer handling, nor is it guaranteed to
12566 match the setting that might have been in effect during a past run,
12567 for instance if you are looking at frames from a trace file.
12572 @item set trace-buffer-size @var{n}
12573 @itemx set trace-buffer-size unlimited
12574 @kindex set trace-buffer-size
12575 Request that the target use a trace buffer of @var{n} bytes. Not all
12576 targets will honor the request; they may have a compiled-in size for
12577 the trace buffer, or some other limitation. Set to a value of
12578 @code{unlimited} or @code{-1} to let the target use whatever size it
12579 likes. This is also the default.
12581 @item show trace-buffer-size
12582 @kindex show trace-buffer-size
12583 Show the current requested size for the trace buffer. Note that this
12584 will only match the actual size if the target supports size-setting,
12585 and was able to handle the requested size. For instance, if the
12586 target can only change buffer size between runs, this variable will
12587 not reflect the change until the next run starts. Use @code{tstatus}
12588 to get a report of the actual buffer size.
12592 @item set trace-user @var{text}
12593 @kindex set trace-user
12595 @item show trace-user
12596 @kindex show trace-user
12598 @item set trace-notes @var{text}
12599 @kindex set trace-notes
12600 Set the trace run's notes.
12602 @item show trace-notes
12603 @kindex show trace-notes
12604 Show the trace run's notes.
12606 @item set trace-stop-notes @var{text}
12607 @kindex set trace-stop-notes
12608 Set the trace run's stop notes. The handling of the note is as for
12609 @code{tstop} arguments; the set command is convenient way to fix a
12610 stop note that is mistaken or incomplete.
12612 @item show trace-stop-notes
12613 @kindex show trace-stop-notes
12614 Show the trace run's stop notes.
12618 @node Tracepoint Restrictions
12619 @subsection Tracepoint Restrictions
12621 @cindex tracepoint restrictions
12622 There are a number of restrictions on the use of tracepoints. As
12623 described above, tracepoint data gathering occurs on the target
12624 without interaction from @value{GDBN}. Thus the full capabilities of
12625 the debugger are not available during data gathering, and then at data
12626 examination time, you will be limited by only having what was
12627 collected. The following items describe some common problems, but it
12628 is not exhaustive, and you may run into additional difficulties not
12634 Tracepoint expressions are intended to gather objects (lvalues). Thus
12635 the full flexibility of GDB's expression evaluator is not available.
12636 You cannot call functions, cast objects to aggregate types, access
12637 convenience variables or modify values (except by assignment to trace
12638 state variables). Some language features may implicitly call
12639 functions (for instance Objective-C fields with accessors), and therefore
12640 cannot be collected either.
12643 Collection of local variables, either individually or in bulk with
12644 @code{$locals} or @code{$args}, during @code{while-stepping} may
12645 behave erratically. The stepping action may enter a new scope (for
12646 instance by stepping into a function), or the location of the variable
12647 may change (for instance it is loaded into a register). The
12648 tracepoint data recorded uses the location information for the
12649 variables that is correct for the tracepoint location. When the
12650 tracepoint is created, it is not possible, in general, to determine
12651 where the steps of a @code{while-stepping} sequence will advance the
12652 program---particularly if a conditional branch is stepped.
12655 Collection of an incompletely-initialized or partially-destroyed object
12656 may result in something that @value{GDBN} cannot display, or displays
12657 in a misleading way.
12660 When @value{GDBN} displays a pointer to character it automatically
12661 dereferences the pointer to also display characters of the string
12662 being pointed to. However, collecting the pointer during tracing does
12663 not automatically collect the string. You need to explicitly
12664 dereference the pointer and provide size information if you want to
12665 collect not only the pointer, but the memory pointed to. For example,
12666 @code{*ptr@@50} can be used to collect the 50 element array pointed to
12670 It is not possible to collect a complete stack backtrace at a
12671 tracepoint. Instead, you may collect the registers and a few hundred
12672 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
12673 (adjust to use the name of the actual stack pointer register on your
12674 target architecture, and the amount of stack you wish to capture).
12675 Then the @code{backtrace} command will show a partial backtrace when
12676 using a trace frame. The number of stack frames that can be examined
12677 depends on the sizes of the frames in the collected stack. Note that
12678 if you ask for a block so large that it goes past the bottom of the
12679 stack, the target agent may report an error trying to read from an
12683 If you do not collect registers at a tracepoint, @value{GDBN} can
12684 infer that the value of @code{$pc} must be the same as the address of
12685 the tracepoint and use that when you are looking at a trace frame
12686 for that tracepoint. However, this cannot work if the tracepoint has
12687 multiple locations (for instance if it was set in a function that was
12688 inlined), or if it has a @code{while-stepping} loop. In those cases
12689 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
12694 @node Analyze Collected Data
12695 @section Using the Collected Data
12697 After the tracepoint experiment ends, you use @value{GDBN} commands
12698 for examining the trace data. The basic idea is that each tracepoint
12699 collects a trace @dfn{snapshot} every time it is hit and another
12700 snapshot every time it single-steps. All these snapshots are
12701 consecutively numbered from zero and go into a buffer, and you can
12702 examine them later. The way you examine them is to @dfn{focus} on a
12703 specific trace snapshot. When the remote stub is focused on a trace
12704 snapshot, it will respond to all @value{GDBN} requests for memory and
12705 registers by reading from the buffer which belongs to that snapshot,
12706 rather than from @emph{real} memory or registers of the program being
12707 debugged. This means that @strong{all} @value{GDBN} commands
12708 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
12709 behave as if we were currently debugging the program state as it was
12710 when the tracepoint occurred. Any requests for data that are not in
12711 the buffer will fail.
12714 * tfind:: How to select a trace snapshot
12715 * tdump:: How to display all data for a snapshot
12716 * save tracepoints:: How to save tracepoints for a future run
12720 @subsection @code{tfind @var{n}}
12723 @cindex select trace snapshot
12724 @cindex find trace snapshot
12725 The basic command for selecting a trace snapshot from the buffer is
12726 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
12727 counting from zero. If no argument @var{n} is given, the next
12728 snapshot is selected.
12730 Here are the various forms of using the @code{tfind} command.
12734 Find the first snapshot in the buffer. This is a synonym for
12735 @code{tfind 0} (since 0 is the number of the first snapshot).
12738 Stop debugging trace snapshots, resume @emph{live} debugging.
12741 Same as @samp{tfind none}.
12744 No argument means find the next trace snapshot.
12747 Find the previous trace snapshot before the current one. This permits
12748 retracing earlier steps.
12750 @item tfind tracepoint @var{num}
12751 Find the next snapshot associated with tracepoint @var{num}. Search
12752 proceeds forward from the last examined trace snapshot. If no
12753 argument @var{num} is given, it means find the next snapshot collected
12754 for the same tracepoint as the current snapshot.
12756 @item tfind pc @var{addr}
12757 Find the next snapshot associated with the value @var{addr} of the
12758 program counter. Search proceeds forward from the last examined trace
12759 snapshot. If no argument @var{addr} is given, it means find the next
12760 snapshot with the same value of PC as the current snapshot.
12762 @item tfind outside @var{addr1}, @var{addr2}
12763 Find the next snapshot whose PC is outside the given range of
12764 addresses (exclusive).
12766 @item tfind range @var{addr1}, @var{addr2}
12767 Find the next snapshot whose PC is between @var{addr1} and
12768 @var{addr2} (inclusive).
12770 @item tfind line @r{[}@var{file}:@r{]}@var{n}
12771 Find the next snapshot associated with the source line @var{n}. If
12772 the optional argument @var{file} is given, refer to line @var{n} in
12773 that source file. Search proceeds forward from the last examined
12774 trace snapshot. If no argument @var{n} is given, it means find the
12775 next line other than the one currently being examined; thus saying
12776 @code{tfind line} repeatedly can appear to have the same effect as
12777 stepping from line to line in a @emph{live} debugging session.
12780 The default arguments for the @code{tfind} commands are specifically
12781 designed to make it easy to scan through the trace buffer. For
12782 instance, @code{tfind} with no argument selects the next trace
12783 snapshot, and @code{tfind -} with no argument selects the previous
12784 trace snapshot. So, by giving one @code{tfind} command, and then
12785 simply hitting @key{RET} repeatedly you can examine all the trace
12786 snapshots in order. Or, by saying @code{tfind -} and then hitting
12787 @key{RET} repeatedly you can examine the snapshots in reverse order.
12788 The @code{tfind line} command with no argument selects the snapshot
12789 for the next source line executed. The @code{tfind pc} command with
12790 no argument selects the next snapshot with the same program counter
12791 (PC) as the current frame. The @code{tfind tracepoint} command with
12792 no argument selects the next trace snapshot collected by the same
12793 tracepoint as the current one.
12795 In addition to letting you scan through the trace buffer manually,
12796 these commands make it easy to construct @value{GDBN} scripts that
12797 scan through the trace buffer and print out whatever collected data
12798 you are interested in. Thus, if we want to examine the PC, FP, and SP
12799 registers from each trace frame in the buffer, we can say this:
12802 (@value{GDBP}) @b{tfind start}
12803 (@value{GDBP}) @b{while ($trace_frame != -1)}
12804 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
12805 $trace_frame, $pc, $sp, $fp
12809 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
12810 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
12811 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
12812 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
12813 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
12814 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
12815 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
12816 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
12817 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
12818 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
12819 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
12822 Or, if we want to examine the variable @code{X} at each source line in
12826 (@value{GDBP}) @b{tfind start}
12827 (@value{GDBP}) @b{while ($trace_frame != -1)}
12828 > printf "Frame %d, X == %d\n", $trace_frame, X
12838 @subsection @code{tdump}
12840 @cindex dump all data collected at tracepoint
12841 @cindex tracepoint data, display
12843 This command takes no arguments. It prints all the data collected at
12844 the current trace snapshot.
12847 (@value{GDBP}) @b{trace 444}
12848 (@value{GDBP}) @b{actions}
12849 Enter actions for tracepoint #2, one per line:
12850 > collect $regs, $locals, $args, gdb_long_test
12853 (@value{GDBP}) @b{tstart}
12855 (@value{GDBP}) @b{tfind line 444}
12856 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
12858 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
12860 (@value{GDBP}) @b{tdump}
12861 Data collected at tracepoint 2, trace frame 1:
12862 d0 0xc4aa0085 -995491707
12866 d4 0x71aea3d 119204413
12869 d7 0x380035 3670069
12870 a0 0x19e24a 1696330
12871 a1 0x3000668 50333288
12873 a3 0x322000 3284992
12874 a4 0x3000698 50333336
12875 a5 0x1ad3cc 1758156
12876 fp 0x30bf3c 0x30bf3c
12877 sp 0x30bf34 0x30bf34
12879 pc 0x20b2c8 0x20b2c8
12883 p = 0x20e5b4 "gdb-test"
12890 gdb_long_test = 17 '\021'
12895 @code{tdump} works by scanning the tracepoint's current collection
12896 actions and printing the value of each expression listed. So
12897 @code{tdump} can fail, if after a run, you change the tracepoint's
12898 actions to mention variables that were not collected during the run.
12900 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
12901 uses the collected value of @code{$pc} to distinguish between trace
12902 frames that were collected at the tracepoint hit, and frames that were
12903 collected while stepping. This allows it to correctly choose whether
12904 to display the basic list of collections, or the collections from the
12905 body of the while-stepping loop. However, if @code{$pc} was not collected,
12906 then @code{tdump} will always attempt to dump using the basic collection
12907 list, and may fail if a while-stepping frame does not include all the
12908 same data that is collected at the tracepoint hit.
12909 @c This is getting pretty arcane, example would be good.
12911 @node save tracepoints
12912 @subsection @code{save tracepoints @var{filename}}
12913 @kindex save tracepoints
12914 @kindex save-tracepoints
12915 @cindex save tracepoints for future sessions
12917 This command saves all current tracepoint definitions together with
12918 their actions and passcounts, into a file @file{@var{filename}}
12919 suitable for use in a later debugging session. To read the saved
12920 tracepoint definitions, use the @code{source} command (@pxref{Command
12921 Files}). The @w{@code{save-tracepoints}} command is a deprecated
12922 alias for @w{@code{save tracepoints}}
12924 @node Tracepoint Variables
12925 @section Convenience Variables for Tracepoints
12926 @cindex tracepoint variables
12927 @cindex convenience variables for tracepoints
12930 @vindex $trace_frame
12931 @item (int) $trace_frame
12932 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
12933 snapshot is selected.
12935 @vindex $tracepoint
12936 @item (int) $tracepoint
12937 The tracepoint for the current trace snapshot.
12939 @vindex $trace_line
12940 @item (int) $trace_line
12941 The line number for the current trace snapshot.
12943 @vindex $trace_file
12944 @item (char []) $trace_file
12945 The source file for the current trace snapshot.
12947 @vindex $trace_func
12948 @item (char []) $trace_func
12949 The name of the function containing @code{$tracepoint}.
12952 Note: @code{$trace_file} is not suitable for use in @code{printf},
12953 use @code{output} instead.
12955 Here's a simple example of using these convenience variables for
12956 stepping through all the trace snapshots and printing some of their
12957 data. Note that these are not the same as trace state variables,
12958 which are managed by the target.
12961 (@value{GDBP}) @b{tfind start}
12963 (@value{GDBP}) @b{while $trace_frame != -1}
12964 > output $trace_file
12965 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
12971 @section Using Trace Files
12972 @cindex trace files
12974 In some situations, the target running a trace experiment may no
12975 longer be available; perhaps it crashed, or the hardware was needed
12976 for a different activity. To handle these cases, you can arrange to
12977 dump the trace data into a file, and later use that file as a source
12978 of trace data, via the @code{target tfile} command.
12983 @item tsave [ -r ] @var{filename}
12984 @itemx tsave [-ctf] @var{dirname}
12985 Save the trace data to @var{filename}. By default, this command
12986 assumes that @var{filename} refers to the host filesystem, so if
12987 necessary @value{GDBN} will copy raw trace data up from the target and
12988 then save it. If the target supports it, you can also supply the
12989 optional argument @code{-r} (``remote'') to direct the target to save
12990 the data directly into @var{filename} in its own filesystem, which may be
12991 more efficient if the trace buffer is very large. (Note, however, that
12992 @code{target tfile} can only read from files accessible to the host.)
12993 By default, this command will save trace frame in tfile format.
12994 You can supply the optional argument @code{-ctf} to save date in CTF
12995 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
12996 that can be shared by multiple debugging and tracing tools. Please go to
12997 @indicateurl{http://www.efficios.com/ctf} to get more information.
12999 @kindex target tfile
13003 @item target tfile @var{filename}
13004 @itemx target ctf @var{dirname}
13005 Use the file named @var{filename} or directory named @var{dirname} as
13006 a source of trace data. Commands that examine data work as they do with
13007 a live target, but it is not possible to run any new trace experiments.
13008 @code{tstatus} will report the state of the trace run at the moment
13009 the data was saved, as well as the current trace frame you are examining.
13010 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
13014 (@value{GDBP}) target ctf ctf.ctf
13015 (@value{GDBP}) tfind
13016 Found trace frame 0, tracepoint 2
13017 39 ++a; /* set tracepoint 1 here */
13018 (@value{GDBP}) tdump
13019 Data collected at tracepoint 2, trace frame 0:
13023 c = @{"123", "456", "789", "123", "456", "789"@}
13024 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
13032 @chapter Debugging Programs That Use Overlays
13035 If your program is too large to fit completely in your target system's
13036 memory, you can sometimes use @dfn{overlays} to work around this
13037 problem. @value{GDBN} provides some support for debugging programs that
13041 * How Overlays Work:: A general explanation of overlays.
13042 * Overlay Commands:: Managing overlays in @value{GDBN}.
13043 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
13044 mapped by asking the inferior.
13045 * Overlay Sample Program:: A sample program using overlays.
13048 @node How Overlays Work
13049 @section How Overlays Work
13050 @cindex mapped overlays
13051 @cindex unmapped overlays
13052 @cindex load address, overlay's
13053 @cindex mapped address
13054 @cindex overlay area
13056 Suppose you have a computer whose instruction address space is only 64
13057 kilobytes long, but which has much more memory which can be accessed by
13058 other means: special instructions, segment registers, or memory
13059 management hardware, for example. Suppose further that you want to
13060 adapt a program which is larger than 64 kilobytes to run on this system.
13062 One solution is to identify modules of your program which are relatively
13063 independent, and need not call each other directly; call these modules
13064 @dfn{overlays}. Separate the overlays from the main program, and place
13065 their machine code in the larger memory. Place your main program in
13066 instruction memory, but leave at least enough space there to hold the
13067 largest overlay as well.
13069 Now, to call a function located in an overlay, you must first copy that
13070 overlay's machine code from the large memory into the space set aside
13071 for it in the instruction memory, and then jump to its entry point
13074 @c NB: In the below the mapped area's size is greater or equal to the
13075 @c size of all overlays. This is intentional to remind the developer
13076 @c that overlays don't necessarily need to be the same size.
13080 Data Instruction Larger
13081 Address Space Address Space Address Space
13082 +-----------+ +-----------+ +-----------+
13084 +-----------+ +-----------+ +-----------+<-- overlay 1
13085 | program | | main | .----| overlay 1 | load address
13086 | variables | | program | | +-----------+
13087 | and heap | | | | | |
13088 +-----------+ | | | +-----------+<-- overlay 2
13089 | | +-----------+ | | | load address
13090 +-----------+ | | | .-| overlay 2 |
13092 mapped --->+-----------+ | | +-----------+
13093 address | | | | | |
13094 | overlay | <-' | | |
13095 | area | <---' +-----------+<-- overlay 3
13096 | | <---. | | load address
13097 +-----------+ `--| overlay 3 |
13104 @anchor{A code overlay}A code overlay
13108 The diagram (@pxref{A code overlay}) shows a system with separate data
13109 and instruction address spaces. To map an overlay, the program copies
13110 its code from the larger address space to the instruction address space.
13111 Since the overlays shown here all use the same mapped address, only one
13112 may be mapped at a time. For a system with a single address space for
13113 data and instructions, the diagram would be similar, except that the
13114 program variables and heap would share an address space with the main
13115 program and the overlay area.
13117 An overlay loaded into instruction memory and ready for use is called a
13118 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
13119 instruction memory. An overlay not present (or only partially present)
13120 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
13121 is its address in the larger memory. The mapped address is also called
13122 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
13123 called the @dfn{load memory address}, or @dfn{LMA}.
13125 Unfortunately, overlays are not a completely transparent way to adapt a
13126 program to limited instruction memory. They introduce a new set of
13127 global constraints you must keep in mind as you design your program:
13132 Before calling or returning to a function in an overlay, your program
13133 must make sure that overlay is actually mapped. Otherwise, the call or
13134 return will transfer control to the right address, but in the wrong
13135 overlay, and your program will probably crash.
13138 If the process of mapping an overlay is expensive on your system, you
13139 will need to choose your overlays carefully to minimize their effect on
13140 your program's performance.
13143 The executable file you load onto your system must contain each
13144 overlay's instructions, appearing at the overlay's load address, not its
13145 mapped address. However, each overlay's instructions must be relocated
13146 and its symbols defined as if the overlay were at its mapped address.
13147 You can use GNU linker scripts to specify different load and relocation
13148 addresses for pieces of your program; see @ref{Overlay Description,,,
13149 ld.info, Using ld: the GNU linker}.
13152 The procedure for loading executable files onto your system must be able
13153 to load their contents into the larger address space as well as the
13154 instruction and data spaces.
13158 The overlay system described above is rather simple, and could be
13159 improved in many ways:
13164 If your system has suitable bank switch registers or memory management
13165 hardware, you could use those facilities to make an overlay's load area
13166 contents simply appear at their mapped address in instruction space.
13167 This would probably be faster than copying the overlay to its mapped
13168 area in the usual way.
13171 If your overlays are small enough, you could set aside more than one
13172 overlay area, and have more than one overlay mapped at a time.
13175 You can use overlays to manage data, as well as instructions. In
13176 general, data overlays are even less transparent to your design than
13177 code overlays: whereas code overlays only require care when you call or
13178 return to functions, data overlays require care every time you access
13179 the data. Also, if you change the contents of a data overlay, you
13180 must copy its contents back out to its load address before you can copy a
13181 different data overlay into the same mapped area.
13186 @node Overlay Commands
13187 @section Overlay Commands
13189 To use @value{GDBN}'s overlay support, each overlay in your program must
13190 correspond to a separate section of the executable file. The section's
13191 virtual memory address and load memory address must be the overlay's
13192 mapped and load addresses. Identifying overlays with sections allows
13193 @value{GDBN} to determine the appropriate address of a function or
13194 variable, depending on whether the overlay is mapped or not.
13196 @value{GDBN}'s overlay commands all start with the word @code{overlay};
13197 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
13202 Disable @value{GDBN}'s overlay support. When overlay support is
13203 disabled, @value{GDBN} assumes that all functions and variables are
13204 always present at their mapped addresses. By default, @value{GDBN}'s
13205 overlay support is disabled.
13207 @item overlay manual
13208 @cindex manual overlay debugging
13209 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
13210 relies on you to tell it which overlays are mapped, and which are not,
13211 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
13212 commands described below.
13214 @item overlay map-overlay @var{overlay}
13215 @itemx overlay map @var{overlay}
13216 @cindex map an overlay
13217 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
13218 be the name of the object file section containing the overlay. When an
13219 overlay is mapped, @value{GDBN} assumes it can find the overlay's
13220 functions and variables at their mapped addresses. @value{GDBN} assumes
13221 that any other overlays whose mapped ranges overlap that of
13222 @var{overlay} are now unmapped.
13224 @item overlay unmap-overlay @var{overlay}
13225 @itemx overlay unmap @var{overlay}
13226 @cindex unmap an overlay
13227 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
13228 must be the name of the object file section containing the overlay.
13229 When an overlay is unmapped, @value{GDBN} assumes it can find the
13230 overlay's functions and variables at their load addresses.
13233 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
13234 consults a data structure the overlay manager maintains in the inferior
13235 to see which overlays are mapped. For details, see @ref{Automatic
13236 Overlay Debugging}.
13238 @item overlay load-target
13239 @itemx overlay load
13240 @cindex reloading the overlay table
13241 Re-read the overlay table from the inferior. Normally, @value{GDBN}
13242 re-reads the table @value{GDBN} automatically each time the inferior
13243 stops, so this command should only be necessary if you have changed the
13244 overlay mapping yourself using @value{GDBN}. This command is only
13245 useful when using automatic overlay debugging.
13247 @item overlay list-overlays
13248 @itemx overlay list
13249 @cindex listing mapped overlays
13250 Display a list of the overlays currently mapped, along with their mapped
13251 addresses, load addresses, and sizes.
13255 Normally, when @value{GDBN} prints a code address, it includes the name
13256 of the function the address falls in:
13259 (@value{GDBP}) print main
13260 $3 = @{int ()@} 0x11a0 <main>
13263 When overlay debugging is enabled, @value{GDBN} recognizes code in
13264 unmapped overlays, and prints the names of unmapped functions with
13265 asterisks around them. For example, if @code{foo} is a function in an
13266 unmapped overlay, @value{GDBN} prints it this way:
13269 (@value{GDBP}) overlay list
13270 No sections are mapped.
13271 (@value{GDBP}) print foo
13272 $5 = @{int (int)@} 0x100000 <*foo*>
13275 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
13279 (@value{GDBP}) overlay list
13280 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
13281 mapped at 0x1016 - 0x104a
13282 (@value{GDBP}) print foo
13283 $6 = @{int (int)@} 0x1016 <foo>
13286 When overlay debugging is enabled, @value{GDBN} can find the correct
13287 address for functions and variables in an overlay, whether or not the
13288 overlay is mapped. This allows most @value{GDBN} commands, like
13289 @code{break} and @code{disassemble}, to work normally, even on unmapped
13290 code. However, @value{GDBN}'s breakpoint support has some limitations:
13294 @cindex breakpoints in overlays
13295 @cindex overlays, setting breakpoints in
13296 You can set breakpoints in functions in unmapped overlays, as long as
13297 @value{GDBN} can write to the overlay at its load address.
13299 @value{GDBN} can not set hardware or simulator-based breakpoints in
13300 unmapped overlays. However, if you set a breakpoint at the end of your
13301 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
13302 you are using manual overlay management), @value{GDBN} will re-set its
13303 breakpoints properly.
13307 @node Automatic Overlay Debugging
13308 @section Automatic Overlay Debugging
13309 @cindex automatic overlay debugging
13311 @value{GDBN} can automatically track which overlays are mapped and which
13312 are not, given some simple co-operation from the overlay manager in the
13313 inferior. If you enable automatic overlay debugging with the
13314 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
13315 looks in the inferior's memory for certain variables describing the
13316 current state of the overlays.
13318 Here are the variables your overlay manager must define to support
13319 @value{GDBN}'s automatic overlay debugging:
13323 @item @code{_ovly_table}:
13324 This variable must be an array of the following structures:
13329 /* The overlay's mapped address. */
13332 /* The size of the overlay, in bytes. */
13333 unsigned long size;
13335 /* The overlay's load address. */
13338 /* Non-zero if the overlay is currently mapped;
13340 unsigned long mapped;
13344 @item @code{_novlys}:
13345 This variable must be a four-byte signed integer, holding the total
13346 number of elements in @code{_ovly_table}.
13350 To decide whether a particular overlay is mapped or not, @value{GDBN}
13351 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
13352 @code{lma} members equal the VMA and LMA of the overlay's section in the
13353 executable file. When @value{GDBN} finds a matching entry, it consults
13354 the entry's @code{mapped} member to determine whether the overlay is
13357 In addition, your overlay manager may define a function called
13358 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
13359 will silently set a breakpoint there. If the overlay manager then
13360 calls this function whenever it has changed the overlay table, this
13361 will enable @value{GDBN} to accurately keep track of which overlays
13362 are in program memory, and update any breakpoints that may be set
13363 in overlays. This will allow breakpoints to work even if the
13364 overlays are kept in ROM or other non-writable memory while they
13365 are not being executed.
13367 @node Overlay Sample Program
13368 @section Overlay Sample Program
13369 @cindex overlay example program
13371 When linking a program which uses overlays, you must place the overlays
13372 at their load addresses, while relocating them to run at their mapped
13373 addresses. To do this, you must write a linker script (@pxref{Overlay
13374 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
13375 since linker scripts are specific to a particular host system, target
13376 architecture, and target memory layout, this manual cannot provide
13377 portable sample code demonstrating @value{GDBN}'s overlay support.
13379 However, the @value{GDBN} source distribution does contain an overlaid
13380 program, with linker scripts for a few systems, as part of its test
13381 suite. The program consists of the following files from
13382 @file{gdb/testsuite/gdb.base}:
13386 The main program file.
13388 A simple overlay manager, used by @file{overlays.c}.
13393 Overlay modules, loaded and used by @file{overlays.c}.
13396 Linker scripts for linking the test program on the @code{d10v-elf}
13397 and @code{m32r-elf} targets.
13400 You can build the test program using the @code{d10v-elf} GCC
13401 cross-compiler like this:
13404 $ d10v-elf-gcc -g -c overlays.c
13405 $ d10v-elf-gcc -g -c ovlymgr.c
13406 $ d10v-elf-gcc -g -c foo.c
13407 $ d10v-elf-gcc -g -c bar.c
13408 $ d10v-elf-gcc -g -c baz.c
13409 $ d10v-elf-gcc -g -c grbx.c
13410 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
13411 baz.o grbx.o -Wl,-Td10v.ld -o overlays
13414 The build process is identical for any other architecture, except that
13415 you must substitute the appropriate compiler and linker script for the
13416 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
13420 @chapter Using @value{GDBN} with Different Languages
13423 Although programming languages generally have common aspects, they are
13424 rarely expressed in the same manner. For instance, in ANSI C,
13425 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
13426 Modula-2, it is accomplished by @code{p^}. Values can also be
13427 represented (and displayed) differently. Hex numbers in C appear as
13428 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
13430 @cindex working language
13431 Language-specific information is built into @value{GDBN} for some languages,
13432 allowing you to express operations like the above in your program's
13433 native language, and allowing @value{GDBN} to output values in a manner
13434 consistent with the syntax of your program's native language. The
13435 language you use to build expressions is called the @dfn{working
13439 * Setting:: Switching between source languages
13440 * Show:: Displaying the language
13441 * Checks:: Type and range checks
13442 * Supported Languages:: Supported languages
13443 * Unsupported Languages:: Unsupported languages
13447 @section Switching Between Source Languages
13449 There are two ways to control the working language---either have @value{GDBN}
13450 set it automatically, or select it manually yourself. You can use the
13451 @code{set language} command for either purpose. On startup, @value{GDBN}
13452 defaults to setting the language automatically. The working language is
13453 used to determine how expressions you type are interpreted, how values
13456 In addition to the working language, every source file that
13457 @value{GDBN} knows about has its own working language. For some object
13458 file formats, the compiler might indicate which language a particular
13459 source file is in. However, most of the time @value{GDBN} infers the
13460 language from the name of the file. The language of a source file
13461 controls whether C@t{++} names are demangled---this way @code{backtrace} can
13462 show each frame appropriately for its own language. There is no way to
13463 set the language of a source file from within @value{GDBN}, but you can
13464 set the language associated with a filename extension. @xref{Show, ,
13465 Displaying the Language}.
13467 This is most commonly a problem when you use a program, such
13468 as @code{cfront} or @code{f2c}, that generates C but is written in
13469 another language. In that case, make the
13470 program use @code{#line} directives in its C output; that way
13471 @value{GDBN} will know the correct language of the source code of the original
13472 program, and will display that source code, not the generated C code.
13475 * Filenames:: Filename extensions and languages.
13476 * Manually:: Setting the working language manually
13477 * Automatically:: Having @value{GDBN} infer the source language
13481 @subsection List of Filename Extensions and Languages
13483 If a source file name ends in one of the following extensions, then
13484 @value{GDBN} infers that its language is the one indicated.
13502 C@t{++} source file
13508 Objective-C source file
13512 Fortran source file
13515 Modula-2 source file
13519 Assembler source file. This actually behaves almost like C, but
13520 @value{GDBN} does not skip over function prologues when stepping.
13523 In addition, you may set the language associated with a filename
13524 extension. @xref{Show, , Displaying the Language}.
13527 @subsection Setting the Working Language
13529 If you allow @value{GDBN} to set the language automatically,
13530 expressions are interpreted the same way in your debugging session and
13533 @kindex set language
13534 If you wish, you may set the language manually. To do this, issue the
13535 command @samp{set language @var{lang}}, where @var{lang} is the name of
13536 a language, such as
13537 @code{c} or @code{modula-2}.
13538 For a list of the supported languages, type @samp{set language}.
13540 Setting the language manually prevents @value{GDBN} from updating the working
13541 language automatically. This can lead to confusion if you try
13542 to debug a program when the working language is not the same as the
13543 source language, when an expression is acceptable to both
13544 languages---but means different things. For instance, if the current
13545 source file were written in C, and @value{GDBN} was parsing Modula-2, a
13553 might not have the effect you intended. In C, this means to add
13554 @code{b} and @code{c} and place the result in @code{a}. The result
13555 printed would be the value of @code{a}. In Modula-2, this means to compare
13556 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
13558 @node Automatically
13559 @subsection Having @value{GDBN} Infer the Source Language
13561 To have @value{GDBN} set the working language automatically, use
13562 @samp{set language local} or @samp{set language auto}. @value{GDBN}
13563 then infers the working language. That is, when your program stops in a
13564 frame (usually by encountering a breakpoint), @value{GDBN} sets the
13565 working language to the language recorded for the function in that
13566 frame. If the language for a frame is unknown (that is, if the function
13567 or block corresponding to the frame was defined in a source file that
13568 does not have a recognized extension), the current working language is
13569 not changed, and @value{GDBN} issues a warning.
13571 This may not seem necessary for most programs, which are written
13572 entirely in one source language. However, program modules and libraries
13573 written in one source language can be used by a main program written in
13574 a different source language. Using @samp{set language auto} in this
13575 case frees you from having to set the working language manually.
13578 @section Displaying the Language
13580 The following commands help you find out which language is the
13581 working language, and also what language source files were written in.
13584 @item show language
13585 @anchor{show language}
13586 @kindex show language
13587 Display the current working language. This is the
13588 language you can use with commands such as @code{print} to
13589 build and compute expressions that may involve variables in your program.
13592 @kindex info frame@r{, show the source language}
13593 Display the source language for this frame. This language becomes the
13594 working language if you use an identifier from this frame.
13595 @xref{Frame Info, ,Information about a Frame}, to identify the other
13596 information listed here.
13599 @kindex info source@r{, show the source language}
13600 Display the source language of this source file.
13601 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
13602 information listed here.
13605 In unusual circumstances, you may have source files with extensions
13606 not in the standard list. You can then set the extension associated
13607 with a language explicitly:
13610 @item set extension-language @var{ext} @var{language}
13611 @kindex set extension-language
13612 Tell @value{GDBN} that source files with extension @var{ext} are to be
13613 assumed as written in the source language @var{language}.
13615 @item info extensions
13616 @kindex info extensions
13617 List all the filename extensions and the associated languages.
13621 @section Type and Range Checking
13623 Some languages are designed to guard you against making seemingly common
13624 errors through a series of compile- and run-time checks. These include
13625 checking the type of arguments to functions and operators and making
13626 sure mathematical overflows are caught at run time. Checks such as
13627 these help to ensure a program's correctness once it has been compiled
13628 by eliminating type mismatches and providing active checks for range
13629 errors when your program is running.
13631 By default @value{GDBN} checks for these errors according to the
13632 rules of the current source language. Although @value{GDBN} does not check
13633 the statements in your program, it can check expressions entered directly
13634 into @value{GDBN} for evaluation via the @code{print} command, for example.
13637 * Type Checking:: An overview of type checking
13638 * Range Checking:: An overview of range checking
13641 @cindex type checking
13642 @cindex checks, type
13643 @node Type Checking
13644 @subsection An Overview of Type Checking
13646 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
13647 arguments to operators and functions have to be of the correct type,
13648 otherwise an error occurs. These checks prevent type mismatch
13649 errors from ever causing any run-time problems. For example,
13652 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
13654 (@value{GDBP}) print obj.my_method (0)
13657 (@value{GDBP}) print obj.my_method (0x1234)
13658 Cannot resolve method klass::my_method to any overloaded instance
13661 The second example fails because in C@t{++} the integer constant
13662 @samp{0x1234} is not type-compatible with the pointer parameter type.
13664 For the expressions you use in @value{GDBN} commands, you can tell
13665 @value{GDBN} to not enforce strict type checking or
13666 to treat any mismatches as errors and abandon the expression;
13667 When type checking is disabled, @value{GDBN} successfully evaluates
13668 expressions like the second example above.
13670 Even if type checking is off, there may be other reasons
13671 related to type that prevent @value{GDBN} from evaluating an expression.
13672 For instance, @value{GDBN} does not know how to add an @code{int} and
13673 a @code{struct foo}. These particular type errors have nothing to do
13674 with the language in use and usually arise from expressions which make
13675 little sense to evaluate anyway.
13677 @value{GDBN} provides some additional commands for controlling type checking:
13679 @kindex set check type
13680 @kindex show check type
13682 @item set check type on
13683 @itemx set check type off
13684 Set strict type checking on or off. If any type mismatches occur in
13685 evaluating an expression while type checking is on, @value{GDBN} prints a
13686 message and aborts evaluation of the expression.
13688 @item show check type
13689 Show the current setting of type checking and whether @value{GDBN}
13690 is enforcing strict type checking rules.
13693 @cindex range checking
13694 @cindex checks, range
13695 @node Range Checking
13696 @subsection An Overview of Range Checking
13698 In some languages (such as Modula-2), it is an error to exceed the
13699 bounds of a type; this is enforced with run-time checks. Such range
13700 checking is meant to ensure program correctness by making sure
13701 computations do not overflow, or indices on an array element access do
13702 not exceed the bounds of the array.
13704 For expressions you use in @value{GDBN} commands, you can tell
13705 @value{GDBN} to treat range errors in one of three ways: ignore them,
13706 always treat them as errors and abandon the expression, or issue
13707 warnings but evaluate the expression anyway.
13709 A range error can result from numerical overflow, from exceeding an
13710 array index bound, or when you type a constant that is not a member
13711 of any type. Some languages, however, do not treat overflows as an
13712 error. In many implementations of C, mathematical overflow causes the
13713 result to ``wrap around'' to lower values---for example, if @var{m} is
13714 the largest integer value, and @var{s} is the smallest, then
13717 @var{m} + 1 @result{} @var{s}
13720 This, too, is specific to individual languages, and in some cases
13721 specific to individual compilers or machines. @xref{Supported Languages, ,
13722 Supported Languages}, for further details on specific languages.
13724 @value{GDBN} provides some additional commands for controlling the range checker:
13726 @kindex set check range
13727 @kindex show check range
13729 @item set check range auto
13730 Set range checking on or off based on the current working language.
13731 @xref{Supported Languages, ,Supported Languages}, for the default settings for
13734 @item set check range on
13735 @itemx set check range off
13736 Set range checking on or off, overriding the default setting for the
13737 current working language. A warning is issued if the setting does not
13738 match the language default. If a range error occurs and range checking is on,
13739 then a message is printed and evaluation of the expression is aborted.
13741 @item set check range warn
13742 Output messages when the @value{GDBN} range checker detects a range error,
13743 but attempt to evaluate the expression anyway. Evaluating the
13744 expression may still be impossible for other reasons, such as accessing
13745 memory that the process does not own (a typical example from many Unix
13749 Show the current setting of the range checker, and whether or not it is
13750 being set automatically by @value{GDBN}.
13753 @node Supported Languages
13754 @section Supported Languages
13756 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
13757 OpenCL C, Pascal, assembly, Modula-2, and Ada.
13758 @c This is false ...
13759 Some @value{GDBN} features may be used in expressions regardless of the
13760 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
13761 and the @samp{@{type@}addr} construct (@pxref{Expressions,
13762 ,Expressions}) can be used with the constructs of any supported
13765 The following sections detail to what degree each source language is
13766 supported by @value{GDBN}. These sections are not meant to be language
13767 tutorials or references, but serve only as a reference guide to what the
13768 @value{GDBN} expression parser accepts, and what input and output
13769 formats should look like for different languages. There are many good
13770 books written on each of these languages; please look to these for a
13771 language reference or tutorial.
13774 * C:: C and C@t{++}
13777 * Objective-C:: Objective-C
13778 * OpenCL C:: OpenCL C
13779 * Fortran:: Fortran
13781 * Modula-2:: Modula-2
13786 @subsection C and C@t{++}
13788 @cindex C and C@t{++}
13789 @cindex expressions in C or C@t{++}
13791 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
13792 to both languages. Whenever this is the case, we discuss those languages
13796 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
13797 @cindex @sc{gnu} C@t{++}
13798 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
13799 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
13800 effectively, you must compile your C@t{++} programs with a supported
13801 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
13802 compiler (@code{aCC}).
13805 * C Operators:: C and C@t{++} operators
13806 * C Constants:: C and C@t{++} constants
13807 * C Plus Plus Expressions:: C@t{++} expressions
13808 * C Defaults:: Default settings for C and C@t{++}
13809 * C Checks:: C and C@t{++} type and range checks
13810 * Debugging C:: @value{GDBN} and C
13811 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
13812 * Decimal Floating Point:: Numbers in Decimal Floating Point format
13816 @subsubsection C and C@t{++} Operators
13818 @cindex C and C@t{++} operators
13820 Operators must be defined on values of specific types. For instance,
13821 @code{+} is defined on numbers, but not on structures. Operators are
13822 often defined on groups of types.
13824 For the purposes of C and C@t{++}, the following definitions hold:
13829 @emph{Integral types} include @code{int} with any of its storage-class
13830 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
13833 @emph{Floating-point types} include @code{float}, @code{double}, and
13834 @code{long double} (if supported by the target platform).
13837 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
13840 @emph{Scalar types} include all of the above.
13845 The following operators are supported. They are listed here
13846 in order of increasing precedence:
13850 The comma or sequencing operator. Expressions in a comma-separated list
13851 are evaluated from left to right, with the result of the entire
13852 expression being the last expression evaluated.
13855 Assignment. The value of an assignment expression is the value
13856 assigned. Defined on scalar types.
13859 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
13860 and translated to @w{@code{@var{a} = @var{a op b}}}.
13861 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
13862 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
13863 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
13866 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
13867 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
13868 should be of an integral type.
13871 Logical @sc{or}. Defined on integral types.
13874 Logical @sc{and}. Defined on integral types.
13877 Bitwise @sc{or}. Defined on integral types.
13880 Bitwise exclusive-@sc{or}. Defined on integral types.
13883 Bitwise @sc{and}. Defined on integral types.
13886 Equality and inequality. Defined on scalar types. The value of these
13887 expressions is 0 for false and non-zero for true.
13889 @item <@r{, }>@r{, }<=@r{, }>=
13890 Less than, greater than, less than or equal, greater than or equal.
13891 Defined on scalar types. The value of these expressions is 0 for false
13892 and non-zero for true.
13895 left shift, and right shift. Defined on integral types.
13898 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13901 Addition and subtraction. Defined on integral types, floating-point types and
13904 @item *@r{, }/@r{, }%
13905 Multiplication, division, and modulus. Multiplication and division are
13906 defined on integral and floating-point types. Modulus is defined on
13910 Increment and decrement. When appearing before a variable, the
13911 operation is performed before the variable is used in an expression;
13912 when appearing after it, the variable's value is used before the
13913 operation takes place.
13916 Pointer dereferencing. Defined on pointer types. Same precedence as
13920 Address operator. Defined on variables. Same precedence as @code{++}.
13922 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
13923 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
13924 to examine the address
13925 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
13929 Negative. Defined on integral and floating-point types. Same
13930 precedence as @code{++}.
13933 Logical negation. Defined on integral types. Same precedence as
13937 Bitwise complement operator. Defined on integral types. Same precedence as
13942 Structure member, and pointer-to-structure member. For convenience,
13943 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
13944 pointer based on the stored type information.
13945 Defined on @code{struct} and @code{union} data.
13948 Dereferences of pointers to members.
13951 Array indexing. @code{@var{a}[@var{i}]} is defined as
13952 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
13955 Function parameter list. Same precedence as @code{->}.
13958 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
13959 and @code{class} types.
13962 Doubled colons also represent the @value{GDBN} scope operator
13963 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
13967 If an operator is redefined in the user code, @value{GDBN} usually
13968 attempts to invoke the redefined version instead of using the operator's
13969 predefined meaning.
13972 @subsubsection C and C@t{++} Constants
13974 @cindex C and C@t{++} constants
13976 @value{GDBN} allows you to express the constants of C and C@t{++} in the
13981 Integer constants are a sequence of digits. Octal constants are
13982 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
13983 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
13984 @samp{l}, specifying that the constant should be treated as a
13988 Floating point constants are a sequence of digits, followed by a decimal
13989 point, followed by a sequence of digits, and optionally followed by an
13990 exponent. An exponent is of the form:
13991 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
13992 sequence of digits. The @samp{+} is optional for positive exponents.
13993 A floating-point constant may also end with a letter @samp{f} or
13994 @samp{F}, specifying that the constant should be treated as being of
13995 the @code{float} (as opposed to the default @code{double}) type; or with
13996 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
14000 Enumerated constants consist of enumerated identifiers, or their
14001 integral equivalents.
14004 Character constants are a single character surrounded by single quotes
14005 (@code{'}), or a number---the ordinal value of the corresponding character
14006 (usually its @sc{ascii} value). Within quotes, the single character may
14007 be represented by a letter or by @dfn{escape sequences}, which are of
14008 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
14009 of the character's ordinal value; or of the form @samp{\@var{x}}, where
14010 @samp{@var{x}} is a predefined special character---for example,
14011 @samp{\n} for newline.
14013 Wide character constants can be written by prefixing a character
14014 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
14015 form of @samp{x}. The target wide character set is used when
14016 computing the value of this constant (@pxref{Character Sets}).
14019 String constants are a sequence of character constants surrounded by
14020 double quotes (@code{"}). Any valid character constant (as described
14021 above) may appear. Double quotes within the string must be preceded by
14022 a backslash, so for instance @samp{"a\"b'c"} is a string of five
14025 Wide string constants can be written by prefixing a string constant
14026 with @samp{L}, as in C. The target wide character set is used when
14027 computing the value of this constant (@pxref{Character Sets}).
14030 Pointer constants are an integral value. You can also write pointers
14031 to constants using the C operator @samp{&}.
14034 Array constants are comma-separated lists surrounded by braces @samp{@{}
14035 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
14036 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
14037 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
14040 @node C Plus Plus Expressions
14041 @subsubsection C@t{++} Expressions
14043 @cindex expressions in C@t{++}
14044 @value{GDBN} expression handling can interpret most C@t{++} expressions.
14046 @cindex debugging C@t{++} programs
14047 @cindex C@t{++} compilers
14048 @cindex debug formats and C@t{++}
14049 @cindex @value{NGCC} and C@t{++}
14051 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
14052 the proper compiler and the proper debug format. Currently,
14053 @value{GDBN} works best when debugging C@t{++} code that is compiled
14054 with the most recent version of @value{NGCC} possible. The DWARF
14055 debugging format is preferred; @value{NGCC} defaults to this on most
14056 popular platforms. Other compilers and/or debug formats are likely to
14057 work badly or not at all when using @value{GDBN} to debug C@t{++}
14058 code. @xref{Compilation}.
14063 @cindex member functions
14065 Member function calls are allowed; you can use expressions like
14068 count = aml->GetOriginal(x, y)
14071 @vindex this@r{, inside C@t{++} member functions}
14072 @cindex namespace in C@t{++}
14074 While a member function is active (in the selected stack frame), your
14075 expressions have the same namespace available as the member function;
14076 that is, @value{GDBN} allows implicit references to the class instance
14077 pointer @code{this} following the same rules as C@t{++}. @code{using}
14078 declarations in the current scope are also respected by @value{GDBN}.
14080 @cindex call overloaded functions
14081 @cindex overloaded functions, calling
14082 @cindex type conversions in C@t{++}
14084 You can call overloaded functions; @value{GDBN} resolves the function
14085 call to the right definition, with some restrictions. @value{GDBN} does not
14086 perform overload resolution involving user-defined type conversions,
14087 calls to constructors, or instantiations of templates that do not exist
14088 in the program. It also cannot handle ellipsis argument lists or
14091 It does perform integral conversions and promotions, floating-point
14092 promotions, arithmetic conversions, pointer conversions, conversions of
14093 class objects to base classes, and standard conversions such as those of
14094 functions or arrays to pointers; it requires an exact match on the
14095 number of function arguments.
14097 Overload resolution is always performed, unless you have specified
14098 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
14099 ,@value{GDBN} Features for C@t{++}}.
14101 You must specify @code{set overload-resolution off} in order to use an
14102 explicit function signature to call an overloaded function, as in
14104 p 'foo(char,int)'('x', 13)
14107 The @value{GDBN} command-completion facility can simplify this;
14108 see @ref{Completion, ,Command Completion}.
14110 @cindex reference declarations
14112 @value{GDBN} understands variables declared as C@t{++} references; you can use
14113 them in expressions just as you do in C@t{++} source---they are automatically
14116 In the parameter list shown when @value{GDBN} displays a frame, the values of
14117 reference variables are not displayed (unlike other variables); this
14118 avoids clutter, since references are often used for large structures.
14119 The @emph{address} of a reference variable is always shown, unless
14120 you have specified @samp{set print address off}.
14123 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
14124 expressions can use it just as expressions in your program do. Since
14125 one scope may be defined in another, you can use @code{::} repeatedly if
14126 necessary, for example in an expression like
14127 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
14128 resolving name scope by reference to source files, in both C and C@t{++}
14129 debugging (@pxref{Variables, ,Program Variables}).
14132 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
14137 @subsubsection C and C@t{++} Defaults
14139 @cindex C and C@t{++} defaults
14141 If you allow @value{GDBN} to set range checking automatically, it
14142 defaults to @code{off} whenever the working language changes to
14143 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
14144 selects the working language.
14146 If you allow @value{GDBN} to set the language automatically, it
14147 recognizes source files whose names end with @file{.c}, @file{.C}, or
14148 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
14149 these files, it sets the working language to C or C@t{++}.
14150 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
14151 for further details.
14154 @subsubsection C and C@t{++} Type and Range Checks
14156 @cindex C and C@t{++} checks
14158 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
14159 checking is used. However, if you turn type checking off, @value{GDBN}
14160 will allow certain non-standard conversions, such as promoting integer
14161 constants to pointers.
14163 Range checking, if turned on, is done on mathematical operations. Array
14164 indices are not checked, since they are often used to index a pointer
14165 that is not itself an array.
14168 @subsubsection @value{GDBN} and C
14170 The @code{set print union} and @code{show print union} commands apply to
14171 the @code{union} type. When set to @samp{on}, any @code{union} that is
14172 inside a @code{struct} or @code{class} is also printed. Otherwise, it
14173 appears as @samp{@{...@}}.
14175 The @code{@@} operator aids in the debugging of dynamic arrays, formed
14176 with pointers and a memory allocation function. @xref{Expressions,
14179 @node Debugging C Plus Plus
14180 @subsubsection @value{GDBN} Features for C@t{++}
14182 @cindex commands for C@t{++}
14184 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
14185 designed specifically for use with C@t{++}. Here is a summary:
14188 @cindex break in overloaded functions
14189 @item @r{breakpoint menus}
14190 When you want a breakpoint in a function whose name is overloaded,
14191 @value{GDBN} has the capability to display a menu of possible breakpoint
14192 locations to help you specify which function definition you want.
14193 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
14195 @cindex overloading in C@t{++}
14196 @item rbreak @var{regex}
14197 Setting breakpoints using regular expressions is helpful for setting
14198 breakpoints on overloaded functions that are not members of any special
14200 @xref{Set Breaks, ,Setting Breakpoints}.
14202 @cindex C@t{++} exception handling
14204 @itemx catch rethrow
14206 Debug C@t{++} exception handling using these commands. @xref{Set
14207 Catchpoints, , Setting Catchpoints}.
14209 @cindex inheritance
14210 @item ptype @var{typename}
14211 Print inheritance relationships as well as other information for type
14213 @xref{Symbols, ,Examining the Symbol Table}.
14215 @item info vtbl @var{expression}.
14216 The @code{info vtbl} command can be used to display the virtual
14217 method tables of the object computed by @var{expression}. This shows
14218 one entry per virtual table; there may be multiple virtual tables when
14219 multiple inheritance is in use.
14221 @cindex C@t{++} demangling
14222 @item demangle @var{name}
14223 Demangle @var{name}.
14224 @xref{Symbols}, for a more complete description of the @code{demangle} command.
14226 @cindex C@t{++} symbol display
14227 @item set print demangle
14228 @itemx show print demangle
14229 @itemx set print asm-demangle
14230 @itemx show print asm-demangle
14231 Control whether C@t{++} symbols display in their source form, both when
14232 displaying code as C@t{++} source and when displaying disassemblies.
14233 @xref{Print Settings, ,Print Settings}.
14235 @item set print object
14236 @itemx show print object
14237 Choose whether to print derived (actual) or declared types of objects.
14238 @xref{Print Settings, ,Print Settings}.
14240 @item set print vtbl
14241 @itemx show print vtbl
14242 Control the format for printing virtual function tables.
14243 @xref{Print Settings, ,Print Settings}.
14244 (The @code{vtbl} commands do not work on programs compiled with the HP
14245 ANSI C@t{++} compiler (@code{aCC}).)
14247 @kindex set overload-resolution
14248 @cindex overloaded functions, overload resolution
14249 @item set overload-resolution on
14250 Enable overload resolution for C@t{++} expression evaluation. The default
14251 is on. For overloaded functions, @value{GDBN} evaluates the arguments
14252 and searches for a function whose signature matches the argument types,
14253 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
14254 Expressions, ,C@t{++} Expressions}, for details).
14255 If it cannot find a match, it emits a message.
14257 @item set overload-resolution off
14258 Disable overload resolution for C@t{++} expression evaluation. For
14259 overloaded functions that are not class member functions, @value{GDBN}
14260 chooses the first function of the specified name that it finds in the
14261 symbol table, whether or not its arguments are of the correct type. For
14262 overloaded functions that are class member functions, @value{GDBN}
14263 searches for a function whose signature @emph{exactly} matches the
14266 @kindex show overload-resolution
14267 @item show overload-resolution
14268 Show the current setting of overload resolution.
14270 @item @r{Overloaded symbol names}
14271 You can specify a particular definition of an overloaded symbol, using
14272 the same notation that is used to declare such symbols in C@t{++}: type
14273 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
14274 also use the @value{GDBN} command-line word completion facilities to list the
14275 available choices, or to finish the type list for you.
14276 @xref{Completion,, Command Completion}, for details on how to do this.
14279 @node Decimal Floating Point
14280 @subsubsection Decimal Floating Point format
14281 @cindex decimal floating point format
14283 @value{GDBN} can examine, set and perform computations with numbers in
14284 decimal floating point format, which in the C language correspond to the
14285 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
14286 specified by the extension to support decimal floating-point arithmetic.
14288 There are two encodings in use, depending on the architecture: BID (Binary
14289 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
14290 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
14293 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
14294 to manipulate decimal floating point numbers, it is not possible to convert
14295 (using a cast, for example) integers wider than 32-bit to decimal float.
14297 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
14298 point computations, error checking in decimal float operations ignores
14299 underflow, overflow and divide by zero exceptions.
14301 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
14302 to inspect @code{_Decimal128} values stored in floating point registers.
14303 See @ref{PowerPC,,PowerPC} for more details.
14309 @value{GDBN} can be used to debug programs written in D and compiled with
14310 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
14311 specific feature --- dynamic arrays.
14316 @cindex Go (programming language)
14317 @value{GDBN} can be used to debug programs written in Go and compiled with
14318 @file{gccgo} or @file{6g} compilers.
14320 Here is a summary of the Go-specific features and restrictions:
14323 @cindex current Go package
14324 @item The current Go package
14325 The name of the current package does not need to be specified when
14326 specifying global variables and functions.
14328 For example, given the program:
14332 var myglob = "Shall we?"
14338 When stopped inside @code{main} either of these work:
14342 (gdb) p main.myglob
14345 @cindex builtin Go types
14346 @item Builtin Go types
14347 The @code{string} type is recognized by @value{GDBN} and is printed
14350 @cindex builtin Go functions
14351 @item Builtin Go functions
14352 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
14353 function and handles it internally.
14355 @cindex restrictions on Go expressions
14356 @item Restrictions on Go expressions
14357 All Go operators are supported except @code{&^}.
14358 The Go @code{_} ``blank identifier'' is not supported.
14359 Automatic dereferencing of pointers is not supported.
14363 @subsection Objective-C
14365 @cindex Objective-C
14366 This section provides information about some commands and command
14367 options that are useful for debugging Objective-C code. See also
14368 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
14369 few more commands specific to Objective-C support.
14372 * Method Names in Commands::
14373 * The Print Command with Objective-C::
14376 @node Method Names in Commands
14377 @subsubsection Method Names in Commands
14379 The following commands have been extended to accept Objective-C method
14380 names as line specifications:
14382 @kindex clear@r{, and Objective-C}
14383 @kindex break@r{, and Objective-C}
14384 @kindex info line@r{, and Objective-C}
14385 @kindex jump@r{, and Objective-C}
14386 @kindex list@r{, and Objective-C}
14390 @item @code{info line}
14395 A fully qualified Objective-C method name is specified as
14398 -[@var{Class} @var{methodName}]
14401 where the minus sign is used to indicate an instance method and a
14402 plus sign (not shown) is used to indicate a class method. The class
14403 name @var{Class} and method name @var{methodName} are enclosed in
14404 brackets, similar to the way messages are specified in Objective-C
14405 source code. For example, to set a breakpoint at the @code{create}
14406 instance method of class @code{Fruit} in the program currently being
14410 break -[Fruit create]
14413 To list ten program lines around the @code{initialize} class method,
14417 list +[NSText initialize]
14420 In the current version of @value{GDBN}, the plus or minus sign is
14421 required. In future versions of @value{GDBN}, the plus or minus
14422 sign will be optional, but you can use it to narrow the search. It
14423 is also possible to specify just a method name:
14429 You must specify the complete method name, including any colons. If
14430 your program's source files contain more than one @code{create} method,
14431 you'll be presented with a numbered list of classes that implement that
14432 method. Indicate your choice by number, or type @samp{0} to exit if
14435 As another example, to clear a breakpoint established at the
14436 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
14439 clear -[NSWindow makeKeyAndOrderFront:]
14442 @node The Print Command with Objective-C
14443 @subsubsection The Print Command With Objective-C
14444 @cindex Objective-C, print objects
14445 @kindex print-object
14446 @kindex po @r{(@code{print-object})}
14448 The print command has also been extended to accept methods. For example:
14451 print -[@var{object} hash]
14454 @cindex print an Objective-C object description
14455 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
14457 will tell @value{GDBN} to send the @code{hash} message to @var{object}
14458 and print the result. Also, an additional command has been added,
14459 @code{print-object} or @code{po} for short, which is meant to print
14460 the description of an object. However, this command may only work
14461 with certain Objective-C libraries that have a particular hook
14462 function, @code{_NSPrintForDebugger}, defined.
14465 @subsection OpenCL C
14468 This section provides information about @value{GDBN}s OpenCL C support.
14471 * OpenCL C Datatypes::
14472 * OpenCL C Expressions::
14473 * OpenCL C Operators::
14476 @node OpenCL C Datatypes
14477 @subsubsection OpenCL C Datatypes
14479 @cindex OpenCL C Datatypes
14480 @value{GDBN} supports the builtin scalar and vector datatypes specified
14481 by OpenCL 1.1. In addition the half- and double-precision floating point
14482 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
14483 extensions are also known to @value{GDBN}.
14485 @node OpenCL C Expressions
14486 @subsubsection OpenCL C Expressions
14488 @cindex OpenCL C Expressions
14489 @value{GDBN} supports accesses to vector components including the access as
14490 lvalue where possible. Since OpenCL C is based on C99 most C expressions
14491 supported by @value{GDBN} can be used as well.
14493 @node OpenCL C Operators
14494 @subsubsection OpenCL C Operators
14496 @cindex OpenCL C Operators
14497 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
14501 @subsection Fortran
14502 @cindex Fortran-specific support in @value{GDBN}
14504 @value{GDBN} can be used to debug programs written in Fortran, but it
14505 currently supports only the features of Fortran 77 language.
14507 @cindex trailing underscore, in Fortran symbols
14508 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
14509 among them) append an underscore to the names of variables and
14510 functions. When you debug programs compiled by those compilers, you
14511 will need to refer to variables and functions with a trailing
14515 * Fortran Operators:: Fortran operators and expressions
14516 * Fortran Defaults:: Default settings for Fortran
14517 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
14520 @node Fortran Operators
14521 @subsubsection Fortran Operators and Expressions
14523 @cindex Fortran operators and expressions
14525 Operators must be defined on values of specific types. For instance,
14526 @code{+} is defined on numbers, but not on characters or other non-
14527 arithmetic types. Operators are often defined on groups of types.
14531 The exponentiation operator. It raises the first operand to the power
14535 The range operator. Normally used in the form of array(low:high) to
14536 represent a section of array.
14539 The access component operator. Normally used to access elements in derived
14540 types. Also suitable for unions. As unions aren't part of regular Fortran,
14541 this can only happen when accessing a register that uses a gdbarch-defined
14545 @node Fortran Defaults
14546 @subsubsection Fortran Defaults
14548 @cindex Fortran Defaults
14550 Fortran symbols are usually case-insensitive, so @value{GDBN} by
14551 default uses case-insensitive matches for Fortran symbols. You can
14552 change that with the @samp{set case-insensitive} command, see
14553 @ref{Symbols}, for the details.
14555 @node Special Fortran Commands
14556 @subsubsection Special Fortran Commands
14558 @cindex Special Fortran commands
14560 @value{GDBN} has some commands to support Fortran-specific features,
14561 such as displaying common blocks.
14564 @cindex @code{COMMON} blocks, Fortran
14565 @kindex info common
14566 @item info common @r{[}@var{common-name}@r{]}
14567 This command prints the values contained in the Fortran @code{COMMON}
14568 block whose name is @var{common-name}. With no argument, the names of
14569 all @code{COMMON} blocks visible at the current program location are
14576 @cindex Pascal support in @value{GDBN}, limitations
14577 Debugging Pascal programs which use sets, subranges, file variables, or
14578 nested functions does not currently work. @value{GDBN} does not support
14579 entering expressions, printing values, or similar features using Pascal
14582 The Pascal-specific command @code{set print pascal_static-members}
14583 controls whether static members of Pascal objects are displayed.
14584 @xref{Print Settings, pascal_static-members}.
14587 @subsection Modula-2
14589 @cindex Modula-2, @value{GDBN} support
14591 The extensions made to @value{GDBN} to support Modula-2 only support
14592 output from the @sc{gnu} Modula-2 compiler (which is currently being
14593 developed). Other Modula-2 compilers are not currently supported, and
14594 attempting to debug executables produced by them is most likely
14595 to give an error as @value{GDBN} reads in the executable's symbol
14598 @cindex expressions in Modula-2
14600 * M2 Operators:: Built-in operators
14601 * Built-In Func/Proc:: Built-in functions and procedures
14602 * M2 Constants:: Modula-2 constants
14603 * M2 Types:: Modula-2 types
14604 * M2 Defaults:: Default settings for Modula-2
14605 * Deviations:: Deviations from standard Modula-2
14606 * M2 Checks:: Modula-2 type and range checks
14607 * M2 Scope:: The scope operators @code{::} and @code{.}
14608 * GDB/M2:: @value{GDBN} and Modula-2
14612 @subsubsection Operators
14613 @cindex Modula-2 operators
14615 Operators must be defined on values of specific types. For instance,
14616 @code{+} is defined on numbers, but not on structures. Operators are
14617 often defined on groups of types. For the purposes of Modula-2, the
14618 following definitions hold:
14623 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
14627 @emph{Character types} consist of @code{CHAR} and its subranges.
14630 @emph{Floating-point types} consist of @code{REAL}.
14633 @emph{Pointer types} consist of anything declared as @code{POINTER TO
14637 @emph{Scalar types} consist of all of the above.
14640 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
14643 @emph{Boolean types} consist of @code{BOOLEAN}.
14647 The following operators are supported, and appear in order of
14648 increasing precedence:
14652 Function argument or array index separator.
14655 Assignment. The value of @var{var} @code{:=} @var{value} is
14659 Less than, greater than on integral, floating-point, or enumerated
14663 Less than or equal to, greater than or equal to
14664 on integral, floating-point and enumerated types, or set inclusion on
14665 set types. Same precedence as @code{<}.
14667 @item =@r{, }<>@r{, }#
14668 Equality and two ways of expressing inequality, valid on scalar types.
14669 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
14670 available for inequality, since @code{#} conflicts with the script
14674 Set membership. Defined on set types and the types of their members.
14675 Same precedence as @code{<}.
14678 Boolean disjunction. Defined on boolean types.
14681 Boolean conjunction. Defined on boolean types.
14684 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14687 Addition and subtraction on integral and floating-point types, or union
14688 and difference on set types.
14691 Multiplication on integral and floating-point types, or set intersection
14695 Division on floating-point types, or symmetric set difference on set
14696 types. Same precedence as @code{*}.
14699 Integer division and remainder. Defined on integral types. Same
14700 precedence as @code{*}.
14703 Negative. Defined on @code{INTEGER} and @code{REAL} data.
14706 Pointer dereferencing. Defined on pointer types.
14709 Boolean negation. Defined on boolean types. Same precedence as
14713 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
14714 precedence as @code{^}.
14717 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
14720 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
14724 @value{GDBN} and Modula-2 scope operators.
14728 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
14729 treats the use of the operator @code{IN}, or the use of operators
14730 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
14731 @code{<=}, and @code{>=} on sets as an error.
14735 @node Built-In Func/Proc
14736 @subsubsection Built-in Functions and Procedures
14737 @cindex Modula-2 built-ins
14739 Modula-2 also makes available several built-in procedures and functions.
14740 In describing these, the following metavariables are used:
14745 represents an @code{ARRAY} variable.
14748 represents a @code{CHAR} constant or variable.
14751 represents a variable or constant of integral type.
14754 represents an identifier that belongs to a set. Generally used in the
14755 same function with the metavariable @var{s}. The type of @var{s} should
14756 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
14759 represents a variable or constant of integral or floating-point type.
14762 represents a variable or constant of floating-point type.
14768 represents a variable.
14771 represents a variable or constant of one of many types. See the
14772 explanation of the function for details.
14775 All Modula-2 built-in procedures also return a result, described below.
14779 Returns the absolute value of @var{n}.
14782 If @var{c} is a lower case letter, it returns its upper case
14783 equivalent, otherwise it returns its argument.
14786 Returns the character whose ordinal value is @var{i}.
14789 Decrements the value in the variable @var{v} by one. Returns the new value.
14791 @item DEC(@var{v},@var{i})
14792 Decrements the value in the variable @var{v} by @var{i}. Returns the
14795 @item EXCL(@var{m},@var{s})
14796 Removes the element @var{m} from the set @var{s}. Returns the new
14799 @item FLOAT(@var{i})
14800 Returns the floating point equivalent of the integer @var{i}.
14802 @item HIGH(@var{a})
14803 Returns the index of the last member of @var{a}.
14806 Increments the value in the variable @var{v} by one. Returns the new value.
14808 @item INC(@var{v},@var{i})
14809 Increments the value in the variable @var{v} by @var{i}. Returns the
14812 @item INCL(@var{m},@var{s})
14813 Adds the element @var{m} to the set @var{s} if it is not already
14814 there. Returns the new set.
14817 Returns the maximum value of the type @var{t}.
14820 Returns the minimum value of the type @var{t}.
14823 Returns boolean TRUE if @var{i} is an odd number.
14826 Returns the ordinal value of its argument. For example, the ordinal
14827 value of a character is its @sc{ascii} value (on machines supporting
14828 the @sc{ascii} character set). The argument @var{x} must be of an
14829 ordered type, which include integral, character and enumerated types.
14831 @item SIZE(@var{x})
14832 Returns the size of its argument. The argument @var{x} can be a
14833 variable or a type.
14835 @item TRUNC(@var{r})
14836 Returns the integral part of @var{r}.
14838 @item TSIZE(@var{x})
14839 Returns the size of its argument. The argument @var{x} can be a
14840 variable or a type.
14842 @item VAL(@var{t},@var{i})
14843 Returns the member of the type @var{t} whose ordinal value is @var{i}.
14847 @emph{Warning:} Sets and their operations are not yet supported, so
14848 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
14852 @cindex Modula-2 constants
14854 @subsubsection Constants
14856 @value{GDBN} allows you to express the constants of Modula-2 in the following
14862 Integer constants are simply a sequence of digits. When used in an
14863 expression, a constant is interpreted to be type-compatible with the
14864 rest of the expression. Hexadecimal integers are specified by a
14865 trailing @samp{H}, and octal integers by a trailing @samp{B}.
14868 Floating point constants appear as a sequence of digits, followed by a
14869 decimal point and another sequence of digits. An optional exponent can
14870 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
14871 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
14872 digits of the floating point constant must be valid decimal (base 10)
14876 Character constants consist of a single character enclosed by a pair of
14877 like quotes, either single (@code{'}) or double (@code{"}). They may
14878 also be expressed by their ordinal value (their @sc{ascii} value, usually)
14879 followed by a @samp{C}.
14882 String constants consist of a sequence of characters enclosed by a
14883 pair of like quotes, either single (@code{'}) or double (@code{"}).
14884 Escape sequences in the style of C are also allowed. @xref{C
14885 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
14889 Enumerated constants consist of an enumerated identifier.
14892 Boolean constants consist of the identifiers @code{TRUE} and
14896 Pointer constants consist of integral values only.
14899 Set constants are not yet supported.
14903 @subsubsection Modula-2 Types
14904 @cindex Modula-2 types
14906 Currently @value{GDBN} can print the following data types in Modula-2
14907 syntax: array types, record types, set types, pointer types, procedure
14908 types, enumerated types, subrange types and base types. You can also
14909 print the contents of variables declared using these type.
14910 This section gives a number of simple source code examples together with
14911 sample @value{GDBN} sessions.
14913 The first example contains the following section of code:
14922 and you can request @value{GDBN} to interrogate the type and value of
14923 @code{r} and @code{s}.
14926 (@value{GDBP}) print s
14928 (@value{GDBP}) ptype s
14930 (@value{GDBP}) print r
14932 (@value{GDBP}) ptype r
14937 Likewise if your source code declares @code{s} as:
14941 s: SET ['A'..'Z'] ;
14945 then you may query the type of @code{s} by:
14948 (@value{GDBP}) ptype s
14949 type = SET ['A'..'Z']
14953 Note that at present you cannot interactively manipulate set
14954 expressions using the debugger.
14956 The following example shows how you might declare an array in Modula-2
14957 and how you can interact with @value{GDBN} to print its type and contents:
14961 s: ARRAY [-10..10] OF CHAR ;
14965 (@value{GDBP}) ptype s
14966 ARRAY [-10..10] OF CHAR
14969 Note that the array handling is not yet complete and although the type
14970 is printed correctly, expression handling still assumes that all
14971 arrays have a lower bound of zero and not @code{-10} as in the example
14974 Here are some more type related Modula-2 examples:
14978 colour = (blue, red, yellow, green) ;
14979 t = [blue..yellow] ;
14987 The @value{GDBN} interaction shows how you can query the data type
14988 and value of a variable.
14991 (@value{GDBP}) print s
14993 (@value{GDBP}) ptype t
14994 type = [blue..yellow]
14998 In this example a Modula-2 array is declared and its contents
14999 displayed. Observe that the contents are written in the same way as
15000 their @code{C} counterparts.
15004 s: ARRAY [1..5] OF CARDINAL ;
15010 (@value{GDBP}) print s
15011 $1 = @{1, 0, 0, 0, 0@}
15012 (@value{GDBP}) ptype s
15013 type = ARRAY [1..5] OF CARDINAL
15016 The Modula-2 language interface to @value{GDBN} also understands
15017 pointer types as shown in this example:
15021 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
15028 and you can request that @value{GDBN} describes the type of @code{s}.
15031 (@value{GDBP}) ptype s
15032 type = POINTER TO ARRAY [1..5] OF CARDINAL
15035 @value{GDBN} handles compound types as we can see in this example.
15036 Here we combine array types, record types, pointer types and subrange
15047 myarray = ARRAY myrange OF CARDINAL ;
15048 myrange = [-2..2] ;
15050 s: POINTER TO ARRAY myrange OF foo ;
15054 and you can ask @value{GDBN} to describe the type of @code{s} as shown
15058 (@value{GDBP}) ptype s
15059 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
15062 f3 : ARRAY [-2..2] OF CARDINAL;
15067 @subsubsection Modula-2 Defaults
15068 @cindex Modula-2 defaults
15070 If type and range checking are set automatically by @value{GDBN}, they
15071 both default to @code{on} whenever the working language changes to
15072 Modula-2. This happens regardless of whether you or @value{GDBN}
15073 selected the working language.
15075 If you allow @value{GDBN} to set the language automatically, then entering
15076 code compiled from a file whose name ends with @file{.mod} sets the
15077 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
15078 Infer the Source Language}, for further details.
15081 @subsubsection Deviations from Standard Modula-2
15082 @cindex Modula-2, deviations from
15084 A few changes have been made to make Modula-2 programs easier to debug.
15085 This is done primarily via loosening its type strictness:
15089 Unlike in standard Modula-2, pointer constants can be formed by
15090 integers. This allows you to modify pointer variables during
15091 debugging. (In standard Modula-2, the actual address contained in a
15092 pointer variable is hidden from you; it can only be modified
15093 through direct assignment to another pointer variable or expression that
15094 returned a pointer.)
15097 C escape sequences can be used in strings and characters to represent
15098 non-printable characters. @value{GDBN} prints out strings with these
15099 escape sequences embedded. Single non-printable characters are
15100 printed using the @samp{CHR(@var{nnn})} format.
15103 The assignment operator (@code{:=}) returns the value of its right-hand
15107 All built-in procedures both modify @emph{and} return their argument.
15111 @subsubsection Modula-2 Type and Range Checks
15112 @cindex Modula-2 checks
15115 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
15118 @c FIXME remove warning when type/range checks added
15120 @value{GDBN} considers two Modula-2 variables type equivalent if:
15124 They are of types that have been declared equivalent via a @code{TYPE
15125 @var{t1} = @var{t2}} statement
15128 They have been declared on the same line. (Note: This is true of the
15129 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
15132 As long as type checking is enabled, any attempt to combine variables
15133 whose types are not equivalent is an error.
15135 Range checking is done on all mathematical operations, assignment, array
15136 index bounds, and all built-in functions and procedures.
15139 @subsubsection The Scope Operators @code{::} and @code{.}
15141 @cindex @code{.}, Modula-2 scope operator
15142 @cindex colon, doubled as scope operator
15144 @vindex colon-colon@r{, in Modula-2}
15145 @c Info cannot handle :: but TeX can.
15148 @vindex ::@r{, in Modula-2}
15151 There are a few subtle differences between the Modula-2 scope operator
15152 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
15157 @var{module} . @var{id}
15158 @var{scope} :: @var{id}
15162 where @var{scope} is the name of a module or a procedure,
15163 @var{module} the name of a module, and @var{id} is any declared
15164 identifier within your program, except another module.
15166 Using the @code{::} operator makes @value{GDBN} search the scope
15167 specified by @var{scope} for the identifier @var{id}. If it is not
15168 found in the specified scope, then @value{GDBN} searches all scopes
15169 enclosing the one specified by @var{scope}.
15171 Using the @code{.} operator makes @value{GDBN} search the current scope for
15172 the identifier specified by @var{id} that was imported from the
15173 definition module specified by @var{module}. With this operator, it is
15174 an error if the identifier @var{id} was not imported from definition
15175 module @var{module}, or if @var{id} is not an identifier in
15179 @subsubsection @value{GDBN} and Modula-2
15181 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
15182 Five subcommands of @code{set print} and @code{show print} apply
15183 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
15184 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
15185 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
15186 analogue in Modula-2.
15188 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
15189 with any language, is not useful with Modula-2. Its
15190 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
15191 created in Modula-2 as they can in C or C@t{++}. However, because an
15192 address can be specified by an integral constant, the construct
15193 @samp{@{@var{type}@}@var{adrexp}} is still useful.
15195 @cindex @code{#} in Modula-2
15196 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
15197 interpreted as the beginning of a comment. Use @code{<>} instead.
15203 The extensions made to @value{GDBN} for Ada only support
15204 output from the @sc{gnu} Ada (GNAT) compiler.
15205 Other Ada compilers are not currently supported, and
15206 attempting to debug executables produced by them is most likely
15210 @cindex expressions in Ada
15212 * Ada Mode Intro:: General remarks on the Ada syntax
15213 and semantics supported by Ada mode
15215 * Omissions from Ada:: Restrictions on the Ada expression syntax.
15216 * Additions to Ada:: Extensions of the Ada expression syntax.
15217 * Stopping Before Main Program:: Debugging the program during elaboration.
15218 * Ada Exceptions:: Ada Exceptions
15219 * Ada Tasks:: Listing and setting breakpoints in tasks.
15220 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
15221 * Ravenscar Profile:: Tasking Support when using the Ravenscar
15223 * Ada Glitches:: Known peculiarities of Ada mode.
15226 @node Ada Mode Intro
15227 @subsubsection Introduction
15228 @cindex Ada mode, general
15230 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
15231 syntax, with some extensions.
15232 The philosophy behind the design of this subset is
15236 That @value{GDBN} should provide basic literals and access to operations for
15237 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
15238 leaving more sophisticated computations to subprograms written into the
15239 program (which therefore may be called from @value{GDBN}).
15242 That type safety and strict adherence to Ada language restrictions
15243 are not particularly important to the @value{GDBN} user.
15246 That brevity is important to the @value{GDBN} user.
15249 Thus, for brevity, the debugger acts as if all names declared in
15250 user-written packages are directly visible, even if they are not visible
15251 according to Ada rules, thus making it unnecessary to fully qualify most
15252 names with their packages, regardless of context. Where this causes
15253 ambiguity, @value{GDBN} asks the user's intent.
15255 The debugger will start in Ada mode if it detects an Ada main program.
15256 As for other languages, it will enter Ada mode when stopped in a program that
15257 was translated from an Ada source file.
15259 While in Ada mode, you may use `@t{--}' for comments. This is useful
15260 mostly for documenting command files. The standard @value{GDBN} comment
15261 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
15262 middle (to allow based literals).
15264 The debugger supports limited overloading. Given a subprogram call in which
15265 the function symbol has multiple definitions, it will use the number of
15266 actual parameters and some information about their types to attempt to narrow
15267 the set of definitions. It also makes very limited use of context, preferring
15268 procedures to functions in the context of the @code{call} command, and
15269 functions to procedures elsewhere.
15271 @node Omissions from Ada
15272 @subsubsection Omissions from Ada
15273 @cindex Ada, omissions from
15275 Here are the notable omissions from the subset:
15279 Only a subset of the attributes are supported:
15283 @t{'First}, @t{'Last}, and @t{'Length}
15284 on array objects (not on types and subtypes).
15287 @t{'Min} and @t{'Max}.
15290 @t{'Pos} and @t{'Val}.
15296 @t{'Range} on array objects (not subtypes), but only as the right
15297 operand of the membership (@code{in}) operator.
15300 @t{'Access}, @t{'Unchecked_Access}, and
15301 @t{'Unrestricted_Access} (a GNAT extension).
15309 @code{Characters.Latin_1} are not available and
15310 concatenation is not implemented. Thus, escape characters in strings are
15311 not currently available.
15314 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
15315 equality of representations. They will generally work correctly
15316 for strings and arrays whose elements have integer or enumeration types.
15317 They may not work correctly for arrays whose element
15318 types have user-defined equality, for arrays of real values
15319 (in particular, IEEE-conformant floating point, because of negative
15320 zeroes and NaNs), and for arrays whose elements contain unused bits with
15321 indeterminate values.
15324 The other component-by-component array operations (@code{and}, @code{or},
15325 @code{xor}, @code{not}, and relational tests other than equality)
15326 are not implemented.
15329 @cindex array aggregates (Ada)
15330 @cindex record aggregates (Ada)
15331 @cindex aggregates (Ada)
15332 There is limited support for array and record aggregates. They are
15333 permitted only on the right sides of assignments, as in these examples:
15336 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
15337 (@value{GDBP}) set An_Array := (1, others => 0)
15338 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
15339 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
15340 (@value{GDBP}) set A_Record := (1, "Peter", True);
15341 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
15345 discriminant's value by assigning an aggregate has an
15346 undefined effect if that discriminant is used within the record.
15347 However, you can first modify discriminants by directly assigning to
15348 them (which normally would not be allowed in Ada), and then performing an
15349 aggregate assignment. For example, given a variable @code{A_Rec}
15350 declared to have a type such as:
15353 type Rec (Len : Small_Integer := 0) is record
15355 Vals : IntArray (1 .. Len);
15359 you can assign a value with a different size of @code{Vals} with two
15363 (@value{GDBP}) set A_Rec.Len := 4
15364 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
15367 As this example also illustrates, @value{GDBN} is very loose about the usual
15368 rules concerning aggregates. You may leave out some of the
15369 components of an array or record aggregate (such as the @code{Len}
15370 component in the assignment to @code{A_Rec} above); they will retain their
15371 original values upon assignment. You may freely use dynamic values as
15372 indices in component associations. You may even use overlapping or
15373 redundant component associations, although which component values are
15374 assigned in such cases is not defined.
15377 Calls to dispatching subprograms are not implemented.
15380 The overloading algorithm is much more limited (i.e., less selective)
15381 than that of real Ada. It makes only limited use of the context in
15382 which a subexpression appears to resolve its meaning, and it is much
15383 looser in its rules for allowing type matches. As a result, some
15384 function calls will be ambiguous, and the user will be asked to choose
15385 the proper resolution.
15388 The @code{new} operator is not implemented.
15391 Entry calls are not implemented.
15394 Aside from printing, arithmetic operations on the native VAX floating-point
15395 formats are not supported.
15398 It is not possible to slice a packed array.
15401 The names @code{True} and @code{False}, when not part of a qualified name,
15402 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
15404 Should your program
15405 redefine these names in a package or procedure (at best a dubious practice),
15406 you will have to use fully qualified names to access their new definitions.
15409 @node Additions to Ada
15410 @subsubsection Additions to Ada
15411 @cindex Ada, deviations from
15413 As it does for other languages, @value{GDBN} makes certain generic
15414 extensions to Ada (@pxref{Expressions}):
15418 If the expression @var{E} is a variable residing in memory (typically
15419 a local variable or array element) and @var{N} is a positive integer,
15420 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
15421 @var{N}-1 adjacent variables following it in memory as an array. In
15422 Ada, this operator is generally not necessary, since its prime use is
15423 in displaying parts of an array, and slicing will usually do this in
15424 Ada. However, there are occasional uses when debugging programs in
15425 which certain debugging information has been optimized away.
15428 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
15429 appears in function or file @var{B}.'' When @var{B} is a file name,
15430 you must typically surround it in single quotes.
15433 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
15434 @var{type} that appears at address @var{addr}.''
15437 A name starting with @samp{$} is a convenience variable
15438 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
15441 In addition, @value{GDBN} provides a few other shortcuts and outright
15442 additions specific to Ada:
15446 The assignment statement is allowed as an expression, returning
15447 its right-hand operand as its value. Thus, you may enter
15450 (@value{GDBP}) set x := y + 3
15451 (@value{GDBP}) print A(tmp := y + 1)
15455 The semicolon is allowed as an ``operator,'' returning as its value
15456 the value of its right-hand operand.
15457 This allows, for example,
15458 complex conditional breaks:
15461 (@value{GDBP}) break f
15462 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
15466 Rather than use catenation and symbolic character names to introduce special
15467 characters into strings, one may instead use a special bracket notation,
15468 which is also used to print strings. A sequence of characters of the form
15469 @samp{["@var{XX}"]} within a string or character literal denotes the
15470 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
15471 sequence of characters @samp{["""]} also denotes a single quotation mark
15472 in strings. For example,
15474 "One line.["0a"]Next line.["0a"]"
15477 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
15481 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
15482 @t{'Max} is optional (and is ignored in any case). For example, it is valid
15486 (@value{GDBP}) print 'max(x, y)
15490 When printing arrays, @value{GDBN} uses positional notation when the
15491 array has a lower bound of 1, and uses a modified named notation otherwise.
15492 For example, a one-dimensional array of three integers with a lower bound
15493 of 3 might print as
15500 That is, in contrast to valid Ada, only the first component has a @code{=>}
15504 You may abbreviate attributes in expressions with any unique,
15505 multi-character subsequence of
15506 their names (an exact match gets preference).
15507 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
15508 in place of @t{a'length}.
15511 @cindex quoting Ada internal identifiers
15512 Since Ada is case-insensitive, the debugger normally maps identifiers you type
15513 to lower case. The GNAT compiler uses upper-case characters for
15514 some of its internal identifiers, which are normally of no interest to users.
15515 For the rare occasions when you actually have to look at them,
15516 enclose them in angle brackets to avoid the lower-case mapping.
15519 (@value{GDBP}) print <JMPBUF_SAVE>[0]
15523 Printing an object of class-wide type or dereferencing an
15524 access-to-class-wide value will display all the components of the object's
15525 specific type (as indicated by its run-time tag). Likewise, component
15526 selection on such a value will operate on the specific type of the
15531 @node Stopping Before Main Program
15532 @subsubsection Stopping at the Very Beginning
15534 @cindex breakpointing Ada elaboration code
15535 It is sometimes necessary to debug the program during elaboration, and
15536 before reaching the main procedure.
15537 As defined in the Ada Reference
15538 Manual, the elaboration code is invoked from a procedure called
15539 @code{adainit}. To run your program up to the beginning of
15540 elaboration, simply use the following two commands:
15541 @code{tbreak adainit} and @code{run}.
15543 @node Ada Exceptions
15544 @subsubsection Ada Exceptions
15546 A command is provided to list all Ada exceptions:
15549 @kindex info exceptions
15550 @item info exceptions
15551 @itemx info exceptions @var{regexp}
15552 The @code{info exceptions} command allows you to list all Ada exceptions
15553 defined within the program being debugged, as well as their addresses.
15554 With a regular expression, @var{regexp}, as argument, only those exceptions
15555 whose names match @var{regexp} are listed.
15558 Below is a small example, showing how the command can be used, first
15559 without argument, and next with a regular expression passed as an
15563 (@value{GDBP}) info exceptions
15564 All defined Ada exceptions:
15565 constraint_error: 0x613da0
15566 program_error: 0x613d20
15567 storage_error: 0x613ce0
15568 tasking_error: 0x613ca0
15569 const.aint_global_e: 0x613b00
15570 (@value{GDBP}) info exceptions const.aint
15571 All Ada exceptions matching regular expression "const.aint":
15572 constraint_error: 0x613da0
15573 const.aint_global_e: 0x613b00
15576 It is also possible to ask @value{GDBN} to stop your program's execution
15577 when an exception is raised. For more details, see @ref{Set Catchpoints}.
15580 @subsubsection Extensions for Ada Tasks
15581 @cindex Ada, tasking
15583 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
15584 @value{GDBN} provides the following task-related commands:
15589 This command shows a list of current Ada tasks, as in the following example:
15596 (@value{GDBP}) info tasks
15597 ID TID P-ID Pri State Name
15598 1 8088000 0 15 Child Activation Wait main_task
15599 2 80a4000 1 15 Accept Statement b
15600 3 809a800 1 15 Child Activation Wait a
15601 * 4 80ae800 3 15 Runnable c
15606 In this listing, the asterisk before the last task indicates it to be the
15607 task currently being inspected.
15611 Represents @value{GDBN}'s internal task number.
15617 The parent's task ID (@value{GDBN}'s internal task number).
15620 The base priority of the task.
15623 Current state of the task.
15627 The task has been created but has not been activated. It cannot be
15631 The task is not blocked for any reason known to Ada. (It may be waiting
15632 for a mutex, though.) It is conceptually "executing" in normal mode.
15635 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
15636 that were waiting on terminate alternatives have been awakened and have
15637 terminated themselves.
15639 @item Child Activation Wait
15640 The task is waiting for created tasks to complete activation.
15642 @item Accept Statement
15643 The task is waiting on an accept or selective wait statement.
15645 @item Waiting on entry call
15646 The task is waiting on an entry call.
15648 @item Async Select Wait
15649 The task is waiting to start the abortable part of an asynchronous
15653 The task is waiting on a select statement with only a delay
15656 @item Child Termination Wait
15657 The task is sleeping having completed a master within itself, and is
15658 waiting for the tasks dependent on that master to become terminated or
15659 waiting on a terminate Phase.
15661 @item Wait Child in Term Alt
15662 The task is sleeping waiting for tasks on terminate alternatives to
15663 finish terminating.
15665 @item Accepting RV with @var{taskno}
15666 The task is accepting a rendez-vous with the task @var{taskno}.
15670 Name of the task in the program.
15674 @kindex info task @var{taskno}
15675 @item info task @var{taskno}
15676 This command shows detailled informations on the specified task, as in
15677 the following example:
15682 (@value{GDBP}) info tasks
15683 ID TID P-ID Pri State Name
15684 1 8077880 0 15 Child Activation Wait main_task
15685 * 2 807c468 1 15 Runnable task_1
15686 (@value{GDBP}) info task 2
15687 Ada Task: 0x807c468
15690 Parent: 1 (main_task)
15696 @kindex task@r{ (Ada)}
15697 @cindex current Ada task ID
15698 This command prints the ID of the current task.
15704 (@value{GDBP}) info tasks
15705 ID TID P-ID Pri State Name
15706 1 8077870 0 15 Child Activation Wait main_task
15707 * 2 807c458 1 15 Runnable t
15708 (@value{GDBP}) task
15709 [Current task is 2]
15712 @item task @var{taskno}
15713 @cindex Ada task switching
15714 This command is like the @code{thread @var{threadno}}
15715 command (@pxref{Threads}). It switches the context of debugging
15716 from the current task to the given task.
15722 (@value{GDBP}) info tasks
15723 ID TID P-ID Pri State Name
15724 1 8077870 0 15 Child Activation Wait main_task
15725 * 2 807c458 1 15 Runnable t
15726 (@value{GDBP}) task 1
15727 [Switching to task 1]
15728 #0 0x8067726 in pthread_cond_wait ()
15730 #0 0x8067726 in pthread_cond_wait ()
15731 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
15732 #2 0x805cb63 in system.task_primitives.operations.sleep ()
15733 #3 0x806153e in system.tasking.stages.activate_tasks ()
15734 #4 0x804aacc in un () at un.adb:5
15737 @item break @var{linespec} task @var{taskno}
15738 @itemx break @var{linespec} task @var{taskno} if @dots{}
15739 @cindex breakpoints and tasks, in Ada
15740 @cindex task breakpoints, in Ada
15741 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
15742 These commands are like the @code{break @dots{} thread @dots{}}
15743 command (@pxref{Thread Stops}). The
15744 @var{linespec} argument specifies source lines, as described
15745 in @ref{Specify Location}.
15747 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
15748 to specify that you only want @value{GDBN} to stop the program when a
15749 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
15750 numeric task identifiers assigned by @value{GDBN}, shown in the first
15751 column of the @samp{info tasks} display.
15753 If you do not specify @samp{task @var{taskno}} when you set a
15754 breakpoint, the breakpoint applies to @emph{all} tasks of your
15757 You can use the @code{task} qualifier on conditional breakpoints as
15758 well; in this case, place @samp{task @var{taskno}} before the
15759 breakpoint condition (before the @code{if}).
15767 (@value{GDBP}) info tasks
15768 ID TID P-ID Pri State Name
15769 1 140022020 0 15 Child Activation Wait main_task
15770 2 140045060 1 15 Accept/Select Wait t2
15771 3 140044840 1 15 Runnable t1
15772 * 4 140056040 1 15 Runnable t3
15773 (@value{GDBP}) b 15 task 2
15774 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
15775 (@value{GDBP}) cont
15780 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
15782 (@value{GDBP}) info tasks
15783 ID TID P-ID Pri State Name
15784 1 140022020 0 15 Child Activation Wait main_task
15785 * 2 140045060 1 15 Runnable t2
15786 3 140044840 1 15 Runnable t1
15787 4 140056040 1 15 Delay Sleep t3
15791 @node Ada Tasks and Core Files
15792 @subsubsection Tasking Support when Debugging Core Files
15793 @cindex Ada tasking and core file debugging
15795 When inspecting a core file, as opposed to debugging a live program,
15796 tasking support may be limited or even unavailable, depending on
15797 the platform being used.
15798 For instance, on x86-linux, the list of tasks is available, but task
15799 switching is not supported.
15801 On certain platforms, the debugger needs to perform some
15802 memory writes in order to provide Ada tasking support. When inspecting
15803 a core file, this means that the core file must be opened with read-write
15804 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
15805 Under these circumstances, you should make a backup copy of the core
15806 file before inspecting it with @value{GDBN}.
15808 @node Ravenscar Profile
15809 @subsubsection Tasking Support when using the Ravenscar Profile
15810 @cindex Ravenscar Profile
15812 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
15813 specifically designed for systems with safety-critical real-time
15817 @kindex set ravenscar task-switching on
15818 @cindex task switching with program using Ravenscar Profile
15819 @item set ravenscar task-switching on
15820 Allows task switching when debugging a program that uses the Ravenscar
15821 Profile. This is the default.
15823 @kindex set ravenscar task-switching off
15824 @item set ravenscar task-switching off
15825 Turn off task switching when debugging a program that uses the Ravenscar
15826 Profile. This is mostly intended to disable the code that adds support
15827 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
15828 the Ravenscar runtime is preventing @value{GDBN} from working properly.
15829 To be effective, this command should be run before the program is started.
15831 @kindex show ravenscar task-switching
15832 @item show ravenscar task-switching
15833 Show whether it is possible to switch from task to task in a program
15834 using the Ravenscar Profile.
15839 @subsubsection Known Peculiarities of Ada Mode
15840 @cindex Ada, problems
15842 Besides the omissions listed previously (@pxref{Omissions from Ada}),
15843 we know of several problems with and limitations of Ada mode in
15845 some of which will be fixed with planned future releases of the debugger
15846 and the GNU Ada compiler.
15850 Static constants that the compiler chooses not to materialize as objects in
15851 storage are invisible to the debugger.
15854 Named parameter associations in function argument lists are ignored (the
15855 argument lists are treated as positional).
15858 Many useful library packages are currently invisible to the debugger.
15861 Fixed-point arithmetic, conversions, input, and output is carried out using
15862 floating-point arithmetic, and may give results that only approximate those on
15866 The GNAT compiler never generates the prefix @code{Standard} for any of
15867 the standard symbols defined by the Ada language. @value{GDBN} knows about
15868 this: it will strip the prefix from names when you use it, and will never
15869 look for a name you have so qualified among local symbols, nor match against
15870 symbols in other packages or subprograms. If you have
15871 defined entities anywhere in your program other than parameters and
15872 local variables whose simple names match names in @code{Standard},
15873 GNAT's lack of qualification here can cause confusion. When this happens,
15874 you can usually resolve the confusion
15875 by qualifying the problematic names with package
15876 @code{Standard} explicitly.
15879 Older versions of the compiler sometimes generate erroneous debugging
15880 information, resulting in the debugger incorrectly printing the value
15881 of affected entities. In some cases, the debugger is able to work
15882 around an issue automatically. In other cases, the debugger is able
15883 to work around the issue, but the work-around has to be specifically
15886 @kindex set ada trust-PAD-over-XVS
15887 @kindex show ada trust-PAD-over-XVS
15890 @item set ada trust-PAD-over-XVS on
15891 Configure GDB to strictly follow the GNAT encoding when computing the
15892 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
15893 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
15894 a complete description of the encoding used by the GNAT compiler).
15895 This is the default.
15897 @item set ada trust-PAD-over-XVS off
15898 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
15899 sometimes prints the wrong value for certain entities, changing @code{ada
15900 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
15901 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
15902 @code{off}, but this incurs a slight performance penalty, so it is
15903 recommended to leave this setting to @code{on} unless necessary.
15907 @cindex GNAT descriptive types
15908 @cindex GNAT encoding
15909 Internally, the debugger also relies on the compiler following a number
15910 of conventions known as the @samp{GNAT Encoding}, all documented in
15911 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
15912 how the debugging information should be generated for certain types.
15913 In particular, this convention makes use of @dfn{descriptive types},
15914 which are artificial types generated purely to help the debugger.
15916 These encodings were defined at a time when the debugging information
15917 format used was not powerful enough to describe some of the more complex
15918 types available in Ada. Since DWARF allows us to express nearly all
15919 Ada features, the long-term goal is to slowly replace these descriptive
15920 types by their pure DWARF equivalent. To facilitate that transition,
15921 a new maintenance option is available to force the debugger to ignore
15922 those descriptive types. It allows the user to quickly evaluate how
15923 well @value{GDBN} works without them.
15927 @kindex maint ada set ignore-descriptive-types
15928 @item maintenance ada set ignore-descriptive-types [on|off]
15929 Control whether the debugger should ignore descriptive types.
15930 The default is not to ignore descriptives types (@code{off}).
15932 @kindex maint ada show ignore-descriptive-types
15933 @item maintenance ada show ignore-descriptive-types
15934 Show if descriptive types are ignored by @value{GDBN}.
15938 @node Unsupported Languages
15939 @section Unsupported Languages
15941 @cindex unsupported languages
15942 @cindex minimal language
15943 In addition to the other fully-supported programming languages,
15944 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
15945 It does not represent a real programming language, but provides a set
15946 of capabilities close to what the C or assembly languages provide.
15947 This should allow most simple operations to be performed while debugging
15948 an application that uses a language currently not supported by @value{GDBN}.
15950 If the language is set to @code{auto}, @value{GDBN} will automatically
15951 select this language if the current frame corresponds to an unsupported
15955 @chapter Examining the Symbol Table
15957 The commands described in this chapter allow you to inquire about the
15958 symbols (names of variables, functions and types) defined in your
15959 program. This information is inherent in the text of your program and
15960 does not change as your program executes. @value{GDBN} finds it in your
15961 program's symbol table, in the file indicated when you started @value{GDBN}
15962 (@pxref{File Options, ,Choosing Files}), or by one of the
15963 file-management commands (@pxref{Files, ,Commands to Specify Files}).
15965 @cindex symbol names
15966 @cindex names of symbols
15967 @cindex quoting names
15968 Occasionally, you may need to refer to symbols that contain unusual
15969 characters, which @value{GDBN} ordinarily treats as word delimiters. The
15970 most frequent case is in referring to static variables in other
15971 source files (@pxref{Variables,,Program Variables}). File names
15972 are recorded in object files as debugging symbols, but @value{GDBN} would
15973 ordinarily parse a typical file name, like @file{foo.c}, as the three words
15974 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
15975 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
15982 looks up the value of @code{x} in the scope of the file @file{foo.c}.
15985 @cindex case-insensitive symbol names
15986 @cindex case sensitivity in symbol names
15987 @kindex set case-sensitive
15988 @item set case-sensitive on
15989 @itemx set case-sensitive off
15990 @itemx set case-sensitive auto
15991 Normally, when @value{GDBN} looks up symbols, it matches their names
15992 with case sensitivity determined by the current source language.
15993 Occasionally, you may wish to control that. The command @code{set
15994 case-sensitive} lets you do that by specifying @code{on} for
15995 case-sensitive matches or @code{off} for case-insensitive ones. If
15996 you specify @code{auto}, case sensitivity is reset to the default
15997 suitable for the source language. The default is case-sensitive
15998 matches for all languages except for Fortran, for which the default is
15999 case-insensitive matches.
16001 @kindex show case-sensitive
16002 @item show case-sensitive
16003 This command shows the current setting of case sensitivity for symbols
16006 @kindex set print type methods
16007 @item set print type methods
16008 @itemx set print type methods on
16009 @itemx set print type methods off
16010 Normally, when @value{GDBN} prints a class, it displays any methods
16011 declared in that class. You can control this behavior either by
16012 passing the appropriate flag to @code{ptype}, or using @command{set
16013 print type methods}. Specifying @code{on} will cause @value{GDBN} to
16014 display the methods; this is the default. Specifying @code{off} will
16015 cause @value{GDBN} to omit the methods.
16017 @kindex show print type methods
16018 @item show print type methods
16019 This command shows the current setting of method display when printing
16022 @kindex set print type typedefs
16023 @item set print type typedefs
16024 @itemx set print type typedefs on
16025 @itemx set print type typedefs off
16027 Normally, when @value{GDBN} prints a class, it displays any typedefs
16028 defined in that class. You can control this behavior either by
16029 passing the appropriate flag to @code{ptype}, or using @command{set
16030 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
16031 display the typedef definitions; this is the default. Specifying
16032 @code{off} will cause @value{GDBN} to omit the typedef definitions.
16033 Note that this controls whether the typedef definition itself is
16034 printed, not whether typedef names are substituted when printing other
16037 @kindex show print type typedefs
16038 @item show print type typedefs
16039 This command shows the current setting of typedef display when
16042 @kindex info address
16043 @cindex address of a symbol
16044 @item info address @var{symbol}
16045 Describe where the data for @var{symbol} is stored. For a register
16046 variable, this says which register it is kept in. For a non-register
16047 local variable, this prints the stack-frame offset at which the variable
16050 Note the contrast with @samp{print &@var{symbol}}, which does not work
16051 at all for a register variable, and for a stack local variable prints
16052 the exact address of the current instantiation of the variable.
16054 @kindex info symbol
16055 @cindex symbol from address
16056 @cindex closest symbol and offset for an address
16057 @item info symbol @var{addr}
16058 Print the name of a symbol which is stored at the address @var{addr}.
16059 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
16060 nearest symbol and an offset from it:
16063 (@value{GDBP}) info symbol 0x54320
16064 _initialize_vx + 396 in section .text
16068 This is the opposite of the @code{info address} command. You can use
16069 it to find out the name of a variable or a function given its address.
16071 For dynamically linked executables, the name of executable or shared
16072 library containing the symbol is also printed:
16075 (@value{GDBP}) info symbol 0x400225
16076 _start + 5 in section .text of /tmp/a.out
16077 (@value{GDBP}) info symbol 0x2aaaac2811cf
16078 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
16083 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
16084 Demangle @var{name}.
16085 If @var{language} is provided it is the name of the language to demangle
16086 @var{name} in. Otherwise @var{name} is demangled in the current language.
16088 The @samp{--} option specifies the end of options,
16089 and is useful when @var{name} begins with a dash.
16091 The parameter @code{demangle-style} specifies how to interpret the kind
16092 of mangling used. @xref{Print Settings}.
16095 @item whatis[/@var{flags}] [@var{arg}]
16096 Print the data type of @var{arg}, which can be either an expression
16097 or a name of a data type. With no argument, print the data type of
16098 @code{$}, the last value in the value history.
16100 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
16101 is not actually evaluated, and any side-effecting operations (such as
16102 assignments or function calls) inside it do not take place.
16104 If @var{arg} is a variable or an expression, @code{whatis} prints its
16105 literal type as it is used in the source code. If the type was
16106 defined using a @code{typedef}, @code{whatis} will @emph{not} print
16107 the data type underlying the @code{typedef}. If the type of the
16108 variable or the expression is a compound data type, such as
16109 @code{struct} or @code{class}, @code{whatis} never prints their
16110 fields or methods. It just prints the @code{struct}/@code{class}
16111 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
16112 such a compound data type, use @code{ptype}.
16114 If @var{arg} is a type name that was defined using @code{typedef},
16115 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
16116 Unrolling means that @code{whatis} will show the underlying type used
16117 in the @code{typedef} declaration of @var{arg}. However, if that
16118 underlying type is also a @code{typedef}, @code{whatis} will not
16121 For C code, the type names may also have the form @samp{class
16122 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
16123 @var{union-tag}} or @samp{enum @var{enum-tag}}.
16125 @var{flags} can be used to modify how the type is displayed.
16126 Available flags are:
16130 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
16131 parameters and typedefs defined in a class when printing the class'
16132 members. The @code{/r} flag disables this.
16135 Do not print methods defined in the class.
16138 Print methods defined in the class. This is the default, but the flag
16139 exists in case you change the default with @command{set print type methods}.
16142 Do not print typedefs defined in the class. Note that this controls
16143 whether the typedef definition itself is printed, not whether typedef
16144 names are substituted when printing other types.
16147 Print typedefs defined in the class. This is the default, but the flag
16148 exists in case you change the default with @command{set print type typedefs}.
16152 @item ptype[/@var{flags}] [@var{arg}]
16153 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
16154 detailed description of the type, instead of just the name of the type.
16155 @xref{Expressions, ,Expressions}.
16157 Contrary to @code{whatis}, @code{ptype} always unrolls any
16158 @code{typedef}s in its argument declaration, whether the argument is
16159 a variable, expression, or a data type. This means that @code{ptype}
16160 of a variable or an expression will not print literally its type as
16161 present in the source code---use @code{whatis} for that. @code{typedef}s at
16162 the pointer or reference targets are also unrolled. Only @code{typedef}s of
16163 fields, methods and inner @code{class typedef}s of @code{struct}s,
16164 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
16166 For example, for this variable declaration:
16169 typedef double real_t;
16170 struct complex @{ real_t real; double imag; @};
16171 typedef struct complex complex_t;
16173 real_t *real_pointer_var;
16177 the two commands give this output:
16181 (@value{GDBP}) whatis var
16183 (@value{GDBP}) ptype var
16184 type = struct complex @{
16188 (@value{GDBP}) whatis complex_t
16189 type = struct complex
16190 (@value{GDBP}) whatis struct complex
16191 type = struct complex
16192 (@value{GDBP}) ptype struct complex
16193 type = struct complex @{
16197 (@value{GDBP}) whatis real_pointer_var
16199 (@value{GDBP}) ptype real_pointer_var
16205 As with @code{whatis}, using @code{ptype} without an argument refers to
16206 the type of @code{$}, the last value in the value history.
16208 @cindex incomplete type
16209 Sometimes, programs use opaque data types or incomplete specifications
16210 of complex data structure. If the debug information included in the
16211 program does not allow @value{GDBN} to display a full declaration of
16212 the data type, it will say @samp{<incomplete type>}. For example,
16213 given these declarations:
16217 struct foo *fooptr;
16221 but no definition for @code{struct foo} itself, @value{GDBN} will say:
16224 (@value{GDBP}) ptype foo
16225 $1 = <incomplete type>
16229 ``Incomplete type'' is C terminology for data types that are not
16230 completely specified.
16233 @item info types @var{regexp}
16235 Print a brief description of all types whose names match the regular
16236 expression @var{regexp} (or all types in your program, if you supply
16237 no argument). Each complete typename is matched as though it were a
16238 complete line; thus, @samp{i type value} gives information on all
16239 types in your program whose names include the string @code{value}, but
16240 @samp{i type ^value$} gives information only on types whose complete
16241 name is @code{value}.
16243 This command differs from @code{ptype} in two ways: first, like
16244 @code{whatis}, it does not print a detailed description; second, it
16245 lists all source files where a type is defined.
16247 @kindex info type-printers
16248 @item info type-printers
16249 Versions of @value{GDBN} that ship with Python scripting enabled may
16250 have ``type printers'' available. When using @command{ptype} or
16251 @command{whatis}, these printers are consulted when the name of a type
16252 is needed. @xref{Type Printing API}, for more information on writing
16255 @code{info type-printers} displays all the available type printers.
16257 @kindex enable type-printer
16258 @kindex disable type-printer
16259 @item enable type-printer @var{name}@dots{}
16260 @item disable type-printer @var{name}@dots{}
16261 These commands can be used to enable or disable type printers.
16264 @cindex local variables
16265 @item info scope @var{location}
16266 List all the variables local to a particular scope. This command
16267 accepts a @var{location} argument---a function name, a source line, or
16268 an address preceded by a @samp{*}, and prints all the variables local
16269 to the scope defined by that location. (@xref{Specify Location}, for
16270 details about supported forms of @var{location}.) For example:
16273 (@value{GDBP}) @b{info scope command_line_handler}
16274 Scope for command_line_handler:
16275 Symbol rl is an argument at stack/frame offset 8, length 4.
16276 Symbol linebuffer is in static storage at address 0x150a18, length 4.
16277 Symbol linelength is in static storage at address 0x150a1c, length 4.
16278 Symbol p is a local variable in register $esi, length 4.
16279 Symbol p1 is a local variable in register $ebx, length 4.
16280 Symbol nline is a local variable in register $edx, length 4.
16281 Symbol repeat is a local variable at frame offset -8, length 4.
16285 This command is especially useful for determining what data to collect
16286 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
16289 @kindex info source
16291 Show information about the current source file---that is, the source file for
16292 the function containing the current point of execution:
16295 the name of the source file, and the directory containing it,
16297 the directory it was compiled in,
16299 its length, in lines,
16301 which programming language it is written in,
16303 if the debug information provides it, the program that compiled the file
16304 (which may include, e.g., the compiler version and command line arguments),
16306 whether the executable includes debugging information for that file, and
16307 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
16309 whether the debugging information includes information about
16310 preprocessor macros.
16314 @kindex info sources
16316 Print the names of all source files in your program for which there is
16317 debugging information, organized into two lists: files whose symbols
16318 have already been read, and files whose symbols will be read when needed.
16320 @kindex info functions
16321 @item info functions
16322 Print the names and data types of all defined functions.
16324 @item info functions @var{regexp}
16325 Print the names and data types of all defined functions
16326 whose names contain a match for regular expression @var{regexp}.
16327 Thus, @samp{info fun step} finds all functions whose names
16328 include @code{step}; @samp{info fun ^step} finds those whose names
16329 start with @code{step}. If a function name contains characters
16330 that conflict with the regular expression language (e.g.@:
16331 @samp{operator*()}), they may be quoted with a backslash.
16333 @kindex info variables
16334 @item info variables
16335 Print the names and data types of all variables that are defined
16336 outside of functions (i.e.@: excluding local variables).
16338 @item info variables @var{regexp}
16339 Print the names and data types of all variables (except for local
16340 variables) whose names contain a match for regular expression
16343 @kindex info classes
16344 @cindex Objective-C, classes and selectors
16346 @itemx info classes @var{regexp}
16347 Display all Objective-C classes in your program, or
16348 (with the @var{regexp} argument) all those matching a particular regular
16351 @kindex info selectors
16352 @item info selectors
16353 @itemx info selectors @var{regexp}
16354 Display all Objective-C selectors in your program, or
16355 (with the @var{regexp} argument) all those matching a particular regular
16359 This was never implemented.
16360 @kindex info methods
16362 @itemx info methods @var{regexp}
16363 The @code{info methods} command permits the user to examine all defined
16364 methods within C@t{++} program, or (with the @var{regexp} argument) a
16365 specific set of methods found in the various C@t{++} classes. Many
16366 C@t{++} classes provide a large number of methods. Thus, the output
16367 from the @code{ptype} command can be overwhelming and hard to use. The
16368 @code{info-methods} command filters the methods, printing only those
16369 which match the regular-expression @var{regexp}.
16372 @cindex opaque data types
16373 @kindex set opaque-type-resolution
16374 @item set opaque-type-resolution on
16375 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
16376 declared as a pointer to a @code{struct}, @code{class}, or
16377 @code{union}---for example, @code{struct MyType *}---that is used in one
16378 source file although the full declaration of @code{struct MyType} is in
16379 another source file. The default is on.
16381 A change in the setting of this subcommand will not take effect until
16382 the next time symbols for a file are loaded.
16384 @item set opaque-type-resolution off
16385 Tell @value{GDBN} not to resolve opaque types. In this case, the type
16386 is printed as follows:
16388 @{<no data fields>@}
16391 @kindex show opaque-type-resolution
16392 @item show opaque-type-resolution
16393 Show whether opaque types are resolved or not.
16395 @kindex set print symbol-loading
16396 @cindex print messages when symbols are loaded
16397 @item set print symbol-loading
16398 @itemx set print symbol-loading full
16399 @itemx set print symbol-loading brief
16400 @itemx set print symbol-loading off
16401 The @code{set print symbol-loading} command allows you to control the
16402 printing of messages when @value{GDBN} loads symbol information.
16403 By default a message is printed for the executable and one for each
16404 shared library, and normally this is what you want. However, when
16405 debugging apps with large numbers of shared libraries these messages
16407 When set to @code{brief} a message is printed for each executable,
16408 and when @value{GDBN} loads a collection of shared libraries at once
16409 it will only print one message regardless of the number of shared
16410 libraries. When set to @code{off} no messages are printed.
16412 @kindex show print symbol-loading
16413 @item show print symbol-loading
16414 Show whether messages will be printed when a @value{GDBN} command
16415 entered from the keyboard causes symbol information to be loaded.
16417 @kindex maint print symbols
16418 @cindex symbol dump
16419 @kindex maint print psymbols
16420 @cindex partial symbol dump
16421 @kindex maint print msymbols
16422 @cindex minimal symbol dump
16423 @item maint print symbols @var{filename}
16424 @itemx maint print psymbols @var{filename}
16425 @itemx maint print msymbols @var{filename}
16426 Write a dump of debugging symbol data into the file @var{filename}.
16427 These commands are used to debug the @value{GDBN} symbol-reading code. Only
16428 symbols with debugging data are included. If you use @samp{maint print
16429 symbols}, @value{GDBN} includes all the symbols for which it has already
16430 collected full details: that is, @var{filename} reflects symbols for
16431 only those files whose symbols @value{GDBN} has read. You can use the
16432 command @code{info sources} to find out which files these are. If you
16433 use @samp{maint print psymbols} instead, the dump shows information about
16434 symbols that @value{GDBN} only knows partially---that is, symbols defined in
16435 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
16436 @samp{maint print msymbols} dumps just the minimal symbol information
16437 required for each object file from which @value{GDBN} has read some symbols.
16438 @xref{Files, ,Commands to Specify Files}, for a discussion of how
16439 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
16441 @kindex maint info symtabs
16442 @kindex maint info psymtabs
16443 @cindex listing @value{GDBN}'s internal symbol tables
16444 @cindex symbol tables, listing @value{GDBN}'s internal
16445 @cindex full symbol tables, listing @value{GDBN}'s internal
16446 @cindex partial symbol tables, listing @value{GDBN}'s internal
16447 @item maint info symtabs @r{[} @var{regexp} @r{]}
16448 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
16450 List the @code{struct symtab} or @code{struct partial_symtab}
16451 structures whose names match @var{regexp}. If @var{regexp} is not
16452 given, list them all. The output includes expressions which you can
16453 copy into a @value{GDBN} debugging this one to examine a particular
16454 structure in more detail. For example:
16457 (@value{GDBP}) maint info psymtabs dwarf2read
16458 @{ objfile /home/gnu/build/gdb/gdb
16459 ((struct objfile *) 0x82e69d0)
16460 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
16461 ((struct partial_symtab *) 0x8474b10)
16464 text addresses 0x814d3c8 -- 0x8158074
16465 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
16466 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
16467 dependencies (none)
16470 (@value{GDBP}) maint info symtabs
16474 We see that there is one partial symbol table whose filename contains
16475 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
16476 and we see that @value{GDBN} has not read in any symtabs yet at all.
16477 If we set a breakpoint on a function, that will cause @value{GDBN} to
16478 read the symtab for the compilation unit containing that function:
16481 (@value{GDBP}) break dwarf2_psymtab_to_symtab
16482 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
16484 (@value{GDBP}) maint info symtabs
16485 @{ objfile /home/gnu/build/gdb/gdb
16486 ((struct objfile *) 0x82e69d0)
16487 @{ symtab /home/gnu/src/gdb/dwarf2read.c
16488 ((struct symtab *) 0x86c1f38)
16491 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
16492 linetable ((struct linetable *) 0x8370fa0)
16493 debugformat DWARF 2
16502 @chapter Altering Execution
16504 Once you think you have found an error in your program, you might want to
16505 find out for certain whether correcting the apparent error would lead to
16506 correct results in the rest of the run. You can find the answer by
16507 experiment, using the @value{GDBN} features for altering execution of the
16510 For example, you can store new values into variables or memory
16511 locations, give your program a signal, restart it at a different
16512 address, or even return prematurely from a function.
16515 * Assignment:: Assignment to variables
16516 * Jumping:: Continuing at a different address
16517 * Signaling:: Giving your program a signal
16518 * Returning:: Returning from a function
16519 * Calling:: Calling your program's functions
16520 * Patching:: Patching your program
16521 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
16525 @section Assignment to Variables
16528 @cindex setting variables
16529 To alter the value of a variable, evaluate an assignment expression.
16530 @xref{Expressions, ,Expressions}. For example,
16537 stores the value 4 into the variable @code{x}, and then prints the
16538 value of the assignment expression (which is 4).
16539 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
16540 information on operators in supported languages.
16542 @kindex set variable
16543 @cindex variables, setting
16544 If you are not interested in seeing the value of the assignment, use the
16545 @code{set} command instead of the @code{print} command. @code{set} is
16546 really the same as @code{print} except that the expression's value is
16547 not printed and is not put in the value history (@pxref{Value History,
16548 ,Value History}). The expression is evaluated only for its effects.
16550 If the beginning of the argument string of the @code{set} command
16551 appears identical to a @code{set} subcommand, use the @code{set
16552 variable} command instead of just @code{set}. This command is identical
16553 to @code{set} except for its lack of subcommands. For example, if your
16554 program has a variable @code{width}, you get an error if you try to set
16555 a new value with just @samp{set width=13}, because @value{GDBN} has the
16556 command @code{set width}:
16559 (@value{GDBP}) whatis width
16561 (@value{GDBP}) p width
16563 (@value{GDBP}) set width=47
16564 Invalid syntax in expression.
16568 The invalid expression, of course, is @samp{=47}. In
16569 order to actually set the program's variable @code{width}, use
16572 (@value{GDBP}) set var width=47
16575 Because the @code{set} command has many subcommands that can conflict
16576 with the names of program variables, it is a good idea to use the
16577 @code{set variable} command instead of just @code{set}. For example, if
16578 your program has a variable @code{g}, you run into problems if you try
16579 to set a new value with just @samp{set g=4}, because @value{GDBN} has
16580 the command @code{set gnutarget}, abbreviated @code{set g}:
16584 (@value{GDBP}) whatis g
16588 (@value{GDBP}) set g=4
16592 The program being debugged has been started already.
16593 Start it from the beginning? (y or n) y
16594 Starting program: /home/smith/cc_progs/a.out
16595 "/home/smith/cc_progs/a.out": can't open to read symbols:
16596 Invalid bfd target.
16597 (@value{GDBP}) show g
16598 The current BFD target is "=4".
16603 The program variable @code{g} did not change, and you silently set the
16604 @code{gnutarget} to an invalid value. In order to set the variable
16608 (@value{GDBP}) set var g=4
16611 @value{GDBN} allows more implicit conversions in assignments than C; you can
16612 freely store an integer value into a pointer variable or vice versa,
16613 and you can convert any structure to any other structure that is the
16614 same length or shorter.
16615 @comment FIXME: how do structs align/pad in these conversions?
16616 @comment /doc@cygnus.com 18dec1990
16618 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
16619 construct to generate a value of specified type at a specified address
16620 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
16621 to memory location @code{0x83040} as an integer (which implies a certain size
16622 and representation in memory), and
16625 set @{int@}0x83040 = 4
16629 stores the value 4 into that memory location.
16632 @section Continuing at a Different Address
16634 Ordinarily, when you continue your program, you do so at the place where
16635 it stopped, with the @code{continue} command. You can instead continue at
16636 an address of your own choosing, with the following commands:
16640 @kindex j @r{(@code{jump})}
16641 @item jump @var{linespec}
16642 @itemx j @var{linespec}
16643 @itemx jump @var{location}
16644 @itemx j @var{location}
16645 Resume execution at line @var{linespec} or at address given by
16646 @var{location}. Execution stops again immediately if there is a
16647 breakpoint there. @xref{Specify Location}, for a description of the
16648 different forms of @var{linespec} and @var{location}. It is common
16649 practice to use the @code{tbreak} command in conjunction with
16650 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
16652 The @code{jump} command does not change the current stack frame, or
16653 the stack pointer, or the contents of any memory location or any
16654 register other than the program counter. If line @var{linespec} is in
16655 a different function from the one currently executing, the results may
16656 be bizarre if the two functions expect different patterns of arguments or
16657 of local variables. For this reason, the @code{jump} command requests
16658 confirmation if the specified line is not in the function currently
16659 executing. However, even bizarre results are predictable if you are
16660 well acquainted with the machine-language code of your program.
16663 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
16664 On many systems, you can get much the same effect as the @code{jump}
16665 command by storing a new value into the register @code{$pc}. The
16666 difference is that this does not start your program running; it only
16667 changes the address of where it @emph{will} run when you continue. For
16675 makes the next @code{continue} command or stepping command execute at
16676 address @code{0x485}, rather than at the address where your program stopped.
16677 @xref{Continuing and Stepping, ,Continuing and Stepping}.
16679 The most common occasion to use the @code{jump} command is to back
16680 up---perhaps with more breakpoints set---over a portion of a program
16681 that has already executed, in order to examine its execution in more
16686 @section Giving your Program a Signal
16687 @cindex deliver a signal to a program
16691 @item signal @var{signal}
16692 Resume execution where your program is stopped, but immediately give it the
16693 signal @var{signal}. The @var{signal} can be the name or the number of a
16694 signal. For example, on many systems @code{signal 2} and @code{signal
16695 SIGINT} are both ways of sending an interrupt signal.
16697 Alternatively, if @var{signal} is zero, continue execution without
16698 giving a signal. This is useful when your program stopped on account of
16699 a signal and would ordinarily see the signal when resumed with the
16700 @code{continue} command; @samp{signal 0} causes it to resume without a
16703 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
16704 delivered to the currently selected thread, not the thread that last
16705 reported a stop. This includes the situation where a thread was
16706 stopped due to a signal. So if you want to continue execution
16707 suppressing the signal that stopped a thread, you should select that
16708 same thread before issuing the @samp{signal 0} command. If you issue
16709 the @samp{signal 0} command with another thread as the selected one,
16710 @value{GDBN} detects that and asks for confirmation.
16712 Invoking the @code{signal} command is not the same as invoking the
16713 @code{kill} utility from the shell. Sending a signal with @code{kill}
16714 causes @value{GDBN} to decide what to do with the signal depending on
16715 the signal handling tables (@pxref{Signals}). The @code{signal} command
16716 passes the signal directly to your program.
16718 @code{signal} does not repeat when you press @key{RET} a second time
16719 after executing the command.
16721 @kindex queue-signal
16722 @item queue-signal @var{signal}
16723 Queue @var{signal} to be delivered immediately to the current thread
16724 when execution of the thread resumes. The @var{signal} can be the name or
16725 the number of a signal. For example, on many systems @code{signal 2} and
16726 @code{signal SIGINT} are both ways of sending an interrupt signal.
16727 The handling of the signal must be set to pass the signal to the program,
16728 otherwise @value{GDBN} will report an error.
16729 You can control the handling of signals from @value{GDBN} with the
16730 @code{handle} command (@pxref{Signals}).
16732 Alternatively, if @var{signal} is zero, any currently queued signal
16733 for the current thread is discarded and when execution resumes no signal
16734 will be delivered. This is useful when your program stopped on account
16735 of a signal and would ordinarily see the signal when resumed with the
16736 @code{continue} command.
16738 This command differs from the @code{signal} command in that the signal
16739 is just queued, execution is not resumed. And @code{queue-signal} cannot
16740 be used to pass a signal whose handling state has been set to @code{nopass}
16745 @xref{stepping into signal handlers}, for information on how stepping
16746 commands behave when the thread has a signal queued.
16749 @section Returning from a Function
16752 @cindex returning from a function
16755 @itemx return @var{expression}
16756 You can cancel execution of a function call with the @code{return}
16757 command. If you give an
16758 @var{expression} argument, its value is used as the function's return
16762 When you use @code{return}, @value{GDBN} discards the selected stack frame
16763 (and all frames within it). You can think of this as making the
16764 discarded frame return prematurely. If you wish to specify a value to
16765 be returned, give that value as the argument to @code{return}.
16767 This pops the selected stack frame (@pxref{Selection, ,Selecting a
16768 Frame}), and any other frames inside of it, leaving its caller as the
16769 innermost remaining frame. That frame becomes selected. The
16770 specified value is stored in the registers used for returning values
16773 The @code{return} command does not resume execution; it leaves the
16774 program stopped in the state that would exist if the function had just
16775 returned. In contrast, the @code{finish} command (@pxref{Continuing
16776 and Stepping, ,Continuing and Stepping}) resumes execution until the
16777 selected stack frame returns naturally.
16779 @value{GDBN} needs to know how the @var{expression} argument should be set for
16780 the inferior. The concrete registers assignment depends on the OS ABI and the
16781 type being returned by the selected stack frame. For example it is common for
16782 OS ABI to return floating point values in FPU registers while integer values in
16783 CPU registers. Still some ABIs return even floating point values in CPU
16784 registers. Larger integer widths (such as @code{long long int}) also have
16785 specific placement rules. @value{GDBN} already knows the OS ABI from its
16786 current target so it needs to find out also the type being returned to make the
16787 assignment into the right register(s).
16789 Normally, the selected stack frame has debug info. @value{GDBN} will always
16790 use the debug info instead of the implicit type of @var{expression} when the
16791 debug info is available. For example, if you type @kbd{return -1}, and the
16792 function in the current stack frame is declared to return a @code{long long
16793 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
16794 into a @code{long long int}:
16797 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
16799 (@value{GDBP}) return -1
16800 Make func return now? (y or n) y
16801 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
16802 43 printf ("result=%lld\n", func ());
16806 However, if the selected stack frame does not have a debug info, e.g., if the
16807 function was compiled without debug info, @value{GDBN} has to find out the type
16808 to return from user. Specifying a different type by mistake may set the value
16809 in different inferior registers than the caller code expects. For example,
16810 typing @kbd{return -1} with its implicit type @code{int} would set only a part
16811 of a @code{long long int} result for a debug info less function (on 32-bit
16812 architectures). Therefore the user is required to specify the return type by
16813 an appropriate cast explicitly:
16816 Breakpoint 2, 0x0040050b in func ()
16817 (@value{GDBP}) return -1
16818 Return value type not available for selected stack frame.
16819 Please use an explicit cast of the value to return.
16820 (@value{GDBP}) return (long long int) -1
16821 Make selected stack frame return now? (y or n) y
16822 #0 0x00400526 in main ()
16827 @section Calling Program Functions
16830 @cindex calling functions
16831 @cindex inferior functions, calling
16832 @item print @var{expr}
16833 Evaluate the expression @var{expr} and display the resulting value.
16834 The expression may include calls to functions in the program being
16838 @item call @var{expr}
16839 Evaluate the expression @var{expr} without displaying @code{void}
16842 You can use this variant of the @code{print} command if you want to
16843 execute a function from your program that does not return anything
16844 (a.k.a.@: @dfn{a void function}), but without cluttering the output
16845 with @code{void} returned values that @value{GDBN} will otherwise
16846 print. If the result is not void, it is printed and saved in the
16850 It is possible for the function you call via the @code{print} or
16851 @code{call} command to generate a signal (e.g., if there's a bug in
16852 the function, or if you passed it incorrect arguments). What happens
16853 in that case is controlled by the @code{set unwindonsignal} command.
16855 Similarly, with a C@t{++} program it is possible for the function you
16856 call via the @code{print} or @code{call} command to generate an
16857 exception that is not handled due to the constraints of the dummy
16858 frame. In this case, any exception that is raised in the frame, but has
16859 an out-of-frame exception handler will not be found. GDB builds a
16860 dummy-frame for the inferior function call, and the unwinder cannot
16861 seek for exception handlers outside of this dummy-frame. What happens
16862 in that case is controlled by the
16863 @code{set unwind-on-terminating-exception} command.
16866 @item set unwindonsignal
16867 @kindex set unwindonsignal
16868 @cindex unwind stack in called functions
16869 @cindex call dummy stack unwinding
16870 Set unwinding of the stack if a signal is received while in a function
16871 that @value{GDBN} called in the program being debugged. If set to on,
16872 @value{GDBN} unwinds the stack it created for the call and restores
16873 the context to what it was before the call. If set to off (the
16874 default), @value{GDBN} stops in the frame where the signal was
16877 @item show unwindonsignal
16878 @kindex show unwindonsignal
16879 Show the current setting of stack unwinding in the functions called by
16882 @item set unwind-on-terminating-exception
16883 @kindex set unwind-on-terminating-exception
16884 @cindex unwind stack in called functions with unhandled exceptions
16885 @cindex call dummy stack unwinding on unhandled exception.
16886 Set unwinding of the stack if a C@t{++} exception is raised, but left
16887 unhandled while in a function that @value{GDBN} called in the program being
16888 debugged. If set to on (the default), @value{GDBN} unwinds the stack
16889 it created for the call and restores the context to what it was before
16890 the call. If set to off, @value{GDBN} the exception is delivered to
16891 the default C@t{++} exception handler and the inferior terminated.
16893 @item show unwind-on-terminating-exception
16894 @kindex show unwind-on-terminating-exception
16895 Show the current setting of stack unwinding in the functions called by
16900 @cindex weak alias functions
16901 Sometimes, a function you wish to call is actually a @dfn{weak alias}
16902 for another function. In such case, @value{GDBN} might not pick up
16903 the type information, including the types of the function arguments,
16904 which causes @value{GDBN} to call the inferior function incorrectly.
16905 As a result, the called function will function erroneously and may
16906 even crash. A solution to that is to use the name of the aliased
16910 @section Patching Programs
16912 @cindex patching binaries
16913 @cindex writing into executables
16914 @cindex writing into corefiles
16916 By default, @value{GDBN} opens the file containing your program's
16917 executable code (or the corefile) read-only. This prevents accidental
16918 alterations to machine code; but it also prevents you from intentionally
16919 patching your program's binary.
16921 If you'd like to be able to patch the binary, you can specify that
16922 explicitly with the @code{set write} command. For example, you might
16923 want to turn on internal debugging flags, or even to make emergency
16929 @itemx set write off
16930 If you specify @samp{set write on}, @value{GDBN} opens executable and
16931 core files for both reading and writing; if you specify @kbd{set write
16932 off} (the default), @value{GDBN} opens them read-only.
16934 If you have already loaded a file, you must load it again (using the
16935 @code{exec-file} or @code{core-file} command) after changing @code{set
16936 write}, for your new setting to take effect.
16940 Display whether executable files and core files are opened for writing
16941 as well as reading.
16944 @node Compiling and Injecting Code
16945 @section Compiling and injecting code in @value{GDBN}
16946 @cindex injecting code
16947 @cindex writing into executables
16948 @cindex compiling code
16950 @value{GDBN} supports on-demand compilation and code injection into
16951 programs running under @value{GDBN}. GCC 5.0 or higher built with
16952 @file{libcc1.so} must be installed for this functionality to be enabled.
16953 This functionality is implemented with the following commands.
16956 @kindex compile code
16957 @item compile code @var{source-code}
16958 @itemx compile code -raw @var{--} @var{source-code}
16959 Compile @var{source-code} with the compiler language found as the current
16960 language in @value{GDBN} (@pxref{Languages}). If compilation and
16961 injection is not supported with the current language specified in
16962 @value{GDBN}, or the compiler does not support this feature, an error
16963 message will be printed. If @var{source-code} compiles and links
16964 successfully, @value{GDBN} will load the object-code emitted,
16965 and execute it within the context of the currently selected inferior.
16966 It is important to note that the compiled code is executed immediately.
16967 After execution, the compiled code is removed from @value{GDBN} and any
16968 new types or variables you have defined will be deleted.
16970 The command allows you to specify @var{source-code} in two ways.
16971 The simplest method is to provide a single line of code to the command.
16975 compile code printf ("hello world\n");
16978 If you specify options on the command line as well as source code, they
16979 may conflict. The @samp{--} delimiter can be used to separate options
16980 from actual source code. E.g.:
16983 compile code -r -- printf ("hello world\n");
16986 Alternatively you can enter source code as multiple lines of text. To
16987 enter this mode, invoke the @samp{compile code} command without any text
16988 following the command. This will start the multiple-line editor and
16989 allow you to type as many lines of source code as required. When you
16990 have completed typing, enter @samp{end} on its own line to exit the
16995 >printf ("hello\n");
16996 >printf ("world\n");
17000 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
17001 provided @var{source-code} in a callable scope. In this case, you must
17002 specify the entry point of the code by defining a function named
17003 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
17004 inferior. Using @samp{-raw} option may be needed for example when
17005 @var{source-code} requires @samp{#include} lines which may conflict with
17006 inferior symbols otherwise.
17008 @kindex compile file
17009 @item compile file @var{filename}
17010 @itemx compile file -raw @var{filename}
17011 Like @code{compile code}, but take the source code from @var{filename}.
17014 compile file /home/user/example.c
17018 @subsection Caveats when using the @code{compile} command
17020 There are a few caveats to keep in mind when using the @code{compile}
17021 command. As the caveats are different per language, the table below
17022 highlights specific issues on a per language basis.
17025 @item C code examples and caveats
17026 When the language in @value{GDBN} is set to @samp{C}, the compiler will
17027 attempt to compile the source code with a @samp{C} compiler. The source
17028 code provided to the @code{compile} command will have much the same
17029 access to variables and types as it normally would if it were part of
17030 the program currently being debugged in @value{GDBN}.
17032 Below is a sample program that forms the basis of the examples that
17033 follow. This program has been compiled and loaded into @value{GDBN},
17034 much like any other normal debugging session.
17037 void function1 (void)
17040 printf ("function 1\n");
17043 void function2 (void)
17058 For the purposes of the examples in this section, the program above has
17059 been compiled, loaded into @value{GDBN}, stopped at the function
17060 @code{main}, and @value{GDBN} is awaiting input from the user.
17062 To access variables and types for any program in @value{GDBN}, the
17063 program must be compiled and packaged with debug information. The
17064 @code{compile} command is not an exception to this rule. Without debug
17065 information, you can still use the @code{compile} command, but you will
17066 be very limited in what variables and types you can access.
17068 So with that in mind, the example above has been compiled with debug
17069 information enabled. The @code{compile} command will have access to
17070 all variables and types (except those that may have been optimized
17071 out). Currently, as @value{GDBN} has stopped the program in the
17072 @code{main} function, the @code{compile} command would have access to
17073 the variable @code{k}. You could invoke the @code{compile} command
17074 and type some source code to set the value of @code{k}. You can also
17075 read it, or do anything with that variable you would normally do in
17076 @code{C}. Be aware that changes to inferior variables in the
17077 @code{compile} command are persistent. In the following example:
17080 compile code k = 3;
17084 the variable @code{k} is now 3. It will retain that value until
17085 something else in the example program changes it, or another
17086 @code{compile} command changes it.
17088 Normal scope and access rules apply to source code compiled and
17089 injected by the @code{compile} command. In the example, the variables
17090 @code{j} and @code{k} are not accessible yet, because the program is
17091 currently stopped in the @code{main} function, where these variables
17092 are not in scope. Therefore, the following command
17095 compile code j = 3;
17099 will result in a compilation error message.
17101 Once the program is continued, execution will bring these variables in
17102 scope, and they will become accessible; then the code you specify via
17103 the @code{compile} command will be able to access them.
17105 You can create variables and types with the @code{compile} command as
17106 part of your source code. Variables and types that are created as part
17107 of the @code{compile} command are not visible to the rest of the program for
17108 the duration of its run. This example is valid:
17111 compile code int ff = 5; printf ("ff is %d\n", ff);
17114 However, if you were to type the following into @value{GDBN} after that
17115 command has completed:
17118 compile code printf ("ff is %d\n'', ff);
17122 a compiler error would be raised as the variable @code{ff} no longer
17123 exists. Object code generated and injected by the @code{compile}
17124 command is removed when its execution ends. Caution is advised
17125 when assigning to program variables values of variables created by the
17126 code submitted to the @code{compile} command. This example is valid:
17129 compile code int ff = 5; k = ff;
17132 The value of the variable @code{ff} is assigned to @code{k}. The variable
17133 @code{k} does not require the existence of @code{ff} to maintain the value
17134 it has been assigned. However, pointers require particular care in
17135 assignment. If the source code compiled with the @code{compile} command
17136 changed the address of a pointer in the example program, perhaps to a
17137 variable created in the @code{compile} command, that pointer would point
17138 to an invalid location when the command exits. The following example
17139 would likely cause issues with your debugged program:
17142 compile code int ff = 5; p = &ff;
17145 In this example, @code{p} would point to @code{ff} when the
17146 @code{compile} command is executing the source code provided to it.
17147 However, as variables in the (example) program persist with their
17148 assigned values, the variable @code{p} would point to an invalid
17149 location when the command exists. A general rule should be followed
17150 in that you should either assign @code{NULL} to any assigned pointers,
17151 or restore a valid location to the pointer before the command exits.
17153 Similar caution must be exercised with any structs, unions, and typedefs
17154 defined in @code{compile} command. Types defined in the @code{compile}
17155 command will no longer be available in the next @code{compile} command.
17156 Therefore, if you cast a variable to a type defined in the
17157 @code{compile} command, care must be taken to ensure that any future
17158 need to resolve the type can be achieved.
17161 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
17162 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
17163 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
17164 Compilation failed.
17165 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
17169 Variables that have been optimized away by the compiler are not
17170 accessible to the code submitted to the @code{compile} command.
17171 Access to those variables will generate a compiler error which @value{GDBN}
17172 will print to the console.
17176 @chapter @value{GDBN} Files
17178 @value{GDBN} needs to know the file name of the program to be debugged,
17179 both in order to read its symbol table and in order to start your
17180 program. To debug a core dump of a previous run, you must also tell
17181 @value{GDBN} the name of the core dump file.
17184 * Files:: Commands to specify files
17185 * Separate Debug Files:: Debugging information in separate files
17186 * MiniDebugInfo:: Debugging information in a special section
17187 * Index Files:: Index files speed up GDB
17188 * Symbol Errors:: Errors reading symbol files
17189 * Data Files:: GDB data files
17193 @section Commands to Specify Files
17195 @cindex symbol table
17196 @cindex core dump file
17198 You may want to specify executable and core dump file names. The usual
17199 way to do this is at start-up time, using the arguments to
17200 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
17201 Out of @value{GDBN}}).
17203 Occasionally it is necessary to change to a different file during a
17204 @value{GDBN} session. Or you may run @value{GDBN} and forget to
17205 specify a file you want to use. Or you are debugging a remote target
17206 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
17207 Program}). In these situations the @value{GDBN} commands to specify
17208 new files are useful.
17211 @cindex executable file
17213 @item file @var{filename}
17214 Use @var{filename} as the program to be debugged. It is read for its
17215 symbols and for the contents of pure memory. It is also the program
17216 executed when you use the @code{run} command. If you do not specify a
17217 directory and the file is not found in the @value{GDBN} working directory,
17218 @value{GDBN} uses the environment variable @code{PATH} as a list of
17219 directories to search, just as the shell does when looking for a program
17220 to run. You can change the value of this variable, for both @value{GDBN}
17221 and your program, using the @code{path} command.
17223 @cindex unlinked object files
17224 @cindex patching object files
17225 You can load unlinked object @file{.o} files into @value{GDBN} using
17226 the @code{file} command. You will not be able to ``run'' an object
17227 file, but you can disassemble functions and inspect variables. Also,
17228 if the underlying BFD functionality supports it, you could use
17229 @kbd{gdb -write} to patch object files using this technique. Note
17230 that @value{GDBN} can neither interpret nor modify relocations in this
17231 case, so branches and some initialized variables will appear to go to
17232 the wrong place. But this feature is still handy from time to time.
17235 @code{file} with no argument makes @value{GDBN} discard any information it
17236 has on both executable file and the symbol table.
17239 @item exec-file @r{[} @var{filename} @r{]}
17240 Specify that the program to be run (but not the symbol table) is found
17241 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
17242 if necessary to locate your program. Omitting @var{filename} means to
17243 discard information on the executable file.
17245 @kindex symbol-file
17246 @item symbol-file @r{[} @var{filename} @r{]}
17247 Read symbol table information from file @var{filename}. @code{PATH} is
17248 searched when necessary. Use the @code{file} command to get both symbol
17249 table and program to run from the same file.
17251 @code{symbol-file} with no argument clears out @value{GDBN} information on your
17252 program's symbol table.
17254 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
17255 some breakpoints and auto-display expressions. This is because they may
17256 contain pointers to the internal data recording symbols and data types,
17257 which are part of the old symbol table data being discarded inside
17260 @code{symbol-file} does not repeat if you press @key{RET} again after
17263 When @value{GDBN} is configured for a particular environment, it
17264 understands debugging information in whatever format is the standard
17265 generated for that environment; you may use either a @sc{gnu} compiler, or
17266 other compilers that adhere to the local conventions.
17267 Best results are usually obtained from @sc{gnu} compilers; for example,
17268 using @code{@value{NGCC}} you can generate debugging information for
17271 For most kinds of object files, with the exception of old SVR3 systems
17272 using COFF, the @code{symbol-file} command does not normally read the
17273 symbol table in full right away. Instead, it scans the symbol table
17274 quickly to find which source files and which symbols are present. The
17275 details are read later, one source file at a time, as they are needed.
17277 The purpose of this two-stage reading strategy is to make @value{GDBN}
17278 start up faster. For the most part, it is invisible except for
17279 occasional pauses while the symbol table details for a particular source
17280 file are being read. (The @code{set verbose} command can turn these
17281 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
17282 Warnings and Messages}.)
17284 We have not implemented the two-stage strategy for COFF yet. When the
17285 symbol table is stored in COFF format, @code{symbol-file} reads the
17286 symbol table data in full right away. Note that ``stabs-in-COFF''
17287 still does the two-stage strategy, since the debug info is actually
17291 @cindex reading symbols immediately
17292 @cindex symbols, reading immediately
17293 @item symbol-file @r{[} -readnow @r{]} @var{filename}
17294 @itemx file @r{[} -readnow @r{]} @var{filename}
17295 You can override the @value{GDBN} two-stage strategy for reading symbol
17296 tables by using the @samp{-readnow} option with any of the commands that
17297 load symbol table information, if you want to be sure @value{GDBN} has the
17298 entire symbol table available.
17300 @c FIXME: for now no mention of directories, since this seems to be in
17301 @c flux. 13mar1992 status is that in theory GDB would look either in
17302 @c current dir or in same dir as myprog; but issues like competing
17303 @c GDB's, or clutter in system dirs, mean that in practice right now
17304 @c only current dir is used. FFish says maybe a special GDB hierarchy
17305 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
17309 @item core-file @r{[}@var{filename}@r{]}
17311 Specify the whereabouts of a core dump file to be used as the ``contents
17312 of memory''. Traditionally, core files contain only some parts of the
17313 address space of the process that generated them; @value{GDBN} can access the
17314 executable file itself for other parts.
17316 @code{core-file} with no argument specifies that no core file is
17319 Note that the core file is ignored when your program is actually running
17320 under @value{GDBN}. So, if you have been running your program and you
17321 wish to debug a core file instead, you must kill the subprocess in which
17322 the program is running. To do this, use the @code{kill} command
17323 (@pxref{Kill Process, ,Killing the Child Process}).
17325 @kindex add-symbol-file
17326 @cindex dynamic linking
17327 @item add-symbol-file @var{filename} @var{address}
17328 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
17329 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
17330 The @code{add-symbol-file} command reads additional symbol table
17331 information from the file @var{filename}. You would use this command
17332 when @var{filename} has been dynamically loaded (by some other means)
17333 into the program that is running. The @var{address} should give the memory
17334 address at which the file has been loaded; @value{GDBN} cannot figure
17335 this out for itself. You can additionally specify an arbitrary number
17336 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
17337 section name and base address for that section. You can specify any
17338 @var{address} as an expression.
17340 The symbol table of the file @var{filename} is added to the symbol table
17341 originally read with the @code{symbol-file} command. You can use the
17342 @code{add-symbol-file} command any number of times; the new symbol data
17343 thus read is kept in addition to the old.
17345 Changes can be reverted using the command @code{remove-symbol-file}.
17347 @cindex relocatable object files, reading symbols from
17348 @cindex object files, relocatable, reading symbols from
17349 @cindex reading symbols from relocatable object files
17350 @cindex symbols, reading from relocatable object files
17351 @cindex @file{.o} files, reading symbols from
17352 Although @var{filename} is typically a shared library file, an
17353 executable file, or some other object file which has been fully
17354 relocated for loading into a process, you can also load symbolic
17355 information from relocatable @file{.o} files, as long as:
17359 the file's symbolic information refers only to linker symbols defined in
17360 that file, not to symbols defined by other object files,
17362 every section the file's symbolic information refers to has actually
17363 been loaded into the inferior, as it appears in the file, and
17365 you can determine the address at which every section was loaded, and
17366 provide these to the @code{add-symbol-file} command.
17370 Some embedded operating systems, like Sun Chorus and VxWorks, can load
17371 relocatable files into an already running program; such systems
17372 typically make the requirements above easy to meet. However, it's
17373 important to recognize that many native systems use complex link
17374 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
17375 assembly, for example) that make the requirements difficult to meet. In
17376 general, one cannot assume that using @code{add-symbol-file} to read a
17377 relocatable object file's symbolic information will have the same effect
17378 as linking the relocatable object file into the program in the normal
17381 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
17383 @kindex remove-symbol-file
17384 @item remove-symbol-file @var{filename}
17385 @item remove-symbol-file -a @var{address}
17386 Remove a symbol file added via the @code{add-symbol-file} command. The
17387 file to remove can be identified by its @var{filename} or by an @var{address}
17388 that lies within the boundaries of this symbol file in memory. Example:
17391 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
17392 add symbol table from file "/home/user/gdb/mylib.so" at
17393 .text_addr = 0x7ffff7ff9480
17395 Reading symbols from /home/user/gdb/mylib.so...done.
17396 (gdb) remove-symbol-file -a 0x7ffff7ff9480
17397 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
17402 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
17404 @kindex add-symbol-file-from-memory
17405 @cindex @code{syscall DSO}
17406 @cindex load symbols from memory
17407 @item add-symbol-file-from-memory @var{address}
17408 Load symbols from the given @var{address} in a dynamically loaded
17409 object file whose image is mapped directly into the inferior's memory.
17410 For example, the Linux kernel maps a @code{syscall DSO} into each
17411 process's address space; this DSO provides kernel-specific code for
17412 some system calls. The argument can be any expression whose
17413 evaluation yields the address of the file's shared object file header.
17414 For this command to work, you must have used @code{symbol-file} or
17415 @code{exec-file} commands in advance.
17418 @item section @var{section} @var{addr}
17419 The @code{section} command changes the base address of the named
17420 @var{section} of the exec file to @var{addr}. This can be used if the
17421 exec file does not contain section addresses, (such as in the
17422 @code{a.out} format), or when the addresses specified in the file
17423 itself are wrong. Each section must be changed separately. The
17424 @code{info files} command, described below, lists all the sections and
17428 @kindex info target
17431 @code{info files} and @code{info target} are synonymous; both print the
17432 current target (@pxref{Targets, ,Specifying a Debugging Target}),
17433 including the names of the executable and core dump files currently in
17434 use by @value{GDBN}, and the files from which symbols were loaded. The
17435 command @code{help target} lists all possible targets rather than
17438 @kindex maint info sections
17439 @item maint info sections
17440 Another command that can give you extra information about program sections
17441 is @code{maint info sections}. In addition to the section information
17442 displayed by @code{info files}, this command displays the flags and file
17443 offset of each section in the executable and core dump files. In addition,
17444 @code{maint info sections} provides the following command options (which
17445 may be arbitrarily combined):
17449 Display sections for all loaded object files, including shared libraries.
17450 @item @var{sections}
17451 Display info only for named @var{sections}.
17452 @item @var{section-flags}
17453 Display info only for sections for which @var{section-flags} are true.
17454 The section flags that @value{GDBN} currently knows about are:
17457 Section will have space allocated in the process when loaded.
17458 Set for all sections except those containing debug information.
17460 Section will be loaded from the file into the child process memory.
17461 Set for pre-initialized code and data, clear for @code{.bss} sections.
17463 Section needs to be relocated before loading.
17465 Section cannot be modified by the child process.
17467 Section contains executable code only.
17469 Section contains data only (no executable code).
17471 Section will reside in ROM.
17473 Section contains data for constructor/destructor lists.
17475 Section is not empty.
17477 An instruction to the linker to not output the section.
17478 @item COFF_SHARED_LIBRARY
17479 A notification to the linker that the section contains
17480 COFF shared library information.
17482 Section contains common symbols.
17485 @kindex set trust-readonly-sections
17486 @cindex read-only sections
17487 @item set trust-readonly-sections on
17488 Tell @value{GDBN} that readonly sections in your object file
17489 really are read-only (i.e.@: that their contents will not change).
17490 In that case, @value{GDBN} can fetch values from these sections
17491 out of the object file, rather than from the target program.
17492 For some targets (notably embedded ones), this can be a significant
17493 enhancement to debugging performance.
17495 The default is off.
17497 @item set trust-readonly-sections off
17498 Tell @value{GDBN} not to trust readonly sections. This means that
17499 the contents of the section might change while the program is running,
17500 and must therefore be fetched from the target when needed.
17502 @item show trust-readonly-sections
17503 Show the current setting of trusting readonly sections.
17506 All file-specifying commands allow both absolute and relative file names
17507 as arguments. @value{GDBN} always converts the file name to an absolute file
17508 name and remembers it that way.
17510 @cindex shared libraries
17511 @anchor{Shared Libraries}
17512 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
17513 and IBM RS/6000 AIX shared libraries.
17515 On MS-Windows @value{GDBN} must be linked with the Expat library to support
17516 shared libraries. @xref{Expat}.
17518 @value{GDBN} automatically loads symbol definitions from shared libraries
17519 when you use the @code{run} command, or when you examine a core file.
17520 (Before you issue the @code{run} command, @value{GDBN} does not understand
17521 references to a function in a shared library, however---unless you are
17522 debugging a core file).
17524 On HP-UX, if the program loads a library explicitly, @value{GDBN}
17525 automatically loads the symbols at the time of the @code{shl_load} call.
17527 @c FIXME: some @value{GDBN} release may permit some refs to undef
17528 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
17529 @c FIXME...lib; check this from time to time when updating manual
17531 There are times, however, when you may wish to not automatically load
17532 symbol definitions from shared libraries, such as when they are
17533 particularly large or there are many of them.
17535 To control the automatic loading of shared library symbols, use the
17539 @kindex set auto-solib-add
17540 @item set auto-solib-add @var{mode}
17541 If @var{mode} is @code{on}, symbols from all shared object libraries
17542 will be loaded automatically when the inferior begins execution, you
17543 attach to an independently started inferior, or when the dynamic linker
17544 informs @value{GDBN} that a new library has been loaded. If @var{mode}
17545 is @code{off}, symbols must be loaded manually, using the
17546 @code{sharedlibrary} command. The default value is @code{on}.
17548 @cindex memory used for symbol tables
17549 If your program uses lots of shared libraries with debug info that
17550 takes large amounts of memory, you can decrease the @value{GDBN}
17551 memory footprint by preventing it from automatically loading the
17552 symbols from shared libraries. To that end, type @kbd{set
17553 auto-solib-add off} before running the inferior, then load each
17554 library whose debug symbols you do need with @kbd{sharedlibrary
17555 @var{regexp}}, where @var{regexp} is a regular expression that matches
17556 the libraries whose symbols you want to be loaded.
17558 @kindex show auto-solib-add
17559 @item show auto-solib-add
17560 Display the current autoloading mode.
17563 @cindex load shared library
17564 To explicitly load shared library symbols, use the @code{sharedlibrary}
17568 @kindex info sharedlibrary
17570 @item info share @var{regex}
17571 @itemx info sharedlibrary @var{regex}
17572 Print the names of the shared libraries which are currently loaded
17573 that match @var{regex}. If @var{regex} is omitted then print
17574 all shared libraries that are loaded.
17576 @kindex sharedlibrary
17578 @item sharedlibrary @var{regex}
17579 @itemx share @var{regex}
17580 Load shared object library symbols for files matching a
17581 Unix regular expression.
17582 As with files loaded automatically, it only loads shared libraries
17583 required by your program for a core file or after typing @code{run}. If
17584 @var{regex} is omitted all shared libraries required by your program are
17587 @item nosharedlibrary
17588 @kindex nosharedlibrary
17589 @cindex unload symbols from shared libraries
17590 Unload all shared object library symbols. This discards all symbols
17591 that have been loaded from all shared libraries. Symbols from shared
17592 libraries that were loaded by explicit user requests are not
17596 Sometimes you may wish that @value{GDBN} stops and gives you control
17597 when any of shared library events happen. The best way to do this is
17598 to use @code{catch load} and @code{catch unload} (@pxref{Set
17601 @value{GDBN} also supports the the @code{set stop-on-solib-events}
17602 command for this. This command exists for historical reasons. It is
17603 less useful than setting a catchpoint, because it does not allow for
17604 conditions or commands as a catchpoint does.
17607 @item set stop-on-solib-events
17608 @kindex set stop-on-solib-events
17609 This command controls whether @value{GDBN} should give you control
17610 when the dynamic linker notifies it about some shared library event.
17611 The most common event of interest is loading or unloading of a new
17614 @item show stop-on-solib-events
17615 @kindex show stop-on-solib-events
17616 Show whether @value{GDBN} stops and gives you control when shared
17617 library events happen.
17620 Shared libraries are also supported in many cross or remote debugging
17621 configurations. @value{GDBN} needs to have access to the target's libraries;
17622 this can be accomplished either by providing copies of the libraries
17623 on the host system, or by asking @value{GDBN} to automatically retrieve the
17624 libraries from the target. If copies of the target libraries are
17625 provided, they need to be the same as the target libraries, although the
17626 copies on the target can be stripped as long as the copies on the host are
17629 @cindex where to look for shared libraries
17630 For remote debugging, you need to tell @value{GDBN} where the target
17631 libraries are, so that it can load the correct copies---otherwise, it
17632 may try to load the host's libraries. @value{GDBN} has two variables
17633 to specify the search directories for target libraries.
17636 @cindex prefix for shared library file names
17637 @cindex system root, alternate
17638 @kindex set solib-absolute-prefix
17639 @kindex set sysroot
17640 @item set sysroot @var{path}
17641 Use @var{path} as the system root for the program being debugged. Any
17642 absolute shared library paths will be prefixed with @var{path}; many
17643 runtime loaders store the absolute paths to the shared library in the
17644 target program's memory. If you use @code{set sysroot} to find shared
17645 libraries, they need to be laid out in the same way that they are on
17646 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
17649 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
17650 retrieve the target libraries from the remote system. This is only
17651 supported when using a remote target that supports the @code{remote get}
17652 command (@pxref{File Transfer,,Sending files to a remote system}).
17653 The part of @var{path} following the initial @file{remote:}
17654 (if present) is used as system root prefix on the remote file system.
17655 @footnote{If you want to specify a local system root using a directory
17656 that happens to be named @file{remote:}, you need to use some equivalent
17657 variant of the name like @file{./remote:}.}
17659 For targets with an MS-DOS based filesystem, such as MS-Windows and
17660 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
17661 absolute file name with @var{path}. But first, on Unix hosts,
17662 @value{GDBN} converts all backslash directory separators into forward
17663 slashes, because the backslash is not a directory separator on Unix:
17666 c:\foo\bar.dll @result{} c:/foo/bar.dll
17669 Then, @value{GDBN} attempts prefixing the target file name with
17670 @var{path}, and looks for the resulting file name in the host file
17674 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
17677 If that does not find the shared library, @value{GDBN} tries removing
17678 the @samp{:} character from the drive spec, both for convenience, and,
17679 for the case of the host file system not supporting file names with
17683 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
17686 This makes it possible to have a system root that mirrors a target
17687 with more than one drive. E.g., you may want to setup your local
17688 copies of the target system shared libraries like so (note @samp{c} vs
17692 @file{/path/to/sysroot/c/sys/bin/foo.dll}
17693 @file{/path/to/sysroot/c/sys/bin/bar.dll}
17694 @file{/path/to/sysroot/z/sys/bin/bar.dll}
17698 and point the system root at @file{/path/to/sysroot}, so that
17699 @value{GDBN} can find the correct copies of both
17700 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
17702 If that still does not find the shared library, @value{GDBN} tries
17703 removing the whole drive spec from the target file name:
17706 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
17709 This last lookup makes it possible to not care about the drive name,
17710 if you don't want or need to.
17712 The @code{set solib-absolute-prefix} command is an alias for @code{set
17715 @cindex default system root
17716 @cindex @samp{--with-sysroot}
17717 You can set the default system root by using the configure-time
17718 @samp{--with-sysroot} option. If the system root is inside
17719 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17720 @samp{--exec-prefix}), then the default system root will be updated
17721 automatically if the installed @value{GDBN} is moved to a new
17724 @kindex show sysroot
17726 Display the current shared library prefix.
17728 @kindex set solib-search-path
17729 @item set solib-search-path @var{path}
17730 If this variable is set, @var{path} is a colon-separated list of
17731 directories to search for shared libraries. @samp{solib-search-path}
17732 is used after @samp{sysroot} fails to locate the library, or if the
17733 path to the library is relative instead of absolute. If you want to
17734 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
17735 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
17736 finding your host's libraries. @samp{sysroot} is preferred; setting
17737 it to a nonexistent directory may interfere with automatic loading
17738 of shared library symbols.
17740 @kindex show solib-search-path
17741 @item show solib-search-path
17742 Display the current shared library search path.
17744 @cindex DOS file-name semantics of file names.
17745 @kindex set target-file-system-kind (unix|dos-based|auto)
17746 @kindex show target-file-system-kind
17747 @item set target-file-system-kind @var{kind}
17748 Set assumed file system kind for target reported file names.
17750 Shared library file names as reported by the target system may not
17751 make sense as is on the system @value{GDBN} is running on. For
17752 example, when remote debugging a target that has MS-DOS based file
17753 system semantics, from a Unix host, the target may be reporting to
17754 @value{GDBN} a list of loaded shared libraries with file names such as
17755 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
17756 drive letters, so the @samp{c:\} prefix is not normally understood as
17757 indicating an absolute file name, and neither is the backslash
17758 normally considered a directory separator character. In that case,
17759 the native file system would interpret this whole absolute file name
17760 as a relative file name with no directory components. This would make
17761 it impossible to point @value{GDBN} at a copy of the remote target's
17762 shared libraries on the host using @code{set sysroot}, and impractical
17763 with @code{set solib-search-path}. Setting
17764 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
17765 to interpret such file names similarly to how the target would, and to
17766 map them to file names valid on @value{GDBN}'s native file system
17767 semantics. The value of @var{kind} can be @code{"auto"}, in addition
17768 to one of the supported file system kinds. In that case, @value{GDBN}
17769 tries to determine the appropriate file system variant based on the
17770 current target's operating system (@pxref{ABI, ,Configuring the
17771 Current ABI}). The supported file system settings are:
17775 Instruct @value{GDBN} to assume the target file system is of Unix
17776 kind. Only file names starting the forward slash (@samp{/}) character
17777 are considered absolute, and the directory separator character is also
17781 Instruct @value{GDBN} to assume the target file system is DOS based.
17782 File names starting with either a forward slash, or a drive letter
17783 followed by a colon (e.g., @samp{c:}), are considered absolute, and
17784 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
17785 considered directory separators.
17788 Instruct @value{GDBN} to use the file system kind associated with the
17789 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
17790 This is the default.
17794 @cindex file name canonicalization
17795 @cindex base name differences
17796 When processing file names provided by the user, @value{GDBN}
17797 frequently needs to compare them to the file names recorded in the
17798 program's debug info. Normally, @value{GDBN} compares just the
17799 @dfn{base names} of the files as strings, which is reasonably fast
17800 even for very large programs. (The base name of a file is the last
17801 portion of its name, after stripping all the leading directories.)
17802 This shortcut in comparison is based upon the assumption that files
17803 cannot have more than one base name. This is usually true, but
17804 references to files that use symlinks or similar filesystem
17805 facilities violate that assumption. If your program records files
17806 using such facilities, or if you provide file names to @value{GDBN}
17807 using symlinks etc., you can set @code{basenames-may-differ} to
17808 @code{true} to instruct @value{GDBN} to completely canonicalize each
17809 pair of file names it needs to compare. This will make file-name
17810 comparisons accurate, but at a price of a significant slowdown.
17813 @item set basenames-may-differ
17814 @kindex set basenames-may-differ
17815 Set whether a source file may have multiple base names.
17817 @item show basenames-may-differ
17818 @kindex show basenames-may-differ
17819 Show whether a source file may have multiple base names.
17822 @node Separate Debug Files
17823 @section Debugging Information in Separate Files
17824 @cindex separate debugging information files
17825 @cindex debugging information in separate files
17826 @cindex @file{.debug} subdirectories
17827 @cindex debugging information directory, global
17828 @cindex global debugging information directories
17829 @cindex build ID, and separate debugging files
17830 @cindex @file{.build-id} directory
17832 @value{GDBN} allows you to put a program's debugging information in a
17833 file separate from the executable itself, in a way that allows
17834 @value{GDBN} to find and load the debugging information automatically.
17835 Since debugging information can be very large---sometimes larger
17836 than the executable code itself---some systems distribute debugging
17837 information for their executables in separate files, which users can
17838 install only when they need to debug a problem.
17840 @value{GDBN} supports two ways of specifying the separate debug info
17845 The executable contains a @dfn{debug link} that specifies the name of
17846 the separate debug info file. The separate debug file's name is
17847 usually @file{@var{executable}.debug}, where @var{executable} is the
17848 name of the corresponding executable file without leading directories
17849 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
17850 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
17851 checksum for the debug file, which @value{GDBN} uses to validate that
17852 the executable and the debug file came from the same build.
17855 The executable contains a @dfn{build ID}, a unique bit string that is
17856 also present in the corresponding debug info file. (This is supported
17857 only on some operating systems, notably those which use the ELF format
17858 for binary files and the @sc{gnu} Binutils.) For more details about
17859 this feature, see the description of the @option{--build-id}
17860 command-line option in @ref{Options, , Command Line Options, ld.info,
17861 The GNU Linker}. The debug info file's name is not specified
17862 explicitly by the build ID, but can be computed from the build ID, see
17866 Depending on the way the debug info file is specified, @value{GDBN}
17867 uses two different methods of looking for the debug file:
17871 For the ``debug link'' method, @value{GDBN} looks up the named file in
17872 the directory of the executable file, then in a subdirectory of that
17873 directory named @file{.debug}, and finally under each one of the global debug
17874 directories, in a subdirectory whose name is identical to the leading
17875 directories of the executable's absolute file name.
17878 For the ``build ID'' method, @value{GDBN} looks in the
17879 @file{.build-id} subdirectory of each one of the global debug directories for
17880 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
17881 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
17882 are the rest of the bit string. (Real build ID strings are 32 or more
17883 hex characters, not 10.)
17886 So, for example, suppose you ask @value{GDBN} to debug
17887 @file{/usr/bin/ls}, which has a debug link that specifies the
17888 file @file{ls.debug}, and a build ID whose value in hex is
17889 @code{abcdef1234}. If the list of the global debug directories includes
17890 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
17891 debug information files, in the indicated order:
17895 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
17897 @file{/usr/bin/ls.debug}
17899 @file{/usr/bin/.debug/ls.debug}
17901 @file{/usr/lib/debug/usr/bin/ls.debug}.
17904 @anchor{debug-file-directory}
17905 Global debugging info directories default to what is set by @value{GDBN}
17906 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
17907 you can also set the global debugging info directories, and view the list
17908 @value{GDBN} is currently using.
17912 @kindex set debug-file-directory
17913 @item set debug-file-directory @var{directories}
17914 Set the directories which @value{GDBN} searches for separate debugging
17915 information files to @var{directory}. Multiple path components can be set
17916 concatenating them by a path separator.
17918 @kindex show debug-file-directory
17919 @item show debug-file-directory
17920 Show the directories @value{GDBN} searches for separate debugging
17925 @cindex @code{.gnu_debuglink} sections
17926 @cindex debug link sections
17927 A debug link is a special section of the executable file named
17928 @code{.gnu_debuglink}. The section must contain:
17932 A filename, with any leading directory components removed, followed by
17935 zero to three bytes of padding, as needed to reach the next four-byte
17936 boundary within the section, and
17938 a four-byte CRC checksum, stored in the same endianness used for the
17939 executable file itself. The checksum is computed on the debugging
17940 information file's full contents by the function given below, passing
17941 zero as the @var{crc} argument.
17944 Any executable file format can carry a debug link, as long as it can
17945 contain a section named @code{.gnu_debuglink} with the contents
17948 @cindex @code{.note.gnu.build-id} sections
17949 @cindex build ID sections
17950 The build ID is a special section in the executable file (and in other
17951 ELF binary files that @value{GDBN} may consider). This section is
17952 often named @code{.note.gnu.build-id}, but that name is not mandatory.
17953 It contains unique identification for the built files---the ID remains
17954 the same across multiple builds of the same build tree. The default
17955 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
17956 content for the build ID string. The same section with an identical
17957 value is present in the original built binary with symbols, in its
17958 stripped variant, and in the separate debugging information file.
17960 The debugging information file itself should be an ordinary
17961 executable, containing a full set of linker symbols, sections, and
17962 debugging information. The sections of the debugging information file
17963 should have the same names, addresses, and sizes as the original file,
17964 but they need not contain any data---much like a @code{.bss} section
17965 in an ordinary executable.
17967 The @sc{gnu} binary utilities (Binutils) package includes the
17968 @samp{objcopy} utility that can produce
17969 the separated executable / debugging information file pairs using the
17970 following commands:
17973 @kbd{objcopy --only-keep-debug foo foo.debug}
17978 These commands remove the debugging
17979 information from the executable file @file{foo} and place it in the file
17980 @file{foo.debug}. You can use the first, second or both methods to link the
17985 The debug link method needs the following additional command to also leave
17986 behind a debug link in @file{foo}:
17989 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
17992 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
17993 a version of the @code{strip} command such that the command @kbd{strip foo -f
17994 foo.debug} has the same functionality as the two @code{objcopy} commands and
17995 the @code{ln -s} command above, together.
17998 Build ID gets embedded into the main executable using @code{ld --build-id} or
17999 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
18000 compatibility fixes for debug files separation are present in @sc{gnu} binary
18001 utilities (Binutils) package since version 2.18.
18006 @cindex CRC algorithm definition
18007 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
18008 IEEE 802.3 using the polynomial:
18010 @c TexInfo requires naked braces for multi-digit exponents for Tex
18011 @c output, but this causes HTML output to barf. HTML has to be set using
18012 @c raw commands. So we end up having to specify this equation in 2
18017 <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>
18018 + <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
18024 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
18025 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
18029 The function is computed byte at a time, taking the least
18030 significant bit of each byte first. The initial pattern
18031 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
18032 the final result is inverted to ensure trailing zeros also affect the
18035 @emph{Note:} This is the same CRC polynomial as used in handling the
18036 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
18037 However in the case of the Remote Serial Protocol, the CRC is computed
18038 @emph{most} significant bit first, and the result is not inverted, so
18039 trailing zeros have no effect on the CRC value.
18041 To complete the description, we show below the code of the function
18042 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
18043 initially supplied @code{crc} argument means that an initial call to
18044 this function passing in zero will start computing the CRC using
18047 @kindex gnu_debuglink_crc32
18050 gnu_debuglink_crc32 (unsigned long crc,
18051 unsigned char *buf, size_t len)
18053 static const unsigned long crc32_table[256] =
18055 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
18056 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
18057 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
18058 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
18059 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
18060 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
18061 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
18062 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
18063 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
18064 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
18065 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
18066 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
18067 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
18068 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
18069 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
18070 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
18071 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
18072 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
18073 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
18074 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
18075 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
18076 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
18077 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
18078 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
18079 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
18080 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
18081 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
18082 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
18083 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
18084 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
18085 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
18086 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
18087 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
18088 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
18089 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
18090 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
18091 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
18092 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
18093 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
18094 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
18095 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
18096 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
18097 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
18098 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
18099 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
18100 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
18101 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
18102 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
18103 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
18104 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
18105 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
18108 unsigned char *end;
18110 crc = ~crc & 0xffffffff;
18111 for (end = buf + len; buf < end; ++buf)
18112 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
18113 return ~crc & 0xffffffff;
18118 This computation does not apply to the ``build ID'' method.
18120 @node MiniDebugInfo
18121 @section Debugging information in a special section
18122 @cindex separate debug sections
18123 @cindex @samp{.gnu_debugdata} section
18125 Some systems ship pre-built executables and libraries that have a
18126 special @samp{.gnu_debugdata} section. This feature is called
18127 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
18128 is used to supply extra symbols for backtraces.
18130 The intent of this section is to provide extra minimal debugging
18131 information for use in simple backtraces. It is not intended to be a
18132 replacement for full separate debugging information (@pxref{Separate
18133 Debug Files}). The example below shows the intended use; however,
18134 @value{GDBN} does not currently put restrictions on what sort of
18135 debugging information might be included in the section.
18137 @value{GDBN} has support for this extension. If the section exists,
18138 then it is used provided that no other source of debugging information
18139 can be found, and that @value{GDBN} was configured with LZMA support.
18141 This section can be easily created using @command{objcopy} and other
18142 standard utilities:
18145 # Extract the dynamic symbols from the main binary, there is no need
18146 # to also have these in the normal symbol table.
18147 nm -D @var{binary} --format=posix --defined-only \
18148 | awk '@{ print $1 @}' | sort > dynsyms
18150 # Extract all the text (i.e. function) symbols from the debuginfo.
18151 # (Note that we actually also accept "D" symbols, for the benefit
18152 # of platforms like PowerPC64 that use function descriptors.)
18153 nm @var{binary} --format=posix --defined-only \
18154 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
18157 # Keep all the function symbols not already in the dynamic symbol
18159 comm -13 dynsyms funcsyms > keep_symbols
18161 # Separate full debug info into debug binary.
18162 objcopy --only-keep-debug @var{binary} debug
18164 # Copy the full debuginfo, keeping only a minimal set of symbols and
18165 # removing some unnecessary sections.
18166 objcopy -S --remove-section .gdb_index --remove-section .comment \
18167 --keep-symbols=keep_symbols debug mini_debuginfo
18169 # Drop the full debug info from the original binary.
18170 strip --strip-all -R .comment @var{binary}
18172 # Inject the compressed data into the .gnu_debugdata section of the
18175 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
18179 @section Index Files Speed Up @value{GDBN}
18180 @cindex index files
18181 @cindex @samp{.gdb_index} section
18183 When @value{GDBN} finds a symbol file, it scans the symbols in the
18184 file in order to construct an internal symbol table. This lets most
18185 @value{GDBN} operations work quickly---at the cost of a delay early
18186 on. For large programs, this delay can be quite lengthy, so
18187 @value{GDBN} provides a way to build an index, which speeds up
18190 The index is stored as a section in the symbol file. @value{GDBN} can
18191 write the index to a file, then you can put it into the symbol file
18192 using @command{objcopy}.
18194 To create an index file, use the @code{save gdb-index} command:
18197 @item save gdb-index @var{directory}
18198 @kindex save gdb-index
18199 Create an index file for each symbol file currently known by
18200 @value{GDBN}. Each file is named after its corresponding symbol file,
18201 with @samp{.gdb-index} appended, and is written into the given
18205 Once you have created an index file you can merge it into your symbol
18206 file, here named @file{symfile}, using @command{objcopy}:
18209 $ objcopy --add-section .gdb_index=symfile.gdb-index \
18210 --set-section-flags .gdb_index=readonly symfile symfile
18213 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
18214 sections that have been deprecated. Usually they are deprecated because
18215 they are missing a new feature or have performance issues.
18216 To tell @value{GDBN} to use a deprecated index section anyway
18217 specify @code{set use-deprecated-index-sections on}.
18218 The default is @code{off}.
18219 This can speed up startup, but may result in some functionality being lost.
18220 @xref{Index Section Format}.
18222 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
18223 must be done before gdb reads the file. The following will not work:
18226 $ gdb -ex "set use-deprecated-index-sections on" <program>
18229 Instead you must do, for example,
18232 $ gdb -iex "set use-deprecated-index-sections on" <program>
18235 There are currently some limitation on indices. They only work when
18236 for DWARF debugging information, not stabs. And, they do not
18237 currently work for programs using Ada.
18239 @node Symbol Errors
18240 @section Errors Reading Symbol Files
18242 While reading a symbol file, @value{GDBN} occasionally encounters problems,
18243 such as symbol types it does not recognize, or known bugs in compiler
18244 output. By default, @value{GDBN} does not notify you of such problems, since
18245 they are relatively common and primarily of interest to people
18246 debugging compilers. If you are interested in seeing information
18247 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
18248 only one message about each such type of problem, no matter how many
18249 times the problem occurs; or you can ask @value{GDBN} to print more messages,
18250 to see how many times the problems occur, with the @code{set
18251 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
18254 The messages currently printed, and their meanings, include:
18257 @item inner block not inside outer block in @var{symbol}
18259 The symbol information shows where symbol scopes begin and end
18260 (such as at the start of a function or a block of statements). This
18261 error indicates that an inner scope block is not fully contained
18262 in its outer scope blocks.
18264 @value{GDBN} circumvents the problem by treating the inner block as if it had
18265 the same scope as the outer block. In the error message, @var{symbol}
18266 may be shown as ``@code{(don't know)}'' if the outer block is not a
18269 @item block at @var{address} out of order
18271 The symbol information for symbol scope blocks should occur in
18272 order of increasing addresses. This error indicates that it does not
18275 @value{GDBN} does not circumvent this problem, and has trouble
18276 locating symbols in the source file whose symbols it is reading. (You
18277 can often determine what source file is affected by specifying
18278 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
18281 @item bad block start address patched
18283 The symbol information for a symbol scope block has a start address
18284 smaller than the address of the preceding source line. This is known
18285 to occur in the SunOS 4.1.1 (and earlier) C compiler.
18287 @value{GDBN} circumvents the problem by treating the symbol scope block as
18288 starting on the previous source line.
18290 @item bad string table offset in symbol @var{n}
18293 Symbol number @var{n} contains a pointer into the string table which is
18294 larger than the size of the string table.
18296 @value{GDBN} circumvents the problem by considering the symbol to have the
18297 name @code{foo}, which may cause other problems if many symbols end up
18300 @item unknown symbol type @code{0x@var{nn}}
18302 The symbol information contains new data types that @value{GDBN} does
18303 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
18304 uncomprehended information, in hexadecimal.
18306 @value{GDBN} circumvents the error by ignoring this symbol information.
18307 This usually allows you to debug your program, though certain symbols
18308 are not accessible. If you encounter such a problem and feel like
18309 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
18310 on @code{complain}, then go up to the function @code{read_dbx_symtab}
18311 and examine @code{*bufp} to see the symbol.
18313 @item stub type has NULL name
18315 @value{GDBN} could not find the full definition for a struct or class.
18317 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
18318 The symbol information for a C@t{++} member function is missing some
18319 information that recent versions of the compiler should have output for
18322 @item info mismatch between compiler and debugger
18324 @value{GDBN} could not parse a type specification output by the compiler.
18329 @section GDB Data Files
18331 @cindex prefix for data files
18332 @value{GDBN} will sometimes read an auxiliary data file. These files
18333 are kept in a directory known as the @dfn{data directory}.
18335 You can set the data directory's name, and view the name @value{GDBN}
18336 is currently using.
18339 @kindex set data-directory
18340 @item set data-directory @var{directory}
18341 Set the directory which @value{GDBN} searches for auxiliary data files
18342 to @var{directory}.
18344 @kindex show data-directory
18345 @item show data-directory
18346 Show the directory @value{GDBN} searches for auxiliary data files.
18349 @cindex default data directory
18350 @cindex @samp{--with-gdb-datadir}
18351 You can set the default data directory by using the configure-time
18352 @samp{--with-gdb-datadir} option. If the data directory is inside
18353 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
18354 @samp{--exec-prefix}), then the default data directory will be updated
18355 automatically if the installed @value{GDBN} is moved to a new
18358 The data directory may also be specified with the
18359 @code{--data-directory} command line option.
18360 @xref{Mode Options}.
18363 @chapter Specifying a Debugging Target
18365 @cindex debugging target
18366 A @dfn{target} is the execution environment occupied by your program.
18368 Often, @value{GDBN} runs in the same host environment as your program;
18369 in that case, the debugging target is specified as a side effect when
18370 you use the @code{file} or @code{core} commands. When you need more
18371 flexibility---for example, running @value{GDBN} on a physically separate
18372 host, or controlling a standalone system over a serial port or a
18373 realtime system over a TCP/IP connection---you can use the @code{target}
18374 command to specify one of the target types configured for @value{GDBN}
18375 (@pxref{Target Commands, ,Commands for Managing Targets}).
18377 @cindex target architecture
18378 It is possible to build @value{GDBN} for several different @dfn{target
18379 architectures}. When @value{GDBN} is built like that, you can choose
18380 one of the available architectures with the @kbd{set architecture}
18384 @kindex set architecture
18385 @kindex show architecture
18386 @item set architecture @var{arch}
18387 This command sets the current target architecture to @var{arch}. The
18388 value of @var{arch} can be @code{"auto"}, in addition to one of the
18389 supported architectures.
18391 @item show architecture
18392 Show the current target architecture.
18394 @item set processor
18396 @kindex set processor
18397 @kindex show processor
18398 These are alias commands for, respectively, @code{set architecture}
18399 and @code{show architecture}.
18403 * Active Targets:: Active targets
18404 * Target Commands:: Commands for managing targets
18405 * Byte Order:: Choosing target byte order
18408 @node Active Targets
18409 @section Active Targets
18411 @cindex stacking targets
18412 @cindex active targets
18413 @cindex multiple targets
18415 There are multiple classes of targets such as: processes, executable files or
18416 recording sessions. Core files belong to the process class, making core file
18417 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
18418 on multiple active targets, one in each class. This allows you to (for
18419 example) start a process and inspect its activity, while still having access to
18420 the executable file after the process finishes. Or if you start process
18421 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
18422 presented a virtual layer of the recording target, while the process target
18423 remains stopped at the chronologically last point of the process execution.
18425 Use the @code{core-file} and @code{exec-file} commands to select a new core
18426 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
18427 specify as a target a process that is already running, use the @code{attach}
18428 command (@pxref{Attach, ,Debugging an Already-running Process}).
18430 @node Target Commands
18431 @section Commands for Managing Targets
18434 @item target @var{type} @var{parameters}
18435 Connects the @value{GDBN} host environment to a target machine or
18436 process. A target is typically a protocol for talking to debugging
18437 facilities. You use the argument @var{type} to specify the type or
18438 protocol of the target machine.
18440 Further @var{parameters} are interpreted by the target protocol, but
18441 typically include things like device names or host names to connect
18442 with, process numbers, and baud rates.
18444 The @code{target} command does not repeat if you press @key{RET} again
18445 after executing the command.
18447 @kindex help target
18449 Displays the names of all targets available. To display targets
18450 currently selected, use either @code{info target} or @code{info files}
18451 (@pxref{Files, ,Commands to Specify Files}).
18453 @item help target @var{name}
18454 Describe a particular target, including any parameters necessary to
18457 @kindex set gnutarget
18458 @item set gnutarget @var{args}
18459 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
18460 knows whether it is reading an @dfn{executable},
18461 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
18462 with the @code{set gnutarget} command. Unlike most @code{target} commands,
18463 with @code{gnutarget} the @code{target} refers to a program, not a machine.
18466 @emph{Warning:} To specify a file format with @code{set gnutarget},
18467 you must know the actual BFD name.
18471 @xref{Files, , Commands to Specify Files}.
18473 @kindex show gnutarget
18474 @item show gnutarget
18475 Use the @code{show gnutarget} command to display what file format
18476 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
18477 @value{GDBN} will determine the file format for each file automatically,
18478 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
18481 @cindex common targets
18482 Here are some common targets (available, or not, depending on the GDB
18487 @item target exec @var{program}
18488 @cindex executable file target
18489 An executable file. @samp{target exec @var{program}} is the same as
18490 @samp{exec-file @var{program}}.
18492 @item target core @var{filename}
18493 @cindex core dump file target
18494 A core dump file. @samp{target core @var{filename}} is the same as
18495 @samp{core-file @var{filename}}.
18497 @item target remote @var{medium}
18498 @cindex remote target
18499 A remote system connected to @value{GDBN} via a serial line or network
18500 connection. This command tells @value{GDBN} to use its own remote
18501 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
18503 For example, if you have a board connected to @file{/dev/ttya} on the
18504 machine running @value{GDBN}, you could say:
18507 target remote /dev/ttya
18510 @code{target remote} supports the @code{load} command. This is only
18511 useful if you have some other way of getting the stub to the target
18512 system, and you can put it somewhere in memory where it won't get
18513 clobbered by the download.
18515 @item target sim @r{[}@var{simargs}@r{]} @dots{}
18516 @cindex built-in simulator target
18517 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
18525 works; however, you cannot assume that a specific memory map, device
18526 drivers, or even basic I/O is available, although some simulators do
18527 provide these. For info about any processor-specific simulator details,
18528 see the appropriate section in @ref{Embedded Processors, ,Embedded
18531 @item target native
18532 @cindex native target
18533 Setup for local/native process debugging. Useful to make the
18534 @code{run} command spawn native processes (likewise @code{attach},
18535 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
18536 (@pxref{set auto-connect-native-target}).
18540 Different targets are available on different configurations of @value{GDBN};
18541 your configuration may have more or fewer targets.
18543 Many remote targets require you to download the executable's code once
18544 you've successfully established a connection. You may wish to control
18545 various aspects of this process.
18550 @kindex set hash@r{, for remote monitors}
18551 @cindex hash mark while downloading
18552 This command controls whether a hash mark @samp{#} is displayed while
18553 downloading a file to the remote monitor. If on, a hash mark is
18554 displayed after each S-record is successfully downloaded to the
18558 @kindex show hash@r{, for remote monitors}
18559 Show the current status of displaying the hash mark.
18561 @item set debug monitor
18562 @kindex set debug monitor
18563 @cindex display remote monitor communications
18564 Enable or disable display of communications messages between
18565 @value{GDBN} and the remote monitor.
18567 @item show debug monitor
18568 @kindex show debug monitor
18569 Show the current status of displaying communications between
18570 @value{GDBN} and the remote monitor.
18575 @kindex load @var{filename}
18576 @item load @var{filename}
18578 Depending on what remote debugging facilities are configured into
18579 @value{GDBN}, the @code{load} command may be available. Where it exists, it
18580 is meant to make @var{filename} (an executable) available for debugging
18581 on the remote system---by downloading, or dynamic linking, for example.
18582 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
18583 the @code{add-symbol-file} command.
18585 If your @value{GDBN} does not have a @code{load} command, attempting to
18586 execute it gets the error message ``@code{You can't do that when your
18587 target is @dots{}}''
18589 The file is loaded at whatever address is specified in the executable.
18590 For some object file formats, you can specify the load address when you
18591 link the program; for other formats, like a.out, the object file format
18592 specifies a fixed address.
18593 @c FIXME! This would be a good place for an xref to the GNU linker doc.
18595 Depending on the remote side capabilities, @value{GDBN} may be able to
18596 load programs into flash memory.
18598 @code{load} does not repeat if you press @key{RET} again after using it.
18602 @section Choosing Target Byte Order
18604 @cindex choosing target byte order
18605 @cindex target byte order
18607 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
18608 offer the ability to run either big-endian or little-endian byte
18609 orders. Usually the executable or symbol will include a bit to
18610 designate the endian-ness, and you will not need to worry about
18611 which to use. However, you may still find it useful to adjust
18612 @value{GDBN}'s idea of processor endian-ness manually.
18616 @item set endian big
18617 Instruct @value{GDBN} to assume the target is big-endian.
18619 @item set endian little
18620 Instruct @value{GDBN} to assume the target is little-endian.
18622 @item set endian auto
18623 Instruct @value{GDBN} to use the byte order associated with the
18627 Display @value{GDBN}'s current idea of the target byte order.
18631 Note that these commands merely adjust interpretation of symbolic
18632 data on the host, and that they have absolutely no effect on the
18636 @node Remote Debugging
18637 @chapter Debugging Remote Programs
18638 @cindex remote debugging
18640 If you are trying to debug a program running on a machine that cannot run
18641 @value{GDBN} in the usual way, it is often useful to use remote debugging.
18642 For example, you might use remote debugging on an operating system kernel,
18643 or on a small system which does not have a general purpose operating system
18644 powerful enough to run a full-featured debugger.
18646 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
18647 to make this work with particular debugging targets. In addition,
18648 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
18649 but not specific to any particular target system) which you can use if you
18650 write the remote stubs---the code that runs on the remote system to
18651 communicate with @value{GDBN}.
18653 Other remote targets may be available in your
18654 configuration of @value{GDBN}; use @code{help target} to list them.
18657 * Connecting:: Connecting to a remote target
18658 * File Transfer:: Sending files to a remote system
18659 * Server:: Using the gdbserver program
18660 * Remote Configuration:: Remote configuration
18661 * Remote Stub:: Implementing a remote stub
18665 @section Connecting to a Remote Target
18667 On the @value{GDBN} host machine, you will need an unstripped copy of
18668 your program, since @value{GDBN} needs symbol and debugging information.
18669 Start up @value{GDBN} as usual, using the name of the local copy of your
18670 program as the first argument.
18672 @cindex @code{target remote}
18673 @value{GDBN} can communicate with the target over a serial line, or
18674 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
18675 each case, @value{GDBN} uses the same protocol for debugging your
18676 program; only the medium carrying the debugging packets varies. The
18677 @code{target remote} command establishes a connection to the target.
18678 Its arguments indicate which medium to use:
18682 @item target remote @var{serial-device}
18683 @cindex serial line, @code{target remote}
18684 Use @var{serial-device} to communicate with the target. For example,
18685 to use a serial line connected to the device named @file{/dev/ttyb}:
18688 target remote /dev/ttyb
18691 If you're using a serial line, you may want to give @value{GDBN} the
18692 @samp{--baud} option, or use the @code{set serial baud} command
18693 (@pxref{Remote Configuration, set serial baud}) before the
18694 @code{target} command.
18696 @item target remote @code{@var{host}:@var{port}}
18697 @itemx target remote @code{tcp:@var{host}:@var{port}}
18698 @cindex @acronym{TCP} port, @code{target remote}
18699 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
18700 The @var{host} may be either a host name or a numeric @acronym{IP}
18701 address; @var{port} must be a decimal number. The @var{host} could be
18702 the target machine itself, if it is directly connected to the net, or
18703 it might be a terminal server which in turn has a serial line to the
18706 For example, to connect to port 2828 on a terminal server named
18710 target remote manyfarms:2828
18713 If your remote target is actually running on the same machine as your
18714 debugger session (e.g.@: a simulator for your target running on the
18715 same host), you can omit the hostname. For example, to connect to
18716 port 1234 on your local machine:
18719 target remote :1234
18723 Note that the colon is still required here.
18725 @item target remote @code{udp:@var{host}:@var{port}}
18726 @cindex @acronym{UDP} port, @code{target remote}
18727 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
18728 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
18731 target remote udp:manyfarms:2828
18734 When using a @acronym{UDP} connection for remote debugging, you should
18735 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
18736 can silently drop packets on busy or unreliable networks, which will
18737 cause havoc with your debugging session.
18739 @item target remote | @var{command}
18740 @cindex pipe, @code{target remote} to
18741 Run @var{command} in the background and communicate with it using a
18742 pipe. The @var{command} is a shell command, to be parsed and expanded
18743 by the system's command shell, @code{/bin/sh}; it should expect remote
18744 protocol packets on its standard input, and send replies on its
18745 standard output. You could use this to run a stand-alone simulator
18746 that speaks the remote debugging protocol, to make net connections
18747 using programs like @code{ssh}, or for other similar tricks.
18749 If @var{command} closes its standard output (perhaps by exiting),
18750 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
18751 program has already exited, this will have no effect.)
18755 Once the connection has been established, you can use all the usual
18756 commands to examine and change data. The remote program is already
18757 running; you can use @kbd{step} and @kbd{continue}, and you do not
18758 need to use @kbd{run}.
18760 @cindex interrupting remote programs
18761 @cindex remote programs, interrupting
18762 Whenever @value{GDBN} is waiting for the remote program, if you type the
18763 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
18764 program. This may or may not succeed, depending in part on the hardware
18765 and the serial drivers the remote system uses. If you type the
18766 interrupt character once again, @value{GDBN} displays this prompt:
18769 Interrupted while waiting for the program.
18770 Give up (and stop debugging it)? (y or n)
18773 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
18774 (If you decide you want to try again later, you can use @samp{target
18775 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
18776 goes back to waiting.
18779 @kindex detach (remote)
18781 When you have finished debugging the remote program, you can use the
18782 @code{detach} command to release it from @value{GDBN} control.
18783 Detaching from the target normally resumes its execution, but the results
18784 will depend on your particular remote stub. After the @code{detach}
18785 command, @value{GDBN} is free to connect to another target.
18789 The @code{disconnect} command behaves like @code{detach}, except that
18790 the target is generally not resumed. It will wait for @value{GDBN}
18791 (this instance or another one) to connect and continue debugging. After
18792 the @code{disconnect} command, @value{GDBN} is again free to connect to
18795 @cindex send command to remote monitor
18796 @cindex extend @value{GDBN} for remote targets
18797 @cindex add new commands for external monitor
18799 @item monitor @var{cmd}
18800 This command allows you to send arbitrary commands directly to the
18801 remote monitor. Since @value{GDBN} doesn't care about the commands it
18802 sends like this, this command is the way to extend @value{GDBN}---you
18803 can add new commands that only the external monitor will understand
18807 @node File Transfer
18808 @section Sending files to a remote system
18809 @cindex remote target, file transfer
18810 @cindex file transfer
18811 @cindex sending files to remote systems
18813 Some remote targets offer the ability to transfer files over the same
18814 connection used to communicate with @value{GDBN}. This is convenient
18815 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
18816 running @code{gdbserver} over a network interface. For other targets,
18817 e.g.@: embedded devices with only a single serial port, this may be
18818 the only way to upload or download files.
18820 Not all remote targets support these commands.
18824 @item remote put @var{hostfile} @var{targetfile}
18825 Copy file @var{hostfile} from the host system (the machine running
18826 @value{GDBN}) to @var{targetfile} on the target system.
18829 @item remote get @var{targetfile} @var{hostfile}
18830 Copy file @var{targetfile} from the target system to @var{hostfile}
18831 on the host system.
18833 @kindex remote delete
18834 @item remote delete @var{targetfile}
18835 Delete @var{targetfile} from the target system.
18840 @section Using the @code{gdbserver} Program
18843 @cindex remote connection without stubs
18844 @code{gdbserver} is a control program for Unix-like systems, which
18845 allows you to connect your program with a remote @value{GDBN} via
18846 @code{target remote}---but without linking in the usual debugging stub.
18848 @code{gdbserver} is not a complete replacement for the debugging stubs,
18849 because it requires essentially the same operating-system facilities
18850 that @value{GDBN} itself does. In fact, a system that can run
18851 @code{gdbserver} to connect to a remote @value{GDBN} could also run
18852 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
18853 because it is a much smaller program than @value{GDBN} itself. It is
18854 also easier to port than all of @value{GDBN}, so you may be able to get
18855 started more quickly on a new system by using @code{gdbserver}.
18856 Finally, if you develop code for real-time systems, you may find that
18857 the tradeoffs involved in real-time operation make it more convenient to
18858 do as much development work as possible on another system, for example
18859 by cross-compiling. You can use @code{gdbserver} to make a similar
18860 choice for debugging.
18862 @value{GDBN} and @code{gdbserver} communicate via either a serial line
18863 or a TCP connection, using the standard @value{GDBN} remote serial
18867 @emph{Warning:} @code{gdbserver} does not have any built-in security.
18868 Do not run @code{gdbserver} connected to any public network; a
18869 @value{GDBN} connection to @code{gdbserver} provides access to the
18870 target system with the same privileges as the user running
18874 @subsection Running @code{gdbserver}
18875 @cindex arguments, to @code{gdbserver}
18876 @cindex @code{gdbserver}, command-line arguments
18878 Run @code{gdbserver} on the target system. You need a copy of the
18879 program you want to debug, including any libraries it requires.
18880 @code{gdbserver} does not need your program's symbol table, so you can
18881 strip the program if necessary to save space. @value{GDBN} on the host
18882 system does all the symbol handling.
18884 To use the server, you must tell it how to communicate with @value{GDBN};
18885 the name of your program; and the arguments for your program. The usual
18889 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
18892 @var{comm} is either a device name (to use a serial line), or a TCP
18893 hostname and portnumber, or @code{-} or @code{stdio} to use
18894 stdin/stdout of @code{gdbserver}.
18895 For example, to debug Emacs with the argument
18896 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
18900 target> gdbserver /dev/com1 emacs foo.txt
18903 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
18906 To use a TCP connection instead of a serial line:
18909 target> gdbserver host:2345 emacs foo.txt
18912 The only difference from the previous example is the first argument,
18913 specifying that you are communicating with the host @value{GDBN} via
18914 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
18915 expect a TCP connection from machine @samp{host} to local TCP port 2345.
18916 (Currently, the @samp{host} part is ignored.) You can choose any number
18917 you want for the port number as long as it does not conflict with any
18918 TCP ports already in use on the target system (for example, @code{23} is
18919 reserved for @code{telnet}).@footnote{If you choose a port number that
18920 conflicts with another service, @code{gdbserver} prints an error message
18921 and exits.} You must use the same port number with the host @value{GDBN}
18922 @code{target remote} command.
18924 The @code{stdio} connection is useful when starting @code{gdbserver}
18928 (gdb) target remote | ssh -T hostname gdbserver - hello
18931 The @samp{-T} option to ssh is provided because we don't need a remote pty,
18932 and we don't want escape-character handling. Ssh does this by default when
18933 a command is provided, the flag is provided to make it explicit.
18934 You could elide it if you want to.
18936 Programs started with stdio-connected gdbserver have @file{/dev/null} for
18937 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
18938 display through a pipe connected to gdbserver.
18939 Both @code{stdout} and @code{stderr} use the same pipe.
18941 @subsubsection Attaching to a Running Program
18942 @cindex attach to a program, @code{gdbserver}
18943 @cindex @option{--attach}, @code{gdbserver} option
18945 On some targets, @code{gdbserver} can also attach to running programs.
18946 This is accomplished via the @code{--attach} argument. The syntax is:
18949 target> gdbserver --attach @var{comm} @var{pid}
18952 @var{pid} is the process ID of a currently running process. It isn't necessary
18953 to point @code{gdbserver} at a binary for the running process.
18956 You can debug processes by name instead of process ID if your target has the
18957 @code{pidof} utility:
18960 target> gdbserver --attach @var{comm} `pidof @var{program}`
18963 In case more than one copy of @var{program} is running, or @var{program}
18964 has multiple threads, most versions of @code{pidof} support the
18965 @code{-s} option to only return the first process ID.
18967 @subsubsection Multi-Process Mode for @code{gdbserver}
18968 @cindex @code{gdbserver}, multiple processes
18969 @cindex multiple processes with @code{gdbserver}
18971 When you connect to @code{gdbserver} using @code{target remote},
18972 @code{gdbserver} debugs the specified program only once. When the
18973 program exits, or you detach from it, @value{GDBN} closes the connection
18974 and @code{gdbserver} exits.
18976 If you connect using @kbd{target extended-remote}, @code{gdbserver}
18977 enters multi-process mode. When the debugged program exits, or you
18978 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
18979 though no program is running. The @code{run} and @code{attach}
18980 commands instruct @code{gdbserver} to run or attach to a new program.
18981 The @code{run} command uses @code{set remote exec-file} (@pxref{set
18982 remote exec-file}) to select the program to run. Command line
18983 arguments are supported, except for wildcard expansion and I/O
18984 redirection (@pxref{Arguments}).
18986 @cindex @option{--multi}, @code{gdbserver} option
18987 To start @code{gdbserver} without supplying an initial command to run
18988 or process ID to attach, use the @option{--multi} command line option.
18989 Then you can connect using @kbd{target extended-remote} and start
18990 the program you want to debug.
18992 In multi-process mode @code{gdbserver} does not automatically exit unless you
18993 use the option @option{--once}. You can terminate it by using
18994 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
18995 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
18996 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
18997 @option{--multi} option to @code{gdbserver} has no influence on that.
18999 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
19001 This section applies only when @code{gdbserver} is run to listen on a TCP port.
19003 @code{gdbserver} normally terminates after all of its debugged processes have
19004 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
19005 extended-remote}, @code{gdbserver} stays running even with no processes left.
19006 @value{GDBN} normally terminates the spawned debugged process on its exit,
19007 which normally also terminates @code{gdbserver} in the @kbd{target remote}
19008 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
19009 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
19010 stays running even in the @kbd{target remote} mode.
19012 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
19013 Such reconnecting is useful for features like @ref{disconnected tracing}. For
19014 completeness, at most one @value{GDBN} can be connected at a time.
19016 @cindex @option{--once}, @code{gdbserver} option
19017 By default, @code{gdbserver} keeps the listening TCP port open, so that
19018 subsequent connections are possible. However, if you start @code{gdbserver}
19019 with the @option{--once} option, it will stop listening for any further
19020 connection attempts after connecting to the first @value{GDBN} session. This
19021 means no further connections to @code{gdbserver} will be possible after the
19022 first one. It also means @code{gdbserver} will terminate after the first
19023 connection with remote @value{GDBN} has closed, even for unexpectedly closed
19024 connections and even in the @kbd{target extended-remote} mode. The
19025 @option{--once} option allows reusing the same port number for connecting to
19026 multiple instances of @code{gdbserver} running on the same host, since each
19027 instance closes its port after the first connection.
19029 @anchor{Other Command-Line Arguments for gdbserver}
19030 @subsubsection Other Command-Line Arguments for @code{gdbserver}
19032 @cindex @option{--debug}, @code{gdbserver} option
19033 The @option{--debug} option tells @code{gdbserver} to display extra
19034 status information about the debugging process.
19035 @cindex @option{--remote-debug}, @code{gdbserver} option
19036 The @option{--remote-debug} option tells @code{gdbserver} to display
19037 remote protocol debug output. These options are intended for
19038 @code{gdbserver} development and for bug reports to the developers.
19040 @cindex @option{--debug-format}, @code{gdbserver} option
19041 The @option{--debug-format=option1[,option2,...]} option tells
19042 @code{gdbserver} to include additional information in each output.
19043 Possible options are:
19047 Turn off all extra information in debugging output.
19049 Turn on all extra information in debugging output.
19051 Include a timestamp in each line of debugging output.
19054 Options are processed in order. Thus, for example, if @option{none}
19055 appears last then no additional information is added to debugging output.
19057 @cindex @option{--wrapper}, @code{gdbserver} option
19058 The @option{--wrapper} option specifies a wrapper to launch programs
19059 for debugging. The option should be followed by the name of the
19060 wrapper, then any command-line arguments to pass to the wrapper, then
19061 @kbd{--} indicating the end of the wrapper arguments.
19063 @code{gdbserver} runs the specified wrapper program with a combined
19064 command line including the wrapper arguments, then the name of the
19065 program to debug, then any arguments to the program. The wrapper
19066 runs until it executes your program, and then @value{GDBN} gains control.
19068 You can use any program that eventually calls @code{execve} with
19069 its arguments as a wrapper. Several standard Unix utilities do
19070 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
19071 with @code{exec "$@@"} will also work.
19073 For example, you can use @code{env} to pass an environment variable to
19074 the debugged program, without setting the variable in @code{gdbserver}'s
19078 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
19081 @subsection Connecting to @code{gdbserver}
19083 Run @value{GDBN} on the host system.
19085 First make sure you have the necessary symbol files. Load symbols for
19086 your application using the @code{file} command before you connect. Use
19087 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
19088 was compiled with the correct sysroot using @code{--with-sysroot}).
19090 The symbol file and target libraries must exactly match the executable
19091 and libraries on the target, with one exception: the files on the host
19092 system should not be stripped, even if the files on the target system
19093 are. Mismatched or missing files will lead to confusing results
19094 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
19095 files may also prevent @code{gdbserver} from debugging multi-threaded
19098 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
19099 For TCP connections, you must start up @code{gdbserver} prior to using
19100 the @code{target remote} command. Otherwise you may get an error whose
19101 text depends on the host system, but which usually looks something like
19102 @samp{Connection refused}. Don't use the @code{load}
19103 command in @value{GDBN} when using @code{gdbserver}, since the program is
19104 already on the target.
19106 @subsection Monitor Commands for @code{gdbserver}
19107 @cindex monitor commands, for @code{gdbserver}
19108 @anchor{Monitor Commands for gdbserver}
19110 During a @value{GDBN} session using @code{gdbserver}, you can use the
19111 @code{monitor} command to send special requests to @code{gdbserver}.
19112 Here are the available commands.
19116 List the available monitor commands.
19118 @item monitor set debug 0
19119 @itemx monitor set debug 1
19120 Disable or enable general debugging messages.
19122 @item monitor set remote-debug 0
19123 @itemx monitor set remote-debug 1
19124 Disable or enable specific debugging messages associated with the remote
19125 protocol (@pxref{Remote Protocol}).
19127 @item monitor set debug-format option1@r{[},option2,...@r{]}
19128 Specify additional text to add to debugging messages.
19129 Possible options are:
19133 Turn off all extra information in debugging output.
19135 Turn on all extra information in debugging output.
19137 Include a timestamp in each line of debugging output.
19140 Options are processed in order. Thus, for example, if @option{none}
19141 appears last then no additional information is added to debugging output.
19143 @item monitor set libthread-db-search-path [PATH]
19144 @cindex gdbserver, search path for @code{libthread_db}
19145 When this command is issued, @var{path} is a colon-separated list of
19146 directories to search for @code{libthread_db} (@pxref{Threads,,set
19147 libthread-db-search-path}). If you omit @var{path},
19148 @samp{libthread-db-search-path} will be reset to its default value.
19150 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
19151 not supported in @code{gdbserver}.
19154 Tell gdbserver to exit immediately. This command should be followed by
19155 @code{disconnect} to close the debugging session. @code{gdbserver} will
19156 detach from any attached processes and kill any processes it created.
19157 Use @code{monitor exit} to terminate @code{gdbserver} at the end
19158 of a multi-process mode debug session.
19162 @subsection Tracepoints support in @code{gdbserver}
19163 @cindex tracepoints support in @code{gdbserver}
19165 On some targets, @code{gdbserver} supports tracepoints, fast
19166 tracepoints and static tracepoints.
19168 For fast or static tracepoints to work, a special library called the
19169 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
19170 This library is built and distributed as an integral part of
19171 @code{gdbserver}. In addition, support for static tracepoints
19172 requires building the in-process agent library with static tracepoints
19173 support. At present, the UST (LTTng Userspace Tracer,
19174 @url{http://lttng.org/ust}) tracing engine is supported. This support
19175 is automatically available if UST development headers are found in the
19176 standard include path when @code{gdbserver} is built, or if
19177 @code{gdbserver} was explicitly configured using @option{--with-ust}
19178 to point at such headers. You can explicitly disable the support
19179 using @option{--with-ust=no}.
19181 There are several ways to load the in-process agent in your program:
19184 @item Specifying it as dependency at link time
19186 You can link your program dynamically with the in-process agent
19187 library. On most systems, this is accomplished by adding
19188 @code{-linproctrace} to the link command.
19190 @item Using the system's preloading mechanisms
19192 You can force loading the in-process agent at startup time by using
19193 your system's support for preloading shared libraries. Many Unixes
19194 support the concept of preloading user defined libraries. In most
19195 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
19196 in the environment. See also the description of @code{gdbserver}'s
19197 @option{--wrapper} command line option.
19199 @item Using @value{GDBN} to force loading the agent at run time
19201 On some systems, you can force the inferior to load a shared library,
19202 by calling a dynamic loader function in the inferior that takes care
19203 of dynamically looking up and loading a shared library. On most Unix
19204 systems, the function is @code{dlopen}. You'll use the @code{call}
19205 command for that. For example:
19208 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
19211 Note that on most Unix systems, for the @code{dlopen} function to be
19212 available, the program needs to be linked with @code{-ldl}.
19215 On systems that have a userspace dynamic loader, like most Unix
19216 systems, when you connect to @code{gdbserver} using @code{target
19217 remote}, you'll find that the program is stopped at the dynamic
19218 loader's entry point, and no shared library has been loaded in the
19219 program's address space yet, including the in-process agent. In that
19220 case, before being able to use any of the fast or static tracepoints
19221 features, you need to let the loader run and load the shared
19222 libraries. The simplest way to do that is to run the program to the
19223 main procedure. E.g., if debugging a C or C@t{++} program, start
19224 @code{gdbserver} like so:
19227 $ gdbserver :9999 myprogram
19230 Start GDB and connect to @code{gdbserver} like so, and run to main:
19234 (@value{GDBP}) target remote myhost:9999
19235 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
19236 (@value{GDBP}) b main
19237 (@value{GDBP}) continue
19240 The in-process tracing agent library should now be loaded into the
19241 process; you can confirm it with the @code{info sharedlibrary}
19242 command, which will list @file{libinproctrace.so} as loaded in the
19243 process. You are now ready to install fast tracepoints, list static
19244 tracepoint markers, probe static tracepoints markers, and start
19247 @node Remote Configuration
19248 @section Remote Configuration
19251 @kindex show remote
19252 This section documents the configuration options available when
19253 debugging remote programs. For the options related to the File I/O
19254 extensions of the remote protocol, see @ref{system,
19255 system-call-allowed}.
19258 @item set remoteaddresssize @var{bits}
19259 @cindex address size for remote targets
19260 @cindex bits in remote address
19261 Set the maximum size of address in a memory packet to the specified
19262 number of bits. @value{GDBN} will mask off the address bits above
19263 that number, when it passes addresses to the remote target. The
19264 default value is the number of bits in the target's address.
19266 @item show remoteaddresssize
19267 Show the current value of remote address size in bits.
19269 @item set serial baud @var{n}
19270 @cindex baud rate for remote targets
19271 Set the baud rate for the remote serial I/O to @var{n} baud. The
19272 value is used to set the speed of the serial port used for debugging
19275 @item show serial baud
19276 Show the current speed of the remote connection.
19278 @item set remotebreak
19279 @cindex interrupt remote programs
19280 @cindex BREAK signal instead of Ctrl-C
19281 @anchor{set remotebreak}
19282 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
19283 when you type @kbd{Ctrl-c} to interrupt the program running
19284 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
19285 character instead. The default is off, since most remote systems
19286 expect to see @samp{Ctrl-C} as the interrupt signal.
19288 @item show remotebreak
19289 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
19290 interrupt the remote program.
19292 @item set remoteflow on
19293 @itemx set remoteflow off
19294 @kindex set remoteflow
19295 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
19296 on the serial port used to communicate to the remote target.
19298 @item show remoteflow
19299 @kindex show remoteflow
19300 Show the current setting of hardware flow control.
19302 @item set remotelogbase @var{base}
19303 Set the base (a.k.a.@: radix) of logging serial protocol
19304 communications to @var{base}. Supported values of @var{base} are:
19305 @code{ascii}, @code{octal}, and @code{hex}. The default is
19308 @item show remotelogbase
19309 Show the current setting of the radix for logging remote serial
19312 @item set remotelogfile @var{file}
19313 @cindex record serial communications on file
19314 Record remote serial communications on the named @var{file}. The
19315 default is not to record at all.
19317 @item show remotelogfile.
19318 Show the current setting of the file name on which to record the
19319 serial communications.
19321 @item set remotetimeout @var{num}
19322 @cindex timeout for serial communications
19323 @cindex remote timeout
19324 Set the timeout limit to wait for the remote target to respond to
19325 @var{num} seconds. The default is 2 seconds.
19327 @item show remotetimeout
19328 Show the current number of seconds to wait for the remote target
19331 @cindex limit hardware breakpoints and watchpoints
19332 @cindex remote target, limit break- and watchpoints
19333 @anchor{set remote hardware-watchpoint-limit}
19334 @anchor{set remote hardware-breakpoint-limit}
19335 @item set remote hardware-watchpoint-limit @var{limit}
19336 @itemx set remote hardware-breakpoint-limit @var{limit}
19337 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
19338 watchpoints. A limit of -1, the default, is treated as unlimited.
19340 @cindex limit hardware watchpoints length
19341 @cindex remote target, limit watchpoints length
19342 @anchor{set remote hardware-watchpoint-length-limit}
19343 @item set remote hardware-watchpoint-length-limit @var{limit}
19344 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
19345 a remote hardware watchpoint. A limit of -1, the default, is treated
19348 @item show remote hardware-watchpoint-length-limit
19349 Show the current limit (in bytes) of the maximum length of
19350 a remote hardware watchpoint.
19352 @item set remote exec-file @var{filename}
19353 @itemx show remote exec-file
19354 @anchor{set remote exec-file}
19355 @cindex executable file, for remote target
19356 Select the file used for @code{run} with @code{target
19357 extended-remote}. This should be set to a filename valid on the
19358 target system. If it is not set, the target will use a default
19359 filename (e.g.@: the last program run).
19361 @item set remote interrupt-sequence
19362 @cindex interrupt remote programs
19363 @cindex select Ctrl-C, BREAK or BREAK-g
19364 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
19365 @samp{BREAK-g} as the
19366 sequence to the remote target in order to interrupt the execution.
19367 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
19368 is high level of serial line for some certain time.
19369 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
19370 It is @code{BREAK} signal followed by character @code{g}.
19372 @item show interrupt-sequence
19373 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
19374 is sent by @value{GDBN} to interrupt the remote program.
19375 @code{BREAK-g} is BREAK signal followed by @code{g} and
19376 also known as Magic SysRq g.
19378 @item set remote interrupt-on-connect
19379 @cindex send interrupt-sequence on start
19380 Specify whether interrupt-sequence is sent to remote target when
19381 @value{GDBN} connects to it. This is mostly needed when you debug
19382 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
19383 which is known as Magic SysRq g in order to connect @value{GDBN}.
19385 @item show interrupt-on-connect
19386 Show whether interrupt-sequence is sent
19387 to remote target when @value{GDBN} connects to it.
19391 @item set tcp auto-retry on
19392 @cindex auto-retry, for remote TCP target
19393 Enable auto-retry for remote TCP connections. This is useful if the remote
19394 debugging agent is launched in parallel with @value{GDBN}; there is a race
19395 condition because the agent may not become ready to accept the connection
19396 before @value{GDBN} attempts to connect. When auto-retry is
19397 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
19398 to establish the connection using the timeout specified by
19399 @code{set tcp connect-timeout}.
19401 @item set tcp auto-retry off
19402 Do not auto-retry failed TCP connections.
19404 @item show tcp auto-retry
19405 Show the current auto-retry setting.
19407 @item set tcp connect-timeout @var{seconds}
19408 @itemx set tcp connect-timeout unlimited
19409 @cindex connection timeout, for remote TCP target
19410 @cindex timeout, for remote target connection
19411 Set the timeout for establishing a TCP connection to the remote target to
19412 @var{seconds}. The timeout affects both polling to retry failed connections
19413 (enabled by @code{set tcp auto-retry on}) and waiting for connections
19414 that are merely slow to complete, and represents an approximate cumulative
19415 value. If @var{seconds} is @code{unlimited}, there is no timeout and
19416 @value{GDBN} will keep attempting to establish a connection forever,
19417 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
19419 @item show tcp connect-timeout
19420 Show the current connection timeout setting.
19423 @cindex remote packets, enabling and disabling
19424 The @value{GDBN} remote protocol autodetects the packets supported by
19425 your debugging stub. If you need to override the autodetection, you
19426 can use these commands to enable or disable individual packets. Each
19427 packet can be set to @samp{on} (the remote target supports this
19428 packet), @samp{off} (the remote target does not support this packet),
19429 or @samp{auto} (detect remote target support for this packet). They
19430 all default to @samp{auto}. For more information about each packet,
19431 see @ref{Remote Protocol}.
19433 During normal use, you should not have to use any of these commands.
19434 If you do, that may be a bug in your remote debugging stub, or a bug
19435 in @value{GDBN}. You may want to report the problem to the
19436 @value{GDBN} developers.
19438 For each packet @var{name}, the command to enable or disable the
19439 packet is @code{set remote @var{name}-packet}. The available settings
19442 @multitable @columnfractions 0.28 0.32 0.25
19445 @tab Related Features
19447 @item @code{fetch-register}
19449 @tab @code{info registers}
19451 @item @code{set-register}
19455 @item @code{binary-download}
19457 @tab @code{load}, @code{set}
19459 @item @code{read-aux-vector}
19460 @tab @code{qXfer:auxv:read}
19461 @tab @code{info auxv}
19463 @item @code{symbol-lookup}
19464 @tab @code{qSymbol}
19465 @tab Detecting multiple threads
19467 @item @code{attach}
19468 @tab @code{vAttach}
19471 @item @code{verbose-resume}
19473 @tab Stepping or resuming multiple threads
19479 @item @code{software-breakpoint}
19483 @item @code{hardware-breakpoint}
19487 @item @code{write-watchpoint}
19491 @item @code{read-watchpoint}
19495 @item @code{access-watchpoint}
19499 @item @code{target-features}
19500 @tab @code{qXfer:features:read}
19501 @tab @code{set architecture}
19503 @item @code{library-info}
19504 @tab @code{qXfer:libraries:read}
19505 @tab @code{info sharedlibrary}
19507 @item @code{memory-map}
19508 @tab @code{qXfer:memory-map:read}
19509 @tab @code{info mem}
19511 @item @code{read-sdata-object}
19512 @tab @code{qXfer:sdata:read}
19513 @tab @code{print $_sdata}
19515 @item @code{read-spu-object}
19516 @tab @code{qXfer:spu:read}
19517 @tab @code{info spu}
19519 @item @code{write-spu-object}
19520 @tab @code{qXfer:spu:write}
19521 @tab @code{info spu}
19523 @item @code{read-siginfo-object}
19524 @tab @code{qXfer:siginfo:read}
19525 @tab @code{print $_siginfo}
19527 @item @code{write-siginfo-object}
19528 @tab @code{qXfer:siginfo:write}
19529 @tab @code{set $_siginfo}
19531 @item @code{threads}
19532 @tab @code{qXfer:threads:read}
19533 @tab @code{info threads}
19535 @item @code{get-thread-local-@*storage-address}
19536 @tab @code{qGetTLSAddr}
19537 @tab Displaying @code{__thread} variables
19539 @item @code{get-thread-information-block-address}
19540 @tab @code{qGetTIBAddr}
19541 @tab Display MS-Windows Thread Information Block.
19543 @item @code{search-memory}
19544 @tab @code{qSearch:memory}
19547 @item @code{supported-packets}
19548 @tab @code{qSupported}
19549 @tab Remote communications parameters
19551 @item @code{pass-signals}
19552 @tab @code{QPassSignals}
19553 @tab @code{handle @var{signal}}
19555 @item @code{program-signals}
19556 @tab @code{QProgramSignals}
19557 @tab @code{handle @var{signal}}
19559 @item @code{hostio-close-packet}
19560 @tab @code{vFile:close}
19561 @tab @code{remote get}, @code{remote put}
19563 @item @code{hostio-open-packet}
19564 @tab @code{vFile:open}
19565 @tab @code{remote get}, @code{remote put}
19567 @item @code{hostio-pread-packet}
19568 @tab @code{vFile:pread}
19569 @tab @code{remote get}, @code{remote put}
19571 @item @code{hostio-pwrite-packet}
19572 @tab @code{vFile:pwrite}
19573 @tab @code{remote get}, @code{remote put}
19575 @item @code{hostio-unlink-packet}
19576 @tab @code{vFile:unlink}
19577 @tab @code{remote delete}
19579 @item @code{hostio-readlink-packet}
19580 @tab @code{vFile:readlink}
19583 @item @code{noack-packet}
19584 @tab @code{QStartNoAckMode}
19585 @tab Packet acknowledgment
19587 @item @code{osdata}
19588 @tab @code{qXfer:osdata:read}
19589 @tab @code{info os}
19591 @item @code{query-attached}
19592 @tab @code{qAttached}
19593 @tab Querying remote process attach state.
19595 @item @code{trace-buffer-size}
19596 @tab @code{QTBuffer:size}
19597 @tab @code{set trace-buffer-size}
19599 @item @code{trace-status}
19600 @tab @code{qTStatus}
19601 @tab @code{tstatus}
19603 @item @code{traceframe-info}
19604 @tab @code{qXfer:traceframe-info:read}
19605 @tab Traceframe info
19607 @item @code{install-in-trace}
19608 @tab @code{InstallInTrace}
19609 @tab Install tracepoint in tracing
19611 @item @code{disable-randomization}
19612 @tab @code{QDisableRandomization}
19613 @tab @code{set disable-randomization}
19615 @item @code{conditional-breakpoints-packet}
19616 @tab @code{Z0 and Z1}
19617 @tab @code{Support for target-side breakpoint condition evaluation}
19621 @section Implementing a Remote Stub
19623 @cindex debugging stub, example
19624 @cindex remote stub, example
19625 @cindex stub example, remote debugging
19626 The stub files provided with @value{GDBN} implement the target side of the
19627 communication protocol, and the @value{GDBN} side is implemented in the
19628 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
19629 these subroutines to communicate, and ignore the details. (If you're
19630 implementing your own stub file, you can still ignore the details: start
19631 with one of the existing stub files. @file{sparc-stub.c} is the best
19632 organized, and therefore the easiest to read.)
19634 @cindex remote serial debugging, overview
19635 To debug a program running on another machine (the debugging
19636 @dfn{target} machine), you must first arrange for all the usual
19637 prerequisites for the program to run by itself. For example, for a C
19642 A startup routine to set up the C runtime environment; these usually
19643 have a name like @file{crt0}. The startup routine may be supplied by
19644 your hardware supplier, or you may have to write your own.
19647 A C subroutine library to support your program's
19648 subroutine calls, notably managing input and output.
19651 A way of getting your program to the other machine---for example, a
19652 download program. These are often supplied by the hardware
19653 manufacturer, but you may have to write your own from hardware
19657 The next step is to arrange for your program to use a serial port to
19658 communicate with the machine where @value{GDBN} is running (the @dfn{host}
19659 machine). In general terms, the scheme looks like this:
19663 @value{GDBN} already understands how to use this protocol; when everything
19664 else is set up, you can simply use the @samp{target remote} command
19665 (@pxref{Targets,,Specifying a Debugging Target}).
19667 @item On the target,
19668 you must link with your program a few special-purpose subroutines that
19669 implement the @value{GDBN} remote serial protocol. The file containing these
19670 subroutines is called a @dfn{debugging stub}.
19672 On certain remote targets, you can use an auxiliary program
19673 @code{gdbserver} instead of linking a stub into your program.
19674 @xref{Server,,Using the @code{gdbserver} Program}, for details.
19677 The debugging stub is specific to the architecture of the remote
19678 machine; for example, use @file{sparc-stub.c} to debug programs on
19681 @cindex remote serial stub list
19682 These working remote stubs are distributed with @value{GDBN}:
19687 @cindex @file{i386-stub.c}
19690 For Intel 386 and compatible architectures.
19693 @cindex @file{m68k-stub.c}
19694 @cindex Motorola 680x0
19696 For Motorola 680x0 architectures.
19699 @cindex @file{sh-stub.c}
19702 For Renesas SH architectures.
19705 @cindex @file{sparc-stub.c}
19707 For @sc{sparc} architectures.
19709 @item sparcl-stub.c
19710 @cindex @file{sparcl-stub.c}
19713 For Fujitsu @sc{sparclite} architectures.
19717 The @file{README} file in the @value{GDBN} distribution may list other
19718 recently added stubs.
19721 * Stub Contents:: What the stub can do for you
19722 * Bootstrapping:: What you must do for the stub
19723 * Debug Session:: Putting it all together
19726 @node Stub Contents
19727 @subsection What the Stub Can Do for You
19729 @cindex remote serial stub
19730 The debugging stub for your architecture supplies these three
19734 @item set_debug_traps
19735 @findex set_debug_traps
19736 @cindex remote serial stub, initialization
19737 This routine arranges for @code{handle_exception} to run when your
19738 program stops. You must call this subroutine explicitly in your
19739 program's startup code.
19741 @item handle_exception
19742 @findex handle_exception
19743 @cindex remote serial stub, main routine
19744 This is the central workhorse, but your program never calls it
19745 explicitly---the setup code arranges for @code{handle_exception} to
19746 run when a trap is triggered.
19748 @code{handle_exception} takes control when your program stops during
19749 execution (for example, on a breakpoint), and mediates communications
19750 with @value{GDBN} on the host machine. This is where the communications
19751 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
19752 representative on the target machine. It begins by sending summary
19753 information on the state of your program, then continues to execute,
19754 retrieving and transmitting any information @value{GDBN} needs, until you
19755 execute a @value{GDBN} command that makes your program resume; at that point,
19756 @code{handle_exception} returns control to your own code on the target
19760 @cindex @code{breakpoint} subroutine, remote
19761 Use this auxiliary subroutine to make your program contain a
19762 breakpoint. Depending on the particular situation, this may be the only
19763 way for @value{GDBN} to get control. For instance, if your target
19764 machine has some sort of interrupt button, you won't need to call this;
19765 pressing the interrupt button transfers control to
19766 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
19767 simply receiving characters on the serial port may also trigger a trap;
19768 again, in that situation, you don't need to call @code{breakpoint} from
19769 your own program---simply running @samp{target remote} from the host
19770 @value{GDBN} session gets control.
19772 Call @code{breakpoint} if none of these is true, or if you simply want
19773 to make certain your program stops at a predetermined point for the
19774 start of your debugging session.
19777 @node Bootstrapping
19778 @subsection What You Must Do for the Stub
19780 @cindex remote stub, support routines
19781 The debugging stubs that come with @value{GDBN} are set up for a particular
19782 chip architecture, but they have no information about the rest of your
19783 debugging target machine.
19785 First of all you need to tell the stub how to communicate with the
19789 @item int getDebugChar()
19790 @findex getDebugChar
19791 Write this subroutine to read a single character from the serial port.
19792 It may be identical to @code{getchar} for your target system; a
19793 different name is used to allow you to distinguish the two if you wish.
19795 @item void putDebugChar(int)
19796 @findex putDebugChar
19797 Write this subroutine to write a single character to the serial port.
19798 It may be identical to @code{putchar} for your target system; a
19799 different name is used to allow you to distinguish the two if you wish.
19802 @cindex control C, and remote debugging
19803 @cindex interrupting remote targets
19804 If you want @value{GDBN} to be able to stop your program while it is
19805 running, you need to use an interrupt-driven serial driver, and arrange
19806 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
19807 character). That is the character which @value{GDBN} uses to tell the
19808 remote system to stop.
19810 Getting the debugging target to return the proper status to @value{GDBN}
19811 probably requires changes to the standard stub; one quick and dirty way
19812 is to just execute a breakpoint instruction (the ``dirty'' part is that
19813 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
19815 Other routines you need to supply are:
19818 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
19819 @findex exceptionHandler
19820 Write this function to install @var{exception_address} in the exception
19821 handling tables. You need to do this because the stub does not have any
19822 way of knowing what the exception handling tables on your target system
19823 are like (for example, the processor's table might be in @sc{rom},
19824 containing entries which point to a table in @sc{ram}).
19825 The @var{exception_number} specifies the exception which should be changed;
19826 its meaning is architecture-dependent (for example, different numbers
19827 might represent divide by zero, misaligned access, etc). When this
19828 exception occurs, control should be transferred directly to
19829 @var{exception_address}, and the processor state (stack, registers,
19830 and so on) should be just as it is when a processor exception occurs. So if
19831 you want to use a jump instruction to reach @var{exception_address}, it
19832 should be a simple jump, not a jump to subroutine.
19834 For the 386, @var{exception_address} should be installed as an interrupt
19835 gate so that interrupts are masked while the handler runs. The gate
19836 should be at privilege level 0 (the most privileged level). The
19837 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
19838 help from @code{exceptionHandler}.
19840 @item void flush_i_cache()
19841 @findex flush_i_cache
19842 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
19843 instruction cache, if any, on your target machine. If there is no
19844 instruction cache, this subroutine may be a no-op.
19846 On target machines that have instruction caches, @value{GDBN} requires this
19847 function to make certain that the state of your program is stable.
19851 You must also make sure this library routine is available:
19854 @item void *memset(void *, int, int)
19856 This is the standard library function @code{memset} that sets an area of
19857 memory to a known value. If you have one of the free versions of
19858 @code{libc.a}, @code{memset} can be found there; otherwise, you must
19859 either obtain it from your hardware manufacturer, or write your own.
19862 If you do not use the GNU C compiler, you may need other standard
19863 library subroutines as well; this varies from one stub to another,
19864 but in general the stubs are likely to use any of the common library
19865 subroutines which @code{@value{NGCC}} generates as inline code.
19868 @node Debug Session
19869 @subsection Putting it All Together
19871 @cindex remote serial debugging summary
19872 In summary, when your program is ready to debug, you must follow these
19877 Make sure you have defined the supporting low-level routines
19878 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
19880 @code{getDebugChar}, @code{putDebugChar},
19881 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
19885 Insert these lines in your program's startup code, before the main
19886 procedure is called:
19893 On some machines, when a breakpoint trap is raised, the hardware
19894 automatically makes the PC point to the instruction after the
19895 breakpoint. If your machine doesn't do that, you may need to adjust
19896 @code{handle_exception} to arrange for it to return to the instruction
19897 after the breakpoint on this first invocation, so that your program
19898 doesn't keep hitting the initial breakpoint instead of making
19902 For the 680x0 stub only, you need to provide a variable called
19903 @code{exceptionHook}. Normally you just use:
19906 void (*exceptionHook)() = 0;
19910 but if before calling @code{set_debug_traps}, you set it to point to a
19911 function in your program, that function is called when
19912 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
19913 error). The function indicated by @code{exceptionHook} is called with
19914 one parameter: an @code{int} which is the exception number.
19917 Compile and link together: your program, the @value{GDBN} debugging stub for
19918 your target architecture, and the supporting subroutines.
19921 Make sure you have a serial connection between your target machine and
19922 the @value{GDBN} host, and identify the serial port on the host.
19925 @c The "remote" target now provides a `load' command, so we should
19926 @c document that. FIXME.
19927 Download your program to your target machine (or get it there by
19928 whatever means the manufacturer provides), and start it.
19931 Start @value{GDBN} on the host, and connect to the target
19932 (@pxref{Connecting,,Connecting to a Remote Target}).
19936 @node Configurations
19937 @chapter Configuration-Specific Information
19939 While nearly all @value{GDBN} commands are available for all native and
19940 cross versions of the debugger, there are some exceptions. This chapter
19941 describes things that are only available in certain configurations.
19943 There are three major categories of configurations: native
19944 configurations, where the host and target are the same, embedded
19945 operating system configurations, which are usually the same for several
19946 different processor architectures, and bare embedded processors, which
19947 are quite different from each other.
19952 * Embedded Processors::
19959 This section describes details specific to particular native
19964 * BSD libkvm Interface:: Debugging BSD kernel memory images
19965 * SVR4 Process Information:: SVR4 process information
19966 * DJGPP Native:: Features specific to the DJGPP port
19967 * Cygwin Native:: Features specific to the Cygwin port
19968 * Hurd Native:: Features specific to @sc{gnu} Hurd
19969 * Darwin:: Features specific to Darwin
19975 On HP-UX systems, if you refer to a function or variable name that
19976 begins with a dollar sign, @value{GDBN} searches for a user or system
19977 name first, before it searches for a convenience variable.
19980 @node BSD libkvm Interface
19981 @subsection BSD libkvm Interface
19984 @cindex kernel memory image
19985 @cindex kernel crash dump
19987 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
19988 interface that provides a uniform interface for accessing kernel virtual
19989 memory images, including live systems and crash dumps. @value{GDBN}
19990 uses this interface to allow you to debug live kernels and kernel crash
19991 dumps on many native BSD configurations. This is implemented as a
19992 special @code{kvm} debugging target. For debugging a live system, load
19993 the currently running kernel into @value{GDBN} and connect to the
19997 (@value{GDBP}) @b{target kvm}
20000 For debugging crash dumps, provide the file name of the crash dump as an
20004 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
20007 Once connected to the @code{kvm} target, the following commands are
20013 Set current context from the @dfn{Process Control Block} (PCB) address.
20016 Set current context from proc address. This command isn't available on
20017 modern FreeBSD systems.
20020 @node SVR4 Process Information
20021 @subsection SVR4 Process Information
20023 @cindex examine process image
20024 @cindex process info via @file{/proc}
20026 Many versions of SVR4 and compatible systems provide a facility called
20027 @samp{/proc} that can be used to examine the image of a running
20028 process using file-system subroutines.
20030 If @value{GDBN} is configured for an operating system with this
20031 facility, the command @code{info proc} is available to report
20032 information about the process running your program, or about any
20033 process running on your system. This includes, as of this writing,
20034 @sc{gnu}/Linux and Solaris, but not HP-UX, for example.
20036 This command may also work on core files that were created on a system
20037 that has the @samp{/proc} facility.
20043 @itemx info proc @var{process-id}
20044 Summarize available information about any running process. If a
20045 process ID is specified by @var{process-id}, display information about
20046 that process; otherwise display information about the program being
20047 debugged. The summary includes the debugged process ID, the command
20048 line used to invoke it, its current working directory, and its
20049 executable file's absolute file name.
20051 On some systems, @var{process-id} can be of the form
20052 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
20053 within a process. If the optional @var{pid} part is missing, it means
20054 a thread from the process being debugged (the leading @samp{/} still
20055 needs to be present, or else @value{GDBN} will interpret the number as
20056 a process ID rather than a thread ID).
20058 @item info proc cmdline
20059 @cindex info proc cmdline
20060 Show the original command line of the process. This command is
20061 specific to @sc{gnu}/Linux.
20063 @item info proc cwd
20064 @cindex info proc cwd
20065 Show the current working directory of the process. This command is
20066 specific to @sc{gnu}/Linux.
20068 @item info proc exe
20069 @cindex info proc exe
20070 Show the name of executable of the process. This command is specific
20073 @item info proc mappings
20074 @cindex memory address space mappings
20075 Report the memory address space ranges accessible in the program, with
20076 information on whether the process has read, write, or execute access
20077 rights to each range. On @sc{gnu}/Linux systems, each memory range
20078 includes the object file which is mapped to that range, instead of the
20079 memory access rights to that range.
20081 @item info proc stat
20082 @itemx info proc status
20083 @cindex process detailed status information
20084 These subcommands are specific to @sc{gnu}/Linux systems. They show
20085 the process-related information, including the user ID and group ID;
20086 how many threads are there in the process; its virtual memory usage;
20087 the signals that are pending, blocked, and ignored; its TTY; its
20088 consumption of system and user time; its stack size; its @samp{nice}
20089 value; etc. For more information, see the @samp{proc} man page
20090 (type @kbd{man 5 proc} from your shell prompt).
20092 @item info proc all
20093 Show all the information about the process described under all of the
20094 above @code{info proc} subcommands.
20097 @comment These sub-options of 'info proc' were not included when
20098 @comment procfs.c was re-written. Keep their descriptions around
20099 @comment against the day when someone finds the time to put them back in.
20100 @kindex info proc times
20101 @item info proc times
20102 Starting time, user CPU time, and system CPU time for your program and
20105 @kindex info proc id
20107 Report on the process IDs related to your program: its own process ID,
20108 the ID of its parent, the process group ID, and the session ID.
20111 @item set procfs-trace
20112 @kindex set procfs-trace
20113 @cindex @code{procfs} API calls
20114 This command enables and disables tracing of @code{procfs} API calls.
20116 @item show procfs-trace
20117 @kindex show procfs-trace
20118 Show the current state of @code{procfs} API call tracing.
20120 @item set procfs-file @var{file}
20121 @kindex set procfs-file
20122 Tell @value{GDBN} to write @code{procfs} API trace to the named
20123 @var{file}. @value{GDBN} appends the trace info to the previous
20124 contents of the file. The default is to display the trace on the
20127 @item show procfs-file
20128 @kindex show procfs-file
20129 Show the file to which @code{procfs} API trace is written.
20131 @item proc-trace-entry
20132 @itemx proc-trace-exit
20133 @itemx proc-untrace-entry
20134 @itemx proc-untrace-exit
20135 @kindex proc-trace-entry
20136 @kindex proc-trace-exit
20137 @kindex proc-untrace-entry
20138 @kindex proc-untrace-exit
20139 These commands enable and disable tracing of entries into and exits
20140 from the @code{syscall} interface.
20143 @kindex info pidlist
20144 @cindex process list, QNX Neutrino
20145 For QNX Neutrino only, this command displays the list of all the
20146 processes and all the threads within each process.
20149 @kindex info meminfo
20150 @cindex mapinfo list, QNX Neutrino
20151 For QNX Neutrino only, this command displays the list of all mapinfos.
20155 @subsection Features for Debugging @sc{djgpp} Programs
20156 @cindex @sc{djgpp} debugging
20157 @cindex native @sc{djgpp} debugging
20158 @cindex MS-DOS-specific commands
20161 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
20162 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
20163 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
20164 top of real-mode DOS systems and their emulations.
20166 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
20167 defines a few commands specific to the @sc{djgpp} port. This
20168 subsection describes those commands.
20173 This is a prefix of @sc{djgpp}-specific commands which print
20174 information about the target system and important OS structures.
20177 @cindex MS-DOS system info
20178 @cindex free memory information (MS-DOS)
20179 @item info dos sysinfo
20180 This command displays assorted information about the underlying
20181 platform: the CPU type and features, the OS version and flavor, the
20182 DPMI version, and the available conventional and DPMI memory.
20187 @cindex segment descriptor tables
20188 @cindex descriptor tables display
20190 @itemx info dos ldt
20191 @itemx info dos idt
20192 These 3 commands display entries from, respectively, Global, Local,
20193 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
20194 tables are data structures which store a descriptor for each segment
20195 that is currently in use. The segment's selector is an index into a
20196 descriptor table; the table entry for that index holds the
20197 descriptor's base address and limit, and its attributes and access
20200 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
20201 segment (used for both data and the stack), and a DOS segment (which
20202 allows access to DOS/BIOS data structures and absolute addresses in
20203 conventional memory). However, the DPMI host will usually define
20204 additional segments in order to support the DPMI environment.
20206 @cindex garbled pointers
20207 These commands allow to display entries from the descriptor tables.
20208 Without an argument, all entries from the specified table are
20209 displayed. An argument, which should be an integer expression, means
20210 display a single entry whose index is given by the argument. For
20211 example, here's a convenient way to display information about the
20212 debugged program's data segment:
20215 @exdent @code{(@value{GDBP}) info dos ldt $ds}
20216 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
20220 This comes in handy when you want to see whether a pointer is outside
20221 the data segment's limit (i.e.@: @dfn{garbled}).
20223 @cindex page tables display (MS-DOS)
20225 @itemx info dos pte
20226 These two commands display entries from, respectively, the Page
20227 Directory and the Page Tables. Page Directories and Page Tables are
20228 data structures which control how virtual memory addresses are mapped
20229 into physical addresses. A Page Table includes an entry for every
20230 page of memory that is mapped into the program's address space; there
20231 may be several Page Tables, each one holding up to 4096 entries. A
20232 Page Directory has up to 4096 entries, one each for every Page Table
20233 that is currently in use.
20235 Without an argument, @kbd{info dos pde} displays the entire Page
20236 Directory, and @kbd{info dos pte} displays all the entries in all of
20237 the Page Tables. An argument, an integer expression, given to the
20238 @kbd{info dos pde} command means display only that entry from the Page
20239 Directory table. An argument given to the @kbd{info dos pte} command
20240 means display entries from a single Page Table, the one pointed to by
20241 the specified entry in the Page Directory.
20243 @cindex direct memory access (DMA) on MS-DOS
20244 These commands are useful when your program uses @dfn{DMA} (Direct
20245 Memory Access), which needs physical addresses to program the DMA
20248 These commands are supported only with some DPMI servers.
20250 @cindex physical address from linear address
20251 @item info dos address-pte @var{addr}
20252 This command displays the Page Table entry for a specified linear
20253 address. The argument @var{addr} is a linear address which should
20254 already have the appropriate segment's base address added to it,
20255 because this command accepts addresses which may belong to @emph{any}
20256 segment. For example, here's how to display the Page Table entry for
20257 the page where a variable @code{i} is stored:
20260 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
20261 @exdent @code{Page Table entry for address 0x11a00d30:}
20262 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
20266 This says that @code{i} is stored at offset @code{0xd30} from the page
20267 whose physical base address is @code{0x02698000}, and shows all the
20268 attributes of that page.
20270 Note that you must cast the addresses of variables to a @code{char *},
20271 since otherwise the value of @code{__djgpp_base_address}, the base
20272 address of all variables and functions in a @sc{djgpp} program, will
20273 be added using the rules of C pointer arithmetics: if @code{i} is
20274 declared an @code{int}, @value{GDBN} will add 4 times the value of
20275 @code{__djgpp_base_address} to the address of @code{i}.
20277 Here's another example, it displays the Page Table entry for the
20281 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
20282 @exdent @code{Page Table entry for address 0x29110:}
20283 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
20287 (The @code{+ 3} offset is because the transfer buffer's address is the
20288 3rd member of the @code{_go32_info_block} structure.) The output
20289 clearly shows that this DPMI server maps the addresses in conventional
20290 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
20291 linear (@code{0x29110}) addresses are identical.
20293 This command is supported only with some DPMI servers.
20296 @cindex DOS serial data link, remote debugging
20297 In addition to native debugging, the DJGPP port supports remote
20298 debugging via a serial data link. The following commands are specific
20299 to remote serial debugging in the DJGPP port of @value{GDBN}.
20302 @kindex set com1base
20303 @kindex set com1irq
20304 @kindex set com2base
20305 @kindex set com2irq
20306 @kindex set com3base
20307 @kindex set com3irq
20308 @kindex set com4base
20309 @kindex set com4irq
20310 @item set com1base @var{addr}
20311 This command sets the base I/O port address of the @file{COM1} serial
20314 @item set com1irq @var{irq}
20315 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
20316 for the @file{COM1} serial port.
20318 There are similar commands @samp{set com2base}, @samp{set com3irq},
20319 etc.@: for setting the port address and the @code{IRQ} lines for the
20322 @kindex show com1base
20323 @kindex show com1irq
20324 @kindex show com2base
20325 @kindex show com2irq
20326 @kindex show com3base
20327 @kindex show com3irq
20328 @kindex show com4base
20329 @kindex show com4irq
20330 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
20331 display the current settings of the base address and the @code{IRQ}
20332 lines used by the COM ports.
20335 @kindex info serial
20336 @cindex DOS serial port status
20337 This command prints the status of the 4 DOS serial ports. For each
20338 port, it prints whether it's active or not, its I/O base address and
20339 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
20340 counts of various errors encountered so far.
20344 @node Cygwin Native
20345 @subsection Features for Debugging MS Windows PE Executables
20346 @cindex MS Windows debugging
20347 @cindex native Cygwin debugging
20348 @cindex Cygwin-specific commands
20350 @value{GDBN} supports native debugging of MS Windows programs, including
20351 DLLs with and without symbolic debugging information.
20353 @cindex Ctrl-BREAK, MS-Windows
20354 @cindex interrupt debuggee on MS-Windows
20355 MS-Windows programs that call @code{SetConsoleMode} to switch off the
20356 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
20357 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
20358 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
20359 sequence, which can be used to interrupt the debuggee even if it
20362 There are various additional Cygwin-specific commands, described in
20363 this section. Working with DLLs that have no debugging symbols is
20364 described in @ref{Non-debug DLL Symbols}.
20369 This is a prefix of MS Windows-specific commands which print
20370 information about the target system and important OS structures.
20372 @item info w32 selector
20373 This command displays information returned by
20374 the Win32 API @code{GetThreadSelectorEntry} function.
20375 It takes an optional argument that is evaluated to
20376 a long value to give the information about this given selector.
20377 Without argument, this command displays information
20378 about the six segment registers.
20380 @item info w32 thread-information-block
20381 This command displays thread specific information stored in the
20382 Thread Information Block (readable on the X86 CPU family using @code{$fs}
20383 selector for 32-bit programs and @code{$gs} for 64-bit programs).
20387 This is a Cygwin-specific alias of @code{info shared}.
20389 @kindex set cygwin-exceptions
20390 @cindex debugging the Cygwin DLL
20391 @cindex Cygwin DLL, debugging
20392 @item set cygwin-exceptions @var{mode}
20393 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
20394 happen inside the Cygwin DLL. If @var{mode} is @code{off},
20395 @value{GDBN} will delay recognition of exceptions, and may ignore some
20396 exceptions which seem to be caused by internal Cygwin DLL
20397 ``bookkeeping''. This option is meant primarily for debugging the
20398 Cygwin DLL itself; the default value is @code{off} to avoid annoying
20399 @value{GDBN} users with false @code{SIGSEGV} signals.
20401 @kindex show cygwin-exceptions
20402 @item show cygwin-exceptions
20403 Displays whether @value{GDBN} will break on exceptions that happen
20404 inside the Cygwin DLL itself.
20406 @kindex set new-console
20407 @item set new-console @var{mode}
20408 If @var{mode} is @code{on} the debuggee will
20409 be started in a new console on next start.
20410 If @var{mode} is @code{off}, the debuggee will
20411 be started in the same console as the debugger.
20413 @kindex show new-console
20414 @item show new-console
20415 Displays whether a new console is used
20416 when the debuggee is started.
20418 @kindex set new-group
20419 @item set new-group @var{mode}
20420 This boolean value controls whether the debuggee should
20421 start a new group or stay in the same group as the debugger.
20422 This affects the way the Windows OS handles
20425 @kindex show new-group
20426 @item show new-group
20427 Displays current value of new-group boolean.
20429 @kindex set debugevents
20430 @item set debugevents
20431 This boolean value adds debug output concerning kernel events related
20432 to the debuggee seen by the debugger. This includes events that
20433 signal thread and process creation and exit, DLL loading and
20434 unloading, console interrupts, and debugging messages produced by the
20435 Windows @code{OutputDebugString} API call.
20437 @kindex set debugexec
20438 @item set debugexec
20439 This boolean value adds debug output concerning execute events
20440 (such as resume thread) seen by the debugger.
20442 @kindex set debugexceptions
20443 @item set debugexceptions
20444 This boolean value adds debug output concerning exceptions in the
20445 debuggee seen by the debugger.
20447 @kindex set debugmemory
20448 @item set debugmemory
20449 This boolean value adds debug output concerning debuggee memory reads
20450 and writes by the debugger.
20454 This boolean values specifies whether the debuggee is called
20455 via a shell or directly (default value is on).
20459 Displays if the debuggee will be started with a shell.
20464 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
20467 @node Non-debug DLL Symbols
20468 @subsubsection Support for DLLs without Debugging Symbols
20469 @cindex DLLs with no debugging symbols
20470 @cindex Minimal symbols and DLLs
20472 Very often on windows, some of the DLLs that your program relies on do
20473 not include symbolic debugging information (for example,
20474 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
20475 symbols in a DLL, it relies on the minimal amount of symbolic
20476 information contained in the DLL's export table. This section
20477 describes working with such symbols, known internally to @value{GDBN} as
20478 ``minimal symbols''.
20480 Note that before the debugged program has started execution, no DLLs
20481 will have been loaded. The easiest way around this problem is simply to
20482 start the program --- either by setting a breakpoint or letting the
20483 program run once to completion.
20485 @subsubsection DLL Name Prefixes
20487 In keeping with the naming conventions used by the Microsoft debugging
20488 tools, DLL export symbols are made available with a prefix based on the
20489 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
20490 also entered into the symbol table, so @code{CreateFileA} is often
20491 sufficient. In some cases there will be name clashes within a program
20492 (particularly if the executable itself includes full debugging symbols)
20493 necessitating the use of the fully qualified name when referring to the
20494 contents of the DLL. Use single-quotes around the name to avoid the
20495 exclamation mark (``!'') being interpreted as a language operator.
20497 Note that the internal name of the DLL may be all upper-case, even
20498 though the file name of the DLL is lower-case, or vice-versa. Since
20499 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
20500 some confusion. If in doubt, try the @code{info functions} and
20501 @code{info variables} commands or even @code{maint print msymbols}
20502 (@pxref{Symbols}). Here's an example:
20505 (@value{GDBP}) info function CreateFileA
20506 All functions matching regular expression "CreateFileA":
20508 Non-debugging symbols:
20509 0x77e885f4 CreateFileA
20510 0x77e885f4 KERNEL32!CreateFileA
20514 (@value{GDBP}) info function !
20515 All functions matching regular expression "!":
20517 Non-debugging symbols:
20518 0x6100114c cygwin1!__assert
20519 0x61004034 cygwin1!_dll_crt0@@0
20520 0x61004240 cygwin1!dll_crt0(per_process *)
20524 @subsubsection Working with Minimal Symbols
20526 Symbols extracted from a DLL's export table do not contain very much
20527 type information. All that @value{GDBN} can do is guess whether a symbol
20528 refers to a function or variable depending on the linker section that
20529 contains the symbol. Also note that the actual contents of the memory
20530 contained in a DLL are not available unless the program is running. This
20531 means that you cannot examine the contents of a variable or disassemble
20532 a function within a DLL without a running program.
20534 Variables are generally treated as pointers and dereferenced
20535 automatically. For this reason, it is often necessary to prefix a
20536 variable name with the address-of operator (``&'') and provide explicit
20537 type information in the command. Here's an example of the type of
20541 (@value{GDBP}) print 'cygwin1!__argv'
20546 (@value{GDBP}) x 'cygwin1!__argv'
20547 0x10021610: "\230y\""
20550 And two possible solutions:
20553 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
20554 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
20558 (@value{GDBP}) x/2x &'cygwin1!__argv'
20559 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
20560 (@value{GDBP}) x/x 0x10021608
20561 0x10021608: 0x0022fd98
20562 (@value{GDBP}) x/s 0x0022fd98
20563 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
20566 Setting a break point within a DLL is possible even before the program
20567 starts execution. However, under these circumstances, @value{GDBN} can't
20568 examine the initial instructions of the function in order to skip the
20569 function's frame set-up code. You can work around this by using ``*&''
20570 to set the breakpoint at a raw memory address:
20573 (@value{GDBP}) break *&'python22!PyOS_Readline'
20574 Breakpoint 1 at 0x1e04eff0
20577 The author of these extensions is not entirely convinced that setting a
20578 break point within a shared DLL like @file{kernel32.dll} is completely
20582 @subsection Commands Specific to @sc{gnu} Hurd Systems
20583 @cindex @sc{gnu} Hurd debugging
20585 This subsection describes @value{GDBN} commands specific to the
20586 @sc{gnu} Hurd native debugging.
20591 @kindex set signals@r{, Hurd command}
20592 @kindex set sigs@r{, Hurd command}
20593 This command toggles the state of inferior signal interception by
20594 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
20595 affected by this command. @code{sigs} is a shorthand alias for
20600 @kindex show signals@r{, Hurd command}
20601 @kindex show sigs@r{, Hurd command}
20602 Show the current state of intercepting inferior's signals.
20604 @item set signal-thread
20605 @itemx set sigthread
20606 @kindex set signal-thread
20607 @kindex set sigthread
20608 This command tells @value{GDBN} which thread is the @code{libc} signal
20609 thread. That thread is run when a signal is delivered to a running
20610 process. @code{set sigthread} is the shorthand alias of @code{set
20613 @item show signal-thread
20614 @itemx show sigthread
20615 @kindex show signal-thread
20616 @kindex show sigthread
20617 These two commands show which thread will run when the inferior is
20618 delivered a signal.
20621 @kindex set stopped@r{, Hurd command}
20622 This commands tells @value{GDBN} that the inferior process is stopped,
20623 as with the @code{SIGSTOP} signal. The stopped process can be
20624 continued by delivering a signal to it.
20627 @kindex show stopped@r{, Hurd command}
20628 This command shows whether @value{GDBN} thinks the debuggee is
20631 @item set exceptions
20632 @kindex set exceptions@r{, Hurd command}
20633 Use this command to turn off trapping of exceptions in the inferior.
20634 When exception trapping is off, neither breakpoints nor
20635 single-stepping will work. To restore the default, set exception
20638 @item show exceptions
20639 @kindex show exceptions@r{, Hurd command}
20640 Show the current state of trapping exceptions in the inferior.
20642 @item set task pause
20643 @kindex set task@r{, Hurd commands}
20644 @cindex task attributes (@sc{gnu} Hurd)
20645 @cindex pause current task (@sc{gnu} Hurd)
20646 This command toggles task suspension when @value{GDBN} has control.
20647 Setting it to on takes effect immediately, and the task is suspended
20648 whenever @value{GDBN} gets control. Setting it to off will take
20649 effect the next time the inferior is continued. If this option is set
20650 to off, you can use @code{set thread default pause on} or @code{set
20651 thread pause on} (see below) to pause individual threads.
20653 @item show task pause
20654 @kindex show task@r{, Hurd commands}
20655 Show the current state of task suspension.
20657 @item set task detach-suspend-count
20658 @cindex task suspend count
20659 @cindex detach from task, @sc{gnu} Hurd
20660 This command sets the suspend count the task will be left with when
20661 @value{GDBN} detaches from it.
20663 @item show task detach-suspend-count
20664 Show the suspend count the task will be left with when detaching.
20666 @item set task exception-port
20667 @itemx set task excp
20668 @cindex task exception port, @sc{gnu} Hurd
20669 This command sets the task exception port to which @value{GDBN} will
20670 forward exceptions. The argument should be the value of the @dfn{send
20671 rights} of the task. @code{set task excp} is a shorthand alias.
20673 @item set noninvasive
20674 @cindex noninvasive task options
20675 This command switches @value{GDBN} to a mode that is the least
20676 invasive as far as interfering with the inferior is concerned. This
20677 is the same as using @code{set task pause}, @code{set exceptions}, and
20678 @code{set signals} to values opposite to the defaults.
20680 @item info send-rights
20681 @itemx info receive-rights
20682 @itemx info port-rights
20683 @itemx info port-sets
20684 @itemx info dead-names
20687 @cindex send rights, @sc{gnu} Hurd
20688 @cindex receive rights, @sc{gnu} Hurd
20689 @cindex port rights, @sc{gnu} Hurd
20690 @cindex port sets, @sc{gnu} Hurd
20691 @cindex dead names, @sc{gnu} Hurd
20692 These commands display information about, respectively, send rights,
20693 receive rights, port rights, port sets, and dead names of a task.
20694 There are also shorthand aliases: @code{info ports} for @code{info
20695 port-rights} and @code{info psets} for @code{info port-sets}.
20697 @item set thread pause
20698 @kindex set thread@r{, Hurd command}
20699 @cindex thread properties, @sc{gnu} Hurd
20700 @cindex pause current thread (@sc{gnu} Hurd)
20701 This command toggles current thread suspension when @value{GDBN} has
20702 control. Setting it to on takes effect immediately, and the current
20703 thread is suspended whenever @value{GDBN} gets control. Setting it to
20704 off will take effect the next time the inferior is continued.
20705 Normally, this command has no effect, since when @value{GDBN} has
20706 control, the whole task is suspended. However, if you used @code{set
20707 task pause off} (see above), this command comes in handy to suspend
20708 only the current thread.
20710 @item show thread pause
20711 @kindex show thread@r{, Hurd command}
20712 This command shows the state of current thread suspension.
20714 @item set thread run
20715 This command sets whether the current thread is allowed to run.
20717 @item show thread run
20718 Show whether the current thread is allowed to run.
20720 @item set thread detach-suspend-count
20721 @cindex thread suspend count, @sc{gnu} Hurd
20722 @cindex detach from thread, @sc{gnu} Hurd
20723 This command sets the suspend count @value{GDBN} will leave on a
20724 thread when detaching. This number is relative to the suspend count
20725 found by @value{GDBN} when it notices the thread; use @code{set thread
20726 takeover-suspend-count} to force it to an absolute value.
20728 @item show thread detach-suspend-count
20729 Show the suspend count @value{GDBN} will leave on the thread when
20732 @item set thread exception-port
20733 @itemx set thread excp
20734 Set the thread exception port to which to forward exceptions. This
20735 overrides the port set by @code{set task exception-port} (see above).
20736 @code{set thread excp} is the shorthand alias.
20738 @item set thread takeover-suspend-count
20739 Normally, @value{GDBN}'s thread suspend counts are relative to the
20740 value @value{GDBN} finds when it notices each thread. This command
20741 changes the suspend counts to be absolute instead.
20743 @item set thread default
20744 @itemx show thread default
20745 @cindex thread default settings, @sc{gnu} Hurd
20746 Each of the above @code{set thread} commands has a @code{set thread
20747 default} counterpart (e.g., @code{set thread default pause}, @code{set
20748 thread default exception-port}, etc.). The @code{thread default}
20749 variety of commands sets the default thread properties for all
20750 threads; you can then change the properties of individual threads with
20751 the non-default commands.
20758 @value{GDBN} provides the following commands specific to the Darwin target:
20761 @item set debug darwin @var{num}
20762 @kindex set debug darwin
20763 When set to a non zero value, enables debugging messages specific to
20764 the Darwin support. Higher values produce more verbose output.
20766 @item show debug darwin
20767 @kindex show debug darwin
20768 Show the current state of Darwin messages.
20770 @item set debug mach-o @var{num}
20771 @kindex set debug mach-o
20772 When set to a non zero value, enables debugging messages while
20773 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
20774 file format used on Darwin for object and executable files.) Higher
20775 values produce more verbose output. This is a command to diagnose
20776 problems internal to @value{GDBN} and should not be needed in normal
20779 @item show debug mach-o
20780 @kindex show debug mach-o
20781 Show the current state of Mach-O file messages.
20783 @item set mach-exceptions on
20784 @itemx set mach-exceptions off
20785 @kindex set mach-exceptions
20786 On Darwin, faults are first reported as a Mach exception and are then
20787 mapped to a Posix signal. Use this command to turn on trapping of
20788 Mach exceptions in the inferior. This might be sometimes useful to
20789 better understand the cause of a fault. The default is off.
20791 @item show mach-exceptions
20792 @kindex show mach-exceptions
20793 Show the current state of exceptions trapping.
20798 @section Embedded Operating Systems
20800 This section describes configurations involving the debugging of
20801 embedded operating systems that are available for several different
20804 @value{GDBN} includes the ability to debug programs running on
20805 various real-time operating systems.
20807 @node Embedded Processors
20808 @section Embedded Processors
20810 This section goes into details specific to particular embedded
20813 @cindex send command to simulator
20814 Whenever a specific embedded processor has a simulator, @value{GDBN}
20815 allows to send an arbitrary command to the simulator.
20818 @item sim @var{command}
20819 @kindex sim@r{, a command}
20820 Send an arbitrary @var{command} string to the simulator. Consult the
20821 documentation for the specific simulator in use for information about
20822 acceptable commands.
20828 * M32R/D:: Renesas M32R/D
20829 * M68K:: Motorola M68K
20830 * MicroBlaze:: Xilinx MicroBlaze
20831 * MIPS Embedded:: MIPS Embedded
20832 * PowerPC Embedded:: PowerPC Embedded
20833 * PA:: HP PA Embedded
20834 * Sparclet:: Tsqware Sparclet
20835 * Sparclite:: Fujitsu Sparclite
20836 * Z8000:: Zilog Z8000
20839 * Super-H:: Renesas Super-H
20848 @item target rdi @var{dev}
20849 ARM Angel monitor, via RDI library interface to ADP protocol. You may
20850 use this target to communicate with both boards running the Angel
20851 monitor, or with the EmbeddedICE JTAG debug device.
20854 @item target rdp @var{dev}
20859 @value{GDBN} provides the following ARM-specific commands:
20862 @item set arm disassembler
20864 This commands selects from a list of disassembly styles. The
20865 @code{"std"} style is the standard style.
20867 @item show arm disassembler
20869 Show the current disassembly style.
20871 @item set arm apcs32
20872 @cindex ARM 32-bit mode
20873 This command toggles ARM operation mode between 32-bit and 26-bit.
20875 @item show arm apcs32
20876 Display the current usage of the ARM 32-bit mode.
20878 @item set arm fpu @var{fputype}
20879 This command sets the ARM floating-point unit (FPU) type. The
20880 argument @var{fputype} can be one of these:
20884 Determine the FPU type by querying the OS ABI.
20886 Software FPU, with mixed-endian doubles on little-endian ARM
20889 GCC-compiled FPA co-processor.
20891 Software FPU with pure-endian doubles.
20897 Show the current type of the FPU.
20900 This command forces @value{GDBN} to use the specified ABI.
20903 Show the currently used ABI.
20905 @item set arm fallback-mode (arm|thumb|auto)
20906 @value{GDBN} uses the symbol table, when available, to determine
20907 whether instructions are ARM or Thumb. This command controls
20908 @value{GDBN}'s default behavior when the symbol table is not
20909 available. The default is @samp{auto}, which causes @value{GDBN} to
20910 use the current execution mode (from the @code{T} bit in the @code{CPSR}
20913 @item show arm fallback-mode
20914 Show the current fallback instruction mode.
20916 @item set arm force-mode (arm|thumb|auto)
20917 This command overrides use of the symbol table to determine whether
20918 instructions are ARM or Thumb. The default is @samp{auto}, which
20919 causes @value{GDBN} to use the symbol table and then the setting
20920 of @samp{set arm fallback-mode}.
20922 @item show arm force-mode
20923 Show the current forced instruction mode.
20925 @item set debug arm
20926 Toggle whether to display ARM-specific debugging messages from the ARM
20927 target support subsystem.
20929 @item show debug arm
20930 Show whether ARM-specific debugging messages are enabled.
20933 The following commands are available when an ARM target is debugged
20934 using the RDI interface:
20937 @item rdilogfile @r{[}@var{file}@r{]}
20939 @cindex ADP (Angel Debugger Protocol) logging
20940 Set the filename for the ADP (Angel Debugger Protocol) packet log.
20941 With an argument, sets the log file to the specified @var{file}. With
20942 no argument, show the current log file name. The default log file is
20945 @item rdilogenable @r{[}@var{arg}@r{]}
20946 @kindex rdilogenable
20947 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
20948 enables logging, with an argument 0 or @code{"no"} disables it. With
20949 no arguments displays the current setting. When logging is enabled,
20950 ADP packets exchanged between @value{GDBN} and the RDI target device
20951 are logged to a file.
20953 @item set rdiromatzero
20954 @kindex set rdiromatzero
20955 @cindex ROM at zero address, RDI
20956 Tell @value{GDBN} whether the target has ROM at address 0. If on,
20957 vector catching is disabled, so that zero address can be used. If off
20958 (the default), vector catching is enabled. For this command to take
20959 effect, it needs to be invoked prior to the @code{target rdi} command.
20961 @item show rdiromatzero
20962 @kindex show rdiromatzero
20963 Show the current setting of ROM at zero address.
20965 @item set rdiheartbeat
20966 @kindex set rdiheartbeat
20967 @cindex RDI heartbeat
20968 Enable or disable RDI heartbeat packets. It is not recommended to
20969 turn on this option, since it confuses ARM and EPI JTAG interface, as
20970 well as the Angel monitor.
20972 @item show rdiheartbeat
20973 @kindex show rdiheartbeat
20974 Show the setting of RDI heartbeat packets.
20978 @item target sim @r{[}@var{simargs}@r{]} @dots{}
20979 The @value{GDBN} ARM simulator accepts the following optional arguments.
20982 @item --swi-support=@var{type}
20983 Tell the simulator which SWI interfaces to support. The argument
20984 @var{type} may be a comma separated list of the following values.
20985 The default value is @code{all}.
20998 @subsection Renesas M32R/D and M32R/SDI
21001 @kindex target m32r
21002 @item target m32r @var{dev}
21003 Renesas M32R/D ROM monitor.
21005 @kindex target m32rsdi
21006 @item target m32rsdi @var{dev}
21007 Renesas M32R SDI server, connected via parallel port to the board.
21010 The following @value{GDBN} commands are specific to the M32R monitor:
21013 @item set download-path @var{path}
21014 @kindex set download-path
21015 @cindex find downloadable @sc{srec} files (M32R)
21016 Set the default path for finding downloadable @sc{srec} files.
21018 @item show download-path
21019 @kindex show download-path
21020 Show the default path for downloadable @sc{srec} files.
21022 @item set board-address @var{addr}
21023 @kindex set board-address
21024 @cindex M32-EVA target board address
21025 Set the IP address for the M32R-EVA target board.
21027 @item show board-address
21028 @kindex show board-address
21029 Show the current IP address of the target board.
21031 @item set server-address @var{addr}
21032 @kindex set server-address
21033 @cindex download server address (M32R)
21034 Set the IP address for the download server, which is the @value{GDBN}'s
21037 @item show server-address
21038 @kindex show server-address
21039 Display the IP address of the download server.
21041 @item upload @r{[}@var{file}@r{]}
21042 @kindex upload@r{, M32R}
21043 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
21044 upload capability. If no @var{file} argument is given, the current
21045 executable file is uploaded.
21047 @item tload @r{[}@var{file}@r{]}
21048 @kindex tload@r{, M32R}
21049 Test the @code{upload} command.
21052 The following commands are available for M32R/SDI:
21057 @cindex reset SDI connection, M32R
21058 This command resets the SDI connection.
21062 This command shows the SDI connection status.
21065 @kindex debug_chaos
21066 @cindex M32R/Chaos debugging
21067 Instructs the remote that M32R/Chaos debugging is to be used.
21069 @item use_debug_dma
21070 @kindex use_debug_dma
21071 Instructs the remote to use the DEBUG_DMA method of accessing memory.
21074 @kindex use_mon_code
21075 Instructs the remote to use the MON_CODE method of accessing memory.
21078 @kindex use_ib_break
21079 Instructs the remote to set breakpoints by IB break.
21081 @item use_dbt_break
21082 @kindex use_dbt_break
21083 Instructs the remote to set breakpoints by DBT.
21089 The Motorola m68k configuration includes ColdFire support, and a
21090 target command for the following ROM monitor.
21094 @kindex target dbug
21095 @item target dbug @var{dev}
21096 dBUG ROM monitor for Motorola ColdFire.
21101 @subsection MicroBlaze
21102 @cindex Xilinx MicroBlaze
21103 @cindex XMD, Xilinx Microprocessor Debugger
21105 The MicroBlaze is a soft-core processor supported on various Xilinx
21106 FPGAs, such as Spartan or Virtex series. Boards with these processors
21107 usually have JTAG ports which connect to a host system running the Xilinx
21108 Embedded Development Kit (EDK) or Software Development Kit (SDK).
21109 This host system is used to download the configuration bitstream to
21110 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
21111 communicates with the target board using the JTAG interface and
21112 presents a @code{gdbserver} interface to the board. By default
21113 @code{xmd} uses port @code{1234}. (While it is possible to change
21114 this default port, it requires the use of undocumented @code{xmd}
21115 commands. Contact Xilinx support if you need to do this.)
21117 Use these GDB commands to connect to the MicroBlaze target processor.
21120 @item target remote :1234
21121 Use this command to connect to the target if you are running @value{GDBN}
21122 on the same system as @code{xmd}.
21124 @item target remote @var{xmd-host}:1234
21125 Use this command to connect to the target if it is connected to @code{xmd}
21126 running on a different system named @var{xmd-host}.
21129 Use this command to download a program to the MicroBlaze target.
21131 @item set debug microblaze @var{n}
21132 Enable MicroBlaze-specific debugging messages if non-zero.
21134 @item show debug microblaze @var{n}
21135 Show MicroBlaze-specific debugging level.
21138 @node MIPS Embedded
21139 @subsection @acronym{MIPS} Embedded
21141 @cindex @acronym{MIPS} boards
21142 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
21143 @acronym{MIPS} board attached to a serial line. This is available when
21144 you configure @value{GDBN} with @samp{--target=mips-elf}.
21147 Use these @value{GDBN} commands to specify the connection to your target board:
21150 @item target mips @var{port}
21151 @kindex target mips @var{port}
21152 To run a program on the board, start up @code{@value{GDBP}} with the
21153 name of your program as the argument. To connect to the board, use the
21154 command @samp{target mips @var{port}}, where @var{port} is the name of
21155 the serial port connected to the board. If the program has not already
21156 been downloaded to the board, you may use the @code{load} command to
21157 download it. You can then use all the usual @value{GDBN} commands.
21159 For example, this sequence connects to the target board through a serial
21160 port, and loads and runs a program called @var{prog} through the
21164 host$ @value{GDBP} @var{prog}
21165 @value{GDBN} is free software and @dots{}
21166 (@value{GDBP}) target mips /dev/ttyb
21167 (@value{GDBP}) load @var{prog}
21171 @item target mips @var{hostname}:@var{portnumber}
21172 On some @value{GDBN} host configurations, you can specify a TCP
21173 connection (for instance, to a serial line managed by a terminal
21174 concentrator) instead of a serial port, using the syntax
21175 @samp{@var{hostname}:@var{portnumber}}.
21177 @item target pmon @var{port}
21178 @kindex target pmon @var{port}
21181 @item target ddb @var{port}
21182 @kindex target ddb @var{port}
21183 NEC's DDB variant of PMON for Vr4300.
21185 @item target lsi @var{port}
21186 @kindex target lsi @var{port}
21187 LSI variant of PMON.
21189 @kindex target r3900
21190 @item target r3900 @var{dev}
21191 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
21193 @kindex target array
21194 @item target array @var{dev}
21195 Array Tech LSI33K RAID controller board.
21201 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
21204 @item set mipsfpu double
21205 @itemx set mipsfpu single
21206 @itemx set mipsfpu none
21207 @itemx set mipsfpu auto
21208 @itemx show mipsfpu
21209 @kindex set mipsfpu
21210 @kindex show mipsfpu
21211 @cindex @acronym{MIPS} remote floating point
21212 @cindex floating point, @acronym{MIPS} remote
21213 If your target board does not support the @acronym{MIPS} floating point
21214 coprocessor, you should use the command @samp{set mipsfpu none} (if you
21215 need this, you may wish to put the command in your @value{GDBN} init
21216 file). This tells @value{GDBN} how to find the return value of
21217 functions which return floating point values. It also allows
21218 @value{GDBN} to avoid saving the floating point registers when calling
21219 functions on the board. If you are using a floating point coprocessor
21220 with only single precision floating point support, as on the @sc{r4650}
21221 processor, use the command @samp{set mipsfpu single}. The default
21222 double precision floating point coprocessor may be selected using
21223 @samp{set mipsfpu double}.
21225 In previous versions the only choices were double precision or no
21226 floating point, so @samp{set mipsfpu on} will select double precision
21227 and @samp{set mipsfpu off} will select no floating point.
21229 As usual, you can inquire about the @code{mipsfpu} variable with
21230 @samp{show mipsfpu}.
21232 @item set timeout @var{seconds}
21233 @itemx set retransmit-timeout @var{seconds}
21234 @itemx show timeout
21235 @itemx show retransmit-timeout
21236 @cindex @code{timeout}, @acronym{MIPS} protocol
21237 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
21238 @kindex set timeout
21239 @kindex show timeout
21240 @kindex set retransmit-timeout
21241 @kindex show retransmit-timeout
21242 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
21243 remote protocol, with the @code{set timeout @var{seconds}} command. The
21244 default is 5 seconds. Similarly, you can control the timeout used while
21245 waiting for an acknowledgment of a packet with the @code{set
21246 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
21247 You can inspect both values with @code{show timeout} and @code{show
21248 retransmit-timeout}. (These commands are @emph{only} available when
21249 @value{GDBN} is configured for @samp{--target=mips-elf}.)
21251 The timeout set by @code{set timeout} does not apply when @value{GDBN}
21252 is waiting for your program to stop. In that case, @value{GDBN} waits
21253 forever because it has no way of knowing how long the program is going
21254 to run before stopping.
21256 @item set syn-garbage-limit @var{num}
21257 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
21258 @cindex synchronize with remote @acronym{MIPS} target
21259 Limit the maximum number of characters @value{GDBN} should ignore when
21260 it tries to synchronize with the remote target. The default is 10
21261 characters. Setting the limit to -1 means there's no limit.
21263 @item show syn-garbage-limit
21264 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
21265 Show the current limit on the number of characters to ignore when
21266 trying to synchronize with the remote system.
21268 @item set monitor-prompt @var{prompt}
21269 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
21270 @cindex remote monitor prompt
21271 Tell @value{GDBN} to expect the specified @var{prompt} string from the
21272 remote monitor. The default depends on the target:
21282 @item show monitor-prompt
21283 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
21284 Show the current strings @value{GDBN} expects as the prompt from the
21287 @item set monitor-warnings
21288 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
21289 Enable or disable monitor warnings about hardware breakpoints. This
21290 has effect only for the @code{lsi} target. When on, @value{GDBN} will
21291 display warning messages whose codes are returned by the @code{lsi}
21292 PMON monitor for breakpoint commands.
21294 @item show monitor-warnings
21295 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
21296 Show the current setting of printing monitor warnings.
21298 @item pmon @var{command}
21299 @kindex pmon@r{, @acronym{MIPS} remote}
21300 @cindex send PMON command
21301 This command allows sending an arbitrary @var{command} string to the
21302 monitor. The monitor must be in debug mode for this to work.
21305 @node PowerPC Embedded
21306 @subsection PowerPC Embedded
21308 @cindex DVC register
21309 @value{GDBN} supports using the DVC (Data Value Compare) register to
21310 implement in hardware simple hardware watchpoint conditions of the form:
21313 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
21314 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
21317 The DVC register will be automatically used when @value{GDBN} detects
21318 such pattern in a condition expression, and the created watchpoint uses one
21319 debug register (either the @code{exact-watchpoints} option is on and the
21320 variable is scalar, or the variable has a length of one byte). This feature
21321 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
21324 When running on PowerPC embedded processors, @value{GDBN} automatically uses
21325 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
21326 in which case watchpoints using only one debug register are created when
21327 watching variables of scalar types.
21329 You can create an artificial array to watch an arbitrary memory
21330 region using one of the following commands (@pxref{Expressions}):
21333 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
21334 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
21337 PowerPC embedded processors support masked watchpoints. See the discussion
21338 about the @code{mask} argument in @ref{Set Watchpoints}.
21340 @cindex ranged breakpoint
21341 PowerPC embedded processors support hardware accelerated
21342 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
21343 the inferior whenever it executes an instruction at any address within
21344 the range it specifies. To set a ranged breakpoint in @value{GDBN},
21345 use the @code{break-range} command.
21347 @value{GDBN} provides the following PowerPC-specific commands:
21350 @kindex break-range
21351 @item break-range @var{start-location}, @var{end-location}
21352 Set a breakpoint for an address range given by
21353 @var{start-location} and @var{end-location}, which can specify a function name,
21354 a line number, an offset of lines from the current line or from the start
21355 location, or an address of an instruction (see @ref{Specify Location},
21356 for a list of all the possible ways to specify a @var{location}.)
21357 The breakpoint will stop execution of the inferior whenever it
21358 executes an instruction at any address within the specified range,
21359 (including @var{start-location} and @var{end-location}.)
21361 @kindex set powerpc
21362 @item set powerpc soft-float
21363 @itemx show powerpc soft-float
21364 Force @value{GDBN} to use (or not use) a software floating point calling
21365 convention. By default, @value{GDBN} selects the calling convention based
21366 on the selected architecture and the provided executable file.
21368 @item set powerpc vector-abi
21369 @itemx show powerpc vector-abi
21370 Force @value{GDBN} to use the specified calling convention for vector
21371 arguments and return values. The valid options are @samp{auto};
21372 @samp{generic}, to avoid vector registers even if they are present;
21373 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
21374 registers. By default, @value{GDBN} selects the calling convention
21375 based on the selected architecture and the provided executable file.
21377 @item set powerpc exact-watchpoints
21378 @itemx show powerpc exact-watchpoints
21379 Allow @value{GDBN} to use only one debug register when watching a variable
21380 of scalar type, thus assuming that the variable is accessed through the
21381 address of its first byte.
21383 @kindex target dink32
21384 @item target dink32 @var{dev}
21385 DINK32 ROM monitor.
21387 @kindex target ppcbug
21388 @item target ppcbug @var{dev}
21389 @kindex target ppcbug1
21390 @item target ppcbug1 @var{dev}
21391 PPCBUG ROM monitor for PowerPC.
21394 @item target sds @var{dev}
21395 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
21398 @cindex SDS protocol
21399 The following commands specific to the SDS protocol are supported
21403 @item set sdstimeout @var{nsec}
21404 @kindex set sdstimeout
21405 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
21406 default is 2 seconds.
21408 @item show sdstimeout
21409 @kindex show sdstimeout
21410 Show the current value of the SDS timeout.
21412 @item sds @var{command}
21413 @kindex sds@r{, a command}
21414 Send the specified @var{command} string to the SDS monitor.
21419 @subsection HP PA Embedded
21423 @kindex target op50n
21424 @item target op50n @var{dev}
21425 OP50N monitor, running on an OKI HPPA board.
21427 @kindex target w89k
21428 @item target w89k @var{dev}
21429 W89K monitor, running on a Winbond HPPA board.
21434 @subsection Tsqware Sparclet
21438 @value{GDBN} enables developers to debug tasks running on
21439 Sparclet targets from a Unix host.
21440 @value{GDBN} uses code that runs on
21441 both the Unix host and on the Sparclet target. The program
21442 @code{@value{GDBP}} is installed and executed on the Unix host.
21445 @item remotetimeout @var{args}
21446 @kindex remotetimeout
21447 @value{GDBN} supports the option @code{remotetimeout}.
21448 This option is set by the user, and @var{args} represents the number of
21449 seconds @value{GDBN} waits for responses.
21452 @cindex compiling, on Sparclet
21453 When compiling for debugging, include the options @samp{-g} to get debug
21454 information and @samp{-Ttext} to relocate the program to where you wish to
21455 load it on the target. You may also want to add the options @samp{-n} or
21456 @samp{-N} in order to reduce the size of the sections. Example:
21459 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
21462 You can use @code{objdump} to verify that the addresses are what you intended:
21465 sparclet-aout-objdump --headers --syms prog
21468 @cindex running, on Sparclet
21470 your Unix execution search path to find @value{GDBN}, you are ready to
21471 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
21472 (or @code{sparclet-aout-gdb}, depending on your installation).
21474 @value{GDBN} comes up showing the prompt:
21481 * Sparclet File:: Setting the file to debug
21482 * Sparclet Connection:: Connecting to Sparclet
21483 * Sparclet Download:: Sparclet download
21484 * Sparclet Execution:: Running and debugging
21487 @node Sparclet File
21488 @subsubsection Setting File to Debug
21490 The @value{GDBN} command @code{file} lets you choose with program to debug.
21493 (gdbslet) file prog
21497 @value{GDBN} then attempts to read the symbol table of @file{prog}.
21498 @value{GDBN} locates
21499 the file by searching the directories listed in the command search
21501 If the file was compiled with debug information (option @samp{-g}), source
21502 files will be searched as well.
21503 @value{GDBN} locates
21504 the source files by searching the directories listed in the directory search
21505 path (@pxref{Environment, ,Your Program's Environment}).
21507 to find a file, it displays a message such as:
21510 prog: No such file or directory.
21513 When this happens, add the appropriate directories to the search paths with
21514 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
21515 @code{target} command again.
21517 @node Sparclet Connection
21518 @subsubsection Connecting to Sparclet
21520 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
21521 To connect to a target on serial port ``@code{ttya}'', type:
21524 (gdbslet) target sparclet /dev/ttya
21525 Remote target sparclet connected to /dev/ttya
21526 main () at ../prog.c:3
21530 @value{GDBN} displays messages like these:
21536 @node Sparclet Download
21537 @subsubsection Sparclet Download
21539 @cindex download to Sparclet
21540 Once connected to the Sparclet target,
21541 you can use the @value{GDBN}
21542 @code{load} command to download the file from the host to the target.
21543 The file name and load offset should be given as arguments to the @code{load}
21545 Since the file format is aout, the program must be loaded to the starting
21546 address. You can use @code{objdump} to find out what this value is. The load
21547 offset is an offset which is added to the VMA (virtual memory address)
21548 of each of the file's sections.
21549 For instance, if the program
21550 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
21551 and bss at 0x12010170, in @value{GDBN}, type:
21554 (gdbslet) load prog 0x12010000
21555 Loading section .text, size 0xdb0 vma 0x12010000
21558 If the code is loaded at a different address then what the program was linked
21559 to, you may need to use the @code{section} and @code{add-symbol-file} commands
21560 to tell @value{GDBN} where to map the symbol table.
21562 @node Sparclet Execution
21563 @subsubsection Running and Debugging
21565 @cindex running and debugging Sparclet programs
21566 You can now begin debugging the task using @value{GDBN}'s execution control
21567 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
21568 manual for the list of commands.
21572 Breakpoint 1 at 0x12010000: file prog.c, line 3.
21574 Starting program: prog
21575 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
21576 3 char *symarg = 0;
21578 4 char *execarg = "hello!";
21583 @subsection Fujitsu Sparclite
21587 @kindex target sparclite
21588 @item target sparclite @var{dev}
21589 Fujitsu sparclite boards, used only for the purpose of loading.
21590 You must use an additional command to debug the program.
21591 For example: target remote @var{dev} using @value{GDBN} standard
21597 @subsection Zilog Z8000
21600 @cindex simulator, Z8000
21601 @cindex Zilog Z8000 simulator
21603 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
21606 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
21607 unsegmented variant of the Z8000 architecture) or the Z8001 (the
21608 segmented variant). The simulator recognizes which architecture is
21609 appropriate by inspecting the object code.
21612 @item target sim @var{args}
21614 @kindex target sim@r{, with Z8000}
21615 Debug programs on a simulated CPU. If the simulator supports setup
21616 options, specify them via @var{args}.
21620 After specifying this target, you can debug programs for the simulated
21621 CPU in the same style as programs for your host computer; use the
21622 @code{file} command to load a new program image, the @code{run} command
21623 to run your program, and so on.
21625 As well as making available all the usual machine registers
21626 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
21627 additional items of information as specially named registers:
21632 Counts clock-ticks in the simulator.
21635 Counts instructions run in the simulator.
21638 Execution time in 60ths of a second.
21642 You can refer to these values in @value{GDBN} expressions with the usual
21643 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
21644 conditional breakpoint that suspends only after at least 5000
21645 simulated clock ticks.
21648 @subsection Atmel AVR
21651 When configured for debugging the Atmel AVR, @value{GDBN} supports the
21652 following AVR-specific commands:
21655 @item info io_registers
21656 @kindex info io_registers@r{, AVR}
21657 @cindex I/O registers (Atmel AVR)
21658 This command displays information about the AVR I/O registers. For
21659 each register, @value{GDBN} prints its number and value.
21666 When configured for debugging CRIS, @value{GDBN} provides the
21667 following CRIS-specific commands:
21670 @item set cris-version @var{ver}
21671 @cindex CRIS version
21672 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
21673 The CRIS version affects register names and sizes. This command is useful in
21674 case autodetection of the CRIS version fails.
21676 @item show cris-version
21677 Show the current CRIS version.
21679 @item set cris-dwarf2-cfi
21680 @cindex DWARF-2 CFI and CRIS
21681 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
21682 Change to @samp{off} when using @code{gcc-cris} whose version is below
21685 @item show cris-dwarf2-cfi
21686 Show the current state of using DWARF-2 CFI.
21688 @item set cris-mode @var{mode}
21690 Set the current CRIS mode to @var{mode}. It should only be changed when
21691 debugging in guru mode, in which case it should be set to
21692 @samp{guru} (the default is @samp{normal}).
21694 @item show cris-mode
21695 Show the current CRIS mode.
21699 @subsection Renesas Super-H
21702 For the Renesas Super-H processor, @value{GDBN} provides these
21706 @item set sh calling-convention @var{convention}
21707 @kindex set sh calling-convention
21708 Set the calling-convention used when calling functions from @value{GDBN}.
21709 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
21710 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
21711 convention. If the DWARF-2 information of the called function specifies
21712 that the function follows the Renesas calling convention, the function
21713 is called using the Renesas calling convention. If the calling convention
21714 is set to @samp{renesas}, the Renesas calling convention is always used,
21715 regardless of the DWARF-2 information. This can be used to override the
21716 default of @samp{gcc} if debug information is missing, or the compiler
21717 does not emit the DWARF-2 calling convention entry for a function.
21719 @item show sh calling-convention
21720 @kindex show sh calling-convention
21721 Show the current calling convention setting.
21726 @node Architectures
21727 @section Architectures
21729 This section describes characteristics of architectures that affect
21730 all uses of @value{GDBN} with the architecture, both native and cross.
21737 * HPPA:: HP PA architecture
21738 * SPU:: Cell Broadband Engine SPU architecture
21744 @subsection AArch64
21745 @cindex AArch64 support
21747 When @value{GDBN} is debugging the AArch64 architecture, it provides the
21748 following special commands:
21751 @item set debug aarch64
21752 @kindex set debug aarch64
21753 This command determines whether AArch64 architecture-specific debugging
21754 messages are to be displayed.
21756 @item show debug aarch64
21757 Show whether AArch64 debugging messages are displayed.
21762 @subsection x86 Architecture-specific Issues
21765 @item set struct-convention @var{mode}
21766 @kindex set struct-convention
21767 @cindex struct return convention
21768 @cindex struct/union returned in registers
21769 Set the convention used by the inferior to return @code{struct}s and
21770 @code{union}s from functions to @var{mode}. Possible values of
21771 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
21772 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
21773 are returned on the stack, while @code{"reg"} means that a
21774 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
21775 be returned in a register.
21777 @item show struct-convention
21778 @kindex show struct-convention
21779 Show the current setting of the convention to return @code{struct}s
21783 @subsubsection Intel(R) @dfn{Memory Protection Extensions} (MPX).
21784 @cindex Intel(R) Memory Protection Extensions (MPX).
21786 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
21787 @footnote{The register named with capital letters represent the architecture
21788 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
21789 which are the lower bound and upper bound. Bounds are effective addresses or
21790 memory locations. The upper bounds are architecturally represented in 1's
21791 complement form. A bound having lower bound = 0, and upper bound = 0
21792 (1's complement of all bits set) will allow access to the entire address space.
21794 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
21795 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
21796 display the upper bound performing the complement of one operation on the
21797 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
21798 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
21799 can also be noted that the upper bounds are inclusive.
21801 As an example, assume that the register BND0 holds bounds for a pointer having
21802 access allowed for the range between 0x32 and 0x71. The values present on
21803 bnd0raw and bnd registers are presented as follows:
21806 bnd0raw = @{0x32, 0xffffffff8e@}
21807 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
21810 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
21811 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
21812 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
21813 Python, the display includes the memory size, in bits, accessible to
21819 See the following section.
21822 @subsection @acronym{MIPS}
21824 @cindex stack on Alpha
21825 @cindex stack on @acronym{MIPS}
21826 @cindex Alpha stack
21827 @cindex @acronym{MIPS} stack
21828 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
21829 sometimes requires @value{GDBN} to search backward in the object code to
21830 find the beginning of a function.
21832 @cindex response time, @acronym{MIPS} debugging
21833 To improve response time (especially for embedded applications, where
21834 @value{GDBN} may be restricted to a slow serial line for this search)
21835 you may want to limit the size of this search, using one of these
21839 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
21840 @item set heuristic-fence-post @var{limit}
21841 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
21842 search for the beginning of a function. A value of @var{0} (the
21843 default) means there is no limit. However, except for @var{0}, the
21844 larger the limit the more bytes @code{heuristic-fence-post} must search
21845 and therefore the longer it takes to run. You should only need to use
21846 this command when debugging a stripped executable.
21848 @item show heuristic-fence-post
21849 Display the current limit.
21853 These commands are available @emph{only} when @value{GDBN} is configured
21854 for debugging programs on Alpha or @acronym{MIPS} processors.
21856 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
21860 @item set mips abi @var{arg}
21861 @kindex set mips abi
21862 @cindex set ABI for @acronym{MIPS}
21863 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
21864 values of @var{arg} are:
21868 The default ABI associated with the current binary (this is the
21878 @item show mips abi
21879 @kindex show mips abi
21880 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
21882 @item set mips compression @var{arg}
21883 @kindex set mips compression
21884 @cindex code compression, @acronym{MIPS}
21885 Tell @value{GDBN} which @acronym{MIPS} compressed
21886 @acronym{ISA, Instruction Set Architecture} encoding is used by the
21887 inferior. @value{GDBN} uses this for code disassembly and other
21888 internal interpretation purposes. This setting is only referred to
21889 when no executable has been associated with the debugging session or
21890 the executable does not provide information about the encoding it uses.
21891 Otherwise this setting is automatically updated from information
21892 provided by the executable.
21894 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
21895 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
21896 executables containing @acronym{MIPS16} code frequently are not
21897 identified as such.
21899 This setting is ``sticky''; that is, it retains its value across
21900 debugging sessions until reset either explicitly with this command or
21901 implicitly from an executable.
21903 The compiler and/or assembler typically add symbol table annotations to
21904 identify functions compiled for the @acronym{MIPS16} or
21905 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
21906 are present, @value{GDBN} uses them in preference to the global
21907 compressed @acronym{ISA} encoding setting.
21909 @item show mips compression
21910 @kindex show mips compression
21911 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
21912 @value{GDBN} to debug the inferior.
21915 @itemx show mipsfpu
21916 @xref{MIPS Embedded, set mipsfpu}.
21918 @item set mips mask-address @var{arg}
21919 @kindex set mips mask-address
21920 @cindex @acronym{MIPS} addresses, masking
21921 This command determines whether the most-significant 32 bits of 64-bit
21922 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
21923 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
21924 setting, which lets @value{GDBN} determine the correct value.
21926 @item show mips mask-address
21927 @kindex show mips mask-address
21928 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
21931 @item set remote-mips64-transfers-32bit-regs
21932 @kindex set remote-mips64-transfers-32bit-regs
21933 This command controls compatibility with 64-bit @acronym{MIPS} targets that
21934 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
21935 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
21936 and 64 bits for other registers, set this option to @samp{on}.
21938 @item show remote-mips64-transfers-32bit-regs
21939 @kindex show remote-mips64-transfers-32bit-regs
21940 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
21942 @item set debug mips
21943 @kindex set debug mips
21944 This command turns on and off debugging messages for the @acronym{MIPS}-specific
21945 target code in @value{GDBN}.
21947 @item show debug mips
21948 @kindex show debug mips
21949 Show the current setting of @acronym{MIPS} debugging messages.
21955 @cindex HPPA support
21957 When @value{GDBN} is debugging the HP PA architecture, it provides the
21958 following special commands:
21961 @item set debug hppa
21962 @kindex set debug hppa
21963 This command determines whether HPPA architecture-specific debugging
21964 messages are to be displayed.
21966 @item show debug hppa
21967 Show whether HPPA debugging messages are displayed.
21969 @item maint print unwind @var{address}
21970 @kindex maint print unwind@r{, HPPA}
21971 This command displays the contents of the unwind table entry at the
21972 given @var{address}.
21978 @subsection Cell Broadband Engine SPU architecture
21979 @cindex Cell Broadband Engine
21982 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
21983 it provides the following special commands:
21986 @item info spu event
21988 Display SPU event facility status. Shows current event mask
21989 and pending event status.
21991 @item info spu signal
21992 Display SPU signal notification facility status. Shows pending
21993 signal-control word and signal notification mode of both signal
21994 notification channels.
21996 @item info spu mailbox
21997 Display SPU mailbox facility status. Shows all pending entries,
21998 in order of processing, in each of the SPU Write Outbound,
21999 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
22002 Display MFC DMA status. Shows all pending commands in the MFC
22003 DMA queue. For each entry, opcode, tag, class IDs, effective
22004 and local store addresses and transfer size are shown.
22006 @item info spu proxydma
22007 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
22008 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
22009 and local store addresses and transfer size are shown.
22013 When @value{GDBN} is debugging a combined PowerPC/SPU application
22014 on the Cell Broadband Engine, it provides in addition the following
22018 @item set spu stop-on-load @var{arg}
22020 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
22021 will give control to the user when a new SPE thread enters its @code{main}
22022 function. The default is @code{off}.
22024 @item show spu stop-on-load
22026 Show whether to stop for new SPE threads.
22028 @item set spu auto-flush-cache @var{arg}
22029 Set whether to automatically flush the software-managed cache. When set to
22030 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
22031 cache to be flushed whenever SPE execution stops. This provides a consistent
22032 view of PowerPC memory that is accessed via the cache. If an application
22033 does not use the software-managed cache, this option has no effect.
22035 @item show spu auto-flush-cache
22036 Show whether to automatically flush the software-managed cache.
22041 @subsection PowerPC
22042 @cindex PowerPC architecture
22044 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
22045 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
22046 numbers stored in the floating point registers. These values must be stored
22047 in two consecutive registers, always starting at an even register like
22048 @code{f0} or @code{f2}.
22050 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
22051 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
22052 @code{f2} and @code{f3} for @code{$dl1} and so on.
22054 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
22055 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
22058 @subsection Nios II
22059 @cindex Nios II architecture
22061 When @value{GDBN} is debugging the Nios II architecture,
22062 it provides the following special commands:
22066 @item set debug nios2
22067 @kindex set debug nios2
22068 This command turns on and off debugging messages for the Nios II
22069 target code in @value{GDBN}.
22071 @item show debug nios2
22072 @kindex show debug nios2
22073 Show the current setting of Nios II debugging messages.
22076 @node Controlling GDB
22077 @chapter Controlling @value{GDBN}
22079 You can alter the way @value{GDBN} interacts with you by using the
22080 @code{set} command. For commands controlling how @value{GDBN} displays
22081 data, see @ref{Print Settings, ,Print Settings}. Other settings are
22086 * Editing:: Command editing
22087 * Command History:: Command history
22088 * Screen Size:: Screen size
22089 * Numbers:: Numbers
22090 * ABI:: Configuring the current ABI
22091 * Auto-loading:: Automatically loading associated files
22092 * Messages/Warnings:: Optional warnings and messages
22093 * Debugging Output:: Optional messages about internal happenings
22094 * Other Misc Settings:: Other Miscellaneous Settings
22102 @value{GDBN} indicates its readiness to read a command by printing a string
22103 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
22104 can change the prompt string with the @code{set prompt} command. For
22105 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
22106 the prompt in one of the @value{GDBN} sessions so that you can always tell
22107 which one you are talking to.
22109 @emph{Note:} @code{set prompt} does not add a space for you after the
22110 prompt you set. This allows you to set a prompt which ends in a space
22111 or a prompt that does not.
22115 @item set prompt @var{newprompt}
22116 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
22118 @kindex show prompt
22120 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
22123 Versions of @value{GDBN} that ship with Python scripting enabled have
22124 prompt extensions. The commands for interacting with these extensions
22128 @kindex set extended-prompt
22129 @item set extended-prompt @var{prompt}
22130 Set an extended prompt that allows for substitutions.
22131 @xref{gdb.prompt}, for a list of escape sequences that can be used for
22132 substitution. Any escape sequences specified as part of the prompt
22133 string are replaced with the corresponding strings each time the prompt
22139 set extended-prompt Current working directory: \w (gdb)
22142 Note that when an extended-prompt is set, it takes control of the
22143 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
22145 @kindex show extended-prompt
22146 @item show extended-prompt
22147 Prints the extended prompt. Any escape sequences specified as part of
22148 the prompt string with @code{set extended-prompt}, are replaced with the
22149 corresponding strings each time the prompt is displayed.
22153 @section Command Editing
22155 @cindex command line editing
22157 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
22158 @sc{gnu} library provides consistent behavior for programs which provide a
22159 command line interface to the user. Advantages are @sc{gnu} Emacs-style
22160 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
22161 substitution, and a storage and recall of command history across
22162 debugging sessions.
22164 You may control the behavior of command line editing in @value{GDBN} with the
22165 command @code{set}.
22168 @kindex set editing
22171 @itemx set editing on
22172 Enable command line editing (enabled by default).
22174 @item set editing off
22175 Disable command line editing.
22177 @kindex show editing
22179 Show whether command line editing is enabled.
22182 @ifset SYSTEM_READLINE
22183 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
22185 @ifclear SYSTEM_READLINE
22186 @xref{Command Line Editing},
22188 for more details about the Readline
22189 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
22190 encouraged to read that chapter.
22192 @node Command History
22193 @section Command History
22194 @cindex command history
22196 @value{GDBN} can keep track of the commands you type during your
22197 debugging sessions, so that you can be certain of precisely what
22198 happened. Use these commands to manage the @value{GDBN} command
22201 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
22202 package, to provide the history facility.
22203 @ifset SYSTEM_READLINE
22204 @xref{Using History Interactively, , , history, GNU History Library},
22206 @ifclear SYSTEM_READLINE
22207 @xref{Using History Interactively},
22209 for the detailed description of the History library.
22211 To issue a command to @value{GDBN} without affecting certain aspects of
22212 the state which is seen by users, prefix it with @samp{server }
22213 (@pxref{Server Prefix}). This
22214 means that this command will not affect the command history, nor will it
22215 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
22216 pressed on a line by itself.
22218 @cindex @code{server}, command prefix
22219 The server prefix does not affect the recording of values into the value
22220 history; to print a value without recording it into the value history,
22221 use the @code{output} command instead of the @code{print} command.
22223 Here is the description of @value{GDBN} commands related to command
22227 @cindex history substitution
22228 @cindex history file
22229 @kindex set history filename
22230 @cindex @env{GDBHISTFILE}, environment variable
22231 @item set history filename @var{fname}
22232 Set the name of the @value{GDBN} command history file to @var{fname}.
22233 This is the file where @value{GDBN} reads an initial command history
22234 list, and where it writes the command history from this session when it
22235 exits. You can access this list through history expansion or through
22236 the history command editing characters listed below. This file defaults
22237 to the value of the environment variable @code{GDBHISTFILE}, or to
22238 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
22241 @cindex save command history
22242 @kindex set history save
22243 @item set history save
22244 @itemx set history save on
22245 Record command history in a file, whose name may be specified with the
22246 @code{set history filename} command. By default, this option is disabled.
22248 @item set history save off
22249 Stop recording command history in a file.
22251 @cindex history size
22252 @kindex set history size
22253 @cindex @env{HISTSIZE}, environment variable
22254 @item set history size @var{size}
22255 @itemx set history size unlimited
22256 Set the number of commands which @value{GDBN} keeps in its history list.
22257 This defaults to the value of the environment variable
22258 @code{HISTSIZE}, or to 256 if this variable is not set. If @var{size}
22259 is @code{unlimited}, the number of commands @value{GDBN} keeps in the
22260 history list is unlimited.
22263 History expansion assigns special meaning to the character @kbd{!}.
22264 @ifset SYSTEM_READLINE
22265 @xref{Event Designators, , , history, GNU History Library},
22267 @ifclear SYSTEM_READLINE
22268 @xref{Event Designators},
22272 @cindex history expansion, turn on/off
22273 Since @kbd{!} is also the logical not operator in C, history expansion
22274 is off by default. If you decide to enable history expansion with the
22275 @code{set history expansion on} command, you may sometimes need to
22276 follow @kbd{!} (when it is used as logical not, in an expression) with
22277 a space or a tab to prevent it from being expanded. The readline
22278 history facilities do not attempt substitution on the strings
22279 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
22281 The commands to control history expansion are:
22284 @item set history expansion on
22285 @itemx set history expansion
22286 @kindex set history expansion
22287 Enable history expansion. History expansion is off by default.
22289 @item set history expansion off
22290 Disable history expansion.
22293 @kindex show history
22295 @itemx show history filename
22296 @itemx show history save
22297 @itemx show history size
22298 @itemx show history expansion
22299 These commands display the state of the @value{GDBN} history parameters.
22300 @code{show history} by itself displays all four states.
22305 @kindex show commands
22306 @cindex show last commands
22307 @cindex display command history
22308 @item show commands
22309 Display the last ten commands in the command history.
22311 @item show commands @var{n}
22312 Print ten commands centered on command number @var{n}.
22314 @item show commands +
22315 Print ten commands just after the commands last printed.
22319 @section Screen Size
22320 @cindex size of screen
22321 @cindex screen size
22324 @cindex pauses in output
22326 Certain commands to @value{GDBN} may produce large amounts of
22327 information output to the screen. To help you read all of it,
22328 @value{GDBN} pauses and asks you for input at the end of each page of
22329 output. Type @key{RET} when you want to continue the output, or @kbd{q}
22330 to discard the remaining output. Also, the screen width setting
22331 determines when to wrap lines of output. Depending on what is being
22332 printed, @value{GDBN} tries to break the line at a readable place,
22333 rather than simply letting it overflow onto the following line.
22335 Normally @value{GDBN} knows the size of the screen from the terminal
22336 driver software. For example, on Unix @value{GDBN} uses the termcap data base
22337 together with the value of the @code{TERM} environment variable and the
22338 @code{stty rows} and @code{stty cols} settings. If this is not correct,
22339 you can override it with the @code{set height} and @code{set
22346 @kindex show height
22347 @item set height @var{lpp}
22348 @itemx set height unlimited
22350 @itemx set width @var{cpl}
22351 @itemx set width unlimited
22353 These @code{set} commands specify a screen height of @var{lpp} lines and
22354 a screen width of @var{cpl} characters. The associated @code{show}
22355 commands display the current settings.
22357 If you specify a height of either @code{unlimited} or zero lines,
22358 @value{GDBN} does not pause during output no matter how long the
22359 output is. This is useful if output is to a file or to an editor
22362 Likewise, you can specify @samp{set width unlimited} or @samp{set
22363 width 0} to prevent @value{GDBN} from wrapping its output.
22365 @item set pagination on
22366 @itemx set pagination off
22367 @kindex set pagination
22368 Turn the output pagination on or off; the default is on. Turning
22369 pagination off is the alternative to @code{set height unlimited}. Note that
22370 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
22371 Options, -batch}) also automatically disables pagination.
22373 @item show pagination
22374 @kindex show pagination
22375 Show the current pagination mode.
22380 @cindex number representation
22381 @cindex entering numbers
22383 You can always enter numbers in octal, decimal, or hexadecimal in
22384 @value{GDBN} by the usual conventions: octal numbers begin with
22385 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
22386 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
22387 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
22388 10; likewise, the default display for numbers---when no particular
22389 format is specified---is base 10. You can change the default base for
22390 both input and output with the commands described below.
22393 @kindex set input-radix
22394 @item set input-radix @var{base}
22395 Set the default base for numeric input. Supported choices
22396 for @var{base} are decimal 8, 10, or 16. The base must itself be
22397 specified either unambiguously or using the current input radix; for
22401 set input-radix 012
22402 set input-radix 10.
22403 set input-radix 0xa
22407 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
22408 leaves the input radix unchanged, no matter what it was, since
22409 @samp{10}, being without any leading or trailing signs of its base, is
22410 interpreted in the current radix. Thus, if the current radix is 16,
22411 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
22414 @kindex set output-radix
22415 @item set output-radix @var{base}
22416 Set the default base for numeric display. Supported choices
22417 for @var{base} are decimal 8, 10, or 16. The base must itself be
22418 specified either unambiguously or using the current input radix.
22420 @kindex show input-radix
22421 @item show input-radix
22422 Display the current default base for numeric input.
22424 @kindex show output-radix
22425 @item show output-radix
22426 Display the current default base for numeric display.
22428 @item set radix @r{[}@var{base}@r{]}
22432 These commands set and show the default base for both input and output
22433 of numbers. @code{set radix} sets the radix of input and output to
22434 the same base; without an argument, it resets the radix back to its
22435 default value of 10.
22440 @section Configuring the Current ABI
22442 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
22443 application automatically. However, sometimes you need to override its
22444 conclusions. Use these commands to manage @value{GDBN}'s view of the
22450 @cindex Newlib OS ABI and its influence on the longjmp handling
22452 One @value{GDBN} configuration can debug binaries for multiple operating
22453 system targets, either via remote debugging or native emulation.
22454 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
22455 but you can override its conclusion using the @code{set osabi} command.
22456 One example where this is useful is in debugging of binaries which use
22457 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
22458 not have the same identifying marks that the standard C library for your
22461 When @value{GDBN} is debugging the AArch64 architecture, it provides a
22462 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
22463 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
22464 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
22468 Show the OS ABI currently in use.
22471 With no argument, show the list of registered available OS ABI's.
22473 @item set osabi @var{abi}
22474 Set the current OS ABI to @var{abi}.
22477 @cindex float promotion
22479 Generally, the way that an argument of type @code{float} is passed to a
22480 function depends on whether the function is prototyped. For a prototyped
22481 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
22482 according to the architecture's convention for @code{float}. For unprototyped
22483 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
22484 @code{double} and then passed.
22486 Unfortunately, some forms of debug information do not reliably indicate whether
22487 a function is prototyped. If @value{GDBN} calls a function that is not marked
22488 as prototyped, it consults @kbd{set coerce-float-to-double}.
22491 @kindex set coerce-float-to-double
22492 @item set coerce-float-to-double
22493 @itemx set coerce-float-to-double on
22494 Arguments of type @code{float} will be promoted to @code{double} when passed
22495 to an unprototyped function. This is the default setting.
22497 @item set coerce-float-to-double off
22498 Arguments of type @code{float} will be passed directly to unprototyped
22501 @kindex show coerce-float-to-double
22502 @item show coerce-float-to-double
22503 Show the current setting of promoting @code{float} to @code{double}.
22507 @kindex show cp-abi
22508 @value{GDBN} needs to know the ABI used for your program's C@t{++}
22509 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
22510 used to build your application. @value{GDBN} only fully supports
22511 programs with a single C@t{++} ABI; if your program contains code using
22512 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
22513 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
22514 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
22515 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
22516 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
22517 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
22522 Show the C@t{++} ABI currently in use.
22525 With no argument, show the list of supported C@t{++} ABI's.
22527 @item set cp-abi @var{abi}
22528 @itemx set cp-abi auto
22529 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
22533 @section Automatically loading associated files
22534 @cindex auto-loading
22536 @value{GDBN} sometimes reads files with commands and settings automatically,
22537 without being explicitly told so by the user. We call this feature
22538 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
22539 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
22540 results or introduce security risks (e.g., if the file comes from untrusted
22544 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
22545 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
22547 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
22548 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
22551 There are various kinds of files @value{GDBN} can automatically load.
22552 In addition to these files, @value{GDBN} supports auto-loading code written
22553 in various extension languages. @xref{Auto-loading extensions}.
22555 Note that loading of these associated files (including the local @file{.gdbinit}
22556 file) requires accordingly configured @code{auto-load safe-path}
22557 (@pxref{Auto-loading safe path}).
22559 For these reasons, @value{GDBN} includes commands and options to let you
22560 control when to auto-load files and which files should be auto-loaded.
22563 @anchor{set auto-load off}
22564 @kindex set auto-load off
22565 @item set auto-load off
22566 Globally disable loading of all auto-loaded files.
22567 You may want to use this command with the @samp{-iex} option
22568 (@pxref{Option -init-eval-command}) such as:
22570 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
22573 Be aware that system init file (@pxref{System-wide configuration})
22574 and init files from your home directory (@pxref{Home Directory Init File})
22575 still get read (as they come from generally trusted directories).
22576 To prevent @value{GDBN} from auto-loading even those init files, use the
22577 @option{-nx} option (@pxref{Mode Options}), in addition to
22578 @code{set auto-load no}.
22580 @anchor{show auto-load}
22581 @kindex show auto-load
22582 @item show auto-load
22583 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
22587 (gdb) show auto-load
22588 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
22589 libthread-db: Auto-loading of inferior specific libthread_db is on.
22590 local-gdbinit: Auto-loading of .gdbinit script from current directory
22592 python-scripts: Auto-loading of Python scripts is on.
22593 safe-path: List of directories from which it is safe to auto-load files
22594 is $debugdir:$datadir/auto-load.
22595 scripts-directory: List of directories from which to load auto-loaded scripts
22596 is $debugdir:$datadir/auto-load.
22599 @anchor{info auto-load}
22600 @kindex info auto-load
22601 @item info auto-load
22602 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
22606 (gdb) info auto-load
22609 Yes /home/user/gdb/gdb-gdb.gdb
22610 libthread-db: No auto-loaded libthread-db.
22611 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
22615 Yes /home/user/gdb/gdb-gdb.py
22619 These are @value{GDBN} control commands for the auto-loading:
22621 @multitable @columnfractions .5 .5
22622 @item @xref{set auto-load off}.
22623 @tab Disable auto-loading globally.
22624 @item @xref{show auto-load}.
22625 @tab Show setting of all kinds of files.
22626 @item @xref{info auto-load}.
22627 @tab Show state of all kinds of files.
22628 @item @xref{set auto-load gdb-scripts}.
22629 @tab Control for @value{GDBN} command scripts.
22630 @item @xref{show auto-load gdb-scripts}.
22631 @tab Show setting of @value{GDBN} command scripts.
22632 @item @xref{info auto-load gdb-scripts}.
22633 @tab Show state of @value{GDBN} command scripts.
22634 @item @xref{set auto-load python-scripts}.
22635 @tab Control for @value{GDBN} Python scripts.
22636 @item @xref{show auto-load python-scripts}.
22637 @tab Show setting of @value{GDBN} Python scripts.
22638 @item @xref{info auto-load python-scripts}.
22639 @tab Show state of @value{GDBN} Python scripts.
22640 @item @xref{set auto-load guile-scripts}.
22641 @tab Control for @value{GDBN} Guile scripts.
22642 @item @xref{show auto-load guile-scripts}.
22643 @tab Show setting of @value{GDBN} Guile scripts.
22644 @item @xref{info auto-load guile-scripts}.
22645 @tab Show state of @value{GDBN} Guile scripts.
22646 @item @xref{set auto-load scripts-directory}.
22647 @tab Control for @value{GDBN} auto-loaded scripts location.
22648 @item @xref{show auto-load scripts-directory}.
22649 @tab Show @value{GDBN} auto-loaded scripts location.
22650 @item @xref{add-auto-load-scripts-directory}.
22651 @tab Add directory for auto-loaded scripts location list.
22652 @item @xref{set auto-load local-gdbinit}.
22653 @tab Control for init file in the current directory.
22654 @item @xref{show auto-load local-gdbinit}.
22655 @tab Show setting of init file in the current directory.
22656 @item @xref{info auto-load local-gdbinit}.
22657 @tab Show state of init file in the current directory.
22658 @item @xref{set auto-load libthread-db}.
22659 @tab Control for thread debugging library.
22660 @item @xref{show auto-load libthread-db}.
22661 @tab Show setting of thread debugging library.
22662 @item @xref{info auto-load libthread-db}.
22663 @tab Show state of thread debugging library.
22664 @item @xref{set auto-load safe-path}.
22665 @tab Control directories trusted for automatic loading.
22666 @item @xref{show auto-load safe-path}.
22667 @tab Show directories trusted for automatic loading.
22668 @item @xref{add-auto-load-safe-path}.
22669 @tab Add directory trusted for automatic loading.
22672 @node Init File in the Current Directory
22673 @subsection Automatically loading init file in the current directory
22674 @cindex auto-loading init file in the current directory
22676 By default, @value{GDBN} reads and executes the canned sequences of commands
22677 from init file (if any) in the current working directory,
22678 see @ref{Init File in the Current Directory during Startup}.
22680 Note that loading of this local @file{.gdbinit} file also requires accordingly
22681 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22684 @anchor{set auto-load local-gdbinit}
22685 @kindex set auto-load local-gdbinit
22686 @item set auto-load local-gdbinit [on|off]
22687 Enable or disable the auto-loading of canned sequences of commands
22688 (@pxref{Sequences}) found in init file in the current directory.
22690 @anchor{show auto-load local-gdbinit}
22691 @kindex show auto-load local-gdbinit
22692 @item show auto-load local-gdbinit
22693 Show whether auto-loading of canned sequences of commands from init file in the
22694 current directory is enabled or disabled.
22696 @anchor{info auto-load local-gdbinit}
22697 @kindex info auto-load local-gdbinit
22698 @item info auto-load local-gdbinit
22699 Print whether canned sequences of commands from init file in the
22700 current directory have been auto-loaded.
22703 @node libthread_db.so.1 file
22704 @subsection Automatically loading thread debugging library
22705 @cindex auto-loading libthread_db.so.1
22707 This feature is currently present only on @sc{gnu}/Linux native hosts.
22709 @value{GDBN} reads in some cases thread debugging library from places specific
22710 to the inferior (@pxref{set libthread-db-search-path}).
22712 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
22713 without checking this @samp{set auto-load libthread-db} switch as system
22714 libraries have to be trusted in general. In all other cases of
22715 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
22716 auto-load libthread-db} is enabled before trying to open such thread debugging
22719 Note that loading of this debugging library also requires accordingly configured
22720 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22723 @anchor{set auto-load libthread-db}
22724 @kindex set auto-load libthread-db
22725 @item set auto-load libthread-db [on|off]
22726 Enable or disable the auto-loading of inferior specific thread debugging library.
22728 @anchor{show auto-load libthread-db}
22729 @kindex show auto-load libthread-db
22730 @item show auto-load libthread-db
22731 Show whether auto-loading of inferior specific thread debugging library is
22732 enabled or disabled.
22734 @anchor{info auto-load libthread-db}
22735 @kindex info auto-load libthread-db
22736 @item info auto-load libthread-db
22737 Print the list of all loaded inferior specific thread debugging libraries and
22738 for each such library print list of inferior @var{pid}s using it.
22741 @node Auto-loading safe path
22742 @subsection Security restriction for auto-loading
22743 @cindex auto-loading safe-path
22745 As the files of inferior can come from untrusted source (such as submitted by
22746 an application user) @value{GDBN} does not always load any files automatically.
22747 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
22748 directories trusted for loading files not explicitly requested by user.
22749 Each directory can also be a shell wildcard pattern.
22751 If the path is not set properly you will see a warning and the file will not
22756 Reading symbols from /home/user/gdb/gdb...done.
22757 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
22758 declined by your `auto-load safe-path' set
22759 to "$debugdir:$datadir/auto-load".
22760 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
22761 declined by your `auto-load safe-path' set
22762 to "$debugdir:$datadir/auto-load".
22766 To instruct @value{GDBN} to go ahead and use the init files anyway,
22767 invoke @value{GDBN} like this:
22770 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
22773 The list of trusted directories is controlled by the following commands:
22776 @anchor{set auto-load safe-path}
22777 @kindex set auto-load safe-path
22778 @item set auto-load safe-path @r{[}@var{directories}@r{]}
22779 Set the list of directories (and their subdirectories) trusted for automatic
22780 loading and execution of scripts. You can also enter a specific trusted file.
22781 Each directory can also be a shell wildcard pattern; wildcards do not match
22782 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
22783 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
22784 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
22785 its default value as specified during @value{GDBN} compilation.
22787 The list of directories uses path separator (@samp{:} on GNU and Unix
22788 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
22789 to the @env{PATH} environment variable.
22791 @anchor{show auto-load safe-path}
22792 @kindex show auto-load safe-path
22793 @item show auto-load safe-path
22794 Show the list of directories trusted for automatic loading and execution of
22797 @anchor{add-auto-load-safe-path}
22798 @kindex add-auto-load-safe-path
22799 @item add-auto-load-safe-path
22800 Add an entry (or list of entries) to the list of directories trusted for
22801 automatic loading and execution of scripts. Multiple entries may be delimited
22802 by the host platform path separator in use.
22805 This variable defaults to what @code{--with-auto-load-dir} has been configured
22806 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
22807 substitution applies the same as for @ref{set auto-load scripts-directory}.
22808 The default @code{set auto-load safe-path} value can be also overriden by
22809 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
22811 Setting this variable to @file{/} disables this security protection,
22812 corresponding @value{GDBN} configuration option is
22813 @option{--without-auto-load-safe-path}.
22814 This variable is supposed to be set to the system directories writable by the
22815 system superuser only. Users can add their source directories in init files in
22816 their home directories (@pxref{Home Directory Init File}). See also deprecated
22817 init file in the current directory
22818 (@pxref{Init File in the Current Directory during Startup}).
22820 To force @value{GDBN} to load the files it declined to load in the previous
22821 example, you could use one of the following ways:
22824 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
22825 Specify this trusted directory (or a file) as additional component of the list.
22826 You have to specify also any existing directories displayed by
22827 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
22829 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
22830 Specify this directory as in the previous case but just for a single
22831 @value{GDBN} session.
22833 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
22834 Disable auto-loading safety for a single @value{GDBN} session.
22835 This assumes all the files you debug during this @value{GDBN} session will come
22836 from trusted sources.
22838 @item @kbd{./configure --without-auto-load-safe-path}
22839 During compilation of @value{GDBN} you may disable any auto-loading safety.
22840 This assumes all the files you will ever debug with this @value{GDBN} come from
22844 On the other hand you can also explicitly forbid automatic files loading which
22845 also suppresses any such warning messages:
22848 @item @kbd{gdb -iex "set auto-load no" @dots{}}
22849 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
22851 @item @file{~/.gdbinit}: @samp{set auto-load no}
22852 Disable auto-loading globally for the user
22853 (@pxref{Home Directory Init File}). While it is improbable, you could also
22854 use system init file instead (@pxref{System-wide configuration}).
22857 This setting applies to the file names as entered by user. If no entry matches
22858 @value{GDBN} tries as a last resort to also resolve all the file names into
22859 their canonical form (typically resolving symbolic links) and compare the
22860 entries again. @value{GDBN} already canonicalizes most of the filenames on its
22861 own before starting the comparison so a canonical form of directories is
22862 recommended to be entered.
22864 @node Auto-loading verbose mode
22865 @subsection Displaying files tried for auto-load
22866 @cindex auto-loading verbose mode
22868 For better visibility of all the file locations where you can place scripts to
22869 be auto-loaded with inferior --- or to protect yourself against accidental
22870 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
22871 all the files attempted to be loaded. Both existing and non-existing files may
22874 For example the list of directories from which it is safe to auto-load files
22875 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
22876 may not be too obvious while setting it up.
22879 (gdb) set debug auto-load on
22880 (gdb) file ~/src/t/true
22881 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
22882 for objfile "/tmp/true".
22883 auto-load: Updating directories of "/usr:/opt".
22884 auto-load: Using directory "/usr".
22885 auto-load: Using directory "/opt".
22886 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
22887 by your `auto-load safe-path' set to "/usr:/opt".
22891 @anchor{set debug auto-load}
22892 @kindex set debug auto-load
22893 @item set debug auto-load [on|off]
22894 Set whether to print the filenames attempted to be auto-loaded.
22896 @anchor{show debug auto-load}
22897 @kindex show debug auto-load
22898 @item show debug auto-load
22899 Show whether printing of the filenames attempted to be auto-loaded is turned
22903 @node Messages/Warnings
22904 @section Optional Warnings and Messages
22906 @cindex verbose operation
22907 @cindex optional warnings
22908 By default, @value{GDBN} is silent about its inner workings. If you are
22909 running on a slow machine, you may want to use the @code{set verbose}
22910 command. This makes @value{GDBN} tell you when it does a lengthy
22911 internal operation, so you will not think it has crashed.
22913 Currently, the messages controlled by @code{set verbose} are those
22914 which announce that the symbol table for a source file is being read;
22915 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
22918 @kindex set verbose
22919 @item set verbose on
22920 Enables @value{GDBN} output of certain informational messages.
22922 @item set verbose off
22923 Disables @value{GDBN} output of certain informational messages.
22925 @kindex show verbose
22927 Displays whether @code{set verbose} is on or off.
22930 By default, if @value{GDBN} encounters bugs in the symbol table of an
22931 object file, it is silent; but if you are debugging a compiler, you may
22932 find this information useful (@pxref{Symbol Errors, ,Errors Reading
22937 @kindex set complaints
22938 @item set complaints @var{limit}
22939 Permits @value{GDBN} to output @var{limit} complaints about each type of
22940 unusual symbols before becoming silent about the problem. Set
22941 @var{limit} to zero to suppress all complaints; set it to a large number
22942 to prevent complaints from being suppressed.
22944 @kindex show complaints
22945 @item show complaints
22946 Displays how many symbol complaints @value{GDBN} is permitted to produce.
22950 @anchor{confirmation requests}
22951 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
22952 lot of stupid questions to confirm certain commands. For example, if
22953 you try to run a program which is already running:
22957 The program being debugged has been started already.
22958 Start it from the beginning? (y or n)
22961 If you are willing to unflinchingly face the consequences of your own
22962 commands, you can disable this ``feature'':
22966 @kindex set confirm
22968 @cindex confirmation
22969 @cindex stupid questions
22970 @item set confirm off
22971 Disables confirmation requests. Note that running @value{GDBN} with
22972 the @option{--batch} option (@pxref{Mode Options, -batch}) also
22973 automatically disables confirmation requests.
22975 @item set confirm on
22976 Enables confirmation requests (the default).
22978 @kindex show confirm
22980 Displays state of confirmation requests.
22984 @cindex command tracing
22985 If you need to debug user-defined commands or sourced files you may find it
22986 useful to enable @dfn{command tracing}. In this mode each command will be
22987 printed as it is executed, prefixed with one or more @samp{+} symbols, the
22988 quantity denoting the call depth of each command.
22991 @kindex set trace-commands
22992 @cindex command scripts, debugging
22993 @item set trace-commands on
22994 Enable command tracing.
22995 @item set trace-commands off
22996 Disable command tracing.
22997 @item show trace-commands
22998 Display the current state of command tracing.
23001 @node Debugging Output
23002 @section Optional Messages about Internal Happenings
23003 @cindex optional debugging messages
23005 @value{GDBN} has commands that enable optional debugging messages from
23006 various @value{GDBN} subsystems; normally these commands are of
23007 interest to @value{GDBN} maintainers, or when reporting a bug. This
23008 section documents those commands.
23011 @kindex set exec-done-display
23012 @item set exec-done-display
23013 Turns on or off the notification of asynchronous commands'
23014 completion. When on, @value{GDBN} will print a message when an
23015 asynchronous command finishes its execution. The default is off.
23016 @kindex show exec-done-display
23017 @item show exec-done-display
23018 Displays the current setting of asynchronous command completion
23021 @cindex ARM AArch64
23022 @item set debug aarch64
23023 Turns on or off display of debugging messages related to ARM AArch64.
23024 The default is off.
23026 @item show debug aarch64
23027 Displays the current state of displaying debugging messages related to
23029 @cindex gdbarch debugging info
23030 @cindex architecture debugging info
23031 @item set debug arch
23032 Turns on or off display of gdbarch debugging info. The default is off
23033 @item show debug arch
23034 Displays the current state of displaying gdbarch debugging info.
23035 @item set debug aix-solib
23036 @cindex AIX shared library debugging
23037 Control display of debugging messages from the AIX shared library
23038 support module. The default is off.
23039 @item show debug aix-thread
23040 Show the current state of displaying AIX shared library debugging messages.
23041 @item set debug aix-thread
23042 @cindex AIX threads
23043 Display debugging messages about inner workings of the AIX thread
23045 @item show debug aix-thread
23046 Show the current state of AIX thread debugging info display.
23047 @item set debug check-physname
23049 Check the results of the ``physname'' computation. When reading DWARF
23050 debugging information for C@t{++}, @value{GDBN} attempts to compute
23051 each entity's name. @value{GDBN} can do this computation in two
23052 different ways, depending on exactly what information is present.
23053 When enabled, this setting causes @value{GDBN} to compute the names
23054 both ways and display any discrepancies.
23055 @item show debug check-physname
23056 Show the current state of ``physname'' checking.
23057 @item set debug coff-pe-read
23058 @cindex COFF/PE exported symbols
23059 Control display of debugging messages related to reading of COFF/PE
23060 exported symbols. The default is off.
23061 @item show debug coff-pe-read
23062 Displays the current state of displaying debugging messages related to
23063 reading of COFF/PE exported symbols.
23064 @item set debug dwarf2-die
23065 @cindex DWARF2 DIEs
23066 Dump DWARF2 DIEs after they are read in.
23067 The value is the number of nesting levels to print.
23068 A value of zero turns off the display.
23069 @item show debug dwarf2-die
23070 Show the current state of DWARF2 DIE debugging.
23071 @item set debug dwarf2-read
23072 @cindex DWARF2 Reading
23073 Turns on or off display of debugging messages related to reading
23074 DWARF debug info. The default is 0 (off).
23075 A value of 1 provides basic information.
23076 A value greater than 1 provides more verbose information.
23077 @item show debug dwarf2-read
23078 Show the current state of DWARF2 reader debugging.
23079 @item set debug displaced
23080 @cindex displaced stepping debugging info
23081 Turns on or off display of @value{GDBN} debugging info for the
23082 displaced stepping support. The default is off.
23083 @item show debug displaced
23084 Displays the current state of displaying @value{GDBN} debugging info
23085 related to displaced stepping.
23086 @item set debug event
23087 @cindex event debugging info
23088 Turns on or off display of @value{GDBN} event debugging info. The
23090 @item show debug event
23091 Displays the current state of displaying @value{GDBN} event debugging
23093 @item set debug expression
23094 @cindex expression debugging info
23095 Turns on or off display of debugging info about @value{GDBN}
23096 expression parsing. The default is off.
23097 @item show debug expression
23098 Displays the current state of displaying debugging info about
23099 @value{GDBN} expression parsing.
23100 @item set debug frame
23101 @cindex frame debugging info
23102 Turns on or off display of @value{GDBN} frame debugging info. The
23104 @item show debug frame
23105 Displays the current state of displaying @value{GDBN} frame debugging
23107 @item set debug gnu-nat
23108 @cindex @sc{gnu}/Hurd debug messages
23109 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
23110 @item show debug gnu-nat
23111 Show the current state of @sc{gnu}/Hurd debugging messages.
23112 @item set debug infrun
23113 @cindex inferior debugging info
23114 Turns on or off display of @value{GDBN} debugging info for running the inferior.
23115 The default is off. @file{infrun.c} contains GDB's runtime state machine used
23116 for implementing operations such as single-stepping the inferior.
23117 @item show debug infrun
23118 Displays the current state of @value{GDBN} inferior debugging.
23119 @item set debug jit
23120 @cindex just-in-time compilation, debugging messages
23121 Turns on or off debugging messages from JIT debug support.
23122 @item show debug jit
23123 Displays the current state of @value{GDBN} JIT debugging.
23124 @item set debug lin-lwp
23125 @cindex @sc{gnu}/Linux LWP debug messages
23126 @cindex Linux lightweight processes
23127 Turns on or off debugging messages from the Linux LWP debug support.
23128 @item show debug lin-lwp
23129 Show the current state of Linux LWP debugging messages.
23130 @item set debug mach-o
23131 @cindex Mach-O symbols processing
23132 Control display of debugging messages related to Mach-O symbols
23133 processing. The default is off.
23134 @item show debug mach-o
23135 Displays the current state of displaying debugging messages related to
23136 reading of COFF/PE exported symbols.
23137 @item set debug notification
23138 @cindex remote async notification debugging info
23139 Turns on or off debugging messages about remote async notification.
23140 The default is off.
23141 @item show debug notification
23142 Displays the current state of remote async notification debugging messages.
23143 @item set debug observer
23144 @cindex observer debugging info
23145 Turns on or off display of @value{GDBN} observer debugging. This
23146 includes info such as the notification of observable events.
23147 @item show debug observer
23148 Displays the current state of observer debugging.
23149 @item set debug overload
23150 @cindex C@t{++} overload debugging info
23151 Turns on or off display of @value{GDBN} C@t{++} overload debugging
23152 info. This includes info such as ranking of functions, etc. The default
23154 @item show debug overload
23155 Displays the current state of displaying @value{GDBN} C@t{++} overload
23157 @cindex expression parser, debugging info
23158 @cindex debug expression parser
23159 @item set debug parser
23160 Turns on or off the display of expression parser debugging output.
23161 Internally, this sets the @code{yydebug} variable in the expression
23162 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
23163 details. The default is off.
23164 @item show debug parser
23165 Show the current state of expression parser debugging.
23166 @cindex packets, reporting on stdout
23167 @cindex serial connections, debugging
23168 @cindex debug remote protocol
23169 @cindex remote protocol debugging
23170 @cindex display remote packets
23171 @item set debug remote
23172 Turns on or off display of reports on all packets sent back and forth across
23173 the serial line to the remote machine. The info is printed on the
23174 @value{GDBN} standard output stream. The default is off.
23175 @item show debug remote
23176 Displays the state of display of remote packets.
23177 @item set debug serial
23178 Turns on or off display of @value{GDBN} serial debugging info. The
23180 @item show debug serial
23181 Displays the current state of displaying @value{GDBN} serial debugging
23183 @item set debug solib-frv
23184 @cindex FR-V shared-library debugging
23185 Turns on or off debugging messages for FR-V shared-library code.
23186 @item show debug solib-frv
23187 Display the current state of FR-V shared-library code debugging
23189 @item set debug symbol-lookup
23190 @cindex symbol lookup
23191 Turns on or off display of debugging messages related to symbol lookup.
23192 The default is 0 (off).
23193 A value of 1 provides basic information.
23194 A value greater than 1 provides more verbose information.
23195 @item show debug symbol-lookup
23196 Show the current state of symbol lookup debugging messages.
23197 @item set debug symfile
23198 @cindex symbol file functions
23199 Turns on or off display of debugging messages related to symbol file functions.
23200 The default is off. @xref{Files}.
23201 @item show debug symfile
23202 Show the current state of symbol file debugging messages.
23203 @item set debug symtab-create
23204 @cindex symbol table creation
23205 Turns on or off display of debugging messages related to symbol table creation.
23206 The default is 0 (off).
23207 A value of 1 provides basic information.
23208 A value greater than 1 provides more verbose information.
23209 @item show debug symtab-create
23210 Show the current state of symbol table creation debugging.
23211 @item set debug target
23212 @cindex target debugging info
23213 Turns on or off display of @value{GDBN} target debugging info. This info
23214 includes what is going on at the target level of GDB, as it happens. The
23215 default is 0. Set it to 1 to track events, and to 2 to also track the
23216 value of large memory transfers.
23217 @item show debug target
23218 Displays the current state of displaying @value{GDBN} target debugging
23220 @item set debug timestamp
23221 @cindex timestampping debugging info
23222 Turns on or off display of timestamps with @value{GDBN} debugging info.
23223 When enabled, seconds and microseconds are displayed before each debugging
23225 @item show debug timestamp
23226 Displays the current state of displaying timestamps with @value{GDBN}
23228 @item set debug varobj
23229 @cindex variable object debugging info
23230 Turns on or off display of @value{GDBN} variable object debugging
23231 info. The default is off.
23232 @item show debug varobj
23233 Displays the current state of displaying @value{GDBN} variable object
23235 @item set debug xml
23236 @cindex XML parser debugging
23237 Turns on or off debugging messages for built-in XML parsers.
23238 @item show debug xml
23239 Displays the current state of XML debugging messages.
23242 @node Other Misc Settings
23243 @section Other Miscellaneous Settings
23244 @cindex miscellaneous settings
23247 @kindex set interactive-mode
23248 @item set interactive-mode
23249 If @code{on}, forces @value{GDBN} to assume that GDB was started
23250 in a terminal. In practice, this means that @value{GDBN} should wait
23251 for the user to answer queries generated by commands entered at
23252 the command prompt. If @code{off}, forces @value{GDBN} to operate
23253 in the opposite mode, and it uses the default answers to all queries.
23254 If @code{auto} (the default), @value{GDBN} tries to determine whether
23255 its standard input is a terminal, and works in interactive-mode if it
23256 is, non-interactively otherwise.
23258 In the vast majority of cases, the debugger should be able to guess
23259 correctly which mode should be used. But this setting can be useful
23260 in certain specific cases, such as running a MinGW @value{GDBN}
23261 inside a cygwin window.
23263 @kindex show interactive-mode
23264 @item show interactive-mode
23265 Displays whether the debugger is operating in interactive mode or not.
23268 @node Extending GDB
23269 @chapter Extending @value{GDBN}
23270 @cindex extending GDB
23272 @value{GDBN} provides several mechanisms for extension.
23273 @value{GDBN} also provides the ability to automatically load
23274 extensions when it reads a file for debugging. This allows the
23275 user to automatically customize @value{GDBN} for the program
23279 * Sequences:: Canned Sequences of @value{GDBN} Commands
23280 * Python:: Extending @value{GDBN} using Python
23281 * Guile:: Extending @value{GDBN} using Guile
23282 * Auto-loading extensions:: Automatically loading extensions
23283 * Multiple Extension Languages:: Working with multiple extension languages
23284 * Aliases:: Creating new spellings of existing commands
23287 To facilitate the use of extension languages, @value{GDBN} is capable
23288 of evaluating the contents of a file. When doing so, @value{GDBN}
23289 can recognize which extension language is being used by looking at
23290 the filename extension. Files with an unrecognized filename extension
23291 are always treated as a @value{GDBN} Command Files.
23292 @xref{Command Files,, Command files}.
23294 You can control how @value{GDBN} evaluates these files with the following
23298 @kindex set script-extension
23299 @kindex show script-extension
23300 @item set script-extension off
23301 All scripts are always evaluated as @value{GDBN} Command Files.
23303 @item set script-extension soft
23304 The debugger determines the scripting language based on filename
23305 extension. If this scripting language is supported, @value{GDBN}
23306 evaluates the script using that language. Otherwise, it evaluates
23307 the file as a @value{GDBN} Command File.
23309 @item set script-extension strict
23310 The debugger determines the scripting language based on filename
23311 extension, and evaluates the script using that language. If the
23312 language is not supported, then the evaluation fails.
23314 @item show script-extension
23315 Display the current value of the @code{script-extension} option.
23320 @section Canned Sequences of Commands
23322 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
23323 Command Lists}), @value{GDBN} provides two ways to store sequences of
23324 commands for execution as a unit: user-defined commands and command
23328 * Define:: How to define your own commands
23329 * Hooks:: Hooks for user-defined commands
23330 * Command Files:: How to write scripts of commands to be stored in a file
23331 * Output:: Commands for controlled output
23332 * Auto-loading sequences:: Controlling auto-loaded command files
23336 @subsection User-defined Commands
23338 @cindex user-defined command
23339 @cindex arguments, to user-defined commands
23340 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
23341 which you assign a new name as a command. This is done with the
23342 @code{define} command. User commands may accept up to 10 arguments
23343 separated by whitespace. Arguments are accessed within the user command
23344 via @code{$arg0@dots{}$arg9}. A trivial example:
23348 print $arg0 + $arg1 + $arg2
23353 To execute the command use:
23360 This defines the command @code{adder}, which prints the sum of
23361 its three arguments. Note the arguments are text substitutions, so they may
23362 reference variables, use complex expressions, or even perform inferior
23365 @cindex argument count in user-defined commands
23366 @cindex how many arguments (user-defined commands)
23367 In addition, @code{$argc} may be used to find out how many arguments have
23368 been passed. This expands to a number in the range 0@dots{}10.
23373 print $arg0 + $arg1
23376 print $arg0 + $arg1 + $arg2
23384 @item define @var{commandname}
23385 Define a command named @var{commandname}. If there is already a command
23386 by that name, you are asked to confirm that you want to redefine it.
23387 The argument @var{commandname} may be a bare command name consisting of letters,
23388 numbers, dashes, and underscores. It may also start with any predefined
23389 prefix command. For example, @samp{define target my-target} creates
23390 a user-defined @samp{target my-target} command.
23392 The definition of the command is made up of other @value{GDBN} command lines,
23393 which are given following the @code{define} command. The end of these
23394 commands is marked by a line containing @code{end}.
23397 @kindex end@r{ (user-defined commands)}
23398 @item document @var{commandname}
23399 Document the user-defined command @var{commandname}, so that it can be
23400 accessed by @code{help}. The command @var{commandname} must already be
23401 defined. This command reads lines of documentation just as @code{define}
23402 reads the lines of the command definition, ending with @code{end}.
23403 After the @code{document} command is finished, @code{help} on command
23404 @var{commandname} displays the documentation you have written.
23406 You may use the @code{document} command again to change the
23407 documentation of a command. Redefining the command with @code{define}
23408 does not change the documentation.
23410 @kindex dont-repeat
23411 @cindex don't repeat command
23413 Used inside a user-defined command, this tells @value{GDBN} that this
23414 command should not be repeated when the user hits @key{RET}
23415 (@pxref{Command Syntax, repeat last command}).
23417 @kindex help user-defined
23418 @item help user-defined
23419 List all user-defined commands and all python commands defined in class
23420 COMAND_USER. The first line of the documentation or docstring is
23425 @itemx show user @var{commandname}
23426 Display the @value{GDBN} commands used to define @var{commandname} (but
23427 not its documentation). If no @var{commandname} is given, display the
23428 definitions for all user-defined commands.
23429 This does not work for user-defined python commands.
23431 @cindex infinite recursion in user-defined commands
23432 @kindex show max-user-call-depth
23433 @kindex set max-user-call-depth
23434 @item show max-user-call-depth
23435 @itemx set max-user-call-depth
23436 The value of @code{max-user-call-depth} controls how many recursion
23437 levels are allowed in user-defined commands before @value{GDBN} suspects an
23438 infinite recursion and aborts the command.
23439 This does not apply to user-defined python commands.
23442 In addition to the above commands, user-defined commands frequently
23443 use control flow commands, described in @ref{Command Files}.
23445 When user-defined commands are executed, the
23446 commands of the definition are not printed. An error in any command
23447 stops execution of the user-defined command.
23449 If used interactively, commands that would ask for confirmation proceed
23450 without asking when used inside a user-defined command. Many @value{GDBN}
23451 commands that normally print messages to say what they are doing omit the
23452 messages when used in a user-defined command.
23455 @subsection User-defined Command Hooks
23456 @cindex command hooks
23457 @cindex hooks, for commands
23458 @cindex hooks, pre-command
23461 You may define @dfn{hooks}, which are a special kind of user-defined
23462 command. Whenever you run the command @samp{foo}, if the user-defined
23463 command @samp{hook-foo} exists, it is executed (with no arguments)
23464 before that command.
23466 @cindex hooks, post-command
23468 A hook may also be defined which is run after the command you executed.
23469 Whenever you run the command @samp{foo}, if the user-defined command
23470 @samp{hookpost-foo} exists, it is executed (with no arguments) after
23471 that command. Post-execution hooks may exist simultaneously with
23472 pre-execution hooks, for the same command.
23474 It is valid for a hook to call the command which it hooks. If this
23475 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
23477 @c It would be nice if hookpost could be passed a parameter indicating
23478 @c if the command it hooks executed properly or not. FIXME!
23480 @kindex stop@r{, a pseudo-command}
23481 In addition, a pseudo-command, @samp{stop} exists. Defining
23482 (@samp{hook-stop}) makes the associated commands execute every time
23483 execution stops in your program: before breakpoint commands are run,
23484 displays are printed, or the stack frame is printed.
23486 For example, to ignore @code{SIGALRM} signals while
23487 single-stepping, but treat them normally during normal execution,
23492 handle SIGALRM nopass
23496 handle SIGALRM pass
23499 define hook-continue
23500 handle SIGALRM pass
23504 As a further example, to hook at the beginning and end of the @code{echo}
23505 command, and to add extra text to the beginning and end of the message,
23513 define hookpost-echo
23517 (@value{GDBP}) echo Hello World
23518 <<<---Hello World--->>>
23523 You can define a hook for any single-word command in @value{GDBN}, but
23524 not for command aliases; you should define a hook for the basic command
23525 name, e.g.@: @code{backtrace} rather than @code{bt}.
23526 @c FIXME! So how does Joe User discover whether a command is an alias
23528 You can hook a multi-word command by adding @code{hook-} or
23529 @code{hookpost-} to the last word of the command, e.g.@:
23530 @samp{define target hook-remote} to add a hook to @samp{target remote}.
23532 If an error occurs during the execution of your hook, execution of
23533 @value{GDBN} commands stops and @value{GDBN} issues a prompt
23534 (before the command that you actually typed had a chance to run).
23536 If you try to define a hook which does not match any known command, you
23537 get a warning from the @code{define} command.
23539 @node Command Files
23540 @subsection Command Files
23542 @cindex command files
23543 @cindex scripting commands
23544 A command file for @value{GDBN} is a text file made of lines that are
23545 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
23546 also be included. An empty line in a command file does nothing; it
23547 does not mean to repeat the last command, as it would from the
23550 You can request the execution of a command file with the @code{source}
23551 command. Note that the @code{source} command is also used to evaluate
23552 scripts that are not Command Files. The exact behavior can be configured
23553 using the @code{script-extension} setting.
23554 @xref{Extending GDB,, Extending GDB}.
23558 @cindex execute commands from a file
23559 @item source [-s] [-v] @var{filename}
23560 Execute the command file @var{filename}.
23563 The lines in a command file are generally executed sequentially,
23564 unless the order of execution is changed by one of the
23565 @emph{flow-control commands} described below. The commands are not
23566 printed as they are executed. An error in any command terminates
23567 execution of the command file and control is returned to the console.
23569 @value{GDBN} first searches for @var{filename} in the current directory.
23570 If the file is not found there, and @var{filename} does not specify a
23571 directory, then @value{GDBN} also looks for the file on the source search path
23572 (specified with the @samp{directory} command);
23573 except that @file{$cdir} is not searched because the compilation directory
23574 is not relevant to scripts.
23576 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
23577 on the search path even if @var{filename} specifies a directory.
23578 The search is done by appending @var{filename} to each element of the
23579 search path. So, for example, if @var{filename} is @file{mylib/myscript}
23580 and the search path contains @file{/home/user} then @value{GDBN} will
23581 look for the script @file{/home/user/mylib/myscript}.
23582 The search is also done if @var{filename} is an absolute path.
23583 For example, if @var{filename} is @file{/tmp/myscript} and
23584 the search path contains @file{/home/user} then @value{GDBN} will
23585 look for the script @file{/home/user/tmp/myscript}.
23586 For DOS-like systems, if @var{filename} contains a drive specification,
23587 it is stripped before concatenation. For example, if @var{filename} is
23588 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
23589 will look for the script @file{c:/tmp/myscript}.
23591 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
23592 each command as it is executed. The option must be given before
23593 @var{filename}, and is interpreted as part of the filename anywhere else.
23595 Commands that would ask for confirmation if used interactively proceed
23596 without asking when used in a command file. Many @value{GDBN} commands that
23597 normally print messages to say what they are doing omit the messages
23598 when called from command files.
23600 @value{GDBN} also accepts command input from standard input. In this
23601 mode, normal output goes to standard output and error output goes to
23602 standard error. Errors in a command file supplied on standard input do
23603 not terminate execution of the command file---execution continues with
23607 gdb < cmds > log 2>&1
23610 (The syntax above will vary depending on the shell used.) This example
23611 will execute commands from the file @file{cmds}. All output and errors
23612 would be directed to @file{log}.
23614 Since commands stored on command files tend to be more general than
23615 commands typed interactively, they frequently need to deal with
23616 complicated situations, such as different or unexpected values of
23617 variables and symbols, changes in how the program being debugged is
23618 built, etc. @value{GDBN} provides a set of flow-control commands to
23619 deal with these complexities. Using these commands, you can write
23620 complex scripts that loop over data structures, execute commands
23621 conditionally, etc.
23628 This command allows to include in your script conditionally executed
23629 commands. The @code{if} command takes a single argument, which is an
23630 expression to evaluate. It is followed by a series of commands that
23631 are executed only if the expression is true (its value is nonzero).
23632 There can then optionally be an @code{else} line, followed by a series
23633 of commands that are only executed if the expression was false. The
23634 end of the list is marked by a line containing @code{end}.
23638 This command allows to write loops. Its syntax is similar to
23639 @code{if}: the command takes a single argument, which is an expression
23640 to evaluate, and must be followed by the commands to execute, one per
23641 line, terminated by an @code{end}. These commands are called the
23642 @dfn{body} of the loop. The commands in the body of @code{while} are
23643 executed repeatedly as long as the expression evaluates to true.
23647 This command exits the @code{while} loop in whose body it is included.
23648 Execution of the script continues after that @code{while}s @code{end}
23651 @kindex loop_continue
23652 @item loop_continue
23653 This command skips the execution of the rest of the body of commands
23654 in the @code{while} loop in whose body it is included. Execution
23655 branches to the beginning of the @code{while} loop, where it evaluates
23656 the controlling expression.
23658 @kindex end@r{ (if/else/while commands)}
23660 Terminate the block of commands that are the body of @code{if},
23661 @code{else}, or @code{while} flow-control commands.
23666 @subsection Commands for Controlled Output
23668 During the execution of a command file or a user-defined command, normal
23669 @value{GDBN} output is suppressed; the only output that appears is what is
23670 explicitly printed by the commands in the definition. This section
23671 describes three commands useful for generating exactly the output you
23676 @item echo @var{text}
23677 @c I do not consider backslash-space a standard C escape sequence
23678 @c because it is not in ANSI.
23679 Print @var{text}. Nonprinting characters can be included in
23680 @var{text} using C escape sequences, such as @samp{\n} to print a
23681 newline. @strong{No newline is printed unless you specify one.}
23682 In addition to the standard C escape sequences, a backslash followed
23683 by a space stands for a space. This is useful for displaying a
23684 string with spaces at the beginning or the end, since leading and
23685 trailing spaces are otherwise trimmed from all arguments.
23686 To print @samp{@w{ }and foo =@w{ }}, use the command
23687 @samp{echo \@w{ }and foo = \@w{ }}.
23689 A backslash at the end of @var{text} can be used, as in C, to continue
23690 the command onto subsequent lines. For example,
23693 echo This is some text\n\
23694 which is continued\n\
23695 onto several lines.\n
23698 produces the same output as
23701 echo This is some text\n
23702 echo which is continued\n
23703 echo onto several lines.\n
23707 @item output @var{expression}
23708 Print the value of @var{expression} and nothing but that value: no
23709 newlines, no @samp{$@var{nn} = }. The value is not entered in the
23710 value history either. @xref{Expressions, ,Expressions}, for more information
23713 @item output/@var{fmt} @var{expression}
23714 Print the value of @var{expression} in format @var{fmt}. You can use
23715 the same formats as for @code{print}. @xref{Output Formats,,Output
23716 Formats}, for more information.
23719 @item printf @var{template}, @var{expressions}@dots{}
23720 Print the values of one or more @var{expressions} under the control of
23721 the string @var{template}. To print several values, make
23722 @var{expressions} be a comma-separated list of individual expressions,
23723 which may be either numbers or pointers. Their values are printed as
23724 specified by @var{template}, exactly as a C program would do by
23725 executing the code below:
23728 printf (@var{template}, @var{expressions}@dots{});
23731 As in @code{C} @code{printf}, ordinary characters in @var{template}
23732 are printed verbatim, while @dfn{conversion specification} introduced
23733 by the @samp{%} character cause subsequent @var{expressions} to be
23734 evaluated, their values converted and formatted according to type and
23735 style information encoded in the conversion specifications, and then
23738 For example, you can print two values in hex like this:
23741 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
23744 @code{printf} supports all the standard @code{C} conversion
23745 specifications, including the flags and modifiers between the @samp{%}
23746 character and the conversion letter, with the following exceptions:
23750 The argument-ordering modifiers, such as @samp{2$}, are not supported.
23753 The modifier @samp{*} is not supported for specifying precision or
23757 The @samp{'} flag (for separation of digits into groups according to
23758 @code{LC_NUMERIC'}) is not supported.
23761 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
23765 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
23768 The conversion letters @samp{a} and @samp{A} are not supported.
23772 Note that the @samp{ll} type modifier is supported only if the
23773 underlying @code{C} implementation used to build @value{GDBN} supports
23774 the @code{long long int} type, and the @samp{L} type modifier is
23775 supported only if @code{long double} type is available.
23777 As in @code{C}, @code{printf} supports simple backslash-escape
23778 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
23779 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
23780 single character. Octal and hexadecimal escape sequences are not
23783 Additionally, @code{printf} supports conversion specifications for DFP
23784 (@dfn{Decimal Floating Point}) types using the following length modifiers
23785 together with a floating point specifier.
23790 @samp{H} for printing @code{Decimal32} types.
23793 @samp{D} for printing @code{Decimal64} types.
23796 @samp{DD} for printing @code{Decimal128} types.
23799 If the underlying @code{C} implementation used to build @value{GDBN} has
23800 support for the three length modifiers for DFP types, other modifiers
23801 such as width and precision will also be available for @value{GDBN} to use.
23803 In case there is no such @code{C} support, no additional modifiers will be
23804 available and the value will be printed in the standard way.
23806 Here's an example of printing DFP types using the above conversion letters:
23808 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
23812 @item eval @var{template}, @var{expressions}@dots{}
23813 Convert the values of one or more @var{expressions} under the control of
23814 the string @var{template} to a command line, and call it.
23818 @node Auto-loading sequences
23819 @subsection Controlling auto-loading native @value{GDBN} scripts
23820 @cindex native script auto-loading
23822 When a new object file is read (for example, due to the @code{file}
23823 command, or because the inferior has loaded a shared library),
23824 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
23825 @xref{Auto-loading extensions}.
23827 Auto-loading can be enabled or disabled,
23828 and the list of auto-loaded scripts can be printed.
23831 @anchor{set auto-load gdb-scripts}
23832 @kindex set auto-load gdb-scripts
23833 @item set auto-load gdb-scripts [on|off]
23834 Enable or disable the auto-loading of canned sequences of commands scripts.
23836 @anchor{show auto-load gdb-scripts}
23837 @kindex show auto-load gdb-scripts
23838 @item show auto-load gdb-scripts
23839 Show whether auto-loading of canned sequences of commands scripts is enabled or
23842 @anchor{info auto-load gdb-scripts}
23843 @kindex info auto-load gdb-scripts
23844 @cindex print list of auto-loaded canned sequences of commands scripts
23845 @item info auto-load gdb-scripts [@var{regexp}]
23846 Print the list of all canned sequences of commands scripts that @value{GDBN}
23850 If @var{regexp} is supplied only canned sequences of commands scripts with
23851 matching names are printed.
23853 @c Python docs live in a separate file.
23854 @include python.texi
23856 @c Guile docs live in a separate file.
23857 @include guile.texi
23859 @node Auto-loading extensions
23860 @section Auto-loading extensions
23861 @cindex auto-loading extensions
23863 @value{GDBN} provides two mechanisms for automatically loading extensions
23864 when a new object file is read (for example, due to the @code{file}
23865 command, or because the inferior has loaded a shared library):
23866 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
23867 section of modern file formats like ELF.
23870 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
23871 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
23872 * Which flavor to choose?::
23875 The auto-loading feature is useful for supplying application-specific
23876 debugging commands and features.
23878 Auto-loading can be enabled or disabled,
23879 and the list of auto-loaded scripts can be printed.
23880 See the @samp{auto-loading} section of each extension language
23881 for more information.
23882 For @value{GDBN} command files see @ref{Auto-loading sequences}.
23883 For Python files see @ref{Python Auto-loading}.
23885 Note that loading of this script file also requires accordingly configured
23886 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23888 @node objfile-gdbdotext file
23889 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
23890 @cindex @file{@var{objfile}-gdb.gdb}
23891 @cindex @file{@var{objfile}-gdb.py}
23892 @cindex @file{@var{objfile}-gdb.scm}
23894 When a new object file is read, @value{GDBN} looks for a file named
23895 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
23896 where @var{objfile} is the object file's name and
23897 where @var{ext} is the file extension for the extension language:
23900 @item @file{@var{objfile}-gdb.gdb}
23901 GDB's own command language
23902 @item @file{@var{objfile}-gdb.py}
23904 @item @file{@var{objfile}-gdb.scm}
23908 @var{script-name} is formed by ensuring that the file name of @var{objfile}
23909 is absolute, following all symlinks, and resolving @code{.} and @code{..}
23910 components, and appending the @file{-gdb.@var{ext}} suffix.
23911 If this file exists and is readable, @value{GDBN} will evaluate it as a
23912 script in the specified extension language.
23914 If this file does not exist, then @value{GDBN} will look for
23915 @var{script-name} file in all of the directories as specified below.
23917 Note that loading of these files requires an accordingly configured
23918 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23920 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
23921 scripts normally according to its @file{.exe} filename. But if no scripts are
23922 found @value{GDBN} also tries script filenames matching the object file without
23923 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
23924 is attempted on any platform. This makes the script filenames compatible
23925 between Unix and MS-Windows hosts.
23928 @anchor{set auto-load scripts-directory}
23929 @kindex set auto-load scripts-directory
23930 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
23931 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
23932 may be delimited by the host platform path separator in use
23933 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
23935 Each entry here needs to be covered also by the security setting
23936 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
23938 @anchor{with-auto-load-dir}
23939 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
23940 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
23941 configuration option @option{--with-auto-load-dir}.
23943 Any reference to @file{$debugdir} will get replaced by
23944 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
23945 reference to @file{$datadir} will get replaced by @var{data-directory} which is
23946 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
23947 @file{$datadir} must be placed as a directory component --- either alone or
23948 delimited by @file{/} or @file{\} directory separators, depending on the host
23951 The list of directories uses path separator (@samp{:} on GNU and Unix
23952 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
23953 to the @env{PATH} environment variable.
23955 @anchor{show auto-load scripts-directory}
23956 @kindex show auto-load scripts-directory
23957 @item show auto-load scripts-directory
23958 Show @value{GDBN} auto-loaded scripts location.
23960 @anchor{add-auto-load-scripts-directory}
23961 @kindex add-auto-load-scripts-directory
23962 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
23963 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
23964 Multiple entries may be delimited by the host platform path separator in use.
23967 @value{GDBN} does not track which files it has already auto-loaded this way.
23968 @value{GDBN} will load the associated script every time the corresponding
23969 @var{objfile} is opened.
23970 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
23971 is evaluated more than once.
23973 @node dotdebug_gdb_scripts section
23974 @subsection The @code{.debug_gdb_scripts} section
23975 @cindex @code{.debug_gdb_scripts} section
23977 For systems using file formats like ELF and COFF,
23978 when @value{GDBN} loads a new object file
23979 it will look for a special section named @code{.debug_gdb_scripts}.
23980 If this section exists, its contents is a list of NUL-terminated names
23981 of scripts to load. Each entry begins with a non-NULL prefix byte that
23982 specifies the kind of entry, typically the extension language.
23984 @value{GDBN} will look for each specified script file first in the
23985 current directory and then along the source search path
23986 (@pxref{Source Path, ,Specifying Source Directories}),
23987 except that @file{$cdir} is not searched, since the compilation
23988 directory is not relevant to scripts.
23990 Entries can be placed in section @code{.debug_gdb_scripts} with,
23991 for example, this GCC macro for Python scripts.
23994 /* Note: The "MS" section flags are to remove duplicates. */
23995 #define DEFINE_GDB_PY_SCRIPT(script_name) \
23997 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
23998 .byte 1 /* Python */\n\
23999 .asciz \"" script_name "\"\n\
24005 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
24006 Then one can reference the macro in a header or source file like this:
24009 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
24012 The script name may include directories if desired.
24014 Note that loading of this script file also requires accordingly configured
24015 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24017 If the macro invocation is put in a header, any application or library
24018 using this header will get a reference to the specified script,
24019 and with the use of @code{"MS"} attributes on the section, the linker
24020 will remove duplicates.
24022 @node Which flavor to choose?
24023 @subsection Which flavor to choose?
24025 Given the multiple ways of auto-loading extensions, it might not always
24026 be clear which one to choose. This section provides some guidance.
24029 Benefits of the @file{-gdb.@var{ext}} way:
24033 Can be used with file formats that don't support multiple sections.
24036 Ease of finding scripts for public libraries.
24038 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
24039 in the source search path.
24040 For publicly installed libraries, e.g., @file{libstdc++}, there typically
24041 isn't a source directory in which to find the script.
24044 Doesn't require source code additions.
24048 Benefits of the @code{.debug_gdb_scripts} way:
24052 Works with static linking.
24054 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
24055 trigger their loading. When an application is statically linked the only
24056 objfile available is the executable, and it is cumbersome to attach all the
24057 scripts from all the input libraries to the executable's
24058 @file{-gdb.@var{ext}} script.
24061 Works with classes that are entirely inlined.
24063 Some classes can be entirely inlined, and thus there may not be an associated
24064 shared library to attach a @file{-gdb.@var{ext}} script to.
24067 Scripts needn't be copied out of the source tree.
24069 In some circumstances, apps can be built out of large collections of internal
24070 libraries, and the build infrastructure necessary to install the
24071 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
24072 cumbersome. It may be easier to specify the scripts in the
24073 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
24074 top of the source tree to the source search path.
24077 @node Multiple Extension Languages
24078 @section Multiple Extension Languages
24080 The Guile and Python extension languages do not share any state,
24081 and generally do not interfere with each other.
24082 There are some things to be aware of, however.
24084 @subsection Python comes first
24086 Python was @value{GDBN}'s first extension language, and to avoid breaking
24087 existing behaviour Python comes first. This is generally solved by the
24088 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
24089 extension languages, and when it makes a call to an extension language,
24090 (say to pretty-print a value), it tries each in turn until an extension
24091 language indicates it has performed the request (e.g., has returned the
24092 pretty-printed form of a value).
24093 This extends to errors while performing such requests: If an error happens
24094 while, for example, trying to pretty-print an object then the error is
24095 reported and any following extension languages are not tried.
24098 @section Creating new spellings of existing commands
24099 @cindex aliases for commands
24101 It is often useful to define alternate spellings of existing commands.
24102 For example, if a new @value{GDBN} command defined in Python has
24103 a long name to type, it is handy to have an abbreviated version of it
24104 that involves less typing.
24106 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
24107 of the @samp{step} command even though it is otherwise an ambiguous
24108 abbreviation of other commands like @samp{set} and @samp{show}.
24110 Aliases are also used to provide shortened or more common versions
24111 of multi-word commands. For example, @value{GDBN} provides the
24112 @samp{tty} alias of the @samp{set inferior-tty} command.
24114 You can define a new alias with the @samp{alias} command.
24119 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
24123 @var{ALIAS} specifies the name of the new alias.
24124 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
24127 @var{COMMAND} specifies the name of an existing command
24128 that is being aliased.
24130 The @samp{-a} option specifies that the new alias is an abbreviation
24131 of the command. Abbreviations are not shown in command
24132 lists displayed by the @samp{help} command.
24134 The @samp{--} option specifies the end of options,
24135 and is useful when @var{ALIAS} begins with a dash.
24137 Here is a simple example showing how to make an abbreviation
24138 of a command so that there is less to type.
24139 Suppose you were tired of typing @samp{disas}, the current
24140 shortest unambiguous abbreviation of the @samp{disassemble} command
24141 and you wanted an even shorter version named @samp{di}.
24142 The following will accomplish this.
24145 (gdb) alias -a di = disas
24148 Note that aliases are different from user-defined commands.
24149 With a user-defined command, you also need to write documentation
24150 for it with the @samp{document} command.
24151 An alias automatically picks up the documentation of the existing command.
24153 Here is an example where we make @samp{elms} an abbreviation of
24154 @samp{elements} in the @samp{set print elements} command.
24155 This is to show that you can make an abbreviation of any part
24159 (gdb) alias -a set print elms = set print elements
24160 (gdb) alias -a show print elms = show print elements
24161 (gdb) set p elms 20
24163 Limit on string chars or array elements to print is 200.
24166 Note that if you are defining an alias of a @samp{set} command,
24167 and you want to have an alias for the corresponding @samp{show}
24168 command, then you need to define the latter separately.
24170 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
24171 @var{ALIAS}, just as they are normally.
24174 (gdb) alias -a set pr elms = set p ele
24177 Finally, here is an example showing the creation of a one word
24178 alias for a more complex command.
24179 This creates alias @samp{spe} of the command @samp{set print elements}.
24182 (gdb) alias spe = set print elements
24187 @chapter Command Interpreters
24188 @cindex command interpreters
24190 @value{GDBN} supports multiple command interpreters, and some command
24191 infrastructure to allow users or user interface writers to switch
24192 between interpreters or run commands in other interpreters.
24194 @value{GDBN} currently supports two command interpreters, the console
24195 interpreter (sometimes called the command-line interpreter or @sc{cli})
24196 and the machine interface interpreter (or @sc{gdb/mi}). This manual
24197 describes both of these interfaces in great detail.
24199 By default, @value{GDBN} will start with the console interpreter.
24200 However, the user may choose to start @value{GDBN} with another
24201 interpreter by specifying the @option{-i} or @option{--interpreter}
24202 startup options. Defined interpreters include:
24206 @cindex console interpreter
24207 The traditional console or command-line interpreter. This is the most often
24208 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
24209 @value{GDBN} will use this interpreter.
24212 @cindex mi interpreter
24213 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
24214 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
24215 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
24219 @cindex mi2 interpreter
24220 The current @sc{gdb/mi} interface.
24223 @cindex mi1 interpreter
24224 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
24228 @cindex invoke another interpreter
24229 The interpreter being used by @value{GDBN} may not be dynamically
24230 switched at runtime. Although possible, this could lead to a very
24231 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
24232 enters the command "interpreter-set console" in a console view,
24233 @value{GDBN} would switch to using the console interpreter, rendering
24234 the IDE inoperable!
24236 @kindex interpreter-exec
24237 Although you may only choose a single interpreter at startup, you may execute
24238 commands in any interpreter from the current interpreter using the appropriate
24239 command. If you are running the console interpreter, simply use the
24240 @code{interpreter-exec} command:
24243 interpreter-exec mi "-data-list-register-names"
24246 @sc{gdb/mi} has a similar command, although it is only available in versions of
24247 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
24250 @chapter @value{GDBN} Text User Interface
24252 @cindex Text User Interface
24255 * TUI Overview:: TUI overview
24256 * TUI Keys:: TUI key bindings
24257 * TUI Single Key Mode:: TUI single key mode
24258 * TUI Commands:: TUI-specific commands
24259 * TUI Configuration:: TUI configuration variables
24262 The @value{GDBN} Text User Interface (TUI) is a terminal
24263 interface which uses the @code{curses} library to show the source
24264 file, the assembly output, the program registers and @value{GDBN}
24265 commands in separate text windows. The TUI mode is supported only
24266 on platforms where a suitable version of the @code{curses} library
24269 The TUI mode is enabled by default when you invoke @value{GDBN} as
24270 @samp{@value{GDBP} -tui}.
24271 You can also switch in and out of TUI mode while @value{GDBN} runs by
24272 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
24273 @xref{TUI Keys, ,TUI Key Bindings}.
24276 @section TUI Overview
24278 In TUI mode, @value{GDBN} can display several text windows:
24282 This window is the @value{GDBN} command window with the @value{GDBN}
24283 prompt and the @value{GDBN} output. The @value{GDBN} input is still
24284 managed using readline.
24287 The source window shows the source file of the program. The current
24288 line and active breakpoints are displayed in this window.
24291 The assembly window shows the disassembly output of the program.
24294 This window shows the processor registers. Registers are highlighted
24295 when their values change.
24298 The source and assembly windows show the current program position
24299 by highlighting the current line and marking it with a @samp{>} marker.
24300 Breakpoints are indicated with two markers. The first marker
24301 indicates the breakpoint type:
24305 Breakpoint which was hit at least once.
24308 Breakpoint which was never hit.
24311 Hardware breakpoint which was hit at least once.
24314 Hardware breakpoint which was never hit.
24317 The second marker indicates whether the breakpoint is enabled or not:
24321 Breakpoint is enabled.
24324 Breakpoint is disabled.
24327 The source, assembly and register windows are updated when the current
24328 thread changes, when the frame changes, or when the program counter
24331 These windows are not all visible at the same time. The command
24332 window is always visible. The others can be arranged in several
24343 source and assembly,
24346 source and registers, or
24349 assembly and registers.
24352 A status line above the command window shows the following information:
24356 Indicates the current @value{GDBN} target.
24357 (@pxref{Targets, ,Specifying a Debugging Target}).
24360 Gives the current process or thread number.
24361 When no process is being debugged, this field is set to @code{No process}.
24364 Gives the current function name for the selected frame.
24365 The name is demangled if demangling is turned on (@pxref{Print Settings}).
24366 When there is no symbol corresponding to the current program counter,
24367 the string @code{??} is displayed.
24370 Indicates the current line number for the selected frame.
24371 When the current line number is not known, the string @code{??} is displayed.
24374 Indicates the current program counter address.
24378 @section TUI Key Bindings
24379 @cindex TUI key bindings
24381 The TUI installs several key bindings in the readline keymaps
24382 @ifset SYSTEM_READLINE
24383 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
24385 @ifclear SYSTEM_READLINE
24386 (@pxref{Command Line Editing}).
24388 The following key bindings are installed for both TUI mode and the
24389 @value{GDBN} standard mode.
24398 Enter or leave the TUI mode. When leaving the TUI mode,
24399 the curses window management stops and @value{GDBN} operates using
24400 its standard mode, writing on the terminal directly. When reentering
24401 the TUI mode, control is given back to the curses windows.
24402 The screen is then refreshed.
24406 Use a TUI layout with only one window. The layout will
24407 either be @samp{source} or @samp{assembly}. When the TUI mode
24408 is not active, it will switch to the TUI mode.
24410 Think of this key binding as the Emacs @kbd{C-x 1} binding.
24414 Use a TUI layout with at least two windows. When the current
24415 layout already has two windows, the next layout with two windows is used.
24416 When a new layout is chosen, one window will always be common to the
24417 previous layout and the new one.
24419 Think of it as the Emacs @kbd{C-x 2} binding.
24423 Change the active window. The TUI associates several key bindings
24424 (like scrolling and arrow keys) with the active window. This command
24425 gives the focus to the next TUI window.
24427 Think of it as the Emacs @kbd{C-x o} binding.
24431 Switch in and out of the TUI SingleKey mode that binds single
24432 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
24435 The following key bindings only work in the TUI mode:
24440 Scroll the active window one page up.
24444 Scroll the active window one page down.
24448 Scroll the active window one line up.
24452 Scroll the active window one line down.
24456 Scroll the active window one column left.
24460 Scroll the active window one column right.
24464 Refresh the screen.
24467 Because the arrow keys scroll the active window in the TUI mode, they
24468 are not available for their normal use by readline unless the command
24469 window has the focus. When another window is active, you must use
24470 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
24471 and @kbd{C-f} to control the command window.
24473 @node TUI Single Key Mode
24474 @section TUI Single Key Mode
24475 @cindex TUI single key mode
24477 The TUI also provides a @dfn{SingleKey} mode, which binds several
24478 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
24479 switch into this mode, where the following key bindings are used:
24482 @kindex c @r{(SingleKey TUI key)}
24486 @kindex d @r{(SingleKey TUI key)}
24490 @kindex f @r{(SingleKey TUI key)}
24494 @kindex n @r{(SingleKey TUI key)}
24498 @kindex q @r{(SingleKey TUI key)}
24500 exit the SingleKey mode.
24502 @kindex r @r{(SingleKey TUI key)}
24506 @kindex s @r{(SingleKey TUI key)}
24510 @kindex u @r{(SingleKey TUI key)}
24514 @kindex v @r{(SingleKey TUI key)}
24518 @kindex w @r{(SingleKey TUI key)}
24523 Other keys temporarily switch to the @value{GDBN} command prompt.
24524 The key that was pressed is inserted in the editing buffer so that
24525 it is possible to type most @value{GDBN} commands without interaction
24526 with the TUI SingleKey mode. Once the command is entered the TUI
24527 SingleKey mode is restored. The only way to permanently leave
24528 this mode is by typing @kbd{q} or @kbd{C-x s}.
24532 @section TUI-specific Commands
24533 @cindex TUI commands
24535 The TUI has specific commands to control the text windows.
24536 These commands are always available, even when @value{GDBN} is not in
24537 the TUI mode. When @value{GDBN} is in the standard mode, most
24538 of these commands will automatically switch to the TUI mode.
24540 Note that if @value{GDBN}'s @code{stdout} is not connected to a
24541 terminal, or @value{GDBN} has been started with the machine interface
24542 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
24543 these commands will fail with an error, because it would not be
24544 possible or desirable to enable curses window management.
24549 List and give the size of all displayed windows.
24553 Display the next layout.
24556 Display the previous layout.
24559 Display the source window only.
24562 Display the assembly window only.
24565 Display the source and assembly window.
24568 Display the register window together with the source or assembly window.
24572 Make the next window active for scrolling.
24575 Make the previous window active for scrolling.
24578 Make the source window active for scrolling.
24581 Make the assembly window active for scrolling.
24584 Make the register window active for scrolling.
24587 Make the command window active for scrolling.
24591 Refresh the screen. This is similar to typing @kbd{C-L}.
24593 @item tui reg float
24595 Show the floating point registers in the register window.
24597 @item tui reg general
24598 Show the general registers in the register window.
24601 Show the next register group. The list of register groups as well as
24602 their order is target specific. The predefined register groups are the
24603 following: @code{general}, @code{float}, @code{system}, @code{vector},
24604 @code{all}, @code{save}, @code{restore}.
24606 @item tui reg system
24607 Show the system registers in the register window.
24611 Update the source window and the current execution point.
24613 @item winheight @var{name} +@var{count}
24614 @itemx winheight @var{name} -@var{count}
24616 Change the height of the window @var{name} by @var{count}
24617 lines. Positive counts increase the height, while negative counts
24618 decrease it. The @var{name} parameter can be one of @code{src} (the
24619 source window), @code{cmd} (the command window), @code{asm} (the
24620 disassembly window), or @code{regs} (the register display window).
24622 @item tabset @var{nchars}
24624 Set the width of tab stops to be @var{nchars} characters. This
24625 setting affects the display of TAB characters in the source and
24629 @node TUI Configuration
24630 @section TUI Configuration Variables
24631 @cindex TUI configuration variables
24633 Several configuration variables control the appearance of TUI windows.
24636 @item set tui border-kind @var{kind}
24637 @kindex set tui border-kind
24638 Select the border appearance for the source, assembly and register windows.
24639 The possible values are the following:
24642 Use a space character to draw the border.
24645 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
24648 Use the Alternate Character Set to draw the border. The border is
24649 drawn using character line graphics if the terminal supports them.
24652 @item set tui border-mode @var{mode}
24653 @kindex set tui border-mode
24654 @itemx set tui active-border-mode @var{mode}
24655 @kindex set tui active-border-mode
24656 Select the display attributes for the borders of the inactive windows
24657 or the active window. The @var{mode} can be one of the following:
24660 Use normal attributes to display the border.
24666 Use reverse video mode.
24669 Use half bright mode.
24671 @item half-standout
24672 Use half bright and standout mode.
24675 Use extra bright or bold mode.
24677 @item bold-standout
24678 Use extra bright or bold and standout mode.
24683 @chapter Using @value{GDBN} under @sc{gnu} Emacs
24686 @cindex @sc{gnu} Emacs
24687 A special interface allows you to use @sc{gnu} Emacs to view (and
24688 edit) the source files for the program you are debugging with
24691 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
24692 executable file you want to debug as an argument. This command starts
24693 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
24694 created Emacs buffer.
24695 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
24697 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
24702 All ``terminal'' input and output goes through an Emacs buffer, called
24705 This applies both to @value{GDBN} commands and their output, and to the input
24706 and output done by the program you are debugging.
24708 This is useful because it means that you can copy the text of previous
24709 commands and input them again; you can even use parts of the output
24712 All the facilities of Emacs' Shell mode are available for interacting
24713 with your program. In particular, you can send signals the usual
24714 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
24718 @value{GDBN} displays source code through Emacs.
24720 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
24721 source file for that frame and puts an arrow (@samp{=>}) at the
24722 left margin of the current line. Emacs uses a separate buffer for
24723 source display, and splits the screen to show both your @value{GDBN} session
24726 Explicit @value{GDBN} @code{list} or search commands still produce output as
24727 usual, but you probably have no reason to use them from Emacs.
24730 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
24731 a graphical mode, enabled by default, which provides further buffers
24732 that can control the execution and describe the state of your program.
24733 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
24735 If you specify an absolute file name when prompted for the @kbd{M-x
24736 gdb} argument, then Emacs sets your current working directory to where
24737 your program resides. If you only specify the file name, then Emacs
24738 sets your current working directory to the directory associated
24739 with the previous buffer. In this case, @value{GDBN} may find your
24740 program by searching your environment's @code{PATH} variable, but on
24741 some operating systems it might not find the source. So, although the
24742 @value{GDBN} input and output session proceeds normally, the auxiliary
24743 buffer does not display the current source and line of execution.
24745 The initial working directory of @value{GDBN} is printed on the top
24746 line of the GUD buffer and this serves as a default for the commands
24747 that specify files for @value{GDBN} to operate on. @xref{Files,
24748 ,Commands to Specify Files}.
24750 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
24751 need to call @value{GDBN} by a different name (for example, if you
24752 keep several configurations around, with different names) you can
24753 customize the Emacs variable @code{gud-gdb-command-name} to run the
24756 In the GUD buffer, you can use these special Emacs commands in
24757 addition to the standard Shell mode commands:
24761 Describe the features of Emacs' GUD Mode.
24764 Execute to another source line, like the @value{GDBN} @code{step} command; also
24765 update the display window to show the current file and location.
24768 Execute to next source line in this function, skipping all function
24769 calls, like the @value{GDBN} @code{next} command. Then update the display window
24770 to show the current file and location.
24773 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
24774 display window accordingly.
24777 Execute until exit from the selected stack frame, like the @value{GDBN}
24778 @code{finish} command.
24781 Continue execution of your program, like the @value{GDBN} @code{continue}
24785 Go up the number of frames indicated by the numeric argument
24786 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
24787 like the @value{GDBN} @code{up} command.
24790 Go down the number of frames indicated by the numeric argument, like the
24791 @value{GDBN} @code{down} command.
24794 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
24795 tells @value{GDBN} to set a breakpoint on the source line point is on.
24797 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
24798 separate frame which shows a backtrace when the GUD buffer is current.
24799 Move point to any frame in the stack and type @key{RET} to make it
24800 become the current frame and display the associated source in the
24801 source buffer. Alternatively, click @kbd{Mouse-2} to make the
24802 selected frame become the current one. In graphical mode, the
24803 speedbar displays watch expressions.
24805 If you accidentally delete the source-display buffer, an easy way to get
24806 it back is to type the command @code{f} in the @value{GDBN} buffer, to
24807 request a frame display; when you run under Emacs, this recreates
24808 the source buffer if necessary to show you the context of the current
24811 The source files displayed in Emacs are in ordinary Emacs buffers
24812 which are visiting the source files in the usual way. You can edit
24813 the files with these buffers if you wish; but keep in mind that @value{GDBN}
24814 communicates with Emacs in terms of line numbers. If you add or
24815 delete lines from the text, the line numbers that @value{GDBN} knows cease
24816 to correspond properly with the code.
24818 A more detailed description of Emacs' interaction with @value{GDBN} is
24819 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
24823 @chapter The @sc{gdb/mi} Interface
24825 @unnumberedsec Function and Purpose
24827 @cindex @sc{gdb/mi}, its purpose
24828 @sc{gdb/mi} is a line based machine oriented text interface to
24829 @value{GDBN} and is activated by specifying using the
24830 @option{--interpreter} command line option (@pxref{Mode Options}). It
24831 is specifically intended to support the development of systems which
24832 use the debugger as just one small component of a larger system.
24834 This chapter is a specification of the @sc{gdb/mi} interface. It is written
24835 in the form of a reference manual.
24837 Note that @sc{gdb/mi} is still under construction, so some of the
24838 features described below are incomplete and subject to change
24839 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
24841 @unnumberedsec Notation and Terminology
24843 @cindex notational conventions, for @sc{gdb/mi}
24844 This chapter uses the following notation:
24848 @code{|} separates two alternatives.
24851 @code{[ @var{something} ]} indicates that @var{something} is optional:
24852 it may or may not be given.
24855 @code{( @var{group} )*} means that @var{group} inside the parentheses
24856 may repeat zero or more times.
24859 @code{( @var{group} )+} means that @var{group} inside the parentheses
24860 may repeat one or more times.
24863 @code{"@var{string}"} means a literal @var{string}.
24867 @heading Dependencies
24871 * GDB/MI General Design::
24872 * GDB/MI Command Syntax::
24873 * GDB/MI Compatibility with CLI::
24874 * GDB/MI Development and Front Ends::
24875 * GDB/MI Output Records::
24876 * GDB/MI Simple Examples::
24877 * GDB/MI Command Description Format::
24878 * GDB/MI Breakpoint Commands::
24879 * GDB/MI Catchpoint Commands::
24880 * GDB/MI Program Context::
24881 * GDB/MI Thread Commands::
24882 * GDB/MI Ada Tasking Commands::
24883 * GDB/MI Program Execution::
24884 * GDB/MI Stack Manipulation::
24885 * GDB/MI Variable Objects::
24886 * GDB/MI Data Manipulation::
24887 * GDB/MI Tracepoint Commands::
24888 * GDB/MI Symbol Query::
24889 * GDB/MI File Commands::
24891 * GDB/MI Kod Commands::
24892 * GDB/MI Memory Overlay Commands::
24893 * GDB/MI Signal Handling Commands::
24895 * GDB/MI Target Manipulation::
24896 * GDB/MI File Transfer Commands::
24897 * GDB/MI Ada Exceptions Commands::
24898 * GDB/MI Support Commands::
24899 * GDB/MI Miscellaneous Commands::
24902 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24903 @node GDB/MI General Design
24904 @section @sc{gdb/mi} General Design
24905 @cindex GDB/MI General Design
24907 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
24908 parts---commands sent to @value{GDBN}, responses to those commands
24909 and notifications. Each command results in exactly one response,
24910 indicating either successful completion of the command, or an error.
24911 For the commands that do not resume the target, the response contains the
24912 requested information. For the commands that resume the target, the
24913 response only indicates whether the target was successfully resumed.
24914 Notifications is the mechanism for reporting changes in the state of the
24915 target, or in @value{GDBN} state, that cannot conveniently be associated with
24916 a command and reported as part of that command response.
24918 The important examples of notifications are:
24922 Exec notifications. These are used to report changes in
24923 target state---when a target is resumed, or stopped. It would not
24924 be feasible to include this information in response of resuming
24925 commands, because one resume commands can result in multiple events in
24926 different threads. Also, quite some time may pass before any event
24927 happens in the target, while a frontend needs to know whether the resuming
24928 command itself was successfully executed.
24931 Console output, and status notifications. Console output
24932 notifications are used to report output of CLI commands, as well as
24933 diagnostics for other commands. Status notifications are used to
24934 report the progress of a long-running operation. Naturally, including
24935 this information in command response would mean no output is produced
24936 until the command is finished, which is undesirable.
24939 General notifications. Commands may have various side effects on
24940 the @value{GDBN} or target state beyond their official purpose. For example,
24941 a command may change the selected thread. Although such changes can
24942 be included in command response, using notification allows for more
24943 orthogonal frontend design.
24947 There's no guarantee that whenever an MI command reports an error,
24948 @value{GDBN} or the target are in any specific state, and especially,
24949 the state is not reverted to the state before the MI command was
24950 processed. Therefore, whenever an MI command results in an error,
24951 we recommend that the frontend refreshes all the information shown in
24952 the user interface.
24956 * Context management::
24957 * Asynchronous and non-stop modes::
24961 @node Context management
24962 @subsection Context management
24964 @subsubsection Threads and Frames
24966 In most cases when @value{GDBN} accesses the target, this access is
24967 done in context of a specific thread and frame (@pxref{Frames}).
24968 Often, even when accessing global data, the target requires that a thread
24969 be specified. The CLI interface maintains the selected thread and frame,
24970 and supplies them to target on each command. This is convenient,
24971 because a command line user would not want to specify that information
24972 explicitly on each command, and because user interacts with
24973 @value{GDBN} via a single terminal, so no confusion is possible as
24974 to what thread and frame are the current ones.
24976 In the case of MI, the concept of selected thread and frame is less
24977 useful. First, a frontend can easily remember this information
24978 itself. Second, a graphical frontend can have more than one window,
24979 each one used for debugging a different thread, and the frontend might
24980 want to access additional threads for internal purposes. This
24981 increases the risk that by relying on implicitly selected thread, the
24982 frontend may be operating on a wrong one. Therefore, each MI command
24983 should explicitly specify which thread and frame to operate on. To
24984 make it possible, each MI command accepts the @samp{--thread} and
24985 @samp{--frame} options, the value to each is @value{GDBN} identifier
24986 for thread and frame to operate on.
24988 Usually, each top-level window in a frontend allows the user to select
24989 a thread and a frame, and remembers the user selection for further
24990 operations. However, in some cases @value{GDBN} may suggest that the
24991 current thread be changed. For example, when stopping on a breakpoint
24992 it is reasonable to switch to the thread where breakpoint is hit. For
24993 another example, if the user issues the CLI @samp{thread} command via
24994 the frontend, it is desirable to change the frontend's selected thread to the
24995 one specified by user. @value{GDBN} communicates the suggestion to
24996 change current thread using the @samp{=thread-selected} notification.
24997 No such notification is available for the selected frame at the moment.
24999 Note that historically, MI shares the selected thread with CLI, so
25000 frontends used the @code{-thread-select} to execute commands in the
25001 right context. However, getting this to work right is cumbersome. The
25002 simplest way is for frontend to emit @code{-thread-select} command
25003 before every command. This doubles the number of commands that need
25004 to be sent. The alternative approach is to suppress @code{-thread-select}
25005 if the selected thread in @value{GDBN} is supposed to be identical to the
25006 thread the frontend wants to operate on. However, getting this
25007 optimization right can be tricky. In particular, if the frontend
25008 sends several commands to @value{GDBN}, and one of the commands changes the
25009 selected thread, then the behaviour of subsequent commands will
25010 change. So, a frontend should either wait for response from such
25011 problematic commands, or explicitly add @code{-thread-select} for
25012 all subsequent commands. No frontend is known to do this exactly
25013 right, so it is suggested to just always pass the @samp{--thread} and
25014 @samp{--frame} options.
25016 @subsubsection Language
25018 The execution of several commands depends on which language is selected.
25019 By default, the current language (@pxref{show language}) is used.
25020 But for commands known to be language-sensitive, it is recommended
25021 to use the @samp{--language} option. This option takes one argument,
25022 which is the name of the language to use while executing the command.
25026 -data-evaluate-expression --language c "sizeof (void*)"
25031 The valid language names are the same names accepted by the
25032 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
25033 @samp{local} or @samp{unknown}.
25035 @node Asynchronous and non-stop modes
25036 @subsection Asynchronous command execution and non-stop mode
25038 On some targets, @value{GDBN} is capable of processing MI commands
25039 even while the target is running. This is called @dfn{asynchronous
25040 command execution} (@pxref{Background Execution}). The frontend may
25041 specify a preferrence for asynchronous execution using the
25042 @code{-gdb-set mi-async 1} command, which should be emitted before
25043 either running the executable or attaching to the target. After the
25044 frontend has started the executable or attached to the target, it can
25045 find if asynchronous execution is enabled using the
25046 @code{-list-target-features} command.
25049 @item -gdb-set mi-async on
25050 @item -gdb-set mi-async off
25051 Set whether MI is in asynchronous mode.
25053 When @code{off}, which is the default, MI execution commands (e.g.,
25054 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
25055 for the program to stop before processing further commands.
25057 When @code{on}, MI execution commands are background execution
25058 commands (e.g., @code{-exec-continue} becomes the equivalent of the
25059 @code{c&} CLI command), and so @value{GDBN} is capable of processing
25060 MI commands even while the target is running.
25062 @item -gdb-show mi-async
25063 Show whether MI asynchronous mode is enabled.
25066 Note: In @value{GDBN} version 7.7 and earlier, this option was called
25067 @code{target-async} instead of @code{mi-async}, and it had the effect
25068 of both putting MI in asynchronous mode and making CLI background
25069 commands possible. CLI background commands are now always possible
25070 ``out of the box'' if the target supports them. The old spelling is
25071 kept as a deprecated alias for backwards compatibility.
25073 Even if @value{GDBN} can accept a command while target is running,
25074 many commands that access the target do not work when the target is
25075 running. Therefore, asynchronous command execution is most useful
25076 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
25077 it is possible to examine the state of one thread, while other threads
25080 When a given thread is running, MI commands that try to access the
25081 target in the context of that thread may not work, or may work only on
25082 some targets. In particular, commands that try to operate on thread's
25083 stack will not work, on any target. Commands that read memory, or
25084 modify breakpoints, may work or not work, depending on the target. Note
25085 that even commands that operate on global state, such as @code{print},
25086 @code{set}, and breakpoint commands, still access the target in the
25087 context of a specific thread, so frontend should try to find a
25088 stopped thread and perform the operation on that thread (using the
25089 @samp{--thread} option).
25091 Which commands will work in the context of a running thread is
25092 highly target dependent. However, the two commands
25093 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
25094 to find the state of a thread, will always work.
25096 @node Thread groups
25097 @subsection Thread groups
25098 @value{GDBN} may be used to debug several processes at the same time.
25099 On some platfroms, @value{GDBN} may support debugging of several
25100 hardware systems, each one having several cores with several different
25101 processes running on each core. This section describes the MI
25102 mechanism to support such debugging scenarios.
25104 The key observation is that regardless of the structure of the
25105 target, MI can have a global list of threads, because most commands that
25106 accept the @samp{--thread} option do not need to know what process that
25107 thread belongs to. Therefore, it is not necessary to introduce
25108 neither additional @samp{--process} option, nor an notion of the
25109 current process in the MI interface. The only strictly new feature
25110 that is required is the ability to find how the threads are grouped
25113 To allow the user to discover such grouping, and to support arbitrary
25114 hierarchy of machines/cores/processes, MI introduces the concept of a
25115 @dfn{thread group}. Thread group is a collection of threads and other
25116 thread groups. A thread group always has a string identifier, a type,
25117 and may have additional attributes specific to the type. A new
25118 command, @code{-list-thread-groups}, returns the list of top-level
25119 thread groups, which correspond to processes that @value{GDBN} is
25120 debugging at the moment. By passing an identifier of a thread group
25121 to the @code{-list-thread-groups} command, it is possible to obtain
25122 the members of specific thread group.
25124 To allow the user to easily discover processes, and other objects, he
25125 wishes to debug, a concept of @dfn{available thread group} is
25126 introduced. Available thread group is an thread group that
25127 @value{GDBN} is not debugging, but that can be attached to, using the
25128 @code{-target-attach} command. The list of available top-level thread
25129 groups can be obtained using @samp{-list-thread-groups --available}.
25130 In general, the content of a thread group may be only retrieved only
25131 after attaching to that thread group.
25133 Thread groups are related to inferiors (@pxref{Inferiors and
25134 Programs}). Each inferior corresponds to a thread group of a special
25135 type @samp{process}, and some additional operations are permitted on
25136 such thread groups.
25138 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25139 @node GDB/MI Command Syntax
25140 @section @sc{gdb/mi} Command Syntax
25143 * GDB/MI Input Syntax::
25144 * GDB/MI Output Syntax::
25147 @node GDB/MI Input Syntax
25148 @subsection @sc{gdb/mi} Input Syntax
25150 @cindex input syntax for @sc{gdb/mi}
25151 @cindex @sc{gdb/mi}, input syntax
25153 @item @var{command} @expansion{}
25154 @code{@var{cli-command} | @var{mi-command}}
25156 @item @var{cli-command} @expansion{}
25157 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
25158 @var{cli-command} is any existing @value{GDBN} CLI command.
25160 @item @var{mi-command} @expansion{}
25161 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
25162 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
25164 @item @var{token} @expansion{}
25165 "any sequence of digits"
25167 @item @var{option} @expansion{}
25168 @code{"-" @var{parameter} [ " " @var{parameter} ]}
25170 @item @var{parameter} @expansion{}
25171 @code{@var{non-blank-sequence} | @var{c-string}}
25173 @item @var{operation} @expansion{}
25174 @emph{any of the operations described in this chapter}
25176 @item @var{non-blank-sequence} @expansion{}
25177 @emph{anything, provided it doesn't contain special characters such as
25178 "-", @var{nl}, """ and of course " "}
25180 @item @var{c-string} @expansion{}
25181 @code{""" @var{seven-bit-iso-c-string-content} """}
25183 @item @var{nl} @expansion{}
25192 The CLI commands are still handled by the @sc{mi} interpreter; their
25193 output is described below.
25196 The @code{@var{token}}, when present, is passed back when the command
25200 Some @sc{mi} commands accept optional arguments as part of the parameter
25201 list. Each option is identified by a leading @samp{-} (dash) and may be
25202 followed by an optional argument parameter. Options occur first in the
25203 parameter list and can be delimited from normal parameters using
25204 @samp{--} (this is useful when some parameters begin with a dash).
25211 We want easy access to the existing CLI syntax (for debugging).
25214 We want it to be easy to spot a @sc{mi} operation.
25217 @node GDB/MI Output Syntax
25218 @subsection @sc{gdb/mi} Output Syntax
25220 @cindex output syntax of @sc{gdb/mi}
25221 @cindex @sc{gdb/mi}, output syntax
25222 The output from @sc{gdb/mi} consists of zero or more out-of-band records
25223 followed, optionally, by a single result record. This result record
25224 is for the most recent command. The sequence of output records is
25225 terminated by @samp{(gdb)}.
25227 If an input command was prefixed with a @code{@var{token}} then the
25228 corresponding output for that command will also be prefixed by that same
25232 @item @var{output} @expansion{}
25233 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
25235 @item @var{result-record} @expansion{}
25236 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
25238 @item @var{out-of-band-record} @expansion{}
25239 @code{@var{async-record} | @var{stream-record}}
25241 @item @var{async-record} @expansion{}
25242 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
25244 @item @var{exec-async-output} @expansion{}
25245 @code{[ @var{token} ] "*" @var{async-output nl}}
25247 @item @var{status-async-output} @expansion{}
25248 @code{[ @var{token} ] "+" @var{async-output nl}}
25250 @item @var{notify-async-output} @expansion{}
25251 @code{[ @var{token} ] "=" @var{async-output nl}}
25253 @item @var{async-output} @expansion{}
25254 @code{@var{async-class} ( "," @var{result} )*}
25256 @item @var{result-class} @expansion{}
25257 @code{"done" | "running" | "connected" | "error" | "exit"}
25259 @item @var{async-class} @expansion{}
25260 @code{"stopped" | @var{others}} (where @var{others} will be added
25261 depending on the needs---this is still in development).
25263 @item @var{result} @expansion{}
25264 @code{ @var{variable} "=" @var{value}}
25266 @item @var{variable} @expansion{}
25267 @code{ @var{string} }
25269 @item @var{value} @expansion{}
25270 @code{ @var{const} | @var{tuple} | @var{list} }
25272 @item @var{const} @expansion{}
25273 @code{@var{c-string}}
25275 @item @var{tuple} @expansion{}
25276 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
25278 @item @var{list} @expansion{}
25279 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
25280 @var{result} ( "," @var{result} )* "]" }
25282 @item @var{stream-record} @expansion{}
25283 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
25285 @item @var{console-stream-output} @expansion{}
25286 @code{"~" @var{c-string nl}}
25288 @item @var{target-stream-output} @expansion{}
25289 @code{"@@" @var{c-string nl}}
25291 @item @var{log-stream-output} @expansion{}
25292 @code{"&" @var{c-string nl}}
25294 @item @var{nl} @expansion{}
25297 @item @var{token} @expansion{}
25298 @emph{any sequence of digits}.
25306 All output sequences end in a single line containing a period.
25309 The @code{@var{token}} is from the corresponding request. Note that
25310 for all async output, while the token is allowed by the grammar and
25311 may be output by future versions of @value{GDBN} for select async
25312 output messages, it is generally omitted. Frontends should treat
25313 all async output as reporting general changes in the state of the
25314 target and there should be no need to associate async output to any
25318 @cindex status output in @sc{gdb/mi}
25319 @var{status-async-output} contains on-going status information about the
25320 progress of a slow operation. It can be discarded. All status output is
25321 prefixed by @samp{+}.
25324 @cindex async output in @sc{gdb/mi}
25325 @var{exec-async-output} contains asynchronous state change on the target
25326 (stopped, started, disappeared). All async output is prefixed by
25330 @cindex notify output in @sc{gdb/mi}
25331 @var{notify-async-output} contains supplementary information that the
25332 client should handle (e.g., a new breakpoint information). All notify
25333 output is prefixed by @samp{=}.
25336 @cindex console output in @sc{gdb/mi}
25337 @var{console-stream-output} is output that should be displayed as is in the
25338 console. It is the textual response to a CLI command. All the console
25339 output is prefixed by @samp{~}.
25342 @cindex target output in @sc{gdb/mi}
25343 @var{target-stream-output} is the output produced by the target program.
25344 All the target output is prefixed by @samp{@@}.
25347 @cindex log output in @sc{gdb/mi}
25348 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
25349 instance messages that should be displayed as part of an error log. All
25350 the log output is prefixed by @samp{&}.
25353 @cindex list output in @sc{gdb/mi}
25354 New @sc{gdb/mi} commands should only output @var{lists} containing
25360 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
25361 details about the various output records.
25363 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25364 @node GDB/MI Compatibility with CLI
25365 @section @sc{gdb/mi} Compatibility with CLI
25367 @cindex compatibility, @sc{gdb/mi} and CLI
25368 @cindex @sc{gdb/mi}, compatibility with CLI
25370 For the developers convenience CLI commands can be entered directly,
25371 but there may be some unexpected behaviour. For example, commands
25372 that query the user will behave as if the user replied yes, breakpoint
25373 command lists are not executed and some CLI commands, such as
25374 @code{if}, @code{when} and @code{define}, prompt for further input with
25375 @samp{>}, which is not valid MI output.
25377 This feature may be removed at some stage in the future and it is
25378 recommended that front ends use the @code{-interpreter-exec} command
25379 (@pxref{-interpreter-exec}).
25381 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25382 @node GDB/MI Development and Front Ends
25383 @section @sc{gdb/mi} Development and Front Ends
25384 @cindex @sc{gdb/mi} development
25386 The application which takes the MI output and presents the state of the
25387 program being debugged to the user is called a @dfn{front end}.
25389 Although @sc{gdb/mi} is still incomplete, it is currently being used
25390 by a variety of front ends to @value{GDBN}. This makes it difficult
25391 to introduce new functionality without breaking existing usage. This
25392 section tries to minimize the problems by describing how the protocol
25395 Some changes in MI need not break a carefully designed front end, and
25396 for these the MI version will remain unchanged. The following is a
25397 list of changes that may occur within one level, so front ends should
25398 parse MI output in a way that can handle them:
25402 New MI commands may be added.
25405 New fields may be added to the output of any MI command.
25408 The range of values for fields with specified values, e.g.,
25409 @code{in_scope} (@pxref{-var-update}) may be extended.
25411 @c The format of field's content e.g type prefix, may change so parse it
25412 @c at your own risk. Yes, in general?
25414 @c The order of fields may change? Shouldn't really matter but it might
25415 @c resolve inconsistencies.
25418 If the changes are likely to break front ends, the MI version level
25419 will be increased by one. This will allow the front end to parse the
25420 output according to the MI version. Apart from mi0, new versions of
25421 @value{GDBN} will not support old versions of MI and it will be the
25422 responsibility of the front end to work with the new one.
25424 @c Starting with mi3, add a new command -mi-version that prints the MI
25427 The best way to avoid unexpected changes in MI that might break your front
25428 end is to make your project known to @value{GDBN} developers and
25429 follow development on @email{gdb@@sourceware.org} and
25430 @email{gdb-patches@@sourceware.org}.
25431 @cindex mailing lists
25433 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25434 @node GDB/MI Output Records
25435 @section @sc{gdb/mi} Output Records
25438 * GDB/MI Result Records::
25439 * GDB/MI Stream Records::
25440 * GDB/MI Async Records::
25441 * GDB/MI Breakpoint Information::
25442 * GDB/MI Frame Information::
25443 * GDB/MI Thread Information::
25444 * GDB/MI Ada Exception Information::
25447 @node GDB/MI Result Records
25448 @subsection @sc{gdb/mi} Result Records
25450 @cindex result records in @sc{gdb/mi}
25451 @cindex @sc{gdb/mi}, result records
25452 In addition to a number of out-of-band notifications, the response to a
25453 @sc{gdb/mi} command includes one of the following result indications:
25457 @item "^done" [ "," @var{results} ]
25458 The synchronous operation was successful, @code{@var{results}} are the return
25463 This result record is equivalent to @samp{^done}. Historically, it
25464 was output instead of @samp{^done} if the command has resumed the
25465 target. This behaviour is maintained for backward compatibility, but
25466 all frontends should treat @samp{^done} and @samp{^running}
25467 identically and rely on the @samp{*running} output record to determine
25468 which threads are resumed.
25472 @value{GDBN} has connected to a remote target.
25474 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
25476 The operation failed. The @code{msg=@var{c-string}} variable contains
25477 the corresponding error message.
25479 If present, the @code{code=@var{c-string}} variable provides an error
25480 code on which consumers can rely on to detect the corresponding
25481 error condition. At present, only one error code is defined:
25484 @item "undefined-command"
25485 Indicates that the command causing the error does not exist.
25490 @value{GDBN} has terminated.
25494 @node GDB/MI Stream Records
25495 @subsection @sc{gdb/mi} Stream Records
25497 @cindex @sc{gdb/mi}, stream records
25498 @cindex stream records in @sc{gdb/mi}
25499 @value{GDBN} internally maintains a number of output streams: the console, the
25500 target, and the log. The output intended for each of these streams is
25501 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
25503 Each stream record begins with a unique @dfn{prefix character} which
25504 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
25505 Syntax}). In addition to the prefix, each stream record contains a
25506 @code{@var{string-output}}. This is either raw text (with an implicit new
25507 line) or a quoted C string (which does not contain an implicit newline).
25510 @item "~" @var{string-output}
25511 The console output stream contains text that should be displayed in the
25512 CLI console window. It contains the textual responses to CLI commands.
25514 @item "@@" @var{string-output}
25515 The target output stream contains any textual output from the running
25516 target. This is only present when GDB's event loop is truly
25517 asynchronous, which is currently only the case for remote targets.
25519 @item "&" @var{string-output}
25520 The log stream contains debugging messages being produced by @value{GDBN}'s
25524 @node GDB/MI Async Records
25525 @subsection @sc{gdb/mi} Async Records
25527 @cindex async records in @sc{gdb/mi}
25528 @cindex @sc{gdb/mi}, async records
25529 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
25530 additional changes that have occurred. Those changes can either be a
25531 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
25532 target activity (e.g., target stopped).
25534 The following is the list of possible async records:
25538 @item *running,thread-id="@var{thread}"
25539 The target is now running. The @var{thread} field tells which
25540 specific thread is now running, and can be @samp{all} if all threads
25541 are running. The frontend should assume that no interaction with a
25542 running thread is possible after this notification is produced.
25543 The frontend should not assume that this notification is output
25544 only once for any command. @value{GDBN} may emit this notification
25545 several times, either for different threads, because it cannot resume
25546 all threads together, or even for a single thread, if the thread must
25547 be stepped though some code before letting it run freely.
25549 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
25550 The target has stopped. The @var{reason} field can have one of the
25554 @item breakpoint-hit
25555 A breakpoint was reached.
25556 @item watchpoint-trigger
25557 A watchpoint was triggered.
25558 @item read-watchpoint-trigger
25559 A read watchpoint was triggered.
25560 @item access-watchpoint-trigger
25561 An access watchpoint was triggered.
25562 @item function-finished
25563 An -exec-finish or similar CLI command was accomplished.
25564 @item location-reached
25565 An -exec-until or similar CLI command was accomplished.
25566 @item watchpoint-scope
25567 A watchpoint has gone out of scope.
25568 @item end-stepping-range
25569 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
25570 similar CLI command was accomplished.
25571 @item exited-signalled
25572 The inferior exited because of a signal.
25574 The inferior exited.
25575 @item exited-normally
25576 The inferior exited normally.
25577 @item signal-received
25578 A signal was received by the inferior.
25580 The inferior has stopped due to a library being loaded or unloaded.
25581 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
25582 set or when a @code{catch load} or @code{catch unload} catchpoint is
25583 in use (@pxref{Set Catchpoints}).
25585 The inferior has forked. This is reported when @code{catch fork}
25586 (@pxref{Set Catchpoints}) has been used.
25588 The inferior has vforked. This is reported in when @code{catch vfork}
25589 (@pxref{Set Catchpoints}) has been used.
25590 @item syscall-entry
25591 The inferior entered a system call. This is reported when @code{catch
25592 syscall} (@pxref{Set Catchpoints}) has been used.
25593 @item syscall-entry
25594 The inferior returned from a system call. This is reported when
25595 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
25597 The inferior called @code{exec}. This is reported when @code{catch exec}
25598 (@pxref{Set Catchpoints}) has been used.
25601 The @var{id} field identifies the thread that directly caused the stop
25602 -- for example by hitting a breakpoint. Depending on whether all-stop
25603 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
25604 stop all threads, or only the thread that directly triggered the stop.
25605 If all threads are stopped, the @var{stopped} field will have the
25606 value of @code{"all"}. Otherwise, the value of the @var{stopped}
25607 field will be a list of thread identifiers. Presently, this list will
25608 always include a single thread, but frontend should be prepared to see
25609 several threads in the list. The @var{core} field reports the
25610 processor core on which the stop event has happened. This field may be absent
25611 if such information is not available.
25613 @item =thread-group-added,id="@var{id}"
25614 @itemx =thread-group-removed,id="@var{id}"
25615 A thread group was either added or removed. The @var{id} field
25616 contains the @value{GDBN} identifier of the thread group. When a thread
25617 group is added, it generally might not be associated with a running
25618 process. When a thread group is removed, its id becomes invalid and
25619 cannot be used in any way.
25621 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
25622 A thread group became associated with a running program,
25623 either because the program was just started or the thread group
25624 was attached to a program. The @var{id} field contains the
25625 @value{GDBN} identifier of the thread group. The @var{pid} field
25626 contains process identifier, specific to the operating system.
25628 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
25629 A thread group is no longer associated with a running program,
25630 either because the program has exited, or because it was detached
25631 from. The @var{id} field contains the @value{GDBN} identifier of the
25632 thread group. The @var{code} field is the exit code of the inferior; it exists
25633 only when the inferior exited with some code.
25635 @item =thread-created,id="@var{id}",group-id="@var{gid}"
25636 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
25637 A thread either was created, or has exited. The @var{id} field
25638 contains the @value{GDBN} identifier of the thread. The @var{gid}
25639 field identifies the thread group this thread belongs to.
25641 @item =thread-selected,id="@var{id}"
25642 Informs that the selected thread was changed as result of the last
25643 command. This notification is not emitted as result of @code{-thread-select}
25644 command but is emitted whenever an MI command that is not documented
25645 to change the selected thread actually changes it. In particular,
25646 invoking, directly or indirectly (via user-defined command), the CLI
25647 @code{thread} command, will generate this notification.
25649 We suggest that in response to this notification, front ends
25650 highlight the selected thread and cause subsequent commands to apply to
25653 @item =library-loaded,...
25654 Reports that a new library file was loaded by the program. This
25655 notification has 4 fields---@var{id}, @var{target-name},
25656 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
25657 opaque identifier of the library. For remote debugging case,
25658 @var{target-name} and @var{host-name} fields give the name of the
25659 library file on the target, and on the host respectively. For native
25660 debugging, both those fields have the same value. The
25661 @var{symbols-loaded} field is emitted only for backward compatibility
25662 and should not be relied on to convey any useful information. The
25663 @var{thread-group} field, if present, specifies the id of the thread
25664 group in whose context the library was loaded. If the field is
25665 absent, it means the library was loaded in the context of all present
25668 @item =library-unloaded,...
25669 Reports that a library was unloaded by the program. This notification
25670 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
25671 the same meaning as for the @code{=library-loaded} notification.
25672 The @var{thread-group} field, if present, specifies the id of the
25673 thread group in whose context the library was unloaded. If the field is
25674 absent, it means the library was unloaded in the context of all present
25677 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
25678 @itemx =traceframe-changed,end
25679 Reports that the trace frame was changed and its new number is
25680 @var{tfnum}. The number of the tracepoint associated with this trace
25681 frame is @var{tpnum}.
25683 @item =tsv-created,name=@var{name},initial=@var{initial}
25684 Reports that the new trace state variable @var{name} is created with
25685 initial value @var{initial}.
25687 @item =tsv-deleted,name=@var{name}
25688 @itemx =tsv-deleted
25689 Reports that the trace state variable @var{name} is deleted or all
25690 trace state variables are deleted.
25692 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
25693 Reports that the trace state variable @var{name} is modified with
25694 the initial value @var{initial}. The current value @var{current} of
25695 trace state variable is optional and is reported if the current
25696 value of trace state variable is known.
25698 @item =breakpoint-created,bkpt=@{...@}
25699 @itemx =breakpoint-modified,bkpt=@{...@}
25700 @itemx =breakpoint-deleted,id=@var{number}
25701 Reports that a breakpoint was created, modified, or deleted,
25702 respectively. Only user-visible breakpoints are reported to the MI
25705 The @var{bkpt} argument is of the same form as returned by the various
25706 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
25707 @var{number} is the ordinal number of the breakpoint.
25709 Note that if a breakpoint is emitted in the result record of a
25710 command, then it will not also be emitted in an async record.
25712 @item =record-started,thread-group="@var{id}"
25713 @itemx =record-stopped,thread-group="@var{id}"
25714 Execution log recording was either started or stopped on an
25715 inferior. The @var{id} is the @value{GDBN} identifier of the thread
25716 group corresponding to the affected inferior.
25718 @item =cmd-param-changed,param=@var{param},value=@var{value}
25719 Reports that a parameter of the command @code{set @var{param}} is
25720 changed to @var{value}. In the multi-word @code{set} command,
25721 the @var{param} is the whole parameter list to @code{set} command.
25722 For example, In command @code{set check type on}, @var{param}
25723 is @code{check type} and @var{value} is @code{on}.
25725 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
25726 Reports that bytes from @var{addr} to @var{data} + @var{len} were
25727 written in an inferior. The @var{id} is the identifier of the
25728 thread group corresponding to the affected inferior. The optional
25729 @code{type="code"} part is reported if the memory written to holds
25733 @node GDB/MI Breakpoint Information
25734 @subsection @sc{gdb/mi} Breakpoint Information
25736 When @value{GDBN} reports information about a breakpoint, a
25737 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
25742 The breakpoint number. For a breakpoint that represents one location
25743 of a multi-location breakpoint, this will be a dotted pair, like
25747 The type of the breakpoint. For ordinary breakpoints this will be
25748 @samp{breakpoint}, but many values are possible.
25751 If the type of the breakpoint is @samp{catchpoint}, then this
25752 indicates the exact type of catchpoint.
25755 This is the breakpoint disposition---either @samp{del}, meaning that
25756 the breakpoint will be deleted at the next stop, or @samp{keep},
25757 meaning that the breakpoint will not be deleted.
25760 This indicates whether the breakpoint is enabled, in which case the
25761 value is @samp{y}, or disabled, in which case the value is @samp{n}.
25762 Note that this is not the same as the field @code{enable}.
25765 The address of the breakpoint. This may be a hexidecimal number,
25766 giving the address; or the string @samp{<PENDING>}, for a pending
25767 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
25768 multiple locations. This field will not be present if no address can
25769 be determined. For example, a watchpoint does not have an address.
25772 If known, the function in which the breakpoint appears.
25773 If not known, this field is not present.
25776 The name of the source file which contains this function, if known.
25777 If not known, this field is not present.
25780 The full file name of the source file which contains this function, if
25781 known. If not known, this field is not present.
25784 The line number at which this breakpoint appears, if known.
25785 If not known, this field is not present.
25788 If the source file is not known, this field may be provided. If
25789 provided, this holds the address of the breakpoint, possibly followed
25793 If this breakpoint is pending, this field is present and holds the
25794 text used to set the breakpoint, as entered by the user.
25797 Where this breakpoint's condition is evaluated, either @samp{host} or
25801 If this is a thread-specific breakpoint, then this identifies the
25802 thread in which the breakpoint can trigger.
25805 If this breakpoint is restricted to a particular Ada task, then this
25806 field will hold the task identifier.
25809 If the breakpoint is conditional, this is the condition expression.
25812 The ignore count of the breakpoint.
25815 The enable count of the breakpoint.
25817 @item traceframe-usage
25820 @item static-tracepoint-marker-string-id
25821 For a static tracepoint, the name of the static tracepoint marker.
25824 For a masked watchpoint, this is the mask.
25827 A tracepoint's pass count.
25829 @item original-location
25830 The location of the breakpoint as originally specified by the user.
25831 This field is optional.
25834 The number of times the breakpoint has been hit.
25837 This field is only given for tracepoints. This is either @samp{y},
25838 meaning that the tracepoint is installed, or @samp{n}, meaning that it
25842 Some extra data, the exact contents of which are type-dependent.
25846 For example, here is what the output of @code{-break-insert}
25847 (@pxref{GDB/MI Breakpoint Commands}) might be:
25850 -> -break-insert main
25851 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25852 enabled="y",addr="0x08048564",func="main",file="myprog.c",
25853 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
25858 @node GDB/MI Frame Information
25859 @subsection @sc{gdb/mi} Frame Information
25861 Response from many MI commands includes an information about stack
25862 frame. This information is a tuple that may have the following
25867 The level of the stack frame. The innermost frame has the level of
25868 zero. This field is always present.
25871 The name of the function corresponding to the frame. This field may
25872 be absent if @value{GDBN} is unable to determine the function name.
25875 The code address for the frame. This field is always present.
25878 The name of the source files that correspond to the frame's code
25879 address. This field may be absent.
25882 The source line corresponding to the frames' code address. This field
25886 The name of the binary file (either executable or shared library) the
25887 corresponds to the frame's code address. This field may be absent.
25891 @node GDB/MI Thread Information
25892 @subsection @sc{gdb/mi} Thread Information
25894 Whenever @value{GDBN} has to report an information about a thread, it
25895 uses a tuple with the following fields:
25899 The numeric id assigned to the thread by @value{GDBN}. This field is
25903 Target-specific string identifying the thread. This field is always present.
25906 Additional information about the thread provided by the target.
25907 It is supposed to be human-readable and not interpreted by the
25908 frontend. This field is optional.
25911 Either @samp{stopped} or @samp{running}, depending on whether the
25912 thread is presently running. This field is always present.
25915 The value of this field is an integer number of the processor core the
25916 thread was last seen on. This field is optional.
25919 @node GDB/MI Ada Exception Information
25920 @subsection @sc{gdb/mi} Ada Exception Information
25922 Whenever a @code{*stopped} record is emitted because the program
25923 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
25924 @value{GDBN} provides the name of the exception that was raised via
25925 the @code{exception-name} field.
25927 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25928 @node GDB/MI Simple Examples
25929 @section Simple Examples of @sc{gdb/mi} Interaction
25930 @cindex @sc{gdb/mi}, simple examples
25932 This subsection presents several simple examples of interaction using
25933 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
25934 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
25935 the output received from @sc{gdb/mi}.
25937 Note the line breaks shown in the examples are here only for
25938 readability, they don't appear in the real output.
25940 @subheading Setting a Breakpoint
25942 Setting a breakpoint generates synchronous output which contains detailed
25943 information of the breakpoint.
25946 -> -break-insert main
25947 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25948 enabled="y",addr="0x08048564",func="main",file="myprog.c",
25949 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
25954 @subheading Program Execution
25956 Program execution generates asynchronous records and MI gives the
25957 reason that execution stopped.
25963 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
25964 frame=@{addr="0x08048564",func="main",
25965 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
25966 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
25971 <- *stopped,reason="exited-normally"
25975 @subheading Quitting @value{GDBN}
25977 Quitting @value{GDBN} just prints the result class @samp{^exit}.
25985 Please note that @samp{^exit} is printed immediately, but it might
25986 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
25987 performs necessary cleanups, including killing programs being debugged
25988 or disconnecting from debug hardware, so the frontend should wait till
25989 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
25990 fails to exit in reasonable time.
25992 @subheading A Bad Command
25994 Here's what happens if you pass a non-existent command:
25998 <- ^error,msg="Undefined MI command: rubbish"
26003 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26004 @node GDB/MI Command Description Format
26005 @section @sc{gdb/mi} Command Description Format
26007 The remaining sections describe blocks of commands. Each block of
26008 commands is laid out in a fashion similar to this section.
26010 @subheading Motivation
26012 The motivation for this collection of commands.
26014 @subheading Introduction
26016 A brief introduction to this collection of commands as a whole.
26018 @subheading Commands
26020 For each command in the block, the following is described:
26022 @subsubheading Synopsis
26025 -command @var{args}@dots{}
26028 @subsubheading Result
26030 @subsubheading @value{GDBN} Command
26032 The corresponding @value{GDBN} CLI command(s), if any.
26034 @subsubheading Example
26036 Example(s) formatted for readability. Some of the described commands have
26037 not been implemented yet and these are labeled N.A.@: (not available).
26040 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26041 @node GDB/MI Breakpoint Commands
26042 @section @sc{gdb/mi} Breakpoint Commands
26044 @cindex breakpoint commands for @sc{gdb/mi}
26045 @cindex @sc{gdb/mi}, breakpoint commands
26046 This section documents @sc{gdb/mi} commands for manipulating
26049 @subheading The @code{-break-after} Command
26050 @findex -break-after
26052 @subsubheading Synopsis
26055 -break-after @var{number} @var{count}
26058 The breakpoint number @var{number} is not in effect until it has been
26059 hit @var{count} times. To see how this is reflected in the output of
26060 the @samp{-break-list} command, see the description of the
26061 @samp{-break-list} command below.
26063 @subsubheading @value{GDBN} Command
26065 The corresponding @value{GDBN} command is @samp{ignore}.
26067 @subsubheading Example
26072 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26073 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26074 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26082 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26083 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26084 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26085 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26086 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26087 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26088 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26089 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26090 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26091 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
26096 @subheading The @code{-break-catch} Command
26097 @findex -break-catch
26100 @subheading The @code{-break-commands} Command
26101 @findex -break-commands
26103 @subsubheading Synopsis
26106 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
26109 Specifies the CLI commands that should be executed when breakpoint
26110 @var{number} is hit. The parameters @var{command1} to @var{commandN}
26111 are the commands. If no command is specified, any previously-set
26112 commands are cleared. @xref{Break Commands}. Typical use of this
26113 functionality is tracing a program, that is, printing of values of
26114 some variables whenever breakpoint is hit and then continuing.
26116 @subsubheading @value{GDBN} Command
26118 The corresponding @value{GDBN} command is @samp{commands}.
26120 @subsubheading Example
26125 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26126 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26127 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26130 -break-commands 1 "print v" "continue"
26135 @subheading The @code{-break-condition} Command
26136 @findex -break-condition
26138 @subsubheading Synopsis
26141 -break-condition @var{number} @var{expr}
26144 Breakpoint @var{number} will stop the program only if the condition in
26145 @var{expr} is true. The condition becomes part of the
26146 @samp{-break-list} output (see the description of the @samp{-break-list}
26149 @subsubheading @value{GDBN} Command
26151 The corresponding @value{GDBN} command is @samp{condition}.
26153 @subsubheading Example
26157 -break-condition 1 1
26161 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26162 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26163 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26164 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26165 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26166 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26167 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26168 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26169 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26170 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
26174 @subheading The @code{-break-delete} Command
26175 @findex -break-delete
26177 @subsubheading Synopsis
26180 -break-delete ( @var{breakpoint} )+
26183 Delete the breakpoint(s) whose number(s) are specified in the argument
26184 list. This is obviously reflected in the breakpoint list.
26186 @subsubheading @value{GDBN} Command
26188 The corresponding @value{GDBN} command is @samp{delete}.
26190 @subsubheading Example
26198 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26199 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26200 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26201 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26202 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26203 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26204 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26209 @subheading The @code{-break-disable} Command
26210 @findex -break-disable
26212 @subsubheading Synopsis
26215 -break-disable ( @var{breakpoint} )+
26218 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
26219 break list is now set to @samp{n} for the named @var{breakpoint}(s).
26221 @subsubheading @value{GDBN} Command
26223 The corresponding @value{GDBN} command is @samp{disable}.
26225 @subsubheading Example
26233 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26234 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26235 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26236 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26237 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26238 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26239 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26240 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
26241 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26242 line="5",thread-groups=["i1"],times="0"@}]@}
26246 @subheading The @code{-break-enable} Command
26247 @findex -break-enable
26249 @subsubheading Synopsis
26252 -break-enable ( @var{breakpoint} )+
26255 Enable (previously disabled) @var{breakpoint}(s).
26257 @subsubheading @value{GDBN} Command
26259 The corresponding @value{GDBN} command is @samp{enable}.
26261 @subsubheading Example
26269 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26270 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26271 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26272 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26273 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26274 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26275 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26276 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26277 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26278 line="5",thread-groups=["i1"],times="0"@}]@}
26282 @subheading The @code{-break-info} Command
26283 @findex -break-info
26285 @subsubheading Synopsis
26288 -break-info @var{breakpoint}
26292 Get information about a single breakpoint.
26294 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
26295 Information}, for details on the format of each breakpoint in the
26298 @subsubheading @value{GDBN} Command
26300 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
26302 @subsubheading Example
26305 @subheading The @code{-break-insert} Command
26306 @findex -break-insert
26308 @subsubheading Synopsis
26311 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
26312 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26313 [ -p @var{thread-id} ] [ @var{location} ]
26317 If specified, @var{location}, can be one of:
26324 @item filename:linenum
26325 @item filename:function
26329 The possible optional parameters of this command are:
26333 Insert a temporary breakpoint.
26335 Insert a hardware breakpoint.
26337 If @var{location} cannot be parsed (for example if it
26338 refers to unknown files or functions), create a pending
26339 breakpoint. Without this flag, @value{GDBN} will report
26340 an error, and won't create a breakpoint, if @var{location}
26343 Create a disabled breakpoint.
26345 Create a tracepoint. @xref{Tracepoints}. When this parameter
26346 is used together with @samp{-h}, a fast tracepoint is created.
26347 @item -c @var{condition}
26348 Make the breakpoint conditional on @var{condition}.
26349 @item -i @var{ignore-count}
26350 Initialize the @var{ignore-count}.
26351 @item -p @var{thread-id}
26352 Restrict the breakpoint to the specified @var{thread-id}.
26355 @subsubheading Result
26357 @xref{GDB/MI Breakpoint Information}, for details on the format of the
26358 resulting breakpoint.
26360 Note: this format is open to change.
26361 @c An out-of-band breakpoint instead of part of the result?
26363 @subsubheading @value{GDBN} Command
26365 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
26366 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
26368 @subsubheading Example
26373 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
26374 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
26377 -break-insert -t foo
26378 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
26379 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
26383 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26384 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26385 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26386 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26387 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26388 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26389 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26390 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26391 addr="0x0001072c", func="main",file="recursive2.c",
26392 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
26394 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
26395 addr="0x00010774",func="foo",file="recursive2.c",
26396 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
26399 @c -break-insert -r foo.*
26400 @c ~int foo(int, int);
26401 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
26402 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
26407 @subheading The @code{-dprintf-insert} Command
26408 @findex -dprintf-insert
26410 @subsubheading Synopsis
26413 -dprintf-insert [ -t ] [ -f ] [ -d ]
26414 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26415 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
26420 If specified, @var{location}, can be one of:
26423 @item @var{function}
26426 @c @item @var{linenum}
26427 @item @var{filename}:@var{linenum}
26428 @item @var{filename}:function
26429 @item *@var{address}
26432 The possible optional parameters of this command are:
26436 Insert a temporary breakpoint.
26438 If @var{location} cannot be parsed (for example, if it
26439 refers to unknown files or functions), create a pending
26440 breakpoint. Without this flag, @value{GDBN} will report
26441 an error, and won't create a breakpoint, if @var{location}
26444 Create a disabled breakpoint.
26445 @item -c @var{condition}
26446 Make the breakpoint conditional on @var{condition}.
26447 @item -i @var{ignore-count}
26448 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
26449 to @var{ignore-count}.
26450 @item -p @var{thread-id}
26451 Restrict the breakpoint to the specified @var{thread-id}.
26454 @subsubheading Result
26456 @xref{GDB/MI Breakpoint Information}, for details on the format of the
26457 resulting breakpoint.
26459 @c An out-of-band breakpoint instead of part of the result?
26461 @subsubheading @value{GDBN} Command
26463 The corresponding @value{GDBN} command is @samp{dprintf}.
26465 @subsubheading Example
26469 4-dprintf-insert foo "At foo entry\n"
26470 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
26471 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
26472 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
26473 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
26474 original-location="foo"@}
26476 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
26477 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
26478 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
26479 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
26480 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
26481 original-location="mi-dprintf.c:26"@}
26485 @subheading The @code{-break-list} Command
26486 @findex -break-list
26488 @subsubheading Synopsis
26494 Displays the list of inserted breakpoints, showing the following fields:
26498 number of the breakpoint
26500 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
26502 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
26505 is the breakpoint enabled or no: @samp{y} or @samp{n}
26507 memory location at which the breakpoint is set
26509 logical location of the breakpoint, expressed by function name, file
26511 @item Thread-groups
26512 list of thread groups to which this breakpoint applies
26514 number of times the breakpoint has been hit
26517 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
26518 @code{body} field is an empty list.
26520 @subsubheading @value{GDBN} Command
26522 The corresponding @value{GDBN} command is @samp{info break}.
26524 @subsubheading Example
26529 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26530 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26531 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26532 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26533 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26534 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26535 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26536 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26537 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
26539 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26540 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
26541 line="13",thread-groups=["i1"],times="0"@}]@}
26545 Here's an example of the result when there are no breakpoints:
26550 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26551 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26552 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26553 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26554 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26555 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26556 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26561 @subheading The @code{-break-passcount} Command
26562 @findex -break-passcount
26564 @subsubheading Synopsis
26567 -break-passcount @var{tracepoint-number} @var{passcount}
26570 Set the passcount for tracepoint @var{tracepoint-number} to
26571 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
26572 is not a tracepoint, error is emitted. This corresponds to CLI
26573 command @samp{passcount}.
26575 @subheading The @code{-break-watch} Command
26576 @findex -break-watch
26578 @subsubheading Synopsis
26581 -break-watch [ -a | -r ]
26584 Create a watchpoint. With the @samp{-a} option it will create an
26585 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
26586 read from or on a write to the memory location. With the @samp{-r}
26587 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
26588 trigger only when the memory location is accessed for reading. Without
26589 either of the options, the watchpoint created is a regular watchpoint,
26590 i.e., it will trigger when the memory location is accessed for writing.
26591 @xref{Set Watchpoints, , Setting Watchpoints}.
26593 Note that @samp{-break-list} will report a single list of watchpoints and
26594 breakpoints inserted.
26596 @subsubheading @value{GDBN} Command
26598 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
26601 @subsubheading Example
26603 Setting a watchpoint on a variable in the @code{main} function:
26608 ^done,wpt=@{number="2",exp="x"@}
26613 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
26614 value=@{old="-268439212",new="55"@},
26615 frame=@{func="main",args=[],file="recursive2.c",
26616 fullname="/home/foo/bar/recursive2.c",line="5"@}
26620 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
26621 the program execution twice: first for the variable changing value, then
26622 for the watchpoint going out of scope.
26627 ^done,wpt=@{number="5",exp="C"@}
26632 *stopped,reason="watchpoint-trigger",
26633 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
26634 frame=@{func="callee4",args=[],
26635 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26636 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
26641 *stopped,reason="watchpoint-scope",wpnum="5",
26642 frame=@{func="callee3",args=[@{name="strarg",
26643 value="0x11940 \"A string argument.\""@}],
26644 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26645 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26649 Listing breakpoints and watchpoints, at different points in the program
26650 execution. Note that once the watchpoint goes out of scope, it is
26656 ^done,wpt=@{number="2",exp="C"@}
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="0x00010734",func="callee4",
26668 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26669 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
26671 bkpt=@{number="2",type="watchpoint",disp="keep",
26672 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
26677 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
26678 value=@{old="-276895068",new="3"@},
26679 frame=@{func="callee4",args=[],
26680 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26681 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
26684 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26685 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26686 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26687 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26688 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26689 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26690 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26691 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26692 addr="0x00010734",func="callee4",
26693 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26694 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
26696 bkpt=@{number="2",type="watchpoint",disp="keep",
26697 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
26701 ^done,reason="watchpoint-scope",wpnum="2",
26702 frame=@{func="callee3",args=[@{name="strarg",
26703 value="0x11940 \"A string argument.\""@}],
26704 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26705 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26708 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26709 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26710 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26711 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26712 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26713 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26714 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26715 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26716 addr="0x00010734",func="callee4",
26717 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26718 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
26719 thread-groups=["i1"],times="1"@}]@}
26724 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26725 @node GDB/MI Catchpoint Commands
26726 @section @sc{gdb/mi} Catchpoint Commands
26728 This section documents @sc{gdb/mi} commands for manipulating
26732 * Shared Library GDB/MI Catchpoint Commands::
26733 * Ada Exception GDB/MI Catchpoint Commands::
26736 @node Shared Library GDB/MI Catchpoint Commands
26737 @subsection Shared Library @sc{gdb/mi} Catchpoints
26739 @subheading The @code{-catch-load} Command
26740 @findex -catch-load
26742 @subsubheading Synopsis
26745 -catch-load [ -t ] [ -d ] @var{regexp}
26748 Add a catchpoint for library load events. If the @samp{-t} option is used,
26749 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
26750 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
26751 in a disabled state. The @samp{regexp} argument is a regular
26752 expression used to match the name of the loaded library.
26755 @subsubheading @value{GDBN} Command
26757 The corresponding @value{GDBN} command is @samp{catch load}.
26759 @subsubheading Example
26762 -catch-load -t foo.so
26763 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
26764 what="load of library matching foo.so",catch-type="load",times="0"@}
26769 @subheading The @code{-catch-unload} Command
26770 @findex -catch-unload
26772 @subsubheading Synopsis
26775 -catch-unload [ -t ] [ -d ] @var{regexp}
26778 Add a catchpoint for library unload events. If the @samp{-t} option is
26779 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
26780 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
26781 created in a disabled state. The @samp{regexp} argument is a regular
26782 expression used to match the name of the unloaded library.
26784 @subsubheading @value{GDBN} Command
26786 The corresponding @value{GDBN} command is @samp{catch unload}.
26788 @subsubheading Example
26791 -catch-unload -d bar.so
26792 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
26793 what="load of library matching bar.so",catch-type="unload",times="0"@}
26797 @node Ada Exception GDB/MI Catchpoint Commands
26798 @subsection Ada Exception @sc{gdb/mi} Catchpoints
26800 The following @sc{gdb/mi} commands can be used to create catchpoints
26801 that stop the execution when Ada exceptions are being raised.
26803 @subheading The @code{-catch-assert} Command
26804 @findex -catch-assert
26806 @subsubheading Synopsis
26809 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
26812 Add a catchpoint for failed Ada assertions.
26814 The possible optional parameters for this command are:
26817 @item -c @var{condition}
26818 Make the catchpoint conditional on @var{condition}.
26820 Create a disabled catchpoint.
26822 Create a temporary catchpoint.
26825 @subsubheading @value{GDBN} Command
26827 The corresponding @value{GDBN} command is @samp{catch assert}.
26829 @subsubheading Example
26833 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
26834 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
26835 thread-groups=["i1"],times="0",
26836 original-location="__gnat_debug_raise_assert_failure"@}
26840 @subheading The @code{-catch-exception} Command
26841 @findex -catch-exception
26843 @subsubheading Synopsis
26846 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
26850 Add a catchpoint stopping when Ada exceptions are raised.
26851 By default, the command stops the program when any Ada exception
26852 gets raised. But it is also possible, by using some of the
26853 optional parameters described below, to create more selective
26856 The possible optional parameters for this command are:
26859 @item -c @var{condition}
26860 Make the catchpoint conditional on @var{condition}.
26862 Create a disabled catchpoint.
26863 @item -e @var{exception-name}
26864 Only stop when @var{exception-name} is raised. This option cannot
26865 be used combined with @samp{-u}.
26867 Create a temporary catchpoint.
26869 Stop only when an unhandled exception gets raised. This option
26870 cannot be used combined with @samp{-e}.
26873 @subsubheading @value{GDBN} Command
26875 The corresponding @value{GDBN} commands are @samp{catch exception}
26876 and @samp{catch exception unhandled}.
26878 @subsubheading Example
26881 -catch-exception -e Program_Error
26882 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
26883 enabled="y",addr="0x0000000000404874",
26884 what="`Program_Error' Ada exception", thread-groups=["i1"],
26885 times="0",original-location="__gnat_debug_raise_exception"@}
26889 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26890 @node GDB/MI Program Context
26891 @section @sc{gdb/mi} Program Context
26893 @subheading The @code{-exec-arguments} Command
26894 @findex -exec-arguments
26897 @subsubheading Synopsis
26900 -exec-arguments @var{args}
26903 Set the inferior program arguments, to be used in the next
26906 @subsubheading @value{GDBN} Command
26908 The corresponding @value{GDBN} command is @samp{set args}.
26910 @subsubheading Example
26914 -exec-arguments -v word
26921 @subheading The @code{-exec-show-arguments} Command
26922 @findex -exec-show-arguments
26924 @subsubheading Synopsis
26927 -exec-show-arguments
26930 Print the arguments of the program.
26932 @subsubheading @value{GDBN} Command
26934 The corresponding @value{GDBN} command is @samp{show args}.
26936 @subsubheading Example
26941 @subheading The @code{-environment-cd} Command
26942 @findex -environment-cd
26944 @subsubheading Synopsis
26947 -environment-cd @var{pathdir}
26950 Set @value{GDBN}'s working directory.
26952 @subsubheading @value{GDBN} Command
26954 The corresponding @value{GDBN} command is @samp{cd}.
26956 @subsubheading Example
26960 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
26966 @subheading The @code{-environment-directory} Command
26967 @findex -environment-directory
26969 @subsubheading Synopsis
26972 -environment-directory [ -r ] [ @var{pathdir} ]+
26975 Add directories @var{pathdir} to beginning of search path for source files.
26976 If the @samp{-r} option is used, the search path is reset to the default
26977 search path. If directories @var{pathdir} are supplied in addition to the
26978 @samp{-r} option, the search path is first reset and then addition
26980 Multiple directories may be specified, separated by blanks. Specifying
26981 multiple directories in a single command
26982 results in the directories added to the beginning of the
26983 search path in the same order they were presented in the command.
26984 If blanks are needed as
26985 part of a directory name, double-quotes should be used around
26986 the name. In the command output, the path will show up separated
26987 by the system directory-separator character. The directory-separator
26988 character must not be used
26989 in any directory name.
26990 If no directories are specified, the current search path is displayed.
26992 @subsubheading @value{GDBN} Command
26994 The corresponding @value{GDBN} command is @samp{dir}.
26996 @subsubheading Example
27000 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27001 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27003 -environment-directory ""
27004 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27006 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
27007 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
27009 -environment-directory -r
27010 ^done,source-path="$cdir:$cwd"
27015 @subheading The @code{-environment-path} Command
27016 @findex -environment-path
27018 @subsubheading Synopsis
27021 -environment-path [ -r ] [ @var{pathdir} ]+
27024 Add directories @var{pathdir} to beginning of search path for object files.
27025 If the @samp{-r} option is used, the search path is reset to the original
27026 search path that existed at gdb start-up. If directories @var{pathdir} are
27027 supplied in addition to the
27028 @samp{-r} option, the search path is first reset and then addition
27030 Multiple directories may be specified, separated by blanks. Specifying
27031 multiple directories in a single command
27032 results in the directories added to the beginning of the
27033 search path in the same order they were presented in the command.
27034 If blanks are needed as
27035 part of a directory name, double-quotes should be used around
27036 the name. In the command output, the path will show up separated
27037 by the system directory-separator character. The directory-separator
27038 character must not be used
27039 in any directory name.
27040 If no directories are specified, the current path is displayed.
27043 @subsubheading @value{GDBN} Command
27045 The corresponding @value{GDBN} command is @samp{path}.
27047 @subsubheading Example
27052 ^done,path="/usr/bin"
27054 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
27055 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
27057 -environment-path -r /usr/local/bin
27058 ^done,path="/usr/local/bin:/usr/bin"
27063 @subheading The @code{-environment-pwd} Command
27064 @findex -environment-pwd
27066 @subsubheading Synopsis
27072 Show the current working directory.
27074 @subsubheading @value{GDBN} Command
27076 The corresponding @value{GDBN} command is @samp{pwd}.
27078 @subsubheading Example
27083 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
27087 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27088 @node GDB/MI Thread Commands
27089 @section @sc{gdb/mi} Thread Commands
27092 @subheading The @code{-thread-info} Command
27093 @findex -thread-info
27095 @subsubheading Synopsis
27098 -thread-info [ @var{thread-id} ]
27101 Reports information about either a specific thread, if
27102 the @var{thread-id} parameter is present, or about all
27103 threads. When printing information about all threads,
27104 also reports the current thread.
27106 @subsubheading @value{GDBN} Command
27108 The @samp{info thread} command prints the same information
27111 @subsubheading Result
27113 The result is a list of threads. The following attributes are
27114 defined for a given thread:
27118 This field exists only for the current thread. It has the value @samp{*}.
27121 The identifier that @value{GDBN} uses to refer to the thread.
27124 The identifier that the target uses to refer to the thread.
27127 Extra information about the thread, in a target-specific format. This
27131 The name of the thread. If the user specified a name using the
27132 @code{thread name} command, then this name is given. Otherwise, if
27133 @value{GDBN} can extract the thread name from the target, then that
27134 name is given. If @value{GDBN} cannot find the thread name, then this
27138 The stack frame currently executing in the thread.
27141 The thread's state. The @samp{state} field may have the following
27146 The thread is stopped. Frame information is available for stopped
27150 The thread is running. There's no frame information for running
27156 If @value{GDBN} can find the CPU core on which this thread is running,
27157 then this field is the core identifier. This field is optional.
27161 @subsubheading Example
27166 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
27167 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
27168 args=[]@},state="running"@},
27169 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
27170 frame=@{level="0",addr="0x0804891f",func="foo",
27171 args=[@{name="i",value="10"@}],
27172 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
27173 state="running"@}],
27174 current-thread-id="1"
27178 @subheading The @code{-thread-list-ids} Command
27179 @findex -thread-list-ids
27181 @subsubheading Synopsis
27187 Produces a list of the currently known @value{GDBN} thread ids. At the
27188 end of the list it also prints the total number of such threads.
27190 This command is retained for historical reasons, the
27191 @code{-thread-info} command should be used instead.
27193 @subsubheading @value{GDBN} Command
27195 Part of @samp{info threads} supplies the same information.
27197 @subsubheading Example
27202 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27203 current-thread-id="1",number-of-threads="3"
27208 @subheading The @code{-thread-select} Command
27209 @findex -thread-select
27211 @subsubheading Synopsis
27214 -thread-select @var{threadnum}
27217 Make @var{threadnum} the current thread. It prints the number of the new
27218 current thread, and the topmost frame for that thread.
27220 This command is deprecated in favor of explicitly using the
27221 @samp{--thread} option to each command.
27223 @subsubheading @value{GDBN} Command
27225 The corresponding @value{GDBN} command is @samp{thread}.
27227 @subsubheading Example
27234 *stopped,reason="end-stepping-range",thread-id="2",line="187",
27235 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
27239 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27240 number-of-threads="3"
27243 ^done,new-thread-id="3",
27244 frame=@{level="0",func="vprintf",
27245 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
27246 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
27250 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27251 @node GDB/MI Ada Tasking Commands
27252 @section @sc{gdb/mi} Ada Tasking Commands
27254 @subheading The @code{-ada-task-info} Command
27255 @findex -ada-task-info
27257 @subsubheading Synopsis
27260 -ada-task-info [ @var{task-id} ]
27263 Reports information about either a specific Ada task, if the
27264 @var{task-id} parameter is present, or about all Ada tasks.
27266 @subsubheading @value{GDBN} Command
27268 The @samp{info tasks} command prints the same information
27269 about all Ada tasks (@pxref{Ada Tasks}).
27271 @subsubheading Result
27273 The result is a table of Ada tasks. The following columns are
27274 defined for each Ada task:
27278 This field exists only for the current thread. It has the value @samp{*}.
27281 The identifier that @value{GDBN} uses to refer to the Ada task.
27284 The identifier that the target uses to refer to the Ada task.
27287 The identifier of the thread corresponding to the Ada task.
27289 This field should always exist, as Ada tasks are always implemented
27290 on top of a thread. But if @value{GDBN} cannot find this corresponding
27291 thread for any reason, the field is omitted.
27294 This field exists only when the task was created by another task.
27295 In this case, it provides the ID of the parent task.
27298 The base priority of the task.
27301 The current state of the task. For a detailed description of the
27302 possible states, see @ref{Ada Tasks}.
27305 The name of the task.
27309 @subsubheading Example
27313 ^done,tasks=@{nr_rows="3",nr_cols="8",
27314 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
27315 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
27316 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
27317 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
27318 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
27319 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
27320 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
27321 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
27322 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
27323 state="Child Termination Wait",name="main_task"@}]@}
27327 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27328 @node GDB/MI Program Execution
27329 @section @sc{gdb/mi} Program Execution
27331 These are the asynchronous commands which generate the out-of-band
27332 record @samp{*stopped}. Currently @value{GDBN} only really executes
27333 asynchronously with remote targets and this interaction is mimicked in
27336 @subheading The @code{-exec-continue} Command
27337 @findex -exec-continue
27339 @subsubheading Synopsis
27342 -exec-continue [--reverse] [--all|--thread-group N]
27345 Resumes the execution of the inferior program, which will continue
27346 to execute until it reaches a debugger stop event. If the
27347 @samp{--reverse} option is specified, execution resumes in reverse until
27348 it reaches a stop event. Stop events may include
27351 breakpoints or watchpoints
27353 signals or exceptions
27355 the end of the process (or its beginning under @samp{--reverse})
27357 the end or beginning of a replay log if one is being used.
27359 In all-stop mode (@pxref{All-Stop
27360 Mode}), may resume only one thread, or all threads, depending on the
27361 value of the @samp{scheduler-locking} variable. If @samp{--all} is
27362 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
27363 ignored in all-stop mode. If the @samp{--thread-group} options is
27364 specified, then all threads in that thread group are resumed.
27366 @subsubheading @value{GDBN} Command
27368 The corresponding @value{GDBN} corresponding is @samp{continue}.
27370 @subsubheading Example
27377 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
27378 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
27384 @subheading The @code{-exec-finish} Command
27385 @findex -exec-finish
27387 @subsubheading Synopsis
27390 -exec-finish [--reverse]
27393 Resumes the execution of the inferior program until the current
27394 function is exited. Displays the results returned by the function.
27395 If the @samp{--reverse} option is specified, resumes the reverse
27396 execution of the inferior program until the point where current
27397 function was called.
27399 @subsubheading @value{GDBN} Command
27401 The corresponding @value{GDBN} command is @samp{finish}.
27403 @subsubheading Example
27405 Function returning @code{void}.
27412 *stopped,reason="function-finished",frame=@{func="main",args=[],
27413 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
27417 Function returning other than @code{void}. The name of the internal
27418 @value{GDBN} variable storing the result is printed, together with the
27425 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
27426 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
27427 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27428 gdb-result-var="$1",return-value="0"
27433 @subheading The @code{-exec-interrupt} Command
27434 @findex -exec-interrupt
27436 @subsubheading Synopsis
27439 -exec-interrupt [--all|--thread-group N]
27442 Interrupts the background execution of the target. Note how the token
27443 associated with the stop message is the one for the execution command
27444 that has been interrupted. The token for the interrupt itself only
27445 appears in the @samp{^done} output. If the user is trying to
27446 interrupt a non-running program, an error message will be printed.
27448 Note that when asynchronous execution is enabled, this command is
27449 asynchronous just like other execution commands. That is, first the
27450 @samp{^done} response will be printed, and the target stop will be
27451 reported after that using the @samp{*stopped} notification.
27453 In non-stop mode, only the context thread is interrupted by default.
27454 All threads (in all inferiors) will be interrupted if the
27455 @samp{--all} option is specified. If the @samp{--thread-group}
27456 option is specified, all threads in that group will be interrupted.
27458 @subsubheading @value{GDBN} Command
27460 The corresponding @value{GDBN} command is @samp{interrupt}.
27462 @subsubheading Example
27473 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
27474 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
27475 fullname="/home/foo/bar/try.c",line="13"@}
27480 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
27484 @subheading The @code{-exec-jump} Command
27487 @subsubheading Synopsis
27490 -exec-jump @var{location}
27493 Resumes execution of the inferior program at the location specified by
27494 parameter. @xref{Specify Location}, for a description of the
27495 different forms of @var{location}.
27497 @subsubheading @value{GDBN} Command
27499 The corresponding @value{GDBN} command is @samp{jump}.
27501 @subsubheading Example
27504 -exec-jump foo.c:10
27505 *running,thread-id="all"
27510 @subheading The @code{-exec-next} Command
27513 @subsubheading Synopsis
27516 -exec-next [--reverse]
27519 Resumes execution of the inferior program, stopping when the beginning
27520 of the next source line is reached.
27522 If the @samp{--reverse} option is specified, resumes reverse execution
27523 of the inferior program, stopping at the beginning of the previous
27524 source line. If you issue this command on the first line of a
27525 function, it will take you back to the caller of that function, to the
27526 source line where the function was called.
27529 @subsubheading @value{GDBN} Command
27531 The corresponding @value{GDBN} command is @samp{next}.
27533 @subsubheading Example
27539 *stopped,reason="end-stepping-range",line="8",file="hello.c"
27544 @subheading The @code{-exec-next-instruction} Command
27545 @findex -exec-next-instruction
27547 @subsubheading Synopsis
27550 -exec-next-instruction [--reverse]
27553 Executes one machine instruction. If the instruction is a function
27554 call, continues until the function returns. If the program stops at an
27555 instruction in the middle of a source line, the address will be
27558 If the @samp{--reverse} option is specified, resumes reverse execution
27559 of the inferior program, stopping at the previous instruction. If the
27560 previously executed instruction was a return from another function,
27561 it will continue to execute in reverse until the call to that function
27562 (from the current stack frame) is reached.
27564 @subsubheading @value{GDBN} Command
27566 The corresponding @value{GDBN} command is @samp{nexti}.
27568 @subsubheading Example
27572 -exec-next-instruction
27576 *stopped,reason="end-stepping-range",
27577 addr="0x000100d4",line="5",file="hello.c"
27582 @subheading The @code{-exec-return} Command
27583 @findex -exec-return
27585 @subsubheading Synopsis
27591 Makes current function return immediately. Doesn't execute the inferior.
27592 Displays the new current frame.
27594 @subsubheading @value{GDBN} Command
27596 The corresponding @value{GDBN} command is @samp{return}.
27598 @subsubheading Example
27602 200-break-insert callee4
27603 200^done,bkpt=@{number="1",addr="0x00010734",
27604 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27609 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27610 frame=@{func="callee4",args=[],
27611 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27612 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27618 111^done,frame=@{level="0",func="callee3",
27619 args=[@{name="strarg",
27620 value="0x11940 \"A string argument.\""@}],
27621 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27622 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27627 @subheading The @code{-exec-run} Command
27630 @subsubheading Synopsis
27633 -exec-run [ --all | --thread-group N ] [ --start ]
27636 Starts execution of the inferior from the beginning. The inferior
27637 executes until either a breakpoint is encountered or the program
27638 exits. In the latter case the output will include an exit code, if
27639 the program has exited exceptionally.
27641 When neither the @samp{--all} nor the @samp{--thread-group} option
27642 is specified, the current inferior is started. If the
27643 @samp{--thread-group} option is specified, it should refer to a thread
27644 group of type @samp{process}, and that thread group will be started.
27645 If the @samp{--all} option is specified, then all inferiors will be started.
27647 Using the @samp{--start} option instructs the debugger to stop
27648 the execution at the start of the inferior's main subprogram,
27649 following the same behavior as the @code{start} command
27650 (@pxref{Starting}).
27652 @subsubheading @value{GDBN} Command
27654 The corresponding @value{GDBN} command is @samp{run}.
27656 @subsubheading Examples
27661 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
27666 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27667 frame=@{func="main",args=[],file="recursive2.c",
27668 fullname="/home/foo/bar/recursive2.c",line="4"@}
27673 Program exited normally:
27681 *stopped,reason="exited-normally"
27686 Program exited exceptionally:
27694 *stopped,reason="exited",exit-code="01"
27698 Another way the program can terminate is if it receives a signal such as
27699 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
27703 *stopped,reason="exited-signalled",signal-name="SIGINT",
27704 signal-meaning="Interrupt"
27708 @c @subheading -exec-signal
27711 @subheading The @code{-exec-step} Command
27714 @subsubheading Synopsis
27717 -exec-step [--reverse]
27720 Resumes execution of the inferior program, stopping when the beginning
27721 of the next source line is reached, if the next source line is not a
27722 function call. If it is, stop at the first instruction of the called
27723 function. If the @samp{--reverse} option is specified, resumes reverse
27724 execution of the inferior program, stopping at the beginning of the
27725 previously executed source line.
27727 @subsubheading @value{GDBN} Command
27729 The corresponding @value{GDBN} command is @samp{step}.
27731 @subsubheading Example
27733 Stepping into a function:
27739 *stopped,reason="end-stepping-range",
27740 frame=@{func="foo",args=[@{name="a",value="10"@},
27741 @{name="b",value="0"@}],file="recursive2.c",
27742 fullname="/home/foo/bar/recursive2.c",line="11"@}
27752 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
27757 @subheading The @code{-exec-step-instruction} Command
27758 @findex -exec-step-instruction
27760 @subsubheading Synopsis
27763 -exec-step-instruction [--reverse]
27766 Resumes the inferior which executes one machine instruction. If the
27767 @samp{--reverse} option is specified, resumes reverse execution of the
27768 inferior program, stopping at the previously executed instruction.
27769 The output, once @value{GDBN} has stopped, will vary depending on
27770 whether we have stopped in the middle of a source line or not. In the
27771 former case, the address at which the program stopped will be printed
27774 @subsubheading @value{GDBN} Command
27776 The corresponding @value{GDBN} command is @samp{stepi}.
27778 @subsubheading Example
27782 -exec-step-instruction
27786 *stopped,reason="end-stepping-range",
27787 frame=@{func="foo",args=[],file="try.c",
27788 fullname="/home/foo/bar/try.c",line="10"@}
27790 -exec-step-instruction
27794 *stopped,reason="end-stepping-range",
27795 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
27796 fullname="/home/foo/bar/try.c",line="10"@}
27801 @subheading The @code{-exec-until} Command
27802 @findex -exec-until
27804 @subsubheading Synopsis
27807 -exec-until [ @var{location} ]
27810 Executes the inferior until the @var{location} specified in the
27811 argument is reached. If there is no argument, the inferior executes
27812 until a source line greater than the current one is reached. The
27813 reason for stopping in this case will be @samp{location-reached}.
27815 @subsubheading @value{GDBN} Command
27817 The corresponding @value{GDBN} command is @samp{until}.
27819 @subsubheading Example
27823 -exec-until recursive2.c:6
27827 *stopped,reason="location-reached",frame=@{func="main",args=[],
27828 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
27833 @subheading -file-clear
27834 Is this going away????
27837 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27838 @node GDB/MI Stack Manipulation
27839 @section @sc{gdb/mi} Stack Manipulation Commands
27841 @subheading The @code{-enable-frame-filters} Command
27842 @findex -enable-frame-filters
27845 -enable-frame-filters
27848 @value{GDBN} allows Python-based frame filters to affect the output of
27849 the MI commands relating to stack traces. As there is no way to
27850 implement this in a fully backward-compatible way, a front end must
27851 request that this functionality be enabled.
27853 Once enabled, this feature cannot be disabled.
27855 Note that if Python support has not been compiled into @value{GDBN},
27856 this command will still succeed (and do nothing).
27858 @subheading The @code{-stack-info-frame} Command
27859 @findex -stack-info-frame
27861 @subsubheading Synopsis
27867 Get info on the selected frame.
27869 @subsubheading @value{GDBN} Command
27871 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
27872 (without arguments).
27874 @subsubheading Example
27879 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
27880 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27881 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
27885 @subheading The @code{-stack-info-depth} Command
27886 @findex -stack-info-depth
27888 @subsubheading Synopsis
27891 -stack-info-depth [ @var{max-depth} ]
27894 Return the depth of the stack. If the integer argument @var{max-depth}
27895 is specified, do not count beyond @var{max-depth} frames.
27897 @subsubheading @value{GDBN} Command
27899 There's no equivalent @value{GDBN} command.
27901 @subsubheading Example
27903 For a stack with frame levels 0 through 11:
27910 -stack-info-depth 4
27913 -stack-info-depth 12
27916 -stack-info-depth 11
27919 -stack-info-depth 13
27924 @anchor{-stack-list-arguments}
27925 @subheading The @code{-stack-list-arguments} Command
27926 @findex -stack-list-arguments
27928 @subsubheading Synopsis
27931 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
27932 [ @var{low-frame} @var{high-frame} ]
27935 Display a list of the arguments for the frames between @var{low-frame}
27936 and @var{high-frame} (inclusive). If @var{low-frame} and
27937 @var{high-frame} are not provided, list the arguments for the whole
27938 call stack. If the two arguments are equal, show the single frame
27939 at the corresponding level. It is an error if @var{low-frame} is
27940 larger than the actual number of frames. On the other hand,
27941 @var{high-frame} may be larger than the actual number of frames, in
27942 which case only existing frames will be returned.
27944 If @var{print-values} is 0 or @code{--no-values}, print only the names of
27945 the variables; if it is 1 or @code{--all-values}, print also their
27946 values; and if it is 2 or @code{--simple-values}, print the name,
27947 type and value for simple data types, and the name and type for arrays,
27948 structures and unions. If the option @code{--no-frame-filters} is
27949 supplied, then Python frame filters will not be executed.
27951 If the @code{--skip-unavailable} option is specified, arguments that
27952 are not available are not listed. Partially available arguments
27953 are still displayed, however.
27955 Use of this command to obtain arguments in a single frame is
27956 deprecated in favor of the @samp{-stack-list-variables} command.
27958 @subsubheading @value{GDBN} Command
27960 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
27961 @samp{gdb_get_args} command which partially overlaps with the
27962 functionality of @samp{-stack-list-arguments}.
27964 @subsubheading Example
27971 frame=@{level="0",addr="0x00010734",func="callee4",
27972 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27973 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
27974 frame=@{level="1",addr="0x0001076c",func="callee3",
27975 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27976 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
27977 frame=@{level="2",addr="0x0001078c",func="callee2",
27978 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27979 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
27980 frame=@{level="3",addr="0x000107b4",func="callee1",
27981 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27982 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
27983 frame=@{level="4",addr="0x000107e0",func="main",
27984 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27985 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
27987 -stack-list-arguments 0
27990 frame=@{level="0",args=[]@},
27991 frame=@{level="1",args=[name="strarg"]@},
27992 frame=@{level="2",args=[name="intarg",name="strarg"]@},
27993 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
27994 frame=@{level="4",args=[]@}]
27996 -stack-list-arguments 1
27999 frame=@{level="0",args=[]@},
28001 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28002 frame=@{level="2",args=[
28003 @{name="intarg",value="2"@},
28004 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28005 @{frame=@{level="3",args=[
28006 @{name="intarg",value="2"@},
28007 @{name="strarg",value="0x11940 \"A string argument.\""@},
28008 @{name="fltarg",value="3.5"@}]@},
28009 frame=@{level="4",args=[]@}]
28011 -stack-list-arguments 0 2 2
28012 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
28014 -stack-list-arguments 1 2 2
28015 ^done,stack-args=[frame=@{level="2",
28016 args=[@{name="intarg",value="2"@},
28017 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
28021 @c @subheading -stack-list-exception-handlers
28024 @anchor{-stack-list-frames}
28025 @subheading The @code{-stack-list-frames} Command
28026 @findex -stack-list-frames
28028 @subsubheading Synopsis
28031 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
28034 List the frames currently on the stack. For each frame it displays the
28039 The frame number, 0 being the topmost frame, i.e., the innermost function.
28041 The @code{$pc} value for that frame.
28045 File name of the source file where the function lives.
28046 @item @var{fullname}
28047 The full file name of the source file where the function lives.
28049 Line number corresponding to the @code{$pc}.
28051 The shared library where this function is defined. This is only given
28052 if the frame's function is not known.
28055 If invoked without arguments, this command prints a backtrace for the
28056 whole stack. If given two integer arguments, it shows the frames whose
28057 levels are between the two arguments (inclusive). If the two arguments
28058 are equal, it shows the single frame at the corresponding level. It is
28059 an error if @var{low-frame} is larger than the actual number of
28060 frames. On the other hand, @var{high-frame} may be larger than the
28061 actual number of frames, in which case only existing frames will be
28062 returned. If the option @code{--no-frame-filters} is supplied, then
28063 Python frame filters will not be executed.
28065 @subsubheading @value{GDBN} Command
28067 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
28069 @subsubheading Example
28071 Full stack backtrace:
28077 [frame=@{level="0",addr="0x0001076c",func="foo",
28078 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
28079 frame=@{level="1",addr="0x000107a4",func="foo",
28080 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28081 frame=@{level="2",addr="0x000107a4",func="foo",
28082 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28083 frame=@{level="3",addr="0x000107a4",func="foo",
28084 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28085 frame=@{level="4",addr="0x000107a4",func="foo",
28086 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28087 frame=@{level="5",addr="0x000107a4",func="foo",
28088 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28089 frame=@{level="6",addr="0x000107a4",func="foo",
28090 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28091 frame=@{level="7",addr="0x000107a4",func="foo",
28092 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28093 frame=@{level="8",addr="0x000107a4",func="foo",
28094 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28095 frame=@{level="9",addr="0x000107a4",func="foo",
28096 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28097 frame=@{level="10",addr="0x000107a4",func="foo",
28098 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28099 frame=@{level="11",addr="0x00010738",func="main",
28100 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
28104 Show frames between @var{low_frame} and @var{high_frame}:
28108 -stack-list-frames 3 5
28110 [frame=@{level="3",addr="0x000107a4",func="foo",
28111 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28112 frame=@{level="4",addr="0x000107a4",func="foo",
28113 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28114 frame=@{level="5",addr="0x000107a4",func="foo",
28115 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28119 Show a single frame:
28123 -stack-list-frames 3 3
28125 [frame=@{level="3",addr="0x000107a4",func="foo",
28126 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28131 @subheading The @code{-stack-list-locals} Command
28132 @findex -stack-list-locals
28133 @anchor{-stack-list-locals}
28135 @subsubheading Synopsis
28138 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28141 Display the local variable names for the selected frame. If
28142 @var{print-values} is 0 or @code{--no-values}, print only the names of
28143 the variables; if it is 1 or @code{--all-values}, print also their
28144 values; and if it is 2 or @code{--simple-values}, print the name,
28145 type and value for simple data types, and the name and type for arrays,
28146 structures and unions. In this last case, a frontend can immediately
28147 display the value of simple data types and create variable objects for
28148 other data types when the user wishes to explore their values in
28149 more detail. If the option @code{--no-frame-filters} is supplied, then
28150 Python frame filters will not be executed.
28152 If the @code{--skip-unavailable} option is specified, local variables
28153 that are not available are not listed. Partially available local
28154 variables are still displayed, however.
28156 This command is deprecated in favor of the
28157 @samp{-stack-list-variables} command.
28159 @subsubheading @value{GDBN} Command
28161 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
28163 @subsubheading Example
28167 -stack-list-locals 0
28168 ^done,locals=[name="A",name="B",name="C"]
28170 -stack-list-locals --all-values
28171 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
28172 @{name="C",value="@{1, 2, 3@}"@}]
28173 -stack-list-locals --simple-values
28174 ^done,locals=[@{name="A",type="int",value="1"@},
28175 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
28179 @anchor{-stack-list-variables}
28180 @subheading The @code{-stack-list-variables} Command
28181 @findex -stack-list-variables
28183 @subsubheading Synopsis
28186 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28189 Display the names of local variables and function arguments for the selected frame. If
28190 @var{print-values} is 0 or @code{--no-values}, print only the names of
28191 the variables; if it is 1 or @code{--all-values}, print also their
28192 values; and if it is 2 or @code{--simple-values}, print the name,
28193 type and value for simple data types, and the name and type for arrays,
28194 structures and unions. If the option @code{--no-frame-filters} is
28195 supplied, then Python frame filters will not be executed.
28197 If the @code{--skip-unavailable} option is specified, local variables
28198 and arguments that are not available are not listed. Partially
28199 available arguments and local variables are still displayed, however.
28201 @subsubheading Example
28205 -stack-list-variables --thread 1 --frame 0 --all-values
28206 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
28211 @subheading The @code{-stack-select-frame} Command
28212 @findex -stack-select-frame
28214 @subsubheading Synopsis
28217 -stack-select-frame @var{framenum}
28220 Change the selected frame. Select a different frame @var{framenum} on
28223 This command in deprecated in favor of passing the @samp{--frame}
28224 option to every command.
28226 @subsubheading @value{GDBN} Command
28228 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
28229 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
28231 @subsubheading Example
28235 -stack-select-frame 2
28240 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28241 @node GDB/MI Variable Objects
28242 @section @sc{gdb/mi} Variable Objects
28246 @subheading Motivation for Variable Objects in @sc{gdb/mi}
28248 For the implementation of a variable debugger window (locals, watched
28249 expressions, etc.), we are proposing the adaptation of the existing code
28250 used by @code{Insight}.
28252 The two main reasons for that are:
28256 It has been proven in practice (it is already on its second generation).
28259 It will shorten development time (needless to say how important it is
28263 The original interface was designed to be used by Tcl code, so it was
28264 slightly changed so it could be used through @sc{gdb/mi}. This section
28265 describes the @sc{gdb/mi} operations that will be available and gives some
28266 hints about their use.
28268 @emph{Note}: In addition to the set of operations described here, we
28269 expect the @sc{gui} implementation of a variable window to require, at
28270 least, the following operations:
28273 @item @code{-gdb-show} @code{output-radix}
28274 @item @code{-stack-list-arguments}
28275 @item @code{-stack-list-locals}
28276 @item @code{-stack-select-frame}
28281 @subheading Introduction to Variable Objects
28283 @cindex variable objects in @sc{gdb/mi}
28285 Variable objects are "object-oriented" MI interface for examining and
28286 changing values of expressions. Unlike some other MI interfaces that
28287 work with expressions, variable objects are specifically designed for
28288 simple and efficient presentation in the frontend. A variable object
28289 is identified by string name. When a variable object is created, the
28290 frontend specifies the expression for that variable object. The
28291 expression can be a simple variable, or it can be an arbitrary complex
28292 expression, and can even involve CPU registers. After creating a
28293 variable object, the frontend can invoke other variable object
28294 operations---for example to obtain or change the value of a variable
28295 object, or to change display format.
28297 Variable objects have hierarchical tree structure. Any variable object
28298 that corresponds to a composite type, such as structure in C, has
28299 a number of child variable objects, for example corresponding to each
28300 element of a structure. A child variable object can itself have
28301 children, recursively. Recursion ends when we reach
28302 leaf variable objects, which always have built-in types. Child variable
28303 objects are created only by explicit request, so if a frontend
28304 is not interested in the children of a particular variable object, no
28305 child will be created.
28307 For a leaf variable object it is possible to obtain its value as a
28308 string, or set the value from a string. String value can be also
28309 obtained for a non-leaf variable object, but it's generally a string
28310 that only indicates the type of the object, and does not list its
28311 contents. Assignment to a non-leaf variable object is not allowed.
28313 A frontend does not need to read the values of all variable objects each time
28314 the program stops. Instead, MI provides an update command that lists all
28315 variable objects whose values has changed since the last update
28316 operation. This considerably reduces the amount of data that must
28317 be transferred to the frontend. As noted above, children variable
28318 objects are created on demand, and only leaf variable objects have a
28319 real value. As result, gdb will read target memory only for leaf
28320 variables that frontend has created.
28322 The automatic update is not always desirable. For example, a frontend
28323 might want to keep a value of some expression for future reference,
28324 and never update it. For another example, fetching memory is
28325 relatively slow for embedded targets, so a frontend might want
28326 to disable automatic update for the variables that are either not
28327 visible on the screen, or ``closed''. This is possible using so
28328 called ``frozen variable objects''. Such variable objects are never
28329 implicitly updated.
28331 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
28332 fixed variable object, the expression is parsed when the variable
28333 object is created, including associating identifiers to specific
28334 variables. The meaning of expression never changes. For a floating
28335 variable object the values of variables whose names appear in the
28336 expressions are re-evaluated every time in the context of the current
28337 frame. Consider this example:
28342 struct work_state state;
28349 If a fixed variable object for the @code{state} variable is created in
28350 this function, and we enter the recursive call, the variable
28351 object will report the value of @code{state} in the top-level
28352 @code{do_work} invocation. On the other hand, a floating variable
28353 object will report the value of @code{state} in the current frame.
28355 If an expression specified when creating a fixed variable object
28356 refers to a local variable, the variable object becomes bound to the
28357 thread and frame in which the variable object is created. When such
28358 variable object is updated, @value{GDBN} makes sure that the
28359 thread/frame combination the variable object is bound to still exists,
28360 and re-evaluates the variable object in context of that thread/frame.
28362 The following is the complete set of @sc{gdb/mi} operations defined to
28363 access this functionality:
28365 @multitable @columnfractions .4 .6
28366 @item @strong{Operation}
28367 @tab @strong{Description}
28369 @item @code{-enable-pretty-printing}
28370 @tab enable Python-based pretty-printing
28371 @item @code{-var-create}
28372 @tab create a variable object
28373 @item @code{-var-delete}
28374 @tab delete the variable object and/or its children
28375 @item @code{-var-set-format}
28376 @tab set the display format of this variable
28377 @item @code{-var-show-format}
28378 @tab show the display format of this variable
28379 @item @code{-var-info-num-children}
28380 @tab tells how many children this object has
28381 @item @code{-var-list-children}
28382 @tab return a list of the object's children
28383 @item @code{-var-info-type}
28384 @tab show the type of this variable object
28385 @item @code{-var-info-expression}
28386 @tab print parent-relative expression that this variable object represents
28387 @item @code{-var-info-path-expression}
28388 @tab print full expression that this variable object represents
28389 @item @code{-var-show-attributes}
28390 @tab is this variable editable? does it exist here?
28391 @item @code{-var-evaluate-expression}
28392 @tab get the value of this variable
28393 @item @code{-var-assign}
28394 @tab set the value of this variable
28395 @item @code{-var-update}
28396 @tab update the variable and its children
28397 @item @code{-var-set-frozen}
28398 @tab set frozeness attribute
28399 @item @code{-var-set-update-range}
28400 @tab set range of children to display on update
28403 In the next subsection we describe each operation in detail and suggest
28404 how it can be used.
28406 @subheading Description And Use of Operations on Variable Objects
28408 @subheading The @code{-enable-pretty-printing} Command
28409 @findex -enable-pretty-printing
28412 -enable-pretty-printing
28415 @value{GDBN} allows Python-based visualizers to affect the output of the
28416 MI variable object commands. However, because there was no way to
28417 implement this in a fully backward-compatible way, a front end must
28418 request that this functionality be enabled.
28420 Once enabled, this feature cannot be disabled.
28422 Note that if Python support has not been compiled into @value{GDBN},
28423 this command will still succeed (and do nothing).
28425 This feature is currently (as of @value{GDBN} 7.0) experimental, and
28426 may work differently in future versions of @value{GDBN}.
28428 @subheading The @code{-var-create} Command
28429 @findex -var-create
28431 @subsubheading Synopsis
28434 -var-create @{@var{name} | "-"@}
28435 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
28438 This operation creates a variable object, which allows the monitoring of
28439 a variable, the result of an expression, a memory cell or a CPU
28442 The @var{name} parameter is the string by which the object can be
28443 referenced. It must be unique. If @samp{-} is specified, the varobj
28444 system will generate a string ``varNNNNNN'' automatically. It will be
28445 unique provided that one does not specify @var{name} of that format.
28446 The command fails if a duplicate name is found.
28448 The frame under which the expression should be evaluated can be
28449 specified by @var{frame-addr}. A @samp{*} indicates that the current
28450 frame should be used. A @samp{@@} indicates that a floating variable
28451 object must be created.
28453 @var{expression} is any expression valid on the current language set (must not
28454 begin with a @samp{*}), or one of the following:
28458 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
28461 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
28464 @samp{$@var{regname}} --- a CPU register name
28467 @cindex dynamic varobj
28468 A varobj's contents may be provided by a Python-based pretty-printer. In this
28469 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
28470 have slightly different semantics in some cases. If the
28471 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
28472 will never create a dynamic varobj. This ensures backward
28473 compatibility for existing clients.
28475 @subsubheading Result
28477 This operation returns attributes of the newly-created varobj. These
28482 The name of the varobj.
28485 The number of children of the varobj. This number is not necessarily
28486 reliable for a dynamic varobj. Instead, you must examine the
28487 @samp{has_more} attribute.
28490 The varobj's scalar value. For a varobj whose type is some sort of
28491 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
28492 will not be interesting.
28495 The varobj's type. This is a string representation of the type, as
28496 would be printed by the @value{GDBN} CLI. If @samp{print object}
28497 (@pxref{Print Settings, set print object}) is set to @code{on}, the
28498 @emph{actual} (derived) type of the object is shown rather than the
28499 @emph{declared} one.
28502 If a variable object is bound to a specific thread, then this is the
28503 thread's identifier.
28506 For a dynamic varobj, this indicates whether there appear to be any
28507 children available. For a non-dynamic varobj, this will be 0.
28510 This attribute will be present and have the value @samp{1} if the
28511 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28512 then this attribute will not be present.
28515 A dynamic varobj can supply a display hint to the front end. The
28516 value comes directly from the Python pretty-printer object's
28517 @code{display_hint} method. @xref{Pretty Printing API}.
28520 Typical output will look like this:
28523 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
28524 has_more="@var{has_more}"
28528 @subheading The @code{-var-delete} Command
28529 @findex -var-delete
28531 @subsubheading Synopsis
28534 -var-delete [ -c ] @var{name}
28537 Deletes a previously created variable object and all of its children.
28538 With the @samp{-c} option, just deletes the children.
28540 Returns an error if the object @var{name} is not found.
28543 @subheading The @code{-var-set-format} Command
28544 @findex -var-set-format
28546 @subsubheading Synopsis
28549 -var-set-format @var{name} @var{format-spec}
28552 Sets the output format for the value of the object @var{name} to be
28555 @anchor{-var-set-format}
28556 The syntax for the @var{format-spec} is as follows:
28559 @var{format-spec} @expansion{}
28560 @{binary | decimal | hexadecimal | octal | natural@}
28563 The natural format is the default format choosen automatically
28564 based on the variable type (like decimal for an @code{int}, hex
28565 for pointers, etc.).
28567 For a variable with children, the format is set only on the
28568 variable itself, and the children are not affected.
28570 @subheading The @code{-var-show-format} Command
28571 @findex -var-show-format
28573 @subsubheading Synopsis
28576 -var-show-format @var{name}
28579 Returns the format used to display the value of the object @var{name}.
28582 @var{format} @expansion{}
28587 @subheading The @code{-var-info-num-children} Command
28588 @findex -var-info-num-children
28590 @subsubheading Synopsis
28593 -var-info-num-children @var{name}
28596 Returns the number of children of a variable object @var{name}:
28602 Note that this number is not completely reliable for a dynamic varobj.
28603 It will return the current number of children, but more children may
28607 @subheading The @code{-var-list-children} Command
28608 @findex -var-list-children
28610 @subsubheading Synopsis
28613 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
28615 @anchor{-var-list-children}
28617 Return a list of the children of the specified variable object and
28618 create variable objects for them, if they do not already exist. With
28619 a single argument or if @var{print-values} has a value of 0 or
28620 @code{--no-values}, print only the names of the variables; if
28621 @var{print-values} is 1 or @code{--all-values}, also print their
28622 values; and if it is 2 or @code{--simple-values} print the name and
28623 value for simple data types and just the name for arrays, structures
28626 @var{from} and @var{to}, if specified, indicate the range of children
28627 to report. If @var{from} or @var{to} is less than zero, the range is
28628 reset and all children will be reported. Otherwise, children starting
28629 at @var{from} (zero-based) and up to and excluding @var{to} will be
28632 If a child range is requested, it will only affect the current call to
28633 @code{-var-list-children}, but not future calls to @code{-var-update}.
28634 For this, you must instead use @code{-var-set-update-range}. The
28635 intent of this approach is to enable a front end to implement any
28636 update approach it likes; for example, scrolling a view may cause the
28637 front end to request more children with @code{-var-list-children}, and
28638 then the front end could call @code{-var-set-update-range} with a
28639 different range to ensure that future updates are restricted to just
28642 For each child the following results are returned:
28647 Name of the variable object created for this child.
28650 The expression to be shown to the user by the front end to designate this child.
28651 For example this may be the name of a structure member.
28653 For a dynamic varobj, this value cannot be used to form an
28654 expression. There is no way to do this at all with a dynamic varobj.
28656 For C/C@t{++} structures there are several pseudo children returned to
28657 designate access qualifiers. For these pseudo children @var{exp} is
28658 @samp{public}, @samp{private}, or @samp{protected}. In this case the
28659 type and value are not present.
28661 A dynamic varobj will not report the access qualifying
28662 pseudo-children, regardless of the language. This information is not
28663 available at all with a dynamic varobj.
28666 Number of children this child has. For a dynamic varobj, this will be
28670 The type of the child. If @samp{print object}
28671 (@pxref{Print Settings, set print object}) is set to @code{on}, the
28672 @emph{actual} (derived) type of the object is shown rather than the
28673 @emph{declared} one.
28676 If values were requested, this is the value.
28679 If this variable object is associated with a thread, this is the thread id.
28680 Otherwise this result is not present.
28683 If the variable object is frozen, this variable will be present with a value of 1.
28686 A dynamic varobj can supply a display hint to the front end. The
28687 value comes directly from the Python pretty-printer object's
28688 @code{display_hint} method. @xref{Pretty Printing API}.
28691 This attribute will be present and have the value @samp{1} if the
28692 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28693 then this attribute will not be present.
28697 The result may have its own attributes:
28701 A dynamic varobj can supply a display hint to the front end. The
28702 value comes directly from the Python pretty-printer object's
28703 @code{display_hint} method. @xref{Pretty Printing API}.
28706 This is an integer attribute which is nonzero if there are children
28707 remaining after the end of the selected range.
28710 @subsubheading Example
28714 -var-list-children n
28715 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28716 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
28718 -var-list-children --all-values n
28719 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28720 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
28724 @subheading The @code{-var-info-type} Command
28725 @findex -var-info-type
28727 @subsubheading Synopsis
28730 -var-info-type @var{name}
28733 Returns the type of the specified variable @var{name}. The type is
28734 returned as a string in the same format as it is output by the
28738 type=@var{typename}
28742 @subheading The @code{-var-info-expression} Command
28743 @findex -var-info-expression
28745 @subsubheading Synopsis
28748 -var-info-expression @var{name}
28751 Returns a string that is suitable for presenting this
28752 variable object in user interface. The string is generally
28753 not valid expression in the current language, and cannot be evaluated.
28755 For example, if @code{a} is an array, and variable object
28756 @code{A} was created for @code{a}, then we'll get this output:
28759 (gdb) -var-info-expression A.1
28760 ^done,lang="C",exp="1"
28764 Here, the value of @code{lang} is the language name, which can be
28765 found in @ref{Supported Languages}.
28767 Note that the output of the @code{-var-list-children} command also
28768 includes those expressions, so the @code{-var-info-expression} command
28771 @subheading The @code{-var-info-path-expression} Command
28772 @findex -var-info-path-expression
28774 @subsubheading Synopsis
28777 -var-info-path-expression @var{name}
28780 Returns an expression that can be evaluated in the current
28781 context and will yield the same value that a variable object has.
28782 Compare this with the @code{-var-info-expression} command, which
28783 result can be used only for UI presentation. Typical use of
28784 the @code{-var-info-path-expression} command is creating a
28785 watchpoint from a variable object.
28787 This command is currently not valid for children of a dynamic varobj,
28788 and will give an error when invoked on one.
28790 For example, suppose @code{C} is a C@t{++} class, derived from class
28791 @code{Base}, and that the @code{Base} class has a member called
28792 @code{m_size}. Assume a variable @code{c} is has the type of
28793 @code{C} and a variable object @code{C} was created for variable
28794 @code{c}. Then, we'll get this output:
28796 (gdb) -var-info-path-expression C.Base.public.m_size
28797 ^done,path_expr=((Base)c).m_size)
28800 @subheading The @code{-var-show-attributes} Command
28801 @findex -var-show-attributes
28803 @subsubheading Synopsis
28806 -var-show-attributes @var{name}
28809 List attributes of the specified variable object @var{name}:
28812 status=@var{attr} [ ( ,@var{attr} )* ]
28816 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
28818 @subheading The @code{-var-evaluate-expression} Command
28819 @findex -var-evaluate-expression
28821 @subsubheading Synopsis
28824 -var-evaluate-expression [-f @var{format-spec}] @var{name}
28827 Evaluates the expression that is represented by the specified variable
28828 object and returns its value as a string. The format of the string
28829 can be specified with the @samp{-f} option. The possible values of
28830 this option are the same as for @code{-var-set-format}
28831 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
28832 the current display format will be used. The current display format
28833 can be changed using the @code{-var-set-format} command.
28839 Note that one must invoke @code{-var-list-children} for a variable
28840 before the value of a child variable can be evaluated.
28842 @subheading The @code{-var-assign} Command
28843 @findex -var-assign
28845 @subsubheading Synopsis
28848 -var-assign @var{name} @var{expression}
28851 Assigns the value of @var{expression} to the variable object specified
28852 by @var{name}. The object must be @samp{editable}. If the variable's
28853 value is altered by the assign, the variable will show up in any
28854 subsequent @code{-var-update} list.
28856 @subsubheading Example
28864 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
28868 @subheading The @code{-var-update} Command
28869 @findex -var-update
28871 @subsubheading Synopsis
28874 -var-update [@var{print-values}] @{@var{name} | "*"@}
28877 Reevaluate the expressions corresponding to the variable object
28878 @var{name} and all its direct and indirect children, and return the
28879 list of variable objects whose values have changed; @var{name} must
28880 be a root variable object. Here, ``changed'' means that the result of
28881 @code{-var-evaluate-expression} before and after the
28882 @code{-var-update} is different. If @samp{*} is used as the variable
28883 object names, all existing variable objects are updated, except
28884 for frozen ones (@pxref{-var-set-frozen}). The option
28885 @var{print-values} determines whether both names and values, or just
28886 names are printed. The possible values of this option are the same
28887 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
28888 recommended to use the @samp{--all-values} option, to reduce the
28889 number of MI commands needed on each program stop.
28891 With the @samp{*} parameter, if a variable object is bound to a
28892 currently running thread, it will not be updated, without any
28895 If @code{-var-set-update-range} was previously used on a varobj, then
28896 only the selected range of children will be reported.
28898 @code{-var-update} reports all the changed varobjs in a tuple named
28901 Each item in the change list is itself a tuple holding:
28905 The name of the varobj.
28908 If values were requested for this update, then this field will be
28909 present and will hold the value of the varobj.
28912 @anchor{-var-update}
28913 This field is a string which may take one of three values:
28917 The variable object's current value is valid.
28920 The variable object does not currently hold a valid value but it may
28921 hold one in the future if its associated expression comes back into
28925 The variable object no longer holds a valid value.
28926 This can occur when the executable file being debugged has changed,
28927 either through recompilation or by using the @value{GDBN} @code{file}
28928 command. The front end should normally choose to delete these variable
28932 In the future new values may be added to this list so the front should
28933 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
28936 This is only present if the varobj is still valid. If the type
28937 changed, then this will be the string @samp{true}; otherwise it will
28940 When a varobj's type changes, its children are also likely to have
28941 become incorrect. Therefore, the varobj's children are automatically
28942 deleted when this attribute is @samp{true}. Also, the varobj's update
28943 range, when set using the @code{-var-set-update-range} command, is
28947 If the varobj's type changed, then this field will be present and will
28950 @item new_num_children
28951 For a dynamic varobj, if the number of children changed, or if the
28952 type changed, this will be the new number of children.
28954 The @samp{numchild} field in other varobj responses is generally not
28955 valid for a dynamic varobj -- it will show the number of children that
28956 @value{GDBN} knows about, but because dynamic varobjs lazily
28957 instantiate their children, this will not reflect the number of
28958 children which may be available.
28960 The @samp{new_num_children} attribute only reports changes to the
28961 number of children known by @value{GDBN}. This is the only way to
28962 detect whether an update has removed children (which necessarily can
28963 only happen at the end of the update range).
28966 The display hint, if any.
28969 This is an integer value, which will be 1 if there are more children
28970 available outside the varobj's update range.
28973 This attribute will be present and have the value @samp{1} if the
28974 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28975 then this attribute will not be present.
28978 If new children were added to a dynamic varobj within the selected
28979 update range (as set by @code{-var-set-update-range}), then they will
28980 be listed in this attribute.
28983 @subsubheading Example
28990 -var-update --all-values var1
28991 ^done,changelist=[@{name="var1",value="3",in_scope="true",
28992 type_changed="false"@}]
28996 @subheading The @code{-var-set-frozen} Command
28997 @findex -var-set-frozen
28998 @anchor{-var-set-frozen}
29000 @subsubheading Synopsis
29003 -var-set-frozen @var{name} @var{flag}
29006 Set the frozenness flag on the variable object @var{name}. The
29007 @var{flag} parameter should be either @samp{1} to make the variable
29008 frozen or @samp{0} to make it unfrozen. If a variable object is
29009 frozen, then neither itself, nor any of its children, are
29010 implicitly updated by @code{-var-update} of
29011 a parent variable or by @code{-var-update *}. Only
29012 @code{-var-update} of the variable itself will update its value and
29013 values of its children. After a variable object is unfrozen, it is
29014 implicitly updated by all subsequent @code{-var-update} operations.
29015 Unfreezing a variable does not update it, only subsequent
29016 @code{-var-update} does.
29018 @subsubheading Example
29022 -var-set-frozen V 1
29027 @subheading The @code{-var-set-update-range} command
29028 @findex -var-set-update-range
29029 @anchor{-var-set-update-range}
29031 @subsubheading Synopsis
29034 -var-set-update-range @var{name} @var{from} @var{to}
29037 Set the range of children to be returned by future invocations of
29038 @code{-var-update}.
29040 @var{from} and @var{to} indicate the range of children to report. If
29041 @var{from} or @var{to} is less than zero, the range is reset and all
29042 children will be reported. Otherwise, children starting at @var{from}
29043 (zero-based) and up to and excluding @var{to} will be reported.
29045 @subsubheading Example
29049 -var-set-update-range V 1 2
29053 @subheading The @code{-var-set-visualizer} command
29054 @findex -var-set-visualizer
29055 @anchor{-var-set-visualizer}
29057 @subsubheading Synopsis
29060 -var-set-visualizer @var{name} @var{visualizer}
29063 Set a visualizer for the variable object @var{name}.
29065 @var{visualizer} is the visualizer to use. The special value
29066 @samp{None} means to disable any visualizer in use.
29068 If not @samp{None}, @var{visualizer} must be a Python expression.
29069 This expression must evaluate to a callable object which accepts a
29070 single argument. @value{GDBN} will call this object with the value of
29071 the varobj @var{name} as an argument (this is done so that the same
29072 Python pretty-printing code can be used for both the CLI and MI).
29073 When called, this object must return an object which conforms to the
29074 pretty-printing interface (@pxref{Pretty Printing API}).
29076 The pre-defined function @code{gdb.default_visualizer} may be used to
29077 select a visualizer by following the built-in process
29078 (@pxref{Selecting Pretty-Printers}). This is done automatically when
29079 a varobj is created, and so ordinarily is not needed.
29081 This feature is only available if Python support is enabled. The MI
29082 command @code{-list-features} (@pxref{GDB/MI Support Commands})
29083 can be used to check this.
29085 @subsubheading Example
29087 Resetting the visualizer:
29091 -var-set-visualizer V None
29095 Reselecting the default (type-based) visualizer:
29099 -var-set-visualizer V gdb.default_visualizer
29103 Suppose @code{SomeClass} is a visualizer class. A lambda expression
29104 can be used to instantiate this class for a varobj:
29108 -var-set-visualizer V "lambda val: SomeClass()"
29112 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29113 @node GDB/MI Data Manipulation
29114 @section @sc{gdb/mi} Data Manipulation
29116 @cindex data manipulation, in @sc{gdb/mi}
29117 @cindex @sc{gdb/mi}, data manipulation
29118 This section describes the @sc{gdb/mi} commands that manipulate data:
29119 examine memory and registers, evaluate expressions, etc.
29121 @c REMOVED FROM THE INTERFACE.
29122 @c @subheading -data-assign
29123 @c Change the value of a program variable. Plenty of side effects.
29124 @c @subsubheading GDB Command
29126 @c @subsubheading Example
29129 @subheading The @code{-data-disassemble} Command
29130 @findex -data-disassemble
29132 @subsubheading Synopsis
29136 [ -s @var{start-addr} -e @var{end-addr} ]
29137 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
29145 @item @var{start-addr}
29146 is the beginning address (or @code{$pc})
29147 @item @var{end-addr}
29149 @item @var{filename}
29150 is the name of the file to disassemble
29151 @item @var{linenum}
29152 is the line number to disassemble around
29154 is the number of disassembly lines to be produced. If it is -1,
29155 the whole function will be disassembled, in case no @var{end-addr} is
29156 specified. If @var{end-addr} is specified as a non-zero value, and
29157 @var{lines} is lower than the number of disassembly lines between
29158 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
29159 displayed; if @var{lines} is higher than the number of lines between
29160 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
29163 is either 0 (meaning only disassembly), 1 (meaning mixed source and
29164 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
29165 mixed source and disassembly with raw opcodes).
29168 @subsubheading Result
29170 The result of the @code{-data-disassemble} command will be a list named
29171 @samp{asm_insns}, the contents of this list depend on the @var{mode}
29172 used with the @code{-data-disassemble} command.
29174 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
29179 The address at which this instruction was disassembled.
29182 The name of the function this instruction is within.
29185 The decimal offset in bytes from the start of @samp{func-name}.
29188 The text disassembly for this @samp{address}.
29191 This field is only present for mode 2. This contains the raw opcode
29192 bytes for the @samp{inst} field.
29196 For modes 1 and 3 the @samp{asm_insns} list contains tuples named
29197 @samp{src_and_asm_line}, each of which has the following fields:
29201 The line number within @samp{file}.
29204 The file name from the compilation unit. This might be an absolute
29205 file name or a relative file name depending on the compile command
29209 Absolute file name of @samp{file}. It is converted to a canonical form
29210 using the source file search path
29211 (@pxref{Source Path, ,Specifying Source Directories})
29212 and after resolving all the symbolic links.
29214 If the source file is not found this field will contain the path as
29215 present in the debug information.
29217 @item line_asm_insn
29218 This is a list of tuples containing the disassembly for @samp{line} in
29219 @samp{file}. The fields of each tuple are the same as for
29220 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
29221 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
29226 Note that whatever included in the @samp{inst} field, is not
29227 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
29230 @subsubheading @value{GDBN} Command
29232 The corresponding @value{GDBN} command is @samp{disassemble}.
29234 @subsubheading Example
29236 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
29240 -data-disassemble -s $pc -e "$pc + 20" -- 0
29243 @{address="0x000107c0",func-name="main",offset="4",
29244 inst="mov 2, %o0"@},
29245 @{address="0x000107c4",func-name="main",offset="8",
29246 inst="sethi %hi(0x11800), %o2"@},
29247 @{address="0x000107c8",func-name="main",offset="12",
29248 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
29249 @{address="0x000107cc",func-name="main",offset="16",
29250 inst="sethi %hi(0x11800), %o2"@},
29251 @{address="0x000107d0",func-name="main",offset="20",
29252 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
29256 Disassemble the whole @code{main} function. Line 32 is part of
29260 -data-disassemble -f basics.c -l 32 -- 0
29262 @{address="0x000107bc",func-name="main",offset="0",
29263 inst="save %sp, -112, %sp"@},
29264 @{address="0x000107c0",func-name="main",offset="4",
29265 inst="mov 2, %o0"@},
29266 @{address="0x000107c4",func-name="main",offset="8",
29267 inst="sethi %hi(0x11800), %o2"@},
29269 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
29270 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
29274 Disassemble 3 instructions from the start of @code{main}:
29278 -data-disassemble -f basics.c -l 32 -n 3 -- 0
29280 @{address="0x000107bc",func-name="main",offset="0",
29281 inst="save %sp, -112, %sp"@},
29282 @{address="0x000107c0",func-name="main",offset="4",
29283 inst="mov 2, %o0"@},
29284 @{address="0x000107c4",func-name="main",offset="8",
29285 inst="sethi %hi(0x11800), %o2"@}]
29289 Disassemble 3 instructions from the start of @code{main} in mixed mode:
29293 -data-disassemble -f basics.c -l 32 -n 3 -- 1
29295 src_and_asm_line=@{line="31",
29296 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
29297 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
29298 line_asm_insn=[@{address="0x000107bc",
29299 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
29300 src_and_asm_line=@{line="32",
29301 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
29302 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
29303 line_asm_insn=[@{address="0x000107c0",
29304 func-name="main",offset="4",inst="mov 2, %o0"@},
29305 @{address="0x000107c4",func-name="main",offset="8",
29306 inst="sethi %hi(0x11800), %o2"@}]@}]
29311 @subheading The @code{-data-evaluate-expression} Command
29312 @findex -data-evaluate-expression
29314 @subsubheading Synopsis
29317 -data-evaluate-expression @var{expr}
29320 Evaluate @var{expr} as an expression. The expression could contain an
29321 inferior function call. The function call will execute synchronously.
29322 If the expression contains spaces, it must be enclosed in double quotes.
29324 @subsubheading @value{GDBN} Command
29326 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
29327 @samp{call}. In @code{gdbtk} only, there's a corresponding
29328 @samp{gdb_eval} command.
29330 @subsubheading Example
29332 In the following example, the numbers that precede the commands are the
29333 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
29334 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
29338 211-data-evaluate-expression A
29341 311-data-evaluate-expression &A
29342 311^done,value="0xefffeb7c"
29344 411-data-evaluate-expression A+3
29347 511-data-evaluate-expression "A + 3"
29353 @subheading The @code{-data-list-changed-registers} Command
29354 @findex -data-list-changed-registers
29356 @subsubheading Synopsis
29359 -data-list-changed-registers
29362 Display a list of the registers that have changed.
29364 @subsubheading @value{GDBN} Command
29366 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
29367 has the corresponding command @samp{gdb_changed_register_list}.
29369 @subsubheading Example
29371 On a PPC MBX board:
29379 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
29380 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
29383 -data-list-changed-registers
29384 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
29385 "10","11","13","14","15","16","17","18","19","20","21","22","23",
29386 "24","25","26","27","28","30","31","64","65","66","67","69"]
29391 @subheading The @code{-data-list-register-names} Command
29392 @findex -data-list-register-names
29394 @subsubheading Synopsis
29397 -data-list-register-names [ ( @var{regno} )+ ]
29400 Show a list of register names for the current target. If no arguments
29401 are given, it shows a list of the names of all the registers. If
29402 integer numbers are given as arguments, it will print a list of the
29403 names of the registers corresponding to the arguments. To ensure
29404 consistency between a register name and its number, the output list may
29405 include empty register names.
29407 @subsubheading @value{GDBN} Command
29409 @value{GDBN} does not have a command which corresponds to
29410 @samp{-data-list-register-names}. In @code{gdbtk} there is a
29411 corresponding command @samp{gdb_regnames}.
29413 @subsubheading Example
29415 For the PPC MBX board:
29418 -data-list-register-names
29419 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
29420 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
29421 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
29422 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
29423 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
29424 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
29425 "", "pc","ps","cr","lr","ctr","xer"]
29427 -data-list-register-names 1 2 3
29428 ^done,register-names=["r1","r2","r3"]
29432 @subheading The @code{-data-list-register-values} Command
29433 @findex -data-list-register-values
29435 @subsubheading Synopsis
29438 -data-list-register-values
29439 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
29442 Display the registers' contents. The format according to which the
29443 registers' contents are to be returned is given by @var{fmt}, followed
29444 by an optional list of numbers specifying the registers to display. A
29445 missing list of numbers indicates that the contents of all the
29446 registers must be returned. The @code{--skip-unavailable} option
29447 indicates that only the available registers are to be returned.
29449 Allowed formats for @var{fmt} are:
29466 @subsubheading @value{GDBN} Command
29468 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
29469 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
29471 @subsubheading Example
29473 For a PPC MBX board (note: line breaks are for readability only, they
29474 don't appear in the actual output):
29478 -data-list-register-values r 64 65
29479 ^done,register-values=[@{number="64",value="0xfe00a300"@},
29480 @{number="65",value="0x00029002"@}]
29482 -data-list-register-values x
29483 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
29484 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
29485 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
29486 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
29487 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
29488 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
29489 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
29490 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
29491 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
29492 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
29493 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
29494 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
29495 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
29496 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
29497 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
29498 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
29499 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
29500 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
29501 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
29502 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
29503 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
29504 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
29505 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
29506 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
29507 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
29508 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
29509 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
29510 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
29511 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
29512 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
29513 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
29514 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
29515 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
29516 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
29517 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
29518 @{number="69",value="0x20002b03"@}]
29523 @subheading The @code{-data-read-memory} Command
29524 @findex -data-read-memory
29526 This command is deprecated, use @code{-data-read-memory-bytes} instead.
29528 @subsubheading Synopsis
29531 -data-read-memory [ -o @var{byte-offset} ]
29532 @var{address} @var{word-format} @var{word-size}
29533 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
29540 @item @var{address}
29541 An expression specifying the address of the first memory word to be
29542 read. Complex expressions containing embedded white space should be
29543 quoted using the C convention.
29545 @item @var{word-format}
29546 The format to be used to print the memory words. The notation is the
29547 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
29550 @item @var{word-size}
29551 The size of each memory word in bytes.
29553 @item @var{nr-rows}
29554 The number of rows in the output table.
29556 @item @var{nr-cols}
29557 The number of columns in the output table.
29560 If present, indicates that each row should include an @sc{ascii} dump. The
29561 value of @var{aschar} is used as a padding character when a byte is not a
29562 member of the printable @sc{ascii} character set (printable @sc{ascii}
29563 characters are those whose code is between 32 and 126, inclusively).
29565 @item @var{byte-offset}
29566 An offset to add to the @var{address} before fetching memory.
29569 This command displays memory contents as a table of @var{nr-rows} by
29570 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
29571 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
29572 (returned as @samp{total-bytes}). Should less than the requested number
29573 of bytes be returned by the target, the missing words are identified
29574 using @samp{N/A}. The number of bytes read from the target is returned
29575 in @samp{nr-bytes} and the starting address used to read memory in
29578 The address of the next/previous row or page is available in
29579 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
29582 @subsubheading @value{GDBN} Command
29584 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
29585 @samp{gdb_get_mem} memory read command.
29587 @subsubheading Example
29589 Read six bytes of memory starting at @code{bytes+6} but then offset by
29590 @code{-6} bytes. Format as three rows of two columns. One byte per
29591 word. Display each word in hex.
29595 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
29596 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
29597 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
29598 prev-page="0x0000138a",memory=[
29599 @{addr="0x00001390",data=["0x00","0x01"]@},
29600 @{addr="0x00001392",data=["0x02","0x03"]@},
29601 @{addr="0x00001394",data=["0x04","0x05"]@}]
29605 Read two bytes of memory starting at address @code{shorts + 64} and
29606 display as a single word formatted in decimal.
29610 5-data-read-memory shorts+64 d 2 1 1
29611 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
29612 next-row="0x00001512",prev-row="0x0000150e",
29613 next-page="0x00001512",prev-page="0x0000150e",memory=[
29614 @{addr="0x00001510",data=["128"]@}]
29618 Read thirty two bytes of memory starting at @code{bytes+16} and format
29619 as eight rows of four columns. Include a string encoding with @samp{x}
29620 used as the non-printable character.
29624 4-data-read-memory bytes+16 x 1 8 4 x
29625 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
29626 next-row="0x000013c0",prev-row="0x0000139c",
29627 next-page="0x000013c0",prev-page="0x00001380",memory=[
29628 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
29629 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
29630 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
29631 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
29632 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
29633 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
29634 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
29635 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
29639 @subheading The @code{-data-read-memory-bytes} Command
29640 @findex -data-read-memory-bytes
29642 @subsubheading Synopsis
29645 -data-read-memory-bytes [ -o @var{byte-offset} ]
29646 @var{address} @var{count}
29653 @item @var{address}
29654 An expression specifying the address of the first memory word to be
29655 read. Complex expressions containing embedded white space should be
29656 quoted using the C convention.
29659 The number of bytes to read. This should be an integer literal.
29661 @item @var{byte-offset}
29662 The offsets in bytes relative to @var{address} at which to start
29663 reading. This should be an integer literal. This option is provided
29664 so that a frontend is not required to first evaluate address and then
29665 perform address arithmetics itself.
29669 This command attempts to read all accessible memory regions in the
29670 specified range. First, all regions marked as unreadable in the memory
29671 map (if one is defined) will be skipped. @xref{Memory Region
29672 Attributes}. Second, @value{GDBN} will attempt to read the remaining
29673 regions. For each one, if reading full region results in an errors,
29674 @value{GDBN} will try to read a subset of the region.
29676 In general, every single byte in the region may be readable or not,
29677 and the only way to read every readable byte is to try a read at
29678 every address, which is not practical. Therefore, @value{GDBN} will
29679 attempt to read all accessible bytes at either beginning or the end
29680 of the region, using a binary division scheme. This heuristic works
29681 well for reading accross a memory map boundary. Note that if a region
29682 has a readable range that is neither at the beginning or the end,
29683 @value{GDBN} will not read it.
29685 The result record (@pxref{GDB/MI Result Records}) that is output of
29686 the command includes a field named @samp{memory} whose content is a
29687 list of tuples. Each tuple represent a successfully read memory block
29688 and has the following fields:
29692 The start address of the memory block, as hexadecimal literal.
29695 The end address of the memory block, as hexadecimal literal.
29698 The offset of the memory block, as hexadecimal literal, relative to
29699 the start address passed to @code{-data-read-memory-bytes}.
29702 The contents of the memory block, in hex.
29708 @subsubheading @value{GDBN} Command
29710 The corresponding @value{GDBN} command is @samp{x}.
29712 @subsubheading Example
29716 -data-read-memory-bytes &a 10
29717 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
29719 contents="01000000020000000300"@}]
29724 @subheading The @code{-data-write-memory-bytes} Command
29725 @findex -data-write-memory-bytes
29727 @subsubheading Synopsis
29730 -data-write-memory-bytes @var{address} @var{contents}
29731 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
29738 @item @var{address}
29739 An expression specifying the address of the first memory word to be
29740 read. Complex expressions containing embedded white space should be
29741 quoted using the C convention.
29743 @item @var{contents}
29744 The hex-encoded bytes to write.
29747 Optional argument indicating the number of bytes to be written. If @var{count}
29748 is greater than @var{contents}' length, @value{GDBN} will repeatedly
29749 write @var{contents} until it fills @var{count} bytes.
29753 @subsubheading @value{GDBN} Command
29755 There's no corresponding @value{GDBN} command.
29757 @subsubheading Example
29761 -data-write-memory-bytes &a "aabbccdd"
29768 -data-write-memory-bytes &a "aabbccdd" 16e
29773 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29774 @node GDB/MI Tracepoint Commands
29775 @section @sc{gdb/mi} Tracepoint Commands
29777 The commands defined in this section implement MI support for
29778 tracepoints. For detailed introduction, see @ref{Tracepoints}.
29780 @subheading The @code{-trace-find} Command
29781 @findex -trace-find
29783 @subsubheading Synopsis
29786 -trace-find @var{mode} [@var{parameters}@dots{}]
29789 Find a trace frame using criteria defined by @var{mode} and
29790 @var{parameters}. The following table lists permissible
29791 modes and their parameters. For details of operation, see @ref{tfind}.
29796 No parameters are required. Stops examining trace frames.
29799 An integer is required as parameter. Selects tracepoint frame with
29802 @item tracepoint-number
29803 An integer is required as parameter. Finds next
29804 trace frame that corresponds to tracepoint with the specified number.
29807 An address is required as parameter. Finds
29808 next trace frame that corresponds to any tracepoint at the specified
29811 @item pc-inside-range
29812 Two addresses are required as parameters. Finds next trace
29813 frame that corresponds to a tracepoint at an address inside the
29814 specified range. Both bounds are considered to be inside the range.
29816 @item pc-outside-range
29817 Two addresses are required as parameters. Finds
29818 next trace frame that corresponds to a tracepoint at an address outside
29819 the specified range. Both bounds are considered to be inside the range.
29822 Line specification is required as parameter. @xref{Specify Location}.
29823 Finds next trace frame that corresponds to a tracepoint at
29824 the specified location.
29828 If @samp{none} was passed as @var{mode}, the response does not
29829 have fields. Otherwise, the response may have the following fields:
29833 This field has either @samp{0} or @samp{1} as the value, depending
29834 on whether a matching tracepoint was found.
29837 The index of the found traceframe. This field is present iff
29838 the @samp{found} field has value of @samp{1}.
29841 The index of the found tracepoint. This field is present iff
29842 the @samp{found} field has value of @samp{1}.
29845 The information about the frame corresponding to the found trace
29846 frame. This field is present only if a trace frame was found.
29847 @xref{GDB/MI Frame Information}, for description of this field.
29851 @subsubheading @value{GDBN} Command
29853 The corresponding @value{GDBN} command is @samp{tfind}.
29855 @subheading -trace-define-variable
29856 @findex -trace-define-variable
29858 @subsubheading Synopsis
29861 -trace-define-variable @var{name} [ @var{value} ]
29864 Create trace variable @var{name} if it does not exist. If
29865 @var{value} is specified, sets the initial value of the specified
29866 trace variable to that value. Note that the @var{name} should start
29867 with the @samp{$} character.
29869 @subsubheading @value{GDBN} Command
29871 The corresponding @value{GDBN} command is @samp{tvariable}.
29873 @subheading The @code{-trace-frame-collected} Command
29874 @findex -trace-frame-collected
29876 @subsubheading Synopsis
29879 -trace-frame-collected
29880 [--var-print-values @var{var_pval}]
29881 [--comp-print-values @var{comp_pval}]
29882 [--registers-format @var{regformat}]
29883 [--memory-contents]
29886 This command returns the set of collected objects, register names,
29887 trace state variable names, memory ranges and computed expressions
29888 that have been collected at a particular trace frame. The optional
29889 parameters to the command affect the output format in different ways.
29890 See the output description table below for more details.
29892 The reported names can be used in the normal manner to create
29893 varobjs and inspect the objects themselves. The items returned by
29894 this command are categorized so that it is clear which is a variable,
29895 which is a register, which is a trace state variable, which is a
29896 memory range and which is a computed expression.
29898 For instance, if the actions were
29900 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
29901 collect *(int*)0xaf02bef0@@40
29905 the object collected in its entirety would be @code{myVar}. The
29906 object @code{myArray} would be partially collected, because only the
29907 element at index @code{myIndex} would be collected. The remaining
29908 objects would be computed expressions.
29910 An example output would be:
29914 -trace-frame-collected
29916 explicit-variables=[@{name="myVar",value="1"@}],
29917 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
29918 @{name="myObj.field",value="0"@},
29919 @{name="myPtr->field",value="1"@},
29920 @{name="myCount + 2",value="3"@},
29921 @{name="$tvar1 + 1",value="43970027"@}],
29922 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
29923 @{number="1",value="0x0"@},
29924 @{number="2",value="0x4"@},
29926 @{number="125",value="0x0"@}],
29927 tvars=[@{name="$tvar1",current="43970026"@}],
29928 memory=[@{address="0x0000000000602264",length="4"@},
29929 @{address="0x0000000000615bc0",length="4"@}]
29936 @item explicit-variables
29937 The set of objects that have been collected in their entirety (as
29938 opposed to collecting just a few elements of an array or a few struct
29939 members). For each object, its name and value are printed.
29940 The @code{--var-print-values} option affects how or whether the value
29941 field is output. If @var{var_pval} is 0, then print only the names;
29942 if it is 1, print also their values; and if it is 2, print the name,
29943 type and value for simple data types, and the name and type for
29944 arrays, structures and unions.
29946 @item computed-expressions
29947 The set of computed expressions that have been collected at the
29948 current trace frame. The @code{--comp-print-values} option affects
29949 this set like the @code{--var-print-values} option affects the
29950 @code{explicit-variables} set. See above.
29953 The registers that have been collected at the current trace frame.
29954 For each register collected, the name and current value are returned.
29955 The value is formatted according to the @code{--registers-format}
29956 option. See the @command{-data-list-register-values} command for a
29957 list of the allowed formats. The default is @samp{x}.
29960 The trace state variables that have been collected at the current
29961 trace frame. For each trace state variable collected, the name and
29962 current value are returned.
29965 The set of memory ranges that have been collected at the current trace
29966 frame. Its content is a list of tuples. Each tuple represents a
29967 collected memory range and has the following fields:
29971 The start address of the memory range, as hexadecimal literal.
29974 The length of the memory range, as decimal literal.
29977 The contents of the memory block, in hex. This field is only present
29978 if the @code{--memory-contents} option is specified.
29984 @subsubheading @value{GDBN} Command
29986 There is no corresponding @value{GDBN} command.
29988 @subsubheading Example
29990 @subheading -trace-list-variables
29991 @findex -trace-list-variables
29993 @subsubheading Synopsis
29996 -trace-list-variables
29999 Return a table of all defined trace variables. Each element of the
30000 table has the following fields:
30004 The name of the trace variable. This field is always present.
30007 The initial value. This is a 64-bit signed integer. This
30008 field is always present.
30011 The value the trace variable has at the moment. This is a 64-bit
30012 signed integer. This field is absent iff current value is
30013 not defined, for example if the trace was never run, or is
30018 @subsubheading @value{GDBN} Command
30020 The corresponding @value{GDBN} command is @samp{tvariables}.
30022 @subsubheading Example
30026 -trace-list-variables
30027 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
30028 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
30029 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
30030 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
30031 body=[variable=@{name="$trace_timestamp",initial="0"@}
30032 variable=@{name="$foo",initial="10",current="15"@}]@}
30036 @subheading -trace-save
30037 @findex -trace-save
30039 @subsubheading Synopsis
30042 -trace-save [-r ] @var{filename}
30045 Saves the collected trace data to @var{filename}. Without the
30046 @samp{-r} option, the data is downloaded from the target and saved
30047 in a local file. With the @samp{-r} option the target is asked
30048 to perform the save.
30050 @subsubheading @value{GDBN} Command
30052 The corresponding @value{GDBN} command is @samp{tsave}.
30055 @subheading -trace-start
30056 @findex -trace-start
30058 @subsubheading Synopsis
30064 Starts a tracing experiments. The result of this command does not
30067 @subsubheading @value{GDBN} Command
30069 The corresponding @value{GDBN} command is @samp{tstart}.
30071 @subheading -trace-status
30072 @findex -trace-status
30074 @subsubheading Synopsis
30080 Obtains the status of a tracing experiment. The result may include
30081 the following fields:
30086 May have a value of either @samp{0}, when no tracing operations are
30087 supported, @samp{1}, when all tracing operations are supported, or
30088 @samp{file} when examining trace file. In the latter case, examining
30089 of trace frame is possible but new tracing experiement cannot be
30090 started. This field is always present.
30093 May have a value of either @samp{0} or @samp{1} depending on whether
30094 tracing experiement is in progress on target. This field is present
30095 if @samp{supported} field is not @samp{0}.
30098 Report the reason why the tracing was stopped last time. This field
30099 may be absent iff tracing was never stopped on target yet. The
30100 value of @samp{request} means the tracing was stopped as result of
30101 the @code{-trace-stop} command. The value of @samp{overflow} means
30102 the tracing buffer is full. The value of @samp{disconnection} means
30103 tracing was automatically stopped when @value{GDBN} has disconnected.
30104 The value of @samp{passcount} means tracing was stopped when a
30105 tracepoint was passed a maximal number of times for that tracepoint.
30106 This field is present if @samp{supported} field is not @samp{0}.
30108 @item stopping-tracepoint
30109 The number of tracepoint whose passcount as exceeded. This field is
30110 present iff the @samp{stop-reason} field has the value of
30114 @itemx frames-created
30115 The @samp{frames} field is a count of the total number of trace frames
30116 in the trace buffer, while @samp{frames-created} is the total created
30117 during the run, including ones that were discarded, such as when a
30118 circular trace buffer filled up. Both fields are optional.
30122 These fields tell the current size of the tracing buffer and the
30123 remaining space. These fields are optional.
30126 The value of the circular trace buffer flag. @code{1} means that the
30127 trace buffer is circular and old trace frames will be discarded if
30128 necessary to make room, @code{0} means that the trace buffer is linear
30132 The value of the disconnected tracing flag. @code{1} means that
30133 tracing will continue after @value{GDBN} disconnects, @code{0} means
30134 that the trace run will stop.
30137 The filename of the trace file being examined. This field is
30138 optional, and only present when examining a trace file.
30142 @subsubheading @value{GDBN} Command
30144 The corresponding @value{GDBN} command is @samp{tstatus}.
30146 @subheading -trace-stop
30147 @findex -trace-stop
30149 @subsubheading Synopsis
30155 Stops a tracing experiment. The result of this command has the same
30156 fields as @code{-trace-status}, except that the @samp{supported} and
30157 @samp{running} fields are not output.
30159 @subsubheading @value{GDBN} Command
30161 The corresponding @value{GDBN} command is @samp{tstop}.
30164 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30165 @node GDB/MI Symbol Query
30166 @section @sc{gdb/mi} Symbol Query Commands
30170 @subheading The @code{-symbol-info-address} Command
30171 @findex -symbol-info-address
30173 @subsubheading Synopsis
30176 -symbol-info-address @var{symbol}
30179 Describe where @var{symbol} is stored.
30181 @subsubheading @value{GDBN} Command
30183 The corresponding @value{GDBN} command is @samp{info address}.
30185 @subsubheading Example
30189 @subheading The @code{-symbol-info-file} Command
30190 @findex -symbol-info-file
30192 @subsubheading Synopsis
30198 Show the file for the symbol.
30200 @subsubheading @value{GDBN} Command
30202 There's no equivalent @value{GDBN} command. @code{gdbtk} has
30203 @samp{gdb_find_file}.
30205 @subsubheading Example
30209 @subheading The @code{-symbol-info-function} Command
30210 @findex -symbol-info-function
30212 @subsubheading Synopsis
30215 -symbol-info-function
30218 Show which function the symbol lives in.
30220 @subsubheading @value{GDBN} Command
30222 @samp{gdb_get_function} in @code{gdbtk}.
30224 @subsubheading Example
30228 @subheading The @code{-symbol-info-line} Command
30229 @findex -symbol-info-line
30231 @subsubheading Synopsis
30237 Show the core addresses of the code for a source line.
30239 @subsubheading @value{GDBN} Command
30241 The corresponding @value{GDBN} command is @samp{info line}.
30242 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
30244 @subsubheading Example
30248 @subheading The @code{-symbol-info-symbol} Command
30249 @findex -symbol-info-symbol
30251 @subsubheading Synopsis
30254 -symbol-info-symbol @var{addr}
30257 Describe what symbol is at location @var{addr}.
30259 @subsubheading @value{GDBN} Command
30261 The corresponding @value{GDBN} command is @samp{info symbol}.
30263 @subsubheading Example
30267 @subheading The @code{-symbol-list-functions} Command
30268 @findex -symbol-list-functions
30270 @subsubheading Synopsis
30273 -symbol-list-functions
30276 List the functions in the executable.
30278 @subsubheading @value{GDBN} Command
30280 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
30281 @samp{gdb_search} in @code{gdbtk}.
30283 @subsubheading Example
30288 @subheading The @code{-symbol-list-lines} Command
30289 @findex -symbol-list-lines
30291 @subsubheading Synopsis
30294 -symbol-list-lines @var{filename}
30297 Print the list of lines that contain code and their associated program
30298 addresses for the given source filename. The entries are sorted in
30299 ascending PC order.
30301 @subsubheading @value{GDBN} Command
30303 There is no corresponding @value{GDBN} command.
30305 @subsubheading Example
30308 -symbol-list-lines basics.c
30309 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
30315 @subheading The @code{-symbol-list-types} Command
30316 @findex -symbol-list-types
30318 @subsubheading Synopsis
30324 List all the type names.
30326 @subsubheading @value{GDBN} Command
30328 The corresponding commands are @samp{info types} in @value{GDBN},
30329 @samp{gdb_search} in @code{gdbtk}.
30331 @subsubheading Example
30335 @subheading The @code{-symbol-list-variables} Command
30336 @findex -symbol-list-variables
30338 @subsubheading Synopsis
30341 -symbol-list-variables
30344 List all the global and static variable names.
30346 @subsubheading @value{GDBN} Command
30348 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
30350 @subsubheading Example
30354 @subheading The @code{-symbol-locate} Command
30355 @findex -symbol-locate
30357 @subsubheading Synopsis
30363 @subsubheading @value{GDBN} Command
30365 @samp{gdb_loc} in @code{gdbtk}.
30367 @subsubheading Example
30371 @subheading The @code{-symbol-type} Command
30372 @findex -symbol-type
30374 @subsubheading Synopsis
30377 -symbol-type @var{variable}
30380 Show type of @var{variable}.
30382 @subsubheading @value{GDBN} Command
30384 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
30385 @samp{gdb_obj_variable}.
30387 @subsubheading Example
30392 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30393 @node GDB/MI File Commands
30394 @section @sc{gdb/mi} File Commands
30396 This section describes the GDB/MI commands to specify executable file names
30397 and to read in and obtain symbol table information.
30399 @subheading The @code{-file-exec-and-symbols} Command
30400 @findex -file-exec-and-symbols
30402 @subsubheading Synopsis
30405 -file-exec-and-symbols @var{file}
30408 Specify the executable file to be debugged. This file is the one from
30409 which the symbol table is also read. If no file is specified, the
30410 command clears the executable and symbol information. If breakpoints
30411 are set when using this command with no arguments, @value{GDBN} will produce
30412 error messages. Otherwise, no output is produced, except a completion
30415 @subsubheading @value{GDBN} Command
30417 The corresponding @value{GDBN} command is @samp{file}.
30419 @subsubheading Example
30423 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30429 @subheading The @code{-file-exec-file} Command
30430 @findex -file-exec-file
30432 @subsubheading Synopsis
30435 -file-exec-file @var{file}
30438 Specify the executable file to be debugged. Unlike
30439 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
30440 from this file. If used without argument, @value{GDBN} clears the information
30441 about the executable file. No output is produced, except a completion
30444 @subsubheading @value{GDBN} Command
30446 The corresponding @value{GDBN} command is @samp{exec-file}.
30448 @subsubheading Example
30452 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30459 @subheading The @code{-file-list-exec-sections} Command
30460 @findex -file-list-exec-sections
30462 @subsubheading Synopsis
30465 -file-list-exec-sections
30468 List the sections of the current executable file.
30470 @subsubheading @value{GDBN} Command
30472 The @value{GDBN} command @samp{info file} shows, among the rest, the same
30473 information as this command. @code{gdbtk} has a corresponding command
30474 @samp{gdb_load_info}.
30476 @subsubheading Example
30481 @subheading The @code{-file-list-exec-source-file} Command
30482 @findex -file-list-exec-source-file
30484 @subsubheading Synopsis
30487 -file-list-exec-source-file
30490 List the line number, the current source file, and the absolute path
30491 to the current source file for the current executable. The macro
30492 information field has a value of @samp{1} or @samp{0} depending on
30493 whether or not the file includes preprocessor macro information.
30495 @subsubheading @value{GDBN} Command
30497 The @value{GDBN} equivalent is @samp{info source}
30499 @subsubheading Example
30503 123-file-list-exec-source-file
30504 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
30509 @subheading The @code{-file-list-exec-source-files} Command
30510 @findex -file-list-exec-source-files
30512 @subsubheading Synopsis
30515 -file-list-exec-source-files
30518 List the source files for the current executable.
30520 It will always output both the filename and fullname (absolute file
30521 name) of a source file.
30523 @subsubheading @value{GDBN} Command
30525 The @value{GDBN} equivalent is @samp{info sources}.
30526 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
30528 @subsubheading Example
30531 -file-list-exec-source-files
30533 @{file=foo.c,fullname=/home/foo.c@},
30534 @{file=/home/bar.c,fullname=/home/bar.c@},
30535 @{file=gdb_could_not_find_fullpath.c@}]
30540 @subheading The @code{-file-list-shared-libraries} Command
30541 @findex -file-list-shared-libraries
30543 @subsubheading Synopsis
30546 -file-list-shared-libraries
30549 List the shared libraries in the program.
30551 @subsubheading @value{GDBN} Command
30553 The corresponding @value{GDBN} command is @samp{info shared}.
30555 @subsubheading Example
30559 @subheading The @code{-file-list-symbol-files} Command
30560 @findex -file-list-symbol-files
30562 @subsubheading Synopsis
30565 -file-list-symbol-files
30570 @subsubheading @value{GDBN} Command
30572 The corresponding @value{GDBN} command is @samp{info file} (part of it).
30574 @subsubheading Example
30579 @subheading The @code{-file-symbol-file} Command
30580 @findex -file-symbol-file
30582 @subsubheading Synopsis
30585 -file-symbol-file @var{file}
30588 Read symbol table info from the specified @var{file} argument. When
30589 used without arguments, clears @value{GDBN}'s symbol table info. No output is
30590 produced, except for a completion notification.
30592 @subsubheading @value{GDBN} Command
30594 The corresponding @value{GDBN} command is @samp{symbol-file}.
30596 @subsubheading Example
30600 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30606 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30607 @node GDB/MI Memory Overlay Commands
30608 @section @sc{gdb/mi} Memory Overlay Commands
30610 The memory overlay commands are not implemented.
30612 @c @subheading -overlay-auto
30614 @c @subheading -overlay-list-mapping-state
30616 @c @subheading -overlay-list-overlays
30618 @c @subheading -overlay-map
30620 @c @subheading -overlay-off
30622 @c @subheading -overlay-on
30624 @c @subheading -overlay-unmap
30626 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30627 @node GDB/MI Signal Handling Commands
30628 @section @sc{gdb/mi} Signal Handling Commands
30630 Signal handling commands are not implemented.
30632 @c @subheading -signal-handle
30634 @c @subheading -signal-list-handle-actions
30636 @c @subheading -signal-list-signal-types
30640 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30641 @node GDB/MI Target Manipulation
30642 @section @sc{gdb/mi} Target Manipulation Commands
30645 @subheading The @code{-target-attach} Command
30646 @findex -target-attach
30648 @subsubheading Synopsis
30651 -target-attach @var{pid} | @var{gid} | @var{file}
30654 Attach to a process @var{pid} or a file @var{file} outside of
30655 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
30656 group, the id previously returned by
30657 @samp{-list-thread-groups --available} must be used.
30659 @subsubheading @value{GDBN} Command
30661 The corresponding @value{GDBN} command is @samp{attach}.
30663 @subsubheading Example
30667 =thread-created,id="1"
30668 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
30674 @subheading The @code{-target-compare-sections} Command
30675 @findex -target-compare-sections
30677 @subsubheading Synopsis
30680 -target-compare-sections [ @var{section} ]
30683 Compare data of section @var{section} on target to the exec file.
30684 Without the argument, all sections are compared.
30686 @subsubheading @value{GDBN} Command
30688 The @value{GDBN} equivalent is @samp{compare-sections}.
30690 @subsubheading Example
30695 @subheading The @code{-target-detach} Command
30696 @findex -target-detach
30698 @subsubheading Synopsis
30701 -target-detach [ @var{pid} | @var{gid} ]
30704 Detach from the remote target which normally resumes its execution.
30705 If either @var{pid} or @var{gid} is specified, detaches from either
30706 the specified process, or specified thread group. There's no output.
30708 @subsubheading @value{GDBN} Command
30710 The corresponding @value{GDBN} command is @samp{detach}.
30712 @subsubheading Example
30722 @subheading The @code{-target-disconnect} Command
30723 @findex -target-disconnect
30725 @subsubheading Synopsis
30731 Disconnect from the remote target. There's no output and the target is
30732 generally not resumed.
30734 @subsubheading @value{GDBN} Command
30736 The corresponding @value{GDBN} command is @samp{disconnect}.
30738 @subsubheading Example
30748 @subheading The @code{-target-download} Command
30749 @findex -target-download
30751 @subsubheading Synopsis
30757 Loads the executable onto the remote target.
30758 It prints out an update message every half second, which includes the fields:
30762 The name of the section.
30764 The size of what has been sent so far for that section.
30766 The size of the section.
30768 The total size of what was sent so far (the current and the previous sections).
30770 The size of the overall executable to download.
30774 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
30775 @sc{gdb/mi} Output Syntax}).
30777 In addition, it prints the name and size of the sections, as they are
30778 downloaded. These messages include the following fields:
30782 The name of the section.
30784 The size of the section.
30786 The size of the overall executable to download.
30790 At the end, a summary is printed.
30792 @subsubheading @value{GDBN} Command
30794 The corresponding @value{GDBN} command is @samp{load}.
30796 @subsubheading Example
30798 Note: each status message appears on a single line. Here the messages
30799 have been broken down so that they can fit onto a page.
30804 +download,@{section=".text",section-size="6668",total-size="9880"@}
30805 +download,@{section=".text",section-sent="512",section-size="6668",
30806 total-sent="512",total-size="9880"@}
30807 +download,@{section=".text",section-sent="1024",section-size="6668",
30808 total-sent="1024",total-size="9880"@}
30809 +download,@{section=".text",section-sent="1536",section-size="6668",
30810 total-sent="1536",total-size="9880"@}
30811 +download,@{section=".text",section-sent="2048",section-size="6668",
30812 total-sent="2048",total-size="9880"@}
30813 +download,@{section=".text",section-sent="2560",section-size="6668",
30814 total-sent="2560",total-size="9880"@}
30815 +download,@{section=".text",section-sent="3072",section-size="6668",
30816 total-sent="3072",total-size="9880"@}
30817 +download,@{section=".text",section-sent="3584",section-size="6668",
30818 total-sent="3584",total-size="9880"@}
30819 +download,@{section=".text",section-sent="4096",section-size="6668",
30820 total-sent="4096",total-size="9880"@}
30821 +download,@{section=".text",section-sent="4608",section-size="6668",
30822 total-sent="4608",total-size="9880"@}
30823 +download,@{section=".text",section-sent="5120",section-size="6668",
30824 total-sent="5120",total-size="9880"@}
30825 +download,@{section=".text",section-sent="5632",section-size="6668",
30826 total-sent="5632",total-size="9880"@}
30827 +download,@{section=".text",section-sent="6144",section-size="6668",
30828 total-sent="6144",total-size="9880"@}
30829 +download,@{section=".text",section-sent="6656",section-size="6668",
30830 total-sent="6656",total-size="9880"@}
30831 +download,@{section=".init",section-size="28",total-size="9880"@}
30832 +download,@{section=".fini",section-size="28",total-size="9880"@}
30833 +download,@{section=".data",section-size="3156",total-size="9880"@}
30834 +download,@{section=".data",section-sent="512",section-size="3156",
30835 total-sent="7236",total-size="9880"@}
30836 +download,@{section=".data",section-sent="1024",section-size="3156",
30837 total-sent="7748",total-size="9880"@}
30838 +download,@{section=".data",section-sent="1536",section-size="3156",
30839 total-sent="8260",total-size="9880"@}
30840 +download,@{section=".data",section-sent="2048",section-size="3156",
30841 total-sent="8772",total-size="9880"@}
30842 +download,@{section=".data",section-sent="2560",section-size="3156",
30843 total-sent="9284",total-size="9880"@}
30844 +download,@{section=".data",section-sent="3072",section-size="3156",
30845 total-sent="9796",total-size="9880"@}
30846 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
30853 @subheading The @code{-target-exec-status} Command
30854 @findex -target-exec-status
30856 @subsubheading Synopsis
30859 -target-exec-status
30862 Provide information on the state of the target (whether it is running or
30863 not, for instance).
30865 @subsubheading @value{GDBN} Command
30867 There's no equivalent @value{GDBN} command.
30869 @subsubheading Example
30873 @subheading The @code{-target-list-available-targets} Command
30874 @findex -target-list-available-targets
30876 @subsubheading Synopsis
30879 -target-list-available-targets
30882 List the possible targets to connect to.
30884 @subsubheading @value{GDBN} Command
30886 The corresponding @value{GDBN} command is @samp{help target}.
30888 @subsubheading Example
30892 @subheading The @code{-target-list-current-targets} Command
30893 @findex -target-list-current-targets
30895 @subsubheading Synopsis
30898 -target-list-current-targets
30901 Describe the current target.
30903 @subsubheading @value{GDBN} Command
30905 The corresponding information is printed by @samp{info file} (among
30908 @subsubheading Example
30912 @subheading The @code{-target-list-parameters} Command
30913 @findex -target-list-parameters
30915 @subsubheading Synopsis
30918 -target-list-parameters
30924 @subsubheading @value{GDBN} Command
30928 @subsubheading Example
30932 @subheading The @code{-target-select} Command
30933 @findex -target-select
30935 @subsubheading Synopsis
30938 -target-select @var{type} @var{parameters @dots{}}
30941 Connect @value{GDBN} to the remote target. This command takes two args:
30945 The type of target, for instance @samp{remote}, etc.
30946 @item @var{parameters}
30947 Device names, host names and the like. @xref{Target Commands, ,
30948 Commands for Managing Targets}, for more details.
30951 The output is a connection notification, followed by the address at
30952 which the target program is, in the following form:
30955 ^connected,addr="@var{address}",func="@var{function name}",
30956 args=[@var{arg list}]
30959 @subsubheading @value{GDBN} Command
30961 The corresponding @value{GDBN} command is @samp{target}.
30963 @subsubheading Example
30967 -target-select remote /dev/ttya
30968 ^connected,addr="0xfe00a300",func="??",args=[]
30972 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30973 @node GDB/MI File Transfer Commands
30974 @section @sc{gdb/mi} File Transfer Commands
30977 @subheading The @code{-target-file-put} Command
30978 @findex -target-file-put
30980 @subsubheading Synopsis
30983 -target-file-put @var{hostfile} @var{targetfile}
30986 Copy file @var{hostfile} from the host system (the machine running
30987 @value{GDBN}) to @var{targetfile} on the target system.
30989 @subsubheading @value{GDBN} Command
30991 The corresponding @value{GDBN} command is @samp{remote put}.
30993 @subsubheading Example
30997 -target-file-put localfile remotefile
31003 @subheading The @code{-target-file-get} Command
31004 @findex -target-file-get
31006 @subsubheading Synopsis
31009 -target-file-get @var{targetfile} @var{hostfile}
31012 Copy file @var{targetfile} from the target system to @var{hostfile}
31013 on the host system.
31015 @subsubheading @value{GDBN} Command
31017 The corresponding @value{GDBN} command is @samp{remote get}.
31019 @subsubheading Example
31023 -target-file-get remotefile localfile
31029 @subheading The @code{-target-file-delete} Command
31030 @findex -target-file-delete
31032 @subsubheading Synopsis
31035 -target-file-delete @var{targetfile}
31038 Delete @var{targetfile} from the target system.
31040 @subsubheading @value{GDBN} Command
31042 The corresponding @value{GDBN} command is @samp{remote delete}.
31044 @subsubheading Example
31048 -target-file-delete remotefile
31054 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31055 @node GDB/MI Ada Exceptions Commands
31056 @section Ada Exceptions @sc{gdb/mi} Commands
31058 @subheading The @code{-info-ada-exceptions} Command
31059 @findex -info-ada-exceptions
31061 @subsubheading Synopsis
31064 -info-ada-exceptions [ @var{regexp}]
31067 List all Ada exceptions defined within the program being debugged.
31068 With a regular expression @var{regexp}, only those exceptions whose
31069 names match @var{regexp} are listed.
31071 @subsubheading @value{GDBN} Command
31073 The corresponding @value{GDBN} command is @samp{info exceptions}.
31075 @subsubheading Result
31077 The result is a table of Ada exceptions. The following columns are
31078 defined for each exception:
31082 The name of the exception.
31085 The address of the exception.
31089 @subsubheading Example
31092 -info-ada-exceptions aint
31093 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
31094 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
31095 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
31096 body=[@{name="constraint_error",address="0x0000000000613da0"@},
31097 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
31100 @subheading Catching Ada Exceptions
31102 The commands describing how to ask @value{GDBN} to stop when a program
31103 raises an exception are described at @ref{Ada Exception GDB/MI
31104 Catchpoint Commands}.
31107 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31108 @node GDB/MI Support Commands
31109 @section @sc{gdb/mi} Support Commands
31111 Since new commands and features get regularly added to @sc{gdb/mi},
31112 some commands are available to help front-ends query the debugger
31113 about support for these capabilities. Similarly, it is also possible
31114 to query @value{GDBN} about target support of certain features.
31116 @subheading The @code{-info-gdb-mi-command} Command
31117 @cindex @code{-info-gdb-mi-command}
31118 @findex -info-gdb-mi-command
31120 @subsubheading Synopsis
31123 -info-gdb-mi-command @var{cmd_name}
31126 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
31128 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
31129 is technically not part of the command name (@pxref{GDB/MI Input
31130 Syntax}), and thus should be omitted in @var{cmd_name}. However,
31131 for ease of use, this command also accepts the form with the leading
31134 @subsubheading @value{GDBN} Command
31136 There is no corresponding @value{GDBN} command.
31138 @subsubheading Result
31140 The result is a tuple. There is currently only one field:
31144 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
31145 @code{"false"} otherwise.
31149 @subsubheading Example
31151 Here is an example where the @sc{gdb/mi} command does not exist:
31154 -info-gdb-mi-command unsupported-command
31155 ^done,command=@{exists="false"@}
31159 And here is an example where the @sc{gdb/mi} command is known
31163 -info-gdb-mi-command symbol-list-lines
31164 ^done,command=@{exists="true"@}
31167 @subheading The @code{-list-features} Command
31168 @findex -list-features
31169 @cindex supported @sc{gdb/mi} features, list
31171 Returns a list of particular features of the MI protocol that
31172 this version of gdb implements. A feature can be a command,
31173 or a new field in an output of some command, or even an
31174 important bugfix. While a frontend can sometimes detect presence
31175 of a feature at runtime, it is easier to perform detection at debugger
31178 The command returns a list of strings, with each string naming an
31179 available feature. Each returned string is just a name, it does not
31180 have any internal structure. The list of possible feature names
31186 (gdb) -list-features
31187 ^done,result=["feature1","feature2"]
31190 The current list of features is:
31193 @item frozen-varobjs
31194 Indicates support for the @code{-var-set-frozen} command, as well
31195 as possible presense of the @code{frozen} field in the output
31196 of @code{-varobj-create}.
31197 @item pending-breakpoints
31198 Indicates support for the @option{-f} option to the @code{-break-insert}
31201 Indicates Python scripting support, Python-based
31202 pretty-printing commands, and possible presence of the
31203 @samp{display_hint} field in the output of @code{-var-list-children}
31205 Indicates support for the @code{-thread-info} command.
31206 @item data-read-memory-bytes
31207 Indicates support for the @code{-data-read-memory-bytes} and the
31208 @code{-data-write-memory-bytes} commands.
31209 @item breakpoint-notifications
31210 Indicates that changes to breakpoints and breakpoints created via the
31211 CLI will be announced via async records.
31212 @item ada-task-info
31213 Indicates support for the @code{-ada-task-info} command.
31214 @item language-option
31215 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
31216 option (@pxref{Context management}).
31217 @item info-gdb-mi-command
31218 Indicates support for the @code{-info-gdb-mi-command} command.
31219 @item undefined-command-error-code
31220 Indicates support for the "undefined-command" error code in error result
31221 records, produced when trying to execute an undefined @sc{gdb/mi} command
31222 (@pxref{GDB/MI Result Records}).
31223 @item exec-run-start-option
31224 Indicates that the @code{-exec-run} command supports the @option{--start}
31225 option (@pxref{GDB/MI Program Execution}).
31228 @subheading The @code{-list-target-features} Command
31229 @findex -list-target-features
31231 Returns a list of particular features that are supported by the
31232 target. Those features affect the permitted MI commands, but
31233 unlike the features reported by the @code{-list-features} command, the
31234 features depend on which target GDB is using at the moment. Whenever
31235 a target can change, due to commands such as @code{-target-select},
31236 @code{-target-attach} or @code{-exec-run}, the list of target features
31237 may change, and the frontend should obtain it again.
31241 (gdb) -list-target-features
31242 ^done,result=["async"]
31245 The current list of features is:
31249 Indicates that the target is capable of asynchronous command
31250 execution, which means that @value{GDBN} will accept further commands
31251 while the target is running.
31254 Indicates that the target is capable of reverse execution.
31255 @xref{Reverse Execution}, for more information.
31259 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31260 @node GDB/MI Miscellaneous Commands
31261 @section Miscellaneous @sc{gdb/mi} Commands
31263 @c @subheading -gdb-complete
31265 @subheading The @code{-gdb-exit} Command
31268 @subsubheading Synopsis
31274 Exit @value{GDBN} immediately.
31276 @subsubheading @value{GDBN} Command
31278 Approximately corresponds to @samp{quit}.
31280 @subsubheading Example
31290 @subheading The @code{-exec-abort} Command
31291 @findex -exec-abort
31293 @subsubheading Synopsis
31299 Kill the inferior running program.
31301 @subsubheading @value{GDBN} Command
31303 The corresponding @value{GDBN} command is @samp{kill}.
31305 @subsubheading Example
31310 @subheading The @code{-gdb-set} Command
31313 @subsubheading Synopsis
31319 Set an internal @value{GDBN} variable.
31320 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
31322 @subsubheading @value{GDBN} Command
31324 The corresponding @value{GDBN} command is @samp{set}.
31326 @subsubheading Example
31336 @subheading The @code{-gdb-show} Command
31339 @subsubheading Synopsis
31345 Show the current value of a @value{GDBN} variable.
31347 @subsubheading @value{GDBN} Command
31349 The corresponding @value{GDBN} command is @samp{show}.
31351 @subsubheading Example
31360 @c @subheading -gdb-source
31363 @subheading The @code{-gdb-version} Command
31364 @findex -gdb-version
31366 @subsubheading Synopsis
31372 Show version information for @value{GDBN}. Used mostly in testing.
31374 @subsubheading @value{GDBN} Command
31376 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
31377 default shows this information when you start an interactive session.
31379 @subsubheading Example
31381 @c This example modifies the actual output from GDB to avoid overfull
31387 ~Copyright 2000 Free Software Foundation, Inc.
31388 ~GDB is free software, covered by the GNU General Public License, and
31389 ~you are welcome to change it and/or distribute copies of it under
31390 ~ certain conditions.
31391 ~Type "show copying" to see the conditions.
31392 ~There is absolutely no warranty for GDB. Type "show warranty" for
31394 ~This GDB was configured as
31395 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
31400 @subheading The @code{-list-thread-groups} Command
31401 @findex -list-thread-groups
31403 @subheading Synopsis
31406 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
31409 Lists thread groups (@pxref{Thread groups}). When a single thread
31410 group is passed as the argument, lists the children of that group.
31411 When several thread group are passed, lists information about those
31412 thread groups. Without any parameters, lists information about all
31413 top-level thread groups.
31415 Normally, thread groups that are being debugged are reported.
31416 With the @samp{--available} option, @value{GDBN} reports thread groups
31417 available on the target.
31419 The output of this command may have either a @samp{threads} result or
31420 a @samp{groups} result. The @samp{thread} result has a list of tuples
31421 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
31422 Information}). The @samp{groups} result has a list of tuples as value,
31423 each tuple describing a thread group. If top-level groups are
31424 requested (that is, no parameter is passed), or when several groups
31425 are passed, the output always has a @samp{groups} result. The format
31426 of the @samp{group} result is described below.
31428 To reduce the number of roundtrips it's possible to list thread groups
31429 together with their children, by passing the @samp{--recurse} option
31430 and the recursion depth. Presently, only recursion depth of 1 is
31431 permitted. If this option is present, then every reported thread group
31432 will also include its children, either as @samp{group} or
31433 @samp{threads} field.
31435 In general, any combination of option and parameters is permitted, with
31436 the following caveats:
31440 When a single thread group is passed, the output will typically
31441 be the @samp{threads} result. Because threads may not contain
31442 anything, the @samp{recurse} option will be ignored.
31445 When the @samp{--available} option is passed, limited information may
31446 be available. In particular, the list of threads of a process might
31447 be inaccessible. Further, specifying specific thread groups might
31448 not give any performance advantage over listing all thread groups.
31449 The frontend should assume that @samp{-list-thread-groups --available}
31450 is always an expensive operation and cache the results.
31454 The @samp{groups} result is a list of tuples, where each tuple may
31455 have the following fields:
31459 Identifier of the thread group. This field is always present.
31460 The identifier is an opaque string; frontends should not try to
31461 convert it to an integer, even though it might look like one.
31464 The type of the thread group. At present, only @samp{process} is a
31468 The target-specific process identifier. This field is only present
31469 for thread groups of type @samp{process} and only if the process exists.
31472 The exit code of this group's last exited thread, formatted in octal.
31473 This field is only present for thread groups of type @samp{process} and
31474 only if the process is not running.
31477 The number of children this thread group has. This field may be
31478 absent for an available thread group.
31481 This field has a list of tuples as value, each tuple describing a
31482 thread. It may be present if the @samp{--recurse} option is
31483 specified, and it's actually possible to obtain the threads.
31486 This field is a list of integers, each identifying a core that one
31487 thread of the group is running on. This field may be absent if
31488 such information is not available.
31491 The name of the executable file that corresponds to this thread group.
31492 The field is only present for thread groups of type @samp{process},
31493 and only if there is a corresponding executable file.
31497 @subheading Example
31501 -list-thread-groups
31502 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
31503 -list-thread-groups 17
31504 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31505 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
31506 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31507 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
31508 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
31509 -list-thread-groups --available
31510 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
31511 -list-thread-groups --available --recurse 1
31512 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31513 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31514 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
31515 -list-thread-groups --available --recurse 1 17 18
31516 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31517 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31518 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
31521 @subheading The @code{-info-os} Command
31524 @subsubheading Synopsis
31527 -info-os [ @var{type} ]
31530 If no argument is supplied, the command returns a table of available
31531 operating-system-specific information types. If one of these types is
31532 supplied as an argument @var{type}, then the command returns a table
31533 of data of that type.
31535 The types of information available depend on the target operating
31538 @subsubheading @value{GDBN} Command
31540 The corresponding @value{GDBN} command is @samp{info os}.
31542 @subsubheading Example
31544 When run on a @sc{gnu}/Linux system, the output will look something
31550 ^done,OSDataTable=@{nr_rows="9",nr_cols="3",
31551 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
31552 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
31553 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
31554 body=[item=@{col0="processes",col1="Listing of all processes",
31555 col2="Processes"@},
31556 item=@{col0="procgroups",col1="Listing of all process groups",
31557 col2="Process groups"@},
31558 item=@{col0="threads",col1="Listing of all threads",
31560 item=@{col0="files",col1="Listing of all file descriptors",
31561 col2="File descriptors"@},
31562 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
31564 item=@{col0="shm",col1="Listing of all shared-memory regions",
31565 col2="Shared-memory regions"@},
31566 item=@{col0="semaphores",col1="Listing of all semaphores",
31567 col2="Semaphores"@},
31568 item=@{col0="msg",col1="Listing of all message queues",
31569 col2="Message queues"@},
31570 item=@{col0="modules",col1="Listing of all loaded kernel modules",
31571 col2="Kernel modules"@}]@}
31574 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
31575 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
31576 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
31577 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
31578 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
31579 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
31580 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
31581 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
31583 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
31584 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
31588 (Note that the MI output here includes a @code{"Title"} column that
31589 does not appear in command-line @code{info os}; this column is useful
31590 for MI clients that want to enumerate the types of data, such as in a
31591 popup menu, but is needless clutter on the command line, and
31592 @code{info os} omits it.)
31594 @subheading The @code{-add-inferior} Command
31595 @findex -add-inferior
31597 @subheading Synopsis
31603 Creates a new inferior (@pxref{Inferiors and Programs}). The created
31604 inferior is not associated with any executable. Such association may
31605 be established with the @samp{-file-exec-and-symbols} command
31606 (@pxref{GDB/MI File Commands}). The command response has a single
31607 field, @samp{inferior}, whose value is the identifier of the
31608 thread group corresponding to the new inferior.
31610 @subheading Example
31615 ^done,inferior="i3"
31618 @subheading The @code{-interpreter-exec} Command
31619 @findex -interpreter-exec
31621 @subheading Synopsis
31624 -interpreter-exec @var{interpreter} @var{command}
31626 @anchor{-interpreter-exec}
31628 Execute the specified @var{command} in the given @var{interpreter}.
31630 @subheading @value{GDBN} Command
31632 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
31634 @subheading Example
31638 -interpreter-exec console "break main"
31639 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
31640 &"During symbol reading, bad structure-type format.\n"
31641 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
31646 @subheading The @code{-inferior-tty-set} Command
31647 @findex -inferior-tty-set
31649 @subheading Synopsis
31652 -inferior-tty-set /dev/pts/1
31655 Set terminal for future runs of the program being debugged.
31657 @subheading @value{GDBN} Command
31659 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
31661 @subheading Example
31665 -inferior-tty-set /dev/pts/1
31670 @subheading The @code{-inferior-tty-show} Command
31671 @findex -inferior-tty-show
31673 @subheading Synopsis
31679 Show terminal for future runs of program being debugged.
31681 @subheading @value{GDBN} Command
31683 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
31685 @subheading Example
31689 -inferior-tty-set /dev/pts/1
31693 ^done,inferior_tty_terminal="/dev/pts/1"
31697 @subheading The @code{-enable-timings} Command
31698 @findex -enable-timings
31700 @subheading Synopsis
31703 -enable-timings [yes | no]
31706 Toggle the printing of the wallclock, user and system times for an MI
31707 command as a field in its output. This command is to help frontend
31708 developers optimize the performance of their code. No argument is
31709 equivalent to @samp{yes}.
31711 @subheading @value{GDBN} Command
31715 @subheading Example
31723 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31724 addr="0x080484ed",func="main",file="myprog.c",
31725 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
31727 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
31735 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
31736 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
31737 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
31738 fullname="/home/nickrob/myprog.c",line="73"@}
31743 @chapter @value{GDBN} Annotations
31745 This chapter describes annotations in @value{GDBN}. Annotations were
31746 designed to interface @value{GDBN} to graphical user interfaces or other
31747 similar programs which want to interact with @value{GDBN} at a
31748 relatively high level.
31750 The annotation mechanism has largely been superseded by @sc{gdb/mi}
31754 This is Edition @value{EDITION}, @value{DATE}.
31758 * Annotations Overview:: What annotations are; the general syntax.
31759 * Server Prefix:: Issuing a command without affecting user state.
31760 * Prompting:: Annotations marking @value{GDBN}'s need for input.
31761 * Errors:: Annotations for error messages.
31762 * Invalidation:: Some annotations describe things now invalid.
31763 * Annotations for Running::
31764 Whether the program is running, how it stopped, etc.
31765 * Source Annotations:: Annotations describing source code.
31768 @node Annotations Overview
31769 @section What is an Annotation?
31770 @cindex annotations
31772 Annotations start with a newline character, two @samp{control-z}
31773 characters, and the name of the annotation. If there is no additional
31774 information associated with this annotation, the name of the annotation
31775 is followed immediately by a newline. If there is additional
31776 information, the name of the annotation is followed by a space, the
31777 additional information, and a newline. The additional information
31778 cannot contain newline characters.
31780 Any output not beginning with a newline and two @samp{control-z}
31781 characters denotes literal output from @value{GDBN}. Currently there is
31782 no need for @value{GDBN} to output a newline followed by two
31783 @samp{control-z} characters, but if there was such a need, the
31784 annotations could be extended with an @samp{escape} annotation which
31785 means those three characters as output.
31787 The annotation @var{level}, which is specified using the
31788 @option{--annotate} command line option (@pxref{Mode Options}), controls
31789 how much information @value{GDBN} prints together with its prompt,
31790 values of expressions, source lines, and other types of output. Level 0
31791 is for no annotations, level 1 is for use when @value{GDBN} is run as a
31792 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
31793 for programs that control @value{GDBN}, and level 2 annotations have
31794 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
31795 Interface, annotate, GDB's Obsolete Annotations}).
31798 @kindex set annotate
31799 @item set annotate @var{level}
31800 The @value{GDBN} command @code{set annotate} sets the level of
31801 annotations to the specified @var{level}.
31803 @item show annotate
31804 @kindex show annotate
31805 Show the current annotation level.
31808 This chapter describes level 3 annotations.
31810 A simple example of starting up @value{GDBN} with annotations is:
31813 $ @kbd{gdb --annotate=3}
31815 Copyright 2003 Free Software Foundation, Inc.
31816 GDB is free software, covered by the GNU General Public License,
31817 and you are welcome to change it and/or distribute copies of it
31818 under certain conditions.
31819 Type "show copying" to see the conditions.
31820 There is absolutely no warranty for GDB. Type "show warranty"
31822 This GDB was configured as "i386-pc-linux-gnu"
31833 Here @samp{quit} is input to @value{GDBN}; the rest is output from
31834 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
31835 denotes a @samp{control-z} character) are annotations; the rest is
31836 output from @value{GDBN}.
31838 @node Server Prefix
31839 @section The Server Prefix
31840 @cindex server prefix
31842 If you prefix a command with @samp{server } then it will not affect
31843 the command history, nor will it affect @value{GDBN}'s notion of which
31844 command to repeat if @key{RET} is pressed on a line by itself. This
31845 means that commands can be run behind a user's back by a front-end in
31846 a transparent manner.
31848 The @code{server } prefix does not affect the recording of values into
31849 the value history; to print a value without recording it into the
31850 value history, use the @code{output} command instead of the
31851 @code{print} command.
31853 Using this prefix also disables confirmation requests
31854 (@pxref{confirmation requests}).
31857 @section Annotation for @value{GDBN} Input
31859 @cindex annotations for prompts
31860 When @value{GDBN} prompts for input, it annotates this fact so it is possible
31861 to know when to send output, when the output from a given command is
31864 Different kinds of input each have a different @dfn{input type}. Each
31865 input type has three annotations: a @code{pre-} annotation, which
31866 denotes the beginning of any prompt which is being output, a plain
31867 annotation, which denotes the end of the prompt, and then a @code{post-}
31868 annotation which denotes the end of any echo which may (or may not) be
31869 associated with the input. For example, the @code{prompt} input type
31870 features the following annotations:
31878 The input types are
31881 @findex pre-prompt annotation
31882 @findex prompt annotation
31883 @findex post-prompt annotation
31885 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
31887 @findex pre-commands annotation
31888 @findex commands annotation
31889 @findex post-commands annotation
31891 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
31892 command. The annotations are repeated for each command which is input.
31894 @findex pre-overload-choice annotation
31895 @findex overload-choice annotation
31896 @findex post-overload-choice annotation
31897 @item overload-choice
31898 When @value{GDBN} wants the user to select between various overloaded functions.
31900 @findex pre-query annotation
31901 @findex query annotation
31902 @findex post-query annotation
31904 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
31906 @findex pre-prompt-for-continue annotation
31907 @findex prompt-for-continue annotation
31908 @findex post-prompt-for-continue annotation
31909 @item prompt-for-continue
31910 When @value{GDBN} is asking the user to press return to continue. Note: Don't
31911 expect this to work well; instead use @code{set height 0} to disable
31912 prompting. This is because the counting of lines is buggy in the
31913 presence of annotations.
31918 @cindex annotations for errors, warnings and interrupts
31920 @findex quit annotation
31925 This annotation occurs right before @value{GDBN} responds to an interrupt.
31927 @findex error annotation
31932 This annotation occurs right before @value{GDBN} responds to an error.
31934 Quit and error annotations indicate that any annotations which @value{GDBN} was
31935 in the middle of may end abruptly. For example, if a
31936 @code{value-history-begin} annotation is followed by a @code{error}, one
31937 cannot expect to receive the matching @code{value-history-end}. One
31938 cannot expect not to receive it either, however; an error annotation
31939 does not necessarily mean that @value{GDBN} is immediately returning all the way
31942 @findex error-begin annotation
31943 A quit or error annotation may be preceded by
31949 Any output between that and the quit or error annotation is the error
31952 Warning messages are not yet annotated.
31953 @c If we want to change that, need to fix warning(), type_error(),
31954 @c range_error(), and possibly other places.
31957 @section Invalidation Notices
31959 @cindex annotations for invalidation messages
31960 The following annotations say that certain pieces of state may have
31964 @findex frames-invalid annotation
31965 @item ^Z^Zframes-invalid
31967 The frames (for example, output from the @code{backtrace} command) may
31970 @findex breakpoints-invalid annotation
31971 @item ^Z^Zbreakpoints-invalid
31973 The breakpoints may have changed. For example, the user just added or
31974 deleted a breakpoint.
31977 @node Annotations for Running
31978 @section Running the Program
31979 @cindex annotations for running programs
31981 @findex starting annotation
31982 @findex stopping annotation
31983 When the program starts executing due to a @value{GDBN} command such as
31984 @code{step} or @code{continue},
31990 is output. When the program stops,
31996 is output. Before the @code{stopped} annotation, a variety of
31997 annotations describe how the program stopped.
32000 @findex exited annotation
32001 @item ^Z^Zexited @var{exit-status}
32002 The program exited, and @var{exit-status} is the exit status (zero for
32003 successful exit, otherwise nonzero).
32005 @findex signalled annotation
32006 @findex signal-name annotation
32007 @findex signal-name-end annotation
32008 @findex signal-string annotation
32009 @findex signal-string-end annotation
32010 @item ^Z^Zsignalled
32011 The program exited with a signal. After the @code{^Z^Zsignalled}, the
32012 annotation continues:
32018 ^Z^Zsignal-name-end
32022 ^Z^Zsignal-string-end
32027 where @var{name} is the name of the signal, such as @code{SIGILL} or
32028 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
32029 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
32030 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
32031 user's benefit and have no particular format.
32033 @findex signal annotation
32035 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
32036 just saying that the program received the signal, not that it was
32037 terminated with it.
32039 @findex breakpoint annotation
32040 @item ^Z^Zbreakpoint @var{number}
32041 The program hit breakpoint number @var{number}.
32043 @findex watchpoint annotation
32044 @item ^Z^Zwatchpoint @var{number}
32045 The program hit watchpoint number @var{number}.
32048 @node Source Annotations
32049 @section Displaying Source
32050 @cindex annotations for source display
32052 @findex source annotation
32053 The following annotation is used instead of displaying source code:
32056 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
32059 where @var{filename} is an absolute file name indicating which source
32060 file, @var{line} is the line number within that file (where 1 is the
32061 first line in the file), @var{character} is the character position
32062 within the file (where 0 is the first character in the file) (for most
32063 debug formats this will necessarily point to the beginning of a line),
32064 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
32065 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
32066 @var{addr} is the address in the target program associated with the
32067 source which is being displayed. The @var{addr} is in the form @samp{0x}
32068 followed by one or more lowercase hex digits (note that this does not
32069 depend on the language).
32071 @node JIT Interface
32072 @chapter JIT Compilation Interface
32073 @cindex just-in-time compilation
32074 @cindex JIT compilation interface
32076 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
32077 interface. A JIT compiler is a program or library that generates native
32078 executable code at runtime and executes it, usually in order to achieve good
32079 performance while maintaining platform independence.
32081 Programs that use JIT compilation are normally difficult to debug because
32082 portions of their code are generated at runtime, instead of being loaded from
32083 object files, which is where @value{GDBN} normally finds the program's symbols
32084 and debug information. In order to debug programs that use JIT compilation,
32085 @value{GDBN} has an interface that allows the program to register in-memory
32086 symbol files with @value{GDBN} at runtime.
32088 If you are using @value{GDBN} to debug a program that uses this interface, then
32089 it should work transparently so long as you have not stripped the binary. If
32090 you are developing a JIT compiler, then the interface is documented in the rest
32091 of this chapter. At this time, the only known client of this interface is the
32094 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
32095 JIT compiler communicates with @value{GDBN} by writing data into a global
32096 variable and calling a fuction at a well-known symbol. When @value{GDBN}
32097 attaches, it reads a linked list of symbol files from the global variable to
32098 find existing code, and puts a breakpoint in the function so that it can find
32099 out about additional code.
32102 * Declarations:: Relevant C struct declarations
32103 * Registering Code:: Steps to register code
32104 * Unregistering Code:: Steps to unregister code
32105 * Custom Debug Info:: Emit debug information in a custom format
32109 @section JIT Declarations
32111 These are the relevant struct declarations that a C program should include to
32112 implement the interface:
32122 struct jit_code_entry
32124 struct jit_code_entry *next_entry;
32125 struct jit_code_entry *prev_entry;
32126 const char *symfile_addr;
32127 uint64_t symfile_size;
32130 struct jit_descriptor
32133 /* This type should be jit_actions_t, but we use uint32_t
32134 to be explicit about the bitwidth. */
32135 uint32_t action_flag;
32136 struct jit_code_entry *relevant_entry;
32137 struct jit_code_entry *first_entry;
32140 /* GDB puts a breakpoint in this function. */
32141 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
32143 /* Make sure to specify the version statically, because the
32144 debugger may check the version before we can set it. */
32145 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
32148 If the JIT is multi-threaded, then it is important that the JIT synchronize any
32149 modifications to this global data properly, which can easily be done by putting
32150 a global mutex around modifications to these structures.
32152 @node Registering Code
32153 @section Registering Code
32155 To register code with @value{GDBN}, the JIT should follow this protocol:
32159 Generate an object file in memory with symbols and other desired debug
32160 information. The file must include the virtual addresses of the sections.
32163 Create a code entry for the file, which gives the start and size of the symbol
32167 Add it to the linked list in the JIT descriptor.
32170 Point the relevant_entry field of the descriptor at the entry.
32173 Set @code{action_flag} to @code{JIT_REGISTER} and call
32174 @code{__jit_debug_register_code}.
32177 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
32178 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
32179 new code. However, the linked list must still be maintained in order to allow
32180 @value{GDBN} to attach to a running process and still find the symbol files.
32182 @node Unregistering Code
32183 @section Unregistering Code
32185 If code is freed, then the JIT should use the following protocol:
32189 Remove the code entry corresponding to the code from the linked list.
32192 Point the @code{relevant_entry} field of the descriptor at the code entry.
32195 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
32196 @code{__jit_debug_register_code}.
32199 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
32200 and the JIT will leak the memory used for the associated symbol files.
32202 @node Custom Debug Info
32203 @section Custom Debug Info
32204 @cindex custom JIT debug info
32205 @cindex JIT debug info reader
32207 Generating debug information in platform-native file formats (like ELF
32208 or COFF) may be an overkill for JIT compilers; especially if all the
32209 debug info is used for is displaying a meaningful backtrace. The
32210 issue can be resolved by having the JIT writers decide on a debug info
32211 format and also provide a reader that parses the debug info generated
32212 by the JIT compiler. This section gives a brief overview on writing
32213 such a parser. More specific details can be found in the source file
32214 @file{gdb/jit-reader.in}, which is also installed as a header at
32215 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
32217 The reader is implemented as a shared object (so this functionality is
32218 not available on platforms which don't allow loading shared objects at
32219 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
32220 @code{jit-reader-unload} are provided, to be used to load and unload
32221 the readers from a preconfigured directory. Once loaded, the shared
32222 object is used the parse the debug information emitted by the JIT
32226 * Using JIT Debug Info Readers:: How to use supplied readers correctly
32227 * Writing JIT Debug Info Readers:: Creating a debug-info reader
32230 @node Using JIT Debug Info Readers
32231 @subsection Using JIT Debug Info Readers
32232 @kindex jit-reader-load
32233 @kindex jit-reader-unload
32235 Readers can be loaded and unloaded using the @code{jit-reader-load}
32236 and @code{jit-reader-unload} commands.
32239 @item jit-reader-load @var{reader}
32240 Load the JIT reader named @var{reader}, which is a shared
32241 object specified as either an absolute or a relative file name. In
32242 the latter case, @value{GDBN} will try to load the reader from a
32243 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
32244 system (here @var{libdir} is the system library directory, often
32245 @file{/usr/local/lib}).
32247 Only one reader can be active at a time; trying to load a second
32248 reader when one is already loaded will result in @value{GDBN}
32249 reporting an error. A new JIT reader can be loaded by first unloading
32250 the current one using @code{jit-reader-unload} and then invoking
32251 @code{jit-reader-load}.
32253 @item jit-reader-unload
32254 Unload the currently loaded JIT reader.
32258 @node Writing JIT Debug Info Readers
32259 @subsection Writing JIT Debug Info Readers
32260 @cindex writing JIT debug info readers
32262 As mentioned, a reader is essentially a shared object conforming to a
32263 certain ABI. This ABI is described in @file{jit-reader.h}.
32265 @file{jit-reader.h} defines the structures, macros and functions
32266 required to write a reader. It is installed (along with
32267 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
32268 the system include directory.
32270 Readers need to be released under a GPL compatible license. A reader
32271 can be declared as released under such a license by placing the macro
32272 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
32274 The entry point for readers is the symbol @code{gdb_init_reader},
32275 which is expected to be a function with the prototype
32277 @findex gdb_init_reader
32279 extern struct gdb_reader_funcs *gdb_init_reader (void);
32282 @cindex @code{struct gdb_reader_funcs}
32284 @code{struct gdb_reader_funcs} contains a set of pointers to callback
32285 functions. These functions are executed to read the debug info
32286 generated by the JIT compiler (@code{read}), to unwind stack frames
32287 (@code{unwind}) and to create canonical frame IDs
32288 (@code{get_Frame_id}). It also has a callback that is called when the
32289 reader is being unloaded (@code{destroy}). The struct looks like this
32292 struct gdb_reader_funcs
32294 /* Must be set to GDB_READER_INTERFACE_VERSION. */
32295 int reader_version;
32297 /* For use by the reader. */
32300 gdb_read_debug_info *read;
32301 gdb_unwind_frame *unwind;
32302 gdb_get_frame_id *get_frame_id;
32303 gdb_destroy_reader *destroy;
32307 @cindex @code{struct gdb_symbol_callbacks}
32308 @cindex @code{struct gdb_unwind_callbacks}
32310 The callbacks are provided with another set of callbacks by
32311 @value{GDBN} to do their job. For @code{read}, these callbacks are
32312 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
32313 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
32314 @code{struct gdb_symbol_callbacks} has callbacks to create new object
32315 files and new symbol tables inside those object files. @code{struct
32316 gdb_unwind_callbacks} has callbacks to read registers off the current
32317 frame and to write out the values of the registers in the previous
32318 frame. Both have a callback (@code{target_read}) to read bytes off the
32319 target's address space.
32321 @node In-Process Agent
32322 @chapter In-Process Agent
32323 @cindex debugging agent
32324 The traditional debugging model is conceptually low-speed, but works fine,
32325 because most bugs can be reproduced in debugging-mode execution. However,
32326 as multi-core or many-core processors are becoming mainstream, and
32327 multi-threaded programs become more and more popular, there should be more
32328 and more bugs that only manifest themselves at normal-mode execution, for
32329 example, thread races, because debugger's interference with the program's
32330 timing may conceal the bugs. On the other hand, in some applications,
32331 it is not feasible for the debugger to interrupt the program's execution
32332 long enough for the developer to learn anything helpful about its behavior.
32333 If the program's correctness depends on its real-time behavior, delays
32334 introduced by a debugger might cause the program to fail, even when the
32335 code itself is correct. It is useful to be able to observe the program's
32336 behavior without interrupting it.
32338 Therefore, traditional debugging model is too intrusive to reproduce
32339 some bugs. In order to reduce the interference with the program, we can
32340 reduce the number of operations performed by debugger. The
32341 @dfn{In-Process Agent}, a shared library, is running within the same
32342 process with inferior, and is able to perform some debugging operations
32343 itself. As a result, debugger is only involved when necessary, and
32344 performance of debugging can be improved accordingly. Note that
32345 interference with program can be reduced but can't be removed completely,
32346 because the in-process agent will still stop or slow down the program.
32348 The in-process agent can interpret and execute Agent Expressions
32349 (@pxref{Agent Expressions}) during performing debugging operations. The
32350 agent expressions can be used for different purposes, such as collecting
32351 data in tracepoints, and condition evaluation in breakpoints.
32353 @anchor{Control Agent}
32354 You can control whether the in-process agent is used as an aid for
32355 debugging with the following commands:
32358 @kindex set agent on
32360 Causes the in-process agent to perform some operations on behalf of the
32361 debugger. Just which operations requested by the user will be done
32362 by the in-process agent depends on the its capabilities. For example,
32363 if you request to evaluate breakpoint conditions in the in-process agent,
32364 and the in-process agent has such capability as well, then breakpoint
32365 conditions will be evaluated in the in-process agent.
32367 @kindex set agent off
32368 @item set agent off
32369 Disables execution of debugging operations by the in-process agent. All
32370 of the operations will be performed by @value{GDBN}.
32374 Display the current setting of execution of debugging operations by
32375 the in-process agent.
32379 * In-Process Agent Protocol::
32382 @node In-Process Agent Protocol
32383 @section In-Process Agent Protocol
32384 @cindex in-process agent protocol
32386 The in-process agent is able to communicate with both @value{GDBN} and
32387 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
32388 used for communications between @value{GDBN} or GDBserver and the IPA.
32389 In general, @value{GDBN} or GDBserver sends commands
32390 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
32391 in-process agent replies back with the return result of the command, or
32392 some other information. The data sent to in-process agent is composed
32393 of primitive data types, such as 4-byte or 8-byte type, and composite
32394 types, which are called objects (@pxref{IPA Protocol Objects}).
32397 * IPA Protocol Objects::
32398 * IPA Protocol Commands::
32401 @node IPA Protocol Objects
32402 @subsection IPA Protocol Objects
32403 @cindex ipa protocol objects
32405 The commands sent to and results received from agent may contain some
32406 complex data types called @dfn{objects}.
32408 The in-process agent is running on the same machine with @value{GDBN}
32409 or GDBserver, so it doesn't have to handle as much differences between
32410 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
32411 However, there are still some differences of two ends in two processes:
32415 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
32416 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
32418 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
32419 GDBserver is compiled with one, and in-process agent is compiled with
32423 Here are the IPA Protocol Objects:
32427 agent expression object. It represents an agent expression
32428 (@pxref{Agent Expressions}).
32429 @anchor{agent expression object}
32431 tracepoint action object. It represents a tracepoint action
32432 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
32433 memory, static trace data and to evaluate expression.
32434 @anchor{tracepoint action object}
32436 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
32437 @anchor{tracepoint object}
32441 The following table describes important attributes of each IPA protocol
32444 @multitable @columnfractions .30 .20 .50
32445 @headitem Name @tab Size @tab Description
32446 @item @emph{agent expression object} @tab @tab
32447 @item length @tab 4 @tab length of bytes code
32448 @item byte code @tab @var{length} @tab contents of byte code
32449 @item @emph{tracepoint action for collecting memory} @tab @tab
32450 @item 'M' @tab 1 @tab type of tracepoint action
32451 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
32452 address of the lowest byte to collect, otherwise @var{addr} is the offset
32453 of @var{basereg} for memory collecting.
32454 @item len @tab 8 @tab length of memory for collecting
32455 @item basereg @tab 4 @tab the register number containing the starting
32456 memory address for collecting.
32457 @item @emph{tracepoint action for collecting registers} @tab @tab
32458 @item 'R' @tab 1 @tab type of tracepoint action
32459 @item @emph{tracepoint action for collecting static trace data} @tab @tab
32460 @item 'L' @tab 1 @tab type of tracepoint action
32461 @item @emph{tracepoint action for expression evaluation} @tab @tab
32462 @item 'X' @tab 1 @tab type of tracepoint action
32463 @item agent expression @tab length of @tab @ref{agent expression object}
32464 @item @emph{tracepoint object} @tab @tab
32465 @item number @tab 4 @tab number of tracepoint
32466 @item address @tab 8 @tab address of tracepoint inserted on
32467 @item type @tab 4 @tab type of tracepoint
32468 @item enabled @tab 1 @tab enable or disable of tracepoint
32469 @item step_count @tab 8 @tab step
32470 @item pass_count @tab 8 @tab pass
32471 @item numactions @tab 4 @tab number of tracepoint actions
32472 @item hit count @tab 8 @tab hit count
32473 @item trace frame usage @tab 8 @tab trace frame usage
32474 @item compiled_cond @tab 8 @tab compiled condition
32475 @item orig_size @tab 8 @tab orig size
32476 @item condition @tab 4 if condition is NULL otherwise length of
32477 @ref{agent expression object}
32478 @tab zero if condition is NULL, otherwise is
32479 @ref{agent expression object}
32480 @item actions @tab variable
32481 @tab numactions number of @ref{tracepoint action object}
32484 @node IPA Protocol Commands
32485 @subsection IPA Protocol Commands
32486 @cindex ipa protocol commands
32488 The spaces in each command are delimiters to ease reading this commands
32489 specification. They don't exist in real commands.
32493 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
32494 Installs a new fast tracepoint described by @var{tracepoint_object}
32495 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
32496 head of @dfn{jumppad}, which is used to jump to data collection routine
32501 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
32502 @var{target_address} is address of tracepoint in the inferior.
32503 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
32504 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
32505 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
32506 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
32513 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
32514 is about to kill inferiors.
32522 @item probe_marker_at:@var{address}
32523 Asks in-process agent to probe the marker at @var{address}.
32530 @item unprobe_marker_at:@var{address}
32531 Asks in-process agent to unprobe the marker at @var{address}.
32535 @chapter Reporting Bugs in @value{GDBN}
32536 @cindex bugs in @value{GDBN}
32537 @cindex reporting bugs in @value{GDBN}
32539 Your bug reports play an essential role in making @value{GDBN} reliable.
32541 Reporting a bug may help you by bringing a solution to your problem, or it
32542 may not. But in any case the principal function of a bug report is to help
32543 the entire community by making the next version of @value{GDBN} work better. Bug
32544 reports are your contribution to the maintenance of @value{GDBN}.
32546 In order for a bug report to serve its purpose, you must include the
32547 information that enables us to fix the bug.
32550 * Bug Criteria:: Have you found a bug?
32551 * Bug Reporting:: How to report bugs
32555 @section Have You Found a Bug?
32556 @cindex bug criteria
32558 If you are not sure whether you have found a bug, here are some guidelines:
32561 @cindex fatal signal
32562 @cindex debugger crash
32563 @cindex crash of debugger
32565 If the debugger gets a fatal signal, for any input whatever, that is a
32566 @value{GDBN} bug. Reliable debuggers never crash.
32568 @cindex error on valid input
32570 If @value{GDBN} produces an error message for valid input, that is a
32571 bug. (Note that if you're cross debugging, the problem may also be
32572 somewhere in the connection to the target.)
32574 @cindex invalid input
32576 If @value{GDBN} does not produce an error message for invalid input,
32577 that is a bug. However, you should note that your idea of
32578 ``invalid input'' might be our idea of ``an extension'' or ``support
32579 for traditional practice''.
32582 If you are an experienced user of debugging tools, your suggestions
32583 for improvement of @value{GDBN} are welcome in any case.
32586 @node Bug Reporting
32587 @section How to Report Bugs
32588 @cindex bug reports
32589 @cindex @value{GDBN} bugs, reporting
32591 A number of companies and individuals offer support for @sc{gnu} products.
32592 If you obtained @value{GDBN} from a support organization, we recommend you
32593 contact that organization first.
32595 You can find contact information for many support companies and
32596 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
32598 @c should add a web page ref...
32601 @ifset BUGURL_DEFAULT
32602 In any event, we also recommend that you submit bug reports for
32603 @value{GDBN}. The preferred method is to submit them directly using
32604 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
32605 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
32608 @strong{Do not send bug reports to @samp{info-gdb}, or to
32609 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
32610 not want to receive bug reports. Those that do have arranged to receive
32613 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
32614 serves as a repeater. The mailing list and the newsgroup carry exactly
32615 the same messages. Often people think of posting bug reports to the
32616 newsgroup instead of mailing them. This appears to work, but it has one
32617 problem which can be crucial: a newsgroup posting often lacks a mail
32618 path back to the sender. Thus, if we need to ask for more information,
32619 we may be unable to reach you. For this reason, it is better to send
32620 bug reports to the mailing list.
32622 @ifclear BUGURL_DEFAULT
32623 In any event, we also recommend that you submit bug reports for
32624 @value{GDBN} to @value{BUGURL}.
32628 The fundamental principle of reporting bugs usefully is this:
32629 @strong{report all the facts}. If you are not sure whether to state a
32630 fact or leave it out, state it!
32632 Often people omit facts because they think they know what causes the
32633 problem and assume that some details do not matter. Thus, you might
32634 assume that the name of the variable you use in an example does not matter.
32635 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
32636 stray memory reference which happens to fetch from the location where that
32637 name is stored in memory; perhaps, if the name were different, the contents
32638 of that location would fool the debugger into doing the right thing despite
32639 the bug. Play it safe and give a specific, complete example. That is the
32640 easiest thing for you to do, and the most helpful.
32642 Keep in mind that the purpose of a bug report is to enable us to fix the
32643 bug. It may be that the bug has been reported previously, but neither
32644 you nor we can know that unless your bug report is complete and
32647 Sometimes people give a few sketchy facts and ask, ``Does this ring a
32648 bell?'' Those bug reports are useless, and we urge everyone to
32649 @emph{refuse to respond to them} except to chide the sender to report
32652 To enable us to fix the bug, you should include all these things:
32656 The version of @value{GDBN}. @value{GDBN} announces it if you start
32657 with no arguments; you can also print it at any time using @code{show
32660 Without this, we will not know whether there is any point in looking for
32661 the bug in the current version of @value{GDBN}.
32664 The type of machine you are using, and the operating system name and
32668 The details of the @value{GDBN} build-time configuration.
32669 @value{GDBN} shows these details if you invoke it with the
32670 @option{--configuration} command-line option, or if you type
32671 @code{show configuration} at @value{GDBN}'s prompt.
32674 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
32675 ``@value{GCC}--2.8.1''.
32678 What compiler (and its version) was used to compile the program you are
32679 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
32680 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
32681 to get this information; for other compilers, see the documentation for
32685 The command arguments you gave the compiler to compile your example and
32686 observe the bug. For example, did you use @samp{-O}? To guarantee
32687 you will not omit something important, list them all. A copy of the
32688 Makefile (or the output from make) is sufficient.
32690 If we were to try to guess the arguments, we would probably guess wrong
32691 and then we might not encounter the bug.
32694 A complete input script, and all necessary source files, that will
32698 A description of what behavior you observe that you believe is
32699 incorrect. For example, ``It gets a fatal signal.''
32701 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
32702 will certainly notice it. But if the bug is incorrect output, we might
32703 not notice unless it is glaringly wrong. You might as well not give us
32704 a chance to make a mistake.
32706 Even if the problem you experience is a fatal signal, you should still
32707 say so explicitly. Suppose something strange is going on, such as, your
32708 copy of @value{GDBN} is out of synch, or you have encountered a bug in
32709 the C library on your system. (This has happened!) Your copy might
32710 crash and ours would not. If you told us to expect a crash, then when
32711 ours fails to crash, we would know that the bug was not happening for
32712 us. If you had not told us to expect a crash, then we would not be able
32713 to draw any conclusion from our observations.
32716 @cindex recording a session script
32717 To collect all this information, you can use a session recording program
32718 such as @command{script}, which is available on many Unix systems.
32719 Just run your @value{GDBN} session inside @command{script} and then
32720 include the @file{typescript} file with your bug report.
32722 Another way to record a @value{GDBN} session is to run @value{GDBN}
32723 inside Emacs and then save the entire buffer to a file.
32726 If you wish to suggest changes to the @value{GDBN} source, send us context
32727 diffs. If you even discuss something in the @value{GDBN} source, refer to
32728 it by context, not by line number.
32730 The line numbers in our development sources will not match those in your
32731 sources. Your line numbers would convey no useful information to us.
32735 Here are some things that are not necessary:
32739 A description of the envelope of the bug.
32741 Often people who encounter a bug spend a lot of time investigating
32742 which changes to the input file will make the bug go away and which
32743 changes will not affect it.
32745 This is often time consuming and not very useful, because the way we
32746 will find the bug is by running a single example under the debugger
32747 with breakpoints, not by pure deduction from a series of examples.
32748 We recommend that you save your time for something else.
32750 Of course, if you can find a simpler example to report @emph{instead}
32751 of the original one, that is a convenience for us. Errors in the
32752 output will be easier to spot, running under the debugger will take
32753 less time, and so on.
32755 However, simplification is not vital; if you do not want to do this,
32756 report the bug anyway and send us the entire test case you used.
32759 A patch for the bug.
32761 A patch for the bug does help us if it is a good one. But do not omit
32762 the necessary information, such as the test case, on the assumption that
32763 a patch is all we need. We might see problems with your patch and decide
32764 to fix the problem another way, or we might not understand it at all.
32766 Sometimes with a program as complicated as @value{GDBN} it is very hard to
32767 construct an example that will make the program follow a certain path
32768 through the code. If you do not send us the example, we will not be able
32769 to construct one, so we will not be able to verify that the bug is fixed.
32771 And if we cannot understand what bug you are trying to fix, or why your
32772 patch should be an improvement, we will not install it. A test case will
32773 help us to understand.
32776 A guess about what the bug is or what it depends on.
32778 Such guesses are usually wrong. Even we cannot guess right about such
32779 things without first using the debugger to find the facts.
32782 @c The readline documentation is distributed with the readline code
32783 @c and consists of the two following files:
32786 @c Use -I with makeinfo to point to the appropriate directory,
32787 @c environment var TEXINPUTS with TeX.
32788 @ifclear SYSTEM_READLINE
32789 @include rluser.texi
32790 @include hsuser.texi
32794 @appendix In Memoriam
32796 The @value{GDBN} project mourns the loss of the following long-time
32801 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
32802 to Free Software in general. Outside of @value{GDBN}, he was known in
32803 the Amiga world for his series of Fish Disks, and the GeekGadget project.
32805 @item Michael Snyder
32806 Michael was one of the Global Maintainers of the @value{GDBN} project,
32807 with contributions recorded as early as 1996, until 2011. In addition
32808 to his day to day participation, he was a large driving force behind
32809 adding Reverse Debugging to @value{GDBN}.
32812 Beyond their technical contributions to the project, they were also
32813 enjoyable members of the Free Software Community. We will miss them.
32815 @node Formatting Documentation
32816 @appendix Formatting Documentation
32818 @cindex @value{GDBN} reference card
32819 @cindex reference card
32820 The @value{GDBN} 4 release includes an already-formatted reference card, ready
32821 for printing with PostScript or Ghostscript, in the @file{gdb}
32822 subdirectory of the main source directory@footnote{In
32823 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
32824 release.}. If you can use PostScript or Ghostscript with your printer,
32825 you can print the reference card immediately with @file{refcard.ps}.
32827 The release also includes the source for the reference card. You
32828 can format it, using @TeX{}, by typing:
32834 The @value{GDBN} reference card is designed to print in @dfn{landscape}
32835 mode on US ``letter'' size paper;
32836 that is, on a sheet 11 inches wide by 8.5 inches
32837 high. You will need to specify this form of printing as an option to
32838 your @sc{dvi} output program.
32840 @cindex documentation
32842 All the documentation for @value{GDBN} comes as part of the machine-readable
32843 distribution. The documentation is written in Texinfo format, which is
32844 a documentation system that uses a single source file to produce both
32845 on-line information and a printed manual. You can use one of the Info
32846 formatting commands to create the on-line version of the documentation
32847 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
32849 @value{GDBN} includes an already formatted copy of the on-line Info
32850 version of this manual in the @file{gdb} subdirectory. The main Info
32851 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
32852 subordinate files matching @samp{gdb.info*} in the same directory. If
32853 necessary, you can print out these files, or read them with any editor;
32854 but they are easier to read using the @code{info} subsystem in @sc{gnu}
32855 Emacs or the standalone @code{info} program, available as part of the
32856 @sc{gnu} Texinfo distribution.
32858 If you want to format these Info files yourself, you need one of the
32859 Info formatting programs, such as @code{texinfo-format-buffer} or
32862 If you have @code{makeinfo} installed, and are in the top level
32863 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
32864 version @value{GDBVN}), you can make the Info file by typing:
32871 If you want to typeset and print copies of this manual, you need @TeX{},
32872 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
32873 Texinfo definitions file.
32875 @TeX{} is a typesetting program; it does not print files directly, but
32876 produces output files called @sc{dvi} files. To print a typeset
32877 document, you need a program to print @sc{dvi} files. If your system
32878 has @TeX{} installed, chances are it has such a program. The precise
32879 command to use depends on your system; @kbd{lpr -d} is common; another
32880 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
32881 require a file name without any extension or a @samp{.dvi} extension.
32883 @TeX{} also requires a macro definitions file called
32884 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
32885 written in Texinfo format. On its own, @TeX{} cannot either read or
32886 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
32887 and is located in the @file{gdb-@var{version-number}/texinfo}
32890 If you have @TeX{} and a @sc{dvi} printer program installed, you can
32891 typeset and print this manual. First switch to the @file{gdb}
32892 subdirectory of the main source directory (for example, to
32893 @file{gdb-@value{GDBVN}/gdb}) and type:
32899 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
32901 @node Installing GDB
32902 @appendix Installing @value{GDBN}
32903 @cindex installation
32906 * Requirements:: Requirements for building @value{GDBN}
32907 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
32908 * Separate Objdir:: Compiling @value{GDBN} in another directory
32909 * Config Names:: Specifying names for hosts and targets
32910 * Configure Options:: Summary of options for configure
32911 * System-wide configuration:: Having a system-wide init file
32915 @section Requirements for Building @value{GDBN}
32916 @cindex building @value{GDBN}, requirements for
32918 Building @value{GDBN} requires various tools and packages to be available.
32919 Other packages will be used only if they are found.
32921 @heading Tools/Packages Necessary for Building @value{GDBN}
32923 @item ISO C90 compiler
32924 @value{GDBN} is written in ISO C90. It should be buildable with any
32925 working C90 compiler, e.g.@: GCC.
32929 @heading Tools/Packages Optional for Building @value{GDBN}
32933 @value{GDBN} can use the Expat XML parsing library. This library may be
32934 included with your operating system distribution; if it is not, you
32935 can get the latest version from @url{http://expat.sourceforge.net}.
32936 The @file{configure} script will search for this library in several
32937 standard locations; if it is installed in an unusual path, you can
32938 use the @option{--with-libexpat-prefix} option to specify its location.
32944 Remote protocol memory maps (@pxref{Memory Map Format})
32946 Target descriptions (@pxref{Target Descriptions})
32948 Remote shared library lists (@xref{Library List Format},
32949 or alternatively @pxref{Library List Format for SVR4 Targets})
32951 MS-Windows shared libraries (@pxref{Shared Libraries})
32953 Traceframe info (@pxref{Traceframe Info Format})
32955 Branch trace (@pxref{Branch Trace Format})
32959 @cindex compressed debug sections
32960 @value{GDBN} will use the @samp{zlib} library, if available, to read
32961 compressed debug sections. Some linkers, such as GNU gold, are capable
32962 of producing binaries with compressed debug sections. If @value{GDBN}
32963 is compiled with @samp{zlib}, it will be able to read the debug
32964 information in such binaries.
32966 The @samp{zlib} library is likely included with your operating system
32967 distribution; if it is not, you can get the latest version from
32968 @url{http://zlib.net}.
32971 @value{GDBN}'s features related to character sets (@pxref{Character
32972 Sets}) require a functioning @code{iconv} implementation. If you are
32973 on a GNU system, then this is provided by the GNU C Library. Some
32974 other systems also provide a working @code{iconv}.
32976 If @value{GDBN} is using the @code{iconv} program which is installed
32977 in a non-standard place, you will need to tell @value{GDBN} where to find it.
32978 This is done with @option{--with-iconv-bin} which specifies the
32979 directory that contains the @code{iconv} program.
32981 On systems without @code{iconv}, you can install GNU Libiconv. If you
32982 have previously installed Libiconv, you can use the
32983 @option{--with-libiconv-prefix} option to configure.
32985 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
32986 arrange to build Libiconv if a directory named @file{libiconv} appears
32987 in the top-most source directory. If Libiconv is built this way, and
32988 if the operating system does not provide a suitable @code{iconv}
32989 implementation, then the just-built library will automatically be used
32990 by @value{GDBN}. One easy way to set this up is to download GNU
32991 Libiconv, unpack it, and then rename the directory holding the
32992 Libiconv source code to @samp{libiconv}.
32995 @node Running Configure
32996 @section Invoking the @value{GDBN} @file{configure} Script
32997 @cindex configuring @value{GDBN}
32998 @value{GDBN} comes with a @file{configure} script that automates the process
32999 of preparing @value{GDBN} for installation; you can then use @code{make} to
33000 build the @code{gdb} program.
33002 @c irrelevant in info file; it's as current as the code it lives with.
33003 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
33004 look at the @file{README} file in the sources; we may have improved the
33005 installation procedures since publishing this manual.}
33008 The @value{GDBN} distribution includes all the source code you need for
33009 @value{GDBN} in a single directory, whose name is usually composed by
33010 appending the version number to @samp{gdb}.
33012 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
33013 @file{gdb-@value{GDBVN}} directory. That directory contains:
33016 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
33017 script for configuring @value{GDBN} and all its supporting libraries
33019 @item gdb-@value{GDBVN}/gdb
33020 the source specific to @value{GDBN} itself
33022 @item gdb-@value{GDBVN}/bfd
33023 source for the Binary File Descriptor library
33025 @item gdb-@value{GDBVN}/include
33026 @sc{gnu} include files
33028 @item gdb-@value{GDBVN}/libiberty
33029 source for the @samp{-liberty} free software library
33031 @item gdb-@value{GDBVN}/opcodes
33032 source for the library of opcode tables and disassemblers
33034 @item gdb-@value{GDBVN}/readline
33035 source for the @sc{gnu} command-line interface
33037 @item gdb-@value{GDBVN}/glob
33038 source for the @sc{gnu} filename pattern-matching subroutine
33040 @item gdb-@value{GDBVN}/mmalloc
33041 source for the @sc{gnu} memory-mapped malloc package
33044 The simplest way to configure and build @value{GDBN} is to run @file{configure}
33045 from the @file{gdb-@var{version-number}} source directory, which in
33046 this example is the @file{gdb-@value{GDBVN}} directory.
33048 First switch to the @file{gdb-@var{version-number}} source directory
33049 if you are not already in it; then run @file{configure}. Pass the
33050 identifier for the platform on which @value{GDBN} will run as an
33056 cd gdb-@value{GDBVN}
33057 ./configure @var{host}
33062 where @var{host} is an identifier such as @samp{sun4} or
33063 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
33064 (You can often leave off @var{host}; @file{configure} tries to guess the
33065 correct value by examining your system.)
33067 Running @samp{configure @var{host}} and then running @code{make} builds the
33068 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
33069 libraries, then @code{gdb} itself. The configured source files, and the
33070 binaries, are left in the corresponding source directories.
33073 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
33074 system does not recognize this automatically when you run a different
33075 shell, you may need to run @code{sh} on it explicitly:
33078 sh configure @var{host}
33081 If you run @file{configure} from a directory that contains source
33082 directories for multiple libraries or programs, such as the
33083 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
33085 creates configuration files for every directory level underneath (unless
33086 you tell it not to, with the @samp{--norecursion} option).
33088 You should run the @file{configure} script from the top directory in the
33089 source tree, the @file{gdb-@var{version-number}} directory. If you run
33090 @file{configure} from one of the subdirectories, you will configure only
33091 that subdirectory. That is usually not what you want. In particular,
33092 if you run the first @file{configure} from the @file{gdb} subdirectory
33093 of the @file{gdb-@var{version-number}} directory, you will omit the
33094 configuration of @file{bfd}, @file{readline}, and other sibling
33095 directories of the @file{gdb} subdirectory. This leads to build errors
33096 about missing include files such as @file{bfd/bfd.h}.
33098 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
33099 However, you should make sure that the shell on your path (named by
33100 the @samp{SHELL} environment variable) is publicly readable. Remember
33101 that @value{GDBN} uses the shell to start your program---some systems refuse to
33102 let @value{GDBN} debug child processes whose programs are not readable.
33104 @node Separate Objdir
33105 @section Compiling @value{GDBN} in Another Directory
33107 If you want to run @value{GDBN} versions for several host or target machines,
33108 you need a different @code{gdb} compiled for each combination of
33109 host and target. @file{configure} is designed to make this easy by
33110 allowing you to generate each configuration in a separate subdirectory,
33111 rather than in the source directory. If your @code{make} program
33112 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
33113 @code{make} in each of these directories builds the @code{gdb}
33114 program specified there.
33116 To build @code{gdb} in a separate directory, run @file{configure}
33117 with the @samp{--srcdir} option to specify where to find the source.
33118 (You also need to specify a path to find @file{configure}
33119 itself from your working directory. If the path to @file{configure}
33120 would be the same as the argument to @samp{--srcdir}, you can leave out
33121 the @samp{--srcdir} option; it is assumed.)
33123 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
33124 separate directory for a Sun 4 like this:
33128 cd gdb-@value{GDBVN}
33131 ../gdb-@value{GDBVN}/configure sun4
33136 When @file{configure} builds a configuration using a remote source
33137 directory, it creates a tree for the binaries with the same structure
33138 (and using the same names) as the tree under the source directory. In
33139 the example, you'd find the Sun 4 library @file{libiberty.a} in the
33140 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
33141 @file{gdb-sun4/gdb}.
33143 Make sure that your path to the @file{configure} script has just one
33144 instance of @file{gdb} in it. If your path to @file{configure} looks
33145 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
33146 one subdirectory of @value{GDBN}, not the whole package. This leads to
33147 build errors about missing include files such as @file{bfd/bfd.h}.
33149 One popular reason to build several @value{GDBN} configurations in separate
33150 directories is to configure @value{GDBN} for cross-compiling (where
33151 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
33152 programs that run on another machine---the @dfn{target}).
33153 You specify a cross-debugging target by
33154 giving the @samp{--target=@var{target}} option to @file{configure}.
33156 When you run @code{make} to build a program or library, you must run
33157 it in a configured directory---whatever directory you were in when you
33158 called @file{configure} (or one of its subdirectories).
33160 The @code{Makefile} that @file{configure} generates in each source
33161 directory also runs recursively. If you type @code{make} in a source
33162 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
33163 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
33164 will build all the required libraries, and then build GDB.
33166 When you have multiple hosts or targets configured in separate
33167 directories, you can run @code{make} on them in parallel (for example,
33168 if they are NFS-mounted on each of the hosts); they will not interfere
33172 @section Specifying Names for Hosts and Targets
33174 The specifications used for hosts and targets in the @file{configure}
33175 script are based on a three-part naming scheme, but some short predefined
33176 aliases are also supported. The full naming scheme encodes three pieces
33177 of information in the following pattern:
33180 @var{architecture}-@var{vendor}-@var{os}
33183 For example, you can use the alias @code{sun4} as a @var{host} argument,
33184 or as the value for @var{target} in a @code{--target=@var{target}}
33185 option. The equivalent full name is @samp{sparc-sun-sunos4}.
33187 The @file{configure} script accompanying @value{GDBN} does not provide
33188 any query facility to list all supported host and target names or
33189 aliases. @file{configure} calls the Bourne shell script
33190 @code{config.sub} to map abbreviations to full names; you can read the
33191 script, if you wish, or you can use it to test your guesses on
33192 abbreviations---for example:
33195 % sh config.sub i386-linux
33197 % sh config.sub alpha-linux
33198 alpha-unknown-linux-gnu
33199 % sh config.sub hp9k700
33201 % sh config.sub sun4
33202 sparc-sun-sunos4.1.1
33203 % sh config.sub sun3
33204 m68k-sun-sunos4.1.1
33205 % sh config.sub i986v
33206 Invalid configuration `i986v': machine `i986v' not recognized
33210 @code{config.sub} is also distributed in the @value{GDBN} source
33211 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
33213 @node Configure Options
33214 @section @file{configure} Options
33216 Here is a summary of the @file{configure} options and arguments that
33217 are most often useful for building @value{GDBN}. @file{configure} also has
33218 several other options not listed here. @inforef{What Configure
33219 Does,,configure.info}, for a full explanation of @file{configure}.
33222 configure @r{[}--help@r{]}
33223 @r{[}--prefix=@var{dir}@r{]}
33224 @r{[}--exec-prefix=@var{dir}@r{]}
33225 @r{[}--srcdir=@var{dirname}@r{]}
33226 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
33227 @r{[}--target=@var{target}@r{]}
33232 You may introduce options with a single @samp{-} rather than
33233 @samp{--} if you prefer; but you may abbreviate option names if you use
33238 Display a quick summary of how to invoke @file{configure}.
33240 @item --prefix=@var{dir}
33241 Configure the source to install programs and files under directory
33244 @item --exec-prefix=@var{dir}
33245 Configure the source to install programs under directory
33248 @c avoid splitting the warning from the explanation:
33250 @item --srcdir=@var{dirname}
33251 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
33252 @code{make} that implements the @code{VPATH} feature.}@*
33253 Use this option to make configurations in directories separate from the
33254 @value{GDBN} source directories. Among other things, you can use this to
33255 build (or maintain) several configurations simultaneously, in separate
33256 directories. @file{configure} writes configuration-specific files in
33257 the current directory, but arranges for them to use the source in the
33258 directory @var{dirname}. @file{configure} creates directories under
33259 the working directory in parallel to the source directories below
33262 @item --norecursion
33263 Configure only the directory level where @file{configure} is executed; do not
33264 propagate configuration to subdirectories.
33266 @item --target=@var{target}
33267 Configure @value{GDBN} for cross-debugging programs running on the specified
33268 @var{target}. Without this option, @value{GDBN} is configured to debug
33269 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
33271 There is no convenient way to generate a list of all available targets.
33273 @item @var{host} @dots{}
33274 Configure @value{GDBN} to run on the specified @var{host}.
33276 There is no convenient way to generate a list of all available hosts.
33279 There are many other options available as well, but they are generally
33280 needed for special purposes only.
33282 @node System-wide configuration
33283 @section System-wide configuration and settings
33284 @cindex system-wide init file
33286 @value{GDBN} can be configured to have a system-wide init file;
33287 this file will be read and executed at startup (@pxref{Startup, , What
33288 @value{GDBN} does during startup}).
33290 Here is the corresponding configure option:
33293 @item --with-system-gdbinit=@var{file}
33294 Specify that the default location of the system-wide init file is
33298 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
33299 it may be subject to relocation. Two possible cases:
33303 If the default location of this init file contains @file{$prefix},
33304 it will be subject to relocation. Suppose that the configure options
33305 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
33306 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
33307 init file is looked for as @file{$install/etc/gdbinit} instead of
33308 @file{$prefix/etc/gdbinit}.
33311 By contrast, if the default location does not contain the prefix,
33312 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
33313 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
33314 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
33315 wherever @value{GDBN} is installed.
33318 If the configured location of the system-wide init file (as given by the
33319 @option{--with-system-gdbinit} option at configure time) is in the
33320 data-directory (as specified by @option{--with-gdb-datadir} at configure
33321 time) or in one of its subdirectories, then @value{GDBN} will look for the
33322 system-wide init file in the directory specified by the
33323 @option{--data-directory} command-line option.
33324 Note that the system-wide init file is only read once, during @value{GDBN}
33325 initialization. If the data-directory is changed after @value{GDBN} has
33326 started with the @code{set data-directory} command, the file will not be
33330 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
33333 @node System-wide Configuration Scripts
33334 @subsection Installed System-wide Configuration Scripts
33335 @cindex system-wide configuration scripts
33337 The @file{system-gdbinit} directory, located inside the data-directory
33338 (as specified by @option{--with-gdb-datadir} at configure time) contains
33339 a number of scripts which can be used as system-wide init files. To
33340 automatically source those scripts at startup, @value{GDBN} should be
33341 configured with @option{--with-system-gdbinit}. Otherwise, any user
33342 should be able to source them by hand as needed.
33344 The following scripts are currently available:
33347 @item @file{elinos.py}
33349 @cindex ELinOS system-wide configuration script
33350 This script is useful when debugging a program on an ELinOS target.
33351 It takes advantage of the environment variables defined in a standard
33352 ELinOS environment in order to determine the location of the system
33353 shared libraries, and then sets the @samp{solib-absolute-prefix}
33354 and @samp{solib-search-path} variables appropriately.
33356 @item @file{wrs-linux.py}
33357 @pindex wrs-linux.py
33358 @cindex Wind River Linux system-wide configuration script
33359 This script is useful when debugging a program on a target running
33360 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
33361 the host-side sysroot used by the target system.
33365 @node Maintenance Commands
33366 @appendix Maintenance Commands
33367 @cindex maintenance commands
33368 @cindex internal commands
33370 In addition to commands intended for @value{GDBN} users, @value{GDBN}
33371 includes a number of commands intended for @value{GDBN} developers,
33372 that are not documented elsewhere in this manual. These commands are
33373 provided here for reference. (For commands that turn on debugging
33374 messages, see @ref{Debugging Output}.)
33377 @kindex maint agent
33378 @kindex maint agent-eval
33379 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
33380 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
33381 Translate the given @var{expression} into remote agent bytecodes.
33382 This command is useful for debugging the Agent Expression mechanism
33383 (@pxref{Agent Expressions}). The @samp{agent} version produces an
33384 expression useful for data collection, such as by tracepoints, while
33385 @samp{maint agent-eval} produces an expression that evaluates directly
33386 to a result. For instance, a collection expression for @code{globa +
33387 globb} will include bytecodes to record four bytes of memory at each
33388 of the addresses of @code{globa} and @code{globb}, while discarding
33389 the result of the addition, while an evaluation expression will do the
33390 addition and return the sum.
33391 If @code{-at} is given, generate remote agent bytecode for @var{location}.
33392 If not, generate remote agent bytecode for current frame PC address.
33394 @kindex maint agent-printf
33395 @item maint agent-printf @var{format},@var{expr},...
33396 Translate the given format string and list of argument expressions
33397 into remote agent bytecodes and display them as a disassembled list.
33398 This command is useful for debugging the agent version of dynamic
33399 printf (@pxref{Dynamic Printf}).
33401 @kindex maint info breakpoints
33402 @item @anchor{maint info breakpoints}maint info breakpoints
33403 Using the same format as @samp{info breakpoints}, display both the
33404 breakpoints you've set explicitly, and those @value{GDBN} is using for
33405 internal purposes. Internal breakpoints are shown with negative
33406 breakpoint numbers. The type column identifies what kind of breakpoint
33411 Normal, explicitly set breakpoint.
33414 Normal, explicitly set watchpoint.
33417 Internal breakpoint, used to handle correctly stepping through
33418 @code{longjmp} calls.
33420 @item longjmp resume
33421 Internal breakpoint at the target of a @code{longjmp}.
33424 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
33427 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
33430 Shared library events.
33434 @kindex maint info bfds
33435 @item maint info bfds
33436 This prints information about each @code{bfd} object that is known to
33437 @value{GDBN}. @xref{Top, , BFD, bfd, The Binary File Descriptor Library}.
33439 @kindex set displaced-stepping
33440 @kindex show displaced-stepping
33441 @cindex displaced stepping support
33442 @cindex out-of-line single-stepping
33443 @item set displaced-stepping
33444 @itemx show displaced-stepping
33445 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
33446 if the target supports it. Displaced stepping is a way to single-step
33447 over breakpoints without removing them from the inferior, by executing
33448 an out-of-line copy of the instruction that was originally at the
33449 breakpoint location. It is also known as out-of-line single-stepping.
33452 @item set displaced-stepping on
33453 If the target architecture supports it, @value{GDBN} will use
33454 displaced stepping to step over breakpoints.
33456 @item set displaced-stepping off
33457 @value{GDBN} will not use displaced stepping to step over breakpoints,
33458 even if such is supported by the target architecture.
33460 @cindex non-stop mode, and @samp{set displaced-stepping}
33461 @item set displaced-stepping auto
33462 This is the default mode. @value{GDBN} will use displaced stepping
33463 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
33464 architecture supports displaced stepping.
33467 @kindex maint check-psymtabs
33468 @item maint check-psymtabs
33469 Check the consistency of currently expanded psymtabs versus symtabs.
33470 Use this to check, for example, whether a symbol is in one but not the other.
33472 @kindex maint check-symtabs
33473 @item maint check-symtabs
33474 Check the consistency of currently expanded symtabs.
33476 @kindex maint expand-symtabs
33477 @item maint expand-symtabs [@var{regexp}]
33478 Expand symbol tables.
33479 If @var{regexp} is specified, only expand symbol tables for file
33480 names matching @var{regexp}.
33482 @kindex maint set catch-demangler-crashes
33483 @kindex maint show catch-demangler-crashes
33484 @cindex demangler crashes
33485 @item maint set catch-demangler-crashes [on|off]
33486 @itemx maint show catch-demangler-crashes
33487 Control whether @value{GDBN} should attempt to catch crashes in the
33488 symbol name demangler. The default is to attempt to catch crashes.
33489 If enabled, the first time a crash is caught, a core file is created,
33490 the offending symbol is displayed and the user is presented with the
33491 option to terminate the current session.
33493 @kindex maint cplus first_component
33494 @item maint cplus first_component @var{name}
33495 Print the first C@t{++} class/namespace component of @var{name}.
33497 @kindex maint cplus namespace
33498 @item maint cplus namespace
33499 Print the list of possible C@t{++} namespaces.
33501 @kindex maint deprecate
33502 @kindex maint undeprecate
33503 @cindex deprecated commands
33504 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
33505 @itemx maint undeprecate @var{command}
33506 Deprecate or undeprecate the named @var{command}. Deprecated commands
33507 cause @value{GDBN} to issue a warning when you use them. The optional
33508 argument @var{replacement} says which newer command should be used in
33509 favor of the deprecated one; if it is given, @value{GDBN} will mention
33510 the replacement as part of the warning.
33512 @kindex maint dump-me
33513 @item maint dump-me
33514 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
33515 Cause a fatal signal in the debugger and force it to dump its core.
33516 This is supported only on systems which support aborting a program
33517 with the @code{SIGQUIT} signal.
33519 @kindex maint internal-error
33520 @kindex maint internal-warning
33521 @kindex maint demangler-warning
33522 @cindex demangler crashes
33523 @item maint internal-error @r{[}@var{message-text}@r{]}
33524 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
33525 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
33527 Cause @value{GDBN} to call the internal function @code{internal_error},
33528 @code{internal_warning} or @code{demangler_warning} and hence behave
33529 as though an internal problam has been detected. In addition to
33530 reporting the internal problem, these functions give the user the
33531 opportunity to either quit @value{GDBN} or (for @code{internal_error}
33532 and @code{internal_warning}) create a core file of the current
33533 @value{GDBN} session.
33535 These commands take an optional parameter @var{message-text} that is
33536 used as the text of the error or warning message.
33538 Here's an example of using @code{internal-error}:
33541 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
33542 @dots{}/maint.c:121: internal-error: testing, 1, 2
33543 A problem internal to GDB has been detected. Further
33544 debugging may prove unreliable.
33545 Quit this debugging session? (y or n) @kbd{n}
33546 Create a core file? (y or n) @kbd{n}
33550 @cindex @value{GDBN} internal error
33551 @cindex internal errors, control of @value{GDBN} behavior
33552 @cindex demangler crashes
33554 @kindex maint set internal-error
33555 @kindex maint show internal-error
33556 @kindex maint set internal-warning
33557 @kindex maint show internal-warning
33558 @kindex maint set demangler-warning
33559 @kindex maint show demangler-warning
33560 @item maint set internal-error @var{action} [ask|yes|no]
33561 @itemx maint show internal-error @var{action}
33562 @itemx maint set internal-warning @var{action} [ask|yes|no]
33563 @itemx maint show internal-warning @var{action}
33564 @itemx maint set demangler-warning @var{action} [ask|yes|no]
33565 @itemx maint show demangler-warning @var{action}
33566 When @value{GDBN} reports an internal problem (error or warning) it
33567 gives the user the opportunity to both quit @value{GDBN} and create a
33568 core file of the current @value{GDBN} session. These commands let you
33569 override the default behaviour for each particular @var{action},
33570 described in the table below.
33574 You can specify that @value{GDBN} should always (yes) or never (no)
33575 quit. The default is to ask the user what to do.
33578 You can specify that @value{GDBN} should always (yes) or never (no)
33579 create a core file. The default is to ask the user what to do. Note
33580 that there is no @code{corefile} option for @code{demangler-warning}:
33581 demangler warnings always create a core file and this cannot be
33585 @kindex maint packet
33586 @item maint packet @var{text}
33587 If @value{GDBN} is talking to an inferior via the serial protocol,
33588 then this command sends the string @var{text} to the inferior, and
33589 displays the response packet. @value{GDBN} supplies the initial
33590 @samp{$} character, the terminating @samp{#} character, and the
33593 @kindex maint print architecture
33594 @item maint print architecture @r{[}@var{file}@r{]}
33595 Print the entire architecture configuration. The optional argument
33596 @var{file} names the file where the output goes.
33598 @kindex maint print c-tdesc
33599 @item maint print c-tdesc
33600 Print the current target description (@pxref{Target Descriptions}) as
33601 a C source file. The created source file can be used in @value{GDBN}
33602 when an XML parser is not available to parse the description.
33604 @kindex maint print dummy-frames
33605 @item maint print dummy-frames
33606 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
33609 (@value{GDBP}) @kbd{b add}
33611 (@value{GDBP}) @kbd{print add(2,3)}
33612 Breakpoint 2, add (a=2, b=3) at @dots{}
33614 The program being debugged stopped while in a function called from GDB.
33616 (@value{GDBP}) @kbd{maint print dummy-frames}
33617 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
33621 Takes an optional file parameter.
33623 @kindex maint print registers
33624 @kindex maint print raw-registers
33625 @kindex maint print cooked-registers
33626 @kindex maint print register-groups
33627 @kindex maint print remote-registers
33628 @item maint print registers @r{[}@var{file}@r{]}
33629 @itemx maint print raw-registers @r{[}@var{file}@r{]}
33630 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
33631 @itemx maint print register-groups @r{[}@var{file}@r{]}
33632 @itemx maint print remote-registers @r{[}@var{file}@r{]}
33633 Print @value{GDBN}'s internal register data structures.
33635 The command @code{maint print raw-registers} includes the contents of
33636 the raw register cache; the command @code{maint print
33637 cooked-registers} includes the (cooked) value of all registers,
33638 including registers which aren't available on the target nor visible
33639 to user; the command @code{maint print register-groups} includes the
33640 groups that each register is a member of; and the command @code{maint
33641 print remote-registers} includes the remote target's register numbers
33642 and offsets in the `G' packets.
33644 These commands take an optional parameter, a file name to which to
33645 write the information.
33647 @kindex maint print reggroups
33648 @item maint print reggroups @r{[}@var{file}@r{]}
33649 Print @value{GDBN}'s internal register group data structures. The
33650 optional argument @var{file} tells to what file to write the
33653 The register groups info looks like this:
33656 (@value{GDBP}) @kbd{maint print reggroups}
33669 This command forces @value{GDBN} to flush its internal register cache.
33671 @kindex maint print objfiles
33672 @cindex info for known object files
33673 @item maint print objfiles @r{[}@var{regexp}@r{]}
33674 Print a dump of all known object files.
33675 If @var{regexp} is specified, only print object files whose names
33676 match @var{regexp}. For each object file, this command prints its name,
33677 address in memory, and all of its psymtabs and symtabs.
33679 @kindex maint print user-registers
33680 @cindex user registers
33681 @item maint print user-registers
33682 List all currently available @dfn{user registers}. User registers
33683 typically provide alternate names for actual hardware registers. They
33684 include the four ``standard'' registers @code{$fp}, @code{$pc},
33685 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
33686 registers can be used in expressions in the same way as the canonical
33687 register names, but only the latter are listed by the @code{info
33688 registers} and @code{maint print registers} commands.
33690 @kindex maint print section-scripts
33691 @cindex info for known .debug_gdb_scripts-loaded scripts
33692 @item maint print section-scripts [@var{regexp}]
33693 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
33694 If @var{regexp} is specified, only print scripts loaded by object files
33695 matching @var{regexp}.
33696 For each script, this command prints its name as specified in the objfile,
33697 and the full path if known.
33698 @xref{dotdebug_gdb_scripts section}.
33700 @kindex maint print statistics
33701 @cindex bcache statistics
33702 @item maint print statistics
33703 This command prints, for each object file in the program, various data
33704 about that object file followed by the byte cache (@dfn{bcache})
33705 statistics for the object file. The objfile data includes the number
33706 of minimal, partial, full, and stabs symbols, the number of types
33707 defined by the objfile, the number of as yet unexpanded psym tables,
33708 the number of line tables and string tables, and the amount of memory
33709 used by the various tables. The bcache statistics include the counts,
33710 sizes, and counts of duplicates of all and unique objects, max,
33711 average, and median entry size, total memory used and its overhead and
33712 savings, and various measures of the hash table size and chain
33715 @kindex maint print target-stack
33716 @cindex target stack description
33717 @item maint print target-stack
33718 A @dfn{target} is an interface between the debugger and a particular
33719 kind of file or process. Targets can be stacked in @dfn{strata},
33720 so that more than one target can potentially respond to a request.
33721 In particular, memory accesses will walk down the stack of targets
33722 until they find a target that is interested in handling that particular
33725 This command prints a short description of each layer that was pushed on
33726 the @dfn{target stack}, starting from the top layer down to the bottom one.
33728 @kindex maint print type
33729 @cindex type chain of a data type
33730 @item maint print type @var{expr}
33731 Print the type chain for a type specified by @var{expr}. The argument
33732 can be either a type name or a symbol. If it is a symbol, the type of
33733 that symbol is described. The type chain produced by this command is
33734 a recursive definition of the data type as stored in @value{GDBN}'s
33735 data structures, including its flags and contained types.
33737 @kindex maint set dwarf2 always-disassemble
33738 @kindex maint show dwarf2 always-disassemble
33739 @item maint set dwarf2 always-disassemble
33740 @item maint show dwarf2 always-disassemble
33741 Control the behavior of @code{info address} when using DWARF debugging
33744 The default is @code{off}, which means that @value{GDBN} should try to
33745 describe a variable's location in an easily readable format. When
33746 @code{on}, @value{GDBN} will instead display the DWARF location
33747 expression in an assembly-like format. Note that some locations are
33748 too complex for @value{GDBN} to describe simply; in this case you will
33749 always see the disassembly form.
33751 Here is an example of the resulting disassembly:
33754 (gdb) info addr argc
33755 Symbol "argc" is a complex DWARF expression:
33759 For more information on these expressions, see
33760 @uref{http://www.dwarfstd.org/, the DWARF standard}.
33762 @kindex maint set dwarf2 max-cache-age
33763 @kindex maint show dwarf2 max-cache-age
33764 @item maint set dwarf2 max-cache-age
33765 @itemx maint show dwarf2 max-cache-age
33766 Control the DWARF 2 compilation unit cache.
33768 @cindex DWARF 2 compilation units cache
33769 In object files with inter-compilation-unit references, such as those
33770 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
33771 reader needs to frequently refer to previously read compilation units.
33772 This setting controls how long a compilation unit will remain in the
33773 cache if it is not referenced. A higher limit means that cached
33774 compilation units will be stored in memory longer, and more total
33775 memory will be used. Setting it to zero disables caching, which will
33776 slow down @value{GDBN} startup, but reduce memory consumption.
33778 @kindex maint set profile
33779 @kindex maint show profile
33780 @cindex profiling GDB
33781 @item maint set profile
33782 @itemx maint show profile
33783 Control profiling of @value{GDBN}.
33785 Profiling will be disabled until you use the @samp{maint set profile}
33786 command to enable it. When you enable profiling, the system will begin
33787 collecting timing and execution count data; when you disable profiling or
33788 exit @value{GDBN}, the results will be written to a log file. Remember that
33789 if you use profiling, @value{GDBN} will overwrite the profiling log file
33790 (often called @file{gmon.out}). If you have a record of important profiling
33791 data in a @file{gmon.out} file, be sure to move it to a safe location.
33793 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
33794 compiled with the @samp{-pg} compiler option.
33796 @kindex maint set show-debug-regs
33797 @kindex maint show show-debug-regs
33798 @cindex hardware debug registers
33799 @item maint set show-debug-regs
33800 @itemx maint show show-debug-regs
33801 Control whether to show variables that mirror the hardware debug
33802 registers. Use @code{on} to enable, @code{off} to disable. If
33803 enabled, the debug registers values are shown when @value{GDBN} inserts or
33804 removes a hardware breakpoint or watchpoint, and when the inferior
33805 triggers a hardware-assisted breakpoint or watchpoint.
33807 @kindex maint set show-all-tib
33808 @kindex maint show show-all-tib
33809 @item maint set show-all-tib
33810 @itemx maint show show-all-tib
33811 Control whether to show all non zero areas within a 1k block starting
33812 at thread local base, when using the @samp{info w32 thread-information-block}
33815 @kindex maint set target-async
33816 @kindex maint show target-async
33817 @item maint set target-async
33818 @itemx maint show target-async
33819 This controls whether @value{GDBN} targets operate in synchronous or
33820 asynchronous mode (@pxref{Background Execution}). Normally the
33821 default is asynchronous, if it is available; but this can be changed
33822 to more easily debug problems occurring only in synchronous mode.
33824 @kindex maint set per-command
33825 @kindex maint show per-command
33826 @item maint set per-command
33827 @itemx maint show per-command
33828 @cindex resources used by commands
33830 @value{GDBN} can display the resources used by each command.
33831 This is useful in debugging performance problems.
33834 @item maint set per-command space [on|off]
33835 @itemx maint show per-command space
33836 Enable or disable the printing of the memory used by GDB for each command.
33837 If enabled, @value{GDBN} will display how much memory each command
33838 took, following the command's own output.
33839 This can also be requested by invoking @value{GDBN} with the
33840 @option{--statistics} command-line switch (@pxref{Mode Options}).
33842 @item maint set per-command time [on|off]
33843 @itemx maint show per-command time
33844 Enable or disable the printing of the execution time of @value{GDBN}
33846 If enabled, @value{GDBN} will display how much time it
33847 took to execute each command, following the command's own output.
33848 Both CPU time and wallclock time are printed.
33849 Printing both is useful when trying to determine whether the cost is
33850 CPU or, e.g., disk/network latency.
33851 Note that the CPU time printed is for @value{GDBN} only, it does not include
33852 the execution time of the inferior because there's no mechanism currently
33853 to compute how much time was spent by @value{GDBN} and how much time was
33854 spent by the program been debugged.
33855 This can also be requested by invoking @value{GDBN} with the
33856 @option{--statistics} command-line switch (@pxref{Mode Options}).
33858 @item maint set per-command symtab [on|off]
33859 @itemx maint show per-command symtab
33860 Enable or disable the printing of basic symbol table statistics
33862 If enabled, @value{GDBN} will display the following information:
33866 number of symbol tables
33868 number of primary symbol tables
33870 number of blocks in the blockvector
33874 @kindex maint space
33875 @cindex memory used by commands
33876 @item maint space @var{value}
33877 An alias for @code{maint set per-command space}.
33878 A non-zero value enables it, zero disables it.
33881 @cindex time of command execution
33882 @item maint time @var{value}
33883 An alias for @code{maint set per-command time}.
33884 A non-zero value enables it, zero disables it.
33886 @kindex maint translate-address
33887 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
33888 Find the symbol stored at the location specified by the address
33889 @var{addr} and an optional section name @var{section}. If found,
33890 @value{GDBN} prints the name of the closest symbol and an offset from
33891 the symbol's location to the specified address. This is similar to
33892 the @code{info address} command (@pxref{Symbols}), except that this
33893 command also allows to find symbols in other sections.
33895 If section was not specified, the section in which the symbol was found
33896 is also printed. For dynamically linked executables, the name of
33897 executable or shared library containing the symbol is printed as well.
33901 The following command is useful for non-interactive invocations of
33902 @value{GDBN}, such as in the test suite.
33905 @item set watchdog @var{nsec}
33906 @kindex set watchdog
33907 @cindex watchdog timer
33908 @cindex timeout for commands
33909 Set the maximum number of seconds @value{GDBN} will wait for the
33910 target operation to finish. If this time expires, @value{GDBN}
33911 reports and error and the command is aborted.
33913 @item show watchdog
33914 Show the current setting of the target wait timeout.
33917 @node Remote Protocol
33918 @appendix @value{GDBN} Remote Serial Protocol
33923 * Stop Reply Packets::
33924 * General Query Packets::
33925 * Architecture-Specific Protocol Details::
33926 * Tracepoint Packets::
33927 * Host I/O Packets::
33929 * Notification Packets::
33930 * Remote Non-Stop::
33931 * Packet Acknowledgment::
33933 * File-I/O Remote Protocol Extension::
33934 * Library List Format::
33935 * Library List Format for SVR4 Targets::
33936 * Memory Map Format::
33937 * Thread List Format::
33938 * Traceframe Info Format::
33939 * Branch Trace Format::
33945 There may be occasions when you need to know something about the
33946 protocol---for example, if there is only one serial port to your target
33947 machine, you might want your program to do something special if it
33948 recognizes a packet meant for @value{GDBN}.
33950 In the examples below, @samp{->} and @samp{<-} are used to indicate
33951 transmitted and received data, respectively.
33953 @cindex protocol, @value{GDBN} remote serial
33954 @cindex serial protocol, @value{GDBN} remote
33955 @cindex remote serial protocol
33956 All @value{GDBN} commands and responses (other than acknowledgments
33957 and notifications, see @ref{Notification Packets}) are sent as a
33958 @var{packet}. A @var{packet} is introduced with the character
33959 @samp{$}, the actual @var{packet-data}, and the terminating character
33960 @samp{#} followed by a two-digit @var{checksum}:
33963 @code{$}@var{packet-data}@code{#}@var{checksum}
33967 @cindex checksum, for @value{GDBN} remote
33969 The two-digit @var{checksum} is computed as the modulo 256 sum of all
33970 characters between the leading @samp{$} and the trailing @samp{#} (an
33971 eight bit unsigned checksum).
33973 Implementors should note that prior to @value{GDBN} 5.0 the protocol
33974 specification also included an optional two-digit @var{sequence-id}:
33977 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
33980 @cindex sequence-id, for @value{GDBN} remote
33982 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
33983 has never output @var{sequence-id}s. Stubs that handle packets added
33984 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
33986 When either the host or the target machine receives a packet, the first
33987 response expected is an acknowledgment: either @samp{+} (to indicate
33988 the package was received correctly) or @samp{-} (to request
33992 -> @code{$}@var{packet-data}@code{#}@var{checksum}
33997 The @samp{+}/@samp{-} acknowledgments can be disabled
33998 once a connection is established.
33999 @xref{Packet Acknowledgment}, for details.
34001 The host (@value{GDBN}) sends @var{command}s, and the target (the
34002 debugging stub incorporated in your program) sends a @var{response}. In
34003 the case of step and continue @var{command}s, the response is only sent
34004 when the operation has completed, and the target has again stopped all
34005 threads in all attached processes. This is the default all-stop mode
34006 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
34007 execution mode; see @ref{Remote Non-Stop}, for details.
34009 @var{packet-data} consists of a sequence of characters with the
34010 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
34013 @cindex remote protocol, field separator
34014 Fields within the packet should be separated using @samp{,} @samp{;} or
34015 @samp{:}. Except where otherwise noted all numbers are represented in
34016 @sc{hex} with leading zeros suppressed.
34018 Implementors should note that prior to @value{GDBN} 5.0, the character
34019 @samp{:} could not appear as the third character in a packet (as it
34020 would potentially conflict with the @var{sequence-id}).
34022 @cindex remote protocol, binary data
34023 @anchor{Binary Data}
34024 Binary data in most packets is encoded either as two hexadecimal
34025 digits per byte of binary data. This allowed the traditional remote
34026 protocol to work over connections which were only seven-bit clean.
34027 Some packets designed more recently assume an eight-bit clean
34028 connection, and use a more efficient encoding to send and receive
34031 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
34032 as an escape character. Any escaped byte is transmitted as the escape
34033 character followed by the original character XORed with @code{0x20}.
34034 For example, the byte @code{0x7d} would be transmitted as the two
34035 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
34036 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
34037 @samp{@}}) must always be escaped. Responses sent by the stub
34038 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
34039 is not interpreted as the start of a run-length encoded sequence
34042 Response @var{data} can be run-length encoded to save space.
34043 Run-length encoding replaces runs of identical characters with one
34044 instance of the repeated character, followed by a @samp{*} and a
34045 repeat count. The repeat count is itself sent encoded, to avoid
34046 binary characters in @var{data}: a value of @var{n} is sent as
34047 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
34048 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
34049 code 32) for a repeat count of 3. (This is because run-length
34050 encoding starts to win for counts 3 or more.) Thus, for example,
34051 @samp{0* } is a run-length encoding of ``0000'': the space character
34052 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
34055 The printable characters @samp{#} and @samp{$} or with a numeric value
34056 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
34057 seven repeats (@samp{$}) can be expanded using a repeat count of only
34058 five (@samp{"}). For example, @samp{00000000} can be encoded as
34061 The error response returned for some packets includes a two character
34062 error number. That number is not well defined.
34064 @cindex empty response, for unsupported packets
34065 For any @var{command} not supported by the stub, an empty response
34066 (@samp{$#00}) should be returned. That way it is possible to extend the
34067 protocol. A newer @value{GDBN} can tell if a packet is supported based
34070 At a minimum, a stub is required to support the @samp{g} and @samp{G}
34071 commands for register access, and the @samp{m} and @samp{M} commands
34072 for memory access. Stubs that only control single-threaded targets
34073 can implement run control with the @samp{c} (continue), and @samp{s}
34074 (step) commands. Stubs that support multi-threading targets should
34075 support the @samp{vCont} command. All other commands are optional.
34080 The following table provides a complete list of all currently defined
34081 @var{command}s and their corresponding response @var{data}.
34082 @xref{File-I/O Remote Protocol Extension}, for details about the File
34083 I/O extension of the remote protocol.
34085 Each packet's description has a template showing the packet's overall
34086 syntax, followed by an explanation of the packet's meaning. We
34087 include spaces in some of the templates for clarity; these are not
34088 part of the packet's syntax. No @value{GDBN} packet uses spaces to
34089 separate its components. For example, a template like @samp{foo
34090 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
34091 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
34092 @var{baz}. @value{GDBN} does not transmit a space character between the
34093 @samp{foo} and the @var{bar}, or between the @var{bar} and the
34096 @cindex @var{thread-id}, in remote protocol
34097 @anchor{thread-id syntax}
34098 Several packets and replies include a @var{thread-id} field to identify
34099 a thread. Normally these are positive numbers with a target-specific
34100 interpretation, formatted as big-endian hex strings. A @var{thread-id}
34101 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
34104 In addition, the remote protocol supports a multiprocess feature in
34105 which the @var{thread-id} syntax is extended to optionally include both
34106 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
34107 The @var{pid} (process) and @var{tid} (thread) components each have the
34108 format described above: a positive number with target-specific
34109 interpretation formatted as a big-endian hex string, literal @samp{-1}
34110 to indicate all processes or threads (respectively), or @samp{0} to
34111 indicate an arbitrary process or thread. Specifying just a process, as
34112 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
34113 error to specify all processes but a specific thread, such as
34114 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
34115 for those packets and replies explicitly documented to include a process
34116 ID, rather than a @var{thread-id}.
34118 The multiprocess @var{thread-id} syntax extensions are only used if both
34119 @value{GDBN} and the stub report support for the @samp{multiprocess}
34120 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
34123 Note that all packet forms beginning with an upper- or lower-case
34124 letter, other than those described here, are reserved for future use.
34126 Here are the packet descriptions.
34131 @cindex @samp{!} packet
34132 @anchor{extended mode}
34133 Enable extended mode. In extended mode, the remote server is made
34134 persistent. The @samp{R} packet is used to restart the program being
34140 The remote target both supports and has enabled extended mode.
34144 @cindex @samp{?} packet
34146 Indicate the reason the target halted. The reply is the same as for
34147 step and continue. This packet has a special interpretation when the
34148 target is in non-stop mode; see @ref{Remote Non-Stop}.
34151 @xref{Stop Reply Packets}, for the reply specifications.
34153 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
34154 @cindex @samp{A} packet
34155 Initialized @code{argv[]} array passed into program. @var{arglen}
34156 specifies the number of bytes in the hex encoded byte stream
34157 @var{arg}. See @code{gdbserver} for more details.
34162 The arguments were set.
34168 @cindex @samp{b} packet
34169 (Don't use this packet; its behavior is not well-defined.)
34170 Change the serial line speed to @var{baud}.
34172 JTC: @emph{When does the transport layer state change? When it's
34173 received, or after the ACK is transmitted. In either case, there are
34174 problems if the command or the acknowledgment packet is dropped.}
34176 Stan: @emph{If people really wanted to add something like this, and get
34177 it working for the first time, they ought to modify ser-unix.c to send
34178 some kind of out-of-band message to a specially-setup stub and have the
34179 switch happen "in between" packets, so that from remote protocol's point
34180 of view, nothing actually happened.}
34182 @item B @var{addr},@var{mode}
34183 @cindex @samp{B} packet
34184 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
34185 breakpoint at @var{addr}.
34187 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
34188 (@pxref{insert breakpoint or watchpoint packet}).
34190 @cindex @samp{bc} packet
34193 Backward continue. Execute the target system in reverse. No parameter.
34194 @xref{Reverse Execution}, for more information.
34197 @xref{Stop Reply Packets}, for the reply specifications.
34199 @cindex @samp{bs} packet
34202 Backward single step. Execute one instruction in reverse. No parameter.
34203 @xref{Reverse Execution}, for more information.
34206 @xref{Stop Reply Packets}, for the reply specifications.
34208 @item c @r{[}@var{addr}@r{]}
34209 @cindex @samp{c} packet
34210 Continue at @var{addr}, which is the address to resume. If @var{addr}
34211 is omitted, resume at current address.
34213 This packet is deprecated for multi-threading support. @xref{vCont
34217 @xref{Stop Reply Packets}, for the reply specifications.
34219 @item C @var{sig}@r{[};@var{addr}@r{]}
34220 @cindex @samp{C} packet
34221 Continue with signal @var{sig} (hex signal number). If
34222 @samp{;@var{addr}} is omitted, resume at same address.
34224 This packet is deprecated for multi-threading support. @xref{vCont
34228 @xref{Stop Reply Packets}, for the reply specifications.
34231 @cindex @samp{d} packet
34234 Don't use this packet; instead, define a general set packet
34235 (@pxref{General Query Packets}).
34239 @cindex @samp{D} packet
34240 The first form of the packet is used to detach @value{GDBN} from the
34241 remote system. It is sent to the remote target
34242 before @value{GDBN} disconnects via the @code{detach} command.
34244 The second form, including a process ID, is used when multiprocess
34245 protocol extensions are enabled (@pxref{multiprocess extensions}), to
34246 detach only a specific process. The @var{pid} is specified as a
34247 big-endian hex string.
34257 @item F @var{RC},@var{EE},@var{CF};@var{XX}
34258 @cindex @samp{F} packet
34259 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
34260 This is part of the File-I/O protocol extension. @xref{File-I/O
34261 Remote Protocol Extension}, for the specification.
34264 @anchor{read registers packet}
34265 @cindex @samp{g} packet
34266 Read general registers.
34270 @item @var{XX@dots{}}
34271 Each byte of register data is described by two hex digits. The bytes
34272 with the register are transmitted in target byte order. The size of
34273 each register and their position within the @samp{g} packet are
34274 determined by the @value{GDBN} internal gdbarch functions
34275 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
34276 specification of several standard @samp{g} packets is specified below.
34278 When reading registers from a trace frame (@pxref{Analyze Collected
34279 Data,,Using the Collected Data}), the stub may also return a string of
34280 literal @samp{x}'s in place of the register data digits, to indicate
34281 that the corresponding register has not been collected, thus its value
34282 is unavailable. For example, for an architecture with 4 registers of
34283 4 bytes each, the following reply indicates to @value{GDBN} that
34284 registers 0 and 2 have not been collected, while registers 1 and 3
34285 have been collected, and both have zero value:
34289 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
34296 @item G @var{XX@dots{}}
34297 @cindex @samp{G} packet
34298 Write general registers. @xref{read registers packet}, for a
34299 description of the @var{XX@dots{}} data.
34309 @item H @var{op} @var{thread-id}
34310 @cindex @samp{H} packet
34311 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
34312 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
34313 should be @samp{c} for step and continue operations (note that this
34314 is deprecated, supporting the @samp{vCont} command is a better
34315 option), and @samp{g} for other operations. The thread designator
34316 @var{thread-id} has the format and interpretation described in
34317 @ref{thread-id syntax}.
34328 @c 'H': How restrictive (or permissive) is the thread model. If a
34329 @c thread is selected and stopped, are other threads allowed
34330 @c to continue to execute? As I mentioned above, I think the
34331 @c semantics of each command when a thread is selected must be
34332 @c described. For example:
34334 @c 'g': If the stub supports threads and a specific thread is
34335 @c selected, returns the register block from that thread;
34336 @c otherwise returns current registers.
34338 @c 'G' If the stub supports threads and a specific thread is
34339 @c selected, sets the registers of the register block of
34340 @c that thread; otherwise sets current registers.
34342 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
34343 @anchor{cycle step packet}
34344 @cindex @samp{i} packet
34345 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
34346 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
34347 step starting at that address.
34350 @cindex @samp{I} packet
34351 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
34355 @cindex @samp{k} packet
34358 The exact effect of this packet is not specified.
34360 For a bare-metal target, it may power cycle or reset the target
34361 system. For that reason, the @samp{k} packet has no reply.
34363 For a single-process target, it may kill that process if possible.
34365 A multiple-process target may choose to kill just one process, or all
34366 that are under @value{GDBN}'s control. For more precise control, use
34367 the vKill packet (@pxref{vKill packet}).
34369 If the target system immediately closes the connection in response to
34370 @samp{k}, @value{GDBN} does not consider the lack of packet
34371 acknowledgment to be an error, and assumes the kill was successful.
34373 If connected using @kbd{target extended-remote}, and the target does
34374 not close the connection in response to a kill request, @value{GDBN}
34375 probes the target state as if a new connection was opened
34376 (@pxref{? packet}).
34378 @item m @var{addr},@var{length}
34379 @cindex @samp{m} packet
34380 Read @var{length} bytes of memory starting at address @var{addr}.
34381 Note that @var{addr} may not be aligned to any particular boundary.
34383 The stub need not use any particular size or alignment when gathering
34384 data from memory for the response; even if @var{addr} is word-aligned
34385 and @var{length} is a multiple of the word size, the stub is free to
34386 use byte accesses, or not. For this reason, this packet may not be
34387 suitable for accessing memory-mapped I/O devices.
34388 @cindex alignment of remote memory accesses
34389 @cindex size of remote memory accesses
34390 @cindex memory, alignment and size of remote accesses
34394 @item @var{XX@dots{}}
34395 Memory contents; each byte is transmitted as a two-digit hexadecimal
34396 number. The reply may contain fewer bytes than requested if the
34397 server was able to read only part of the region of memory.
34402 @item M @var{addr},@var{length}:@var{XX@dots{}}
34403 @cindex @samp{M} packet
34404 Write @var{length} bytes of memory starting at address @var{addr}.
34405 The data is given by @var{XX@dots{}}; each byte is transmitted as a two-digit
34406 hexadecimal number.
34413 for an error (this includes the case where only part of the data was
34418 @cindex @samp{p} packet
34419 Read the value of register @var{n}; @var{n} is in hex.
34420 @xref{read registers packet}, for a description of how the returned
34421 register value is encoded.
34425 @item @var{XX@dots{}}
34426 the register's value
34430 Indicating an unrecognized @var{query}.
34433 @item P @var{n@dots{}}=@var{r@dots{}}
34434 @anchor{write register packet}
34435 @cindex @samp{P} packet
34436 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
34437 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
34438 digits for each byte in the register (target byte order).
34448 @item q @var{name} @var{params}@dots{}
34449 @itemx Q @var{name} @var{params}@dots{}
34450 @cindex @samp{q} packet
34451 @cindex @samp{Q} packet
34452 General query (@samp{q}) and set (@samp{Q}). These packets are
34453 described fully in @ref{General Query Packets}.
34456 @cindex @samp{r} packet
34457 Reset the entire system.
34459 Don't use this packet; use the @samp{R} packet instead.
34462 @cindex @samp{R} packet
34463 Restart the program being debugged. The @var{XX}, while needed, is ignored.
34464 This packet is only available in extended mode (@pxref{extended mode}).
34466 The @samp{R} packet has no reply.
34468 @item s @r{[}@var{addr}@r{]}
34469 @cindex @samp{s} packet
34470 Single step, resuming at @var{addr}. If
34471 @var{addr} is omitted, resume at same address.
34473 This packet is deprecated for multi-threading support. @xref{vCont
34477 @xref{Stop Reply Packets}, for the reply specifications.
34479 @item S @var{sig}@r{[};@var{addr}@r{]}
34480 @anchor{step with signal packet}
34481 @cindex @samp{S} packet
34482 Step with signal. This is analogous to the @samp{C} packet, but
34483 requests a single-step, rather than a normal resumption of execution.
34485 This packet is deprecated for multi-threading support. @xref{vCont
34489 @xref{Stop Reply Packets}, for the reply specifications.
34491 @item t @var{addr}:@var{PP},@var{MM}
34492 @cindex @samp{t} packet
34493 Search backwards starting at address @var{addr} for a match with pattern
34494 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
34495 There must be at least 3 digits in @var{addr}.
34497 @item T @var{thread-id}
34498 @cindex @samp{T} packet
34499 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
34504 thread is still alive
34510 Packets starting with @samp{v} are identified by a multi-letter name,
34511 up to the first @samp{;} or @samp{?} (or the end of the packet).
34513 @item vAttach;@var{pid}
34514 @cindex @samp{vAttach} packet
34515 Attach to a new process with the specified process ID @var{pid}.
34516 The process ID is a
34517 hexadecimal integer identifying the process. In all-stop mode, all
34518 threads in the attached process are stopped; in non-stop mode, it may be
34519 attached without being stopped if that is supported by the target.
34521 @c In non-stop mode, on a successful vAttach, the stub should set the
34522 @c current thread to a thread of the newly-attached process. After
34523 @c attaching, GDB queries for the attached process's thread ID with qC.
34524 @c Also note that, from a user perspective, whether or not the
34525 @c target is stopped on attach in non-stop mode depends on whether you
34526 @c use the foreground or background version of the attach command, not
34527 @c on what vAttach does; GDB does the right thing with respect to either
34528 @c stopping or restarting threads.
34530 This packet is only available in extended mode (@pxref{extended mode}).
34536 @item @r{Any stop packet}
34537 for success in all-stop mode (@pxref{Stop Reply Packets})
34539 for success in non-stop mode (@pxref{Remote Non-Stop})
34542 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
34543 @cindex @samp{vCont} packet
34544 @anchor{vCont packet}
34545 Resume the inferior, specifying different actions for each thread.
34546 If an action is specified with no @var{thread-id}, then it is applied to any
34547 threads that don't have a specific action specified; if no default action is
34548 specified then other threads should remain stopped in all-stop mode and
34549 in their current state in non-stop mode.
34550 Specifying multiple
34551 default actions is an error; specifying no actions is also an error.
34552 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
34554 Currently supported actions are:
34560 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
34564 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
34567 @item r @var{start},@var{end}
34568 Step once, and then keep stepping as long as the thread stops at
34569 addresses between @var{start} (inclusive) and @var{end} (exclusive).
34570 The remote stub reports a stop reply when either the thread goes out
34571 of the range or is stopped due to an unrelated reason, such as hitting
34572 a breakpoint. @xref{range stepping}.
34574 If the range is empty (@var{start} == @var{end}), then the action
34575 becomes equivalent to the @samp{s} action. In other words,
34576 single-step once, and report the stop (even if the stepped instruction
34577 jumps to @var{start}).
34579 (A stop reply may be sent at any point even if the PC is still within
34580 the stepping range; for example, it is valid to implement this packet
34581 in a degenerate way as a single instruction step operation.)
34585 The optional argument @var{addr} normally associated with the
34586 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
34587 not supported in @samp{vCont}.
34589 The @samp{t} action is only relevant in non-stop mode
34590 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
34591 A stop reply should be generated for any affected thread not already stopped.
34592 When a thread is stopped by means of a @samp{t} action,
34593 the corresponding stop reply should indicate that the thread has stopped with
34594 signal @samp{0}, regardless of whether the target uses some other signal
34595 as an implementation detail.
34597 The stub must support @samp{vCont} if it reports support for
34598 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
34599 this case @samp{vCont} actions can be specified to apply to all threads
34600 in a process by using the @samp{p@var{pid}.-1} form of the
34604 @xref{Stop Reply Packets}, for the reply specifications.
34607 @cindex @samp{vCont?} packet
34608 Request a list of actions supported by the @samp{vCont} packet.
34612 @item vCont@r{[};@var{action}@dots{}@r{]}
34613 The @samp{vCont} packet is supported. Each @var{action} is a supported
34614 command in the @samp{vCont} packet.
34616 The @samp{vCont} packet is not supported.
34619 @item vFile:@var{operation}:@var{parameter}@dots{}
34620 @cindex @samp{vFile} packet
34621 Perform a file operation on the target system. For details,
34622 see @ref{Host I/O Packets}.
34624 @item vFlashErase:@var{addr},@var{length}
34625 @cindex @samp{vFlashErase} packet
34626 Direct the stub to erase @var{length} bytes of flash starting at
34627 @var{addr}. The region may enclose any number of flash blocks, but
34628 its start and end must fall on block boundaries, as indicated by the
34629 flash block size appearing in the memory map (@pxref{Memory Map
34630 Format}). @value{GDBN} groups flash memory programming operations
34631 together, and sends a @samp{vFlashDone} request after each group; the
34632 stub is allowed to delay erase operation until the @samp{vFlashDone}
34633 packet is received.
34643 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
34644 @cindex @samp{vFlashWrite} packet
34645 Direct the stub to write data to flash address @var{addr}. The data
34646 is passed in binary form using the same encoding as for the @samp{X}
34647 packet (@pxref{Binary Data}). The memory ranges specified by
34648 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
34649 not overlap, and must appear in order of increasing addresses
34650 (although @samp{vFlashErase} packets for higher addresses may already
34651 have been received; the ordering is guaranteed only between
34652 @samp{vFlashWrite} packets). If a packet writes to an address that was
34653 neither erased by a preceding @samp{vFlashErase} packet nor by some other
34654 target-specific method, the results are unpredictable.
34662 for vFlashWrite addressing non-flash memory
34668 @cindex @samp{vFlashDone} packet
34669 Indicate to the stub that flash programming operation is finished.
34670 The stub is permitted to delay or batch the effects of a group of
34671 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
34672 @samp{vFlashDone} packet is received. The contents of the affected
34673 regions of flash memory are unpredictable until the @samp{vFlashDone}
34674 request is completed.
34676 @item vKill;@var{pid}
34677 @cindex @samp{vKill} packet
34678 @anchor{vKill packet}
34679 Kill the process with the specified process ID @var{pid}, which is a
34680 hexadecimal integer identifying the process. This packet is used in
34681 preference to @samp{k} when multiprocess protocol extensions are
34682 supported; see @ref{multiprocess extensions}.
34692 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
34693 @cindex @samp{vRun} packet
34694 Run the program @var{filename}, passing it each @var{argument} on its
34695 command line. The file and arguments are hex-encoded strings. If
34696 @var{filename} is an empty string, the stub may use a default program
34697 (e.g.@: the last program run). The program is created in the stopped
34700 @c FIXME: What about non-stop mode?
34702 This packet is only available in extended mode (@pxref{extended mode}).
34708 @item @r{Any stop packet}
34709 for success (@pxref{Stop Reply Packets})
34713 @cindex @samp{vStopped} packet
34714 @xref{Notification Packets}.
34716 @item X @var{addr},@var{length}:@var{XX@dots{}}
34718 @cindex @samp{X} packet
34719 Write data to memory, where the data is transmitted in binary.
34720 Memory is specified by its address @var{addr} and number of bytes @var{length};
34721 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
34731 @item z @var{type},@var{addr},@var{kind}
34732 @itemx Z @var{type},@var{addr},@var{kind}
34733 @anchor{insert breakpoint or watchpoint packet}
34734 @cindex @samp{z} packet
34735 @cindex @samp{Z} packets
34736 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
34737 watchpoint starting at address @var{address} of kind @var{kind}.
34739 Each breakpoint and watchpoint packet @var{type} is documented
34742 @emph{Implementation notes: A remote target shall return an empty string
34743 for an unrecognized breakpoint or watchpoint packet @var{type}. A
34744 remote target shall support either both or neither of a given
34745 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
34746 avoid potential problems with duplicate packets, the operations should
34747 be implemented in an idempotent way.}
34749 @item z0,@var{addr},@var{kind}
34750 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
34751 @cindex @samp{z0} packet
34752 @cindex @samp{Z0} packet
34753 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
34754 @var{addr} of type @var{kind}.
34756 A memory breakpoint is implemented by replacing the instruction at
34757 @var{addr} with a software breakpoint or trap instruction. The
34758 @var{kind} is target-specific and typically indicates the size of
34759 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
34760 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
34761 architectures have additional meanings for @var{kind};
34762 @var{cond_list} is an optional list of conditional expressions in bytecode
34763 form that should be evaluated on the target's side. These are the
34764 conditions that should be taken into consideration when deciding if
34765 the breakpoint trigger should be reported back to @var{GDBN}.
34767 The @var{cond_list} parameter is comprised of a series of expressions,
34768 concatenated without separators. Each expression has the following form:
34772 @item X @var{len},@var{expr}
34773 @var{len} is the length of the bytecode expression and @var{expr} is the
34774 actual conditional expression in bytecode form.
34778 The optional @var{cmd_list} parameter introduces commands that may be
34779 run on the target, rather than being reported back to @value{GDBN}.
34780 The parameter starts with a numeric flag @var{persist}; if the flag is
34781 nonzero, then the breakpoint may remain active and the commands
34782 continue to be run even when @value{GDBN} disconnects from the target.
34783 Following this flag is a series of expressions concatenated with no
34784 separators. Each expression has the following form:
34788 @item X @var{len},@var{expr}
34789 @var{len} is the length of the bytecode expression and @var{expr} is the
34790 actual conditional expression in bytecode form.
34794 see @ref{Architecture-Specific Protocol Details}.
34796 @emph{Implementation note: It is possible for a target to copy or move
34797 code that contains memory breakpoints (e.g., when implementing
34798 overlays). The behavior of this packet, in the presence of such a
34799 target, is not defined.}
34811 @item z1,@var{addr},@var{kind}
34812 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
34813 @cindex @samp{z1} packet
34814 @cindex @samp{Z1} packet
34815 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
34816 address @var{addr}.
34818 A hardware breakpoint is implemented using a mechanism that is not
34819 dependant on being able to modify the target's memory. The @var{kind}
34820 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
34822 @emph{Implementation note: A hardware breakpoint is not affected by code
34835 @item z2,@var{addr},@var{kind}
34836 @itemx Z2,@var{addr},@var{kind}
34837 @cindex @samp{z2} packet
34838 @cindex @samp{Z2} packet
34839 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
34840 The number of bytes to watch is specified by @var{kind}.
34852 @item z3,@var{addr},@var{kind}
34853 @itemx Z3,@var{addr},@var{kind}
34854 @cindex @samp{z3} packet
34855 @cindex @samp{Z3} packet
34856 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
34857 The number of bytes to watch is specified by @var{kind}.
34869 @item z4,@var{addr},@var{kind}
34870 @itemx Z4,@var{addr},@var{kind}
34871 @cindex @samp{z4} packet
34872 @cindex @samp{Z4} packet
34873 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
34874 The number of bytes to watch is specified by @var{kind}.
34888 @node Stop Reply Packets
34889 @section Stop Reply Packets
34890 @cindex stop reply packets
34892 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
34893 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
34894 receive any of the below as a reply. Except for @samp{?}
34895 and @samp{vStopped}, that reply is only returned
34896 when the target halts. In the below the exact meaning of @dfn{signal
34897 number} is defined by the header @file{include/gdb/signals.h} in the
34898 @value{GDBN} source code.
34900 As in the description of request packets, we include spaces in the
34901 reply templates for clarity; these are not part of the reply packet's
34902 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
34908 The program received signal number @var{AA} (a two-digit hexadecimal
34909 number). This is equivalent to a @samp{T} response with no
34910 @var{n}:@var{r} pairs.
34912 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
34913 @cindex @samp{T} packet reply
34914 The program received signal number @var{AA} (a two-digit hexadecimal
34915 number). This is equivalent to an @samp{S} response, except that the
34916 @samp{@var{n}:@var{r}} pairs can carry values of important registers
34917 and other information directly in the stop reply packet, reducing
34918 round-trip latency. Single-step and breakpoint traps are reported
34919 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
34923 If @var{n} is a hexadecimal number, it is a register number, and the
34924 corresponding @var{r} gives that register's value. The data @var{r} is a
34925 series of bytes in target byte order, with each byte given by a
34926 two-digit hex number.
34929 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
34930 the stopped thread, as specified in @ref{thread-id syntax}.
34933 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
34934 the core on which the stop event was detected.
34937 If @var{n} is a recognized @dfn{stop reason}, it describes a more
34938 specific event that stopped the target. The currently defined stop
34939 reasons are listed below. The @var{aa} should be @samp{05}, the trap
34940 signal. At most one stop reason should be present.
34943 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
34944 and go on to the next; this allows us to extend the protocol in the
34948 The currently defined stop reasons are:
34954 The packet indicates a watchpoint hit, and @var{r} is the data address, in
34957 @cindex shared library events, remote reply
34959 The packet indicates that the loaded libraries have changed.
34960 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
34961 list of loaded libraries. The @var{r} part is ignored.
34963 @cindex replay log events, remote reply
34965 The packet indicates that the target cannot continue replaying
34966 logged execution events, because it has reached the end (or the
34967 beginning when executing backward) of the log. The value of @var{r}
34968 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
34969 for more information.
34973 @itemx W @var{AA} ; process:@var{pid}
34974 The process exited, and @var{AA} is the exit status. This is only
34975 applicable to certain targets.
34977 The second form of the response, including the process ID of the exited
34978 process, can be used only when @value{GDBN} has reported support for
34979 multiprocess protocol extensions; see @ref{multiprocess extensions}.
34980 The @var{pid} is formatted as a big-endian hex string.
34983 @itemx X @var{AA} ; process:@var{pid}
34984 The process terminated with signal @var{AA}.
34986 The second form of the response, including the process ID of the
34987 terminated process, can be used only when @value{GDBN} has reported
34988 support for multiprocess protocol extensions; see @ref{multiprocess
34989 extensions}. The @var{pid} is formatted as a big-endian hex string.
34991 @item O @var{XX}@dots{}
34992 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
34993 written as the program's console output. This can happen at any time
34994 while the program is running and the debugger should continue to wait
34995 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
34997 @item F @var{call-id},@var{parameter}@dots{}
34998 @var{call-id} is the identifier which says which host system call should
34999 be called. This is just the name of the function. Translation into the
35000 correct system call is only applicable as it's defined in @value{GDBN}.
35001 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
35004 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
35005 this very system call.
35007 The target replies with this packet when it expects @value{GDBN} to
35008 call a host system call on behalf of the target. @value{GDBN} replies
35009 with an appropriate @samp{F} packet and keeps up waiting for the next
35010 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
35011 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
35012 Protocol Extension}, for more details.
35016 @node General Query Packets
35017 @section General Query Packets
35018 @cindex remote query requests
35020 Packets starting with @samp{q} are @dfn{general query packets};
35021 packets starting with @samp{Q} are @dfn{general set packets}. General
35022 query and set packets are a semi-unified form for retrieving and
35023 sending information to and from the stub.
35025 The initial letter of a query or set packet is followed by a name
35026 indicating what sort of thing the packet applies to. For example,
35027 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
35028 definitions with the stub. These packet names follow some
35033 The name must not contain commas, colons or semicolons.
35035 Most @value{GDBN} query and set packets have a leading upper case
35038 The names of custom vendor packets should use a company prefix, in
35039 lower case, followed by a period. For example, packets designed at
35040 the Acme Corporation might begin with @samp{qacme.foo} (for querying
35041 foos) or @samp{Qacme.bar} (for setting bars).
35044 The name of a query or set packet should be separated from any
35045 parameters by a @samp{:}; the parameters themselves should be
35046 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
35047 full packet name, and check for a separator or the end of the packet,
35048 in case two packet names share a common prefix. New packets should not begin
35049 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
35050 packets predate these conventions, and have arguments without any terminator
35051 for the packet name; we suspect they are in widespread use in places that
35052 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
35053 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
35056 Like the descriptions of the other packets, each description here
35057 has a template showing the packet's overall syntax, followed by an
35058 explanation of the packet's meaning. We include spaces in some of the
35059 templates for clarity; these are not part of the packet's syntax. No
35060 @value{GDBN} packet uses spaces to separate its components.
35062 Here are the currently defined query and set packets:
35068 Turn on or off the agent as a helper to perform some debugging operations
35069 delegated from @value{GDBN} (@pxref{Control Agent}).
35071 @item QAllow:@var{op}:@var{val}@dots{}
35072 @cindex @samp{QAllow} packet
35073 Specify which operations @value{GDBN} expects to request of the
35074 target, as a semicolon-separated list of operation name and value
35075 pairs. Possible values for @var{op} include @samp{WriteReg},
35076 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
35077 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
35078 indicating that @value{GDBN} will not request the operation, or 1,
35079 indicating that it may. (The target can then use this to set up its
35080 own internals optimally, for instance if the debugger never expects to
35081 insert breakpoints, it may not need to install its own trap handler.)
35084 @cindex current thread, remote request
35085 @cindex @samp{qC} packet
35086 Return the current thread ID.
35090 @item QC @var{thread-id}
35091 Where @var{thread-id} is a thread ID as documented in
35092 @ref{thread-id syntax}.
35093 @item @r{(anything else)}
35094 Any other reply implies the old thread ID.
35097 @item qCRC:@var{addr},@var{length}
35098 @cindex CRC of memory block, remote request
35099 @cindex @samp{qCRC} packet
35100 @anchor{qCRC packet}
35101 Compute the CRC checksum of a block of memory using CRC-32 defined in
35102 IEEE 802.3. The CRC is computed byte at a time, taking the most
35103 significant bit of each byte first. The initial pattern code
35104 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
35106 @emph{Note:} This is the same CRC used in validating separate debug
35107 files (@pxref{Separate Debug Files, , Debugging Information in Separate
35108 Files}). However the algorithm is slightly different. When validating
35109 separate debug files, the CRC is computed taking the @emph{least}
35110 significant bit of each byte first, and the final result is inverted to
35111 detect trailing zeros.
35116 An error (such as memory fault)
35117 @item C @var{crc32}
35118 The specified memory region's checksum is @var{crc32}.
35121 @item QDisableRandomization:@var{value}
35122 @cindex disable address space randomization, remote request
35123 @cindex @samp{QDisableRandomization} packet
35124 Some target operating systems will randomize the virtual address space
35125 of the inferior process as a security feature, but provide a feature
35126 to disable such randomization, e.g.@: to allow for a more deterministic
35127 debugging experience. On such systems, this packet with a @var{value}
35128 of 1 directs the target to disable address space randomization for
35129 processes subsequently started via @samp{vRun} packets, while a packet
35130 with a @var{value} of 0 tells the target to enable address space
35133 This packet is only available in extended mode (@pxref{extended mode}).
35138 The request succeeded.
35141 An error occurred. The error number @var{nn} is given as hex digits.
35144 An empty reply indicates that @samp{QDisableRandomization} is not supported
35148 This packet is not probed by default; the remote stub must request it,
35149 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35150 This should only be done on targets that actually support disabling
35151 address space randomization.
35154 @itemx qsThreadInfo
35155 @cindex list active threads, remote request
35156 @cindex @samp{qfThreadInfo} packet
35157 @cindex @samp{qsThreadInfo} packet
35158 Obtain a list of all active thread IDs from the target (OS). Since there
35159 may be too many active threads to fit into one reply packet, this query
35160 works iteratively: it may require more than one query/reply sequence to
35161 obtain the entire list of threads. The first query of the sequence will
35162 be the @samp{qfThreadInfo} query; subsequent queries in the
35163 sequence will be the @samp{qsThreadInfo} query.
35165 NOTE: This packet replaces the @samp{qL} query (see below).
35169 @item m @var{thread-id}
35171 @item m @var{thread-id},@var{thread-id}@dots{}
35172 a comma-separated list of thread IDs
35174 (lower case letter @samp{L}) denotes end of list.
35177 In response to each query, the target will reply with a list of one or
35178 more thread IDs, separated by commas.
35179 @value{GDBN} will respond to each reply with a request for more thread
35180 ids (using the @samp{qs} form of the query), until the target responds
35181 with @samp{l} (lower-case ell, for @dfn{last}).
35182 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
35185 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
35186 initial connection with the remote target, and the very first thread ID
35187 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
35188 message. Therefore, the stub should ensure that the first thread ID in
35189 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
35191 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
35192 @cindex get thread-local storage address, remote request
35193 @cindex @samp{qGetTLSAddr} packet
35194 Fetch the address associated with thread local storage specified
35195 by @var{thread-id}, @var{offset}, and @var{lm}.
35197 @var{thread-id} is the thread ID associated with the
35198 thread for which to fetch the TLS address. @xref{thread-id syntax}.
35200 @var{offset} is the (big endian, hex encoded) offset associated with the
35201 thread local variable. (This offset is obtained from the debug
35202 information associated with the variable.)
35204 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
35205 load module associated with the thread local storage. For example,
35206 a @sc{gnu}/Linux system will pass the link map address of the shared
35207 object associated with the thread local storage under consideration.
35208 Other operating environments may choose to represent the load module
35209 differently, so the precise meaning of this parameter will vary.
35213 @item @var{XX}@dots{}
35214 Hex encoded (big endian) bytes representing the address of the thread
35215 local storage requested.
35218 An error occurred. The error number @var{nn} is given as hex digits.
35221 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
35224 @item qGetTIBAddr:@var{thread-id}
35225 @cindex get thread information block address
35226 @cindex @samp{qGetTIBAddr} packet
35227 Fetch address of the Windows OS specific Thread Information Block.
35229 @var{thread-id} is the thread ID associated with the thread.
35233 @item @var{XX}@dots{}
35234 Hex encoded (big endian) bytes representing the linear address of the
35235 thread information block.
35238 An error occured. This means that either the thread was not found, or the
35239 address could not be retrieved.
35242 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
35245 @item qL @var{startflag} @var{threadcount} @var{nextthread}
35246 Obtain thread information from RTOS. Where: @var{startflag} (one hex
35247 digit) is one to indicate the first query and zero to indicate a
35248 subsequent query; @var{threadcount} (two hex digits) is the maximum
35249 number of threads the response packet can contain; and @var{nextthread}
35250 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
35251 returned in the response as @var{argthread}.
35253 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
35257 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
35258 Where: @var{count} (two hex digits) is the number of threads being
35259 returned; @var{done} (one hex digit) is zero to indicate more threads
35260 and one indicates no further threads; @var{argthreadid} (eight hex
35261 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
35262 is a sequence of thread IDs, @var{threadid} (eight hex
35263 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
35267 @cindex section offsets, remote request
35268 @cindex @samp{qOffsets} packet
35269 Get section offsets that the target used when relocating the downloaded
35274 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
35275 Relocate the @code{Text} section by @var{xxx} from its original address.
35276 Relocate the @code{Data} section by @var{yyy} from its original address.
35277 If the object file format provides segment information (e.g.@: @sc{elf}
35278 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
35279 segments by the supplied offsets.
35281 @emph{Note: while a @code{Bss} offset may be included in the response,
35282 @value{GDBN} ignores this and instead applies the @code{Data} offset
35283 to the @code{Bss} section.}
35285 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
35286 Relocate the first segment of the object file, which conventionally
35287 contains program code, to a starting address of @var{xxx}. If
35288 @samp{DataSeg} is specified, relocate the second segment, which
35289 conventionally contains modifiable data, to a starting address of
35290 @var{yyy}. @value{GDBN} will report an error if the object file
35291 does not contain segment information, or does not contain at least
35292 as many segments as mentioned in the reply. Extra segments are
35293 kept at fixed offsets relative to the last relocated segment.
35296 @item qP @var{mode} @var{thread-id}
35297 @cindex thread information, remote request
35298 @cindex @samp{qP} packet
35299 Returns information on @var{thread-id}. Where: @var{mode} is a hex
35300 encoded 32 bit mode; @var{thread-id} is a thread ID
35301 (@pxref{thread-id syntax}).
35303 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
35306 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
35310 @cindex non-stop mode, remote request
35311 @cindex @samp{QNonStop} packet
35313 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
35314 @xref{Remote Non-Stop}, for more information.
35319 The request succeeded.
35322 An error occurred. The error number @var{nn} is given as hex digits.
35325 An empty reply indicates that @samp{QNonStop} is not supported by
35329 This packet is not probed by default; the remote stub must request it,
35330 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35331 Use of this packet is controlled by the @code{set non-stop} command;
35332 @pxref{Non-Stop Mode}.
35334 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
35335 @cindex pass signals to inferior, remote request
35336 @cindex @samp{QPassSignals} packet
35337 @anchor{QPassSignals}
35338 Each listed @var{signal} should be passed directly to the inferior process.
35339 Signals are numbered identically to continue packets and stop replies
35340 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
35341 strictly greater than the previous item. These signals do not need to stop
35342 the inferior, or be reported to @value{GDBN}. All other signals should be
35343 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
35344 combine; any earlier @samp{QPassSignals} list is completely replaced by the
35345 new list. This packet improves performance when using @samp{handle
35346 @var{signal} nostop noprint pass}.
35351 The request succeeded.
35354 An error occurred. The error number @var{nn} is given as hex digits.
35357 An empty reply indicates that @samp{QPassSignals} is not supported by
35361 Use of this packet is controlled by the @code{set remote pass-signals}
35362 command (@pxref{Remote Configuration, set remote pass-signals}).
35363 This packet is not probed by default; the remote stub must request it,
35364 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35366 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
35367 @cindex signals the inferior may see, remote request
35368 @cindex @samp{QProgramSignals} packet
35369 @anchor{QProgramSignals}
35370 Each listed @var{signal} may be delivered to the inferior process.
35371 Others should be silently discarded.
35373 In some cases, the remote stub may need to decide whether to deliver a
35374 signal to the program or not without @value{GDBN} involvement. One
35375 example of that is while detaching --- the program's threads may have
35376 stopped for signals that haven't yet had a chance of being reported to
35377 @value{GDBN}, and so the remote stub can use the signal list specified
35378 by this packet to know whether to deliver or ignore those pending
35381 This does not influence whether to deliver a signal as requested by a
35382 resumption packet (@pxref{vCont packet}).
35384 Signals are numbered identically to continue packets and stop replies
35385 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
35386 strictly greater than the previous item. Multiple
35387 @samp{QProgramSignals} packets do not combine; any earlier
35388 @samp{QProgramSignals} list is completely replaced by the new list.
35393 The request succeeded.
35396 An error occurred. The error number @var{nn} is given as hex digits.
35399 An empty reply indicates that @samp{QProgramSignals} is not supported
35403 Use of this packet is controlled by the @code{set remote program-signals}
35404 command (@pxref{Remote Configuration, set remote program-signals}).
35405 This packet is not probed by default; the remote stub must request it,
35406 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35408 @item qRcmd,@var{command}
35409 @cindex execute remote command, remote request
35410 @cindex @samp{qRcmd} packet
35411 @var{command} (hex encoded) is passed to the local interpreter for
35412 execution. Invalid commands should be reported using the output
35413 string. Before the final result packet, the target may also respond
35414 with a number of intermediate @samp{O@var{output}} console output
35415 packets. @emph{Implementors should note that providing access to a
35416 stubs's interpreter may have security implications}.
35421 A command response with no output.
35423 A command response with the hex encoded output string @var{OUTPUT}.
35425 Indicate a badly formed request.
35427 An empty reply indicates that @samp{qRcmd} is not recognized.
35430 (Note that the @code{qRcmd} packet's name is separated from the
35431 command by a @samp{,}, not a @samp{:}, contrary to the naming
35432 conventions above. Please don't use this packet as a model for new
35435 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
35436 @cindex searching memory, in remote debugging
35438 @cindex @samp{qSearch:memory} packet
35440 @cindex @samp{qSearch memory} packet
35441 @anchor{qSearch memory}
35442 Search @var{length} bytes at @var{address} for @var{search-pattern}.
35443 Both @var{address} and @var{length} are encoded in hex;
35444 @var{search-pattern} is a sequence of bytes, also hex encoded.
35449 The pattern was not found.
35451 The pattern was found at @var{address}.
35453 A badly formed request or an error was encountered while searching memory.
35455 An empty reply indicates that @samp{qSearch:memory} is not recognized.
35458 @item QStartNoAckMode
35459 @cindex @samp{QStartNoAckMode} packet
35460 @anchor{QStartNoAckMode}
35461 Request that the remote stub disable the normal @samp{+}/@samp{-}
35462 protocol acknowledgments (@pxref{Packet Acknowledgment}).
35467 The stub has switched to no-acknowledgment mode.
35468 @value{GDBN} acknowledges this reponse,
35469 but neither the stub nor @value{GDBN} shall send or expect further
35470 @samp{+}/@samp{-} acknowledgments in the current connection.
35472 An empty reply indicates that the stub does not support no-acknowledgment mode.
35475 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
35476 @cindex supported packets, remote query
35477 @cindex features of the remote protocol
35478 @cindex @samp{qSupported} packet
35479 @anchor{qSupported}
35480 Tell the remote stub about features supported by @value{GDBN}, and
35481 query the stub for features it supports. This packet allows
35482 @value{GDBN} and the remote stub to take advantage of each others'
35483 features. @samp{qSupported} also consolidates multiple feature probes
35484 at startup, to improve @value{GDBN} performance---a single larger
35485 packet performs better than multiple smaller probe packets on
35486 high-latency links. Some features may enable behavior which must not
35487 be on by default, e.g.@: because it would confuse older clients or
35488 stubs. Other features may describe packets which could be
35489 automatically probed for, but are not. These features must be
35490 reported before @value{GDBN} will use them. This ``default
35491 unsupported'' behavior is not appropriate for all packets, but it
35492 helps to keep the initial connection time under control with new
35493 versions of @value{GDBN} which support increasing numbers of packets.
35497 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
35498 The stub supports or does not support each returned @var{stubfeature},
35499 depending on the form of each @var{stubfeature} (see below for the
35502 An empty reply indicates that @samp{qSupported} is not recognized,
35503 or that no features needed to be reported to @value{GDBN}.
35506 The allowed forms for each feature (either a @var{gdbfeature} in the
35507 @samp{qSupported} packet, or a @var{stubfeature} in the response)
35511 @item @var{name}=@var{value}
35512 The remote protocol feature @var{name} is supported, and associated
35513 with the specified @var{value}. The format of @var{value} depends
35514 on the feature, but it must not include a semicolon.
35516 The remote protocol feature @var{name} is supported, and does not
35517 need an associated value.
35519 The remote protocol feature @var{name} is not supported.
35521 The remote protocol feature @var{name} may be supported, and
35522 @value{GDBN} should auto-detect support in some other way when it is
35523 needed. This form will not be used for @var{gdbfeature} notifications,
35524 but may be used for @var{stubfeature} responses.
35527 Whenever the stub receives a @samp{qSupported} request, the
35528 supplied set of @value{GDBN} features should override any previous
35529 request. This allows @value{GDBN} to put the stub in a known
35530 state, even if the stub had previously been communicating with
35531 a different version of @value{GDBN}.
35533 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
35538 This feature indicates whether @value{GDBN} supports multiprocess
35539 extensions to the remote protocol. @value{GDBN} does not use such
35540 extensions unless the stub also reports that it supports them by
35541 including @samp{multiprocess+} in its @samp{qSupported} reply.
35542 @xref{multiprocess extensions}, for details.
35545 This feature indicates that @value{GDBN} supports the XML target
35546 description. If the stub sees @samp{xmlRegisters=} with target
35547 specific strings separated by a comma, it will report register
35551 This feature indicates whether @value{GDBN} supports the
35552 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
35553 instruction reply packet}).
35556 Stubs should ignore any unknown values for
35557 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
35558 packet supports receiving packets of unlimited length (earlier
35559 versions of @value{GDBN} may reject overly long responses). Additional values
35560 for @var{gdbfeature} may be defined in the future to let the stub take
35561 advantage of new features in @value{GDBN}, e.g.@: incompatible
35562 improvements in the remote protocol---the @samp{multiprocess} feature is
35563 an example of such a feature. The stub's reply should be independent
35564 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
35565 describes all the features it supports, and then the stub replies with
35566 all the features it supports.
35568 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
35569 responses, as long as each response uses one of the standard forms.
35571 Some features are flags. A stub which supports a flag feature
35572 should respond with a @samp{+} form response. Other features
35573 require values, and the stub should respond with an @samp{=}
35576 Each feature has a default value, which @value{GDBN} will use if
35577 @samp{qSupported} is not available or if the feature is not mentioned
35578 in the @samp{qSupported} response. The default values are fixed; a
35579 stub is free to omit any feature responses that match the defaults.
35581 Not all features can be probed, but for those which can, the probing
35582 mechanism is useful: in some cases, a stub's internal
35583 architecture may not allow the protocol layer to know some information
35584 about the underlying target in advance. This is especially common in
35585 stubs which may be configured for multiple targets.
35587 These are the currently defined stub features and their properties:
35589 @multitable @columnfractions 0.35 0.2 0.12 0.2
35590 @c NOTE: The first row should be @headitem, but we do not yet require
35591 @c a new enough version of Texinfo (4.7) to use @headitem.
35593 @tab Value Required
35597 @item @samp{PacketSize}
35602 @item @samp{qXfer:auxv:read}
35607 @item @samp{qXfer:btrace:read}
35612 @item @samp{qXfer:features:read}
35617 @item @samp{qXfer:libraries:read}
35622 @item @samp{qXfer:libraries-svr4:read}
35627 @item @samp{augmented-libraries-svr4-read}
35632 @item @samp{qXfer:memory-map:read}
35637 @item @samp{qXfer:sdata:read}
35642 @item @samp{qXfer:spu:read}
35647 @item @samp{qXfer:spu:write}
35652 @item @samp{qXfer:siginfo:read}
35657 @item @samp{qXfer:siginfo:write}
35662 @item @samp{qXfer:threads:read}
35667 @item @samp{qXfer:traceframe-info:read}
35672 @item @samp{qXfer:uib:read}
35677 @item @samp{qXfer:fdpic:read}
35682 @item @samp{Qbtrace:off}
35687 @item @samp{Qbtrace:bts}
35692 @item @samp{QNonStop}
35697 @item @samp{QPassSignals}
35702 @item @samp{QStartNoAckMode}
35707 @item @samp{multiprocess}
35712 @item @samp{ConditionalBreakpoints}
35717 @item @samp{ConditionalTracepoints}
35722 @item @samp{ReverseContinue}
35727 @item @samp{ReverseStep}
35732 @item @samp{TracepointSource}
35737 @item @samp{QAgent}
35742 @item @samp{QAllow}
35747 @item @samp{QDisableRandomization}
35752 @item @samp{EnableDisableTracepoints}
35757 @item @samp{QTBuffer:size}
35762 @item @samp{tracenz}
35767 @item @samp{BreakpointCommands}
35774 These are the currently defined stub features, in more detail:
35777 @cindex packet size, remote protocol
35778 @item PacketSize=@var{bytes}
35779 The remote stub can accept packets up to at least @var{bytes} in
35780 length. @value{GDBN} will send packets up to this size for bulk
35781 transfers, and will never send larger packets. This is a limit on the
35782 data characters in the packet, including the frame and checksum.
35783 There is no trailing NUL byte in a remote protocol packet; if the stub
35784 stores packets in a NUL-terminated format, it should allow an extra
35785 byte in its buffer for the NUL. If this stub feature is not supported,
35786 @value{GDBN} guesses based on the size of the @samp{g} packet response.
35788 @item qXfer:auxv:read
35789 The remote stub understands the @samp{qXfer:auxv:read} packet
35790 (@pxref{qXfer auxiliary vector read}).
35792 @item qXfer:btrace:read
35793 The remote stub understands the @samp{qXfer:btrace:read}
35794 packet (@pxref{qXfer btrace read}).
35796 @item qXfer:features:read
35797 The remote stub understands the @samp{qXfer:features:read} packet
35798 (@pxref{qXfer target description read}).
35800 @item qXfer:libraries:read
35801 The remote stub understands the @samp{qXfer:libraries:read} packet
35802 (@pxref{qXfer library list read}).
35804 @item qXfer:libraries-svr4:read
35805 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
35806 (@pxref{qXfer svr4 library list read}).
35808 @item augmented-libraries-svr4-read
35809 The remote stub understands the augmented form of the
35810 @samp{qXfer:libraries-svr4:read} packet
35811 (@pxref{qXfer svr4 library list read}).
35813 @item qXfer:memory-map:read
35814 The remote stub understands the @samp{qXfer:memory-map:read} packet
35815 (@pxref{qXfer memory map read}).
35817 @item qXfer:sdata:read
35818 The remote stub understands the @samp{qXfer:sdata:read} packet
35819 (@pxref{qXfer sdata read}).
35821 @item qXfer:spu:read
35822 The remote stub understands the @samp{qXfer:spu:read} packet
35823 (@pxref{qXfer spu read}).
35825 @item qXfer:spu:write
35826 The remote stub understands the @samp{qXfer:spu:write} packet
35827 (@pxref{qXfer spu write}).
35829 @item qXfer:siginfo:read
35830 The remote stub understands the @samp{qXfer:siginfo:read} packet
35831 (@pxref{qXfer siginfo read}).
35833 @item qXfer:siginfo:write
35834 The remote stub understands the @samp{qXfer:siginfo:write} packet
35835 (@pxref{qXfer siginfo write}).
35837 @item qXfer:threads:read
35838 The remote stub understands the @samp{qXfer:threads:read} packet
35839 (@pxref{qXfer threads read}).
35841 @item qXfer:traceframe-info:read
35842 The remote stub understands the @samp{qXfer:traceframe-info:read}
35843 packet (@pxref{qXfer traceframe info read}).
35845 @item qXfer:uib:read
35846 The remote stub understands the @samp{qXfer:uib:read}
35847 packet (@pxref{qXfer unwind info block}).
35849 @item qXfer:fdpic:read
35850 The remote stub understands the @samp{qXfer:fdpic:read}
35851 packet (@pxref{qXfer fdpic loadmap read}).
35854 The remote stub understands the @samp{QNonStop} packet
35855 (@pxref{QNonStop}).
35858 The remote stub understands the @samp{QPassSignals} packet
35859 (@pxref{QPassSignals}).
35861 @item QStartNoAckMode
35862 The remote stub understands the @samp{QStartNoAckMode} packet and
35863 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
35866 @anchor{multiprocess extensions}
35867 @cindex multiprocess extensions, in remote protocol
35868 The remote stub understands the multiprocess extensions to the remote
35869 protocol syntax. The multiprocess extensions affect the syntax of
35870 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
35871 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
35872 replies. Note that reporting this feature indicates support for the
35873 syntactic extensions only, not that the stub necessarily supports
35874 debugging of more than one process at a time. The stub must not use
35875 multiprocess extensions in packet replies unless @value{GDBN} has also
35876 indicated it supports them in its @samp{qSupported} request.
35878 @item qXfer:osdata:read
35879 The remote stub understands the @samp{qXfer:osdata:read} packet
35880 ((@pxref{qXfer osdata read}).
35882 @item ConditionalBreakpoints
35883 The target accepts and implements evaluation of conditional expressions
35884 defined for breakpoints. The target will only report breakpoint triggers
35885 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
35887 @item ConditionalTracepoints
35888 The remote stub accepts and implements conditional expressions defined
35889 for tracepoints (@pxref{Tracepoint Conditions}).
35891 @item ReverseContinue
35892 The remote stub accepts and implements the reverse continue packet
35896 The remote stub accepts and implements the reverse step packet
35899 @item TracepointSource
35900 The remote stub understands the @samp{QTDPsrc} packet that supplies
35901 the source form of tracepoint definitions.
35904 The remote stub understands the @samp{QAgent} packet.
35907 The remote stub understands the @samp{QAllow} packet.
35909 @item QDisableRandomization
35910 The remote stub understands the @samp{QDisableRandomization} packet.
35912 @item StaticTracepoint
35913 @cindex static tracepoints, in remote protocol
35914 The remote stub supports static tracepoints.
35916 @item InstallInTrace
35917 @anchor{install tracepoint in tracing}
35918 The remote stub supports installing tracepoint in tracing.
35920 @item EnableDisableTracepoints
35921 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
35922 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
35923 to be enabled and disabled while a trace experiment is running.
35925 @item QTBuffer:size
35926 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
35927 packet that allows to change the size of the trace buffer.
35930 @cindex string tracing, in remote protocol
35931 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
35932 See @ref{Bytecode Descriptions} for details about the bytecode.
35934 @item BreakpointCommands
35935 @cindex breakpoint commands, in remote protocol
35936 The remote stub supports running a breakpoint's command list itself,
35937 rather than reporting the hit to @value{GDBN}.
35940 The remote stub understands the @samp{Qbtrace:off} packet.
35943 The remote stub understands the @samp{Qbtrace:bts} packet.
35948 @cindex symbol lookup, remote request
35949 @cindex @samp{qSymbol} packet
35950 Notify the target that @value{GDBN} is prepared to serve symbol lookup
35951 requests. Accept requests from the target for the values of symbols.
35956 The target does not need to look up any (more) symbols.
35957 @item qSymbol:@var{sym_name}
35958 The target requests the value of symbol @var{sym_name} (hex encoded).
35959 @value{GDBN} may provide the value by using the
35960 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
35964 @item qSymbol:@var{sym_value}:@var{sym_name}
35965 Set the value of @var{sym_name} to @var{sym_value}.
35967 @var{sym_name} (hex encoded) is the name of a symbol whose value the
35968 target has previously requested.
35970 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
35971 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
35977 The target does not need to look up any (more) symbols.
35978 @item qSymbol:@var{sym_name}
35979 The target requests the value of a new symbol @var{sym_name} (hex
35980 encoded). @value{GDBN} will continue to supply the values of symbols
35981 (if available), until the target ceases to request them.
35986 @itemx QTDisconnected
35993 @itemx qTMinFTPILen
35995 @xref{Tracepoint Packets}.
35997 @item qThreadExtraInfo,@var{thread-id}
35998 @cindex thread attributes info, remote request
35999 @cindex @samp{qThreadExtraInfo} packet
36000 Obtain from the target OS a printable string description of thread
36001 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
36002 for the forms of @var{thread-id}. This
36003 string may contain anything that the target OS thinks is interesting
36004 for @value{GDBN} to tell the user about the thread. The string is
36005 displayed in @value{GDBN}'s @code{info threads} display. Some
36006 examples of possible thread extra info strings are @samp{Runnable}, or
36007 @samp{Blocked on Mutex}.
36011 @item @var{XX}@dots{}
36012 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
36013 comprising the printable string containing the extra information about
36014 the thread's attributes.
36017 (Note that the @code{qThreadExtraInfo} packet's name is separated from
36018 the command by a @samp{,}, not a @samp{:}, contrary to the naming
36019 conventions above. Please don't use this packet as a model for new
36038 @xref{Tracepoint Packets}.
36040 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
36041 @cindex read special object, remote request
36042 @cindex @samp{qXfer} packet
36043 @anchor{qXfer read}
36044 Read uninterpreted bytes from the target's special data area
36045 identified by the keyword @var{object}. Request @var{length} bytes
36046 starting at @var{offset} bytes into the data. The content and
36047 encoding of @var{annex} is specific to @var{object}; it can supply
36048 additional details about what data to access.
36050 Here are the specific requests of this form defined so far. All
36051 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
36052 formats, listed below.
36055 @item qXfer:auxv:read::@var{offset},@var{length}
36056 @anchor{qXfer auxiliary vector read}
36057 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
36058 auxiliary vector}. Note @var{annex} must be empty.
36060 This packet is not probed by default; the remote stub must request it,
36061 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36063 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
36064 @anchor{qXfer btrace read}
36066 Return a description of the current branch trace.
36067 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
36068 packet may have one of the following values:
36072 Returns all available branch trace.
36075 Returns all available branch trace if the branch trace changed since
36076 the last read request.
36079 Returns the new branch trace since the last read request. Adds a new
36080 block to the end of the trace that begins at zero and ends at the source
36081 location of the first branch in the trace buffer. This extra block is
36082 used to stitch traces together.
36084 If the trace buffer overflowed, returns an error indicating the overflow.
36087 This packet is not probed by default; the remote stub must request it
36088 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36090 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
36091 @anchor{qXfer target description read}
36092 Access the @dfn{target description}. @xref{Target Descriptions}. The
36093 annex specifies which XML document to access. The main description is
36094 always loaded from the @samp{target.xml} annex.
36096 This packet is not probed by default; the remote stub must request it,
36097 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36099 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
36100 @anchor{qXfer library list read}
36101 Access the target's list of loaded libraries. @xref{Library List Format}.
36102 The annex part of the generic @samp{qXfer} packet must be empty
36103 (@pxref{qXfer read}).
36105 Targets which maintain a list of libraries in the program's memory do
36106 not need to implement this packet; it is designed for platforms where
36107 the operating system manages the list of loaded libraries.
36109 This packet is not probed by default; the remote stub must request it,
36110 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36112 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
36113 @anchor{qXfer svr4 library list read}
36114 Access the target's list of loaded libraries when the target is an SVR4
36115 platform. @xref{Library List Format for SVR4 Targets}. The annex part
36116 of the generic @samp{qXfer} packet must be empty unless the remote
36117 stub indicated it supports the augmented form of this packet
36118 by supplying an appropriate @samp{qSupported} response
36119 (@pxref{qXfer read}, @ref{qSupported}).
36121 This packet is optional for better performance on SVR4 targets.
36122 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
36124 This packet is not probed by default; the remote stub must request it,
36125 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36127 If the remote stub indicates it supports the augmented form of this
36128 packet then the annex part of the generic @samp{qXfer} packet may
36129 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
36130 arguments. The currently supported arguments are:
36133 @item start=@var{address}
36134 A hexadecimal number specifying the address of the @samp{struct
36135 link_map} to start reading the library list from. If unset or zero
36136 then the first @samp{struct link_map} in the library list will be
36137 chosen as the starting point.
36139 @item prev=@var{address}
36140 A hexadecimal number specifying the address of the @samp{struct
36141 link_map} immediately preceding the @samp{struct link_map}
36142 specified by the @samp{start} argument. If unset or zero then
36143 the remote stub will expect that no @samp{struct link_map}
36144 exists prior to the starting point.
36148 Arguments that are not understood by the remote stub will be silently
36151 @item qXfer:memory-map:read::@var{offset},@var{length}
36152 @anchor{qXfer memory map read}
36153 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
36154 annex part of the generic @samp{qXfer} packet must be empty
36155 (@pxref{qXfer read}).
36157 This packet is not probed by default; the remote stub must request it,
36158 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36160 @item qXfer:sdata:read::@var{offset},@var{length}
36161 @anchor{qXfer sdata read}
36163 Read contents of the extra collected static tracepoint marker
36164 information. The annex part of the generic @samp{qXfer} packet must
36165 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
36168 This packet is not probed by default; the remote stub must request it,
36169 by supplying an appropriate @samp{qSupported} response
36170 (@pxref{qSupported}).
36172 @item qXfer:siginfo:read::@var{offset},@var{length}
36173 @anchor{qXfer siginfo read}
36174 Read contents of the extra signal information on the target
36175 system. The annex part of the generic @samp{qXfer} packet must be
36176 empty (@pxref{qXfer read}).
36178 This packet is not probed by default; the remote stub must request it,
36179 by supplying an appropriate @samp{qSupported} response
36180 (@pxref{qSupported}).
36182 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
36183 @anchor{qXfer spu read}
36184 Read contents of an @code{spufs} file on the target system. The
36185 annex specifies which file to read; it must be of the form
36186 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
36187 in the target process, and @var{name} identifes the @code{spufs} file
36188 in that context to be accessed.
36190 This packet is not probed by default; the remote stub must request it,
36191 by supplying an appropriate @samp{qSupported} response
36192 (@pxref{qSupported}).
36194 @item qXfer:threads:read::@var{offset},@var{length}
36195 @anchor{qXfer threads read}
36196 Access the list of threads on target. @xref{Thread List Format}. The
36197 annex part of the generic @samp{qXfer} packet must be empty
36198 (@pxref{qXfer read}).
36200 This packet is not probed by default; the remote stub must request it,
36201 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36203 @item qXfer:traceframe-info:read::@var{offset},@var{length}
36204 @anchor{qXfer traceframe info read}
36206 Return a description of the current traceframe's contents.
36207 @xref{Traceframe Info Format}. The annex part of the generic
36208 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
36210 This packet is not probed by default; the remote stub must request it,
36211 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36213 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
36214 @anchor{qXfer unwind info block}
36216 Return the unwind information block for @var{pc}. This packet is used
36217 on OpenVMS/ia64 to ask the kernel unwind information.
36219 This packet is not probed by default.
36221 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
36222 @anchor{qXfer fdpic loadmap read}
36223 Read contents of @code{loadmap}s on the target system. The
36224 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
36225 executable @code{loadmap} or interpreter @code{loadmap} to read.
36227 This packet is not probed by default; the remote stub must request it,
36228 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36230 @item qXfer:osdata:read::@var{offset},@var{length}
36231 @anchor{qXfer osdata read}
36232 Access the target's @dfn{operating system information}.
36233 @xref{Operating System Information}.
36240 Data @var{data} (@pxref{Binary Data}) has been read from the
36241 target. There may be more data at a higher address (although
36242 it is permitted to return @samp{m} even for the last valid
36243 block of data, as long as at least one byte of data was read).
36244 It is possible for @var{data} to have fewer bytes than the @var{length} in the
36248 Data @var{data} (@pxref{Binary Data}) has been read from the target.
36249 There is no more data to be read. It is possible for @var{data} to
36250 have fewer bytes than the @var{length} in the request.
36253 The @var{offset} in the request is at the end of the data.
36254 There is no more data to be read.
36257 The request was malformed, or @var{annex} was invalid.
36260 The offset was invalid, or there was an error encountered reading the data.
36261 The @var{nn} part is a hex-encoded @code{errno} value.
36264 An empty reply indicates the @var{object} string was not recognized by
36265 the stub, or that the object does not support reading.
36268 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
36269 @cindex write data into object, remote request
36270 @anchor{qXfer write}
36271 Write uninterpreted bytes into the target's special data area
36272 identified by the keyword @var{object}, starting at @var{offset} bytes
36273 into the data. The binary-encoded data (@pxref{Binary Data}) to be
36274 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
36275 is specific to @var{object}; it can supply additional details about what data
36278 Here are the specific requests of this form defined so far. All
36279 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
36280 formats, listed below.
36283 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
36284 @anchor{qXfer siginfo write}
36285 Write @var{data} to the extra signal information on the target system.
36286 The annex part of the generic @samp{qXfer} packet must be
36287 empty (@pxref{qXfer write}).
36289 This packet is not probed by default; the remote stub must request it,
36290 by supplying an appropriate @samp{qSupported} response
36291 (@pxref{qSupported}).
36293 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
36294 @anchor{qXfer spu write}
36295 Write @var{data} to an @code{spufs} file on the target system. The
36296 annex specifies which file to write; it must be of the form
36297 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
36298 in the target process, and @var{name} identifes the @code{spufs} file
36299 in that context to be accessed.
36301 This packet is not probed by default; the remote stub must request it,
36302 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36308 @var{nn} (hex encoded) is the number of bytes written.
36309 This may be fewer bytes than supplied in the request.
36312 The request was malformed, or @var{annex} was invalid.
36315 The offset was invalid, or there was an error encountered writing the data.
36316 The @var{nn} part is a hex-encoded @code{errno} value.
36319 An empty reply indicates the @var{object} string was not
36320 recognized by the stub, or that the object does not support writing.
36323 @item qXfer:@var{object}:@var{operation}:@dots{}
36324 Requests of this form may be added in the future. When a stub does
36325 not recognize the @var{object} keyword, or its support for
36326 @var{object} does not recognize the @var{operation} keyword, the stub
36327 must respond with an empty packet.
36329 @item qAttached:@var{pid}
36330 @cindex query attached, remote request
36331 @cindex @samp{qAttached} packet
36332 Return an indication of whether the remote server attached to an
36333 existing process or created a new process. When the multiprocess
36334 protocol extensions are supported (@pxref{multiprocess extensions}),
36335 @var{pid} is an integer in hexadecimal format identifying the target
36336 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
36337 the query packet will be simplified as @samp{qAttached}.
36339 This query is used, for example, to know whether the remote process
36340 should be detached or killed when a @value{GDBN} session is ended with
36341 the @code{quit} command.
36346 The remote server attached to an existing process.
36348 The remote server created a new process.
36350 A badly formed request or an error was encountered.
36354 Enable branch tracing for the current thread using bts tracing.
36359 Branch tracing has been enabled.
36361 A badly formed request or an error was encountered.
36365 Disable branch tracing for the current thread.
36370 Branch tracing has been disabled.
36372 A badly formed request or an error was encountered.
36377 @node Architecture-Specific Protocol Details
36378 @section Architecture-Specific Protocol Details
36380 This section describes how the remote protocol is applied to specific
36381 target architectures. Also see @ref{Standard Target Features}, for
36382 details of XML target descriptions for each architecture.
36385 * ARM-Specific Protocol Details::
36386 * MIPS-Specific Protocol Details::
36389 @node ARM-Specific Protocol Details
36390 @subsection @acronym{ARM}-specific Protocol Details
36393 * ARM Breakpoint Kinds::
36396 @node ARM Breakpoint Kinds
36397 @subsubsection @acronym{ARM} Breakpoint Kinds
36398 @cindex breakpoint kinds, @acronym{ARM}
36400 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
36405 16-bit Thumb mode breakpoint.
36408 32-bit Thumb mode (Thumb-2) breakpoint.
36411 32-bit @acronym{ARM} mode breakpoint.
36415 @node MIPS-Specific Protocol Details
36416 @subsection @acronym{MIPS}-specific Protocol Details
36419 * MIPS Register packet Format::
36420 * MIPS Breakpoint Kinds::
36423 @node MIPS Register packet Format
36424 @subsubsection @acronym{MIPS} Register Packet Format
36425 @cindex register packet format, @acronym{MIPS}
36427 The following @code{g}/@code{G} packets have previously been defined.
36428 In the below, some thirty-two bit registers are transferred as
36429 sixty-four bits. Those registers should be zero/sign extended (which?)
36430 to fill the space allocated. Register bytes are transferred in target
36431 byte order. The two nibbles within a register byte are transferred
36432 most-significant -- least-significant.
36437 All registers are transferred as thirty-two bit quantities in the order:
36438 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
36439 registers; fsr; fir; fp.
36442 All registers are transferred as sixty-four bit quantities (including
36443 thirty-two bit registers such as @code{sr}). The ordering is the same
36448 @node MIPS Breakpoint Kinds
36449 @subsubsection @acronym{MIPS} Breakpoint Kinds
36450 @cindex breakpoint kinds, @acronym{MIPS}
36452 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
36457 16-bit @acronym{MIPS16} mode breakpoint.
36460 16-bit @acronym{microMIPS} mode breakpoint.
36463 32-bit standard @acronym{MIPS} mode breakpoint.
36466 32-bit @acronym{microMIPS} mode breakpoint.
36470 @node Tracepoint Packets
36471 @section Tracepoint Packets
36472 @cindex tracepoint packets
36473 @cindex packets, tracepoint
36475 Here we describe the packets @value{GDBN} uses to implement
36476 tracepoints (@pxref{Tracepoints}).
36480 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
36481 @cindex @samp{QTDP} packet
36482 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
36483 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
36484 the tracepoint is disabled. The @var{step} gives the tracepoint's step
36485 count, and @var{pass} gives its pass count. If an @samp{F} is present,
36486 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
36487 the number of bytes that the target should copy elsewhere to make room
36488 for the tracepoint. If an @samp{X} is present, it introduces a
36489 tracepoint condition, which consists of a hexadecimal length, followed
36490 by a comma and hex-encoded bytes, in a manner similar to action
36491 encodings as described below. If the trailing @samp{-} is present,
36492 further @samp{QTDP} packets will follow to specify this tracepoint's
36498 The packet was understood and carried out.
36500 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
36502 The packet was not recognized.
36505 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
36506 Define actions to be taken when a tracepoint is hit. The @var{n} and
36507 @var{addr} must be the same as in the initial @samp{QTDP} packet for
36508 this tracepoint. This packet may only be sent immediately after
36509 another @samp{QTDP} packet that ended with a @samp{-}. If the
36510 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
36511 specifying more actions for this tracepoint.
36513 In the series of action packets for a given tracepoint, at most one
36514 can have an @samp{S} before its first @var{action}. If such a packet
36515 is sent, it and the following packets define ``while-stepping''
36516 actions. Any prior packets define ordinary actions --- that is, those
36517 taken when the tracepoint is first hit. If no action packet has an
36518 @samp{S}, then all the packets in the series specify ordinary
36519 tracepoint actions.
36521 The @samp{@var{action}@dots{}} portion of the packet is a series of
36522 actions, concatenated without separators. Each action has one of the
36528 Collect the registers whose bits are set in @var{mask},
36529 a hexadecimal number whose @var{i}'th bit is set if register number
36530 @var{i} should be collected. (The least significant bit is numbered
36531 zero.) Note that @var{mask} may be any number of digits long; it may
36532 not fit in a 32-bit word.
36534 @item M @var{basereg},@var{offset},@var{len}
36535 Collect @var{len} bytes of memory starting at the address in register
36536 number @var{basereg}, plus @var{offset}. If @var{basereg} is
36537 @samp{-1}, then the range has a fixed address: @var{offset} is the
36538 address of the lowest byte to collect. The @var{basereg},
36539 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
36540 values (the @samp{-1} value for @var{basereg} is a special case).
36542 @item X @var{len},@var{expr}
36543 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
36544 it directs. The agent expression @var{expr} is as described in
36545 @ref{Agent Expressions}. Each byte of the expression is encoded as a
36546 two-digit hex number in the packet; @var{len} is the number of bytes
36547 in the expression (and thus one-half the number of hex digits in the
36552 Any number of actions may be packed together in a single @samp{QTDP}
36553 packet, as long as the packet does not exceed the maximum packet
36554 length (400 bytes, for many stubs). There may be only one @samp{R}
36555 action per tracepoint, and it must precede any @samp{M} or @samp{X}
36556 actions. Any registers referred to by @samp{M} and @samp{X} actions
36557 must be collected by a preceding @samp{R} action. (The
36558 ``while-stepping'' actions are treated as if they were attached to a
36559 separate tracepoint, as far as these restrictions are concerned.)
36564 The packet was understood and carried out.
36566 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
36568 The packet was not recognized.
36571 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
36572 @cindex @samp{QTDPsrc} packet
36573 Specify a source string of tracepoint @var{n} at address @var{addr}.
36574 This is useful to get accurate reproduction of the tracepoints
36575 originally downloaded at the beginning of the trace run. The @var{type}
36576 is the name of the tracepoint part, such as @samp{cond} for the
36577 tracepoint's conditional expression (see below for a list of types), while
36578 @var{bytes} is the string, encoded in hexadecimal.
36580 @var{start} is the offset of the @var{bytes} within the overall source
36581 string, while @var{slen} is the total length of the source string.
36582 This is intended for handling source strings that are longer than will
36583 fit in a single packet.
36584 @c Add detailed example when this info is moved into a dedicated
36585 @c tracepoint descriptions section.
36587 The available string types are @samp{at} for the location,
36588 @samp{cond} for the conditional, and @samp{cmd} for an action command.
36589 @value{GDBN} sends a separate packet for each command in the action
36590 list, in the same order in which the commands are stored in the list.
36592 The target does not need to do anything with source strings except
36593 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
36596 Although this packet is optional, and @value{GDBN} will only send it
36597 if the target replies with @samp{TracepointSource} @xref{General
36598 Query Packets}, it makes both disconnected tracing and trace files
36599 much easier to use. Otherwise the user must be careful that the
36600 tracepoints in effect while looking at trace frames are identical to
36601 the ones in effect during the trace run; even a small discrepancy
36602 could cause @samp{tdump} not to work, or a particular trace frame not
36605 @item QTDV:@var{n}:@var{value}
36606 @cindex define trace state variable, remote request
36607 @cindex @samp{QTDV} packet
36608 Create a new trace state variable, number @var{n}, with an initial
36609 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
36610 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
36611 the option of not using this packet for initial values of zero; the
36612 target should simply create the trace state variables as they are
36613 mentioned in expressions.
36615 @item QTFrame:@var{n}
36616 @cindex @samp{QTFrame} packet
36617 Select the @var{n}'th tracepoint frame from the buffer, and use the
36618 register and memory contents recorded there to answer subsequent
36619 request packets from @value{GDBN}.
36621 A successful reply from the stub indicates that the stub has found the
36622 requested frame. The response is a series of parts, concatenated
36623 without separators, describing the frame we selected. Each part has
36624 one of the following forms:
36628 The selected frame is number @var{n} in the trace frame buffer;
36629 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
36630 was no frame matching the criteria in the request packet.
36633 The selected trace frame records a hit of tracepoint number @var{t};
36634 @var{t} is a hexadecimal number.
36638 @item QTFrame:pc:@var{addr}
36639 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36640 currently selected frame whose PC is @var{addr};
36641 @var{addr} is a hexadecimal number.
36643 @item QTFrame:tdp:@var{t}
36644 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36645 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
36646 is a hexadecimal number.
36648 @item QTFrame:range:@var{start}:@var{end}
36649 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36650 currently selected frame whose PC is between @var{start} (inclusive)
36651 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
36654 @item QTFrame:outside:@var{start}:@var{end}
36655 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
36656 frame @emph{outside} the given range of addresses (exclusive).
36659 @cindex @samp{qTMinFTPILen} packet
36660 This packet requests the minimum length of instruction at which a fast
36661 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
36662 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
36663 it depends on the target system being able to create trampolines in
36664 the first 64K of memory, which might or might not be possible for that
36665 system. So the reply to this packet will be 4 if it is able to
36672 The minimum instruction length is currently unknown.
36674 The minimum instruction length is @var{length}, where @var{length}
36675 is a hexadecimal number greater or equal to 1. A reply
36676 of 1 means that a fast tracepoint may be placed on any instruction
36677 regardless of size.
36679 An error has occurred.
36681 An empty reply indicates that the request is not supported by the stub.
36685 @cindex @samp{QTStart} packet
36686 Begin the tracepoint experiment. Begin collecting data from
36687 tracepoint hits in the trace frame buffer. This packet supports the
36688 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
36689 instruction reply packet}).
36692 @cindex @samp{QTStop} packet
36693 End the tracepoint experiment. Stop collecting trace frames.
36695 @item QTEnable:@var{n}:@var{addr}
36697 @cindex @samp{QTEnable} packet
36698 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
36699 experiment. If the tracepoint was previously disabled, then collection
36700 of data from it will resume.
36702 @item QTDisable:@var{n}:@var{addr}
36704 @cindex @samp{QTDisable} packet
36705 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
36706 experiment. No more data will be collected from the tracepoint unless
36707 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
36710 @cindex @samp{QTinit} packet
36711 Clear the table of tracepoints, and empty the trace frame buffer.
36713 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
36714 @cindex @samp{QTro} packet
36715 Establish the given ranges of memory as ``transparent''. The stub
36716 will answer requests for these ranges from memory's current contents,
36717 if they were not collected as part of the tracepoint hit.
36719 @value{GDBN} uses this to mark read-only regions of memory, like those
36720 containing program code. Since these areas never change, they should
36721 still have the same contents they did when the tracepoint was hit, so
36722 there's no reason for the stub to refuse to provide their contents.
36724 @item QTDisconnected:@var{value}
36725 @cindex @samp{QTDisconnected} packet
36726 Set the choice to what to do with the tracing run when @value{GDBN}
36727 disconnects from the target. A @var{value} of 1 directs the target to
36728 continue the tracing run, while 0 tells the target to stop tracing if
36729 @value{GDBN} is no longer in the picture.
36732 @cindex @samp{qTStatus} packet
36733 Ask the stub if there is a trace experiment running right now.
36735 The reply has the form:
36739 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
36740 @var{running} is a single digit @code{1} if the trace is presently
36741 running, or @code{0} if not. It is followed by semicolon-separated
36742 optional fields that an agent may use to report additional status.
36746 If the trace is not running, the agent may report any of several
36747 explanations as one of the optional fields:
36752 No trace has been run yet.
36754 @item tstop[:@var{text}]:0
36755 The trace was stopped by a user-originated stop command. The optional
36756 @var{text} field is a user-supplied string supplied as part of the
36757 stop command (for instance, an explanation of why the trace was
36758 stopped manually). It is hex-encoded.
36761 The trace stopped because the trace buffer filled up.
36763 @item tdisconnected:0
36764 The trace stopped because @value{GDBN} disconnected from the target.
36766 @item tpasscount:@var{tpnum}
36767 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
36769 @item terror:@var{text}:@var{tpnum}
36770 The trace stopped because tracepoint @var{tpnum} had an error. The
36771 string @var{text} is available to describe the nature of the error
36772 (for instance, a divide by zero in the condition expression); it
36776 The trace stopped for some other reason.
36780 Additional optional fields supply statistical and other information.
36781 Although not required, they are extremely useful for users monitoring
36782 the progress of a trace run. If a trace has stopped, and these
36783 numbers are reported, they must reflect the state of the just-stopped
36788 @item tframes:@var{n}
36789 The number of trace frames in the buffer.
36791 @item tcreated:@var{n}
36792 The total number of trace frames created during the run. This may
36793 be larger than the trace frame count, if the buffer is circular.
36795 @item tsize:@var{n}
36796 The total size of the trace buffer, in bytes.
36798 @item tfree:@var{n}
36799 The number of bytes still unused in the buffer.
36801 @item circular:@var{n}
36802 The value of the circular trace buffer flag. @code{1} means that the
36803 trace buffer is circular and old trace frames will be discarded if
36804 necessary to make room, @code{0} means that the trace buffer is linear
36807 @item disconn:@var{n}
36808 The value of the disconnected tracing flag. @code{1} means that
36809 tracing will continue after @value{GDBN} disconnects, @code{0} means
36810 that the trace run will stop.
36814 @item qTP:@var{tp}:@var{addr}
36815 @cindex tracepoint status, remote request
36816 @cindex @samp{qTP} packet
36817 Ask the stub for the current state of tracepoint number @var{tp} at
36818 address @var{addr}.
36822 @item V@var{hits}:@var{usage}
36823 The tracepoint has been hit @var{hits} times so far during the trace
36824 run, and accounts for @var{usage} in the trace buffer. Note that
36825 @code{while-stepping} steps are not counted as separate hits, but the
36826 steps' space consumption is added into the usage number.
36830 @item qTV:@var{var}
36831 @cindex trace state variable value, remote request
36832 @cindex @samp{qTV} packet
36833 Ask the stub for the value of the trace state variable number @var{var}.
36838 The value of the variable is @var{value}. This will be the current
36839 value of the variable if the user is examining a running target, or a
36840 saved value if the variable was collected in the trace frame that the
36841 user is looking at. Note that multiple requests may result in
36842 different reply values, such as when requesting values while the
36843 program is running.
36846 The value of the variable is unknown. This would occur, for example,
36847 if the user is examining a trace frame in which the requested variable
36852 @cindex @samp{qTfP} packet
36854 @cindex @samp{qTsP} packet
36855 These packets request data about tracepoints that are being used by
36856 the target. @value{GDBN} sends @code{qTfP} to get the first piece
36857 of data, and multiple @code{qTsP} to get additional pieces. Replies
36858 to these packets generally take the form of the @code{QTDP} packets
36859 that define tracepoints. (FIXME add detailed syntax)
36862 @cindex @samp{qTfV} packet
36864 @cindex @samp{qTsV} packet
36865 These packets request data about trace state variables that are on the
36866 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
36867 and multiple @code{qTsV} to get additional variables. Replies to
36868 these packets follow the syntax of the @code{QTDV} packets that define
36869 trace state variables.
36875 @cindex @samp{qTfSTM} packet
36876 @cindex @samp{qTsSTM} packet
36877 These packets request data about static tracepoint markers that exist
36878 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
36879 first piece of data, and multiple @code{qTsSTM} to get additional
36880 pieces. Replies to these packets take the following form:
36884 @item m @var{address}:@var{id}:@var{extra}
36886 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
36887 a comma-separated list of markers
36889 (lower case letter @samp{L}) denotes end of list.
36891 An error occurred. The error number @var{nn} is given as hex digits.
36893 An empty reply indicates that the request is not supported by the
36897 The @var{address} is encoded in hex;
36898 @var{id} and @var{extra} are strings encoded in hex.
36900 In response to each query, the target will reply with a list of one or
36901 more markers, separated by commas. @value{GDBN} will respond to each
36902 reply with a request for more markers (using the @samp{qs} form of the
36903 query), until the target responds with @samp{l} (lower-case ell, for
36906 @item qTSTMat:@var{address}
36908 @cindex @samp{qTSTMat} packet
36909 This packets requests data about static tracepoint markers in the
36910 target program at @var{address}. Replies to this packet follow the
36911 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
36912 tracepoint markers.
36914 @item QTSave:@var{filename}
36915 @cindex @samp{QTSave} packet
36916 This packet directs the target to save trace data to the file name
36917 @var{filename} in the target's filesystem. The @var{filename} is encoded
36918 as a hex string; the interpretation of the file name (relative vs
36919 absolute, wild cards, etc) is up to the target.
36921 @item qTBuffer:@var{offset},@var{len}
36922 @cindex @samp{qTBuffer} packet
36923 Return up to @var{len} bytes of the current contents of trace buffer,
36924 starting at @var{offset}. The trace buffer is treated as if it were
36925 a contiguous collection of traceframes, as per the trace file format.
36926 The reply consists as many hex-encoded bytes as the target can deliver
36927 in a packet; it is not an error to return fewer than were asked for.
36928 A reply consisting of just @code{l} indicates that no bytes are
36931 @item QTBuffer:circular:@var{value}
36932 This packet directs the target to use a circular trace buffer if
36933 @var{value} is 1, or a linear buffer if the value is 0.
36935 @item QTBuffer:size:@var{size}
36936 @anchor{QTBuffer-size}
36937 @cindex @samp{QTBuffer size} packet
36938 This packet directs the target to make the trace buffer be of size
36939 @var{size} if possible. A value of @code{-1} tells the target to
36940 use whatever size it prefers.
36942 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
36943 @cindex @samp{QTNotes} packet
36944 This packet adds optional textual notes to the trace run. Allowable
36945 types include @code{user}, @code{notes}, and @code{tstop}, the
36946 @var{text} fields are arbitrary strings, hex-encoded.
36950 @subsection Relocate instruction reply packet
36951 When installing fast tracepoints in memory, the target may need to
36952 relocate the instruction currently at the tracepoint address to a
36953 different address in memory. For most instructions, a simple copy is
36954 enough, but, for example, call instructions that implicitly push the
36955 return address on the stack, and relative branches or other
36956 PC-relative instructions require offset adjustment, so that the effect
36957 of executing the instruction at a different address is the same as if
36958 it had executed in the original location.
36960 In response to several of the tracepoint packets, the target may also
36961 respond with a number of intermediate @samp{qRelocInsn} request
36962 packets before the final result packet, to have @value{GDBN} handle
36963 this relocation operation. If a packet supports this mechanism, its
36964 documentation will explicitly say so. See for example the above
36965 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
36966 format of the request is:
36969 @item qRelocInsn:@var{from};@var{to}
36971 This requests @value{GDBN} to copy instruction at address @var{from}
36972 to address @var{to}, possibly adjusted so that executing the
36973 instruction at @var{to} has the same effect as executing it at
36974 @var{from}. @value{GDBN} writes the adjusted instruction to target
36975 memory starting at @var{to}.
36980 @item qRelocInsn:@var{adjusted_size}
36981 Informs the stub the relocation is complete. The @var{adjusted_size} is
36982 the length in bytes of resulting relocated instruction sequence.
36984 A badly formed request was detected, or an error was encountered while
36985 relocating the instruction.
36988 @node Host I/O Packets
36989 @section Host I/O Packets
36990 @cindex Host I/O, remote protocol
36991 @cindex file transfer, remote protocol
36993 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
36994 operations on the far side of a remote link. For example, Host I/O is
36995 used to upload and download files to a remote target with its own
36996 filesystem. Host I/O uses the same constant values and data structure
36997 layout as the target-initiated File-I/O protocol. However, the
36998 Host I/O packets are structured differently. The target-initiated
36999 protocol relies on target memory to store parameters and buffers.
37000 Host I/O requests are initiated by @value{GDBN}, and the
37001 target's memory is not involved. @xref{File-I/O Remote Protocol
37002 Extension}, for more details on the target-initiated protocol.
37004 The Host I/O request packets all encode a single operation along with
37005 its arguments. They have this format:
37009 @item vFile:@var{operation}: @var{parameter}@dots{}
37010 @var{operation} is the name of the particular request; the target
37011 should compare the entire packet name up to the second colon when checking
37012 for a supported operation. The format of @var{parameter} depends on
37013 the operation. Numbers are always passed in hexadecimal. Negative
37014 numbers have an explicit minus sign (i.e.@: two's complement is not
37015 used). Strings (e.g.@: filenames) are encoded as a series of
37016 hexadecimal bytes. The last argument to a system call may be a
37017 buffer of escaped binary data (@pxref{Binary Data}).
37021 The valid responses to Host I/O packets are:
37025 @item F @var{result} [, @var{errno}] [; @var{attachment}]
37026 @var{result} is the integer value returned by this operation, usually
37027 non-negative for success and -1 for errors. If an error has occured,
37028 @var{errno} will be included in the result specifying a
37029 value defined by the File-I/O protocol (@pxref{Errno Values}). For
37030 operations which return data, @var{attachment} supplies the data as a
37031 binary buffer. Binary buffers in response packets are escaped in the
37032 normal way (@pxref{Binary Data}). See the individual packet
37033 documentation for the interpretation of @var{result} and
37037 An empty response indicates that this operation is not recognized.
37041 These are the supported Host I/O operations:
37044 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
37045 Open a file at @var{filename} and return a file descriptor for it, or
37046 return -1 if an error occurs. The @var{filename} is a string,
37047 @var{flags} is an integer indicating a mask of open flags
37048 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
37049 of mode bits to use if the file is created (@pxref{mode_t Values}).
37050 @xref{open}, for details of the open flags and mode values.
37052 @item vFile:close: @var{fd}
37053 Close the open file corresponding to @var{fd} and return 0, or
37054 -1 if an error occurs.
37056 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
37057 Read data from the open file corresponding to @var{fd}. Up to
37058 @var{count} bytes will be read from the file, starting at @var{offset}
37059 relative to the start of the file. The target may read fewer bytes;
37060 common reasons include packet size limits and an end-of-file
37061 condition. The number of bytes read is returned. Zero should only be
37062 returned for a successful read at the end of the file, or if
37063 @var{count} was zero.
37065 The data read should be returned as a binary attachment on success.
37066 If zero bytes were read, the response should include an empty binary
37067 attachment (i.e.@: a trailing semicolon). The return value is the
37068 number of target bytes read; the binary attachment may be longer if
37069 some characters were escaped.
37071 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
37072 Write @var{data} (a binary buffer) to the open file corresponding
37073 to @var{fd}. Start the write at @var{offset} from the start of the
37074 file. Unlike many @code{write} system calls, there is no
37075 separate @var{count} argument; the length of @var{data} in the
37076 packet is used. @samp{vFile:write} returns the number of bytes written,
37077 which may be shorter than the length of @var{data}, or -1 if an
37080 @item vFile:unlink: @var{filename}
37081 Delete the file at @var{filename} on the target. Return 0,
37082 or -1 if an error occurs. The @var{filename} is a string.
37084 @item vFile:readlink: @var{filename}
37085 Read value of symbolic link @var{filename} on the target. Return
37086 the number of bytes read, or -1 if an error occurs.
37088 The data read should be returned as a binary attachment on success.
37089 If zero bytes were read, the response should include an empty binary
37090 attachment (i.e.@: a trailing semicolon). The return value is the
37091 number of target bytes read; the binary attachment may be longer if
37092 some characters were escaped.
37097 @section Interrupts
37098 @cindex interrupts (remote protocol)
37100 When a program on the remote target is running, @value{GDBN} may
37101 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
37102 a @code{BREAK} followed by @code{g},
37103 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
37105 The precise meaning of @code{BREAK} is defined by the transport
37106 mechanism and may, in fact, be undefined. @value{GDBN} does not
37107 currently define a @code{BREAK} mechanism for any of the network
37108 interfaces except for TCP, in which case @value{GDBN} sends the
37109 @code{telnet} BREAK sequence.
37111 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
37112 transport mechanisms. It is represented by sending the single byte
37113 @code{0x03} without any of the usual packet overhead described in
37114 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
37115 transmitted as part of a packet, it is considered to be packet data
37116 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
37117 (@pxref{X packet}), used for binary downloads, may include an unescaped
37118 @code{0x03} as part of its packet.
37120 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
37121 When Linux kernel receives this sequence from serial port,
37122 it stops execution and connects to gdb.
37124 Stubs are not required to recognize these interrupt mechanisms and the
37125 precise meaning associated with receipt of the interrupt is
37126 implementation defined. If the target supports debugging of multiple
37127 threads and/or processes, it should attempt to interrupt all
37128 currently-executing threads and processes.
37129 If the stub is successful at interrupting the
37130 running program, it should send one of the stop
37131 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
37132 of successfully stopping the program in all-stop mode, and a stop reply
37133 for each stopped thread in non-stop mode.
37134 Interrupts received while the
37135 program is stopped are discarded.
37137 @node Notification Packets
37138 @section Notification Packets
37139 @cindex notification packets
37140 @cindex packets, notification
37142 The @value{GDBN} remote serial protocol includes @dfn{notifications},
37143 packets that require no acknowledgment. Both the GDB and the stub
37144 may send notifications (although the only notifications defined at
37145 present are sent by the stub). Notifications carry information
37146 without incurring the round-trip latency of an acknowledgment, and so
37147 are useful for low-impact communications where occasional packet loss
37150 A notification packet has the form @samp{% @var{data} #
37151 @var{checksum}}, where @var{data} is the content of the notification,
37152 and @var{checksum} is a checksum of @var{data}, computed and formatted
37153 as for ordinary @value{GDBN} packets. A notification's @var{data}
37154 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
37155 receiving a notification, the recipient sends no @samp{+} or @samp{-}
37156 to acknowledge the notification's receipt or to report its corruption.
37158 Every notification's @var{data} begins with a name, which contains no
37159 colon characters, followed by a colon character.
37161 Recipients should silently ignore corrupted notifications and
37162 notifications they do not understand. Recipients should restart
37163 timeout periods on receipt of a well-formed notification, whether or
37164 not they understand it.
37166 Senders should only send the notifications described here when this
37167 protocol description specifies that they are permitted. In the
37168 future, we may extend the protocol to permit existing notifications in
37169 new contexts; this rule helps older senders avoid confusing newer
37172 (Older versions of @value{GDBN} ignore bytes received until they see
37173 the @samp{$} byte that begins an ordinary packet, so new stubs may
37174 transmit notifications without fear of confusing older clients. There
37175 are no notifications defined for @value{GDBN} to send at the moment, but we
37176 assume that most older stubs would ignore them, as well.)
37178 Each notification is comprised of three parts:
37180 @item @var{name}:@var{event}
37181 The notification packet is sent by the side that initiates the
37182 exchange (currently, only the stub does that), with @var{event}
37183 carrying the specific information about the notification, and
37184 @var{name} specifying the name of the notification.
37186 The acknowledge sent by the other side, usually @value{GDBN}, to
37187 acknowledge the exchange and request the event.
37190 The purpose of an asynchronous notification mechanism is to report to
37191 @value{GDBN} that something interesting happened in the remote stub.
37193 The remote stub may send notification @var{name}:@var{event}
37194 at any time, but @value{GDBN} acknowledges the notification when
37195 appropriate. The notification event is pending before @value{GDBN}
37196 acknowledges. Only one notification at a time may be pending; if
37197 additional events occur before @value{GDBN} has acknowledged the
37198 previous notification, they must be queued by the stub for later
37199 synchronous transmission in response to @var{ack} packets from
37200 @value{GDBN}. Because the notification mechanism is unreliable,
37201 the stub is permitted to resend a notification if it believes
37202 @value{GDBN} may not have received it.
37204 Specifically, notifications may appear when @value{GDBN} is not
37205 otherwise reading input from the stub, or when @value{GDBN} is
37206 expecting to read a normal synchronous response or a
37207 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
37208 Notification packets are distinct from any other communication from
37209 the stub so there is no ambiguity.
37211 After receiving a notification, @value{GDBN} shall acknowledge it by
37212 sending a @var{ack} packet as a regular, synchronous request to the
37213 stub. Such acknowledgment is not required to happen immediately, as
37214 @value{GDBN} is permitted to send other, unrelated packets to the
37215 stub first, which the stub should process normally.
37217 Upon receiving a @var{ack} packet, if the stub has other queued
37218 events to report to @value{GDBN}, it shall respond by sending a
37219 normal @var{event}. @value{GDBN} shall then send another @var{ack}
37220 packet to solicit further responses; again, it is permitted to send
37221 other, unrelated packets as well which the stub should process
37224 If the stub receives a @var{ack} packet and there are no additional
37225 @var{event} to report, the stub shall return an @samp{OK} response.
37226 At this point, @value{GDBN} has finished processing a notification
37227 and the stub has completed sending any queued events. @value{GDBN}
37228 won't accept any new notifications until the final @samp{OK} is
37229 received . If further notification events occur, the stub shall send
37230 a new notification, @value{GDBN} shall accept the notification, and
37231 the process shall be repeated.
37233 The process of asynchronous notification can be illustrated by the
37236 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
37239 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
37241 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
37246 The following notifications are defined:
37247 @multitable @columnfractions 0.12 0.12 0.38 0.38
37256 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
37257 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
37258 for information on how these notifications are acknowledged by
37260 @tab Report an asynchronous stop event in non-stop mode.
37264 @node Remote Non-Stop
37265 @section Remote Protocol Support for Non-Stop Mode
37267 @value{GDBN}'s remote protocol supports non-stop debugging of
37268 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
37269 supports non-stop mode, it should report that to @value{GDBN} by including
37270 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
37272 @value{GDBN} typically sends a @samp{QNonStop} packet only when
37273 establishing a new connection with the stub. Entering non-stop mode
37274 does not alter the state of any currently-running threads, but targets
37275 must stop all threads in any already-attached processes when entering
37276 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
37277 probe the target state after a mode change.
37279 In non-stop mode, when an attached process encounters an event that
37280 would otherwise be reported with a stop reply, it uses the
37281 asynchronous notification mechanism (@pxref{Notification Packets}) to
37282 inform @value{GDBN}. In contrast to all-stop mode, where all threads
37283 in all processes are stopped when a stop reply is sent, in non-stop
37284 mode only the thread reporting the stop event is stopped. That is,
37285 when reporting a @samp{S} or @samp{T} response to indicate completion
37286 of a step operation, hitting a breakpoint, or a fault, only the
37287 affected thread is stopped; any other still-running threads continue
37288 to run. When reporting a @samp{W} or @samp{X} response, all running
37289 threads belonging to other attached processes continue to run.
37291 In non-stop mode, the target shall respond to the @samp{?} packet as
37292 follows. First, any incomplete stop reply notification/@samp{vStopped}
37293 sequence in progress is abandoned. The target must begin a new
37294 sequence reporting stop events for all stopped threads, whether or not
37295 it has previously reported those events to @value{GDBN}. The first
37296 stop reply is sent as a synchronous reply to the @samp{?} packet, and
37297 subsequent stop replies are sent as responses to @samp{vStopped} packets
37298 using the mechanism described above. The target must not send
37299 asynchronous stop reply notifications until the sequence is complete.
37300 If all threads are running when the target receives the @samp{?} packet,
37301 or if the target is not attached to any process, it shall respond
37304 @node Packet Acknowledgment
37305 @section Packet Acknowledgment
37307 @cindex acknowledgment, for @value{GDBN} remote
37308 @cindex packet acknowledgment, for @value{GDBN} remote
37309 By default, when either the host or the target machine receives a packet,
37310 the first response expected is an acknowledgment: either @samp{+} (to indicate
37311 the package was received correctly) or @samp{-} (to request retransmission).
37312 This mechanism allows the @value{GDBN} remote protocol to operate over
37313 unreliable transport mechanisms, such as a serial line.
37315 In cases where the transport mechanism is itself reliable (such as a pipe or
37316 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
37317 It may be desirable to disable them in that case to reduce communication
37318 overhead, or for other reasons. This can be accomplished by means of the
37319 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
37321 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
37322 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
37323 and response format still includes the normal checksum, as described in
37324 @ref{Overview}, but the checksum may be ignored by the receiver.
37326 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
37327 no-acknowledgment mode, it should report that to @value{GDBN}
37328 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
37329 @pxref{qSupported}.
37330 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
37331 disabled via the @code{set remote noack-packet off} command
37332 (@pxref{Remote Configuration}),
37333 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
37334 Only then may the stub actually turn off packet acknowledgments.
37335 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
37336 response, which can be safely ignored by the stub.
37338 Note that @code{set remote noack-packet} command only affects negotiation
37339 between @value{GDBN} and the stub when subsequent connections are made;
37340 it does not affect the protocol acknowledgment state for any current
37342 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
37343 new connection is established,
37344 there is also no protocol request to re-enable the acknowledgments
37345 for the current connection, once disabled.
37350 Example sequence of a target being re-started. Notice how the restart
37351 does not get any direct output:
37356 @emph{target restarts}
37359 <- @code{T001:1234123412341234}
37363 Example sequence of a target being stepped by a single instruction:
37366 -> @code{G1445@dots{}}
37371 <- @code{T001:1234123412341234}
37375 <- @code{1455@dots{}}
37379 @node File-I/O Remote Protocol Extension
37380 @section File-I/O Remote Protocol Extension
37381 @cindex File-I/O remote protocol extension
37384 * File-I/O Overview::
37385 * Protocol Basics::
37386 * The F Request Packet::
37387 * The F Reply Packet::
37388 * The Ctrl-C Message::
37390 * List of Supported Calls::
37391 * Protocol-specific Representation of Datatypes::
37393 * File-I/O Examples::
37396 @node File-I/O Overview
37397 @subsection File-I/O Overview
37398 @cindex file-i/o overview
37400 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
37401 target to use the host's file system and console I/O to perform various
37402 system calls. System calls on the target system are translated into a
37403 remote protocol packet to the host system, which then performs the needed
37404 actions and returns a response packet to the target system.
37405 This simulates file system operations even on targets that lack file systems.
37407 The protocol is defined to be independent of both the host and target systems.
37408 It uses its own internal representation of datatypes and values. Both
37409 @value{GDBN} and the target's @value{GDBN} stub are responsible for
37410 translating the system-dependent value representations into the internal
37411 protocol representations when data is transmitted.
37413 The communication is synchronous. A system call is possible only when
37414 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
37415 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
37416 the target is stopped to allow deterministic access to the target's
37417 memory. Therefore File-I/O is not interruptible by target signals. On
37418 the other hand, it is possible to interrupt File-I/O by a user interrupt
37419 (@samp{Ctrl-C}) within @value{GDBN}.
37421 The target's request to perform a host system call does not finish
37422 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
37423 after finishing the system call, the target returns to continuing the
37424 previous activity (continue, step). No additional continue or step
37425 request from @value{GDBN} is required.
37428 (@value{GDBP}) continue
37429 <- target requests 'system call X'
37430 target is stopped, @value{GDBN} executes system call
37431 -> @value{GDBN} returns result
37432 ... target continues, @value{GDBN} returns to wait for the target
37433 <- target hits breakpoint and sends a Txx packet
37436 The protocol only supports I/O on the console and to regular files on
37437 the host file system. Character or block special devices, pipes,
37438 named pipes, sockets or any other communication method on the host
37439 system are not supported by this protocol.
37441 File I/O is not supported in non-stop mode.
37443 @node Protocol Basics
37444 @subsection Protocol Basics
37445 @cindex protocol basics, file-i/o
37447 The File-I/O protocol uses the @code{F} packet as the request as well
37448 as reply packet. Since a File-I/O system call can only occur when
37449 @value{GDBN} is waiting for a response from the continuing or stepping target,
37450 the File-I/O request is a reply that @value{GDBN} has to expect as a result
37451 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
37452 This @code{F} packet contains all information needed to allow @value{GDBN}
37453 to call the appropriate host system call:
37457 A unique identifier for the requested system call.
37460 All parameters to the system call. Pointers are given as addresses
37461 in the target memory address space. Pointers to strings are given as
37462 pointer/length pair. Numerical values are given as they are.
37463 Numerical control flags are given in a protocol-specific representation.
37467 At this point, @value{GDBN} has to perform the following actions.
37471 If the parameters include pointer values to data needed as input to a
37472 system call, @value{GDBN} requests this data from the target with a
37473 standard @code{m} packet request. This additional communication has to be
37474 expected by the target implementation and is handled as any other @code{m}
37478 @value{GDBN} translates all value from protocol representation to host
37479 representation as needed. Datatypes are coerced into the host types.
37482 @value{GDBN} calls the system call.
37485 It then coerces datatypes back to protocol representation.
37488 If the system call is expected to return data in buffer space specified
37489 by pointer parameters to the call, the data is transmitted to the
37490 target using a @code{M} or @code{X} packet. This packet has to be expected
37491 by the target implementation and is handled as any other @code{M} or @code{X}
37496 Eventually @value{GDBN} replies with another @code{F} packet which contains all
37497 necessary information for the target to continue. This at least contains
37504 @code{errno}, if has been changed by the system call.
37511 After having done the needed type and value coercion, the target continues
37512 the latest continue or step action.
37514 @node The F Request Packet
37515 @subsection The @code{F} Request Packet
37516 @cindex file-i/o request packet
37517 @cindex @code{F} request packet
37519 The @code{F} request packet has the following format:
37522 @item F@var{call-id},@var{parameter@dots{}}
37524 @var{call-id} is the identifier to indicate the host system call to be called.
37525 This is just the name of the function.
37527 @var{parameter@dots{}} are the parameters to the system call.
37528 Parameters are hexadecimal integer values, either the actual values in case
37529 of scalar datatypes, pointers to target buffer space in case of compound
37530 datatypes and unspecified memory areas, or pointer/length pairs in case
37531 of string parameters. These are appended to the @var{call-id} as a
37532 comma-delimited list. All values are transmitted in ASCII
37533 string representation, pointer/length pairs separated by a slash.
37539 @node The F Reply Packet
37540 @subsection The @code{F} Reply Packet
37541 @cindex file-i/o reply packet
37542 @cindex @code{F} reply packet
37544 The @code{F} reply packet has the following format:
37548 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
37550 @var{retcode} is the return code of the system call as hexadecimal value.
37552 @var{errno} is the @code{errno} set by the call, in protocol-specific
37554 This parameter can be omitted if the call was successful.
37556 @var{Ctrl-C flag} is only sent if the user requested a break. In this
37557 case, @var{errno} must be sent as well, even if the call was successful.
37558 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
37565 or, if the call was interrupted before the host call has been performed:
37572 assuming 4 is the protocol-specific representation of @code{EINTR}.
37577 @node The Ctrl-C Message
37578 @subsection The @samp{Ctrl-C} Message
37579 @cindex ctrl-c message, in file-i/o protocol
37581 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
37582 reply packet (@pxref{The F Reply Packet}),
37583 the target should behave as if it had
37584 gotten a break message. The meaning for the target is ``system call
37585 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
37586 (as with a break message) and return to @value{GDBN} with a @code{T02}
37589 It's important for the target to know in which
37590 state the system call was interrupted. There are two possible cases:
37594 The system call hasn't been performed on the host yet.
37597 The system call on the host has been finished.
37601 These two states can be distinguished by the target by the value of the
37602 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
37603 call hasn't been performed. This is equivalent to the @code{EINTR} handling
37604 on POSIX systems. In any other case, the target may presume that the
37605 system call has been finished --- successfully or not --- and should behave
37606 as if the break message arrived right after the system call.
37608 @value{GDBN} must behave reliably. If the system call has not been called
37609 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
37610 @code{errno} in the packet. If the system call on the host has been finished
37611 before the user requests a break, the full action must be finished by
37612 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
37613 The @code{F} packet may only be sent when either nothing has happened
37614 or the full action has been completed.
37617 @subsection Console I/O
37618 @cindex console i/o as part of file-i/o
37620 By default and if not explicitly closed by the target system, the file
37621 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
37622 on the @value{GDBN} console is handled as any other file output operation
37623 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
37624 by @value{GDBN} so that after the target read request from file descriptor
37625 0 all following typing is buffered until either one of the following
37630 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
37632 system call is treated as finished.
37635 The user presses @key{RET}. This is treated as end of input with a trailing
37639 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
37640 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
37644 If the user has typed more characters than fit in the buffer given to
37645 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
37646 either another @code{read(0, @dots{})} is requested by the target, or debugging
37647 is stopped at the user's request.
37650 @node List of Supported Calls
37651 @subsection List of Supported Calls
37652 @cindex list of supported file-i/o calls
37669 @unnumberedsubsubsec open
37670 @cindex open, file-i/o system call
37675 int open(const char *pathname, int flags);
37676 int open(const char *pathname, int flags, mode_t mode);
37680 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
37683 @var{flags} is the bitwise @code{OR} of the following values:
37687 If the file does not exist it will be created. The host
37688 rules apply as far as file ownership and time stamps
37692 When used with @code{O_CREAT}, if the file already exists it is
37693 an error and open() fails.
37696 If the file already exists and the open mode allows
37697 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
37698 truncated to zero length.
37701 The file is opened in append mode.
37704 The file is opened for reading only.
37707 The file is opened for writing only.
37710 The file is opened for reading and writing.
37714 Other bits are silently ignored.
37718 @var{mode} is the bitwise @code{OR} of the following values:
37722 User has read permission.
37725 User has write permission.
37728 Group has read permission.
37731 Group has write permission.
37734 Others have read permission.
37737 Others have write permission.
37741 Other bits are silently ignored.
37744 @item Return value:
37745 @code{open} returns the new file descriptor or -1 if an error
37752 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
37755 @var{pathname} refers to a directory.
37758 The requested access is not allowed.
37761 @var{pathname} was too long.
37764 A directory component in @var{pathname} does not exist.
37767 @var{pathname} refers to a device, pipe, named pipe or socket.
37770 @var{pathname} refers to a file on a read-only filesystem and
37771 write access was requested.
37774 @var{pathname} is an invalid pointer value.
37777 No space on device to create the file.
37780 The process already has the maximum number of files open.
37783 The limit on the total number of files open on the system
37787 The call was interrupted by the user.
37793 @unnumberedsubsubsec close
37794 @cindex close, file-i/o system call
37803 @samp{Fclose,@var{fd}}
37805 @item Return value:
37806 @code{close} returns zero on success, or -1 if an error occurred.
37812 @var{fd} isn't a valid open file descriptor.
37815 The call was interrupted by the user.
37821 @unnumberedsubsubsec read
37822 @cindex read, file-i/o system call
37827 int read(int fd, void *buf, unsigned int count);
37831 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
37833 @item Return value:
37834 On success, the number of bytes read is returned.
37835 Zero indicates end of file. If count is zero, read
37836 returns zero as well. On error, -1 is returned.
37842 @var{fd} is not a valid file descriptor or is not open for
37846 @var{bufptr} is an invalid pointer value.
37849 The call was interrupted by the user.
37855 @unnumberedsubsubsec write
37856 @cindex write, file-i/o system call
37861 int write(int fd, const void *buf, unsigned int count);
37865 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
37867 @item Return value:
37868 On success, the number of bytes written are returned.
37869 Zero indicates nothing was written. On error, -1
37876 @var{fd} is not a valid file descriptor or is not open for
37880 @var{bufptr} is an invalid pointer value.
37883 An attempt was made to write a file that exceeds the
37884 host-specific maximum file size allowed.
37887 No space on device to write the data.
37890 The call was interrupted by the user.
37896 @unnumberedsubsubsec lseek
37897 @cindex lseek, file-i/o system call
37902 long lseek (int fd, long offset, int flag);
37906 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
37908 @var{flag} is one of:
37912 The offset is set to @var{offset} bytes.
37915 The offset is set to its current location plus @var{offset}
37919 The offset is set to the size of the file plus @var{offset}
37923 @item Return value:
37924 On success, the resulting unsigned offset in bytes from
37925 the beginning of the file is returned. Otherwise, a
37926 value of -1 is returned.
37932 @var{fd} is not a valid open file descriptor.
37935 @var{fd} is associated with the @value{GDBN} console.
37938 @var{flag} is not a proper value.
37941 The call was interrupted by the user.
37947 @unnumberedsubsubsec rename
37948 @cindex rename, file-i/o system call
37953 int rename(const char *oldpath, const char *newpath);
37957 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
37959 @item Return value:
37960 On success, zero is returned. On error, -1 is returned.
37966 @var{newpath} is an existing directory, but @var{oldpath} is not a
37970 @var{newpath} is a non-empty directory.
37973 @var{oldpath} or @var{newpath} is a directory that is in use by some
37977 An attempt was made to make a directory a subdirectory
37981 A component used as a directory in @var{oldpath} or new
37982 path is not a directory. Or @var{oldpath} is a directory
37983 and @var{newpath} exists but is not a directory.
37986 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
37989 No access to the file or the path of the file.
37993 @var{oldpath} or @var{newpath} was too long.
37996 A directory component in @var{oldpath} or @var{newpath} does not exist.
37999 The file is on a read-only filesystem.
38002 The device containing the file has no room for the new
38006 The call was interrupted by the user.
38012 @unnumberedsubsubsec unlink
38013 @cindex unlink, file-i/o system call
38018 int unlink(const char *pathname);
38022 @samp{Funlink,@var{pathnameptr}/@var{len}}
38024 @item Return value:
38025 On success, zero is returned. On error, -1 is returned.
38031 No access to the file or the path of the file.
38034 The system does not allow unlinking of directories.
38037 The file @var{pathname} cannot be unlinked because it's
38038 being used by another process.
38041 @var{pathnameptr} is an invalid pointer value.
38044 @var{pathname} was too long.
38047 A directory component in @var{pathname} does not exist.
38050 A component of the path is not a directory.
38053 The file is on a read-only filesystem.
38056 The call was interrupted by the user.
38062 @unnumberedsubsubsec stat/fstat
38063 @cindex fstat, file-i/o system call
38064 @cindex stat, file-i/o system call
38069 int stat(const char *pathname, struct stat *buf);
38070 int fstat(int fd, struct stat *buf);
38074 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
38075 @samp{Ffstat,@var{fd},@var{bufptr}}
38077 @item Return value:
38078 On success, zero is returned. On error, -1 is returned.
38084 @var{fd} is not a valid open file.
38087 A directory component in @var{pathname} does not exist or the
38088 path is an empty string.
38091 A component of the path is not a directory.
38094 @var{pathnameptr} is an invalid pointer value.
38097 No access to the file or the path of the file.
38100 @var{pathname} was too long.
38103 The call was interrupted by the user.
38109 @unnumberedsubsubsec gettimeofday
38110 @cindex gettimeofday, file-i/o system call
38115 int gettimeofday(struct timeval *tv, void *tz);
38119 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
38121 @item Return value:
38122 On success, 0 is returned, -1 otherwise.
38128 @var{tz} is a non-NULL pointer.
38131 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
38137 @unnumberedsubsubsec isatty
38138 @cindex isatty, file-i/o system call
38143 int isatty(int fd);
38147 @samp{Fisatty,@var{fd}}
38149 @item Return value:
38150 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
38156 The call was interrupted by the user.
38161 Note that the @code{isatty} call is treated as a special case: it returns
38162 1 to the target if the file descriptor is attached
38163 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
38164 would require implementing @code{ioctl} and would be more complex than
38169 @unnumberedsubsubsec system
38170 @cindex system, file-i/o system call
38175 int system(const char *command);
38179 @samp{Fsystem,@var{commandptr}/@var{len}}
38181 @item Return value:
38182 If @var{len} is zero, the return value indicates whether a shell is
38183 available. A zero return value indicates a shell is not available.
38184 For non-zero @var{len}, the value returned is -1 on error and the
38185 return status of the command otherwise. Only the exit status of the
38186 command is returned, which is extracted from the host's @code{system}
38187 return value by calling @code{WEXITSTATUS(retval)}. In case
38188 @file{/bin/sh} could not be executed, 127 is returned.
38194 The call was interrupted by the user.
38199 @value{GDBN} takes over the full task of calling the necessary host calls
38200 to perform the @code{system} call. The return value of @code{system} on
38201 the host is simplified before it's returned
38202 to the target. Any termination signal information from the child process
38203 is discarded, and the return value consists
38204 entirely of the exit status of the called command.
38206 Due to security concerns, the @code{system} call is by default refused
38207 by @value{GDBN}. The user has to allow this call explicitly with the
38208 @code{set remote system-call-allowed 1} command.
38211 @item set remote system-call-allowed
38212 @kindex set remote system-call-allowed
38213 Control whether to allow the @code{system} calls in the File I/O
38214 protocol for the remote target. The default is zero (disabled).
38216 @item show remote system-call-allowed
38217 @kindex show remote system-call-allowed
38218 Show whether the @code{system} calls are allowed in the File I/O
38222 @node Protocol-specific Representation of Datatypes
38223 @subsection Protocol-specific Representation of Datatypes
38224 @cindex protocol-specific representation of datatypes, in file-i/o protocol
38227 * Integral Datatypes::
38229 * Memory Transfer::
38234 @node Integral Datatypes
38235 @unnumberedsubsubsec Integral Datatypes
38236 @cindex integral datatypes, in file-i/o protocol
38238 The integral datatypes used in the system calls are @code{int},
38239 @code{unsigned int}, @code{long}, @code{unsigned long},
38240 @code{mode_t}, and @code{time_t}.
38242 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
38243 implemented as 32 bit values in this protocol.
38245 @code{long} and @code{unsigned long} are implemented as 64 bit types.
38247 @xref{Limits}, for corresponding MIN and MAX values (similar to those
38248 in @file{limits.h}) to allow range checking on host and target.
38250 @code{time_t} datatypes are defined as seconds since the Epoch.
38252 All integral datatypes transferred as part of a memory read or write of a
38253 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
38256 @node Pointer Values
38257 @unnumberedsubsubsec Pointer Values
38258 @cindex pointer values, in file-i/o protocol
38260 Pointers to target data are transmitted as they are. An exception
38261 is made for pointers to buffers for which the length isn't
38262 transmitted as part of the function call, namely strings. Strings
38263 are transmitted as a pointer/length pair, both as hex values, e.g.@:
38270 which is a pointer to data of length 18 bytes at position 0x1aaf.
38271 The length is defined as the full string length in bytes, including
38272 the trailing null byte. For example, the string @code{"hello world"}
38273 at address 0x123456 is transmitted as
38279 @node Memory Transfer
38280 @unnumberedsubsubsec Memory Transfer
38281 @cindex memory transfer, in file-i/o protocol
38283 Structured data which is transferred using a memory read or write (for
38284 example, a @code{struct stat}) is expected to be in a protocol-specific format
38285 with all scalar multibyte datatypes being big endian. Translation to
38286 this representation needs to be done both by the target before the @code{F}
38287 packet is sent, and by @value{GDBN} before
38288 it transfers memory to the target. Transferred pointers to structured
38289 data should point to the already-coerced data at any time.
38293 @unnumberedsubsubsec struct stat
38294 @cindex struct stat, in file-i/o protocol
38296 The buffer of type @code{struct stat} used by the target and @value{GDBN}
38297 is defined as follows:
38301 unsigned int st_dev; /* device */
38302 unsigned int st_ino; /* inode */
38303 mode_t st_mode; /* protection */
38304 unsigned int st_nlink; /* number of hard links */
38305 unsigned int st_uid; /* user ID of owner */
38306 unsigned int st_gid; /* group ID of owner */
38307 unsigned int st_rdev; /* device type (if inode device) */
38308 unsigned long st_size; /* total size, in bytes */
38309 unsigned long st_blksize; /* blocksize for filesystem I/O */
38310 unsigned long st_blocks; /* number of blocks allocated */
38311 time_t st_atime; /* time of last access */
38312 time_t st_mtime; /* time of last modification */
38313 time_t st_ctime; /* time of last change */
38317 The integral datatypes conform to the definitions given in the
38318 appropriate section (see @ref{Integral Datatypes}, for details) so this
38319 structure is of size 64 bytes.
38321 The values of several fields have a restricted meaning and/or
38327 A value of 0 represents a file, 1 the console.
38330 No valid meaning for the target. Transmitted unchanged.
38333 Valid mode bits are described in @ref{Constants}. Any other
38334 bits have currently no meaning for the target.
38339 No valid meaning for the target. Transmitted unchanged.
38344 These values have a host and file system dependent
38345 accuracy. Especially on Windows hosts, the file system may not
38346 support exact timing values.
38349 The target gets a @code{struct stat} of the above representation and is
38350 responsible for coercing it to the target representation before
38353 Note that due to size differences between the host, target, and protocol
38354 representations of @code{struct stat} members, these members could eventually
38355 get truncated on the target.
38357 @node struct timeval
38358 @unnumberedsubsubsec struct timeval
38359 @cindex struct timeval, in file-i/o protocol
38361 The buffer of type @code{struct timeval} used by the File-I/O protocol
38362 is defined as follows:
38366 time_t tv_sec; /* second */
38367 long tv_usec; /* microsecond */
38371 The integral datatypes conform to the definitions given in the
38372 appropriate section (see @ref{Integral Datatypes}, for details) so this
38373 structure is of size 8 bytes.
38376 @subsection Constants
38377 @cindex constants, in file-i/o protocol
38379 The following values are used for the constants inside of the
38380 protocol. @value{GDBN} and target are responsible for translating these
38381 values before and after the call as needed.
38392 @unnumberedsubsubsec Open Flags
38393 @cindex open flags, in file-i/o protocol
38395 All values are given in hexadecimal representation.
38407 @node mode_t Values
38408 @unnumberedsubsubsec mode_t Values
38409 @cindex mode_t values, in file-i/o protocol
38411 All values are given in octal representation.
38428 @unnumberedsubsubsec Errno Values
38429 @cindex errno values, in file-i/o protocol
38431 All values are given in decimal representation.
38456 @code{EUNKNOWN} is used as a fallback error value if a host system returns
38457 any error value not in the list of supported error numbers.
38460 @unnumberedsubsubsec Lseek Flags
38461 @cindex lseek flags, in file-i/o protocol
38470 @unnumberedsubsubsec Limits
38471 @cindex limits, in file-i/o protocol
38473 All values are given in decimal representation.
38476 INT_MIN -2147483648
38478 UINT_MAX 4294967295
38479 LONG_MIN -9223372036854775808
38480 LONG_MAX 9223372036854775807
38481 ULONG_MAX 18446744073709551615
38484 @node File-I/O Examples
38485 @subsection File-I/O Examples
38486 @cindex file-i/o examples
38488 Example sequence of a write call, file descriptor 3, buffer is at target
38489 address 0x1234, 6 bytes should be written:
38492 <- @code{Fwrite,3,1234,6}
38493 @emph{request memory read from target}
38496 @emph{return "6 bytes written"}
38500 Example sequence of a read call, file descriptor 3, buffer is at target
38501 address 0x1234, 6 bytes should be read:
38504 <- @code{Fread,3,1234,6}
38505 @emph{request memory write to target}
38506 -> @code{X1234,6:XXXXXX}
38507 @emph{return "6 bytes read"}
38511 Example sequence of a read call, call fails on the host due to invalid
38512 file descriptor (@code{EBADF}):
38515 <- @code{Fread,3,1234,6}
38519 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
38523 <- @code{Fread,3,1234,6}
38528 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
38532 <- @code{Fread,3,1234,6}
38533 -> @code{X1234,6:XXXXXX}
38537 @node Library List Format
38538 @section Library List Format
38539 @cindex library list format, remote protocol
38541 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
38542 same process as your application to manage libraries. In this case,
38543 @value{GDBN} can use the loader's symbol table and normal memory
38544 operations to maintain a list of shared libraries. On other
38545 platforms, the operating system manages loaded libraries.
38546 @value{GDBN} can not retrieve the list of currently loaded libraries
38547 through memory operations, so it uses the @samp{qXfer:libraries:read}
38548 packet (@pxref{qXfer library list read}) instead. The remote stub
38549 queries the target's operating system and reports which libraries
38552 The @samp{qXfer:libraries:read} packet returns an XML document which
38553 lists loaded libraries and their offsets. Each library has an
38554 associated name and one or more segment or section base addresses,
38555 which report where the library was loaded in memory.
38557 For the common case of libraries that are fully linked binaries, the
38558 library should have a list of segments. If the target supports
38559 dynamic linking of a relocatable object file, its library XML element
38560 should instead include a list of allocated sections. The segment or
38561 section bases are start addresses, not relocation offsets; they do not
38562 depend on the library's link-time base addresses.
38564 @value{GDBN} must be linked with the Expat library to support XML
38565 library lists. @xref{Expat}.
38567 A simple memory map, with one loaded library relocated by a single
38568 offset, looks like this:
38572 <library name="/lib/libc.so.6">
38573 <segment address="0x10000000"/>
38578 Another simple memory map, with one loaded library with three
38579 allocated sections (.text, .data, .bss), looks like this:
38583 <library name="sharedlib.o">
38584 <section address="0x10000000"/>
38585 <section address="0x20000000"/>
38586 <section address="0x30000000"/>
38591 The format of a library list is described by this DTD:
38594 <!-- library-list: Root element with versioning -->
38595 <!ELEMENT library-list (library)*>
38596 <!ATTLIST library-list version CDATA #FIXED "1.0">
38597 <!ELEMENT library (segment*, section*)>
38598 <!ATTLIST library name CDATA #REQUIRED>
38599 <!ELEMENT segment EMPTY>
38600 <!ATTLIST segment address CDATA #REQUIRED>
38601 <!ELEMENT section EMPTY>
38602 <!ATTLIST section address CDATA #REQUIRED>
38605 In addition, segments and section descriptors cannot be mixed within a
38606 single library element, and you must supply at least one segment or
38607 section for each library.
38609 @node Library List Format for SVR4 Targets
38610 @section Library List Format for SVR4 Targets
38611 @cindex library list format, remote protocol
38613 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
38614 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
38615 shared libraries. Still a special library list provided by this packet is
38616 more efficient for the @value{GDBN} remote protocol.
38618 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
38619 loaded libraries and their SVR4 linker parameters. For each library on SVR4
38620 target, the following parameters are reported:
38624 @code{name}, the absolute file name from the @code{l_name} field of
38625 @code{struct link_map}.
38627 @code{lm} with address of @code{struct link_map} used for TLS
38628 (Thread Local Storage) access.
38630 @code{l_addr}, the displacement as read from the field @code{l_addr} of
38631 @code{struct link_map}. For prelinked libraries this is not an absolute
38632 memory address. It is a displacement of absolute memory address against
38633 address the file was prelinked to during the library load.
38635 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
38638 Additionally the single @code{main-lm} attribute specifies address of
38639 @code{struct link_map} used for the main executable. This parameter is used
38640 for TLS access and its presence is optional.
38642 @value{GDBN} must be linked with the Expat library to support XML
38643 SVR4 library lists. @xref{Expat}.
38645 A simple memory map, with two loaded libraries (which do not use prelink),
38649 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
38650 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
38652 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
38654 </library-list-svr>
38657 The format of an SVR4 library list is described by this DTD:
38660 <!-- library-list-svr4: Root element with versioning -->
38661 <!ELEMENT library-list-svr4 (library)*>
38662 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
38663 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
38664 <!ELEMENT library EMPTY>
38665 <!ATTLIST library name CDATA #REQUIRED>
38666 <!ATTLIST library lm CDATA #REQUIRED>
38667 <!ATTLIST library l_addr CDATA #REQUIRED>
38668 <!ATTLIST library l_ld CDATA #REQUIRED>
38671 @node Memory Map Format
38672 @section Memory Map Format
38673 @cindex memory map format
38675 To be able to write into flash memory, @value{GDBN} needs to obtain a
38676 memory map from the target. This section describes the format of the
38679 The memory map is obtained using the @samp{qXfer:memory-map:read}
38680 (@pxref{qXfer memory map read}) packet and is an XML document that
38681 lists memory regions.
38683 @value{GDBN} must be linked with the Expat library to support XML
38684 memory maps. @xref{Expat}.
38686 The top-level structure of the document is shown below:
38689 <?xml version="1.0"?>
38690 <!DOCTYPE memory-map
38691 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
38692 "http://sourceware.org/gdb/gdb-memory-map.dtd">
38698 Each region can be either:
38703 A region of RAM starting at @var{addr} and extending for @var{length}
38707 <memory type="ram" start="@var{addr}" length="@var{length}"/>
38712 A region of read-only memory:
38715 <memory type="rom" start="@var{addr}" length="@var{length}"/>
38720 A region of flash memory, with erasure blocks @var{blocksize}
38724 <memory type="flash" start="@var{addr}" length="@var{length}">
38725 <property name="blocksize">@var{blocksize}</property>
38731 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
38732 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
38733 packets to write to addresses in such ranges.
38735 The formal DTD for memory map format is given below:
38738 <!-- ................................................... -->
38739 <!-- Memory Map XML DTD ................................ -->
38740 <!-- File: memory-map.dtd .............................. -->
38741 <!-- .................................... .............. -->
38742 <!-- memory-map.dtd -->
38743 <!-- memory-map: Root element with versioning -->
38744 <!ELEMENT memory-map (memory | property)>
38745 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
38746 <!ELEMENT memory (property)>
38747 <!-- memory: Specifies a memory region,
38748 and its type, or device. -->
38749 <!ATTLIST memory type CDATA #REQUIRED
38750 start CDATA #REQUIRED
38751 length CDATA #REQUIRED
38752 device CDATA #IMPLIED>
38753 <!-- property: Generic attribute tag -->
38754 <!ELEMENT property (#PCDATA | property)*>
38755 <!ATTLIST property name CDATA #REQUIRED>
38758 @node Thread List Format
38759 @section Thread List Format
38760 @cindex thread list format
38762 To efficiently update the list of threads and their attributes,
38763 @value{GDBN} issues the @samp{qXfer:threads:read} packet
38764 (@pxref{qXfer threads read}) and obtains the XML document with
38765 the following structure:
38768 <?xml version="1.0"?>
38770 <thread id="id" core="0">
38771 ... description ...
38776 Each @samp{thread} element must have the @samp{id} attribute that
38777 identifies the thread (@pxref{thread-id syntax}). The
38778 @samp{core} attribute, if present, specifies which processor core
38779 the thread was last executing on. The content of the of @samp{thread}
38780 element is interpreted as human-readable auxilliary information.
38782 @node Traceframe Info Format
38783 @section Traceframe Info Format
38784 @cindex traceframe info format
38786 To be able to know which objects in the inferior can be examined when
38787 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
38788 memory ranges, registers and trace state variables that have been
38789 collected in a traceframe.
38791 This list is obtained using the @samp{qXfer:traceframe-info:read}
38792 (@pxref{qXfer traceframe info read}) packet and is an XML document.
38794 @value{GDBN} must be linked with the Expat library to support XML
38795 traceframe info discovery. @xref{Expat}.
38797 The top-level structure of the document is shown below:
38800 <?xml version="1.0"?>
38801 <!DOCTYPE traceframe-info
38802 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
38803 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
38809 Each traceframe block can be either:
38814 A region of collected memory starting at @var{addr} and extending for
38815 @var{length} bytes from there:
38818 <memory start="@var{addr}" length="@var{length}"/>
38822 A block indicating trace state variable numbered @var{number} has been
38826 <tvar id="@var{number}"/>
38831 The formal DTD for the traceframe info format is given below:
38834 <!ELEMENT traceframe-info (memory | tvar)* >
38835 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
38837 <!ELEMENT memory EMPTY>
38838 <!ATTLIST memory start CDATA #REQUIRED
38839 length CDATA #REQUIRED>
38841 <!ATTLIST tvar id CDATA #REQUIRED>
38844 @node Branch Trace Format
38845 @section Branch Trace Format
38846 @cindex branch trace format
38848 In order to display the branch trace of an inferior thread,
38849 @value{GDBN} needs to obtain the list of branches. This list is
38850 represented as list of sequential code blocks that are connected via
38851 branches. The code in each block has been executed sequentially.
38853 This list is obtained using the @samp{qXfer:btrace:read}
38854 (@pxref{qXfer btrace read}) packet and is an XML document.
38856 @value{GDBN} must be linked with the Expat library to support XML
38857 traceframe info discovery. @xref{Expat}.
38859 The top-level structure of the document is shown below:
38862 <?xml version="1.0"?>
38864 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
38865 "http://sourceware.org/gdb/gdb-btrace.dtd">
38874 A block of sequentially executed instructions starting at @var{begin}
38875 and ending at @var{end}:
38878 <block begin="@var{begin}" end="@var{end}"/>
38883 The formal DTD for the branch trace format is given below:
38886 <!ELEMENT btrace (block)* >
38887 <!ATTLIST btrace version CDATA #FIXED "1.0">
38889 <!ELEMENT block EMPTY>
38890 <!ATTLIST block begin CDATA #REQUIRED
38891 end CDATA #REQUIRED>
38894 @include agentexpr.texi
38896 @node Target Descriptions
38897 @appendix Target Descriptions
38898 @cindex target descriptions
38900 One of the challenges of using @value{GDBN} to debug embedded systems
38901 is that there are so many minor variants of each processor
38902 architecture in use. It is common practice for vendors to start with
38903 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
38904 and then make changes to adapt it to a particular market niche. Some
38905 architectures have hundreds of variants, available from dozens of
38906 vendors. This leads to a number of problems:
38910 With so many different customized processors, it is difficult for
38911 the @value{GDBN} maintainers to keep up with the changes.
38913 Since individual variants may have short lifetimes or limited
38914 audiences, it may not be worthwhile to carry information about every
38915 variant in the @value{GDBN} source tree.
38917 When @value{GDBN} does support the architecture of the embedded system
38918 at hand, the task of finding the correct architecture name to give the
38919 @command{set architecture} command can be error-prone.
38922 To address these problems, the @value{GDBN} remote protocol allows a
38923 target system to not only identify itself to @value{GDBN}, but to
38924 actually describe its own features. This lets @value{GDBN} support
38925 processor variants it has never seen before --- to the extent that the
38926 descriptions are accurate, and that @value{GDBN} understands them.
38928 @value{GDBN} must be linked with the Expat library to support XML
38929 target descriptions. @xref{Expat}.
38932 * Retrieving Descriptions:: How descriptions are fetched from a target.
38933 * Target Description Format:: The contents of a target description.
38934 * Predefined Target Types:: Standard types available for target
38936 * Standard Target Features:: Features @value{GDBN} knows about.
38939 @node Retrieving Descriptions
38940 @section Retrieving Descriptions
38942 Target descriptions can be read from the target automatically, or
38943 specified by the user manually. The default behavior is to read the
38944 description from the target. @value{GDBN} retrieves it via the remote
38945 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
38946 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
38947 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
38948 XML document, of the form described in @ref{Target Description
38951 Alternatively, you can specify a file to read for the target description.
38952 If a file is set, the target will not be queried. The commands to
38953 specify a file are:
38956 @cindex set tdesc filename
38957 @item set tdesc filename @var{path}
38958 Read the target description from @var{path}.
38960 @cindex unset tdesc filename
38961 @item unset tdesc filename
38962 Do not read the XML target description from a file. @value{GDBN}
38963 will use the description supplied by the current target.
38965 @cindex show tdesc filename
38966 @item show tdesc filename
38967 Show the filename to read for a target description, if any.
38971 @node Target Description Format
38972 @section Target Description Format
38973 @cindex target descriptions, XML format
38975 A target description annex is an @uref{http://www.w3.org/XML/, XML}
38976 document which complies with the Document Type Definition provided in
38977 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
38978 means you can use generally available tools like @command{xmllint} to
38979 check that your feature descriptions are well-formed and valid.
38980 However, to help people unfamiliar with XML write descriptions for
38981 their targets, we also describe the grammar here.
38983 Target descriptions can identify the architecture of the remote target
38984 and (for some architectures) provide information about custom register
38985 sets. They can also identify the OS ABI of the remote target.
38986 @value{GDBN} can use this information to autoconfigure for your
38987 target, or to warn you if you connect to an unsupported target.
38989 Here is a simple target description:
38992 <target version="1.0">
38993 <architecture>i386:x86-64</architecture>
38998 This minimal description only says that the target uses
38999 the x86-64 architecture.
39001 A target description has the following overall form, with [ ] marking
39002 optional elements and @dots{} marking repeatable elements. The elements
39003 are explained further below.
39006 <?xml version="1.0"?>
39007 <!DOCTYPE target SYSTEM "gdb-target.dtd">
39008 <target version="1.0">
39009 @r{[}@var{architecture}@r{]}
39010 @r{[}@var{osabi}@r{]}
39011 @r{[}@var{compatible}@r{]}
39012 @r{[}@var{feature}@dots{}@r{]}
39017 The description is generally insensitive to whitespace and line
39018 breaks, under the usual common-sense rules. The XML version
39019 declaration and document type declaration can generally be omitted
39020 (@value{GDBN} does not require them), but specifying them may be
39021 useful for XML validation tools. The @samp{version} attribute for
39022 @samp{<target>} may also be omitted, but we recommend
39023 including it; if future versions of @value{GDBN} use an incompatible
39024 revision of @file{gdb-target.dtd}, they will detect and report
39025 the version mismatch.
39027 @subsection Inclusion
39028 @cindex target descriptions, inclusion
39031 @cindex <xi:include>
39034 It can sometimes be valuable to split a target description up into
39035 several different annexes, either for organizational purposes, or to
39036 share files between different possible target descriptions. You can
39037 divide a description into multiple files by replacing any element of
39038 the target description with an inclusion directive of the form:
39041 <xi:include href="@var{document}"/>
39045 When @value{GDBN} encounters an element of this form, it will retrieve
39046 the named XML @var{document}, and replace the inclusion directive with
39047 the contents of that document. If the current description was read
39048 using @samp{qXfer}, then so will be the included document;
39049 @var{document} will be interpreted as the name of an annex. If the
39050 current description was read from a file, @value{GDBN} will look for
39051 @var{document} as a file in the same directory where it found the
39052 original description.
39054 @subsection Architecture
39055 @cindex <architecture>
39057 An @samp{<architecture>} element has this form:
39060 <architecture>@var{arch}</architecture>
39063 @var{arch} is one of the architectures from the set accepted by
39064 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
39067 @cindex @code{<osabi>}
39069 This optional field was introduced in @value{GDBN} version 7.0.
39070 Previous versions of @value{GDBN} ignore it.
39072 An @samp{<osabi>} element has this form:
39075 <osabi>@var{abi-name}</osabi>
39078 @var{abi-name} is an OS ABI name from the same selection accepted by
39079 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
39081 @subsection Compatible Architecture
39082 @cindex @code{<compatible>}
39084 This optional field was introduced in @value{GDBN} version 7.0.
39085 Previous versions of @value{GDBN} ignore it.
39087 A @samp{<compatible>} element has this form:
39090 <compatible>@var{arch}</compatible>
39093 @var{arch} is one of the architectures from the set accepted by
39094 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
39096 A @samp{<compatible>} element is used to specify that the target
39097 is able to run binaries in some other than the main target architecture
39098 given by the @samp{<architecture>} element. For example, on the
39099 Cell Broadband Engine, the main architecture is @code{powerpc:common}
39100 or @code{powerpc:common64}, but the system is able to run binaries
39101 in the @code{spu} architecture as well. The way to describe this
39102 capability with @samp{<compatible>} is as follows:
39105 <architecture>powerpc:common</architecture>
39106 <compatible>spu</compatible>
39109 @subsection Features
39112 Each @samp{<feature>} describes some logical portion of the target
39113 system. Features are currently used to describe available CPU
39114 registers and the types of their contents. A @samp{<feature>} element
39118 <feature name="@var{name}">
39119 @r{[}@var{type}@dots{}@r{]}
39125 Each feature's name should be unique within the description. The name
39126 of a feature does not matter unless @value{GDBN} has some special
39127 knowledge of the contents of that feature; if it does, the feature
39128 should have its standard name. @xref{Standard Target Features}.
39132 Any register's value is a collection of bits which @value{GDBN} must
39133 interpret. The default interpretation is a two's complement integer,
39134 but other types can be requested by name in the register description.
39135 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
39136 Target Types}), and the description can define additional composite types.
39138 Each type element must have an @samp{id} attribute, which gives
39139 a unique (within the containing @samp{<feature>}) name to the type.
39140 Types must be defined before they are used.
39143 Some targets offer vector registers, which can be treated as arrays
39144 of scalar elements. These types are written as @samp{<vector>} elements,
39145 specifying the array element type, @var{type}, and the number of elements,
39149 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
39153 If a register's value is usefully viewed in multiple ways, define it
39154 with a union type containing the useful representations. The
39155 @samp{<union>} element contains one or more @samp{<field>} elements,
39156 each of which has a @var{name} and a @var{type}:
39159 <union id="@var{id}">
39160 <field name="@var{name}" type="@var{type}"/>
39166 If a register's value is composed from several separate values, define
39167 it with a structure type. There are two forms of the @samp{<struct>}
39168 element; a @samp{<struct>} element must either contain only bitfields
39169 or contain no bitfields. If the structure contains only bitfields,
39170 its total size in bytes must be specified, each bitfield must have an
39171 explicit start and end, and bitfields are automatically assigned an
39172 integer type. The field's @var{start} should be less than or
39173 equal to its @var{end}, and zero represents the least significant bit.
39176 <struct id="@var{id}" size="@var{size}">
39177 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
39182 If the structure contains no bitfields, then each field has an
39183 explicit type, and no implicit padding is added.
39186 <struct id="@var{id}">
39187 <field name="@var{name}" type="@var{type}"/>
39193 If a register's value is a series of single-bit flags, define it with
39194 a flags type. The @samp{<flags>} element has an explicit @var{size}
39195 and contains one or more @samp{<field>} elements. Each field has a
39196 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
39200 <flags id="@var{id}" size="@var{size}">
39201 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
39206 @subsection Registers
39209 Each register is represented as an element with this form:
39212 <reg name="@var{name}"
39213 bitsize="@var{size}"
39214 @r{[}regnum="@var{num}"@r{]}
39215 @r{[}save-restore="@var{save-restore}"@r{]}
39216 @r{[}type="@var{type}"@r{]}
39217 @r{[}group="@var{group}"@r{]}/>
39221 The components are as follows:
39226 The register's name; it must be unique within the target description.
39229 The register's size, in bits.
39232 The register's number. If omitted, a register's number is one greater
39233 than that of the previous register (either in the current feature or in
39234 a preceding feature); the first register in the target description
39235 defaults to zero. This register number is used to read or write
39236 the register; e.g.@: it is used in the remote @code{p} and @code{P}
39237 packets, and registers appear in the @code{g} and @code{G} packets
39238 in order of increasing register number.
39241 Whether the register should be preserved across inferior function
39242 calls; this must be either @code{yes} or @code{no}. The default is
39243 @code{yes}, which is appropriate for most registers except for
39244 some system control registers; this is not related to the target's
39248 The type of the register. It may be a predefined type, a type
39249 defined in the current feature, or one of the special types @code{int}
39250 and @code{float}. @code{int} is an integer type of the correct size
39251 for @var{bitsize}, and @code{float} is a floating point type (in the
39252 architecture's normal floating point format) of the correct size for
39253 @var{bitsize}. The default is @code{int}.
39256 The register group to which this register belongs. It must
39257 be either @code{general}, @code{float}, or @code{vector}. If no
39258 @var{group} is specified, @value{GDBN} will not display the register
39259 in @code{info registers}.
39263 @node Predefined Target Types
39264 @section Predefined Target Types
39265 @cindex target descriptions, predefined types
39267 Type definitions in the self-description can build up composite types
39268 from basic building blocks, but can not define fundamental types. Instead,
39269 standard identifiers are provided by @value{GDBN} for the fundamental
39270 types. The currently supported types are:
39279 Signed integer types holding the specified number of bits.
39286 Unsigned integer types holding the specified number of bits.
39290 Pointers to unspecified code and data. The program counter and
39291 any dedicated return address register may be marked as code
39292 pointers; printing a code pointer converts it into a symbolic
39293 address. The stack pointer and any dedicated address registers
39294 may be marked as data pointers.
39297 Single precision IEEE floating point.
39300 Double precision IEEE floating point.
39303 The 12-byte extended precision format used by ARM FPA registers.
39306 The 10-byte extended precision format used by x87 registers.
39309 32bit @sc{eflags} register used by x86.
39312 32bit @sc{mxcsr} register used by x86.
39316 @node Standard Target Features
39317 @section Standard Target Features
39318 @cindex target descriptions, standard features
39320 A target description must contain either no registers or all the
39321 target's registers. If the description contains no registers, then
39322 @value{GDBN} will assume a default register layout, selected based on
39323 the architecture. If the description contains any registers, the
39324 default layout will not be used; the standard registers must be
39325 described in the target description, in such a way that @value{GDBN}
39326 can recognize them.
39328 This is accomplished by giving specific names to feature elements
39329 which contain standard registers. @value{GDBN} will look for features
39330 with those names and verify that they contain the expected registers;
39331 if any known feature is missing required registers, or if any required
39332 feature is missing, @value{GDBN} will reject the target
39333 description. You can add additional registers to any of the
39334 standard features --- @value{GDBN} will display them just as if
39335 they were added to an unrecognized feature.
39337 This section lists the known features and their expected contents.
39338 Sample XML documents for these features are included in the
39339 @value{GDBN} source tree, in the directory @file{gdb/features}.
39341 Names recognized by @value{GDBN} should include the name of the
39342 company or organization which selected the name, and the overall
39343 architecture to which the feature applies; so e.g.@: the feature
39344 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
39346 The names of registers are not case sensitive for the purpose
39347 of recognizing standard features, but @value{GDBN} will only display
39348 registers using the capitalization used in the description.
39351 * AArch64 Features::
39354 * MicroBlaze Features::
39357 * Nios II Features::
39358 * PowerPC Features::
39359 * S/390 and System z Features::
39364 @node AArch64 Features
39365 @subsection AArch64 Features
39366 @cindex target descriptions, AArch64 features
39368 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
39369 targets. It should contain registers @samp{x0} through @samp{x30},
39370 @samp{sp}, @samp{pc}, and @samp{cpsr}.
39372 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
39373 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
39377 @subsection ARM Features
39378 @cindex target descriptions, ARM features
39380 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
39382 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
39383 @samp{lr}, @samp{pc}, and @samp{cpsr}.
39385 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
39386 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
39387 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
39390 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
39391 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
39393 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
39394 it should contain at least registers @samp{wR0} through @samp{wR15} and
39395 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
39396 @samp{wCSSF}, and @samp{wCASF} registers are optional.
39398 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
39399 should contain at least registers @samp{d0} through @samp{d15}. If
39400 they are present, @samp{d16} through @samp{d31} should also be included.
39401 @value{GDBN} will synthesize the single-precision registers from
39402 halves of the double-precision registers.
39404 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
39405 need to contain registers; it instructs @value{GDBN} to display the
39406 VFP double-precision registers as vectors and to synthesize the
39407 quad-precision registers from pairs of double-precision registers.
39408 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
39409 be present and include 32 double-precision registers.
39411 @node i386 Features
39412 @subsection i386 Features
39413 @cindex target descriptions, i386 features
39415 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
39416 targets. It should describe the following registers:
39420 @samp{eax} through @samp{edi} plus @samp{eip} for i386
39422 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
39424 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
39425 @samp{fs}, @samp{gs}
39427 @samp{st0} through @samp{st7}
39429 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
39430 @samp{foseg}, @samp{fooff} and @samp{fop}
39433 The register sets may be different, depending on the target.
39435 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
39436 describe registers:
39440 @samp{xmm0} through @samp{xmm7} for i386
39442 @samp{xmm0} through @samp{xmm15} for amd64
39447 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
39448 @samp{org.gnu.gdb.i386.sse} feature. It should
39449 describe the upper 128 bits of @sc{ymm} registers:
39453 @samp{ymm0h} through @samp{ymm7h} for i386
39455 @samp{ymm0h} through @samp{ymm15h} for amd64
39458 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel(R)
39459 Memory Protection Extension (MPX). It should describe the following registers:
39463 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
39465 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
39468 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
39469 describe a single register, @samp{orig_eax}.
39471 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
39472 @samp{org.gnu.gdb.i386.avx} feature. It should
39473 describe additional @sc{xmm} registers:
39477 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
39480 It should describe the upper 128 bits of additional @sc{ymm} registers:
39484 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
39488 describe the upper 256 bits of @sc{zmm} registers:
39492 @samp{zmm0h} through @samp{zmm7h} for i386.
39494 @samp{zmm0h} through @samp{zmm15h} for amd64.
39498 describe the additional @sc{zmm} registers:
39502 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
39505 @node MicroBlaze Features
39506 @subsection MicroBlaze Features
39507 @cindex target descriptions, MicroBlaze features
39509 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
39510 targets. It should contain registers @samp{r0} through @samp{r31},
39511 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
39512 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
39513 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
39515 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
39516 If present, it should contain registers @samp{rshr} and @samp{rslr}
39518 @node MIPS Features
39519 @subsection @acronym{MIPS} Features
39520 @cindex target descriptions, @acronym{MIPS} features
39522 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
39523 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
39524 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
39527 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
39528 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
39529 registers. They may be 32-bit or 64-bit depending on the target.
39531 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
39532 it may be optional in a future version of @value{GDBN}. It should
39533 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
39534 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
39536 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
39537 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
39538 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
39539 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
39541 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
39542 contain a single register, @samp{restart}, which is used by the
39543 Linux kernel to control restartable syscalls.
39545 @node M68K Features
39546 @subsection M68K Features
39547 @cindex target descriptions, M68K features
39550 @item @samp{org.gnu.gdb.m68k.core}
39551 @itemx @samp{org.gnu.gdb.coldfire.core}
39552 @itemx @samp{org.gnu.gdb.fido.core}
39553 One of those features must be always present.
39554 The feature that is present determines which flavor of m68k is
39555 used. The feature that is present should contain registers
39556 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
39557 @samp{sp}, @samp{ps} and @samp{pc}.
39559 @item @samp{org.gnu.gdb.coldfire.fp}
39560 This feature is optional. If present, it should contain registers
39561 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
39565 @node Nios II Features
39566 @subsection Nios II Features
39567 @cindex target descriptions, Nios II features
39569 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
39570 targets. It should contain the 32 core registers (@samp{zero},
39571 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
39572 @samp{pc}, and the 16 control registers (@samp{status} through
39575 @node PowerPC Features
39576 @subsection PowerPC Features
39577 @cindex target descriptions, PowerPC features
39579 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
39580 targets. It should contain registers @samp{r0} through @samp{r31},
39581 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
39582 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
39584 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
39585 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
39587 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
39588 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
39591 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
39592 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
39593 will combine these registers with the floating point registers
39594 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
39595 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
39596 through @samp{vs63}, the set of vector registers for POWER7.
39598 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
39599 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
39600 @samp{spefscr}. SPE targets should provide 32-bit registers in
39601 @samp{org.gnu.gdb.power.core} and provide the upper halves in
39602 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
39603 these to present registers @samp{ev0} through @samp{ev31} to the
39606 @node S/390 and System z Features
39607 @subsection S/390 and System z Features
39608 @cindex target descriptions, S/390 features
39609 @cindex target descriptions, System z features
39611 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
39612 System z targets. It should contain the PSW and the 16 general
39613 registers. In particular, System z targets should provide the 64-bit
39614 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
39615 S/390 targets should provide the 32-bit versions of these registers.
39616 A System z target that runs in 31-bit addressing mode should provide
39617 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
39618 register's upper halves @samp{r0h} through @samp{r15h}, and their
39619 lower halves @samp{r0l} through @samp{r15l}.
39621 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
39622 contain the 64-bit registers @samp{f0} through @samp{f15}, and
39625 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
39626 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
39628 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
39629 contain the register @samp{orig_r2}, which is 64-bit wide on System z
39630 targets and 32-bit otherwise. In addition, the feature may contain
39631 the @samp{last_break} register, whose width depends on the addressing
39632 mode, as well as the @samp{system_call} register, which is always
39635 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
39636 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
39637 @samp{atia}, and @samp{tr0} through @samp{tr15}.
39639 @node TIC6x Features
39640 @subsection TMS320C6x Features
39641 @cindex target descriptions, TIC6x features
39642 @cindex target descriptions, TMS320C6x features
39643 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
39644 targets. It should contain registers @samp{A0} through @samp{A15},
39645 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
39647 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
39648 contain registers @samp{A16} through @samp{A31} and @samp{B16}
39649 through @samp{B31}.
39651 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
39652 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
39654 @node Operating System Information
39655 @appendix Operating System Information
39656 @cindex operating system information
39662 Users of @value{GDBN} often wish to obtain information about the state of
39663 the operating system running on the target---for example the list of
39664 processes, or the list of open files. This section describes the
39665 mechanism that makes it possible. This mechanism is similar to the
39666 target features mechanism (@pxref{Target Descriptions}), but focuses
39667 on a different aspect of target.
39669 Operating system information is retrived from the target via the
39670 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
39671 read}). The object name in the request should be @samp{osdata}, and
39672 the @var{annex} identifies the data to be fetched.
39675 @appendixsection Process list
39676 @cindex operating system information, process list
39678 When requesting the process list, the @var{annex} field in the
39679 @samp{qXfer} request should be @samp{processes}. The returned data is
39680 an XML document. The formal syntax of this document is defined in
39681 @file{gdb/features/osdata.dtd}.
39683 An example document is:
39686 <?xml version="1.0"?>
39687 <!DOCTYPE target SYSTEM "osdata.dtd">
39688 <osdata type="processes">
39690 <column name="pid">1</column>
39691 <column name="user">root</column>
39692 <column name="command">/sbin/init</column>
39693 <column name="cores">1,2,3</column>
39698 Each item should include a column whose name is @samp{pid}. The value
39699 of that column should identify the process on the target. The
39700 @samp{user} and @samp{command} columns are optional, and will be
39701 displayed by @value{GDBN}. The @samp{cores} column, if present,
39702 should contain a comma-separated list of cores that this process
39703 is running on. Target may provide additional columns,
39704 which @value{GDBN} currently ignores.
39706 @node Trace File Format
39707 @appendix Trace File Format
39708 @cindex trace file format
39710 The trace file comes in three parts: a header, a textual description
39711 section, and a trace frame section with binary data.
39713 The header has the form @code{\x7fTRACE0\n}. The first byte is
39714 @code{0x7f} so as to indicate that the file contains binary data,
39715 while the @code{0} is a version number that may have different values
39718 The description section consists of multiple lines of @sc{ascii} text
39719 separated by newline characters (@code{0xa}). The lines may include a
39720 variety of optional descriptive or context-setting information, such
39721 as tracepoint definitions or register set size. @value{GDBN} will
39722 ignore any line that it does not recognize. An empty line marks the end
39725 @c FIXME add some specific types of data
39727 The trace frame section consists of a number of consecutive frames.
39728 Each frame begins with a two-byte tracepoint number, followed by a
39729 four-byte size giving the amount of data in the frame. The data in
39730 the frame consists of a number of blocks, each introduced by a
39731 character indicating its type (at least register, memory, and trace
39732 state variable). The data in this section is raw binary, not a
39733 hexadecimal or other encoding; its endianness matches the target's
39736 @c FIXME bi-arch may require endianness/arch info in description section
39739 @item R @var{bytes}
39740 Register block. The number and ordering of bytes matches that of a
39741 @code{g} packet in the remote protocol. Note that these are the
39742 actual bytes, in target order and @value{GDBN} register order, not a
39743 hexadecimal encoding.
39745 @item M @var{address} @var{length} @var{bytes}...
39746 Memory block. This is a contiguous block of memory, at the 8-byte
39747 address @var{address}, with a 2-byte length @var{length}, followed by
39748 @var{length} bytes.
39750 @item V @var{number} @var{value}
39751 Trace state variable block. This records the 8-byte signed value
39752 @var{value} of trace state variable numbered @var{number}.
39756 Future enhancements of the trace file format may include additional types
39759 @node Index Section Format
39760 @appendix @code{.gdb_index} section format
39761 @cindex .gdb_index section format
39762 @cindex index section format
39764 This section documents the index section that is created by @code{save
39765 gdb-index} (@pxref{Index Files}). The index section is
39766 DWARF-specific; some knowledge of DWARF is assumed in this
39769 The mapped index file format is designed to be directly
39770 @code{mmap}able on any architecture. In most cases, a datum is
39771 represented using a little-endian 32-bit integer value, called an
39772 @code{offset_type}. Big endian machines must byte-swap the values
39773 before using them. Exceptions to this rule are noted. The data is
39774 laid out such that alignment is always respected.
39776 A mapped index consists of several areas, laid out in order.
39780 The file header. This is a sequence of values, of @code{offset_type}
39781 unless otherwise noted:
39785 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
39786 Version 4 uses a different hashing function from versions 5 and 6.
39787 Version 6 includes symbols for inlined functions, whereas versions 4
39788 and 5 do not. Version 7 adds attributes to the CU indices in the
39789 symbol table. Version 8 specifies that symbols from DWARF type units
39790 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
39791 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
39793 @value{GDBN} will only read version 4, 5, or 6 indices
39794 by specifying @code{set use-deprecated-index-sections on}.
39795 GDB has a workaround for potentially broken version 7 indices so it is
39796 currently not flagged as deprecated.
39799 The offset, from the start of the file, of the CU list.
39802 The offset, from the start of the file, of the types CU list. Note
39803 that this area can be empty, in which case this offset will be equal
39804 to the next offset.
39807 The offset, from the start of the file, of the address area.
39810 The offset, from the start of the file, of the symbol table.
39813 The offset, from the start of the file, of the constant pool.
39817 The CU list. This is a sequence of pairs of 64-bit little-endian
39818 values, sorted by the CU offset. The first element in each pair is
39819 the offset of a CU in the @code{.debug_info} section. The second
39820 element in each pair is the length of that CU. References to a CU
39821 elsewhere in the map are done using a CU index, which is just the
39822 0-based index into this table. Note that if there are type CUs, then
39823 conceptually CUs and type CUs form a single list for the purposes of
39827 The types CU list. This is a sequence of triplets of 64-bit
39828 little-endian values. In a triplet, the first value is the CU offset,
39829 the second value is the type offset in the CU, and the third value is
39830 the type signature. The types CU list is not sorted.
39833 The address area. The address area consists of a sequence of address
39834 entries. Each address entry has three elements:
39838 The low address. This is a 64-bit little-endian value.
39841 The high address. This is a 64-bit little-endian value. Like
39842 @code{DW_AT_high_pc}, the value is one byte beyond the end.
39845 The CU index. This is an @code{offset_type} value.
39849 The symbol table. This is an open-addressed hash table. The size of
39850 the hash table is always a power of 2.
39852 Each slot in the hash table consists of a pair of @code{offset_type}
39853 values. The first value is the offset of the symbol's name in the
39854 constant pool. The second value is the offset of the CU vector in the
39857 If both values are 0, then this slot in the hash table is empty. This
39858 is ok because while 0 is a valid constant pool index, it cannot be a
39859 valid index for both a string and a CU vector.
39861 The hash value for a table entry is computed by applying an
39862 iterative hash function to the symbol's name. Starting with an
39863 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
39864 the string is incorporated into the hash using the formula depending on the
39869 The formula is @code{r = r * 67 + c - 113}.
39871 @item Versions 5 to 7
39872 The formula is @code{r = r * 67 + tolower (c) - 113}.
39875 The terminating @samp{\0} is not incorporated into the hash.
39877 The step size used in the hash table is computed via
39878 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
39879 value, and @samp{size} is the size of the hash table. The step size
39880 is used to find the next candidate slot when handling a hash
39883 The names of C@t{++} symbols in the hash table are canonicalized. We
39884 don't currently have a simple description of the canonicalization
39885 algorithm; if you intend to create new index sections, you must read
39889 The constant pool. This is simply a bunch of bytes. It is organized
39890 so that alignment is correct: CU vectors are stored first, followed by
39893 A CU vector in the constant pool is a sequence of @code{offset_type}
39894 values. The first value is the number of CU indices in the vector.
39895 Each subsequent value is the index and symbol attributes of a CU in
39896 the CU list. This element in the hash table is used to indicate which
39897 CUs define the symbol and how the symbol is used.
39898 See below for the format of each CU index+attributes entry.
39900 A string in the constant pool is zero-terminated.
39903 Attributes were added to CU index values in @code{.gdb_index} version 7.
39904 If a symbol has multiple uses within a CU then there is one
39905 CU index+attributes value for each use.
39907 The format of each CU index+attributes entry is as follows
39913 This is the index of the CU in the CU list.
39915 These bits are reserved for future purposes and must be zero.
39917 The kind of the symbol in the CU.
39921 This value is reserved and should not be used.
39922 By reserving zero the full @code{offset_type} value is backwards compatible
39923 with previous versions of the index.
39925 The symbol is a type.
39927 The symbol is a variable or an enum value.
39929 The symbol is a function.
39931 Any other kind of symbol.
39933 These values are reserved.
39937 This bit is zero if the value is global and one if it is static.
39939 The determination of whether a symbol is global or static is complicated.
39940 The authorative reference is the file @file{dwarf2read.c} in
39941 @value{GDBN} sources.
39945 This pseudo-code describes the computation of a symbol's kind and
39946 global/static attributes in the index.
39949 is_external = get_attribute (die, DW_AT_external);
39950 language = get_attribute (cu_die, DW_AT_language);
39953 case DW_TAG_typedef:
39954 case DW_TAG_base_type:
39955 case DW_TAG_subrange_type:
39959 case DW_TAG_enumerator:
39961 is_static = (language != CPLUS && language != JAVA);
39963 case DW_TAG_subprogram:
39965 is_static = ! (is_external || language == ADA);
39967 case DW_TAG_constant:
39969 is_static = ! is_external;
39971 case DW_TAG_variable:
39973 is_static = ! is_external;
39975 case DW_TAG_namespace:
39979 case DW_TAG_class_type:
39980 case DW_TAG_interface_type:
39981 case DW_TAG_structure_type:
39982 case DW_TAG_union_type:
39983 case DW_TAG_enumeration_type:
39985 is_static = (language != CPLUS && language != JAVA);
39993 @appendix Manual pages
39997 * gdb man:: The GNU Debugger man page
39998 * gdbserver man:: Remote Server for the GNU Debugger man page
39999 * gcore man:: Generate a core file of a running program
40000 * gdbinit man:: gdbinit scripts
40006 @c man title gdb The GNU Debugger
40008 @c man begin SYNOPSIS gdb
40009 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
40010 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
40011 [@option{-b}@w{ }@var{bps}]
40012 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
40013 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
40014 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
40015 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
40016 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
40019 @c man begin DESCRIPTION gdb
40020 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
40021 going on ``inside'' another program while it executes -- or what another
40022 program was doing at the moment it crashed.
40024 @value{GDBN} can do four main kinds of things (plus other things in support of
40025 these) to help you catch bugs in the act:
40029 Start your program, specifying anything that might affect its behavior.
40032 Make your program stop on specified conditions.
40035 Examine what has happened, when your program has stopped.
40038 Change things in your program, so you can experiment with correcting the
40039 effects of one bug and go on to learn about another.
40042 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
40045 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
40046 commands from the terminal until you tell it to exit with the @value{GDBN}
40047 command @code{quit}. You can get online help from @value{GDBN} itself
40048 by using the command @code{help}.
40050 You can run @code{gdb} with no arguments or options; but the most
40051 usual way to start @value{GDBN} is with one argument or two, specifying an
40052 executable program as the argument:
40058 You can also start with both an executable program and a core file specified:
40064 You can, instead, specify a process ID as a second argument, if you want
40065 to debug a running process:
40073 would attach @value{GDBN} to process @code{1234} (unless you also have a file
40074 named @file{1234}; @value{GDBN} does check for a core file first).
40075 With option @option{-p} you can omit the @var{program} filename.
40077 Here are some of the most frequently needed @value{GDBN} commands:
40079 @c pod2man highlights the right hand side of the @item lines.
40081 @item break [@var{file}:]@var{functiop}
40082 Set a breakpoint at @var{function} (in @var{file}).
40084 @item run [@var{arglist}]
40085 Start your program (with @var{arglist}, if specified).
40088 Backtrace: display the program stack.
40090 @item print @var{expr}
40091 Display the value of an expression.
40094 Continue running your program (after stopping, e.g. at a breakpoint).
40097 Execute next program line (after stopping); step @emph{over} any
40098 function calls in the line.
40100 @item edit [@var{file}:]@var{function}
40101 look at the program line where it is presently stopped.
40103 @item list [@var{file}:]@var{function}
40104 type the text of the program in the vicinity of where it is presently stopped.
40107 Execute next program line (after stopping); step @emph{into} any
40108 function calls in the line.
40110 @item help [@var{name}]
40111 Show information about @value{GDBN} command @var{name}, or general information
40112 about using @value{GDBN}.
40115 Exit from @value{GDBN}.
40119 For full details on @value{GDBN},
40120 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40121 by Richard M. Stallman and Roland H. Pesch. The same text is available online
40122 as the @code{gdb} entry in the @code{info} program.
40126 @c man begin OPTIONS gdb
40127 Any arguments other than options specify an executable
40128 file and core file (or process ID); that is, the first argument
40129 encountered with no
40130 associated option flag is equivalent to a @option{-se} option, and the second,
40131 if any, is equivalent to a @option{-c} option if it's the name of a file.
40133 both long and short forms; both are shown here. The long forms are also
40134 recognized if you truncate them, so long as enough of the option is
40135 present to be unambiguous. (If you prefer, you can flag option
40136 arguments with @option{+} rather than @option{-}, though we illustrate the
40137 more usual convention.)
40139 All the options and command line arguments you give are processed
40140 in sequential order. The order makes a difference when the @option{-x}
40146 List all options, with brief explanations.
40148 @item -symbols=@var{file}
40149 @itemx -s @var{file}
40150 Read symbol table from file @var{file}.
40153 Enable writing into executable and core files.
40155 @item -exec=@var{file}
40156 @itemx -e @var{file}
40157 Use file @var{file} as the executable file to execute when
40158 appropriate, and for examining pure data in conjunction with a core
40161 @item -se=@var{file}
40162 Read symbol table from file @var{file} and use it as the executable
40165 @item -core=@var{file}
40166 @itemx -c @var{file}
40167 Use file @var{file} as a core dump to examine.
40169 @item -command=@var{file}
40170 @itemx -x @var{file}
40171 Execute @value{GDBN} commands from file @var{file}.
40173 @item -ex @var{command}
40174 Execute given @value{GDBN} @var{command}.
40176 @item -directory=@var{directory}
40177 @itemx -d @var{directory}
40178 Add @var{directory} to the path to search for source files.
40181 Do not execute commands from @file{~/.gdbinit}.
40185 Do not execute commands from any @file{.gdbinit} initialization files.
40189 ``Quiet''. Do not print the introductory and copyright messages. These
40190 messages are also suppressed in batch mode.
40193 Run in batch mode. Exit with status @code{0} after processing all the command
40194 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
40195 Exit with nonzero status if an error occurs in executing the @value{GDBN}
40196 commands in the command files.
40198 Batch mode may be useful for running @value{GDBN} as a filter, for example to
40199 download and run a program on another computer; in order to make this
40200 more useful, the message
40203 Program exited normally.
40207 (which is ordinarily issued whenever a program running under @value{GDBN} control
40208 terminates) is not issued when running in batch mode.
40210 @item -cd=@var{directory}
40211 Run @value{GDBN} using @var{directory} as its working directory,
40212 instead of the current directory.
40216 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
40217 @value{GDBN} to output the full file name and line number in a standard,
40218 recognizable fashion each time a stack frame is displayed (which
40219 includes each time the program stops). This recognizable format looks
40220 like two @samp{\032} characters, followed by the file name, line number
40221 and character position separated by colons, and a newline. The
40222 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
40223 characters as a signal to display the source code for the frame.
40226 Set the line speed (baud rate or bits per second) of any serial
40227 interface used by @value{GDBN} for remote debugging.
40229 @item -tty=@var{device}
40230 Run using @var{device} for your program's standard input and output.
40234 @c man begin SEEALSO gdb
40236 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
40237 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
40238 documentation are properly installed at your site, the command
40245 should give you access to the complete manual.
40247 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40248 Richard M. Stallman and Roland H. Pesch, July 1991.
40252 @node gdbserver man
40253 @heading gdbserver man
40255 @c man title gdbserver Remote Server for the GNU Debugger
40257 @c man begin SYNOPSIS gdbserver
40258 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
40260 gdbserver --attach @var{comm} @var{pid}
40262 gdbserver --multi @var{comm}
40266 @c man begin DESCRIPTION gdbserver
40267 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
40268 than the one which is running the program being debugged.
40271 @subheading Usage (server (target) side)
40274 Usage (server (target) side):
40277 First, you need to have a copy of the program you want to debug put onto
40278 the target system. The program can be stripped to save space if needed, as
40279 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
40280 the @value{GDBN} running on the host system.
40282 To use the server, you log on to the target system, and run the @command{gdbserver}
40283 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
40284 your program, and (c) its arguments. The general syntax is:
40287 target> gdbserver @var{comm} @var{program} [@var{args} ...]
40290 For example, using a serial port, you might say:
40294 @c @file would wrap it as F</dev/com1>.
40295 target> gdbserver /dev/com1 emacs foo.txt
40298 target> gdbserver @file{/dev/com1} emacs foo.txt
40302 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
40303 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
40304 waits patiently for the host @value{GDBN} to communicate with it.
40306 To use a TCP connection, you could say:
40309 target> gdbserver host:2345 emacs foo.txt
40312 This says pretty much the same thing as the last example, except that we are
40313 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
40314 that we are expecting to see a TCP connection from @code{host} to local TCP port
40315 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
40316 want for the port number as long as it does not conflict with any existing TCP
40317 ports on the target system. This same port number must be used in the host
40318 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
40319 you chose a port number that conflicts with another service, @command{gdbserver} will
40320 print an error message and exit.
40322 @command{gdbserver} can also attach to running programs.
40323 This is accomplished via the @option{--attach} argument. The syntax is:
40326 target> gdbserver --attach @var{comm} @var{pid}
40329 @var{pid} is the process ID of a currently running process. It isn't
40330 necessary to point @command{gdbserver} at a binary for the running process.
40332 To start @code{gdbserver} without supplying an initial command to run
40333 or process ID to attach, use the @option{--multi} command line option.
40334 In such case you should connect using @kbd{target extended-remote} to start
40335 the program you want to debug.
40338 target> gdbserver --multi @var{comm}
40342 @subheading Usage (host side)
40348 You need an unstripped copy of the target program on your host system, since
40349 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
40350 would, with the target program as the first argument. (You may need to use the
40351 @option{--baud} option if the serial line is running at anything except 9600 baud.)
40352 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
40353 new command you need to know about is @code{target remote}
40354 (or @code{target extended-remote}). Its argument is either
40355 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
40356 descriptor. For example:
40360 @c @file would wrap it as F</dev/ttyb>.
40361 (gdb) target remote /dev/ttyb
40364 (gdb) target remote @file{/dev/ttyb}
40369 communicates with the server via serial line @file{/dev/ttyb}, and:
40372 (gdb) target remote the-target:2345
40376 communicates via a TCP connection to port 2345 on host `the-target', where
40377 you previously started up @command{gdbserver} with the same port number. Note that for
40378 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
40379 command, otherwise you may get an error that looks something like
40380 `Connection refused'.
40382 @command{gdbserver} can also debug multiple inferiors at once,
40385 the @value{GDBN} manual in node @code{Inferiors and Programs}
40386 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
40389 @ref{Inferiors and Programs}.
40391 In such case use the @code{extended-remote} @value{GDBN} command variant:
40394 (gdb) target extended-remote the-target:2345
40397 The @command{gdbserver} option @option{--multi} may or may not be used in such
40401 @c man begin OPTIONS gdbserver
40402 There are three different modes for invoking @command{gdbserver}:
40407 Debug a specific program specified by its program name:
40410 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
40413 The @var{comm} parameter specifies how should the server communicate
40414 with @value{GDBN}; it is either a device name (to use a serial line),
40415 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
40416 stdin/stdout of @code{gdbserver}. Specify the name of the program to
40417 debug in @var{prog}. Any remaining arguments will be passed to the
40418 program verbatim. When the program exits, @value{GDBN} will close the
40419 connection, and @code{gdbserver} will exit.
40422 Debug a specific program by specifying the process ID of a running
40426 gdbserver --attach @var{comm} @var{pid}
40429 The @var{comm} parameter is as described above. Supply the process ID
40430 of a running program in @var{pid}; @value{GDBN} will do everything
40431 else. Like with the previous mode, when the process @var{pid} exits,
40432 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
40435 Multi-process mode -- debug more than one program/process:
40438 gdbserver --multi @var{comm}
40441 In this mode, @value{GDBN} can instruct @command{gdbserver} which
40442 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
40443 close the connection when a process being debugged exits, so you can
40444 debug several processes in the same session.
40447 In each of the modes you may specify these options:
40452 List all options, with brief explanations.
40455 This option causes @command{gdbserver} to print its version number and exit.
40458 @command{gdbserver} will attach to a running program. The syntax is:
40461 target> gdbserver --attach @var{comm} @var{pid}
40464 @var{pid} is the process ID of a currently running process. It isn't
40465 necessary to point @command{gdbserver} at a binary for the running process.
40468 To start @code{gdbserver} without supplying an initial command to run
40469 or process ID to attach, use this command line option.
40470 Then you can connect using @kbd{target extended-remote} and start
40471 the program you want to debug. The syntax is:
40474 target> gdbserver --multi @var{comm}
40478 Instruct @code{gdbserver} to display extra status information about the debugging
40480 This option is intended for @code{gdbserver} development and for bug reports to
40483 @item --remote-debug
40484 Instruct @code{gdbserver} to display remote protocol debug output.
40485 This option is intended for @code{gdbserver} development and for bug reports to
40488 @item --debug-format=option1@r{[},option2,...@r{]}
40489 Instruct @code{gdbserver} to include extra information in each line
40490 of debugging output.
40491 @xref{Other Command-Line Arguments for gdbserver}.
40494 Specify a wrapper to launch programs
40495 for debugging. The option should be followed by the name of the
40496 wrapper, then any command-line arguments to pass to the wrapper, then
40497 @kbd{--} indicating the end of the wrapper arguments.
40500 By default, @command{gdbserver} keeps the listening TCP port open, so that
40501 additional connections are possible. However, if you start @code{gdbserver}
40502 with the @option{--once} option, it will stop listening for any further
40503 connection attempts after connecting to the first @value{GDBN} session.
40505 @c --disable-packet is not documented for users.
40507 @c --disable-randomization and --no-disable-randomization are superseded by
40508 @c QDisableRandomization.
40513 @c man begin SEEALSO gdbserver
40515 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
40516 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
40517 documentation are properly installed at your site, the command
40523 should give you access to the complete manual.
40525 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40526 Richard M. Stallman and Roland H. Pesch, July 1991.
40533 @c man title gcore Generate a core file of a running program
40536 @c man begin SYNOPSIS gcore
40537 gcore [-o @var{filename}] @var{pid}
40541 @c man begin DESCRIPTION gcore
40542 Generate a core dump of a running program with process ID @var{pid}.
40543 Produced file is equivalent to a kernel produced core file as if the process
40544 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
40545 limit). Unlike after a crash, after @command{gcore} the program remains
40546 running without any change.
40549 @c man begin OPTIONS gcore
40551 @item -o @var{filename}
40552 The optional argument
40553 @var{filename} specifies the file name where to put the core dump.
40554 If not specified, the file name defaults to @file{core.@var{pid}},
40555 where @var{pid} is the running program process ID.
40559 @c man begin SEEALSO gcore
40561 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
40562 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
40563 documentation are properly installed at your site, the command
40570 should give you access to the complete manual.
40572 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40573 Richard M. Stallman and Roland H. Pesch, July 1991.
40580 @c man title gdbinit GDB initialization scripts
40583 @c man begin SYNOPSIS gdbinit
40584 @ifset SYSTEM_GDBINIT
40585 @value{SYSTEM_GDBINIT}
40594 @c man begin DESCRIPTION gdbinit
40595 These files contain @value{GDBN} commands to automatically execute during
40596 @value{GDBN} startup. The lines of contents are canned sequences of commands,
40599 the @value{GDBN} manual in node @code{Sequences}
40600 -- shell command @code{info -f gdb -n Sequences}.
40606 Please read more in
40608 the @value{GDBN} manual in node @code{Startup}
40609 -- shell command @code{info -f gdb -n Startup}.
40616 @ifset SYSTEM_GDBINIT
40617 @item @value{SYSTEM_GDBINIT}
40619 @ifclear SYSTEM_GDBINIT
40620 @item (not enabled with @code{--with-system-gdbinit} during compilation)
40622 System-wide initialization file. It is executed unless user specified
40623 @value{GDBN} option @code{-nx} or @code{-n}.
40626 the @value{GDBN} manual in node @code{System-wide configuration}
40627 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
40630 @ref{System-wide configuration}.
40634 User initialization file. It is executed unless user specified
40635 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
40638 Initialization file for current directory. It may need to be enabled with
40639 @value{GDBN} security command @code{set auto-load local-gdbinit}.
40642 the @value{GDBN} manual in node @code{Init File in the Current Directory}
40643 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
40646 @ref{Init File in the Current Directory}.
40651 @c man begin SEEALSO gdbinit
40653 gdb(1), @code{info -f gdb -n Startup}
40655 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
40656 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
40657 documentation are properly installed at your site, the command
40663 should give you access to the complete manual.
40665 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40666 Richard M. Stallman and Roland H. Pesch, July 1991.
40672 @node GNU Free Documentation License
40673 @appendix GNU Free Documentation License
40676 @node Concept Index
40677 @unnumbered Concept Index
40681 @node Command and Variable Index
40682 @unnumbered Command, Variable, and Function Index
40687 % I think something like @@colophon should be in texinfo. In the
40689 \long\def\colophon{\hbox to0pt{}\vfill
40690 \centerline{The body of this manual is set in}
40691 \centerline{\fontname\tenrm,}
40692 \centerline{with headings in {\bf\fontname\tenbf}}
40693 \centerline{and examples in {\tt\fontname\tentt}.}
40694 \centerline{{\it\fontname\tenit\/},}
40695 \centerline{{\bf\fontname\tenbf}, and}
40696 \centerline{{\sl\fontname\tensl\/}}
40697 \centerline{are used for emphasis.}\vfill}
40699 % Blame: doc@@cygnus.com, 1991.