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] @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 a
2969 command to all threads, type @kbd{thread apply all @var{command}}.
2972 @cindex name a thread
2973 @item thread name [@var{name}]
2974 This command assigns a name to the current thread. If no argument is
2975 given, any existing user-specified name is removed. The thread name
2976 appears in the @samp{info threads} display.
2978 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2979 determine the name of the thread as given by the OS. On these
2980 systems, a name specified with @samp{thread name} will override the
2981 system-give name, and removing the user-specified name will cause
2982 @value{GDBN} to once again display the system-specified name.
2985 @cindex search for a thread
2986 @item thread find [@var{regexp}]
2987 Search for and display thread ids whose name or @var{systag}
2988 matches the supplied regular expression.
2990 As well as being the complement to the @samp{thread name} command,
2991 this command also allows you to identify a thread by its target
2992 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2996 (@value{GDBN}) thread find 26688
2997 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2998 (@value{GDBN}) info thread 4
3000 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3003 @kindex set print thread-events
3004 @cindex print messages on thread start and exit
3005 @item set print thread-events
3006 @itemx set print thread-events on
3007 @itemx set print thread-events off
3008 The @code{set print thread-events} command allows you to enable or
3009 disable printing of messages when @value{GDBN} notices that new threads have
3010 started or that threads have exited. By default, these messages will
3011 be printed if detection of these events is supported by the target.
3012 Note that these messages cannot be disabled on all targets.
3014 @kindex show print thread-events
3015 @item show print thread-events
3016 Show whether messages will be printed when @value{GDBN} detects that threads
3017 have started and exited.
3020 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3021 more information about how @value{GDBN} behaves when you stop and start
3022 programs with multiple threads.
3024 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3025 watchpoints in programs with multiple threads.
3027 @anchor{set libthread-db-search-path}
3029 @kindex set libthread-db-search-path
3030 @cindex search path for @code{libthread_db}
3031 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3032 If this variable is set, @var{path} is a colon-separated list of
3033 directories @value{GDBN} will use to search for @code{libthread_db}.
3034 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3035 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3036 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3039 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3040 @code{libthread_db} library to obtain information about threads in the
3041 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3042 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3043 specific thread debugging library loading is enabled
3044 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3046 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3047 refers to the default system directories that are
3048 normally searched for loading shared libraries. The @samp{$sdir} entry
3049 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3050 (@pxref{libthread_db.so.1 file}).
3052 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3053 refers to the directory from which @code{libpthread}
3054 was loaded in the inferior process.
3056 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3057 @value{GDBN} attempts to initialize it with the current inferior process.
3058 If this initialization fails (which could happen because of a version
3059 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3060 will unload @code{libthread_db}, and continue with the next directory.
3061 If none of @code{libthread_db} libraries initialize successfully,
3062 @value{GDBN} will issue a warning and thread debugging will be disabled.
3064 Setting @code{libthread-db-search-path} is currently implemented
3065 only on some platforms.
3067 @kindex show libthread-db-search-path
3068 @item show libthread-db-search-path
3069 Display current libthread_db search path.
3071 @kindex set debug libthread-db
3072 @kindex show debug libthread-db
3073 @cindex debugging @code{libthread_db}
3074 @item set debug libthread-db
3075 @itemx show debug libthread-db
3076 Turns on or off display of @code{libthread_db}-related events.
3077 Use @code{1} to enable, @code{0} to disable.
3081 @section Debugging Forks
3083 @cindex fork, debugging programs which call
3084 @cindex multiple processes
3085 @cindex processes, multiple
3086 On most systems, @value{GDBN} has no special support for debugging
3087 programs which create additional processes using the @code{fork}
3088 function. When a program forks, @value{GDBN} will continue to debug the
3089 parent process and the child process will run unimpeded. If you have
3090 set a breakpoint in any code which the child then executes, the child
3091 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3092 will cause it to terminate.
3094 However, if you want to debug the child process there is a workaround
3095 which isn't too painful. Put a call to @code{sleep} in the code which
3096 the child process executes after the fork. It may be useful to sleep
3097 only if a certain environment variable is set, or a certain file exists,
3098 so that the delay need not occur when you don't want to run @value{GDBN}
3099 on the child. While the child is sleeping, use the @code{ps} program to
3100 get its process ID. Then tell @value{GDBN} (a new invocation of
3101 @value{GDBN} if you are also debugging the parent process) to attach to
3102 the child process (@pxref{Attach}). From that point on you can debug
3103 the child process just like any other process which you attached to.
3105 On some systems, @value{GDBN} provides support for debugging programs that
3106 create additional processes using the @code{fork} or @code{vfork} functions.
3107 Currently, the only platforms with this feature are HP-UX (11.x and later
3108 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
3110 By default, when a program forks, @value{GDBN} will continue to debug
3111 the parent process and the child process will run unimpeded.
3113 If you want to follow the child process instead of the parent process,
3114 use the command @w{@code{set follow-fork-mode}}.
3117 @kindex set follow-fork-mode
3118 @item set follow-fork-mode @var{mode}
3119 Set the debugger response to a program call of @code{fork} or
3120 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3121 process. The @var{mode} argument can be:
3125 The original process is debugged after a fork. The child process runs
3126 unimpeded. This is the default.
3129 The new process is debugged after a fork. The parent process runs
3134 @kindex show follow-fork-mode
3135 @item show follow-fork-mode
3136 Display the current debugger response to a @code{fork} or @code{vfork} call.
3139 @cindex debugging multiple processes
3140 On Linux, if you want to debug both the parent and child processes, use the
3141 command @w{@code{set detach-on-fork}}.
3144 @kindex set detach-on-fork
3145 @item set detach-on-fork @var{mode}
3146 Tells gdb whether to detach one of the processes after a fork, or
3147 retain debugger control over them both.
3151 The child process (or parent process, depending on the value of
3152 @code{follow-fork-mode}) will be detached and allowed to run
3153 independently. This is the default.
3156 Both processes will be held under the control of @value{GDBN}.
3157 One process (child or parent, depending on the value of
3158 @code{follow-fork-mode}) is debugged as usual, while the other
3163 @kindex show detach-on-fork
3164 @item show detach-on-fork
3165 Show whether detach-on-fork mode is on/off.
3168 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3169 will retain control of all forked processes (including nested forks).
3170 You can list the forked processes under the control of @value{GDBN} by
3171 using the @w{@code{info inferiors}} command, and switch from one fork
3172 to another by using the @code{inferior} command (@pxref{Inferiors and
3173 Programs, ,Debugging Multiple Inferiors and Programs}).
3175 To quit debugging one of the forked processes, you can either detach
3176 from it by using the @w{@code{detach inferiors}} command (allowing it
3177 to run independently), or kill it using the @w{@code{kill inferiors}}
3178 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3181 If you ask to debug a child process and a @code{vfork} is followed by an
3182 @code{exec}, @value{GDBN} executes the new target up to the first
3183 breakpoint in the new target. If you have a breakpoint set on
3184 @code{main} in your original program, the breakpoint will also be set on
3185 the child process's @code{main}.
3187 On some systems, when a child process is spawned by @code{vfork}, you
3188 cannot debug the child or parent until an @code{exec} call completes.
3190 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3191 call executes, the new target restarts. To restart the parent
3192 process, use the @code{file} command with the parent executable name
3193 as its argument. By default, after an @code{exec} call executes,
3194 @value{GDBN} discards the symbols of the previous executable image.
3195 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3199 @kindex set follow-exec-mode
3200 @item set follow-exec-mode @var{mode}
3202 Set debugger response to a program call of @code{exec}. An
3203 @code{exec} call replaces the program image of a process.
3205 @code{follow-exec-mode} can be:
3209 @value{GDBN} creates a new inferior and rebinds the process to this
3210 new inferior. The program the process was running before the
3211 @code{exec} call can be restarted afterwards by restarting the
3217 (@value{GDBP}) info inferiors
3219 Id Description Executable
3222 process 12020 is executing new program: prog2
3223 Program exited normally.
3224 (@value{GDBP}) info inferiors
3225 Id Description Executable
3231 @value{GDBN} keeps the process bound to the same inferior. The new
3232 executable image replaces the previous executable loaded in the
3233 inferior. Restarting the inferior after the @code{exec} call, with
3234 e.g., the @code{run} command, restarts the executable the process was
3235 running after the @code{exec} call. This is the default mode.
3240 (@value{GDBP}) info inferiors
3241 Id Description Executable
3244 process 12020 is executing new program: prog2
3245 Program exited normally.
3246 (@value{GDBP}) info inferiors
3247 Id Description Executable
3254 You can use the @code{catch} command to make @value{GDBN} stop whenever
3255 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3256 Catchpoints, ,Setting Catchpoints}.
3258 @node Checkpoint/Restart
3259 @section Setting a @emph{Bookmark} to Return to Later
3264 @cindex snapshot of a process
3265 @cindex rewind program state
3267 On certain operating systems@footnote{Currently, only
3268 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3269 program's state, called a @dfn{checkpoint}, and come back to it
3272 Returning to a checkpoint effectively undoes everything that has
3273 happened in the program since the @code{checkpoint} was saved. This
3274 includes changes in memory, registers, and even (within some limits)
3275 system state. Effectively, it is like going back in time to the
3276 moment when the checkpoint was saved.
3278 Thus, if you're stepping thru a program and you think you're
3279 getting close to the point where things go wrong, you can save
3280 a checkpoint. Then, if you accidentally go too far and miss
3281 the critical statement, instead of having to restart your program
3282 from the beginning, you can just go back to the checkpoint and
3283 start again from there.
3285 This can be especially useful if it takes a lot of time or
3286 steps to reach the point where you think the bug occurs.
3288 To use the @code{checkpoint}/@code{restart} method of debugging:
3293 Save a snapshot of the debugged program's current execution state.
3294 The @code{checkpoint} command takes no arguments, but each checkpoint
3295 is assigned a small integer id, similar to a breakpoint id.
3297 @kindex info checkpoints
3298 @item info checkpoints
3299 List the checkpoints that have been saved in the current debugging
3300 session. For each checkpoint, the following information will be
3307 @item Source line, or label
3310 @kindex restart @var{checkpoint-id}
3311 @item restart @var{checkpoint-id}
3312 Restore the program state that was saved as checkpoint number
3313 @var{checkpoint-id}. All program variables, registers, stack frames
3314 etc.@: will be returned to the values that they had when the checkpoint
3315 was saved. In essence, gdb will ``wind back the clock'' to the point
3316 in time when the checkpoint was saved.
3318 Note that breakpoints, @value{GDBN} variables, command history etc.
3319 are not affected by restoring a checkpoint. In general, a checkpoint
3320 only restores things that reside in the program being debugged, not in
3323 @kindex delete checkpoint @var{checkpoint-id}
3324 @item delete checkpoint @var{checkpoint-id}
3325 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3329 Returning to a previously saved checkpoint will restore the user state
3330 of the program being debugged, plus a significant subset of the system
3331 (OS) state, including file pointers. It won't ``un-write'' data from
3332 a file, but it will rewind the file pointer to the previous location,
3333 so that the previously written data can be overwritten. For files
3334 opened in read mode, the pointer will also be restored so that the
3335 previously read data can be read again.
3337 Of course, characters that have been sent to a printer (or other
3338 external device) cannot be ``snatched back'', and characters received
3339 from eg.@: a serial device can be removed from internal program buffers,
3340 but they cannot be ``pushed back'' into the serial pipeline, ready to
3341 be received again. Similarly, the actual contents of files that have
3342 been changed cannot be restored (at this time).
3344 However, within those constraints, you actually can ``rewind'' your
3345 program to a previously saved point in time, and begin debugging it
3346 again --- and you can change the course of events so as to debug a
3347 different execution path this time.
3349 @cindex checkpoints and process id
3350 Finally, there is one bit of internal program state that will be
3351 different when you return to a checkpoint --- the program's process
3352 id. Each checkpoint will have a unique process id (or @var{pid}),
3353 and each will be different from the program's original @var{pid}.
3354 If your program has saved a local copy of its process id, this could
3355 potentially pose a problem.
3357 @subsection A Non-obvious Benefit of Using Checkpoints
3359 On some systems such as @sc{gnu}/Linux, address space randomization
3360 is performed on new processes for security reasons. This makes it
3361 difficult or impossible to set a breakpoint, or watchpoint, on an
3362 absolute address if you have to restart the program, since the
3363 absolute location of a symbol will change from one execution to the
3366 A checkpoint, however, is an @emph{identical} copy of a process.
3367 Therefore if you create a checkpoint at (eg.@:) the start of main,
3368 and simply return to that checkpoint instead of restarting the
3369 process, you can avoid the effects of address randomization and
3370 your symbols will all stay in the same place.
3373 @chapter Stopping and Continuing
3375 The principal purposes of using a debugger are so that you can stop your
3376 program before it terminates; or so that, if your program runs into
3377 trouble, you can investigate and find out why.
3379 Inside @value{GDBN}, your program may stop for any of several reasons,
3380 such as a signal, a breakpoint, or reaching a new line after a
3381 @value{GDBN} command such as @code{step}. You may then examine and
3382 change variables, set new breakpoints or remove old ones, and then
3383 continue execution. Usually, the messages shown by @value{GDBN} provide
3384 ample explanation of the status of your program---but you can also
3385 explicitly request this information at any time.
3388 @kindex info program
3390 Display information about the status of your program: whether it is
3391 running or not, what process it is, and why it stopped.
3395 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3396 * Continuing and Stepping:: Resuming execution
3397 * Skipping Over Functions and Files::
3398 Skipping over functions and files
3400 * Thread Stops:: Stopping and starting multi-thread programs
3404 @section Breakpoints, Watchpoints, and Catchpoints
3407 A @dfn{breakpoint} makes your program stop whenever a certain point in
3408 the program is reached. For each breakpoint, you can add conditions to
3409 control in finer detail whether your program stops. You can set
3410 breakpoints with the @code{break} command and its variants (@pxref{Set
3411 Breaks, ,Setting Breakpoints}), to specify the place where your program
3412 should stop by line number, function name or exact address in the
3415 On some systems, you can set breakpoints in shared libraries before
3416 the executable is run. There is a minor limitation on HP-UX systems:
3417 you must wait until the executable is run in order to set breakpoints
3418 in shared library routines that are not called directly by the program
3419 (for example, routines that are arguments in a @code{pthread_create}
3423 @cindex data breakpoints
3424 @cindex memory tracing
3425 @cindex breakpoint on memory address
3426 @cindex breakpoint on variable modification
3427 A @dfn{watchpoint} is a special breakpoint that stops your program
3428 when the value of an expression changes. The expression may be a value
3429 of a variable, or it could involve values of one or more variables
3430 combined by operators, such as @samp{a + b}. This is sometimes called
3431 @dfn{data breakpoints}. You must use a different command to set
3432 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3433 from that, you can manage a watchpoint like any other breakpoint: you
3434 enable, disable, and delete both breakpoints and watchpoints using the
3437 You can arrange to have values from your program displayed automatically
3438 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3442 @cindex breakpoint on events
3443 A @dfn{catchpoint} is another special breakpoint that stops your program
3444 when a certain kind of event occurs, such as the throwing of a C@t{++}
3445 exception or the loading of a library. As with watchpoints, you use a
3446 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3447 Catchpoints}), but aside from that, you can manage a catchpoint like any
3448 other breakpoint. (To stop when your program receives a signal, use the
3449 @code{handle} command; see @ref{Signals, ,Signals}.)
3451 @cindex breakpoint numbers
3452 @cindex numbers for breakpoints
3453 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3454 catchpoint when you create it; these numbers are successive integers
3455 starting with one. In many of the commands for controlling various
3456 features of breakpoints you use the breakpoint number to say which
3457 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3458 @dfn{disabled}; if disabled, it has no effect on your program until you
3461 @cindex breakpoint ranges
3462 @cindex ranges of breakpoints
3463 Some @value{GDBN} commands accept a range of breakpoints on which to
3464 operate. A breakpoint range is either a single breakpoint number, like
3465 @samp{5}, or two such numbers, in increasing order, separated by a
3466 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3467 all breakpoints in that range are operated on.
3470 * Set Breaks:: Setting breakpoints
3471 * Set Watchpoints:: Setting watchpoints
3472 * Set Catchpoints:: Setting catchpoints
3473 * Delete Breaks:: Deleting breakpoints
3474 * Disabling:: Disabling breakpoints
3475 * Conditions:: Break conditions
3476 * Break Commands:: Breakpoint command lists
3477 * Dynamic Printf:: Dynamic printf
3478 * Save Breakpoints:: How to save breakpoints in a file
3479 * Static Probe Points:: Listing static probe points
3480 * Error in Breakpoints:: ``Cannot insert breakpoints''
3481 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3485 @subsection Setting Breakpoints
3487 @c FIXME LMB what does GDB do if no code on line of breakpt?
3488 @c consider in particular declaration with/without initialization.
3490 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3493 @kindex b @r{(@code{break})}
3494 @vindex $bpnum@r{, convenience variable}
3495 @cindex latest breakpoint
3496 Breakpoints are set with the @code{break} command (abbreviated
3497 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3498 number of the breakpoint you've set most recently; see @ref{Convenience
3499 Vars,, Convenience Variables}, for a discussion of what you can do with
3500 convenience variables.
3503 @item break @var{location}
3504 Set a breakpoint at the given @var{location}, which can specify a
3505 function name, a line number, or an address of an instruction.
3506 (@xref{Specify Location}, for a list of all the possible ways to
3507 specify a @var{location}.) The breakpoint will stop your program just
3508 before it executes any of the code in the specified @var{location}.
3510 When using source languages that permit overloading of symbols, such as
3511 C@t{++}, a function name may refer to more than one possible place to break.
3512 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3515 It is also possible to insert a breakpoint that will stop the program
3516 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3517 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3520 When called without any arguments, @code{break} sets a breakpoint at
3521 the next instruction to be executed in the selected stack frame
3522 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3523 innermost, this makes your program stop as soon as control
3524 returns to that frame. This is similar to the effect of a
3525 @code{finish} command in the frame inside the selected frame---except
3526 that @code{finish} does not leave an active breakpoint. If you use
3527 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3528 the next time it reaches the current location; this may be useful
3531 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3532 least one instruction has been executed. If it did not do this, you
3533 would be unable to proceed past a breakpoint without first disabling the
3534 breakpoint. This rule applies whether or not the breakpoint already
3535 existed when your program stopped.
3537 @item break @dots{} if @var{cond}
3538 Set a breakpoint with condition @var{cond}; evaluate the expression
3539 @var{cond} each time the breakpoint is reached, and stop only if the
3540 value is nonzero---that is, if @var{cond} evaluates as true.
3541 @samp{@dots{}} stands for one of the possible arguments described
3542 above (or no argument) specifying where to break. @xref{Conditions,
3543 ,Break Conditions}, for more information on breakpoint conditions.
3546 @item tbreak @var{args}
3547 Set a breakpoint enabled only for one stop. The @var{args} are the
3548 same as for the @code{break} command, and the breakpoint is set in the same
3549 way, but the breakpoint is automatically deleted after the first time your
3550 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3553 @cindex hardware breakpoints
3554 @item hbreak @var{args}
3555 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
3556 @code{break} command and the breakpoint is set in the same way, but the
3557 breakpoint requires hardware support and some target hardware may not
3558 have this support. The main purpose of this is EPROM/ROM code
3559 debugging, so you can set a breakpoint at an instruction without
3560 changing the instruction. This can be used with the new trap-generation
3561 provided by SPARClite DSU and most x86-based targets. These targets
3562 will generate traps when a program accesses some data or instruction
3563 address that is assigned to the debug registers. However the hardware
3564 breakpoint registers can take a limited number of breakpoints. For
3565 example, on the DSU, only two data breakpoints can be set at a time, and
3566 @value{GDBN} will reject this command if more than two are used. Delete
3567 or disable unused hardware breakpoints before setting new ones
3568 (@pxref{Disabling, ,Disabling Breakpoints}).
3569 @xref{Conditions, ,Break Conditions}.
3570 For remote targets, you can restrict the number of hardware
3571 breakpoints @value{GDBN} will use, see @ref{set remote
3572 hardware-breakpoint-limit}.
3575 @item thbreak @var{args}
3576 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
3577 are the same as for the @code{hbreak} command and the breakpoint is set in
3578 the same way. However, like the @code{tbreak} command,
3579 the breakpoint is automatically deleted after the
3580 first time your program stops there. Also, like the @code{hbreak}
3581 command, the breakpoint requires hardware support and some target hardware
3582 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3583 See also @ref{Conditions, ,Break Conditions}.
3586 @cindex regular expression
3587 @cindex breakpoints at functions matching a regexp
3588 @cindex set breakpoints in many functions
3589 @item rbreak @var{regex}
3590 Set breakpoints on all functions matching the regular expression
3591 @var{regex}. This command sets an unconditional breakpoint on all
3592 matches, printing a list of all breakpoints it set. Once these
3593 breakpoints are set, they are treated just like the breakpoints set with
3594 the @code{break} command. You can delete them, disable them, or make
3595 them conditional the same way as any other breakpoint.
3597 The syntax of the regular expression is the standard one used with tools
3598 like @file{grep}. Note that this is different from the syntax used by
3599 shells, so for instance @code{foo*} matches all functions that include
3600 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3601 @code{.*} leading and trailing the regular expression you supply, so to
3602 match only functions that begin with @code{foo}, use @code{^foo}.
3604 @cindex non-member C@t{++} functions, set breakpoint in
3605 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3606 breakpoints on overloaded functions that are not members of any special
3609 @cindex set breakpoints on all functions
3610 The @code{rbreak} command can be used to set breakpoints in
3611 @strong{all} the functions in a program, like this:
3614 (@value{GDBP}) rbreak .
3617 @item rbreak @var{file}:@var{regex}
3618 If @code{rbreak} is called with a filename qualification, it limits
3619 the search for functions matching the given regular expression to the
3620 specified @var{file}. This can be used, for example, to set breakpoints on
3621 every function in a given file:
3624 (@value{GDBP}) rbreak file.c:.
3627 The colon separating the filename qualifier from the regex may
3628 optionally be surrounded by spaces.
3630 @kindex info breakpoints
3631 @cindex @code{$_} and @code{info breakpoints}
3632 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3633 @itemx info break @r{[}@var{n}@dots{}@r{]}
3634 Print a table of all breakpoints, watchpoints, and catchpoints set and
3635 not deleted. Optional argument @var{n} means print information only
3636 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3637 For each breakpoint, following columns are printed:
3640 @item Breakpoint Numbers
3642 Breakpoint, watchpoint, or catchpoint.
3644 Whether the breakpoint is marked to be disabled or deleted when hit.
3645 @item Enabled or Disabled
3646 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3647 that are not enabled.
3649 Where the breakpoint is in your program, as a memory address. For a
3650 pending breakpoint whose address is not yet known, this field will
3651 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3652 library that has the symbol or line referred by breakpoint is loaded.
3653 See below for details. A breakpoint with several locations will
3654 have @samp{<MULTIPLE>} in this field---see below for details.
3656 Where the breakpoint is in the source for your program, as a file and
3657 line number. For a pending breakpoint, the original string passed to
3658 the breakpoint command will be listed as it cannot be resolved until
3659 the appropriate shared library is loaded in the future.
3663 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3664 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3665 @value{GDBN} on the host's side. If it is ``target'', then the condition
3666 is evaluated by the target. The @code{info break} command shows
3667 the condition on the line following the affected breakpoint, together with
3668 its condition evaluation mode in between parentheses.
3670 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3671 allowed to have a condition specified for it. The condition is not parsed for
3672 validity until a shared library is loaded that allows the pending
3673 breakpoint to resolve to a valid location.
3676 @code{info break} with a breakpoint
3677 number @var{n} as argument lists only that breakpoint. The
3678 convenience variable @code{$_} and the default examining-address for
3679 the @code{x} command are set to the address of the last breakpoint
3680 listed (@pxref{Memory, ,Examining Memory}).
3683 @code{info break} displays a count of the number of times the breakpoint
3684 has been hit. This is especially useful in conjunction with the
3685 @code{ignore} command. You can ignore a large number of breakpoint
3686 hits, look at the breakpoint info to see how many times the breakpoint
3687 was hit, and then run again, ignoring one less than that number. This
3688 will get you quickly to the last hit of that breakpoint.
3691 For a breakpoints with an enable count (xref) greater than 1,
3692 @code{info break} also displays that count.
3696 @value{GDBN} allows you to set any number of breakpoints at the same place in
3697 your program. There is nothing silly or meaningless about this. When
3698 the breakpoints are conditional, this is even useful
3699 (@pxref{Conditions, ,Break Conditions}).
3701 @cindex multiple locations, breakpoints
3702 @cindex breakpoints, multiple locations
3703 It is possible that a breakpoint corresponds to several locations
3704 in your program. Examples of this situation are:
3708 Multiple functions in the program may have the same name.
3711 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3712 instances of the function body, used in different cases.
3715 For a C@t{++} template function, a given line in the function can
3716 correspond to any number of instantiations.
3719 For an inlined function, a given source line can correspond to
3720 several places where that function is inlined.
3723 In all those cases, @value{GDBN} will insert a breakpoint at all
3724 the relevant locations.
3726 A breakpoint with multiple locations is displayed in the breakpoint
3727 table using several rows---one header row, followed by one row for
3728 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3729 address column. The rows for individual locations contain the actual
3730 addresses for locations, and show the functions to which those
3731 locations belong. The number column for a location is of the form
3732 @var{breakpoint-number}.@var{location-number}.
3737 Num Type Disp Enb Address What
3738 1 breakpoint keep y <MULTIPLE>
3740 breakpoint already hit 1 time
3741 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3742 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3745 Each location can be individually enabled or disabled by passing
3746 @var{breakpoint-number}.@var{location-number} as argument to the
3747 @code{enable} and @code{disable} commands. Note that you cannot
3748 delete the individual locations from the list, you can only delete the
3749 entire list of locations that belong to their parent breakpoint (with
3750 the @kbd{delete @var{num}} command, where @var{num} is the number of
3751 the parent breakpoint, 1 in the above example). Disabling or enabling
3752 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3753 that belong to that breakpoint.
3755 @cindex pending breakpoints
3756 It's quite common to have a breakpoint inside a shared library.
3757 Shared libraries can be loaded and unloaded explicitly,
3758 and possibly repeatedly, as the program is executed. To support
3759 this use case, @value{GDBN} updates breakpoint locations whenever
3760 any shared library is loaded or unloaded. Typically, you would
3761 set a breakpoint in a shared library at the beginning of your
3762 debugging session, when the library is not loaded, and when the
3763 symbols from the library are not available. When you try to set
3764 breakpoint, @value{GDBN} will ask you if you want to set
3765 a so called @dfn{pending breakpoint}---breakpoint whose address
3766 is not yet resolved.
3768 After the program is run, whenever a new shared library is loaded,
3769 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3770 shared library contains the symbol or line referred to by some
3771 pending breakpoint, that breakpoint is resolved and becomes an
3772 ordinary breakpoint. When a library is unloaded, all breakpoints
3773 that refer to its symbols or source lines become pending again.
3775 This logic works for breakpoints with multiple locations, too. For
3776 example, if you have a breakpoint in a C@t{++} template function, and
3777 a newly loaded shared library has an instantiation of that template,
3778 a new location is added to the list of locations for the breakpoint.
3780 Except for having unresolved address, pending breakpoints do not
3781 differ from regular breakpoints. You can set conditions or commands,
3782 enable and disable them and perform other breakpoint operations.
3784 @value{GDBN} provides some additional commands for controlling what
3785 happens when the @samp{break} command cannot resolve breakpoint
3786 address specification to an address:
3788 @kindex set breakpoint pending
3789 @kindex show breakpoint pending
3791 @item set breakpoint pending auto
3792 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3793 location, it queries you whether a pending breakpoint should be created.
3795 @item set breakpoint pending on
3796 This indicates that an unrecognized breakpoint location should automatically
3797 result in a pending breakpoint being created.
3799 @item set breakpoint pending off
3800 This indicates that pending breakpoints are not to be created. Any
3801 unrecognized breakpoint location results in an error. This setting does
3802 not affect any pending breakpoints previously created.
3804 @item show breakpoint pending
3805 Show the current behavior setting for creating pending breakpoints.
3808 The settings above only affect the @code{break} command and its
3809 variants. Once breakpoint is set, it will be automatically updated
3810 as shared libraries are loaded and unloaded.
3812 @cindex automatic hardware breakpoints
3813 For some targets, @value{GDBN} can automatically decide if hardware or
3814 software breakpoints should be used, depending on whether the
3815 breakpoint address is read-only or read-write. This applies to
3816 breakpoints set with the @code{break} command as well as to internal
3817 breakpoints set by commands like @code{next} and @code{finish}. For
3818 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3821 You can control this automatic behaviour with the following commands::
3823 @kindex set breakpoint auto-hw
3824 @kindex show breakpoint auto-hw
3826 @item set breakpoint auto-hw on
3827 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3828 will try to use the target memory map to decide if software or hardware
3829 breakpoint must be used.
3831 @item set breakpoint auto-hw off
3832 This indicates @value{GDBN} should not automatically select breakpoint
3833 type. If the target provides a memory map, @value{GDBN} will warn when
3834 trying to set software breakpoint at a read-only address.
3837 @value{GDBN} normally implements breakpoints by replacing the program code
3838 at the breakpoint address with a special instruction, which, when
3839 executed, given control to the debugger. By default, the program
3840 code is so modified only when the program is resumed. As soon as
3841 the program stops, @value{GDBN} restores the original instructions. This
3842 behaviour guards against leaving breakpoints inserted in the
3843 target should gdb abrubptly disconnect. However, with slow remote
3844 targets, inserting and removing breakpoint can reduce the performance.
3845 This behavior can be controlled with the following commands::
3847 @kindex set breakpoint always-inserted
3848 @kindex show breakpoint always-inserted
3850 @item set breakpoint always-inserted off
3851 All breakpoints, including newly added by the user, are inserted in
3852 the target only when the target is resumed. All breakpoints are
3853 removed from the target when it stops. This is the default mode.
3855 @item set breakpoint always-inserted on
3856 Causes all breakpoints to be inserted in the target at all times. If
3857 the user adds a new breakpoint, or changes an existing breakpoint, the
3858 breakpoints in the target are updated immediately. A breakpoint is
3859 removed from the target only when breakpoint itself is deleted.
3862 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3863 when a breakpoint breaks. If the condition is true, then the process being
3864 debugged stops, otherwise the process is resumed.
3866 If the target supports evaluating conditions on its end, @value{GDBN} may
3867 download the breakpoint, together with its conditions, to it.
3869 This feature can be controlled via the following commands:
3871 @kindex set breakpoint condition-evaluation
3872 @kindex show breakpoint condition-evaluation
3874 @item set breakpoint condition-evaluation host
3875 This option commands @value{GDBN} to evaluate the breakpoint
3876 conditions on the host's side. Unconditional breakpoints are sent to
3877 the target which in turn receives the triggers and reports them back to GDB
3878 for condition evaluation. This is the standard evaluation mode.
3880 @item set breakpoint condition-evaluation target
3881 This option commands @value{GDBN} to download breakpoint conditions
3882 to the target at the moment of their insertion. The target
3883 is responsible for evaluating the conditional expression and reporting
3884 breakpoint stop events back to @value{GDBN} whenever the condition
3885 is true. Due to limitations of target-side evaluation, some conditions
3886 cannot be evaluated there, e.g., conditions that depend on local data
3887 that is only known to the host. Examples include
3888 conditional expressions involving convenience variables, complex types
3889 that cannot be handled by the agent expression parser and expressions
3890 that are too long to be sent over to the target, specially when the
3891 target is a remote system. In these cases, the conditions will be
3892 evaluated by @value{GDBN}.
3894 @item set breakpoint condition-evaluation auto
3895 This is the default mode. If the target supports evaluating breakpoint
3896 conditions on its end, @value{GDBN} will download breakpoint conditions to
3897 the target (limitations mentioned previously apply). If the target does
3898 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3899 to evaluating all these conditions on the host's side.
3903 @cindex negative breakpoint numbers
3904 @cindex internal @value{GDBN} breakpoints
3905 @value{GDBN} itself sometimes sets breakpoints in your program for
3906 special purposes, such as proper handling of @code{longjmp} (in C
3907 programs). These internal breakpoints are assigned negative numbers,
3908 starting with @code{-1}; @samp{info breakpoints} does not display them.
3909 You can see these breakpoints with the @value{GDBN} maintenance command
3910 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3913 @node Set Watchpoints
3914 @subsection Setting Watchpoints
3916 @cindex setting watchpoints
3917 You can use a watchpoint to stop execution whenever the value of an
3918 expression changes, without having to predict a particular place where
3919 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3920 The expression may be as simple as the value of a single variable, or
3921 as complex as many variables combined by operators. Examples include:
3925 A reference to the value of a single variable.
3928 An address cast to an appropriate data type. For example,
3929 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3930 address (assuming an @code{int} occupies 4 bytes).
3933 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3934 expression can use any operators valid in the program's native
3935 language (@pxref{Languages}).
3938 You can set a watchpoint on an expression even if the expression can
3939 not be evaluated yet. For instance, you can set a watchpoint on
3940 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3941 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3942 the expression produces a valid value. If the expression becomes
3943 valid in some other way than changing a variable (e.g.@: if the memory
3944 pointed to by @samp{*global_ptr} becomes readable as the result of a
3945 @code{malloc} call), @value{GDBN} may not stop until the next time
3946 the expression changes.
3948 @cindex software watchpoints
3949 @cindex hardware watchpoints
3950 Depending on your system, watchpoints may be implemented in software or
3951 hardware. @value{GDBN} does software watchpointing by single-stepping your
3952 program and testing the variable's value each time, which is hundreds of
3953 times slower than normal execution. (But this may still be worth it, to
3954 catch errors where you have no clue what part of your program is the
3957 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3958 x86-based targets, @value{GDBN} includes support for hardware
3959 watchpoints, which do not slow down the running of your program.
3963 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3964 Set a watchpoint for an expression. @value{GDBN} will break when the
3965 expression @var{expr} is written into by the program and its value
3966 changes. The simplest (and the most popular) use of this command is
3967 to watch the value of a single variable:
3970 (@value{GDBP}) watch foo
3973 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3974 argument, @value{GDBN} breaks only when the thread identified by
3975 @var{threadnum} changes the value of @var{expr}. If any other threads
3976 change the value of @var{expr}, @value{GDBN} will not break. Note
3977 that watchpoints restricted to a single thread in this way only work
3978 with Hardware Watchpoints.
3980 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3981 (see below). The @code{-location} argument tells @value{GDBN} to
3982 instead watch the memory referred to by @var{expr}. In this case,
3983 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3984 and watch the memory at that address. The type of the result is used
3985 to determine the size of the watched memory. If the expression's
3986 result does not have an address, then @value{GDBN} will print an
3989 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3990 of masked watchpoints, if the current architecture supports this
3991 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3992 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3993 to an address to watch. The mask specifies that some bits of an address
3994 (the bits which are reset in the mask) should be ignored when matching
3995 the address accessed by the inferior against the watchpoint address.
3996 Thus, a masked watchpoint watches many addresses simultaneously---those
3997 addresses whose unmasked bits are identical to the unmasked bits in the
3998 watchpoint address. The @code{mask} argument implies @code{-location}.
4002 (@value{GDBP}) watch foo mask 0xffff00ff
4003 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4007 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
4008 Set a watchpoint that will break when the value of @var{expr} is read
4012 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
4013 Set a watchpoint that will break when @var{expr} is either read from
4014 or written into by the program.
4016 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
4017 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
4018 This command prints a list of watchpoints, using the same format as
4019 @code{info break} (@pxref{Set Breaks}).
4022 If you watch for a change in a numerically entered address you need to
4023 dereference it, as the address itself is just a constant number which will
4024 never change. @value{GDBN} refuses to create a watchpoint that watches
4025 a never-changing value:
4028 (@value{GDBP}) watch 0x600850
4029 Cannot watch constant value 0x600850.
4030 (@value{GDBP}) watch *(int *) 0x600850
4031 Watchpoint 1: *(int *) 6293584
4034 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4035 watchpoints execute very quickly, and the debugger reports a change in
4036 value at the exact instruction where the change occurs. If @value{GDBN}
4037 cannot set a hardware watchpoint, it sets a software watchpoint, which
4038 executes more slowly and reports the change in value at the next
4039 @emph{statement}, not the instruction, after the change occurs.
4041 @cindex use only software watchpoints
4042 You can force @value{GDBN} to use only software watchpoints with the
4043 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4044 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4045 the underlying system supports them. (Note that hardware-assisted
4046 watchpoints that were set @emph{before} setting
4047 @code{can-use-hw-watchpoints} to zero will still use the hardware
4048 mechanism of watching expression values.)
4051 @item set can-use-hw-watchpoints
4052 @kindex set can-use-hw-watchpoints
4053 Set whether or not to use hardware watchpoints.
4055 @item show can-use-hw-watchpoints
4056 @kindex show can-use-hw-watchpoints
4057 Show the current mode of using hardware watchpoints.
4060 For remote targets, you can restrict the number of hardware
4061 watchpoints @value{GDBN} will use, see @ref{set remote
4062 hardware-breakpoint-limit}.
4064 When you issue the @code{watch} command, @value{GDBN} reports
4067 Hardware watchpoint @var{num}: @var{expr}
4071 if it was able to set a hardware watchpoint.
4073 Currently, the @code{awatch} and @code{rwatch} commands can only set
4074 hardware watchpoints, because accesses to data that don't change the
4075 value of the watched expression cannot be detected without examining
4076 every instruction as it is being executed, and @value{GDBN} does not do
4077 that currently. If @value{GDBN} finds that it is unable to set a
4078 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4079 will print a message like this:
4082 Expression cannot be implemented with read/access watchpoint.
4085 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4086 data type of the watched expression is wider than what a hardware
4087 watchpoint on the target machine can handle. For example, some systems
4088 can only watch regions that are up to 4 bytes wide; on such systems you
4089 cannot set hardware watchpoints for an expression that yields a
4090 double-precision floating-point number (which is typically 8 bytes
4091 wide). As a work-around, it might be possible to break the large region
4092 into a series of smaller ones and watch them with separate watchpoints.
4094 If you set too many hardware watchpoints, @value{GDBN} might be unable
4095 to insert all of them when you resume the execution of your program.
4096 Since the precise number of active watchpoints is unknown until such
4097 time as the program is about to be resumed, @value{GDBN} might not be
4098 able to warn you about this when you set the watchpoints, and the
4099 warning will be printed only when the program is resumed:
4102 Hardware watchpoint @var{num}: Could not insert watchpoint
4106 If this happens, delete or disable some of the watchpoints.
4108 Watching complex expressions that reference many variables can also
4109 exhaust the resources available for hardware-assisted watchpoints.
4110 That's because @value{GDBN} needs to watch every variable in the
4111 expression with separately allocated resources.
4113 If you call a function interactively using @code{print} or @code{call},
4114 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4115 kind of breakpoint or the call completes.
4117 @value{GDBN} automatically deletes watchpoints that watch local
4118 (automatic) variables, or expressions that involve such variables, when
4119 they go out of scope, that is, when the execution leaves the block in
4120 which these variables were defined. In particular, when the program
4121 being debugged terminates, @emph{all} local variables go out of scope,
4122 and so only watchpoints that watch global variables remain set. If you
4123 rerun the program, you will need to set all such watchpoints again. One
4124 way of doing that would be to set a code breakpoint at the entry to the
4125 @code{main} function and when it breaks, set all the watchpoints.
4127 @cindex watchpoints and threads
4128 @cindex threads and watchpoints
4129 In multi-threaded programs, watchpoints will detect changes to the
4130 watched expression from every thread.
4133 @emph{Warning:} In multi-threaded programs, software watchpoints
4134 have only limited usefulness. If @value{GDBN} creates a software
4135 watchpoint, it can only watch the value of an expression @emph{in a
4136 single thread}. If you are confident that the expression can only
4137 change due to the current thread's activity (and if you are also
4138 confident that no other thread can become current), then you can use
4139 software watchpoints as usual. However, @value{GDBN} may not notice
4140 when a non-current thread's activity changes the expression. (Hardware
4141 watchpoints, in contrast, watch an expression in all threads.)
4144 @xref{set remote hardware-watchpoint-limit}.
4146 @node Set Catchpoints
4147 @subsection Setting Catchpoints
4148 @cindex catchpoints, setting
4149 @cindex exception handlers
4150 @cindex event handling
4152 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4153 kinds of program events, such as C@t{++} exceptions or the loading of a
4154 shared library. Use the @code{catch} command to set a catchpoint.
4158 @item catch @var{event}
4159 Stop when @var{event} occurs. The @var{event} can be any of the following:
4162 @item throw @r{[}@var{regexp}@r{]}
4163 @itemx rethrow @r{[}@var{regexp}@r{]}
4164 @itemx catch @r{[}@var{regexp}@r{]}
4166 @kindex catch rethrow
4168 @cindex stop on C@t{++} exceptions
4169 The throwing, re-throwing, or catching of a C@t{++} exception.
4171 If @var{regexp} is given, then only exceptions whose type matches the
4172 regular expression will be caught.
4174 @vindex $_exception@r{, convenience variable}
4175 The convenience variable @code{$_exception} is available at an
4176 exception-related catchpoint, on some systems. This holds the
4177 exception being thrown.
4179 There are currently some limitations to C@t{++} exception handling in
4184 The support for these commands is system-dependent. Currently, only
4185 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4189 The regular expression feature and the @code{$_exception} convenience
4190 variable rely on the presence of some SDT probes in @code{libstdc++}.
4191 If these probes are not present, then these features cannot be used.
4192 These probes were first available in the GCC 4.8 release, but whether
4193 or not they are available in your GCC also depends on how it was
4197 The @code{$_exception} convenience variable is only valid at the
4198 instruction at which an exception-related catchpoint is set.
4201 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4202 location in the system library which implements runtime exception
4203 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4204 (@pxref{Selection}) to get to your code.
4207 If you call a function interactively, @value{GDBN} normally returns
4208 control to you when the function has finished executing. If the call
4209 raises an exception, however, the call may bypass the mechanism that
4210 returns control to you and cause your program either to abort or to
4211 simply continue running until it hits a breakpoint, catches a signal
4212 that @value{GDBN} is listening for, or exits. This is the case even if
4213 you set a catchpoint for the exception; catchpoints on exceptions are
4214 disabled within interactive calls. @xref{Calling}, for information on
4215 controlling this with @code{set unwind-on-terminating-exception}.
4218 You cannot raise an exception interactively.
4221 You cannot install an exception handler interactively.
4225 @kindex catch exception
4226 @cindex Ada exception catching
4227 @cindex catch Ada exceptions
4228 An Ada exception being raised. If an exception name is specified
4229 at the end of the command (eg @code{catch exception Program_Error}),
4230 the debugger will stop only when this specific exception is raised.
4231 Otherwise, the debugger stops execution when any Ada exception is raised.
4233 When inserting an exception catchpoint on a user-defined exception whose
4234 name is identical to one of the exceptions defined by the language, the
4235 fully qualified name must be used as the exception name. Otherwise,
4236 @value{GDBN} will assume that it should stop on the pre-defined exception
4237 rather than the user-defined one. For instance, assuming an exception
4238 called @code{Constraint_Error} is defined in package @code{Pck}, then
4239 the command to use to catch such exceptions is @kbd{catch exception
4240 Pck.Constraint_Error}.
4242 @item exception unhandled
4243 @kindex catch exception unhandled
4244 An exception that was raised but is not handled by the program.
4247 @kindex catch assert
4248 A failed Ada assertion.
4252 @cindex break on fork/exec
4253 A call to @code{exec}. This is currently only available for HP-UX
4257 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4258 @kindex catch syscall
4259 @cindex break on a system call.
4260 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4261 syscall is a mechanism for application programs to request a service
4262 from the operating system (OS) or one of the OS system services.
4263 @value{GDBN} can catch some or all of the syscalls issued by the
4264 debuggee, and show the related information for each syscall. If no
4265 argument is specified, calls to and returns from all system calls
4268 @var{name} can be any system call name that is valid for the
4269 underlying OS. Just what syscalls are valid depends on the OS. On
4270 GNU and Unix systems, you can find the full list of valid syscall
4271 names on @file{/usr/include/asm/unistd.h}.
4273 @c For MS-Windows, the syscall names and the corresponding numbers
4274 @c can be found, e.g., on this URL:
4275 @c http://www.metasploit.com/users/opcode/syscalls.html
4276 @c but we don't support Windows syscalls yet.
4278 Normally, @value{GDBN} knows in advance which syscalls are valid for
4279 each OS, so you can use the @value{GDBN} command-line completion
4280 facilities (@pxref{Completion,, command completion}) to list the
4283 You may also specify the system call numerically. A syscall's
4284 number is the value passed to the OS's syscall dispatcher to
4285 identify the requested service. When you specify the syscall by its
4286 name, @value{GDBN} uses its database of syscalls to convert the name
4287 into the corresponding numeric code, but using the number directly
4288 may be useful if @value{GDBN}'s database does not have the complete
4289 list of syscalls on your system (e.g., because @value{GDBN} lags
4290 behind the OS upgrades).
4292 The example below illustrates how this command works if you don't provide
4296 (@value{GDBP}) catch syscall
4297 Catchpoint 1 (syscall)
4299 Starting program: /tmp/catch-syscall
4301 Catchpoint 1 (call to syscall 'close'), \
4302 0xffffe424 in __kernel_vsyscall ()
4306 Catchpoint 1 (returned from syscall 'close'), \
4307 0xffffe424 in __kernel_vsyscall ()
4311 Here is an example of catching a system call by name:
4314 (@value{GDBP}) catch syscall chroot
4315 Catchpoint 1 (syscall 'chroot' [61])
4317 Starting program: /tmp/catch-syscall
4319 Catchpoint 1 (call to syscall 'chroot'), \
4320 0xffffe424 in __kernel_vsyscall ()
4324 Catchpoint 1 (returned from syscall 'chroot'), \
4325 0xffffe424 in __kernel_vsyscall ()
4329 An example of specifying a system call numerically. In the case
4330 below, the syscall number has a corresponding entry in the XML
4331 file, so @value{GDBN} finds its name and prints it:
4334 (@value{GDBP}) catch syscall 252
4335 Catchpoint 1 (syscall(s) 'exit_group')
4337 Starting program: /tmp/catch-syscall
4339 Catchpoint 1 (call to syscall 'exit_group'), \
4340 0xffffe424 in __kernel_vsyscall ()
4344 Program exited normally.
4348 However, there can be situations when there is no corresponding name
4349 in XML file for that syscall number. In this case, @value{GDBN} prints
4350 a warning message saying that it was not able to find the syscall name,
4351 but the catchpoint will be set anyway. See the example below:
4354 (@value{GDBP}) catch syscall 764
4355 warning: The number '764' does not represent a known syscall.
4356 Catchpoint 2 (syscall 764)
4360 If you configure @value{GDBN} using the @samp{--without-expat} option,
4361 it will not be able to display syscall names. Also, if your
4362 architecture does not have an XML file describing its system calls,
4363 you will not be able to see the syscall names. It is important to
4364 notice that these two features are used for accessing the syscall
4365 name database. In either case, you will see a warning like this:
4368 (@value{GDBP}) catch syscall
4369 warning: Could not open "syscalls/i386-linux.xml"
4370 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4371 GDB will not be able to display syscall names.
4372 Catchpoint 1 (syscall)
4376 Of course, the file name will change depending on your architecture and system.
4378 Still using the example above, you can also try to catch a syscall by its
4379 number. In this case, you would see something like:
4382 (@value{GDBP}) catch syscall 252
4383 Catchpoint 1 (syscall(s) 252)
4386 Again, in this case @value{GDBN} would not be able to display syscall's names.
4390 A call to @code{fork}. This is currently only available for HP-UX
4395 A call to @code{vfork}. This is currently only available for HP-UX
4398 @item load @r{[}regexp@r{]}
4399 @itemx unload @r{[}regexp@r{]}
4401 @kindex catch unload
4402 The loading or unloading of a shared library. If @var{regexp} is
4403 given, then the catchpoint will stop only if the regular expression
4404 matches one of the affected libraries.
4406 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4407 @kindex catch signal
4408 The delivery of a signal.
4410 With no arguments, this catchpoint will catch any signal that is not
4411 used internally by @value{GDBN}, specifically, all signals except
4412 @samp{SIGTRAP} and @samp{SIGINT}.
4414 With the argument @samp{all}, all signals, including those used by
4415 @value{GDBN}, will be caught. This argument cannot be used with other
4418 Otherwise, the arguments are a list of signal names as given to
4419 @code{handle} (@pxref{Signals}). Only signals specified in this list
4422 One reason that @code{catch signal} can be more useful than
4423 @code{handle} is that you can attach commands and conditions to the
4426 When a signal is caught by a catchpoint, the signal's @code{stop} and
4427 @code{print} settings, as specified by @code{handle}, are ignored.
4428 However, whether the signal is still delivered to the inferior depends
4429 on the @code{pass} setting; this can be changed in the catchpoint's
4434 @item tcatch @var{event}
4436 Set a catchpoint that is enabled only for one stop. The catchpoint is
4437 automatically deleted after the first time the event is caught.
4441 Use the @code{info break} command to list the current catchpoints.
4445 @subsection Deleting Breakpoints
4447 @cindex clearing breakpoints, watchpoints, catchpoints
4448 @cindex deleting breakpoints, watchpoints, catchpoints
4449 It is often necessary to eliminate a breakpoint, watchpoint, or
4450 catchpoint once it has done its job and you no longer want your program
4451 to stop there. This is called @dfn{deleting} the breakpoint. A
4452 breakpoint that has been deleted no longer exists; it is forgotten.
4454 With the @code{clear} command you can delete breakpoints according to
4455 where they are in your program. With the @code{delete} command you can
4456 delete individual breakpoints, watchpoints, or catchpoints by specifying
4457 their breakpoint numbers.
4459 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4460 automatically ignores breakpoints on the first instruction to be executed
4461 when you continue execution without changing the execution address.
4466 Delete any breakpoints at the next instruction to be executed in the
4467 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4468 the innermost frame is selected, this is a good way to delete a
4469 breakpoint where your program just stopped.
4471 @item clear @var{location}
4472 Delete any breakpoints set at the specified @var{location}.
4473 @xref{Specify Location}, for the various forms of @var{location}; the
4474 most useful ones are listed below:
4477 @item clear @var{function}
4478 @itemx clear @var{filename}:@var{function}
4479 Delete any breakpoints set at entry to the named @var{function}.
4481 @item clear @var{linenum}
4482 @itemx clear @var{filename}:@var{linenum}
4483 Delete any breakpoints set at or within the code of the specified
4484 @var{linenum} of the specified @var{filename}.
4487 @cindex delete breakpoints
4489 @kindex d @r{(@code{delete})}
4490 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4491 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4492 ranges specified as arguments. If no argument is specified, delete all
4493 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4494 confirm off}). You can abbreviate this command as @code{d}.
4498 @subsection Disabling Breakpoints
4500 @cindex enable/disable a breakpoint
4501 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4502 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4503 it had been deleted, but remembers the information on the breakpoint so
4504 that you can @dfn{enable} it again later.
4506 You disable and enable breakpoints, watchpoints, and catchpoints with
4507 the @code{enable} and @code{disable} commands, optionally specifying
4508 one or more breakpoint numbers as arguments. Use @code{info break} to
4509 print a list of all breakpoints, watchpoints, and catchpoints if you
4510 do not know which numbers to use.
4512 Disabling and enabling a breakpoint that has multiple locations
4513 affects all of its locations.
4515 A breakpoint, watchpoint, or catchpoint can have any of several
4516 different states of enablement:
4520 Enabled. The breakpoint stops your program. A breakpoint set
4521 with the @code{break} command starts out in this state.
4523 Disabled. The breakpoint has no effect on your program.
4525 Enabled once. The breakpoint stops your program, but then becomes
4528 Enabled for a count. The breakpoint stops your program for the next
4529 N times, then becomes disabled.
4531 Enabled for deletion. The breakpoint stops your program, but
4532 immediately after it does so it is deleted permanently. A breakpoint
4533 set with the @code{tbreak} command starts out in this state.
4536 You can use the following commands to enable or disable breakpoints,
4537 watchpoints, and catchpoints:
4541 @kindex dis @r{(@code{disable})}
4542 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4543 Disable the specified breakpoints---or all breakpoints, if none are
4544 listed. A disabled breakpoint has no effect but is not forgotten. All
4545 options such as ignore-counts, conditions and commands are remembered in
4546 case the breakpoint is enabled again later. You may abbreviate
4547 @code{disable} as @code{dis}.
4550 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4551 Enable the specified breakpoints (or all defined breakpoints). They
4552 become effective once again in stopping your program.
4554 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4555 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4556 of these breakpoints immediately after stopping your program.
4558 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4559 Enable the specified breakpoints temporarily. @value{GDBN} records
4560 @var{count} with each of the specified breakpoints, and decrements a
4561 breakpoint's count when it is hit. When any count reaches 0,
4562 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4563 count (@pxref{Conditions, ,Break Conditions}), that will be
4564 decremented to 0 before @var{count} is affected.
4566 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4567 Enable the specified breakpoints to work once, then die. @value{GDBN}
4568 deletes any of these breakpoints as soon as your program stops there.
4569 Breakpoints set by the @code{tbreak} command start out in this state.
4572 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4573 @c confusing: tbreak is also initially enabled.
4574 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4575 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4576 subsequently, they become disabled or enabled only when you use one of
4577 the commands above. (The command @code{until} can set and delete a
4578 breakpoint of its own, but it does not change the state of your other
4579 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4583 @subsection Break Conditions
4584 @cindex conditional breakpoints
4585 @cindex breakpoint conditions
4587 @c FIXME what is scope of break condition expr? Context where wanted?
4588 @c in particular for a watchpoint?
4589 The simplest sort of breakpoint breaks every time your program reaches a
4590 specified place. You can also specify a @dfn{condition} for a
4591 breakpoint. A condition is just a Boolean expression in your
4592 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4593 a condition evaluates the expression each time your program reaches it,
4594 and your program stops only if the condition is @emph{true}.
4596 This is the converse of using assertions for program validation; in that
4597 situation, you want to stop when the assertion is violated---that is,
4598 when the condition is false. In C, if you want to test an assertion expressed
4599 by the condition @var{assert}, you should set the condition
4600 @samp{! @var{assert}} on the appropriate breakpoint.
4602 Conditions are also accepted for watchpoints; you may not need them,
4603 since a watchpoint is inspecting the value of an expression anyhow---but
4604 it might be simpler, say, to just set a watchpoint on a variable name,
4605 and specify a condition that tests whether the new value is an interesting
4608 Break conditions can have side effects, and may even call functions in
4609 your program. This can be useful, for example, to activate functions
4610 that log program progress, or to use your own print functions to
4611 format special data structures. The effects are completely predictable
4612 unless there is another enabled breakpoint at the same address. (In
4613 that case, @value{GDBN} might see the other breakpoint first and stop your
4614 program without checking the condition of this one.) Note that
4615 breakpoint commands are usually more convenient and flexible than break
4617 purpose of performing side effects when a breakpoint is reached
4618 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4620 Breakpoint conditions can also be evaluated on the target's side if
4621 the target supports it. Instead of evaluating the conditions locally,
4622 @value{GDBN} encodes the expression into an agent expression
4623 (@pxref{Agent Expressions}) suitable for execution on the target,
4624 independently of @value{GDBN}. Global variables become raw memory
4625 locations, locals become stack accesses, and so forth.
4627 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4628 when its condition evaluates to true. This mechanism may provide faster
4629 response times depending on the performance characteristics of the target
4630 since it does not need to keep @value{GDBN} informed about
4631 every breakpoint trigger, even those with false conditions.
4633 Break conditions can be specified when a breakpoint is set, by using
4634 @samp{if} in the arguments to the @code{break} command. @xref{Set
4635 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4636 with the @code{condition} command.
4638 You can also use the @code{if} keyword with the @code{watch} command.
4639 The @code{catch} command does not recognize the @code{if} keyword;
4640 @code{condition} is the only way to impose a further condition on a
4645 @item condition @var{bnum} @var{expression}
4646 Specify @var{expression} as the break condition for breakpoint,
4647 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4648 breakpoint @var{bnum} stops your program only if the value of
4649 @var{expression} is true (nonzero, in C). When you use
4650 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4651 syntactic correctness, and to determine whether symbols in it have
4652 referents in the context of your breakpoint. If @var{expression} uses
4653 symbols not referenced in the context of the breakpoint, @value{GDBN}
4654 prints an error message:
4657 No symbol "foo" in current context.
4662 not actually evaluate @var{expression} at the time the @code{condition}
4663 command (or a command that sets a breakpoint with a condition, like
4664 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4666 @item condition @var{bnum}
4667 Remove the condition from breakpoint number @var{bnum}. It becomes
4668 an ordinary unconditional breakpoint.
4671 @cindex ignore count (of breakpoint)
4672 A special case of a breakpoint condition is to stop only when the
4673 breakpoint has been reached a certain number of times. This is so
4674 useful that there is a special way to do it, using the @dfn{ignore
4675 count} of the breakpoint. Every breakpoint has an ignore count, which
4676 is an integer. Most of the time, the ignore count is zero, and
4677 therefore has no effect. But if your program reaches a breakpoint whose
4678 ignore count is positive, then instead of stopping, it just decrements
4679 the ignore count by one and continues. As a result, if the ignore count
4680 value is @var{n}, the breakpoint does not stop the next @var{n} times
4681 your program reaches it.
4685 @item ignore @var{bnum} @var{count}
4686 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4687 The next @var{count} times the breakpoint is reached, your program's
4688 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4691 To make the breakpoint stop the next time it is reached, specify
4694 When you use @code{continue} to resume execution of your program from a
4695 breakpoint, you can specify an ignore count directly as an argument to
4696 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4697 Stepping,,Continuing and Stepping}.
4699 If a breakpoint has a positive ignore count and a condition, the
4700 condition is not checked. Once the ignore count reaches zero,
4701 @value{GDBN} resumes checking the condition.
4703 You could achieve the effect of the ignore count with a condition such
4704 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4705 is decremented each time. @xref{Convenience Vars, ,Convenience
4709 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4712 @node Break Commands
4713 @subsection Breakpoint Command Lists
4715 @cindex breakpoint commands
4716 You can give any breakpoint (or watchpoint or catchpoint) a series of
4717 commands to execute when your program stops due to that breakpoint. For
4718 example, you might want to print the values of certain expressions, or
4719 enable other breakpoints.
4723 @kindex end@r{ (breakpoint commands)}
4724 @item commands @r{[}@var{range}@dots{}@r{]}
4725 @itemx @dots{} @var{command-list} @dots{}
4727 Specify a list of commands for the given breakpoints. The commands
4728 themselves appear on the following lines. Type a line containing just
4729 @code{end} to terminate the commands.
4731 To remove all commands from a breakpoint, type @code{commands} and
4732 follow it immediately with @code{end}; that is, give no commands.
4734 With no argument, @code{commands} refers to the last breakpoint,
4735 watchpoint, or catchpoint set (not to the breakpoint most recently
4736 encountered). If the most recent breakpoints were set with a single
4737 command, then the @code{commands} will apply to all the breakpoints
4738 set by that command. This applies to breakpoints set by
4739 @code{rbreak}, and also applies when a single @code{break} command
4740 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4744 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4745 disabled within a @var{command-list}.
4747 You can use breakpoint commands to start your program up again. Simply
4748 use the @code{continue} command, or @code{step}, or any other command
4749 that resumes execution.
4751 Any other commands in the command list, after a command that resumes
4752 execution, are ignored. This is because any time you resume execution
4753 (even with a simple @code{next} or @code{step}), you may encounter
4754 another breakpoint---which could have its own command list, leading to
4755 ambiguities about which list to execute.
4758 If the first command you specify in a command list is @code{silent}, the
4759 usual message about stopping at a breakpoint is not printed. This may
4760 be desirable for breakpoints that are to print a specific message and
4761 then continue. If none of the remaining commands print anything, you
4762 see no sign that the breakpoint was reached. @code{silent} is
4763 meaningful only at the beginning of a breakpoint command list.
4765 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4766 print precisely controlled output, and are often useful in silent
4767 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4769 For example, here is how you could use breakpoint commands to print the
4770 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4776 printf "x is %d\n",x
4781 One application for breakpoint commands is to compensate for one bug so
4782 you can test for another. Put a breakpoint just after the erroneous line
4783 of code, give it a condition to detect the case in which something
4784 erroneous has been done, and give it commands to assign correct values
4785 to any variables that need them. End with the @code{continue} command
4786 so that your program does not stop, and start with the @code{silent}
4787 command so that no output is produced. Here is an example:
4798 @node Dynamic Printf
4799 @subsection Dynamic Printf
4801 @cindex dynamic printf
4803 The dynamic printf command @code{dprintf} combines a breakpoint with
4804 formatted printing of your program's data to give you the effect of
4805 inserting @code{printf} calls into your program on-the-fly, without
4806 having to recompile it.
4808 In its most basic form, the output goes to the GDB console. However,
4809 you can set the variable @code{dprintf-style} for alternate handling.
4810 For instance, you can ask to format the output by calling your
4811 program's @code{printf} function. This has the advantage that the
4812 characters go to the program's output device, so they can recorded in
4813 redirects to files and so forth.
4815 If you are doing remote debugging with a stub or agent, you can also
4816 ask to have the printf handled by the remote agent. In addition to
4817 ensuring that the output goes to the remote program's device along
4818 with any other output the program might produce, you can also ask that
4819 the dprintf remain active even after disconnecting from the remote
4820 target. Using the stub/agent is also more efficient, as it can do
4821 everything without needing to communicate with @value{GDBN}.
4825 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4826 Whenever execution reaches @var{location}, print the values of one or
4827 more @var{expressions} under the control of the string @var{template}.
4828 To print several values, separate them with commas.
4830 @item set dprintf-style @var{style}
4831 Set the dprintf output to be handled in one of several different
4832 styles enumerated below. A change of style affects all existing
4833 dynamic printfs immediately. (If you need individual control over the
4834 print commands, simply define normal breakpoints with
4835 explicitly-supplied command lists.)
4838 @kindex dprintf-style gdb
4839 Handle the output using the @value{GDBN} @code{printf} command.
4842 @kindex dprintf-style call
4843 Handle the output by calling a function in your program (normally
4847 @kindex dprintf-style agent
4848 Have the remote debugging agent (such as @code{gdbserver}) handle
4849 the output itself. This style is only available for agents that
4850 support running commands on the target.
4852 @item set dprintf-function @var{function}
4853 Set the function to call if the dprintf style is @code{call}. By
4854 default its value is @code{printf}. You may set it to any expression.
4855 that @value{GDBN} can evaluate to a function, as per the @code{call}
4858 @item set dprintf-channel @var{channel}
4859 Set a ``channel'' for dprintf. If set to a non-empty value,
4860 @value{GDBN} will evaluate it as an expression and pass the result as
4861 a first argument to the @code{dprintf-function}, in the manner of
4862 @code{fprintf} and similar functions. Otherwise, the dprintf format
4863 string will be the first argument, in the manner of @code{printf}.
4865 As an example, if you wanted @code{dprintf} output to go to a logfile
4866 that is a standard I/O stream assigned to the variable @code{mylog},
4867 you could do the following:
4870 (gdb) set dprintf-style call
4871 (gdb) set dprintf-function fprintf
4872 (gdb) set dprintf-channel mylog
4873 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4874 Dprintf 1 at 0x123456: file main.c, line 25.
4876 1 dprintf keep y 0x00123456 in main at main.c:25
4877 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
4882 Note that the @code{info break} displays the dynamic printf commands
4883 as normal breakpoint commands; you can thus easily see the effect of
4884 the variable settings.
4886 @item set disconnected-dprintf on
4887 @itemx set disconnected-dprintf off
4888 @kindex set disconnected-dprintf
4889 Choose whether @code{dprintf} commands should continue to run if
4890 @value{GDBN} has disconnected from the target. This only applies
4891 if the @code{dprintf-style} is @code{agent}.
4893 @item show disconnected-dprintf off
4894 @kindex show disconnected-dprintf
4895 Show the current choice for disconnected @code{dprintf}.
4899 @value{GDBN} does not check the validity of function and channel,
4900 relying on you to supply values that are meaningful for the contexts
4901 in which they are being used. For instance, the function and channel
4902 may be the values of local variables, but if that is the case, then
4903 all enabled dynamic prints must be at locations within the scope of
4904 those locals. If evaluation fails, @value{GDBN} will report an error.
4906 @node Save Breakpoints
4907 @subsection How to save breakpoints to a file
4909 To save breakpoint definitions to a file use the @w{@code{save
4910 breakpoints}} command.
4913 @kindex save breakpoints
4914 @cindex save breakpoints to a file for future sessions
4915 @item save breakpoints [@var{filename}]
4916 This command saves all current breakpoint definitions together with
4917 their commands and ignore counts, into a file @file{@var{filename}}
4918 suitable for use in a later debugging session. This includes all
4919 types of breakpoints (breakpoints, watchpoints, catchpoints,
4920 tracepoints). To read the saved breakpoint definitions, use the
4921 @code{source} command (@pxref{Command Files}). Note that watchpoints
4922 with expressions involving local variables may fail to be recreated
4923 because it may not be possible to access the context where the
4924 watchpoint is valid anymore. Because the saved breakpoint definitions
4925 are simply a sequence of @value{GDBN} commands that recreate the
4926 breakpoints, you can edit the file in your favorite editing program,
4927 and remove the breakpoint definitions you're not interested in, or
4928 that can no longer be recreated.
4931 @node Static Probe Points
4932 @subsection Static Probe Points
4934 @cindex static probe point, SystemTap
4935 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
4936 for Statically Defined Tracing, and the probes are designed to have a tiny
4937 runtime code and data footprint, and no dynamic relocations. They are
4938 usable from assembly, C and C@t{++} languages. See
4939 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
4940 for a good reference on how the @acronym{SDT} probes are implemented.
4942 Currently, @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
4943 @acronym{SDT} probes are supported on ELF-compatible systems. See
4944 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
4945 for more information on how to add @code{SystemTap} @acronym{SDT} probes
4946 in your applications.
4948 @cindex semaphores on static probe points
4949 Some probes have an associated semaphore variable; for instance, this
4950 happens automatically if you defined your probe using a DTrace-style
4951 @file{.d} file. If your probe has a semaphore, @value{GDBN} will
4952 automatically enable it when you specify a breakpoint using the
4953 @samp{-probe-stap} notation. But, if you put a breakpoint at a probe's
4954 location by some other method (e.g., @code{break file:line}), then
4955 @value{GDBN} will not automatically set the semaphore.
4957 You can examine the available static static probes using @code{info
4958 probes}, with optional arguments:
4962 @item info probes stap @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
4963 If given, @var{provider} is a regular expression used to match against provider
4964 names when selecting which probes to list. If omitted, probes by all
4965 probes from all providers are listed.
4967 If given, @var{name} is a regular expression to match against probe names
4968 when selecting which probes to list. If omitted, probe names are not
4969 considered when deciding whether to display them.
4971 If given, @var{objfile} is a regular expression used to select which
4972 object files (executable or shared libraries) to examine. If not
4973 given, all object files are considered.
4975 @item info probes all
4976 List the available static probes, from all types.
4979 @vindex $_probe_arg@r{, convenience variable}
4980 A probe may specify up to twelve arguments. These are available at the
4981 point at which the probe is defined---that is, when the current PC is
4982 at the probe's location. The arguments are available using the
4983 convenience variables (@pxref{Convenience Vars})
4984 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. Each probe argument is
4985 an integer of the appropriate size; types are not preserved. The
4986 convenience variable @code{$_probe_argc} holds the number of arguments
4987 at the current probe point.
4989 These variables are always available, but attempts to access them at
4990 any location other than a probe point will cause @value{GDBN} to give
4994 @c @ifclear BARETARGET
4995 @node Error in Breakpoints
4996 @subsection ``Cannot insert breakpoints''
4998 If you request too many active hardware-assisted breakpoints and
4999 watchpoints, you will see this error message:
5001 @c FIXME: the precise wording of this message may change; the relevant
5002 @c source change is not committed yet (Sep 3, 1999).
5004 Stopped; cannot insert breakpoints.
5005 You may have requested too many hardware breakpoints and watchpoints.
5009 This message is printed when you attempt to resume the program, since
5010 only then @value{GDBN} knows exactly how many hardware breakpoints and
5011 watchpoints it needs to insert.
5013 When this message is printed, you need to disable or remove some of the
5014 hardware-assisted breakpoints and watchpoints, and then continue.
5016 @node Breakpoint-related Warnings
5017 @subsection ``Breakpoint address adjusted...''
5018 @cindex breakpoint address adjusted
5020 Some processor architectures place constraints on the addresses at
5021 which breakpoints may be placed. For architectures thus constrained,
5022 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5023 with the constraints dictated by the architecture.
5025 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5026 a VLIW architecture in which a number of RISC-like instructions may be
5027 bundled together for parallel execution. The FR-V architecture
5028 constrains the location of a breakpoint instruction within such a
5029 bundle to the instruction with the lowest address. @value{GDBN}
5030 honors this constraint by adjusting a breakpoint's address to the
5031 first in the bundle.
5033 It is not uncommon for optimized code to have bundles which contain
5034 instructions from different source statements, thus it may happen that
5035 a breakpoint's address will be adjusted from one source statement to
5036 another. Since this adjustment may significantly alter @value{GDBN}'s
5037 breakpoint related behavior from what the user expects, a warning is
5038 printed when the breakpoint is first set and also when the breakpoint
5041 A warning like the one below is printed when setting a breakpoint
5042 that's been subject to address adjustment:
5045 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5048 Such warnings are printed both for user settable and @value{GDBN}'s
5049 internal breakpoints. If you see one of these warnings, you should
5050 verify that a breakpoint set at the adjusted address will have the
5051 desired affect. If not, the breakpoint in question may be removed and
5052 other breakpoints may be set which will have the desired behavior.
5053 E.g., it may be sufficient to place the breakpoint at a later
5054 instruction. A conditional breakpoint may also be useful in some
5055 cases to prevent the breakpoint from triggering too often.
5057 @value{GDBN} will also issue a warning when stopping at one of these
5058 adjusted breakpoints:
5061 warning: Breakpoint 1 address previously adjusted from 0x00010414
5065 When this warning is encountered, it may be too late to take remedial
5066 action except in cases where the breakpoint is hit earlier or more
5067 frequently than expected.
5069 @node Continuing and Stepping
5070 @section Continuing and Stepping
5074 @cindex resuming execution
5075 @dfn{Continuing} means resuming program execution until your program
5076 completes normally. In contrast, @dfn{stepping} means executing just
5077 one more ``step'' of your program, where ``step'' may mean either one
5078 line of source code, or one machine instruction (depending on what
5079 particular command you use). Either when continuing or when stepping,
5080 your program may stop even sooner, due to a breakpoint or a signal. (If
5081 it stops due to a signal, you may want to use @code{handle}, or use
5082 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5083 or you may step into the signal's handler (@pxref{stepping and signal
5088 @kindex c @r{(@code{continue})}
5089 @kindex fg @r{(resume foreground execution)}
5090 @item continue @r{[}@var{ignore-count}@r{]}
5091 @itemx c @r{[}@var{ignore-count}@r{]}
5092 @itemx fg @r{[}@var{ignore-count}@r{]}
5093 Resume program execution, at the address where your program last stopped;
5094 any breakpoints set at that address are bypassed. The optional argument
5095 @var{ignore-count} allows you to specify a further number of times to
5096 ignore a breakpoint at this location; its effect is like that of
5097 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5099 The argument @var{ignore-count} is meaningful only when your program
5100 stopped due to a breakpoint. At other times, the argument to
5101 @code{continue} is ignored.
5103 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5104 debugged program is deemed to be the foreground program) are provided
5105 purely for convenience, and have exactly the same behavior as
5109 To resume execution at a different place, you can use @code{return}
5110 (@pxref{Returning, ,Returning from a Function}) to go back to the
5111 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5112 Different Address}) to go to an arbitrary location in your program.
5114 A typical technique for using stepping is to set a breakpoint
5115 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5116 beginning of the function or the section of your program where a problem
5117 is believed to lie, run your program until it stops at that breakpoint,
5118 and then step through the suspect area, examining the variables that are
5119 interesting, until you see the problem happen.
5123 @kindex s @r{(@code{step})}
5125 Continue running your program until control reaches a different source
5126 line, then stop it and return control to @value{GDBN}. This command is
5127 abbreviated @code{s}.
5130 @c "without debugging information" is imprecise; actually "without line
5131 @c numbers in the debugging information". (gcc -g1 has debugging info but
5132 @c not line numbers). But it seems complex to try to make that
5133 @c distinction here.
5134 @emph{Warning:} If you use the @code{step} command while control is
5135 within a function that was compiled without debugging information,
5136 execution proceeds until control reaches a function that does have
5137 debugging information. Likewise, it will not step into a function which
5138 is compiled without debugging information. To step through functions
5139 without debugging information, use the @code{stepi} command, described
5143 The @code{step} command only stops at the first instruction of a source
5144 line. This prevents the multiple stops that could otherwise occur in
5145 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5146 to stop if a function that has debugging information is called within
5147 the line. In other words, @code{step} @emph{steps inside} any functions
5148 called within the line.
5150 Also, the @code{step} command only enters a function if there is line
5151 number information for the function. Otherwise it acts like the
5152 @code{next} command. This avoids problems when using @code{cc -gl}
5153 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5154 was any debugging information about the routine.
5156 @item step @var{count}
5157 Continue running as in @code{step}, but do so @var{count} times. If a
5158 breakpoint is reached, or a signal not related to stepping occurs before
5159 @var{count} steps, stepping stops right away.
5162 @kindex n @r{(@code{next})}
5163 @item next @r{[}@var{count}@r{]}
5164 Continue to the next source line in the current (innermost) stack frame.
5165 This is similar to @code{step}, but function calls that appear within
5166 the line of code are executed without stopping. Execution stops when
5167 control reaches a different line of code at the original stack level
5168 that was executing when you gave the @code{next} command. This command
5169 is abbreviated @code{n}.
5171 An argument @var{count} is a repeat count, as for @code{step}.
5174 @c FIX ME!! Do we delete this, or is there a way it fits in with
5175 @c the following paragraph? --- Vctoria
5177 @c @code{next} within a function that lacks debugging information acts like
5178 @c @code{step}, but any function calls appearing within the code of the
5179 @c function are executed without stopping.
5181 The @code{next} command only stops at the first instruction of a
5182 source line. This prevents multiple stops that could otherwise occur in
5183 @code{switch} statements, @code{for} loops, etc.
5185 @kindex set step-mode
5187 @cindex functions without line info, and stepping
5188 @cindex stepping into functions with no line info
5189 @itemx set step-mode on
5190 The @code{set step-mode on} command causes the @code{step} command to
5191 stop at the first instruction of a function which contains no debug line
5192 information rather than stepping over it.
5194 This is useful in cases where you may be interested in inspecting the
5195 machine instructions of a function which has no symbolic info and do not
5196 want @value{GDBN} to automatically skip over this function.
5198 @item set step-mode off
5199 Causes the @code{step} command to step over any functions which contains no
5200 debug information. This is the default.
5202 @item show step-mode
5203 Show whether @value{GDBN} will stop in or step over functions without
5204 source line debug information.
5207 @kindex fin @r{(@code{finish})}
5209 Continue running until just after function in the selected stack frame
5210 returns. Print the returned value (if any). This command can be
5211 abbreviated as @code{fin}.
5213 Contrast this with the @code{return} command (@pxref{Returning,
5214 ,Returning from a Function}).
5217 @kindex u @r{(@code{until})}
5218 @cindex run until specified location
5221 Continue running until a source line past the current line, in the
5222 current stack frame, is reached. This command is used to avoid single
5223 stepping through a loop more than once. It is like the @code{next}
5224 command, except that when @code{until} encounters a jump, it
5225 automatically continues execution until the program counter is greater
5226 than the address of the jump.
5228 This means that when you reach the end of a loop after single stepping
5229 though it, @code{until} makes your program continue execution until it
5230 exits the loop. In contrast, a @code{next} command at the end of a loop
5231 simply steps back to the beginning of the loop, which forces you to step
5232 through the next iteration.
5234 @code{until} always stops your program if it attempts to exit the current
5237 @code{until} may produce somewhat counterintuitive results if the order
5238 of machine code does not match the order of the source lines. For
5239 example, in the following excerpt from a debugging session, the @code{f}
5240 (@code{frame}) command shows that execution is stopped at line
5241 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5245 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5247 (@value{GDBP}) until
5248 195 for ( ; argc > 0; NEXTARG) @{
5251 This happened because, for execution efficiency, the compiler had
5252 generated code for the loop closure test at the end, rather than the
5253 start, of the loop---even though the test in a C @code{for}-loop is
5254 written before the body of the loop. The @code{until} command appeared
5255 to step back to the beginning of the loop when it advanced to this
5256 expression; however, it has not really gone to an earlier
5257 statement---not in terms of the actual machine code.
5259 @code{until} with no argument works by means of single
5260 instruction stepping, and hence is slower than @code{until} with an
5263 @item until @var{location}
5264 @itemx u @var{location}
5265 Continue running your program until either the specified @var{location} is
5266 reached, or the current stack frame returns. The location is any of
5267 the forms described in @ref{Specify Location}.
5268 This form of the command uses temporary breakpoints, and
5269 hence is quicker than @code{until} without an argument. The specified
5270 location is actually reached only if it is in the current frame. This
5271 implies that @code{until} can be used to skip over recursive function
5272 invocations. For instance in the code below, if the current location is
5273 line @code{96}, issuing @code{until 99} will execute the program up to
5274 line @code{99} in the same invocation of factorial, i.e., after the inner
5275 invocations have returned.
5278 94 int factorial (int value)
5280 96 if (value > 1) @{
5281 97 value *= factorial (value - 1);
5288 @kindex advance @var{location}
5289 @item advance @var{location}
5290 Continue running the program up to the given @var{location}. An argument is
5291 required, which should be of one of the forms described in
5292 @ref{Specify Location}.
5293 Execution will also stop upon exit from the current stack
5294 frame. This command is similar to @code{until}, but @code{advance} will
5295 not skip over recursive function calls, and the target location doesn't
5296 have to be in the same frame as the current one.
5300 @kindex si @r{(@code{stepi})}
5302 @itemx stepi @var{arg}
5304 Execute one machine instruction, then stop and return to the debugger.
5306 It is often useful to do @samp{display/i $pc} when stepping by machine
5307 instructions. This makes @value{GDBN} automatically display the next
5308 instruction to be executed, each time your program stops. @xref{Auto
5309 Display,, Automatic Display}.
5311 An argument is a repeat count, as in @code{step}.
5315 @kindex ni @r{(@code{nexti})}
5317 @itemx nexti @var{arg}
5319 Execute one machine instruction, but if it is a function call,
5320 proceed until the function returns.
5322 An argument is a repeat count, as in @code{next}.
5326 @anchor{range stepping}
5327 @cindex range stepping
5328 @cindex target-assisted range stepping
5329 By default, and if available, @value{GDBN} makes use of
5330 target-assisted @dfn{range stepping}. In other words, whenever you
5331 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5332 tells the target to step the corresponding range of instruction
5333 addresses instead of issuing multiple single-steps. This speeds up
5334 line stepping, particularly for remote targets. Ideally, there should
5335 be no reason you would want to turn range stepping off. However, it's
5336 possible that a bug in the debug info, a bug in the remote stub (for
5337 remote targets), or even a bug in @value{GDBN} could make line
5338 stepping behave incorrectly when target-assisted range stepping is
5339 enabled. You can use the following command to turn off range stepping
5343 @kindex set range-stepping
5344 @kindex show range-stepping
5345 @item set range-stepping
5346 @itemx show range-stepping
5347 Control whether range stepping is enabled.
5349 If @code{on}, and the target supports it, @value{GDBN} tells the
5350 target to step a range of addresses itself, instead of issuing
5351 multiple single-steps. If @code{off}, @value{GDBN} always issues
5352 single-steps, even if range stepping is supported by the target. The
5353 default is @code{on}.
5357 @node Skipping Over Functions and Files
5358 @section Skipping Over Functions and Files
5359 @cindex skipping over functions and files
5361 The program you are debugging may contain some functions which are
5362 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
5363 skip a function or all functions in a file when stepping.
5365 For example, consider the following C function:
5376 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5377 are not interested in stepping through @code{boring}. If you run @code{step}
5378 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5379 step over both @code{foo} and @code{boring}!
5381 One solution is to @code{step} into @code{boring} and use the @code{finish}
5382 command to immediately exit it. But this can become tedious if @code{boring}
5383 is called from many places.
5385 A more flexible solution is to execute @kbd{skip boring}. This instructs
5386 @value{GDBN} never to step into @code{boring}. Now when you execute
5387 @code{step} at line 103, you'll step over @code{boring} and directly into
5390 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5391 example, @code{skip file boring.c}.
5394 @kindex skip function
5395 @item skip @r{[}@var{linespec}@r{]}
5396 @itemx skip function @r{[}@var{linespec}@r{]}
5397 After running this command, the function named by @var{linespec} or the
5398 function containing the line named by @var{linespec} will be skipped over when
5399 stepping. @xref{Specify Location}.
5401 If you do not specify @var{linespec}, the function you're currently debugging
5404 (If you have a function called @code{file} that you want to skip, use
5405 @kbd{skip function file}.)
5408 @item skip file @r{[}@var{filename}@r{]}
5409 After running this command, any function whose source lives in @var{filename}
5410 will be skipped over when stepping.
5412 If you do not specify @var{filename}, functions whose source lives in the file
5413 you're currently debugging will be skipped.
5416 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5417 These are the commands for managing your list of skips:
5421 @item info skip @r{[}@var{range}@r{]}
5422 Print details about the specified skip(s). If @var{range} is not specified,
5423 print a table with details about all functions and files marked for skipping.
5424 @code{info skip} prints the following information about each skip:
5428 A number identifying this skip.
5430 The type of this skip, either @samp{function} or @samp{file}.
5431 @item Enabled or Disabled
5432 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5434 For function skips, this column indicates the address in memory of the function
5435 being skipped. If you've set a function skip on a function which has not yet
5436 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5437 which has the function is loaded, @code{info skip} will show the function's
5440 For file skips, this field contains the filename being skipped. For functions
5441 skips, this field contains the function name and its line number in the file
5442 where it is defined.
5446 @item skip delete @r{[}@var{range}@r{]}
5447 Delete the specified skip(s). If @var{range} is not specified, delete all
5451 @item skip enable @r{[}@var{range}@r{]}
5452 Enable the specified skip(s). If @var{range} is not specified, enable all
5455 @kindex skip disable
5456 @item skip disable @r{[}@var{range}@r{]}
5457 Disable the specified skip(s). If @var{range} is not specified, disable all
5466 A signal is an asynchronous event that can happen in a program. The
5467 operating system defines the possible kinds of signals, and gives each
5468 kind a name and a number. For example, in Unix @code{SIGINT} is the
5469 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5470 @code{SIGSEGV} is the signal a program gets from referencing a place in
5471 memory far away from all the areas in use; @code{SIGALRM} occurs when
5472 the alarm clock timer goes off (which happens only if your program has
5473 requested an alarm).
5475 @cindex fatal signals
5476 Some signals, including @code{SIGALRM}, are a normal part of the
5477 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5478 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5479 program has not specified in advance some other way to handle the signal.
5480 @code{SIGINT} does not indicate an error in your program, but it is normally
5481 fatal so it can carry out the purpose of the interrupt: to kill the program.
5483 @value{GDBN} has the ability to detect any occurrence of a signal in your
5484 program. You can tell @value{GDBN} in advance what to do for each kind of
5487 @cindex handling signals
5488 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5489 @code{SIGALRM} be silently passed to your program
5490 (so as not to interfere with their role in the program's functioning)
5491 but to stop your program immediately whenever an error signal happens.
5492 You can change these settings with the @code{handle} command.
5495 @kindex info signals
5499 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5500 handle each one. You can use this to see the signal numbers of all
5501 the defined types of signals.
5503 @item info signals @var{sig}
5504 Similar, but print information only about the specified signal number.
5506 @code{info handle} is an alias for @code{info signals}.
5508 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5509 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5510 for details about this command.
5513 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5514 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5515 can be the number of a signal or its name (with or without the
5516 @samp{SIG} at the beginning); a list of signal numbers of the form
5517 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5518 known signals. Optional arguments @var{keywords}, described below,
5519 say what change to make.
5523 The keywords allowed by the @code{handle} command can be abbreviated.
5524 Their full names are:
5528 @value{GDBN} should not stop your program when this signal happens. It may
5529 still print a message telling you that the signal has come in.
5532 @value{GDBN} should stop your program when this signal happens. This implies
5533 the @code{print} keyword as well.
5536 @value{GDBN} should print a message when this signal happens.
5539 @value{GDBN} should not mention the occurrence of the signal at all. This
5540 implies the @code{nostop} keyword as well.
5544 @value{GDBN} should allow your program to see this signal; your program
5545 can handle the signal, or else it may terminate if the signal is fatal
5546 and not handled. @code{pass} and @code{noignore} are synonyms.
5550 @value{GDBN} should not allow your program to see this signal.
5551 @code{nopass} and @code{ignore} are synonyms.
5555 When a signal stops your program, the signal is not visible to the
5557 continue. Your program sees the signal then, if @code{pass} is in
5558 effect for the signal in question @emph{at that time}. In other words,
5559 after @value{GDBN} reports a signal, you can use the @code{handle}
5560 command with @code{pass} or @code{nopass} to control whether your
5561 program sees that signal when you continue.
5563 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5564 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5565 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5568 You can also use the @code{signal} command to prevent your program from
5569 seeing a signal, or cause it to see a signal it normally would not see,
5570 or to give it any signal at any time. For example, if your program stopped
5571 due to some sort of memory reference error, you might store correct
5572 values into the erroneous variables and continue, hoping to see more
5573 execution; but your program would probably terminate immediately as
5574 a result of the fatal signal once it saw the signal. To prevent this,
5575 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5578 @cindex stepping and signal handlers
5579 @anchor{stepping and signal handlers}
5581 @value{GDBN} optimizes for stepping the mainline code. If a signal
5582 that has @code{handle nostop} and @code{handle pass} set arrives while
5583 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
5584 in progress, @value{GDBN} lets the signal handler run and then resumes
5585 stepping the mainline code once the signal handler returns. In other
5586 words, @value{GDBN} steps over the signal handler. This prevents
5587 signals that you've specified as not interesting (with @code{handle
5588 nostop}) from changing the focus of debugging unexpectedly. Note that
5589 the signal handler itself may still hit a breakpoint, stop for another
5590 signal that has @code{handle stop} in effect, or for any other event
5591 that normally results in stopping the stepping command sooner. Also
5592 note that @value{GDBN} still informs you that the program received a
5593 signal if @code{handle print} is set.
5595 @anchor{stepping into signal handlers}
5597 If you set @code{handle pass} for a signal, and your program sets up a
5598 handler for it, then issuing a stepping command, such as @code{step}
5599 or @code{stepi}, when your program is stopped due to the signal will
5600 step @emph{into} the signal handler (if the target supports that).
5602 Likewise, if you use the @code{queue-signal} command to queue a signal
5603 to be delivered to the current thread when execution of the thread
5604 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
5605 stepping command will step into the signal handler.
5607 Here's an example, using @code{stepi} to step to the first instruction
5608 of @code{SIGUSR1}'s handler:
5611 (@value{GDBP}) handle SIGUSR1
5612 Signal Stop Print Pass to program Description
5613 SIGUSR1 Yes Yes Yes User defined signal 1
5617 Program received signal SIGUSR1, User defined signal 1.
5618 main () sigusr1.c:28
5621 sigusr1_handler () at sigusr1.c:9
5625 The same, but using @code{queue-signal} instead of waiting for the
5626 program to receive the signal first:
5631 (@value{GDBP}) queue-signal SIGUSR1
5633 sigusr1_handler () at sigusr1.c:9
5638 @cindex extra signal information
5639 @anchor{extra signal information}
5641 On some targets, @value{GDBN} can inspect extra signal information
5642 associated with the intercepted signal, before it is actually
5643 delivered to the program being debugged. This information is exported
5644 by the convenience variable @code{$_siginfo}, and consists of data
5645 that is passed by the kernel to the signal handler at the time of the
5646 receipt of a signal. The data type of the information itself is
5647 target dependent. You can see the data type using the @code{ptype
5648 $_siginfo} command. On Unix systems, it typically corresponds to the
5649 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5652 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5653 referenced address that raised a segmentation fault.
5657 (@value{GDBP}) continue
5658 Program received signal SIGSEGV, Segmentation fault.
5659 0x0000000000400766 in main ()
5661 (@value{GDBP}) ptype $_siginfo
5668 struct @{...@} _kill;
5669 struct @{...@} _timer;
5671 struct @{...@} _sigchld;
5672 struct @{...@} _sigfault;
5673 struct @{...@} _sigpoll;
5676 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5680 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5681 $1 = (void *) 0x7ffff7ff7000
5685 Depending on target support, @code{$_siginfo} may also be writable.
5688 @section Stopping and Starting Multi-thread Programs
5690 @cindex stopped threads
5691 @cindex threads, stopped
5693 @cindex continuing threads
5694 @cindex threads, continuing
5696 @value{GDBN} supports debugging programs with multiple threads
5697 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5698 are two modes of controlling execution of your program within the
5699 debugger. In the default mode, referred to as @dfn{all-stop mode},
5700 when any thread in your program stops (for example, at a breakpoint
5701 or while being stepped), all other threads in the program are also stopped by
5702 @value{GDBN}. On some targets, @value{GDBN} also supports
5703 @dfn{non-stop mode}, in which other threads can continue to run freely while
5704 you examine the stopped thread in the debugger.
5707 * All-Stop Mode:: All threads stop when GDB takes control
5708 * Non-Stop Mode:: Other threads continue to execute
5709 * Background Execution:: Running your program asynchronously
5710 * Thread-Specific Breakpoints:: Controlling breakpoints
5711 * Interrupted System Calls:: GDB may interfere with system calls
5712 * Observer Mode:: GDB does not alter program behavior
5716 @subsection All-Stop Mode
5718 @cindex all-stop mode
5720 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5721 @emph{all} threads of execution stop, not just the current thread. This
5722 allows you to examine the overall state of the program, including
5723 switching between threads, without worrying that things may change
5726 Conversely, whenever you restart the program, @emph{all} threads start
5727 executing. @emph{This is true even when single-stepping} with commands
5728 like @code{step} or @code{next}.
5730 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5731 Since thread scheduling is up to your debugging target's operating
5732 system (not controlled by @value{GDBN}), other threads may
5733 execute more than one statement while the current thread completes a
5734 single step. Moreover, in general other threads stop in the middle of a
5735 statement, rather than at a clean statement boundary, when the program
5738 You might even find your program stopped in another thread after
5739 continuing or even single-stepping. This happens whenever some other
5740 thread runs into a breakpoint, a signal, or an exception before the
5741 first thread completes whatever you requested.
5743 @cindex automatic thread selection
5744 @cindex switching threads automatically
5745 @cindex threads, automatic switching
5746 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5747 signal, it automatically selects the thread where that breakpoint or
5748 signal happened. @value{GDBN} alerts you to the context switch with a
5749 message such as @samp{[Switching to Thread @var{n}]} to identify the
5752 On some OSes, you can modify @value{GDBN}'s default behavior by
5753 locking the OS scheduler to allow only a single thread to run.
5756 @item set scheduler-locking @var{mode}
5757 @cindex scheduler locking mode
5758 @cindex lock scheduler
5759 Set the scheduler locking mode. If it is @code{off}, then there is no
5760 locking and any thread may run at any time. If @code{on}, then only the
5761 current thread may run when the inferior is resumed. The @code{step}
5762 mode optimizes for single-stepping; it prevents other threads
5763 from preempting the current thread while you are stepping, so that
5764 the focus of debugging does not change unexpectedly.
5765 Other threads only rarely (or never) get a chance to run
5766 when you step. They are more likely to run when you @samp{next} over a
5767 function call, and they are completely free to run when you use commands
5768 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5769 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5770 the current thread away from the thread that you are debugging.
5772 @item show scheduler-locking
5773 Display the current scheduler locking mode.
5776 @cindex resume threads of multiple processes simultaneously
5777 By default, when you issue one of the execution commands such as
5778 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5779 threads of the current inferior to run. For example, if @value{GDBN}
5780 is attached to two inferiors, each with two threads, the
5781 @code{continue} command resumes only the two threads of the current
5782 inferior. This is useful, for example, when you debug a program that
5783 forks and you want to hold the parent stopped (so that, for instance,
5784 it doesn't run to exit), while you debug the child. In other
5785 situations, you may not be interested in inspecting the current state
5786 of any of the processes @value{GDBN} is attached to, and you may want
5787 to resume them all until some breakpoint is hit. In the latter case,
5788 you can instruct @value{GDBN} to allow all threads of all the
5789 inferiors to run with the @w{@code{set schedule-multiple}} command.
5792 @kindex set schedule-multiple
5793 @item set schedule-multiple
5794 Set the mode for allowing threads of multiple processes to be resumed
5795 when an execution command is issued. When @code{on}, all threads of
5796 all processes are allowed to run. When @code{off}, only the threads
5797 of the current process are resumed. The default is @code{off}. The
5798 @code{scheduler-locking} mode takes precedence when set to @code{on},
5799 or while you are stepping and set to @code{step}.
5801 @item show schedule-multiple
5802 Display the current mode for resuming the execution of threads of
5807 @subsection Non-Stop Mode
5809 @cindex non-stop mode
5811 @c This section is really only a place-holder, and needs to be expanded
5812 @c with more details.
5814 For some multi-threaded targets, @value{GDBN} supports an optional
5815 mode of operation in which you can examine stopped program threads in
5816 the debugger while other threads continue to execute freely. This
5817 minimizes intrusion when debugging live systems, such as programs
5818 where some threads have real-time constraints or must continue to
5819 respond to external events. This is referred to as @dfn{non-stop} mode.
5821 In non-stop mode, when a thread stops to report a debugging event,
5822 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5823 threads as well, in contrast to the all-stop mode behavior. Additionally,
5824 execution commands such as @code{continue} and @code{step} apply by default
5825 only to the current thread in non-stop mode, rather than all threads as
5826 in all-stop mode. This allows you to control threads explicitly in
5827 ways that are not possible in all-stop mode --- for example, stepping
5828 one thread while allowing others to run freely, stepping
5829 one thread while holding all others stopped, or stepping several threads
5830 independently and simultaneously.
5832 To enter non-stop mode, use this sequence of commands before you run
5833 or attach to your program:
5836 # If using the CLI, pagination breaks non-stop.
5839 # Finally, turn it on!
5843 You can use these commands to manipulate the non-stop mode setting:
5846 @kindex set non-stop
5847 @item set non-stop on
5848 Enable selection of non-stop mode.
5849 @item set non-stop off
5850 Disable selection of non-stop mode.
5851 @kindex show non-stop
5853 Show the current non-stop enablement setting.
5856 Note these commands only reflect whether non-stop mode is enabled,
5857 not whether the currently-executing program is being run in non-stop mode.
5858 In particular, the @code{set non-stop} preference is only consulted when
5859 @value{GDBN} starts or connects to the target program, and it is generally
5860 not possible to switch modes once debugging has started. Furthermore,
5861 since not all targets support non-stop mode, even when you have enabled
5862 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5865 In non-stop mode, all execution commands apply only to the current thread
5866 by default. That is, @code{continue} only continues one thread.
5867 To continue all threads, issue @code{continue -a} or @code{c -a}.
5869 You can use @value{GDBN}'s background execution commands
5870 (@pxref{Background Execution}) to run some threads in the background
5871 while you continue to examine or step others from @value{GDBN}.
5872 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5873 always executed asynchronously in non-stop mode.
5875 Suspending execution is done with the @code{interrupt} command when
5876 running in the background, or @kbd{Ctrl-c} during foreground execution.
5877 In all-stop mode, this stops the whole process;
5878 but in non-stop mode the interrupt applies only to the current thread.
5879 To stop the whole program, use @code{interrupt -a}.
5881 Other execution commands do not currently support the @code{-a} option.
5883 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5884 that thread current, as it does in all-stop mode. This is because the
5885 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5886 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5887 changed to a different thread just as you entered a command to operate on the
5888 previously current thread.
5890 @node Background Execution
5891 @subsection Background Execution
5893 @cindex foreground execution
5894 @cindex background execution
5895 @cindex asynchronous execution
5896 @cindex execution, foreground, background and asynchronous
5898 @value{GDBN}'s execution commands have two variants: the normal
5899 foreground (synchronous) behavior, and a background
5900 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5901 the program to report that some thread has stopped before prompting for
5902 another command. In background execution, @value{GDBN} immediately gives
5903 a command prompt so that you can issue other commands while your program runs.
5905 If the target doesn't support async mode, @value{GDBN} issues an error
5906 message if you attempt to use the background execution commands.
5908 To specify background execution, add a @code{&} to the command. For example,
5909 the background form of the @code{continue} command is @code{continue&}, or
5910 just @code{c&}. The execution commands that accept background execution
5916 @xref{Starting, , Starting your Program}.
5920 @xref{Attach, , Debugging an Already-running Process}.
5924 @xref{Continuing and Stepping, step}.
5928 @xref{Continuing and Stepping, stepi}.
5932 @xref{Continuing and Stepping, next}.
5936 @xref{Continuing and Stepping, nexti}.
5940 @xref{Continuing and Stepping, continue}.
5944 @xref{Continuing and Stepping, finish}.
5948 @xref{Continuing and Stepping, until}.
5952 Background execution is especially useful in conjunction with non-stop
5953 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5954 However, you can also use these commands in the normal all-stop mode with
5955 the restriction that you cannot issue another execution command until the
5956 previous one finishes. Examples of commands that are valid in all-stop
5957 mode while the program is running include @code{help} and @code{info break}.
5959 You can interrupt your program while it is running in the background by
5960 using the @code{interrupt} command.
5967 Suspend execution of the running program. In all-stop mode,
5968 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5969 only the current thread. To stop the whole program in non-stop mode,
5970 use @code{interrupt -a}.
5973 @node Thread-Specific Breakpoints
5974 @subsection Thread-Specific Breakpoints
5976 When your program has multiple threads (@pxref{Threads,, Debugging
5977 Programs with Multiple Threads}), you can choose whether to set
5978 breakpoints on all threads, or on a particular thread.
5981 @cindex breakpoints and threads
5982 @cindex thread breakpoints
5983 @kindex break @dots{} thread @var{threadno}
5984 @item break @var{linespec} thread @var{threadno}
5985 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5986 @var{linespec} specifies source lines; there are several ways of
5987 writing them (@pxref{Specify Location}), but the effect is always to
5988 specify some source line.
5990 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5991 to specify that you only want @value{GDBN} to stop the program when a
5992 particular thread reaches this breakpoint. The @var{threadno} specifier
5993 is one of the numeric thread identifiers assigned by @value{GDBN}, shown
5994 in the first column of the @samp{info threads} display.
5996 If you do not specify @samp{thread @var{threadno}} when you set a
5997 breakpoint, the breakpoint applies to @emph{all} threads of your
6000 You can use the @code{thread} qualifier on conditional breakpoints as
6001 well; in this case, place @samp{thread @var{threadno}} before or
6002 after the breakpoint condition, like this:
6005 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6010 Thread-specific breakpoints are automatically deleted when
6011 @value{GDBN} detects the corresponding thread is no longer in the
6012 thread list. For example:
6016 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6019 There are several ways for a thread to disappear, such as a regular
6020 thread exit, but also when you detach from the process with the
6021 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6022 Process}), or if @value{GDBN} loses the remote connection
6023 (@pxref{Remote Debugging}), etc. Note that with some targets,
6024 @value{GDBN} is only able to detect a thread has exited when the user
6025 explictly asks for the thread list with the @code{info threads}
6028 @node Interrupted System Calls
6029 @subsection Interrupted System Calls
6031 @cindex thread breakpoints and system calls
6032 @cindex system calls and thread breakpoints
6033 @cindex premature return from system calls
6034 There is an unfortunate side effect when using @value{GDBN} to debug
6035 multi-threaded programs. If one thread stops for a
6036 breakpoint, or for some other reason, and another thread is blocked in a
6037 system call, then the system call may return prematurely. This is a
6038 consequence of the interaction between multiple threads and the signals
6039 that @value{GDBN} uses to implement breakpoints and other events that
6042 To handle this problem, your program should check the return value of
6043 each system call and react appropriately. This is good programming
6046 For example, do not write code like this:
6052 The call to @code{sleep} will return early if a different thread stops
6053 at a breakpoint or for some other reason.
6055 Instead, write this:
6060 unslept = sleep (unslept);
6063 A system call is allowed to return early, so the system is still
6064 conforming to its specification. But @value{GDBN} does cause your
6065 multi-threaded program to behave differently than it would without
6068 Also, @value{GDBN} uses internal breakpoints in the thread library to
6069 monitor certain events such as thread creation and thread destruction.
6070 When such an event happens, a system call in another thread may return
6071 prematurely, even though your program does not appear to stop.
6074 @subsection Observer Mode
6076 If you want to build on non-stop mode and observe program behavior
6077 without any chance of disruption by @value{GDBN}, you can set
6078 variables to disable all of the debugger's attempts to modify state,
6079 whether by writing memory, inserting breakpoints, etc. These operate
6080 at a low level, intercepting operations from all commands.
6082 When all of these are set to @code{off}, then @value{GDBN} is said to
6083 be @dfn{observer mode}. As a convenience, the variable
6084 @code{observer} can be set to disable these, plus enable non-stop
6087 Note that @value{GDBN} will not prevent you from making nonsensical
6088 combinations of these settings. For instance, if you have enabled
6089 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6090 then breakpoints that work by writing trap instructions into the code
6091 stream will still not be able to be placed.
6096 @item set observer on
6097 @itemx set observer off
6098 When set to @code{on}, this disables all the permission variables
6099 below (except for @code{insert-fast-tracepoints}), plus enables
6100 non-stop debugging. Setting this to @code{off} switches back to
6101 normal debugging, though remaining in non-stop mode.
6104 Show whether observer mode is on or off.
6106 @kindex may-write-registers
6107 @item set may-write-registers on
6108 @itemx set may-write-registers off
6109 This controls whether @value{GDBN} will attempt to alter the values of
6110 registers, such as with assignment expressions in @code{print}, or the
6111 @code{jump} command. It defaults to @code{on}.
6113 @item show may-write-registers
6114 Show the current permission to write registers.
6116 @kindex may-write-memory
6117 @item set may-write-memory on
6118 @itemx set may-write-memory off
6119 This controls whether @value{GDBN} will attempt to alter the contents
6120 of memory, such as with assignment expressions in @code{print}. It
6121 defaults to @code{on}.
6123 @item show may-write-memory
6124 Show the current permission to write memory.
6126 @kindex may-insert-breakpoints
6127 @item set may-insert-breakpoints on
6128 @itemx set may-insert-breakpoints off
6129 This controls whether @value{GDBN} will attempt to insert breakpoints.
6130 This affects all breakpoints, including internal breakpoints defined
6131 by @value{GDBN}. It defaults to @code{on}.
6133 @item show may-insert-breakpoints
6134 Show the current permission to insert breakpoints.
6136 @kindex may-insert-tracepoints
6137 @item set may-insert-tracepoints on
6138 @itemx set may-insert-tracepoints off
6139 This controls whether @value{GDBN} will attempt to insert (regular)
6140 tracepoints at the beginning of a tracing experiment. It affects only
6141 non-fast tracepoints, fast tracepoints being under the control of
6142 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6144 @item show may-insert-tracepoints
6145 Show the current permission to insert tracepoints.
6147 @kindex may-insert-fast-tracepoints
6148 @item set may-insert-fast-tracepoints on
6149 @itemx set may-insert-fast-tracepoints off
6150 This controls whether @value{GDBN} will attempt to insert fast
6151 tracepoints at the beginning of a tracing experiment. It affects only
6152 fast tracepoints, regular (non-fast) tracepoints being under the
6153 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6155 @item show may-insert-fast-tracepoints
6156 Show the current permission to insert fast tracepoints.
6158 @kindex may-interrupt
6159 @item set may-interrupt on
6160 @itemx set may-interrupt off
6161 This controls whether @value{GDBN} will attempt to interrupt or stop
6162 program execution. When this variable is @code{off}, the
6163 @code{interrupt} command will have no effect, nor will
6164 @kbd{Ctrl-c}. It defaults to @code{on}.
6166 @item show may-interrupt
6167 Show the current permission to interrupt or stop the program.
6171 @node Reverse Execution
6172 @chapter Running programs backward
6173 @cindex reverse execution
6174 @cindex running programs backward
6176 When you are debugging a program, it is not unusual to realize that
6177 you have gone too far, and some event of interest has already happened.
6178 If the target environment supports it, @value{GDBN} can allow you to
6179 ``rewind'' the program by running it backward.
6181 A target environment that supports reverse execution should be able
6182 to ``undo'' the changes in machine state that have taken place as the
6183 program was executing normally. Variables, registers etc.@: should
6184 revert to their previous values. Obviously this requires a great
6185 deal of sophistication on the part of the target environment; not
6186 all target environments can support reverse execution.
6188 When a program is executed in reverse, the instructions that
6189 have most recently been executed are ``un-executed'', in reverse
6190 order. The program counter runs backward, following the previous
6191 thread of execution in reverse. As each instruction is ``un-executed'',
6192 the values of memory and/or registers that were changed by that
6193 instruction are reverted to their previous states. After executing
6194 a piece of source code in reverse, all side effects of that code
6195 should be ``undone'', and all variables should be returned to their
6196 prior values@footnote{
6197 Note that some side effects are easier to undo than others. For instance,
6198 memory and registers are relatively easy, but device I/O is hard. Some
6199 targets may be able undo things like device I/O, and some may not.
6201 The contract between @value{GDBN} and the reverse executing target
6202 requires only that the target do something reasonable when
6203 @value{GDBN} tells it to execute backwards, and then report the
6204 results back to @value{GDBN}. Whatever the target reports back to
6205 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6206 assumes that the memory and registers that the target reports are in a
6207 consistant state, but @value{GDBN} accepts whatever it is given.
6210 If you are debugging in a target environment that supports
6211 reverse execution, @value{GDBN} provides the following commands.
6214 @kindex reverse-continue
6215 @kindex rc @r{(@code{reverse-continue})}
6216 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6217 @itemx rc @r{[}@var{ignore-count}@r{]}
6218 Beginning at the point where your program last stopped, start executing
6219 in reverse. Reverse execution will stop for breakpoints and synchronous
6220 exceptions (signals), just like normal execution. Behavior of
6221 asynchronous signals depends on the target environment.
6223 @kindex reverse-step
6224 @kindex rs @r{(@code{step})}
6225 @item reverse-step @r{[}@var{count}@r{]}
6226 Run the program backward until control reaches the start of a
6227 different source line; then stop it, and return control to @value{GDBN}.
6229 Like the @code{step} command, @code{reverse-step} will only stop
6230 at the beginning of a source line. It ``un-executes'' the previously
6231 executed source line. If the previous source line included calls to
6232 debuggable functions, @code{reverse-step} will step (backward) into
6233 the called function, stopping at the beginning of the @emph{last}
6234 statement in the called function (typically a return statement).
6236 Also, as with the @code{step} command, if non-debuggable functions are
6237 called, @code{reverse-step} will run thru them backward without stopping.
6239 @kindex reverse-stepi
6240 @kindex rsi @r{(@code{reverse-stepi})}
6241 @item reverse-stepi @r{[}@var{count}@r{]}
6242 Reverse-execute one machine instruction. Note that the instruction
6243 to be reverse-executed is @emph{not} the one pointed to by the program
6244 counter, but the instruction executed prior to that one. For instance,
6245 if the last instruction was a jump, @code{reverse-stepi} will take you
6246 back from the destination of the jump to the jump instruction itself.
6248 @kindex reverse-next
6249 @kindex rn @r{(@code{reverse-next})}
6250 @item reverse-next @r{[}@var{count}@r{]}
6251 Run backward to the beginning of the previous line executed in
6252 the current (innermost) stack frame. If the line contains function
6253 calls, they will be ``un-executed'' without stopping. Starting from
6254 the first line of a function, @code{reverse-next} will take you back
6255 to the caller of that function, @emph{before} the function was called,
6256 just as the normal @code{next} command would take you from the last
6257 line of a function back to its return to its caller
6258 @footnote{Unless the code is too heavily optimized.}.
6260 @kindex reverse-nexti
6261 @kindex rni @r{(@code{reverse-nexti})}
6262 @item reverse-nexti @r{[}@var{count}@r{]}
6263 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6264 in reverse, except that called functions are ``un-executed'' atomically.
6265 That is, if the previously executed instruction was a return from
6266 another function, @code{reverse-nexti} will continue to execute
6267 in reverse until the call to that function (from the current stack
6270 @kindex reverse-finish
6271 @item reverse-finish
6272 Just as the @code{finish} command takes you to the point where the
6273 current function returns, @code{reverse-finish} takes you to the point
6274 where it was called. Instead of ending up at the end of the current
6275 function invocation, you end up at the beginning.
6277 @kindex set exec-direction
6278 @item set exec-direction
6279 Set the direction of target execution.
6280 @item set exec-direction reverse
6281 @cindex execute forward or backward in time
6282 @value{GDBN} will perform all execution commands in reverse, until the
6283 exec-direction mode is changed to ``forward''. Affected commands include
6284 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6285 command cannot be used in reverse mode.
6286 @item set exec-direction forward
6287 @value{GDBN} will perform all execution commands in the normal fashion.
6288 This is the default.
6292 @node Process Record and Replay
6293 @chapter Recording Inferior's Execution and Replaying It
6294 @cindex process record and replay
6295 @cindex recording inferior's execution and replaying it
6297 On some platforms, @value{GDBN} provides a special @dfn{process record
6298 and replay} target that can record a log of the process execution, and
6299 replay it later with both forward and reverse execution commands.
6302 When this target is in use, if the execution log includes the record
6303 for the next instruction, @value{GDBN} will debug in @dfn{replay
6304 mode}. In the replay mode, the inferior does not really execute code
6305 instructions. Instead, all the events that normally happen during
6306 code execution are taken from the execution log. While code is not
6307 really executed in replay mode, the values of registers (including the
6308 program counter register) and the memory of the inferior are still
6309 changed as they normally would. Their contents are taken from the
6313 If the record for the next instruction is not in the execution log,
6314 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6315 inferior executes normally, and @value{GDBN} records the execution log
6318 The process record and replay target supports reverse execution
6319 (@pxref{Reverse Execution}), even if the platform on which the
6320 inferior runs does not. However, the reverse execution is limited in
6321 this case by the range of the instructions recorded in the execution
6322 log. In other words, reverse execution on platforms that don't
6323 support it directly can only be done in the replay mode.
6325 When debugging in the reverse direction, @value{GDBN} will work in
6326 replay mode as long as the execution log includes the record for the
6327 previous instruction; otherwise, it will work in record mode, if the
6328 platform supports reverse execution, or stop if not.
6330 For architecture environments that support process record and replay,
6331 @value{GDBN} provides the following commands:
6334 @kindex target record
6335 @kindex target record-full
6336 @kindex target record-btrace
6339 @kindex record btrace
6343 @item record @var{method}
6344 This command starts the process record and replay target. The
6345 recording method can be specified as parameter. Without a parameter
6346 the command uses the @code{full} recording method. The following
6347 recording methods are available:
6351 Full record/replay recording using @value{GDBN}'s software record and
6352 replay implementation. This method allows replaying and reverse
6356 Hardware-supported instruction recording. This method does not record
6357 data. Further, the data is collected in a ring buffer so old data will
6358 be overwritten when the buffer is full. It allows limited replay and
6361 This recording method may not be available on all processors.
6364 The process record and replay target can only debug a process that is
6365 already running. Therefore, you need first to start the process with
6366 the @kbd{run} or @kbd{start} commands, and then start the recording
6367 with the @kbd{record @var{method}} command.
6369 Both @code{record @var{method}} and @code{rec @var{method}} are
6370 aliases of @code{target record-@var{method}}.
6372 @cindex displaced stepping, and process record and replay
6373 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6374 will be automatically disabled when process record and replay target
6375 is started. That's because the process record and replay target
6376 doesn't support displaced stepping.
6378 @cindex non-stop mode, and process record and replay
6379 @cindex asynchronous execution, and process record and replay
6380 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6381 the asynchronous execution mode (@pxref{Background Execution}), not
6382 all recording methods are available. The @code{full} recording method
6383 does not support these two modes.
6388 Stop the process record and replay target. When process record and
6389 replay target stops, the entire execution log will be deleted and the
6390 inferior will either be terminated, or will remain in its final state.
6392 When you stop the process record and replay target in record mode (at
6393 the end of the execution log), the inferior will be stopped at the
6394 next instruction that would have been recorded. In other words, if
6395 you record for a while and then stop recording, the inferior process
6396 will be left in the same state as if the recording never happened.
6398 On the other hand, if the process record and replay target is stopped
6399 while in replay mode (that is, not at the end of the execution log,
6400 but at some earlier point), the inferior process will become ``live''
6401 at that earlier state, and it will then be possible to continue the
6402 usual ``live'' debugging of the process from that state.
6404 When the inferior process exits, or @value{GDBN} detaches from it,
6405 process record and replay target will automatically stop itself.
6409 Go to a specific location in the execution log. There are several
6410 ways to specify the location to go to:
6413 @item record goto begin
6414 @itemx record goto start
6415 Go to the beginning of the execution log.
6417 @item record goto end
6418 Go to the end of the execution log.
6420 @item record goto @var{n}
6421 Go to instruction number @var{n} in the execution log.
6425 @item record save @var{filename}
6426 Save the execution log to a file @file{@var{filename}}.
6427 Default filename is @file{gdb_record.@var{process_id}}, where
6428 @var{process_id} is the process ID of the inferior.
6430 This command may not be available for all recording methods.
6432 @kindex record restore
6433 @item record restore @var{filename}
6434 Restore the execution log from a file @file{@var{filename}}.
6435 File must have been created with @code{record save}.
6437 @kindex set record full
6438 @item set record full insn-number-max @var{limit}
6439 @itemx set record full insn-number-max unlimited
6440 Set the limit of instructions to be recorded for the @code{full}
6441 recording method. Default value is 200000.
6443 If @var{limit} is a positive number, then @value{GDBN} will start
6444 deleting instructions from the log once the number of the record
6445 instructions becomes greater than @var{limit}. For every new recorded
6446 instruction, @value{GDBN} will delete the earliest recorded
6447 instruction to keep the number of recorded instructions at the limit.
6448 (Since deleting recorded instructions loses information, @value{GDBN}
6449 lets you control what happens when the limit is reached, by means of
6450 the @code{stop-at-limit} option, described below.)
6452 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6453 delete recorded instructions from the execution log. The number of
6454 recorded instructions is limited only by the available memory.
6456 @kindex show record full
6457 @item show record full insn-number-max
6458 Show the limit of instructions to be recorded with the @code{full}
6461 @item set record full stop-at-limit
6462 Control the behavior of the @code{full} recording method when the
6463 number of recorded instructions reaches the limit. If ON (the
6464 default), @value{GDBN} will stop when the limit is reached for the
6465 first time and ask you whether you want to stop the inferior or
6466 continue running it and recording the execution log. If you decide
6467 to continue recording, each new recorded instruction will cause the
6468 oldest one to be deleted.
6470 If this option is OFF, @value{GDBN} will automatically delete the
6471 oldest record to make room for each new one, without asking.
6473 @item show record full stop-at-limit
6474 Show the current setting of @code{stop-at-limit}.
6476 @item set record full memory-query
6477 Control the behavior when @value{GDBN} is unable to record memory
6478 changes caused by an instruction for the @code{full} recording method.
6479 If ON, @value{GDBN} will query whether to stop the inferior in that
6482 If this option is OFF (the default), @value{GDBN} will automatically
6483 ignore the effect of such instructions on memory. Later, when
6484 @value{GDBN} replays this execution log, it will mark the log of this
6485 instruction as not accessible, and it will not affect the replay
6488 @item show record full memory-query
6489 Show the current setting of @code{memory-query}.
6491 @kindex set record btrace
6492 The @code{btrace} record target does not trace data. As a
6493 convenience, when replaying, @value{GDBN} reads read-only memory off
6494 the live program directly, assuming that the addresses of the
6495 read-only areas don't change. This for example makes it possible to
6496 disassemble code while replaying, but not to print variables.
6497 In some cases, being able to inspect variables might be useful.
6498 You can use the following command for that:
6500 @item set record btrace replay-memory-access
6501 Control the behavior of the @code{btrace} recording method when
6502 accessing memory during replay. If @code{read-only} (the default),
6503 @value{GDBN} will only allow accesses to read-only memory.
6504 If @code{read-write}, @value{GDBN} will allow accesses to read-only
6505 and to read-write memory. Beware that the accessed memory corresponds
6506 to the live target and not necessarily to the current replay
6509 @kindex show record btrace
6510 @item show record btrace replay-memory-access
6511 Show the current setting of @code{replay-memory-access}.
6515 Show various statistics about the recording depending on the recording
6520 For the @code{full} recording method, it shows the state of process
6521 record and its in-memory execution log buffer, including:
6525 Whether in record mode or replay mode.
6527 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6529 Highest recorded instruction number.
6531 Current instruction about to be replayed (if in replay mode).
6533 Number of instructions contained in the execution log.
6535 Maximum number of instructions that may be contained in the execution log.
6539 For the @code{btrace} recording method, it shows the number of
6540 instructions that have been recorded and the number of blocks of
6541 sequential control-flow that is formed by the recorded instructions.
6544 @kindex record delete
6547 When record target runs in replay mode (``in the past''), delete the
6548 subsequent execution log and begin to record a new execution log starting
6549 from the current address. This means you will abandon the previously
6550 recorded ``future'' and begin recording a new ``future''.
6552 @kindex record instruction-history
6553 @kindex rec instruction-history
6554 @item record instruction-history
6555 Disassembles instructions from the recorded execution log. By
6556 default, ten instructions are disassembled. This can be changed using
6557 the @code{set record instruction-history-size} command. Instructions
6558 are printed in execution order. There are several ways to specify
6559 what part of the execution log to disassemble:
6562 @item record instruction-history @var{insn}
6563 Disassembles ten instructions starting from instruction number
6566 @item record instruction-history @var{insn}, +/-@var{n}
6567 Disassembles @var{n} instructions around instruction number
6568 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6569 @var{n} instructions after instruction number @var{insn}. If
6570 @var{n} is preceded with @code{-}, disassembles @var{n}
6571 instructions before instruction number @var{insn}.
6573 @item record instruction-history
6574 Disassembles ten more instructions after the last disassembly.
6576 @item record instruction-history -
6577 Disassembles ten more instructions before the last disassembly.
6579 @item record instruction-history @var{begin} @var{end}
6580 Disassembles instructions beginning with instruction number
6581 @var{begin} until instruction number @var{end}. The instruction
6582 number @var{end} is included.
6585 This command may not be available for all recording methods.
6588 @item set record instruction-history-size @var{size}
6589 @itemx set record instruction-history-size unlimited
6590 Define how many instructions to disassemble in the @code{record
6591 instruction-history} command. The default value is 10.
6592 A @var{size} of @code{unlimited} means unlimited instructions.
6595 @item show record instruction-history-size
6596 Show how many instructions to disassemble in the @code{record
6597 instruction-history} command.
6599 @kindex record function-call-history
6600 @kindex rec function-call-history
6601 @item record function-call-history
6602 Prints the execution history at function granularity. It prints one
6603 line for each sequence of instructions that belong to the same
6604 function giving the name of that function, the source lines
6605 for this instruction sequence (if the @code{/l} modifier is
6606 specified), and the instructions numbers that form the sequence (if
6607 the @code{/i} modifier is specified). The function names are indented
6608 to reflect the call stack depth if the @code{/c} modifier is
6609 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
6613 (@value{GDBP}) @b{list 1, 10}
6624 (@value{GDBP}) @b{record function-call-history /ilc}
6625 1 bar inst 1,4 at foo.c:6,8
6626 2 foo inst 5,10 at foo.c:2,3
6627 3 bar inst 11,13 at foo.c:9,10
6630 By default, ten lines are printed. This can be changed using the
6631 @code{set record function-call-history-size} command. Functions are
6632 printed in execution order. There are several ways to specify what
6636 @item record function-call-history @var{func}
6637 Prints ten functions starting from function number @var{func}.
6639 @item record function-call-history @var{func}, +/-@var{n}
6640 Prints @var{n} functions around function number @var{func}. If
6641 @var{n} is preceded with @code{+}, prints @var{n} functions after
6642 function number @var{func}. If @var{n} is preceded with @code{-},
6643 prints @var{n} functions before function number @var{func}.
6645 @item record function-call-history
6646 Prints ten more functions after the last ten-line print.
6648 @item record function-call-history -
6649 Prints ten more functions before the last ten-line print.
6651 @item record function-call-history @var{begin} @var{end}
6652 Prints functions beginning with function number @var{begin} until
6653 function number @var{end}. The function number @var{end} is included.
6656 This command may not be available for all recording methods.
6658 @item set record function-call-history-size @var{size}
6659 @itemx set record function-call-history-size unlimited
6660 Define how many lines to print in the
6661 @code{record function-call-history} command. The default value is 10.
6662 A size of @code{unlimited} means unlimited lines.
6664 @item show record function-call-history-size
6665 Show how many lines to print in the
6666 @code{record function-call-history} command.
6671 @chapter Examining the Stack
6673 When your program has stopped, the first thing you need to know is where it
6674 stopped and how it got there.
6677 Each time your program performs a function call, information about the call
6679 That information includes the location of the call in your program,
6680 the arguments of the call,
6681 and the local variables of the function being called.
6682 The information is saved in a block of data called a @dfn{stack frame}.
6683 The stack frames are allocated in a region of memory called the @dfn{call
6686 When your program stops, the @value{GDBN} commands for examining the
6687 stack allow you to see all of this information.
6689 @cindex selected frame
6690 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6691 @value{GDBN} commands refer implicitly to the selected frame. In
6692 particular, whenever you ask @value{GDBN} for the value of a variable in
6693 your program, the value is found in the selected frame. There are
6694 special @value{GDBN} commands to select whichever frame you are
6695 interested in. @xref{Selection, ,Selecting a Frame}.
6697 When your program stops, @value{GDBN} automatically selects the
6698 currently executing frame and describes it briefly, similar to the
6699 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6702 * Frames:: Stack frames
6703 * Backtrace:: Backtraces
6704 * Frame Filter Management:: Managing frame filters
6705 * Selection:: Selecting a frame
6706 * Frame Info:: Information on a frame
6711 @section Stack Frames
6713 @cindex frame, definition
6715 The call stack is divided up into contiguous pieces called @dfn{stack
6716 frames}, or @dfn{frames} for short; each frame is the data associated
6717 with one call to one function. The frame contains the arguments given
6718 to the function, the function's local variables, and the address at
6719 which the function is executing.
6721 @cindex initial frame
6722 @cindex outermost frame
6723 @cindex innermost frame
6724 When your program is started, the stack has only one frame, that of the
6725 function @code{main}. This is called the @dfn{initial} frame or the
6726 @dfn{outermost} frame. Each time a function is called, a new frame is
6727 made. Each time a function returns, the frame for that function invocation
6728 is eliminated. If a function is recursive, there can be many frames for
6729 the same function. The frame for the function in which execution is
6730 actually occurring is called the @dfn{innermost} frame. This is the most
6731 recently created of all the stack frames that still exist.
6733 @cindex frame pointer
6734 Inside your program, stack frames are identified by their addresses. A
6735 stack frame consists of many bytes, each of which has its own address; each
6736 kind of computer has a convention for choosing one byte whose
6737 address serves as the address of the frame. Usually this address is kept
6738 in a register called the @dfn{frame pointer register}
6739 (@pxref{Registers, $fp}) while execution is going on in that frame.
6741 @cindex frame number
6742 @value{GDBN} assigns numbers to all existing stack frames, starting with
6743 zero for the innermost frame, one for the frame that called it,
6744 and so on upward. These numbers do not really exist in your program;
6745 they are assigned by @value{GDBN} to give you a way of designating stack
6746 frames in @value{GDBN} commands.
6748 @c The -fomit-frame-pointer below perennially causes hbox overflow
6749 @c underflow problems.
6750 @cindex frameless execution
6751 Some compilers provide a way to compile functions so that they operate
6752 without stack frames. (For example, the @value{NGCC} option
6754 @samp{-fomit-frame-pointer}
6756 generates functions without a frame.)
6757 This is occasionally done with heavily used library functions to save
6758 the frame setup time. @value{GDBN} has limited facilities for dealing
6759 with these function invocations. If the innermost function invocation
6760 has no stack frame, @value{GDBN} nevertheless regards it as though
6761 it had a separate frame, which is numbered zero as usual, allowing
6762 correct tracing of the function call chain. However, @value{GDBN} has
6763 no provision for frameless functions elsewhere in the stack.
6766 @kindex frame@r{, command}
6767 @cindex current stack frame
6768 @item frame @r{[}@var{framespec}@r{]}
6769 The @code{frame} command allows you to move from one stack frame to another,
6770 and to print the stack frame you select. The @var{framespec} may be either the
6771 address of the frame or the stack frame number. Without an argument,
6772 @code{frame} prints the current stack frame.
6774 @kindex select-frame
6775 @cindex selecting frame silently
6777 The @code{select-frame} command allows you to move from one stack frame
6778 to another without printing the frame. This is the silent version of
6786 @cindex call stack traces
6787 A backtrace is a summary of how your program got where it is. It shows one
6788 line per frame, for many frames, starting with the currently executing
6789 frame (frame zero), followed by its caller (frame one), and on up the
6792 @anchor{backtrace-command}
6795 @kindex bt @r{(@code{backtrace})}
6798 Print a backtrace of the entire stack: one line per frame for all
6799 frames in the stack.
6801 You can stop the backtrace at any time by typing the system interrupt
6802 character, normally @kbd{Ctrl-c}.
6804 @item backtrace @var{n}
6806 Similar, but print only the innermost @var{n} frames.
6808 @item backtrace -@var{n}
6810 Similar, but print only the outermost @var{n} frames.
6812 @item backtrace full
6814 @itemx bt full @var{n}
6815 @itemx bt full -@var{n}
6816 Print the values of the local variables also. As described above,
6817 @var{n} specifies the number of frames to print.
6819 @item backtrace no-filters
6820 @itemx bt no-filters
6821 @itemx bt no-filters @var{n}
6822 @itemx bt no-filters -@var{n}
6823 @itemx bt no-filters full
6824 @itemx bt no-filters full @var{n}
6825 @itemx bt no-filters full -@var{n}
6826 Do not run Python frame filters on this backtrace. @xref{Frame
6827 Filter API}, for more information. Additionally use @ref{disable
6828 frame-filter all} to turn off all frame filters. This is only
6829 relevant when @value{GDBN} has been configured with @code{Python}
6835 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6836 are additional aliases for @code{backtrace}.
6838 @cindex multiple threads, backtrace
6839 In a multi-threaded program, @value{GDBN} by default shows the
6840 backtrace only for the current thread. To display the backtrace for
6841 several or all of the threads, use the command @code{thread apply}
6842 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6843 apply all backtrace}, @value{GDBN} will display the backtrace for all
6844 the threads; this is handy when you debug a core dump of a
6845 multi-threaded program.
6847 Each line in the backtrace shows the frame number and the function name.
6848 The program counter value is also shown---unless you use @code{set
6849 print address off}. The backtrace also shows the source file name and
6850 line number, as well as the arguments to the function. The program
6851 counter value is omitted if it is at the beginning of the code for that
6854 Here is an example of a backtrace. It was made with the command
6855 @samp{bt 3}, so it shows the innermost three frames.
6859 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6861 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6862 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6864 (More stack frames follow...)
6869 The display for frame zero does not begin with a program counter
6870 value, indicating that your program has stopped at the beginning of the
6871 code for line @code{993} of @code{builtin.c}.
6874 The value of parameter @code{data} in frame 1 has been replaced by
6875 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6876 only if it is a scalar (integer, pointer, enumeration, etc). See command
6877 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6878 on how to configure the way function parameter values are printed.
6880 @cindex optimized out, in backtrace
6881 @cindex function call arguments, optimized out
6882 If your program was compiled with optimizations, some compilers will
6883 optimize away arguments passed to functions if those arguments are
6884 never used after the call. Such optimizations generate code that
6885 passes arguments through registers, but doesn't store those arguments
6886 in the stack frame. @value{GDBN} has no way of displaying such
6887 arguments in stack frames other than the innermost one. Here's what
6888 such a backtrace might look like:
6892 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6894 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6895 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6897 (More stack frames follow...)
6902 The values of arguments that were not saved in their stack frames are
6903 shown as @samp{<optimized out>}.
6905 If you need to display the values of such optimized-out arguments,
6906 either deduce that from other variables whose values depend on the one
6907 you are interested in, or recompile without optimizations.
6909 @cindex backtrace beyond @code{main} function
6910 @cindex program entry point
6911 @cindex startup code, and backtrace
6912 Most programs have a standard user entry point---a place where system
6913 libraries and startup code transition into user code. For C this is
6914 @code{main}@footnote{
6915 Note that embedded programs (the so-called ``free-standing''
6916 environment) are not required to have a @code{main} function as the
6917 entry point. They could even have multiple entry points.}.
6918 When @value{GDBN} finds the entry function in a backtrace
6919 it will terminate the backtrace, to avoid tracing into highly
6920 system-specific (and generally uninteresting) code.
6922 If you need to examine the startup code, or limit the number of levels
6923 in a backtrace, you can change this behavior:
6926 @item set backtrace past-main
6927 @itemx set backtrace past-main on
6928 @kindex set backtrace
6929 Backtraces will continue past the user entry point.
6931 @item set backtrace past-main off
6932 Backtraces will stop when they encounter the user entry point. This is the
6935 @item show backtrace past-main
6936 @kindex show backtrace
6937 Display the current user entry point backtrace policy.
6939 @item set backtrace past-entry
6940 @itemx set backtrace past-entry on
6941 Backtraces will continue past the internal entry point of an application.
6942 This entry point is encoded by the linker when the application is built,
6943 and is likely before the user entry point @code{main} (or equivalent) is called.
6945 @item set backtrace past-entry off
6946 Backtraces will stop when they encounter the internal entry point of an
6947 application. This is the default.
6949 @item show backtrace past-entry
6950 Display the current internal entry point backtrace policy.
6952 @item set backtrace limit @var{n}
6953 @itemx set backtrace limit 0
6954 @itemx set backtrace limit unlimited
6955 @cindex backtrace limit
6956 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
6957 or zero means unlimited levels.
6959 @item show backtrace limit
6960 Display the current limit on backtrace levels.
6963 You can control how file names are displayed.
6966 @item set filename-display
6967 @itemx set filename-display relative
6968 @cindex filename-display
6969 Display file names relative to the compilation directory. This is the default.
6971 @item set filename-display basename
6972 Display only basename of a filename.
6974 @item set filename-display absolute
6975 Display an absolute filename.
6977 @item show filename-display
6978 Show the current way to display filenames.
6981 @node Frame Filter Management
6982 @section Management of Frame Filters.
6983 @cindex managing frame filters
6985 Frame filters are Python based utilities to manage and decorate the
6986 output of frames. @xref{Frame Filter API}, for further information.
6988 Managing frame filters is performed by several commands available
6989 within @value{GDBN}, detailed here.
6992 @kindex info frame-filter
6993 @item info frame-filter
6994 Print a list of installed frame filters from all dictionaries, showing
6995 their name, priority and enabled status.
6997 @kindex disable frame-filter
6998 @anchor{disable frame-filter all}
6999 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
7000 Disable a frame filter in the dictionary matching
7001 @var{filter-dictionary} and @var{filter-name}. The
7002 @var{filter-dictionary} may be @code{all}, @code{global},
7003 @code{progspace}, or the name of the object file where the frame filter
7004 dictionary resides. When @code{all} is specified, all frame filters
7005 across all dictionaries are disabled. The @var{filter-name} is the name
7006 of the frame filter and is used when @code{all} is not the option for
7007 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
7008 may be enabled again later.
7010 @kindex enable frame-filter
7011 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
7012 Enable a frame filter in the dictionary matching
7013 @var{filter-dictionary} and @var{filter-name}. The
7014 @var{filter-dictionary} may be @code{all}, @code{global},
7015 @code{progspace} or the name of the object file where the frame filter
7016 dictionary resides. When @code{all} is specified, all frame filters across
7017 all dictionaries are enabled. The @var{filter-name} is the name of the frame
7018 filter and is used when @code{all} is not the option for
7019 @var{filter-dictionary}.
7024 (gdb) info frame-filter
7026 global frame-filters:
7027 Priority Enabled Name
7028 1000 No PrimaryFunctionFilter
7031 progspace /build/test frame-filters:
7032 Priority Enabled Name
7033 100 Yes ProgspaceFilter
7035 objfile /build/test frame-filters:
7036 Priority Enabled Name
7037 999 Yes BuildProgra Filter
7039 (gdb) disable frame-filter /build/test BuildProgramFilter
7040 (gdb) info frame-filter
7042 global frame-filters:
7043 Priority Enabled Name
7044 1000 No PrimaryFunctionFilter
7047 progspace /build/test frame-filters:
7048 Priority Enabled Name
7049 100 Yes ProgspaceFilter
7051 objfile /build/test frame-filters:
7052 Priority Enabled Name
7053 999 No BuildProgramFilter
7055 (gdb) enable frame-filter global PrimaryFunctionFilter
7056 (gdb) info frame-filter
7058 global frame-filters:
7059 Priority Enabled Name
7060 1000 Yes PrimaryFunctionFilter
7063 progspace /build/test frame-filters:
7064 Priority Enabled Name
7065 100 Yes ProgspaceFilter
7067 objfile /build/test frame-filters:
7068 Priority Enabled Name
7069 999 No BuildProgramFilter
7072 @kindex set frame-filter priority
7073 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
7074 Set the @var{priority} of a frame filter in the dictionary matching
7075 @var{filter-dictionary}, and the frame filter name matching
7076 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7077 @code{progspace} or the name of the object file where the frame filter
7078 dictionary resides. The @var{priority} is an integer.
7080 @kindex show frame-filter priority
7081 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
7082 Show the @var{priority} of a frame filter in the dictionary matching
7083 @var{filter-dictionary}, and the frame filter name matching
7084 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7085 @code{progspace} or the name of the object file where the frame filter
7091 (gdb) info frame-filter
7093 global frame-filters:
7094 Priority Enabled Name
7095 1000 Yes PrimaryFunctionFilter
7098 progspace /build/test frame-filters:
7099 Priority Enabled Name
7100 100 Yes ProgspaceFilter
7102 objfile /build/test frame-filters:
7103 Priority Enabled Name
7104 999 No BuildProgramFilter
7106 (gdb) set frame-filter priority global Reverse 50
7107 (gdb) info frame-filter
7109 global frame-filters:
7110 Priority Enabled Name
7111 1000 Yes PrimaryFunctionFilter
7114 progspace /build/test frame-filters:
7115 Priority Enabled Name
7116 100 Yes ProgspaceFilter
7118 objfile /build/test frame-filters:
7119 Priority Enabled Name
7120 999 No BuildProgramFilter
7125 @section Selecting a Frame
7127 Most commands for examining the stack and other data in your program work on
7128 whichever stack frame is selected at the moment. Here are the commands for
7129 selecting a stack frame; all of them finish by printing a brief description
7130 of the stack frame just selected.
7133 @kindex frame@r{, selecting}
7134 @kindex f @r{(@code{frame})}
7137 Select frame number @var{n}. Recall that frame zero is the innermost
7138 (currently executing) frame, frame one is the frame that called the
7139 innermost one, and so on. The highest-numbered frame is the one for
7142 @item frame @var{addr}
7144 Select the frame at address @var{addr}. This is useful mainly if the
7145 chaining of stack frames has been damaged by a bug, making it
7146 impossible for @value{GDBN} to assign numbers properly to all frames. In
7147 addition, this can be useful when your program has multiple stacks and
7148 switches between them.
7150 On the SPARC architecture, @code{frame} needs two addresses to
7151 select an arbitrary frame: a frame pointer and a stack pointer.
7153 On the @acronym{MIPS} and Alpha architecture, it needs two addresses: a stack
7154 pointer and a program counter.
7156 On the 29k architecture, it needs three addresses: a register stack
7157 pointer, a program counter, and a memory stack pointer.
7161 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7162 numbers @var{n}, this advances toward the outermost frame, to higher
7163 frame numbers, to frames that have existed longer.
7166 @kindex do @r{(@code{down})}
7168 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7169 positive numbers @var{n}, this advances toward the innermost frame, to
7170 lower frame numbers, to frames that were created more recently.
7171 You may abbreviate @code{down} as @code{do}.
7174 All of these commands end by printing two lines of output describing the
7175 frame. The first line shows the frame number, the function name, the
7176 arguments, and the source file and line number of execution in that
7177 frame. The second line shows the text of that source line.
7185 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7187 10 read_input_file (argv[i]);
7191 After such a printout, the @code{list} command with no arguments
7192 prints ten lines centered on the point of execution in the frame.
7193 You can also edit the program at the point of execution with your favorite
7194 editing program by typing @code{edit}.
7195 @xref{List, ,Printing Source Lines},
7199 @kindex down-silently
7201 @item up-silently @var{n}
7202 @itemx down-silently @var{n}
7203 These two commands are variants of @code{up} and @code{down},
7204 respectively; they differ in that they do their work silently, without
7205 causing display of the new frame. They are intended primarily for use
7206 in @value{GDBN} command scripts, where the output might be unnecessary and
7211 @section Information About a Frame
7213 There are several other commands to print information about the selected
7219 When used without any argument, this command does not change which
7220 frame is selected, but prints a brief description of the currently
7221 selected stack frame. It can be abbreviated @code{f}. With an
7222 argument, this command is used to select a stack frame.
7223 @xref{Selection, ,Selecting a Frame}.
7226 @kindex info f @r{(@code{info frame})}
7229 This command prints a verbose description of the selected stack frame,
7234 the address of the frame
7236 the address of the next frame down (called by this frame)
7238 the address of the next frame up (caller of this frame)
7240 the language in which the source code corresponding to this frame is written
7242 the address of the frame's arguments
7244 the address of the frame's local variables
7246 the program counter saved in it (the address of execution in the caller frame)
7248 which registers were saved in the frame
7251 @noindent The verbose description is useful when
7252 something has gone wrong that has made the stack format fail to fit
7253 the usual conventions.
7255 @item info frame @var{addr}
7256 @itemx info f @var{addr}
7257 Print a verbose description of the frame at address @var{addr}, without
7258 selecting that frame. The selected frame remains unchanged by this
7259 command. This requires the same kind of address (more than one for some
7260 architectures) that you specify in the @code{frame} command.
7261 @xref{Selection, ,Selecting a Frame}.
7265 Print the arguments of the selected frame, each on a separate line.
7269 Print the local variables of the selected frame, each on a separate
7270 line. These are all variables (declared either static or automatic)
7271 accessible at the point of execution of the selected frame.
7277 @chapter Examining Source Files
7279 @value{GDBN} can print parts of your program's source, since the debugging
7280 information recorded in the program tells @value{GDBN} what source files were
7281 used to build it. When your program stops, @value{GDBN} spontaneously prints
7282 the line where it stopped. Likewise, when you select a stack frame
7283 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7284 execution in that frame has stopped. You can print other portions of
7285 source files by explicit command.
7287 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7288 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7289 @value{GDBN} under @sc{gnu} Emacs}.
7292 * List:: Printing source lines
7293 * Specify Location:: How to specify code locations
7294 * Edit:: Editing source files
7295 * Search:: Searching source files
7296 * Source Path:: Specifying source directories
7297 * Machine Code:: Source and machine code
7301 @section Printing Source Lines
7304 @kindex l @r{(@code{list})}
7305 To print lines from a source file, use the @code{list} command
7306 (abbreviated @code{l}). By default, ten lines are printed.
7307 There are several ways to specify what part of the file you want to
7308 print; see @ref{Specify Location}, for the full list.
7310 Here are the forms of the @code{list} command most commonly used:
7313 @item list @var{linenum}
7314 Print lines centered around line number @var{linenum} in the
7315 current source file.
7317 @item list @var{function}
7318 Print lines centered around the beginning of function
7322 Print more lines. If the last lines printed were printed with a
7323 @code{list} command, this prints lines following the last lines
7324 printed; however, if the last line printed was a solitary line printed
7325 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7326 Stack}), this prints lines centered around that line.
7329 Print lines just before the lines last printed.
7332 @cindex @code{list}, how many lines to display
7333 By default, @value{GDBN} prints ten source lines with any of these forms of
7334 the @code{list} command. You can change this using @code{set listsize}:
7337 @kindex set listsize
7338 @item set listsize @var{count}
7339 @itemx set listsize unlimited
7340 Make the @code{list} command display @var{count} source lines (unless
7341 the @code{list} argument explicitly specifies some other number).
7342 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7344 @kindex show listsize
7346 Display the number of lines that @code{list} prints.
7349 Repeating a @code{list} command with @key{RET} discards the argument,
7350 so it is equivalent to typing just @code{list}. This is more useful
7351 than listing the same lines again. An exception is made for an
7352 argument of @samp{-}; that argument is preserved in repetition so that
7353 each repetition moves up in the source file.
7355 In general, the @code{list} command expects you to supply zero, one or two
7356 @dfn{linespecs}. Linespecs specify source lines; there are several ways
7357 of writing them (@pxref{Specify Location}), but the effect is always
7358 to specify some source line.
7360 Here is a complete description of the possible arguments for @code{list}:
7363 @item list @var{linespec}
7364 Print lines centered around the line specified by @var{linespec}.
7366 @item list @var{first},@var{last}
7367 Print lines from @var{first} to @var{last}. Both arguments are
7368 linespecs. When a @code{list} command has two linespecs, and the
7369 source file of the second linespec is omitted, this refers to
7370 the same source file as the first linespec.
7372 @item list ,@var{last}
7373 Print lines ending with @var{last}.
7375 @item list @var{first},
7376 Print lines starting with @var{first}.
7379 Print lines just after the lines last printed.
7382 Print lines just before the lines last printed.
7385 As described in the preceding table.
7388 @node Specify Location
7389 @section Specifying a Location
7390 @cindex specifying location
7393 Several @value{GDBN} commands accept arguments that specify a location
7394 of your program's code. Since @value{GDBN} is a source-level
7395 debugger, a location usually specifies some line in the source code;
7396 for that reason, locations are also known as @dfn{linespecs}.
7398 Here are all the different ways of specifying a code location that
7399 @value{GDBN} understands:
7403 Specifies the line number @var{linenum} of the current source file.
7406 @itemx +@var{offset}
7407 Specifies the line @var{offset} lines before or after the @dfn{current
7408 line}. For the @code{list} command, the current line is the last one
7409 printed; for the breakpoint commands, this is the line at which
7410 execution stopped in the currently selected @dfn{stack frame}
7411 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7412 used as the second of the two linespecs in a @code{list} command,
7413 this specifies the line @var{offset} lines up or down from the first
7416 @item @var{filename}:@var{linenum}
7417 Specifies the line @var{linenum} in the source file @var{filename}.
7418 If @var{filename} is a relative file name, then it will match any
7419 source file name with the same trailing components. For example, if
7420 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7421 name of @file{/build/trunk/gcc/expr.c}, but not
7422 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7424 @item @var{function}
7425 Specifies the line that begins the body of the function @var{function}.
7426 For example, in C, this is the line with the open brace.
7428 @item @var{function}:@var{label}
7429 Specifies the line where @var{label} appears in @var{function}.
7431 @item @var{filename}:@var{function}
7432 Specifies the line that begins the body of the function @var{function}
7433 in the file @var{filename}. You only need the file name with a
7434 function name to avoid ambiguity when there are identically named
7435 functions in different source files.
7438 Specifies the line at which the label named @var{label} appears.
7439 @value{GDBN} searches for the label in the function corresponding to
7440 the currently selected stack frame. If there is no current selected
7441 stack frame (for instance, if the inferior is not running), then
7442 @value{GDBN} will not search for a label.
7444 @item *@var{address}
7445 Specifies the program address @var{address}. For line-oriented
7446 commands, such as @code{list} and @code{edit}, this specifies a source
7447 line that contains @var{address}. For @code{break} and other
7448 breakpoint oriented commands, this can be used to set breakpoints in
7449 parts of your program which do not have debugging information or
7452 Here @var{address} may be any expression valid in the current working
7453 language (@pxref{Languages, working language}) that specifies a code
7454 address. In addition, as a convenience, @value{GDBN} extends the
7455 semantics of expressions used in locations to cover the situations
7456 that frequently happen during debugging. Here are the various forms
7460 @item @var{expression}
7461 Any expression valid in the current working language.
7463 @item @var{funcaddr}
7464 An address of a function or procedure derived from its name. In C,
7465 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
7466 simply the function's name @var{function} (and actually a special case
7467 of a valid expression). In Pascal and Modula-2, this is
7468 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7469 (although the Pascal form also works).
7471 This form specifies the address of the function's first instruction,
7472 before the stack frame and arguments have been set up.
7474 @item '@var{filename}'::@var{funcaddr}
7475 Like @var{funcaddr} above, but also specifies the name of the source
7476 file explicitly. This is useful if the name of the function does not
7477 specify the function unambiguously, e.g., if there are several
7478 functions with identical names in different source files.
7481 @cindex breakpoint at static probe point
7482 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7483 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7484 applications to embed static probes. @xref{Static Probe Points}, for more
7485 information on finding and using static probes. This form of linespec
7486 specifies the location of such a static probe.
7488 If @var{objfile} is given, only probes coming from that shared library
7489 or executable matching @var{objfile} as a regular expression are considered.
7490 If @var{provider} is given, then only probes from that provider are considered.
7491 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7492 each one of those probes.
7498 @section Editing Source Files
7499 @cindex editing source files
7502 @kindex e @r{(@code{edit})}
7503 To edit the lines in a source file, use the @code{edit} command.
7504 The editing program of your choice
7505 is invoked with the current line set to
7506 the active line in the program.
7507 Alternatively, there are several ways to specify what part of the file you
7508 want to print if you want to see other parts of the program:
7511 @item edit @var{location}
7512 Edit the source file specified by @code{location}. Editing starts at
7513 that @var{location}, e.g., at the specified source line of the
7514 specified file. @xref{Specify Location}, for all the possible forms
7515 of the @var{location} argument; here are the forms of the @code{edit}
7516 command most commonly used:
7519 @item edit @var{number}
7520 Edit the current source file with @var{number} as the active line number.
7522 @item edit @var{function}
7523 Edit the file containing @var{function} at the beginning of its definition.
7528 @subsection Choosing your Editor
7529 You can customize @value{GDBN} to use any editor you want
7531 The only restriction is that your editor (say @code{ex}), recognizes the
7532 following command-line syntax:
7534 ex +@var{number} file
7536 The optional numeric value +@var{number} specifies the number of the line in
7537 the file where to start editing.}.
7538 By default, it is @file{@value{EDITOR}}, but you can change this
7539 by setting the environment variable @code{EDITOR} before using
7540 @value{GDBN}. For example, to configure @value{GDBN} to use the
7541 @code{vi} editor, you could use these commands with the @code{sh} shell:
7547 or in the @code{csh} shell,
7549 setenv EDITOR /usr/bin/vi
7554 @section Searching Source Files
7555 @cindex searching source files
7557 There are two commands for searching through the current source file for a
7562 @kindex forward-search
7563 @kindex fo @r{(@code{forward-search})}
7564 @item forward-search @var{regexp}
7565 @itemx search @var{regexp}
7566 The command @samp{forward-search @var{regexp}} checks each line,
7567 starting with the one following the last line listed, for a match for
7568 @var{regexp}. It lists the line that is found. You can use the
7569 synonym @samp{search @var{regexp}} or abbreviate the command name as
7572 @kindex reverse-search
7573 @item reverse-search @var{regexp}
7574 The command @samp{reverse-search @var{regexp}} checks each line, starting
7575 with the one before the last line listed and going backward, for a match
7576 for @var{regexp}. It lists the line that is found. You can abbreviate
7577 this command as @code{rev}.
7581 @section Specifying Source Directories
7584 @cindex directories for source files
7585 Executable programs sometimes do not record the directories of the source
7586 files from which they were compiled, just the names. Even when they do,
7587 the directories could be moved between the compilation and your debugging
7588 session. @value{GDBN} has a list of directories to search for source files;
7589 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
7590 it tries all the directories in the list, in the order they are present
7591 in the list, until it finds a file with the desired name.
7593 For example, suppose an executable references the file
7594 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
7595 @file{/mnt/cross}. The file is first looked up literally; if this
7596 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
7597 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
7598 message is printed. @value{GDBN} does not look up the parts of the
7599 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
7600 Likewise, the subdirectories of the source path are not searched: if
7601 the source path is @file{/mnt/cross}, and the binary refers to
7602 @file{foo.c}, @value{GDBN} would not find it under
7603 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7605 Plain file names, relative file names with leading directories, file
7606 names containing dots, etc.@: are all treated as described above; for
7607 instance, if the source path is @file{/mnt/cross}, and the source file
7608 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7609 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7610 that---@file{/mnt/cross/foo.c}.
7612 Note that the executable search path is @emph{not} used to locate the
7615 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7616 any information it has cached about where source files are found and where
7617 each line is in the file.
7621 When you start @value{GDBN}, its source path includes only @samp{cdir}
7622 and @samp{cwd}, in that order.
7623 To add other directories, use the @code{directory} command.
7625 The search path is used to find both program source files and @value{GDBN}
7626 script files (read using the @samp{-command} option and @samp{source} command).
7628 In addition to the source path, @value{GDBN} provides a set of commands
7629 that manage a list of source path substitution rules. A @dfn{substitution
7630 rule} specifies how to rewrite source directories stored in the program's
7631 debug information in case the sources were moved to a different
7632 directory between compilation and debugging. A rule is made of
7633 two strings, the first specifying what needs to be rewritten in
7634 the path, and the second specifying how it should be rewritten.
7635 In @ref{set substitute-path}, we name these two parts @var{from} and
7636 @var{to} respectively. @value{GDBN} does a simple string replacement
7637 of @var{from} with @var{to} at the start of the directory part of the
7638 source file name, and uses that result instead of the original file
7639 name to look up the sources.
7641 Using the previous example, suppose the @file{foo-1.0} tree has been
7642 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7643 @value{GDBN} to replace @file{/usr/src} in all source path names with
7644 @file{/mnt/cross}. The first lookup will then be
7645 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7646 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7647 substitution rule, use the @code{set substitute-path} command
7648 (@pxref{set substitute-path}).
7650 To avoid unexpected substitution results, a rule is applied only if the
7651 @var{from} part of the directory name ends at a directory separator.
7652 For instance, a rule substituting @file{/usr/source} into
7653 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7654 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7655 is applied only at the beginning of the directory name, this rule will
7656 not be applied to @file{/root/usr/source/baz.c} either.
7658 In many cases, you can achieve the same result using the @code{directory}
7659 command. However, @code{set substitute-path} can be more efficient in
7660 the case where the sources are organized in a complex tree with multiple
7661 subdirectories. With the @code{directory} command, you need to add each
7662 subdirectory of your project. If you moved the entire tree while
7663 preserving its internal organization, then @code{set substitute-path}
7664 allows you to direct the debugger to all the sources with one single
7667 @code{set substitute-path} is also more than just a shortcut command.
7668 The source path is only used if the file at the original location no
7669 longer exists. On the other hand, @code{set substitute-path} modifies
7670 the debugger behavior to look at the rewritten location instead. So, if
7671 for any reason a source file that is not relevant to your executable is
7672 located at the original location, a substitution rule is the only
7673 method available to point @value{GDBN} at the new location.
7675 @cindex @samp{--with-relocated-sources}
7676 @cindex default source path substitution
7677 You can configure a default source path substitution rule by
7678 configuring @value{GDBN} with the
7679 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7680 should be the name of a directory under @value{GDBN}'s configured
7681 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7682 directory names in debug information under @var{dir} will be adjusted
7683 automatically if the installed @value{GDBN} is moved to a new
7684 location. This is useful if @value{GDBN}, libraries or executables
7685 with debug information and corresponding source code are being moved
7689 @item directory @var{dirname} @dots{}
7690 @item dir @var{dirname} @dots{}
7691 Add directory @var{dirname} to the front of the source path. Several
7692 directory names may be given to this command, separated by @samp{:}
7693 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7694 part of absolute file names) or
7695 whitespace. You may specify a directory that is already in the source
7696 path; this moves it forward, so @value{GDBN} searches it sooner.
7700 @vindex $cdir@r{, convenience variable}
7701 @vindex $cwd@r{, convenience variable}
7702 @cindex compilation directory
7703 @cindex current directory
7704 @cindex working directory
7705 @cindex directory, current
7706 @cindex directory, compilation
7707 You can use the string @samp{$cdir} to refer to the compilation
7708 directory (if one is recorded), and @samp{$cwd} to refer to the current
7709 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7710 tracks the current working directory as it changes during your @value{GDBN}
7711 session, while the latter is immediately expanded to the current
7712 directory at the time you add an entry to the source path.
7715 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7717 @c RET-repeat for @code{directory} is explicitly disabled, but since
7718 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7720 @item set directories @var{path-list}
7721 @kindex set directories
7722 Set the source path to @var{path-list}.
7723 @samp{$cdir:$cwd} are added if missing.
7725 @item show directories
7726 @kindex show directories
7727 Print the source path: show which directories it contains.
7729 @anchor{set substitute-path}
7730 @item set substitute-path @var{from} @var{to}
7731 @kindex set substitute-path
7732 Define a source path substitution rule, and add it at the end of the
7733 current list of existing substitution rules. If a rule with the same
7734 @var{from} was already defined, then the old rule is also deleted.
7736 For example, if the file @file{/foo/bar/baz.c} was moved to
7737 @file{/mnt/cross/baz.c}, then the command
7740 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
7744 will tell @value{GDBN} to replace @samp{/usr/src} with
7745 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7746 @file{baz.c} even though it was moved.
7748 In the case when more than one substitution rule have been defined,
7749 the rules are evaluated one by one in the order where they have been
7750 defined. The first one matching, if any, is selected to perform
7753 For instance, if we had entered the following commands:
7756 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
7757 (@value{GDBP}) set substitute-path /usr/src /mnt/src
7761 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
7762 @file{/mnt/include/defs.h} by using the first rule. However, it would
7763 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
7764 @file{/mnt/src/lib/foo.c}.
7767 @item unset substitute-path [path]
7768 @kindex unset substitute-path
7769 If a path is specified, search the current list of substitution rules
7770 for a rule that would rewrite that path. Delete that rule if found.
7771 A warning is emitted by the debugger if no rule could be found.
7773 If no path is specified, then all substitution rules are deleted.
7775 @item show substitute-path [path]
7776 @kindex show substitute-path
7777 If a path is specified, then print the source path substitution rule
7778 which would rewrite that path, if any.
7780 If no path is specified, then print all existing source path substitution
7785 If your source path is cluttered with directories that are no longer of
7786 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
7787 versions of source. You can correct the situation as follows:
7791 Use @code{directory} with no argument to reset the source path to its default value.
7794 Use @code{directory} with suitable arguments to reinstall the
7795 directories you want in the source path. You can add all the
7796 directories in one command.
7800 @section Source and Machine Code
7801 @cindex source line and its code address
7803 You can use the command @code{info line} to map source lines to program
7804 addresses (and vice versa), and the command @code{disassemble} to display
7805 a range of addresses as machine instructions. You can use the command
7806 @code{set disassemble-next-line} to set whether to disassemble next
7807 source line when execution stops. When run under @sc{gnu} Emacs
7808 mode, the @code{info line} command causes the arrow to point to the
7809 line specified. Also, @code{info line} prints addresses in symbolic form as
7814 @item info line @var{linespec}
7815 Print the starting and ending addresses of the compiled code for
7816 source line @var{linespec}. You can specify source lines in any of
7817 the ways documented in @ref{Specify Location}.
7820 For example, we can use @code{info line} to discover the location of
7821 the object code for the first line of function
7822 @code{m4_changequote}:
7824 @c FIXME: I think this example should also show the addresses in
7825 @c symbolic form, as they usually would be displayed.
7827 (@value{GDBP}) info line m4_changequote
7828 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
7832 @cindex code address and its source line
7833 We can also inquire (using @code{*@var{addr}} as the form for
7834 @var{linespec}) what source line covers a particular address:
7836 (@value{GDBP}) info line *0x63ff
7837 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
7840 @cindex @code{$_} and @code{info line}
7841 @cindex @code{x} command, default address
7842 @kindex x@r{(examine), and} info line
7843 After @code{info line}, the default address for the @code{x} command
7844 is changed to the starting address of the line, so that @samp{x/i} is
7845 sufficient to begin examining the machine code (@pxref{Memory,
7846 ,Examining Memory}). Also, this address is saved as the value of the
7847 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
7852 @cindex assembly instructions
7853 @cindex instructions, assembly
7854 @cindex machine instructions
7855 @cindex listing machine instructions
7857 @itemx disassemble /m
7858 @itemx disassemble /r
7859 This specialized command dumps a range of memory as machine
7860 instructions. It can also print mixed source+disassembly by specifying
7861 the @code{/m} modifier and print the raw instructions in hex as well as
7862 in symbolic form by specifying the @code{/r}.
7863 The default memory range is the function surrounding the
7864 program counter of the selected frame. A single argument to this
7865 command is a program counter value; @value{GDBN} dumps the function
7866 surrounding this value. When two arguments are given, they should
7867 be separated by a comma, possibly surrounded by whitespace. The
7868 arguments specify a range of addresses to dump, in one of two forms:
7871 @item @var{start},@var{end}
7872 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
7873 @item @var{start},+@var{length}
7874 the addresses from @var{start} (inclusive) to
7875 @code{@var{start}+@var{length}} (exclusive).
7879 When 2 arguments are specified, the name of the function is also
7880 printed (since there could be several functions in the given range).
7882 The argument(s) can be any expression yielding a numeric value, such as
7883 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
7885 If the range of memory being disassembled contains current program counter,
7886 the instruction at that location is shown with a @code{=>} marker.
7889 The following example shows the disassembly of a range of addresses of
7890 HP PA-RISC 2.0 code:
7893 (@value{GDBP}) disas 0x32c4, 0x32e4
7894 Dump of assembler code from 0x32c4 to 0x32e4:
7895 0x32c4 <main+204>: addil 0,dp
7896 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
7897 0x32cc <main+212>: ldil 0x3000,r31
7898 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
7899 0x32d4 <main+220>: ldo 0(r31),rp
7900 0x32d8 <main+224>: addil -0x800,dp
7901 0x32dc <main+228>: ldo 0x588(r1),r26
7902 0x32e0 <main+232>: ldil 0x3000,r31
7903 End of assembler dump.
7906 Here is an example showing mixed source+assembly for Intel x86, when the
7907 program is stopped just after function prologue:
7910 (@value{GDBP}) disas /m main
7911 Dump of assembler code for function main:
7913 0x08048330 <+0>: push %ebp
7914 0x08048331 <+1>: mov %esp,%ebp
7915 0x08048333 <+3>: sub $0x8,%esp
7916 0x08048336 <+6>: and $0xfffffff0,%esp
7917 0x08048339 <+9>: sub $0x10,%esp
7919 6 printf ("Hello.\n");
7920 => 0x0804833c <+12>: movl $0x8048440,(%esp)
7921 0x08048343 <+19>: call 0x8048284 <puts@@plt>
7925 0x08048348 <+24>: mov $0x0,%eax
7926 0x0804834d <+29>: leave
7927 0x0804834e <+30>: ret
7929 End of assembler dump.
7932 Here is another example showing raw instructions in hex for AMD x86-64,
7935 (gdb) disas /r 0x400281,+10
7936 Dump of assembler code from 0x400281 to 0x40028b:
7937 0x0000000000400281: 38 36 cmp %dh,(%rsi)
7938 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
7939 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
7940 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7941 End of assembler dump.
7944 Addresses cannot be specified as a linespec (@pxref{Specify Location}).
7945 So, for example, if you want to disassemble function @code{bar}
7946 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
7947 and not @samp{disassemble foo.c:bar}.
7949 Some architectures have more than one commonly-used set of instruction
7950 mnemonics or other syntax.
7952 For programs that were dynamically linked and use shared libraries,
7953 instructions that call functions or branch to locations in the shared
7954 libraries might show a seemingly bogus location---it's actually a
7955 location of the relocation table. On some architectures, @value{GDBN}
7956 might be able to resolve these to actual function names.
7959 @kindex set disassembly-flavor
7960 @cindex Intel disassembly flavor
7961 @cindex AT&T disassembly flavor
7962 @item set disassembly-flavor @var{instruction-set}
7963 Select the instruction set to use when disassembling the
7964 program via the @code{disassemble} or @code{x/i} commands.
7966 Currently this command is only defined for the Intel x86 family. You
7967 can set @var{instruction-set} to either @code{intel} or @code{att}.
7968 The default is @code{att}, the AT&T flavor used by default by Unix
7969 assemblers for x86-based targets.
7971 @kindex show disassembly-flavor
7972 @item show disassembly-flavor
7973 Show the current setting of the disassembly flavor.
7977 @kindex set disassemble-next-line
7978 @kindex show disassemble-next-line
7979 @item set disassemble-next-line
7980 @itemx show disassemble-next-line
7981 Control whether or not @value{GDBN} will disassemble the next source
7982 line or instruction when execution stops. If ON, @value{GDBN} will
7983 display disassembly of the next source line when execution of the
7984 program being debugged stops. This is @emph{in addition} to
7985 displaying the source line itself, which @value{GDBN} always does if
7986 possible. If the next source line cannot be displayed for some reason
7987 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7988 info in the debug info), @value{GDBN} will display disassembly of the
7989 next @emph{instruction} instead of showing the next source line. If
7990 AUTO, @value{GDBN} will display disassembly of next instruction only
7991 if the source line cannot be displayed. This setting causes
7992 @value{GDBN} to display some feedback when you step through a function
7993 with no line info or whose source file is unavailable. The default is
7994 OFF, which means never display the disassembly of the next line or
8000 @chapter Examining Data
8002 @cindex printing data
8003 @cindex examining data
8006 The usual way to examine data in your program is with the @code{print}
8007 command (abbreviated @code{p}), or its synonym @code{inspect}. It
8008 evaluates and prints the value of an expression of the language your
8009 program is written in (@pxref{Languages, ,Using @value{GDBN} with
8010 Different Languages}). It may also print the expression using a
8011 Python-based pretty-printer (@pxref{Pretty Printing}).
8014 @item print @var{expr}
8015 @itemx print /@var{f} @var{expr}
8016 @var{expr} is an expression (in the source language). By default the
8017 value of @var{expr} is printed in a format appropriate to its data type;
8018 you can choose a different format by specifying @samp{/@var{f}}, where
8019 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
8023 @itemx print /@var{f}
8024 @cindex reprint the last value
8025 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
8026 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
8027 conveniently inspect the same value in an alternative format.
8030 A more low-level way of examining data is with the @code{x} command.
8031 It examines data in memory at a specified address and prints it in a
8032 specified format. @xref{Memory, ,Examining Memory}.
8034 If you are interested in information about types, or about how the
8035 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
8036 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
8039 @cindex exploring hierarchical data structures
8041 Another way of examining values of expressions and type information is
8042 through the Python extension command @code{explore} (available only if
8043 the @value{GDBN} build is configured with @code{--with-python}). It
8044 offers an interactive way to start at the highest level (or, the most
8045 abstract level) of the data type of an expression (or, the data type
8046 itself) and explore all the way down to leaf scalar values/fields
8047 embedded in the higher level data types.
8050 @item explore @var{arg}
8051 @var{arg} is either an expression (in the source language), or a type
8052 visible in the current context of the program being debugged.
8055 The working of the @code{explore} command can be illustrated with an
8056 example. If a data type @code{struct ComplexStruct} is defined in your
8066 struct ComplexStruct
8068 struct SimpleStruct *ss_p;
8074 followed by variable declarations as
8077 struct SimpleStruct ss = @{ 10, 1.11 @};
8078 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
8082 then, the value of the variable @code{cs} can be explored using the
8083 @code{explore} command as follows.
8087 The value of `cs' is a struct/class of type `struct ComplexStruct' with
8088 the following fields:
8090 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
8091 arr = <Enter 1 to explore this field of type `int [10]'>
8093 Enter the field number of choice:
8097 Since the fields of @code{cs} are not scalar values, you are being
8098 prompted to chose the field you want to explore. Let's say you choose
8099 the field @code{ss_p} by entering @code{0}. Then, since this field is a
8100 pointer, you will be asked if it is pointing to a single value. From
8101 the declaration of @code{cs} above, it is indeed pointing to a single
8102 value, hence you enter @code{y}. If you enter @code{n}, then you will
8103 be asked if it were pointing to an array of values, in which case this
8104 field will be explored as if it were an array.
8107 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
8108 Continue exploring it as a pointer to a single value [y/n]: y
8109 The value of `*(cs.ss_p)' is a struct/class of type `struct
8110 SimpleStruct' with the following fields:
8112 i = 10 .. (Value of type `int')
8113 d = 1.1100000000000001 .. (Value of type `double')
8115 Press enter to return to parent value:
8119 If the field @code{arr} of @code{cs} was chosen for exploration by
8120 entering @code{1} earlier, then since it is as array, you will be
8121 prompted to enter the index of the element in the array that you want
8125 `cs.arr' is an array of `int'.
8126 Enter the index of the element you want to explore in `cs.arr': 5
8128 `(cs.arr)[5]' is a scalar value of type `int'.
8132 Press enter to return to parent value:
8135 In general, at any stage of exploration, you can go deeper towards the
8136 leaf values by responding to the prompts appropriately, or hit the
8137 return key to return to the enclosing data structure (the @i{higher}
8138 level data structure).
8140 Similar to exploring values, you can use the @code{explore} command to
8141 explore types. Instead of specifying a value (which is typically a
8142 variable name or an expression valid in the current context of the
8143 program being debugged), you specify a type name. If you consider the
8144 same example as above, your can explore the type
8145 @code{struct ComplexStruct} by passing the argument
8146 @code{struct ComplexStruct} to the @code{explore} command.
8149 (gdb) explore struct ComplexStruct
8153 By responding to the prompts appropriately in the subsequent interactive
8154 session, you can explore the type @code{struct ComplexStruct} in a
8155 manner similar to how the value @code{cs} was explored in the above
8158 The @code{explore} command also has two sub-commands,
8159 @code{explore value} and @code{explore type}. The former sub-command is
8160 a way to explicitly specify that value exploration of the argument is
8161 being invoked, while the latter is a way to explicitly specify that type
8162 exploration of the argument is being invoked.
8165 @item explore value @var{expr}
8166 @cindex explore value
8167 This sub-command of @code{explore} explores the value of the
8168 expression @var{expr} (if @var{expr} is an expression valid in the
8169 current context of the program being debugged). The behavior of this
8170 command is identical to that of the behavior of the @code{explore}
8171 command being passed the argument @var{expr}.
8173 @item explore type @var{arg}
8174 @cindex explore type
8175 This sub-command of @code{explore} explores the type of @var{arg} (if
8176 @var{arg} is a type visible in the current context of program being
8177 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8178 is an expression valid in the current context of the program being
8179 debugged). If @var{arg} is a type, then the behavior of this command is
8180 identical to that of the @code{explore} command being passed the
8181 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8182 this command will be identical to that of the @code{explore} command
8183 being passed the type of @var{arg} as the argument.
8187 * Expressions:: Expressions
8188 * Ambiguous Expressions:: Ambiguous Expressions
8189 * Variables:: Program variables
8190 * Arrays:: Artificial arrays
8191 * Output Formats:: Output formats
8192 * Memory:: Examining memory
8193 * Auto Display:: Automatic display
8194 * Print Settings:: Print settings
8195 * Pretty Printing:: Python pretty printing
8196 * Value History:: Value history
8197 * Convenience Vars:: Convenience variables
8198 * Convenience Funs:: Convenience functions
8199 * Registers:: Registers
8200 * Floating Point Hardware:: Floating point hardware
8201 * Vector Unit:: Vector Unit
8202 * OS Information:: Auxiliary data provided by operating system
8203 * Memory Region Attributes:: Memory region attributes
8204 * Dump/Restore Files:: Copy between memory and a file
8205 * Core File Generation:: Cause a program dump its core
8206 * Character Sets:: Debugging programs that use a different
8207 character set than GDB does
8208 * Caching Target Data:: Data caching for targets
8209 * Searching Memory:: Searching memory for a sequence of bytes
8213 @section Expressions
8216 @code{print} and many other @value{GDBN} commands accept an expression and
8217 compute its value. Any kind of constant, variable or operator defined
8218 by the programming language you are using is valid in an expression in
8219 @value{GDBN}. This includes conditional expressions, function calls,
8220 casts, and string constants. It also includes preprocessor macros, if
8221 you compiled your program to include this information; see
8224 @cindex arrays in expressions
8225 @value{GDBN} supports array constants in expressions input by
8226 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8227 you can use the command @code{print @{1, 2, 3@}} to create an array
8228 of three integers. If you pass an array to a function or assign it
8229 to a program variable, @value{GDBN} copies the array to memory that
8230 is @code{malloc}ed in the target program.
8232 Because C is so widespread, most of the expressions shown in examples in
8233 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8234 Languages}, for information on how to use expressions in other
8237 In this section, we discuss operators that you can use in @value{GDBN}
8238 expressions regardless of your programming language.
8240 @cindex casts, in expressions
8241 Casts are supported in all languages, not just in C, because it is so
8242 useful to cast a number into a pointer in order to examine a structure
8243 at that address in memory.
8244 @c FIXME: casts supported---Mod2 true?
8246 @value{GDBN} supports these operators, in addition to those common
8247 to programming languages:
8251 @samp{@@} is a binary operator for treating parts of memory as arrays.
8252 @xref{Arrays, ,Artificial Arrays}, for more information.
8255 @samp{::} allows you to specify a variable in terms of the file or
8256 function where it is defined. @xref{Variables, ,Program Variables}.
8258 @cindex @{@var{type}@}
8259 @cindex type casting memory
8260 @cindex memory, viewing as typed object
8261 @cindex casts, to view memory
8262 @item @{@var{type}@} @var{addr}
8263 Refers to an object of type @var{type} stored at address @var{addr} in
8264 memory. The address @var{addr} may be any expression whose value is
8265 an integer or pointer (but parentheses are required around binary
8266 operators, just as in a cast). This construct is allowed regardless
8267 of what kind of data is normally supposed to reside at @var{addr}.
8270 @node Ambiguous Expressions
8271 @section Ambiguous Expressions
8272 @cindex ambiguous expressions
8274 Expressions can sometimes contain some ambiguous elements. For instance,
8275 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8276 a single function name to be defined several times, for application in
8277 different contexts. This is called @dfn{overloading}. Another example
8278 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8279 templates and is typically instantiated several times, resulting in
8280 the same function name being defined in different contexts.
8282 In some cases and depending on the language, it is possible to adjust
8283 the expression to remove the ambiguity. For instance in C@t{++}, you
8284 can specify the signature of the function you want to break on, as in
8285 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8286 qualified name of your function often makes the expression unambiguous
8289 When an ambiguity that needs to be resolved is detected, the debugger
8290 has the capability to display a menu of numbered choices for each
8291 possibility, and then waits for the selection with the prompt @samp{>}.
8292 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
8293 aborts the current command. If the command in which the expression was
8294 used allows more than one choice to be selected, the next option in the
8295 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
8298 For example, the following session excerpt shows an attempt to set a
8299 breakpoint at the overloaded symbol @code{String::after}.
8300 We choose three particular definitions of that function name:
8302 @c FIXME! This is likely to change to show arg type lists, at least
8305 (@value{GDBP}) b String::after
8308 [2] file:String.cc; line number:867
8309 [3] file:String.cc; line number:860
8310 [4] file:String.cc; line number:875
8311 [5] file:String.cc; line number:853
8312 [6] file:String.cc; line number:846
8313 [7] file:String.cc; line number:735
8315 Breakpoint 1 at 0xb26c: file String.cc, line 867.
8316 Breakpoint 2 at 0xb344: file String.cc, line 875.
8317 Breakpoint 3 at 0xafcc: file String.cc, line 846.
8318 Multiple breakpoints were set.
8319 Use the "delete" command to delete unwanted
8326 @kindex set multiple-symbols
8327 @item set multiple-symbols @var{mode}
8328 @cindex multiple-symbols menu
8330 This option allows you to adjust the debugger behavior when an expression
8333 By default, @var{mode} is set to @code{all}. If the command with which
8334 the expression is used allows more than one choice, then @value{GDBN}
8335 automatically selects all possible choices. For instance, inserting
8336 a breakpoint on a function using an ambiguous name results in a breakpoint
8337 inserted on each possible match. However, if a unique choice must be made,
8338 then @value{GDBN} uses the menu to help you disambiguate the expression.
8339 For instance, printing the address of an overloaded function will result
8340 in the use of the menu.
8342 When @var{mode} is set to @code{ask}, the debugger always uses the menu
8343 when an ambiguity is detected.
8345 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
8346 an error due to the ambiguity and the command is aborted.
8348 @kindex show multiple-symbols
8349 @item show multiple-symbols
8350 Show the current value of the @code{multiple-symbols} setting.
8354 @section Program Variables
8356 The most common kind of expression to use is the name of a variable
8359 Variables in expressions are understood in the selected stack frame
8360 (@pxref{Selection, ,Selecting a Frame}); they must be either:
8364 global (or file-static)
8371 visible according to the scope rules of the
8372 programming language from the point of execution in that frame
8375 @noindent This means that in the function
8390 you can examine and use the variable @code{a} whenever your program is
8391 executing within the function @code{foo}, but you can only use or
8392 examine the variable @code{b} while your program is executing inside
8393 the block where @code{b} is declared.
8395 @cindex variable name conflict
8396 There is an exception: you can refer to a variable or function whose
8397 scope is a single source file even if the current execution point is not
8398 in this file. But it is possible to have more than one such variable or
8399 function with the same name (in different source files). If that
8400 happens, referring to that name has unpredictable effects. If you wish,
8401 you can specify a static variable in a particular function or file by
8402 using the colon-colon (@code{::}) notation:
8404 @cindex colon-colon, context for variables/functions
8406 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
8407 @cindex @code{::}, context for variables/functions
8410 @var{file}::@var{variable}
8411 @var{function}::@var{variable}
8415 Here @var{file} or @var{function} is the name of the context for the
8416 static @var{variable}. In the case of file names, you can use quotes to
8417 make sure @value{GDBN} parses the file name as a single word---for example,
8418 to print a global value of @code{x} defined in @file{f2.c}:
8421 (@value{GDBP}) p 'f2.c'::x
8424 The @code{::} notation is normally used for referring to
8425 static variables, since you typically disambiguate uses of local variables
8426 in functions by selecting the appropriate frame and using the
8427 simple name of the variable. However, you may also use this notation
8428 to refer to local variables in frames enclosing the selected frame:
8437 process (a); /* Stop here */
8448 For example, if there is a breakpoint at the commented line,
8449 here is what you might see
8450 when the program stops after executing the call @code{bar(0)}:
8455 (@value{GDBP}) p bar::a
8458 #2 0x080483d0 in foo (a=5) at foobar.c:12
8461 (@value{GDBP}) p bar::a
8465 @cindex C@t{++} scope resolution
8466 These uses of @samp{::} are very rarely in conflict with the very
8467 similar use of the same notation in C@t{++}. When they are in
8468 conflict, the C@t{++} meaning takes precedence; however, this can be
8469 overridden by quoting the file or function name with single quotes.
8471 For example, suppose the program is stopped in a method of a class
8472 that has a field named @code{includefile}, and there is also an
8473 include file named @file{includefile} that defines a variable,
8477 (@value{GDBP}) p includefile
8479 (@value{GDBP}) p includefile::some_global
8480 A syntax error in expression, near `'.
8481 (@value{GDBP}) p 'includefile'::some_global
8485 @cindex wrong values
8486 @cindex variable values, wrong
8487 @cindex function entry/exit, wrong values of variables
8488 @cindex optimized code, wrong values of variables
8490 @emph{Warning:} Occasionally, a local variable may appear to have the
8491 wrong value at certain points in a function---just after entry to a new
8492 scope, and just before exit.
8494 You may see this problem when you are stepping by machine instructions.
8495 This is because, on most machines, it takes more than one instruction to
8496 set up a stack frame (including local variable definitions); if you are
8497 stepping by machine instructions, variables may appear to have the wrong
8498 values until the stack frame is completely built. On exit, it usually
8499 also takes more than one machine instruction to destroy a stack frame;
8500 after you begin stepping through that group of instructions, local
8501 variable definitions may be gone.
8503 This may also happen when the compiler does significant optimizations.
8504 To be sure of always seeing accurate values, turn off all optimization
8507 @cindex ``No symbol "foo" in current context''
8508 Another possible effect of compiler optimizations is to optimize
8509 unused variables out of existence, or assign variables to registers (as
8510 opposed to memory addresses). Depending on the support for such cases
8511 offered by the debug info format used by the compiler, @value{GDBN}
8512 might not be able to display values for such local variables. If that
8513 happens, @value{GDBN} will print a message like this:
8516 No symbol "foo" in current context.
8519 To solve such problems, either recompile without optimizations, or use a
8520 different debug info format, if the compiler supports several such
8521 formats. @xref{Compilation}, for more information on choosing compiler
8522 options. @xref{C, ,C and C@t{++}}, for more information about debug
8523 info formats that are best suited to C@t{++} programs.
8525 If you ask to print an object whose contents are unknown to
8526 @value{GDBN}, e.g., because its data type is not completely specified
8527 by the debug information, @value{GDBN} will say @samp{<incomplete
8528 type>}. @xref{Symbols, incomplete type}, for more about this.
8530 If you append @kbd{@@entry} string to a function parameter name you get its
8531 value at the time the function got called. If the value is not available an
8532 error message is printed. Entry values are available only with some compilers.
8533 Entry values are normally also printed at the function parameter list according
8534 to @ref{set print entry-values}.
8537 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
8543 (gdb) print i@@entry
8547 Strings are identified as arrays of @code{char} values without specified
8548 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
8549 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
8550 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
8551 defines literal string type @code{"char"} as @code{char} without a sign.
8556 signed char var1[] = "A";
8559 You get during debugging
8564 $2 = @{65 'A', 0 '\0'@}
8568 @section Artificial Arrays
8570 @cindex artificial array
8572 @kindex @@@r{, referencing memory as an array}
8573 It is often useful to print out several successive objects of the
8574 same type in memory; a section of an array, or an array of
8575 dynamically determined size for which only a pointer exists in the
8578 You can do this by referring to a contiguous span of memory as an
8579 @dfn{artificial array}, using the binary operator @samp{@@}. The left
8580 operand of @samp{@@} should be the first element of the desired array
8581 and be an individual object. The right operand should be the desired length
8582 of the array. The result is an array value whose elements are all of
8583 the type of the left argument. The first element is actually the left
8584 argument; the second element comes from bytes of memory immediately
8585 following those that hold the first element, and so on. Here is an
8586 example. If a program says
8589 int *array = (int *) malloc (len * sizeof (int));
8593 you can print the contents of @code{array} with
8599 The left operand of @samp{@@} must reside in memory. Array values made
8600 with @samp{@@} in this way behave just like other arrays in terms of
8601 subscripting, and are coerced to pointers when used in expressions.
8602 Artificial arrays most often appear in expressions via the value history
8603 (@pxref{Value History, ,Value History}), after printing one out.
8605 Another way to create an artificial array is to use a cast.
8606 This re-interprets a value as if it were an array.
8607 The value need not be in memory:
8609 (@value{GDBP}) p/x (short[2])0x12345678
8610 $1 = @{0x1234, 0x5678@}
8613 As a convenience, if you leave the array length out (as in
8614 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
8615 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
8617 (@value{GDBP}) p/x (short[])0x12345678
8618 $2 = @{0x1234, 0x5678@}
8621 Sometimes the artificial array mechanism is not quite enough; in
8622 moderately complex data structures, the elements of interest may not
8623 actually be adjacent---for example, if you are interested in the values
8624 of pointers in an array. One useful work-around in this situation is
8625 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8626 Variables}) as a counter in an expression that prints the first
8627 interesting value, and then repeat that expression via @key{RET}. For
8628 instance, suppose you have an array @code{dtab} of pointers to
8629 structures, and you are interested in the values of a field @code{fv}
8630 in each structure. Here is an example of what you might type:
8640 @node Output Formats
8641 @section Output Formats
8643 @cindex formatted output
8644 @cindex output formats
8645 By default, @value{GDBN} prints a value according to its data type. Sometimes
8646 this is not what you want. For example, you might want to print a number
8647 in hex, or a pointer in decimal. Or you might want to view data in memory
8648 at a certain address as a character string or as an instruction. To do
8649 these things, specify an @dfn{output format} when you print a value.
8651 The simplest use of output formats is to say how to print a value
8652 already computed. This is done by starting the arguments of the
8653 @code{print} command with a slash and a format letter. The format
8654 letters supported are:
8658 Regard the bits of the value as an integer, and print the integer in
8662 Print as integer in signed decimal.
8665 Print as integer in unsigned decimal.
8668 Print as integer in octal.
8671 Print as integer in binary. The letter @samp{t} stands for ``two''.
8672 @footnote{@samp{b} cannot be used because these format letters are also
8673 used with the @code{x} command, where @samp{b} stands for ``byte'';
8674 see @ref{Memory,,Examining Memory}.}
8677 @cindex unknown address, locating
8678 @cindex locate address
8679 Print as an address, both absolute in hexadecimal and as an offset from
8680 the nearest preceding symbol. You can use this format used to discover
8681 where (in what function) an unknown address is located:
8684 (@value{GDBP}) p/a 0x54320
8685 $3 = 0x54320 <_initialize_vx+396>
8689 The command @code{info symbol 0x54320} yields similar results.
8690 @xref{Symbols, info symbol}.
8693 Regard as an integer and print it as a character constant. This
8694 prints both the numerical value and its character representation. The
8695 character representation is replaced with the octal escape @samp{\nnn}
8696 for characters outside the 7-bit @sc{ascii} range.
8698 Without this format, @value{GDBN} displays @code{char},
8699 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
8700 constants. Single-byte members of vectors are displayed as integer
8704 Regard the bits of the value as a floating point number and print
8705 using typical floating point syntax.
8708 @cindex printing strings
8709 @cindex printing byte arrays
8710 Regard as a string, if possible. With this format, pointers to single-byte
8711 data are displayed as null-terminated strings and arrays of single-byte data
8712 are displayed as fixed-length strings. Other values are displayed in their
8715 Without this format, @value{GDBN} displays pointers to and arrays of
8716 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
8717 strings. Single-byte members of a vector are displayed as an integer
8721 Like @samp{x} formatting, the value is treated as an integer and
8722 printed as hexadecimal, but leading zeros are printed to pad the value
8723 to the size of the integer type.
8726 @cindex raw printing
8727 Print using the @samp{raw} formatting. By default, @value{GDBN} will
8728 use a Python-based pretty-printer, if one is available (@pxref{Pretty
8729 Printing}). This typically results in a higher-level display of the
8730 value's contents. The @samp{r} format bypasses any Python
8731 pretty-printer which might exist.
8734 For example, to print the program counter in hex (@pxref{Registers}), type
8741 Note that no space is required before the slash; this is because command
8742 names in @value{GDBN} cannot contain a slash.
8744 To reprint the last value in the value history with a different format,
8745 you can use the @code{print} command with just a format and no
8746 expression. For example, @samp{p/x} reprints the last value in hex.
8749 @section Examining Memory
8751 You can use the command @code{x} (for ``examine'') to examine memory in
8752 any of several formats, independently of your program's data types.
8754 @cindex examining memory
8756 @kindex x @r{(examine memory)}
8757 @item x/@var{nfu} @var{addr}
8760 Use the @code{x} command to examine memory.
8763 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
8764 much memory to display and how to format it; @var{addr} is an
8765 expression giving the address where you want to start displaying memory.
8766 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
8767 Several commands set convenient defaults for @var{addr}.
8770 @item @var{n}, the repeat count
8771 The repeat count is a decimal integer; the default is 1. It specifies
8772 how much memory (counting by units @var{u}) to display.
8773 @c This really is **decimal**; unaffected by 'set radix' as of GDB
8776 @item @var{f}, the display format
8777 The display format is one of the formats used by @code{print}
8778 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
8779 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
8780 The default is @samp{x} (hexadecimal) initially. The default changes
8781 each time you use either @code{x} or @code{print}.
8783 @item @var{u}, the unit size
8784 The unit size is any of
8790 Halfwords (two bytes).
8792 Words (four bytes). This is the initial default.
8794 Giant words (eight bytes).
8797 Each time you specify a unit size with @code{x}, that size becomes the
8798 default unit the next time you use @code{x}. For the @samp{i} format,
8799 the unit size is ignored and is normally not written. For the @samp{s} format,
8800 the unit size defaults to @samp{b}, unless it is explicitly given.
8801 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
8802 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
8803 Note that the results depend on the programming language of the
8804 current compilation unit. If the language is C, the @samp{s}
8805 modifier will use the UTF-16 encoding while @samp{w} will use
8806 UTF-32. The encoding is set by the programming language and cannot
8809 @item @var{addr}, starting display address
8810 @var{addr} is the address where you want @value{GDBN} to begin displaying
8811 memory. The expression need not have a pointer value (though it may);
8812 it is always interpreted as an integer address of a byte of memory.
8813 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
8814 @var{addr} is usually just after the last address examined---but several
8815 other commands also set the default address: @code{info breakpoints} (to
8816 the address of the last breakpoint listed), @code{info line} (to the
8817 starting address of a line), and @code{print} (if you use it to display
8818 a value from memory).
8821 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
8822 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
8823 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
8824 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
8825 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
8827 Since the letters indicating unit sizes are all distinct from the
8828 letters specifying output formats, you do not have to remember whether
8829 unit size or format comes first; either order works. The output
8830 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
8831 (However, the count @var{n} must come first; @samp{wx4} does not work.)
8833 Even though the unit size @var{u} is ignored for the formats @samp{s}
8834 and @samp{i}, you might still want to use a count @var{n}; for example,
8835 @samp{3i} specifies that you want to see three machine instructions,
8836 including any operands. For convenience, especially when used with
8837 the @code{display} command, the @samp{i} format also prints branch delay
8838 slot instructions, if any, beyond the count specified, which immediately
8839 follow the last instruction that is within the count. The command
8840 @code{disassemble} gives an alternative way of inspecting machine
8841 instructions; see @ref{Machine Code,,Source and Machine Code}.
8843 All the defaults for the arguments to @code{x} are designed to make it
8844 easy to continue scanning memory with minimal specifications each time
8845 you use @code{x}. For example, after you have inspected three machine
8846 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
8847 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
8848 the repeat count @var{n} is used again; the other arguments default as
8849 for successive uses of @code{x}.
8851 When examining machine instructions, the instruction at current program
8852 counter is shown with a @code{=>} marker. For example:
8855 (@value{GDBP}) x/5i $pc-6
8856 0x804837f <main+11>: mov %esp,%ebp
8857 0x8048381 <main+13>: push %ecx
8858 0x8048382 <main+14>: sub $0x4,%esp
8859 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
8860 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
8863 @cindex @code{$_}, @code{$__}, and value history
8864 The addresses and contents printed by the @code{x} command are not saved
8865 in the value history because there is often too much of them and they
8866 would get in the way. Instead, @value{GDBN} makes these values available for
8867 subsequent use in expressions as values of the convenience variables
8868 @code{$_} and @code{$__}. After an @code{x} command, the last address
8869 examined is available for use in expressions in the convenience variable
8870 @code{$_}. The contents of that address, as examined, are available in
8871 the convenience variable @code{$__}.
8873 If the @code{x} command has a repeat count, the address and contents saved
8874 are from the last memory unit printed; this is not the same as the last
8875 address printed if several units were printed on the last line of output.
8877 @cindex remote memory comparison
8878 @cindex target memory comparison
8879 @cindex verify remote memory image
8880 @cindex verify target memory image
8881 When you are debugging a program running on a remote target machine
8882 (@pxref{Remote Debugging}), you may wish to verify the program's image
8883 in the remote machine's memory against the executable file you
8884 downloaded to the target. Or, on any target, you may want to check
8885 whether the program has corrupted its own read-only sections. The
8886 @code{compare-sections} command is provided for such situations.
8889 @kindex compare-sections
8890 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
8891 Compare the data of a loadable section @var{section-name} in the
8892 executable file of the program being debugged with the same section in
8893 the target machine's memory, and report any mismatches. With no
8894 arguments, compares all loadable sections. With an argument of
8895 @code{-r}, compares all loadable read-only sections.
8897 Note: for remote targets, this command can be accelerated if the
8898 target supports computing the CRC checksum of a block of memory
8899 (@pxref{qCRC packet}).
8903 @section Automatic Display
8904 @cindex automatic display
8905 @cindex display of expressions
8907 If you find that you want to print the value of an expression frequently
8908 (to see how it changes), you might want to add it to the @dfn{automatic
8909 display list} so that @value{GDBN} prints its value each time your program stops.
8910 Each expression added to the list is given a number to identify it;
8911 to remove an expression from the list, you specify that number.
8912 The automatic display looks like this:
8916 3: bar[5] = (struct hack *) 0x3804
8920 This display shows item numbers, expressions and their current values. As with
8921 displays you request manually using @code{x} or @code{print}, you can
8922 specify the output format you prefer; in fact, @code{display} decides
8923 whether to use @code{print} or @code{x} depending your format
8924 specification---it uses @code{x} if you specify either the @samp{i}
8925 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
8929 @item display @var{expr}
8930 Add the expression @var{expr} to the list of expressions to display
8931 each time your program stops. @xref{Expressions, ,Expressions}.
8933 @code{display} does not repeat if you press @key{RET} again after using it.
8935 @item display/@var{fmt} @var{expr}
8936 For @var{fmt} specifying only a display format and not a size or
8937 count, add the expression @var{expr} to the auto-display list but
8938 arrange to display it each time in the specified format @var{fmt}.
8939 @xref{Output Formats,,Output Formats}.
8941 @item display/@var{fmt} @var{addr}
8942 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
8943 number of units, add the expression @var{addr} as a memory address to
8944 be examined each time your program stops. Examining means in effect
8945 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
8948 For example, @samp{display/i $pc} can be helpful, to see the machine
8949 instruction about to be executed each time execution stops (@samp{$pc}
8950 is a common name for the program counter; @pxref{Registers, ,Registers}).
8953 @kindex delete display
8955 @item undisplay @var{dnums}@dots{}
8956 @itemx delete display @var{dnums}@dots{}
8957 Remove items from the list of expressions to display. Specify the
8958 numbers of the displays that you want affected with the command
8959 argument @var{dnums}. It can be a single display number, one of the
8960 numbers shown in the first field of the @samp{info display} display;
8961 or it could be a range of display numbers, as in @code{2-4}.
8963 @code{undisplay} does not repeat if you press @key{RET} after using it.
8964 (Otherwise you would just get the error @samp{No display number @dots{}}.)
8966 @kindex disable display
8967 @item disable display @var{dnums}@dots{}
8968 Disable the display of item numbers @var{dnums}. A disabled display
8969 item is not printed automatically, but is not forgotten. It may be
8970 enabled again later. Specify the numbers of the displays that you
8971 want affected with the command argument @var{dnums}. It can be a
8972 single display number, one of the numbers shown in the first field of
8973 the @samp{info display} display; or it could be a range of display
8974 numbers, as in @code{2-4}.
8976 @kindex enable display
8977 @item enable display @var{dnums}@dots{}
8978 Enable display of item numbers @var{dnums}. It becomes effective once
8979 again in auto display of its expression, until you specify otherwise.
8980 Specify the numbers of the displays that you want affected with the
8981 command argument @var{dnums}. It can be a single display number, one
8982 of the numbers shown in the first field of the @samp{info display}
8983 display; or it could be a range of display numbers, as in @code{2-4}.
8986 Display the current values of the expressions on the list, just as is
8987 done when your program stops.
8989 @kindex info display
8991 Print the list of expressions previously set up to display
8992 automatically, each one with its item number, but without showing the
8993 values. This includes disabled expressions, which are marked as such.
8994 It also includes expressions which would not be displayed right now
8995 because they refer to automatic variables not currently available.
8998 @cindex display disabled out of scope
8999 If a display expression refers to local variables, then it does not make
9000 sense outside the lexical context for which it was set up. Such an
9001 expression is disabled when execution enters a context where one of its
9002 variables is not defined. For example, if you give the command
9003 @code{display last_char} while inside a function with an argument
9004 @code{last_char}, @value{GDBN} displays this argument while your program
9005 continues to stop inside that function. When it stops elsewhere---where
9006 there is no variable @code{last_char}---the display is disabled
9007 automatically. The next time your program stops where @code{last_char}
9008 is meaningful, you can enable the display expression once again.
9010 @node Print Settings
9011 @section Print Settings
9013 @cindex format options
9014 @cindex print settings
9015 @value{GDBN} provides the following ways to control how arrays, structures,
9016 and symbols are printed.
9019 These settings are useful for debugging programs in any language:
9023 @item set print address
9024 @itemx set print address on
9025 @cindex print/don't print memory addresses
9026 @value{GDBN} prints memory addresses showing the location of stack
9027 traces, structure values, pointer values, breakpoints, and so forth,
9028 even when it also displays the contents of those addresses. The default
9029 is @code{on}. For example, this is what a stack frame display looks like with
9030 @code{set print address on}:
9035 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
9037 530 if (lquote != def_lquote)
9041 @item set print address off
9042 Do not print addresses when displaying their contents. For example,
9043 this is the same stack frame displayed with @code{set print address off}:
9047 (@value{GDBP}) set print addr off
9049 #0 set_quotes (lq="<<", rq=">>") at input.c:530
9050 530 if (lquote != def_lquote)
9054 You can use @samp{set print address off} to eliminate all machine
9055 dependent displays from the @value{GDBN} interface. For example, with
9056 @code{print address off}, you should get the same text for backtraces on
9057 all machines---whether or not they involve pointer arguments.
9060 @item show print address
9061 Show whether or not addresses are to be printed.
9064 When @value{GDBN} prints a symbolic address, it normally prints the
9065 closest earlier symbol plus an offset. If that symbol does not uniquely
9066 identify the address (for example, it is a name whose scope is a single
9067 source file), you may need to clarify. One way to do this is with
9068 @code{info line}, for example @samp{info line *0x4537}. Alternately,
9069 you can set @value{GDBN} to print the source file and line number when
9070 it prints a symbolic address:
9073 @item set print symbol-filename on
9074 @cindex source file and line of a symbol
9075 @cindex symbol, source file and line
9076 Tell @value{GDBN} to print the source file name and line number of a
9077 symbol in the symbolic form of an address.
9079 @item set print symbol-filename off
9080 Do not print source file name and line number of a symbol. This is the
9083 @item show print symbol-filename
9084 Show whether or not @value{GDBN} will print the source file name and
9085 line number of a symbol in the symbolic form of an address.
9088 Another situation where it is helpful to show symbol filenames and line
9089 numbers is when disassembling code; @value{GDBN} shows you the line
9090 number and source file that corresponds to each instruction.
9092 Also, you may wish to see the symbolic form only if the address being
9093 printed is reasonably close to the closest earlier symbol:
9096 @item set print max-symbolic-offset @var{max-offset}
9097 @itemx set print max-symbolic-offset unlimited
9098 @cindex maximum value for offset of closest symbol
9099 Tell @value{GDBN} to only display the symbolic form of an address if the
9100 offset between the closest earlier symbol and the address is less than
9101 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
9102 to always print the symbolic form of an address if any symbol precedes
9103 it. Zero is equivalent to @code{unlimited}.
9105 @item show print max-symbolic-offset
9106 Ask how large the maximum offset is that @value{GDBN} prints in a
9110 @cindex wild pointer, interpreting
9111 @cindex pointer, finding referent
9112 If you have a pointer and you are not sure where it points, try
9113 @samp{set print symbol-filename on}. Then you can determine the name
9114 and source file location of the variable where it points, using
9115 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
9116 For example, here @value{GDBN} shows that a variable @code{ptt} points
9117 at another variable @code{t}, defined in @file{hi2.c}:
9120 (@value{GDBP}) set print symbol-filename on
9121 (@value{GDBP}) p/a ptt
9122 $4 = 0xe008 <t in hi2.c>
9126 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
9127 does not show the symbol name and filename of the referent, even with
9128 the appropriate @code{set print} options turned on.
9131 You can also enable @samp{/a}-like formatting all the time using
9132 @samp{set print symbol on}:
9135 @item set print symbol on
9136 Tell @value{GDBN} to print the symbol corresponding to an address, if
9139 @item set print symbol off
9140 Tell @value{GDBN} not to print the symbol corresponding to an
9141 address. In this mode, @value{GDBN} will still print the symbol
9142 corresponding to pointers to functions. This is the default.
9144 @item show print symbol
9145 Show whether @value{GDBN} will display the symbol corresponding to an
9149 Other settings control how different kinds of objects are printed:
9152 @item set print array
9153 @itemx set print array on
9154 @cindex pretty print arrays
9155 Pretty print arrays. This format is more convenient to read,
9156 but uses more space. The default is off.
9158 @item set print array off
9159 Return to compressed format for arrays.
9161 @item show print array
9162 Show whether compressed or pretty format is selected for displaying
9165 @cindex print array indexes
9166 @item set print array-indexes
9167 @itemx set print array-indexes on
9168 Print the index of each element when displaying arrays. May be more
9169 convenient to locate a given element in the array or quickly find the
9170 index of a given element in that printed array. The default is off.
9172 @item set print array-indexes off
9173 Stop printing element indexes when displaying arrays.
9175 @item show print array-indexes
9176 Show whether the index of each element is printed when displaying
9179 @item set print elements @var{number-of-elements}
9180 @itemx set print elements unlimited
9181 @cindex number of array elements to print
9182 @cindex limit on number of printed array elements
9183 Set a limit on how many elements of an array @value{GDBN} will print.
9184 If @value{GDBN} is printing a large array, it stops printing after it has
9185 printed the number of elements set by the @code{set print elements} command.
9186 This limit also applies to the display of strings.
9187 When @value{GDBN} starts, this limit is set to 200.
9188 Setting @var{number-of-elements} to @code{unlimited} or zero means
9189 that the number of elements to print is unlimited.
9191 @item show print elements
9192 Display the number of elements of a large array that @value{GDBN} will print.
9193 If the number is 0, then the printing is unlimited.
9195 @item set print frame-arguments @var{value}
9196 @kindex set print frame-arguments
9197 @cindex printing frame argument values
9198 @cindex print all frame argument values
9199 @cindex print frame argument values for scalars only
9200 @cindex do not print frame argument values
9201 This command allows to control how the values of arguments are printed
9202 when the debugger prints a frame (@pxref{Frames}). The possible
9207 The values of all arguments are printed.
9210 Print the value of an argument only if it is a scalar. The value of more
9211 complex arguments such as arrays, structures, unions, etc, is replaced
9212 by @code{@dots{}}. This is the default. Here is an example where
9213 only scalar arguments are shown:
9216 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9221 None of the argument values are printed. Instead, the value of each argument
9222 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9225 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9230 By default, only scalar arguments are printed. This command can be used
9231 to configure the debugger to print the value of all arguments, regardless
9232 of their type. However, it is often advantageous to not print the value
9233 of more complex parameters. For instance, it reduces the amount of
9234 information printed in each frame, making the backtrace more readable.
9235 Also, it improves performance when displaying Ada frames, because
9236 the computation of large arguments can sometimes be CPU-intensive,
9237 especially in large applications. Setting @code{print frame-arguments}
9238 to @code{scalars} (the default) or @code{none} avoids this computation,
9239 thus speeding up the display of each Ada frame.
9241 @item show print frame-arguments
9242 Show how the value of arguments should be displayed when printing a frame.
9244 @item set print raw frame-arguments on
9245 Print frame arguments in raw, non pretty-printed, form.
9247 @item set print raw frame-arguments off
9248 Print frame arguments in pretty-printed form, if there is a pretty-printer
9249 for the value (@pxref{Pretty Printing}),
9250 otherwise print the value in raw form.
9251 This is the default.
9253 @item show print raw frame-arguments
9254 Show whether to print frame arguments in raw form.
9256 @anchor{set print entry-values}
9257 @item set print entry-values @var{value}
9258 @kindex set print entry-values
9259 Set printing of frame argument values at function entry. In some cases
9260 @value{GDBN} can determine the value of function argument which was passed by
9261 the function caller, even if the value was modified inside the called function
9262 and therefore is different. With optimized code, the current value could be
9263 unavailable, but the entry value may still be known.
9265 The default value is @code{default} (see below for its description). Older
9266 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
9267 this feature will behave in the @code{default} setting the same way as with the
9270 This functionality is currently supported only by DWARF 2 debugging format and
9271 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9272 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9275 The @var{value} parameter can be one of the following:
9279 Print only actual parameter values, never print values from function entry
9283 #0 different (val=6)
9284 #0 lost (val=<optimized out>)
9286 #0 invalid (val=<optimized out>)
9290 Print only parameter values from function entry point. The actual parameter
9291 values are never printed.
9293 #0 equal (val@@entry=5)
9294 #0 different (val@@entry=5)
9295 #0 lost (val@@entry=5)
9296 #0 born (val@@entry=<optimized out>)
9297 #0 invalid (val@@entry=<optimized out>)
9301 Print only parameter values from function entry point. If value from function
9302 entry point is not known while the actual value is known, print the actual
9303 value for such parameter.
9305 #0 equal (val@@entry=5)
9306 #0 different (val@@entry=5)
9307 #0 lost (val@@entry=5)
9309 #0 invalid (val@@entry=<optimized out>)
9313 Print actual parameter values. If actual parameter value is not known while
9314 value from function entry point is known, print the entry point value for such
9318 #0 different (val=6)
9319 #0 lost (val@@entry=5)
9321 #0 invalid (val=<optimized out>)
9325 Always print both the actual parameter value and its value from function entry
9326 point, even if values of one or both are not available due to compiler
9329 #0 equal (val=5, val@@entry=5)
9330 #0 different (val=6, val@@entry=5)
9331 #0 lost (val=<optimized out>, val@@entry=5)
9332 #0 born (val=10, val@@entry=<optimized out>)
9333 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
9337 Print the actual parameter value if it is known and also its value from
9338 function entry point if it is known. If neither is known, print for the actual
9339 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
9340 values are known and identical, print the shortened
9341 @code{param=param@@entry=VALUE} notation.
9343 #0 equal (val=val@@entry=5)
9344 #0 different (val=6, val@@entry=5)
9345 #0 lost (val@@entry=5)
9347 #0 invalid (val=<optimized out>)
9351 Always print the actual parameter value. Print also its value from function
9352 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
9353 if both values are known and identical, print the shortened
9354 @code{param=param@@entry=VALUE} notation.
9356 #0 equal (val=val@@entry=5)
9357 #0 different (val=6, val@@entry=5)
9358 #0 lost (val=<optimized out>, val@@entry=5)
9360 #0 invalid (val=<optimized out>)
9364 For analysis messages on possible failures of frame argument values at function
9365 entry resolution see @ref{set debug entry-values}.
9367 @item show print entry-values
9368 Show the method being used for printing of frame argument values at function
9371 @item set print repeats @var{number-of-repeats}
9372 @itemx set print repeats unlimited
9373 @cindex repeated array elements
9374 Set the threshold for suppressing display of repeated array
9375 elements. When the number of consecutive identical elements of an
9376 array exceeds the threshold, @value{GDBN} prints the string
9377 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
9378 identical repetitions, instead of displaying the identical elements
9379 themselves. Setting the threshold to @code{unlimited} or zero will
9380 cause all elements to be individually printed. The default threshold
9383 @item show print repeats
9384 Display the current threshold for printing repeated identical
9387 @item set print null-stop
9388 @cindex @sc{null} elements in arrays
9389 Cause @value{GDBN} to stop printing the characters of an array when the first
9390 @sc{null} is encountered. This is useful when large arrays actually
9391 contain only short strings.
9394 @item show print null-stop
9395 Show whether @value{GDBN} stops printing an array on the first
9396 @sc{null} character.
9398 @item set print pretty on
9399 @cindex print structures in indented form
9400 @cindex indentation in structure display
9401 Cause @value{GDBN} to print structures in an indented format with one member
9402 per line, like this:
9417 @item set print pretty off
9418 Cause @value{GDBN} to print structures in a compact format, like this:
9422 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
9423 meat = 0x54 "Pork"@}
9428 This is the default format.
9430 @item show print pretty
9431 Show which format @value{GDBN} is using to print structures.
9433 @item set print sevenbit-strings on
9434 @cindex eight-bit characters in strings
9435 @cindex octal escapes in strings
9436 Print using only seven-bit characters; if this option is set,
9437 @value{GDBN} displays any eight-bit characters (in strings or
9438 character values) using the notation @code{\}@var{nnn}. This setting is
9439 best if you are working in English (@sc{ascii}) and you use the
9440 high-order bit of characters as a marker or ``meta'' bit.
9442 @item set print sevenbit-strings off
9443 Print full eight-bit characters. This allows the use of more
9444 international character sets, and is the default.
9446 @item show print sevenbit-strings
9447 Show whether or not @value{GDBN} is printing only seven-bit characters.
9449 @item set print union on
9450 @cindex unions in structures, printing
9451 Tell @value{GDBN} to print unions which are contained in structures
9452 and other unions. This is the default setting.
9454 @item set print union off
9455 Tell @value{GDBN} not to print unions which are contained in
9456 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
9459 @item show print union
9460 Ask @value{GDBN} whether or not it will print unions which are contained in
9461 structures and other unions.
9463 For example, given the declarations
9466 typedef enum @{Tree, Bug@} Species;
9467 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
9468 typedef enum @{Caterpillar, Cocoon, Butterfly@}
9479 struct thing foo = @{Tree, @{Acorn@}@};
9483 with @code{set print union on} in effect @samp{p foo} would print
9486 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
9490 and with @code{set print union off} in effect it would print
9493 $1 = @{it = Tree, form = @{...@}@}
9497 @code{set print union} affects programs written in C-like languages
9503 These settings are of interest when debugging C@t{++} programs:
9506 @cindex demangling C@t{++} names
9507 @item set print demangle
9508 @itemx set print demangle on
9509 Print C@t{++} names in their source form rather than in the encoded
9510 (``mangled'') form passed to the assembler and linker for type-safe
9511 linkage. The default is on.
9513 @item show print demangle
9514 Show whether C@t{++} names are printed in mangled or demangled form.
9516 @item set print asm-demangle
9517 @itemx set print asm-demangle on
9518 Print C@t{++} names in their source form rather than their mangled form, even
9519 in assembler code printouts such as instruction disassemblies.
9522 @item show print asm-demangle
9523 Show whether C@t{++} names in assembly listings are printed in mangled
9526 @cindex C@t{++} symbol decoding style
9527 @cindex symbol decoding style, C@t{++}
9528 @kindex set demangle-style
9529 @item set demangle-style @var{style}
9530 Choose among several encoding schemes used by different compilers to
9531 represent C@t{++} names. The choices for @var{style} are currently:
9535 Allow @value{GDBN} to choose a decoding style by inspecting your program.
9536 This is the default.
9539 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
9542 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
9545 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
9548 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
9549 @strong{Warning:} this setting alone is not sufficient to allow
9550 debugging @code{cfront}-generated executables. @value{GDBN} would
9551 require further enhancement to permit that.
9554 If you omit @var{style}, you will see a list of possible formats.
9556 @item show demangle-style
9557 Display the encoding style currently in use for decoding C@t{++} symbols.
9559 @item set print object
9560 @itemx set print object on
9561 @cindex derived type of an object, printing
9562 @cindex display derived types
9563 When displaying a pointer to an object, identify the @emph{actual}
9564 (derived) type of the object rather than the @emph{declared} type, using
9565 the virtual function table. Note that the virtual function table is
9566 required---this feature can only work for objects that have run-time
9567 type identification; a single virtual method in the object's declared
9568 type is sufficient. Note that this setting is also taken into account when
9569 working with variable objects via MI (@pxref{GDB/MI}).
9571 @item set print object off
9572 Display only the declared type of objects, without reference to the
9573 virtual function table. This is the default setting.
9575 @item show print object
9576 Show whether actual, or declared, object types are displayed.
9578 @item set print static-members
9579 @itemx set print static-members on
9580 @cindex static members of C@t{++} objects
9581 Print static members when displaying a C@t{++} object. The default is on.
9583 @item set print static-members off
9584 Do not print static members when displaying a C@t{++} object.
9586 @item show print static-members
9587 Show whether C@t{++} static members are printed or not.
9589 @item set print pascal_static-members
9590 @itemx set print pascal_static-members on
9591 @cindex static members of Pascal objects
9592 @cindex Pascal objects, static members display
9593 Print static members when displaying a Pascal object. The default is on.
9595 @item set print pascal_static-members off
9596 Do not print static members when displaying a Pascal object.
9598 @item show print pascal_static-members
9599 Show whether Pascal static members are printed or not.
9601 @c These don't work with HP ANSI C++ yet.
9602 @item set print vtbl
9603 @itemx set print vtbl on
9604 @cindex pretty print C@t{++} virtual function tables
9605 @cindex virtual functions (C@t{++}) display
9606 @cindex VTBL display
9607 Pretty print C@t{++} virtual function tables. The default is off.
9608 (The @code{vtbl} commands do not work on programs compiled with the HP
9609 ANSI C@t{++} compiler (@code{aCC}).)
9611 @item set print vtbl off
9612 Do not pretty print C@t{++} virtual function tables.
9614 @item show print vtbl
9615 Show whether C@t{++} virtual function tables are pretty printed, or not.
9618 @node Pretty Printing
9619 @section Pretty Printing
9621 @value{GDBN} provides a mechanism to allow pretty-printing of values using
9622 Python code. It greatly simplifies the display of complex objects. This
9623 mechanism works for both MI and the CLI.
9626 * Pretty-Printer Introduction:: Introduction to pretty-printers
9627 * Pretty-Printer Example:: An example pretty-printer
9628 * Pretty-Printer Commands:: Pretty-printer commands
9631 @node Pretty-Printer Introduction
9632 @subsection Pretty-Printer Introduction
9634 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
9635 registered for the value. If there is then @value{GDBN} invokes the
9636 pretty-printer to print the value. Otherwise the value is printed normally.
9638 Pretty-printers are normally named. This makes them easy to manage.
9639 The @samp{info pretty-printer} command will list all the installed
9640 pretty-printers with their names.
9641 If a pretty-printer can handle multiple data types, then its
9642 @dfn{subprinters} are the printers for the individual data types.
9643 Each such subprinter has its own name.
9644 The format of the name is @var{printer-name};@var{subprinter-name}.
9646 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
9647 Typically they are automatically loaded and registered when the corresponding
9648 debug information is loaded, thus making them available without having to
9649 do anything special.
9651 There are three places where a pretty-printer can be registered.
9655 Pretty-printers registered globally are available when debugging
9659 Pretty-printers registered with a program space are available only
9660 when debugging that program.
9661 @xref{Progspaces In Python}, for more details on program spaces in Python.
9664 Pretty-printers registered with an objfile are loaded and unloaded
9665 with the corresponding objfile (e.g., shared library).
9666 @xref{Objfiles In Python}, for more details on objfiles in Python.
9669 @xref{Selecting Pretty-Printers}, for further information on how
9670 pretty-printers are selected,
9672 @xref{Writing a Pretty-Printer}, for implementing pretty printers
9675 @node Pretty-Printer Example
9676 @subsection Pretty-Printer Example
9678 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
9681 (@value{GDBP}) print s
9683 static npos = 4294967295,
9685 <std::allocator<char>> = @{
9686 <__gnu_cxx::new_allocator<char>> = @{
9687 <No data fields>@}, <No data fields>
9689 members of std::basic_string<char, std::char_traits<char>,
9690 std::allocator<char> >::_Alloc_hider:
9691 _M_p = 0x804a014 "abcd"
9696 With a pretty-printer for @code{std::string} only the contents are printed:
9699 (@value{GDBP}) print s
9703 @node Pretty-Printer Commands
9704 @subsection Pretty-Printer Commands
9705 @cindex pretty-printer commands
9708 @kindex info pretty-printer
9709 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9710 Print the list of installed pretty-printers.
9711 This includes disabled pretty-printers, which are marked as such.
9713 @var{object-regexp} is a regular expression matching the objects
9714 whose pretty-printers to list.
9715 Objects can be @code{global}, the program space's file
9716 (@pxref{Progspaces In Python}),
9717 and the object files within that program space (@pxref{Objfiles In Python}).
9718 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
9719 looks up a printer from these three objects.
9721 @var{name-regexp} is a regular expression matching the name of the printers
9724 @kindex disable pretty-printer
9725 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9726 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9727 A disabled pretty-printer is not forgotten, it may be enabled again later.
9729 @kindex enable pretty-printer
9730 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9731 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9736 Suppose we have three pretty-printers installed: one from library1.so
9737 named @code{foo} that prints objects of type @code{foo}, and
9738 another from library2.so named @code{bar} that prints two types of objects,
9739 @code{bar1} and @code{bar2}.
9742 (gdb) info pretty-printer
9749 (gdb) info pretty-printer library2
9754 (gdb) disable pretty-printer library1
9756 2 of 3 printers enabled
9757 (gdb) info pretty-printer
9764 (gdb) disable pretty-printer library2 bar:bar1
9766 1 of 3 printers enabled
9767 (gdb) info pretty-printer library2
9774 (gdb) disable pretty-printer library2 bar
9776 0 of 3 printers enabled
9777 (gdb) info pretty-printer library2
9786 Note that for @code{bar} the entire printer can be disabled,
9787 as can each individual subprinter.
9790 @section Value History
9792 @cindex value history
9793 @cindex history of values printed by @value{GDBN}
9794 Values printed by the @code{print} command are saved in the @value{GDBN}
9795 @dfn{value history}. This allows you to refer to them in other expressions.
9796 Values are kept until the symbol table is re-read or discarded
9797 (for example with the @code{file} or @code{symbol-file} commands).
9798 When the symbol table changes, the value history is discarded,
9799 since the values may contain pointers back to the types defined in the
9804 @cindex history number
9805 The values printed are given @dfn{history numbers} by which you can
9806 refer to them. These are successive integers starting with one.
9807 @code{print} shows you the history number assigned to a value by
9808 printing @samp{$@var{num} = } before the value; here @var{num} is the
9811 To refer to any previous value, use @samp{$} followed by the value's
9812 history number. The way @code{print} labels its output is designed to
9813 remind you of this. Just @code{$} refers to the most recent value in
9814 the history, and @code{$$} refers to the value before that.
9815 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
9816 is the value just prior to @code{$$}, @code{$$1} is equivalent to
9817 @code{$$}, and @code{$$0} is equivalent to @code{$}.
9819 For example, suppose you have just printed a pointer to a structure and
9820 want to see the contents of the structure. It suffices to type
9826 If you have a chain of structures where the component @code{next} points
9827 to the next one, you can print the contents of the next one with this:
9834 You can print successive links in the chain by repeating this
9835 command---which you can do by just typing @key{RET}.
9837 Note that the history records values, not expressions. If the value of
9838 @code{x} is 4 and you type these commands:
9846 then the value recorded in the value history by the @code{print} command
9847 remains 4 even though the value of @code{x} has changed.
9852 Print the last ten values in the value history, with their item numbers.
9853 This is like @samp{p@ $$9} repeated ten times, except that @code{show
9854 values} does not change the history.
9856 @item show values @var{n}
9857 Print ten history values centered on history item number @var{n}.
9860 Print ten history values just after the values last printed. If no more
9861 values are available, @code{show values +} produces no display.
9864 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
9865 same effect as @samp{show values +}.
9867 @node Convenience Vars
9868 @section Convenience Variables
9870 @cindex convenience variables
9871 @cindex user-defined variables
9872 @value{GDBN} provides @dfn{convenience variables} that you can use within
9873 @value{GDBN} to hold on to a value and refer to it later. These variables
9874 exist entirely within @value{GDBN}; they are not part of your program, and
9875 setting a convenience variable has no direct effect on further execution
9876 of your program. That is why you can use them freely.
9878 Convenience variables are prefixed with @samp{$}. Any name preceded by
9879 @samp{$} can be used for a convenience variable, unless it is one of
9880 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
9881 (Value history references, in contrast, are @emph{numbers} preceded
9882 by @samp{$}. @xref{Value History, ,Value History}.)
9884 You can save a value in a convenience variable with an assignment
9885 expression, just as you would set a variable in your program.
9889 set $foo = *object_ptr
9893 would save in @code{$foo} the value contained in the object pointed to by
9896 Using a convenience variable for the first time creates it, but its
9897 value is @code{void} until you assign a new value. You can alter the
9898 value with another assignment at any time.
9900 Convenience variables have no fixed types. You can assign a convenience
9901 variable any type of value, including structures and arrays, even if
9902 that variable already has a value of a different type. The convenience
9903 variable, when used as an expression, has the type of its current value.
9906 @kindex show convenience
9907 @cindex show all user variables and functions
9908 @item show convenience
9909 Print a list of convenience variables used so far, and their values,
9910 as well as a list of the convenience functions.
9911 Abbreviated @code{show conv}.
9913 @kindex init-if-undefined
9914 @cindex convenience variables, initializing
9915 @item init-if-undefined $@var{variable} = @var{expression}
9916 Set a convenience variable if it has not already been set. This is useful
9917 for user-defined commands that keep some state. It is similar, in concept,
9918 to using local static variables with initializers in C (except that
9919 convenience variables are global). It can also be used to allow users to
9920 override default values used in a command script.
9922 If the variable is already defined then the expression is not evaluated so
9923 any side-effects do not occur.
9926 One of the ways to use a convenience variable is as a counter to be
9927 incremented or a pointer to be advanced. For example, to print
9928 a field from successive elements of an array of structures:
9932 print bar[$i++]->contents
9936 Repeat that command by typing @key{RET}.
9938 Some convenience variables are created automatically by @value{GDBN} and given
9939 values likely to be useful.
9942 @vindex $_@r{, convenience variable}
9944 The variable @code{$_} is automatically set by the @code{x} command to
9945 the last address examined (@pxref{Memory, ,Examining Memory}). Other
9946 commands which provide a default address for @code{x} to examine also
9947 set @code{$_} to that address; these commands include @code{info line}
9948 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
9949 except when set by the @code{x} command, in which case it is a pointer
9950 to the type of @code{$__}.
9952 @vindex $__@r{, convenience variable}
9954 The variable @code{$__} is automatically set by the @code{x} command
9955 to the value found in the last address examined. Its type is chosen
9956 to match the format in which the data was printed.
9959 @vindex $_exitcode@r{, convenience variable}
9960 When the program being debugged terminates normally, @value{GDBN}
9961 automatically sets this variable to the exit code of the program, and
9962 resets @code{$_exitsignal} to @code{void}.
9965 @vindex $_exitsignal@r{, convenience variable}
9966 When the program being debugged dies due to an uncaught signal,
9967 @value{GDBN} automatically sets this variable to that signal's number,
9968 and resets @code{$_exitcode} to @code{void}.
9970 To distinguish between whether the program being debugged has exited
9971 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
9972 @code{$_exitsignal} is not @code{void}), the convenience function
9973 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
9974 Functions}). For example, considering the following source code:
9980 main (int argc, char *argv[])
9987 A valid way of telling whether the program being debugged has exited
9988 or signalled would be:
9991 (@value{GDBP}) define has_exited_or_signalled
9992 Type commands for definition of ``has_exited_or_signalled''.
9993 End with a line saying just ``end''.
9994 >if $_isvoid ($_exitsignal)
9995 >echo The program has exited\n
9997 >echo The program has signalled\n
10003 Program terminated with signal SIGALRM, Alarm clock.
10004 The program no longer exists.
10005 (@value{GDBP}) has_exited_or_signalled
10006 The program has signalled
10009 As can be seen, @value{GDBN} correctly informs that the program being
10010 debugged has signalled, since it calls @code{raise} and raises a
10011 @code{SIGALRM} signal. If the program being debugged had not called
10012 @code{raise}, then @value{GDBN} would report a normal exit:
10015 (@value{GDBP}) has_exited_or_signalled
10016 The program has exited
10020 The variable @code{$_exception} is set to the exception object being
10021 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
10024 @itemx $_probe_arg0@dots{}$_probe_arg11
10025 Arguments to a static probe. @xref{Static Probe Points}.
10028 @vindex $_sdata@r{, inspect, convenience variable}
10029 The variable @code{$_sdata} contains extra collected static tracepoint
10030 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
10031 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
10032 if extra static tracepoint data has not been collected.
10035 @vindex $_siginfo@r{, convenience variable}
10036 The variable @code{$_siginfo} contains extra signal information
10037 (@pxref{extra signal information}). Note that @code{$_siginfo}
10038 could be empty, if the application has not yet received any signals.
10039 For example, it will be empty before you execute the @code{run} command.
10042 @vindex $_tlb@r{, convenience variable}
10043 The variable @code{$_tlb} is automatically set when debugging
10044 applications running on MS-Windows in native mode or connected to
10045 gdbserver that supports the @code{qGetTIBAddr} request.
10046 @xref{General Query Packets}.
10047 This variable contains the address of the thread information block.
10051 On HP-UX systems, if you refer to a function or variable name that
10052 begins with a dollar sign, @value{GDBN} searches for a user or system
10053 name first, before it searches for a convenience variable.
10055 @node Convenience Funs
10056 @section Convenience Functions
10058 @cindex convenience functions
10059 @value{GDBN} also supplies some @dfn{convenience functions}. These
10060 have a syntax similar to convenience variables. A convenience
10061 function can be used in an expression just like an ordinary function;
10062 however, a convenience function is implemented internally to
10065 These functions do not require @value{GDBN} to be configured with
10066 @code{Python} support, which means that they are always available.
10070 @item $_isvoid (@var{expr})
10071 @findex $_isvoid@r{, convenience function}
10072 Return one if the expression @var{expr} is @code{void}. Otherwise it
10075 A @code{void} expression is an expression where the type of the result
10076 is @code{void}. For example, you can examine a convenience variable
10077 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
10081 (@value{GDBP}) print $_exitcode
10083 (@value{GDBP}) print $_isvoid ($_exitcode)
10086 Starting program: ./a.out
10087 [Inferior 1 (process 29572) exited normally]
10088 (@value{GDBP}) print $_exitcode
10090 (@value{GDBP}) print $_isvoid ($_exitcode)
10094 In the example above, we used @code{$_isvoid} to check whether
10095 @code{$_exitcode} is @code{void} before and after the execution of the
10096 program being debugged. Before the execution there is no exit code to
10097 be examined, therefore @code{$_exitcode} is @code{void}. After the
10098 execution the program being debugged returned zero, therefore
10099 @code{$_exitcode} is zero, which means that it is not @code{void}
10102 The @code{void} expression can also be a call of a function from the
10103 program being debugged. For example, given the following function:
10112 The result of calling it inside @value{GDBN} is @code{void}:
10115 (@value{GDBP}) print foo ()
10117 (@value{GDBP}) print $_isvoid (foo ())
10119 (@value{GDBP}) set $v = foo ()
10120 (@value{GDBP}) print $v
10122 (@value{GDBP}) print $_isvoid ($v)
10128 These functions require @value{GDBN} to be configured with
10129 @code{Python} support.
10133 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10134 @findex $_memeq@r{, convenience function}
10135 Returns one if the @var{length} bytes at the addresses given by
10136 @var{buf1} and @var{buf2} are equal.
10137 Otherwise it returns zero.
10139 @item $_regex(@var{str}, @var{regex})
10140 @findex $_regex@r{, convenience function}
10141 Returns one if the string @var{str} matches the regular expression
10142 @var{regex}. Otherwise it returns zero.
10143 The syntax of the regular expression is that specified by @code{Python}'s
10144 regular expression support.
10146 @item $_streq(@var{str1}, @var{str2})
10147 @findex $_streq@r{, convenience function}
10148 Returns one if the strings @var{str1} and @var{str2} are equal.
10149 Otherwise it returns zero.
10151 @item $_strlen(@var{str})
10152 @findex $_strlen@r{, convenience function}
10153 Returns the length of string @var{str}.
10155 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10156 @findex $_caller_is@r{, convenience function}
10157 Returns one if the calling function's name is equal to @var{name}.
10158 Otherwise it returns zero.
10160 If the optional argument @var{number_of_frames} is provided,
10161 it is the number of frames up in the stack to look.
10169 at testsuite/gdb.python/py-caller-is.c:21
10170 #1 0x00000000004005a0 in middle_func ()
10171 at testsuite/gdb.python/py-caller-is.c:27
10172 #2 0x00000000004005ab in top_func ()
10173 at testsuite/gdb.python/py-caller-is.c:33
10174 #3 0x00000000004005b6 in main ()
10175 at testsuite/gdb.python/py-caller-is.c:39
10176 (gdb) print $_caller_is ("middle_func")
10178 (gdb) print $_caller_is ("top_func", 2)
10182 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10183 @findex $_caller_matches@r{, convenience function}
10184 Returns one if the calling function's name matches the regular expression
10185 @var{regexp}. Otherwise it returns zero.
10187 If the optional argument @var{number_of_frames} is provided,
10188 it is the number of frames up in the stack to look.
10191 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10192 @findex $_any_caller_is@r{, convenience function}
10193 Returns one if any calling function's name is equal to @var{name}.
10194 Otherwise it returns zero.
10196 If the optional argument @var{number_of_frames} is provided,
10197 it is the number of frames up in the stack to look.
10200 This function differs from @code{$_caller_is} in that this function
10201 checks all stack frames from the immediate caller to the frame specified
10202 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
10203 frame specified by @var{number_of_frames}.
10205 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10206 @findex $_any_caller_matches@r{, convenience function}
10207 Returns one if any calling function's name matches the regular expression
10208 @var{regexp}. Otherwise it returns zero.
10210 If the optional argument @var{number_of_frames} is provided,
10211 it is the number of frames up in the stack to look.
10214 This function differs from @code{$_caller_matches} in that this function
10215 checks all stack frames from the immediate caller to the frame specified
10216 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
10217 frame specified by @var{number_of_frames}.
10221 @value{GDBN} provides the ability to list and get help on
10222 convenience functions.
10225 @item help function
10226 @kindex help function
10227 @cindex show all convenience functions
10228 Print a list of all convenience functions.
10235 You can refer to machine register contents, in expressions, as variables
10236 with names starting with @samp{$}. The names of registers are different
10237 for each machine; use @code{info registers} to see the names used on
10241 @kindex info registers
10242 @item info registers
10243 Print the names and values of all registers except floating-point
10244 and vector registers (in the selected stack frame).
10246 @kindex info all-registers
10247 @cindex floating point registers
10248 @item info all-registers
10249 Print the names and values of all registers, including floating-point
10250 and vector registers (in the selected stack frame).
10252 @item info registers @var{regname} @dots{}
10253 Print the @dfn{relativized} value of each specified register @var{regname}.
10254 As discussed in detail below, register values are normally relative to
10255 the selected stack frame. The @var{regname} may be any register name valid on
10256 the machine you are using, with or without the initial @samp{$}.
10259 @anchor{standard registers}
10260 @cindex stack pointer register
10261 @cindex program counter register
10262 @cindex process status register
10263 @cindex frame pointer register
10264 @cindex standard registers
10265 @value{GDBN} has four ``standard'' register names that are available (in
10266 expressions) on most machines---whenever they do not conflict with an
10267 architecture's canonical mnemonics for registers. The register names
10268 @code{$pc} and @code{$sp} are used for the program counter register and
10269 the stack pointer. @code{$fp} is used for a register that contains a
10270 pointer to the current stack frame, and @code{$ps} is used for a
10271 register that contains the processor status. For example,
10272 you could print the program counter in hex with
10279 or print the instruction to be executed next with
10286 or add four to the stack pointer@footnote{This is a way of removing
10287 one word from the stack, on machines where stacks grow downward in
10288 memory (most machines, nowadays). This assumes that the innermost
10289 stack frame is selected; setting @code{$sp} is not allowed when other
10290 stack frames are selected. To pop entire frames off the stack,
10291 regardless of machine architecture, use @code{return};
10292 see @ref{Returning, ,Returning from a Function}.} with
10298 Whenever possible, these four standard register names are available on
10299 your machine even though the machine has different canonical mnemonics,
10300 so long as there is no conflict. The @code{info registers} command
10301 shows the canonical names. For example, on the SPARC, @code{info
10302 registers} displays the processor status register as @code{$psr} but you
10303 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
10304 is an alias for the @sc{eflags} register.
10306 @value{GDBN} always considers the contents of an ordinary register as an
10307 integer when the register is examined in this way. Some machines have
10308 special registers which can hold nothing but floating point; these
10309 registers are considered to have floating point values. There is no way
10310 to refer to the contents of an ordinary register as floating point value
10311 (although you can @emph{print} it as a floating point value with
10312 @samp{print/f $@var{regname}}).
10314 Some registers have distinct ``raw'' and ``virtual'' data formats. This
10315 means that the data format in which the register contents are saved by
10316 the operating system is not the same one that your program normally
10317 sees. For example, the registers of the 68881 floating point
10318 coprocessor are always saved in ``extended'' (raw) format, but all C
10319 programs expect to work with ``double'' (virtual) format. In such
10320 cases, @value{GDBN} normally works with the virtual format only (the format
10321 that makes sense for your program), but the @code{info registers} command
10322 prints the data in both formats.
10324 @cindex SSE registers (x86)
10325 @cindex MMX registers (x86)
10326 Some machines have special registers whose contents can be interpreted
10327 in several different ways. For example, modern x86-based machines
10328 have SSE and MMX registers that can hold several values packed
10329 together in several different formats. @value{GDBN} refers to such
10330 registers in @code{struct} notation:
10333 (@value{GDBP}) print $xmm1
10335 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
10336 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
10337 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
10338 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
10339 v4_int32 = @{0, 20657912, 11, 13@},
10340 v2_int64 = @{88725056443645952, 55834574859@},
10341 uint128 = 0x0000000d0000000b013b36f800000000
10346 To set values of such registers, you need to tell @value{GDBN} which
10347 view of the register you wish to change, as if you were assigning
10348 value to a @code{struct} member:
10351 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
10354 Normally, register values are relative to the selected stack frame
10355 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
10356 value that the register would contain if all stack frames farther in
10357 were exited and their saved registers restored. In order to see the
10358 true contents of hardware registers, you must select the innermost
10359 frame (with @samp{frame 0}).
10361 @cindex caller-saved registers
10362 @cindex call-clobbered registers
10363 @cindex volatile registers
10364 @cindex <not saved> values
10365 Usually ABIs reserve some registers as not needed to be saved by the
10366 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
10367 registers). It may therefore not be possible for @value{GDBN} to know
10368 the value a register had before the call (in other words, in the outer
10369 frame), if the register value has since been changed by the callee.
10370 @value{GDBN} tries to deduce where the inner frame saved
10371 (``callee-saved'') registers, from the debug info, unwind info, or the
10372 machine code generated by your compiler. If some register is not
10373 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
10374 its own knowledge of the ABI, or because the debug/unwind info
10375 explicitly says the register's value is undefined), @value{GDBN}
10376 displays @w{@samp{<not saved>}} as the register's value. With targets
10377 that @value{GDBN} has no knowledge of the register saving convention,
10378 if a register was not saved by the callee, then its value and location
10379 in the outer frame are assumed to be the same of the inner frame.
10380 This is usually harmless, because if the register is call-clobbered,
10381 the caller either does not care what is in the register after the
10382 call, or has code to restore the value that it does care about. Note,
10383 however, that if you change such a register in the outer frame, you
10384 may also be affecting the inner frame. Also, the more ``outer'' the
10385 frame is you're looking at, the more likely a call-clobbered
10386 register's value is to be wrong, in the sense that it doesn't actually
10387 represent the value the register had just before the call.
10389 @node Floating Point Hardware
10390 @section Floating Point Hardware
10391 @cindex floating point
10393 Depending on the configuration, @value{GDBN} may be able to give
10394 you more information about the status of the floating point hardware.
10399 Display hardware-dependent information about the floating
10400 point unit. The exact contents and layout vary depending on the
10401 floating point chip. Currently, @samp{info float} is supported on
10402 the ARM and x86 machines.
10406 @section Vector Unit
10407 @cindex vector unit
10409 Depending on the configuration, @value{GDBN} may be able to give you
10410 more information about the status of the vector unit.
10413 @kindex info vector
10415 Display information about the vector unit. The exact contents and
10416 layout vary depending on the hardware.
10419 @node OS Information
10420 @section Operating System Auxiliary Information
10421 @cindex OS information
10423 @value{GDBN} provides interfaces to useful OS facilities that can help
10424 you debug your program.
10426 @cindex auxiliary vector
10427 @cindex vector, auxiliary
10428 Some operating systems supply an @dfn{auxiliary vector} to programs at
10429 startup. This is akin to the arguments and environment that you
10430 specify for a program, but contains a system-dependent variety of
10431 binary values that tell system libraries important details about the
10432 hardware, operating system, and process. Each value's purpose is
10433 identified by an integer tag; the meanings are well-known but system-specific.
10434 Depending on the configuration and operating system facilities,
10435 @value{GDBN} may be able to show you this information. For remote
10436 targets, this functionality may further depend on the remote stub's
10437 support of the @samp{qXfer:auxv:read} packet, see
10438 @ref{qXfer auxiliary vector read}.
10443 Display the auxiliary vector of the inferior, which can be either a
10444 live process or a core dump file. @value{GDBN} prints each tag value
10445 numerically, and also shows names and text descriptions for recognized
10446 tags. Some values in the vector are numbers, some bit masks, and some
10447 pointers to strings or other data. @value{GDBN} displays each value in the
10448 most appropriate form for a recognized tag, and in hexadecimal for
10449 an unrecognized tag.
10452 On some targets, @value{GDBN} can access operating system-specific
10453 information and show it to you. The types of information available
10454 will differ depending on the type of operating system running on the
10455 target. The mechanism used to fetch the data is described in
10456 @ref{Operating System Information}. For remote targets, this
10457 functionality depends on the remote stub's support of the
10458 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
10462 @item info os @var{infotype}
10464 Display OS information of the requested type.
10466 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
10468 @anchor{linux info os infotypes}
10470 @kindex info os processes
10472 Display the list of processes on the target. For each process,
10473 @value{GDBN} prints the process identifier, the name of the user, the
10474 command corresponding to the process, and the list of processor cores
10475 that the process is currently running on. (To understand what these
10476 properties mean, for this and the following info types, please consult
10477 the general @sc{gnu}/Linux documentation.)
10479 @kindex info os procgroups
10481 Display the list of process groups on the target. For each process,
10482 @value{GDBN} prints the identifier of the process group that it belongs
10483 to, the command corresponding to the process group leader, the process
10484 identifier, and the command line of the process. The list is sorted
10485 first by the process group identifier, then by the process identifier,
10486 so that processes belonging to the same process group are grouped together
10487 and the process group leader is listed first.
10489 @kindex info os threads
10491 Display the list of threads running on the target. For each thread,
10492 @value{GDBN} prints the identifier of the process that the thread
10493 belongs to, the command of the process, the thread identifier, and the
10494 processor core that it is currently running on. The main thread of a
10495 process is not listed.
10497 @kindex info os files
10499 Display the list of open file descriptors on the target. For each
10500 file descriptor, @value{GDBN} prints the identifier of the process
10501 owning the descriptor, the command of the owning process, the value
10502 of the descriptor, and the target of the descriptor.
10504 @kindex info os sockets
10506 Display the list of Internet-domain sockets on the target. For each
10507 socket, @value{GDBN} prints the address and port of the local and
10508 remote endpoints, the current state of the connection, the creator of
10509 the socket, the IP address family of the socket, and the type of the
10512 @kindex info os shm
10514 Display the list of all System V shared-memory regions on the target.
10515 For each shared-memory region, @value{GDBN} prints the region key,
10516 the shared-memory identifier, the access permissions, the size of the
10517 region, the process that created the region, the process that last
10518 attached to or detached from the region, the current number of live
10519 attaches to the region, and the times at which the region was last
10520 attached to, detach from, and changed.
10522 @kindex info os semaphores
10524 Display the list of all System V semaphore sets on the target. For each
10525 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
10526 set identifier, the access permissions, the number of semaphores in the
10527 set, the user and group of the owner and creator of the semaphore set,
10528 and the times at which the semaphore set was operated upon and changed.
10530 @kindex info os msg
10532 Display the list of all System V message queues on the target. For each
10533 message queue, @value{GDBN} prints the message queue key, the message
10534 queue identifier, the access permissions, the current number of bytes
10535 on the queue, the current number of messages on the queue, the processes
10536 that last sent and received a message on the queue, the user and group
10537 of the owner and creator of the message queue, the times at which a
10538 message was last sent and received on the queue, and the time at which
10539 the message queue was last changed.
10541 @kindex info os modules
10543 Display the list of all loaded kernel modules on the target. For each
10544 module, @value{GDBN} prints the module name, the size of the module in
10545 bytes, the number of times the module is used, the dependencies of the
10546 module, the status of the module, and the address of the loaded module
10551 If @var{infotype} is omitted, then list the possible values for
10552 @var{infotype} and the kind of OS information available for each
10553 @var{infotype}. If the target does not return a list of possible
10554 types, this command will report an error.
10557 @node Memory Region Attributes
10558 @section Memory Region Attributes
10559 @cindex memory region attributes
10561 @dfn{Memory region attributes} allow you to describe special handling
10562 required by regions of your target's memory. @value{GDBN} uses
10563 attributes to determine whether to allow certain types of memory
10564 accesses; whether to use specific width accesses; and whether to cache
10565 target memory. By default the description of memory regions is
10566 fetched from the target (if the current target supports this), but the
10567 user can override the fetched regions.
10569 Defined memory regions can be individually enabled and disabled. When a
10570 memory region is disabled, @value{GDBN} uses the default attributes when
10571 accessing memory in that region. Similarly, if no memory regions have
10572 been defined, @value{GDBN} uses the default attributes when accessing
10575 When a memory region is defined, it is given a number to identify it;
10576 to enable, disable, or remove a memory region, you specify that number.
10580 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
10581 Define a memory region bounded by @var{lower} and @var{upper} with
10582 attributes @var{attributes}@dots{}, and add it to the list of regions
10583 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
10584 case: it is treated as the target's maximum memory address.
10585 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
10588 Discard any user changes to the memory regions and use target-supplied
10589 regions, if available, or no regions if the target does not support.
10592 @item delete mem @var{nums}@dots{}
10593 Remove memory regions @var{nums}@dots{} from the list of regions
10594 monitored by @value{GDBN}.
10596 @kindex disable mem
10597 @item disable mem @var{nums}@dots{}
10598 Disable monitoring of memory regions @var{nums}@dots{}.
10599 A disabled memory region is not forgotten.
10600 It may be enabled again later.
10603 @item enable mem @var{nums}@dots{}
10604 Enable monitoring of memory regions @var{nums}@dots{}.
10608 Print a table of all defined memory regions, with the following columns
10612 @item Memory Region Number
10613 @item Enabled or Disabled.
10614 Enabled memory regions are marked with @samp{y}.
10615 Disabled memory regions are marked with @samp{n}.
10618 The address defining the inclusive lower bound of the memory region.
10621 The address defining the exclusive upper bound of the memory region.
10624 The list of attributes set for this memory region.
10629 @subsection Attributes
10631 @subsubsection Memory Access Mode
10632 The access mode attributes set whether @value{GDBN} may make read or
10633 write accesses to a memory region.
10635 While these attributes prevent @value{GDBN} from performing invalid
10636 memory accesses, they do nothing to prevent the target system, I/O DMA,
10637 etc.@: from accessing memory.
10641 Memory is read only.
10643 Memory is write only.
10645 Memory is read/write. This is the default.
10648 @subsubsection Memory Access Size
10649 The access size attribute tells @value{GDBN} to use specific sized
10650 accesses in the memory region. Often memory mapped device registers
10651 require specific sized accesses. If no access size attribute is
10652 specified, @value{GDBN} may use accesses of any size.
10656 Use 8 bit memory accesses.
10658 Use 16 bit memory accesses.
10660 Use 32 bit memory accesses.
10662 Use 64 bit memory accesses.
10665 @c @subsubsection Hardware/Software Breakpoints
10666 @c The hardware/software breakpoint attributes set whether @value{GDBN}
10667 @c will use hardware or software breakpoints for the internal breakpoints
10668 @c used by the step, next, finish, until, etc. commands.
10672 @c Always use hardware breakpoints
10673 @c @item swbreak (default)
10676 @subsubsection Data Cache
10677 The data cache attributes set whether @value{GDBN} will cache target
10678 memory. While this generally improves performance by reducing debug
10679 protocol overhead, it can lead to incorrect results because @value{GDBN}
10680 does not know about volatile variables or memory mapped device
10685 Enable @value{GDBN} to cache target memory.
10687 Disable @value{GDBN} from caching target memory. This is the default.
10690 @subsection Memory Access Checking
10691 @value{GDBN} can be instructed to refuse accesses to memory that is
10692 not explicitly described. This can be useful if accessing such
10693 regions has undesired effects for a specific target, or to provide
10694 better error checking. The following commands control this behaviour.
10697 @kindex set mem inaccessible-by-default
10698 @item set mem inaccessible-by-default [on|off]
10699 If @code{on} is specified, make @value{GDBN} treat memory not
10700 explicitly described by the memory ranges as non-existent and refuse accesses
10701 to such memory. The checks are only performed if there's at least one
10702 memory range defined. If @code{off} is specified, make @value{GDBN}
10703 treat the memory not explicitly described by the memory ranges as RAM.
10704 The default value is @code{on}.
10705 @kindex show mem inaccessible-by-default
10706 @item show mem inaccessible-by-default
10707 Show the current handling of accesses to unknown memory.
10711 @c @subsubsection Memory Write Verification
10712 @c The memory write verification attributes set whether @value{GDBN}
10713 @c will re-reads data after each write to verify the write was successful.
10717 @c @item noverify (default)
10720 @node Dump/Restore Files
10721 @section Copy Between Memory and a File
10722 @cindex dump/restore files
10723 @cindex append data to a file
10724 @cindex dump data to a file
10725 @cindex restore data from a file
10727 You can use the commands @code{dump}, @code{append}, and
10728 @code{restore} to copy data between target memory and a file. The
10729 @code{dump} and @code{append} commands write data to a file, and the
10730 @code{restore} command reads data from a file back into the inferior's
10731 memory. Files may be in binary, Motorola S-record, Intel hex, or
10732 Tektronix Hex format; however, @value{GDBN} can only append to binary
10738 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10739 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
10740 Dump the contents of memory from @var{start_addr} to @var{end_addr},
10741 or the value of @var{expr}, to @var{filename} in the given format.
10743 The @var{format} parameter may be any one of:
10750 Motorola S-record format.
10752 Tektronix Hex format.
10755 @value{GDBN} uses the same definitions of these formats as the
10756 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
10757 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
10761 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10762 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
10763 Append the contents of memory from @var{start_addr} to @var{end_addr},
10764 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
10765 (@value{GDBN} can only append data to files in raw binary form.)
10768 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
10769 Restore the contents of file @var{filename} into memory. The
10770 @code{restore} command can automatically recognize any known @sc{bfd}
10771 file format, except for raw binary. To restore a raw binary file you
10772 must specify the optional keyword @code{binary} after the filename.
10774 If @var{bias} is non-zero, its value will be added to the addresses
10775 contained in the file. Binary files always start at address zero, so
10776 they will be restored at address @var{bias}. Other bfd files have
10777 a built-in location; they will be restored at offset @var{bias}
10778 from that location.
10780 If @var{start} and/or @var{end} are non-zero, then only data between
10781 file offset @var{start} and file offset @var{end} will be restored.
10782 These offsets are relative to the addresses in the file, before
10783 the @var{bias} argument is applied.
10787 @node Core File Generation
10788 @section How to Produce a Core File from Your Program
10789 @cindex dump core from inferior
10791 A @dfn{core file} or @dfn{core dump} is a file that records the memory
10792 image of a running process and its process status (register values
10793 etc.). Its primary use is post-mortem debugging of a program that
10794 crashed while it ran outside a debugger. A program that crashes
10795 automatically produces a core file, unless this feature is disabled by
10796 the user. @xref{Files}, for information on invoking @value{GDBN} in
10797 the post-mortem debugging mode.
10799 Occasionally, you may wish to produce a core file of the program you
10800 are debugging in order to preserve a snapshot of its state.
10801 @value{GDBN} has a special command for that.
10805 @kindex generate-core-file
10806 @item generate-core-file [@var{file}]
10807 @itemx gcore [@var{file}]
10808 Produce a core dump of the inferior process. The optional argument
10809 @var{file} specifies the file name where to put the core dump. If not
10810 specified, the file name defaults to @file{core.@var{pid}}, where
10811 @var{pid} is the inferior process ID.
10813 Note that this command is implemented only for some systems (as of
10814 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
10817 @node Character Sets
10818 @section Character Sets
10819 @cindex character sets
10821 @cindex translating between character sets
10822 @cindex host character set
10823 @cindex target character set
10825 If the program you are debugging uses a different character set to
10826 represent characters and strings than the one @value{GDBN} uses itself,
10827 @value{GDBN} can automatically translate between the character sets for
10828 you. The character set @value{GDBN} uses we call the @dfn{host
10829 character set}; the one the inferior program uses we call the
10830 @dfn{target character set}.
10832 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
10833 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
10834 remote protocol (@pxref{Remote Debugging}) to debug a program
10835 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
10836 then the host character set is Latin-1, and the target character set is
10837 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
10838 target-charset EBCDIC-US}, then @value{GDBN} translates between
10839 @sc{ebcdic} and Latin 1 as you print character or string values, or use
10840 character and string literals in expressions.
10842 @value{GDBN} has no way to automatically recognize which character set
10843 the inferior program uses; you must tell it, using the @code{set
10844 target-charset} command, described below.
10846 Here are the commands for controlling @value{GDBN}'s character set
10850 @item set target-charset @var{charset}
10851 @kindex set target-charset
10852 Set the current target character set to @var{charset}. To display the
10853 list of supported target character sets, type
10854 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
10856 @item set host-charset @var{charset}
10857 @kindex set host-charset
10858 Set the current host character set to @var{charset}.
10860 By default, @value{GDBN} uses a host character set appropriate to the
10861 system it is running on; you can override that default using the
10862 @code{set host-charset} command. On some systems, @value{GDBN} cannot
10863 automatically determine the appropriate host character set. In this
10864 case, @value{GDBN} uses @samp{UTF-8}.
10866 @value{GDBN} can only use certain character sets as its host character
10867 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
10868 @value{GDBN} will list the host character sets it supports.
10870 @item set charset @var{charset}
10871 @kindex set charset
10872 Set the current host and target character sets to @var{charset}. As
10873 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
10874 @value{GDBN} will list the names of the character sets that can be used
10875 for both host and target.
10878 @kindex show charset
10879 Show the names of the current host and target character sets.
10881 @item show host-charset
10882 @kindex show host-charset
10883 Show the name of the current host character set.
10885 @item show target-charset
10886 @kindex show target-charset
10887 Show the name of the current target character set.
10889 @item set target-wide-charset @var{charset}
10890 @kindex set target-wide-charset
10891 Set the current target's wide character set to @var{charset}. This is
10892 the character set used by the target's @code{wchar_t} type. To
10893 display the list of supported wide character sets, type
10894 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
10896 @item show target-wide-charset
10897 @kindex show target-wide-charset
10898 Show the name of the current target's wide character set.
10901 Here is an example of @value{GDBN}'s character set support in action.
10902 Assume that the following source code has been placed in the file
10903 @file{charset-test.c}:
10909 = @{72, 101, 108, 108, 111, 44, 32, 119,
10910 111, 114, 108, 100, 33, 10, 0@};
10911 char ibm1047_hello[]
10912 = @{200, 133, 147, 147, 150, 107, 64, 166,
10913 150, 153, 147, 132, 90, 37, 0@};
10917 printf ("Hello, world!\n");
10921 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
10922 containing the string @samp{Hello, world!} followed by a newline,
10923 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
10925 We compile the program, and invoke the debugger on it:
10928 $ gcc -g charset-test.c -o charset-test
10929 $ gdb -nw charset-test
10930 GNU gdb 2001-12-19-cvs
10931 Copyright 2001 Free Software Foundation, Inc.
10936 We can use the @code{show charset} command to see what character sets
10937 @value{GDBN} is currently using to interpret and display characters and
10941 (@value{GDBP}) show charset
10942 The current host and target character set is `ISO-8859-1'.
10946 For the sake of printing this manual, let's use @sc{ascii} as our
10947 initial character set:
10949 (@value{GDBP}) set charset ASCII
10950 (@value{GDBP}) show charset
10951 The current host and target character set is `ASCII'.
10955 Let's assume that @sc{ascii} is indeed the correct character set for our
10956 host system --- in other words, let's assume that if @value{GDBN} prints
10957 characters using the @sc{ascii} character set, our terminal will display
10958 them properly. Since our current target character set is also
10959 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
10962 (@value{GDBP}) print ascii_hello
10963 $1 = 0x401698 "Hello, world!\n"
10964 (@value{GDBP}) print ascii_hello[0]
10969 @value{GDBN} uses the target character set for character and string
10970 literals you use in expressions:
10973 (@value{GDBP}) print '+'
10978 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
10981 @value{GDBN} relies on the user to tell it which character set the
10982 target program uses. If we print @code{ibm1047_hello} while our target
10983 character set is still @sc{ascii}, we get jibberish:
10986 (@value{GDBP}) print ibm1047_hello
10987 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
10988 (@value{GDBP}) print ibm1047_hello[0]
10993 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
10994 @value{GDBN} tells us the character sets it supports:
10997 (@value{GDBP}) set target-charset
10998 ASCII EBCDIC-US IBM1047 ISO-8859-1
10999 (@value{GDBP}) set target-charset
11002 We can select @sc{ibm1047} as our target character set, and examine the
11003 program's strings again. Now the @sc{ascii} string is wrong, but
11004 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
11005 target character set, @sc{ibm1047}, to the host character set,
11006 @sc{ascii}, and they display correctly:
11009 (@value{GDBP}) set target-charset IBM1047
11010 (@value{GDBP}) show charset
11011 The current host character set is `ASCII'.
11012 The current target character set is `IBM1047'.
11013 (@value{GDBP}) print ascii_hello
11014 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
11015 (@value{GDBP}) print ascii_hello[0]
11017 (@value{GDBP}) print ibm1047_hello
11018 $8 = 0x4016a8 "Hello, world!\n"
11019 (@value{GDBP}) print ibm1047_hello[0]
11024 As above, @value{GDBN} uses the target character set for character and
11025 string literals you use in expressions:
11028 (@value{GDBP}) print '+'
11033 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
11036 @node Caching Target Data
11037 @section Caching Data of Targets
11038 @cindex caching data of targets
11040 @value{GDBN} caches data exchanged between the debugger and a target.
11041 Each cache is associated with the address space of the inferior.
11042 @xref{Inferiors and Programs}, about inferior and address space.
11043 Such caching generally improves performance in remote debugging
11044 (@pxref{Remote Debugging}), because it reduces the overhead of the
11045 remote protocol by bundling memory reads and writes into large chunks.
11046 Unfortunately, simply caching everything would lead to incorrect results,
11047 since @value{GDBN} does not necessarily know anything about volatile
11048 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
11049 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
11051 Therefore, by default, @value{GDBN} only caches data
11052 known to be on the stack@footnote{In non-stop mode, it is moderately
11053 rare for a running thread to modify the stack of a stopped thread
11054 in a way that would interfere with a backtrace, and caching of
11055 stack reads provides a significant speed up of remote backtraces.} or
11056 in the code segment.
11057 Other regions of memory can be explicitly marked as
11058 cacheable; @pxref{Memory Region Attributes}.
11061 @kindex set remotecache
11062 @item set remotecache on
11063 @itemx set remotecache off
11064 This option no longer does anything; it exists for compatibility
11067 @kindex show remotecache
11068 @item show remotecache
11069 Show the current state of the obsolete remotecache flag.
11071 @kindex set stack-cache
11072 @item set stack-cache on
11073 @itemx set stack-cache off
11074 Enable or disable caching of stack accesses. When @code{on}, use
11075 caching. By default, this option is @code{on}.
11077 @kindex show stack-cache
11078 @item show stack-cache
11079 Show the current state of data caching for memory accesses.
11081 @kindex set code-cache
11082 @item set code-cache on
11083 @itemx set code-cache off
11084 Enable or disable caching of code segment accesses. When @code{on},
11085 use caching. By default, this option is @code{on}. This improves
11086 performance of disassembly in remote debugging.
11088 @kindex show code-cache
11089 @item show code-cache
11090 Show the current state of target memory cache for code segment
11093 @kindex info dcache
11094 @item info dcache @r{[}line@r{]}
11095 Print the information about the performance of data cache of the
11096 current inferior's address space. The information displayed
11097 includes the dcache width and depth, and for each cache line, its
11098 number, address, and how many times it was referenced. This
11099 command is useful for debugging the data cache operation.
11101 If a line number is specified, the contents of that line will be
11104 @item set dcache size @var{size}
11105 @cindex dcache size
11106 @kindex set dcache size
11107 Set maximum number of entries in dcache (dcache depth above).
11109 @item set dcache line-size @var{line-size}
11110 @cindex dcache line-size
11111 @kindex set dcache line-size
11112 Set number of bytes each dcache entry caches (dcache width above).
11113 Must be a power of 2.
11115 @item show dcache size
11116 @kindex show dcache size
11117 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
11119 @item show dcache line-size
11120 @kindex show dcache line-size
11121 Show default size of dcache lines.
11125 @node Searching Memory
11126 @section Search Memory
11127 @cindex searching memory
11129 Memory can be searched for a particular sequence of bytes with the
11130 @code{find} command.
11134 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11135 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11136 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
11137 etc. The search begins at address @var{start_addr} and continues for either
11138 @var{len} bytes or through to @var{end_addr} inclusive.
11141 @var{s} and @var{n} are optional parameters.
11142 They may be specified in either order, apart or together.
11145 @item @var{s}, search query size
11146 The size of each search query value.
11152 halfwords (two bytes)
11156 giant words (eight bytes)
11159 All values are interpreted in the current language.
11160 This means, for example, that if the current source language is C/C@t{++}
11161 then searching for the string ``hello'' includes the trailing '\0'.
11163 If the value size is not specified, it is taken from the
11164 value's type in the current language.
11165 This is useful when one wants to specify the search
11166 pattern as a mixture of types.
11167 Note that this means, for example, that in the case of C-like languages
11168 a search for an untyped 0x42 will search for @samp{(int) 0x42}
11169 which is typically four bytes.
11171 @item @var{n}, maximum number of finds
11172 The maximum number of matches to print. The default is to print all finds.
11175 You can use strings as search values. Quote them with double-quotes
11177 The string value is copied into the search pattern byte by byte,
11178 regardless of the endianness of the target and the size specification.
11180 The address of each match found is printed as well as a count of the
11181 number of matches found.
11183 The address of the last value found is stored in convenience variable
11185 A count of the number of matches is stored in @samp{$numfound}.
11187 For example, if stopped at the @code{printf} in this function:
11193 static char hello[] = "hello-hello";
11194 static struct @{ char c; short s; int i; @}
11195 __attribute__ ((packed)) mixed
11196 = @{ 'c', 0x1234, 0x87654321 @};
11197 printf ("%s\n", hello);
11202 you get during debugging:
11205 (gdb) find &hello[0], +sizeof(hello), "hello"
11206 0x804956d <hello.1620+6>
11208 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
11209 0x8049567 <hello.1620>
11210 0x804956d <hello.1620+6>
11212 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
11213 0x8049567 <hello.1620>
11215 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
11216 0x8049560 <mixed.1625>
11218 (gdb) print $numfound
11221 $2 = (void *) 0x8049560
11224 @node Optimized Code
11225 @chapter Debugging Optimized Code
11226 @cindex optimized code, debugging
11227 @cindex debugging optimized code
11229 Almost all compilers support optimization. With optimization
11230 disabled, the compiler generates assembly code that corresponds
11231 directly to your source code, in a simplistic way. As the compiler
11232 applies more powerful optimizations, the generated assembly code
11233 diverges from your original source code. With help from debugging
11234 information generated by the compiler, @value{GDBN} can map from
11235 the running program back to constructs from your original source.
11237 @value{GDBN} is more accurate with optimization disabled. If you
11238 can recompile without optimization, it is easier to follow the
11239 progress of your program during debugging. But, there are many cases
11240 where you may need to debug an optimized version.
11242 When you debug a program compiled with @samp{-g -O}, remember that the
11243 optimizer has rearranged your code; the debugger shows you what is
11244 really there. Do not be too surprised when the execution path does not
11245 exactly match your source file! An extreme example: if you define a
11246 variable, but never use it, @value{GDBN} never sees that
11247 variable---because the compiler optimizes it out of existence.
11249 Some things do not work as well with @samp{-g -O} as with just
11250 @samp{-g}, particularly on machines with instruction scheduling. If in
11251 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
11252 please report it to us as a bug (including a test case!).
11253 @xref{Variables}, for more information about debugging optimized code.
11256 * Inline Functions:: How @value{GDBN} presents inlining
11257 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
11260 @node Inline Functions
11261 @section Inline Functions
11262 @cindex inline functions, debugging
11264 @dfn{Inlining} is an optimization that inserts a copy of the function
11265 body directly at each call site, instead of jumping to a shared
11266 routine. @value{GDBN} displays inlined functions just like
11267 non-inlined functions. They appear in backtraces. You can view their
11268 arguments and local variables, step into them with @code{step}, skip
11269 them with @code{next}, and escape from them with @code{finish}.
11270 You can check whether a function was inlined by using the
11271 @code{info frame} command.
11273 For @value{GDBN} to support inlined functions, the compiler must
11274 record information about inlining in the debug information ---
11275 @value{NGCC} using the @sc{dwarf 2} format does this, and several
11276 other compilers do also. @value{GDBN} only supports inlined functions
11277 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
11278 do not emit two required attributes (@samp{DW_AT_call_file} and
11279 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
11280 function calls with earlier versions of @value{NGCC}. It instead
11281 displays the arguments and local variables of inlined functions as
11282 local variables in the caller.
11284 The body of an inlined function is directly included at its call site;
11285 unlike a non-inlined function, there are no instructions devoted to
11286 the call. @value{GDBN} still pretends that the call site and the
11287 start of the inlined function are different instructions. Stepping to
11288 the call site shows the call site, and then stepping again shows
11289 the first line of the inlined function, even though no additional
11290 instructions are executed.
11292 This makes source-level debugging much clearer; you can see both the
11293 context of the call and then the effect of the call. Only stepping by
11294 a single instruction using @code{stepi} or @code{nexti} does not do
11295 this; single instruction steps always show the inlined body.
11297 There are some ways that @value{GDBN} does not pretend that inlined
11298 function calls are the same as normal calls:
11302 Setting breakpoints at the call site of an inlined function may not
11303 work, because the call site does not contain any code. @value{GDBN}
11304 may incorrectly move the breakpoint to the next line of the enclosing
11305 function, after the call. This limitation will be removed in a future
11306 version of @value{GDBN}; until then, set a breakpoint on an earlier line
11307 or inside the inlined function instead.
11310 @value{GDBN} cannot locate the return value of inlined calls after
11311 using the @code{finish} command. This is a limitation of compiler-generated
11312 debugging information; after @code{finish}, you can step to the next line
11313 and print a variable where your program stored the return value.
11317 @node Tail Call Frames
11318 @section Tail Call Frames
11319 @cindex tail call frames, debugging
11321 Function @code{B} can call function @code{C} in its very last statement. In
11322 unoptimized compilation the call of @code{C} is immediately followed by return
11323 instruction at the end of @code{B} code. Optimizing compiler may replace the
11324 call and return in function @code{B} into one jump to function @code{C}
11325 instead. Such use of a jump instruction is called @dfn{tail call}.
11327 During execution of function @code{C}, there will be no indication in the
11328 function call stack frames that it was tail-called from @code{B}. If function
11329 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
11330 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
11331 some cases @value{GDBN} can determine that @code{C} was tail-called from
11332 @code{B}, and it will then create fictitious call frame for that, with the
11333 return address set up as if @code{B} called @code{C} normally.
11335 This functionality is currently supported only by DWARF 2 debugging format and
11336 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
11337 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11340 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
11341 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
11345 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
11347 Stack level 1, frame at 0x7fffffffda30:
11348 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
11349 tail call frame, caller of frame at 0x7fffffffda30
11350 source language c++.
11351 Arglist at unknown address.
11352 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
11355 The detection of all the possible code path executions can find them ambiguous.
11356 There is no execution history stored (possible @ref{Reverse Execution} is never
11357 used for this purpose) and the last known caller could have reached the known
11358 callee by multiple different jump sequences. In such case @value{GDBN} still
11359 tries to show at least all the unambiguous top tail callers and all the
11360 unambiguous bottom tail calees, if any.
11363 @anchor{set debug entry-values}
11364 @item set debug entry-values
11365 @kindex set debug entry-values
11366 When set to on, enables printing of analysis messages for both frame argument
11367 values at function entry and tail calls. It will show all the possible valid
11368 tail calls code paths it has considered. It will also print the intersection
11369 of them with the final unambiguous (possibly partial or even empty) code path
11372 @item show debug entry-values
11373 @kindex show debug entry-values
11374 Show the current state of analysis messages printing for both frame argument
11375 values at function entry and tail calls.
11378 The analysis messages for tail calls can for example show why the virtual tail
11379 call frame for function @code{c} has not been recognized (due to the indirect
11380 reference by variable @code{x}):
11383 static void __attribute__((noinline, noclone)) c (void);
11384 void (*x) (void) = c;
11385 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11386 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
11387 int main (void) @{ x (); return 0; @}
11389 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
11390 DW_TAG_GNU_call_site 0x40039a in main
11392 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11395 #1 0x000000000040039a in main () at t.c:5
11398 Another possibility is an ambiguous virtual tail call frames resolution:
11402 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
11403 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
11404 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
11405 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
11406 static void __attribute__((noinline, noclone)) b (void)
11407 @{ if (i) c (); else e (); @}
11408 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
11409 int main (void) @{ a (); return 0; @}
11411 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
11412 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
11413 tailcall: reduced: 0x4004d2(a) |
11416 #1 0x00000000004004d2 in a () at t.c:8
11417 #2 0x0000000000400395 in main () at t.c:9
11420 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
11421 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
11423 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
11424 @ifset HAVE_MAKEINFO_CLICK
11425 @set ARROW @click{}
11426 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
11427 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
11429 @ifclear HAVE_MAKEINFO_CLICK
11431 @set CALLSEQ1B @value{CALLSEQ1A}
11432 @set CALLSEQ2B @value{CALLSEQ2A}
11435 Frames #0 and #2 are real, #1 is a virtual tail call frame.
11436 The code can have possible execution paths @value{CALLSEQ1B} or
11437 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
11439 @code{initial:} state shows some random possible calling sequence @value{GDBN}
11440 has found. It then finds another possible calling sequcen - that one is
11441 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
11442 printed as the @code{reduced:} calling sequence. That one could have many
11443 futher @code{compare:} and @code{reduced:} statements as long as there remain
11444 any non-ambiguous sequence entries.
11446 For the frame of function @code{b} in both cases there are different possible
11447 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
11448 also ambigous. The only non-ambiguous frame is the one for function @code{a},
11449 therefore this one is displayed to the user while the ambiguous frames are
11452 There can be also reasons why printing of frame argument values at function
11457 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
11458 static void __attribute__((noinline, noclone)) a (int i);
11459 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
11460 static void __attribute__((noinline, noclone)) a (int i)
11461 @{ if (i) b (i - 1); else c (0); @}
11462 int main (void) @{ a (5); return 0; @}
11465 #0 c (i=i@@entry=0) at t.c:2
11466 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
11467 function "a" at 0x400420 can call itself via tail calls
11468 i=<optimized out>) at t.c:6
11469 #2 0x000000000040036e in main () at t.c:7
11472 @value{GDBN} cannot find out from the inferior state if and how many times did
11473 function @code{a} call itself (via function @code{b}) as these calls would be
11474 tail calls. Such tail calls would modify thue @code{i} variable, therefore
11475 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
11476 prints @code{<optimized out>} instead.
11479 @chapter C Preprocessor Macros
11481 Some languages, such as C and C@t{++}, provide a way to define and invoke
11482 ``preprocessor macros'' which expand into strings of tokens.
11483 @value{GDBN} can evaluate expressions containing macro invocations, show
11484 the result of macro expansion, and show a macro's definition, including
11485 where it was defined.
11487 You may need to compile your program specially to provide @value{GDBN}
11488 with information about preprocessor macros. Most compilers do not
11489 include macros in their debugging information, even when you compile
11490 with the @option{-g} flag. @xref{Compilation}.
11492 A program may define a macro at one point, remove that definition later,
11493 and then provide a different definition after that. Thus, at different
11494 points in the program, a macro may have different definitions, or have
11495 no definition at all. If there is a current stack frame, @value{GDBN}
11496 uses the macros in scope at that frame's source code line. Otherwise,
11497 @value{GDBN} uses the macros in scope at the current listing location;
11500 Whenever @value{GDBN} evaluates an expression, it always expands any
11501 macro invocations present in the expression. @value{GDBN} also provides
11502 the following commands for working with macros explicitly.
11506 @kindex macro expand
11507 @cindex macro expansion, showing the results of preprocessor
11508 @cindex preprocessor macro expansion, showing the results of
11509 @cindex expanding preprocessor macros
11510 @item macro expand @var{expression}
11511 @itemx macro exp @var{expression}
11512 Show the results of expanding all preprocessor macro invocations in
11513 @var{expression}. Since @value{GDBN} simply expands macros, but does
11514 not parse the result, @var{expression} need not be a valid expression;
11515 it can be any string of tokens.
11518 @item macro expand-once @var{expression}
11519 @itemx macro exp1 @var{expression}
11520 @cindex expand macro once
11521 @i{(This command is not yet implemented.)} Show the results of
11522 expanding those preprocessor macro invocations that appear explicitly in
11523 @var{expression}. Macro invocations appearing in that expansion are
11524 left unchanged. This command allows you to see the effect of a
11525 particular macro more clearly, without being confused by further
11526 expansions. Since @value{GDBN} simply expands macros, but does not
11527 parse the result, @var{expression} need not be a valid expression; it
11528 can be any string of tokens.
11531 @cindex macro definition, showing
11532 @cindex definition of a macro, showing
11533 @cindex macros, from debug info
11534 @item info macro [-a|-all] [--] @var{macro}
11535 Show the current definition or all definitions of the named @var{macro},
11536 and describe the source location or compiler command-line where that
11537 definition was established. The optional double dash is to signify the end of
11538 argument processing and the beginning of @var{macro} for non C-like macros where
11539 the macro may begin with a hyphen.
11541 @kindex info macros
11542 @item info macros @var{linespec}
11543 Show all macro definitions that are in effect at the location specified
11544 by @var{linespec}, and describe the source location or compiler
11545 command-line where those definitions were established.
11547 @kindex macro define
11548 @cindex user-defined macros
11549 @cindex defining macros interactively
11550 @cindex macros, user-defined
11551 @item macro define @var{macro} @var{replacement-list}
11552 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
11553 Introduce a definition for a preprocessor macro named @var{macro},
11554 invocations of which are replaced by the tokens given in
11555 @var{replacement-list}. The first form of this command defines an
11556 ``object-like'' macro, which takes no arguments; the second form
11557 defines a ``function-like'' macro, which takes the arguments given in
11560 A definition introduced by this command is in scope in every
11561 expression evaluated in @value{GDBN}, until it is removed with the
11562 @code{macro undef} command, described below. The definition overrides
11563 all definitions for @var{macro} present in the program being debugged,
11564 as well as any previous user-supplied definition.
11566 @kindex macro undef
11567 @item macro undef @var{macro}
11568 Remove any user-supplied definition for the macro named @var{macro}.
11569 This command only affects definitions provided with the @code{macro
11570 define} command, described above; it cannot remove definitions present
11571 in the program being debugged.
11575 List all the macros defined using the @code{macro define} command.
11578 @cindex macros, example of debugging with
11579 Here is a transcript showing the above commands in action. First, we
11580 show our source files:
11585 #include "sample.h"
11588 #define ADD(x) (M + x)
11593 printf ("Hello, world!\n");
11595 printf ("We're so creative.\n");
11597 printf ("Goodbye, world!\n");
11604 Now, we compile the program using the @sc{gnu} C compiler,
11605 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
11606 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
11607 and @option{-gdwarf-4}; we recommend always choosing the most recent
11608 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
11609 includes information about preprocessor macros in the debugging
11613 $ gcc -gdwarf-2 -g3 sample.c -o sample
11617 Now, we start @value{GDBN} on our sample program:
11621 GNU gdb 2002-05-06-cvs
11622 Copyright 2002 Free Software Foundation, Inc.
11623 GDB is free software, @dots{}
11627 We can expand macros and examine their definitions, even when the
11628 program is not running. @value{GDBN} uses the current listing position
11629 to decide which macro definitions are in scope:
11632 (@value{GDBP}) list main
11635 5 #define ADD(x) (M + x)
11640 10 printf ("Hello, world!\n");
11642 12 printf ("We're so creative.\n");
11643 (@value{GDBP}) info macro ADD
11644 Defined at /home/jimb/gdb/macros/play/sample.c:5
11645 #define ADD(x) (M + x)
11646 (@value{GDBP}) info macro Q
11647 Defined at /home/jimb/gdb/macros/play/sample.h:1
11648 included at /home/jimb/gdb/macros/play/sample.c:2
11650 (@value{GDBP}) macro expand ADD(1)
11651 expands to: (42 + 1)
11652 (@value{GDBP}) macro expand-once ADD(1)
11653 expands to: once (M + 1)
11657 In the example above, note that @code{macro expand-once} expands only
11658 the macro invocation explicit in the original text --- the invocation of
11659 @code{ADD} --- but does not expand the invocation of the macro @code{M},
11660 which was introduced by @code{ADD}.
11662 Once the program is running, @value{GDBN} uses the macro definitions in
11663 force at the source line of the current stack frame:
11666 (@value{GDBP}) break main
11667 Breakpoint 1 at 0x8048370: file sample.c, line 10.
11669 Starting program: /home/jimb/gdb/macros/play/sample
11671 Breakpoint 1, main () at sample.c:10
11672 10 printf ("Hello, world!\n");
11676 At line 10, the definition of the macro @code{N} at line 9 is in force:
11679 (@value{GDBP}) info macro N
11680 Defined at /home/jimb/gdb/macros/play/sample.c:9
11682 (@value{GDBP}) macro expand N Q M
11683 expands to: 28 < 42
11684 (@value{GDBP}) print N Q M
11689 As we step over directives that remove @code{N}'s definition, and then
11690 give it a new definition, @value{GDBN} finds the definition (or lack
11691 thereof) in force at each point:
11694 (@value{GDBP}) next
11696 12 printf ("We're so creative.\n");
11697 (@value{GDBP}) info macro N
11698 The symbol `N' has no definition as a C/C++ preprocessor macro
11699 at /home/jimb/gdb/macros/play/sample.c:12
11700 (@value{GDBP}) next
11702 14 printf ("Goodbye, world!\n");
11703 (@value{GDBP}) info macro N
11704 Defined at /home/jimb/gdb/macros/play/sample.c:13
11706 (@value{GDBP}) macro expand N Q M
11707 expands to: 1729 < 42
11708 (@value{GDBP}) print N Q M
11713 In addition to source files, macros can be defined on the compilation command
11714 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
11715 such a way, @value{GDBN} displays the location of their definition as line zero
11716 of the source file submitted to the compiler.
11719 (@value{GDBP}) info macro __STDC__
11720 Defined at /home/jimb/gdb/macros/play/sample.c:0
11727 @chapter Tracepoints
11728 @c This chapter is based on the documentation written by Michael
11729 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
11731 @cindex tracepoints
11732 In some applications, it is not feasible for the debugger to interrupt
11733 the program's execution long enough for the developer to learn
11734 anything helpful about its behavior. If the program's correctness
11735 depends on its real-time behavior, delays introduced by a debugger
11736 might cause the program to change its behavior drastically, or perhaps
11737 fail, even when the code itself is correct. It is useful to be able
11738 to observe the program's behavior without interrupting it.
11740 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
11741 specify locations in the program, called @dfn{tracepoints}, and
11742 arbitrary expressions to evaluate when those tracepoints are reached.
11743 Later, using the @code{tfind} command, you can examine the values
11744 those expressions had when the program hit the tracepoints. The
11745 expressions may also denote objects in memory---structures or arrays,
11746 for example---whose values @value{GDBN} should record; while visiting
11747 a particular tracepoint, you may inspect those objects as if they were
11748 in memory at that moment. However, because @value{GDBN} records these
11749 values without interacting with you, it can do so quickly and
11750 unobtrusively, hopefully not disturbing the program's behavior.
11752 The tracepoint facility is currently available only for remote
11753 targets. @xref{Targets}. In addition, your remote target must know
11754 how to collect trace data. This functionality is implemented in the
11755 remote stub; however, none of the stubs distributed with @value{GDBN}
11756 support tracepoints as of this writing. The format of the remote
11757 packets used to implement tracepoints are described in @ref{Tracepoint
11760 It is also possible to get trace data from a file, in a manner reminiscent
11761 of corefiles; you specify the filename, and use @code{tfind} to search
11762 through the file. @xref{Trace Files}, for more details.
11764 This chapter describes the tracepoint commands and features.
11767 * Set Tracepoints::
11768 * Analyze Collected Data::
11769 * Tracepoint Variables::
11773 @node Set Tracepoints
11774 @section Commands to Set Tracepoints
11776 Before running such a @dfn{trace experiment}, an arbitrary number of
11777 tracepoints can be set. A tracepoint is actually a special type of
11778 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
11779 standard breakpoint commands. For instance, as with breakpoints,
11780 tracepoint numbers are successive integers starting from one, and many
11781 of the commands associated with tracepoints take the tracepoint number
11782 as their argument, to identify which tracepoint to work on.
11784 For each tracepoint, you can specify, in advance, some arbitrary set
11785 of data that you want the target to collect in the trace buffer when
11786 it hits that tracepoint. The collected data can include registers,
11787 local variables, or global data. Later, you can use @value{GDBN}
11788 commands to examine the values these data had at the time the
11789 tracepoint was hit.
11791 Tracepoints do not support every breakpoint feature. Ignore counts on
11792 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
11793 commands when they are hit. Tracepoints may not be thread-specific
11796 @cindex fast tracepoints
11797 Some targets may support @dfn{fast tracepoints}, which are inserted in
11798 a different way (such as with a jump instead of a trap), that is
11799 faster but possibly restricted in where they may be installed.
11801 @cindex static tracepoints
11802 @cindex markers, static tracepoints
11803 @cindex probing markers, static tracepoints
11804 Regular and fast tracepoints are dynamic tracing facilities, meaning
11805 that they can be used to insert tracepoints at (almost) any location
11806 in the target. Some targets may also support controlling @dfn{static
11807 tracepoints} from @value{GDBN}. With static tracing, a set of
11808 instrumentation points, also known as @dfn{markers}, are embedded in
11809 the target program, and can be activated or deactivated by name or
11810 address. These are usually placed at locations which facilitate
11811 investigating what the target is actually doing. @value{GDBN}'s
11812 support for static tracing includes being able to list instrumentation
11813 points, and attach them with @value{GDBN} defined high level
11814 tracepoints that expose the whole range of convenience of
11815 @value{GDBN}'s tracepoints support. Namely, support for collecting
11816 registers values and values of global or local (to the instrumentation
11817 point) variables; tracepoint conditions and trace state variables.
11818 The act of installing a @value{GDBN} static tracepoint on an
11819 instrumentation point, or marker, is referred to as @dfn{probing} a
11820 static tracepoint marker.
11822 @code{gdbserver} supports tracepoints on some target systems.
11823 @xref{Server,,Tracepoints support in @code{gdbserver}}.
11825 This section describes commands to set tracepoints and associated
11826 conditions and actions.
11829 * Create and Delete Tracepoints::
11830 * Enable and Disable Tracepoints::
11831 * Tracepoint Passcounts::
11832 * Tracepoint Conditions::
11833 * Trace State Variables::
11834 * Tracepoint Actions::
11835 * Listing Tracepoints::
11836 * Listing Static Tracepoint Markers::
11837 * Starting and Stopping Trace Experiments::
11838 * Tracepoint Restrictions::
11841 @node Create and Delete Tracepoints
11842 @subsection Create and Delete Tracepoints
11845 @cindex set tracepoint
11847 @item trace @var{location}
11848 The @code{trace} command is very similar to the @code{break} command.
11849 Its argument @var{location} can be a source line, a function name, or
11850 an address in the target program. @xref{Specify Location}. The
11851 @code{trace} command defines a tracepoint, which is a point in the
11852 target program where the debugger will briefly stop, collect some
11853 data, and then allow the program to continue. Setting a tracepoint or
11854 changing its actions takes effect immediately if the remote stub
11855 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
11857 If remote stub doesn't support the @samp{InstallInTrace} feature, all
11858 these changes don't take effect until the next @code{tstart}
11859 command, and once a trace experiment is running, further changes will
11860 not have any effect until the next trace experiment starts. In addition,
11861 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
11862 address is not yet resolved. (This is similar to pending breakpoints.)
11863 Pending tracepoints are not downloaded to the target and not installed
11864 until they are resolved. The resolution of pending tracepoints requires
11865 @value{GDBN} support---when debugging with the remote target, and
11866 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
11867 tracing}), pending tracepoints can not be resolved (and downloaded to
11868 the remote stub) while @value{GDBN} is disconnected.
11870 Here are some examples of using the @code{trace} command:
11873 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
11875 (@value{GDBP}) @b{trace +2} // 2 lines forward
11877 (@value{GDBP}) @b{trace my_function} // first source line of function
11879 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
11881 (@value{GDBP}) @b{trace *0x2117c4} // an address
11885 You can abbreviate @code{trace} as @code{tr}.
11887 @item trace @var{location} if @var{cond}
11888 Set a tracepoint with condition @var{cond}; evaluate the expression
11889 @var{cond} each time the tracepoint is reached, and collect data only
11890 if the value is nonzero---that is, if @var{cond} evaluates as true.
11891 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
11892 information on tracepoint conditions.
11894 @item ftrace @var{location} [ if @var{cond} ]
11895 @cindex set fast tracepoint
11896 @cindex fast tracepoints, setting
11898 The @code{ftrace} command sets a fast tracepoint. For targets that
11899 support them, fast tracepoints will use a more efficient but possibly
11900 less general technique to trigger data collection, such as a jump
11901 instruction instead of a trap, or some sort of hardware support. It
11902 may not be possible to create a fast tracepoint at the desired
11903 location, in which case the command will exit with an explanatory
11906 @value{GDBN} handles arguments to @code{ftrace} exactly as for
11909 On 32-bit x86-architecture systems, fast tracepoints normally need to
11910 be placed at an instruction that is 5 bytes or longer, but can be
11911 placed at 4-byte instructions if the low 64K of memory of the target
11912 program is available to install trampolines. Some Unix-type systems,
11913 such as @sc{gnu}/Linux, exclude low addresses from the program's
11914 address space; but for instance with the Linux kernel it is possible
11915 to let @value{GDBN} use this area by doing a @command{sysctl} command
11916 to set the @code{mmap_min_addr} kernel parameter, as in
11919 sudo sysctl -w vm.mmap_min_addr=32768
11923 which sets the low address to 32K, which leaves plenty of room for
11924 trampolines. The minimum address should be set to a page boundary.
11926 @item strace @var{location} [ if @var{cond} ]
11927 @cindex set static tracepoint
11928 @cindex static tracepoints, setting
11929 @cindex probe static tracepoint marker
11931 The @code{strace} command sets a static tracepoint. For targets that
11932 support it, setting a static tracepoint probes a static
11933 instrumentation point, or marker, found at @var{location}. It may not
11934 be possible to set a static tracepoint at the desired location, in
11935 which case the command will exit with an explanatory message.
11937 @value{GDBN} handles arguments to @code{strace} exactly as for
11938 @code{trace}, with the addition that the user can also specify
11939 @code{-m @var{marker}} as @var{location}. This probes the marker
11940 identified by the @var{marker} string identifier. This identifier
11941 depends on the static tracepoint backend library your program is
11942 using. You can find all the marker identifiers in the @samp{ID} field
11943 of the @code{info static-tracepoint-markers} command output.
11944 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
11945 Markers}. For example, in the following small program using the UST
11951 trace_mark(ust, bar33, "str %s", "FOOBAZ");
11956 the marker id is composed of joining the first two arguments to the
11957 @code{trace_mark} call with a slash, which translates to:
11960 (@value{GDBP}) info static-tracepoint-markers
11961 Cnt Enb ID Address What
11962 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
11968 so you may probe the marker above with:
11971 (@value{GDBP}) strace -m ust/bar33
11974 Static tracepoints accept an extra collect action --- @code{collect
11975 $_sdata}. This collects arbitrary user data passed in the probe point
11976 call to the tracing library. In the UST example above, you'll see
11977 that the third argument to @code{trace_mark} is a printf-like format
11978 string. The user data is then the result of running that formating
11979 string against the following arguments. Note that @code{info
11980 static-tracepoint-markers} command output lists that format string in
11981 the @samp{Data:} field.
11983 You can inspect this data when analyzing the trace buffer, by printing
11984 the $_sdata variable like any other variable available to
11985 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
11988 @cindex last tracepoint number
11989 @cindex recent tracepoint number
11990 @cindex tracepoint number
11991 The convenience variable @code{$tpnum} records the tracepoint number
11992 of the most recently set tracepoint.
11994 @kindex delete tracepoint
11995 @cindex tracepoint deletion
11996 @item delete tracepoint @r{[}@var{num}@r{]}
11997 Permanently delete one or more tracepoints. With no argument, the
11998 default is to delete all tracepoints. Note that the regular
11999 @code{delete} command can remove tracepoints also.
12004 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
12006 (@value{GDBP}) @b{delete trace} // remove all tracepoints
12010 You can abbreviate this command as @code{del tr}.
12013 @node Enable and Disable Tracepoints
12014 @subsection Enable and Disable Tracepoints
12016 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
12019 @kindex disable tracepoint
12020 @item disable tracepoint @r{[}@var{num}@r{]}
12021 Disable tracepoint @var{num}, or all tracepoints if no argument
12022 @var{num} is given. A disabled tracepoint will have no effect during
12023 a trace experiment, but it is not forgotten. You can re-enable
12024 a disabled tracepoint using the @code{enable tracepoint} command.
12025 If the command is issued during a trace experiment and the debug target
12026 has support for disabling tracepoints during a trace experiment, then the
12027 change will be effective immediately. Otherwise, it will be applied to the
12028 next trace experiment.
12030 @kindex enable tracepoint
12031 @item enable tracepoint @r{[}@var{num}@r{]}
12032 Enable tracepoint @var{num}, or all tracepoints. If this command is
12033 issued during a trace experiment and the debug target supports enabling
12034 tracepoints during a trace experiment, then the enabled tracepoints will
12035 become effective immediately. Otherwise, they will become effective the
12036 next time a trace experiment is run.
12039 @node Tracepoint Passcounts
12040 @subsection Tracepoint Passcounts
12044 @cindex tracepoint pass count
12045 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
12046 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
12047 automatically stop a trace experiment. If a tracepoint's passcount is
12048 @var{n}, then the trace experiment will be automatically stopped on
12049 the @var{n}'th time that tracepoint is hit. If the tracepoint number
12050 @var{num} is not specified, the @code{passcount} command sets the
12051 passcount of the most recently defined tracepoint. If no passcount is
12052 given, the trace experiment will run until stopped explicitly by the
12058 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
12059 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
12061 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
12062 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
12063 (@value{GDBP}) @b{trace foo}
12064 (@value{GDBP}) @b{pass 3}
12065 (@value{GDBP}) @b{trace bar}
12066 (@value{GDBP}) @b{pass 2}
12067 (@value{GDBP}) @b{trace baz}
12068 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
12069 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
12070 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
12071 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
12075 @node Tracepoint Conditions
12076 @subsection Tracepoint Conditions
12077 @cindex conditional tracepoints
12078 @cindex tracepoint conditions
12080 The simplest sort of tracepoint collects data every time your program
12081 reaches a specified place. You can also specify a @dfn{condition} for
12082 a tracepoint. A condition is just a Boolean expression in your
12083 programming language (@pxref{Expressions, ,Expressions}). A
12084 tracepoint with a condition evaluates the expression each time your
12085 program reaches it, and data collection happens only if the condition
12088 Tracepoint conditions can be specified when a tracepoint is set, by
12089 using @samp{if} in the arguments to the @code{trace} command.
12090 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
12091 also be set or changed at any time with the @code{condition} command,
12092 just as with breakpoints.
12094 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
12095 the conditional expression itself. Instead, @value{GDBN} encodes the
12096 expression into an agent expression (@pxref{Agent Expressions})
12097 suitable for execution on the target, independently of @value{GDBN}.
12098 Global variables become raw memory locations, locals become stack
12099 accesses, and so forth.
12101 For instance, suppose you have a function that is usually called
12102 frequently, but should not be called after an error has occurred. You
12103 could use the following tracepoint command to collect data about calls
12104 of that function that happen while the error code is propagating
12105 through the program; an unconditional tracepoint could end up
12106 collecting thousands of useless trace frames that you would have to
12110 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
12113 @node Trace State Variables
12114 @subsection Trace State Variables
12115 @cindex trace state variables
12117 A @dfn{trace state variable} is a special type of variable that is
12118 created and managed by target-side code. The syntax is the same as
12119 that for GDB's convenience variables (a string prefixed with ``$''),
12120 but they are stored on the target. They must be created explicitly,
12121 using a @code{tvariable} command. They are always 64-bit signed
12124 Trace state variables are remembered by @value{GDBN}, and downloaded
12125 to the target along with tracepoint information when the trace
12126 experiment starts. There are no intrinsic limits on the number of
12127 trace state variables, beyond memory limitations of the target.
12129 @cindex convenience variables, and trace state variables
12130 Although trace state variables are managed by the target, you can use
12131 them in print commands and expressions as if they were convenience
12132 variables; @value{GDBN} will get the current value from the target
12133 while the trace experiment is running. Trace state variables share
12134 the same namespace as other ``$'' variables, which means that you
12135 cannot have trace state variables with names like @code{$23} or
12136 @code{$pc}, nor can you have a trace state variable and a convenience
12137 variable with the same name.
12141 @item tvariable $@var{name} [ = @var{expression} ]
12143 The @code{tvariable} command creates a new trace state variable named
12144 @code{$@var{name}}, and optionally gives it an initial value of
12145 @var{expression}. The @var{expression} is evaluated when this command is
12146 entered; the result will be converted to an integer if possible,
12147 otherwise @value{GDBN} will report an error. A subsequent
12148 @code{tvariable} command specifying the same name does not create a
12149 variable, but instead assigns the supplied initial value to the
12150 existing variable of that name, overwriting any previous initial
12151 value. The default initial value is 0.
12153 @item info tvariables
12154 @kindex info tvariables
12155 List all the trace state variables along with their initial values.
12156 Their current values may also be displayed, if the trace experiment is
12159 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
12160 @kindex delete tvariable
12161 Delete the given trace state variables, or all of them if no arguments
12166 @node Tracepoint Actions
12167 @subsection Tracepoint Action Lists
12171 @cindex tracepoint actions
12172 @item actions @r{[}@var{num}@r{]}
12173 This command will prompt for a list of actions to be taken when the
12174 tracepoint is hit. If the tracepoint number @var{num} is not
12175 specified, this command sets the actions for the one that was most
12176 recently defined (so that you can define a tracepoint and then say
12177 @code{actions} without bothering about its number). You specify the
12178 actions themselves on the following lines, one action at a time, and
12179 terminate the actions list with a line containing just @code{end}. So
12180 far, the only defined actions are @code{collect}, @code{teval}, and
12181 @code{while-stepping}.
12183 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
12184 Commands, ,Breakpoint Command Lists}), except that only the defined
12185 actions are allowed; any other @value{GDBN} command is rejected.
12187 @cindex remove actions from a tracepoint
12188 To remove all actions from a tracepoint, type @samp{actions @var{num}}
12189 and follow it immediately with @samp{end}.
12192 (@value{GDBP}) @b{collect @var{data}} // collect some data
12194 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
12196 (@value{GDBP}) @b{end} // signals the end of actions.
12199 In the following example, the action list begins with @code{collect}
12200 commands indicating the things to be collected when the tracepoint is
12201 hit. Then, in order to single-step and collect additional data
12202 following the tracepoint, a @code{while-stepping} command is used,
12203 followed by the list of things to be collected after each step in a
12204 sequence of single steps. The @code{while-stepping} command is
12205 terminated by its own separate @code{end} command. Lastly, the action
12206 list is terminated by an @code{end} command.
12209 (@value{GDBP}) @b{trace foo}
12210 (@value{GDBP}) @b{actions}
12211 Enter actions for tracepoint 1, one per line:
12214 > while-stepping 12
12215 > collect $pc, arr[i]
12220 @kindex collect @r{(tracepoints)}
12221 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
12222 Collect values of the given expressions when the tracepoint is hit.
12223 This command accepts a comma-separated list of any valid expressions.
12224 In addition to global, static, or local variables, the following
12225 special arguments are supported:
12229 Collect all registers.
12232 Collect all function arguments.
12235 Collect all local variables.
12238 Collect the return address. This is helpful if you want to see more
12242 Collects the number of arguments from the static probe at which the
12243 tracepoint is located.
12244 @xref{Static Probe Points}.
12246 @item $_probe_arg@var{n}
12247 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
12248 from the static probe at which the tracepoint is located.
12249 @xref{Static Probe Points}.
12252 @vindex $_sdata@r{, collect}
12253 Collect static tracepoint marker specific data. Only available for
12254 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
12255 Lists}. On the UST static tracepoints library backend, an
12256 instrumentation point resembles a @code{printf} function call. The
12257 tracing library is able to collect user specified data formatted to a
12258 character string using the format provided by the programmer that
12259 instrumented the program. Other backends have similar mechanisms.
12260 Here's an example of a UST marker call:
12263 const char master_name[] = "$your_name";
12264 trace_mark(channel1, marker1, "hello %s", master_name)
12267 In this case, collecting @code{$_sdata} collects the string
12268 @samp{hello $yourname}. When analyzing the trace buffer, you can
12269 inspect @samp{$_sdata} like any other variable available to
12273 You can give several consecutive @code{collect} commands, each one
12274 with a single argument, or one @code{collect} command with several
12275 arguments separated by commas; the effect is the same.
12277 The optional @var{mods} changes the usual handling of the arguments.
12278 @code{s} requests that pointers to chars be handled as strings, in
12279 particular collecting the contents of the memory being pointed at, up
12280 to the first zero. The upper bound is by default the value of the
12281 @code{print elements} variable; if @code{s} is followed by a decimal
12282 number, that is the upper bound instead. So for instance
12283 @samp{collect/s25 mystr} collects as many as 25 characters at
12286 The command @code{info scope} (@pxref{Symbols, info scope}) is
12287 particularly useful for figuring out what data to collect.
12289 @kindex teval @r{(tracepoints)}
12290 @item teval @var{expr1}, @var{expr2}, @dots{}
12291 Evaluate the given expressions when the tracepoint is hit. This
12292 command accepts a comma-separated list of expressions. The results
12293 are discarded, so this is mainly useful for assigning values to trace
12294 state variables (@pxref{Trace State Variables}) without adding those
12295 values to the trace buffer, as would be the case if the @code{collect}
12298 @kindex while-stepping @r{(tracepoints)}
12299 @item while-stepping @var{n}
12300 Perform @var{n} single-step instruction traces after the tracepoint,
12301 collecting new data after each step. The @code{while-stepping}
12302 command is followed by the list of what to collect while stepping
12303 (followed by its own @code{end} command):
12306 > while-stepping 12
12307 > collect $regs, myglobal
12313 Note that @code{$pc} is not automatically collected by
12314 @code{while-stepping}; you need to explicitly collect that register if
12315 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
12318 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
12319 @kindex set default-collect
12320 @cindex default collection action
12321 This variable is a list of expressions to collect at each tracepoint
12322 hit. It is effectively an additional @code{collect} action prepended
12323 to every tracepoint action list. The expressions are parsed
12324 individually for each tracepoint, so for instance a variable named
12325 @code{xyz} may be interpreted as a global for one tracepoint, and a
12326 local for another, as appropriate to the tracepoint's location.
12328 @item show default-collect
12329 @kindex show default-collect
12330 Show the list of expressions that are collected by default at each
12335 @node Listing Tracepoints
12336 @subsection Listing Tracepoints
12339 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
12340 @kindex info tp @r{[}@var{n}@dots{}@r{]}
12341 @cindex information about tracepoints
12342 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
12343 Display information about the tracepoint @var{num}. If you don't
12344 specify a tracepoint number, displays information about all the
12345 tracepoints defined so far. The format is similar to that used for
12346 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
12347 command, simply restricting itself to tracepoints.
12349 A tracepoint's listing may include additional information specific to
12354 its passcount as given by the @code{passcount @var{n}} command
12357 the state about installed on target of each location
12361 (@value{GDBP}) @b{info trace}
12362 Num Type Disp Enb Address What
12363 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
12365 collect globfoo, $regs
12370 2 tracepoint keep y <MULTIPLE>
12372 2.1 y 0x0804859c in func4 at change-loc.h:35
12373 installed on target
12374 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
12375 installed on target
12376 2.3 y <PENDING> set_tracepoint
12377 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
12378 not installed on target
12383 This command can be abbreviated @code{info tp}.
12386 @node Listing Static Tracepoint Markers
12387 @subsection Listing Static Tracepoint Markers
12390 @kindex info static-tracepoint-markers
12391 @cindex information about static tracepoint markers
12392 @item info static-tracepoint-markers
12393 Display information about all static tracepoint markers defined in the
12396 For each marker, the following columns are printed:
12400 An incrementing counter, output to help readability. This is not a
12403 The marker ID, as reported by the target.
12404 @item Enabled or Disabled
12405 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
12406 that are not enabled.
12408 Where the marker is in your program, as a memory address.
12410 Where the marker is in the source for your program, as a file and line
12411 number. If the debug information included in the program does not
12412 allow @value{GDBN} to locate the source of the marker, this column
12413 will be left blank.
12417 In addition, the following information may be printed for each marker:
12421 User data passed to the tracing library by the marker call. In the
12422 UST backend, this is the format string passed as argument to the
12424 @item Static tracepoints probing the marker
12425 The list of static tracepoints attached to the marker.
12429 (@value{GDBP}) info static-tracepoint-markers
12430 Cnt ID Enb Address What
12431 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
12432 Data: number1 %d number2 %d
12433 Probed by static tracepoints: #2
12434 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
12440 @node Starting and Stopping Trace Experiments
12441 @subsection Starting and Stopping Trace Experiments
12444 @kindex tstart [ @var{notes} ]
12445 @cindex start a new trace experiment
12446 @cindex collected data discarded
12448 This command starts the trace experiment, and begins collecting data.
12449 It has the side effect of discarding all the data collected in the
12450 trace buffer during the previous trace experiment. If any arguments
12451 are supplied, they are taken as a note and stored with the trace
12452 experiment's state. The notes may be arbitrary text, and are
12453 especially useful with disconnected tracing in a multi-user context;
12454 the notes can explain what the trace is doing, supply user contact
12455 information, and so forth.
12457 @kindex tstop [ @var{notes} ]
12458 @cindex stop a running trace experiment
12460 This command stops the trace experiment. If any arguments are
12461 supplied, they are recorded with the experiment as a note. This is
12462 useful if you are stopping a trace started by someone else, for
12463 instance if the trace is interfering with the system's behavior and
12464 needs to be stopped quickly.
12466 @strong{Note}: a trace experiment and data collection may stop
12467 automatically if any tracepoint's passcount is reached
12468 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
12471 @cindex status of trace data collection
12472 @cindex trace experiment, status of
12474 This command displays the status of the current trace data
12478 Here is an example of the commands we described so far:
12481 (@value{GDBP}) @b{trace gdb_c_test}
12482 (@value{GDBP}) @b{actions}
12483 Enter actions for tracepoint #1, one per line.
12484 > collect $regs,$locals,$args
12485 > while-stepping 11
12489 (@value{GDBP}) @b{tstart}
12490 [time passes @dots{}]
12491 (@value{GDBP}) @b{tstop}
12494 @anchor{disconnected tracing}
12495 @cindex disconnected tracing
12496 You can choose to continue running the trace experiment even if
12497 @value{GDBN} disconnects from the target, voluntarily or
12498 involuntarily. For commands such as @code{detach}, the debugger will
12499 ask what you want to do with the trace. But for unexpected
12500 terminations (@value{GDBN} crash, network outage), it would be
12501 unfortunate to lose hard-won trace data, so the variable
12502 @code{disconnected-tracing} lets you decide whether the trace should
12503 continue running without @value{GDBN}.
12506 @item set disconnected-tracing on
12507 @itemx set disconnected-tracing off
12508 @kindex set disconnected-tracing
12509 Choose whether a tracing run should continue to run if @value{GDBN}
12510 has disconnected from the target. Note that @code{detach} or
12511 @code{quit} will ask you directly what to do about a running trace no
12512 matter what this variable's setting, so the variable is mainly useful
12513 for handling unexpected situations, such as loss of the network.
12515 @item show disconnected-tracing
12516 @kindex show disconnected-tracing
12517 Show the current choice for disconnected tracing.
12521 When you reconnect to the target, the trace experiment may or may not
12522 still be running; it might have filled the trace buffer in the
12523 meantime, or stopped for one of the other reasons. If it is running,
12524 it will continue after reconnection.
12526 Upon reconnection, the target will upload information about the
12527 tracepoints in effect. @value{GDBN} will then compare that
12528 information to the set of tracepoints currently defined, and attempt
12529 to match them up, allowing for the possibility that the numbers may
12530 have changed due to creation and deletion in the meantime. If one of
12531 the target's tracepoints does not match any in @value{GDBN}, the
12532 debugger will create a new tracepoint, so that you have a number with
12533 which to specify that tracepoint. This matching-up process is
12534 necessarily heuristic, and it may result in useless tracepoints being
12535 created; you may simply delete them if they are of no use.
12537 @cindex circular trace buffer
12538 If your target agent supports a @dfn{circular trace buffer}, then you
12539 can run a trace experiment indefinitely without filling the trace
12540 buffer; when space runs out, the agent deletes already-collected trace
12541 frames, oldest first, until there is enough room to continue
12542 collecting. This is especially useful if your tracepoints are being
12543 hit too often, and your trace gets terminated prematurely because the
12544 buffer is full. To ask for a circular trace buffer, simply set
12545 @samp{circular-trace-buffer} to on. You can set this at any time,
12546 including during tracing; if the agent can do it, it will change
12547 buffer handling on the fly, otherwise it will not take effect until
12551 @item set circular-trace-buffer on
12552 @itemx set circular-trace-buffer off
12553 @kindex set circular-trace-buffer
12554 Choose whether a tracing run should use a linear or circular buffer
12555 for trace data. A linear buffer will not lose any trace data, but may
12556 fill up prematurely, while a circular buffer will discard old trace
12557 data, but it will have always room for the latest tracepoint hits.
12559 @item show circular-trace-buffer
12560 @kindex show circular-trace-buffer
12561 Show the current choice for the trace buffer. Note that this may not
12562 match the agent's current buffer handling, nor is it guaranteed to
12563 match the setting that might have been in effect during a past run,
12564 for instance if you are looking at frames from a trace file.
12569 @item set trace-buffer-size @var{n}
12570 @itemx set trace-buffer-size unlimited
12571 @kindex set trace-buffer-size
12572 Request that the target use a trace buffer of @var{n} bytes. Not all
12573 targets will honor the request; they may have a compiled-in size for
12574 the trace buffer, or some other limitation. Set to a value of
12575 @code{unlimited} or @code{-1} to let the target use whatever size it
12576 likes. This is also the default.
12578 @item show trace-buffer-size
12579 @kindex show trace-buffer-size
12580 Show the current requested size for the trace buffer. Note that this
12581 will only match the actual size if the target supports size-setting,
12582 and was able to handle the requested size. For instance, if the
12583 target can only change buffer size between runs, this variable will
12584 not reflect the change until the next run starts. Use @code{tstatus}
12585 to get a report of the actual buffer size.
12589 @item set trace-user @var{text}
12590 @kindex set trace-user
12592 @item show trace-user
12593 @kindex show trace-user
12595 @item set trace-notes @var{text}
12596 @kindex set trace-notes
12597 Set the trace run's notes.
12599 @item show trace-notes
12600 @kindex show trace-notes
12601 Show the trace run's notes.
12603 @item set trace-stop-notes @var{text}
12604 @kindex set trace-stop-notes
12605 Set the trace run's stop notes. The handling of the note is as for
12606 @code{tstop} arguments; the set command is convenient way to fix a
12607 stop note that is mistaken or incomplete.
12609 @item show trace-stop-notes
12610 @kindex show trace-stop-notes
12611 Show the trace run's stop notes.
12615 @node Tracepoint Restrictions
12616 @subsection Tracepoint Restrictions
12618 @cindex tracepoint restrictions
12619 There are a number of restrictions on the use of tracepoints. As
12620 described above, tracepoint data gathering occurs on the target
12621 without interaction from @value{GDBN}. Thus the full capabilities of
12622 the debugger are not available during data gathering, and then at data
12623 examination time, you will be limited by only having what was
12624 collected. The following items describe some common problems, but it
12625 is not exhaustive, and you may run into additional difficulties not
12631 Tracepoint expressions are intended to gather objects (lvalues). Thus
12632 the full flexibility of GDB's expression evaluator is not available.
12633 You cannot call functions, cast objects to aggregate types, access
12634 convenience variables or modify values (except by assignment to trace
12635 state variables). Some language features may implicitly call
12636 functions (for instance Objective-C fields with accessors), and therefore
12637 cannot be collected either.
12640 Collection of local variables, either individually or in bulk with
12641 @code{$locals} or @code{$args}, during @code{while-stepping} may
12642 behave erratically. The stepping action may enter a new scope (for
12643 instance by stepping into a function), or the location of the variable
12644 may change (for instance it is loaded into a register). The
12645 tracepoint data recorded uses the location information for the
12646 variables that is correct for the tracepoint location. When the
12647 tracepoint is created, it is not possible, in general, to determine
12648 where the steps of a @code{while-stepping} sequence will advance the
12649 program---particularly if a conditional branch is stepped.
12652 Collection of an incompletely-initialized or partially-destroyed object
12653 may result in something that @value{GDBN} cannot display, or displays
12654 in a misleading way.
12657 When @value{GDBN} displays a pointer to character it automatically
12658 dereferences the pointer to also display characters of the string
12659 being pointed to. However, collecting the pointer during tracing does
12660 not automatically collect the string. You need to explicitly
12661 dereference the pointer and provide size information if you want to
12662 collect not only the pointer, but the memory pointed to. For example,
12663 @code{*ptr@@50} can be used to collect the 50 element array pointed to
12667 It is not possible to collect a complete stack backtrace at a
12668 tracepoint. Instead, you may collect the registers and a few hundred
12669 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
12670 (adjust to use the name of the actual stack pointer register on your
12671 target architecture, and the amount of stack you wish to capture).
12672 Then the @code{backtrace} command will show a partial backtrace when
12673 using a trace frame. The number of stack frames that can be examined
12674 depends on the sizes of the frames in the collected stack. Note that
12675 if you ask for a block so large that it goes past the bottom of the
12676 stack, the target agent may report an error trying to read from an
12680 If you do not collect registers at a tracepoint, @value{GDBN} can
12681 infer that the value of @code{$pc} must be the same as the address of
12682 the tracepoint and use that when you are looking at a trace frame
12683 for that tracepoint. However, this cannot work if the tracepoint has
12684 multiple locations (for instance if it was set in a function that was
12685 inlined), or if it has a @code{while-stepping} loop. In those cases
12686 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
12691 @node Analyze Collected Data
12692 @section Using the Collected Data
12694 After the tracepoint experiment ends, you use @value{GDBN} commands
12695 for examining the trace data. The basic idea is that each tracepoint
12696 collects a trace @dfn{snapshot} every time it is hit and another
12697 snapshot every time it single-steps. All these snapshots are
12698 consecutively numbered from zero and go into a buffer, and you can
12699 examine them later. The way you examine them is to @dfn{focus} on a
12700 specific trace snapshot. When the remote stub is focused on a trace
12701 snapshot, it will respond to all @value{GDBN} requests for memory and
12702 registers by reading from the buffer which belongs to that snapshot,
12703 rather than from @emph{real} memory or registers of the program being
12704 debugged. This means that @strong{all} @value{GDBN} commands
12705 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
12706 behave as if we were currently debugging the program state as it was
12707 when the tracepoint occurred. Any requests for data that are not in
12708 the buffer will fail.
12711 * tfind:: How to select a trace snapshot
12712 * tdump:: How to display all data for a snapshot
12713 * save tracepoints:: How to save tracepoints for a future run
12717 @subsection @code{tfind @var{n}}
12720 @cindex select trace snapshot
12721 @cindex find trace snapshot
12722 The basic command for selecting a trace snapshot from the buffer is
12723 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
12724 counting from zero. If no argument @var{n} is given, the next
12725 snapshot is selected.
12727 Here are the various forms of using the @code{tfind} command.
12731 Find the first snapshot in the buffer. This is a synonym for
12732 @code{tfind 0} (since 0 is the number of the first snapshot).
12735 Stop debugging trace snapshots, resume @emph{live} debugging.
12738 Same as @samp{tfind none}.
12741 No argument means find the next trace snapshot.
12744 Find the previous trace snapshot before the current one. This permits
12745 retracing earlier steps.
12747 @item tfind tracepoint @var{num}
12748 Find the next snapshot associated with tracepoint @var{num}. Search
12749 proceeds forward from the last examined trace snapshot. If no
12750 argument @var{num} is given, it means find the next snapshot collected
12751 for the same tracepoint as the current snapshot.
12753 @item tfind pc @var{addr}
12754 Find the next snapshot associated with the value @var{addr} of the
12755 program counter. Search proceeds forward from the last examined trace
12756 snapshot. If no argument @var{addr} is given, it means find the next
12757 snapshot with the same value of PC as the current snapshot.
12759 @item tfind outside @var{addr1}, @var{addr2}
12760 Find the next snapshot whose PC is outside the given range of
12761 addresses (exclusive).
12763 @item tfind range @var{addr1}, @var{addr2}
12764 Find the next snapshot whose PC is between @var{addr1} and
12765 @var{addr2} (inclusive).
12767 @item tfind line @r{[}@var{file}:@r{]}@var{n}
12768 Find the next snapshot associated with the source line @var{n}. If
12769 the optional argument @var{file} is given, refer to line @var{n} in
12770 that source file. Search proceeds forward from the last examined
12771 trace snapshot. If no argument @var{n} is given, it means find the
12772 next line other than the one currently being examined; thus saying
12773 @code{tfind line} repeatedly can appear to have the same effect as
12774 stepping from line to line in a @emph{live} debugging session.
12777 The default arguments for the @code{tfind} commands are specifically
12778 designed to make it easy to scan through the trace buffer. For
12779 instance, @code{tfind} with no argument selects the next trace
12780 snapshot, and @code{tfind -} with no argument selects the previous
12781 trace snapshot. So, by giving one @code{tfind} command, and then
12782 simply hitting @key{RET} repeatedly you can examine all the trace
12783 snapshots in order. Or, by saying @code{tfind -} and then hitting
12784 @key{RET} repeatedly you can examine the snapshots in reverse order.
12785 The @code{tfind line} command with no argument selects the snapshot
12786 for the next source line executed. The @code{tfind pc} command with
12787 no argument selects the next snapshot with the same program counter
12788 (PC) as the current frame. The @code{tfind tracepoint} command with
12789 no argument selects the next trace snapshot collected by the same
12790 tracepoint as the current one.
12792 In addition to letting you scan through the trace buffer manually,
12793 these commands make it easy to construct @value{GDBN} scripts that
12794 scan through the trace buffer and print out whatever collected data
12795 you are interested in. Thus, if we want to examine the PC, FP, and SP
12796 registers from each trace frame in the buffer, we can say this:
12799 (@value{GDBP}) @b{tfind start}
12800 (@value{GDBP}) @b{while ($trace_frame != -1)}
12801 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
12802 $trace_frame, $pc, $sp, $fp
12806 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
12807 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
12808 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
12809 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
12810 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
12811 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
12812 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
12813 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
12814 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
12815 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
12816 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
12819 Or, if we want to examine the variable @code{X} at each source line in
12823 (@value{GDBP}) @b{tfind start}
12824 (@value{GDBP}) @b{while ($trace_frame != -1)}
12825 > printf "Frame %d, X == %d\n", $trace_frame, X
12835 @subsection @code{tdump}
12837 @cindex dump all data collected at tracepoint
12838 @cindex tracepoint data, display
12840 This command takes no arguments. It prints all the data collected at
12841 the current trace snapshot.
12844 (@value{GDBP}) @b{trace 444}
12845 (@value{GDBP}) @b{actions}
12846 Enter actions for tracepoint #2, one per line:
12847 > collect $regs, $locals, $args, gdb_long_test
12850 (@value{GDBP}) @b{tstart}
12852 (@value{GDBP}) @b{tfind line 444}
12853 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
12855 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
12857 (@value{GDBP}) @b{tdump}
12858 Data collected at tracepoint 2, trace frame 1:
12859 d0 0xc4aa0085 -995491707
12863 d4 0x71aea3d 119204413
12866 d7 0x380035 3670069
12867 a0 0x19e24a 1696330
12868 a1 0x3000668 50333288
12870 a3 0x322000 3284992
12871 a4 0x3000698 50333336
12872 a5 0x1ad3cc 1758156
12873 fp 0x30bf3c 0x30bf3c
12874 sp 0x30bf34 0x30bf34
12876 pc 0x20b2c8 0x20b2c8
12880 p = 0x20e5b4 "gdb-test"
12887 gdb_long_test = 17 '\021'
12892 @code{tdump} works by scanning the tracepoint's current collection
12893 actions and printing the value of each expression listed. So
12894 @code{tdump} can fail, if after a run, you change the tracepoint's
12895 actions to mention variables that were not collected during the run.
12897 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
12898 uses the collected value of @code{$pc} to distinguish between trace
12899 frames that were collected at the tracepoint hit, and frames that were
12900 collected while stepping. This allows it to correctly choose whether
12901 to display the basic list of collections, or the collections from the
12902 body of the while-stepping loop. However, if @code{$pc} was not collected,
12903 then @code{tdump} will always attempt to dump using the basic collection
12904 list, and may fail if a while-stepping frame does not include all the
12905 same data that is collected at the tracepoint hit.
12906 @c This is getting pretty arcane, example would be good.
12908 @node save tracepoints
12909 @subsection @code{save tracepoints @var{filename}}
12910 @kindex save tracepoints
12911 @kindex save-tracepoints
12912 @cindex save tracepoints for future sessions
12914 This command saves all current tracepoint definitions together with
12915 their actions and passcounts, into a file @file{@var{filename}}
12916 suitable for use in a later debugging session. To read the saved
12917 tracepoint definitions, use the @code{source} command (@pxref{Command
12918 Files}). The @w{@code{save-tracepoints}} command is a deprecated
12919 alias for @w{@code{save tracepoints}}
12921 @node Tracepoint Variables
12922 @section Convenience Variables for Tracepoints
12923 @cindex tracepoint variables
12924 @cindex convenience variables for tracepoints
12927 @vindex $trace_frame
12928 @item (int) $trace_frame
12929 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
12930 snapshot is selected.
12932 @vindex $tracepoint
12933 @item (int) $tracepoint
12934 The tracepoint for the current trace snapshot.
12936 @vindex $trace_line
12937 @item (int) $trace_line
12938 The line number for the current trace snapshot.
12940 @vindex $trace_file
12941 @item (char []) $trace_file
12942 The source file for the current trace snapshot.
12944 @vindex $trace_func
12945 @item (char []) $trace_func
12946 The name of the function containing @code{$tracepoint}.
12949 Note: @code{$trace_file} is not suitable for use in @code{printf},
12950 use @code{output} instead.
12952 Here's a simple example of using these convenience variables for
12953 stepping through all the trace snapshots and printing some of their
12954 data. Note that these are not the same as trace state variables,
12955 which are managed by the target.
12958 (@value{GDBP}) @b{tfind start}
12960 (@value{GDBP}) @b{while $trace_frame != -1}
12961 > output $trace_file
12962 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
12968 @section Using Trace Files
12969 @cindex trace files
12971 In some situations, the target running a trace experiment may no
12972 longer be available; perhaps it crashed, or the hardware was needed
12973 for a different activity. To handle these cases, you can arrange to
12974 dump the trace data into a file, and later use that file as a source
12975 of trace data, via the @code{target tfile} command.
12980 @item tsave [ -r ] @var{filename}
12981 @itemx tsave [-ctf] @var{dirname}
12982 Save the trace data to @var{filename}. By default, this command
12983 assumes that @var{filename} refers to the host filesystem, so if
12984 necessary @value{GDBN} will copy raw trace data up from the target and
12985 then save it. If the target supports it, you can also supply the
12986 optional argument @code{-r} (``remote'') to direct the target to save
12987 the data directly into @var{filename} in its own filesystem, which may be
12988 more efficient if the trace buffer is very large. (Note, however, that
12989 @code{target tfile} can only read from files accessible to the host.)
12990 By default, this command will save trace frame in tfile format.
12991 You can supply the optional argument @code{-ctf} to save date in CTF
12992 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
12993 that can be shared by multiple debugging and tracing tools. Please go to
12994 @indicateurl{http://www.efficios.com/ctf} to get more information.
12996 @kindex target tfile
13000 @item target tfile @var{filename}
13001 @itemx target ctf @var{dirname}
13002 Use the file named @var{filename} or directory named @var{dirname} as
13003 a source of trace data. Commands that examine data work as they do with
13004 a live target, but it is not possible to run any new trace experiments.
13005 @code{tstatus} will report the state of the trace run at the moment
13006 the data was saved, as well as the current trace frame you are examining.
13007 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
13011 (@value{GDBP}) target ctf ctf.ctf
13012 (@value{GDBP}) tfind
13013 Found trace frame 0, tracepoint 2
13014 39 ++a; /* set tracepoint 1 here */
13015 (@value{GDBP}) tdump
13016 Data collected at tracepoint 2, trace frame 0:
13020 c = @{"123", "456", "789", "123", "456", "789"@}
13021 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
13029 @chapter Debugging Programs That Use Overlays
13032 If your program is too large to fit completely in your target system's
13033 memory, you can sometimes use @dfn{overlays} to work around this
13034 problem. @value{GDBN} provides some support for debugging programs that
13038 * How Overlays Work:: A general explanation of overlays.
13039 * Overlay Commands:: Managing overlays in @value{GDBN}.
13040 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
13041 mapped by asking the inferior.
13042 * Overlay Sample Program:: A sample program using overlays.
13045 @node How Overlays Work
13046 @section How Overlays Work
13047 @cindex mapped overlays
13048 @cindex unmapped overlays
13049 @cindex load address, overlay's
13050 @cindex mapped address
13051 @cindex overlay area
13053 Suppose you have a computer whose instruction address space is only 64
13054 kilobytes long, but which has much more memory which can be accessed by
13055 other means: special instructions, segment registers, or memory
13056 management hardware, for example. Suppose further that you want to
13057 adapt a program which is larger than 64 kilobytes to run on this system.
13059 One solution is to identify modules of your program which are relatively
13060 independent, and need not call each other directly; call these modules
13061 @dfn{overlays}. Separate the overlays from the main program, and place
13062 their machine code in the larger memory. Place your main program in
13063 instruction memory, but leave at least enough space there to hold the
13064 largest overlay as well.
13066 Now, to call a function located in an overlay, you must first copy that
13067 overlay's machine code from the large memory into the space set aside
13068 for it in the instruction memory, and then jump to its entry point
13071 @c NB: In the below the mapped area's size is greater or equal to the
13072 @c size of all overlays. This is intentional to remind the developer
13073 @c that overlays don't necessarily need to be the same size.
13077 Data Instruction Larger
13078 Address Space Address Space Address Space
13079 +-----------+ +-----------+ +-----------+
13081 +-----------+ +-----------+ +-----------+<-- overlay 1
13082 | program | | main | .----| overlay 1 | load address
13083 | variables | | program | | +-----------+
13084 | and heap | | | | | |
13085 +-----------+ | | | +-----------+<-- overlay 2
13086 | | +-----------+ | | | load address
13087 +-----------+ | | | .-| overlay 2 |
13089 mapped --->+-----------+ | | +-----------+
13090 address | | | | | |
13091 | overlay | <-' | | |
13092 | area | <---' +-----------+<-- overlay 3
13093 | | <---. | | load address
13094 +-----------+ `--| overlay 3 |
13101 @anchor{A code overlay}A code overlay
13105 The diagram (@pxref{A code overlay}) shows a system with separate data
13106 and instruction address spaces. To map an overlay, the program copies
13107 its code from the larger address space to the instruction address space.
13108 Since the overlays shown here all use the same mapped address, only one
13109 may be mapped at a time. For a system with a single address space for
13110 data and instructions, the diagram would be similar, except that the
13111 program variables and heap would share an address space with the main
13112 program and the overlay area.
13114 An overlay loaded into instruction memory and ready for use is called a
13115 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
13116 instruction memory. An overlay not present (or only partially present)
13117 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
13118 is its address in the larger memory. The mapped address is also called
13119 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
13120 called the @dfn{load memory address}, or @dfn{LMA}.
13122 Unfortunately, overlays are not a completely transparent way to adapt a
13123 program to limited instruction memory. They introduce a new set of
13124 global constraints you must keep in mind as you design your program:
13129 Before calling or returning to a function in an overlay, your program
13130 must make sure that overlay is actually mapped. Otherwise, the call or
13131 return will transfer control to the right address, but in the wrong
13132 overlay, and your program will probably crash.
13135 If the process of mapping an overlay is expensive on your system, you
13136 will need to choose your overlays carefully to minimize their effect on
13137 your program's performance.
13140 The executable file you load onto your system must contain each
13141 overlay's instructions, appearing at the overlay's load address, not its
13142 mapped address. However, each overlay's instructions must be relocated
13143 and its symbols defined as if the overlay were at its mapped address.
13144 You can use GNU linker scripts to specify different load and relocation
13145 addresses for pieces of your program; see @ref{Overlay Description,,,
13146 ld.info, Using ld: the GNU linker}.
13149 The procedure for loading executable files onto your system must be able
13150 to load their contents into the larger address space as well as the
13151 instruction and data spaces.
13155 The overlay system described above is rather simple, and could be
13156 improved in many ways:
13161 If your system has suitable bank switch registers or memory management
13162 hardware, you could use those facilities to make an overlay's load area
13163 contents simply appear at their mapped address in instruction space.
13164 This would probably be faster than copying the overlay to its mapped
13165 area in the usual way.
13168 If your overlays are small enough, you could set aside more than one
13169 overlay area, and have more than one overlay mapped at a time.
13172 You can use overlays to manage data, as well as instructions. In
13173 general, data overlays are even less transparent to your design than
13174 code overlays: whereas code overlays only require care when you call or
13175 return to functions, data overlays require care every time you access
13176 the data. Also, if you change the contents of a data overlay, you
13177 must copy its contents back out to its load address before you can copy a
13178 different data overlay into the same mapped area.
13183 @node Overlay Commands
13184 @section Overlay Commands
13186 To use @value{GDBN}'s overlay support, each overlay in your program must
13187 correspond to a separate section of the executable file. The section's
13188 virtual memory address and load memory address must be the overlay's
13189 mapped and load addresses. Identifying overlays with sections allows
13190 @value{GDBN} to determine the appropriate address of a function or
13191 variable, depending on whether the overlay is mapped or not.
13193 @value{GDBN}'s overlay commands all start with the word @code{overlay};
13194 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
13199 Disable @value{GDBN}'s overlay support. When overlay support is
13200 disabled, @value{GDBN} assumes that all functions and variables are
13201 always present at their mapped addresses. By default, @value{GDBN}'s
13202 overlay support is disabled.
13204 @item overlay manual
13205 @cindex manual overlay debugging
13206 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
13207 relies on you to tell it which overlays are mapped, and which are not,
13208 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
13209 commands described below.
13211 @item overlay map-overlay @var{overlay}
13212 @itemx overlay map @var{overlay}
13213 @cindex map an overlay
13214 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
13215 be the name of the object file section containing the overlay. When an
13216 overlay is mapped, @value{GDBN} assumes it can find the overlay's
13217 functions and variables at their mapped addresses. @value{GDBN} assumes
13218 that any other overlays whose mapped ranges overlap that of
13219 @var{overlay} are now unmapped.
13221 @item overlay unmap-overlay @var{overlay}
13222 @itemx overlay unmap @var{overlay}
13223 @cindex unmap an overlay
13224 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
13225 must be the name of the object file section containing the overlay.
13226 When an overlay is unmapped, @value{GDBN} assumes it can find the
13227 overlay's functions and variables at their load addresses.
13230 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
13231 consults a data structure the overlay manager maintains in the inferior
13232 to see which overlays are mapped. For details, see @ref{Automatic
13233 Overlay Debugging}.
13235 @item overlay load-target
13236 @itemx overlay load
13237 @cindex reloading the overlay table
13238 Re-read the overlay table from the inferior. Normally, @value{GDBN}
13239 re-reads the table @value{GDBN} automatically each time the inferior
13240 stops, so this command should only be necessary if you have changed the
13241 overlay mapping yourself using @value{GDBN}. This command is only
13242 useful when using automatic overlay debugging.
13244 @item overlay list-overlays
13245 @itemx overlay list
13246 @cindex listing mapped overlays
13247 Display a list of the overlays currently mapped, along with their mapped
13248 addresses, load addresses, and sizes.
13252 Normally, when @value{GDBN} prints a code address, it includes the name
13253 of the function the address falls in:
13256 (@value{GDBP}) print main
13257 $3 = @{int ()@} 0x11a0 <main>
13260 When overlay debugging is enabled, @value{GDBN} recognizes code in
13261 unmapped overlays, and prints the names of unmapped functions with
13262 asterisks around them. For example, if @code{foo} is a function in an
13263 unmapped overlay, @value{GDBN} prints it this way:
13266 (@value{GDBP}) overlay list
13267 No sections are mapped.
13268 (@value{GDBP}) print foo
13269 $5 = @{int (int)@} 0x100000 <*foo*>
13272 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
13276 (@value{GDBP}) overlay list
13277 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
13278 mapped at 0x1016 - 0x104a
13279 (@value{GDBP}) print foo
13280 $6 = @{int (int)@} 0x1016 <foo>
13283 When overlay debugging is enabled, @value{GDBN} can find the correct
13284 address for functions and variables in an overlay, whether or not the
13285 overlay is mapped. This allows most @value{GDBN} commands, like
13286 @code{break} and @code{disassemble}, to work normally, even on unmapped
13287 code. However, @value{GDBN}'s breakpoint support has some limitations:
13291 @cindex breakpoints in overlays
13292 @cindex overlays, setting breakpoints in
13293 You can set breakpoints in functions in unmapped overlays, as long as
13294 @value{GDBN} can write to the overlay at its load address.
13296 @value{GDBN} can not set hardware or simulator-based breakpoints in
13297 unmapped overlays. However, if you set a breakpoint at the end of your
13298 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
13299 you are using manual overlay management), @value{GDBN} will re-set its
13300 breakpoints properly.
13304 @node Automatic Overlay Debugging
13305 @section Automatic Overlay Debugging
13306 @cindex automatic overlay debugging
13308 @value{GDBN} can automatically track which overlays are mapped and which
13309 are not, given some simple co-operation from the overlay manager in the
13310 inferior. If you enable automatic overlay debugging with the
13311 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
13312 looks in the inferior's memory for certain variables describing the
13313 current state of the overlays.
13315 Here are the variables your overlay manager must define to support
13316 @value{GDBN}'s automatic overlay debugging:
13320 @item @code{_ovly_table}:
13321 This variable must be an array of the following structures:
13326 /* The overlay's mapped address. */
13329 /* The size of the overlay, in bytes. */
13330 unsigned long size;
13332 /* The overlay's load address. */
13335 /* Non-zero if the overlay is currently mapped;
13337 unsigned long mapped;
13341 @item @code{_novlys}:
13342 This variable must be a four-byte signed integer, holding the total
13343 number of elements in @code{_ovly_table}.
13347 To decide whether a particular overlay is mapped or not, @value{GDBN}
13348 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
13349 @code{lma} members equal the VMA and LMA of the overlay's section in the
13350 executable file. When @value{GDBN} finds a matching entry, it consults
13351 the entry's @code{mapped} member to determine whether the overlay is
13354 In addition, your overlay manager may define a function called
13355 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
13356 will silently set a breakpoint there. If the overlay manager then
13357 calls this function whenever it has changed the overlay table, this
13358 will enable @value{GDBN} to accurately keep track of which overlays
13359 are in program memory, and update any breakpoints that may be set
13360 in overlays. This will allow breakpoints to work even if the
13361 overlays are kept in ROM or other non-writable memory while they
13362 are not being executed.
13364 @node Overlay Sample Program
13365 @section Overlay Sample Program
13366 @cindex overlay example program
13368 When linking a program which uses overlays, you must place the overlays
13369 at their load addresses, while relocating them to run at their mapped
13370 addresses. To do this, you must write a linker script (@pxref{Overlay
13371 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
13372 since linker scripts are specific to a particular host system, target
13373 architecture, and target memory layout, this manual cannot provide
13374 portable sample code demonstrating @value{GDBN}'s overlay support.
13376 However, the @value{GDBN} source distribution does contain an overlaid
13377 program, with linker scripts for a few systems, as part of its test
13378 suite. The program consists of the following files from
13379 @file{gdb/testsuite/gdb.base}:
13383 The main program file.
13385 A simple overlay manager, used by @file{overlays.c}.
13390 Overlay modules, loaded and used by @file{overlays.c}.
13393 Linker scripts for linking the test program on the @code{d10v-elf}
13394 and @code{m32r-elf} targets.
13397 You can build the test program using the @code{d10v-elf} GCC
13398 cross-compiler like this:
13401 $ d10v-elf-gcc -g -c overlays.c
13402 $ d10v-elf-gcc -g -c ovlymgr.c
13403 $ d10v-elf-gcc -g -c foo.c
13404 $ d10v-elf-gcc -g -c bar.c
13405 $ d10v-elf-gcc -g -c baz.c
13406 $ d10v-elf-gcc -g -c grbx.c
13407 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
13408 baz.o grbx.o -Wl,-Td10v.ld -o overlays
13411 The build process is identical for any other architecture, except that
13412 you must substitute the appropriate compiler and linker script for the
13413 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
13417 @chapter Using @value{GDBN} with Different Languages
13420 Although programming languages generally have common aspects, they are
13421 rarely expressed in the same manner. For instance, in ANSI C,
13422 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
13423 Modula-2, it is accomplished by @code{p^}. Values can also be
13424 represented (and displayed) differently. Hex numbers in C appear as
13425 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
13427 @cindex working language
13428 Language-specific information is built into @value{GDBN} for some languages,
13429 allowing you to express operations like the above in your program's
13430 native language, and allowing @value{GDBN} to output values in a manner
13431 consistent with the syntax of your program's native language. The
13432 language you use to build expressions is called the @dfn{working
13436 * Setting:: Switching between source languages
13437 * Show:: Displaying the language
13438 * Checks:: Type and range checks
13439 * Supported Languages:: Supported languages
13440 * Unsupported Languages:: Unsupported languages
13444 @section Switching Between Source Languages
13446 There are two ways to control the working language---either have @value{GDBN}
13447 set it automatically, or select it manually yourself. You can use the
13448 @code{set language} command for either purpose. On startup, @value{GDBN}
13449 defaults to setting the language automatically. The working language is
13450 used to determine how expressions you type are interpreted, how values
13453 In addition to the working language, every source file that
13454 @value{GDBN} knows about has its own working language. For some object
13455 file formats, the compiler might indicate which language a particular
13456 source file is in. However, most of the time @value{GDBN} infers the
13457 language from the name of the file. The language of a source file
13458 controls whether C@t{++} names are demangled---this way @code{backtrace} can
13459 show each frame appropriately for its own language. There is no way to
13460 set the language of a source file from within @value{GDBN}, but you can
13461 set the language associated with a filename extension. @xref{Show, ,
13462 Displaying the Language}.
13464 This is most commonly a problem when you use a program, such
13465 as @code{cfront} or @code{f2c}, that generates C but is written in
13466 another language. In that case, make the
13467 program use @code{#line} directives in its C output; that way
13468 @value{GDBN} will know the correct language of the source code of the original
13469 program, and will display that source code, not the generated C code.
13472 * Filenames:: Filename extensions and languages.
13473 * Manually:: Setting the working language manually
13474 * Automatically:: Having @value{GDBN} infer the source language
13478 @subsection List of Filename Extensions and Languages
13480 If a source file name ends in one of the following extensions, then
13481 @value{GDBN} infers that its language is the one indicated.
13499 C@t{++} source file
13505 Objective-C source file
13509 Fortran source file
13512 Modula-2 source file
13516 Assembler source file. This actually behaves almost like C, but
13517 @value{GDBN} does not skip over function prologues when stepping.
13520 In addition, you may set the language associated with a filename
13521 extension. @xref{Show, , Displaying the Language}.
13524 @subsection Setting the Working Language
13526 If you allow @value{GDBN} to set the language automatically,
13527 expressions are interpreted the same way in your debugging session and
13530 @kindex set language
13531 If you wish, you may set the language manually. To do this, issue the
13532 command @samp{set language @var{lang}}, where @var{lang} is the name of
13533 a language, such as
13534 @code{c} or @code{modula-2}.
13535 For a list of the supported languages, type @samp{set language}.
13537 Setting the language manually prevents @value{GDBN} from updating the working
13538 language automatically. This can lead to confusion if you try
13539 to debug a program when the working language is not the same as the
13540 source language, when an expression is acceptable to both
13541 languages---but means different things. For instance, if the current
13542 source file were written in C, and @value{GDBN} was parsing Modula-2, a
13550 might not have the effect you intended. In C, this means to add
13551 @code{b} and @code{c} and place the result in @code{a}. The result
13552 printed would be the value of @code{a}. In Modula-2, this means to compare
13553 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
13555 @node Automatically
13556 @subsection Having @value{GDBN} Infer the Source Language
13558 To have @value{GDBN} set the working language automatically, use
13559 @samp{set language local} or @samp{set language auto}. @value{GDBN}
13560 then infers the working language. That is, when your program stops in a
13561 frame (usually by encountering a breakpoint), @value{GDBN} sets the
13562 working language to the language recorded for the function in that
13563 frame. If the language for a frame is unknown (that is, if the function
13564 or block corresponding to the frame was defined in a source file that
13565 does not have a recognized extension), the current working language is
13566 not changed, and @value{GDBN} issues a warning.
13568 This may not seem necessary for most programs, which are written
13569 entirely in one source language. However, program modules and libraries
13570 written in one source language can be used by a main program written in
13571 a different source language. Using @samp{set language auto} in this
13572 case frees you from having to set the working language manually.
13575 @section Displaying the Language
13577 The following commands help you find out which language is the
13578 working language, and also what language source files were written in.
13581 @item show language
13582 @anchor{show language}
13583 @kindex show language
13584 Display the current working language. This is the
13585 language you can use with commands such as @code{print} to
13586 build and compute expressions that may involve variables in your program.
13589 @kindex info frame@r{, show the source language}
13590 Display the source language for this frame. This language becomes the
13591 working language if you use an identifier from this frame.
13592 @xref{Frame Info, ,Information about a Frame}, to identify the other
13593 information listed here.
13596 @kindex info source@r{, show the source language}
13597 Display the source language of this source file.
13598 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
13599 information listed here.
13602 In unusual circumstances, you may have source files with extensions
13603 not in the standard list. You can then set the extension associated
13604 with a language explicitly:
13607 @item set extension-language @var{ext} @var{language}
13608 @kindex set extension-language
13609 Tell @value{GDBN} that source files with extension @var{ext} are to be
13610 assumed as written in the source language @var{language}.
13612 @item info extensions
13613 @kindex info extensions
13614 List all the filename extensions and the associated languages.
13618 @section Type and Range Checking
13620 Some languages are designed to guard you against making seemingly common
13621 errors through a series of compile- and run-time checks. These include
13622 checking the type of arguments to functions and operators and making
13623 sure mathematical overflows are caught at run time. Checks such as
13624 these help to ensure a program's correctness once it has been compiled
13625 by eliminating type mismatches and providing active checks for range
13626 errors when your program is running.
13628 By default @value{GDBN} checks for these errors according to the
13629 rules of the current source language. Although @value{GDBN} does not check
13630 the statements in your program, it can check expressions entered directly
13631 into @value{GDBN} for evaluation via the @code{print} command, for example.
13634 * Type Checking:: An overview of type checking
13635 * Range Checking:: An overview of range checking
13638 @cindex type checking
13639 @cindex checks, type
13640 @node Type Checking
13641 @subsection An Overview of Type Checking
13643 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
13644 arguments to operators and functions have to be of the correct type,
13645 otherwise an error occurs. These checks prevent type mismatch
13646 errors from ever causing any run-time problems. For example,
13649 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
13651 (@value{GDBP}) print obj.my_method (0)
13654 (@value{GDBP}) print obj.my_method (0x1234)
13655 Cannot resolve method klass::my_method to any overloaded instance
13658 The second example fails because in C@t{++} the integer constant
13659 @samp{0x1234} is not type-compatible with the pointer parameter type.
13661 For the expressions you use in @value{GDBN} commands, you can tell
13662 @value{GDBN} to not enforce strict type checking or
13663 to treat any mismatches as errors and abandon the expression;
13664 When type checking is disabled, @value{GDBN} successfully evaluates
13665 expressions like the second example above.
13667 Even if type checking is off, there may be other reasons
13668 related to type that prevent @value{GDBN} from evaluating an expression.
13669 For instance, @value{GDBN} does not know how to add an @code{int} and
13670 a @code{struct foo}. These particular type errors have nothing to do
13671 with the language in use and usually arise from expressions which make
13672 little sense to evaluate anyway.
13674 @value{GDBN} provides some additional commands for controlling type checking:
13676 @kindex set check type
13677 @kindex show check type
13679 @item set check type on
13680 @itemx set check type off
13681 Set strict type checking on or off. If any type mismatches occur in
13682 evaluating an expression while type checking is on, @value{GDBN} prints a
13683 message and aborts evaluation of the expression.
13685 @item show check type
13686 Show the current setting of type checking and whether @value{GDBN}
13687 is enforcing strict type checking rules.
13690 @cindex range checking
13691 @cindex checks, range
13692 @node Range Checking
13693 @subsection An Overview of Range Checking
13695 In some languages (such as Modula-2), it is an error to exceed the
13696 bounds of a type; this is enforced with run-time checks. Such range
13697 checking is meant to ensure program correctness by making sure
13698 computations do not overflow, or indices on an array element access do
13699 not exceed the bounds of the array.
13701 For expressions you use in @value{GDBN} commands, you can tell
13702 @value{GDBN} to treat range errors in one of three ways: ignore them,
13703 always treat them as errors and abandon the expression, or issue
13704 warnings but evaluate the expression anyway.
13706 A range error can result from numerical overflow, from exceeding an
13707 array index bound, or when you type a constant that is not a member
13708 of any type. Some languages, however, do not treat overflows as an
13709 error. In many implementations of C, mathematical overflow causes the
13710 result to ``wrap around'' to lower values---for example, if @var{m} is
13711 the largest integer value, and @var{s} is the smallest, then
13714 @var{m} + 1 @result{} @var{s}
13717 This, too, is specific to individual languages, and in some cases
13718 specific to individual compilers or machines. @xref{Supported Languages, ,
13719 Supported Languages}, for further details on specific languages.
13721 @value{GDBN} provides some additional commands for controlling the range checker:
13723 @kindex set check range
13724 @kindex show check range
13726 @item set check range auto
13727 Set range checking on or off based on the current working language.
13728 @xref{Supported Languages, ,Supported Languages}, for the default settings for
13731 @item set check range on
13732 @itemx set check range off
13733 Set range checking on or off, overriding the default setting for the
13734 current working language. A warning is issued if the setting does not
13735 match the language default. If a range error occurs and range checking is on,
13736 then a message is printed and evaluation of the expression is aborted.
13738 @item set check range warn
13739 Output messages when the @value{GDBN} range checker detects a range error,
13740 but attempt to evaluate the expression anyway. Evaluating the
13741 expression may still be impossible for other reasons, such as accessing
13742 memory that the process does not own (a typical example from many Unix
13746 Show the current setting of the range checker, and whether or not it is
13747 being set automatically by @value{GDBN}.
13750 @node Supported Languages
13751 @section Supported Languages
13753 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
13754 OpenCL C, Pascal, assembly, Modula-2, and Ada.
13755 @c This is false ...
13756 Some @value{GDBN} features may be used in expressions regardless of the
13757 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
13758 and the @samp{@{type@}addr} construct (@pxref{Expressions,
13759 ,Expressions}) can be used with the constructs of any supported
13762 The following sections detail to what degree each source language is
13763 supported by @value{GDBN}. These sections are not meant to be language
13764 tutorials or references, but serve only as a reference guide to what the
13765 @value{GDBN} expression parser accepts, and what input and output
13766 formats should look like for different languages. There are many good
13767 books written on each of these languages; please look to these for a
13768 language reference or tutorial.
13771 * C:: C and C@t{++}
13774 * Objective-C:: Objective-C
13775 * OpenCL C:: OpenCL C
13776 * Fortran:: Fortran
13778 * Modula-2:: Modula-2
13783 @subsection C and C@t{++}
13785 @cindex C and C@t{++}
13786 @cindex expressions in C or C@t{++}
13788 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
13789 to both languages. Whenever this is the case, we discuss those languages
13793 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
13794 @cindex @sc{gnu} C@t{++}
13795 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
13796 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
13797 effectively, you must compile your C@t{++} programs with a supported
13798 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
13799 compiler (@code{aCC}).
13802 * C Operators:: C and C@t{++} operators
13803 * C Constants:: C and C@t{++} constants
13804 * C Plus Plus Expressions:: C@t{++} expressions
13805 * C Defaults:: Default settings for C and C@t{++}
13806 * C Checks:: C and C@t{++} type and range checks
13807 * Debugging C:: @value{GDBN} and C
13808 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
13809 * Decimal Floating Point:: Numbers in Decimal Floating Point format
13813 @subsubsection C and C@t{++} Operators
13815 @cindex C and C@t{++} operators
13817 Operators must be defined on values of specific types. For instance,
13818 @code{+} is defined on numbers, but not on structures. Operators are
13819 often defined on groups of types.
13821 For the purposes of C and C@t{++}, the following definitions hold:
13826 @emph{Integral types} include @code{int} with any of its storage-class
13827 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
13830 @emph{Floating-point types} include @code{float}, @code{double}, and
13831 @code{long double} (if supported by the target platform).
13834 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
13837 @emph{Scalar types} include all of the above.
13842 The following operators are supported. They are listed here
13843 in order of increasing precedence:
13847 The comma or sequencing operator. Expressions in a comma-separated list
13848 are evaluated from left to right, with the result of the entire
13849 expression being the last expression evaluated.
13852 Assignment. The value of an assignment expression is the value
13853 assigned. Defined on scalar types.
13856 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
13857 and translated to @w{@code{@var{a} = @var{a op b}}}.
13858 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
13859 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
13860 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
13863 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
13864 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
13865 should be of an integral type.
13868 Logical @sc{or}. Defined on integral types.
13871 Logical @sc{and}. Defined on integral types.
13874 Bitwise @sc{or}. Defined on integral types.
13877 Bitwise exclusive-@sc{or}. Defined on integral types.
13880 Bitwise @sc{and}. Defined on integral types.
13883 Equality and inequality. Defined on scalar types. The value of these
13884 expressions is 0 for false and non-zero for true.
13886 @item <@r{, }>@r{, }<=@r{, }>=
13887 Less than, greater than, less than or equal, greater than or equal.
13888 Defined on scalar types. The value of these expressions is 0 for false
13889 and non-zero for true.
13892 left shift, and right shift. Defined on integral types.
13895 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13898 Addition and subtraction. Defined on integral types, floating-point types and
13901 @item *@r{, }/@r{, }%
13902 Multiplication, division, and modulus. Multiplication and division are
13903 defined on integral and floating-point types. Modulus is defined on
13907 Increment and decrement. When appearing before a variable, the
13908 operation is performed before the variable is used in an expression;
13909 when appearing after it, the variable's value is used before the
13910 operation takes place.
13913 Pointer dereferencing. Defined on pointer types. Same precedence as
13917 Address operator. Defined on variables. Same precedence as @code{++}.
13919 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
13920 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
13921 to examine the address
13922 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
13926 Negative. Defined on integral and floating-point types. Same
13927 precedence as @code{++}.
13930 Logical negation. Defined on integral types. Same precedence as
13934 Bitwise complement operator. Defined on integral types. Same precedence as
13939 Structure member, and pointer-to-structure member. For convenience,
13940 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
13941 pointer based on the stored type information.
13942 Defined on @code{struct} and @code{union} data.
13945 Dereferences of pointers to members.
13948 Array indexing. @code{@var{a}[@var{i}]} is defined as
13949 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
13952 Function parameter list. Same precedence as @code{->}.
13955 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
13956 and @code{class} types.
13959 Doubled colons also represent the @value{GDBN} scope operator
13960 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
13964 If an operator is redefined in the user code, @value{GDBN} usually
13965 attempts to invoke the redefined version instead of using the operator's
13966 predefined meaning.
13969 @subsubsection C and C@t{++} Constants
13971 @cindex C and C@t{++} constants
13973 @value{GDBN} allows you to express the constants of C and C@t{++} in the
13978 Integer constants are a sequence of digits. Octal constants are
13979 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
13980 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
13981 @samp{l}, specifying that the constant should be treated as a
13985 Floating point constants are a sequence of digits, followed by a decimal
13986 point, followed by a sequence of digits, and optionally followed by an
13987 exponent. An exponent is of the form:
13988 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
13989 sequence of digits. The @samp{+} is optional for positive exponents.
13990 A floating-point constant may also end with a letter @samp{f} or
13991 @samp{F}, specifying that the constant should be treated as being of
13992 the @code{float} (as opposed to the default @code{double}) type; or with
13993 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
13997 Enumerated constants consist of enumerated identifiers, or their
13998 integral equivalents.
14001 Character constants are a single character surrounded by single quotes
14002 (@code{'}), or a number---the ordinal value of the corresponding character
14003 (usually its @sc{ascii} value). Within quotes, the single character may
14004 be represented by a letter or by @dfn{escape sequences}, which are of
14005 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
14006 of the character's ordinal value; or of the form @samp{\@var{x}}, where
14007 @samp{@var{x}} is a predefined special character---for example,
14008 @samp{\n} for newline.
14010 Wide character constants can be written by prefixing a character
14011 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
14012 form of @samp{x}. The target wide character set is used when
14013 computing the value of this constant (@pxref{Character Sets}).
14016 String constants are a sequence of character constants surrounded by
14017 double quotes (@code{"}). Any valid character constant (as described
14018 above) may appear. Double quotes within the string must be preceded by
14019 a backslash, so for instance @samp{"a\"b'c"} is a string of five
14022 Wide string constants can be written by prefixing a string constant
14023 with @samp{L}, as in C. The target wide character set is used when
14024 computing the value of this constant (@pxref{Character Sets}).
14027 Pointer constants are an integral value. You can also write pointers
14028 to constants using the C operator @samp{&}.
14031 Array constants are comma-separated lists surrounded by braces @samp{@{}
14032 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
14033 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
14034 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
14037 @node C Plus Plus Expressions
14038 @subsubsection C@t{++} Expressions
14040 @cindex expressions in C@t{++}
14041 @value{GDBN} expression handling can interpret most C@t{++} expressions.
14043 @cindex debugging C@t{++} programs
14044 @cindex C@t{++} compilers
14045 @cindex debug formats and C@t{++}
14046 @cindex @value{NGCC} and C@t{++}
14048 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
14049 the proper compiler and the proper debug format. Currently,
14050 @value{GDBN} works best when debugging C@t{++} code that is compiled
14051 with the most recent version of @value{NGCC} possible. The DWARF
14052 debugging format is preferred; @value{NGCC} defaults to this on most
14053 popular platforms. Other compilers and/or debug formats are likely to
14054 work badly or not at all when using @value{GDBN} to debug C@t{++}
14055 code. @xref{Compilation}.
14060 @cindex member functions
14062 Member function calls are allowed; you can use expressions like
14065 count = aml->GetOriginal(x, y)
14068 @vindex this@r{, inside C@t{++} member functions}
14069 @cindex namespace in C@t{++}
14071 While a member function is active (in the selected stack frame), your
14072 expressions have the same namespace available as the member function;
14073 that is, @value{GDBN} allows implicit references to the class instance
14074 pointer @code{this} following the same rules as C@t{++}. @code{using}
14075 declarations in the current scope are also respected by @value{GDBN}.
14077 @cindex call overloaded functions
14078 @cindex overloaded functions, calling
14079 @cindex type conversions in C@t{++}
14081 You can call overloaded functions; @value{GDBN} resolves the function
14082 call to the right definition, with some restrictions. @value{GDBN} does not
14083 perform overload resolution involving user-defined type conversions,
14084 calls to constructors, or instantiations of templates that do not exist
14085 in the program. It also cannot handle ellipsis argument lists or
14088 It does perform integral conversions and promotions, floating-point
14089 promotions, arithmetic conversions, pointer conversions, conversions of
14090 class objects to base classes, and standard conversions such as those of
14091 functions or arrays to pointers; it requires an exact match on the
14092 number of function arguments.
14094 Overload resolution is always performed, unless you have specified
14095 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
14096 ,@value{GDBN} Features for C@t{++}}.
14098 You must specify @code{set overload-resolution off} in order to use an
14099 explicit function signature to call an overloaded function, as in
14101 p 'foo(char,int)'('x', 13)
14104 The @value{GDBN} command-completion facility can simplify this;
14105 see @ref{Completion, ,Command Completion}.
14107 @cindex reference declarations
14109 @value{GDBN} understands variables declared as C@t{++} references; you can use
14110 them in expressions just as you do in C@t{++} source---they are automatically
14113 In the parameter list shown when @value{GDBN} displays a frame, the values of
14114 reference variables are not displayed (unlike other variables); this
14115 avoids clutter, since references are often used for large structures.
14116 The @emph{address} of a reference variable is always shown, unless
14117 you have specified @samp{set print address off}.
14120 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
14121 expressions can use it just as expressions in your program do. Since
14122 one scope may be defined in another, you can use @code{::} repeatedly if
14123 necessary, for example in an expression like
14124 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
14125 resolving name scope by reference to source files, in both C and C@t{++}
14126 debugging (@pxref{Variables, ,Program Variables}).
14129 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
14134 @subsubsection C and C@t{++} Defaults
14136 @cindex C and C@t{++} defaults
14138 If you allow @value{GDBN} to set range checking automatically, it
14139 defaults to @code{off} whenever the working language changes to
14140 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
14141 selects the working language.
14143 If you allow @value{GDBN} to set the language automatically, it
14144 recognizes source files whose names end with @file{.c}, @file{.C}, or
14145 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
14146 these files, it sets the working language to C or C@t{++}.
14147 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
14148 for further details.
14151 @subsubsection C and C@t{++} Type and Range Checks
14153 @cindex C and C@t{++} checks
14155 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
14156 checking is used. However, if you turn type checking off, @value{GDBN}
14157 will allow certain non-standard conversions, such as promoting integer
14158 constants to pointers.
14160 Range checking, if turned on, is done on mathematical operations. Array
14161 indices are not checked, since they are often used to index a pointer
14162 that is not itself an array.
14165 @subsubsection @value{GDBN} and C
14167 The @code{set print union} and @code{show print union} commands apply to
14168 the @code{union} type. When set to @samp{on}, any @code{union} that is
14169 inside a @code{struct} or @code{class} is also printed. Otherwise, it
14170 appears as @samp{@{...@}}.
14172 The @code{@@} operator aids in the debugging of dynamic arrays, formed
14173 with pointers and a memory allocation function. @xref{Expressions,
14176 @node Debugging C Plus Plus
14177 @subsubsection @value{GDBN} Features for C@t{++}
14179 @cindex commands for C@t{++}
14181 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
14182 designed specifically for use with C@t{++}. Here is a summary:
14185 @cindex break in overloaded functions
14186 @item @r{breakpoint menus}
14187 When you want a breakpoint in a function whose name is overloaded,
14188 @value{GDBN} has the capability to display a menu of possible breakpoint
14189 locations to help you specify which function definition you want.
14190 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
14192 @cindex overloading in C@t{++}
14193 @item rbreak @var{regex}
14194 Setting breakpoints using regular expressions is helpful for setting
14195 breakpoints on overloaded functions that are not members of any special
14197 @xref{Set Breaks, ,Setting Breakpoints}.
14199 @cindex C@t{++} exception handling
14201 @itemx catch rethrow
14203 Debug C@t{++} exception handling using these commands. @xref{Set
14204 Catchpoints, , Setting Catchpoints}.
14206 @cindex inheritance
14207 @item ptype @var{typename}
14208 Print inheritance relationships as well as other information for type
14210 @xref{Symbols, ,Examining the Symbol Table}.
14212 @item info vtbl @var{expression}.
14213 The @code{info vtbl} command can be used to display the virtual
14214 method tables of the object computed by @var{expression}. This shows
14215 one entry per virtual table; there may be multiple virtual tables when
14216 multiple inheritance is in use.
14218 @cindex C@t{++} demangling
14219 @item demangle @var{name}
14220 Demangle @var{name}.
14221 @xref{Symbols}, for a more complete description of the @code{demangle} command.
14223 @cindex C@t{++} symbol display
14224 @item set print demangle
14225 @itemx show print demangle
14226 @itemx set print asm-demangle
14227 @itemx show print asm-demangle
14228 Control whether C@t{++} symbols display in their source form, both when
14229 displaying code as C@t{++} source and when displaying disassemblies.
14230 @xref{Print Settings, ,Print Settings}.
14232 @item set print object
14233 @itemx show print object
14234 Choose whether to print derived (actual) or declared types of objects.
14235 @xref{Print Settings, ,Print Settings}.
14237 @item set print vtbl
14238 @itemx show print vtbl
14239 Control the format for printing virtual function tables.
14240 @xref{Print Settings, ,Print Settings}.
14241 (The @code{vtbl} commands do not work on programs compiled with the HP
14242 ANSI C@t{++} compiler (@code{aCC}).)
14244 @kindex set overload-resolution
14245 @cindex overloaded functions, overload resolution
14246 @item set overload-resolution on
14247 Enable overload resolution for C@t{++} expression evaluation. The default
14248 is on. For overloaded functions, @value{GDBN} evaluates the arguments
14249 and searches for a function whose signature matches the argument types,
14250 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
14251 Expressions, ,C@t{++} Expressions}, for details).
14252 If it cannot find a match, it emits a message.
14254 @item set overload-resolution off
14255 Disable overload resolution for C@t{++} expression evaluation. For
14256 overloaded functions that are not class member functions, @value{GDBN}
14257 chooses the first function of the specified name that it finds in the
14258 symbol table, whether or not its arguments are of the correct type. For
14259 overloaded functions that are class member functions, @value{GDBN}
14260 searches for a function whose signature @emph{exactly} matches the
14263 @kindex show overload-resolution
14264 @item show overload-resolution
14265 Show the current setting of overload resolution.
14267 @item @r{Overloaded symbol names}
14268 You can specify a particular definition of an overloaded symbol, using
14269 the same notation that is used to declare such symbols in C@t{++}: type
14270 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
14271 also use the @value{GDBN} command-line word completion facilities to list the
14272 available choices, or to finish the type list for you.
14273 @xref{Completion,, Command Completion}, for details on how to do this.
14276 @node Decimal Floating Point
14277 @subsubsection Decimal Floating Point format
14278 @cindex decimal floating point format
14280 @value{GDBN} can examine, set and perform computations with numbers in
14281 decimal floating point format, which in the C language correspond to the
14282 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
14283 specified by the extension to support decimal floating-point arithmetic.
14285 There are two encodings in use, depending on the architecture: BID (Binary
14286 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
14287 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
14290 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
14291 to manipulate decimal floating point numbers, it is not possible to convert
14292 (using a cast, for example) integers wider than 32-bit to decimal float.
14294 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
14295 point computations, error checking in decimal float operations ignores
14296 underflow, overflow and divide by zero exceptions.
14298 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
14299 to inspect @code{_Decimal128} values stored in floating point registers.
14300 See @ref{PowerPC,,PowerPC} for more details.
14306 @value{GDBN} can be used to debug programs written in D and compiled with
14307 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
14308 specific feature --- dynamic arrays.
14313 @cindex Go (programming language)
14314 @value{GDBN} can be used to debug programs written in Go and compiled with
14315 @file{gccgo} or @file{6g} compilers.
14317 Here is a summary of the Go-specific features and restrictions:
14320 @cindex current Go package
14321 @item The current Go package
14322 The name of the current package does not need to be specified when
14323 specifying global variables and functions.
14325 For example, given the program:
14329 var myglob = "Shall we?"
14335 When stopped inside @code{main} either of these work:
14339 (gdb) p main.myglob
14342 @cindex builtin Go types
14343 @item Builtin Go types
14344 The @code{string} type is recognized by @value{GDBN} and is printed
14347 @cindex builtin Go functions
14348 @item Builtin Go functions
14349 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
14350 function and handles it internally.
14352 @cindex restrictions on Go expressions
14353 @item Restrictions on Go expressions
14354 All Go operators are supported except @code{&^}.
14355 The Go @code{_} ``blank identifier'' is not supported.
14356 Automatic dereferencing of pointers is not supported.
14360 @subsection Objective-C
14362 @cindex Objective-C
14363 This section provides information about some commands and command
14364 options that are useful for debugging Objective-C code. See also
14365 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
14366 few more commands specific to Objective-C support.
14369 * Method Names in Commands::
14370 * The Print Command with Objective-C::
14373 @node Method Names in Commands
14374 @subsubsection Method Names in Commands
14376 The following commands have been extended to accept Objective-C method
14377 names as line specifications:
14379 @kindex clear@r{, and Objective-C}
14380 @kindex break@r{, and Objective-C}
14381 @kindex info line@r{, and Objective-C}
14382 @kindex jump@r{, and Objective-C}
14383 @kindex list@r{, and Objective-C}
14387 @item @code{info line}
14392 A fully qualified Objective-C method name is specified as
14395 -[@var{Class} @var{methodName}]
14398 where the minus sign is used to indicate an instance method and a
14399 plus sign (not shown) is used to indicate a class method. The class
14400 name @var{Class} and method name @var{methodName} are enclosed in
14401 brackets, similar to the way messages are specified in Objective-C
14402 source code. For example, to set a breakpoint at the @code{create}
14403 instance method of class @code{Fruit} in the program currently being
14407 break -[Fruit create]
14410 To list ten program lines around the @code{initialize} class method,
14414 list +[NSText initialize]
14417 In the current version of @value{GDBN}, the plus or minus sign is
14418 required. In future versions of @value{GDBN}, the plus or minus
14419 sign will be optional, but you can use it to narrow the search. It
14420 is also possible to specify just a method name:
14426 You must specify the complete method name, including any colons. If
14427 your program's source files contain more than one @code{create} method,
14428 you'll be presented with a numbered list of classes that implement that
14429 method. Indicate your choice by number, or type @samp{0} to exit if
14432 As another example, to clear a breakpoint established at the
14433 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
14436 clear -[NSWindow makeKeyAndOrderFront:]
14439 @node The Print Command with Objective-C
14440 @subsubsection The Print Command With Objective-C
14441 @cindex Objective-C, print objects
14442 @kindex print-object
14443 @kindex po @r{(@code{print-object})}
14445 The print command has also been extended to accept methods. For example:
14448 print -[@var{object} hash]
14451 @cindex print an Objective-C object description
14452 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
14454 will tell @value{GDBN} to send the @code{hash} message to @var{object}
14455 and print the result. Also, an additional command has been added,
14456 @code{print-object} or @code{po} for short, which is meant to print
14457 the description of an object. However, this command may only work
14458 with certain Objective-C libraries that have a particular hook
14459 function, @code{_NSPrintForDebugger}, defined.
14462 @subsection OpenCL C
14465 This section provides information about @value{GDBN}s OpenCL C support.
14468 * OpenCL C Datatypes::
14469 * OpenCL C Expressions::
14470 * OpenCL C Operators::
14473 @node OpenCL C Datatypes
14474 @subsubsection OpenCL C Datatypes
14476 @cindex OpenCL C Datatypes
14477 @value{GDBN} supports the builtin scalar and vector datatypes specified
14478 by OpenCL 1.1. In addition the half- and double-precision floating point
14479 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
14480 extensions are also known to @value{GDBN}.
14482 @node OpenCL C Expressions
14483 @subsubsection OpenCL C Expressions
14485 @cindex OpenCL C Expressions
14486 @value{GDBN} supports accesses to vector components including the access as
14487 lvalue where possible. Since OpenCL C is based on C99 most C expressions
14488 supported by @value{GDBN} can be used as well.
14490 @node OpenCL C Operators
14491 @subsubsection OpenCL C Operators
14493 @cindex OpenCL C Operators
14494 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
14498 @subsection Fortran
14499 @cindex Fortran-specific support in @value{GDBN}
14501 @value{GDBN} can be used to debug programs written in Fortran, but it
14502 currently supports only the features of Fortran 77 language.
14504 @cindex trailing underscore, in Fortran symbols
14505 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
14506 among them) append an underscore to the names of variables and
14507 functions. When you debug programs compiled by those compilers, you
14508 will need to refer to variables and functions with a trailing
14512 * Fortran Operators:: Fortran operators and expressions
14513 * Fortran Defaults:: Default settings for Fortran
14514 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
14517 @node Fortran Operators
14518 @subsubsection Fortran Operators and Expressions
14520 @cindex Fortran operators and expressions
14522 Operators must be defined on values of specific types. For instance,
14523 @code{+} is defined on numbers, but not on characters or other non-
14524 arithmetic types. Operators are often defined on groups of types.
14528 The exponentiation operator. It raises the first operand to the power
14532 The range operator. Normally used in the form of array(low:high) to
14533 represent a section of array.
14536 The access component operator. Normally used to access elements in derived
14537 types. Also suitable for unions. As unions aren't part of regular Fortran,
14538 this can only happen when accessing a register that uses a gdbarch-defined
14542 @node Fortran Defaults
14543 @subsubsection Fortran Defaults
14545 @cindex Fortran Defaults
14547 Fortran symbols are usually case-insensitive, so @value{GDBN} by
14548 default uses case-insensitive matches for Fortran symbols. You can
14549 change that with the @samp{set case-insensitive} command, see
14550 @ref{Symbols}, for the details.
14552 @node Special Fortran Commands
14553 @subsubsection Special Fortran Commands
14555 @cindex Special Fortran commands
14557 @value{GDBN} has some commands to support Fortran-specific features,
14558 such as displaying common blocks.
14561 @cindex @code{COMMON} blocks, Fortran
14562 @kindex info common
14563 @item info common @r{[}@var{common-name}@r{]}
14564 This command prints the values contained in the Fortran @code{COMMON}
14565 block whose name is @var{common-name}. With no argument, the names of
14566 all @code{COMMON} blocks visible at the current program location are
14573 @cindex Pascal support in @value{GDBN}, limitations
14574 Debugging Pascal programs which use sets, subranges, file variables, or
14575 nested functions does not currently work. @value{GDBN} does not support
14576 entering expressions, printing values, or similar features using Pascal
14579 The Pascal-specific command @code{set print pascal_static-members}
14580 controls whether static members of Pascal objects are displayed.
14581 @xref{Print Settings, pascal_static-members}.
14584 @subsection Modula-2
14586 @cindex Modula-2, @value{GDBN} support
14588 The extensions made to @value{GDBN} to support Modula-2 only support
14589 output from the @sc{gnu} Modula-2 compiler (which is currently being
14590 developed). Other Modula-2 compilers are not currently supported, and
14591 attempting to debug executables produced by them is most likely
14592 to give an error as @value{GDBN} reads in the executable's symbol
14595 @cindex expressions in Modula-2
14597 * M2 Operators:: Built-in operators
14598 * Built-In Func/Proc:: Built-in functions and procedures
14599 * M2 Constants:: Modula-2 constants
14600 * M2 Types:: Modula-2 types
14601 * M2 Defaults:: Default settings for Modula-2
14602 * Deviations:: Deviations from standard Modula-2
14603 * M2 Checks:: Modula-2 type and range checks
14604 * M2 Scope:: The scope operators @code{::} and @code{.}
14605 * GDB/M2:: @value{GDBN} and Modula-2
14609 @subsubsection Operators
14610 @cindex Modula-2 operators
14612 Operators must be defined on values of specific types. For instance,
14613 @code{+} is defined on numbers, but not on structures. Operators are
14614 often defined on groups of types. For the purposes of Modula-2, the
14615 following definitions hold:
14620 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
14624 @emph{Character types} consist of @code{CHAR} and its subranges.
14627 @emph{Floating-point types} consist of @code{REAL}.
14630 @emph{Pointer types} consist of anything declared as @code{POINTER TO
14634 @emph{Scalar types} consist of all of the above.
14637 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
14640 @emph{Boolean types} consist of @code{BOOLEAN}.
14644 The following operators are supported, and appear in order of
14645 increasing precedence:
14649 Function argument or array index separator.
14652 Assignment. The value of @var{var} @code{:=} @var{value} is
14656 Less than, greater than on integral, floating-point, or enumerated
14660 Less than or equal to, greater than or equal to
14661 on integral, floating-point and enumerated types, or set inclusion on
14662 set types. Same precedence as @code{<}.
14664 @item =@r{, }<>@r{, }#
14665 Equality and two ways of expressing inequality, valid on scalar types.
14666 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
14667 available for inequality, since @code{#} conflicts with the script
14671 Set membership. Defined on set types and the types of their members.
14672 Same precedence as @code{<}.
14675 Boolean disjunction. Defined on boolean types.
14678 Boolean conjunction. Defined on boolean types.
14681 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14684 Addition and subtraction on integral and floating-point types, or union
14685 and difference on set types.
14688 Multiplication on integral and floating-point types, or set intersection
14692 Division on floating-point types, or symmetric set difference on set
14693 types. Same precedence as @code{*}.
14696 Integer division and remainder. Defined on integral types. Same
14697 precedence as @code{*}.
14700 Negative. Defined on @code{INTEGER} and @code{REAL} data.
14703 Pointer dereferencing. Defined on pointer types.
14706 Boolean negation. Defined on boolean types. Same precedence as
14710 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
14711 precedence as @code{^}.
14714 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
14717 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
14721 @value{GDBN} and Modula-2 scope operators.
14725 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
14726 treats the use of the operator @code{IN}, or the use of operators
14727 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
14728 @code{<=}, and @code{>=} on sets as an error.
14732 @node Built-In Func/Proc
14733 @subsubsection Built-in Functions and Procedures
14734 @cindex Modula-2 built-ins
14736 Modula-2 also makes available several built-in procedures and functions.
14737 In describing these, the following metavariables are used:
14742 represents an @code{ARRAY} variable.
14745 represents a @code{CHAR} constant or variable.
14748 represents a variable or constant of integral type.
14751 represents an identifier that belongs to a set. Generally used in the
14752 same function with the metavariable @var{s}. The type of @var{s} should
14753 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
14756 represents a variable or constant of integral or floating-point type.
14759 represents a variable or constant of floating-point type.
14765 represents a variable.
14768 represents a variable or constant of one of many types. See the
14769 explanation of the function for details.
14772 All Modula-2 built-in procedures also return a result, described below.
14776 Returns the absolute value of @var{n}.
14779 If @var{c} is a lower case letter, it returns its upper case
14780 equivalent, otherwise it returns its argument.
14783 Returns the character whose ordinal value is @var{i}.
14786 Decrements the value in the variable @var{v} by one. Returns the new value.
14788 @item DEC(@var{v},@var{i})
14789 Decrements the value in the variable @var{v} by @var{i}. Returns the
14792 @item EXCL(@var{m},@var{s})
14793 Removes the element @var{m} from the set @var{s}. Returns the new
14796 @item FLOAT(@var{i})
14797 Returns the floating point equivalent of the integer @var{i}.
14799 @item HIGH(@var{a})
14800 Returns the index of the last member of @var{a}.
14803 Increments the value in the variable @var{v} by one. Returns the new value.
14805 @item INC(@var{v},@var{i})
14806 Increments the value in the variable @var{v} by @var{i}. Returns the
14809 @item INCL(@var{m},@var{s})
14810 Adds the element @var{m} to the set @var{s} if it is not already
14811 there. Returns the new set.
14814 Returns the maximum value of the type @var{t}.
14817 Returns the minimum value of the type @var{t}.
14820 Returns boolean TRUE if @var{i} is an odd number.
14823 Returns the ordinal value of its argument. For example, the ordinal
14824 value of a character is its @sc{ascii} value (on machines supporting
14825 the @sc{ascii} character set). The argument @var{x} must be of an
14826 ordered type, which include integral, character and enumerated types.
14828 @item SIZE(@var{x})
14829 Returns the size of its argument. The argument @var{x} can be a
14830 variable or a type.
14832 @item TRUNC(@var{r})
14833 Returns the integral part of @var{r}.
14835 @item TSIZE(@var{x})
14836 Returns the size of its argument. The argument @var{x} can be a
14837 variable or a type.
14839 @item VAL(@var{t},@var{i})
14840 Returns the member of the type @var{t} whose ordinal value is @var{i}.
14844 @emph{Warning:} Sets and their operations are not yet supported, so
14845 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
14849 @cindex Modula-2 constants
14851 @subsubsection Constants
14853 @value{GDBN} allows you to express the constants of Modula-2 in the following
14859 Integer constants are simply a sequence of digits. When used in an
14860 expression, a constant is interpreted to be type-compatible with the
14861 rest of the expression. Hexadecimal integers are specified by a
14862 trailing @samp{H}, and octal integers by a trailing @samp{B}.
14865 Floating point constants appear as a sequence of digits, followed by a
14866 decimal point and another sequence of digits. An optional exponent can
14867 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
14868 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
14869 digits of the floating point constant must be valid decimal (base 10)
14873 Character constants consist of a single character enclosed by a pair of
14874 like quotes, either single (@code{'}) or double (@code{"}). They may
14875 also be expressed by their ordinal value (their @sc{ascii} value, usually)
14876 followed by a @samp{C}.
14879 String constants consist of a sequence of characters enclosed by a
14880 pair of like quotes, either single (@code{'}) or double (@code{"}).
14881 Escape sequences in the style of C are also allowed. @xref{C
14882 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
14886 Enumerated constants consist of an enumerated identifier.
14889 Boolean constants consist of the identifiers @code{TRUE} and
14893 Pointer constants consist of integral values only.
14896 Set constants are not yet supported.
14900 @subsubsection Modula-2 Types
14901 @cindex Modula-2 types
14903 Currently @value{GDBN} can print the following data types in Modula-2
14904 syntax: array types, record types, set types, pointer types, procedure
14905 types, enumerated types, subrange types and base types. You can also
14906 print the contents of variables declared using these type.
14907 This section gives a number of simple source code examples together with
14908 sample @value{GDBN} sessions.
14910 The first example contains the following section of code:
14919 and you can request @value{GDBN} to interrogate the type and value of
14920 @code{r} and @code{s}.
14923 (@value{GDBP}) print s
14925 (@value{GDBP}) ptype s
14927 (@value{GDBP}) print r
14929 (@value{GDBP}) ptype r
14934 Likewise if your source code declares @code{s} as:
14938 s: SET ['A'..'Z'] ;
14942 then you may query the type of @code{s} by:
14945 (@value{GDBP}) ptype s
14946 type = SET ['A'..'Z']
14950 Note that at present you cannot interactively manipulate set
14951 expressions using the debugger.
14953 The following example shows how you might declare an array in Modula-2
14954 and how you can interact with @value{GDBN} to print its type and contents:
14958 s: ARRAY [-10..10] OF CHAR ;
14962 (@value{GDBP}) ptype s
14963 ARRAY [-10..10] OF CHAR
14966 Note that the array handling is not yet complete and although the type
14967 is printed correctly, expression handling still assumes that all
14968 arrays have a lower bound of zero and not @code{-10} as in the example
14971 Here are some more type related Modula-2 examples:
14975 colour = (blue, red, yellow, green) ;
14976 t = [blue..yellow] ;
14984 The @value{GDBN} interaction shows how you can query the data type
14985 and value of a variable.
14988 (@value{GDBP}) print s
14990 (@value{GDBP}) ptype t
14991 type = [blue..yellow]
14995 In this example a Modula-2 array is declared and its contents
14996 displayed. Observe that the contents are written in the same way as
14997 their @code{C} counterparts.
15001 s: ARRAY [1..5] OF CARDINAL ;
15007 (@value{GDBP}) print s
15008 $1 = @{1, 0, 0, 0, 0@}
15009 (@value{GDBP}) ptype s
15010 type = ARRAY [1..5] OF CARDINAL
15013 The Modula-2 language interface to @value{GDBN} also understands
15014 pointer types as shown in this example:
15018 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
15025 and you can request that @value{GDBN} describes the type of @code{s}.
15028 (@value{GDBP}) ptype s
15029 type = POINTER TO ARRAY [1..5] OF CARDINAL
15032 @value{GDBN} handles compound types as we can see in this example.
15033 Here we combine array types, record types, pointer types and subrange
15044 myarray = ARRAY myrange OF CARDINAL ;
15045 myrange = [-2..2] ;
15047 s: POINTER TO ARRAY myrange OF foo ;
15051 and you can ask @value{GDBN} to describe the type of @code{s} as shown
15055 (@value{GDBP}) ptype s
15056 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
15059 f3 : ARRAY [-2..2] OF CARDINAL;
15064 @subsubsection Modula-2 Defaults
15065 @cindex Modula-2 defaults
15067 If type and range checking are set automatically by @value{GDBN}, they
15068 both default to @code{on} whenever the working language changes to
15069 Modula-2. This happens regardless of whether you or @value{GDBN}
15070 selected the working language.
15072 If you allow @value{GDBN} to set the language automatically, then entering
15073 code compiled from a file whose name ends with @file{.mod} sets the
15074 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
15075 Infer the Source Language}, for further details.
15078 @subsubsection Deviations from Standard Modula-2
15079 @cindex Modula-2, deviations from
15081 A few changes have been made to make Modula-2 programs easier to debug.
15082 This is done primarily via loosening its type strictness:
15086 Unlike in standard Modula-2, pointer constants can be formed by
15087 integers. This allows you to modify pointer variables during
15088 debugging. (In standard Modula-2, the actual address contained in a
15089 pointer variable is hidden from you; it can only be modified
15090 through direct assignment to another pointer variable or expression that
15091 returned a pointer.)
15094 C escape sequences can be used in strings and characters to represent
15095 non-printable characters. @value{GDBN} prints out strings with these
15096 escape sequences embedded. Single non-printable characters are
15097 printed using the @samp{CHR(@var{nnn})} format.
15100 The assignment operator (@code{:=}) returns the value of its right-hand
15104 All built-in procedures both modify @emph{and} return their argument.
15108 @subsubsection Modula-2 Type and Range Checks
15109 @cindex Modula-2 checks
15112 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
15115 @c FIXME remove warning when type/range checks added
15117 @value{GDBN} considers two Modula-2 variables type equivalent if:
15121 They are of types that have been declared equivalent via a @code{TYPE
15122 @var{t1} = @var{t2}} statement
15125 They have been declared on the same line. (Note: This is true of the
15126 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
15129 As long as type checking is enabled, any attempt to combine variables
15130 whose types are not equivalent is an error.
15132 Range checking is done on all mathematical operations, assignment, array
15133 index bounds, and all built-in functions and procedures.
15136 @subsubsection The Scope Operators @code{::} and @code{.}
15138 @cindex @code{.}, Modula-2 scope operator
15139 @cindex colon, doubled as scope operator
15141 @vindex colon-colon@r{, in Modula-2}
15142 @c Info cannot handle :: but TeX can.
15145 @vindex ::@r{, in Modula-2}
15148 There are a few subtle differences between the Modula-2 scope operator
15149 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
15154 @var{module} . @var{id}
15155 @var{scope} :: @var{id}
15159 where @var{scope} is the name of a module or a procedure,
15160 @var{module} the name of a module, and @var{id} is any declared
15161 identifier within your program, except another module.
15163 Using the @code{::} operator makes @value{GDBN} search the scope
15164 specified by @var{scope} for the identifier @var{id}. If it is not
15165 found in the specified scope, then @value{GDBN} searches all scopes
15166 enclosing the one specified by @var{scope}.
15168 Using the @code{.} operator makes @value{GDBN} search the current scope for
15169 the identifier specified by @var{id} that was imported from the
15170 definition module specified by @var{module}. With this operator, it is
15171 an error if the identifier @var{id} was not imported from definition
15172 module @var{module}, or if @var{id} is not an identifier in
15176 @subsubsection @value{GDBN} and Modula-2
15178 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
15179 Five subcommands of @code{set print} and @code{show print} apply
15180 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
15181 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
15182 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
15183 analogue in Modula-2.
15185 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
15186 with any language, is not useful with Modula-2. Its
15187 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
15188 created in Modula-2 as they can in C or C@t{++}. However, because an
15189 address can be specified by an integral constant, the construct
15190 @samp{@{@var{type}@}@var{adrexp}} is still useful.
15192 @cindex @code{#} in Modula-2
15193 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
15194 interpreted as the beginning of a comment. Use @code{<>} instead.
15200 The extensions made to @value{GDBN} for Ada only support
15201 output from the @sc{gnu} Ada (GNAT) compiler.
15202 Other Ada compilers are not currently supported, and
15203 attempting to debug executables produced by them is most likely
15207 @cindex expressions in Ada
15209 * Ada Mode Intro:: General remarks on the Ada syntax
15210 and semantics supported by Ada mode
15212 * Omissions from Ada:: Restrictions on the Ada expression syntax.
15213 * Additions to Ada:: Extensions of the Ada expression syntax.
15214 * Stopping Before Main Program:: Debugging the program during elaboration.
15215 * Ada Exceptions:: Ada Exceptions
15216 * Ada Tasks:: Listing and setting breakpoints in tasks.
15217 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
15218 * Ravenscar Profile:: Tasking Support when using the Ravenscar
15220 * Ada Glitches:: Known peculiarities of Ada mode.
15223 @node Ada Mode Intro
15224 @subsubsection Introduction
15225 @cindex Ada mode, general
15227 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
15228 syntax, with some extensions.
15229 The philosophy behind the design of this subset is
15233 That @value{GDBN} should provide basic literals and access to operations for
15234 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
15235 leaving more sophisticated computations to subprograms written into the
15236 program (which therefore may be called from @value{GDBN}).
15239 That type safety and strict adherence to Ada language restrictions
15240 are not particularly important to the @value{GDBN} user.
15243 That brevity is important to the @value{GDBN} user.
15246 Thus, for brevity, the debugger acts as if all names declared in
15247 user-written packages are directly visible, even if they are not visible
15248 according to Ada rules, thus making it unnecessary to fully qualify most
15249 names with their packages, regardless of context. Where this causes
15250 ambiguity, @value{GDBN} asks the user's intent.
15252 The debugger will start in Ada mode if it detects an Ada main program.
15253 As for other languages, it will enter Ada mode when stopped in a program that
15254 was translated from an Ada source file.
15256 While in Ada mode, you may use `@t{--}' for comments. This is useful
15257 mostly for documenting command files. The standard @value{GDBN} comment
15258 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
15259 middle (to allow based literals).
15261 The debugger supports limited overloading. Given a subprogram call in which
15262 the function symbol has multiple definitions, it will use the number of
15263 actual parameters and some information about their types to attempt to narrow
15264 the set of definitions. It also makes very limited use of context, preferring
15265 procedures to functions in the context of the @code{call} command, and
15266 functions to procedures elsewhere.
15268 @node Omissions from Ada
15269 @subsubsection Omissions from Ada
15270 @cindex Ada, omissions from
15272 Here are the notable omissions from the subset:
15276 Only a subset of the attributes are supported:
15280 @t{'First}, @t{'Last}, and @t{'Length}
15281 on array objects (not on types and subtypes).
15284 @t{'Min} and @t{'Max}.
15287 @t{'Pos} and @t{'Val}.
15293 @t{'Range} on array objects (not subtypes), but only as the right
15294 operand of the membership (@code{in}) operator.
15297 @t{'Access}, @t{'Unchecked_Access}, and
15298 @t{'Unrestricted_Access} (a GNAT extension).
15306 @code{Characters.Latin_1} are not available and
15307 concatenation is not implemented. Thus, escape characters in strings are
15308 not currently available.
15311 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
15312 equality of representations. They will generally work correctly
15313 for strings and arrays whose elements have integer or enumeration types.
15314 They may not work correctly for arrays whose element
15315 types have user-defined equality, for arrays of real values
15316 (in particular, IEEE-conformant floating point, because of negative
15317 zeroes and NaNs), and for arrays whose elements contain unused bits with
15318 indeterminate values.
15321 The other component-by-component array operations (@code{and}, @code{or},
15322 @code{xor}, @code{not}, and relational tests other than equality)
15323 are not implemented.
15326 @cindex array aggregates (Ada)
15327 @cindex record aggregates (Ada)
15328 @cindex aggregates (Ada)
15329 There is limited support for array and record aggregates. They are
15330 permitted only on the right sides of assignments, as in these examples:
15333 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
15334 (@value{GDBP}) set An_Array := (1, others => 0)
15335 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
15336 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
15337 (@value{GDBP}) set A_Record := (1, "Peter", True);
15338 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
15342 discriminant's value by assigning an aggregate has an
15343 undefined effect if that discriminant is used within the record.
15344 However, you can first modify discriminants by directly assigning to
15345 them (which normally would not be allowed in Ada), and then performing an
15346 aggregate assignment. For example, given a variable @code{A_Rec}
15347 declared to have a type such as:
15350 type Rec (Len : Small_Integer := 0) is record
15352 Vals : IntArray (1 .. Len);
15356 you can assign a value with a different size of @code{Vals} with two
15360 (@value{GDBP}) set A_Rec.Len := 4
15361 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
15364 As this example also illustrates, @value{GDBN} is very loose about the usual
15365 rules concerning aggregates. You may leave out some of the
15366 components of an array or record aggregate (such as the @code{Len}
15367 component in the assignment to @code{A_Rec} above); they will retain their
15368 original values upon assignment. You may freely use dynamic values as
15369 indices in component associations. You may even use overlapping or
15370 redundant component associations, although which component values are
15371 assigned in such cases is not defined.
15374 Calls to dispatching subprograms are not implemented.
15377 The overloading algorithm is much more limited (i.e., less selective)
15378 than that of real Ada. It makes only limited use of the context in
15379 which a subexpression appears to resolve its meaning, and it is much
15380 looser in its rules for allowing type matches. As a result, some
15381 function calls will be ambiguous, and the user will be asked to choose
15382 the proper resolution.
15385 The @code{new} operator is not implemented.
15388 Entry calls are not implemented.
15391 Aside from printing, arithmetic operations on the native VAX floating-point
15392 formats are not supported.
15395 It is not possible to slice a packed array.
15398 The names @code{True} and @code{False}, when not part of a qualified name,
15399 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
15401 Should your program
15402 redefine these names in a package or procedure (at best a dubious practice),
15403 you will have to use fully qualified names to access their new definitions.
15406 @node Additions to Ada
15407 @subsubsection Additions to Ada
15408 @cindex Ada, deviations from
15410 As it does for other languages, @value{GDBN} makes certain generic
15411 extensions to Ada (@pxref{Expressions}):
15415 If the expression @var{E} is a variable residing in memory (typically
15416 a local variable or array element) and @var{N} is a positive integer,
15417 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
15418 @var{N}-1 adjacent variables following it in memory as an array. In
15419 Ada, this operator is generally not necessary, since its prime use is
15420 in displaying parts of an array, and slicing will usually do this in
15421 Ada. However, there are occasional uses when debugging programs in
15422 which certain debugging information has been optimized away.
15425 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
15426 appears in function or file @var{B}.'' When @var{B} is a file name,
15427 you must typically surround it in single quotes.
15430 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
15431 @var{type} that appears at address @var{addr}.''
15434 A name starting with @samp{$} is a convenience variable
15435 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
15438 In addition, @value{GDBN} provides a few other shortcuts and outright
15439 additions specific to Ada:
15443 The assignment statement is allowed as an expression, returning
15444 its right-hand operand as its value. Thus, you may enter
15447 (@value{GDBP}) set x := y + 3
15448 (@value{GDBP}) print A(tmp := y + 1)
15452 The semicolon is allowed as an ``operator,'' returning as its value
15453 the value of its right-hand operand.
15454 This allows, for example,
15455 complex conditional breaks:
15458 (@value{GDBP}) break f
15459 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
15463 Rather than use catenation and symbolic character names to introduce special
15464 characters into strings, one may instead use a special bracket notation,
15465 which is also used to print strings. A sequence of characters of the form
15466 @samp{["@var{XX}"]} within a string or character literal denotes the
15467 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
15468 sequence of characters @samp{["""]} also denotes a single quotation mark
15469 in strings. For example,
15471 "One line.["0a"]Next line.["0a"]"
15474 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
15478 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
15479 @t{'Max} is optional (and is ignored in any case). For example, it is valid
15483 (@value{GDBP}) print 'max(x, y)
15487 When printing arrays, @value{GDBN} uses positional notation when the
15488 array has a lower bound of 1, and uses a modified named notation otherwise.
15489 For example, a one-dimensional array of three integers with a lower bound
15490 of 3 might print as
15497 That is, in contrast to valid Ada, only the first component has a @code{=>}
15501 You may abbreviate attributes in expressions with any unique,
15502 multi-character subsequence of
15503 their names (an exact match gets preference).
15504 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
15505 in place of @t{a'length}.
15508 @cindex quoting Ada internal identifiers
15509 Since Ada is case-insensitive, the debugger normally maps identifiers you type
15510 to lower case. The GNAT compiler uses upper-case characters for
15511 some of its internal identifiers, which are normally of no interest to users.
15512 For the rare occasions when you actually have to look at them,
15513 enclose them in angle brackets to avoid the lower-case mapping.
15516 (@value{GDBP}) print <JMPBUF_SAVE>[0]
15520 Printing an object of class-wide type or dereferencing an
15521 access-to-class-wide value will display all the components of the object's
15522 specific type (as indicated by its run-time tag). Likewise, component
15523 selection on such a value will operate on the specific type of the
15528 @node Stopping Before Main Program
15529 @subsubsection Stopping at the Very Beginning
15531 @cindex breakpointing Ada elaboration code
15532 It is sometimes necessary to debug the program during elaboration, and
15533 before reaching the main procedure.
15534 As defined in the Ada Reference
15535 Manual, the elaboration code is invoked from a procedure called
15536 @code{adainit}. To run your program up to the beginning of
15537 elaboration, simply use the following two commands:
15538 @code{tbreak adainit} and @code{run}.
15540 @node Ada Exceptions
15541 @subsubsection Ada Exceptions
15543 A command is provided to list all Ada exceptions:
15546 @kindex info exceptions
15547 @item info exceptions
15548 @itemx info exceptions @var{regexp}
15549 The @code{info exceptions} command allows you to list all Ada exceptions
15550 defined within the program being debugged, as well as their addresses.
15551 With a regular expression, @var{regexp}, as argument, only those exceptions
15552 whose names match @var{regexp} are listed.
15555 Below is a small example, showing how the command can be used, first
15556 without argument, and next with a regular expression passed as an
15560 (@value{GDBP}) info exceptions
15561 All defined Ada exceptions:
15562 constraint_error: 0x613da0
15563 program_error: 0x613d20
15564 storage_error: 0x613ce0
15565 tasking_error: 0x613ca0
15566 const.aint_global_e: 0x613b00
15567 (@value{GDBP}) info exceptions const.aint
15568 All Ada exceptions matching regular expression "const.aint":
15569 constraint_error: 0x613da0
15570 const.aint_global_e: 0x613b00
15573 It is also possible to ask @value{GDBN} to stop your program's execution
15574 when an exception is raised. For more details, see @ref{Set Catchpoints}.
15577 @subsubsection Extensions for Ada Tasks
15578 @cindex Ada, tasking
15580 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
15581 @value{GDBN} provides the following task-related commands:
15586 This command shows a list of current Ada tasks, as in the following example:
15593 (@value{GDBP}) info tasks
15594 ID TID P-ID Pri State Name
15595 1 8088000 0 15 Child Activation Wait main_task
15596 2 80a4000 1 15 Accept Statement b
15597 3 809a800 1 15 Child Activation Wait a
15598 * 4 80ae800 3 15 Runnable c
15603 In this listing, the asterisk before the last task indicates it to be the
15604 task currently being inspected.
15608 Represents @value{GDBN}'s internal task number.
15614 The parent's task ID (@value{GDBN}'s internal task number).
15617 The base priority of the task.
15620 Current state of the task.
15624 The task has been created but has not been activated. It cannot be
15628 The task is not blocked for any reason known to Ada. (It may be waiting
15629 for a mutex, though.) It is conceptually "executing" in normal mode.
15632 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
15633 that were waiting on terminate alternatives have been awakened and have
15634 terminated themselves.
15636 @item Child Activation Wait
15637 The task is waiting for created tasks to complete activation.
15639 @item Accept Statement
15640 The task is waiting on an accept or selective wait statement.
15642 @item Waiting on entry call
15643 The task is waiting on an entry call.
15645 @item Async Select Wait
15646 The task is waiting to start the abortable part of an asynchronous
15650 The task is waiting on a select statement with only a delay
15653 @item Child Termination Wait
15654 The task is sleeping having completed a master within itself, and is
15655 waiting for the tasks dependent on that master to become terminated or
15656 waiting on a terminate Phase.
15658 @item Wait Child in Term Alt
15659 The task is sleeping waiting for tasks on terminate alternatives to
15660 finish terminating.
15662 @item Accepting RV with @var{taskno}
15663 The task is accepting a rendez-vous with the task @var{taskno}.
15667 Name of the task in the program.
15671 @kindex info task @var{taskno}
15672 @item info task @var{taskno}
15673 This command shows detailled informations on the specified task, as in
15674 the following example:
15679 (@value{GDBP}) info tasks
15680 ID TID P-ID Pri State Name
15681 1 8077880 0 15 Child Activation Wait main_task
15682 * 2 807c468 1 15 Runnable task_1
15683 (@value{GDBP}) info task 2
15684 Ada Task: 0x807c468
15687 Parent: 1 (main_task)
15693 @kindex task@r{ (Ada)}
15694 @cindex current Ada task ID
15695 This command prints the ID of the current task.
15701 (@value{GDBP}) info tasks
15702 ID TID P-ID Pri State Name
15703 1 8077870 0 15 Child Activation Wait main_task
15704 * 2 807c458 1 15 Runnable t
15705 (@value{GDBP}) task
15706 [Current task is 2]
15709 @item task @var{taskno}
15710 @cindex Ada task switching
15711 This command is like the @code{thread @var{threadno}}
15712 command (@pxref{Threads}). It switches the context of debugging
15713 from the current task to the given task.
15719 (@value{GDBP}) info tasks
15720 ID TID P-ID Pri State Name
15721 1 8077870 0 15 Child Activation Wait main_task
15722 * 2 807c458 1 15 Runnable t
15723 (@value{GDBP}) task 1
15724 [Switching to task 1]
15725 #0 0x8067726 in pthread_cond_wait ()
15727 #0 0x8067726 in pthread_cond_wait ()
15728 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
15729 #2 0x805cb63 in system.task_primitives.operations.sleep ()
15730 #3 0x806153e in system.tasking.stages.activate_tasks ()
15731 #4 0x804aacc in un () at un.adb:5
15734 @item break @var{linespec} task @var{taskno}
15735 @itemx break @var{linespec} task @var{taskno} if @dots{}
15736 @cindex breakpoints and tasks, in Ada
15737 @cindex task breakpoints, in Ada
15738 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
15739 These commands are like the @code{break @dots{} thread @dots{}}
15740 command (@pxref{Thread Stops}). The
15741 @var{linespec} argument specifies source lines, as described
15742 in @ref{Specify Location}.
15744 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
15745 to specify that you only want @value{GDBN} to stop the program when a
15746 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
15747 numeric task identifiers assigned by @value{GDBN}, shown in the first
15748 column of the @samp{info tasks} display.
15750 If you do not specify @samp{task @var{taskno}} when you set a
15751 breakpoint, the breakpoint applies to @emph{all} tasks of your
15754 You can use the @code{task} qualifier on conditional breakpoints as
15755 well; in this case, place @samp{task @var{taskno}} before the
15756 breakpoint condition (before the @code{if}).
15764 (@value{GDBP}) info tasks
15765 ID TID P-ID Pri State Name
15766 1 140022020 0 15 Child Activation Wait main_task
15767 2 140045060 1 15 Accept/Select Wait t2
15768 3 140044840 1 15 Runnable t1
15769 * 4 140056040 1 15 Runnable t3
15770 (@value{GDBP}) b 15 task 2
15771 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
15772 (@value{GDBP}) cont
15777 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
15779 (@value{GDBP}) info tasks
15780 ID TID P-ID Pri State Name
15781 1 140022020 0 15 Child Activation Wait main_task
15782 * 2 140045060 1 15 Runnable t2
15783 3 140044840 1 15 Runnable t1
15784 4 140056040 1 15 Delay Sleep t3
15788 @node Ada Tasks and Core Files
15789 @subsubsection Tasking Support when Debugging Core Files
15790 @cindex Ada tasking and core file debugging
15792 When inspecting a core file, as opposed to debugging a live program,
15793 tasking support may be limited or even unavailable, depending on
15794 the platform being used.
15795 For instance, on x86-linux, the list of tasks is available, but task
15796 switching is not supported.
15798 On certain platforms, the debugger needs to perform some
15799 memory writes in order to provide Ada tasking support. When inspecting
15800 a core file, this means that the core file must be opened with read-write
15801 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
15802 Under these circumstances, you should make a backup copy of the core
15803 file before inspecting it with @value{GDBN}.
15805 @node Ravenscar Profile
15806 @subsubsection Tasking Support when using the Ravenscar Profile
15807 @cindex Ravenscar Profile
15809 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
15810 specifically designed for systems with safety-critical real-time
15814 @kindex set ravenscar task-switching on
15815 @cindex task switching with program using Ravenscar Profile
15816 @item set ravenscar task-switching on
15817 Allows task switching when debugging a program that uses the Ravenscar
15818 Profile. This is the default.
15820 @kindex set ravenscar task-switching off
15821 @item set ravenscar task-switching off
15822 Turn off task switching when debugging a program that uses the Ravenscar
15823 Profile. This is mostly intended to disable the code that adds support
15824 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
15825 the Ravenscar runtime is preventing @value{GDBN} from working properly.
15826 To be effective, this command should be run before the program is started.
15828 @kindex show ravenscar task-switching
15829 @item show ravenscar task-switching
15830 Show whether it is possible to switch from task to task in a program
15831 using the Ravenscar Profile.
15836 @subsubsection Known Peculiarities of Ada Mode
15837 @cindex Ada, problems
15839 Besides the omissions listed previously (@pxref{Omissions from Ada}),
15840 we know of several problems with and limitations of Ada mode in
15842 some of which will be fixed with planned future releases of the debugger
15843 and the GNU Ada compiler.
15847 Static constants that the compiler chooses not to materialize as objects in
15848 storage are invisible to the debugger.
15851 Named parameter associations in function argument lists are ignored (the
15852 argument lists are treated as positional).
15855 Many useful library packages are currently invisible to the debugger.
15858 Fixed-point arithmetic, conversions, input, and output is carried out using
15859 floating-point arithmetic, and may give results that only approximate those on
15863 The GNAT compiler never generates the prefix @code{Standard} for any of
15864 the standard symbols defined by the Ada language. @value{GDBN} knows about
15865 this: it will strip the prefix from names when you use it, and will never
15866 look for a name you have so qualified among local symbols, nor match against
15867 symbols in other packages or subprograms. If you have
15868 defined entities anywhere in your program other than parameters and
15869 local variables whose simple names match names in @code{Standard},
15870 GNAT's lack of qualification here can cause confusion. When this happens,
15871 you can usually resolve the confusion
15872 by qualifying the problematic names with package
15873 @code{Standard} explicitly.
15876 Older versions of the compiler sometimes generate erroneous debugging
15877 information, resulting in the debugger incorrectly printing the value
15878 of affected entities. In some cases, the debugger is able to work
15879 around an issue automatically. In other cases, the debugger is able
15880 to work around the issue, but the work-around has to be specifically
15883 @kindex set ada trust-PAD-over-XVS
15884 @kindex show ada trust-PAD-over-XVS
15887 @item set ada trust-PAD-over-XVS on
15888 Configure GDB to strictly follow the GNAT encoding when computing the
15889 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
15890 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
15891 a complete description of the encoding used by the GNAT compiler).
15892 This is the default.
15894 @item set ada trust-PAD-over-XVS off
15895 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
15896 sometimes prints the wrong value for certain entities, changing @code{ada
15897 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
15898 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
15899 @code{off}, but this incurs a slight performance penalty, so it is
15900 recommended to leave this setting to @code{on} unless necessary.
15904 @cindex GNAT descriptive types
15905 @cindex GNAT encoding
15906 Internally, the debugger also relies on the compiler following a number
15907 of conventions known as the @samp{GNAT Encoding}, all documented in
15908 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
15909 how the debugging information should be generated for certain types.
15910 In particular, this convention makes use of @dfn{descriptive types},
15911 which are artificial types generated purely to help the debugger.
15913 These encodings were defined at a time when the debugging information
15914 format used was not powerful enough to describe some of the more complex
15915 types available in Ada. Since DWARF allows us to express nearly all
15916 Ada features, the long-term goal is to slowly replace these descriptive
15917 types by their pure DWARF equivalent. To facilitate that transition,
15918 a new maintenance option is available to force the debugger to ignore
15919 those descriptive types. It allows the user to quickly evaluate how
15920 well @value{GDBN} works without them.
15924 @kindex maint ada set ignore-descriptive-types
15925 @item maintenance ada set ignore-descriptive-types [on|off]
15926 Control whether the debugger should ignore descriptive types.
15927 The default is not to ignore descriptives types (@code{off}).
15929 @kindex maint ada show ignore-descriptive-types
15930 @item maintenance ada show ignore-descriptive-types
15931 Show if descriptive types are ignored by @value{GDBN}.
15935 @node Unsupported Languages
15936 @section Unsupported Languages
15938 @cindex unsupported languages
15939 @cindex minimal language
15940 In addition to the other fully-supported programming languages,
15941 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
15942 It does not represent a real programming language, but provides a set
15943 of capabilities close to what the C or assembly languages provide.
15944 This should allow most simple operations to be performed while debugging
15945 an application that uses a language currently not supported by @value{GDBN}.
15947 If the language is set to @code{auto}, @value{GDBN} will automatically
15948 select this language if the current frame corresponds to an unsupported
15952 @chapter Examining the Symbol Table
15954 The commands described in this chapter allow you to inquire about the
15955 symbols (names of variables, functions and types) defined in your
15956 program. This information is inherent in the text of your program and
15957 does not change as your program executes. @value{GDBN} finds it in your
15958 program's symbol table, in the file indicated when you started @value{GDBN}
15959 (@pxref{File Options, ,Choosing Files}), or by one of the
15960 file-management commands (@pxref{Files, ,Commands to Specify Files}).
15962 @cindex symbol names
15963 @cindex names of symbols
15964 @cindex quoting names
15965 Occasionally, you may need to refer to symbols that contain unusual
15966 characters, which @value{GDBN} ordinarily treats as word delimiters. The
15967 most frequent case is in referring to static variables in other
15968 source files (@pxref{Variables,,Program Variables}). File names
15969 are recorded in object files as debugging symbols, but @value{GDBN} would
15970 ordinarily parse a typical file name, like @file{foo.c}, as the three words
15971 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
15972 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
15979 looks up the value of @code{x} in the scope of the file @file{foo.c}.
15982 @cindex case-insensitive symbol names
15983 @cindex case sensitivity in symbol names
15984 @kindex set case-sensitive
15985 @item set case-sensitive on
15986 @itemx set case-sensitive off
15987 @itemx set case-sensitive auto
15988 Normally, when @value{GDBN} looks up symbols, it matches their names
15989 with case sensitivity determined by the current source language.
15990 Occasionally, you may wish to control that. The command @code{set
15991 case-sensitive} lets you do that by specifying @code{on} for
15992 case-sensitive matches or @code{off} for case-insensitive ones. If
15993 you specify @code{auto}, case sensitivity is reset to the default
15994 suitable for the source language. The default is case-sensitive
15995 matches for all languages except for Fortran, for which the default is
15996 case-insensitive matches.
15998 @kindex show case-sensitive
15999 @item show case-sensitive
16000 This command shows the current setting of case sensitivity for symbols
16003 @kindex set print type methods
16004 @item set print type methods
16005 @itemx set print type methods on
16006 @itemx set print type methods off
16007 Normally, when @value{GDBN} prints a class, it displays any methods
16008 declared in that class. You can control this behavior either by
16009 passing the appropriate flag to @code{ptype}, or using @command{set
16010 print type methods}. Specifying @code{on} will cause @value{GDBN} to
16011 display the methods; this is the default. Specifying @code{off} will
16012 cause @value{GDBN} to omit the methods.
16014 @kindex show print type methods
16015 @item show print type methods
16016 This command shows the current setting of method display when printing
16019 @kindex set print type typedefs
16020 @item set print type typedefs
16021 @itemx set print type typedefs on
16022 @itemx set print type typedefs off
16024 Normally, when @value{GDBN} prints a class, it displays any typedefs
16025 defined in that class. You can control this behavior either by
16026 passing the appropriate flag to @code{ptype}, or using @command{set
16027 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
16028 display the typedef definitions; this is the default. Specifying
16029 @code{off} will cause @value{GDBN} to omit the typedef definitions.
16030 Note that this controls whether the typedef definition itself is
16031 printed, not whether typedef names are substituted when printing other
16034 @kindex show print type typedefs
16035 @item show print type typedefs
16036 This command shows the current setting of typedef display when
16039 @kindex info address
16040 @cindex address of a symbol
16041 @item info address @var{symbol}
16042 Describe where the data for @var{symbol} is stored. For a register
16043 variable, this says which register it is kept in. For a non-register
16044 local variable, this prints the stack-frame offset at which the variable
16047 Note the contrast with @samp{print &@var{symbol}}, which does not work
16048 at all for a register variable, and for a stack local variable prints
16049 the exact address of the current instantiation of the variable.
16051 @kindex info symbol
16052 @cindex symbol from address
16053 @cindex closest symbol and offset for an address
16054 @item info symbol @var{addr}
16055 Print the name of a symbol which is stored at the address @var{addr}.
16056 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
16057 nearest symbol and an offset from it:
16060 (@value{GDBP}) info symbol 0x54320
16061 _initialize_vx + 396 in section .text
16065 This is the opposite of the @code{info address} command. You can use
16066 it to find out the name of a variable or a function given its address.
16068 For dynamically linked executables, the name of executable or shared
16069 library containing the symbol is also printed:
16072 (@value{GDBP}) info symbol 0x400225
16073 _start + 5 in section .text of /tmp/a.out
16074 (@value{GDBP}) info symbol 0x2aaaac2811cf
16075 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
16080 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
16081 Demangle @var{name}.
16082 If @var{language} is provided it is the name of the language to demangle
16083 @var{name} in. Otherwise @var{name} is demangled in the current language.
16085 The @samp{--} option specifies the end of options,
16086 and is useful when @var{name} begins with a dash.
16088 The parameter @code{demangle-style} specifies how to interpret the kind
16089 of mangling used. @xref{Print Settings}.
16092 @item whatis[/@var{flags}] [@var{arg}]
16093 Print the data type of @var{arg}, which can be either an expression
16094 or a name of a data type. With no argument, print the data type of
16095 @code{$}, the last value in the value history.
16097 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
16098 is not actually evaluated, and any side-effecting operations (such as
16099 assignments or function calls) inside it do not take place.
16101 If @var{arg} is a variable or an expression, @code{whatis} prints its
16102 literal type as it is used in the source code. If the type was
16103 defined using a @code{typedef}, @code{whatis} will @emph{not} print
16104 the data type underlying the @code{typedef}. If the type of the
16105 variable or the expression is a compound data type, such as
16106 @code{struct} or @code{class}, @code{whatis} never prints their
16107 fields or methods. It just prints the @code{struct}/@code{class}
16108 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
16109 such a compound data type, use @code{ptype}.
16111 If @var{arg} is a type name that was defined using @code{typedef},
16112 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
16113 Unrolling means that @code{whatis} will show the underlying type used
16114 in the @code{typedef} declaration of @var{arg}. However, if that
16115 underlying type is also a @code{typedef}, @code{whatis} will not
16118 For C code, the type names may also have the form @samp{class
16119 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
16120 @var{union-tag}} or @samp{enum @var{enum-tag}}.
16122 @var{flags} can be used to modify how the type is displayed.
16123 Available flags are:
16127 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
16128 parameters and typedefs defined in a class when printing the class'
16129 members. The @code{/r} flag disables this.
16132 Do not print methods defined in the class.
16135 Print methods defined in the class. This is the default, but the flag
16136 exists in case you change the default with @command{set print type methods}.
16139 Do not print typedefs defined in the class. Note that this controls
16140 whether the typedef definition itself is printed, not whether typedef
16141 names are substituted when printing other types.
16144 Print typedefs defined in the class. This is the default, but the flag
16145 exists in case you change the default with @command{set print type typedefs}.
16149 @item ptype[/@var{flags}] [@var{arg}]
16150 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
16151 detailed description of the type, instead of just the name of the type.
16152 @xref{Expressions, ,Expressions}.
16154 Contrary to @code{whatis}, @code{ptype} always unrolls any
16155 @code{typedef}s in its argument declaration, whether the argument is
16156 a variable, expression, or a data type. This means that @code{ptype}
16157 of a variable or an expression will not print literally its type as
16158 present in the source code---use @code{whatis} for that. @code{typedef}s at
16159 the pointer or reference targets are also unrolled. Only @code{typedef}s of
16160 fields, methods and inner @code{class typedef}s of @code{struct}s,
16161 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
16163 For example, for this variable declaration:
16166 typedef double real_t;
16167 struct complex @{ real_t real; double imag; @};
16168 typedef struct complex complex_t;
16170 real_t *real_pointer_var;
16174 the two commands give this output:
16178 (@value{GDBP}) whatis var
16180 (@value{GDBP}) ptype var
16181 type = struct complex @{
16185 (@value{GDBP}) whatis complex_t
16186 type = struct complex
16187 (@value{GDBP}) whatis struct complex
16188 type = struct complex
16189 (@value{GDBP}) ptype struct complex
16190 type = struct complex @{
16194 (@value{GDBP}) whatis real_pointer_var
16196 (@value{GDBP}) ptype real_pointer_var
16202 As with @code{whatis}, using @code{ptype} without an argument refers to
16203 the type of @code{$}, the last value in the value history.
16205 @cindex incomplete type
16206 Sometimes, programs use opaque data types or incomplete specifications
16207 of complex data structure. If the debug information included in the
16208 program does not allow @value{GDBN} to display a full declaration of
16209 the data type, it will say @samp{<incomplete type>}. For example,
16210 given these declarations:
16214 struct foo *fooptr;
16218 but no definition for @code{struct foo} itself, @value{GDBN} will say:
16221 (@value{GDBP}) ptype foo
16222 $1 = <incomplete type>
16226 ``Incomplete type'' is C terminology for data types that are not
16227 completely specified.
16230 @item info types @var{regexp}
16232 Print a brief description of all types whose names match the regular
16233 expression @var{regexp} (or all types in your program, if you supply
16234 no argument). Each complete typename is matched as though it were a
16235 complete line; thus, @samp{i type value} gives information on all
16236 types in your program whose names include the string @code{value}, but
16237 @samp{i type ^value$} gives information only on types whose complete
16238 name is @code{value}.
16240 This command differs from @code{ptype} in two ways: first, like
16241 @code{whatis}, it does not print a detailed description; second, it
16242 lists all source files where a type is defined.
16244 @kindex info type-printers
16245 @item info type-printers
16246 Versions of @value{GDBN} that ship with Python scripting enabled may
16247 have ``type printers'' available. When using @command{ptype} or
16248 @command{whatis}, these printers are consulted when the name of a type
16249 is needed. @xref{Type Printing API}, for more information on writing
16252 @code{info type-printers} displays all the available type printers.
16254 @kindex enable type-printer
16255 @kindex disable type-printer
16256 @item enable type-printer @var{name}@dots{}
16257 @item disable type-printer @var{name}@dots{}
16258 These commands can be used to enable or disable type printers.
16261 @cindex local variables
16262 @item info scope @var{location}
16263 List all the variables local to a particular scope. This command
16264 accepts a @var{location} argument---a function name, a source line, or
16265 an address preceded by a @samp{*}, and prints all the variables local
16266 to the scope defined by that location. (@xref{Specify Location}, for
16267 details about supported forms of @var{location}.) For example:
16270 (@value{GDBP}) @b{info scope command_line_handler}
16271 Scope for command_line_handler:
16272 Symbol rl is an argument at stack/frame offset 8, length 4.
16273 Symbol linebuffer is in static storage at address 0x150a18, length 4.
16274 Symbol linelength is in static storage at address 0x150a1c, length 4.
16275 Symbol p is a local variable in register $esi, length 4.
16276 Symbol p1 is a local variable in register $ebx, length 4.
16277 Symbol nline is a local variable in register $edx, length 4.
16278 Symbol repeat is a local variable at frame offset -8, length 4.
16282 This command is especially useful for determining what data to collect
16283 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
16286 @kindex info source
16288 Show information about the current source file---that is, the source file for
16289 the function containing the current point of execution:
16292 the name of the source file, and the directory containing it,
16294 the directory it was compiled in,
16296 its length, in lines,
16298 which programming language it is written in,
16300 whether the executable includes debugging information for that file, and
16301 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
16303 whether the debugging information includes information about
16304 preprocessor macros.
16308 @kindex info sources
16310 Print the names of all source files in your program for which there is
16311 debugging information, organized into two lists: files whose symbols
16312 have already been read, and files whose symbols will be read when needed.
16314 @kindex info functions
16315 @item info functions
16316 Print the names and data types of all defined functions.
16318 @item info functions @var{regexp}
16319 Print the names and data types of all defined functions
16320 whose names contain a match for regular expression @var{regexp}.
16321 Thus, @samp{info fun step} finds all functions whose names
16322 include @code{step}; @samp{info fun ^step} finds those whose names
16323 start with @code{step}. If a function name contains characters
16324 that conflict with the regular expression language (e.g.@:
16325 @samp{operator*()}), they may be quoted with a backslash.
16327 @kindex info variables
16328 @item info variables
16329 Print the names and data types of all variables that are defined
16330 outside of functions (i.e.@: excluding local variables).
16332 @item info variables @var{regexp}
16333 Print the names and data types of all variables (except for local
16334 variables) whose names contain a match for regular expression
16337 @kindex info classes
16338 @cindex Objective-C, classes and selectors
16340 @itemx info classes @var{regexp}
16341 Display all Objective-C classes in your program, or
16342 (with the @var{regexp} argument) all those matching a particular regular
16345 @kindex info selectors
16346 @item info selectors
16347 @itemx info selectors @var{regexp}
16348 Display all Objective-C selectors in your program, or
16349 (with the @var{regexp} argument) all those matching a particular regular
16353 This was never implemented.
16354 @kindex info methods
16356 @itemx info methods @var{regexp}
16357 The @code{info methods} command permits the user to examine all defined
16358 methods within C@t{++} program, or (with the @var{regexp} argument) a
16359 specific set of methods found in the various C@t{++} classes. Many
16360 C@t{++} classes provide a large number of methods. Thus, the output
16361 from the @code{ptype} command can be overwhelming and hard to use. The
16362 @code{info-methods} command filters the methods, printing only those
16363 which match the regular-expression @var{regexp}.
16366 @cindex opaque data types
16367 @kindex set opaque-type-resolution
16368 @item set opaque-type-resolution on
16369 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
16370 declared as a pointer to a @code{struct}, @code{class}, or
16371 @code{union}---for example, @code{struct MyType *}---that is used in one
16372 source file although the full declaration of @code{struct MyType} is in
16373 another source file. The default is on.
16375 A change in the setting of this subcommand will not take effect until
16376 the next time symbols for a file are loaded.
16378 @item set opaque-type-resolution off
16379 Tell @value{GDBN} not to resolve opaque types. In this case, the type
16380 is printed as follows:
16382 @{<no data fields>@}
16385 @kindex show opaque-type-resolution
16386 @item show opaque-type-resolution
16387 Show whether opaque types are resolved or not.
16389 @kindex set print symbol-loading
16390 @cindex print messages when symbols are loaded
16391 @item set print symbol-loading
16392 @itemx set print symbol-loading full
16393 @itemx set print symbol-loading brief
16394 @itemx set print symbol-loading off
16395 The @code{set print symbol-loading} command allows you to control the
16396 printing of messages when @value{GDBN} loads symbol information.
16397 By default a message is printed for the executable and one for each
16398 shared library, and normally this is what you want. However, when
16399 debugging apps with large numbers of shared libraries these messages
16401 When set to @code{brief} a message is printed for each executable,
16402 and when @value{GDBN} loads a collection of shared libraries at once
16403 it will only print one message regardless of the number of shared
16404 libraries. When set to @code{off} no messages are printed.
16406 @kindex show print symbol-loading
16407 @item show print symbol-loading
16408 Show whether messages will be printed when a @value{GDBN} command
16409 entered from the keyboard causes symbol information to be loaded.
16411 @kindex maint print symbols
16412 @cindex symbol dump
16413 @kindex maint print psymbols
16414 @cindex partial symbol dump
16415 @kindex maint print msymbols
16416 @cindex minimal symbol dump
16417 @item maint print symbols @var{filename}
16418 @itemx maint print psymbols @var{filename}
16419 @itemx maint print msymbols @var{filename}
16420 Write a dump of debugging symbol data into the file @var{filename}.
16421 These commands are used to debug the @value{GDBN} symbol-reading code. Only
16422 symbols with debugging data are included. If you use @samp{maint print
16423 symbols}, @value{GDBN} includes all the symbols for which it has already
16424 collected full details: that is, @var{filename} reflects symbols for
16425 only those files whose symbols @value{GDBN} has read. You can use the
16426 command @code{info sources} to find out which files these are. If you
16427 use @samp{maint print psymbols} instead, the dump shows information about
16428 symbols that @value{GDBN} only knows partially---that is, symbols defined in
16429 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
16430 @samp{maint print msymbols} dumps just the minimal symbol information
16431 required for each object file from which @value{GDBN} has read some symbols.
16432 @xref{Files, ,Commands to Specify Files}, for a discussion of how
16433 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
16435 @kindex maint info symtabs
16436 @kindex maint info psymtabs
16437 @cindex listing @value{GDBN}'s internal symbol tables
16438 @cindex symbol tables, listing @value{GDBN}'s internal
16439 @cindex full symbol tables, listing @value{GDBN}'s internal
16440 @cindex partial symbol tables, listing @value{GDBN}'s internal
16441 @item maint info symtabs @r{[} @var{regexp} @r{]}
16442 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
16444 List the @code{struct symtab} or @code{struct partial_symtab}
16445 structures whose names match @var{regexp}. If @var{regexp} is not
16446 given, list them all. The output includes expressions which you can
16447 copy into a @value{GDBN} debugging this one to examine a particular
16448 structure in more detail. For example:
16451 (@value{GDBP}) maint info psymtabs dwarf2read
16452 @{ objfile /home/gnu/build/gdb/gdb
16453 ((struct objfile *) 0x82e69d0)
16454 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
16455 ((struct partial_symtab *) 0x8474b10)
16458 text addresses 0x814d3c8 -- 0x8158074
16459 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
16460 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
16461 dependencies (none)
16464 (@value{GDBP}) maint info symtabs
16468 We see that there is one partial symbol table whose filename contains
16469 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
16470 and we see that @value{GDBN} has not read in any symtabs yet at all.
16471 If we set a breakpoint on a function, that will cause @value{GDBN} to
16472 read the symtab for the compilation unit containing that function:
16475 (@value{GDBP}) break dwarf2_psymtab_to_symtab
16476 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
16478 (@value{GDBP}) maint info symtabs
16479 @{ objfile /home/gnu/build/gdb/gdb
16480 ((struct objfile *) 0x82e69d0)
16481 @{ symtab /home/gnu/src/gdb/dwarf2read.c
16482 ((struct symtab *) 0x86c1f38)
16485 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
16486 linetable ((struct linetable *) 0x8370fa0)
16487 debugformat DWARF 2
16496 @chapter Altering Execution
16498 Once you think you have found an error in your program, you might want to
16499 find out for certain whether correcting the apparent error would lead to
16500 correct results in the rest of the run. You can find the answer by
16501 experiment, using the @value{GDBN} features for altering execution of the
16504 For example, you can store new values into variables or memory
16505 locations, give your program a signal, restart it at a different
16506 address, or even return prematurely from a function.
16509 * Assignment:: Assignment to variables
16510 * Jumping:: Continuing at a different address
16511 * Signaling:: Giving your program a signal
16512 * Returning:: Returning from a function
16513 * Calling:: Calling your program's functions
16514 * Patching:: Patching your program
16515 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
16519 @section Assignment to Variables
16522 @cindex setting variables
16523 To alter the value of a variable, evaluate an assignment expression.
16524 @xref{Expressions, ,Expressions}. For example,
16531 stores the value 4 into the variable @code{x}, and then prints the
16532 value of the assignment expression (which is 4).
16533 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
16534 information on operators in supported languages.
16536 @kindex set variable
16537 @cindex variables, setting
16538 If you are not interested in seeing the value of the assignment, use the
16539 @code{set} command instead of the @code{print} command. @code{set} is
16540 really the same as @code{print} except that the expression's value is
16541 not printed and is not put in the value history (@pxref{Value History,
16542 ,Value History}). The expression is evaluated only for its effects.
16544 If the beginning of the argument string of the @code{set} command
16545 appears identical to a @code{set} subcommand, use the @code{set
16546 variable} command instead of just @code{set}. This command is identical
16547 to @code{set} except for its lack of subcommands. For example, if your
16548 program has a variable @code{width}, you get an error if you try to set
16549 a new value with just @samp{set width=13}, because @value{GDBN} has the
16550 command @code{set width}:
16553 (@value{GDBP}) whatis width
16555 (@value{GDBP}) p width
16557 (@value{GDBP}) set width=47
16558 Invalid syntax in expression.
16562 The invalid expression, of course, is @samp{=47}. In
16563 order to actually set the program's variable @code{width}, use
16566 (@value{GDBP}) set var width=47
16569 Because the @code{set} command has many subcommands that can conflict
16570 with the names of program variables, it is a good idea to use the
16571 @code{set variable} command instead of just @code{set}. For example, if
16572 your program has a variable @code{g}, you run into problems if you try
16573 to set a new value with just @samp{set g=4}, because @value{GDBN} has
16574 the command @code{set gnutarget}, abbreviated @code{set g}:
16578 (@value{GDBP}) whatis g
16582 (@value{GDBP}) set g=4
16586 The program being debugged has been started already.
16587 Start it from the beginning? (y or n) y
16588 Starting program: /home/smith/cc_progs/a.out
16589 "/home/smith/cc_progs/a.out": can't open to read symbols:
16590 Invalid bfd target.
16591 (@value{GDBP}) show g
16592 The current BFD target is "=4".
16597 The program variable @code{g} did not change, and you silently set the
16598 @code{gnutarget} to an invalid value. In order to set the variable
16602 (@value{GDBP}) set var g=4
16605 @value{GDBN} allows more implicit conversions in assignments than C; you can
16606 freely store an integer value into a pointer variable or vice versa,
16607 and you can convert any structure to any other structure that is the
16608 same length or shorter.
16609 @comment FIXME: how do structs align/pad in these conversions?
16610 @comment /doc@cygnus.com 18dec1990
16612 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
16613 construct to generate a value of specified type at a specified address
16614 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
16615 to memory location @code{0x83040} as an integer (which implies a certain size
16616 and representation in memory), and
16619 set @{int@}0x83040 = 4
16623 stores the value 4 into that memory location.
16626 @section Continuing at a Different Address
16628 Ordinarily, when you continue your program, you do so at the place where
16629 it stopped, with the @code{continue} command. You can instead continue at
16630 an address of your own choosing, with the following commands:
16634 @kindex j @r{(@code{jump})}
16635 @item jump @var{linespec}
16636 @itemx j @var{linespec}
16637 @itemx jump @var{location}
16638 @itemx j @var{location}
16639 Resume execution at line @var{linespec} or at address given by
16640 @var{location}. Execution stops again immediately if there is a
16641 breakpoint there. @xref{Specify Location}, for a description of the
16642 different forms of @var{linespec} and @var{location}. It is common
16643 practice to use the @code{tbreak} command in conjunction with
16644 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
16646 The @code{jump} command does not change the current stack frame, or
16647 the stack pointer, or the contents of any memory location or any
16648 register other than the program counter. If line @var{linespec} is in
16649 a different function from the one currently executing, the results may
16650 be bizarre if the two functions expect different patterns of arguments or
16651 of local variables. For this reason, the @code{jump} command requests
16652 confirmation if the specified line is not in the function currently
16653 executing. However, even bizarre results are predictable if you are
16654 well acquainted with the machine-language code of your program.
16657 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
16658 On many systems, you can get much the same effect as the @code{jump}
16659 command by storing a new value into the register @code{$pc}. The
16660 difference is that this does not start your program running; it only
16661 changes the address of where it @emph{will} run when you continue. For
16669 makes the next @code{continue} command or stepping command execute at
16670 address @code{0x485}, rather than at the address where your program stopped.
16671 @xref{Continuing and Stepping, ,Continuing and Stepping}.
16673 The most common occasion to use the @code{jump} command is to back
16674 up---perhaps with more breakpoints set---over a portion of a program
16675 that has already executed, in order to examine its execution in more
16680 @section Giving your Program a Signal
16681 @cindex deliver a signal to a program
16685 @item signal @var{signal}
16686 Resume execution where your program is stopped, but immediately give it the
16687 signal @var{signal}. The @var{signal} can be the name or the number of a
16688 signal. For example, on many systems @code{signal 2} and @code{signal
16689 SIGINT} are both ways of sending an interrupt signal.
16691 Alternatively, if @var{signal} is zero, continue execution without
16692 giving a signal. This is useful when your program stopped on account of
16693 a signal and would ordinarily see the signal when resumed with the
16694 @code{continue} command; @samp{signal 0} causes it to resume without a
16697 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
16698 delivered to the currently selected thread, not the thread that last
16699 reported a stop. This includes the situation where a thread was
16700 stopped due to a signal. So if you want to continue execution
16701 suppressing the signal that stopped a thread, you should select that
16702 same thread before issuing the @samp{signal 0} command. If you issue
16703 the @samp{signal 0} command with another thread as the selected one,
16704 @value{GDBN} detects that and asks for confirmation.
16706 Invoking the @code{signal} command is not the same as invoking the
16707 @code{kill} utility from the shell. Sending a signal with @code{kill}
16708 causes @value{GDBN} to decide what to do with the signal depending on
16709 the signal handling tables (@pxref{Signals}). The @code{signal} command
16710 passes the signal directly to your program.
16712 @code{signal} does not repeat when you press @key{RET} a second time
16713 after executing the command.
16715 @kindex queue-signal
16716 @item queue-signal @var{signal}
16717 Queue @var{signal} to be delivered immediately to the current thread
16718 when execution of the thread resumes. The @var{signal} can be the name or
16719 the number of a signal. For example, on many systems @code{signal 2} and
16720 @code{signal SIGINT} are both ways of sending an interrupt signal.
16721 The handling of the signal must be set to pass the signal to the program,
16722 otherwise @value{GDBN} will report an error.
16723 You can control the handling of signals from @value{GDBN} with the
16724 @code{handle} command (@pxref{Signals}).
16726 Alternatively, if @var{signal} is zero, any currently queued signal
16727 for the current thread is discarded and when execution resumes no signal
16728 will be delivered. This is useful when your program stopped on account
16729 of a signal and would ordinarily see the signal when resumed with the
16730 @code{continue} command.
16732 This command differs from the @code{signal} command in that the signal
16733 is just queued, execution is not resumed. And @code{queue-signal} cannot
16734 be used to pass a signal whose handling state has been set to @code{nopass}
16739 @xref{stepping into signal handlers}, for information on how stepping
16740 commands behave when the thread has a signal queued.
16743 @section Returning from a Function
16746 @cindex returning from a function
16749 @itemx return @var{expression}
16750 You can cancel execution of a function call with the @code{return}
16751 command. If you give an
16752 @var{expression} argument, its value is used as the function's return
16756 When you use @code{return}, @value{GDBN} discards the selected stack frame
16757 (and all frames within it). You can think of this as making the
16758 discarded frame return prematurely. If you wish to specify a value to
16759 be returned, give that value as the argument to @code{return}.
16761 This pops the selected stack frame (@pxref{Selection, ,Selecting a
16762 Frame}), and any other frames inside of it, leaving its caller as the
16763 innermost remaining frame. That frame becomes selected. The
16764 specified value is stored in the registers used for returning values
16767 The @code{return} command does not resume execution; it leaves the
16768 program stopped in the state that would exist if the function had just
16769 returned. In contrast, the @code{finish} command (@pxref{Continuing
16770 and Stepping, ,Continuing and Stepping}) resumes execution until the
16771 selected stack frame returns naturally.
16773 @value{GDBN} needs to know how the @var{expression} argument should be set for
16774 the inferior. The concrete registers assignment depends on the OS ABI and the
16775 type being returned by the selected stack frame. For example it is common for
16776 OS ABI to return floating point values in FPU registers while integer values in
16777 CPU registers. Still some ABIs return even floating point values in CPU
16778 registers. Larger integer widths (such as @code{long long int}) also have
16779 specific placement rules. @value{GDBN} already knows the OS ABI from its
16780 current target so it needs to find out also the type being returned to make the
16781 assignment into the right register(s).
16783 Normally, the selected stack frame has debug info. @value{GDBN} will always
16784 use the debug info instead of the implicit type of @var{expression} when the
16785 debug info is available. For example, if you type @kbd{return -1}, and the
16786 function in the current stack frame is declared to return a @code{long long
16787 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
16788 into a @code{long long int}:
16791 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
16793 (@value{GDBP}) return -1
16794 Make func return now? (y or n) y
16795 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
16796 43 printf ("result=%lld\n", func ());
16800 However, if the selected stack frame does not have a debug info, e.g., if the
16801 function was compiled without debug info, @value{GDBN} has to find out the type
16802 to return from user. Specifying a different type by mistake may set the value
16803 in different inferior registers than the caller code expects. For example,
16804 typing @kbd{return -1} with its implicit type @code{int} would set only a part
16805 of a @code{long long int} result for a debug info less function (on 32-bit
16806 architectures). Therefore the user is required to specify the return type by
16807 an appropriate cast explicitly:
16810 Breakpoint 2, 0x0040050b in func ()
16811 (@value{GDBP}) return -1
16812 Return value type not available for selected stack frame.
16813 Please use an explicit cast of the value to return.
16814 (@value{GDBP}) return (long long int) -1
16815 Make selected stack frame return now? (y or n) y
16816 #0 0x00400526 in main ()
16821 @section Calling Program Functions
16824 @cindex calling functions
16825 @cindex inferior functions, calling
16826 @item print @var{expr}
16827 Evaluate the expression @var{expr} and display the resulting value.
16828 The expression may include calls to functions in the program being
16832 @item call @var{expr}
16833 Evaluate the expression @var{expr} without displaying @code{void}
16836 You can use this variant of the @code{print} command if you want to
16837 execute a function from your program that does not return anything
16838 (a.k.a.@: @dfn{a void function}), but without cluttering the output
16839 with @code{void} returned values that @value{GDBN} will otherwise
16840 print. If the result is not void, it is printed and saved in the
16844 It is possible for the function you call via the @code{print} or
16845 @code{call} command to generate a signal (e.g., if there's a bug in
16846 the function, or if you passed it incorrect arguments). What happens
16847 in that case is controlled by the @code{set unwindonsignal} command.
16849 Similarly, with a C@t{++} program it is possible for the function you
16850 call via the @code{print} or @code{call} command to generate an
16851 exception that is not handled due to the constraints of the dummy
16852 frame. In this case, any exception that is raised in the frame, but has
16853 an out-of-frame exception handler will not be found. GDB builds a
16854 dummy-frame for the inferior function call, and the unwinder cannot
16855 seek for exception handlers outside of this dummy-frame. What happens
16856 in that case is controlled by the
16857 @code{set unwind-on-terminating-exception} command.
16860 @item set unwindonsignal
16861 @kindex set unwindonsignal
16862 @cindex unwind stack in called functions
16863 @cindex call dummy stack unwinding
16864 Set unwinding of the stack if a signal is received while in a function
16865 that @value{GDBN} called in the program being debugged. If set to on,
16866 @value{GDBN} unwinds the stack it created for the call and restores
16867 the context to what it was before the call. If set to off (the
16868 default), @value{GDBN} stops in the frame where the signal was
16871 @item show unwindonsignal
16872 @kindex show unwindonsignal
16873 Show the current setting of stack unwinding in the functions called by
16876 @item set unwind-on-terminating-exception
16877 @kindex set unwind-on-terminating-exception
16878 @cindex unwind stack in called functions with unhandled exceptions
16879 @cindex call dummy stack unwinding on unhandled exception.
16880 Set unwinding of the stack if a C@t{++} exception is raised, but left
16881 unhandled while in a function that @value{GDBN} called in the program being
16882 debugged. If set to on (the default), @value{GDBN} unwinds the stack
16883 it created for the call and restores the context to what it was before
16884 the call. If set to off, @value{GDBN} the exception is delivered to
16885 the default C@t{++} exception handler and the inferior terminated.
16887 @item show unwind-on-terminating-exception
16888 @kindex show unwind-on-terminating-exception
16889 Show the current setting of stack unwinding in the functions called by
16894 @cindex weak alias functions
16895 Sometimes, a function you wish to call is actually a @dfn{weak alias}
16896 for another function. In such case, @value{GDBN} might not pick up
16897 the type information, including the types of the function arguments,
16898 which causes @value{GDBN} to call the inferior function incorrectly.
16899 As a result, the called function will function erroneously and may
16900 even crash. A solution to that is to use the name of the aliased
16904 @section Patching Programs
16906 @cindex patching binaries
16907 @cindex writing into executables
16908 @cindex writing into corefiles
16910 By default, @value{GDBN} opens the file containing your program's
16911 executable code (or the corefile) read-only. This prevents accidental
16912 alterations to machine code; but it also prevents you from intentionally
16913 patching your program's binary.
16915 If you'd like to be able to patch the binary, you can specify that
16916 explicitly with the @code{set write} command. For example, you might
16917 want to turn on internal debugging flags, or even to make emergency
16923 @itemx set write off
16924 If you specify @samp{set write on}, @value{GDBN} opens executable and
16925 core files for both reading and writing; if you specify @kbd{set write
16926 off} (the default), @value{GDBN} opens them read-only.
16928 If you have already loaded a file, you must load it again (using the
16929 @code{exec-file} or @code{core-file} command) after changing @code{set
16930 write}, for your new setting to take effect.
16934 Display whether executable files and core files are opened for writing
16935 as well as reading.
16938 @node Compiling and Injecting Code
16939 @section Compiling and injecting code in @value{GDBN}
16940 @cindex injecting code
16941 @cindex writing into executables
16942 @cindex compiling code
16944 @value{GDBN} supports on-demand compilation and code injection into
16945 programs running under @value{GDBN}. GCC 5.0 or higher built with
16946 @file{libcc1.so} must be installed for this functionality to be enabled.
16947 This functionality is implemented with the following commands.
16950 @kindex compile code
16951 @item compile code @var{source-code}
16952 @itemx compile code -raw @var{--} @var{source-code}
16953 Compile @var{source-code} with the compiler language found as the current
16954 language in @value{GDBN} (@pxref{Languages}). If compilation and
16955 injection is not supported with the current language specified in
16956 @value{GDBN}, or the compiler does not support this feature, an error
16957 message will be printed. If @var{source-code} compiles and links
16958 successfully, @value{GDBN} will load the object-code emitted,
16959 and execute it within the context of the currently selected inferior.
16960 It is important to note that the compiled code is executed immediately.
16961 After execution, the compiled code is removed from @value{GDBN} and any
16962 new types or variables you have defined will be deleted.
16964 The command allows you to specify @var{source-code} in two ways.
16965 The simplest method is to provide a single line of code to the command.
16969 compile code printf ("hello world\n");
16972 If you specify options on the command line as well as source code, they
16973 may conflict. The @samp{--} delimiter can be used to separate options
16974 from actual source code. E.g.:
16977 compile code -r -- printf ("hello world\n");
16980 Alternatively you can enter source code as multiple lines of text. To
16981 enter this mode, invoke the @samp{compile code} command without any text
16982 following the command. This will start the multiple-line editor and
16983 allow you to type as many lines of source code as required. When you
16984 have completed typing, enter @samp{end} on its own line to exit the
16989 >printf ("hello\n");
16990 >printf ("world\n");
16994 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
16995 provided @var{source-code} in a callable scope. In this case, you must
16996 specify the entry point of the code by defining a function named
16997 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
16998 inferior. Using @samp{-raw} option may be needed for example when
16999 @var{source-code} requires @samp{#include} lines which may conflict with
17000 inferior symbols otherwise.
17002 @kindex compile file
17003 @item compile file @var{filename}
17004 @itemx compile file -raw @var{filename}
17005 Like @code{compile code}, but take the source code from @var{filename}.
17008 compile file /home/user/example.c
17012 @subsection Caveats when using the @code{compile} command
17014 There are a few caveats to keep in mind when using the @code{compile}
17015 command. As the caveats are different per language, the table below
17016 highlights specific issues on a per language basis.
17019 @item C code examples and caveats
17020 When the language in @value{GDBN} is set to @samp{C}, the compiler will
17021 attempt to compile the source code with a @samp{C} compiler. The source
17022 code provided to the @code{compile} command will have much the same
17023 access to variables and types as it normally would if it were part of
17024 the program currently being debugged in @value{GDBN}.
17026 Below is a sample program that forms the basis of the examples that
17027 follow. This program has been compiled and loaded into @value{GDBN},
17028 much like any other normal debugging session.
17031 void function1 (void)
17034 printf ("function 1\n");
17037 void function2 (void)
17052 For the purposes of the examples in this section, the program above has
17053 been compiled, loaded into @value{GDBN}, stopped at the function
17054 @code{main}, and @value{GDBN} is awaiting input from the user.
17056 To access variables and types for any program in @value{GDBN}, the
17057 program must be compiled and packaged with debug information. The
17058 @code{compile} command is not an exception to this rule. Without debug
17059 information, you can still use the @code{compile} command, but you will
17060 be very limited in what variables and types you can access.
17062 So with that in mind, the example above has been compiled with debug
17063 information enabled. The @code{compile} command will have access to
17064 all variables and types (except those that may have been optimized
17065 out). Currently, as @value{GDBN} has stopped the program in the
17066 @code{main} function, the @code{compile} command would have access to
17067 the variable @code{k}. You could invoke the @code{compile} command
17068 and type some source code to set the value of @code{k}. You can also
17069 read it, or do anything with that variable you would normally do in
17070 @code{C}. Be aware that changes to inferior variables in the
17071 @code{compile} command are persistent. In the following example:
17074 compile code k = 3;
17078 the variable @code{k} is now 3. It will retain that value until
17079 something else in the example program changes it, or another
17080 @code{compile} command changes it.
17082 Normal scope and access rules apply to source code compiled and
17083 injected by the @code{compile} command. In the example, the variables
17084 @code{j} and @code{k} are not accessible yet, because the program is
17085 currently stopped in the @code{main} function, where these variables
17086 are not in scope. Therefore, the following command
17089 compile code j = 3;
17093 will result in a compilation error message.
17095 Once the program is continued, execution will bring these variables in
17096 scope, and they will become accessible; then the code you specify via
17097 the @code{compile} command will be able to access them.
17099 You can create variables and types with the @code{compile} command as
17100 part of your source code. Variables and types that are created as part
17101 of the @code{compile} command are not visible to the rest of the program for
17102 the duration of its run. This example is valid:
17105 compile code int ff = 5; printf ("ff is %d\n", ff);
17108 However, if you were to type the following into @value{GDBN} after that
17109 command has completed:
17112 compile code printf ("ff is %d\n'', ff);
17116 a compiler error would be raised as the variable @code{ff} no longer
17117 exists. Object code generated and injected by the @code{compile}
17118 command is removed when its execution ends. Caution is advised
17119 when assigning to program variables values of variables created by the
17120 code submitted to the @code{compile} command. This example is valid:
17123 compile code int ff = 5; k = ff;
17126 The value of the variable @code{ff} is assigned to @code{k}. The variable
17127 @code{k} does not require the existence of @code{ff} to maintain the value
17128 it has been assigned. However, pointers require particular care in
17129 assignment. If the source code compiled with the @code{compile} command
17130 changed the address of a pointer in the example program, perhaps to a
17131 variable created in the @code{compile} command, that pointer would point
17132 to an invalid location when the command exits. The following example
17133 would likely cause issues with your debugged program:
17136 compile code int ff = 5; p = &ff;
17139 In this example, @code{p} would point to @code{ff} when the
17140 @code{compile} command is executing the source code provided to it.
17141 However, as variables in the (example) program persist with their
17142 assigned values, the variable @code{p} would point to an invalid
17143 location when the command exists. A general rule should be followed
17144 in that you should either assign @code{NULL} to any assigned pointers,
17145 or restore a valid location to the pointer before the command exits.
17147 Similar caution must be exercised with any structs, unions, and typedefs
17148 defined in @code{compile} command. Types defined in the @code{compile}
17149 command will no longer be available in the next @code{compile} command.
17150 Therefore, if you cast a variable to a type defined in the
17151 @code{compile} command, care must be taken to ensure that any future
17152 need to resolve the type can be achieved.
17155 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
17156 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
17157 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
17158 Compilation failed.
17159 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
17163 Variables that have been optimized away by the compiler are not
17164 accessible to the code submitted to the @code{compile} command.
17165 Access to those variables will generate a compiler error which @value{GDBN}
17166 will print to the console.
17170 @chapter @value{GDBN} Files
17172 @value{GDBN} needs to know the file name of the program to be debugged,
17173 both in order to read its symbol table and in order to start your
17174 program. To debug a core dump of a previous run, you must also tell
17175 @value{GDBN} the name of the core dump file.
17178 * Files:: Commands to specify files
17179 * Separate Debug Files:: Debugging information in separate files
17180 * MiniDebugInfo:: Debugging information in a special section
17181 * Index Files:: Index files speed up GDB
17182 * Symbol Errors:: Errors reading symbol files
17183 * Data Files:: GDB data files
17187 @section Commands to Specify Files
17189 @cindex symbol table
17190 @cindex core dump file
17192 You may want to specify executable and core dump file names. The usual
17193 way to do this is at start-up time, using the arguments to
17194 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
17195 Out of @value{GDBN}}).
17197 Occasionally it is necessary to change to a different file during a
17198 @value{GDBN} session. Or you may run @value{GDBN} and forget to
17199 specify a file you want to use. Or you are debugging a remote target
17200 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
17201 Program}). In these situations the @value{GDBN} commands to specify
17202 new files are useful.
17205 @cindex executable file
17207 @item file @var{filename}
17208 Use @var{filename} as the program to be debugged. It is read for its
17209 symbols and for the contents of pure memory. It is also the program
17210 executed when you use the @code{run} command. If you do not specify a
17211 directory and the file is not found in the @value{GDBN} working directory,
17212 @value{GDBN} uses the environment variable @code{PATH} as a list of
17213 directories to search, just as the shell does when looking for a program
17214 to run. You can change the value of this variable, for both @value{GDBN}
17215 and your program, using the @code{path} command.
17217 @cindex unlinked object files
17218 @cindex patching object files
17219 You can load unlinked object @file{.o} files into @value{GDBN} using
17220 the @code{file} command. You will not be able to ``run'' an object
17221 file, but you can disassemble functions and inspect variables. Also,
17222 if the underlying BFD functionality supports it, you could use
17223 @kbd{gdb -write} to patch object files using this technique. Note
17224 that @value{GDBN} can neither interpret nor modify relocations in this
17225 case, so branches and some initialized variables will appear to go to
17226 the wrong place. But this feature is still handy from time to time.
17229 @code{file} with no argument makes @value{GDBN} discard any information it
17230 has on both executable file and the symbol table.
17233 @item exec-file @r{[} @var{filename} @r{]}
17234 Specify that the program to be run (but not the symbol table) is found
17235 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
17236 if necessary to locate your program. Omitting @var{filename} means to
17237 discard information on the executable file.
17239 @kindex symbol-file
17240 @item symbol-file @r{[} @var{filename} @r{]}
17241 Read symbol table information from file @var{filename}. @code{PATH} is
17242 searched when necessary. Use the @code{file} command to get both symbol
17243 table and program to run from the same file.
17245 @code{symbol-file} with no argument clears out @value{GDBN} information on your
17246 program's symbol table.
17248 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
17249 some breakpoints and auto-display expressions. This is because they may
17250 contain pointers to the internal data recording symbols and data types,
17251 which are part of the old symbol table data being discarded inside
17254 @code{symbol-file} does not repeat if you press @key{RET} again after
17257 When @value{GDBN} is configured for a particular environment, it
17258 understands debugging information in whatever format is the standard
17259 generated for that environment; you may use either a @sc{gnu} compiler, or
17260 other compilers that adhere to the local conventions.
17261 Best results are usually obtained from @sc{gnu} compilers; for example,
17262 using @code{@value{NGCC}} you can generate debugging information for
17265 For most kinds of object files, with the exception of old SVR3 systems
17266 using COFF, the @code{symbol-file} command does not normally read the
17267 symbol table in full right away. Instead, it scans the symbol table
17268 quickly to find which source files and which symbols are present. The
17269 details are read later, one source file at a time, as they are needed.
17271 The purpose of this two-stage reading strategy is to make @value{GDBN}
17272 start up faster. For the most part, it is invisible except for
17273 occasional pauses while the symbol table details for a particular source
17274 file are being read. (The @code{set verbose} command can turn these
17275 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
17276 Warnings and Messages}.)
17278 We have not implemented the two-stage strategy for COFF yet. When the
17279 symbol table is stored in COFF format, @code{symbol-file} reads the
17280 symbol table data in full right away. Note that ``stabs-in-COFF''
17281 still does the two-stage strategy, since the debug info is actually
17285 @cindex reading symbols immediately
17286 @cindex symbols, reading immediately
17287 @item symbol-file @r{[} -readnow @r{]} @var{filename}
17288 @itemx file @r{[} -readnow @r{]} @var{filename}
17289 You can override the @value{GDBN} two-stage strategy for reading symbol
17290 tables by using the @samp{-readnow} option with any of the commands that
17291 load symbol table information, if you want to be sure @value{GDBN} has the
17292 entire symbol table available.
17294 @c FIXME: for now no mention of directories, since this seems to be in
17295 @c flux. 13mar1992 status is that in theory GDB would look either in
17296 @c current dir or in same dir as myprog; but issues like competing
17297 @c GDB's, or clutter in system dirs, mean that in practice right now
17298 @c only current dir is used. FFish says maybe a special GDB hierarchy
17299 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
17303 @item core-file @r{[}@var{filename}@r{]}
17305 Specify the whereabouts of a core dump file to be used as the ``contents
17306 of memory''. Traditionally, core files contain only some parts of the
17307 address space of the process that generated them; @value{GDBN} can access the
17308 executable file itself for other parts.
17310 @code{core-file} with no argument specifies that no core file is
17313 Note that the core file is ignored when your program is actually running
17314 under @value{GDBN}. So, if you have been running your program and you
17315 wish to debug a core file instead, you must kill the subprocess in which
17316 the program is running. To do this, use the @code{kill} command
17317 (@pxref{Kill Process, ,Killing the Child Process}).
17319 @kindex add-symbol-file
17320 @cindex dynamic linking
17321 @item add-symbol-file @var{filename} @var{address}
17322 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
17323 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
17324 The @code{add-symbol-file} command reads additional symbol table
17325 information from the file @var{filename}. You would use this command
17326 when @var{filename} has been dynamically loaded (by some other means)
17327 into the program that is running. The @var{address} should give the memory
17328 address at which the file has been loaded; @value{GDBN} cannot figure
17329 this out for itself. You can additionally specify an arbitrary number
17330 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
17331 section name and base address for that section. You can specify any
17332 @var{address} as an expression.
17334 The symbol table of the file @var{filename} is added to the symbol table
17335 originally read with the @code{symbol-file} command. You can use the
17336 @code{add-symbol-file} command any number of times; the new symbol data
17337 thus read is kept in addition to the old.
17339 Changes can be reverted using the command @code{remove-symbol-file}.
17341 @cindex relocatable object files, reading symbols from
17342 @cindex object files, relocatable, reading symbols from
17343 @cindex reading symbols from relocatable object files
17344 @cindex symbols, reading from relocatable object files
17345 @cindex @file{.o} files, reading symbols from
17346 Although @var{filename} is typically a shared library file, an
17347 executable file, or some other object file which has been fully
17348 relocated for loading into a process, you can also load symbolic
17349 information from relocatable @file{.o} files, as long as:
17353 the file's symbolic information refers only to linker symbols defined in
17354 that file, not to symbols defined by other object files,
17356 every section the file's symbolic information refers to has actually
17357 been loaded into the inferior, as it appears in the file, and
17359 you can determine the address at which every section was loaded, and
17360 provide these to the @code{add-symbol-file} command.
17364 Some embedded operating systems, like Sun Chorus and VxWorks, can load
17365 relocatable files into an already running program; such systems
17366 typically make the requirements above easy to meet. However, it's
17367 important to recognize that many native systems use complex link
17368 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
17369 assembly, for example) that make the requirements difficult to meet. In
17370 general, one cannot assume that using @code{add-symbol-file} to read a
17371 relocatable object file's symbolic information will have the same effect
17372 as linking the relocatable object file into the program in the normal
17375 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
17377 @kindex remove-symbol-file
17378 @item remove-symbol-file @var{filename}
17379 @item remove-symbol-file -a @var{address}
17380 Remove a symbol file added via the @code{add-symbol-file} command. The
17381 file to remove can be identified by its @var{filename} or by an @var{address}
17382 that lies within the boundaries of this symbol file in memory. Example:
17385 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
17386 add symbol table from file "/home/user/gdb/mylib.so" at
17387 .text_addr = 0x7ffff7ff9480
17389 Reading symbols from /home/user/gdb/mylib.so...done.
17390 (gdb) remove-symbol-file -a 0x7ffff7ff9480
17391 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
17396 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
17398 @kindex add-symbol-file-from-memory
17399 @cindex @code{syscall DSO}
17400 @cindex load symbols from memory
17401 @item add-symbol-file-from-memory @var{address}
17402 Load symbols from the given @var{address} in a dynamically loaded
17403 object file whose image is mapped directly into the inferior's memory.
17404 For example, the Linux kernel maps a @code{syscall DSO} into each
17405 process's address space; this DSO provides kernel-specific code for
17406 some system calls. The argument can be any expression whose
17407 evaluation yields the address of the file's shared object file header.
17408 For this command to work, you must have used @code{symbol-file} or
17409 @code{exec-file} commands in advance.
17412 @item section @var{section} @var{addr}
17413 The @code{section} command changes the base address of the named
17414 @var{section} of the exec file to @var{addr}. This can be used if the
17415 exec file does not contain section addresses, (such as in the
17416 @code{a.out} format), or when the addresses specified in the file
17417 itself are wrong. Each section must be changed separately. The
17418 @code{info files} command, described below, lists all the sections and
17422 @kindex info target
17425 @code{info files} and @code{info target} are synonymous; both print the
17426 current target (@pxref{Targets, ,Specifying a Debugging Target}),
17427 including the names of the executable and core dump files currently in
17428 use by @value{GDBN}, and the files from which symbols were loaded. The
17429 command @code{help target} lists all possible targets rather than
17432 @kindex maint info sections
17433 @item maint info sections
17434 Another command that can give you extra information about program sections
17435 is @code{maint info sections}. In addition to the section information
17436 displayed by @code{info files}, this command displays the flags and file
17437 offset of each section in the executable and core dump files. In addition,
17438 @code{maint info sections} provides the following command options (which
17439 may be arbitrarily combined):
17443 Display sections for all loaded object files, including shared libraries.
17444 @item @var{sections}
17445 Display info only for named @var{sections}.
17446 @item @var{section-flags}
17447 Display info only for sections for which @var{section-flags} are true.
17448 The section flags that @value{GDBN} currently knows about are:
17451 Section will have space allocated in the process when loaded.
17452 Set for all sections except those containing debug information.
17454 Section will be loaded from the file into the child process memory.
17455 Set for pre-initialized code and data, clear for @code{.bss} sections.
17457 Section needs to be relocated before loading.
17459 Section cannot be modified by the child process.
17461 Section contains executable code only.
17463 Section contains data only (no executable code).
17465 Section will reside in ROM.
17467 Section contains data for constructor/destructor lists.
17469 Section is not empty.
17471 An instruction to the linker to not output the section.
17472 @item COFF_SHARED_LIBRARY
17473 A notification to the linker that the section contains
17474 COFF shared library information.
17476 Section contains common symbols.
17479 @kindex set trust-readonly-sections
17480 @cindex read-only sections
17481 @item set trust-readonly-sections on
17482 Tell @value{GDBN} that readonly sections in your object file
17483 really are read-only (i.e.@: that their contents will not change).
17484 In that case, @value{GDBN} can fetch values from these sections
17485 out of the object file, rather than from the target program.
17486 For some targets (notably embedded ones), this can be a significant
17487 enhancement to debugging performance.
17489 The default is off.
17491 @item set trust-readonly-sections off
17492 Tell @value{GDBN} not to trust readonly sections. This means that
17493 the contents of the section might change while the program is running,
17494 and must therefore be fetched from the target when needed.
17496 @item show trust-readonly-sections
17497 Show the current setting of trusting readonly sections.
17500 All file-specifying commands allow both absolute and relative file names
17501 as arguments. @value{GDBN} always converts the file name to an absolute file
17502 name and remembers it that way.
17504 @cindex shared libraries
17505 @anchor{Shared Libraries}
17506 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
17507 and IBM RS/6000 AIX shared libraries.
17509 On MS-Windows @value{GDBN} must be linked with the Expat library to support
17510 shared libraries. @xref{Expat}.
17512 @value{GDBN} automatically loads symbol definitions from shared libraries
17513 when you use the @code{run} command, or when you examine a core file.
17514 (Before you issue the @code{run} command, @value{GDBN} does not understand
17515 references to a function in a shared library, however---unless you are
17516 debugging a core file).
17518 On HP-UX, if the program loads a library explicitly, @value{GDBN}
17519 automatically loads the symbols at the time of the @code{shl_load} call.
17521 @c FIXME: some @value{GDBN} release may permit some refs to undef
17522 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
17523 @c FIXME...lib; check this from time to time when updating manual
17525 There are times, however, when you may wish to not automatically load
17526 symbol definitions from shared libraries, such as when they are
17527 particularly large or there are many of them.
17529 To control the automatic loading of shared library symbols, use the
17533 @kindex set auto-solib-add
17534 @item set auto-solib-add @var{mode}
17535 If @var{mode} is @code{on}, symbols from all shared object libraries
17536 will be loaded automatically when the inferior begins execution, you
17537 attach to an independently started inferior, or when the dynamic linker
17538 informs @value{GDBN} that a new library has been loaded. If @var{mode}
17539 is @code{off}, symbols must be loaded manually, using the
17540 @code{sharedlibrary} command. The default value is @code{on}.
17542 @cindex memory used for symbol tables
17543 If your program uses lots of shared libraries with debug info that
17544 takes large amounts of memory, you can decrease the @value{GDBN}
17545 memory footprint by preventing it from automatically loading the
17546 symbols from shared libraries. To that end, type @kbd{set
17547 auto-solib-add off} before running the inferior, then load each
17548 library whose debug symbols you do need with @kbd{sharedlibrary
17549 @var{regexp}}, where @var{regexp} is a regular expression that matches
17550 the libraries whose symbols you want to be loaded.
17552 @kindex show auto-solib-add
17553 @item show auto-solib-add
17554 Display the current autoloading mode.
17557 @cindex load shared library
17558 To explicitly load shared library symbols, use the @code{sharedlibrary}
17562 @kindex info sharedlibrary
17564 @item info share @var{regex}
17565 @itemx info sharedlibrary @var{regex}
17566 Print the names of the shared libraries which are currently loaded
17567 that match @var{regex}. If @var{regex} is omitted then print
17568 all shared libraries that are loaded.
17570 @kindex sharedlibrary
17572 @item sharedlibrary @var{regex}
17573 @itemx share @var{regex}
17574 Load shared object library symbols for files matching a
17575 Unix regular expression.
17576 As with files loaded automatically, it only loads shared libraries
17577 required by your program for a core file or after typing @code{run}. If
17578 @var{regex} is omitted all shared libraries required by your program are
17581 @item nosharedlibrary
17582 @kindex nosharedlibrary
17583 @cindex unload symbols from shared libraries
17584 Unload all shared object library symbols. This discards all symbols
17585 that have been loaded from all shared libraries. Symbols from shared
17586 libraries that were loaded by explicit user requests are not
17590 Sometimes you may wish that @value{GDBN} stops and gives you control
17591 when any of shared library events happen. The best way to do this is
17592 to use @code{catch load} and @code{catch unload} (@pxref{Set
17595 @value{GDBN} also supports the the @code{set stop-on-solib-events}
17596 command for this. This command exists for historical reasons. It is
17597 less useful than setting a catchpoint, because it does not allow for
17598 conditions or commands as a catchpoint does.
17601 @item set stop-on-solib-events
17602 @kindex set stop-on-solib-events
17603 This command controls whether @value{GDBN} should give you control
17604 when the dynamic linker notifies it about some shared library event.
17605 The most common event of interest is loading or unloading of a new
17608 @item show stop-on-solib-events
17609 @kindex show stop-on-solib-events
17610 Show whether @value{GDBN} stops and gives you control when shared
17611 library events happen.
17614 Shared libraries are also supported in many cross or remote debugging
17615 configurations. @value{GDBN} needs to have access to the target's libraries;
17616 this can be accomplished either by providing copies of the libraries
17617 on the host system, or by asking @value{GDBN} to automatically retrieve the
17618 libraries from the target. If copies of the target libraries are
17619 provided, they need to be the same as the target libraries, although the
17620 copies on the target can be stripped as long as the copies on the host are
17623 @cindex where to look for shared libraries
17624 For remote debugging, you need to tell @value{GDBN} where the target
17625 libraries are, so that it can load the correct copies---otherwise, it
17626 may try to load the host's libraries. @value{GDBN} has two variables
17627 to specify the search directories for target libraries.
17630 @cindex prefix for shared library file names
17631 @cindex system root, alternate
17632 @kindex set solib-absolute-prefix
17633 @kindex set sysroot
17634 @item set sysroot @var{path}
17635 Use @var{path} as the system root for the program being debugged. Any
17636 absolute shared library paths will be prefixed with @var{path}; many
17637 runtime loaders store the absolute paths to the shared library in the
17638 target program's memory. If you use @code{set sysroot} to find shared
17639 libraries, they need to be laid out in the same way that they are on
17640 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
17643 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
17644 retrieve the target libraries from the remote system. This is only
17645 supported when using a remote target that supports the @code{remote get}
17646 command (@pxref{File Transfer,,Sending files to a remote system}).
17647 The part of @var{path} following the initial @file{remote:}
17648 (if present) is used as system root prefix on the remote file system.
17649 @footnote{If you want to specify a local system root using a directory
17650 that happens to be named @file{remote:}, you need to use some equivalent
17651 variant of the name like @file{./remote:}.}
17653 For targets with an MS-DOS based filesystem, such as MS-Windows and
17654 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
17655 absolute file name with @var{path}. But first, on Unix hosts,
17656 @value{GDBN} converts all backslash directory separators into forward
17657 slashes, because the backslash is not a directory separator on Unix:
17660 c:\foo\bar.dll @result{} c:/foo/bar.dll
17663 Then, @value{GDBN} attempts prefixing the target file name with
17664 @var{path}, and looks for the resulting file name in the host file
17668 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
17671 If that does not find the shared library, @value{GDBN} tries removing
17672 the @samp{:} character from the drive spec, both for convenience, and,
17673 for the case of the host file system not supporting file names with
17677 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
17680 This makes it possible to have a system root that mirrors a target
17681 with more than one drive. E.g., you may want to setup your local
17682 copies of the target system shared libraries like so (note @samp{c} vs
17686 @file{/path/to/sysroot/c/sys/bin/foo.dll}
17687 @file{/path/to/sysroot/c/sys/bin/bar.dll}
17688 @file{/path/to/sysroot/z/sys/bin/bar.dll}
17692 and point the system root at @file{/path/to/sysroot}, so that
17693 @value{GDBN} can find the correct copies of both
17694 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
17696 If that still does not find the shared library, @value{GDBN} tries
17697 removing the whole drive spec from the target file name:
17700 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
17703 This last lookup makes it possible to not care about the drive name,
17704 if you don't want or need to.
17706 The @code{set solib-absolute-prefix} command is an alias for @code{set
17709 @cindex default system root
17710 @cindex @samp{--with-sysroot}
17711 You can set the default system root by using the configure-time
17712 @samp{--with-sysroot} option. If the system root is inside
17713 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17714 @samp{--exec-prefix}), then the default system root will be updated
17715 automatically if the installed @value{GDBN} is moved to a new
17718 @kindex show sysroot
17720 Display the current shared library prefix.
17722 @kindex set solib-search-path
17723 @item set solib-search-path @var{path}
17724 If this variable is set, @var{path} is a colon-separated list of
17725 directories to search for shared libraries. @samp{solib-search-path}
17726 is used after @samp{sysroot} fails to locate the library, or if the
17727 path to the library is relative instead of absolute. If you want to
17728 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
17729 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
17730 finding your host's libraries. @samp{sysroot} is preferred; setting
17731 it to a nonexistent directory may interfere with automatic loading
17732 of shared library symbols.
17734 @kindex show solib-search-path
17735 @item show solib-search-path
17736 Display the current shared library search path.
17738 @cindex DOS file-name semantics of file names.
17739 @kindex set target-file-system-kind (unix|dos-based|auto)
17740 @kindex show target-file-system-kind
17741 @item set target-file-system-kind @var{kind}
17742 Set assumed file system kind for target reported file names.
17744 Shared library file names as reported by the target system may not
17745 make sense as is on the system @value{GDBN} is running on. For
17746 example, when remote debugging a target that has MS-DOS based file
17747 system semantics, from a Unix host, the target may be reporting to
17748 @value{GDBN} a list of loaded shared libraries with file names such as
17749 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
17750 drive letters, so the @samp{c:\} prefix is not normally understood as
17751 indicating an absolute file name, and neither is the backslash
17752 normally considered a directory separator character. In that case,
17753 the native file system would interpret this whole absolute file name
17754 as a relative file name with no directory components. This would make
17755 it impossible to point @value{GDBN} at a copy of the remote target's
17756 shared libraries on the host using @code{set sysroot}, and impractical
17757 with @code{set solib-search-path}. Setting
17758 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
17759 to interpret such file names similarly to how the target would, and to
17760 map them to file names valid on @value{GDBN}'s native file system
17761 semantics. The value of @var{kind} can be @code{"auto"}, in addition
17762 to one of the supported file system kinds. In that case, @value{GDBN}
17763 tries to determine the appropriate file system variant based on the
17764 current target's operating system (@pxref{ABI, ,Configuring the
17765 Current ABI}). The supported file system settings are:
17769 Instruct @value{GDBN} to assume the target file system is of Unix
17770 kind. Only file names starting the forward slash (@samp{/}) character
17771 are considered absolute, and the directory separator character is also
17775 Instruct @value{GDBN} to assume the target file system is DOS based.
17776 File names starting with either a forward slash, or a drive letter
17777 followed by a colon (e.g., @samp{c:}), are considered absolute, and
17778 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
17779 considered directory separators.
17782 Instruct @value{GDBN} to use the file system kind associated with the
17783 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
17784 This is the default.
17788 @cindex file name canonicalization
17789 @cindex base name differences
17790 When processing file names provided by the user, @value{GDBN}
17791 frequently needs to compare them to the file names recorded in the
17792 program's debug info. Normally, @value{GDBN} compares just the
17793 @dfn{base names} of the files as strings, which is reasonably fast
17794 even for very large programs. (The base name of a file is the last
17795 portion of its name, after stripping all the leading directories.)
17796 This shortcut in comparison is based upon the assumption that files
17797 cannot have more than one base name. This is usually true, but
17798 references to files that use symlinks or similar filesystem
17799 facilities violate that assumption. If your program records files
17800 using such facilities, or if you provide file names to @value{GDBN}
17801 using symlinks etc., you can set @code{basenames-may-differ} to
17802 @code{true} to instruct @value{GDBN} to completely canonicalize each
17803 pair of file names it needs to compare. This will make file-name
17804 comparisons accurate, but at a price of a significant slowdown.
17807 @item set basenames-may-differ
17808 @kindex set basenames-may-differ
17809 Set whether a source file may have multiple base names.
17811 @item show basenames-may-differ
17812 @kindex show basenames-may-differ
17813 Show whether a source file may have multiple base names.
17816 @node Separate Debug Files
17817 @section Debugging Information in Separate Files
17818 @cindex separate debugging information files
17819 @cindex debugging information in separate files
17820 @cindex @file{.debug} subdirectories
17821 @cindex debugging information directory, global
17822 @cindex global debugging information directories
17823 @cindex build ID, and separate debugging files
17824 @cindex @file{.build-id} directory
17826 @value{GDBN} allows you to put a program's debugging information in a
17827 file separate from the executable itself, in a way that allows
17828 @value{GDBN} to find and load the debugging information automatically.
17829 Since debugging information can be very large---sometimes larger
17830 than the executable code itself---some systems distribute debugging
17831 information for their executables in separate files, which users can
17832 install only when they need to debug a problem.
17834 @value{GDBN} supports two ways of specifying the separate debug info
17839 The executable contains a @dfn{debug link} that specifies the name of
17840 the separate debug info file. The separate debug file's name is
17841 usually @file{@var{executable}.debug}, where @var{executable} is the
17842 name of the corresponding executable file without leading directories
17843 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
17844 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
17845 checksum for the debug file, which @value{GDBN} uses to validate that
17846 the executable and the debug file came from the same build.
17849 The executable contains a @dfn{build ID}, a unique bit string that is
17850 also present in the corresponding debug info file. (This is supported
17851 only on some operating systems, notably those which use the ELF format
17852 for binary files and the @sc{gnu} Binutils.) For more details about
17853 this feature, see the description of the @option{--build-id}
17854 command-line option in @ref{Options, , Command Line Options, ld.info,
17855 The GNU Linker}. The debug info file's name is not specified
17856 explicitly by the build ID, but can be computed from the build ID, see
17860 Depending on the way the debug info file is specified, @value{GDBN}
17861 uses two different methods of looking for the debug file:
17865 For the ``debug link'' method, @value{GDBN} looks up the named file in
17866 the directory of the executable file, then in a subdirectory of that
17867 directory named @file{.debug}, and finally under each one of the global debug
17868 directories, in a subdirectory whose name is identical to the leading
17869 directories of the executable's absolute file name.
17872 For the ``build ID'' method, @value{GDBN} looks in the
17873 @file{.build-id} subdirectory of each one of the global debug directories for
17874 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
17875 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
17876 are the rest of the bit string. (Real build ID strings are 32 or more
17877 hex characters, not 10.)
17880 So, for example, suppose you ask @value{GDBN} to debug
17881 @file{/usr/bin/ls}, which has a debug link that specifies the
17882 file @file{ls.debug}, and a build ID whose value in hex is
17883 @code{abcdef1234}. If the list of the global debug directories includes
17884 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
17885 debug information files, in the indicated order:
17889 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
17891 @file{/usr/bin/ls.debug}
17893 @file{/usr/bin/.debug/ls.debug}
17895 @file{/usr/lib/debug/usr/bin/ls.debug}.
17898 @anchor{debug-file-directory}
17899 Global debugging info directories default to what is set by @value{GDBN}
17900 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
17901 you can also set the global debugging info directories, and view the list
17902 @value{GDBN} is currently using.
17906 @kindex set debug-file-directory
17907 @item set debug-file-directory @var{directories}
17908 Set the directories which @value{GDBN} searches for separate debugging
17909 information files to @var{directory}. Multiple path components can be set
17910 concatenating them by a path separator.
17912 @kindex show debug-file-directory
17913 @item show debug-file-directory
17914 Show the directories @value{GDBN} searches for separate debugging
17919 @cindex @code{.gnu_debuglink} sections
17920 @cindex debug link sections
17921 A debug link is a special section of the executable file named
17922 @code{.gnu_debuglink}. The section must contain:
17926 A filename, with any leading directory components removed, followed by
17929 zero to three bytes of padding, as needed to reach the next four-byte
17930 boundary within the section, and
17932 a four-byte CRC checksum, stored in the same endianness used for the
17933 executable file itself. The checksum is computed on the debugging
17934 information file's full contents by the function given below, passing
17935 zero as the @var{crc} argument.
17938 Any executable file format can carry a debug link, as long as it can
17939 contain a section named @code{.gnu_debuglink} with the contents
17942 @cindex @code{.note.gnu.build-id} sections
17943 @cindex build ID sections
17944 The build ID is a special section in the executable file (and in other
17945 ELF binary files that @value{GDBN} may consider). This section is
17946 often named @code{.note.gnu.build-id}, but that name is not mandatory.
17947 It contains unique identification for the built files---the ID remains
17948 the same across multiple builds of the same build tree. The default
17949 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
17950 content for the build ID string. The same section with an identical
17951 value is present in the original built binary with symbols, in its
17952 stripped variant, and in the separate debugging information file.
17954 The debugging information file itself should be an ordinary
17955 executable, containing a full set of linker symbols, sections, and
17956 debugging information. The sections of the debugging information file
17957 should have the same names, addresses, and sizes as the original file,
17958 but they need not contain any data---much like a @code{.bss} section
17959 in an ordinary executable.
17961 The @sc{gnu} binary utilities (Binutils) package includes the
17962 @samp{objcopy} utility that can produce
17963 the separated executable / debugging information file pairs using the
17964 following commands:
17967 @kbd{objcopy --only-keep-debug foo foo.debug}
17972 These commands remove the debugging
17973 information from the executable file @file{foo} and place it in the file
17974 @file{foo.debug}. You can use the first, second or both methods to link the
17979 The debug link method needs the following additional command to also leave
17980 behind a debug link in @file{foo}:
17983 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
17986 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
17987 a version of the @code{strip} command such that the command @kbd{strip foo -f
17988 foo.debug} has the same functionality as the two @code{objcopy} commands and
17989 the @code{ln -s} command above, together.
17992 Build ID gets embedded into the main executable using @code{ld --build-id} or
17993 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
17994 compatibility fixes for debug files separation are present in @sc{gnu} binary
17995 utilities (Binutils) package since version 2.18.
18000 @cindex CRC algorithm definition
18001 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
18002 IEEE 802.3 using the polynomial:
18004 @c TexInfo requires naked braces for multi-digit exponents for Tex
18005 @c output, but this causes HTML output to barf. HTML has to be set using
18006 @c raw commands. So we end up having to specify this equation in 2
18011 <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>
18012 + <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
18018 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
18019 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
18023 The function is computed byte at a time, taking the least
18024 significant bit of each byte first. The initial pattern
18025 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
18026 the final result is inverted to ensure trailing zeros also affect the
18029 @emph{Note:} This is the same CRC polynomial as used in handling the
18030 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
18031 However in the case of the Remote Serial Protocol, the CRC is computed
18032 @emph{most} significant bit first, and the result is not inverted, so
18033 trailing zeros have no effect on the CRC value.
18035 To complete the description, we show below the code of the function
18036 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
18037 initially supplied @code{crc} argument means that an initial call to
18038 this function passing in zero will start computing the CRC using
18041 @kindex gnu_debuglink_crc32
18044 gnu_debuglink_crc32 (unsigned long crc,
18045 unsigned char *buf, size_t len)
18047 static const unsigned long crc32_table[256] =
18049 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
18050 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
18051 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
18052 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
18053 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
18054 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
18055 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
18056 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
18057 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
18058 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
18059 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
18060 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
18061 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
18062 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
18063 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
18064 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
18065 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
18066 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
18067 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
18068 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
18069 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
18070 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
18071 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
18072 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
18073 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
18074 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
18075 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
18076 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
18077 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
18078 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
18079 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
18080 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
18081 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
18082 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
18083 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
18084 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
18085 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
18086 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
18087 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
18088 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
18089 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
18090 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
18091 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
18092 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
18093 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
18094 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
18095 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
18096 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
18097 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
18098 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
18099 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
18102 unsigned char *end;
18104 crc = ~crc & 0xffffffff;
18105 for (end = buf + len; buf < end; ++buf)
18106 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
18107 return ~crc & 0xffffffff;
18112 This computation does not apply to the ``build ID'' method.
18114 @node MiniDebugInfo
18115 @section Debugging information in a special section
18116 @cindex separate debug sections
18117 @cindex @samp{.gnu_debugdata} section
18119 Some systems ship pre-built executables and libraries that have a
18120 special @samp{.gnu_debugdata} section. This feature is called
18121 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
18122 is used to supply extra symbols for backtraces.
18124 The intent of this section is to provide extra minimal debugging
18125 information for use in simple backtraces. It is not intended to be a
18126 replacement for full separate debugging information (@pxref{Separate
18127 Debug Files}). The example below shows the intended use; however,
18128 @value{GDBN} does not currently put restrictions on what sort of
18129 debugging information might be included in the section.
18131 @value{GDBN} has support for this extension. If the section exists,
18132 then it is used provided that no other source of debugging information
18133 can be found, and that @value{GDBN} was configured with LZMA support.
18135 This section can be easily created using @command{objcopy} and other
18136 standard utilities:
18139 # Extract the dynamic symbols from the main binary, there is no need
18140 # to also have these in the normal symbol table.
18141 nm -D @var{binary} --format=posix --defined-only \
18142 | awk '@{ print $1 @}' | sort > dynsyms
18144 # Extract all the text (i.e. function) symbols from the debuginfo.
18145 # (Note that we actually also accept "D" symbols, for the benefit
18146 # of platforms like PowerPC64 that use function descriptors.)
18147 nm @var{binary} --format=posix --defined-only \
18148 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
18151 # Keep all the function symbols not already in the dynamic symbol
18153 comm -13 dynsyms funcsyms > keep_symbols
18155 # Separate full debug info into debug binary.
18156 objcopy --only-keep-debug @var{binary} debug
18158 # Copy the full debuginfo, keeping only a minimal set of symbols and
18159 # removing some unnecessary sections.
18160 objcopy -S --remove-section .gdb_index --remove-section .comment \
18161 --keep-symbols=keep_symbols debug mini_debuginfo
18163 # Drop the full debug info from the original binary.
18164 strip --strip-all -R .comment @var{binary}
18166 # Inject the compressed data into the .gnu_debugdata section of the
18169 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
18173 @section Index Files Speed Up @value{GDBN}
18174 @cindex index files
18175 @cindex @samp{.gdb_index} section
18177 When @value{GDBN} finds a symbol file, it scans the symbols in the
18178 file in order to construct an internal symbol table. This lets most
18179 @value{GDBN} operations work quickly---at the cost of a delay early
18180 on. For large programs, this delay can be quite lengthy, so
18181 @value{GDBN} provides a way to build an index, which speeds up
18184 The index is stored as a section in the symbol file. @value{GDBN} can
18185 write the index to a file, then you can put it into the symbol file
18186 using @command{objcopy}.
18188 To create an index file, use the @code{save gdb-index} command:
18191 @item save gdb-index @var{directory}
18192 @kindex save gdb-index
18193 Create an index file for each symbol file currently known by
18194 @value{GDBN}. Each file is named after its corresponding symbol file,
18195 with @samp{.gdb-index} appended, and is written into the given
18199 Once you have created an index file you can merge it into your symbol
18200 file, here named @file{symfile}, using @command{objcopy}:
18203 $ objcopy --add-section .gdb_index=symfile.gdb-index \
18204 --set-section-flags .gdb_index=readonly symfile symfile
18207 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
18208 sections that have been deprecated. Usually they are deprecated because
18209 they are missing a new feature or have performance issues.
18210 To tell @value{GDBN} to use a deprecated index section anyway
18211 specify @code{set use-deprecated-index-sections on}.
18212 The default is @code{off}.
18213 This can speed up startup, but may result in some functionality being lost.
18214 @xref{Index Section Format}.
18216 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
18217 must be done before gdb reads the file. The following will not work:
18220 $ gdb -ex "set use-deprecated-index-sections on" <program>
18223 Instead you must do, for example,
18226 $ gdb -iex "set use-deprecated-index-sections on" <program>
18229 There are currently some limitation on indices. They only work when
18230 for DWARF debugging information, not stabs. And, they do not
18231 currently work for programs using Ada.
18233 @node Symbol Errors
18234 @section Errors Reading Symbol Files
18236 While reading a symbol file, @value{GDBN} occasionally encounters problems,
18237 such as symbol types it does not recognize, or known bugs in compiler
18238 output. By default, @value{GDBN} does not notify you of such problems, since
18239 they are relatively common and primarily of interest to people
18240 debugging compilers. If you are interested in seeing information
18241 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
18242 only one message about each such type of problem, no matter how many
18243 times the problem occurs; or you can ask @value{GDBN} to print more messages,
18244 to see how many times the problems occur, with the @code{set
18245 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
18248 The messages currently printed, and their meanings, include:
18251 @item inner block not inside outer block in @var{symbol}
18253 The symbol information shows where symbol scopes begin and end
18254 (such as at the start of a function or a block of statements). This
18255 error indicates that an inner scope block is not fully contained
18256 in its outer scope blocks.
18258 @value{GDBN} circumvents the problem by treating the inner block as if it had
18259 the same scope as the outer block. In the error message, @var{symbol}
18260 may be shown as ``@code{(don't know)}'' if the outer block is not a
18263 @item block at @var{address} out of order
18265 The symbol information for symbol scope blocks should occur in
18266 order of increasing addresses. This error indicates that it does not
18269 @value{GDBN} does not circumvent this problem, and has trouble
18270 locating symbols in the source file whose symbols it is reading. (You
18271 can often determine what source file is affected by specifying
18272 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
18275 @item bad block start address patched
18277 The symbol information for a symbol scope block has a start address
18278 smaller than the address of the preceding source line. This is known
18279 to occur in the SunOS 4.1.1 (and earlier) C compiler.
18281 @value{GDBN} circumvents the problem by treating the symbol scope block as
18282 starting on the previous source line.
18284 @item bad string table offset in symbol @var{n}
18287 Symbol number @var{n} contains a pointer into the string table which is
18288 larger than the size of the string table.
18290 @value{GDBN} circumvents the problem by considering the symbol to have the
18291 name @code{foo}, which may cause other problems if many symbols end up
18294 @item unknown symbol type @code{0x@var{nn}}
18296 The symbol information contains new data types that @value{GDBN} does
18297 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
18298 uncomprehended information, in hexadecimal.
18300 @value{GDBN} circumvents the error by ignoring this symbol information.
18301 This usually allows you to debug your program, though certain symbols
18302 are not accessible. If you encounter such a problem and feel like
18303 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
18304 on @code{complain}, then go up to the function @code{read_dbx_symtab}
18305 and examine @code{*bufp} to see the symbol.
18307 @item stub type has NULL name
18309 @value{GDBN} could not find the full definition for a struct or class.
18311 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
18312 The symbol information for a C@t{++} member function is missing some
18313 information that recent versions of the compiler should have output for
18316 @item info mismatch between compiler and debugger
18318 @value{GDBN} could not parse a type specification output by the compiler.
18323 @section GDB Data Files
18325 @cindex prefix for data files
18326 @value{GDBN} will sometimes read an auxiliary data file. These files
18327 are kept in a directory known as the @dfn{data directory}.
18329 You can set the data directory's name, and view the name @value{GDBN}
18330 is currently using.
18333 @kindex set data-directory
18334 @item set data-directory @var{directory}
18335 Set the directory which @value{GDBN} searches for auxiliary data files
18336 to @var{directory}.
18338 @kindex show data-directory
18339 @item show data-directory
18340 Show the directory @value{GDBN} searches for auxiliary data files.
18343 @cindex default data directory
18344 @cindex @samp{--with-gdb-datadir}
18345 You can set the default data directory by using the configure-time
18346 @samp{--with-gdb-datadir} option. If the data directory is inside
18347 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
18348 @samp{--exec-prefix}), then the default data directory will be updated
18349 automatically if the installed @value{GDBN} is moved to a new
18352 The data directory may also be specified with the
18353 @code{--data-directory} command line option.
18354 @xref{Mode Options}.
18357 @chapter Specifying a Debugging Target
18359 @cindex debugging target
18360 A @dfn{target} is the execution environment occupied by your program.
18362 Often, @value{GDBN} runs in the same host environment as your program;
18363 in that case, the debugging target is specified as a side effect when
18364 you use the @code{file} or @code{core} commands. When you need more
18365 flexibility---for example, running @value{GDBN} on a physically separate
18366 host, or controlling a standalone system over a serial port or a
18367 realtime system over a TCP/IP connection---you can use the @code{target}
18368 command to specify one of the target types configured for @value{GDBN}
18369 (@pxref{Target Commands, ,Commands for Managing Targets}).
18371 @cindex target architecture
18372 It is possible to build @value{GDBN} for several different @dfn{target
18373 architectures}. When @value{GDBN} is built like that, you can choose
18374 one of the available architectures with the @kbd{set architecture}
18378 @kindex set architecture
18379 @kindex show architecture
18380 @item set architecture @var{arch}
18381 This command sets the current target architecture to @var{arch}. The
18382 value of @var{arch} can be @code{"auto"}, in addition to one of the
18383 supported architectures.
18385 @item show architecture
18386 Show the current target architecture.
18388 @item set processor
18390 @kindex set processor
18391 @kindex show processor
18392 These are alias commands for, respectively, @code{set architecture}
18393 and @code{show architecture}.
18397 * Active Targets:: Active targets
18398 * Target Commands:: Commands for managing targets
18399 * Byte Order:: Choosing target byte order
18402 @node Active Targets
18403 @section Active Targets
18405 @cindex stacking targets
18406 @cindex active targets
18407 @cindex multiple targets
18409 There are multiple classes of targets such as: processes, executable files or
18410 recording sessions. Core files belong to the process class, making core file
18411 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
18412 on multiple active targets, one in each class. This allows you to (for
18413 example) start a process and inspect its activity, while still having access to
18414 the executable file after the process finishes. Or if you start process
18415 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
18416 presented a virtual layer of the recording target, while the process target
18417 remains stopped at the chronologically last point of the process execution.
18419 Use the @code{core-file} and @code{exec-file} commands to select a new core
18420 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
18421 specify as a target a process that is already running, use the @code{attach}
18422 command (@pxref{Attach, ,Debugging an Already-running Process}).
18424 @node Target Commands
18425 @section Commands for Managing Targets
18428 @item target @var{type} @var{parameters}
18429 Connects the @value{GDBN} host environment to a target machine or
18430 process. A target is typically a protocol for talking to debugging
18431 facilities. You use the argument @var{type} to specify the type or
18432 protocol of the target machine.
18434 Further @var{parameters} are interpreted by the target protocol, but
18435 typically include things like device names or host names to connect
18436 with, process numbers, and baud rates.
18438 The @code{target} command does not repeat if you press @key{RET} again
18439 after executing the command.
18441 @kindex help target
18443 Displays the names of all targets available. To display targets
18444 currently selected, use either @code{info target} or @code{info files}
18445 (@pxref{Files, ,Commands to Specify Files}).
18447 @item help target @var{name}
18448 Describe a particular target, including any parameters necessary to
18451 @kindex set gnutarget
18452 @item set gnutarget @var{args}
18453 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
18454 knows whether it is reading an @dfn{executable},
18455 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
18456 with the @code{set gnutarget} command. Unlike most @code{target} commands,
18457 with @code{gnutarget} the @code{target} refers to a program, not a machine.
18460 @emph{Warning:} To specify a file format with @code{set gnutarget},
18461 you must know the actual BFD name.
18465 @xref{Files, , Commands to Specify Files}.
18467 @kindex show gnutarget
18468 @item show gnutarget
18469 Use the @code{show gnutarget} command to display what file format
18470 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
18471 @value{GDBN} will determine the file format for each file automatically,
18472 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
18475 @cindex common targets
18476 Here are some common targets (available, or not, depending on the GDB
18481 @item target exec @var{program}
18482 @cindex executable file target
18483 An executable file. @samp{target exec @var{program}} is the same as
18484 @samp{exec-file @var{program}}.
18486 @item target core @var{filename}
18487 @cindex core dump file target
18488 A core dump file. @samp{target core @var{filename}} is the same as
18489 @samp{core-file @var{filename}}.
18491 @item target remote @var{medium}
18492 @cindex remote target
18493 A remote system connected to @value{GDBN} via a serial line or network
18494 connection. This command tells @value{GDBN} to use its own remote
18495 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
18497 For example, if you have a board connected to @file{/dev/ttya} on the
18498 machine running @value{GDBN}, you could say:
18501 target remote /dev/ttya
18504 @code{target remote} supports the @code{load} command. This is only
18505 useful if you have some other way of getting the stub to the target
18506 system, and you can put it somewhere in memory where it won't get
18507 clobbered by the download.
18509 @item target sim @r{[}@var{simargs}@r{]} @dots{}
18510 @cindex built-in simulator target
18511 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
18519 works; however, you cannot assume that a specific memory map, device
18520 drivers, or even basic I/O is available, although some simulators do
18521 provide these. For info about any processor-specific simulator details,
18522 see the appropriate section in @ref{Embedded Processors, ,Embedded
18525 @item target native
18526 @cindex native target
18527 Setup for local/native process debugging. Useful to make the
18528 @code{run} command spawn native processes (likewise @code{attach},
18529 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
18530 (@pxref{set auto-connect-native-target}).
18534 Different targets are available on different configurations of @value{GDBN};
18535 your configuration may have more or fewer targets.
18537 Many remote targets require you to download the executable's code once
18538 you've successfully established a connection. You may wish to control
18539 various aspects of this process.
18544 @kindex set hash@r{, for remote monitors}
18545 @cindex hash mark while downloading
18546 This command controls whether a hash mark @samp{#} is displayed while
18547 downloading a file to the remote monitor. If on, a hash mark is
18548 displayed after each S-record is successfully downloaded to the
18552 @kindex show hash@r{, for remote monitors}
18553 Show the current status of displaying the hash mark.
18555 @item set debug monitor
18556 @kindex set debug monitor
18557 @cindex display remote monitor communications
18558 Enable or disable display of communications messages between
18559 @value{GDBN} and the remote monitor.
18561 @item show debug monitor
18562 @kindex show debug monitor
18563 Show the current status of displaying communications between
18564 @value{GDBN} and the remote monitor.
18569 @kindex load @var{filename}
18570 @item load @var{filename}
18572 Depending on what remote debugging facilities are configured into
18573 @value{GDBN}, the @code{load} command may be available. Where it exists, it
18574 is meant to make @var{filename} (an executable) available for debugging
18575 on the remote system---by downloading, or dynamic linking, for example.
18576 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
18577 the @code{add-symbol-file} command.
18579 If your @value{GDBN} does not have a @code{load} command, attempting to
18580 execute it gets the error message ``@code{You can't do that when your
18581 target is @dots{}}''
18583 The file is loaded at whatever address is specified in the executable.
18584 For some object file formats, you can specify the load address when you
18585 link the program; for other formats, like a.out, the object file format
18586 specifies a fixed address.
18587 @c FIXME! This would be a good place for an xref to the GNU linker doc.
18589 Depending on the remote side capabilities, @value{GDBN} may be able to
18590 load programs into flash memory.
18592 @code{load} does not repeat if you press @key{RET} again after using it.
18596 @section Choosing Target Byte Order
18598 @cindex choosing target byte order
18599 @cindex target byte order
18601 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
18602 offer the ability to run either big-endian or little-endian byte
18603 orders. Usually the executable or symbol will include a bit to
18604 designate the endian-ness, and you will not need to worry about
18605 which to use. However, you may still find it useful to adjust
18606 @value{GDBN}'s idea of processor endian-ness manually.
18610 @item set endian big
18611 Instruct @value{GDBN} to assume the target is big-endian.
18613 @item set endian little
18614 Instruct @value{GDBN} to assume the target is little-endian.
18616 @item set endian auto
18617 Instruct @value{GDBN} to use the byte order associated with the
18621 Display @value{GDBN}'s current idea of the target byte order.
18625 Note that these commands merely adjust interpretation of symbolic
18626 data on the host, and that they have absolutely no effect on the
18630 @node Remote Debugging
18631 @chapter Debugging Remote Programs
18632 @cindex remote debugging
18634 If you are trying to debug a program running on a machine that cannot run
18635 @value{GDBN} in the usual way, it is often useful to use remote debugging.
18636 For example, you might use remote debugging on an operating system kernel,
18637 or on a small system which does not have a general purpose operating system
18638 powerful enough to run a full-featured debugger.
18640 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
18641 to make this work with particular debugging targets. In addition,
18642 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
18643 but not specific to any particular target system) which you can use if you
18644 write the remote stubs---the code that runs on the remote system to
18645 communicate with @value{GDBN}.
18647 Other remote targets may be available in your
18648 configuration of @value{GDBN}; use @code{help target} to list them.
18651 * Connecting:: Connecting to a remote target
18652 * File Transfer:: Sending files to a remote system
18653 * Server:: Using the gdbserver program
18654 * Remote Configuration:: Remote configuration
18655 * Remote Stub:: Implementing a remote stub
18659 @section Connecting to a Remote Target
18661 On the @value{GDBN} host machine, you will need an unstripped copy of
18662 your program, since @value{GDBN} needs symbol and debugging information.
18663 Start up @value{GDBN} as usual, using the name of the local copy of your
18664 program as the first argument.
18666 @cindex @code{target remote}
18667 @value{GDBN} can communicate with the target over a serial line, or
18668 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
18669 each case, @value{GDBN} uses the same protocol for debugging your
18670 program; only the medium carrying the debugging packets varies. The
18671 @code{target remote} command establishes a connection to the target.
18672 Its arguments indicate which medium to use:
18676 @item target remote @var{serial-device}
18677 @cindex serial line, @code{target remote}
18678 Use @var{serial-device} to communicate with the target. For example,
18679 to use a serial line connected to the device named @file{/dev/ttyb}:
18682 target remote /dev/ttyb
18685 If you're using a serial line, you may want to give @value{GDBN} the
18686 @samp{--baud} option, or use the @code{set serial baud} command
18687 (@pxref{Remote Configuration, set serial baud}) before the
18688 @code{target} command.
18690 @item target remote @code{@var{host}:@var{port}}
18691 @itemx target remote @code{tcp:@var{host}:@var{port}}
18692 @cindex @acronym{TCP} port, @code{target remote}
18693 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
18694 The @var{host} may be either a host name or a numeric @acronym{IP}
18695 address; @var{port} must be a decimal number. The @var{host} could be
18696 the target machine itself, if it is directly connected to the net, or
18697 it might be a terminal server which in turn has a serial line to the
18700 For example, to connect to port 2828 on a terminal server named
18704 target remote manyfarms:2828
18707 If your remote target is actually running on the same machine as your
18708 debugger session (e.g.@: a simulator for your target running on the
18709 same host), you can omit the hostname. For example, to connect to
18710 port 1234 on your local machine:
18713 target remote :1234
18717 Note that the colon is still required here.
18719 @item target remote @code{udp:@var{host}:@var{port}}
18720 @cindex @acronym{UDP} port, @code{target remote}
18721 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
18722 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
18725 target remote udp:manyfarms:2828
18728 When using a @acronym{UDP} connection for remote debugging, you should
18729 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
18730 can silently drop packets on busy or unreliable networks, which will
18731 cause havoc with your debugging session.
18733 @item target remote | @var{command}
18734 @cindex pipe, @code{target remote} to
18735 Run @var{command} in the background and communicate with it using a
18736 pipe. The @var{command} is a shell command, to be parsed and expanded
18737 by the system's command shell, @code{/bin/sh}; it should expect remote
18738 protocol packets on its standard input, and send replies on its
18739 standard output. You could use this to run a stand-alone simulator
18740 that speaks the remote debugging protocol, to make net connections
18741 using programs like @code{ssh}, or for other similar tricks.
18743 If @var{command} closes its standard output (perhaps by exiting),
18744 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
18745 program has already exited, this will have no effect.)
18749 Once the connection has been established, you can use all the usual
18750 commands to examine and change data. The remote program is already
18751 running; you can use @kbd{step} and @kbd{continue}, and you do not
18752 need to use @kbd{run}.
18754 @cindex interrupting remote programs
18755 @cindex remote programs, interrupting
18756 Whenever @value{GDBN} is waiting for the remote program, if you type the
18757 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
18758 program. This may or may not succeed, depending in part on the hardware
18759 and the serial drivers the remote system uses. If you type the
18760 interrupt character once again, @value{GDBN} displays this prompt:
18763 Interrupted while waiting for the program.
18764 Give up (and stop debugging it)? (y or n)
18767 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
18768 (If you decide you want to try again later, you can use @samp{target
18769 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
18770 goes back to waiting.
18773 @kindex detach (remote)
18775 When you have finished debugging the remote program, you can use the
18776 @code{detach} command to release it from @value{GDBN} control.
18777 Detaching from the target normally resumes its execution, but the results
18778 will depend on your particular remote stub. After the @code{detach}
18779 command, @value{GDBN} is free to connect to another target.
18783 The @code{disconnect} command behaves like @code{detach}, except that
18784 the target is generally not resumed. It will wait for @value{GDBN}
18785 (this instance or another one) to connect and continue debugging. After
18786 the @code{disconnect} command, @value{GDBN} is again free to connect to
18789 @cindex send command to remote monitor
18790 @cindex extend @value{GDBN} for remote targets
18791 @cindex add new commands for external monitor
18793 @item monitor @var{cmd}
18794 This command allows you to send arbitrary commands directly to the
18795 remote monitor. Since @value{GDBN} doesn't care about the commands it
18796 sends like this, this command is the way to extend @value{GDBN}---you
18797 can add new commands that only the external monitor will understand
18801 @node File Transfer
18802 @section Sending files to a remote system
18803 @cindex remote target, file transfer
18804 @cindex file transfer
18805 @cindex sending files to remote systems
18807 Some remote targets offer the ability to transfer files over the same
18808 connection used to communicate with @value{GDBN}. This is convenient
18809 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
18810 running @code{gdbserver} over a network interface. For other targets,
18811 e.g.@: embedded devices with only a single serial port, this may be
18812 the only way to upload or download files.
18814 Not all remote targets support these commands.
18818 @item remote put @var{hostfile} @var{targetfile}
18819 Copy file @var{hostfile} from the host system (the machine running
18820 @value{GDBN}) to @var{targetfile} on the target system.
18823 @item remote get @var{targetfile} @var{hostfile}
18824 Copy file @var{targetfile} from the target system to @var{hostfile}
18825 on the host system.
18827 @kindex remote delete
18828 @item remote delete @var{targetfile}
18829 Delete @var{targetfile} from the target system.
18834 @section Using the @code{gdbserver} Program
18837 @cindex remote connection without stubs
18838 @code{gdbserver} is a control program for Unix-like systems, which
18839 allows you to connect your program with a remote @value{GDBN} via
18840 @code{target remote}---but without linking in the usual debugging stub.
18842 @code{gdbserver} is not a complete replacement for the debugging stubs,
18843 because it requires essentially the same operating-system facilities
18844 that @value{GDBN} itself does. In fact, a system that can run
18845 @code{gdbserver} to connect to a remote @value{GDBN} could also run
18846 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
18847 because it is a much smaller program than @value{GDBN} itself. It is
18848 also easier to port than all of @value{GDBN}, so you may be able to get
18849 started more quickly on a new system by using @code{gdbserver}.
18850 Finally, if you develop code for real-time systems, you may find that
18851 the tradeoffs involved in real-time operation make it more convenient to
18852 do as much development work as possible on another system, for example
18853 by cross-compiling. You can use @code{gdbserver} to make a similar
18854 choice for debugging.
18856 @value{GDBN} and @code{gdbserver} communicate via either a serial line
18857 or a TCP connection, using the standard @value{GDBN} remote serial
18861 @emph{Warning:} @code{gdbserver} does not have any built-in security.
18862 Do not run @code{gdbserver} connected to any public network; a
18863 @value{GDBN} connection to @code{gdbserver} provides access to the
18864 target system with the same privileges as the user running
18868 @subsection Running @code{gdbserver}
18869 @cindex arguments, to @code{gdbserver}
18870 @cindex @code{gdbserver}, command-line arguments
18872 Run @code{gdbserver} on the target system. You need a copy of the
18873 program you want to debug, including any libraries it requires.
18874 @code{gdbserver} does not need your program's symbol table, so you can
18875 strip the program if necessary to save space. @value{GDBN} on the host
18876 system does all the symbol handling.
18878 To use the server, you must tell it how to communicate with @value{GDBN};
18879 the name of your program; and the arguments for your program. The usual
18883 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
18886 @var{comm} is either a device name (to use a serial line), or a TCP
18887 hostname and portnumber, or @code{-} or @code{stdio} to use
18888 stdin/stdout of @code{gdbserver}.
18889 For example, to debug Emacs with the argument
18890 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
18894 target> gdbserver /dev/com1 emacs foo.txt
18897 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
18900 To use a TCP connection instead of a serial line:
18903 target> gdbserver host:2345 emacs foo.txt
18906 The only difference from the previous example is the first argument,
18907 specifying that you are communicating with the host @value{GDBN} via
18908 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
18909 expect a TCP connection from machine @samp{host} to local TCP port 2345.
18910 (Currently, the @samp{host} part is ignored.) You can choose any number
18911 you want for the port number as long as it does not conflict with any
18912 TCP ports already in use on the target system (for example, @code{23} is
18913 reserved for @code{telnet}).@footnote{If you choose a port number that
18914 conflicts with another service, @code{gdbserver} prints an error message
18915 and exits.} You must use the same port number with the host @value{GDBN}
18916 @code{target remote} command.
18918 The @code{stdio} connection is useful when starting @code{gdbserver}
18922 (gdb) target remote | ssh -T hostname gdbserver - hello
18925 The @samp{-T} option to ssh is provided because we don't need a remote pty,
18926 and we don't want escape-character handling. Ssh does this by default when
18927 a command is provided, the flag is provided to make it explicit.
18928 You could elide it if you want to.
18930 Programs started with stdio-connected gdbserver have @file{/dev/null} for
18931 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
18932 display through a pipe connected to gdbserver.
18933 Both @code{stdout} and @code{stderr} use the same pipe.
18935 @subsubsection Attaching to a Running Program
18936 @cindex attach to a program, @code{gdbserver}
18937 @cindex @option{--attach}, @code{gdbserver} option
18939 On some targets, @code{gdbserver} can also attach to running programs.
18940 This is accomplished via the @code{--attach} argument. The syntax is:
18943 target> gdbserver --attach @var{comm} @var{pid}
18946 @var{pid} is the process ID of a currently running process. It isn't necessary
18947 to point @code{gdbserver} at a binary for the running process.
18950 You can debug processes by name instead of process ID if your target has the
18951 @code{pidof} utility:
18954 target> gdbserver --attach @var{comm} `pidof @var{program}`
18957 In case more than one copy of @var{program} is running, or @var{program}
18958 has multiple threads, most versions of @code{pidof} support the
18959 @code{-s} option to only return the first process ID.
18961 @subsubsection Multi-Process Mode for @code{gdbserver}
18962 @cindex @code{gdbserver}, multiple processes
18963 @cindex multiple processes with @code{gdbserver}
18965 When you connect to @code{gdbserver} using @code{target remote},
18966 @code{gdbserver} debugs the specified program only once. When the
18967 program exits, or you detach from it, @value{GDBN} closes the connection
18968 and @code{gdbserver} exits.
18970 If you connect using @kbd{target extended-remote}, @code{gdbserver}
18971 enters multi-process mode. When the debugged program exits, or you
18972 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
18973 though no program is running. The @code{run} and @code{attach}
18974 commands instruct @code{gdbserver} to run or attach to a new program.
18975 The @code{run} command uses @code{set remote exec-file} (@pxref{set
18976 remote exec-file}) to select the program to run. Command line
18977 arguments are supported, except for wildcard expansion and I/O
18978 redirection (@pxref{Arguments}).
18980 @cindex @option{--multi}, @code{gdbserver} option
18981 To start @code{gdbserver} without supplying an initial command to run
18982 or process ID to attach, use the @option{--multi} command line option.
18983 Then you can connect using @kbd{target extended-remote} and start
18984 the program you want to debug.
18986 In multi-process mode @code{gdbserver} does not automatically exit unless you
18987 use the option @option{--once}. You can terminate it by using
18988 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
18989 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
18990 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
18991 @option{--multi} option to @code{gdbserver} has no influence on that.
18993 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
18995 This section applies only when @code{gdbserver} is run to listen on a TCP port.
18997 @code{gdbserver} normally terminates after all of its debugged processes have
18998 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
18999 extended-remote}, @code{gdbserver} stays running even with no processes left.
19000 @value{GDBN} normally terminates the spawned debugged process on its exit,
19001 which normally also terminates @code{gdbserver} in the @kbd{target remote}
19002 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
19003 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
19004 stays running even in the @kbd{target remote} mode.
19006 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
19007 Such reconnecting is useful for features like @ref{disconnected tracing}. For
19008 completeness, at most one @value{GDBN} can be connected at a time.
19010 @cindex @option{--once}, @code{gdbserver} option
19011 By default, @code{gdbserver} keeps the listening TCP port open, so that
19012 subsequent connections are possible. However, if you start @code{gdbserver}
19013 with the @option{--once} option, it will stop listening for any further
19014 connection attempts after connecting to the first @value{GDBN} session. This
19015 means no further connections to @code{gdbserver} will be possible after the
19016 first one. It also means @code{gdbserver} will terminate after the first
19017 connection with remote @value{GDBN} has closed, even for unexpectedly closed
19018 connections and even in the @kbd{target extended-remote} mode. The
19019 @option{--once} option allows reusing the same port number for connecting to
19020 multiple instances of @code{gdbserver} running on the same host, since each
19021 instance closes its port after the first connection.
19023 @anchor{Other Command-Line Arguments for gdbserver}
19024 @subsubsection Other Command-Line Arguments for @code{gdbserver}
19026 @cindex @option{--debug}, @code{gdbserver} option
19027 The @option{--debug} option tells @code{gdbserver} to display extra
19028 status information about the debugging process.
19029 @cindex @option{--remote-debug}, @code{gdbserver} option
19030 The @option{--remote-debug} option tells @code{gdbserver} to display
19031 remote protocol debug output. These options are intended for
19032 @code{gdbserver} development and for bug reports to the developers.
19034 @cindex @option{--debug-format}, @code{gdbserver} option
19035 The @option{--debug-format=option1[,option2,...]} option tells
19036 @code{gdbserver} to include additional information in each output.
19037 Possible options are:
19041 Turn off all extra information in debugging output.
19043 Turn on all extra information in debugging output.
19045 Include a timestamp in each line of debugging output.
19048 Options are processed in order. Thus, for example, if @option{none}
19049 appears last then no additional information is added to debugging output.
19051 @cindex @option{--wrapper}, @code{gdbserver} option
19052 The @option{--wrapper} option specifies a wrapper to launch programs
19053 for debugging. The option should be followed by the name of the
19054 wrapper, then any command-line arguments to pass to the wrapper, then
19055 @kbd{--} indicating the end of the wrapper arguments.
19057 @code{gdbserver} runs the specified wrapper program with a combined
19058 command line including the wrapper arguments, then the name of the
19059 program to debug, then any arguments to the program. The wrapper
19060 runs until it executes your program, and then @value{GDBN} gains control.
19062 You can use any program that eventually calls @code{execve} with
19063 its arguments as a wrapper. Several standard Unix utilities do
19064 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
19065 with @code{exec "$@@"} will also work.
19067 For example, you can use @code{env} to pass an environment variable to
19068 the debugged program, without setting the variable in @code{gdbserver}'s
19072 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
19075 @subsection Connecting to @code{gdbserver}
19077 Run @value{GDBN} on the host system.
19079 First make sure you have the necessary symbol files. Load symbols for
19080 your application using the @code{file} command before you connect. Use
19081 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
19082 was compiled with the correct sysroot using @code{--with-sysroot}).
19084 The symbol file and target libraries must exactly match the executable
19085 and libraries on the target, with one exception: the files on the host
19086 system should not be stripped, even if the files on the target system
19087 are. Mismatched or missing files will lead to confusing results
19088 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
19089 files may also prevent @code{gdbserver} from debugging multi-threaded
19092 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
19093 For TCP connections, you must start up @code{gdbserver} prior to using
19094 the @code{target remote} command. Otherwise you may get an error whose
19095 text depends on the host system, but which usually looks something like
19096 @samp{Connection refused}. Don't use the @code{load}
19097 command in @value{GDBN} when using @code{gdbserver}, since the program is
19098 already on the target.
19100 @subsection Monitor Commands for @code{gdbserver}
19101 @cindex monitor commands, for @code{gdbserver}
19102 @anchor{Monitor Commands for gdbserver}
19104 During a @value{GDBN} session using @code{gdbserver}, you can use the
19105 @code{monitor} command to send special requests to @code{gdbserver}.
19106 Here are the available commands.
19110 List the available monitor commands.
19112 @item monitor set debug 0
19113 @itemx monitor set debug 1
19114 Disable or enable general debugging messages.
19116 @item monitor set remote-debug 0
19117 @itemx monitor set remote-debug 1
19118 Disable or enable specific debugging messages associated with the remote
19119 protocol (@pxref{Remote Protocol}).
19121 @item monitor set debug-format option1@r{[},option2,...@r{]}
19122 Specify additional text to add to debugging messages.
19123 Possible options are:
19127 Turn off all extra information in debugging output.
19129 Turn on all extra information in debugging output.
19131 Include a timestamp in each line of debugging output.
19134 Options are processed in order. Thus, for example, if @option{none}
19135 appears last then no additional information is added to debugging output.
19137 @item monitor set libthread-db-search-path [PATH]
19138 @cindex gdbserver, search path for @code{libthread_db}
19139 When this command is issued, @var{path} is a colon-separated list of
19140 directories to search for @code{libthread_db} (@pxref{Threads,,set
19141 libthread-db-search-path}). If you omit @var{path},
19142 @samp{libthread-db-search-path} will be reset to its default value.
19144 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
19145 not supported in @code{gdbserver}.
19148 Tell gdbserver to exit immediately. This command should be followed by
19149 @code{disconnect} to close the debugging session. @code{gdbserver} will
19150 detach from any attached processes and kill any processes it created.
19151 Use @code{monitor exit} to terminate @code{gdbserver} at the end
19152 of a multi-process mode debug session.
19156 @subsection Tracepoints support in @code{gdbserver}
19157 @cindex tracepoints support in @code{gdbserver}
19159 On some targets, @code{gdbserver} supports tracepoints, fast
19160 tracepoints and static tracepoints.
19162 For fast or static tracepoints to work, a special library called the
19163 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
19164 This library is built and distributed as an integral part of
19165 @code{gdbserver}. In addition, support for static tracepoints
19166 requires building the in-process agent library with static tracepoints
19167 support. At present, the UST (LTTng Userspace Tracer,
19168 @url{http://lttng.org/ust}) tracing engine is supported. This support
19169 is automatically available if UST development headers are found in the
19170 standard include path when @code{gdbserver} is built, or if
19171 @code{gdbserver} was explicitly configured using @option{--with-ust}
19172 to point at such headers. You can explicitly disable the support
19173 using @option{--with-ust=no}.
19175 There are several ways to load the in-process agent in your program:
19178 @item Specifying it as dependency at link time
19180 You can link your program dynamically with the in-process agent
19181 library. On most systems, this is accomplished by adding
19182 @code{-linproctrace} to the link command.
19184 @item Using the system's preloading mechanisms
19186 You can force loading the in-process agent at startup time by using
19187 your system's support for preloading shared libraries. Many Unixes
19188 support the concept of preloading user defined libraries. In most
19189 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
19190 in the environment. See also the description of @code{gdbserver}'s
19191 @option{--wrapper} command line option.
19193 @item Using @value{GDBN} to force loading the agent at run time
19195 On some systems, you can force the inferior to load a shared library,
19196 by calling a dynamic loader function in the inferior that takes care
19197 of dynamically looking up and loading a shared library. On most Unix
19198 systems, the function is @code{dlopen}. You'll use the @code{call}
19199 command for that. For example:
19202 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
19205 Note that on most Unix systems, for the @code{dlopen} function to be
19206 available, the program needs to be linked with @code{-ldl}.
19209 On systems that have a userspace dynamic loader, like most Unix
19210 systems, when you connect to @code{gdbserver} using @code{target
19211 remote}, you'll find that the program is stopped at the dynamic
19212 loader's entry point, and no shared library has been loaded in the
19213 program's address space yet, including the in-process agent. In that
19214 case, before being able to use any of the fast or static tracepoints
19215 features, you need to let the loader run and load the shared
19216 libraries. The simplest way to do that is to run the program to the
19217 main procedure. E.g., if debugging a C or C@t{++} program, start
19218 @code{gdbserver} like so:
19221 $ gdbserver :9999 myprogram
19224 Start GDB and connect to @code{gdbserver} like so, and run to main:
19228 (@value{GDBP}) target remote myhost:9999
19229 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
19230 (@value{GDBP}) b main
19231 (@value{GDBP}) continue
19234 The in-process tracing agent library should now be loaded into the
19235 process; you can confirm it with the @code{info sharedlibrary}
19236 command, which will list @file{libinproctrace.so} as loaded in the
19237 process. You are now ready to install fast tracepoints, list static
19238 tracepoint markers, probe static tracepoints markers, and start
19241 @node Remote Configuration
19242 @section Remote Configuration
19245 @kindex show remote
19246 This section documents the configuration options available when
19247 debugging remote programs. For the options related to the File I/O
19248 extensions of the remote protocol, see @ref{system,
19249 system-call-allowed}.
19252 @item set remoteaddresssize @var{bits}
19253 @cindex address size for remote targets
19254 @cindex bits in remote address
19255 Set the maximum size of address in a memory packet to the specified
19256 number of bits. @value{GDBN} will mask off the address bits above
19257 that number, when it passes addresses to the remote target. The
19258 default value is the number of bits in the target's address.
19260 @item show remoteaddresssize
19261 Show the current value of remote address size in bits.
19263 @item set serial baud @var{n}
19264 @cindex baud rate for remote targets
19265 Set the baud rate for the remote serial I/O to @var{n} baud. The
19266 value is used to set the speed of the serial port used for debugging
19269 @item show serial baud
19270 Show the current speed of the remote connection.
19272 @item set remotebreak
19273 @cindex interrupt remote programs
19274 @cindex BREAK signal instead of Ctrl-C
19275 @anchor{set remotebreak}
19276 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
19277 when you type @kbd{Ctrl-c} to interrupt the program running
19278 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
19279 character instead. The default is off, since most remote systems
19280 expect to see @samp{Ctrl-C} as the interrupt signal.
19282 @item show remotebreak
19283 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
19284 interrupt the remote program.
19286 @item set remoteflow on
19287 @itemx set remoteflow off
19288 @kindex set remoteflow
19289 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
19290 on the serial port used to communicate to the remote target.
19292 @item show remoteflow
19293 @kindex show remoteflow
19294 Show the current setting of hardware flow control.
19296 @item set remotelogbase @var{base}
19297 Set the base (a.k.a.@: radix) of logging serial protocol
19298 communications to @var{base}. Supported values of @var{base} are:
19299 @code{ascii}, @code{octal}, and @code{hex}. The default is
19302 @item show remotelogbase
19303 Show the current setting of the radix for logging remote serial
19306 @item set remotelogfile @var{file}
19307 @cindex record serial communications on file
19308 Record remote serial communications on the named @var{file}. The
19309 default is not to record at all.
19311 @item show remotelogfile.
19312 Show the current setting of the file name on which to record the
19313 serial communications.
19315 @item set remotetimeout @var{num}
19316 @cindex timeout for serial communications
19317 @cindex remote timeout
19318 Set the timeout limit to wait for the remote target to respond to
19319 @var{num} seconds. The default is 2 seconds.
19321 @item show remotetimeout
19322 Show the current number of seconds to wait for the remote target
19325 @cindex limit hardware breakpoints and watchpoints
19326 @cindex remote target, limit break- and watchpoints
19327 @anchor{set remote hardware-watchpoint-limit}
19328 @anchor{set remote hardware-breakpoint-limit}
19329 @item set remote hardware-watchpoint-limit @var{limit}
19330 @itemx set remote hardware-breakpoint-limit @var{limit}
19331 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
19332 watchpoints. A limit of -1, the default, is treated as unlimited.
19334 @cindex limit hardware watchpoints length
19335 @cindex remote target, limit watchpoints length
19336 @anchor{set remote hardware-watchpoint-length-limit}
19337 @item set remote hardware-watchpoint-length-limit @var{limit}
19338 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
19339 a remote hardware watchpoint. A limit of -1, the default, is treated
19342 @item show remote hardware-watchpoint-length-limit
19343 Show the current limit (in bytes) of the maximum length of
19344 a remote hardware watchpoint.
19346 @item set remote exec-file @var{filename}
19347 @itemx show remote exec-file
19348 @anchor{set remote exec-file}
19349 @cindex executable file, for remote target
19350 Select the file used for @code{run} with @code{target
19351 extended-remote}. This should be set to a filename valid on the
19352 target system. If it is not set, the target will use a default
19353 filename (e.g.@: the last program run).
19355 @item set remote interrupt-sequence
19356 @cindex interrupt remote programs
19357 @cindex select Ctrl-C, BREAK or BREAK-g
19358 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
19359 @samp{BREAK-g} as the
19360 sequence to the remote target in order to interrupt the execution.
19361 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
19362 is high level of serial line for some certain time.
19363 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
19364 It is @code{BREAK} signal followed by character @code{g}.
19366 @item show interrupt-sequence
19367 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
19368 is sent by @value{GDBN} to interrupt the remote program.
19369 @code{BREAK-g} is BREAK signal followed by @code{g} and
19370 also known as Magic SysRq g.
19372 @item set remote interrupt-on-connect
19373 @cindex send interrupt-sequence on start
19374 Specify whether interrupt-sequence is sent to remote target when
19375 @value{GDBN} connects to it. This is mostly needed when you debug
19376 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
19377 which is known as Magic SysRq g in order to connect @value{GDBN}.
19379 @item show interrupt-on-connect
19380 Show whether interrupt-sequence is sent
19381 to remote target when @value{GDBN} connects to it.
19385 @item set tcp auto-retry on
19386 @cindex auto-retry, for remote TCP target
19387 Enable auto-retry for remote TCP connections. This is useful if the remote
19388 debugging agent is launched in parallel with @value{GDBN}; there is a race
19389 condition because the agent may not become ready to accept the connection
19390 before @value{GDBN} attempts to connect. When auto-retry is
19391 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
19392 to establish the connection using the timeout specified by
19393 @code{set tcp connect-timeout}.
19395 @item set tcp auto-retry off
19396 Do not auto-retry failed TCP connections.
19398 @item show tcp auto-retry
19399 Show the current auto-retry setting.
19401 @item set tcp connect-timeout @var{seconds}
19402 @itemx set tcp connect-timeout unlimited
19403 @cindex connection timeout, for remote TCP target
19404 @cindex timeout, for remote target connection
19405 Set the timeout for establishing a TCP connection to the remote target to
19406 @var{seconds}. The timeout affects both polling to retry failed connections
19407 (enabled by @code{set tcp auto-retry on}) and waiting for connections
19408 that are merely slow to complete, and represents an approximate cumulative
19409 value. If @var{seconds} is @code{unlimited}, there is no timeout and
19410 @value{GDBN} will keep attempting to establish a connection forever,
19411 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
19413 @item show tcp connect-timeout
19414 Show the current connection timeout setting.
19417 @cindex remote packets, enabling and disabling
19418 The @value{GDBN} remote protocol autodetects the packets supported by
19419 your debugging stub. If you need to override the autodetection, you
19420 can use these commands to enable or disable individual packets. Each
19421 packet can be set to @samp{on} (the remote target supports this
19422 packet), @samp{off} (the remote target does not support this packet),
19423 or @samp{auto} (detect remote target support for this packet). They
19424 all default to @samp{auto}. For more information about each packet,
19425 see @ref{Remote Protocol}.
19427 During normal use, you should not have to use any of these commands.
19428 If you do, that may be a bug in your remote debugging stub, or a bug
19429 in @value{GDBN}. You may want to report the problem to the
19430 @value{GDBN} developers.
19432 For each packet @var{name}, the command to enable or disable the
19433 packet is @code{set remote @var{name}-packet}. The available settings
19436 @multitable @columnfractions 0.28 0.32 0.25
19439 @tab Related Features
19441 @item @code{fetch-register}
19443 @tab @code{info registers}
19445 @item @code{set-register}
19449 @item @code{binary-download}
19451 @tab @code{load}, @code{set}
19453 @item @code{read-aux-vector}
19454 @tab @code{qXfer:auxv:read}
19455 @tab @code{info auxv}
19457 @item @code{symbol-lookup}
19458 @tab @code{qSymbol}
19459 @tab Detecting multiple threads
19461 @item @code{attach}
19462 @tab @code{vAttach}
19465 @item @code{verbose-resume}
19467 @tab Stepping or resuming multiple threads
19473 @item @code{software-breakpoint}
19477 @item @code{hardware-breakpoint}
19481 @item @code{write-watchpoint}
19485 @item @code{read-watchpoint}
19489 @item @code{access-watchpoint}
19493 @item @code{target-features}
19494 @tab @code{qXfer:features:read}
19495 @tab @code{set architecture}
19497 @item @code{library-info}
19498 @tab @code{qXfer:libraries:read}
19499 @tab @code{info sharedlibrary}
19501 @item @code{memory-map}
19502 @tab @code{qXfer:memory-map:read}
19503 @tab @code{info mem}
19505 @item @code{read-sdata-object}
19506 @tab @code{qXfer:sdata:read}
19507 @tab @code{print $_sdata}
19509 @item @code{read-spu-object}
19510 @tab @code{qXfer:spu:read}
19511 @tab @code{info spu}
19513 @item @code{write-spu-object}
19514 @tab @code{qXfer:spu:write}
19515 @tab @code{info spu}
19517 @item @code{read-siginfo-object}
19518 @tab @code{qXfer:siginfo:read}
19519 @tab @code{print $_siginfo}
19521 @item @code{write-siginfo-object}
19522 @tab @code{qXfer:siginfo:write}
19523 @tab @code{set $_siginfo}
19525 @item @code{threads}
19526 @tab @code{qXfer:threads:read}
19527 @tab @code{info threads}
19529 @item @code{get-thread-local-@*storage-address}
19530 @tab @code{qGetTLSAddr}
19531 @tab Displaying @code{__thread} variables
19533 @item @code{get-thread-information-block-address}
19534 @tab @code{qGetTIBAddr}
19535 @tab Display MS-Windows Thread Information Block.
19537 @item @code{search-memory}
19538 @tab @code{qSearch:memory}
19541 @item @code{supported-packets}
19542 @tab @code{qSupported}
19543 @tab Remote communications parameters
19545 @item @code{pass-signals}
19546 @tab @code{QPassSignals}
19547 @tab @code{handle @var{signal}}
19549 @item @code{program-signals}
19550 @tab @code{QProgramSignals}
19551 @tab @code{handle @var{signal}}
19553 @item @code{hostio-close-packet}
19554 @tab @code{vFile:close}
19555 @tab @code{remote get}, @code{remote put}
19557 @item @code{hostio-open-packet}
19558 @tab @code{vFile:open}
19559 @tab @code{remote get}, @code{remote put}
19561 @item @code{hostio-pread-packet}
19562 @tab @code{vFile:pread}
19563 @tab @code{remote get}, @code{remote put}
19565 @item @code{hostio-pwrite-packet}
19566 @tab @code{vFile:pwrite}
19567 @tab @code{remote get}, @code{remote put}
19569 @item @code{hostio-unlink-packet}
19570 @tab @code{vFile:unlink}
19571 @tab @code{remote delete}
19573 @item @code{hostio-readlink-packet}
19574 @tab @code{vFile:readlink}
19577 @item @code{noack-packet}
19578 @tab @code{QStartNoAckMode}
19579 @tab Packet acknowledgment
19581 @item @code{osdata}
19582 @tab @code{qXfer:osdata:read}
19583 @tab @code{info os}
19585 @item @code{query-attached}
19586 @tab @code{qAttached}
19587 @tab Querying remote process attach state.
19589 @item @code{trace-buffer-size}
19590 @tab @code{QTBuffer:size}
19591 @tab @code{set trace-buffer-size}
19593 @item @code{trace-status}
19594 @tab @code{qTStatus}
19595 @tab @code{tstatus}
19597 @item @code{traceframe-info}
19598 @tab @code{qXfer:traceframe-info:read}
19599 @tab Traceframe info
19601 @item @code{install-in-trace}
19602 @tab @code{InstallInTrace}
19603 @tab Install tracepoint in tracing
19605 @item @code{disable-randomization}
19606 @tab @code{QDisableRandomization}
19607 @tab @code{set disable-randomization}
19609 @item @code{conditional-breakpoints-packet}
19610 @tab @code{Z0 and Z1}
19611 @tab @code{Support for target-side breakpoint condition evaluation}
19615 @section Implementing a Remote Stub
19617 @cindex debugging stub, example
19618 @cindex remote stub, example
19619 @cindex stub example, remote debugging
19620 The stub files provided with @value{GDBN} implement the target side of the
19621 communication protocol, and the @value{GDBN} side is implemented in the
19622 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
19623 these subroutines to communicate, and ignore the details. (If you're
19624 implementing your own stub file, you can still ignore the details: start
19625 with one of the existing stub files. @file{sparc-stub.c} is the best
19626 organized, and therefore the easiest to read.)
19628 @cindex remote serial debugging, overview
19629 To debug a program running on another machine (the debugging
19630 @dfn{target} machine), you must first arrange for all the usual
19631 prerequisites for the program to run by itself. For example, for a C
19636 A startup routine to set up the C runtime environment; these usually
19637 have a name like @file{crt0}. The startup routine may be supplied by
19638 your hardware supplier, or you may have to write your own.
19641 A C subroutine library to support your program's
19642 subroutine calls, notably managing input and output.
19645 A way of getting your program to the other machine---for example, a
19646 download program. These are often supplied by the hardware
19647 manufacturer, but you may have to write your own from hardware
19651 The next step is to arrange for your program to use a serial port to
19652 communicate with the machine where @value{GDBN} is running (the @dfn{host}
19653 machine). In general terms, the scheme looks like this:
19657 @value{GDBN} already understands how to use this protocol; when everything
19658 else is set up, you can simply use the @samp{target remote} command
19659 (@pxref{Targets,,Specifying a Debugging Target}).
19661 @item On the target,
19662 you must link with your program a few special-purpose subroutines that
19663 implement the @value{GDBN} remote serial protocol. The file containing these
19664 subroutines is called a @dfn{debugging stub}.
19666 On certain remote targets, you can use an auxiliary program
19667 @code{gdbserver} instead of linking a stub into your program.
19668 @xref{Server,,Using the @code{gdbserver} Program}, for details.
19671 The debugging stub is specific to the architecture of the remote
19672 machine; for example, use @file{sparc-stub.c} to debug programs on
19675 @cindex remote serial stub list
19676 These working remote stubs are distributed with @value{GDBN}:
19681 @cindex @file{i386-stub.c}
19684 For Intel 386 and compatible architectures.
19687 @cindex @file{m68k-stub.c}
19688 @cindex Motorola 680x0
19690 For Motorola 680x0 architectures.
19693 @cindex @file{sh-stub.c}
19696 For Renesas SH architectures.
19699 @cindex @file{sparc-stub.c}
19701 For @sc{sparc} architectures.
19703 @item sparcl-stub.c
19704 @cindex @file{sparcl-stub.c}
19707 For Fujitsu @sc{sparclite} architectures.
19711 The @file{README} file in the @value{GDBN} distribution may list other
19712 recently added stubs.
19715 * Stub Contents:: What the stub can do for you
19716 * Bootstrapping:: What you must do for the stub
19717 * Debug Session:: Putting it all together
19720 @node Stub Contents
19721 @subsection What the Stub Can Do for You
19723 @cindex remote serial stub
19724 The debugging stub for your architecture supplies these three
19728 @item set_debug_traps
19729 @findex set_debug_traps
19730 @cindex remote serial stub, initialization
19731 This routine arranges for @code{handle_exception} to run when your
19732 program stops. You must call this subroutine explicitly in your
19733 program's startup code.
19735 @item handle_exception
19736 @findex handle_exception
19737 @cindex remote serial stub, main routine
19738 This is the central workhorse, but your program never calls it
19739 explicitly---the setup code arranges for @code{handle_exception} to
19740 run when a trap is triggered.
19742 @code{handle_exception} takes control when your program stops during
19743 execution (for example, on a breakpoint), and mediates communications
19744 with @value{GDBN} on the host machine. This is where the communications
19745 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
19746 representative on the target machine. It begins by sending summary
19747 information on the state of your program, then continues to execute,
19748 retrieving and transmitting any information @value{GDBN} needs, until you
19749 execute a @value{GDBN} command that makes your program resume; at that point,
19750 @code{handle_exception} returns control to your own code on the target
19754 @cindex @code{breakpoint} subroutine, remote
19755 Use this auxiliary subroutine to make your program contain a
19756 breakpoint. Depending on the particular situation, this may be the only
19757 way for @value{GDBN} to get control. For instance, if your target
19758 machine has some sort of interrupt button, you won't need to call this;
19759 pressing the interrupt button transfers control to
19760 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
19761 simply receiving characters on the serial port may also trigger a trap;
19762 again, in that situation, you don't need to call @code{breakpoint} from
19763 your own program---simply running @samp{target remote} from the host
19764 @value{GDBN} session gets control.
19766 Call @code{breakpoint} if none of these is true, or if you simply want
19767 to make certain your program stops at a predetermined point for the
19768 start of your debugging session.
19771 @node Bootstrapping
19772 @subsection What You Must Do for the Stub
19774 @cindex remote stub, support routines
19775 The debugging stubs that come with @value{GDBN} are set up for a particular
19776 chip architecture, but they have no information about the rest of your
19777 debugging target machine.
19779 First of all you need to tell the stub how to communicate with the
19783 @item int getDebugChar()
19784 @findex getDebugChar
19785 Write this subroutine to read a single character from the serial port.
19786 It may be identical to @code{getchar} for your target system; a
19787 different name is used to allow you to distinguish the two if you wish.
19789 @item void putDebugChar(int)
19790 @findex putDebugChar
19791 Write this subroutine to write a single character to the serial port.
19792 It may be identical to @code{putchar} for your target system; a
19793 different name is used to allow you to distinguish the two if you wish.
19796 @cindex control C, and remote debugging
19797 @cindex interrupting remote targets
19798 If you want @value{GDBN} to be able to stop your program while it is
19799 running, you need to use an interrupt-driven serial driver, and arrange
19800 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
19801 character). That is the character which @value{GDBN} uses to tell the
19802 remote system to stop.
19804 Getting the debugging target to return the proper status to @value{GDBN}
19805 probably requires changes to the standard stub; one quick and dirty way
19806 is to just execute a breakpoint instruction (the ``dirty'' part is that
19807 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
19809 Other routines you need to supply are:
19812 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
19813 @findex exceptionHandler
19814 Write this function to install @var{exception_address} in the exception
19815 handling tables. You need to do this because the stub does not have any
19816 way of knowing what the exception handling tables on your target system
19817 are like (for example, the processor's table might be in @sc{rom},
19818 containing entries which point to a table in @sc{ram}).
19819 The @var{exception_number} specifies the exception which should be changed;
19820 its meaning is architecture-dependent (for example, different numbers
19821 might represent divide by zero, misaligned access, etc). When this
19822 exception occurs, control should be transferred directly to
19823 @var{exception_address}, and the processor state (stack, registers,
19824 and so on) should be just as it is when a processor exception occurs. So if
19825 you want to use a jump instruction to reach @var{exception_address}, it
19826 should be a simple jump, not a jump to subroutine.
19828 For the 386, @var{exception_address} should be installed as an interrupt
19829 gate so that interrupts are masked while the handler runs. The gate
19830 should be at privilege level 0 (the most privileged level). The
19831 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
19832 help from @code{exceptionHandler}.
19834 @item void flush_i_cache()
19835 @findex flush_i_cache
19836 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
19837 instruction cache, if any, on your target machine. If there is no
19838 instruction cache, this subroutine may be a no-op.
19840 On target machines that have instruction caches, @value{GDBN} requires this
19841 function to make certain that the state of your program is stable.
19845 You must also make sure this library routine is available:
19848 @item void *memset(void *, int, int)
19850 This is the standard library function @code{memset} that sets an area of
19851 memory to a known value. If you have one of the free versions of
19852 @code{libc.a}, @code{memset} can be found there; otherwise, you must
19853 either obtain it from your hardware manufacturer, or write your own.
19856 If you do not use the GNU C compiler, you may need other standard
19857 library subroutines as well; this varies from one stub to another,
19858 but in general the stubs are likely to use any of the common library
19859 subroutines which @code{@value{NGCC}} generates as inline code.
19862 @node Debug Session
19863 @subsection Putting it All Together
19865 @cindex remote serial debugging summary
19866 In summary, when your program is ready to debug, you must follow these
19871 Make sure you have defined the supporting low-level routines
19872 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
19874 @code{getDebugChar}, @code{putDebugChar},
19875 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
19879 Insert these lines in your program's startup code, before the main
19880 procedure is called:
19887 On some machines, when a breakpoint trap is raised, the hardware
19888 automatically makes the PC point to the instruction after the
19889 breakpoint. If your machine doesn't do that, you may need to adjust
19890 @code{handle_exception} to arrange for it to return to the instruction
19891 after the breakpoint on this first invocation, so that your program
19892 doesn't keep hitting the initial breakpoint instead of making
19896 For the 680x0 stub only, you need to provide a variable called
19897 @code{exceptionHook}. Normally you just use:
19900 void (*exceptionHook)() = 0;
19904 but if before calling @code{set_debug_traps}, you set it to point to a
19905 function in your program, that function is called when
19906 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
19907 error). The function indicated by @code{exceptionHook} is called with
19908 one parameter: an @code{int} which is the exception number.
19911 Compile and link together: your program, the @value{GDBN} debugging stub for
19912 your target architecture, and the supporting subroutines.
19915 Make sure you have a serial connection between your target machine and
19916 the @value{GDBN} host, and identify the serial port on the host.
19919 @c The "remote" target now provides a `load' command, so we should
19920 @c document that. FIXME.
19921 Download your program to your target machine (or get it there by
19922 whatever means the manufacturer provides), and start it.
19925 Start @value{GDBN} on the host, and connect to the target
19926 (@pxref{Connecting,,Connecting to a Remote Target}).
19930 @node Configurations
19931 @chapter Configuration-Specific Information
19933 While nearly all @value{GDBN} commands are available for all native and
19934 cross versions of the debugger, there are some exceptions. This chapter
19935 describes things that are only available in certain configurations.
19937 There are three major categories of configurations: native
19938 configurations, where the host and target are the same, embedded
19939 operating system configurations, which are usually the same for several
19940 different processor architectures, and bare embedded processors, which
19941 are quite different from each other.
19946 * Embedded Processors::
19953 This section describes details specific to particular native
19958 * BSD libkvm Interface:: Debugging BSD kernel memory images
19959 * SVR4 Process Information:: SVR4 process information
19960 * DJGPP Native:: Features specific to the DJGPP port
19961 * Cygwin Native:: Features specific to the Cygwin port
19962 * Hurd Native:: Features specific to @sc{gnu} Hurd
19963 * Darwin:: Features specific to Darwin
19969 On HP-UX systems, if you refer to a function or variable name that
19970 begins with a dollar sign, @value{GDBN} searches for a user or system
19971 name first, before it searches for a convenience variable.
19974 @node BSD libkvm Interface
19975 @subsection BSD libkvm Interface
19978 @cindex kernel memory image
19979 @cindex kernel crash dump
19981 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
19982 interface that provides a uniform interface for accessing kernel virtual
19983 memory images, including live systems and crash dumps. @value{GDBN}
19984 uses this interface to allow you to debug live kernels and kernel crash
19985 dumps on many native BSD configurations. This is implemented as a
19986 special @code{kvm} debugging target. For debugging a live system, load
19987 the currently running kernel into @value{GDBN} and connect to the
19991 (@value{GDBP}) @b{target kvm}
19994 For debugging crash dumps, provide the file name of the crash dump as an
19998 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
20001 Once connected to the @code{kvm} target, the following commands are
20007 Set current context from the @dfn{Process Control Block} (PCB) address.
20010 Set current context from proc address. This command isn't available on
20011 modern FreeBSD systems.
20014 @node SVR4 Process Information
20015 @subsection SVR4 Process Information
20017 @cindex examine process image
20018 @cindex process info via @file{/proc}
20020 Many versions of SVR4 and compatible systems provide a facility called
20021 @samp{/proc} that can be used to examine the image of a running
20022 process using file-system subroutines.
20024 If @value{GDBN} is configured for an operating system with this
20025 facility, the command @code{info proc} is available to report
20026 information about the process running your program, or about any
20027 process running on your system. This includes, as of this writing,
20028 @sc{gnu}/Linux and Solaris, but not HP-UX, for example.
20030 This command may also work on core files that were created on a system
20031 that has the @samp{/proc} facility.
20037 @itemx info proc @var{process-id}
20038 Summarize available information about any running process. If a
20039 process ID is specified by @var{process-id}, display information about
20040 that process; otherwise display information about the program being
20041 debugged. The summary includes the debugged process ID, the command
20042 line used to invoke it, its current working directory, and its
20043 executable file's absolute file name.
20045 On some systems, @var{process-id} can be of the form
20046 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
20047 within a process. If the optional @var{pid} part is missing, it means
20048 a thread from the process being debugged (the leading @samp{/} still
20049 needs to be present, or else @value{GDBN} will interpret the number as
20050 a process ID rather than a thread ID).
20052 @item info proc cmdline
20053 @cindex info proc cmdline
20054 Show the original command line of the process. This command is
20055 specific to @sc{gnu}/Linux.
20057 @item info proc cwd
20058 @cindex info proc cwd
20059 Show the current working directory of the process. This command is
20060 specific to @sc{gnu}/Linux.
20062 @item info proc exe
20063 @cindex info proc exe
20064 Show the name of executable of the process. This command is specific
20067 @item info proc mappings
20068 @cindex memory address space mappings
20069 Report the memory address space ranges accessible in the program, with
20070 information on whether the process has read, write, or execute access
20071 rights to each range. On @sc{gnu}/Linux systems, each memory range
20072 includes the object file which is mapped to that range, instead of the
20073 memory access rights to that range.
20075 @item info proc stat
20076 @itemx info proc status
20077 @cindex process detailed status information
20078 These subcommands are specific to @sc{gnu}/Linux systems. They show
20079 the process-related information, including the user ID and group ID;
20080 how many threads are there in the process; its virtual memory usage;
20081 the signals that are pending, blocked, and ignored; its TTY; its
20082 consumption of system and user time; its stack size; its @samp{nice}
20083 value; etc. For more information, see the @samp{proc} man page
20084 (type @kbd{man 5 proc} from your shell prompt).
20086 @item info proc all
20087 Show all the information about the process described under all of the
20088 above @code{info proc} subcommands.
20091 @comment These sub-options of 'info proc' were not included when
20092 @comment procfs.c was re-written. Keep their descriptions around
20093 @comment against the day when someone finds the time to put them back in.
20094 @kindex info proc times
20095 @item info proc times
20096 Starting time, user CPU time, and system CPU time for your program and
20099 @kindex info proc id
20101 Report on the process IDs related to your program: its own process ID,
20102 the ID of its parent, the process group ID, and the session ID.
20105 @item set procfs-trace
20106 @kindex set procfs-trace
20107 @cindex @code{procfs} API calls
20108 This command enables and disables tracing of @code{procfs} API calls.
20110 @item show procfs-trace
20111 @kindex show procfs-trace
20112 Show the current state of @code{procfs} API call tracing.
20114 @item set procfs-file @var{file}
20115 @kindex set procfs-file
20116 Tell @value{GDBN} to write @code{procfs} API trace to the named
20117 @var{file}. @value{GDBN} appends the trace info to the previous
20118 contents of the file. The default is to display the trace on the
20121 @item show procfs-file
20122 @kindex show procfs-file
20123 Show the file to which @code{procfs} API trace is written.
20125 @item proc-trace-entry
20126 @itemx proc-trace-exit
20127 @itemx proc-untrace-entry
20128 @itemx proc-untrace-exit
20129 @kindex proc-trace-entry
20130 @kindex proc-trace-exit
20131 @kindex proc-untrace-entry
20132 @kindex proc-untrace-exit
20133 These commands enable and disable tracing of entries into and exits
20134 from the @code{syscall} interface.
20137 @kindex info pidlist
20138 @cindex process list, QNX Neutrino
20139 For QNX Neutrino only, this command displays the list of all the
20140 processes and all the threads within each process.
20143 @kindex info meminfo
20144 @cindex mapinfo list, QNX Neutrino
20145 For QNX Neutrino only, this command displays the list of all mapinfos.
20149 @subsection Features for Debugging @sc{djgpp} Programs
20150 @cindex @sc{djgpp} debugging
20151 @cindex native @sc{djgpp} debugging
20152 @cindex MS-DOS-specific commands
20155 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
20156 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
20157 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
20158 top of real-mode DOS systems and their emulations.
20160 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
20161 defines a few commands specific to the @sc{djgpp} port. This
20162 subsection describes those commands.
20167 This is a prefix of @sc{djgpp}-specific commands which print
20168 information about the target system and important OS structures.
20171 @cindex MS-DOS system info
20172 @cindex free memory information (MS-DOS)
20173 @item info dos sysinfo
20174 This command displays assorted information about the underlying
20175 platform: the CPU type and features, the OS version and flavor, the
20176 DPMI version, and the available conventional and DPMI memory.
20181 @cindex segment descriptor tables
20182 @cindex descriptor tables display
20184 @itemx info dos ldt
20185 @itemx info dos idt
20186 These 3 commands display entries from, respectively, Global, Local,
20187 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
20188 tables are data structures which store a descriptor for each segment
20189 that is currently in use. The segment's selector is an index into a
20190 descriptor table; the table entry for that index holds the
20191 descriptor's base address and limit, and its attributes and access
20194 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
20195 segment (used for both data and the stack), and a DOS segment (which
20196 allows access to DOS/BIOS data structures and absolute addresses in
20197 conventional memory). However, the DPMI host will usually define
20198 additional segments in order to support the DPMI environment.
20200 @cindex garbled pointers
20201 These commands allow to display entries from the descriptor tables.
20202 Without an argument, all entries from the specified table are
20203 displayed. An argument, which should be an integer expression, means
20204 display a single entry whose index is given by the argument. For
20205 example, here's a convenient way to display information about the
20206 debugged program's data segment:
20209 @exdent @code{(@value{GDBP}) info dos ldt $ds}
20210 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
20214 This comes in handy when you want to see whether a pointer is outside
20215 the data segment's limit (i.e.@: @dfn{garbled}).
20217 @cindex page tables display (MS-DOS)
20219 @itemx info dos pte
20220 These two commands display entries from, respectively, the Page
20221 Directory and the Page Tables. Page Directories and Page Tables are
20222 data structures which control how virtual memory addresses are mapped
20223 into physical addresses. A Page Table includes an entry for every
20224 page of memory that is mapped into the program's address space; there
20225 may be several Page Tables, each one holding up to 4096 entries. A
20226 Page Directory has up to 4096 entries, one each for every Page Table
20227 that is currently in use.
20229 Without an argument, @kbd{info dos pde} displays the entire Page
20230 Directory, and @kbd{info dos pte} displays all the entries in all of
20231 the Page Tables. An argument, an integer expression, given to the
20232 @kbd{info dos pde} command means display only that entry from the Page
20233 Directory table. An argument given to the @kbd{info dos pte} command
20234 means display entries from a single Page Table, the one pointed to by
20235 the specified entry in the Page Directory.
20237 @cindex direct memory access (DMA) on MS-DOS
20238 These commands are useful when your program uses @dfn{DMA} (Direct
20239 Memory Access), which needs physical addresses to program the DMA
20242 These commands are supported only with some DPMI servers.
20244 @cindex physical address from linear address
20245 @item info dos address-pte @var{addr}
20246 This command displays the Page Table entry for a specified linear
20247 address. The argument @var{addr} is a linear address which should
20248 already have the appropriate segment's base address added to it,
20249 because this command accepts addresses which may belong to @emph{any}
20250 segment. For example, here's how to display the Page Table entry for
20251 the page where a variable @code{i} is stored:
20254 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
20255 @exdent @code{Page Table entry for address 0x11a00d30:}
20256 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
20260 This says that @code{i} is stored at offset @code{0xd30} from the page
20261 whose physical base address is @code{0x02698000}, and shows all the
20262 attributes of that page.
20264 Note that you must cast the addresses of variables to a @code{char *},
20265 since otherwise the value of @code{__djgpp_base_address}, the base
20266 address of all variables and functions in a @sc{djgpp} program, will
20267 be added using the rules of C pointer arithmetics: if @code{i} is
20268 declared an @code{int}, @value{GDBN} will add 4 times the value of
20269 @code{__djgpp_base_address} to the address of @code{i}.
20271 Here's another example, it displays the Page Table entry for the
20275 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
20276 @exdent @code{Page Table entry for address 0x29110:}
20277 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
20281 (The @code{+ 3} offset is because the transfer buffer's address is the
20282 3rd member of the @code{_go32_info_block} structure.) The output
20283 clearly shows that this DPMI server maps the addresses in conventional
20284 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
20285 linear (@code{0x29110}) addresses are identical.
20287 This command is supported only with some DPMI servers.
20290 @cindex DOS serial data link, remote debugging
20291 In addition to native debugging, the DJGPP port supports remote
20292 debugging via a serial data link. The following commands are specific
20293 to remote serial debugging in the DJGPP port of @value{GDBN}.
20296 @kindex set com1base
20297 @kindex set com1irq
20298 @kindex set com2base
20299 @kindex set com2irq
20300 @kindex set com3base
20301 @kindex set com3irq
20302 @kindex set com4base
20303 @kindex set com4irq
20304 @item set com1base @var{addr}
20305 This command sets the base I/O port address of the @file{COM1} serial
20308 @item set com1irq @var{irq}
20309 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
20310 for the @file{COM1} serial port.
20312 There are similar commands @samp{set com2base}, @samp{set com3irq},
20313 etc.@: for setting the port address and the @code{IRQ} lines for the
20316 @kindex show com1base
20317 @kindex show com1irq
20318 @kindex show com2base
20319 @kindex show com2irq
20320 @kindex show com3base
20321 @kindex show com3irq
20322 @kindex show com4base
20323 @kindex show com4irq
20324 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
20325 display the current settings of the base address and the @code{IRQ}
20326 lines used by the COM ports.
20329 @kindex info serial
20330 @cindex DOS serial port status
20331 This command prints the status of the 4 DOS serial ports. For each
20332 port, it prints whether it's active or not, its I/O base address and
20333 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
20334 counts of various errors encountered so far.
20338 @node Cygwin Native
20339 @subsection Features for Debugging MS Windows PE Executables
20340 @cindex MS Windows debugging
20341 @cindex native Cygwin debugging
20342 @cindex Cygwin-specific commands
20344 @value{GDBN} supports native debugging of MS Windows programs, including
20345 DLLs with and without symbolic debugging information.
20347 @cindex Ctrl-BREAK, MS-Windows
20348 @cindex interrupt debuggee on MS-Windows
20349 MS-Windows programs that call @code{SetConsoleMode} to switch off the
20350 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
20351 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
20352 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
20353 sequence, which can be used to interrupt the debuggee even if it
20356 There are various additional Cygwin-specific commands, described in
20357 this section. Working with DLLs that have no debugging symbols is
20358 described in @ref{Non-debug DLL Symbols}.
20363 This is a prefix of MS Windows-specific commands which print
20364 information about the target system and important OS structures.
20366 @item info w32 selector
20367 This command displays information returned by
20368 the Win32 API @code{GetThreadSelectorEntry} function.
20369 It takes an optional argument that is evaluated to
20370 a long value to give the information about this given selector.
20371 Without argument, this command displays information
20372 about the six segment registers.
20374 @item info w32 thread-information-block
20375 This command displays thread specific information stored in the
20376 Thread Information Block (readable on the X86 CPU family using @code{$fs}
20377 selector for 32-bit programs and @code{$gs} for 64-bit programs).
20381 This is a Cygwin-specific alias of @code{info shared}.
20383 @kindex set cygwin-exceptions
20384 @cindex debugging the Cygwin DLL
20385 @cindex Cygwin DLL, debugging
20386 @item set cygwin-exceptions @var{mode}
20387 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
20388 happen inside the Cygwin DLL. If @var{mode} is @code{off},
20389 @value{GDBN} will delay recognition of exceptions, and may ignore some
20390 exceptions which seem to be caused by internal Cygwin DLL
20391 ``bookkeeping''. This option is meant primarily for debugging the
20392 Cygwin DLL itself; the default value is @code{off} to avoid annoying
20393 @value{GDBN} users with false @code{SIGSEGV} signals.
20395 @kindex show cygwin-exceptions
20396 @item show cygwin-exceptions
20397 Displays whether @value{GDBN} will break on exceptions that happen
20398 inside the Cygwin DLL itself.
20400 @kindex set new-console
20401 @item set new-console @var{mode}
20402 If @var{mode} is @code{on} the debuggee will
20403 be started in a new console on next start.
20404 If @var{mode} is @code{off}, the debuggee will
20405 be started in the same console as the debugger.
20407 @kindex show new-console
20408 @item show new-console
20409 Displays whether a new console is used
20410 when the debuggee is started.
20412 @kindex set new-group
20413 @item set new-group @var{mode}
20414 This boolean value controls whether the debuggee should
20415 start a new group or stay in the same group as the debugger.
20416 This affects the way the Windows OS handles
20419 @kindex show new-group
20420 @item show new-group
20421 Displays current value of new-group boolean.
20423 @kindex set debugevents
20424 @item set debugevents
20425 This boolean value adds debug output concerning kernel events related
20426 to the debuggee seen by the debugger. This includes events that
20427 signal thread and process creation and exit, DLL loading and
20428 unloading, console interrupts, and debugging messages produced by the
20429 Windows @code{OutputDebugString} API call.
20431 @kindex set debugexec
20432 @item set debugexec
20433 This boolean value adds debug output concerning execute events
20434 (such as resume thread) seen by the debugger.
20436 @kindex set debugexceptions
20437 @item set debugexceptions
20438 This boolean value adds debug output concerning exceptions in the
20439 debuggee seen by the debugger.
20441 @kindex set debugmemory
20442 @item set debugmemory
20443 This boolean value adds debug output concerning debuggee memory reads
20444 and writes by the debugger.
20448 This boolean values specifies whether the debuggee is called
20449 via a shell or directly (default value is on).
20453 Displays if the debuggee will be started with a shell.
20458 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
20461 @node Non-debug DLL Symbols
20462 @subsubsection Support for DLLs without Debugging Symbols
20463 @cindex DLLs with no debugging symbols
20464 @cindex Minimal symbols and DLLs
20466 Very often on windows, some of the DLLs that your program relies on do
20467 not include symbolic debugging information (for example,
20468 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
20469 symbols in a DLL, it relies on the minimal amount of symbolic
20470 information contained in the DLL's export table. This section
20471 describes working with such symbols, known internally to @value{GDBN} as
20472 ``minimal symbols''.
20474 Note that before the debugged program has started execution, no DLLs
20475 will have been loaded. The easiest way around this problem is simply to
20476 start the program --- either by setting a breakpoint or letting the
20477 program run once to completion.
20479 @subsubsection DLL Name Prefixes
20481 In keeping with the naming conventions used by the Microsoft debugging
20482 tools, DLL export symbols are made available with a prefix based on the
20483 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
20484 also entered into the symbol table, so @code{CreateFileA} is often
20485 sufficient. In some cases there will be name clashes within a program
20486 (particularly if the executable itself includes full debugging symbols)
20487 necessitating the use of the fully qualified name when referring to the
20488 contents of the DLL. Use single-quotes around the name to avoid the
20489 exclamation mark (``!'') being interpreted as a language operator.
20491 Note that the internal name of the DLL may be all upper-case, even
20492 though the file name of the DLL is lower-case, or vice-versa. Since
20493 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
20494 some confusion. If in doubt, try the @code{info functions} and
20495 @code{info variables} commands or even @code{maint print msymbols}
20496 (@pxref{Symbols}). Here's an example:
20499 (@value{GDBP}) info function CreateFileA
20500 All functions matching regular expression "CreateFileA":
20502 Non-debugging symbols:
20503 0x77e885f4 CreateFileA
20504 0x77e885f4 KERNEL32!CreateFileA
20508 (@value{GDBP}) info function !
20509 All functions matching regular expression "!":
20511 Non-debugging symbols:
20512 0x6100114c cygwin1!__assert
20513 0x61004034 cygwin1!_dll_crt0@@0
20514 0x61004240 cygwin1!dll_crt0(per_process *)
20518 @subsubsection Working with Minimal Symbols
20520 Symbols extracted from a DLL's export table do not contain very much
20521 type information. All that @value{GDBN} can do is guess whether a symbol
20522 refers to a function or variable depending on the linker section that
20523 contains the symbol. Also note that the actual contents of the memory
20524 contained in a DLL are not available unless the program is running. This
20525 means that you cannot examine the contents of a variable or disassemble
20526 a function within a DLL without a running program.
20528 Variables are generally treated as pointers and dereferenced
20529 automatically. For this reason, it is often necessary to prefix a
20530 variable name with the address-of operator (``&'') and provide explicit
20531 type information in the command. Here's an example of the type of
20535 (@value{GDBP}) print 'cygwin1!__argv'
20540 (@value{GDBP}) x 'cygwin1!__argv'
20541 0x10021610: "\230y\""
20544 And two possible solutions:
20547 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
20548 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
20552 (@value{GDBP}) x/2x &'cygwin1!__argv'
20553 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
20554 (@value{GDBP}) x/x 0x10021608
20555 0x10021608: 0x0022fd98
20556 (@value{GDBP}) x/s 0x0022fd98
20557 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
20560 Setting a break point within a DLL is possible even before the program
20561 starts execution. However, under these circumstances, @value{GDBN} can't
20562 examine the initial instructions of the function in order to skip the
20563 function's frame set-up code. You can work around this by using ``*&''
20564 to set the breakpoint at a raw memory address:
20567 (@value{GDBP}) break *&'python22!PyOS_Readline'
20568 Breakpoint 1 at 0x1e04eff0
20571 The author of these extensions is not entirely convinced that setting a
20572 break point within a shared DLL like @file{kernel32.dll} is completely
20576 @subsection Commands Specific to @sc{gnu} Hurd Systems
20577 @cindex @sc{gnu} Hurd debugging
20579 This subsection describes @value{GDBN} commands specific to the
20580 @sc{gnu} Hurd native debugging.
20585 @kindex set signals@r{, Hurd command}
20586 @kindex set sigs@r{, Hurd command}
20587 This command toggles the state of inferior signal interception by
20588 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
20589 affected by this command. @code{sigs} is a shorthand alias for
20594 @kindex show signals@r{, Hurd command}
20595 @kindex show sigs@r{, Hurd command}
20596 Show the current state of intercepting inferior's signals.
20598 @item set signal-thread
20599 @itemx set sigthread
20600 @kindex set signal-thread
20601 @kindex set sigthread
20602 This command tells @value{GDBN} which thread is the @code{libc} signal
20603 thread. That thread is run when a signal is delivered to a running
20604 process. @code{set sigthread} is the shorthand alias of @code{set
20607 @item show signal-thread
20608 @itemx show sigthread
20609 @kindex show signal-thread
20610 @kindex show sigthread
20611 These two commands show which thread will run when the inferior is
20612 delivered a signal.
20615 @kindex set stopped@r{, Hurd command}
20616 This commands tells @value{GDBN} that the inferior process is stopped,
20617 as with the @code{SIGSTOP} signal. The stopped process can be
20618 continued by delivering a signal to it.
20621 @kindex show stopped@r{, Hurd command}
20622 This command shows whether @value{GDBN} thinks the debuggee is
20625 @item set exceptions
20626 @kindex set exceptions@r{, Hurd command}
20627 Use this command to turn off trapping of exceptions in the inferior.
20628 When exception trapping is off, neither breakpoints nor
20629 single-stepping will work. To restore the default, set exception
20632 @item show exceptions
20633 @kindex show exceptions@r{, Hurd command}
20634 Show the current state of trapping exceptions in the inferior.
20636 @item set task pause
20637 @kindex set task@r{, Hurd commands}
20638 @cindex task attributes (@sc{gnu} Hurd)
20639 @cindex pause current task (@sc{gnu} Hurd)
20640 This command toggles task suspension when @value{GDBN} has control.
20641 Setting it to on takes effect immediately, and the task is suspended
20642 whenever @value{GDBN} gets control. Setting it to off will take
20643 effect the next time the inferior is continued. If this option is set
20644 to off, you can use @code{set thread default pause on} or @code{set
20645 thread pause on} (see below) to pause individual threads.
20647 @item show task pause
20648 @kindex show task@r{, Hurd commands}
20649 Show the current state of task suspension.
20651 @item set task detach-suspend-count
20652 @cindex task suspend count
20653 @cindex detach from task, @sc{gnu} Hurd
20654 This command sets the suspend count the task will be left with when
20655 @value{GDBN} detaches from it.
20657 @item show task detach-suspend-count
20658 Show the suspend count the task will be left with when detaching.
20660 @item set task exception-port
20661 @itemx set task excp
20662 @cindex task exception port, @sc{gnu} Hurd
20663 This command sets the task exception port to which @value{GDBN} will
20664 forward exceptions. The argument should be the value of the @dfn{send
20665 rights} of the task. @code{set task excp} is a shorthand alias.
20667 @item set noninvasive
20668 @cindex noninvasive task options
20669 This command switches @value{GDBN} to a mode that is the least
20670 invasive as far as interfering with the inferior is concerned. This
20671 is the same as using @code{set task pause}, @code{set exceptions}, and
20672 @code{set signals} to values opposite to the defaults.
20674 @item info send-rights
20675 @itemx info receive-rights
20676 @itemx info port-rights
20677 @itemx info port-sets
20678 @itemx info dead-names
20681 @cindex send rights, @sc{gnu} Hurd
20682 @cindex receive rights, @sc{gnu} Hurd
20683 @cindex port rights, @sc{gnu} Hurd
20684 @cindex port sets, @sc{gnu} Hurd
20685 @cindex dead names, @sc{gnu} Hurd
20686 These commands display information about, respectively, send rights,
20687 receive rights, port rights, port sets, and dead names of a task.
20688 There are also shorthand aliases: @code{info ports} for @code{info
20689 port-rights} and @code{info psets} for @code{info port-sets}.
20691 @item set thread pause
20692 @kindex set thread@r{, Hurd command}
20693 @cindex thread properties, @sc{gnu} Hurd
20694 @cindex pause current thread (@sc{gnu} Hurd)
20695 This command toggles current thread suspension when @value{GDBN} has
20696 control. Setting it to on takes effect immediately, and the current
20697 thread is suspended whenever @value{GDBN} gets control. Setting it to
20698 off will take effect the next time the inferior is continued.
20699 Normally, this command has no effect, since when @value{GDBN} has
20700 control, the whole task is suspended. However, if you used @code{set
20701 task pause off} (see above), this command comes in handy to suspend
20702 only the current thread.
20704 @item show thread pause
20705 @kindex show thread@r{, Hurd command}
20706 This command shows the state of current thread suspension.
20708 @item set thread run
20709 This command sets whether the current thread is allowed to run.
20711 @item show thread run
20712 Show whether the current thread is allowed to run.
20714 @item set thread detach-suspend-count
20715 @cindex thread suspend count, @sc{gnu} Hurd
20716 @cindex detach from thread, @sc{gnu} Hurd
20717 This command sets the suspend count @value{GDBN} will leave on a
20718 thread when detaching. This number is relative to the suspend count
20719 found by @value{GDBN} when it notices the thread; use @code{set thread
20720 takeover-suspend-count} to force it to an absolute value.
20722 @item show thread detach-suspend-count
20723 Show the suspend count @value{GDBN} will leave on the thread when
20726 @item set thread exception-port
20727 @itemx set thread excp
20728 Set the thread exception port to which to forward exceptions. This
20729 overrides the port set by @code{set task exception-port} (see above).
20730 @code{set thread excp} is the shorthand alias.
20732 @item set thread takeover-suspend-count
20733 Normally, @value{GDBN}'s thread suspend counts are relative to the
20734 value @value{GDBN} finds when it notices each thread. This command
20735 changes the suspend counts to be absolute instead.
20737 @item set thread default
20738 @itemx show thread default
20739 @cindex thread default settings, @sc{gnu} Hurd
20740 Each of the above @code{set thread} commands has a @code{set thread
20741 default} counterpart (e.g., @code{set thread default pause}, @code{set
20742 thread default exception-port}, etc.). The @code{thread default}
20743 variety of commands sets the default thread properties for all
20744 threads; you can then change the properties of individual threads with
20745 the non-default commands.
20752 @value{GDBN} provides the following commands specific to the Darwin target:
20755 @item set debug darwin @var{num}
20756 @kindex set debug darwin
20757 When set to a non zero value, enables debugging messages specific to
20758 the Darwin support. Higher values produce more verbose output.
20760 @item show debug darwin
20761 @kindex show debug darwin
20762 Show the current state of Darwin messages.
20764 @item set debug mach-o @var{num}
20765 @kindex set debug mach-o
20766 When set to a non zero value, enables debugging messages while
20767 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
20768 file format used on Darwin for object and executable files.) Higher
20769 values produce more verbose output. This is a command to diagnose
20770 problems internal to @value{GDBN} and should not be needed in normal
20773 @item show debug mach-o
20774 @kindex show debug mach-o
20775 Show the current state of Mach-O file messages.
20777 @item set mach-exceptions on
20778 @itemx set mach-exceptions off
20779 @kindex set mach-exceptions
20780 On Darwin, faults are first reported as a Mach exception and are then
20781 mapped to a Posix signal. Use this command to turn on trapping of
20782 Mach exceptions in the inferior. This might be sometimes useful to
20783 better understand the cause of a fault. The default is off.
20785 @item show mach-exceptions
20786 @kindex show mach-exceptions
20787 Show the current state of exceptions trapping.
20792 @section Embedded Operating Systems
20794 This section describes configurations involving the debugging of
20795 embedded operating systems that are available for several different
20798 @value{GDBN} includes the ability to debug programs running on
20799 various real-time operating systems.
20801 @node Embedded Processors
20802 @section Embedded Processors
20804 This section goes into details specific to particular embedded
20807 @cindex send command to simulator
20808 Whenever a specific embedded processor has a simulator, @value{GDBN}
20809 allows to send an arbitrary command to the simulator.
20812 @item sim @var{command}
20813 @kindex sim@r{, a command}
20814 Send an arbitrary @var{command} string to the simulator. Consult the
20815 documentation for the specific simulator in use for information about
20816 acceptable commands.
20822 * M32R/D:: Renesas M32R/D
20823 * M68K:: Motorola M68K
20824 * MicroBlaze:: Xilinx MicroBlaze
20825 * MIPS Embedded:: MIPS Embedded
20826 * PowerPC Embedded:: PowerPC Embedded
20827 * PA:: HP PA Embedded
20828 * Sparclet:: Tsqware Sparclet
20829 * Sparclite:: Fujitsu Sparclite
20830 * Z8000:: Zilog Z8000
20833 * Super-H:: Renesas Super-H
20842 @item target rdi @var{dev}
20843 ARM Angel monitor, via RDI library interface to ADP protocol. You may
20844 use this target to communicate with both boards running the Angel
20845 monitor, or with the EmbeddedICE JTAG debug device.
20848 @item target rdp @var{dev}
20853 @value{GDBN} provides the following ARM-specific commands:
20856 @item set arm disassembler
20858 This commands selects from a list of disassembly styles. The
20859 @code{"std"} style is the standard style.
20861 @item show arm disassembler
20863 Show the current disassembly style.
20865 @item set arm apcs32
20866 @cindex ARM 32-bit mode
20867 This command toggles ARM operation mode between 32-bit and 26-bit.
20869 @item show arm apcs32
20870 Display the current usage of the ARM 32-bit mode.
20872 @item set arm fpu @var{fputype}
20873 This command sets the ARM floating-point unit (FPU) type. The
20874 argument @var{fputype} can be one of these:
20878 Determine the FPU type by querying the OS ABI.
20880 Software FPU, with mixed-endian doubles on little-endian ARM
20883 GCC-compiled FPA co-processor.
20885 Software FPU with pure-endian doubles.
20891 Show the current type of the FPU.
20894 This command forces @value{GDBN} to use the specified ABI.
20897 Show the currently used ABI.
20899 @item set arm fallback-mode (arm|thumb|auto)
20900 @value{GDBN} uses the symbol table, when available, to determine
20901 whether instructions are ARM or Thumb. This command controls
20902 @value{GDBN}'s default behavior when the symbol table is not
20903 available. The default is @samp{auto}, which causes @value{GDBN} to
20904 use the current execution mode (from the @code{T} bit in the @code{CPSR}
20907 @item show arm fallback-mode
20908 Show the current fallback instruction mode.
20910 @item set arm force-mode (arm|thumb|auto)
20911 This command overrides use of the symbol table to determine whether
20912 instructions are ARM or Thumb. The default is @samp{auto}, which
20913 causes @value{GDBN} to use the symbol table and then the setting
20914 of @samp{set arm fallback-mode}.
20916 @item show arm force-mode
20917 Show the current forced instruction mode.
20919 @item set debug arm
20920 Toggle whether to display ARM-specific debugging messages from the ARM
20921 target support subsystem.
20923 @item show debug arm
20924 Show whether ARM-specific debugging messages are enabled.
20927 The following commands are available when an ARM target is debugged
20928 using the RDI interface:
20931 @item rdilogfile @r{[}@var{file}@r{]}
20933 @cindex ADP (Angel Debugger Protocol) logging
20934 Set the filename for the ADP (Angel Debugger Protocol) packet log.
20935 With an argument, sets the log file to the specified @var{file}. With
20936 no argument, show the current log file name. The default log file is
20939 @item rdilogenable @r{[}@var{arg}@r{]}
20940 @kindex rdilogenable
20941 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
20942 enables logging, with an argument 0 or @code{"no"} disables it. With
20943 no arguments displays the current setting. When logging is enabled,
20944 ADP packets exchanged between @value{GDBN} and the RDI target device
20945 are logged to a file.
20947 @item set rdiromatzero
20948 @kindex set rdiromatzero
20949 @cindex ROM at zero address, RDI
20950 Tell @value{GDBN} whether the target has ROM at address 0. If on,
20951 vector catching is disabled, so that zero address can be used. If off
20952 (the default), vector catching is enabled. For this command to take
20953 effect, it needs to be invoked prior to the @code{target rdi} command.
20955 @item show rdiromatzero
20956 @kindex show rdiromatzero
20957 Show the current setting of ROM at zero address.
20959 @item set rdiheartbeat
20960 @kindex set rdiheartbeat
20961 @cindex RDI heartbeat
20962 Enable or disable RDI heartbeat packets. It is not recommended to
20963 turn on this option, since it confuses ARM and EPI JTAG interface, as
20964 well as the Angel monitor.
20966 @item show rdiheartbeat
20967 @kindex show rdiheartbeat
20968 Show the setting of RDI heartbeat packets.
20972 @item target sim @r{[}@var{simargs}@r{]} @dots{}
20973 The @value{GDBN} ARM simulator accepts the following optional arguments.
20976 @item --swi-support=@var{type}
20977 Tell the simulator which SWI interfaces to support. The argument
20978 @var{type} may be a comma separated list of the following values.
20979 The default value is @code{all}.
20992 @subsection Renesas M32R/D and M32R/SDI
20995 @kindex target m32r
20996 @item target m32r @var{dev}
20997 Renesas M32R/D ROM monitor.
20999 @kindex target m32rsdi
21000 @item target m32rsdi @var{dev}
21001 Renesas M32R SDI server, connected via parallel port to the board.
21004 The following @value{GDBN} commands are specific to the M32R monitor:
21007 @item set download-path @var{path}
21008 @kindex set download-path
21009 @cindex find downloadable @sc{srec} files (M32R)
21010 Set the default path for finding downloadable @sc{srec} files.
21012 @item show download-path
21013 @kindex show download-path
21014 Show the default path for downloadable @sc{srec} files.
21016 @item set board-address @var{addr}
21017 @kindex set board-address
21018 @cindex M32-EVA target board address
21019 Set the IP address for the M32R-EVA target board.
21021 @item show board-address
21022 @kindex show board-address
21023 Show the current IP address of the target board.
21025 @item set server-address @var{addr}
21026 @kindex set server-address
21027 @cindex download server address (M32R)
21028 Set the IP address for the download server, which is the @value{GDBN}'s
21031 @item show server-address
21032 @kindex show server-address
21033 Display the IP address of the download server.
21035 @item upload @r{[}@var{file}@r{]}
21036 @kindex upload@r{, M32R}
21037 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
21038 upload capability. If no @var{file} argument is given, the current
21039 executable file is uploaded.
21041 @item tload @r{[}@var{file}@r{]}
21042 @kindex tload@r{, M32R}
21043 Test the @code{upload} command.
21046 The following commands are available for M32R/SDI:
21051 @cindex reset SDI connection, M32R
21052 This command resets the SDI connection.
21056 This command shows the SDI connection status.
21059 @kindex debug_chaos
21060 @cindex M32R/Chaos debugging
21061 Instructs the remote that M32R/Chaos debugging is to be used.
21063 @item use_debug_dma
21064 @kindex use_debug_dma
21065 Instructs the remote to use the DEBUG_DMA method of accessing memory.
21068 @kindex use_mon_code
21069 Instructs the remote to use the MON_CODE method of accessing memory.
21072 @kindex use_ib_break
21073 Instructs the remote to set breakpoints by IB break.
21075 @item use_dbt_break
21076 @kindex use_dbt_break
21077 Instructs the remote to set breakpoints by DBT.
21083 The Motorola m68k configuration includes ColdFire support, and a
21084 target command for the following ROM monitor.
21088 @kindex target dbug
21089 @item target dbug @var{dev}
21090 dBUG ROM monitor for Motorola ColdFire.
21095 @subsection MicroBlaze
21096 @cindex Xilinx MicroBlaze
21097 @cindex XMD, Xilinx Microprocessor Debugger
21099 The MicroBlaze is a soft-core processor supported on various Xilinx
21100 FPGAs, such as Spartan or Virtex series. Boards with these processors
21101 usually have JTAG ports which connect to a host system running the Xilinx
21102 Embedded Development Kit (EDK) or Software Development Kit (SDK).
21103 This host system is used to download the configuration bitstream to
21104 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
21105 communicates with the target board using the JTAG interface and
21106 presents a @code{gdbserver} interface to the board. By default
21107 @code{xmd} uses port @code{1234}. (While it is possible to change
21108 this default port, it requires the use of undocumented @code{xmd}
21109 commands. Contact Xilinx support if you need to do this.)
21111 Use these GDB commands to connect to the MicroBlaze target processor.
21114 @item target remote :1234
21115 Use this command to connect to the target if you are running @value{GDBN}
21116 on the same system as @code{xmd}.
21118 @item target remote @var{xmd-host}:1234
21119 Use this command to connect to the target if it is connected to @code{xmd}
21120 running on a different system named @var{xmd-host}.
21123 Use this command to download a program to the MicroBlaze target.
21125 @item set debug microblaze @var{n}
21126 Enable MicroBlaze-specific debugging messages if non-zero.
21128 @item show debug microblaze @var{n}
21129 Show MicroBlaze-specific debugging level.
21132 @node MIPS Embedded
21133 @subsection @acronym{MIPS} Embedded
21135 @cindex @acronym{MIPS} boards
21136 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
21137 @acronym{MIPS} board attached to a serial line. This is available when
21138 you configure @value{GDBN} with @samp{--target=mips-elf}.
21141 Use these @value{GDBN} commands to specify the connection to your target board:
21144 @item target mips @var{port}
21145 @kindex target mips @var{port}
21146 To run a program on the board, start up @code{@value{GDBP}} with the
21147 name of your program as the argument. To connect to the board, use the
21148 command @samp{target mips @var{port}}, where @var{port} is the name of
21149 the serial port connected to the board. If the program has not already
21150 been downloaded to the board, you may use the @code{load} command to
21151 download it. You can then use all the usual @value{GDBN} commands.
21153 For example, this sequence connects to the target board through a serial
21154 port, and loads and runs a program called @var{prog} through the
21158 host$ @value{GDBP} @var{prog}
21159 @value{GDBN} is free software and @dots{}
21160 (@value{GDBP}) target mips /dev/ttyb
21161 (@value{GDBP}) load @var{prog}
21165 @item target mips @var{hostname}:@var{portnumber}
21166 On some @value{GDBN} host configurations, you can specify a TCP
21167 connection (for instance, to a serial line managed by a terminal
21168 concentrator) instead of a serial port, using the syntax
21169 @samp{@var{hostname}:@var{portnumber}}.
21171 @item target pmon @var{port}
21172 @kindex target pmon @var{port}
21175 @item target ddb @var{port}
21176 @kindex target ddb @var{port}
21177 NEC's DDB variant of PMON for Vr4300.
21179 @item target lsi @var{port}
21180 @kindex target lsi @var{port}
21181 LSI variant of PMON.
21183 @kindex target r3900
21184 @item target r3900 @var{dev}
21185 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
21187 @kindex target array
21188 @item target array @var{dev}
21189 Array Tech LSI33K RAID controller board.
21195 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
21198 @item set mipsfpu double
21199 @itemx set mipsfpu single
21200 @itemx set mipsfpu none
21201 @itemx set mipsfpu auto
21202 @itemx show mipsfpu
21203 @kindex set mipsfpu
21204 @kindex show mipsfpu
21205 @cindex @acronym{MIPS} remote floating point
21206 @cindex floating point, @acronym{MIPS} remote
21207 If your target board does not support the @acronym{MIPS} floating point
21208 coprocessor, you should use the command @samp{set mipsfpu none} (if you
21209 need this, you may wish to put the command in your @value{GDBN} init
21210 file). This tells @value{GDBN} how to find the return value of
21211 functions which return floating point values. It also allows
21212 @value{GDBN} to avoid saving the floating point registers when calling
21213 functions on the board. If you are using a floating point coprocessor
21214 with only single precision floating point support, as on the @sc{r4650}
21215 processor, use the command @samp{set mipsfpu single}. The default
21216 double precision floating point coprocessor may be selected using
21217 @samp{set mipsfpu double}.
21219 In previous versions the only choices were double precision or no
21220 floating point, so @samp{set mipsfpu on} will select double precision
21221 and @samp{set mipsfpu off} will select no floating point.
21223 As usual, you can inquire about the @code{mipsfpu} variable with
21224 @samp{show mipsfpu}.
21226 @item set timeout @var{seconds}
21227 @itemx set retransmit-timeout @var{seconds}
21228 @itemx show timeout
21229 @itemx show retransmit-timeout
21230 @cindex @code{timeout}, @acronym{MIPS} protocol
21231 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
21232 @kindex set timeout
21233 @kindex show timeout
21234 @kindex set retransmit-timeout
21235 @kindex show retransmit-timeout
21236 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
21237 remote protocol, with the @code{set timeout @var{seconds}} command. The
21238 default is 5 seconds. Similarly, you can control the timeout used while
21239 waiting for an acknowledgment of a packet with the @code{set
21240 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
21241 You can inspect both values with @code{show timeout} and @code{show
21242 retransmit-timeout}. (These commands are @emph{only} available when
21243 @value{GDBN} is configured for @samp{--target=mips-elf}.)
21245 The timeout set by @code{set timeout} does not apply when @value{GDBN}
21246 is waiting for your program to stop. In that case, @value{GDBN} waits
21247 forever because it has no way of knowing how long the program is going
21248 to run before stopping.
21250 @item set syn-garbage-limit @var{num}
21251 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
21252 @cindex synchronize with remote @acronym{MIPS} target
21253 Limit the maximum number of characters @value{GDBN} should ignore when
21254 it tries to synchronize with the remote target. The default is 10
21255 characters. Setting the limit to -1 means there's no limit.
21257 @item show syn-garbage-limit
21258 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
21259 Show the current limit on the number of characters to ignore when
21260 trying to synchronize with the remote system.
21262 @item set monitor-prompt @var{prompt}
21263 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
21264 @cindex remote monitor prompt
21265 Tell @value{GDBN} to expect the specified @var{prompt} string from the
21266 remote monitor. The default depends on the target:
21276 @item show monitor-prompt
21277 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
21278 Show the current strings @value{GDBN} expects as the prompt from the
21281 @item set monitor-warnings
21282 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
21283 Enable or disable monitor warnings about hardware breakpoints. This
21284 has effect only for the @code{lsi} target. When on, @value{GDBN} will
21285 display warning messages whose codes are returned by the @code{lsi}
21286 PMON monitor for breakpoint commands.
21288 @item show monitor-warnings
21289 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
21290 Show the current setting of printing monitor warnings.
21292 @item pmon @var{command}
21293 @kindex pmon@r{, @acronym{MIPS} remote}
21294 @cindex send PMON command
21295 This command allows sending an arbitrary @var{command} string to the
21296 monitor. The monitor must be in debug mode for this to work.
21299 @node PowerPC Embedded
21300 @subsection PowerPC Embedded
21302 @cindex DVC register
21303 @value{GDBN} supports using the DVC (Data Value Compare) register to
21304 implement in hardware simple hardware watchpoint conditions of the form:
21307 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
21308 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
21311 The DVC register will be automatically used when @value{GDBN} detects
21312 such pattern in a condition expression, and the created watchpoint uses one
21313 debug register (either the @code{exact-watchpoints} option is on and the
21314 variable is scalar, or the variable has a length of one byte). This feature
21315 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
21318 When running on PowerPC embedded processors, @value{GDBN} automatically uses
21319 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
21320 in which case watchpoints using only one debug register are created when
21321 watching variables of scalar types.
21323 You can create an artificial array to watch an arbitrary memory
21324 region using one of the following commands (@pxref{Expressions}):
21327 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
21328 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
21331 PowerPC embedded processors support masked watchpoints. See the discussion
21332 about the @code{mask} argument in @ref{Set Watchpoints}.
21334 @cindex ranged breakpoint
21335 PowerPC embedded processors support hardware accelerated
21336 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
21337 the inferior whenever it executes an instruction at any address within
21338 the range it specifies. To set a ranged breakpoint in @value{GDBN},
21339 use the @code{break-range} command.
21341 @value{GDBN} provides the following PowerPC-specific commands:
21344 @kindex break-range
21345 @item break-range @var{start-location}, @var{end-location}
21346 Set a breakpoint for an address range given by
21347 @var{start-location} and @var{end-location}, which can specify a function name,
21348 a line number, an offset of lines from the current line or from the start
21349 location, or an address of an instruction (see @ref{Specify Location},
21350 for a list of all the possible ways to specify a @var{location}.)
21351 The breakpoint will stop execution of the inferior whenever it
21352 executes an instruction at any address within the specified range,
21353 (including @var{start-location} and @var{end-location}.)
21355 @kindex set powerpc
21356 @item set powerpc soft-float
21357 @itemx show powerpc soft-float
21358 Force @value{GDBN} to use (or not use) a software floating point calling
21359 convention. By default, @value{GDBN} selects the calling convention based
21360 on the selected architecture and the provided executable file.
21362 @item set powerpc vector-abi
21363 @itemx show powerpc vector-abi
21364 Force @value{GDBN} to use the specified calling convention for vector
21365 arguments and return values. The valid options are @samp{auto};
21366 @samp{generic}, to avoid vector registers even if they are present;
21367 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
21368 registers. By default, @value{GDBN} selects the calling convention
21369 based on the selected architecture and the provided executable file.
21371 @item set powerpc exact-watchpoints
21372 @itemx show powerpc exact-watchpoints
21373 Allow @value{GDBN} to use only one debug register when watching a variable
21374 of scalar type, thus assuming that the variable is accessed through the
21375 address of its first byte.
21377 @kindex target dink32
21378 @item target dink32 @var{dev}
21379 DINK32 ROM monitor.
21381 @kindex target ppcbug
21382 @item target ppcbug @var{dev}
21383 @kindex target ppcbug1
21384 @item target ppcbug1 @var{dev}
21385 PPCBUG ROM monitor for PowerPC.
21388 @item target sds @var{dev}
21389 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
21392 @cindex SDS protocol
21393 The following commands specific to the SDS protocol are supported
21397 @item set sdstimeout @var{nsec}
21398 @kindex set sdstimeout
21399 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
21400 default is 2 seconds.
21402 @item show sdstimeout
21403 @kindex show sdstimeout
21404 Show the current value of the SDS timeout.
21406 @item sds @var{command}
21407 @kindex sds@r{, a command}
21408 Send the specified @var{command} string to the SDS monitor.
21413 @subsection HP PA Embedded
21417 @kindex target op50n
21418 @item target op50n @var{dev}
21419 OP50N monitor, running on an OKI HPPA board.
21421 @kindex target w89k
21422 @item target w89k @var{dev}
21423 W89K monitor, running on a Winbond HPPA board.
21428 @subsection Tsqware Sparclet
21432 @value{GDBN} enables developers to debug tasks running on
21433 Sparclet targets from a Unix host.
21434 @value{GDBN} uses code that runs on
21435 both the Unix host and on the Sparclet target. The program
21436 @code{@value{GDBP}} is installed and executed on the Unix host.
21439 @item remotetimeout @var{args}
21440 @kindex remotetimeout
21441 @value{GDBN} supports the option @code{remotetimeout}.
21442 This option is set by the user, and @var{args} represents the number of
21443 seconds @value{GDBN} waits for responses.
21446 @cindex compiling, on Sparclet
21447 When compiling for debugging, include the options @samp{-g} to get debug
21448 information and @samp{-Ttext} to relocate the program to where you wish to
21449 load it on the target. You may also want to add the options @samp{-n} or
21450 @samp{-N} in order to reduce the size of the sections. Example:
21453 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
21456 You can use @code{objdump} to verify that the addresses are what you intended:
21459 sparclet-aout-objdump --headers --syms prog
21462 @cindex running, on Sparclet
21464 your Unix execution search path to find @value{GDBN}, you are ready to
21465 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
21466 (or @code{sparclet-aout-gdb}, depending on your installation).
21468 @value{GDBN} comes up showing the prompt:
21475 * Sparclet File:: Setting the file to debug
21476 * Sparclet Connection:: Connecting to Sparclet
21477 * Sparclet Download:: Sparclet download
21478 * Sparclet Execution:: Running and debugging
21481 @node Sparclet File
21482 @subsubsection Setting File to Debug
21484 The @value{GDBN} command @code{file} lets you choose with program to debug.
21487 (gdbslet) file prog
21491 @value{GDBN} then attempts to read the symbol table of @file{prog}.
21492 @value{GDBN} locates
21493 the file by searching the directories listed in the command search
21495 If the file was compiled with debug information (option @samp{-g}), source
21496 files will be searched as well.
21497 @value{GDBN} locates
21498 the source files by searching the directories listed in the directory search
21499 path (@pxref{Environment, ,Your Program's Environment}).
21501 to find a file, it displays a message such as:
21504 prog: No such file or directory.
21507 When this happens, add the appropriate directories to the search paths with
21508 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
21509 @code{target} command again.
21511 @node Sparclet Connection
21512 @subsubsection Connecting to Sparclet
21514 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
21515 To connect to a target on serial port ``@code{ttya}'', type:
21518 (gdbslet) target sparclet /dev/ttya
21519 Remote target sparclet connected to /dev/ttya
21520 main () at ../prog.c:3
21524 @value{GDBN} displays messages like these:
21530 @node Sparclet Download
21531 @subsubsection Sparclet Download
21533 @cindex download to Sparclet
21534 Once connected to the Sparclet target,
21535 you can use the @value{GDBN}
21536 @code{load} command to download the file from the host to the target.
21537 The file name and load offset should be given as arguments to the @code{load}
21539 Since the file format is aout, the program must be loaded to the starting
21540 address. You can use @code{objdump} to find out what this value is. The load
21541 offset is an offset which is added to the VMA (virtual memory address)
21542 of each of the file's sections.
21543 For instance, if the program
21544 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
21545 and bss at 0x12010170, in @value{GDBN}, type:
21548 (gdbslet) load prog 0x12010000
21549 Loading section .text, size 0xdb0 vma 0x12010000
21552 If the code is loaded at a different address then what the program was linked
21553 to, you may need to use the @code{section} and @code{add-symbol-file} commands
21554 to tell @value{GDBN} where to map the symbol table.
21556 @node Sparclet Execution
21557 @subsubsection Running and Debugging
21559 @cindex running and debugging Sparclet programs
21560 You can now begin debugging the task using @value{GDBN}'s execution control
21561 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
21562 manual for the list of commands.
21566 Breakpoint 1 at 0x12010000: file prog.c, line 3.
21568 Starting program: prog
21569 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
21570 3 char *symarg = 0;
21572 4 char *execarg = "hello!";
21577 @subsection Fujitsu Sparclite
21581 @kindex target sparclite
21582 @item target sparclite @var{dev}
21583 Fujitsu sparclite boards, used only for the purpose of loading.
21584 You must use an additional command to debug the program.
21585 For example: target remote @var{dev} using @value{GDBN} standard
21591 @subsection Zilog Z8000
21594 @cindex simulator, Z8000
21595 @cindex Zilog Z8000 simulator
21597 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
21600 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
21601 unsegmented variant of the Z8000 architecture) or the Z8001 (the
21602 segmented variant). The simulator recognizes which architecture is
21603 appropriate by inspecting the object code.
21606 @item target sim @var{args}
21608 @kindex target sim@r{, with Z8000}
21609 Debug programs on a simulated CPU. If the simulator supports setup
21610 options, specify them via @var{args}.
21614 After specifying this target, you can debug programs for the simulated
21615 CPU in the same style as programs for your host computer; use the
21616 @code{file} command to load a new program image, the @code{run} command
21617 to run your program, and so on.
21619 As well as making available all the usual machine registers
21620 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
21621 additional items of information as specially named registers:
21626 Counts clock-ticks in the simulator.
21629 Counts instructions run in the simulator.
21632 Execution time in 60ths of a second.
21636 You can refer to these values in @value{GDBN} expressions with the usual
21637 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
21638 conditional breakpoint that suspends only after at least 5000
21639 simulated clock ticks.
21642 @subsection Atmel AVR
21645 When configured for debugging the Atmel AVR, @value{GDBN} supports the
21646 following AVR-specific commands:
21649 @item info io_registers
21650 @kindex info io_registers@r{, AVR}
21651 @cindex I/O registers (Atmel AVR)
21652 This command displays information about the AVR I/O registers. For
21653 each register, @value{GDBN} prints its number and value.
21660 When configured for debugging CRIS, @value{GDBN} provides the
21661 following CRIS-specific commands:
21664 @item set cris-version @var{ver}
21665 @cindex CRIS version
21666 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
21667 The CRIS version affects register names and sizes. This command is useful in
21668 case autodetection of the CRIS version fails.
21670 @item show cris-version
21671 Show the current CRIS version.
21673 @item set cris-dwarf2-cfi
21674 @cindex DWARF-2 CFI and CRIS
21675 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
21676 Change to @samp{off} when using @code{gcc-cris} whose version is below
21679 @item show cris-dwarf2-cfi
21680 Show the current state of using DWARF-2 CFI.
21682 @item set cris-mode @var{mode}
21684 Set the current CRIS mode to @var{mode}. It should only be changed when
21685 debugging in guru mode, in which case it should be set to
21686 @samp{guru} (the default is @samp{normal}).
21688 @item show cris-mode
21689 Show the current CRIS mode.
21693 @subsection Renesas Super-H
21696 For the Renesas Super-H processor, @value{GDBN} provides these
21700 @item set sh calling-convention @var{convention}
21701 @kindex set sh calling-convention
21702 Set the calling-convention used when calling functions from @value{GDBN}.
21703 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
21704 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
21705 convention. If the DWARF-2 information of the called function specifies
21706 that the function follows the Renesas calling convention, the function
21707 is called using the Renesas calling convention. If the calling convention
21708 is set to @samp{renesas}, the Renesas calling convention is always used,
21709 regardless of the DWARF-2 information. This can be used to override the
21710 default of @samp{gcc} if debug information is missing, or the compiler
21711 does not emit the DWARF-2 calling convention entry for a function.
21713 @item show sh calling-convention
21714 @kindex show sh calling-convention
21715 Show the current calling convention setting.
21720 @node Architectures
21721 @section Architectures
21723 This section describes characteristics of architectures that affect
21724 all uses of @value{GDBN} with the architecture, both native and cross.
21731 * HPPA:: HP PA architecture
21732 * SPU:: Cell Broadband Engine SPU architecture
21738 @subsection AArch64
21739 @cindex AArch64 support
21741 When @value{GDBN} is debugging the AArch64 architecture, it provides the
21742 following special commands:
21745 @item set debug aarch64
21746 @kindex set debug aarch64
21747 This command determines whether AArch64 architecture-specific debugging
21748 messages are to be displayed.
21750 @item show debug aarch64
21751 Show whether AArch64 debugging messages are displayed.
21756 @subsection x86 Architecture-specific Issues
21759 @item set struct-convention @var{mode}
21760 @kindex set struct-convention
21761 @cindex struct return convention
21762 @cindex struct/union returned in registers
21763 Set the convention used by the inferior to return @code{struct}s and
21764 @code{union}s from functions to @var{mode}. Possible values of
21765 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
21766 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
21767 are returned on the stack, while @code{"reg"} means that a
21768 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
21769 be returned in a register.
21771 @item show struct-convention
21772 @kindex show struct-convention
21773 Show the current setting of the convention to return @code{struct}s
21777 @subsubsection Intel(R) @dfn{Memory Protection Extensions} (MPX).
21778 @cindex Intel(R) Memory Protection Extensions (MPX).
21780 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
21781 @footnote{The register named with capital letters represent the architecture
21782 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
21783 which are the lower bound and upper bound. Bounds are effective addresses or
21784 memory locations. The upper bounds are architecturally represented in 1's
21785 complement form. A bound having lower bound = 0, and upper bound = 0
21786 (1's complement of all bits set) will allow access to the entire address space.
21788 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
21789 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
21790 display the upper bound performing the complement of one operation on the
21791 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
21792 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
21793 can also be noted that the upper bounds are inclusive.
21795 As an example, assume that the register BND0 holds bounds for a pointer having
21796 access allowed for the range between 0x32 and 0x71. The values present on
21797 bnd0raw and bnd registers are presented as follows:
21800 bnd0raw = @{0x32, 0xffffffff8e@}
21801 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
21804 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
21805 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
21806 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
21807 Python, the display includes the memory size, in bits, accessible to
21813 See the following section.
21816 @subsection @acronym{MIPS}
21818 @cindex stack on Alpha
21819 @cindex stack on @acronym{MIPS}
21820 @cindex Alpha stack
21821 @cindex @acronym{MIPS} stack
21822 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
21823 sometimes requires @value{GDBN} to search backward in the object code to
21824 find the beginning of a function.
21826 @cindex response time, @acronym{MIPS} debugging
21827 To improve response time (especially for embedded applications, where
21828 @value{GDBN} may be restricted to a slow serial line for this search)
21829 you may want to limit the size of this search, using one of these
21833 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
21834 @item set heuristic-fence-post @var{limit}
21835 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
21836 search for the beginning of a function. A value of @var{0} (the
21837 default) means there is no limit. However, except for @var{0}, the
21838 larger the limit the more bytes @code{heuristic-fence-post} must search
21839 and therefore the longer it takes to run. You should only need to use
21840 this command when debugging a stripped executable.
21842 @item show heuristic-fence-post
21843 Display the current limit.
21847 These commands are available @emph{only} when @value{GDBN} is configured
21848 for debugging programs on Alpha or @acronym{MIPS} processors.
21850 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
21854 @item set mips abi @var{arg}
21855 @kindex set mips abi
21856 @cindex set ABI for @acronym{MIPS}
21857 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
21858 values of @var{arg} are:
21862 The default ABI associated with the current binary (this is the
21872 @item show mips abi
21873 @kindex show mips abi
21874 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
21876 @item set mips compression @var{arg}
21877 @kindex set mips compression
21878 @cindex code compression, @acronym{MIPS}
21879 Tell @value{GDBN} which @acronym{MIPS} compressed
21880 @acronym{ISA, Instruction Set Architecture} encoding is used by the
21881 inferior. @value{GDBN} uses this for code disassembly and other
21882 internal interpretation purposes. This setting is only referred to
21883 when no executable has been associated with the debugging session or
21884 the executable does not provide information about the encoding it uses.
21885 Otherwise this setting is automatically updated from information
21886 provided by the executable.
21888 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
21889 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
21890 executables containing @acronym{MIPS16} code frequently are not
21891 identified as such.
21893 This setting is ``sticky''; that is, it retains its value across
21894 debugging sessions until reset either explicitly with this command or
21895 implicitly from an executable.
21897 The compiler and/or assembler typically add symbol table annotations to
21898 identify functions compiled for the @acronym{MIPS16} or
21899 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
21900 are present, @value{GDBN} uses them in preference to the global
21901 compressed @acronym{ISA} encoding setting.
21903 @item show mips compression
21904 @kindex show mips compression
21905 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
21906 @value{GDBN} to debug the inferior.
21909 @itemx show mipsfpu
21910 @xref{MIPS Embedded, set mipsfpu}.
21912 @item set mips mask-address @var{arg}
21913 @kindex set mips mask-address
21914 @cindex @acronym{MIPS} addresses, masking
21915 This command determines whether the most-significant 32 bits of 64-bit
21916 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
21917 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
21918 setting, which lets @value{GDBN} determine the correct value.
21920 @item show mips mask-address
21921 @kindex show mips mask-address
21922 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
21925 @item set remote-mips64-transfers-32bit-regs
21926 @kindex set remote-mips64-transfers-32bit-regs
21927 This command controls compatibility with 64-bit @acronym{MIPS} targets that
21928 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
21929 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
21930 and 64 bits for other registers, set this option to @samp{on}.
21932 @item show remote-mips64-transfers-32bit-regs
21933 @kindex show remote-mips64-transfers-32bit-regs
21934 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
21936 @item set debug mips
21937 @kindex set debug mips
21938 This command turns on and off debugging messages for the @acronym{MIPS}-specific
21939 target code in @value{GDBN}.
21941 @item show debug mips
21942 @kindex show debug mips
21943 Show the current setting of @acronym{MIPS} debugging messages.
21949 @cindex HPPA support
21951 When @value{GDBN} is debugging the HP PA architecture, it provides the
21952 following special commands:
21955 @item set debug hppa
21956 @kindex set debug hppa
21957 This command determines whether HPPA architecture-specific debugging
21958 messages are to be displayed.
21960 @item show debug hppa
21961 Show whether HPPA debugging messages are displayed.
21963 @item maint print unwind @var{address}
21964 @kindex maint print unwind@r{, HPPA}
21965 This command displays the contents of the unwind table entry at the
21966 given @var{address}.
21972 @subsection Cell Broadband Engine SPU architecture
21973 @cindex Cell Broadband Engine
21976 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
21977 it provides the following special commands:
21980 @item info spu event
21982 Display SPU event facility status. Shows current event mask
21983 and pending event status.
21985 @item info spu signal
21986 Display SPU signal notification facility status. Shows pending
21987 signal-control word and signal notification mode of both signal
21988 notification channels.
21990 @item info spu mailbox
21991 Display SPU mailbox facility status. Shows all pending entries,
21992 in order of processing, in each of the SPU Write Outbound,
21993 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
21996 Display MFC DMA status. Shows all pending commands in the MFC
21997 DMA queue. For each entry, opcode, tag, class IDs, effective
21998 and local store addresses and transfer size are shown.
22000 @item info spu proxydma
22001 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
22002 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
22003 and local store addresses and transfer size are shown.
22007 When @value{GDBN} is debugging a combined PowerPC/SPU application
22008 on the Cell Broadband Engine, it provides in addition the following
22012 @item set spu stop-on-load @var{arg}
22014 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
22015 will give control to the user when a new SPE thread enters its @code{main}
22016 function. The default is @code{off}.
22018 @item show spu stop-on-load
22020 Show whether to stop for new SPE threads.
22022 @item set spu auto-flush-cache @var{arg}
22023 Set whether to automatically flush the software-managed cache. When set to
22024 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
22025 cache to be flushed whenever SPE execution stops. This provides a consistent
22026 view of PowerPC memory that is accessed via the cache. If an application
22027 does not use the software-managed cache, this option has no effect.
22029 @item show spu auto-flush-cache
22030 Show whether to automatically flush the software-managed cache.
22035 @subsection PowerPC
22036 @cindex PowerPC architecture
22038 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
22039 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
22040 numbers stored in the floating point registers. These values must be stored
22041 in two consecutive registers, always starting at an even register like
22042 @code{f0} or @code{f2}.
22044 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
22045 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
22046 @code{f2} and @code{f3} for @code{$dl1} and so on.
22048 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
22049 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
22052 @subsection Nios II
22053 @cindex Nios II architecture
22055 When @value{GDBN} is debugging the Nios II architecture,
22056 it provides the following special commands:
22060 @item set debug nios2
22061 @kindex set debug nios2
22062 This command turns on and off debugging messages for the Nios II
22063 target code in @value{GDBN}.
22065 @item show debug nios2
22066 @kindex show debug nios2
22067 Show the current setting of Nios II debugging messages.
22070 @node Controlling GDB
22071 @chapter Controlling @value{GDBN}
22073 You can alter the way @value{GDBN} interacts with you by using the
22074 @code{set} command. For commands controlling how @value{GDBN} displays
22075 data, see @ref{Print Settings, ,Print Settings}. Other settings are
22080 * Editing:: Command editing
22081 * Command History:: Command history
22082 * Screen Size:: Screen size
22083 * Numbers:: Numbers
22084 * ABI:: Configuring the current ABI
22085 * Auto-loading:: Automatically loading associated files
22086 * Messages/Warnings:: Optional warnings and messages
22087 * Debugging Output:: Optional messages about internal happenings
22088 * Other Misc Settings:: Other Miscellaneous Settings
22096 @value{GDBN} indicates its readiness to read a command by printing a string
22097 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
22098 can change the prompt string with the @code{set prompt} command. For
22099 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
22100 the prompt in one of the @value{GDBN} sessions so that you can always tell
22101 which one you are talking to.
22103 @emph{Note:} @code{set prompt} does not add a space for you after the
22104 prompt you set. This allows you to set a prompt which ends in a space
22105 or a prompt that does not.
22109 @item set prompt @var{newprompt}
22110 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
22112 @kindex show prompt
22114 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
22117 Versions of @value{GDBN} that ship with Python scripting enabled have
22118 prompt extensions. The commands for interacting with these extensions
22122 @kindex set extended-prompt
22123 @item set extended-prompt @var{prompt}
22124 Set an extended prompt that allows for substitutions.
22125 @xref{gdb.prompt}, for a list of escape sequences that can be used for
22126 substitution. Any escape sequences specified as part of the prompt
22127 string are replaced with the corresponding strings each time the prompt
22133 set extended-prompt Current working directory: \w (gdb)
22136 Note that when an extended-prompt is set, it takes control of the
22137 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
22139 @kindex show extended-prompt
22140 @item show extended-prompt
22141 Prints the extended prompt. Any escape sequences specified as part of
22142 the prompt string with @code{set extended-prompt}, are replaced with the
22143 corresponding strings each time the prompt is displayed.
22147 @section Command Editing
22149 @cindex command line editing
22151 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
22152 @sc{gnu} library provides consistent behavior for programs which provide a
22153 command line interface to the user. Advantages are @sc{gnu} Emacs-style
22154 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
22155 substitution, and a storage and recall of command history across
22156 debugging sessions.
22158 You may control the behavior of command line editing in @value{GDBN} with the
22159 command @code{set}.
22162 @kindex set editing
22165 @itemx set editing on
22166 Enable command line editing (enabled by default).
22168 @item set editing off
22169 Disable command line editing.
22171 @kindex show editing
22173 Show whether command line editing is enabled.
22176 @ifset SYSTEM_READLINE
22177 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
22179 @ifclear SYSTEM_READLINE
22180 @xref{Command Line Editing},
22182 for more details about the Readline
22183 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
22184 encouraged to read that chapter.
22186 @node Command History
22187 @section Command History
22188 @cindex command history
22190 @value{GDBN} can keep track of the commands you type during your
22191 debugging sessions, so that you can be certain of precisely what
22192 happened. Use these commands to manage the @value{GDBN} command
22195 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
22196 package, to provide the history facility.
22197 @ifset SYSTEM_READLINE
22198 @xref{Using History Interactively, , , history, GNU History Library},
22200 @ifclear SYSTEM_READLINE
22201 @xref{Using History Interactively},
22203 for the detailed description of the History library.
22205 To issue a command to @value{GDBN} without affecting certain aspects of
22206 the state which is seen by users, prefix it with @samp{server }
22207 (@pxref{Server Prefix}). This
22208 means that this command will not affect the command history, nor will it
22209 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
22210 pressed on a line by itself.
22212 @cindex @code{server}, command prefix
22213 The server prefix does not affect the recording of values into the value
22214 history; to print a value without recording it into the value history,
22215 use the @code{output} command instead of the @code{print} command.
22217 Here is the description of @value{GDBN} commands related to command
22221 @cindex history substitution
22222 @cindex history file
22223 @kindex set history filename
22224 @cindex @env{GDBHISTFILE}, environment variable
22225 @item set history filename @var{fname}
22226 Set the name of the @value{GDBN} command history file to @var{fname}.
22227 This is the file where @value{GDBN} reads an initial command history
22228 list, and where it writes the command history from this session when it
22229 exits. You can access this list through history expansion or through
22230 the history command editing characters listed below. This file defaults
22231 to the value of the environment variable @code{GDBHISTFILE}, or to
22232 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
22235 @cindex save command history
22236 @kindex set history save
22237 @item set history save
22238 @itemx set history save on
22239 Record command history in a file, whose name may be specified with the
22240 @code{set history filename} command. By default, this option is disabled.
22242 @item set history save off
22243 Stop recording command history in a file.
22245 @cindex history size
22246 @kindex set history size
22247 @cindex @env{HISTSIZE}, environment variable
22248 @item set history size @var{size}
22249 @itemx set history size unlimited
22250 Set the number of commands which @value{GDBN} keeps in its history list.
22251 This defaults to the value of the environment variable
22252 @code{HISTSIZE}, or to 256 if this variable is not set. If @var{size}
22253 is @code{unlimited}, the number of commands @value{GDBN} keeps in the
22254 history list is unlimited.
22257 History expansion assigns special meaning to the character @kbd{!}.
22258 @ifset SYSTEM_READLINE
22259 @xref{Event Designators, , , history, GNU History Library},
22261 @ifclear SYSTEM_READLINE
22262 @xref{Event Designators},
22266 @cindex history expansion, turn on/off
22267 Since @kbd{!} is also the logical not operator in C, history expansion
22268 is off by default. If you decide to enable history expansion with the
22269 @code{set history expansion on} command, you may sometimes need to
22270 follow @kbd{!} (when it is used as logical not, in an expression) with
22271 a space or a tab to prevent it from being expanded. The readline
22272 history facilities do not attempt substitution on the strings
22273 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
22275 The commands to control history expansion are:
22278 @item set history expansion on
22279 @itemx set history expansion
22280 @kindex set history expansion
22281 Enable history expansion. History expansion is off by default.
22283 @item set history expansion off
22284 Disable history expansion.
22287 @kindex show history
22289 @itemx show history filename
22290 @itemx show history save
22291 @itemx show history size
22292 @itemx show history expansion
22293 These commands display the state of the @value{GDBN} history parameters.
22294 @code{show history} by itself displays all four states.
22299 @kindex show commands
22300 @cindex show last commands
22301 @cindex display command history
22302 @item show commands
22303 Display the last ten commands in the command history.
22305 @item show commands @var{n}
22306 Print ten commands centered on command number @var{n}.
22308 @item show commands +
22309 Print ten commands just after the commands last printed.
22313 @section Screen Size
22314 @cindex size of screen
22315 @cindex screen size
22318 @cindex pauses in output
22320 Certain commands to @value{GDBN} may produce large amounts of
22321 information output to the screen. To help you read all of it,
22322 @value{GDBN} pauses and asks you for input at the end of each page of
22323 output. Type @key{RET} when you want to continue the output, or @kbd{q}
22324 to discard the remaining output. Also, the screen width setting
22325 determines when to wrap lines of output. Depending on what is being
22326 printed, @value{GDBN} tries to break the line at a readable place,
22327 rather than simply letting it overflow onto the following line.
22329 Normally @value{GDBN} knows the size of the screen from the terminal
22330 driver software. For example, on Unix @value{GDBN} uses the termcap data base
22331 together with the value of the @code{TERM} environment variable and the
22332 @code{stty rows} and @code{stty cols} settings. If this is not correct,
22333 you can override it with the @code{set height} and @code{set
22340 @kindex show height
22341 @item set height @var{lpp}
22342 @itemx set height unlimited
22344 @itemx set width @var{cpl}
22345 @itemx set width unlimited
22347 These @code{set} commands specify a screen height of @var{lpp} lines and
22348 a screen width of @var{cpl} characters. The associated @code{show}
22349 commands display the current settings.
22351 If you specify a height of either @code{unlimited} or zero lines,
22352 @value{GDBN} does not pause during output no matter how long the
22353 output is. This is useful if output is to a file or to an editor
22356 Likewise, you can specify @samp{set width unlimited} or @samp{set
22357 width 0} to prevent @value{GDBN} from wrapping its output.
22359 @item set pagination on
22360 @itemx set pagination off
22361 @kindex set pagination
22362 Turn the output pagination on or off; the default is on. Turning
22363 pagination off is the alternative to @code{set height unlimited}. Note that
22364 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
22365 Options, -batch}) also automatically disables pagination.
22367 @item show pagination
22368 @kindex show pagination
22369 Show the current pagination mode.
22374 @cindex number representation
22375 @cindex entering numbers
22377 You can always enter numbers in octal, decimal, or hexadecimal in
22378 @value{GDBN} by the usual conventions: octal numbers begin with
22379 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
22380 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
22381 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
22382 10; likewise, the default display for numbers---when no particular
22383 format is specified---is base 10. You can change the default base for
22384 both input and output with the commands described below.
22387 @kindex set input-radix
22388 @item set input-radix @var{base}
22389 Set the default base for numeric input. Supported choices
22390 for @var{base} are decimal 8, 10, or 16. The base must itself be
22391 specified either unambiguously or using the current input radix; for
22395 set input-radix 012
22396 set input-radix 10.
22397 set input-radix 0xa
22401 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
22402 leaves the input radix unchanged, no matter what it was, since
22403 @samp{10}, being without any leading or trailing signs of its base, is
22404 interpreted in the current radix. Thus, if the current radix is 16,
22405 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
22408 @kindex set output-radix
22409 @item set output-radix @var{base}
22410 Set the default base for numeric display. Supported choices
22411 for @var{base} are decimal 8, 10, or 16. The base must itself be
22412 specified either unambiguously or using the current input radix.
22414 @kindex show input-radix
22415 @item show input-radix
22416 Display the current default base for numeric input.
22418 @kindex show output-radix
22419 @item show output-radix
22420 Display the current default base for numeric display.
22422 @item set radix @r{[}@var{base}@r{]}
22426 These commands set and show the default base for both input and output
22427 of numbers. @code{set radix} sets the radix of input and output to
22428 the same base; without an argument, it resets the radix back to its
22429 default value of 10.
22434 @section Configuring the Current ABI
22436 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
22437 application automatically. However, sometimes you need to override its
22438 conclusions. Use these commands to manage @value{GDBN}'s view of the
22444 @cindex Newlib OS ABI and its influence on the longjmp handling
22446 One @value{GDBN} configuration can debug binaries for multiple operating
22447 system targets, either via remote debugging or native emulation.
22448 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
22449 but you can override its conclusion using the @code{set osabi} command.
22450 One example where this is useful is in debugging of binaries which use
22451 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
22452 not have the same identifying marks that the standard C library for your
22455 When @value{GDBN} is debugging the AArch64 architecture, it provides a
22456 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
22457 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
22458 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
22462 Show the OS ABI currently in use.
22465 With no argument, show the list of registered available OS ABI's.
22467 @item set osabi @var{abi}
22468 Set the current OS ABI to @var{abi}.
22471 @cindex float promotion
22473 Generally, the way that an argument of type @code{float} is passed to a
22474 function depends on whether the function is prototyped. For a prototyped
22475 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
22476 according to the architecture's convention for @code{float}. For unprototyped
22477 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
22478 @code{double} and then passed.
22480 Unfortunately, some forms of debug information do not reliably indicate whether
22481 a function is prototyped. If @value{GDBN} calls a function that is not marked
22482 as prototyped, it consults @kbd{set coerce-float-to-double}.
22485 @kindex set coerce-float-to-double
22486 @item set coerce-float-to-double
22487 @itemx set coerce-float-to-double on
22488 Arguments of type @code{float} will be promoted to @code{double} when passed
22489 to an unprototyped function. This is the default setting.
22491 @item set coerce-float-to-double off
22492 Arguments of type @code{float} will be passed directly to unprototyped
22495 @kindex show coerce-float-to-double
22496 @item show coerce-float-to-double
22497 Show the current setting of promoting @code{float} to @code{double}.
22501 @kindex show cp-abi
22502 @value{GDBN} needs to know the ABI used for your program's C@t{++}
22503 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
22504 used to build your application. @value{GDBN} only fully supports
22505 programs with a single C@t{++} ABI; if your program contains code using
22506 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
22507 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
22508 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
22509 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
22510 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
22511 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
22516 Show the C@t{++} ABI currently in use.
22519 With no argument, show the list of supported C@t{++} ABI's.
22521 @item set cp-abi @var{abi}
22522 @itemx set cp-abi auto
22523 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
22527 @section Automatically loading associated files
22528 @cindex auto-loading
22530 @value{GDBN} sometimes reads files with commands and settings automatically,
22531 without being explicitly told so by the user. We call this feature
22532 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
22533 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
22534 results or introduce security risks (e.g., if the file comes from untrusted
22538 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
22539 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
22541 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
22542 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
22545 There are various kinds of files @value{GDBN} can automatically load.
22546 In addition to these files, @value{GDBN} supports auto-loading code written
22547 in various extension languages. @xref{Auto-loading extensions}.
22549 Note that loading of these associated files (including the local @file{.gdbinit}
22550 file) requires accordingly configured @code{auto-load safe-path}
22551 (@pxref{Auto-loading safe path}).
22553 For these reasons, @value{GDBN} includes commands and options to let you
22554 control when to auto-load files and which files should be auto-loaded.
22557 @anchor{set auto-load off}
22558 @kindex set auto-load off
22559 @item set auto-load off
22560 Globally disable loading of all auto-loaded files.
22561 You may want to use this command with the @samp{-iex} option
22562 (@pxref{Option -init-eval-command}) such as:
22564 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
22567 Be aware that system init file (@pxref{System-wide configuration})
22568 and init files from your home directory (@pxref{Home Directory Init File})
22569 still get read (as they come from generally trusted directories).
22570 To prevent @value{GDBN} from auto-loading even those init files, use the
22571 @option{-nx} option (@pxref{Mode Options}), in addition to
22572 @code{set auto-load no}.
22574 @anchor{show auto-load}
22575 @kindex show auto-load
22576 @item show auto-load
22577 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
22581 (gdb) show auto-load
22582 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
22583 libthread-db: Auto-loading of inferior specific libthread_db is on.
22584 local-gdbinit: Auto-loading of .gdbinit script from current directory
22586 python-scripts: Auto-loading of Python scripts is on.
22587 safe-path: List of directories from which it is safe to auto-load files
22588 is $debugdir:$datadir/auto-load.
22589 scripts-directory: List of directories from which to load auto-loaded scripts
22590 is $debugdir:$datadir/auto-load.
22593 @anchor{info auto-load}
22594 @kindex info auto-load
22595 @item info auto-load
22596 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
22600 (gdb) info auto-load
22603 Yes /home/user/gdb/gdb-gdb.gdb
22604 libthread-db: No auto-loaded libthread-db.
22605 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
22609 Yes /home/user/gdb/gdb-gdb.py
22613 These are @value{GDBN} control commands for the auto-loading:
22615 @multitable @columnfractions .5 .5
22616 @item @xref{set auto-load off}.
22617 @tab Disable auto-loading globally.
22618 @item @xref{show auto-load}.
22619 @tab Show setting of all kinds of files.
22620 @item @xref{info auto-load}.
22621 @tab Show state of all kinds of files.
22622 @item @xref{set auto-load gdb-scripts}.
22623 @tab Control for @value{GDBN} command scripts.
22624 @item @xref{show auto-load gdb-scripts}.
22625 @tab Show setting of @value{GDBN} command scripts.
22626 @item @xref{info auto-load gdb-scripts}.
22627 @tab Show state of @value{GDBN} command scripts.
22628 @item @xref{set auto-load python-scripts}.
22629 @tab Control for @value{GDBN} Python scripts.
22630 @item @xref{show auto-load python-scripts}.
22631 @tab Show setting of @value{GDBN} Python scripts.
22632 @item @xref{info auto-load python-scripts}.
22633 @tab Show state of @value{GDBN} Python scripts.
22634 @item @xref{set auto-load guile-scripts}.
22635 @tab Control for @value{GDBN} Guile scripts.
22636 @item @xref{show auto-load guile-scripts}.
22637 @tab Show setting of @value{GDBN} Guile scripts.
22638 @item @xref{info auto-load guile-scripts}.
22639 @tab Show state of @value{GDBN} Guile scripts.
22640 @item @xref{set auto-load scripts-directory}.
22641 @tab Control for @value{GDBN} auto-loaded scripts location.
22642 @item @xref{show auto-load scripts-directory}.
22643 @tab Show @value{GDBN} auto-loaded scripts location.
22644 @item @xref{add-auto-load-scripts-directory}.
22645 @tab Add directory for auto-loaded scripts location list.
22646 @item @xref{set auto-load local-gdbinit}.
22647 @tab Control for init file in the current directory.
22648 @item @xref{show auto-load local-gdbinit}.
22649 @tab Show setting of init file in the current directory.
22650 @item @xref{info auto-load local-gdbinit}.
22651 @tab Show state of init file in the current directory.
22652 @item @xref{set auto-load libthread-db}.
22653 @tab Control for thread debugging library.
22654 @item @xref{show auto-load libthread-db}.
22655 @tab Show setting of thread debugging library.
22656 @item @xref{info auto-load libthread-db}.
22657 @tab Show state of thread debugging library.
22658 @item @xref{set auto-load safe-path}.
22659 @tab Control directories trusted for automatic loading.
22660 @item @xref{show auto-load safe-path}.
22661 @tab Show directories trusted for automatic loading.
22662 @item @xref{add-auto-load-safe-path}.
22663 @tab Add directory trusted for automatic loading.
22666 @node Init File in the Current Directory
22667 @subsection Automatically loading init file in the current directory
22668 @cindex auto-loading init file in the current directory
22670 By default, @value{GDBN} reads and executes the canned sequences of commands
22671 from init file (if any) in the current working directory,
22672 see @ref{Init File in the Current Directory during Startup}.
22674 Note that loading of this local @file{.gdbinit} file also requires accordingly
22675 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22678 @anchor{set auto-load local-gdbinit}
22679 @kindex set auto-load local-gdbinit
22680 @item set auto-load local-gdbinit [on|off]
22681 Enable or disable the auto-loading of canned sequences of commands
22682 (@pxref{Sequences}) found in init file in the current directory.
22684 @anchor{show auto-load local-gdbinit}
22685 @kindex show auto-load local-gdbinit
22686 @item show auto-load local-gdbinit
22687 Show whether auto-loading of canned sequences of commands from init file in the
22688 current directory is enabled or disabled.
22690 @anchor{info auto-load local-gdbinit}
22691 @kindex info auto-load local-gdbinit
22692 @item info auto-load local-gdbinit
22693 Print whether canned sequences of commands from init file in the
22694 current directory have been auto-loaded.
22697 @node libthread_db.so.1 file
22698 @subsection Automatically loading thread debugging library
22699 @cindex auto-loading libthread_db.so.1
22701 This feature is currently present only on @sc{gnu}/Linux native hosts.
22703 @value{GDBN} reads in some cases thread debugging library from places specific
22704 to the inferior (@pxref{set libthread-db-search-path}).
22706 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
22707 without checking this @samp{set auto-load libthread-db} switch as system
22708 libraries have to be trusted in general. In all other cases of
22709 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
22710 auto-load libthread-db} is enabled before trying to open such thread debugging
22713 Note that loading of this debugging library also requires accordingly configured
22714 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22717 @anchor{set auto-load libthread-db}
22718 @kindex set auto-load libthread-db
22719 @item set auto-load libthread-db [on|off]
22720 Enable or disable the auto-loading of inferior specific thread debugging library.
22722 @anchor{show auto-load libthread-db}
22723 @kindex show auto-load libthread-db
22724 @item show auto-load libthread-db
22725 Show whether auto-loading of inferior specific thread debugging library is
22726 enabled or disabled.
22728 @anchor{info auto-load libthread-db}
22729 @kindex info auto-load libthread-db
22730 @item info auto-load libthread-db
22731 Print the list of all loaded inferior specific thread debugging libraries and
22732 for each such library print list of inferior @var{pid}s using it.
22735 @node Auto-loading safe path
22736 @subsection Security restriction for auto-loading
22737 @cindex auto-loading safe-path
22739 As the files of inferior can come from untrusted source (such as submitted by
22740 an application user) @value{GDBN} does not always load any files automatically.
22741 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
22742 directories trusted for loading files not explicitly requested by user.
22743 Each directory can also be a shell wildcard pattern.
22745 If the path is not set properly you will see a warning and the file will not
22750 Reading symbols from /home/user/gdb/gdb...done.
22751 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
22752 declined by your `auto-load safe-path' set
22753 to "$debugdir:$datadir/auto-load".
22754 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
22755 declined by your `auto-load safe-path' set
22756 to "$debugdir:$datadir/auto-load".
22760 To instruct @value{GDBN} to go ahead and use the init files anyway,
22761 invoke @value{GDBN} like this:
22764 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
22767 The list of trusted directories is controlled by the following commands:
22770 @anchor{set auto-load safe-path}
22771 @kindex set auto-load safe-path
22772 @item set auto-load safe-path @r{[}@var{directories}@r{]}
22773 Set the list of directories (and their subdirectories) trusted for automatic
22774 loading and execution of scripts. You can also enter a specific trusted file.
22775 Each directory can also be a shell wildcard pattern; wildcards do not match
22776 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
22777 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
22778 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
22779 its default value as specified during @value{GDBN} compilation.
22781 The list of directories uses path separator (@samp{:} on GNU and Unix
22782 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
22783 to the @env{PATH} environment variable.
22785 @anchor{show auto-load safe-path}
22786 @kindex show auto-load safe-path
22787 @item show auto-load safe-path
22788 Show the list of directories trusted for automatic loading and execution of
22791 @anchor{add-auto-load-safe-path}
22792 @kindex add-auto-load-safe-path
22793 @item add-auto-load-safe-path
22794 Add an entry (or list of entries) to the list of directories trusted for
22795 automatic loading and execution of scripts. Multiple entries may be delimited
22796 by the host platform path separator in use.
22799 This variable defaults to what @code{--with-auto-load-dir} has been configured
22800 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
22801 substitution applies the same as for @ref{set auto-load scripts-directory}.
22802 The default @code{set auto-load safe-path} value can be also overriden by
22803 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
22805 Setting this variable to @file{/} disables this security protection,
22806 corresponding @value{GDBN} configuration option is
22807 @option{--without-auto-load-safe-path}.
22808 This variable is supposed to be set to the system directories writable by the
22809 system superuser only. Users can add their source directories in init files in
22810 their home directories (@pxref{Home Directory Init File}). See also deprecated
22811 init file in the current directory
22812 (@pxref{Init File in the Current Directory during Startup}).
22814 To force @value{GDBN} to load the files it declined to load in the previous
22815 example, you could use one of the following ways:
22818 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
22819 Specify this trusted directory (or a file) as additional component of the list.
22820 You have to specify also any existing directories displayed by
22821 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
22823 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
22824 Specify this directory as in the previous case but just for a single
22825 @value{GDBN} session.
22827 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
22828 Disable auto-loading safety for a single @value{GDBN} session.
22829 This assumes all the files you debug during this @value{GDBN} session will come
22830 from trusted sources.
22832 @item @kbd{./configure --without-auto-load-safe-path}
22833 During compilation of @value{GDBN} you may disable any auto-loading safety.
22834 This assumes all the files you will ever debug with this @value{GDBN} come from
22838 On the other hand you can also explicitly forbid automatic files loading which
22839 also suppresses any such warning messages:
22842 @item @kbd{gdb -iex "set auto-load no" @dots{}}
22843 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
22845 @item @file{~/.gdbinit}: @samp{set auto-load no}
22846 Disable auto-loading globally for the user
22847 (@pxref{Home Directory Init File}). While it is improbable, you could also
22848 use system init file instead (@pxref{System-wide configuration}).
22851 This setting applies to the file names as entered by user. If no entry matches
22852 @value{GDBN} tries as a last resort to also resolve all the file names into
22853 their canonical form (typically resolving symbolic links) and compare the
22854 entries again. @value{GDBN} already canonicalizes most of the filenames on its
22855 own before starting the comparison so a canonical form of directories is
22856 recommended to be entered.
22858 @node Auto-loading verbose mode
22859 @subsection Displaying files tried for auto-load
22860 @cindex auto-loading verbose mode
22862 For better visibility of all the file locations where you can place scripts to
22863 be auto-loaded with inferior --- or to protect yourself against accidental
22864 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
22865 all the files attempted to be loaded. Both existing and non-existing files may
22868 For example the list of directories from which it is safe to auto-load files
22869 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
22870 may not be too obvious while setting it up.
22873 (gdb) set debug auto-load on
22874 (gdb) file ~/src/t/true
22875 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
22876 for objfile "/tmp/true".
22877 auto-load: Updating directories of "/usr:/opt".
22878 auto-load: Using directory "/usr".
22879 auto-load: Using directory "/opt".
22880 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
22881 by your `auto-load safe-path' set to "/usr:/opt".
22885 @anchor{set debug auto-load}
22886 @kindex set debug auto-load
22887 @item set debug auto-load [on|off]
22888 Set whether to print the filenames attempted to be auto-loaded.
22890 @anchor{show debug auto-load}
22891 @kindex show debug auto-load
22892 @item show debug auto-load
22893 Show whether printing of the filenames attempted to be auto-loaded is turned
22897 @node Messages/Warnings
22898 @section Optional Warnings and Messages
22900 @cindex verbose operation
22901 @cindex optional warnings
22902 By default, @value{GDBN} is silent about its inner workings. If you are
22903 running on a slow machine, you may want to use the @code{set verbose}
22904 command. This makes @value{GDBN} tell you when it does a lengthy
22905 internal operation, so you will not think it has crashed.
22907 Currently, the messages controlled by @code{set verbose} are those
22908 which announce that the symbol table for a source file is being read;
22909 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
22912 @kindex set verbose
22913 @item set verbose on
22914 Enables @value{GDBN} output of certain informational messages.
22916 @item set verbose off
22917 Disables @value{GDBN} output of certain informational messages.
22919 @kindex show verbose
22921 Displays whether @code{set verbose} is on or off.
22924 By default, if @value{GDBN} encounters bugs in the symbol table of an
22925 object file, it is silent; but if you are debugging a compiler, you may
22926 find this information useful (@pxref{Symbol Errors, ,Errors Reading
22931 @kindex set complaints
22932 @item set complaints @var{limit}
22933 Permits @value{GDBN} to output @var{limit} complaints about each type of
22934 unusual symbols before becoming silent about the problem. Set
22935 @var{limit} to zero to suppress all complaints; set it to a large number
22936 to prevent complaints from being suppressed.
22938 @kindex show complaints
22939 @item show complaints
22940 Displays how many symbol complaints @value{GDBN} is permitted to produce.
22944 @anchor{confirmation requests}
22945 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
22946 lot of stupid questions to confirm certain commands. For example, if
22947 you try to run a program which is already running:
22951 The program being debugged has been started already.
22952 Start it from the beginning? (y or n)
22955 If you are willing to unflinchingly face the consequences of your own
22956 commands, you can disable this ``feature'':
22960 @kindex set confirm
22962 @cindex confirmation
22963 @cindex stupid questions
22964 @item set confirm off
22965 Disables confirmation requests. Note that running @value{GDBN} with
22966 the @option{--batch} option (@pxref{Mode Options, -batch}) also
22967 automatically disables confirmation requests.
22969 @item set confirm on
22970 Enables confirmation requests (the default).
22972 @kindex show confirm
22974 Displays state of confirmation requests.
22978 @cindex command tracing
22979 If you need to debug user-defined commands or sourced files you may find it
22980 useful to enable @dfn{command tracing}. In this mode each command will be
22981 printed as it is executed, prefixed with one or more @samp{+} symbols, the
22982 quantity denoting the call depth of each command.
22985 @kindex set trace-commands
22986 @cindex command scripts, debugging
22987 @item set trace-commands on
22988 Enable command tracing.
22989 @item set trace-commands off
22990 Disable command tracing.
22991 @item show trace-commands
22992 Display the current state of command tracing.
22995 @node Debugging Output
22996 @section Optional Messages about Internal Happenings
22997 @cindex optional debugging messages
22999 @value{GDBN} has commands that enable optional debugging messages from
23000 various @value{GDBN} subsystems; normally these commands are of
23001 interest to @value{GDBN} maintainers, or when reporting a bug. This
23002 section documents those commands.
23005 @kindex set exec-done-display
23006 @item set exec-done-display
23007 Turns on or off the notification of asynchronous commands'
23008 completion. When on, @value{GDBN} will print a message when an
23009 asynchronous command finishes its execution. The default is off.
23010 @kindex show exec-done-display
23011 @item show exec-done-display
23012 Displays the current setting of asynchronous command completion
23015 @cindex ARM AArch64
23016 @item set debug aarch64
23017 Turns on or off display of debugging messages related to ARM AArch64.
23018 The default is off.
23020 @item show debug aarch64
23021 Displays the current state of displaying debugging messages related to
23023 @cindex gdbarch debugging info
23024 @cindex architecture debugging info
23025 @item set debug arch
23026 Turns on or off display of gdbarch debugging info. The default is off
23027 @item show debug arch
23028 Displays the current state of displaying gdbarch debugging info.
23029 @item set debug aix-solib
23030 @cindex AIX shared library debugging
23031 Control display of debugging messages from the AIX shared library
23032 support module. The default is off.
23033 @item show debug aix-thread
23034 Show the current state of displaying AIX shared library debugging messages.
23035 @item set debug aix-thread
23036 @cindex AIX threads
23037 Display debugging messages about inner workings of the AIX thread
23039 @item show debug aix-thread
23040 Show the current state of AIX thread debugging info display.
23041 @item set debug check-physname
23043 Check the results of the ``physname'' computation. When reading DWARF
23044 debugging information for C@t{++}, @value{GDBN} attempts to compute
23045 each entity's name. @value{GDBN} can do this computation in two
23046 different ways, depending on exactly what information is present.
23047 When enabled, this setting causes @value{GDBN} to compute the names
23048 both ways and display any discrepancies.
23049 @item show debug check-physname
23050 Show the current state of ``physname'' checking.
23051 @item set debug coff-pe-read
23052 @cindex COFF/PE exported symbols
23053 Control display of debugging messages related to reading of COFF/PE
23054 exported symbols. The default is off.
23055 @item show debug coff-pe-read
23056 Displays the current state of displaying debugging messages related to
23057 reading of COFF/PE exported symbols.
23058 @item set debug dwarf2-die
23059 @cindex DWARF2 DIEs
23060 Dump DWARF2 DIEs after they are read in.
23061 The value is the number of nesting levels to print.
23062 A value of zero turns off the display.
23063 @item show debug dwarf2-die
23064 Show the current state of DWARF2 DIE debugging.
23065 @item set debug dwarf2-read
23066 @cindex DWARF2 Reading
23067 Turns on or off display of debugging messages related to reading
23068 DWARF debug info. The default is 0 (off).
23069 A value of 1 provides basic information.
23070 A value greater than 1 provides more verbose information.
23071 @item show debug dwarf2-read
23072 Show the current state of DWARF2 reader debugging.
23073 @item set debug displaced
23074 @cindex displaced stepping debugging info
23075 Turns on or off display of @value{GDBN} debugging info for the
23076 displaced stepping support. The default is off.
23077 @item show debug displaced
23078 Displays the current state of displaying @value{GDBN} debugging info
23079 related to displaced stepping.
23080 @item set debug event
23081 @cindex event debugging info
23082 Turns on or off display of @value{GDBN} event debugging info. The
23084 @item show debug event
23085 Displays the current state of displaying @value{GDBN} event debugging
23087 @item set debug expression
23088 @cindex expression debugging info
23089 Turns on or off display of debugging info about @value{GDBN}
23090 expression parsing. The default is off.
23091 @item show debug expression
23092 Displays the current state of displaying debugging info about
23093 @value{GDBN} expression parsing.
23094 @item set debug frame
23095 @cindex frame debugging info
23096 Turns on or off display of @value{GDBN} frame debugging info. The
23098 @item show debug frame
23099 Displays the current state of displaying @value{GDBN} frame debugging
23101 @item set debug gnu-nat
23102 @cindex @sc{gnu}/Hurd debug messages
23103 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
23104 @item show debug gnu-nat
23105 Show the current state of @sc{gnu}/Hurd debugging messages.
23106 @item set debug infrun
23107 @cindex inferior debugging info
23108 Turns on or off display of @value{GDBN} debugging info for running the inferior.
23109 The default is off. @file{infrun.c} contains GDB's runtime state machine used
23110 for implementing operations such as single-stepping the inferior.
23111 @item show debug infrun
23112 Displays the current state of @value{GDBN} inferior debugging.
23113 @item set debug jit
23114 @cindex just-in-time compilation, debugging messages
23115 Turns on or off debugging messages from JIT debug support.
23116 @item show debug jit
23117 Displays the current state of @value{GDBN} JIT debugging.
23118 @item set debug lin-lwp
23119 @cindex @sc{gnu}/Linux LWP debug messages
23120 @cindex Linux lightweight processes
23121 Turns on or off debugging messages from the Linux LWP debug support.
23122 @item show debug lin-lwp
23123 Show the current state of Linux LWP debugging messages.
23124 @item set debug mach-o
23125 @cindex Mach-O symbols processing
23126 Control display of debugging messages related to Mach-O symbols
23127 processing. The default is off.
23128 @item show debug mach-o
23129 Displays the current state of displaying debugging messages related to
23130 reading of COFF/PE exported symbols.
23131 @item set debug notification
23132 @cindex remote async notification debugging info
23133 Turns on or off debugging messages about remote async notification.
23134 The default is off.
23135 @item show debug notification
23136 Displays the current state of remote async notification debugging messages.
23137 @item set debug observer
23138 @cindex observer debugging info
23139 Turns on or off display of @value{GDBN} observer debugging. This
23140 includes info such as the notification of observable events.
23141 @item show debug observer
23142 Displays the current state of observer debugging.
23143 @item set debug overload
23144 @cindex C@t{++} overload debugging info
23145 Turns on or off display of @value{GDBN} C@t{++} overload debugging
23146 info. This includes info such as ranking of functions, etc. The default
23148 @item show debug overload
23149 Displays the current state of displaying @value{GDBN} C@t{++} overload
23151 @cindex expression parser, debugging info
23152 @cindex debug expression parser
23153 @item set debug parser
23154 Turns on or off the display of expression parser debugging output.
23155 Internally, this sets the @code{yydebug} variable in the expression
23156 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
23157 details. The default is off.
23158 @item show debug parser
23159 Show the current state of expression parser debugging.
23160 @cindex packets, reporting on stdout
23161 @cindex serial connections, debugging
23162 @cindex debug remote protocol
23163 @cindex remote protocol debugging
23164 @cindex display remote packets
23165 @item set debug remote
23166 Turns on or off display of reports on all packets sent back and forth across
23167 the serial line to the remote machine. The info is printed on the
23168 @value{GDBN} standard output stream. The default is off.
23169 @item show debug remote
23170 Displays the state of display of remote packets.
23171 @item set debug serial
23172 Turns on or off display of @value{GDBN} serial debugging info. The
23174 @item show debug serial
23175 Displays the current state of displaying @value{GDBN} serial debugging
23177 @item set debug solib-frv
23178 @cindex FR-V shared-library debugging
23179 Turns on or off debugging messages for FR-V shared-library code.
23180 @item show debug solib-frv
23181 Display the current state of FR-V shared-library code debugging
23183 @item set debug symbol-lookup
23184 @cindex symbol lookup
23185 Turns on or off display of debugging messages related to symbol lookup.
23186 The default is 0 (off).
23187 A value of 1 provides basic information.
23188 A value greater than 1 provides more verbose information.
23189 @item show debug symbol-lookup
23190 Show the current state of symbol lookup debugging messages.
23191 @item set debug symfile
23192 @cindex symbol file functions
23193 Turns on or off display of debugging messages related to symbol file functions.
23194 The default is off. @xref{Files}.
23195 @item show debug symfile
23196 Show the current state of symbol file debugging messages.
23197 @item set debug symtab-create
23198 @cindex symbol table creation
23199 Turns on or off display of debugging messages related to symbol table creation.
23200 The default is 0 (off).
23201 A value of 1 provides basic information.
23202 A value greater than 1 provides more verbose information.
23203 @item show debug symtab-create
23204 Show the current state of symbol table creation debugging.
23205 @item set debug target
23206 @cindex target debugging info
23207 Turns on or off display of @value{GDBN} target debugging info. This info
23208 includes what is going on at the target level of GDB, as it happens. The
23209 default is 0. Set it to 1 to track events, and to 2 to also track the
23210 value of large memory transfers.
23211 @item show debug target
23212 Displays the current state of displaying @value{GDBN} target debugging
23214 @item set debug timestamp
23215 @cindex timestampping debugging info
23216 Turns on or off display of timestamps with @value{GDBN} debugging info.
23217 When enabled, seconds and microseconds are displayed before each debugging
23219 @item show debug timestamp
23220 Displays the current state of displaying timestamps with @value{GDBN}
23222 @item set debug varobj
23223 @cindex variable object debugging info
23224 Turns on or off display of @value{GDBN} variable object debugging
23225 info. The default is off.
23226 @item show debug varobj
23227 Displays the current state of displaying @value{GDBN} variable object
23229 @item set debug xml
23230 @cindex XML parser debugging
23231 Turns on or off debugging messages for built-in XML parsers.
23232 @item show debug xml
23233 Displays the current state of XML debugging messages.
23236 @node Other Misc Settings
23237 @section Other Miscellaneous Settings
23238 @cindex miscellaneous settings
23241 @kindex set interactive-mode
23242 @item set interactive-mode
23243 If @code{on}, forces @value{GDBN} to assume that GDB was started
23244 in a terminal. In practice, this means that @value{GDBN} should wait
23245 for the user to answer queries generated by commands entered at
23246 the command prompt. If @code{off}, forces @value{GDBN} to operate
23247 in the opposite mode, and it uses the default answers to all queries.
23248 If @code{auto} (the default), @value{GDBN} tries to determine whether
23249 its standard input is a terminal, and works in interactive-mode if it
23250 is, non-interactively otherwise.
23252 In the vast majority of cases, the debugger should be able to guess
23253 correctly which mode should be used. But this setting can be useful
23254 in certain specific cases, such as running a MinGW @value{GDBN}
23255 inside a cygwin window.
23257 @kindex show interactive-mode
23258 @item show interactive-mode
23259 Displays whether the debugger is operating in interactive mode or not.
23262 @node Extending GDB
23263 @chapter Extending @value{GDBN}
23264 @cindex extending GDB
23266 @value{GDBN} provides several mechanisms for extension.
23267 @value{GDBN} also provides the ability to automatically load
23268 extensions when it reads a file for debugging. This allows the
23269 user to automatically customize @value{GDBN} for the program
23273 * Sequences:: Canned Sequences of @value{GDBN} Commands
23274 * Python:: Extending @value{GDBN} using Python
23275 * Guile:: Extending @value{GDBN} using Guile
23276 * Auto-loading extensions:: Automatically loading extensions
23277 * Multiple Extension Languages:: Working with multiple extension languages
23278 * Aliases:: Creating new spellings of existing commands
23281 To facilitate the use of extension languages, @value{GDBN} is capable
23282 of evaluating the contents of a file. When doing so, @value{GDBN}
23283 can recognize which extension language is being used by looking at
23284 the filename extension. Files with an unrecognized filename extension
23285 are always treated as a @value{GDBN} Command Files.
23286 @xref{Command Files,, Command files}.
23288 You can control how @value{GDBN} evaluates these files with the following
23292 @kindex set script-extension
23293 @kindex show script-extension
23294 @item set script-extension off
23295 All scripts are always evaluated as @value{GDBN} Command Files.
23297 @item set script-extension soft
23298 The debugger determines the scripting language based on filename
23299 extension. If this scripting language is supported, @value{GDBN}
23300 evaluates the script using that language. Otherwise, it evaluates
23301 the file as a @value{GDBN} Command File.
23303 @item set script-extension strict
23304 The debugger determines the scripting language based on filename
23305 extension, and evaluates the script using that language. If the
23306 language is not supported, then the evaluation fails.
23308 @item show script-extension
23309 Display the current value of the @code{script-extension} option.
23314 @section Canned Sequences of Commands
23316 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
23317 Command Lists}), @value{GDBN} provides two ways to store sequences of
23318 commands for execution as a unit: user-defined commands and command
23322 * Define:: How to define your own commands
23323 * Hooks:: Hooks for user-defined commands
23324 * Command Files:: How to write scripts of commands to be stored in a file
23325 * Output:: Commands for controlled output
23326 * Auto-loading sequences:: Controlling auto-loaded command files
23330 @subsection User-defined Commands
23332 @cindex user-defined command
23333 @cindex arguments, to user-defined commands
23334 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
23335 which you assign a new name as a command. This is done with the
23336 @code{define} command. User commands may accept up to 10 arguments
23337 separated by whitespace. Arguments are accessed within the user command
23338 via @code{$arg0@dots{}$arg9}. A trivial example:
23342 print $arg0 + $arg1 + $arg2
23347 To execute the command use:
23354 This defines the command @code{adder}, which prints the sum of
23355 its three arguments. Note the arguments are text substitutions, so they may
23356 reference variables, use complex expressions, or even perform inferior
23359 @cindex argument count in user-defined commands
23360 @cindex how many arguments (user-defined commands)
23361 In addition, @code{$argc} may be used to find out how many arguments have
23362 been passed. This expands to a number in the range 0@dots{}10.
23367 print $arg0 + $arg1
23370 print $arg0 + $arg1 + $arg2
23378 @item define @var{commandname}
23379 Define a command named @var{commandname}. If there is already a command
23380 by that name, you are asked to confirm that you want to redefine it.
23381 The argument @var{commandname} may be a bare command name consisting of letters,
23382 numbers, dashes, and underscores. It may also start with any predefined
23383 prefix command. For example, @samp{define target my-target} creates
23384 a user-defined @samp{target my-target} command.
23386 The definition of the command is made up of other @value{GDBN} command lines,
23387 which are given following the @code{define} command. The end of these
23388 commands is marked by a line containing @code{end}.
23391 @kindex end@r{ (user-defined commands)}
23392 @item document @var{commandname}
23393 Document the user-defined command @var{commandname}, so that it can be
23394 accessed by @code{help}. The command @var{commandname} must already be
23395 defined. This command reads lines of documentation just as @code{define}
23396 reads the lines of the command definition, ending with @code{end}.
23397 After the @code{document} command is finished, @code{help} on command
23398 @var{commandname} displays the documentation you have written.
23400 You may use the @code{document} command again to change the
23401 documentation of a command. Redefining the command with @code{define}
23402 does not change the documentation.
23404 @kindex dont-repeat
23405 @cindex don't repeat command
23407 Used inside a user-defined command, this tells @value{GDBN} that this
23408 command should not be repeated when the user hits @key{RET}
23409 (@pxref{Command Syntax, repeat last command}).
23411 @kindex help user-defined
23412 @item help user-defined
23413 List all user-defined commands and all python commands defined in class
23414 COMAND_USER. The first line of the documentation or docstring is
23419 @itemx show user @var{commandname}
23420 Display the @value{GDBN} commands used to define @var{commandname} (but
23421 not its documentation). If no @var{commandname} is given, display the
23422 definitions for all user-defined commands.
23423 This does not work for user-defined python commands.
23425 @cindex infinite recursion in user-defined commands
23426 @kindex show max-user-call-depth
23427 @kindex set max-user-call-depth
23428 @item show max-user-call-depth
23429 @itemx set max-user-call-depth
23430 The value of @code{max-user-call-depth} controls how many recursion
23431 levels are allowed in user-defined commands before @value{GDBN} suspects an
23432 infinite recursion and aborts the command.
23433 This does not apply to user-defined python commands.
23436 In addition to the above commands, user-defined commands frequently
23437 use control flow commands, described in @ref{Command Files}.
23439 When user-defined commands are executed, the
23440 commands of the definition are not printed. An error in any command
23441 stops execution of the user-defined command.
23443 If used interactively, commands that would ask for confirmation proceed
23444 without asking when used inside a user-defined command. Many @value{GDBN}
23445 commands that normally print messages to say what they are doing omit the
23446 messages when used in a user-defined command.
23449 @subsection User-defined Command Hooks
23450 @cindex command hooks
23451 @cindex hooks, for commands
23452 @cindex hooks, pre-command
23455 You may define @dfn{hooks}, which are a special kind of user-defined
23456 command. Whenever you run the command @samp{foo}, if the user-defined
23457 command @samp{hook-foo} exists, it is executed (with no arguments)
23458 before that command.
23460 @cindex hooks, post-command
23462 A hook may also be defined which is run after the command you executed.
23463 Whenever you run the command @samp{foo}, if the user-defined command
23464 @samp{hookpost-foo} exists, it is executed (with no arguments) after
23465 that command. Post-execution hooks may exist simultaneously with
23466 pre-execution hooks, for the same command.
23468 It is valid for a hook to call the command which it hooks. If this
23469 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
23471 @c It would be nice if hookpost could be passed a parameter indicating
23472 @c if the command it hooks executed properly or not. FIXME!
23474 @kindex stop@r{, a pseudo-command}
23475 In addition, a pseudo-command, @samp{stop} exists. Defining
23476 (@samp{hook-stop}) makes the associated commands execute every time
23477 execution stops in your program: before breakpoint commands are run,
23478 displays are printed, or the stack frame is printed.
23480 For example, to ignore @code{SIGALRM} signals while
23481 single-stepping, but treat them normally during normal execution,
23486 handle SIGALRM nopass
23490 handle SIGALRM pass
23493 define hook-continue
23494 handle SIGALRM pass
23498 As a further example, to hook at the beginning and end of the @code{echo}
23499 command, and to add extra text to the beginning and end of the message,
23507 define hookpost-echo
23511 (@value{GDBP}) echo Hello World
23512 <<<---Hello World--->>>
23517 You can define a hook for any single-word command in @value{GDBN}, but
23518 not for command aliases; you should define a hook for the basic command
23519 name, e.g.@: @code{backtrace} rather than @code{bt}.
23520 @c FIXME! So how does Joe User discover whether a command is an alias
23522 You can hook a multi-word command by adding @code{hook-} or
23523 @code{hookpost-} to the last word of the command, e.g.@:
23524 @samp{define target hook-remote} to add a hook to @samp{target remote}.
23526 If an error occurs during the execution of your hook, execution of
23527 @value{GDBN} commands stops and @value{GDBN} issues a prompt
23528 (before the command that you actually typed had a chance to run).
23530 If you try to define a hook which does not match any known command, you
23531 get a warning from the @code{define} command.
23533 @node Command Files
23534 @subsection Command Files
23536 @cindex command files
23537 @cindex scripting commands
23538 A command file for @value{GDBN} is a text file made of lines that are
23539 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
23540 also be included. An empty line in a command file does nothing; it
23541 does not mean to repeat the last command, as it would from the
23544 You can request the execution of a command file with the @code{source}
23545 command. Note that the @code{source} command is also used to evaluate
23546 scripts that are not Command Files. The exact behavior can be configured
23547 using the @code{script-extension} setting.
23548 @xref{Extending GDB,, Extending GDB}.
23552 @cindex execute commands from a file
23553 @item source [-s] [-v] @var{filename}
23554 Execute the command file @var{filename}.
23557 The lines in a command file are generally executed sequentially,
23558 unless the order of execution is changed by one of the
23559 @emph{flow-control commands} described below. The commands are not
23560 printed as they are executed. An error in any command terminates
23561 execution of the command file and control is returned to the console.
23563 @value{GDBN} first searches for @var{filename} in the current directory.
23564 If the file is not found there, and @var{filename} does not specify a
23565 directory, then @value{GDBN} also looks for the file on the source search path
23566 (specified with the @samp{directory} command);
23567 except that @file{$cdir} is not searched because the compilation directory
23568 is not relevant to scripts.
23570 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
23571 on the search path even if @var{filename} specifies a directory.
23572 The search is done by appending @var{filename} to each element of the
23573 search path. So, for example, if @var{filename} is @file{mylib/myscript}
23574 and the search path contains @file{/home/user} then @value{GDBN} will
23575 look for the script @file{/home/user/mylib/myscript}.
23576 The search is also done if @var{filename} is an absolute path.
23577 For example, if @var{filename} is @file{/tmp/myscript} and
23578 the search path contains @file{/home/user} then @value{GDBN} will
23579 look for the script @file{/home/user/tmp/myscript}.
23580 For DOS-like systems, if @var{filename} contains a drive specification,
23581 it is stripped before concatenation. For example, if @var{filename} is
23582 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
23583 will look for the script @file{c:/tmp/myscript}.
23585 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
23586 each command as it is executed. The option must be given before
23587 @var{filename}, and is interpreted as part of the filename anywhere else.
23589 Commands that would ask for confirmation if used interactively proceed
23590 without asking when used in a command file. Many @value{GDBN} commands that
23591 normally print messages to say what they are doing omit the messages
23592 when called from command files.
23594 @value{GDBN} also accepts command input from standard input. In this
23595 mode, normal output goes to standard output and error output goes to
23596 standard error. Errors in a command file supplied on standard input do
23597 not terminate execution of the command file---execution continues with
23601 gdb < cmds > log 2>&1
23604 (The syntax above will vary depending on the shell used.) This example
23605 will execute commands from the file @file{cmds}. All output and errors
23606 would be directed to @file{log}.
23608 Since commands stored on command files tend to be more general than
23609 commands typed interactively, they frequently need to deal with
23610 complicated situations, such as different or unexpected values of
23611 variables and symbols, changes in how the program being debugged is
23612 built, etc. @value{GDBN} provides a set of flow-control commands to
23613 deal with these complexities. Using these commands, you can write
23614 complex scripts that loop over data structures, execute commands
23615 conditionally, etc.
23622 This command allows to include in your script conditionally executed
23623 commands. The @code{if} command takes a single argument, which is an
23624 expression to evaluate. It is followed by a series of commands that
23625 are executed only if the expression is true (its value is nonzero).
23626 There can then optionally be an @code{else} line, followed by a series
23627 of commands that are only executed if the expression was false. The
23628 end of the list is marked by a line containing @code{end}.
23632 This command allows to write loops. Its syntax is similar to
23633 @code{if}: the command takes a single argument, which is an expression
23634 to evaluate, and must be followed by the commands to execute, one per
23635 line, terminated by an @code{end}. These commands are called the
23636 @dfn{body} of the loop. The commands in the body of @code{while} are
23637 executed repeatedly as long as the expression evaluates to true.
23641 This command exits the @code{while} loop in whose body it is included.
23642 Execution of the script continues after that @code{while}s @code{end}
23645 @kindex loop_continue
23646 @item loop_continue
23647 This command skips the execution of the rest of the body of commands
23648 in the @code{while} loop in whose body it is included. Execution
23649 branches to the beginning of the @code{while} loop, where it evaluates
23650 the controlling expression.
23652 @kindex end@r{ (if/else/while commands)}
23654 Terminate the block of commands that are the body of @code{if},
23655 @code{else}, or @code{while} flow-control commands.
23660 @subsection Commands for Controlled Output
23662 During the execution of a command file or a user-defined command, normal
23663 @value{GDBN} output is suppressed; the only output that appears is what is
23664 explicitly printed by the commands in the definition. This section
23665 describes three commands useful for generating exactly the output you
23670 @item echo @var{text}
23671 @c I do not consider backslash-space a standard C escape sequence
23672 @c because it is not in ANSI.
23673 Print @var{text}. Nonprinting characters can be included in
23674 @var{text} using C escape sequences, such as @samp{\n} to print a
23675 newline. @strong{No newline is printed unless you specify one.}
23676 In addition to the standard C escape sequences, a backslash followed
23677 by a space stands for a space. This is useful for displaying a
23678 string with spaces at the beginning or the end, since leading and
23679 trailing spaces are otherwise trimmed from all arguments.
23680 To print @samp{@w{ }and foo =@w{ }}, use the command
23681 @samp{echo \@w{ }and foo = \@w{ }}.
23683 A backslash at the end of @var{text} can be used, as in C, to continue
23684 the command onto subsequent lines. For example,
23687 echo This is some text\n\
23688 which is continued\n\
23689 onto several lines.\n
23692 produces the same output as
23695 echo This is some text\n
23696 echo which is continued\n
23697 echo onto several lines.\n
23701 @item output @var{expression}
23702 Print the value of @var{expression} and nothing but that value: no
23703 newlines, no @samp{$@var{nn} = }. The value is not entered in the
23704 value history either. @xref{Expressions, ,Expressions}, for more information
23707 @item output/@var{fmt} @var{expression}
23708 Print the value of @var{expression} in format @var{fmt}. You can use
23709 the same formats as for @code{print}. @xref{Output Formats,,Output
23710 Formats}, for more information.
23713 @item printf @var{template}, @var{expressions}@dots{}
23714 Print the values of one or more @var{expressions} under the control of
23715 the string @var{template}. To print several values, make
23716 @var{expressions} be a comma-separated list of individual expressions,
23717 which may be either numbers or pointers. Their values are printed as
23718 specified by @var{template}, exactly as a C program would do by
23719 executing the code below:
23722 printf (@var{template}, @var{expressions}@dots{});
23725 As in @code{C} @code{printf}, ordinary characters in @var{template}
23726 are printed verbatim, while @dfn{conversion specification} introduced
23727 by the @samp{%} character cause subsequent @var{expressions} to be
23728 evaluated, their values converted and formatted according to type and
23729 style information encoded in the conversion specifications, and then
23732 For example, you can print two values in hex like this:
23735 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
23738 @code{printf} supports all the standard @code{C} conversion
23739 specifications, including the flags and modifiers between the @samp{%}
23740 character and the conversion letter, with the following exceptions:
23744 The argument-ordering modifiers, such as @samp{2$}, are not supported.
23747 The modifier @samp{*} is not supported for specifying precision or
23751 The @samp{'} flag (for separation of digits into groups according to
23752 @code{LC_NUMERIC'}) is not supported.
23755 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
23759 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
23762 The conversion letters @samp{a} and @samp{A} are not supported.
23766 Note that the @samp{ll} type modifier is supported only if the
23767 underlying @code{C} implementation used to build @value{GDBN} supports
23768 the @code{long long int} type, and the @samp{L} type modifier is
23769 supported only if @code{long double} type is available.
23771 As in @code{C}, @code{printf} supports simple backslash-escape
23772 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
23773 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
23774 single character. Octal and hexadecimal escape sequences are not
23777 Additionally, @code{printf} supports conversion specifications for DFP
23778 (@dfn{Decimal Floating Point}) types using the following length modifiers
23779 together with a floating point specifier.
23784 @samp{H} for printing @code{Decimal32} types.
23787 @samp{D} for printing @code{Decimal64} types.
23790 @samp{DD} for printing @code{Decimal128} types.
23793 If the underlying @code{C} implementation used to build @value{GDBN} has
23794 support for the three length modifiers for DFP types, other modifiers
23795 such as width and precision will also be available for @value{GDBN} to use.
23797 In case there is no such @code{C} support, no additional modifiers will be
23798 available and the value will be printed in the standard way.
23800 Here's an example of printing DFP types using the above conversion letters:
23802 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
23806 @item eval @var{template}, @var{expressions}@dots{}
23807 Convert the values of one or more @var{expressions} under the control of
23808 the string @var{template} to a command line, and call it.
23812 @node Auto-loading sequences
23813 @subsection Controlling auto-loading native @value{GDBN} scripts
23814 @cindex native script auto-loading
23816 When a new object file is read (for example, due to the @code{file}
23817 command, or because the inferior has loaded a shared library),
23818 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
23819 @xref{Auto-loading extensions}.
23821 Auto-loading can be enabled or disabled,
23822 and the list of auto-loaded scripts can be printed.
23825 @anchor{set auto-load gdb-scripts}
23826 @kindex set auto-load gdb-scripts
23827 @item set auto-load gdb-scripts [on|off]
23828 Enable or disable the auto-loading of canned sequences of commands scripts.
23830 @anchor{show auto-load gdb-scripts}
23831 @kindex show auto-load gdb-scripts
23832 @item show auto-load gdb-scripts
23833 Show whether auto-loading of canned sequences of commands scripts is enabled or
23836 @anchor{info auto-load gdb-scripts}
23837 @kindex info auto-load gdb-scripts
23838 @cindex print list of auto-loaded canned sequences of commands scripts
23839 @item info auto-load gdb-scripts [@var{regexp}]
23840 Print the list of all canned sequences of commands scripts that @value{GDBN}
23844 If @var{regexp} is supplied only canned sequences of commands scripts with
23845 matching names are printed.
23847 @c Python docs live in a separate file.
23848 @include python.texi
23850 @c Guile docs live in a separate file.
23851 @include guile.texi
23853 @node Auto-loading extensions
23854 @section Auto-loading extensions
23855 @cindex auto-loading extensions
23857 @value{GDBN} provides two mechanisms for automatically loading extensions
23858 when a new object file is read (for example, due to the @code{file}
23859 command, or because the inferior has loaded a shared library):
23860 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
23861 section of modern file formats like ELF.
23864 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
23865 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
23866 * Which flavor to choose?::
23869 The auto-loading feature is useful for supplying application-specific
23870 debugging commands and features.
23872 Auto-loading can be enabled or disabled,
23873 and the list of auto-loaded scripts can be printed.
23874 See the @samp{auto-loading} section of each extension language
23875 for more information.
23876 For @value{GDBN} command files see @ref{Auto-loading sequences}.
23877 For Python files see @ref{Python Auto-loading}.
23879 Note that loading of this script file also requires accordingly configured
23880 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23882 @node objfile-gdbdotext file
23883 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
23884 @cindex @file{@var{objfile}-gdb.gdb}
23885 @cindex @file{@var{objfile}-gdb.py}
23886 @cindex @file{@var{objfile}-gdb.scm}
23888 When a new object file is read, @value{GDBN} looks for a file named
23889 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
23890 where @var{objfile} is the object file's name and
23891 where @var{ext} is the file extension for the extension language:
23894 @item @file{@var{objfile}-gdb.gdb}
23895 GDB's own command language
23896 @item @file{@var{objfile}-gdb.py}
23898 @item @file{@var{objfile}-gdb.scm}
23902 @var{script-name} is formed by ensuring that the file name of @var{objfile}
23903 is absolute, following all symlinks, and resolving @code{.} and @code{..}
23904 components, and appending the @file{-gdb.@var{ext}} suffix.
23905 If this file exists and is readable, @value{GDBN} will evaluate it as a
23906 script in the specified extension language.
23908 If this file does not exist, then @value{GDBN} will look for
23909 @var{script-name} file in all of the directories as specified below.
23911 Note that loading of these files requires an accordingly configured
23912 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23914 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
23915 scripts normally according to its @file{.exe} filename. But if no scripts are
23916 found @value{GDBN} also tries script filenames matching the object file without
23917 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
23918 is attempted on any platform. This makes the script filenames compatible
23919 between Unix and MS-Windows hosts.
23922 @anchor{set auto-load scripts-directory}
23923 @kindex set auto-load scripts-directory
23924 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
23925 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
23926 may be delimited by the host platform path separator in use
23927 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
23929 Each entry here needs to be covered also by the security setting
23930 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
23932 @anchor{with-auto-load-dir}
23933 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
23934 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
23935 configuration option @option{--with-auto-load-dir}.
23937 Any reference to @file{$debugdir} will get replaced by
23938 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
23939 reference to @file{$datadir} will get replaced by @var{data-directory} which is
23940 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
23941 @file{$datadir} must be placed as a directory component --- either alone or
23942 delimited by @file{/} or @file{\} directory separators, depending on the host
23945 The list of directories uses path separator (@samp{:} on GNU and Unix
23946 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
23947 to the @env{PATH} environment variable.
23949 @anchor{show auto-load scripts-directory}
23950 @kindex show auto-load scripts-directory
23951 @item show auto-load scripts-directory
23952 Show @value{GDBN} auto-loaded scripts location.
23954 @anchor{add-auto-load-scripts-directory}
23955 @kindex add-auto-load-scripts-directory
23956 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
23957 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
23958 Multiple entries may be delimited by the host platform path separator in use.
23961 @value{GDBN} does not track which files it has already auto-loaded this way.
23962 @value{GDBN} will load the associated script every time the corresponding
23963 @var{objfile} is opened.
23964 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
23965 is evaluated more than once.
23967 @node dotdebug_gdb_scripts section
23968 @subsection The @code{.debug_gdb_scripts} section
23969 @cindex @code{.debug_gdb_scripts} section
23971 For systems using file formats like ELF and COFF,
23972 when @value{GDBN} loads a new object file
23973 it will look for a special section named @code{.debug_gdb_scripts}.
23974 If this section exists, its contents is a list of NUL-terminated names
23975 of scripts to load. Each entry begins with a non-NULL prefix byte that
23976 specifies the kind of entry, typically the extension language.
23978 @value{GDBN} will look for each specified script file first in the
23979 current directory and then along the source search path
23980 (@pxref{Source Path, ,Specifying Source Directories}),
23981 except that @file{$cdir} is not searched, since the compilation
23982 directory is not relevant to scripts.
23984 Entries can be placed in section @code{.debug_gdb_scripts} with,
23985 for example, this GCC macro for Python scripts.
23988 /* Note: The "MS" section flags are to remove duplicates. */
23989 #define DEFINE_GDB_PY_SCRIPT(script_name) \
23991 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
23992 .byte 1 /* Python */\n\
23993 .asciz \"" script_name "\"\n\
23999 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
24000 Then one can reference the macro in a header or source file like this:
24003 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
24006 The script name may include directories if desired.
24008 Note that loading of this script file also requires accordingly configured
24009 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24011 If the macro invocation is put in a header, any application or library
24012 using this header will get a reference to the specified script,
24013 and with the use of @code{"MS"} attributes on the section, the linker
24014 will remove duplicates.
24016 @node Which flavor to choose?
24017 @subsection Which flavor to choose?
24019 Given the multiple ways of auto-loading extensions, it might not always
24020 be clear which one to choose. This section provides some guidance.
24023 Benefits of the @file{-gdb.@var{ext}} way:
24027 Can be used with file formats that don't support multiple sections.
24030 Ease of finding scripts for public libraries.
24032 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
24033 in the source search path.
24034 For publicly installed libraries, e.g., @file{libstdc++}, there typically
24035 isn't a source directory in which to find the script.
24038 Doesn't require source code additions.
24042 Benefits of the @code{.debug_gdb_scripts} way:
24046 Works with static linking.
24048 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
24049 trigger their loading. When an application is statically linked the only
24050 objfile available is the executable, and it is cumbersome to attach all the
24051 scripts from all the input libraries to the executable's
24052 @file{-gdb.@var{ext}} script.
24055 Works with classes that are entirely inlined.
24057 Some classes can be entirely inlined, and thus there may not be an associated
24058 shared library to attach a @file{-gdb.@var{ext}} script to.
24061 Scripts needn't be copied out of the source tree.
24063 In some circumstances, apps can be built out of large collections of internal
24064 libraries, and the build infrastructure necessary to install the
24065 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
24066 cumbersome. It may be easier to specify the scripts in the
24067 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
24068 top of the source tree to the source search path.
24071 @node Multiple Extension Languages
24072 @section Multiple Extension Languages
24074 The Guile and Python extension languages do not share any state,
24075 and generally do not interfere with each other.
24076 There are some things to be aware of, however.
24078 @subsection Python comes first
24080 Python was @value{GDBN}'s first extension language, and to avoid breaking
24081 existing behaviour Python comes first. This is generally solved by the
24082 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
24083 extension languages, and when it makes a call to an extension language,
24084 (say to pretty-print a value), it tries each in turn until an extension
24085 language indicates it has performed the request (e.g., has returned the
24086 pretty-printed form of a value).
24087 This extends to errors while performing such requests: If an error happens
24088 while, for example, trying to pretty-print an object then the error is
24089 reported and any following extension languages are not tried.
24092 @section Creating new spellings of existing commands
24093 @cindex aliases for commands
24095 It is often useful to define alternate spellings of existing commands.
24096 For example, if a new @value{GDBN} command defined in Python has
24097 a long name to type, it is handy to have an abbreviated version of it
24098 that involves less typing.
24100 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
24101 of the @samp{step} command even though it is otherwise an ambiguous
24102 abbreviation of other commands like @samp{set} and @samp{show}.
24104 Aliases are also used to provide shortened or more common versions
24105 of multi-word commands. For example, @value{GDBN} provides the
24106 @samp{tty} alias of the @samp{set inferior-tty} command.
24108 You can define a new alias with the @samp{alias} command.
24113 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
24117 @var{ALIAS} specifies the name of the new alias.
24118 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
24121 @var{COMMAND} specifies the name of an existing command
24122 that is being aliased.
24124 The @samp{-a} option specifies that the new alias is an abbreviation
24125 of the command. Abbreviations are not shown in command
24126 lists displayed by the @samp{help} command.
24128 The @samp{--} option specifies the end of options,
24129 and is useful when @var{ALIAS} begins with a dash.
24131 Here is a simple example showing how to make an abbreviation
24132 of a command so that there is less to type.
24133 Suppose you were tired of typing @samp{disas}, the current
24134 shortest unambiguous abbreviation of the @samp{disassemble} command
24135 and you wanted an even shorter version named @samp{di}.
24136 The following will accomplish this.
24139 (gdb) alias -a di = disas
24142 Note that aliases are different from user-defined commands.
24143 With a user-defined command, you also need to write documentation
24144 for it with the @samp{document} command.
24145 An alias automatically picks up the documentation of the existing command.
24147 Here is an example where we make @samp{elms} an abbreviation of
24148 @samp{elements} in the @samp{set print elements} command.
24149 This is to show that you can make an abbreviation of any part
24153 (gdb) alias -a set print elms = set print elements
24154 (gdb) alias -a show print elms = show print elements
24155 (gdb) set p elms 20
24157 Limit on string chars or array elements to print is 200.
24160 Note that if you are defining an alias of a @samp{set} command,
24161 and you want to have an alias for the corresponding @samp{show}
24162 command, then you need to define the latter separately.
24164 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
24165 @var{ALIAS}, just as they are normally.
24168 (gdb) alias -a set pr elms = set p ele
24171 Finally, here is an example showing the creation of a one word
24172 alias for a more complex command.
24173 This creates alias @samp{spe} of the command @samp{set print elements}.
24176 (gdb) alias spe = set print elements
24181 @chapter Command Interpreters
24182 @cindex command interpreters
24184 @value{GDBN} supports multiple command interpreters, and some command
24185 infrastructure to allow users or user interface writers to switch
24186 between interpreters or run commands in other interpreters.
24188 @value{GDBN} currently supports two command interpreters, the console
24189 interpreter (sometimes called the command-line interpreter or @sc{cli})
24190 and the machine interface interpreter (or @sc{gdb/mi}). This manual
24191 describes both of these interfaces in great detail.
24193 By default, @value{GDBN} will start with the console interpreter.
24194 However, the user may choose to start @value{GDBN} with another
24195 interpreter by specifying the @option{-i} or @option{--interpreter}
24196 startup options. Defined interpreters include:
24200 @cindex console interpreter
24201 The traditional console or command-line interpreter. This is the most often
24202 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
24203 @value{GDBN} will use this interpreter.
24206 @cindex mi interpreter
24207 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
24208 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
24209 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
24213 @cindex mi2 interpreter
24214 The current @sc{gdb/mi} interface.
24217 @cindex mi1 interpreter
24218 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
24222 @cindex invoke another interpreter
24223 The interpreter being used by @value{GDBN} may not be dynamically
24224 switched at runtime. Although possible, this could lead to a very
24225 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
24226 enters the command "interpreter-set console" in a console view,
24227 @value{GDBN} would switch to using the console interpreter, rendering
24228 the IDE inoperable!
24230 @kindex interpreter-exec
24231 Although you may only choose a single interpreter at startup, you may execute
24232 commands in any interpreter from the current interpreter using the appropriate
24233 command. If you are running the console interpreter, simply use the
24234 @code{interpreter-exec} command:
24237 interpreter-exec mi "-data-list-register-names"
24240 @sc{gdb/mi} has a similar command, although it is only available in versions of
24241 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
24244 @chapter @value{GDBN} Text User Interface
24246 @cindex Text User Interface
24249 * TUI Overview:: TUI overview
24250 * TUI Keys:: TUI key bindings
24251 * TUI Single Key Mode:: TUI single key mode
24252 * TUI Commands:: TUI-specific commands
24253 * TUI Configuration:: TUI configuration variables
24256 The @value{GDBN} Text User Interface (TUI) is a terminal
24257 interface which uses the @code{curses} library to show the source
24258 file, the assembly output, the program registers and @value{GDBN}
24259 commands in separate text windows. The TUI mode is supported only
24260 on platforms where a suitable version of the @code{curses} library
24263 The TUI mode is enabled by default when you invoke @value{GDBN} as
24264 @samp{@value{GDBP} -tui}.
24265 You can also switch in and out of TUI mode while @value{GDBN} runs by
24266 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
24267 @xref{TUI Keys, ,TUI Key Bindings}.
24270 @section TUI Overview
24272 In TUI mode, @value{GDBN} can display several text windows:
24276 This window is the @value{GDBN} command window with the @value{GDBN}
24277 prompt and the @value{GDBN} output. The @value{GDBN} input is still
24278 managed using readline.
24281 The source window shows the source file of the program. The current
24282 line and active breakpoints are displayed in this window.
24285 The assembly window shows the disassembly output of the program.
24288 This window shows the processor registers. Registers are highlighted
24289 when their values change.
24292 The source and assembly windows show the current program position
24293 by highlighting the current line and marking it with a @samp{>} marker.
24294 Breakpoints are indicated with two markers. The first marker
24295 indicates the breakpoint type:
24299 Breakpoint which was hit at least once.
24302 Breakpoint which was never hit.
24305 Hardware breakpoint which was hit at least once.
24308 Hardware breakpoint which was never hit.
24311 The second marker indicates whether the breakpoint is enabled or not:
24315 Breakpoint is enabled.
24318 Breakpoint is disabled.
24321 The source, assembly and register windows are updated when the current
24322 thread changes, when the frame changes, or when the program counter
24325 These windows are not all visible at the same time. The command
24326 window is always visible. The others can be arranged in several
24337 source and assembly,
24340 source and registers, or
24343 assembly and registers.
24346 A status line above the command window shows the following information:
24350 Indicates the current @value{GDBN} target.
24351 (@pxref{Targets, ,Specifying a Debugging Target}).
24354 Gives the current process or thread number.
24355 When no process is being debugged, this field is set to @code{No process}.
24358 Gives the current function name for the selected frame.
24359 The name is demangled if demangling is turned on (@pxref{Print Settings}).
24360 When there is no symbol corresponding to the current program counter,
24361 the string @code{??} is displayed.
24364 Indicates the current line number for the selected frame.
24365 When the current line number is not known, the string @code{??} is displayed.
24368 Indicates the current program counter address.
24372 @section TUI Key Bindings
24373 @cindex TUI key bindings
24375 The TUI installs several key bindings in the readline keymaps
24376 @ifset SYSTEM_READLINE
24377 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
24379 @ifclear SYSTEM_READLINE
24380 (@pxref{Command Line Editing}).
24382 The following key bindings are installed for both TUI mode and the
24383 @value{GDBN} standard mode.
24392 Enter or leave the TUI mode. When leaving the TUI mode,
24393 the curses window management stops and @value{GDBN} operates using
24394 its standard mode, writing on the terminal directly. When reentering
24395 the TUI mode, control is given back to the curses windows.
24396 The screen is then refreshed.
24400 Use a TUI layout with only one window. The layout will
24401 either be @samp{source} or @samp{assembly}. When the TUI mode
24402 is not active, it will switch to the TUI mode.
24404 Think of this key binding as the Emacs @kbd{C-x 1} binding.
24408 Use a TUI layout with at least two windows. When the current
24409 layout already has two windows, the next layout with two windows is used.
24410 When a new layout is chosen, one window will always be common to the
24411 previous layout and the new one.
24413 Think of it as the Emacs @kbd{C-x 2} binding.
24417 Change the active window. The TUI associates several key bindings
24418 (like scrolling and arrow keys) with the active window. This command
24419 gives the focus to the next TUI window.
24421 Think of it as the Emacs @kbd{C-x o} binding.
24425 Switch in and out of the TUI SingleKey mode that binds single
24426 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
24429 The following key bindings only work in the TUI mode:
24434 Scroll the active window one page up.
24438 Scroll the active window one page down.
24442 Scroll the active window one line up.
24446 Scroll the active window one line down.
24450 Scroll the active window one column left.
24454 Scroll the active window one column right.
24458 Refresh the screen.
24461 Because the arrow keys scroll the active window in the TUI mode, they
24462 are not available for their normal use by readline unless the command
24463 window has the focus. When another window is active, you must use
24464 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
24465 and @kbd{C-f} to control the command window.
24467 @node TUI Single Key Mode
24468 @section TUI Single Key Mode
24469 @cindex TUI single key mode
24471 The TUI also provides a @dfn{SingleKey} mode, which binds several
24472 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
24473 switch into this mode, where the following key bindings are used:
24476 @kindex c @r{(SingleKey TUI key)}
24480 @kindex d @r{(SingleKey TUI key)}
24484 @kindex f @r{(SingleKey TUI key)}
24488 @kindex n @r{(SingleKey TUI key)}
24492 @kindex q @r{(SingleKey TUI key)}
24494 exit the SingleKey mode.
24496 @kindex r @r{(SingleKey TUI key)}
24500 @kindex s @r{(SingleKey TUI key)}
24504 @kindex u @r{(SingleKey TUI key)}
24508 @kindex v @r{(SingleKey TUI key)}
24512 @kindex w @r{(SingleKey TUI key)}
24517 Other keys temporarily switch to the @value{GDBN} command prompt.
24518 The key that was pressed is inserted in the editing buffer so that
24519 it is possible to type most @value{GDBN} commands without interaction
24520 with the TUI SingleKey mode. Once the command is entered the TUI
24521 SingleKey mode is restored. The only way to permanently leave
24522 this mode is by typing @kbd{q} or @kbd{C-x s}.
24526 @section TUI-specific Commands
24527 @cindex TUI commands
24529 The TUI has specific commands to control the text windows.
24530 These commands are always available, even when @value{GDBN} is not in
24531 the TUI mode. When @value{GDBN} is in the standard mode, most
24532 of these commands will automatically switch to the TUI mode.
24534 Note that if @value{GDBN}'s @code{stdout} is not connected to a
24535 terminal, or @value{GDBN} has been started with the machine interface
24536 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
24537 these commands will fail with an error, because it would not be
24538 possible or desirable to enable curses window management.
24543 List and give the size of all displayed windows.
24547 Display the next layout.
24550 Display the previous layout.
24553 Display the source window only.
24556 Display the assembly window only.
24559 Display the source and assembly window.
24562 Display the register window together with the source or assembly window.
24566 Make the next window active for scrolling.
24569 Make the previous window active for scrolling.
24572 Make the source window active for scrolling.
24575 Make the assembly window active for scrolling.
24578 Make the register window active for scrolling.
24581 Make the command window active for scrolling.
24585 Refresh the screen. This is similar to typing @kbd{C-L}.
24587 @item tui reg float
24589 Show the floating point registers in the register window.
24591 @item tui reg general
24592 Show the general registers in the register window.
24595 Show the next register group. The list of register groups as well as
24596 their order is target specific. The predefined register groups are the
24597 following: @code{general}, @code{float}, @code{system}, @code{vector},
24598 @code{all}, @code{save}, @code{restore}.
24600 @item tui reg system
24601 Show the system registers in the register window.
24605 Update the source window and the current execution point.
24607 @item winheight @var{name} +@var{count}
24608 @itemx winheight @var{name} -@var{count}
24610 Change the height of the window @var{name} by @var{count}
24611 lines. Positive counts increase the height, while negative counts
24614 @item tabset @var{nchars}
24616 Set the width of tab stops to be @var{nchars} characters.
24619 @node TUI Configuration
24620 @section TUI Configuration Variables
24621 @cindex TUI configuration variables
24623 Several configuration variables control the appearance of TUI windows.
24626 @item set tui border-kind @var{kind}
24627 @kindex set tui border-kind
24628 Select the border appearance for the source, assembly and register windows.
24629 The possible values are the following:
24632 Use a space character to draw the border.
24635 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
24638 Use the Alternate Character Set to draw the border. The border is
24639 drawn using character line graphics if the terminal supports them.
24642 @item set tui border-mode @var{mode}
24643 @kindex set tui border-mode
24644 @itemx set tui active-border-mode @var{mode}
24645 @kindex set tui active-border-mode
24646 Select the display attributes for the borders of the inactive windows
24647 or the active window. The @var{mode} can be one of the following:
24650 Use normal attributes to display the border.
24656 Use reverse video mode.
24659 Use half bright mode.
24661 @item half-standout
24662 Use half bright and standout mode.
24665 Use extra bright or bold mode.
24667 @item bold-standout
24668 Use extra bright or bold and standout mode.
24673 @chapter Using @value{GDBN} under @sc{gnu} Emacs
24676 @cindex @sc{gnu} Emacs
24677 A special interface allows you to use @sc{gnu} Emacs to view (and
24678 edit) the source files for the program you are debugging with
24681 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
24682 executable file you want to debug as an argument. This command starts
24683 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
24684 created Emacs buffer.
24685 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
24687 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
24692 All ``terminal'' input and output goes through an Emacs buffer, called
24695 This applies both to @value{GDBN} commands and their output, and to the input
24696 and output done by the program you are debugging.
24698 This is useful because it means that you can copy the text of previous
24699 commands and input them again; you can even use parts of the output
24702 All the facilities of Emacs' Shell mode are available for interacting
24703 with your program. In particular, you can send signals the usual
24704 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
24708 @value{GDBN} displays source code through Emacs.
24710 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
24711 source file for that frame and puts an arrow (@samp{=>}) at the
24712 left margin of the current line. Emacs uses a separate buffer for
24713 source display, and splits the screen to show both your @value{GDBN} session
24716 Explicit @value{GDBN} @code{list} or search commands still produce output as
24717 usual, but you probably have no reason to use them from Emacs.
24720 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
24721 a graphical mode, enabled by default, which provides further buffers
24722 that can control the execution and describe the state of your program.
24723 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
24725 If you specify an absolute file name when prompted for the @kbd{M-x
24726 gdb} argument, then Emacs sets your current working directory to where
24727 your program resides. If you only specify the file name, then Emacs
24728 sets your current working directory to the directory associated
24729 with the previous buffer. In this case, @value{GDBN} may find your
24730 program by searching your environment's @code{PATH} variable, but on
24731 some operating systems it might not find the source. So, although the
24732 @value{GDBN} input and output session proceeds normally, the auxiliary
24733 buffer does not display the current source and line of execution.
24735 The initial working directory of @value{GDBN} is printed on the top
24736 line of the GUD buffer and this serves as a default for the commands
24737 that specify files for @value{GDBN} to operate on. @xref{Files,
24738 ,Commands to Specify Files}.
24740 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
24741 need to call @value{GDBN} by a different name (for example, if you
24742 keep several configurations around, with different names) you can
24743 customize the Emacs variable @code{gud-gdb-command-name} to run the
24746 In the GUD buffer, you can use these special Emacs commands in
24747 addition to the standard Shell mode commands:
24751 Describe the features of Emacs' GUD Mode.
24754 Execute to another source line, like the @value{GDBN} @code{step} command; also
24755 update the display window to show the current file and location.
24758 Execute to next source line in this function, skipping all function
24759 calls, like the @value{GDBN} @code{next} command. Then update the display window
24760 to show the current file and location.
24763 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
24764 display window accordingly.
24767 Execute until exit from the selected stack frame, like the @value{GDBN}
24768 @code{finish} command.
24771 Continue execution of your program, like the @value{GDBN} @code{continue}
24775 Go up the number of frames indicated by the numeric argument
24776 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
24777 like the @value{GDBN} @code{up} command.
24780 Go down the number of frames indicated by the numeric argument, like the
24781 @value{GDBN} @code{down} command.
24784 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
24785 tells @value{GDBN} to set a breakpoint on the source line point is on.
24787 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
24788 separate frame which shows a backtrace when the GUD buffer is current.
24789 Move point to any frame in the stack and type @key{RET} to make it
24790 become the current frame and display the associated source in the
24791 source buffer. Alternatively, click @kbd{Mouse-2} to make the
24792 selected frame become the current one. In graphical mode, the
24793 speedbar displays watch expressions.
24795 If you accidentally delete the source-display buffer, an easy way to get
24796 it back is to type the command @code{f} in the @value{GDBN} buffer, to
24797 request a frame display; when you run under Emacs, this recreates
24798 the source buffer if necessary to show you the context of the current
24801 The source files displayed in Emacs are in ordinary Emacs buffers
24802 which are visiting the source files in the usual way. You can edit
24803 the files with these buffers if you wish; but keep in mind that @value{GDBN}
24804 communicates with Emacs in terms of line numbers. If you add or
24805 delete lines from the text, the line numbers that @value{GDBN} knows cease
24806 to correspond properly with the code.
24808 A more detailed description of Emacs' interaction with @value{GDBN} is
24809 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
24813 @chapter The @sc{gdb/mi} Interface
24815 @unnumberedsec Function and Purpose
24817 @cindex @sc{gdb/mi}, its purpose
24818 @sc{gdb/mi} is a line based machine oriented text interface to
24819 @value{GDBN} and is activated by specifying using the
24820 @option{--interpreter} command line option (@pxref{Mode Options}). It
24821 is specifically intended to support the development of systems which
24822 use the debugger as just one small component of a larger system.
24824 This chapter is a specification of the @sc{gdb/mi} interface. It is written
24825 in the form of a reference manual.
24827 Note that @sc{gdb/mi} is still under construction, so some of the
24828 features described below are incomplete and subject to change
24829 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
24831 @unnumberedsec Notation and Terminology
24833 @cindex notational conventions, for @sc{gdb/mi}
24834 This chapter uses the following notation:
24838 @code{|} separates two alternatives.
24841 @code{[ @var{something} ]} indicates that @var{something} is optional:
24842 it may or may not be given.
24845 @code{( @var{group} )*} means that @var{group} inside the parentheses
24846 may repeat zero or more times.
24849 @code{( @var{group} )+} means that @var{group} inside the parentheses
24850 may repeat one or more times.
24853 @code{"@var{string}"} means a literal @var{string}.
24857 @heading Dependencies
24861 * GDB/MI General Design::
24862 * GDB/MI Command Syntax::
24863 * GDB/MI Compatibility with CLI::
24864 * GDB/MI Development and Front Ends::
24865 * GDB/MI Output Records::
24866 * GDB/MI Simple Examples::
24867 * GDB/MI Command Description Format::
24868 * GDB/MI Breakpoint Commands::
24869 * GDB/MI Catchpoint Commands::
24870 * GDB/MI Program Context::
24871 * GDB/MI Thread Commands::
24872 * GDB/MI Ada Tasking Commands::
24873 * GDB/MI Program Execution::
24874 * GDB/MI Stack Manipulation::
24875 * GDB/MI Variable Objects::
24876 * GDB/MI Data Manipulation::
24877 * GDB/MI Tracepoint Commands::
24878 * GDB/MI Symbol Query::
24879 * GDB/MI File Commands::
24881 * GDB/MI Kod Commands::
24882 * GDB/MI Memory Overlay Commands::
24883 * GDB/MI Signal Handling Commands::
24885 * GDB/MI Target Manipulation::
24886 * GDB/MI File Transfer Commands::
24887 * GDB/MI Ada Exceptions Commands::
24888 * GDB/MI Support Commands::
24889 * GDB/MI Miscellaneous Commands::
24892 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24893 @node GDB/MI General Design
24894 @section @sc{gdb/mi} General Design
24895 @cindex GDB/MI General Design
24897 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
24898 parts---commands sent to @value{GDBN}, responses to those commands
24899 and notifications. Each command results in exactly one response,
24900 indicating either successful completion of the command, or an error.
24901 For the commands that do not resume the target, the response contains the
24902 requested information. For the commands that resume the target, the
24903 response only indicates whether the target was successfully resumed.
24904 Notifications is the mechanism for reporting changes in the state of the
24905 target, or in @value{GDBN} state, that cannot conveniently be associated with
24906 a command and reported as part of that command response.
24908 The important examples of notifications are:
24912 Exec notifications. These are used to report changes in
24913 target state---when a target is resumed, or stopped. It would not
24914 be feasible to include this information in response of resuming
24915 commands, because one resume commands can result in multiple events in
24916 different threads. Also, quite some time may pass before any event
24917 happens in the target, while a frontend needs to know whether the resuming
24918 command itself was successfully executed.
24921 Console output, and status notifications. Console output
24922 notifications are used to report output of CLI commands, as well as
24923 diagnostics for other commands. Status notifications are used to
24924 report the progress of a long-running operation. Naturally, including
24925 this information in command response would mean no output is produced
24926 until the command is finished, which is undesirable.
24929 General notifications. Commands may have various side effects on
24930 the @value{GDBN} or target state beyond their official purpose. For example,
24931 a command may change the selected thread. Although such changes can
24932 be included in command response, using notification allows for more
24933 orthogonal frontend design.
24937 There's no guarantee that whenever an MI command reports an error,
24938 @value{GDBN} or the target are in any specific state, and especially,
24939 the state is not reverted to the state before the MI command was
24940 processed. Therefore, whenever an MI command results in an error,
24941 we recommend that the frontend refreshes all the information shown in
24942 the user interface.
24946 * Context management::
24947 * Asynchronous and non-stop modes::
24951 @node Context management
24952 @subsection Context management
24954 @subsubsection Threads and Frames
24956 In most cases when @value{GDBN} accesses the target, this access is
24957 done in context of a specific thread and frame (@pxref{Frames}).
24958 Often, even when accessing global data, the target requires that a thread
24959 be specified. The CLI interface maintains the selected thread and frame,
24960 and supplies them to target on each command. This is convenient,
24961 because a command line user would not want to specify that information
24962 explicitly on each command, and because user interacts with
24963 @value{GDBN} via a single terminal, so no confusion is possible as
24964 to what thread and frame are the current ones.
24966 In the case of MI, the concept of selected thread and frame is less
24967 useful. First, a frontend can easily remember this information
24968 itself. Second, a graphical frontend can have more than one window,
24969 each one used for debugging a different thread, and the frontend might
24970 want to access additional threads for internal purposes. This
24971 increases the risk that by relying on implicitly selected thread, the
24972 frontend may be operating on a wrong one. Therefore, each MI command
24973 should explicitly specify which thread and frame to operate on. To
24974 make it possible, each MI command accepts the @samp{--thread} and
24975 @samp{--frame} options, the value to each is @value{GDBN} identifier
24976 for thread and frame to operate on.
24978 Usually, each top-level window in a frontend allows the user to select
24979 a thread and a frame, and remembers the user selection for further
24980 operations. However, in some cases @value{GDBN} may suggest that the
24981 current thread be changed. For example, when stopping on a breakpoint
24982 it is reasonable to switch to the thread where breakpoint is hit. For
24983 another example, if the user issues the CLI @samp{thread} command via
24984 the frontend, it is desirable to change the frontend's selected thread to the
24985 one specified by user. @value{GDBN} communicates the suggestion to
24986 change current thread using the @samp{=thread-selected} notification.
24987 No such notification is available for the selected frame at the moment.
24989 Note that historically, MI shares the selected thread with CLI, so
24990 frontends used the @code{-thread-select} to execute commands in the
24991 right context. However, getting this to work right is cumbersome. The
24992 simplest way is for frontend to emit @code{-thread-select} command
24993 before every command. This doubles the number of commands that need
24994 to be sent. The alternative approach is to suppress @code{-thread-select}
24995 if the selected thread in @value{GDBN} is supposed to be identical to the
24996 thread the frontend wants to operate on. However, getting this
24997 optimization right can be tricky. In particular, if the frontend
24998 sends several commands to @value{GDBN}, and one of the commands changes the
24999 selected thread, then the behaviour of subsequent commands will
25000 change. So, a frontend should either wait for response from such
25001 problematic commands, or explicitly add @code{-thread-select} for
25002 all subsequent commands. No frontend is known to do this exactly
25003 right, so it is suggested to just always pass the @samp{--thread} and
25004 @samp{--frame} options.
25006 @subsubsection Language
25008 The execution of several commands depends on which language is selected.
25009 By default, the current language (@pxref{show language}) is used.
25010 But for commands known to be language-sensitive, it is recommended
25011 to use the @samp{--language} option. This option takes one argument,
25012 which is the name of the language to use while executing the command.
25016 -data-evaluate-expression --language c "sizeof (void*)"
25021 The valid language names are the same names accepted by the
25022 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
25023 @samp{local} or @samp{unknown}.
25025 @node Asynchronous and non-stop modes
25026 @subsection Asynchronous command execution and non-stop mode
25028 On some targets, @value{GDBN} is capable of processing MI commands
25029 even while the target is running. This is called @dfn{asynchronous
25030 command execution} (@pxref{Background Execution}). The frontend may
25031 specify a preferrence for asynchronous execution using the
25032 @code{-gdb-set mi-async 1} command, which should be emitted before
25033 either running the executable or attaching to the target. After the
25034 frontend has started the executable or attached to the target, it can
25035 find if asynchronous execution is enabled using the
25036 @code{-list-target-features} command.
25039 @item -gdb-set mi-async on
25040 @item -gdb-set mi-async off
25041 Set whether MI is in asynchronous mode.
25043 When @code{off}, which is the default, MI execution commands (e.g.,
25044 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
25045 for the program to stop before processing further commands.
25047 When @code{on}, MI execution commands are background execution
25048 commands (e.g., @code{-exec-continue} becomes the equivalent of the
25049 @code{c&} CLI command), and so @value{GDBN} is capable of processing
25050 MI commands even while the target is running.
25052 @item -gdb-show mi-async
25053 Show whether MI asynchronous mode is enabled.
25056 Note: In @value{GDBN} version 7.7 and earlier, this option was called
25057 @code{target-async} instead of @code{mi-async}, and it had the effect
25058 of both putting MI in asynchronous mode and making CLI background
25059 commands possible. CLI background commands are now always possible
25060 ``out of the box'' if the target supports them. The old spelling is
25061 kept as a deprecated alias for backwards compatibility.
25063 Even if @value{GDBN} can accept a command while target is running,
25064 many commands that access the target do not work when the target is
25065 running. Therefore, asynchronous command execution is most useful
25066 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
25067 it is possible to examine the state of one thread, while other threads
25070 When a given thread is running, MI commands that try to access the
25071 target in the context of that thread may not work, or may work only on
25072 some targets. In particular, commands that try to operate on thread's
25073 stack will not work, on any target. Commands that read memory, or
25074 modify breakpoints, may work or not work, depending on the target. Note
25075 that even commands that operate on global state, such as @code{print},
25076 @code{set}, and breakpoint commands, still access the target in the
25077 context of a specific thread, so frontend should try to find a
25078 stopped thread and perform the operation on that thread (using the
25079 @samp{--thread} option).
25081 Which commands will work in the context of a running thread is
25082 highly target dependent. However, the two commands
25083 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
25084 to find the state of a thread, will always work.
25086 @node Thread groups
25087 @subsection Thread groups
25088 @value{GDBN} may be used to debug several processes at the same time.
25089 On some platfroms, @value{GDBN} may support debugging of several
25090 hardware systems, each one having several cores with several different
25091 processes running on each core. This section describes the MI
25092 mechanism to support such debugging scenarios.
25094 The key observation is that regardless of the structure of the
25095 target, MI can have a global list of threads, because most commands that
25096 accept the @samp{--thread} option do not need to know what process that
25097 thread belongs to. Therefore, it is not necessary to introduce
25098 neither additional @samp{--process} option, nor an notion of the
25099 current process in the MI interface. The only strictly new feature
25100 that is required is the ability to find how the threads are grouped
25103 To allow the user to discover such grouping, and to support arbitrary
25104 hierarchy of machines/cores/processes, MI introduces the concept of a
25105 @dfn{thread group}. Thread group is a collection of threads and other
25106 thread groups. A thread group always has a string identifier, a type,
25107 and may have additional attributes specific to the type. A new
25108 command, @code{-list-thread-groups}, returns the list of top-level
25109 thread groups, which correspond to processes that @value{GDBN} is
25110 debugging at the moment. By passing an identifier of a thread group
25111 to the @code{-list-thread-groups} command, it is possible to obtain
25112 the members of specific thread group.
25114 To allow the user to easily discover processes, and other objects, he
25115 wishes to debug, a concept of @dfn{available thread group} is
25116 introduced. Available thread group is an thread group that
25117 @value{GDBN} is not debugging, but that can be attached to, using the
25118 @code{-target-attach} command. The list of available top-level thread
25119 groups can be obtained using @samp{-list-thread-groups --available}.
25120 In general, the content of a thread group may be only retrieved only
25121 after attaching to that thread group.
25123 Thread groups are related to inferiors (@pxref{Inferiors and
25124 Programs}). Each inferior corresponds to a thread group of a special
25125 type @samp{process}, and some additional operations are permitted on
25126 such thread groups.
25128 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25129 @node GDB/MI Command Syntax
25130 @section @sc{gdb/mi} Command Syntax
25133 * GDB/MI Input Syntax::
25134 * GDB/MI Output Syntax::
25137 @node GDB/MI Input Syntax
25138 @subsection @sc{gdb/mi} Input Syntax
25140 @cindex input syntax for @sc{gdb/mi}
25141 @cindex @sc{gdb/mi}, input syntax
25143 @item @var{command} @expansion{}
25144 @code{@var{cli-command} | @var{mi-command}}
25146 @item @var{cli-command} @expansion{}
25147 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
25148 @var{cli-command} is any existing @value{GDBN} CLI command.
25150 @item @var{mi-command} @expansion{}
25151 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
25152 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
25154 @item @var{token} @expansion{}
25155 "any sequence of digits"
25157 @item @var{option} @expansion{}
25158 @code{"-" @var{parameter} [ " " @var{parameter} ]}
25160 @item @var{parameter} @expansion{}
25161 @code{@var{non-blank-sequence} | @var{c-string}}
25163 @item @var{operation} @expansion{}
25164 @emph{any of the operations described in this chapter}
25166 @item @var{non-blank-sequence} @expansion{}
25167 @emph{anything, provided it doesn't contain special characters such as
25168 "-", @var{nl}, """ and of course " "}
25170 @item @var{c-string} @expansion{}
25171 @code{""" @var{seven-bit-iso-c-string-content} """}
25173 @item @var{nl} @expansion{}
25182 The CLI commands are still handled by the @sc{mi} interpreter; their
25183 output is described below.
25186 The @code{@var{token}}, when present, is passed back when the command
25190 Some @sc{mi} commands accept optional arguments as part of the parameter
25191 list. Each option is identified by a leading @samp{-} (dash) and may be
25192 followed by an optional argument parameter. Options occur first in the
25193 parameter list and can be delimited from normal parameters using
25194 @samp{--} (this is useful when some parameters begin with a dash).
25201 We want easy access to the existing CLI syntax (for debugging).
25204 We want it to be easy to spot a @sc{mi} operation.
25207 @node GDB/MI Output Syntax
25208 @subsection @sc{gdb/mi} Output Syntax
25210 @cindex output syntax of @sc{gdb/mi}
25211 @cindex @sc{gdb/mi}, output syntax
25212 The output from @sc{gdb/mi} consists of zero or more out-of-band records
25213 followed, optionally, by a single result record. This result record
25214 is for the most recent command. The sequence of output records is
25215 terminated by @samp{(gdb)}.
25217 If an input command was prefixed with a @code{@var{token}} then the
25218 corresponding output for that command will also be prefixed by that same
25222 @item @var{output} @expansion{}
25223 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
25225 @item @var{result-record} @expansion{}
25226 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
25228 @item @var{out-of-band-record} @expansion{}
25229 @code{@var{async-record} | @var{stream-record}}
25231 @item @var{async-record} @expansion{}
25232 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
25234 @item @var{exec-async-output} @expansion{}
25235 @code{[ @var{token} ] "*" @var{async-output nl}}
25237 @item @var{status-async-output} @expansion{}
25238 @code{[ @var{token} ] "+" @var{async-output nl}}
25240 @item @var{notify-async-output} @expansion{}
25241 @code{[ @var{token} ] "=" @var{async-output nl}}
25243 @item @var{async-output} @expansion{}
25244 @code{@var{async-class} ( "," @var{result} )*}
25246 @item @var{result-class} @expansion{}
25247 @code{"done" | "running" | "connected" | "error" | "exit"}
25249 @item @var{async-class} @expansion{}
25250 @code{"stopped" | @var{others}} (where @var{others} will be added
25251 depending on the needs---this is still in development).
25253 @item @var{result} @expansion{}
25254 @code{ @var{variable} "=" @var{value}}
25256 @item @var{variable} @expansion{}
25257 @code{ @var{string} }
25259 @item @var{value} @expansion{}
25260 @code{ @var{const} | @var{tuple} | @var{list} }
25262 @item @var{const} @expansion{}
25263 @code{@var{c-string}}
25265 @item @var{tuple} @expansion{}
25266 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
25268 @item @var{list} @expansion{}
25269 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
25270 @var{result} ( "," @var{result} )* "]" }
25272 @item @var{stream-record} @expansion{}
25273 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
25275 @item @var{console-stream-output} @expansion{}
25276 @code{"~" @var{c-string nl}}
25278 @item @var{target-stream-output} @expansion{}
25279 @code{"@@" @var{c-string nl}}
25281 @item @var{log-stream-output} @expansion{}
25282 @code{"&" @var{c-string nl}}
25284 @item @var{nl} @expansion{}
25287 @item @var{token} @expansion{}
25288 @emph{any sequence of digits}.
25296 All output sequences end in a single line containing a period.
25299 The @code{@var{token}} is from the corresponding request. Note that
25300 for all async output, while the token is allowed by the grammar and
25301 may be output by future versions of @value{GDBN} for select async
25302 output messages, it is generally omitted. Frontends should treat
25303 all async output as reporting general changes in the state of the
25304 target and there should be no need to associate async output to any
25308 @cindex status output in @sc{gdb/mi}
25309 @var{status-async-output} contains on-going status information about the
25310 progress of a slow operation. It can be discarded. All status output is
25311 prefixed by @samp{+}.
25314 @cindex async output in @sc{gdb/mi}
25315 @var{exec-async-output} contains asynchronous state change on the target
25316 (stopped, started, disappeared). All async output is prefixed by
25320 @cindex notify output in @sc{gdb/mi}
25321 @var{notify-async-output} contains supplementary information that the
25322 client should handle (e.g., a new breakpoint information). All notify
25323 output is prefixed by @samp{=}.
25326 @cindex console output in @sc{gdb/mi}
25327 @var{console-stream-output} is output that should be displayed as is in the
25328 console. It is the textual response to a CLI command. All the console
25329 output is prefixed by @samp{~}.
25332 @cindex target output in @sc{gdb/mi}
25333 @var{target-stream-output} is the output produced by the target program.
25334 All the target output is prefixed by @samp{@@}.
25337 @cindex log output in @sc{gdb/mi}
25338 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
25339 instance messages that should be displayed as part of an error log. All
25340 the log output is prefixed by @samp{&}.
25343 @cindex list output in @sc{gdb/mi}
25344 New @sc{gdb/mi} commands should only output @var{lists} containing
25350 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
25351 details about the various output records.
25353 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25354 @node GDB/MI Compatibility with CLI
25355 @section @sc{gdb/mi} Compatibility with CLI
25357 @cindex compatibility, @sc{gdb/mi} and CLI
25358 @cindex @sc{gdb/mi}, compatibility with CLI
25360 For the developers convenience CLI commands can be entered directly,
25361 but there may be some unexpected behaviour. For example, commands
25362 that query the user will behave as if the user replied yes, breakpoint
25363 command lists are not executed and some CLI commands, such as
25364 @code{if}, @code{when} and @code{define}, prompt for further input with
25365 @samp{>}, which is not valid MI output.
25367 This feature may be removed at some stage in the future and it is
25368 recommended that front ends use the @code{-interpreter-exec} command
25369 (@pxref{-interpreter-exec}).
25371 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25372 @node GDB/MI Development and Front Ends
25373 @section @sc{gdb/mi} Development and Front Ends
25374 @cindex @sc{gdb/mi} development
25376 The application which takes the MI output and presents the state of the
25377 program being debugged to the user is called a @dfn{front end}.
25379 Although @sc{gdb/mi} is still incomplete, it is currently being used
25380 by a variety of front ends to @value{GDBN}. This makes it difficult
25381 to introduce new functionality without breaking existing usage. This
25382 section tries to minimize the problems by describing how the protocol
25385 Some changes in MI need not break a carefully designed front end, and
25386 for these the MI version will remain unchanged. The following is a
25387 list of changes that may occur within one level, so front ends should
25388 parse MI output in a way that can handle them:
25392 New MI commands may be added.
25395 New fields may be added to the output of any MI command.
25398 The range of values for fields with specified values, e.g.,
25399 @code{in_scope} (@pxref{-var-update}) may be extended.
25401 @c The format of field's content e.g type prefix, may change so parse it
25402 @c at your own risk. Yes, in general?
25404 @c The order of fields may change? Shouldn't really matter but it might
25405 @c resolve inconsistencies.
25408 If the changes are likely to break front ends, the MI version level
25409 will be increased by one. This will allow the front end to parse the
25410 output according to the MI version. Apart from mi0, new versions of
25411 @value{GDBN} will not support old versions of MI and it will be the
25412 responsibility of the front end to work with the new one.
25414 @c Starting with mi3, add a new command -mi-version that prints the MI
25417 The best way to avoid unexpected changes in MI that might break your front
25418 end is to make your project known to @value{GDBN} developers and
25419 follow development on @email{gdb@@sourceware.org} and
25420 @email{gdb-patches@@sourceware.org}.
25421 @cindex mailing lists
25423 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25424 @node GDB/MI Output Records
25425 @section @sc{gdb/mi} Output Records
25428 * GDB/MI Result Records::
25429 * GDB/MI Stream Records::
25430 * GDB/MI Async Records::
25431 * GDB/MI Breakpoint Information::
25432 * GDB/MI Frame Information::
25433 * GDB/MI Thread Information::
25434 * GDB/MI Ada Exception Information::
25437 @node GDB/MI Result Records
25438 @subsection @sc{gdb/mi} Result Records
25440 @cindex result records in @sc{gdb/mi}
25441 @cindex @sc{gdb/mi}, result records
25442 In addition to a number of out-of-band notifications, the response to a
25443 @sc{gdb/mi} command includes one of the following result indications:
25447 @item "^done" [ "," @var{results} ]
25448 The synchronous operation was successful, @code{@var{results}} are the return
25453 This result record is equivalent to @samp{^done}. Historically, it
25454 was output instead of @samp{^done} if the command has resumed the
25455 target. This behaviour is maintained for backward compatibility, but
25456 all frontends should treat @samp{^done} and @samp{^running}
25457 identically and rely on the @samp{*running} output record to determine
25458 which threads are resumed.
25462 @value{GDBN} has connected to a remote target.
25464 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
25466 The operation failed. The @code{msg=@var{c-string}} variable contains
25467 the corresponding error message.
25469 If present, the @code{code=@var{c-string}} variable provides an error
25470 code on which consumers can rely on to detect the corresponding
25471 error condition. At present, only one error code is defined:
25474 @item "undefined-command"
25475 Indicates that the command causing the error does not exist.
25480 @value{GDBN} has terminated.
25484 @node GDB/MI Stream Records
25485 @subsection @sc{gdb/mi} Stream Records
25487 @cindex @sc{gdb/mi}, stream records
25488 @cindex stream records in @sc{gdb/mi}
25489 @value{GDBN} internally maintains a number of output streams: the console, the
25490 target, and the log. The output intended for each of these streams is
25491 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
25493 Each stream record begins with a unique @dfn{prefix character} which
25494 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
25495 Syntax}). In addition to the prefix, each stream record contains a
25496 @code{@var{string-output}}. This is either raw text (with an implicit new
25497 line) or a quoted C string (which does not contain an implicit newline).
25500 @item "~" @var{string-output}
25501 The console output stream contains text that should be displayed in the
25502 CLI console window. It contains the textual responses to CLI commands.
25504 @item "@@" @var{string-output}
25505 The target output stream contains any textual output from the running
25506 target. This is only present when GDB's event loop is truly
25507 asynchronous, which is currently only the case for remote targets.
25509 @item "&" @var{string-output}
25510 The log stream contains debugging messages being produced by @value{GDBN}'s
25514 @node GDB/MI Async Records
25515 @subsection @sc{gdb/mi} Async Records
25517 @cindex async records in @sc{gdb/mi}
25518 @cindex @sc{gdb/mi}, async records
25519 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
25520 additional changes that have occurred. Those changes can either be a
25521 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
25522 target activity (e.g., target stopped).
25524 The following is the list of possible async records:
25528 @item *running,thread-id="@var{thread}"
25529 The target is now running. The @var{thread} field tells which
25530 specific thread is now running, and can be @samp{all} if all threads
25531 are running. The frontend should assume that no interaction with a
25532 running thread is possible after this notification is produced.
25533 The frontend should not assume that this notification is output
25534 only once for any command. @value{GDBN} may emit this notification
25535 several times, either for different threads, because it cannot resume
25536 all threads together, or even for a single thread, if the thread must
25537 be stepped though some code before letting it run freely.
25539 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
25540 The target has stopped. The @var{reason} field can have one of the
25544 @item breakpoint-hit
25545 A breakpoint was reached.
25546 @item watchpoint-trigger
25547 A watchpoint was triggered.
25548 @item read-watchpoint-trigger
25549 A read watchpoint was triggered.
25550 @item access-watchpoint-trigger
25551 An access watchpoint was triggered.
25552 @item function-finished
25553 An -exec-finish or similar CLI command was accomplished.
25554 @item location-reached
25555 An -exec-until or similar CLI command was accomplished.
25556 @item watchpoint-scope
25557 A watchpoint has gone out of scope.
25558 @item end-stepping-range
25559 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
25560 similar CLI command was accomplished.
25561 @item exited-signalled
25562 The inferior exited because of a signal.
25564 The inferior exited.
25565 @item exited-normally
25566 The inferior exited normally.
25567 @item signal-received
25568 A signal was received by the inferior.
25570 The inferior has stopped due to a library being loaded or unloaded.
25571 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
25572 set or when a @code{catch load} or @code{catch unload} catchpoint is
25573 in use (@pxref{Set Catchpoints}).
25575 The inferior has forked. This is reported when @code{catch fork}
25576 (@pxref{Set Catchpoints}) has been used.
25578 The inferior has vforked. This is reported in when @code{catch vfork}
25579 (@pxref{Set Catchpoints}) has been used.
25580 @item syscall-entry
25581 The inferior entered a system call. This is reported when @code{catch
25582 syscall} (@pxref{Set Catchpoints}) has been used.
25583 @item syscall-entry
25584 The inferior returned from a system call. This is reported when
25585 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
25587 The inferior called @code{exec}. This is reported when @code{catch exec}
25588 (@pxref{Set Catchpoints}) has been used.
25591 The @var{id} field identifies the thread that directly caused the stop
25592 -- for example by hitting a breakpoint. Depending on whether all-stop
25593 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
25594 stop all threads, or only the thread that directly triggered the stop.
25595 If all threads are stopped, the @var{stopped} field will have the
25596 value of @code{"all"}. Otherwise, the value of the @var{stopped}
25597 field will be a list of thread identifiers. Presently, this list will
25598 always include a single thread, but frontend should be prepared to see
25599 several threads in the list. The @var{core} field reports the
25600 processor core on which the stop event has happened. This field may be absent
25601 if such information is not available.
25603 @item =thread-group-added,id="@var{id}"
25604 @itemx =thread-group-removed,id="@var{id}"
25605 A thread group was either added or removed. The @var{id} field
25606 contains the @value{GDBN} identifier of the thread group. When a thread
25607 group is added, it generally might not be associated with a running
25608 process. When a thread group is removed, its id becomes invalid and
25609 cannot be used in any way.
25611 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
25612 A thread group became associated with a running program,
25613 either because the program was just started or the thread group
25614 was attached to a program. The @var{id} field contains the
25615 @value{GDBN} identifier of the thread group. The @var{pid} field
25616 contains process identifier, specific to the operating system.
25618 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
25619 A thread group is no longer associated with a running program,
25620 either because the program has exited, or because it was detached
25621 from. The @var{id} field contains the @value{GDBN} identifier of the
25622 thread group. The @var{code} field is the exit code of the inferior; it exists
25623 only when the inferior exited with some code.
25625 @item =thread-created,id="@var{id}",group-id="@var{gid}"
25626 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
25627 A thread either was created, or has exited. The @var{id} field
25628 contains the @value{GDBN} identifier of the thread. The @var{gid}
25629 field identifies the thread group this thread belongs to.
25631 @item =thread-selected,id="@var{id}"
25632 Informs that the selected thread was changed as result of the last
25633 command. This notification is not emitted as result of @code{-thread-select}
25634 command but is emitted whenever an MI command that is not documented
25635 to change the selected thread actually changes it. In particular,
25636 invoking, directly or indirectly (via user-defined command), the CLI
25637 @code{thread} command, will generate this notification.
25639 We suggest that in response to this notification, front ends
25640 highlight the selected thread and cause subsequent commands to apply to
25643 @item =library-loaded,...
25644 Reports that a new library file was loaded by the program. This
25645 notification has 4 fields---@var{id}, @var{target-name},
25646 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
25647 opaque identifier of the library. For remote debugging case,
25648 @var{target-name} and @var{host-name} fields give the name of the
25649 library file on the target, and on the host respectively. For native
25650 debugging, both those fields have the same value. The
25651 @var{symbols-loaded} field is emitted only for backward compatibility
25652 and should not be relied on to convey any useful information. The
25653 @var{thread-group} field, if present, specifies the id of the thread
25654 group in whose context the library was loaded. If the field is
25655 absent, it means the library was loaded in the context of all present
25658 @item =library-unloaded,...
25659 Reports that a library was unloaded by the program. This notification
25660 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
25661 the same meaning as for the @code{=library-loaded} notification.
25662 The @var{thread-group} field, if present, specifies the id of the
25663 thread group in whose context the library was unloaded. If the field is
25664 absent, it means the library was unloaded in the context of all present
25667 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
25668 @itemx =traceframe-changed,end
25669 Reports that the trace frame was changed and its new number is
25670 @var{tfnum}. The number of the tracepoint associated with this trace
25671 frame is @var{tpnum}.
25673 @item =tsv-created,name=@var{name},initial=@var{initial}
25674 Reports that the new trace state variable @var{name} is created with
25675 initial value @var{initial}.
25677 @item =tsv-deleted,name=@var{name}
25678 @itemx =tsv-deleted
25679 Reports that the trace state variable @var{name} is deleted or all
25680 trace state variables are deleted.
25682 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
25683 Reports that the trace state variable @var{name} is modified with
25684 the initial value @var{initial}. The current value @var{current} of
25685 trace state variable is optional and is reported if the current
25686 value of trace state variable is known.
25688 @item =breakpoint-created,bkpt=@{...@}
25689 @itemx =breakpoint-modified,bkpt=@{...@}
25690 @itemx =breakpoint-deleted,id=@var{number}
25691 Reports that a breakpoint was created, modified, or deleted,
25692 respectively. Only user-visible breakpoints are reported to the MI
25695 The @var{bkpt} argument is of the same form as returned by the various
25696 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
25697 @var{number} is the ordinal number of the breakpoint.
25699 Note that if a breakpoint is emitted in the result record of a
25700 command, then it will not also be emitted in an async record.
25702 @item =record-started,thread-group="@var{id}"
25703 @itemx =record-stopped,thread-group="@var{id}"
25704 Execution log recording was either started or stopped on an
25705 inferior. The @var{id} is the @value{GDBN} identifier of the thread
25706 group corresponding to the affected inferior.
25708 @item =cmd-param-changed,param=@var{param},value=@var{value}
25709 Reports that a parameter of the command @code{set @var{param}} is
25710 changed to @var{value}. In the multi-word @code{set} command,
25711 the @var{param} is the whole parameter list to @code{set} command.
25712 For example, In command @code{set check type on}, @var{param}
25713 is @code{check type} and @var{value} is @code{on}.
25715 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
25716 Reports that bytes from @var{addr} to @var{data} + @var{len} were
25717 written in an inferior. The @var{id} is the identifier of the
25718 thread group corresponding to the affected inferior. The optional
25719 @code{type="code"} part is reported if the memory written to holds
25723 @node GDB/MI Breakpoint Information
25724 @subsection @sc{gdb/mi} Breakpoint Information
25726 When @value{GDBN} reports information about a breakpoint, a
25727 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
25732 The breakpoint number. For a breakpoint that represents one location
25733 of a multi-location breakpoint, this will be a dotted pair, like
25737 The type of the breakpoint. For ordinary breakpoints this will be
25738 @samp{breakpoint}, but many values are possible.
25741 If the type of the breakpoint is @samp{catchpoint}, then this
25742 indicates the exact type of catchpoint.
25745 This is the breakpoint disposition---either @samp{del}, meaning that
25746 the breakpoint will be deleted at the next stop, or @samp{keep},
25747 meaning that the breakpoint will not be deleted.
25750 This indicates whether the breakpoint is enabled, in which case the
25751 value is @samp{y}, or disabled, in which case the value is @samp{n}.
25752 Note that this is not the same as the field @code{enable}.
25755 The address of the breakpoint. This may be a hexidecimal number,
25756 giving the address; or the string @samp{<PENDING>}, for a pending
25757 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
25758 multiple locations. This field will not be present if no address can
25759 be determined. For example, a watchpoint does not have an address.
25762 If known, the function in which the breakpoint appears.
25763 If not known, this field is not present.
25766 The name of the source file which contains this function, if known.
25767 If not known, this field is not present.
25770 The full file name of the source file which contains this function, if
25771 known. If not known, this field is not present.
25774 The line number at which this breakpoint appears, if known.
25775 If not known, this field is not present.
25778 If the source file is not known, this field may be provided. If
25779 provided, this holds the address of the breakpoint, possibly followed
25783 If this breakpoint is pending, this field is present and holds the
25784 text used to set the breakpoint, as entered by the user.
25787 Where this breakpoint's condition is evaluated, either @samp{host} or
25791 If this is a thread-specific breakpoint, then this identifies the
25792 thread in which the breakpoint can trigger.
25795 If this breakpoint is restricted to a particular Ada task, then this
25796 field will hold the task identifier.
25799 If the breakpoint is conditional, this is the condition expression.
25802 The ignore count of the breakpoint.
25805 The enable count of the breakpoint.
25807 @item traceframe-usage
25810 @item static-tracepoint-marker-string-id
25811 For a static tracepoint, the name of the static tracepoint marker.
25814 For a masked watchpoint, this is the mask.
25817 A tracepoint's pass count.
25819 @item original-location
25820 The location of the breakpoint as originally specified by the user.
25821 This field is optional.
25824 The number of times the breakpoint has been hit.
25827 This field is only given for tracepoints. This is either @samp{y},
25828 meaning that the tracepoint is installed, or @samp{n}, meaning that it
25832 Some extra data, the exact contents of which are type-dependent.
25836 For example, here is what the output of @code{-break-insert}
25837 (@pxref{GDB/MI Breakpoint Commands}) might be:
25840 -> -break-insert main
25841 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25842 enabled="y",addr="0x08048564",func="main",file="myprog.c",
25843 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
25848 @node GDB/MI Frame Information
25849 @subsection @sc{gdb/mi} Frame Information
25851 Response from many MI commands includes an information about stack
25852 frame. This information is a tuple that may have the following
25857 The level of the stack frame. The innermost frame has the level of
25858 zero. This field is always present.
25861 The name of the function corresponding to the frame. This field may
25862 be absent if @value{GDBN} is unable to determine the function name.
25865 The code address for the frame. This field is always present.
25868 The name of the source files that correspond to the frame's code
25869 address. This field may be absent.
25872 The source line corresponding to the frames' code address. This field
25876 The name of the binary file (either executable or shared library) the
25877 corresponds to the frame's code address. This field may be absent.
25881 @node GDB/MI Thread Information
25882 @subsection @sc{gdb/mi} Thread Information
25884 Whenever @value{GDBN} has to report an information about a thread, it
25885 uses a tuple with the following fields:
25889 The numeric id assigned to the thread by @value{GDBN}. This field is
25893 Target-specific string identifying the thread. This field is always present.
25896 Additional information about the thread provided by the target.
25897 It is supposed to be human-readable and not interpreted by the
25898 frontend. This field is optional.
25901 Either @samp{stopped} or @samp{running}, depending on whether the
25902 thread is presently running. This field is always present.
25905 The value of this field is an integer number of the processor core the
25906 thread was last seen on. This field is optional.
25909 @node GDB/MI Ada Exception Information
25910 @subsection @sc{gdb/mi} Ada Exception Information
25912 Whenever a @code{*stopped} record is emitted because the program
25913 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
25914 @value{GDBN} provides the name of the exception that was raised via
25915 the @code{exception-name} field.
25917 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25918 @node GDB/MI Simple Examples
25919 @section Simple Examples of @sc{gdb/mi} Interaction
25920 @cindex @sc{gdb/mi}, simple examples
25922 This subsection presents several simple examples of interaction using
25923 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
25924 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
25925 the output received from @sc{gdb/mi}.
25927 Note the line breaks shown in the examples are here only for
25928 readability, they don't appear in the real output.
25930 @subheading Setting a Breakpoint
25932 Setting a breakpoint generates synchronous output which contains detailed
25933 information of the breakpoint.
25936 -> -break-insert main
25937 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25938 enabled="y",addr="0x08048564",func="main",file="myprog.c",
25939 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
25944 @subheading Program Execution
25946 Program execution generates asynchronous records and MI gives the
25947 reason that execution stopped.
25953 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
25954 frame=@{addr="0x08048564",func="main",
25955 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
25956 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
25961 <- *stopped,reason="exited-normally"
25965 @subheading Quitting @value{GDBN}
25967 Quitting @value{GDBN} just prints the result class @samp{^exit}.
25975 Please note that @samp{^exit} is printed immediately, but it might
25976 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
25977 performs necessary cleanups, including killing programs being debugged
25978 or disconnecting from debug hardware, so the frontend should wait till
25979 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
25980 fails to exit in reasonable time.
25982 @subheading A Bad Command
25984 Here's what happens if you pass a non-existent command:
25988 <- ^error,msg="Undefined MI command: rubbish"
25993 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25994 @node GDB/MI Command Description Format
25995 @section @sc{gdb/mi} Command Description Format
25997 The remaining sections describe blocks of commands. Each block of
25998 commands is laid out in a fashion similar to this section.
26000 @subheading Motivation
26002 The motivation for this collection of commands.
26004 @subheading Introduction
26006 A brief introduction to this collection of commands as a whole.
26008 @subheading Commands
26010 For each command in the block, the following is described:
26012 @subsubheading Synopsis
26015 -command @var{args}@dots{}
26018 @subsubheading Result
26020 @subsubheading @value{GDBN} Command
26022 The corresponding @value{GDBN} CLI command(s), if any.
26024 @subsubheading Example
26026 Example(s) formatted for readability. Some of the described commands have
26027 not been implemented yet and these are labeled N.A.@: (not available).
26030 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26031 @node GDB/MI Breakpoint Commands
26032 @section @sc{gdb/mi} Breakpoint Commands
26034 @cindex breakpoint commands for @sc{gdb/mi}
26035 @cindex @sc{gdb/mi}, breakpoint commands
26036 This section documents @sc{gdb/mi} commands for manipulating
26039 @subheading The @code{-break-after} Command
26040 @findex -break-after
26042 @subsubheading Synopsis
26045 -break-after @var{number} @var{count}
26048 The breakpoint number @var{number} is not in effect until it has been
26049 hit @var{count} times. To see how this is reflected in the output of
26050 the @samp{-break-list} command, see the description of the
26051 @samp{-break-list} command below.
26053 @subsubheading @value{GDBN} Command
26055 The corresponding @value{GDBN} command is @samp{ignore}.
26057 @subsubheading Example
26062 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26063 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26064 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26072 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26073 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26074 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26075 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26076 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26077 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26078 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26079 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26080 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26081 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
26086 @subheading The @code{-break-catch} Command
26087 @findex -break-catch
26090 @subheading The @code{-break-commands} Command
26091 @findex -break-commands
26093 @subsubheading Synopsis
26096 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
26099 Specifies the CLI commands that should be executed when breakpoint
26100 @var{number} is hit. The parameters @var{command1} to @var{commandN}
26101 are the commands. If no command is specified, any previously-set
26102 commands are cleared. @xref{Break Commands}. Typical use of this
26103 functionality is tracing a program, that is, printing of values of
26104 some variables whenever breakpoint is hit and then continuing.
26106 @subsubheading @value{GDBN} Command
26108 The corresponding @value{GDBN} command is @samp{commands}.
26110 @subsubheading Example
26115 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26116 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26117 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26120 -break-commands 1 "print v" "continue"
26125 @subheading The @code{-break-condition} Command
26126 @findex -break-condition
26128 @subsubheading Synopsis
26131 -break-condition @var{number} @var{expr}
26134 Breakpoint @var{number} will stop the program only if the condition in
26135 @var{expr} is true. The condition becomes part of the
26136 @samp{-break-list} output (see the description of the @samp{-break-list}
26139 @subsubheading @value{GDBN} Command
26141 The corresponding @value{GDBN} command is @samp{condition}.
26143 @subsubheading Example
26147 -break-condition 1 1
26151 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26152 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26153 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26154 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26155 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26156 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26157 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26158 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26159 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26160 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
26164 @subheading The @code{-break-delete} Command
26165 @findex -break-delete
26167 @subsubheading Synopsis
26170 -break-delete ( @var{breakpoint} )+
26173 Delete the breakpoint(s) whose number(s) are specified in the argument
26174 list. This is obviously reflected in the breakpoint list.
26176 @subsubheading @value{GDBN} Command
26178 The corresponding @value{GDBN} command is @samp{delete}.
26180 @subsubheading Example
26188 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26189 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26190 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26191 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26192 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26193 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26194 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26199 @subheading The @code{-break-disable} Command
26200 @findex -break-disable
26202 @subsubheading Synopsis
26205 -break-disable ( @var{breakpoint} )+
26208 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
26209 break list is now set to @samp{n} for the named @var{breakpoint}(s).
26211 @subsubheading @value{GDBN} Command
26213 The corresponding @value{GDBN} command is @samp{disable}.
26215 @subsubheading Example
26223 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26224 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26225 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26226 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26227 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26228 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26229 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26230 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
26231 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26232 line="5",thread-groups=["i1"],times="0"@}]@}
26236 @subheading The @code{-break-enable} Command
26237 @findex -break-enable
26239 @subsubheading Synopsis
26242 -break-enable ( @var{breakpoint} )+
26245 Enable (previously disabled) @var{breakpoint}(s).
26247 @subsubheading @value{GDBN} Command
26249 The corresponding @value{GDBN} command is @samp{enable}.
26251 @subsubheading Example
26259 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26260 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26261 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26262 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26263 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26264 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26265 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26266 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26267 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26268 line="5",thread-groups=["i1"],times="0"@}]@}
26272 @subheading The @code{-break-info} Command
26273 @findex -break-info
26275 @subsubheading Synopsis
26278 -break-info @var{breakpoint}
26282 Get information about a single breakpoint.
26284 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
26285 Information}, for details on the format of each breakpoint in the
26288 @subsubheading @value{GDBN} Command
26290 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
26292 @subsubheading Example
26295 @subheading The @code{-break-insert} Command
26296 @findex -break-insert
26298 @subsubheading Synopsis
26301 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
26302 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26303 [ -p @var{thread-id} ] [ @var{location} ]
26307 If specified, @var{location}, can be one of:
26314 @item filename:linenum
26315 @item filename:function
26319 The possible optional parameters of this command are:
26323 Insert a temporary breakpoint.
26325 Insert a hardware breakpoint.
26327 If @var{location} cannot be parsed (for example if it
26328 refers to unknown files or functions), create a pending
26329 breakpoint. Without this flag, @value{GDBN} will report
26330 an error, and won't create a breakpoint, if @var{location}
26333 Create a disabled breakpoint.
26335 Create a tracepoint. @xref{Tracepoints}. When this parameter
26336 is used together with @samp{-h}, a fast tracepoint is created.
26337 @item -c @var{condition}
26338 Make the breakpoint conditional on @var{condition}.
26339 @item -i @var{ignore-count}
26340 Initialize the @var{ignore-count}.
26341 @item -p @var{thread-id}
26342 Restrict the breakpoint to the specified @var{thread-id}.
26345 @subsubheading Result
26347 @xref{GDB/MI Breakpoint Information}, for details on the format of the
26348 resulting breakpoint.
26350 Note: this format is open to change.
26351 @c An out-of-band breakpoint instead of part of the result?
26353 @subsubheading @value{GDBN} Command
26355 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
26356 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
26358 @subsubheading Example
26363 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
26364 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
26367 -break-insert -t foo
26368 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
26369 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
26373 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26374 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26375 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26376 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26377 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26378 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26379 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26380 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26381 addr="0x0001072c", func="main",file="recursive2.c",
26382 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
26384 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
26385 addr="0x00010774",func="foo",file="recursive2.c",
26386 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
26389 @c -break-insert -r foo.*
26390 @c ~int foo(int, int);
26391 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
26392 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
26397 @subheading The @code{-dprintf-insert} Command
26398 @findex -dprintf-insert
26400 @subsubheading Synopsis
26403 -dprintf-insert [ -t ] [ -f ] [ -d ]
26404 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26405 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
26410 If specified, @var{location}, can be one of:
26413 @item @var{function}
26416 @c @item @var{linenum}
26417 @item @var{filename}:@var{linenum}
26418 @item @var{filename}:function
26419 @item *@var{address}
26422 The possible optional parameters of this command are:
26426 Insert a temporary breakpoint.
26428 If @var{location} cannot be parsed (for example, if it
26429 refers to unknown files or functions), create a pending
26430 breakpoint. Without this flag, @value{GDBN} will report
26431 an error, and won't create a breakpoint, if @var{location}
26434 Create a disabled breakpoint.
26435 @item -c @var{condition}
26436 Make the breakpoint conditional on @var{condition}.
26437 @item -i @var{ignore-count}
26438 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
26439 to @var{ignore-count}.
26440 @item -p @var{thread-id}
26441 Restrict the breakpoint to the specified @var{thread-id}.
26444 @subsubheading Result
26446 @xref{GDB/MI Breakpoint Information}, for details on the format of the
26447 resulting breakpoint.
26449 @c An out-of-band breakpoint instead of part of the result?
26451 @subsubheading @value{GDBN} Command
26453 The corresponding @value{GDBN} command is @samp{dprintf}.
26455 @subsubheading Example
26459 4-dprintf-insert foo "At foo entry\n"
26460 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
26461 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
26462 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
26463 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
26464 original-location="foo"@}
26466 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
26467 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
26468 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
26469 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
26470 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
26471 original-location="mi-dprintf.c:26"@}
26475 @subheading The @code{-break-list} Command
26476 @findex -break-list
26478 @subsubheading Synopsis
26484 Displays the list of inserted breakpoints, showing the following fields:
26488 number of the breakpoint
26490 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
26492 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
26495 is the breakpoint enabled or no: @samp{y} or @samp{n}
26497 memory location at which the breakpoint is set
26499 logical location of the breakpoint, expressed by function name, file
26501 @item Thread-groups
26502 list of thread groups to which this breakpoint applies
26504 number of times the breakpoint has been hit
26507 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
26508 @code{body} field is an empty list.
26510 @subsubheading @value{GDBN} Command
26512 The corresponding @value{GDBN} command is @samp{info break}.
26514 @subsubheading Example
26519 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26520 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26521 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26522 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26523 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26524 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26525 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26526 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26527 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
26529 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26530 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
26531 line="13",thread-groups=["i1"],times="0"@}]@}
26535 Here's an example of the result when there are no breakpoints:
26540 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26541 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26542 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26543 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26544 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26545 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26546 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26551 @subheading The @code{-break-passcount} Command
26552 @findex -break-passcount
26554 @subsubheading Synopsis
26557 -break-passcount @var{tracepoint-number} @var{passcount}
26560 Set the passcount for tracepoint @var{tracepoint-number} to
26561 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
26562 is not a tracepoint, error is emitted. This corresponds to CLI
26563 command @samp{passcount}.
26565 @subheading The @code{-break-watch} Command
26566 @findex -break-watch
26568 @subsubheading Synopsis
26571 -break-watch [ -a | -r ]
26574 Create a watchpoint. With the @samp{-a} option it will create an
26575 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
26576 read from or on a write to the memory location. With the @samp{-r}
26577 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
26578 trigger only when the memory location is accessed for reading. Without
26579 either of the options, the watchpoint created is a regular watchpoint,
26580 i.e., it will trigger when the memory location is accessed for writing.
26581 @xref{Set Watchpoints, , Setting Watchpoints}.
26583 Note that @samp{-break-list} will report a single list of watchpoints and
26584 breakpoints inserted.
26586 @subsubheading @value{GDBN} Command
26588 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
26591 @subsubheading Example
26593 Setting a watchpoint on a variable in the @code{main} function:
26598 ^done,wpt=@{number="2",exp="x"@}
26603 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
26604 value=@{old="-268439212",new="55"@},
26605 frame=@{func="main",args=[],file="recursive2.c",
26606 fullname="/home/foo/bar/recursive2.c",line="5"@}
26610 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
26611 the program execution twice: first for the variable changing value, then
26612 for the watchpoint going out of scope.
26617 ^done,wpt=@{number="5",exp="C"@}
26622 *stopped,reason="watchpoint-trigger",
26623 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
26624 frame=@{func="callee4",args=[],
26625 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26626 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
26631 *stopped,reason="watchpoint-scope",wpnum="5",
26632 frame=@{func="callee3",args=[@{name="strarg",
26633 value="0x11940 \"A string argument.\""@}],
26634 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26635 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26639 Listing breakpoints and watchpoints, at different points in the program
26640 execution. Note that once the watchpoint goes out of scope, it is
26646 ^done,wpt=@{number="2",exp="C"@}
26649 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26650 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26651 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26652 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26653 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26654 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26655 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26656 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26657 addr="0x00010734",func="callee4",
26658 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26659 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
26661 bkpt=@{number="2",type="watchpoint",disp="keep",
26662 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
26667 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
26668 value=@{old="-276895068",new="3"@},
26669 frame=@{func="callee4",args=[],
26670 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26671 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
26674 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26675 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26676 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26677 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26678 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26679 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26680 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26681 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26682 addr="0x00010734",func="callee4",
26683 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26684 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
26686 bkpt=@{number="2",type="watchpoint",disp="keep",
26687 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
26691 ^done,reason="watchpoint-scope",wpnum="2",
26692 frame=@{func="callee3",args=[@{name="strarg",
26693 value="0x11940 \"A string argument.\""@}],
26694 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26695 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26698 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26699 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26700 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26701 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26702 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26703 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26704 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26705 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26706 addr="0x00010734",func="callee4",
26707 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26708 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
26709 thread-groups=["i1"],times="1"@}]@}
26714 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26715 @node GDB/MI Catchpoint Commands
26716 @section @sc{gdb/mi} Catchpoint Commands
26718 This section documents @sc{gdb/mi} commands for manipulating
26722 * Shared Library GDB/MI Catchpoint Commands::
26723 * Ada Exception GDB/MI Catchpoint Commands::
26726 @node Shared Library GDB/MI Catchpoint Commands
26727 @subsection Shared Library @sc{gdb/mi} Catchpoints
26729 @subheading The @code{-catch-load} Command
26730 @findex -catch-load
26732 @subsubheading Synopsis
26735 -catch-load [ -t ] [ -d ] @var{regexp}
26738 Add a catchpoint for library load events. If the @samp{-t} option is used,
26739 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
26740 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
26741 in a disabled state. The @samp{regexp} argument is a regular
26742 expression used to match the name of the loaded library.
26745 @subsubheading @value{GDBN} Command
26747 The corresponding @value{GDBN} command is @samp{catch load}.
26749 @subsubheading Example
26752 -catch-load -t foo.so
26753 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
26754 what="load of library matching foo.so",catch-type="load",times="0"@}
26759 @subheading The @code{-catch-unload} Command
26760 @findex -catch-unload
26762 @subsubheading Synopsis
26765 -catch-unload [ -t ] [ -d ] @var{regexp}
26768 Add a catchpoint for library unload events. If the @samp{-t} option is
26769 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
26770 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
26771 created in a disabled state. The @samp{regexp} argument is a regular
26772 expression used to match the name of the unloaded library.
26774 @subsubheading @value{GDBN} Command
26776 The corresponding @value{GDBN} command is @samp{catch unload}.
26778 @subsubheading Example
26781 -catch-unload -d bar.so
26782 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
26783 what="load of library matching bar.so",catch-type="unload",times="0"@}
26787 @node Ada Exception GDB/MI Catchpoint Commands
26788 @subsection Ada Exception @sc{gdb/mi} Catchpoints
26790 The following @sc{gdb/mi} commands can be used to create catchpoints
26791 that stop the execution when Ada exceptions are being raised.
26793 @subheading The @code{-catch-assert} Command
26794 @findex -catch-assert
26796 @subsubheading Synopsis
26799 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
26802 Add a catchpoint for failed Ada assertions.
26804 The possible optional parameters for this command are:
26807 @item -c @var{condition}
26808 Make the catchpoint conditional on @var{condition}.
26810 Create a disabled catchpoint.
26812 Create a temporary catchpoint.
26815 @subsubheading @value{GDBN} Command
26817 The corresponding @value{GDBN} command is @samp{catch assert}.
26819 @subsubheading Example
26823 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
26824 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
26825 thread-groups=["i1"],times="0",
26826 original-location="__gnat_debug_raise_assert_failure"@}
26830 @subheading The @code{-catch-exception} Command
26831 @findex -catch-exception
26833 @subsubheading Synopsis
26836 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
26840 Add a catchpoint stopping when Ada exceptions are raised.
26841 By default, the command stops the program when any Ada exception
26842 gets raised. But it is also possible, by using some of the
26843 optional parameters described below, to create more selective
26846 The possible optional parameters for this command are:
26849 @item -c @var{condition}
26850 Make the catchpoint conditional on @var{condition}.
26852 Create a disabled catchpoint.
26853 @item -e @var{exception-name}
26854 Only stop when @var{exception-name} is raised. This option cannot
26855 be used combined with @samp{-u}.
26857 Create a temporary catchpoint.
26859 Stop only when an unhandled exception gets raised. This option
26860 cannot be used combined with @samp{-e}.
26863 @subsubheading @value{GDBN} Command
26865 The corresponding @value{GDBN} commands are @samp{catch exception}
26866 and @samp{catch exception unhandled}.
26868 @subsubheading Example
26871 -catch-exception -e Program_Error
26872 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
26873 enabled="y",addr="0x0000000000404874",
26874 what="`Program_Error' Ada exception", thread-groups=["i1"],
26875 times="0",original-location="__gnat_debug_raise_exception"@}
26879 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26880 @node GDB/MI Program Context
26881 @section @sc{gdb/mi} Program Context
26883 @subheading The @code{-exec-arguments} Command
26884 @findex -exec-arguments
26887 @subsubheading Synopsis
26890 -exec-arguments @var{args}
26893 Set the inferior program arguments, to be used in the next
26896 @subsubheading @value{GDBN} Command
26898 The corresponding @value{GDBN} command is @samp{set args}.
26900 @subsubheading Example
26904 -exec-arguments -v word
26911 @subheading The @code{-exec-show-arguments} Command
26912 @findex -exec-show-arguments
26914 @subsubheading Synopsis
26917 -exec-show-arguments
26920 Print the arguments of the program.
26922 @subsubheading @value{GDBN} Command
26924 The corresponding @value{GDBN} command is @samp{show args}.
26926 @subsubheading Example
26931 @subheading The @code{-environment-cd} Command
26932 @findex -environment-cd
26934 @subsubheading Synopsis
26937 -environment-cd @var{pathdir}
26940 Set @value{GDBN}'s working directory.
26942 @subsubheading @value{GDBN} Command
26944 The corresponding @value{GDBN} command is @samp{cd}.
26946 @subsubheading Example
26950 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
26956 @subheading The @code{-environment-directory} Command
26957 @findex -environment-directory
26959 @subsubheading Synopsis
26962 -environment-directory [ -r ] [ @var{pathdir} ]+
26965 Add directories @var{pathdir} to beginning of search path for source files.
26966 If the @samp{-r} option is used, the search path is reset to the default
26967 search path. If directories @var{pathdir} are supplied in addition to the
26968 @samp{-r} option, the search path is first reset and then addition
26970 Multiple directories may be specified, separated by blanks. Specifying
26971 multiple directories in a single command
26972 results in the directories added to the beginning of the
26973 search path in the same order they were presented in the command.
26974 If blanks are needed as
26975 part of a directory name, double-quotes should be used around
26976 the name. In the command output, the path will show up separated
26977 by the system directory-separator character. The directory-separator
26978 character must not be used
26979 in any directory name.
26980 If no directories are specified, the current search path is displayed.
26982 @subsubheading @value{GDBN} Command
26984 The corresponding @value{GDBN} command is @samp{dir}.
26986 @subsubheading Example
26990 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
26991 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
26993 -environment-directory ""
26994 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
26996 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
26997 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
26999 -environment-directory -r
27000 ^done,source-path="$cdir:$cwd"
27005 @subheading The @code{-environment-path} Command
27006 @findex -environment-path
27008 @subsubheading Synopsis
27011 -environment-path [ -r ] [ @var{pathdir} ]+
27014 Add directories @var{pathdir} to beginning of search path for object files.
27015 If the @samp{-r} option is used, the search path is reset to the original
27016 search path that existed at gdb start-up. If directories @var{pathdir} are
27017 supplied in addition to the
27018 @samp{-r} option, the search path is first reset and then addition
27020 Multiple directories may be specified, separated by blanks. Specifying
27021 multiple directories in a single command
27022 results in the directories added to the beginning of the
27023 search path in the same order they were presented in the command.
27024 If blanks are needed as
27025 part of a directory name, double-quotes should be used around
27026 the name. In the command output, the path will show up separated
27027 by the system directory-separator character. The directory-separator
27028 character must not be used
27029 in any directory name.
27030 If no directories are specified, the current path is displayed.
27033 @subsubheading @value{GDBN} Command
27035 The corresponding @value{GDBN} command is @samp{path}.
27037 @subsubheading Example
27042 ^done,path="/usr/bin"
27044 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
27045 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
27047 -environment-path -r /usr/local/bin
27048 ^done,path="/usr/local/bin:/usr/bin"
27053 @subheading The @code{-environment-pwd} Command
27054 @findex -environment-pwd
27056 @subsubheading Synopsis
27062 Show the current working directory.
27064 @subsubheading @value{GDBN} Command
27066 The corresponding @value{GDBN} command is @samp{pwd}.
27068 @subsubheading Example
27073 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
27077 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27078 @node GDB/MI Thread Commands
27079 @section @sc{gdb/mi} Thread Commands
27082 @subheading The @code{-thread-info} Command
27083 @findex -thread-info
27085 @subsubheading Synopsis
27088 -thread-info [ @var{thread-id} ]
27091 Reports information about either a specific thread, if
27092 the @var{thread-id} parameter is present, or about all
27093 threads. When printing information about all threads,
27094 also reports the current thread.
27096 @subsubheading @value{GDBN} Command
27098 The @samp{info thread} command prints the same information
27101 @subsubheading Result
27103 The result is a list of threads. The following attributes are
27104 defined for a given thread:
27108 This field exists only for the current thread. It has the value @samp{*}.
27111 The identifier that @value{GDBN} uses to refer to the thread.
27114 The identifier that the target uses to refer to the thread.
27117 Extra information about the thread, in a target-specific format. This
27121 The name of the thread. If the user specified a name using the
27122 @code{thread name} command, then this name is given. Otherwise, if
27123 @value{GDBN} can extract the thread name from the target, then that
27124 name is given. If @value{GDBN} cannot find the thread name, then this
27128 The stack frame currently executing in the thread.
27131 The thread's state. The @samp{state} field may have the following
27136 The thread is stopped. Frame information is available for stopped
27140 The thread is running. There's no frame information for running
27146 If @value{GDBN} can find the CPU core on which this thread is running,
27147 then this field is the core identifier. This field is optional.
27151 @subsubheading Example
27156 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
27157 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
27158 args=[]@},state="running"@},
27159 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
27160 frame=@{level="0",addr="0x0804891f",func="foo",
27161 args=[@{name="i",value="10"@}],
27162 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
27163 state="running"@}],
27164 current-thread-id="1"
27168 @subheading The @code{-thread-list-ids} Command
27169 @findex -thread-list-ids
27171 @subsubheading Synopsis
27177 Produces a list of the currently known @value{GDBN} thread ids. At the
27178 end of the list it also prints the total number of such threads.
27180 This command is retained for historical reasons, the
27181 @code{-thread-info} command should be used instead.
27183 @subsubheading @value{GDBN} Command
27185 Part of @samp{info threads} supplies the same information.
27187 @subsubheading Example
27192 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27193 current-thread-id="1",number-of-threads="3"
27198 @subheading The @code{-thread-select} Command
27199 @findex -thread-select
27201 @subsubheading Synopsis
27204 -thread-select @var{threadnum}
27207 Make @var{threadnum} the current thread. It prints the number of the new
27208 current thread, and the topmost frame for that thread.
27210 This command is deprecated in favor of explicitly using the
27211 @samp{--thread} option to each command.
27213 @subsubheading @value{GDBN} Command
27215 The corresponding @value{GDBN} command is @samp{thread}.
27217 @subsubheading Example
27224 *stopped,reason="end-stepping-range",thread-id="2",line="187",
27225 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
27229 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27230 number-of-threads="3"
27233 ^done,new-thread-id="3",
27234 frame=@{level="0",func="vprintf",
27235 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
27236 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
27240 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27241 @node GDB/MI Ada Tasking Commands
27242 @section @sc{gdb/mi} Ada Tasking Commands
27244 @subheading The @code{-ada-task-info} Command
27245 @findex -ada-task-info
27247 @subsubheading Synopsis
27250 -ada-task-info [ @var{task-id} ]
27253 Reports information about either a specific Ada task, if the
27254 @var{task-id} parameter is present, or about all Ada tasks.
27256 @subsubheading @value{GDBN} Command
27258 The @samp{info tasks} command prints the same information
27259 about all Ada tasks (@pxref{Ada Tasks}).
27261 @subsubheading Result
27263 The result is a table of Ada tasks. The following columns are
27264 defined for each Ada task:
27268 This field exists only for the current thread. It has the value @samp{*}.
27271 The identifier that @value{GDBN} uses to refer to the Ada task.
27274 The identifier that the target uses to refer to the Ada task.
27277 The identifier of the thread corresponding to the Ada task.
27279 This field should always exist, as Ada tasks are always implemented
27280 on top of a thread. But if @value{GDBN} cannot find this corresponding
27281 thread for any reason, the field is omitted.
27284 This field exists only when the task was created by another task.
27285 In this case, it provides the ID of the parent task.
27288 The base priority of the task.
27291 The current state of the task. For a detailed description of the
27292 possible states, see @ref{Ada Tasks}.
27295 The name of the task.
27299 @subsubheading Example
27303 ^done,tasks=@{nr_rows="3",nr_cols="8",
27304 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
27305 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
27306 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
27307 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
27308 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
27309 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
27310 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
27311 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
27312 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
27313 state="Child Termination Wait",name="main_task"@}]@}
27317 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27318 @node GDB/MI Program Execution
27319 @section @sc{gdb/mi} Program Execution
27321 These are the asynchronous commands which generate the out-of-band
27322 record @samp{*stopped}. Currently @value{GDBN} only really executes
27323 asynchronously with remote targets and this interaction is mimicked in
27326 @subheading The @code{-exec-continue} Command
27327 @findex -exec-continue
27329 @subsubheading Synopsis
27332 -exec-continue [--reverse] [--all|--thread-group N]
27335 Resumes the execution of the inferior program, which will continue
27336 to execute until it reaches a debugger stop event. If the
27337 @samp{--reverse} option is specified, execution resumes in reverse until
27338 it reaches a stop event. Stop events may include
27341 breakpoints or watchpoints
27343 signals or exceptions
27345 the end of the process (or its beginning under @samp{--reverse})
27347 the end or beginning of a replay log if one is being used.
27349 In all-stop mode (@pxref{All-Stop
27350 Mode}), may resume only one thread, or all threads, depending on the
27351 value of the @samp{scheduler-locking} variable. If @samp{--all} is
27352 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
27353 ignored in all-stop mode. If the @samp{--thread-group} options is
27354 specified, then all threads in that thread group are resumed.
27356 @subsubheading @value{GDBN} Command
27358 The corresponding @value{GDBN} corresponding is @samp{continue}.
27360 @subsubheading Example
27367 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
27368 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
27374 @subheading The @code{-exec-finish} Command
27375 @findex -exec-finish
27377 @subsubheading Synopsis
27380 -exec-finish [--reverse]
27383 Resumes the execution of the inferior program until the current
27384 function is exited. Displays the results returned by the function.
27385 If the @samp{--reverse} option is specified, resumes the reverse
27386 execution of the inferior program until the point where current
27387 function was called.
27389 @subsubheading @value{GDBN} Command
27391 The corresponding @value{GDBN} command is @samp{finish}.
27393 @subsubheading Example
27395 Function returning @code{void}.
27402 *stopped,reason="function-finished",frame=@{func="main",args=[],
27403 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
27407 Function returning other than @code{void}. The name of the internal
27408 @value{GDBN} variable storing the result is printed, together with the
27415 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
27416 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
27417 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27418 gdb-result-var="$1",return-value="0"
27423 @subheading The @code{-exec-interrupt} Command
27424 @findex -exec-interrupt
27426 @subsubheading Synopsis
27429 -exec-interrupt [--all|--thread-group N]
27432 Interrupts the background execution of the target. Note how the token
27433 associated with the stop message is the one for the execution command
27434 that has been interrupted. The token for the interrupt itself only
27435 appears in the @samp{^done} output. If the user is trying to
27436 interrupt a non-running program, an error message will be printed.
27438 Note that when asynchronous execution is enabled, this command is
27439 asynchronous just like other execution commands. That is, first the
27440 @samp{^done} response will be printed, and the target stop will be
27441 reported after that using the @samp{*stopped} notification.
27443 In non-stop mode, only the context thread is interrupted by default.
27444 All threads (in all inferiors) will be interrupted if the
27445 @samp{--all} option is specified. If the @samp{--thread-group}
27446 option is specified, all threads in that group will be interrupted.
27448 @subsubheading @value{GDBN} Command
27450 The corresponding @value{GDBN} command is @samp{interrupt}.
27452 @subsubheading Example
27463 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
27464 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
27465 fullname="/home/foo/bar/try.c",line="13"@}
27470 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
27474 @subheading The @code{-exec-jump} Command
27477 @subsubheading Synopsis
27480 -exec-jump @var{location}
27483 Resumes execution of the inferior program at the location specified by
27484 parameter. @xref{Specify Location}, for a description of the
27485 different forms of @var{location}.
27487 @subsubheading @value{GDBN} Command
27489 The corresponding @value{GDBN} command is @samp{jump}.
27491 @subsubheading Example
27494 -exec-jump foo.c:10
27495 *running,thread-id="all"
27500 @subheading The @code{-exec-next} Command
27503 @subsubheading Synopsis
27506 -exec-next [--reverse]
27509 Resumes execution of the inferior program, stopping when the beginning
27510 of the next source line is reached.
27512 If the @samp{--reverse} option is specified, resumes reverse execution
27513 of the inferior program, stopping at the beginning of the previous
27514 source line. If you issue this command on the first line of a
27515 function, it will take you back to the caller of that function, to the
27516 source line where the function was called.
27519 @subsubheading @value{GDBN} Command
27521 The corresponding @value{GDBN} command is @samp{next}.
27523 @subsubheading Example
27529 *stopped,reason="end-stepping-range",line="8",file="hello.c"
27534 @subheading The @code{-exec-next-instruction} Command
27535 @findex -exec-next-instruction
27537 @subsubheading Synopsis
27540 -exec-next-instruction [--reverse]
27543 Executes one machine instruction. If the instruction is a function
27544 call, continues until the function returns. If the program stops at an
27545 instruction in the middle of a source line, the address will be
27548 If the @samp{--reverse} option is specified, resumes reverse execution
27549 of the inferior program, stopping at the previous instruction. If the
27550 previously executed instruction was a return from another function,
27551 it will continue to execute in reverse until the call to that function
27552 (from the current stack frame) is reached.
27554 @subsubheading @value{GDBN} Command
27556 The corresponding @value{GDBN} command is @samp{nexti}.
27558 @subsubheading Example
27562 -exec-next-instruction
27566 *stopped,reason="end-stepping-range",
27567 addr="0x000100d4",line="5",file="hello.c"
27572 @subheading The @code{-exec-return} Command
27573 @findex -exec-return
27575 @subsubheading Synopsis
27581 Makes current function return immediately. Doesn't execute the inferior.
27582 Displays the new current frame.
27584 @subsubheading @value{GDBN} Command
27586 The corresponding @value{GDBN} command is @samp{return}.
27588 @subsubheading Example
27592 200-break-insert callee4
27593 200^done,bkpt=@{number="1",addr="0x00010734",
27594 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27599 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27600 frame=@{func="callee4",args=[],
27601 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27602 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27608 111^done,frame=@{level="0",func="callee3",
27609 args=[@{name="strarg",
27610 value="0x11940 \"A string argument.\""@}],
27611 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27612 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27617 @subheading The @code{-exec-run} Command
27620 @subsubheading Synopsis
27623 -exec-run [ --all | --thread-group N ] [ --start ]
27626 Starts execution of the inferior from the beginning. The inferior
27627 executes until either a breakpoint is encountered or the program
27628 exits. In the latter case the output will include an exit code, if
27629 the program has exited exceptionally.
27631 When neither the @samp{--all} nor the @samp{--thread-group} option
27632 is specified, the current inferior is started. If the
27633 @samp{--thread-group} option is specified, it should refer to a thread
27634 group of type @samp{process}, and that thread group will be started.
27635 If the @samp{--all} option is specified, then all inferiors will be started.
27637 Using the @samp{--start} option instructs the debugger to stop
27638 the execution at the start of the inferior's main subprogram,
27639 following the same behavior as the @code{start} command
27640 (@pxref{Starting}).
27642 @subsubheading @value{GDBN} Command
27644 The corresponding @value{GDBN} command is @samp{run}.
27646 @subsubheading Examples
27651 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
27656 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27657 frame=@{func="main",args=[],file="recursive2.c",
27658 fullname="/home/foo/bar/recursive2.c",line="4"@}
27663 Program exited normally:
27671 *stopped,reason="exited-normally"
27676 Program exited exceptionally:
27684 *stopped,reason="exited",exit-code="01"
27688 Another way the program can terminate is if it receives a signal such as
27689 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
27693 *stopped,reason="exited-signalled",signal-name="SIGINT",
27694 signal-meaning="Interrupt"
27698 @c @subheading -exec-signal
27701 @subheading The @code{-exec-step} Command
27704 @subsubheading Synopsis
27707 -exec-step [--reverse]
27710 Resumes execution of the inferior program, stopping when the beginning
27711 of the next source line is reached, if the next source line is not a
27712 function call. If it is, stop at the first instruction of the called
27713 function. If the @samp{--reverse} option is specified, resumes reverse
27714 execution of the inferior program, stopping at the beginning of the
27715 previously executed source line.
27717 @subsubheading @value{GDBN} Command
27719 The corresponding @value{GDBN} command is @samp{step}.
27721 @subsubheading Example
27723 Stepping into a function:
27729 *stopped,reason="end-stepping-range",
27730 frame=@{func="foo",args=[@{name="a",value="10"@},
27731 @{name="b",value="0"@}],file="recursive2.c",
27732 fullname="/home/foo/bar/recursive2.c",line="11"@}
27742 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
27747 @subheading The @code{-exec-step-instruction} Command
27748 @findex -exec-step-instruction
27750 @subsubheading Synopsis
27753 -exec-step-instruction [--reverse]
27756 Resumes the inferior which executes one machine instruction. If the
27757 @samp{--reverse} option is specified, resumes reverse execution of the
27758 inferior program, stopping at the previously executed instruction.
27759 The output, once @value{GDBN} has stopped, will vary depending on
27760 whether we have stopped in the middle of a source line or not. In the
27761 former case, the address at which the program stopped will be printed
27764 @subsubheading @value{GDBN} Command
27766 The corresponding @value{GDBN} command is @samp{stepi}.
27768 @subsubheading Example
27772 -exec-step-instruction
27776 *stopped,reason="end-stepping-range",
27777 frame=@{func="foo",args=[],file="try.c",
27778 fullname="/home/foo/bar/try.c",line="10"@}
27780 -exec-step-instruction
27784 *stopped,reason="end-stepping-range",
27785 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
27786 fullname="/home/foo/bar/try.c",line="10"@}
27791 @subheading The @code{-exec-until} Command
27792 @findex -exec-until
27794 @subsubheading Synopsis
27797 -exec-until [ @var{location} ]
27800 Executes the inferior until the @var{location} specified in the
27801 argument is reached. If there is no argument, the inferior executes
27802 until a source line greater than the current one is reached. The
27803 reason for stopping in this case will be @samp{location-reached}.
27805 @subsubheading @value{GDBN} Command
27807 The corresponding @value{GDBN} command is @samp{until}.
27809 @subsubheading Example
27813 -exec-until recursive2.c:6
27817 *stopped,reason="location-reached",frame=@{func="main",args=[],
27818 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
27823 @subheading -file-clear
27824 Is this going away????
27827 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27828 @node GDB/MI Stack Manipulation
27829 @section @sc{gdb/mi} Stack Manipulation Commands
27831 @subheading The @code{-enable-frame-filters} Command
27832 @findex -enable-frame-filters
27835 -enable-frame-filters
27838 @value{GDBN} allows Python-based frame filters to affect the output of
27839 the MI commands relating to stack traces. As there is no way to
27840 implement this in a fully backward-compatible way, a front end must
27841 request that this functionality be enabled.
27843 Once enabled, this feature cannot be disabled.
27845 Note that if Python support has not been compiled into @value{GDBN},
27846 this command will still succeed (and do nothing).
27848 @subheading The @code{-stack-info-frame} Command
27849 @findex -stack-info-frame
27851 @subsubheading Synopsis
27857 Get info on the selected frame.
27859 @subsubheading @value{GDBN} Command
27861 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
27862 (without arguments).
27864 @subsubheading Example
27869 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
27870 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27871 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
27875 @subheading The @code{-stack-info-depth} Command
27876 @findex -stack-info-depth
27878 @subsubheading Synopsis
27881 -stack-info-depth [ @var{max-depth} ]
27884 Return the depth of the stack. If the integer argument @var{max-depth}
27885 is specified, do not count beyond @var{max-depth} frames.
27887 @subsubheading @value{GDBN} Command
27889 There's no equivalent @value{GDBN} command.
27891 @subsubheading Example
27893 For a stack with frame levels 0 through 11:
27900 -stack-info-depth 4
27903 -stack-info-depth 12
27906 -stack-info-depth 11
27909 -stack-info-depth 13
27914 @anchor{-stack-list-arguments}
27915 @subheading The @code{-stack-list-arguments} Command
27916 @findex -stack-list-arguments
27918 @subsubheading Synopsis
27921 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
27922 [ @var{low-frame} @var{high-frame} ]
27925 Display a list of the arguments for the frames between @var{low-frame}
27926 and @var{high-frame} (inclusive). If @var{low-frame} and
27927 @var{high-frame} are not provided, list the arguments for the whole
27928 call stack. If the two arguments are equal, show the single frame
27929 at the corresponding level. It is an error if @var{low-frame} is
27930 larger than the actual number of frames. On the other hand,
27931 @var{high-frame} may be larger than the actual number of frames, in
27932 which case only existing frames will be returned.
27934 If @var{print-values} is 0 or @code{--no-values}, print only the names of
27935 the variables; if it is 1 or @code{--all-values}, print also their
27936 values; and if it is 2 or @code{--simple-values}, print the name,
27937 type and value for simple data types, and the name and type for arrays,
27938 structures and unions. If the option @code{--no-frame-filters} is
27939 supplied, then Python frame filters will not be executed.
27941 If the @code{--skip-unavailable} option is specified, arguments that
27942 are not available are not listed. Partially available arguments
27943 are still displayed, however.
27945 Use of this command to obtain arguments in a single frame is
27946 deprecated in favor of the @samp{-stack-list-variables} command.
27948 @subsubheading @value{GDBN} Command
27950 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
27951 @samp{gdb_get_args} command which partially overlaps with the
27952 functionality of @samp{-stack-list-arguments}.
27954 @subsubheading Example
27961 frame=@{level="0",addr="0x00010734",func="callee4",
27962 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27963 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
27964 frame=@{level="1",addr="0x0001076c",func="callee3",
27965 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27966 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
27967 frame=@{level="2",addr="0x0001078c",func="callee2",
27968 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27969 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
27970 frame=@{level="3",addr="0x000107b4",func="callee1",
27971 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27972 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
27973 frame=@{level="4",addr="0x000107e0",func="main",
27974 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27975 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
27977 -stack-list-arguments 0
27980 frame=@{level="0",args=[]@},
27981 frame=@{level="1",args=[name="strarg"]@},
27982 frame=@{level="2",args=[name="intarg",name="strarg"]@},
27983 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
27984 frame=@{level="4",args=[]@}]
27986 -stack-list-arguments 1
27989 frame=@{level="0",args=[]@},
27991 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
27992 frame=@{level="2",args=[
27993 @{name="intarg",value="2"@},
27994 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
27995 @{frame=@{level="3",args=[
27996 @{name="intarg",value="2"@},
27997 @{name="strarg",value="0x11940 \"A string argument.\""@},
27998 @{name="fltarg",value="3.5"@}]@},
27999 frame=@{level="4",args=[]@}]
28001 -stack-list-arguments 0 2 2
28002 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
28004 -stack-list-arguments 1 2 2
28005 ^done,stack-args=[frame=@{level="2",
28006 args=[@{name="intarg",value="2"@},
28007 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
28011 @c @subheading -stack-list-exception-handlers
28014 @anchor{-stack-list-frames}
28015 @subheading The @code{-stack-list-frames} Command
28016 @findex -stack-list-frames
28018 @subsubheading Synopsis
28021 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
28024 List the frames currently on the stack. For each frame it displays the
28029 The frame number, 0 being the topmost frame, i.e., the innermost function.
28031 The @code{$pc} value for that frame.
28035 File name of the source file where the function lives.
28036 @item @var{fullname}
28037 The full file name of the source file where the function lives.
28039 Line number corresponding to the @code{$pc}.
28041 The shared library where this function is defined. This is only given
28042 if the frame's function is not known.
28045 If invoked without arguments, this command prints a backtrace for the
28046 whole stack. If given two integer arguments, it shows the frames whose
28047 levels are between the two arguments (inclusive). If the two arguments
28048 are equal, it shows the single frame at the corresponding level. It is
28049 an error if @var{low-frame} is larger than the actual number of
28050 frames. On the other hand, @var{high-frame} may be larger than the
28051 actual number of frames, in which case only existing frames will be
28052 returned. If the option @code{--no-frame-filters} is supplied, then
28053 Python frame filters will not be executed.
28055 @subsubheading @value{GDBN} Command
28057 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
28059 @subsubheading Example
28061 Full stack backtrace:
28067 [frame=@{level="0",addr="0x0001076c",func="foo",
28068 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
28069 frame=@{level="1",addr="0x000107a4",func="foo",
28070 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28071 frame=@{level="2",addr="0x000107a4",func="foo",
28072 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28073 frame=@{level="3",addr="0x000107a4",func="foo",
28074 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28075 frame=@{level="4",addr="0x000107a4",func="foo",
28076 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28077 frame=@{level="5",addr="0x000107a4",func="foo",
28078 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28079 frame=@{level="6",addr="0x000107a4",func="foo",
28080 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28081 frame=@{level="7",addr="0x000107a4",func="foo",
28082 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28083 frame=@{level="8",addr="0x000107a4",func="foo",
28084 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28085 frame=@{level="9",addr="0x000107a4",func="foo",
28086 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28087 frame=@{level="10",addr="0x000107a4",func="foo",
28088 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28089 frame=@{level="11",addr="0x00010738",func="main",
28090 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
28094 Show frames between @var{low_frame} and @var{high_frame}:
28098 -stack-list-frames 3 5
28100 [frame=@{level="3",addr="0x000107a4",func="foo",
28101 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28102 frame=@{level="4",addr="0x000107a4",func="foo",
28103 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28104 frame=@{level="5",addr="0x000107a4",func="foo",
28105 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28109 Show a single frame:
28113 -stack-list-frames 3 3
28115 [frame=@{level="3",addr="0x000107a4",func="foo",
28116 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28121 @subheading The @code{-stack-list-locals} Command
28122 @findex -stack-list-locals
28123 @anchor{-stack-list-locals}
28125 @subsubheading Synopsis
28128 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28131 Display the local variable names for the selected frame. If
28132 @var{print-values} is 0 or @code{--no-values}, print only the names of
28133 the variables; if it is 1 or @code{--all-values}, print also their
28134 values; and if it is 2 or @code{--simple-values}, print the name,
28135 type and value for simple data types, and the name and type for arrays,
28136 structures and unions. In this last case, a frontend can immediately
28137 display the value of simple data types and create variable objects for
28138 other data types when the user wishes to explore their values in
28139 more detail. If the option @code{--no-frame-filters} is supplied, then
28140 Python frame filters will not be executed.
28142 If the @code{--skip-unavailable} option is specified, local variables
28143 that are not available are not listed. Partially available local
28144 variables are still displayed, however.
28146 This command is deprecated in favor of the
28147 @samp{-stack-list-variables} command.
28149 @subsubheading @value{GDBN} Command
28151 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
28153 @subsubheading Example
28157 -stack-list-locals 0
28158 ^done,locals=[name="A",name="B",name="C"]
28160 -stack-list-locals --all-values
28161 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
28162 @{name="C",value="@{1, 2, 3@}"@}]
28163 -stack-list-locals --simple-values
28164 ^done,locals=[@{name="A",type="int",value="1"@},
28165 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
28169 @anchor{-stack-list-variables}
28170 @subheading The @code{-stack-list-variables} Command
28171 @findex -stack-list-variables
28173 @subsubheading Synopsis
28176 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28179 Display the names of local variables and function arguments for the selected frame. If
28180 @var{print-values} is 0 or @code{--no-values}, print only the names of
28181 the variables; if it is 1 or @code{--all-values}, print also their
28182 values; and if it is 2 or @code{--simple-values}, print the name,
28183 type and value for simple data types, and the name and type for arrays,
28184 structures and unions. If the option @code{--no-frame-filters} is
28185 supplied, then Python frame filters will not be executed.
28187 If the @code{--skip-unavailable} option is specified, local variables
28188 and arguments that are not available are not listed. Partially
28189 available arguments and local variables are still displayed, however.
28191 @subsubheading Example
28195 -stack-list-variables --thread 1 --frame 0 --all-values
28196 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
28201 @subheading The @code{-stack-select-frame} Command
28202 @findex -stack-select-frame
28204 @subsubheading Synopsis
28207 -stack-select-frame @var{framenum}
28210 Change the selected frame. Select a different frame @var{framenum} on
28213 This command in deprecated in favor of passing the @samp{--frame}
28214 option to every command.
28216 @subsubheading @value{GDBN} Command
28218 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
28219 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
28221 @subsubheading Example
28225 -stack-select-frame 2
28230 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28231 @node GDB/MI Variable Objects
28232 @section @sc{gdb/mi} Variable Objects
28236 @subheading Motivation for Variable Objects in @sc{gdb/mi}
28238 For the implementation of a variable debugger window (locals, watched
28239 expressions, etc.), we are proposing the adaptation of the existing code
28240 used by @code{Insight}.
28242 The two main reasons for that are:
28246 It has been proven in practice (it is already on its second generation).
28249 It will shorten development time (needless to say how important it is
28253 The original interface was designed to be used by Tcl code, so it was
28254 slightly changed so it could be used through @sc{gdb/mi}. This section
28255 describes the @sc{gdb/mi} operations that will be available and gives some
28256 hints about their use.
28258 @emph{Note}: In addition to the set of operations described here, we
28259 expect the @sc{gui} implementation of a variable window to require, at
28260 least, the following operations:
28263 @item @code{-gdb-show} @code{output-radix}
28264 @item @code{-stack-list-arguments}
28265 @item @code{-stack-list-locals}
28266 @item @code{-stack-select-frame}
28271 @subheading Introduction to Variable Objects
28273 @cindex variable objects in @sc{gdb/mi}
28275 Variable objects are "object-oriented" MI interface for examining and
28276 changing values of expressions. Unlike some other MI interfaces that
28277 work with expressions, variable objects are specifically designed for
28278 simple and efficient presentation in the frontend. A variable object
28279 is identified by string name. When a variable object is created, the
28280 frontend specifies the expression for that variable object. The
28281 expression can be a simple variable, or it can be an arbitrary complex
28282 expression, and can even involve CPU registers. After creating a
28283 variable object, the frontend can invoke other variable object
28284 operations---for example to obtain or change the value of a variable
28285 object, or to change display format.
28287 Variable objects have hierarchical tree structure. Any variable object
28288 that corresponds to a composite type, such as structure in C, has
28289 a number of child variable objects, for example corresponding to each
28290 element of a structure. A child variable object can itself have
28291 children, recursively. Recursion ends when we reach
28292 leaf variable objects, which always have built-in types. Child variable
28293 objects are created only by explicit request, so if a frontend
28294 is not interested in the children of a particular variable object, no
28295 child will be created.
28297 For a leaf variable object it is possible to obtain its value as a
28298 string, or set the value from a string. String value can be also
28299 obtained for a non-leaf variable object, but it's generally a string
28300 that only indicates the type of the object, and does not list its
28301 contents. Assignment to a non-leaf variable object is not allowed.
28303 A frontend does not need to read the values of all variable objects each time
28304 the program stops. Instead, MI provides an update command that lists all
28305 variable objects whose values has changed since the last update
28306 operation. This considerably reduces the amount of data that must
28307 be transferred to the frontend. As noted above, children variable
28308 objects are created on demand, and only leaf variable objects have a
28309 real value. As result, gdb will read target memory only for leaf
28310 variables that frontend has created.
28312 The automatic update is not always desirable. For example, a frontend
28313 might want to keep a value of some expression for future reference,
28314 and never update it. For another example, fetching memory is
28315 relatively slow for embedded targets, so a frontend might want
28316 to disable automatic update for the variables that are either not
28317 visible on the screen, or ``closed''. This is possible using so
28318 called ``frozen variable objects''. Such variable objects are never
28319 implicitly updated.
28321 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
28322 fixed variable object, the expression is parsed when the variable
28323 object is created, including associating identifiers to specific
28324 variables. The meaning of expression never changes. For a floating
28325 variable object the values of variables whose names appear in the
28326 expressions are re-evaluated every time in the context of the current
28327 frame. Consider this example:
28332 struct work_state state;
28339 If a fixed variable object for the @code{state} variable is created in
28340 this function, and we enter the recursive call, the variable
28341 object will report the value of @code{state} in the top-level
28342 @code{do_work} invocation. On the other hand, a floating variable
28343 object will report the value of @code{state} in the current frame.
28345 If an expression specified when creating a fixed variable object
28346 refers to a local variable, the variable object becomes bound to the
28347 thread and frame in which the variable object is created. When such
28348 variable object is updated, @value{GDBN} makes sure that the
28349 thread/frame combination the variable object is bound to still exists,
28350 and re-evaluates the variable object in context of that thread/frame.
28352 The following is the complete set of @sc{gdb/mi} operations defined to
28353 access this functionality:
28355 @multitable @columnfractions .4 .6
28356 @item @strong{Operation}
28357 @tab @strong{Description}
28359 @item @code{-enable-pretty-printing}
28360 @tab enable Python-based pretty-printing
28361 @item @code{-var-create}
28362 @tab create a variable object
28363 @item @code{-var-delete}
28364 @tab delete the variable object and/or its children
28365 @item @code{-var-set-format}
28366 @tab set the display format of this variable
28367 @item @code{-var-show-format}
28368 @tab show the display format of this variable
28369 @item @code{-var-info-num-children}
28370 @tab tells how many children this object has
28371 @item @code{-var-list-children}
28372 @tab return a list of the object's children
28373 @item @code{-var-info-type}
28374 @tab show the type of this variable object
28375 @item @code{-var-info-expression}
28376 @tab print parent-relative expression that this variable object represents
28377 @item @code{-var-info-path-expression}
28378 @tab print full expression that this variable object represents
28379 @item @code{-var-show-attributes}
28380 @tab is this variable editable? does it exist here?
28381 @item @code{-var-evaluate-expression}
28382 @tab get the value of this variable
28383 @item @code{-var-assign}
28384 @tab set the value of this variable
28385 @item @code{-var-update}
28386 @tab update the variable and its children
28387 @item @code{-var-set-frozen}
28388 @tab set frozeness attribute
28389 @item @code{-var-set-update-range}
28390 @tab set range of children to display on update
28393 In the next subsection we describe each operation in detail and suggest
28394 how it can be used.
28396 @subheading Description And Use of Operations on Variable Objects
28398 @subheading The @code{-enable-pretty-printing} Command
28399 @findex -enable-pretty-printing
28402 -enable-pretty-printing
28405 @value{GDBN} allows Python-based visualizers to affect the output of the
28406 MI variable object commands. However, because there was no way to
28407 implement this in a fully backward-compatible way, a front end must
28408 request that this functionality be enabled.
28410 Once enabled, this feature cannot be disabled.
28412 Note that if Python support has not been compiled into @value{GDBN},
28413 this command will still succeed (and do nothing).
28415 This feature is currently (as of @value{GDBN} 7.0) experimental, and
28416 may work differently in future versions of @value{GDBN}.
28418 @subheading The @code{-var-create} Command
28419 @findex -var-create
28421 @subsubheading Synopsis
28424 -var-create @{@var{name} | "-"@}
28425 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
28428 This operation creates a variable object, which allows the monitoring of
28429 a variable, the result of an expression, a memory cell or a CPU
28432 The @var{name} parameter is the string by which the object can be
28433 referenced. It must be unique. If @samp{-} is specified, the varobj
28434 system will generate a string ``varNNNNNN'' automatically. It will be
28435 unique provided that one does not specify @var{name} of that format.
28436 The command fails if a duplicate name is found.
28438 The frame under which the expression should be evaluated can be
28439 specified by @var{frame-addr}. A @samp{*} indicates that the current
28440 frame should be used. A @samp{@@} indicates that a floating variable
28441 object must be created.
28443 @var{expression} is any expression valid on the current language set (must not
28444 begin with a @samp{*}), or one of the following:
28448 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
28451 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
28454 @samp{$@var{regname}} --- a CPU register name
28457 @cindex dynamic varobj
28458 A varobj's contents may be provided by a Python-based pretty-printer. In this
28459 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
28460 have slightly different semantics in some cases. If the
28461 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
28462 will never create a dynamic varobj. This ensures backward
28463 compatibility for existing clients.
28465 @subsubheading Result
28467 This operation returns attributes of the newly-created varobj. These
28472 The name of the varobj.
28475 The number of children of the varobj. This number is not necessarily
28476 reliable for a dynamic varobj. Instead, you must examine the
28477 @samp{has_more} attribute.
28480 The varobj's scalar value. For a varobj whose type is some sort of
28481 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
28482 will not be interesting.
28485 The varobj's type. This is a string representation of the type, as
28486 would be printed by the @value{GDBN} CLI. If @samp{print object}
28487 (@pxref{Print Settings, set print object}) is set to @code{on}, the
28488 @emph{actual} (derived) type of the object is shown rather than the
28489 @emph{declared} one.
28492 If a variable object is bound to a specific thread, then this is the
28493 thread's identifier.
28496 For a dynamic varobj, this indicates whether there appear to be any
28497 children available. For a non-dynamic varobj, this will be 0.
28500 This attribute will be present and have the value @samp{1} if the
28501 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28502 then this attribute will not be present.
28505 A dynamic varobj can supply a display hint to the front end. The
28506 value comes directly from the Python pretty-printer object's
28507 @code{display_hint} method. @xref{Pretty Printing API}.
28510 Typical output will look like this:
28513 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
28514 has_more="@var{has_more}"
28518 @subheading The @code{-var-delete} Command
28519 @findex -var-delete
28521 @subsubheading Synopsis
28524 -var-delete [ -c ] @var{name}
28527 Deletes a previously created variable object and all of its children.
28528 With the @samp{-c} option, just deletes the children.
28530 Returns an error if the object @var{name} is not found.
28533 @subheading The @code{-var-set-format} Command
28534 @findex -var-set-format
28536 @subsubheading Synopsis
28539 -var-set-format @var{name} @var{format-spec}
28542 Sets the output format for the value of the object @var{name} to be
28545 @anchor{-var-set-format}
28546 The syntax for the @var{format-spec} is as follows:
28549 @var{format-spec} @expansion{}
28550 @{binary | decimal | hexadecimal | octal | natural@}
28553 The natural format is the default format choosen automatically
28554 based on the variable type (like decimal for an @code{int}, hex
28555 for pointers, etc.).
28557 For a variable with children, the format is set only on the
28558 variable itself, and the children are not affected.
28560 @subheading The @code{-var-show-format} Command
28561 @findex -var-show-format
28563 @subsubheading Synopsis
28566 -var-show-format @var{name}
28569 Returns the format used to display the value of the object @var{name}.
28572 @var{format} @expansion{}
28577 @subheading The @code{-var-info-num-children} Command
28578 @findex -var-info-num-children
28580 @subsubheading Synopsis
28583 -var-info-num-children @var{name}
28586 Returns the number of children of a variable object @var{name}:
28592 Note that this number is not completely reliable for a dynamic varobj.
28593 It will return the current number of children, but more children may
28597 @subheading The @code{-var-list-children} Command
28598 @findex -var-list-children
28600 @subsubheading Synopsis
28603 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
28605 @anchor{-var-list-children}
28607 Return a list of the children of the specified variable object and
28608 create variable objects for them, if they do not already exist. With
28609 a single argument or if @var{print-values} has a value of 0 or
28610 @code{--no-values}, print only the names of the variables; if
28611 @var{print-values} is 1 or @code{--all-values}, also print their
28612 values; and if it is 2 or @code{--simple-values} print the name and
28613 value for simple data types and just the name for arrays, structures
28616 @var{from} and @var{to}, if specified, indicate the range of children
28617 to report. If @var{from} or @var{to} is less than zero, the range is
28618 reset and all children will be reported. Otherwise, children starting
28619 at @var{from} (zero-based) and up to and excluding @var{to} will be
28622 If a child range is requested, it will only affect the current call to
28623 @code{-var-list-children}, but not future calls to @code{-var-update}.
28624 For this, you must instead use @code{-var-set-update-range}. The
28625 intent of this approach is to enable a front end to implement any
28626 update approach it likes; for example, scrolling a view may cause the
28627 front end to request more children with @code{-var-list-children}, and
28628 then the front end could call @code{-var-set-update-range} with a
28629 different range to ensure that future updates are restricted to just
28632 For each child the following results are returned:
28637 Name of the variable object created for this child.
28640 The expression to be shown to the user by the front end to designate this child.
28641 For example this may be the name of a structure member.
28643 For a dynamic varobj, this value cannot be used to form an
28644 expression. There is no way to do this at all with a dynamic varobj.
28646 For C/C@t{++} structures there are several pseudo children returned to
28647 designate access qualifiers. For these pseudo children @var{exp} is
28648 @samp{public}, @samp{private}, or @samp{protected}. In this case the
28649 type and value are not present.
28651 A dynamic varobj will not report the access qualifying
28652 pseudo-children, regardless of the language. This information is not
28653 available at all with a dynamic varobj.
28656 Number of children this child has. For a dynamic varobj, this will be
28660 The type of the child. If @samp{print object}
28661 (@pxref{Print Settings, set print object}) is set to @code{on}, the
28662 @emph{actual} (derived) type of the object is shown rather than the
28663 @emph{declared} one.
28666 If values were requested, this is the value.
28669 If this variable object is associated with a thread, this is the thread id.
28670 Otherwise this result is not present.
28673 If the variable object is frozen, this variable will be present with a value of 1.
28676 A dynamic varobj can supply a display hint to the front end. The
28677 value comes directly from the Python pretty-printer object's
28678 @code{display_hint} method. @xref{Pretty Printing API}.
28681 This attribute will be present and have the value @samp{1} if the
28682 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28683 then this attribute will not be present.
28687 The result may have its own attributes:
28691 A dynamic varobj can supply a display hint to the front end. The
28692 value comes directly from the Python pretty-printer object's
28693 @code{display_hint} method. @xref{Pretty Printing API}.
28696 This is an integer attribute which is nonzero if there are children
28697 remaining after the end of the selected range.
28700 @subsubheading Example
28704 -var-list-children n
28705 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28706 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
28708 -var-list-children --all-values n
28709 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28710 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
28714 @subheading The @code{-var-info-type} Command
28715 @findex -var-info-type
28717 @subsubheading Synopsis
28720 -var-info-type @var{name}
28723 Returns the type of the specified variable @var{name}. The type is
28724 returned as a string in the same format as it is output by the
28728 type=@var{typename}
28732 @subheading The @code{-var-info-expression} Command
28733 @findex -var-info-expression
28735 @subsubheading Synopsis
28738 -var-info-expression @var{name}
28741 Returns a string that is suitable for presenting this
28742 variable object in user interface. The string is generally
28743 not valid expression in the current language, and cannot be evaluated.
28745 For example, if @code{a} is an array, and variable object
28746 @code{A} was created for @code{a}, then we'll get this output:
28749 (gdb) -var-info-expression A.1
28750 ^done,lang="C",exp="1"
28754 Here, the value of @code{lang} is the language name, which can be
28755 found in @ref{Supported Languages}.
28757 Note that the output of the @code{-var-list-children} command also
28758 includes those expressions, so the @code{-var-info-expression} command
28761 @subheading The @code{-var-info-path-expression} Command
28762 @findex -var-info-path-expression
28764 @subsubheading Synopsis
28767 -var-info-path-expression @var{name}
28770 Returns an expression that can be evaluated in the current
28771 context and will yield the same value that a variable object has.
28772 Compare this with the @code{-var-info-expression} command, which
28773 result can be used only for UI presentation. Typical use of
28774 the @code{-var-info-path-expression} command is creating a
28775 watchpoint from a variable object.
28777 This command is currently not valid for children of a dynamic varobj,
28778 and will give an error when invoked on one.
28780 For example, suppose @code{C} is a C@t{++} class, derived from class
28781 @code{Base}, and that the @code{Base} class has a member called
28782 @code{m_size}. Assume a variable @code{c} is has the type of
28783 @code{C} and a variable object @code{C} was created for variable
28784 @code{c}. Then, we'll get this output:
28786 (gdb) -var-info-path-expression C.Base.public.m_size
28787 ^done,path_expr=((Base)c).m_size)
28790 @subheading The @code{-var-show-attributes} Command
28791 @findex -var-show-attributes
28793 @subsubheading Synopsis
28796 -var-show-attributes @var{name}
28799 List attributes of the specified variable object @var{name}:
28802 status=@var{attr} [ ( ,@var{attr} )* ]
28806 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
28808 @subheading The @code{-var-evaluate-expression} Command
28809 @findex -var-evaluate-expression
28811 @subsubheading Synopsis
28814 -var-evaluate-expression [-f @var{format-spec}] @var{name}
28817 Evaluates the expression that is represented by the specified variable
28818 object and returns its value as a string. The format of the string
28819 can be specified with the @samp{-f} option. The possible values of
28820 this option are the same as for @code{-var-set-format}
28821 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
28822 the current display format will be used. The current display format
28823 can be changed using the @code{-var-set-format} command.
28829 Note that one must invoke @code{-var-list-children} for a variable
28830 before the value of a child variable can be evaluated.
28832 @subheading The @code{-var-assign} Command
28833 @findex -var-assign
28835 @subsubheading Synopsis
28838 -var-assign @var{name} @var{expression}
28841 Assigns the value of @var{expression} to the variable object specified
28842 by @var{name}. The object must be @samp{editable}. If the variable's
28843 value is altered by the assign, the variable will show up in any
28844 subsequent @code{-var-update} list.
28846 @subsubheading Example
28854 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
28858 @subheading The @code{-var-update} Command
28859 @findex -var-update
28861 @subsubheading Synopsis
28864 -var-update [@var{print-values}] @{@var{name} | "*"@}
28867 Reevaluate the expressions corresponding to the variable object
28868 @var{name} and all its direct and indirect children, and return the
28869 list of variable objects whose values have changed; @var{name} must
28870 be a root variable object. Here, ``changed'' means that the result of
28871 @code{-var-evaluate-expression} before and after the
28872 @code{-var-update} is different. If @samp{*} is used as the variable
28873 object names, all existing variable objects are updated, except
28874 for frozen ones (@pxref{-var-set-frozen}). The option
28875 @var{print-values} determines whether both names and values, or just
28876 names are printed. The possible values of this option are the same
28877 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
28878 recommended to use the @samp{--all-values} option, to reduce the
28879 number of MI commands needed on each program stop.
28881 With the @samp{*} parameter, if a variable object is bound to a
28882 currently running thread, it will not be updated, without any
28885 If @code{-var-set-update-range} was previously used on a varobj, then
28886 only the selected range of children will be reported.
28888 @code{-var-update} reports all the changed varobjs in a tuple named
28891 Each item in the change list is itself a tuple holding:
28895 The name of the varobj.
28898 If values were requested for this update, then this field will be
28899 present and will hold the value of the varobj.
28902 @anchor{-var-update}
28903 This field is a string which may take one of three values:
28907 The variable object's current value is valid.
28910 The variable object does not currently hold a valid value but it may
28911 hold one in the future if its associated expression comes back into
28915 The variable object no longer holds a valid value.
28916 This can occur when the executable file being debugged has changed,
28917 either through recompilation or by using the @value{GDBN} @code{file}
28918 command. The front end should normally choose to delete these variable
28922 In the future new values may be added to this list so the front should
28923 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
28926 This is only present if the varobj is still valid. If the type
28927 changed, then this will be the string @samp{true}; otherwise it will
28930 When a varobj's type changes, its children are also likely to have
28931 become incorrect. Therefore, the varobj's children are automatically
28932 deleted when this attribute is @samp{true}. Also, the varobj's update
28933 range, when set using the @code{-var-set-update-range} command, is
28937 If the varobj's type changed, then this field will be present and will
28940 @item new_num_children
28941 For a dynamic varobj, if the number of children changed, or if the
28942 type changed, this will be the new number of children.
28944 The @samp{numchild} field in other varobj responses is generally not
28945 valid for a dynamic varobj -- it will show the number of children that
28946 @value{GDBN} knows about, but because dynamic varobjs lazily
28947 instantiate their children, this will not reflect the number of
28948 children which may be available.
28950 The @samp{new_num_children} attribute only reports changes to the
28951 number of children known by @value{GDBN}. This is the only way to
28952 detect whether an update has removed children (which necessarily can
28953 only happen at the end of the update range).
28956 The display hint, if any.
28959 This is an integer value, which will be 1 if there are more children
28960 available outside the varobj's update range.
28963 This attribute will be present and have the value @samp{1} if the
28964 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28965 then this attribute will not be present.
28968 If new children were added to a dynamic varobj within the selected
28969 update range (as set by @code{-var-set-update-range}), then they will
28970 be listed in this attribute.
28973 @subsubheading Example
28980 -var-update --all-values var1
28981 ^done,changelist=[@{name="var1",value="3",in_scope="true",
28982 type_changed="false"@}]
28986 @subheading The @code{-var-set-frozen} Command
28987 @findex -var-set-frozen
28988 @anchor{-var-set-frozen}
28990 @subsubheading Synopsis
28993 -var-set-frozen @var{name} @var{flag}
28996 Set the frozenness flag on the variable object @var{name}. The
28997 @var{flag} parameter should be either @samp{1} to make the variable
28998 frozen or @samp{0} to make it unfrozen. If a variable object is
28999 frozen, then neither itself, nor any of its children, are
29000 implicitly updated by @code{-var-update} of
29001 a parent variable or by @code{-var-update *}. Only
29002 @code{-var-update} of the variable itself will update its value and
29003 values of its children. After a variable object is unfrozen, it is
29004 implicitly updated by all subsequent @code{-var-update} operations.
29005 Unfreezing a variable does not update it, only subsequent
29006 @code{-var-update} does.
29008 @subsubheading Example
29012 -var-set-frozen V 1
29017 @subheading The @code{-var-set-update-range} command
29018 @findex -var-set-update-range
29019 @anchor{-var-set-update-range}
29021 @subsubheading Synopsis
29024 -var-set-update-range @var{name} @var{from} @var{to}
29027 Set the range of children to be returned by future invocations of
29028 @code{-var-update}.
29030 @var{from} and @var{to} indicate the range of children to report. If
29031 @var{from} or @var{to} is less than zero, the range is reset and all
29032 children will be reported. Otherwise, children starting at @var{from}
29033 (zero-based) and up to and excluding @var{to} will be reported.
29035 @subsubheading Example
29039 -var-set-update-range V 1 2
29043 @subheading The @code{-var-set-visualizer} command
29044 @findex -var-set-visualizer
29045 @anchor{-var-set-visualizer}
29047 @subsubheading Synopsis
29050 -var-set-visualizer @var{name} @var{visualizer}
29053 Set a visualizer for the variable object @var{name}.
29055 @var{visualizer} is the visualizer to use. The special value
29056 @samp{None} means to disable any visualizer in use.
29058 If not @samp{None}, @var{visualizer} must be a Python expression.
29059 This expression must evaluate to a callable object which accepts a
29060 single argument. @value{GDBN} will call this object with the value of
29061 the varobj @var{name} as an argument (this is done so that the same
29062 Python pretty-printing code can be used for both the CLI and MI).
29063 When called, this object must return an object which conforms to the
29064 pretty-printing interface (@pxref{Pretty Printing API}).
29066 The pre-defined function @code{gdb.default_visualizer} may be used to
29067 select a visualizer by following the built-in process
29068 (@pxref{Selecting Pretty-Printers}). This is done automatically when
29069 a varobj is created, and so ordinarily is not needed.
29071 This feature is only available if Python support is enabled. The MI
29072 command @code{-list-features} (@pxref{GDB/MI Support Commands})
29073 can be used to check this.
29075 @subsubheading Example
29077 Resetting the visualizer:
29081 -var-set-visualizer V None
29085 Reselecting the default (type-based) visualizer:
29089 -var-set-visualizer V gdb.default_visualizer
29093 Suppose @code{SomeClass} is a visualizer class. A lambda expression
29094 can be used to instantiate this class for a varobj:
29098 -var-set-visualizer V "lambda val: SomeClass()"
29102 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29103 @node GDB/MI Data Manipulation
29104 @section @sc{gdb/mi} Data Manipulation
29106 @cindex data manipulation, in @sc{gdb/mi}
29107 @cindex @sc{gdb/mi}, data manipulation
29108 This section describes the @sc{gdb/mi} commands that manipulate data:
29109 examine memory and registers, evaluate expressions, etc.
29111 @c REMOVED FROM THE INTERFACE.
29112 @c @subheading -data-assign
29113 @c Change the value of a program variable. Plenty of side effects.
29114 @c @subsubheading GDB Command
29116 @c @subsubheading Example
29119 @subheading The @code{-data-disassemble} Command
29120 @findex -data-disassemble
29122 @subsubheading Synopsis
29126 [ -s @var{start-addr} -e @var{end-addr} ]
29127 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
29135 @item @var{start-addr}
29136 is the beginning address (or @code{$pc})
29137 @item @var{end-addr}
29139 @item @var{filename}
29140 is the name of the file to disassemble
29141 @item @var{linenum}
29142 is the line number to disassemble around
29144 is the number of disassembly lines to be produced. If it is -1,
29145 the whole function will be disassembled, in case no @var{end-addr} is
29146 specified. If @var{end-addr} is specified as a non-zero value, and
29147 @var{lines} is lower than the number of disassembly lines between
29148 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
29149 displayed; if @var{lines} is higher than the number of lines between
29150 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
29153 is either 0 (meaning only disassembly), 1 (meaning mixed source and
29154 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
29155 mixed source and disassembly with raw opcodes).
29158 @subsubheading Result
29160 The result of the @code{-data-disassemble} command will be a list named
29161 @samp{asm_insns}, the contents of this list depend on the @var{mode}
29162 used with the @code{-data-disassemble} command.
29164 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
29169 The address at which this instruction was disassembled.
29172 The name of the function this instruction is within.
29175 The decimal offset in bytes from the start of @samp{func-name}.
29178 The text disassembly for this @samp{address}.
29181 This field is only present for mode 2. This contains the raw opcode
29182 bytes for the @samp{inst} field.
29186 For modes 1 and 3 the @samp{asm_insns} list contains tuples named
29187 @samp{src_and_asm_line}, each of which has the following fields:
29191 The line number within @samp{file}.
29194 The file name from the compilation unit. This might be an absolute
29195 file name or a relative file name depending on the compile command
29199 Absolute file name of @samp{file}. It is converted to a canonical form
29200 using the source file search path
29201 (@pxref{Source Path, ,Specifying Source Directories})
29202 and after resolving all the symbolic links.
29204 If the source file is not found this field will contain the path as
29205 present in the debug information.
29207 @item line_asm_insn
29208 This is a list of tuples containing the disassembly for @samp{line} in
29209 @samp{file}. The fields of each tuple are the same as for
29210 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
29211 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
29216 Note that whatever included in the @samp{inst} field, is not
29217 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
29220 @subsubheading @value{GDBN} Command
29222 The corresponding @value{GDBN} command is @samp{disassemble}.
29224 @subsubheading Example
29226 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
29230 -data-disassemble -s $pc -e "$pc + 20" -- 0
29233 @{address="0x000107c0",func-name="main",offset="4",
29234 inst="mov 2, %o0"@},
29235 @{address="0x000107c4",func-name="main",offset="8",
29236 inst="sethi %hi(0x11800), %o2"@},
29237 @{address="0x000107c8",func-name="main",offset="12",
29238 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
29239 @{address="0x000107cc",func-name="main",offset="16",
29240 inst="sethi %hi(0x11800), %o2"@},
29241 @{address="0x000107d0",func-name="main",offset="20",
29242 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
29246 Disassemble the whole @code{main} function. Line 32 is part of
29250 -data-disassemble -f basics.c -l 32 -- 0
29252 @{address="0x000107bc",func-name="main",offset="0",
29253 inst="save %sp, -112, %sp"@},
29254 @{address="0x000107c0",func-name="main",offset="4",
29255 inst="mov 2, %o0"@},
29256 @{address="0x000107c4",func-name="main",offset="8",
29257 inst="sethi %hi(0x11800), %o2"@},
29259 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
29260 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
29264 Disassemble 3 instructions from the start of @code{main}:
29268 -data-disassemble -f basics.c -l 32 -n 3 -- 0
29270 @{address="0x000107bc",func-name="main",offset="0",
29271 inst="save %sp, -112, %sp"@},
29272 @{address="0x000107c0",func-name="main",offset="4",
29273 inst="mov 2, %o0"@},
29274 @{address="0x000107c4",func-name="main",offset="8",
29275 inst="sethi %hi(0x11800), %o2"@}]
29279 Disassemble 3 instructions from the start of @code{main} in mixed mode:
29283 -data-disassemble -f basics.c -l 32 -n 3 -- 1
29285 src_and_asm_line=@{line="31",
29286 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
29287 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
29288 line_asm_insn=[@{address="0x000107bc",
29289 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
29290 src_and_asm_line=@{line="32",
29291 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
29292 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
29293 line_asm_insn=[@{address="0x000107c0",
29294 func-name="main",offset="4",inst="mov 2, %o0"@},
29295 @{address="0x000107c4",func-name="main",offset="8",
29296 inst="sethi %hi(0x11800), %o2"@}]@}]
29301 @subheading The @code{-data-evaluate-expression} Command
29302 @findex -data-evaluate-expression
29304 @subsubheading Synopsis
29307 -data-evaluate-expression @var{expr}
29310 Evaluate @var{expr} as an expression. The expression could contain an
29311 inferior function call. The function call will execute synchronously.
29312 If the expression contains spaces, it must be enclosed in double quotes.
29314 @subsubheading @value{GDBN} Command
29316 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
29317 @samp{call}. In @code{gdbtk} only, there's a corresponding
29318 @samp{gdb_eval} command.
29320 @subsubheading Example
29322 In the following example, the numbers that precede the commands are the
29323 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
29324 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
29328 211-data-evaluate-expression A
29331 311-data-evaluate-expression &A
29332 311^done,value="0xefffeb7c"
29334 411-data-evaluate-expression A+3
29337 511-data-evaluate-expression "A + 3"
29343 @subheading The @code{-data-list-changed-registers} Command
29344 @findex -data-list-changed-registers
29346 @subsubheading Synopsis
29349 -data-list-changed-registers
29352 Display a list of the registers that have changed.
29354 @subsubheading @value{GDBN} Command
29356 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
29357 has the corresponding command @samp{gdb_changed_register_list}.
29359 @subsubheading Example
29361 On a PPC MBX board:
29369 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
29370 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
29373 -data-list-changed-registers
29374 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
29375 "10","11","13","14","15","16","17","18","19","20","21","22","23",
29376 "24","25","26","27","28","30","31","64","65","66","67","69"]
29381 @subheading The @code{-data-list-register-names} Command
29382 @findex -data-list-register-names
29384 @subsubheading Synopsis
29387 -data-list-register-names [ ( @var{regno} )+ ]
29390 Show a list of register names for the current target. If no arguments
29391 are given, it shows a list of the names of all the registers. If
29392 integer numbers are given as arguments, it will print a list of the
29393 names of the registers corresponding to the arguments. To ensure
29394 consistency between a register name and its number, the output list may
29395 include empty register names.
29397 @subsubheading @value{GDBN} Command
29399 @value{GDBN} does not have a command which corresponds to
29400 @samp{-data-list-register-names}. In @code{gdbtk} there is a
29401 corresponding command @samp{gdb_regnames}.
29403 @subsubheading Example
29405 For the PPC MBX board:
29408 -data-list-register-names
29409 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
29410 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
29411 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
29412 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
29413 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
29414 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
29415 "", "pc","ps","cr","lr","ctr","xer"]
29417 -data-list-register-names 1 2 3
29418 ^done,register-names=["r1","r2","r3"]
29422 @subheading The @code{-data-list-register-values} Command
29423 @findex -data-list-register-values
29425 @subsubheading Synopsis
29428 -data-list-register-values
29429 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
29432 Display the registers' contents. The format according to which the
29433 registers' contents are to be returned is given by @var{fmt}, followed
29434 by an optional list of numbers specifying the registers to display. A
29435 missing list of numbers indicates that the contents of all the
29436 registers must be returned. The @code{--skip-unavailable} option
29437 indicates that only the available registers are to be returned.
29439 Allowed formats for @var{fmt} are:
29456 @subsubheading @value{GDBN} Command
29458 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
29459 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
29461 @subsubheading Example
29463 For a PPC MBX board (note: line breaks are for readability only, they
29464 don't appear in the actual output):
29468 -data-list-register-values r 64 65
29469 ^done,register-values=[@{number="64",value="0xfe00a300"@},
29470 @{number="65",value="0x00029002"@}]
29472 -data-list-register-values x
29473 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
29474 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
29475 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
29476 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
29477 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
29478 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
29479 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
29480 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
29481 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
29482 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
29483 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
29484 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
29485 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
29486 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
29487 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
29488 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
29489 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
29490 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
29491 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
29492 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
29493 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
29494 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
29495 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
29496 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
29497 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
29498 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
29499 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
29500 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
29501 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
29502 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
29503 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
29504 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
29505 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
29506 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
29507 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
29508 @{number="69",value="0x20002b03"@}]
29513 @subheading The @code{-data-read-memory} Command
29514 @findex -data-read-memory
29516 This command is deprecated, use @code{-data-read-memory-bytes} instead.
29518 @subsubheading Synopsis
29521 -data-read-memory [ -o @var{byte-offset} ]
29522 @var{address} @var{word-format} @var{word-size}
29523 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
29530 @item @var{address}
29531 An expression specifying the address of the first memory word to be
29532 read. Complex expressions containing embedded white space should be
29533 quoted using the C convention.
29535 @item @var{word-format}
29536 The format to be used to print the memory words. The notation is the
29537 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
29540 @item @var{word-size}
29541 The size of each memory word in bytes.
29543 @item @var{nr-rows}
29544 The number of rows in the output table.
29546 @item @var{nr-cols}
29547 The number of columns in the output table.
29550 If present, indicates that each row should include an @sc{ascii} dump. The
29551 value of @var{aschar} is used as a padding character when a byte is not a
29552 member of the printable @sc{ascii} character set (printable @sc{ascii}
29553 characters are those whose code is between 32 and 126, inclusively).
29555 @item @var{byte-offset}
29556 An offset to add to the @var{address} before fetching memory.
29559 This command displays memory contents as a table of @var{nr-rows} by
29560 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
29561 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
29562 (returned as @samp{total-bytes}). Should less than the requested number
29563 of bytes be returned by the target, the missing words are identified
29564 using @samp{N/A}. The number of bytes read from the target is returned
29565 in @samp{nr-bytes} and the starting address used to read memory in
29568 The address of the next/previous row or page is available in
29569 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
29572 @subsubheading @value{GDBN} Command
29574 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
29575 @samp{gdb_get_mem} memory read command.
29577 @subsubheading Example
29579 Read six bytes of memory starting at @code{bytes+6} but then offset by
29580 @code{-6} bytes. Format as three rows of two columns. One byte per
29581 word. Display each word in hex.
29585 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
29586 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
29587 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
29588 prev-page="0x0000138a",memory=[
29589 @{addr="0x00001390",data=["0x00","0x01"]@},
29590 @{addr="0x00001392",data=["0x02","0x03"]@},
29591 @{addr="0x00001394",data=["0x04","0x05"]@}]
29595 Read two bytes of memory starting at address @code{shorts + 64} and
29596 display as a single word formatted in decimal.
29600 5-data-read-memory shorts+64 d 2 1 1
29601 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
29602 next-row="0x00001512",prev-row="0x0000150e",
29603 next-page="0x00001512",prev-page="0x0000150e",memory=[
29604 @{addr="0x00001510",data=["128"]@}]
29608 Read thirty two bytes of memory starting at @code{bytes+16} and format
29609 as eight rows of four columns. Include a string encoding with @samp{x}
29610 used as the non-printable character.
29614 4-data-read-memory bytes+16 x 1 8 4 x
29615 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
29616 next-row="0x000013c0",prev-row="0x0000139c",
29617 next-page="0x000013c0",prev-page="0x00001380",memory=[
29618 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
29619 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
29620 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
29621 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
29622 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
29623 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
29624 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
29625 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
29629 @subheading The @code{-data-read-memory-bytes} Command
29630 @findex -data-read-memory-bytes
29632 @subsubheading Synopsis
29635 -data-read-memory-bytes [ -o @var{byte-offset} ]
29636 @var{address} @var{count}
29643 @item @var{address}
29644 An expression specifying the address of the first memory word to be
29645 read. Complex expressions containing embedded white space should be
29646 quoted using the C convention.
29649 The number of bytes to read. This should be an integer literal.
29651 @item @var{byte-offset}
29652 The offsets in bytes relative to @var{address} at which to start
29653 reading. This should be an integer literal. This option is provided
29654 so that a frontend is not required to first evaluate address and then
29655 perform address arithmetics itself.
29659 This command attempts to read all accessible memory regions in the
29660 specified range. First, all regions marked as unreadable in the memory
29661 map (if one is defined) will be skipped. @xref{Memory Region
29662 Attributes}. Second, @value{GDBN} will attempt to read the remaining
29663 regions. For each one, if reading full region results in an errors,
29664 @value{GDBN} will try to read a subset of the region.
29666 In general, every single byte in the region may be readable or not,
29667 and the only way to read every readable byte is to try a read at
29668 every address, which is not practical. Therefore, @value{GDBN} will
29669 attempt to read all accessible bytes at either beginning or the end
29670 of the region, using a binary division scheme. This heuristic works
29671 well for reading accross a memory map boundary. Note that if a region
29672 has a readable range that is neither at the beginning or the end,
29673 @value{GDBN} will not read it.
29675 The result record (@pxref{GDB/MI Result Records}) that is output of
29676 the command includes a field named @samp{memory} whose content is a
29677 list of tuples. Each tuple represent a successfully read memory block
29678 and has the following fields:
29682 The start address of the memory block, as hexadecimal literal.
29685 The end address of the memory block, as hexadecimal literal.
29688 The offset of the memory block, as hexadecimal literal, relative to
29689 the start address passed to @code{-data-read-memory-bytes}.
29692 The contents of the memory block, in hex.
29698 @subsubheading @value{GDBN} Command
29700 The corresponding @value{GDBN} command is @samp{x}.
29702 @subsubheading Example
29706 -data-read-memory-bytes &a 10
29707 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
29709 contents="01000000020000000300"@}]
29714 @subheading The @code{-data-write-memory-bytes} Command
29715 @findex -data-write-memory-bytes
29717 @subsubheading Synopsis
29720 -data-write-memory-bytes @var{address} @var{contents}
29721 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
29728 @item @var{address}
29729 An expression specifying the address of the first memory word to be
29730 read. Complex expressions containing embedded white space should be
29731 quoted using the C convention.
29733 @item @var{contents}
29734 The hex-encoded bytes to write.
29737 Optional argument indicating the number of bytes to be written. If @var{count}
29738 is greater than @var{contents}' length, @value{GDBN} will repeatedly
29739 write @var{contents} until it fills @var{count} bytes.
29743 @subsubheading @value{GDBN} Command
29745 There's no corresponding @value{GDBN} command.
29747 @subsubheading Example
29751 -data-write-memory-bytes &a "aabbccdd"
29758 -data-write-memory-bytes &a "aabbccdd" 16e
29763 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29764 @node GDB/MI Tracepoint Commands
29765 @section @sc{gdb/mi} Tracepoint Commands
29767 The commands defined in this section implement MI support for
29768 tracepoints. For detailed introduction, see @ref{Tracepoints}.
29770 @subheading The @code{-trace-find} Command
29771 @findex -trace-find
29773 @subsubheading Synopsis
29776 -trace-find @var{mode} [@var{parameters}@dots{}]
29779 Find a trace frame using criteria defined by @var{mode} and
29780 @var{parameters}. The following table lists permissible
29781 modes and their parameters. For details of operation, see @ref{tfind}.
29786 No parameters are required. Stops examining trace frames.
29789 An integer is required as parameter. Selects tracepoint frame with
29792 @item tracepoint-number
29793 An integer is required as parameter. Finds next
29794 trace frame that corresponds to tracepoint with the specified number.
29797 An address is required as parameter. Finds
29798 next trace frame that corresponds to any tracepoint at the specified
29801 @item pc-inside-range
29802 Two addresses are required as parameters. Finds next trace
29803 frame that corresponds to a tracepoint at an address inside the
29804 specified range. Both bounds are considered to be inside the range.
29806 @item pc-outside-range
29807 Two addresses are required as parameters. Finds
29808 next trace frame that corresponds to a tracepoint at an address outside
29809 the specified range. Both bounds are considered to be inside the range.
29812 Line specification is required as parameter. @xref{Specify Location}.
29813 Finds next trace frame that corresponds to a tracepoint at
29814 the specified location.
29818 If @samp{none} was passed as @var{mode}, the response does not
29819 have fields. Otherwise, the response may have the following fields:
29823 This field has either @samp{0} or @samp{1} as the value, depending
29824 on whether a matching tracepoint was found.
29827 The index of the found traceframe. This field is present iff
29828 the @samp{found} field has value of @samp{1}.
29831 The index of the found tracepoint. This field is present iff
29832 the @samp{found} field has value of @samp{1}.
29835 The information about the frame corresponding to the found trace
29836 frame. This field is present only if a trace frame was found.
29837 @xref{GDB/MI Frame Information}, for description of this field.
29841 @subsubheading @value{GDBN} Command
29843 The corresponding @value{GDBN} command is @samp{tfind}.
29845 @subheading -trace-define-variable
29846 @findex -trace-define-variable
29848 @subsubheading Synopsis
29851 -trace-define-variable @var{name} [ @var{value} ]
29854 Create trace variable @var{name} if it does not exist. If
29855 @var{value} is specified, sets the initial value of the specified
29856 trace variable to that value. Note that the @var{name} should start
29857 with the @samp{$} character.
29859 @subsubheading @value{GDBN} Command
29861 The corresponding @value{GDBN} command is @samp{tvariable}.
29863 @subheading The @code{-trace-frame-collected} Command
29864 @findex -trace-frame-collected
29866 @subsubheading Synopsis
29869 -trace-frame-collected
29870 [--var-print-values @var{var_pval}]
29871 [--comp-print-values @var{comp_pval}]
29872 [--registers-format @var{regformat}]
29873 [--memory-contents]
29876 This command returns the set of collected objects, register names,
29877 trace state variable names, memory ranges and computed expressions
29878 that have been collected at a particular trace frame. The optional
29879 parameters to the command affect the output format in different ways.
29880 See the output description table below for more details.
29882 The reported names can be used in the normal manner to create
29883 varobjs and inspect the objects themselves. The items returned by
29884 this command are categorized so that it is clear which is a variable,
29885 which is a register, which is a trace state variable, which is a
29886 memory range and which is a computed expression.
29888 For instance, if the actions were
29890 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
29891 collect *(int*)0xaf02bef0@@40
29895 the object collected in its entirety would be @code{myVar}. The
29896 object @code{myArray} would be partially collected, because only the
29897 element at index @code{myIndex} would be collected. The remaining
29898 objects would be computed expressions.
29900 An example output would be:
29904 -trace-frame-collected
29906 explicit-variables=[@{name="myVar",value="1"@}],
29907 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
29908 @{name="myObj.field",value="0"@},
29909 @{name="myPtr->field",value="1"@},
29910 @{name="myCount + 2",value="3"@},
29911 @{name="$tvar1 + 1",value="43970027"@}],
29912 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
29913 @{number="1",value="0x0"@},
29914 @{number="2",value="0x4"@},
29916 @{number="125",value="0x0"@}],
29917 tvars=[@{name="$tvar1",current="43970026"@}],
29918 memory=[@{address="0x0000000000602264",length="4"@},
29919 @{address="0x0000000000615bc0",length="4"@}]
29926 @item explicit-variables
29927 The set of objects that have been collected in their entirety (as
29928 opposed to collecting just a few elements of an array or a few struct
29929 members). For each object, its name and value are printed.
29930 The @code{--var-print-values} option affects how or whether the value
29931 field is output. If @var{var_pval} is 0, then print only the names;
29932 if it is 1, print also their values; and if it is 2, print the name,
29933 type and value for simple data types, and the name and type for
29934 arrays, structures and unions.
29936 @item computed-expressions
29937 The set of computed expressions that have been collected at the
29938 current trace frame. The @code{--comp-print-values} option affects
29939 this set like the @code{--var-print-values} option affects the
29940 @code{explicit-variables} set. See above.
29943 The registers that have been collected at the current trace frame.
29944 For each register collected, the name and current value are returned.
29945 The value is formatted according to the @code{--registers-format}
29946 option. See the @command{-data-list-register-values} command for a
29947 list of the allowed formats. The default is @samp{x}.
29950 The trace state variables that have been collected at the current
29951 trace frame. For each trace state variable collected, the name and
29952 current value are returned.
29955 The set of memory ranges that have been collected at the current trace
29956 frame. Its content is a list of tuples. Each tuple represents a
29957 collected memory range and has the following fields:
29961 The start address of the memory range, as hexadecimal literal.
29964 The length of the memory range, as decimal literal.
29967 The contents of the memory block, in hex. This field is only present
29968 if the @code{--memory-contents} option is specified.
29974 @subsubheading @value{GDBN} Command
29976 There is no corresponding @value{GDBN} command.
29978 @subsubheading Example
29980 @subheading -trace-list-variables
29981 @findex -trace-list-variables
29983 @subsubheading Synopsis
29986 -trace-list-variables
29989 Return a table of all defined trace variables. Each element of the
29990 table has the following fields:
29994 The name of the trace variable. This field is always present.
29997 The initial value. This is a 64-bit signed integer. This
29998 field is always present.
30001 The value the trace variable has at the moment. This is a 64-bit
30002 signed integer. This field is absent iff current value is
30003 not defined, for example if the trace was never run, or is
30008 @subsubheading @value{GDBN} Command
30010 The corresponding @value{GDBN} command is @samp{tvariables}.
30012 @subsubheading Example
30016 -trace-list-variables
30017 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
30018 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
30019 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
30020 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
30021 body=[variable=@{name="$trace_timestamp",initial="0"@}
30022 variable=@{name="$foo",initial="10",current="15"@}]@}
30026 @subheading -trace-save
30027 @findex -trace-save
30029 @subsubheading Synopsis
30032 -trace-save [-r ] @var{filename}
30035 Saves the collected trace data to @var{filename}. Without the
30036 @samp{-r} option, the data is downloaded from the target and saved
30037 in a local file. With the @samp{-r} option the target is asked
30038 to perform the save.
30040 @subsubheading @value{GDBN} Command
30042 The corresponding @value{GDBN} command is @samp{tsave}.
30045 @subheading -trace-start
30046 @findex -trace-start
30048 @subsubheading Synopsis
30054 Starts a tracing experiments. The result of this command does not
30057 @subsubheading @value{GDBN} Command
30059 The corresponding @value{GDBN} command is @samp{tstart}.
30061 @subheading -trace-status
30062 @findex -trace-status
30064 @subsubheading Synopsis
30070 Obtains the status of a tracing experiment. The result may include
30071 the following fields:
30076 May have a value of either @samp{0}, when no tracing operations are
30077 supported, @samp{1}, when all tracing operations are supported, or
30078 @samp{file} when examining trace file. In the latter case, examining
30079 of trace frame is possible but new tracing experiement cannot be
30080 started. This field is always present.
30083 May have a value of either @samp{0} or @samp{1} depending on whether
30084 tracing experiement is in progress on target. This field is present
30085 if @samp{supported} field is not @samp{0}.
30088 Report the reason why the tracing was stopped last time. This field
30089 may be absent iff tracing was never stopped on target yet. The
30090 value of @samp{request} means the tracing was stopped as result of
30091 the @code{-trace-stop} command. The value of @samp{overflow} means
30092 the tracing buffer is full. The value of @samp{disconnection} means
30093 tracing was automatically stopped when @value{GDBN} has disconnected.
30094 The value of @samp{passcount} means tracing was stopped when a
30095 tracepoint was passed a maximal number of times for that tracepoint.
30096 This field is present if @samp{supported} field is not @samp{0}.
30098 @item stopping-tracepoint
30099 The number of tracepoint whose passcount as exceeded. This field is
30100 present iff the @samp{stop-reason} field has the value of
30104 @itemx frames-created
30105 The @samp{frames} field is a count of the total number of trace frames
30106 in the trace buffer, while @samp{frames-created} is the total created
30107 during the run, including ones that were discarded, such as when a
30108 circular trace buffer filled up. Both fields are optional.
30112 These fields tell the current size of the tracing buffer and the
30113 remaining space. These fields are optional.
30116 The value of the circular trace buffer flag. @code{1} means that the
30117 trace buffer is circular and old trace frames will be discarded if
30118 necessary to make room, @code{0} means that the trace buffer is linear
30122 The value of the disconnected tracing flag. @code{1} means that
30123 tracing will continue after @value{GDBN} disconnects, @code{0} means
30124 that the trace run will stop.
30127 The filename of the trace file being examined. This field is
30128 optional, and only present when examining a trace file.
30132 @subsubheading @value{GDBN} Command
30134 The corresponding @value{GDBN} command is @samp{tstatus}.
30136 @subheading -trace-stop
30137 @findex -trace-stop
30139 @subsubheading Synopsis
30145 Stops a tracing experiment. The result of this command has the same
30146 fields as @code{-trace-status}, except that the @samp{supported} and
30147 @samp{running} fields are not output.
30149 @subsubheading @value{GDBN} Command
30151 The corresponding @value{GDBN} command is @samp{tstop}.
30154 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30155 @node GDB/MI Symbol Query
30156 @section @sc{gdb/mi} Symbol Query Commands
30160 @subheading The @code{-symbol-info-address} Command
30161 @findex -symbol-info-address
30163 @subsubheading Synopsis
30166 -symbol-info-address @var{symbol}
30169 Describe where @var{symbol} is stored.
30171 @subsubheading @value{GDBN} Command
30173 The corresponding @value{GDBN} command is @samp{info address}.
30175 @subsubheading Example
30179 @subheading The @code{-symbol-info-file} Command
30180 @findex -symbol-info-file
30182 @subsubheading Synopsis
30188 Show the file for the symbol.
30190 @subsubheading @value{GDBN} Command
30192 There's no equivalent @value{GDBN} command. @code{gdbtk} has
30193 @samp{gdb_find_file}.
30195 @subsubheading Example
30199 @subheading The @code{-symbol-info-function} Command
30200 @findex -symbol-info-function
30202 @subsubheading Synopsis
30205 -symbol-info-function
30208 Show which function the symbol lives in.
30210 @subsubheading @value{GDBN} Command
30212 @samp{gdb_get_function} in @code{gdbtk}.
30214 @subsubheading Example
30218 @subheading The @code{-symbol-info-line} Command
30219 @findex -symbol-info-line
30221 @subsubheading Synopsis
30227 Show the core addresses of the code for a source line.
30229 @subsubheading @value{GDBN} Command
30231 The corresponding @value{GDBN} command is @samp{info line}.
30232 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
30234 @subsubheading Example
30238 @subheading The @code{-symbol-info-symbol} Command
30239 @findex -symbol-info-symbol
30241 @subsubheading Synopsis
30244 -symbol-info-symbol @var{addr}
30247 Describe what symbol is at location @var{addr}.
30249 @subsubheading @value{GDBN} Command
30251 The corresponding @value{GDBN} command is @samp{info symbol}.
30253 @subsubheading Example
30257 @subheading The @code{-symbol-list-functions} Command
30258 @findex -symbol-list-functions
30260 @subsubheading Synopsis
30263 -symbol-list-functions
30266 List the functions in the executable.
30268 @subsubheading @value{GDBN} Command
30270 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
30271 @samp{gdb_search} in @code{gdbtk}.
30273 @subsubheading Example
30278 @subheading The @code{-symbol-list-lines} Command
30279 @findex -symbol-list-lines
30281 @subsubheading Synopsis
30284 -symbol-list-lines @var{filename}
30287 Print the list of lines that contain code and their associated program
30288 addresses for the given source filename. The entries are sorted in
30289 ascending PC order.
30291 @subsubheading @value{GDBN} Command
30293 There is no corresponding @value{GDBN} command.
30295 @subsubheading Example
30298 -symbol-list-lines basics.c
30299 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
30305 @subheading The @code{-symbol-list-types} Command
30306 @findex -symbol-list-types
30308 @subsubheading Synopsis
30314 List all the type names.
30316 @subsubheading @value{GDBN} Command
30318 The corresponding commands are @samp{info types} in @value{GDBN},
30319 @samp{gdb_search} in @code{gdbtk}.
30321 @subsubheading Example
30325 @subheading The @code{-symbol-list-variables} Command
30326 @findex -symbol-list-variables
30328 @subsubheading Synopsis
30331 -symbol-list-variables
30334 List all the global and static variable names.
30336 @subsubheading @value{GDBN} Command
30338 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
30340 @subsubheading Example
30344 @subheading The @code{-symbol-locate} Command
30345 @findex -symbol-locate
30347 @subsubheading Synopsis
30353 @subsubheading @value{GDBN} Command
30355 @samp{gdb_loc} in @code{gdbtk}.
30357 @subsubheading Example
30361 @subheading The @code{-symbol-type} Command
30362 @findex -symbol-type
30364 @subsubheading Synopsis
30367 -symbol-type @var{variable}
30370 Show type of @var{variable}.
30372 @subsubheading @value{GDBN} Command
30374 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
30375 @samp{gdb_obj_variable}.
30377 @subsubheading Example
30382 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30383 @node GDB/MI File Commands
30384 @section @sc{gdb/mi} File Commands
30386 This section describes the GDB/MI commands to specify executable file names
30387 and to read in and obtain symbol table information.
30389 @subheading The @code{-file-exec-and-symbols} Command
30390 @findex -file-exec-and-symbols
30392 @subsubheading Synopsis
30395 -file-exec-and-symbols @var{file}
30398 Specify the executable file to be debugged. This file is the one from
30399 which the symbol table is also read. If no file is specified, the
30400 command clears the executable and symbol information. If breakpoints
30401 are set when using this command with no arguments, @value{GDBN} will produce
30402 error messages. Otherwise, no output is produced, except a completion
30405 @subsubheading @value{GDBN} Command
30407 The corresponding @value{GDBN} command is @samp{file}.
30409 @subsubheading Example
30413 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30419 @subheading The @code{-file-exec-file} Command
30420 @findex -file-exec-file
30422 @subsubheading Synopsis
30425 -file-exec-file @var{file}
30428 Specify the executable file to be debugged. Unlike
30429 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
30430 from this file. If used without argument, @value{GDBN} clears the information
30431 about the executable file. No output is produced, except a completion
30434 @subsubheading @value{GDBN} Command
30436 The corresponding @value{GDBN} command is @samp{exec-file}.
30438 @subsubheading Example
30442 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30449 @subheading The @code{-file-list-exec-sections} Command
30450 @findex -file-list-exec-sections
30452 @subsubheading Synopsis
30455 -file-list-exec-sections
30458 List the sections of the current executable file.
30460 @subsubheading @value{GDBN} Command
30462 The @value{GDBN} command @samp{info file} shows, among the rest, the same
30463 information as this command. @code{gdbtk} has a corresponding command
30464 @samp{gdb_load_info}.
30466 @subsubheading Example
30471 @subheading The @code{-file-list-exec-source-file} Command
30472 @findex -file-list-exec-source-file
30474 @subsubheading Synopsis
30477 -file-list-exec-source-file
30480 List the line number, the current source file, and the absolute path
30481 to the current source file for the current executable. The macro
30482 information field has a value of @samp{1} or @samp{0} depending on
30483 whether or not the file includes preprocessor macro information.
30485 @subsubheading @value{GDBN} Command
30487 The @value{GDBN} equivalent is @samp{info source}
30489 @subsubheading Example
30493 123-file-list-exec-source-file
30494 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
30499 @subheading The @code{-file-list-exec-source-files} Command
30500 @findex -file-list-exec-source-files
30502 @subsubheading Synopsis
30505 -file-list-exec-source-files
30508 List the source files for the current executable.
30510 It will always output both the filename and fullname (absolute file
30511 name) of a source file.
30513 @subsubheading @value{GDBN} Command
30515 The @value{GDBN} equivalent is @samp{info sources}.
30516 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
30518 @subsubheading Example
30521 -file-list-exec-source-files
30523 @{file=foo.c,fullname=/home/foo.c@},
30524 @{file=/home/bar.c,fullname=/home/bar.c@},
30525 @{file=gdb_could_not_find_fullpath.c@}]
30530 @subheading The @code{-file-list-shared-libraries} Command
30531 @findex -file-list-shared-libraries
30533 @subsubheading Synopsis
30536 -file-list-shared-libraries
30539 List the shared libraries in the program.
30541 @subsubheading @value{GDBN} Command
30543 The corresponding @value{GDBN} command is @samp{info shared}.
30545 @subsubheading Example
30549 @subheading The @code{-file-list-symbol-files} Command
30550 @findex -file-list-symbol-files
30552 @subsubheading Synopsis
30555 -file-list-symbol-files
30560 @subsubheading @value{GDBN} Command
30562 The corresponding @value{GDBN} command is @samp{info file} (part of it).
30564 @subsubheading Example
30569 @subheading The @code{-file-symbol-file} Command
30570 @findex -file-symbol-file
30572 @subsubheading Synopsis
30575 -file-symbol-file @var{file}
30578 Read symbol table info from the specified @var{file} argument. When
30579 used without arguments, clears @value{GDBN}'s symbol table info. No output is
30580 produced, except for a completion notification.
30582 @subsubheading @value{GDBN} Command
30584 The corresponding @value{GDBN} command is @samp{symbol-file}.
30586 @subsubheading Example
30590 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30596 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30597 @node GDB/MI Memory Overlay Commands
30598 @section @sc{gdb/mi} Memory Overlay Commands
30600 The memory overlay commands are not implemented.
30602 @c @subheading -overlay-auto
30604 @c @subheading -overlay-list-mapping-state
30606 @c @subheading -overlay-list-overlays
30608 @c @subheading -overlay-map
30610 @c @subheading -overlay-off
30612 @c @subheading -overlay-on
30614 @c @subheading -overlay-unmap
30616 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30617 @node GDB/MI Signal Handling Commands
30618 @section @sc{gdb/mi} Signal Handling Commands
30620 Signal handling commands are not implemented.
30622 @c @subheading -signal-handle
30624 @c @subheading -signal-list-handle-actions
30626 @c @subheading -signal-list-signal-types
30630 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30631 @node GDB/MI Target Manipulation
30632 @section @sc{gdb/mi} Target Manipulation Commands
30635 @subheading The @code{-target-attach} Command
30636 @findex -target-attach
30638 @subsubheading Synopsis
30641 -target-attach @var{pid} | @var{gid} | @var{file}
30644 Attach to a process @var{pid} or a file @var{file} outside of
30645 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
30646 group, the id previously returned by
30647 @samp{-list-thread-groups --available} must be used.
30649 @subsubheading @value{GDBN} Command
30651 The corresponding @value{GDBN} command is @samp{attach}.
30653 @subsubheading Example
30657 =thread-created,id="1"
30658 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
30664 @subheading The @code{-target-compare-sections} Command
30665 @findex -target-compare-sections
30667 @subsubheading Synopsis
30670 -target-compare-sections [ @var{section} ]
30673 Compare data of section @var{section} on target to the exec file.
30674 Without the argument, all sections are compared.
30676 @subsubheading @value{GDBN} Command
30678 The @value{GDBN} equivalent is @samp{compare-sections}.
30680 @subsubheading Example
30685 @subheading The @code{-target-detach} Command
30686 @findex -target-detach
30688 @subsubheading Synopsis
30691 -target-detach [ @var{pid} | @var{gid} ]
30694 Detach from the remote target which normally resumes its execution.
30695 If either @var{pid} or @var{gid} is specified, detaches from either
30696 the specified process, or specified thread group. There's no output.
30698 @subsubheading @value{GDBN} Command
30700 The corresponding @value{GDBN} command is @samp{detach}.
30702 @subsubheading Example
30712 @subheading The @code{-target-disconnect} Command
30713 @findex -target-disconnect
30715 @subsubheading Synopsis
30721 Disconnect from the remote target. There's no output and the target is
30722 generally not resumed.
30724 @subsubheading @value{GDBN} Command
30726 The corresponding @value{GDBN} command is @samp{disconnect}.
30728 @subsubheading Example
30738 @subheading The @code{-target-download} Command
30739 @findex -target-download
30741 @subsubheading Synopsis
30747 Loads the executable onto the remote target.
30748 It prints out an update message every half second, which includes the fields:
30752 The name of the section.
30754 The size of what has been sent so far for that section.
30756 The size of the section.
30758 The total size of what was sent so far (the current and the previous sections).
30760 The size of the overall executable to download.
30764 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
30765 @sc{gdb/mi} Output Syntax}).
30767 In addition, it prints the name and size of the sections, as they are
30768 downloaded. These messages include the following fields:
30772 The name of the section.
30774 The size of the section.
30776 The size of the overall executable to download.
30780 At the end, a summary is printed.
30782 @subsubheading @value{GDBN} Command
30784 The corresponding @value{GDBN} command is @samp{load}.
30786 @subsubheading Example
30788 Note: each status message appears on a single line. Here the messages
30789 have been broken down so that they can fit onto a page.
30794 +download,@{section=".text",section-size="6668",total-size="9880"@}
30795 +download,@{section=".text",section-sent="512",section-size="6668",
30796 total-sent="512",total-size="9880"@}
30797 +download,@{section=".text",section-sent="1024",section-size="6668",
30798 total-sent="1024",total-size="9880"@}
30799 +download,@{section=".text",section-sent="1536",section-size="6668",
30800 total-sent="1536",total-size="9880"@}
30801 +download,@{section=".text",section-sent="2048",section-size="6668",
30802 total-sent="2048",total-size="9880"@}
30803 +download,@{section=".text",section-sent="2560",section-size="6668",
30804 total-sent="2560",total-size="9880"@}
30805 +download,@{section=".text",section-sent="3072",section-size="6668",
30806 total-sent="3072",total-size="9880"@}
30807 +download,@{section=".text",section-sent="3584",section-size="6668",
30808 total-sent="3584",total-size="9880"@}
30809 +download,@{section=".text",section-sent="4096",section-size="6668",
30810 total-sent="4096",total-size="9880"@}
30811 +download,@{section=".text",section-sent="4608",section-size="6668",
30812 total-sent="4608",total-size="9880"@}
30813 +download,@{section=".text",section-sent="5120",section-size="6668",
30814 total-sent="5120",total-size="9880"@}
30815 +download,@{section=".text",section-sent="5632",section-size="6668",
30816 total-sent="5632",total-size="9880"@}
30817 +download,@{section=".text",section-sent="6144",section-size="6668",
30818 total-sent="6144",total-size="9880"@}
30819 +download,@{section=".text",section-sent="6656",section-size="6668",
30820 total-sent="6656",total-size="9880"@}
30821 +download,@{section=".init",section-size="28",total-size="9880"@}
30822 +download,@{section=".fini",section-size="28",total-size="9880"@}
30823 +download,@{section=".data",section-size="3156",total-size="9880"@}
30824 +download,@{section=".data",section-sent="512",section-size="3156",
30825 total-sent="7236",total-size="9880"@}
30826 +download,@{section=".data",section-sent="1024",section-size="3156",
30827 total-sent="7748",total-size="9880"@}
30828 +download,@{section=".data",section-sent="1536",section-size="3156",
30829 total-sent="8260",total-size="9880"@}
30830 +download,@{section=".data",section-sent="2048",section-size="3156",
30831 total-sent="8772",total-size="9880"@}
30832 +download,@{section=".data",section-sent="2560",section-size="3156",
30833 total-sent="9284",total-size="9880"@}
30834 +download,@{section=".data",section-sent="3072",section-size="3156",
30835 total-sent="9796",total-size="9880"@}
30836 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
30843 @subheading The @code{-target-exec-status} Command
30844 @findex -target-exec-status
30846 @subsubheading Synopsis
30849 -target-exec-status
30852 Provide information on the state of the target (whether it is running or
30853 not, for instance).
30855 @subsubheading @value{GDBN} Command
30857 There's no equivalent @value{GDBN} command.
30859 @subsubheading Example
30863 @subheading The @code{-target-list-available-targets} Command
30864 @findex -target-list-available-targets
30866 @subsubheading Synopsis
30869 -target-list-available-targets
30872 List the possible targets to connect to.
30874 @subsubheading @value{GDBN} Command
30876 The corresponding @value{GDBN} command is @samp{help target}.
30878 @subsubheading Example
30882 @subheading The @code{-target-list-current-targets} Command
30883 @findex -target-list-current-targets
30885 @subsubheading Synopsis
30888 -target-list-current-targets
30891 Describe the current target.
30893 @subsubheading @value{GDBN} Command
30895 The corresponding information is printed by @samp{info file} (among
30898 @subsubheading Example
30902 @subheading The @code{-target-list-parameters} Command
30903 @findex -target-list-parameters
30905 @subsubheading Synopsis
30908 -target-list-parameters
30914 @subsubheading @value{GDBN} Command
30918 @subsubheading Example
30922 @subheading The @code{-target-select} Command
30923 @findex -target-select
30925 @subsubheading Synopsis
30928 -target-select @var{type} @var{parameters @dots{}}
30931 Connect @value{GDBN} to the remote target. This command takes two args:
30935 The type of target, for instance @samp{remote}, etc.
30936 @item @var{parameters}
30937 Device names, host names and the like. @xref{Target Commands, ,
30938 Commands for Managing Targets}, for more details.
30941 The output is a connection notification, followed by the address at
30942 which the target program is, in the following form:
30945 ^connected,addr="@var{address}",func="@var{function name}",
30946 args=[@var{arg list}]
30949 @subsubheading @value{GDBN} Command
30951 The corresponding @value{GDBN} command is @samp{target}.
30953 @subsubheading Example
30957 -target-select remote /dev/ttya
30958 ^connected,addr="0xfe00a300",func="??",args=[]
30962 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30963 @node GDB/MI File Transfer Commands
30964 @section @sc{gdb/mi} File Transfer Commands
30967 @subheading The @code{-target-file-put} Command
30968 @findex -target-file-put
30970 @subsubheading Synopsis
30973 -target-file-put @var{hostfile} @var{targetfile}
30976 Copy file @var{hostfile} from the host system (the machine running
30977 @value{GDBN}) to @var{targetfile} on the target system.
30979 @subsubheading @value{GDBN} Command
30981 The corresponding @value{GDBN} command is @samp{remote put}.
30983 @subsubheading Example
30987 -target-file-put localfile remotefile
30993 @subheading The @code{-target-file-get} Command
30994 @findex -target-file-get
30996 @subsubheading Synopsis
30999 -target-file-get @var{targetfile} @var{hostfile}
31002 Copy file @var{targetfile} from the target system to @var{hostfile}
31003 on the host system.
31005 @subsubheading @value{GDBN} Command
31007 The corresponding @value{GDBN} command is @samp{remote get}.
31009 @subsubheading Example
31013 -target-file-get remotefile localfile
31019 @subheading The @code{-target-file-delete} Command
31020 @findex -target-file-delete
31022 @subsubheading Synopsis
31025 -target-file-delete @var{targetfile}
31028 Delete @var{targetfile} from the target system.
31030 @subsubheading @value{GDBN} Command
31032 The corresponding @value{GDBN} command is @samp{remote delete}.
31034 @subsubheading Example
31038 -target-file-delete remotefile
31044 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31045 @node GDB/MI Ada Exceptions Commands
31046 @section Ada Exceptions @sc{gdb/mi} Commands
31048 @subheading The @code{-info-ada-exceptions} Command
31049 @findex -info-ada-exceptions
31051 @subsubheading Synopsis
31054 -info-ada-exceptions [ @var{regexp}]
31057 List all Ada exceptions defined within the program being debugged.
31058 With a regular expression @var{regexp}, only those exceptions whose
31059 names match @var{regexp} are listed.
31061 @subsubheading @value{GDBN} Command
31063 The corresponding @value{GDBN} command is @samp{info exceptions}.
31065 @subsubheading Result
31067 The result is a table of Ada exceptions. The following columns are
31068 defined for each exception:
31072 The name of the exception.
31075 The address of the exception.
31079 @subsubheading Example
31082 -info-ada-exceptions aint
31083 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
31084 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
31085 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
31086 body=[@{name="constraint_error",address="0x0000000000613da0"@},
31087 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
31090 @subheading Catching Ada Exceptions
31092 The commands describing how to ask @value{GDBN} to stop when a program
31093 raises an exception are described at @ref{Ada Exception GDB/MI
31094 Catchpoint Commands}.
31097 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31098 @node GDB/MI Support Commands
31099 @section @sc{gdb/mi} Support Commands
31101 Since new commands and features get regularly added to @sc{gdb/mi},
31102 some commands are available to help front-ends query the debugger
31103 about support for these capabilities. Similarly, it is also possible
31104 to query @value{GDBN} about target support of certain features.
31106 @subheading The @code{-info-gdb-mi-command} Command
31107 @cindex @code{-info-gdb-mi-command}
31108 @findex -info-gdb-mi-command
31110 @subsubheading Synopsis
31113 -info-gdb-mi-command @var{cmd_name}
31116 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
31118 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
31119 is technically not part of the command name (@pxref{GDB/MI Input
31120 Syntax}), and thus should be omitted in @var{cmd_name}. However,
31121 for ease of use, this command also accepts the form with the leading
31124 @subsubheading @value{GDBN} Command
31126 There is no corresponding @value{GDBN} command.
31128 @subsubheading Result
31130 The result is a tuple. There is currently only one field:
31134 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
31135 @code{"false"} otherwise.
31139 @subsubheading Example
31141 Here is an example where the @sc{gdb/mi} command does not exist:
31144 -info-gdb-mi-command unsupported-command
31145 ^done,command=@{exists="false"@}
31149 And here is an example where the @sc{gdb/mi} command is known
31153 -info-gdb-mi-command symbol-list-lines
31154 ^done,command=@{exists="true"@}
31157 @subheading The @code{-list-features} Command
31158 @findex -list-features
31159 @cindex supported @sc{gdb/mi} features, list
31161 Returns a list of particular features of the MI protocol that
31162 this version of gdb implements. A feature can be a command,
31163 or a new field in an output of some command, or even an
31164 important bugfix. While a frontend can sometimes detect presence
31165 of a feature at runtime, it is easier to perform detection at debugger
31168 The command returns a list of strings, with each string naming an
31169 available feature. Each returned string is just a name, it does not
31170 have any internal structure. The list of possible feature names
31176 (gdb) -list-features
31177 ^done,result=["feature1","feature2"]
31180 The current list of features is:
31183 @item frozen-varobjs
31184 Indicates support for the @code{-var-set-frozen} command, as well
31185 as possible presense of the @code{frozen} field in the output
31186 of @code{-varobj-create}.
31187 @item pending-breakpoints
31188 Indicates support for the @option{-f} option to the @code{-break-insert}
31191 Indicates Python scripting support, Python-based
31192 pretty-printing commands, and possible presence of the
31193 @samp{display_hint} field in the output of @code{-var-list-children}
31195 Indicates support for the @code{-thread-info} command.
31196 @item data-read-memory-bytes
31197 Indicates support for the @code{-data-read-memory-bytes} and the
31198 @code{-data-write-memory-bytes} commands.
31199 @item breakpoint-notifications
31200 Indicates that changes to breakpoints and breakpoints created via the
31201 CLI will be announced via async records.
31202 @item ada-task-info
31203 Indicates support for the @code{-ada-task-info} command.
31204 @item language-option
31205 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
31206 option (@pxref{Context management}).
31207 @item info-gdb-mi-command
31208 Indicates support for the @code{-info-gdb-mi-command} command.
31209 @item undefined-command-error-code
31210 Indicates support for the "undefined-command" error code in error result
31211 records, produced when trying to execute an undefined @sc{gdb/mi} command
31212 (@pxref{GDB/MI Result Records}).
31213 @item exec-run-start-option
31214 Indicates that the @code{-exec-run} command supports the @option{--start}
31215 option (@pxref{GDB/MI Program Execution}).
31218 @subheading The @code{-list-target-features} Command
31219 @findex -list-target-features
31221 Returns a list of particular features that are supported by the
31222 target. Those features affect the permitted MI commands, but
31223 unlike the features reported by the @code{-list-features} command, the
31224 features depend on which target GDB is using at the moment. Whenever
31225 a target can change, due to commands such as @code{-target-select},
31226 @code{-target-attach} or @code{-exec-run}, the list of target features
31227 may change, and the frontend should obtain it again.
31231 (gdb) -list-target-features
31232 ^done,result=["async"]
31235 The current list of features is:
31239 Indicates that the target is capable of asynchronous command
31240 execution, which means that @value{GDBN} will accept further commands
31241 while the target is running.
31244 Indicates that the target is capable of reverse execution.
31245 @xref{Reverse Execution}, for more information.
31249 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31250 @node GDB/MI Miscellaneous Commands
31251 @section Miscellaneous @sc{gdb/mi} Commands
31253 @c @subheading -gdb-complete
31255 @subheading The @code{-gdb-exit} Command
31258 @subsubheading Synopsis
31264 Exit @value{GDBN} immediately.
31266 @subsubheading @value{GDBN} Command
31268 Approximately corresponds to @samp{quit}.
31270 @subsubheading Example
31280 @subheading The @code{-exec-abort} Command
31281 @findex -exec-abort
31283 @subsubheading Synopsis
31289 Kill the inferior running program.
31291 @subsubheading @value{GDBN} Command
31293 The corresponding @value{GDBN} command is @samp{kill}.
31295 @subsubheading Example
31300 @subheading The @code{-gdb-set} Command
31303 @subsubheading Synopsis
31309 Set an internal @value{GDBN} variable.
31310 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
31312 @subsubheading @value{GDBN} Command
31314 The corresponding @value{GDBN} command is @samp{set}.
31316 @subsubheading Example
31326 @subheading The @code{-gdb-show} Command
31329 @subsubheading Synopsis
31335 Show the current value of a @value{GDBN} variable.
31337 @subsubheading @value{GDBN} Command
31339 The corresponding @value{GDBN} command is @samp{show}.
31341 @subsubheading Example
31350 @c @subheading -gdb-source
31353 @subheading The @code{-gdb-version} Command
31354 @findex -gdb-version
31356 @subsubheading Synopsis
31362 Show version information for @value{GDBN}. Used mostly in testing.
31364 @subsubheading @value{GDBN} Command
31366 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
31367 default shows this information when you start an interactive session.
31369 @subsubheading Example
31371 @c This example modifies the actual output from GDB to avoid overfull
31377 ~Copyright 2000 Free Software Foundation, Inc.
31378 ~GDB is free software, covered by the GNU General Public License, and
31379 ~you are welcome to change it and/or distribute copies of it under
31380 ~ certain conditions.
31381 ~Type "show copying" to see the conditions.
31382 ~There is absolutely no warranty for GDB. Type "show warranty" for
31384 ~This GDB was configured as
31385 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
31390 @subheading The @code{-list-thread-groups} Command
31391 @findex -list-thread-groups
31393 @subheading Synopsis
31396 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
31399 Lists thread groups (@pxref{Thread groups}). When a single thread
31400 group is passed as the argument, lists the children of that group.
31401 When several thread group are passed, lists information about those
31402 thread groups. Without any parameters, lists information about all
31403 top-level thread groups.
31405 Normally, thread groups that are being debugged are reported.
31406 With the @samp{--available} option, @value{GDBN} reports thread groups
31407 available on the target.
31409 The output of this command may have either a @samp{threads} result or
31410 a @samp{groups} result. The @samp{thread} result has a list of tuples
31411 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
31412 Information}). The @samp{groups} result has a list of tuples as value,
31413 each tuple describing a thread group. If top-level groups are
31414 requested (that is, no parameter is passed), or when several groups
31415 are passed, the output always has a @samp{groups} result. The format
31416 of the @samp{group} result is described below.
31418 To reduce the number of roundtrips it's possible to list thread groups
31419 together with their children, by passing the @samp{--recurse} option
31420 and the recursion depth. Presently, only recursion depth of 1 is
31421 permitted. If this option is present, then every reported thread group
31422 will also include its children, either as @samp{group} or
31423 @samp{threads} field.
31425 In general, any combination of option and parameters is permitted, with
31426 the following caveats:
31430 When a single thread group is passed, the output will typically
31431 be the @samp{threads} result. Because threads may not contain
31432 anything, the @samp{recurse} option will be ignored.
31435 When the @samp{--available} option is passed, limited information may
31436 be available. In particular, the list of threads of a process might
31437 be inaccessible. Further, specifying specific thread groups might
31438 not give any performance advantage over listing all thread groups.
31439 The frontend should assume that @samp{-list-thread-groups --available}
31440 is always an expensive operation and cache the results.
31444 The @samp{groups} result is a list of tuples, where each tuple may
31445 have the following fields:
31449 Identifier of the thread group. This field is always present.
31450 The identifier is an opaque string; frontends should not try to
31451 convert it to an integer, even though it might look like one.
31454 The type of the thread group. At present, only @samp{process} is a
31458 The target-specific process identifier. This field is only present
31459 for thread groups of type @samp{process} and only if the process exists.
31462 The exit code of this group's last exited thread, formatted in octal.
31463 This field is only present for thread groups of type @samp{process} and
31464 only if the process is not running.
31467 The number of children this thread group has. This field may be
31468 absent for an available thread group.
31471 This field has a list of tuples as value, each tuple describing a
31472 thread. It may be present if the @samp{--recurse} option is
31473 specified, and it's actually possible to obtain the threads.
31476 This field is a list of integers, each identifying a core that one
31477 thread of the group is running on. This field may be absent if
31478 such information is not available.
31481 The name of the executable file that corresponds to this thread group.
31482 The field is only present for thread groups of type @samp{process},
31483 and only if there is a corresponding executable file.
31487 @subheading Example
31491 -list-thread-groups
31492 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
31493 -list-thread-groups 17
31494 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31495 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
31496 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31497 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
31498 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
31499 -list-thread-groups --available
31500 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
31501 -list-thread-groups --available --recurse 1
31502 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31503 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31504 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
31505 -list-thread-groups --available --recurse 1 17 18
31506 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31507 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31508 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
31511 @subheading The @code{-info-os} Command
31514 @subsubheading Synopsis
31517 -info-os [ @var{type} ]
31520 If no argument is supplied, the command returns a table of available
31521 operating-system-specific information types. If one of these types is
31522 supplied as an argument @var{type}, then the command returns a table
31523 of data of that type.
31525 The types of information available depend on the target operating
31528 @subsubheading @value{GDBN} Command
31530 The corresponding @value{GDBN} command is @samp{info os}.
31532 @subsubheading Example
31534 When run on a @sc{gnu}/Linux system, the output will look something
31540 ^done,OSDataTable=@{nr_rows="9",nr_cols="3",
31541 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
31542 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
31543 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
31544 body=[item=@{col0="processes",col1="Listing of all processes",
31545 col2="Processes"@},
31546 item=@{col0="procgroups",col1="Listing of all process groups",
31547 col2="Process groups"@},
31548 item=@{col0="threads",col1="Listing of all threads",
31550 item=@{col0="files",col1="Listing of all file descriptors",
31551 col2="File descriptors"@},
31552 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
31554 item=@{col0="shm",col1="Listing of all shared-memory regions",
31555 col2="Shared-memory regions"@},
31556 item=@{col0="semaphores",col1="Listing of all semaphores",
31557 col2="Semaphores"@},
31558 item=@{col0="msg",col1="Listing of all message queues",
31559 col2="Message queues"@},
31560 item=@{col0="modules",col1="Listing of all loaded kernel modules",
31561 col2="Kernel modules"@}]@}
31564 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
31565 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
31566 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
31567 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
31568 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
31569 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
31570 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
31571 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
31573 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
31574 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
31578 (Note that the MI output here includes a @code{"Title"} column that
31579 does not appear in command-line @code{info os}; this column is useful
31580 for MI clients that want to enumerate the types of data, such as in a
31581 popup menu, but is needless clutter on the command line, and
31582 @code{info os} omits it.)
31584 @subheading The @code{-add-inferior} Command
31585 @findex -add-inferior
31587 @subheading Synopsis
31593 Creates a new inferior (@pxref{Inferiors and Programs}). The created
31594 inferior is not associated with any executable. Such association may
31595 be established with the @samp{-file-exec-and-symbols} command
31596 (@pxref{GDB/MI File Commands}). The command response has a single
31597 field, @samp{inferior}, whose value is the identifier of the
31598 thread group corresponding to the new inferior.
31600 @subheading Example
31605 ^done,inferior="i3"
31608 @subheading The @code{-interpreter-exec} Command
31609 @findex -interpreter-exec
31611 @subheading Synopsis
31614 -interpreter-exec @var{interpreter} @var{command}
31616 @anchor{-interpreter-exec}
31618 Execute the specified @var{command} in the given @var{interpreter}.
31620 @subheading @value{GDBN} Command
31622 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
31624 @subheading Example
31628 -interpreter-exec console "break main"
31629 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
31630 &"During symbol reading, bad structure-type format.\n"
31631 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
31636 @subheading The @code{-inferior-tty-set} Command
31637 @findex -inferior-tty-set
31639 @subheading Synopsis
31642 -inferior-tty-set /dev/pts/1
31645 Set terminal for future runs of the program being debugged.
31647 @subheading @value{GDBN} Command
31649 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
31651 @subheading Example
31655 -inferior-tty-set /dev/pts/1
31660 @subheading The @code{-inferior-tty-show} Command
31661 @findex -inferior-tty-show
31663 @subheading Synopsis
31669 Show terminal for future runs of program being debugged.
31671 @subheading @value{GDBN} Command
31673 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
31675 @subheading Example
31679 -inferior-tty-set /dev/pts/1
31683 ^done,inferior_tty_terminal="/dev/pts/1"
31687 @subheading The @code{-enable-timings} Command
31688 @findex -enable-timings
31690 @subheading Synopsis
31693 -enable-timings [yes | no]
31696 Toggle the printing of the wallclock, user and system times for an MI
31697 command as a field in its output. This command is to help frontend
31698 developers optimize the performance of their code. No argument is
31699 equivalent to @samp{yes}.
31701 @subheading @value{GDBN} Command
31705 @subheading Example
31713 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31714 addr="0x080484ed",func="main",file="myprog.c",
31715 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
31717 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
31725 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
31726 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
31727 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
31728 fullname="/home/nickrob/myprog.c",line="73"@}
31733 @chapter @value{GDBN} Annotations
31735 This chapter describes annotations in @value{GDBN}. Annotations were
31736 designed to interface @value{GDBN} to graphical user interfaces or other
31737 similar programs which want to interact with @value{GDBN} at a
31738 relatively high level.
31740 The annotation mechanism has largely been superseded by @sc{gdb/mi}
31744 This is Edition @value{EDITION}, @value{DATE}.
31748 * Annotations Overview:: What annotations are; the general syntax.
31749 * Server Prefix:: Issuing a command without affecting user state.
31750 * Prompting:: Annotations marking @value{GDBN}'s need for input.
31751 * Errors:: Annotations for error messages.
31752 * Invalidation:: Some annotations describe things now invalid.
31753 * Annotations for Running::
31754 Whether the program is running, how it stopped, etc.
31755 * Source Annotations:: Annotations describing source code.
31758 @node Annotations Overview
31759 @section What is an Annotation?
31760 @cindex annotations
31762 Annotations start with a newline character, two @samp{control-z}
31763 characters, and the name of the annotation. If there is no additional
31764 information associated with this annotation, the name of the annotation
31765 is followed immediately by a newline. If there is additional
31766 information, the name of the annotation is followed by a space, the
31767 additional information, and a newline. The additional information
31768 cannot contain newline characters.
31770 Any output not beginning with a newline and two @samp{control-z}
31771 characters denotes literal output from @value{GDBN}. Currently there is
31772 no need for @value{GDBN} to output a newline followed by two
31773 @samp{control-z} characters, but if there was such a need, the
31774 annotations could be extended with an @samp{escape} annotation which
31775 means those three characters as output.
31777 The annotation @var{level}, which is specified using the
31778 @option{--annotate} command line option (@pxref{Mode Options}), controls
31779 how much information @value{GDBN} prints together with its prompt,
31780 values of expressions, source lines, and other types of output. Level 0
31781 is for no annotations, level 1 is for use when @value{GDBN} is run as a
31782 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
31783 for programs that control @value{GDBN}, and level 2 annotations have
31784 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
31785 Interface, annotate, GDB's Obsolete Annotations}).
31788 @kindex set annotate
31789 @item set annotate @var{level}
31790 The @value{GDBN} command @code{set annotate} sets the level of
31791 annotations to the specified @var{level}.
31793 @item show annotate
31794 @kindex show annotate
31795 Show the current annotation level.
31798 This chapter describes level 3 annotations.
31800 A simple example of starting up @value{GDBN} with annotations is:
31803 $ @kbd{gdb --annotate=3}
31805 Copyright 2003 Free Software Foundation, Inc.
31806 GDB is free software, covered by the GNU General Public License,
31807 and you are welcome to change it and/or distribute copies of it
31808 under certain conditions.
31809 Type "show copying" to see the conditions.
31810 There is absolutely no warranty for GDB. Type "show warranty"
31812 This GDB was configured as "i386-pc-linux-gnu"
31823 Here @samp{quit} is input to @value{GDBN}; the rest is output from
31824 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
31825 denotes a @samp{control-z} character) are annotations; the rest is
31826 output from @value{GDBN}.
31828 @node Server Prefix
31829 @section The Server Prefix
31830 @cindex server prefix
31832 If you prefix a command with @samp{server } then it will not affect
31833 the command history, nor will it affect @value{GDBN}'s notion of which
31834 command to repeat if @key{RET} is pressed on a line by itself. This
31835 means that commands can be run behind a user's back by a front-end in
31836 a transparent manner.
31838 The @code{server } prefix does not affect the recording of values into
31839 the value history; to print a value without recording it into the
31840 value history, use the @code{output} command instead of the
31841 @code{print} command.
31843 Using this prefix also disables confirmation requests
31844 (@pxref{confirmation requests}).
31847 @section Annotation for @value{GDBN} Input
31849 @cindex annotations for prompts
31850 When @value{GDBN} prompts for input, it annotates this fact so it is possible
31851 to know when to send output, when the output from a given command is
31854 Different kinds of input each have a different @dfn{input type}. Each
31855 input type has three annotations: a @code{pre-} annotation, which
31856 denotes the beginning of any prompt which is being output, a plain
31857 annotation, which denotes the end of the prompt, and then a @code{post-}
31858 annotation which denotes the end of any echo which may (or may not) be
31859 associated with the input. For example, the @code{prompt} input type
31860 features the following annotations:
31868 The input types are
31871 @findex pre-prompt annotation
31872 @findex prompt annotation
31873 @findex post-prompt annotation
31875 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
31877 @findex pre-commands annotation
31878 @findex commands annotation
31879 @findex post-commands annotation
31881 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
31882 command. The annotations are repeated for each command which is input.
31884 @findex pre-overload-choice annotation
31885 @findex overload-choice annotation
31886 @findex post-overload-choice annotation
31887 @item overload-choice
31888 When @value{GDBN} wants the user to select between various overloaded functions.
31890 @findex pre-query annotation
31891 @findex query annotation
31892 @findex post-query annotation
31894 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
31896 @findex pre-prompt-for-continue annotation
31897 @findex prompt-for-continue annotation
31898 @findex post-prompt-for-continue annotation
31899 @item prompt-for-continue
31900 When @value{GDBN} is asking the user to press return to continue. Note: Don't
31901 expect this to work well; instead use @code{set height 0} to disable
31902 prompting. This is because the counting of lines is buggy in the
31903 presence of annotations.
31908 @cindex annotations for errors, warnings and interrupts
31910 @findex quit annotation
31915 This annotation occurs right before @value{GDBN} responds to an interrupt.
31917 @findex error annotation
31922 This annotation occurs right before @value{GDBN} responds to an error.
31924 Quit and error annotations indicate that any annotations which @value{GDBN} was
31925 in the middle of may end abruptly. For example, if a
31926 @code{value-history-begin} annotation is followed by a @code{error}, one
31927 cannot expect to receive the matching @code{value-history-end}. One
31928 cannot expect not to receive it either, however; an error annotation
31929 does not necessarily mean that @value{GDBN} is immediately returning all the way
31932 @findex error-begin annotation
31933 A quit or error annotation may be preceded by
31939 Any output between that and the quit or error annotation is the error
31942 Warning messages are not yet annotated.
31943 @c If we want to change that, need to fix warning(), type_error(),
31944 @c range_error(), and possibly other places.
31947 @section Invalidation Notices
31949 @cindex annotations for invalidation messages
31950 The following annotations say that certain pieces of state may have
31954 @findex frames-invalid annotation
31955 @item ^Z^Zframes-invalid
31957 The frames (for example, output from the @code{backtrace} command) may
31960 @findex breakpoints-invalid annotation
31961 @item ^Z^Zbreakpoints-invalid
31963 The breakpoints may have changed. For example, the user just added or
31964 deleted a breakpoint.
31967 @node Annotations for Running
31968 @section Running the Program
31969 @cindex annotations for running programs
31971 @findex starting annotation
31972 @findex stopping annotation
31973 When the program starts executing due to a @value{GDBN} command such as
31974 @code{step} or @code{continue},
31980 is output. When the program stops,
31986 is output. Before the @code{stopped} annotation, a variety of
31987 annotations describe how the program stopped.
31990 @findex exited annotation
31991 @item ^Z^Zexited @var{exit-status}
31992 The program exited, and @var{exit-status} is the exit status (zero for
31993 successful exit, otherwise nonzero).
31995 @findex signalled annotation
31996 @findex signal-name annotation
31997 @findex signal-name-end annotation
31998 @findex signal-string annotation
31999 @findex signal-string-end annotation
32000 @item ^Z^Zsignalled
32001 The program exited with a signal. After the @code{^Z^Zsignalled}, the
32002 annotation continues:
32008 ^Z^Zsignal-name-end
32012 ^Z^Zsignal-string-end
32017 where @var{name} is the name of the signal, such as @code{SIGILL} or
32018 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
32019 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
32020 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
32021 user's benefit and have no particular format.
32023 @findex signal annotation
32025 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
32026 just saying that the program received the signal, not that it was
32027 terminated with it.
32029 @findex breakpoint annotation
32030 @item ^Z^Zbreakpoint @var{number}
32031 The program hit breakpoint number @var{number}.
32033 @findex watchpoint annotation
32034 @item ^Z^Zwatchpoint @var{number}
32035 The program hit watchpoint number @var{number}.
32038 @node Source Annotations
32039 @section Displaying Source
32040 @cindex annotations for source display
32042 @findex source annotation
32043 The following annotation is used instead of displaying source code:
32046 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
32049 where @var{filename} is an absolute file name indicating which source
32050 file, @var{line} is the line number within that file (where 1 is the
32051 first line in the file), @var{character} is the character position
32052 within the file (where 0 is the first character in the file) (for most
32053 debug formats this will necessarily point to the beginning of a line),
32054 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
32055 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
32056 @var{addr} is the address in the target program associated with the
32057 source which is being displayed. The @var{addr} is in the form @samp{0x}
32058 followed by one or more lowercase hex digits (note that this does not
32059 depend on the language).
32061 @node JIT Interface
32062 @chapter JIT Compilation Interface
32063 @cindex just-in-time compilation
32064 @cindex JIT compilation interface
32066 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
32067 interface. A JIT compiler is a program or library that generates native
32068 executable code at runtime and executes it, usually in order to achieve good
32069 performance while maintaining platform independence.
32071 Programs that use JIT compilation are normally difficult to debug because
32072 portions of their code are generated at runtime, instead of being loaded from
32073 object files, which is where @value{GDBN} normally finds the program's symbols
32074 and debug information. In order to debug programs that use JIT compilation,
32075 @value{GDBN} has an interface that allows the program to register in-memory
32076 symbol files with @value{GDBN} at runtime.
32078 If you are using @value{GDBN} to debug a program that uses this interface, then
32079 it should work transparently so long as you have not stripped the binary. If
32080 you are developing a JIT compiler, then the interface is documented in the rest
32081 of this chapter. At this time, the only known client of this interface is the
32084 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
32085 JIT compiler communicates with @value{GDBN} by writing data into a global
32086 variable and calling a fuction at a well-known symbol. When @value{GDBN}
32087 attaches, it reads a linked list of symbol files from the global variable to
32088 find existing code, and puts a breakpoint in the function so that it can find
32089 out about additional code.
32092 * Declarations:: Relevant C struct declarations
32093 * Registering Code:: Steps to register code
32094 * Unregistering Code:: Steps to unregister code
32095 * Custom Debug Info:: Emit debug information in a custom format
32099 @section JIT Declarations
32101 These are the relevant struct declarations that a C program should include to
32102 implement the interface:
32112 struct jit_code_entry
32114 struct jit_code_entry *next_entry;
32115 struct jit_code_entry *prev_entry;
32116 const char *symfile_addr;
32117 uint64_t symfile_size;
32120 struct jit_descriptor
32123 /* This type should be jit_actions_t, but we use uint32_t
32124 to be explicit about the bitwidth. */
32125 uint32_t action_flag;
32126 struct jit_code_entry *relevant_entry;
32127 struct jit_code_entry *first_entry;
32130 /* GDB puts a breakpoint in this function. */
32131 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
32133 /* Make sure to specify the version statically, because the
32134 debugger may check the version before we can set it. */
32135 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
32138 If the JIT is multi-threaded, then it is important that the JIT synchronize any
32139 modifications to this global data properly, which can easily be done by putting
32140 a global mutex around modifications to these structures.
32142 @node Registering Code
32143 @section Registering Code
32145 To register code with @value{GDBN}, the JIT should follow this protocol:
32149 Generate an object file in memory with symbols and other desired debug
32150 information. The file must include the virtual addresses of the sections.
32153 Create a code entry for the file, which gives the start and size of the symbol
32157 Add it to the linked list in the JIT descriptor.
32160 Point the relevant_entry field of the descriptor at the entry.
32163 Set @code{action_flag} to @code{JIT_REGISTER} and call
32164 @code{__jit_debug_register_code}.
32167 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
32168 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
32169 new code. However, the linked list must still be maintained in order to allow
32170 @value{GDBN} to attach to a running process and still find the symbol files.
32172 @node Unregistering Code
32173 @section Unregistering Code
32175 If code is freed, then the JIT should use the following protocol:
32179 Remove the code entry corresponding to the code from the linked list.
32182 Point the @code{relevant_entry} field of the descriptor at the code entry.
32185 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
32186 @code{__jit_debug_register_code}.
32189 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
32190 and the JIT will leak the memory used for the associated symbol files.
32192 @node Custom Debug Info
32193 @section Custom Debug Info
32194 @cindex custom JIT debug info
32195 @cindex JIT debug info reader
32197 Generating debug information in platform-native file formats (like ELF
32198 or COFF) may be an overkill for JIT compilers; especially if all the
32199 debug info is used for is displaying a meaningful backtrace. The
32200 issue can be resolved by having the JIT writers decide on a debug info
32201 format and also provide a reader that parses the debug info generated
32202 by the JIT compiler. This section gives a brief overview on writing
32203 such a parser. More specific details can be found in the source file
32204 @file{gdb/jit-reader.in}, which is also installed as a header at
32205 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
32207 The reader is implemented as a shared object (so this functionality is
32208 not available on platforms which don't allow loading shared objects at
32209 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
32210 @code{jit-reader-unload} are provided, to be used to load and unload
32211 the readers from a preconfigured directory. Once loaded, the shared
32212 object is used the parse the debug information emitted by the JIT
32216 * Using JIT Debug Info Readers:: How to use supplied readers correctly
32217 * Writing JIT Debug Info Readers:: Creating a debug-info reader
32220 @node Using JIT Debug Info Readers
32221 @subsection Using JIT Debug Info Readers
32222 @kindex jit-reader-load
32223 @kindex jit-reader-unload
32225 Readers can be loaded and unloaded using the @code{jit-reader-load}
32226 and @code{jit-reader-unload} commands.
32229 @item jit-reader-load @var{reader}
32230 Load the JIT reader named @var{reader}, which is a shared
32231 object specified as either an absolute or a relative file name. In
32232 the latter case, @value{GDBN} will try to load the reader from a
32233 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
32234 system (here @var{libdir} is the system library directory, often
32235 @file{/usr/local/lib}).
32237 Only one reader can be active at a time; trying to load a second
32238 reader when one is already loaded will result in @value{GDBN}
32239 reporting an error. A new JIT reader can be loaded by first unloading
32240 the current one using @code{jit-reader-unload} and then invoking
32241 @code{jit-reader-load}.
32243 @item jit-reader-unload
32244 Unload the currently loaded JIT reader.
32248 @node Writing JIT Debug Info Readers
32249 @subsection Writing JIT Debug Info Readers
32250 @cindex writing JIT debug info readers
32252 As mentioned, a reader is essentially a shared object conforming to a
32253 certain ABI. This ABI is described in @file{jit-reader.h}.
32255 @file{jit-reader.h} defines the structures, macros and functions
32256 required to write a reader. It is installed (along with
32257 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
32258 the system include directory.
32260 Readers need to be released under a GPL compatible license. A reader
32261 can be declared as released under such a license by placing the macro
32262 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
32264 The entry point for readers is the symbol @code{gdb_init_reader},
32265 which is expected to be a function with the prototype
32267 @findex gdb_init_reader
32269 extern struct gdb_reader_funcs *gdb_init_reader (void);
32272 @cindex @code{struct gdb_reader_funcs}
32274 @code{struct gdb_reader_funcs} contains a set of pointers to callback
32275 functions. These functions are executed to read the debug info
32276 generated by the JIT compiler (@code{read}), to unwind stack frames
32277 (@code{unwind}) and to create canonical frame IDs
32278 (@code{get_Frame_id}). It also has a callback that is called when the
32279 reader is being unloaded (@code{destroy}). The struct looks like this
32282 struct gdb_reader_funcs
32284 /* Must be set to GDB_READER_INTERFACE_VERSION. */
32285 int reader_version;
32287 /* For use by the reader. */
32290 gdb_read_debug_info *read;
32291 gdb_unwind_frame *unwind;
32292 gdb_get_frame_id *get_frame_id;
32293 gdb_destroy_reader *destroy;
32297 @cindex @code{struct gdb_symbol_callbacks}
32298 @cindex @code{struct gdb_unwind_callbacks}
32300 The callbacks are provided with another set of callbacks by
32301 @value{GDBN} to do their job. For @code{read}, these callbacks are
32302 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
32303 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
32304 @code{struct gdb_symbol_callbacks} has callbacks to create new object
32305 files and new symbol tables inside those object files. @code{struct
32306 gdb_unwind_callbacks} has callbacks to read registers off the current
32307 frame and to write out the values of the registers in the previous
32308 frame. Both have a callback (@code{target_read}) to read bytes off the
32309 target's address space.
32311 @node In-Process Agent
32312 @chapter In-Process Agent
32313 @cindex debugging agent
32314 The traditional debugging model is conceptually low-speed, but works fine,
32315 because most bugs can be reproduced in debugging-mode execution. However,
32316 as multi-core or many-core processors are becoming mainstream, and
32317 multi-threaded programs become more and more popular, there should be more
32318 and more bugs that only manifest themselves at normal-mode execution, for
32319 example, thread races, because debugger's interference with the program's
32320 timing may conceal the bugs. On the other hand, in some applications,
32321 it is not feasible for the debugger to interrupt the program's execution
32322 long enough for the developer to learn anything helpful about its behavior.
32323 If the program's correctness depends on its real-time behavior, delays
32324 introduced by a debugger might cause the program to fail, even when the
32325 code itself is correct. It is useful to be able to observe the program's
32326 behavior without interrupting it.
32328 Therefore, traditional debugging model is too intrusive to reproduce
32329 some bugs. In order to reduce the interference with the program, we can
32330 reduce the number of operations performed by debugger. The
32331 @dfn{In-Process Agent}, a shared library, is running within the same
32332 process with inferior, and is able to perform some debugging operations
32333 itself. As a result, debugger is only involved when necessary, and
32334 performance of debugging can be improved accordingly. Note that
32335 interference with program can be reduced but can't be removed completely,
32336 because the in-process agent will still stop or slow down the program.
32338 The in-process agent can interpret and execute Agent Expressions
32339 (@pxref{Agent Expressions}) during performing debugging operations. The
32340 agent expressions can be used for different purposes, such as collecting
32341 data in tracepoints, and condition evaluation in breakpoints.
32343 @anchor{Control Agent}
32344 You can control whether the in-process agent is used as an aid for
32345 debugging with the following commands:
32348 @kindex set agent on
32350 Causes the in-process agent to perform some operations on behalf of the
32351 debugger. Just which operations requested by the user will be done
32352 by the in-process agent depends on the its capabilities. For example,
32353 if you request to evaluate breakpoint conditions in the in-process agent,
32354 and the in-process agent has such capability as well, then breakpoint
32355 conditions will be evaluated in the in-process agent.
32357 @kindex set agent off
32358 @item set agent off
32359 Disables execution of debugging operations by the in-process agent. All
32360 of the operations will be performed by @value{GDBN}.
32364 Display the current setting of execution of debugging operations by
32365 the in-process agent.
32369 * In-Process Agent Protocol::
32372 @node In-Process Agent Protocol
32373 @section In-Process Agent Protocol
32374 @cindex in-process agent protocol
32376 The in-process agent is able to communicate with both @value{GDBN} and
32377 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
32378 used for communications between @value{GDBN} or GDBserver and the IPA.
32379 In general, @value{GDBN} or GDBserver sends commands
32380 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
32381 in-process agent replies back with the return result of the command, or
32382 some other information. The data sent to in-process agent is composed
32383 of primitive data types, such as 4-byte or 8-byte type, and composite
32384 types, which are called objects (@pxref{IPA Protocol Objects}).
32387 * IPA Protocol Objects::
32388 * IPA Protocol Commands::
32391 @node IPA Protocol Objects
32392 @subsection IPA Protocol Objects
32393 @cindex ipa protocol objects
32395 The commands sent to and results received from agent may contain some
32396 complex data types called @dfn{objects}.
32398 The in-process agent is running on the same machine with @value{GDBN}
32399 or GDBserver, so it doesn't have to handle as much differences between
32400 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
32401 However, there are still some differences of two ends in two processes:
32405 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
32406 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
32408 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
32409 GDBserver is compiled with one, and in-process agent is compiled with
32413 Here are the IPA Protocol Objects:
32417 agent expression object. It represents an agent expression
32418 (@pxref{Agent Expressions}).
32419 @anchor{agent expression object}
32421 tracepoint action object. It represents a tracepoint action
32422 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
32423 memory, static trace data and to evaluate expression.
32424 @anchor{tracepoint action object}
32426 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
32427 @anchor{tracepoint object}
32431 The following table describes important attributes of each IPA protocol
32434 @multitable @columnfractions .30 .20 .50
32435 @headitem Name @tab Size @tab Description
32436 @item @emph{agent expression object} @tab @tab
32437 @item length @tab 4 @tab length of bytes code
32438 @item byte code @tab @var{length} @tab contents of byte code
32439 @item @emph{tracepoint action for collecting memory} @tab @tab
32440 @item 'M' @tab 1 @tab type of tracepoint action
32441 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
32442 address of the lowest byte to collect, otherwise @var{addr} is the offset
32443 of @var{basereg} for memory collecting.
32444 @item len @tab 8 @tab length of memory for collecting
32445 @item basereg @tab 4 @tab the register number containing the starting
32446 memory address for collecting.
32447 @item @emph{tracepoint action for collecting registers} @tab @tab
32448 @item 'R' @tab 1 @tab type of tracepoint action
32449 @item @emph{tracepoint action for collecting static trace data} @tab @tab
32450 @item 'L' @tab 1 @tab type of tracepoint action
32451 @item @emph{tracepoint action for expression evaluation} @tab @tab
32452 @item 'X' @tab 1 @tab type of tracepoint action
32453 @item agent expression @tab length of @tab @ref{agent expression object}
32454 @item @emph{tracepoint object} @tab @tab
32455 @item number @tab 4 @tab number of tracepoint
32456 @item address @tab 8 @tab address of tracepoint inserted on
32457 @item type @tab 4 @tab type of tracepoint
32458 @item enabled @tab 1 @tab enable or disable of tracepoint
32459 @item step_count @tab 8 @tab step
32460 @item pass_count @tab 8 @tab pass
32461 @item numactions @tab 4 @tab number of tracepoint actions
32462 @item hit count @tab 8 @tab hit count
32463 @item trace frame usage @tab 8 @tab trace frame usage
32464 @item compiled_cond @tab 8 @tab compiled condition
32465 @item orig_size @tab 8 @tab orig size
32466 @item condition @tab 4 if condition is NULL otherwise length of
32467 @ref{agent expression object}
32468 @tab zero if condition is NULL, otherwise is
32469 @ref{agent expression object}
32470 @item actions @tab variable
32471 @tab numactions number of @ref{tracepoint action object}
32474 @node IPA Protocol Commands
32475 @subsection IPA Protocol Commands
32476 @cindex ipa protocol commands
32478 The spaces in each command are delimiters to ease reading this commands
32479 specification. They don't exist in real commands.
32483 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
32484 Installs a new fast tracepoint described by @var{tracepoint_object}
32485 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
32486 head of @dfn{jumppad}, which is used to jump to data collection routine
32491 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
32492 @var{target_address} is address of tracepoint in the inferior.
32493 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
32494 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
32495 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
32496 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
32503 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
32504 is about to kill inferiors.
32512 @item probe_marker_at:@var{address}
32513 Asks in-process agent to probe the marker at @var{address}.
32520 @item unprobe_marker_at:@var{address}
32521 Asks in-process agent to unprobe the marker at @var{address}.
32525 @chapter Reporting Bugs in @value{GDBN}
32526 @cindex bugs in @value{GDBN}
32527 @cindex reporting bugs in @value{GDBN}
32529 Your bug reports play an essential role in making @value{GDBN} reliable.
32531 Reporting a bug may help you by bringing a solution to your problem, or it
32532 may not. But in any case the principal function of a bug report is to help
32533 the entire community by making the next version of @value{GDBN} work better. Bug
32534 reports are your contribution to the maintenance of @value{GDBN}.
32536 In order for a bug report to serve its purpose, you must include the
32537 information that enables us to fix the bug.
32540 * Bug Criteria:: Have you found a bug?
32541 * Bug Reporting:: How to report bugs
32545 @section Have You Found a Bug?
32546 @cindex bug criteria
32548 If you are not sure whether you have found a bug, here are some guidelines:
32551 @cindex fatal signal
32552 @cindex debugger crash
32553 @cindex crash of debugger
32555 If the debugger gets a fatal signal, for any input whatever, that is a
32556 @value{GDBN} bug. Reliable debuggers never crash.
32558 @cindex error on valid input
32560 If @value{GDBN} produces an error message for valid input, that is a
32561 bug. (Note that if you're cross debugging, the problem may also be
32562 somewhere in the connection to the target.)
32564 @cindex invalid input
32566 If @value{GDBN} does not produce an error message for invalid input,
32567 that is a bug. However, you should note that your idea of
32568 ``invalid input'' might be our idea of ``an extension'' or ``support
32569 for traditional practice''.
32572 If you are an experienced user of debugging tools, your suggestions
32573 for improvement of @value{GDBN} are welcome in any case.
32576 @node Bug Reporting
32577 @section How to Report Bugs
32578 @cindex bug reports
32579 @cindex @value{GDBN} bugs, reporting
32581 A number of companies and individuals offer support for @sc{gnu} products.
32582 If you obtained @value{GDBN} from a support organization, we recommend you
32583 contact that organization first.
32585 You can find contact information for many support companies and
32586 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
32588 @c should add a web page ref...
32591 @ifset BUGURL_DEFAULT
32592 In any event, we also recommend that you submit bug reports for
32593 @value{GDBN}. The preferred method is to submit them directly using
32594 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
32595 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
32598 @strong{Do not send bug reports to @samp{info-gdb}, or to
32599 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
32600 not want to receive bug reports. Those that do have arranged to receive
32603 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
32604 serves as a repeater. The mailing list and the newsgroup carry exactly
32605 the same messages. Often people think of posting bug reports to the
32606 newsgroup instead of mailing them. This appears to work, but it has one
32607 problem which can be crucial: a newsgroup posting often lacks a mail
32608 path back to the sender. Thus, if we need to ask for more information,
32609 we may be unable to reach you. For this reason, it is better to send
32610 bug reports to the mailing list.
32612 @ifclear BUGURL_DEFAULT
32613 In any event, we also recommend that you submit bug reports for
32614 @value{GDBN} to @value{BUGURL}.
32618 The fundamental principle of reporting bugs usefully is this:
32619 @strong{report all the facts}. If you are not sure whether to state a
32620 fact or leave it out, state it!
32622 Often people omit facts because they think they know what causes the
32623 problem and assume that some details do not matter. Thus, you might
32624 assume that the name of the variable you use in an example does not matter.
32625 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
32626 stray memory reference which happens to fetch from the location where that
32627 name is stored in memory; perhaps, if the name were different, the contents
32628 of that location would fool the debugger into doing the right thing despite
32629 the bug. Play it safe and give a specific, complete example. That is the
32630 easiest thing for you to do, and the most helpful.
32632 Keep in mind that the purpose of a bug report is to enable us to fix the
32633 bug. It may be that the bug has been reported previously, but neither
32634 you nor we can know that unless your bug report is complete and
32637 Sometimes people give a few sketchy facts and ask, ``Does this ring a
32638 bell?'' Those bug reports are useless, and we urge everyone to
32639 @emph{refuse to respond to them} except to chide the sender to report
32642 To enable us to fix the bug, you should include all these things:
32646 The version of @value{GDBN}. @value{GDBN} announces it if you start
32647 with no arguments; you can also print it at any time using @code{show
32650 Without this, we will not know whether there is any point in looking for
32651 the bug in the current version of @value{GDBN}.
32654 The type of machine you are using, and the operating system name and
32658 The details of the @value{GDBN} build-time configuration.
32659 @value{GDBN} shows these details if you invoke it with the
32660 @option{--configuration} command-line option, or if you type
32661 @code{show configuration} at @value{GDBN}'s prompt.
32664 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
32665 ``@value{GCC}--2.8.1''.
32668 What compiler (and its version) was used to compile the program you are
32669 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
32670 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
32671 to get this information; for other compilers, see the documentation for
32675 The command arguments you gave the compiler to compile your example and
32676 observe the bug. For example, did you use @samp{-O}? To guarantee
32677 you will not omit something important, list them all. A copy of the
32678 Makefile (or the output from make) is sufficient.
32680 If we were to try to guess the arguments, we would probably guess wrong
32681 and then we might not encounter the bug.
32684 A complete input script, and all necessary source files, that will
32688 A description of what behavior you observe that you believe is
32689 incorrect. For example, ``It gets a fatal signal.''
32691 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
32692 will certainly notice it. But if the bug is incorrect output, we might
32693 not notice unless it is glaringly wrong. You might as well not give us
32694 a chance to make a mistake.
32696 Even if the problem you experience is a fatal signal, you should still
32697 say so explicitly. Suppose something strange is going on, such as, your
32698 copy of @value{GDBN} is out of synch, or you have encountered a bug in
32699 the C library on your system. (This has happened!) Your copy might
32700 crash and ours would not. If you told us to expect a crash, then when
32701 ours fails to crash, we would know that the bug was not happening for
32702 us. If you had not told us to expect a crash, then we would not be able
32703 to draw any conclusion from our observations.
32706 @cindex recording a session script
32707 To collect all this information, you can use a session recording program
32708 such as @command{script}, which is available on many Unix systems.
32709 Just run your @value{GDBN} session inside @command{script} and then
32710 include the @file{typescript} file with your bug report.
32712 Another way to record a @value{GDBN} session is to run @value{GDBN}
32713 inside Emacs and then save the entire buffer to a file.
32716 If you wish to suggest changes to the @value{GDBN} source, send us context
32717 diffs. If you even discuss something in the @value{GDBN} source, refer to
32718 it by context, not by line number.
32720 The line numbers in our development sources will not match those in your
32721 sources. Your line numbers would convey no useful information to us.
32725 Here are some things that are not necessary:
32729 A description of the envelope of the bug.
32731 Often people who encounter a bug spend a lot of time investigating
32732 which changes to the input file will make the bug go away and which
32733 changes will not affect it.
32735 This is often time consuming and not very useful, because the way we
32736 will find the bug is by running a single example under the debugger
32737 with breakpoints, not by pure deduction from a series of examples.
32738 We recommend that you save your time for something else.
32740 Of course, if you can find a simpler example to report @emph{instead}
32741 of the original one, that is a convenience for us. Errors in the
32742 output will be easier to spot, running under the debugger will take
32743 less time, and so on.
32745 However, simplification is not vital; if you do not want to do this,
32746 report the bug anyway and send us the entire test case you used.
32749 A patch for the bug.
32751 A patch for the bug does help us if it is a good one. But do not omit
32752 the necessary information, such as the test case, on the assumption that
32753 a patch is all we need. We might see problems with your patch and decide
32754 to fix the problem another way, or we might not understand it at all.
32756 Sometimes with a program as complicated as @value{GDBN} it is very hard to
32757 construct an example that will make the program follow a certain path
32758 through the code. If you do not send us the example, we will not be able
32759 to construct one, so we will not be able to verify that the bug is fixed.
32761 And if we cannot understand what bug you are trying to fix, or why your
32762 patch should be an improvement, we will not install it. A test case will
32763 help us to understand.
32766 A guess about what the bug is or what it depends on.
32768 Such guesses are usually wrong. Even we cannot guess right about such
32769 things without first using the debugger to find the facts.
32772 @c The readline documentation is distributed with the readline code
32773 @c and consists of the two following files:
32776 @c Use -I with makeinfo to point to the appropriate directory,
32777 @c environment var TEXINPUTS with TeX.
32778 @ifclear SYSTEM_READLINE
32779 @include rluser.texi
32780 @include hsuser.texi
32784 @appendix In Memoriam
32786 The @value{GDBN} project mourns the loss of the following long-time
32791 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
32792 to Free Software in general. Outside of @value{GDBN}, he was known in
32793 the Amiga world for his series of Fish Disks, and the GeekGadget project.
32795 @item Michael Snyder
32796 Michael was one of the Global Maintainers of the @value{GDBN} project,
32797 with contributions recorded as early as 1996, until 2011. In addition
32798 to his day to day participation, he was a large driving force behind
32799 adding Reverse Debugging to @value{GDBN}.
32802 Beyond their technical contributions to the project, they were also
32803 enjoyable members of the Free Software Community. We will miss them.
32805 @node Formatting Documentation
32806 @appendix Formatting Documentation
32808 @cindex @value{GDBN} reference card
32809 @cindex reference card
32810 The @value{GDBN} 4 release includes an already-formatted reference card, ready
32811 for printing with PostScript or Ghostscript, in the @file{gdb}
32812 subdirectory of the main source directory@footnote{In
32813 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
32814 release.}. If you can use PostScript or Ghostscript with your printer,
32815 you can print the reference card immediately with @file{refcard.ps}.
32817 The release also includes the source for the reference card. You
32818 can format it, using @TeX{}, by typing:
32824 The @value{GDBN} reference card is designed to print in @dfn{landscape}
32825 mode on US ``letter'' size paper;
32826 that is, on a sheet 11 inches wide by 8.5 inches
32827 high. You will need to specify this form of printing as an option to
32828 your @sc{dvi} output program.
32830 @cindex documentation
32832 All the documentation for @value{GDBN} comes as part of the machine-readable
32833 distribution. The documentation is written in Texinfo format, which is
32834 a documentation system that uses a single source file to produce both
32835 on-line information and a printed manual. You can use one of the Info
32836 formatting commands to create the on-line version of the documentation
32837 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
32839 @value{GDBN} includes an already formatted copy of the on-line Info
32840 version of this manual in the @file{gdb} subdirectory. The main Info
32841 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
32842 subordinate files matching @samp{gdb.info*} in the same directory. If
32843 necessary, you can print out these files, or read them with any editor;
32844 but they are easier to read using the @code{info} subsystem in @sc{gnu}
32845 Emacs or the standalone @code{info} program, available as part of the
32846 @sc{gnu} Texinfo distribution.
32848 If you want to format these Info files yourself, you need one of the
32849 Info formatting programs, such as @code{texinfo-format-buffer} or
32852 If you have @code{makeinfo} installed, and are in the top level
32853 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
32854 version @value{GDBVN}), you can make the Info file by typing:
32861 If you want to typeset and print copies of this manual, you need @TeX{},
32862 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
32863 Texinfo definitions file.
32865 @TeX{} is a typesetting program; it does not print files directly, but
32866 produces output files called @sc{dvi} files. To print a typeset
32867 document, you need a program to print @sc{dvi} files. If your system
32868 has @TeX{} installed, chances are it has such a program. The precise
32869 command to use depends on your system; @kbd{lpr -d} is common; another
32870 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
32871 require a file name without any extension or a @samp{.dvi} extension.
32873 @TeX{} also requires a macro definitions file called
32874 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
32875 written in Texinfo format. On its own, @TeX{} cannot either read or
32876 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
32877 and is located in the @file{gdb-@var{version-number}/texinfo}
32880 If you have @TeX{} and a @sc{dvi} printer program installed, you can
32881 typeset and print this manual. First switch to the @file{gdb}
32882 subdirectory of the main source directory (for example, to
32883 @file{gdb-@value{GDBVN}/gdb}) and type:
32889 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
32891 @node Installing GDB
32892 @appendix Installing @value{GDBN}
32893 @cindex installation
32896 * Requirements:: Requirements for building @value{GDBN}
32897 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
32898 * Separate Objdir:: Compiling @value{GDBN} in another directory
32899 * Config Names:: Specifying names for hosts and targets
32900 * Configure Options:: Summary of options for configure
32901 * System-wide configuration:: Having a system-wide init file
32905 @section Requirements for Building @value{GDBN}
32906 @cindex building @value{GDBN}, requirements for
32908 Building @value{GDBN} requires various tools and packages to be available.
32909 Other packages will be used only if they are found.
32911 @heading Tools/Packages Necessary for Building @value{GDBN}
32913 @item ISO C90 compiler
32914 @value{GDBN} is written in ISO C90. It should be buildable with any
32915 working C90 compiler, e.g.@: GCC.
32919 @heading Tools/Packages Optional for Building @value{GDBN}
32923 @value{GDBN} can use the Expat XML parsing library. This library may be
32924 included with your operating system distribution; if it is not, you
32925 can get the latest version from @url{http://expat.sourceforge.net}.
32926 The @file{configure} script will search for this library in several
32927 standard locations; if it is installed in an unusual path, you can
32928 use the @option{--with-libexpat-prefix} option to specify its location.
32934 Remote protocol memory maps (@pxref{Memory Map Format})
32936 Target descriptions (@pxref{Target Descriptions})
32938 Remote shared library lists (@xref{Library List Format},
32939 or alternatively @pxref{Library List Format for SVR4 Targets})
32941 MS-Windows shared libraries (@pxref{Shared Libraries})
32943 Traceframe info (@pxref{Traceframe Info Format})
32945 Branch trace (@pxref{Branch Trace Format})
32949 @cindex compressed debug sections
32950 @value{GDBN} will use the @samp{zlib} library, if available, to read
32951 compressed debug sections. Some linkers, such as GNU gold, are capable
32952 of producing binaries with compressed debug sections. If @value{GDBN}
32953 is compiled with @samp{zlib}, it will be able to read the debug
32954 information in such binaries.
32956 The @samp{zlib} library is likely included with your operating system
32957 distribution; if it is not, you can get the latest version from
32958 @url{http://zlib.net}.
32961 @value{GDBN}'s features related to character sets (@pxref{Character
32962 Sets}) require a functioning @code{iconv} implementation. If you are
32963 on a GNU system, then this is provided by the GNU C Library. Some
32964 other systems also provide a working @code{iconv}.
32966 If @value{GDBN} is using the @code{iconv} program which is installed
32967 in a non-standard place, you will need to tell @value{GDBN} where to find it.
32968 This is done with @option{--with-iconv-bin} which specifies the
32969 directory that contains the @code{iconv} program.
32971 On systems without @code{iconv}, you can install GNU Libiconv. If you
32972 have previously installed Libiconv, you can use the
32973 @option{--with-libiconv-prefix} option to configure.
32975 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
32976 arrange to build Libiconv if a directory named @file{libiconv} appears
32977 in the top-most source directory. If Libiconv is built this way, and
32978 if the operating system does not provide a suitable @code{iconv}
32979 implementation, then the just-built library will automatically be used
32980 by @value{GDBN}. One easy way to set this up is to download GNU
32981 Libiconv, unpack it, and then rename the directory holding the
32982 Libiconv source code to @samp{libiconv}.
32985 @node Running Configure
32986 @section Invoking the @value{GDBN} @file{configure} Script
32987 @cindex configuring @value{GDBN}
32988 @value{GDBN} comes with a @file{configure} script that automates the process
32989 of preparing @value{GDBN} for installation; you can then use @code{make} to
32990 build the @code{gdb} program.
32992 @c irrelevant in info file; it's as current as the code it lives with.
32993 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
32994 look at the @file{README} file in the sources; we may have improved the
32995 installation procedures since publishing this manual.}
32998 The @value{GDBN} distribution includes all the source code you need for
32999 @value{GDBN} in a single directory, whose name is usually composed by
33000 appending the version number to @samp{gdb}.
33002 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
33003 @file{gdb-@value{GDBVN}} directory. That directory contains:
33006 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
33007 script for configuring @value{GDBN} and all its supporting libraries
33009 @item gdb-@value{GDBVN}/gdb
33010 the source specific to @value{GDBN} itself
33012 @item gdb-@value{GDBVN}/bfd
33013 source for the Binary File Descriptor library
33015 @item gdb-@value{GDBVN}/include
33016 @sc{gnu} include files
33018 @item gdb-@value{GDBVN}/libiberty
33019 source for the @samp{-liberty} free software library
33021 @item gdb-@value{GDBVN}/opcodes
33022 source for the library of opcode tables and disassemblers
33024 @item gdb-@value{GDBVN}/readline
33025 source for the @sc{gnu} command-line interface
33027 @item gdb-@value{GDBVN}/glob
33028 source for the @sc{gnu} filename pattern-matching subroutine
33030 @item gdb-@value{GDBVN}/mmalloc
33031 source for the @sc{gnu} memory-mapped malloc package
33034 The simplest way to configure and build @value{GDBN} is to run @file{configure}
33035 from the @file{gdb-@var{version-number}} source directory, which in
33036 this example is the @file{gdb-@value{GDBVN}} directory.
33038 First switch to the @file{gdb-@var{version-number}} source directory
33039 if you are not already in it; then run @file{configure}. Pass the
33040 identifier for the platform on which @value{GDBN} will run as an
33046 cd gdb-@value{GDBVN}
33047 ./configure @var{host}
33052 where @var{host} is an identifier such as @samp{sun4} or
33053 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
33054 (You can often leave off @var{host}; @file{configure} tries to guess the
33055 correct value by examining your system.)
33057 Running @samp{configure @var{host}} and then running @code{make} builds the
33058 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
33059 libraries, then @code{gdb} itself. The configured source files, and the
33060 binaries, are left in the corresponding source directories.
33063 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
33064 system does not recognize this automatically when you run a different
33065 shell, you may need to run @code{sh} on it explicitly:
33068 sh configure @var{host}
33071 If you run @file{configure} from a directory that contains source
33072 directories for multiple libraries or programs, such as the
33073 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
33075 creates configuration files for every directory level underneath (unless
33076 you tell it not to, with the @samp{--norecursion} option).
33078 You should run the @file{configure} script from the top directory in the
33079 source tree, the @file{gdb-@var{version-number}} directory. If you run
33080 @file{configure} from one of the subdirectories, you will configure only
33081 that subdirectory. That is usually not what you want. In particular,
33082 if you run the first @file{configure} from the @file{gdb} subdirectory
33083 of the @file{gdb-@var{version-number}} directory, you will omit the
33084 configuration of @file{bfd}, @file{readline}, and other sibling
33085 directories of the @file{gdb} subdirectory. This leads to build errors
33086 about missing include files such as @file{bfd/bfd.h}.
33088 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
33089 However, you should make sure that the shell on your path (named by
33090 the @samp{SHELL} environment variable) is publicly readable. Remember
33091 that @value{GDBN} uses the shell to start your program---some systems refuse to
33092 let @value{GDBN} debug child processes whose programs are not readable.
33094 @node Separate Objdir
33095 @section Compiling @value{GDBN} in Another Directory
33097 If you want to run @value{GDBN} versions for several host or target machines,
33098 you need a different @code{gdb} compiled for each combination of
33099 host and target. @file{configure} is designed to make this easy by
33100 allowing you to generate each configuration in a separate subdirectory,
33101 rather than in the source directory. If your @code{make} program
33102 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
33103 @code{make} in each of these directories builds the @code{gdb}
33104 program specified there.
33106 To build @code{gdb} in a separate directory, run @file{configure}
33107 with the @samp{--srcdir} option to specify where to find the source.
33108 (You also need to specify a path to find @file{configure}
33109 itself from your working directory. If the path to @file{configure}
33110 would be the same as the argument to @samp{--srcdir}, you can leave out
33111 the @samp{--srcdir} option; it is assumed.)
33113 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
33114 separate directory for a Sun 4 like this:
33118 cd gdb-@value{GDBVN}
33121 ../gdb-@value{GDBVN}/configure sun4
33126 When @file{configure} builds a configuration using a remote source
33127 directory, it creates a tree for the binaries with the same structure
33128 (and using the same names) as the tree under the source directory. In
33129 the example, you'd find the Sun 4 library @file{libiberty.a} in the
33130 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
33131 @file{gdb-sun4/gdb}.
33133 Make sure that your path to the @file{configure} script has just one
33134 instance of @file{gdb} in it. If your path to @file{configure} looks
33135 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
33136 one subdirectory of @value{GDBN}, not the whole package. This leads to
33137 build errors about missing include files such as @file{bfd/bfd.h}.
33139 One popular reason to build several @value{GDBN} configurations in separate
33140 directories is to configure @value{GDBN} for cross-compiling (where
33141 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
33142 programs that run on another machine---the @dfn{target}).
33143 You specify a cross-debugging target by
33144 giving the @samp{--target=@var{target}} option to @file{configure}.
33146 When you run @code{make} to build a program or library, you must run
33147 it in a configured directory---whatever directory you were in when you
33148 called @file{configure} (or one of its subdirectories).
33150 The @code{Makefile} that @file{configure} generates in each source
33151 directory also runs recursively. If you type @code{make} in a source
33152 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
33153 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
33154 will build all the required libraries, and then build GDB.
33156 When you have multiple hosts or targets configured in separate
33157 directories, you can run @code{make} on them in parallel (for example,
33158 if they are NFS-mounted on each of the hosts); they will not interfere
33162 @section Specifying Names for Hosts and Targets
33164 The specifications used for hosts and targets in the @file{configure}
33165 script are based on a three-part naming scheme, but some short predefined
33166 aliases are also supported. The full naming scheme encodes three pieces
33167 of information in the following pattern:
33170 @var{architecture}-@var{vendor}-@var{os}
33173 For example, you can use the alias @code{sun4} as a @var{host} argument,
33174 or as the value for @var{target} in a @code{--target=@var{target}}
33175 option. The equivalent full name is @samp{sparc-sun-sunos4}.
33177 The @file{configure} script accompanying @value{GDBN} does not provide
33178 any query facility to list all supported host and target names or
33179 aliases. @file{configure} calls the Bourne shell script
33180 @code{config.sub} to map abbreviations to full names; you can read the
33181 script, if you wish, or you can use it to test your guesses on
33182 abbreviations---for example:
33185 % sh config.sub i386-linux
33187 % sh config.sub alpha-linux
33188 alpha-unknown-linux-gnu
33189 % sh config.sub hp9k700
33191 % sh config.sub sun4
33192 sparc-sun-sunos4.1.1
33193 % sh config.sub sun3
33194 m68k-sun-sunos4.1.1
33195 % sh config.sub i986v
33196 Invalid configuration `i986v': machine `i986v' not recognized
33200 @code{config.sub} is also distributed in the @value{GDBN} source
33201 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
33203 @node Configure Options
33204 @section @file{configure} Options
33206 Here is a summary of the @file{configure} options and arguments that
33207 are most often useful for building @value{GDBN}. @file{configure} also has
33208 several other options not listed here. @inforef{What Configure
33209 Does,,configure.info}, for a full explanation of @file{configure}.
33212 configure @r{[}--help@r{]}
33213 @r{[}--prefix=@var{dir}@r{]}
33214 @r{[}--exec-prefix=@var{dir}@r{]}
33215 @r{[}--srcdir=@var{dirname}@r{]}
33216 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
33217 @r{[}--target=@var{target}@r{]}
33222 You may introduce options with a single @samp{-} rather than
33223 @samp{--} if you prefer; but you may abbreviate option names if you use
33228 Display a quick summary of how to invoke @file{configure}.
33230 @item --prefix=@var{dir}
33231 Configure the source to install programs and files under directory
33234 @item --exec-prefix=@var{dir}
33235 Configure the source to install programs under directory
33238 @c avoid splitting the warning from the explanation:
33240 @item --srcdir=@var{dirname}
33241 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
33242 @code{make} that implements the @code{VPATH} feature.}@*
33243 Use this option to make configurations in directories separate from the
33244 @value{GDBN} source directories. Among other things, you can use this to
33245 build (or maintain) several configurations simultaneously, in separate
33246 directories. @file{configure} writes configuration-specific files in
33247 the current directory, but arranges for them to use the source in the
33248 directory @var{dirname}. @file{configure} creates directories under
33249 the working directory in parallel to the source directories below
33252 @item --norecursion
33253 Configure only the directory level where @file{configure} is executed; do not
33254 propagate configuration to subdirectories.
33256 @item --target=@var{target}
33257 Configure @value{GDBN} for cross-debugging programs running on the specified
33258 @var{target}. Without this option, @value{GDBN} is configured to debug
33259 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
33261 There is no convenient way to generate a list of all available targets.
33263 @item @var{host} @dots{}
33264 Configure @value{GDBN} to run on the specified @var{host}.
33266 There is no convenient way to generate a list of all available hosts.
33269 There are many other options available as well, but they are generally
33270 needed for special purposes only.
33272 @node System-wide configuration
33273 @section System-wide configuration and settings
33274 @cindex system-wide init file
33276 @value{GDBN} can be configured to have a system-wide init file;
33277 this file will be read and executed at startup (@pxref{Startup, , What
33278 @value{GDBN} does during startup}).
33280 Here is the corresponding configure option:
33283 @item --with-system-gdbinit=@var{file}
33284 Specify that the default location of the system-wide init file is
33288 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
33289 it may be subject to relocation. Two possible cases:
33293 If the default location of this init file contains @file{$prefix},
33294 it will be subject to relocation. Suppose that the configure options
33295 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
33296 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
33297 init file is looked for as @file{$install/etc/gdbinit} instead of
33298 @file{$prefix/etc/gdbinit}.
33301 By contrast, if the default location does not contain the prefix,
33302 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
33303 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
33304 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
33305 wherever @value{GDBN} is installed.
33308 If the configured location of the system-wide init file (as given by the
33309 @option{--with-system-gdbinit} option at configure time) is in the
33310 data-directory (as specified by @option{--with-gdb-datadir} at configure
33311 time) or in one of its subdirectories, then @value{GDBN} will look for the
33312 system-wide init file in the directory specified by the
33313 @option{--data-directory} command-line option.
33314 Note that the system-wide init file is only read once, during @value{GDBN}
33315 initialization. If the data-directory is changed after @value{GDBN} has
33316 started with the @code{set data-directory} command, the file will not be
33320 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
33323 @node System-wide Configuration Scripts
33324 @subsection Installed System-wide Configuration Scripts
33325 @cindex system-wide configuration scripts
33327 The @file{system-gdbinit} directory, located inside the data-directory
33328 (as specified by @option{--with-gdb-datadir} at configure time) contains
33329 a number of scripts which can be used as system-wide init files. To
33330 automatically source those scripts at startup, @value{GDBN} should be
33331 configured with @option{--with-system-gdbinit}. Otherwise, any user
33332 should be able to source them by hand as needed.
33334 The following scripts are currently available:
33337 @item @file{elinos.py}
33339 @cindex ELinOS system-wide configuration script
33340 This script is useful when debugging a program on an ELinOS target.
33341 It takes advantage of the environment variables defined in a standard
33342 ELinOS environment in order to determine the location of the system
33343 shared libraries, and then sets the @samp{solib-absolute-prefix}
33344 and @samp{solib-search-path} variables appropriately.
33346 @item @file{wrs-linux.py}
33347 @pindex wrs-linux.py
33348 @cindex Wind River Linux system-wide configuration script
33349 This script is useful when debugging a program on a target running
33350 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
33351 the host-side sysroot used by the target system.
33355 @node Maintenance Commands
33356 @appendix Maintenance Commands
33357 @cindex maintenance commands
33358 @cindex internal commands
33360 In addition to commands intended for @value{GDBN} users, @value{GDBN}
33361 includes a number of commands intended for @value{GDBN} developers,
33362 that are not documented elsewhere in this manual. These commands are
33363 provided here for reference. (For commands that turn on debugging
33364 messages, see @ref{Debugging Output}.)
33367 @kindex maint agent
33368 @kindex maint agent-eval
33369 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
33370 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
33371 Translate the given @var{expression} into remote agent bytecodes.
33372 This command is useful for debugging the Agent Expression mechanism
33373 (@pxref{Agent Expressions}). The @samp{agent} version produces an
33374 expression useful for data collection, such as by tracepoints, while
33375 @samp{maint agent-eval} produces an expression that evaluates directly
33376 to a result. For instance, a collection expression for @code{globa +
33377 globb} will include bytecodes to record four bytes of memory at each
33378 of the addresses of @code{globa} and @code{globb}, while discarding
33379 the result of the addition, while an evaluation expression will do the
33380 addition and return the sum.
33381 If @code{-at} is given, generate remote agent bytecode for @var{location}.
33382 If not, generate remote agent bytecode for current frame PC address.
33384 @kindex maint agent-printf
33385 @item maint agent-printf @var{format},@var{expr},...
33386 Translate the given format string and list of argument expressions
33387 into remote agent bytecodes and display them as a disassembled list.
33388 This command is useful for debugging the agent version of dynamic
33389 printf (@pxref{Dynamic Printf}).
33391 @kindex maint info breakpoints
33392 @item @anchor{maint info breakpoints}maint info breakpoints
33393 Using the same format as @samp{info breakpoints}, display both the
33394 breakpoints you've set explicitly, and those @value{GDBN} is using for
33395 internal purposes. Internal breakpoints are shown with negative
33396 breakpoint numbers. The type column identifies what kind of breakpoint
33401 Normal, explicitly set breakpoint.
33404 Normal, explicitly set watchpoint.
33407 Internal breakpoint, used to handle correctly stepping through
33408 @code{longjmp} calls.
33410 @item longjmp resume
33411 Internal breakpoint at the target of a @code{longjmp}.
33414 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
33417 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
33420 Shared library events.
33424 @kindex maint info bfds
33425 @item maint info bfds
33426 This prints information about each @code{bfd} object that is known to
33427 @value{GDBN}. @xref{Top, , BFD, bfd, The Binary File Descriptor Library}.
33429 @kindex set displaced-stepping
33430 @kindex show displaced-stepping
33431 @cindex displaced stepping support
33432 @cindex out-of-line single-stepping
33433 @item set displaced-stepping
33434 @itemx show displaced-stepping
33435 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
33436 if the target supports it. Displaced stepping is a way to single-step
33437 over breakpoints without removing them from the inferior, by executing
33438 an out-of-line copy of the instruction that was originally at the
33439 breakpoint location. It is also known as out-of-line single-stepping.
33442 @item set displaced-stepping on
33443 If the target architecture supports it, @value{GDBN} will use
33444 displaced stepping to step over breakpoints.
33446 @item set displaced-stepping off
33447 @value{GDBN} will not use displaced stepping to step over breakpoints,
33448 even if such is supported by the target architecture.
33450 @cindex non-stop mode, and @samp{set displaced-stepping}
33451 @item set displaced-stepping auto
33452 This is the default mode. @value{GDBN} will use displaced stepping
33453 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
33454 architecture supports displaced stepping.
33457 @kindex maint check-psymtabs
33458 @item maint check-psymtabs
33459 Check the consistency of currently expanded psymtabs versus symtabs.
33460 Use this to check, for example, whether a symbol is in one but not the other.
33462 @kindex maint check-symtabs
33463 @item maint check-symtabs
33464 Check the consistency of currently expanded symtabs.
33466 @kindex maint expand-symtabs
33467 @item maint expand-symtabs [@var{regexp}]
33468 Expand symbol tables.
33469 If @var{regexp} is specified, only expand symbol tables for file
33470 names matching @var{regexp}.
33472 @kindex maint set catch-demangler-crashes
33473 @kindex maint show catch-demangler-crashes
33474 @cindex demangler crashes
33475 @item maint set catch-demangler-crashes [on|off]
33476 @itemx maint show catch-demangler-crashes
33477 Control whether @value{GDBN} should attempt to catch crashes in the
33478 symbol name demangler. The default is to attempt to catch crashes.
33479 If enabled, the first time a crash is caught, a core file is created,
33480 the offending symbol is displayed and the user is presented with the
33481 option to terminate the current session.
33483 @kindex maint cplus first_component
33484 @item maint cplus first_component @var{name}
33485 Print the first C@t{++} class/namespace component of @var{name}.
33487 @kindex maint cplus namespace
33488 @item maint cplus namespace
33489 Print the list of possible C@t{++} namespaces.
33491 @kindex maint deprecate
33492 @kindex maint undeprecate
33493 @cindex deprecated commands
33494 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
33495 @itemx maint undeprecate @var{command}
33496 Deprecate or undeprecate the named @var{command}. Deprecated commands
33497 cause @value{GDBN} to issue a warning when you use them. The optional
33498 argument @var{replacement} says which newer command should be used in
33499 favor of the deprecated one; if it is given, @value{GDBN} will mention
33500 the replacement as part of the warning.
33502 @kindex maint dump-me
33503 @item maint dump-me
33504 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
33505 Cause a fatal signal in the debugger and force it to dump its core.
33506 This is supported only on systems which support aborting a program
33507 with the @code{SIGQUIT} signal.
33509 @kindex maint internal-error
33510 @kindex maint internal-warning
33511 @kindex maint demangler-warning
33512 @cindex demangler crashes
33513 @item maint internal-error @r{[}@var{message-text}@r{]}
33514 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
33515 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
33517 Cause @value{GDBN} to call the internal function @code{internal_error},
33518 @code{internal_warning} or @code{demangler_warning} and hence behave
33519 as though an internal problam has been detected. In addition to
33520 reporting the internal problem, these functions give the user the
33521 opportunity to either quit @value{GDBN} or (for @code{internal_error}
33522 and @code{internal_warning}) create a core file of the current
33523 @value{GDBN} session.
33525 These commands take an optional parameter @var{message-text} that is
33526 used as the text of the error or warning message.
33528 Here's an example of using @code{internal-error}:
33531 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
33532 @dots{}/maint.c:121: internal-error: testing, 1, 2
33533 A problem internal to GDB has been detected. Further
33534 debugging may prove unreliable.
33535 Quit this debugging session? (y or n) @kbd{n}
33536 Create a core file? (y or n) @kbd{n}
33540 @cindex @value{GDBN} internal error
33541 @cindex internal errors, control of @value{GDBN} behavior
33542 @cindex demangler crashes
33544 @kindex maint set internal-error
33545 @kindex maint show internal-error
33546 @kindex maint set internal-warning
33547 @kindex maint show internal-warning
33548 @kindex maint set demangler-warning
33549 @kindex maint show demangler-warning
33550 @item maint set internal-error @var{action} [ask|yes|no]
33551 @itemx maint show internal-error @var{action}
33552 @itemx maint set internal-warning @var{action} [ask|yes|no]
33553 @itemx maint show internal-warning @var{action}
33554 @itemx maint set demangler-warning @var{action} [ask|yes|no]
33555 @itemx maint show demangler-warning @var{action}
33556 When @value{GDBN} reports an internal problem (error or warning) it
33557 gives the user the opportunity to both quit @value{GDBN} and create a
33558 core file of the current @value{GDBN} session. These commands let you
33559 override the default behaviour for each particular @var{action},
33560 described in the table below.
33564 You can specify that @value{GDBN} should always (yes) or never (no)
33565 quit. The default is to ask the user what to do.
33568 You can specify that @value{GDBN} should always (yes) or never (no)
33569 create a core file. The default is to ask the user what to do. Note
33570 that there is no @code{corefile} option for @code{demangler-warning}:
33571 demangler warnings always create a core file and this cannot be
33575 @kindex maint packet
33576 @item maint packet @var{text}
33577 If @value{GDBN} is talking to an inferior via the serial protocol,
33578 then this command sends the string @var{text} to the inferior, and
33579 displays the response packet. @value{GDBN} supplies the initial
33580 @samp{$} character, the terminating @samp{#} character, and the
33583 @kindex maint print architecture
33584 @item maint print architecture @r{[}@var{file}@r{]}
33585 Print the entire architecture configuration. The optional argument
33586 @var{file} names the file where the output goes.
33588 @kindex maint print c-tdesc
33589 @item maint print c-tdesc
33590 Print the current target description (@pxref{Target Descriptions}) as
33591 a C source file. The created source file can be used in @value{GDBN}
33592 when an XML parser is not available to parse the description.
33594 @kindex maint print dummy-frames
33595 @item maint print dummy-frames
33596 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
33599 (@value{GDBP}) @kbd{b add}
33601 (@value{GDBP}) @kbd{print add(2,3)}
33602 Breakpoint 2, add (a=2, b=3) at @dots{}
33604 The program being debugged stopped while in a function called from GDB.
33606 (@value{GDBP}) @kbd{maint print dummy-frames}
33607 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
33611 Takes an optional file parameter.
33613 @kindex maint print registers
33614 @kindex maint print raw-registers
33615 @kindex maint print cooked-registers
33616 @kindex maint print register-groups
33617 @kindex maint print remote-registers
33618 @item maint print registers @r{[}@var{file}@r{]}
33619 @itemx maint print raw-registers @r{[}@var{file}@r{]}
33620 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
33621 @itemx maint print register-groups @r{[}@var{file}@r{]}
33622 @itemx maint print remote-registers @r{[}@var{file}@r{]}
33623 Print @value{GDBN}'s internal register data structures.
33625 The command @code{maint print raw-registers} includes the contents of
33626 the raw register cache; the command @code{maint print
33627 cooked-registers} includes the (cooked) value of all registers,
33628 including registers which aren't available on the target nor visible
33629 to user; the command @code{maint print register-groups} includes the
33630 groups that each register is a member of; and the command @code{maint
33631 print remote-registers} includes the remote target's register numbers
33632 and offsets in the `G' packets.
33634 These commands take an optional parameter, a file name to which to
33635 write the information.
33637 @kindex maint print reggroups
33638 @item maint print reggroups @r{[}@var{file}@r{]}
33639 Print @value{GDBN}'s internal register group data structures. The
33640 optional argument @var{file} tells to what file to write the
33643 The register groups info looks like this:
33646 (@value{GDBP}) @kbd{maint print reggroups}
33659 This command forces @value{GDBN} to flush its internal register cache.
33661 @kindex maint print objfiles
33662 @cindex info for known object files
33663 @item maint print objfiles @r{[}@var{regexp}@r{]}
33664 Print a dump of all known object files.
33665 If @var{regexp} is specified, only print object files whose names
33666 match @var{regexp}. For each object file, this command prints its name,
33667 address in memory, and all of its psymtabs and symtabs.
33669 @kindex maint print user-registers
33670 @cindex user registers
33671 @item maint print user-registers
33672 List all currently available @dfn{user registers}. User registers
33673 typically provide alternate names for actual hardware registers. They
33674 include the four ``standard'' registers @code{$fp}, @code{$pc},
33675 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
33676 registers can be used in expressions in the same way as the canonical
33677 register names, but only the latter are listed by the @code{info
33678 registers} and @code{maint print registers} commands.
33680 @kindex maint print section-scripts
33681 @cindex info for known .debug_gdb_scripts-loaded scripts
33682 @item maint print section-scripts [@var{regexp}]
33683 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
33684 If @var{regexp} is specified, only print scripts loaded by object files
33685 matching @var{regexp}.
33686 For each script, this command prints its name as specified in the objfile,
33687 and the full path if known.
33688 @xref{dotdebug_gdb_scripts section}.
33690 @kindex maint print statistics
33691 @cindex bcache statistics
33692 @item maint print statistics
33693 This command prints, for each object file in the program, various data
33694 about that object file followed by the byte cache (@dfn{bcache})
33695 statistics for the object file. The objfile data includes the number
33696 of minimal, partial, full, and stabs symbols, the number of types
33697 defined by the objfile, the number of as yet unexpanded psym tables,
33698 the number of line tables and string tables, and the amount of memory
33699 used by the various tables. The bcache statistics include the counts,
33700 sizes, and counts of duplicates of all and unique objects, max,
33701 average, and median entry size, total memory used and its overhead and
33702 savings, and various measures of the hash table size and chain
33705 @kindex maint print target-stack
33706 @cindex target stack description
33707 @item maint print target-stack
33708 A @dfn{target} is an interface between the debugger and a particular
33709 kind of file or process. Targets can be stacked in @dfn{strata},
33710 so that more than one target can potentially respond to a request.
33711 In particular, memory accesses will walk down the stack of targets
33712 until they find a target that is interested in handling that particular
33715 This command prints a short description of each layer that was pushed on
33716 the @dfn{target stack}, starting from the top layer down to the bottom one.
33718 @kindex maint print type
33719 @cindex type chain of a data type
33720 @item maint print type @var{expr}
33721 Print the type chain for a type specified by @var{expr}. The argument
33722 can be either a type name or a symbol. If it is a symbol, the type of
33723 that symbol is described. The type chain produced by this command is
33724 a recursive definition of the data type as stored in @value{GDBN}'s
33725 data structures, including its flags and contained types.
33727 @kindex maint set dwarf2 always-disassemble
33728 @kindex maint show dwarf2 always-disassemble
33729 @item maint set dwarf2 always-disassemble
33730 @item maint show dwarf2 always-disassemble
33731 Control the behavior of @code{info address} when using DWARF debugging
33734 The default is @code{off}, which means that @value{GDBN} should try to
33735 describe a variable's location in an easily readable format. When
33736 @code{on}, @value{GDBN} will instead display the DWARF location
33737 expression in an assembly-like format. Note that some locations are
33738 too complex for @value{GDBN} to describe simply; in this case you will
33739 always see the disassembly form.
33741 Here is an example of the resulting disassembly:
33744 (gdb) info addr argc
33745 Symbol "argc" is a complex DWARF expression:
33749 For more information on these expressions, see
33750 @uref{http://www.dwarfstd.org/, the DWARF standard}.
33752 @kindex maint set dwarf2 max-cache-age
33753 @kindex maint show dwarf2 max-cache-age
33754 @item maint set dwarf2 max-cache-age
33755 @itemx maint show dwarf2 max-cache-age
33756 Control the DWARF 2 compilation unit cache.
33758 @cindex DWARF 2 compilation units cache
33759 In object files with inter-compilation-unit references, such as those
33760 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
33761 reader needs to frequently refer to previously read compilation units.
33762 This setting controls how long a compilation unit will remain in the
33763 cache if it is not referenced. A higher limit means that cached
33764 compilation units will be stored in memory longer, and more total
33765 memory will be used. Setting it to zero disables caching, which will
33766 slow down @value{GDBN} startup, but reduce memory consumption.
33768 @kindex maint set profile
33769 @kindex maint show profile
33770 @cindex profiling GDB
33771 @item maint set profile
33772 @itemx maint show profile
33773 Control profiling of @value{GDBN}.
33775 Profiling will be disabled until you use the @samp{maint set profile}
33776 command to enable it. When you enable profiling, the system will begin
33777 collecting timing and execution count data; when you disable profiling or
33778 exit @value{GDBN}, the results will be written to a log file. Remember that
33779 if you use profiling, @value{GDBN} will overwrite the profiling log file
33780 (often called @file{gmon.out}). If you have a record of important profiling
33781 data in a @file{gmon.out} file, be sure to move it to a safe location.
33783 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
33784 compiled with the @samp{-pg} compiler option.
33786 @kindex maint set show-debug-regs
33787 @kindex maint show show-debug-regs
33788 @cindex hardware debug registers
33789 @item maint set show-debug-regs
33790 @itemx maint show show-debug-regs
33791 Control whether to show variables that mirror the hardware debug
33792 registers. Use @code{on} to enable, @code{off} to disable. If
33793 enabled, the debug registers values are shown when @value{GDBN} inserts or
33794 removes a hardware breakpoint or watchpoint, and when the inferior
33795 triggers a hardware-assisted breakpoint or watchpoint.
33797 @kindex maint set show-all-tib
33798 @kindex maint show show-all-tib
33799 @item maint set show-all-tib
33800 @itemx maint show show-all-tib
33801 Control whether to show all non zero areas within a 1k block starting
33802 at thread local base, when using the @samp{info w32 thread-information-block}
33805 @kindex maint set target-async
33806 @kindex maint show target-async
33807 @item maint set target-async
33808 @itemx maint show target-async
33809 This controls whether @value{GDBN} targets operate in synchronous or
33810 asynchronous mode (@pxref{Background Execution}). Normally the
33811 default is asynchronous, if it is available; but this can be changed
33812 to more easily debug problems occurring only in synchronous mode.
33814 @kindex maint set per-command
33815 @kindex maint show per-command
33816 @item maint set per-command
33817 @itemx maint show per-command
33818 @cindex resources used by commands
33820 @value{GDBN} can display the resources used by each command.
33821 This is useful in debugging performance problems.
33824 @item maint set per-command space [on|off]
33825 @itemx maint show per-command space
33826 Enable or disable the printing of the memory used by GDB for each command.
33827 If enabled, @value{GDBN} will display how much memory each command
33828 took, following the command's own output.
33829 This can also be requested by invoking @value{GDBN} with the
33830 @option{--statistics} command-line switch (@pxref{Mode Options}).
33832 @item maint set per-command time [on|off]
33833 @itemx maint show per-command time
33834 Enable or disable the printing of the execution time of @value{GDBN}
33836 If enabled, @value{GDBN} will display how much time it
33837 took to execute each command, following the command's own output.
33838 Both CPU time and wallclock time are printed.
33839 Printing both is useful when trying to determine whether the cost is
33840 CPU or, e.g., disk/network latency.
33841 Note that the CPU time printed is for @value{GDBN} only, it does not include
33842 the execution time of the inferior because there's no mechanism currently
33843 to compute how much time was spent by @value{GDBN} and how much time was
33844 spent by the program been debugged.
33845 This can also be requested by invoking @value{GDBN} with the
33846 @option{--statistics} command-line switch (@pxref{Mode Options}).
33848 @item maint set per-command symtab [on|off]
33849 @itemx maint show per-command symtab
33850 Enable or disable the printing of basic symbol table statistics
33852 If enabled, @value{GDBN} will display the following information:
33856 number of symbol tables
33858 number of primary symbol tables
33860 number of blocks in the blockvector
33864 @kindex maint space
33865 @cindex memory used by commands
33866 @item maint space @var{value}
33867 An alias for @code{maint set per-command space}.
33868 A non-zero value enables it, zero disables it.
33871 @cindex time of command execution
33872 @item maint time @var{value}
33873 An alias for @code{maint set per-command time}.
33874 A non-zero value enables it, zero disables it.
33876 @kindex maint translate-address
33877 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
33878 Find the symbol stored at the location specified by the address
33879 @var{addr} and an optional section name @var{section}. If found,
33880 @value{GDBN} prints the name of the closest symbol and an offset from
33881 the symbol's location to the specified address. This is similar to
33882 the @code{info address} command (@pxref{Symbols}), except that this
33883 command also allows to find symbols in other sections.
33885 If section was not specified, the section in which the symbol was found
33886 is also printed. For dynamically linked executables, the name of
33887 executable or shared library containing the symbol is printed as well.
33891 The following command is useful for non-interactive invocations of
33892 @value{GDBN}, such as in the test suite.
33895 @item set watchdog @var{nsec}
33896 @kindex set watchdog
33897 @cindex watchdog timer
33898 @cindex timeout for commands
33899 Set the maximum number of seconds @value{GDBN} will wait for the
33900 target operation to finish. If this time expires, @value{GDBN}
33901 reports and error and the command is aborted.
33903 @item show watchdog
33904 Show the current setting of the target wait timeout.
33907 @node Remote Protocol
33908 @appendix @value{GDBN} Remote Serial Protocol
33913 * Stop Reply Packets::
33914 * General Query Packets::
33915 * Architecture-Specific Protocol Details::
33916 * Tracepoint Packets::
33917 * Host I/O Packets::
33919 * Notification Packets::
33920 * Remote Non-Stop::
33921 * Packet Acknowledgment::
33923 * File-I/O Remote Protocol Extension::
33924 * Library List Format::
33925 * Library List Format for SVR4 Targets::
33926 * Memory Map Format::
33927 * Thread List Format::
33928 * Traceframe Info Format::
33929 * Branch Trace Format::
33935 There may be occasions when you need to know something about the
33936 protocol---for example, if there is only one serial port to your target
33937 machine, you might want your program to do something special if it
33938 recognizes a packet meant for @value{GDBN}.
33940 In the examples below, @samp{->} and @samp{<-} are used to indicate
33941 transmitted and received data, respectively.
33943 @cindex protocol, @value{GDBN} remote serial
33944 @cindex serial protocol, @value{GDBN} remote
33945 @cindex remote serial protocol
33946 All @value{GDBN} commands and responses (other than acknowledgments
33947 and notifications, see @ref{Notification Packets}) are sent as a
33948 @var{packet}. A @var{packet} is introduced with the character
33949 @samp{$}, the actual @var{packet-data}, and the terminating character
33950 @samp{#} followed by a two-digit @var{checksum}:
33953 @code{$}@var{packet-data}@code{#}@var{checksum}
33957 @cindex checksum, for @value{GDBN} remote
33959 The two-digit @var{checksum} is computed as the modulo 256 sum of all
33960 characters between the leading @samp{$} and the trailing @samp{#} (an
33961 eight bit unsigned checksum).
33963 Implementors should note that prior to @value{GDBN} 5.0 the protocol
33964 specification also included an optional two-digit @var{sequence-id}:
33967 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
33970 @cindex sequence-id, for @value{GDBN} remote
33972 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
33973 has never output @var{sequence-id}s. Stubs that handle packets added
33974 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
33976 When either the host or the target machine receives a packet, the first
33977 response expected is an acknowledgment: either @samp{+} (to indicate
33978 the package was received correctly) or @samp{-} (to request
33982 -> @code{$}@var{packet-data}@code{#}@var{checksum}
33987 The @samp{+}/@samp{-} acknowledgments can be disabled
33988 once a connection is established.
33989 @xref{Packet Acknowledgment}, for details.
33991 The host (@value{GDBN}) sends @var{command}s, and the target (the
33992 debugging stub incorporated in your program) sends a @var{response}. In
33993 the case of step and continue @var{command}s, the response is only sent
33994 when the operation has completed, and the target has again stopped all
33995 threads in all attached processes. This is the default all-stop mode
33996 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
33997 execution mode; see @ref{Remote Non-Stop}, for details.
33999 @var{packet-data} consists of a sequence of characters with the
34000 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
34003 @cindex remote protocol, field separator
34004 Fields within the packet should be separated using @samp{,} @samp{;} or
34005 @samp{:}. Except where otherwise noted all numbers are represented in
34006 @sc{hex} with leading zeros suppressed.
34008 Implementors should note that prior to @value{GDBN} 5.0, the character
34009 @samp{:} could not appear as the third character in a packet (as it
34010 would potentially conflict with the @var{sequence-id}).
34012 @cindex remote protocol, binary data
34013 @anchor{Binary Data}
34014 Binary data in most packets is encoded either as two hexadecimal
34015 digits per byte of binary data. This allowed the traditional remote
34016 protocol to work over connections which were only seven-bit clean.
34017 Some packets designed more recently assume an eight-bit clean
34018 connection, and use a more efficient encoding to send and receive
34021 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
34022 as an escape character. Any escaped byte is transmitted as the escape
34023 character followed by the original character XORed with @code{0x20}.
34024 For example, the byte @code{0x7d} would be transmitted as the two
34025 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
34026 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
34027 @samp{@}}) must always be escaped. Responses sent by the stub
34028 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
34029 is not interpreted as the start of a run-length encoded sequence
34032 Response @var{data} can be run-length encoded to save space.
34033 Run-length encoding replaces runs of identical characters with one
34034 instance of the repeated character, followed by a @samp{*} and a
34035 repeat count. The repeat count is itself sent encoded, to avoid
34036 binary characters in @var{data}: a value of @var{n} is sent as
34037 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
34038 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
34039 code 32) for a repeat count of 3. (This is because run-length
34040 encoding starts to win for counts 3 or more.) Thus, for example,
34041 @samp{0* } is a run-length encoding of ``0000'': the space character
34042 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
34045 The printable characters @samp{#} and @samp{$} or with a numeric value
34046 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
34047 seven repeats (@samp{$}) can be expanded using a repeat count of only
34048 five (@samp{"}). For example, @samp{00000000} can be encoded as
34051 The error response returned for some packets includes a two character
34052 error number. That number is not well defined.
34054 @cindex empty response, for unsupported packets
34055 For any @var{command} not supported by the stub, an empty response
34056 (@samp{$#00}) should be returned. That way it is possible to extend the
34057 protocol. A newer @value{GDBN} can tell if a packet is supported based
34060 At a minimum, a stub is required to support the @samp{g} and @samp{G}
34061 commands for register access, and the @samp{m} and @samp{M} commands
34062 for memory access. Stubs that only control single-threaded targets
34063 can implement run control with the @samp{c} (continue), and @samp{s}
34064 (step) commands. Stubs that support multi-threading targets should
34065 support the @samp{vCont} command. All other commands are optional.
34070 The following table provides a complete list of all currently defined
34071 @var{command}s and their corresponding response @var{data}.
34072 @xref{File-I/O Remote Protocol Extension}, for details about the File
34073 I/O extension of the remote protocol.
34075 Each packet's description has a template showing the packet's overall
34076 syntax, followed by an explanation of the packet's meaning. We
34077 include spaces in some of the templates for clarity; these are not
34078 part of the packet's syntax. No @value{GDBN} packet uses spaces to
34079 separate its components. For example, a template like @samp{foo
34080 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
34081 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
34082 @var{baz}. @value{GDBN} does not transmit a space character between the
34083 @samp{foo} and the @var{bar}, or between the @var{bar} and the
34086 @cindex @var{thread-id}, in remote protocol
34087 @anchor{thread-id syntax}
34088 Several packets and replies include a @var{thread-id} field to identify
34089 a thread. Normally these are positive numbers with a target-specific
34090 interpretation, formatted as big-endian hex strings. A @var{thread-id}
34091 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
34094 In addition, the remote protocol supports a multiprocess feature in
34095 which the @var{thread-id} syntax is extended to optionally include both
34096 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
34097 The @var{pid} (process) and @var{tid} (thread) components each have the
34098 format described above: a positive number with target-specific
34099 interpretation formatted as a big-endian hex string, literal @samp{-1}
34100 to indicate all processes or threads (respectively), or @samp{0} to
34101 indicate an arbitrary process or thread. Specifying just a process, as
34102 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
34103 error to specify all processes but a specific thread, such as
34104 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
34105 for those packets and replies explicitly documented to include a process
34106 ID, rather than a @var{thread-id}.
34108 The multiprocess @var{thread-id} syntax extensions are only used if both
34109 @value{GDBN} and the stub report support for the @samp{multiprocess}
34110 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
34113 Note that all packet forms beginning with an upper- or lower-case
34114 letter, other than those described here, are reserved for future use.
34116 Here are the packet descriptions.
34121 @cindex @samp{!} packet
34122 @anchor{extended mode}
34123 Enable extended mode. In extended mode, the remote server is made
34124 persistent. The @samp{R} packet is used to restart the program being
34130 The remote target both supports and has enabled extended mode.
34134 @cindex @samp{?} packet
34136 Indicate the reason the target halted. The reply is the same as for
34137 step and continue. This packet has a special interpretation when the
34138 target is in non-stop mode; see @ref{Remote Non-Stop}.
34141 @xref{Stop Reply Packets}, for the reply specifications.
34143 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
34144 @cindex @samp{A} packet
34145 Initialized @code{argv[]} array passed into program. @var{arglen}
34146 specifies the number of bytes in the hex encoded byte stream
34147 @var{arg}. See @code{gdbserver} for more details.
34152 The arguments were set.
34158 @cindex @samp{b} packet
34159 (Don't use this packet; its behavior is not well-defined.)
34160 Change the serial line speed to @var{baud}.
34162 JTC: @emph{When does the transport layer state change? When it's
34163 received, or after the ACK is transmitted. In either case, there are
34164 problems if the command or the acknowledgment packet is dropped.}
34166 Stan: @emph{If people really wanted to add something like this, and get
34167 it working for the first time, they ought to modify ser-unix.c to send
34168 some kind of out-of-band message to a specially-setup stub and have the
34169 switch happen "in between" packets, so that from remote protocol's point
34170 of view, nothing actually happened.}
34172 @item B @var{addr},@var{mode}
34173 @cindex @samp{B} packet
34174 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
34175 breakpoint at @var{addr}.
34177 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
34178 (@pxref{insert breakpoint or watchpoint packet}).
34180 @cindex @samp{bc} packet
34183 Backward continue. Execute the target system in reverse. No parameter.
34184 @xref{Reverse Execution}, for more information.
34187 @xref{Stop Reply Packets}, for the reply specifications.
34189 @cindex @samp{bs} packet
34192 Backward single step. Execute one instruction in reverse. No parameter.
34193 @xref{Reverse Execution}, for more information.
34196 @xref{Stop Reply Packets}, for the reply specifications.
34198 @item c @r{[}@var{addr}@r{]}
34199 @cindex @samp{c} packet
34200 Continue at @var{addr}, which is the address to resume. If @var{addr}
34201 is omitted, resume at current address.
34203 This packet is deprecated for multi-threading support. @xref{vCont
34207 @xref{Stop Reply Packets}, for the reply specifications.
34209 @item C @var{sig}@r{[};@var{addr}@r{]}
34210 @cindex @samp{C} packet
34211 Continue with signal @var{sig} (hex signal number). If
34212 @samp{;@var{addr}} is omitted, resume at same address.
34214 This packet is deprecated for multi-threading support. @xref{vCont
34218 @xref{Stop Reply Packets}, for the reply specifications.
34221 @cindex @samp{d} packet
34224 Don't use this packet; instead, define a general set packet
34225 (@pxref{General Query Packets}).
34229 @cindex @samp{D} packet
34230 The first form of the packet is used to detach @value{GDBN} from the
34231 remote system. It is sent to the remote target
34232 before @value{GDBN} disconnects via the @code{detach} command.
34234 The second form, including a process ID, is used when multiprocess
34235 protocol extensions are enabled (@pxref{multiprocess extensions}), to
34236 detach only a specific process. The @var{pid} is specified as a
34237 big-endian hex string.
34247 @item F @var{RC},@var{EE},@var{CF};@var{XX}
34248 @cindex @samp{F} packet
34249 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
34250 This is part of the File-I/O protocol extension. @xref{File-I/O
34251 Remote Protocol Extension}, for the specification.
34254 @anchor{read registers packet}
34255 @cindex @samp{g} packet
34256 Read general registers.
34260 @item @var{XX@dots{}}
34261 Each byte of register data is described by two hex digits. The bytes
34262 with the register are transmitted in target byte order. The size of
34263 each register and their position within the @samp{g} packet are
34264 determined by the @value{GDBN} internal gdbarch functions
34265 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
34266 specification of several standard @samp{g} packets is specified below.
34268 When reading registers from a trace frame (@pxref{Analyze Collected
34269 Data,,Using the Collected Data}), the stub may also return a string of
34270 literal @samp{x}'s in place of the register data digits, to indicate
34271 that the corresponding register has not been collected, thus its value
34272 is unavailable. For example, for an architecture with 4 registers of
34273 4 bytes each, the following reply indicates to @value{GDBN} that
34274 registers 0 and 2 have not been collected, while registers 1 and 3
34275 have been collected, and both have zero value:
34279 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
34286 @item G @var{XX@dots{}}
34287 @cindex @samp{G} packet
34288 Write general registers. @xref{read registers packet}, for a
34289 description of the @var{XX@dots{}} data.
34299 @item H @var{op} @var{thread-id}
34300 @cindex @samp{H} packet
34301 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
34302 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
34303 should be @samp{c} for step and continue operations (note that this
34304 is deprecated, supporting the @samp{vCont} command is a better
34305 option), and @samp{g} for other operations. The thread designator
34306 @var{thread-id} has the format and interpretation described in
34307 @ref{thread-id syntax}.
34318 @c 'H': How restrictive (or permissive) is the thread model. If a
34319 @c thread is selected and stopped, are other threads allowed
34320 @c to continue to execute? As I mentioned above, I think the
34321 @c semantics of each command when a thread is selected must be
34322 @c described. For example:
34324 @c 'g': If the stub supports threads and a specific thread is
34325 @c selected, returns the register block from that thread;
34326 @c otherwise returns current registers.
34328 @c 'G' If the stub supports threads and a specific thread is
34329 @c selected, sets the registers of the register block of
34330 @c that thread; otherwise sets current registers.
34332 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
34333 @anchor{cycle step packet}
34334 @cindex @samp{i} packet
34335 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
34336 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
34337 step starting at that address.
34340 @cindex @samp{I} packet
34341 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
34345 @cindex @samp{k} packet
34348 The exact effect of this packet is not specified.
34350 For a bare-metal target, it may power cycle or reset the target
34351 system. For that reason, the @samp{k} packet has no reply.
34353 For a single-process target, it may kill that process if possible.
34355 A multiple-process target may choose to kill just one process, or all
34356 that are under @value{GDBN}'s control. For more precise control, use
34357 the vKill packet (@pxref{vKill packet}).
34359 If the target system immediately closes the connection in response to
34360 @samp{k}, @value{GDBN} does not consider the lack of packet
34361 acknowledgment to be an error, and assumes the kill was successful.
34363 If connected using @kbd{target extended-remote}, and the target does
34364 not close the connection in response to a kill request, @value{GDBN}
34365 probes the target state as if a new connection was opened
34366 (@pxref{? packet}).
34368 @item m @var{addr},@var{length}
34369 @cindex @samp{m} packet
34370 Read @var{length} bytes of memory starting at address @var{addr}.
34371 Note that @var{addr} may not be aligned to any particular boundary.
34373 The stub need not use any particular size or alignment when gathering
34374 data from memory for the response; even if @var{addr} is word-aligned
34375 and @var{length} is a multiple of the word size, the stub is free to
34376 use byte accesses, or not. For this reason, this packet may not be
34377 suitable for accessing memory-mapped I/O devices.
34378 @cindex alignment of remote memory accesses
34379 @cindex size of remote memory accesses
34380 @cindex memory, alignment and size of remote accesses
34384 @item @var{XX@dots{}}
34385 Memory contents; each byte is transmitted as a two-digit hexadecimal
34386 number. The reply may contain fewer bytes than requested if the
34387 server was able to read only part of the region of memory.
34392 @item M @var{addr},@var{length}:@var{XX@dots{}}
34393 @cindex @samp{M} packet
34394 Write @var{length} bytes of memory starting at address @var{addr}.
34395 The data is given by @var{XX@dots{}}; each byte is transmitted as a two-digit
34396 hexadecimal number.
34403 for an error (this includes the case where only part of the data was
34408 @cindex @samp{p} packet
34409 Read the value of register @var{n}; @var{n} is in hex.
34410 @xref{read registers packet}, for a description of how the returned
34411 register value is encoded.
34415 @item @var{XX@dots{}}
34416 the register's value
34420 Indicating an unrecognized @var{query}.
34423 @item P @var{n@dots{}}=@var{r@dots{}}
34424 @anchor{write register packet}
34425 @cindex @samp{P} packet
34426 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
34427 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
34428 digits for each byte in the register (target byte order).
34438 @item q @var{name} @var{params}@dots{}
34439 @itemx Q @var{name} @var{params}@dots{}
34440 @cindex @samp{q} packet
34441 @cindex @samp{Q} packet
34442 General query (@samp{q}) and set (@samp{Q}). These packets are
34443 described fully in @ref{General Query Packets}.
34446 @cindex @samp{r} packet
34447 Reset the entire system.
34449 Don't use this packet; use the @samp{R} packet instead.
34452 @cindex @samp{R} packet
34453 Restart the program being debugged. The @var{XX}, while needed, is ignored.
34454 This packet is only available in extended mode (@pxref{extended mode}).
34456 The @samp{R} packet has no reply.
34458 @item s @r{[}@var{addr}@r{]}
34459 @cindex @samp{s} packet
34460 Single step, resuming at @var{addr}. If
34461 @var{addr} is omitted, resume at same address.
34463 This packet is deprecated for multi-threading support. @xref{vCont
34467 @xref{Stop Reply Packets}, for the reply specifications.
34469 @item S @var{sig}@r{[};@var{addr}@r{]}
34470 @anchor{step with signal packet}
34471 @cindex @samp{S} packet
34472 Step with signal. This is analogous to the @samp{C} packet, but
34473 requests a single-step, rather than a normal resumption of execution.
34475 This packet is deprecated for multi-threading support. @xref{vCont
34479 @xref{Stop Reply Packets}, for the reply specifications.
34481 @item t @var{addr}:@var{PP},@var{MM}
34482 @cindex @samp{t} packet
34483 Search backwards starting at address @var{addr} for a match with pattern
34484 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
34485 There must be at least 3 digits in @var{addr}.
34487 @item T @var{thread-id}
34488 @cindex @samp{T} packet
34489 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
34494 thread is still alive
34500 Packets starting with @samp{v} are identified by a multi-letter name,
34501 up to the first @samp{;} or @samp{?} (or the end of the packet).
34503 @item vAttach;@var{pid}
34504 @cindex @samp{vAttach} packet
34505 Attach to a new process with the specified process ID @var{pid}.
34506 The process ID is a
34507 hexadecimal integer identifying the process. In all-stop mode, all
34508 threads in the attached process are stopped; in non-stop mode, it may be
34509 attached without being stopped if that is supported by the target.
34511 @c In non-stop mode, on a successful vAttach, the stub should set the
34512 @c current thread to a thread of the newly-attached process. After
34513 @c attaching, GDB queries for the attached process's thread ID with qC.
34514 @c Also note that, from a user perspective, whether or not the
34515 @c target is stopped on attach in non-stop mode depends on whether you
34516 @c use the foreground or background version of the attach command, not
34517 @c on what vAttach does; GDB does the right thing with respect to either
34518 @c stopping or restarting threads.
34520 This packet is only available in extended mode (@pxref{extended mode}).
34526 @item @r{Any stop packet}
34527 for success in all-stop mode (@pxref{Stop Reply Packets})
34529 for success in non-stop mode (@pxref{Remote Non-Stop})
34532 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
34533 @cindex @samp{vCont} packet
34534 @anchor{vCont packet}
34535 Resume the inferior, specifying different actions for each thread.
34536 If an action is specified with no @var{thread-id}, then it is applied to any
34537 threads that don't have a specific action specified; if no default action is
34538 specified then other threads should remain stopped in all-stop mode and
34539 in their current state in non-stop mode.
34540 Specifying multiple
34541 default actions is an error; specifying no actions is also an error.
34542 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
34544 Currently supported actions are:
34550 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
34554 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
34557 @item r @var{start},@var{end}
34558 Step once, and then keep stepping as long as the thread stops at
34559 addresses between @var{start} (inclusive) and @var{end} (exclusive).
34560 The remote stub reports a stop reply when either the thread goes out
34561 of the range or is stopped due to an unrelated reason, such as hitting
34562 a breakpoint. @xref{range stepping}.
34564 If the range is empty (@var{start} == @var{end}), then the action
34565 becomes equivalent to the @samp{s} action. In other words,
34566 single-step once, and report the stop (even if the stepped instruction
34567 jumps to @var{start}).
34569 (A stop reply may be sent at any point even if the PC is still within
34570 the stepping range; for example, it is valid to implement this packet
34571 in a degenerate way as a single instruction step operation.)
34575 The optional argument @var{addr} normally associated with the
34576 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
34577 not supported in @samp{vCont}.
34579 The @samp{t} action is only relevant in non-stop mode
34580 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
34581 A stop reply should be generated for any affected thread not already stopped.
34582 When a thread is stopped by means of a @samp{t} action,
34583 the corresponding stop reply should indicate that the thread has stopped with
34584 signal @samp{0}, regardless of whether the target uses some other signal
34585 as an implementation detail.
34587 The stub must support @samp{vCont} if it reports support for
34588 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
34589 this case @samp{vCont} actions can be specified to apply to all threads
34590 in a process by using the @samp{p@var{pid}.-1} form of the
34594 @xref{Stop Reply Packets}, for the reply specifications.
34597 @cindex @samp{vCont?} packet
34598 Request a list of actions supported by the @samp{vCont} packet.
34602 @item vCont@r{[};@var{action}@dots{}@r{]}
34603 The @samp{vCont} packet is supported. Each @var{action} is a supported
34604 command in the @samp{vCont} packet.
34606 The @samp{vCont} packet is not supported.
34609 @item vFile:@var{operation}:@var{parameter}@dots{}
34610 @cindex @samp{vFile} packet
34611 Perform a file operation on the target system. For details,
34612 see @ref{Host I/O Packets}.
34614 @item vFlashErase:@var{addr},@var{length}
34615 @cindex @samp{vFlashErase} packet
34616 Direct the stub to erase @var{length} bytes of flash starting at
34617 @var{addr}. The region may enclose any number of flash blocks, but
34618 its start and end must fall on block boundaries, as indicated by the
34619 flash block size appearing in the memory map (@pxref{Memory Map
34620 Format}). @value{GDBN} groups flash memory programming operations
34621 together, and sends a @samp{vFlashDone} request after each group; the
34622 stub is allowed to delay erase operation until the @samp{vFlashDone}
34623 packet is received.
34633 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
34634 @cindex @samp{vFlashWrite} packet
34635 Direct the stub to write data to flash address @var{addr}. The data
34636 is passed in binary form using the same encoding as for the @samp{X}
34637 packet (@pxref{Binary Data}). The memory ranges specified by
34638 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
34639 not overlap, and must appear in order of increasing addresses
34640 (although @samp{vFlashErase} packets for higher addresses may already
34641 have been received; the ordering is guaranteed only between
34642 @samp{vFlashWrite} packets). If a packet writes to an address that was
34643 neither erased by a preceding @samp{vFlashErase} packet nor by some other
34644 target-specific method, the results are unpredictable.
34652 for vFlashWrite addressing non-flash memory
34658 @cindex @samp{vFlashDone} packet
34659 Indicate to the stub that flash programming operation is finished.
34660 The stub is permitted to delay or batch the effects of a group of
34661 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
34662 @samp{vFlashDone} packet is received. The contents of the affected
34663 regions of flash memory are unpredictable until the @samp{vFlashDone}
34664 request is completed.
34666 @item vKill;@var{pid}
34667 @cindex @samp{vKill} packet
34668 @anchor{vKill packet}
34669 Kill the process with the specified process ID @var{pid}, which is a
34670 hexadecimal integer identifying the process. This packet is used in
34671 preference to @samp{k} when multiprocess protocol extensions are
34672 supported; see @ref{multiprocess extensions}.
34682 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
34683 @cindex @samp{vRun} packet
34684 Run the program @var{filename}, passing it each @var{argument} on its
34685 command line. The file and arguments are hex-encoded strings. If
34686 @var{filename} is an empty string, the stub may use a default program
34687 (e.g.@: the last program run). The program is created in the stopped
34690 @c FIXME: What about non-stop mode?
34692 This packet is only available in extended mode (@pxref{extended mode}).
34698 @item @r{Any stop packet}
34699 for success (@pxref{Stop Reply Packets})
34703 @cindex @samp{vStopped} packet
34704 @xref{Notification Packets}.
34706 @item X @var{addr},@var{length}:@var{XX@dots{}}
34708 @cindex @samp{X} packet
34709 Write data to memory, where the data is transmitted in binary.
34710 Memory is specified by its address @var{addr} and number of bytes @var{length};
34711 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
34721 @item z @var{type},@var{addr},@var{kind}
34722 @itemx Z @var{type},@var{addr},@var{kind}
34723 @anchor{insert breakpoint or watchpoint packet}
34724 @cindex @samp{z} packet
34725 @cindex @samp{Z} packets
34726 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
34727 watchpoint starting at address @var{address} of kind @var{kind}.
34729 Each breakpoint and watchpoint packet @var{type} is documented
34732 @emph{Implementation notes: A remote target shall return an empty string
34733 for an unrecognized breakpoint or watchpoint packet @var{type}. A
34734 remote target shall support either both or neither of a given
34735 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
34736 avoid potential problems with duplicate packets, the operations should
34737 be implemented in an idempotent way.}
34739 @item z0,@var{addr},@var{kind}
34740 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
34741 @cindex @samp{z0} packet
34742 @cindex @samp{Z0} packet
34743 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
34744 @var{addr} of type @var{kind}.
34746 A memory breakpoint is implemented by replacing the instruction at
34747 @var{addr} with a software breakpoint or trap instruction. The
34748 @var{kind} is target-specific and typically indicates the size of
34749 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
34750 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
34751 architectures have additional meanings for @var{kind};
34752 @var{cond_list} is an optional list of conditional expressions in bytecode
34753 form that should be evaluated on the target's side. These are the
34754 conditions that should be taken into consideration when deciding if
34755 the breakpoint trigger should be reported back to @var{GDBN}.
34757 The @var{cond_list} parameter is comprised of a series of expressions,
34758 concatenated without separators. Each expression has the following form:
34762 @item X @var{len},@var{expr}
34763 @var{len} is the length of the bytecode expression and @var{expr} is the
34764 actual conditional expression in bytecode form.
34768 The optional @var{cmd_list} parameter introduces commands that may be
34769 run on the target, rather than being reported back to @value{GDBN}.
34770 The parameter starts with a numeric flag @var{persist}; if the flag is
34771 nonzero, then the breakpoint may remain active and the commands
34772 continue to be run even when @value{GDBN} disconnects from the target.
34773 Following this flag is a series of expressions concatenated with no
34774 separators. Each expression has the following form:
34778 @item X @var{len},@var{expr}
34779 @var{len} is the length of the bytecode expression and @var{expr} is the
34780 actual conditional expression in bytecode form.
34784 see @ref{Architecture-Specific Protocol Details}.
34786 @emph{Implementation note: It is possible for a target to copy or move
34787 code that contains memory breakpoints (e.g., when implementing
34788 overlays). The behavior of this packet, in the presence of such a
34789 target, is not defined.}
34801 @item z1,@var{addr},@var{kind}
34802 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
34803 @cindex @samp{z1} packet
34804 @cindex @samp{Z1} packet
34805 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
34806 address @var{addr}.
34808 A hardware breakpoint is implemented using a mechanism that is not
34809 dependant on being able to modify the target's memory. The @var{kind}
34810 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
34812 @emph{Implementation note: A hardware breakpoint is not affected by code
34825 @item z2,@var{addr},@var{kind}
34826 @itemx Z2,@var{addr},@var{kind}
34827 @cindex @samp{z2} packet
34828 @cindex @samp{Z2} packet
34829 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
34830 The number of bytes to watch is specified by @var{kind}.
34842 @item z3,@var{addr},@var{kind}
34843 @itemx Z3,@var{addr},@var{kind}
34844 @cindex @samp{z3} packet
34845 @cindex @samp{Z3} packet
34846 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
34847 The number of bytes to watch is specified by @var{kind}.
34859 @item z4,@var{addr},@var{kind}
34860 @itemx Z4,@var{addr},@var{kind}
34861 @cindex @samp{z4} packet
34862 @cindex @samp{Z4} packet
34863 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
34864 The number of bytes to watch is specified by @var{kind}.
34878 @node Stop Reply Packets
34879 @section Stop Reply Packets
34880 @cindex stop reply packets
34882 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
34883 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
34884 receive any of the below as a reply. Except for @samp{?}
34885 and @samp{vStopped}, that reply is only returned
34886 when the target halts. In the below the exact meaning of @dfn{signal
34887 number} is defined by the header @file{include/gdb/signals.h} in the
34888 @value{GDBN} source code.
34890 As in the description of request packets, we include spaces in the
34891 reply templates for clarity; these are not part of the reply packet's
34892 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
34898 The program received signal number @var{AA} (a two-digit hexadecimal
34899 number). This is equivalent to a @samp{T} response with no
34900 @var{n}:@var{r} pairs.
34902 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
34903 @cindex @samp{T} packet reply
34904 The program received signal number @var{AA} (a two-digit hexadecimal
34905 number). This is equivalent to an @samp{S} response, except that the
34906 @samp{@var{n}:@var{r}} pairs can carry values of important registers
34907 and other information directly in the stop reply packet, reducing
34908 round-trip latency. Single-step and breakpoint traps are reported
34909 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
34913 If @var{n} is a hexadecimal number, it is a register number, and the
34914 corresponding @var{r} gives that register's value. The data @var{r} is a
34915 series of bytes in target byte order, with each byte given by a
34916 two-digit hex number.
34919 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
34920 the stopped thread, as specified in @ref{thread-id syntax}.
34923 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
34924 the core on which the stop event was detected.
34927 If @var{n} is a recognized @dfn{stop reason}, it describes a more
34928 specific event that stopped the target. The currently defined stop
34929 reasons are listed below. The @var{aa} should be @samp{05}, the trap
34930 signal. At most one stop reason should be present.
34933 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
34934 and go on to the next; this allows us to extend the protocol in the
34938 The currently defined stop reasons are:
34944 The packet indicates a watchpoint hit, and @var{r} is the data address, in
34947 @cindex shared library events, remote reply
34949 The packet indicates that the loaded libraries have changed.
34950 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
34951 list of loaded libraries. The @var{r} part is ignored.
34953 @cindex replay log events, remote reply
34955 The packet indicates that the target cannot continue replaying
34956 logged execution events, because it has reached the end (or the
34957 beginning when executing backward) of the log. The value of @var{r}
34958 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
34959 for more information.
34963 @itemx W @var{AA} ; process:@var{pid}
34964 The process exited, and @var{AA} is the exit status. This is only
34965 applicable to certain targets.
34967 The second form of the response, including the process ID of the exited
34968 process, can be used only when @value{GDBN} has reported support for
34969 multiprocess protocol extensions; see @ref{multiprocess extensions}.
34970 The @var{pid} is formatted as a big-endian hex string.
34973 @itemx X @var{AA} ; process:@var{pid}
34974 The process terminated with signal @var{AA}.
34976 The second form of the response, including the process ID of the
34977 terminated process, can be used only when @value{GDBN} has reported
34978 support for multiprocess protocol extensions; see @ref{multiprocess
34979 extensions}. The @var{pid} is formatted as a big-endian hex string.
34981 @item O @var{XX}@dots{}
34982 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
34983 written as the program's console output. This can happen at any time
34984 while the program is running and the debugger should continue to wait
34985 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
34987 @item F @var{call-id},@var{parameter}@dots{}
34988 @var{call-id} is the identifier which says which host system call should
34989 be called. This is just the name of the function. Translation into the
34990 correct system call is only applicable as it's defined in @value{GDBN}.
34991 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
34994 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
34995 this very system call.
34997 The target replies with this packet when it expects @value{GDBN} to
34998 call a host system call on behalf of the target. @value{GDBN} replies
34999 with an appropriate @samp{F} packet and keeps up waiting for the next
35000 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
35001 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
35002 Protocol Extension}, for more details.
35006 @node General Query Packets
35007 @section General Query Packets
35008 @cindex remote query requests
35010 Packets starting with @samp{q} are @dfn{general query packets};
35011 packets starting with @samp{Q} are @dfn{general set packets}. General
35012 query and set packets are a semi-unified form for retrieving and
35013 sending information to and from the stub.
35015 The initial letter of a query or set packet is followed by a name
35016 indicating what sort of thing the packet applies to. For example,
35017 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
35018 definitions with the stub. These packet names follow some
35023 The name must not contain commas, colons or semicolons.
35025 Most @value{GDBN} query and set packets have a leading upper case
35028 The names of custom vendor packets should use a company prefix, in
35029 lower case, followed by a period. For example, packets designed at
35030 the Acme Corporation might begin with @samp{qacme.foo} (for querying
35031 foos) or @samp{Qacme.bar} (for setting bars).
35034 The name of a query or set packet should be separated from any
35035 parameters by a @samp{:}; the parameters themselves should be
35036 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
35037 full packet name, and check for a separator or the end of the packet,
35038 in case two packet names share a common prefix. New packets should not begin
35039 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
35040 packets predate these conventions, and have arguments without any terminator
35041 for the packet name; we suspect they are in widespread use in places that
35042 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
35043 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
35046 Like the descriptions of the other packets, each description here
35047 has a template showing the packet's overall syntax, followed by an
35048 explanation of the packet's meaning. We include spaces in some of the
35049 templates for clarity; these are not part of the packet's syntax. No
35050 @value{GDBN} packet uses spaces to separate its components.
35052 Here are the currently defined query and set packets:
35058 Turn on or off the agent as a helper to perform some debugging operations
35059 delegated from @value{GDBN} (@pxref{Control Agent}).
35061 @item QAllow:@var{op}:@var{val}@dots{}
35062 @cindex @samp{QAllow} packet
35063 Specify which operations @value{GDBN} expects to request of the
35064 target, as a semicolon-separated list of operation name and value
35065 pairs. Possible values for @var{op} include @samp{WriteReg},
35066 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
35067 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
35068 indicating that @value{GDBN} will not request the operation, or 1,
35069 indicating that it may. (The target can then use this to set up its
35070 own internals optimally, for instance if the debugger never expects to
35071 insert breakpoints, it may not need to install its own trap handler.)
35074 @cindex current thread, remote request
35075 @cindex @samp{qC} packet
35076 Return the current thread ID.
35080 @item QC @var{thread-id}
35081 Where @var{thread-id} is a thread ID as documented in
35082 @ref{thread-id syntax}.
35083 @item @r{(anything else)}
35084 Any other reply implies the old thread ID.
35087 @item qCRC:@var{addr},@var{length}
35088 @cindex CRC of memory block, remote request
35089 @cindex @samp{qCRC} packet
35090 @anchor{qCRC packet}
35091 Compute the CRC checksum of a block of memory using CRC-32 defined in
35092 IEEE 802.3. The CRC is computed byte at a time, taking the most
35093 significant bit of each byte first. The initial pattern code
35094 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
35096 @emph{Note:} This is the same CRC used in validating separate debug
35097 files (@pxref{Separate Debug Files, , Debugging Information in Separate
35098 Files}). However the algorithm is slightly different. When validating
35099 separate debug files, the CRC is computed taking the @emph{least}
35100 significant bit of each byte first, and the final result is inverted to
35101 detect trailing zeros.
35106 An error (such as memory fault)
35107 @item C @var{crc32}
35108 The specified memory region's checksum is @var{crc32}.
35111 @item QDisableRandomization:@var{value}
35112 @cindex disable address space randomization, remote request
35113 @cindex @samp{QDisableRandomization} packet
35114 Some target operating systems will randomize the virtual address space
35115 of the inferior process as a security feature, but provide a feature
35116 to disable such randomization, e.g.@: to allow for a more deterministic
35117 debugging experience. On such systems, this packet with a @var{value}
35118 of 1 directs the target to disable address space randomization for
35119 processes subsequently started via @samp{vRun} packets, while a packet
35120 with a @var{value} of 0 tells the target to enable address space
35123 This packet is only available in extended mode (@pxref{extended mode}).
35128 The request succeeded.
35131 An error occurred. The error number @var{nn} is given as hex digits.
35134 An empty reply indicates that @samp{QDisableRandomization} is not supported
35138 This packet is not probed by default; the remote stub must request it,
35139 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35140 This should only be done on targets that actually support disabling
35141 address space randomization.
35144 @itemx qsThreadInfo
35145 @cindex list active threads, remote request
35146 @cindex @samp{qfThreadInfo} packet
35147 @cindex @samp{qsThreadInfo} packet
35148 Obtain a list of all active thread IDs from the target (OS). Since there
35149 may be too many active threads to fit into one reply packet, this query
35150 works iteratively: it may require more than one query/reply sequence to
35151 obtain the entire list of threads. The first query of the sequence will
35152 be the @samp{qfThreadInfo} query; subsequent queries in the
35153 sequence will be the @samp{qsThreadInfo} query.
35155 NOTE: This packet replaces the @samp{qL} query (see below).
35159 @item m @var{thread-id}
35161 @item m @var{thread-id},@var{thread-id}@dots{}
35162 a comma-separated list of thread IDs
35164 (lower case letter @samp{L}) denotes end of list.
35167 In response to each query, the target will reply with a list of one or
35168 more thread IDs, separated by commas.
35169 @value{GDBN} will respond to each reply with a request for more thread
35170 ids (using the @samp{qs} form of the query), until the target responds
35171 with @samp{l} (lower-case ell, for @dfn{last}).
35172 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
35175 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
35176 initial connection with the remote target, and the very first thread ID
35177 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
35178 message. Therefore, the stub should ensure that the first thread ID in
35179 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
35181 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
35182 @cindex get thread-local storage address, remote request
35183 @cindex @samp{qGetTLSAddr} packet
35184 Fetch the address associated with thread local storage specified
35185 by @var{thread-id}, @var{offset}, and @var{lm}.
35187 @var{thread-id} is the thread ID associated with the
35188 thread for which to fetch the TLS address. @xref{thread-id syntax}.
35190 @var{offset} is the (big endian, hex encoded) offset associated with the
35191 thread local variable. (This offset is obtained from the debug
35192 information associated with the variable.)
35194 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
35195 load module associated with the thread local storage. For example,
35196 a @sc{gnu}/Linux system will pass the link map address of the shared
35197 object associated with the thread local storage under consideration.
35198 Other operating environments may choose to represent the load module
35199 differently, so the precise meaning of this parameter will vary.
35203 @item @var{XX}@dots{}
35204 Hex encoded (big endian) bytes representing the address of the thread
35205 local storage requested.
35208 An error occurred. The error number @var{nn} is given as hex digits.
35211 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
35214 @item qGetTIBAddr:@var{thread-id}
35215 @cindex get thread information block address
35216 @cindex @samp{qGetTIBAddr} packet
35217 Fetch address of the Windows OS specific Thread Information Block.
35219 @var{thread-id} is the thread ID associated with the thread.
35223 @item @var{XX}@dots{}
35224 Hex encoded (big endian) bytes representing the linear address of the
35225 thread information block.
35228 An error occured. This means that either the thread was not found, or the
35229 address could not be retrieved.
35232 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
35235 @item qL @var{startflag} @var{threadcount} @var{nextthread}
35236 Obtain thread information from RTOS. Where: @var{startflag} (one hex
35237 digit) is one to indicate the first query and zero to indicate a
35238 subsequent query; @var{threadcount} (two hex digits) is the maximum
35239 number of threads the response packet can contain; and @var{nextthread}
35240 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
35241 returned in the response as @var{argthread}.
35243 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
35247 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
35248 Where: @var{count} (two hex digits) is the number of threads being
35249 returned; @var{done} (one hex digit) is zero to indicate more threads
35250 and one indicates no further threads; @var{argthreadid} (eight hex
35251 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
35252 is a sequence of thread IDs, @var{threadid} (eight hex
35253 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
35257 @cindex section offsets, remote request
35258 @cindex @samp{qOffsets} packet
35259 Get section offsets that the target used when relocating the downloaded
35264 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
35265 Relocate the @code{Text} section by @var{xxx} from its original address.
35266 Relocate the @code{Data} section by @var{yyy} from its original address.
35267 If the object file format provides segment information (e.g.@: @sc{elf}
35268 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
35269 segments by the supplied offsets.
35271 @emph{Note: while a @code{Bss} offset may be included in the response,
35272 @value{GDBN} ignores this and instead applies the @code{Data} offset
35273 to the @code{Bss} section.}
35275 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
35276 Relocate the first segment of the object file, which conventionally
35277 contains program code, to a starting address of @var{xxx}. If
35278 @samp{DataSeg} is specified, relocate the second segment, which
35279 conventionally contains modifiable data, to a starting address of
35280 @var{yyy}. @value{GDBN} will report an error if the object file
35281 does not contain segment information, or does not contain at least
35282 as many segments as mentioned in the reply. Extra segments are
35283 kept at fixed offsets relative to the last relocated segment.
35286 @item qP @var{mode} @var{thread-id}
35287 @cindex thread information, remote request
35288 @cindex @samp{qP} packet
35289 Returns information on @var{thread-id}. Where: @var{mode} is a hex
35290 encoded 32 bit mode; @var{thread-id} is a thread ID
35291 (@pxref{thread-id syntax}).
35293 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
35296 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
35300 @cindex non-stop mode, remote request
35301 @cindex @samp{QNonStop} packet
35303 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
35304 @xref{Remote Non-Stop}, for more information.
35309 The request succeeded.
35312 An error occurred. The error number @var{nn} is given as hex digits.
35315 An empty reply indicates that @samp{QNonStop} is not supported by
35319 This packet is not probed by default; the remote stub must request it,
35320 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35321 Use of this packet is controlled by the @code{set non-stop} command;
35322 @pxref{Non-Stop Mode}.
35324 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
35325 @cindex pass signals to inferior, remote request
35326 @cindex @samp{QPassSignals} packet
35327 @anchor{QPassSignals}
35328 Each listed @var{signal} should be passed directly to the inferior process.
35329 Signals are numbered identically to continue packets and stop replies
35330 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
35331 strictly greater than the previous item. These signals do not need to stop
35332 the inferior, or be reported to @value{GDBN}. All other signals should be
35333 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
35334 combine; any earlier @samp{QPassSignals} list is completely replaced by the
35335 new list. This packet improves performance when using @samp{handle
35336 @var{signal} nostop noprint pass}.
35341 The request succeeded.
35344 An error occurred. The error number @var{nn} is given as hex digits.
35347 An empty reply indicates that @samp{QPassSignals} is not supported by
35351 Use of this packet is controlled by the @code{set remote pass-signals}
35352 command (@pxref{Remote Configuration, set remote pass-signals}).
35353 This packet is not probed by default; the remote stub must request it,
35354 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35356 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
35357 @cindex signals the inferior may see, remote request
35358 @cindex @samp{QProgramSignals} packet
35359 @anchor{QProgramSignals}
35360 Each listed @var{signal} may be delivered to the inferior process.
35361 Others should be silently discarded.
35363 In some cases, the remote stub may need to decide whether to deliver a
35364 signal to the program or not without @value{GDBN} involvement. One
35365 example of that is while detaching --- the program's threads may have
35366 stopped for signals that haven't yet had a chance of being reported to
35367 @value{GDBN}, and so the remote stub can use the signal list specified
35368 by this packet to know whether to deliver or ignore those pending
35371 This does not influence whether to deliver a signal as requested by a
35372 resumption packet (@pxref{vCont packet}).
35374 Signals are numbered identically to continue packets and stop replies
35375 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
35376 strictly greater than the previous item. Multiple
35377 @samp{QProgramSignals} packets do not combine; any earlier
35378 @samp{QProgramSignals} list is completely replaced by the new list.
35383 The request succeeded.
35386 An error occurred. The error number @var{nn} is given as hex digits.
35389 An empty reply indicates that @samp{QProgramSignals} is not supported
35393 Use of this packet is controlled by the @code{set remote program-signals}
35394 command (@pxref{Remote Configuration, set remote program-signals}).
35395 This packet is not probed by default; the remote stub must request it,
35396 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35398 @item qRcmd,@var{command}
35399 @cindex execute remote command, remote request
35400 @cindex @samp{qRcmd} packet
35401 @var{command} (hex encoded) is passed to the local interpreter for
35402 execution. Invalid commands should be reported using the output
35403 string. Before the final result packet, the target may also respond
35404 with a number of intermediate @samp{O@var{output}} console output
35405 packets. @emph{Implementors should note that providing access to a
35406 stubs's interpreter may have security implications}.
35411 A command response with no output.
35413 A command response with the hex encoded output string @var{OUTPUT}.
35415 Indicate a badly formed request.
35417 An empty reply indicates that @samp{qRcmd} is not recognized.
35420 (Note that the @code{qRcmd} packet's name is separated from the
35421 command by a @samp{,}, not a @samp{:}, contrary to the naming
35422 conventions above. Please don't use this packet as a model for new
35425 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
35426 @cindex searching memory, in remote debugging
35428 @cindex @samp{qSearch:memory} packet
35430 @cindex @samp{qSearch memory} packet
35431 @anchor{qSearch memory}
35432 Search @var{length} bytes at @var{address} for @var{search-pattern}.
35433 Both @var{address} and @var{length} are encoded in hex;
35434 @var{search-pattern} is a sequence of bytes, also hex encoded.
35439 The pattern was not found.
35441 The pattern was found at @var{address}.
35443 A badly formed request or an error was encountered while searching memory.
35445 An empty reply indicates that @samp{qSearch:memory} is not recognized.
35448 @item QStartNoAckMode
35449 @cindex @samp{QStartNoAckMode} packet
35450 @anchor{QStartNoAckMode}
35451 Request that the remote stub disable the normal @samp{+}/@samp{-}
35452 protocol acknowledgments (@pxref{Packet Acknowledgment}).
35457 The stub has switched to no-acknowledgment mode.
35458 @value{GDBN} acknowledges this reponse,
35459 but neither the stub nor @value{GDBN} shall send or expect further
35460 @samp{+}/@samp{-} acknowledgments in the current connection.
35462 An empty reply indicates that the stub does not support no-acknowledgment mode.
35465 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
35466 @cindex supported packets, remote query
35467 @cindex features of the remote protocol
35468 @cindex @samp{qSupported} packet
35469 @anchor{qSupported}
35470 Tell the remote stub about features supported by @value{GDBN}, and
35471 query the stub for features it supports. This packet allows
35472 @value{GDBN} and the remote stub to take advantage of each others'
35473 features. @samp{qSupported} also consolidates multiple feature probes
35474 at startup, to improve @value{GDBN} performance---a single larger
35475 packet performs better than multiple smaller probe packets on
35476 high-latency links. Some features may enable behavior which must not
35477 be on by default, e.g.@: because it would confuse older clients or
35478 stubs. Other features may describe packets which could be
35479 automatically probed for, but are not. These features must be
35480 reported before @value{GDBN} will use them. This ``default
35481 unsupported'' behavior is not appropriate for all packets, but it
35482 helps to keep the initial connection time under control with new
35483 versions of @value{GDBN} which support increasing numbers of packets.
35487 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
35488 The stub supports or does not support each returned @var{stubfeature},
35489 depending on the form of each @var{stubfeature} (see below for the
35492 An empty reply indicates that @samp{qSupported} is not recognized,
35493 or that no features needed to be reported to @value{GDBN}.
35496 The allowed forms for each feature (either a @var{gdbfeature} in the
35497 @samp{qSupported} packet, or a @var{stubfeature} in the response)
35501 @item @var{name}=@var{value}
35502 The remote protocol feature @var{name} is supported, and associated
35503 with the specified @var{value}. The format of @var{value} depends
35504 on the feature, but it must not include a semicolon.
35506 The remote protocol feature @var{name} is supported, and does not
35507 need an associated value.
35509 The remote protocol feature @var{name} is not supported.
35511 The remote protocol feature @var{name} may be supported, and
35512 @value{GDBN} should auto-detect support in some other way when it is
35513 needed. This form will not be used for @var{gdbfeature} notifications,
35514 but may be used for @var{stubfeature} responses.
35517 Whenever the stub receives a @samp{qSupported} request, the
35518 supplied set of @value{GDBN} features should override any previous
35519 request. This allows @value{GDBN} to put the stub in a known
35520 state, even if the stub had previously been communicating with
35521 a different version of @value{GDBN}.
35523 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
35528 This feature indicates whether @value{GDBN} supports multiprocess
35529 extensions to the remote protocol. @value{GDBN} does not use such
35530 extensions unless the stub also reports that it supports them by
35531 including @samp{multiprocess+} in its @samp{qSupported} reply.
35532 @xref{multiprocess extensions}, for details.
35535 This feature indicates that @value{GDBN} supports the XML target
35536 description. If the stub sees @samp{xmlRegisters=} with target
35537 specific strings separated by a comma, it will report register
35541 This feature indicates whether @value{GDBN} supports the
35542 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
35543 instruction reply packet}).
35546 Stubs should ignore any unknown values for
35547 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
35548 packet supports receiving packets of unlimited length (earlier
35549 versions of @value{GDBN} may reject overly long responses). Additional values
35550 for @var{gdbfeature} may be defined in the future to let the stub take
35551 advantage of new features in @value{GDBN}, e.g.@: incompatible
35552 improvements in the remote protocol---the @samp{multiprocess} feature is
35553 an example of such a feature. The stub's reply should be independent
35554 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
35555 describes all the features it supports, and then the stub replies with
35556 all the features it supports.
35558 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
35559 responses, as long as each response uses one of the standard forms.
35561 Some features are flags. A stub which supports a flag feature
35562 should respond with a @samp{+} form response. Other features
35563 require values, and the stub should respond with an @samp{=}
35566 Each feature has a default value, which @value{GDBN} will use if
35567 @samp{qSupported} is not available or if the feature is not mentioned
35568 in the @samp{qSupported} response. The default values are fixed; a
35569 stub is free to omit any feature responses that match the defaults.
35571 Not all features can be probed, but for those which can, the probing
35572 mechanism is useful: in some cases, a stub's internal
35573 architecture may not allow the protocol layer to know some information
35574 about the underlying target in advance. This is especially common in
35575 stubs which may be configured for multiple targets.
35577 These are the currently defined stub features and their properties:
35579 @multitable @columnfractions 0.35 0.2 0.12 0.2
35580 @c NOTE: The first row should be @headitem, but we do not yet require
35581 @c a new enough version of Texinfo (4.7) to use @headitem.
35583 @tab Value Required
35587 @item @samp{PacketSize}
35592 @item @samp{qXfer:auxv:read}
35597 @item @samp{qXfer:btrace:read}
35602 @item @samp{qXfer:features:read}
35607 @item @samp{qXfer:libraries:read}
35612 @item @samp{qXfer:libraries-svr4:read}
35617 @item @samp{augmented-libraries-svr4-read}
35622 @item @samp{qXfer:memory-map:read}
35627 @item @samp{qXfer:sdata:read}
35632 @item @samp{qXfer:spu:read}
35637 @item @samp{qXfer:spu:write}
35642 @item @samp{qXfer:siginfo:read}
35647 @item @samp{qXfer:siginfo:write}
35652 @item @samp{qXfer:threads:read}
35657 @item @samp{qXfer:traceframe-info:read}
35662 @item @samp{qXfer:uib:read}
35667 @item @samp{qXfer:fdpic:read}
35672 @item @samp{Qbtrace:off}
35677 @item @samp{Qbtrace:bts}
35682 @item @samp{QNonStop}
35687 @item @samp{QPassSignals}
35692 @item @samp{QStartNoAckMode}
35697 @item @samp{multiprocess}
35702 @item @samp{ConditionalBreakpoints}
35707 @item @samp{ConditionalTracepoints}
35712 @item @samp{ReverseContinue}
35717 @item @samp{ReverseStep}
35722 @item @samp{TracepointSource}
35727 @item @samp{QAgent}
35732 @item @samp{QAllow}
35737 @item @samp{QDisableRandomization}
35742 @item @samp{EnableDisableTracepoints}
35747 @item @samp{QTBuffer:size}
35752 @item @samp{tracenz}
35757 @item @samp{BreakpointCommands}
35764 These are the currently defined stub features, in more detail:
35767 @cindex packet size, remote protocol
35768 @item PacketSize=@var{bytes}
35769 The remote stub can accept packets up to at least @var{bytes} in
35770 length. @value{GDBN} will send packets up to this size for bulk
35771 transfers, and will never send larger packets. This is a limit on the
35772 data characters in the packet, including the frame and checksum.
35773 There is no trailing NUL byte in a remote protocol packet; if the stub
35774 stores packets in a NUL-terminated format, it should allow an extra
35775 byte in its buffer for the NUL. If this stub feature is not supported,
35776 @value{GDBN} guesses based on the size of the @samp{g} packet response.
35778 @item qXfer:auxv:read
35779 The remote stub understands the @samp{qXfer:auxv:read} packet
35780 (@pxref{qXfer auxiliary vector read}).
35782 @item qXfer:btrace:read
35783 The remote stub understands the @samp{qXfer:btrace:read}
35784 packet (@pxref{qXfer btrace read}).
35786 @item qXfer:features:read
35787 The remote stub understands the @samp{qXfer:features:read} packet
35788 (@pxref{qXfer target description read}).
35790 @item qXfer:libraries:read
35791 The remote stub understands the @samp{qXfer:libraries:read} packet
35792 (@pxref{qXfer library list read}).
35794 @item qXfer:libraries-svr4:read
35795 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
35796 (@pxref{qXfer svr4 library list read}).
35798 @item augmented-libraries-svr4-read
35799 The remote stub understands the augmented form of the
35800 @samp{qXfer:libraries-svr4:read} packet
35801 (@pxref{qXfer svr4 library list read}).
35803 @item qXfer:memory-map:read
35804 The remote stub understands the @samp{qXfer:memory-map:read} packet
35805 (@pxref{qXfer memory map read}).
35807 @item qXfer:sdata:read
35808 The remote stub understands the @samp{qXfer:sdata:read} packet
35809 (@pxref{qXfer sdata read}).
35811 @item qXfer:spu:read
35812 The remote stub understands the @samp{qXfer:spu:read} packet
35813 (@pxref{qXfer spu read}).
35815 @item qXfer:spu:write
35816 The remote stub understands the @samp{qXfer:spu:write} packet
35817 (@pxref{qXfer spu write}).
35819 @item qXfer:siginfo:read
35820 The remote stub understands the @samp{qXfer:siginfo:read} packet
35821 (@pxref{qXfer siginfo read}).
35823 @item qXfer:siginfo:write
35824 The remote stub understands the @samp{qXfer:siginfo:write} packet
35825 (@pxref{qXfer siginfo write}).
35827 @item qXfer:threads:read
35828 The remote stub understands the @samp{qXfer:threads:read} packet
35829 (@pxref{qXfer threads read}).
35831 @item qXfer:traceframe-info:read
35832 The remote stub understands the @samp{qXfer:traceframe-info:read}
35833 packet (@pxref{qXfer traceframe info read}).
35835 @item qXfer:uib:read
35836 The remote stub understands the @samp{qXfer:uib:read}
35837 packet (@pxref{qXfer unwind info block}).
35839 @item qXfer:fdpic:read
35840 The remote stub understands the @samp{qXfer:fdpic:read}
35841 packet (@pxref{qXfer fdpic loadmap read}).
35844 The remote stub understands the @samp{QNonStop} packet
35845 (@pxref{QNonStop}).
35848 The remote stub understands the @samp{QPassSignals} packet
35849 (@pxref{QPassSignals}).
35851 @item QStartNoAckMode
35852 The remote stub understands the @samp{QStartNoAckMode} packet and
35853 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
35856 @anchor{multiprocess extensions}
35857 @cindex multiprocess extensions, in remote protocol
35858 The remote stub understands the multiprocess extensions to the remote
35859 protocol syntax. The multiprocess extensions affect the syntax of
35860 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
35861 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
35862 replies. Note that reporting this feature indicates support for the
35863 syntactic extensions only, not that the stub necessarily supports
35864 debugging of more than one process at a time. The stub must not use
35865 multiprocess extensions in packet replies unless @value{GDBN} has also
35866 indicated it supports them in its @samp{qSupported} request.
35868 @item qXfer:osdata:read
35869 The remote stub understands the @samp{qXfer:osdata:read} packet
35870 ((@pxref{qXfer osdata read}).
35872 @item ConditionalBreakpoints
35873 The target accepts and implements evaluation of conditional expressions
35874 defined for breakpoints. The target will only report breakpoint triggers
35875 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
35877 @item ConditionalTracepoints
35878 The remote stub accepts and implements conditional expressions defined
35879 for tracepoints (@pxref{Tracepoint Conditions}).
35881 @item ReverseContinue
35882 The remote stub accepts and implements the reverse continue packet
35886 The remote stub accepts and implements the reverse step packet
35889 @item TracepointSource
35890 The remote stub understands the @samp{QTDPsrc} packet that supplies
35891 the source form of tracepoint definitions.
35894 The remote stub understands the @samp{QAgent} packet.
35897 The remote stub understands the @samp{QAllow} packet.
35899 @item QDisableRandomization
35900 The remote stub understands the @samp{QDisableRandomization} packet.
35902 @item StaticTracepoint
35903 @cindex static tracepoints, in remote protocol
35904 The remote stub supports static tracepoints.
35906 @item InstallInTrace
35907 @anchor{install tracepoint in tracing}
35908 The remote stub supports installing tracepoint in tracing.
35910 @item EnableDisableTracepoints
35911 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
35912 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
35913 to be enabled and disabled while a trace experiment is running.
35915 @item QTBuffer:size
35916 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
35917 packet that allows to change the size of the trace buffer.
35920 @cindex string tracing, in remote protocol
35921 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
35922 See @ref{Bytecode Descriptions} for details about the bytecode.
35924 @item BreakpointCommands
35925 @cindex breakpoint commands, in remote protocol
35926 The remote stub supports running a breakpoint's command list itself,
35927 rather than reporting the hit to @value{GDBN}.
35930 The remote stub understands the @samp{Qbtrace:off} packet.
35933 The remote stub understands the @samp{Qbtrace:bts} packet.
35938 @cindex symbol lookup, remote request
35939 @cindex @samp{qSymbol} packet
35940 Notify the target that @value{GDBN} is prepared to serve symbol lookup
35941 requests. Accept requests from the target for the values of symbols.
35946 The target does not need to look up any (more) symbols.
35947 @item qSymbol:@var{sym_name}
35948 The target requests the value of symbol @var{sym_name} (hex encoded).
35949 @value{GDBN} may provide the value by using the
35950 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
35954 @item qSymbol:@var{sym_value}:@var{sym_name}
35955 Set the value of @var{sym_name} to @var{sym_value}.
35957 @var{sym_name} (hex encoded) is the name of a symbol whose value the
35958 target has previously requested.
35960 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
35961 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
35967 The target does not need to look up any (more) symbols.
35968 @item qSymbol:@var{sym_name}
35969 The target requests the value of a new symbol @var{sym_name} (hex
35970 encoded). @value{GDBN} will continue to supply the values of symbols
35971 (if available), until the target ceases to request them.
35976 @itemx QTDisconnected
35983 @itemx qTMinFTPILen
35985 @xref{Tracepoint Packets}.
35987 @item qThreadExtraInfo,@var{thread-id}
35988 @cindex thread attributes info, remote request
35989 @cindex @samp{qThreadExtraInfo} packet
35990 Obtain from the target OS a printable string description of thread
35991 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
35992 for the forms of @var{thread-id}. This
35993 string may contain anything that the target OS thinks is interesting
35994 for @value{GDBN} to tell the user about the thread. The string is
35995 displayed in @value{GDBN}'s @code{info threads} display. Some
35996 examples of possible thread extra info strings are @samp{Runnable}, or
35997 @samp{Blocked on Mutex}.
36001 @item @var{XX}@dots{}
36002 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
36003 comprising the printable string containing the extra information about
36004 the thread's attributes.
36007 (Note that the @code{qThreadExtraInfo} packet's name is separated from
36008 the command by a @samp{,}, not a @samp{:}, contrary to the naming
36009 conventions above. Please don't use this packet as a model for new
36028 @xref{Tracepoint Packets}.
36030 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
36031 @cindex read special object, remote request
36032 @cindex @samp{qXfer} packet
36033 @anchor{qXfer read}
36034 Read uninterpreted bytes from the target's special data area
36035 identified by the keyword @var{object}. Request @var{length} bytes
36036 starting at @var{offset} bytes into the data. The content and
36037 encoding of @var{annex} is specific to @var{object}; it can supply
36038 additional details about what data to access.
36040 Here are the specific requests of this form defined so far. All
36041 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
36042 formats, listed below.
36045 @item qXfer:auxv:read::@var{offset},@var{length}
36046 @anchor{qXfer auxiliary vector read}
36047 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
36048 auxiliary vector}. Note @var{annex} must be empty.
36050 This packet is not probed by default; the remote stub must request it,
36051 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36053 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
36054 @anchor{qXfer btrace read}
36056 Return a description of the current branch trace.
36057 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
36058 packet may have one of the following values:
36062 Returns all available branch trace.
36065 Returns all available branch trace if the branch trace changed since
36066 the last read request.
36069 Returns the new branch trace since the last read request. Adds a new
36070 block to the end of the trace that begins at zero and ends at the source
36071 location of the first branch in the trace buffer. This extra block is
36072 used to stitch traces together.
36074 If the trace buffer overflowed, returns an error indicating the overflow.
36077 This packet is not probed by default; the remote stub must request it
36078 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36080 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
36081 @anchor{qXfer target description read}
36082 Access the @dfn{target description}. @xref{Target Descriptions}. The
36083 annex specifies which XML document to access. The main description is
36084 always loaded from the @samp{target.xml} annex.
36086 This packet is not probed by default; the remote stub must request it,
36087 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36089 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
36090 @anchor{qXfer library list read}
36091 Access the target's list of loaded libraries. @xref{Library List Format}.
36092 The annex part of the generic @samp{qXfer} packet must be empty
36093 (@pxref{qXfer read}).
36095 Targets which maintain a list of libraries in the program's memory do
36096 not need to implement this packet; it is designed for platforms where
36097 the operating system manages the list of loaded libraries.
36099 This packet is not probed by default; the remote stub must request it,
36100 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36102 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
36103 @anchor{qXfer svr4 library list read}
36104 Access the target's list of loaded libraries when the target is an SVR4
36105 platform. @xref{Library List Format for SVR4 Targets}. The annex part
36106 of the generic @samp{qXfer} packet must be empty unless the remote
36107 stub indicated it supports the augmented form of this packet
36108 by supplying an appropriate @samp{qSupported} response
36109 (@pxref{qXfer read}, @ref{qSupported}).
36111 This packet is optional for better performance on SVR4 targets.
36112 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
36114 This packet is not probed by default; the remote stub must request it,
36115 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36117 If the remote stub indicates it supports the augmented form of this
36118 packet then the annex part of the generic @samp{qXfer} packet may
36119 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
36120 arguments. The currently supported arguments are:
36123 @item start=@var{address}
36124 A hexadecimal number specifying the address of the @samp{struct
36125 link_map} to start reading the library list from. If unset or zero
36126 then the first @samp{struct link_map} in the library list will be
36127 chosen as the starting point.
36129 @item prev=@var{address}
36130 A hexadecimal number specifying the address of the @samp{struct
36131 link_map} immediately preceding the @samp{struct link_map}
36132 specified by the @samp{start} argument. If unset or zero then
36133 the remote stub will expect that no @samp{struct link_map}
36134 exists prior to the starting point.
36138 Arguments that are not understood by the remote stub will be silently
36141 @item qXfer:memory-map:read::@var{offset},@var{length}
36142 @anchor{qXfer memory map read}
36143 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
36144 annex part of the generic @samp{qXfer} packet must be empty
36145 (@pxref{qXfer read}).
36147 This packet is not probed by default; the remote stub must request it,
36148 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36150 @item qXfer:sdata:read::@var{offset},@var{length}
36151 @anchor{qXfer sdata read}
36153 Read contents of the extra collected static tracepoint marker
36154 information. The annex part of the generic @samp{qXfer} packet must
36155 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
36158 This packet is not probed by default; the remote stub must request it,
36159 by supplying an appropriate @samp{qSupported} response
36160 (@pxref{qSupported}).
36162 @item qXfer:siginfo:read::@var{offset},@var{length}
36163 @anchor{qXfer siginfo read}
36164 Read contents of the extra signal information on the target
36165 system. The annex part of the generic @samp{qXfer} packet must be
36166 empty (@pxref{qXfer read}).
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:spu:read:@var{annex}:@var{offset},@var{length}
36173 @anchor{qXfer spu read}
36174 Read contents of an @code{spufs} file on the target system. The
36175 annex specifies which file to read; it must be of the form
36176 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
36177 in the target process, and @var{name} identifes the @code{spufs} file
36178 in that context to be accessed.
36180 This packet is not probed by default; the remote stub must request it,
36181 by supplying an appropriate @samp{qSupported} response
36182 (@pxref{qSupported}).
36184 @item qXfer:threads:read::@var{offset},@var{length}
36185 @anchor{qXfer threads read}
36186 Access the list of threads on target. @xref{Thread List Format}. The
36187 annex part of the generic @samp{qXfer} packet must be empty
36188 (@pxref{qXfer read}).
36190 This packet is not probed by default; the remote stub must request it,
36191 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36193 @item qXfer:traceframe-info:read::@var{offset},@var{length}
36194 @anchor{qXfer traceframe info read}
36196 Return a description of the current traceframe's contents.
36197 @xref{Traceframe Info Format}. The annex part of the generic
36198 @samp{qXfer} packet must be empty (@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:uib:read:@var{pc}:@var{offset},@var{length}
36204 @anchor{qXfer unwind info block}
36206 Return the unwind information block for @var{pc}. This packet is used
36207 on OpenVMS/ia64 to ask the kernel unwind information.
36209 This packet is not probed by default.
36211 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
36212 @anchor{qXfer fdpic loadmap read}
36213 Read contents of @code{loadmap}s on the target system. The
36214 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
36215 executable @code{loadmap} or interpreter @code{loadmap} to read.
36217 This packet is not probed by default; the remote stub must request it,
36218 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36220 @item qXfer:osdata:read::@var{offset},@var{length}
36221 @anchor{qXfer osdata read}
36222 Access the target's @dfn{operating system information}.
36223 @xref{Operating System Information}.
36230 Data @var{data} (@pxref{Binary Data}) has been read from the
36231 target. There may be more data at a higher address (although
36232 it is permitted to return @samp{m} even for the last valid
36233 block of data, as long as at least one byte of data was read).
36234 It is possible for @var{data} to have fewer bytes than the @var{length} in the
36238 Data @var{data} (@pxref{Binary Data}) has been read from the target.
36239 There is no more data to be read. It is possible for @var{data} to
36240 have fewer bytes than the @var{length} in the request.
36243 The @var{offset} in the request is at the end of the data.
36244 There is no more data to be read.
36247 The request was malformed, or @var{annex} was invalid.
36250 The offset was invalid, or there was an error encountered reading the data.
36251 The @var{nn} part is a hex-encoded @code{errno} value.
36254 An empty reply indicates the @var{object} string was not recognized by
36255 the stub, or that the object does not support reading.
36258 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
36259 @cindex write data into object, remote request
36260 @anchor{qXfer write}
36261 Write uninterpreted bytes into the target's special data area
36262 identified by the keyword @var{object}, starting at @var{offset} bytes
36263 into the data. The binary-encoded data (@pxref{Binary Data}) to be
36264 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
36265 is specific to @var{object}; it can supply additional details about what data
36268 Here are the specific requests of this form defined so far. All
36269 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
36270 formats, listed below.
36273 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
36274 @anchor{qXfer siginfo write}
36275 Write @var{data} to the extra signal information on the target system.
36276 The annex part of the generic @samp{qXfer} packet must be
36277 empty (@pxref{qXfer write}).
36279 This packet is not probed by default; the remote stub must request it,
36280 by supplying an appropriate @samp{qSupported} response
36281 (@pxref{qSupported}).
36283 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
36284 @anchor{qXfer spu write}
36285 Write @var{data} to an @code{spufs} file on the target system. The
36286 annex specifies which file to write; it must be of the form
36287 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
36288 in the target process, and @var{name} identifes the @code{spufs} file
36289 in that context to be accessed.
36291 This packet is not probed by default; the remote stub must request it,
36292 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36298 @var{nn} (hex encoded) is the number of bytes written.
36299 This may be fewer bytes than supplied in the request.
36302 The request was malformed, or @var{annex} was invalid.
36305 The offset was invalid, or there was an error encountered writing the data.
36306 The @var{nn} part is a hex-encoded @code{errno} value.
36309 An empty reply indicates the @var{object} string was not
36310 recognized by the stub, or that the object does not support writing.
36313 @item qXfer:@var{object}:@var{operation}:@dots{}
36314 Requests of this form may be added in the future. When a stub does
36315 not recognize the @var{object} keyword, or its support for
36316 @var{object} does not recognize the @var{operation} keyword, the stub
36317 must respond with an empty packet.
36319 @item qAttached:@var{pid}
36320 @cindex query attached, remote request
36321 @cindex @samp{qAttached} packet
36322 Return an indication of whether the remote server attached to an
36323 existing process or created a new process. When the multiprocess
36324 protocol extensions are supported (@pxref{multiprocess extensions}),
36325 @var{pid} is an integer in hexadecimal format identifying the target
36326 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
36327 the query packet will be simplified as @samp{qAttached}.
36329 This query is used, for example, to know whether the remote process
36330 should be detached or killed when a @value{GDBN} session is ended with
36331 the @code{quit} command.
36336 The remote server attached to an existing process.
36338 The remote server created a new process.
36340 A badly formed request or an error was encountered.
36344 Enable branch tracing for the current thread using bts tracing.
36349 Branch tracing has been enabled.
36351 A badly formed request or an error was encountered.
36355 Disable branch tracing for the current thread.
36360 Branch tracing has been disabled.
36362 A badly formed request or an error was encountered.
36367 @node Architecture-Specific Protocol Details
36368 @section Architecture-Specific Protocol Details
36370 This section describes how the remote protocol is applied to specific
36371 target architectures. Also see @ref{Standard Target Features}, for
36372 details of XML target descriptions for each architecture.
36375 * ARM-Specific Protocol Details::
36376 * MIPS-Specific Protocol Details::
36379 @node ARM-Specific Protocol Details
36380 @subsection @acronym{ARM}-specific Protocol Details
36383 * ARM Breakpoint Kinds::
36386 @node ARM Breakpoint Kinds
36387 @subsubsection @acronym{ARM} Breakpoint Kinds
36388 @cindex breakpoint kinds, @acronym{ARM}
36390 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
36395 16-bit Thumb mode breakpoint.
36398 32-bit Thumb mode (Thumb-2) breakpoint.
36401 32-bit @acronym{ARM} mode breakpoint.
36405 @node MIPS-Specific Protocol Details
36406 @subsection @acronym{MIPS}-specific Protocol Details
36409 * MIPS Register packet Format::
36410 * MIPS Breakpoint Kinds::
36413 @node MIPS Register packet Format
36414 @subsubsection @acronym{MIPS} Register Packet Format
36415 @cindex register packet format, @acronym{MIPS}
36417 The following @code{g}/@code{G} packets have previously been defined.
36418 In the below, some thirty-two bit registers are transferred as
36419 sixty-four bits. Those registers should be zero/sign extended (which?)
36420 to fill the space allocated. Register bytes are transferred in target
36421 byte order. The two nibbles within a register byte are transferred
36422 most-significant -- least-significant.
36427 All registers are transferred as thirty-two bit quantities in the order:
36428 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
36429 registers; fsr; fir; fp.
36432 All registers are transferred as sixty-four bit quantities (including
36433 thirty-two bit registers such as @code{sr}). The ordering is the same
36438 @node MIPS Breakpoint Kinds
36439 @subsubsection @acronym{MIPS} Breakpoint Kinds
36440 @cindex breakpoint kinds, @acronym{MIPS}
36442 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
36447 16-bit @acronym{MIPS16} mode breakpoint.
36450 16-bit @acronym{microMIPS} mode breakpoint.
36453 32-bit standard @acronym{MIPS} mode breakpoint.
36456 32-bit @acronym{microMIPS} mode breakpoint.
36460 @node Tracepoint Packets
36461 @section Tracepoint Packets
36462 @cindex tracepoint packets
36463 @cindex packets, tracepoint
36465 Here we describe the packets @value{GDBN} uses to implement
36466 tracepoints (@pxref{Tracepoints}).
36470 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
36471 @cindex @samp{QTDP} packet
36472 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
36473 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
36474 the tracepoint is disabled. The @var{step} gives the tracepoint's step
36475 count, and @var{pass} gives its pass count. If an @samp{F} is present,
36476 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
36477 the number of bytes that the target should copy elsewhere to make room
36478 for the tracepoint. If an @samp{X} is present, it introduces a
36479 tracepoint condition, which consists of a hexadecimal length, followed
36480 by a comma and hex-encoded bytes, in a manner similar to action
36481 encodings as described below. If the trailing @samp{-} is present,
36482 further @samp{QTDP} packets will follow to specify this tracepoint's
36488 The packet was understood and carried out.
36490 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
36492 The packet was not recognized.
36495 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
36496 Define actions to be taken when a tracepoint is hit. The @var{n} and
36497 @var{addr} must be the same as in the initial @samp{QTDP} packet for
36498 this tracepoint. This packet may only be sent immediately after
36499 another @samp{QTDP} packet that ended with a @samp{-}. If the
36500 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
36501 specifying more actions for this tracepoint.
36503 In the series of action packets for a given tracepoint, at most one
36504 can have an @samp{S} before its first @var{action}. If such a packet
36505 is sent, it and the following packets define ``while-stepping''
36506 actions. Any prior packets define ordinary actions --- that is, those
36507 taken when the tracepoint is first hit. If no action packet has an
36508 @samp{S}, then all the packets in the series specify ordinary
36509 tracepoint actions.
36511 The @samp{@var{action}@dots{}} portion of the packet is a series of
36512 actions, concatenated without separators. Each action has one of the
36518 Collect the registers whose bits are set in @var{mask},
36519 a hexadecimal number whose @var{i}'th bit is set if register number
36520 @var{i} should be collected. (The least significant bit is numbered
36521 zero.) Note that @var{mask} may be any number of digits long; it may
36522 not fit in a 32-bit word.
36524 @item M @var{basereg},@var{offset},@var{len}
36525 Collect @var{len} bytes of memory starting at the address in register
36526 number @var{basereg}, plus @var{offset}. If @var{basereg} is
36527 @samp{-1}, then the range has a fixed address: @var{offset} is the
36528 address of the lowest byte to collect. The @var{basereg},
36529 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
36530 values (the @samp{-1} value for @var{basereg} is a special case).
36532 @item X @var{len},@var{expr}
36533 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
36534 it directs. The agent expression @var{expr} is as described in
36535 @ref{Agent Expressions}. Each byte of the expression is encoded as a
36536 two-digit hex number in the packet; @var{len} is the number of bytes
36537 in the expression (and thus one-half the number of hex digits in the
36542 Any number of actions may be packed together in a single @samp{QTDP}
36543 packet, as long as the packet does not exceed the maximum packet
36544 length (400 bytes, for many stubs). There may be only one @samp{R}
36545 action per tracepoint, and it must precede any @samp{M} or @samp{X}
36546 actions. Any registers referred to by @samp{M} and @samp{X} actions
36547 must be collected by a preceding @samp{R} action. (The
36548 ``while-stepping'' actions are treated as if they were attached to a
36549 separate tracepoint, as far as these restrictions are concerned.)
36554 The packet was understood and carried out.
36556 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
36558 The packet was not recognized.
36561 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
36562 @cindex @samp{QTDPsrc} packet
36563 Specify a source string of tracepoint @var{n} at address @var{addr}.
36564 This is useful to get accurate reproduction of the tracepoints
36565 originally downloaded at the beginning of the trace run. The @var{type}
36566 is the name of the tracepoint part, such as @samp{cond} for the
36567 tracepoint's conditional expression (see below for a list of types), while
36568 @var{bytes} is the string, encoded in hexadecimal.
36570 @var{start} is the offset of the @var{bytes} within the overall source
36571 string, while @var{slen} is the total length of the source string.
36572 This is intended for handling source strings that are longer than will
36573 fit in a single packet.
36574 @c Add detailed example when this info is moved into a dedicated
36575 @c tracepoint descriptions section.
36577 The available string types are @samp{at} for the location,
36578 @samp{cond} for the conditional, and @samp{cmd} for an action command.
36579 @value{GDBN} sends a separate packet for each command in the action
36580 list, in the same order in which the commands are stored in the list.
36582 The target does not need to do anything with source strings except
36583 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
36586 Although this packet is optional, and @value{GDBN} will only send it
36587 if the target replies with @samp{TracepointSource} @xref{General
36588 Query Packets}, it makes both disconnected tracing and trace files
36589 much easier to use. Otherwise the user must be careful that the
36590 tracepoints in effect while looking at trace frames are identical to
36591 the ones in effect during the trace run; even a small discrepancy
36592 could cause @samp{tdump} not to work, or a particular trace frame not
36595 @item QTDV:@var{n}:@var{value}
36596 @cindex define trace state variable, remote request
36597 @cindex @samp{QTDV} packet
36598 Create a new trace state variable, number @var{n}, with an initial
36599 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
36600 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
36601 the option of not using this packet for initial values of zero; the
36602 target should simply create the trace state variables as they are
36603 mentioned in expressions.
36605 @item QTFrame:@var{n}
36606 @cindex @samp{QTFrame} packet
36607 Select the @var{n}'th tracepoint frame from the buffer, and use the
36608 register and memory contents recorded there to answer subsequent
36609 request packets from @value{GDBN}.
36611 A successful reply from the stub indicates that the stub has found the
36612 requested frame. The response is a series of parts, concatenated
36613 without separators, describing the frame we selected. Each part has
36614 one of the following forms:
36618 The selected frame is number @var{n} in the trace frame buffer;
36619 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
36620 was no frame matching the criteria in the request packet.
36623 The selected trace frame records a hit of tracepoint number @var{t};
36624 @var{t} is a hexadecimal number.
36628 @item QTFrame:pc:@var{addr}
36629 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36630 currently selected frame whose PC is @var{addr};
36631 @var{addr} is a hexadecimal number.
36633 @item QTFrame:tdp:@var{t}
36634 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36635 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
36636 is a hexadecimal number.
36638 @item QTFrame:range:@var{start}:@var{end}
36639 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36640 currently selected frame whose PC is between @var{start} (inclusive)
36641 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
36644 @item QTFrame:outside:@var{start}:@var{end}
36645 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
36646 frame @emph{outside} the given range of addresses (exclusive).
36649 @cindex @samp{qTMinFTPILen} packet
36650 This packet requests the minimum length of instruction at which a fast
36651 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
36652 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
36653 it depends on the target system being able to create trampolines in
36654 the first 64K of memory, which might or might not be possible for that
36655 system. So the reply to this packet will be 4 if it is able to
36662 The minimum instruction length is currently unknown.
36664 The minimum instruction length is @var{length}, where @var{length}
36665 is a hexadecimal number greater or equal to 1. A reply
36666 of 1 means that a fast tracepoint may be placed on any instruction
36667 regardless of size.
36669 An error has occurred.
36671 An empty reply indicates that the request is not supported by the stub.
36675 @cindex @samp{QTStart} packet
36676 Begin the tracepoint experiment. Begin collecting data from
36677 tracepoint hits in the trace frame buffer. This packet supports the
36678 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
36679 instruction reply packet}).
36682 @cindex @samp{QTStop} packet
36683 End the tracepoint experiment. Stop collecting trace frames.
36685 @item QTEnable:@var{n}:@var{addr}
36687 @cindex @samp{QTEnable} packet
36688 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
36689 experiment. If the tracepoint was previously disabled, then collection
36690 of data from it will resume.
36692 @item QTDisable:@var{n}:@var{addr}
36694 @cindex @samp{QTDisable} packet
36695 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
36696 experiment. No more data will be collected from the tracepoint unless
36697 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
36700 @cindex @samp{QTinit} packet
36701 Clear the table of tracepoints, and empty the trace frame buffer.
36703 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
36704 @cindex @samp{QTro} packet
36705 Establish the given ranges of memory as ``transparent''. The stub
36706 will answer requests for these ranges from memory's current contents,
36707 if they were not collected as part of the tracepoint hit.
36709 @value{GDBN} uses this to mark read-only regions of memory, like those
36710 containing program code. Since these areas never change, they should
36711 still have the same contents they did when the tracepoint was hit, so
36712 there's no reason for the stub to refuse to provide their contents.
36714 @item QTDisconnected:@var{value}
36715 @cindex @samp{QTDisconnected} packet
36716 Set the choice to what to do with the tracing run when @value{GDBN}
36717 disconnects from the target. A @var{value} of 1 directs the target to
36718 continue the tracing run, while 0 tells the target to stop tracing if
36719 @value{GDBN} is no longer in the picture.
36722 @cindex @samp{qTStatus} packet
36723 Ask the stub if there is a trace experiment running right now.
36725 The reply has the form:
36729 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
36730 @var{running} is a single digit @code{1} if the trace is presently
36731 running, or @code{0} if not. It is followed by semicolon-separated
36732 optional fields that an agent may use to report additional status.
36736 If the trace is not running, the agent may report any of several
36737 explanations as one of the optional fields:
36742 No trace has been run yet.
36744 @item tstop[:@var{text}]:0
36745 The trace was stopped by a user-originated stop command. The optional
36746 @var{text} field is a user-supplied string supplied as part of the
36747 stop command (for instance, an explanation of why the trace was
36748 stopped manually). It is hex-encoded.
36751 The trace stopped because the trace buffer filled up.
36753 @item tdisconnected:0
36754 The trace stopped because @value{GDBN} disconnected from the target.
36756 @item tpasscount:@var{tpnum}
36757 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
36759 @item terror:@var{text}:@var{tpnum}
36760 The trace stopped because tracepoint @var{tpnum} had an error. The
36761 string @var{text} is available to describe the nature of the error
36762 (for instance, a divide by zero in the condition expression); it
36766 The trace stopped for some other reason.
36770 Additional optional fields supply statistical and other information.
36771 Although not required, they are extremely useful for users monitoring
36772 the progress of a trace run. If a trace has stopped, and these
36773 numbers are reported, they must reflect the state of the just-stopped
36778 @item tframes:@var{n}
36779 The number of trace frames in the buffer.
36781 @item tcreated:@var{n}
36782 The total number of trace frames created during the run. This may
36783 be larger than the trace frame count, if the buffer is circular.
36785 @item tsize:@var{n}
36786 The total size of the trace buffer, in bytes.
36788 @item tfree:@var{n}
36789 The number of bytes still unused in the buffer.
36791 @item circular:@var{n}
36792 The value of the circular trace buffer flag. @code{1} means that the
36793 trace buffer is circular and old trace frames will be discarded if
36794 necessary to make room, @code{0} means that the trace buffer is linear
36797 @item disconn:@var{n}
36798 The value of the disconnected tracing flag. @code{1} means that
36799 tracing will continue after @value{GDBN} disconnects, @code{0} means
36800 that the trace run will stop.
36804 @item qTP:@var{tp}:@var{addr}
36805 @cindex tracepoint status, remote request
36806 @cindex @samp{qTP} packet
36807 Ask the stub for the current state of tracepoint number @var{tp} at
36808 address @var{addr}.
36812 @item V@var{hits}:@var{usage}
36813 The tracepoint has been hit @var{hits} times so far during the trace
36814 run, and accounts for @var{usage} in the trace buffer. Note that
36815 @code{while-stepping} steps are not counted as separate hits, but the
36816 steps' space consumption is added into the usage number.
36820 @item qTV:@var{var}
36821 @cindex trace state variable value, remote request
36822 @cindex @samp{qTV} packet
36823 Ask the stub for the value of the trace state variable number @var{var}.
36828 The value of the variable is @var{value}. This will be the current
36829 value of the variable if the user is examining a running target, or a
36830 saved value if the variable was collected in the trace frame that the
36831 user is looking at. Note that multiple requests may result in
36832 different reply values, such as when requesting values while the
36833 program is running.
36836 The value of the variable is unknown. This would occur, for example,
36837 if the user is examining a trace frame in which the requested variable
36842 @cindex @samp{qTfP} packet
36844 @cindex @samp{qTsP} packet
36845 These packets request data about tracepoints that are being used by
36846 the target. @value{GDBN} sends @code{qTfP} to get the first piece
36847 of data, and multiple @code{qTsP} to get additional pieces. Replies
36848 to these packets generally take the form of the @code{QTDP} packets
36849 that define tracepoints. (FIXME add detailed syntax)
36852 @cindex @samp{qTfV} packet
36854 @cindex @samp{qTsV} packet
36855 These packets request data about trace state variables that are on the
36856 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
36857 and multiple @code{qTsV} to get additional variables. Replies to
36858 these packets follow the syntax of the @code{QTDV} packets that define
36859 trace state variables.
36865 @cindex @samp{qTfSTM} packet
36866 @cindex @samp{qTsSTM} packet
36867 These packets request data about static tracepoint markers that exist
36868 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
36869 first piece of data, and multiple @code{qTsSTM} to get additional
36870 pieces. Replies to these packets take the following form:
36874 @item m @var{address}:@var{id}:@var{extra}
36876 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
36877 a comma-separated list of markers
36879 (lower case letter @samp{L}) denotes end of list.
36881 An error occurred. The error number @var{nn} is given as hex digits.
36883 An empty reply indicates that the request is not supported by the
36887 The @var{address} is encoded in hex;
36888 @var{id} and @var{extra} are strings encoded in hex.
36890 In response to each query, the target will reply with a list of one or
36891 more markers, separated by commas. @value{GDBN} will respond to each
36892 reply with a request for more markers (using the @samp{qs} form of the
36893 query), until the target responds with @samp{l} (lower-case ell, for
36896 @item qTSTMat:@var{address}
36898 @cindex @samp{qTSTMat} packet
36899 This packets requests data about static tracepoint markers in the
36900 target program at @var{address}. Replies to this packet follow the
36901 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
36902 tracepoint markers.
36904 @item QTSave:@var{filename}
36905 @cindex @samp{QTSave} packet
36906 This packet directs the target to save trace data to the file name
36907 @var{filename} in the target's filesystem. The @var{filename} is encoded
36908 as a hex string; the interpretation of the file name (relative vs
36909 absolute, wild cards, etc) is up to the target.
36911 @item qTBuffer:@var{offset},@var{len}
36912 @cindex @samp{qTBuffer} packet
36913 Return up to @var{len} bytes of the current contents of trace buffer,
36914 starting at @var{offset}. The trace buffer is treated as if it were
36915 a contiguous collection of traceframes, as per the trace file format.
36916 The reply consists as many hex-encoded bytes as the target can deliver
36917 in a packet; it is not an error to return fewer than were asked for.
36918 A reply consisting of just @code{l} indicates that no bytes are
36921 @item QTBuffer:circular:@var{value}
36922 This packet directs the target to use a circular trace buffer if
36923 @var{value} is 1, or a linear buffer if the value is 0.
36925 @item QTBuffer:size:@var{size}
36926 @anchor{QTBuffer-size}
36927 @cindex @samp{QTBuffer size} packet
36928 This packet directs the target to make the trace buffer be of size
36929 @var{size} if possible. A value of @code{-1} tells the target to
36930 use whatever size it prefers.
36932 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
36933 @cindex @samp{QTNotes} packet
36934 This packet adds optional textual notes to the trace run. Allowable
36935 types include @code{user}, @code{notes}, and @code{tstop}, the
36936 @var{text} fields are arbitrary strings, hex-encoded.
36940 @subsection Relocate instruction reply packet
36941 When installing fast tracepoints in memory, the target may need to
36942 relocate the instruction currently at the tracepoint address to a
36943 different address in memory. For most instructions, a simple copy is
36944 enough, but, for example, call instructions that implicitly push the
36945 return address on the stack, and relative branches or other
36946 PC-relative instructions require offset adjustment, so that the effect
36947 of executing the instruction at a different address is the same as if
36948 it had executed in the original location.
36950 In response to several of the tracepoint packets, the target may also
36951 respond with a number of intermediate @samp{qRelocInsn} request
36952 packets before the final result packet, to have @value{GDBN} handle
36953 this relocation operation. If a packet supports this mechanism, its
36954 documentation will explicitly say so. See for example the above
36955 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
36956 format of the request is:
36959 @item qRelocInsn:@var{from};@var{to}
36961 This requests @value{GDBN} to copy instruction at address @var{from}
36962 to address @var{to}, possibly adjusted so that executing the
36963 instruction at @var{to} has the same effect as executing it at
36964 @var{from}. @value{GDBN} writes the adjusted instruction to target
36965 memory starting at @var{to}.
36970 @item qRelocInsn:@var{adjusted_size}
36971 Informs the stub the relocation is complete. The @var{adjusted_size} is
36972 the length in bytes of resulting relocated instruction sequence.
36974 A badly formed request was detected, or an error was encountered while
36975 relocating the instruction.
36978 @node Host I/O Packets
36979 @section Host I/O Packets
36980 @cindex Host I/O, remote protocol
36981 @cindex file transfer, remote protocol
36983 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
36984 operations on the far side of a remote link. For example, Host I/O is
36985 used to upload and download files to a remote target with its own
36986 filesystem. Host I/O uses the same constant values and data structure
36987 layout as the target-initiated File-I/O protocol. However, the
36988 Host I/O packets are structured differently. The target-initiated
36989 protocol relies on target memory to store parameters and buffers.
36990 Host I/O requests are initiated by @value{GDBN}, and the
36991 target's memory is not involved. @xref{File-I/O Remote Protocol
36992 Extension}, for more details on the target-initiated protocol.
36994 The Host I/O request packets all encode a single operation along with
36995 its arguments. They have this format:
36999 @item vFile:@var{operation}: @var{parameter}@dots{}
37000 @var{operation} is the name of the particular request; the target
37001 should compare the entire packet name up to the second colon when checking
37002 for a supported operation. The format of @var{parameter} depends on
37003 the operation. Numbers are always passed in hexadecimal. Negative
37004 numbers have an explicit minus sign (i.e.@: two's complement is not
37005 used). Strings (e.g.@: filenames) are encoded as a series of
37006 hexadecimal bytes. The last argument to a system call may be a
37007 buffer of escaped binary data (@pxref{Binary Data}).
37011 The valid responses to Host I/O packets are:
37015 @item F @var{result} [, @var{errno}] [; @var{attachment}]
37016 @var{result} is the integer value returned by this operation, usually
37017 non-negative for success and -1 for errors. If an error has occured,
37018 @var{errno} will be included in the result specifying a
37019 value defined by the File-I/O protocol (@pxref{Errno Values}). For
37020 operations which return data, @var{attachment} supplies the data as a
37021 binary buffer. Binary buffers in response packets are escaped in the
37022 normal way (@pxref{Binary Data}). See the individual packet
37023 documentation for the interpretation of @var{result} and
37027 An empty response indicates that this operation is not recognized.
37031 These are the supported Host I/O operations:
37034 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
37035 Open a file at @var{filename} and return a file descriptor for it, or
37036 return -1 if an error occurs. The @var{filename} is a string,
37037 @var{flags} is an integer indicating a mask of open flags
37038 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
37039 of mode bits to use if the file is created (@pxref{mode_t Values}).
37040 @xref{open}, for details of the open flags and mode values.
37042 @item vFile:close: @var{fd}
37043 Close the open file corresponding to @var{fd} and return 0, or
37044 -1 if an error occurs.
37046 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
37047 Read data from the open file corresponding to @var{fd}. Up to
37048 @var{count} bytes will be read from the file, starting at @var{offset}
37049 relative to the start of the file. The target may read fewer bytes;
37050 common reasons include packet size limits and an end-of-file
37051 condition. The number of bytes read is returned. Zero should only be
37052 returned for a successful read at the end of the file, or if
37053 @var{count} was zero.
37055 The data read should be returned as a binary attachment on success.
37056 If zero bytes were read, the response should include an empty binary
37057 attachment (i.e.@: a trailing semicolon). The return value is the
37058 number of target bytes read; the binary attachment may be longer if
37059 some characters were escaped.
37061 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
37062 Write @var{data} (a binary buffer) to the open file corresponding
37063 to @var{fd}. Start the write at @var{offset} from the start of the
37064 file. Unlike many @code{write} system calls, there is no
37065 separate @var{count} argument; the length of @var{data} in the
37066 packet is used. @samp{vFile:write} returns the number of bytes written,
37067 which may be shorter than the length of @var{data}, or -1 if an
37070 @item vFile:unlink: @var{filename}
37071 Delete the file at @var{filename} on the target. Return 0,
37072 or -1 if an error occurs. The @var{filename} is a string.
37074 @item vFile:readlink: @var{filename}
37075 Read value of symbolic link @var{filename} on the target. Return
37076 the number of bytes read, or -1 if an error occurs.
37078 The data read should be returned as a binary attachment on success.
37079 If zero bytes were read, the response should include an empty binary
37080 attachment (i.e.@: a trailing semicolon). The return value is the
37081 number of target bytes read; the binary attachment may be longer if
37082 some characters were escaped.
37087 @section Interrupts
37088 @cindex interrupts (remote protocol)
37090 When a program on the remote target is running, @value{GDBN} may
37091 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
37092 a @code{BREAK} followed by @code{g},
37093 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
37095 The precise meaning of @code{BREAK} is defined by the transport
37096 mechanism and may, in fact, be undefined. @value{GDBN} does not
37097 currently define a @code{BREAK} mechanism for any of the network
37098 interfaces except for TCP, in which case @value{GDBN} sends the
37099 @code{telnet} BREAK sequence.
37101 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
37102 transport mechanisms. It is represented by sending the single byte
37103 @code{0x03} without any of the usual packet overhead described in
37104 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
37105 transmitted as part of a packet, it is considered to be packet data
37106 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
37107 (@pxref{X packet}), used for binary downloads, may include an unescaped
37108 @code{0x03} as part of its packet.
37110 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
37111 When Linux kernel receives this sequence from serial port,
37112 it stops execution and connects to gdb.
37114 Stubs are not required to recognize these interrupt mechanisms and the
37115 precise meaning associated with receipt of the interrupt is
37116 implementation defined. If the target supports debugging of multiple
37117 threads and/or processes, it should attempt to interrupt all
37118 currently-executing threads and processes.
37119 If the stub is successful at interrupting the
37120 running program, it should send one of the stop
37121 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
37122 of successfully stopping the program in all-stop mode, and a stop reply
37123 for each stopped thread in non-stop mode.
37124 Interrupts received while the
37125 program is stopped are discarded.
37127 @node Notification Packets
37128 @section Notification Packets
37129 @cindex notification packets
37130 @cindex packets, notification
37132 The @value{GDBN} remote serial protocol includes @dfn{notifications},
37133 packets that require no acknowledgment. Both the GDB and the stub
37134 may send notifications (although the only notifications defined at
37135 present are sent by the stub). Notifications carry information
37136 without incurring the round-trip latency of an acknowledgment, and so
37137 are useful for low-impact communications where occasional packet loss
37140 A notification packet has the form @samp{% @var{data} #
37141 @var{checksum}}, where @var{data} is the content of the notification,
37142 and @var{checksum} is a checksum of @var{data}, computed and formatted
37143 as for ordinary @value{GDBN} packets. A notification's @var{data}
37144 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
37145 receiving a notification, the recipient sends no @samp{+} or @samp{-}
37146 to acknowledge the notification's receipt or to report its corruption.
37148 Every notification's @var{data} begins with a name, which contains no
37149 colon characters, followed by a colon character.
37151 Recipients should silently ignore corrupted notifications and
37152 notifications they do not understand. Recipients should restart
37153 timeout periods on receipt of a well-formed notification, whether or
37154 not they understand it.
37156 Senders should only send the notifications described here when this
37157 protocol description specifies that they are permitted. In the
37158 future, we may extend the protocol to permit existing notifications in
37159 new contexts; this rule helps older senders avoid confusing newer
37162 (Older versions of @value{GDBN} ignore bytes received until they see
37163 the @samp{$} byte that begins an ordinary packet, so new stubs may
37164 transmit notifications without fear of confusing older clients. There
37165 are no notifications defined for @value{GDBN} to send at the moment, but we
37166 assume that most older stubs would ignore them, as well.)
37168 Each notification is comprised of three parts:
37170 @item @var{name}:@var{event}
37171 The notification packet is sent by the side that initiates the
37172 exchange (currently, only the stub does that), with @var{event}
37173 carrying the specific information about the notification, and
37174 @var{name} specifying the name of the notification.
37176 The acknowledge sent by the other side, usually @value{GDBN}, to
37177 acknowledge the exchange and request the event.
37180 The purpose of an asynchronous notification mechanism is to report to
37181 @value{GDBN} that something interesting happened in the remote stub.
37183 The remote stub may send notification @var{name}:@var{event}
37184 at any time, but @value{GDBN} acknowledges the notification when
37185 appropriate. The notification event is pending before @value{GDBN}
37186 acknowledges. Only one notification at a time may be pending; if
37187 additional events occur before @value{GDBN} has acknowledged the
37188 previous notification, they must be queued by the stub for later
37189 synchronous transmission in response to @var{ack} packets from
37190 @value{GDBN}. Because the notification mechanism is unreliable,
37191 the stub is permitted to resend a notification if it believes
37192 @value{GDBN} may not have received it.
37194 Specifically, notifications may appear when @value{GDBN} is not
37195 otherwise reading input from the stub, or when @value{GDBN} is
37196 expecting to read a normal synchronous response or a
37197 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
37198 Notification packets are distinct from any other communication from
37199 the stub so there is no ambiguity.
37201 After receiving a notification, @value{GDBN} shall acknowledge it by
37202 sending a @var{ack} packet as a regular, synchronous request to the
37203 stub. Such acknowledgment is not required to happen immediately, as
37204 @value{GDBN} is permitted to send other, unrelated packets to the
37205 stub first, which the stub should process normally.
37207 Upon receiving a @var{ack} packet, if the stub has other queued
37208 events to report to @value{GDBN}, it shall respond by sending a
37209 normal @var{event}. @value{GDBN} shall then send another @var{ack}
37210 packet to solicit further responses; again, it is permitted to send
37211 other, unrelated packets as well which the stub should process
37214 If the stub receives a @var{ack} packet and there are no additional
37215 @var{event} to report, the stub shall return an @samp{OK} response.
37216 At this point, @value{GDBN} has finished processing a notification
37217 and the stub has completed sending any queued events. @value{GDBN}
37218 won't accept any new notifications until the final @samp{OK} is
37219 received . If further notification events occur, the stub shall send
37220 a new notification, @value{GDBN} shall accept the notification, and
37221 the process shall be repeated.
37223 The process of asynchronous notification can be illustrated by the
37226 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
37229 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
37231 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
37236 The following notifications are defined:
37237 @multitable @columnfractions 0.12 0.12 0.38 0.38
37246 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
37247 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
37248 for information on how these notifications are acknowledged by
37250 @tab Report an asynchronous stop event in non-stop mode.
37254 @node Remote Non-Stop
37255 @section Remote Protocol Support for Non-Stop Mode
37257 @value{GDBN}'s remote protocol supports non-stop debugging of
37258 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
37259 supports non-stop mode, it should report that to @value{GDBN} by including
37260 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
37262 @value{GDBN} typically sends a @samp{QNonStop} packet only when
37263 establishing a new connection with the stub. Entering non-stop mode
37264 does not alter the state of any currently-running threads, but targets
37265 must stop all threads in any already-attached processes when entering
37266 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
37267 probe the target state after a mode change.
37269 In non-stop mode, when an attached process encounters an event that
37270 would otherwise be reported with a stop reply, it uses the
37271 asynchronous notification mechanism (@pxref{Notification Packets}) to
37272 inform @value{GDBN}. In contrast to all-stop mode, where all threads
37273 in all processes are stopped when a stop reply is sent, in non-stop
37274 mode only the thread reporting the stop event is stopped. That is,
37275 when reporting a @samp{S} or @samp{T} response to indicate completion
37276 of a step operation, hitting a breakpoint, or a fault, only the
37277 affected thread is stopped; any other still-running threads continue
37278 to run. When reporting a @samp{W} or @samp{X} response, all running
37279 threads belonging to other attached processes continue to run.
37281 In non-stop mode, the target shall respond to the @samp{?} packet as
37282 follows. First, any incomplete stop reply notification/@samp{vStopped}
37283 sequence in progress is abandoned. The target must begin a new
37284 sequence reporting stop events for all stopped threads, whether or not
37285 it has previously reported those events to @value{GDBN}. The first
37286 stop reply is sent as a synchronous reply to the @samp{?} packet, and
37287 subsequent stop replies are sent as responses to @samp{vStopped} packets
37288 using the mechanism described above. The target must not send
37289 asynchronous stop reply notifications until the sequence is complete.
37290 If all threads are running when the target receives the @samp{?} packet,
37291 or if the target is not attached to any process, it shall respond
37294 @node Packet Acknowledgment
37295 @section Packet Acknowledgment
37297 @cindex acknowledgment, for @value{GDBN} remote
37298 @cindex packet acknowledgment, for @value{GDBN} remote
37299 By default, when either the host or the target machine receives a packet,
37300 the first response expected is an acknowledgment: either @samp{+} (to indicate
37301 the package was received correctly) or @samp{-} (to request retransmission).
37302 This mechanism allows the @value{GDBN} remote protocol to operate over
37303 unreliable transport mechanisms, such as a serial line.
37305 In cases where the transport mechanism is itself reliable (such as a pipe or
37306 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
37307 It may be desirable to disable them in that case to reduce communication
37308 overhead, or for other reasons. This can be accomplished by means of the
37309 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
37311 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
37312 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
37313 and response format still includes the normal checksum, as described in
37314 @ref{Overview}, but the checksum may be ignored by the receiver.
37316 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
37317 no-acknowledgment mode, it should report that to @value{GDBN}
37318 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
37319 @pxref{qSupported}.
37320 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
37321 disabled via the @code{set remote noack-packet off} command
37322 (@pxref{Remote Configuration}),
37323 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
37324 Only then may the stub actually turn off packet acknowledgments.
37325 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
37326 response, which can be safely ignored by the stub.
37328 Note that @code{set remote noack-packet} command only affects negotiation
37329 between @value{GDBN} and the stub when subsequent connections are made;
37330 it does not affect the protocol acknowledgment state for any current
37332 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
37333 new connection is established,
37334 there is also no protocol request to re-enable the acknowledgments
37335 for the current connection, once disabled.
37340 Example sequence of a target being re-started. Notice how the restart
37341 does not get any direct output:
37346 @emph{target restarts}
37349 <- @code{T001:1234123412341234}
37353 Example sequence of a target being stepped by a single instruction:
37356 -> @code{G1445@dots{}}
37361 <- @code{T001:1234123412341234}
37365 <- @code{1455@dots{}}
37369 @node File-I/O Remote Protocol Extension
37370 @section File-I/O Remote Protocol Extension
37371 @cindex File-I/O remote protocol extension
37374 * File-I/O Overview::
37375 * Protocol Basics::
37376 * The F Request Packet::
37377 * The F Reply Packet::
37378 * The Ctrl-C Message::
37380 * List of Supported Calls::
37381 * Protocol-specific Representation of Datatypes::
37383 * File-I/O Examples::
37386 @node File-I/O Overview
37387 @subsection File-I/O Overview
37388 @cindex file-i/o overview
37390 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
37391 target to use the host's file system and console I/O to perform various
37392 system calls. System calls on the target system are translated into a
37393 remote protocol packet to the host system, which then performs the needed
37394 actions and returns a response packet to the target system.
37395 This simulates file system operations even on targets that lack file systems.
37397 The protocol is defined to be independent of both the host and target systems.
37398 It uses its own internal representation of datatypes and values. Both
37399 @value{GDBN} and the target's @value{GDBN} stub are responsible for
37400 translating the system-dependent value representations into the internal
37401 protocol representations when data is transmitted.
37403 The communication is synchronous. A system call is possible only when
37404 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
37405 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
37406 the target is stopped to allow deterministic access to the target's
37407 memory. Therefore File-I/O is not interruptible by target signals. On
37408 the other hand, it is possible to interrupt File-I/O by a user interrupt
37409 (@samp{Ctrl-C}) within @value{GDBN}.
37411 The target's request to perform a host system call does not finish
37412 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
37413 after finishing the system call, the target returns to continuing the
37414 previous activity (continue, step). No additional continue or step
37415 request from @value{GDBN} is required.
37418 (@value{GDBP}) continue
37419 <- target requests 'system call X'
37420 target is stopped, @value{GDBN} executes system call
37421 -> @value{GDBN} returns result
37422 ... target continues, @value{GDBN} returns to wait for the target
37423 <- target hits breakpoint and sends a Txx packet
37426 The protocol only supports I/O on the console and to regular files on
37427 the host file system. Character or block special devices, pipes,
37428 named pipes, sockets or any other communication method on the host
37429 system are not supported by this protocol.
37431 File I/O is not supported in non-stop mode.
37433 @node Protocol Basics
37434 @subsection Protocol Basics
37435 @cindex protocol basics, file-i/o
37437 The File-I/O protocol uses the @code{F} packet as the request as well
37438 as reply packet. Since a File-I/O system call can only occur when
37439 @value{GDBN} is waiting for a response from the continuing or stepping target,
37440 the File-I/O request is a reply that @value{GDBN} has to expect as a result
37441 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
37442 This @code{F} packet contains all information needed to allow @value{GDBN}
37443 to call the appropriate host system call:
37447 A unique identifier for the requested system call.
37450 All parameters to the system call. Pointers are given as addresses
37451 in the target memory address space. Pointers to strings are given as
37452 pointer/length pair. Numerical values are given as they are.
37453 Numerical control flags are given in a protocol-specific representation.
37457 At this point, @value{GDBN} has to perform the following actions.
37461 If the parameters include pointer values to data needed as input to a
37462 system call, @value{GDBN} requests this data from the target with a
37463 standard @code{m} packet request. This additional communication has to be
37464 expected by the target implementation and is handled as any other @code{m}
37468 @value{GDBN} translates all value from protocol representation to host
37469 representation as needed. Datatypes are coerced into the host types.
37472 @value{GDBN} calls the system call.
37475 It then coerces datatypes back to protocol representation.
37478 If the system call is expected to return data in buffer space specified
37479 by pointer parameters to the call, the data is transmitted to the
37480 target using a @code{M} or @code{X} packet. This packet has to be expected
37481 by the target implementation and is handled as any other @code{M} or @code{X}
37486 Eventually @value{GDBN} replies with another @code{F} packet which contains all
37487 necessary information for the target to continue. This at least contains
37494 @code{errno}, if has been changed by the system call.
37501 After having done the needed type and value coercion, the target continues
37502 the latest continue or step action.
37504 @node The F Request Packet
37505 @subsection The @code{F} Request Packet
37506 @cindex file-i/o request packet
37507 @cindex @code{F} request packet
37509 The @code{F} request packet has the following format:
37512 @item F@var{call-id},@var{parameter@dots{}}
37514 @var{call-id} is the identifier to indicate the host system call to be called.
37515 This is just the name of the function.
37517 @var{parameter@dots{}} are the parameters to the system call.
37518 Parameters are hexadecimal integer values, either the actual values in case
37519 of scalar datatypes, pointers to target buffer space in case of compound
37520 datatypes and unspecified memory areas, or pointer/length pairs in case
37521 of string parameters. These are appended to the @var{call-id} as a
37522 comma-delimited list. All values are transmitted in ASCII
37523 string representation, pointer/length pairs separated by a slash.
37529 @node The F Reply Packet
37530 @subsection The @code{F} Reply Packet
37531 @cindex file-i/o reply packet
37532 @cindex @code{F} reply packet
37534 The @code{F} reply packet has the following format:
37538 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
37540 @var{retcode} is the return code of the system call as hexadecimal value.
37542 @var{errno} is the @code{errno} set by the call, in protocol-specific
37544 This parameter can be omitted if the call was successful.
37546 @var{Ctrl-C flag} is only sent if the user requested a break. In this
37547 case, @var{errno} must be sent as well, even if the call was successful.
37548 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
37555 or, if the call was interrupted before the host call has been performed:
37562 assuming 4 is the protocol-specific representation of @code{EINTR}.
37567 @node The Ctrl-C Message
37568 @subsection The @samp{Ctrl-C} Message
37569 @cindex ctrl-c message, in file-i/o protocol
37571 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
37572 reply packet (@pxref{The F Reply Packet}),
37573 the target should behave as if it had
37574 gotten a break message. The meaning for the target is ``system call
37575 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
37576 (as with a break message) and return to @value{GDBN} with a @code{T02}
37579 It's important for the target to know in which
37580 state the system call was interrupted. There are two possible cases:
37584 The system call hasn't been performed on the host yet.
37587 The system call on the host has been finished.
37591 These two states can be distinguished by the target by the value of the
37592 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
37593 call hasn't been performed. This is equivalent to the @code{EINTR} handling
37594 on POSIX systems. In any other case, the target may presume that the
37595 system call has been finished --- successfully or not --- and should behave
37596 as if the break message arrived right after the system call.
37598 @value{GDBN} must behave reliably. If the system call has not been called
37599 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
37600 @code{errno} in the packet. If the system call on the host has been finished
37601 before the user requests a break, the full action must be finished by
37602 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
37603 The @code{F} packet may only be sent when either nothing has happened
37604 or the full action has been completed.
37607 @subsection Console I/O
37608 @cindex console i/o as part of file-i/o
37610 By default and if not explicitly closed by the target system, the file
37611 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
37612 on the @value{GDBN} console is handled as any other file output operation
37613 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
37614 by @value{GDBN} so that after the target read request from file descriptor
37615 0 all following typing is buffered until either one of the following
37620 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
37622 system call is treated as finished.
37625 The user presses @key{RET}. This is treated as end of input with a trailing
37629 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
37630 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
37634 If the user has typed more characters than fit in the buffer given to
37635 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
37636 either another @code{read(0, @dots{})} is requested by the target, or debugging
37637 is stopped at the user's request.
37640 @node List of Supported Calls
37641 @subsection List of Supported Calls
37642 @cindex list of supported file-i/o calls
37659 @unnumberedsubsubsec open
37660 @cindex open, file-i/o system call
37665 int open(const char *pathname, int flags);
37666 int open(const char *pathname, int flags, mode_t mode);
37670 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
37673 @var{flags} is the bitwise @code{OR} of the following values:
37677 If the file does not exist it will be created. The host
37678 rules apply as far as file ownership and time stamps
37682 When used with @code{O_CREAT}, if the file already exists it is
37683 an error and open() fails.
37686 If the file already exists and the open mode allows
37687 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
37688 truncated to zero length.
37691 The file is opened in append mode.
37694 The file is opened for reading only.
37697 The file is opened for writing only.
37700 The file is opened for reading and writing.
37704 Other bits are silently ignored.
37708 @var{mode} is the bitwise @code{OR} of the following values:
37712 User has read permission.
37715 User has write permission.
37718 Group has read permission.
37721 Group has write permission.
37724 Others have read permission.
37727 Others have write permission.
37731 Other bits are silently ignored.
37734 @item Return value:
37735 @code{open} returns the new file descriptor or -1 if an error
37742 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
37745 @var{pathname} refers to a directory.
37748 The requested access is not allowed.
37751 @var{pathname} was too long.
37754 A directory component in @var{pathname} does not exist.
37757 @var{pathname} refers to a device, pipe, named pipe or socket.
37760 @var{pathname} refers to a file on a read-only filesystem and
37761 write access was requested.
37764 @var{pathname} is an invalid pointer value.
37767 No space on device to create the file.
37770 The process already has the maximum number of files open.
37773 The limit on the total number of files open on the system
37777 The call was interrupted by the user.
37783 @unnumberedsubsubsec close
37784 @cindex close, file-i/o system call
37793 @samp{Fclose,@var{fd}}
37795 @item Return value:
37796 @code{close} returns zero on success, or -1 if an error occurred.
37802 @var{fd} isn't a valid open file descriptor.
37805 The call was interrupted by the user.
37811 @unnumberedsubsubsec read
37812 @cindex read, file-i/o system call
37817 int read(int fd, void *buf, unsigned int count);
37821 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
37823 @item Return value:
37824 On success, the number of bytes read is returned.
37825 Zero indicates end of file. If count is zero, read
37826 returns zero as well. On error, -1 is returned.
37832 @var{fd} is not a valid file descriptor or is not open for
37836 @var{bufptr} is an invalid pointer value.
37839 The call was interrupted by the user.
37845 @unnumberedsubsubsec write
37846 @cindex write, file-i/o system call
37851 int write(int fd, const void *buf, unsigned int count);
37855 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
37857 @item Return value:
37858 On success, the number of bytes written are returned.
37859 Zero indicates nothing was written. On error, -1
37866 @var{fd} is not a valid file descriptor or is not open for
37870 @var{bufptr} is an invalid pointer value.
37873 An attempt was made to write a file that exceeds the
37874 host-specific maximum file size allowed.
37877 No space on device to write the data.
37880 The call was interrupted by the user.
37886 @unnumberedsubsubsec lseek
37887 @cindex lseek, file-i/o system call
37892 long lseek (int fd, long offset, int flag);
37896 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
37898 @var{flag} is one of:
37902 The offset is set to @var{offset} bytes.
37905 The offset is set to its current location plus @var{offset}
37909 The offset is set to the size of the file plus @var{offset}
37913 @item Return value:
37914 On success, the resulting unsigned offset in bytes from
37915 the beginning of the file is returned. Otherwise, a
37916 value of -1 is returned.
37922 @var{fd} is not a valid open file descriptor.
37925 @var{fd} is associated with the @value{GDBN} console.
37928 @var{flag} is not a proper value.
37931 The call was interrupted by the user.
37937 @unnumberedsubsubsec rename
37938 @cindex rename, file-i/o system call
37943 int rename(const char *oldpath, const char *newpath);
37947 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
37949 @item Return value:
37950 On success, zero is returned. On error, -1 is returned.
37956 @var{newpath} is an existing directory, but @var{oldpath} is not a
37960 @var{newpath} is a non-empty directory.
37963 @var{oldpath} or @var{newpath} is a directory that is in use by some
37967 An attempt was made to make a directory a subdirectory
37971 A component used as a directory in @var{oldpath} or new
37972 path is not a directory. Or @var{oldpath} is a directory
37973 and @var{newpath} exists but is not a directory.
37976 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
37979 No access to the file or the path of the file.
37983 @var{oldpath} or @var{newpath} was too long.
37986 A directory component in @var{oldpath} or @var{newpath} does not exist.
37989 The file is on a read-only filesystem.
37992 The device containing the file has no room for the new
37996 The call was interrupted by the user.
38002 @unnumberedsubsubsec unlink
38003 @cindex unlink, file-i/o system call
38008 int unlink(const char *pathname);
38012 @samp{Funlink,@var{pathnameptr}/@var{len}}
38014 @item Return value:
38015 On success, zero is returned. On error, -1 is returned.
38021 No access to the file or the path of the file.
38024 The system does not allow unlinking of directories.
38027 The file @var{pathname} cannot be unlinked because it's
38028 being used by another process.
38031 @var{pathnameptr} is an invalid pointer value.
38034 @var{pathname} was too long.
38037 A directory component in @var{pathname} does not exist.
38040 A component of the path is not a directory.
38043 The file is on a read-only filesystem.
38046 The call was interrupted by the user.
38052 @unnumberedsubsubsec stat/fstat
38053 @cindex fstat, file-i/o system call
38054 @cindex stat, file-i/o system call
38059 int stat(const char *pathname, struct stat *buf);
38060 int fstat(int fd, struct stat *buf);
38064 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
38065 @samp{Ffstat,@var{fd},@var{bufptr}}
38067 @item Return value:
38068 On success, zero is returned. On error, -1 is returned.
38074 @var{fd} is not a valid open file.
38077 A directory component in @var{pathname} does not exist or the
38078 path is an empty string.
38081 A component of the path is not a directory.
38084 @var{pathnameptr} is an invalid pointer value.
38087 No access to the file or the path of the file.
38090 @var{pathname} was too long.
38093 The call was interrupted by the user.
38099 @unnumberedsubsubsec gettimeofday
38100 @cindex gettimeofday, file-i/o system call
38105 int gettimeofday(struct timeval *tv, void *tz);
38109 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
38111 @item Return value:
38112 On success, 0 is returned, -1 otherwise.
38118 @var{tz} is a non-NULL pointer.
38121 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
38127 @unnumberedsubsubsec isatty
38128 @cindex isatty, file-i/o system call
38133 int isatty(int fd);
38137 @samp{Fisatty,@var{fd}}
38139 @item Return value:
38140 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
38146 The call was interrupted by the user.
38151 Note that the @code{isatty} call is treated as a special case: it returns
38152 1 to the target if the file descriptor is attached
38153 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
38154 would require implementing @code{ioctl} and would be more complex than
38159 @unnumberedsubsubsec system
38160 @cindex system, file-i/o system call
38165 int system(const char *command);
38169 @samp{Fsystem,@var{commandptr}/@var{len}}
38171 @item Return value:
38172 If @var{len} is zero, the return value indicates whether a shell is
38173 available. A zero return value indicates a shell is not available.
38174 For non-zero @var{len}, the value returned is -1 on error and the
38175 return status of the command otherwise. Only the exit status of the
38176 command is returned, which is extracted from the host's @code{system}
38177 return value by calling @code{WEXITSTATUS(retval)}. In case
38178 @file{/bin/sh} could not be executed, 127 is returned.
38184 The call was interrupted by the user.
38189 @value{GDBN} takes over the full task of calling the necessary host calls
38190 to perform the @code{system} call. The return value of @code{system} on
38191 the host is simplified before it's returned
38192 to the target. Any termination signal information from the child process
38193 is discarded, and the return value consists
38194 entirely of the exit status of the called command.
38196 Due to security concerns, the @code{system} call is by default refused
38197 by @value{GDBN}. The user has to allow this call explicitly with the
38198 @code{set remote system-call-allowed 1} command.
38201 @item set remote system-call-allowed
38202 @kindex set remote system-call-allowed
38203 Control whether to allow the @code{system} calls in the File I/O
38204 protocol for the remote target. The default is zero (disabled).
38206 @item show remote system-call-allowed
38207 @kindex show remote system-call-allowed
38208 Show whether the @code{system} calls are allowed in the File I/O
38212 @node Protocol-specific Representation of Datatypes
38213 @subsection Protocol-specific Representation of Datatypes
38214 @cindex protocol-specific representation of datatypes, in file-i/o protocol
38217 * Integral Datatypes::
38219 * Memory Transfer::
38224 @node Integral Datatypes
38225 @unnumberedsubsubsec Integral Datatypes
38226 @cindex integral datatypes, in file-i/o protocol
38228 The integral datatypes used in the system calls are @code{int},
38229 @code{unsigned int}, @code{long}, @code{unsigned long},
38230 @code{mode_t}, and @code{time_t}.
38232 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
38233 implemented as 32 bit values in this protocol.
38235 @code{long} and @code{unsigned long} are implemented as 64 bit types.
38237 @xref{Limits}, for corresponding MIN and MAX values (similar to those
38238 in @file{limits.h}) to allow range checking on host and target.
38240 @code{time_t} datatypes are defined as seconds since the Epoch.
38242 All integral datatypes transferred as part of a memory read or write of a
38243 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
38246 @node Pointer Values
38247 @unnumberedsubsubsec Pointer Values
38248 @cindex pointer values, in file-i/o protocol
38250 Pointers to target data are transmitted as they are. An exception
38251 is made for pointers to buffers for which the length isn't
38252 transmitted as part of the function call, namely strings. Strings
38253 are transmitted as a pointer/length pair, both as hex values, e.g.@:
38260 which is a pointer to data of length 18 bytes at position 0x1aaf.
38261 The length is defined as the full string length in bytes, including
38262 the trailing null byte. For example, the string @code{"hello world"}
38263 at address 0x123456 is transmitted as
38269 @node Memory Transfer
38270 @unnumberedsubsubsec Memory Transfer
38271 @cindex memory transfer, in file-i/o protocol
38273 Structured data which is transferred using a memory read or write (for
38274 example, a @code{struct stat}) is expected to be in a protocol-specific format
38275 with all scalar multibyte datatypes being big endian. Translation to
38276 this representation needs to be done both by the target before the @code{F}
38277 packet is sent, and by @value{GDBN} before
38278 it transfers memory to the target. Transferred pointers to structured
38279 data should point to the already-coerced data at any time.
38283 @unnumberedsubsubsec struct stat
38284 @cindex struct stat, in file-i/o protocol
38286 The buffer of type @code{struct stat} used by the target and @value{GDBN}
38287 is defined as follows:
38291 unsigned int st_dev; /* device */
38292 unsigned int st_ino; /* inode */
38293 mode_t st_mode; /* protection */
38294 unsigned int st_nlink; /* number of hard links */
38295 unsigned int st_uid; /* user ID of owner */
38296 unsigned int st_gid; /* group ID of owner */
38297 unsigned int st_rdev; /* device type (if inode device) */
38298 unsigned long st_size; /* total size, in bytes */
38299 unsigned long st_blksize; /* blocksize for filesystem I/O */
38300 unsigned long st_blocks; /* number of blocks allocated */
38301 time_t st_atime; /* time of last access */
38302 time_t st_mtime; /* time of last modification */
38303 time_t st_ctime; /* time of last change */
38307 The integral datatypes conform to the definitions given in the
38308 appropriate section (see @ref{Integral Datatypes}, for details) so this
38309 structure is of size 64 bytes.
38311 The values of several fields have a restricted meaning and/or
38317 A value of 0 represents a file, 1 the console.
38320 No valid meaning for the target. Transmitted unchanged.
38323 Valid mode bits are described in @ref{Constants}. Any other
38324 bits have currently no meaning for the target.
38329 No valid meaning for the target. Transmitted unchanged.
38334 These values have a host and file system dependent
38335 accuracy. Especially on Windows hosts, the file system may not
38336 support exact timing values.
38339 The target gets a @code{struct stat} of the above representation and is
38340 responsible for coercing it to the target representation before
38343 Note that due to size differences between the host, target, and protocol
38344 representations of @code{struct stat} members, these members could eventually
38345 get truncated on the target.
38347 @node struct timeval
38348 @unnumberedsubsubsec struct timeval
38349 @cindex struct timeval, in file-i/o protocol
38351 The buffer of type @code{struct timeval} used by the File-I/O protocol
38352 is defined as follows:
38356 time_t tv_sec; /* second */
38357 long tv_usec; /* microsecond */
38361 The integral datatypes conform to the definitions given in the
38362 appropriate section (see @ref{Integral Datatypes}, for details) so this
38363 structure is of size 8 bytes.
38366 @subsection Constants
38367 @cindex constants, in file-i/o protocol
38369 The following values are used for the constants inside of the
38370 protocol. @value{GDBN} and target are responsible for translating these
38371 values before and after the call as needed.
38382 @unnumberedsubsubsec Open Flags
38383 @cindex open flags, in file-i/o protocol
38385 All values are given in hexadecimal representation.
38397 @node mode_t Values
38398 @unnumberedsubsubsec mode_t Values
38399 @cindex mode_t values, in file-i/o protocol
38401 All values are given in octal representation.
38418 @unnumberedsubsubsec Errno Values
38419 @cindex errno values, in file-i/o protocol
38421 All values are given in decimal representation.
38446 @code{EUNKNOWN} is used as a fallback error value if a host system returns
38447 any error value not in the list of supported error numbers.
38450 @unnumberedsubsubsec Lseek Flags
38451 @cindex lseek flags, in file-i/o protocol
38460 @unnumberedsubsubsec Limits
38461 @cindex limits, in file-i/o protocol
38463 All values are given in decimal representation.
38466 INT_MIN -2147483648
38468 UINT_MAX 4294967295
38469 LONG_MIN -9223372036854775808
38470 LONG_MAX 9223372036854775807
38471 ULONG_MAX 18446744073709551615
38474 @node File-I/O Examples
38475 @subsection File-I/O Examples
38476 @cindex file-i/o examples
38478 Example sequence of a write call, file descriptor 3, buffer is at target
38479 address 0x1234, 6 bytes should be written:
38482 <- @code{Fwrite,3,1234,6}
38483 @emph{request memory read from target}
38486 @emph{return "6 bytes written"}
38490 Example sequence of a read call, file descriptor 3, buffer is at target
38491 address 0x1234, 6 bytes should be read:
38494 <- @code{Fread,3,1234,6}
38495 @emph{request memory write to target}
38496 -> @code{X1234,6:XXXXXX}
38497 @emph{return "6 bytes read"}
38501 Example sequence of a read call, call fails on the host due to invalid
38502 file descriptor (@code{EBADF}):
38505 <- @code{Fread,3,1234,6}
38509 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
38513 <- @code{Fread,3,1234,6}
38518 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
38522 <- @code{Fread,3,1234,6}
38523 -> @code{X1234,6:XXXXXX}
38527 @node Library List Format
38528 @section Library List Format
38529 @cindex library list format, remote protocol
38531 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
38532 same process as your application to manage libraries. In this case,
38533 @value{GDBN} can use the loader's symbol table and normal memory
38534 operations to maintain a list of shared libraries. On other
38535 platforms, the operating system manages loaded libraries.
38536 @value{GDBN} can not retrieve the list of currently loaded libraries
38537 through memory operations, so it uses the @samp{qXfer:libraries:read}
38538 packet (@pxref{qXfer library list read}) instead. The remote stub
38539 queries the target's operating system and reports which libraries
38542 The @samp{qXfer:libraries:read} packet returns an XML document which
38543 lists loaded libraries and their offsets. Each library has an
38544 associated name and one or more segment or section base addresses,
38545 which report where the library was loaded in memory.
38547 For the common case of libraries that are fully linked binaries, the
38548 library should have a list of segments. If the target supports
38549 dynamic linking of a relocatable object file, its library XML element
38550 should instead include a list of allocated sections. The segment or
38551 section bases are start addresses, not relocation offsets; they do not
38552 depend on the library's link-time base addresses.
38554 @value{GDBN} must be linked with the Expat library to support XML
38555 library lists. @xref{Expat}.
38557 A simple memory map, with one loaded library relocated by a single
38558 offset, looks like this:
38562 <library name="/lib/libc.so.6">
38563 <segment address="0x10000000"/>
38568 Another simple memory map, with one loaded library with three
38569 allocated sections (.text, .data, .bss), looks like this:
38573 <library name="sharedlib.o">
38574 <section address="0x10000000"/>
38575 <section address="0x20000000"/>
38576 <section address="0x30000000"/>
38581 The format of a library list is described by this DTD:
38584 <!-- library-list: Root element with versioning -->
38585 <!ELEMENT library-list (library)*>
38586 <!ATTLIST library-list version CDATA #FIXED "1.0">
38587 <!ELEMENT library (segment*, section*)>
38588 <!ATTLIST library name CDATA #REQUIRED>
38589 <!ELEMENT segment EMPTY>
38590 <!ATTLIST segment address CDATA #REQUIRED>
38591 <!ELEMENT section EMPTY>
38592 <!ATTLIST section address CDATA #REQUIRED>
38595 In addition, segments and section descriptors cannot be mixed within a
38596 single library element, and you must supply at least one segment or
38597 section for each library.
38599 @node Library List Format for SVR4 Targets
38600 @section Library List Format for SVR4 Targets
38601 @cindex library list format, remote protocol
38603 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
38604 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
38605 shared libraries. Still a special library list provided by this packet is
38606 more efficient for the @value{GDBN} remote protocol.
38608 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
38609 loaded libraries and their SVR4 linker parameters. For each library on SVR4
38610 target, the following parameters are reported:
38614 @code{name}, the absolute file name from the @code{l_name} field of
38615 @code{struct link_map}.
38617 @code{lm} with address of @code{struct link_map} used for TLS
38618 (Thread Local Storage) access.
38620 @code{l_addr}, the displacement as read from the field @code{l_addr} of
38621 @code{struct link_map}. For prelinked libraries this is not an absolute
38622 memory address. It is a displacement of absolute memory address against
38623 address the file was prelinked to during the library load.
38625 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
38628 Additionally the single @code{main-lm} attribute specifies address of
38629 @code{struct link_map} used for the main executable. This parameter is used
38630 for TLS access and its presence is optional.
38632 @value{GDBN} must be linked with the Expat library to support XML
38633 SVR4 library lists. @xref{Expat}.
38635 A simple memory map, with two loaded libraries (which do not use prelink),
38639 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
38640 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
38642 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
38644 </library-list-svr>
38647 The format of an SVR4 library list is described by this DTD:
38650 <!-- library-list-svr4: Root element with versioning -->
38651 <!ELEMENT library-list-svr4 (library)*>
38652 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
38653 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
38654 <!ELEMENT library EMPTY>
38655 <!ATTLIST library name CDATA #REQUIRED>
38656 <!ATTLIST library lm CDATA #REQUIRED>
38657 <!ATTLIST library l_addr CDATA #REQUIRED>
38658 <!ATTLIST library l_ld CDATA #REQUIRED>
38661 @node Memory Map Format
38662 @section Memory Map Format
38663 @cindex memory map format
38665 To be able to write into flash memory, @value{GDBN} needs to obtain a
38666 memory map from the target. This section describes the format of the
38669 The memory map is obtained using the @samp{qXfer:memory-map:read}
38670 (@pxref{qXfer memory map read}) packet and is an XML document that
38671 lists memory regions.
38673 @value{GDBN} must be linked with the Expat library to support XML
38674 memory maps. @xref{Expat}.
38676 The top-level structure of the document is shown below:
38679 <?xml version="1.0"?>
38680 <!DOCTYPE memory-map
38681 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
38682 "http://sourceware.org/gdb/gdb-memory-map.dtd">
38688 Each region can be either:
38693 A region of RAM starting at @var{addr} and extending for @var{length}
38697 <memory type="ram" start="@var{addr}" length="@var{length}"/>
38702 A region of read-only memory:
38705 <memory type="rom" start="@var{addr}" length="@var{length}"/>
38710 A region of flash memory, with erasure blocks @var{blocksize}
38714 <memory type="flash" start="@var{addr}" length="@var{length}">
38715 <property name="blocksize">@var{blocksize}</property>
38721 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
38722 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
38723 packets to write to addresses in such ranges.
38725 The formal DTD for memory map format is given below:
38728 <!-- ................................................... -->
38729 <!-- Memory Map XML DTD ................................ -->
38730 <!-- File: memory-map.dtd .............................. -->
38731 <!-- .................................... .............. -->
38732 <!-- memory-map.dtd -->
38733 <!-- memory-map: Root element with versioning -->
38734 <!ELEMENT memory-map (memory | property)>
38735 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
38736 <!ELEMENT memory (property)>
38737 <!-- memory: Specifies a memory region,
38738 and its type, or device. -->
38739 <!ATTLIST memory type CDATA #REQUIRED
38740 start CDATA #REQUIRED
38741 length CDATA #REQUIRED
38742 device CDATA #IMPLIED>
38743 <!-- property: Generic attribute tag -->
38744 <!ELEMENT property (#PCDATA | property)*>
38745 <!ATTLIST property name CDATA #REQUIRED>
38748 @node Thread List Format
38749 @section Thread List Format
38750 @cindex thread list format
38752 To efficiently update the list of threads and their attributes,
38753 @value{GDBN} issues the @samp{qXfer:threads:read} packet
38754 (@pxref{qXfer threads read}) and obtains the XML document with
38755 the following structure:
38758 <?xml version="1.0"?>
38760 <thread id="id" core="0">
38761 ... description ...
38766 Each @samp{thread} element must have the @samp{id} attribute that
38767 identifies the thread (@pxref{thread-id syntax}). The
38768 @samp{core} attribute, if present, specifies which processor core
38769 the thread was last executing on. The content of the of @samp{thread}
38770 element is interpreted as human-readable auxilliary information.
38772 @node Traceframe Info Format
38773 @section Traceframe Info Format
38774 @cindex traceframe info format
38776 To be able to know which objects in the inferior can be examined when
38777 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
38778 memory ranges, registers and trace state variables that have been
38779 collected in a traceframe.
38781 This list is obtained using the @samp{qXfer:traceframe-info:read}
38782 (@pxref{qXfer traceframe info read}) packet and is an XML document.
38784 @value{GDBN} must be linked with the Expat library to support XML
38785 traceframe info discovery. @xref{Expat}.
38787 The top-level structure of the document is shown below:
38790 <?xml version="1.0"?>
38791 <!DOCTYPE traceframe-info
38792 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
38793 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
38799 Each traceframe block can be either:
38804 A region of collected memory starting at @var{addr} and extending for
38805 @var{length} bytes from there:
38808 <memory start="@var{addr}" length="@var{length}"/>
38812 A block indicating trace state variable numbered @var{number} has been
38816 <tvar id="@var{number}"/>
38821 The formal DTD for the traceframe info format is given below:
38824 <!ELEMENT traceframe-info (memory | tvar)* >
38825 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
38827 <!ELEMENT memory EMPTY>
38828 <!ATTLIST memory start CDATA #REQUIRED
38829 length CDATA #REQUIRED>
38831 <!ATTLIST tvar id CDATA #REQUIRED>
38834 @node Branch Trace Format
38835 @section Branch Trace Format
38836 @cindex branch trace format
38838 In order to display the branch trace of an inferior thread,
38839 @value{GDBN} needs to obtain the list of branches. This list is
38840 represented as list of sequential code blocks that are connected via
38841 branches. The code in each block has been executed sequentially.
38843 This list is obtained using the @samp{qXfer:btrace:read}
38844 (@pxref{qXfer btrace read}) packet and is an XML document.
38846 @value{GDBN} must be linked with the Expat library to support XML
38847 traceframe info discovery. @xref{Expat}.
38849 The top-level structure of the document is shown below:
38852 <?xml version="1.0"?>
38854 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
38855 "http://sourceware.org/gdb/gdb-btrace.dtd">
38864 A block of sequentially executed instructions starting at @var{begin}
38865 and ending at @var{end}:
38868 <block begin="@var{begin}" end="@var{end}"/>
38873 The formal DTD for the branch trace format is given below:
38876 <!ELEMENT btrace (block)* >
38877 <!ATTLIST btrace version CDATA #FIXED "1.0">
38879 <!ELEMENT block EMPTY>
38880 <!ATTLIST block begin CDATA #REQUIRED
38881 end CDATA #REQUIRED>
38884 @include agentexpr.texi
38886 @node Target Descriptions
38887 @appendix Target Descriptions
38888 @cindex target descriptions
38890 One of the challenges of using @value{GDBN} to debug embedded systems
38891 is that there are so many minor variants of each processor
38892 architecture in use. It is common practice for vendors to start with
38893 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
38894 and then make changes to adapt it to a particular market niche. Some
38895 architectures have hundreds of variants, available from dozens of
38896 vendors. This leads to a number of problems:
38900 With so many different customized processors, it is difficult for
38901 the @value{GDBN} maintainers to keep up with the changes.
38903 Since individual variants may have short lifetimes or limited
38904 audiences, it may not be worthwhile to carry information about every
38905 variant in the @value{GDBN} source tree.
38907 When @value{GDBN} does support the architecture of the embedded system
38908 at hand, the task of finding the correct architecture name to give the
38909 @command{set architecture} command can be error-prone.
38912 To address these problems, the @value{GDBN} remote protocol allows a
38913 target system to not only identify itself to @value{GDBN}, but to
38914 actually describe its own features. This lets @value{GDBN} support
38915 processor variants it has never seen before --- to the extent that the
38916 descriptions are accurate, and that @value{GDBN} understands them.
38918 @value{GDBN} must be linked with the Expat library to support XML
38919 target descriptions. @xref{Expat}.
38922 * Retrieving Descriptions:: How descriptions are fetched from a target.
38923 * Target Description Format:: The contents of a target description.
38924 * Predefined Target Types:: Standard types available for target
38926 * Standard Target Features:: Features @value{GDBN} knows about.
38929 @node Retrieving Descriptions
38930 @section Retrieving Descriptions
38932 Target descriptions can be read from the target automatically, or
38933 specified by the user manually. The default behavior is to read the
38934 description from the target. @value{GDBN} retrieves it via the remote
38935 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
38936 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
38937 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
38938 XML document, of the form described in @ref{Target Description
38941 Alternatively, you can specify a file to read for the target description.
38942 If a file is set, the target will not be queried. The commands to
38943 specify a file are:
38946 @cindex set tdesc filename
38947 @item set tdesc filename @var{path}
38948 Read the target description from @var{path}.
38950 @cindex unset tdesc filename
38951 @item unset tdesc filename
38952 Do not read the XML target description from a file. @value{GDBN}
38953 will use the description supplied by the current target.
38955 @cindex show tdesc filename
38956 @item show tdesc filename
38957 Show the filename to read for a target description, if any.
38961 @node Target Description Format
38962 @section Target Description Format
38963 @cindex target descriptions, XML format
38965 A target description annex is an @uref{http://www.w3.org/XML/, XML}
38966 document which complies with the Document Type Definition provided in
38967 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
38968 means you can use generally available tools like @command{xmllint} to
38969 check that your feature descriptions are well-formed and valid.
38970 However, to help people unfamiliar with XML write descriptions for
38971 their targets, we also describe the grammar here.
38973 Target descriptions can identify the architecture of the remote target
38974 and (for some architectures) provide information about custom register
38975 sets. They can also identify the OS ABI of the remote target.
38976 @value{GDBN} can use this information to autoconfigure for your
38977 target, or to warn you if you connect to an unsupported target.
38979 Here is a simple target description:
38982 <target version="1.0">
38983 <architecture>i386:x86-64</architecture>
38988 This minimal description only says that the target uses
38989 the x86-64 architecture.
38991 A target description has the following overall form, with [ ] marking
38992 optional elements and @dots{} marking repeatable elements. The elements
38993 are explained further below.
38996 <?xml version="1.0"?>
38997 <!DOCTYPE target SYSTEM "gdb-target.dtd">
38998 <target version="1.0">
38999 @r{[}@var{architecture}@r{]}
39000 @r{[}@var{osabi}@r{]}
39001 @r{[}@var{compatible}@r{]}
39002 @r{[}@var{feature}@dots{}@r{]}
39007 The description is generally insensitive to whitespace and line
39008 breaks, under the usual common-sense rules. The XML version
39009 declaration and document type declaration can generally be omitted
39010 (@value{GDBN} does not require them), but specifying them may be
39011 useful for XML validation tools. The @samp{version} attribute for
39012 @samp{<target>} may also be omitted, but we recommend
39013 including it; if future versions of @value{GDBN} use an incompatible
39014 revision of @file{gdb-target.dtd}, they will detect and report
39015 the version mismatch.
39017 @subsection Inclusion
39018 @cindex target descriptions, inclusion
39021 @cindex <xi:include>
39024 It can sometimes be valuable to split a target description up into
39025 several different annexes, either for organizational purposes, or to
39026 share files between different possible target descriptions. You can
39027 divide a description into multiple files by replacing any element of
39028 the target description with an inclusion directive of the form:
39031 <xi:include href="@var{document}"/>
39035 When @value{GDBN} encounters an element of this form, it will retrieve
39036 the named XML @var{document}, and replace the inclusion directive with
39037 the contents of that document. If the current description was read
39038 using @samp{qXfer}, then so will be the included document;
39039 @var{document} will be interpreted as the name of an annex. If the
39040 current description was read from a file, @value{GDBN} will look for
39041 @var{document} as a file in the same directory where it found the
39042 original description.
39044 @subsection Architecture
39045 @cindex <architecture>
39047 An @samp{<architecture>} element has this form:
39050 <architecture>@var{arch}</architecture>
39053 @var{arch} is one of the architectures from the set accepted by
39054 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
39057 @cindex @code{<osabi>}
39059 This optional field was introduced in @value{GDBN} version 7.0.
39060 Previous versions of @value{GDBN} ignore it.
39062 An @samp{<osabi>} element has this form:
39065 <osabi>@var{abi-name}</osabi>
39068 @var{abi-name} is an OS ABI name from the same selection accepted by
39069 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
39071 @subsection Compatible Architecture
39072 @cindex @code{<compatible>}
39074 This optional field was introduced in @value{GDBN} version 7.0.
39075 Previous versions of @value{GDBN} ignore it.
39077 A @samp{<compatible>} element has this form:
39080 <compatible>@var{arch}</compatible>
39083 @var{arch} is one of the architectures from the set accepted by
39084 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
39086 A @samp{<compatible>} element is used to specify that the target
39087 is able to run binaries in some other than the main target architecture
39088 given by the @samp{<architecture>} element. For example, on the
39089 Cell Broadband Engine, the main architecture is @code{powerpc:common}
39090 or @code{powerpc:common64}, but the system is able to run binaries
39091 in the @code{spu} architecture as well. The way to describe this
39092 capability with @samp{<compatible>} is as follows:
39095 <architecture>powerpc:common</architecture>
39096 <compatible>spu</compatible>
39099 @subsection Features
39102 Each @samp{<feature>} describes some logical portion of the target
39103 system. Features are currently used to describe available CPU
39104 registers and the types of their contents. A @samp{<feature>} element
39108 <feature name="@var{name}">
39109 @r{[}@var{type}@dots{}@r{]}
39115 Each feature's name should be unique within the description. The name
39116 of a feature does not matter unless @value{GDBN} has some special
39117 knowledge of the contents of that feature; if it does, the feature
39118 should have its standard name. @xref{Standard Target Features}.
39122 Any register's value is a collection of bits which @value{GDBN} must
39123 interpret. The default interpretation is a two's complement integer,
39124 but other types can be requested by name in the register description.
39125 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
39126 Target Types}), and the description can define additional composite types.
39128 Each type element must have an @samp{id} attribute, which gives
39129 a unique (within the containing @samp{<feature>}) name to the type.
39130 Types must be defined before they are used.
39133 Some targets offer vector registers, which can be treated as arrays
39134 of scalar elements. These types are written as @samp{<vector>} elements,
39135 specifying the array element type, @var{type}, and the number of elements,
39139 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
39143 If a register's value is usefully viewed in multiple ways, define it
39144 with a union type containing the useful representations. The
39145 @samp{<union>} element contains one or more @samp{<field>} elements,
39146 each of which has a @var{name} and a @var{type}:
39149 <union id="@var{id}">
39150 <field name="@var{name}" type="@var{type}"/>
39156 If a register's value is composed from several separate values, define
39157 it with a structure type. There are two forms of the @samp{<struct>}
39158 element; a @samp{<struct>} element must either contain only bitfields
39159 or contain no bitfields. If the structure contains only bitfields,
39160 its total size in bytes must be specified, each bitfield must have an
39161 explicit start and end, and bitfields are automatically assigned an
39162 integer type. The field's @var{start} should be less than or
39163 equal to its @var{end}, and zero represents the least significant bit.
39166 <struct id="@var{id}" size="@var{size}">
39167 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
39172 If the structure contains no bitfields, then each field has an
39173 explicit type, and no implicit padding is added.
39176 <struct id="@var{id}">
39177 <field name="@var{name}" type="@var{type}"/>
39183 If a register's value is a series of single-bit flags, define it with
39184 a flags type. The @samp{<flags>} element has an explicit @var{size}
39185 and contains one or more @samp{<field>} elements. Each field has a
39186 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
39190 <flags id="@var{id}" size="@var{size}">
39191 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
39196 @subsection Registers
39199 Each register is represented as an element with this form:
39202 <reg name="@var{name}"
39203 bitsize="@var{size}"
39204 @r{[}regnum="@var{num}"@r{]}
39205 @r{[}save-restore="@var{save-restore}"@r{]}
39206 @r{[}type="@var{type}"@r{]}
39207 @r{[}group="@var{group}"@r{]}/>
39211 The components are as follows:
39216 The register's name; it must be unique within the target description.
39219 The register's size, in bits.
39222 The register's number. If omitted, a register's number is one greater
39223 than that of the previous register (either in the current feature or in
39224 a preceding feature); the first register in the target description
39225 defaults to zero. This register number is used to read or write
39226 the register; e.g.@: it is used in the remote @code{p} and @code{P}
39227 packets, and registers appear in the @code{g} and @code{G} packets
39228 in order of increasing register number.
39231 Whether the register should be preserved across inferior function
39232 calls; this must be either @code{yes} or @code{no}. The default is
39233 @code{yes}, which is appropriate for most registers except for
39234 some system control registers; this is not related to the target's
39238 The type of the register. It may be a predefined type, a type
39239 defined in the current feature, or one of the special types @code{int}
39240 and @code{float}. @code{int} is an integer type of the correct size
39241 for @var{bitsize}, and @code{float} is a floating point type (in the
39242 architecture's normal floating point format) of the correct size for
39243 @var{bitsize}. The default is @code{int}.
39246 The register group to which this register belongs. It must
39247 be either @code{general}, @code{float}, or @code{vector}. If no
39248 @var{group} is specified, @value{GDBN} will not display the register
39249 in @code{info registers}.
39253 @node Predefined Target Types
39254 @section Predefined Target Types
39255 @cindex target descriptions, predefined types
39257 Type definitions in the self-description can build up composite types
39258 from basic building blocks, but can not define fundamental types. Instead,
39259 standard identifiers are provided by @value{GDBN} for the fundamental
39260 types. The currently supported types are:
39269 Signed integer types holding the specified number of bits.
39276 Unsigned integer types holding the specified number of bits.
39280 Pointers to unspecified code and data. The program counter and
39281 any dedicated return address register may be marked as code
39282 pointers; printing a code pointer converts it into a symbolic
39283 address. The stack pointer and any dedicated address registers
39284 may be marked as data pointers.
39287 Single precision IEEE floating point.
39290 Double precision IEEE floating point.
39293 The 12-byte extended precision format used by ARM FPA registers.
39296 The 10-byte extended precision format used by x87 registers.
39299 32bit @sc{eflags} register used by x86.
39302 32bit @sc{mxcsr} register used by x86.
39306 @node Standard Target Features
39307 @section Standard Target Features
39308 @cindex target descriptions, standard features
39310 A target description must contain either no registers or all the
39311 target's registers. If the description contains no registers, then
39312 @value{GDBN} will assume a default register layout, selected based on
39313 the architecture. If the description contains any registers, the
39314 default layout will not be used; the standard registers must be
39315 described in the target description, in such a way that @value{GDBN}
39316 can recognize them.
39318 This is accomplished by giving specific names to feature elements
39319 which contain standard registers. @value{GDBN} will look for features
39320 with those names and verify that they contain the expected registers;
39321 if any known feature is missing required registers, or if any required
39322 feature is missing, @value{GDBN} will reject the target
39323 description. You can add additional registers to any of the
39324 standard features --- @value{GDBN} will display them just as if
39325 they were added to an unrecognized feature.
39327 This section lists the known features and their expected contents.
39328 Sample XML documents for these features are included in the
39329 @value{GDBN} source tree, in the directory @file{gdb/features}.
39331 Names recognized by @value{GDBN} should include the name of the
39332 company or organization which selected the name, and the overall
39333 architecture to which the feature applies; so e.g.@: the feature
39334 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
39336 The names of registers are not case sensitive for the purpose
39337 of recognizing standard features, but @value{GDBN} will only display
39338 registers using the capitalization used in the description.
39341 * AArch64 Features::
39344 * MicroBlaze Features::
39347 * Nios II Features::
39348 * PowerPC Features::
39349 * S/390 and System z Features::
39354 @node AArch64 Features
39355 @subsection AArch64 Features
39356 @cindex target descriptions, AArch64 features
39358 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
39359 targets. It should contain registers @samp{x0} through @samp{x30},
39360 @samp{sp}, @samp{pc}, and @samp{cpsr}.
39362 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
39363 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
39367 @subsection ARM Features
39368 @cindex target descriptions, ARM features
39370 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
39372 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
39373 @samp{lr}, @samp{pc}, and @samp{cpsr}.
39375 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
39376 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
39377 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
39380 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
39381 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
39383 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
39384 it should contain at least registers @samp{wR0} through @samp{wR15} and
39385 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
39386 @samp{wCSSF}, and @samp{wCASF} registers are optional.
39388 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
39389 should contain at least registers @samp{d0} through @samp{d15}. If
39390 they are present, @samp{d16} through @samp{d31} should also be included.
39391 @value{GDBN} will synthesize the single-precision registers from
39392 halves of the double-precision registers.
39394 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
39395 need to contain registers; it instructs @value{GDBN} to display the
39396 VFP double-precision registers as vectors and to synthesize the
39397 quad-precision registers from pairs of double-precision registers.
39398 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
39399 be present and include 32 double-precision registers.
39401 @node i386 Features
39402 @subsection i386 Features
39403 @cindex target descriptions, i386 features
39405 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
39406 targets. It should describe the following registers:
39410 @samp{eax} through @samp{edi} plus @samp{eip} for i386
39412 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
39414 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
39415 @samp{fs}, @samp{gs}
39417 @samp{st0} through @samp{st7}
39419 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
39420 @samp{foseg}, @samp{fooff} and @samp{fop}
39423 The register sets may be different, depending on the target.
39425 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
39426 describe registers:
39430 @samp{xmm0} through @samp{xmm7} for i386
39432 @samp{xmm0} through @samp{xmm15} for amd64
39437 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
39438 @samp{org.gnu.gdb.i386.sse} feature. It should
39439 describe the upper 128 bits of @sc{ymm} registers:
39443 @samp{ymm0h} through @samp{ymm7h} for i386
39445 @samp{ymm0h} through @samp{ymm15h} for amd64
39448 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel(R)
39449 Memory Protection Extension (MPX). It should describe the following registers:
39453 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
39455 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
39458 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
39459 describe a single register, @samp{orig_eax}.
39461 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
39462 @samp{org.gnu.gdb.i386.avx} feature. It should
39463 describe additional @sc{xmm} registers:
39467 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
39470 It should describe the upper 128 bits of additional @sc{ymm} registers:
39474 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
39478 describe the upper 256 bits of @sc{zmm} registers:
39482 @samp{zmm0h} through @samp{zmm7h} for i386.
39484 @samp{zmm0h} through @samp{zmm15h} for amd64.
39488 describe the additional @sc{zmm} registers:
39492 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
39495 @node MicroBlaze Features
39496 @subsection MicroBlaze Features
39497 @cindex target descriptions, MicroBlaze features
39499 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
39500 targets. It should contain registers @samp{r0} through @samp{r31},
39501 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
39502 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
39503 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
39505 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
39506 If present, it should contain registers @samp{rshr} and @samp{rslr}
39508 @node MIPS Features
39509 @subsection @acronym{MIPS} Features
39510 @cindex target descriptions, @acronym{MIPS} features
39512 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
39513 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
39514 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
39517 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
39518 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
39519 registers. They may be 32-bit or 64-bit depending on the target.
39521 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
39522 it may be optional in a future version of @value{GDBN}. It should
39523 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
39524 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
39526 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
39527 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
39528 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
39529 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
39531 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
39532 contain a single register, @samp{restart}, which is used by the
39533 Linux kernel to control restartable syscalls.
39535 @node M68K Features
39536 @subsection M68K Features
39537 @cindex target descriptions, M68K features
39540 @item @samp{org.gnu.gdb.m68k.core}
39541 @itemx @samp{org.gnu.gdb.coldfire.core}
39542 @itemx @samp{org.gnu.gdb.fido.core}
39543 One of those features must be always present.
39544 The feature that is present determines which flavor of m68k is
39545 used. The feature that is present should contain registers
39546 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
39547 @samp{sp}, @samp{ps} and @samp{pc}.
39549 @item @samp{org.gnu.gdb.coldfire.fp}
39550 This feature is optional. If present, it should contain registers
39551 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
39555 @node Nios II Features
39556 @subsection Nios II Features
39557 @cindex target descriptions, Nios II features
39559 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
39560 targets. It should contain the 32 core registers (@samp{zero},
39561 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
39562 @samp{pc}, and the 16 control registers (@samp{status} through
39565 @node PowerPC Features
39566 @subsection PowerPC Features
39567 @cindex target descriptions, PowerPC features
39569 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
39570 targets. It should contain registers @samp{r0} through @samp{r31},
39571 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
39572 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
39574 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
39575 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
39577 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
39578 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
39581 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
39582 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
39583 will combine these registers with the floating point registers
39584 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
39585 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
39586 through @samp{vs63}, the set of vector registers for POWER7.
39588 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
39589 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
39590 @samp{spefscr}. SPE targets should provide 32-bit registers in
39591 @samp{org.gnu.gdb.power.core} and provide the upper halves in
39592 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
39593 these to present registers @samp{ev0} through @samp{ev31} to the
39596 @node S/390 and System z Features
39597 @subsection S/390 and System z Features
39598 @cindex target descriptions, S/390 features
39599 @cindex target descriptions, System z features
39601 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
39602 System z targets. It should contain the PSW and the 16 general
39603 registers. In particular, System z targets should provide the 64-bit
39604 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
39605 S/390 targets should provide the 32-bit versions of these registers.
39606 A System z target that runs in 31-bit addressing mode should provide
39607 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
39608 register's upper halves @samp{r0h} through @samp{r15h}, and their
39609 lower halves @samp{r0l} through @samp{r15l}.
39611 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
39612 contain the 64-bit registers @samp{f0} through @samp{f15}, and
39615 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
39616 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
39618 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
39619 contain the register @samp{orig_r2}, which is 64-bit wide on System z
39620 targets and 32-bit otherwise. In addition, the feature may contain
39621 the @samp{last_break} register, whose width depends on the addressing
39622 mode, as well as the @samp{system_call} register, which is always
39625 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
39626 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
39627 @samp{atia}, and @samp{tr0} through @samp{tr15}.
39629 @node TIC6x Features
39630 @subsection TMS320C6x Features
39631 @cindex target descriptions, TIC6x features
39632 @cindex target descriptions, TMS320C6x features
39633 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
39634 targets. It should contain registers @samp{A0} through @samp{A15},
39635 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
39637 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
39638 contain registers @samp{A16} through @samp{A31} and @samp{B16}
39639 through @samp{B31}.
39641 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
39642 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
39644 @node Operating System Information
39645 @appendix Operating System Information
39646 @cindex operating system information
39652 Users of @value{GDBN} often wish to obtain information about the state of
39653 the operating system running on the target---for example the list of
39654 processes, or the list of open files. This section describes the
39655 mechanism that makes it possible. This mechanism is similar to the
39656 target features mechanism (@pxref{Target Descriptions}), but focuses
39657 on a different aspect of target.
39659 Operating system information is retrived from the target via the
39660 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
39661 read}). The object name in the request should be @samp{osdata}, and
39662 the @var{annex} identifies the data to be fetched.
39665 @appendixsection Process list
39666 @cindex operating system information, process list
39668 When requesting the process list, the @var{annex} field in the
39669 @samp{qXfer} request should be @samp{processes}. The returned data is
39670 an XML document. The formal syntax of this document is defined in
39671 @file{gdb/features/osdata.dtd}.
39673 An example document is:
39676 <?xml version="1.0"?>
39677 <!DOCTYPE target SYSTEM "osdata.dtd">
39678 <osdata type="processes">
39680 <column name="pid">1</column>
39681 <column name="user">root</column>
39682 <column name="command">/sbin/init</column>
39683 <column name="cores">1,2,3</column>
39688 Each item should include a column whose name is @samp{pid}. The value
39689 of that column should identify the process on the target. The
39690 @samp{user} and @samp{command} columns are optional, and will be
39691 displayed by @value{GDBN}. The @samp{cores} column, if present,
39692 should contain a comma-separated list of cores that this process
39693 is running on. Target may provide additional columns,
39694 which @value{GDBN} currently ignores.
39696 @node Trace File Format
39697 @appendix Trace File Format
39698 @cindex trace file format
39700 The trace file comes in three parts: a header, a textual description
39701 section, and a trace frame section with binary data.
39703 The header has the form @code{\x7fTRACE0\n}. The first byte is
39704 @code{0x7f} so as to indicate that the file contains binary data,
39705 while the @code{0} is a version number that may have different values
39708 The description section consists of multiple lines of @sc{ascii} text
39709 separated by newline characters (@code{0xa}). The lines may include a
39710 variety of optional descriptive or context-setting information, such
39711 as tracepoint definitions or register set size. @value{GDBN} will
39712 ignore any line that it does not recognize. An empty line marks the end
39715 @c FIXME add some specific types of data
39717 The trace frame section consists of a number of consecutive frames.
39718 Each frame begins with a two-byte tracepoint number, followed by a
39719 four-byte size giving the amount of data in the frame. The data in
39720 the frame consists of a number of blocks, each introduced by a
39721 character indicating its type (at least register, memory, and trace
39722 state variable). The data in this section is raw binary, not a
39723 hexadecimal or other encoding; its endianness matches the target's
39726 @c FIXME bi-arch may require endianness/arch info in description section
39729 @item R @var{bytes}
39730 Register block. The number and ordering of bytes matches that of a
39731 @code{g} packet in the remote protocol. Note that these are the
39732 actual bytes, in target order and @value{GDBN} register order, not a
39733 hexadecimal encoding.
39735 @item M @var{address} @var{length} @var{bytes}...
39736 Memory block. This is a contiguous block of memory, at the 8-byte
39737 address @var{address}, with a 2-byte length @var{length}, followed by
39738 @var{length} bytes.
39740 @item V @var{number} @var{value}
39741 Trace state variable block. This records the 8-byte signed value
39742 @var{value} of trace state variable numbered @var{number}.
39746 Future enhancements of the trace file format may include additional types
39749 @node Index Section Format
39750 @appendix @code{.gdb_index} section format
39751 @cindex .gdb_index section format
39752 @cindex index section format
39754 This section documents the index section that is created by @code{save
39755 gdb-index} (@pxref{Index Files}). The index section is
39756 DWARF-specific; some knowledge of DWARF is assumed in this
39759 The mapped index file format is designed to be directly
39760 @code{mmap}able on any architecture. In most cases, a datum is
39761 represented using a little-endian 32-bit integer value, called an
39762 @code{offset_type}. Big endian machines must byte-swap the values
39763 before using them. Exceptions to this rule are noted. The data is
39764 laid out such that alignment is always respected.
39766 A mapped index consists of several areas, laid out in order.
39770 The file header. This is a sequence of values, of @code{offset_type}
39771 unless otherwise noted:
39775 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
39776 Version 4 uses a different hashing function from versions 5 and 6.
39777 Version 6 includes symbols for inlined functions, whereas versions 4
39778 and 5 do not. Version 7 adds attributes to the CU indices in the
39779 symbol table. Version 8 specifies that symbols from DWARF type units
39780 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
39781 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
39783 @value{GDBN} will only read version 4, 5, or 6 indices
39784 by specifying @code{set use-deprecated-index-sections on}.
39785 GDB has a workaround for potentially broken version 7 indices so it is
39786 currently not flagged as deprecated.
39789 The offset, from the start of the file, of the CU list.
39792 The offset, from the start of the file, of the types CU list. Note
39793 that this area can be empty, in which case this offset will be equal
39794 to the next offset.
39797 The offset, from the start of the file, of the address area.
39800 The offset, from the start of the file, of the symbol table.
39803 The offset, from the start of the file, of the constant pool.
39807 The CU list. This is a sequence of pairs of 64-bit little-endian
39808 values, sorted by the CU offset. The first element in each pair is
39809 the offset of a CU in the @code{.debug_info} section. The second
39810 element in each pair is the length of that CU. References to a CU
39811 elsewhere in the map are done using a CU index, which is just the
39812 0-based index into this table. Note that if there are type CUs, then
39813 conceptually CUs and type CUs form a single list for the purposes of
39817 The types CU list. This is a sequence of triplets of 64-bit
39818 little-endian values. In a triplet, the first value is the CU offset,
39819 the second value is the type offset in the CU, and the third value is
39820 the type signature. The types CU list is not sorted.
39823 The address area. The address area consists of a sequence of address
39824 entries. Each address entry has three elements:
39828 The low address. This is a 64-bit little-endian value.
39831 The high address. This is a 64-bit little-endian value. Like
39832 @code{DW_AT_high_pc}, the value is one byte beyond the end.
39835 The CU index. This is an @code{offset_type} value.
39839 The symbol table. This is an open-addressed hash table. The size of
39840 the hash table is always a power of 2.
39842 Each slot in the hash table consists of a pair of @code{offset_type}
39843 values. The first value is the offset of the symbol's name in the
39844 constant pool. The second value is the offset of the CU vector in the
39847 If both values are 0, then this slot in the hash table is empty. This
39848 is ok because while 0 is a valid constant pool index, it cannot be a
39849 valid index for both a string and a CU vector.
39851 The hash value for a table entry is computed by applying an
39852 iterative hash function to the symbol's name. Starting with an
39853 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
39854 the string is incorporated into the hash using the formula depending on the
39859 The formula is @code{r = r * 67 + c - 113}.
39861 @item Versions 5 to 7
39862 The formula is @code{r = r * 67 + tolower (c) - 113}.
39865 The terminating @samp{\0} is not incorporated into the hash.
39867 The step size used in the hash table is computed via
39868 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
39869 value, and @samp{size} is the size of the hash table. The step size
39870 is used to find the next candidate slot when handling a hash
39873 The names of C@t{++} symbols in the hash table are canonicalized. We
39874 don't currently have a simple description of the canonicalization
39875 algorithm; if you intend to create new index sections, you must read
39879 The constant pool. This is simply a bunch of bytes. It is organized
39880 so that alignment is correct: CU vectors are stored first, followed by
39883 A CU vector in the constant pool is a sequence of @code{offset_type}
39884 values. The first value is the number of CU indices in the vector.
39885 Each subsequent value is the index and symbol attributes of a CU in
39886 the CU list. This element in the hash table is used to indicate which
39887 CUs define the symbol and how the symbol is used.
39888 See below for the format of each CU index+attributes entry.
39890 A string in the constant pool is zero-terminated.
39893 Attributes were added to CU index values in @code{.gdb_index} version 7.
39894 If a symbol has multiple uses within a CU then there is one
39895 CU index+attributes value for each use.
39897 The format of each CU index+attributes entry is as follows
39903 This is the index of the CU in the CU list.
39905 These bits are reserved for future purposes and must be zero.
39907 The kind of the symbol in the CU.
39911 This value is reserved and should not be used.
39912 By reserving zero the full @code{offset_type} value is backwards compatible
39913 with previous versions of the index.
39915 The symbol is a type.
39917 The symbol is a variable or an enum value.
39919 The symbol is a function.
39921 Any other kind of symbol.
39923 These values are reserved.
39927 This bit is zero if the value is global and one if it is static.
39929 The determination of whether a symbol is global or static is complicated.
39930 The authorative reference is the file @file{dwarf2read.c} in
39931 @value{GDBN} sources.
39935 This pseudo-code describes the computation of a symbol's kind and
39936 global/static attributes in the index.
39939 is_external = get_attribute (die, DW_AT_external);
39940 language = get_attribute (cu_die, DW_AT_language);
39943 case DW_TAG_typedef:
39944 case DW_TAG_base_type:
39945 case DW_TAG_subrange_type:
39949 case DW_TAG_enumerator:
39951 is_static = (language != CPLUS && language != JAVA);
39953 case DW_TAG_subprogram:
39955 is_static = ! (is_external || language == ADA);
39957 case DW_TAG_constant:
39959 is_static = ! is_external;
39961 case DW_TAG_variable:
39963 is_static = ! is_external;
39965 case DW_TAG_namespace:
39969 case DW_TAG_class_type:
39970 case DW_TAG_interface_type:
39971 case DW_TAG_structure_type:
39972 case DW_TAG_union_type:
39973 case DW_TAG_enumeration_type:
39975 is_static = (language != CPLUS && language != JAVA);
39983 @appendix Manual pages
39987 * gdb man:: The GNU Debugger man page
39988 * gdbserver man:: Remote Server for the GNU Debugger man page
39989 * gcore man:: Generate a core file of a running program
39990 * gdbinit man:: gdbinit scripts
39996 @c man title gdb The GNU Debugger
39998 @c man begin SYNOPSIS gdb
39999 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
40000 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
40001 [@option{-b}@w{ }@var{bps}]
40002 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
40003 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
40004 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
40005 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
40006 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
40009 @c man begin DESCRIPTION gdb
40010 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
40011 going on ``inside'' another program while it executes -- or what another
40012 program was doing at the moment it crashed.
40014 @value{GDBN} can do four main kinds of things (plus other things in support of
40015 these) to help you catch bugs in the act:
40019 Start your program, specifying anything that might affect its behavior.
40022 Make your program stop on specified conditions.
40025 Examine what has happened, when your program has stopped.
40028 Change things in your program, so you can experiment with correcting the
40029 effects of one bug and go on to learn about another.
40032 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
40035 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
40036 commands from the terminal until you tell it to exit with the @value{GDBN}
40037 command @code{quit}. You can get online help from @value{GDBN} itself
40038 by using the command @code{help}.
40040 You can run @code{gdb} with no arguments or options; but the most
40041 usual way to start @value{GDBN} is with one argument or two, specifying an
40042 executable program as the argument:
40048 You can also start with both an executable program and a core file specified:
40054 You can, instead, specify a process ID as a second argument, if you want
40055 to debug a running process:
40063 would attach @value{GDBN} to process @code{1234} (unless you also have a file
40064 named @file{1234}; @value{GDBN} does check for a core file first).
40065 With option @option{-p} you can omit the @var{program} filename.
40067 Here are some of the most frequently needed @value{GDBN} commands:
40069 @c pod2man highlights the right hand side of the @item lines.
40071 @item break [@var{file}:]@var{functiop}
40072 Set a breakpoint at @var{function} (in @var{file}).
40074 @item run [@var{arglist}]
40075 Start your program (with @var{arglist}, if specified).
40078 Backtrace: display the program stack.
40080 @item print @var{expr}
40081 Display the value of an expression.
40084 Continue running your program (after stopping, e.g. at a breakpoint).
40087 Execute next program line (after stopping); step @emph{over} any
40088 function calls in the line.
40090 @item edit [@var{file}:]@var{function}
40091 look at the program line where it is presently stopped.
40093 @item list [@var{file}:]@var{function}
40094 type the text of the program in the vicinity of where it is presently stopped.
40097 Execute next program line (after stopping); step @emph{into} any
40098 function calls in the line.
40100 @item help [@var{name}]
40101 Show information about @value{GDBN} command @var{name}, or general information
40102 about using @value{GDBN}.
40105 Exit from @value{GDBN}.
40109 For full details on @value{GDBN},
40110 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40111 by Richard M. Stallman and Roland H. Pesch. The same text is available online
40112 as the @code{gdb} entry in the @code{info} program.
40116 @c man begin OPTIONS gdb
40117 Any arguments other than options specify an executable
40118 file and core file (or process ID); that is, the first argument
40119 encountered with no
40120 associated option flag is equivalent to a @option{-se} option, and the second,
40121 if any, is equivalent to a @option{-c} option if it's the name of a file.
40123 both long and short forms; both are shown here. The long forms are also
40124 recognized if you truncate them, so long as enough of the option is
40125 present to be unambiguous. (If you prefer, you can flag option
40126 arguments with @option{+} rather than @option{-}, though we illustrate the
40127 more usual convention.)
40129 All the options and command line arguments you give are processed
40130 in sequential order. The order makes a difference when the @option{-x}
40136 List all options, with brief explanations.
40138 @item -symbols=@var{file}
40139 @itemx -s @var{file}
40140 Read symbol table from file @var{file}.
40143 Enable writing into executable and core files.
40145 @item -exec=@var{file}
40146 @itemx -e @var{file}
40147 Use file @var{file} as the executable file to execute when
40148 appropriate, and for examining pure data in conjunction with a core
40151 @item -se=@var{file}
40152 Read symbol table from file @var{file} and use it as the executable
40155 @item -core=@var{file}
40156 @itemx -c @var{file}
40157 Use file @var{file} as a core dump to examine.
40159 @item -command=@var{file}
40160 @itemx -x @var{file}
40161 Execute @value{GDBN} commands from file @var{file}.
40163 @item -ex @var{command}
40164 Execute given @value{GDBN} @var{command}.
40166 @item -directory=@var{directory}
40167 @itemx -d @var{directory}
40168 Add @var{directory} to the path to search for source files.
40171 Do not execute commands from @file{~/.gdbinit}.
40175 Do not execute commands from any @file{.gdbinit} initialization files.
40179 ``Quiet''. Do not print the introductory and copyright messages. These
40180 messages are also suppressed in batch mode.
40183 Run in batch mode. Exit with status @code{0} after processing all the command
40184 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
40185 Exit with nonzero status if an error occurs in executing the @value{GDBN}
40186 commands in the command files.
40188 Batch mode may be useful for running @value{GDBN} as a filter, for example to
40189 download and run a program on another computer; in order to make this
40190 more useful, the message
40193 Program exited normally.
40197 (which is ordinarily issued whenever a program running under @value{GDBN} control
40198 terminates) is not issued when running in batch mode.
40200 @item -cd=@var{directory}
40201 Run @value{GDBN} using @var{directory} as its working directory,
40202 instead of the current directory.
40206 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
40207 @value{GDBN} to output the full file name and line number in a standard,
40208 recognizable fashion each time a stack frame is displayed (which
40209 includes each time the program stops). This recognizable format looks
40210 like two @samp{\032} characters, followed by the file name, line number
40211 and character position separated by colons, and a newline. The
40212 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
40213 characters as a signal to display the source code for the frame.
40216 Set the line speed (baud rate or bits per second) of any serial
40217 interface used by @value{GDBN} for remote debugging.
40219 @item -tty=@var{device}
40220 Run using @var{device} for your program's standard input and output.
40224 @c man begin SEEALSO gdb
40226 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
40227 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
40228 documentation are properly installed at your site, the command
40235 should give you access to the complete manual.
40237 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40238 Richard M. Stallman and Roland H. Pesch, July 1991.
40242 @node gdbserver man
40243 @heading gdbserver man
40245 @c man title gdbserver Remote Server for the GNU Debugger
40247 @c man begin SYNOPSIS gdbserver
40248 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
40250 gdbserver --attach @var{comm} @var{pid}
40252 gdbserver --multi @var{comm}
40256 @c man begin DESCRIPTION gdbserver
40257 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
40258 than the one which is running the program being debugged.
40261 @subheading Usage (server (target) side)
40264 Usage (server (target) side):
40267 First, you need to have a copy of the program you want to debug put onto
40268 the target system. The program can be stripped to save space if needed, as
40269 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
40270 the @value{GDBN} running on the host system.
40272 To use the server, you log on to the target system, and run the @command{gdbserver}
40273 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
40274 your program, and (c) its arguments. The general syntax is:
40277 target> gdbserver @var{comm} @var{program} [@var{args} ...]
40280 For example, using a serial port, you might say:
40284 @c @file would wrap it as F</dev/com1>.
40285 target> gdbserver /dev/com1 emacs foo.txt
40288 target> gdbserver @file{/dev/com1} emacs foo.txt
40292 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
40293 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
40294 waits patiently for the host @value{GDBN} to communicate with it.
40296 To use a TCP connection, you could say:
40299 target> gdbserver host:2345 emacs foo.txt
40302 This says pretty much the same thing as the last example, except that we are
40303 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
40304 that we are expecting to see a TCP connection from @code{host} to local TCP port
40305 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
40306 want for the port number as long as it does not conflict with any existing TCP
40307 ports on the target system. This same port number must be used in the host
40308 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
40309 you chose a port number that conflicts with another service, @command{gdbserver} will
40310 print an error message and exit.
40312 @command{gdbserver} can also attach to running programs.
40313 This is accomplished via the @option{--attach} argument. The syntax is:
40316 target> gdbserver --attach @var{comm} @var{pid}
40319 @var{pid} is the process ID of a currently running process. It isn't
40320 necessary to point @command{gdbserver} at a binary for the running process.
40322 To start @code{gdbserver} without supplying an initial command to run
40323 or process ID to attach, use the @option{--multi} command line option.
40324 In such case you should connect using @kbd{target extended-remote} to start
40325 the program you want to debug.
40328 target> gdbserver --multi @var{comm}
40332 @subheading Usage (host side)
40338 You need an unstripped copy of the target program on your host system, since
40339 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
40340 would, with the target program as the first argument. (You may need to use the
40341 @option{--baud} option if the serial line is running at anything except 9600 baud.)
40342 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
40343 new command you need to know about is @code{target remote}
40344 (or @code{target extended-remote}). Its argument is either
40345 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
40346 descriptor. For example:
40350 @c @file would wrap it as F</dev/ttyb>.
40351 (gdb) target remote /dev/ttyb
40354 (gdb) target remote @file{/dev/ttyb}
40359 communicates with the server via serial line @file{/dev/ttyb}, and:
40362 (gdb) target remote the-target:2345
40366 communicates via a TCP connection to port 2345 on host `the-target', where
40367 you previously started up @command{gdbserver} with the same port number. Note that for
40368 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
40369 command, otherwise you may get an error that looks something like
40370 `Connection refused'.
40372 @command{gdbserver} can also debug multiple inferiors at once,
40375 the @value{GDBN} manual in node @code{Inferiors and Programs}
40376 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
40379 @ref{Inferiors and Programs}.
40381 In such case use the @code{extended-remote} @value{GDBN} command variant:
40384 (gdb) target extended-remote the-target:2345
40387 The @command{gdbserver} option @option{--multi} may or may not be used in such
40391 @c man begin OPTIONS gdbserver
40392 There are three different modes for invoking @command{gdbserver}:
40397 Debug a specific program specified by its program name:
40400 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
40403 The @var{comm} parameter specifies how should the server communicate
40404 with @value{GDBN}; it is either a device name (to use a serial line),
40405 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
40406 stdin/stdout of @code{gdbserver}. Specify the name of the program to
40407 debug in @var{prog}. Any remaining arguments will be passed to the
40408 program verbatim. When the program exits, @value{GDBN} will close the
40409 connection, and @code{gdbserver} will exit.
40412 Debug a specific program by specifying the process ID of a running
40416 gdbserver --attach @var{comm} @var{pid}
40419 The @var{comm} parameter is as described above. Supply the process ID
40420 of a running program in @var{pid}; @value{GDBN} will do everything
40421 else. Like with the previous mode, when the process @var{pid} exits,
40422 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
40425 Multi-process mode -- debug more than one program/process:
40428 gdbserver --multi @var{comm}
40431 In this mode, @value{GDBN} can instruct @command{gdbserver} which
40432 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
40433 close the connection when a process being debugged exits, so you can
40434 debug several processes in the same session.
40437 In each of the modes you may specify these options:
40442 List all options, with brief explanations.
40445 This option causes @command{gdbserver} to print its version number and exit.
40448 @command{gdbserver} will attach to a running program. The syntax is:
40451 target> gdbserver --attach @var{comm} @var{pid}
40454 @var{pid} is the process ID of a currently running process. It isn't
40455 necessary to point @command{gdbserver} at a binary for the running process.
40458 To start @code{gdbserver} without supplying an initial command to run
40459 or process ID to attach, use this command line option.
40460 Then you can connect using @kbd{target extended-remote} and start
40461 the program you want to debug. The syntax is:
40464 target> gdbserver --multi @var{comm}
40468 Instruct @code{gdbserver} to display extra status information about the debugging
40470 This option is intended for @code{gdbserver} development and for bug reports to
40473 @item --remote-debug
40474 Instruct @code{gdbserver} to display remote protocol debug output.
40475 This option is intended for @code{gdbserver} development and for bug reports to
40478 @item --debug-format=option1@r{[},option2,...@r{]}
40479 Instruct @code{gdbserver} to include extra information in each line
40480 of debugging output.
40481 @xref{Other Command-Line Arguments for gdbserver}.
40484 Specify a wrapper to launch programs
40485 for debugging. The option should be followed by the name of the
40486 wrapper, then any command-line arguments to pass to the wrapper, then
40487 @kbd{--} indicating the end of the wrapper arguments.
40490 By default, @command{gdbserver} keeps the listening TCP port open, so that
40491 additional connections are possible. However, if you start @code{gdbserver}
40492 with the @option{--once} option, it will stop listening for any further
40493 connection attempts after connecting to the first @value{GDBN} session.
40495 @c --disable-packet is not documented for users.
40497 @c --disable-randomization and --no-disable-randomization are superseded by
40498 @c QDisableRandomization.
40503 @c man begin SEEALSO gdbserver
40505 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
40506 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
40507 documentation are properly installed at your site, the command
40513 should give you access to the complete manual.
40515 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40516 Richard M. Stallman and Roland H. Pesch, July 1991.
40523 @c man title gcore Generate a core file of a running program
40526 @c man begin SYNOPSIS gcore
40527 gcore [-o @var{filename}] @var{pid}
40531 @c man begin DESCRIPTION gcore
40532 Generate a core dump of a running program with process ID @var{pid}.
40533 Produced file is equivalent to a kernel produced core file as if the process
40534 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
40535 limit). Unlike after a crash, after @command{gcore} the program remains
40536 running without any change.
40539 @c man begin OPTIONS gcore
40541 @item -o @var{filename}
40542 The optional argument
40543 @var{filename} specifies the file name where to put the core dump.
40544 If not specified, the file name defaults to @file{core.@var{pid}},
40545 where @var{pid} is the running program process ID.
40549 @c man begin SEEALSO gcore
40551 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
40552 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
40553 documentation are properly installed at your site, the command
40560 should give you access to the complete manual.
40562 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40563 Richard M. Stallman and Roland H. Pesch, July 1991.
40570 @c man title gdbinit GDB initialization scripts
40573 @c man begin SYNOPSIS gdbinit
40574 @ifset SYSTEM_GDBINIT
40575 @value{SYSTEM_GDBINIT}
40584 @c man begin DESCRIPTION gdbinit
40585 These files contain @value{GDBN} commands to automatically execute during
40586 @value{GDBN} startup. The lines of contents are canned sequences of commands,
40589 the @value{GDBN} manual in node @code{Sequences}
40590 -- shell command @code{info -f gdb -n Sequences}.
40596 Please read more in
40598 the @value{GDBN} manual in node @code{Startup}
40599 -- shell command @code{info -f gdb -n Startup}.
40606 @ifset SYSTEM_GDBINIT
40607 @item @value{SYSTEM_GDBINIT}
40609 @ifclear SYSTEM_GDBINIT
40610 @item (not enabled with @code{--with-system-gdbinit} during compilation)
40612 System-wide initialization file. It is executed unless user specified
40613 @value{GDBN} option @code{-nx} or @code{-n}.
40616 the @value{GDBN} manual in node @code{System-wide configuration}
40617 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
40620 @ref{System-wide configuration}.
40624 User initialization file. It is executed unless user specified
40625 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
40628 Initialization file for current directory. It may need to be enabled with
40629 @value{GDBN} security command @code{set auto-load local-gdbinit}.
40632 the @value{GDBN} manual in node @code{Init File in the Current Directory}
40633 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
40636 @ref{Init File in the Current Directory}.
40641 @c man begin SEEALSO gdbinit
40643 gdb(1), @code{info -f gdb -n Startup}
40645 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
40646 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
40647 documentation are properly installed at your site, the command
40653 should give you access to the complete manual.
40655 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40656 Richard M. Stallman and Roland H. Pesch, July 1991.
40662 @node GNU Free Documentation License
40663 @appendix GNU Free Documentation License
40666 @node Concept Index
40667 @unnumbered Concept Index
40671 @node Command and Variable Index
40672 @unnumbered Command, Variable, and Function Index
40677 % I think something like @@colophon should be in texinfo. In the
40679 \long\def\colophon{\hbox to0pt{}\vfill
40680 \centerline{The body of this manual is set in}
40681 \centerline{\fontname\tenrm,}
40682 \centerline{with headings in {\bf\fontname\tenbf}}
40683 \centerline{and examples in {\tt\fontname\tentt}.}
40684 \centerline{{\it\fontname\tenit\/},}
40685 \centerline{{\bf\fontname\tenbf}, and}
40686 \centerline{{\sl\fontname\tensl\/}}
40687 \centerline{are used for emphasis.}\vfill}
40689 % Blame: doc@@cygnus.com, 1991.